scholarly journals The impact of the Pliensbachian–Toarcian crisis on belemnite assemblages and size distribution

2021 ◽  
Vol 140 (1) ◽  
Author(s):  
Kenneth De Baets ◽  
Paulina S. Nätscher ◽  
Patricia Rita ◽  
Emmanuel Fara ◽  
Pascal Neige ◽  
...  
Keyword(s):  
Body Size ◽  
Size Distribution ◽  
Marine Organisms ◽  
Second Order ◽  
Regional Diversity ◽  
Oceanic Anoxic Event ◽  
Quantitative Studies ◽  
Anoxic Event ◽  
The Impact

AbstractThe second-order Pliensbachian–Toarcian crisis affected major groups of marine organisms. While its impact has been intensively studied for ammonites, the response of belemnites is only currently emerging through quantitative studies. Novel overall and regional diversity analyses suggest that belemnite richness in the NW-Tethys drops at the Pliensbachian–Toarcian boundary, while overall diversity slightly increases in NW-Tethys assemblages during the Toarcian Oceanic Anoxic event (T-OAE), mostly driven by NW European assemblages (e.g., Yorkshire). The T-OAE coincides with marked taxonomic turnover within individual basins, which is associated with an increase in median rostrum size of specimens in taxa at most localities. The changes in median body size across the Pliensbachian–Toarcian boundary are less consistent and driven by changes in body size within individual lineages crossing the boundary. However, our analyses also illustrate differences in sampling across the Pliensbachian–Toarcian crisis, which needs to be considered in further studies.

The impact of the Pliensbachian-Toarcian crisis on belemnite diversity and size distribution

2020 ◽  
Author(s):  
Kenneth De Baets ◽  
Patrícia Rita ◽  
Luís Vítor Duarte ◽  
Pascal Neige ◽  
Laura Piñuela ◽  
...  
Keyword(s):  
High Resolution ◽  
Species Turnover ◽  
Adult Size ◽  
Oceanic Anoxic Event ◽  
Species Cluster ◽  
Anoxic Event ◽  
Major Bottleneck ◽  
Scaling Analyses ◽  
The Impact ◽  
Lusitanian Basin

<p>The Pliensbachian–Toarcian transition has been considered a major bottleneck in the early evolution of belemnites, probably related to major palaeoenvironmental and climatic changes during the Early Toarcian. Previous research has focused on the study of belemnites from higher, temperate latitudes, while high-resolution studies on diversity and size of subtropical belemnite assemblages in the northwest Tethys are comparatively rare. The lack of high-resolution (ammonoid subzone) abundance data on diversity and size distributions of belemnite assemblages does not allow separating changes during the Pliensbachian–Toarcian boundary event from those during the Toarcian anoxic event. Sample standardized diversity analyses on new data from Iberian sections suggest the Pliensbachian–Toarcian corresponds to a slight decrease in diversity and an adult size decrease within dominant species. Cluster and non-metric multidimensional scaling analyses, however, indicate that the largest changes in diversity and palaeogeographic distribution of belemnite assemblages occurred during the Toarcian oceanic anoxic event (TOAE) rather than the Pliensbachian–Toarcian boundary. In southern basins like the Lusitanian Basin and Riff Mountains, belemnites even disappear entirely during the TOAE. More generally, the TOAE corresponds with an increase in body size of belemnite assemblages driven by species turnover. The lack of widespread anoxia in southern basins of the northwest Tethys indicates that direct impact of warming or increased pCO2 triggered by volcanism as well as indirect effects on nutrient availability and productivity might have played an important role during both crises.</p>

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.

scholarly journals Mechanisms and drivers of belemnite body-size dynamics across the Pliensbachian–Toarcian crisis

2019 ◽  
Vol 6 (12) ◽  
pp. 190494 ◽  
Author(s):  
Patrícia Rita ◽  
Paulina Nätscher ◽  
Luís V. Duarte ◽  
Robert Weis ◽  
Kenneth De Baets
Keyword(s):  
Body Size ◽  
Environmental Drivers ◽  
Adult Size ◽  
Oceanic Anoxic Event ◽  
Anoxic Event ◽  
Potential Link ◽  
Hyperthermal Events ◽  
Stable Oxygen ◽  
The Individual ◽  
Lusitanian Basin

Body-size reduction is considered an important response to current climate warming and has been observed during past biotic crises, including the Pliensbachian–Toarcian crisis, a second-order mass extinction. However, in fossil cephalopod studies, the mechanisms and their potential link with climate are rarely investigated and palaeobiological scales of organization are not usually differentiated. Here, we hypothesize that belemnites reduce their adult size across the Pliensbachian–Toarcian boundary warming event. Belemnite body-size dynamics across the Pliensbachian–Toarcian boundary in the Peniche section (Lusitanian Basin, Portugal) were analysed based on the newly collected field data. We disentangle the mechanisms and the environmental drivers of the size fluctuations observed from the individual to the assemblage scale. Despite the lack of a major taxonomic turnover, a 40% decrease in rostrum volume is observed across the Pliensbachian–Toarcian boundary, before the Toarcian Oceanic Anoxic Event where belemnites go locally extinct. The pattern is mainly driven by a reduction in adult size of the two dominant species, Pseudohastites longiformis and Passaloteuthis bisulcata. Belemnite-size distribution is best correlated with fluctuations in a palaeotemperature proxy (stable oxygen isotopes); however, potential indirect effects of volcanism and carbon cycle perturbations may also play a role. This highlights the complex interplay between environmental stressors (warming, deoxygenation, nutrient input) and biotic variables (productivity, competition, migration) associated with these hyperthermal events in driving belemnite body-size.

