M.Sc. (Environmental Management) / Wetlands play a significant role in our environment as they provide a variety of goods, services and benefits to living species ranging from humans, animals and plants to microorganisms. Despite their importance, wetlands have somewhat been neglected over the past few years which has led to a rapid deterioration of wetland conditions and functions. Wetlands provide unique functions that cannot be provided by any other ecosystem; their value was recognised in the 1960s. Prior to this realisation the value of wetlands had been seriously underestimated to the extent where they were even previously labelled as “wastelands”. The reality is that to date minimal measures have been put in place to assist in the rehabilitation and future conservation of wetlands. The lack of wetland management and monitoring can be attributed to the fact that very little is known about the functioning of some of the wetland systems. Endorheic wetlands have recently been emerging as ecosystems of importance. Very little is known about endorheic wetlands and their ecological functioning. To date a fair amount of studies have been conducted on the pans in Mpumalanga and in the Free State but minimal information exists on the pans in the North West Province. The objectives of this study were therefore to compare the abiotic and biotic composition of pans in Mpumalanga and North West Provinces, in order to contribute to the knowledge which will eventually assist in devising rehabilitation measures and future conservation of pans in the area. Three different water ecosystem components were studied; these included aquatic invertebrate communities, water quality and sediment characteristics. The collected water samples were taken to an accredited laboratory to be analysed. When compared between the two provinces, the water-quality results indicated differences between provinces as well as among individual pans. However, most of the pans in both provinces show characteristics of being dystrophic alkaline systems. The invertebrates were collected using sweep nets and stored in jars containing 5% neutrally buffered formalin and a staining agent (Rose Bengal). The sediment characteristics were determined by using standard techniques and results showed that there were no obvious similarities between the different pans in the different provinces. Water-quality analyses were performed on samples taken during both winter- and summer-sampling surveys and these samples were analysed by a reputable laboratory. Based on the analyses of the invertebrate community samples, 25 taxa were identified; results show similarities in the structure of communities in both provinces with the exception of one or two different species. Sampling was conducted over a period of two seasons at all sampling points and several species were found belonging to different families. Invertebrates sampled in Mpumalanga pans were similar to those reported in previous studies done in the area and most of the invertebrates sampled in Mpumalanga and the North West are known to be commonly found in temporary habitats. Spatial and temporal variations in invertebrate assemblages were determined; this analysis displayed differences in the different variables (biotic, physical and chemical) tested over the two seasons. The pans in Mpumalanga were dominated by coarse sand. Large amounts of coarse sand accompanied by poor water quality were observed in MP Pan A in Mpumalanga Province; this could be an indication of somewhat poor catchment management. The results of the abiotic and biotic comparison show that there are minor similarities and differences among the selected pans studied in each province. The knowledge acquired can now be utilised to enhance the available literature on these pans. Long-term studies have to be done to better understand the ecological functioning of the pans in the North West Province in order to devise mitigation measures as well as appropriate rehabilitation strategies and conservation measures.

M.Sc. (Geology) / The Mzimvubu River, situated in the Eastern Cape Province of South Africa, drains essentially strata of the Late Carboniferous to Jurassic Karoo Supergroup with minor intersection of the underlying Devonian Msikaba Formation near the mouth of the river at Port St. Johns. Rock- and river sediment samples were collected at specific points from within the Mzimvubu River drainage basin, based on changes in the geology through which the rivers flow. Detrital zircon age population data was obtained by LA-ICP-MS for each sample in order to meet the two-fold objective of the study; firstly to investigate the reliability of using detrital zircon grains as indicators of sedimentary provenance and secondly to determine possible source areas for the Karoo strata and underlying Msikaba Formation. Through the comparison of detrital zircon age population data for the rock units of the Karoo Supergroup and Msikaba Formation to that of the river sediment, it is concluded that detrital zircon grains hold value in deciphering the geological history of a sedimentary basin. This interpretation is based on similar distributions and trends that are present in both the zircon age populations of the rock- and sediment samples. However, complexities associated with detrital zircon analysis pertaining to rock type and depositional settings are noted and therefore certain procedures that can be implemented during field sampling have been suggested in this study so as to ensure accurate results are obtained. This will further ensure that reliable interpretations of the geological history of a sedimentary basin are achieved. Additionally, by utilising the detrital zircon population data obtained in the first part of the study in conjunction with published scientific data, the provenance of the Karoo Supergroup in the southeastern part of the Main Karoo Basin has been determined. From this data it was determined that, especially the upper part of the Karoo Supergroup in the Eastern Cape Province of South Africa, was deposited much later than previously thought and that many of the stratigraphic layers in the Karoo Basin were deposited coevally in different parts of the basin with lithostratigraphic boundaries being time-transgressive. Ultimately the data allowed for the construction of a tectono-sedimentary model to explain the deposition of the upper Cape- and Karoo Supergroups that started with the deposition of the Msikaba Formation in a passive continental margin setting, to deposition of the lower part of the Karoo Supergroup in an Andean type of foreland basin, with rifting starting during the times of deposition of the Molteno Formation. The deposition of the Molteno-, Elliot- and Clarens Formations took place as Gondwanaland was breaking apart coeval with the formation of the Karoo Igneous Province.

