Transition from faulting to noncylindrical folding, involving rapid plunge change at the fold closure, is the primary displacement transfer mechanism at the northern end of the South Appalachian foreland fold and thrust belt. Regional thrust faults, including the Saltville, Narrows, and St. Clair, terminate in regional, overturned asymmetric anticlines. This mechanism of displacement transfer is distinct from thrust terminations where fold complexes of smaller, noncylindrical folds converge toward the end of the fault trace. The Saltville thrust transition to the Sinking Creek anticline is representative of the southern Appalachian structures. Deformation intensity patterns, reflected by cleavage development, mesoscopic folding, and faulting, suggest that the Sinking Creek anticline formed due to upwarping from shear thrusting at depth. Laboratory deformation analogs of folds formed above ramps support this contention. Experimentally produced folds are asymmetric overturned structures with high strains on overturned limbs and very low strains on upright limbs. A deformation sequence involving shear thrusting with subsequent break thrusting may characterize fault propagation at thrust termini. This will be important for layered sedimentary sequences where thick, rigid members low in the sedimentary pile are overlain by thinner, interbedded, mechanically anisotropic strata.

First Page Preview

First page PDF preview
You do not currently have access to this article.