The Pleistocene tectono-stratigraphic evolution of the northern Po Plain (Italy) around the Castenedolo and Ciliverghe hillocks

Abstract

Abstract We studied the Pleistocene subsurface stratigraphy of an area in the northern Po Plain around the isolated tectonic hillocks of Castenedolo and Ciliverghe (Brescia, Italy) in order to estimate their long-term rates of tectonic deformation. Integrated stratigraphy of a new 100-m-long core (RL13) allowed better definition of the regional Y (0.45 Ma) and R (0.87 Ma) surfaces and the related magnetostratigraphically calibrated PS1, PS2, and PS3 depositional sequences. The Y surface in the RL13 core was placed at the base of the PS3 proximal braided river system that was deposited during middle Pleistocene within the Brunhes chron. The R surface is considered to be eroded within the PS2 braid-plain deposits at ca. 0.87 Ma between the top of Jaramillo subchron and the Bruhnes chron during the late Early Pleistocene. Based on different datasets, we evaluated the sedimentation rate, which has decreased from 0.09 mm/yr with deposition of PS2, to 0.06 mm/yr with deposition of PS3. The tectonic uplift, with an average rate of ~0.1 mm/yr in the last ca. 0.87 Ma, is interpreted to be associated with a fault and related fault-propagation folding. The Castenedolo and Ciliverghe hillocks then formed due to tectonic uplift during a change in the sedimentation regime since 0.45 Ma.