Pleistocene sea-level fluctuations and human evolution on the southern coastal plain of South Africa

Humans evolved in Africa, but where and how remain unclear. Here it is proposed that the southern coastal plain (SCP) of South Africa may have served as a geographical point of origin through periodic expansion and contraction (isolation) in response to glacial/interglacial changes in sea level and climate. During Pleistocene interglacial highstands when sea level was above ?75 m human populations were isolated for periods of 360–3400 25-yr generations on the SCP by the rugged mountains of the Cape Fold Belt, climate and vegetation barriers. The SCP expands five-fold as sea level falls from ?75 to ?120 m during glacial maxima to form a continuous, unobstructed coastal plain accessible to the interior. An expanded and wet glacial SCP may have served as a refuge to humans and large migratory herds and resulted in the mixing of previously isolated groups. The expansive glacial SCP habitat abruptly contracts, by as much as one-third in 300 yr, during the rapid rise in sea level associated with glacial terminations. Rapid flooding may have increased population density and competition on the SCP to select for humans who expanded their diet to include marine resources or hunted large animals. Successful adaptations developed on an isolated SCP are predicted to widely disperse during glacial terminations when the SCP rapidly contracts or during the initial opening of the SCP in the transition to glacial maxima. The hypothesis that periodic expansion and contraction of the SCP, as well as the coastal plain of North Africa, contributed to the stepwise origin of our species over the last 800 thousand years (kyr) is evaluated by comparing the archeological, DNA and sea-level records. These records generally support the hypothesis, but more complete and well dated records are required to resolve the extent to which sea-level fluctuations influenced the complex history of human evolution.     

Sediment provenance of the Wilderness barrier dunes,southern Cape coast,South Africa

Trace‐element geochemistry has been used to discern the provenance of sediments derived from geologically distinct sources found in a range of depositional settings. This study investigates whether this approach can also identify provenance signatures in sediments derived from clastic sedimentary rocks of similar origins, within a complex coastal transport environment. The potential local sediment sources of a coastal barrier dune in South Africa were analysed to assess their relationships with the barrier and whether these have varied with time. Results indicate that the oldest part of the barrier, partly formed during MIS 6 when sea levels were lower than at present, has a closer affinity to fluvial sediment provided by local rivers than either younger samples from the barrier′s seaward flank or the Holocene dunes atop its crest, both formed during sea‐level highstands. Constraints on the timing of barrier formation provided by OSL dating proved helpful in discriminating between provenance and weathering signals. Terra Nova, 00, 000–000, 2010     

The evolution of a grospydite from the Roberts Victor mine,South Africa

A grospydite from Roberts Victor contains the most Ca-rich garnets yet found in South African kimberlite xenoliths and also sub-micron sized sodic nepheline in melted and quenched clinopyroxene. Three stages can be recognised in the textural evolution of the grospydite. The first is the development of a layering of large kyanite laths. Kyanite together with complex aluminous clinopyroxene precipitated and accumulated from an evolved residual eclogitic liquid which has penetrated across the garnet join so that garnet no longer precipitated. Solidus conditions for the Roberts Victor grospydite are estimated as T = 1350–1550 ° C, P = 27–39 kbars. Adjacent layers in the grospydite have slightly different mineral compositions suggesting that the small-scale layering (1–5 cm) in this, and associated rocks, may be related to varying activities of R₂O₃ components and possibly to f _{o 2}.The second stage is represented by a necklace texture in which all the garnet and some kyanite developed along grain boundaries of clinopyroxenes with triple-point textures. This is interpreted as an example of incoherent, grain-boundary exsolution resulting from large subsolidus volume changes. The conditions for subsolidus equilibration are estimated to be T= 1120–1320 ° C, P = 42–56 kbars.Moderate Ca-contents in garnet and excess Al^[6] in clinopyroxene may be subsolidus indicators of eclogite samples evolving towards grospydite at the solidus.The third stage is represented by the melting of jadeite-rich clinopyroxenes and quenching to glass, nepheline and plagioclase. Most of the glass has a composition similar to clinopyroxene, except for K₂O, though local areas of different glass, possibly the result of phase separation, also occur. The melting process seems to be a low-pressure feature involving limited addition of H₂O at temperatures between 900–1000 ° C. Water-absent melting could indicate temperatures up to 1500 ° C.The temperatures and pressures assigned to the three-stage evolution of this grospydite imply formation at moderate pressures and subsolidus equilibration at higher pressures. This is equated with downgoing mantle/asthenosphere tectonic processes. After entrainment in a kimberlite magma the grospydite fragment apparently ascended rapidly, thus allowing low-pressure melting and quenching.     

