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Cenomanian ammonites from northern aquitaine
Abstract
Ammonites from the Cenomanian of northern Aquitaine include Neolobites vibrayeanus (d'Orbigny, 1841), Calycoceras (Calycoceras) naviculare(Mantell, 1822), C. cenomanense(d'Archiac, 1846), Pseudocalycoceras cf. dentonense(Moreman, 1942), Eucalycoceras sp., Acanthoceras (Acanthoceras) pseudorenevieri(Spath, 1926), A. (A.) sp. juv. and Metoicoceras geslinianum(d'Orbigny, 1850). These are cosmopolitan taxa, and occur in a Mesogean sequence with a rudistid-larger benthonic foraminifer-dominated fauna, and permit a precise correlation with the boreal ammonite sequences of Sarthe and the Anglo-Paris Basin.
... These second-order hemicycles encompass five third-order cycles: C A , C B , C C , C D and C E (Fig. 2B, Platel, 1996). The ammonite biozonation for the northern Aquitaine platform (Moreau et al., 1983, Moreau, 1996, coupled with the benthic foraminifer faunal associations defined by Moreau (1996) were used to establish a reliable biostratigraphical framework for the sedimentary sections (Fig. 3). The ammonites are very rare and only 40 specimens have been studied from the Atlantic coast to Angoulême (Moreau et al., 1983). ...
... The ammonite biozonation for the northern Aquitaine platform (Moreau et al., 1983, Moreau, 1996, coupled with the benthic foraminifer faunal associations defined by Moreau (1996) were used to establish a reliable biostratigraphical framework for the sedimentary sections (Fig. 3). The ammonites are very rare and only 40 specimens have been studied from the Atlantic coast to Angoulême (Moreau et al., 1983). The oldest specimen found in the northern Aquitaine Cenomanian platform is Engonoceras sp., but this ammonite does not allow a reliable attribution to a precise biozone of the "Gr es et Sables verts" Formation (Moreau et al., 1983). ...
... The ammonites are very rare and only 40 specimens have been studied from the Atlantic coast to Angoulême (Moreau et al., 1983). The oldest specimen found in the northern Aquitaine Cenomanian platform is Engonoceras sp., but this ammonite does not allow a reliable attribution to a precise biozone of the "Gr es et Sables verts" Formation (Moreau et al., 1983). The ammonite (Acanthoceras (Acanthoceras) pseudorenevieri, Moreau et al., 1983) coming from the top of the B 3 sub-unit at Rioux (Charente-Maritime; Fig. 3) provides the oldest precise biozonation attribution. ...
The Mid-Cenomanian Event was a positive carbon-isotope (d 13 C) excursion recorded in hemipelagic basins of the western Tethyan Sea, North to Tropical Atlantic Ocean, and Japan. It is thought of as a prelude to the Oceanic Anoxic Event 2. However, the Mid-Cenomanian Event has never been studied in detail in shallow marine platform deposits and it is not known how it relates to carbonate production and stratigraphic geometry. To better understand how this carbon cycle disruption influenced the neritic biological communities in shallow carbonates during the Cenomanian, a facies, geochemical, diagenetic, and sequence stratigraphic study of the northern Aquitaine platform has been conducted. Seventy-six d 13 C and d 18 O measurements have been made on micrite, rudists, and diagenetic cements. Fifteen sedimentary facies have been arranged into four depositional environments. Three third-order sequences (C B , C C , C D) are defined from late early Cenomanian to early late Cenomanian and are well correlated with eustatic cycles in European basins. Two peaks of the Mid-Cenomanian Event (MCE1a, þ1.2‰, and MCE1b, þ1.7‰) have been identified for the first time in shallow marine carbonates. Analysis of diagenetic blocky calcite cements suggests that diagenesis did not affect the d 13 C of micrite, which can be discussed in terms of the initial signal. The Mid-Cenomanian Event was synchronous with a turnover in neritic carbonate producers marking a transition from photozoan to heterozoan facies. This facies change resulted from the establishment of mesotrophic to eutrophic conditions at the early/mid-Cenomanian transition, reflecting a clear connection between the Mid-Cenomanian Event and neritic biological communities. Depositional geometry and carbonate production varied with d 13 C during the Mid-Cenomanian Event on the Aquitaine platform. When d 13 C values were between 2.5‰ and 3‰, the geometry was a flat platform with a high carbonate sedimentation rate leading to the formation of sandbars and rudist bioherms (Accommodation/Sedimentation ratio less than 1, A/S < 1). When the d 13 C value exceeded 3‰, a carbonate demise occurred and clays and marls were deposited in the lower offshore environment (A/S >> 1). The general carbonate demise affecting the northern Aquitaine platform during the mid-Cenomanian can be explained by both a eustatic sea-level rise and the establishment of eutrophic conditions. The coincidence of the Mid-Cenomanian Event with both (1) the occurrence of mesotrophic to eutrophic conditions marked by carbonate producer turnover from pho-tozoan to heterozoan facies and (2) the transgressive cycles, suggests that eustatic sea-level rise leading to high trophic conditions could explain this positive d 13 C excursion in the Atlantic and western Tethyan domain. During the mid-Cenomanian, carbon cycle perturbations largely controlled the neritic biological communities on shallow carbonate platforms in a part of the western Tethyan domain.
