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    STUDIA GEOLOGIA - Ediţia nr.1 din 2007  
         
  Articol:   CARBON, NITROGEN AND SULFUR ISOTOPES AS EVIDENCE FOR AN ANOMALOUS OCEAN DURING RECOVERY FROM THE END PERMIAN MASS EXTINCTION.

Autori:  VIOREL ATUDOREI, SPENCER LUCAS, MICHAEL ORCHARD, JOHN-PAUL ZONNEVELD, JEAN GUEX. 		 
       
         
  Rezumat:  The Early Triassic carbon, sulfur, nitrogen, and strontium isotope records show patterns that, in concert, are unprecedented in the earth history. At the aftermath of the end-Permian mass extinction, the ocean chemistry underwent profound changes, as outlined by geochemical, sedimentological and paleontological observations. The Early Triassic carbon isotope record is marked by three positive excursions, outstanding not only by their abruptness, but also by their extreme magnitude, comparable only with Precambrian and Early Cambrian counterparts. The nitrogen isotope profile displays a negative excursion of 1.5‰ across the Lower – Middle Triassic boundary, mirroring the last carbon isotope excursion. The decrease in 􀀄15N values indicates increased nitrate availability, consistent with the onset of an upwelling system indicated by sedimentological evidence. While the nitrogen isotope anomaly is likely to be local, confined to the North American upwelling zone, it suggests a sudden increase in ocean productivity, in agreement with the carbon isotope positive excursion. Another remarkable feature of the Early Triassic stable isotope record is represented by a large sulfur isotope shift, as recorded in sedimentary sulfates, however its timing and relationship with the carbon isotope record is poorly constrained.  
         
     
         
         
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