Digital Geologic Map of the northern Lake Tahoe-Donner Pass Region,

northern Sierra Nevada, California

by

Arthur G. Sylvester, William S. Wise, Jordan T. Hastings, and Lorre A. Moyer

October 2007

This web site presents a GIS compilation of the geology in the following six 7.5'quadrangles: Norden, Truckee, Martis Peak, Granite Chief, Tahoe City, and Kings Beach, comprising nearly 1300 sq km. A separate site presents UCSB student mapping in 2007 of the Sagehen Creek and Independence Lake basins, which are parts of the Independence Lake and Hobart Mills 7.5' quadrangles.

View a JPEG image of the Tahoe-Donner compilation here: (full size, high resolution or 11"x14" medium resolution). These particular images are NOT in a digitally active form.

All or parts of the following quadrangles have been mapped: Independence Lake, Soda Springs, Norden, Truckee, Martis Peak, Mt.Rose, Granite Chief, Tahoe City, Kings Beach, Wentworth Springs, and Homewood. Raster images of all the mapping were presented publically for the first time at the 2nd Biennial Conference on Tahoe Environmental Concerns, May 19, 2004, and again at a Tahoe basin core workshop, September 15, 2005. The compiled digital map of six of the quadrangles will be presented May 8, 2007, at the Rocky Mountain Section meeting of the Geological Society of America in St. George, Utah (Sylvester et al., 2007).

The field mapping was done by UCSB students and teaching assistants under the supervision of Sylvester and Wise in summers 1987, 1990, 1992,1993, 2003, 2004, 2005, and 2006 as part of their summer field camp requirements. Their mapping was field checked by Sylvester and Wise and compiled by Sylvester onto orothophoto vellums at a scale of 1:24,000. We have adopted much of the Quaternary geology in the Tahoe City, Truckee, and Martis Peak quadrangles from a hand-colored copy of Birkeland's original field map compilation. Our GIS compilation contains faults that Richard A. Schweickert and his associates (2000) mapped in the region. Many of those faults have been presented in the publication cited below.

Each of the maps has been digitized with ArcMap 9.1 and may be presented here ultimately as pdf files. In the meantime, the digital form of the map has been submitted to the US Geological Survey for review and eventual publication in its Digital Data Series. The map will be accompanied by a pamphlet that describes the map units and the geology depicted in the map, and provides the data on all available radiometric ages of rocks in the region.

Schweickert, R. A., M. M. Lahren, R. E. Karlin, K. D. Smith, and J. F. Howle, 2000. Preliminary Map of Pleistocene to Holocene Faults in the Lake Tahoe Basin, California and Nevada. Nevada Bureau of Mines and Geology Open-File Report 2000-4, Scale 1:100,000.

Sylvester, A.G., W.S. Wise, J.T. Hastings, and L.A. Moyer, 2007. New digital geologic map of the northern Lake Tahoe-Donner Pass region, northern Sierra Nevada, California. Abstracts with Programs 39, No. 5.

Weird and strange mafic enclaves with aplitic haloes - see them here!