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Abstract

Lesotho provides a unique context for palaeoclimatic research. The small country is entirely landlocked by South Africa, yet has considerable variation in topography, climate, and associated vegetation over an approximate east–west transect. The region has been of archaeological interest for over a century, and hosts many Early to Late Stone Age sites with occupation preceding 80 000 years before present. The eastern Lesotho highlands are of interest to periglacial and glacial geomorphologists because of their well-preserved relict landforms and contentious evidence for permafrost and niche glaciation during the late Quaternary. However, continuous proxy records for palaeoenvironmental reconstructions for Lesotho are scarce and hampered by a range of methodological shortfalls. These challenges include uncertain ages, poor sampling resolution, and proxies extracted from archaeological excavations for which there may be bias in selection. Inferences on palaeoclimates are thus based predominantly on archaeological and palaeogeomorphological evidence for discrete periods during the late Quaternary. This review paper presents a more detailed multidisciplinary synthesis of late Quaternary conditions in Lesotho. We simultaneously considered the varying data that contribute to the under-studied palaeoenvironmental record for southern Africa. The collective palaeoenvironmental data for eastern Lesotho were shown to be relatively contradictory, with considerable variations in contemporaneous palaeoclimatic conditions within the study area. We argue that although methodological challenges may contribute to this variation, the marked changes in topography result in contrasting late Quaternary palaeoenvironments. Such environments are characterised by similar contrasting microclimates and niche ecologies as are witnessed in the contemporary landscape. These spatial variations within a relatively small landlocked country are of importance in understanding broader southern African palaeoenvironmental change.

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... The Drakensberg-Maloti has been a region of hydrological importance from at least the Early Stone Age (Lombard et al., 2012). While the cold conditions associated with the high altitude posed challenges to human settlement, the consistent moisture availability resulted in refugia during dry seasons and prolonged dry periods (Fitchett et al., 2016a). Today, water forms one of the key exports for the Lesotho economy through the Lesotho Highlands Water Project (Mwangi, 2007). ...
... This combination of climate-environmental factors should present the ideal context for palaeoenvironmental studies, with good potential for preservation of a range of proxies in these wetland peat archives, where the remainder of southern Africa struggles with poor preservation arising from aridity (Chase and Meadows, 2007;Fitchett et al., 2017b). The rich archaeological heritage (Stewart and Mitchell, 2018), and the presence of unique periglacial and niche-glacial palaeogeomorphological features (Grab et al., 2012) provides opportunity for interdisciplinary research and the triangulation of climate and environmental interpretations and reconstructions (Fitchett et al., 2016a). However, difficulties in accessing sites through the rugged topography and rural landscape have resulted in a relatively late onset of archaeological and geomorphological research in the region, and a paucity of temporally continuous palaeoenvironmental reconstructions (Fitchett et al., 2016a;Stewart and Mitchell, 2018). ...
... The rich archaeological heritage (Stewart and Mitchell, 2018), and the presence of unique periglacial and niche-glacial palaeogeomorphological features (Grab et al., 2012) provides opportunity for interdisciplinary research and the triangulation of climate and environmental interpretations and reconstructions (Fitchett et al., 2016a). However, difficulties in accessing sites through the rugged topography and rural landscape have resulted in a relatively late onset of archaeological and geomorphological research in the region, and a paucity of temporally continuous palaeoenvironmental reconstructions (Fitchett et al., 2016a;Stewart and Mitchell, 2018). ...
Article
The Drakensberg-Maloti has been a region of great hydrological importance for thousands of years, captured in the archaeological record as a region of refuge under dry conditions, and in recent decades supplying adjacent South Africa with water through the Lesotho Highlands Water Scheme. This is due in large part to its high amounts of orographically induced rainfall. The high amounts of rainfall mean the area lends itself well to the preservation of multiple proxies in the region's many wetlands, a very valuable resource for palaeoecological studies in the generally dry southern Africa. However, there have been few quantitative palaeoclimatic studies taking advantage of this, and none using multiple sites within the Drakensberg-Maloti region. This study represents the first attempt at such a regional synthesis. We utilised all published pollen records from the area to produce a dataset from which the standard Modern Analogue Technique was performed to reconstruct mean temperature of the warmest month, mean annual precipitation, mean winter precipitation and an annual climatic moisture index for the past 8000 years. The moisture index showed a very low amount of variation, most likely due to the low amount of variation in the modern climate data associated with the sites in the modern calibration dataset, being so near the saturation point of this index. We found evidence for a cool, wet period at around 2 cal ka BP, a period that has been identified in records from across South Africa as a Neoglacial, and which is consistent with diatom and sedimentary records from the Drakensberg-Maloti.
... Our results shed light on the relationship between patterns of behavioural change and palaeoenvironmental variability in southeastern southern Africa specifically, and on hunter-gatherer behavioural variability in montane environments more generally. increasingly detailed reconstructions of regional palaeoenvironments (for reviews see Fitchett et al., 2016;Stewart and Mitchell, 2018a), has granted improved understandings of the regional archaeological sequence from MIS 3 onwards. The dramatic relief of the Maloti-Drakensberg region structures strong https://doi. ...
... Arguably the most conspicuous of these was the transition from the Middle to the Later Stone Age, which included a shift to miniaturized lithic technologies and the more regular and widespread adoption of compound hafted tools and symbolic material culture, including beads and other ornaments. Large-scale shifts in temperature and rainfall over this period, climaxing over the Last Glacial Maximum (LGM: regionally defined as 24-17.5 kcalBP; Chevalier and Chase, 2016;Fitchett et al., 2016), drove substantial palaeoenvironmental changes across much of the subcontinent, potentially framing adaptive responses from hunter-gatherer populations. ...
... The timing of the LGM we use here follows a regionally appropriate definition for the summer rainfall region from Chevalier and Chase (2016) (24-17.5 ka). In the Maloti-Drakensberg Mountains, marginal glaciation is only securely, although not very tightly, dated towards the end of the LGM at c. 19.5-17.5 kcalBP (see review in Fitchett et al., 2016), suggesting that highland sites were abandoned prior to the development of fully stadial conditions. Stewart and colleagues (2016) have argued that highland Lesotho would have provided a refuge for groups from lower-lying areas during periods of drying or instability given their considerable attractions: greater topographic and resource diversity, an abundance of rockshelters, high quality lithic raw Fig. 6. ...
... Temperature reconstructions for the region are less robust, but include evidence for cold conditions during the late Pleistocene (Fitchett et al., 2016b) and brief cold periods coinciding with the Younger Dryas (Loftus et al., 2015), 8.2 kyr event (Fitchett et al., 2017b) and the Little Ice Age (LIA, ca. AD 1250-1850) (Fitchett et al., 2016a). Although the exact timing and duration remains unclear, warmer than present conditions, such as the global Holocene Altithermal, have been confirmed for eastern Lesotho and the South African Drakensberg (Fitchett et al., 2016b;Neumann et al., 2014). ...
... Although the exact timing and duration remains unclear, warmer than present conditions, such as the global Holocene Altithermal, have been confirmed for eastern Lesotho and the South African Drakensberg (Fitchett et al., 2016b;Neumann et al., 2014). The late-Holocene (last ca. 2 millennia) has not been adequately studied in Lesotho (Fitchett et al., 2016a;Parker et al., 2011), and particularly multiproxy approaches are lacking for the periods associated with the LIA and the Medieval Climatic Anomaly (MCA, ca. AD 900-1250). ...
... The δ 13 C can also be affected by large-scale shifts between major terrestrial vegetation groups (grasses, shrubs, herbs); however, previous pollen studies suggest a relatively stable representation between these functional types during the late-Holocene (Fitchett et al., 2016a(Fitchett et al., , 2016bNorström et al., 2014Norström et al., , 2009Lodder et al., 2017), with grasses and sedges together representing 60-80% of all recorded taxa since 8000 cal. yrs BP (Fitchett et al., 2016b). ...
