Constraining the Passive to Active Margin Tectonics of the Internal Central Apennines: Insights from Biostratigraphy, Structural, and Seismic Analysis

Giovanni Luca Cardello,Eugenio Carminati,Carlo Doglioni,Giuseppe Vico,Monia Sabbatino,Lorenzo Consorti

doi:10.3390/geosciences11040160

Abstract

The polyphase structural evolution of a sector of the internal Central Apennines, where the significance of pelagic deposits atop neritic carbonate platform and active margin sediments has been long debated, is here documented. The results of a new geological survey in the Volsci Range, supported by new stratigraphic constraints from the syn-orogenic deposits, are integrated with the analysis of 2D seismic reflection lines and available wells in the adjacent Latin Valley. Late Cretaceous syn-sedimentary faults are documented and interpreted as steps linking a carbonate platform to the adjacent pelagic basin, located to the west. During Tortonian time, the pelagic deposits were squeezed off and juxtaposed as mélange units on top of the carbonate platform. Subsurface data highlighted stacked thrust sheets that were first involved into an initial in-sequence propagation with top-to-the-ENE, synchronous to late Tortonian foredeep to wedge-top sedimentation. We distinguish up to four groups of thrust faults that occurred during in-sequence shortening (thrusts 1–3; about 55–60 km) and backthrusting (thrust 4). During Pliocene to recent times, the area has been uplifted and subsequently extended by normal faults cross-cutting the accretionary wedge. Beside regional interest, our findings bear implications on the kinematic evolution of an orogenic wedge affected by far-traveled units.

Highlights

Carbonate platforms are a type of passive margin sedimentary succession that can be commonly involved in the thrust-sheet imbrication of an orogenic wedge [1,2,3]
We present a geological cross section, interpretative of the deep structures produced after the integration of field and subsurface structures (Figure 14), that includes pre-orogenic passive margin deposits, mélange units, foredeep, and wedge-top deposits
By studying the top of the Mesozoic carbonate platform both in the Lower Volsci Unit and in the blocks embedded in the Chaotic complex (Appendix B; Figure S1), we have reported the occurrence of an irregular surface at the top of the platform

Summary

Introduction

Carbonate platforms are a type of passive margin sedimentary succession that can be commonly involved in the thrust-sheet imbrication of an orogenic wedge [1,2,3]. The wedge-related deformation style may strongly depend on the stratigraphic architecture and in particular on the presence and depth of décollement layers within the stratigraphic successions (i.e., salt [9]). In this sense, thick-skinned deformation (see, e.g., in [10]) can dominate when there is no suitable detachment horizon. At the transition between such structural domains, strain localization can occur, nucleating thrusts by inverting previous listric boundary extensional faults (see, e.g., in [13])

Methods

Results

Discussion

Conclusion