Provenence and paleogeographic evolution in a multi-source foreland: the Cenozoic Venetian Basin (NE Italy)

ABSTRACT: Diachronous deformation and exhumation of the Dinaric, eastern Southern Alps, and Northern Apennine belts caused a complex pattern of sedimentation and dispersal in the Venetian–Friulian Basin. Our dataset provides, for the first time, a comprehensive picture of the Cenozoic evolution across the whole basin. Growth and erosion of the three chains feeding the Venetian–Friulian Basin are here traced by combination of multiple analytical techniques. We examine the terrigenous and intrabasinal supply to the basin by using arenite petrography (gross composition, heavy minerals) and apatite fission-track analysis framed in an updated stratigraphy. Data come from both outcropping and subsurface Eocene to Pleistocene strata and are compared with the modern river sediments of the study area. On the basis of this approach, we present a schematic temporal and paleogeographic evolution of the Venetian–Friulian Basin from the Eocene to Present. During the Eocene most sediments were derived from erosion of carbonate successions within the growing Dinaric thrust belt to the east, and from its peripheral bulge to the west, where some carbonate factories were active. Oceanic rocks, probably located in the Vardar suture zone to the north, contributed little. Once Dinaric thrusting ceased, most of the detritus was derived from the northern basement of the Austroalpine realm. An abrupt paleogeographic variation caused by activation of southward-verging thrusts in the Southalpine domain occurred during the Serravallian. The drainage divide moved southward and most of the detritus was derived from the basement and related sedimentary covers of the Southern Alps. Sand composition of modern river sediments and of the Plio-Pleistocene deposits indicates that the modern hydrographic pattern of this area was already established in the Pleistocene