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The age and properties of detrital zircon in a sediment reflect properties of the rocks in which the zircon crystallized, and not necessarily the immediate precursor of the host sediment. Where clastic sediments are recycled, these properties are preserved so that U‐Pb ages and Lu‐Hf data on zircon grains will no longer give information on the routing of detritus. Because the crustal evolution and sedimentary recycling history of Southern Africa is well‐established, Holocene sediments in the region provide a good test example for detrital zircon geochronology applied to sands or sandstones with a complex recycling history. Data from 16 samples of unconsolidated sand, including dunes from the southern part of the Kalahari Basin, beach sands at the Atlantic coast, and isolated inland dune occurrences, yield ranges of early Mesozoic to late Archaean ages. Uranium–lead and lutetium–hafnium isotope data provide no evidence of direct derivation of zircon from protosources in crystalline bedrock. The complex distribution patterns can be decomposed into seven 'provenance components' that have previously been encountered in Palaeoproterozoic to Jurassic sedimentary rocks in the region. These components occur in non‐random combinations, in proportions that suggest mixing of recycled material from different sedimentary precursors. Taking pre‐Cenozoic geology, Cretaceous to Pleistocene drainage history of southern Africa and Holocene wind and current patterns into account, it is possible to work out a consistent model for transport of detritus from sedimentary precursors into the basin, followed by aeolian remobilization within the basin itself. The detrital zircon distributions can thus be interpreted from prior knowledge of the basin filling history, regional geology, geomorphology, drainage evolution and wind pattern. This amounts to a line of reasoning from 'sink back to (intermediate) 'source', which is the opposite of the '(proto)source‐to‐sink' paradigm commonly invoked in detrital zircon studies. [ABSTRACT FROM AUTHOR]

Recent advances in sequencing technology and phylogenetic methods allow us to solve puzzling taxonomic questions using detailed analyses of genetic diversity of populations and gene flow between them. The genus of solitary-living dune mole-rat, Bathyergus, is quite unique among six genera of African mole-rats. The animals are by far the largest and the only scratch digging mole-rat genus possessing a skull less adapted to digging, grooved upper incisors, and more surface locomotor activity. Most authors recognize two species of dune mole-rats, B. suillus and B. janetta, but according to others, the genus is monotypic. In addition, recent molecular studies have revealed cryptic genetic diversity and suggested the existence of up to four species. In our study, we used mitochondrial and genome-wide nuclear data collected throughout the distribution of the genus to investigate the number of species. In agreement with previous studies, we found Bathyergus to be differentiated into several distinct lineages, but we also found evidence for a degree of gene flow between some of them. Furthermore, we confirmed that B. janetta is nested within B. suillus, making the latter paraphyletic and we documented an instance of local mitochondrial introgression between these two nominal species. Phylogeographic structure of the genus was found to be very shallow. Although traditionally dated to the Miocene, we found the first split within the genus to be much younger estimated to 0.82 Ma before present. Genealogical distinctiveness of some lineages was very low, and the coancestry matrix showed extensive sharing of closely related haplotypes throughout the genus. Accordingly, Infomap clustering on the matrix showed all populations to form a single cluster. Overall, our study tends to support the existence of only one species of Bathyergus namely, B. suillus. Environmental niche modelling confirmed its dependence on sandy soils and the preference for soils with relatively high carbon content. Bayesian skyline plots indicate recent population decline in the janetta lineage, probably related to global environmental change., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Inc. All rights reserved.)

This study highlights a significant methodological and practical issue involving the use of a magnetic compass in aeolian studies in the field. Geomagnetic declination can significantly affect field measurements of wind direction from anemometers as well as measurement of the orientation of geomorphic features such as sand dunes, depending on geographic location. It is therefore surprising how often methodological descriptions of published aeolian studies, including those in southern Africa, neglect to describe any declination corrections applied to field measurements or instrumental records. This results in uncertainty in the validity of data reported in such studies, particularly where actual wind directions may be very different (>20° in some cases) from measured values. Drawing from examples in the literature from southern Africa and other key locations globally, this study discusses the need for greater clarity in the declination corrections applied when wind direction is being measured and reported, especially where wind datasets from different sources are being used or integrated, or when published studies are being compared. [ABSTRACT FROM AUTHOR]

