published_or_final_version / Applied Geosciences / Master / Master of Science

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The main objective of this thesis is to investigate the impact of microbial extracellular polymeric substances (EPS) on sediment stability and the related factors which influence “biogenic stabilisation” as a basis to the prediction of sediment erosion and transport. The ability to make direct and sensitive measurements of the physical properties of the biofilm is a critical demand to further understanding of the overall biostabilisation processes. Therefore, attention has been focused on developing a new technique, Magnetic Particle Induction (MagPI) for measuring the adhesive properties of the biofilm. MagPI determines the relative adhesive properties or “stickiness” of the test surface, whether a biofilm, a sediment or other submerged material. The technique may have future applications in physical, environmental and biomedical research. Newly developed Magnetic Particle Induction(MagPI) and traditional techniques Cohesive Strength Meter (CSM) for the determination of the adhesion/cohesion of the substratum were used to assess the biostabilisation capacity of aquatic microorganisms. Whilst these devices determine slightly different surface properties of the bed, they were found to complement each other, increasing the range of measurements that could be made and presented a strong correlation in the overlapping portion of the data. It is recognized that microorganisms inhabiting natural sediments significantly mediate the erosive response of the bed (“ecosystem engineers”) through the secretion of naturally adhesive organic material (EPS: extracellular polymeric substances). Interactions between main biofilm consortia microalgae, cyanobacteria and bacteria in terms of their individual contribution to the EPS pool and their relative functional contribution to substratum stabilisation were investigated. The overall stabilisation potential of the various assemblages was impressive, as compared to controls. The substratum stabilisation by estuarine microbial assemblages was due to the secreted EPS matrix, and both EPS quality (carbohydrates and proteins) and quantity (concentration) were important in determining stabilisation. Stabilisation was significantly higher for the bacterial assemblages than for axenic microalgal assemblages. The peak of engineering effect was significantly greater in the mixed assemblage as compared to the bacterial and axenic diatom culture. This work confirmed the important role of heterotrophic bacteria in “biostabilisation” and highlighted the interactions between autotrophic and heterotrophic biofilm components of the consortia. An additional approach, to investigate the impact of toxins on biostabilisation capacity of aquatic organism was performed on cultured bacterial and natural freshwater biofilm. The data suggest a different mode of triclosan (TCS) action ranging from suppressing metabolisms to bactericidal effects depending on the TCS concentration. The inhibitory effect of triclosanon bacterial and freshwater biofilms was confirmed. This information contributes to the conceptual understanding of the microbial sediment engineering that represents an important ecosystem function and service in aquatic habitats.

M.Sc. / Doornfontein Gold Mine is the westernmost member of a group of mines in the West Wits Line, extending from Westonaria to Carletonville. A study of the sedimentology and gold distribution of the Middelvlei Reef was carried out with the aim to acquire an understanding of the processes responsible for the economic concentration of gold ...

The Nyl River and its floodplain are situated on the eastern foothills of the Waterberg mountain range in the Limpopo Province of South Africa. Tributaries flowing out of the Waterberg range display unusual downstream changes, as they approach and converge with the Nylsvlei (or Nyl floodplain). Tributary channels decrease in size downstream until, eventually, they disappear altogether forming unchannellized floodouts. On one such floodout, on the farm Driefontein, an actively aggrading piedmont has formed adjacent to the famous Wonderkrater peat mound, known for its pollen record dating back ~45,000 years. Sediments from the aggrading piedmont interlace with Wonderkrater’s peat layers, suggesting that as the piedmont aggrades so too does the peat mound. This setting presents a unique opportunity to study active aggradational processes, and their products, on hillslope deposits and floodout environments. This study aims to describe the geomorphology and nature of depositional processes along the length of the piedmont adjacent to the Wonderkrater peat mound. Cross-sections, drainage channels and vegetation indices based on topographic maps, orthophotographs and hyperspectral images, were created using ArcGIS in order to describe and determine the surface morphology and hydrology of the Driefontein piedmont in detail. Surface soil samples were collected in order to determine particle size distribution, which were in turn compared to vegetation indices and changes in slope elevation. Further grain samples were collected from depth for age dating using Optically Stimulated Luminescence (OSL), as well as to determine grain size distribution in relation to surface sediments and other fluvial environments. Hyperspectral indices were found to correlate to surface grain size distribution, demonstrating that the presence of vegetation acts as a retaining mechanism for particles along hillslopes where incline should be too steep to support fine-grained sedimentary material. Surface sediments were found to demonstrate the characteristics of an alluvial floodout system, affected greatly by the presence of vegetation and slope inclination. Sub-surface samples were characteristic of a colluvial setting, suggesting that pediment retreat and basin fill, coupled with evidential climatic changes, were dominant controls on the pediment’s morphological and aggradational mechanisms. OSL age results estimated the sediments to be between 37.33 and 58.66 ka old. As a result of its unique sedimentary characteristics, a new type of ‘slow creep fan’ class was established in order to describe the characteristics of the Driefontein piedmont.

