Paleontology Photo by Ernie Cowan - Anza Borrego Photography Institute
|
Rich Fossil Record |
|
| Rich Fossil Record
As revealed in its rich fossil record, as recently as 1 million years ago the area that would become Anza-Borrego Desert State Park was a land of rivers, fresh water lakes, and savannas having a temperate climate with a decided marine influence. The Peninsular Range had yet to cast its rain shadow on these ancestral parklands. Instead of lizards, jackrabbits, and coyotes of today the environment supported a significant population of large herbivores such as horses, llamas, camels, ground sloths, and mammoths. Saber tooth cats, and giant short-faced bears, among other formidable carnivores, hunted the savannas, riverbanks, and lakeshores. The fossilized remains of these and many other vertebrate and invertebrate animals are found today in the Borrego and Fish Creek-Vallecito Creek badlands. These badlands, so named for their desolate appearance and scant vegetation, are the uplifted and eroded sedimentary beds that were originally deposited in the ancestral Gulf of California, in the Colorado River delta, and in fresh water lakes and streams. |
 Paleontologist George Jefferson briefs volunteers at the beginning of a field trip. |
7 Million Years A nearly continuous 7 million year record of sedimentation, that began during the Miocene, and continued almost without interruption until slightly less than 1 million years ago, occurs within the Anza-Borrego Desert badlands. The resulting approximately 6,000 meters (19,000 ft.) of sediments contain a rich variety of fossil remains such as leaf impressions, fossil woods, footprints, shells, bone and teeth. Six million years ago tropical marine waters of the Gulf of California extended north through the Salton Trough to beyond the present day city of Palm Springs. Sediments from this period, prominently revealed in the Fish Creek/Vallecito Creek badlands, yield a profusion of fossilized marine organisms including foraminifera, corals, mollusks, echinoderms, sharks, rays, bony fish, sea turtles, dugon, walrus, and baleen whales. Many of the invertebrate fossils are closely related to Caribbean counterparts as they were deposited during a period before the formation of the Isthmus of Panama |
|
| Colorado River Influence Starting approximately 5 million years ago the Colorado River began depositing sediments, eroded from the Colorado Plateau, into this ancient sea. The resulting Colorado River delta eventually isolated the northern portion of the Gulf of California from contact with the marine waters to the south. Subsequent freshwater inflow from the Colorado River, and from local streams and rivers, into this isolated basin produced a 3 million-year continuum of sediments formed first in marine and brackish waters and then later in fresh water. These sediments preserved a particularly rich variety of terrestrial vertebrate fossils including mammoths, horses, camels, llamas, giant ground sloths, several species of bear, various predatory dogs and cats, smaller mammals such as rodents and rabbits, as well as numerous reptiles. |
|
Colorado District Stout Research Center Most of the fossils collected from the Anza-Borrego Desert parklands are now housed in the Colorado Desert District Stout Research Center, located at the Anza-Borrego Desert State Park Headquarters in Borrego Springs, California. The approximately 13,000 specimens in the Park collection represent more than 550 types of plants and animals. Discovery of new fossil types continue to be made. During the field season of 2007/2008, for example, a crocodile jaw fossil was found in the Fish Creek-Vallecito Creek Badlands. This is the first example of a crocodile found in the Park, and for its time the first one west of Texas. The collection, open to qualified scientists throughout the world for scholarly research, is an extremely valuable paleontology resource. It contains, for example, fossils from both the Pliocene-Pleistocene time boundary and the Blancan-Irvingtonian North America Land Mammal Age boundary. |
|
| The award wining book "Fossil Treasures of the Anza-Borrego Desert", (George T. Jefferson, and Lowell Lindsay, editors, published in 2006 by Sunbelt Publications) is highly recommended to anyone who wishes to learn more about paleontology at Anza-Borrego Desert State Park. Much of the information for this essay was adapted from the introductory chapter, by G. T. Jefferson, and L. Lindsay, of the Fossil Treasures book. | |
| Richard Ingwall July 2008 |
