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The AAPG/Datapages Combined Publications Database

AAPG Bulletin

Abstract


Volume: 38 (1954)

Issue: 11. (November)

First Page: 2302

Last Page: 2323

Title: Moodys Branch-Cockfield Contact in Sabine Parish, Louisiana, and Adjacent Areas

Author(s): Robert C. Treadwell (2)

Abstract:

Brackish or marginal-marine upper Cockfield sediments are exposed between the Red and Sabine rivers in western Louisiana. These clays, silts, and sands are complexly lenticular and interfinger with many deltaic fresh-water beds of similar composition. The Jacksonian Moodys Branch formation, overlying the Cockfield, consists of rather uniform, glauconitic, marine sands throughout its known outcrop in this area.

Two sedimentary facies comprise the Cockfield directly below the Moodys Branch. In southwest Sabine Parish marginal-marine deposits (Creola member) predominate; elsewhere, fresh-water deltaic sediments underlie the marine beds of the Moodys Branch. Brackish deposits occur in places stratigraphically below these fresh-water deposits. In both occurrences the contact is sharp. However, "borings," extending from the Moodys Branch several feet into the Cockfield, are commonly encountered. At one locality deltaic fresh-water Cockfield grades through several feet into the Moodys Branch.

Analysis of the microfauna found in the Creola and Moodys Branch sediments shows that more than half of the species collected do not cross the Moodys Branch-Cockfield boundary. Furthermore, the Creola fauna is much less abundant. This change, although indicative of some break in deposition, is considered primarily ecologic.

In this area there is small, but apparent, stratigraphic discontinuity between the Moodys Branch and Cockfield formations. The term diastem most nearly expresses this relationship when viewed locally. These strata and their contact relationships are favorably comparable with conditions in parts of the Louisiana coast where marine sands are encroaching on contemporaneous and slightly older brackish and limnic sediments.

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