Regional Geology

The Clayton Valley-Montezuma range is underlain by a thick body of tuffaceous sediments, ranging from upper Miocene to Pliocene in age. The volcanic sequence has been named the Esmeralda formation and consists of approximately 15,000 feet of lucustrine volcanic sediments which include poorly sorted conglomerates and sandstones, limestone, mudstones and tuffaceous units. Fossils suggest a relatively fresh environment of deposition.

Two major volcanic events where recorded in the Tertiary sediments. An early Pliocene volcanic episode is represented by a single welded tuff unit with an age of 22 million years and is exposed on the northern end of the Silver Peak Range. The tuff was ejected prior to the block faulting that disturbed the drainage of the Silver Peak region and created several closed basins into which the lower part of the Esmeralda formation was deposited.

A second period of volcanic eruptions with major faulting occurred during the middle Pliocene and resulted in the deformation of the lower Esmeralda sediments creating an angular unconformity. The oldest sediments above the unconformity were assigned to the upper Esmeralda unit and have been dated at 6.9 million years. The widespread ash fall tuff that crops out around Clayton Valley and the Montezuma peak area has the same age as the upper Esmeralda sediments (6.9 million years) and has been subjected to major faulting which created the present topography.

The uplift of the Sierra Nevada at the beginning of the Pleistocene caused the climate of the Basin and Range Province to become generally arid. Pluvial periods, correlative with the glacial stages in the highlands, resulted in increased runoff and formation of temporary lakes in the basins. The interpluvial periods were more arid and led to the concentration of the lake waters the remnants of which are the lithium rich evaporities.