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The AAPG/Datapages Combined Publications Database

AAPG Bulletin

Abstract


Volume: 69 (1985)

Issue: 9. (September)

First Page: 1419

Last Page: 1420

Title: Depositional Systems and Distribution of Cotton Valley Blanket Sandstones in Northern Louisiana: ABSTRACT

Author(s): Lori G. Eversull

Article Type: Meeting abstract

Abstract:

In northern Louisiana, the Terryville Sandstone of the Cotton Valley Group is composed of four regressive, massive sandstone members. These sandstones lie stratigraphically between the underlying marine shales of the Bossier Formation and the overlying Knowles Limestone. Extending updip from the two youngest sandstone members of the Terryville are at least 14 distinct sandstone tongues, or blanket sandstones.

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These blanket sandstones thin progressively updip and eventually pinch out into the time-equivalent Hico Shale.

The sandstones can be divided into two groups based on thickness and extent. Sandstones of group I are generally less than 70 ft (21 m) thick and extend across most of northern Louisiana. In group II, sandstones are rarely greater than 30 ft (9 m) thick and are far less extensive, commonly occurring in isolated pods. Sandstones of both types are stacked vertically and are distributed across northern Louisiana in an elongate, arcuate belt.

The Terryville sediments were delivered to a slowly subsiding shelf by two major marine-dominated delta systems. Marine processes spread the sediments across the shelf, forming massive sandstones. The blanket sandstones were produced when minor marine transgressions--resulting from eustatic sea level rise, deltaic subsidence, or both--caused the transportation of sediments northward from the area of massive sand accumulation. Local topographic relief on the shelf apparently had little effect on the distribution of the blanket sandstones, although overall deposition of the Cotton Valley Group was influenced by several local structures.

Cross sections and isopach maps produced in this study define precisely the distribution of the blanket sandstones and demonstrate the repetitive nature of the Cotton Valley sandstones.

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