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Palaeogeographical map of the Early Cretaceous, 120 Ma, modified after Scotese (2016) and Copestake et al. (2003). The climatic belts were modified after Chumakov et al. (1995) and Hay and Floegel (2012). D = Danish basin, Denmark (this study), I = Isle of Wight, England (Ruffell and Worden, 2000), P = Paris Basin, France (Deconinck et al., 2021), V = Vocontian basin, France (Stein et al., 2012), Maestrat Basin, Spain (Cors et al., 2015), B = Bir Oum Ali, Tunisia (Godet et al., 2014).
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The understanding of the climatic evolution during the Early Cretaceous in general, and across Oceanic Anoxic Event 1a (OAE-1a) in particular, has generally been derived from Tethyan localities, implying large uncertainties about their significance at a global scale. In this study, high-resolution clay-mineral assemblage analyses have been performe...
Citations
... For location of the Dareh Sefid section see Fig. 1. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.) Blok et al., 2022). ...
The biotic, environmental, climatic, oceanic, and sea-level perturbations during the Early Aptian oceanic anoxic event (OAE) 1a have been extensively documented from both deep- and shallow-marine deposits worldwide. However, there has been relatively little comparative assessment of the simultaneous interplay among organic carbon burial, redox conditions, terrigenous output, and productivity, leading to a lack of precise constraints on these relationships. Here, we use analyses of stable carbon isotopes (δ13Corg, δ13Ccarb, and Δ13C), total organic carbon (TOC), detrital proxies (Al, Si, Ti, K), redox-sensitive (RSTE: U, V, Mo) and productive-sensitive (PSTE: P, Cu, Ni) trace elements from a continuous, predominantly carbonate succession of the Kazhdumi Intrashelf Basin to evaluate the culprits for the OAE1a-associated changes in bottom-water oxygenation, organic-rich layer formation, and biotic shifts along the Arabian margin of the Neo-Tethys. Concentrations of Al-normalized RSTE and TOC values indicate that the bottom-water conditions ranged from oxic prior to and at the onset of the OAE 1a (carbon-isotope segments C2 to basalmost C4 sensu Menegatti et al., 1998), to anoxic-suboxic but not euxinic (Mo < 25 ppm) during the lower C4 through C5 + C6 segments, and then returned to oxic-suboxic in the remaining C5 + C6 segment. The increase in Al-normalized PSTE coupled with TOC concentrations in the basal C4 is coeval with a change from predominantly orbitolinid-ostreid to planktic foraminifera-radiolarian biota. The periodically high productivity, driven both by the surface-water productivity as well as by phosphorus recycling from the sediments, continued through the C5 + C6 segments as evidenced by matching Si/Al and PSTE peaks (Cu/Al and Ni/Al). The study sheds new light on the causes of variations in bottom-water deoxygenation, organic content, nutrient availability, and biotic shifts in semi-restricted, relatively deep (>100 m), continental-margin basins during major oceanic perturbations.
... Notably, the FSM corresponds to the globally recorded carbon-cycle crisis of the early Aptian Oceanic Anoxic Event 1a (OAE-1a; e.g. Schlanger and Jenkyns 1976;Arthur et al. 1990;Malkočet al. 2010;Mutterlose and Bottini 2013;Haq 2014;Mutterlose et al. 2014;Blok et al. 2022). ...
... A multidisciplinary effort to improve the understanding of the Tuxen and Sola Formations, primarily in the Valdemar and Adda Fields, has recently been undertaken. This initiative includes studies on the sedimentology and stratigraphy (Ineson et al. 2022a, b;Jelby et al. 2022;Sheldon et al. 2022), geochemistry and climate (Blok et al. 2022(Blok et al. , 2023, and structural geology (Glad et al. 2022;Lorentzen et al. 2022), supplemented by a palaeoecological study of time-equivalent (Hauterivian-Aptian) carbonates in the Danish Basin (Lauridsen et al. 2022). ...
