Dorrel Rock (75°26′S 111°22′W / 75.433°S 111.367°W / -75.433; -111.367) is a nunatak located 20 km (12 mi) southwest of the summit of Mount Murphy, protruding through the ice near the head of Pope Glacier, on the Walgreen Coast, Marie Byrd Land.
[1][2] Dorrel Rock is an 2 km (1.2 mi) in diameter exposure of gabbro cut by dikes of benmoreite and trachyte.
The gabbro is coarse-grained and composed of labradorite, diopside and ilmenite, with minor titanomagnetite, kaersutite, biotite, and amphibole.
The benmoreite dikes consist largely of sodic oligoclase, hastingsite-ferropargasite, scarce magnetite, and minor biotite.
Since the gabbro cooled as deep as 3 km (1.9 mi) beneath the surface, this age indicates that 3 km (1.9 mi) of the block of Antarctica's crust containing Dorrel Rock has been uplifted and removed by erosion over the past 34 million years in response the formation of the West Antarctic Rift.