MSGID: 1:317/3 63d4a4f4   
   PID: hpt/lnx 1.9.0-cur 2019-01-08   
   TID: hpt/lnx 1.9.0-cur 2019-01-08   
    Mercury helps to detail Earth's most massive extinction event    
      
     Date:   
         January 27, 2023   
     Source:   
         University of Connecticut   
     Summary:   
         Scientists are working to understand the cause and how the events   
         of the LPME unfolded by focusing on mercury from Siberian volcanoes   
         that ended up in sediments in Australia and South Africa.   
      
      
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   FULL STORY   
   ==========================================================================   
   The Latest Permian Mass Extinction (LPME) was the largest extinction in   
   Earth's history to date, killing between 80-90% of life on the planet,   
   though finding definitive evidence for what caused the dramatic changes   
   in climate has eluded experts.   
      
      
   ==========================================================================   
   An international team of scientists, including UConn Department of   
   Earth Sciences researchers Professor and Department Head Tracy Frank and   
   Professor Christopher Fielding, are working to understand the cause and   
   how the events of the LPME unfolded by focusing on mercury from Siberian   
   volcanoes that ended up in sediments in Australia and South Africa. The   
   research has been published in Nature Communications.   
      
   Though the LPME happened over 250 million years ago, there are   
   similarities to the major climate changes happening today, explains   
   Frank: "It's relevant to understanding what might happen on earth in   
   the future. The main cause of climate change is related to a massive   
   injection of carbon dioxide into the atmosphere around the time of the   
   extinction, which led to rapid warming."  In the case of the LPME, it   
   is widely accepted that the rapid warming associated with the event is   
   linked to massive volcanism occurring at a huge deposit of lava called   
   the Siberian Traps Large Igneous Province (STLIP), says Frank, but direct   
   evidence was still lacking.   
      
   Volcanos leave helpful clues in the geological record. With the outpouring   
   of lava, there was also a huge quantity of gases released, such as CO2   
   and methane, along with particulates and heavy metals that were launched   
   into the atmosphere and deposited around the globe.   
      
   "However, it's hard to directly link something like that to the extinction   
   event," says Frank. "As geologists, we're looking for a signature of some   
   kind -- a smoking gun -- so that we can absolutely point to the cause."   
   In this case, the smoking gun the researchers focused on was mercury,   
   one of the heavy metals associated with volcanic eruptions. The trick   
   is finding areas where that record still exists.   
      
   Frank explains there is a continuous record of the earth's history   
   contained in sediments in marine environments which acts almost like a   
   tape recorder because deposits are quickly buried and protected. These   
   sediments yield an abundance of data about the extinction and how it   
   unfolded in the oceans. On land, it is more difficult to find such   
   well-preserved records from this time period.   
      
   To illustrate this, Frank uses Connecticut as an example: the state is   
   rich with 400-500-million-year-old metamorphic rocks at or near the   
   surface, with a covering of glacial deposits dating to around 23,000   
   years ago.   
      
   "There's a big gap in the record here. You have to be lucky to preserve   
   terrestrial records and that's why they aren't as well studied, because   
   there are fewer of them out there," says Frank.   
      
   Not all terrains around the world have such massive gaps in the geologic   
   record, and previous studies of the LPME have focused primarily on sites   
   found in the northern hemisphere. However, the Sydney Basin in Eastern   
   Australia and the Karoo Basin in South Africa are two areas in the   
   southern hemisphere that happen to have an excellent record of the event,   
   and are areas Frank and Fielding have studied previously. A colleague   
   and co-author, Jun Shen from the State Key Laboratory of Geological   
   Processes and Mineral Resources at the China University of Geosciences,   
   reached out and connected with Frank, Fielding, and other co-authors   
   for samples, with hopes to analyze them for mercury isotopes.   
      
   Shen was able to analyze the mercury isotopes in the samples and tie   
   all the data together says Frank.   
      
   "It turns out that volcanic emissions of mercury have a very specific   
   isotopic composition of the mercury that accumulated at the extinction   
   horizon. Knowing the age of these deposits, we can more definitively tie   
   the timing of the extinction to this massive eruption in Siberia. What   
   is different about this paper is we looked not only at mercury, but the   
   isotopic composition of the mercury from samples in the high southern   
   latitudes, both for the first time."  This definitive timing is something   
   that scientists have been working on refining, but as Fielding points out,   
   the more that we learn, the more complicated it gets.   
      
   "As a starting point, geologists have pinpointed the timing of the major   
   extinction event at 251.9 million years with a high degree of precision   
   from radiogenic isotope dating methods. Researchers know that is when   
   the major extinction event happened in the marine environment and it   
   was just assumed that the terrestrial extinction event happened at the   
   same time."  In Frank and Fielding's previous research, they found that   
   the extinction event on land happened 200-600,000 years earlier, however.   
      
   "That suggests that the event itself wasn't just one big whammy that   
   happened instantaneously. It wasn't just one very bad day on Earth,   
   so to speak, it took some time to build and this feeds in well into   
   the new results because it suggests the volcanism was the root cause,"   
   says Fielding. "That's just the first impact of the biotic crisis that   
   happened on land, and it happened early.   
      
   It took time to be transmitted into the oceans. The event 251.9 million   
   years ago was the major tipping point in environmental conditions in   
   the ocean that had deteriorated over some time."  Retracing the events   
   relies on knowledge from many different geologists all specializing   
   in different methods, from sedimentology, geochemistry, paleontology,   
   and geochronology, says Frank, "This type of work requires a lot of   
   collaboration. It all started with fieldwork when a group of us went   
   down to Australia, where we studied the stratigraphic sections that   
   preserved the time interval in question. The main point is that we now   
   have a chemical signature in the form of mercury isotope signatures,   
   that definitively ties the extinction horizon in these terrestrial   
   sections that provide a record of what was happening on land due to   
   Siberian Traps volcanism."   
       * RELATED_TOPICS   
             o Earth_&_Climate   
                   # Climate # Global_Warming # Geology # Earth_Science   
             o Fossils_&_Ruins   
                   # Early_Climate # Fossils # Dinosaurs # Origin_of_Life   
       * RELATED_TERMS   
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             Timeline_of_environmental_events o Mountain   
      
   ==========================================================================   
   Story Source: Materials provided by University_of_Connecticut. Original   
   written by Elaina Hancock. Note: Content may be edited for style and   
   length.   
      
      
   ==========================================================================   
   Journal Reference:   
      1. Jun Shen, Jiubin Chen, Jianxin Yu, Thomas J. Algeo, Roger   
      M. H. Smith,   
         Jennifer Botha, Tracy D. Frank, Christopher R. Fielding, Peter   
         D. Ward, Tamsin A. Mather. Mercury evidence from southern Pangea   
         terrestrial sections for end-Permian global volcanic effects. Nature   
         Communications, 2023; 14 (1) DOI: 10.1038/s41467-022-35272-8   
   ==========================================================================   
      
   Link to news story:   
   https://www.sciencedaily.com/releases/2023/01/230127131139.htm   
      
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