Paleocene Sea Level Movements with a 430,000 Year Quasi-Periodic Cyclicity

Abstract

Sea level movements with quasi-periodicity of 430,000 years are identified in the marine sedimentary units of the Eastern Gulf Coastal Plain of Mississippi, Alabama and Georgia which represent a 5.8 million year record of strandline displacement during Paleocene time. Principal component analysis of the benthic foraminiferal fauna yielded six assemblages which when combined with two other qualitatively derived assemblages provided paleoecologic information which clearly reflects the influence of paleocirculation and paleoclimatic regime of the Eastern Gulf Coastal Plain. The presence of the planktonic foraminiferal taxa Subbotina trinidadensis and Planorotalites pseudomenardii as well as paleolatitudes ranging from 15{degree} N (for the Campeche Shelf) to 25{degree} N (for the Coastal Plain) emphasizes a paleoclimatic regime which is dominantly tropical. A paleoceanographic model was derived which suggests that normal marine waters were brought into the Gulf of Mexico by two major currents. Strandline displacements are related to transgressive and regressive sea level movements in an ice free Paleocene world. The well delineated 430,000 year quasi-periodic cycle observed in the sea level curve is identified as being astronomical in character. These results support the view that changes in the Earth's orbit may trigger changes in the geometry of the Earth's surface in a waymore » which causes sea level to oscillate with a quasi-periodicity of 430,000 years.« less