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The AAPG/Datapages Combined Publications Database

AAPG Bulletin

Abstract


Volume: 53 (1969)

Issue: 9. (September)

First Page: 2034

Last Page: 2035

Title: Upper Jurassic Carbonate Rocks in Northern Texas and Adjoining Parts of Arkansas and Louisiana: ABSTRACT

Author(s): Kendall A. Dickinson

Article Type: Meeting abstract

Abstract:

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Carbonate rocks make up only a small part of the total Upper Jurassic sequence, but they are widespread and are sensitive indicators of their environments of deposition. Consequently, carbonate studies have yielded data vital for stratigraphic correlation and interpretation of environment. Rocks of Upper Jurassic age include, in ascending order, the Smackover and Buckner Formations and the Bossier and Schuler Formations of the Cotton Valley Group. These rocks are in the subsurface at depths ranging from 3,000 to 12,000 ft.

The Smackover Formation contains three informal members. The lower member, one of the most widespread and easily recognized units of Late Jurassic age, consists of dark-gray, commonly laminated, silty to argillaceous limestone, that was deposited throughout a deep, possibly stagnant, basin. The middle member, generally restricted to basin margins, consists of medium-brown pelletoid or structureless limestone deposited in the shallower parts of a basin that supported a relatively abundant fauna. The upper member, also limited to basin margins, consists mostly of light-brown to black oolitic to pisolitic limestone that represents deposition in a shallow-water high-energy environment. This member includes the petroleum-producing Reynold's oolite.

The Buckner Formation contains two members. The lowest member consists mostly of laminated micrograined anhydrite and anhydritic mudstone, but in restricted areas consists of fine-grained dolomite. It represents deposition in an evaporitic basin and associated mudflats. The upper member consists mostly of nodular anhydritic mudstone that represents deposition in evaporitic mudflat. It contains a bed of limestone, known locally as the A zone, that represents a temporary advancement of the sea across the mudflat.

The Bossier Formation represents the offshore equivalent of the Buckner and parts of the Smackover and Schuler Formations. It consists mostly of dark-gray splintery calcareous shale, but contains shell material in various amounts. A limestone at the base of the Q tongue consists mostly of silty micrite containing a fossil assortment that is characterized by algal-encrusted grains but also includes foraminifers, gastropods, ostracods, and echinoid fragments.

The Schuler Formation, which includes a marine and nonmarine facies, consists mostly of mudstone, shale, and sandstone but contains some limestone in the marine facies. Algal micrite is present in the upper part, and some argillaceous coquina and phosphatic clastic limestone that apparently represent beach environments are present near the base.

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