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

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

Major (Fe, Mn, Al) and minor (Cr, Mo, Pb, Zn, Cd) element analyses of metalliferous sediments in cores from the East Pacific Rise and Bauer Deep indicate that the Bauer Deep sediments are similar in chemistry and origin to metalliferous sediments of the East Pacific Rises. Fe, Pb, and Zn are strongly associated in both cores and are probably related to the hydrothermal processes which are postulated to occur on the East Pacific Rise. Incomplete Cd data suggest that Cd may also be released during hydrothermal leaching of basalt Mn may originate by precipitation from hydrothermal solutions or by normal authigenic precipitation from sea water. The similar accumulation rates of Mo in both cores, and poor correlation of Mo with Fe imply that Mo is being extracted from sea water. The low abundances of Cr and Al in metalliferous sediments suggest that detritus is a minor component of the sediments. Poorly crystalline smectites constitute a major mineralogical phase of metalliferous sediments. Chemical and mineralogical studies indicate that the smectite is an iron-rich montmorillonite, similar in composition to the bulk sediment. Information on sedimentation rates in the two cores indicate that most elements are accumulating faster on the East Pacific Rise than in the Bauer Deep. Accumulation rates of metals in the Bauer Deep have decreased up to the present and are currently similar to those for normal pelagic sediments. It is inferred that the sedimentation rates in the Bauer Deep are influenced by the proximity of the East Pacific Rise, It appears that sediments in the Bauer Deep are largely the product of hydrothermal processes on the East Pacific Rise, and that the precipitates are transported in suspension to the Bauer Deep. Authigenic precipitation of elements from sea water also occurs, having a stronger influence on the sediments as the precipitation of rise-crest material decreases away from the ridge. / Graduation date: 1974

The staghorn sculpin Leptocottus armatus is abundant in the Yaquina Bay estuary on the central Oregon coast and also occurs offshore in shallow water. A total of 560 L. armatus were collected at three locations in Yaquina Bay and between 7 and 11 kilometers offshore in depths of 40 to 80 meters. Staghorn sculpins were present in all areas where collections were made throughout the year except during the summer when most offshore sculpins moved into Yaquina Bay. Leptocottus armatus spawned primarily in the bay during the fall and early winter. The young fish remained in Yaquina Bay for about one year at which time they were about 12.0 cm in length. Subsequently, some of them moved offshore. Seventeen different species of parasites were collected from the 526 L. armatus examined. Genolinea laticauda was collected from the stomachs of 25.1% of the fish and had greater incidence and intensity in larger fish. Recruitment of immature forms began in April and the average life span was about seven months. The life cycle was most efficient in the lower estuary. Tubulovesicula lindbergi occurred in the stomachs of 50.8% of the fish and had greater incidence and intensity in small fish. Recruitment of immature individuals occurred all year, but was greatest in June. The life cycle was most efficient in the upper estuary. Podocotyle atomon was found in 42.6% of the fish and was most abundant in the larger fish. Bucephalopsis ozakii was collected in 38.8% of the L. armatus and was more abundant in large fish, as were larval tetraphyllidean cestodes which were present in 40.7% of the fish. These two parasites were found to be positively associated because they were both more likely to parasitize larger fish. Nematodes believed to be Contracaecum cornutum were found in ulcers in the stomach of 28.0% of the fish. This was the only parasite that was obviously pathogenic. Echinorhynchus gadi occurred in 47.4% of the fish. Immature worms were obtained all year, but only from fish in the upper estuary. Other parasites encountered were the protozoans Scyphidia sp., Trichodina sp. and Ceratomyxa sp.; the trematodes Gyrodactylus sp., Neopodocotyloides sinusaccus and Derogenes sp.; the nematode Contracaecum aduncum; a piscicolid leech; the copepod Acanthochondria rectangularis and the isopod Lironeca vulgaris. It was concluded that all the parasites of L. armatus could be acquired in Yaquina Bay, although it was more likely that the larval cestode was acquired offshore. The parasite data could not be used to determine movements of L. armatus in and out of Yaquina Bay, but the data were utilized to show that movements between the upper and lower estuary were not extensive. / Graduation date: 1973

A total of 57 core top samples from the Panama Basin were used in a quantitative study of complete radiolarian thanatocoenoses to determine whether surface oceanographic conditions are reflected in the microplankton faunas deposited onto and buried in the sea floor. Information obtained from this study was used to resolve the sequence of temporal fluctuations in oceanographic and climatologic conditions in the eastern equatorial Pacific. Four piston cores from within the basin were sampled on the basis of carbonate stratigraphies to levels no older than 130,000 years B.P. Although the sample intervals are irregular and samples are not closely spaced, this procedure allowed reasonably good stratigraphic resolution. Because of high diversity at low latitudes, the 131 radiolarian taxa recognized in this study accounted for only 37-61% of the individuals encountered in counts of >1000 specimens. Q-mode factor analysis of the surface sediment samples yielded three end member samples, which allowed recognition of three different assemblages. The dominant assemblage can be identified with a tropical fauna and the least important assemblage is considered to be associated with the Peru Current fauna, The distribution of the tropical assemblage does not reflect surface oceanographic conditions whereas the distribution of the Peru Current assemblage shows a weak association with surface conditions, The other assemblage shows no coherent distribution pattern. The nature of this assemblage is best explained by considering it to be a residual of the tropical fauna resulting from chemical and mechanical modification in the water column and at the sea floor. All evidence suggests that solution, winnowing and lateral transport are major processes in determining the distribution of the faunal assemblages in the sediments of the Panama Basin. The signal of the Peru Current assemblage in the surface study was used for a quantitative analysis of the subsurface samples. This analysis yielded the following results: 1) During most of the last glacial, assemblages associated with the Peru Current.were deposited in the Panama Basin, indicating a northward shift of current boundaries, This has important climatological implications since such a shift must be associated with a shift of the major wind belts and of the South Pacific high pressure cell towards the equator. 2) At least once during, the last glacial, from approximately 50,000 to 40,000 years B.P., warmer conditions are indicated by a re-appearance of tropical assemblages. 3) The previous interglacial appears to have been slightly cooler than present interglacial conditions. 4) The warming trend towards present conditions began between 15,000 and 20,000 years B.P. This is earlier than observed in the North Atlantic. These results are correlative with records of oceanographic and climatic changes in the southeast Pacific, northwestern South America and the Galapagos Islands. / Graduation date: 1974

A study has been made of the vertical distributions and migrations of a large number of zooplankton species at Weather Station "P" in the Subarctic Pacific. Simultaneously towed horizontal opening-closing nets were used for the study. The distributions and migrations of 104 taxa have been subjectively grouped into seven basic patterns. A few taxa could not be so grouped. Examination of hydrographic features reveals correlations between animal distributions and strong hydrographic gradients. It is concluded that: 1. In boreal oceanic waters, few animals perform diurnal migrations, 2. Depth ranges for most zooplankton are on the order of hundreds of meters, and 3. Hydrographic features may influence the vertical distributions and migrations of zooplankton. / Graduation date: 1974