•Extraterrestrial organic matter is detected by EPR in 3.33 Ga sediments.•It is associated with Ni-Cr-rich ferrite “cosmic” spinel nanoparticles.•A challenge for the research for organic traces of ...extinct life in Mars.
Electron paramagnetic resonance (EPR) analysis of carbonaceous, volcanic, tidal sediments from the 3.33 Ga-old Josefsdal Chert (Kromberg Formation, Barberton Greenstone Belt), documents the presence of two types of insoluble organic matter (IOM): (1) IOM similar to that previously found in Archean cherts from numerous other sedimentary rocks in the world and of purported biogenic origin; (2) anomalous IOM localized in a 2 mm-thick sedimentary horizon. Detailed analysis by continuous-wave-EPR and pulse-EPR reveals that IOM in this layer is similar to the insoluble component of the hydrogenated organic matter in carbonaceous chondrites, suggesting that this narrow sedimentary horizon has preserved organic matter of extraterrestrial origin. This conclusion is supported by the presence in this thin layer of another anomalous EPR signal at g = 3 attributed to Ni-Cr-Al ferrite spinel nanoparticles, which are known to form during atmospheric entry of cosmic objects. From this EPR analysis, it was deduced that the anomalous sedimentary layer originates from deposition, in a nearshore environment, of a cloud of tiny dust particles originating from a flux of micrometeorites falling through the oxygen-poor Archean atmosphere.
Studies worldwide have highlighted the acute and long-term depressive impacts of psychosocial stressors due to the 2019 coronavirus disease (COVID-19) pandemic, particularly in low- and middle-income ...countries. Among the wide range of risk factors for depression that transpired during pandemic, greater perceptions of individual vulnerability to the COVID-19 have emerged as a major predictor of increased depressive risk and severity in adults.
We estimated the extent to which COVID-19 risk perceptions affected adult depressive symptoms in a longitudinal, nationally representative sample in South Africa. We used covariate balanced propensity scores to minimize the bias from treatment assignment to estimate average causal effects of COVID-19 risk perceptions.
The point prevalence of perceived COVID-19 infection risk increased between the third and fifth months of the pandemic, which corresponded with elevations in national COVID-19 infection rates. Approximately 33% of adults met or surpassed the PHQ-2 cut-off score of 2. An increase in perceived risk of COVID-19 infection predicted worse depressive symptoms in adults four months later.
Our findings highlight the widespread mental health burdens of the COVID-19 pandemic and emphasize the importance of greater psychological resources and structural changes to promote equitable access to COVID-19 risk mitigation policies.
•We assessed the effect of COVID-19 risk perceptions on adult depression in a nationally representative sample in South Africa•We used covariate balanced propensity scores to minimize bias from treatment assignment to estimate average causal effects•Approximately 33% of adults met or surpassed the cut-off score for depressive risk.•An increase in perceived risk of COVID-19 infection predicted worse depressive symptoms in adults four months later.•Greater psychological resources and structural changes are needed to promote equitable COVID-19 risk mitigation policies.
High amplitude climate fluctuations have been inferred from marine isotope data in the early Neogene, but few well documented terrestrial records exist from this era to gauge the effects of these ...high latitude events on continental climates and ecosystems. The extensive, three-dimensional exposures of Miocene fluvial and fluvio-lacustrine sediments in the Rondeberg clay pit near Cape Town provide a unique window on this era. Palaeomagnetic data suggests that the deposits accumulated over a period of <1Ma. The presence of meso-megathermic palynoforms (Palmae, Ilex-type, Euphorb-type, Rhamnaceae) and mesothermic (Podocarpus-type) palynofloras suggests a humid subtropical/tropical climate. However, abundant charcoal, charred in situ tree stumps, overall poor preservation of organics, evidence for upward-drying lacustrine successions and an appreciable fynbos presence, point to cyclical periods of drought. We suggest that these climate fluctuations may have been influenced by the orbital pacing seen in the marine isotope record of the earlier Miocene, pointing to a high latitude link with mid-latitude terrestrial climate patterns. Earlier studies of pollen spectra from the nearby, slightly older Noordhoek deposits show cyclical alternations from tropical to cooler climates and more recent biogeochemical work has shown dramatic coincident fluctuations in depositional temperature. These vegetation changes were previously correlated with major global events embracing the entire Neogene from the Oligo–Miocene (late Oligocene to early Miocene) to the Pliocene. We offer a different interpretation, suggesting that the deposits represent a much shorter time interval in the earlier Miocene and that these climate fluctuations may have been influenced by orbital forcing evinced in the marine isotope record. Along the northern west coast, the Arrisdrift vertebrate fossil assemblage in Early–Middle Miocene terrace deposits of the Orange River indicate a tropical climate but possibly less humid than in the south, with more open vegetation patterns. The presence of pedogenic calcretes and gypcretes in the deposits suggests periodic extremes of aridity not seen in south; the current pronounced north-aridity gradient from humid temperate to hyper-arid may have had its inception in the earlier Miocene.
