Subsurface Stratigraphy of the Morrow Formation in Southeastern Texas County, Oklahoma

ABSTRACT Regional cross sections, detailed isopach mapping and structural studies serve as a framework for interpreting subsurface stratigraphic relations of oil and gas bearing Morrow sandstones in the southeastern part of Texas County, Oklahoma, an area on the northwestern shelf of the Anadarko basin. The location of a Mississippian/Pennsylvanian unconformity was established here by making many log correlations through the Mississippian section to the unconformity surface, and this work was augmented by the examination of well cuttings. Seven regional cross sections aided in constructing an isopach map which helped to relate the distribution and configuration of the lowest Pennsylvanian sandstones to the Mississippian topographic surface. This isopach map, which actually represents inverted pre-Pennsylvanian topography, reveals a southwest sloping paleosurface. Rocks exposed on this surface were shales and carbonates of Mississippian age. Lower Morrow sandstones, shales and carbonates were deposited as linear, mixed clastic and carbonate shoreline sequences during a marine transgression to the northeast. Upper Morrow sandstones represent distributary channels on a prograding shoreline. Marine conditions resumed with the deposition of the Thirteen Finger Limestone. Structural mapping of the area shows an undulating surface with a gradual slope to the southeast. The only abrupt structural feature is an apparently downfaulted block on the edge of an uplifted region in the northwest part of the map area. This abstract is approved as to form and content. Bruce F. CurtisFaculty member in charge of thesis