Pg. 30, 31; GSA Bull., v. 19, p. 557, 1909 [abs.]. Collier shale. Dark, soft, graphitic, clay shale, containing widely separated thin beds of dense, black, and intensely fractured chert. As result of squeezing and shearing practically all traces of bedding have disappeared. In places slaty cleavage is visible. Upper 100 feet or more is calcareous; limestone occurring in dark-colored crystalline lenses and layers and in beds several feet thick. Upper part of limestone is conglomeratic. Thickness several hundred feet; only upper 200 feet exposed. Age unknown. Underlies, probably unconformably, Crystal Mountain sandstone. [Recognized in southwestern Arkansas and southeastern Oklahoma (McCurtain County). Age is Cambrian.]
[Named from Collier Creek, Montgomery Co., southwestern AR.]

Source: US geologic names lexicon (USGS Bull. 896, p. 489-490).

Is the oldest known formation in the Wichita Mountains of Oklahoma and Arkansas, in the Ouachita tectonic belt province. Cambrian age assignment in earlier reports was based on position beneath a formation with Early Ordovician graptolites. Ordovician age assignment in earlier reports was based on presence of Early Ordovician conodonts in the Benton uplift. Shelf trilobites were found by authors of present report in the lower part of the Collier from seven localities near Jessieville, Garland County, Arkansas, from the ELVINIA Zone of the Franconian Stage of the Late Cambrian. Conodonts of Early Ordovician age were found by authors of present report near Jessieville in the upper part of the Collier. Age is changed to Late Cambrian and Early Ordovician.

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