Ecometrics and the paleoecological implications of Pleistocene faunas from the western coastal plains of the Cape Floristic Region,South Africa

The Pleistocene ungulate communities from the western coastal plains of South Africa's Cape Floristic Region (CFR) are diverse and dominated by grazers, in contrast to the region's Holocene and historical faunas, which are relatively species-poor and dominated by small-bodied browsers and mixed feeders. An expansion of grassy habitats is clearly implied by the Pleistocene faunas, but the presence of ruminant grazers that cannot survive the summer dry season typical of the region today suggests other important paleoecological changes. Here we use dental ecometrics to explore the paleoecological implications of the region's Pleistocene faunas. We show that the dental traits (hypsodonty and occlusal topography) of the ungulates that occurred historically in the CFR track annual and summer aridity, and we use these relationships to reconstruct past aridity. Our results indicate that the Pleistocene faunas signal paleoenvironments that were on average less arid than today, including during the summer, consistent with other lines of evidence that suggest a higher water table and expansion of well-watered habitats. Greater water availability can be explained by lower temperature and reduced evapotranspiration during cooler phases of the Pleistocene, probably coupled with enhanced groundwater recharge due to increased winter precipitation.     

Regenerating rural economies: The case of Limehill, South Africa

The issue of the quality of life of rural South Africans has become a key focus of attention of the national and provincial governments in postapartheid South Africa. This focus stems from legislation that enshrines concurrent responsibility for rural development to both these spheres of government. However, post-1995 legislation including the introduction of wall-to-wall municipal authorities and the subsequent initiatives by municipalities to assume responsibility for service delivery in their areas have infused considerable complexity into the development landscape at the local level. Within this context and against the background of different perspectives and strategies for rural development, this paper examines, in a case study of the Limehill Complex within the Ndaka Municipality in KwaZulu-Natal, the specific development problems that the `deep' rural communities experience. The paper then discusses strategic interventions that the Ndaka Municipality, in conjunction with other role players and the different spheres of government, needs to consider for implementation in order to regenerate the rural economy of the Limehill Complex and assist in the alleviation of widespread poverty in the area. This revised version was published online in July 2006 with corrections to the Cover Date.     

Classification of paraglacial barrier systems: coastal New England, USA

The New England coast harbours a wide variety of barrier forms, which we organize into six barrier-coastline types. The barriers develop in response to the relative importance of several spatially and temporally variable parameters, particularly antecedent topography and geology, sediment abundance and size, exposure to wave and tidal energy and sea-level history. The six coastline types can also be identified in other paraglacial regions. Existing barrier-coastline classification schemes do not allow consistent subdivision of paraglacial barrier coasts. This paper presents a new scheme that is applicable to paraglacial and non-paraglacial barrier coasts alike. Aside from hydrodynamic regime, which forms the basis of the barrier classification most commonly used to date, it includes a compartmentalization factor. Sediment-starved ‘isolated’ (‘type 1’) barrier coastlines are characterized by short, widely spaced barriers. Small, localized updrift and offshore sources have provided sediment for short barriers along ‘clustered headland-separated’ (‘type 2’) barrier coastlines. Various amounts of sediment from larger updrift and offshore glaciofluvial deposits or directly from rivers have formed the longer barriers along ‘wave-dominated mainland-segmented’ (‘type 3a’), ‘mixed-energy mainland-segmented’ (‘type 3b’), ‘wave-dominated inlet-segmented’ (‘type 4a’) and ‘mixed-energy inlet-segmented’ (‘type 4b’) barrier coastlines. Geomorphic form, grain size and stratigraphy can be used to characterize individual barriers along barrier coastlines. Most paraglacial barriers form as spits, but many are transformed subsequently. Welded barriers are common along ‘type 1’ and ‘type 2’ coasts. Baymouth barriers are characteristic of ‘type 3’ coasts, and barrier islands occur exclusively along ‘type 4’ coasts. The coarsest grained barriers are located along ‘type 1’ and ‘type 2’ coasts. Progradational barrier sections are concentrated along ‘type 3’ and ‘type 4’ coasts with abundant sediment supply, but are also present along ‘type 2’ coasts. Temporary increases in sediment supply, common in paraglacial regions, result in transitions between retrogradational and progradational barrier behaviour, which may be recognized on shore-perpendicular stratigraphic cross-sections.     

Invisible towns: A case study in the cartography of South Africa

Many large Black settlements are downgraded or made invisible on maps of South Africa. This form of subjective generalisation gives a false prominence to small White towns. A more realistic map of the major settlements in South Africa is presented. The problems associated with mapping of Black settlements are discussed. These include the lack of census data, absence of official recognition of places, difficulties of place naming and the lack of functional imcomparability with other places.     

