Smackover Grainstones in Miller County, Arkansas, by Champe A. Fisher, Jr., Pages 87 - 94
from:
East Texas Geological Society Publication: The Jurassic of East Texas, Edited by Mark W. Presley
Copyright 1984 by East Texas Geological Society. All rights reserved.

Smackover Grainstones in Miller County, Arkansas

Champe A. Fisher, Jr.
Department of Geology, University of Arkansas,
Fayetteville, Arkansas 72701

ABSTRACT

Smackover (Upper Jurassic) oolitic carbonates in central Miller County, Arkansas, exhibit secondary oomoldic porosity, but only minor permeability. These oolitic grainstones were deposited in updip areas of Smackover shelf environments. The original grainstone sediments were composed mainly of oolites, with minor pisolites and composite grains. Since deposition, the rocks have been extensively leached, recrystallized and cemented. During the early stages of diagenesis there was micritization of oolites. Some oolites were partially leached, and subsequently collapsed to leave broken and sheared grains. Early-stage fibrous-rim cements formed over these broken oolites, as well as other grains, in areas where there were appropriate phreatic conditions. With continued diagenesis, calcite spar filled pores; the spar cement subsequently supported molds of oolites in many intervals as leaching of grains continued. This diagenesis has left a variety of oolite-derived grain forms which are grouped into nine categories in this study.