Fluvial systems are dynamic systems in which variables in a catchment and river channel affect the morphology of river reaches. South African rivers are increasingly being exposed to stresses from a combination of factors, one of the most prevalent being the impacts of damming rivers which result in varying downstream sediment fluxes and flow regimes. The sediment load combined with flow characteristics for respective river channels provides the physical habitat for aquatic ecosystems. The damming of the Tsitsa River, through the construction of the Ntabelanga Dam, will change the overall downstream geomorphology. This creates an opportunity for research in the preconstruction window. The current condition of the Tsitsa River was monitored by completing a baseline survey of the channel geomorphology with specific reference to the influence of sediment on river habitats and ecosystem health. Five sites were established in variable reaches of the Tsitsa River, with Site 1 located above the proposed Ntabelanga Dam inundation and Sites 2-5 below the proposed dam wall. Each site included a range of features that can be monitored for their response to the dam. Physical variables, water quality and biota were monitored seasonally to note changes in habitat quality. A baseline survey of the present geomorphology and associated instream habitats of the selected reaches was set up by conducting cross-sectional surveys of channel topography, water slope surveys, discharge measurements and visual and quantitative assessments of substrate. Level loggers were installed at each site to collect continuous data on variations in depth and temperature. Monitoring surveys, in terms of fine sediment accumulation, were conducted to characterise dynamic habitat arrangements and macroinvertebrate community composition. A taxa related physical habitat score for the Tsitsa River was created. The relationship between water quality, physical and ecological characteristics of the Tsitsa River will aid further research in the area as well as create a better understanding of the influence of sediment on river habitats and ecosystem health. Monitoring sites can be used to monitor the impact of catchment-wide rehabilitation on river health prior to the dam being built. After dam construction, the top site above the dam inundation can still be used as a point to monitor the impact of catchment rehabilitation on ecosystem health in terms of fine sediment accumulation.

Le TOC des sédiments du système Gange-Brahmapoutre croît linéairement avec la proportion de phylosilicates et de particules fines. La proportion de Corg fossile est ~ 20 % dans les MES et > 50 % dans les sédiments de fond. Plus de 50 % du Corg dérivé de l'Himalaya est oxydé et remplacé lors du transport dans la plaine du Gange. La charge en Corg est similaire dans les sédiments du Cône et dans les sédiments de rivière. L'abondance et le d13C des biomarqueurs indique que le Corg est dominé par les apports terrigènes. Par conséquent, l'efficacité d'enfouissement du Corg terrigène est proche de 100 %. Dans le système himalayen, nous estimons les flux d'enfouissement de Corg récent et fossile à respectivement 3.1±0.3 × 1011 mol/an et 0.9±0.4 × 1011 mol/an. L'enfouissement de Corg représente donc ~ 80 % de la consommation de CO2 engendrée par l'érosion de l'Himalaya. De manière générale, les orogènes actifs se caractérisent probablement par un enfouissement efficace de Corg / In the Ganga-Brahmaputra system, TOC linearly increases with the relative proportion of philosilicates and fine grain minerals. The proportion of fossil Corg in the suspended and bed sediments is respectively ~ 20 % and > 50 % of the TOC. During the Gangetic floodplain transit, more than 50 % of recent Corg derived from the Himalaya is oxidised and is replaced by Corg derived from the floodplain. The Corg loadings of river and recent Bengal Fan sediments are comparable. Biomarker abundance and ð13C show that Corg is dominated by terrestrial inputs. Consequently, the terrestrial Corg burial efficiency must be around 100 %. In the Himalayan basin, we estimate the burial fluxes or recent and fossil Corg to be respectively 3.1±0.3 × 1011 mol/yr and 0.9±0.4 × 1011 mol/yr. Corg burial therefore account for ~ 80 % of atmospheric CO2 consumption generated by Himalayan erosion. Efficient burial of Corg is likely a characteristic of high physical erosion typical of active orogenic systems

Indiana University-Purdue University Indianapolis (IUPUI) / An investigation of mercury (Hg) in soils and stream sediments was conducted to understand the impact of urbanization on Hg deposition and accumulation on the upper west fork of the White River watershed in central Indiana. Samples were collected to the north and east (i.e., downwind) of emission sources to understand the anthropogenic influences on Hg distribution in soil. Stream sediment sampling was designed to characterize the riverine particulate deposition of Hg through Indianapolis and to predict the potential for stream sediments with high Hg to become sources of methylmercury (MeHg). Spatial analysis revealed that soil Hg was elevated downwind of known industrial emission sites, indicating a local footprint of Hg deposition in central Indiana. Hg in streambank sediments was generally low in up-river sites to the northeast of Indianapolis, and increased markedly as the White River flowed through downtown, with high Hg persisting to downstream rural locations far to the south approximately 40 miles. The stream sediment results also revealed variations in total Hg (Hg(T)) as a function of local depositional sources, sub-watershed location, combined sewer outflows (CSOs), and impoundments along the White River. Low Hg values were recorded where the White River flow rate increased south of the 16th street dam at the confluence of the Fall Creek, where bankside industry and development confine the river. Three tributaries feeding into the White River were included in this study site, all having CSOs. Fall Creek and Pleasant Run have higher values of Hg with Lick Creek having lower values in comparison to the White River and other tributaries. The highest values occur right before confluences to the White River where the flow rate slows and drops sediment. Mercury values typically increased immediately downstream of dams and impoundments. Hg(T) deposition and transport processes pose a problem to anglers fishing south of Indianapolis who may not be aware of the potential dangers related to elevated stream sediment Hg values and the greater potential for MeHg production from these sediments.

