This study has analyzed Pb-210 activity in cores taken from northern coastal South China Sea (SCS) and the area west of the Luzon Strait (LS) in order to estimate the sedimentation rates and the mass accumulate rates which allow a direct comparison with measured settling particulate fluxes. Also, the particulate and dissolved Po-210 and Pb-210 distributions in a water column located to the west of the LS were measured and compared with earlier data. Core samples were collected at Stations G and H (box cores) during the ORI-688 cruise (July, 2003) and at M1, F and 1 (box cores) during the ORI-722 cruise (June and July, 2004). The water column samples were collected at S7 during the ORI-763 curise (August, 2005). Stations H, G and 1 are located in the continental shelf of the northern SCS; Stations, M1, F and S7 are located in the deep water area west of the LS. The water content of the cores at F and M1 west of the LS is mostly around 40%~55%, while that of the cores at H, G and 1 in the coastal area of the northern SCS ranges about 25%~37%. The total organic matter as estimated from the total loss on ignition at F and M1 is, respectively, about 6% and 12% on the average. The coastal cores contain about 3%~8% total organic matter. The Pb-210 activity generally decreases with the core depth but reaches a constant at a certain depth, below which the excess Pb-210 vanishes in the core. Based on the excess Pb-210 distributions in the cores, the estimated sedimentation rates vary between 16 and 52cm/100yr. At M1 station, the mean Pb-210 flux and the mean mass flux are, respectively, 129 dpm/m2/d and 0.55 g/m2/d as determined from the deepest sediment trap(2848m) (Chung et al., 2004). These values are much smaller than what were estimated from the cores: the Pb-210 flux at 201 dpm/m2/d and the mass flux at 5.3 g/m2/d. The Pb-210 flux obtained from the trap is 65% of that measured from the core, and the mass flux from the trap is only 10% of that from the core. These large differences may arise from an over estimation of the sedimentation rate in the core (due to bioturbation) and near-bottom lateral transport of sediments from elsewhere. Compared to the basin west of the LS, the mass flux at the coastal area is much higher but the Pb-210 flux is much lower, probably due to the fact that shallow water has little amount of Pb-210 to be scavenged and no boundary scavenging effect has been observed. The Pb-210 specific activity at S7 station ranges from 155 to 900 dpm/g; the Po-210 activity at this station ranges from 78 to 507dpm/g. The particulate Po/Pb ratio is about unity at 1800m depth, but the ratio at all other depths is less than unity, indicating that the Po-210 is deficient relative to Pb-210 in particles at this station. The total (dissolved + particulate) Po/Pb ratio in the water column is generally less than unity, showing Po-210 deficiency relative to Pb-210 probably due to absorption and/or adsorption of Po-210 by plankton and other organisms. The Po/Pb ratio for the water column averages about 0.6, corresponding to a mean residence time of 0.83yr for Po-210 removal.

Sediment sampling, bathymetric data, and seismic reflection profiling were used to classify sediment deposition patterns on the Carnegie Ridge. Core sampling was used to relate compositional characteristics between equivalent areas, and seismic profiling to establish vertical variations. Three study areas were selected based on core distribution along the ridge. Grids of the following parameters were obtained: slope, elevation, percentage of carbonate, SiO2, and organic carbon contents. The general CaCO3 content distribution is highest on the ridge except in the areas affected by terrigenous deposition from the mainland, and volcanic debris from Galapagos Volcanic Platform. The general SiO2 content distribution is highest south of the Equator, bordering the west ridge. The organic carbon content is high in the equatorial upwelling area and close to the mainland. The relationship between organic carbon and carbonate was determined through correlation analysis. Based on those analyses, and considering the mixture of sedimentary sources and tectonic processes, the carbonate sediment is more important to this area. Sediments on the Carnegie Ridge above the lysocline are affected by three different types of processes controlling the sediment deposition. The first is the location of the high productivity zone in which pelagic settling is the source of sediment. The second is the difference in sea water properties between the Panama and Peru Basins surrounding the ridge, which creates different depositional environments. These properties create horizontal and vertical variations within water masses. Intermediate depths are affected by northward Pacific Central Water and bottom waters by northward Pacific Deep Water. The deflection of the bottom water flow by the existence of the Carnegie Ridge as a natural barrier produces scouring effects on the south flank. The third process controlling deposition is underwater dissolution on the saddle and east ridge by organic carbon degradation, which is enhanced by bottom water flow. Significant differences in sedimentation types were found in areas with hilltops, contrasted slopes, and slope bases, primarily related to changing depths and water flows, and lateral transport along the steepest north scarp.

