Structure and Stratigraphy of a Complex Anticlinal Feature, Backbone Anticline, Arkoma Basin, Arkansas.

摘要

The Arkoma Basin of Arkansas and Oklahoma formed in the Ouachita foreland during the late Mississippian and Pennsylvanian periods (about 290- to 330 million years ago). The basin developed in response to convergent tectonic boundaries that closed obliquely from west to east associated with Ouachita orogenic event. The Backbone anticline in the northern Arkoma Basin is a prominent product of this convergence, and represents the first major component of this study. The structure is asymmetric with beds on the southern limb dipping steeply to the south. It is also expressed topographically as a prominent ridge that trends eastward from the Oklahoma-Arkansas border approximately 30 miles. The ridge is bounded on the northern side by a steeply dipping normal fault with most of the sedimentary exposure occupying a position on the southern hanging wall of the structure. Strata involved in the structure are sandstone and shale units from the middle and upper part of the Atoka Formation. A recent road cut in southern Sebastian County, Arkansas exposes a complete and continuous section of more than 600 feet in thickness through an upper Atoka sandstone unit along the Backbone anticline.;A subsurface stratigraphic study of the middle of the Backbone anticline was also conducted. Several normal and some reverse faults were noted from cross-sections of the subsurface using IHS PETRARTM software program. The upper 5400 feet of the Atoka Formation includes intervals from the middle and upper part of the formation. This interval extending from the Casey Sand to the Upper Alma Formation was examined by means of three cross-sections prepared from wire line logs to determine the role of faulting in the sedimentary section.