2015 GSA Annual Meeting in Baltimore, Maryland, USA (1-4 November 2015)

Paper No. 18-4
Presentation Time: 8:50 AM

ENVIRONMENTAL CONTROLS ON THE RECOVERY OF BENTHIC INVERTEBRATE COMMUNITIES IN THE WAKE OF THE LATE PERMIAN MASS EXTINCTION


FOSTER, William J., Department of Geological Sciences, University of Texas at Austin, 1 University Station C1100, Austin, TX 78712, DANISE, Silvia, Department of Geology, University of Georgia, 210 Field Street, Athens, GA 30602; School of Geography, Earth and Environmental Sciences, Plymouth University, Drake Circus, Plymouth, PL4 8AA, United Kingdom, SEDLACEK, Alexa R.C., Department of Earth Science, University of Northern Iowa, Cedar Falls, IA 50614 and TWITCHETT, Richard J., Department of Earth Sciences, The Natural History Museum, Cromwell Rd., London, SW7 5BD, United Kingdom, william.foster@plymouth.ac.uk

Climate warming during the late Permian is associated with the most severe mass extinction event of the Phanerozoic, and the expansion of hypoxic and anoxic conditions in shallow shelf settings. It has been hypothesised that wave aeration provided an oxygenated ‘habitable zone’ in the shallowest environments that allowed some survival and a rapid recovery of benthic invertebrates during the Early Triassic. Here, we use multivariate analyses to investigate the temporal and environmental distribution of benthic invertebrates from the Lower Triassic succession of the Aggtelek Karst, Hungary, which was deposited in a mixed siliciclastic-carbonate ramp setting on the northwestern margin of the Paleotethys Ocean. Nearshore settings recorded in the Griesbachian, Dienerian, Smithian and Spathian are characterised by taxonomically homogenous assemblages of low diversity and low evenness. Ecological and taxonomic recovery in this environmental setting was hampered by persistent environmental stress, attributed to increased runoff that resulted in large salinity fluctuations, increased sedimentation rates and eutrophication leading to an environment only favourable for opportunistic taxa. In contrast, facies representing shoal and mid-ramp settings further offshore are characterised by assemblages with high diversity and functional complexity, including the presence of both erect and deep-infaunal tier taxa. Prior to the upper Spathian, Tirolites carniolicus Zone, the shelly fossils and trace fossils are limited to - facies that were deposited under wave activity, which supports the ‘habitable zone’ hypothesis. In the Tirolites carniolicus Zone itself, however, the oxygen minimum zone apparently retreated offshore and the habitable deeper shelf settings became rapidly colonised by shallow-water taxa, and these facies record the highest levels of diversity and bioturbation.