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Ancient tools at High Desert site go back 135,000 years |
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Written by Xiuhcoatl
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Nov 24, 2005 at 02:20 PM |
Ancient tools at High Desert site go back 135,000 years
Chuck Mueller, Staff Writer
SBSUN.com
BARSTOW - In the multicolored hills overlooking the Mojave River
Valley, the excavation of stone tools and flakes reveals human
activities from the distant past.
A new system of geologic dating has confirmed that an alluvial deposit
bearing the stone tools and flakes at the Calico archaeological site is
about 135,000 years old.
But the site could even be older.
Calico project director Fred Budinger Jr. said a soil sample, taken at
a depth of 17 1/2 feet in one of three master pits at the dig near
Yermo, verifies that the deposit dates to the Middle Pleistocene Epoch
- the Ice Age.
"This new date confirms earlier estimates that humans were in the Manix
Basin, near the base of the Calico Mountains, as early as 125,000 to
200,000 years ago," Budinger said.
The dating system, known as thermo-luminescence, reflects the amount of
time that has elapsed since a layer of sediment was exposed to sunlight.
Another system, called uranium-thorium dating, pushed the age of
sedimentary layers at the digging site to about 200,000 years ago.
But studies now under way with beryllium 10, an element used in dating
exposed surfaces, could open the door into the more distant geological
past.
"Beryllium 10 can date rock forms back almost to the formation of Earth
itself,' said Budinger, senior archaeologist with Tetra Tech Inc., an
environmental engineering and consulting firm with offices in San
Bernardino.
Meanwhile, another system of dating known as optically stimulated
luminescence also may be used to determine the age of artifact-bearing
beds at the Calico site. This system is used to date sand dune layers.
Lewis Owen, a former geology professor at UC Riverside and now with the
University of Cincinnati, is in charge of the new research.
"No other archaeological site has made use of these dating methods,"
Budinger said. "And until we get results (from Owen), expected this
winter, we say the Calico site is 100,000 to 200,000 years old."
Humans who inhabited the Manix Basin chipped tools from chalcedony and
chert, rocks that break like glass, to serve as scrapers, choppers,
gravers, saws and digging tools. The Calico area was a workshop, and no
direct evidence of man, such as bones or teeth, have been found at the
site.
Manix Lake, a 91-square-mile freshwater lake extending from present-day
Yermo to Afton Canyon, drained 18,000 years ago. A unique combination
of environmental factors - erosion, faulting, and folding - exposed the
alluvial deposits.
Excavations at the Calico Early Man site, often simply called the Calico Digs, began in November 1964.
Heading the project was
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world-renowned archaeologist Louis Leakey, famed for discoveries with
his wife, Mary, at the Olduvai Gorge in Tanzania over three decades.
Among their finds was Zinjanthropus, an early man dating back 1.75
million years. Louis Leakey was project director at Calico from 1965
until his death in 1972.
San Bernardino County archaeologist Ruth DeEtte Simpson, field director under Leakey, then became project director.
Calico's current site manager, retired electronics engineer Chris Christensen, served as Leakey's chauffeur and body guard.
"The archaeological world was concerned with his safety out here," Christensen recalled.
He now oversees digging operations and guides visitors to the site.
"Volunteers from as far away as Berkeley and San Diego take part in
digs the first weekend of every month from October through May," he
said. "Some are professional geologists and archaeologists."
Since excavations began, more than 64,000 tools, flakes and stone chips
have been collected at Calico, said Johanna Lytle, president of the
nonprofit Friends of Calico. Most are housed in the San Bernardino
County Museum in Redlands.
Extensive improvements have been added to the site, which includes three master digging pits and 22 test pits.
"One of Louis Leakey's favorite tools was 'the Calico Cutter,' as he
called it," Christensen said, displaying a replica of the artifact in
the small museum on the grounds. "It shows bifacial flaking and
use-wear patterns ... evidence of human activity that could not be
caused by nature."
The site, two miles off Interstate 15 at Minneola Road, attracts visitors from across the nation and around the world.
Dennis and Patricia Pollet of Redondo Beach stopped by Wednesday.
"While my wife and I are very interested in ancient man, this is our
first chance to see a dig of consequence," Dennis said. "People who
visit Calico have a rare opportunity to see an actual excavation site."
"You can actually get the feel of an old civilization here," said Patricia. "You get a chance to touch our human past."
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Archaeology 