La Brea Tar Pits is an active paleontological research site in urban
Los Angeles
Los Angeles ( ; es, Los Ángeles, link=no , ), often referred to by its initials L.A., is the largest city in the state of California and the second most populous city in the United States after New York City, as well as one of the world ...
.
Hancock Park was formed around a group of
tar pit
Tar pits, sometimes referred to as asphalt pits, are large asphalt deposits. They form in the presence of oil, which is created when decayed organic matter is subjected to pressure underground. If this crude oil seeps upward via fractures, cond ...
s where natural
asphalt
Asphalt, also known as bitumen (, ), is a sticky, black, highly viscous liquid or semi-solid form of petroleum. It may be found in natural deposits or may be a refined product, and is classed as a pitch. Before the 20th century, the term ...
(also called asphaltum, bitumen, or pitch; ''brea'' in Spanish) has seeped up from the ground for tens of thousands of years. Over many centuries, the bones of trapped animals have been preserved. The
George C. Page Museum is dedicated to researching the tar pits and displaying specimens from the animals that died there. La Brea Tar Pits is a registered
National Natural Landmark.
Formation
Tar pits are composed of
heavy oil fractions called
gilsonite, which seeps from the Earth as oil.
Crude oil
Petroleum, also known as crude oil, or simply oil, is a naturally occurring yellowish-black liquid mixture of mainly hydrocarbons, and is found in geological formations. The name ''petroleum'' covers both naturally occurring unprocessed crude ...
seeps up along the 6th Street Fault from the
Salt Lake Oil Field, which underlies much of the Fairfax District north of
Hancock Park.
The oil reaches the surface and forms pools, becoming asphalt as the lighter fractions of the petroleum
biodegrade or evaporate.
The asphalt then normally hardens into stubby mounds. The pools and mounds can be seen in several areas of the park.
This seepage has been happening for tens of thousands of years, during which the asphalt sometimes formed a deposit thick enough to trap animals. The deposit would become covered over with water, dust, or leaves. Animals would wander in, become trapped, and die. Predators would enter to eat the trapped animals and would also become stuck. As the bones of a dead animal sink, the asphalt soaks into them, turning them dark-brown or black in color. Lighter
fractions of petroleum evaporate from the asphalt, leaving a more solid substance, which then encases the bones. Dramatic fossils of large mammals have been extricated but the asphalt also preserves
microfossils: wood and plant remnants, rodent bones, insects, mollusks, dust, seeds, leaves, and pollen grains. Examples of some of these are on display in the George C. Page Museum.
Radiometric dating
Radiometric dating, radioactive dating or radioisotope dating is a technique which is used to date materials such as rocks or carbon, in which trace radioactive impurities were selectively incorporated when they were formed. The method compares ...
of preserved wood and bones has given an age of 38,000 years for the oldest known material from the La Brea seeps.
History
The Native American
Chumash and
Tongva people living in the area built boats unlike any others in North America. Pulling fallen Northern
California redwood
''Sequoia sempervirens'' ()''Sunset Western Garden Book,'' 1995:606–607 is the sole living species of the genus '' Sequoia'' in the cypress family Cupressaceae (formerly treated in Taxodiaceae). Common names include coast redwood, coastal ...
trunks and pieces of driftwood from the
Santa Barbara Channel, their ancestors learned to seal the cracks between the boards of the large wooden plank canoes by using the natural resource of tar. This innovative form of transportation allowed access up and down the coastline and to the
Channel Islands
The Channel Islands ( nrf, Îles d'la Manche; french: îles Anglo-Normandes or ''îles de la Manche'') are an archipelago in the English Channel, off the French coast of Normandy. They include two Crown Dependencies: the Bailiwick of Jersey, ...
. The
Portolá expedition, a group of Spanish explorers led by
Gaspar de Portolá
Gaspar de Portolá y Rovira (January 1, 1716 – October 10, 1786) was a Spanish military officer, best known for leading the Portolá expedition into California and for serving as the first Governor of the Californias. His expedition laid t ...
