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24 pages, 7181 KiB

Open AccessArticle

Stratigraphic Modelling of the Lower/Middle Oxfordian (Upper Jurassic) Outer Ramp Deposits from the NE Paris Basin (France)

by Chloé Morales, Pierre Pellenard, Benoit Vincent, Franck Smektala, Fleur Daniau and Philippe Landrein

Geosciences 2022, 12(10), 375; https://0-doi-org.brum.beds.ac.uk/10.3390/geosciences12100375 - 10 Oct 2022

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Abstract

We investigate herein the lateral and vertical lithological heterogeneities of the Lower/Middle Oxfordian deposits (“Terrain à Chailles” and “Marnes des Eparges” formations) in the north-eastern Paris Basin. This new detailed stratigraphic framework documents the evolution at high resolution of an outer ramp based [...] Read more.

We investigate herein the lateral and vertical lithological heterogeneities of the Lower/Middle Oxfordian deposits (“Terrain à Chailles” and “Marnes des Eparges” formations) in the north-eastern Paris Basin. This new detailed stratigraphic framework documents the evolution at high resolution of an outer ramp based on regional correlations in order to constrain the evolution of petrological properties between the clayey “Argiles de la Woëvre” Formation and the more calcareous “Marnes et Calcaires à Coraux de Foug Formation. The “Argiles de la Woëvre” Formation is targeted for the deep storage of nuclear waste in north-eastern France. Nine wells are correlated over the “Zone of Interest for Further Research” (ZIRA), defined by the French agency for radioactive waste management (Andra), with a resolution of 0.5–1.0 m. The architecture and the age control of these formations have been refined, revealing that the “Terrain à Chailles” Formation is characterised by a regular slightly inclined sedimentation gently deeping in the SW direction and shows a lithological evolution from silty claystones to an increased occurrence of its calcareous content towards the top (Lower Oxfordian, uppermost mariae and cordatum ammonite zones). The above “Marnes des Eparges” Formation, characterised by claystone limestone alternations, is assigned to the Middle Oxfordian (plicatilis ammonite zone), deposited during a slightly enhanced subsidence phase in the SE part of the basin and documented and associated with onlaps geometries on the more proximal areas. However, this change in geometry does not affect petrological properties over ZIRA, as this is not accompanied by lithological changes. The environmental factors controlling petrological heterogeneities over ZIRA are also discussed. The stepwise increase in the carbonate content and the decrease in the detrital content towards the Lower to Middle Oxfordian deposits was likely triggered by a climate change towards drier conditions, modulated by sea level changes on a ramp morphology. A major condensation phase encompassing most of the Lower Oxfordian cordatum ammonite zone is also highlighted. The occurrence of a maximum regressive surface associated with gentle slope topography is a probable trigger for condensation. Changes in geometries are, however, associated with the activity of the Metz Fault, which potentially had an influence on the subsidence rates of the basin at that time. Full article

(This article belongs to the Special Issue Jurassic Paleoenvironments)

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29 pages, 6319 KiB

Open AccessArticle

Evaluating the Existence of Vertebrate Deadfall Communities from the Early Jurassic Posidonienschiefer Formation

by Erin E. Maxwell, Samuel L. A. Cooper, Eudald Mujal, Feiko Miedema, Giovanni Serafini and Günter Schweigert

Geosciences 2022, 12(4), 158; https://0-doi-org.brum.beds.ac.uk/10.3390/geosciences12040158 - 01 Apr 2022

Cited by 9 | Viewed by 3778

Abstract

Large vertebrate carcasses contain significant amounts of nutrients that upon death are transferred from the water column to the benthos, enriching the immediate environment. The organisms exploiting these ephemeral resources vary as the carcass decays, creating an ecological succession: mobile scavengers arrive first, [...] Read more.