Urbanization, often characterized by high impervious surface area, can result in excessive inputs of fine sediments into urban streams. Excessive fine sediments can blanket the stream bed filling the interstitial space in the substratum, which may have adverse effects on stream biota. A field survey was conducted in Oregon urban and non-urban basins to investigate the relationship between fine sediments and stream macroinvertebrates. Physical, chemical, and biological data were collected from 59 stream sites in two urban and two rural streams. The stream sites fulfilled a continuous sediment gradient, which ranged from a low of 2% of fine sediment in the substrate to a high of 64% with an average of 22%. The % fines, in Clear Creek (rural basin) was significantly lower than in the urban basins (Johnson Creek and Tryon Creek) (p=0.005). Johnson Creek (mean=23%) had approximately three times more fine sediment than Clear Creek (mean=7%), while Tryon Creek (mean=32%) had nearly five times as much fine sediment as Clear Creek. EPT taxa richness was significantly higher in both rural streams than in both urban streams (p0.05). For example, regression analysis of EPT taxa richness vs. % fine sediments displayed a coefficient of determination (r2) value of 0.2. Other macro invertebrates metrics displayed similar patterns. The lack of significant correlations may be due to the cumulative effect of basin-wide "historical land use past". Past land use activity may have resulted in long-term reductions of sensitive taxa in the basin taxa pool and efforts to improve local habitats may not be quickly colonized by pollution sensitive taxa. Long-term degradation to the urban streams resulted in a relatively homogenous assemblage of macro invertebrates, which may have confounded the quantitative relationship between sediments and macroinvertebrates. This study suggests there is a clear difference between urban and non-urban streams in terms of macro invertebrates, which may be likely due to sediments, but the quantitative relationship between fine sediments and macro invertebrates is weak.

No description available.

Thesis (M.Phil.)--Chinese University of Hong Kong, 1996. / Includes bibliographical references (leaves 113-120). / Abstract --- p.i / Acknowledgement --- p.iii / Table of Contents --- p.iv / List of Tables --- p.viii / List of Figures --- p.xii / Chapter CHAPTER 1. --- INTRODUCTION --- p.1 / Chapter 1.1 --- Previous Heavy Metal Studies of Hong Kong Marine Waters and Sediments --- p.4 / Chapter 1.2 --- Speciation of Metals in Aquatic Environment --- p.6 / Chapter 1.2.1 --- Speciation of Metals in Water --- p.7 / Chapter 1.2.2 --- Speciation of Metals in Bottom Sediments --- p.7 / Chapter 1.3 --- AVS in Marine Sediments --- p.10 / Chapter 1.3.1 --- Formation of AVS --- p.10 / Chapter 1.3.2 --- Seasonal and Spatial Variation of AVS --- p.11 / Chapter 1.3.3 --- AVS as Mediator of Metal Toxicity --- p.13 / Chapter 1.3.4 --- Chemical Basis for AVS Sediment Normalization --- p.15 / Chapter 1.3.5 --- Analysis of Pore Water Metals --- p.17 / Chapter 1.4 --- Significance of the Research --- p.18 / Chapter 1.4.1 --- Importance of Metal Bioavailability Study in Hong Kong --- p.18 / Chapter 1.4.2 --- Importance of AVS Study in Hong Kong --- p.19 / Chapter 1.4.3 --- Approach of the Present Study --- p.21 / Chapter 1.5 --- Organization of the Thesis --- p.22 / Chapter CHAPTER 2. --- METHODOLOGY --- p.23 / Chapter 2.1 --- Study Area --- p.24 / Chapter 2.2 --- Sampling Strategy --- p.25 / Chapter 2.2.1 --- Sampling Locations --- p.25 / Chapter 2.2.2 --- Sampling Dates --- p.28 / Chapter 2.2.3 --- Sample Collection and Handling --- p.28 / Chapter 2.3 --- Sample Analysis --- p.32 / Chapter 2.3.1 --- Sediment Analysis --- p.32 / Chapter 2.3.2 --- Pore Water and Overlying Water Analysis --- p.34 / Chapter 2.3.3 --- Limitations --- p.36 / Chapter 2.4 --- Statistical Analysis --- p.39 / Chapter CHAPTER 3. --- METALS IN WATER AND BOTTOM SEDIMENTS --- p.40 / Chapter 3.1 --- Metals in the Water --- p.40 / Chapter 3.1.1 --- Variation of Metal Concentrations --- p.41 / Chapter 3.1.2 --- Metal Pollution Level of the Overlying Water --- p.42 / Chapter 3.2 --- Metals in Bottom Sediments --- p.44 / Chapter 3.2.1 --- Spatial Distribution Pattern of Heavy Metals --- p.44 / Chapter 3.2.2 --- Temporal Variation of Metal Content in the Bottom Sediments --- p.48 / Chapter 3.2.3 --- Metal Pollution Level of the Bottom Sediments --- p.49 / Chapter 3.3 --- Conclusion --- p.50 / Chapter CHAPTER 4. --- SPECIATION OF METALS