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Evolution of the Urgonian shallow-water carbonate platform on the Helvetic shelf during the late Early Cretaceous

April 2019
Sedimentary Geology 387(Supplement 1)

April 2019
387(Supplement 1)

DOI:10.1016/j.sedgeo.2019.04.005

Authors:

Lucie Bonvallet

University of Lausanne

Annie Arnaud-Vanneau

University Joseph Fourier - Grenoble 1

Thierry Adatte

University of Lausanne

Show all 8 authorsHide

Carbon-isotope records and phosphorus contents in the studied sections arranged along a palinspastic transect. The carbon-isotope records are correlated with the hemipelagic reference section of Angles -Combes Lambert (Godet et al., 2006).

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Stratigraphic distribution of Orbitolinids and Neotrocholina friburgensis in the Helvetic nappes (modified after Arnaud et al., 1998). The colored markers correspond to the sequences for which these species are characteristic: pink: sequence B2; green: sequence B3; yellow: sequence B4; blue: sequence B5; orange: sequence A1. Ammonite biostratigraphy from Reboulet et al. (2018). A selection of identified benthic foraminifera are illustrated in Fig. 10. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)

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Close-up on an annelid-rich interval associated with the TST of sequence B3 of the Lower Schrattenkalk Mb in the section at Valsloch.

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Photomicrographs illustrating the emersion phase associated with SB B4: (A) early dissolution cracks, filled in by micrite (Valsloch section; VA 139); (B) early dissolution, filled in by peloids (Valsloch section; VA 141); (C. and H) polyphased karst infilling (Tierwis section; TW 34); (D) amber meteoric cement (Tierwis section; TW 36); (E) pedogenic cement in rosette (Tierwis section; TW 35); (F and I) green marl associated with soil deposit (Tierwis and Morschach sections; TW 34 and MC 153); (G) dolomitic infilling of an early dissolution pocket (Tierwis section; TW 34); (J) root trace (Morschach section; MC 152); (K) epikarstic features (Morschach section; MC 152); (L) dolomite facies (Harder section; HA 251). (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)

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UNCORRECTED PROOF

1Q1 Evolution of the Urgonian shallow-water carbonate platform on the

2Helvetic shelf during the late Early Cretaceous

3Q2Q3 Lucie Bonvallet

a,b

,Annie Arnaud-Vanneau

, Hubert Arnaud

b,†

, Thierry Adatte

, Jorge E. Spangenberg

4Melody Stein

, Alexis Godet

,Karl B. Föllmi

⁎

Institut des Sciences de la Terre, Géopolis, Université de Lausanne, 1015 Lausanne, Switzerland

Association Dolomieu, 8 Chemin des Grenouilles, 38700 La Tronche, France

Institut des Dynamiques de la Surface Terrestre, Université de Lausanne, 1015 Lausanne, Switzerland

Institut de Physique du Globe de Strasbourg, Université Strasbourg, 67074 Strasbourg, France

Department of Geological Sciences, University ofTexas at San Antonio, 1 UTSA Circle, San Antonio, TX 78249, USA

abstract11 article info

12 Article history:

13 Received 25 January 2019

14 Received in revised form 11 April 2019

15 Accepted 14 April 2019

16 Available online xxxx

18 Editor: J. Knight

1920212223

Urgonian platform carbonate (Cretaceous; Barremian, Aptian) forms an important lithostratigraphic unit in the

25Helvetic fold- and thrust unit of the northern Swiss Alps. Its widespread distribution and ubiquity allow for an

26integrated high-resolution study of macro- and microfacies, benthic foraminiferal biostratigraphy, sequence

27stratigraphy, and carbon-isotope and phosphorus records.The resulting data conﬁrm the importance of e nviron-

28mental forcing and sea level change on the style of carbonate production and accumulation along the margin of

29the northern Tethys during the late Early Cretaceous. Stratal geometries, the succession of microfacies, the

30identiﬁcation of major emersion surfaces, and biostratigraphy observed and analysedin twelve sections through

31the inner, middle, and outer platform, and in the panorama of the Churﬁrsten range, permit subdivision of the

32analysed succession into eight depositional sequences. The succession starts with a phase of sedimentary con-

33densation(Altmann Member (Mb); late Hauterivian –late early Barremian; sequences H7, H8, and B1), followed

34by the deposition of hemipelagic sediments (Drusberg Mb; restricted to sequence B2 of the late early Barremian

35on the inner platform; and covering the late early Barremian to the middle late Barremian on the outer platform,

36and to the early Aptian on the outer shelf, thereby showing an important diachroneity of its upper boundary

37related to the inception and progradation of the Urgonian platform), and the development of predominantly la-

38goonal carbonate (Schrattenkalk Formation (Fm); early late Barremian –early Aptian; sequences B3, B4, B5, and

39A1). The Schrattenkalk Fm documents important progradation and aggradation of the carbonate platform, and

40the change from a ramp-like to ﬂat-topped geometry. The oldest, allochthonous remains of the shallow-water

41carbonate platform were identiﬁed intercalated in and on top of the lower Barremian Drusberg Mb (sequence

42B2). Sequence boundary (SB) B3 resulted from an important regressive phase near the early-late Barremian

43boundary, which led to the emersion of the hemipelagic sediments of the Drusberg Mb in the inner part of the

44shelf and to thedeposition of a lowstandsystems tract at the base of theLower SchrattenkalkMb (late Barremian;

45sequences B3–5) in intermediate and distal domains. Deposition of in-situ platform carbonate started during the

46following transgressive phase in the middle late Barremian, which ﬂooded the entire investigated area. The

47associated faunal assemblages and phosphorus contents indicate a concomitant increase in nutrient input,

48which led to a mixed photozoan-heterozoan platform association dominated by annelids and ﬂat orbitolinids,

49and the formation of a condensed phosphate-rich bed on the outer shelf (Chopf Bed; middle late Barremian).

50The subsequent sea-level highstand allowed for the deposition of the ﬁrst typical Urgonian carbonates rich in

51corals and rudists. This depositional sequence (B3) terminated by the important inﬁlling of accommodation

52space combined with sea-level fall of at least 15 m. Later on, close to the Barremian-Aptian boundary,a further,

53major emersion phase (SB A1) was triggered by sea-level fall, estimated here as at least 16 m, which terminated

54this ﬁrst phase in the deposition of rudist and coral-rich platform carbonates covering the middle late to latest

55Barremian (B3–B5). The overlying Rawil Mb (lowermost Aptian; transgressive systems tract A1) resulted from

56progressive deepening and document a phase of increasing eutrophication of the depositional environment,

57resulting in a mixed siliciclastic-carbonate platform build-up, characterized by sea-grass facies and the massive

58occurrence of Palorbitolina lenticularis. The overlying Upper Schrattenkalk Mb (lower Aptian; highstand systems

59tract A1) records recovery of the rudist-rich photozoan Urgonian platform. Its subsequent demise occurred well

69 Keywords:

70 Tethys

71 Urgonian

72 Barremian

73 Aptian

74 Isotopes

75 Alps

Sedimentary Geology xxx (xxxx) xxx

⁎Corresponding author.

E-mail address: karl.foellmi@unil.ch (K.B. Föllmi).

†

Deceased.

SEDGEO-05482; No of Pages 39

https://doi.org/10.1016/j.sedgeo.2019.04.005

Contents lists available at ScienceDirect

Sedimentary Geology

journal homepage: www.elsevier.com/locate/sedgeo

Please cite this article as: L. Bonvallet, A. Arnaud-Vanneau, H.Arnaud, et al., Evolution of the Urgonian shallow-water carbonate platform on the

Helvetic shelf during the late Ear..., Sedimentary Geology, https://doi.org/10.1016/j.sedgeo.2019.04.005

UNCORRECTED PROOF

60before the Selli oceanic anoxic episode (OAE 1a). It was initiated by emersion of the platform due to high-

61amplitude sea-level fall (SB A2), followed by eutrophication during the subsequent transgressive phase.

62The carbon-isotope records show an increase towards more positive values during the Lower Schrattenkalk Mb

63and the base of the Rawil Mb, interrupted in most sections by an excursion to lower values near the Barremian–

64Aptian boundary. A shift to lower values occurred also in the uppermost part of the Rawil Mb, followed by vari-

65able trends in the Upper Schrattenkalk Mb. These long-term trends are well correlated with the basinal record

66(Angles, La Bédoule). Deviations in the correlations are related to the inﬂuence of facies and microfacies, primary

67mineralogy, emersion phases, and post-depositional alteration.

7677

80 1. Introduction

81 During the late Early Cretaceous, photozoan shallow-water carbon-

82 ates rich in rudists, corals,chaetetids, and stromatoporoids accumulated

83 in tropical and subtropical seas to build up the largest and most wide-

84 spread platforms of the entire Mesozoic (Ager, 1981;Michalik, 1994;

85 Philip, 2003;Simo et al., 2003). Relicts of these so-called Urgonian plat-

86 forms crop out around theworld, such asfrom Spain to Pakistan on the

87 northern Tethyan margin (Portugal, Rey, 1979; Spain, Vilas et al., 1995;

88 Millán et al., 2011;Sardinia,Dieni et al., 1963; France, Masse, 1976;

89 Masse and Fenerci-Masse, 2012;Arnaud et al., 2017;Frau et al., 2018;

90 Alps, Bollinger, 1988;Schenk, 1992;Bonvallet, 2015; Slovenia, Croatia,

91 Velic, 2007; Hungary, Peybernès, 1979;Serbia,Sudar et al., 2008;

92 Romania, Bucur, 1997;Iran,Wilmsen et al., 2013;Pakistan,Pudsey

93 et al., 1985), and from Morocco to the Middle East for the southern Te-

94 thyan margin (Morocco-Algeria-Tunisia, Canérot et al., 1986;Godet

95 et al., 2014; Italy, Chiochini et al., 2012;Graziano and Raspini, 2018;

96 Israel, Bachmann and Hirsch, 2006;Turkey,Masse et al., 2009;Middle

97 East, Van Buchem et al., 2010). They also appear in the Paciﬁc Ocean

98 (Indonesia, Hashimoto and Matsumaru, 1971; Hokaido, Matsumaru,

99 2005; Resolution Guyot, Arnaud et al., 1995;Arnaud-Vanneau and

100 Sliter, 1995), and in South and Central America (Venezuela, Arnaud

101 et al., 1994, 2000;Mexico,Omana-Pulido and Pantoja-Alor, 1998;

102 Barragan-Manzo and Diaz-Otero, 2004).

103 The installation and evolution of these platforms mirror the history

104 of sea-level change and paleoclimatic and environmental conditions in

105 general. Oceanic anoxia and eutrophication events interfered in partic-

106 ular with the evolution of Urgonian platforms. For example, the demise

107 of the Urgonian platform along the northwestern margin of the Tethys

108 was linked to the unfolding of the early Aptian Oceanic Anoxic Event

109 1a (OAE1a; Schlanger and Jenkyns, 1976;Föllmi et al., 2006, 2007;

110 Tejada et al., 2009;Jenkyns, 2010;Huck et al., 2011). A further example

111 is the change from Urgonian-type facies rich in rudists and corals to a

112 mixed siliciclastic–carbonate depositional system near the Barremian-

113 Aptian boundary in central Europe (“Lower Orbitolina Beds”), which

114 was associated with climate perturbations and concomitant changes

115 in terrigenous and nutrient input (Stein et al., 2012a, 2012b;Carević

116 et al., 2013).

117 Climate perturbations and regional to global oceanic anoxia were

118 important in the late Early Cretaceous and were the likely consequence

119 of episodes of increased volcanic activity, such as related to the forma-

120 tion of the Ontong-Java large igneous province (LIP; e.g., Kuroda et al.,

121 2011), which started in the late Barremian. In spite of these proposed

122 links between the evolution of theUrgonian platform and climate, envi-

123 ronment, and sea level, many details are not yet known, such as the con-

124 ditions allowing for the development of Urgonian platforms. This is

125 often related to the difﬁculty to obtain precise time control, resulting

126 in different and often conﬂicting age models (e.g., Clavel et al., 2013;

127 Frau et al., 2018), in spite of recent advances in the use of carbon- and

128 strontium-isotope records in the dating and correlation of shallow-

129 water carbonates (Wissler et al., 2003;Millán et al., 2011;Godet et al.,

130 2011;Huck et al., 2011;Huck and Heimhofer, 2015).

131 In the area of the northern Tethyan platform presently preserved in

132 the Swiss Helvetic Alps, the distal part of the Urgonian platform crops

133out in form of the Schrattenkalk Formation (Fm), offering access to a

134transect of over 80 km across the platform (Trümpy, 1969;Ferrazzini

135and Schüler, 1979). The “Helvetic”Urgonian represents an important

136platform segment, which is hitherto less well studied than its equiva-

137lents in the Jura Mountains and eastern France (e.g., Arnaud-Vanneau

138and Arnaud, 1990;Arnaud, 2005;Godet et al., 2010;Huck et al., 2011;

139Masse and Fenerci-Masse, 2012;Clavel et al., 2013), and in the eastern

140Alps (e.g., Bollinger, 1988), in spite of its presence as prominent cliff-

141forming rocks in the northern Alps. Especially poorly known are the

142ages of both the oldest shallow-water carbonates in the Urgonian suc-

143cession, as well as the oldest typical Urgonian carbonate association in-

144cluding rudists, stromatoporoids, chaetetids and corals. Unclear is also

145the relationship between the presence of a phosphatic bed of middle

146late Barremian age (Chopf Bed; Bodin et al., 2006b) in the outer shelf

147and facies change within the Urgonian succession. Questions remain

148also with regards to the pause in Urgonian-type carbonate production

149close to the Barremian-Aptian boundary, documented by the Rawil

150Member (“Lower Orbitolina Beds”), which is build up by a partly

151heterozoan assemblage. Unclearis also the inﬂuence of sea-level change

152in the formation of the Urgonian succession and the impact of sea-level

153fall associated with phases of platform emersion in the overall evolution

154of the platform. A ﬁnal question concerns the modalities of evolution

155of the Urgonian succession and its correspondence to general

156paleoceanographic trends shown by the pelagic carbon-isotope record,

157and the relationship between facies change on the platform with the

158occurrence of phosphate- and organic-rich deposits in basins.

159With these questions in mind, we examined, logged, and sampled in

160detail 12 representative sections of the Drusberg Fm, occurring below

161or distally substituting the Urgonian Schrattenkalk Fm, and the

162Schrattenkalk Fm itself (Bonvallet, 2015). Based on partly quantitative

163trends in facies and microfacies, and on the stratal geometries observed

164in the sections and in a panorama across the Churﬁrsten (eastern

165Switzerland), we propose a sequence-stratigraphic framework. We

166also analysed the whole-rock carbon-isotope and phosphorus records

167with the goal to elucidate the interactions of local and more regional

168changes in the carbon cycle and its effects on the platform and vice

169versa the inﬂuence carbonate production and platform biology on the

170carbon-isotope record. The overall aim of this study is thus to reconstruct

171the evolution of the Helvetic Urgonian platform during the Barremian and

172earliest Aptian in high detail and to relate it to paleoenvironmental

173changes shaping shallow marine carbonate production during the late

174Early Cretaceous.

175It is importantto note here that this study would not have been pos-

176sible without the previous and partly pioneering contributions by

177Kaufmann (1867),Heim (1910–1916),Oberholzer (1933),Heim and

178Baumberger (1933),Fichter (1934),Lienert (1965),Bollinger (1988),

179Schenk (1992),Funk et al. (1993),Wissler et al. (2003),Linder et al.

180(2006),andStein et al. (2012a).

1812. Geological setting

182The Helvetic thrust-and-fold complex of the central European Alps

183was formed during the Alpine orogen y and represents the former north-

184ern passive margin of the Tethys (e.g., Heim, 1910–1916;Ramsay, 1981;

2L. Bonvallet et al. / Sedimentary Geology xxx (xxxx) xxx

Please cite this article as: L. Bonvallet, A. Arnaud-Vanneau, H.Arnaud, et al., Evolution of the Urgonian shallow-water carbonate platform on the

Helvetic shelf during the late Ear..., Sedimentary Geology, https://doi.org/10.1016/j.sedgeo.2019.04.005

UNCORRECTED PROOF

185 Pﬁffner, 1993)(Fig. 1). Trümpy (1969),Ferrazzini and Schüler (1979),

186 and Kempf and Pﬁffner (2004) developed palinspastic reconstructions

187 of the Helvetic complex in order to place the tectonic nappes in their

188 original paleogeographic position on the northern Tethyan shelf

189 (Fig. 2). These reconstructions are used here to locate the sections in

190 their original depositional context.

191 The studied sections are located in the Swiss Alps and cover the

192 Tierwis Fm (late Hauterivian to early Barremian on the platform and

193 up to early Aptian on the outer shelf beyond the platform margin) and

194 Schrattenkalk Fm (latest early Barremian or early late Barremian to

195 early Aptian; Figs. 3–5). They were selected according to their position

196 on the platform, allowing building up a data base representative for

197 the Helvetic Urgonian platform (Table 1). The sections at Kistenpass,

198 Tierwis, and L'Ecuelle representthe proximal, inner area of the platform.

199 The intermediate part close to the platform margin is documented by

200 the sections at Justistal, Harder, Morschach, and Valsloch. The transition

201 to the distal, outer shelf beyond the platform margin is embodied by the

202 sections at Brienzer Rothorn and Alvier. The location of the platform

203 margin can be traced by the disappearance of the Schrattenkalk Fm

204 and the presence of hemipelagic sediments of the Drusberg Mb replac-

205 ing the Schrattenkalk Fm. This is the case in the southern part of the

206 Wildhorn nappe (Prabé synclinal; Crêta Besse–Chamosaire–Bella Lui

207 area; Badoux et al., 1959), the area south of the Lake of Thun, in the

208 southeastern part of the Lungerersee area, the southern part of the

209 Engelberg valley (Hantke, 1961), and in the eastern part of the Säntis

210 nappe in the Alvier region and Vorarlberg (Briegel, 1972;Föllmi, 1986;

211 Bollinger, 1988). The substitution of the Schrattenkalk Fm by the

212 Drusberg Mb is also illustrated in the isopach maps of Zerlauth et al.

213(2014). The platform-outer shelf transition zone runs almost parallel

214to the Alps according to Heim (1910–1916). In this zone the lateral

215change between shallow-water platform and hemipelagic facies is ac-

216complished in b10 km across strike (Heim, 1910–1916;Ziegler, 1967).

217The section at Rawil represents the type locality of the Rawil Mb

218(Schenk, 1992;Stein et al., 2012a). The section at Valsloch is chosen as

219a reference section for the Schrattenkalk Fm, since it presents the

220most complete and expanded section measured. It is located in the

221Churﬁrsten range, and is part of the panorama of its southern cliff. The

222panorama encompasses the range between Schären (Swiss c oordinates:

223736.004/223.075; international coordinates: N 44° 53.416/E -1° 50.322)

224to Nideri (744.344/223.305; N 44° 53.417/E -1° 50.329), and provides

225information on depositional geometries and lateral facies changes.

2263. Methods

2273.1. Field work and sample preparation

228The twelve sections mentioned above were described, documented

229and measured in detail for their lithology, facies, and sedimentology,

230and well over 2000 samplesfor microfacies and geochemical investiga-

231tions were collected in intervals of 1 m or less. Higher sample densities

232were applied across facies boundaries and discontinuity surfaces. The

233samples were sawn in order to remove weathered surfaces and veins,

234and the micritic part of the rock samples wasprivileged for the chemical

235analyses, if present. Rock powders were obtained by using a mechanical

236agate mill.

Fig. 1. Location of the Helvetic realm on a paleogeographic map of the western Tethys for the Aptian (from Godet et al., 2013; redrawn after Masse et al., 1993).

