6 research outputs found
A new chronology for the end-Triassic mass extinction
The transition from the Triassic to Jurassic Period, initiating the 'Age of the dinosaurs', approximately 200 Ma, is marked by a profound mass extinction with more than 50% genus loss in both marine and continental realms. This event closely coincides with a period of extensive volcanism in the Central Atlantic Magmatic Province (CAMP) associated with the initial break-up of Pangaea but a causal relationship is still debated. The Triassic-Jurassic (T-J) boundary is recently proposed in the marine record at the first occurrence datum of Jurassic ammonites, post-dating the extinction interval that concurs with two distinct perturbations in the carbon isotope record. The continental record shows a major palynological turnover together with a prominent change in tetrapod taxa, but a direct link to the marine events is still equivocal. Here we develop an accurate chronostratigraphic framework for the T-J boundary interval and establish detailed trans-Atlantic and marine-continental correlations by integrating astrochronology, paleomagnetism, basalt geochemistry and geobiology. We show that the oldest CAMP basalts are diachronous by 20 kyr across the Atlantic Ocean, and that these two volcanic pulses coincide with the end-Triassic extinction interval in the marine realm. Our results support the hypotheses of Phanerozoic mass extinctions resulting from emplacement of Large Igneous Provinces (LIPs) and provide crucial time constraints for numerical modelling of Triassic-Jurassic climate change and global carbon-cycle perturbations. © 2010 Elsevier B.V. All rights reserved
Tracking Taphonomic Regimes Using Chemical and Mechanical Damage of Pollen and Spores: An Example from the Triassic–Jurassic Mass Extinction
Bentho-planktonic evidence from the Austrian Alps for a decline in sea-surface carbonate production at the end of the Triassic
A high-resolution micropalaeontological study, combined with geochemical
and sedimentological analyses was performed on the Tiefengraben,
Schlossgraben and Eiberg sections (Austrian Alps) in order to
characterize sea-surface carbonate production during the end-Triassic
crisis. At the end-Rhaetian, the dominant calcareous nannofossil
Prinsiosphaera triassica shows a decrease in abundance and size and this
is correlated with a increase in delta O-18 and a gradual decline in
delta C-13(carb) values. Simultaneously, benthic foraminiferal
assemblages show a decrease in diversity and abundance of calcareous
taxa and a dominance of infaunal agglutinated taxa. The smaller size of
calcareous nannofossils disturbed the vertical export balance of the
biological carbon pump towards the sea-bottom, resulting in changes in
feeding strategies within the benthic foraminiferal assemblages from
deposit feeders to detritus feeders and bacterial scavengers. These
micropalaeontological data combined with geochemical proxies suggest
that changes in seawater chemistry and/or cooling episodes might have
occurred in the latest Triassic, leading to a marked decrease of
carbonate production. This in turn culminated in the quasi-absence of
calcareous nannofossils and benthic foraminifers in the latest Triassic.
The aftermath (latest Triassic earliest Jurassic) was characterised by
abundance peaks of ``disaster'' epifaunal agglutinated foraminifera
Trochammina on the sea-floor. Central Atlantic Magmatic Province (CAMP)
paroxysmal activity, superimposed on a major worldwide regressive phase,
is assumed to be responsible for a deterioration in marine
palaeoenvironments. CAMP sulfuric emissions might have been the trigger
for cooling episodes and seawater acidification leading to disturbance
of the surface carbonate production at the very end-Triassic