The Southeast Durham and Southwest Durham 7.5-minute Quadrangles encompass an area of approximately 300 square kilometers. The quadrangles include a large part of the Durham Triassic basin and small areas of the adjacent Piedmont region. A significant amount of the study area is urban and suburban. Large portions of Durham, Research Triangle Park, and Raleigh-Durham International Airport are located within the study area as are developing sections of Raleigh and Chapel Hill. The specific objective was to provide detailed surface geologic mapping of the study area. Toward this end, lithofacies within the Triassic sedimentary rocks of the two quadrangles were identified and mapped. The lithofacies are defined chiefly by field criteria including mineralogical composition and sedimentary textures and structures. By Charles W. Hoffman and Patricia E. Gallagher, 1989, reprinted 1995. 34 pages, 2 plates included, maps of each quadrangle at approximately 1:50,000 scale. Maps also available at 1:24,000 scale as Open-File Report 89-1 (Southeast Durham) and 89-2 (Southwest Durham).