Coastal environmental changes in the Gulf Coast of Mexico through Late Eocene to Early Oligocene: implication from geochemistry in shelf sediments of Mississippi

The Eocene-Oligocene climatic transition may have accompany notable climatic cooling and sea-level fall with enhanced weathering and primary productivity in coastal environments. To discuss coastal environmental changes related to the Eocene-Oligocene climatic transition, we present an X-ray fluorescence core scanner record for late Eocene-early Oligocene (36.5-33.4 Ma) shelf sediments of the Mossy Grove Core in Hinds County, Mississippi. Paleodepth of the shelf sediments varies from 20 to 200 m depth. The sediments display coarsening upward. Indicators of terrigenous sediment input (K/Al, Fe/Al, and Ti/Al ratios) display peaks through 35.54 to 35.37 Ma, through 33.64 to 33.62 Ma, and through 33.55 to 33.50 Ma. The peaks indicate increase in the terrigenous input. Ti/K ratios notably increase at ~33.5 Ma, indicating changes in sources of the sediments with changes in energy and paleocoastal position. Proxies of export productivity (Ba/Fe, Ba/Ti, and Ba/Al ratios) and that of biogenic silicate (Si/Al ratio) show peaks at ~36.0, 35.1, 33.8, 33.7, and 33.6 Ma. The geochemical proxies indicate frequent changes in terrigenous sediment input and export productivity during the early Oligocene.