Thesis submitted in fulfillment of the requirements for the Degree of Doctor of Philosophy University of the Witwatersrand South Africa 2015 / A multidisciplinary sedimentological, stratigraphic, mineralogical and geochronological analysis of a small, fossil-bearing, Holocene hillslope deposit, flanking a mesa, has enabled a reconstruction of the palaeo-environmental history of the region. The hillslope deposit, located on the farm Heelbo in the eastern Free State Povince, South Africa, overlies Jurassic mudrock and sandstone of the Elliot Formation, Karoo Supergroup. The deposit is located on a steep (~10°) slope and covers an area of ~7 km2 in two separate sections. It extends ~475 m downslope and reaches a maximum thickness of at least 6-8 m towards the base. Mineralogy indicates the deposit is sourced from the mesa but its fine grain size and location on a steep slope position Heelbo outside the scope of traditionally described alluvial fans or colluvial deposits. The hillslope deposit is described as an alluvial slope based on the morphology of the deposit and the grain size distribution against the slope gradient. The deposit comprises fine-sand to silt- grain size, but is found on a steep (~10°) slope. The source of the sediment is shown to be the sediment of the mesa, rather than input from an aeolian source. The grains are described as sub-angular and poorly sorted which also suggests a local provenance for the sediment. Microscopic and XRF analysis confirm the derivation of the sediment from the Elliot Formation, with the lithic fragments derived from subarkoses to arkoses of the underlying bedrock of the Upper Elliot Formation (UEF) in the Karoo Supergroup. Secondary calcite was visible in only two of the thin sections, thus it is likely due to a diagenetic overprint that is constrained by depth from the surface or time and not to specific layers. The deposit is cut by several mature and continuous gully networks with V-shaped profiles in the proximal slope, and combined V- and U-shaped profiles in the medial and distal sections. Gully formation is linked to both the sodium adsorption ratio (SARs), and high soil clay content, which facilitates swelling and shrinking. The Heelbo deposit comprises two palaeosols (BT1 and BT2) and four sediment (B1, B2, RB and TS) horizons. Through luminescence dating, the ages were found to be approximately 6390 ± 740 years BP for the oldest Brown (B1) horizon and 250 ± 170 years BP for the Red Brown (RB) horizon. The radiocarbon ages of the sediment were inconclusive, but the 14C ages of the fossil bones were in agreement with the luminescence ages. The multiple palaeosol horizons identified suggest two cycles of deposition, pedogenesis and erosion of the alluvial succession. The palaeosols and the presence of calcareous nodules and rhizocretions, and smectite and mixed-layer clay minerals, together with the total absence of illite and kaolinite, suggest protracted, dry periods with intermittent short periods of high rainfall. This is a similar climate regime to what the region experiences currently. Main findings: The Heelbo alluvial slope comprises locally derived sediment, rather than an aeolian source. Heelbo suggests that the hillslope deposits classification system needs to be re-evaluated and opens opportunities for wider study of Pleistocene-Holocene hillslope deposits in central / northern South Africa. This study also contributes to climate change debates in the Holocene.

Open-coast beach-dune environments are vulnerable to erosion, such as from storms or interruption of littoral drift. Although protected from event-driven wave energy, backbarrier shorelines are also susceptible to erosion, due to tidal currents and boat wakes. A common response to mitigate erosion is to place sediment and restore the environment. For placement on beaches, a significant effort has been made to identify offshore resources available; however, offshore resources have seldom been considered for dune or backbarrier shoreline restoration. This study evaluates the geotechnical sediment properties of offshore sediments in proven borrow areas for beach nourishment and reclassifies them for placement in dunes and along the backbarrier in Palm Beach County, Florida. Two different methods calculate volume of offshore resources available for dune or backbarrier projects, including numerical calculations and interpolation of volume through SURFER. Because existing proven borrow areas are delineated for beach nourishment, less volume of sediment available in these areas for other coastal environments. The results of this study suggest that identifying offshore sediment sources for lower-energy environments would not adversely impact sediment needed for beach nourishment. As coastal environments are increasingly threatened by climate change and sea level rise, sediment resources become scarcer, the need to efficiently and effectively use sediments will be of utmost importance for scientists, engineers, and managers in their efforts to protect coastal habitat and communities. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2019. / FAU Electronic Theses and Dissertations Collection

