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

Abstract

The architecture of foreland basins and the resulting distribution of clastic sediments are related to the constant interplay between tectonics and sedimentation. Specifically, basin floor modifications strongly influence dimensions, continuity and connections of sand‐size and fine‐grained deposits. Given the increasing need to identify deep potential reservoir deposits, the large‐scale definition of clastic porous targets and their seals is a matter of interest for oil and gas industry. Here, we present the reconstruction of the Po Plain and Northern Adriatic Foreland Basin (with an extent of ca. 40,000 km2) and its Pliocene–Pleistocene evolution, as an example of a sedimentary clastic system controlled by strongly non‐cylindrical foreland geometry. The study is based on the basin‐scale mapping of six unconformity‐bounded sequences, performed by interpreting a dense network of seismic lines and correlating well‐log data. This provides a three‐dimensional model of the step‐by‐step evolution of the basin and a description of the sediment dispersal pattern. We found that the basin records the change from a continuous (cylindrical) to highly fragmented (non‐cylindrical) foredeep geometry during Late Pliocene. In the Northern Apennines case, the main factors driving the development of a non‐cylindrical geometry are mainly related to inherited inhomogeneity in the downgoing block linked to its Mesozoic extensional faulting, and the relative orientation of these lineaments with respect to the direction of orogen migration. During the late Pliocene–Pleistocene the two directions progressively became close to parallel, and the Northern Apennines system reacted changing from a cylindrical to a non‐cylindrical state.

Active Fold‐Thrust Belt to Foreland Transition in Northern Adria, Italy, Tracked by Seismic Reflection Profiles and GPS Offshore Data

“…Most data used in this work derive from the ViDEPI public database (http://www.videpi.com), mainly consisting of 2‐D seismic‐reflection profiles from the “A” Italian commercial zone (northern Adriatic area), borehole composite logs, and structural maps in the time domain (Figure 3; seismic reflection profiles from the ViDEPI project organized in a 3‐D environment by means of Move® software are available in the GFZ Data Services Repository: http://doi.org/10.5880/fidgeo.2020.027, Maffucci et al, 2020). Furthermore, we collected seismic profiles, structural geological maps, and geological profiles from Bally (1986), Argnani (1998), Franciosi and Vignolo (2002), Casero (2004), Finetti and Del Ben (2005), Fantoni and Franciosi (2009), Kastelic et al (2013), Wrigley et al (2015), and Amadori et al (2019).…”

Factors controlling natural subsidence in the Po Plain

“…The Po Basin fill shows a shallowing-upward trend from deepmarine turbidites to coastal and continental units (Ghielmi et al, 2013). The rhythmical alternation of Middle-Late Pleis- tocene coastal and alluvial deposits reflects glacio-eustatic fluctuations at the Milankovitch scale (Amorosi et al, 2004). Two transgressive-regressive coastal wedges in the uppermost 130 m were assigned to the Last (MIS 5e) and to the Present (MIS 1) Interglacials based on pollen data, 14 C dates and electron-spin-resonance age determinations (Ferranti et al, 2006).…”

“…Subsidence rates between 120-116 and 5.6-0 cal kyr BP were compared with SR averaged over the last 1.5 Myr. The 1.5 Myr unconformity (Amadori et al, 2019) is marked in exploration-well logs by the first occurrence of Hyalinea Baltica (Carminati and di Donato, 1999).…”

“…The Po Plain is a ∼ 40 000 km 2 -wide alluvial plain bounded by the Alps to the north and by the Apennines to the south. Frontal thrusts of both chains are sealed beneath the Po Plain (Amadori et al, 2019). The Apennine thrusts are north-verging and exhibit arcuate shapes.…”

“…As sediment deposition presumably took place in a water body < 1 m deep, an error of ±0.5 m was taken into account in SR calculation. The MIS 5e lagoon horizon likely accumulated in water depths < 2 m (associated error of ±1 m; Amorosi et al, 2004). An additional error of ±1 m was added to compensate possible inaccuracy in correlation due to low chronologic resolution.…”