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131-460: The West Montalvo Oil Field is a large and productive oil field on the coast of Ventura County, California , in the United States, in and adjacent to the city of Oxnard, California . Discovered in 1947, it has produced approximately 50 million barrels (7,900,000 m) of oil, and originally contained up to 650 million barrels of oil in both the onshore and offshore areas. The offshore portion of

262-648: A Phanerozoic low in diversity by the late Oligocene, and the temperate forests and jungles of the Eocene were replaced by forest and scrubland. The closing of the Tethys Seaway destroyed its tropical biota. The Oi1 event of the Eocene-Oligocene transition covered the continent of Antarctica with ice sheets, leaving Nothofagus and mosses and ferns clinging to life around the periphery of Antarctica in tundra conditions. Angiosperms continued their expansion throughout

393-668: A broader trend of global cooling lasting from the Bartonian to the Rupelian. The transition is marked by the Oi1 event, an oxygen isotope excursion occurring approximately 33.55 million years ago, during which oxygen isotope ratios decreased by 1.3 ‰ . About 0.3–0.4 ‰ of this is estimated to be due to major expansion of Antarctic ice sheets. The remaining 0.9 to 1.0 ‰ was due to about 5 to 6 °C (9 to 10 °F) of global cooling . The transition likely took place in three closely spaced steps over

524-430: A component of the more extensive Los Angeles–Long Beach, CA Combined Statistical Area , the second most populous combined statistical area and primary statistical area of the United States as of July 1, 2012. In 2019, the county faced a weak economic outlook due to the declining housing affordability and lack of job growth. Oligocene The Oligocene is often considered an important time of transition,

655-467: A considerable range in climate because of differences in topography between one part of the county and another. Rainfall is limited in summer and crops have to be irrigated. The average annual temperature is near 60 °F at low elevations near the ocean, in the 50s over most of the northern two-thirds of the county, and less than 45 °F in the Topatopa Mountains . The annual range in temperature

786-487: A critical threshold value. Brachiopod oxygen isotope ratios from New Zealand suggest that a proto-Subtropical Convergence developed during the Early Oligocene, with northern New Zealand being subtropical and southern and eastern New Zealand being cooled by cold, subantarctic water. Oligocene climate following the Eocene-Oligocene event is poorly known. There were several pulses of glaciation in middle Oligocene, about

917-426: A household in the county was $ 59,666, and the median income for a family was $ 65,285. Males had a median income of $ 45,310, versus $ 32,216 for females. The per capita income for the county was $ 24,600. About 6.4% of families and 9.2% of the population were below the poverty line , including 11.6% of those under age 18 and 6.3% of those aged 65 or over. According to an updated 2005 US Census, median household income

1048-603: A link between the archaic world of the tropical Eocene and the more modern ecosystems of the Miocene. Major changes during the Oligocene included a global expansion of grasslands , and a regression of tropical broad leaf forests to the equatorial belt . The start of the Oligocene is marked by a notable extinction event called the Grande Coupure ; it featured the replacement of European fauna with Asian fauna , except for

1179-519: A major mountain chain in the Oligocene, as subduction became more direct into the coastline. Climate during the Oligocene reflected a general cooling trend following the Early Eocene Climatic Optimum . This transformed the Earth's climate from a greenhouse to an icehouse climate. The Eocene-Oligocene transition was a major cooling event and reorganization of the biosphere, being part of

1310-460: A quarry at Massignano , Italy . However, this GSSP has been criticized as excluding the uppermost part of the type Eocene Priabonian Stage and because it is slightly earlier than important climate shifts that form natural markers for the boundary, such as the global oxygen isotope shift marking the expansion of Antarctic glaciation (the Oi1 event). The upper boundary of the Oligocene is defined by its GSSP at Carrosio , Italy , which coincides with

1441-460: A semiarid prairie home and included entelodonts like Archaeotherium , camelids (such as Poebrotherium ), running rhinoceratoids , three-toed equids (such as Mesohippus ), nimravids , protoceratids , and early canids like Hesperocyon . Merycoidodonts, an endemic American group, were very diverse during this time. Australia and South America became geographically isolated and developed their own distinctive endemic fauna. These included

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1572-418: A walled enclosure is allowed to remain. This oil well is one of the most productive in the entire field, producing nearly 70,000 barrels (11,000 m) of oil in 2009 alone, around 190 barrels per day (30 m/d). The climate in the region is Mediterranean , with cool, rainy winters and warm, rainless summers, in which the heat is moderated by frequent morning coastal low clouds and fog. Annual precipitation

1703-547: Is a county located in the southern part of the U.S. state of California . As of the 2020 census , the population was 843,843. The largest city is Oxnard , and the county seat is the city of Ventura . Ventura County comprises the Oxnard–Thousand Oaks–Ventura, CA Metropolitan Statistical Area, which is part of the Greater Los Angeles area (Los Angeles–Long Beach, CA Combined Statistical Area). It

1834-760: Is also considered the southernmost county along the California Central Coast . Two of the Channel Islands are part of the county: Anacapa Island , which is the most visited island in Channel Islands National Park , and San Nicolas Island . Ventura County was historically inhabited by the Chumash people , who also settled much of Santa Barbara and San Luis Obispo Counties, with their presence dating back 10,000–12,000 years. The Chumash were hunter-gatherers , fishermen, and also traders with

1965-459: Is around 15 inches (380 mm), almost all in the winter, and all in the form of rain. The mean annual temperature is 56 to 60 degrees Fahrenheit; freezes occur rarely. The Montalvo field is an accumulation of oil within an eastward-plunging anticline . Within the anticline, numerous Pliocene -age sand units contain petroleum of various types. These sand units pinch out, and many are lenticular, with impermeable units above and below. The anticline

2096-505: Is between 70 °F and 80 °F on the Coastal Plain and as much as 100 °F in the interior. For July, the average maximum temperature is between 70 °F and 80 °F on the Coastal Plain but exceeds 90 °F in the upper part of the Ventura- and Cuyama River Valleys. For January, the average minimum temperature is near 40 °F on the coast but in the lower 30s and upper 20s in

2227-650: Is bounded on the north by a branch of the Oakridge Fault, and the anticline itself is broken in many places by small faults perpendicular to the Oakridge. Within the upper Pico Formation , many lenticular sand units contain natural gas; underneath this unit is the McGrath Zone, which was the first to be discovered, and which contains oil at an API gravity of 28. Beneath the McGrath, and separated by an unconformity , portions of

