Geological history of Point Lobos

Last updated
Point Lobos State Reserve
Rock formation at Point Lobos 04-072010.jpg
Location Point Lobos,
Monterey County, California
Nearest city Carmel-by-the-Sea
Coordinates 36°31′1.56″N121°56′33.36″W / 36.5171000°N 121.9426000°W / 36.5171000; -121.9426000 Coordinates: 36°31′1.56″N121°56′33.36″W / 36.5171000°N 121.9426000°W / 36.5171000; -121.9426000
Governing body California Department of Parks and Recreation

The geological history of Point Lobos, regarding the Point Lobos headland on the Central Coast in Monterey County, California.

Contents

The area's geology encompasses the last 80 million years. The oldest rocks exposed here were formed during the Cretaceous Period of the Mesozoic Era, when the dinosaurs still roamed the earth and pterodactyls dominated the sky. The area forms part of the Salinian Block, a sliver of continental crust caught up in the transform boundary between the Pacific and North American Plates. [1]

Point Lobos is the common name for the landform and area, which include Point Lobos State Reserve on land; and two adjoining marine protected areas: Point Lobos State Marine Reserve (SMR) and Point Lobos State Marine Conservation Area.

Santa Lucia Granodiorite

During the Cretaceous period the west coast of North America was the site of an active chain of volcanoes. Active subduction created magma chambers that fed the volcanoes. This magma cooled slowly at depths of 10–20 km below the earth's surface to form a granitic intrusion known as the Santa Lucia Granodiorite. Granodiorite is made of quartz, orthoclase, plagioclase, amphibole, and biotite mica. Radiometric data indicate an age of 79.5 million years for the granodiorite. [2] Over the next 30 million years the Santa Lucia Granodiorite rose to the earth's surface and was eroded. The granodiorite provides the basement rock for the younger sedimentary deposits of Point Lobos.

Carmelo Formation at Point Lobos. Carmelo Formation at Point Lobos.jpg
Carmelo Formation at Point Lobos.

Carmelo Formation

Around 55 million years ago, in the Paleocene Epoch of the Paleogene Period (Cenozoic Era), a submarine canyon cut down through the granodiorite basement rock and sediments comprising the Carmelo Formation were deposited. The Carmelo consists of pebble to cobble conglomerate, medium to coarse grained sandstone and mudstone. The included pebbles are mostly of volcanic origin. They were brought by rivers draining volcanic highlands. During transport their rough shape became rounded and polished. The sediments were deposited as submarine landslides and turbidity currents. [3]

Fossils include shells, burrows that were made up by worms, and mysterious seaweed-like trace fossils. The shells, pebbles, and other material were deposited, together with sand and mud, within the walls of submarine canyons and became lithified. The Carmelo Formation is the second major rock type at Point Lobos. The Carmelo is easily recognizable along the southern shore of Point Lobos. [4] [5]

Sandstone rock formation at Point Lobos. Point Lobos 20 at 04-07-2010.jpg
Sandstone rock formation at Point Lobos.

Marine terraces

About 18,000 years ago, during the Pleistocene Epoch of the Quaternary Period (Cenozoic Era), the level of the Pacific Ocean was considerably lower than it is now (because more water was in the polar ice-caps and continental glaciers). Deep submarine canyons were cut in the Monterey Bay area, as an extension of the Salinas River.

