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The blue antelope (Hippotragus leucophaeus) is the only large African mammal species to have become extinct in historical times, yet no nuclear genomic information is available for this species. A recent study showed that many alleged blue antelope museum specimens are either roan (Hippotragus equinus) or sable (Hippotragus niger) antelopes, further reducing the possibilities for obtaining genomic information for this extinct species. While the blue antelope has a rich fossil record from South Africa, climatic conditions in the region are generally unfavorable to the preservation of ancient DNA. Nevertheless, we recovered two blue antelope draft genomes, one at 3.4× mean coverage from a historical specimen (∼200 years old) and one at 2.1× mean coverage from a fossil specimen dating to 9,800–9,300 cal years BP, making it currently the oldest paleogenome from Africa. Phylogenomic analyses show that blue and sable antelope are sister species, confirming previous mitogenomic results, and demonstrate ancient gene flow from roan into blue antelope. We show that blue antelope genomic diversity was much lower than in roan and sable antelope, indicative of a low population size since at least the early Holocene. This supports observations from the fossil record documenting major decreases in the abundance of blue antelope after the Pleistocene–Holocene transition. Finally, the persistence of this species throughout the Holocene despite low population size suggests that colonial-era human impact was likely the decisive factor in the blue antelope's extinction. [ABSTRACT FROM AUTHOR]

The chronostratigraphy of the Bushmanland Ore District and the Namaqua-Natal Province has long been debated, but recent microbeam dating has resolved several issues. An important aspect is the precise age of the sedimentaryexhalative ores and their tectonostratigraphic context. Published constraints on the maximum age of the ores from detrital zircon dating are 1 285 ± 14 Ma (n=4, Gamsberg ore), 1 215 ± 18 Ma (n=6, Wortel Formation) and a tentative 1 118 ± 33 Ma (n=3, Hotson Formation at Black Mountain). The ore is older than the 1 130 ± 35 Ma Koeris Formation metabasalt which unconformably overlies it. Aplite dykes, which intrude the ore of the Black Mountain deposit, provide another potential minimum age constraint on the ore. A sample was dated at 1 175 ± 15 Ma by ion probe U-Pb zircon dating. This shows that the aplite dykes belong to the late-collisional Springputs Suite of granitoids which includes the 1 163 ± 11 Ma Achab and 1 149 ± 15 Ma Hoogoor Gneisses, for which the field relationship with the ores had not been established. The regional M2 metamorphism was recorded in aplite zircon rims at 1 027 ± 9 Ma and at 1 030 ± 6 Ma in monazite and xenotime in the Hotson Formation host rock schists. Detrital zircons, dated by Laser Ablation ICPMS in a host rock schist sample, reflect a dominant Palaeoproterozoic provenance with major age group at 2 003 ± 17 Ma and minor groups at 1 847 and 2 105 Ma. Only 16 analyses were made, which probably accounts for the absence of minor Mesoproterozoic provenance components found in other published datasets. The age of the Black Mountain ore is now constrained between 1 215 ± 18 Ma and 1 175 ± 15 Ma. The tentative 1 118 ± 33 Ma detrital zircon maximum age is shown to be unreliable in view of two younger magmatic rocks with older dates (1 175 and 1 130 Ma). The SEDEX ores thus formed during or just before the ~1 210 Ma assembly of Namaqua terranes and before the ~1 150 Ma syntectonic Springputs Suite granitoid magmatism. [ABSTRACT FROM AUTHOR]

