ABSTRACT

Examination of pressure-dissolution surfaces (stylolites and dissolution seams) in carbonate rocks from the mideastern U.S. demonstrates that the morphology of these surfaces varies with rock fabric. One can quantify the morphology of these pressure-dissolution surfaces using four parameters: thickness T of the insoluble residue defining the surface, amplitude of irregularity I of the surface between vertical offsets, amplitude of vertical offsets O of the surface, and frequency F of vertical 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 the formation of offsets. Mean values of F, O, and T are greater in grainstones and packstones than in mudstones and wackestones, and the abundance of dissolution seams relative to that of stylolites decreases through the lithologic spectrum from mudstones to grainstones. These relationships suggest that development of pressure-dissolution surfaces to form large stylolites depends on the heterogeneity of the limestone fabric.

Maximum values of T and O in grainstones correlate with cement abundance. T and O are low in grain-rich, cement-poor grainstones, even though grains are favored as leading or penetrating elements of stylolite columns. Dissolution seams (surfaces with O and F near zero) are found only in rocks containing fine-grained dolomite. T and I of those seams decrease with increasing dolomite abundance in dolomitic limestones, and T and O are lower in dolostones than in limestones. Taken together, these relationships suggest that extreme abundance of pressure-resistant components, such as carbonate grains and dolomite, inhibit development of pressure-dissolution surfaces. In contrast, stylolites are most extensively developed (i.e., I>T, O, and F are greatest) in carbonate rocks in which these pressure-resistant elements are mixed with less resistant components, such as cement and carbonate mud. The latter rocks, which include packstones, well cemented grainstones, and slightly dolomitic limestones, may undergo preferential removal from the stratigraphic record by pressure dissolution.