The Lee Canyon Argillite was named for exposures in a north trending belt that centers on Lee Canyon in T.30 N., R. 52 E., along the western flank of the Pinon Range (Smith and Ketner, 1975).

The Lee Canyon Argillite is considered Early Mississippian in age. It is equivalent to part of the Webb Formation and to the lower portion of the Chainman Formation (Smith and Ketner, 1975).

The Lee Canyon Argillite has a basal thrust contact with underlying Woodruff and Webb Formations, and is locally in fault contact with the underlying Chainman Formation (Smith and Ketner, 1975). Locally the argillite is overlain conformably by the Chainman Formation (Smith and Ketner, 1975). Its relationship with the Chainman Formation is cryptic in this writer’s opinion. It is possible that the unit, which is only locally exposed in the Carlin-Pinon area, is actually a metamorphosed slice of the Chainman Formation.

The Lee Canyon Argillite is composed of aphanitic, dense, black, carbonaceous argillite. In thin section, this rock is about 80 percent quartz silt, less than 10 percent potash feldspar, and less than 10 percent clay, with minor pyrite and diopside making up a fraction to 30 percent of the rock (Smith and Ketner, 1975). Essentially the rock is a siltstone that has been metamorphosed by a buried intrusive body in the Pine Mountain area. The upper portion of the Lee Canyon contains a few beds and lenses of black and gray chert granule and pebble conglomerate that are a few feet thick. These granule and pebble conglomerates are similar or identical to lithologies exposed within the Chainman Formation in the Pinon Range (Smith and Ketner, 1975).

The thickness of the Lee Canyon Argillite is complicated by thrusting and folding in a relatively uniform and massive lithology. Smith and Ketner (1975) estimated a thickness of about 5,000 feet assuming no structural repetition or omission.

The Lee Canyon Argillite has been delineated only within the Pinon Range.

Smith and Ketner (1975) interpreted the Lee Canyon Argillite as an allochthonous unit thrust westward based upon contact relationships and vergence of folds within the unit. The unit is composed of metamorphosed quartz siltstones and chert-pebble conglomerates similar if not identical to those in the overlying and underlying Chainman Formation. It is possible that the Lee Canyon is simply a locally metamorphosed portion of the Chainman Formation and represents units originally deposited as fine and coarse-grained fan-delta sediments.