... At the end of the Cenomanian stage, the generally deeper deposits are characterized by the lack of continental vertebrate remains within poorly diversified assemblages. The diversification of the ammonite fauna (Moreau et al., 1983) and the appearance of the shark genera Cretolamna and Ptychodus in Charentes during the late Cenomanian indicate a more open marine environment. At the scale of the whole stage, the palaeoenvironmental evolution of the vertebrate assemblages from the Cenomanian of Charentes displays a pattern similar to that observed within the Cenomanian-Turonian series of the Tafilalt basin (SE Morocco) . ...
Cenomanian paralic deposits of Charentes (southwestern France) have yielded abundant vertebrate microremains, including rather diversified continental taxa (e.g., frogs, turtles, crocodilians, dinosaurs, pterosaurs, lizards, and mammals). In this short report, the succession of faunal assemblages observed is briefly described in relation to palaeoenvironmental change resulting from the Cenomanian-early Turonian transgressive episode. Continental forms occur commonly in estuarine and shallow marine rocks of the lower part of the Cenomanian stage, but seem to be lacking in younger strata deposited in more open marine settings. Among an unexpected biodiversity, several non-marine groups (e.g., ziphodont crocodilians, carcharodontosaurid and troodontid dinosaurs, marsupial-like mammals) are recorded for the first time in the lower Upper Cretaceous of Europe, thus providing new palaeobiogeographical indications for this poorly documented part of the world.
Part 7 presents the stratigraphical results of the revision of the Ammonoidea of the Lower Chalk. Localities key to the establishment of the revised zonal and subzonal scheme are described and discussed. The limits of the Cenomanian Stage are reviewed, as is the global correlation of Cenomanian ammonite faunas.
The Cenomanian ammonitefaunas of the Munster Basin are systematically and stratigraphically revised. They comprise 75 species, referred to 33 genera. In addition to SCHLUTER's (1871-1876) type-material, the specimens figured by WIEDMANN AND SCHNEIDER (1979) and KAPLAN, KELLER AND WIEDMANN (1985) are redescribed and partially refigured. The ammonites occur in four different facies associations: the arenaceous glauconitic Essen-Greensand in the west, the red limestone pocket of Muhlheim-Broich within the Essen Greensand depositional area, the Planer limestone-facies in the east, and chalks in the north of the Munster basin. The ammonite occurrences are described in the context of biostratigraphy, of regional lithostratigraphy, sequence stratigraphy, and cyclostratigraphy. The ammonite zones recognized are closely comparable to those of the Anglo Paris basin, especially these of southern England. The bio- and event stratigraphic correlation with the Cenomanian of Poland, Mangyshlak and the Crimea is described and discussed.
The shell of an ammonoid is a kind of autobiography of the animal that once occupied it. Different parts of the shell tell different parts of the life history. The growth lines and the tiny intervals in between, along with the shape of the shell itself, record what was happening at the anterior end of the body. The septa and their sutures relate the tale of the other extremity.
