These are four SEM photomicrographs of the Silurian Clinch Sandstone from Thorn Hill, Tennessee. They were generated by graduate student Mike Jordan with the help of Technician Cathy Kelloes of the Center for Advanced Ultrastructural Research as part of Mike's class project for GEOL 8180 (Sandstone Petrology) at the University of Georgia.

    The Clinch is a quartz-rich sandstone generated during one of the tectonically quiet phases of the Appalachians' otherwise active Paleozoic history. These SEM images show that, after 400 million years, the Clinch still has some primary intergranular porosity (as shown at the arrow in the upper left lowest-magnification image). However, euhedral quartz overgrowths on detrital quartz grains have filled much of the intergranular space, as shown in the three higher-magnification images at upper right and lower left and right. Circles in the lower two images enclose areas where the euhedral quartz crystal faces have small pits indicative of dissolution. Such evidence suggests that the silica-saturated porewaters that precipitated the quartz overgrowth cements were followed by undersaturated waters that caused dissolution and corrosion of those cements. Such dissolution may have happened long ago or may be the result of weathering by modern meteoric waters.

   

  Four SEM images

   

 

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