News / Science & Technology

Lake Sediment Could Better Date Ancient Finds

This 24,700-year-old leaf, dated by radiocarbon, was found in sediment cores from Japan’s Lake Suigetsu. (Credit: Richard Staff)
This 24,700-year-old leaf, dated by radiocarbon, was found in sediment cores from Japan’s Lake Suigetsu. (Credit: Richard Staff)
Rosanne Skirble
Core samples found at the bottom of a Japanese lake could provide much more precise timelines for important archeological finds and climate-history questions.  

Radiocarbon dating is the best-known and most widely used method to determine the age of organic material, such as bone or wood or plant matter. All such material contains radioactive carbon atoms, known as carbon-14, that decay at an understood and measurable rate. 

Oxford University radiocarbon dating expert Christopher Ramsey and his colleagues were looking for organic material preserved for long periods of time in a still and airless environment, where radiocarbon levels would not have been affected by interactions with ocean water or groundwater.

They found what they were looking for in core samples taken from deep sediment at the bottom of Japan’s Lake Suigetsu.  Ramsey, who reports on the find in Science, says the alternating layers of fossilized leaves and algae that settled to the lake-bottom offer a perfectly preserved record of more than 50,000 thousand years.  

Radiocarbon Dating Breakthrough
Radiocarbon Dating Breakthroughi
|| 0:00:00
...    
🔇
X


“What’s special about Lake Suigetsu is that we have an alternative dating technique that we can use there, which is essentially counting the annual layers, which are deposited in the sediment of Lake Suigetsu," Ramsey says. "And so putting that together with the radiocarbon dates, it gives us a sort of tool, if you like, for saying if we’ve got a radiocarbon measurement for a particular value, then we can now put that into an accurate, absolute date.”

  • This 24,700 year-old leaf dated by radiocarbon was found in sediment cores from Japan’s Lake Suigetsu. (Credit: Richard Staff)
  • This 24,700 year-old leaf dated by radiocarbon was found in sediment cores from Japan’s Lake Suigetsu. (Credit: Richard Staff)
  • This 33,800 year-old leaf dated by radiocarbon found in Lake Suigetsu sediment extends radiocarbon dating by thousands of years. (Credit: Richard Staff)
  • This 33,800 year-old leaf dated by radiocarbon found in Lake Suigetsu sediment extends radiocarbon dating by thousands of years. (Credit: Richard Staff)
  • Scientists find perfectly preserved organic materials in sediment cores in Japan’s Lake Suigetsu. (Credit: Christopher Bronk Ramsey)
  • With sediment cores from Lake Suigetsu scientists can  now date with great accuracy the entire radiocarbon lifespan.  (Credit: Christopher Bronk Ramsey)
  • The Oxford Radiocarbon Accelerator can identify radiocarbon dates from much smaller samples than needed for standard radiocarbon dating. (Credit: Christopher Bronk Ramsey)
  • Plant samples are readied for radiocarbon dating. (Credit: Richard Staff)
  • Suigestu sediments in natural light. (Credit: Gordon Schlolaut)
  • Suigestu sediments in polarized light. (Credit: Gordon Schlolaut)
  • Varved or layers of sediments from Lake Suigetsu cores. (Credit: Gordon Schlolaut)
  • Cores are temporarily stored in the cold room of the local fishermen's union near Lake Suigetsu. (Credit: Takeshi Nakagawa)
  • Core photography and sub-sampling were performed in this open-air workshop. (Credit: Takeshi Nakagawa)


Ramsey says radiocarbon as a dating tool must be anchored in time with some other technique to compare for accuracy. The only other physical record of atmospheric carbon comes from tree rings, which don’t go back nearly as far as the Japanese lake sediment.

“The step forward here is that for the first time we have a complete record that actually covers the whole last 50,000 years or so of radiocarbon in the atmosphere with known age samples," he says, "whereas before we only had that for the last 12,000 or 13,000 years.

The radiocarbon in the core-sample leaf fossils, like the carbon in tree rings, comes directly from the atmosphere.  It is not subject to the chemical changes that can affect radiocarbon in ocean-floor sediment or in cave environments, where dripping groundwater and minerals form structures known as stalagmites and stalactites. 

Ramsey says dating using the lake-sediment record is more accurate. 

“People have tried to do this before, but they have been limited to using marine sediments and using stalagmites and stalactites in caves. And all of those have the problem that the carbon in the oceans and the stalagmites and stalactites isn’t exactly the same as that in the atmosphere. So it’s a bit more difficult to work out what’s going on with those.”

According to Ramsey, the new record will help refine the dating of organic material by centuries. It can also help clarify the chain of events that led to the advance and retreat of ice sheets during the last ice age.

“It will enable us to pinpoint much more precisely, exactly when changes take place in the environment and when we get changes in the archeological record, exactly how those relate to other changes that are taking place in the world which are recorded in things like the Greenland ice cores where we have a very good record of the climate."

Ramsey adds the improved radiocarbon reference will also provide more precise dates for when Neanderthals died out and modern humans spread across Europe.

