Abstract

The lower Victoria and Wright valleys are relatively ice-free and hence ideal to determine the pre-Devonian structural and metamorphic history of the basement complex. The rocks have suffered polyphase deformation with possibly four fold generations being recognised. F1 produced isoclinal folds which have been refolded during later events. F2 is the dominant fold generation, producing close to isoclinal asymmetric folds and a well-developed, subvertical, NW-SE striking axial surface foliation. Fold axes have variable plunges within this plane. F3 and F4 are localised in extent. Some Theseus Granodiorite dykes contain the S3 foliation and hence are pre-F3 in age, whereas the Vanda porphyries and lamprophyres are unfolded and hence post-F3 in age. The field studies confirm a complicated pre-Devonian structural and metamorphic history of the McMurdo region of the Transantarctic Mountains.