Article
The eastern Lesotho highlands are of considerable hydrological importance to southern Africa as a so-called ‘water tower’ for the surrounding region. Here, we contribute proxy-data inferring climate and vegetation changes over the past 1600 years, assessing in parallel inorganic and organic chemical analyses on a sediment core from Ladybird wetland, eastern Lesotho. Several proxies were used to determine changes in local vegetation dynamics, productivity, hydrology (δ¹³ C, δ¹⁵ N, C/N, TOC) and the input and source of the detrital components (Ca/Ti, CIA). The first part of the multi-proxy record (AD 400–800) shows stable terrestrial conditions and low detrital input, followed by higher variability in almost all proxies between ca. AD 900 and 1200. The δ¹³ C record infers a higher proportion of C4 vegetation, tentatively associated with higher temperatures during this phase, coeval with the Medieval Climate Anomaly (MCA). After AD 1200, local conditions change gradually from purely terrestrial, towards the typical wetland environment prevailing today. A higher proportion of C3 plants and possibly an increase in aquatic organisms within the organic matrix corresponds with decreasing detrital input, suggesting locally high available moisture in this part of Lesotho during the Little Ice Age (LIA). Although age-model constraints impedes a robust regional comparison, the inferred climate variability is discussed as a tentative response to enhanced mid-latitude cyclonic activity during LIA, and the variable MCA climate conditions as indirectly dictated by changes in solar activity.
... Arguably the most conspicuous of these was the transition from the Middle to the Later Stone Age, which included a shift to miniaturized lithic technologies and the more regular and widespread adoption of compound hafted tools and symbolic material culture, including beads and other ornaments. Large-scale shifts in temperature and rainfall over this period, climaxing over the Last Glacial Maximum (LGM: regionally defined as 24-17.5 kcalBP; Chevalier and Chase, 2016;Fitchett et al., 2016), drove substantial palaeoenvironmental changes across much of the subcontinent, potentially framing adaptive responses from huntergatherer populations. ...
... The timing of the LGM we use here follows a regionally appropriate definition for the summer rainfall region from Chevalier and Chase (2016) (24-17.5 ka). In the Maloti-Drakensberg Mountains, marginal glaciation is only securely, although not very tightly, dated towards the end of the LGM at c. 19.5-17.5 kcalBP (see review in Fitchett et al., 2016), suggesting that highland sites were abandoned prior to the development of fully stadial conditions. Stewart and colleagues (2016) have argued that highland Lesotho would have provided a refuge for groups from lower-lying areas during periods of drying or instability given their considerable attractions: greater topographic and resource diversity, an abundance of rockshelters, high quality lithic raw Fig. 6. ...
Article
Sehonghong rock shelter is situated in the eastern Lesotho highlands, a climatically extreme region of southern Africa. The site is one of a handful in southern Africa that preserves human occupations before, during, and after the Last Glacial Maximum (LGM). The site's long and well-preserved sequence makes it relevant to addressing questions of human mobility, subsistence, and technology in relation to broader environmental change. Here we present a Bayesian-modelled radiocarbon chronology for the LGM and terminal Pleistocene occupations at Sehonghong. Our model incorporates previously published radiocarbon dates and new accelerator mass spec-trometry ages. We also present archaeological evidence to test the hypothesis that Sehonghong was occupied in a series of punctuated events, and that some of these occupations were more intensive than others. Previous chronological and archaeological data were insufficient for testing these hypotheses. The new dates and archaeological data confirm that the site was occupied intensively in the early LGM and immediately thereafter. The site was otherwise occupied sporadically. We find that greater site occupation density is not always correlated with intensified use of local resources as measured by increased bipolar reduction and fish consumption. The new dates further confirm that Sehonghong contains some of the oldest evidence for systematic freshwater fishing in southern Africa. The availability of fish, a high fat protein source, probably stimulated human occupation, however sporadic, of such montane environments during cooler and drier periods. These findings suggest behavioural variability in response to shifting mobility and subsistence strategies. Our brief discussion informs upon hunter-gatherer occupation of southern African montane environments more broadly and human behavioural variability during the LGM.
... Further research has interpreted conspicuous debris ridges on the south-facing aspect of the Sekhokong Range as small glacial moraines (Mills et al., 2009). While these past studies have provided valuable information on contemporary geo-ecological stresses and some insights into past environments in the region, no biological proxies have yet been investigated in these records, limiting their interpretative capacity and potential for regional corroboration (Grab et al., 2005;Fitchett et al., 2016). ...
... Any climatic change can potentially lead to the extirpation of certain plant groups, as particularly low temperatures restrict elevational range shifts (Parmesan and Yohe, 2003;Carbutt and Edwards, 2006;Inouye, 2008). Botanical responses to smaller climatic shifts are therefore more likely to be detected at high altitudes than at adjacent down-slope locations (Fitchett et al., 2016). ...
Article
The eastern Lesotho Highlands host an array of periglacial and glacial geomorphic features. Their analysis has provided past climate interpretations predominantly for cold periods, yet no multi-proxy temporally continuous palaeoenvironmental records exist. This study presents a palaeoenvironmental reconstruction based on sedimentary characteristics, fossil pollen and diatoms from an alpine wetland located in the Sekhokong Mountain Range. The record commences in the late Pleistocene with a wet period from ?16?450 to 14?440 cal a BP, interrupted by dry conditions from ?16?350 to 15?870?cal a BP. From ?14 150 to 8560 cal a BP, drier conditions are inferred, slowly transitioning to warmer, wetter conditions. Warmer, dry conditions are inferred for ?8560?7430?cal a BP, followed by cold, wet conditions from ?7280 to 6560?cal a BP. A dry, warmer period occurs from ?6560 to 3640?cal a BP indicated by pollen, diatom and sedimentary records, followed by cool, wet conditions from ?3400 to 1200?cal a BP. The period from ?1110?cal a BP to the present is characterized by progressive drying. Pronounced cold events are detected from the diatom record. Moisture records appear relatively specific to the topographic setting of Sekhokong near the Great Escarpment edge, probably driven by orographically constrained synoptic controls.
... South Africa is therefore similarly characterised by summer, winter, and year-round rainfall regimes (Roffe et al., 2019). There has been considerable effort in South African palaeoclimate science to quantify the changes in rainfall seasonality of the late Quaternary, as this has significant implications regarding firstly the veracity of palaeogeomorphological evidence for niche glaciation in the eastern Lesotho highlands, and secondly the use of the landscape by Stone Age communities (Fitchett et al., 2016a;Stewart and Mitchell, 2018). The evidence for niche glaciation suggests that the winter rainfall zone may have extended as far north as Lesotho, but this same evidence requires additional proxies to validate these interpretations (Mills et al., 2012). ...
Article
Mounting evidence suggests that the Southern Westerly Winds were significantly equatorially displaced and more intense during the last glacial maximum (LGM), prompting deliberate research identifying proxies to reconstruct these changes. This has focused on rainfall seasonality to track changes in major circulation patterns across the southern hemisphere midlatitude regions. Using a common methodology to reconstruct climatic changes aids comparability and makes it easier to draw significant conclusions regarding general circulation movements. We assess the applicability of Coetzee's (1967) Poaceae:Asteraceae pollen ratio, which has been used successfully in South Africa, in the Australian context. The ratio scores from modern samples fail to capture the weak seasonality in the southeast and on Tasmania but is successful for the rest of the continent. The periods of greatest change compared to present day match known periods of distinct climatic events, namely the mid-Holocene (6–7 cal ka BP), the last deglacial period (15–17 cal ka BP), and two periods during the LGM (20–22 and 31–33 cal ka BP), suggesting large parts of Australia experienced a “double peak” of rainfall seasonality change during the LGM. This confirms that the Poaceae:Asteraceae pollen ratio can be used on records outside of South Africa.
