Author: D.D. LaPointe, J.G. Price, D.A. Davis, and Craig M. dePolo
Year: 2011
Series: Educational Series 51
Version:
Format: 23 pages, color brochure
Scale:

National Earth Science Week (ESW) 2011 encourages people everywhere to explore the natural world and learn about the geosciences. The Nevada Bureau of Mines and Geology (NBMG) welcomes you to participate in its fourteenth annual Earth Science Week field trip. In keeping with the National ESW theme, “Our Ever-Changing Earth,” this year’s trip will focus on the Cenozoic geology of the region around Grimes Point and the Lahontan Mountains, including evidence for a large Pleistocene lake in the area; volcanism related to crustal extension in the Basin and Range Province of the western United States; hydrothermal (hot water) activity associated with volcanism; tilting of volcanic and sedimentary rocks related to faulting and extension; and production of electricity using geothermal power, related to hot water that gets close to the surface along extension-related faults. Many of the features we will explore are related to ongoing geologic processes that continue to alter the face of the Earth. Frequent reference will be made to recently published NBMG geologic maps of the Lahontan Mountains quadrangle and the Grimes Point quadrangle, by NBMG geologist John Bell and others.

Stops will include the following:

Stop 1. On the west side of Sehoo Mountain, where we will examine beach deposits from the shore of Pleistocene Lake Lahontan and collect tufa-coated Pliocene basalt. Shorelines of Lake Lahontan, expressed as wave-cut terraces or beach deposits, are visible throughout the area.

Stop 2. Eagles House, where we will examine and collect unaltered and altered Miocene rhyolite. Crystals in the unaltered rhyolite include quartz, biotite, sanidine,and hornblende.

Stop 3. Near Eagles House, where we will examine and collect Miocene tuff that was silicified and pyritized then later oxidized to make the rock commonly known as “Nevada wonderstone.”

Stop 4. Also near Eagles House, where we will examine and collect breccia (containing silicified and oxidized fragments of Miocene lacustrine siltstone) and calcite.

Stop 5. At Grimes Point, where we will examine (but not collect) petroglyphs carved by prehistoric humans along the shore of the receding Lake Lahontan a few thousand years ago.

Stop 6. Near Grimes Point, where we will examine and collect pebbles of banded, silicified, oxidized Miocene air-fall tuff that were naturally polished by stream and wave activity along the shores of Lake Lahontan.

Stop 7. At a green hill between Salt Wells Mountain and Rainbow Mountain, where we will examine and collect silicified, celadonite-altered Miocene pumice and conglomerate.

Related publications:
The Tufas of Pyramid Lake (USGS Fact Sheet 2004-3044)
https://pubs.usgs.gov/fs/2004/3044/

The Tufas of Pyramid Lake, Nevada (USGS Circular 1267)
https://pubs.usgs.gov/circ/2004/1267/


Original Product Code: E51