, made the first written record of the tar pits in 1769. Father
Juan Crespí wrote,
While crossing the basin, the scouts reported having seen some geysers of tar issuing from the ground like springs; it boils up molten, and the water runs to one side and the tar to the other. The scouts reported that they had come across many of these springs and had seen large swamps of them, enough, they said, to caulk many vessels. We were not so lucky ourselves as to see these tar geysers, much though we wished it; as it was some distance out of the way we were to take, the Governor ortoládid not want us to go past them. We christened them ''Los Volcanes de Brea'' he Tar Volcanoes[.]
Harrison Rogers, who accompanied
Jedediah Smith on his 1826 expedition to California, was shown a piece of the solidified asphalt while at
Mission San Gabriel, and noted in his journal, "The Citizens of the Country make great use of it to pitch the roofs of their houses".
The La Brea Tar Pits and Hancock Park are situated within what was once the
Mexican land grant of
Rancho La Brea. For some years, tar-covered bones were found on the Rancho La Brea property, but were not initially recognized as fossils because the ranch had lost various animals–including horses, cattle, dogs, and even camels–whose bones closely resemble several of the fossil species. The original Rancho La Brea land grant stipulated that the tar pits be open to the public for the use of the local
Pueblo. Initially, they mistook the bones in the pits for the remains of
pronghorn (''Antilocapra americana'') or cattle that had become mired.
In 1886, the first excavation for land pitch in the village of La Brea was undertaken by ''Messrs Turnbull, Stewart & co.''.
Union Oil geologist
W. W. Orcutt is credited, in 1901, with first recognizing that fossilized prehistoric animal bones were preserved in pools of asphalt on the Hancock Ranch. In commemoration of Orcutt's initial discovery, paleontologists named the
La Brea coyote (''Canis latrans orcutti'') in his honor.
John C. Merriam of the
University of California
The University of California (UC) is a public land-grant research university system in the U.S. state of California. The system is composed of the campuses at Berkeley, Davis, University of California, Irvine, Irvine, University of Califor ...
led much of the original work in this area early in the 1900s.
Contemporary excavations of the bones started in 1913–1915. In the 1940s and 1950s, public excitement was generated by the preparation of previously recovered large mammal bones.
A subsequent study demonstrated the fossil vertebrate material was well preserved, with little evidence of bacterial degradation of bone protein. They are believed to be some 10–20,000 years old, dating from the
last glacial period.
Excavation of "Project 23" and newly uncovered pits
On February 18, 2009, George C. Page Museum announced the 2006 discovery of 16 fossil deposits that had been removed from the ground during the construction of an underground parking garage for the
Los Angeles County Museum of Art
The Los Angeles County Museum of Art (LACMA) is an art museum located on Wilshire Boulevard in the Miracle Mile vicinity of Los Angeles. LACMA is on Museum Row, adjacent to the La Brea Tar Pits (George C. Page Museum).
LACMA was founded in 19 ...
next to the tar pits.
Among the finds are remains of a
saber-toothed cat
Machairodontinae is an extinct subfamily of carnivoran mammals of the family Felidae (true cats). They were found in Asia, Africa, North America, South America, and Europe from the Miocene to the Pleistocene, living from about 16 million ...
,
dire wolves
The dire wolf (''Aenocyon dirus'' ) is an extinct canine. It is one of the most famous prehistoric carnivores in North America, along with its extinct competitor ''Smilodon''. The dire wolf lived in the Americas and eastern Asia during the Lat ...
,
bison
Bison are large bovines in the genus ''Bison'' (Greek: "wild ox" (bison)) within the tribe Bovini. Two extant and numerous extinct species are recognised.
Of the two surviving species, the American bison, ''B. bison'', found only in North A ...