... This oceanographic shift is believed to have occurred in response to the transgression associated with the OAE-1a (e.g. Malkočet al. 2010;Mutterlose and Bottini 2013;Mutterlose et al. 2014;Blok et al. 2022). ...
The Lower Cretaceous (upper Hauterivian - Albian) pelagic and hemipelagic carbonates of the Tuxen and Sola Formations in the Danish Central Graben, North Sea, constitute one of the oldest chalk successions recorded globally, but have received less attention than the Upper Cretaceous - Danian Chalk Group. This paper presents an updated depositional model for the succession drawn from synthesis of the latest published sedimentological and stratigraphic results and correlation of 11 wells in the Valdemar, Boje, Adda and Tyra Fields. Four depositional sequences, deposited on a relatively deep subphotic shelf, record c. 20 Myr of transgressive-regressive cycles, including: (i) late Hauterivian - earliest Barremian highstand and differential subsidence, resulting in aggradation across a westward-dipping ramp; (ii) early Barremian eastern (Adda Field) inversion causing plateau condensation, sediment bypass and sourcing of gravity flows, followed by lowstand-controlled basin isolation and associated anoxia (Munk Marl Bed), and finally late Barremian tectonic quiescence and highstand with deposition of clean reservoir chalk; (iii) latest Barremian lowstand causing filling of local depocentres, interrupted by early Aptian transgression-controlled anoxia during the global Oceanic Anoxic Event 1a (Fischschiefer Member), and finally late Aptian highstand; and (iv) latest Aptian - earliest Albian lowstand causing local erosion and heightened influx of clay.
... As the subsidence rates increased during the late Kimmeridgian, and more accommodation space was created, the DCG was filled with the organic-rich marine mudstones of the Lola and Farsund Formations (Ponsaing et al. 2020). However, subsidence was less pronounced on the complexly faulted Heno Plateau, especially in the north shallow-marine sandstones might indicate that the water depths were shallower than in the rest The Lower Cretaceous succession in the Danish Central Graben (DCG) has been studied to better understand the tectonic (Vejbaek 1986;Japsen et al. 2003;van Buchem et al. 2017), palaeoecological (Jeremiah 2001;Mutterlose & Bottini 2013), palaeoceanographic (Mutterlose & Böckel 1998) and palaeoclimatic (Chenot et al. 2018;Blok et al. 2022) basin evolution. The succession is characterised by alternating marlstone and chalk, composed of pelagic calcareous nannofossils, micritic grains and hemipelagic detrital material (Ineson 1993). ...
... The succession is characterised by alternating marlstone and chalk, composed of pelagic calcareous nannofossils, micritic grains and hemipelagic detrital material (Ineson 1993). A systematic study of the carbonate facies has recently been conducted (Jelby et al. 2022). However, the exact geographic origin of the detrital material, specifically of the clay minerals that were transported into the DCG, remains largely unknown. ...
... If these structural highs contain sandstones with diagenetic kaolinite or are rich in feldspars, kaolinite would potentially have washed out into the basin (Exley 1976;Chamley 1989;Lanson et al. 2002). The gradual differences between amounts of kaolinite in the two newly studied wells and the North Jens-1 well (Blok et al. 2022) are used to determine the main source area. ...
