Limestone Response to Stress: Pressure Solution and Dolomitization

Abstract

ABSTRACT Limestones that have been subjected to overburden or tectonic stress can be expected to have changed by some combination of deformation (plastic or brittle), neomorphism (as micrite conversion to microspar or aggrading pseudospar), and solution. Specific limestone units (beds, structures, or grains) may be preferentially resistant or responsive to change and with or without impurities (especially magnesium ions and clay particles) that will influence the character of change. Three styles of pressure solution response are recognized in Paleozoic limestones studied from Arizona, western Maryland, and southeast Kansas. Sutured-seam solution (common stylolites and grain-contact sutures) occurs in limestones that have structural resistance to stress and very little clay or platy silt content. Non-sutured seam solution (microstylolites, microstylolite swarms, and clay seams) occurs in limestones that have significant amounts of clay or platy silt. These limestones may be structurally resistant or responsive. Stress is accommodated both by solution and by lateral movement along microstylolite surfaces. Dolomite rhomb growth may or may not occur along microstylolite surfaces. Non-seam solution (pervasive solution thinning of a unit) occurs in clean limestones that have little or no structural resistance to stress. Dolomite growth is always observed to be associated with non-seam solution, but pervasive pressure solution without associated dolomitization should also be possible. Where clean, structurally resistant limestone units interface with responsive limestones or silty, clayey limestones, solution surfaces are not sutured. Nodular limestones are a characteristic product of non-sutured seam solution in silty, clayey limestones. Form and scale of fitted nodules may or may not be influenced by primary structure. The three forms of limestone pressure solution produce some types of finely crystalline stratigraphic dolomite, provide local sources of magnesium for dolomitization and calcite for porosity-filling cement, and severely distort primary sedimentary structures or create secondary structures.