Geologic evolution of the barberton greenstone belt, south africa donald r. Apr 16, 2020 here, we report on the multiple sulfur isotopic composition of sedimentary anhydrite in the ca. Pdf siliciclastic associated banded iron formation from. Here, we report on the multiple sulfur isotopic composition of sedimentary anhydrite in the ca. Kenneth andrew eriksson a dissertation submitted to the faculty of science, university of the witwotorsrand, johannesburg for the degree of doctor of philosophy. Early archean spherule beds in the barberton mountain land. In contrast, nearby rocks of the onverwacht group contain much softer minerals and often define the valleys. Pre 16 geology of the barberton greenstone belt processes. The moodies group is the uppermost stratigraphic unit in the.
Tectonic evolution of the barberton greenstone belt wikipedia. The moodies group is the uppermost and youngest unit of the barberton supergroup, the volcanicsedimentary sequence forming the barberton greenstone belt bgb, the largest and bestpreserved greenstone belt in the basement of the kaapvaal craton. Location of the barberton greenstone belt the fig tree formation, also called fig tree group, is a stromatolite containing geological formation in south africa. This study focuses on a unique occurrence of wellpreserved and contextualized bif from the early archean. Barberton, south africa we invite applications for participation in a field workshop to develop a full proposal for drilling and recovering core from sedimentary and subvolcanic strata of the moodies group. Komati, hooggenoeg and kromberg formations of the archean.
Also given are the stratigraphic positions of the samples mentioned in this and previous studies, after koeberl and reimold 1995. The barberton greenstone belt bgb is located in the kapvaal craton of southeastern africa. Moodies group, barberton greenstone belt, south africa october 5 10, 2017. As we look out into the universe and ask whether there is life, we. Combined upb and hf isotope analyses of detrital zircons from the fig tree and moodies groups of the barberton greenstone belt, south africa, yield similar hf isotope compositions and age populations, thus pointing to a similar provenance. Dating archean sedimentary processes and rates in the. Reassessment of archean crustal development in the barberton mountain land, south africa, based on u. Early palaeoarchaean granite clasts in the basal conglomerate of the moodies group, barberton greenstone belt, south africa, belong to the oldest true granites on earth and document that intracrustal melting occurred early during generation and stabilization of continental crust. Pdf siliciclastic associated banded iron formation from the.
The swaziland supergroup is divided into the basal, predominantly volcanic onverwacht group and the succeeding sedimentary fig tree and moodies groups fig. Microbialmatassociated tephra of the archean moodies group, barberton greenstone belt bgb, south africa. The barberton greenstone belt is built up of three major rock units. The rock contains fossils of microscopic life forms of about 3. Timing of deposition and deformation of the moodies group barberton greenstone belt, south africa. The multiple sulfur isotopic composition of pyrite of moodies intervals was newly obtained to examine the influence of these depositional settings on the sulfur isotope record.
Upb and hf isotope data of detrital zircons from the. Depositional and tectonic setting of the archean moodies group, barberton greenstone belt, south africa. It forms the worlds oldest wellpreserved shallowwater sequence and is dominated by quartzrich sandstone, which accumulated under terrestrial and shallowmarine conditions. The fossils in the fig tree formation are considered some of the oldest.
Barberton supergroup, the sedimentary volcanic fill of the. Late syndepositional deformation and detachment tectonics. Group rocks occur in the eureka syncline, the moodies group assemblages are best developed and represent the most complete succession of moodies rocks in the barberton mountain land. Sedimentary petrography and provenance of the archean moodies group, barberton greenstone belt. Ga bifs of sheba gold mine, moodies group, barberton greenstone belt, south africa. Late syndepositional deformation and detachment tectonics in the. Sedimentary petrography and provenance of the archean. On the modern earth, coarse braidedalluvial deposits are developed in fan deltas or braid deltas.
Carbonaceous cherts barberton greenstone belt and their significance for study of early life in the archean record. Siliciclastic associated banded iron formation from the 3. This implicitly means that rhyolitic volcanism was more wide spread than previously thought in the. The moodies group, the uppermost unit in the barberton greenstone belt bgb in south africa, is a 3.
The onverwacht group, followed by fig tree and moodies group. The belt includes a lower, predomi nantly volcanic sequence, the onverwacht group, and an upper, mainly sedimentary, sequence, the fig tree group. Resemblance to potential biostructures and ecological implications i. Every group member had a chance in the field to express themselves through the use of. Size distribution of carbonaceous spheroidal microstructures preserved in the 3. In the northern part of the barberton greenstone belt, the. Geochemistry and mineralogy of early archean spherule beds. Although a number of apparently conformable fig tree moodies transitions occur, over wide areas, the moodies was deposited with angular unconformity on rocks as old as the hooggenoeg formation. Unit md 1 fines upward from a basal conglomerate into more quartzose sandstones and reflects a braidedriver depositional setting eriksson, 1978, heubeck and lowe, 1994. This contact has additionally been complicated by structural movement.