The Namib Desert and the Kalahari constitute the drylands of southern Africa, with the current relatively humid portions of the latter having experienced periodically drier conditions during the Late Quaternary. This study explores the range of dryland archives and proxies available for the past ~190 ka. These include classic dryland geomorphological proxies, such as sand dunes, as well as water-lain sediments within former lakes and ephemeral fluvial systems, lake shorelines, sand ramps, water-lain calcrete and tufa sediments at the interface of surface hydrological and hydrogeological, speleothems and groundwater hydrogeological records, and hyrax middens. Palaeoenvironmental evidence can also be contained within geoarchaeological archives in caves, overhangs and rockshelters. This integration of records is undertaken with the aim of identifying a (or a number of) terrestrial regional chronostratigraphic framework(s) for this time period within southern Africa, because this is missing from the Quaternary stratigraphy lexicon. Owing to a lack of long, near-continuous terrestrial sequences in these drylands, the correspondence between nearby terrestrial records are explored as a basis for parasequences to build this chronostratigraphy. Recognising the modern climatological diversity across the subcontinent, four broad spatial subdivisions are used to explore potential sub-regional parasequences, which capture current climatic gradients, including the hyper-arid west coast and the decrease in aridity from the southwest Kalahari toward the north and east. These are the Namib Desert, the northern Kalahari, the southern Kalahari and the eastern fringes of the southern Kalahari. Terrestrial chronostratigraphies must start from premise that climate-driven environmental shifts may have occurred independently to those in other terrestrial locations and may be diachronous compared to the marine oxygen isotope stratigraphy (MIS), which serves as a global-scale master climatostratigraphy relating to global ice volume. The fragmented nature of preserved evidence means that we are still some way from producing unambiguous parasequences. There is however, a rich record to consider, compile and compare, within which seven broad wetter intervals are identified, with breaks between these inferred to be relatively drier, and some also have proxy evidence for drying. The onset and cessation of these wetter intervals does not align with MIS: they occur with greater frequency, but not with regular periodicity. Precession-paced insolation forcing is often invoked as a key control on southern African climate, but this does not explain the pacing of all of the identified events. Overall, the pattern is complex with some corresponding wetter intervals across space and others with opposing west-east trends. The evidence for drying over the past 10 ka is pronounced in the west (Namib Desert), with ephemerally wet conditions in the south (southern Kalahari). The patterns identified here provide a framework to be scrutinised and to inspire refinements to nearproposed terrestrial chronostratigraphies for southern Africa. Considering changes across this large geographic area also highlights the complexity in environmental responses across space as we continue to test a range of hypotheses about the nature of climatic forcing in this region. [ABSTRACT FROM AUTHOR]

A combined magneto-mineralogical approach is used to diagnose maghemitization in magnetic grains of basaltic rock fragments from sand dunes in the Namibian desert in SW Africa. Data were obtained from static magnetic analysis, ferromagnetic resonance (FMR) spectroscopy, micro-Raman spectroscopy and electron microscopy. Micro-Raman spectroscopy showed that the magnetic grains in the lithic fragments form oxidative solid solution series with magnetite and maghemite as end-members. The five active Raman modes at 712, 665, 507, 380 and 344 cm−1 indicate that maghemite in the magnetic grains has well-defined structural properties. The FMR spectral analysis provides evidence for long-range dipolar coupling, which suggests intergrowth of the magnetic phases of the oxidative solid solution series. Thermomagnetic experiments and hysteresis measurements reveal a Curie temperature of about 890 K for this maghemite. Upon heating to 970 K part of the maghemite is altered to thermodynamically more stable hematite. After selective thermal decomposition of the maghemite in a protected atmosphere, the remaining magnetic phase has a Curie temperature of 850 K, characteristic for magnetite. The unique thermal stability of this natural maghemite above its Curie temperature is explained by the well-defined mineral structure, which formed during slow oxidative alteration of magnetite under arid climate conditions. [ABSTRACT FROM AUTHOR]

Abstract: Geomorphological and lithostratigraphic mapping of dune systems on the Maputaland coastal plain of northeastern KwaZulu-Natal Province, South Africa has defined the relative-age relationships between the complex pattern of Quaternary parabolic and hummocky dunes, sand megaridges and the composite coastal barrier dune cordon. Here infra-red-stimulated luminescence (IRSL) ages are presented in the context of regional stratigraphic relationships and serve to bracket the period of accumulation of the main dune systems. The luminescence ages challenge the widely held belief that the north–south aligned dune pattern reflects a coastward-younging sequence. The framework of ages highlights the spatial variations in dune mobilization and long accretion history on some dune forms. Weathered dune and interdune wetland sediments spanning from prior to marine isotope stages (MIS) 11 and up to MIS 7 underlie the coastal plain. At least two generations of decalcified aeolianite of MIS 5 and 4 form the core of the complex coastal barrier dune. On the coastal plain, frequent sand mobilization events during MIS 3–2 resulted in the development of discrete complexes of highly extended, northward directed parabolic dune systems and reworking of the crest of the central sand megaridge. The luminescence-dated dune mobilization history brackets the period of formation of interdune and lacustrine peat and diatomite deposits. During the Holocene marine transgression at least four laterally extensive, complex transverse ridges of coalesced ascending parabolic dunes accreted against the aeolianite core of the coastal barrier. Polyphase dune formation and remobilization is discussed in the context of the regional groundwater and vegetation responses to global climatic changes, wind regimes and glacio-eustatic sea-level fluctuations. [Copyright &y& Elsevier]