Thesis (M.S. in Meteorology and Physical Oceanography)--Naval Postgraduate School, June 2004. / Thesis advisor(s): Peter C. Chu. Includes bibliographical references (p. 45). Also available online.

Thesis (M.S. in E.A.S.)--School of Earth and Atmospheric Sciences, Georgia Institute of Technology, 2004. Directed by Martial Taillefert. / Includes bibliographical references (leaves 72-79).

Thesis (Ph. D.)--University of Washington, 2001. / Vita. Includes bibliographical references (leaves 132-152).

Thesis (Ph. D.)--University of Washington, 2001. / Vita. Includes bibliographical references (leaves 110-132).

Thesis (Ph. D.)--Joint Program in Marine Geology and Geophysics (Massachusetts Institute of Technology, Dept. of Earth, Atmospheric and Planetary Sciences, and the Woods Hole Oceanographic Institution), 2003. / Includes bibliographical references.

Contaminated surficial sediments represent a potential point of entry into the food web for environmental pollutants that are toxic to fish, wildlife, and humans. One approach for managing polluted sediments is in situ capping, the placement of clean fill material, such as sand, atop the polluted sediments. A cap stabilizes the underlying sediment and physically separates pollutants from benthic organisms that inhabit the sediment/water interface. Additionally, a sediment cap can be amended with sorbents to sequester hydrophobic organic chemicals. While the physical processes affecting contaminant transport in sediment caps are readily modeled, fate and transport processes mediated by sediment bacteria are location-specific and thus highly uncertain. Laboratory bench-scale tests were employed to aid in the design of a sediment cap in Onondaga Lake. Recognizing the importance of bacterial activity beneath the benthic zone for affecting the risks of contaminant exposure, anaerobic processes were emphasized. A combination of batch and column tests were used to determine whether (1) bacteria in sediments were capable of biotransforming methylated and chlorinated benzenes, (2) the ability to biotransform the contaminants of interest would be translated from the sediments to a sand cap, (3) the rate of biogenic gas production in sediments would threaten the integrity of a sand cap, and (4) the contribution of gas-phase contaminant transport to the overall transport of contaminants from the sediments was significant. The apparent anaerobic biotransformation of toluene in a sand cap was supported by detection of a genetic biomarker for anaerobic toluene degradation, the development of substantial biomass in the sand column, apparent anaerobic biotransformation of toluene in sediment slurries, and the concomitant reduction of iron in the sand column. The dissimilarity in bacterial community composition between sediment and sand cap samples suggests that contaminant biotransformation capability cannot be predicted from community analysis. For sediments that failed to demonstrate biotransformation potential, amending a sand column with organophilic clay proved effective at retarding transport of the contaminants of interest. This work advances methods for characterizing bacterial processes in sediments and demonstrates the potential for anaerobic biotransformation of organic contaminants in sand caps. / text

