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The oldest terrestrial vertebrate fossils from the [[Colorado Desert]] predate the late [[Miocene]] invasion of the [[Sea of Cortez]]. These very rare fossils, which include a [[gomphothere]] (elephant-like mammal), [[rodent]], [[felid]] and small [[camelid]], and were collected from 10-12 million year old [[riverine]] and near shore lake deposits. However, the most significant and abundant vertebrate fossils have been recovered from the latest [[Miocene]] through late-[[Pleistocene]] riverine and flood plane deposits of the Palm Spring Formation in the Vallecito and Fish Creek Badlands and Ocotillo Conglomerate exposed in the Borrego Badlands. These fossil assemblages occur in a 3.5 million year long uninterrupted stratigraphic sequence that has been dated using horizons of volcanic ash and [[paleomagnetic]] methods.
The oldest terrestrial vertebrate fossils from the [[Colorado Desert]] predate the late [[Miocene]] invasion of the [[Sea of Cortez]]. These very rare fossils, which include a [[gomphothere]] (elephant-like mammal), [[rodent]], [[felid]] and small [[camelid]], and were collected from 10-12 million year old [[riverine]] and near shore lake deposits. However, the most significant and abundant vertebrate fossils have been recovered from the latest [[Miocene]] through late-[[Pleistocene]] riverine and flood plane deposits of the Palm Spring Formation in the Vallecito and Fish Creek Badlands and Ocotillo Conglomerate exposed in the Borrego Badlands. These fossil assemblages occur in a 3.5 million year long uninterrupted stratigraphic sequence that has been dated using horizons of volcanic ash and [[paleomagnetic]] methods.


The bestiary for this [[savannah]] landscape reads like a who's-who for some of the most unique creatures to inhabit North America, animals like: ''[[Geochelone]]'', a giant bathtub-sized tortoise; ''[[Aiolornis incredibilis]]'', the largest flying bird of the northern hemisphere, with 17 foot wing span; ''Paramylodon'', ''[[Megalonyx]]'' and ''[[Nothrotheriops]]'', giant ground sloths, some with bony armor within their skin; ''Pewelagus'', a very small rabbit (paleontologists do have a sense of humor); ''[[Borophagus]]'', a hyena-like dog; ''Acrtodus'', a giant short-faced bear; ''[[Smilodon]]'', a sabertoothed cat; ''[[Miracinonyx]]'', the North American cheetah; ''[[Mammuthus imperator]]'', the largest known mammoth; ''[[Tapirus]]'', an extinct tapir; ''[[Equus scotti]]'', an extinct Pleistocene horse; ''Gigantocamelus'' a giant camel; and ''[[Capromeryx]]'', the dwarf pronghorn.
The bestiary for this [[savannah]] landscape reads like a who's-who for some of the most unique creatures to inhabit North America, animals like: ''[[Geochelone]]'', a giant bathtub-sized tortoise; ''[[Aiolornis incredibilis]]'', the largest flying bird of the northern hemisphere, with 17 foot wing span; ''Paramylodon'', ''[[Megalonyx]]'' and ''[[Nothrotheriops]]'', giant ground sloths, some with bony armor within their skin; ''Pewelagus'', a very small rabbit (paleontologists do have a sense of humor); ''[[Borophagus]]'', a hyena-like dog; ''Acrtodus'', a giant short-faced bear; ''[[Smilodon]]'', a sabertoothed cat; ''[[Miracinonyx]]'', the North American cheetah; ''[[Mammuthus imperator]]'', the largest known mammoth; ''[[Tapirus]]'', an extinct tapir; ''Equus enormis'' and ''[[Equus scotti]]'', two species of extinct Pleistocene horse; ''Gigantocamelus'' a giant camel; and ''[[Capromeryx]]'', the dwarf pronghorn.


