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

US, Brazil's Climate-Change Plan: More Renewables, Less Deforestation

Officials say joint initiative on climate change will allow Brazil, United States to strengthen and accelerate cooperation on issues ranging from land use to clean energy More

Video Blind Somali Journalist Defies Odds in Mogadishu

Reporting from Somali capital for past decade, Abdifatah Hassan Kalgacal has been working at one of Mogadishu's leading radio stations covering parliament More

After Nearly a Century, Voodoo Opera Rises Again

Opera centers on character named Lolo, a Louisiana plantation worker and Voodoo priestess 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.
Blind Somali Journalist Defies Odds in Mogadishui
X
Abdulaziz Billow
June 30, 2015 2:16 PM
Despite improving security in the last few years, Somalia remains one of the most dangerous countries to be a journalist – even more so for someone who cannot see. Abdulaziz Billow has the story of journalist Abdifatah Hassan Kalgacal, who has been reporting from the Somali capital for the last decade despite being blind.
Video

Video Blind Somali Journalist Defies Odds in Mogadishu

Despite improving security in the last few years, Somalia remains one of the most dangerous countries to be a journalist – even more so for someone who cannot see. Abdulaziz Billow has the story of journalist Abdifatah Hassan Kalgacal, who has been reporting from the Somali capital for the last decade despite being blind.
Video

Video Texas Defies Same-Sex Marriage Ruling

Texas state officials have criticized the US Supreme Court decision giving same-sex couples the right to marry nationwide. The attorney general of Texas says last week's decision did not overrule constitutional "rights of religious liberty," and therefore officials performing wedding services can refuse to perform them for same-sex couples if it is against their religious beliefs. Zlatica Hoke reports on the controversy.
Video

Video US Gay Marriage Ruling Yields Real-life Impact

Friday’s landmark Supreme Court decision legalizing same-sex marriage throughout the United States is an outcome few thought possible just years ago, and shows a nation that increasingly tolerates and even celebrates the hopes and aspirations of gay people. VOA’s Michael Bowman spoke to a same-sex couple that will benefit from the high court ruling, and to a Christian scholar who is apprehensive about its potential consequences for America’s faith community.
Video

Video Syrians Flee IS Advance in Hasaka

The Syrian government said Monday it has taken back one of several districts in Hasaka overrun by Islamic State militants. But continued fighting elsewhere in the northern city has forced thousands of civilians from their homes. In this report narrated by Bill Rodgers, VOA Kurdish Service reporter Zana Omer describes the scene in Amouda, where some of the displaced are taking refuge.
Video

Video Rabbi Hits Road to Heal Jewish-Muslim Relations in France

France is on high alert after last week's terrorist attack near the city Lyon, just six months after deadly Paris shootings. The attack have added new tensions to relations between French Jews and Muslims. France’s Jewish and Muslim communities also share a common heritage, though, and as far as one French rabbi is concerned, they are destined to be friends. From the Paris suburb of La Courneuve, Lisa Bryant reports about Rabbi Michel Serfaty and his friendship bus.
Video

Video S. Korea Christians Protest Gay Rights Festival

The U.S. Supreme Court decision mandating marriage equality nationwide has energized gay rights supporters around the world. Gay rights remain a highly contentious issue in a key U.S. ally, South Korea, where police did a deft job Sunday of preventing potential clashes between Christian protesters and gay activists. Kurt Achin reports from Seoul.
Video

Video Saudi Leaks Expose ‘Checkbook Diplomacy’ In Battle With Iran

Saudi Arabia’s willingness to wield its oil money on the global diplomatic stage appears to have been laid bare, after the website WikiLeaks published tens of thousands of leaked cables from Riyadh’s Ministry of Foreign Affairs. VOA's Henry Ridgwell reports.
Video

Video Nubians in Kenya Face Land Challenges

East Africa's ethnic Nubians have a rich cultural history that dates back thousands of years, but in Kenya they are facing hardships, including the loss of lands they have lived on for generations. They say the government has reneged on its pledge to award them title deeds for the plots. VOA's Lenny Ruvaga reports.
Video

Video Syrian Refugees Return to Tal Abyad

Syrian refugees in Turkey confirm they left their hometown of Tal Abyad because of intense fighting and coalition airstrikes, not because Kurdish fighters were engaged in ethnic cleansing, as some Turkish officials charged. VOA Kurdish Service reporter Zana Omer, in Tal Abyad, finds that civilians coming back to the town agree, as we hear in this report narrated by Roger Wilkison.
Video

Video Military Experts Question New Russian Tank Capabilities

Russia has been showing off its new tank design – the Armata T-14. Designers claim it is 20 years ahead of current Western designs - and driving it feels like playing a computer game. But military analysts question those assertions, and warn the cost could be too heavy a burden for Russia’s struggling economy. Henry Ridgwell reports.
Video

Video In Kenya, Police Said to Shoot First, Ask Questions Later

An organization that documents torture and extrajudicial killings says Kenyan police were responsible for 1,252 shooting deaths in five cities, including Nairobi, between 2009 and 2014, representing 67 percent of all gun deaths in the areas reviewed. Gabe Joselow has more from Nairobi.
Video

Video In Syrian Crisis, Social Media Offer Small Comforts

Za’atari, a makeshift city in Jordan, may be the only Syrian refugee camp to tweet its activities, in an effort to keep donors motivated as the war in Syria intensifies and the humanitarian crisis deepens. Inside the camp, families say mobile phone applications help hold together families that are physically torn apart. VOA’s Heather Murdock reports.

VOA Blogs