IN THE OVERLYING WATER AND BOTTOM SEDIMENTS --- p.51 / Chapter 4.1 --- Speciation of Metals in the Overlying Water --- p.51 / Chapter 4.1.1 --- Concentration of Labile Metals in the Overlying Water --- p.52 / Chapter 4.1.2 --- Seasonal and Spatial Variation in the Concentration of Labile Metals in the Overlying Water --- p.54 / Chapter 4.1.3 --- Percentage of Labile Fraction in Total Metals --- p.55 / Chapter 4.2 --- Speciation of Metals in the Bottom Sediments --- p.59 / Chapter 4.2.1 --- Proportion of Various Metal Species in the Sediments --- p.60 / Chapter 4.2.2 --- Variation of the Overlying Water Properties --- p.63 / Chapter 4.2.2.1 --- Chemical Properties of the Water in the Study Area --- p.63 / Chapter 4.2.2.2 --- Seasonal Variation of Water Properties --- p.67 / Chapter 4.2.2.3 --- Stratification of the Water Column --- p.69 / Chapter 4.2.3 --- Implication of the Changes of Water Quality on Metal Remobilization --- p.73 / Chapter CHAPTER 5. --- VARIATION OF AVS AND ITS ROLE IN METAL TOXICITY MEDIATION --- p.77 / Chapter 5.1 --- Variation of AVS in the Study Area --- p.78 / Chapter 5.1.1 --- Spatial Variation of AVS --- p.78 / Chapter 5.1.2 --- Seasonal Variation of AVS --- p.81 / Chapter 5.1.3 --- Vertical Variation of AVS --- p.85 / Chapter 5.1.4 --- Effects of AVS Variation on Metal Bioavailability --- p.88 / Chapter 5.2 --- Role of AVS in Metal Toxicity Mediation --- p.91 / Chapter 5.2.1 --- SEM/AVS Molar Ratio --- p.91 / Chapter 5.2.2 --- Fraction of SEM in Total Metals of the Sediments --- p.94 / Chapter 5.2.3 --- Labile Metals in Pore Water --- p.96 / Chapter 5.2.4 --- Dissolved Sulfides in the Pore Water and Overlying Water --- p.99 / Chapter 5.3 --- Conclusion --- p.100 / Chapter CHAPTER 6. --- CONCLUSION --- p.102 / Chapter 6.1 --- Introduction --- p.102 / Chapter 6.2 --- Major Findings --- p.103 / Chapter 6.3 --- Practical Implication of the Findings --- p.108 / Chapter 6.4 --- Suggestion for Further Studies --- p.110 / Bibliography --- p.113 / Appendix A. AVS Extraction and Detection Method --- p.121 / Appendix B. Sequential Extraction Method for Metals Speciation Analysis --- p.123 / Appendix C. Instrument List for the Experiments --- p.125 / Appendix D. Monthly Total Rainfall and Mean Temperature of1995 --- p.127 / Appendix E. Analytical Results of the Overlying Water --- p.128 / Appendix F. Analytical Results of the Bottom Sediments --- p.132 / Appendix G. Analytical Results of the Pore Water --- p.136 / Appendix H. Concentration (μg/g) and Fraction (%) of Pbin Sediments --- p.140 / Appendix I. Concentration (μg/g) and Fraction (%) of Cuin Sediments --- p.142 / Appendix J. Concentration (μg/g) and Fraction (%) of Cdin Sediments --- p.144 / Appendix K. Concentration (μg/g) and Fraction (%) of Znin Sediments --- p.146 / Appendix L. Concentration (μg/g) and Fraction (%) of Niin Sediments --- p.148 / Appendix M. Fraction of Different Speciations of Metals in the Sediments --- p.150 / Appendix N. Vertical Profile of Dissolved Oxygen in the Overlying Water --- p.155 / Appendix O. Vertical Profile of Salinity in the Overlying Water --- p.159 / Appendix P. Vertical Profile of Temperature in the Overlying Water --- p.163 / Appendix Q. Vertical Profile of pH in the Overlying Water --- p.167

Thesis (PhD)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: The discovery of lucrative diamond deposits along the west coast of Southern Africa about 1200 kilometres from the Kimberley region during the period 1908 to 1927, gave rise to a number of different theories with respect to their possible provenance. These included the transportation of diamonds from unknown sources in southern Namibia by south-flowing rivers, hidden on- and off-shore kimberlites along the coast, and transportation by west-bound rivers from the hinterland. Subsequent research has shown that the latter is the only plausible theory. The discovery of marine and coastal diamond deposits as far south as the Olifants River estuary showed that the Vaal-Orange drainage in its current form could not have been the only conduit for diamonds to the coast, and the drainage evolution of southern Africa was interpreted as comprising essentially the following two main palaeo-fluvial systems active in the formation of the world's only known diamond mega-placer deposit:  The Karoo River with its headwaters similar to those of the modern Orange and Vaal Rivers and entering the Atlantic Ocean via the present-day Olifants River;  The Kalahari River that drained southern Botswana and followed the route of the