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The Lower Cretaceous DeQueen Formation crops out in a narrow sinuous band extending east-west from Pike County, Arkansas, to near Broken Bow, Oklahoma. Natural exposures are poor, but quarrying has exposed excellent vertical sections of the formation about 75 ft (23 m) thick at several localities. The DeQueen is composed of a lower sulfate facies and an upper sandstone-limestone-shale facies. The lower facies which is correlated with the subsurface Ferry Lake Anhydrite, is about 40 ft (12 m) thick. It is 60% gypsum and 40% dark shale, with minor interbedded mudstones. The upper facies, which is also about 40 ft (12 m) thick, is unconformably overlain by Upper Cretaceous clastic sediments. The upper facies is predominantly shale, with interbedded thin beds of sandstone, sa dy limestone, and celestite. This facies is equivalent to the lowermost beds of the Mooringsport Formation of the subsurface.
The environments of deposition of units within the lower sulfate facies have been interpreted from a sparse faunal assemblage, sedimentary structures, and trace fossils. However, the most intensive study has been concerned with the more richly fossiliferous beds of the upper facies of the DeQueen. Present in this unit are well-preserved pseudomorphs of displacive halite hoppers, calcite pseudomorphs after gypsum, and preserved intrastratal gypsum nodules. Oscillation ripples, current ripples, and a variety of trace fossils are very common in these beds also. Body fossil assemblages range from a less diverse restricted pelecypod-ostracod assemblage to a more diverse gastropod-pelecypod-ostracod-serpulid worm assemblage. Marine and terrestrial vertebrates are also common in these upper eds.
All of the above information has been incorporated with subsurface data in order to reconstruct the local and regional depositional framework of the DeQueen and its subsurface equivalents. A better understanding of the depositional environment of these rocks will promote interest in, and may lead to the development of, undiscovered hydrocarbon reserves within less-well-known downdip areas.
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