... Derived from both archaeology-and non-archaeology-bearing sedimentary sequences, they reflect the work of multiple researchers over many years, often operating in logistically challenging conditions (e.g. Fitchett et al., 2016aFitchett et al., , 2016bFitchett et al., , 2017aGrab and Mills, 2011;Grab et al., 2005;Parker et al., 2011;Plug and Mitchell, 2008;Roberts et al., 2013;Smith et al., 2002;Stewart et al., 2012Stewart et al., , 2016. Individually and collectively these archives nevertheless still contain many spatiotemporal gaps. ...
Article
The Maloti-Drakensberg Mountains are southern Africa's highest and lie at a crucial interface between the sub-continent's drier, colder, more seasonal interior and its perennially productive subtropical coastal belt. Their location, high elevation, and topography make them ideal for exploring human responses to late Quaternary climatic change. This paper reviews and synthesizes palaeoclimatic and palaeoenvironmental data from the Maloti-Drakensberg region over the past 50,000 years. It then employs 325 calibrated radiocarbon dates to examine human occupational trends across the region and its component parts, discuss human-environment dynamics over this time-span, and explore patterning between particular phases of climatic change and the timing, mode, and motives of its exploitation by people. Key findings are that the region's Lesotho core may have served as a refugium for human populations during drier, more unstable climatic periods and that intensified exploitation of freshwater fish likely helped address resource stress in cooler ones. An agenda for future palaeoenvironmental and archaeological research is also mapped out.
... This in turn would require a significant northward shift in the extent of the Westerlies to~28 S. The timing of these occurrences of high ratio scores at Mafadi, Sekhokong, Clarens, Braamhoek and Florisbad does not reflect uniformity of the influence of winter-rainfall seasonality observed for the southwestern tip of the Cape. This is not, however, unexpected, due to the complex topography of the region (Sene et al., 1998;Fitchett et al., 2016a). The varied topography would induce orographic rainfall at the first approach of the mid-latitude cyclone, with the potential for moisture transported further north to the latitudinal extent of the Westerlies being dependant on the strength of the frontal system (Sene et al., 1998;Mills et al., 2012). ...
Article
Situated at the transition between the mid-latitudes and the sub-tropics, southern Africa has a climatic dichotomy between winter- and summer-rainfall zones (WRZ and SRZ). The latitudinal extent of the winter-rainfall zone during the late Pleistocene remains contentiously debated within the regional palaeoscience literature. One method posited to reflect the seasonality of rainfall at a given location throughout late Pleistocene records for South Africa is the ratio of fossil pollen Asteraceae to Poaceae. Although adopted for a range of southern African locations, the veracity of this method has not been tested. This study explores the extent to which this ratio can discriminate between the SRZ and WRZ, and the extent of the region subject to fluctuation during the late Quaternary. The ratio is found to successfully discriminate regions which are, and would have remained during the past 20,000 cal yr BP, in the SRZ and WRZ exclusively. On the basis of these statistics, it appears that WRZ conditions can be inferred from ratio scores >0.6 and SRZ conditions from scores <0.2. For locations situated between 28 and 32°S, no clear discrimination can be made. It is argued that this region has been subjected to fluctuations in the latitudinal extent of the Westerlies and consequently in the influence of mid-latitude cyclones over the past 20,000 cal yr BP, with the rugged topography of the Drakensberg Mountains resulting in a complex precipitation climatology controlled by both frontal and orographic uplift.
... The only detailed Holocene palaeoenvironmental records for Lesotho stem from the western lowlands, based on charcoal assemblages and grazer tooth enamel in the Phuthiatsana-ea-Thaba Bosiu Basin (Esterhuysen and Mitchell, 1996;Roberts et al., 2013;Smith et al., 2002), sedimentary and phytolith records from an exposed sedimentary sequence in a gully of the Tsoaing Basin and from central Lesotho, based on phytoliths and stable isotopes (Parker et al., 2011). Many of these studies explore palaeoenvironmental proxies extracted from archaeological excavations and therefore are limited because of potential biases of material selection (Esterhuysen and Mitchell, 1996;Fitchett et al., 2016). ...
Article
The eastern Lesotho Highlands experience climate patterns distinct from those of surrounding lower altitude regions, representing a niche environment with a unique biodiversity, leading to well-adapted but restricted vegetation. This study explores changes in the Holocene composition of diatoms and pollen at southern Africa’s highest altitude wetland (Mafadi: 3390 m a.s.l.). The palaeoenvironmental record for Mafadi Wetland indicates fluctuations between cold, wet conditions, prevalent between ~8140 and 7580 cal. yr BP and between ~5500 and 1100 cal. yr BP, and warmer, drier periods between ~7520 and 6680 cal. yr BP and between ~6160 and 5700 cal. yr BP. Marked climatic variability is noted from ~1100 cal. yr BP with colder conditions at ~150 kyr BP. Notably, the first of these cold periods occurs soon after the Northern Hemisphere 8.2 kyr event, while a second period of notably cold conditions occurs around 1100 cal. yr BP. Variability exists between the moisture reconstructions presented in this study and those from adjacent lower altitude sites, which is hypothesised to reflect variations in the strength and extent of the Westerlies throughout the Holocene.
Article
The process for the formal ratification of the proposed Anthropocene Epoch involves the identification of a globally isochronous stratigraphic signal to mark its starting point. The search for a Global Boundary Stratotype Section and Point (GSSP), a unique reference sequence that would be used to fix the start of the epoch, is in progress but none of the candidate sections are located in Africa. We assessed the currently available stratigraphic evidence for the possible markers of the Anthropocene in southern Africa and found that, although most markers have been identified in the region, the robustly dated, high resolution records required for the GSSP are very sparse. We then assessed the extent and stratigraphic resolution of a range of potential natural archives and conclude that a small number of permanent lakes, as well as marine sediments, corals and peats from selected locations in southern Africa could provide the temporal resolution required. With sufficient chronological control and multi-proxy analyses, one of these archives could provide a useful auxiliary stratotype thereby helping to confirm the global reach, and extending the utility, of the selected Anthropocene GSSP.
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Southern Africa sits at the junction of tropical and temperate systems, leading to the formation of seasonal precipitation zones. Understanding late Quaternary paleoclimatic change in this vulnerable region is hampered by a lack of available, reliably-dated records. Here we present a sequence from a well-stratified sedimentary infill occupying a lower slope basin which covers 17,060 to 13,400 cal yr BP with the aim to reconstruct paleoclimatic variability in the high Drakensberg during the Late Glacial. We use a combination of pollen, total organic carbon and nitrogen, δ ¹³ C, Fourier transform infrared spectroscopy attenuated total reflectance (FTIR-ATR) spectral and elemental data on contiguous samples with high temporal resolution (10 to 80 years per sample). Our data support a relatively humid environment with considerable cold season precipitation during what might have been the final stage of niche-glaciation on the adjoining southern aspects around 17,000 cal yr BP. Then, after an initial warmer and drier period starting ~15,600 cal yr BP, we identify a return to colder and drier conditions with more winter precipitation starting ~14,380 cal yr BP, which represents the first local evidence for the Antarctic Cold Reversal (ACR) in this region. On decadal to centennial timescales, the Late Glacial period was one marked by considerable climatic fluctuation and bi-directional environmental change, which has not been identified in previous studies for this region. Our study shows complex changes in both moisture and thermal conditions providing a more nuanced picture of the Late Glacial for the high Drakensburg.
