Geologic map of the Caetano caldera, Lander and Eureka counties, Nevada

The Eocene (34 Ma) Caetano caldera in north-central
Nevada offers an exceptional opportunity to study the
physical and petrogenetic evolution of a large (20 km by
10–18 km pre-extensional dimensions) silicic magma
chamber, from precursor magmatism to caldera collapse
and intrusion of resurgent plutons. Caldera-related rocks
shown on this map include two units of crystal-rich
intracaldera tuff totaling over 4 km thickness, caldera
collapse breccias, tuff dikes that fed the eruption,
hydrothermally altered post-eruption rocks, and two
generations of resurgent granitic intrusions (John et al.,
2008). The map also depicts middle Miocene (about 16–12
Ma) normal faults and synextensional basins that
accommodated >100 percent extension and tilted the
caldera into a series of ~40° east-dipping blocks,
producing exceptional 3-D exposures of the caldera
interior (Colgan et al., 2008).

This 1:75,000-scale map is a compilation of published
maps and extensive new mapping by the authors (fig. 1),
and supersedes a preliminary 1:100,000-scale map
published by Colgan et al. (2008) and John et al. (2008).
New mapping focused on the margins of the Caetano
caldera, the distribution and lithology of rocks within the
caldera, and on the Miocene normal faults and sedimentary
basins that record Neogene extensional faulting. The
definition of geologic units and their distribution within
the caldera is based entirely on new mapping, except in the
northern Toiyabe Range, where mapping by Gilluly and
Gates (1965) was modified with new field observations.
The distribution of pre-Cenozoic rocks outside the caldera
was largely compiled from existing sources with minor
modifications, with the exception of the northeastern
caldera margin (west of the Cortez Hills Mine), which was
remapped in the course of this work and published as a
stand-alone 1:6000-scale map (Moore and Henry, 2010).