The alternating marlstone and chalk of the Lower Cretaceous succession in the Danish Central Graben (DCG) are important for the understanding of the evolution of the larger North Sea Basin. This study focusses on the clay mineral assemblages of the upper Hauterivian – lower Aptian in the DCG and Danish Basin (DB) and their implications. Clay mineral assemblages are predominantly used to assess palaeoclimate. In this study, however, they were additionally used in a source-to-sink context. Kaolinite was found to form a dominant component of the clay mineral assemblage in the sampled wells of the DCG and in the DB, suggesting that a feldspar- or kaolinite-rich source was present and actively eroded in the region during the Early Cretaceous. Moreover, a decreasing gradient west to east of average kaolinite content is observed in the three studied wells for the early Hauterivian to late Barremian (BC9-BC17), with the highest content observed in the North Jens-1 well (av. 74%), followed by the Boje-2C well (av. 49%) and lastly in the Vinding-1 well (av. 39%). Due to the relatively rapid settling of kaolinite in marine environments compared to other clay minerals, this gradient suggests that the main clay mineral source was located in the south-western part of the DCG. Isochore maps, a new palaeogeographic map of the DCG and the western part of the German sector of the North Sea illustrates where Lower Cretaceous rocks are absent in this region, due to either erosion or non-deposition. Potential subaerially exposed highs included the distant Baltic Shield to the north, the Ringkøbing–Fyn High to the east and the Heno Plateau within the DCG, with the latter being located closest to the North Jens-1 well and containing feldspar-rich sandstones of the Heno Formation (upper Kimmeridgian – lowermost Volgian/Tithonian). During the Early Cretaceous, part of the Heno Formation was potentially subaerially exposed or subject to wave reworking/erosion in parts of the Danish and German sectors. The sandstones could weather into kaolinite and this structural high is therefore suggested to have been the main source area for this part of the DCG, with minor sediment influxes from the Ringkøbing–Fyn High and Baltic Shield. In addition, the overall decrease in kaolinite in the DCG from the late Hauterivian to the late Barremian indicates a climatic change towards drier conditions, with some minor, slightly more humid periods.
... marls and limestones that deposited along the Iberian continental margin (TOC in segments C2-C6 ranges between 0 and 6%; Charbonnier et al., 2018), the epicontinental Ionian Basin deposits (TOC also range between 0 and 6%; Karakitsios, 1995), or from other coeval intrashelf or deep-pelagic basinal sections worldwide , and references therein). It is important to note, that the organic-rich deposits were geographically restricted and characterized by a diachronous occurrence between different basins and carbonate platforms (e.g., Huck et al., 2010;Föllmi, 2012;Husinec et al., 2012;Mutterlose et al., 2014;Blok et al., 2022). ...
This study reports the first high‐resolution, integrated facies analysis of the lowermost Albian Pietraroja Lagerstätten (Apennine Carbonate Platform) which yields the first dinosaur ( Scipionyx samniticus ) found in Italy and other terrestrial vertebrates and plants. Aiming to clarify the long‐debated palaeoenvironmental significance of the Pietraroja succession, the following have been carried out: (i) a field survey to establish stratigraphic position and number of the fossil Lagerstätten; (ii) the centimetre‐scale facies analysis of a new section, ca 15 m‐thick, consisting of two new lithostratigraphic units, the ‘Cyclically organized Limestones’ and the ‘Cherty Limestones’ ; (iii) the scanning electron microscopy – energy dispersive X‐ray spectroscopy and backscattered electron – energy dispersive X‐ray spectroscopy analyses of clay mineral proxies for palaeoclimate and non‐carbonate grains; and (iv) the regional and supra‐regional investigation of the event stratigraphical context of the fossil Lagerstätten, in order to elucidate the controls on their formation. The section includes two out of the three observed fossil‐rich Lagerstätten, each up to 1.5 m‐thick. The arrangement of lithofacies and early diagenetic overprint defines shallow‐water depositional cycles suggestive of precession and short‐eccentricity periodicities. The Middle Lagerstätte yielding Scipionyx samniticus consists of three intervals. The lower, paralic interval was deposited during arid conditions and passes gradually to the plant‐rich, coastal wetland carbonaceous marls of the upper interval. The ‘ Cherty Limestones’ , yielding the Upper Lagerstätte with terrestrial vertebrates, contains two spiculitic intervals suggesting the development of siliceous sponge meadows in a shallow, restricted lagoon. Genetic stratigraphy suggests that the Pietraroja Lagerstätten were formed during glacioeustatic lowstands; interestingly, the Middle Lagerstätte mirrors the earliest Albian sea‐level lowstand (KAl1 event, ca 111.2 Myr), during a semi‐continuous supply of windblown volcaniclastics. Findings herein substantiate the pivotal role of paralic‐continental Lagerstätten for deriving high‐frequency palaeoclimatic dynamics and glacioeustacy from carbonate platform archives. The origin of Tethyan continental bridges between Africa and Europe during the late Aptian–earliest Albian cold interval is discussed.
