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

Abstract

The 1:10,000 geological map of the San Colombano hill covers 60 km 2 in the Po Plain, south of Milan. The new and the historical surface geological data-sets are managed by a GeoDB aiming to contribute to re-interpret the Quaternary evolution at the Po Plain-Northern Apennine border. On the hill, the Calabrian shallow marine San Colombano Fm. unconformably overlies the truncated deeper-marine Miocene formations, up-thrusted by the external fronts of the Apennine Emilian Arc during Mio-Pliocene. Late Pleistocene alluvial units rest in unconformity above the marine succession both on the uplifted hilltop and on the surrounding plain. Fault-related offset of Late Pleistocene units, stratigraphic and morphostructural evidences (facets, relic surfaces and drainage patterns), document the Quaternary tectonic history. Early to Middle Pleistocene ongoing thrust-folding at the northernmost buried reaches of the Emilian Arc was followed by Latest Pleistocene-Holocene transtension, possibly relating to the NNE striking Pavia-Casteggio lateral ramp.

From cylindrical to non‐cylindrical foreland basin: Pliocene–Pleistocene evolution of the Po Plain–Northern Adriatic basin (Italy)

“…in Figure a). Example of a rare NA outcrop can be found in the San Colombano hill, an isolated relief in the middle of the plain (Toscani et al, ; Zuffetti, Bersezio, Contini, & Petrizzo, ; Zuffetti, Bersezio, & Trombino, ) (a in Figure a). According to several authors, the origin of the structural salients was strongly controlled by thickness variations in the stratigraphic succession on the downbending Adria microplate, corresponding to abrupt, tectonic‐controlled rheological changes (Ravaglia, Seno, Toscani, & Fantoni, ; Ravaglia, Turrini, & Seno, ; Turrini et al, , ).…”

Soil evolution and origin of landscape in a late Quaternary tectonically mobile setting: The Po Plain-Northern Apennines border in Lombardy (Italy)

“…Since the Pleistocene, the San Colombano structure has been involved in uplift and dextral wrenching, driven by the Nwards propagation of the S. Angelo Lodigiano frontal thrust along the Pavia lateral ramp (SAT and PR, respectively, Fig. 1; Bigi et al, 1990;Benedetti et al, 2003) and dissected by repetitive faulting events up to the Latest Pleistocene (Zuffetti et al, 2018). To the East, the S. Angelo thrust intersects the WNW-ESE oriented Mio-Pliocene structures buried below the Casalpusterlengo and Zorlesco reliefs (Desio, 1965;Cremaschi, 1987;Anfossi et al, 1971), where recent stratigraphic studies documented active folding and uplift during the Middle-Late Pleistocene (Bersezio et al, 2016(Bersezio et al, , 2010.…”

“…The area belongs to the Quaternary Po Basin, which represents the foredeep of the Northern Apennines, pinched in between this N-wards verging orogen and the Alpine chain to the North. Quaternary Apennine faulting and folding affected the gently SE-wards sloping, Alpine-sourced alluvial sediments, resulting in the origin of some tectonic reliefs which at present stand isolated in the centre of the Po alluvial plain and close to both the Alpine and Apennine basin margins (Alfano and Mancuso, 1996;Anfossi et al, 1971;Ariati et al, 1988;Benedetti et al, 2003;Boni, 1967;Bresciani and Perotti, 2014;Burrato et al, 2003;Castiglioni and Pellegrini, 2001;Cremaschi, 1987;Desio, 1965;Livio et al, 2014;Pellegrini et al, 2003;Pieri and Groppi, 1981;Zuffetti et al, 2018; Fig. 1A).…”

“…However, the available geological maps (Anfossi et al, 1971;Boni, 1967;Pellegrini et al, 2003) and the pedological studies performed on the study area (ERSAL, 2013(ERSAL, , 2001a(ERSAL, , 2001b(ERSAL, , 2000 have neither accounted for a detailed analysis of paleosols, nor they have been properly integrated into an evolutionary model of the structures during the Late Pleistocene; ii) the reliefs are located at the hinge belt between the Po Plain and the Northern Apennine chain, where the chronology of the Late Quaternary morpho-tectonic increments is still under debate (Benedetti et al, 2003;Burrato et al, 2012Burrato et al, , 2003Pellegrini et al, 2003). Recent studies on the San Colombano relief revealed that latest Quaternary faulting contributed to shape the geomorphology of the hill and that tectonic increments affected soil evolution and led to their displacement (Zuffetti et al, 2018). Hence, the issues we address in the present paper are: I) do superposed paleosols represent tectono-stratigraphic markers along the isolated reliefs of the southern Po Plain?…”

“…SAT: Sant'Angelo Lodigiano Frontal Thrust; PR: Pavia lateral ramp. B) The main landscape units of the study area (modified after Bersezio et al, 2010;Zuffetti et al, 2018).…”