Magister Scientiae - MSc / This study described porosity and permeability distribution in the deep marine play of the central Bredasdorp Basin, Block 9, offshore South Africa using methods that include thin section petrography, X-ray diffraction, and scanning electron microscopy, in order to characterize their porosity and permeability distributions, cementation and clay types that affect the porosity and permeability distribution. The study included core samples from nine wells taken from selected depths within the Basin. / South Africa

The Witwatersrand basin is unique in terms of its mineral wealth. The gold in the Witwatersrand basin is mainly concentrated in the placers and two types of unconformities are associated with the placer formation. This paper attempts to quantitatively describe the origin and depositional process of placers within the context of basin analysis, geohistory and sequences stratigraphic framework. Several tectonic models have been proposed for the evolution of the Witwater~rand basin and it seems as if a cratonic foreland basin accounts for many of the observed features observed the Central Rand Group basin. The tectonic subsidence curve generated for the Witwatersrand Basin clearly implies foreland basin response which was superimposed an older, deep seated extensional basin. These compressive tectonics can be superimposed on extensional basins, where the shift from extensional to compressional tectonics lead to inversion processes. The critical issues about the Witwatersrand basin which were addresed in this review, is the validity of basin wide correlation of placer unconformuties and whether sequence stratigraphy is applicable to fluvial systems of the Witwatersrand sequence. It is believed that the Central Rand Group was deposited as alluvial - fan deltas by fluvially dominated, braidplain systems with minor marine interaction which had a considerable impact on the preservation of economically viable placers. Most important to the exploration geologist is the recognition of stacking patterns of the fluvial strata to determine change in the rate at which accommodation was created. Identifying sequence boundaries and other relevant surfaces important for identifying these stacking patterns of the sequences, depends entirely on the recognition of a hierarchy of stratal units including beds, bedsets, parasequences, parasequence sets and the surfaces bounding sequences. Placers are closely associated with the development of disconformities and therefore become important to recognise in fluvial strata. If these placers are to become economic, the duration of subaerial exposure of the unconformities that allowed the placers to become reworked and concentrated must be determined. In order to preserve the placer, a sudden marine transgression is necessary to allow for minimal shoreline reworking and to cap the placer to prevent it from being dispersed. The placers in the Witwatersrand basin occur in four major gold-bearing placer zones in the Central Rand Group. Accordingly they can be assigned to four supercycles, which are cyclical and therefore predictive. It is the predictive nature of these rocks and the ability of sequence stratigraphy to enhance this aspect, which is a pre-requisite for an effective exploration tool in the search for new ore bodies or their extension in the Witwatersrand basin.

Large, infrequent "episodic" sediment transfers are commonly considered differently from "normal-regime" sediment-transfer activity. For example, in the important hillslope-gully-stream sediment cascade pathway in coastal British Columbia, debris slides and debris torrents are considered as "episodic events". On the other hand, lower-magnitude hillslope to gully-channel sediment transfers and fluvial sediment tranSport within gully and stream channels are usually considered as "normal-regime" activity, represented by annual yields. However, the results of this study illustrate the highly episodic nature of normal-regime fine-sediment transfers, which are closely linked to hydrometeorological and sediment-supply conditions. The results indicate that qualitative modelling of fine-sediment transfer activity, at the synoptic or event scale, should be possible based upon hydrometeorological and sediment-supply information. From such a model ~ the elements of which are presented in the concluding chapter ~ fine-sediment transfer activity could be forecast based upon regional weather forecasts. The study was conducted in Russell Creek Basin, on northern Vancouver Island, British Columbia. Fine-sediment transfer activity was monitored at a nested hierarchy of sites representing fine-sediment transfers from unstable hillslopes to a gully channel, suspended sediment transport out of the unstable gully and a nearby stable gully, and suspended sediment transport in Russell Creek near the mouth. Russell Creek Basin is located within Tsitika Watershed, which is the site of a British Columbia Ministry of Forests study dedicated to determining relative fine-sediment contributions from natural and logging-related sediment sources. The results of the Russell Creek study indicate that an event-based sediment sampling program is desirable and that at least some automated sampling is required. Furthermore, development of a qualitative sediment-transfer activity forecast model would be useful in interpretation of sample data and would allow efforts to be concentrated during the periods of greatest sediment-transfer activity. / Arts, Faculty of / Geography, Department of / Graduate

