Mineralogy of fine-grained alluvium from borehole U11g, expl. 1, northern Frenchman Flat area, Nevada Test Site

The mineralogy of matrix fines in alluvium from borehole Ullg, expl. 1, north of Frenchman Flat, Nevada Test Site, has been examined for evidence of past variations in water table elevation. Although an abundance of zeolite and slightly expanded basal spacings in smectite clays suggest effects of increased hydration of material up to 50 m above the present water table, these differences might also be related to provenance or environment of deposition. However, the relative uniformity of clay hydration properties in the 50 meters above the current water table suggests long-term stability near the present level, perhaps through most of the Quaternary.