•Suspension, mixed, and bedload Miocene rivers flowed on South Africa's west coast.•Mixed and bedload rivers aggraded during rising Oligo–Miocene sea levels.•Suspension load rivers occupied a stable, low relief costal plane.•We use palynology, sedimentology and pedology to track Miocene climates.•The pronounced Miocene climate fluctuations were linked to global events.•The present steep west coast climate gradient may have earlier Miocene origins.
In the years since the end of apartheid, South Africans have enjoyed a progressive constitution, considerable access to social services for the poor and sick, and a booming economy that has made ...their nation into one of the wealthiest on the continent. At the same time, South Africa experiences extremely unequal income distribution, and its citizens suffer the highest prevalence of HIV in the world. As Archbishop Desmond Tutu has noted, "AIDS is South Africa's new apartheid."In Ancestors and Antiretrovirals, Claire Laurier Decoteau backs up Tutu's assertion with powerful arguments about how this came to pass. Decoteau traces the historical shifts in health policy after apartheid and describes their effects, detailing, in particular, the changing relationship between biomedical and indigenous health care, both at the national and the local level. Decoteau tells this story from the perspective of those living with and dying from AIDS in Johannesburg's squatter camps. At the same time, she exposes the complex and often contradictory ways that the South African government has failed to balance the demands of neoliberal capital with the considerable health needs of its population.
Until the end of the First World War, urban growth in Johannesburg proceeded unevenly and haphazardly, but under the impact of a wave of militant struggles by black workers and in the context of the ...devastating impact of the 1918 influenza epidemic, the state became determined to better manage the movement of Africans into the urban areas and to place them in properly controlled locations. The promulgation of the Native (Urban) Areas Act of 1923 was intended to meet these objectives. The Act was a hybrid piece of legislation. On the one hand, it espoused the principles enunciated by the Stallard Commission of 1922, which had infamously declared that an African ‘should only be allowed into the urban areas, which are essentially the white man's creation, when he is willing to enter and minister to the needs of the white man, and should depart therefrom when he ceases so to minister’. On the other hand, when it empowered local authorities to set aside land for black residential purposes, it recognised the need to create conditions for the settlement of an urban African population in order to provide a reliable supply of labour to secondary industry. The growing demand for housing led the government to establish Orlando (named after the chairman of the Native Affairs Committee, Edwin Orlando Leake) in 1931, when thousands of African families were evicted from urban slums in and around the city centre and moved there. The authorities described this as a ‘model native township’ that was supposedly planned along the lines of a garden city. The new location, it promised, would be characterised by tree-lined streets, business opportunities and recreation facilities. Reflecting the views of a somewhat conservative section of the African urban elite, the popular African newspaper Bantu World predicted on 14 May 1932 that the new township ‘will undoubtedly be somewhat of a paradise that will enhance the status of the Bantu within the ambit of progress and civilisation.’ Orlando West, Soweto illuminates the genesis of Orlando township and its well-known subsequent history, which is inextricably linked with the lives of prominent South Africans such as Nelson Mandela and Desmond Tutu, amongst many others. A beautiful photographic essay complements the testimony from residents, who describe the way things were, and the way they are now, in the heart of Soweto, South Africa's most iconic African township.
Large parts of the urban land between Pretoria (City of Tshwane Municipality, South Africa's capital city) and Johannesburg (South Africa's largest city) are situated on Proterozoic dolomites of the ...Malmani Subgroup (Chuniespoort Group, Transvaal Supergroup) formed in the Transvaal Basin. As South Africa's economic hub, development is progressively becoming denser, higher, and deeper underground, increasing the risks posed by surface subsidence and sinkholes. Tshwane also sources more than 40 million liters of drinking water per day (5–8% of requirements) from the dolomite aquifers. A second basin comprising the Ghaap Group is found to the more arid western portions of the country. Even though a fair understanding exists with respect to the karst aquifer hydraulics and the surface stability issues, a distinct knowledge gap exists in the karst vadose zone. Recent research efforts focused on vadose zone hydrology has resulted in a significantly improved understanding of the behaviour of variable saturated soil and fractured rock systems, both at discreet localities and on a regional scale. However, with more than 90% of the sinkholes in this region forming due to water ingress from leaking pipelines (especially given that the latter non-revenue water is estimated in the order of 30% of the reticulated supply), the flow mechanisms, and unsaturated or vadose zone behaviour of the karst system becomes increasingly important. The ingress scenario results in downward erosion of soil (chert rubble, residual dolomite, transported soil or other residual products of younger caprock) with percolating water. The high lithological variability in South African karst adds to the uncertainty, and is related to chert abundance, the presence of residual dolomite (wad), subsurface cavities (receptacles) and so forth contributing to the heterogeneity and anisotropy. The review paper presents state-of-the-science on the karst vadose zone, including recent advances, appropriate geological models, and knowledge gaps.