Although paleontological exploration of Anza-Borrego Desert State Park has stepped firmly into the twenty-first century with the application of [[GIS]] and computer assisted analyses to field surveys and resource management, many questions still remain. Expanding the detail and clarity of our paleontological view of the region's vanished past and improving our understanding of its significance is an on going challenge. Exploration, conservation, research and interpretation continue as new fossils are discovered.
Although paleontological exploration of Anza-Borrego Desert State Park has stepped firmly into the twenty-first century with the application of [[GIS]] and computer assisted analyses to field surveys and resource management, many questions still remain. Expanding the detail and clarity of our paleontological view of the region's vanished past and improving our understanding of its significance is an on going challenge. Exploration, conservation, research and interpretation continue as new fossils are discovered.

Revision as of 22:58, 19 October 2009

Anza-Borrego Desert State Park
View from Font's Point
LocationSan Diego County,
Imperial County,
Riverside County, California, USA
Nearest cityJulian and Borrego Springs
Area600,000 acres (2,420 km²)
Governing bodyCalifornia State Parks

Anza-Borrego Desert State Park is a state protected land located in Southern California primarily within eastern San Diego County, with portions within Imperial and Riverside counties. At 600,000 acres (2,400 km2) and one fifth of San Diego County within its borders, Anza-Borrego Desert is the largest state park in California and the second largest within the continental United States after Adirondack Park in New York. The park is a two-hour drive away from the cities of San Diego, Riverside and Palm Springs. The park is named after Spanish explorer Juan Bautista de Anza and the Spanish word borrego, for bighorn sheep.

Vista of the desert
Panoramic image looking west from Font's Point.
Bighorn Sheep at Palm Canyon.

The park includes 500 miles (804 km) of dirt roads, 12 wilderness areas and 110 miles (180 km) of hiking trails provide visitors with an opportunity to experience the Colorado Desert. Listening devices for the hearing impaired are available in the visitor center. Anza-Borrego Desert State Park is one of 55 California State Parks with wi-fi access in one or more areas. Footage shot at this park was used in the 2005 feature film Serenity.

Many visitors approach from the east via California Highways S22, S2, or 78. Visitors from San Diego via Highways 79 and 78 have the added pleasure of driving through the mountainous Cuyamaca Rancho State Park—quite a different experience from Anza-Borrego. The highways from the east climb to 2,400 feet (731 m) or so and then descend about 2,000 feet (609 m) to the valley. Where the highway breaks out of the high-country vegetation, it reveals the great bowl of the Anza-Borrego desert. The valley spreads below, and there are mountains all around. The highest are to the north—the Santa Rosa Mountains. The highest mountains are wilderness, with no paved roads in or through. They have the only all-year-flowing watercourse in the park.

Ecology

The park features washes, wildflowers, palm groves, cacti, ocotillo and sweeping vistas. Visitors may also have the chance to see greater roadrunner, golden eagles, kit foxes, mule deer and bighorn sheep as well as desert iguanas, chuckwallas and the red diamond rattlesnake. Some of the Park is habitat of the peninsular bighorn sheep, often called the Desert Bighorn. Few park visitors ever see them, and the sheep are justly wary. A patient few observers each year see and count them, to study the population decline of this endangered species responding to human encroachment and human overpopulation. The California Fan Palm, Washingtonia filifera, is also found within Anza-Borrego Desert State Park.[1]

Borrego Desert Nature Center

The Anza-Borrego Desert Natural History Association operates the Borrego Desert Nature Center in Borrego Springs, California. The nature center offers educational, environmental, and recreational programs for all ages including desert tours, guided hikes and lectures.