The Pliensbachian/Toarcian boundary (Pl/To) event precedes by ca. 1 Myr the onset of the Toarcian Oceanic Anoxic Event. It corresponds to a second order mass extinction associated with an outstanding collapse of shallow marine ecosystems at global scale. Yet, our knowledge about its exact driver(s) and unfolding is relatively ambiguous due to the numerous hiatuses present in the sedimentary record during this critical time interval. In this study, an integrated carbon isotope chemostratigraphy and sequence stratigraphy approach is applied to two case studies (the upper Pliensbachian in South-East France and the Pliensbachian–Toarcian transition in Morocco) to demonstrate how the major changes in sea-level and sedimentation supply accompanying the Pl/To event led to the formation of ubiquitous, often cryptic hiatal surfaces in the sedimentary record. Hence, as a consequence of strongly progradational stacking pattern during the latest Pliensbachian related to a global sea-level lowstand associated with cold greenhouse climate, proximal settings were characterized by bypass and/or erosion, inducing an incomplete record of the Spinatum chronozone in localities situated in the outer part of sedimentary basins. In the earliest Toarcian, the collapse of the neritic carbonate factory led to a halt of carbonate mud export into the basin, resulting in sediment starvation in most basins characterized by a carbonate-dominated sedimentation regime before the environmental perturbation. Only localities where vigorous siliciclastic sediment supply took over are likely to have a more complete sedimentary record of the immediate aftermath of the carbonate production collapse. This combination of causes explains the ubiquitous incompleteness of the record of the Pliensbachian/Toarcian transition in numerous European localities where the bulk of our current understanding about the Pl/To event derives from. A comparison between the two known most expanded and complete records of the Pliensbachian–Toarcian transition of the Llanbedr (Mochras Farm) core in Wales and Bou Oumardoul n'Imazighn section in Morocco shows that the onset of the environmental perturbations is associated with a positive carbon isotope excursion spanning the Pliensbachian/Toarcian boundary. This is followed by a negative carbon isotope excursion during the earliest Toarcian that coincides with the global collapse of neritic carbonate factory and an ample sea-level fall.
An integrated seismic-stratigraphic study of the Lower Cretaceous Cromer Knoll Group was undertaken as part of a recent comprehensive analysis of the Upper Jurassic-lowermost Cretaceous petroleum system in the Danish Central Graben. This study of the basal group of the post-rift package yielded an updated regional assessment of the distribution of the Valhall, Tuxen, Sola and Rødby Formations. This is documented by four high resolution isochore maps (presented here) that record temporal shifts in subsidence patterns from the latest Ryazanian to the earliest Cenomanian. The distribution and thickness variation of the mud-dominated Valhall Formation (latest Ryazanian-early Hauterivian) at the base of the group attests to the progressive fill of inherited syn-rift morphology. The dominant depositional theme is thus ponding in, and onlap from, the main inherited depocentres, although growth faults and incipient inversion locally controlled stratigraphic architecture, and new depocentres were initiated in the east of the graben (Ål and Outer Rough Basins). The isochores for the succeeding, increasingly chalk-rich Tuxen, Sola and Rødby Formations (Hauterivian-earliest Cenomanian) document the regional weakening of syn-rift patterns but emphasize the shift in sedimentation patterns controlled by accelerating inversion activity in the east (Adda-Tyra area, Søgne Basin) and increased local subsidence. The latter sometimes coincided with syn-rift depo-centres, such as the Roar Basin and the Arne-Elin Graben, but was also significant in the new Early Cretaceous depocentres in the west of the graben, particularly the Outer Rough Basin. The evolution of the Early Cretaceous basin recorded by this dataset reveals significant shifts in the subsidence pattern in the late Valanginian-early Hauterivian, in large part due to early inversion in the east, and during the late Aptian-early Albian when subsidence was focussed in central and western sub-basins, probably locally due to salt withdrawal. These events, in combination with sea-level change, had implications for the accumulation and preservation of Barremian and early Aptian reservoir chalks.
