Geochronology and calibration of global Milankovitch cyclicity at the Cenomanian-Turonian boundary

New Ar-40/Ar-39 geochronology and global cyclostratigraphic calibration pro vide high-resolution insights into the timing of geochemical fluctuations a cross oceanic anoxic event II (OAE II). Five new Ar-40/Ar-39 data from a si ngle section in western Canada suggest an age of 96.4 +/- 1 Ma for the Ceno manian-Turonian (C-T) boundary. This is similar to3 m.y. older than previou sly dated. Time-series analysis (e.g., wavelet transform) reveals that OAE II was synchronously deposited worldwide over a period of similar to 320 k. y. The preservation and stationarity of Milankovitch cyclicity in sections across the Atlantic indicates that no major fluctuations in sedimentation r ate occur across the OAE II, except for a minor shortterm decrease in the r ate just before the C-T boundary. A delta C-13(org) increase of >2 parts pe r thousand took place at the beginning of OAE II over a period of similar t o 110 k.y., and likely represents a period of worldwide excessive organic c arbon burial during transgression, leading to a C-12 depletion of seawater and sedimentation. This interval was followed by a three-step decrease to p re-OAF II delta C-13 values.