2358-460: Is currently operated by CalNRG Operating LLC. The oil field underlies the portion of coastline just south of the outlet of the Santa Clara River , including several state and county parks (including McGrath State Beach , Mandalay Beach Park , and Oxnard Shores Park). While parts of the oil field are within the city of Oxnard, California , most of it is within an unincorporated region east of

2489-617: Is discernible in pollen counts from the Tibetan Plateau, which also show that the South Asian Monsoon had already developed by the late Oligocene. Around 25.8 Ma, the South Asian Monsoon underwent an episode of major intensification brought on by the uplift of the Tibetan Plateau. A deep 400,000-year glaciated Oligocene-Miocene boundary event is recorded at McMurdo Sound and King George Island . The early Eocene climate

2620-513: Is in greenbelts between the cities. Because of this, its private low-key location, its country feel, and its proximity to Los Angeles, the Conejo Valley area has become a very attractive place to live. Like most areas of Ventura County, it once had relatively inexpensive real estate, but prices have risen sharply. For example, real estate in Newbury Park has increased in price by more than 250% in

2751-551: Is known for its steep coastal terrain with little beach access, nearby County Line Beach in the south coast community of Solromar is part of the fabled Malibu coastline. Ventura County has plenty of other surf spots along the coast including the notable surf spot, Rincon Point , on the Santa Barbara County-line. The Channel Islands in Ventura County are Anacapa and San Nicholas Islands . Ventura County has

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2882-569: Is north of and adjacent to Mandalay Beach Park. An oil-gas separator adjacent to the Mandalay plant processes gas from the offshore Santa Clara and Hueneme fields and sells the gas to Reliant for use at the power plant. Mandalay Beach Park consists of 94 acres (38 ha) of land left in its natural state, without amenities, and contains habitat for the endangered snowy plover . "McGrath 4 Well No. 1218", an oil well within Mandalay Beach Park, in

3013-422: Is small, conserving water and obtaining water from additional sources outside of Ventura County are vital concerns. The climate, though mostly mild and dry, varies because of the variations in topography through for instance differences in elevation and physical geography. The Santa Clara River is the principal waterway. Lake Casitas , an artificial reservoir, is the largest body of water. The highest peaks in

3144-467: Is to the west and southwest, via a system of canals. Total productive area of the field is 780 acres (316 ha), with 200 of that being offshore. Some oil field and power generation facilities are in enclosures within the parks and open spaces. A row of wells near McGrath Lake drill into the offshore portion of the field; visitors to McGrath State Beach can walk past them along the beach. Reliant Energy 's 560-megawatt gas-fired Mandalay Generating Station

3275-549: The Chumash Wilderness in the northernmost portion, adjacent to Kern County , as well as the large Sespe Wilderness and portions of both the Dick Smith Wilderness and Matilija Wilderness (both of these protected areas straddle the line with Santa Barbara County). All of the wilderness areas are within the jurisdiction of Los Padres National Forest. The coastal plain was formed by the deposition of sediments from

3406-508: The Miocene -age Santa Margarita and Monterey Formations show in drilling logs; yet another unconformity marks the top of the Colonia Zone, of Oligocene age, which contains more lenticular and pinched-out reservoirs of oil sands containing crude oil with an API gravity of around 15-18. Due to the relatively high reservoir temperature and geothermal gradient, the oil flows satisfactorily through

3537-665: The Mojave , Yokuts , and Tongva Indians. The Chumash are also known for their rock paintings and for their great basketry. Chumash Indian Museum in Thousand Oaks has several reconstructed Chumash houses ('apa) and there are several Chumash pictographs in the county, including the Burro Flats Painted Cave in Simi Valley. The plank canoe, called a tomol in Chumash , was important to their way of life. Canoe launching points on

3668-673: The Oxnard Oil Field upon which the refinery is located. Other petroleum processing facilities nearby include one west of the intersection of Harbor Boulevard and Gonzales Road, as well as two near the Santa Clara River, east of Harbor Boulevard. In 1991, an unknown amount of oil was spilled. In 1994, 2 barrels of oil were spilled. 34°12′53″N 119°14′20″W  /  34.2146°N 119.2390°W  / 34.2146; -119.2390 Ventura County, California Ventura County ( / v ɛ n ˈ t ʊər ə / )

3799-525: The Santa Clara River and from the streams of the Calleguas-Conejo drainage system. It has a mean elevation of fifty feet (15 m), but at points south of the Santa Clara River, the elevation is as much as 150 feet (46 m), and at points north of the river, as much as 300 feet (91 m). The coastal plain is generally known as the Oxnard Plain with the part that centers on Camarillo lying east of

3930-614: The U.S. 101 corridor and sent population rising in West County cities as well. The largest population growth there has been in Camarillo, Oxnard, and Ventura. Development in the East County and along the US 101 corridor is rare today, because most of these cities, such as Thousand Oaks and Simi Valley, are approaching build-out. Although the area still has plenty of open space and land, almost all of it

4061-649: The Ventura River is a narrow valley north of Ventura . Ojai Valley is connected to the Ventura River Valley by San Antonio Creek. The small Upper Ojai Valley , east of Ojai Valley and 300 to 500 feet (91 to 152 m) higher, drains to the Ventura River on the west and to Santa Paula Creek on the east. Ojai and Upper Ojai Valleys are surrounded by mountains and are rich agricultural areas. The Ventura River flows south and drains an area of 226 square miles (590 km ). Over South Mountain and Oak Ridge, south of

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4192-426: The archaeocete cetaceans began to decrease in diversity due to their lack of echolocation, which was very useful as the water became colder and cloudier. Other factors to their decline could include climate changes and competition with today's modern cetaceans and the requiem sharks , which also appeared in this epoch. Early desmostylians , like Behemotops , are known from the Oligocene. Pinnipeds appeared near

4323-651: The creodonts that had dominated the Paleocene in the Old World. Rodents and rabbits underwent tremendous diversification due to the increase in suitable habitats for ground-dwelling seed eaters, as habitats for squirrel-like nut- and fruit-eaters diminished. The primates, once present in Eurasia, were reduced in range to Africa and South America. Many groups, such as equids , entelodonts , rhinos , merycoidodonts , and camelids , became more able to run during this time, adapting to

