The biostratigraphy of Early Tertiary macroinvertebrates from the La Meseta Formation, Seymour Island, Antarctic Peninsula. M.Sc. thesis

This investigation was initiated to provide a detailed systematic catalogue of the middle Eocene-earliest Oligocene? molluscan fauna of the La Meseta Formation, and to use these data for biostratigraphic, biostratinomic, paleobiogeographic, and paleoecologic interpretations. The formation was mapped in terms of seven units (Telm1-Telm7), based on sedimentology and shelly macrofaunal content. Faunal diversity is low in unit Telm1 and steadily increases up-section to a peak in the shell lenses of Telm5. A sharp decrease in diversity occurs near the contact of Talm5 and Telm6 and is believed to be either a reflection of facies change or mark the documented severe decrease in sea-surface temperatures in the southern oceans at the closing of the Eocene Epoch. Four provisional local-range zones are identified from the formation. Clastic sediments of the La Meseta Formation were deposited in a temperate-cool temperate climate in a wide variety of shallow (intertidal to subtidal), marine environments of varying hydrodynamic condition. A mixed wave-tide barrier bay model is preferred. -from Author