Large vertebrate carcasses contain significant amounts of nutrients that upon death are transferred from the water column to the benthos, enriching the immediate environment. The organisms exploiting these ephemeral resources vary as the carcass decays, creating an ecological succession: mobile scavengers arrive first, followed by enrichment opportunists, sulfophilic taxa, and lastly reef species encrusting the exposed bones. Such communities have been postulated to subsist on the carcasses of Mesozoic marine vertebrates, but are rarely documented in the Jurassic. In particular, these communities are virtually unknown from the Early Jurassic, despite the occurrence of several productive fossil Lagerstätte that have produced thousands of vertebrate bones and skeletons. We review published occurrences and present new findings related to the development of deadfall communities in the Toarcian Posidonienschiefer Formation of southwestern Germany, focusing on the classic locality of Holzmaden. We report the presence of the mobile scavenger, enrichment opportunist, and reef stages, and found potential evidence for the poorly documented sulfophilic stage. Although rare in the Posidonienschiefer Formation, such communities do occur in association with exceptionally preserved vertebrate specimens, complementing a growing body of evidence that a temporarily oxygenated benthic environment does not preclude exceptional vertebrate fossil preservation. Full article

(This article belongs to the Special Issue Jurassic Paleoenvironments)

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21 pages, 37109 KiB

Open AccessArticle

Early Jurassic–Early Cretaceous Calcareous Nannofossil Biostratigraphy and Geochemistry, Northeastern Iraqi Kurdistan: Implications for Paleoclimate and Paleoecological Conditions

by Nagham Omar, Tom McCann, Ali I. Al-Juboury, Maria A. Ustinova and Arkan O. Sharezwri

Geosciences 2022, 12(2), 94; https://0-doi-org.brum.beds.ac.uk/10.3390/geosciences12020094 - 17 Feb 2022

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Abstract

Early Jurassic- to Early Cretaceous-age calcareous nannofossils from the Sarki, Sehkanyian, Sargelu, Naokelekan, Barsarin and Chia Gara formations are investigated for the first time from the Warte area, northeastern Iraqi Kurdistan. A range of isotopic and inorganic geochemical analyses are carried out in [...] Read more.

Early Jurassic- to Early Cretaceous-age calcareous nannofossils from the Sarki, Sehkanyian, Sargelu, Naokelekan, Barsarin and Chia Gara formations are investigated for the first time from the Warte area, northeastern Iraqi Kurdistan. A range of isotopic and inorganic geochemical analyses are carried out in order to reconstruct the paleoecological and paleoclimatic conditions during which the Sarki, Sehkanyian, Sargelu, Naokelekan, Barsarin and Chia Gara formations were deposited. The age of the Sargelu Formation was determined as Bajocian–Callovian based on the first occurrence of Cyclagelosphaera margerelii, Watznaueria britannica, W. fossacincta, W. manivitiae, Watznaueria barnesiae and Watznaueria ovata. Geochemical proxies (Sr, Ca, Al, Rb/Sr, Sr/Cu and Sr/Ba) for paleoclimate and paleoecological conditions, along with oxygen isotopes (δ¹⁸O) data, suggest that warm and arid climatic conditions were predominant during the Early Jurassic–Early Cretaceous period. Full article

(This article belongs to the Special Issue Jurassic Paleoenvironments)

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17 pages, 3381 KiB

Open AccessArticle

Ostracod Response to a Major Middle Jurassic Sea-Level Fall: A Case Study from Southern Tunisia (North Gondwana) with Implications on Regional Stratigraphy and Palaeoenvironmental Reconstruction

by Khaled Trabelsi, Lassad Tiss, Benjamin Sames, Yassine Houla, Amine Hanini, Faycel Elferhi, Ahmed Skanji, Fekri Kamoun, Mohamed Faouzi Zagrarni and Michael Wagreich

Geosciences 2022, 12(2), 93; https://0-doi-org.brum.beds.ac.uk/10.3390/geosciences12020093 - 17 Feb 2022

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Abstract

Marginal-marine to non-marine ostracod assemblages from the Bajocian (Mid-Jurassic) of southern Tunisia, precisely from the Krachoua Formation at the Kef El Anneba section near the Beni Kheddache area, are here described and tested for their utility to improve the stratigraphic accuracy and palaeoenvironmental [...] Read more.

