The Island of Oahu is third in size in the Hawaiian group and lies in the mid-Pacific about 2,100 miles southwest of San Francisco. Honolulu, the capital and principal port of this group, is on Oahu. Two dissected volcanic domes, the Waianae Range (4,035 feet high) and the Koolau Range (3,105 feet high) make up the island. They are surrounded by a nearly continuous coastal plain, in places reaching nearly 6 miles in width and consisting of emerged Pleistocene reef limestone and terrigenous deposits. A living coral reef fringes all of the island except the east and west ends (Fig. 1).
The benches described below are with one exception found on Oahu or on islets near Oahu. They were studied from 1930 to 1934 by the writer while making a systematic survey of the geology and ground-water resources of Oahu for the Ground-Water Division of the United States Geological . . .