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Sedimentation of Shelf Sandstones in Queen Formation, McFarland and Means Fields, Central Basin Platform of Permian Basin

A. Malicse, J. Mazzullo, C. Holley, S. J. Mazzullo

The Queen Formation is a sequence of carbonates, evaporites, and sandstones of Permian (Guadalupian) age that is found across the subsurface of the Central Basin platform of the Permian basin. The formation is a major hydrocarbon reservoir in this region, and its primary reservoir facies are porous shelf sandstones and dolomites. Cores and well logs from McFarland and Means fields (on the northwest margin of the Central Basin platform) were examined to determine the sedimentary history of the shelf sandstones.

Cores were taken from the two reservoir sandstones in the fields, designated the Queen A and Queen B sandstones and separated by 10-15 ft of anhydrite, dolomite, and/or mudstone. The two sandstones range in thickness from 15 to 35 ft (mean is 25 ft), and they thicken in a series of elongate northwest-southeast-trending bodies. The Queen A sandstone is underlain by massive or laminated dolomite; the Queen B sandstone is underlain by red and green mudstone with root traces and anhydrite nodules. Both sandstones are overlain by massive or laminated silty dolomite and anhydrite. The lower and upper contacts of the sandstones are always sharp and erosive; the lower contacts are generally overlain by gravel-size rock fragments and plant debris.

The Queen A and B sandstones are generally composed of well-sorted arkosic and subarkosic very fine sand and silt with minor amounts of clay. The lower parts of the Queen A and B contain an upward-fining sequence of (1) massive and tabular cross-bedded sandstone, (2) trough cross-bedded sandstone, (3) planar-laminated sandstone, and (4) wavy and lenticular ripple-laminated sandstone and siltstone. This sandstone was apparently deposited in fluvial (wadi) channel and flood-plain environments, and is the major reservoir lithology within the Queen Formation. The upper parts of the Queen A and B contain wavy-laminated and moderately to highly bioturbated siltstone with very thin claystone laminae and soft-sediment deformation features. They were apparently deposited in estuarine and tidal flat environments.

Deposition of both the Queen A and B sandstones in McFarland and Means fields was initiated by a rapid drop in sea level. This fall in sea level exposed highstand shelf and sabkha deposits (carbonates and evaporites) to subaerial erosion and weathering, and it allowed fluvial (wadi) environments to prograde seaward (southwestward) across the shelf. The deposition of the sandstones was terminated by a low rise in sea level and the resultant transgression of the fluvial environments by estuarine, tidal-flat, and shelf environments.

AAPG Search and Discovery Article #91034©1988 AAPG Southwest Section, El Paso, Texas, 21-23 February 1988.