Radar facies of paraglacial barrier systems: coastal New England, USA

Analysis of a large data base of ground-penetrating-radar (GPR) profiles from both natural and developed paraglacial barriers along the coast of New England has allowed identification of eight reflection configurations that characterize this type of mid- to high-latitude coastal environment. Bedrock anchor points yield primarily hyperbolic configurations, whereas glacial anchor points and sediment-source areas are characterized by chaotic, parallel, and tangential-oblique configurations. Beaches and dunes produce predominantly sigmoidal oblique, hummocky, reflection-free, and bounding-surface configurations. Back-barrier sediments may yield basin-fill configurations, but generally include abundant signal-attenuating units.
The GPR data, calibrated with information from cores, were collected across swash-aligned and drift-aligned barriers in a variety of wave- and tidal-energy settings. Application of a 120-MHz antenna, as used in this study, enables portrayal of a range of sedimentary units, from individual bedforms (on single records) to entire barrier elements (using large numbers of intersecting GPR sections), at maximum vertical resolutions that vary between 0·2 m and 0·7 m.
The most important drawback of GPR in the coastal environment is attenuation of the electromagnetic (EM) signal by layers of salt-marsh peat or by brackish or salty groundwater, primarily along barrier edges. This disadvantage is offset by many benefits. Data can be collected at rates of several km per day, making GPR an excellent reconnaissance tool. A core that is used in the calibration of GPR data can be matched with great accuracy to its position on the complementary GPR record, allowing detailed correlation between lithostratigraphy and reflection configuration.     

A sand budget for the Alexandria coastal dunefield, South Africa

The sand in the Alexandria coastal dunefield is derived from the sandy beach which forms the seaward boundary of the dunefield. Sand is blown off the beach onto the dunefield by the high-energy onshore-directed dominant wind. The dunefield has been forming over the past 6500 years. Sand transport rates calculated from dune movement rates and wind data range from 15 to 30 m³ m ^-1 yr^-1 in an ENE direction. The sand transport rate decreases with increasing distance from the sea due to a reduction in wind speed resulting from the higher drag imposed upon the wind by the land surface. Aeolian sand movement rates of this order are typical of dunefields around the world. The total volume of sand blown into the dunefield is 375 000 m³ yr^-1. Sand is being lost to the sea by wave erosion along the eastern third of the dunefield at a rate of 45 000 m³ yr ^-1. The dunefield thus gains 330 000 m³ of sand per year. This results in dunefield growth by vertical accretion at about 1.5 mm yr^-1 and landward movement at about 0.25 m yr^-1. The dunefield is a significant sand sink in the coastal sand transport system. The rate of deposition in coastal dunefields can be 10 times as high as rates of deposition in continental sand seas. The higher rate of deposition may result from the abundant sand supply on sandy beaches, and the higher energy of coastal winds. Wind transport is slow and steady compared to fluvial or longshore drift transport of sediment, and catastrophic aeolian events do not seem to be significant in wind-laid deposits.     

Problems of planning for urbanization and development in South Africa: the case of Natal's coastal margins

The growth of urban settlements along the Natal coast serves as a case study with which to evaluate the South African government's emerging concept of ‘planned urbanization’. Changing emphases in South African urban and regional policy are situated within the context of the contemporary legitimacy crisis of the South African state. Data on the experience of urbanization on the Natal coast, and particularly black perceptions of this experience, are presented. Recent government proposals dealing with urbanization—particularly the newly legislated Regional Services Councils—are assessed against this background.     

A dating intercomparison study on Late Stone Age coastal midden deposits,South Africa

The southern and western coastlines of South Africa have an extensive archaeological record with many sites associated with widespread eolian deposits. While much of this rich archaeological record is based on cave sites, evidence of Late Stone Age occupation is additionally preserved in the form of open‐site shell middens. We present here a comparative study of the application of amino acid racemization (AAR), optically stimulated luminescence (OSL), and radiocarbon analyses to three Late Stone Age (LSA) midden sites found within dunes on the southern coastline of South Africa. Preliminary geochronological analyses suggest that middens offer opportunity to fill in gaps in what is still a fragmentary archaeological record. Results show OSL and radiocarbon ages in good agreement, illustrating the potential to date not only the middens but also the surrounding dunes that constituted the dwelling sites. AAR results show increasing ratios with age and also that the application of paired shell and “whole rock” AAR can provide insights into the degree of biogenic sediment recycling at buried midden sites. However, the work also highlights that caution is required when OSL sampling sediment associated with middens which may have undergone human disturbance and that further work is required to improve the regional marine reservoir correction for radiocarbon dating in this part of South Africa. The study also illustrates that AAR will only provide useful data provided that middens have been sufficiently deeply buried to overcome fluctuations in environmental variables that affect the racemization rate and that inter‐genus comparisons should be avoided. © 2008 Wiley Periodicals, Inc.     

