Increase In Thermal Maturity Research Articles

Detailed cathodoluminescent petrography and scanning electron microscopy reveal that grain size and thermal maturity have significantly influenced intergranular pressure solution and quartz cementation in the quartz-rich Hartshorne Sandstone of the Arkoma basin. Mean grain size of Hartshorne sandstones ranges from very fine to medium-grained. In any stratigraphic section, a negative, linear relationship exists between grain size and volume of silica dissolved via intergranular pressure solution. In contrast, either a positive, linear relationship or no significant relationship End_Page 583------------------------------ exists between grain size and volume of quartz cement. These relationships indicate that silica was selectively dissolved via intergranular pressure solution in finer grained sandstones and that, at least locally, quartz cement was selectively precipitated as overgrowths on detrital grains in coarser grained sandstones. Little primary porosity is preserved in the pressolved, finer grained sandstones, whereas appreciable primary porosity may be retained in coarser grained sandstones that contain more quartz cement. These relationships are also sensitive to thermal maturity, which increases eastward across the basin. This thermal trend is probably related to elevated temperatures associated with intrusions in as much as maximum burial depth of the Hartshorne decreases eastward. As thermal maturity increases, more intergranular pressure solution is evident for a given grain size whereas the volume of quartz cement does not change significantly. Thus, primary porosity tends to be preferentially preserved in areas of lower thermal maturity. In areas of higher thermal maturity, the sandstones have lost more silica via intergranular pressure solution than has been precipitated as quartz cement whereas the opposite is true in areas of lower thermal maturity. End_of_Article - Last_Page 584------------

Read full abstract