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Lithostratigraphy sedimentology and provenance of the Balfour Formation Beaufort Group in the Fort Beaufort Alice area Eastern Cape Province South AfricaKatemaunzanga, David January 2009 (has links)
A traverse through the Balfour Formation was chosen in the area around the towns of Fort Beaufort and Alice in the Eastern Cape Province. The main objectives of the study were to map the lithological variations within the Balfour Formation and to distinguish it from the underlying Middleton Formation and the overlying Katberg Formation. A combined desktop, field and laboratory approach was used in this study. Aerial photographs, satellite images and digital topographical maps formed the basis of the desktop work. After desktop mapping, a number of field traverses were measured through the study area. Sedimentary structures were observed, photomosaics were done, stratigraphic sections were measured and samples were collected for thin sectioning, heavy mineral separation and major, trace and REE analysis. Sedimentological development of the Balfour Formation has been outlined in relation to its provenance during the Late Permian. Lithological variation of the Balfour Formation is characterised by alternating sandstone-dominated and mudstone-dominated members. Arenaceous Oudeberg and Barberskrans Members are contain facies ranging from intraformational conglomerates (Gmm), massive sandstones (Sm & Ss), horizontally laminated sandstones (Sh), planar and trough cross-bedded sandstones (Sp, Sl & St), trough cross-laminated sandstones (Sr) and fine-grained sediments (Fm & Fl), whereas the mudstone dominated members are characterised by the facies Fm and Fl. Lithofacies together with bedforms observed in the Balfour Formation were used in architecturalelement analysis. Sandstone–rich members are dominated by channel fill elements such as LS, DA, SB, LA and CH, whereas the fine-grained component consists of mainly, FF iii element. The mudstone-dominated members contain FF, CS and LV elements, with LA, SB and CH in the subordinate sandstones. Petrography, geochemistry and palaeocurrent analysis indicated that the source of the Balfour Formation was to the south-east and the rocks had a transitional/dissected magmatic arc signature. This led to the postulation of the Karoo Basin to have developed in a retro-arc foreland basin where there was supralithospheric loading in the Cape Fold Belt due to a compressional regime initiated by the subduction of Palaeo-Pacific plate underneath the Gondwana plate. The tectonic loading was episodic with eight major paroxysms affecting the Karoo Supergroup. The Balfour Formation coincides with the fourth paroxysm, this paroxysm in turn consists of two third-order paroxysm that initiated the deposition of the Oudeberg and Barberskrans Members in low sinuosity streams. Each paroxysm was followed by a period of quiescence and these resulted in the deposition of the Daggaboersnek, Elandsberg and Palingkloof Members in meandering streams. Depositional environments were determined mainly from the sedimentary structures and 3D architecture of the rock types. Sandstone rich members were formed by seasonal and ephemeral high energy low sinuous streams whereas the fine-grained rich members were formed by ephemeral meandering streams. Palaeoclimates have been equated to the present temperate climates; they were semi-arid becoming arid towards the top of the Balfour Formation. This has been determined geochemistry (CIA), sedimentary structures and other rock properties like colour.
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Sedimentology and stratigraphy of deep-water reservoirs in the 9A to 14A Sequences of the central Bredasdorp Basin, offshore South AfricaMegner-Allogo, Alain-Cedrique 12 1900 (has links)
Thesis (MSc)--University of Stellenbosch, 2006. / ENGLISH ABSTRACT: The Barremian to Albian siliciclastic deep-water deposits of the central
Bredasdorp Basin were investigated primarily in terms of their stratigraphic
evolution, depositional characteristics and facies distribution. Cores from the
deep-water deposits reveal that the facies successions are composed of
massive, ripple cross- to parallel-laminated sandstones, conglomerate,
massive claystone, alternating laminated to interbedded sandstone/siltstone
and claystone, laminated and clay-rich siltstone. These facies are grouped
into channel-fill, sheet-lobe, overbank and basin plain deposits, by inference.
The application of sequence stratigraphy, based on gamma ray and resistivity
log patterns, reveals that all 3rd-order depositional sequences comprise 4thorder
cycles. The latter are subdivided into three components (lowstand,
transgressive and highstand systems tracts), based on vertical facies changes
and internal stratigraphic key surfaces.