Marginal-marine to non-marine ostracod assemblages from the Bajocian (Mid-Jurassic) of southern Tunisia, precisely from the Krachoua Formation at the Kef El Anneba section near the Beni Kheddache area, are here described and tested for their utility to improve the stratigraphic accuracy and palaeoenvironmental reconstructions. This particular microfauna consists of 11 species belonging to 6 genera and represents 2 distinct types of species-rich assemblages from this time interval, allowing the interpretation of the depositional setting of the fossiliferous horizon from which the samples derive. The first ostracod assemblage is mainly composed of the brackish to shallow marine species Fastigatocythere sp. Mette, 1995; Vernoniella aff. V. bajociana Bate, 1965b; Paracypris sp. A, Paracypris sp. B, Fabanella sarda Malz et al., 1985; Marslatourella aff. M. bathonica Andreu, 1999; and Fabanella aff. F. bathonica Oertli, 1957. This ostracod biofacies reflects marginal marine (shallow platform, restricted lagoon) conditions in the studied area. In contrast, the second ostracod assemblage is exclusively dominated by the non-marine limnic species Alicenula sp., Theriosynoecum pusilla Rohr, 1976; Theriosynoecum aff. T. aveyronensis Rohr, 1976; and Theriosynoecum sp. Such ostracod biofacies reflects the establishment of (a) permanent freshwater lake(s) in the studied area, triggered by the total emersion of the Bajocian Krachoua platform, presumably as response to the short-term sea-level fall event JBj3 of Haq (2017). The recognized ostracod species from the upper part of the Krachoua Formation at Kef El Anneba section (Medenine area) are particularly similar to those already described from the neighbouring sections of Kezzani (Dhaher area) and Krachoua (Tataouine area), facilitating a stratigraphic calibration of the Krachoua Formation, as well as regional correlations of the respective Bajocian continental event within the southern Tunisian palaeogeographic domain. Moreover, the biogeography of the studied ostracod microfauna from the Mid-Jurassic of southern Tunisia provides further arguments to support the hypothesis of significant biological exchanges between Laurasian and Gondwanan islands, as recently demonstrated by means of a charophyte microflora, indicating that Peri-Tethyan biogeography remained relatively uniform during that time interval and challenging the previous assumption of their endemism. Full article

(This article belongs to the Special Issue Jurassic Paleoenvironments)

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9 pages, 2687 KiB

Open AccessArticle

Ontogenetic Trends of Sutural Complexity in Jurassic Ammonites

by Katherine Marriott, Sara Olson, Daniella Balassa, Casey Cleaveland, Kristin I. Watmore, Rhiannon J. LaVine, Robert Olson and Donald R. Prothero

Geosciences 2022, 12(2), 66; https://0-doi-org.brum.beds.ac.uk/10.3390/geosciences12020066 - 31 Jan 2022

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Abstract

Ontogenetic sequencing of suture fractal dimensions from a single ammonite specimen was not previously accessible without extreme measures. The necessity for destruction of the full conch due to whorl overlap or, alternatively, the prohibitively expensive or inaccessible imaging equipment for use by paleontologists [...] Read more.

