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Clastic dikes in the Bishop Tuff (Pleistocene, 760 ka; Sherwin Summit, Owens Valley, California, USA) 2

Clastic dikes in the Bishop Tuff (Pleistocene, 760 ka; Sherwin Summit, Owens Valley, California, USA) 2

Clastic dikes in rhyolitic ash & pumice beds in the Pleistocene of California, USA.

This outcrop consists of a volcanic unit called the Bishop Tuff (it's not really a volcanic tuff, however), a ~760,000 year old rhyolitic pyroclastic flow deposit. It was emplaced during a caldera-forming eruption of the nearby Long Valley Volcano. The base of the unit consists of air-fall rhyolite pumice beds. The overlying layers are pyroclastic flows having ash and pumice.

The protruding, subvertical features in the exposure are clastic dikes - cracks / fissures in the Bishop Tuff got filled in by sediments from above. In general, clastic dikes can also form from the bottom-up.

Locality: Sherwin Summit (= Big Pumice Roadcut) - roadcut along the northern side of Route 395, immediately east of intersection with Lower Rock Creek Road (= Sherwin Grade; = Old Route 395), just east of the “town” of Tom’s Place, Owens Valley, Mono County, eastern California, USA (37° 33' 28.80" North latitude, 118° 39' 26.23" West longitude)

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Photo taken on 7 July 2010 (© James St. John / Flickr)

Related tags :
 bishop, tuff, pleistocene, rhyolite, rhyolitic, pumice, sherwin, summit, big, roadcut, owens, valley, mono, county, california, clastic, dike, dikes
 

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