409 results on '"T. C. Partridge"'
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2. Paleoclimate and Evolution with Emphasis on Human Origins. E. S. Vrba , G. H. Denton , T. C. Partridge , L. H. Burckle
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Lawrence Guy Straus
- Subjects
Arts and Humanities (miscellaneous) ,Evolutionary biology ,Anthropology ,Biology - Published
- 1997
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Catalog
3. Early Acheulean technology in the Rietputs Formation, South Africa, dated with cosmogenic nuclides
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Darryl E. Granger, Ryan J. Gibbon, T. C. Partridge, and Kathleen Kuman
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Technology ,Burial ,engineering.material ,South Africa ,Paleontology ,Absolute dating ,Aggradation ,Homo ergaster ,Animals ,Humans ,Cosmogenic nuclide ,History, Ancient ,Ecology, Evolution, Behavior and Systematics ,Stone tool ,biology ,Fossils ,Radiometric Dating ,Hominidae ,biology.organism_classification ,Archaeology ,Anthropology ,engineering ,Radiometric dating ,Alluvium ,Geology ,Acheulean - Abstract
An absolute dating technique based on the build-up and decay of 26 Al and 10 Be in the mineral quartz provides crucial evidence regarding early Acheulean hominid distribution in South Africa. Cosmogenic nuclide burial dating of an ancient alluvial deposit of the Vaal River (Rietputs Formation) in the western interior of South Africa shows that coarse gravel and sand aggradation there occurred ca 1.57 ± 0.22 Ma, with individual ages of samples ranging from 1.89 ± 0.19 to 1.34 ± 0.22 Ma. This was followed by aggradation of laminated and cross-bedded fine alluvium at ca 1.26 ± 0.10 Ma. The Rietputs Formation provides an ideal situation for the use of the cosmogenic nuclide burial dating method, as samples could be obtained from deep mining pits at depths ranging from 7 to 16 meters. Individual dates provide only a minimum age for the stone tool technology preserved within the deposits. Each assemblage represents a time averaged collection. Bifacial tools distributed throughout the coarse gravel and sand unit can be assigned to an early phase of the Acheulean. This is the first absolute radiometric dated evidence for early Acheulean artefacts in South Africa that have been found outside of the early hominid sites of the Gauteng Province. These absolute dates also indicate that handaxe-using hominids inhabited southern Africa as early as their counterparts in East Africa. The simultaneous appearance of the Acheulean in different parts of the continent implies relatively rapid technology development and the widespread use of large cutting tools in the African continent by ca 1.6 Ma. more...
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- 2009
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4. Reconstruction of environmental and climate changes at Braamhoek wetland, eastern escarpment South Africa, during the last 16,000 years with emphasis on the Pleistocene–Holocene transition
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Elin Norström, Karin Holmgren, T. C. Partridge, Jan Risberg, and Louis Scott
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Palynology ,geography ,geography.geographical_feature_category ,Peat ,Pleistocene ,Paleontology ,Climate change ,Escarpment ,Oceanography ,Convergence zone ,Climatology ,Paleoclimatology ,Physical geography ,Ecology, Evolution, Behavior and Systematics ,Geology ,Holocene ,Earth-Surface Processes - Abstract
A paleo-environmental record covering the last 16 ka (16,000 cal yrs BP) from the eastern areas of the summer rainfall region in South Africa is presented. This area is until now sparsely investigated due to the lack of well preserved natural archives. For this study, we used a peat section from a wetland situated close to the Drakensberg escarpment, where the high annual rainfall amounts supported a continuous peat accumulation since c. 16 ka. One peat core was analysed in terms of fossil pollen composition, carbon and nitrogen content, isotope composition (δ13C, δ15N) and microscopic charcoal concentration. The greatest degree of temporal resolution was achieved from the late Pleistocene and early Holocene section, where proxy-records indicate relatively dry conditions between ca. 16–13.7 ka, 12.8–10.5 ka, 9.5–8.2 ka, and wet conditions between c. 13.7–12.8 ka and 10.5–9.5 ka. A weak moisture signal is also evident at c. 8.2–7.5 ka. The late Pleistocene to early Holocene period was relatively cool, while conditions became generally warmer after 11–8 ka. The interpretation of the mid- and late-Holocene sequence is limited due to a slow accumulation and low sample resolution, but the available data suggest relatively dry conditions until c. 1.5 ka, followed by more humid conditions until c. 0.5 ka. We suggest that the millennial scale variability within the record can be attributed to shifts in the circulation systems dominating the region, i.e. the latitudinal movements of the inter-tropical convergence zone (ITCZ) and the dynamics of the mid-latitude low pressure belts. more...
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- 2009
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5. Persistent millennial-scale climatic variability over the past 25,000 years in Southern Africa
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Riashna Sithaldeen, A. Siep Talma, T. C. Partridge, Julia A. Lee-Thorp, P. D. Tyson, Katarina Lundblad, Karin Holmgren, Louis Scott, and Gordon R. J. Cooper
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Archeology ,Global and Planetary Change ,geography ,geography.geographical_feature_category ,Pleistocene ,Atmospheric circulation ,Climate change ,Speleothem ,Geology ,Stalagmite ,Antarctic Cold Reversal ,Climatology ,Southern Hemisphere ,Ecology, Evolution, Behavior and Systematics ,Holocene - Abstract
Data from stalagmites in the Makapansgat Valley, South Africa, document regional climatic change in southern Africa in the Late Pleistocene and Holocene. A new TIMS U-series dated stalagmite indicates speleothem growth from 24.4 to 12.7 ka and from 10.2 to 0 ka, interrupted by a 2.5 ka hiatus. High-resolution oxygen and carbon stable isotope data suggest that postglacial warming was first initiated ∼17 ka, was interrupted by cooling, probably associated with the Antarctic Cold Reversal, and was followed by strong warming after 13.5 ka. The Early Holocene experienced warm, evaporative conditions with fewer C4 grasses. Cooling is evident from ∼6 to 2.5 ka, followed by warming between 1.5 and 2.5 ka and briefly at ∼AD 1200. Maximum Holocene cooling occurred at AD 1700. The new stalagmite largely confirms results from shorter Holocene stalagmites reported earlier. The strongest variability superimposed on more general trends has a quasi-periodicity between 2.5 and 4.0 ka. Also present are weaker ∼1.0 ka and ∼100-year oscillations, the latter probably solar induced. Given similarities to the Antarctic records, the proximate driving force producing millennial- and centennial-scale changes in the Makapansgat record is postulated to be atmospheric circulation changes associated with change in the Southern Hemisphere circumpolar westerly wind vortex. more...
- Published
- 2003
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6. Lower Pliocene Hominid Remains from Sterkfontein
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Darryl E. Granger, Marc W. Caffee, Ronald J. Clarke, and T. C. Partridge
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Australopithecus sediba ,geography ,Multidisciplinary ,geography.geographical_feature_category ,Australopithecus anamensis ,biology ,biology.organism_classification ,Neogene ,Paleontology ,Australopithecus ,Cave ,Eutheria ,Cosmogenic nuclide ,Cenozoic ,Geology - Abstract
Cosmogenic aluminum-26 and beryllium-10 burial dates of low-lying fossiliferous breccia in the caves at Sterkfontein, South Africa, show that associated hominid fossils accumulated in the Lower Pliocene. These dates indicate that the skeleton StW 573 and newly discovered specimens from Jacovec Cavern have much the same age: approximately 4 million years. These specimens are thus of an age similar to Australopithecus anamensis from East Africa. more...
- Published
- 2003
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7. Temporal lobe evolution in Hominidae and the origin of human lobe proportions.
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Pearson A and Polly PD
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- Animals, Humans, Phylogeny, Female, Male, Anthropology, Physical, Tomography, X-Ray Computed, Organ Size, Hominidae anatomy & histology, Temporal Lobe anatomy & histology, Temporal Lobe diagnostic imaging, Biological Evolution, Fossils
- Abstract
Objectives Evolutionary changes in hominin social complexity have been associated with increases in absolute brain size. The temporal lobes are nestled in the middle cranial fossae (MCF) of the skull, the dimensions of which allow estimation of temporal lobe volume (TLV) in extant and fossil taxa. Materials and Methods The main aim of this study is to determine where along the hominid phylogeny, major temporal lobe size transitions occurred. We used computed tomography (CT) scans of crania, 3D photogrammetry data, and laser surface scans of endocranial casts to measure seven MCF metrics in 11 extant anthropoid taxa using multiple regressions to estimate TLV in 5 extant hominids and 10 fossil hominins. Phylogenetic comparative methods mapped temporal lobe size, brain size, and temporal lobe proportions onto phylogenetic trees broadly for Hominidae and specifically for Hominini. Results Extant Homo sapiens were not an outlier in relative brain size, temporal lobe size, or proportions of the temporal lobes, but some proportions within the lobe were uniquely altered. The most notable changes in relative temporal lobe size and proportions saw a decrease in relative temporal lobe size and proportions in the genus Pan compared to other extant great apes and fossil hominins while there was a relative increase in the temporal lobe width and length in Australopithecus-Paranthropus clade compared to the genus Homo and other extant great apes including modern humans. Discussion We do not find support for the social brain, environmental or functional craniology hypotheses alone but think it prudent to consider the implications of cerebral reorganization between the temporal lobes and other regions of the brain within the context of these hypotheses and with future investigation is warranted., (© 2024 The Author(s). American Journal of Biological Anthropology published by Wiley Periodicals LLC.) more...
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- 2024
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8. The new hominid skeleton from Sterkfontein, South Africa: age and preliminary assessment
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David Heslop, Ronald J. Clarke, T. C. Partridge, and John Shaw
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Magnetic polarity ,biology ,Range (biology) ,Paleontology ,Foot Bones ,Biostratigraphy ,biology.organism_classification ,Skeleton (computer programming) ,Archaeology ,Sequence (geology) ,Arts and Humanities (miscellaneous) ,Australopithecus ,Earth and Planetary Sciences (miscellaneous) ,Geology - Abstract
A new hominid skeleton from Sterkfontein Member 2 attaches to foot bones recovered from loose blocks during the 1980s and first described in 1995. Several flowstone horizons are present above and below the skeleton and have given clear palaeomagnetic signatures. Five changes in magnetic polarity have been identified; when constrained by the available biostratigraphy, this sequence can be placed confidently between 3.22 and 3.58 Ma. Interpolation of sedimentation rates over the small intervals between reversals allows this range to be reduced to 3.30–3.33 Ma. The skeleton is thus the oldest yet discovered and is considered to belong to a species of Australopithecus other than africanus. Copyright © 1999 John Wiley & Sons, Ltd. more...