3L. Bonvallet et al. / Sedimentary Geology xxx (xxxx) xxx

Please cite this article as: L. Bonvallet, A. Arnaud-Vanneau, H.Arnaud, et al., Evolution of the Urgonian shallow-water carbonate platform on the

Helvetic shelf during the late Ear..., Sedimentary Geology, https://doi.org/10.1016/j.sedgeo.2019.04.005

UNCORRECTED PROOF

Fig. 2. (A)Tectonic map of the Helvetic nappes, redrawnafter the tectonic map of Switzerland 1:500′000 (Swiss Federal Ofﬁce of Topography –Swisstopo, Berne).(B) Palinspastic recon-

struction of the Helvetic nappes, redrawn after Kempf and Pﬁffner (2004). Identical colors are used for the nappes on both panels.

4L. Bonvallet et al. / Sedimentary Geology xxx (xxxx) xxx

Please cite this article as: L. Bonvallet, A. Arnaud-Vanneau, H.Arnaud, et al., Evolution of the Urgonian shallow-water carbonate platform on the

Helvetic shelf during the late Ear..., Sedimentary Geology, https://doi.org/10.1016/j.sedgeo.2019.04.005

UNCORRECTED PROOF

237 3.2. Microfacies analysis

238 A total of 1931 thin sections was studied, using conventional optical

239 microscopy. An Olympus BX51 microscope (Olympus, Tokyo, Japan)

240 equipped with an Olympus Altra 20 camera and the Olympus Image

241 Analysis© software was used for digital photomicrography.

242 The microfacies classiﬁcation of Arnaud-Vanneau and Arnaud

243 (2005) (Fig. 6) established in the Urgonian limestone of the Chartreuse

244 and Vercors areas was used for this study. This classiﬁcation is based on

245 present-day analogues with regards to the environmental position of or-

246 ganisms and certain carbonate components (ooids), in addition to the

247 effects of light, salinity, currents, and trophic levels. It consists of 12

248 microfacies types, which are arranged on a proximal –to-distal platform

249 transect, from the most external F0 characterized by a pelagic faunal as-

250 sociation, to the shallowest F11, which represents an internal lagoonal

251 facies close to emersion (Fig. 6). Three annex microfacies types (FT1,

252 FT2, and FT3) are used to characterize the main transgressive phases

253 during the deposition of the Rawil Mb, according to Arnaud-Vanneau

254 and Arnaud (2005): FT1: reworking and lag; FT2: accumulation of

255 Palorbitolina lenticularis, associated with detrital quartz, annelids, and

256 Choffatella decipiens; and FT3: accumulation of Dasycladaceae.

257 These microfacies types were regrouped into six microfacies associ-

258 ations (AF1 to AF6), according to comparable bathymetries, grain-size

259 sorting and biotic content. AF1 represents hemipelagic facies (F0–2),

260 AF2 outer-shelf facies (F3–4), AF3 platform-margin facies (F5–7), AF4

261 lagoonal facies (F8–10), and AF5 supratidal facies (F11). An additional

262 microfacies association is identiﬁed, which is used to characterize the

263 main transgressive phases (AF6). It consists of wackestone/packstone

264 including reworked grains.

265 For the section at Valsloch, a counting technique was performed on

266 77 thin sections (Bernaus, 1998;González-Lara, 2001;Hfaiedh et al.,

2672013;Raddadi et al., 2005). On a reference surface of 1.2 ×1.7 cm, all

268visible, entirely preserved or fragmented components (such as forami-

269nifera, oncolites, algae, etc.) were counted on each selected thin section.

270The countedcomponents are grouped in assemblages representing sim-

271ilar ecologic environments, which range from deeper, open-marine, to

272conﬁned and estuarine depositional settings. This quantitative approach

273allowed us to reﬁne the scale used for the distribution of microfacies

274assemblages relative to the qualitative approach used for the other

275sections, and as such, nine assemblages were determined (A1–A9) for

276the section at Valsloch (rather than the six associations (AF1–6) used

277for the microfacies analysis of all other sections).

2783.3. Sequence stratigraphic analysis

279In this study, key surfaces were identiﬁed using ﬁeld observations

280and sedimentological and paleoecological analyses of thin sections.

281Once identiﬁed, the surfaces and trends in facies and microfacies

282allowed us to adopt a sequence-stratigraphic scheme, which is corre-

283latable with the one developed in the Vercors region of SE France

284by Arnaud and Arnaud-Vanneau (1989, 1991),Arnaud-Vanneau and

285Arnaud (1990),andHunt and Tucker (1993), and which is based on

286the model developed by Vail et al. (1977) and subsequently described

287in numerous publications (e.g., Van Wagoner et al., 1988;Emery

288and Myers, 1996;Coe et al., 2003;Catuneanu et al., 2009). The

289sequence-stratigraphic model is chronostratigraphically calibrated in

290the Angles section of the Vocontian Trough, where the presence of

291ammonites allows for biostratigraphic time control, as shown in

292Fig. 4. The same sequence-stratigraphic approach was applied in pre-

293vious studies for the Rawil Mb in the Helvetic Alps (Embry, 2005;

294Stein et al., 2012a).

Fig. 3. Synthetic representation of the succession of upper Hauterivian to lower Aptian lithostratigraphic units in a proximal and distal setting, and their relation to the sequence

stratigraphic schemeadopted here (ammonite biostratigraphy fromReboulet et al., 2018;sequence stratigraphy from Arnaudet al., 1998; syntheticlogs modiﬁed afterBodin et al., 2006b).

5L. Bonvallet et al. / Sedimentary Geology xxx (xxxx) xxx

Please cite this article as: L. Bonvallet, A. Arnaud-Vanneau, H.Arnaud, et al., Evolution of the Urgonian shallow-water carbonate platform on the

Helvetic shelf during the late Ear..., Sedimentary Geology, https://doi.org/10.1016/j.sedgeo.2019.04.005

UNCORRECTED PROOF

295 3.4.PanoramaoftheChurﬁrsten range

296 The panorama was photographed from the southern side of the lake

297 of Walensee (between Quarten and Oberterzen; 738.349/218.339;

298N 44° 53.414/E -1° 50.325) in a high-resolution fashion by the stacking

299of 460 photos. The photos were taken by a Canon EOS 7D, a zoom lens

300Canon EF image stabilizer 70–200 mm, an automatic x2 tele-converter

301Kenko Teleplus MC 7 DG, and a robotic camera mount Gigapan Epic

Fig. 4. Chronostratigraphy of the inner platform (left) to outer shelf successions of latest Hauterivian to early Aptian age through theHelvetic realm. Sequencestratigraphic framework is

based on Arnaud (2005) and ammonite biostratigraphy on Reboulet et al. (2018). Mb = Member; Fm = Formation; Sb = sequence boundary.

Fig. 5. Photosfrom a selection ofinvestigated sections and cores; (A) base ofthe section at Valsloch. The Altmann Mb is covered by vegetation; (B) section at Alvier. On the rightside is the

locality Glännli (Briegel, 1972); (C) section of Kistenpass; (D) general overview of the section at L'Ecuelle; (E) section at Brienzer Rothorn (from Ribaux, 2012); (F) section at justistal;

(g) overview of the lower part of the section at Harder; (H-J) core from Morschach: (H) Drusberg Mb, rich in bioturbation (arrows); (I) Rawil Mb, showing lag levels associated with

tempestite deposits (arrow for an example); (J) Upper Schrattenkalk Mb, showing light grey carbonate rich inrudists (arrows); (K) near the base of the Drusberg Mb in the section at

Harder. The lower part of the Drusberg Mb is composed of marl-carbonate alternations (base of photographed outcrop) intercalated with massive bioclastic carbonate beds, which

show hummocks at their stratigraphic top (pointed at by the corresponding author); (L) section at Tierwis; (M) close-up of the Lower Schrattenkalk Mb of the section at Valsloch;

(N) section at Lämmerenplatten;KF = Kieselkalk Fm; AM = Altmann Mb; DM = Drusberg Mb; SF = Schrattenkalk Fm; LSM = Lower Schrattenkalk Mb; RM = Rawil Mb; USM =

Upper Schrattenkalk Mb; GF = Garschella Fm.

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302Pro. The software used to combine the photos is the Gigapan stitch soft-

303ware. The interpretation of this panorama is based on the visual observa-

304tion of the evolution of marker beds and intervals through the panorama.

305Sequence stratigraphic interpretations and in particular the identiﬁcation

306of sequence boundaries were controlled in the section at Valsloch, which

307is located in the eastern part of the Churﬁrsten range (Fig. 2).

3083.5. Carbon and oxygen isotope analysis

309A total of 1958 samples was analysed for their stable carbon and

310oxygen isotope composition at the Institute of Earth Surface Dynamics

311of the University of Lausanne using the procedures described by

312Revesz et al. (2001). Analyses of aliquots of all samples were performed

313using a Thermo Fisher Scientiﬁc (formerly ThermoQuest/Finnigan,

314Bremen, Germany) GasBench II preparation device interfaced with a

315Thermo Fisher Scientiﬁc Delta Plus XL continuous ﬂow isotope-

316ratio mass spectrometer (IRMS). The CO

extraction was performed at

31790 °C. The carbon and oxygen-isotope ratios were reported in the

318delta (δ) notation as the per mil (‰) deviation relative to the Vienna–

319Pee Dee belemnite standard (VPDB). Analytical uncertainty (1 σ), mon-

320itored by replicate analyses of the international calcite standard NBS-19

321and the laboratory standards Carrara Marble were not greater than ±

3220.05‰for δ

C and ±0.1‰for δ

323To assess the possible heterogeneity of the carbon and oxygen iso-

324tope composition within a hand specimen, a detailed micro-drilling

325subsampling (100 to 300 μg) was performed on eight selected samples.

326These samples contain facies-representative bioclasts, and calcite vein-

327lets within the micritic matrix. A total of 54 subsamples was analysed

328for their C and O isotope composition and the results were compared

329to those of the corresponding whole-rock δ

Candδ

O values.

3303.6.Phosphoruscontent

331The total phosphorus content was measured on 1182 samples from

332the sections at L'Ecuelle, Tierwis, Interlaken, Kistenpass, Harder,

333Brienzer-Rothorn, and Valsloch, using the ascorbic acid molybdate

334blue method (Eaton et al., 1995) and following the procedure described

335in Bodin et al. (2006c). The phosphorus content was determined by a

336UV/Vis Perkin Elmer Lambda 25 spectrophotometer at the Institute of

337Earth Sciences of the University of Lausanne, and calibrated with inter-

338nal standard solutions providing a precision better than 5%.

3393.7. Bulk-rock mineralogy

340The bulk-rock mineralogy was analysed on 68 samples from the

341section at Valsloch on a Scintag XRD 2000 diffractometer in the Institute

342of Earth Sciences at the University of Lausanne, based on procedures de-

343scribed by Kübler (1983) and Adatte et al. (1996). This method permits

344the semi-quantiﬁcation of its mineralogy using external standards with

345an error of 5%.

3464. Results

3474.1. Brief description of the investigated lithostratigraphic units

348In the following, we provide a brief description of all investigated

349lithostratigraphic units. They are interpreted more in detail with regards

350to their (micro-)facies and sequence stratigraphy in Section 5.2.

351The Altmann Member (Mb) is the basal member of the Tierwis Fm

352and consists of mostly strongly condensed, phosphate and glauconite-

353rich deposits (Fichter, 1934;Funk, 1969, 1971;Wyssling, 1986;Bodin

354et al., 2006a;Föllmi et al., 2007;Godet et al., 2013)(Figs. 3, 4). In the

355more expanded sections (Säntis and Fluhbrig regions), a marly, crinoid-

356rich carbonate including several phosphate and glauconite-enriched

357hardgrounds and condensed beds is present (Rick, 1985;Bodin et al.,

3582006a). The age of the Altmann Mb is based on ammonite biostratigraphy

t1:1Table 1

t1:2List of the outcrop and drill-hole localities.

t1:3Name Locality Tectonic unit Position on

platform

Canton Swiss

coordinates

International

coordinates

Figures References

t1:4Kistenpass East of Bifertenstock Infrahelvetics Inner platform Grisons 722.715/185.749 N 44° 53.449/E -1° 50.308 2, 5C, 7, 9, S1

t1:5L'Ecuelle 2.5 km from Anzeindaz Morcles nappe, normal limb Inner platform Vaud 579.336/124.832 N 44° 53.419/E -1° 50.355 2, 5D, 7, 9, 19, 25, S2

t1:6Lämmerenplatten Close to the col. of Gemmi Dolderhorn nappe Inner platform Valais 613.081/140.041 N 44° 53.424/E -1° 50.304 2, 5N, 9, S3

t1:7Justistal In Loubenegg Wildhorn nappe Inner platform Berne 628.427/176.557 N 44° 53.445/E -1° 50.313 2, 5F, 7, 9, 17, 25, S4 Ziegler, 1967;Schenk, 1992

t1:8Interlaken Along road and railway Wildhorn nappe Intermediate platform Berne 631.347/169.493 N 44° 53.441/E -1° 50.315 2, 9, S5

t1:9Harder Northern side of Interlaken Wildhorn nappe (overturned) Intermediate platform Berne 631.250/170.991 N 44° 53.442/E -1° 50.315 2, 5G, 5H, 7, 9,S6 Schenk, 1992;Bodin et al., 2006a

t1:10 Brienzer Rothorn North of Brienz Wildhorn nappe (overturned) Distal platform Berne 645.955/182.008 N 44° 53.448/E -1° 50.326 2, 5E, 7, 9, S7 Ribaux, 2012

t1:11 Rawil Midway station of cablecar Wildhorn nappe Intermediate platform Berne 601.157/137.186 N 44° 53.422/E -1° 50.295 2, 9, 16, 20, 25, S8 Schenk, 1992;Stein et al., 2012a

t1:12 Morschach (drill hole) Golf course of Morschach Drusberg nappe Intermediate platform Schwyz 690.299/205.511 N 44° 53.410/E -1° 50.365 2, 5H-J, 7, 9, 25, S9

t1:13 Tierwis Close to the Säntis summit Säntis nappe Inner platform St. Gall 742.970/234.730 N 44° 53.423/E -1° 50.327 2, 3, 5L, 7, 9, 23, 25, S10 Bodin et al., 2006a;Stein et al., 2012a

t1:14 Valsloch Churﬁrsten range Säntis nappe Intermediate platform St. Gall 742.224/224.041 N 44° 53.417/E -1° 50.327 2, 5A, 5M, 7, 9, 23, 25, S11 Wissler et al., 2003;Stein et al., 2012a

t1:15 Alvier Eastern side of the Alvier Säntis nappe Distal platform St. Gall 749.644/222.586 N 44° 53.417/E -1° 50.333 2, 3, 5B, 7, 9, 23, S12 Briegel, 1972;Wissler et al., 2003

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359 and includes the time span between the late Hauterivian to the late early

360 Barremian (Balearites balearis to Kotetishvilia compressissima zones;

361 Fichter, 1934;Rick, 1985;Wyssling, 1986;Bodin et al., 2006a)(Fig. 4).

362 The Altmann Mb is mostly extremely thin (b1m)orevenabsent(like

363 in the Glarus and Mürtschen Nappes representing the proximal part of

364 the shelf; Funk, 1971;Funk et al., 1993)(Figs. 7, 8A).

365 The overlying Drusberg Mb is characterized by an alternation of

366 hemipelagic marl and marly limestone beds, and in proximal sections

367 by important oyster accumulations (e.g., Kistenpass; Figs. 3, 4). In the

368 sections at Justistal and Harder, the Drusberg Mb includes important in-

369 tervals of bioclastic carbonate. These intercalations represent approxi-

370 mately 20% of the total Drusberg Mb for the section at Harder

371 (Fig. 5K). Where the Drusberg Mb is overlain by the Schrattenkalk Fm,

372 the age of the Drusberg Mb is restricted to the latest early Barremian

373 in proximal areas and conﬁned to a single sequence (B2). It extends to

374 the middle late Barremian (Moutoniceras moutonianum to Gerhardtia

375 sartousiana zones; Bodin et al., 2006b, 2006c) in intermediate areas. In

376 distal areas, the hemipelagic facies of the Drusberg Mb replaces the

377 Schrattenkalk Fm entirely and as such it persists through the late

378 Barremian and early Aptian (Heim and Baumberger, 1933;Föllmi,

379 1986;Bollinger, 1988). The maximum thickness of this member is ob-

380 served in intermediate and external parts of the platform, and maxi-

381 mum accommodation occurred in the section at Alvier, where the

382 thickness of the unit reaches 120 m. The sediment-accumulation rate

383 is minimal for sections located on the inner platform (Tierwis and

384 Kistenpass), where the thickness does not exceed 40 m.

385 The Schrattenkalk Fm diachronically overlies theDrusberg Mb and is

386 subdivided into a Lower and an Upper Schrattenkalk Member (Mb) by

387 the Rawil Mb - an equivalent of the “Lower Orbitolina Beds”(Schenk,

388 1992;Stein et al., 2012a)(Figs.3,4). The Lower Schrattenkalk Mb con-

389 sists generally of a thickly bedded or massive shallow-water platform

390 carbonate reaching a maximal thickness of 100 m (Heim, 1910–1916;

391 Schenk, 1992)(Figs. 5, 7, 8C–E). Stratigraphic microfacies, stratal geom-

392 etries and the presence of important emersion surfaces enables three

393 sequences to be distinguished (B3–B5). Its age encompasses the latest

394 most early Barremian and the entire late Barremian in proximal areas,

395 whereas towards more distal areas this unit starts later, such as in the

396 middle late Barremian Gerhardtia sartousiana Zone at Tierwis (Bodin

397 et al., 2006b)(Fig. 4).

398 The Lower Schrattenkalk Mb is overlain by the Rawil Mb, which

399 distinguishes itself from the under- and overlying Schrattenkalk Mbs

400 by an increase in detrital material and the resulting presence of marl

401 and sandy carbonate (Stein et al., 2012a)(Figs. 3–5, 7, 8F). The regional

402 distribution of detritus is quite variable, and in certain regions, such as in

403 Vorarlberg (western Austria), detrital levels are very low and the Rawil

404 Mb cannot be distinguished as such (Heim and Baumberger, 1933;

405 Bollinger, 1988). Three subunits are observed within the Rawil Mb,

406 which are labelled A, B, and C (cf. Section 5.2). The sediment thickness

407 is minimal in the inner part of the platform (22 m and 32m for the sec-

408 tions of L'Ecuelle and Tierwis) and in the section at Justistal, where only

409 the ﬁrst 6.5 m are recorded. In intermediate and distal parts, this unit

410 has a comparable thickness, comprised between 40 m and 50 m. The

411 Rawil Mb represents the transgressive and earliest highstand systems

412 tracts of sequence A1 and its age is restricted to the early Aptian

413 Deshayesites oglanlensis and the early Deshayesites forbesi Zones (Stein

414 et al., 2012a)(Fig. 4).

415 The Upper Schrattenkalk Mb is composed of a thickly bedded or mas-

416 sive carbonate, which altogether represents a succession of thinning- and

417 shallowing-upward parasequences (Figs. 3–5, 7, 8G). It has a comparable

418 thickness in all investigated platform sections, with approximately 20 m

419 at L'Ecuelle and 33 m at Rawil on the inner platform. The maximum thick-

420 ness occurs at Alvier (about 50 m). The Upper Schrattenkalk Mb repre-

421 sents the remainder of the HST of sequence A1. Its age is restricted to

422 the late Deshayesites forbesi Zone (Arnaud, 2005)(Fig. 4).

423 In the sections at Valsloch, Morschach, and Rawil, the top of the

424 Upper Schrattenkalk Mb is overlain by carbonates with a deeper water

425facies, rich in echinoderms and annelids. This unit is identiﬁed as repre-

426sentative of the overlying Grünten Mb, which is an equivalent of the

427“Upper Orbitolina Beds”(Wissler et al., 2003;Linder et al., 2006), and

428which represents the basal member of the Garschella Fm. In the section

429at L'Ecuelle, the top of the Schrattenkalk Fm is directly covered by the

430coarse-grained sandstones of the upper Aptian Brisi Mb (middle mem-

431ber of the Garschella Fm), and large extraclasts composed of Orbitolina-

432rich carbonates of likely Grünten Mb origin are present in the inﬁllings

433of karst pockets. At Tierwis, the Schrattenkalk Fm is covered by glauco-

434nitic deposits of the Albian Selun Mb (upper member of the Garschella

435Fm). At Justistal, the Upper Schrattenkalk Mb and the upper part of

436unit B and the entire unit C of the Rawil Mb were removed by erosion.