During late Cenozoic Era, because of sustained transpression of the Pacific Plate onto the American Plate along the nearby San Andreas Fault Zone, there was continued uplift of the entire coastline of California, so that erosive action of marine waves cut these terraces in the Monterey Bay area. Those Pleistocene marine terraces are composed of clay, silt, sand and gravel with a basal unconformity of gravel on top of rock. The creation of uplifted marine terraces that started to appear during the Pleistocene Epoch continues throughout the (present) Holocene Epoch of the Quaternary Period due to transpression of the Pacific Plate onto the American Plate. During the October 1989 Loma Prieta earthquake, the marine terraces of the Monterey Bay were further uplifted. Both Monterey and Santa Cruz have classical uplifted wave-cut shorelines with multiple sets of uplifted and exposed marine terraces. [4]

Sand and gravel

The fourth and the youngest type of rocks is sand and gravel. It is found along the beaches. Once again it has been created by the action of waves and rain that cause erosion of the others type of rocks. The age of this kind of rocks varies from ten thousand years ago up to the present day. [4]

See also

Related Research Articles

Geology of the Yosemite area

The exposed geology of the Yosemite area includes primarily granitic rocks with some older metamorphic rock. The first rocks were laid down in Precambrian times, when the area around Yosemite National Park was on the edge of a very young North American continent. The sediment that formed the area first settled in the waters of a shallow sea, and compressive forces from a subduction zone in the mid-Paleozoic fused the seabed rocks and sediments, appending them to the continent. Heat generated from the subduction created island arcs of volcanoes that were also thrust into the area of the park. In time, the igneous and sedimentary rocks of the area were later heavily metamorphosed.

Geology of the United States national geology

The richly textured landscape of the United States is a product of the dueling forces of plate tectonics, weathering and erosion. Over the 4.5 billion-year history of our Earth, tectonic upheavals and colliding plates have raised great mountain ranges while the forces of erosion and weathering worked to tear them down. Even after many millions of years, records of Earth's great upheavals remain imprinted as textural variations and surface patterns that define distinctive landscapes or provinces.

Los Angeles Basin Sedimentary basin in California

The Los Angeles Basin is a sedimentary basin located in southern California, in a region known as the Peninsular Ranges. The basin is also connected to an anomalous group of east-west trending chains of mountains collectively known as the Transverse Ranges. The present basin is a coastal lowland area, whose floor is marked by elongate low ridges and groups of hills that is located on the edge of the Pacific Plate. The Los Angeles Basin, along with the Santa Barbara Channel, the Ventura Basin, the San Fernando Valley, and the San Gabriel Basin, lies within the greater southern California region. On the north, northeast, and east, the lowland basin is bound by the Santa Monica Mountains and Puente, Elysian, and Repetto hills. To the southeast, the basin is bordered by the Santa Ana Mountains and the San Joaquin Hills. The western boundary of the basin is marked by the Continental Borderland and is part of the onshore portion. The California borderland is characterized by northwest trending offshore ridges and basins. The Los Angeles Basin is notable for its great structural relief and complexity in relation to its geologic youth and small size for its prolific oil production. Yerkes et al. identify five major stages of the basin's evolution, which began in the Upper Cretaceous and ended in the Pleistocene. This basin can be classified as an irregular pull-apart basin accompanied by rotational tectonics during the post-early Miocene.

Geology of the Grand Teton area

The geology of the Grand Teton area consists of some of the oldest rocks and one of the youngest mountain ranges in North America. The Teton Range, partly located in Grand Teton National Park, started to grow some 9 million years ago. An older feature, Jackson Hole, is a basin that sits aside the range.

Vasquez Rocks Natural Area Park in California

Vasquez Rocks Natural Area Park is a 932-acre (377-hectare) park located in the Sierra Pelona Mountains in northern Los Angeles County, California. It is known for its rock formations, the result of sedimentary layering and later seismic uplift. It is located near the town of Agua Dulce, between the cities of Santa Clarita and Palmdale. The area is visible from the Antelope Valley Freeway. It has been used as a location for films and television programs on many occasions.

Kaikōura Peninsula

The Kaikōura Peninsula is located in the northeast of New Zealand's South Island. It protrudes five kilometres into the Pacific Ocean. The town of Kaikōura is located on the north shore of the peninsula. The peninsula has been settled by Maori for approximately 1000 years, and by Europeans since the 1800s, when whaling operations began off the Kaikōura Coast. Since the end of whaling in 1922 whales have been allowed to thrive and the region is now a popular whale watching destination.

