ABSTRACT

Stratigraphy of the upper Lower Wilcox and Middle Wilcox of east central Louisiana (ECLA) developed, in part, as a function of sea level fluctuation in the upper Paleocene. Beginning in upper lower Wilcox, a major fall in sea level resulted in basinward progradation of thick, massive Minter distributary channel sands. With ensuing sea level rise, a long period of transgression followed. Oil production is commonly found in the upper Minter beds "on the cusp" between the sea level fall and rise. It is critical that the detailed relationships between the fluctuations, sediments, and hydrocarbon occurrence in this interval be understood.

The extended period of sea level rise produced a transgressive systems tract (TST), the Baker Shale TST, which includes the Nichols and Artman transgressive barrier oil sands of Lake Curry Field of T4N-R6E, Concordia Parish, Louisiana. The Baker Shale TST is overlain by the C5/Turner, a basin margin facies equivalent of a condensed section. A succession of aggradational para-sequences follows the C5/Turner. These sequences are overlain in turn by the Big Shale TST. Oil is found in A-1 transgressive barriers near the base of the Big Shale TST. The upper surface of the Big Shale TST may be an incised valley system formed during a dramatic sea level fall dated at 54.8 Ma.

Stratigraphic evidence suggests that the sea level curve cited in this paper is probably more irregular and without the smoothness shown.