(mär'bət) , 1863–1935, American geologist, b. Verona, Mo., grad. Univ. of Missouri (B.S., 1889) and Harvard (M.A., 1844). As professor of geology at the Univ. of Missouri, he became interested in soil morphology and classification and developed soil survey maps of southern Missouri. Later working for the U.S. Dept. of Agriculture, he completed a similar survey of the entire Ozark region. In 1913 he devoted himself to the establishment of a permanent system of soil classification for the entire United States. He thus became known as the father of modern soil classification, including soil genesis, morphology, and mapping. Marbut organized and led numerous geological excursions throughout the world and also worked on setting up an international system of soil classification. His most important publication was Soils of the United States (1935).