La Brea Tar Pits
The La Brea Tar Pits ( Spanish : la brea " bad luck ", English tar pits "asphalt pits"), also Rancho La Brea Tar Pits , are a collection of pits of various sizes filled with natural asphalt in Hancock Park in the middle of the American city Los Angeles . They are eponymous for La Brea Avenue.
The asphalt pits are known to be one of the richest fossil sites of the Pleistocene . It is a concentrate deposit in which a complete ecosystem has been handed down from 40,000 to 10,000 years ago. Mammals in particular are represented there - from the almost four meter high "imperial mammoth " ( Mammuthus imperator ; today counted as a prairie mammoth ) to the Californian pocket mouse - but also birds such as the yellow-billed lobster , bony fish , amphibians , reptiles , molluscs , arthropods and numerous plants , pollen and Seeds . A total of four million fossil specimens have so far been recovered from the asphalt pits, which come from around 600 different species .
The natural asphalt, also known as pitch or tar, comes from large underground deposits in the Los Angeles Basin . It was used as fuel and for sealing by the first European settlers in the area. The fossils found during asphalt mining were wrongly mistaken for the bones of dead domestic cattle .
Paleofauna
Around 300 different animal species have been identified in the fossil material that was recovered from the pits. Around 100 of these are vertebrates , of which only three species are not terrestrial vertebrates . Among the terrestrial vertebrates, mammals make up the majority with around 60 species. About 90% of mammal remains come from predators . The most common species is the extinct wolf Canis dirus . The second most common, but probably best known, species is the saber-toothed cat Smilodon fatalis , the state fossil of the US state of California . A total of 166,000 individual bones were collected from her. It is estimated that at least 2,500 saber-toothed cats perished in the asphalt pits over a period of 25,000 years. At least 5,000 bones show signs of illness and injury, including broken vertebrae and limbs. However, many of these bones also show signs of healing processes, although the animals remained restricted in their ability to move and were therefore only able to hunt to a limited extent. This has been interpreted as an indication that Smilodon - similar to lions today - lived in social associations. In addition to the lion-sized smilodon , bones of other large cats - American lion , puma , bobcat and jaguar - have been handed down in the asphalt. A particularly large predator of the La Brea fauna is the giant short-snouted bear .
Large carnivores, known as apex predators , are usually the smallest number of individuals in natural ecosystems in the area. The therefore completely disproportionately high proportion of large predatory mammals in the La Brea fauna is explained by the fact that the asphalt pits acted as natural predator traps. The smell or calls of animals caught in the asphalt attracted the robbers, who then got stuck themselves. The extinct bison Bison antiquus is often an involuntary decoy. With remains of an estimated at least 300 individuals, including numerous young animals, it is the most common large herbivore. Other large herbivorous mammals in the La Brea fauna are mammoths , the more primitive trumpet representative Mammut pacificus and the up to 2.8 meter long, ground-dwelling giant sloth Paramylodon harlani . One of the most common bird species in the deposit is the yellow-billed magpie ( Pica nuttalli ).
The George C. Page Museum
Attached to the La Brea Tar Pits is the George C. Page Museum. Both the asphalt pits and the museum are very easy to reach for tourists as they are located in the middle of the Los Angeles metropolitan area. A special attraction in the museum is the so-called "fishbowl" - the museum's paleontological laboratory. Here, museum visitors can watch scientists and volunteers at work.
The fossils are cleaned and prepared in the laboratory. Some employees dedicate themselves to a very time-consuming process, sorting microfossils with the help of a magnifying glass. Microfossils are found in the sediment of the excavations, e. B. insects (or parts of insects), plants, plant seeds, mussels, small bone particles (e.g. the smallest parts of bone marrow) and other interesting and fascinating microfossils such as salamander scales, teeth of mice and much more. The laboratory is under the direction of Shelley Cox. She was already working at the tar pits before the museum was built with a generous donation from George C. Page . Before the museum was built, there was only a container on site, in which work was carried out in a small space. Shelley Cox (lab) and Christopher Shaw (collection manager) both came to the tar pits as young students and volunteered before becoming employees. Volunteers are of essential importance for the museum - every year the contribution of the volunteers is generally recognized with a large celebration and outstanding achievements are recognized.
At the end of 2019, the plans for a new conception of the site were presented. The contract went to the New York architecture firm Weiss / Manfredi. A new museum wing is to be built on 6th Street. To this end, the hill on which the previous museum stands will be artificially expanded and the landscape adapted to the new shapes. Footpaths allow new walkways, including a curved bridge over the largest of the pits. According to Lori Bettison-Varga, Director of the Natural History Museum of Los Angeles County , the tar pits should enable sustainable infrastructure, expanded access for the population and optimal protection of exhibits and features for the next 50 years.
Pit 91
Grube 91 ("Pit 91") is one of many asphalt pits on the museum grounds. Pit 91 is currently the only active excavation site in the museum. Excavations are carried out every summer for a period of two months. It is possible for museum and park visitors to follow the excavation work from a viewing platform.
literature
- Paul A. Selden, John R. Nudds: Window to Evolution. Famous fossil sites in the world . Elsevier, Spektrum Akademischer Verlag, Heidelberg 2007, ISBN 978-3-8274-1771-8 , pp. 142 ff.
- John M. Harris (Ed.): La Brea and Beyond - The Paleontology of Asphalt-Preserved Biotas. Natural History Museum of Los Angeles County Science Series. Vol. 42, 2015 ( PDF 4.8 MB; English)
Web links
- Site of the La Brea Tar Pits Museum (English)
- The La Brea Tar Pits on the website of the University of California Museum of Paleontology (UCMP) (English)
Individual evidence
- ↑ Alton C. Dooley Jr, Eric Scott, Jeremy Green, Kathleen B. Springer, Brett S. Dooley, Gregory James Smith: Mammut pacificus sp. nov., a newly recognized species of mastodon from the Pleistocene of western North America. PeerJ. Vol. 7, 2019, item no. e6614, doi: 10.7717 / peerj.6614 .
- ^ Chester Stock: A Census of the Pleistocene Mammals of Rancho La Brea, Based on the Collections of the Los Angeles Museum. Journal of Mammalogy. Vol. 10, No. 4, 1929, pp. 281-289, JSTOR .
- ^ Leslie F. Marcus: A census of the abundant large Pleistocene mammals from Rancho La Brea. Contributions in Science. Vol. 38, 1960, pp. 1-11, BHL .
- ↑ Walt Koenig, Mark Reynolds: Yellow-billed Magpie (Pica nuttalli) . In: A. Poole: The Birds of North America Online . Cornell Lab of Ornithology, Ithaca 2009. doi: 10.2173 / bna.180 . Retrieved June 3, 2012.
- ↑ Curbed: Winning design selected for La Brea Tar Pits makeover , December 11, 2019
Coordinates: 34 ° 3 '46.2 " N , 118 ° 21' 21.6" W.