ABSTRACT

Cathodoluminescence petrography and scanning electron microscopy (SEM) reveal that grain size and temperature significantly influenced intergranular pressure solution, quartz cementation, and porosity evolution in the quartzose Hartshorne Sandstone (Middle Pennsylvanian) of the Arkoma basin. Among samples from each locality, a negative, linear relationship exists between mean grain size and volume of quartz dissolved by intergranular pressure solution. In contrast, a generally positive relationship exists between mean grain size and volume of quartz cement, although considerable variability exists in this relationship. A positive relationship also exists between mean grain size and porosity. Intergranular pressure solution directly reduced minus-cement porosity by causing tighter pack ng of detrital grains; it thereby controlled volumes of both cement and primary porosity. For this reason, little primary porosity is preserved in pressolved, finer-grained sandstones even though they contain small absolute volumes of quartz cement. Appreciably more primary porosity may be retained by unpressolved, coarser-grained sandstones even though they contain larger absolute volumes of quartz cement.

These relationships also vary with thermal maturity, which increases eastward across the basin. This thermal maturity trend is the result of elevated temperatures associated with Mesozoic rifting and intrusive events in the Mississippi embayment. Among samples of equal grain size, more intergranular pressure solution, less quartz cement, and less porosity are evident in areas of higher thermal maturity. As is the case with grain size, the influence that temperature exerted on intergranular pressure solution is, in turn, reflected in volumes of quartz cement and porosity. Thus, primary porosity tends to be preserved preferentially in areas of lower thermal maturity even though the absolute volume of quartz cement is generally higher.

In areas of higher thermal maturity, more quartz has been dissolved by intergranular pressure solution than is present as cement whereas the opposite is true in areas of lower thermal maturity. This suggests that intergranular pressure solution was an important agent of mass transfer during diagenesis of these quartzose sandstones.