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Ntsikeni wetland is one of the largest high-altitude wetlands in southern Africa (∼1795 m asl) located in the Swartberg area of the foothills of the Maloti-Drakensberg, southern Africa. The site has been designated a Ramsar Wetland of International Importance which, with limited anthropogenic influence, renders it ideal for palaeoenvironmental investigation. This study presents a pollen-derived palaeoenvironmental reconstruction for Ntsikeni, spanning the period ∼25,100-650 cal BP, one of the longest, continuous records for southern Africa. The record commences with evidence of coldest conditions consistent with the peak of the Last Glacial Maximum. This is followed by progressive climatic amelioration, culminating in a warm, moist period from ∼7500 to 5500 cal BP. Pronounced cold periods at ∼13,500 cal BP, ∼8500 cal BP and ∼4000 cal BP are broadly consistent with coeval global scale temperature fluctuations. Two distinct dry events are inferred from the pollen record, spanning ∼19,600-18,000 and ∼6500-4900 cal BP. Wet events occur more frequently throughout the record, resulting in fluctuations in moisture availability, and are inferred to result in the expansion and contraction of the wetland extent similar to those recorded in the palaeorecords of the Lesotho Highlands. The Ntsikeni record provides a longer-term temporal framework with which the shorter sequences for adjacent sites in the Maloti-Drakensberg can be compared, and supports evidence for the significance of the rugged topography in inducing lags in moisture transitions.
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The results of the analysis of charcoal assemblages from three rock-shelters in the Caledon Valley of western Lesotho are discussed. In addition to clear differences in species composition, attributed to differential frost intensity, between shelters lying close to and further away from the Phuthiatsana-ea-Thaba Bosiu river, our data suggest that there were two mesic episodes in the early/mid-Holocene, one centred around 8700 yr BP and the second, which was significantly wetter, between 6900 and 5000 yr BP. Drier conditions prevailed between these two periods. Our conclusions match those obtained from charcoal and faunal analyses elsewhere in the Caledon Valley, as well as sedimentary observations from the Lesotho highlands. However, the palaeoclimatic record of western Lesotho appears to have been partly out of phase with that of South Africa's north Eastern Cape Province. The restriction of Acacia sp. to very recent horizons and the absence from our assemblages of several common present day firewoods that are weed invaders of disturbed land may be consistent with a recent age for ongoing xerification of plant communities. Further observations on patterns of fuel selection evident in our data are also made and the implications of our findings for hunter-gatherer settlement of the wider Caledon Valley discussed.
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Evidence for human occupation of southern Africa's high-altitude Maloti–Drakensberg Mountains is surprisingly common in the last glacial, yet the attraction of this relatively severe, cold region for hunter-foragers remains unclear. Sehonghong Rockshelter (1870 m asl), in the eastern Lesotho Highlands, provides evidence for human occupation spanning Marine Isotope Stage 3 through the late Holocene. Excellent organic preservation provides opportunities for establishing multiple palaeoenvironmental proxy records to address this conundrum. In high-altitude zones, the proportions of C 3 and C 4 plants archived in soil organic matter and faunal enamel provide sensitive indicators of past temperature shifts. We first extended the radiocarbon chronology to ca. 35 ka using ABOx-SC radiocarbon dates of charcoals. Next we analysed stable isotopes in soil organic matter from the sedimentary sequence, and in faunal tooth enamel from the newly dated lower strata. The results suggest, predictably, that C 3 vegetation and low temperatures prevailed until early warming at ca. 15 ka, with a series of sharp shifts thereafter. Low values for d 13 C and d 18 O in faunal enamel ca. 33 ka suggest a negative temperature excursion at this time, and potentially greater precipitation as snowfall in the highlands compared with lower altitudes.
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Significant numbers of fish bones have been identified from three Later Stone Age sites in the Lesotho Highlands. They comprise two rock-shelters on the Sehonghong River, Sehonghong and Pitsaneng, and one open-air campsite on the banks of the Senqu River, Likoaeng. Pitsaneng was occupied during the second millennium AD and Likoaeng for much of the Post-classic Wilton, ca 4000-1200 bp. Sehonghong, in contrast, has a history of fish exploitation spanning at least 26,000 years, from before the Last Glacial Maximum (LGM) to the second millennium AD. Fish were identified from all levels of this site, but three distinct periods can be distinguished when fishing was of particular importance, namely around 20,000 bp, 12,200 bp and again after 1700 bp. The same five species were identified throughout the deposits. Labeobarbus aeneus overwhelmingly dominates all the assemblages, but Labeo capensis and Austroglanis sclateri may have become more important during the Holocene. Standard Length estimates reveal that fishes caught during the Holocene were mostly of pre-breeding size, whereas the fishes caught during the Pleistocene were mostly of breeding age. Sehonghong and Pitsaneng show similarities in the relative abundances of different fish, but present a marked contrast with Likoaeng. The likely ages of the fish also differ. Overall, the Sehonghong sequence confirms the late Pleistocene antiquity of fishing in the interior of southern Africa and helps contest suggestions that fishing only became important in the late Holocene.
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The high-altitude grasslands and wetlands of eastern Lesotho (Maloti-Drakensberg) have been transformed by livestock grazing, burning and fuelwood collection over the past decades. Multifunctional utilisation of vegetation resources contributes to contemporary land cover changes in the peripheral high mountain region of southern Africa. The sustainability of regional land use patterns has been challenged by ongoing grassland degradation and accelerated soil erosion as a result of a generally high and continuous anthropo-zoogenic impact. A better understanding of recent landscape changes and land degradation in pastorally transformed environments requires an assessment of natural resource potentials, vegetation status and erosion processes.
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Quaternary palynology as a discipline evolved historically in northern hemisphere temperate environments where conditions favourable to the preservation of pollen facilitated its application to the reconstruction of vegetation history and, through interpretation, palaeoenvironments. Such studies in Africa started much later and, in southern Africa, were only initiated when E.M. van Zinderen Bakker joined the Department of Botany in what is now known as the University of the Free State in the late 1940s. This paper explores the early work and influence of van Zinderen Bakker and his first PhD student, J.A. (Joey) Coetzee and tracks the course of the emerging science through to the present day. The sustained basis of van Zinderen Bakker's work was pollen analysis and the laboratory quickly developed a substantial pollen reference collection to support the research. Forays into tropical Africa were followed by work on organic sediments in South Africa. The relatively limited occurrence of suitable wetland deposits in the region led to the group exploring opportunities for what were (at least in the 1970s and 1980s) regarded as less ‘conventional’ deposits, including pan sediments, cave sediments and even coprolites. A second Quaternary palaeoecological research centre was developed by the author, initially at Rhodes University, and led to palaeoecological laboratories being established at the University of Cape Town and subsequently at the University of KwaZulu-Natal. Meanwhile, at the University of the Witwatersrand, a strong palaeontological and palaeoanthropological research thrust led to the development of related studies there. While typically associated with only small numbers of Masters and PhD students, initiatives at all three of these centres have been associated with an increase in the number and geographical range of studies as well as in the diversity of palaeoecological proxies. The rise in international collaboration together with methodological developments and improvements in temporal resolution have enabled Quaternary palynological studies in the region to play an important role in the understanding of past environments in southern Africa.
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The Drakensberg Alpine Centre (DAC) comprises the 40,000km 2 high-altitude range of hills, mountain peaks and escarpment plateau bordering the eastern interior of southern Africa. Renowned for its species-rich flora and high levels of endemism, the DAC is here shown to support over 2800 specific and infraspecific native taxa, with c.16% of the angiosperm taxa being endemic, the latter equalling the flora of KwaZulu-Natal. Comparisons of the DAC's largest families and genera are made with those of the Cape Floral Region and KwaZulu-Natal, and the largest families are also compared with those of the Afromontane and Pondoland regions. In addition, comparisons are made between the high-altitude floras of southern and south-central Africa on the basis of their Cape element.
