During the drilling of GT-2 and EE-1, 27 cores totaling about 35 m were collected from the Precambrian section. Samples of each different lithology in each core were taken for petrographic and whole-rock major and trace-element analyses. Whole-rock analyses are now completed on 37 samples. From these data we recognize four major Precambrian units at the Fenton Hillsite . Geophysical logs and cuttings have been used to extrapolate between cores. abundant rock type is an extremely variable gneissic unit comprising about 75% of the rock penetrated