No description available.

A lacustrine sedimentary process study was undertaken at Kluane Lake, which is a large, glacier-fed, alpine lake in the southwestern corner of Yukon Territory. Data from moored instruments, sediment traps, water column profiling, and high-resolution sub-bottom acoustic surveys were collected over the peak melt seasons of 2006 and 2007 in order to document the spatial and temporal lacustrine sedimentation patterns. A river monitoring station was also established to continuously record the inflow variations of Slims River, which drains meltwater from Kaskawulsh Glacier. Kluane Lake receives sediment-laden (up to 5 g/l) water from Slims River, which varies diurnally in terms of both discharge and suspended sediment concentration. While evidence of seasonal sediment exhaustion is present within the system, the diurnal hysteresis relationship between discharge and suspended sediment is either insignificant or more commonly counterclockwise. The high suspended sediment load delivered by Slims River produces continuous, diurnally fluctuating turbidity currents with maximum velocities in excess of 0.6 m/s at delta-proximal locations, although velocities between 0.2 and 0.4 m/s are more typical. During peak flow conditions, variations in current velocity can be traced to the deepest portion of the lake, over 4 km from the point of inflow. The longitudinal changes in the vertical concentration profiles, suspended sediment load, and mass accumulation rates suggest that the flow structure of the turbidity currents changes rapidly along the first several kilometres of flow. Sedimentation in the Kluane Lake basin is dominated by turbidity currents; overflows occur intermittently and contribute less than 2% to sediment accumulation along the lake bed. The highest rate of deposition occurs approximately 1 km from the delta and is consistent with an accumulation of approximately 0.4 m/a; closer to the delta, high current velocities appear to inhibit sediment deposition. The sediment in Kluane Lake is dominated by silt-size particles and contains virtually no sand except in small amounts very close to the delta. The diurnal pattern of turbidity current activity produces daily rhythmites in sediment traps deployed near the lake bottom, but these laminations do not occur consistently over time or space. / Thesis (Master, Geography) -- Queen's University, 2008-05-22 13:42:20.629

A three component drag probe has been built, calibrated, and used to measure velocities beneath deep water ocean waves and turbulence in a tidal channel. Simple variable inductance devices which may be submerged in water were used as displacement transducers and the associated electronics provided voltage outputs which were proportional to the three components of force that were exerted on a small 5 cm diameter sphere. The force components were due to both the water drag force and the water inertial force in an accelerating flow field. Techniques are described for interpreting measurements made with the drag probe and for obtaining the three velocity components from the measured force components. From the drag probe calibration and its use in the field, it is concluded that the drag probe is a suitable instrument for the measurement of wave velocities and turbulence. Modifications are suggested to improve the performance of the drag probe. For the wave velocity measurements, the experimental results indicate that linear wave theory is adequate to describe the relations between the wave pressure and the wave velocity components. At frequencies higher than the predominant wave frequency the velocity spectra are roughly proportional to f⁻³ where f is the frequency in Hz. The wave velocity components were used to obtain an estimate of the directional energy spectrum. From the measurements in a tidal channel, it appears that the instrument is suitable to measure turbulent fluctuations with scale sizes larger than about 20 cm. If the turbulence were isotropic the velocity spectra would be proportional to f[⁻⁵/³]. Due to the influence of boundaries, the flow was not isotropic but the results appear to be consistent with other observations that turbulent velocity spectra usually show a f⁻¹ to f⁻² behavior and are quite different from wave velocity spectra. / Graduation date: 1971

Thesis (Ph. D.)--Joint Program in Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Dept. of Biology; and the Woods Hole Oceanographic Institution), 2005. / Includes bibliographical references.

Dissertation (PhD)--University of Stellenbosch, 2008. / Bibliography. Also available via the Internet.

Thesis (M.S.)--Naval Postgraduate School, 1974. / Includes bibliographical references (leaves 149-152).

Thesis. 1975. M.S.--Massachusetts Institute of Technology. Dept. of Earth and Planetary Sciences. / Bibliography: leaves 36-37. / M.S.

