Holtedahl was among the last of a generation of geologists that mastered the subject in all its breadth. He delivered a significant contribution, not only in Norway but also for large areas of the Arctic and Antarctic. His first geological work dealt with the Oslo Rift in the Cambrosilurian period, and he was part of the 1909-11 expeditions to Svalbard. Between 1914-17, he explored the geology of Lapland, and in 1918, he worked at Bear Island. In 1921 he led a Norwegian expedition to Novaya Zemlya. He joined the 1927-28 Antarctic expeditions of Lars Christensen, and he edited the scientific results from these expeditions . He was the doctoral advisor of Bjørn G. Andersen, whose subsequent works on Quaternary geology he greatly influenced.