Origin and terminal architecture of a submarine slide: a case study from the Permian Vischkuil Formation,Karoo Basin,South Africa

Submarine mass movement deposits exposed in the Vischkuil Formation, Laingsburg Karoo Basin, South Africa, provide a rare opportunity to analyse and interpret their emplacement history and deformation processes at a scale comparable to seismic examples. An up to 80 m thick slide deposit, continuously exposed in two 2 km long sub‐parallel sections, passes from extensionally deformed material (clastic dykes and down‐dip facing low‐angle shear surfaces) down‐dip into a compressional toe zone with large (tens of metres amplitude) folds dissected by steep, up‐dip facing thrust planes. The compressional shear planes sole out onto a highly sheared décollement and cross‐cutting relationships indicate an up‐depositional dip younging in the timing of fold dissection. Lithofacies characteristics and detailed correlation of volcanic ash and other marker beds over more than 500 km² in the bounding undeformed stratigraphy indicate a low‐gradient (<0·1°) basin floor setting. The slide is abruptly overlain by an up to 50 m thick debrite with sandy clasts supported by an argillaceous matrix. Shear loading of the debris flow is interpreted to have driven large‐scale deformation of the substrate through the generation of high shear stresses at a rheological interface due to: (i) the abrupt contact between the slide and the debrite; (ii) the coincident thickness distributions of the debrite and slide; (iii) the distribution of the most intense folding and thrusting under the thickest parts of the debrite; (iv) the preservation of fold crests with only minor erosion along fold limbs; (v) the presence of the debrite under overturned folds; (vi) the presence of laterally extensive marker beds directly above deformation units indicating minimal depositional topography; and (vii) the demonstrably local derivation of the slide as individual folded beds are mapped into undeformed strata outside the areas of deformation. The debrite is directly overlain by fine‐grained turbidite sandstone beds that show widespread vertical foundering into the debrite. This case study demonstrates that intensely deformed strata can be generated by negligible amounts of down‐dip movement in a low‐gradient, fine‐grained basin floor setting with the driver for movement and deformation being the mass imbalance resulting from emplacement of episodic debris flows. Simple interpretation of an unstable slope setting based on the presence of such deformed strata should be treated with caution.     

Sedimentary evolution of a late Pleistocene wetland indicating extreme coastal uplift in southern Tanzania

Facies analyses of Pleistocene deposits from southern coastal Tanzania (Lindi District) document that sediments formed in a wetland evolving on a coastal terrace in the Lindi Fracture Zone foreland. The exposed succession shows a marked sedimentary change from tidal to terrestrial facies. ¹⁴C analyses on gastropod shells indicate the emergence of the Lindi coast at ∼ 44 ¹⁴C ka BP. Emergence and subsequent elevation of terraces to 21 m above present-day sea level was linked to the falling eustatic sea level prior to the last glacial maximum, and to a periodic elevation due to extensional tectonic episodes in the eastern branch of the East African Rift System (EARS). Since ∼ 44 ¹⁴C ka BP tectonic uplift at the coast was 80-110 m, comparable to that in the extreme uplift areas of the EARS.     

Inner city gentrification in South Africa: The case of Woodstock,Cape Town

The focus in this paper is residential change taking place since 1980 in the innercity suburb of Woodstock, Cape Town. This area is significant as it was one of the few multiracial spaces which survived the deliberate whitening of South African cities during the apartheid era. The paper analyses the major threat posed to the longstanding multi-racial complexion of Woodstock by the state's attempt to declare part of the suburb for exclusive coloured residence under Group Areas legislation. Nonetheless, while community resistance in the form of the Open Woodstock campaign was successful in halting enforced residential change, processes of gentrification have shaped a new class composition in this inner-city suburb.     

Volunteer tourism: The case of Habitat for Humanity South Africa

Volunteer tourism as a subset of alternative tourism is the focus of analysis. This paper contributes to the limited writings on volunteer tourism by investigating the activities in South Africa of Habitat for Humanity, a grassroots ecumenical Christian organization that works in partnership with communities to eliminate poverty through the provision of shelter. A profile of the volunteer tourist and of their tourism experience in South Africa is presented which is based largely upon the return of 123 questionnaires from volunteer tourists in South Africa working with the local branch of Habitat for Humanity. This revised version was published online in August 2006 with corrections to the Cover Date.     