- Published
- 1999
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9. Cainozoic environmental change in southern Africa, with special emphasis on the last 200 000 years
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T. C. Partridge
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010506 paleontology ,010504 meteorology & atmospheric sciences ,Pleistocene ,Geography, Planning and Development ,Neogene ,01 natural sciences ,Paleontology ,Tectonic uplift ,Aridification ,Paleoclimatology ,Earth and Planetary Sciences (miscellaneous) ,General Earth and Planetary Sciences ,Quaternary ,Cenozoic ,Paleogene ,Geology ,0105 earth and related environmental sciences - Abstract
Since the end of the Cretaceous, Africa's latitudinal drift has been relatively small and has not significantly modified the general pattern of stepwise cooling and aridification that has characterized the Cainozoic era. Tectonic uplift has, in contrast, strongly influenced regional climates in east and southern Africa, especially during the late Neogene, and has accentuated the east-west moisture gradient which has prevailed, with minor interruptions, since the Oligocene. In common with most other midlatitude regions, southern African environments responded dramatically to the global episode of cooling and drying between 2.8 and 2.6 myr which ushered in the cyclical fluctuations of the Pleistocene. The establishment of a winter rainfall regime in the southwestern part of the subcontinent probably dates from around 2.6 myr. In the north east, new proxy data spanning the last 200 000 years indicate that summer rainfall varied in relation to receipts of solar insolation at precessional frequencies. Superimposed upon these cyclical changes were a number of less regular variations which, on the basis of the larger body of evidence available for the Holocene, elicited specific localized responses. These diachronistic changes argue for the involvement of factors other than solar insolation alone in the more recent evolution of southern African climates. more...
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- 1997
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10. Orbital forcing of climate over South Africa: A 200,000-year rainfall record from the pretoria saltpan
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M J Paiker, Peter B deMenocal, T. C. Partridge, J.C. Vogel, and Simon Lorentz
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Archeology ,Global and Planetary Change ,geography ,Plateau ,geography.geographical_feature_category ,Pleistocene ,Orbital forcing ,Geology ,Subtropics ,Forcing (mathematics) ,Climatology ,Crater lake ,Climate model ,Southern Hemisphere ,Ecology, Evolution, Behavior and Systematics - Abstract
Late Pleistocene variations in rainfall in subtropical southern African are estimated from sediments preserved in the Pretoria Saltpan, a 200000 year-old closed-basin crater lake on the interior plateau of South Africa. We show that South African summer rainfall covaried with changes in southern hemisphere summer insolation resulting from orbital precession. As predicted by orbital precession geometry (Berger, 1978), this South African record is out of phase with North African palaeomonsoon indices (Street and Grove, 1979; Rossignol-Strick, 1983; McIntyre et al., 1989); the amplitude of the rainfall response to insolation forcing agrees with climate model estimates (Prell and Kutzbach, 1987). These results document the importance of direct orbital insolation forcing on both subtropical North and South African climate as well as the predicted antiphase sensitivity to precessional insolation forcing. more...
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- 1997
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11. New Isotopic and Sedimentological Measurements of the Thabaseek Deposits (South Africa) and the Dating of the Taung Hominid
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Jeffrey K. McKee, H Dieter Oschadleus, Phillip V. Tobias, T. C. Partridge, and John C. Vogel
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010506 paleontology ,010504 meteorology & atmospheric sciences ,biology ,Fluvial ,Australopithecine ,biology.organism_classification ,01 natural sciences ,Archaeology ,Paleontology ,Arts and Humanities (miscellaneous) ,Tufa ,General Earth and Planetary Sciences ,Australopithecus africanus ,Geology ,0105 earth and related environmental sciences ,Earth-Surface Processes - Abstract
Earlier attempts to date the Taung hominid type specimen of Australopithecus africanus Dart yielded conflicting results. Recent faunal studies pointed to an age of 2.3 myr. Radioisotopic results suggested 1.0 myr. New uranium studies reveal that the Thabaseek (the oldest Taung tufa) was not a closed system and that younger uranium entered the tufa after initial deposition, producing an apparent isotopic age younger than the age of deposition. The Thabaseek isotopic dates provide only a terminus ad quem and this technique is therefore not applicable to the older Taung tufas. Delson's dating (2.3 myr) of cercopithecoids from Hrdlicka's pinnacle ca. 50 m from the hominid site provides the best available approximation to the age of the hominid. In our new Taung excavation, stratigraphic analysis indicates that the hominid may somewhat predate most identified fauna. Sedimentologically the hominid matrix proves to be of fluvial deposition, and hence closely resembles one Hrdlicka deposit, both samples differing appreciably from all other Taung samples which bespeak eolian deposition. Thus, the conditions under which the hominid-bearing stratum was deposited were virtually identical to those pertaining to one of the Hrdlicka deposits. The newest results show that Taung was not the youngest South African australopithecine site and eliminate the discrepancy between the relative ages of the Taung A. africanus africanus and the Sterkfontein A. africanus transvaalensis. more...
- Published
- 1993
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12. PRIORITIES FOR URBAN EXPANSION WITHIN THE PWV METROPOLITAN REGION: THE PRIMACY OF GEOTECHNICAL CONSTRAINTS
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T. C. Partridge, C. K. Wood, and A. B.A. Brink
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Government ,geography.geographical_feature_category ,business.industry ,Sinkhole ,Geography, Planning and Development ,Distribution (economics) ,Karst ,Metropolitan area ,Urban expansion ,Geography ,Urban planning ,General Earth and Planetary Sciences ,Geotechnical engineering ,business ,Subdivision - Abstract
One of the most urgent problems confronting future development in the PWV metropolitan region is the provision of low-cost housing for its large and rapidly increasing homeless population. Priorities for the location of this housing are set not only by considerations of land availability and infrastructure, but also by new models of urban development, and by the serious constraints imposed by geotechnical factors. Among the most important of these are the distribution of dolomitic rocks, with their associated problems of instability resulting from subsurface karst weathering, and areas of shallow undermining in which government regulations have hitherto precluded housing development. In view of the costs of assessing the risks associated with the construction of high-density housing and accompanying infrastructure on dolomite, and the fact that the risk of sinkhole development can never be completely excluded even after detailed investigation, it is proposed that the dolomitic “girdle” surroundin... more...
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- 1993
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13. The Pretoria Saltpan: a 200,000 year Southern African lacustrine sequence
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S.J. Kerr, A.S. Talma, Louis Scott, J.C. Vogel, S.E. Metcalfe, and T. C. Partridge
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geography ,geography.geographical_feature_category ,Bedrock ,Paleontology ,Oceanography ,Absolute dating ,Clastic rock ,Crater lake ,Paleoclimatology ,Sedimentary rock ,Quaternary ,Ecology, Evolution, Behavior and Systematics ,Holocene ,Geology ,Earth-Surface Processes - Abstract
The Pretoria Saltpan is a circular crater 1130 m in diameter and is situated some 40 km N of Pretoria (lat. 25°34′30″/long. 28°04′59″E). A recent tube sampling and core drilling programme has revealed an infilling consisting of some 90 m of fine lacustrine sediments (chiefly organic muds, underlain below 30 m depth by micrites) which rest upon a further 61 m of coarse clastic debris. Granite bedrock was encountered at − 151 m. Broad sedimentary zones correspond with major phases in the evolution of the crater lake. Superimposed cyclical patterns of accumulation reflect environmental changes on millenial to seasonal timescales. 14C age determinations on algal debris from the upper 20 m of the core indicate a mean rate of sedimentation of about 1 m/2000 yr, suggesting that the lacustrine sequence may span almost 200,000 yr. Over this period major environmental changes are apparent from sedimentological, chemical, mineralogical and isotopic analyses of the core and studies of the pollen spectra and diatom assemblages present within it. This long continental sequence is therefore providing a high-resolution palaeoenvironmental record for southern mid-latitudes over much the same period as is covered by the Vostok ice-core in Antarctica. more...
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- 1993
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14. Biomarker and stable carbon isotope analyses of sedimentary organic matter from Lake Tswaing: evidence for deglacial wetness and early Holocene drought from South Africa
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Heinz Wilkes, J. Thorpe, I. Kristen, Birgit Plessen, A. Vieth, K.-G. Zink, T. C. Partridge, and Hedi Oberhänsli
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chemistry.chemical_classification ,Ancient lake ,Geochemistry ,550 - Earth sciences ,Aquatic Science ,Carbon cycle ,Oceanography ,Biomarker (petroleum) ,chemistry ,Isotopes of carbon ,Sedimentary organic matter ,Organic matter ,Glacial period ,Sedimentology ,Geology ,Holocene ,Earth-Surface Processes - Abstract
Comparing the organic matter (OM) composition of modern and past lake sediments contributes to the understanding of changes in lacustrine environments over time. We investigate modern plant and lake-water samples as well as modern and ancient sediment samples from the Tswaing Crater in South Africa using biomarker and stable carbon isotope analyses on bulk OM and specific biomarker compounds. The characteristic molecular markers for higher land plants (predominantly C3-type deciduous angiosperms) in Lake Tswaing are long-chain n-alkanes (n-C27−33), n-alkanols (n-C28+30), stigmasterol, β-sitosterol, β-amyrin, α-amyrin and lupeol. The C17 n-alkane, tetrahymanol, gammaceran-3-one and C29 sterols dominate the lipid fraction of autochthonously produced OM. By comparing stable carbon isotope analyses on bulk OM and the characteristic biomarkers, we follow the modern carbon cycle in the crater environment and find indications for methanotrophic activity in the lake from isotopically depleted moretene. A comparative study of core sediments reveals changes in the terrestrial (C3 versus C4) and aquatic bioproductivity and allows insights into the variability of the carbon cycle under the influence of changing climatic conditions for the time from the end of the last glacial (Termination I) to the late Holocene, ca. 14,000–2,000 calibrated years before present (years BP). The most pronounced changes occur in the aquatic realm after ca. 10,000 years BP when our results imply climate swings from more humid to more arid and after 7,500 years BP to gradually more humid conditions again, which can be related to a shift in the position of the Inter-Tropical Convergence Zone or to changes in the tropical atmosphere–ocean interaction. Long-chain alkenones (LCAs) have been identified in ancient lake sediments from Africa for the first time. They occur in samples older than 7,500 years BP and their distribution (dominance of C38 and of tri- over tetra-unsaturated LCAs) is distinctly different from other published records suggesting a to date unknown source organism. more...
