Bivalve Richness and Ecological Diversity of the End-Triassic Mass Extinction: Faunal Analyses from the West-Tethyan Lombardy, La Spezia and K?ssen Basins (Italy and Austria)

Suny College At Cortland, Cortland NY

Investigators

Abstract

Late Triassic extinctions are known to have severely affected many invertebrate and vertebrate taxa from the marine and non-marine realms; however, the precise timing, magnitude, and ultimate cause(s) of the biotic crisis remain poorly understood. Recently published and unpublished high-resolution isotope stratigraphy coupled with preliminary bivalve collections reveals an abundance of ecologically significant bivalves near an initial negative excursion in -13C and now permits precise correlation between nearly all known Triassic-Jurassic boundary sections. To understand better which organisms were affected and the sequence of events in the late Triassic, I propose research involving an analysis of taxonomic richness and paleoecology of Triassic-Jurassic bivalve faunas of the Lombardy, La Spezia and Kossen Basins of the western Tethys By virtue of their abundance and richness in Triassic/Jurassic boundary beds within these key sections, bivalve mollusks provide an ideal group with which to test hypotheses surrounding the tempo and mode of extinction. Two related hypotheses will be investigated: (i) following a period of ecologic stability, the end-Triassic bivalve extinction was both severe and abrupt; and (ii) bivalves within the extinction and early survival interval exhibit an ecologic pattern of selective extinction and survival. To address these questions, I propose intensive field and institutional based research to: (i) revise and develop new taxonomic data on latest Triassic through earliest Jurassic bivalve fauna from the western Tethyan realm; and (ii) to develop high-resolution paleoecologic and paleoenvironmental data from identified stratigraphic sections spanning the Triassic/Jurassic boundary from five critical sections identified from the Lombardy, La Spezia and Kossen Basins of Italy and Austria. A taxonomic revision of west-Tethyan bivalves, which will involve extensive institutional-based research at major European repositories, has never been attempted and is long overdue. Paleoecologic analyses will entail bed-by-bed analyses of boundary intervals in which abundance, diversity, and trophic data will be collected from statistically large samples combined with taphonomic and sedimentologic data within a high-resolution biochronologic and chemostratigraphic framework. This work will involve substantial new collaborations with scientists from Italy, Austria and The Netherlands with expertise in micropaleontology, palynology, stable isotope geochemistry and regional geology, The research will also actively involve undergraduate students, both as assistants and as independent researchers and provide for their training and preparation for future graduate studies. The work proposed here will have broad significance for the interpretation of biotic patterns surrounding the end- Triassic mass extinction. The expected outcome of a revised taxonomy of Rhaetian/Hettangian bivalves of the Kossen Basin will, after more than 100 years, finally provide sound base-line taxonomic data from which to test hypotheses surrounding the timing, magnitude, and mode of the end-Triassic extinction.