Ontogenetic sequencing of suture fractal dimensions from a single ammonite specimen was not previously accessible without extreme measures. The necessity for destruction of the full conch due to whorl overlap or, alternatively, the prohibitively expensive or inaccessible imaging equipment for use by paleontologists has led to this rich source of data remaining elusive. Tracings of ontogenetic sequences of sutures have rarely been published since the middle of the last century. These studies only focused on the outermost whorl of a given specimen or composited several specimens. Oftentimes, they focused only on the umbilical and juvenile stages of shell growth. Complete or multi-whorled ontogenetic sequences, including those of subadult and mature specimens, are especially uncommon. Using methods published in 2021 to address the accessibility problem in sutural ontogenies, our paper represents the first comparisons of the fractal trajectories of ammonoids and includes several significant Jurassic ammonite families. We found that ammonite sutures did not steadily increase in complexity, as was previously suggested. Instead, juvenile ammonoids were more likely to exhibit ups and downs in their fractal ontogeny. We also found that pathologies must be considered as extremely common phenomena for ammonoids. Finally, we explored the ways that the unsteady ontogenetic trends of fractal complexity in ammonoids offer insights into the formation mechanism of ammonoid septa. Full article

(This article belongs to the Special Issue Jurassic Paleoenvironments)

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17 pages, 2838 KiB

Open AccessArticle

A New Calcareous Nannofossil Record from the Lower Jurassic of Kermanshah, Western Iran: Implications for Biostratigraphy and Evolutionary Reconstructions

by Asad Abdi, Emanuela Mattioli and Beatriz Bádenas

Geosciences 2022, 12(2), 59; https://0-doi-org.brum.beds.ac.uk/10.3390/geosciences12020059 - 27 Jan 2022

Cited by 1 | Viewed by 2118

Abstract

Calcareous nannofossils are used here for the first time in order to establish a precise biostratigraphic framework for the Kermanshah Radiolarite Formation, an outcropping in Western Iran. The new data presented here challenge the previous tentative age interpretations (Pliensbachian to early Toarcian) based [...] Read more.

Calcareous nannofossils are used here for the first time in order to establish a precise biostratigraphic framework for the Kermanshah Radiolarite Formation, an outcropping in Western Iran. The new data presented here challenge the previous tentative age interpretations (Pliensbachian to early Toarcian) based upon radiolarians. Calcareous nannofossil assemblages and events unequivocally indicated that the pelagic limestones and marls are late Sinemurian in age (NJT 3b nannofossil subzone), and that these are thrusted over shales and cherts dated as uppermost Sinemurian (NJT 3b-c nannofossil subzone) and lowermost Pliensbachian (NJT 4 nannofossil zone). This result leads not only to reconsideration of the age of the radiolarite formations, which are widespread in the Zagros orogenic system, but also a better understanding of the stratigraphic relationships between the various lithological units known in the area. Besides these new stratigraphic inferences, the calcareous nannofossil assemblages of the uppermost Sinemurian–lowermost Pliensbachian successions revealed the common presence of new morphologies of the Mitrolithus genus, never described before. These findings allow for the description of three new species, M. montgolfieri, M. pseudonannoconus, and M. tethysiensis, and reveal the existence of homeomorphy between the spine structure of conical Lower Jurassic coccoliths and the widespread Cretaceous nannoconids. Full article

(This article belongs to the Special Issue Jurassic Paleoenvironments)

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32 pages, 24365 KiB

Open AccessArticle

Palynostratigraphy, Palynofacies, T-R Cycles and Paleoenvironments in the Middle Jurassic–Early Cretaceous Ramså Basin, Andøya, Northern Norway

by Morten Smelror

Geosciences 2021, 11(9), 354; https://0-doi-org.brum.beds.ac.uk/10.3390/geosciences11090354 - 24 Aug 2021

Cited by 5 | Viewed by 2619

Abstract

Palynostratigraphy and palynofacies analyses are applied to identify transgressive-regressive sequences and changes in paleoenvironment through the Middle Jurassic–Early Cretaceous succession of the Ramså Basin on Andøya. The conglomerate, the succeeding lacustrine-swamp deposits of the Hestberget and Kullgrøfta members (Ramså Formation) and the overlying [...] Read more.

