Named as formation in Late Pennsylvanian (Desmoinesian) Marmaton Group (revised) and as a member of the Desmoinesian Holdenville Shale (revised). If the Lost Branch Formation is extended southward as the upper part of the type Holdenville Shale in east-central OK, the Holdenville, there, could be raised in rank to group and component beds of the Lost Branch raised in rank to member. If the Holdenville is retained as a formation, the Lost Branch can be recognized as its upper member in that part of OK, retaining its component beds as currently ranked. Name probably taken from Lost Branch, which is a tributary of Pumpkin Creek. Type locality is described as an excellent exposure in a cutbank on the west side of Lost Branch near center NE1/4 NE1/4 NE1/4 sec 10, T33S,R18E, just southwest of Mound Valley; and a composite stratotype with sections of higher strata from west highbank of Pumpkin Creek (as well as exposures in a selected ravine and gullies) along the east line of SW1/4 SW1/4 NE1/4 sec 10, T33S,R18E, which are 1 mi (1.6 km) southwest of Mound Valley, Mound Valley 7.5-min quad, Labette Co, southeastern KS. The Lost Branch (formerly called the Desmoinesian Holdenville Shale in KS) is a thin but continuous horizon of gray to black marine shales with thin, pure to impure, limestones developed between terrestrial deposits at the top of the Marmaton, and is here traced by cores and wire-line logs for several hundred miles along the Midcontinent Pennsylvanian outcrop belt and the subsurface in OK, MO, IA, and NE, as well as in KS. In KS, a marine sandy limestone-calcareous sandstone unit (previously assigned to [basal] Hepler sandstone by Oakes and Jewett, 1943) is here regarded as merely an upward continuation of the marine Lost Branch; and it is probably a northern time equivalent of the Glenpool limestone bed of Bennison (1984) in northeastern OK. The stratotype consists of (ascending) slightly micaceous, sandy, soft dark-gray shale containing abundant megaspores, carbonized wood fragments, and weathered invertebrate skeletal debris, including a gastropod and conodonts; informal Desmoinesian Nuyaka Creek black shale bed of Bennison (1981, Type areas of the Seminole and Holdenville Formations, Western Arkoma Basin: AAPG Midcontinent Regional Meeting, Oklahoma City, Field Trip 2, September 19, 1981, p. 1-10) (first used); and finally capped by fossiliferous gray shale that carries diverse fauna, including the Desmoinesian brachiopod, MESOLOBUS (Moore, 1937; Oakes and Jewett, 1943). In MO, IA, and NE, the Desmoinesian Sni Mills Limestone Member (revised) is assigned to the Lost Branch; in IA and NE, the Desmoinesian Cooper Creek Limestone Member (revised) is also assigned to it. In OK, the informal Desmoinesian Glenpool and Homer School limestone beds (both first used), as well as the Nuyaka Creek, are identified in it. Total thickness at type, in KS, is 15 ft (4.6 m); ranges southward to as much as 65 ft (20 m) in east-central OK; and thins northward to 4 ft (1.2 m) in subsurface of southeastern NE. At type locality, overlies informal Desmoinesian Dawson coal bed and (or) its equivalent Memorial and (or) Lenapah Shale (both revised). In small gully just southwest of type, underlies, with sharp contact, Late Pennsylvanian (Missourian) Hepler unit (here used informally) (KS, MO) and (or) its equivalent South Mound Shale (KS); as well as Seminole Formation (OK), and Pleasanton Formation or Group (KS, MO, IA, NE) (all are Desmoinesian, all revised). Correlates with Lonsdale and West Franklin Limestone Members of the Illinois basin. Age is Middle Pennsylvanian (Desmoinesian) based on youngest known Midcontinent occurrences of conodont NEOGNATHODUS, brachiopod MESOLOBUS, and several typically Desmoinesian ammonoid taxa (Boardman and Mapes, 1984; Swade, 1982, 1985). Age further confirmed by the Dawson, which contains youngest known occurrence of a typical Desmoinesian miospore flora rich in LYCOSPORA (R. A. Peppers, personal commun., 1982, 1983). Age is constrained by the reliably overlying and terrestrial Hepler unit. Report includes correlation charts, measured sections, cross sections, geologic map, and columnar section.

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