4454-552: The first appearance of the foraminiferan Paragloborotalia kugleri and with the base of magnetic polarity chronozone C6Cn.2n. Oligocene faunal stages from youngest to oldest are: During the Oligocene Epoch, the continents continued to drift toward their present positions. Antarctica became more isolated as deep ocean channels were established between Antarctica and Australia and South America . Australia had been very slowly rifting away from West Antarctica since

4585-578: The Antarctic Circumpolar Current. There is some evidence that it occurred much earlier, during the early Eocene. The other major oceanic gateway opening during this time was the Tasman, or Tasmanian, depending on the paper, gateway between Australia and Antarctica. The time frame for this opening is less disputed than the Drake Passage and is largely considered to have occurred around 34 Ma. As

4716-689: The Arctic may have influenced this oceanic cooling, though the extent of this influence is still a matter of some significant dispute. The opening and closing of ocean gateways: the opening of the Drake Passage ; the opening of the Tasmanian Gateway and the closing of the Tethys seaway; along with the final formation of the Greenland – Iceland – Faroes Ridge; played vital parts in reshaping oceanic currents during

4847-477: The Chumash language that was spoken in Ventura County was Ventureño . Several place names in the county has originated from Chumash, including Ojai , which means moon, and Simi Valley, which originates from the word Shimiyi and refers to the stringy, thread-like clouds that typify the region. Others include Point Mugu from the word Muwu (meaning "beach"), Saticoy from the word Sa'aqtiko'y (meaning "sheltered for

4978-613: The Conejo Grade. Geographically East County is the end of the Santa Monica Mountains , in which the Conejo Valley is located, and where there is a considerable increase in elevation. Communities which are considered to be in the East County are Thousand Oaks , Newbury Park , Lake Sherwood , Hidden Valley , Santa Rosa Valley, part of Westlake Village, Oak Park , Moorpark, and Simi Valley. A majority of these communities are in

5109-466: The Conejo Valley. West County, which is everything west of the Conejo Grade, consists of communities such as Camarillo , Oxnard, Somis, Point Mugu, Port Hueneme, Ventura, Ojai, Santa Paula, and Fillmore. West County consists of some of the first developed cities in the county. The largest beach communities are located in West County on the coastline of the Channel Islands Harbor. Starting in

5240-528: The Dong Ho Formation of Oligocene age shows that the Oligocene flora of what is now Vietnam was very similar to its present flora. Kelps make their first appearance in the fossil record during the earliest Oligocene. Most extant mammal families had appeared by the end of the Oligocene. These included primitive three-toed horses, rhinoceroses, camels, deer, and peccaries. Carnivores such as dogs , nimravids , bears, weasels, and raccoons began to replace

5371-402: The Drake Passage may also have been in place by the end of the early Oligocene. This may have been interrupted by a temporary constriction of the Drake Passage from sometime in the middle to late Oligocene (29 to 22 mya) to the middle Miocene (15 mya). The reorganization of the oceanic tectonic plates of the northeastern Pacific, which had begun in the Paleocene, culminated with the arrival of

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5502-512: The Drake Passage opened and enabled the formation of the Antarctic Circumpolar Current (ACC), which would have kept the cold waters of Antarctica circulating around that continent and strengthened the formation of Antarctic Bottom Water (ABW). With the cold water concentrated around Antarctica, sea surface temperatures and, consequently, continental temperatures would have dropped. The onset of Antarctic glaciation occurred during

5633-928: The East African large igneous province , which also initiated rifting along the Red Sea and Gulf of Aden . The Alps were rapidly rising in Europe as the African Plate continued to push north into the Eurasian Plate , isolating the remnants of the Tethys Sea . Sea levels were lower in the Oligocene than in the early Eocene, exposing large coastal plains in Europe and the Gulf Coast and Atlantic Coast of North America. The Obik Sea , which had separated Europe from Asia, retreated early in

5764-555: The Eocene-Oligocene transition are not yet fully understood. The timing is wrong for this to be caused either by known impact events or by the volcanic activity on the Ethiopean Plateau. Two other possible drivers of climate change, not mutually exclusive, have been proposed. The first is thermal isolation of the continent of Antarctica by development of the Antarctic Circumpolar Current . Deep sea cores from south of New Zealand suggest that cold deep-sea currents were present by

5895-655: The Grande Coupure. The lowering of sea levels closed the Turgai Strait across the Obik Sea, which had previously separated Asia from Europe. This allowed Asian mammals, such as rhinoceroses and ruminants , to enter Europe and drive endemic species to extinction. Lesser faunal turnovers occurred simultaneously with the Oi2 event and towards the end of the Oligocene. There was significant diversification of mammals in Eurasia, including

6026-499: The Jurassic, but the exact timing of the establishment of ocean channels between the two continents remains uncertain. However, one estimate is that a deep channel was in place between the two continents by the end of the early Oligocene. The timing of the formation of the Drake Passage between South America and Antarctica is also uncertain, with estimates ranging from 49 to 17 mya (early Eocene to Miocene), but oceanic circulation through

6157-685: The King of Spain was now owned by the nation of Mexico. By the 1830s, Mission San Buenaventura was in a decline with fewer neophytes joining the mission. The number of cattle owned by the mission dropped from first to fifteenth ranking in the California Missions. The missions were secularized by the Mexican government in 1834 . The Mexican governors began granting land rights to Mexican Californians, often retiring soldiers. By 1846, there were 19 rancho grants in Ventura County. In 1836, Mission San Buenaventura

6288-677: The Las Posas-Simi area from the Santa Rosa Valley and Tierra Rejada Valley. The intermountain valley of the Santa Clara River is the most prominent valley in the county and trends east–southwest. The Santa Clara River drains an area of 1,605 square miles (4,160 km ) and flows from its headwaters in Los Angeles to where it empties into the Pacific. Its principal tributaries are Piru Creek , Santa Paula Creek, and Sespe Creek . The valley of

6419-615: The Mission. Fremont and the Battalion continued south to sign the Treaty of Cahuenga with General Andrés Pico . The Treaty of Guadalupe Hidalgo formally transferred California to the United States in 1848. By 1849, a constitution had been adopted for the California territory. The new Legislature met and divided the pending state into 27 counties. At the time, the area that would become Ventura County

6550-717: The Murray and Mendocino Fracture Zones at the North American subduction zone in the Oligocene. This initiated strike-slip movement along the San Andreas Fault and extensional tectonics in the Basin and Range province , ended volcanism south of the Cascades, and produced clockwise rotation of many western North American terranes. The Rocky Mountains were at their peak. A new volcanic arc was established in western North America, far inland from