An integrated seismic–stratigraphic study of the Lower Cretaceous Cromer Knoll Group was undertaken as part of a recent comprehensive analysis of the Upper Jurassic – lowermost Cretaceous petroleum system in the Danish Central Graben. This study of the basal group of the post-rift package yielded an updated regional assessment of the distribution of the Valhall, Tuxen, Sola and Rødby Formations. This is documented by four high resolution isochore maps (presented here) that record temporal shifts in subsidence patterns from the latest Ryazanian to the earliest Cenomanian. The distribution and thickness variation of the mud-dominated Valhall Formation (latest Ryazanian – early Hauterivian) at the base of the group attests to the progressive fill of inherited syn-rift morphology. The dominant depositional theme is thus ponding in, and onlap from, the main inherited depocentres, although growth faults and incipient inversion locally controlled stratigraphic architecture, and new depocentres were initiated in the east of the graben (Ål and Outer Rough Basins). The isochores for the succeeding, increasingly chalk-rich Tuxen, Sola and Rødby Formations (Hauterivian – earliest Cenomanian) document the regional weakening of syn-rift patterns but emphasize the shift in sedimentation patterns controlled by accelerating inversion activity in the east (Adda–Tyra area, Søgne Basin) and increased local subsidence. The latter sometimes coincided with syn-rift depocentres, such as the Roar Basin and the Arne-Elin Graben, but was also significant in the new Early Cretaceous depocentres in the west of the graben, particularly the Outer Rough Basin. The evolution of the Early Cretaceous basin recorded by this dataset reveals significant shifts in the subsidence pattern in the late Valanginian – early Hauterivian, in large part due to early inversion in the east, and during the late Aptian – early Albian when subsidence was focussed in central and western sub-basins, probably locally due to salt withdrawal. These events, in combination with sea-level change, had implications for the accumulation and preservation of Barremian and early Aptian reservoir chalks.
The Lower Cretaceous Tuxen (lower Hauterivian - upper Barremian) and Sola (upper Barremian - Albian) Formations in the Danish Central Graben (North Sea) constitute one of the oldest chalk successions recorded globally, but have received little attention with regards to sedimentary facies and depositional processes. This study presents the first comprehensive carbonate facies analysis of the succession, retrieved from seven drill cores from the Valdemar and Adda Fields. A total of 50 facies are identified , based on a continuum of six lithologies ranging from chalk to marlstone and tuffaceous siltstone to sandstone that display eight different sedimentary structures or fabrics, and two redox-associated lithological color variations (green and red) in the Adda Field. The eight sedimentary structures record: (i) comprehensive bioturbation of homogeneous sediment during fully oxygenated benthic conditions and low sedimentation rates; (ii) a similar bioturbation process but in heterogeneous sediment with lithological contrasts permitting visible burrows to form, perhaps due to rhythmic alternation between pelagic (clay-poor) and hemipelagic (clay-rich) sedimentation; (iii) pelagic to hemipelagic suspension settling in dysoxic to anoxic bottom-water conditions; (iv) patchy cementation of the shallow sea bed during incipient hardground formation; (v) reworking of bioclasts and chalk intraclasts by bottom or wave-induced currents and cohesive debris flows; (vi) pressure solution during late burial diagenesis; (vii) shear deformation by intense plastic deformation of unlithified sediment from limited lateral displacement; and (viii) silicification during burial diagenesis. The facies distribution indicates that active tectonism took place prior to the onset of anoxia that resulted in deposition of the Munk Marl Bed, which in the Valdemar Field was followed by tectonic waning and repeated anoxia. The Valdemar Field constituted a basinal depocenter and was flanked to the east by an early inversion high in the Adda Field characterized by condensation and bypass. The Fischschiefer Member represents a return to prevailing anoxia, consistent with global records of the early Aptian Oceanic Anoxic Event 1a (OAE-1a).
