Evolution of the Foraminiferal Genus Lepidocyclina in the Middle Eocene and Its Implication for Gulf Coast Stratigraphy: ABSTRACT

Abstract

ABSTRACT Based on data from some 40 samples, the first appearance of the Lepidocyclina ariana larger foraminiferal species group occurs at a horizon within the transgressive depositional system of Baum and Vail's TE3.1 sequence, as recently defined by Baum and others in the Bay Minette corehole, Alabama. The last occurrence of the genus Polylepidina Vaughan is observed in the same system in this core. These events also occur within the upper part of the Lisbon Formation as defined in the classical surface section at Little Stave Creek, Alabama, and at other localities in the Gulf Coast, corresponding to a biostratigraphic horizon near that of the boundary between the NP16 and NP17 calcareous nannofossil zones, of middle Eocene, Bartonian age. We illustrate the implication for dating and correlation at horizons near the middle Eocene - late Eocene boundary by the presentation of a correlation of part of the Bay Minette corehole with the section at Little Stave Creek, based on larger foraminiferal and calcareous nannofossil data. We discuss this correlation in relation to other selected localities in the Gulf Coast.