Ford Ranges
Marie Byrd Land - Rocks exposed in western Marie Byrd Land on the Edward VII Peninsula and within the Ford Ranges are candidates for basement in the eastern Ross Sea. The oldest rocks are Permian sediments of the Swanson Formation, which is slightly metamorphosed. The Ford granodiorite of Devonian age intrudes these sediments. Cretaceous Byrd Coast granite in turn intrudes the older rocks. The Byrd Coast and older formations have been cut by basalt dikes. Scattered through the Ford Ranges and Fosdick Mountains are late Cenozoic volcanic rocks that are not found to the west on Edward VII Peninsula. Metamorphic rocks, migmatites, are found in the Fosdick Mountains and Alexandra Mountains. These were metamorphosed and deformed in the Cretaceous.