Multistratigraphic records of the Lower Cretaceous (Valanginian-Cenomanian) Puez key area in N. Italy

摘要

We present a stratigraphic investigation of a Hauterivian to Cenomanian hemipelagic succession from Col Puez, in the Dolomites (Southern Alps, northern Italy). A composite section of seven segments was studied with bio-, magneto-, and chemostratigraphy, which enabled detailed and robust age calibration of the Puez succession. It also revealed the paleoceanographic history and helped identify the important global climatic events of that period. The age of the Lower Cretaceous Puez Formation in the Dolomites is refined as late Hauterivian to early Cenomanian. Ammonoids provide a detailed biostratigraphic subdivision that forms the basis for analyses of the faunal distribution and the paleoenvironmental evolution of basins and plateaus across the Tethys. The succession consists of fades similar to those of coeval units in the Tethys, apart from the late Barremian to late Aptian interval, which is marked by a major hiatus followed by a few-meters-thick redbed of late Aptian age. The Lower Cretaceous was characterized by a weak (similar to 1%.) positive delta C-13 trend, punctuated by a positive shift in the late Hauterivian corresponding to the Faraoni Level. Oxygen isotope values show a decreasing trend from the Hauterivian to the Albian/Cenomanian, which mirrors a long-term increasing trend in paleotemperatures from similar to 15-18 degrees C to similar to 25-30 degrees C. This is in agreement with global paleotemperature reconstructions for this period representing the onset of mid-Cretaceous super-greenhouse conditions. Nonetheless, no black shale occurs at the intervals equivalent to Aptian-Albian oceanic anoxic events (OAE), suggesting unique paleoceanographic conditions (enhanced current activity on a submarine height) on the Trento Plateau area during the mid Cretaceous. (C) 2016 Elsevier B.V. All rights reserved.