You May Like

Obama: Alaskans Feel Signs of Climate Change

They're seeing bigger storm surges as sea ice melts, more wildfires, erosion of glaciers, shorelines More

Katrina Brought Enduring Changes to New Orleans

The city’s recovery is the result of the people and culture the city is famous for, as well as newcomers and start-up industries More

Magical Photo Slides Show Native Americans in Late 1800s

Walter McClintock spent 20 years photographing the Blackfoot Indians and their vanishing culture at the dawn of the modern age More

This forum has been closed.
Comments
     
There are no comments in this forum. Be first and add one

Featured Videos

Your JavaScript is turned off or you have an old version of Adobe's Flash Player. Get the latest Flash player.
Colombians Flee Venezuela as Border Crisis Escalatesi
X
August 27, 2015 2:08 AM
Hundreds of Colombians have fled Venezuela since last week, amid an escalating border crisis between the two countries. Last week, Venezuelan President Nicolas Maduro ordered the closure of a key border crossing after smugglers injured three Venezuelan soldiers and a civilian. The president also ordered the deportation of Colombians who are in Venezuela illegally. Zlatica Hoke reports.
Video

Video Colombians Flee Venezuela as Border Crisis Escalates

Hundreds of Colombians have fled Venezuela since last week, amid an escalating border crisis between the two countries. Last week, Venezuelan President Nicolas Maduro ordered the closure of a key border crossing after smugglers injured three Venezuelan soldiers and a civilian. The president also ordered the deportation of Colombians who are in Venezuela illegally. Zlatica Hoke reports.
Video

Video Is China's Economic Data Accurate?

Some investors say China's wild stock market gyrations have been made worse by worries about the reliability of that nation's economic data. And some critics say the reports can mislead investors by painting an unrealistically-strong picture of the economy. A key China scholar says Beijing is not fudging ((manipulating)) the numbers, but that the economy is evolving quickly from smoke-stack industries to services, and the ways of tracking new economic activity are falling behind the change. V
Video

Video Next to Iran, Climate at Forefront of Obama Agenda

President Barack Obama this week announced new initiatives aimed at making it easier for Americans to access renewable energy sources such as solar and wind. Obama is not slowing down when it comes to pushing through climate change measures, an issue he says is the greatest threat to the country’s national security. VOA correspondent Aru Pande has more from the White House.
Video

Video Shipping Containers Provide Experimental Housing

Housing prices around the San Francisco Bay area are out of reach for many people, so some young entrepreneurs, artists and tech industry workers are creating their own houses using converted shipping containers. But as VOA's Mike O’Sullivan reports from Oakland, the effort requires ingenuity and dealing with restrictive local laws.
Video

Video Arctic Draws International Competition for Oil

A new geopolitical “Great Game” is underway in earth’s northernmost region, the Arctic, where Russia has claimed a large area for resource development and President Barack Obama recently approved Shell Oil Company’s test-drilling project in an area under U.S. control. Greg Flakus reports.
Video

Video Philippine Maritime Police: Chinese Fishermen a Threat to Country’s Security

China and the Philippines both claim maritime rights in the South China Sea.  That includes the right to fish in those waters. Jason Strother reports on how the Philippines is catching Chinese nationals it says are illegal poachers. He has the story from Palawan province.
Video

Video Technique May Eliminate Drill-and-Fill Dental Care

Many people dread visiting dentists because they're afraid of drills. Now, however, a technology developed by a British firm promises to eliminate the need for mechanical cleaning of dental cavities by speeding a natural process of tooth repair. VOA’s George Putic reports.
Video

Video China's Spratly Island Building Said to Light Up the Night 'Like A City'

Southeast Asian countries claim China has illegally seized territory in the Spratly islands. It is especially a concern for a Philippine mayor who says Beijing is occupying parts of his municipality. Jason Strother reports from the capital of Palawan province, Puerto Princesa.
Video

Video Ages-old Ice Reveals Secrets of Climate Change

Ice caps don't just exist at the world's poles. There are also tropical ice caps, and the largest sits atop the Peruvian Andes - but it is melting, quickly, and may be gone within the next 20 years. George Putic reports scientists are now rushing to take samples to get at the valuable information about climate change locked in the ice.
Video

Video French Experiment in Integrating Roma Under Threat

Plans to destroy France’s oldest slum have sparked an outcry on the part of its Roma residents. As Lisa Bryant reports from the Paris suburb of La Courneuve, rights groups argue the community is a fledgling experiment on integrating Roma who are often outcasts in many parts of Europe.
Video

Video Kenyans Turn to Agriculture for Business

Each year Kenyan universities continue to churn out graduates for the job market despite the already existing high rate of unemployment among youth in the country. Some of these young men and women have realized that agriculture can be as rewarding as any other business or job, and they are resorting to agribusiness in large numbers as a way of tackling unemployment. Rael Ombuor reports for VOA.
Video

Video First Women Graduate Elite Army Ranger School

Two women are making history for the U.S. Army by proving they are among the toughest of the tough. VOA's Carla Babb reports from Fort Benning, Georgia as 94 men and those two women rise as graduates of the difficult Ranger school.

VOA Blogs