437The remainder of the Rawil Mb is directly overlain by Eocene sedimen-

438tary rocks.

439Detailed lithologs of each analysed section including the carbon-

440isotope and phosphorus data and sequence-stratigraphic and

441microfacies interpretations are present in the Supplementary data set

442(Figs. S1–S12).

4434.2. Carbon-isotope records

4444.2.1. Individual subsamples

445The δ

Candδ

O values of the micro-drilled subsamples are

446presented in Table 2 and compared with the values obtained for

447whole-rock powder of the same samples. For most samples, the values

448obtained for the micro-drilled micrite and whole-rock powder differ

449b0.2‰for δ

C and 0.3‰for δ

O. In some samples (e.g., EC 166, MC

450137, and KP 61), the different components in the subsamples (rudist,

451oncolite, oyster, recrystallized bioclasts, and cement) differ up to 4‰

452for δ

Cand3.8‰for δ

O(bothinEC166).

4534.2.2. Whole-rock samples

454In the Altmann Mb, carbon-isotope values are comprised between

455+0.5‰and 1.5‰. For the Drusberg Mb, a distinction between three

456groups of sections is made with regards to their δ

C records (Figs. 9,

457S1–S12). Those of Kistenpass, L'Ecuelle, and Morschach, which are all

458part of the proximal platform domain, show a plateau with a mean

459value of 1.1‰,1.5‰,and2.4‰, respectively. The sections at Tierwis and

460Justistal display an excursion to higher δ

Cvaluesfollowedbyadecrease.

461The Valsloch, Harder, Alvier, and Brienzer Rothorn sections, which are

462representative of the distal platform, exhibit two well-developed trends

463towards more positive values with a maximum of +2.5‰for Harder

464and around +2‰for the sections at Valsloch, Alvier, and Brienzer

465Rothorn.

466For the basal part of the Lower Schrattenkalk Mb (sequence B3), the

467sections at Valsloch, Justistal, Harder, and Brienzer Rothorn show a pla-

468teau in δ

C values, with a mean value of 2.2‰,1.8‰,2.6‰, and 2.2‰,

469respectively. The δ

C curves from Morschach and Tierwis indicate

470also a plateau (mean value of 2.2‰and 1.5‰, respectively), followed

471in the upper 10 m by a shift to higher values, which reaches a maximum

472of 3.8‰and 2.5‰, respectively. The δ

C record of the section at

473L'Ecuelle displays an abrupt decrease to a plateau of negative values,

474with a minimum of −2.6‰, interrupted by an excursion to higher

475values (maximum of 1.6‰) 10 m below the top of this unit.

476The middle part of the Lower Schrattenkalk Mb (sequence B4) is

477characterized by a plateau for the sections at Tierwis (mean value

4782.5‰), Morschach (mean value 3.5‰), Justistal (mean value of 2.2‰),

479and Harder (mean value of 2.7‰). For the section at L'Ecuelle, the δ

480record presents a shift to higher values (maximum of −0.8‰). The sec-

481tion at Valsloch shows saw-tooth variations in its δ

C record, followed

482by an excursion to lower values (minimum of 1‰), which is directly

483followed by a shift to higher values (maximum value of 3‰). The

484sections atAlvier and Brienzer Rothorn are characterized by a slight in-

485crease in the δ

C values (maxima of 3.2‰and 3‰, respectively).

486The δ

CrecordoftheupperpartoftheLowerSchrattenkalkMb(se-

487quence B5) represents a plateau in the sections at Morschach (mean

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488 value 3.3‰), Valsloch (mean value 3.3‰), Rawil (mean value 1.8‰), and

489 Harder (mean value 2.5‰). A progressive shift to lower values is observed

490 at L'Ecuelle (minimum value 1.5‰), Justistal (minimum value 1.6‰), and

491 Alvier (minimum value 1‰). The sections at Tierwis and Brienzer

492 Rothorn show a shift to higher values followed by a change to lower

493 values in the last meters (maxima of 3.1‰and 3.3‰, and minima of

494 0.1‰and 0.6‰, respectively).

495 The Rawil Mb is characterized by an excursion to higher δ

C values,

496 followed by a shift to lower values in the sections at Tierwis, L'Ecuelle,

497 Justistal, Rawil, and Brienzer Rothorn. In the sections at Valsloch and

498 Morschach, the plateau reached in the previous unit is continued at

499 the base and followed by a shift to lower values (mean values of

500 −1.5‰and −2.6‰, respectively). In contrast, the section at Harder

501 presents a plateau followed by an excursion to higher values at the

502 top of the Rawil Mb (maximum value 3‰).

503 The δ

C record of the Upper Schrattenkalk Mb is highly ﬂuctuating in

504 the sections at Tierwis, L'Ecuelle, and Valsloch. In the sections at Morschach

505 and Rawil, a plateau is reached (mean values of 3.5‰and 2.4‰,respec-

506 tively). In the section at Valsloch, the δ

Crecordexhibitsatrendtohigher

507 values towards the Grünten Mb (maximum value of 3.7‰;Fig. 9).

508 4.3. Total phosphorus content

509 The phosphorus (P) content was measured in the sections at L'Ecuelle,

510 Interlaken, Harder, Brienzer Rothorn, Tierwis, and Valsloch (Figs. 9,S1–

511 S12). For all sections, the P content shows an upward decreasing trend

512 from the base of the Tierwis Fm to the Schrattenkalk Fm. The highest

513 values are recorded in the Altmann Mb and the ﬁrst few meters of the

514 Drusberg Mb with values ranging between 500 ppm and 1000 ppm,

515 and maximum values of 11,700 ppm reached in the upper Altmann Mb

516 hardground at Tierwis. The Drusberg Mb is characterized by relatively

517 high P contents: above 100 ppm for the sections at Tierwis, Valsloch,

518 Harder, and Brienzer Rothorn, and above 50 ppm for L'Ecuelle (mean

519 value 128 ppm). The base of the Lower Schrattenkalk Mb is marked by

520 a decrease in P content in all sections, with a mean value of 78, 44, 91,

521 87, and 121 ppm for the sections at Tierwis, L'Ecuelle, Valsloch, Harder,

522 and Brienzer Rothorn, respectively. An enrichment is observed in the

523 lower part of the Lower Schrattenkalk Member showing the accumula-

524 tion of Eopalorbitolina transiens,Choffatella, and annelids at L'Ecuelle and

525 Valsloch. The middle and upper parts of the Lower Schrattenkalk Mb

526 show a slight decrease in Pvalues, with minimum values in the upper

527 part of the member of 4, 12, 10, 33, and 81 ppm for the sections at Tierwis,

528 L'Ecuelle, Valsloch, Harder, and Brienzer Rothorn, respectively. The over-

529 lying Rawil Mb is characterized by an increase in P content (Stein et al.,

530 2012a). In the sections at Tierwis, L'Ecuelle, and Harder, this increase oc-

531 curs directly above the boundary with the underlying Lower

532 Schrattenkalk Mb. In Valsloch, the P content exhibits higher values in

533 the upper part of the Rawil Mb and top interval. The values decrease

534 in the Upper Schrattenkalk Member until the last meters, where the P

535 content reaches higher values, likely due to inﬁltrations from the super-

536 jacent Garschella Fm (Fig. 9).

537 5. Discussion and interpretations

538 5.1.Biostratigraphy

539 Ammonites and benthic foraminifera (especially orbitolinids) were

540 used to obtain a biostratigraphic framework for the successions studied.

541 The sequences identiﬁed in the Helvetic Alps were also correlated with

542those from the Vercors, where the stratigraphic ranges of orbitolinids

543were calibrated (Arnaud-Vanneau, 1980;Arnaud-Vanneau and Arnaud,

5441990;Arnaud et al., 1998;Arnaud, 2005).

545Ammonites constrain the basal Altmann Member to the interval be-

546tween the latest Hauterivian to late early Barremian (Balearites balearis

547to the Kotetishvilia compressissima zones), if the deﬁnition of the upper

548boundary of the Altmann Member at Tierwis proposed in Section 5.2.1

549is adopted (Fichter, 1934;Rick, 1985;Wyssling, 1986;Bodin et al.,

5502006a). In the hemipelagic deposits of the Drusberg Mb, the biostrati-

551graphic markers are ammonites and circalittoral foraminifera

552(Lenticulina). In the bioclastic carbonate beds of the Drusberg Mb, the

553presence of Paleodictyoconus sp., Cribellopsis elongata,Falsurgonina sp.,

554and Paracoskinolina sunnilandensis is observed. The lower part of

555the Lower Schrattenkalk Mb (sequence B3) is characterized by the

556presence of Praedictyorbitolina carthusiana,Paleodictyoconus actinostoma,

557Paleodictyoconus cuvillieri,Eopalorbitolina/Palorbitolina transiens,

558Orbitolinopsis debelmasi,Falsurgonina sp., Montseciella sp., and

559Paracoskinolina sunnilandensis,andtheﬁrst occurrence of Paracoskinolina

560reicheli and Neotrocholina friburgensis (Figs. 10, 11). The middle part of the

561Lower Schrattenkalk Mb (sequence B4) is characterized by the presence

562of Neotrocholina friburgensis,Paleodictyoconus cuvillieri,Cribellopsis

563neoelongata, and Parakoskinolina maynci, like sequences B3 and B5

564(Fig. 11). The upper part of the Lower Schrattenkalk Mb (sequence B5)

565is characterized by the last occurrence of Neotrocholina friburgensis,and

566by the presence of Palorbitolina lenticularis,Orbitolinopsis buccifer,

567Paracoskinolina maynci,andParacoskinolina cf. hispanica (Figs. 10, 11).

568Close to the Barremian–Aptian boundary, a major change in the

569composition of the benthic foraminiferal associations is observed,

570which is in particular characterized by the disappearance of

571Neotrocholina friburgensis,Paracoskinolina hispanica,P. reicheli,

572Paleodictyoconuscuvillieri,andP. actinostoma (temporary disappearance

573of the latter in the basal interval of the Rawil Mb, unit A, which is essen-

574tially devoid of large benthic foraminifera), the high abundance of

575Palorbitolina lenticularis,Paracoskinolina maynci,Orbitolinopsis buccifer,

576O. kiliani,andO. cuvillieri; andthe appearance of Paracoskinolina arcuata,

577Orbitolinopsis briacensis,andO. pygmaea (Arnaud-Vanneau, 1980;

578Raddadi, 2005). The base of the Upper Schrattenkalk Mb is character-

579ized by the ﬁrst occurrence of Orbitolinopsis briacensis,Orbitolinopsis

580pygmaea,andParacoskinolina arcuata (Figs. 10, 11).

581In general, the benthic foraminiferal successions are well comparable

582between the Helvetic and Subalpine Chains sections. The biostratigraphic

583observations indicate an age from the Moutoniceras moutonianum tothe

584Gerhardtia sartousiana zones for the onset of the Lower Schrattenkalk

585Mb, depending on the position on the platform. The age of the Rawil

586Mb corresponds to the Deshayesites oglanlensis zone and early

587Deshayesites forbesi zone. The Upper Schrattenkalk Mb as a whole belongs

588to the late Deshayesites forbesi zone (Fig. 4).

589Note that alternative and conﬂicting age models exist for equivalent

590units of the Urgonian in France and the French-Swiss Jura (e.g., Clavel

591et al., 2013;Frau et al., 2018). The ages proposed here for the Helvetic

592succession are the ones adopted by the Swiss commission of stratigra-

593phy (www.strati.ch) and already earlier used by different authors

594(e.g., Bollinger, 1988;Funk et al., 1993;Wissler et al., 2003).

5955.2. Facies evolution and sequence stratigraphy

5965.2.1. Sequences H6, H7, and B1 (Altmann Member)

597Bodin et al. (2006a) attributed sequence B1 and the transgressive

598systems tract (TST) B2 to the Altmann Mb, whereas the highstand

Fig. 6. Distributionof principal microfacies typesalong a rimmed platform(redrawn afterGodet et al., 2010,andArnaud-Vanneau and Arnaud, 2005) andexamples of microfaciestypes F0

to F11 and FT. (A)F0, pelagic facies richin radiolaria (Valsloch, VA 317); (B) F1,facies rich in sponge spicules (Morschach, MC 259); (C) F2,facies with irregularsea urchin (Morschach, MC

238); (D) F3, facies with circalittoral foraminifera (arrows) (Harder, HA46); (E) F3a, facies rich in colonial annelids (L'Ecuelle, EC 61); (F) F3b, accumulation of Eopalorbitolina transiens

(Morschach, MC 206); (G) F4, facies with branched bryozoans (L'Ecuelle, EC 38); (H) F5, facies with rounded debris (Harder, HA 179); (I) F6, oolitic facies (Tierwis, TW 25); (J) F7,

facies with corals (Morschach, MC 173); (K) F8, facies with canaliculate rudists (Morschach, MC 154); (L) F9, facies with rudists (Morschach, MC 163); (M) F10, oncolitic facies

(Morschach, MC 165); (N) F11a, facies with keystone vugs (Valsloch, VA 26); (O) F11b, conﬁned supratidal facies (Tierwis, TW 32); (P) FT, reworked facies (Valsloch, VA 255).

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Fig. 7. Sedimentological logs of a selection of representative sections and their microfacies distribution along a proximal to distal transect through the Helvetic platform. The grey line corresponds to the top of the Altmann Mb.

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UNCORRECTED PROOF

599 systems tract (HST) B2 and the TST B3 belong to the Drusberg Mb

600 (Figs. 4, 7). In this contribution, the boundary between the Altmann

601 Mb and the Drusberg Mb in the reference section at Tierwis is placed

602 on top of a siliceous and phosphatic hardground, which is below the

603 original boundary described by Bodin et al. (2006a). This implies a read-

604 justment of the sequence stratigraphic framework of Bodin et al.

605 (2006a) such that the whole depositional sequence B2 belongs to the

606 Drusberg Mb. With this amendment, the mostly strongly condensed

607 Altmann Mb includes three sequences (H6, H7, and B1).

608 5.2.2. Sequence B2 (Drusberg Member)

609 The Drusberg Mb is dominated by outer-shelf facies (F0 to F3) rich

610 in sponge spicules, irregular echinoids, circalittoral foraminifera,

611 calcispheres, and radiolaria (Figs.4,7,8B). In the sections at Justistal

612 and Harder, intervals are present, which are composed of bioclastic

613 shallow-water facies (F4–F6, FT) including ooids, dasycladal

614 algae, orbitolinids, and miliolids. These compounds were reworked

615 and transported by storms, as is indicated by their intercalation

616 in hemipelagic sediments (F1, F2), the presence of sharp and

617 partly erosive boundaries, and hummocks (in the section at Harder;

618 Fig. 5K).

619 In proximal areas, the Drusberg Mb constitutes a single sequence

620 (B2). Its transgressive systems tract (TST) is composed of sedimentary

621 rocks with open-marine facies (F0–F2). In the Churﬁrsten area west

622 of the section at Valsloch - on the western side of Zuestoll, the presence

623 of a massive bioclastic carbonate body below sequence boundary

624 (SB) B3 is observed, which is interpreted as part of the highstand sys-

625 tems tract (HST) of sequence B2 (cf., Section 5.3). Lithostratigraphically

626 speaking, in this area, this unit needs to be consideredas part of thebase

627 of the Schrattenkalk Fm, because of its carbonate composition and its

628 presence directly underneath the carbonate of sequence B3.

629 In proximal and intermediate parts of the inner platform (sections

630 at Tierwis and L'Ecuelle, and the core of Morschach), the contact

631 between the hemipelagic deposits of the Drusberg Mb and the

632 shallow-water carbonate of the overlying Lower Schrattenkalk Mb

633 represents an emersion surface, which is identiﬁed as SB B3. In the

634 section at Tierwis, the top of the Drusberg Mb is represented by a

635 5 m-thick bed of marl, covered by an early cemented, fractured

636 grainstone. These microfractures are ﬁlled by mud, which formed dur-

637 ing emersion (Fig. 12C, D). In the section at L'Ecuelle, microfacies

638 types F3 and F4 are present in the upper part of the Drusberg Mb

639 and in the basal part of the Lower Schrattenkalk Mb. However, at

640 75 m from the base of the Drusberg Mb, we observed a paleosol

641 with rootcasts associated with partial early dissolution and a vadose

642 silt present in root molds (Fig. 12A, B), which we interpreted as SB

643 B3. In the section at Morschach, the Drusberg Mb is interrupted and

644 covered by a bioclastic limestone showing various extraclasts from

645 different origins: oolitic wackestone, orbitolinid-rich or calcisphere-

646 rich packstone (Fig. 12G, I, J). The grainstone is early cemented and

647 partially dissolved (Fig. 12E, F). The shallow-water deposits are com-

648 posed of a laminated tidal grainstone showing early cementation

649 with meniscus cement (Fig. 12H).

650 In more external parts of the Helvetic shelf, lag deposits showing a

651 mix of different types of shallow-water grains in an outer-shelf matrix

652 characterize the boundary between the Drusberg Mb and the Lower

653 Schrattenkalk Mb. This is also the case west of Zuestoll, where a

654 bioclastic carbonate at the base of the Lower Schrattenkalk Mb is attrib-

655 uted to this interval, due to its massive structure and the presence of

656 reworked grains, which occur also in the same interval in the nearby

657 section at Valsloch (Fig. 12K). In the section at Harder, the presence of

658 nuclei surrounded by an iron-oxide coating in storm-deposited

659 bioclastic sedimentary rocks suggests that the reworked material was

660 partly derived from soils (Fig. 12L–N). In the sections at Alvier and

661 Brienzer Rothorn, this level is correlated with the ﬁrst occurrence of

662 shallower facies (Ribaux, 2012).

6635.2.3. Sequence B3 (lower part of the Lower Schrattenkalk Member)

664Lowstand systems tracts (LSTs) are usually not preserved on a

665shallow-water platform and are embodied in the hiatus of the SBs. An

666exception is found in the sections at Valsloch and Justistal, where the

667Lower Schrattenkalk Mb includes an LST (LST B3) at its base (Justistal),

668or near its base (Valsloch, on top of thebioclastic carbonate of HST B2).

669LST B3 consists of a bioclastic accumulation (F5–F7), which shows a

670characteristic progradation (Justistal, Valsloch). In the section at Alvier,

671LST B3 is characterized bythe occurrence of outer-shelf facies F3 and F4.

672This unit is overlain by a lagdeposit representing the transgressive sur-

673face (TS) B3. TST B3 is extremely thick and bioclastic in Valsloch. The

674trend in facies in this section is shallowing upward, as is indicated by

675the development of patch reefs. In the sections at Tierwis, L'Ecuelle,

676and Morschach, the Lower Schrattenkalk Mb starts with the late TST

677B3 and dominant components are small echinoderm fragments, bryo-

678zoan clasts, and conic orbitolinids. In the sections at Justistal and

679Valsloch, the TST B3 and following deposits are dominated by oolite

680and bioclastic, partly reworked carbonate rich in green algae, miliolids,

681Neotrocholina,Sabaudia,andPalorbitolina transiens.

682The maximum ﬂooding surface (MFS) B3 is characterized by the

683deepest, outer-platform bioclastic facies (F3, F4), with the important oc-

684currence of colonial and isolated annelids (Fig. 13)andofEopalorbitolina

685transiens. This fauna association reﬂects dysoxic and mesotrophic

686conditions (Martínez-Taberner et al., 1993;Fornós et al., 1997). In distal

687settings, the deepening of the environment is marked by reduced sedi-

688mentation rates, leading to the deposition of a condensed glauconitic

689and phosphatic interval, which is called the Chopf Bed (Gerhardtia

690sartousiana zone; Briegel, 1972;Bodin et al., 2006b).

691On the Helvetic shelf, lagoonal faciesrich in rudists makesits ﬁrst ap-

692pearance in HST B3. This unit starts with bioclastic facies in the sections

693at Tierwis and Valsloch, followed by the installation of lagoonal facies,

694which arrives earlier on the inner platform at Tierwis than at Valsloch.