Taking the 13Amfs as the stratigraphic datum for each well, correlation was
possible on a regional basis. Lowstand deposits, comprising thick
amalgamated massive sandstones, were interpreted to represent channelfills.
Their vertical and horizontal stacking forms channel-fill complexes above
Type 1 unconformities. Adjacent thin-bedded intervals, comprising parallel- to
ripple cross-laminated sandstones, were interpreted as levee/overbank
deposits, whereas clay-rich intervals were interpreted to represent basin plain
deposits of hemipelagic origin. Facies associations and their distribution have revealed that channel-fills are
associated with overflow deposits and sheet sand units. These deposits, as
well as downdip sheet sands associated with small channel-fills within the 9A,
11A/12A, 13A Sequences and the 14A Sequence were interpreted to have
been deposited in a middle fan to upper fan setting. A similar association
occurs in the 10A Sequence, except that thick conglomerate units are present
at the base of proximal channel-fills. This led to interpret the 10A Sequence
as being deposited in a base-of-slope to upper fan setting.
The thickness of each sequence, as revealed by isochore maps, shows
sinuous axial flow path which corresponds to channel-fill conduit. The
continuous decrease of this sinuosity upward in the succession was
interpreted as being related to basin floor control along the main sand
fairways. Successive flows result in erosion-fill-spill processes, which locally
favour connectivity of reservoirs over large areas.
Recognition of higher-order sequences and key stratigraphic surfaces helps to
understand internal stratigraphic relationships and reveals a complex and
dynamic depositional history for 3rd-order sequences. However, sparse well
control and uneven distribution of boreholes, as well as lack of seismic and
other data, limited the models derived for this study. / AFRIKAANSE OPSOMMING: Die Barremiaanse tot Albiaanse silisiklastiese diepwater afsettings van die
sentrale Bredasdorp Kom is hoofsaaklik in terme van stratigrafiese evolusie,
afsettingskarakteristieke en fasies distribusie ondersoek. Kerne van die
diepwater afsettings toon dat die fasies opeenvolgings uit massiewe,
riffelkruis- tot parallel-gelamineerde sandstene, konglomerate, massiewe
kleistene, afwisselende gelamineerde tot intergelaagde sandstene/slikstene
en kleistene, sowel as gelamineerde en klei-ryke slikstene bestaan. Hierdie
fasies word onderverdeel in kanaalopvulsel, plaatlob, oewerwal en komvlakte
afsettings.
Die toepassing van opeenvolgingsstratigrafie gebaseer op gammastraal en
resistiwiteit log patrone toon dat alle 3de-orde afsettingsopeenvolgings uit 4deorde
siklusse bestaan. Laasgenoemde word onderverdeel in drie komponente
(lae-stand, transgressie en hoë-stand sisteemgedeeltes), gebaseer op
vertikale fasies veranderinge en interne stratigrafiese sleutel vlakke.
Korrelasie op ‘n regionale basis is moontlik gemaak deur die 13Amfs as die
stratigrafiese verwysing vir elke boorgat te neem. Lae-stand afsettings, wat uit
dik saamgevoegde massiewe sandstene bestaan, word geïnterpreteer as
kanaalopvulsels. Die vertikale en horisontale stapeling van die sandstene
vorm kanaalopvulsel komplekse bo Tipe 1 diskordansies. Naasliggende dungelaagde
intervalle, wat uit parallel- tot kruisgelaagde sandstene bestaan,
word geïnterpreteer as oewerwal afsettings, terwyl klei-ryke intervalle geïnterpreteer word as verteenwoordigend van komvlakte afsettings van
hemipelagiese oorsprong.
