Dating thrust Events Using 87Sr/86Sr: an example from the Northern Apennines, Italy

Isotopic and petrographic analyses of the major thrust zone (Calcare Cavernoso) in the Apuane region of the Northern Apennines are used to date the timing of motion on that thrust zone and to document the type and the amount of fluid focused there. 87Sr/86Sr isotopic compositions of clasts and matrix from around the entire Apuane region are very uniform, with values that average 0.70811. The strontium data suggest recrystallization of the entire thrust zone by huge volumes of focused fluid flow that caused complete and uniform resetting of the original Triassic Sr isotopic signature by Oligocene sea water during Oligocene thrusting.