This field guide is designed to provide an opportunity to observe a variety of facies that are the fundamental blocks with which principal depositional systems have been fabricated. Available data is provided and a genetic interpretation is proposed.

Upper Pensylvanian and lower Permian rocks of the Eastern Shelf in North-central Texas are composed of 10 to 15 repetitive sequences including open shelf, deltaic, fluvial, and interdeltaic depositional systems.

Nelson and others (1962) define a bank as " ... a skeletal deposit formed by organisms which do not have the ecologic potential to erect a rigid wave-resistant structure." They explain that a bank may have any geometry.

Pennsylvanian clastic and carbonate strata were deposited in a variety of environments within the Palo Duro Basin. Maximum accumulation (totaling 750 m or 2,400 ft) occurred along a northwest-southeast axis.

Cores from deep stratigraphic test wells provide an excellent basis for determination of source-rock quality and thermal maturity of potential hydrocarbon source rocks in the Palo Duro Basin. Total organic carbon (TOC) content in Pennsylvanian and Wolfcampian rocks is highest in basinal shales.

Three mappable members in the upper part of the Thrifty formation (Blach Ranch limestone, unnamed shale, and Breckenridge limestone), two in the lower part of the overlying Harpersville formation (Quinn clay and Crystal Falls limestone), and six minor lentils, all in the outcropping Cisco group,