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)

点击翻译按钮获取中文摘要

Late Triassic extinctions are known to have severely affected many invertebrate andvertebrate taxa from the marine and non-marine realms; however, the precise timing,magnitude, and ultimate cause(s) of the biotic crisis remain poorly understood. Recentlypublished and unpublished high-resolution isotope stratigraphy coupled with preliminarybivalve collections reveals an abundance of ecologically significant bivalves near aninitial negative excursion in -13C and now permits precise correlation between nearly allknown Triassic-Jurassic boundary sections. To understand better which organisms wereaffected and the sequence of events in the late Triassic, I propose research involving ananalysis of taxonomic richness and paleoecology of Triassic-Jurassic bivalve faunas ofthe Lombardy, La Spezia and Kossen Basins of the western Tethys By virtue of theirabundance and richness in Triassic/Jurassic boundary beds within these key sections,bivalve mollusks provide an ideal group with which to test hypotheses surrounding thetempo and mode of extinction. Two related hypotheses will be investigated: (i) followinga period of ecologic stability, the end-Triassic bivalve extinction was both severe andabrupt; and (ii) bivalves within the extinction and early survival interval exhibit anecologic pattern of selective extinction and survival. To address these questions, Ipropose intensive field and institutional based research to: (i) revise and develop newtaxonomic data on latest Triassic through earliest Jurassic bivalve fauna from the westernTethyan realm; and (ii) to develop high-resolution paleoecologic and paleoenvironmentaldata from identified stratigraphic sections spanning the Triassic/Jurassic boundary fromfive critical sections identified from the Lombardy, La Spezia and Kossen Basins of Italyand Austria. A taxonomic revision of west-Tethyan bivalves, which will involveextensive institutional-based research at major European repositories, has never beenattempted and is long overdue. Paleoecologic analyses will entail bed-by-bed analyses ofboundary intervals in which abundance, diversity, and trophic data will be collected fromstatistically large samples combined with taphonomic and sedimentologic data within ahigh-resolution biochronologic and chemostratigraphic framework. This work willinvolve substantial new collaborations with scientists from Italy, Austria and TheNetherlands with expertise in micropaleontology, palynology, stable isotopegeochemistry and regional geology, The research will also actively involveundergraduate students, both as assistants and as independent researchers and provide fortheir training and preparation for future graduate studies. The work proposed here willhave broad significance for the interpretation of biotic patterns surrounding the end-Triassic mass extinction. The expected outcome of a revised taxonomy ofRhaetian/Hettangian bivalves of the Kossen Basin will, after more than 100 years, finallyprovide sound base-line taxonomic data from which to test hypotheses surrounding thetiming, magnitude, and mode of the end-Triassic extinction.