- Published
- 2010
15. Explaining the uniqueness of the Cape flora: incorporating geomorphic evolution as a factor for explaining its diversification
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Şerban Procheş, T. C. Partridge, and Richard M. Cowling
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Geography ,Ecology ,Genetic Speciation ,Climate ,Biodiversity ,Species diversity ,Edaphic ,Biology ,Late Miocene ,Plants ,Biological Evolution ,Models, Biological ,Africa, Southern ,Soil ,Habitat ,Cape ,Genetics ,Molecular Biology ,Ecology, Evolution, Behavior and Systematics ,Global biodiversity - Abstract
The plant diversity of the Cape Floristic Region is regarded as being exceptional in an ecological and evolutionary context. The region supports about double the number of species predicted by models based on water-energy variables for regional floras globally. However, contemporary diversity patterns are profoundly influenced by evolutionary processes contingent upon idiosyncrasies of history and geography. The relatively recent appearance of dated molecular phylogenies, and their optimization in relation to habitat and geography, has provided hitherto unsurpassed opportunities to generate knowledge about the evolution of the Cape flora. Almost all studies invoke climatic deterioration during the Mio-Pliocene as the major trigger of radiations and subsequent speciation of Cape clades. While some do show the importance of edaphic heterogeneity for clade radiation, the evolution of this heterogeneity is not considered. Here, we review the literature on the late Cenozoic geomorphic evolution of the Cape in order to assess the extent to which the changing nature of scenery and soils could act as a stimulus for plant diversification. Despite dating uncertainties associated with both the phylogenetic and geomorphic data, it appears that moderate uplift in the early and late Miocene, which significantly increased the topo-edaphic heterogeneity of the Cape was an important driver of plant diversification. In particular, the massive increase in heterogeneity after the late Miocene event probably acted in synergy with rapid climatic deterioration, to produce the extraordinarily rapid diversification recorded for some Cape clades at that time. A comparison of the plant diversity and palaeoenvironmetal patterns of mediterranean-climate regions provide insights regarding the "remarkable environmental conditions" of the Cape that have generated the high diversification and low extinction rates necessary to produce such a rich flora. These conditions are a gradual increase in topo-edaphic heterogeneity and relative climatic stability during the late Cenozoic. more...
- Published
- 2007
16. Climate and Vegetation History of the Subtropical Crater Lake 'Tswaing', South Africa
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I. Kristen, Heinz Wilkes, A. Fuhrmann, Hedi Oberhänsli, G. H. Haug, Brian Horsfield, and T. C. Partridge
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550 - Earth sciences - Published
- 2006
17. Dating the Sterkfontein Fossils
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Ronald J. Clarke, Darryl E. Granger, T. C. Partridge, and M.W. Caffe
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geography ,Multidisciplinary ,geography.geographical_feature_category ,biology ,Australopithecus anamensis ,Outcrop ,Bedrock ,biology.organism_classification ,Paleontology ,Stratigraphy ,Cave ,Australopithecus ,Stage (stratigraphy) ,Breccia ,Geology - Abstract
In an article (“Great age suggested for South African hominids,” News of the Week, 25 April, p. [562][1]) published in conjunction with our announcement of new absolute dates and early hominid specimens from Sterkfontein (“Lower Pliocene hominid remains from Sterkfontein,” T. C. Partridge et al. , Research Article, 25 April, p. [607][2]), Ann Gibbons writes, “co-author Clarke says that Little Foot does not resemble A. anamensis in crucial aspects. And he says that the new Jacovec fossils, which [co-author] Granger dated to 4 million years ago, may represent two types of australopithecines—suggesting a diversity of 4-million-year-old hominids.” These statements by Gibbons are incorrect. Clarke told Gibbons that it was not possible at this stage to compare the australopithecines at Jacovec Cavern with Australopithecus anamensis because the most diagnostic part of A. anamensis , the mandible, was not represented in the Jacovec fossil sample. Furthermore, the Little Foot skeleton, including the mandible, is still embedded in breccia and thus cannot yet be compared directly to A. anamensis or any other Australopithecus species. In the text of our paper, we observed that there are two forms of femur represented in the Member 4 breccia of Sterkfontein and that one of these, the long-necked form, is present in Jacovec. We state, “This suggests that two different forms of Australopithecus might be represented by the Sterkfontein femurs.” We did not say, and do not even consider, that two forms are currently represented in the Jacovec sample. We take this opportunity to correct other misconceptions about the dating. The stratigraphy at Sterkfontein is not particularly complex and is well documented in numerous surface and underground exposures, as well as by five stratigraphic boreholes [see ( 2 , 5 ) in our Research Article]. The validity of our results is, however, constrained by local relationships and not by overall stratigraphy. The hominid-bearing deposits that we dated were the first to accumulate after the cave opened to the surface via two vertical shafts. The sampling sites are in deep chambers whose dolomite roofs remain intact and exceed 20 m in thickness. These deposits overlie a basal sequence (Member 1) made up of roof-collapse blocks and insoluble components of the dolomite bedrock (mainly manganese and iron oxides) that accumulated as a fine residue during phreatic solution (i.e., below the water table); no extracavernous elements have been found within Member 1. Careful examination of the surface of the Sterkfontein hill, which consists largely of outcropping dolomite bedrock, as well as the shaft conduits themselves, has failed to reveal any infill deposits that could have contaminated soil entering the cave from the hill slopes outside. The shafts themselves are dolomite-walled and vertical and are not a source of quartz particles. It must also be pointed out that contamination from infills at depths shallower than 20 m would result in a reduction in apparent age, as such deposits would, regardless of their true age, have accumulated recent 26Al and 10Be. The sequence within the Silberberg Grotto that contains the skeleton is well layered and includes four thick and laterally persistent layers of hard calcite flowstone that occur within a vertical interval of 3 m; after each of the intervening soil layers fell from above, it was sealed off by the next flowstone, precluding vertical mixing. The skeleton is sandwiched between the second and third flowstones, both of which were intact when our excavations began. # Response {#article-title-2} The article should have said that there were two types of australopithecines at Sterkfontein rather than in the Jacovec caverns, and I regret the error. On the question of hominid diversity in Africa, I asked co-author Ron Clarke if the skeleton called Little Foot (Stw 573) was a member of Australopithecus anamensis , which lived in East Africa at the same time, and he replied in a telephone interview: “No, we cannot say it is like anamensis .” He added that he did not have the “right parts” to settle the taxonomic question, but then continued, “This was another indication that there were many species of australopithecines ranging all over Africa, just as there were multiple species of Miocene apes. There were multiple species of ape-men.” I gave all the authors an opportunity to check facts in the final draft of the article. Granger made minor corrections on the dating, Partridge did not respond to e-mail or a telephone message for 4 days, which was after deadline, and Clarke was unavailable. [1]: /lookup/doi/10.1126/science.300.5619.562 [2]: /lookup/doi/10.1126/science.1081651 more...
- Published
- 2003
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18. Cosmogenic nuclide dating of Australopithecus at Sterkfontein, South Africa.
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Granger, Darryl E., Stratford, Dominic, Bruxelles, Laurent, Gibbon, Ryan J., Clarke, Ronald J., and Kuman, Kathleen
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COSMOGENIC nuclides ,SPELEOTHEMS ,EROSION ,BRECCIA ,FOSSILS - Abstract
Sterkfontein is the most prolific single source of Australopithecus fossils, the vast majority of which were recovered from Member 4, a cave breccia now exposed by erosion and weathering at the landscape surface. A few other Australopithecus fossils, including the StW 573 skeleton, come from subterranean deposits [T. C. Partridge et al., Science 300, 607-612 (2003); R. J. Clarke, K. Kuman, J. Hum. Evol. 134, 102634 (2019)]. Here, we report a cosmogenic nuclide isochron burial date of 3.41 ± 0.11 million years (My) within the lower middle part of Member 4, and simple burial dates of 3.49 ± 0.19 My in the upper middle part of Member 4 and 3.61 ± 0.09 My in Jacovec Cavern. Together with a previously published isochron burial date of 3.67 ± 0.16 My for StW 573 [D. E. Granger et al., Nature 522, 85-88 (2015)], these results place nearly the entire Australopithecus assemblage at Sterkfontein in the mid-Pliocene, contemporaneous with Australopithecus afarensis in East Africa. Our ages for the fossil-bearing breccia in Member 4 are considerably older than the previous ages of ca. 2.1 to 2.6 My interpreted from flowstones associated with the same deposit. We show that these previously dated flowstones are stratigraphically intrusive within Member 4 and that they therefore underestimate the true age of the fossils. [ABSTRACT FROM AUTHOR] more...
- Published
- 2022
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19. Late Neogene Uplift in Eastern and Southern Africa and Its Paleoclimatic Implications
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T. C. Partridge
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African Plate ,Paleontology ,Plate tectonics ,Passive margin ,East African Rift ,Period (geology) ,Late Miocene ,Neogene ,Cretaceous ,Geology - Abstract
With the exception of the Mediterranean and Red Sea littorals, Africa is one of the few continents whose underlying plate is entirely bounded by passive margins. The absolute motion of the African plate has, indeed, been relatively small since the end of the Cretaceous, amounting to no more than 14° of northward movement.1 However, the rate of drift toward the Eurasian and Indian-Arabian boundaries has not been constant through this period: its progress was significantly influenced by global patterns of plate movement, especially during the Neogene.2 more...
