The Salinian Block or Salinian terrane is a geologic

terrane In geology, a terrane (; in full, a tectonostratigraphic terrane) is a crust fragment formed on a tectonic plate (or broken off from it) and accreted or " sutured" to crust lying on another plate. The crustal block or fragment preserves its ow ...

which lies west of the main trace of the

San Andreas Fault The San Andreas Fault is a continental transform fault that extends roughly through California. It forms the tectonic boundary between the Pacific Plate and the North American Plate, and its motion is right-lateral strike-slip (horizontal) ...

system in

California California is a state in the Western United States, located along the Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the most populous U.S. state and the 3rd largest by area. It is also the ...

. It is bounded on the south by the Big Pine Fault in

Ventura County Ventura County () is a County (United States), county in Southern California, the southern part of the U.S. state of California. As of the 2020 United States Census, 2020 census, the population was 843,843. The largest city is Oxnard, California ...

and on the west by the Nacimiento Fault. It was named for the

Salinas Valley The Salinas Valley is one of the major valleys and most productive agricultural regions in California. It is located west of the San Joaquin Valley and south of San Francisco Bay and the Santa Clara Valley. The Salinas River, which geologicall ...

Monterey County, California Monterey County ( ), officially the County of Monterey, is a county located on the Pacific coast in the U.S. state of California. As of the 2020 census, its population was 439,035. The county's largest city and county seat is Salinas. Monte ...

Geology

The Salinian Block is largely

granitic A granitoid is a generic term for a diverse category of coarse-grained igneous rocks that consist predominantly of quartz, plagioclase, and alkali feldspar. Granitoids range from plagioclase-rich tonalites to alkali-rich syenites and from quart ...

, in accordance with its

continental crust Continental crust is the layer of igneous, sedimentary, and metamorphic rocks that forms the geological continents and the areas of shallow seabed close to their shores, known as continental shelves. This layer is sometimes called '' sial' ...

al origin. This composition 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 A batholith () is a large mass of intrusive igneous rock (also called plutonic rock), larger than in area, that forms from cooled magma deep in Earth's crust. Batholiths are almost always made mostly of felsic or intermediate rock types, su ...

of the

Peninsular Ranges The Peninsular Ranges (also called the Lower California province) are a group of mountain ranges that stretch from Southern California to the southern tip of the Baja California peninsula; they are part of the North American Coast Ranges, whic ...

, shares its origins with the Sierra Nevada mountains far to the east. During the past 30 million years the North American Plate has been overriding the

East Pacific Rise The East Pacific Rise is a mid-ocean rise (termed an oceanic rise and not a mid-ocean ridge due to its higher rate of spreading that results in less elevation increase and more regular terrain), a divergent tectonic plate boundary located alon ...

and transform faulting along the developing San Andreas fault zone. Successive "stretched out" slivers of the Sierra Nevada - the Peninsular Batholith - have been and currently still are moving to the northwest to their current location. The granitic plutons of the Salinas block stretch from

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 northwest of San Francisco and approximately west of Santa Rosa. The peninsula, which ...

() in the north to Mount Pinos () at the southern end of the block. In the years since the 1974 study by Johnson and Normark the connection with the southern Sierra Nevada has been questioned, stating that "it more nearly resembles granite in the Mojave Desert".

Notable Features

Some of the more notable portions of the block are visible as: * * * * * * * * * * * Much of the mountainous terrain along the Salinian Block is protected under the

US Forest Service The United States Forest Service (USFS) is an agency of the U.S. Department of Agriculture that administers the nation's 154 national forests and 20 national grasslands. The Forest Service manages of land. Major divisions of the agency inc ...

and U.S. Fish and Wildlife Service, most notably within

Los Padres National Forest Los Padres National Forest is a United States national forest in southern and central California. Administered by the United States Forest Service, Los Padres includes most of the mountainous land along the California coast from Ventura to Mon ...

, Julia Pfeiffer Burns State Park, and

Point Reyes National Seashore Point Reyes National Seashore is a park preserve located on the Point Reyes Peninsula in Marin County, California. As a national seashore, it is maintained by the US National Park Service as an important nature preserve. Some existing agricul ...

References

External links

Marin College: "Feldspar Staining of the Plutonic Rocks of the Salinian Terrane"
Terranes Geologic formations of California Geology of Marin County, California Geology of Monterey County, California Geology of San Luis Obispo County, California Geology of Santa Cruz County, California Salinian Block {{US-geology-stub