Evolution of Tethyan phosphogenesis along the （古地中海的进化phosphogenesis沿着）.pdf

Earth-Science Reviews 78 (2006) 27 – 57 /locate/earscirev Evolution of Tethyan phosphogenesis along the northern edges of the Arabian–African shield during the Cretaceous–Eocene as deduced from temporal variations of Ca and Nd isotopes and rates of P accumulation D. Soudry a,⁎, C.R. Glenn b,1 , Y. Nathan a,2 , I. Segal a,2 , D. VonderHaar b,1 a Geological Survey Israel, 30 Malkhe Israel St., Jerusalem 95501, Israel b Department of Geology and Geophysics, University of Hawaii, Honolulu, Hawaii 96822, USA Received 19 September 2005; accepted 27 March 2006 Available online 15 May 2006 Abstract The evolution of Tethyan phosphogenesis during the Cretaceous–Eocene is examined to try to explain fluctuations of phosphogenesis through time, and whether or not they reflect long-term changes in ocean circulation or in continental weathering. Twenty-seven time-stratigraphic phosphate levels in various Tethyan sites, covering a time span of about 90 Myr from the Hauterivian to the Eocene, were analyzed for 44Ca/42Ca and 143Nd/ 144Nd in their carbonate fluorapatite (CFA) fraction. P and Ca accumulation rates and bulk sedimentation rates were quantified throughout the Cretaceous–Eocene Negev sequence to examine how changes in 44Ca/42Ca and 143Nd/ 144Nd are reflected in the intensity of phosphogenesis. A clear-cut change occurs in εNd( T) and δ44Ca and in the rates of P and Ca accumulation and bulk sedimentation through the time analyzed. εNd( T) is much lower in the Hauterivian–Lower Cenomanian (− 12.8 to − 10.9) than in the U