EVOLUTION OF SOLUTION STRUCTURES IN A DEFORMED QUARTZ ARENITE - GEOMETRIC CHANGES RELATED TO PERMEABILITY CHANGES

Quartz arenite of the Silurian Keefer Sandstone at a site in West Virg inia, U.S.A., records an early pervasive solution-related deformation by grain interpenetration. Volume losses measured by the PSS method sh ow shortening directions from both diagenetic compaction and early tec tonic layer-parallel shortening. Later solution-related tectonic defor mation during folding formed transgranular stylolites along pre-existi ng faults or in rock volumes with abundant microfractures. Thus, the g eometry of solution-related deformation changed progressively from per vasive at grain scale to focused along transgranular surfaces. We prop ose that this geometric change resulted from intense porosity and perm eability reduction during diagenetic cementation and early layer-paral lel shortening, which required fluids to exploit tectonically created pathways along faults or networks of microfractures during later defor mation. (C) 1997 Elsevier Science Ltd.