modern-day Molopo River, entering the Atlantic Ocean in the vicinity of the present Orange River mouth. An important shortcoming of the above model is that it could not account for the fact that diamond distribution along the west coast shows a marked increase in grade and average stone size at the estuaries of all the major rivers draining from the escarpment to the Atlantic between the Olifants and the Orange Rivers. The presence of fluvial diamond deposits along the courses of the Buffels, Swartlintjies, Spoeg, Horees and Groen Rivers confirms that the increased grade and diamond size at their estuaries is not a function of large bays and rougher bottom topography associated with the rivers, although these could have contributed to this phenomenon. This proves that the catchments of the rivers between the Olifants and Orange Rivers also had access to diamondiferous debris, although they were not in contact with these two major drainages. A number of researchers proposed that diamonds liberated from pre-Karoo kimberlites were moved from their primary hosts to the south-western parts of the subcontinent by Dwyka glacials. From the above it is clear that nearly a century after the discovery of diamonds along the west coast of southern Africa consensus regarding their origin had not been reached. The aim of this study was therefore to establish a model explaining the most likely sources and distribution history of the more important alluvial diamond deposits in southern Africa. The methodology comprised a study of 1878 diamonds collected from 25 alluvial and two kimberlitic sources for comparison with known similar data from 12 kimberlitic populations in southern Africa. The diamond study was supplemented by a study of sedimentary clasts from bulk gravel samples taken along the Middle and Lower Orange River as well as Scanning Electron-microscope (SEM) Analyses of garnet grains and zircon geochronology. The evidence from the study does not support the postulated existence of a former Karoo River. The surface features of diamonds, notably brown spots indicating – in the context of southern Africa - liberation from pre-Karoo kimberlites, as well as the results of Fourier Transform Infrared analyses revealed that the populations at Kwaggaskop along the Sout River, previously considered an erosion remnant of the Lower Karoo River and those occurring south of Brandvlei and Van Wyksvlei in the valley of the Sak River, previously considered to have been reworked from the Middle Karoo River, differ profoundly from each other. In addition, the surface feature studies and Fourier Transform Infrared Analyses clearly show major distinctions between the diamond populations from the Sout River-Olifants River estuary and those from the Kimberley kimberlite province which was said to have supplied diamonds in large quantities to the Olifants River estuary via the postulated Karoo River. Furthermore the idea of a palaeo-Gamoep River playing a significant role in the transportation of diamonds to the west coast is favoured by the presence of brown-spotted diamonds and diamonds with Platelet Preservation Indices revealing severe platelet destruction that could be traced through Bosluispan in the Koa River valley, the Buffels River valley, the Buffels River estuary and to the shallow marine environment north of the Buffels River. Zircon geochronology confirmed the role of the Orange River in the denudation of the sub-continent. With respect to the drainage evolution and diamond distribution in southern Africa the results of this study indicate a complex diamond dispersal model that differs in some respects from prevailing theories. It shows that diamonds liberated from pre- Karoo kimberlites in the north-eastern part of the sub-continent were initially moved in a south-westerly direction by pre-Karoo drainages, then by Dwyka glaciers and ice sheets. Ultimately, after liberation from exhumed glacial and fluvial deposits and together with diamonds subsequently liberated from Jurassic and Cretaceous kimberlites, Cretaceous and younger drainages provided the transport toward the Atlantic Ocean where the diamonds were concentrated along shorelines and in bedrock trap sites. Significant quantities did not reach the coast, but were locked up in fluvial sediments in erosion remnants like terraces, karstic depressions and other segments of palaeo-channels along the way. The presence of diamonds with FTIR characteristics reminiscent of those from Orapa and Jwaneng in the Orange River deposits as well as in a