Carbon and oxygen isotope data for carbonates and benthic foraminifers from ODP Hole 113-689B

A simultaneous surface-water productivity increase, as interpreted from d13C data, is explained by enhanced water-column mixing due to increased latitudinal temperature gradients.

These isotope data appear to be in concert with organic-walled dinoflagellate-cyst records across the same microkrystite-bearing impact-ejecta layer in the mid-latitude Massignano section (central Italy). In particular, the strong abundance increase of Thalassiphora pelagica is interpreted to indicate cooling or increased productivity at Massignano. Because impact-induced cooling processes are active on time scales of a few years at most, the estimated 100 k.y. duration of the cooling event appears to be too long to be explained by impact scenarios alone.