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Alpine cryospheric hazards are becoming increasingly prominent under current global/regional climate change scenarios and receiving wide scientific coverage from, in particular, northern hemisphere mountain regions associated with glaciers, permafrost, and extensive seasonal snow cover. However, there is a general paucity of knowledge and attention on cryospheric hazards associated with mountain environments only occasionally/rarely impacted by heavy seasonal snowfalls or severe frost events, particularly those in developing and southern hemisphere regions. Prolonged snow cover in the Lesotho Highlands sometimes carries the consequence of human and livestock deaths owing to isolation and exposure in this developing region. We use daily Moderate Resolution Imaging Spectroradiometer snow cover images for the period 2003–2010, to establish the frequency, extent, and timing of snowfalls across Lesotho. In addition, a digital shape file containing the location, name, and district attributes of 2,016 villages across Lesotho was used to assist in the construction of a village exposure to snow index. A ranking system was applied to each village according to the seasonal duration of snow cover, and the accessibility and proximity to the nearest road. Snowfalls occur on average between 1 and 8 times per annum, with village exposure to snow (potential vulnerability) being generally low, particularly for the lowlands and Senqu River Valley. However, the study identifies that some high-altitude (>2,500 m) villages such as Thoteng, Letseng-la-Terae, and Mabalane are, on occasion, highly exposed to prolonged snow cover, and particularly so during the mid-snow season of July/August. We demonstrate the importance of applying spatiotemporal assessments on infrequent snow occurrences (which carry associated hazards) in developing mountain regions such as Lesotho, with implications to reduce livelihood risks through improved disaster preparedness and a well-informed, focused emergency response.
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This paper provides a preliminary chronostratigraphic and palaeoenvironmental framework for the Late Pleistocene archaeological sequence at Melikane Rockshelter in mountainous eastern Lesotho. Renewed excavations at Melikane form part of a larger project investigating marginal landscape use by Late Pleistocene foragers in southern Africa. Geoarchaeological work undertaken at the site supports in-field observations that Melikane experienced regular, often intensive, input of groundwater via fissures in the shelter's rear wall. This strong hydrogeological connection resulted in episodic disturbances of the sedimentary sequence, exacerbated by other processes such as bioturbation. Despite this taphonomic complexity, a robust chronology for Melikane has been developed, based on tightly cross-correlated accelerator mass spectrometry (AMS) C-14 with acid-base-wet oxidation stepped-combustion (ABOx-SC) pretreatment and single-grain optically stimulated luminescence (OSL) dating. The results show that human occupation of Melikane was strongly pulsed, with episodes of Late Pleistocene occupation at similar to 80, similar to 60, similar to 50, similar to 46-38 and similar to 24 ka. At least three additional occupational pulses occurred in the Holocene at similar to 9 ka, similar to 3 ka and in the second millennium AD, but these are dealt with only briefly in this paper. Implications of the Late Pleistocene pulsing for the colonisation of high elevations by early modern humans in Africa ahead of dispersals into challenging landscapes beyond the continent are discussed. (c) 2011 Elsevier Ltd and INQUA. All rights reserved.
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TWO DISTINCT DATA SETS ON THE QUATERnary geomorphology of the Lesotho highlands, on the north-facing hollows and the coarse colluvial slope deposits, are reviewed and reconciled in a new model of landscape development. To date, the interpretation of each set has resulted in conflicting palaeonvironmental models. However, the combined record illustrates a distinct asymmetry in slope development and denudational history in the highlands. Based on existing regional data on valley asymmetry, a new model for Quaternary slope dynamics is presented and its palaeoenvironmental implications discussed. It highlights the relative importance of chemical weathering and slope wash processes, with a periglacial overprint on slopes of cooler aspect where sediments are preserved. Areas for further research to test the new model are also presented.
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The activities of hunter-gatherers are often captured in rockshelters, but here the authors present a study of a riverside settlement outside one, with a rich sequence from 1300 BC to AD 800. Thanks to frequent flooding, periods of occupation were sealed and could be examined in situ. The phytolith and faunal record, especially fish, chronicle changing climate and patterns of subsistence, emphasising that the story here is no predictable one-way journey from huntergatherer to farmer. Right up to the period of the famous nineteenth-century rock paintings in the surrounding Maloti-Drakensberg region, adaptation was dynamic and historically contingent.
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A peat-sequence covering the last 16 ka (16 000 cal. yr BP) from Braamhoek wetland, eastern South Africa, was analysed in terms of phytolith and diatom composition. The fossil peat was rich in phytoliths, while diatoms were less prominent, probably as a result of degradation during wetland plant growth associated with silica uptake. With this study we present the first continuous phytolith and diatom record from South Africa covering the Late Pleistocene and Holocene period. The phytolith assemblages indicate a clear dominance of C3-grasses within the wetland throughout the sequence. The fossil diatom record infer changes in past moisture conditions. Unlike the modern wetland, which is dominated by benthic and aerophilic diatoms, the Late Pleistocene—early Holocene wetland favoured growth of planktonic species. Abundance of planktonic diatoms suggests three main phases when water depth was deeper than today; at c.13.6 ka, 11.3 ka and 10.4—10.0 ka. These indications of past fluctuations in humidity mostly provide confirmation of previously published indications of pollen, charcoal fragments and isotopes in the same core, but the siliceous microfossil data also help to refine the paleo-environmental interpretation of the sequence.
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This paper summarizes the evidence adduced from two sites, at Sani Tip and adjacent to Tlaeeng Pass, and draws environmental inferences. Dates from the organic sediments permit a firm chronology which corresponds well with the Quaternary chronology proposed for the eastern Highveld, summer rainfall region. The Lesotho evidence provides confirmation of that chronology and presents further evidence for high altitude environments. -from Author
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Sequences of sediments exposed by gullies incising into deposits held within cirques in the highlands of Lesotho have already enabled a Quaternary chronology to be established for high altitudes in eastern southern Africa. The chronology was fixed with twelve radiocarbon dates from Lesotho: eight from Sani Top and four from Tlaeeng. Two additional dates are now available from Tlaeeng Section B2, thus permitting further refinement of the Holocene record. This paper reports the two new dates and discusses their significance with respect to the later Holocene chronology.
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Results of the excavation of four small rock-shelters in northern, western and southern Lesotho are presented. All the deposits date to the second half of the Holocene. Combining these data with others from intensive field survey in the Phuthiatsana-ea-Thaba Bosiu Basin and along the Southern Perimeter Road, pronounced differences in settlement pattern are indicated between the early and the late Holocene, along with the possibility of a hiatus of considerable duration in Later Stone Age occupation of the Caledon Valley. Marked inter-assemblage variability on a local scale is also evident. Archaeological evidence for interaction between hunter-gatherers and agropastoralists is considered and the potential for further research in this field in Lesotho is stressed.
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The late Holocene assemblages with pottery from recent excavations at Sehonghong rock shelter, Lesotho, are described. Reoccupation of Sehonghong after a gap of several millennia seems to have been part of a general pattern in the southern Drakensberg and Maluti Mountains at this time, perhaps linked to the end of the period of neoglacial advance. Radiocarbon dates associated with pottery at Sehonghong are consistent with recent suggestions that ceramics were adopted in southeastern southern Africa in advance of the spread of an agricultural economy into the region. The establishment of Early Iron Age populations in KwaZulu-Natal may, however, have hindered the access of people using Sehonghong to seashell ornaments derived from the Indian Ocean coast. Conversely, large numbers of ostrich eggshell beads and finds of pressure-flaked stone arrow tips from Sehonghong and other sites in the Lesotho highlands point to a strengthening of social ties with areas to the west during the late Holocene.
