LEAD STORY – RMAG On-the-Rocks Field Trip Medicine Bow Mountains
Snowy Range, August 17th, 2013: The Time Machine to the Paleoproterozoic Text and photos by Ronald L. Parker, Senior Geologist, Fronterra Geosciences, 700 17th Street, Suite 1700, Denver, Colorado 80202 The RMAG field trip to the Snowy Range in the Dr. Snoke has been teaching field-oriented structural Medicine Bow Mountains of SE Wyoming, August 17th, geology at Wyoming almost since the Paleoproterozoic, 2013, continued a superb string of field trips run under having arrived in Laramie in 1974 after 10 years at the “On-the-Rocks” (OTR) banner. Simply, these are the University of South Carolina. Dr. Snoke has a among the best one-day field trip opportunities to be had wide-ranging interest that is reflected in his numerous in the Rockies, and, they are free. As elucidated in the April publications from many parts of the world (Tobago, 2013 Outcrop “RMAG OTR trips provide participants with Italy, Tunisia, California, Oregon, Nevada, South opportunities to explore Carolina and, of course, site geology, together Wyoming). http://www. with a trip expert and uwyo.edu/geolgeophys/ the camaraderie of those faculty/arthur-snoke. who are willing to share html). We were rewarded geologic knowledge.” by his vast reserve of This summer has been knowledge. On top of it rich with five OTR field all, Professor Snoke is trip offerings and they also a world-class nice have all been resounding guy. successes. Praise is The OTR field trip to due RMAG organizing the Snowy Range of the committee members Medicine Bow Mountains (Catherine Campbell, was a substantial Dan Plazak, Denis Foley, departure from the rest Jeff Glossa, John Ladd, of the RMAG OTR retinue Sandra Mark, Phyllis Professor Art Snoke at the start of the trip pointing out the for the summer in that we Scott and Ron Pritchett) variation of exposures visited rocks from deep and field trip leaders (Jeff in time. The Medicine May, Donna Anderson, Bob Raynolds, Paul Morgan, Art Bow Mountains display the tectonic boundary between Snoke and David Noe) for enriching lucky participants. the Archean Wyoming Province (3.6-3.0 Ga) and the As Don Rasmussen quipped at the conclusion of Bob accreted terranes that added to the southern margin of Raynold’s Eagle Basin trip ,“this was the best field trip I Laurentia (Hoffman, 1988). During the Paleoproterozoic, have been on in years…including my own.” the southern edge of the Wyoming Province was an The Snowy Range field trip was excellent for several Atlantic-style rifted passive margin that consisted reasons. First, it was a scintillating, high pressure, blue of a thick layer (~10 km) of 2.4-2.1 Ga miogeoclinal sky day which made everyone cheerful. Professor Art sediments (Snowy Pass Supergroup) atop 2.7-2.5 Ga Snoke, from the Department of Geology & Geophysics Archean basement (Whitmeyer, 2007). The Snowy Pass at the University of Wyoming, was the perfect leader. Supergroup is comprised of the 3.6 km thick Deep Vol. 62, No. 11
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November 2013