The 36 samples collected with a 22-foot semi-balloon shrimp trawl at depths from 40 to 1,829 meters off the central coast of Oregon between July 1961 and June 1962 provided preliminary data on the distribution, species composition, and associations of benthic fishes with respect to depth and sediment type. Sixty-seven species of bottom fishes representing 21 families were collected; 86 percent of the total number of fishes was composed of specimens from the families Pleuronectidae, Scorpaenidae, and Bothidae. Four communities of benthic fishes were found off the central Oregon coast within the depth interval from 40 to 1 ,829 meters. They were characterized by two or three dominant species, depth, and average sediment type. Ninety-seven percent of the species occurring in the communities showed high abundance in only one community. Some species also demonstrated size segregation by communities. The total number of species collected in progressively deeper communities was 26 (42 to 73 meters), 31 (119 to 199 meters), 20 (594 to 1,143 meters), and 9 (1,383 to 1,829 meters). Therefore the highest number of speciesoccurred in the community on the outer continental shelf and upper slope, while the lowest number of species occurred at the extreme depths on the continental slope. The number of species found on the continental shelf and slope were similar. Species inhabiting the continental slope, however, usually occurred over greater depth ranges. A comparison of the catches of the 22-foot shrimp trawl and a 94-foot fish trawl indicated that the small trawl used in this study retained comparatively few large fishes or semi-pelagic species. Fishes of the genus Sebastodes were grossly undersampled and probably comprised a major portion of the fish population, especially between the depths of 183 to 547 meters. / Graduation date: 1968

Graduation date: 1968

The abundance and distribution of biogenic, terrigenous and volcanic particles in the Panama Basin are markedly dependent on bottom topography and dissolution of calcite in the deeper parts of the basin. Of the coarse fraction (>62μ), foraminiferal tests and acidic volcanic glass shards are concentrated on the Cocos and Carnegie Ridges as lag deposits. Foraminiferal fragments are found on these ridge flanks and on the Malpelo Ridge due to reworking by bottom currents accentuated by dissolution of calcite with increasing depth. The finest calcite, probably coccoliths with fine foraminiferal fragments, together with the hydrodynamically light radiolarian skeletons are concentrated by bottom currents in the basin adjacent to the ridges. The foraminiferal calcite compensation depth in the basin is 3400 m. This relatively shallow depth probably reflects the high surface water productivity over the basin, although the pattern of productivity is not reflected in the pattern of biogenic sediments. Acidic volcanic glass appears to have been carried into the basin from Costa Rica, Colombia and Ecuador by easterly winds at altitudes of 1500 to 6000 m. Basaltic shards from the Galapagos Islands have been dispersed only over short distances to the west. Terrigenous sand-sized material is found on the edge of the continental shelf, where associated glauconite points to a relict origin, and along the northern Cocos Ridge, where contour currents may act as the dispersal mechanism. / Graduation date: 1973

Holocene hemipelagic deposition of terrigenous silts and clays dominates sedimentation on most of the Oregon and Washington continental slope. The sources of these sediments, the mechanisms causing sediment dispersal, and the relative contributions of the various continental sources to the marine deposits have been investigated using quantitative mineral and geochemical data for the 2-20 μm and the <2 μm size fractions. In the 2-20 μm size fraction, material derived from the Klamath Mountains and the California and Washington Coast Ranges contains chlorite and illite, but only Klamath material contains hornblende. Columbia River material lacks chlorite, and the Oregon Coast Range source is dominated by smectite. In the <2 μm fraction, source area compositions are less distinctive due to the ubiquity of smectite, but the northern and southern sources again contain both chlorite and illite. Regional and local mineralogic and textural variations in the fluvial sediments reflect geologic and geographic changes between drainage basins. Amorphous material is a minor component in the 2-20 μm fraction of the fluvial sediments, but may form 25-50% of the <2 μm fraction in some source areas. Sediments derived from all source areas are transported north and northwestward across the margin, either by a poleward-flowing undercurrent along the slope, by wind-driven surface currents on the shelf and associated turbid layers on the slope, or by a combination of the two processes. Columbia River <2 μm material may also be carried southward along the shelf and upper slope by summer surface currents. The poleward undercurrent (an eastern boundary undercurrent) appears to have limited sedimentological significance when compared to the role of the western boundary undercurrent in sediment transport and deposition on the continental slope and rise of the eastern United States. Linear programming has been applied successfully to estimate source area contributions to the 2-20 μm marine sediments. The influence of each source is largest in proximal environments, and the contribution estimates indicate that material derived from each source area is transported northward along the margin. Similar estimates for the <2 μm material are considered unreliable because of internal inconsistencies and the uniform nature of the <2 μm compositions used in the modelling. The contributions have been used to calculate a sediment budget for the 2-20 μm fraction. This budget indicates that the mass accumulating on the entire slope within the study area contains 47% Columbia River, 32% Klamath Mountain, and 21% California Coast Range material in the 2-20 μm fraction, and demonstrates the importance of multiple sediment sources and sediment mixing in the formation of hemipelagic sediments on the continental margin. / Graduation date: 1982