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An increasing number of large dam projects present a major threat to cultural heritage in much of Africa. This paper asks how such destructive projects can be held to account; not only to mitigate damage, but also to develop local heritage management structures and increase public awareness. It focuses on the situation in Lesotho, which has a history of large dam projects, but a severely under-resourced archaeological and heritage management community. The main emphasis is on a recent and ongoing project in advance of the Metolong Dam in western Lesotho that was founded with training and skills transfer as a primary aim. In addition to some practical suggestions for Lesotho that take into account its particular geopolitical context, this case study brings three broader interrelated issues into view, none of which are new, but all of which deserve fresh attention: the unsuitability of a solely commercial, contract-based response to the threat from development; the negative effects of using unskilled 'labour'; and the imperative to develop an archaeology that is relevant to and actively involves the rural African communities within which we work.
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Two aspects of the study of prehistoric seasonal mobility are discussed. First, the viability of such studies is questioned in the light of the considerable range of environmental variation that can be shown to exist over any given period of time. Second, the assumption that hunter-gatherer adaptive strategy throughout southern Africa always involved some form of seasonal mobility is tested by the use of historical data from the northern Cape. It is suggested that current models of prehistoric seasonal mobility represent idealized abstractions that in all probability do not reflect what actually happened in the past.
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A palynological and sedimentological record from the Mahwaqa Mountain in KwaZulu-Natal, South Africa, provides evidence of the vegetation dynamics in this part of the Grassland Biome during the last c. 18,000 years. The wetland is located at 1,850 m on an isolated outlier of the Ukhahlamba–Drakensberg Mountain range on an ecotone along a climatic gradient. The vegetation responded to humidity and temperature changes during the late Pleistocene and Holocene. The period c. 18,000–13,500 cal. BP is characterized by high Ericaceae and Restionaceae percentages and decreasing values of charred particles, indicating cool conditions. Around 13,500–8,500 cal. BP, Ericaceae were gradually replaced by Poaceae, signaling climate warming. Growing environmental wetness during the same time period is inferred from Phragmites-type and Cliffortia pollen percentages. Since c. 8,500 cal. BP, Cliffortia, Restionaceae, and Phragmites-type percentages have maintained low levels. Ericaceae were almost completely replaced by grasses and Asteraceae by c. 7,500 cal. BP. All indications are that warm and fluctuating moisture conditions followed until 4,600 cal. BP but they became driest between c. 4,600 and 3,500 cal. BP, when high Asteraceae, Pentzia-type and Scabiosa percentages were prominent. From c. 3,500–800 cal. BP, the increase of sedges, Aponogeton and grass pollen (including Phragmites-type) at the expense of Asteraceae pollen suggests the return of slightly more humid conditions. Since c. 1,000 cal. BP an increase of water demanding Podocarpus and Cliffortia occurred. Pine pollen indicates the recent introduction of alien plants in the 19th and 20th centuries.
Article
The dimensions and sorting characteristics of miniature sorted stripes at Mafadi summit in the high Drakensberg are determined. Water induced mechanisms, wind action, anthropogenic factors, frost heave and thermal creep are considered as possible contributing factors responsible for contemporary particle movement and stripe formation on the Mafadi slopes. The sorted stripes are frost-induced landforms which are degrading under present environmental conditions. It is suggested that the pronounced altitudinal climatic cooling at higher Lesotho summits has prevented vegetation establishment but enabled the preservation of cold-region landforms.
Article
This is a comment on: Hall, K., 2010. The shape of glacial valleys and implications for southern African glaciation. South African Geographical Journal, 92, 35–44.
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Although alpine pans have been reported from a variety of mountain regions, these have received limited research attention and are thus amongst the least known of ‘closed basins’. This study investigates macro- and fine-scale morphological attributes and the process dynamics of alpine turf exfoliation pans in the high Drakensberg of Lesotho, southern Africa. Climate data (temperature, precipitation and wind) are used to better ascertain climate–surface process linkages and how these may be associated with the observed morphological phenomena. Thirty pans were assessed for both macro- and fine-scale aspect-controlled morphological attributes. During 2005, Tinytag™ temperature loggers recorded ground temperatures on various pan riser aspects to establish the potential for cryogenic activity. Similarly, wind speed and direction data from 2001 were used to identify the potential role of wind as an erosion and transportation mechanism. The number and total weight of detached turf clumps accumulated at the base of various pan riser aspects were determined in July 1999, September 2001 and September 2004. It is suggested that the pans originated through initial turf disruption by animal trampling and turf burning, followed by the cryogenic up-heave of sediments. The pans typically elongate towards the southeast as they enlarge, demonstrate most active erosion on eastern and southeastern riser aspects, and host seasonal micro-echo and micro-climbing dunes along such riser aspects. It is concluded that an annual cyclic (seasonal) pattern of contemporary climate-driven geomorphic processes, dominated by strong northwesterly winds, control the fine-scale morphological evolution of alpine turf exfoliation pans in the Lesotho highlands.
Article
The late Holocene environmental history of the Lesotho highlands, southern Africa, is poorly understood with few detailed studies to date. At Likoaeng, Senqu Valley, Lesotho, a 3m stratified sedimentary sequence from an open-air archaeological site records vegetation development for the period 3400–1070cal.BP. Phytolith analyses and bulk sediment organic matter δ13C indicate that C4 grassland dominated the lower part of the sequence until approximately 2960cal.BP when there was a switch to C3 Pooid grassland (2960–2160cal.BP). Also noted was a change from hunting mainly bovids to a dominance of fishing at the site. The change in grassland type and archaeological subsistence strategies corresponds with an episode of neoglacial cooling and the expansion of Alpine sourgrasses into lower altitudes. From 2160 to 1600cal.BP grassland became a mix of C3 and C4 types and by 1600–1070cal.BP there was a return to C4 dominated grassland. During this latter phase there was a reversal from fishing to hunting again (and eventually some keeping of domestic livestock) at the site. These data outline the vegetation response to latitudinal shifts of frontal systems, and relatively strong atmospheric circulation variability, perhaps underpinned by variations of polar water into the Benguela Current during the late Holocene.
Article
Detailed examination of sediments retained in two north-facing cirques south of Sani Top (latitude 29°30'S; longitude 29°2'E) has been undertaken as a contribution to the Late Quaternary history of highland Lesotho. The sediments are exposed by gullies incised through the deposits. Nine sections are discussed in detail. Inorganic sediments, matrix-supported diamictons and derived orange gravels as well as organic dark clays and peats are present. Eight dated organic samples range in age from 13490BP, currently the oldest organic carbon date from highland Lesotho, to 2310 BP. The sedimentary sequences are interpreted to present a sequence of Late Quaternary events with climatic implications.
Article
Recent research in the eastern highlands of South Africa and Lesotho has increased our knowledge of Late Pleistocene and Holocene human activities in the region. The faunal remains from different sites provide insight into the animal populations of the area during the various climatic phases of the past 21,000 years. During the Last Glacial the variety of species was limited and territorial small bovids were poorly represented. With the onset of the Holocene and better climatological conditions, plant and animal species' diversity increased. The improved conditions and increase in food supplies led to the expansion of the human population. During the Late Pleistocene only a few sites were sporadically occupied, but there is a marked increase in occupied shelters from the early to the mid-Holocene. The species' diversity is reflected in the faunal samples and small bovids feature prominently in the bone assemblages.
Article
Archaeological research in Lesotho over the last 120 years is reviewed. Particular emphasis is given to P. Carter's excavation and survey project in eastern Lesotho and to contract archaeology projects in other parts of the country. Current research and projects involving the study of rock art are also considered. The archaeological potential of Lesotho for addressing a number of themes is discussed. These themes include the reconstruction of prehistoric seasonal mobility patterns, hunter-gatherer adaptations at the Last Glacial Maximum and relations between hunter-gatherer and farming populations. Lesotho's geographical situation lends itself to examining these questions across two distinct ecological gradients, but the richness of its rock art also demonstrates its potential for investigating Stone Age social relations. The importance of developing a more effective national archaeological infrastructure is stressed.
