Our research group uses fossils preserved in asphaltic sediments to investigate big questions related to climate change, evolution, and paleoecology.
Because Rancho La Brea represents the largest collection of late Pleistocene asphaltic fossils in the world, we use this opportunity to train students, build collections through excavation, prepare and conserve fossils in our public viewing Fossil Lab and curate this massive collection onsite. Our staff also use these collections to study scientific questions with visiting academics. Much of the current research could not be possible without the unique geological circumstances that occur in the LA Basin and the efforts of the paleontologists who came before us.
LA BREA TAR PITSGeology around Rancho La Brea
The existence of asphalt seeps (oil) and dense fossil accumulations at Rancho La Brea is dependent on the unique tectonic history of Southern California. The evolution of the San Andreas Fault zone is complicated and dependent on a number of past events.During the Miocene (between 23 - 5 million years ago) the tectonic plates in the Southern California region changed from subduction to transform (strike-slip) faults. The crustal plates rotated which in turn stretched the L.A. region and formed a deep structural basin. Large amounts of marine sediments were deposited forming up to 6 miles deep! The L.A. Basin is one of the richest oil basins in the world in proportion to its size and volume. Later the Santa Monica Mountains uplifted and rivers flowing down brought large amounts of sands and gravels that subsequently buried the remains of plants and animals trapped on the surface of the asphalt seeps at Rancho La Brea.
LA BREA TAR PITSHistoric Excavations
The asphalt seeps of Rancho La Brea have been of interest to humans since prehistoric times.Native Americans used the asphalt as a glue or caulk, and early Angelenos used it as a roofing material. Though the first recorded mention of the asphalt dates back to the 1769 Portola Expedition, it wasn't until 1875 that the animal remains found in the seeps were recognized as fossils by Professor William Denton. Later in 1908 they were made famous in an article written by J. C. Merriam called "Death Trap of the Ages."
Soon thereafter, more and more paleontologists, amateurs and professionals alike, became interested in the asphaltic fossils. Los Angeles High School biology teacher James Z. Gilbert began a large excavation project in 1909, under the banner of the Southern California Academy of Sciences. Rancho La Brea's long history of encouraging volunteerism in the young started with Gilbert; his excavation team largely consisted of his own students from Los Angeles High School. His finds laid the groundwork for the founding of the Los Angeles County Museum of History, Science, and Art, which is today the Natural History Museum of Los Angeles County. Gilbert's Academy collections were some of the first specimens in the new museum in 1911, and mounted skeletons from Rancho La Brea were among the first displays in the museum when it opened in 1913.
The Hancock family purchased Rancho La Brea in the 1870s and encouraged the scientific investigation of the fossil deposits. While the Hancock family mined the asphalt and later industriously drilled for oil, a few small scale excavations were made between 1901 and 1910. From 1912-1913 a larger scale excavation was conducted by the University of California at Berkeley. In 1913, the Los Angeles County Museum of History, Science, and Art (which later became the Natural History Museum of Los Angeles County) launched a two year excavation project that recovered a million fossil bones from 96 quarries or "pits." The remains of several of these excavations are still on view to the public, including Pits 3, 4, 9, 13, 61/67, and of course, Pit 91.
Led by L. E. Wyman, museum excavators earned $3.50 a day—decent wages for 1913—but worked in terribly dangerous conditions. Shoring methods were primitive, and floods and cave-ins were common. In addition, the newly recovered bones were scrubbed clean of asphalt with heated kerosene that caught fire from time to time. After this massive excavation and preparation effort, much of the ensuing scientific research on the newly discovered fossils was undertaken by Chester Stock. A graduate of the University of California, Berkeley, and a professor at the California Institute of Technology, Stock became one of the more famous North American paleontologists in large part for his research, discoveries, and publications on the fossils of Rancho La Brea.
Excavation at Rancho La Brea has continued, off and on, since the beginning of the twentieth century.
Although much of the surrounding landscape has changed immensely, many of our fundamental excavation techniques have remained the same: bones are excavated using small hand tools and field data is recorded with pen and paper. Even our measurement system has its roots in the grid system laid out by excavators in 1913. We supplement and support these techniques with new technology—digital cameras document day-to-day progress quickly and cheaply, and computerized databases allow us to search through collections with a modicum of ease—but we doubt if anything will ever replace hand tools, pen, paper, and elbow grease. You can learn more about and visit our active excavation site today!
Historic Research at Rancho La Brea
The first scientific article mentioning the fossils of Rancho La Brea was by William Denton, published by the Boston Society of Natural History in 1875.However, it was not until the early 1900s, after W.W. Orcutt, a well known Los Angeles geologist, had amassed a collection of saber-toothed cat, dire wolf, and ground sloth fossils that the site's importance was widely recognized. Explorations by the University of California, the Southern California Academy of Sciences, and Los Angeles High School retrieved large collections of fossils from the site in the first decade of the 1900's. In 1913, the Los Angeles County Museum of History, Science, and Art was built in Exposition Park in part to house the fossils collected by the Southern California Academy of Sciences. Later that year the Hancock family gave sole permission to the newly-renamed Los Angeles County Museum (now the Natural History Museum of Los Angeles County—we know, the name changes are exhausting) to excavate for two years at Rancho La Brea. The result was an immense collection that provided valuable insight to our understanding of the late Pleistocene fauna and flora of North America.
La BREA TAR PITSAs a place-based museum, we are also committed to engaging the communities around us, sharing our research through exhibits, and preserving this National Natural Landmark for future generations.
Thanks La Brea Tar Pits!
