The Upper Pennsylvanian Haymond Formation crops out along the southeast, east, and northeast parts of the Marathon basin, Texas, and consists of two major units of thin- to thick-bedded, fine- to medium-grained sandstone separated by boulder beds. These rock types overlie and grade into the underlying deep-water turbidite sequence which is composed of interbedded fine- and very fine-grained sandstone and dark-gray shale.

The sandstones occur as en echelon, lenticular bodies which have partly erosional bases, and laterally interfingering, gradational upper boundaries. The sandstone beds are massive at the base, grading upward into a

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trough cross-bedded and ripple-bedded top. The lower sandstone unit is interbedded with black to dark-gray, carbonaceous shale and siltstone, whereas the upper sandstone unit is recognized by associated basal conglomerate or interbedded lenticular conglomeratic beds, and poorly bedded, plant-disturbed sandstones. The boulder beds, between the sandstone units are composed of novaculite, limestone, sandstone, and conglomerate, and are interstratified with black, carbonaceous shale and gray siltstone. The boulders are considered to be of tectonic origin, probably derived as a result of faulting and/or uplift of the source area.

The environment of deposition of this facies is shown by features associated with the sandstone units. The erosion channels, occurrence of conglomeratic beds with the sandstones, poorly bedded and plant-disturbed sandstones, interstratification with carbonaceous shale, lack of marine fossils, and development of large-scale cross-bedded sandstones in general suggest a very restricted shallow-water to transitional deep-water depositional environment for these strata.

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