Salinian Block
Encyclopedia
The Salinian Block or Salinian terrane is a geologic terrane
which lies west of the main trace of the San Andreas Fault
system in California
. It is bounded on the south by the Big Pine Fault in Ventura County, and on the west by the Nacimiento Fault. The block was named for the Salinas Valley
in Monterey County
, California.
, in accordance with its continental crust
al origin. This contrasts sharply, and paradoxically, with much of the crust to its east, which is sedimentary and oceanic in origin. The block's granitic core, fragments of the batholith
of the Peninsular Ranges
, shares its origins with the Sierra Nevada Mountains.
During the past 30 Ma the North American Plate overrode the East Pacific Rise
and complex transform faulting
along the developing San Andreas fault zone sliced successive slivers of the Sierra Nevada - Penninsular batholith, moving the "stretched out" slices to the northwest to their current location. The granitic plutons of the Salinas block stretch from Bodega Head
(38°18′39.6"N 123°03′57.6"W) in the north to Mount Pinos
(34°48′46.1"N 119°08′43.4"W) at the southern end of the block.
, Point Reyes
, the Farallon Islands
, and the picturesque coastal scenery of the Monterey Peninsula
, exemplified at Pebble Beach.
Terrane
A terrane in geology is short-hand term for a tectonostratigraphic terrane, which is a fragment of crustal material formed on, or broken off from, one tectonic plate and accreted or "sutured" to crust lying on another plate...
which lies west of the main trace of the San Andreas Fault
San Andreas Fault
The San Andreas Fault is a continental strike-slip fault that runs a length of roughly through California in the United States. The fault's motion is right-lateral strike-slip...
system in California
California
California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...
. It is bounded on the south by the Big Pine Fault in Ventura County, and on the west by the Nacimiento Fault. The block was named for the Salinas Valley
Salinas Valley
The Salinas Valley lies south of San Francisco, California.The word "salina" is spanish for salt marsh, salt lake or salt pan.-Geography:The Salinas Valley runs approximately south-east from Salinas towards King City. The valley lends its name to the geologic province in which it's located, the...
in Monterey County
Monterey County, California
Monterey County is a county located on the Pacific coast of the U.S. state of California, its northwestern section forming the southern half of Monterey Bay. The northern half of the bay is in Santa Cruz County. As of 2010, the population was 415,057. The county seat and largest city is Salinas...
, California.
Geology
The Salinian Block is largely graniticGranite
Granite is a common and widely occurring type of intrusive, felsic, igneous rock. Granite usually has a medium- to coarse-grained texture. Occasionally some individual crystals are larger than the groundmass, in which case the texture is known as porphyritic. A granitic rock with a porphyritic...
, in accordance with its continental crust
Continental crust
The continental crust is the layer of igneous, sedimentary, and metamorphic rocks which form the continents and the areas of shallow seabed close to their shores, known as continental shelves. This layer is sometimes called sial due to more felsic, or granitic, bulk composition, which lies in...
al origin. This contrasts sharply, and paradoxically, with much of the crust to its east, which is sedimentary and oceanic in origin. The block's granitic core, fragments of the batholith
Batholith
A batholith is a large emplacement of igneous intrusive rock that forms from cooled magma deep in the Earth's crust...
of the Peninsular Ranges
Peninsular Ranges
The Peninsular Ranges are a group of mountain ranges, in the Pacific Coast Ranges, which stretch from southern California in the United States to the southern tip of Mexico's Baja California peninsula; they are part of the North American Coast Ranges that run along the Pacific coast from Alaska...
, shares its origins with the Sierra Nevada Mountains.
During the past 30 Ma the North American Plate overrode the East Pacific Rise
East Pacific Rise
The East Pacific Rise is a mid-oceanic ridge, a divergent tectonic plate boundary located along the floor of the Pacific Ocean. It separates the Pacific Plate to the west from the North American Plate, the Rivera Plate, the Cocos Plate, the Nazca Plate, and the Antarctic Plate...
and complex transform faulting
Transform fault
A transform fault or transform boundary, also known as conservative plate boundary since these faults neither create nor destroy lithosphere, is a type of fault whose relative motion is predominantly horizontal in either sinistral or dextral direction. Furthermore, transform faults end abruptly...
along the developing San Andreas fault zone sliced successive slivers of the Sierra Nevada - Penninsular batholith, moving the "stretched out" slices to the northwest to their current location. The granitic plutons of the Salinas block stretch from Bodega Head
Bodega Head
Bodega Head is a small promontory on the Pacific coast of northern California in the United States. It is located in Sonoma County at , approximately 40 mi northwest of San Francisco and approximately 20 mi west of Santa Rosa....
(38°18′39.6"N 123°03′57.6"W) in the north to Mount Pinos
Mount Pinos
Mount Pinos is a mountain located in the Los Padres National Forest on the boundary between Ventura and Kern counties in California. The summit is the highest point in Ventura County.- Geography :...
(34°48′46.1"N 119°08′43.4"W) at the southern end of the block.
Features
Today, northern portions of the block are visible as Bodega HeadBodega Head
Bodega Head is a small promontory on the Pacific coast of northern California in the United States. It is located in Sonoma County at , approximately 40 mi northwest of San Francisco and approximately 20 mi west of Santa Rosa....
, Point Reyes
Point Reyes
Point Reyes is a prominent cape on the Pacific coast of northern California. It is located in Marin County approximately WNW of San Francisco. The term is often applied to the Point Reyes Peninsula, the region bounded by Tomales Bay on the northeast and Bolinas Lagoon on the southeast...
, the Farallon Islands
Farallon Islands
The Farallon Islands, or Farallones , are a group of islands and sea stacks in the Gulf of the Farallones, off the coast of San Francisco, California, USA. They lie outside the Golden Gate and south of Point Reyes, and are visible from the mainland on clear days...
, and the picturesque coastal scenery of the Monterey Peninsula
Monterey Peninsula
The Monterey Peninsula is located on the central California coast and comprises the cities of Monterey, Carmel, and Pacific Grove, and unincorporated areas of Monterey County including the resort and community of Pebble Beach.-Monterey:...
, exemplified at Pebble Beach.