LITHOLOGIC CONTROLS ON MORPHOLOGY OF PRESSURE-DISSOLUTION SURFACES (STYLOLITES AND DISSOLUTION SEAMS) IN PALEOZOIC CARBONATE ROCKS FROM THEMIDEASTERN UNITED-STATES

Examination of pressure-dissolution surfaces (stylolites and dissoluti on seams) in carbonate rocks from the mideastern U.S. demonstrates tha t the morphology of these surfaces varies with rock fabric. One can qu antify the morphology of these pressure-dissolution surfaces using fou r parameters: thickness T of the insoluble residue defining the surfac e, amplitude of irregularity I of the surface between vertical offsets , amplitude of vertical offsets O of the surface, and frequency F of v ertical offsets along the surface. I and O increase with T, reflecting progressive development of stylolites, whereas F is proportional to 1 /T, apparently because the physical strength of a stylolite inhibits t he formation of offsets. Mean values of F, O, and T are greater in gra instones and packstones than in mudstones and wackestones, and the abu ndance of dissolution seams relative to that of stylolites decreases t hrough the lithologic spectrum from mudstones to grainstones. These re lationships suggest that development of pressure-dissolution surfaces to form large stylolites depends on the heterogeneity of the limestone fabric. Maximum values of T and 0 in grainstones correlate with cemen t abundance. T and O are low in grain-rich, cement-poor grainstones, e ven though grains are favored as leading or penetrating elements of st ylolite columns. Dissolution seams (surfaces with O and F near zero) a re found only in rocks containing fine-grained dolomite. T and I of th ose seams decrease with increasing dolomite abundance in dolomitic lim estones, and T and O are lower in dolostones than in limestones. Taken together, these relationships suggest that extreme abundance of press ure-resistant components, such as carbonate grains and dolomite, inhib it development of pressure-dissolution surfaces. In contrast, stylolit es are most extensively developed (i.e., T, O, and F are greatest) in carbonate rocks in which these pressure-resistant elements are mixed w ith less resistant components, such as cement and carbonate mud. The l atter rocks, which include packstones, well cemented grainstones, and slightly dolomitic limestones, may undergo preferential removal from t he stratigraphic record by pressure dissolution.