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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Petrology, geochronology and provenance of the Laingsburg and Tanqua Karoo submarine fan systems, Ecca Group, South Africa

Nguema Mve, Oliver Patrice 12 1900 (has links)
Thesis (MSc (Earth Sciences))—University of Stellenbosch, 2005. / The integration of whole-rock chemistry, heavy mineral chemistry, detrital zircon morphology and age dating has enabled high-resolution characterization of the Permian Laingsburg and Tanqua submarine fan provenance in the Karoo Basin, upper Ecca Group, South Africa. Geochemically, the Laingsburg and Tanqua sandstones are classified as greywacke and litharenite. The chemical index of alteration values for these sandstones suggest low to moderately weathered sources and a relatively cold climate. Abundant angular clastic grains and lithic fragments as well as the predominance of pristine zircons indicate a near provenance and a first cycle derivation. The investigated sandstones originated from a continental island arc and an active continental margin. The source is dominantly intermediate to felsic and includes tonalites, granodiorites, and adamellites or their volcanic equivalents.
2

Stratigraphic evolution and characteristics of lobes : a high-resolution study of Fan 3, Tanqua Karoo, South Africa

Neethling, J. M. 03 1900 (has links)
Thesis (MSc (Earth Sciences))--University of Stellenbosch, 2009. / Fan 3 is one of four basin-floor fans that form part of the Tanqua Karoo Fan Complex in South Africa. It can be subdivided into several sandstone lobes, based on the presence of thin-bedded siltstone intervals above and below major sandstone packages. Six lobes are identified in the mid fan section, as well as two older groups of thin, low-volume turbidite deposits at the base. Some of the lobes are further divided into an upper and lower lobe-element based on depositional behaviour. The volumetrically and spatially larger lobes have a finger-like appearance in plan view, which is attributed to multiple lobe-scale axial zones. This is especially visible towards the eastern margins of Lobes 2, 4 and 5. The stratigraphy and facies distribution are presented on several 2D panels. Computer generated isopach maps are presented for each lobe, lobe-element and interlobe unit. Autogenic control on the depositional pattern of the Fan 3 lobe complex was inferred from the palaeoflow patterns of the composing lobes and lobe-elements. The majority of the lobes show a north-eastern palaeoflow direction in the south, with a gradual westward shift in the north. Inferred controls are basin-floor topography, the presence of pre-existing lobes, and characteristics of the depositional flow, such strength, density, sediment load, palaeoflow direction.
3

Modelling the architecture of distal sand-rich lobe deposits : an example from Fan 2, Skoorsteenberg Formation, Tanqua Karoo, South Africa

Steyn, Rochelle 03 1900 (has links)
MSc / Thesis (MSc (Earth Sciences))—University of Stellenbosch, 2009. / Fan 2, one of five submarine fan systems of the Tanqua fan complex in the south-western Karoo Basin, South Africa, is subdivided into Lower, Middle and Upper units. Here, detailed analysis of the internal architecture and distribution of lithofacies associations of Middle Fan 2 facilitated the 3-D visualisation of the sedimentological and stratigraphical changes towards the pinch-out. Middle Fan 2 is interpreted to be a lower-fan, sand-rich terminal lobe, comprising three sandstone-lobe elements, separated by two siltstone interlobe elements. It is fed by a distributary channel that is hypothetically positioned to the west-southwest of the study area. The sandstone-lobe elements pinch out downdip to the north-east and updip to the southsouthwest in the study area. The consecutive pinch out of lobe elements to the north-east indicates a progradational stacking pattern similar to the entire lobe complex. Palaeocurrent analysis and the interpretation of isopach maps indicate that the transport direction of Middle Fan 2 was in a north-easterly direction. The fringes of the lobe and the distribution of internal elements (channels, amalgamated sheets and sheets) show a finger-like geometry in plan-view, in contrast to simple radial-lobe bodies that are commonly envisaged.
4

Stratigraphy and facies architecture of the uppermost fan system in the Tanqua sub-basin, Permian Ecca Group, South Africa

