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

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

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 processes responsible for transporting and depositing thick sections of coarse-grained terrigenous clastics on the abyssal floor and for forming associated sedimentary structures are still conjectural. Many workers attribute coarse deep-sea sediments and their probable lithified equivalent, the graywackes of flysch deposits to some type of density movement. Deductions concerning the processes operating in a density flow generally are made from flume studies--in which an artificial situation may develop, or from lithified units--where the magnitude of post-depositional change is unknown. Both approaches contribute to our knowledge, but the unconsolidated elastics themselves should contain a unique key to understanding the dynamics of abyssal sedimentation. To test this theory, divisions of parallel lamination, found in deep-sea sand and silt, were selected for analysis. Since individual laminae closely approach discrete populations of particles assembled under contrasting conditions, their use carries environmental sampling to its practical limits. Northeast Pacific sediments of late Pleistocene and Holocene age, from deep-sea channel and abyssal plain environments, and representing two or three provenances were studied. A total of 115 light-colored and 84 dark-colored laminae were sampled from eight sequences at five locations. Samples averaged about 0.8 gram and were quantitatively processed using quarter-phi calibrated sieves and decantation techniques. Statistical evaluation of the procedure shows better than 95 percent sample recovery, and indicates that textural variance between laminae is significantly greater than within-sample variance. The classic concept of density transport--that coarsest material is carried by the nose of the current, and that clastic size grades tail-ward and upward in a uniformly decreasing manner--is not substantiated by moment measures, sand-silt-clay percentages or factor analysis of grain-size distributions, at least during deposition of the coarse division of parallel lamination. Coarse abyssal lamination develops within a narrow range of current velocity, the limits of which are defined texturally. Absolute velocity values for these limits can only be related, at the present time, to the few flume or in situ bottom current measurements available. Texture indicates that while the total amount of sand carried in suspension varies, lamination does not begin to form until a current is essentially depleted of all material coarser than fine sand--establishing an upper competency limit. At that time, coarse suspended material is distributed throughout the flow mostly in large eddies or vortices whose velocities are estimated on the order of about one meter/sec. Mean current velocity must be sufficient to maintain a dispersed traction carpet without deformation of bedform into ripples. This is postulated at about 50 cm/sec. A current model, based on textural evidence, is proposed to account for lamination. It is suggested that the critical stage in the formation of coarse abyssal lamination occurs while sediment is being dragged along the bottom as bedload. The flowing clastic traction carpet acquires kinetic energy as the current bypasses material lost from suspension. In turn, this energy results in grain shear. When the concentration of granular material in traction is large, it dissipates the energy of bottom shear mostly in collision contacts between gliding grains. The dispersive stresses developed tend to maintain grain separation and prevent settling. Eventually, turbulence in seawater entrapped between grains is suppressed and the net path of grans impelled by repeated collisions becomes quasi-laminar. Within this quasi-laminar traction system, dispersive pressure causes some migration of finer sizes toward the base of the carpet and a concentration of coarser grains in the upper bedload. As new material is introduced in large quantities from suspension, the zone of internal shear--the base of the moving carpet--is displaced progressively upward. As it passes, sediment compacts to a fraction of its dispersed thickness and a population of grains with a slightly finer size distribution than the carpet load comes to rest. This is buried by new deposition and a densely-packed, dark layer continues to accrete upward as long as a moving traction carpet is sustained and a dense rain of clastics is contributed from suspension. When a sand-laden eddy impinges on the bottom, it releases its coarsest load into traction and the dark layer then accreting increases significantly in grains larger than 44 microns. Any eddy, whether laden or not, on striking bottom adds to, or deducts its velocity from the velocity of the traction carpet and either increases or decreases bottom shear. Additional impulse given to tractive shear by eddies merely results in more effective size sorting. However, an eddy whose velocity of rotation is opposed to current movement may reduce shear below the critical necessary to maintain a thick carpet by dispersive pressure, The dispersed carpet collapses and instantaneously ceases moving. This less-densely packed layer has a slightly higher sand content than the accreted material below. When partially dried or weathered, alternate layers exhibit different moisture retention properties--the less-porous, accreted layers appearing dark and the more loosely packed layers appearing light. / Graduation date: 1970

A deep source-receiver seismic refraction experiment was conducted on the upper part of the Monterey Deep Sea Fan. The aim of this thesis is to construct the velocity structure of the upper Monterey Fan and to examine the lateral seismic velocity variations among the upper, middle and lower fan subunits. Using primary waves and whispering gallery phases (the multiply-reflected refraction waves), the sediment velocity structure was modeled by the tau-zeta travel time inversion process. The changes in velocity gradients with depth of the upper Monterey Fan are morphologically similar to that found on both the Central Bengal Fan and the Nicobar Fan, an abandoned lower fan of the Bengal Fan Complex. The velocity gradient of the upper Monterey Fan at depth, 0.59 s⁻¹ is significantly lower than both the middle Bengal Fan (0.68 s⁻¹) and the Nicobar Fan (0.81 s⁻¹). The upper fan subunit, which is closer to its sediment source, is characterized by higher porosities caused primarily by a higher sedimentation rate than the lower fan subunits. Since seismic velocity is inversely related to porosity, the upper fan subunit should have lower velocity gradients and seismic velocities than the other fan subunits. If porosity and velocity variations exist, then these variations can be used to constrain various models of deep sea fan formation. No definite conclusion can be drawn at this time due to a fault within 1 km of the Nicobar Fan site; however, a systematic velocity variation pattern of deep sea fans is revealed. Some portions of the Monterey Fan data contain refracted waves which have bottomed within the underlying acoustic basement structure. The entire velocity structure was solved by both the general and the "stripping" solving schemes. The results of basement structure show a velocity ranging from 3.4 to 5.8 km/s indicating that the uppermost part may be pre-existing continental rise sediments. / Graduation date: 1986

Examination of polished sections of manganese micronodules from metalliferous sediments from the Bauer Deep reveals sequences of ferromanganese deposition which are consistent for micronodules from a single sediment sample and imply a common depositional history for members of such assemblages. The relatively simple 'stratigraphy' of manganese micronodules, as compared to macronodules, makes stratigraphic correlation of depositional histories easier and more conclusive for micronodules than macronodules. Quantitative microprobe analysis and X-ray mircodiffraction patterns indicate that the major authigenic silicate component of metalliferous sediment is an iron- and magnesium-rich, low-aluminum nontronite. Microprobe and X-ray microdiffraction analyses of manganese micronodules establish todorokite as the predominant crystalline component. Comparison of the distributions of lanthanum, cerium, and samarium in micronodules and phosphatic fish debris indicates that bulk sediment REE distribution is determined by the relative abundances of cerium-enriched micronodules and cerium-depleted biogenic phosphate. / Graduation date: 1974

Graduation date: 1966