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Geometry and Depositional Sy Tems of the Cromwell Sandstone (Morrowa Lower Dornick Hills) in Parts of Haskell, Latimer, Le Flore Muskogee and Sequoyah Counties, Oklahoma

Abolo, Martin Guy Claude
In the Arkoma Basin of northeastern Oklahoma, the Cromwell Sandstone consists of one single well-distributed member. This member lies disconfonnably on the underlying Pitkin Limestone (Upper Mississippian) and is bounded conformably at its top by the unnamed limestone referred to as the Union Valley Limestone. The petrography of the Cromwell, which includes calcareous sandstones with shale interbeds, is quartz-arenite to sublitharenite. On the basis of evidence provided by subsurface mapping and cores, the Cromwell Sandstone is interpreted as having accumulated in wave-modified riverdominated deltaic systems. Three major delta lobes were identified in the study area. All of them trend from north to south and probably confirm the northerly cratonic source for the sediments. The sandstone contains distributary channel, reworked interdistributary, and delta-fringe deposits of a wave-modified river-dominated delta sequence.