WSGS publishes 2 new geological maps of the central mountains of Laramie | New






The Wyoming State Geological Survey (WSGS) has published bedrock geological maps of the Poe Mountain and Guide Rock quadrangles at a scale of 1: 24,000, located in the Laramie Mountains in southeastern Wyoming. These maps represent decades of work and meaningful collaboration between several universities, the US Geological Survey and the WSGS.

“The maps were made 30 years ago,” says co-author Dr. B. Ronald Frost, professor emeritus in the Department of Geology and Geophysics at the University of Wyoming (UW). “They were going to be published by the US Geological Survey, but were blocked for many years after the death of co-author Dr. George Snyder.”

Frost then approached the WSGS to publish them.

“These two maps are an excellent contribution to understanding the geology of Wyoming,” says Erin Campbell, WSGS director and state geologist. “They reflect a great collaborative effort of geologists from various agencies, and the result is a complete mapping of an area with complex intrusive relationships. “

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At the center of these two maps, which straddle the Albany-Platte County border, is the Laramie Anorthosite Complex (LAC). The 1.4 billion year old LAC contains numerous groups of igneous rocks, in particular anorthosite (a fairly rare intrusive igneous rock characterized by over 90 percent plagioclase feldspar). The maps show the stratification of the Poe Mountain anorthosite, which extends approximately 5 miles across the two quadrangles. The maps also provide details of the intrusive relationships between the Mount Poe anorthosite and the subsequent Sybille intrusion.

“The maps show how the contact between the Sybille intrusion and the host rock is steep in the west and gradually becomes shallower in the east. As the contact becomes shallower, the Sybille intrusion begins to accommodate large rafts of country rock, ”says Frost. “The Poe Mountain Quadrangle shows how the Red Mountain pluton and associated dykes penetrate both the Poe Mountain anorthosite and the Sybille intrusion.”

In addition to Frost and Snyder, students from the Department of Geology and Geophysics at UW, and Dr. Donald H. Lindsley and students from the Department of Geosciences at Stony Brook University in New York wrote the maps .

The maps are available as a free download and in hard copy to purchase from the WSGS sales site.


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