Middle-Late Alpine thermotectonic evolution of the southern Rhodope Massif,Greece

Abstract

The transition from the Alpine tectonic assembly to the exhumation of the units in the Rhodope metamorphic province in northernmost Greece has been refined by ⁴⁰Ar/³⁹Ar laserprobe mica analyses. Preservation of pre-Alpine (~ 280 Ma and 145 Ma) muscovite cooling ages at the western margin of the Rhodope indicate that subsequent events failed to reset the argon system thermally in white mica in the outcropping basement of this region. The central and eastern Rhodope are characterized by white mica cooling ages of 40–35 Ma with ages gradually decreasing to ca. 15 Ma near the eastern margin of the Strymon Valley. The Eo-Oligocene ages reflect the regional exhumation of the metamorphosed units to shallow crustal levels, with corresponding temperatures below ca. 350 °C, by 40–35 Ma. The younger cooling ages are attributed to the initiation and subsequent operation of the Strymon-Thasos detachment system since ca. 30 Ma. This study provides a crucial contribution to future regional tectonic models for the Rhodope region as it recognizes an early stage of development of the Strymon-Thasos detachment system, and has constrained the regional exhumation of the Rhodope metamorphic province since 40 Ma indicating that the regionally observed amphibolite facies metamorphism had terminated by this time. © 2000 Editions scientifiques et médicales Elsevier SAS     

Diachronous evolution of systems tracts in a depositional sequence from the middle Pleistocene palaeo-Tokyo Bay, Japan

Palaeo-Tokyo Bay is a relic of the Plio-Pleistocene Kazusa forearc basin in the Boso Peninsula of Japan. The sedimentary infill of palaeo-Tokyo Bay is characterized by shallow marine to paralic sediments of the middle to upper Pleistocene Shimosa Group. Sequence stratigraphical analysis has been used to describe spatial and temporal variations in the depositional systems of the lowest units of the Shimosa Group, deposited during the early stage of development of palaeo-Tokyo Bay. Three different type of depositional systems were recognized: sand ridge to shelf (SRS), shelf to delta (SDL) and shelf to non-deltaic nearshore (SNS) systems. They overlie early transgressive estuarine deposits infilling lowstand valleys incised in the south-eastern margin of palaeo-Tokyo Bay. These systems were developed during late transgressive through highstand stages of a relative sea level cycle, which may have been controlled by a glacio-eustatic sea level change at about 0·4 Ma. Spatial variation in depositional systems is largely identical to that in modern Tokyo Bay; environmental conditions similar to those prevailing at the present day probably characterized the early history of palaeo-Tokyo Bay. The timing of highstand systems tracts within a high frequency depositional sequence was analysed in terms of the effect of sedimentation rate, based on the mapping of a chronostratigraphical surface marked by the Hy4 volcanic ash layer. From spatial variations in sedimentation rate, it was possible to identify the diachronous evolution of highstand systems tracts from the SDL system, through the SNS system, to the SRS system. Time lag is indicated by major bounding surfaces, such as maximum flooding or downlap surfaces associated with a condensed section, which developed immediately above or below the Hy4 volcanic ash layer. The lag may be of the order of a few thousands to tens of thousands of years within a depositional sequence with a total of duration of about 100 000 years.     

A mixed-feeding Equus species from the Middle Pleistocene of South Africa

The dietary regime of Equus capensis from the Middle Pleistocene of South Africa is investigated by mesowear analysis. Results indicate that the mesowear signature of this species resembles that of two extant mixed feeders, the Grant's Gazelle (Gazella granti) and the Thomson's Gazelle (Gazella thomsoni), suggesting a mixed feeding dietary strategy for E. capensis. The mesowear signature of a contemporaneous population of Equus mosbachensis from Europe (Arago, France) is also determined for comparative purposes and has a typical grazing signature. In general, all extant species of Equus are believed to be almost exclusively grazers. However, a considerable degree of dietary flexibility is recently reported. The dietary signal of E. capensis is considered to be the result of feeding on the unique fynbos vegetation, which was beginning to establish itself at this time in southwestern South Africa. Grasses are a minor component of this floral kingdom. Our findings thus provide further evidence for the unexpected flexibility in feeding strategies of Equus, the most widely distributed equid taxon in the Quaternary. They highlight the potential use of the attrition–abrasion wear equilibrium as a habitat indicator, by mirroring the availability of food items in mammalian herbivore ecosystems.