Sm-Nd model ages on a whole-rock sample of the gneiss at Watersmeet, Michigan, show that these rocks were added to the continental crust about 3,600 m.y. ago. These model ages are calculated by assuming that the rocks were derived from a mantle reservoir with the Sm/Nd ratio of CHUR, which corresponds approximately to the chondritic ratio. These data confirm the U-Th-Pb zircon results that indicated a minimum age of 3,410 m.y. and possibly an age as old as 3,800 m.y. This study further illustrates the utility of Sm-Nd model ages in deciphering the history of complex Precambrian terranes.