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1.
The dietary regimes of 15 ungulate species from the middle Pleistocene levels of the hominid-bearing locality of Elandsfontein, South Africa, are investigated using the mesowear technique. Previous studies, using taxonomic analogy, classified twelve of the studied species as grazers (Redunca arundinum, Hippotragus gigas, Hippotragus leucophaeus, Antidorcas recki, Homoiceras antiquus, Damaliscus aff. lunatus, Connochaetes gnou laticornutus, Rabaticerus arambourgi, Damaliscus niro, Damaliscus sp. nov., an unnamed “spiral horn” antelope and Equus capensis), one as a mixed feeder (Taurotragus oryx) and two as browsers (Tragelaphus strepsiceros and Raphicerus melanotis). Although results from mesowear analysis sustain previous dietary classifications in the majority of cases, five species were reclassified. Three species previously classified as grazers, were reclassified as mixed feeders (H. gigas, D. aff. lunatus and R. arambourgi), one previously classified as a grazer, was reclassified as a browser (the “spiral horn” antelope), and one previously classified as a mixed feeder, was reclassified as a browser (T. oryx). While current results broadly support previous reconstructions of the Elandsfontein middle Pleistocene environment as one which included a substantial C3 grassy component, the reclassifications suggest that trees, broad-leaved bush and fynbos were probably more prominent than what was previously thought.  相似文献   

2.
Construction of the new town of Ennerdale from the mid 1970s occurred within the context of austerity and a concomitant urban policy reoriented toward the privatisation of working-class housing provision. The new town project at Ennerdale presents an opportunity for analysing institutional intervention from the angle of urban design and spatial planning. The financial and planning mechanisms through which the state constructed Ennerdale are examined and the social effects of the new town project are assessed.  相似文献   

3.
4.
New drill core data are provided which support earlier interpretations that the Kalkkop structure, a 600–630 m wide, near-circular feature south-southwest of Graaff-Reinet in the Eastern Cape Province of South Africa, is a meteorite impact crater. Shock metamorphosed clasts in suevitic crater fill and Re---Os isotope data of this breccia indicate the presence of a minor (0.05%) meteoritic component in the suevite. The new data come from a 1992 borehole, which transected the complete crater fill and extended from about 160 to 380 m depth into the sedimentary basement belonging to the Koonap Formation of the Beaufort Group (Karoo Supergroup). Dyke breccias were found in the otherwise coherent Beaufort Group sediments forming the floor to the Kalkkop Crater. Mostly narrow zones of different breccia types, including injections of lithic impact breccia, a possible pseudotachylite veinlet and cataclasite occur predominantly in an approximately 65 m wide zone below the crater floor, with a few other cataclasite occurrences found lower down in the basement. Stratigraphical crater constraints provide information for the depth-diameter scaling and breccia volumes associated with such small, bowl-shaped impact craters formed in sedimentary targets.U---Th series dating of limestone samples from near the top and the bottom of the crater sediment fill constraints the age of the Kalkkop impact event to about 250 ± 50 ka, similar to the age of the Pretoria Saltpan impact crater, also located in South Africa. The variety of different breccia types (polymict and monomict impact breccias; local formations of pseudotachylitic and cataclastic breccias) observed in the crater fill of the Kalkkop Crater indicates the need to carefully distinguish different breccia types in order to assess the respective importance of each formation.  相似文献   

