An active deformation structure in the Po Plain (N Italy): The Romanengo anticline

Abstract

Field surveys, well data and a detailed interpretation of a depth-converted seismic line, reveal that the Romanengo High, an isolated low relief that interrupts the morphological continuity of the Po Plain (N Italy) west of the Oglio River, coincides with a partially buried anticline, still active in recent times (Romanengo anticline). The Pliocene to Holocene evolution of the structure has been reconstructed by sequential restoration based on combined decompaction and unfolding methods, from the early Pliocene to Holocene. The analysis shows that from the beginning of the Pliocene onward, periods of tectonic activity have alternated with periods of quiescence. The more significant tectonic uplift rates are recorded during the late Pliocene (0.33 ± 0.06 mm/yr) and the beginning of Calabrian (0.284 ± 0.12 mm/yr), while at the end of Calabrian the structure was virtually inactive. During the early Pleistocene the reversal in the vergence of the structure indicates the onset of interaction with the Apennines deformational front in the area. From middle Pleistocene to Holocene, a marked increase in the tectonic uplift has been recorded, with an uplift rate of about 0.12 ± 0.05 mm/yr. A preliminary evaluation of the seismic hazards connected to blind thrusts affecting this active frontal sector of the Alpine chain, where it collides with the Apennines buried deformation fronts, is finally discussed.

An electrostratigraphic cross-section across the central Po plain: bearings on subsurface geology and hydrostratigraphy

“…Netto/Capriano del Colle and Castenedolo highs (Alfano and Mancuso 1996;Anfossi et al 1971;Baio et al 2004;Bersezio et al 2010Bersezio et al , 2016Boni, 1967;Bresciani and Perotti, 2014;Burrato et al 2003;Castiglioni and Pellegrini 2001;Cremaschi, 1987;Desio 1965;Livio et al, 2009;Pellegrini et al 2003).…”

“…1) with the following aims:  to obtain a regional electrostratigraphic cross-section of a wide part of the Quaternary Po basin, South and East of Milan, orthogonal to the regional structural grain of the basin (Fig. 1);  to complement the picture of the Plio-Quaternary sequences and structures of the Po foreland basin in Lombardy which are shown at shallow depth with low-resolution and some uncertainties by the currently available deep seismic images (Bresciani and Perotti 2014;Burrato et al 2003;Cassano et al 1986;Fantoni et al 2004;Francese et al 2005;Ghielmi et al 2013;Livio et al 2009;Pieri and Groppi 1981;Toscani et al 2014;Turrini et al 2014), providing new insights on the debated Plio-Quaternary tectono-sedimentary evolution of the Po foreland basin;…”

Restored topography of the Po Plain‐Northern Adriatic region during the Messinian base‐level drop—Implications for the physiography and compartmentalization of the palaeo‐Mediterranean basin

“…The restoration of the tectonic deformation of the basin was carried out removing the vertical component of the main Pliocene-Pleistocene thrusts and anticlines of the Northern Apennines and Western and Southern Alps, according to published uplift data (Scrocca, Carminati, Doglioni, & Marcantoni, 2007;Toscani et al, 2014;Maesano, D'Ambrogi, Burrato, & Toscani, 2015;Bresciani & Perotti, 2014; Table 2) ( Figure 5a). In performing this operation, we neglect horizontal deformation given that previous works suggest between 10 and 20 km of average horizontal shortening (~10% with respect to the basin width) along the Northern Apennine front in the Po basin since the late Messinian (Figure 5b) (Bigi et al, 1995;de Donatis, 2001;Perotti, 1991;Toscani et al, 2014), which translates into minor strain at the basin scale.…”

“…In order to create a 3D time‐surface from scattered data, we used the Delaunay triangulation method and smoothed the resulting surface using a characteristic length scale of 3 km to remove asperities due to the noise in the data and interpolation method. The resultant 3D time‐surface has been depth‐converted using a homogeneous seismic wave velocity value of 2,000 m/s, an average value obtained considering both confidential (time‐velocity tables of ENI wells) and public data (e.g., Bresciani & Perotti, ; ISPRA, ; Molinari, Argnani, Morelli, & Basini, ).…”

Deformation patterns of upper Quaternary strata and their relation to active tectonics, Po Basin, Italy

“…The Po Plain (northern Italy) has been the object of intensive geophysical surveys and drillings by oil companies, aimed at an improved characterization of the petroleum systems in the area (Pieri & Groppi, 1981;Ghielmi et al, 2010Ghielmi et al, , 2013Amadori et al, 2019). Previous stratigraphic studies have focused largely on the deformation of the Pliocene to Middle Pleistocene syntectonic basin fill and prominent basin-scale unconformities have been tracked in the subsurface (Regione Emilia-Romagna & ENI-AGIP, 1998; Regione Lombardia & ENI-Divisione Agip, 2002;Muttoni et al, 2003;Ghielmi et al, 2010Ghielmi et al, , 2013Garzanti et al, 2011;Bresciani & Perotti, 2014;Amadori et al, 2019). In contrast, deformation of Upper Pleistocene-Holocene deposits over the past 125 kyr has received very little study.…”