Facies Patterns and Depositional Models, Pennsylvanian System, Palo Duro Basin, Texas Panhandle: ABSTRACT

Abstract

End_Page 442------------------------------Subsurface study of the Palo Duro basin, Texas Panhandle, indicates that strata of Pennsylvanian age were deposited in a variety of clastic and carbonate environments. Up to 2,400 ft (720 m) of sediment was deposited with maximum accumulation along a NW-SE-trending basin axis. Major rock types include alluvial-fan and fan-delta sandstone and conglomerate, shelf and shelf-margin carbonate rock, and basinal shale and fine-grained sandstone. Erosion of Precambrian basement in the Amarillo and Sierra Grande uplifts supplied arkosic sand (granite wash) to alluvial fans and fan deltas along the northern margin of the basin. Distal-fan sandstones are interbedded with thin shelf limestones; basinward of clastic deposition, shallow-shelf carbonate sediment was deposited across most of the basin. Basinal shales are present only in a small area just north of the Matador arch. Late in the Pennsylvanian, increased subsidence deepened and enlarged the basin. Ultimately, the basin axis trended east-west with a narrow northwest extension. Along the eastern and southwestern margins of the basin, superposed shelf-limestone buildups form an abrupt, massive shelf edge. Along the northern part of the western shelf, however, two shelf margins are recognized, indicating that a younger shelf edge retreated westward as much as 18 mi (29 km). An increase in clastic deposition combined with continued subsidence may have caused the retreat of the limestone shelf margin. Basin filling occurred mainly during periods when clastic sediment entered the basin through feeder channels at the northern and eastern ends of the basin. End_of_Article - Last_Page 443------------