An Archean Geomagnetic Reversal in the Kaap Valley Pluton, South Africa

The Kaap Valley pluton in South Africa is a tonalite intrusion associated with the Archean Barberton Greenstone Belt. Antipodal paleomagnetic directions determined from the central and marginal parts of the pluton record a geomagnetic reversal that occurred as the pluton cooled. The age of the reversal is constrained by an 40Ar/39Ar plateau age from hornblende at 3214 +/- 4 million years, making it the oldest known reversal. The data presented here suggest that Earth has had a reversing, perhaps dipolar, magnetic field since at least 3.2 billion years ago.     

Archean microfossils showing cell division from the swaziland system of South Africa

A newly discovered population of organic walled microstructures from the Swaziland System, South Africa, is considered to be biological on the following grounds: (i) the structures are carbonaceous and occasionally have internal organic contents; (ii) the population has a narrow unimodal size frequency distribution (average diameter, 2.5 micrometers; range, 1 to 4 micrometers); (iii) the structures are not strictly spherical, but are commonly flattened and folded like younger microfossils; (iv) the sedimentary context is consistent with biogenic origins; and (v) various stages of binary division are clearly preserved.     

The Archean Dongwanzi ophiolite complex, North China craton: 2.505-billion-year-old oceanic crust and mantle

We report a thick, laterally extensive 2505 +/- 2.2-million-year-old (uranium-lead ratio in zircon) Archean ophiolite complex in the North China craton. Basal harzburgite tectonite is overlain by cumulate ultramafic rocks, a mafic-ultramafic transition zone of interlayered gabbro and ultramafic cumulates, compositionally layered olivine-gabbro and pyroxenite, and isotropic gabbro. A sheeted dike complex is rooted in the gabbro and overlain by a mixed dike-pillow lava section, chert, and banded iron formation. The documentation of a complete Archean ophiolite implies that mechanisms of oceanic crustal accretion similar to those of today were in operation by 2.5 billion years ago at divergent plate margins and that the temperature of the early mantle was not extremely elevated, as compared to the present-day temperature. Plate tectonic processes similar to those of the present must also have emplaced the ophiolite in a convergent margin setting.     

A 100,000-year-old ochre-processing workshop at Blombos Cave, South Africa

The conceptual ability to source, combine, and store substances that enhance technology or social practices represents a benchmark in the evolution of complex human cognition. Excavations in 2008 at Blombos Cave, South Africa, revealed a processing workshop where a liquefied ochre-rich mixture was produced and stored in two Haliotis midae (abalone) shells 100,000 years ago. Ochre, bone, charcoal, grindstones, and hammerstones form a composite part of this production toolkit. The application of the mixture is unknown, but possibilities include decoration and skin protection.     

Dated rock engravings from wonderwerk cave, South Africa

Radiocarbon dates associated with engraved stones from sealed archeological deposits at Wonderwerk Cave in the northern Cape Province indicate that rock engraving in South Africa is at least 10,000 years old.     

Chromium and nickel in the fig tree shale from South Africa

Exceptionally high contents of chromium and nickel in shales from the early Precambrian Fig Tree series of South Africa ( 3.1 x 10(9) years old) suggest that the ancient crustal rocks from which these sediments were derived were ultramafic in composition.     

Spherules on shatter cone surfaces from the vredefort structure, South Africa

Spherical particles of silicate composition occur on the surface of some shatter cones from the collar rocks around the Vredefort structure, South Africa. They are best developed on shatter cones from a shale horizon but are also found on more arenaceous rocks and banded ironstones. They have not been found on shatter cones from the purer quartzites.     

Abrupt and gradual extinction among Late Permian land vertebrates in the Karoo basin, South Africa

The Karoo basin of South Africa exposes a succession of Upper Permian to Lower Triassic terrestrial strata containing abundant terrestrial vertebrate fossils. Paleomagnetic/magnetostratigraphic and carbon-isotope data allow sections to be correlated across the basin. With this stratigraphy, the vertebrate fossil data show a gradual extinction in the Upper Permian punctuated by an enhanced extinction pulse at the Permian-Triassic boundary interval, particularly among the dicynodont therapsids, coinciding with negative carbon-isotope anomalies.     

南美洲和非洲的农业资源及其开发

随着我国经济的快速发展,城市化进程将更进一步,相应的耕地面积也将减少,如何保障我国粮食安全成为一个应长期关注的问题。通过分析南美洲和非洲的土地资源、人力资源、水资源及相关政策,提出了发展海外农业的新观点及建议。     

Late Pleistocene human skull from Hofmeyr, South Africa, and modern human origins

The lack of Late Pleistocene human fossils from sub-Saharan Africa has limited paleontological testing of competing models of recent human evolution. We have dated a skull from Hofmeyr, South Africa, to 36.2 +/- 3.3 thousand years ago through a combination of optically stimulated luminescence and uranium-series dating methods. The skull is morphologically modern overall but displays some archaic features. Its strongest morphometric affinities are with Upper Paleolithic (UP) Eurasians rather than recent, geographically proximate people. The Hofmeyr cranium is consistent with the hypothesis that UP Eurasians descended from a population that emigrated from sub-Saharan Africa in the Late Pleistocene.     