695The maximum in progradation documented in HST B3 is indicated by

696the presence of reworked bioclasts in the distal, outer-shelf section at

697Alvier.

698The top of sequence B3 (SB B4) is marked by an emersion surface

699and paleosol on the inner and intermediate platform. The sections at

700L'Ecuelle and Valsloch show a superﬁcial karst, which penetrates

701down to ca. 15 m below the SB B4 (Fig. 14A, B). In the sections at Tierwis

702and Morschach, indications for dissolution are associated with paleosol

703features, such as root traces, deposition of green marl, and pedogenic

704cement (arranged in rosettes similar to Microcodium), illustrated in

705Fig. 14C, E–J. In the section at Tierwis, the last meters of sequence B3 ex-

706hibit meteoric amber cement (Fig. 14D). In the sections at Justistal and

707Harder, in the intermediate part of the platform, the top of this sequence

708is marked by intense dolomitization (Fig. 14L). At Justistal, dissolution

709features are present and bioturbations are ﬁlled by dolomitic cement.

710In distal parts, SB B4 is characterized by the maximum abundance of

711grains reworked from the platform. In Alvier, the SB B4 is placed

712above the bed showing a maximum of reworking of very shallow plat-

713form sediments. At Brienzer Rothorn, the SB B4 is placed based on var-

714iations in microfacies, and in particular in the ratio of circalittoral

715foraminifera versus spicules (Ribaux, 2012), which decreases below SB

716B4. The clay mineralogy shows a peak in the ratio of kaolinite versus

717smectite in this level (Ribaux, 2012). This key feature is also known

718from the Angles section in SE France (Godet et al., 2008) and is used

719for correlation here.

7205.2.4. Sequence B4 (middle part of the Lower Schrattenkalk Member)

721In proximal areas, TST B4 starts with lagoonal facies rich in rudists

722(F8, F9). Upwards, with the occurrence of oolites and bioclastic deposits,

723its facies becomes gradually more distal. This trend lasts up to the max-

724imum ﬂooding surface (MFS). In the sections at L'Ecuelle and

725Morschach, the facies is extremely conﬁned up to the MFS, including

726oncoids and Bacinella nodules (F10) intercalated in supratidal facies

727(F11). In the section at L'Ecuelle, the MFS is characterized by a yellowish

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14 L. Bonvallet et al. / Sedimentary Geology xxx (xxxx) xxx

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UNCORRECTED PROOF

728 interval marked by an increase in silt content. In the section at

729 Morschach, the presence of deeper lagoonal facies (F8) including sparse

730 glauconite grains characterizes the MFS. In the section at Tierwis, the

731 MFS is marked by the presence of radiolaria and sponge spicules. In

732 the intermediate area, in the sections at Valsloch, Justistal, and Harder,

733 TST B4 consists mainly of bioclastic (F5) and outer-platform facies

734 (F4), which is characterized by reduced thickness. The sections of the

735 distal realm are composed of open-marine facies (F0–F3) and the MFS

736 is marked by an increase in marly beds. In proximal parts HST B4 is char-

737 acterized by an overall increase in conﬁnement towards the top, which

738 goes alongwith evidence for emersion, and whichis associated with the

739 deposition of supratidal facies and the development of early dissolution

740 features. In intermediate parts of the platform, an evolution is observed

741in HST B4 starting with outer-platform facies (F3–F4) at the base and

742ending with a lagoonal (F8, F9) and supratidal environment at the top.

743The sections at Justistaland Harder are peculiar and show a dominance

744of oolitic parasequences at Justistal, and intense grain reworking at

745Harder, where outer-platform facies occurs. In distal areas, sections ex-

746hibit pelagic and hemipelagic facies corresponding to the Drusberg Mb

747with microfacies types F4 and F5 at the top of B4 at Alvier (Fig. 8D). Se-

748quence B4 was less prograding than the previous one. In the distal part

749of the platform, the shallowest facies reachingthe top of this sequence is

750outer-platform facies (F3–F4).

7515.2.5. Sequence B5 (upper part of the Lower Schrattenkalk Member)

752Sequence B5 is characterized by the widespread development of la-

753goonal facies. In proximal domains, SB B5 is marked by early dissolution,

754and TST B5 starts with supratidal facies, consisting of beach deposits

755with keystone vugs and paleosols (root molds, green marl, and

756pedogenic cements). The TST evolves from a restricted to outer lagoonal

757facies (F10, F8). The MFS is characterized by the occurrence of

758Chondrodontes, stromatoporoids, and glauconite grains, which are

759markers of an open-marine environment. In intermediate parts of the

760shelf, SB B5 is marked by superﬁcial karstiﬁcation. TST B5 begins with

761supratidal facies including beach deposits. In the section at Morschach,

762the TST starts with several levels of Palorbitolina lenticularis accumula-

763tions, which are interpreted as beach deposits. TST B5 continues with

764outer lagoonal facies (F8), followed by outer-platform facies (F5–F7).

765This is also the case for thesection at Justistal,where lagoonal facies ap-

766pears for the ﬁrst time. The MFS is marked by deeper facies. In the sec-

767tion at Rawil, it is characterized by outer-shelf facies, rich in chaetetids,

768planktonic echinoderms, small foraminifera, spicules, and calcispheres,

769and radiolaria (F1). In the sections at Valsloch and Morschach, the

770MFS is marked by detrital input and the presence of ﬂat Palorbitolina.

771In the section at Justistal, the MFS shows the presence of Lithocodium

772nodules without Bacinella. In Harder, the SB B5 is marked by intense do-

773lomitization. There, the following TST B5 is characterized by granular fa-

774cies rich in reworked grains and ooids (F5–F6). The abundance of

775reworked grains in outer-shelf facies (F2–F4) indicates theMFS. In distal

776areas, the facies of TST B5 is characteristic of the outer shelf (F1–F3). In

777the sectionat Alvier, sparse bioclasts are present in the matrix and anne-

778lids are abundant. The MFS is indicated by a marly level. HST B5 is char-

779acterized by restricted lagoonal to supratidal facies (F9–F11) with

780reworked sediment accumulations (by storms?), beach facies including

781keystone vugs, or restricted facies (mudstone/wackestone rich in

782Istriloculina and bird's eyes in proximal and intermediate areas).

783Oncoids and Bacinella nodules are abundant, and karst features over-

784print the facies in the upper part of the HST. In the section at Harder, a

785bioclastic facies (F5–F6) forms the HST. In the section at Alvier,

786reworked rudist shells are recorded in the uppermost part of HST B5.

787The top of this unit is marked by a major emersion surface, associ-

788ated with superﬁcialkarst, the presence of microcaves, early dissolution,

789vadose silt, and asymmetric cements, in particular in the sections at

790Valsloch, Rawil, and Tierwis. This surface includes the Barremian-

791Aptian boundary and coincides with the SB A1. In the section at

792L'Ecuelle, this surface is affected both by intense early dissolution of

793rudist shells, which are inﬁlled by sandstone (Fig. 15A), as well as by

794the presence of a dense network of Thalassinoides partly inﬁlled by a yel-

795lowish sandstone (Fig. 15B), and of dark sandy inﬁltrations composing a

796vertical fracture network. In the section at Tierwis, this SB is placed in

797the same position as previously proposed by Embry (2005) and Stein

798et al. (2012a), in the uppermost part of the massive limestone of the

799Lower Schrattenkalk Mb, where we observe a sudden stop in

800karstiﬁcation and the presence of lag deposits and intense reworking

801above the SB. In the section at Rawil, the SB is marked by a thin layer

Fig. 8. Spatial distribution of microfacies for the Altmann Mb to the Upper SchrattenkalkMb. The size of each pie chart is related to the thickness of the unit. Each analysed site is plottedon

the palinspastic map established byTrümpy (1969),Ferrazzini and Schüler (1979),andKempf and Pﬁffner (2004).

t2:1Table 2

t2:2Comparison of carbon andoxygen-isotope analyses on micro-drilled subsamples and cor-

t2:3responding bulk-rock samples.

t2:4Identiﬁer Type of compound δ

VPDB

t2:5EC 166 BIS (1) Rudist −1.5 −4.2

t2:6EC 166 BIS (2) Micrite −2.3 −4.9

t2:7EC 166 BIS (3) Vein −1.8 −8.1

t2:8EC 166 BIS (4) Vein −5.5 −5.3

t2:9EC 166 BIS (5) Bioturbation −3.8 −5.2

t2:10 EC 166 carb (W-R) Bulk rock (micrite) −2.9 −5.0

t2:11 EC 166 biot (W-R) Bulk rock (bioturbation) −3.9 −8.2

t2:12 KP 61 (1) Oyster layer 1 2.9 −3.9

t2:13 KP 61 (2) Oyster layer 2 1.4 −4.6

t2:14 KP 61 (3) Oyster layer 3 1.5 −4.7

t2:15 KP 61 (4) Micrite 1.4 −4.8

t2:16 KP 61 (W-R) Bulk rock 1.5 −4.9

t2:17 LB 27 (1) Rudist 1 1.8 −3.2

t2:18 LB 27 (2) Rudist 2 1.5 −3.0

t2:19 LB 27 (3) Bioclaste 1.6 −3.1

t2:20 LB 27 (4) Micrite 2.0 −3.0

t2:21 LB 27 (5) Calcitic vein 1.6 −4.8

t2:22 LB 27 (W-R) Bulk rock 1.7 −3.4

t2:23 MC 10 (1) Rudist 1 3.1 −2.4

t2:24 MC 10 (2) Rudist 2 3.9 −3.4

t2:25 MC 10 (3) Echinoderm 3.9 −3.4

t2:26 MC 10 (4) Bioclast 3.3 −3.7

t2:27 MC 10 (5) Micrite 1 3.8 −3.7

t2:28 MC 10 (6) Micrite 2 3.7 −3.4

t2:29 MC 10 (W-R) Bulk rock 3.5 −4.0

t2:30 MC 137 (1) Recrystallized bioclast 1 2.3 −2.6

t2:31 MC 137 (2) Recrystallized bioclast 2 3.6 −5.2

t2:32 MC 137 (3) Recrystallized bioclast 3 1.9 −2.5

t2:33 MC 137 (4) Orbitolinidae 3.3 −2.4

t2:34 MC 137 (5) Micrite 1 3.2 −2.1

t2:35 MC 137 (6) Micrite 2 (dark) 4.4 −3.8

t2:36 MC 137 (W-R) Bulk rock 3.0 −2.5

t2:37 TW-145 (1) Orbitolinidae 2.0 −3.2

t2:38 TW-145 (2) Micrite 2.0 −3.6

t2:39 TW-145 (3) Calcitic vein 2.1 −5.1

t2:40 TW 145 (W-R) Bulk-rock 1.9 −3.5

t2:41 VA 15 (1) Recrystallized bioclast 1 2.4 −6.5

t2:42 VA 15 (2) Recrystallized bioclast 2 2.3 −6.1

t2:43 VA 15 (3) Bivalve 2.6 −7.0

t2:44 VA 15 (4) Coral 1 3.5 −3.6

t2:45 VA 15 (5) Coral 2 3.4 −4.2

t2:46 VA 15 (6) Micrite 3.6 −3.7

t2:47 VA 15 (W-R) Bulk rock 3.4 −3.2

t2:48 VA 122 (1) Rudist (calcite) 1.9 −3.3

t2:49 VA 122 (2) Rudist (recrystallized aragonite = calcite) 2.4 −3.7

t2:50 VA 122 (3) Oncolite 2.7 −3.8

t2:51 VA 122 (4) Micrite 2.6 −4.1

t2:52 VA 122 (5) Dark micrite 2.7 −3.6

t2:53 VA 122 (6) Calcitic vein 2.9 −6.3

t2:54 VA 122 (W-R) Bulk rock 2.6 −4.6

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UNCORRECTED PROOF

802 of terra rossa deposits, and early dissolution and karstiﬁcation affected

803 the section up to at least 15 m below this surface (Fig. 16). In the sec-

804 tions at Valsloch and Justistal, SB A1 was not recognized in the ﬁeld,

805 but was identiﬁed based on microfacies analysis. In the Justistal section,

806 the complex history of this limit is recorded in a single thin section

807 (Fig. 17), which shows that the initial depositional environment

808consisted of muddy supratidal facies (F11). The subsequent emersive

809phase is marked by early dissolution of aragonitic elements such as

810dasycladales, and voids inﬁlled by vadose silt. This event is followed

811by karstiﬁcation and soil formation. Traces of karst associated with

812this emersion surface are recorded up to 16 m below this surface. In

813the core of Morschach, two alternative positions are possible for the

Fig. 9. Carbon-isotope records and phosphorus contents in the studied sections arranged along a palinspastic transect. The carbon-isotope records are correlated with the hemipelagic

reference section of Angles –Combes Lambert (Godet et al., 2006).

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814 attribution of the SB A1. The ﬁrst is based on the δ

C record and its cor-

815 relation with the Valsloch section. The second one is applied here and is

816 based on microfacies analyses, and more precisely on theimportant oc-

817 currence of Palorbitolina lenticularis, green algae, and increased quartz

818 content (Fig. S8). In this core, evidence of subaerial exposure occurs in

819 numerous intervals and none was recognized as a major one.

820 5.2.6. Sequence A1, transgressive systems tract (Rawil Member)

821 The Rawil Mb corresponds to the TST and the early highstand sys-

822 tems tract (HST) of the ﬁrst sequence of the Aptian (sequence A1;

823 Stein et al., 2012a)(Figs. 4, 7), as is documented by the progressive

824 deepening of facies and the general increase in clay input resulting

825 from important transgression (Stein et al., 2012a). In general, the ﬁrst

826 few meters of the Rawil Mb (unit A; Fig. 18) are organized in several

827 cm to dm thick calcareous parasequences, showing features of subaerial

828 exposure at their top. These suggest the rapid inﬁlling of accommoda-

829 tion space. Lag and transgressive microfacies type FT1 is common, and

830 is associated with levels rich in quartz and clay, in particularin the sec-

831 tions at Rawil, Tierwis, L'Ecuelle, and Justistal. This particular facies is

832 interpreted as typical of a lagoonal estuarine depositional environment

833 (Embry, 2005). For example, in the section at Tierwis, the base of the

834 Rawil Mb consists of calcareous sandstone and sandy carbonate, con-

835 taining poorly sorted quartz grains, wood remains, and a marine fauna

836 including miliolids (Embry, 2005;Stein et al., 2012a). Fragments of

837 reworked Charophytes are preserved in the sections at Tierwis, Rawil,

838 and Justistal. Palorbitolina lenticularis or Orbitolinopsis were not ob-

839 served in the basal interval A, and they reappear in the overlying inter-

840 vals B and C. For the section at L'Ecuelle, Palorbitolina is found in the

841 sandy bioturbation inﬁllings, which reach as deep as 10 cm into the

842 emersion surface on top of the Lower Schrattenkalk Mb (Fig. 15D),

843 and whichare covered by a carbonate breccia contained in a laminated

844 sandstone (Fig. 15C). It is likely that unit A is missing in this section,

845 which suggests that the deposits associated with TST A1 did not extend

846 to this proximal region. In the sections at Rawil and Morschach, the ab-

847 sence of unit A may reﬂect the effect of local paleotopographic highs. In

848 the section at Valsloch, above a 2-m observational hiatus, the Rawil Mb

849 is composed of a deeper-water facies (F3), which is followed by a more

850 lagoonal facies including irregular urchins (Nucleopygus roberti), and by

851 a layer rich in small ooids (b100 μm)and Lithocodium-Bacinella nodules.

852 At Alvier, unit A is represented by open-marine facies (F1, F2). In gen-

853 eral, unit A ends with an epikarstic surface.

854 Unit B corresponds to the middle TST A1 and consists of symmetrical

855 parasequences (also described as “cyclic parasequences”in Bernaus

856 (1998) and Arnaud et al. (2000);oras“deep-water cycles”in Bernaus

857 et al. (2003)Q4 )showing progressively outer-shelf facies in most sections

858 through the gradual enrichment in sponge spicules and/or thin

859 grainstone levels rich in small circalittoral foraminifera (e.g., Gaudryina),

860 which goes along with the presence of Palorbitolina lenticularis and

861 Orbitolinopsis (Fig. 18). These parasequences typically consist of a lag de-

862 posit at their base, containing reworked organisms from different habitats

863 (FT1), followed by wackestone rich in green algae (FT3). The overlying

864 deposits are associated with microfacies type FT2, and are rich in annelids,

865 detrital quartz, and foraminifera attributed to sea-grass environments

866 (e.g., Choffatella decipiens,Palorbitolina (Palorbitolina)lenticularis

867 lenticularis;Arnaud-Vanneau, 1980). The parasequences continue with

868 inner lagoonal deposits rich in oncoids (F9–10), and end with supratidal

869 sediments, which are rich in corals, and include stromatoporoids and

870 chaetetids in a muddy sediment, which may be associated with a

871 hardground surface. Tempestite and beach deposits (F11) occur as well

872 (Fig. 15G, H). In the section at L'Ecuelle, this interval is composed of

873 parasequencesandendswithahardgroundontopofabankrichinher-

874 matypic corals, which is bioeroded and sealed by a reddish sandy matrix

875 rich in orbitolinids and echinoids (Fig. 15E–F).

876 Unit C includes the late TST, the MSF, and the early HST of sequence

877 A1 (Fig. 18). It represents a second deepening phase, interpreted as the

878 maximum ﬂooding interval. Its sedimentary rocks display a microfacies

879characteristic of a sea-grass environment rich in dasycladal algae, in-

880cluding massive accumulations of Palorbitolina lenticularis and

881Choffatella, and showing an increase in quartz contents. This speciﬁc

882microfacies is mainly distributed on the proximal platform, becomes

883rare (b10%) in the intermediate sections at Morschach and Valsloch,

884and is missing on the outer platform (Alvier and Brienzer Rothorn).

885Unit C is characterized by the gradual appearance of an open-marine fa-

886cies, within a thicker interval of approximately 20 m for the sections at

887Valsloch, Morschach, and Tierwis, and 10 m for the sections atRawil and

888L'Ecuelle. In these latter sections, the most distal microfacies (F1–F3) is

889found within this interval, with deposits rich in sponge spicules,

890calcispheres, radiolaria, and deeper-water benthic foraminifera

891(e.g., Gaudryina). Echinoderms are also abundant in this interval and

892corals associated with lime mud are present in the section at Rawil.

893The drill core of Morschach shows an enigmatic occurrence of a series

894of emersive horizons intercalated with deposits attributed to

895microfacies type F3, rich in circalittoral foraminifera and small echino-

896derm fragments. In the section at Valsloch, two alternative intervals

897may represent the MFS; the ﬁrst one occurs in the lower part of unit

898C, where the quantiﬁcation of components and the presence of plank-

899tonic foraminifera indicate maximum deepening. The second possible

900interval is in the upper part of unit C, where the last appearance of

901open-marine facies (F3) was observed. Unit C ends with a marly lime-

902stone rich in Palorbitolina lenticularis (close to facies F3). This level is as-

903sociatedwith one or several emersion levels, which deﬁne the boundary

904to the overlying, rudist-bearing Upper Schrattenkalk Mb.

9055.2.7. Sequence A1, highstand systems tract (Upper Schrattenkalk Member)

906The Upper Schrattenkalk Mb embodies the HST of sequence A1

907(Fig. 4). Overall, the member is characterized by shallowing-upward.

