Maximum burial and unroofing of Mt. Judica recess area in Sicily: ?mplication for the Apenninic-Maghrebian wedge dynamics

摘要

We integrated X-ray diffraction (XRD) data concerning the illite content in mixed-layer illite-smectite with data derived from Fourier Transform Infrared spectroscopy (FTIR) on H-rich organic matter to constrain the burial-exhumation path of the Mt. Judica sedimentary succession cropping out in tectonic window in Eastern Sicily.Thermal structural model constrained by organic and inorganic thermal parameters showed that the Mt. Judica succession experienced paleo-temperatures in the range of 100-130°C in deep diagenetic conditions and early mature stage of hydrocarbon generation. Specifically, the illite content in mixed-layer I-S ranges from 50 to 76% and FTIR-derived indexes suggest a thermal maturity equivalent to VR _o values of at least 0.5-0.7%. As a whole, the Mt. Judica succession experienced maximum tectonic burial (ranging between 2.4 and 3.2km) during the Middle Miocene as a result of the emplacement of the allochthonous units atop it. The subsequent breaching phase characterized by up-thrust geometries, and erosion during Pliocene times ruled out the Mt. Judica exhumation. This last tectonic phase did not overprint thermal maturity because the extent of overthrusting was negligible when compared with the magnitude of vertical movements. Restoration of balanced cross sections revealed an increase of shortening from the salient to the Mt. Judica recess with values from 12.3 to 23.9km, consistent with the increase of tectonic thickening of the fold-and-thrust belt. Integration of maximum burial and shortening values along the curvature of the Sicilian fold-and-thrust belt allowed us to reconstruct the wedge paleo-geometry in the Mt. Judica recess area, to investigate the along-strike variations of the tectonic overburden, and to discuss the geodynamic causes of these changes. These results were compared with theoretical models of wedge dynamics.