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- 1997
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20. GUY WHATELY BOND, FRSSAf
- Author
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T. C. Partridge
- Subjects
Polymer science ,Philosophy ,Bond ,General Earth and Planetary Sciences ,General Medicine ,General Agricultural and Biological Sciences ,General Environmental Science - Published
- 1992
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21. Re-appraisal of lithostratigraphy of Makapansgat Limeworks hominid site
- Author
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T. C. Partridge
- Subjects
Paleontology ,Multidisciplinary ,Lithostratigraphy ,Geology - Abstract
A new lithostratigraphic classification is proposed for the Makapansgat Limeworks hominid site. The Makapansgat Formation is defined in terms of constituent members and beds. The new terminology is correlated with that used previously and hominid finds are linked to the newly defined lithostratigraphic units. more...
- Published
- 1979
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22. Re-appraisal of lithostratigraphy of Sterkfontein hominid site
- Author
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T. C. Partridge
- Subjects
Paleontology ,Multidisciplinary ,Lithostratigraphy ,Geology ,Terminology - Abstract
A new lithostratigraphic classification is proposed for the Sterkfontein hominid site. The Sterkfontein Formation is defined in terms of constituent members and beds. The new terminology is correlated with that used previously and, where possible, hominid finds are linked to the newly defined lithostratigraphic units. more...
- Published
- 1978
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23. FRACTURE ANALYSIS IN THE DETERMINATION OF SUB-UNCONFORMITY STRUCTURE: A PHOTOGEOLOGICAL STUDY
- Author
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T. C. Partridge and J. W. Norman
- Subjects
Stress system ,Anticline ,Geochemistry ,Energy Engineering and Power Technology ,Geology ,Unconformity ,Geological structure ,Diagenesis ,Fuel Technology ,Earth and Planetary Sciences (miscellaneous) ,Fracture (geology) ,Structural geology ,Geomorphology - Abstract
This is a record of an attempt to understand the geological structure of an area of several thousand square kilometres where the main interest lies in formations concealed under some 750 to 2500m of unconformable terrestrial sediments. Various fracture trace techniques have been used in an attempt to understand the stress system in the underlying rocks, and to distinguish between movements caused by horizontal and vertical forces. The study resulted in the interpretation of possible anticlines, domes, and drape folds in the underlying rocks, whereas the surface rocks were found to be mainly deformed by differential compaction during diagenesis. more...
- Published
- 1978
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24. Construction upon dolomites of the South-Western Transvaal
- Author
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V. A. Diesel, G. M. Harris, and T. C. Partridge
- Subjects
Mining engineering ,Nature Conservation ,Dolomite ,Geochemistry ,Geology ,Geotechnical Engineering and Engineering Geology ,Groundwater - Abstract
Some 15 000 km2 of the Transvaal Province of South Africa are underlain by soluble dolomite rocks. The south-western part of the Province contains some of the world's largest gold mines. Development and operation of these mines has affected performance of surface structures through groundwater lowering in soil covered areas underlain by cavernous dolomite. more...
- Published
- 1981
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25. Generalist species exhibit more genetic structure in comparison to a habitat specialist: Evidence from a phylogeographic study of two freshwater crabs (Decapoda: Potamonautidae: Potamonautes), implications for habitat conservation.
- Author
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Grobler, Petrus C. J. and Daniels, Savel R.
- Subjects
FRESHWATER crabs ,HABITAT conservation ,ADAPTIVE radiation ,SYMPATRIC speciation ,AQUATIC invertebrates - Abstract
During the present study, the phylogeography of the wetland specialist, freshwater crab, Potamonautes flavusjo, was investigated and compared to that of the ubiquitous, generalist, P. sidneyi, using DNA sequence data from the mitochondrial cytochrome oxidase subunit one (COI). We inferred the evolutionary history of each species and compared their population‐level genetic structure by constructing haplotype networks and using an analysis of molecular variation. Additionally, we explored the evolutionary relationship between southern African lentic and lotic freshwater crab species by examining the usefulness of carapace attributes in relation to genetic indices and a species' assumed dispersal capacity. In the lentic species, P. flavusjo, a single interconnected haplocluster characterized by shared haplotypes was observed, suggesting marked maternal dispersal, a result corroborated by the low FST values. In contrast, for the lotic species, P. sidneyi two distinct haploclusters and marked genetic differentiation was observed indicating the absence of maternal dispersal, a result corroborated by the high FST values. The phylogenetic relationship in P. sidneyi was further investigated using a maximum likelihood and Bayesian inference analyses with the addition of sequence data from the mitochondrial 16S rRNA locus to estimate divergence times. Three species delimitation methods (ASAP, PTP, and bGMYC) were used to explore the presence of distinct lineages in P. sidneyi. The phylogenetic results indicated that within P. sidneyi two clades were present, while divergence time estimates suggest cladogenesis during the middle to late Pleistocene. The species delimitation methods used showed moderate congruence, however all oversplit the number of putative lineages. Our results indicated that P. sidneyi is a species complex comprised of two cryptic lineages, occurring in sympatry contemporarily possibly alluding to secondary contact. Carapace height was found to have no discernible influence on the genetic indices and presumed dispersal capabilities of mainland southern African freshwater crab species. The importance of our results are discussed in terms of conservation of freshwater habitats. [ABSTRACT FROM AUTHOR] more...
- Published
- 2024
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26. Earliest Prepared core technology in Eurasia from Nihewan (China): Implications for early human abilities and dispersals in East Asia.
- Author
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Dong-Dong Ma, Shu-Wen Pei, Fei Xie, Zhi Ye, Fa-Gang Wang, Jing-Yue Xu, Cheng-Long Deng, and de la Torre, Ignacio
- Subjects
STONE implements ,HOMINIDS ,HUMAN beings ,RAW materials - Abstract
Organized flaking techniques to obtain predetermined stone tools have been traced back to the early Acheulean (also known as mode 2) in Africa and are seen as indicative of the emergence of advanced technical abilities and in-depth planning skills among early humans. Here, we report one of the earliest known examples of prepared core technology in the archaeological record, at the Cenjiawan (CJW) site in the Nihewan basin of China, dated 1.1 Mya. The operational schemes reconstructed from the CJW refit sets, together with shaping patterns observed in the retouched tools, suggest that Nihewan basin toolmakers had the technical abilities of mode 2 hominins, and developed different survival strategies to adapt to local raw materials and environments. This finding predates the previously earliest known prepared core technology from Eurasia by 0.3 My, and the earliest known mode 2 sites in East Asia by a similar amount of time, thus suggesting that hominins with advanced technologies may have migrated into high latitude East Asia as early as 1.1 Mya. [ABSTRACT FROM AUTHOR] more...
- Published
- 2024
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27. Let's get high: Cladogenesis in freshwater crabs (Decapoda: Potamonautidae: Potamonautes) supports the mountain gradient speciation hypothesis in the Cape Fold and Drakensberg Mountains, South Africa.
- Author
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Daniels, Savel R., Peer, Nasreen, Myburgh, Angus Macgregor, Barnes, Aaron, and Klaus, Sebastian
- Subjects
FRESHWATER crabs ,ADAPTIVE radiation ,DECAPODA ,TIME perception ,NUMBERS of species ,MOUNTAINS - Abstract
During the present study, the evolutionary relationship within a clade of mountain clade of freshwater crabs (Potamonautes) was examined using mtDNA sequence data for species from the Cape Fold Mountain (CFM) and Great Escarpment (Drakensberg Mountain range). We undertook phylogenetic analyses, divergence time estimation, and an ancestral area reconstruction to explore the period of cladogenesis and understand the biogeographic history in this high‐altitude clade. Furthermore, we applied four species delimitation methods using ASAP, bPTP, bGMYC, and STACEY on the latter clade. Bayesian phylogenetic analyses retrieved a monophyletic freshwater crab clade comprised of two major sister clades, one comprised of the Cape Fold (clade A) and two comprised of Drakensberg Mountains (clade B) species. Divergence time estimation indicated that the two clades underwent Mio/Pliocene cladogenesis. Within the CFM clade (A), P. amathole (Amathola Mountains) was sister to P. parvispina (Cederberg and Kouebokkeveld Mountains) and the latter species were sister to P. parvicorpus (Cape Peninsula, Jonkershoek, and Helderberg Mountains) sister to P. tuerkayi (Overberg Mountains) and P. brincki (Hottentots Holland Mountains). Within the Drakensberg Mountain clade (B), we observed in situ diversification. Specimens from the southcentral Drakensberg Mountains (Dargle Forest, Injasuti, Karkloof, and Impendle) represent a new undescribed lineage Potamonautes sp. nov. 1. The second clade from the northern Drakensberg, representing P. clarus, was sister to a central Drakensberg Mountain clade that comprised P. depressus that was in turn sister to P. baziya from the Eastern Cape Province. The application of species delimitation methods generally overestimated the number of species. The biogeographic analyses indicated that the Eastern Cape Province is the most likely ancestral range area. Ecological niche modelling of representative species in clades A (Cape Fold Mountains) and B (Drakensberg Mountains) demonstrated that temperature and rainfall were the major abiotic drivers that differentiated the two clades. Our data favours the mountain gradient speciation hypothesis. [ABSTRACT FROM AUTHOR] more...
