A structure map was constructed of the continental shelf between Cape Blanco and Coos Bay, Oregon, exclusively from an interpretation of approximately 700 km of continuous seismic profiles. At least ten discernible seismic units were mapped on the bases of acoustic appearance, lateral continuity, angular unconformities, and faults. The offshore units tentatively were correlated with onshore geology and are believed to range in age from the latest Jurassic to late Pleistocene. The sparker profiles reveal that the continental shelf off southern Oregon has experienced significant late Tertiary and Quaternary accretion due to deposition and tectonic uplift. The oldest rock exposures, believed to be the latest Jurassic in age, crop out on the inner continental shelf on the topographic highs off Cape Blanco and Coquille Point. Erosional remnants of probable Late Cretaceous turbidites and the middle Eocene sandstone beds also are exposed on the bathymetric high on the inner shelf southwest of Cape Arago. The initial emplacement of these three uplifted structural blocks is probably a result of late Eocene wrench faulting of the Port Orford shear zone and of the postulated shear zone at Coquille Point. No other early Tertiary sediments apparently are exposed on this portion of the Oregon continental shelf, but they probably extend seaward at depth on the continental margin. Middle Tertiary strata are believed to be exposed on the outer shelf topographic high southwest of Cape Arago. Sediments of Miocene to Pliocene age were deposited throughout much of the continental shelf that was surveyed. The greatest amount of deposition occurred in a north-south trending basin between Cape Blanco and Coquille Bank. Late to post-Pliocene tectonism uplifted and exposed the older underlying rocks on the inner shelf, which are probably of uppermost Jurassic to middle Tertiary age. These same stresses also deformed the Mio-Pliocene sediments into gently undulating structures on the inner shelf. The greatest deformation occurred on the outer shelf and formed Coquille Bank, a north-south trending, doubly plunging, asymmetrical anticline. The terraces or benches on the upper continental slope to the north and south of the Bank are structural features resulting from the doubly plunging anticline. Eustatic sea level lowerings during the Pleistocene truncated the shelf structures as deep as 130 m below present sea level. The detritus was deposited as a wedge of sediments, which forms an unconformable contact with the underlying strata on the outer shelf and upper slope between Coos Bay and Coquille Bank. In areas of deposition there is no distinct break between the shelf and the upper slope; the former merely merges into the latter in a continuous convex curve. In areas of nondeposition, the edge of the shelf is an erosional and structural feature. A possible buried channel was detected northwest of the mouth of the Coquille River. This sediment filled channel is believed to be an erosional remnant of a former course of the Coquille River during a lower stand of sea level. / Graduation date: 1969

From measurements of thermal and electrical conductivities of 64 ocean sediment samples obtained from piston cores taken off the Oregon Coast, and from 37 water-saturated sandstone samples analyzed by Zierfuss and Van der Vliet (1956), as well as 51 thermal conductivities and water contents of ocean sediments analyzed by Ratcliffe (1960), this research shows that a useful relationship can be obtained giving thermal conductivity when electrical conductivity is known. Analysis of the data was made using theoretical concepts which have been known for many years to relate thermal and electrical conductivity to porosity. The results of this research may make possible a convenient determination of in situ thermal conductivity that would give the average conductivity in materials containing large variations in conductivity. / Graduation date: 1966

Sediments on the inner portion of the Oregon continental shelf consist of clean, well-sorted, detrital sand. This sand has an average median diameter of 2.53Φ (. 173 mm) and is both positively and negatively skewed. Deposits with median diameters in the coarse sand and gravel classes occur at depths of 20 to 40 fathoms and probably represent ancient beach or fluviatile deposits formed during lower stands of sea level. The outer shelf and upper slope are covered by poorly sorted sediments with median diameters in the fine sand to fine silt classes. Mean diameters of the sediments are almost always smaller than their median diameters and the sediments are positively skewed. The heavy mineral assemblages are dominated by the amphibole and pyroxene groups and the opaque-garnet association. Pyroxenes are most abundant in the coarser-grained sediments of the inner shelf and decrease in abundance offshore. Amphiboles are most abundant in the finer-grained sediments of the outer shelf and upper slope. Highest concentrations of the opaque-garnet association also are found in the inshore samples. Sediments of the continental shelf are derived from two principal sources, rivers and erosion of coastal terrace deposits. Rivers are probably contributing only fine-grained material to the shelf as much of the coarser fluviatile material is thought to be trapped in the estuaries. The terrace deposits are actively being eroded and are thought to contribute about 21,000,000 cubic feet (.00013 cubic miles) of sediment to the continental shelf annually. Evidence suggests that much of the inner-shelf sand is probably a relict transgressive sheet sand that was deposited during the last rise in sea level. Most of the deposition of the modern sand on the shelf has been confined to the inner portion of the inner shelf. Finer-grained sediments have been deposited on the outer shelf and upper slope. Characteristics of the sediments on the present continental shelves may be useful in identifying continental shelf deposits in the geologic column. / Graduation date: 1966