On the lower continental slope off Vancouver Island near scientific ocean drilling IODP Site U1326, traveltime modeling along several ocean bottom seismograph (OBS) profiles shows anomalous high velocities of about 2.0 km/s at 70 - 100 m depth (compared to a no-hydrate reference of about 1.6 km/s). These velocities are consistent with the Site U1326 downhole sonic logs that show velocities up to 2.8 km/s near these depths. The drillhole high velocities are interpreted as caused by nearly massive hydrate with concentrations as large as 60-80% of the pore space. The OBS seismic velocities show that high hydrate concentrations of at least 20-30% are laterally extensive out to distances of at least 6 km on either side of the drillhole. A grid of migrated single-channel data shows a sequence of 15- to 75-m-high seafloor scarps, cutting across the ridge perpendicular to the deformation front. These are interpreted as normal faults. Two of the largest fault scarps bound a prominent ~2.5-km-wide slump feature on the steep seaward slope of the frontal ridge. This provides strong evidence that the slump is fault-controlled, and the base of the slump is near the base of hydrate stability suggesting that the slumping is also related to the presence of gas hydrate. At IODP drill Site U1327 on the mid-continental slope, seismic data were recorded along a 1-km-long profile of 10 OBSs. Traveltimes from wide-angle and vertical-incidence arrivals were inverted simultaneously for velocity structure. Corresponding hydrate concentrations increase with depth with an average of about 15% in the 100-m-thick layer above the base of hydrate stability . The seismic structure shows that this local hydrate distribution extends on the kilometer-scale away from the drillhole, as also suggested by multichannel interval velocities in the region. At Site U1328 (Bullseye Vent), seismic images derived from the very high resolution deep-towed DTAGS reflection data show that the top of a zone of high reflectivity, 10-25 m in thickness, extends from the seafloor to a depth of ~30 m. This zone likely corresponds to the shallow region of massive methane hydrate detected in the upper 40 m in the drillhole, and may represent a system of fractures through which fluids and gas pass from the main vent to the seafloor.

A high-resolution seismic reflection survey was conducted during the NT07-05 cruise over the Formosa Ridge offshore southwestern Taiwan where strong and continuous bottom simulating reflections (BSR) have been observed. Previous seafloor pictures taken from a deep-towed camera indicate that there are some chemosynthetic colonies. During the NT07-05 cruise, not only large and dense chemosynthetic communities were confirmed at the plume site, ROV Hyper-Dolphin has also discovered that both deep-sea mussel Bathymodiolus platifrons, and galatheid crab Shinkaia crosnieri are vigorously populated at this site. By integrating swatch bathymetry, multichannel seismic and high-resolution seismic reflection data, we now have a better understanding on the structural characters of the cold seep site. The cold seep is situated at the summit of the Formosa Ridge southern peak. Submarine canyons that incised continental slope on both sides of the ridge are the controlling factors of the ridge formation. The sedimentary strata are generally flat lying but have been deformed by mass wasting processes. Strong BSR is observed 400 to 500 ms below the seafloor of the ridge, with many bright reflections beneath it. There is a narrow vertical blanking zone raising from BSR to the crest of the ridge. This narrow zone is interpreted to be the fluid conduit of the seep site. BSR may form a good cap to trap gas below, and this “gas reservoir” is shallower than the canyon floors on either side of the ridge. We suggest that this “ridge type” gas reservoir configuration enables the cold sea water to get into the fluid system, and forms a special kind of “hydrothermal” circulation that feeds the unusual chemosynthetic communities observed at the Formosa Ridge cold seep site.

