Geology of the Curone and Staffora Valleys (NW Italy): field constraints for the Late Cretaceous – Pliocene tectono-stratigraphic evolution of Northern Apennines

Abstract

In the northwestern part of Northern Apennines, between Curone and Staffora Valleys, the tectonic superposition between the External Ligurian Units (i.e. the ophiolitic-bearing chaotic complex of the Groppallo Unit and the non-ophiolitic Cassio Unit), the Middle Eocene-Miocene wedge-top basin Epiligurian Units succession, and the Late Messinian-Pliocene Po Plain succession, records the multistage tectono-stratigraphic evolution from subduction to continental collision. Our geological map, at the 1:20,000 scale, allows us to define 6 main tectonic stages on the basis of (i) the crosscutting relationships between main faults and local to regional stratigraphic unconformities and (ii) the differentiation among different types of chaotic rock unit (olistostromes and broken formations) deposited since Late Cretaceous to late Messinian. This approach provides a new understanding on the tectono-stratigraphic evolution of this sector, and its meaning in the evolution of the northwestern part of Northern Apennines.

Geology of the San Colombano hill, a Quaternary isolated tectonic relief in the Po Plain of Lombardy (Northern Italy)

“…Some uncertainty affects the presence of Pliocene sediments above the SAF at the hillslopes (Anfossi & Brambilla, 1980). This sequence differs from that exposed southwards in the Epiligurian, post-Messinian and Tertiary Piedmont Basin sequences of the Northern Apennine outcrops, which show more complete Mio-Pliocene successions, as well as from the Po Plain subsurface sequences which record the coeval tectonic stages (Figure 1; Barbero, Festa, Fioraso, & Catanzariti, 2017;Ghielmi, Minervini, Nini, Rogledi, & Rossi, 2013;Rossi, 2017;Rossi, Minervini, Ghielmi, & Rogledi, 2015;Vercesi et al, 2015). Furthermore, the Calabrian San Colombano Fm.…”

Short-Term GIS Analysis for the Assessment of the Recent Active-Channel Planform Adjustments in a Widening, Highly Altered River: The Scrivia River, Italy

“…The geologic setting of the Scrivia basin is characterized by the tectonic units involved both in the Alps and the Northern Apennines orogeny. The outcropping geologic formations belong to the Ligurian and Epiligurian Units and to the post-orogenic sedimentary successions of the Tertiary Piedmont Basin [46][47][48][49][50]. These geologic complexes overall consist of a wide range of sedimentary rocks such as shales, marls, marly limestones, mudstones, sandstones and conglomerates.…”

Distinguishing the Mélange-Forming Processes in Subduction-Accretion Complexes: Constraints from the Anisotropy of Magnetic Susceptibility (AMS)

“…The broken formation (sensu [45]) corresponds to the Upper Cretaceous Argille varicolori of the External Ligurian units (Figure 2), which results from the fragmentation and disruption of an originally coherent well-bedded stratigraphic succession made of varicolored clay, shale, and marl, alternating with limestone, sandstone, and manganiferous siltstone in decimeter-thick beds. Its block-in-matrix fabric was mainly acquired through layer-parallel extension/contraction occurring at the wedge front of the Ligurian accretionary complex during the Late Cretaceous-middle Eocene oceanic subduction stage (e.g., [33,34,40,47,74,77,78]).…”

“…During this stage, related to the east-dipping Alpine subduction, a consistent part of the External Ligurian units (i.e., the Basal complex Auct.) was strongly deformed, leading to the formation of different types of chaotic units (i.e., broken formations and tectonic mélanges) (e.g., [18,33,34,40,71,[73][74][75][76][77][78]). Since the middle-late Eocene, the wedge-top basin succession of the Epiligurian units unconformably covered the Ligurian accretionary complex and the north-to northeast-verging thrust-related structures, which formed during the west-dipping Apennine subduction of the thinned continental margin of Adria (e.g., [67,76]).…”

“…Since the middle-late Eocene, the wedge-top basin succession of the Epiligurian units unconformably covered the Ligurian accretionary complex and the north-to northeast-verging thrust-related structures, which formed during the west-dipping Apennine subduction of the thinned continental margin of Adria (e.g., [67,76]). Different types of mass-transport deposit (MTDs), including sedimentary mélanges (i.e., olistostromes), occur at different stratigraphic levels within the wedge-top basins succession, marking different stages of slope instability (e.g., [18,21,34,73,[75][76][77][78][79][80][81][82][83][84][85][86][87]).…”