6681-449: The New World and Old World monkeys. The South American continent was home to animals such as pyrotheres and astrapotheres , as well as litopterns and notoungulates . Sebecosuchians , terror birds , and carnivorous metatheres , like the borhyaenids remained the dominant predators. Africa was also relatively isolated and retained its endemic fauna. These included mastodonts, hyraxes, arsinoitheres, and other archaic forms. Egypt in

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6812-459: The Norwegian-Greenland Sea indicate a drop in winter temperatures at high latitudes of about 5 °C (9.0 °F) just prior to the Oi1 event. Borehole dating from the Southeast Faroes drift indicates that deep-ocean circulation from the Arctic Ocean to the North Atlantic Ocean began in the early Oligocene. The best terrestrial record of Oligocene climate comes from North America, where temperatures dropped by 7 to 11 °C (13 to 20 °F) in

6943-436: The Norwegian-Greenland Sea indicated that glaciers had appeared in Greenland by the start of the Oligocene. Continental ice sheets in Antarctica reached sea level during the transition. Glacially rafted debris of early Oligocene age in the Weddell Sea and Kerguelen Plateau , in combination with Oi1 isotope shift, provides unambiguous evidence of a continental ice sheet on Antarctica by the early Oligocene. The causes of

7074-401: The Oligocene exists mostly in isotopic proxies. Patterns of extinction and patterns of species migration can also be studied to gain insight into ocean conditions. For a while, it was thought that the glaciation of Antarctica may have significantly contributed to the cooling of the ocean, however, recent evidence tends to deny this. Isotopic evidence suggests that during the early Oligocene,

7205-402: The Oligocene was an environment of lush forested deltas. Nevertheless, the Early Oligocene saw a major reduction in the diversity of many Afro-Arabian mammal clades, including hyaenodonts, primates, and hystricognath and anomaluroid rodents. During the Oligocene, the Tethyan marine biodiversity hotspot collapsed as the Tethys Ocean contracted. The seas around Southeast Asia and Australia became

7336-407: The Oligocene, creating a persistent land connection between the continents. The Paratethys Sea stretched from what is now the Balkan Peninsula across Central Asia to the Tian Shan region of what is now Xinjiang . There appears to have been a land bridge in the early Oligocene between North America and Europe, since the faunas of the two regions are very similar. However, towards the end of

7467-440: The Oligocene, there was a brief marine incursion in Europe. The rise of the Himalayas during the Oligocene remains poorly understood. One recent hypothesis is that a separate microcontinent collided with south Asia in the early Eocene, and India itself did not collide with south Asia until the end of the Oligocene. The Tibetan Plateau may have reached nearly its present elevation by the late Oligocene. The Andes first became

7598-404: The Oligocene. The Oligocene saw the emergence of parrotfishes, as the centre of marine biodiversity shifted from the Central Tethys eastward into the Indo-Pacific. The fossil record of marine mammals is a little spotty during this time, and not as well known as the Eocene or Miocene, but some fossils have been found. The baleen whales and toothed whales had just appeared, and their ancestors,

7729-406: The Oligocene. As the continents shifted to a more modern configuration, so too did ocean circulation. The Drake Passage is located between South America and Antarctica . Once the Tasmanian Gateway between Australia and Antarctica opened, all that kept Antarctica from being completely isolated by the Southern Ocean was its connection to South America. As the South American continent moved north,

7860-409: The Oxnard–Thousand Oaks–Ventura, CA Metropolitan Statistical Area. The United States Census Bureau ranked the Oxnard–Thousand Oaks–Ventura, CA Metropolitan Statistical Area as the 66th most populous metropolitan statistical area of the United States as of July 1, 2012. The Office of Management and Budget has further designated the Oxnard–Thousand Oaks–Ventura, CA Metropolitan Statistical Area as

7991-419: The Revelon Slough is called Pleasant Valley. Most of the arable land in the county is found on the coastal plain. Small coastal mountains rim Ventura County on its landward side. They range in elevation from 50 feet (15 m) along the coast south of the coastal plain, to about 3,100 feet (940 m) in the Santa Monica Mountains. The Santa Ynez Mountains, the Topatopa Mountains , and the Piru Mountains make up

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8122-466: The Santa Clara River, are Las Posas Valley and Simi Valley. Las Posas Valley extends eastward from the Oxnard Plain almost to Simi Valley, which is in the east end of Ventura County. The city of Simi Valley is bounded on the east by the Santa Susana Mountains and on the south by the Simi Hills. To the south, over the Camarillo- and Las Posas Hills, are Santa Rosa- and Tierra Rejada Valleys, which extend from Camarillo eastward for ten miles (16 km). In

8253-460: The Santa Clarita Valley killing as many as 600 people, destroying 1,240 homes and flooding 7,900 acres (32 km ) of land, devastating farm fields and orchards. This was the single largest disaster to strike Ventura County and the second largest, in terms of lives lost, in the state. Ventura County can be separated into two major parts, East County and West County, which are divided by the Conejo Grade . East County consists of all cities east of

8384-449: The annual total is more than thirty-three inches. The drier parts of the county get less than five inches of rain annually, and the higher and wetter parts get more than 60 inches annually. Measureable amounts of rainfall in Ventura County are reported on thirty to thirty-five days annually, and half an inch or more on six to twelve days annually. In the northern parts of Ventura County, snowfall averages five inches or more per year, and along

8515-425: The atmosphere, contributing to global cooling. The gradual separation of the clump of continental crust and the deepening of the tectonic ridge in the North Atlantic that would become Greenland, Iceland, and the Faroe Islands helped to increase the deep water flow in that area. More information about the evolution of North Atlantic Deep Water will be given a few sections down. Evidence for ocean-wide cooling during

8646-504: The census of 2000, there were 753,197 people, 243,234 households, and 182,911 families living in the county. The population density was 408 inhabitants per square mile (158/km ). There were 251,712 housing units at an average density of 136 per square mile (53/km ). The racial makeup of the county was 69.9% White , 5.4% Asian , 2.0% Black or African American , 0.9% Native American , 0.2% Pacific Islander , 17.7% from other races , and 3.9% from two or more races. About one third (33.4%) of