raised marine terrace in southern Namaqualand and in marine deposits north of Concession 12A, also negates the possible existence of a palaeo-Kalahari River, unless it was a very young system that did not interrupt the south-bound dispersal of Botswana diamonds during the Late Oligocene-Early Miocene. The study also included microscopic examination of a parcel of diamonds from the enigmatic Skeleton Coast deposits, north-western Namibia. These results confirmed the conclusion based on geological and geomorphic grounds that these diamonds cannot be linked to the Oranjemund deposits, while their surface features showed that pre-Karoo sources comprise the most likely provenance for the Skeleton Coast diamonds. Thus the combination of FTIR analyses and surface feature studies of diamonds, zircon geochronology and SEM analyses of garnets allowed the formulation of a revised model for the distribution of alluvial diamonds and the drainage history of the sub-continent since the Middle Cretaceous, while the study of sedimentary clasts confirmed the repeated occurrence of high energy fluvial conditions – especially evident in the palaeo-Orange River sediments – that contributed to the high percentage of gem stones in the surviving alluvial diamond populations due to the destruction of poor quality diamonds. / AFRIKAANSE OPSOMMING: Die ontdekking van ryk alluviale diamantafsettings aan die suider-Afrikaanse weskus, meer as 1200 kilometer van die Kimberley-omgewing af tussen 1908 en 1927, het 'n aantal teorieë omtrent moontlike provenansgebiede vir hierdie afsettings tot gevolg gehad. Dit het gewissel van die suidwaartse vervoer van diamante vanaf bronne in suidelike Namibië, diamantdraende kimberliete in die kusvlaktes of op die vastelandstoep onder huidige seevlak, tot die vervoer van diamante deur weswaarts-vloeiende riviere vanuit die binneland. Geen ontdekkings wat eersgenoemde teorie kon ondersteun is in Namibië gemaak nie. Verder, namate meer gevorderde navorsingsresultate aan die lig gekom het, het dit duidelik geword dat kimberliete wat weg van 'n antieke kraton geleë is, grootliks sonder diamante is, en gevolglik het die idee van nabygeleë diamantdraende kimberliete in die kusvlakte of op die seebodem as bron, onaanvaarbaar geword. Grootskaalse wes- tot suidweswaartse vervoer van diamante het gevolglik die enigste aanvaarbare alternatief gebied. Die ontdekkiing van aan- en aflandige mariene afsettings tot so ver as suid van die Olifantrsrivier het getoon dat die Vaal-Oranjestelsel in sy huidige vorm nie die enigste vervoerkanaal vir diamante na die weskus kon wees nie. Die dreineringsgeskiedenis van suidelike Afrika was gevolglik vertolk aan die hand van twee voorgestelde groot oer-rivierstelsels, naamlik: - Die Karoorivier met sy bolope naastenby soortgelyk aan dié van die moderne Oranje- en Vaalriviere, en wat langs die huidige Olifantsrivier uitgemond het; - Die Kalaharirivier wat die suide van Botswana gedreineer het, en min of meer die roete van die huidige Moloporivier gevolg het, met sy monding baie naby aan dié van die moderne Oranjerivier. 'n Belangrike tekortkoming in bogenoemde model is die feit dat dit nie 'n verduideliking bied vir die volgende feit nie: Diamant-produksiedata van die Suid-Afrikaanse weskus toon 'n skielike toename in graad (karaat per 100 ton) en gemiddelde steengrootte van diamante by die monding van al die belangrike riviere tussen die Olifants- en Oranjeriviere, wat vanaf die platorand na die Atlantiese Oseaan dreineer. Die feit dat fluviale diamantvoorkomste in die valleie van die Bufffels-, Swartlintjies-, Spoeg-, Horees- en Groenriviere aangetref word, bevestig dat hierdie verskynsel nie net aan die teenwoordigheid van kus-inhamme en ruwer vloertopografie wat met die riviermondings geassosiëer is, toegeskryf kan word nie, alhoewel dit wel „n bydrae tot hierdie waarneming kon maak. Dit bevestig dat hierdie riviere wel in hul opvang-gebiede ook toegang tot diamanthoudende puin gehad het, sonder enige kontak met die Olifants- of Oranjeriviere. 