•Complexity in South African karst affects hydrogeology and surface stability.•Majority of sinkholes occur due to water ingress.•Groundwater is used from dolomite aquifers.•Instability and contamination are both affected by the vadose zone properties.•Improved geological models contribute to safe land and groundwater use.
Toward the end of the nineteenth century, the British embarked on a concerted series of campaigns in South Africa. Within three years they waged five wars against African states with the intent of ...destroying their military might and political independence and unifying southern Africa under imperial control. This is the first work to tell the story of this cluster of conflicts as a single whole and to narrate the experiences of the militarily outmatched African societies.Deftly fusing the widely differing European and African perspectives on events, John Laband details the fateful decisions of individual leaders and generals and explores why many Africans chose to join the British and colonial forces. The Xhosa, Zulu, and other African military cultures are brought to vivid life, showing how varying notions of warrior honor and manliness influenced the outcomes for African fighting men and their societies.
Urban sprawl and the accompanying development is set to increase pressure on the hydrological system. In turn, the hydrology of an area affects the infrastructure. Hydropedology, can assist to ...sustainably manage the infrastructure-hydrology interaction. Even though the hillslope scale is accepted as ideal for hydropedological assessments, regional soil maps have been used when hydropedology assessments were undertaken for larger areas. This study uses a hillslope based approach within a digital soil mapping method to conduct a hydropedological assessment for a large (12,000 ha) urban area under developmental pressure within Johannesburg, South Africa. One hundred and thirty-three hillslopes within the study area were delineated and mean and standard deviation of terrain attributes were calculated for each hillslope. Based on these values, the conditioned Latin hypercube sampling (cLHS) method was used to select 30 hillslopes on which soil observations would be made, in a transect, at the surveyor's discretion. A hydropedological soil map was created with the multinomial logistic regression algorithm and the 142 soil observations made. The soil map attained an acceptable 69% validation point accuracy and a Kappa value of 0.59, and was used to create a hillslope conceptual hydrological response map. The chi-square test and QQ-plots indicated that the cLHS selected hillslopes represented the hillslopes of the study site well, but the observations only represented some of the terrain attributes well. Despite the range of the observation dataset covering at least 98.7% of the pixels for the multi resolution index of valley bottom flatness (MRVBF), topographic wetness index (TWI) and altitude above channel network layers, their site distribution differed statistically from that of the observation distribution. The hillslope based survey approach allowed for an acceptable soil map to be created, while allowing for hillslope based hydropedological interpretations to be made. The “cost” for the hillslope based approach was that the distribution of some covariates for the observations differed from their distributions over the entire site.
•Digital soil mapping is applied to a hydropedological assessment in an urban setting.•Representative hillslopes selected by the conditioned Latin hypercube sampling method•Conceptual hydrological response models are created on actual observation data, while.•A DSM technique is used to create a hydropedological soil map for a large area.•The cost in terms of attribute space not covered is determined by statistical methods.
The study provides a revision of the taxonomic composition (subgenuses, species) of the genus Ambostracon Hazel 1962 and a monographic description of the fossil (Holocene) and Recent marine ostracods ...of the genus Ambostracon of South and South-Eastern Africa. The material examined comes from geological stations on the shelf, continental slope and deep-water depression (32–3059 m water depth) of three areas (from the southern coast Mossel Bay to the eastern coast south of Durban, the outer part of Maputo Bay and the eastern coast of South Africa) and surface sediment samples from lagoons, estuaries and coastal lakes of the eastern coast of the South East Africa (Wilderness area, 0.2–1000 m water depth) (R/V METEOR M123-2016). The validity of the selection of the subgenus Ambostracon Patagonacythere is discussed. Two species (Ambostracon keeleri, A. flabellicostata) and one new species (Ambostracon frenzeli sp. nov.) were described. The systematic section provides data about synonymy (compiled on the results of a revision of the species volume), holotype (paratypes, syntypes), material, diagnosis, description, dimensions (linear, relative), sexual dimorphism, individual and geographic variability (fixation of the manifestations and the range of the variability of the morphological elements of the shell), comparison, remarks, localities, stratigraphical position, geographical distribution, environmental conditions of the site (for recent species), palaeoecology (for fossil species), zoogeography. SEM-images of external and internal structures of the carapace (macro- and mesosculpture, central muscle scar field, hinge, normal pore canals) are provided.
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