The Ra Stua section: A puzzle piece of the Early Cretaceous history of the Dolomites (Trento Plateau, N. Veneto, Italy)

Abstract

A Barremian hemipelagic succession from Ra Stua in the Dolomites (Southern Alps, northern Italy) is investigated stratigraphically. A short Barremian section was studied with regard to biostratigrapy, lithology, chemostratigraphy and geophysics and subsequently compared to known isochronic palaeomagnetic data and sea levels changes. The results are linked to magnetostratigraphic datasets of the same depositional area on the Trento plateau, yielding a detailed and robust age calibration of the Ra Stua succession. The Lower Cretaceous Ra Stua Formation in the Dolomites is assigned as lower Barremian (Taveraidiscus hugii Zone) to lower upper Barremian (Toxancyloceras vandenheckii Zone). Ammonoids enable a first biostratigraphic subdivision for that puzzling section at Ra Stua. This forms the basis for analyses of the faunal distribution and the palaeoenvironmental evolution of the northerneastern Trento Plateau on the western edge of the Cretaceous Tethys. The Ra Stua section is an enigmatic jigsaw piece correlatable to the Barremian of the entirely preserved sections in the Puez area. The succession consists of marlstones to marly limestone alternations of the Lower Cretaceous. These deposits cover only restricted areas in the Dolomites, but the facies type appears isochronically over wide areas in the Tethys. Lower Cretaceous successions from the Ra Stua area are known, but this isolated block is studied in detail for the first time. The Puez Formation occurs at the Ra Stua section with the Puez-Limestone Member, known as the lowermost member at the type section in the Puez area.