Limited possibilities exist for new hydrocarbon exploration regimes in the Pacific Northwest. Our goal in this presentation is to outline recent knowledge concerning a possible new exploration environment in the State of Washington. This frontier area occurs in southwestern Washington where extensive geophysical studies have been used to outline a proposed sedimentary basin hidden beneath volcanic rocks in the southern Cascades region (Stanley et. ai, 1992). Electrical geophysical imaging using the magnetotelluric (MT) method first detected thick, electrically-conductive sequences believed to be associated with Eocene to Oligocene marine sedimentary rocks. The conduct.ive section occurs at depths from about 1 km to 10 km in the southern Cascades region with thicknesses up to 10 km. Careful consideration of physical properties and the correspondence of the morphology of the units to known fold sets suggests that the high conductivities are related to lithologic/stratigraphic units rather than to variations in physical properties. Our preference for the lithology of the anomalous section, based upon a study of. regional geology and structure, is one dominated by marine shales of Eocene and older in age. Other possible lithologies that have been evaluated for the conductive section include non-marine sedimentary units of Tertiary age, highly altered volcanic flows, and pre-Tertiary metasedimentary rocks with large percentages of graphite. We refer to this anomalously conductive region as the southern Washington Cascades conductor (SWCC, Fig. 1).