,
horses, a giant
ground sloth,
turtles,
snail
A snail is, in loose terms, a shelled gastropod. The name is most often applied to land snails, terrestrial pulmonate gastropod molluscs. However, the common name ''snail'' is also used for most of the members of the molluscan class ...
s,
clams,
millipedes,
fish
Fish are Aquatic animal, aquatic, craniate, gill-bearing animals that lack Limb (anatomy), limbs with Digit (anatomy), digits. Included in this definition are the living hagfish, lampreys, and Chondrichthyes, cartilaginous and bony fish as we ...
,
gophers
Pocket gophers, commonly referred to simply as gophers, are burrowing rodents of the family Geomyidae. The roughly 41 speciesSearch results for "Geomyidae" on thASM Mammal Diversity Database are all endemic to North and Central America. They are ...
, and an
American lion
''Panthera atrox'', better known as the American lion, also called the North American lion, or American cave lion, is an extinct pantherine cat that lived in North America during the Pleistocene epoch and the early Holocene epoch, about 340, ...
.
Also discovered is a nearly intact
mammoth
A mammoth is any species of the extinct elephantid genus ''Mammuthus'', one of the many genera that make up the order of trunked mammals called proboscideans. The various species of mammoth were commonly equipped with long, curved tusks an ...
skeleton, nicknamed Zed; the only pieces missing are a rear leg, a vertebra, and the top of its skull, which was sheared off by construction equipment in preparation to build the parking structure.
These fossils were packaged in boxes at the construction site and moved to a compound behind Pit 91, on Page Museum property, so that construction could continue. Twenty-three large accumulations of tar and specimens were taken to the Page Museum. These deposits are worked on under the name "Project 23". As work for the public transit
D Line is
extended
Extension, extend or extended may refer to:
Mathematics
Logic or set theory
* Axiom of extensionality
* Extensible cardinal
* Extension (model theory)
* Extension (predicate logic), the set of tuples of values that satisfy the predicate
* Ext ...
, museum researchers know more tar pits will be uncovered, for example near the intersection of Wilshire and Curson.
In an exploratory subway dig in 2014 on the
Miracle Mile, prehistoric objects unearthed included
geoducks,
sand dollars, and a from a pine tree, of a type now found in
Central California's woodlands.
George C. Page Museum
In 1913,
George Allan Hancock, the owner of
Rancho La Brea, granted the
Natural History Museum of Los Angeles County exclusive excavation rights at the Tar Pits for two years. In those two years, the museum was able to extract 750,000 specimens at 96 sites, guaranteeing that a large collection of fossils would remain consolidated and available to the community.
Then in 1924, Hancock donated to LA County with the stipulation that the county provide for the preservation of the park and the exhibition of fossils found there.
The George C. Page Museum of La Brea Discoveries, part of the Natural History Museum of Los Angeles County, was built next to the tar pits in Hancock Park on
Wilshire Boulevard. Construction began in 1975, and the museum opened to the public in 1977.
The area is part of urban Los Angeles in the
Miracle Mile District.
The museum tells the story of the tar pits and presents specimens excavated from them. Visitors can walk around the park and see the tar pits. On the grounds of the park are life-sized models of prehistoric animals in or near the tar pits. Of more than 100 pits, only Pit 91 is still regularly excavated by researchers and can be seen at the Pit 91 viewing station. In addition to Pit 91, the one other ongoing excavation is called "Project 23". Paleontologists supervise and direct the work of volunteers at both sites.
As a result of a design competition in 2019, the
Natural History Museum of Los Angeles County chose
Weiss/Manfredi
Weiss/Manfredi is a multidisciplinary New York City-based design practice that combines landscape, architecture, infrastructure, and art. The firm's notable projects include the Seattle Art Museum's Olympic Sculpture Park, the Brooklyn Botanic ...
over
Dorte Mandrup
Dorte Mandrup-Poulsen (born 28 July 1961) is a Danish architect. Founder and Creative Director of the architectural practice Dorte Mandrup Arkitekter A/S that has approximately 60 employees. The practice is based in Copenhagen, Denmark and is behi ...
and
Diller Scofidio + Renfro to redesign the park, including by adding a 3,281-foot-long pedestrian walkway framing Lake Pitt.