The so called "Plenus event", characterized by occurrence of belemnite Praeactinocamax plenus, is stratigraphically situated into the Late Cenomanian (geslinianum Zone, G. bentonensis Subzone, W. archaeocretacea Zone) extensive eustatic transgressive cycle (similar to those in Early Turonian A nodosoides zone). The constant rise of sea level caused influx of cooler water masses from Arctica, and the new counter stream started circulate over Czech Massif. During the next eustasy, the surface of epicontinental sea inceased, and the bottom counter stream dissapeared Inside of the geslinianum zone, large hiatii are reported from Anglo-Paris Basin in the West through to Kazakhstan in the East. The Czech Massif was continually uplifted, however the Labe lineament and probable Bohemia-Bavarian channel showed a continuous ebb. The similar event has been recorded in the M. nodosoides zone including also the bottom counter stream, however without any belemnite incursion.
The position of the Cenomanian-Turonian boundary is established for the first time in Charente-Maritime, northwestern Aquitaine (France), on the basis of ammonite occurrences and the δ13C isotope curve, corresponding to Oceanic Anoxic Event 2, that straddles the boundary. The earliest Turonian ammonites recognised are a monospecific occurrence of the early early Turonian pseudotissotiine Bageites bakui Zaborski, 1998, previously known only from northern Nigeria. Newly collected material and well-preserved specimens from existing collections supplement previous records, and include species of Placenticeras, Morrowites, Kamerunoceras, Romaniceras (Romaniceras), Spathites (Jeanrogericeras), Mammites, Fagesia, Neoptychites, Choffaticeras (Leoniceras), Collignoniceras and Lecointriceras. These confirm the presence of the upper lower Turonian nodosoides Zone and the lower middle Turonian turoniense and kallesi zones/subzones of authors.
Eight new localities have been studied in the Gafsa area (South-Central Tunisia). These additional data allow to recognise a succession of 12 stratigraphical units in the Upper Cenomanian and the Lower Turonian. Some of these units (N. vibrayeanus [A], P. pseudonodosoides [E], V. gamai [F], P. flexuosum [H] et à M. nodosoides [L] faunal assemblages) are reproductible at a supra-regional scale including southern Tethys, Transsaharian sea and South Atlantic. They are correlated with the zonation of the Turonian GSSP. Moreover a new species Thomelites (?) numidicus nov. sp. is described.
The distribution of the northern Aquitaine Cenomanian echinoids has been analysed in detail in the outcrops of the Charente-Maritime (France), against the scale of the lithological and sequential units, within an interval corresponding to the transgressive part of a 2nd order facies cycle, with a resolution between 0.3 and 0.1 Ma. Within this half cycle, the faunal variations have been compared with the sequential evolution of the deposits (3rd order sequences, depositional sequences and parasequences, or genetic sequences and genetic units - 4th order and 5th order) and the deduced sea-level changes. This scale of investigations shows that diversity peaks are generally reached during the highest sea-levels, and mainly in rather deep inner shelf environments. The maximum flooding at the Cenomanian-Turonian boundary involves a sea-level too high for the settlement of several groups of echinoids and is marked by a very weak species-diversity. As far as faunal renewals are concerned, the major events generally take place at the base of the sequence, in the rather shallow inner shelf. During these main events, the disappearances become more and more dominant over appearances as the lithologic levels concerned get closer to the Cenomanian-Turonian boundary. The detailed analysis of the appearances structure allows us to distinguish three main steps: (1) Tethyan immigration during early and basal Middle Cenomanian; (2) in situ evolution of lineages already well settled in the South-West France area from Middle Cenomanian to basal late Cenomanian; (3) north-European immigration during late Cenomanian and then during the early Turonian. Moreover, important peaks of survival take place at the end of almost all sequences and underline faunal events that are not perfectly registered by appearances and disappearances, such as the important peak of survivals that takes place at the end of the Cenomanian and emphasises the Cenomanian-Turonian boundary. The changes in biodiversity of the Cenomanian echinoid faunas at the scale of 3rd to 5th order sequences are then compared to the variations of Jurassic echinoid biodiversity studied at the scale of 2nd to 3rd order cycles. The higher time resolution of the Cenomanian analysis gives more homogeneous results than the Jurassic echinoid studies, especially for the timing of the diversity and survival peaks and the appearances/disappearances ratio. The main differences in sharpness between the two approaches are attributed to both methodological and geological time averaging.
