About the Locality...
Located in the Drum Mountains is the Global boundary Stratotype section and Point (GSSP) of the Drumian Stage (Cambrian)*.
The Drum Mountains lie in the Basin and Range Province, which is a series of generally north-south trending mountain ranges and valleys (or basins)extending from central Utah to eastern California, and from southern Idaho into Sonora, Mexico. During the Cambiran, this area was underwater, which produced the marine sediments (limestones and shales) seen today in outcrop. The formations from this time are generally deeper water deposits (ramp-to-basin and outer-shelf).
The base of the Global Stratotype and Point (GSSP) is based on the first appearance of a certain type of trilobite, the agnostid Ptychagnostus atavus. This trilobite makes a good marker because it has one of the broadest distributions in the Cambrian (meaning it is found in a variety of locations worldwide). The section in the Drum Mountains is a complete section(meaning there are no missing gaps in time) and is generally undisturbed, which makes it an excellent location for the Global Stratotype Section and Point (GSSP).
*Information modified from:
Babcock, Loren E; Robison, Richard A; Rees, Margaret N; Peng Shanchi; Saltzman, Matthew R, 2007, "The global boundary stratotype section and point (GSSP) of the Drumian Stage (Cambrian) in the Drum Mountains, Utah, USA". Episodes, vol. 30, no. 2, pp.85-95.