Master of Science (MS)
First Committee Member
Eugene I. Smith
Number of Pages
Five calderas were discovered in the northern Kawich Range, central Nevada. These calderas are filled with intracaldera rhyolite tuffs and caldera collapse breccias. Based on 40Ar/39Ar dating of sanidine and crosscutting relations, the calderas erupted in the following order from oldest to youngest: Clifford Spring (23.67 +/- 0.09 Ma), Tobe Spring (22.77 +/- 0.07 Ma), Cow Canyon (22.78 +/- 0.07 Ma), Bellehelen (22.87 +/- 0.16 Ma), and Warm Springs. Welded tuff lithologies of collapse breccia blocks show that these calderas represent separate events and not a single caldera with piecemeal collapse. Geochemistry shows that the five intracaldera tuffs are chemically similar and therefore cogenetic. The five tuffs are also similar to the Pahranagat Formation and the Pyramid Spring tuff. To explain the eruption of at least seven tuffs of very similar chemistry over a period of 1.06 m.y, a new model for magma production in northern Nye County during the Tertiary ignimbrite flare-up is presented. This model calls for a heat surge producing greater than 50 % partial melting of the lower crust producing rhyolitic melt batches of similar chemistry. Cooling of the crust due to these voluminous eruptions resulted in the suppression of the ignimbrite flare up.
Caldera; Central; Kawich; Nested; Nevada; Northern; Range
University of Nevada, Las Vegas
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Honn, Denise Kelly, "Nested calderas of the northern Kawich Range, central Nevada" (2005). UNLV Retrospective Theses & Dissertations. 1877.