Sausalito Point prospect, Sausalito, Marin Co., California, USA
|Latitude & Longitude (WGS84):||37° 51' 34'' North , 122° 29' 30'' West|
|Latitude & Longitude (decimal):||37.85972,-122.49167|
|Köppen climate type:||Csb : Warm-summer Mediterranean climate|
A former Mn occurrence/mine located in sec. 11 (uncertain), T1S, R6W, MDM, 0.7 km (0.4 mile; 2,200 feet) W of Sausalito. Discovered in 1918. Operated by the Marin Land and Cattle Company. MRDS database accuracy for this location is not stated.
Manganese oxides are associated with massive chert. The oxide is mostly of low-grade, but one lens of good ore is 15 inches thick and can be traced for 6 feet (1.8 meters). Local rocks include rocks of the Franciscan Complex, unit 1 (Coast Ranges).
In 1882 a small amount of Mn ore was mined and used as a flux in a custom smelter in Sausalito.
Commodity ListThis is a list of exploitable or exploited mineral commodities recorded at this locality.
Rock Types Recorded
Select Rock List TypeAlphabetical List Tree Diagram
Entries shown in red are rocks recorded for this region.
This geological map and associated information on rock units at or nearby to the coordinates given for this locality is based on relatively small scale geological maps provided by various national Geological Surveys. This does not necessarily represent the complete geology at this locality but it gives a background for the region in which it is found.
Click on geological units on the map for more information. Click here to view full-screen map on Macrostrat.org
|Cretaceous - Jurassic|
66 - 201.3 Ma
Age: Mesozoic (66 - 201.3 Ma)
Stratigraphic Name: Franciscan Complex
Description: Melange of fragmented and sheared Franciscan complex rocks.
Comments: Coast Ranges. Includes areas of Franciscan rocks specifically distinguished as melange on the Geologic Map of California. Includes parts of central and eastern Franciscan belts of Blake et al. (1988)
Reference: Horton, J.D., C.A. San Juan, and D.B. Stoeser. The State Geologic Map Compilation (SGMC) geodatabase of the conterminous United States. doi: 10.3133/ds1052. U.S. Geological Survey Data Series 1052. 
145 - 201.3 Ma
Age: Jurassic (145 - 201.3 Ma)
Stratigraphic Name: Franciscan Complex
Description: Mélange: A tectonic mixture of variably sheared shale and sandstone containing (1) hard tectonic inclusions largely of greenstone, chert, graywacke, and their metamorphosed equivalents, plus exotic high-grade metamorphic rocks and serpentinite and (2) variably resistant masses of graywacke, greenstone, and serpentinite up to several miles in longest dimension, and including minor discrete masses of limestone too small to be shown. Blocks and resistant masses have survived the extensive shearing evident in the mélanges matrix, and range in abundance from less than 1 to 50 percent or more of the rock mass. The degree of shearing in the unit ranges from gouge to unsheared rock, with resistant masses relatively unsheared and matrix sheared. Severely sheared shale is abundant in areas where blocks are abundant. Fresh, relatively unsheared rock is hard, the larger resistant masses are pervasively fractured, and blocks are commonly tough and relatively unfractured. Sandstone is graywacke, grayish green where fresh, weathering to brown, commonly medium to coarse grained, containing abundant angular lithic grains and no detrital potassium feldspar, except rarely as much as 5 percent. Graywacke is locally veined with quartz and carbonate, and usually contains microscopic secondary pumpellyite. Topography of coherent masses resembles that of unit Kfs, whereas highly sheared matrix typically yields subdued, gently-rounded topography. Good exposures of both sheared matrix and relatively unsheared graywacke and shale occur at the crushed rock quarry just east of the intersection of State Highway 17 and U.S. Highway 101, in Greenbrae (Novato quadrangle)
Reference: Blake, M.C. Jr., R.W. Graymer, and D.L. Jones. Geologic map and map database of parts of Marin, San Francisco, Alameda, Contra Costa, and Sonoma Counties, California. U.S. Geological Survey Miscellaneous Field Studies MF 2337.