The type section of the Sanandinovo Formation between the villages of Sanandinovo and Novachene in northern Bulgaria has yielded numerous ammonites from packages 7-9 of the sequence recognised by previous authors. The assemblage is: Tetragonites subtimotheanus Wiedmann, 1962, Puzosia (Puzosia) mayoriana (D'Orbigny, 1841), Acanthoceras jukesbrownei (Spath, 1926), Protacanthoceras tuberculatum tuberculatum Thomel, 1972, Calycoceras (Newboldiceras) asiaticum asiaticum (Jimbo, 1894), C. (N.) asiaticum spinosum (Kossmat, 1897), C. (N.) planecostatum (Kossmat, 1897). Calycoceras (Proeucalycoceras) picted Wright & Kennedy, 1990, and Scaphites equalis J. Sowerby, 1813. The assemblage indicates the upper Middle Cenomanian Acanthoceras jukesbrownei Zone of Western Europe. We have seen no evidence for either older or younger Cenomanian ammonite zones from the sequence.
Neolobites vibrayeanus brancai ECK, Neolobites vibrayeanus (d'ORBIGNY) s.s. Coilopoceras gr. requienianum (d'ORBIGNY) and Coilopoceras aff. newelli BENA VIDES-CACERES have been collected in the Errachidia-Boudnib-Erfoud basin on the southern side of the Moroccan Central High Atlas. The range of these ammonites includes the lower part of the Upper Cenomanian up to the Upper Turonian. They are placed in their paleogeographical context. They have Tethyan (circum Mediterranean) affinities even if some Atlantic influences cannot be exclude.
Most ammonoids display a distinctly different morphology when they are adults or subadults. Depending on the taxon, these mature modifications may comprise changes in coiling, changes in ornamentation, and conspicuous changes of the terminal aperture. These mature modifications permit, at least when a combination of which occurs, to identify adult specimens. Co-occurrence of adult forms with differences in size, ornament strength, and aperture shape led already half a century ago to the conclusion that many ammonoids display dimorphism. The smaller forms are usually dubbed microconchs and the larger ones macroconchs. The degrees of differences between the antidimorphs vary and are more or less characteristic for certain clades. Such dimorphism is also known from Recent cephalopods. According to actualistic comparisons and considerations concerning reproductive biology of Recent cephalopods, it is commonly assumed that the microconchs represented the males and macroconchs the females. This hypothesis still needs verification from soft-tissue preservation.
Sequence stratigraphic analysis of the Aquitaine, Munster and Paris Basins has shown that many of the major discontinuities found can be traced with good biostratigraphic confidence between the basins, and through a variety of sedimentary, tectonic and palaeobiogeographic regimes. Up to five sequence boundaries appear to be synchronous between the basins when account is taken of the biostratigraphic shortcomings. An extra sequence boundary near the Lower-Middle Cenomanian boundary in the Munster Basin may be a tectonic disruption. Multiple transgressive surfaces are common in deeper water settings, and surfaces of maximum flooding are very poorly developed. -from Author
The Cenomanian formations of Charente-Maritime (France) contain an abundant and diverse fauna of echinoids. The stratigraphic distribution of species (about 60) is detailed and shown to be strongly correlated whith lithofacies. Occurrences and diversification of sea-urchins are strongly affected by the pattern of marine transgressions and regressions. A number of species are restricted to specific lithofacies and this is interpreted in terms of the species palaeoecology. Hemiaster, a genus present throughout the sequence, becomes more gibbous and develops shorter petals in finer grained sediments.
Fifty taxa of Late Cretaceous bivalves, collected between Saintes and Mirambeau during the construction of the A 10 motorway, have been identified. The pectinids, spondylids, limids and oysters are of better preservation and more diverse than the other groups. The faunas of Cenomanian age are from warm temperate to Tethyan seas. The assemblages collected from the Turonian-Coniacian strata are small and not diagnostic. Faunas of Santonian and Campanian age are diversified and the many Plagiostoma and Pycnodonte species indicate an upper shelf environment. These faunas have strong affinities with those from white chalks and other deposits from N.W. Europe. The fauna from the uppermost Campanian (equivalent to the top of the Aubeterre section, stratotype of the Campanian) indicates a much shallower environment and has many elements in common with the fauna from the Maastrichtian stratotype.RésuméParmi les Bivalves récoltés pendant la construction de l'autoroute A 10, entre Saintes et Mirambeau, 50 taxons ont pu t̂tre identifiés. Les Pectinidés, Spondylidés, Limidés et Ostrées sont mieux conservés et plus diversifiés que les autres groupes de Bivalves. Les faunes du Cénomanien indiquent une provenance de mer tempérée plutôt chaude ou mésogéenne. Les assemblages récoltés dans les dépôts turoniens et coniaciens sont pauvres en espèces. Les faunes du Santonien et du Campanien sont très diversifiées et la présence de plusieures espèces de Plagiostoma et de Pycnodonte indique un milieu “upper shelf”. Ces faunes ont beaucoup d'éléments en commun avec celles de la Craie blanche et autres dépôts de l'Europe du NO. Au contraire, la faune du Campanien le plus supérieur (équivalent du sommet de la coupe d'Aubeterre, stratotype du Campanien) représente un milieu peu profond et a beaucoup d'éléments faunistiques communs avec la faune du stratotype du Maastrichtien.