908Its facies distribution shows thedevelopment of an inner lagoonal envi-

909ronment (F8–F10) on the whole platform with supratidal areas

910representing at least 10% in the sections at Tierwis, Valsloch, Rawil,

911and L'Ecuelle (Fig. 8G). The two sections at Alvier and Harder display a

912different facies type.At Alvier, N20% of the Upper Schrattenkalk Mb is

913occupied by granular facies (F5) showing evidence for maximal

914progradation of the carbonate platform. At Harder, the Upper

915Schrattenkalk Mb starts with bioclastic andoolitic facies, and terminates

916with lagoonal facies (20%), which again is indicative of progradation of

917the carbonate platform. In the sections at Valsloch, Rawil, and Tierwis,

918its basal interval consists of oolitic microfacies (F6). In the sections at

919Morschach and l'Ecuelle, the Upper Schrattenkalk Mb directly starts

920with rudist-rich carbonates, which are attributed to a lagoonal environ-

921ment (F8–F9). In the section at Rawil, a reddish erosive surface overlain

922by a nodular level extremely rich in quartz is observed; 15 m below the

923top of the Rawil section, the UpperSchrattenkalk Mb includes a level of

924calcareous lithoclasts in a well-sorted sandy matrix. The matrix is com-

925posed of small angular quartz grains (around 50 μm) and includes small

926muscovite minerals and marine fossil debris (foraminifera, shells, green

927algae). Sigmoidally shaped pebbles present in this level contain a

928lagoonal facies rich in miliolids (F8 type). In the section at Tierwis, a

929succession of parasequences consists of rudist-rich carbonates followed

930by carbonates containing corals and stromatoporoids, which end with

931carbonates including nerineid accumulations. In the drill core of

932Morschach, an internal, conﬁned microfacies containing oncoids (F10)

933and Bacinella nodules are dominant throughout the Upper Schrattenkalk

934Mb.

935The top surface of HST A1 is eroded and deeply karstiﬁed. The termi-

936nal karst shows its maximum thickness in the intermediate part of the

937platform. It reaches up to 26 m deep in the section at Harder, around

93820 m deep in the sections at Valsloch, Morschach and L'Ecuelle

939(Fig. 19), and 15 m deep at Tierwis. The section at Rawil is affected by

940intense karstiﬁcation in the form of a networkof karstic caves, occluded

941by polyphase void ﬁlling to a depth of 90 m (Fig. 20). The oldest inﬁlls

942are sediments belonging to the Grünten Mb.

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943 5.3. Interpretation of the panorama of the Churﬁrsten range

944 The Churﬁrsten panorama represents the transition from the inter-

945 mediate to the distal, south-eastward parts of the platform, in a section

946 oblique to the direction of platform progradation. Several key observa-

947 tions made during the analysis of the geometries are summarized

948 here. The indicated sequences and their respective systems tracts are

949 part of the interpretation provided in Fig. 21–22 and S13–30. It should

950 be noted here that a remarkably detailed geological interpretation of

951 the panorama was already published by Heim (1910–1916).

952 The progradation of the Schrattenkalk Fm above the Drusberg Mb is

953 observed near the base of the panorama. The deposits below SB B3, iden-

954 tiﬁed in the section at Valsloch, are more calcareous on the western side,

955 and change laterally to marl towards the eastern side (Fig. 8). The carbon-

956 ate body belonging to the HST B2 shows eastward progradation, which

957 extends to Schibenstoll. The SB B3 is associated with a jump in the

958 progradation at the base of the calcareous cliff, between HST B2, which

959 ends on the western side of the Schibenstoll, and the LST B3, which

960 ends eastward, on the eastern side of Tristencholben (Figs. 21–22). The

961LST B3 shows a maximum in eastward progradation along a distance of

9622.5 km to Tristencholben (Figs. 21–22).

963We used the sections at Tierwis, Valsloch, and Alvier together with

964the interpretation of the panorama of the Churﬁrsten range to establish

965a chronostratigraphic transect through the intermediate and distal part

966of the platform (Fig. 23).

9675.4. Carbon-isotope records

9685.4.1. Validity of the carbon-isotope records

969Scatter plots of δ

Ovs.δ

C values were used to assess the degree of

970alteration and diagenetic overprint on the isotope record of the studied

971samples (e.g., Choquette and James, 1987). For all studied localities, the

972covariance values are lower than 0.2 except for L'Ecuelle (0.62) and

973Interlaken (0.29; Fig. S31), suggesting that the primary carbonate

974carbon-isotope compositions were not too strongly affected by diage-

975netic modiﬁcations, except for those related to sequence boundaries

976and emersion horizons in general, and those of the sections at

977Kistenpass, Lämmerenplatten, and L'Ecuelle, which were affected by

18 L. Bonvallet et al. / Sedimentary Geology xxx (xxxx) xxx

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UNCORRECTED PROOF

978 low-grade metamorphism (Frey et al., 1980;Burkhard, 1988), and show

979 generally lowered δ

C values as a result (Fig. S31).

980 The δ

Ovs.δ

C scatter plots of selected samples on which micro-

981 drilling subsampling was performed (Fig. 24;Table 2) highlight varia-

982 tions between the different micro-drilled minerals and fossils, and the

983 values obtained on powdered, whole-rock samples. Nevertheless, the

984 values obtained for the micro-drilled micrite and whole-rock powders

985 differ by not more than around 0.2‰in most cases, which is in support

986 of the reliability of the whole-rock δ

Crecordasanoriginalsignal.

987 5.4.2. Interpretation of the carbon-isotope records

988 In the lower part of the sections (sequence B2), the δ

C values show

989 two prominent excursions to higher values without any associated fa-

990 cies change (hemipelagic facies F0–F3). These two excursions are corre-

991 lated with the excursions to higher values observed in the section at

992 Angles (SE France; Godet et al., 2006), which occur in the upper lower

993 Barremian (Kotetishvilia compressissima and Moutoniceras moutonianum

994 zones; Fig. 9).

995 The emersion phase associatedwith SB 3 in the proximal part ofthe

996 platform is not reﬂected in the carbon isotope record. This may be best

997 explained by the fact that the emerged substratum is composed of

998 hemipelagic micritic facies,which was less altered during diagenesisbe-

999 cause of compaction and the likely precipitation of marine cements,

1000 therebyreducing the porosity and hence rock-ﬂuid ratios and the even-

1001 tual presence of thermodynamically stable low magnesium calcite

1002 (Kroh and Nebelsick, 2010;Graziano and Raspini, 2018).

1003 In the Lower Schrattenkalk Mb, the δ

C record is highly inﬂuenced

1004 by the facies type present. The onset in deposition of lagoonal and asso-

1005 ciated sediments (F8–F10) is directly linked with excursions to higher

1006 values. This is especially the case in the sections at Morschach and

1007 Valsloch, with amplitudes of +1.5‰and +2‰, respectively. The same

1008 is also observed in the sections at Rawil, Justistal, and Tierwis, and to a

1009 lesser extent at L'Ecuelle. This trend is diachronous, depending of the

1010 position of the section relative to the platform. In proximal to inner in-

1011 termediate sections it occurs in sequence B3 (HST B3; at Morschach,

1012 Tierwis, and L'Ecuelle), and higher up in intermediate sections

1013 (sequence B4 –HST B4 –at Valsloch; sequence B5 at Justistal).

1014In proximal sections, the boundary betweenthe Lower Schrattenkalk

1015and the Rawil Mbs is characterized by minimal values (Fig. 25), which is

1016likely related to the associated emersion phase. In contrast, the lower

1017part of the Rawil Mb itself shows maximal values, which are associated

1018with lagoonal facies. In distal sections, the boundary interval between

1019the Lower Schrattenkalk Mb and the Rawil Mb is not marked by large

1020shifts in δ

C, but the Rawil Mb shows an upwards trend towards

1021lower values. This trend is also observed for the upper part of the

1022Rawil Mb in proximal sections and may be related to the general,

1023gradual shift towards a heterozoan association dominated by echino-

1024derms. Up to three shorter-term excursions to lower values occur

1025superimposed on this long-term trend, which mark the boundary of

1026units A and B, near the boundary of units B and C (speciﬁcally in the sec-

1027tions at Tierwis and L'Ecuelle), and deﬁne or are close to the boundary

1028between the Rawil and Upper Schrattenkalk Mbs, respectively

1029(Fig. 25). The upper excursion to lower values is especially well deﬁned

1030in the more distal sections, where the basal interval of the Upper

1031Schrattenkalk Mb coincides with the upper limb of the excursion.

1032These excursions associate with emersion horizons. In proximal sec-

1033tions, the long-term trend to lower δ

C values continues well into the

1034Upper Schrattenkalk Mb.

1035In distal sections (Alvier and Brienzer Rothorn), the δ

Crecords

1036seem less inﬂuenced by the compound-speciﬁc isotopic composition

1037and post-depositional alteration. The exportation of aragonitic material

1038from the shelf may, however, explain the higher values (maximum

1039value +3.0‰) compared to the Vocontian record (Angles; Fig. 9).

1040The overall trend in proximal sections correlates quite well with the

1041δ

C records in the Angles and La Bédoule sections in SE France

1042(Moullade et al., 1998;Renard et al., 2005;Wissler et al., 2003;Godet

1043et al., 2006;Kuhnt et al., 2011;Stein et al., 2012b). Similar trends are

1044also seen in the sections at Cluses (Huck et al., 2011, 2013), Balcon des

1045Ecouges (Embry, 2005) and Gorges du Nant in the Vercors area

1046(Bastide, 2014) (Fig. S32). These positive correlations conﬁrm that

1047changes in the global carbon cycle and its imprint on the δ

C record

1048are also recorded on the Urgonian platform, as was already shown by

1049Wissler et al. (2003),Embry (2005),Huck et al. (2011, 2013),and

1050Stein et al. (2012a).

Fig. 10. Photomicrographsof large benthic foraminifera.(1) Neotrocholinafriburgensis,oblique section (Tierwis, TW 4); (2) Palorbitolina-Eopalorbitolina transiens, axialsection through the

embryonic apparatus (Valsloch, VA 186); (3) Praedictyorbito lina carthusiana, oblique section (Morschach, MC 170); (4) Urgonina alpillensis?, oblique section (Justistal, LB 228);

(5) Paleodictyoconus cf. actinostoma, axialsection (Tierwis, TW 18); (6)and (8) Paracoskinolina cf.reicheli, obliquesection (Justistal, LB 106and LB 186). (7) Falsurgonina sp.,oblique section

(Justistal, LB 218); (9) Paleodictyoconus, transverse section (Tierwis section, sample TW23, HST B3); (10) Paleodictyoconus actinostoma, axial section through the embryonic apparatus

(Tierwissection, sample TW62, TST B4); (11) Cribellopsis elongata, transverse section (Justistal section,sample LB 230, HST B2); (12) Paleodictyoconus, sub-axialsection (Valslochsection,

sample VA 255, HST B2); (13) Paleodictyoconus actinostoma, axial section (Tierwis section,sample TW 82); (14) Paleodictyoconus cuvillieri, sub-axial section (Tierwis section, sample TW

47, TST B4);(15) Paleodictyoconus cuvillieri, transverse section(Tierwis section,sample TW 99, HST B4);(16) Paleodictyoconus actinostoma, transverse section (Tierwissection, sample TW

62, TST B4); (17) Praedictyorbitolina?, oblique section (Morschach section, sample MC 217, TST B3); (18) Montseciella, oblique section (Tierwis section, sample TW 46, TST B4);

(19) Montseciella?, transverse section (Justistal section, sample LB 34, HST B5); (20) Paracoskinolina reicheli, sub-axial section (Tierwis section, sample TW40, TST B4); (21) Cribellopsis

elongata, sub-axial section (Justistal section, sample LB 226, HST B2); (22) Praedyctiorbitolina, oblique section (Justistal section, sample LB 217,LST B3); (23) Palorbitolina/Eopalorbitolina

transiens, axial section through the embryonic apparatus (Tierwis section, sample TW 82, HST B4); (24) Falsurgonina, transverse section (Morschach section, sample MC 110, HST B5);

(25) Orbitolinopsis debelmasi, sub-axial section (Tierwis section,sample TW 23, HST B3); (26) Paracoskinolina sunnilandensis of large size, sub-axial section (Morschach section, sample

MC 112, HST B5); (27)Cribellopsis neoelongata, transverse section showing a rowof pores (Valsloch section, sample VA 70,TST A1); (28) Falsurgonina, transverse section(Morschach sec-

tion, sample MC 150, TST B4); (29) Palorbitolina/Eopalorbitolina transiens, axial section through the embryonic apparatus (Tierwis section, sample TW 62, TST B4); (30) Neotrocholina

friburgensis, sub-axial section (Tierwis section, sample TW 100, TST B5); (31) Falsurgonina, sub-axial section (Tierwis section, sample TW 57, TSTB4); (32) Paracoskinolina reicheli, trans-

verse section (Tierwis section, sample TW 46, TSTB4); (33) Paracoskinolina reicheli, sub-axial section (Valsloch section, sample VA 178, TST B3); (34) Paracoskinolina sunnilandensis,sub-

axial section (Tierwissection, sample TW 46, TST B4);(35) Paracoskinolina reicheli,sub-axial section(Justistal section, sample LB 106,HST B3); (36) Neotrocholina friburgensis, axial section

(Tierwis section, sample TW 82, HST B4); (37) Paracoskinolina maynci, transverse section (Valsloch section, sample VA 102, TST B5); (38) Cribellopsis neoelongata, axial section (Tierwis

section, sample TW 89, HST B4); (39) Cribellopsis neoelongata, sub-axial section (Harder section, sample HA 247, TST B4); (40) Paracoskinolina cf hispanica, sub-axial section (Morschach

section, sample MC 112, HST B5); (41) Paracoskinolina cf hispanica, sub-axial section (Harder section, sample HA 244, TST B4); (42) Paracoskinolina arcuata, transverse section (Tierwis

section, sample TW 145, HST A1); (43)Orbitolinopsis pygmaea, sub-axial section (Valsloch section, sample VL 23, TST A1);(44) Palorbitolina lenticularis, axial section through the embry-

onic apparatus (Harder section, sample HA 378,HST A1); (45) Orbito linopsis pygmaea, sub-axial section (Tierwissection, sampleTW 129, HST A1); (46) Orbitolinopsis p ygmaea, transverse

section (Tierwis section, sample TW 129, HST A1); (47) Palorbitolina arenaceous, sub-axial section (Valsloch section, sample VA 63, TST A1); (48) Orbitolinopsis kiliani,transversesection

(Valsloch section, sample VA 45, TST A1); (49) Palorbitolina lenticularis lenticularis, axial section through the embryonic apparatus (Morschach section, sample MC 43, mfs A1);

(50) Paracoskinolina maynci, sub-axial section (Justistal section, sample LB 36, HST B5); (51) Paracoskinolina arcuata, sub-axial section (Tierwis section, sample TW 144, HST A1);

(52) Palorbitolina lenticularis with annular chambers, transverse section (Valsloch section, sample VA 45, TST A1); (53) Paracoskinolina arcuata, sub-axial section (Tierwis section, sample TW

156, HST A1); (54) Orbitolinopsis cuvillieri, sub-axial section (Valsloch section, sample VL 19, TST A1); 55. Orbitolinopsis buccifer,sub-axial section (Morschach section, sample MC 95, HST

B5); (56) Orbitolinopsis buccifer, sub-axial section (Morschach section, sample MC 15, HST A1); (57) Orbitolinopsis briacensis, sub-axial section (Valsloch section, sample VA 6, HST A1); (58)

Orbitolinopsis cuvillieri, sub-axial section (Valsloch section, sample VA 70, TST A1); (59) Paracoskinolina arcuata, sub-axial section (Valsloch section, sample VL 26, TST A1); (60) Orbitolinopsis

briacensis?, sub-axial section (Valsloch section, sample VA 23, TST A1); (61) Orbitolinopsis briacensis, sub-axial section (Tierwis section, sample TW 137, HST A1); (62) Paracoskinolina maynci,

sub-axial section (Valsloch section, sample VA 14, HST A1); (63) Paracoskinolina maynci, sub-axial section (Morschach section, sample MC 99, HST B5); (64) Paracoskinolina maynci,sub-axial

section (Tierwis section, sample TW 100, TST B5); (65) Orbitolinopsis cuvillieri, sub-axial section (Tierwis section, sample TW 130, HST A1); (66) Orbitolinopsis kiliani, sub-axial section

(Morschach section, sample MC 15, HST A1); (67) Orbitolinopsis kiliani, sub-axial section (Tierwis section, sample TW 123, HST A1).

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UNCORRECTED PROOF

1051 Deviations from general trends in the δ

Crecordarerelatedtothe

1052 speciﬁcities of the Urgonian platform and its diagenetic history. In the

1053 following, we explore potential relationships between the trends and

1054 deviations therein and the mineralogical composition (aragonite versus

1055 calcite), primary porosity (e.g., in echinoderms), and the presence of

1056 emersion surfaces. In general, we observe high values in the often con-

1057 ﬁned lagoons (see above), whereas the presence of oolitic and bioclastic

1058 facies (F5, F6) tends to lower δ

C values (e.g., TST B3 at Valsloch; se-

1059 quences B2 to B4 at Justistal; sequences B3 to B5 at Harder). Excursions

1060 to higher δ

C values associated with the transition to lagoonal facies,

1061 and more general on and near carbonate platforms may be related to

1062 an increase in the accumulation and exportation of aragonitic compo-

1063 nents, as was proposed by Godet et al. (2006) and Föllmi et al. (2006,

1064 2007), thereby following Swart and Eberli (2005). To estimate the initial

1065 content of aragonite in the deposits, a systematic quantiﬁcation of com-

1066 ponents in thin sections was performed for the sections at Valsloch

1067 (Fig. S14) and Gorges du Nant in the Vercors area (Fig. S32). Compo-

1068 nents which were originally aragonitic include green algae (Scholle

1069 and Umer-Scholle, 2003;Flügel, 2004), which are partly preserved as

1070fossil debris (e.g., dasycladales), and which may also have contributed

1071to the production of lagoonal micrite (Udoteacean algae; Lowenstam

1072and Epstein, 1957;Neumann and Land, 1975;Milliman et al., 1993;

1073Enríquez and Schubert, 2014). In our quantitative analysis,only the con-

1074tribution of green algae in the form of preserved and recognizable fossils

1075is considered. Aragonite is also important in rudists, where it is part of

1076the inner shell and may represent an important proportion of the total

1077exoskeleton, depending on the species (Steuber, 2002;Skelton and

1078Gili, 2012) and in other mollusk groups such as gastropods, which are

1079exclusively composed of aragonite (Bandel, 1990). A surprisingly good

1080correspondence is seen between reconstructed aragonite contents and

1081the δ

C record in the Gorges du Nant section, whereas the near absence

1082of aragonite in the Valsloch section concurs with the trend to lower

1083values in its δ

Crecord.

1084The intervals with the most negative values in the Valsloch section

1085coincide with oolitic facies. Furthermore, the plateau of low values in

1086the section at Valslochcorresponds to intervals highly enriched in echi-

1087noderms. This group is composed of high‑magnesium calcite, which is

1088unstable under meteoric conditions (Kroh and Nebelsick, 2010).

Fig. 11. Stratigraphic distribution of Orbitolinids and Neotrocholina friburgensis in the Helvetic nappes (modiﬁed after Arnaud et al., 1998). The colored markers correspond to the

sequences for which these species are characteristic: pink: sequence B2; green:sequence B3; yellow: sequence B4; blue: sequence B5; orange: sequence A1. Ammonite biostratigraphy

from Reboulet et al. (2018). A selection of identiﬁed benthic foraminifera are illustrated in Fig. 10.(For interpretation of the references to colour in this ﬁgure legend, the reader is

referred to the web version of this article.)

Fig. 12. Photomicrographs illustrating the observed emersion features associated withsequence boundary SB3 between the Drusberg and Lower Schrattenkalk Mbs; (A) root molds in a

wackestone of microfacies type F4;arrow shows an inﬁlling with vadosesilt (L'Ecuelle;EC 47); (B) early dissolutionof cement (L'Ecuelle; EC 47); (C andD) paleofractures(Tierwis; TW 3);

(E and F) truncation of grains by earlydissolution (Morschach; MC 227); (G, I, and J) lithoclastsof various origin;(G: oolitic limestone; I: packstone with orbitolinidae;J: wackestone with

spicules and calcispheres; all Morschach; MC 227); (H) meniscus cement (Morschach; MC 225); (K) lag deposit containing large ooids in a deeper-water matrix (Valsloch; VA 225);

(L) root traces (Harder;HA 189); (M and N) Iron-coated grains reworked from a paleosol (Harder; HA 188).

