THE KALEIDOSCOPE OF SPELEOGENESIS IN EAST-CENTRAL NEVADA, USA

Speleogenesis in White Pine County, Nevada, within the central Great Basin, USA, resulted from at least five different mechanisms. 1) The earliest caves formed along north-trending listric fault gaps that opened between 17-10 Ma. 2) Upwelling groundwater and gases likely sourced from magmatic activity enlarged some extensional fractures or voids to form caves, and lined or filled many of them with calcite mammillaries near the top of a regional water table during the latest stages of this activity. The oldest mammillary so far documented is 12.4 Ma old. 3) Later epigenic infiltration, likely in the Pleistocene, modified many ancient, hypogenic caves and formed late-stage resurgence caves along extensional Basin and Range faults. 4) Mass wasting formed the youngest caves in the late Pleistocene. Large blocks slid into newly deepened canyons to form deep open fractures, one over 130-m deep, that trend parallel to the adjacent stream bottoms. 5) One studied cave formed within talus below steep, glacier-carved cliffs.

All caves formed within Paleozoic carbonates, mostly the Middle Cambrian Pole Canyon formation and its equivalents. Caves formed in both the upper and lower plates of the Northern Snake Range Décollement. Hypogenic caves are concentrated in the upper plate and scattered throughout the area from low knolls in the Snake Valley desert to alpine ridges above timberline. The demonstrated antiquity of the mammillaries informs us about the rate of relative uplift and stream incision since the Miocene as most of these caves are now hundreds of meters above the adjacent stream beds and Snake Valley. All dominantly epigenic caves are within the temperate pine and juniper forests. Younger, mass wasting caves are on the slopes of deeply incised canyons in the pine forest and above timberline. Nearly all caves in the region are within Humboldt-Toiyabe National Forest, Great Basin National Park, and Bureau of Land Management lands. This research was funded by the Southern Nevada Public Land Management Act program.