Santa Lucia Range

The Santa Lucia Mountains or Santa Lucia Range is a rugged mountain range in coastal central California, running from Carmel southeast for 140 miles (230 km) to the Cuyama River in San Luis Obispo County. The range is never more than 11 miles (18 km) from the coast. The range forms the steepest coastal slope in the contiguous United States. Cone Peak at 5,158 feet (1,572 m) tall and three miles (5 km) from the coast, is the highest peak in proximity to the ocean in the lower 48 United States. The range was a barrier to exploring the coast of central California for early Spanish explorers.

Point Lobos Cape in California, USA

Point Lobos and the Point Lobos State Natural Reserve is the "crown jewel" of California's 280 state parks. Australian-born landscape artist Francis McComas described the point as the "greatest meeting of land and water in the world." Adjoining Point Lobos is "one of the richest marine habitats in California." The ocean habitat is protected by two marine protected areas, the Point Lobos State Marine Reserve and Point Lobos State Marine Conservation Area. The sea near Point Lobos is considered one of the best locations for scuba diving on the Monterey Peninsula and along the California coast.

Geology of Texas Overview of the geology of the U.S. state of Texas

Texas contains a wide variety of geologic settings. The state's stratigraphy has been largely influenced by marine transgressive-regressive cycles during the Phanerozoic, with a lesser but still significant contribution from late Cenozoic tectonic activity, as well as the remnants of a Paleozoic mountain range.

Geology of Bangladesh

The Geology of Bangladesh is affected by the country's location, as Bangladesh is mainly a riverine country. It is the eastern two-thirds of the Ganges and Brahmaputra river delta plain stretching to the north from the Bay of Bengal. There are two small areas of slightly higher land in the north-centre and north-west composed of old alluvium called the Madhupur Tract and the Barind Tract, and steep, folded, hill ranges of older (Tertiary) rocks along the eastern border.

Geology of Kansas

The Geology of Kansas encompasses the geologic history of the US state of Kansas and the present-day rock and soil that is exposed there. Rock that crops out in Kansas was formed during the Phanerozoic eon, which consists of three geologic eras: the Paleozoic, Mesozoic and Cenozoic. Paleozoic rocks at the surface in Kansas are primarily from the Mississippian, Pennsylvanian and Permian periods.

Coyote Mountains

The Coyote Mountains are a small mountain range in San Diego and Imperial Counties in southern California. The Coyotes form a narrow ESE trending 2 mi (3.2 km) wide range with a length of about 12 mi (19 km). The southeast end turns and forms a 2 mi (3.2 km) north trending "hook". The highest point is Carrizo Mountain on the northeast end with an elevation of 2,408 feet (734 m). Mine Peak at the northwest end of the range has an elevation of 1,850 ft (560 m). Coyote Wash along I-8 along the southeast margin of the range is 100 to 300 feet in elevation. Plaster City lies in the Yuha Desert about 5.5 mi (8.9 km) east of the east end of the range.

Geology of Taiwan

The island of Taiwan is active geologically, formed on a complex convergent boundary between the Yangtze Subplate of the Eurasian Plate to the west and north, the Okinawa Plate on the north-east, the Philippine Plate on the east and south, and the Sunda Plate to the southwest. Subduction changes direction at Taiwan. The upper part of the crust on the island is primarily made up of a series of terranes, mostly old island arcs which have been forced together by the collision of the forerunners of the Eurasian Plate and the Philippine Sea Plate, which is moving to the northwest. These have been further uplifted as a result of the detachment of a portion of the Eurasian Plate as it was subducted beneath remnants of the Philippine Sea Plate, a process which left the crust under Taiwan more buoyant.

Great Valley Sequence group of late Mesozoic formations in the Cental Valley of California

The Great Valley Sequence of California is a 40,000-foot (12 km)-thick group of related geologic formations that are Late Jurassic through Cretaceous in age on the geologic time scale. These sedimentary rocks were deposited during the late Mesozoic Era in an ancient seaway that corresponds roughly to the outline of the modern Great Valley of California.