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UNCORRECTED PROOF

1089 Echinoderms are also characterized by important porosity, with a range

1090 of 10–70% volume (Weber, 1969;Weber et al., 1969), which allows for

1091 the circulation of post-depositional ﬂuids. These factors are likely involved

1092 in the generation of the observed trends towards lower values in this

1093 section. The facies-dependent isotope variations are shown in boxplots

1094 for each section in Fig. 26. For the sections at Valsloch, Morschach, and

1095 Rawil, the carbon isotope values are lower for the association of outer-

1096 shelf microfacies types (AF1–AF3) than of the AF4 (lagoonal facies). This

1097 trend is less well expressed in the sections at Tierwis and Justistal, and

1098 is completely inversed in L'Ecuelle. Concerning the values of the AF5

1099 (supratidal) and the AF6 (transgressive facies) associations, no clear

1100 trends are discerned, except for medians lower than those of the AF4,

1101 and a larger range of values, especially for the section at Tierwis.

1102 A further factor to be considered is the coincidence of excursions to

1103 lower values with the presence of evidence for emersion. This relation is

1104 observed both for the boundary interval between the Lower

1105 Schrattenkalk and Rawil Mbs in proximal sections, aswell as for the ex-

1106 cursions to lower values within the Rawil Mb (e.g., in the sections at

1107 L'Ecuelle and Rawil) and near the base of the Upper Schrattenkalk Mb

1108 (e.g., in the sections at L'Ecuelle and Valsloch). It is clear, however,

1109 that not every emersion surface is associated with a δ

C excursion to

1110 lower values, and vice versa.

1111 5.5. The evolution of the Helvetic shelf; tectonic processes and sea-level

1112 change

1113 In spite of its passive-margin conﬁguration and the resulting tectonic

1114 stability (Trümpy, 1980), the northern Tethyan shelf underwent tectonic

1115 readjustment during the Barremian-Aptian, which was related to rota-

1116 tion of the Iberian subcontinent, the continued opening of the Atlantic,

1117 and extension of the northern Tethyan Valais Basin (e.g., Arnaud, 1988;

1118 Olivet, 1996). As a consequence, subsidence rates were relatively high

1119 in the Helvetic domain (Funk, 1985). Furthermore, pre-existing faults be-

1120 came reactivated during this time period, leading to tilting of block seg-

1121 ments, as is observed on the platforms in Vercors, Gard, and southern

1122 Provence (Arnaud, 2005;Bastide, 2014). These tectonic rearrangements

1123 may have also created a complex topography on the Helvetic platform

1124 resulting in sudden changes in the thickness of stratigraphic sequences

1125 and their systems tracts. For instance, the sections at Morschach and

1126 Rawil include a succession of emersive levels overlain by deposits of

1127 deeper water facies. This may have been related to the presence of a

1128 paleotopographic high, where only the maximum transgression of each

1129 parasequence is recorded. Moreover, a complex karst system is present

1130 in the Rawil section, which is ﬁlled by caymanite-type deposits –i.e.

1131 void-ﬁlling, colored and banded dolomite precipitates - (Jones, 1992).

1132 This type of karstiﬁcation affected the section N90 m deep (Fig. 20), and

1133 suggests recurrent subaerial exposure during and following deposition

1134 of the Schrattenkalk Fm. The absence of quartz in the karst inﬁllings

1135indicates that karstiﬁcation occurred prior to deposition of the sand-

1136rich Brisi Mb of the Garschella Fm, as opposed to the section at L'Ecuelle,

1137where fracture inﬁlls include sandstone of the Brisi Mb.

1138Fig. 8 shows the spatial and temporal evolution of the Helvetic realm

1139in a step-by-step, sequence-by-sequence fashion, from the latest

1140Hauterivian to the early Aptian. Sequences H6 to B1 consist of the usu-

1141ally highly condensed Altmann Mb, which formed following the drown-

1142ing of the heterozoan Kieselkalk platform (Bodin et al., 2006a). At

1143Tierwis, a locally expanded section of around 30 m thickness is present,

1144which is probably related to the presence of a normal fault (Bodin et al.,

11452006a). During the late early Barremian (essentially M.moutonianum

1146zone), following this phase of widespread sedimentary condensation,

1147a hemipelagic sedimentation regime was installed in the Helvetic

1148realm. The maximum thickness of the resultingsequence B2 is observed

1149at Alvier. A nearby listric paleofault may have locally enhanced subsi-

1150dence (Trümpy, 1980).

1151Intercalated tempestite calcarenites in the HST of sequence B2

1152(L'Ecuelle, Justistal, Harder, Valsloch, panorama of the Churﬁrsten) indi-

1153cate the arrival of local platform carbonate factories, likely in a proximal

1154positionof the platform. Thismay have been the case in the regionof the

1155Lake of Thun, near Niedernhorn, where Schneeberger (1927) and

1156Ziegler (1967) postulated the presence of a tectonically-induced shoal,

1157which may have favored the early development of a carbonate platform

1158in this area. Filling of accommodation space and seaward progradation

1159of this shoal are illustrated by the decrease in thickness from sequences

1160B3 to B5 at Justistal, whereas the same sequences become thicker at

1161Harder. The inﬁlling is also revealed by the installation of lagoonal facies

1162in Justistal during deposition of sequence B5. Further platform shoals

1163may have developed during the late early Barremian, such as the one

1164which produced the bioclastic deposits in sequence B2 at Valsloch and

1165west of it, as observed in the panorama of the Churﬁrsten.

1166SB B3 documents a phase of important sea-level fall, leading to

1167emersion and soil formation on the inner part of the platform

1168(Fig. 12). The emersion surface on top of hemipelagic facies of the

1169Drusberg Mb illustrates a potentially important time lag. In intermedi-

1170ate domains, the presence of bioclastic beds containing reworked

1171shallow-water grains suggests that shallow-water carbonate sedimen-

1172tation occurred on the inner shelf. On the outer platform, hemipelagic

1173deposition continued during this time. The transition between the

1174inner platform and the external part of the shelf corresponds to ca.

117540 km, as seen from the distance between the sections at Tierwis and

1176Alvier. This suggests a peculiar paleotopography of the shelf, with a

1177steeper slope dividing the platform from the outer shelf, which may

1178have been triggered by synsedimentary faulting, as was proposed by

1179Trümpy (1980) for the eastern part of Switzerland. He suggested the

1180presence of a listric fault between the Säntis and Alvier sections, active

1181until the early Barremian, leading to important variations in subsidence

1182rates in different places of the Helvetic shelf during theEarly Cretaceous

1183in general. He related these observations to observed abrupt facies

1184changes and assumed the presence of tilted blocks.

1185Sequence B3 is characterized by a change in sedimentation pattern

1186and the expansion of the shallow-water carbonate factory, which pro-

1187gressively covered the entire investigated area except for the two distal

1188localities at Brienzer Rothorn and Alvier. The early late Barremian trans-

1189gression ﬂooded proximal, emerged areas, as is shown by the sections at

1190L'Ecuelle, Tierwis, and Morschach. In a seaward direction, we note the

1191presence of a LST composed of bioclastic deposits, which is especially

1192well developed in the thick sections at Valsloch and Justistal.

1193In the following, shallower sediments were deposited at the base of

1194TST B3. Oolite accumulation preceded the arrival and establishment of

1195corals and rudists in the inner and intermediate parts of the platform.

1196During this period, the carbonate platform was characterized by a max-

1197imum in progradation,as suggested by the presence of, reworked parti-

1198cles in the section at Alvier, which are attributed to sequence B3. Fig. 23

1199summarizes the temporal evolution of this platform along a proximal-

1200to-distal transect, as preserved in the Säntis nappe. The period of low

Fig. 13. Close-up on an annelid-rich interval associated with theTST of sequence B3 of the

Lower Schrattenkalk Mb in the section at Valsloch.

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UNCORRECTED PROOF

1201 relative sea level documented in LST B3 is followed by a transgressive

1202 phase, which is associated with the landward development of onlaps

1203 and the deposition of shallow-water granular facies above the emersion

1204 surface. The highest accumulation rate is observed in the intermediate

1205 part of the platform. Deepening of the depositional environment

1206 through the whole shelf marked the maximum marine transgression

1207 phase. Ininner and intermediate locations, the isolated and colonial an-

1208 nelids and ﬂat orbitolinids present in this interval are characteristic of a

1209 mesotrophic environment. A phase of transgression during the early

1210 late Barremian is also indicated in the sea-level chart compiled

1211 by Haq (2014). The termination of sequence B3 is associated with a

1212 phase of sea level fall. The amplitude of the associated regression is

1213 estimated as large as at least 15 m.

1214During deposition of the following sequence B4, the existing plat-

1215form topography was ﬁlled in and leveled out. The areas characterized

1216by important sediment accumulation during sequence B3 were covered

1217by thinner series composing sequence B4 (L'Ecuelle, Morschach, and

1218Valsloch). Tierwis is an exception, because the series above sequence

1219B3 is thicker. In the section at L'Ecuelle, the deposition of large oblique

1220beds in the HST is likely due to synsedimentary slump folds. Justistal

1221and Harder were probably located in a depression because of the abnor-

1222mal thickness of B4, which is rich in oolitic accumulations possibly

1223related to the presence of shoals.In the Alvier and Brienzer Rothorn

1224sections on the outer shelf, sequence B4 still consists of hemipelagic

1225deposits of the Drusberg Mb, which include reworked bioclastic grains

1226(at Alvier).

Fig. 14. Photomicrographs illustrating the emersion phase associated with SB B4: (A) early dissolution cracks, ﬁlled in by micrite (Valsloch section; VA 139); (B) early dissolution, ﬁlled in

by peloids (Valsloch section; VA 141); (C. and H) polyphased karst inﬁlling (Tierwis section;TW 34); (D) amber meteoric cement (Tierwis section; TW 36); (E) pedogenic cement in

rosette (Tierwis section; TW 35); (F and I) green marl associated with soil deposit (Tierwis and Morschach sections; TW 34and MC 153); (G)dolomitic inﬁlling of an early dissolution

pocket (Tierwis section; TW 34); (J) root trace (Morschach section; MC 152); (K) epikarstic features (Morschach section; MC 152); (L) dolomite facies (Harder section; HA 251). (For

interpretation of the references to colour in this ﬁgure legend, the reader is referred to the web version of this article.)

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UNCORRECTED PROOF

1227 Sequences B5 and A1 indicates the presence of a subdued and uni-

1228 form topography on the platform, as is suggested by the comparable

1229 thickness of all sections. The Rawil Mb (TST A1) is characterized by a

1230 generalized upward trend towards open-marine facies, illustrating

1231 deepening of the environment.

1232 All these observations and interpretations imply that the Helvetic

1233 realm evolved in two distinct phases: the ﬁrst phase consisted of the re-

1234 covery in sediment accumulation following a phase of drowning and

1235 sedimentary condensation (Altmann Mb). This phase witnessed the

1236 creation of topography during the deposition of sequences B2 and B3

1237and the shift from a platform ramp sensu Burchette and Wright

1238(1992; cf., Bodin et al., 2006a) towards a ﬂat-topped platform (“open

1239platform”;Pomar et al., 2012), with the deposition of an aggradational

1240bioclastic TST B3 (Pomar and Kendall, 2008) in the section at Valsloch.

1241This is supported by the equivalent total thickness of the sequences

1242and the similarity of facies distribution in the inner and intermediate

1243parts of the platform. In the area of the platform slope, rapid facies

1244changes suggest the presence of a distally steepened platform, as is,

1245for example, indicated by the presence of calciturbidites in the upper

1246part of the section at Brienzer Rothorn (Ribaux, 2012). The platform

Fig. 15. A Photos from the top of the Lower Schrattenkalk Mb and the overlying Rawil Mb atL'Ecuelle: (A) rudist shells showing early dissolution andinﬁll by sandstone on the top surface

of the Lower Schrattenkalk Mb (L'Ecuelle; EC 166); (B) network of Thalassinoides,inﬁlled by yellowish sandstone on the top surface of the Lower Schrattenkalk Mb (L'Ecuelle; EC 166);

(C) carbonate breccia contained in a laminated sandstone(L'Ecuelle;EC 172); (D) impregnations of dark sandstone at the base of the Rawil Mb (L'Ecuelle; EC 170); (E) hardground on

top of unit B of the Rawil Mb, with bioeroded corals (orange lines) sealed by a reddish orbitolinid-rich sediment (L'Ecuelle; EC 197); (F) a bioeroded coral embedded in an orbitolinid-

rich carbonate (L'Ecuelle; EC 197); (Gand H) accumulation of gastropods in atempestitelevel terminating a cyclic parasequence of unit B inthe Rawil Mb (Rawil, RW37).

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UNCORRECTED PROOF

1247 slope mayhave been accentuatedby the activity of paleofaults and asso-

1248 ciated differential subsidence. The second phase comprises the further

1249 development of the Urgonian platform, during which its topography is

1250 leveled out (sequences B4, B5, and A1).

1251The large amplitudes in sea-level change proposed by Haq (2014)

1252for the early Aptian are intriguing. He suggested that in the time inter-

1253vals corresponding to the formation of SB A1 and SB A2 were associated

1254with major sea-level fall, with amplitudes of N75 m. This range of

Fig. 16. Inﬂuence of sea-level fall associated with SB A1 on top of the Lower Schrattenkalk Mb in the section at Rawil. The stratigraphic log shows the levels of interest with numbers

corresponding to the numbers of the photos and photomicrographs. At the sequence boundary (no. 1), evidence for emersion is given by terra rossa (T) deposits on the SB. The

presence of karst (K) is indicated by caymanite (C) inﬁlling, microbreccia, and vadose silt (levels 2 and 3, directly underneath SB A1). Level 4 shows the presence of lithoclasts with

abundant (fresh-water) ostracods (FW-O) within a karst inﬁll. Karst activity is recorded down to level 5, which corresponds to the maximum-ﬂooding surface MFS B5. This interval

contains a hemipelagic facies including calcispheres (Ca), radiolaria (R), and planktonic echinoderm (PE) remains, which shows small karstic ﬁssures ﬁlled in with vadose silt.

Photomicrographs are of sample RW 82 for (2) and (3), sample RW 89 for (4), and sample RW94 for (5).

25L. Bonvallet et al. / Sedimentary Geology xxx (xxxx) xxx

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UNCORRECTED PROOF

1255 amplitudes cannot be conﬁrmed on the Helvetic platform. In the section

1256 at Rawil, relative sea-level fall near the Barremian-Aptian boundary

1257 was at least 15 m, as indicated by the maximal depth of karstiﬁcation

1258 and with that the base of the vadose zone. Sequence A1 ends also by

1259 a major emersion surface (SB A2), which is associated with karst on

1260 the whole platform. The comparable maximal depths of karst inﬂu-

1261 ence (between 15 and 26 m) through the inner and intermediate

1262 platform conﬁrm the absence of major topography, and indicate an

1263 amplitude of sea-level fall of at least 30 m. The range of amplitudes

1264 identiﬁed here concurs well with those indentiﬁed in Russia and

1265 Oman for the late Early and early Late Cretaceous by Immenhauser

1266 (2005).

1267 According to Haq (2014), the regressions corresponding in time to

1268 SB A1 and SB A2 were followed by rapid transgressions. From our facies

1269and microfacies analysis of Unit A at the base of the Rawil Mb, this can-

1270not really be conﬁrmed, as the change in facies is rather gradual. By con-

1271trast, sea-level rise following SB A2 was signiﬁcant and a likely factor in

1272the drowning of the Urgonian platform. The emersive surface is locally

1273covered by a phosphatic hardground (Rohrbachstein Bed), which is

1274overlain by heterozoan deposits of the Lower Grunten Mb (Linder

1275et al., 2006;Föllmi and Gainon, 2008).

12765.6. Phosphorus contents, platform facies, environmental and climate

1277change

1278The faunal and ﬂoral composition of sediments and records of detrital

1279and phosphorus content are used here to infer trophic levels and their ef-

1280fects on the carbonate-producing ecosystems of the Helvetic platform.

Fig. 17. Reconstructed history of the genesis of the sequence boundary on top of the Lower Schrattenkalk Mb (SB A1) within a single thin section from the section at Justistal (LB 16):

(1) initial deposit composed of muddy supratidal facies (F11): top of the Lower Schrattenkalk Mb (HST B5); (2) sea-level fall associated with the SB A1: evidence of emersion marked

by early dissolution of aragonitic organisms and void inﬁlling by vadose silt; (3) pedogenesis and the formation of a paleosol; (4) superﬁcial karst affecting sedimentary rocks in a

depth of N16 m below this sample.

26 L. Bonvallet et al. / Sedimentary Geology xxx (xxxx) xxx

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UNCORRECTED PROOF

1281 Prior to the deposition of “Urgonian”facies, from the Valanginian onward,

1282 platform ecology was dominated by heterozoan assemblages, and its

1283 growth was repeatedly interrupted by extended phases of condensation,

1284 phosphogenesis, and platform demise (Kuhn, 1996;Föllmi et al., 2006,

1285 2007;Godet et al., 2013). The Valangian-Barremian heterozoan assem-

1286 blages are mainly composed of crinoids and bryozoans, and reﬂect an ad-

1287 aptation of the ecosystem to mesotrophic conditions and eventually also

1288 cooler waters (James and Clarke, 1997;Mutti and Hallock, 2003;Van de

1289 Schootbrugge et al., 2003). According to Kuhn (1996),Van de

1290 Schootbrugge et al. (2003),andGodet (2013), the condensation phases

1291 observed in the Helvetic realm were related to upwelling currents,

1292 which led to the repeated collapse of heterozoan carbonate-producing

1293 ecosystems. In addition, a general increase in phosphorus concentrations

1294 in the oceans during the Valanginian and Hauterivian may have favored

1295the long-term presence of mesotrophic conditions on the Helvetic plat-

1296form (Föllmi, 1995).

1297The onset in thedeposition of the condensed Altmann Mb is coarsely

1298correlated with the Faraoni oceanic anoxic event recorded in different

1299southandcentralEuropeanbasins(Cecca et al., 1994;Bodin et al.,

13002006c). The Altmann Mb was deposited under mesotrophic to eutro-

1301phic conditions in a current-dominated depositional system, allowing

1302condensation of the sediments and the formation of macroscopic phos-

1303phate deposits (Bodin et al., 2006a;Godet et al., 2013). On the central

1304and western European continent, climate conditions during the late

1305Hauterivian –early Barremian were postulated as warm and humid

1306(Godet et al., 2008;cf.alsoO'Brien et al., 2017).

1307The long-term negative gradient in phosphorus contents through the

1308Drusberg Mb and Lower Schrattenkalk Mb suggests that nutrient levels

Fig. 18. Synthetic log of the RawilMb and its equivalent in SE France –the Lower Orbitolina Beds -. The three units A–C are shown in light-, medium-,and dark green, respectively. Char-

acteristic sedimentological and faunistic markers are listed for each unit (Arnaud-Vanneau, 1980;Raddadi, 2005). (For interpretation of the references to colour in this ﬁgure legend, the

reader is referred to the web version of this article.)

27L. Bonvallet et al. / Sedimentary Geology xxx (xxxx) xxx

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UNCORRECTED PROOF

1309 were likely still enhanced during deposition of hemipelagic sediments of

1310 the Drusberg Mb (sequence B2), but decreased during shallowing and the

1311 appearance of the Urgonian platform. The Urgonian platform itself is char-

1312 acterized by the presence of a large lagoon, which was rimmed by oolitic

1313 shoals and small patch reefs. Its fauna is dominated by rudists,

1314 stromatoporoids, and corals, which represent a typical oligotrophic,

1315 photozoan association (Mutti and Hallock, 2003). The evolution of re-

1316 gional climate conditions during the Barremian is not as well deﬁned as

1317 desired, and indications are present for warming (TEX86; O'Brien et al.,

1318 2017), more arid conditions (clay minerals, northwestern Europe;

1319 Ruffell et al., 2002), or more humid conditions (clay minerals, central

1320 Europe; Godet et al., 2008). The long-term decreasing trend in detrital

1321 and phosphorus contents, which lasted until the demise of the platform

1322 in the early Aptian, indicates that weathering rates lowered on the adja-

1323 cent continents, enabling the installation and development of the

1324 Urgonian shallow-water carbonate platform. This long-term trend is punc-

1325 tuated by two shifts to higher phosphorus values, which occurred during

1326 the transgressions related with sequences B3 and A1. The resulting succes-

1327 sions are associated with mixed photozoan –heterozoan assemblages.