5.
The Tanqua area of the Karoo basin, South Africa, contains five Permian deep-water turbidite fan systems, almost completely exposed over some 640 km2. Reconstruction of the basin-fill and fan distributions indicates a progradational trend in the 450 m+ thick succession, from distal basin floor (fan 1) through basin-floor subenvironments (fans 2, 3 and 4) to a slope setting (fan 5). Fans are up to 65 m thick with gradational to sharp bases and tops. Facies associations include basin plain claystone and distal turbidite siltstone/claystone and a range of fine-grained sandstone associations, including low- and high-density turbidite current deposits and proportionally minor debris/slurry flows. Architectural elements include sheets of amalgamated and layered styles and channels of five types. Each fan is interpreted as a low-frequency lowstand systems tract with the shaly interfan intervals representing transgressive and highstand systems tracts. All fans show complex internal facies distributions but exhibit a high-frequency internal stratigraphy based on fan-wide zones of relative sediment starvation. These zones are interpreted as transgressive and highstand systems tracts of higher order sequences. Sandy packages between these fine-grained intervals are interpreted as high-frequency lowstand systems tracts and exhibit dominantly progradational stacking patterns, resulting in subtle downdip clinoform geometries. Bases of fans and intrafan packages are interpreted as low- and high-frequency sequence boundaries respectively. Facies juxtapositions across these sequence boundaries are variable and may be gradational, sharp or erosive. In all cases, criteria for a basinward shift of facies are met, but there is no standard 'motif' for sequence boundaries in this system. High-frequency sequences represent the dominant mechanism of active fan growth in the Tanqua deep-water system.  相似文献   

6.
7.
A new multidisciplinary research program, started in 1981, provided new data on the stratigraphy, fauna, and human industries, as well as the first results on paleomagnetism and sedimentology, for the Ternifine site in Algeria, which yielded the earliest hominid remains known in North Africa. The fossils were deposited in a swamp or lake surrounded by a very open, dry environment. The lake was fed by artesian springs that raised the underlying Miocene sands. Although nothing suggests a camp or butchery site, we discovered the first undisputable bone artifact in this site, the earliest known in this part of Africa. According to paleontological data, 700,000 yr B.P. is a likely age for the Ternifine deposits, which is consistent with the paleomagnetic results.  相似文献   

8.
New members of the crichtonite mineral series are described in which K, Ba, Ca and REE are in significant concentrations (5 wt% oxides) filling the A formula position in AM21O38. These phases are chromium (16 wt% Cr2O3) titanates (58 wt% TiO2) enriched in ZrO2 (5 wt%) and constitute a mineral repository for refractory and large ion lithophile elements in the upper mantle. The mineral senes coexists with Mg-Cr-ilmenite, Nb-Cr-rutile, and Ca-Cr (NbZr) armalcolite that have equally unusual chemistries. Kimberlitic crichtonites are depleted in the intermediate lanthanides but highly enriched in LREE and HREE with chondrite normalized abundances of 103 to 105. Crichtonite, armalcolite, and Nb-Cr-rutile occupy a compositional range in TiO2 contents bridging the gap between ilmenite and rutile, two minerals having a widespread distribution in kimberlites and mantle-derived nodule suites.In common with other associations, and based on similarities in mineral chemistry, it is concluded that these minerals formed at P = 20–30 kb, 900–1100°C by reaction of peridotite with metasomatizing fluids. Kimberlitic crichtonite may be expressed as spinel + Cr-ferropseudobrookite, and armalcolite is equivalent to Cr-geikielite + rutile in the system (FeMg)-TiO2-Cr2O3. This system contains a number of Cr-Ti compounds not found as minerals but it is proposed that the ubiquitous occurrence of ilmenite intergrowths in kimberlitic rutile results from decomposition of high pressure αPbO2-type crystallographic shear structures. The new minerals have exotic chemistries and the high K-affinities broaden the scope for the origin of alkalic rocks, the generation of highly potassic magmas in the upper mantle, and suggest that alkali metasomatism may be pervasive.  相似文献   

9.
Radiocarbon dates are described from a section through Lateglacial and early Flandrian sediments at Llanilid, Mid-Glamorgan, South Wales. Comparisons between age determinations on the alkali soluble (humic) and alkali insoluble (humin) organic fractions from 12 biostratigraphic horizons reveal the extent of contamination by both older and younger carbon residues. The Llanilid time-scale suggests that for the Lateglacial, the earliest organic sediments date from around 13 200 yr BP, the early Interstadial Juniperus maximum occurred at ca. 12 400-12 500 yr BP with a marked decline some 200 years later, the main Betula phase lasted only from ca. 11 700 to 11 400 yr BP and the end of the Interstadial occurred around 11 100 yr BP. The beginning of the Flandrian dates from ca. 10 000 yr BP, the Juniperus maximum occurred approximately 200 years later, the expansion of birch woodland began around 9600 yr BP, while the first hazel arrived in the area at ca. 9300 yr BP. These age determinations are discussed in the context of radiocarbon dates from comparable biostratigraphic horizons in western Britain and the dating of Lateglacial events in the ocean core records from the North Atlantic.  相似文献   