'n Aantal navorsers het die gedagte geopper dat diamante wat uit voor-Karoo kimberliete vrygestel was, deur bewegende ysplate en/of gletsers vanaf hul provenansgebiede na die suidweste van die subkontinent vervoer is. Uit die voorafgaande paragrawe is dit duidelik dat, ongeveer ʼn eeu ná die ontdekking van diamante langs die suider-Afrikaanse weskus, daar nog nie eenstemmigheid bereik is oor die oorsprong van hierdie diamante nie. Die doel van hierdie studie was gevolglik die daarstelling van „n model wat „n aanvaarbare verduideliking bied vir die verspreiding en afsetting van sommige voorkomste van spoeldiamante in suidelike Afrika soos tans waargeneem. Vir hierdie doel is 1878 diamante afkomstig vanuit 25 alluviale en twee kimberlietvoorkomste ondersoek. Die resultate is vergelyk met soortgelyke inligting wat bekend is vir diamantpopulasies vanuit 12 suider-Afrikaanse kimberliete. Die diamantstudie is aangevul met die ondersoek van spoelklippe vanuit gruismonsters wat langs die Middel- en Benede Oranjerivier versamel is asook Skanderings-elektron Mikroskoop-analises (SEM) van granaatkorrels en sirkoon-geokronologie. Die resultate van hierdie studie ondersteun nie die hipotese van „n eertydse Karoorivier nie. Die teenwoordigheid van bruin spikkels op diamante wat – in die konteks van die geologiese geskiedenis van suidelike Afrika – vrystelling vanuit vóór- Karoo kimberliete impliseer, asook die resultate van FTIR-analises dui op „n komplekse model wat „n alternatief bied vir bestaande sienswyses. Dit toon dat die diamantpopulasies by Kwaggaskop langs die Soutrivier wat veronderstel was om die Benede Karoorivier te verteenwoordig, en dié wat suid van Brandvlei en Van Wyksvlei in die vallei van die Sakrivier aangetref word en veronderstel was om afkomstig te wees uit die Middel Karoorivier, drasties van mekaar verskil. Dit openbaar ook beduidende verskille tussen die diamantpopulasies van die Olifantsriviermonding en dié van die Kimberley-omgewing waarvandaan die veronderstelde Karoorivier groot hoeveelhede diamante aan die Sout-Olifantsrivier sou gelewer het. Verder verskaf die teenwoordigheid van diamante met bruin spikkels en diamante met eienskappe wat toon dat hul stikstofplaatjies vernietig is, „n skakel tussen Bosluispan in die vallei van die Koarivier en die seegebied noord van die Buffelsrivier, via die Buffelsriviervallei en die Buffelsriviermonding, en hierdie feite ondersteun gevolglik eerder die voorstel dat groot hoeveelhede diamante deur die paleo-Gamoeprivier na die weskus vervoer is. Die teenwoordigheid van diamante met FTIR-kenmerke soortgelyk aan dié van Orapa en Jwaneng in die Mid-Oranje afsettings, 'n mariene terras in die suide van Namakwaland en in mariene konsessies noord van Seegebied 12A, opponeer ook die gedagte van 'n paleo-Kalaharirivier, tensy laasgenoemde 'n baie jong stelsel was wat nie die suidwaartse beweging van Botswana-diamante gedurende die Laat Oligoseen tot Vroeg Mioseen verhinder het nie. Die resultate van die sirkoon-geokronologie het die rol van die Oranjerivier in die afplatting van die subkontinent bevestig. Die volgende model tree uit bogenoemde waarnemings na vore: diamante wat in die noordooste van die subkontinent uit kimberliete met „n voor-Karoo inplasingsouderdom vrygestel is, is aanvanklik suidweswaarts vervoer deur voor-Karoo riviere. Daarna is die diamante deur gletsers en ysplate gedurende die Dwyka-tydperk, en uiteindelik ná vrystelling vanuit ontblote glasiale en paleo-fluviale afsettings tesame met diamante wat intussen vanuit Jura- en Krytouderom kimberliete vrygestel is, deur die dreineringstelsels in die Kryt-tydperk en later, verder suidweswaarts vervoer. Sommige het onderweg in fluviale sedimente (terrasse, karstholtes en ander reste van paleokanale) agtergebly, terwyl „n beduidende hoeveelheid tot in die Atlantiese Oseaan vervoer is waar hulle deur mariene prosesse in ou strandlyne en bodemrots opvangstrukture gekonsentreer is. Die studie het ook die mikroskopiese ondersoek van 'n pakkie diamante afkomstig vanuit die enigmatiese afsettings aan die noordelike Skedelkus van Namibië ingesluit. Op grond van geologiese en geomorfologiese getuienis word die afleiding gemaak dat die Skedelkusdiamante nie met die Oranjemund-afsettings verbind kan word nie, terwyl die mikroskopiese oppervlakteksture toon dat bronne met 'n voor-Karoo inplasingsouderdom die mees waarskynlike provenans vir hierdie diamante is. Die kombinasie van FTIR-analises en oppervlaktekstuur-studies van diamante, sirkoongeokronologie en SEM-analises van granate het die formulering van „n hersiene model vir die subkontinent se dreineringsgeskiedenis sedert die Middel-Kryttydperk en diamantverspreiding moontlik gemaak terwyl die studie van sedimentêre klaste getoon het dat hoë-energietoestande, waardeur diamante van swak gehalte vernietig sou word, herhaaldelik voorgekom het, veral in die paleo-Oranjerivier. Die afleiding word gemaak dat hierdie aspek „n bydrae gelewer het tot die hoë persentasie juweelstene in die oorblywende alluviale diamantpopulasies.