Temporary exposures of chalks spanning the Cenomanian - Turonian boundary to the east of Brionne, Eure, Haute- Normandie, France, yielded well-preserved ammonite faunas. The Metoicoceras geslinianum Zone assemblage is: Pseudocalycoceras angolaense (SPATH, 1931), Sumitomoceras cautisalbae (WRIGHT & KENNEDY, 1981), Calycoceras (Calycoceras) sp. juv., Eucalycoceras pentagonum (JUKES-BROWNE, 1896), Euomphaloceras septemseriatum (CRAGIN, 1893), Metoicoceras geslinianum (D'ORBIGNY, 1850), Hamites cimarronensis (KAUFFMAN & POWELL, 1977), Allocrioceras annulatum (SHUMARD, 1860), and Sciponoceras gracile (SHUMARD, 1860). The succeeding Neocardioceras juddii Zone assemblage is: Thomelites serotinus WRIGHT & KENNEDY, 1981, Neocardioceras juddii juddii (BARROIS & GUERNE, 1878), Neocardioceras juddii barroisi WRIGHT & KENNEDY, 1981, and Thomasites gongilensis (WOODS, 1911). Imprecisely localised are Pachydesmoceras sp., and Nigericeras aff. scotti COBBAN, 1972. The majority of the species are new for northern France, and confirm the northwards extension of typically Tethyan taxa (Thomasites, Nigericeras) into the Boreal region during the uppermost Cenomanian, and previously rec- ognized in southern England, as well as the occurrence of cosmopolitan acanthoceratids well-known at this level in the United States (Pseudocalycoceras, Sumitomoceras).
Our study is a paleontological revision of the ammonite faunas connected with the Sahara Cenomanian-Turonian transgression. It is also a refinement of the biostratigraphical framework in the sedimentary Iullemeden basin (Western and Southern Niger: Mt Iguelela and Damergou). About 700 well preserved ammonites have been collected from 8 outcrops (Berere, Tanout Aviation, Birgimari, Dan Dordo, Bakatchiraba in the Damergou and towards West Abalak, Korahane and Iguelela Mountains). It is possible to recognize, locally, nine horizons permitting the description of three new taxa. The Metoicoceras geslinianum (d’Orbigny) Nigericeras gadeni (Chudeau) association in particular allows an improved correlation with the N. gadeni (Chudeau) levels with North-Western Europe and also with the Western Interior and Texas - New Mexico (USA). In addition the presence of such ammonites as Cibolaites (?) africaensis nov. sp. or Coilopoceras inflatumCobban & Hook also allows acute correlations with USA. However authors admit that the ammonite faunas from Niger essentially have their affinities with the Tethyan realm and even some taxa such as Nigericeras gadeni (Chudeau) and Thomasites nigeriensis (Woods) are endemic in the Saharan countries of the Sahel (Algeria, Niger, Northeast Nigeria). Although the connection between the Tethys and the South Atlantic via the Benue trough is at the moment disputed by some authors for the Cenomanian - Turonian, the ammonite distributions lead to the conclusion of their livinghence sea-connection there. This connection began during the upper part of the Gadeni zone (Upper Cenomanian) and ended about the upper limit of the Nigeriensis zone (Uppermost Lower Turonian). This study also deals with ontogenetic and evolutionary analysis. On the one hand Nigericeras gadeni (Chudeau) - N. jacquetiSchneegans - N. jacqueti involutes nov. subsp. tend to lose their juvenile ornamentation by peramorphosis during their evolution and on the other hand, in Vascoceras (Paravascoceras) cauvini (Chudeau)-V. (P.) proprium (Reyment), the strong adult ornamentation seems to disapear by virtue of an opposite tendency: paedomorphosis. The general tendency shown by the Niger ammonite faunas, is to become smoother and to adopt simplified suture lines. It is probably a response to the extrinsic constraints (synergy of climatic, ecological and physiographical constraints) by development of quite different and perhaps more efficied morphologies for the group (channelling of morphological tendency) as a function of their intrinsic constraints (ontogenetic potential).
