This paper focuses on determining total organic carbon(TOC)from boreholes in the Kalahari Basin,Botswana,using Passey's method.The Kalahari Karoo basin is one of several basins in southern Africa filled with Late ...This paper focuses on determining total organic carbon(TOC)from boreholes in the Kalahari Basin,Botswana,using Passey's method.The Kalahari Karoo basin is one of several basins in southern Africa filled with Late Carboniferous to Jurassic sedimentary strata that host Permian age coal seams.Nine exploration boreholes(wells)drilled in the central Kalahari Karoo basin are used to determine the Total Organic Carbon potential.Vitrinite reflectance(Ro),proximate and ultimate analyses were conducted on cored coal intervals.Passey's DLogR method applied in this study employs resistivity and porosity logs to identify and quantify potential source rocks.Results of Passey's method compared with laboratorymeasured carbon showed that Passey's method effectively identifies coal intervals.In terms of TOC calculations,the method works poorly in coal metamorphosed by dolerite intrusions.The heat affected coal samples had Ro from 0.77% to 5.53% and increased in maturity from primarily maceral controlled to high volatile bituminous and anthracite coal.Results from proximate analysis showed compositional changes in the coal were controlled by proximity to sill intrusion,with a decrease in Fixed Carbon and an increase in ash yield in the contact metamorphism zone(2-12 m from sill).For the unaltered coal that has undergone burial maturation displaying Ro of 0.44%-0.65%,the method works well.In unintruded boreholes,correlations between Carbon and calculated TOC indicate strong relationships.Passey's DLogR method proved to be a suitable method of estimating TOC on coal that has undergone burial maturation.This study has demonstrated that TOC calculated from the sonic log is more reliable in coal not affected by contact metamorphism than TOC calculated from the density log.展开更多
The Balfour Formation has a pronounced lithological variation that is characterized by alternating sandstone- and mudstone-dominated members. The sandstone-dominated Oudeberg and Barberskrans Members are composed of l...The Balfour Formation has a pronounced lithological variation that is characterized by alternating sandstone- and mudstone-dominated members. The sandstone-dominated Oudeberg and Barberskrans Members are composed of lithofacies that range from intraformationai conglomerates to fine-grained sediments, whereas the mudstone-dominated members （Daggaboersnek, Elandsberg, and Palingkloof） are dominated by the facies Fm and FI. Petrography, geochemistry, and a paleocurrent analysis indicated that the source rock of the Balfour Formation was to south east and the rocks had a transitional/dissected magmatic arc signature. The sandstones-rich members were deposited by seasonal and ephemeral high-energy, low-sinuous streams, and the fine-grained-rich members were formed by ephemeral meandering streams. The paleoclimates have been equated to present temperate climates; they were semiarid becoming arid towards the top of the Balfour Formation. This has been determined by reconstructing the paleolatitude of the Karoo Basin, geochemistry, paleontology, sedimentary structures, and other rock properties, like color.展开更多
Aloe dichotoma (Quiver tree) occurs in the arid regions of Namaqualand and Bushman land in South Africa, and in arid regions of southern Namibia. The Quiver trees are not only threatened by agricultural expansion, ove...Aloe dichotoma (Quiver tree) occurs in the arid regions of Namaqualand and Bushman land in South Africa, and in arid regions of southern Namibia. The Quiver trees are not only threatened by agricultural expansion, overgrazing, and mining;but also by climate changes and droughts. Previous studies show that Quiver trees are very sensitive to environmental changes, and do not respond well to extreme hot and dry conditions. This study investigates the current status of the Quiver tree within its existing environment, and also assesses the projected future changes of the Quiver tree habitat under different climatic scenarios. It provided evidence regarding the importance of the study to understanding the climate change impacts on the Quiver tree and its geographical response to climate changes.展开更多