Article
Types of stone-banked lobes are described from the high Drakensberg, southern Africa. One type shows material has moved over areas of shallow rock scarps; the larger clasts are sorted into the peripheral areas of the moving debris masses. A second has a crescent-shaped stony embankment, behind which accumulate smaller cobbles and gravels. A third displays a raised frontal bank with treads comprising an accumulation of open-work block material. The frontal bank heights of some stone-banked lobes appear to be a function of the rapidity and quantity of debris accumulation, rather than of tread dimensions. Different stone-banked lobe types develop under different controlling mechanisms and environmental conditions. Bedrock may act as an impermeable layer and permits contemporary solifluction to take place at some sites. Larger, inactive lobes occupy areas of deep (> 1.5 m) regolith and are the probable products of prolonged seasonal freeze and enhanced gelifluction activity during the Holocene.
Article
Small needle-ice mounds are described from the High Drakensberg. They develop infrequently during periods of several days of uninterrupted cold conditions. Ice growth incorporates sediment and stones. An accumulated segregated ice length of >41 cm was measured, with clasts heaved ∼14 cm. During subsequent thaw phases, the ice ablates from the top downwards, forming sediment veneers and cappings. These mounds contribute towards turf exfoliation, thereby exposing sediment to deflation. Copyright © 2002 John Wiley & Sons, Ltd.
Article
Sehonghong Rock Shelter has been recognised for some time as a key site for understanding late Pleistocene human adaptations in southern Africa as its deposits cover the period preceding, the peak of and the period after the Last Glacial Maximum. Previous interpretations have, however, been constrained by a lack of tight stratigraphic associations. This paper describes the artefact assemblages dating to between 20 000 and 11 000 BP recovered from new, stratigraphically conducted excavations at the site. It is argued that a considerable stress on bladelet production is already evident at 20 000 BP and that all the assemblages described thus form part of the same Robberg-like microlithic tradition. The use of the term 'MSA 9' to refer to the oldest of them (Carter et al. 1988) should therefore be abandoned. Bladelets may, however, have been hafted and/or used differently at 20 000 BP than in the terminal Pleistocene. A preliminary hypothesis is advanced as to how people may have used Sehonghong: the greater range of material culture evident after 12 500 BP suggests a possible shift at this time from a sporadically used hunting station to a home base status for the site.
Article
Although significant environmental and climatic changes are likely to have occurred across the Pleistocene/Holocene transition in southern Africa, records are sparse, with information regarding temperature change especially rare. We thus know little about the conditions facing Later Stone Age human populations at this time, particularly those in the highland interior where temperature shifts would have had strong impacts on floral and faunal distributions. In Lesotho, a well-defined altitudinal distribution of C3 and C4 photosynthetic plant taxa, and their remains in soil organic matter, provides a means of estimating past temperature shifts. We applied this principle to stratified sediments from two archaeological sequences in the Lesotho lowlands (c. 1600m a.s.l.) to produce a palaeotemperature record focusing on the period 14 000–9500 cal a BP. The results show an overall trend from exclusively C3 vegetation at the Last Glacial Maximum towards greater contributions of C4 taxa, and thus warmer conditions, during the Holocene. However, large temperature fluctuations are evident within this trend, with rapid changes of up to 4 °C visible between 11 200 and 9500 cal a BP. The continued presence of hunter-gatherers during this time suggests that the region must have remained attractive to human populations despite significant climatic instability and cool episodes.
Article
Several high south-facing slopes in the southern Drakensberg were glaciated during the Late Quaternary, yet little is known about the slope geomorphic history on equally high slopes that appear not to have been glaciated. To this end, we examine evidence for Late Quaternary slope dynamics in a high alpine valley of eastern Lesotho, with particular attention given to palaeo-environmental signatures offered by deep colluvial mantles along the flanks of the Sehonghong River and pronival ramparts along the upper southerly-facing slopes of the adjoining Thabana-Ntlenyana. Sedimentary exposures were mapped and sampled for clast fabric, clast shape, organic matter content, granulometry and 14C age determination. Similarly, a pronival rampart was mapped and clast size, shape and fabric determined for various micro-topographic settings. A palaeosol beneath the rampart was also Radiocarbon dated. Findings suggest that the deep and extensive debris mantles on lower south-facing slopes are a product of prolonged colluviation, whilst the more stratified sequences on north-facing slopes indicate greater slope geomorphic-process variability over time. Radiocarbon ages suggest sediment accumulation along the north-facing exposure from at least ∼43ka. It is proposed that snowcreep and snowpush on high (>3400m a.s.l.) southeast-facing slopes during a relatively cold, yet moist period at ∼AD 300–1000 initiated boulder movement to form the pronival ramparts.
Article
South Africa experiences a range of different climatic regimes and is thus an ideal region to investigate Late Pleistocene environmental and climate change. However, detailed quantifiable palaeoclimate data are sparse in the region. In particular, reliable palaeoclimatic data are essential to resolve ongoing controversies regarding temperature depression and moisture availability during glacial periods in the sub-continent. Small glaciers close to the glaciation threshold are highly sensitive to changes in temperature and precipitation and are therefore ideal indicators of past climatic conditions during their existence. This paper derives some of the first quantitative data on Last Glacial Maximum (LGM) palaeoprecipitation in southern Africa, based on glacier reconstruction and mass balance modelling for the Lesotho Highlands.
Article
The classic U-shaped valley is a typical expression of glacial erosion, but situations can occur where the glacier effects little to no change in the landscape. Such an occurrence would be where the glacier is cold-based and remains so during its demise – never entering into a warm-based (erosional) phase. Here, two present-day examples are provided where glaciers exist, but the valley form has remained unaltered despite multiple glacial events. The key to such a situation is suggested to be the altitudinal/latitudinal spatial location, such that the ice has completely disappeared before, during the move towards an interglacial, there is time for it to transform into warm-based ice. The argument can then be made that perhaps the same is the situation for the reconstructed, small glaciers in the Lesotho–Drakensberg area. The ice was cold-based due to a combination of its thinness and the cooling effect of shading. Cold-based ice could explain the lack of striated clasts found in the moraines, the absence of any change to the valley form, and the preservation of breaks in the slope observed in the area of the former glacier.
Article
Three seasons’ excavation in Eastern Lesotho have produced a prehistoric sequence from a number of stratified sites that extends back in time at least 43,000 years. Data relating to precipitation increase and temperature decrease were obtained. The effect of climatic change, particularly increased snowfall, on the distribution of sites, is discussed.
Article
Coarse slope deposits, frequently grading into blockstreams, are common throughout the Lesotho highlands, southern Africa. This paper describes one such blockstream. It is interpreted as a typical lag deposit derived from valley-wide colluvial mantles, which contains superimposed and incorporated Late-Pleistocene blocky material. Blocks are largely derived from local scarps but may contain a component of corestones from mobilized regolith. The widespread mantle argues against landscape-scale glaciation in the Lesotho highlands in the Late Pleistocene. Rather, the environment appears to have been conducive to deep seasonal frost during the period of block production. No unequivocal evidence for permafrost is found. Copyright (C) 2002 John Wiley Sons, Ltd.