- Published
- 2024
- Full Text
- View/download PDF
28. Numerical study on the particle distribution of coal for recovery of critical metals.
- Author
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Jha, Vandana Kumari
- Subjects
COAL ,COMPUTATIONAL fluid dynamics ,PARTICLE size distribution ,METALS ,GRANULAR flow ,SUPERCONDUCTING coils - Abstract
Coal is considered to be a significant resource of critical metals and minerals. Recovery of these critical metals is considered to be highly important in terms of advancement and technology. This paper presents a numerical study of the particle size distribution of coal and its impact on the recovery of critical metals. This study uses the computational fluid dynamics (CFD) model to simulate the transport and deposition of coal particles inside a helical domain, which can be used as a device for separating particles. The numerical study , based on the particle tracing model for fluid flow and particle tracing, is used to simulate the behavior of coal particles in a slurry under different flow conditions. The transient study for a six-turn helical coil domain is analyzed for different flow velocities ranging from 4000 ≤ R e ≤ 8000. The simulation results show that the particle size distribution of coal plays a crucial role in the recovery of critical metals. Additionally, the distribution of critical metals inside the domain varies with the size and density of the particles. It is observed that increasing the fluid velocity can significantly increase the recovery of critical metals. Finally, the transmission probability of particles remaining trapped inside the domain is also calculated, which could help in optimizing the helical geometry so that all the particles could come out of the flowing conduit. The number of particles coming out of the helical domain increases with the increase in flow rate. The results of the study show that the particle size distribution of coal plays a significant role in the recovery of critical metals. The findings can help guide the development of more efficient and cost-effective methods for extracting critical metals from coal. [ABSTRACT FROM AUTHOR] more...
- Published
- 2023
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29. The geomorphology and neotectonics of the Vaalputs Radioactive Waste Disposal Facility site, Namaqualand, South Africa: Palaeoseismological and geodynamic implications.
- Author
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Andreoli, M. A. G., Knight, J., Durrheim, R. J., and Evans, M.
- Subjects
RADIOACTIVE wastes ,RADIOACTIVE waste sites ,RADIOACTIVE waste disposal ,NEOTECTONICS ,GEOMORPHOLOGY ,WASTE products ,FAULT zones ,THRUST faults (Geology) - Abstract
The safe disposal of radioactive waste products remains a challenging and controversial issue, yet their burial in a stable geological environment is the option favoured by most countries. Past investigations of the Vaalputs facility in South Africa's semi-arid Bushmanland Plateau demonstrated its suitability for the disposal of low-level, short-lived (<300 years) radioactive waste, but also the need for more data on hazardous seismotectonic and climatic processes for the potential storage of longer-lived spent nuclear fuel. We review and then provide new information on the regional geomorphological and morphotectonic features of the Bushmanland Plateau, focusing on pedogenic features and compressive shear fractures in the trenches excavated over the past two decades. The fractures, provisionally dated between ~75 ka and ~46 ka, resemble east-verging thrust faults of limited horizontal displacement (≤1 m) and die out at depths of 4 m. Having discounted a pedogenic origin, the shear fractures likely represent stress relief structures triggered by the seismogenic reactivation of one of the Quaternary active faults in the area. The most likely candidate is the Santab Fault Zone (SFZ), which has a strike length ≥20 km and a throw of up to ~5 m at its closest point (8 km) to the Vaalputs site. Regional remote sensing and off-site investigations in the Bushmanland Plateau relate the neotectonic episodes at Vaalputs and environs to a late Pleistocene climax of the Namaqualand seismic source zone. This zone is characterised by the Wegener Stress Anomaly, a long-lived ~northwest-southeast oriented compression that, at its apex in the Late Santonian, caused large scale folding and thrusting not only in Bushmanland and parts of central-southern Namibia, but also swept across the entire African plate. [ABSTRACT FROM AUTHOR] more...
- Published
- 2023
- Full Text
- View/download PDF
30. Assessing the subsistence strategies of the earliest North African inhabitants: evidence from the Early Pleistocene site of Ain Boucherit (Algeria)
- Author
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Cáceres, Isabel, Chelli Cheheb, Razika, van der Made, Jan, Harichane, Zoheir, Boulaghraief, Kamel, and Sahnouni, Mohamed
- Abstract
The archaeological data on the earliest hominin behavioral subsistence activities in North Africa are derived primarily from the Early Pleistocene site of Ain Boucherit (northeastern Algeria). Ain Boucherit consists of two archaeological layers, Ain Boucherit Upper (AB-Up) and Ain Boucherit Lower (AB-Lw), estimated to ~ 1.9 Ma and ~ 2.4 Ma, respectively. Cutmarked and hammerstone percussed bones associated with Oldowan stone tools were found in both layers, with AB-Lw yielding the oldest in North Africa. The faunal assemblages from both deposits are dominated by small-sized bovids and equids. Evidence of cutmarks and percussion marks in both assemblages shows that hominins exploited animal carcasses, involving skinning, evisceration and defleshing activities. The evidence of meat and marrow acquisition is more abundant at AB-Lw with carnivore activity being scarce. However, the AB-Up assemblage shows more carnivore damage and less hominin-induced tool marks. Ain Boucherit evidence, is similar, in type and chronology, to that provided by the Early Pleistocene sites in East Africa (e.g., the Gona sites), where the oldest evidence of stone tools used in faunal exploitation have been discovered. This paper reports on the ability of early North African Oldowans to compete successfully for accessing animal resources with other predators. [ABSTRACT FROM AUTHOR] more...
- Published
- 2023
- Full Text
- View/download PDF
31. Paleolakes and socioecological implications of last glacial "greening" of the South African interior.
- Author
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Carr, Andrew S., Chase, Brian M., Birkinshaw, Stephen J., Holmes, Peter J., Rabumbulu, Mulalo, and Stewart, Brian A.
- Subjects
DISTRIBUTED databases ,GLACIATION ,ARCHAEOLOGICAL assemblages ,BODIES of water ,MESOLITHIC Period - Abstract
Determining the timing and drivers of Pleistocene hydrological change in the interior of South Africa is critical for testing hypotheses regarding the presence, dynamics, and resilience of human populations. Combining geological data and physically based distributed hydrological modeling, we demonstrate the presence of large paleolakes in South Africa's central interior during the last glacial period, and infer a regional-scale invigoration of hydrological networks, particularly during marine isotope stages 3 and 2, most notably 55 to 39 ka and 34 to 31 ka. The resulting hydrological reconstructions further permit investigation of regional floral and fauna responses using a modern analog approach. These suggest that the climate change required to sustain these water bodies would have replaced xeric shrubland with more productive, eutrophic grassland or higher grass-cover vegetation, capable of supporting a substantial increase in ungulate diversity and biomass. The existence of such resource-rich landscapes for protracted phases within the last glacial period likely exerted a recurrent draw on human societies, evidenced by extensive pan-side artifact assemblages. Thus, rather than representing a perennially uninhabited hinterland, the central interior's underrepresentation in late Pleistocene archeological narratives likely reflects taphonomic biases stemming from a dearth of rockshelters and regional geomorphic controls. These findings suggest that South Africa's central interior experienced greater climatic, ecological, and cultural dynamism than previously appreciated and potential to host human populations whose archaeological signatures deserve systematic investigation. [ABSTRACT FROM AUTHOR] more...
- Published
- 2023
- Full Text
- View/download PDF
32. Vrba was right: Historical climate fragmentation, and not current climate, explains mammal biogeography.
- Author
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Gamboa S, Galván S, and Varela S
- Subjects
- Animals, Climate, Animal Distribution, Phylogeography, Biological Evolution, Mammals physiology, Climate Change, Biodiversity
- Abstract
Climate plays a crucial role in shaping species distribution and evolution over time. Dr Vrba's Resource-Use hypothesis posited that zones at the extremes of temperature and precipitation conditions should host a greater number of climate specialist species than other zones because of higher historical fragmentation. Here, we tested this hypothesis by examining climate-induced fragmentation over the past 5 million years. Our findings revealed that, as stated by Vrba, the number of climate specialist species increases with historical regional climate fragmentation, whereas climate generalist species richness decreases. This relationship is approximately 40% stronger than the correlation between current climate and species richness for climate specialist species and 77% stronger for generalist species. These evidences suggest that the effect of climate historical fragmentation is more significant than that of current climate conditions in explaining mammal biogeography. These results provide empirical support for the role of historical climate fragmentation and physiography in shaping the distribution and evolution of life on Earth., (© 2024 The Author(s). Global Change Biology published by John Wiley & Sons Ltd.) more...
- Published
- 2024
- Full Text
- View/download PDF
33. Evidence for parallel development of ever-growing molars in Early Pleistocene rodents from southern Spain and their paleoenvironmental implications.
- Author
-
AGUSTÍ, JORDI and PIÑERO, PEDRO
- Subjects
PLEISTOCENE Epoch ,RODENTS ,MOLARS ,APODEMUS ,MURIDAE - Abstract
In this paper, we present a detailed survey on the rodent fauna from the site of Barranco de los Conejos (Guadix-Baza Basin, southern Spain). Its rodent fauna is composed of three arvicolines (Orcemys giberti, Manchenomys oswaldoreigi, and Tibericola vandermeuleni) and two murids (Castillomys rivas and Apodemus atavus). The three arvicoline species present ever-growing molars. Orcemys giberti and Manchenomys oswaldoreigi can be considered as descendants of local Mimomys species (Mimomys medasensis and Mimomys tornensis, respectively), while Tibericola vandermeuleni is an eastern inmigrant. Loosening of roots in Orcemys giberti and Manchenomys oswaldoreigi is explained as an adaptation to a fossorial way of life, in relation to the Early Pleistocene glacial-interglacial dynamics, which led to cooler and drier conditions. This environmental change would also explain the dispersal of Tibericola from the eastern Mediterranean. [ABSTRACT FROM AUTHOR] more...
- Published
- 2023
- Full Text
- View/download PDF
34. Macroseismic analysis and the determination of a focal mechanism of the 31 October 2019, KwaZulu-Natal earthquake in South Africa.
- Author
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Manzunzu, B., Midzi, V., Zulu, T., and Mphahlele, K.
- Subjects
GROUND motion ,EARTHQUAKE intensity ,EARTHQUAKES ,SURFACE fault ruptures ,FAULT zones ,COASTS - Abstract
An earthquake (magnitude, ML = 3.8) occurred on 31 October 2019 at 11:19 hours Greenwich Mean Time (GMT) in the Sunduza area of the KwaZulu-Natal (KZN) Province in South Africa. The earthquake was located near the broad fracture zone of the Ntlakwe-Bongwan fault and was felt along the eastern coast of South Africa. The effects of the event were assessed by conducting macroseismic investigations through interviewing members of the public and completing questionnaires. Analysis of all the collected macroseismic data showed that maximum shaking with Modified Mercalli Intensity of IV-V and V were experienced near the epicentral area as well as along the coast. Similar intensity values were also experienced in some parts of Durban about 100 km northeast of the epicentre. Shaking at such long distances was attributed to ground motion amplification due to site effects. A fault plane solution of the event obtained using both the first motion polarities and amplitude ratios showed normal faulting along a fault oriented in a strike of 185.0°, dipping at 68.0° with a rake of -52.0°. The strike of the focal mechanism solution aligns with the strike of the Ntlakwe-Bongwan fault zone and nearby faults suggesting that the event might have ruptured along one of the fracture segments of this fault mapped to the north. The obtained dip is also in line with a high angle fault comparable to that observed along the Ntlakwe-Bongwan fault. The epicentral region is highly faulted although the activity is not known. [ABSTRACT FROM AUTHOR] more...
