Featured Research

from universities, journals, and other organizations

Absence of evidence for a meteorite impact event 13,000 years ago

Date:
December 14, 2009
Source:
University of Hawaii at Manoa
Summary:
An international team of scientists has found no evidence supporting an extraterrestrial impact event at the onset of the Younger Dryas approximately 13,000 years ago.

Greenland. A black mat layer across North America which is correlated to the Younger Dryas climatic shift is seen in Greenland ice cores dated at 13,000 years ago by radio carbon dating.
Credit: iStockphoto/Frank Van Den Bergh

An international team of scientists led by researchers at the University of Hawaii at Manoa has found no evidence supporting an extraterrestrial impact event at the onset of the Younger Dryas approximately 13,000 years ago.

The Younger Dryas is an abrupt cooling event in Earth's history. It coincided with the extinction of many large mammals including the woolly mammoth, the saber toothed jaguar and many sloths. This cooling period is generally considered to be the result of the complex global climate system, possibly spurred on by a reduction or slowdown of the thermohaline circulation in North America. This paradigm was challenged two years ago by a group of researchers that reported finding high iridium concentrations in terrestrial sediments dated during this time period, which led them to theorise that an impact event was instead the instigator of this climate shift.

A team led by François Paquay, a Doctoral graduate student in the Department of Geology and Geophysics at the University of Hawaii at Manoa (UHM) decided to also investigate this theory, to add more evidence to what they considered a conceptually appealing theory. However, not only were they unable to replicate the results found by the other researchers, but additional lines of evidence failed to support an impact theory for the onset of the Younger Dryas.

Their results will be published in the December 7th early online edition of the Proceedings of the National Academy of Sciences.

The idea that an impact event may have been the instigator for this cooling period was appealing because of several alleged impact markers, especially the high iridium concentrations that the previous team reported. However, it is difficult for proponents of this theory to explain why no impact crater of this age is known. "There is a black mat layer across North America which is correlated to the Younger Dryas climatic shift seen in Greenland ice cores dated at 13,000 years ago by radio carbon," explains Paquay. "Initially I thought this type of layer could be associated with an impact event because concentration in the proxies of widespread wildfires are sky high. That plus very high levels of iridium (which is one indicator used to indicate extraterrestrial impact events). So the theory was conceptually appealing, but because of the missing impact site, the idea of one or multiple airburst arose."

To corroborate the theory, Paquay and his colleagues decided to take a three-pronged approach. The first was to replicate the original researchers data, the second step was to look for other tracers, specifically osmium isotopes, of extraterrestrial matter in those rocks, and the third step was to look for these concentrations in other settings. "Because there are so many aspects to the impact theory, we decided to just focus on geochemical evidence that was associated with it, like the concentration of iridium and other platinum group elements, and the osmium isotopes," says Paquay. "We also decided to look in very high resolution sediment cores across North America, and yet we could find nothing in our data to support their theory."

The team includes American, Belgian and Canadian researchers. Analysis of the sediments was done both at UHM and in Belgium, using the same sediments from the same interval and indepedently did the analysis work and got similar results. Both the marine and terrestrial sediment records do not indicate that an impact event was the trigger for the transition into the Younger Dryas cold period. "The marine and terrestrial record both complement each other to support this finding," concludes Paquay. "That's what makes the beauty of this study."

This project was supported by the Geological Society of America and the National Science Foundation. Sediment samples were provided by the Integrated Ocean Drilling Program.

The other authors from this paper are Greg Ravizza (also from UHM), Steven Goderis and Philippe Claeys from Vrije Universiteit Brussel, Frank Vanhaeck from the Universiteit Ghent, Matthew Boyd from Lakehead University, Todd A. Surovell from the University of Wyoming at Laramie, and Vance T. Holliday and C. Vance Haynes, Jr. from the University of Arizona at Tucson.

This research will be presented at the American Geophysical Union Fall 2009 Meeting in San Francisco. Wednesday December 16th, 2:52 PM -- 3:04 PM, Room 2006 Moscone West


Story Source:

The above story is based on materials provided by University of Hawaii at Manoa. Note: Materials may be edited for content and length.


Journal Reference:

  1. François S. Paquay, Greg Ravizza, Steven Goderis, Philippe Claeys, Steven Goderis, Frank Vanhaeck, Matthew Boyd, Todd A. Surovell, Vance T. Holliday, C. Vance Haynes, Jr. Absence of geochemical evidence for an impact event at the Bølling–Allerød/Younger Dryas transition. Proceedings of the National Academy of Sciences, 2009; DOI: 10.1073/pnas.0908874106

Cite This Page:

University of Hawaii at Manoa. "Absence of evidence for a meteorite impact event 13,000 years ago." ScienceDaily. ScienceDaily, 14 December 2009. <www.sciencedaily.com/releases/2009/12/091208132734.htm>.
University of Hawaii at Manoa. (2009, December 14). Absence of evidence for a meteorite impact event 13,000 years ago. ScienceDaily. Retrieved July 28, 2014 from www.sciencedaily.com/releases/2009/12/091208132734.htm
University of Hawaii at Manoa. "Absence of evidence for a meteorite impact event 13,000 years ago." ScienceDaily. www.sciencedaily.com/releases/2009/12/091208132734.htm (accessed July 28, 2014).

Share This




More Earth & Climate News

Monday, July 28, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Raw: Sea Turtle Hatchlings Emerge from Nest

Raw: Sea Turtle Hatchlings Emerge from Nest

AP (July 27, 2014) — A live-streaming webcam catches loggerhead sea turtle hatchlings emerging from a nest in the Florida Keys. (July 27) Video provided by AP
Powered by NewsLook.com
Trees Could Save More Than 850 Lives Each Year

Trees Could Save More Than 850 Lives Each Year

Newsy (July 27, 2014) — A national study conducted by the USDA Forest Service found that trees collectively save more than 850 lives on an annual basis. Video provided by Newsy
Powered by NewsLook.com
Phoenix Thunderstorm Creates Giant Wall of Dust

Phoenix Thunderstorm Creates Giant Wall of Dust

Reuters - US Online Video (July 26, 2014) — A giant wall of dust slowly moves north over the Phoenix area after a summer monsoon thunderstorm. Mana Rabiee reports. Video provided by Reuters
Powered by NewsLook.com
Rare Lemur Among Baby Animals Debuted at Cleveland Zoo

Rare Lemur Among Baby Animals Debuted at Cleveland Zoo

Reuters - US Online Video (July 26, 2014) — A rare baby Lemur is among several baby animals getting their public debut at a Cleveland zoo. Mana Rabiee reports. Video provided by Reuters
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
 
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:  

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:  

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile iPhone Android Web
Follow Facebook Twitter Google+
Subscribe RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins