Abstract
The Solite Quarry within the Dan River–Danville basin contains an extensive suite of riftrelated structures. The cyclical upper member of the Cow Branch Formation has been deformed both in continuous fashion and via three brittle failure modes, exhibiting fracture partitioning such that failure mode is lithologically dependent. All structures are tectonic; extension estimates are roughly comparable for all failure modes; and there is an absence of bedding-parallel detachment horizons with normal separation. All extensional structures formed in response to Triassic rifting. These observations imply that different beds failed coevally or semicoevally in extension. All contractional structures are consistent with earliest Jurassic inversion. The small normal faults are in most ways like larger faults and occur both as isolated features and as segments of relay systems. The faults exhibit slickensided, mineralized fault surfaces, footwall uplift, hangingwall subsidence, relay ramps, and elliptical fault surfaces, with maximum displacement occurring at fault centers and tapering to zero at the tips. Detailed analysis of these structures and integration with other data sets suggest that faults exhibit linear lengthdisplacement scaling over nine orders of magnitude of fault length. These small faults can be divided into two subsets based on length and on their spatial distribution within the rock volume, with the set of smaller structures exhibiting anticlustering with respect to the larger structures (called master faults), forming fault shields due to the presence of stress-reduction shadows around the master faults.
Published Version
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