Depositional Microfacies and Burial Diagenesis in the Upper Jurassic, Cotton Valley (Haynesville) Limestone, Teague Townsite Field, Texas, by Wayne M. Ahr, R.C. Faucette, and C.K. Steffensen, Pages 107 - 117
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.

Depositional Microfacies and Burial Diagenesis in the Upper Jurassic, Cotton Valley (Haynesville) Limestone, Teague Townsite Field, Texas

Wayne M. Ahr
Texas A&M University, Department of Geology,
College Station, Texas 77843

R.C. Faucette
Getty Oil Co.,
5177 Richmond Ave., Suite 800,
Houston, Texas 77056

C.K. Steffensen
Arco Exploration,
P.O. Box 1346,
Houston, Texas 77251

ABSTRACT

The Cotton Valley Limestone, like the older Smackover Formation, was deposited on a ramp where the monotonous regional topography was punctuated by both salt-generated and basement highs that greatly influenced local depositional environments. Teague Townsite Field is located above anticline with an irregular surface that formed several paleostructural highs, or shoals, where Cotton Valley grainstones were deposited. Open marine wackestones and packstones surrounded the oolite shoals and updip, shaly wackestones were deposited in more restricted environments. Upper Cotton Valley Limestone rocks show an overall increase upward in the ratio of carbonate grains to mud, which is a result of shoaling from a Late Jurassic regional regression. Nine smaller, shoaling-upward cycles are present in the study area; they probably reflect local salt movements. The reservoir at Teague Townsite Field produces mainly from intraparticle porosity which formed by early alteration of metastable allochems in the meteoric phreatic environment; development of this environment was contemporaneous with several of the episodic regressions. Interparticle porosity was filled early by equant and bladed cements. Neomorphism and replacement were common in early diagenesis. Subsequently, there was compaction, stylolitization, sparite cementation, and introduction of saddle dolomite. Whole-rock analyses indicate that the present-day trace element distribution reflects (1) early cementation and flushing of porous zones; (2) comparatively less flushing of muddy zones; and (3) late introduction of subsurface fluids. Whole-rock d¹⁸O/d¹³C values plot within the published range of data on "typical Jurassic cements." The average d¹⁸O values are - 5 and the average ¹³C values are + 2.5 PDB. A tendency toward heavier isotopic composition with increased depth is interpreted to be the result of subsurface fluid influx during burial.