Graduation date: 1973

Graduation date: 1969

Sea level and current data collected near Newport, Oregon are compared to determine an empirical relationship from which the low frequency (f < .1 cpd) alongshore current field over the continental shelf is estimated from observed sea level measurements at the coast. Regression analysis of the near-surface (20-25 m) currents with sea level indicates the surface currents are in geostrophic balance with the sea surface slope. Analysis of the alongshore shear between the near-surface and deep (75-80 m) layers with sea level shows the thermal wind relationship holds. A near-surface regression model is developed from which the mean monthly alongshore current 20-25 m below the surface can be estimated with a standard estimate of error (σ[subscript ER]) less than six cm/sec. The annual range at this depth is nearly 60 cm/sec. A regression model for the alongshore shear is formed from which the mean vertical shear is estimated with a σ[subscript ER] of .07-.10 cm/sec/m. The annual range is approximately .8 cm/sec/m. The surface currents are found to be predominantly driven by the local meteorological conditions. Deep and near-bottom current observations suggest the deep layer currents are primarily influenced by the thermal wind relationship and the location of the California Undercurrent. / Graduation date: 1977

Graduation date: 1974

Direct measurements of vertical water motions were made in the Oregon coastal region during the 1972 summer upwelling season. The instruments used were the Webb-Voorhis vertical current meters which are freely drifting neutrally buoyant floats capable of sensing vertical motion. It was found that in the region studied, water tended to sink at depths of 40 to 60 meters under the influence of strong northward and southward winds but that water tended to rise during the slackening periods of a southward wind. Techniques used in processing the data, some problems encountered, and the results of four good dives are presented along with possible correlations of vertical water movements with wind, sea Level, and isopycnal movements. / Graduation date: 1974

The Geochemical Ocean Sections Study (GEOSECS) program has carried out an intensive study of physical and chemical parameters in the Pacific and Atlantic Ocean. As a result, an enormous collection of high quality data has been amassed for these two oceans. To analyze the Pacific data, fourteen stations extending from about 50°N to 69°S near 180°longitude have been selected for this study. The section chosen provides a good continuous north-south section in the Pacific from near the Bering Sea to the Antarctic. To study this massive extent of the oceanic regime, three methods were adopted. The first was to estimate, using Defant's method, the approximate level of no motion throughout the section. Secondly, vertical section plots were contoured for various physical and chemical parameters to help identify and trace oceanographic features throughout the Pacific. Finally, calculations for stability were applied to each station in the section to evaluate the correlation between features of stability and those seen in the section plots. The depth of the level of no motion showed strong variability in the Pacific Ocean, Generally, deeper levels were found in the higher latitudes with shallowing towards the Equator. In the high southern latitudes, no level of least motion could be identified. This is consonant with the condition that the establishment of a level of no motion involves noticeable stratification of the water column. In high latitudes, the more nearly uniform distribution of density throughout the water column inhibits the formation of layers of high stability and stratified condition. It is also noted that a good general agreement is found between the depths of the layer of no motion and the observed oxygen minimum in the GEOSECS section. This is especially apparent in midlatitudes where the transition layer between the North and South Intermediate Waters and the Pacific Deep Waters is the region of the oxygen minimum. In the layer of the oxygen minimum, biochemical depletion occurs and there is likely to be minimal replenishment by horizontal and vertical advection and diffusion. Therefore, it is suggested that the oxygen minimum layer is closely related to a region of minimal horizontal movement. The calculation of the level of no motion in the Pacific GEOSECS sections supports this hypothesis. The large scale circulation in the Pacific Ocean is clearly pictured by the parameter section plots obtained from the Pacific GEOSECS expedition. The North Pacific and Antarctic Intermediate Waters are clearly defined from their origins to disappearance by low salinity and high nutrient levels. The extent of the Pacific Deep Water throughout the Pacific is seen. This large mass of relatively homogenous water can be seen from the South to the North Pacific. As the water moves northward, a gradual increase in nutrients and decrease in oxygen occurs. A third water type seen in the South Pacific is Antarctic Bottom Water. It intrusion into the South Pacific can be defined in terms of the 27.86 sigma theta surface or by such parameters as oxygen, silicate, and apparent oxygen utilization (AOU). In an attempt to correlate the various features seen in the vertical sections, stability profiles were prepared for each station. The vertical stability profiles did not show any strong features other than shallow and intermediate stability maxima. Recent discussion concerning a "benthic front" associated with the Antarctic Bottom Water intrusion into the South Pacific Ocean is not supported by any stability feature. Gradients in certain physical and chemical parameters do occur but the density gradients maximum expected in a frontal zone is not seen. / Graduation date: 1977