In the Middle East and Africa, the Cenomanian ammonite genus Neolobites occurs, partly in great abundance, in shallow marine shelf set-tings. The genus includes several species but it has remained uncertain to what extent these species reflect biospecies, chronospecies or mor-phological variants. Based on material from Jordan and Egypt, the morphological variation of Neolobites vibrayeanus is described and discussed. From the several species of Neolobites described in the literature, only N. vibrayeanus, N. fourtaui and N. peroni appear to deserve specific separation. Sedimentological and lithological data, notably the common occurrence in strata that were possibly deposited above storm wave base, suggest that Neolobites was able to inhabit shallow marine settings. In these settings, it seems to form a distinct assemblage with the nautiloid Angulithes. Although N. vibrayeanus shows morphological variability between distinct populations, local N. vibrayeanus assemblages seem to develop morphologically stable populations that show only a little morphological overlap with those of other areas. This may be the reason for the earlier taxonomic splitting. The occurrence in habitats in which other stratigraphically significant ammonites are often missing may be the reason for the previous poor dating of Neolobites assemblages.
The present study records eighteen clastic and carbonate microfacies associations within the Cretaceous sediments representing the Malha, Galala, and Adabiya Formations, which are exposed between Khashm El Galala and Wadi Qiseib areas along the eastern scarp of the Northern Galala Plateau. The lithofacies characters and the fossil content of the Malha Formation (Lower Cretaceous) suggest a probable extended shallow marine environment interrupted by moderate fluvial sedimentation with tectonic stability and moderate energy. The fine clastics and the faunal content of the lower part of the Galala Formation indicate shallow oscillating sea with much terreginous outlet in a transgressive phase with the beginning of the Cenomanian, while the limestones and dolostones of the rest of the Galala Formation and the Adabiya Formation suggest the progression of the sea during the Turonian. It was an open shelf of moderately deep warm marine conditions of low energy.Integration of the carbonate and the clastic facies analysis with the lithostratigraphic correlation of the Cretaceous sediments through the Southern and the Northern Galala Plateaux exhibited that the first Tethyan flooding had encroached the area through the Aptian-Albian. The second invasion occurred with the beginning of the Cenomanian and continued throughout the Late Cretaceous on the area of Southern Galala Plateau, which stayed in connection with the Tethys, while the area of Northern Galala Plateau, most probably, had emerged after the Turonian time or the younger Cretaceous ages till Middle Paleocene.
In this part of the revision of the ammonite faunas of the type Cenomanianwe deal with representatives of the genera Borissiakoceras, Austiniceras, Neolobites, Metengonoceras, Placenticeras, Hyphoplites, Schloenbachia, Stoliczkaia (Lamnayella), Stoliczkaia (Shumarinaia), Euhystrichoceras and Forbesiceras.
The distribution of rudists, hermatypic Scleractinia and the larger Foraminifera indicates that the approximate position of the North Temperate/Tethyan (Mesogean) Realm boundary in western France lay, during the Cenomanian, in the Poitou region. The Paris Basin lay to the north of this boundary whilst the Aquitaine Basin lay to the south. The faunal contrasts between these two areas have hindered biostratigraphic correlation across the Realm Boundary and have resulted in uncertainty concerning the relationship between the tripartite division of the Stage in Sarthe (the type area) and northern Aquitaine. Progress in correlation between the two Basins is reviewed and refined in the light of recent evidence. Large-scale (tens of metres) cyclicity associated with hardground development is described by the Paris and Aquitaine Basins and the existing biostratigraphy is shown to allow the correlation of major hardground horizons across the Realm boundary. Eustacy is postulated as the control mechanism responsible for the observed synchronicity of these levels of penecontemporaneous cementation.