8777-464: The chemical waste water, also called produced water, back into the earth. The presence of water injection wells near directionally drilled oil wells lead one investigative journalist to hypothesize that fracking had occurred. Oil produced in the field goes to the small (2,800-barrel (450 m)-per-day) Oxnard Refinery, owned by Tenby Inc., in an unincorporated area on Fifth Street near the eastern Oxnard city limit. This refinery also processes oil from

8908-425: The city remains officially known as San Buenaventura, it is more commonly referred to as Ventura. The rail line to Northern California originally went through Saugus , Fillmore and Santa Paula, providing a boom to those communities along the line. In 1905, Tunnel #26 was completed between Chatsworth and Corriganville near Simi Valley, shortening the rail route. At a length of 7,369 feet (2,246 m), Tunnel #26

9039-413: The coast, reaching from central Mexico through the Mogollon-Datil volcanic field to the San Juan volcanic field , then through Utah and Nevada to the ancestral Northern Cascades. Huge ash deposits from these volcanoes created the White River and Arikaree Groups of the High Plains, with their excellent fossil beds. Between 31 and 26 mya, the Ethiopia-Yemen Continental Flood Basalts were emplaced by

9170-403: The county government is responsible for housing goals in unincorporated areas. Several affordable housing groups that are actively working on building housing for veterans and low income people have long waiting lists. Farmworker housing also has waiting lists though designated units continue to be built. The United States Office of Management and Budget has designated Ventura County as

9301-405: The county include Mount Pinos (8,831 ft; 2,692 m), Frazier Mountain (8,017 ft; 2,444 m), and Reyes Peak (7,525 ft; 2,294 m) in the Transverse Ranges . The uplands are well-timbered with coniferous forests , and receive plentiful snow in the winter. Mount Pinos is sacred to the Chumash Indians. It is known to them as Iwihinmu, and was considered to be the center of

9432-486: The county's total area is made up of national forest. Of the land outside of national forest land, approximately 59 percent is agricultural and 17.5 percent urban. North of Highway 126, the county is mountainous and mostly uninhabited, and contains some of the most unspoiled, rugged and inaccessible wilderness remaining in southern California. Most of this land is in the Los Padres National Forest , and includes

9563-446: The difficulty may be that there were strong regional variations in the response to climate shifts. Evidence of a relatively warm Oligocene suggests an enigmatic climate state, neither hothouse nor icehouse. The late Oligocene (26.5 to 24 mya) likely saw a warming trend in spite of low pCO2 levels, though this appears to vary by region. However, Antarctica remained heavily glaciated during this warming period. The late Oligocene warming

9694-417: The earliest Oligocene. This change is seen from Alaska to the Gulf Coast. Upper Eocene paleosols reflect annual precipitation of over a meter of rain, but early Oligocene precipitation was less than half this. In central North America, the cooling was by 8.2 ± 3.1 °C over a period of 400,000 years, though there is little indication of significant increase in aridity during this interval. Ice-rafted debris in

9825-487: The early Oligocene, and the effect of the Drake Passage opening on this glaciation has been the subject of much research. However, some controversy still exists as to the exact timing of the passage opening, whether it occurred at the start of the Oligocene or nearer the end. Even so, many theories agree that at the Eocene/Oligocene (E/O) boundary, a yet shallow flow existed between South America and Antarctica, permitting

9956-496: The early Oligocene. However, the timing of this event remains controversial. The other possibility, for which there is considerable evidence, is a drop in atmospheric carbon dioxide levels ( pCO2 ) during the transition. The pCO2 is estimated to have dropped just before the transition, to 760 ppm at the peak of ice sheet growth, then rebounded slightly before resuming a more gradual fall. Climate modeling suggests that glaciation of Antarctica took place only when pCO2 dropped below

10087-639: The early intellectual founders of the Franciscan order. The town that grew up around the mission was originally named San Buenaventura (and retains the name officially), it has been known as Ventura since 1891. In the 1790s, the Spanish Governor of California began granting land concessions to Spanish Californians who were often retiring soldiers. These concessions were known as ranchos and consisted of thousands of acres of land that were used primarily as ranch land for livestock. In Ventura County, Rancho Simi

10218-432: The end of the epoch from an otter -like ancestor. The Oligocene sees the beginnings of modern ocean circulation, with tectonic shifts causing the opening and closing of ocean gateways. Cooling of the oceans had already commenced by the Eocene/Oligocene boundary, and they continued to cool as the Oligocene progressed. The formation of permanent Antarctic ice sheets during the early Oligocene and possible glacial activity in

10349-484: The endemic rodent and marsupial families. By contrast, the Oligocene–Miocene boundary is not set at an easily identified worldwide event but rather at regional boundaries between the warmer late Oligocene and the relatively cooler Miocene. The lower boundary of the Oligocene (its Global Boundary Stratotype Section and Point or GSSP) is placed at the last appearance of the foraminiferan genus Hantkenina in

10480-474: The expedition, Father Juan Crespí , kept a journal of the trip and noted that the area was ideal for a mission to be established and it was a "good site to which nothing is lacking". Also on this expedition was Father Junípero Serra , who later founded a mission on this site. On March 31, 1782, the Mission San Buenaventura was founded by Father Serra. It is named after Saint Bonaventure , one of

10611-416: The field is exploited from wells directionally drilled from onshore near McGrath Lake, from within an enclosure above the high-tide line at McGrath State Beach . The West Montalvo field was also the first dry natural gas field of commercial value to be discovered in Ventura County; in its lifetime it has produced over 48 billion cubic feet (1.4 × 10 m) of gas. The field was recently acquired and

10742-423: The field was run under that logo. Chevron sold the field to Bush Oil Company of Taft, California, on May 1, 1990. Bush Oil ran the field for only two years, selling it to Berry Petroleum Company in 1992. In 2007, Venoco acquired the field from Berry Petroleum Company for $ 63 million; it was sold in 2014 to California Resources Corporation for $ 200 million. The field was acquired by CalNRG Operating LLC after

10873-500: The fire caused over $ 2.176 billion (2018 USD) in damages, including more than $ 204.5 million in suppression costs, becoming the seventh-most destructive wildfire in state history. The agriculture industry suffered at least $ 171 million in losses due to the Thomas Fire. Southern California Edison paid the county over $ 11 million in claims related to damages and costs since its equipment was likely associated with one ignition point of

11004-419: The fire near Santa Paula. According to the U.S. Census Bureau , the county has a total area of 2,208 square miles (5,720 km ), of which 1,843 square miles (4,770 km ) is land and 365 square miles (950 km ) (16.5%) is water. Parts of the county are on the Oxnard Plain which includes the cities of Oxnard , Camarillo , Port Hueneme and much of Ventura . Other cities and communities lie in

