scholarly journals Stenopterygiids from the lower Toarcian of Beaujolais and a chemostratigraphic context for ichthyosaur preservation during the Toarcian Oceanic Anoxic Event

2021 ◽  
pp. SP514-2020-232
Author(s):  
Jeremy E. Martin ◽  
Guillaume Suan ◽  
Baptiste Suchéras-Marx ◽  
Louis Rulleau ◽  
Jan Schlögl ◽  
...  
Keyword(s):  
Content Type ◽  
Oceanic Anoxic Event ◽  
Sulfate Reducing ◽  
Exceptional Preservation ◽  
Environmental Perturbations ◽  
Anoxic Event ◽  
European Distribution ◽  
Supplementary Material ◽  
Carbonate Concretion ◽  
Early Carbonate

AbstractWe report new ichthyosaur material excavated in lower Toarcian levels of the LafargeHolcim Val d'Azergues quarry in Beaujolais, SE France. A partially articulated skull and a smaller, unprepared but likely subcomplete skeleton preserved in a carbonate concretion are identified as stenopterygiids, a family of wide European distribution during the Early Jurassic. These specimens are among the finest preserved Toarcian exemplars known from Europe and in one of them, soft tissue preservation is suspected. Their state of preservation is attributed to the combination of prolonged anoxic conditions near the water-sediment interface and early carbonate cementation resulting from the activity of sulfate-reducing bacteria. We also present carbon and strontium isotope values obtained from the study site that allow detailed temporal comparisons with other Toarcian vertebrate-yielding sites and environmental perturbations associated with the Toarcian Oceanic Anoxic Event (T-OAE). These comparisons suggest that the relatively high abundance and good preservation state of Toarcian vertebrates was favoured by a prolonged period of low bottom water oxygenation and accumulation rates. The environmental conditions that prevailed during the T-OAE were probably responsible for the extensive nature of Lagerstätte-type deposits with exceptional preservation of marine organisms. Whether the T-OAE had a biological impact on marine vertebrates requires a precise chemostratigraphic context of the fossil record spanning the Pliensbachian-Toarcian interval.Supplementary material at https://doi.org/10.6084/m9.figshare.c.5315223

Molecular and petrographical evidence for lacustrine environmental and biotic change in the palaeo-Sichuan mega-lake (China) during the Toarcian Oceanic Anoxic Event

2021 ◽  
pp. SP514-2021-2
Author(s):  
Weimu Xu ◽  
Johan W. H. Weijers ◽  
Micha Ruhl ◽  
Erdem F. Idiz ◽  
Hugh C. Jenkyns ◽  
...  
Keyword(s):  
Organic Matter ◽  
Sichuan Basin ◽  
Large Scale ◽  
Algal Growth ◽  
Black Shales ◽  
Content Type ◽  
Oceanic Anoxic Event ◽  
Anoxic Event ◽  
Supplementary Material ◽  
The Sichuan Basin

AbstractThe organic-rich upper Lower Jurassic Da'anzhai Member (Ziliujing Formation) of the Sichuan Basin, China is the first stratigraphically well-constrained lacustrine succession associated with the Toarcian Oceanic Anoxic Event (T-OAE; ∼183 Ma). The formation and/or expansion of the Sichuan mega-lake, likely one of the most extensive fresh-water systems to have existed on the planet, is marked by large-scale lacustrine organic productivity and carbon burial during the T-OAE, possibly due to intensified hydrological cycling and nutrient supply. New molecular biomarker and organic petrographical analyses, combined with bulk organic and inorganic geochemical and palynological data, are presented here, providing insight into aquatic productivity, land-plant biodiversity, and terrestrial ecosystem evolution in continental interiors during the T-OAE. We show that lacustrine algal growth during the T-OAE accounted for a significant organic-matter flux to the lakebed in the palaeo-Sichuan mega-lake. Lacustrine water-column stratification during the T-OAE facilitated the formation of dysoxic-anoxic conditions at the lake bottom, favouring organic-matter preservation and carbon sequestration into organic-rich black shales in the Sichuan Basin. We attribute the palaeo-Sichuan mega-lake expansion to enhanced hydrological cycling in a more vigorous monsoonal climate in the hinterland during the T-OAE greenhouse.Supplementary material at https://doi.org/10.6084/m9.figshare.c.5433544

