Abstract
The External Ligurian and Epiligurian Units in the Northern Apennines of Italy are tectonically juxtaposed with the Tertiary Piedmont Basin along the Villalvernia – Varzi Line, which represents a regional scale fault zone, E-striking. Our map, at the 1:20,000 scale, describes the tectono-stratigraphic evolution of this sector that resulted from multistage faulting along that fault zone. Four main tectonic stages are defined on the basis of the crosscutting relationships between mapped faults and stratigraphic unconformities: late Priabonian – Rupelian, Chattian – early Miocene, late Serravallian – Tortonian, and late Messinian – early Pliocene. Our results demonstrate that since the late Burdigalian, the Villalvernia – Varzi Line was sealed by the gravitational emplacement of a chaotic rock body. The deposition of the late Serravallian – early Messinian succession is controlled by NW-striking strike-slip faults that crosscut to the west the Villalvernia – Varzi Line. Extensional tectonics related to regional scale N-dipping tilting characterized the late Messinian – early Pliocene time interval.
Highlights
The Villalvernia – Varzi Line (Fig. 1) is an E-striking and steeply dipping regional fault zone, separating the External Ligurian Units and Epiligurian Units of the Northern Apennines, to theNorth, from the Tertiary Piedmont Basin, to the South
South of the Villalvernia – Varzi Fault Zone, the Tertiary Piedmont Basin is characterized by a regular NW-dipping Oligocene – Pliocene monocline that is bounded to NW by the NW-striking
Apennines and Tertiary Piedmont Basin, which occur along the Villalvernia – Varzi Fault Zone
Summary
The Villalvernia – Varzi Line (Fig. 1) is an E-striking and steeply dipping regional fault zone, separating the External Ligurian Units and Epiligurian Units of the Northern Apennines, to the. From the Tertiary Piedmont Basin, to the South It has controlled the early Oligocene – Miocene tectono-sedimentary evolution of this area (e.g., Boni, 1961; Gelati et al, 1974; Ghibaudo et al, 1985; Di Giulio and Galbiati, 1995; Mutti et al, 1995; Felletti, 2002; Mosca et al, 2010), and played a significant role in the westward-indentation of the Adria microplate (i.e., part of the African plate) with the Western Alpine belt (see Laubscher et al, 1992; Castellarin, 1994; Mosca et al, 2010 and reference therein). A detailed geological mapping of this regional tectonic “Line” is of societal significance and important to better understand the tectono-stratigraphic evolution of the Northern Apennines and Tertiary Piedmont Basin. The studied sector is crucial for better understanding the multistage tectonic evolution of this “Line” and its geological control on the Oligocene – Miocene tectono-sedimentary evolution in this area located in between the Northern Apennines and the Tertiary Piedmont Basin
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