10.
Measurable characteristics of the decay process of the radioactive isotope Mn55 permit identification of manganese ores by means of neutron logging. The method is outlined.--M. Russell.  相似文献   

11.
Hart GH 《GeoJournal》1996,39(1):27-31
Of the many problems facing South Africa, perhaps one of the most important is that of the illegal alien. The scope, issues and policy implications of the illegal alien problem are examined. Different geographical streams of alien immigration are identified are profiled. Official policy responses are reviewed. The pressures for action to be taken against the rising numbers of illegal aliens in South Africa are discussed. In particular, the cost implications of illegal aliens capturing scarce resources and employment opportunities are set against other pressing demands encapsulated in the Reconstruction and Development Programme.  相似文献   

12.
Cleophas Lado 《GeoJournal》1998,45(3):165-176
In many developing countries, research institutions or centres have been established to develop and/or adapt technologies that would help agricultural development. This is particularly true in Africa where national efforts have been supplemented with international research institutes. Although some modest progress has been achieved in improving agricultural technology, on the whole, the improvement record is not quite encouraging among the small-scale farmers. In many areas, either there are no improved technologies, or where they exist, are unacceptable by farmers. However, where useful technologies exist, their spread has been very limited and where they have been adapted, the benefits only accrue to a small segment of the community. The logical question posed is: why and how do we find ourselves in the current situation? This paper considers the view that to understand fully why the available technologies have remained largely at the research centres, there is need to examine the whole process of research, development, dissemination and utilization of agricultural technology. It is significant to investigate the structural constraints and prospects under which those involved in the process work, their motivations and the interactions between different groups. The traditional ‘top-down’ of development strategy should be supplemented with farmers' indigenous knowledge, and programmes encouraging transfer of agricultural technology should include institutional support. Only by the identification of farmers' environmental and resource utilisation, preferences, socio-economic circumstances and constraints can a development programme of optimum meaning to farmers be devised and implemented with success.  相似文献   

13.
In this study a new geochemical reaction modelling methodology is used to shed light on the geochemical processes within Witwatersrand tailings impoundments and the evaluation of the geochemical impacts for future mining projects is evaluated. Information from international and local studies on tailings sulphidic tailings impoundments is used to develop a conceptual understanding on a typical Witwatersrand gold tailings impoundment. The tailings impoundments consist of 3 distinct geochemical zones: Oxidation Zone (OZ), a Transition Zone (TZ) and a Reduction Zone (RZ). Individual reaction models are developed for each of the 3 zones. The output of one model is used as an input to the next in spatial order. The results of the final model represent the tailings basal seepage characteristics, which indicate the most likely impacts on groundwater resources. The model results agree with existing information on AMD in the Witwatersrand. The results indicate that the tailings basal seepage is likely to be acidic (pH of ∼3.5), containing elevated concentrations of SO4 and trace metals (Al, Co, Cr, Cu, Mn, Ni, Zn and U). Predicted Fe concentrations are low, due to the low fO2 in the TZ and RZ and the buffering effect of the precipitation of K-jarosite in the OZ and TZ. This study therefore indicates that the methodology employed produces results that can be correlated to existing information and can thus be used as a methodology in the assessments of impacts from sulphidic tailings material for future mining projects.  相似文献   

14.
G. H. Pirie 《GeoJournal》1990,22(3):231-240
The geography of air transport to and from South Africa has been shaped powerfully by the world map of anti-apartheid, sanctions-keeping nations which close their airspace to the Republic's state-owned airline. Re-routering, involving notably the offshore west-African link to Europe, revocation of foreign landing rights and a shrinking airline network have resulted. The economic dependence of the Republic's southern African neighbours on their political adversary has dissuaded them from joining an anti-apartheid air blockade. Likewise, the penalties to black African states of denying overfying, landing and traffic rights to west-European airlines plying the South Africa route have diminished the force of the air embargo.  相似文献   

