From: baalke@zagami.jpl.nasa.gov   
      
   Press Office   
   Royal Holloway College   
   University of London   
   Egham, Surrey, U.K.   
      
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   Christine Long, Press & PR Officer   
   01784 443967 email: christine.long@rhul.ac.uk   
      
   5 December 2003   
      
   Global wildfires did not kill the dinosaurs   
      
   New research has revealed that thermal radiation, resulting from the impact of   
   an asteroid colliding with the United States 65 million years ago, was not   
   responsible for the extinction of dinosaurs and other land organisms.   
      
   The massive 65 million year old impact crater, Chicxulub, on the Yucatan   
   Peninsula in Mexico, was first located by Alan Hildebrand and co-workers in   
   1991. The discovery led scientists to conclude that large amounts of thermal   
   radiation released by the asteroid's impact would have raised ground   
   temperatures to around 1000 C, igniting globally extensive forest fires and   
   effectively boiling land organisms alive.   
      
   However, new NERC funded research, shows that although forest fires played an   
   important part in the latest Cretaceous and earliest Tertiary ecosystems, there   
   is no evidence that North America was engulfed by wildfires 65 million years   
   ago.   
      
   The research team from Royal Holloway, University of London, was led by Claire   
   Belcher with co-workers Professor Margaret Collinson, Professor Andrew Scott,   
   and members of the Canadian Geological Survey and University of Calgary. The   
   team studied quantities of fossil charcoal from the Cretaceous-Tertiary (K-T)   
   boundary sediments from non-marine rocks across North America, to test the   
   hypothesis that extensive forest fires occurred as a result of thermal   
   radiation   
   released by the impact. Details of the research will appear in the December   
   issue of Geology (volume 31).   
      
   The latest Cretaceous and earliest Tertiary rocks were found to contain an   
   average of 16.3% charcoal, but neighbouring K-T rocks showed only 1.75%. More   
   surprisingly, the K-T rocks also revealed considerable amounts of unaffected   
   plant remains, with some sites containing as much as 60% non-charred plant   
   fragments.   
      
   "If we assume that extensive wildfires consumed the vegetation across the North   
   American continent, it is hard to imagine a situation where so much plant   
   material remained un-charred. This does not support the theory that North   
   America was engulfed by wildfires at this time," said Claire Belcher, from   
   Royal   
   Holloway's Department of Geology.   
      
   The revelations led Belcher's team to further question the amount of thermal   
   radiation released from the K-T impact. Spontaneous ignition of biomass occurs   
   at around 545 C and vegetation will begin to smoulder when subjected to   
   temperatures around 325 C. This suggests that ground temperatures cannot have   
   been greater than 325 C, and no more than 6 kW.m-2 of thermal power was   
   delivered to the ground for any significant length of time, compared with   
   considerably higher previous estimates of 5000kW.m-2 and 150kW. m-2 .   
      
   Art Sweet, from the Canadian Geological Survey and a co-worker on the project,   
   explains "It is recognised that major disruptions occurred in both plant and   
   animal communities at this time, but the new findings indicate that these are   
   not coincident with increased abundances of charcoal".   
      
   Belcher concludes, "The research we have carried out suggests that the amounts   
   of thermal radiation released by the impact of an asteroid with the Earth 65   
   million years ago, were not as significant as previously thought, and the   
   energy   
   component of the K-T event was not responsible for the extinctions seen at this   
   time".   
      
   Belcher hopes that research may now focus on addressing other hypotheses, which   
   may explain the extinction patterns and disruptions seen at this time,   
   including   
   the death of the dinosaurs.   
      
   ENDS   
      
   Editor's notes   
      
   Claire Belcher -- PhD student at Royal Holloway, University of London. Research   
   focuses on assessing the evidence for extensive wildfires at the K-T boundary.   
   Claire is keen to use the data collected on wildfires to address the amounts of   
   thermal energy released by the K-T impact. Other interests include the   
   preservation of wildfire in the fossil record. (Msc UCL, Micropalaeo, Bsc at   
   Royal Holloway, University of London, Geology)   
      
   Prof. Margaret Collinson -- Reader in plant palaeobiology. She also has a keen   
   interest in the K-T boundary particularly in the water plant Azolla that can be   
   found in and around the K-T boundary deposits across North America. She also   
   continues active research on plant palaeobiology including charred plant   
   specimens.   
      
   Dr. Art Sweet specialises in palynology at the Geological Survey of Canada in   
   Calgary. He has researched the record of plants across the K-T boundary for   
   many   
   years and has published considerable work on the Canadian K-T sites.   
      
   Dr. Alan Hildebrand has worked extensively on the K-T boundary, making one of   
   the largest contributions to this field in recent years by discovering the   
   Chicxulub impact crater. He still actively researches the K-T but is also   
   focusing on planetary geology and asteroid identification.   
      
   Prof. Andrew Scott specialises in coal geology and the Pre Quaternary history   
   of   
   palaeo wildfires. He has probably researched and published more work than any   
   one else on palaeo wildfires.   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)