The Engonoceratidae may well have originated on the shallow marine carbonate platforms of the southern margin of the Mediterranean Province of the Tethyan Realm during the earliest Albian (?latest Aptian). In the entire Tethyan Realm and beyond adaptive radiation of the group was rapid and successful during the early Albian as indicated by endemic centres in the Peruvian Basin and the Western Interior Sea (USA). Later the group successfully enlarged its distribution, and invaded some provinces (Mowry Sea, Canada) of the Boreal Realm. The mode of life of engonoceratids seems to have been nektoplanktonic, epipelagic, and stenohaline, restricted to shallow water and platform or in some cases extremely shallow (littoral and lagoonal) facies which may have helped their radiation. The group is distinctive and consists of nine genera and up to a hundred species, although its origin is still obscure. Their appearance may have been triggered by the oceanic anoxic event (OAE 1b) and their rapid rise may have been helped by their shallow water mode of life and the global mid-Cretaceous warming and rise in sea level. The fall of the engonoceratids coincides with the end-Cenomanian rapid transgression, which may have changed their shallow water habitats. Today the group is considered to have been a successful colonizer, a reliable stratigraphical indicator for shallow marine environments and a pioneer taxon for recognition of transgressive phases.Based on new material and sutural analysis, Engonoceras duboisi is revised and assigned to Parengonoceras. A set of features consisting of a simplified ceratitid suture, lanceolate and compressed oxycone shell together comprising a shallow marine ecotype is pointed out as a successful and repeated morphotype among Mesozoic Ammonoidea, for it was repeated three times during ammonoid evolution.
The boundary between Cenomanian and Turonian (upper Cretaceous) beds in the upper basin of the Esteron river (Alpes-Maritimes, France) is defined on the basis of ammonites and pelagic foraminifera. The rich faunas of these beds are especially important because Cenomanian and Turonian beds in southeastern France are normally very poor in fossils.
Ce travail est une mise au point relative à la présentation du cadre stratigraphique, plus particulièrement en Charente-Maritime où la transgression était depuis longtemps considérée comme Cénomanien supérieur et à la comparaison de la répartition des espèces entre la Provence et la Charente-Maritime.
The ammonite fauna of the Plenus Marls and Middle Chalk (Upper Cenomanian and Turonian) is described; it comprises 49 species and subspecies (8 new), referred to 27 genera. These provide a basis for revision of the ammonite zonation of the Upper Cenomanian and Turonian of Great Britain and correlation with the sequences in the Paris Basin and the stratotype areas in Sarthe and Touraine. It is demonstrated that the Cenomanian—Turonian boundary is best taken between the Neocardioceras juddii Zone below and the Watinoccras coloradoense Zone above.
This paper forms the first part of a revision of the ammonite faunas of the Cenomanian stratotype in the environs of Le Mans, Sarthe, France. The history of research on ammonites in the area is briefly noted, as is the lithostratigraphy. The systematics of the heteromorph ammonites (Ancyloceratina) is described, and the following taxa documented: Hamites simplex d'Orbigny, Sciponoceras baculoides (Mantell), Sciponoceras gracile (Shumard), Anisoceras plicatile (J. Sowerby), A. aff. plicatile, Idiohamites alternatus vectensis Spath, I. ellipticus radiatus Spath, Hypoturrilites gravesianus (d'Orbigny), H. tuberculatus (Bosc), H. mantelli (Sharpe), H. sp., Neostlingoceras carcitanense (Matheron), N. aff. carcitanense, Turrilites costatus Lamarck, T. acutus Passy, T. scheuchzerianus (Bosc), T. boerssumensis Schlüter, Mariella dorsetensis (Spath), M. cenomanensis (Schlüter), M. group of cenomanensis (Schlüter)-lewesiensis (Spath), M. spp., M. (Plesioturrilites) sp., Scaphites equalis J. Sowerby, S. obliquus J. Sowerby, S.(?) sp., and S. sp. juv.
