Graduation date: 1968

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

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

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

Graduation date: 1982

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

Viable cysts collected from natural sediments were induced to excyst. Ten cyst-theca relationships, first established elsewhere, were confirmed for British Columbia (B.C.). These were: Gonyaulax tamarensis, Protoperidinium aspidotum, P. claudicans, P. conicoides, P. conicum, P. cf. denticulatum, P. leonis, P. oblongum, and P. punctulatum. Five cyst-theca relationships were established for the first time: Peridiniopsis cf. hainanensis, Protoperidinium sp. nov., P. thorianum, and two apparently new species of Gonyaulax. P. pentagonum was found to have a cyst different from the cyst of this species in the Atlantic. Forty-five samples from Recent sediments were collected along the coast of B.C. Twenty-three of the samples had very few cysts. Hidden Basin was the chief source of viable cysts for the excystment experiments. Ten cyst-based taxa were described from the sediment samples. These were: Operculodinium centrocarpum, the cyst of Scrippsiella faeroense (= Micrhystridium bifurcatum), Spiniferites belerius, S. bentori, S. bulloideus, S. elongatus, S. membranaceus, S. nodosum, and S. ramosus. Tanyosphaeridium sp. has been recorded previously as the cyst of Polykrikos schwarzi. Two new cyst-based taxa are described for the first time. These are a cyst of Protoperidinium sp., and Spiniferites "sp. A". Cyst assemblages in the Recent sediments of B.C. were similar to many temperate estuarine and neritic areas. Some cysts which are characteristic of these areas in other regions, have not yet been found in B.C. The relative importance of some cysts also varies from that found in similar sediments elsewhere. The dominance of Operculodinium centrocarpum in many of the cyst assemblages, including B.C., is a pattern typical of temperate estuarine conditions. Some cysts appear to be characteristically associated with fjord environments. Scrippsiella faeroense, for example, has been found in Norwegian fjords and Scottish sea lochs as well as some B.C. fjords and inlets. / Science, Faculty of / Botany, Department of / Zoology, Department of / Graduate