Active Faulting and Deep‐Seated Gravitational Slope Deformation in Carbonate Rocks (Central Apennines, Italy): A New "Close‐Up" View. Issue 10 (5th October 2021)

• Record Type: Journal Article
• Authors: Del Rio, Luca; Moro, Marco; Fondriest, Michele; Saroli, Michele; Gori, Stefano; Falcucci, Emanuela; Cavallo, Andrea; Doumaz, Fawzi; Di Toro, Giulio
• Is Part Of: Tectonics. Volume 40:Issue 10(2021)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2021-10-05
• Subjects: active faults -- deep‐seated gravitational slope deformation -- earthquakes -- slip surfaces -- cataclasites -- carbonates; Geology, Structural -- Periodicals; 551.8
• DOI: 10.1029/2021TC006698
• Languages: English
• ISSNs: 0278-7407

Abstract

Abstract: Active faulting and deep‐seated gravitational slope deformation (DGSD) are common geological hazards in mountain belts worldwide. In the Italian central Apennines, kilometer‐thick carbonate sedimentary sequences are cut by major active normal faults that shape the landscape, generating intermontane basins. Geomorphological observations suggest that the DGSDs are commonly located in fault footwalls. We selected five mountain slopes affected by DGSD and exposing the footwall of active seismogenic normal faults exhumed from 2 to 0.5 km depth. Field structural analysis of the slopes shows that DGSDs exploit preexisting surfaces formed both at depth and near the ground surface by tectonic faulting and, locally, by gravitational collapse. Furthermore, the exposure of sharp scarps along mountain slopes in the central Apennines can be enhanced either by surface seismic rupturing or gravitational movements (e.g., DGSD) or by a combination of the two. At the microscale, DGSDs accommodate deformation mechanisms similar to those associated with tectonic faulting. The widespread compaction of micro‐grains (e.g., clast indentation), observed in the matrix of both normal faults and DGSD slip zones, is consistent with clast fragmentation, fluid‐infiltration, and congruent pressure‐solution active at low ambient temperatures (<60°C) and lithostatic pressures (<80 MPa). Although clast comminution is more intense in the slip zones of normal faults because of the larger displacement accommodated, we are not able to find microstructural markers that allow us to uniquely distinguish faults from DGSDs. Key Points: Slip surfaces cutting carbonate rocks in Central Italian Apennines accommodate both normal faulting and deep‐seated gravitational slope deformations (DGSDs) DGSDs are the result of gravity‐induced reactivation of faults and fractures located in the footwall of normal seismogenic faults Deformation mechanisms associated with normal faulting and DGSDs are cataclasis and pressure‐solution active at low ambient temperatures