T183 Excursions, Extinctions, and Environmental Change: New Advances in Geochemical Tools Linked to Critical Intervals of Environmental and Biotic Change in Earth History

Tuesday, 27 September 2016
8:00 AM - 12:00 PM
Room 404

LARGE, RAPID EARLY TRIASSIC SULFUR ISOTOPE SHIFTS RECORDED IN MARINE CARBONATES FROM THE WESTERN U.S

Paper number: T183-15
Program: Technical Sessions
Time: 11:45 AM – 12:00 PM

Authors

Abstract

The Early Triassic records the ~5 My aftermath and delayed biological recovery from the end-Permian mass extinction (~252 Ma). Large perturbations of several isotope systems (C, O, S, Sr, U) have been widely documented from Lower Triassic marine successions. The Early Triassic marine S-isotope record has been of recent interest due to newly published data from South China indicating large magnitude variability. Here, we present a biostratigraphically controlled S-isotope record for the Early Triassic from marine carbonates from the western U.S., to better understand the timing and magnitude of the S-isotope excursions. Our data indicate three large (>20‰), rapid positive S-isotope shifts, which occur with similar timing as the South China record, indicating a global signal. Our data expands on the existing Early Triassic S-isotope record by providing additional sample resolution across the transition between the Smithian and Spathian stages (~250 Ma), where we observe some of the highest S-isotope values for the Phanerozoic, followed by a return to normal marine values by the middle to late Spathian (~248 Ma). As with the South China record, our data show a coupling of the C-and S-isotopic records, indicating contemporaneous global burial of isotopically light organic C and pyrite-S in anoxic environments. The timing of the positive S-isotope shift is inconsistent, however, with other globally distributed, regional marine redox proxy records (e.g., pyritic organic-rich shales). The Smithian-Spathian transition is associated with decreased seawater temperatures following an extremely warm period indicated from conodont oxygen isotopes, a positive carbonate C-isotope shift, and conodont and ammonoid extinctions. The extraordinary S-isotope increase across this transition suggests a sudden and major paleoceanic upheaval preceded the complete global recovery of marine ecosystems.

Geological Society of America Abstracts with Programs. Vol. 48, No. 7

doi: 10.1130/abs/2016AM-286276

© Copyright 2016 The Geological Society of America (GSA), all rights reserved. Permission is hereby granted to the author(s) of this abstract to reproduce and distribute it freely, for noncommercial purposes. Permission is hereby granted to any individual scientist to download a single copy of this electronic file and reproduce up to 20 paper copies for noncommercial purposes advancing science and education, including classroom use, providing all reproductions include the complete content shown here, including the author information. All other forms of reproduction and/or transmittal are prohibited without written permission from GSA Copyright Permissions.