The subsidence history of the Soutpansberg Basin was reconstructed by a tectonic subsidence analysis coupled with backstripping calculations based on data of newly interpreted sequence boundaries. Furthermore, burial ...The subsidence history of the Soutpansberg Basin was reconstructed by a tectonic subsidence analysis coupled with backstripping calculations based on data of newly interpreted sequence boundaries. Furthermore, burial and time plots were constructed in order to understand the burial and thermal history of the basin. Input data were based on facies, lithostratigraphic models and tectonic interpretations. The studied succession is up to 1000 m and is underlain by the Achaean Limpopo Mobile Belt. The subsidence within the basin supports the primary graben system which must have been centred within the present basins, and later became a region of faulting. The subsidence and burial history curves suggests two phases of rapid subsidence during the Early-Late Permian （300–230 Ma） and Middle Triassic （215–230 Ma）. The areas of greater extension subsided more rapidly during these intervals. Two slow subsidence phases are observed during the Late Triassic （215–198 Ma） and Early Jurassic （198–100 Ma）. These intervals represent the post-rift thermal subsidence and are interpreted as slow flexural subsidence. Based on these observations on the subsidence curves, it is possible to infer that the first stage of positive inflexion （300 Ma） is therefore recognised as the first stage of the Soutpansberg Basin formation.展开更多
Coal contains a significant concentration of free radicals as a result of the coalification process. One of the experimental methods sensitive to the presence of radicals is electron spin resonance （ESR）, and differ...Coal contains a significant concentration of free radicals as a result of the coalification process. One of the experimental methods sensitive to the presence of radicals is electron spin resonance （ESR）, and differences in ESR spectra for different macerals may provide insight into coal-forming processes. In this study, ESR data along with the H/C atomic ratio （to infer the aromatic fraction） are used to characterize coal samples with the aim of assessing a fire-origin for dominant inertinite macerals. A medium rank C bituminous Witbank No. 4 Seam Upper coal （the parent） was density- fractionated to create vitrinite-rich and inertinite-rich samples. The parent sample consists of 42 vol% vitrinite and 49 vol% inertinite. The density-fractionated samples comprise of 81 vol% total vitrinite （dominated by collotelinite and collodetrinite）, and 63 vol% total inertinite （dominated by fusinite, semifusinite, and inertodetrinite）. The H/C ratio is 0.74 for the inertinite-rich sample, and 0.85 for the vitrinite-rich counterpart, suggesting the former sample is more aromatic. The ESR spectra obtained for the three samples were found to fit best using a Lorentzian distribution. The fit is noticeably better for the aromatic inertinite-rich sample, for which the spectrum is symmetric. This is attributed to pronounced electron mobility and exchange interactions. The higher radical content of the inertinite-rich and parent samples is attributed to the presence of specific inertinite macerals, namely： fusinite, semifusinite, and inertodetrinite. And, owing to the greater radical content of the inertinite-rich sample, the dominant inertinite macerals are interpreted to have formed through charring of plant matter.展开更多
The Balfour Formation was subdivided into five members based on lithological variation that is characterized by alternating sandstone-and mudstone -dominated members.The sandstone dominated Oudeberg and Barberskrans m...The Balfour Formation was subdivided into five members based on lithological variation that is characterized by alternating sandstone-and mudstone -dominated members.The sandstone dominated Oudeberg and Barberskrans members are composed of lithofacies that range from intraformational conglomerates to fine-grained sediments,whereas the mudstone dominated members(Daggaboersnek, Elandsberg and Palingkloof) are dominated by the fine-grained facies(Fm and F1).Petrography,geochemistry and palaeocurrent analysis indicated that the source rock of the Balfour Formation was to展开更多