The extrusive component of the Karoo Large Igneous Province, the Drakensberg Continental Flood basalts of South Africa and Lesotho, is mainly composed of altered tholeiitic basalts without uraniferous mineral phases that are suitable for high-precision dating (e.g. baddeleyite or zircon), and thus dating is restricted to 40Ar/39Ar groundmass and plagioclase. Previous 40Ar/39Ar dates of plagioclase span from 178.9 ± 4.2 Ma to 189.2 ± 3.3 Ma, while most dates range between 180 and 183 Ma (Jourdan et al., 2007b ; Moulin et al., 2011 ; Moulin et al., 2017). Dating mafic rocks can be hindered by the presence of plagioclase xenocrysts (inherited 40Ar), and the ubiquitous presence of alteration phases. Separation protocols and acid leaching are used to minimize the effect of these issues, although previous 40Ar/39Ar studies of the Drakensburg lavas did not interpret their dates within a petrochronological context, and thus they are open to inaccuracy. We have used cathodoluminescence imaging, QEMSCAN analysis and optical petrology of thin sections to show that two distinct generations of plagioclase occur within the lavas, and at least two different phases of K-rich (adularia and K-rich clays) and Ca- alteration have occurred. 40Ar/39Ar dates have been obtained from some acid-leached and unleached aliquots of groundmass and both plagioclase generations. Our results show that i) large, cluster-forming plagioclase yield older 40Ar/39Ar dates and are interpreted to be xenocrystic, ii) apparently unaltered plagioclase in thin sections hosts secondary Ar reservoirs related to alteration, and iii) alteration and leaching can enhance the effects of 37,39Ar recoil in plagioclase. We conclude that the most accurate date for the Drakensburg lavas that applies to the entire thickness of the lava stacks is 184.4 ± 1.2 Ma, which was obtained from the matrix-forming plagioclase that contains the highest proportion of non-inherited radiogenic 40Ar, is least affected by secondary alteration and did not apparently suffer the effects of Ar isotope recoil. [ABSTRACT FROM AUTHOR]

The Dinaledi Chamber of the Rising Star Cave has yielded 1550 identifiable fossil elements - representing the largest single collection of fossil hominin material found on the African continent to date. The fossil chamber in which Homo naledi was found was accessible only through a near-vertical chute that presented immense practical and methodological limitations on the excavation and recording methods that could be used within the Cave. In response to practical challenges, a multimodal set of recording and survey methods was thus developed and employed: (1) recording of fossils and the excavation process was achieved through the use of white-light photogrammetry and laser scanning; (2) mapping of the Dinaledi Chamber was accomplished by means of high-resolution laser scanning, with scans running from the excavation site to the ground surface and the cave entrance; (3) at ground surface, the integration of conventional surveying techniques as well as photogrammetry with the use of an unmanned aerial vehicle was applied. Point cloud data were used to provide a centralised and common data structure for conversion and to corroborate the influx of different data collection methods and input formats. Data collected with these methods were applied to the excavations, mapping and surveying of the Dinaledi Chamber and the Rising Star Cave. This multimodal approach provides a comprehensive spatial framework from individual bones to landscape level. [ABSTRACT FROM AUTHOR]

Abstract: We evaluate the 190Pt–186Os decay system, measured by laser ablation MC-ICPMS, as a useful geochronometric tool for direct dating of platinum-group minerals (PGM) in large mafic/ultra-mafic intrusions by analysing mineralised rocks from the geochronologically well constrained Bushveld Complex, S. Africa. Mixed PGM (laurite, cooperite, laurite–platarsite, sperrylite and Pt–Fe alloy) from the Merensky Reef yield a Pt–Os isochron age of 1995±50Ma (2σ, n=48, MSWD=1.16, initial 186Os/188Os=0.119819±0.000006). While this is 59Myr younger than the U–Pb zircon age for the Merensky Reef (Scoates and Friedman, 2008) it is consistent with recent Re–Os ages for the Platreef. Considering the younger age recorded by both Re–Os and Pt–Os systems, we propose that the Pt–Os isochron age records a late, low temperature hydrothermal event affecting PGM and sulphides in the Platreef and Merensky Reef. Pt-rich phases may also yield single grain 190Pt–186Os model ages since initial 186Os/188Os can be well constrained. A Pt–Os model age of 2024Ma±101Ma was calculated for a Merensky cooperite; a Pt–Fe alloy from the Onverwacht pipe and a Tweefontein Hill sperrylite give Pt–Os model ages of 2113±106Ma and 2042±102Ma, respectively. A Pt–Os isochron derived from all Bushveld units gives an age of 2012±47Ma (2σ, 186Os/188Osi =0.119818±0.000006) with an MSWD of 1.19, hence PGE mineralisation in different stratigraphic horizons of the complex cannot be distinguished temporally using the Pt–Os chronometer. Nonetheless, the potential for the Pt–Os system in dating events in PGE mineralised systems is evident and the agreement of single grain model ages in high Pt/Os phases with the Pt–Os and Re–Os isochron ages indicates their usefulness in the geochronology of these systems. [Copyright &y& Elsevier]