Detailed bathymetric survey data were collected along the Peruvian continental margin and were compiled by the author and other investigators to construct a new bathymetric map for the area between 6° to 18°S latitude. Based on this map and individual bathymetric profiles, the continental shelf topography is essentially flat. Four different physiographic provinces (A-D) are defined on the continental slope. Each province apparently reflects the structural and tectonic settings in a given area. The trench is separated into three provinces on the basis of regional depth differences. Three sedimentary basins, Sechura, Salaverry, and Pisco, are recognized on the Peruvian continental shelf between 6° to 15°S. The landward migration on the axis of deposition within these basins is interpreted to be the sedimentary response to tectonism (uplift) taking place along the outer edge of the continental margin. Prominent sedimentary basins also occur on the upper continental slope; these basins have been named with respect to their geographic position as the Lima and Arequipa Basins. Landward and seaward migration of the axis of maximum deposition in these basins is interpreted to be the result of variable rates of uplift along the outer margin. Uplift along the seaward edge of these basins suggests that the accretion of trench and oceanic plate deposits is taking place along the lower and middle continental slope. Seismic reflection profiles, extrapolation of regional structural trends onshore to offshore along the Peruvian margin, and positive free-air gravity anomalies off southern Peru (Whitsett, 1975), show that an outer continental shelf high is present off northern and central Peru. This high is believed to be composed of Paleozoic rocks with a possible Precambrian core. The high is linked with the Amotape Mountains in northern Peru and the Coastal Ranges in southern Peru. It is an important element in the development of the Peruvian continental margin. Using all of the data available, a four stage model is proposed for the Mesozoic-Cenozoic evolution of the Peruvian continental margin. Stage I describes conditions prior to the formation of the subduction zone during Triassic time. Plate collision is postulated at the beginning of Stage II with the formation of a Benioff Zone about 180 m.y. ago (Triassic-Jurassic boundary). Accretion of trench and oceanic plate deposits occurs as a result of the initiation of under-thrusting of the South America Block by the Nazca Plate. Stage III describes the continuous seaward growth of the continental slope during middle to late Cretaceous time. During late middle (Turonian) and middle late Cretaceous (Santonian) time diastrophism in southern Peru restricted the marine conditions to central and northern Peru. During late Cenozoic time (Stage IV) the Peruvian margin attained its present configuration through continuous seaward growth of the continental slope and buildup of the sedimentary sequences found in the Sechura, Salaverry, and Pisco Basins, in central and northern Peru. Late Cenozoic volcanism in southern Peru is apparently associated with the large amount of sediments that reached the southern Peru Trench since late Cretaceous time. The Nazca Ridge apparently approached the Peruvian continental margin during Cenozoic time, and locally changed the morphology of the continental slope. The proposed model shows that the Peruvian continental margin is growing seaward and that continental erosion of the crystalline continental block is not necessary along the Peruvian continental margin. The model explains and justifies the presence of the outer continental shelf high off northern and central Peru. / Graduation date: 1976