Hardground, gap and thin black shale: spatial heterogeneity of arrested carbonate sedimentation during the Jenkyns Event (T-OAE) in a Tethyan pelagic basin (Gerecse Mts, Hungary)

2021 ◽  
pp. SP514-2020-266
Author(s):  
Tamás Müller ◽  
Gregory D. Price ◽  
Emanuela Mattioli ◽  
Máté Zs. Leskó ◽  
Ferenc Kristály ◽  
...  
Keyword(s):  
Carbon Isotope ◽  
Black Shale ◽  
Carbonate Production ◽  
Content Type ◽  
Oceanic Anoxic Event ◽  
Carbonate Sedimentation ◽  
Environmental Perturbations ◽  
Carbon Isotope Excursion ◽  
Supplementary Material ◽  
Tethys Ocean

AbstractThe Jenkyns Event or Toarcian Oceanic Anoxic Event (T-OAE) was an episode of severe environmental perturbations reflected in carbon isotope and other geochemical anomalies. Although well studied in the epicontinental basins in NW Europe, its effects are less understood in open marine environments. Here we present new geochemical (carbon isotope, CaCO3, [Mn]) and nannofossil biostratigraphic data from the Tölgyhát and Kisgerecse sections in the Gerecse Hills (Hungary). These sections record pelagic carbonate sedimentation near the margin of the Tethys Ocean. A negative carbon isotope excursion of ∼6‰ is observed in the Tölgyhát section, in a condensed clay and black shale layer where the CaCO3 content drops in association with the Jenkyns Event. At Kisgerecse, bio- and chemostratigraphic data suggest a gap in the lower Toarcian. The presence of an uppermost Pliensbachian hardground, absence of the lowermost Toarcian Tenuicostatum ammonite zone, and the condensed record of the Jenkyns Event at Tölgyhát, together with a condensed Tenuicostatum Zone and the missing negative carbon isotope anomaly at Kisgerecse implies arrested carbonate sedimentation. A calcification crisis and sea-level rise together led to a decrease in carbonate production and terrigenous input, suggesting that volcanogenic CO2-driven global warming may have been their common cause.Supplementary material at https://doi.org/10.6084/m9.figshare.c.5355342

scholarly journals Biotic and stable-isotope characterization of the Toarcian Ocean Anoxic Event through a carbonate-clastic sequence from Somerset, UK

2021 ◽  
pp. SP514-2020-263
Author(s):  
Ian Boomer ◽  
Philip Copestake ◽  
Kevin Page ◽  
John Huxtable ◽  
Tony Loy ◽  
...  
Keyword(s):  
Stable Isotope ◽  
Laminated Sediments ◽  
Content Type ◽  
Oceanic Anoxic Event ◽  
The United Kingdom ◽  
Clastic Sediments ◽  
Carbon Isotope Excursion ◽  
Anoxic Event ◽  
Supplementary Material

AbstractThis study focuses on a condensed sequence of alternating carbonate-clastic sediments of the Barrington Member, Beacon Limestone Formation (latest Pliensbachian to early Toarcian) from Somerset (south west England). Abundant ammonites confirm (apart from the absence of the Clevelandicum and Tenuicostatum ammonite subchronozones) the presence of Hawskerense Subchronozone to Fallaciosum-Bingmanni subchronozones. Well-preserved, sometimes diverse assemblages of ostracods, foraminifera, nannofossils and low diversity dinoflagellate assemblages support the chronostratigraphic framework. Stable-isotope analyses demonstrate the presence of a carbon isotope excursion (CIE), relating to the Toarcian Oceanic Anoxic Event (T-OAE), within the early Toarcian. Faunal, geochemical and sedimentological evidence suggest that deposition largely took place in a relatively deep-water (sub-wave base), mid-outer shelf environment under a well-mixed water column. However, reduced benthic diversity, the presence of weakly-laminated sediments and changes in microplankton assemblage composition within the T-OAE indicates dysoxic, but probably never anoxic, bottom-water conditions during this event. The onset of the CIE coincides with extinction in the nannofossils and benthos, including the disappearance of the ostracod suborder Metacopina. Faunal evidence indicates connectivity with the Mediterranean region, not previously recorded for the United Kingdom during the early Toarcian.Supplementary material at https://doi.org/10.25500/edata.bham.00000574