IUGS geological heritage site
In respect of it being the 'richest paleontological site on Earth for terrestrial fossils of late Quaternary age', the
International Union of Geological Sciences (IUGS) included the 'Late Quaternary asphalt seeps and paleontological site of La Brea Tar Pits' in its assemblage of 100 'geological heritage sites' around the world in a listing published in October 2022. The organisation defines an IUGS Geological Heritage Site as 'a key place with geological elements and/or processes of international scientific relevance, used as a reference, and/or with a substantial contribution to the development of geological sciences through history.'
Flora and fauna
Among the prehistoric species associated with the La Brea Tar Pits are
Pleistocene
The Pleistocene ( , often referred to as the ''Ice age'') is the geological Epoch (geology), epoch that lasted from about 2,580,000 to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was fina ...
mammoth
A mammoth is any species of the extinct elephantid genus ''Mammuthus'', one of the many genera that make up the order of trunked mammals called proboscideans. The various species of mammoth were commonly equipped with long, curved tusks an ...
s,
dire wolves
The dire wolf (''Aenocyon dirus'' ) is an extinct canine. It is one of the most famous prehistoric carnivores in North America, along with its extinct competitor ''Smilodon''. The dire wolf lived in the Americas and eastern Asia during the Lat ...
,
short-faced bears,
American lion
''Panthera atrox'', better known as the American lion, also called the North American lion, or American cave lion, is an extinct pantherine cat that lived in North America during the Pleistocene epoch and the early Holocene epoch, about 340, ...
s,
ground sloths, and, the
state fossil
Most American states have made a state fossil designation, in many cases during the 1980s. It is common to designate one species in which fossilization has occurred, rather than a single specimen, or a category of fossils not limited to a single ...
of
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 m ...
, the
saber-toothed cat
Machairodontinae is an extinct subfamily of carnivoran mammals of the family Felidae (true cats). They were found in Asia, Africa, North America, South America, and Europe from the Miocene to the Pleistocene, living from about 16 million ...
(''Smilodon fatalis'').
The park is known for producing myriad
mammal
Mammals () are a group of vertebrate animals constituting the class Mammalia (), characterized by the presence of mammary glands which in females produce milk for feeding (nursing) their young, a neocortex (a region of the brain), fur ...
fossil
A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...
s dating from the
last glacial period. While mammal fossils generate significant interest, other fossils, including fossilized insects and plants, and even pollen grains, are also valued. These fossils help define a picture of what is thought to have been a cooler, moister climate in the Los Angeles basin during the glacial age. Microfossils are retrieved from the matrix of asphalt and sandy clay by washing with a solvent to remove the petroleum, then picking through the remains under a high-powered lens.
Tar pits around the world are unusual in accumulating more predators than prey. The reason for this is unknown, but one theory is that a large prey animal would die or become stuck in a tar pit, attracting predators across long distances. This
predator trap would catch predators along with their prey. Another theory is that dire wolves and their prey were trapped during a hunt. Since modern
wolves hunt in packs, each prey animal could take several wolves with it. The same may be true of saber-toothed cats known from the area. The most common animals from this area included dire wolves, saber-toothed cats,
coyotes,
ancient bison, and
Jefferson's ground sloth.
Bacteria
Methane
Methane ( , ) is a chemical compound with the chemical formula (one carbon atom bonded to four hydrogen atoms). It is a group-14 hydride, the simplest alkane, and the main constituent of natural gas. The relative abundance of methane ...
gas escapes from the tar pits, causing bubbles that make the asphalt appear to boil. Asphalt and methane appear under surrounding buildings and require special operations for removal to prevent the weakening of building foundations. In 2007, researchers from
UC Riverside discovered that the bubbles were caused by hardy forms of
bacteria
Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were am ...
embedded in the natural asphalt. After consuming petroleum, the bacteria release methane. Around 200 to 300 species of bacteria were newly discovered here.
[Jia-Rui Chong]
"Researchers learn why tar pits are bubbly"
''Los Angeles Times'', May 14, 2007.