Article
a b s t r a c t In order to define criteria for long-term climate change models in Southern Africa, an overview of the available pollen data during the Late Quaternary is needed. Here we reassess the paleo-climatic condi-tions in southern Africa by synthesising available fossil pollen data that can provide new insights in environmental change processes. The data considered here include the latest as well as previously published information that has been difficult to assess. Available calibrated pollen sequences spanning the Late Pleistocene and Holocene were subjected to Principal Components Analysis (PCA) to monitor taxa sensitive to moisture and temperature fluctuations. The PCA values are presented graphically as indicators of climate variability for the region. The results cover different biomes that include the summer-rain region in the north and east, the winter-rain area in the south and the dry zone in the west. The PCA plots directly reflect major changes of terrestrial environments due to variations in temperature and moisture. Mostly sub-humid but fluctuating conditions are indicated during the cold Marine Isotope Stage (MIS) 2, which were followed by a dry phase soon after the beginning of the Holocene but before the middle Holocene in the northern, central and eastern parts of the sub-continent. Marked but non-parallel moisture changes occurred in different subregions during the Holocene suggesting that climatic forcing was not uniform over the entire region. Some events seemed to have had a more uniform effect over the sub-continent, e.g., a relatively dry summer rain event at c. two thousand years ago, which can possibly be related to the ENSO phenomenon. The role of anthropogenic activities in some of the most recent vegetation shifts is likely.
Article
Variations in the nature and extent of southern Africa's winter rainfall zone (WRZ) have the potential to provide important information concerning the nature of long-term climate change at both regional and hemispheric scales. Positioned at the interface between tropical and temperate systems, southern Africa's climate is influenced by shifts in the Intertropical Convergence Zone, the westerlies, and the development and position of continental and oceanic anticyclones. Over the last glacial–interglacial cycle substantial changes in the amount and seasonality of precipitation across the subcontinent have been linked to the relative dominance of these systems. Central to this discussion has been the extent to which the region's glacial climates would have been affected by expansions of Antarctic sea-ice, equatorward migrations of the westerlies, more frequent/intense winter storms and an expanded WRZ. This paper reviews the developing body of evidence pertaining to shifts in the WRZ, and the evolution of ideas that have been presented to explain the patterns observed. Dividing the region into three separate axes, along the western and southern margins of the continent and across the interior into the Karoo and the Kalahari, a range of evidence from both terrestrial sites and marine cores is considered, and potential expansions of the WRZ expansions are explored. Despite the limitations of many of the region's proxy records, a coherent pattern has begun to develop of a significantly expanded WRZ during phases of the last glacial period, with the best-documented being between 32–17 ka. While more detailed inferences will require the recovery and analysis of longer and better-dated records, this synthesis provides a new baseline for further research in this key region.
Article
Conflicting reports appear in the literature from geomorphic studies describing the colder Late Pleistocene environmental conditions of the Lesotho Highlands in southern Africa. Evidence is given for limited glaciation and/or periglacial conditions, with or without permafrost. An investigation of the distribution, morphometric attributes and surface weathering characteristics of relict openwork block accumulations in the area around Thabana-Ntlenyana, the highest summit in the range, supports the contention for a relatively arid periglacial environment during the Last Glacial period. A phase of enhanced block production is evident from the concentration of blocks in the upper layer of colluvium. Slope mobility on south-facing slopes is shown in the blockfield fabrics and the increase in downslope relative age of block surfaces. Block production and slope creep are attributed to depressed temperature conditions and seasonal freeze. Colluvium, within which blocks have been incorporated and superimposed, indicates that slope mantles predate the onset of the colder period and evidence militates against either deep snow cover or localised glaciation of south-facing slopes.
Article
Considerable Quaternary environmental reconstruction for the high Drakensberg is based on geomorphological and sedimentological work undertaken along the northern aspects of the Sekhokong mountain range of eastern Lesotho. Given that no previous investigations have focused on the southern aspects, this paper documents the observed geomorphology and provides a more complete palaeo-environmental picture for this range. Data on the morphology, sedimentology and micromorphology for two linear debris ridges are presented. It is demonstrated that the two ridges are most likely moraines originating from a small niche glacier. The combined use of macro- and micro-scale sedimentology is proven to be an essential tool in ascribing a glacial process origin for the landforms, given the complex depositional history they have undergone. AMS ages obtained from the deposits (14 700 cal. yrs bp and 19 350 cal. yrs bp) places these in the time-scale of the Last Glacial Maximum. The study demonstrates rather contrasting aspect-controlled palaegeomorphological environments along the Sekhokong range, which is also reflected in the dissimilar contemporary biophysical micro-environments. It is suggested that the south-facing slopes were dominated by glacial processes during the Last Glacial Maximum (LGM), as is evident from the moraines, while the proposition for previously described north-facing glacial cirques is rejected based on the absence of erosional/depositional evidence and greater insolation received on these warmerequator-facing slopes. Rather, we propose that the observed north-facing hollows are a product of a multitude of geomorphic processes spanning several tens to hundreds of thousands of years.
Article
Past evaluation of high altitude slope development in Lesotho, southern Africa, is largely based on hypothetical or macro-scale geomorphic approaches. Consequently, the information pertaining to high altitude southern African Quaternary slope environments has remained rather rudimentary. The present study describes the morphology and discusses the likely palaeogeomorphic processes of blockstreams and debris deposits on the Popple Peak and Njesuthi-Mafadi south-facing-slopes in the Drakensberg. The geomorphic evidence provides much needed information to help improve the understanding of south-facing slope processes during past colder periods. A model for high altitude Drakensberg south facing slopes is presented and used to challenge and expand on recent models and ideas on southern African valley asymmetry. It is found that solifluction and debris flows/avalanches were operative on south-facing slopes during past cold periods and thereby contributed to past slope development at some high altitude sites in Lesotho. However, the geomorphological observations do not support the valley asymmetry hypothesis and it is suggested that greater caution be exercised in valley-form interpretations, particularly where geomorphological ground-truthing has been absent.
Article
True ‘periglacial’ forms and deposits of late (and middle) Pleistocene age can be recognized in the Drakensberg and the adjacent parts of the Cape Province in the latitudinal zone 28° 30′-31°20′ S; lower limits in the eastern Cape and Natal appear to lie near 1500–1800 m, rising from southwest to northeast, and at 2600 m in Lesotho. Significant nivation in the Drakensberg is also indicated, but at higher elevations. Alleged ‘periglacial’ phenomena in Rhodesia, the Transvaal, the Cape Folded Ranges and their coastal margin are not acceptable as such and include no evidence for cryonival or geliflual proceses. Nonetheless, there is bonafide evidence for several phases of accelerated Pleistocene frost-weathering, including sections of the Cape Coast that experience next to no frost today and would require a winter temperature depression of at least 10° C. It cannot be disputed that southern Africa has experienced cold, glacial-age climates, but there is a serious problem about many of the geomorphological observations or their interpretation.
Article
Stable carbon and oxygen isotope analyses of ungulate grazers from four archaeological sites located in different environs within the Caledon River Valley have provided a relatively well-dated proxy palaeoenvironmental and palaeoclimatic sequence for the period between 16 000 and 6000 calendar (cal.) yr BP. Within the overall trend towards hot mid-Holocene temperatures and a summer rainfall pattern, stable carbon isotope results show that there were three periods when growth season temperatures were cool enough for C3 grasses to be present: 16 000–14 000; 10 200–9600, and 8400–8000 cal. yr BP. Similar trends were recorded in stable oxygen isotope values, reflecting shifts in either temperature or available moisture. Although having a similar pattern to that of the lower altitude site, sites situated in foothills and montane portions of the valley consistently maintained lower temperatures until the mid-Holocene altithermal. At this time growth season temperatures warmed sufficiently for a 100% C4 grassland to expand in altitude from the warmer low lying localities. In relation to present understanding of synoptic and global climatic patterning, these findings suggest that the early to middle Holocene transition was not a gradual warming trend, but rather it was marked by a series of climatic fluctuations. Of particular note is the possible global, rather than regional, occurrence of the 8200 cal. yr BP ‘event’. Copyright © 2002 John Wiley & Sons, Ltd.