Named as formation in the Chispa Summit region, western Jeff Davis Co, TX in Permian basin. Type locality in the headwaters of Van Horn Creek on the Johnson and Colquitt ranches, in the neighborhood of Needle Peak [reader is referred to Adkins (1932, p. 36, fig. 7)]. Is about 800 ft thick. Derivation of name not given. Overlies Buda limestone, apparently concordantly. Is overlain by Colquitt formation. Described as one of 5 facies of Eagle Ford group in TX. Consists almost entirely of the clay or marl (Mancos) facies, with subordinate amount of thin platy layers and bands of septaria and concretions. Is considered Eagle Ford equivalent in Chispa Summit area. Composite section with fossils (mostly ammonites) presented from Adkins (1931). Age assignments based on ammonite zones given (ascending): NEOCARDIOCERAS zone is late Cenomanian; PSEUDASPIDOCERAS zone is early Turonian; and ROMANICERAS zone, COILOPOCERAS-ROMANICERAS transition zone, and COILOPOCERAS zone are late Turonian.

Source: GNU records (USGS DDS-6; Denver GNULEX).

Collections from septarian limestone concretions and unusual hiatus concretions [stratigraphic positions not stated] assigned a middle Turonian (Late Cretaceous) age based on presence of the ammonite SPATHITES COAHUILAENSIS from USGS Mesozoic localities D10750 and D10751 in vicinity of Needle Peak, Jeff Davis Co, TX in the Permian basin. Associated fauna noted: COLLIGNONICERAS WOOLLGARI, TRAGODESMOCERAS sp., and ROMANICERAS sp.

Source: GNU records (USGS DDS-6; Denver GNULEX).

Is adopted as defined by Adkins (1932). Lower part of formation is assigned a late middle Cenomanian (Late Cretaceous) age based on presence of the ammonite TARRANTOCERAS SELLARDSI from USGS Mesozoic localities D10741, D10742, and D10746 at Chispa Summit, western Jeff Davis Co, TX in the Permian basin. Fauna places lower part of unit in CUNNINGTONICERAS AMPHIBOLUM AMPHIBOLUM subzone of C. AMPHIBOLUM zone.

Source: GNU records (USGS DDS-6; Denver GNULEX).