- Published
- 2023
- Full Text
- View/download PDF
35. Geomorphological evolution and mapping of the littoral of Asturias and Cantabria (Northern Spain) in the area of El Pindal Cave: relations between coastline and karstic morphologies.
- Author
-
Goy, José Luis, Zazo, Caridad, Elez, Javier, Martínez-Graña, Antonio Miguel, Cañaveras, J. C., Dábrio, Cristino José, Duarte, Elsa, De Bustamante, Irene, and Sánchez Moral, Sergio
- Subjects
GEOMORPHOLOGICAL mapping ,CAVES ,COASTS ,GEOMORPHOLOGY ,LANDFORMS ,SHORELINES ,SEA level - Abstract
Along the northern littoral of the Iberian Peninsula, from Cuerres (Asturias) to Oyambre (Cantabria) there are caves, such as El Pindal (World Heritage List). Two geomorphologic maps have been prepared: a general scaled 1:25000, and a detail one of the cave, with erosional and depositional landforms geomorphologic units. A relative Quaternary chronology for the depositional landforms, uses colour spots. Marine morphologies suitable for determining past sea-level positions were surveyed to identify the elevation of past high-stands and reconstructing paleo-shorelines. As a result, the study of seven erosional surfaces (rasas) in quartzites and six on limestones led to reconstructing a general sequence between 275–120 m and 90–1 m above sea level (a.s.l.) respectively. Around the El Pindal cave there are four rasas cut on quartzites (171–160 m) and four cut on limestone (65–32 m). Other additional indicators of paleoshorelines are: 24–25 m entrance to the El Pindal cave, 20–21 m lower Pindal, 15–17 m marine terrace, 9–10 m shelter, 2–3 m notches and 0– 1 m present rasa.Considering the elevation rates for the various rasas, an estimated value of 0.066 mm/y as the most probable, it is concluded that the beginning of Quaternary lays at 172 m a.s.l. [ABSTRACT FROM AUTHOR] more...
- Published
- 2023
- Full Text
- View/download PDF
36. Overlooked or Unimportant? An Overview of the Coprolite Collections at the University of the Witwatersrand, Johannesburg, South Africa.
- Author
-
Zipfel, Bernhard, Montgomery, Chandele, Neumann, Frank H., Scott, Louis, Choiniere, Jonah, and Hancox, John P.
- Abstract
Fossilized feces, termed coprolites, provide unique information on digestive systems, diets, and ecosystems of extinct animals, and are potentially useful for palynology, biostratigraphy and preservation of animal and plant remains. Despite this broad utility, scientific enquiry into coprolites has been relatively sparse. We carried out a systematic investigation into 23 significant South African fossil collections of the Evolutionary Studies Institute (ESI), University of the Witwatersrand, Johannesburg, in search of coprolites. This study spanned a temporal range from the Permian to the recent Cenozoic returning approximately 790 known coprolites in the collections. Of these, only four assemblages have appeared in six coprolite‐specific publications. Others have been mentioned to some extent in publications focused on fauna, palynology or simply mentioned that coprolites were present. Clearly, the coprolite collections at the ESI are understudied and require attention with the intention of stimulating a greater interest in this field. [ABSTRACT FROM AUTHOR] more...
- Published
- 2023
- Full Text
- View/download PDF
37. Between the Cape Fold Mountains and the deep blue sea: Comparative phylogeography of selected codistributed ectotherms reveals asynchronous cladogenesis.
- Author
-
Myburgh, Angus Macgregor and Daniels, Savel Regan
- Subjects
PHYLOGEOGRAPHY ,ADAPTIVE radiation ,PLEISTOCENE Epoch ,COLD-blooded animals ,CLIMATE change ,NUCLEAR DNA ,POPULATION differentiation ,REPTILES - Abstract
We compare the phylogeographic structure of 13 codistributed ectotherms including four reptiles (a snake, a legless skink and two tortoise species) and nine invertebrates (six freshwater crabs and three velvet worm species) to test the presence of congruent evolutionary histories. Phylogenies were estimated and dated using maximum likelihood and Bayesian methods with combined mitochondrial and nuclear DNA sequence datasets. All taxa demonstrated a marked east/west phylogeographic division, separated by the Cape Fold Mountain range. Phylogeographic concordance factors were calculated to assess the degree of evolutionary congruence among the study species and generally supported a shared pattern of diversification along the east/west longitudinal axis. Testing simultaneous divergence between the eastern and western phylogeographic regions indicated pseudocongruent evolutionary histories among the study taxa, with at least three separate divergence events throughout the Mio/Plio/Pleistocene epochs. Climatic refugia were identified for each species using climatic niche modelling, demonstrating taxon‐specific responses to climatic fluctuations. Climate and the Cape Fold Mountain barrier explained the highest proportion of genetic diversity in all taxa, while climate was the most significant individual abiotic variable. This study highlights the complex interactions between the evolutionary history of fauna, the Cape Fold Mountains and past climatic oscillations during the Mio/Plio/Pleistocene. The congruent east/west phylogeographic division observed in all taxa lends support to the conclusion that the longitudinal climatic gradient within the Greater Cape Floristic Region, mediated in part by the barrier to dispersal posed by the Cape Fold Mountains, plays a major role in lineage diversification and population differentiation. [ABSTRACT FROM AUTHOR] more...
- Published
- 2022
- Full Text
- View/download PDF
38. The Western Cameroon Highland margin: Is there any geomorphometric evidence of active tectonics?
- Author
-
Nsangou Ngapna, Moussa, Owona, Sébastien, Balla Ateba, Christian, Mboudou, Germain Marie Monespérance, and Wabo Defo, Pascal Landry
- Subjects
UPLANDS ,DIGITAL elevation models ,EVOLUTIONARY models ,PROTEROZOIC Era - Abstract
The Western Cameroon Highland margin (WCHM) within the West African margin displays an uneven high relief. Its evolutionary model in vogue suggests the tectonic activity of the Cameroon Volcanic Line (CVL). An evident question in this regard is whether there is any geomorphometric evidence in support of what is this widespread view? We evaluate this question using field controls and geomorphometric indices of active tectonics derived for 13 main river basins with the help of digital elevation model (DEM)‐30 m data. The WCHM is developed on Proterozoic granite‐gneissic basement and the Cretaceous to Recent volcano‐sedimentary cover and was affected by regional active tectonic features. It is marked by transient signs of different landscape evolutionary stages recorded by the relief and drainage network; shown by gradual adjustment of rivers to equilibrium stages; and cautioned by a greatest variation of DEM‐based geomorphic indices. These indices, hypsometric integral (HI = 0.10–0.35), topography relief (TR = 595–2,710), topography dissection (TD = 114–829), valley floor width to valley height ratio (Vf arg = 0.61–14.91), transverse topographic symmetric factor (T‐index = 0.18–0.49), and basin asymmetric factor (AF = 1.08–24.37) highlight elevated and roughness character of that margin, from the Benue Trough and culminating to the CVL. River longitudinal profiles reveal variably and deeply incised WCHM by the drainage network, reinforced by ongoing tectonic activities. Knickpoints (Kps), stream length‐gradient (SL), uplift (U = 1.17–2.0), and a variety of normalized steepness (Ksn = 11.63–635.16) evidence the diversity and preeminent tectonic controls. The above results show that the WCHM is widely considered to be the consequence of the mantle dynamisms and regional tectonics since Proterozoic, the CVL activities, and the erosional processes. [ABSTRACT FROM AUTHOR] more...
- Published
- 2022
- Full Text
- View/download PDF
39. Craniodental Morphology and Phylogeny of Marsupials.
- Author
-
Beck, Robin M.D., Voss, Robert S., and Jansa, Sharon A.
- Subjects
MARSUPIALS ,MORPHOLOGY ,PHYLOGENY ,DNA sequencing ,APOLIPOPROTEIN B ,BAYESIAN analysis ,MOLECULAR phylogeny ,BRCA genes ,PARSIMONIOUS models - Abstract
The current literature on marsupial phylogenetics includes numerous studies based on analyses of morphological data with limited sampling of Recent and fossil taxa, and many studies based on analyses of molecular data with dense sampling of Recent taxa, but few studies have combined both data types. Another dichotomy in the marsupial phylogenetic literature is between studies focused on New World taxa and those focused on Sahulian taxa. To date, there has been no attempt to assess the phylogenetic relationships of the global marsupial fauna based on combined analyses of morphology and molecular sequences for a dense sampling of Recent and fossil taxa. For this report, we compiled morphological and molecular data from an unprecedented number of Recent and fossil marsupials. Our morphological data consist of 180 craniodental characters that we scored for 97 terminals representing every currently recognized Recent genus, 42 additional ingroup (crown-clade marsupial) terminals represented by well-preserved fossils, and 5 outgroups (nonmarsupial metatherians). Our molecular data comprise 24.5 kb of DNA sequences from whole-mitochondrial genomes and six nuclear loci (APOB, BRCA1, GHR, RAG1, RBP3 and VWF) for 97 marsupial terminals (the same Recent taxa scored for craniodental morphology) and several placental and monotreme outgroups. The results of separate and combined analyses of these data using a wide range of phylogenetic methods support many currently accepted hypotheses of ingroup (marsupial) relationships, but they also underscore the difficulty of placing fossils with key missing data (e.g., †Evolestes), and the unique difficulty of placing others that exhibit mosaics of plesiomorphic and autapomorphic traits (e.g., †Yalkaparidon). Unique contributions of our study are (1) critical discussions and illustrations of marsupial craniodental morphology including features never previously coded for phylogenetic analysis; (2) critical assessments of relative support for many suprageneric clades; (3) estimates of divergence times derived from tip-and-node dating based on uniquely taxon-dense analyses; and (4) a revised, higher-order classification of marsupials accompanied by lists of supporting craniodental synapomorphies. Far from the last word on these topics, this report lays the foundation for future research that may be enabled by the discovery of new fossil taxa, better-preserved material of previously described taxa, novel morphological characters (e.g., from the postcranium), and improved methods of phylogenetic analysis. [ABSTRACT FROM AUTHOR] more...