1328The ﬁrst shift is associated with the MFS of sequence B3 (middle late

1329Barremian) and was identiﬁed in corresponding successions in L'Ecuelle

1330and Valsloch, where signiﬁcant quantities of ﬂat orbitolinids and colonial

1331and isolated annelids are present. This assemblage is also known from the

1332same sequence in the Vercors and Chartreuse area (Arnaud-Vanneau,

13331980). Recent annelids prefer environments enriched in organic matter,

1334which may be dysoxic (Martínez-Taberner et al., 1993;Fornós et al.,

13351997;Hfaiedh et al., 2013). The phosphatic and glauconitic Chopf Bed in

1336the outer-shelf environment correlates in time to the MFS of B3 and em-

1337bodies the macroscopic expression of the overall phosphorus enrichment

1338during this transgressive time interval. The presence of the condensed

1339phosphatic Chopf Bed and the ubiquity of annelids allow us to postulate

1340that transgression related to sequence B3 led to higher trophic levels

1341and a possible diminution in oxygen conditions on the carbonate plat-

1342form. More speciﬁcally, deeper waters enriched in nutrients may have

1343upwelled on the shelf and reached the platform, thereby affecting the car-

1344bonate factory. The transgression associated with TST B3 may have also

1345induced the deposition of organic-rich sediments in the Lower Saxony

1346Basin (Mutterlose et al., 2010), and may be related to a minor excursion

Fig. 19. Evidence of emersion on top of the Upper Schrattenkalk Mb (SB A2) in the section at L'Ecuelle. The photo with a red star illustrates the irregular contact between the Upper

Schrattenkalk and the Brisi Mbs. The orange box shows the macroscopic aspects of the karstic pocket including blocks of the Grünten Mb. The blue stars indicate shallow-water

carbonate facies of the Upper Schrattenkalk Mb. The green stars indicate the sandy facies of the Brisi Mb. The yellow stars indicate the heterozoan facies of the Grünten Mb, rich in ﬂat

orbitolinids. A: annelids; B: bryozoans; C: crinoids. (For interpretation of the references to colour in this ﬁgure legend, the reader is referred to the web version of this article.)

Fig. 20. Evidence of intense karstiﬁcation related with SB A2 affecting an interval of up to 90 m below the top surface of the Upper Schrattenkalk Mb in the section at Rawil. The

photomicrographs show different features of this major phase of emersion and karstiﬁcation. Their numberscorrespond to the numbers in the stratigraphic log. RW5: early dissolution

of a nerineid gastropod, which is inﬁlled by a vadose silt; RW7: karst with multiple inﬁlls; RW13: Early dissolution and inﬁll by a vadose silt; RW14, RW24, and RW25: early fractures

interrupted by karst inﬁlls; RW39, and RW44: root traces associated with soil formation; RW44: RW 59: Beachrock with pending cements; RW 64: karst with multiple inﬁlls; RW72:

early dissolution of a nerineid gastropod, which is inﬁlled by a vadose silt; RW 82: early dissolution of the aragonitic layer of a bivalve shell and karstic inﬁll by caymanite; RW 82

(second photomicrograph) caymanite and polyphased karst inﬁll.

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UNCORRECTED PROOF

29L. Bonvallet et al. / Sedimentary Geology xxx (xxxx) xxx

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UNCORRECTED PROOF

Fig. 21. Overview of the panorama of the Churﬁrsten range including the section at Valsloch; Interpretation of the panorama in terms of sequence stratigraphy, lithology, and facies. The approximate distance between the summits of Schären and

Tristencholben is 7 km.

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UNCORRECTED PROOF

Fig. 22. (A) Central segment of the Churﬁrsten panorama including th e section at Valsloch; (B and C) interpretation of the panorama in terms of sequence stratigraphy and litholog y;(D and E) focus on the bioclastic carbonate body underneath the SB

B3 (sequence B2). A jump in the degree of progradation between this body and the LST B3 is indicated by a black arrow. The approximate distance between the summits of Brisi and Tristencholben is 4 km.

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UNCORRECTED PROOF

1347 to higher values in the carbon-isotope record (Erba et al., 1999;Godet

1348 et al., 2006).

1349 The second shift to higher phosphorus values is associated with the

1350 Rawil Mb (e.g., sections at Tierwis and Valsloch), where the abundance

1351 of detrital material relative to the underlying and overlying members

1352 suggests that a mixed siliciclastic‑carbonate platform depositional sys-

1353 tem was installed. Based on clay mineral records and more particularly

1354 on the abundance of kaolinite, Stein et al. (2012a) proposed that a

1355 change towards warmer and more humid climate conditions triggered

1356 the increased input of nutrients and terrigenous materials (cf., O'Brien

1357 et al., 2017). The persistence of dasycladacean green algae, coral patch

1358 reefs, and rudists well into the lower part of the Rawil Mb suggests,

1359 however, that nutrient levels were not higher than mesotrophic

1360 (Mutti and Hallock, 2003). These organisms were joined by orbitolinids

1361 (Palorbitolina lenticularis), annelids, and the benthic foraminifer

1362 Choffatella, which were better adapted to mesotrophic conditions and

1363 became abundant and even dominant during deposition of the Rawil

1364 Mb. In its upper part, represented by the top of unit B and by unit C,

1365 light-independent fauna such as circalittoralforaminifera, echinoderms,

1366 and bryozoans became the most dominant groups, whereas corals,

1367 green algae, and rudists were greatly reduced. This progressive shift to a

1368 heterozoan association is explained by elevated nutrient levels and the ef-

1369 fect of relative sea-level rise (Lees and Buller, 1972;Mutti and Hallock,

1370 2003;Schlager, 2005). It shows that during this period the carbonate-

1371 producing ecosystem was able to adapt to changing paleoenvironmental

1372 conditions.

1373 The Rawil Mb is coeval with the deposition of laminated organic-rich

1374 deposits recorded in many basinal sections of the western Tethys and

1375 central Atlantic, such as at El Pui (Sanchez-Hernandez and Maurrasse,

1376 2014) and Igaratza (Millán et al., 2009) in Spain, at Cassis-La Bédoule

1377 in southeastern France (Moullade et al., 1998;Stein et al., 2012b), and

1378 Cismon (Menegatti et al., 1998), Gorgo a Cerbara (Stein et al., 2011),

1379 and Capriolo (Föllmi et al., 2012) in Italy, and in the Lower Saxony

1380 Basin (Mutterlose et al., 2009). This interval wasdescribed as equivalent

1381 to the Taxy episode (Föllmi, 2012), and may have coincided with the

1382 onset of the Ontong Java LIP in the Paciﬁc, according to Tejada et al.

1383 (2009).

1384The return of the Urgonian photozoan carbonate assemblage on

1385the Helvetic platform took place during relative sea-level fall follow-

1386ing the earliest Aptian transgression. The renewal of the oligotrophic

1387fauna in the Upper Schrattenkalk Mb is likely due to a climate shift

1388towards dryer conditions, which triggered a reduction in continental

1389run-off (Stein et al., 2012a, 2012b). This is also indicated by the

1390generally low values in phosphorus and detrital contents of the

1391Upper Schrattenkalk Mb. The Upper Schrattenkalk platform shows

1392maximum platform progradation, which coincided with the general

1393development of Urgonian platforms around the Tethys, as is observed,

1394e.g., in Italy (Amodio et al., 2013), central Iran (Wilmsen et al., 2013),

1395Spain (Vilas et al., 1995), Oman (van Q5Buchem et al., 2002), Serbia

1396(Sudar et al., 2008), Hungary (Peybernès, 1979), Turkey (Masse

1397et al., 2009), and Mexico (Barragan and Melinte, 2006;Skelton and

1398Gili, 2012).

1399In conclusion, the Urgonian platform developed during a

1400prolonged phase of reduced detrital and nutrient input, which was

1401preceded and followed by meso- to eutrophic phases associated

1402with the oceanic anoxic Faraoni and Selli events in the latest

1403Hauterivian and the middle early Aptian, respectively. Superimposed

1404on this long-term trend were two further phases of enhanced nutri-

1405ent input during the middle late Barremian and latest Barremian to

1406earliest Aptian. In general, the late Barremian–early Aptian represents

1407a period of optimal climate conditions for reef and carbonate platform

1408growth, which allowed the development of large Urgonian-type plat-

1409forms in tropical and subtropical environments not only in central

1410Europe, but on a global scale.

1411The Lower and the Upper Schrattenkalk Mbs are well comparable in

1412terms of lithologies, facies, microfacies, and fossil associations (rudists,

1413miliolids, etc.). The widespread twofold appearance of oligotrophic fa-

1414cies duringthe late Barremian and early Aptian is remarkable, especially

1415if one considers the rather high density of anoxic episodes in nearby

1416basins during this time interval (Föllmi et al., 2012). This underlines

1417both the exceptional position of the Urgonian platform in the late

1418Early Cretaceous, - in a time period which was otherwise characterized

1419by meso- to eutrophic conditions, as well as the potential of the late

1420Early Cretaceous environment to rapidly shift between oligo-, meso-,

Fig. 23. Chronostratigraphic cross section based on the sections at Tierwis, Valsloch, and Alvier (all part of the Säntis Nappe). The section at Tierwis represents the internal part of the

platform, Valsloch is located on the edge of the platform, and Alvier is in a distal, outer-shelf position. The length of the hiati shown in this transect are estimations, except for the one

associated with SB B3 in the internal part, which length is based on bio- and sequence stratigraphy.

32 L. Bonvallet et al. / Sedimentary Geology xxx (xxxx) xxx

Please cite this article as: L. Bonvallet, A. Arnaud-Vanneau, H.Arnaud, et al., Evolution of the Urgonian shallow-water carbonate platform on the

Helvetic shelf during the late Ear..., Sedimentary Geology, https://doi.org/10.1016/j.sedgeo.2019.04.005

UNCORRECTED PROOF

Fig. 24. δ

O-δ

C scatter plots of different micro-sampled carbonate components in eight selected samples. Numbers in parentheses behind each data point indicate the drilled

microspots (cf., Table 2).

33L. Bonvallet et al. / Sedimentary Geology xxx (xxxx) xxx

Please cite this article as: L. Bonvallet, A. Arnaud-Vanneau, H.Arnaud, et al., Evolution of the Urgonian shallow-water carbonate platform on the

Helvetic shelf during the late Ear..., Sedimentary Geology, https://doi.org/10.1016/j.sedgeo.2019.04.005

UNCORRECTED PROOF

Fig. 25. Correlationofthesequencestratigraphyandthecarbon-isotoperecordsfrom the Rawil Mb and its equivalents in southeastern and southern France with sections at Cluses, subalpine chains (after Wermeille, 1996;andHuck et al., 2013),

Balcon des Ecouges, Bornes Massif (Raddadi, 2005;Embry, 2005), Gorges du Nant, Vercors massif (Raddadi, 2005;Bastide, 2014), and La Bédoule (Kuhnt et al., 1998, 2011;Stein et al., 2012b).

34 L. Bonvallet et al. / Sedimentary Geology xxx (xxxx) xxx

Please cite this article as: L. Bonvallet, A. Arnaud-Vanneau, H.Arnaud, et al., Evolution of the Urgonian shallow-water carbonate platform on the

Helvetic shelf during the late Ear..., Sedimentary Geology, https://doi.org/10.1016/j.sedgeo.2019.04.005

UNCORRECTED PROOF

Fig. 26. Box plots of carbon and oxygen-isotope values for all facies associations identiﬁed in the sections at Tierwis, Valsloch, Morschach, Justistal, Rawil, and L'Ecuelle.

35L. Bonvallet et al. / Sedimentary Geology xxx (xxxx) xxx

Please cite this article as: L. Bonvallet, A. Arnaud-Vanneau, H.Arnaud, et al., Evolution of the Urgonian shallow-water carbonate platform on the

Helvetic shelf during the late Ear..., Sedimentary Geology, https://doi.org/10.1016/j.sedgeo.2019.04.005

UNCORRECTED PROOF

1421 and eutrophic conditions as a consequence of increased volcanic activ-

1422 ity, general climate change, and associated rapid sea-level change.

1423 The demise of the Urgonian Schrattenkalk platform near the bound-

1424 ary between the forbesi and deshayesi zones coincidedwith that of many

1425 other Urgonian platforms (Föllmi, 2008), such as the Apulian carbonate

1426 platform (Graziano, 2013) and the platform in the subalpine chains,

1427 eastern France (Huck et al., 2013). According to Huck et al. (2011),the

1428 time lag between the demise of the Urgonian platform and the onset

1429 of the Selli oceanic anoxic event is estimated at 300 kyr. This phase of

1430 important platform demise is associated with a change towards warmer

1431 and more humid conditions, associated with an increase in nutrient

1432 ﬂuxes.

1433 6. Conclusions

1434 The evolution of the Urgonian carbonate platform on the Helvetic

1435 shelf along the northern Tethyan margin was analysed for the time

1436 period between the latest Hauterivian and the early Aptian. The

1437 stratigraphic development in microfacies, biostratigraphy based on

1438 benthic foraminifera, δ

C records, phosphorus contents, and the

1439 identiﬁcation of major emersion surfaces in twelve representative sec-

1440 tions are used to propose a sequence-stratigraphic subdivision and a

1441 paleoenvironmental reconstruction.

1442 We observed the following important steps in the development of

1443 the Helvetic platform:

1444 ▪The change from a sedimentary current-dominated, eutrophic re-

1445 gime, which started in the late Hauterivan and resulted in sedimen-

1446 tary condensation, and the formation of thin, glauconite and

1447 phosphate-rich deposits (Altmann Mb), to a phase of widespread

1448 hemipelagic sedimentation (Drusberg Mb) during the late early

1449 Barremian;

1450 ▪The appearance of photozoan carbonate shoals, likely small and

1451 conﬁned to local, tectonically induced highs during the late early

1452 Barremian;

1453 ▪A regressive phase leading to emersion of the inner platform close to

1454 the boundary between the early and late Barremian;

1455 ▪A transgression during the early late Barremian, allowing nutrient-

1456 enriched deeper waters to upwell onto the platform and induce

1457 the appearance of a specialized ecosystem characterized by annelids

1458 and ﬂat orbitolinids. A condensed phosphate- and glauconite-rich

1459 bed formed simultaneously on the outer shelf (Chopf Bed);

1460 ▪The arrival of ﬁrst typical Urgonian carbonates during the early late

1461 Barremian;

1462 ▪The build up and out of an Urgonian platform (Lower Schrattenkalk

1463 Mb) during the late Barremian, whose morphology was progres-

1464 sively transformed from a platform ramp into a ﬂat-topped and dis-

1465 tally steepened platform, and whose evolution was interrupted by

1466 three periods of sea-level fall in the middle late Barremian, the latest

1467 Barremian and close to the Barremian-Aptian boundary;

1468 ▪A prolonged transgressive phase near the onset of the Aptian, which

1469 was associated with increased detrital and nutrient input, and in-

1470 duced the progressive development of a mixed photozoan-

1471 heterozoan carbonate-producing community (Rawil Mb);

1472 ▪Recovery of the Urgonianplatform (Upper SchrattenkalkMb) during

1473 the early part of the early Aptian; and

1474 ▪Emersion and demise of the Urgonian platform during the middle

1475 early Aptian, preceding the onset of the oceanic anoxic Selli episode.

1476

1477 In general, we observe that:

1478 ▪The amplitudes of sea-level fall estimated by the depth of karst for-

1479 mation and as such of the vadose zone during the different emersion

1480 phases never exceed 30 m, which render them comparable to those

1481 measured in other tectonically stable regions (e.g., Immenhauser,

1482 2005);

1483▪The overall long-term trends in the δ

C records are comparable

1484along the NW Tethyan platform and correlate with those of the

1485Vocontian Basin. Shorter-term deviations are related to the speciﬁc-

1486ities of the mineralogy (aragonite versus calcite), the presence of

1487ooids and echinoderms associated with diagenetic inﬁll of pore

1488space, and the presence of emersion surfaces; and

1489▪The overall evolution of the Urgonianplatform was not only related

1490to sea-level change, but also paleoceanographic and paleoclimate

1491conditions, which were responsible for low trophic levels and sub-

1492dued detrital input.

1493

1494

Acknowledgements

1495WearegratefultotheUniversité de Lausanne and the Société

1496Académique Vaudoise for their ﬁnancial support. We also acknowledge

1497the contribution of Laurent Nicod in the manufacturing of numerous

1498thin sections. We furthermore thank the Tiefbauamt of Ct Schwyz and

1499the CDS Ingenieure AG in Kriens for providing the Morschach core,

1500which is stored at the Institute of Earth Sciences of the University of

1501Lausanne. We also thank Hanspeter Funk (Baden) for providing a series

1502of high-resolution airplane photos from the Churﬁrsten range. We

1503highly appreciated the detailed and constructive reviews of Adrian

1504Immenhauser, an anonymous reviewer, and the Editor-in-Chief Jasper

1505Knight, which helped us to substantially improve the manuscript. Q6

1506

Appendix A. Supplementary data

1507Supplementary data to this article can be found online athttps://doi.

1508org/10.1016/j.sedgeo.2019.04.005.

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Helvetic shelf during the late Ear..., Sedimentary Geology, https://doi.org/10.1016/j.sedgeo.2019.04.005

Rise and demise of the Urgonian platform in Switzerland

Article

Nov 2023

Defined in the Provence region of France, the rudist-bearing Urgonian Limestone is typical of northern Tethyan shallow-marine carbonate series, and is dated based on benthic fauna and flora, calcareous nannofossils, and ammonites. This contribution reports on recent findings that refine the stratigraphy of the Urgonian Limestone in the western Swiss Jura and the Helvetic Alps of Switzerland. In the former location, the high-resolution facies and isotope analysis of samples permit the identification of major periods of subaerial exposure while a diverse assemblage of calcareous nannofossils indicates a Barremian age for the Urgonian deposits. In the latter location, biostratigraphic data indicate a Late Barremian - Early Aptian age for Urgonian deposits while the repartition of facies along a proximal-to-distal transect highlights the Late Barremian progradation of the platform. The detailed understanding of the stratigraphy of Urgonian deposits in these regions inscribes them into a broader context that acknowledge paleoclimatic and paleoenvironmental conditions. A warmer and more humid climate prone to continental weathering and transport of nutrient to epicontinental sea characterized the Early Barremian; this was detrimental to the health of carbonate-producing benthic ecosystems. In the Late Barremian, a reduced nutrient supply allowed Urgonian communities to thrive.

Progradation of a shallow carbonate platform developed on a fault-block in the Western Tethys (lower Aptian, Sierra de Bedmar-Jódar, Prebetic of Jaén, Spain)

Article

Apr 2023
FACIES

The Middle Member of the Llopis Fm in the Sierra de Bedmar-Jódar Unit of the Prebetic Zone of Jaén (southern Spain) was deposited on a shallow-marine platform of the Southern Iberian Continental Margin during the earliest Aptian. Detailed field logging of nine stratigraphic sections and facies mapping have allowed seven lithofacies associations (L1–L6) to be distinguished, one siliciclastic (L1) and five carbonate facies (L2–6). The succession is composed of eight consecutive elemental sequences of lithofacies associations L1–L6. Each elemental sequence is interpreted as representing one episode of shallowing-upwards carbonate deposition in a very shallow platform-lagoon that was bounded shoreward by clastic/ooid bars and passed seaward either to stromatoporoid bioconstructions (bioherms and biostromes) or rudist biostromes. The successive elemental sequences show north-eastward progradational geometries. Three phases of platform development are identified: (1) installation of the shallow platform; (2) development of a lagoon bounded by a stromatoporoid barrier and (3) development of an Urgonian-type platform dominated by rudists. During the early Aptian, the Bedmar-Jódar platform was partially isolated from the rest of the Prebetic platform and showed overall progradation towards the NE, in contrast to the general south-eastward progradational trend of the Prebetic platform. Sedimentation was controlled by rift-generated extensional tectonics that resulted in tilting of the platform block, causing the deviation of progradation from the general trends of the Prebetic Platform. In addition, climatic influence is inferred from the presence of siliciclastic sediments derived from weathering of the hinterland, which restricted the carbonate factory.