11135-488: The first high school opening in 1890. Other towns were being established in the county. A plan for Hueneme (later Port Hueneme) was recorded in 1874, and Santa Paula 's plan was recorded in 1875. Along the banks of the Santa Clara River, the township of New Jerusalem (which would eventually be named El Rio ) was founded in 1875 by the owner of general store named Simon Cohen who became its first postmaster and banker in 1882. The community of Nordhoff (later renamed Ojai )

11266-783: The gateway widened, the Antarctic Circumpolar Current strengthened. The Tethys Seaway was not a gateway, but rather a sea in its own right. Its closing during the Oligocene had significant impact on both ocean circulation and climate. The collisions of the African plate with the European plate and of the Indian subcontinent with the Asian plate, cut off the Tethys Seaway that had provided a low-latitude ocean circulation. The closure of Tethys built some new mountains (the Zagros range) and drew down more carbon dioxide from

11397-526: The giant indricotheres , that grew up to 6 meters (20 ft) at the shoulder and weighed up to 20 tons. Paraceratherium was one of the largest land mammals ever to walk the Earth. However, the indricotheres were an exception to a general tendency for Oligocene mammals to be much smaller than their Eocene counterparts. The earliest deer, giraffes, pigs, and cattle appeared in the mid-Oligocene in Eurasia. The first felid , Proailurus , originated in Asia during

11528-568: The hills north of Ventura, was producing 90,000 barrels (14,000 m ) of oil a day, with annual production of over 1.5   million barrels. More oil fields came online in the 1920s and 1930s, with the Rincon field , the second largest, in 1927, and the adjacent San Miguelito in 1931. In the early hours of the morning of March 12–13, 1928, the St. Francis Dam collapsed, sending nearly 12,500 million U.S. gallons (47 gigaliters) of water rushing through

11659-671: The hills south of Santa Rosa Valley is the broad Conejo Valley. Santa Rosa Valley, Conejo Valley, Simi Valley, and Tierra Rejada Valley are drained by Calleguas Creek and its principal tributary, Conejo Creek. These creeks originate in the Santa Susana and Santa Monica Mountains . The county's diverse 43-mile (69 km) coastline features a variety of terrain. There are many State beaches: Emma Wood , San Buenaventura , McGrath , and Mandalay State Beach . Other beaches include Channel Islands Beach , Solimar Beach , Oxnard Beach Park , and Silver Strand Beach . While Point Mugu State Park

11790-578: The intermountain valleys of the Transverse Range. The Santa Clara River Valley is the most prominent valley, while other valleys include Conejo Valley , Simi Valley , Santa Rosa Valley , Tierra Rejada Valley and Las Posas Valley. Other parts of the county are on small coastal mountains, such as the Santa Ynez Mountains , Simi Hills , Santa Monica Mountains and the Piru Mountains. Most of

11921-469: The intersection of Harbor Boulevard and Gonzales Road, a mixed-use area of agricultural fields interspersed with oil wells and associated production and processing facilities. This area was designated a greenbelt through a joint agreement between the cities of Oxnard and Ventura . The terrain is almost all flat, save for berms and sand dunes at the shoreline. Elevations on the field range from sea level to about 40 feet (12 m) above sea level, and drainage

12052-598: The last 10 years. The Thomas Fire was a massive wildfire that affected Ventura and Santa Barbara Counties, and one of multiple wildfires that ignited in Southern California in December 2017. It burned approximately 281,893 acres (440 sq mi; 114,078 ha), becoming the largest wildfire in modern California history , before it was fully contained on January 12, 2018. The Thomas Fire destroyed at least 1,063 structures, while damaging 280 others; and

12183-456: The late Oligocene and spread to Europe. There was only limited migration between Asia and North America. The cooling of central North America at the Eocene-Oligocene transition resulted in a large turnover of gastropods, amphibians, and reptiles. Mammals were much less affected. Crocodilians and pond turtles replaced by dry land tortoises. Molluscs shifted to more drought-tolerant forms. The White River Fauna of central North America inhabited

12314-566: The lease was reassigned in 2024. Field operators have tried several enhanced oil recovery projects to improve production rates. In the McGrath pool, gas injection was used from 1956 to 1968, and the zone has been waterflooded since 1963, in an attempt to boost reservoir pressure. Both methods also have been used on the Colonia pool, with gas injection running from 1964 to 1971, and waterflooding since 1960. Enhanced methods have included using water injection to get more tight oil . Oil companies inject

12445-599: The lingering smell in the dirt to uncover artifacts that showed heavy utilization by mission inhabitants, Indians, early settlers and Spanish and Mexican soldiers. The Mexican–American War began in 1846 but its effect was not felt in Ventura County until 1847. In January of that year, Captain John C. Frémont led the California Battalion into San Buenaventura to find that the Europeans had fled, leaving only Native Americans in

12576-825: The main source of deep water was the North Pacific and the Southern Ocean . As the Greenland-Iceland-Faroe Ridge sank and thereby connected the Norwegian–Greenland sea with the Atlantic Ocean, the deep water of the North Atlantic began to come into play as well. Computer models suggest that once this occurred, a more modern in appearance thermo-haline circulation started. Evidence for the early Oligocene onset of chilled North Atlantic deep water lies in

12707-474: The mainland for trade with the Chumash of the Channel Islands were located at the mouth of the Ventura River , Mugu Lagoon and Point Hueneme. This has led to speculations among archeologists of whether the Chumash could have had a pre-historic contact with Polynesians . According to diachronic linguistics , certain words such as tomolo'o (canoe) could be related to Polynesian languages . The dialect of

12838-682: The mid-20th century, there was a large growth in population in the East County, moving from the San Fernando Valley in Los Angeles and out into the Conejo and Simi Valleys. Part of the Conejo Valley is situated in Los Angeles County . This part consists of Calabasas , Hidden Hills , Agoura Hills , Agoura , and Westlake Village . The other half of the Conejo Valley, which belongs to Ventura County, consists of Lake Sherwood , Hidden Valley , Oak Park , Thousand Oaks , and Newbury Park , which

