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Foraminiferal Biostratigraphy and Paleoecology of Wilcox Group (Paleocene-Eocene), Central Louisiana

Lori Lewis Nunn

The Wilcox Group in east-central and south-central Louisiana consists of 300-1,200 m of mostly clastic marine and nonmarine deposits. Detailed micropaleontologic studies of the Wilcox Group in Louisiana are not available because the strata are generally unfossiliferous, especially in the northern, updip part of the study area. However, the present foraminiferal study, done in conjunction with a comprehensive regional investigation, has yielded significant biostratigraphic and paleoenvironmental information. Well cuttings and conventional cores from wells drilled by various oil companies into Wilcox units in Allen, Avoyelles, St. Landry, St. Martin, and Pointe Coupee Parishes contain planktonic foraminifera that permit their assignment to established regional and worldwide zonation schemes. The section ranges from the Paleocene to the Eocene, and includes the Globorotalia angulata, G. pusilla, G. pseudomenardii, G. velascoensis, and G. subbotinae zones.

Samples from conventional cores drilled through the Wilcox section throughout the study area yield benthic foraminiferal faunas that are dominated by agglutinated species and represent marine environments that range from the inner continental shelf to the continental slope. Core samples of glauconitic sandstones from the uppermost part of the section contain faunas that are dominated by Discocyclina sp. and other species of calcareous larger foraminifera. These faunas indicate shallow-water continental-shelf paleoenvironments.

Many of the producing reservoir sandstones in the downdip part of the study area are stratigraphic traps of a marine depositional origin. This foraminiferal study, in conjunction with the ongoing regional Wilcox synthesis, will yield insight to similar producing trends in the downdip parts of the upper Wilcox.

AAPG Search and Discovery Article #91043©1986 AAPG Annual Convention, Atlanta, Georgia, June 15-18, 1986.