This report describes the Cenozoic geology of the Willamette Lowland physiographic province, and the geologic framework of the regional ground-water flow system. Five regional hydrogeologic units are identified and described. The report includes maps showing the altitude of the top and the thickness of each hydrogeologic unit.
Additional publication details
USGS Numbered Series
Geologic framework of the Willamette Lowland aquifer system, Oregon and Washington
U.S. Dept. of the Interior, U.S. Geological Survey,