Paleontology of Anza-Borrego Desert

When one thinks of Anza-Borrego Desert State Park, he usually envisions wild flowers, bighorn sheep, or vast arid landscapes framed by rugged mountains. Few realize that the expanses of Anza-Borrego's eroded badlands also provide a very different view, a window into the region's long vanished past. The Colorado Desert of southeastern California was not always a seemingly barren wilderness. The key to understanding and engaging this prehistoric world is paleontology, the study of the fossilized remains of ancient life, and Anza-Borrego has an exceptional fossil record. The fossil treasures from the park include preserved plants, a variety of invertebrate shells, animal tracks and an incredible array of bones and teeth. Most Anza-Borrego fossils date from six to less than a half million years old, about 60 million years after the last dinosaurs died.[2]

Anza-Borrego Desert lies in a unique geologic setting along the western margin of the Salton Trough. This major topographic depression, with elevations under 60 m (about 200 feet) below sea level, forms the northernmost end of an active rift valley and a geological continental plate boundary. The Trough extends north from the Sea of Cortez (Gulf of California) to San Gorgonio Pass, and from the eastern rim of the Peninsular Ranges east to the San Andreas Fault Zone. Over the past 7 million years, a relatively complete geologic record of over 6,150 m (20,000 feet) of fossil bearing sediment has been deposited within the Park along the rift valley's western margin. Here, paleontological remains are widespread and exceedingly diverse, and are found scattered over hundreds of square miles of eroded badlands terrain extending south from the Santa Rosa Mountains (California) into northern Baja California, Mexico.

Both marine and terrestrial environments are represented by this long and rich fossil record. Six million years ago the ancestral Gulf of California filled the Salton Trough, extending northward past what would become the city of Palm Springs. These tropical waters supported a profusion of both large and small marine organisms. Through time, the sea gave way as an immense volume of sediment eroded during the formation of the Grand Canyon spilled into the Salton Trough. Bit-by-bit, the ancestral Colorado River built a massive river delta across the sea way. Fossil hard woods from the deltaic sands and associated coastal plain deposits suggest that the region received three times as much rainfall as today.

Anza-Borrego gradually changed from a predominately marine environment in to a system of interrelated terrestrial habitats. North of the delta and intermittently fed by the Colorado River, a sequence of lakes and playa lakes has persisted for over 3 million years. At the same time, sediments eroded from the growing Peninsular Ranges and Santa Rosa Mountains spread east into the Trough. It is these sediments that provide an almost unbroken terrestrial fossil record, ending only a half million years ago. Here, the deposits of ancient streams and rivers trapped the remains of wild life that inhabited a vast brushland savannah laced with riparian woodlands.

This record of changing environments and habitats includes over 550 types of fossil plants and animals, ranging from preserved microscopic plant pollen and algal spores to baleen whale bones and mammoth skeletons. Many of the species are extinct and some are known only from fossil remains recovered from the Park. Combined with a long and complete sedimentary depositional sequence, these diverse fossil assemblages are an unparalleled paleontologic resource of international importance. Both the Pliocene-Pleistocene Epoch boundary and the Blancan-Irvingtonian North American Land Mammal Ages boundary fall within the long geological record from the Anza-Borrego Desert. Environmental changes associated with these geological time divisions are probably better tracked by fossils from Anza-Borrego than in any other North American continental strata. These changes herald the beginning of the Ice Ages, and the strata undoubtedly contain fossil clues to the origin and development of modern southwestern desert landscapes.

The first fossils, marine shells from the ancient Sea of Cortez and fresh water shells from prehistoric Lake Cahuilla, precursor of the Salton Sea, were collected and described by William Blake in 1853. Blake was the geologist and mineralogist for the U.S. Pacific Railroad Exploration commissioned by Congress and President Franklin Pierce to find a railway route to the Pacific. It was Blake who first named this region the Colorado Desert.

Since the late 1800s, numerous scientific studies and published papers have centered on the marine organisms that inhabited the ancestral Sea of Cortez. Fossil assemblages from the classic Imperial Formation include calcareous nanoplankton and dinoflagellates, foraminifera, corals, polychaetes, clams, gastropods, urchins and sand dollars, and crabs and shrimp. The deposits also yield the remains of marine vertebrates such as sharks and rays, bony fish, baleen whale, walrus, and dugong. Marine environments such as outer and inner shelf, platform reef, and near shore beach and lagoon are all represented within the Imperial Formation. As the sea shallowed, estuarine and brackish marine conditions prevailed, typified by thick channel deposits of oyster and pecten shell coquina that now form the Elephant Knees along Fish Creek.

