Progressive offset and surface deformation along a seismogenic blind thrust in the Po Plain foredeep (Southern Alps, Northern Italy)

Abstract

Here we present, for the first time in the Po Plain foredeep (Northern Italy), the middle to late Pleistocene growth history of an outcropping secondary fold and related faults, whose progressive deformation over an intermediate time window (10 5 years) is driven by an underlying seismogenic blind thrust. We trenched and logged an outcropping decametric secondary anticline, related to a deeper blind compressional structure, which deforms fluvial sediments and an overlying loess-paleosol sequence. Folded units were dated, using radiocarbon and optically stimulated luminescence methods, to the late Pleistocene-Holocene and tentatively correlated with glacial-interglacial phases occurring during the time interval from marine isotope stage 6 to the present. A multistep retrodeformation of the fold allowed us to calculate uplift rates for this secondary and shallow anticline, varying between 0.02 and 0.1 mm/yr since circa 200 kyr. Trishear forward deformation modeling of the fold indicates that the amplification of the observed fold could be caused by two shallow thrusts formed through a break-backward activation. This generated a decametric surface fold whose most recent growth was associated with bending-moment normal faulting in the crestal and forelimb region. Our observations demonstrate that near-surface compressive tectonics can be caused by blind thrusting, via a complex array of fault and folds: upward strain propagation and generation of shallow low-angle thrust and related folding seem to be mainly due to secondary fold-related faulting, according to an out-of-syncline thrusting mechanism.

Syn-thrusting polygonal normal faults exposed in the hinge of the Cingoli anticline, northern Apennines, Italy

“…sutured its NE-verging basal thrust. Contractional deformation along the northern Apennines belt is presently active 40-50 km to the north-east and north of the Cingoli anticline, namely in the northern Adriatic basin and Po plain regions (Scrocca et al, 2007;Carminati et al, 2010;Ventura and Di Giovambattista, 2013;Livio et al, 2014). For further stratigraphic and structural information on the Cingoli anticline area the reader is referred to the next sections and past studies (Carloni, 1960(Carloni, , 1964Ciancetti and Nanni, 1989;Calamita et al, 1990;Menichetti, 1991;Marchegiani et al, 1999;Deiana et al, 2002;Mazzoli et al, 2002;Petracchini et al, 2012Petracchini et al, , 2015Antonellini et al, 2014).…”

Lashed by the wind: short-term Middle Palaeolithic occupations within the loess-palaeosoil sequence at Monte Netto (Northern Italy)

“…Since the 2000s, new and intense excavations of the fine deposit aimed to the production of industrial bricks have affected the central part of the flat summit of the hill (Laterizi Danesi quarry) placed about 1 km south of the area of the previous finds, exposing the entire sequence and providing the opportunity for extensive investigation on the morphological evolution of the hill (Livio et al, 2012(Livio et al, , 2014Zerboni et al, 2015). During field surveys, further artefacts have been found and documented embedded in their layers, making possible the cultural contextualization of the Neanderthal frequentations on this mound.…”

“…The Monte Netto Hill area was intensively surveyed in order to reconstruct its geomorphological and sedimentological evolution during the Middle to Upper Pleistocene; the most significant and complex pedosedimentary sequence locates in the area of the Laterizi Danesi clay quarry and was considered for detailed palaeopedological investigations (Livio et al, 2012(Livio et al, , 2014Zerboni et al, 2015).…”

“…Among isolated hills, particularly important are the Castenedolo and Monte Netto hills, which are located in the alluvial plain south of Brescia. These hills have been affected by repeated loess depositions during Marine Isotope Stages (MIS) 4-2 that sealed Mousterian open air sites (Baroni, 1986;Baroni et al, , 1988 https://doi.org/10.1016/j.quaint.2019.01.026 Received 13 August 2018; Received in revised form 6 January 2019; Accepted 21 January 2019 Cremaschi, 1974;Livio et al, 2012Livio et al, , 2014Zerboni et al, 2015).…”

Paleo-Seismicity in the Euganean Hills Province (Northeast Italy): Constraints From Geomechanical and Geophysical Tests in the Schio-Vicenza Fault Area

“…A territory hit by earthquakes generally exhibits distinctive landforms such as compressional and extensional features, ridges, shear planes with displacement, scarps, trenches and fragmented rocks, and gouges (powdered layers and pockets) within bedrock (i.e., Guerrieri et al, 2010;Michetti et al, 2012;Livio et al, 2014). These features have been observed in the central sector of the Italian Southern Alps (Vannoli et al, 2015).…”