Palynostratigraphy and palynofacies analyses are applied to identify transgressive-regressive sequences and changes in paleoenvironment through the Middle Jurassic–Early Cretaceous succession of the Ramså Basin on Andøya. The conglomerate, the succeeding lacustrine-swamp deposits of the Hestberget and Kullgrøfta members (Ramså Formation) and the overlying terrestrial to marginal marine deposits of the lower Bonteigen Member (Ramså Formation), comprise the Bajocian T-R sequence. Bathonian–Oxfordian strata appear to be missing in the studied boreholes, and the second T-R cycle spans the Kimmeridgian to Berriasian open marine deposits of the upper Bonteigen Member and the Dragneset Formation (Breisanden, Taumhølet and Ratjønna members). The overlying Nybrua Formation comprises a condensed marine succession of Valanginian–Early Barremian calcareous sandstone and marl, followed by brownish-red siltstone. The upper T-R sequence (Skarstein Formation) consists of marine transgressive Barremian dark siltstones, silty shales and mudstones, followed by dark mudstone and shale. Marine palynomorphs recovered in these stacked marine slope turbidite sediments are of Late Barremian age, but possibly the youngest T-R cycle also includes Aptian deposits elsewhere in the basin. Full article

(This article belongs to the Special Issue Jurassic Paleoenvironments)

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Review

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26 pages, 4997 KiB

Open AccessReview

On the Rarity and Peculiarity of the Early Toarcian (Lower Jurassic) Leukadiellinae Ammonites—Systematic Review and Insights on the Interplay of Environmental Stress, Evolution and Biodiversity

by Domenico Ridente

Geosciences 2022, 12(11), 411; https://0-doi-org.brum.beds.ac.uk/10.3390/geosciences12110411 - 09 Nov 2022

Cited by 1 | Viewed by 1635

Abstract

The subfamily Leukadiellinae Macchioni and Venturi, 2000 includes the two rare genera Leukadiella Renz, 1913 and Renziceras Arkell, 1953. Genus Leukadiella is characterised by ornamental and structural features unusual to the family Hildoceratidae Hyatt, 1867; for this reason, it has been occasionally grouped [...] Read more.

The subfamily Leukadiellinae Macchioni and Venturi, 2000 includes the two rare genera Leukadiella Renz, 1913 and Renziceras Arkell, 1953. Genus Leukadiella is characterised by ornamental and structural features unusual to the family Hildoceratidae Hyatt, 1867; for this reason, it has been occasionally grouped with other “odd” representatives of this family, as, for instance, Frechiella Prinz, 1904 and Paroniceras Bonarelli, 1893. While Renziceras comprises only one species, the eleven species currently recognised within Leukadiella show a noticeably discontinuous variability field; together with rarity of findings, the interpretation of this variability represents a renowned obstacle to their classification and phylogenetic reconstruction. Following an analysis of the morphological characters commonly used for defining Leukadiella species, a revised taxonomic scheme is herein proposed. Two clusters of characters are defined, based on which two morphologically distinct groups of species are distinguished, referred to as Helenae Group and Ionica Group. The genus name Leukadiella is maintained for species of the Helenae Group, which are restricted via synonymy to Leukadiella helenae Renz, 1913 and Leukadiella jeanneti Renz, 1927. The new genus name Neoleukadiella gen. nov. is proposed for species of the Ionica Group, which, by analogous limitation, are Neoleukadiella ionica Renz and Renz, 1946 and Neoleukadiella gallitellii Pinna, 1965. The reduction in the number of species from eleven to four is consistent with their rarity and limited paleogeographic distribution. The closely related Renziceras is considered the direct progenitor of Leukadiella; in turn, the Apennine genus Cingolites Sassaroli and Venturi, 2010 is proposed as transitional between Hildaites Buckman, 1921 and Renziceras. Conversely, the progenitor of Neoleukadiella remains uncertain, although a possible relationship between Leukadiella and Neoleukadiella species is tentatively traced. Finally, some challenging assumptions are made by emphasizing the role of environmental stress in controlling developmental dynamics that may drive striking phenotypic modification, of the kind observed in the Leukadiellinae species. Full article

(This article belongs to the Special Issue Jurassic Paleoenvironments)

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