12969-502: The new dominant hotspot of marine biodiversity. At sea, 97% of marine snail species, 89% of clams, and 50% of echinoderms of the Gulf Coast did not survive past the earliest Oligocene. New species evolved, but the overall diversity diminished. Cold-water mollusks migrated around the Pacific Rim from Alaska and Siberia. The marine animals of Oligocene oceans resembled today's fauna, such as the bivalves . Calcareous cirratulids appeared in

13100-689: The northern border and Mount Pinos, more than twenty inches. Automobile emissions account for most of the air pollution . Other sources include chemical plants , gasoline stations , paint and cleaning products . Rivers in Ventura County include: The 2010 United States Census reported that Ventura County had a population of 823,318. The racial makeup of Ventura County was 565,804 (68.7%) White , 15,163 (1.8%) African American , 8,068 (1.0%) Native American , 55,446 (6.7%) Asian , 1,643 (0.2%) Pacific Islander , 140,253 (17.0%) from other races , and 36,941 (4.5%) from two or more races. Hispanic or Latino of any race were 331,567 persons (40.3%). As of

13231-764: The northern boundary of the coastal plain, the Santa Susana Mountains are alongside the eastern boundary of the county, and the Simi Hills and the Santa Monica Mountains are along the southern border with Los Angeles County . South Mountain and Oak Ridge are low and long mountains that separate Santa Clara Valley from the Las Posas Valley and Simi Valley . The Camarillo Hills and the Las Posas Hills extend from Camarillo to Simi Valley and separate

13362-473: The northern parts of Ventura County. No temperature data are available for the highest point in the county, Mount Pinos . The length of the growing season ranges more than 300 days near the coast to less than 175 days in the coldest part in northern Ventura County. In both the northern and southern ends of the county, the annual precipitation totals between ten and fifteen inches. In the Topatopa Mountains,

13493-611: The offshore portion of the field in June 1953 by drilling into the Oligocene -age Sespe Formation , where they also found oil at the 11,500-foot (3,500 m) depth. This producing horizon was also part of the Colonia Zone. This unit remains richly productive. By the end of 2008, the field was one of the top ten in California by largest production increase of the preceding year. The field has changed owners several times. In 1977, Standard Oil Company of California became Chevron Corporation , and

13624-566: The opening of the Drake Passage is around 30 Ma. One of the possible issues with this timing was the continental debris cluttering up the seaway between the two plates in question. This debris, along with what is known as the Shackleton Fracture Zone , has been shown in a recent study to be fairly young, only about 8 million years old. The study concludes that the Drake Passage would be free to allow significant deep water flow by around 31 Ma. This would have facilitated an earlier onset of

13755-468: The opening of the Drake Passage is during the early Miocene. Despite the shallow flow between South America and Antarctica, there was not enough of a deep water opening to allow for significant flow to create a true Antarctic Circumpolar Current. If the opening occurred as late as hypothesized, then the Antarctic Circumpolar Current could not have had much of an effect on early Oligocene cooling, as it would not have existed. The earliest hypothesized time for

13886-517: The period from 33.8 to 33.5 mya. By the end of the transition, sea levels had dropped by 105 meters (344 ft), and ice sheets were 25% greater in extent than in the modern world. The effects of the transition can be seen in the geological record at many locations around the world. Ice volumes rose as temperature and sea levels dropped. Playa lakes of the Tibetan Plateau disappeared at the transition, pointing to cooling and aridification of central Asia. Pollen and spore counts in marine sediments of

14017-568: The period, grass was not quite common enough for modern savannas . In North America, much of the dense forest was replaced by patchy scrubland with riparian forests. Subtropical species dominated with cashews and lychee trees present, and temperate woody plants such as roses , beeches , and pines were common. The legumes spread, while sedges and ferns continued their ascent. In Europe, floral assemblages became increasingly affected by strengthening seasonality as it related to wildfire activity. The Ha Long megafossil flora from

14148-406: The petroleum products under Ventura County but none were financially successful, and the oil speculators eventually changed from oil to land development. In 1913, oil exploration began in earnest, with Ralph Lloyd obtaining the financial support of veteran oil man Joseph B. Dabney. Their first well, named "Lloyd No. 1", was started on January 20, 1914. The well struck oil at 2,558 feet (780 m) but

14279-623: The plains that were spreading as the Eocene rainforests receded. Brontotheres died out in the Earliest Oligocene, and creodonts died out outside Africa and the Middle East at the end of the period. Multituberculates , an ancient lineage of primitive mammals that originated back in the Jurassic , also became extinct in the Oligocene, aside from the gondwanatheres . The Eocene-Oligocene transition in Europe and Asia has been characterized as

14410-537: The population is Hispanic or Latino of any race. 9.8% were of German, 7.7% English and 7.1% Irish ancestry according to Census 2000 . 67.1% spoke English, 26.2% Spanish and 1.5% Tagalog as their first language. There were 243,234 households, of which 39.7% had children under the age of 18 living with them, 59.5% were married couples living together, 10.9% had a female householder with no husband present, and 24.8% were non-families. 18.9% of all households were made up of individuals, and 7.4% had someone living alone who

14541-533: The population of Ventura County lives in the southern portion of the county. The major population centers are the Oxnard Plain and the Simi and Conejo Valleys. In local media, the county is usually split between the eastern portion, generally associated with the San Fernando Valley , and the western portion, often referred to as “Oxnard-Ventura". To the east is Los Angeles County . Because the total amount of precipitation

14672-524: The reservoir sands towards the production wells. Standard Oil Company of California discovered the field in April 1947 by drilling into the McGrath producing horizon. The first well produced 154 barrels per day (24.5 m/d), encouraging further exploration. In 1951, the Colonia Pool was found at 11,500 feet (3,500 m), which had a heavier oil with high sulfur content, and following the trend west, discovered

14803-478: The start of an Antarctic Circumpolar Current. Stemming from the issue of when the opening of the Drake Passage took place, is the dispute over how great of an influence the opening of the Drake Passage had on the global climate. While early researchers concluded that the advent of the ACC was highly important, perhaps even the trigger, for Antarctic glaciation and subsequent global cooling, other studies have suggested that

14934-537: The time of the Oi2 oxygen isotope shift. This led to the largest drop of sea level in past 100 million years, by about 75 meters (246 ft). This is reflected in a mid-Oligocene incision of continental shelves and unconformities in marine rocks around the world. Some evidence suggests that the climate remained warm at high latitudes even as ice sheets experienced cyclical growth and retreat in response to orbital forcing and other climate drivers. Other evidence indicates significant cooling at high latitudes. Part of

