SHEAR STRUCTURES WITHIN SOFT-SEDIMENT DEFORMATION FEATURES IN THE EARLY JURASSIC NAVAJO SANDSTONE
The origin of the shear forces producing these structures is sometimes the evident consequence of larger-scale dynamics within the deformation event, driven by gravity or hydraulic pressure, after seismic destabilization (liquefaction) has occurred. Such examples constitute an essential set of case studies, greatly supplementing models derived from experimentation and observation in modern environments. In many instances, however, it is difficult to postulate coherent mechanisms to explain the preserved architectural relationships within the context of current theory and established physical constraints. Identifying these interpretive challenges is a necessary first step in developing more broadly applicable models. To this end, photodocumentation of shear structure diversity is here provided, along with a corresponding array of interpreted dynamics and emerging enigmas.