Carbon-isotope record and palaeoenvironmental changes during the early Toarcian oceanic anoxic event in shallow-marine carbonates of the Adriatic Carbonate Platform in Croatia

2013 ◽  
Vol 150 (6) ◽  
pp. 1085-1102 ◽  
Author(s):  
NADIA SABATINO ◽  
IGOR VLAHOVIĆ ◽  
HUGH C. JENKYNS ◽  
GIOVANNA SCOPELLITI ◽  
RODOLFO NERI ◽  
...  
Keyword(s):  
Shallow Water ◽  
Carbon Isotope ◽  
Carbonate Platform ◽  
Lower Jurassic ◽  
Positive Trend ◽  
Oceanic Anoxic Event ◽  
Anoxic Event ◽  
Isotope Record ◽  
The Impact ◽  
Palaeoenvironmental Changes

AbstractGeochemical (δ13C, δ18O and Mn) compositions of Lower Jurassic shallow-water carbonates cropping out in Croatia were analyzed to elucidate the impact of the early Toarcian oceanic anoxic event (T-OAE) on the Adriatic Carbonate Platform (AdCP). The bulk-rock carbon-isotope records through the studied sections (Velebit-A, Velebit-B and Gornje Jelenje) are characterized by two significant excursions: (i) an initial positive trend interrupted by a pronounced negative shift (c. 2.5‰) that is followed by (ii) an increasing trend of positive values (up to 4.5‰). A comparison with δ13C trends obtained from well-calibrated sections from other localities in Europe shows that the overall character of the early Toarcian negative excursion is clearly reproduced in the curves derived from Croatian shallow-water deposits, which helps to date the sequences and reinforces the global character of the carbon-cycle perturbation. Lower Jurassic sedimentary successions in the studied area show a gradual deepening trend corresponding to deposition of the Toarcian spotted limestones. Assuming that the distinctive negative excursion in the carbon-isotope curves is synchronous across the AdCP, the contact between the spotted limestones and the underlying beds rich in lithiotid bivalves appears to be diachronous within the study area. The Mn record through the Croatian Velebit-A section and, in particular, the rise in concentration (up to 100 ppm) coinciding with the beginning of the δ13Ccarb positive shift, reflects a change in the redox conditions in seawater that allowed diagenetic incorporation of reduced manganese into the calcite structure of the carbonate sediment during the onset of the T-OAE.

scholarly journals Chemostratigraphy of the Toarcian oceanic anoxic event from the Ionian Zone, Greece

2017 ◽  
Vol 47 (2) ◽  
pp. 825
Author(s):  
N. Kafousia ◽  
V. Karakitsios ◽  
E. Mattioli ◽  
H.C. Jenkyns
Keyword(s):  
Carbon Isotope ◽  
Relative Increase ◽  
Geochemical Data ◽  
Oceanic Anoxic Event ◽  
Carbonate Carbon ◽  
Carbon Burial ◽  
Organic Carbon Burial ◽  
Anoxic Event ◽  
The Difference ◽  
The Impact

A global perturbation in the carbon cycle has been recorded in the Early Toarcian (~ 183 Ma) and is marked by enhanced organic-carbon burial and mass extinction. It is also associated with high palaeotemperatures, both positive and negative excursions in carbon-isotope ratios, and the development of anoxic to euxinic conditions in marine environments: together these phenomena have been designated as constituting an Oceanic Anoxic Event. Here we provide a high-resolution, multiproxy biostratigraphic and chemostratigraphic study from a section that belongs to the central Ionian Zone in Greece. Calcareous nannofossil distribution, as well as the TOC, δ13Ccarb and δ13Corg, have all been determined. The nannofossil zones NJT 5b, NJT 6 and NJT 7 have been recognized in the section. In the NJT 5b zone a small positive excursion in TOC and negative excursion in δ13Ccarb is recorded, tentatively assigned to the Pliensbachian/Toarcian boundary. In the NJT 6 zone, the main negative carbon-isotope excursion characteristic of this interval is developed, associated with a relative increase in TOC. The difference in this section, compared with sections from the Pindos Zone but in common with sections elsewhere, is the record of a positive excursion in the NJT 7 zone in both organic and carbonate carbon isotopes. This study offers new biostratigraphic and geochemical data for the Ionian Zone, and further illustrates the impact of Toarcian Oceanic Anoxic Event in the Tethyan region.

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