GEOCHEMICAL EVENTS DOCUMENTED IN INORGANIC CARBON ISOTOPES

Screening of sampling and analytical data is crucial for the detection of real global shifts in marine delta(13)C, against the noise of diag enesis. The real global shifts of C-13 are of two types. (1) long-term secular shifts caused by changes in the fractional burial of organic carbon, and (2) transient shifts caused by abrupt changes of biologica l productivity in the surface photic zone. Both are applicable to stra tigraphic correlation, but differ in their application to modelling of changes in oceanographic or atmospheric composition. A recent compila tion found 34 carbon isotope events in the Phanerozoic and Neoproteroz oic, equally distributed among positive and negative shifts. This in i tself attests to a variety of proximate causes of the shifts. (C) 1997 Elsevier Science B.V.