15.
Carbonate-rich, SiO2-poor residua are developed in some kimberlites solidifying as ocelli, layers, or discrete dikes which satisfy petrographic definitions of carbonatite. Arguments that these rocks have mineralogies, antecedents, and comagmatic rocks differing from those of the carbonatites in alkaline rock complexes, including the specific observation that kimberlites and carbonatites contain ilmenites and spinels of different composition, have been used to refute the alleged kimberlite-carbonatite relationship. New microprobe analyses of ilmenites and spinels from carbonate-rich rocks associated with kimberlites in three South African localities correspond to spinels and ilmenites of carbonatites from alkalic complexes, or have characteristics intermediate between those of carbonatites and kimberlites. The ilmenites are distinguished from kimberlite ilmenites by higher MnO, FeTiO3, and Nb2O5, and by negligible Cr2O3. The spinels are distinguished from kimberlite spinels by their Al2O3 and Cr2O3 contents. There is clearly a genetic relationship between the kimberlites and the carbonate-rich rocks, despite the observation that their ilmenites and spinels are distinctly different, which indicates that the same observation is not a valid argument against a petrogenetic relationship between kimberlites and carbonatites. These rocks are among the diverse products from mantle processes influenced by CO2, and we believe that the petrogenetic links among them are forged in the upper mantle. We see insufficient justification to deny the name carbonatite to carbonate-rich rocks associated with kimberlites if they satisfy the petrographic definition in terms of major mineralogy.  相似文献   

16.
Airborne magnetic data and Landsat imagery, as well as time-domain electromagnetic soundings, were used to assess groundwater potential of the region around the town of Mafikeng in North West Province, South Africa. Lineaments were extracted based on on-screen digital data derived from magnetic and Landsat 7 imagery. The relationship between lineament-intersection density and borehole yield was assessed using statistical analysis. The results were discussed with respect to factors that determine the groundwater potential of the area. Correlation between lineament-intersection frequency and borehole yield is 60?C65% in the south and southeastern parts, and 45?C50% within 5?C30?km radius of Mafikeng. The eastern and western parts of the study area are characterized by weak or no correlation. Areas that correspond to high correlation between lineament-intersection frequency and borehole yield suggest the significance of cross-cutting structures in controlling groundwater potential zones, while results that suggest low or no correlation represent the influence of other factors. The overall results demonstrate that the combined analysis of airborne magnetic data, satellite imagery, borehole yield and ground-based time-domain electromagnetic soundings provide the best approach for groundwater assessment within the hard rock and carbonate terrains of the study area.  相似文献   

17.
B. McCusker  E.R. Carr 《Geoforum》2006,37(5):790-804
Land use change and livelihood systems are often analyzed separately or with one “driving” the other. This “driver-feedback” relationship has been buttressed by approaches to social process that are often far too static. Actors are confronted with a bundle of choices that they must negotiate as they create pathways of change. These choices are always bound up in relations of power and the knowledges that are the conditions for and results of these relations. We suggest that land uses and livelihood are different manifestations of the social processes by which individuals and groups negotiate the everyday conditions that shape their lives. We propose a framework that extends current understandings of the relationship between land use change and livelihoods by treating social relations of power as the entry point into this complex relationship. We underpin our arguments with empirical examples from South Africa and Ghana that locate power/knowledge relations in the context of social change in both study areas.  相似文献   

