Preliminary results are given of field surveys made in 1968 on the pre-Beacon folded basement of the Transantarctic Mts. In the McMurdo Dry Valleys of southern Victoria Land. The data show a metamorphic complex dived into three series, bottom upwards: genies (not less than 4,000m thick), gneiss-schist (2,000m thick) and marble-schist (1,000m thick). The lowest series comprises the gneiss-magmatite pre-Cambrian layer (?), the other two series are related to the Upper-Proterozoic and Lower Paleozoic “Ross Supergroup.” Preorogenic, synorogenic and postorogenic intrusive formations distinguished in the McMurdo oasis are discussed.