The Tillamook Highlands is a largely unmapped volcanic pile located in the north end of the Coast Range of Oregon. The 36 square miles of T. 1 N., R. 8 W., on the southcentral margin of the Highlands, was chosen for detailed study.
The study area is composed of Eocene age sedimentary and volcanic units which were deposited in a filling basin. The lowest units were deposited in moderate to deep marine waters; the uppermost were deposited subaerially
