The Cretaceous formations of southwestern Arkansas consist largely of unconsolidated sand, clay, and marl, but include some beds of limestone, sandstone, and chalk. They rest on a pre-Cretaceous erosion surface, which is cut on folded and faulted Paleozoic rocks and dips to the south and southeast at about 100 feet per mile. The Cretaceous beds dip south and southeast from 65 to 80 feet per mile. The Lower Cretaceous Comanche series in the area includes the Trinity formation, 0-2100 feet thick, consisting of novaculite gravel, limestone, gypsum, fine-grained sand, and variegated red and gray clay; the Goodland limestone, of Frederickburg age, a hard, gray sandy limestone, 0-50 feet thick; and the Kiamichi clay, consisting of green-gray marl and fossiliferous shell beds, 0-20 feet thick.

*Includes: 207 pages, 29 plates, and 4 figures;