Whether one is interested in the geomorphology, hydrology, or ecology of a river, the nature of the bed sediments is of major importance. Despite a long history of interest our ability to predict local grain size is poor, which is unfortunate given the labour and costs associated with bed material sampling. A preliminary model of sediment texture variation at the drainage basin scale, which makes a fundamental distinction between coupled and uncoupled hillslope-channel units, is presented. It is hypothesised that grain size variations in strongly coupled rivers are unstructured as a result of overbank colluvial inputs and special storage elements. These preclude the development of the systematic downstream structure commonly associated with fluvial sorting and abrasion processes in uncoupled channels. This conjecture is assessed empirically using data collected in two rivers on the Queen Charlotte Islands. It is found that distance alone does not explain changes in grain size, and that local variations are dominated by large organic debris jams. Impermeable jams are associated with upstream fining and downstream coarsening but the effect diminishes as the jams become more permeable, often with age. Jam placement is random, but frequent, and consequently at the drainage basin scale, grain size changes dramatically and unpredictably over very short distances. No deterministic structure is apparent. Further analysis reveals that the observed variations of surface median grain size and Fredle index are best regarded as stochastic phenomena. Sampling criteria are then determined which enable the accurate characterisation of such variation, once a stream has been classified by land use and position relative to hillslopes. / Arts, Faculty of / Geography, Department of / Graduate

[Truncated abstract] The realization in 1999 that the authigenic phosphate, xenotime, could be used in geochronological studies to place age constraints on burial events that affected sedimentary basins has opened numerous opportunities for establishing timeframes for sedimentary basin analysis. Since then, the mineral has been used to place new and novel age constraints on diagenesis, metamorphism, and hydrothermal alteration and mineralization events. Whilst these studies were successful, they identified many complexities in xenotime growth and were restricted to specific areas or single basins: they do not convey, demonstrate or explore the immense variety of geological applications in which xenotime may provide unique geochronological constraints. This thesis explores the nature of authigenic xenotime, utilizing studies in three different Proterozoic sedimentary basins: two in Australia, southwestern Australia and the Northern Territory, and the third in the United States of America. The thesis includes a number of discrete studies demonstrating different aspects of xenotime growth, elucidated from detailed petrography, geochronology and geochemistry of authigenic xenotime. An integrated textural, geochemical and geochronological study of authigenic xenotime from the Mt Barren Group, SW Australia, establishes an absolute timescale on some of the many processes involved during the diagenesis of siliciclastic units. ... positions and trends and broadly confirm the chemical discrimination criteria established for an Archaean basin. However, the Proterozoic data are shifted to lower Gd-Dy values and extend beyond the original field outlines, causing more overlap between fields intended to discriminate xenotimes of different origin. The plots were revised to encompass the new data. This study has significantly extended our knowledge of the nature of authigenic xenotime. It was found that xenotime may form in (meta)sediments in response to a large number of post-depositional processes, including early- and latediagenesis, (multiple) basinal hydrothermal events and low-grade metamorphism. A combination of detailed petrography and in situ geochronology provides the best avenue to decipher complex growth histories in xenotime. With further development, it is likely that xenotime geochemistry will also prove diagnostic of origin and can be incorporated into the interpretation of age data. The number of potential applications for xenotime geochronology has been expanded by this study.

