The Galleta Flat West quadrangle includes the northern part of the divide between the Tucson basin to the west and the San Pedro Basin to the east, and the southern part of the Little Rincon Mountains. The region is dominated by Proterozoic and mid-Tertiary granitic rocks bordered by Late Tertiary basin-fill deposits that fill the low divide between the Whetstone Mountains to the south and the Rincon and Little Rincon Mountains to the north. Interstate 10 slices across this low area a few miles south of the quadrangle. Fieldwork was carried out between November, 2000 and April, 2001. This study was done during the same field season as mapping to the south in the Mescal 7.5’ quadrangle (Skotnicki, 2001)