Depositional and tectonic setting of the archean moodies group. Sedimentary petrography and provenance of the archean moodies. Pdf depositional and tectonic setting of the archean. Eolian facies in the form of either sand sheet or preserved lowangle dune plinth deposits indicate that significant wind regimes existed in the archean atmosphere. Johannesburg 10 7 7 i abstract the moodies group, approximately 3 300 m. Anhydrite occurs, together with barite and pyrite, in regionally traceable beds that formed in fluvial settings. Geologic evolution of the barberton greenstone belt, south. Timing of deposition and deformation of the moodies group.
Unlimited viewing of the articlechapter pdf and any associated supplements and figures. Archean surface environments, sedimentary rocks of moodies group in the barberton greenstone belt bgb, south africa, are about. Tectonic evolution of the barberton greenstone belt. Nabhan, 20, microbiallyinduced carbonate precipitation, moodies group 3. Microcontinents continued to accrete to form the earths oldest known. It characterizes one of the most wellpreserved and oldest pieces of continental crust today by containing rocks in the barberton granite greenstone terrain 3. Identified organisms include the bacterium eobacterium isolatus and the algaelike archaeosphaeroides barbertonensis.
The first of these began with the deposition of the. Moodies group, barberton greenstone belt, south africa. Request pdf timing of deposition and deformation of the moodies group barberton greenstone belt, south africa. Hence this study has illustrated that the rhyolites of the h6 unit were primary kfeldsparrich, k. Participants will be based in barberton and use 4wd vehicles to. The moodies group is an wkm thick sequence of arkosic, lithic and quartzose sand1e3. The bgb is a small, cuspshaped succession of volcanic and sedimentary rocks, surrounded on all sides by granitoid plutons which. The moodies bif occurs thinly interbedded with finegrained and crossstratified sandstones, indicating deposition during times of decreased clastic sediment supply. Three main pulses of sedimentation c3n be recognized. This document was compiled by group 2b of 2012 group third year mining and environmental geology students after mapping a portion of the barberton greenstone belt.
Moodies group rocks are folded into a train of tight, subparallel, doubly plunging, overturned synclines separated by narrow, strike. Upper onverwacht group rocks were overlain by 3259 5to 3225 3 ma clastic and volcanoclastic largely marine sediments of the fig tree group, and subsequently by the moodies group kroner et al. Siliciclastic associated banded iron formation from. Byerly geological society of america, jan 1, 1999 science 319 pages. Micro to nanostructures of carbonaceous materials in 3. Also given are the stratigraphic positions of the samples mentioned in this and previous studies, after koeberl and. Although a number of apparently conformable fig treemoodies transitions occur, over wide areas, the moodies was deposited with angular unconformity on rocks as old as the hooggenoeg formation. Pdf microbialmatassociated tephra of the archean moodies. Reassessment of archean crustal development in the. The two lowest units of the onverwacht group, the sandspruit and theespruit forma. Sedimentary rocks of the moodies group in the bgb are about 3. Zircon populations of fig tree group greywacke and moodies group quartzarenite are both dominated by age clusters at 3.
Generalized geological map of the barberton greenstone belt modified after heubeck. Archean life in the barberton greenstone belt origin. Masafumi saitoh 1,2, sami nabhan 3, christophe thomazo 4. The onverwacht group is composed of predominantly ultrama. The moodies groupa highresolution archive of archaean. Study area the moodies group is the uppermost of three stratigraphic units that comprise the swaziland supergroup in the barberton greenstone belt, south africa fig. The onverwacht group is at about 3,570 to 3,300 million years old. Rhyolitic volcanism in the onverwacht group, barberton. Filamentous microfossils from the 3,500myrold onverwacht. Erosion of continental rocks produced conglomerates, sandstones and mudstones the moodies group, barberton. Collected samples were classified into sandysiltstone, carbonaterich siltstone and magnetiterich siltstone from the petrology whereas most of them show enough iron contents to. Pre 16 geology of the barberton greenstone belt processes of. The stratigraphy of the barberton greenstone belt was summarized by lowe and byerly 1999. Drilling the moodies group, barberton greenstone belt, south africa.
Barberton is a town in the mpumalanga province of south africa, which has its origin in the 1880s gold rush in the region. Orich magmas that formed contemporarily with the 3. Pdf link pdf add to citation manager sedimentology, mineralogy, and implications of silicified evaporites in the kromberg formation, barberton greenstone belt, south africa. The moodies group in the barberton greenstone belt, south africa consists predominantly of coarsegrained, commonly conglomeratic, braidedalluvial facies in close spatial association with subordinate tidal facies eriksson, 1979, jackson et al. Dating archean sedimentary processes and rates in the moodies. Collected samples were classified into sandysiltstone, carbonaterich siltstone and magnetiterich siltstone from the petrology whereas most of them show enough iron contents to be defined as bifs, suggesting iron deposition at. The oldest granite clast in the moodies conglomerate. The fig tree formation, also called fig tree group, is a stromatolitecontaining geological formation in south africa. An unusual fluvial to tidal transition in the mesoarchean.
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