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Rapid warming and ostracods mass extinction at the Lower Toarcian (Jurassic) of central Spain

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Gómez Fernández, Juan José and Arias Fernández, María del Carmen (2010) Rapid warming and ostracods mass extinction at the Lower Toarcian (Jurassic) of central Spain. Marine micropaleontology, 74 . pp. 119-135. ISSN 0377-8398

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Official URL: http://www.elsevier.com/locate/marmicro



Abstract

Here we present the results of the study of two Lower Toarcian carbonate sections located in the Iberian
Range of central Spain. Analyses of stable isotope on belemnite calcite allowed calculation of seawater
palaeotemperature variations, which were compared with the stratigraphical distribution of ostracods. These
organisms are particularly sensitive to ratios of temperature and salinity variations and hence are good
indicators of climate changes. From a cooling interval, with seawater temperatures of 13.2 °C recorded at the
Pliensbachian−Toarcian transition, seawater temperature began to rise in the lowermost Toarcian
Tenuicostatum Zone, reaching average temperatures between 14.6 °C and 16.3 °C during the time of
deposition of this Zone. Coinciding with this seawater warming, up to 85% of the ostracods species
progressively disappeared during a period of approximately 300 kyr, marking the extinction interval. The
extinction boundary, located around the Tenuicostatum−Serpentinum zonal boundary, coincides with a
marked increase in temperature in the Serpentinum Zone, on which average seawater temperatures of 22 °C
have been calculated. Warming continued through part of the Middle Toarcian Bifrons Zone, reaching
average temperatures of 24.7 °C. Readjustment of the ostracod population allowed recovery of these faunas
in the upper Serpentinum Zone, although the extinction of a major ostracod group, the healdioids, was also
recorded. The correlation between mass extinction and warming infers a causal relationship. Comparison of
the results with the records of stable isotopes in belemnites and in bulk carbonates, as well as TOC and facies
analysis suggests that the anoxia linked to the Early Toarcian oceanic anoxic event was not the main
responsible for the ostracod mass extinction.


Item Type:Article
Uncontrolled Keywords:Palaeoclimate, Stable isotopes, Ostracods, Mass extinction, Early Toarcian
Subjects:Sciences > Geology > Paleontology
ID Code:26714
Deposited On:16 Sep 2014 10:00
Last Modified:11 Dec 2018 08:42

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