- Published
- 2022
- Full Text
- View/download PDF
40. African climate and geomorphology drive evolution and ghost introgression in sable antelope.
- Author
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Rocha, Joana L., Vaz Pinto, Pedro, Siegismund, Hans R., Meyer, Matthias, Jansen van Vuuren, Bettine, Veríssimo, Luís, Ferrand, Nuno, and Godinho, Raquel
- Subjects
BIOGEOGRAPHY ,ANTELOPES ,INTROGRESSION (Genetics) ,GEOMORPHOLOGY - Abstract
The evolutionary history of African ungulates has been explained largely in the light of Pleistocene climatic oscillations and the way these influenced the distribution of vegetation types, leading to range expansions and/or isolation in refugia. In contrast, comparatively fewer studies have addressed the continent's environmental heterogeneity and the role played by its geomorphological barriers. In this study, we performed a range‐wide analysis of complete mitogenomes of sable antelope (Hippotragus niger) to explore how these different factors may have contributed as drivers of evolution in southcentral Africa. Our results supported two sympatric and deeply divergent mitochondrial lineages in west Tanzanian sables, which can be explained as the result of introgressive hybridization of a mitochondrial ghost lineage from an archaic, as‐yet‐undefined, congener. Phylogeographical subdivisions into three main lineages suggest that sable diversification may not have been driven solely by climatic events affecting populations differently across a continental scale. Often in interplay with climate, geomorphological features have also clearly shaped the species' patterns of vicariance, where the East Africa Rift System and the Eastern Arc Mountains acted as geological barriers. Subsequent splits among southern populations may be linked to rearrangements in the Zambezi system, possibly framing the most recent time when the river attained its current drainage profile. This work underlines how the use of comprehensive mitogenomic data sets on a model species with a wide geographical distribution can contribute to a much‐enhanced understanding of environmental, geomorphological and evolutionary patterns in Africa throughout the Quaternary. [ABSTRACT FROM AUTHOR] more...
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- 2022
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41. Biomarker and stable carbon isotope analyses of sedimentary organic matter from Lake Tswaing: evidence for deglacial wetness and early Holocene drought from South Africa.
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Kristen, I., Wilkes, H., Vieth, A., Zink, K.-G., Plessen, B., Thorpe, J., Partridge, T. C., and Oberhänsli, H.
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CARBON cycle ,LAKE hydrology ,ORGANIC compounds ,SEDIMENT analysis ,METHANOTROPHS - Abstract
Comparing the organic matter (OM) composition of modern and past lake sediments contributes to the understanding of changes in lacustrine environments over time. We investigate modern plant and lake-water samples as well as modern and ancient sediment samples from the Tswaing Crater in South Africa using biomarker and stable carbon isotope analyses on bulk OM and specific biomarker compounds. The characteristic molecular markers for higher land plants (predominantly C3-type deciduous angiosperms) in Lake Tswaing are long-chain n-alkanes ( n-C
27−33 ), n-alkanols ( n-C28+30 ), stigmasterol, β-sitosterol, β-amyrin, α-amyrin and lupeol. The C17 n-alkane, tetrahymanol, gammaceran-3-one and C29 sterols dominate the lipid fraction of autochthonously produced OM. By comparing stable carbon isotope analyses on bulk OM and the characteristic biomarkers, we follow the modern carbon cycle in the crater environment and find indications for methanotrophic activity in the lake from isotopically depleted moretene. A comparative study of core sediments reveals changes in the terrestrial (C3 versus C4) and aquatic bioproductivity and allows insights into the variability of the carbon cycle under the influence of changing climatic conditions for the time from the end of the last glacial (Termination I) to the late Holocene, ca. 14,000–2,000 calibrated years before present (years BP). The most pronounced changes occur in the aquatic realm after ca. 10,000 years BP when our results imply climate swings from more humid to more arid and after 7,500 years BP to gradually more humid conditions again, which can be related to a shift in the position of the Inter-Tropical Convergence Zone or to changes in the tropical atmosphere–ocean interaction. Long-chain alkenones (LCAs) have been identified in ancient lake sediments from Africa for the first time. They occur in samples older than 7,500 years BP and their distribution (dominance of C38 and of tri- over tetra-unsaturated LCAs) is distinctly different from other published records suggesting a to date unknown source organism. [ABSTRACT FROM AUTHOR] more...- Published
- 2010
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42. Plio-Pleistocene environmental variability in Africa and its implications for mammalian evolution.
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Cohen, Andrew S., Du, Andrew, Rowan, John, Yost, Chad L., Billingsley, Anne L., Campisano, Christopher J., Brown, Erik T., Deino, Alan L., Feibel, Craig S., Grant, Katharine, Kingston, John D., Lupien, Rachel L., Muiruri, Veronica, Owen, R. Bernhart, Reed, Kaye E., Russell, James, and Stockhecke, Mona more...
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BIOLOGICAL extinction ,FOSSIL mammals ,OCEAN temperature ,FOSSILS ,PALEOCLIMATOLOGY - Abstract
Understanding the climatic drivers of environmental variability (EV) during the Plio-Pleistocene and EV's influence on mammalian macroevolution are two outstanding foci of research in African paleoclimatology and evolutionary biology. The potential effects of EV are especially relevant for testing the variability selection hypothesis, which predicts a positive relationship between EV and speciation and extinction rates in fossil mammals. Addressing these questions is stymied, however, by 1) a lack of multiple comparable EV records of sufficient temporal resolution and duration, and 2) the incompleteness of the mammalian fossil record. Here, we first compile a composite history of Pan-African EV spanning the Plio-Pleistocene, which allows us to explore which climatic variables influenced EV. We find that EV exhibits 1) a long-term trend of increasing variability since ~3.7 Ma, coincident with rising variability in global ice volume and sea surface temperatures around Africa, and 2) a 400-ky frequency correlated with seasonal insolation variability. We then estimate speciation and extinction rates for fossil mammals from eastern Africa using a method that accounts for sampling variation. We find no statistically significant relationship between EV and estimated speciation or extinction rates across multiple spatial scales. These findings are inconsistent with the variability selection hypothesis as applied to macroevolutionary processes. [ABSTRACT FROM AUTHOR] more...
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- 2022
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43. J. R. LOGAN AND THE ORIGIN OF THE TROPICAL INSELBERGS KNOWN AS NUBBINS (OR KNOLLS).
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TWIDALE, C. ROWLAND
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BEDROCK ,CHEMICAL weathering ,TOPOGRAPHY ,COASTS ,BOULDERS - Abstract
Pulau Ubin is located in the Johor Strait between the Malay Peninsula and Singapore Island. The topography shaped in a granitoid complex of Permo-Triassic age, comprises jungle covered and isolated blocky hills, a flat and marshy central valley floor, and a coastline in which grooved boulders are prominent. In papers published in 1847, 1849 and 1851 (but here reporting their content in modern terminology) J. B. Logan attributed the island landscape to deep differential chemical weathering, followed by exposure of the resulting bedrock morphology. This is characterized by massive blocks protruding between a saprolithic cover—in modern parlance a two-stage etch origin of a group of inselbergs of nubbin (or knoll) type covered by blocks and boulders derived from the breakdown of the outer shell or shells or sheet structures. The Pulau Ubin nubbins carry remnants of a saprolithic veneer and are of 'wet' type by contrast with the saprolith-free 'dry' forms of arid or seasonally arid climes. The conversion of nubbins to bornhardts in arid climes also is noted. Logan identified the crucial aspects of what is still a highly favoured hypothesis of inselberg origin based on field evidence from many parts of the world and articulated by Falconer in 1911. But there was in Logan's time no agreed and appropriate technical terminology. Moreover, some of Logan's reports such as that dated 1849 are disorganized and diffuse, but contain occasional insightful observations and deductions. [ABSTRACT FROM AUTHOR] more...
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- 2022
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44. Large‐Scale Tectonic Forcing of the African Landscape.
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O'Malley, C. P. B., White, N. J., Stephenson, S. N., and Roberts, G. G.
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PLATE tectonics ,FLUVIAL geomorphology ,LANDSCAPES ,EROSION - Abstract
Successful inverse modeling of observed longitudinal river profiles suggests that fluvial landscapes are responsive to continent‐wide tectonic forcing. However, inversion algorithms make simplifying assumptions about landscape erodibility and drainage planform stability that require careful justification. For example, precipitation rate and drainage catchment area are usually assumed to be invariant. Here, we exploit a closed‐loop modeling strategy by inverting drainage networks generated by dynamic landscape simulations in order to investigate the validity of these assumptions. First, we invert 4,018 African river profiles to determine an uplift history that is independently calibrated, and subsequently validated, using separate suites of geologic observations. Second, we use this tectonic forcing to drive landscape simulations that permit divide migration, interfluvial erosion and changes in catchment size. These simulations reproduce large‐scale features of the African landscape, including growth of deltaic deposits. Third, the influence of variable precipitation is investigated by carrying out a series of increasingly severe tests. Inverse modeling of drainage inventories extracted from simulated landscapes can largely recover tectonic forcing. Our closed‐loop modeling strategy suggests that large‐scale tectonic forcing plays the primary role in landscape evolution. One corollary of the integrative solution of the stream‐power equation is that precipitation rate becomes influential only if it varies on time scales longer than ∼1 Ma. We conclude that calibrated inverse modeling of river profiles is a fruitful method for investigating landscape evolution and for testing source‐to‐sink models. Plain Language Summary: There is excellent geologic evidence that large portions of the African landscape were lifted up above sea level over the last 30 million years by upward flow of hot mantle rocks beneath the tectonic plate. The strongest evidence comes from marine deposits which contain fossil fish and sea snakes that are now perched at elevations of hundreds of meters in the middle of the North African desert. Mantle processes gave rise to an egg‐carton pattern of gigantic swells and depressions that characterizes much of the continent. As the landscape evolved, it was sculpted and eroded by the action of massive rivers such as the Niger, the Nile and the Congo. Height along the length of each of these rivers varies and appears to preserve a memory of landscape growth. In that sense, rivers appear to act as tape recorders of tectonic processes such as mantle flow. Here, we use computer simulations of an evolving landscape to test the idea that rivers contain mantle memories. These simulations, which include complexities such as variable rainfall, allow rivers to develop naturally as landscapes grow. Our results suggest that the African landscape and its drainage patterns contain valuable information about deep Earth processes. Key Points: Continent‐wide inventories of longitudinal river profiles preserve recoverable signals of regional upliftTectonically forced landscape simulations enable testing of inverse modeling strategiesClosed‐loop modeling suggests that fluvial landscapes are dominated by tectonic forcing [ABSTRACT FROM AUTHOR] more...