Submarine channels are important conduits for sediment in deep marine environments, and understanding their formation is critical to modeling basin fill processes. Most models describing channel evolution focus on turbidity currents as the erosive and constructive force in channel initiation. However, slope failure and slumping can be significant drivers of channelization, particularly in upper slope and ramp environments. Determining the relative roles of slumping and erosion by turbidity currents can provide important insight into the timing of channelization and the geometries of subsequent deposits. Samples were collected from Guadalupe Mountains National Park from two primary localities at Salt Flat Bench (Figure 2). Three vertical sections were measured at both locations. A total of 16 samples were collected for petrographic analysis and X-ray fluorescence (XRF) imaging. Spectacular outcrop quality makes the Middle Permian Brushy Canyon Formation in Guadalupe Mountains National Park an ideal location for the study of early channel evolution. A detailed facies analysis of fine-grained channel deposits was conducted in the Upper Brushy Canyon Formation in the Salt Flat Bench outcrops. After channelization, an interval of relative condensation dominated by hemipelagic settling of organic matter and silt was followed by an interval of incomplete sediment bypass by turbidity currents. This sequence of events suggests that sea level was at a relative highstand at the time of channel inception, whereas channel inception by turbidity currents is expected during a lowstand. Slumping rather than erosion by turbidity currents is the most likely mechanism to have initiated a channel at the study area. There is no evidence for the existence for high energy currents until after the interval of condensation. However, the action of weak contour currents during early channel evolution is observed in outcrop and microtextural features. Early carbonate cementation of channel-lining silts may have stabilized the slump surface with respect to erosion by later turbidity currents.

Thesis (Ph. D.)--Hong Kong University of Science and Technology, 2003. / Includes bibliographical references (leaves 174-185). Also available in electronic version. Access restricted to campus users.

Turbidity currents, both continuous flow and surge-type, have been detected with acoustic sounders operating at 42.5, 107 and 200, kHz. The turbidity currents are associated with the discharge of mine tailing into Rupert Inlet. A linear relation is obtained between the backscattered acoustic signal at 200 kHz and the one-half power of suspended particulate concentration from 10 to 1000 mg 1⁻¹. This relation is consistent with Rayleigh scattering theory in form and (relative to a standard target) amplitude, and is used to generate a cross-sectional profile of sediment concentration in the discharge plume. Estimates of surge speeds from the acoustic records based on a universal shape for density current heads range from 30 to 120 cm s⁻¹. The excess density of one surge was estimated from the reverberation amplitude to be 0.12 g cm⁻³. The additional attenuation of sound waves by suspended particles is important in turbidity currents and may be used to estimate suspended particulate concentration. Thermal processes contribute very little to the additional attenuation by particles with the grain densities of common minerals. A leveed submarine channel extended from the point of the tailing discharge (outfall) over the surface of the tailing deposit as early as 1974. The upper reach of this system was buried in 1978, and by late 1979 a new channel had developed. In 1976-77, the original channel consisted of: (1) a left-hooking upper reach with an average slope of 2.2°, (2) a middle reach (1° slope) with pronounced meanders (700-1100 m wavelengths) "increasing in curvature with distance downstream and (3) a straight lower reach (0.5° slope). The cross-sectional area of the channel decreased with distance downstream, excepting an increase in the first 100-200 m, until the channel disappeared about 5.5 km from the outfall. Acoustic records of the discharge plume in bends indicate overspill from the outer bank and an upward tilt of the upper interface away from the centre of bend curvature. The interfacial slope is steeper than indicated by the cross-channel difference in levee heights. These records together with observed tidal currents suggest that the left hook in the upper reach is caused by a mechanism similar to that which has been suggested for deep-sea channels. Turbidites in gravity cores from the levees are present as layers of vertically-graded, Cu-rich and Fe-poor sand and silt, some of which have load-casted flame-structures or load-pockets at their basai contacts. These layers comprise more of the sediment column with distance down-channel, suggesting that levee-building by overbank spillage from continuous flow becomes less important, and that most of the material transported through the lower reach is carried by turbidity surges. Surge recurrence intervals of 2-5 d are obtained from the number turbidites per core and the local deposition rate. The latter ranged from 0.3-4 m yr⁻¹, as given by changes in water depth, in tailing thickness from seismic reflection surveys, and in diatom frustule abundance in the cores. A model of continuous turbidity flow in submarine channels including entrainment is applied to the Rupert Inlet channel. Results are consistent with a sediment budget based on changes in the tailing deposit volume, and with turbidity surge recurrence intervals. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate