Depositional Environment, History and Diagenesis of the Weches Formation in Marshal, Texas, Harrison County

The primary objectives of this study were to describe and delineate the facies of, and develop a depositional model for, the Weches Formation in Marshall, Texas. These objectives were met by studying the lithology and sedimentary structures of the Weches Formation and the contact between the Weches and the overlying Sparta Sandstone, by measuring sections in the Weches Formation and by making thin sections and describing the geometry and features seen in them.;The Weches Formation has been studied in other parts of East Texas, but not around Marshall. There are significant differences in the Weches in the Marshall area compared to other parts of East Texas and thus this study provides new information about an important formation.;The main depositional environments of the Weches Formation in Harrison County, Marshall, Texas, are: (1) inner shelf facies, and (2) fluvial deltaic with subordinate prodelta facies.;Kaolinite and smectite were observed in samples under scanning electron microscopy and by energy dispersive spectroscopy. Quartz overgrowths were also observed under scanning electron microscope and are interpreted to be the result of previous diagenetic cycle(s).