Pebbly Mudstone Island is a small island in the southeast part of Duroch Islands. It lies southwest of Halpern Point, Trinity Peninsula. Named by Martin Halpern, leader of the University of Wisconsin (USARP) party during geological mapping of this area, 1961–62. The principal outcrop of pebbly mudstone was found on this island and provides valuable data to the geologic history of the region. See also List of Antarctic and sub-Antarctic islands Islands of the Duroch Islands