Edwards 1986: A reappraisal of depositional environment (barrier bar or submarine fan) for Lower Wilcox sandstones of Valentine Field, Lavaca County, Texas Gulf Coast. South Texas Geol.Soc.; Contributions to the Geology of South Texas. 252-259.

Stratigraphical section through basal Lower Wilcox showing correlation revision - 186k - click to enlarge


Two detailed studies of lower Wilcox sandstone reservoirs of the Valentine and Menking Fields arrived at contrasting conclusions as to the depositional environment of the sandstones. The purpose of this paper is to explain the reason for this conflict and to resolve the observations into a coherent model.

Chuber (1979) regarded the sandstones to have been deposited in barrier bar and related coastal environments, while Berg (1979) favored turbidite deposition in an outer shelf to slope setting. The reason for the divergence of opinions is apparently a miscorrelation of the key Harkins No.1 Paul well log. A new interpretation of this log places the main unconformity below the turbidite sandstones observed in cores from this well. Thus, the turbidite sandstones occur within an erosional channel and are separated from the thick sandstone unit that comprises the main reservoir.

This modification is consistent with Chuber's barrier bar model for the main reservoir sandstones, and also supports Berg's deeper-water interpretation for the overlying non-reservoir sandstones which fill the lower part of a submarine canyon.


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©by Marc B. Edwards
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