15065-463: The town of San Buenaventura was incorporated, becoming the first officially recognized town in what would become Ventura County. On January 1, 1873, Ventura County was officially split from Santa Barbara County, bringing a flurry of change. That same year, a courthouse and wharf were built in San Buenaventura. A bank was opened and the first public library was created. The school system grew, with

15196-407: The train stop. That community, now bearing the name of the factory shortened to the one word train stop Oxnard, has become the largest city in Ventura County. Oil has been known in Ventura County since before the arrival of the Europeans, as the native Chumash people used tar from natural seeps as a sealant and waterproofing for baskets and canoes. In the 1860s, several attempts were made to harvest

15327-538: The universe; being the highest peak in the vicinity, it has unimpeded views in three directions. The USDA Economic Research Service rated Ventura County the most desirable county to live in the 48 contiguous states, using six metrics of climate ("mild, sunny winters, temperate summers, low humidity"), topographic variation, and access to water, "that reflect environmental qualities most people prefer." There are 555,953 acres (224,986 ha) outside of national forest land in Ventura County, which means that 53 percent of

15458-404: The way for development westward. The communities that have seen the most substantial development are Calabasas, Hidden Hills, Agoura Hills, Westlake Village, Thousand Oaks, and Newbury Park. The neighboring East County area of Simi Valley saw its already considerable population of nearly 60,000 inhabitants in 1970 grow to over 100,000 over the following two decades. Development moved farther down

15589-536: The wind"), and Sespe Creek from the word S'eqp'e (meaning "kneecap"). In October 1542, the expedition led by Juan Rodríguez Cabrillo anchored in an inlet near Point Mugu ; its members were the first Europeans to arrive in the area that would become Ventura County. Active occupation of California by Spain began in 1769. Gaspar de Portolà led a military expedition by land from San Diego to Monterey , passing through Ventura County in August of that year. A priest with

15720-401: The world as tropical and sub- tropical forests were replaced by temperate deciduous forests . Open plains and deserts became more common and grasses expanded from their water-bank habitat in the Eocene moving out into open tracts. The decline in pCO2 favored C4 photosynthesis , which is found only in angiosperms and is particularly characteristic of grasses. However, even at the end of

15851-414: The δ O signature is too strong for glaciation to be the main trigger for cooling. Through study of Pacific Ocean sediments, other researchers have shown that the transition from warm Eocene ocean temperatures to cool Oligocene ocean temperatures took only 300,000 years, which strongly implies that feedbacks and factors other than the ACC were integral to the rapid cooling. The latest hypothesized time for

15982-582: Was $ 66,859, while the mean was $ 85,032. Per capita income was up to $ 29,634, making it the 6th wealthiest county in California. Ventura County typically has limited housing inventory, making it a consistently expensive location in Southern California, where it is usually the third-most-expensive county behind Orange and Los Angeles counties. As of March 2018 , the county was not on track to meet its state-mandated housing goals. Individual cities are responsible for meeting their assigned housing goals, while

16113-448: Was 65 years of age or older. The average household size was 3.04 and the average family size was 3.46. In the county, the population was spread out, with 28.4% under the age of 18, 9.0% from 18 to 24, 30.7% from 25 to 44, 21.7% from 45 to 64, and 10.2% who were 65 or older. The median age was 34 years. For every 100 females, there were 99.7 males. For every 100 females age 18 and over, there were 97.5 males. The median income for

16244-567: Was destroyed when it went wild. Other wells met a similar fate, until 1916, when a deal was struck with the Shell Oil Company . 1916 was the year that the large South Mountain Oil Field was discovered; other deals followed with General Petroleum in 1917 and Associated Oil Company in 1920. At its peak, the largest oil field in the county, the Ventura Avenue oilfield , discovered in 1919 in

16375-480: Was formerly an unincorporated area that is now the most westerly part of Thousand Oaks. Many working-class people migrated to this area during the 1960s and 1970s out of East and Central Los Angeles . As a result, there was a large growth in population into the Conejo Valley and into Ventura County through the U.S. Route 101 corridor. Making the U.S. 101 a full freeway in the 1960s, and the expansions that followed, helped make commuting to Los Angeles easier and opened

16506-559: Was granted in 1795 and Rancho El Conejo in 1802. Fernando Tico was granted Ojai and part of Ventura by Gov. Alvarado. In 1822, California was notified of Mexico's independence from Spain and the Governor of California , the Junta, the military in Monterey and the priests and neophytes at Mission San Buenaventura swore allegiance to Mexico on April 11, 1822. California land that had been vested in

16637-454: Was started in 1874. Bardsdale , Fillmore , Piru , and Montalvo were established in 1887. 1892 saw Simi (later Simi Valley), Somis , Saticoy , and Moorpark . Oxnard was a latecomer, not being established until 1898. The Southern Pacific Railroad laid tracks through San Buenaventura in 1887. For convenience in printing their timetables, Southern Pacific shortened San Buenaventura to Ventura. The Post Office soon followed suit. While

16768-500: Was the longest tunnel ever constructed in its day. This tunnel joined to the railroad spur coming the other direction from Montalvo through Camarillo, Moorpark and Simi Valley, making the contemporary main line used today. One stop along the way, at a 90-degree turn, was at a sugar beet processing factory. The factory bore the name of its absentee owners, the Oxnard Brothers. A small community of farm and factory workers grew near

16899-416: Was the southern part of Santa Barbara County . The 1860s brought many changes to the area. A drought caused many of the ranchos to experience financial difficulties and most were divided, sub-divided and sold. Large sections of land were bought by eastern capitalists based on favorable reports of petroleum deposits. A United States Post Office was opened at Mission San Buenaventura in 1861. On April 1, 1866,

17030-527: Was transferred from the Church to a secular administrator. The natives who had been working at the mission gradually left to work on the ranchos. By 1839, only 300 Indians were left at the Mission and it slipped into neglect. Several outhouses dating back to the 1800s were discovered in July 2007, at a site that had been cleared to prepare for development. The area proved to be a treasure trove for archaeologists who braved

17161-583: Was very warm, with crocodilians and temperate plants thriving north of the Arctic Circle . The cooling trend that began in the middle Eocene continued into the Oligocene, bringing both poles well below freezing for the first time in the Phanerozoic . The cooling climate, together with the opening of some land bridges and the closing of others, led to a profound reorganization of the biosphere and loss of taxonomic diversity. Land animals and marine organisms reached

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