Surveyor Deep-Sea Channel extends for approximately 700 km over the northern Alaskan Abyssal Plain. It originates near the base of the continental slope opposite Dry Bay and Alsek Strath and terminates in the Aleutian Trench south of Kodiak Island. East of Giacomini Seamount, the axial gradient of the channel is in the order of 10 m/km and its morphology is in agreement with prediction, assuming a depositional equilibrium with channelized turbidity currents. West of Giacomini Seamount, the axial gradient increases to values as high as 7.5 m/km, as the channel course turns toward the northwest and plunges into the trench. Over this part of its length the measured center channel relief and cross-sectional area of the channel increase, contradicting prediction. The lower channel is found to be erosional in nature, this effect being a response to downwarping of the northern rim of the Pacific Plate into the Aleutian Trench. The channel originated in early to middle Pliocene time coeval with the initiation of pronounced tectonism and intense glaciation in southeastern Alaska. At this time, the channel was located perhaps 200 km south of its present position with relation to the North American Plate, and may have been linked with one of the fossil sea-channels on the eastern Aleutian Abyssal Plain. Throughout its history, the channel has not been linked with any consistent river drainage system, its sediment source instead being the large system of piedmont glaciers in southeastern Alaska. The distribution of coarse sedimentary material over the northern Gulf of Alaska strongly suggests that turbidity current activity has not been confined to only those regions close to Surveyor Deep-Sea Channel. / Graduation date: 1972

Changes in sea level during the past 20,000 years are recorded in sediments taken from the continental shelf off the Rogue River, Oregon. Sea level has risen approximately 125 m. during the Holocene (Curray, 1965) and the general transgression has been interrupted by several stillstands and minor regressions. Box core samples taken in the area of investigation depict the nature of sedimentation during the last rise of sea level as well as present-day equilibrium sediment relationships. Three sediment facies, a recent fine-grained mud, a basal transgressive sand, and an intermediate sediment, believed to be a mixture of the other two, are defined on the shelf on the basis of textural parameters. The mud facies dominates surface sediment on the central shelf while the sand facies is the most commonly exposed on both the inner and outer shelf. The percentage of sand generally increases with depth in the box cores, often producing a change in sediment facies with depth and demonstrating the transgressive nature of the sediments. Grain-size analysis of the sand fraction of the offshore sediments reveals that offshore sands are finer-grained and better sorted than those occurring on the present beaches. The offshore sands most likely represent relict nearshore deposits and not ancient beach sands which would occur lower in the sediment sequence. High concentrations of heavy minerals are found in the sand fraction of the offshore sediments as well as in beach sands in the area. Brief stillstands of sea level may be reflected in depths where the offshore sands contain anomalously high percentages of heavy minerals. Opaque minerals, chiefly magnetite, occur in placer accumulations on the present beaches and high percentages of these minerals in the offshore sands may be indicative of submerged beach environments associated with stillstands of sea level. The magnetite may be concentrated in sufficient quantity in the placers to produce detectable magnetic anomalies, several of which have been recorded in the area. Other lines of evidence used to determine the depths of probable stillstands of sea level are bathymetric relief, the distribution of shallow water fauna in sediments from deep water, and the distribution of rounded gravels on the shelf. A compilation of the several lines of evidence suggests several stillstands of sea level associated with the Holocene transgression occurring at depths of 18, 29, 47, 71, 84, 102, and 150 meters. / Graduation date: 1969

Graduation date: 1974

Holocene bulk sediment and component accumulation rates were measured in twenty-eight piston and gravity cores taken from the floor of the western Panama Basin and on the surrounding ridges. Radiocarbon ages and oxygen isotope curves provided Holocene age control in nine cores. Time datums in nineteen other cores were inferred by correlation of calcium carbonate curves to the dated cores. Dry bulk densities were measured in ten cores and were estimated in the others by an empirical relationship between dry bulk density and the percentages of sand, clay, and calcium carbonate. Other studies of the textural, mineralogical and sand fraction composition of near surface sediments in these cores provided analyses which could be used to obtain accumulation rates for these components. A general similarity between the map pattern of surface productivity and the patterns of carbonate and opal accumulation rates suggests a first order control of biogenic sedimentation by fertility of surface waters. Accumulation rates of terrigenous components are highest near the continents; the map and depth patterns suggest dispersal by currents shallower than 2000 m or by winds. It is inferred from textural component accumulation rate patterns that no significant regional redistribution of sediment by winnowing occurred during the Holocene. Deposition from deep thermohaline circulation probably increased the accumulation rates of silt, clay, and opaline components in the gaps between the western and eastern troughs. Calcium carbonate accumulation rates at equal depths are generally lower within 250 km of the edge of the continental shelf. Below 2000 m in high productivity regions > 250 km from the shelf calcium carbonate accumulation rates decrease linearly with depth according to a gradient of -3.3 gm CaCO₃/cm²/1000 yrs/ km. From this gradient, two independent estimates of the lysocline in this region, and a model of calcium carbonate accumulation, the average Holocene rate of supply of calcite from the surface is calculated to be 5-10 gm/cm²/1000 yrs. / Graduation date: 1976