1. Historical Introduction.
The object of this paper is to compare the beds which form the lower part of the Upper Cretaceous series in those parts of Western France and Western England , which are nearest to one another. In England these beds are known by the names of Gault, Upper Greensand, and Lower Chalk; in France they are classed under d‘Orbigny‘s ‘Albien’ and ‘Cénomanien’ stages. It is well known that in both countries the deposits referable to these groups change their lithological character so greatly, in passing towards the west and south-west, that different observers have formed different opinions in their attempts to correlate one area with another. Further, no geologist has yet endeavoured to make a careful comparison of the French and English types; but it is only by such a comparison that the true stratigraphical position of d‘Orbigny‘s, Cénomanien stage can be determined, and that the limits of this stage in areas outside the typical Cénomanien district can be fixed.
The name ‘Cénomanien’ was introduced by d‘Orbigny in 1847 to designate the lower part of the series which he had previously called ‘Turonien,’ when he found that this lower portion contained a fauna, essentially distinct from that of the upper part. He then proposed to retain the name ‘Turonien’ for the upper part, and to adopt the name ‘Cénomanien’ for the lower part, taking the name from Le Mans, in the Sarthe, the Cenomanum of the Romans,and regarding that district as the typical area of his new
The Lower Chalk of south-eastern England is a richly fossiliferous sequence 54-104 m. thick, spanning most of the Cenomanian Stage. It rests with a slight break or without interruption on Upper Albian dispar-perinflatum Sub-zone sediments of Gault or Upper Greensand facies. The upper limit as here adopted is marked by a slight break at the base of the Cenomanian-Turonian plenus Marls (Metoicoceras gourdoni Zone), the sub-plenus erosion surface of Jefferies (1962, 1963). Of the many groups of fossils present, the ammonites provide the most useful means of subdivision and correlation. The distribution of these, and of other originally aragonitic fossils, is largely controlled by preservation, and there are levels at which there is evidence of seafloor dissolution of aragonite. Nevertheless, three ammonite zones can be recognised:3.Zone of Calycoceras naviculare2.Zone of Acanthoceras rhotomagense1.Zone of Mantelliceras mantelliWithin the M. mantelli Zone three assemblages are identified, characterised by: (a) Hypoturrilites carcitanensis, (b) Mantelliceras saxbii, (c) Mantelliceras gr. dixoni. There are also three assemblages in the Zone of A. rhotomagense, characterised by: (a) Turrilites costatus, (b) Turrilites acutus, (c) Acanthoceras jukes-brownei. The C. naviculare Zone is not subdivided.These zones are comparable to those proposed by Hancock (1959) for the type Cenomanian, and are equivalent to the Lower, Middle and Upper parts of the Stage. Bivalves, corals and brachiopods also have a use in correlation, and even fragments of the commonest fossils—Inoceramus and Holaster—are of local use.
Ammonite faunas consisting of Neolobites vibrayeanus (d'Orbigny), Calycoceras (Calycoceras) naviculare (Mantell), C. (Lotzeites(?)) sp., Pseudocalycoceras lattense Thomel, Metoicoceras geslinianum (d'Orbigny) and Euomphaloceras septemseriatum (Cragin) from Saumur, within the type area of the Turonian stage, are described from the collections of the Château de Saumur. They allow the recognition of two Upper Cenomanian horizons at Saumur, the one equivalent to the Sciponoceras gracile/Metoicoceras geslinianum Zone as developed in the Sables à Catopygus obtusus/Sables de Bousse of the Cenomanian stratotype; the other, older assemblage equates with the Calycoceras naviculare/Eucalycoceras pentagonum Zone fauna known from the Marnes à Ostracées of the type Cenomanian. From lithological comparisons it is suggested that this area is the source of the types of both Metoicoceras geslinianum and Neolobites vibrayeanus, which are redescribed.
Thesis (Ph. D.)--University of Kansas, Geology, 1931. Includes bibliographical references.
Carte Gdologique de France 3 1[50,000. Saumur, xvi-23 el Notice Explicative
- G B R G M Alcayd
- F Am6dro
- A Bidar
- R Damotte
- Manivit
- It
- F Robaszynski
- J Somay
Alcayd6, G. 1970. Carte Gdologique de France 3 1[50,000. Saumur, xvi-23 el Notice Explicative. Orl6ans: B.R.G.M. Am6dro, F., Bidar, A., Damotte, R., Manivit, It., Robaszynski, F. & Somay, J. 1978. ~chelles biostratigraphiques dans le Turonien du Cap Blanc Nez (Pas-de-Calals, F.). Bulletin d'ln[orma-tlon des Gdologues du Bassin de Paris 15, 3-20.