Subsurface Geology of St. Helena, Tangipahoa, Washington and St. Tammany Parishes, Louisiana

Abstract

St. Helena, Tangipahoa, Washington, and St. Tammany Parishes comprise the eastern half of the “Florida Parishes,” an area located between two major producing provinces, the Cretaceous and Wilcox of south Mississippi on the north and the prolific Miocene of south Louisiana on the south.Strata seen to date range in age from surface Pleistocene terraces and Recent alluvium to the Lower Cretaceous. This paper summarizes the stratigraphy, structure, and oil and gas production of the area, and includes a brief discussion of pertinent oil and gas production in the adjacent Mississippi counties.Subsurface structure is shown on a series of maps contoured on datums of the top of the Heterostegina zone, the Wilcox Group, the Clayton-Selma Chalk, the Eutaw Shale, and the lower Tuscaloosa Formation. Four geological cross sections illustrate stratigraphic, structural, and facies relationships. Structural contours demonstrate downflexing of Tertiary strata; show a shifting of strike to a more northerly trend with progressively deeper strata; and are strongly deflected southward by the Hancock County high. Correlation of electric logs shows pronounced structural thinning on the Hancock structure in the Comanchean, Gulfian, Paleocene, Eocene, and Oligocene Series. Truncation of the upper Wilcox, Claiborne, Jackson, and possibly Vicksburg beneath Miocene strata indicates a major period of growth occurred there sometime prior to the early Miocene.History of development, production, and structure of Angie-East Angie-Sandy Hook field is summarized. A map showing the structure of the top of the producing ower Tuscaloosa is included.