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

Turkish Public Fears Jihadists More Than Kurds

Turkey facing twin threats of terrorism by Islamic State and PKK Kurdish separatists, says President Erdogan’s ruling AK Party More

Video One Year After Massacre, Iraq’s Yazidis a Broken People

Minority community still recovering from devastating assault by IS militants which spurred massive outrage More

‘Malvertisements’ Undermine Internet Trust

Hackers increasingly prey on users' trust of major websites to delivery malicious software 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.
Iraqi Yazidis Fear Death of Their Communityi
X
Sharon Behn
August 03, 2015 2:23 PM
A year ago on August 3, Islamic State militants stormed the homelands of Iraq’s Yazidi minority, killing hundreds of men and enslaving thousands of women. The scenes of desperate Yazidi families crowding on the top of Sinjar mountain without food or water spurred Kurdish fighters into action, an emergency airlift and the start of the U.S. airstrike campaign against the Islamic State Sunni extremists. VOA's Sharon Benh reports from northern Iraq.
Video

Video Iraqi Yazidis Fear Death of Their Community

A year ago on August 3, Islamic State militants stormed the homelands of Iraq’s Yazidi minority, killing hundreds of men and enslaving thousands of women. The scenes of desperate Yazidi families crowding on the top of Sinjar mountain without food or water spurred Kurdish fighters into action, an emergency airlift and the start of the U.S. airstrike campaign against the Islamic State Sunni extremists. VOA's Sharon Benh reports from northern Iraq.
Video

Video Bangkok Warned It Soon Could Be Submerged

Italy's Venice and America's New Orleans are not the only cities gradually submerging. The nearly ten million residents of the Bangkok urban area now must confront warnings the city could become uninhabitable in a few decades. VOA Correspondent Steve Herman reports from the Thai capital.
Video

Video Inclusive Gym Gets People With Disabilities in Fitness Spirit

Individuals with special needs are 58 percent more likely to be obese than the general population. According to the U.S. Centers for Disease Control, they also have an increased likelihood of anxiety, depression and social isolation. But a sports club outside Washington wants to make a difference in these people's lives. With Carol Pearson narrating, VOA's June Soh reports.
Video

Video Astronauts Train Underwater for Deep Space Missions

Manned deep space missions are still a long way off, but space agencies are already testing procedures, equipment and human stamina for operations in extreme environment conditions. Small groups of astronauts take turns in spending days in an underwater lab, off Florida’s southern coast, simulating future missions to some remote world. VOA’s George Putic reports.
Video

Video Special Olympics Show Competitors' Skill, Determination

Special Olympics competitions will wrap up Saturday in Los Angeles, and the closing ceremony for athletes with intellectual disabilities will be held Sunday night. In a week of competition, athletes have shown what they can do through skill and determination. VOA's Mike O'Sullivan reports.
Video

Video Civil Rights Leaders Struggled to Achieve Voting Rights Act

Fifty years ago, lawmakers approved, and U.S. President Lyndon Johnson signed, the Voting Rights Act of 1965. The measure outlawed racial discrimination in voting, giving millions of blacks in many parts of the southern United States federal enforcement of the right to vote. Correspondent Chris Simkins introduces us to some civil rights leaders who were on the front lines in the struggle for voting rights.
Video

Video Shooter’s Grill: Serving Food with a Touch of the Second Amendment

Shooter's Grill, a restaurant in Rifle, Colorado, attracts visitors from all over the world as well as local patrons. The reason? Waitresses openly carry loaded firearms as they serve food, and customers are welcome to carry them, too. VOA's Enming Liu and Lin Yang paid a visit to Shooter's Grill, and heard different opinions about this unique establishment.
Video

Video Despite Controversy, Business Owner Continues Sale of Confederate Flags

At Cooter’s, a store in rural Sperryville, Virginia, about 120 kilometers west of Washington, D.C., Confederate flags are flying off the shelves. The red, white and blue battle flag, with 13 white stars representing the Confederate states, was carried by southern forces during the U.S. Civil War in the 1860s. The South had seceded from the Union over several key issues of disagreement, including slavery. VOA’s Deborah Block has the story.
Video

Video Booming London Property a ‘Haven for Dirty Money’

Billions of dollars of so-called ‘dirty money’ from the proceeds of crime - especially from Russia - are being laundered through the London property market, according to anti-corruption activists. As Henry Ridgwell reports from the British capital, the government has pledged to crack down on the practice.
Video

Video Hometown of Boy Scouts of America Founder Reacts to Gay Leader Decision

Ottawa, Illinois, is the hometown of W.D. Boyce, who founded the Boy Scouts of America in 1910. In Ottawa, where Scouting remains an important part of the legacy of the community, the end of the organization's ban on openly gay adult leaders was seen as inevitable. VOA's Kane Farabaugh reports.

VOA Blogs