U-Pb baddeleyite geochronology has become a major tool for dating mafic rocks, especially dikes associated with Large Igneous Provinces. However, in many cases, post-crystallization Pb-loss and intergrowth of baddeleyite and zircon limit the precision and/or accuracy of crystallization ages. We present results from multi-step digestion experiments designed to understand and reduce these effects. Experiments were carried out on Neoproterozoic baddeleyites with zircon inter- and over-growths from the Gannakouriep dike swarm, Namibia, and on fragments of a large Paleoproterozoic baddeleyite from the Phalaborwa carbonatite, South Africa. Multi-step digestion experiments on annealed Phalaborwa baddeleyite were designed to test whether the recently developed chemical abrasion technique for U-Pb zircon geochronology can be applied to baddeleyite. The experiments generated complex results-individual digestion steps were both normally and reversely discordant suggesting that U and Pb were decoupled in the multi-step digestions-and indicate that the current form of multi-step chemical abrasion is not an effective method for reducing the impact of Pb-loss in baddeleyite. A separate set of experiments on the Gannakouriep baddeleyite focused on isolating the zircon and baddeleyite components in composite grains. Conventional single-step digestion experiments for this sample resulted in a discordant suite of analyses with significant scatter attributed to inter- and over-grown zircon and highlight the difficulty of obtaining precise and accurate ages from composite grains. To isolate the baddeleyite and zircon in these grains, a two-step HCl-HF chemical abrasion procedure for annealed grains was developed. This technique was successful at selectively dissolving the baddeleyite and zircon components. Secondary zircon inter- and over-growths of baddeleyite can occur in samples affected by low-temperature alteration to granulite facies metamorphism, and the new HCl-HF chemical abrasion procedure provides a method for resolving both the igneous and metamorphic history of these composite grains. [ABSTRACT FROM AUTHOR]

Abstract: Results of more than 400 in situ U–Th–Pb and Lu–Hf zircon isotope analyses combined with cathodoluminescence images and field relationships reveal that the oldest magmatic rocks of the Limpopo Belt (Musina area) formed during the Palaeoarchaean between 3.40 and 3.27Ga, experienced a first anatexis at 3.24–3.07Ga (M1) and were overlain by sediments mainly between 3.24 and 3.0Ga. Subsequently, the infra- and supracrustal rocks together underwent two high-grade metamorphic overprints, a first during the Neoarchaean at 2.65Ga (M2), and a second at 2.025Ga (M3). Hafnium isotope data additionally reveal that the Palaeoarchaean magmatic rocks result from substantial recycling of much older crust. This is well reflected by nearly chondritic ɛHfint obtained from primary magmatic zircon domains of four Sand River TTG-gneiss samples (ɛHf3.27–3.28Ga =−1.3 to −1.8), from leucosomes within the Sand River Gneisses (ɛHf3.40Ga =−2.0; ɛHf3.28Ga =−1.5), and from two meta-anorthosite samples of the Messina layered intrusion (ɛHf3.35Ga =0.1–1.4). Crustal recycling is also supported by hafnium isotope data of detrital zircon grains from two quartzite samples. These data reflect a general increase of the ɛHfint between 3.65 and 3.2Ga from ca. −4.0 to 0.0, indicating that an Eo- to Palaeoarchaean crust was mixed with juvenile mantel material in the hinterland of the Limpopo Belt. The present study also demonstrates that Hf isotope data provide a powerful tool, which makes it possible to distinguish zircon domains formed during distinct magmatic or metamorphic events, from such affected by a pseudomorphic alteration, even if the investigated zircon grain underwent multiple alteration processes. [Copyright &y& Elsevier]

We describe the geological, geochronological, geomorphological, and faunal context of the Malapa site and the fossils of Australopithecus sediba. The hominins occur with a macrofauna assemblage that existed in Africa between 2.36 and 1.50 million years ago (Ma). The fossils are encased in water-laid, clastic sediments that were deposited along the lower parts of what is now a deeply eroded cave system, immediately above a flowstone layer with a U-Pb date of 2.026 ± 0.021 Ma. The flowstone has a reversed paleomagnetic signature and the overlying hominin-bearing sediments are of normal polarity, indicating deposition during the 1.95- to 1.78-Ma Olduvai Subchron. The two hominin specimens were buried together in a single debris flow that lithified soon after deposition in a phreatic environment inaccessible to scavengers. [ABSTRACT FROM AUTHOR]

Presents preliminary findings of palynological and chronological analysis of the Orange River mudbelt material. Radiocarbon, pollen, stable carbon isotope and [sup 210]Pb analysis of the mud; Environment, vegetation and climate change in the South African interior; Runoff and land use history of the region.

