Stress, strain, and fault behavior at a thrust ramp: Insights from the Naukluft thrust, Namibia

摘要: We report observations from a kilometer-scale thrust ramp on the Naukluft thrust, Namibia. The is low angle that was active at subgreenschist facies conditions and accommodated several tens of kilometers displacement base Nappe Complex in Pan-African Damara Orogeny. fault zone generally planar few meters thick, comprising predominantly dolomite-rich cataclasite. At ramp, fault-rock assemblage increases thickness, hanging-wall, which elsewhere relatively intact, contains high density network inclined quartz veins, subvertical dolomite calcite breccia zones, as well injectites cataclastic rock emanating surface. geometry hanging-wall structures indicates local subhorizontal extension. Local tensile stress can be explained by bending it deformed to slide above structure. High fluid pressures created dynamically during fast slip decarbonation carbonate rock, dewatering footwall under an impermeable interseismic periods, led additional reduction effective compressive stresses. In this location, more optimally oriented for inferred regional field, therefore likely fail before contiguous flats are subparallel maximum principal stress. As such, represents location nucleation slip, could both trigger dynamic failure adjacent faults, produce extensional structures.