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

Video VOA Reporter Tours Devastated Peshawar School

Islamist militants wearing military uniforms and strapped with explosives attacked a military run school Tuesday in the northwestern Pakistani city of Peshawar. At least 141 people were killed in the horrific attack, most of them young students. More

Video Sudan School Becomes Target of Aerial Attacks

Dropout rate at an all-time high in South Kordofan state because many schools have been destroyed during 3-year civil war More

Tennessee Songbirds Fly Coop Long Before Tornadoes Arrive

Researchers say birds apparently alerted to danger by sounds at frequencies below range of human hearing 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.
US: Response to Sony Hack Will Be Proportionali
X
Aru Pande
December 19, 2014 1:45 AM
The White House says President Barack Obama considers the cyberattack on Sony Corp. a serious national security matter and that the U.S. will counter with an "appropriate response." VOA correspondent Aru Pande reports.
Video

Video US: Response to Sony Hack Will Be Proportional

The White House says President Barack Obama considers the cyberattack on Sony Corp. a serious national security matter and that the U.S. will counter with an "appropriate response." VOA correspondent Aru Pande reports.
Video

Video Sudan School Becomes Target of Aerial Attacks

The school dropout rate is at an all-time high in Sudan's South Kordofan state because many schools have been destroyed during the three-year civil war between the government and SPLA-N rebel forces. Adam Bailes visited Sudan's Nuba Mountains' region and reports many children are simply too scared to go to school
Video

Video Nigerians Fleeing Boko Haram Languish in Camp Near Capital

In its five-year effort to impose Islamic law in northeastern Nigeria, the Boko Haram extremist group has killed thousands of people and forced hundreds of thousands to flee. Some of those who ran for their lives now live in squalor on the edges of the capital, Abuja. Chris Stein reports for VOA.
Video

Video Putin Says Russian Economy Will Emerge Stronger

Russian President Vladimir Putin has said his country's sinking economy will not only recover but also become stronger, despite falling oil prices and Western sanctions over Ukraine. VOA's Daniel Schearf reports.
Video

Video Detained Turkish Journalists Follow Teachings of US-Based Preacher

The Turkish government’s jailing of critical journalists has sparked international condemnation and is being seen as an effort to undermine the followers of an ailing Turkish preacher based in the United States. VOA religion reporter Jerome Socolovsky has more.
Video

Video ‘Anti-Islamization’ Marches Increase Tensions In Germany

Anti-immigrant rallies in Germany have been building in recent weeks, peaking Monday night in the city of Dresden where tens of thousands of people turned out to demonstrate against what they call the ‘Islamization’ of the West. Germany has offered asylum to more Syrian refugees than any other country, and this appears to have set off the protests. Henry Ridgwell reports from London.
Video

Video Aceh Rebuilt Decade After Tsunami, But Scars Remain

On December 26, 2004 there was an earthquake in the Indian Ocean so powerful it caused the Earth’s axis to wobble a few centimeters. Onshore on the island of Sumatra, the resulting tsunami was devastating. A decade later, VOA Correspondent Steve Herman reports from Banda Aceh, Indonesia, where although there is little remaining evidence of the physical devastation, the psychological scars among survivors remain.
Video

Video Refugees Living in Kenya Long for Peace in the Home Countries

Kenya is host to numerous refugees seeking safe haven from conflict. Immigrants from Somalia face challenges in their new lives in Kenya. Ahead of International Migrants Day (December 18) Lenny Ruvaga has more for VOA News from the Kenyan capital.

All About America

AppleAndroid