The Carnegie Ridge is a linear, aseismic, submarine ridge lying between the Galapagos Islands and the coast of South America. A 2300 meter deep saddle near 86°W. longitude divides the ridge into western and eastern segments. Surface ship, near bottom, and grain size studies from the saddle have been used to delineate the present geological environment and history of the ridge. Structurally the Carnegie Ridge is rather simple in profile, being bounded by east-west trending scarps which give the ridge a block-faulted appearance. Acoustic basement over the ridge appears smooth on reflection profiles and is composed of chert. The sedimentary sequence above the chert horizon contains a lower chalk unit overlain by calcareous ooze. Where erosion has exposed the chalk a karst-like micro-topography is present which is characterized by steep walled channels and cliffs and consolidated bed forms undergoing erosion and dissolution. The ridge crest has been stripped of almost its entire sediment cover. Thick sequences of sediment are found only in areas protected from north or south flowing bottom currents. Evidence of erosion is provided by extensive channeling on both the north and south flanks of the ridge. Near bottom observations in one channel on the north flank revealed a large field of sand dunes indicating northward, downslope sediment transport. These dunes are found on a manganese-encrusted chalk which floors the channel. Hydrographic data suggest that the northward flow across the ridge may be produced by the spillover of bottom water. Near bottom and surface ship observations are consistent with a southward sediment transport on the south flank of the ridge. The mechanism responsible for this southward flow remains unresolved. Current meters deployed on the north and south flanks recorded only low speed currents, opposite in direction to the inferred sediment transport. Apparently the bottom water flow responsible for erosion and sediment transport over the ridge is episodic in nature and was not recorded during the present survey. The grain size characteristics of surface sediments respond to the same processes which control sediment distribution. Where erosion is evident over the ridge crest, coarse lag deposits of foraminiferal sand are found. Apparently the erosion is most pronounced at the sill depth on the ridge since the sediments tend to become finer both upslope and downslope from that point. Three dominant modes are present in the sand fraction from the ridge. These modes record the initial input and fragmentation of foraminiferal tests. Continued fragmentation and dissolution of these tests creates a large number of finer modes. The age of true basaltic crust over the ridge is between 10 and 26 million years. This crust was probably created during a period of very slow spreading on the Galapagos Rift Zone during the Miocene. Unconformities on the ridge indicate that erosion dates only from the mid-Pliocene. The initiation of erosion was probably in response to further uplift of the ridge. This uplift may have been related to slight southward underthrusting along the north flank of the ridge. / Graduation date: 1975 / Best scan available for figures on p.67, 96. The original is a black and white photocopy.

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

A new technique for determining the amount of opal in deep-sea sediments of any age is described. Using a normative calculation, a portion of the analytical silica concentration of sediments is subtracted as non-biogenic in proportion to the concentration of aluminum in the sample. The ratio of SiO₂:Al₂O₃ used to characterize the non-biogenic sediment fraction was determined by X-ray diffraction analysis of opal-free sediments. The procedure was tested against the X-ray diffraction method for determining opal in deep-sea sediments The biogenic silica content of Cenozoic sediments from 20 Deep Sea Drilling Project sites in the central equatorial Pacific was determined using the normative calculation technique for opal determination. The equatorial Pacific lies beneath the equatorial current system where upwelling of nutrient-rich waters results in high plankton productivity. Accumulation rates of biogenically produced silica were calculated from the opal contents. Maps of these accumulation rates for time intervals during the Cenozoic show that opal accumulation was highest near the equator or paleoequator during the last 50 m.y. Superimposed on this pattern are fluctuations in the rate of opal accumulation in the entire area with time. Regional maxima in opal accumulation in the entire area with time. Regional maxima in opal accumulation occurred during the middle Eocene (42-45 m.y. ago) and the late Miocene (7-10 m.y. ago). The accumulation rates during these maxima are an order of magnitude higher than those during times of minimum accumulation: the late Oligocene (25 m.y. ago) and the present. The percent of biogenic silica in the sediments varies synchronously with the accumulation rates, but is low to the east due to dilution by non-biogenic sediment from terrigenous and volcanic sources. Surface productivity controls the accumulation of opal in the equatorial Pacific and opaline sediments are not subject to differential solution with depth. The opal productivity indicated by opal accumulation rates is not related to changes in sea surface or bottom water temperatures and is therefore not directly governed by climate. The association of equatorial productivity and upwelling suggests that changes in circulation which cause upwelling were the principal factors controlling productivity and accumulation of biogenic silica in the past. / Graduation date: 1976