PALEOECOLOGICAL RESPONSE OF OSTRACODS AND CONCHOSTRACANS TO THE END TRIASSIC EXTINCTION EVENT IN THE HARTFORD BASIN, USA

The Hartford Basin is one in a series of CAMP-induced rift basins along the coast of North America. The Late Triassic-Early Jurassic strata preserved represent a series of lake cycles that record climatic change. Ostracods and conchostracans have been previously reported from the Hartford Basin strata but not explored in depth or utilized as a proxy. This project characterizes faunal response to rising and falling lake level dynamics resulting from the End Triassic Extinction Event, testing the following hypotheses: (1) ostracods and conchostracans responded similarly to other faunal/floral assemblages to the End Triassic Mass Extinction and (2) ostracods and conchostracans occur in shallower water depths, in fresh to brackish salinity, and indicate shallowing conditions in the lake. Neither ostracods nor conchostracans indicate a shallowing or deepening, as their occurrences range across many different facies and lithologies. Darwinulid ostracods are reported in each siliciclastic formation of the Hartford Basin in Connecticut. Preservation and presence of ostracods and conchostracans is likely due to multiple factors, such as oxygenation and depth as well as mixing and wave energy. Molds versus original preservation likely indicate different chemical conditions which should be further explored in relation to overall lake chemistry and salinity. This faunal assemblage is compared to that of the Moenave Formation of southern Utah and northern Arizona which indicates similar trends in preservational mode and presence/absence of Darwinulids and conchostracans, supporting the idea that Darwinulids persisted through the ETE before the onset of the late Mesozoic Cypridoidea and Cytheroidea radiations