The Scurry reef of Scurry County, Texas, is a subsurface feature 23 miles long and 4-8 miles wide that is of Permian and Carboniferous age. The reef is a low mound composed chiefly of clastic organic limestone with minor amounts of black bituminous claystone.

The reef limestone consists of three main textural types: calcilutite, calcarenite, and calcirudite. The calcilutite is composed mainly of particles too fine to be resolved under the petrographic microscope. Part of this fine material appears to be comminuted organic debris; the remainder may be chemically precipitated ooze. The calcarenite forms a gradational series between sorted, rounded debris in clear crystalline calcite cement and unsorted, angular debris in a matrix of lithified lime mud. The calcirudite is composed of angular, granule- to boulder-sized fragments in a matrix of lithified lime mud or lime sand. The fragments consist of organic debris and pre-existing reef limestone and claystone.

The limestone contains minor amounts of secondary calcite, dolomite, and chert. Characteristic structures in the limestone are stylolites, joints, irregular fractures, and slump structures.

The vast bulk of observable porosity was formed by leaching solutions. This condition may have been accomplished principally by the enlargement of primary openings through the removal of the least stable constituents.

The Scurry reef was formed from the hard parts of organisms that lived, died, and were buried in essentially one locality. The two major faunal elements that could be identified in the reef are the Crinoidea and the Foraminifera, principally Fusulinidae. Corals constitute a minor element and are not numerous enough to be important here as reef-forming organisms.

It is suggested that the welding of lime mud and the constant precipitation of calcite cement rigidified the accumulating material and thus acted as a substitute for the rigid organic framework that characterizes many reefs.