--> Abstract: Sedimentary Facies, Structures, and Grain-Size Distribution--Red River in Oklahoma and Texas, by Daniel E. Schwartz; #90965 (1978).
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Abstract: Sedimentary Facies, Structures, and Grain-Size Distribution--Red River in Oklahoma and Texas

Daniel E. Schwartz

The braided-to-meandering transition zone of the Red River in Oklahoma and Texas consists of four principal facies (channel-bar, point-bar, Previous HitfloodNext Hit-flat, and Previous HitfloodNext Hit-plain) and two subfacies (the point-bar facies is divided into sheet-flow and channel-flow point-bar subfacies). Each facies and subfacies contains an assemblage of sedimentary structures which occur in response to the varying discharge regime of this sand-bed stream. The channel-bar facies is characterized by fine-grained sand and a predominance of Pi- and Gamma-cross-stratification, plane-bed stratification, and scouring surfaces. Medium-grained sand with Epsilon- and Pi-cross-stratification, plane-bed stratification, and sand-filled mud cracks characterize the sheet-flow point-bar subfacies, whereas Pi-, Beta- and Nu-cross-stratification and soft-sediment faulting in fine-grained sand characterize the channel-flow point-bar subfacies. Medium-grained sand with Pi- and Gamma-cross-stratification, plane-bed stratification, and scouring surfaces characterize the Previous HitfloodNext Hit-flat facies; and very fine-grained sand, Pi-, Nu-, and Kappa-cross-stratification, mud cracks, desiccated mud beds, thick mud slabs, contorted bedding, and burrows characterize the Previous HitfloodNext Hit-plain facies.

Grain-size distributions and sedimentary textural parameters of these facies and subfacies are distinctive, and can be used to differentiate them. Sediments of the Previous HitfloodNext Hit-plain facies are fine-grained, fine-skewed, and poorly sorted, and channel-flow point-bar subfacies sediments are well sorted. Sediments of the channel-bar facies are fine-skewed, but sheet-flow point-bar subfacies and Previous HitfloodNext Hit-flat facies sediments tend to be coarse-skewed. Mean grain size, standard deviation, and skewness are the most powerful discriminators. Scatter diagrams plotting these parameters display separations between the two point-bar subfacies, the Previous HitfloodNext Hit-flat facies, and the Previous HitfloodTop-plain facies. Sediments of the channel-bar facies were scattered in all plots. Combining structural data with grain-size data is effective in separating transition-zone facies, and may be useful in analyzing ancient fluvial sand bodies.

AAPG Search and Discovery Article #90965©1978 GCAGS and GC Section SEPM, New Orleans, Louisiana