Cores taken from the ridge areas of the Gorda-Juan de Fuca plate have a sedimentation rate that is appropriate for the study of late Quaternary stratigraphy. An analysis of the clay and silt mineralogy of the cores using X-ray diffraction methods and by noting changes in the foraminiferan-radiolarian abundances in the cores were utilized in developing a stratigraphic sequence. The clay fractions of these sediments consists of chlorite, illite and smectite. Cores taken from bathymetric highs contain, on the average, less smectite than do the turbidites from the adjacent lowlands. The low smectite content suggests eolian enrichment of these sediments since dusts collected from the nearby continent also have low smectite concentrations. Changes in the relative abundances of radiolaria and foraminifera are used to put biostratigraphic constraints on the correlation of mineralogical datums. Two changes in the foraminiferan-radiolarian ratios, marked by sharp increases in the abundance of radiolaria, occurred at 12,500 years B.P. and 83,000 years B.P. as dated by carbon-14 and sedimentation rate extrapolations, respectively. Such faunal changes serve as an independent check of correlations of the mineralogical datums. In the 2 to 20 micron, silt fraction, quartz, chlorite, mica and feldspar are the predominant minerals. Intervals in which the relative abundance of quartz changes can be dated by carbon-l4 and sedimentation rates, and related to late Quaternary climatic events. The quartz-rich zones are synchronous with periods of high insolation, high stands of sea-level, and to a lesser degree with the catastrophic floods of the Columbia River. The correlation with high solar radiation reflects quartz enrichment of the sediment due to an increased eolian contribution. The coincident high sea level stands effectively decreased the sedimentation rate of quartz-poor continental detritus that otherwise dilutes the eolian component. The periodic floods of the Columbia River, caused by the failure of ice dams, swept quartz-rich loess from eastern Washington down the river and injected into the marine environment. Such sediment also increased the quartz abundance in the quartz-rich zones on the ridges. Thus, the late Quaternary stratigraphy of the cores can be related to global late Quaternary climatic variations as well as to events recorded on the adjacent continents. The structural development of the Gorda-Juan de Fuca plate over the last 10 million years can be explained by north-south shortening coupled with the normal tectonism associated with a spreading sea floor. This hypothesis for the development of the plate is based on the presently known magnetic anomaly pattern. A series of reconstructions of this pattern back through the past 10 million years shows that both the Gorda and Juan de Fuca portions of the plate have grown steadily smaller. The incorporation of sequentially shorter Gorda ridge anomalies into the Pacific plate appears to have led to the northwest-southeast orientation of the Blanco Fracture Zone, with consequent changes in the direction of spreading of the Juan de Fuca Ridge. On the Juan de Fuca portion of the plate, the shortening was accomplished by shear faulting in Cascadia Basin. Furthermore, this faulting resulted in the rapid subduction of this portion of the plate, which, in turn, produced a disconformity in the sediments of Cascadia Basin. The reconstruction strengthens the notion that right lateral strike slip motion between the Pacific and Gorda-Juan de Fuca plate does, indeed, exist. / Graduation date: 1974

In order to determine whether the sediments found on the landward wall of the Peru Trench are accreted Nazca Plate sediments, the clay mineralogy and organic carbon contents of 52 surface samples were submitted to factor analysis. Q-mode factor analysis resolved the data from the Nazca Plate and Peru continental margin into three factors. The most important factor (oceanic assemblage) is strongly associated with Nazca Plate sediments and is comprised of smectite and aeolian illite. In contrast, upper continental margin sediments are dominated by either of the two continental factors (A or B). The principal difference between the continental factors is that mixed-layer smectite-chlorite clays are characteristic only of continental assemblage A. Lower continental margin sediments are characterized by either an oceanic or continental factor dominance. The boundary between sediments dominated by the oceanic factor and those dominated by the continental factor was as much as 100 km to the west of its present position earlier in the Quaternary. The seaward shift in the boundary is attributed to westward shoreline displacement in response to glacially-induced sea level changes, increased erosion rates on land during more humid times, and deposition of continental factor dominated sediments seaward of the present Peru Trench axis. Quaternary sediments from 27 cores reveal minor fluctuations with time in factor loadings in Nazca Plate and upper continental margin cores and significant variations in some areas near the trench axis and on the middle to lower continental slope. Displacement of oceanic sediments into areas with continental sediments is determined with respect to the factor dominance boundary. Using this method, continental accretion is indicated for five cores, located up to 3000 m above the trench floor. One core on the middle continental slope off Lima, Peru, contains diatom-rich Quaternary dolomite that probably originated as calcareous sediment on the Nazca Ridge. If this is true, left-lateral strike-slip motion of the Nazca Ridge along the Peru Trench axis is indicated. The bulk of the 28 cores recovered from the acoustically complex landward wall of the Peru Trench contain sand-silt turbidites of continental origin. Even though there is a distinct overprint of terrigenous sedimentation, accreted oceanic sediments can be recovered in a tectonically active convergent plate boundary. / Graduation date: 1974