The internal architecture of a beach system can provide clues into the processes involved in its formation, including depositional processes, and/or driving mechanisms (Billy et al., 2014). Several unique events such as cold fronts or Hurricane Irma caused conditions that resulted in erosion and accretion changes in Red Reef Beach - Boca Raton, throughout the year of 2017. Since the lateral extent of these changes is difficult to evaluate using traditional methods such as coring, a Ground Penetrating Radar (GPR) was tested, which allows for a good lateral resolution (cm scale), to image the distribution and evolution of these sediments. The objectives of this study were to 1) explore the lateral variability in the internal architecture of sediments in Red Reef beach in Boca Raton (FL) using an array of ground penetrating radar (GPR) measurements constrained with coring and sediment analysis; 2) explore how dynamics of erosion and accretion induced by changes in wave activity and related to tide variation and storm events, may affect surface topography and the sedimentary internal architecture of beach deposits, using RTK GPS and GPR time-lapse measurements; 3) to explore changes in the lateral extent of the freshsaltwater interface along the beach profile in relation to tide variation and storm events. Reflectors identified in the GPR images showed some evidence of erosional and accretionary surfaces preserved in Red Reef beach. These measurements were repeated over time coinciding with certain events (such as Hurricane Irma) to explore their effects in terms of sediment erosion and accretion as reflected in changes in topography (using time-lapse GPS-RTK measurements), and changes in the internal sedimentary architecture (using time-lapse GPR measurements). The datasets collected also revealed the temporal evolution of the salt-freshwater interface, showing how the lateral extent of saltwater saturated sediment (inferred from areas of GPR signal attenuation along the profiles) evolved over time. This study shows the potential of GPR to provide information about beach sediment processes and dynamics at resolutions beyond traditional measurements (such as coring). It also shows the importance of combining methods that are complementary, such as the use of RTK GPS to explore changes in topography, and GPR that provides information on subsurface sedimentary architecture and the mechanism of change such as post-storm recovery. This study has implications for better understanding changes in coastal sedimentary deposits and processes, both at the subsurface, particularly after high-energy events, such as hurricanes, that result in rapid changes in erosion and/or accretion of sediments. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2017. / FAU Electronic Theses and Dissertations Collection

Bibliography: leaves 280-288. / xix, 288, [36] leaves, [15] leaves of plates : ill. (some col.), maps ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / This study examines the medium sized sedimentary manganese deposit of Dounan, Yunnan Province of China, to determine the sedimentary environments controlling the distribution of ores and rocks, and to establish the relationships between ore mineralization and changes in the sedimentary environment. The thesis also aims to work out the sequence of events after the primary ore is formed, to determine which processes lead to secondary enrichment of the ore. / Thesis (Ph.D.)--University of Adelaide, Dept. of Geology and Geophysics, 1994

The continental terrace west of Oregon between 43° 50'N and 44° 40' N latitude is 50 to 55 miles wide. It consists of a continental shelf, 16 to 35 miles wide, and a continental slope, 16 to 37 miles wide. The eastern portion of the shelf is a smooth, sediment covered area that slopes very gently west. The western portion of the shelf contains four rocky bank areas. The banks are topographically irregular and appear to be of structural origin. West of the banks the shelf edge occurs at depths of 71 to 90 fathoms. The continental slope extends from the edge of the shelf to the abyssal plain at depths of 1530 to 1610 fathoms. A smooth upper slope of less than three degrees extending to depths of 117 to 250 fathoms occurs north and south of Heceta Bank. West of Heceta Bank the upper slope is formed by a scarp that slopes 10° to 16° to 560 to 725 fathoms. West of the upper slope there is an area of irregular topography, including benches, hills and scarps, which extends to depths of 380 to 1100 fathoms. The lower part of the slope is formed by a north-striking scarp which is 3000 to 6000 feet high and slopes 04° to 15°. The bathymetry indicates that the continental slope was formed by step-type, block faulting. Sediments form a thin surface layer over much of: the terrace. Detrital sand, similar to the coastal sand, covers the shelf from the shoreline to approximately 50 fathoms. The deeper areas on the shelf and upper part of the slope are covered by glauconitic sands and silts on the topographic highs and olive green, clayey silts in the topographic lows. The intermediate and lower portions of the slope are blanketed with olive-green, clayey silt. In these sediments the sand fraction, which generally comprises less than five percent of the sample, is composed chiefly of diatoms, Foraminifera, Radiolaria, and sponge spicules. Sands are also present on the intermediate and deep portions of the slope. Dredge hauls west of Newport obtained sand composed mainly of detrital grains which may have been derived from an underlying friable sandstone. Thin layers of sand occur in cores from other portions of the slope. These sands may have been derived by down slope movement of sediment from the upper slope and the shelf. Sedimentary rocks of Upper Miocene and Pliocene age crop out on the shelf banks and on the continental slope. The banks consist of a sequence of diatomaceous, clayey siltstones with interbeds and concretions of calcareous siltstones. Glauconite sandstone, gray wacke sandstone, and limestone breccia are exposed along with the siltstone, on the northern end of Heceta Bank. Most of the rocks obtamed from the slope are similar to those from the shelf. Friable, wacke sandstone is exposed on the slope west of Newport. Foraminifera, the sand fraction compositions, and textural analyses all indicate that the sediment forming the siltstones from the shelf were deposited at lower littoral to lower bathyal depths. The sediments forming the rocks were deposited in one or more sedimentary basins during the Miocene and Pliocene. The subsidence continued until the. Late Pliocene when the area began to rise. The area was uplifted as much as 1000 fathoms by the Late Pleistocene when the shelf was eroded by transgressions and regressions resulting from sea level changes. The last rise in sea level resulted in the erosion of the shelf to its present form and the deposition of a thin layer of sediment. Sand is presently being deposited on the shallow areas adjacent to the continent, and silt and clay are being laid down on the slope and the sheltered areas of the outer shelf. / Graduation date: 1965