18.
Fossil beetles from a last glacial landslide‐generated lake‐forest sequence aged 33 480–34 410 cal. yr BP (late Marine Isotope Stage 3 (MIS 3)) are identified from the Waitotara Valley in South Taranaki, North Island, New Zealand. The stratigraphy indicates that the landslide caused changes to local hydrology, resulting in the formation of a lake‐swamp environment and subsequent transition to forest. Fossil leaves suggest a forest dominated by Nothofagus menziesii, and radiocarbon ages indicate the site was forested for around 4000 yr. A fossil beetle‐based temperature estimate using the maximum likelihood envelope method indicates the climate was cooler than present day. The distributions of the fossil beetle taxa are examined and compared with the modern ecological patterns. The fossil fauna is very typical of a modern‐day Nelson (northern South Island) fauna. None of the beetle species is present in the modern South Taranaki fauna and many taxa such as Platypus caviceps, Alema paradoxa, Rhyzobius consors, Syrphetodes ater, Cyclaxyra impressa and species of Grynoma and Pycnomerus are now absent from part or all of the lower North Island. This is important because the lower North Island is currently an area of low diversity and endemism and these results suggest this biogeographical pattern stems from the last glaciation. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

19.
With a few exceptions, shales from the Archean Witwatersrand Supergroup (~2800 Ma) in South Africa are depleted in Na, Ca, LILE, REE and HFSE compared to Phanerozoic shales. Cr, Co and Ni are enriched in all Witwatersrand shales and Fe and Mg are high in shales from the West Rand Groups (WRG) and lower Central Rand Group (CRG). Shales from the CRG and uppermost WRG are enriched in Na, Al, LILE, REE, HFSE and transition metals relative to shales from the lower WRG. Chondrite-normalized REE patterns for all Witwatersrand shales are enriched in light-REE and exhibit small to moderate negative Eu anomalies. A positive correlation of REE and Al2O3 contents in the shales suggests that REE are contained principally in clay minerals.Relative to shales from the CRG, shales from the WRG exhibit depletions of Na, Ca and Sr, a feature probably reflecting intense chemical weathering of their source rocks. CIA indices in Witwatersrand shales are variable (chiefly 70–98), even within the same shale unit. Such variations reflect chiefly variable climatic zones or rates of tectonic uplift in source areas with perhaps some contribution from provenance and element remobilization during metamorphism.Compared to present-day upper continental crust, all but the Orange Grove, Roodepoort, and K8 shales appear to have been derived from continental sources depleted in LILE, REE, and HFSE and enriched in transition metals. Computer mixing models based on six relatively immobile elements (Th, Hf, Yb, La, Sc, Co) and four source rocks indicate that the relative proportions of granite, basalt and komatiite increased with time in sediment source areas at the expense of tonalite. The contributions of basalt and komatiite appear to reach a maximum during deposition of the Booysens shale, and granite during deposition of the K8 shales and possibly during deposition of the Orange Grove shales.  相似文献   

20.
The copper deposits of the O'okiep District rank amongst the top three S. African producers, with an annual output of 3 million metric tons grading 1.65% Cu on average. They occur in what is now considered the S. extension of the 1200 m. y. Kibaran orogenic belt. Copper mineralization is linked to cross-cutting bodies of "noritoid" RO=0.7126–0.7250) which have been emplaced into the granulite facies metamorphic country rocks 1100 m. y. ago. The results of 150 electron probe analyses show that orthopyroxene in the non-ore-bearing noritoids is En51–52, in the ore-bearing noritoids En60–65. There is a concomitant variation in the composition of phlogopitic mica which carries higher Fe in non-ore-bearing noritoids. The Ticontents of magnetite are below 0.1%; there are significant chromium values. Spinel exsolution lamellae contain up to 14% ZnO. The copper sulphides occur as granular aggregates with silicates, on grain boundaries and on cleavage planes of hypersthene and mica; they also replace altered Fe-Ti-oxides. Pyrite (up to 1.4% Co) and pentlandite (up to 5% Co) are not widespread. The possible derivation of the noritoids from a reservoir of basic magma at depth is considered. A source-bed model, involving generation of noritoid "magma" from Cu-bearing members of the stratigraphic sequence, during the peak of metamorphism (800–1000 °C, 6–8 kb) is tentatively proposed. Stratabound base metal concentrations (Aggeneys, Gamsberg) in lower grade (amphibolite facies) metamorphic terrains to the East have not been mobilized.formerly, Mineralogisch-Petrographisches Institut, Universität Hamburg  相似文献   

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