Field activities in the Britannia Range (Transantarctic Mountains, Antarctica) highlighted new geological
features around the so-called Byrd Glacier discontinuity. Recent field surveys revealed the occurrence of significant
amounts of medium- to high-grade metamorphic rocks, intruded by abundant coarse-grained porphyritic granitoids.
Most of the granitoids are deformed, with foliation parallel to the regional foliation in the metamorphics. Two main
episodes of deformation are observed. Tight to isoclinal folds and penetrative axial plane foliation are related to the D1
phase, open folds to the D2. The main foliation (D1) trends nearly E-W in agreement with the trend in the southern
portion of the Byrd Glacier. In most outcrops, granitic dykes are folded and stretched by the D2 deformation, which
shows similar characteristics with the D2 deformation south of the Byrd Glacier. This suggests the occurrence in the
Ross orogen of an orogen-normal structure south and north of the Byrd Glacier.