In order to reconstruct a long-time tropical terrestrial record of Asian monsoon in South China, the organic carbon in a 120 m lacustrine sediments from Maar Lake Tianyang was analyzed. Results in TOC, C/N and δ13C value show two lines of variations: (1) from a deep lake environment below 42 m to a shallow lake environment of the upper 42 m, (2) environmental changes between glacial and interglacial conditions throughout the lacustrine sediment sequence. In the shallow lake stage, δ13C values change according to glacial and interglacial periods, comparable with other proxies such as pollen, TOC and magnetic susceptibility. However, variations of these proxies including δ13C values are suppressed in the deep lake sequence, a result of the exceptionally high in-situ aquatic (diatom) productivity within this tropical lake. To differentiate the internal productivity and terrigenous high plant input for the deep lake sequence, a three-end-member model (diatom, C3 and C4 land plants) was developed. The result helps extract further information from the deep lake sequence that reveals both the autochthonous productivity caused by lake-level and terrestrial changes by external forcing mechanisms. The n-alkanes indexes from 115 selected samples show distinctive distributions of various chain-length homologues. Most n-alkane indexes (e.g. Paq, CPI and ACL) show more frequent fluctuations than organic carbon records, implying other environmental alterations within the glacial and interglacial periods. Most n-alkanes indexes show a clear relationship with the palaeoclimate history, but further comparison of individual compound concentrations to other environmental indexes (pollen and δ13C values) suggests that n-C29 is a better index of tree concentration while n-C31 has alternative source from flowering trees instead of grasses. Unique appearance of hopanes in the deep lake sediments suggests high activity of methanotrophic bacteria in chemocline. The examination of GDGT concentration from 130 samples indicates pH, temperature and evolution of archaea and bacteria communities. Complications in the interpretation and correction of GDGT results are also discussed and several alternative corrections for palaeo-temperature reconstruction are provided for further investigations. According to both n-alkane and GDGT results, the sediment sequence contains mainly three different stages: the aquatic mixing community (Crenarchaeota and methanotrophic bacteria) from the bottom to 78m; the aquatic methanotrophic community (Euryarchaeota and methanotrophic bacteria); the terrestrial aerobic community (aerobic bacteria). / published_or_final_version / Earth Sciences / Doctoral / Doctor of Philosophy

The Statfjord Formation, reaching a maximum thickness of 1,000 ft in the Brent Field area, comprises a highly heterolithic alluvial sandstone, siltstone, shale and mudstone succession (the Eriksson and Raude Member). The uppermost Statfjord Formation is, however, made up of a thin succession of medium-coarse grained shallow marine sandstones (Nansen Member). Analysis of material from 11 cored wells, and wireline log suites from a further 61 non-cored wells has revealed a distinct pattern of "sequence" development which is present throughout the Statfjord Formation of the Brent Field. A sparsely preserved fossil assemblage (pollen spores etc. ) has precluded biostratigraphic correlation of the main Statfjord Formation fluvial suite. Furthermore, the positions of lithostratigraphic markers (e. g. the base of the Nansen Member) within a sedimentary succession frequently reflect variations in the spatial development of facies, rather than chronostratigraphically equivalent events. Thus, if derived from purely lithostratigraphically driven correlation, the reservoir geologists' perception of parameters essential for flow unit designation prior to field simulation studies (e. g. sandbody connectivity), are often poorly constrained. Palaeosols are abundant within the fluvial Statfjord Formation succession, where they can be readily recognised in core. The palaeosol development is controlled by parent material, climate, biological factor, topography and time. The Statfjord Formation palaeosols are classified into five groups in terms of soil maturity. Understanding of wireline log (i. e. GR, Sonic and CNL) responses of different palaeosols allows identification of the Statfjord Formation palaeosols in non-cored wells. Whole rock geochemical analyses reveal variations between different types of Statfjord Formation palaeosols, however it is difficult to distinguish the five groups of palaeosols purely on the basis of chemical compositional variations because the palaeosols were complicated by mixed parent material. This study has also resulted in subdivision and correlation of the fluvial Statfjord Formation reservoir in the Brent Field into a series of reservoir units which are identified on the basis of their petrophysical and geochemical characteristics. Reservoir units are sequences which have distinctive geochemical compositions, and are recognisable on the basis of their petrophysical log response using a "Formation Lithology Factor" (FLF, defined by this study) based upon variations in sonic and compensated neutron log responses. Variations in geochemical composition are interpreted as reflecting varying amounts of sediment input from different provenances. Variations in FLF for both sandstone and mudstone lithotypes can be used to define reservoir units. This simple and novel technique may be applied to other sandstone suites in understanding reservoir connectivity and flow unit definition. High resolution reservoir correlation using palaeosols has allowed the interpretation of reservoir sandstone interconnectivity within the Statfjord Formation. The successful application of the pedofacies model (Bown and Kraus, 1987) and pedofacies sequences (Kraus, 1987) identified in the Statfjord Formation of the Brent Field has proved that they can be applied to a wide rane of fluvial deposits. In summary, this study has applied a multidisciplinary approach to the problem of correlation using palaeosols as potential indicators of "channel proximity" within a floodbasin. Using these, together with petrophysical, chemostratigraphic, heavy mineral data and field production data has allowed an integrated novel approach to be used in the interpretation of reservoir sandstone interconnectedness.