PALEOCOLOGY OF BENTHIC FORAMINIFERA FROM THE COCKFIELD FORMATION (EOCENE; BARTONIAN) OF THE MOBIL-MISSISSIPPI CORES, WAYNE COUNTY, MISSISSIPPI

The Bartonian age Cockfield Formation in Mississippi consists of fossiliferous, dark gray sand with distributed concentrations of molluscan fossils and glauconitic sand with shell fragments at the base. Overlying the lower Cockfield Formation, is the Creola Member, a moderately to sparsely fossiliferous, brownish gray to brownish black calcareous sand. Sequence stratigraphic interpretations indicate that the Cockfield Formation is a correlative of the Gosport Sand in Alabama and the Yegua Formation of Louisiana and Texas. The Cockfield Formation therefore represents Gulf Coast depositional sequence TE 3.1 in eastern Mississippi.

A total of 207 samples were processed for benthic foraminifera from the lower Cockfield Formation and the Creola Member of the Mobil-Mississippi Office of Geology #1 Ketler core, Wayne County, Mississippi. Of the 207 samples, 75 provided the required amount of foraminifera to be considered in this study. The 75 samples occur in 3 distinct groups separated by zones barren of foraminifera in the section.

Benthic foraminifera are present throughout the Cockfield Formation. The faunas are primarily dominated by the Cibicidoides-Discorbis assemblage. The lower portion of the Cockfield Formation is characterized by the Cibicidoides-Discorbis assemblage but also includes significant percentages of Bulimina, Bolivina and Uvigerina indicative of a deeper water environment. Above this interval, specimens of Nonion become common indicating a shallowing trend. Above this interval, is a 3.8m thick barren interval of sand and silt. Overlying this interval, the Cibicidoides-Discorbis assemblage with Bulimina and Bolivina returns and is capped by an additional 4m thick bed of sand and silt barren of foraminifera. The entire overlying Creola Member is dominated by the Quinqueloculina-Triloculina assemblage representing a near shore depositional environment.

The benthic foraminifera collected in this study are consistent with the accepted sequence stratigraphic interpretation of Sequence TE 3.1 (Gosport-Cockfield-Yegua). The assemblages indicate an overall shallowing upward trend from the base of the Cockfield. The repetition of the Cibicidoides-Discorbis assemblage and barren zones in the Cockfield may reflect the distribution of parasequences within the section.