Choice and voice: creating a community of practice in KwaZulu-Natal,South Africa

The development and utility of genetically modified (GM) crops for smallholders around the world is controversial. Critical questions include what traits and crops are to be developed; how they can be adapted to smallholders’ ecological, social and economic contexts; which dissemination channels should be used to reach smallholders; and which policy environments will enable the greatest benefits for smallholders and the rural poor. A key question is how the voices of smallholders who have experience with or desire to use GM technologies enter the larger debate. Africa has the greatest number of smallholders and poor with the least exposure to GM crops. Because of the well-established use of GM crops in South Africa by commercial farmers, we formed a community of practice (CoP) involving smallholders, extension, researchers, non-profits and agribusiness in KwaZulu-Natal to examine the conditions under which GM crops are used by smallholders, how smallholders interact with GM technologies and what insights smallholders and other stakeholders can provide regarding these questions. One of the advantages of the CoP approach is that it brings stakeholders together in a non-hierarchical way that encourages new ways of thinking and new partnerships. Such interaction around a specific project can enhance the voice of smallholders in a variety of ways. In our project, smallholder participants have increased their knowledge and can make better decisions about GM technologies, which had been barriers for them. Notably, they have also improved their knowledge of maize production practices, accessed new practice networks, and met new researchers and resource providers. They are now being integrated into these networks in a way that should improve their livelihoods and make the wants and needs of smallholders better known. Such knowledge and experience has improved their voice in agriculture and rural development discussions.     

Diamond genesis,seismic structure,and evolution of the Kaapvaal-Zimbabwe craton

The lithospheric mantle beneath the Kaapvaal-Zimbabwe craton of southern Africa shows variations in seismic P-wave velocity at depths within the diamond stability field that correlate with differences in the composition of diamonds and their syngenetic inclusions. Middle Archean mantle depletion events initiated craton keel formation and early harzburgitic diamond formation. Late Archean accretionary events involving an oceanic lithosphere component stabilized the craton and contributed a younger Archean generation of eclogitic diamonds. Subsequent Proterozoic tectonic and magmatic events altered the composition of the continental lithosphere and added new lherzolitic and eclogitic diamonds to the Archean diamond suite.     

U-Pb isotopic age of the StW 573 hominid from Sterkfontein, South Africa

Sterkfontein cave, South Africa, has yielded an australopith skeleton, StW 573, whose completeness has excited great interest in paleoanthropology. StW 573, or "Little Foot," was found 25 meters below the surface in the Silberberg Grotto. 238U-206Pb measurements on speleothems immediately above and below the fossil remains, corrected for initial 234U disequilibrium, yield ages of 2.17 +/- 0.17 million years ago (Ma) and 2.24(-0.07)(+0.09) Ma, respectively, indicating an age for StW 573 of close to 2.2 Ma. This age is in contrast to an age of approximately 3.3 Ma suggested by magnetochronology and ages of approximately 4 Ma based on 10Be and 26Al, but it is compatible with a faunal age range of 4 to 2 Ma.     

埃及、南非农业考察报告

通过埃及,南非农业考察,我们对两国农业发展经验,尤其是两国政府在农业管理的成功作法有了概要了解。两国对农产品市场的建设与管理,农业科研与科技成果应用推广一体化以及农业节水灌溉等值得我们学习和借鉴。     

Middle Stone Age bedding construction and settlement patterns at Sibudu, South Africa

The Middle Stone Age (MSA) is associated with early behavioral innovations, expansions of modern humans within and out of Africa, and occasional population bottlenecks. Several innovations in the MSA are seen in an archaeological sequence in the rock shelter Sibudu (South Africa). At ~77,000 years ago, people constructed plant bedding from sedges and other monocotyledons topped with aromatic leaves containing insecticidal and larvicidal chemicals. Beginning at ~73,000 years ago, bedding was burned, presumably for site maintenance. By ~58,000 years ago, bedding construction, burning, and other forms of site use and maintenance intensified, suggesting that settlement strategies changed. Behavioral differences between ~77,000 and 58,000 years ago may coincide with population fluctuations in Africa.     

南非、坦桑尼亚农业支持和服务体系

一、南非、坦桑尼亚农业概况 南非国土面积122万km^2,其中．可耕地面积约占13％;人口4529万,其中。农业人口约占9％。据世界银行最新统计．2003年南非GDP为1599亿美元．人均3482美元。南非原是一个农牧业国家,随着工矿业的发展．农业占GDP的比重逐步下降．目前仅占GDP的3．2％．     

Alga-like fossils from the early precambrian of South Africa

Micropaleontological studies of carbonaceouis chert from the Fig Tree Series of South Africa (> 3.1 x 10(9) years old) revealed the presence of spheroidal microfossils, here designated Archaeosphaeroides barbertonensis, interpreted as probably representing the remnants of unicellular alga-like organisms. The presumed photosynthetic nature of these primitive microorganisms seems corroborated by organic geochemical and carbon isotopic studies of the Fig Tree organic matter, and is consistent with the geologically and mineralogically indicated Early Precambrian environment. These alga-like spheroids, together with a bacterium-like organism previously described from the Fig Tree chert, are the oldest fossil orgisms now known.