Palaeolatitudinal distribution of the Ediacaran macrobiota

2021 ◽  
pp. jgs2021-030
Author(s):  
Catherine E. Boddy ◽  
Emily G. Mitchell ◽  
Andrew Merdith ◽  
Alexander G. Liu
Keyword(s):  
Taxonomic Composition ◽  
Supplementary Information ◽  
Cambrian Explosion ◽  
Content Type ◽  
Link Type ◽  
Environmental Perturbations ◽  
Significant Difference ◽  
Evolutionary Trajectories ◽  
Cambrian Radiation ◽  
Supplementary Material

Macrofossils of the late Ediacaran Period (c. 579–539 Ma) document diverse, complex multicellular eukaryotes, including early animals, prior to the Cambrian radiation of metazoan phyla. To investigate the relationships between environmental perturbations, biotic responses and early metazoan evolutionary trajectories, it is vital to distinguish between evolutionary and ecological controls on the global distribution of Ediacaran macrofossils. The contributions of temporal, palaeoenvironmental and lithological factors in shaping the observed variations in assemblage taxonomic composition between Ediacaran macrofossil sites are widely discussed, but the role of palaeogeography remains ambiguous. Here we investigate the influence of palaeolatitude on the spatial distribution of Ediacaran macrobiota through the late Ediacaran Period using two leading palaeogeographical reconstructions. We find that overall generic diversity was distributed across all palaeolatitudes. Among specific groups, the distributions of candidate ‘Bilateral’ and Frondomorph taxa exhibit weakly statistically significant and statistically significant differences between low and high palaeolatitudes within our favoured palaeogeographical reconstruction, respectively, whereas Algal, Tubular, Soft-bodied and Biomineralizing taxa show no significant difference. The recognition of statistically significant palaeolatitudinal differences in the distribution of certain morphogroups highlights the importance of considering palaeolatitudinal influences when interrogating trends in Ediacaran taxon distributions.Supplementary material: Supplementary information, data and code are available at https://doi.org/10.6084/m9.figshare.c.5488945Thematic collection: This article is part of the Advances in the Cambrian Explosion collection available at: https://www.lyellcollection.org/cc/advances-cambrian-explosion

Primary versus carbonate production in the Toarcian, a case study from the Llanbedr borehole (Mochras Farm, Wales)

2021 ◽  
pp. SP514-2021-19
Author(s):  
Alessandro Menini ◽  
Emanuela Mattioli ◽  
Stephen P. Hesselbo ◽  
Micha Ruhl ◽  
Guillaume Suan
Keyword(s):  
Sea Water ◽  
Initial Perturbation ◽  
Carbonate Production ◽  
Nutrient Delivery ◽  
Content Type ◽  
High Productivity ◽  
Oceanic Anoxic Event ◽  
The Core ◽  
C Isotopes ◽  
Supplementary Material