Progradation of a shallow carbonate platform developed on a fault-block in the Western Tethys (lower Aptian, Sierra de Bedmar-Jódar, Prebetic of Jaén, Spain)

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Apr 2023

Morphogenesis of Balkhania Balkhanica Mamontova, 1966 (Benthic Foraminifera) from Lower Cretaceous Successions Along the Northern Tethyan Margin (NE and Central Iran): Time and Environmental Control

Preprint

Oct 2023

Carbonate factories and their critical control on the geometry of carbonate platforms (mid-Cretaceous, southern Iran)

Article

Jun 2023
PALAEOGEOGR PALAEOCL

Tropical rimmed platforms represent a much more efficient protection from coastal erosion than carbonate ramps. Understanding the controlling factors of platform geometry is therefore crucial to predict the fate of rimmed platforms under global-warming conditions. Here, we present detailed biostratigraphic, sedimentological, geochemical, and high-resolution carbon-isotope analyses of mid-Cretaceous (Albian-Cenomanian) carbonate rocks well exposed in the Khormoj section located in the Zagros Mountains of southern Iran. Sixteen microfacies were identified, allowing us to define the superposition of different platform geometries, a carbonate ramp in the Albian and a rimmed platform in the Cenomanian. Biostratigraphic and carbon-isotope analyses allowed us to identify the OAE1b, OAE1d, and Middle Cenomanian events in the Khormoj section. The paleodepth changes documented by carbonate microfacies testify to two transgressive events that can be correlated with long-term eustatic curves during the ramp stage. The Albian ramp was formed by orbitolinids under high siliciclastic input whereas the Cenomanian rimmed platform was built by rudists during clear water conditions. These two carbonate factories have drastic different carbonate sedimentation modes. The orbitolinid factory is characterized by a low carbonate production rate and fine carbonate grains resulting in ramp geometry, whereas the rudist factory is characterized by a high carbonate production rate and coarse carbonate grains leading to a rimmed platform geometry.

Facies analysis, depositional sequences and platform evolution of the Sarvak Formation (late Albian-Turonian) in the Zagros Basin, West of Iran

Article

Dec 2022
J AFR EARTH SCI

The Sarvak Formation is a carbonate interval (as part of the Bangestan Group) deposited during the Cretaceous (late Albian-late Turonian), which hosts considerable hydrocarbon reserves. We logged five surface sections west of the Zagros Basin to depict the depositional environment and sequence stratigraphy of the Sarvak Formation. The formation comprises five 3rd order depositional sequences, including six facies belts deposited on a carbonate platform. The lower part of the formation comprises two depositional sequences (late Albian -early Cenomanian) deposited on a ramp. In contrast, the rest of the formation (Cenomanian to early Turonian), composed of three depositional sequences, was deposited on a rimmed shelf. The shift from ramp to the shelf was presumably due to changes in the tectonic regime of the Arabian Plate from passive to active margin, and in part due to the obduction of the Neotethys’ ocean crust during the late Middle Cretaceous, accompanied by the development of shoal complex and rudistic reefs. This resulted in the development of some isolated carbonate platforms bordered by intrashelf basins, particularly in the Lurestan Zone. Active basement faults caused the exhumation of the platform and the development of unconformity on the Cenomanian-Turonian boundary. The five depositional sequences we studied were mainly controlled by eustatic change(s) during Albian, mid-Cenomanian to Turonian.

Depositional geometries in Barremian platform carbonates from south-eastern France

Chapter

Dec 2021

Urgonian limestones from the southern part of the Vercors Massif constitute a seismic-scale outcrop analogue for hydrocarbon-producing carbonate reservoirs in giant fields, especially in the Middle East. The outstanding outcrops allow the understanding of depositional geometries and illustrate several types of carbonate depositional architectures in which reservoir facies can be interpreted at specific time periods during depositional sequences. The geographical distribution, size, quality and accessibility of the exposures allows visualisation of the reservoirs analogue facies in three dimensions.

Questioning carbonate facies model definition with reference to the Lower Cretaceous Urgonian platform (SE France Basin)

Article

Full-text available

Oct 2023
B SOC GEOL FR

Designing carbonate facies models requires the integration, correlation and conceptual interpretation of multiple geological data sets. Potential significant errors are sourced from uncertain stratigraphic correlations, speculative palaeoecological interpretations and poorly recorded palaeotopographic profiles. The present study explores a methodological workflow to define a well-supported facies model. An exhaustive literature review is presented on sedimentary facies and depositional profiles of Urgonian carbonate platform from SE France and Switzerland (Barremian–Aptian interval). The historical evolution of Urgonian facies models and related sedimentological concepts is investigated to contextualise published models. The presented conceptual model and table of depositional facies shows a consistent, process-based organization of specific elementary facies, facies associations and carbonate system. Within the chronostratigraphic framework, the study of synchronous strata correlations provides quantitative analyses of facies-belt extents and palaeobathymetric estimations. The resulting depositional profile is based on general palaeoecological and sedimentological concepts, facies distribution on palaeogeographic maps and stacking trends. In rare locations in the field, direct lateral facies belt transitions are recorded. Proximal ( i.e. emersive and peloidal-foraminiferal) depositional facies are rarely observed; most outcrops record the (i) rudist facies association, which corresponds to distal parts of the inner platform, (ii) coral, ooidal and bioclastic facies associations, which are interpreted to occur on the outer platform, and (iii) calcisiltite, slope and basinal deposits. Key data and concepts allow for the building up of a robust, harmonised facies model that can be used to properly interpret palaeoenvironmental changes, stacking trends and stratigraphic sequence evolution, the resolution of which depends on the available chronostratigraphic framework.

Record of a dense succession of drowning phases in the Alpstein mountains, northeastern Switzerland: Part II—the Lower Cretaceous Schrattenkalk Formation (late Barremian)

Article

Full-text available

Jan 2023
SWISS J GEOSCI

The Schrattenkalk Formation represents a complete succession of Lower Cretaceous shallow-water carbonate platform series cropping out in the Alpstein massif of north-eastern Switzerland. The Schrattenkalk Formation is traditionally divided into two sedimentary units, the “Lower” and the “Upper” Schrattenkalk, separated by the more marly Rawil Member. The “Lower” Schrattenkalk is habitually dated to the late Barremian, while the Rawil Member and the “Upper” Schrattenkalk are dated to the early Aptian. New feld observations, however, call the lithostratigraphic dichotomy of the Schrattenkalk into question, as the neritic carbonates are disrupted by several key surfaces associated with karstic episodes and/or transgressive sediments, corresponding to ammonite-rich hemipelagic deposits on the distal shelf. A large number of ammonites were collected in the Drusberg Member as well as rare ammonites from the Schrattenkalk Formation. These ammonites as well as the neritic macrofauna from the Schrattenkalk Formation allow a precise dating of the onset of the Schrattenkalk Formation across the Alpstein massif and its successive phases of progradation. Three successive carbonate bodies and a fourth sedimentary intermediate rock body at the top of the Schrattenkalk platform are defned, based on new biostratigraphic data and updated interpretations of the sequence stratigraphy and geochemical data. The data shows a progressive onset of the Schrattenkalk carbonate platform along the studied transect, following a SE progradation over time. The oldest deposits refer to the upper Barremian T. vandenheckii Zone and the youngest carbonates to the uppermost Barremian M. sarasini Subzone. The new dating of the discontinuity surfaces and key-beds highlight three successive fooding events. The frst drowning phase, which correlates with the "Sartousiana" event, dates from the middle late Barremian (upper T. vandenheckii—lower G. sartousiana Zone). The second phase, represented by the Rawil Member, is an incipient drowning, which seems to coincide with the latest Barremian Taxy event (usually reported to the I. giraudi and lowermost M. sarasini zones) according to rare ammonite discoveries. The fnal demise of the Schrattenkalk platform, situated close to the Barremian-Aptian boundary, is related to an exposure and consecutive drowning event.

Paleoenvironmental constraints on shallow-marine carbonate production in central and West Texas during the Albian (Early Cretaceous)

Article

Dec 2022
CRETACEOUS RES

Cretaceous sea-surface temperature evolution: Constraints from TEX86 and planktonic foraminiferal oxygen isotopes

Article

Full-text available

Jul 2017
EARTH-SCI REV

It is well established that greenhouse conditions prevailed during the Cretaceous Period (~ 145–66 Ma). Determining the exact nature of the greenhouse-gas forcing, climatic warming and climate sensitivity remains, however, an active topic of research. Quantitative and qualitative geochemical and palaeontological proxies provide valuable observational constraints on Cretaceous climate. In particular, reconstructions of Cretaceous sea-surface temperatures (SSTs) have been revolutionised firstly by the recognition that clay-rich sequences can host exceptionally preserved planktonic foraminifera allowing for reliable oxygen-isotope analyses and, secondly by the development of the organic palaeothermometer TEX86, based on the distribution of marine archaeal membrane lipids. Here we provide a new compilation and synthesis of available planktonic foraminiferal δ¹⁸O (δ¹⁸Opl) and TEX86-SST proxy data for almost the entire Cretaceous Period. The compilation uses SSTs recalculated from published raw data, allowing examination of the sensitivity of each proxy to the calculation method (e.g., choice of calibration) and places all data on a common timescale. Overall, the compilation shows many similarities with trends present in individual records of Cretaceous climate change. For example, both SST proxies and benthic foraminiferal δ¹⁸O records indicate maximum warmth in the Cenomanian–Turonian interval. Our reconstruction of the evolution of latitudinal temperature gradients (low, <±30°, minus higher, >±48°, palaeolatitudes) reveals temporal changes. In the Valanginian–Aptian, the low-to-higher mid-latitudinal temperature gradient was weak (decreasing from ~ 10–17 °C in the Valanginian, to ~ 3–5 °C in the Aptian, based on TEX86-SSTs). In the Cenomanian–Santonian, reconstructed latitudinal temperature contrasts are also small relative to modern (< 14 °C, based on low-latitude TEX86 and δ¹⁸Opl SSTs minus higher latitude δ¹⁸Opl SSTs, compared with ~ 20 °C for the modern). In the mid-Campanian to end-Maastrichtian, latitudinal temperature gradients strengthened (~ 19–21 °C, based on low-latitude TEX86 and δ¹⁸Opl SSTs minus higher latitude δ¹⁸Opl SSTs), with cooling occurring at low-, middle- and higher palaeolatitude sites, implying global surface-ocean cooling and/or changes in ocean heat transport in the Late Cretaceous. These reconstructed long-term trends are resilient, regardless of the choice of proxy (TEX86 or δ¹⁸Opl) or calibration. This new Cretaceous SST synthesis provides an up-to-date target for modelling studies investigating the mechanics of extreme climates.

Evolution of the Tithonian–Aptian Carbonate Platform Along the Northern Tethyan Margin, Eastern Helvetic Alps

Chapter

Jan 1993

Sequences de depot et variations du niveau relatif de la mer au Barremien et a l'Aptien inferieur dans les massifs subalpins septentrionaux et le Jura (sud-est de la France)

Article

May 1989

Report on the 6th International Meeting of the IUGS Lower Cretaceous Ammonite Working Group, the Kilian Group (Vienna, Austria, 20th August 2017)

Article

May 2018

The 6th Kilian Group meeting of the IUGS Lower Cretaceous Ammonite Working Group (the Kilian Group) was held in Vienna, Austria, 20th August 2017. The Group mainly discussed the standard zonation that is suitable for and based mainly on ammonite data of the Mediterranean Province of the MediterraneaneCaucasian Subrealm (Tethyan Realm). Some changes have been made on three stages. The uppermost part of the Berriasian is now characterised by the Tirnovella alpillensis Zone, that is subdivided into a lower T. alpillensis Subzone and an upper “Thurmanniceras” otopeta Subzone; the T. alpillensis (Sub-)Zone is here defined by the first appearance datum (FAD) of the index-species. For the Valanginian, the Neocomites premolicus Subzone is introduced in the lower part of the “Thurmanniceras” pertransiens Zone. The FAD of N. premolicus occurs at the base of the “T.” pertransiens Zone. So this subzone starts at the base of the “T.” pertransiens Zone and provisionally ends at the last occurrence of N. premolicus as the upper part of the zone is not characterised by a subzone for the moment. For the Barremian, the former Holcodiscus fallax, Nicklesia didayana, Heinzia communis, Subtorcapella defayae, Coronites darsi, Heinzia caicedi and Anglesites puzosianum horizons have been abandoned. In agreement with systematic positions, the term “auctorum” is deleted for Taveraidiscus hugii, the index-species of the first zone of this stage. The Kotetishvilia compressissima Zone is subdivided into a lower Holcodiscus fallax Subzone and an upper Holcodiscus caillaudianus Subzone. The Barrancyloceras barremense Subzone (upper subzone of the Toxancyloceras vandenheckii Zone) is replaced by the Gassendiceras alpinum Subzone. The Imerites giraudi Zone is kept but its base should be now defined by the FAD of I. dichotomus, which marks the inception of the genus Imerites. For certain stratigraphic intervals the Group discussed and in some cases strengthened the previous correlations between the standard Mediterranean zonation with the different ammonite zonal schemes of other provinces and realms. Some members of the Group presented the possibility of using regional stages as secondary standards, in accordance with the recommendations of the International Commission on Stratigraphy. The report concludes with an appreciation of the French ammonitologist Jean-Pierre Thieuloy deceased in 2017, the nomination of a vicechair, membership, future work and next meeting of the Kilian Group.

Late Barremian–early Aptian ammonite bioevents from the Urgonian-type series of Provence, southeast France: Regional stratigraphic correlations and implications for dating the peri-Vocontian carbonate platforms

Article

Oct 2018

This work provides a new ammonite age-calibration of the rudistid limestones of the Urgonian-type Provence carbonate platform (Southeast France) based on sampling along three ∼200 km-long platform-to-basin transects and re-examination of historical collections. Ammonite key findings indicate that the first rudistid platform stage (including the Agriopleura and requieniid–monopleurid beds) develops and spreads northward through the Toxancyloceras vandenheckii–Gerhardtia sartousiana zones interval (lower upper Barremian). This stage is interrupted by the tectonically-induced deepening of the southern Provence domain during the Imerites giraudi Zone while the northern regions records the massive deposition of Palorbitolina–Heteraster beds. Recovery of the rudistid carbonate system is illustrated by the development of caprinid-bearing rudistid limestones in the North Provence domain through the Martelites sarasini Subzone (lower Martelites sarasini Zone, uppermost Barremian), which shows a bidirectional progradation toward the South Provence and Vocontian basins. The caprinid-bearing limestones terminate at a short-term exposure and are overlain by cherty–oobioclastic deposits spanning the Pseudocrioceras waagenoides Subzone (upper M. sarasini Zone) to the lower Deshayesites forbesi Zone. A regional-wide flooding of the study area is illustrated by the abrupt change to a marl-dominated regime occurring in the upper D. forbesi Zone. Compared to the previous datings, the Barremian/Aptian boundary should be relocated in the lower part of the post-caprinid, cherty–oobioclastic deposits although its precise level cannot be fixed due to the lack of a continuous ammonite record. Ammonite age-calibration of the surrounding Urgonian rudistid platform series is discussed and gives evidence of a comparable twofold demise of the peri-Vocontian rudistid biota during the uppermost Barremian. Accordingly, the link between the final demise of the peri-Vocontian rudistid biota and the onset and/or culmination of the mid-early Aptian Oceanic Anoxic Event (OAE) 1a should be reconsidered.

High-resolution chronostratigraphy of palaeoecologic and isotopic changes in shallow-marine carbonates: Deciphering the completeness of the Aptian record in the Apennine carbonate platform (southern Italy)

Article

Dec 2017

We present here a companions study dealing with the chemostratigraphy, palaeocology, chronostratigraphy and palaeoclimate of the upper Barremian-lower Aptian in the Mt. Faito section that build on our earlier work on the Apennine Carbonate Platform (ApCP, southern Italy). The high-resolution correlation of the Mt. Faito record with the cyclostratigraphically and chemostratigraphically tuned Mt. Raggeto reference section of the APCP has provided crucial evidence to reappraise previous views of a substantial stratigraphic continuity in the lower Aptian of the region. Combining δ¹³C, δ¹⁸O, palaeoecologic and petrographic data herein with available sedimentologic and biostratigraphic information together with reappraised cyclostratigraphic and astrochronologic analyses for the Mt. Faito section, we document substantial gaps throughout the lower Aptian. The timing of two major unconformities, with duration of 1.43 and 4.94 ± 0.10 Ma, as well as the fidelity and completeness of the stratigraphic record have been established using precession (20 ka), short- (100 ka) and long- (400 ka) eccentricity geochronometers. The adopted high-resolution event stratigraphy (HIRES) anchored to the 2012 Geological Time Scale, has provided further valuable insights for assessing the timing and pace of the observed biofacies and chemostratigraphic changes as well as achieving a highly resolved chronostratigraphic framework of the ApCP record for very detailed regional to supra-regional early Aptian correlations. Our analysis at Mt. Faito encompasses 7.5 ± 0.1 Ma ranging from the latest Barremian to the early late Aptian (Unit A to basal Unit D) and demonstrates that only 15% of the investigated time yields rock record. Two missing intervals, including most of the Selli Level Equivalent (SLE), span the late C2-early C5, and the late C5-early C8 isotope segments. These gaps are interpreted as the erosive and/or non-depositional effects of glacioeustatic sea level falls linked to main global scale cooling episodes prior to (125.6 Ma), during (∼124.6 Ma) and after (123.0 Ma) OAE1a, which appear to be linked with the onset of overall humid climate conditions. The transition from a chlorozoan, “Urgonian”-like carbonate factory (C1–C2 p.p. isotopic segments) to the “warm-water” foramol of the greenhouse Crisis Interval (CI) (middle C2 isotopic segment) and, finally, to the waxing and waning of “temperate-water” foramol and microbial productivity mode interludes (middle C5 isotopic segment) are interpreted as the response of the early Aptian neritic ecosystem of the ApCP to the global-scale palaeoceanographic and palaeoclimatic changes driving the OAE1a. The stratigraphic implications of the icehouse interludes in the greenhouse early Aptian are discussed.

Barremian platform carbonates from the eastern Vercors Massif, France: Organization of depositional geometries

Article

Apr 2017
AAPG BULL

The Vercors Massif of southern France constitutes a world-class and unique opportunity to visualize depositional geometries and diagenetic transformations of a Barremian-early Aptian (early Cretaceous) carbonate system, the Urgonian platform, at a seismic scale and thus to constrain the three-dimensional continuity and connectivity of reservoir-prone facies deposited during periods of high and low sea level. The integration of detailed outcrop analysis, including diagenetic transformations, with the sequence stratigraphic interpretation of cliff provides opportunities to study the precise relationship between sea level changes and facies distribution, including reservoir-prone examples such as slope and fan deposits, to understand how local tectonics affect accommodation space and effects on sedimentation rates. This integrated stratigraphic framework developed at surface conditions provides an analog for major petroleum systems of the Middle East where platform carbonates are involved, such as the Aptian Shu'aiba or the Cenomanian-Turonian Mishrif Formation. Copyright © 2017 The American Association of Petroleum Geologists. All rights reserved.

Les calcaires urgoniens des massifs septentrionaux et du Jura (France): Âge et discussion des données stratigraphiques

Article

Jan 1991

Geologie der Bauen‐Brisen‐Kette am Vierwaldstättersee und die zyklische Gliederung der Kreide und des Malm der helvetischen Decken

Article

H.J. Fichter

Seismic stratigraphy and global change of sea level

Article

Jan 1977

Evolution of the Urgonian shallow-water carbonate platform on the Helvetic shelf during the late Early Cretaceous

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