Questions: Is multi-stemming a survival strategy in response to chronic disturbance? Is multi-stemming under phylogenetic control? What environmental factors are associated with multi-stemming? When do trees initiate growth of multiple stems? Do multi-stemmed trees have limited stature?Location: Subtropical Indian Ocean coastal dune forest at Cape Vidal in the Greater St. Lucia Wetland Park, northeastern South Africa. Methods: Tree physiognomy and environmental conditions were sampled in 20 transects that were 300 m long and 5 m wide. Results: 38.9 % of trees were multi-stemmed, with no correlation between multi-stemming and taxonomic grouping. The multi-stemming trait was most associated with stem decumbency and substrate erosion and multi-stemmed individuals were less common in protected dune slacks. Trees at Cape Vidal appear to facultatively produce multiple stems from an early stage. There was no trade-off between tree height and stem number. Conclusions: Coastal winds and the unstable dune substrate are important environmental correlates of multi-stemming. Both short stature and the high incidence of multi-stemming are related to the tree-disturbance interaction. The taxonomically widespread phenotypic plasticity in this trait indicates the importance of multi-stemming to tree survival even under low levels of disturbance. [ABSTRACT FROM AUTHOR]

Although desert dunes cover 5 per cent of the global land surface and 30 per cent of Africa, the potential impacts of twenty-first century global warming on desert dune systems are not well understood. The inactive Sahel and southern African dune systems, which developed in multiple arid phases since the last interglacial period, are used today by pastoral and agricultural systems that could be disrupted if climate change alters twenty-first century dune dynamics. Empirical data and model simulations have established that the interplay between dune surface erodibility (determined by vegetation cover and moisture availability) and atmospheric erosivity (determined by wind energy) is critical for dunefield dynamics. This relationship between erodibility and erosivity is susceptible to climate-change impacts. Here we use simulations with three global climate models and a range of emission scenarios to assess the potential future activity of three Kalahari dunefields. We determine monthly values of dune activity by modifying and improving an established dune mobility index so that it can account for global climate model data outputs. We find that, regardless of the emission scenario used, significantly enhanced dune activity is simulated in the southern dunefield by 2039, and in the eastern and northern dunefields by 2069. By 2099 all dunefields are highly dynamic, from northern South Africa to Angola and Zambia. Our results suggest that dunefields are likely to be reactivated (the sand will become significantly exposed and move) as a consequence of twenty-first century climate warming. [ABSTRACT FROM AUTHOR]

"Once we got there, there were just stone tools everywhere, so we knew straight away this was an amazing site", says archaeologist Huw Groucutt, Petraglia's colleague at SHH. If you know what to look for in dappled satellite images of desert - slight depressions, subtle color shifts - the dried-up ghosts of prehistoric lakes pop out against the sand fields of the Arabian Peninsula. [Extracted from the article]

Subaqueous dunes are formed on the KwaZuhJ-Natal outer-shelf due to sediment transport by the Agulhas Current (geostrophic current). These dunes occur within two dune fields at depths of - 35 to - 70 m. The net sediment transport direction is south, but short-period reversals ferm northward-migrating bedforms. The dune fields are physically bounded by late Pleistocene beachrock and aeolianite ledges. A bedform hierarchy has been recognized in the dune fields comprising a system of three generations of climbing bedforrns. The outer dunefield has given rise to a sand ridge (H = 12 m; L = 4 km; W = 1.1 km; and an 8° lee slope) whereas the inner dune fields have achieved large-scale dune status. Bedload parting zones within the dune fields occur where the sediment transport direction switches from north to south due to reversals in the geostrophic flow; these zones occur at depths of - 60, -47 and - 45 m. An interpretative stratigraphic model is presented on what such geostrophite deposits would look like in the ancient sedimentary record. [ABSTRACT FROM AUTHOR]