Fasies assosiasies en hul verspreiding toon dat kanaalvul geassosieër word
met oorvloei afsettings en plaatsand eenhede. Hierdie afsettings, sowel as
distale plaatsande geassosieër met klein kanaalopvulsels binne die 9A,
11A/12A, 13A en die 14A Opeenvolgings, word geïnterpreteer as afgeset in ‘n
middelwaaier tot bo-waaier omgewing. ‘n Soortgelyke assosiasie bestaan in
die 10A Opeenvolging, behalwe dat dik konglomeraat eenhede teenwoordig is
by die basis van proksimale kanaalopvullings. Dit het gelei tot die interpretasie
van die 10A Opeenvolging as afgeset in ‘n basis-van-helling tot bo-waaier
omgewing.
Die dikte van elke opeenvolging, soos verkry vanaf isochoor kaarte, toon ‘n
kronkelende aksiale vloeipad wat ooreenkom met ‘n kanaalopvulling
toevoerkanaal. Die aaneenlopende afname van hierdie kronkeling na bo in die
opeenvolging word geïnterpreteer as verwant aan komvloer-beheer langs die
hoof sand roetes. Opeenvolgende vloeie veroorsaak erosie-opvul-oorspoel
prosesse, wat lokaal die konnektiwiteit van reservoirs oor groot areas
bevoordeel.
Herkenning van hoër-orde opeenvolgings en sleutel stratigrafiese vlakke dra
by tot ‘n goeie begrip van die interne stratigrafiese verhoudings en ontbloot ‘n
komplekse en dinamiese afsettingsgeskiedenis vir 3de-orde opeenvolgings.
Beperkte boorgatbeheer en ‘n tekort aan seismiese en ander data het egter ‘n
beperkende rol gespeel in die daarstel van modelle vir hierdie studie.
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Measurement of the bulk flow and transport characteristics of selected fractured rock aquifer systems in South Africa: a case study of the Balfour Formation in the Eastern Cape ProvinceYu, Liuji January 2011 (has links)
Hydrogeologists have faced serious challenges worldwide in the characterization of fractured rock aquifers due to the heterogeneous nature of the imbedded geology. The bulk flow parameters in the Karoo strata in South Africa are specifically uncertain since most models are based on homogenous block systems. As part of a WRC research project, entitled “Measurement of the bulk flow and transport characteristics of selected fractured rock aquifer systems in South Africa”, this study focuses on the characterization, borehole drilling, flow parameter measurements and groundwater quality assessment of the Balfour Formation in the Beaufort Group of the Karoo Supergroup in the Eastern Cape, South Africa, which is seriously heterogeneous in deposition and has also been largely neglected as drilling targets for groundwater. The Balfour Formation comprises mostly mudstone, shale and sandstone, formed in a braided and meandering river system. In addition to the heterogeneous deposition, the flow pathways in this aquifer system are not fully understood due to lack of actual measurement data. The methods used in this study include field mapping, site characterization, borehole drilling, and pumping and tracer testing in order to obtain the borehole yield, aquifer transmissivity, storativity and groundwater flow velocity. In addition, the groundwater chemistry was also studied to determine quality for use and possible connectivity with the nearby Tyume River and to determine potential sources of groundwater contamination. The results obtained include: 1) The study area is predominantly mudstone/shale with thin layers and lenses of siltstone and sandstone, which are interbedded; 2) Two boreholes were successfully drilled, which had yields in excess of 10 l/s in four water levels (at 7, 22, 54 and 65 m); 3) The estimated average transmissivity is 246 m 2/day according to the recovery test; 4) The estimated seepage velocity is 120 m/day according to tracer tests in the aquifer between the two boreholes which are 5 m apart; and 5) The water chemical type is the combination of HCO3-, Cl-and SO42- , which is distinguishable from that of the Tyume river; 6) There is no evidence for groundwater recharge to the deep aquifers from the Tyume river, based on the differences of the water chemistry; 7) The elements Ca, Cl, Na and C are distributed more than 90% as free ion species in BH2 borehole water; and 8) The groundwater in BH2 borehole is undersaturated (negative SI) with respect to some minerals (for example: anhydrite, fluorite, gypsum and halite), oversaturated (positive SI) with respect to some minerals (for example: aragonite, calcite and dolomite). It is concluded that there is a great potential to obtain drilling targets for high yielding boreholes in the sedimentary rocks of the Balfour Formation in the Karoo Supergroup.
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