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` . Sorting is good , except -for the authigenic <br /> clay near the top . Massive and plane-bedded unit predom- <br /> inate, while some cross-bedding , mostly in the form of small <br /> tabular sets , shows a general transport direction of east- <br /> northeast . A number of trough sets have been identified , <br /> with an average transport direction of south-southeast , or <br /> nearly perpendicular to the tabular sets . Ophiomorpha <br /> burrows are the only common fossil remains in the Rollins . <br /> Root marks are locally common in the uppermost part of the <br /> sandstone. <br /> The Rollins represents a complex of delta- <br /> front deposits , including distal and distributary mouth bar , <br /> subaqueous levee, barrier bar-beach, and possible occasional <br /> barrier island environments . Differing transport directions <br /> reflect the transition from long-shore to channel control of <br /> deposition. (Collins , 1977) <br /> Above the Rollins is the Coal Basin Coal <br /> Interval which, as noted, is 20 ' -30' thick and contains the <br /> A and B bed seams.. The coal rests directly on the sandstone <br /> in some places . Generally , however , it is found interbedded <br /> with shales and siltstone, up to 13 ' above the Rollins . <br /> Between the B and Middle bed coal seams lie the Bowie <br /> Shale Submember and the Middle Sandstone Submember of the <br /> Williams Fork Formation. More than 400 ' thick, the lower <br /> Bowie Shale Submember consists of mudstones , sandstones and <br /> shales , a complex of intertonguing deltaic environments , <br /> • <br /> 21 <br />