Van der Merwe, Willem C 12 1900 (has links)
Thesis (MSc)--Stellenbosch University, 2005. / ENGLISH ABSTRACT: Fan System 5 forms the uppermost submarine fan system of the Permian-age Tanqua Fan Complex (Ecca Group) of the southwestern Karoo Basin. It is the most widespread system and represents the final phase of fan deposition in the Tanqua sub-basin. Depositional characteristics differ markedly from the rest of the fan systems, mainly because it lacks sedimentary features indicative of a single point source basin floor fan. The entire system consists of six different stages of fan growth and development in the lower slope settings. A hypothetical model was composed for Fan System 5 to understand the spatial/temporal distribution of reservoir and seal facies in slope turbidite settings. The facies vary from massive amalgamated sandstone beds to thin-bedded, ripple cross-laminated sand and siltstone beds. A thick shale unit identified as a regional marker layer overlies Fan System 5. lts base is defined by the presence of a regionally developed 20 cm thick hemipelagic shale unit. Six sand-rich units with channel-complexes are present in the Klein Hangklip, Groot Hangklip, Kalkgat, Tongberg, Skoorsteenberg and Blauwkop localities. The facies characteristics in the southernmost outcrops of Fan System 5 (Groot Hangklip, Tongberg and Kalkgat) reflect deposition in a lower slope setting where local structural control seems to have played a major role in the distribution and regional development of channel-fill and overbank depositional elements. The channel-fills are arranged in vertical to off-set stacking patterns and are comprised of massive, amalgamated [me to very fine-grained sandstone units up to 30 m in thickness. They are separated by thinner sandstone/siltstone units of varying thickness. The channelization displayed by the more proximal outcrops are interpreted to represent an upper fan, deposited in a lower- to mid-slope setting. In contrast to the channel-fill deposits at Skoorsteenberg, Klein Hangklip and Groot Hangklip, ripple cross-laminated overbank deposits, associated with smaller channel-fill units, predominate in the northeastern and eastern parts of the outcrop area. Massive- and thinbedded frontal sheet sandstones constitute the down-dip extensions to the most northern outcrops of Fan System 5. Highly erosive, stacked base-of-slope channel complexes, seemingly controlled by subtle early structural features, were able to construct significant thicknesses of regionally well-developed overbank deposits, marginal to the channel complexes. These facies changes occur over relatively short distances, which hold significant implications for the prediction of and the heterogeneity of reservoir facies in slope settings. Gradients are much steeper in the lower slope to mid-slope area than on the proximal basin floor. The occurrence of soft-sediment deformation in the overbank and upper parts of the channel-fill deposits supports a slope origin. Weakly developed wave-ripple marks in the uppermost layers of Fan System 5 further indicate that water depths approached wave base prior to deposition of the upper markerbed shales. Paleotransport for Fan System 5 was towards the north, northeast and east. The palaeocurrent directions of the channel-fill complexes in Klein- and Groot Hangklip seem to roughly correspond to the structural trend of synclinal depressions in this area. However, the effect and influences of basin floor topography and structural features on deposition were determined to be minimal on the regional development and local facies control of the fan. / AFRIKAANSE OPSOMMING: Waaiersisteem 5 vorm die laaste submarine waaiersisteem van die Perm-ouderdom Tankwa Waaierkompleks (Ecca Groep) in die suidwestelike Karoo-kom. Dit vorm die mees wydverspreide sisteem en verteenwoordig ook die fmale fase van waaierafsetting in die Tankwa sub-kom. Afsettingseienskappe verskil aansienlik van die onderliggende waaiersisteme, omdat kenmerkende sedimentêre eienskappe van 'n enkele toevoer bron ontbreek. Die hele sisteem bestaan uit ses verskillende periodes van waaiergroei en ontwikkeling in die laer kornhelling omgewmgs. 'n Voorspellingsmodel is opgestel vir Waaiersisteem 5 om die ruimtelike/temporele verspreiding van die reservoir en seël fasies in kornhelling turbidiet omgewings te kan verstaan. Hierdie fasies varieer van massiewe, geamalgameerde sandsteen tot dun gelaagde riffel- lamineerde sand- en sliksteenlae. 'n Dik regionale skalie eenheid oorlê Waaiersisteem 5 en vorm die boonste merkerlaag. Die basis word onderlê deur 'n 20 cm dik regionaalontwikkelde hemipelagiese skalie laag wat die onderste merkerlaag vorm. Ses sandige eenhede met geassosieerde kanaalkomplekse is onderskeidelik teenwoordig in: Klein Hangklip, Groot Hangklip, Kalkgat, Tongberg, Skoorsteenberg en Blauwkop omgewings. Die fasies-eienskappe van die mees suidelike dagsome van Waaiersisteem 5 (Tongberg, Groot Hangklip en Kalkgat) toon afsetting in 'n laer kornhelling omgewing, waar plaaslike tektoniese effekte moontlik 'n groot rol gespeel het in die verspreiding en regionale ontwikkeling van die kanaalvulsels en geassosieerde oewerwal-afsettings. Die gestapelde, wegstand kanaalvulsels-afsettings bestaan uit massiewe, geamalgameerde fyn tot baie fynkorrelrige sandsteen eenhede, wat diktes tot ongeveer 30 m kan bereik. Dit word van mekaar geskei deur dun sandsteenlsliksteen eenhede van afwisselende diktes. Die kanaal komplekse in die mees proksimale dagsome word interpreteer as 'n bo-waaier, wat afgeset is in 'n laer- tot middel kornhelling omgewmg. In teenstelling met die kanaalvulsels in die Skoorsteenberg, Klein Hangklip en Groot Hangklip omgewings, domineer riffel kruisgelamineerde oewerwal-afsettings, geassoseer met klein kanaalvulsels, die noordoostelike en oostelike dagsome van Waaiersisteem 5. Massiewe en dungelaagde frontale plaat sandstene, kom voor in die distale helling-omgewings in die mees noordelike dagsome van Waaiersisteem 5. Hoogs eroderende, gestapelde kanaalkomplekse, aan die basis van die komhelling wat moontlik beheer is deur vroeë komvloer topografie, was die oorsaak vir regionaal goed-ontwikkelde oewerwalafsettings. Hierdie fasies-verandering vind plaas oor 'n baie kort afstand wat betekenisvolle gevolge inhou vir die voorspelling van heterogeniteit van petroleum reservoir fasies in komhelling afsetting-omgewings. Die gradiënt vir die laer komhelling tot mid-komhelling omgewings is baie steiler as die distale komvloer omgewings. Die voorkoms van sagte-sediment deformasies in die oewerwal en boliggende dele van die kanaalvulsels weerspeël 'n moontlike komhelling omgewing. Swakontwikkelde golfriffelmerke in die boonste lae van Waaiersisteem 5 dui 'n waterdiepte aan wat nabyaan golf-basis is, voordat dit deur diepmariene skalies oorlê word. Paleovloeirigtings vir Waaiersisteem 5 was in 'n noord, noordoostelike en oostelike rigting. Die paleovloeirigting vir die Klein- en Groot Hangklip kanaalkomplekse stem min of meer ooreen met die strukturele grein van die sinklinale laagtes in die omgewing. Die effek en beheer van komvloer topografie en ander strukturele faktore op afsetting was minimaalop die regionale ontwikkeling en plaaslike fasies verspreiding van die waaier.

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