Thesis (MSc)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: Diamictites are sedimentary deposits that originate from a number of different environments, the most common being associated with a glacial environment. Although this association is not, in all cases correct, it is still being used due to the lack of knowledge to confidently identify, classify and interpret a depositional environment for diamictite deposits. During the late Carboniferous to early Permian, two diamictite deposits formed during the development of the Cape Basin and Main Karoo Basin in the southern margins of South Africa. These deposits are known as the Miller diamictite and Dwyka diamictite. The latter is well known and was deposited during the Karoo-deglaciation. The Dwyka diamictite is often referred to as Dwyka Tillite. This is an inappropriate reference owing to that not all of the Dwyka deposits are directly formed as a result of glacial contact. The origin of the Miller diamictite is uncertain, but there are suggestions that its origin can be traced to either a glacial or debris flow deposit formed in a deltaic environment, thus referred to by some as a tillite and others as a diamictite. To establish the sedimentary environments of the above mentioned diamictite deposits in the study area, two facies models were presented with a notable bias for the second model. The first model represents a continuous sedimentation cycle between the closing of the Cape Basin and opening of the Main Karoo Basin, whereas the second model demonstrates an erosional break (hiatus) between the depositions of the above mentioned basins. Derived from the use of the second model, it can be concluded that the Miller diamictite can indeed be classified as a diamictite from a textural interpretation. Both diamictites (Miller and Dwyka) cannot be referred to as tillite deposits since none show evidence of direct glacial contact. The Miller and the Dwyka are both diamictites, but were formed in different sedimentary environments. The Miller diamictite is a product of debris flow deposits from the slope of a braided delta, whereas the Dwyka diamictite represents distal glacio-marine “rain-out” deposits. / AFRIKAANSE OPSOMMING: Diamiktiete is sedimentêre neerslae afkomstig vanaf verskillende omgewings en dit word meestal met n glasiale omgewing geassosieer. Alhoewel hierdie assosiasie nie in alle gevalle korrek is nie, word dit nog steeds gemaak as gevolg van die gebrek aan kennis om diamiktiete met selfvertroue te identifiseer, te klassifiseer en 'n afsettingsomgewing vir die sedimente te interpreteer. Gedurende die laat Karboon tot vroeë Permiese tydperk het twee diamiktiet afsettings gevorm gedurende die vorming van die Kaap Supergroep Kom en Karoo Kom in die suidelike grense van Suid-Afrika. Die afsetting staan bekend as die Miller diamiktiet en Dwyka diamiktiet. Laasgenoemde is redelik bekend en is gedurende die Karoo gletser ontvormings tydperk gesedimenteer. Die Dwyka diamiktiet word dikwels Dwyka Tilliet genoem, wat onvanpas is aangesien nie al die Dwyka neerslae direk gevorm het as gevolg van direkte glasiale kontak nie. Die oorsprong van die Miller diamiktiet is egter onseker. Dit word veronderstel dat die Miller diamiktiet óf deur 'n gletser, of puin vloei neerslag gevorm het in 'n deltaiese omgewing, dus word daarna verwys as 'n tilliet of ʼn diamiktiet. Om die sedimentêre omgewings van die twee bogenoemde diamiktiet afsettings in die studie area te bevestig, is twee fasies modelle aangebied met 'n voorkeur aan die tweede model. Die eerste fasies model verteenwoordig n siklus van ongebroke sedimentasie tydens die sluiting van die Kaapse Kom en die opening van die Karoo Kom. Die tweede fasies model verteenwoordig n hiatus tussen die afsetting van die bogenoemde komme. Gegrond op sy teksturele samestelling kan die Miller diamiktiet inderdaad as 'n diamiktiet geklassifiseer word. Beide diamiktiete (Miller en Dwyka) kan nie as tilliet neerslae beskou word nie, aangesien geen bewyse gelewer kan word van afsetting as gevolg van direkte glasiale kontak nie. Die Miller en Dwyka is n diamiktiet, maar is gevorm in verskillende afsettingsomgewings. Die Miller diamiktiet is 'n produk van die puin vloei neerslag vanaf die helling van ‘n delta, terwyl die Dwyka diamiktiet verteenwoordig ‘n afgeleë glasio-mariene “uit-reen” neerslae.

