The Osha Canyon Formation is a geologic formation in the Nacimiento Mountains of New Mexico . It contains fossils characteristic of the Bashkirian stage of the Pennsylvanian period .
7-434: The base of the formation is fossiliferous marine limestone and shale while the upper section is mostly shale with limestone nodules. The topmost bed is calcareous sandstone . The total thickness is 90 feet (27 meters) at the type section . The formation is exposed only in a small area of the southern Nacimiento Mountains. The formation is underlain by Precambrian basement rock or by Mississippian formations, such as
14-461: A lower Pennsylvanian brachiopod , at Guadelupe Box during their 1945 survey. Armstrong found additional examples of what he termed the Schizophoria oklahomae strata, and recognized that these were separated from the overlying middle Pennsylvania stata by an erosional surface, but did not assign a formal unit name to the beds. The formation was formally named by H. DuChene in 1973 for exposures near
21-413: A significant part of the rock, a term " shell limestone " is used. The fossils in these rocks may be of macroscopic or microscopic size. The sort of macroscopic fossils often include crinoid stems, brachiopods , gastropods , and other hard shelled mollusk remains. In some cases, microfossils such as siliceous diatom shells in deposition may convert over time to opal and chert , providing
28-518: The Gilman Tunnels in the Jemez Mountains of New Mexico. Fossiliferous limestone Fossiliferous limestone is a type of limestone that contains noticeable quantities of fossils or fossil traces . If a particular type of fossil dominates, a more specialized term can be used as in " Crinoidal ", "Coralline", "Conchoidal" limestone. If seashells , shell fragments, and shell sand form
35-706: The Log Springs Formation at the type location. It is overlain by the Sandia Formation , with a sharp erosional disconformity separating the uppermost calcareous marine sandstone bed of the Osha Canyon Formation from the basal crossbedded nonmarine sandstone bed of the Sandia Formation. Fossils are characteristic of a marine shelf environment and include the brachiopod Schizophoria oklahomae and foraminifer Millerella characteristic of
42-517: The Morrowan (lower Pennsylvanian .) The lower part of the formation contains several genera of solitary rugose corals , tabulate corals , and the bryozoans Fenestella , Septopora , Rhombopora and Tabulipora . Gastropods and bivalves are also present. No tabulate corals are found in the upper part of the formation, but here the diversity of chonetid brachiopods increases. Northrop and Wood recognized fossils of Schizophoria oklahomae ,
49-454: The only inferred evidence of bioactivity preserved in limestone. Fossiliferous limestone is termed biosparite under the Folk classification of sedimentary rocks . Lagerstätte are a class of fossil bearing rocks that includes fossiliferous limestone. Fossils in general provide geologic clues to the environment of deposition, rock formation, and the types of biological activities present at
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