This study aims to compare iso-rank vitrinite-rich and inertinite-rich coal samples to understand the impact of coal-forming processes on pyrolysis chemistry.A medium rank C bituminous coal was density-fractionated to...This study aims to compare iso-rank vitrinite-rich and inertinite-rich coal samples to understand the impact of coal-forming processes on pyrolysis chemistry.A medium rank C bituminous coal was density-fractionated to create a vitrinite-rich and an inertinite-rich sub-sample.The vitrinite-rich sample has 83 vol% total vitrinite (mineral-matter-free basis),whereas the inertinite-rich counterpart has 66 vol% total inertinite.The vitrinite-rich sample is dominated by collotelinite and collodetrinite.Fusinite,semifusinite,and inertodetrinite are the main macerals of the inertinite-rich sample.Molecular chemistry was assessed using a pyrolysis gas chromatograph (py-GC) equipped with a thermal desorption unit coupled to a time of flight mass spectrometer (MS) (py-GC/MS) and solid-state nuclear magnetic resonance (13C CP-MAS SS NMR).The pyrolysis products of the coal samples are generally similar,comprised of low and high molecular weight alkanes,alkylbenzenes,alkylphenols,and alkyl-subtituted polycyclic aromatic hydrocarbons,although the vitrinite-rich sample is chemically more diverse.The lack of diversity exhibited by the inertinite-rich sample upon pyrolysis may be interpreted to suggest that major components were heated in their geologic history.Based on the 13C CP-MAS SS NMR analysis,the inertinite-rich sample has a greater fraction of phenolics,reflected in the py-GC/MS results as substituted and unsubstituted derivatives.The greater abundance of phenolics for the inertinite-rich sample may suggest a fire-related origin for the dominant macerals of this sample.The C2-alkylbenzene isomers (p-xylene and o-xylene) were detected in the pyrolysis products for the vitrinite-rich and inertinite-rich samples,though more abundant in the former.The presence of these in both samples likely reflects common source vegetation for the dominant vitrinite and inertinite rnacerals.展开更多
The Southern African biomes are complex biotic communities, with its distinctive plant and animal species, and are maintained under the suitable climatic conditions of the region. It includes the Fynbos Biome and the ...The Southern African biomes are complex biotic communities, with its distinctive plant and animal species, and are maintained under the suitable climatic conditions of the region. It includes the Fynbos Biome and the Succulent Karoo Biome, which forms the smallest of the world’s six Floristic Kingdoms, and they are of conservation concern. The other six biomes are Albany Thicket, Desert, Grassland, Indian Ocean Coastal belt, Nama-Karoo, Savanna. The biomes are not only threatened by agricultural expansion, overgrazing, and mining;but also by future climate changes and droughts. This study investigates the how to best model the possible vulnerable biome areas, under future climate changes, and how Southern African geology plays a huge role in the restriction of the biome shifts. It provides evidence regarding the importance of the study to understanding the climate change impacts and the geological variables on the Southern African biomes, in terms of possible future biome habitat loss.展开更多
文摘This paper focuses on determining total organic carbon(TOC)from boreholes in the Kalahari Basin,Botswana,using Passey's method.The Kalahari Karoo basin is one of several basins in southern Africa filled with Late Carboniferous to Jurassic sedimentary strata that host Permian age coal seams.Nine exploration boreholes(wells)drilled in the central Kalahari Karoo basin are used to determine the Total Organic Carbon potential.Vitrinite reflectance(Ro),proximate and ultimate analyses were conducted on cored coal intervals.Passey's DLogR method applied in this study employs resistivity and porosity logs to identify and quantify potential source rocks.Results of Passey's method compared with laboratorymeasured carbon showed that Passey's method effectively identifies coal intervals.In terms of TOC calculations,the method works poorly in coal metamorphosed by dolerite intrusions.The heat affected coal samples had Ro from 0.77% to 5.53% and increased in maturity from primarily maceral controlled to high volatile bituminous and anthracite coal.Results from proximate analysis showed compositional changes in the coal were controlled by proximity to sill intrusion,with a decrease in Fixed Carbon and an increase in ash yield in the contact metamorphism zone(2-12 m from sill).For the unaltered coal that has undergone burial maturation displaying Ro of 0.44%-0.65%,the method works well.In unintruded boreholes,correlations between Carbon and calculated TOC indicate strong relationships.Passey's DLogR method proved to be a suitable method of estimating TOC on coal that has undergone burial maturation.This study has demonstrated that TOC calculated from the sonic log is more reliable in coal not affected by contact metamorphism than TOC calculated from the density log.
