New Study Confirms Bering Land Bridge Flooded Later Than Previously Believed

July 03, 1996

Study Confirms Bering Land Bridge Flooded Later than Previously Believed
July 3, 1996

NEW STUDY CONFIRMS BERING LAND BRIDGE FLOODED LATER THAN PREVIOUSLY BELIEVED

A new study confirms the Bering land bridge that carried ancient wanderers from Asia into North America was not inundated by rising seas until about 11,000 years ago, according to a University of Colorado at Boulder researcher.

The study also shows the Bering land bridge vegetation at the time consisted primarily of tundra plants and shrubs and was unsuitable for long-term habitation by large grazing mammals, said CU-Boulder researcher Scott Elias. Because of the abundance of mammoth and other large animal fossils from adjacent areas, researchers had thought the environment of the land bridge was an arid grassland similar to the steppe region of northern Asia today, said Elias.

A paper by Elias and Susan Short of CU-Boulder's Institute of Arctic and Alpine Research, C. Hans Nelson of the U.S. Geological Survey in Menlo Park, Calif., and Hilary Birks of the Botanical Institute in Bergen, Norway, was published in the July 4 issue of Nature. The newest dates for the inundation of the land bridge corroborate radiocarbon dates calculated by Elias and colleagues in 1992 using seafloor sediment cores.

The Bering land bridge surfaced during Earth's ice ages when sea level in the Bering Sea and Chukchi Sea dropped by 300 feet or more due to a buildup of glacial ice. During the most recent ice age that ended about 10,000 years ago, the land bridge covered 580,000 square miles -- an area roughly twice the size of Texas, Elias said.

Elias and his colleagues analyzed 20 ocean-core samples obtained by U.S. Geological Survey researchers from the shallows of the Bering and Chukchi seas for the study. Taken in the 1970s and 1980s and stored at a USGS facility in Menlo Park, the cores contain layers of organic peat and silt that harbor plant, pollen and insect fossils ranging from about 4,000 years old to roughly 50,000 years old.

"The exciting thing here is that we were able to sample an ancient landscape that no longer exists," said Elias. "We don't have to guess any more as to what the Bering land bridge was like back then."

Plant seeds and stems and insect body parts were radiocarbon dated using an accelerator mass spectrometer at the University of Arizona that accelerates carbon atoms at near the speed of light. The instrument allowed researchers to count the ratio of carbon 14 atoms to carbon 12 atoms from the samples and arrive at the estimated dates for the most recent inundation of the land bridge.

"This study indicates that early people were free to move across the land bridge until about 10,500 years ago, right up to the beginning of the Holocene Period," said Elias. Several Paleo Indian sites in the Nenana Valley of central Alaska that date to about 12,000 years ago are considered the earliest reliable dates for the human occupation of North America, Elias said.

"These new data confirm that the people who spread from Beringia to North America about 14,000 years ago came from a stock able to gain a livelihood from the meager resources of tundra, or perhaps from the sea coast," wrote Paul Colinvaux in an accompanying News and Views article in the July 4 issue of Nature. Colinvaux is a researcher at the Smithsonian Tropical Research Institute in Panama.

Although mammoth, horse and bison fossils unearthed in northern Alaska near the ancient land bridge had indicated it may once have supported a large number of grazing mammals, the new study shows the animals probably migrated through the area rather than living there. "This new evidence tells us the big mammals probably did not linger on the land bridge," said Elias.

Pollen samples from the peat cores dating from 14,000 years ago to 11,000 years ago match pollen from modern Alaskan tundra, which is characterized by clumps of sedges, low-lying willows, dwarf birch shrubs and grasses, he said.

The previous dates for the inundation of the land bridge -- about 14,400 years ago -- came from a 25-year-old radiocarbon sample that now appears to have been contaminated with coal deposits washed into the Bering and Chukchi seas, he said.

The study also indicates summer temperatures on the land bridge were about 8 to 11 degrees F. warmer 11,000 years ago than they are today, said Elias. Since virtually no evolution has occurred in beetles over the past 700,000 years, scientists can compare today's beetles -- which are sensitive indicators of climate change -- with fossil beetles from ancient sites to reliably estimate past temperatures.

Contact: Scott Elias, (303) 492-5158
Jim Scott, 492-3114

Back to News Release Summaries


University of Colorado at Boulder

Related Carbon Articles from Brightsurf:

The biggest trees capture the most carbon: Large trees dominate carbon storage in forests
A recent study examining carbon storage in Pacific Northwest forests demonstrated that although large-diameter trees (21 inches) only comprised 3% of total stems, they accounted for 42% of the total aboveground carbon storage.

Carbon storage from the lab
Researchers at the University of Freiburg established the world's largest collection of moss species for the peat industry and science

Carbon-carbon covalent bonds far more flexible than presumed
A Hokkaido University research group has successfully demonstrated that carbon-carbon (C-C) covalent bonds expand and contract flexibly in response to light and heat.

Metal wires of carbon complete toolbox for carbon-based computers
Carbon-based computers have the potential to be a lot faster and much more energy efficient than silicon-based computers, but 2D graphene and carbon nanotubes have proved challenging to turn into the elements needed to construct transistor circuits.

Cascades with carbon dioxide
Carbon dioxide (CO(2)) is not just an undesirable greenhouse gas, it is also an interesting source of raw materials that are valuable and can be recycled sustainably.

Two-dimensional carbon networks
Lithium-ion batteries usually contain graphitic carbons as anode materials. Scientists have investigated the carbonic nanoweb graphdiyne as a novel two-dimensional carbon network for its suitability in battery applications.

Can wood construction transform cities from carbon source to carbon vault?
A new study by researchers and architects at Yale and the Potsdam Institute for Climate Impact Research predicts that a transition to timber-based wood products in the construction of new housing, buildings, and infrastructure would not only offset enormous amounts of carbon emissions related to concrete and steel production -- it could turn the world's cities into a vast carbon sink.

Investigation of oceanic 'black carbon' uncovers mystery in global carbon cycle
An unexpected finding published today in Nature Communications challenges a long-held assumption about the origin of oceanic black coal, and introduces a tantalizing new mystery: If oceanic black carbon is significantly different from the black carbon found in rivers, where did it come from?

First fully rechargeable carbon dioxide battery with carbon neutrality
Researchers at the University of Illinois at Chicago are the first to show that lithium-carbon dioxide batteries can be designed to operate in a fully rechargeable manner, and they have successfully tested a lithium-carbon dioxide battery prototype running up to 500 consecutive cycles of charge/recharge processes.

How and when was carbon distributed in the Earth?
A magma ocean existing during the core formation is thought to have been highly depleted in carbon due to its high-siderophile (iron loving) behavior.

Read More: Carbon News and Carbon Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.