Abstract

In Virgilian (Late Pennsylvanian) time, terrigenous material was deposited in the Anadarko basin in the form of deltaic fans which range up to 1000 ft. in thickness. The Ouachita foldbelt is considered the principal source of the clastic material. The topset surface of each deltaic wedge is overlain by an extensive shelf-carbonate unit which often grades into a narrow, porous, greatly thickened, shelf-edge carbonate bank located on the outer margin of the delta along the shelf-slope break. Basinward the carbonate bank is contiguous with the succeeding deltaic fan. In Virgilian time thirteen cycles — each consisting of a deltaic wedge and its contiguous shelf-carbonate unit — prograded westward into the Anadarko basin.

To account for this style of cyclic sedimentation, a depositional model is proposed in which (1) the Anadarko basin subsided at a constant rate, (2) the supply of clastic sediments provided by the Ouachita foldbelt was not sufficient to fill the Anadarko basin within a limited time, and (3) periodic lowering of base level through eustatic sea-level changes enabled clastic material to move across the carbonate shelf and into the Anadarko basin.