Tectonic vs. climate forcing in the Cenozoic sedimentary evolution of a foreland basin (Eastern Southalpine system, Italy)

ABSTRACT: This paper discusses the Cenozoic interaction of regional tectonics and climate changes.These processes were responsible for mass fux from mountain belts to depositional basins in the eastern Alpine retro-foreland basin (Venetian-Friulian Basin). Our discussion is based on the depositional architecture and basin- scale depositional rate curves obtained from the decompacted thicknesses of stratigraphic units.We compare these data with the timing of tectonic deformation in the surrounding mountain ranges and the chronology of both long-term trends and short-term highmagnitude (‘aberrant’) episodes of climate change. Our results confirm that climate forcing (and especially aberrant episodes) impacted the depositional evolution of the basin, but that tectonics was the main factor driving sediment fux in the basin up to the LateMiocene.The depositional rate remained below 0.1mmyear1 on average from the Eocene to theMiocene, peaking at around 0.36mmyear1, during periods of maximum tectonic activity in the eastern Southern Alps.This dynamic strongly changed during the Pliocene-Pleistocene, when the basin- scale depositional rate increased to an average of 0.26mmyear1 (Pliocene) and 0.73mmyear1 (Pleistocene).This result fits nicely with the long-term global cooling trend recorded during this time interval.Nevertheless, we note that the timing of the observed increase may be connectedwith the presumed onset of major glaciations in the southern fank of the Alps (0.7-0.9Ma), the acceleration of the global cooling trend (since 3-4Ma) and climate variability (in terms of magnitude and frequency). All these factors suggest that combined high-frequency and high-magnitude cooling-warming cycles are particularly powerful in promoting erosion in mid-latitude mountain belts and therefore in increasing the sediment fux in foreland basins