基金supported by the Govan Mbeki Research Centre(GMRC) at the University of Fort Hare and by the Council for Geoscience
文摘The Balfour Formation has a pronounced lithological variation that is characterized by alternating sandstone- and mudstone-dominated members. The sandstone-dominated Oudeberg and Barberskrans Members are composed of lithofacies that range from intraformationai conglomerates to fine-grained sediments, whereas the mudstone-dominated members （Daggaboersnek, Elandsberg, and Palingkloof） are dominated by the facies Fm and FI. Petrography, geochemistry, and a paleocurrent analysis indicated that the source rock of the Balfour Formation was to south east and the rocks had a transitional/dissected magmatic arc signature. The sandstones-rich members were deposited by seasonal and ephemeral high-energy, low-sinuous streams, and the fine-grained-rich members were formed by ephemeral meandering streams. The paleoclimates have been equated to present temperate climates; they were semiarid becoming arid towards the top of the Balfour Formation. This has been determined by reconstructing the paleolatitude of the Karoo Basin, geochemistry, paleontology, sedimentary structures, and other rock properties, like color.
文摘Aloe dichotoma (Quiver tree) occurs in the arid regions of Namaqualand and Bushman land in South Africa, and in arid regions of southern Namibia. The Quiver trees are not only threatened by agricultural expansion, overgrazing, and mining;but also by climate changes and droughts. Previous studies show that Quiver trees are very sensitive to environmental changes, and do not respond well to extreme hot and dry conditions. This study investigates the current status of the Quiver tree within its existing environment, and also assesses the projected future changes of the Quiver tree habitat under different climatic scenarios. It provided evidence regarding the importance of the study to understanding the climate change impacts on the Quiver tree and its geographical response to climate changes.
基金financially supported by the Coaltech Research Association and the University of Fort Hare
文摘The subsidence history of the Soutpansberg Basin was reconstructed by a tectonic subsidence analysis coupled with backstripping calculations based on data of newly interpreted sequence boundaries. Furthermore, burial and time plots were constructed in order to understand the burial and thermal history of the basin. Input data were based on facies, lithostratigraphic models and tectonic interpretations. The studied succession is up to 1000 m and is underlain by the Achaean Limpopo Mobile Belt. The subsidence within the basin supports the primary graben system which must have been centred within the present basins, and later became a region of faulting. The subsidence and burial history curves suggests two phases of rapid subsidence during the Early-Late Permian （300–230 Ma） and Middle Triassic （215–230 Ma）. The areas of greater extension subsided more rapidly during these intervals. Two slow subsidence phases are observed during the Late Triassic （215–198 Ma） and Early Jurassic （198–100 Ma）. These intervals represent the post-rift thermal subsidence and are interpreted as slow flexural subsidence. Based on these observations on the subsidence curves, it is possible to infer that the first stage of positive inflexion （300 Ma） is therefore recognised as the first stage of the Soutpansberg Basin formation.
文摘Coal contains a significant concentration of free radicals as a result of the coalification process. One of the experimental methods sensitive to the presence of radicals is electron spin resonance （ESR）, and differences in ESR spectra for different macerals may provide insight into coal-forming processes. In this study, ESR data along with the H/C atomic ratio （to infer the aromatic fraction） are used to characterize coal samples with the aim of assessing a fire-origin for dominant inertinite macerals. A medium rank C bituminous Witbank No. 4 Seam Upper coal （the parent） was density- fractionated to create vitrinite-rich and inertinite-rich samples. The parent sample consists of 42 vol% vitrinite and 49 vol% inertinite. The density-fractionated samples comprise of 81 vol% total vitrinite （dominated by collotelinite and collodetrinite）, and 63 vol% total inertinite （dominated by fusinite, semifusinite, and inertodetrinite）. The H/C ratio is 0.74 for the inertinite-rich sample, and 0.85 for the vitrinite-rich counterpart, suggesting the former sample is more aromatic. The ESR spectra obtained for the three samples were found to fit best using a Lorentzian distribution. The fit is noticeably better for the aromatic inertinite-rich sample, for which the spectrum is symmetric. This is attributed to pronounced electron mobility and exchange interactions. The higher radical content of the inertinite-rich and parent samples is attributed to the presence of specific inertinite macerals, namely： fusinite, semifusinite, and inertodetrinite. And, owing to the greater radical content of the inertinite-rich sample, the dominant inertinite macerals are interpreted to have formed through charring of plant matter.