As bacias de Taubaté e Resende são bacias continentais paleógenas do tipo rift, orientadas segundo a direção NE a ENE e fazem parte do segmento central do Rift Continental do Sudeste do Brasil. Ambas foram instaladas durante o Eoceno, resultantes de um campo de esforços distensivo de direção NW-SE. Este campo reativou zonas de cisalhamento de direção NE do embasamento pré-cambriano como falhas normais, importantes durante a instalação e evolução da bacia. Há também inúmeras estruturas transversais ao eixo da bacia, de direções N-S, NE-SW e NW-SE, as quais compreendem falhas e dobras que estiveram ativas durante diferentes intervalos de tempo, embora seus papeis na evolução da bacia ainda sejam pouco conhecidos. A fim de reconhecer estas estruturas em subsuperfície na Bacia de Taubaté, cinco perfis sísmicos longitudinais ao eixo da bacia foram interpretados, demonstrando o caráter distinto dessas estruturas como falhas normais e inversas, que interceptam diferentes unidades sísmicas, indicando uma deformação tectônica polifásica. A presença de altos estruturais transversais, distinguíveis em perfis sísmicos, ativos durante a abertura da bacia, pode estar relacionada com anticlinais formados na capa das falhas, durante uma evolução relacionada ao crescimento das falhas principais de borda em um regime distensivo de direção NW-SE. Ainda, foram descritas em afloramentos falhas sinsedimentares de componente normal, de direção NW-SE e transversais à Bacia de Resende, dispostas em um alto ângulo com relação à orientação ENE das falhas principais de borda. Estas estruturas foram interpretadas como falhas de alívio formadas no mesmo contexto distensivo. As relações estratigráficas e a análise de paleotensões das populações de falhas indicaram que as estruturas transversais estão relacionadas a quatro eventos deformacionais: compressão NE-SW, provavelmente durante o Mioceno; compressão NW-SE, durante o Pleistoceno Superior; distensão E-W a NW-SE durante o Holoceno; e por fim compressão E-W relacionada ao campo de esforços atual. A evolução da Bacia de Santos na porção adjacente offshore durante o Cenozoico pode estar diretamente relacionada à presença de estruturas transversais, mudanças de campo de estresse e a geração e eventos deformacionais nas bacias continentais do tipo rift. / The Taubaté and Resende are NE-to-ENE-oriented Paleogene continental rift basins of the central segment of the Continental Rift of Southeastern Brazil. Both basins were installed during the Eocene as a result of a NW-SE-oriented extensional stress field. This stress field reactivated NE-trending shear zones of the Precambrian basement as normal faults, which played a major role during the basin installation and evolution. There are also numerous N-S, NE-SW and NW-SE-oriented structures transverse to the NE-trending basin axis. These structures comprise faults and folds that were active at different time intervals, but their role in the basin evolution is poorly understood yet. In order to recognize these structures in the subsurface in Taubaté Basin, five longitudinal seismic profiles were interpreted showing their distinctive character as normal and reverse faults, which intersect different seismic units and indicate a polyphasic tectonic deformation. The presence of transverse structural highs, recognizable in the seismic profiles, which were active during the opening of the basin, can be related to anticlines formed in the hangingwall during an evolution related to the growing of the border master faults in a NW-SE-trending extensional regime. Moreover, syn-sedimentary NW-SE-oriented transverse normal faults oblique to the ENE-orientation of the border master faults were described in outcrops in the Resende Basin. These structures are interpreted as release faults and thus formed in the same extensional context. Stratigraphic relationships and paleostress analysis of fault populations indicate that transverse structures are related to four deformational events: a NE-SW-oriented compression probably during the Miocene, a NW-SE-oriented compression in the Late Pleistocene to Holocene, an E-W-to-NW-SE-oriented extension in the Holocene and lastly, an E-W-oriented compression related to the present-day stress field. The evolution of the adjoining offshore Santos Basin during the Cenozoic has a narrow correlation with the formation and evolution of Taubaté and Resende basins. The migration of depocenters in the Santos Basin during the Cenozoic can be associated with the presence of NW-SE-oriented transverse structures, changes in the stress fields, and generation and deformation events in the continental rift basins

"February 2004" / Includes bibliographical references (leaves 216-227) / Each accompanying profile sheet is named and numbered individually. / xvi, 245 leaves : ill. (some col.), maps (col.), charts ; 30 cm. + 1 location map ( 22 x 30 cm. folded to 22 x 15 cm.) + 4 geologic profiles ( 56 x 100 cm. folded to 20 x 29 cm.) ; in pocket inside back cover. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, School of Earth and Environmental Sciences, Discipline of Geology and Geophysics, 2004

