With other factors held constant, quartz content is a positive function of grain size. Examination of changes in this relationship among degradational processes associated with longer transport. In general, sediments become more quartzose in the silt and sand sizes as these processes proceed.

This approach has discriminated between the bordering Appalachian and Ouachita fold belts as sources of the Upper Carboniferous detritus of the Black Warrior basin of Alabama. If an Appalachian source is postulated, all samples taken proximally to the folded zone should be quite similar, being at the same time less quartzose for their grain size than samples collected farther to the west. Conversely, a southern, Ouachita source would yield increasing quartz contents from south to north. Experimental studies indicate the latter condition, with no perceptible Appalachian contribution.

These results form a basis for predicting the character of these rocks beneath the mantling sediments of the Mississippi embayment, as well as clarifying the order of tectonic events of the southeastern United States.

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