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- 2021
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45. Place, space and time: resolving Quaternary records.
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Knight, J. and Fitchett, J. M.
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RADIOACTIVE dating ,TREE-rings - Abstract
Principles of place, space and time can frame an understanding of the context and interpretation of Quaternary palaeo-records, and this is particularly the case for the varied proxies used for late Quaternary climate and environmental reconstruction in southern Africa. Place refers to the specific topographic setting or context of any one record, which has implications for the operation of physical processes in the landscape that control the accumulation of different records. Space refers to the spatial scale or footprint of any one record or proxy, and this varies from one proxy to another. Time refers to not only the time period covered by individual records, but also the temporal resolution of the record, which depends on accumulation rates and availability and quality of any radiometric dating. These three principles are discussed specifically in the context of the Quaternary of southern Africa and through the papers that form this special issue, but are also relevant globally. Future research directions in Quaternary research in southern Africa are identified, including opportunities for refining regional chronostratigraphies. [ABSTRACT FROM AUTHOR] more...
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- 2021
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46. Elemental proxy evidence for late Quaternary palaeoenvironmental change in southern African sedimentary records: interpretation and applications.
- Author
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Humphries, M. S.
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EL Nino ,WESTERLIES ,MARINE sediments ,SOUTHERN oscillation ,CAPES (Coasts) - Abstract
Sediments are the most important source of Late Quaternary palaeoclimate information in southern Africa, but have been little studied from a geochemical perspective. However, recent advances in analytical techniques that allow rapid and near-continuous elemental records to be obtained from sedimentary sequences has resulted in the increasing use of elemental indicators for reconstructing climate. This paper explores the diverse information that can be acquired from the inorganic component of sediments and reviews some of the progress that has been made over the last two decades in interpreting the climatic history of southern Africa using elemental records. Despite the general scarcity of elemental records, excellent examples from the region exist, which provide some of the longest and most highly resolved sequences of environmental change currently available. Records from Tswaing crater and marine deposits on the southern KwaZulu-Natal coastline have provided rare glimpses into hydroclimate variability over the last 200 000 years, suggesting that summer rainfall in the region responded predominantly to insolation forcing on glacialinterglacial timescales. Over shorter timescales, lakes and wetlands found in the Wilderness embayment on the southern Cape coast and along the Maputaland coast in north-eastern South Africa have yielded highly-resolved elemental records of Holocene environmental change, providing insight into the changing interactions between tropical (e.g., El Niño-Southern Oscillation) and temperate (e.g., mid-latitude westerlies) climate systems affecting rainfall variability in the region. The examples discussed demonstrate the multiple environmental processes that can be inferred from elemental proxies and the unique insight this can provide in advancing our understanding of past climate change on different timescales. The interpretation of geochemical data can be complicated by the complex nature of sedimentary environments, various proxy assumptions and analytical challenges, and the reliability of sediment-based climate reconstructions is substantially enhanced through multi-proxy approaches. [ABSTRACT FROM AUTHOR] more...
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- 2021
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47. Pollen, charcoal and phytolith records from the Late Quaternary of southern Africa: vegetation and climate interpretations.
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Bamford, M. K.
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POLLEN ,CHARCOAL ,PLANTS ,TREE-rings ,PHYTOLITHS - Abstract
Although the lack of Late Quaternary pollen, phytolith and charcoal records for southern Africa has been bemoaned by many, there are a surprising number of publications by a relatively small group of researchers. Previous comprehensive reviews covered the research up to 2016 and 2018 so this paper only considers a selection of more recent studies, with a focus on the three types of botanical remains (pollen, phytoliths, micro- and macro-charcoal). The newer works use the traditional approaches of identification of vegetation and the use of modern analogues to reconstruct past climate and relate the results to other works and proxies. Sibudu Cave, with its long record and multi-proxy record is presented as a case study because the vegetation, climate and human behaviour are well integrated together. A more recent and general trend to provide emphasis on identifying climate driving forces and re-interpretation of data have a tendency to obscure the original sound research. [ABSTRACT FROM AUTHOR] more...
- Published
- 2021
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48. Chronostratigraphic palaeo-climate phasing based on southern African wetlands: From the escarpment to the eastern seaboard.
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Norström, E., Kylander, M. E., Sitoe, S. R., and Finch, J. M.
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CLIFFS ,CLIMATE change ,HOLOCENE Epoch ,WETLANDS - Abstract
This paper aims to identify chronostratigraphic palaeo-climatic boundaries based on proxy indications from mountainand coastal wetlands in eastern South Africa and Lesotho. Phase boundaries were identified from timing of climate change inferred by proxies, as well as regime shifts in climate variability. Sometimes magnitude and/or frequency of change was also considered. Summarizing the common palaeo-climatic indications suggest the following chronostratigraphic climate phases: 25 to 18 ka, 18 to 15 ka, 15 to 11.5, 11.5 to 8 ka, 8 to 5.5 ka, 5.5 to 2 ka and 2 to 0 ka. The most robust boundaries were identified at 18 ka, 15 ka and 2 ka, i.e. these boundaries were supported by several proxies/sites. The other boundaries were less clearly detected from available proxies/sites and should be regarded tentative. The timing of a climate shift often coincides at coast and mountain sites. However, the climate conditions within each chronostratigraphic phase sometimes vary between coast and inland sites. The 25 to 18 ka phase was cool and dry with strong and frequent storms, followed by the ca. 18 to 15 ka period when conditions were less severe but still generally cool and dry. At ca. 15 to 11.5 ka several proxies infer warmer climate, with less winter rains. During 11.5 to 8 ka a general increase in wetness is inferred, followed by warming over the 8 to 5.5 ka phase. Between 5.5 and 2 ka a successive change towards wetter is indicated, although timing differ between sites. After 2 ka generally a more variable climate is seen, often with high magnitude shifts between dry and wet. The data resolution, i.e. the number of available wetland records, increases with time from very low during glacial times, to highest resolution during late Holocene. Geographically, sites in the mountain region are overrepresented compared to coastal sites. A comparison with coastal lake records suggests a more variable climate at coastal sites compared to mountain sites during mid- and late Holocene, although different proxy resolution and methodology cannot be ruled out as an explanation. A case study compares multiproxy records from Drakensberg (Sekhokong, Ntsikeni) and the coast (Mfabeni), discussing advantages and problems associated with proxy-comparisons within and between sites. [ABSTRACT FROM AUTHOR] more...
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- 2021
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49. The late Quaternary stratigraphy of coastal dunes and associated deposits in southern Africa.
- Author
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Knight, J.
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SAND dunes ,MARINE sediments ,PALEOPEDOLOGY ,BEACHROCK ,COASTS ,SEDIMENTS - Abstract
Coastal sand dune sediments with associated intraformational aeolianite, palaeosols and beachrock are found throughout much of the southern African coast, and have important roles as both Quaternary environmental archives and in recording the interplay of sediment supply, coastal processes and sea-level change. This paper examines the stratigraphy and palaeoenvironmental significance of coastal sand dunes and associated sediments, using examples mainly from South Africa but also with reference to the sandy coasts of Namibia and southern Mozambique. Based on morphological, sedimentary and dating evidence reported in the diverse literature, the stratigraphic relationship of coastal sand dune sediments to Marine Isotope Stages (MIS) is summarized, and a chronostratigraphic diagram for the period MIS 6 to 1 along the South African coast is used to identify spatially coherent sedimentary units that correspond to different regional climatic and sea-level phases. This framework provides a stratigraphic context to better examine the relationship between coastal sand dunes and external forcing during the late Quaternary in southern Africa, and to guide future field studies. [ABSTRACT FROM AUTHOR] more...
- Published
- 2021
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50. Stratigraphy and palaeoenvironmental interpretation of late Quaternary colluvial slope deposits in southern Africa.
- Author
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Knight, J.
- Subjects
PALEOPEDOLOGY ,COLLUVIUM ,SURFACE stability ,SYSTEM dynamics ,SEDIMENTS - Abstract
Slope and lowland sediment systems throughout southern Africa are dominated by the presence of colluvium with interbedded palaeosols and hardground duricrusts. These sediments correspond to phases of land surface instability and stability, respectively, during the late Quaternary. This study examines the stratigraphy and environmental interpretation of slope sediment records from specific sites in southern Africa for the period of marine isotope stages (MIS) 6 to 1 (~191 ka to present), informed by theoretical ideas of the dynamics of slope systems including sediment supply and accommodation space. Based on this analysis, phases of land surface instability and stability for the period MIS 6 to 1 are identified. The spatial and temporal patterns of land surface conditions are not a simple reflection of climate forcing, but rather reflect the workings of slope systems in response to climate in addition to the role of geologic, edaphic and ecological factors that operate within catchment-scale sediment systems. Considering these systems dynamics can yield a better understanding of the usefulness and limitations of slope sediment stratigraphies. [ABSTRACT FROM AUTHOR] more...
- Published
- 2021
- Full Text
- View/download PDF
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