Plio–Quaternary Structural Evolution of the Outer Sector of the Marche Apennines South of the Conero Promontory, Italy

Abstract

Some new results and preliminary remarks about the Plio–Quaternary structural and evolutionary characteristics of the outer Marche Apennines south in the Conero promontory are presented in this study. The present analysis is based on several subsurface seismic reflection profiles and well data, kindly provided by ENI S.p.A. and available on the VIDEPI list, together with surface geologic–stratigraphic knowledge of Plio–Quaternary evolution from the literature. Examples of negative vs. positive reactivation of inherited structures in fold and thrust belts are highlighted. Here, we present an example from the external domain of the Marche Apennines, which displays interesting reactivation examples from the subsurface geology explored. The study area shows significant evolutionary differences with respect to the northern sector of the Marche region previously investigated by the same research group. The areal distribution of the main structures changes north and south of the ENE–WSW oriented discontinuity close to the Conero promontory. Based on the old tripartite classification of the Pliocene, the results of this work suggest a strong differential subsidence with extension occurring during the Early Pliocene and principal compressive deformation starting from the Middle Pliocene and decreasing or ceasing during the Quaternary. The main structure in this area is the NNW–SSE Coastal Structure, which is composed of E-vergent shallow thrusts and high-angle deep-seated normal faults underneath. An important right-lateral strike–slip component along this feature is also suggested, which is compatible with the principal NNE–SSW shortening direction. As mentioned, the area is largely characterized by tectonic inversion. Starting from Middle Pliocene, most of the Early Pliocene normal faults became E-vergent thrusts.

Pleistocene slope, shallow-marine and continental deposits of eastern central Italy wedge-top basin: a record of sea-level changes and mountain building

“…5): a mildly deformed, very open fault-propagation fold in the northern sector; a complex pop-up structure in the southern sector. The complex pop-up structure also displays several evidence of Mesozoic-Miocene extensional faults inverted during Pliocene-Pleistocene along detachment horizon/s deeper than the Messinian reflector, as also recently recognised by Costa et al (2021).…”

Lithospheric double shear zone unveiled by microseismicity in a region of slow deformation

“…According to others 74 , it is the expression of dominating wrench-faulting regime, with ENE-WSW left-lateral crustal strike-slip faults dissecting the Apennine thrust belt. Still, other Authors 75 propose an important right-lateral strike-slip deformation in the area south of the Conero promontory.…”

Buried Alive: Imaging the 9 November 2022, Mw 5.5 Earthquake Source on the Offshore Adriatic Blind Thrust Front of the Northern Apennines (Italy)

“…Such questioning rested on the weak geologic‐geomorphic deformation signature onshore, the lack of bathymetric signature offshore, and focal mechanisms of small‐magnitude earthquakes (Coward et al., 1999; Di Bucci & Mazzoli, 2002; Mazzoli et al., 2015; Troiani & Della Seta, 2011). The recent offshore activity was also attributed to NW‐SE transpressional tectonics (Costa et al., 2021; Pierantoni et al., 2019). These conclusions have been highly disputed based on the integration of different observations, including geomorphology, extensive geophysical and subsurface geological datasets, historical seismicity, and focal mechanisms of major earthquakes (Basili & Barba, 2007; Burrato et al., 2003; DISS Working Group, 2021; Maesano et al., 2013; Panara et al., 2021; Vannoli et al., 2004, 2015).…”