ABSTRACT: Genetic Stratigraphy of the Lower Paleogene of Central Louisiana
Paul N. Lawless
The Wilcox Group and related Porters Creek Formation were divided into three genetic sequences using 476 well logs and 6 seismic lines, and integrated with sequence stratigraphy. The three genetic sequences are T1 (Midway), T2 (Eolly Springs), and T3 (Carrizo). A genetic sequence is bounded above and below by condensed sections and maximum flooding surfaces, which represent a depositional episode of marine regression followed by transgression. These genetic sequences are locally dominated by highstand systems tract deposits.
T1 was deposited during a very rapid sea level fall and is typified by shingled prograding clinoforms and overlain by a sharp-based shoreface sequence comprising the highstand systems tract. T2 was deposited during
a sea level rise that created extra accommodation space needed for the development of fluvial dominated deltaic morphologies and electric log facies that typify the highstand systems tract. T3 was deposited during a sea level fall and is typified by poorly developed deltaic morphologies and electrofacies in the highstand systems tract. The LaSalle arch had no effect on the deposition of T2 and a very minor and localized effect on T3 and T1.
Each of the three genetic sequences represents separate migration routes for hydrocarbons. At present, crude oil has been produced from T3 and the prolific T2, with no crude being found locally within T1. Because T1 represents a separate migration pathway, sand-rich facies capping T1 may well contain unproven crude oil potential.
AAPG Search and Discovery Article #91003©1990 AAPG Annual Convention, San Francisco, California, June 3-6, 1990