The 18O record of phanerozoic abiotic marine calcite cements
نویسندگان
چکیده
Monomineralic, abiotic marine cements formed in low-latitude Phanerozoic reefs provide the direction and amplitude of secular variation of õ•3C and õ•80 in marine calcite and defines two end member compositions580 to 360 my (-7 to-5 %0 õ•8Om)B) and 360 to present (-3 to 0 %0 õ•8Om)B). Sampling of the Devono-Carboniferous tran ition (375-320 my) at several global sites reveals a rapid change in carbonate isotopic compositions. Bracketed within Fammenian to Early Visean-aged strata, a 7 to 15 my time interval, this shift corresponds toa 2 %0 offset in mean and 3-4 %0 offset in õ•80. The abruptness of such change, and its overall correlation with variations in 87Sr/86Sr, õ-34S, b•3C, and Li/A1 ratios in marine sediments suggests a primary offset in marine water composition.
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