Human presence
Only one human has been found, a partial skeleton of the
La Brea Woman[ (1914) Preliminary report on the discovery of human remains in an asphalt deposit at Rancho La Brea, ''Science'' 40: 197–203] dated to around 10,000
calendar years (about 9,000
radiocarbon years)
BP,
[ (2009) Compilation, calibration, and synthesis of faunal and floral radiocarbon dates, Rancho La Brea, California, ''Contributions in Science'' 518: 1–16] who was 17 to 25 years old at death
[ (1989) A note on the ontogenetic age of the Rancho La Brea hominid, Los Angeles, California, ''Bulletin, Southern California Academy of Sciences'' 88(3): 123–26] and found associated with remains of a domestic dog, so was interpreted to have been ceremonially interred.
[ (1985) Domestic dog associated with human remains at Rancho La Brea, ''Bulletin, Southern California Academy of Sciences'' 84(2): 76–85] In 2016, however, the dog was determined to be much younger in date.
Also, some even older fossils showed possible tool marks, indicating humans active in the area at the time.
Saber-toothed cat
Machairodontinae is an extinct subfamily of carnivoran mammals of the family Felidae (true cats). They were found in Asia, Africa, North America, South America, and Europe from the Miocene to the Pleistocene, living from about 16 million ...
bones from La Brea showing signs of ‘artificial’ cut marks at oblique angles to the long axis of each bone were radiocarbon dated to 15,200 ± 800 B.P. (uncalibrated).
If these cuts are in fact tool marks resultant from butchering activities, then this material would provide the earliest solid evidence for human association with the Los Angeles Basin. Yet it is also possible that there was some residual contamination of the material as a result of saturation by asphaltum, influencing the radiocarbon dates.
Technical report for power plant construction. CULTURAL RESOURCES.
California Energy Commission, Sacramento, California, December 2000
Gallery
File:Tar and flora.jpeg, Tar and wild flower run within La Brea campus (2014)
File:Mammuthus columbi Page.jpg, Columbian mammoth skeleton from the tar pits, displayed in the George C. Page Museum
File:La Brea SW07.jpg, Scimitar-toothed cat display
File:La Brea SW04.jpg, Fossil crate (2021)
File:La Brea SW03.jpg, Lab technician working on recent specimen ZED (2021)
File:La Brea SW02.jpg, Lab technician doing a 3-D scan of a fossil (2021)
See also
* Binagadi asphalt lake
The Binagadi asphalt lake (or Binagadi tar pits) are a cluster of tar pits in urban Baku, Azerbaijan. Asphaltum or tar has seeped up from the ground in this area for tens of thousands of years. The tar is often covered with dust, leaves, or wate ...
* Carpinteria Tar Pits
* Lagerstätten
* Lake Bermudez
Lake Guanoco ( Spanish: ''Lago Guanoco'' or ''Lago de Asfalto de Guanoco'', also Lake Bermudez) is the world's second largest natural tar pit and lies in Venezuela in northern South America.
Lake Guanoco is one of the five natural asphalt l ...
* List of fossil sites
* Los Angeles County Museum of Art
The Los Angeles County Museum of Art (LACMA) is an art museum located on Wilshire Boulevard in the Miracle Mile vicinity of Los Angeles. LACMA is on Museum Row, adjacent to the La Brea Tar Pits (George C. Page Museum).
LACMA was founded in 19 ...
* McKittrick Tar Pits
* Pitch Lake
The Pitch Lake is the largest natural deposit of asphalt in the world, estimated to contain 10 million tons. It is located in La Brea in southwest Trinidad, within the Siparia Regional Corporation. The lake covers about 100 acres (0.405 squ ...
References
External links
Page Museum – La Brea Tar Pits
* ttp://gocalifornia.about.com/od/calamenu/a/tarpits.htm Gocalifornia.com: La Brea Tar Pits– ''visitor guide''.
Palaeo.uk: "Setting the La Brea site in context."
NHM.org: Pit 91 excavations
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