AbstractThe leading hypothesis for the Toarcian oceanic anoxic event (T-OAE; ∼183Ma) and the associated negative C-isotope excursion is the massive release of 12C favouring greenhouse and continental weathering. The nutrient delivery to shallow-basins supported productivity and, because of O2-consumption by organic-matter respiration, anoxia development. However, several works showed that calcareous nannoplankton experienced a decrease during the T-OAE. Nannofossil fluxes measured in the Llanbedr borehole (Mochras Farm; Wales, UK) were the highest prior to the negative C-isotope excursion, along with high amounts of taxa indicative of nutrient-rich environments (Biscutaceae). Such conditions attest to high productivity. Fluxes show the lowest values in the core of the event, along with a size decrease of Schizosphaerella and a peak in Calyculaceae. The recovery of nannofossil fluxes and Schizosphaerella size occurred concomitant with the return of C-isotopes to more positive values. Concomitantly, deep-dwellers (Crepidolithus crassus) dominated, indicating a recovery of the photic-zone productivity. These observations demonstrate that the cascade of environmental responses to the initial perturbation was more complex than previously considered. In spite of elevated nutrient delivery to epicontinental basins in the early Toarcian, carbonate and primary productions of nannoplankton were depressed in the core the T-OAE likely because of prolonged thermohaline sea-water stratification.Supplementary material at https://doi.org/10.6084/m9.figshare.c.5541440

scholarly journals Global controls on phosphatization of fossils during the toarcian oceanic anoxic event

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Sinjini Sinha ◽  
A. D. Muscente ◽  
James D. Schiffbauer ◽  
Matt Williams ◽  
Günter Schweigert ◽  
...  
Keyword(s):  
Lower Jurassic ◽  
X Ray ◽  
Oceanic Anoxic Event ◽  
Exceptional Preservation ◽  
Level Change ◽  
Environmental Controls ◽  
Anoxic Basins ◽  
Anoxic Event ◽  
Anoxic Events ◽  
Posidonia Shale

AbstractKonservat-Lagerstätten—deposits with exceptionally preserved fossils—vary in abundance across geographic and stratigraphic space due to paleoenvironmental heterogeneity. While oceanic anoxic events (OAEs) may have promoted preservation of marine lagerstätten, the environmental controls on their taphonomy remain unclear. Here, we provide new data on the mineralization of fossils in three Lower Jurassic Lagerstätten—Strawberry Bank (UK), Ya Ha Tinda (Canada), and Posidonia Shale (Germany) —and test the hypothesis that they were preserved under similar conditions. Biostratigraphy indicates that all three Lagerstätten were deposited during the Toarcian OAE (TOAE), and scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) show that each deposit contains a variety of taxa preserved as phosphatized skeletons and tissues. Thus, despite their geographic and paleoenvironmental differences, all of these Lagerstätten were deposited in settings conducive to phosphatization, indicating that the TOAE fostered exceptional preservation in marine settings around the world. Phosphatization may have been fueled by phosphate delivery from climatically-driven sea level change and continental weathering, with anoxic basins acting as phosphorus traps.

scholarly journals Cretaceous Oceanic Anoxic Event 2 in eastern England: further palynological and geochemical data from Melton Ross

2020 ◽  
Vol 63 (2) ◽  
pp. 88-123 ◽  
Author(s):  
Paul Dodsworth ◽  
James S. Eldrett ◽  
Malcolm B. Hart
Keyword(s):  
Geochemical Data ◽  
Dinoflagellate Cysts ◽  
Low Oxygen ◽  
Phytoplankton Productivity ◽  
Dinoflagellate Cyst ◽  
Oceanic Anoxic Event ◽  
Oceanic Anoxic Event 2 ◽  
Anoxic Event ◽  
Black Band ◽  
Supplementary Material