The attempt to reconstitute the pluvial and arid periods of Saharan Africa finds, in the Hoggar region. vestiges of what may be humid and dry periods in alternation. It is apparent that the humid periods for the lowland country derive from the extension northward of tropical conditions but that, on the other hand, the humid periods in the highlands are related to the southward spread of mediterranean climatic conditions. Evidence is presented that the Quaternary opens with a warm and humid episode during which tropical fauna extend northward and reach to fairly high elevations, which period may possibly be identified with Lower Villafranchian in the archeologic scale. A drying-out period was followed by a cooler humid period during which the higher mountains show the spread of mediterranean mountain flora (Upper Villafranchian), terminating in at least one period of wet-cool conditions making for solifluction and frost-cleaving. Middle Quaternary conditions suggest an arid period of sand dune accumulation followed by a more moist period in which a tropical fauna again extends northward (Upper Acheulian). Upper Quaternary shows an arid period followed by a short moist period in which savanna flora and fauna spread at the lower elevations and a more xerophilous mediterranean flora and fauna spread though the highlands (Moustero-Aterian). The alternation of climatic periods is not fully regular, and there are many problems remaining in the interpretation of climatic, floral, faunal, and human occupance sequences, but a progressive drying-out does seem indicated. [ABSTRACT FROM AUTHOR]

The article presents a study that analyzes the formation of sand dune in the tropical coast of Africa, specifically located in the eastern province of the Gold Coast. It aims to determine the factors responsible for the sand dune formation, which is not a common feature of coastlines in the tropics. Analysis found that the formation is made possible by the existence of the Scaevola plumiera plant species and unique composition of the region's sand, which has a mixture of broken shell fragments that made salt's binding action on sand inefficient to prevent wind movement.

In this study we (1) mapped the areal extent of current dust sources over Northern Africa between 8°W–31°E and 22°N - Mediterranean coast; and (2) identified and characterized the geomorphic units and soil types that emit dust from these areas. We used the full resolution (3 km) data from the MSG-SEVIRI to map dust sources over a 2-year period between 2005–2006, and examined these regions with remotely sensed images and geomorphic and soil maps. A total of >2600 individual dust emission events were mapped; with frequency up to 34 events in the 2-year study period. The areal extent of dust emission sources exhibited a lognormal distribution with most sources ranging from 20 to 130 km2. Most dust events were singular and related to a variety of specific geomorphic units. Dust events that created hotspots were mostly located over playas and fluvial landforms, and to a lesser extent over sand dunes and anthropogenic affected regions. About 20% of dust hotspots were offset a few kilometers from clear geomorphic units. Quantitative analysis of emissions revealed that dust sourced from various geomorphic units, among them playas (12%) and fluvial systems (10%). The importance of sand dunes as dust-emission sources greatly differs between examined datasets (7% vs. 30%). Our study emphasizes the importance of scattered dust emission events that are not considered as hotspots, as these sources are usually neglected in dust emission modeling. [ABSTRACT FROM AUTHOR]

This article focuses on the role of soil mobility in controlling a vegetation gradient. Much of arid central Australia is covered by longitudinal dunes or sandridges 5-25 m high, separated by interdune corridors or swales 0.2-1.5 km across. They are closely comparable to the arid longitudinal dunefields of India and southern Africa, and an understanding of the pattern and dynamics of their plant cover is therefore of general interest. Soil mobility is likely to exert its most significant effect on the floristic catena during plant regeneration after droughts, when soil moisture is no longer limiting but the soil mobility is still high, and the plants are small.

Aeolian (wind-driven) dust emission has a major impact on many environmental and socioeconomic issues such as climate change, soil ecology and fertility, air pollution and thus on human health. The emission of the mineral dust to the atmosphere is a major process in determining the global dust cycle. Comparisons of global dust emission model results against dust measurements still show large discrepancies due to a number of major uncertainties in our understanding of dust emission processes. Active (dune) sands have been identified, by remote sensing studies, as dust sources in northern Africa, China, and elsewhere. However, there is only limited empirical information on dust generation from sands under natural aeolian conditions of saltation. This study integrates wind tunnel experiments and high resolution laboratory sand analyses to explore dust emission from active sands with a focus on the dust emission mechanisms. Four sand samples were used to represent different sand compositions of grain size, dust content, morphology, and mineralogy. No dust emission was recorded for shear velocities below the saltation threshold. PM10 concentrations were increased with the initial content of dust-sized particles in the sand. The experiments identify clay coatings removal as the dominant mechanism in with an addition of re-emission of existing dust-sized particles in the sand. The results also suggest that aeolian abrasion play only a minor role in PM10 dust generation from sands. [ABSTRACT FROM AUTHOR]