The continental margin off Nova Scotia (the Scotian margin) forms the northern edge of the North American Basin. The Cenozoic stratigraphy and geological history of the outer margin is not well known. This study examines aspects of the Upper Cretaceous-Cenozoic geological history of the outer Scotian margin addressing the following objectives: 1) determine the geological history of a large deep-water depocenter, 2) investigate processes that led to deep-water unconformity formation in the study area, 3) determine the role of deep-ocean circulation in margin evolution, 4) examine the effects of morphological heritage on subsequent depositional patterns. High quality 2-D and 3-D seismic reflection data along with lithostratigraphic and biostratigraphic data from hydrocarbon exploration wells provide the basis for this investigation. The seismic stratigraphy of a large deep-water depocenter along the western Scotian margin was broadly divided into four units. Unit 1 (Upper Cretaceous-Upper Eocene) is attributed to repeated, widespread erosion events interspersed with periods of hemipelagic and pelagic, carbonate-rich sedimentation. Unit 2 (Lower Oligocene-Middle Miocene) consists of a variety of seismic facies overprinted by dense, small-offset faults. Unit 3 (Middle Miocene-Upper Pliocene) is dominated by sediment drift deposition. Unit 4 (Upper Pliocene-present) is characterized by channel development and gravity flow deposition. The processes that led to regional seismic stratigraphic horizons were complex. Both large mass-wasting events and along-slope bottom currents contributed to the formation of unconformities in the study area. Most of the succession preserved in the depocenter belongs to seismic units 2 and 3. These deposits are mainly confined to the area seaward of the Abenaki carbonate bank and landward of shallow salt structures below the slope. Locally, however, modification of the slope profile through mass-wasting and bottom current processes greatly influenced subsequent depositional patterns. The Cenozoic geological evolution of the study area was strongly affected by northeast-to-southwest flowing bottom currents. The earliest indication of bottom current activity was in the Eocene. Upper Miocene and Pliocene sediment drifts represent >50% of the preserved stratigraphic section in the thickest part of the depocenter. It is clear that along-slope sedimentary processes were far more important in shaping the margin than previously understood.

High-resolution electrical-resistivity, seismic-refraction, and seismic-reflection surveys were performed at three locations in the Inner Bluegrass Region of Kentucky along coincident survey lines in order to correlate results and determine which method is most effective at locating karst features in this area. The first two survey locations at Slack’s Cave and the Kentucky Horse Park were chosen in order to investigate known karst features. High and low electrical-resistivity anomalies were correlated to air- and water-filled karst voids, respectively. Seismic velocity anomalies, including parabolic time suppressions, amplitude terminations, and surface-wave backscatters, were also observed and correlated to these karst voids. These findings were applied to a third location along Berea Road in order to investigate undiscovered karst voids. Three seismic targets were selected based on backscatter anomaly locations and were aligned in a northwest trend following the general bedrock dip, joint orientations, and suspected conduit orientation. Overall, the seismic-reflection method provided the highest resolution and least ambiguous results; however, integration of multiple methods was determined to help decrease ambiguities in interpretation created by the inherent non-uniqueness found in the results of each method.

Over 7.8 km of seismic reflection data and 2 km of electrical resistivity data were acquired, processed, and interpreted during this multi-method geophysical study. Objectives included the definition of geologic conditions underlying a contaminant plume in McCracken County, western Kentucky, and the determination of the potential for structural control on the rate and direction of plume migration. Both geophysical methods indicate the presence of multiple high-angle normal faults outlining a series of asymmetric grabens ranging in width from 160 m to almost 300 m and striking between N40°E and N45°E. There was agreement between the two methods on fault location and degree of near-surface offset, with offsets of 1 to 2 m observed at 10 to 20 m below ground surface and 3 to 8 m observed at 20 to 30 m depth. Bedrock displacement was generally 2 to 3 times larger, with offsets of 10 to 26 m observed. The faults appear to have originated in the Paleozoic with predominantly normal reactivation occurring as recently as the Pleistocene. The fault strikes generally approximate the orientation of the northwestern contaminant plume. Observed offset of the Regional Gravel Aquifer may form a preferential flow path for contaminant migration.

Thesis (M.Sc.)--Memorial University of Newfoundland, 1995. / Bibliography: leaves 189-196. Also available online.

Thesis (M.S.)--Brigham Young University. Dept. of Geological Sciences, 2007. / Includes bibliographical references (p. 63-68).

Thesis (Ph. D.)--California Institute of Technology, 1983. / Includes bibliographical references.

Thesis (Ph. D.)--University of Alabama at Birmingham, 2009. / Title from PDF t.p. (viewed July 21, 2010). Additional advisors: Thomas Jannett, Tsun-Zee Mai, S. S. Ravindran, Günter Stolz, Gilbert Weinstein. Includes bibliographical references (p. 59-64).

Thesis (M.Eng.)--University of Pretoria, 2004. / Includes summary. Includes bibliographical references (leaves 92-100).