The basal Atokan Spiro Sandstone Interval of eastern Oklahoma was deposited as an assemblage of marine shelf, wave-dominated deltaic, incised valley-fill channel,-tidal flat, and estuarine environments during a eustatic cycle involving large-scale marine regression followed by a lengthy period of marine transgression. Spiro Interval sedimentation began with high-stand deposition of prodelta shale fed onto the Wapanucka distally steepened ramp by earliest Atokan deltas located in the Fort Smith area. This was followed by eustatic regression that brought about fluvial downcutting into the "pre-Spiro shale" by several channel complexes, collectively termed the Foster channels, that transported coarse-grained siliciclastics from a northerly, cratonic source to lowstand, perched deltas present along the ramp's outer margin.

The subsequent transgression involved both a eustatic rise in sea level and tectonic collapse of the ramp margin, indicating a change from a passive continental margin to collisional plate boundary. Terrestrial strandplain facies of the lowstand deltas were reworked westward parallel to strike along the middle shelf, while the Foster channel incised valleys backfilled with bayhead delta lobes, estuarine deposits, tidal flats, and lastly, bioturbated, inner-shelf marine sediment. Several temporary stillstands allowed local bayhead deltas to spill out onto the middle and inner shelf. Complete collapse of the ramp resulted in the deposition of crinoid-rich sheet sandstone across underlying valley-fill and delta-plain facies and ultimately brought about the retreat of deltaic sedimentation to a new shelf margin more than forty miles to the north.

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