Geology of Germany Overview of the geology of Germany

The geology of Germany is heavily influenced by several phases of orogeny in the Paleozoic and the Cenozoic, by sedimentation in shelf seas and epicontinental seas and on plains in the Permian and Mesozoic as well as by the Quaternary glaciations.

Geology of Madeira

Madeira began to form more than 100 million years ago in the Early Cretaceous, although most of the island has formed in the last 66 million years of the Cenozoic, particularly in the Miocene and Pliocene. The island is an example of hotspot volcanism, with mainly mafic volcanic and igneous rocks, together with smaller deposits of limestone, lignite and other sediments that record its long-running uplift.

The geology of Arizona began to form in the Precambrian. Igneous and metamorphic crystalline basement rock may have been much older, but was overwritten during the Yavapai and Mazatzal orogenies in the Proterozoic. The Grenville orogeny to the east caused Arizona to fill with sediments, shedding into a shallow sea. Limestone formed in the sea was metamorphosed by mafic intrusions. The Great Unconformity is a famous gap in the stratigraphic record, as Arizona experienced 900 million years of terrestrial conditions, except in isolated basins. The region oscillated between terrestrial and shallow ocean conditions during the Paleozoic as multi-cellular life became common and three major orogenies to the east shed sediments before North America became part of the supercontinent Pangaea. The breakup of Pangaea was accompanied by the subduction of the Farallon Plate, which drove volcanism during the Nevadan orogeny and the Sevier orogeny in the Mesozoic, which covered much of Arizona in volcanic debris and sediments. The Mid-Tertiary ignimbrite flare-up created smaller mountain ranges with extensive ash and lava in the Cenozoic, followed by the sinking of the Farallon slab in the mantle throughout the past 14 million years, which has created the Basin and Range Province. Arizona has extensive mineralization in veins, due to hydrothermal fluids and is notable for copper-gold porphyry, lead, zinc, rare minerals formed from copper enrichment and evaporites among other resources.

The geology of Utah includes rocks formed at the edge of the proto-North American continent during the Precambrian. A shallow marine sedimentary environment covered the region for much of the Paleozoic and Mesozoic, followed by dryland conditions, volcanism and the formation of the basin and range terrain in the Cenozoic. Utah is a state in the western United States.

The geology of Laos includes poorly defined oldest rocks. Marine conditions persisted for much of the Paleozoic and parts of the Mesozoic, followed by periods of uplift and erosion. The country has extensive salt, gypsum and potash, but very little hydrocarbons and limited base metals.

The geology of California is highly complex, with numerous mountain ranges, substantial faulting and tectonic activity, rich natural resources and a history of both ancient and comparatively recent intense geological activity. The area formed as a series of small island arcs, deep-ocean sediments and mafic oceanic crust accreted to the western edge of North America, producing a series of deep basins and high mountain ranges.

References

  1. Greene, H.G. "III. Geology and Tectonics". Monterey Bay National Marine Sanctuary Site Characterization Project. Retrieved 16 April 2010.
  2. Clark, J.C.; Dupré, W.R; Rosenberg, L.I. (2009). "GEOLOGIC MAP OF THE MONTEREY AND SEASIDE 7.5-MINUTE QUADRANGLES, MONTEREY COUNTY, CALIFORNIA: A DIGITAL DATABASE". USGS Open File Report.
  3. Clifton, H.E (1981). "Submarine canyon deposits, Point Lobos, California". Pacific Section SEPM Field Trip Guide 6: 79–92.
  4. 1 2 3 Thomson, Jeff. "The Story of the Rocks". Point Lobos State Natural Reserve and Point Lobos Association. Retrieved 15 April 2010.[ permanent dead link ]
  5. VOLCANO-HOME