The Wisconsin Range consists mainly of a composite batholith of Late Precambrian and Early Paleozoic age. It is one of several batholiths that constitute the core of the Transantarctic Mountains. The batholithic rocks are flanked by the metamorphosed greywackes and argillites of the La Gorce Formation and the metavolcanic rocks of the Wyatt Formation that were deposited in the Ross geosyncline in Precambrian time. The metasedimentary and metavolcanic rocks were metamorphosed and partially reconstituted into granitic rocks during the Late Precambrian Mawson Orogeny. The resultant polygenetic batholithic complex ranges in composition from granite to quartz diorite, and has both foliated and massive facies. Some facies are characterised by abundant porphyroblasts of rapakivi feldspars. Tourmaline granite and porphyritic quartz monzonite make up other facies of the complex. The various facies have both gradational and intrusive relations with each other.