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The AAPG/Datapages Combined Publications Database

AAPG Bulletin


Volume: 69 (1985)

Issue: 2. (February)

First Page: 259

Last Page: 259

Title: Influence of Basement Islands and Ridges on Smackover Deposition, Southwest Alabama: ABSTRACT

Author(s): Allen L. Greene

Article Type: Meeting abstract


Pre-Jurassic basement highs, composed of igneous and/or metamorphic rocks, have influenced the deposition of Jurassic Smackover sediments in Clarke, Monroe, Conecuh, and Escambia Counties, Alabama. These basement islands and ridges provided a structural fabric on which Smackover sediments were deposited.

The following 3 basic structural settings illustrate the thickness variations and lithofacies distribution of Smackover sediments on the flanks and crests of these basement highs. Emergent features were never covered by Smackover seas, resulting in nondeposition of Smackover sediments over their crests. Flanking these features are finely crystalline and anhydritic dolomites capped by bedded nodular-mosaic anhydrite. The anhydrite grades upward into Haynesville continental sediments that also overlie the crests of these features. Semi-emergent features were above sea level for most of Smackover deposition. It was not until near the end of Smackover transgression that these islands and ridges were inundated. As the seas regressed, shoaling occurred on the flanks of these features deposi ing predominantly grain-supported limestones that were later dolomitized. The crests of these basement highs are covered by thin, low-porosity, grain- and mud-supported dolomites capped by bedded nodular-mosaic to distorted mosaic anhydrite. Nonemergent features were submerged through most of Smackover deposition. This enabled carbonates to accumulate as thick organic buildups and shoals over crestal portions of the basement highs. These thoroughly dolomitized and highly porous and permeable crestal sediments grade upward into nonporous, mud-supported dolomites capped by bedded nodular-mosaic anhydrite.

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