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.
Highlights
In the Apennines of Italy, and especially the Adriatic foreland domain, it is possible to infer the foreland deformation process and explore the impacts of inherited faults and basins on the subsequent evolution thanks to the milder deformation in the area and the good geological and geophysical record documenting an interaction between normal, thrust, and strike–slip faults.Foreland domains are often affected by inherited rift-related or flexure-related synsedimentary normal faults becoming involved in the advancing fold-and-thrust belt
The eastern area is characterized by W- and E-verging high-angle reverse faults, giving rise to gentle flower structures with an NW–SE trend. These structures were formed from the Middle Pliocene and developed structural highs, some of which were
Compressive deformation stopped during the Upper Pliocene, and Quaternary deposits were not affected
Summary
Foreland domains are often affected by inherited rift-related or flexure-related synsedimentary normal faults becoming involved in the advancing fold-and-thrust belt. This introduces an element of further complications into the evolution of the foredeep systems subsequently involved in the mountain belts, as evidenced by numerous studies in different contexts, such as the Northern Apennines, Po Plain, and South-Eastern Pyrenean foreland basins ([1,2,3,4], among others). The tectonic and structural features of the Umbria-Marche Apennines (Figure 1) are widely described in the literature, and several models have been proposed. The tectonic and structural features of the Umbria-Marche Apennines This model indicates strong shortening (in important is found in [5], which proposes a thin-skinned imbricate belt detached the order of hundreds of kilometres) of the shortening sedimentary above the crystalline basement (see alsoand [6]).important
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