The lowermost 1.45 m of the Welton Chalk Formation, including the regional sedimentary record of Oceanic Anoxic Event 2 (OAE-2), has been sampled at Melton Ross Quarry in eastern England, UK. The section is investigated for organic geochemistry and stable isotopes for the first time, while a detailed palynological study follows previously published preliminary results. It comprises a condensed interval that spans the Cenomanian–Turonian Stage boundary. A locally preserved, lower ‘anomalous’ succession (Beds I–VII) and a ‘Central Limestone’ (Bed A) are shown to correlate respectively with the pre-Plenus sequence and Plenus Bed at Misburg and Wunstorf in the Lower Saxony Basin (LSB), NW Germany. They are overlain by a succession of variegated marls (Bed B to Bed H), including the Black Band (Beds C–E), that can be correlated across eastern England. Based on a carbon isotope (δ13C) profile and dinoflagellate cyst and acritarch bio-event correlation, Beds B–H appear to be a highly attenuated post-Plenus equivalent of the LSB succession, including part of the ‘Fish Shale’. The δ13C profile shows possible ‘precursor’/‘build-up’ events in the lower succession at Melton Ross, with the main OAE-2 δ13C excursion occurring in the Central Limestone and overlying Beds B–H. The darker coloured marls from the Black Band and Bed G contain 1.43–3.47% total organic carbon (TOC), hydrogen index values of 78–203 mg HC/g TOC and oxygen index values of 15–26 mg CO2/g TOC, indicating type III and type II–III organic matter, of mixed terrigenous and marine algal sources. The corresponding palynological assemblages are dominated by marine dinoflagellate cysts, comprising mainly gonyaulacoid taxa, with subordinate terrigenous miospores, mainly gymnosperm bisaccate pollen, consistent with a distal marine setting. The interbedded lighter-coloured marls contain less than 0.4% TOC and lower proportions of miospores and peridinioid dinoflagellate cysts compared with the darker layers. This is suggestive of moderately raised levels of productivity during deposition of the darker layers, possibly related to greater nutrient availability from land-derived sources. The occurrence of the peridinioid taxa Eurydinium saxoniense and Bosedinia spp., together with higher proportions of prasinophyte phycomata in the darker layers, may also point to stimulation of organic-walled phytoplankton productivity by reduced nitrogen chemo-species encroaching the photic zone, possibly by expansion of an oxygen-minimum zone. Exceptionally high concentrations of palynomorphs (in the tens of thousands to lower hundreds of thousands per gramme range) in the darker layers at Melton Ross and eight other eastern England localities is consistent with increased quality of seafloor preservation in a low oxygen environment, coupled with a high degree of stratigraphic condensation. Two new dinoflagellate cyst species are described from Melton Ross, Canninginopsis? lindseyensis sp. nov. and Trithyrodinium maculatum sp. nov., along with two taxa described in open nomenclature.Supplementary material: One pdf file, with detailed sample positions and descriptions, tables of supporting information (also available in Excel format), quarry photographs and a palynological distribution chart, is available at https://doi.org/10.6084/m9.figshare.c.4987205

Effects of the early Toarcian Oceanic Anoxic Event on ichthyosaur body size and faunal composition in the Southwest German Basin

Paleobiology ◽  
2015 ◽  
Vol 42 (1) ◽  
pp. 117-126 ◽  
Author(s):  
Erin E. Maxwell ◽  
Peggy Vincent
Keyword(s):  
Body Size ◽  
Environmental Changes ◽  
Marine Invertebrates ◽  
Abundant Species ◽  
Extinction Rate ◽  
Oceanic Anoxic Event ◽  
Environmental Perturbations ◽  
Anoxic Event ◽  
Posidonia Shale ◽  
German Basin

AbstractThe Early Jurassic Toarcian Oceanic Anoxic Event is considered one of the most dramatic environmental perturbations of the Mesozoic. An elevated extinction rate among marine invertebrates accompanied rapid environmental changes, but effects on large vertebrates are less understood. We examined changes in ichthyosaur body size in the Posidonia Shale of the Southwest German Basin spanning the extinction interval to assess how environmental changes and biotic crisis among prey species affected large reptiles. We report no species-level extinction among the ichthyosaurs coinciding with peak invertebrate extinction. Large ichthyosaurs were absent from the fauna during the extinction interval, but became more abundant in the immediate aftermath.Stenopterygius quadriscissus, the most abundant species during the extinction interval, increased in body size after the biotic event. Rapid invasion by large taxa occurred immediately following the extinction event at the end of the first ammonite zone of the early Toarcian. Greater mobility permitting exploitation of ephemeral resources and opportunistic feeding behavior may minimize the impacts of environmental change on large vertebrates.

Sign in / Sign up

Export Citation Format

Share Document