page_title: Geology and hydrology of the Wichita Falls, Texas area
section_title: Permian Rocks
hierarchical_section_title: Geology and hydrology of the Wichita Falls, Texas area / Permian Rocks
caption_attribution_description: English: Sandstone channel in mudstone within the Petrolia Formation as exposed along Wiley Road, west of Wichita Falls, TX
context_page_description: The exposed strata at the surface in and around Wichita Falls are the products of one ancient period of deposition with a modest amount of recent and modern alteration. In all cases, the strata are products of terrigenous environments dominated by fluvial depositional and erosional systems.
context_section_description: In the Permian geologic period, North-Central Texas was a part of the western coastal zone of equatorial Pangea, a super-continental land mass.  Nearby uplifts and mountainous regions, such as the Muenster Arch and Red River Uplift, the Wichita, Arubckle, and Ouachita mountains developed by the end of the Pennsylvanian, providing elevated topography to the north and east during the Permian.  The rocks of the Permian Basin of West Texas record a contemporaneous shallow inland sea.  The resulting topography provided northeast-to-southwest gradients for stream flow and sediment movement.  The sediments deposited by the Permian streams of North-Central Texas were likely reworked clastic materials from Middle Pennsylvanian stream and fan-delta sediments proximal to the Ouachita foldbelt and Muenster Highlands.
  The Petrolia Formation (of the Late Wolfcampian-Leonardian systems) dominates the exposed Permian strata in Wichita falls, as mapped by the 1987 Texas Atlas of Geology.  The map describes the formation as 360–400 feet of weakly or unstratified mudstone with laminated, cross-bedded sandstone lenses.  The formation increases in mudstone content upsection.  Sandstone lenses contain terrestrial fossils of plants, vertebrates, and footprints.  The unit contains calcareous nodules of varying sizes as well as poorly indurated "conglomerate" with vertebrate fossils.  In general the entire package is only weakly lithified, perhaps indicating that the region was not appreciably covered by a thick package of younger strata.
  Several correlated sandstone units crop out in the immediate region.  These dominate the region adjacent to the Seymour Highway, on the slopes to the south of the Wichita River (locally known as "the bluffs").  The  Texas Atlas of Geology mapped these as ss6.  Most outcrops are buff-colored, medium-grained, well-sorted quartzose sandstones.  These exhibit extensive cross-bedding and soft-sediment deformation features.  Some deposits are friable, others well cemented.  Locally, there appears to be three prominent layers of sandstone separated by mudstone.  Because of variable erosion rates, each influences topography by forming ledges and benches, and in places may form mesa-like landforms.  In and around the city, these occur roughly at 960, 1000, and 1060 feet above sea level.
caption: Sandstone channel in mudstone as exposed along Wiley Road, west of Wichita Falls.  The buff-colored rock preserves numerous fluvial sedimentary structures.
exif: {"Image Software": "Picasa", "Image ExifOffset": "46", "EXIF ExifVersion": "0220", "EXIF ImageUniqueID": "ffec948962f05fb4ad06311bfb22e890"}