Paleoenvironmental Reconstruction of the Oligocene Transgression in the Central-Eastern Tertiary Piedmont Basin (Nw Italy): Insights From Stratigraphy, Paleontology and Gamma-Ray Emissions

This study presents the first integrated lithostratigraphical, paleontological and spectral gamma-ray (SGR) dataset from the central-eastern sector of the Tertiary Piedmont Basin (TPB). The TPB is a late- to post-orogenic sedimentary basin system deposited during a widespread marine transgression. The Molare Formation of the TPB records the evolution of shallow-marine depositional systems developed within a tectonically active basin during the Oligocene. By integrating stratigraphic, sedimentological, and paleontological observations, together with SGR data, from four stratigraphic sections (Sottovalle, Bric Rive, Lemme, and Bosio; Southeastern Piedmont, Italy), this work reconstructs paleoenvironmental conditions and assess lateral variability in the central-eastern sector of the basin. The studied intervals are dominated by conglomerates and medium- to coarse-grained sandstones, recording high-energy shallow-marine sedimentation. Paleontological assemblages are dominated by Larger Benthic Foraminifera (LBF) and scleractinian corals, providing complementary constraints on water depth and energy conditions. SGR of Potassium (K), Uranium (U), Thorium (Th) and the derived Th/U ratio, measured along each succession, were used to evaluate terrigenous input and redox conditions. Results reveal pronounced lateral variability among the sections, with fossil-rich intervals corresponding to phases of reduced sediment input and relatively stable shallow-marine conditions, alternating with barren or poorly fossiliferous intervals associated with high-energy sedimentation and enhanced continental influence. The integrated dataset documents a siliciclastic system characterized by rapid environmental fluctuations driven by variable sediment supply and active tectonics. This study highlights the importance of combining paleontological and gamma-ray proxies to resolve complex depositional architectures in tectonically influenced shallow-marine basins such as the TPB.