Two new analytical methodologies were developed for chlorine and bromine stable isotope analyses of inorganic samples by Continuous-Flow Isotope Ratio Mass Spectrometry (CF-IRMS) coupled with gas chromatography (GC). Inorganic chloride and bromide were precipitated as silver halides (AgCl and AgBr) and then converted to methyl halide (CH3Cl and CH3Br) gases and analyzed. These new techniques require small samples sizes (1.4 µmol of Cl- and 1 µmol of Br-). The internal precision using pure CH3Cl gas is better than ∓0.04 ‰ (∓STDV) while the external precision using seawater standard is better than ∓0.07 ‰ (∓STDV). The internal precision using pure CH3Br gas is better than ∓0.03 ‰ (∓STDV) and the external precision using seawater standard is better than ∓0.06 ‰ (∓STDV). Moreover, the sample analysis time is much shorter than previous techniques. The analyses times for chlorine and bromine stable isotopes are 16 minutes which are 3-5 times shorter than all previous techniques. Formation waters from three sedimentary settings (the Paleozoic sequences in southern Ontario and Michigan, the Williston Basin and the Siberian Platform) were analyzed for 37Cl and 81Br isotopes. The δ37Cl and δ81Br values of the formation waters from these basins are characterized by large variations (between -1.31 ‰ and +1.82 ‰ relative to SMOC and between -1.50 ‰ and +3.35 ‰ relative to SMOB, respectively). A positive trend between δ81Br and δ37Cl values was found in all basins, where an enrichment of δ81Br is coupled by an enrichment of δ37Cl. In the Paleozoic sequences in southern Ontario and Michigan, the δ37Cl and δ81Br signatures of formation water collected from northwest of the Algonquin Arch are distinct from those collected from southeast of the Arch. All of the brines from the northwest of the Algonquin Arch are characterized by depleted isotopic values in comparison with the isotopic values from the brines from southeast of the Arch. The δ81Br signatures of the two brines show total separation with no overlaps. The δ37Cl values show some overlap between the two groups. One of the scenarios that can be put forward is that the Arch forms a water divide, where sediments southeast of the Arch are dominated by Appalachian Basin formation waters, and the sediments located northwest of the Arch are dominated by the Michigan Basin formation waters. The δ81Br and δ37Cl signatures of the Williston Basin brines suggest the existence of several different brines that are isotopically distinct and located in different stratigraphic units, even though they are chemically similar. The relatively wide range of δ37Cl and δ81Br of the formation waters suggests that the ocean isotopic signatures were variable over geologic time. A seawater temporal curve for δ81Br and δ37Cl was proposed with a larger variation of δ81Br in comparison with δ37Cl. The isotopic variations of these two elements agree very well with 87Sr/86Sr seawater variation during the same period. In general, the use of chlorine and bromine stable isotopes can be very useful in assessing the origin and the evolutionary processes involved in evolving formation waters and also in distinguishing different brines (end members). Furthermore, they can be employed to investigate the hydrogeological dynamics of sedimentary basins.

Two new analytical methodologies were developed for chlorine and bromine stable isotope analyses of inorganic samples by Continuous-Flow Isotope Ratio Mass Spectrometry (CF-IRMS) coupled with gas chromatography (GC). Inorganic chloride and bromide were precipitated as silver halides (AgCl and AgBr) and then converted to methyl halide (CH3Cl and CH3Br) gases and analyzed. These new techniques require small samples sizes (1.4 µmol of Cl- and 1 µmol of Br-). The internal precision using pure CH3Cl gas is better than ∓0.04 ‰ (∓STDV) while the external precision using seawater standard is better than ∓0.07 ‰ (∓STDV). The internal precision using pure CH3Br gas is better than ∓0.03 ‰ (∓STDV) and the external precision using seawater standard is better than ∓0.06 ‰ (∓STDV). Moreover, the sample analysis time is much shorter than previous techniques. The analyses times for chlorine and bromine stable isotopes are 16 minutes which are 3-5 times shorter than all previous techniques. Formation waters from three sedimentary settings (the Paleozoic sequences in southern Ontario and Michigan, the Williston Basin and the Siberian Platform) were analyzed for 37Cl and 81Br isotopes. The δ37Cl and δ81Br values of the formation waters from these basins are characterized by large variations (between -1.31 ‰ and +1.82 ‰ relative to SMOC and between -1.50 ‰ and +3.35 ‰ relative to SMOB, respectively). A positive trend between δ81Br and δ37Cl values was found in all basins, where an enrichment of δ81Br is coupled by an enrichment of δ37Cl. In the Paleozoic sequences in southern Ontario and Michigan, the δ37Cl and δ81Br signatures of formation water collected from northwest of the Algonquin Arch are distinct from those collected from southeast of the Arch. All of the brines from the northwest of the Algonquin Arch are characterized by depleted isotopic values in comparison with the isotopic values from the brines from southeast of the Arch. The δ81Br signatures of the two brines show total separation with no overlaps. The δ37Cl values show some overlap between the two groups. One of the scenarios that can be put forward is that the Arch forms a water divide, where sediments southeast of the Arch are dominated by Appalachian Basin formation waters, and the sediments located northwest of the Arch are dominated by the Michigan Basin formation waters. The δ81Br and δ37Cl signatures of the Williston Basin brines suggest the existence of several different brines that are isotopically distinct and located in different stratigraphic units, even though they are chemically similar. The relatively wide range of δ37Cl and δ81Br of the formation waters suggests that the ocean isotopic signatures were variable over geologic time. A seawater temporal curve for δ81Br and δ37Cl was proposed with a larger variation of δ81Br in comparison with δ37Cl. The isotopic variations of these two elements agree very well with 87Sr/86Sr seawater variation during the same period. In general, the use of chlorine and bromine stable isotopes can be very useful in assessing the origin and the evolutionary processes involved in evolving formation waters and also in distinguishing different brines (end members). Furthermore, they can be employed to investigate the hydrogeological dynamics of sedimentary basins.