文摘The Balfour Formation was subdivided into five members based on lithological variation that is characterized by alternating sandstone-and mudstone -dominated members.The sandstone dominated Oudeberg and Barberskrans members are composed of lithofacies that range from intraformational conglomerates to fine-grained sediments,whereas the mudstone dominated members(Daggaboersnek, Elandsberg and Palingkloof) are dominated by the fine-grained facies(Fm and F1).Petrography,geochemistry and palaeocurrent analysis indicated that the source rock of the Balfour Formation was to
基金The lead author acknowledges the Research,Education and Investment(REI)Fund of the Geological Society of South Africa(GSSA),National Research Foundation of South Africa(NRF),and the University of Johannesburg’s(UJ)Centre of Excellence for Integrated Mineral and Energy Resource Analysis(CIMERA)for funding.
文摘This study aims to compare iso-rank vitrinite-rich and inertinite-rich coal samples to understand the impact of coal-forming processes on pyrolysis chemistry.A medium rank C bituminous coal was density-fractionated to create a vitrinite-rich and an inertinite-rich sub-sample.The vitrinite-rich sample has 83 vol% total vitrinite (mineral-matter-free basis),whereas the inertinite-rich counterpart has 66 vol% total inertinite.The vitrinite-rich sample is dominated by collotelinite and collodetrinite.Fusinite,semifusinite,and inertodetrinite are the main macerals of the inertinite-rich sample.Molecular chemistry was assessed using a pyrolysis gas chromatograph (py-GC) equipped with a thermal desorption unit coupled to a time of flight mass spectrometer (MS) (py-GC/MS) and solid-state nuclear magnetic resonance (13C CP-MAS SS NMR).The pyrolysis products of the coal samples are generally similar,comprised of low and high molecular weight alkanes,alkylbenzenes,alkylphenols,and alkyl-subtituted polycyclic aromatic hydrocarbons,although the vitrinite-rich sample is chemically more diverse.The lack of diversity exhibited by the inertinite-rich sample upon pyrolysis may be interpreted to suggest that major components were heated in their geologic history.Based on the 13C CP-MAS SS NMR analysis,the inertinite-rich sample has a greater fraction of phenolics,reflected in the py-GC/MS results as substituted and unsubstituted derivatives.The greater abundance of phenolics for the inertinite-rich sample may suggest a fire-related origin for the dominant macerals of this sample.The C2-alkylbenzene isomers (p-xylene and o-xylene) were detected in the pyrolysis products for the vitrinite-rich and inertinite-rich samples,though more abundant in the former.The presence of these in both samples likely reflects common source vegetation for the dominant vitrinite and inertinite rnacerals.
文摘The Southern African biomes are complex biotic communities, with its distinctive plant and animal species, and are maintained under the suitable climatic conditions of the region. It includes the Fynbos Biome and the Succulent Karoo Biome, which forms the smallest of the world’s six Floristic Kingdoms, and they are of conservation concern. The other six biomes are Albany Thicket, Desert, Grassland, Indian Ocean Coastal belt, Nama-Karoo, Savanna. The biomes are not only threatened by agricultural expansion, overgrazing, and mining;but also by future climate changes and droughts. This study investigates the how to best model the possible vulnerable biome areas, under future climate changes, and how Southern African geology plays a huge role in the restriction of the biome shifts. It provides evidence regarding the importance of the study to understanding the climate change impacts and the geological variables on the Southern African biomes, in terms of possible future biome habitat loss.