Abstract -- Mid- to Upper Devonian strata of the lower Witteberg Group in the Cape Fold Belt of South Africa comprise three principal facies deposited in the shoreface and contiguous inner shelf along a storm-dominated coastal zone. Weakly burrowed mudrock with variable minor proportions of wave-rippled sandstone (linsen, flasers, hummocky cross stratification [HCS]) (facies 1) accumulated in the inner shelf below, near, and just above storm wave base. Very fine- and fine-grained sandstone that displays flat and wavy lamination and HCS, as well as compound wave-ripple lamination (facies 2), was deposited in the lower shoreface above fair-weather wave base. Fine- to coarse-grained sandstone containing cross-lamination, anisotropic HCS, and compound wave-ripple lamination (facies 3) formed in the mid to upper shoreface. Regionally, lower Witteberg strata change from proportionally more facies 2 and 3 at proximal (northern) sites to mostly facies I at distal (southern) sites. The lower Witteberg Group consists of approximately 40 shallowing-upward facies sequences (parasequences) whose average thickness is approximately 12 m. These are grouped into progradational parasequence sets of up to 10 parasequences each for a total of approximately 3.5 parasequence sets in the lower Witteberg. The lowest parasequence set extends from the base of the Karoopoort Formation (top of underlying Bokkeveld Group) and culminates at the top of the Blinkberg Formation in the Witteberg Group, and approximately 2.5 parasequence sets make up the overlying Swartruggens Formation. The characteristics and stratigraphic architecture of the lower Witteberg Group are consequences of the interaction of two different orders of global sea-level fluctuation. The lower Witteberg parasequences had a periodicity between 250 and 300 ka, within the Milankovitch range, and their character and mean thickness are very similar to cyclic patterns recorded in contemporaneous Givetian-Frasnian siliciclast... [ABSTRACT FROM AUTHOR]

Provides geochronometric data on openwork debris flow deposits in a part of the Cederberg Mountains, Western Cape, South Africa. Rock surface hardness assessment; Use of Schmidt hammer technique, lichenometry, determination of weathering rind thickness, and weathering pit diameters.

Presents information on a petrographic and geochronological study of the Voorspoed kimberlite pipe in South Africa. Experimental procedures; Analytical results and interpretation; Discussion and conclusions.

Presents information on a study which tested the hypothesis that the Pilbara and Kaapvaal Cratons were joined as part of a Late Archaean Vaalbara supercontinent. Implications of the results on the Vaalbara hypothesis; Geochronology of the Derdepoort Belt; Paleomagnetism of the Derdepoort basalts.

Dates an episode of intense postimpact metamorphism in the core of the Vredefort impact structure of South Africa, using U-Pb geochronology of single grains of zircon and monazite. Geologic setting and sample descriptions; Indlandsee leucogranofels; Norite; Age of impact and core metamorphism; Causes of thermal imprint.

Determines the ages of the Gaborone and Kanye rapakivi granite sequences in the Witwatersrand basin hinterland in southern Africa by using the Uranium-Lead zircon dating methods of T.E. Krogh. Sampling and geologic relations; Geochemistry of dated samples; Isotope results.

Presents a case study from Phalaborwa Igneous Complex, South Africa using baddeleyite as age determinants of individual intrusions of major igneous episodes. Sample materials and analytical procedures use in the study; Results and discussions; Conclusions.

Investigates the results of lead-evaporation age determinations relating to the lower part of succession in Transvaal basin of South Africa. Geological and geochronological background of the study; Stratigraphic succession of the Transvaal and Griqualand west sequence; Analysis of data; Significance of the analytical procedures in the study; Conclusions.

The article discusses a report by researcher Jourdan and colleagues regarding age-dating of craters. There are 174 characterized impact structures on Earth ranging in size and age from South Africa to Arizona in the U.S. Topics include how understanding their age-size relationship could aid in the assessment of the impact and its relation to events such as extinctions. A brief overview of the difficulties in aging craters is presented.