MSGID: 1:317/3 63f6ebe5   
   PID: hpt/lnx 1.9.0-cur 2019-01-08   
   TID: hpt/lnx 1.9.0-cur 2019-01-08   
    Early Cretaceous shift in the global carbon cycle affected both land and   
   sea    
    New study deepens understanding of present-day changes in Earth's   
   environmental systems    
      
     Date:   
         February 22, 2023   
     Source:   
         University of Nebraska-Lincoln   
     Summary:   
         Geologists doing fieldwork in southeastern Utah's Cedar Mountain   
         Formation found carbon isotope evidence that the site, though   
         on land, experienced the same early Cretaceous carbon-cycle   
         change recorded in marine sedimentary rocks in Europe. This   
         ancient carbon-cycle phenomenon, known as the 'Weissert Event'   
         was driven by large, sustained volcanic eruptions in the Southern   
         Hemisphere that greatly increased carbon dioxide levels in the   
         atmosphere and produced significant greenhouse climate effects   
         over a prolonged time.   
      
      
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   FULL STORY   
   ==========================================================================   
   Scientists continue to refine techniques for understanding present-day   
   changes in Earth's environmental systems, but the planet's distant   
   past also offers crucial information to deepen that understanding. A   
   geological study by University of Nebraska-Lincoln scientist Matt Joeckel   
   and colleagues provides such information.   
      
      
   ==========================================================================   
   Scientific research in recent decades has confirmed that major changes   
   in the global carbon cycle caused significant changes in the Earth's   
   atmosphere and oceans 135 million years ago, during the early Cretaceous   
   Period. A range of questions remain about the details of climate change   
   dynamics in that era. This new research, involving wide-ranging chemical   
   and radioactivity-based analyses of rock strata in Utah's Cedar Mountain   
   Formation, helps fill in that knowledge gap by confirming that such   
   carbon-cycle shifts were recorded on land in ancient North America.   
      
   The carbon cycle is one of Earth's fundamental environmental phenomena,   
   involving the ongoing transfer of carbon among the atmosphere, oceans   
   and living organisms, as well as soils, sediments and rocks in the solid   
   Earth. The cycle is crucial to biological processes for living things   
   on land and sea.   
      
   When large-scale changes in the cycle occur, they can produce major   
   shifts in climate and the oceans' biological conditions.   
      
   "We're studying how the global carbon cycle has functioned in the past,   
   how changes are recorded in the sedimentary rocks around the world," said   
   Joeckel, a professor in the School of Natural Resources at Nebraska. The   
   environmental phenomena he and his colleagues analyzed "are exactly the   
   kind of things we're talking about today, as people increase the input of   
   carbon dioxide into the atmosphere at a much-accelerated rate by burning   
   fossil fuels."  Joeckel, the Nebraska state geologist, headed the Utah   
   fieldwork and organized the study, published as a peer-reviewed paper   
   in a special February issue of the journal Geosciences.   
      
   Over the past two decades, Joeckel and several colleagues have studied   
   a range of geological aspects of southeastern Utah's Cedar Mountain   
   Formation, known for its exceptional dinosaur fossils. The steep,   
   150-foot slope where the scientists conducted their recent carbon-cycle   
   research is known as Utahraptor Ridge, named for the discovery there of   
   raptors, the ferocious bipedal predators familiar to moviegoers through   
   the Jurassic Park movies.   
      
   To determine whether carbon-cycle changes have occurred, scientists   
   analyze the minute amounts of organic carbon held in rocks for major   
   changes in two carbon isotopes. Carbon cycles are evident if scientists   
   find that significant increases and decreases in isotope ratios occurred   
   over time. Joeckel and his colleagues found evidence for two distinct   
   peaks in a curve representing changes in a key isotope ratio during the   
   early Cretaceous period. This discovery indicates that the Utah site,   
   though on land, experienced the same major carbon-cycle change recorded   
   in marine sedimentary rocks in Europe.   
      
   Many geologists refer to this ancient carbon-cycle phenomenon as the   
   "Weissert Event," which was driven by large, sustained volcanic eruptions   
   in the Southern Hemisphere. These eruptions greatly increased carbon   
   dioxide levels in the atmosphere, producing significant greenhouse   
   climate effects over a prolonged time.   
      
   A central uncertainty has been whether carbon-cycle changes recorded in   
   sediments in ancient oceans were also recorded by sediments on land. The   
   work by Joeckel and his colleagues strongly suggests that happened.   
      
   Analyzing the Utah samples for these carbon isotope changes was a   
   challenging scientific endeavor, said Joeckel, director of Nebraska's   
   state Conservation and Survey Division, which conducts a wide array of   
   geological, geographic, water and soil research in the state and beyond.   
      
   "We're talking about a minute amount of organic carbon that has to be   
   very laboriously isolated from fist-sized samples of sedimentary rock,"   
   he said.   
      
   Such complex work is "like having to go through a whole pile of phone   
   books by hand just to get to the point where you can generate numbers,   
   and you have to generate a lot of them. There's a lot of hard work in the   
   laboratory that needs to be done."  To accurately date the carbon-cycle   
   changes, the scientists also analyzed microscopic crystals of the mineral   
   zircon. These crystals "are important because they are a way to actually   
   put an age date on the rocks," Joeckel said.   
      
   The volcanically produced zircon crystals are "nearly indestructible   
   treasure troves of information that are spread all over the place"   
   after an eruption.   
      
   Joeckel's coauthors on the paper are Celina Suarez and Garrett Hatzell of   
   the University of Arkansas; Noah McLean, Andreas Mo"ller, Marina Suarez   
   and Joseph Andrew of the University of Kansas; Gregory Ludvigson and   
   Spencer Kiessling of the Kansas Geological Survey; and James Kirkland   
   of the Utah Geological Survey.   
      
   The project, Joeckel said, illustrates how geology as a discipline   
   continues to reveal new insights.   
      
   "In some ways, the past may be the key to the present, rather than vice   
   versa, as geologists traditionally posited," he said. "The better we   
   understand the ancient carbon cycle and ancient global change, the more   
   we can understand what happens today."   
       * RELATED_TOPICS   
             o Earth_&_Climate   
                   # Geochemistry # Global_Warming # Climate # Earth_Science   
             o Fossils_&_Ruins   
                   # Early_Climate # Fossils # Ancient_Civilizations #   
                   Origin_of_Life   
       * RELATED_TERMS   
             o Carbon_dioxide o Carbon_cycle o Forest o Carbon_dioxide_sink o   
             Global_climate_model o Ocean_acidification o Climate_engineering   
             o Climate_change_mitigation   
      
   ==========================================================================   
   Story Source: Materials provided   
   by University_of_Nebraska-Lincoln. Original written by Geitner   
   Simmons. Note: Content may be edited for style and length.   
      
      
   ==========================================================================   
   Journal Reference:   
      1. Robert M. Joeckel, Celina A. Suarez, Noah M. McLean, Andreas   
      Mo"ller,   
         Gregory A. Ludvigson, Marina B. Suarez, James   
         I. Kirkland, Joseph Andrew, Spencer Kiessling, Garrett   
         A. Hatzell. Berriasian-Valanginian Geochronology and Carbon-Isotope   
         Stratigraphy of the Yellow Cat Member, Cedar Mountain Formation,   
         Eastern Utah, USA. Geosciences, 2023; 13 (2): 32 DOI:   
         10.3390/geosciences13020032   
   ==========================================================================   
      
   Link to news story:   
   https://www.sciencedaily.com/releases/2023/02/230222141149.htm   
      
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