Many of the marine fossils are closely related to forms from the Caribbean Sea. They document a time before the isthmus of Panama formed, when the warm Gulf Stream of the western Atlantic invaded eastern Pacific Ocean waters.

As North and South America connected about 3 million years ago, terrestrial faunal migrations on a continental scale, the Great American Biotic Interchange, are evidenced by Anza-Borrego's fossils. Animals like giant ground sloths and porcupines made their first appearance in North America at this time.

The oldest terrestrial vertebrate fossils from the Colorado Desert predate the late Miocene invasion of the Sea of Cortez. These very rare fossils, which include a gomphothere (elephant-like mammal), rodent, felid and small camelid, and were collected from 10-12 million year old riverine and near shore lake deposits. However, the most significant and abundant vertebrate fossils have been recovered from the latest Miocene through late-Pleistocene riverine and flood plane deposits of the Palm Spring Formation in the Vallecito and Fish Creek Badlands and Ocotillo Conglomerate exposed in the Borrego Badlands. These fossil assemblages occur in a 3.5 million year long uninterrupted stratigraphic sequence that has been dated using horizons of volcanic ash and paleomagnetic methods.

The bestiary for this savannah landscape reads like a who's-who for some of the most unique creatures to inhabit North America, animals like: Geochelone, a giant bathtub-sized tortoise; Aiolornis incredibilis, the largest flying bird of the northern hemisphere, with 17 foot wing span; Paramylodon, Megalonyx and Nothrotheriops, giant ground sloths, some with bony armor within their skin; Pewelagus, a very small rabbit (paleontologists do have a sense of humor); Borophagus, a hyena-like dog; Acrtodus, a giant short-faced bear; Smilodon, a sabertoothed cat; Miracinonyx, the North American cheetah; Mammuthus imperator, the largest known mammoth; Tapirus, an extinct tapir; Equus enormis and Equus scotti, two species of extinct Pleistocene horse; Gigantocamelus a giant camel; and Capromeryx, the dwarf pronghorn.

Although paleontological exploration of Anza-Borrego Desert State Park has stepped firmly into the twenty-first century with the application of GIS and computer assisted analyses to field surveys and resource management, many questions still remain. Expanding the detail and clarity of our paleontological view of the region's vanished past and improving our understanding of its significance is an on going challenge. Exploration, conservation, research and interpretation continue as new fossils are discovered.

ABDSP Paleontology Society started 1993. Colorado Desert District Stout Research Center opened in 1997.

  • Flora and Fauna of Anza-Borrego Desert Park
  • Penninsular Bighorn Sheep in Anza-Borrego.
    Penninsular Bighorn Sheep in Anza-Borrego.
  • An Ocotillo plant common in Anza-Borrego.
    An Ocotillo plant common in Anza-Borrego.
  • A lone Desert Marigold pushes its way through the cracked, sun hardened desert after a rare and substantial rainfall (Spring 2004).
    A lone Desert Marigold pushes its way through the cracked, sun hardened desert after a rare and substantial rainfall (Spring 2004).
  • Common Chuckwalla, Sauromalus ater. Observed during a hike up Palm Canyon.
    Common Chuckwalla, Sauromalus ater. Observed during a hike up Palm Canyon.

Notes

  1. ^ C. Michael Hogan. 2009
  2. ^ George T. Jefferson and Lowell Lindsay

References

Further reading

  • Robin Halford. 2005. Hiking in Anza-Borrego Desert: Over 100 Half-Day Hikes (Anza Borrego Desert Natural History Association, Borrego Springs). ISBN 091080513X
  • Diana Lindsay, 2001. Anza-Borrego A to Z: People, Places, and Things (Sunbelt Publications, San Diego). ISBN 0932653421
  • Lowell Lindsay and Lindsay, Diana. 2006. The Anza-Borrego Desert Region: A Guide to the State Park and Adjacent Areas of the Western Colorado Desert. Fifth Edition (Wilderness Press, Berkeley). ISBN 0899974007
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