Sediment deposit ages inferred from radiocarbon dating of stream bank material were used to estimate residence times of valley-floor deposits in headwater valleys of the Oregon Coast Range, USA. Inherited ages of radiocarbon-dated material, i.e., time between carbon fixation in wood and its incorporation in a sediment deposit, can result in over-estimation of the ages of those deposits and, hence, the residence times of sediment within those units. Calibrated radiocarbon dates of 126 charcoal pieces sampled from Knowles Creek were used to estimate the distribution of inherited ages in fourteen depositional units representing three deposit types: fluvial fines, fluvial gravels, and debris flows. Within a depositional unit, the inherited age distribution of a piece of charcoal was estimated by convolving its calibrated age distribution with that of the piece of charcoal with the smallest weighted-mean calibrated age (i.e., an approximation of a unit's date of deposition) within that unit. All inherited age distributions for a particular deposit type were then added and normalized to provide a probability distribution of inherited ages for that deposit type. Probability distributions of inherited ages average 688, 1506, and 666 yr for fluvial fines, fluvial gravels, and debris flow units, respectively. Curves were fit to inherited age distributions for each deposit type. These curve fits were then convolved with deposit age distributions (i.e., equal to calibrated age distributions of woody material sampled from stream banks) of samples from Bear Creek (Lancaster and Casebeer, 2007) to correct these deposit ages for inherited age. This convolution gives a corrected deposit age. In cases in which means of corrected deposit age distributions for an upper unit were older than those of a lower unit within a stratigraphic column, the upper sample’s corrected deposit age distribution was set to that of the youngest lower in the stratigraphic section. Convolution shifted individual deposit age distributions towards zero and increased their standard deviation by an average of 365%. However, convolution decreased the standard deviations of normalized probability distribution functions of deposit ages inferred from many samples from 1340 to 1197 yr, and from 471 to 416 yr for lower and upper reaches, respectively, of the Bear Creek valley in the Oregon Coast Range. Convolution decreased estimates of mean deposit ages from 1296 to 1051 yr, and from 308 to 245 yr for lower and upper reaches, respectively, of the Bear Creek. Estimates of percentages of basin denudation passing through each reach's deposit ("trapping efficiency") increased from 11.6% to 14.4%, and from 25.4% to 31.9% for lower and upper Bear Creek, respectively. However, basic shapes of residence time distributions and, thus, inferences regarding removal of sediment from the reaches did not change after deposit dates were corrected. Sediment residence times in the lower Bear Creek valley are exponentially distributed, which implies that all sediment has a uniform probability of evacuation from deposits, whereas the power-law-distributed residence times in upper Bear imply preferential evacuation of younger deposits and preservation of older deposits. Much of the sediment transported onto valley floors via debris flows is deposited, and then is evacuated over longer times. Volumes and residence times of stored sediment in these deposits at the transition from debris flow to fluvial evacuation, and their associated width of valley floors, vary throughout a network. Export volumes and frequencies from tributaries are controls on deposit volumes and may control valley widening of mainstem valley floors. In addition, closely spaced tributaries may exert composite effects on valley floor landforms. It is hypothesized that the volumes of sediment stored at confluences increases with contributing watershed area of tributaries to the point where tributary slopes are low enough to cause most debris flows to be deposited within tributary valleys instead of in the mainstem valley. In four ~1 km reaches with contributing watershed areas of 0.3 to 5.0 km², field surveys provided measures of width of valley floors and volume of deposits, and radiocarbon dating of charcoal provided residence times of sediment in these deposits. Mean residence times of reaches vary between 1.1 and 2.5 kyr. Exponential distributions fit to residence times within two of the reaches imply evacuation of sediment independent of deposit ages. Power-law fits to residence times of the other two reaches imply age-dependent evacuation of deposits. Distribution shapes of residence times, and their means, do not vary systematically with contributing watershed area of mainstems. Mean width of mainstem valley floors increases with contributing watershed areas of both mainstems and their respective tributaries. Volumes of sediment stored on the valley floor increase with contributing areas of mainstems, and these volumes at tributary junctions peaked at tributary contributing areas of ~0.1 km². Percentage of basin denudation entering storage decreases with contributing area of mainstem. This decrease may be due to increasing percentages of sediment supply via fluvial transport for larger watersheds, and much, if not most, of this supply routes through the system quickly. / Graduation date: 2012