The Hartshorne Sandstone and associated fine-grained facies of the Arkoma basin were deposited in a high-constructive, tidally influenced delta system which prograded longitudinally from east to west in an elongate, foreland basin during Ouachita suturing.

Prodelta facies (generally mapped as upper Atoka) consists of dark gray, nonfossiliferous shales. Delta front facies deposited near the mouth of an active distributary channel include interlaminated siltstones and sandstones of distal bar origin and ripple-bedded and trough cross-bedded sandstones of distributary-mouth bar origin. Delta front facies deposited in interdistributary areas consists of lenticular, wavy, and flaser-bedded sandstones, siltstones, and shales deposited under the influence of tidal currents. Delta plain facies is sandstone, siltstone, shale, and coal deposited in distributary channels, interdistributary bays, crevasse splays, marshes, and swamps. Distributary channel sandstone bodies display shoestring geometry (50 to 60 m thick), 1 to 3 km wide, tens of km lon ) and internally are unidirectionally trough cross-bedded. Their linear geometry and thickness relative to other delta facies suggest that channels were structurally localized, that the delta was elongate, or a combination of the two. Interdistributary bay facies comprise locally fossiliferous shale and silty shale. Crevasse splay facies coarsen upward from shale through ripple-bedded sandstone to trough cross-bedded sandstone. Marsh and swamp facies are carbonaceous shale and coal.

In Arkansas, the Hartshorne displays a single, progradational sequence of prodelta, delta front, and delta plain facies. In Oklahoma, the prodelta and delta front facies are capped by a complex assemblage of delta plain facies which records at least three episodes of active sedimentation followed by delta plain abandonment. Understanding the genesis of these delta plain facies will enhance petroleum and coal exploitation efforts within the Hartshorne of the Arkoma basin.

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