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《诗经》中粮食安全问题研究 总被引:5,自引:4,他引:1
《诗经》中蕴涵丰富的农史资料,是研究西周到春秋时期社会经济活动的重要文献.以《诗经》中的农史资料为主要依据,对两周春秋时期传统农业萌芽阶段的粮食安全状况及其相关问题进行了初步研究.研究结果表明,有关粮食生产技术和粮食安全状况的文字,散布于《诗经》各篇章之中.虽然文辞简赅,但后世所见解决粮食安全问题的相关措施,在《诗经》中已然大体呈现.如重视农业生产,改进耕作技术,提高粮食产量;防御自然灾害,减轻粮食损失等. 相似文献
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King Talal Dam (KTD) watershed is the most important one in Jordan. At its outlet lies the KTD (80 MCM capacity) which serves
irrigation purposes in the Jordan Valley. However, the dam suffers from accelerated annual sedimentation. Therefore, this
study is directed to assess the erosion risk over the watershed, and to simulate actual annual sediment yield at the dam in
order to devise the appropriate conservation practices. Generalized assessment was first conducted over the watershed on the
basis of drainage texture, rainfall erosion index (R), and the ratio p2/P. As a result, the watershed is divided into zones of severe, high (gullying), high (overland flow) and low erosion risk.
Sediment yield at the dam was evaluated by a simulation model. For model validation the simulation results were compared to
the measured values over 12 years period, and a good agreement was obtained in some of the years. The simulation results allow
us to assess the application of two practical conservation practices: terracing and plantation of trees.
Received: 18 November 1997 · Accepted: 18 May 1998 相似文献
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P. A. Polito T. K. Kyser P. Alexandre E. E. Hiatt C. R. Stanley 《Australian Journal of Earth Sciences》2013,60(5):453-474
The Alligator Rivers Uranium Field (ARUF) includes the mined and unmined Jabiluka, Ranger, Koongarra and Nabarlek unconformity-related uranium deposits and several small prospects including the newly discovered King River prospect. Uranium mineralisation is hosted by a variety of metamorphosed Nimbuwah Domain lithologies that are unconformably overlain by the Kombolgie Subgroup, a basin package of unmetamorphosed arenites and mafic volcanics. All of the uranium deposits and prospects preserve an identical alteration assemblage that is subdivided into a distal and proximal alteration zone. The distal alteration zone comprises an assemblage of sericite and chlorite that replace albite and amphibole. In some cases, this alteration can be traced >1000 m from the proximal alteration zone that is dominated by uraninite, hematite, chlorite and sericite. Uranium precipitated in the basement as uraninite at 1680 Ma at around 200°C from a fluid having δ18Ofluid values of 3.0±2.8‰ and δDfluid values of ?28±13‰ VSMOW reflecting an evolved marine source. These geochemical properties are indistinguishable from those recorded by diagenetic illite and chlorite that were collected from the Kombolgie Subgroup sandstones across the ARUF. The illite and chlorite formed in diagenetic aquifers, and where these aquifers intersected favourable basement rocks, such as those containing graphite or other reductants, U was precipitated as uraninite. Therefore, it is proposed that the Kombolgie Subgroup is the source for fluids that formed the deposits. A post-ore alteration assemblage dominated by chlorite, but also comprising quartz±dolomite±sulfide veins cut the uranium mineralisation at all deposits and has historically been recorded as part of the syn-ore mineralisation event. However, these minerals formed anywhere between 1500 to 630 Ma from fluids that have distinctly lower δ18Ofluid values around 1.5‰ and lower δDfluid values around ?45‰ reflecting a meteoric water origin. Despite unconformity-related uranium deposits having a large alteration halo, they remain difficult to find. The subtle alteration of albite to sericite several hundred metres from mineralisation occurs in isolation of any increase in trace elements such as U and radiogenic Pb and can be difficult or impossible to identify in hand specimen. Whole rock geochemical data indicate that Pearce Element Ratio (PER) analysis and General Element Ratio (GER) analysis may vector into this subtle alteration because it does not rely on an increase in trace elements to identify proximity to ore. PER and GER plots, Al/Ti vs (2Ca + Na + K)/Ti, Na/Al vs (Na + K)/Al, K/Al vs (Na + K)/Al and (Fe + Mg)/Al vs (Na + K)/Al provide a visual guide that readily distinguish unaltered from altered samples. A plot of (Na + K)/Al and (Fe + Mg)/Al on the x-axis against the concentration of trace elements on the y-axis reveals that U, Pb, Mo, Cu, B, Br, Ce, Y, Li, Ni, V and Nd are associated with the most intensely altered samples. The lithogeochemical vectors should aid explorers searching for uranium mineralisation in a prospective basin environment, but exploration must first focus on the characteristics of the basin to assess its mineralisation potential. A holistic model that describes the evolution of the Kombolgie Subgroup from deposition through diagenesis to formation of the uranium deposits in the underlying basement rocks is presented and has application to other basins that are considered prospective for unconformity-related uranium deposits. The model outlines that explorers will need to consider the thickness of the sedimentary pile, its lithological composition relative to depositional setting, the depth to which the sediments were buried during diagenesis and the degree of diagenesis achieved, which may be time dependant, before deciding on the prospectivity of the basin. 相似文献
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R. A. Cayley D. H. Taylor A. H. M. VandenBerg D. H. Moore 《Australian Journal of Earth Sciences》2013,60(2):225-254
Aeromagnetic and field data suggest that meta‐igneous rocks exposed on the south coast of central Victoria at Waratah Bay, Phillip Island, Barrabool Hills and inland near Licola, are continuous—beneath Bass Strait—with Proterozoic/Cambrian igneous rocks in King Island and Tasmania. This correlation is supported by a pre‐Early Ordovician unconformity above gabbro protomylonite at Waratah Bay, age equivalent to the Tasmanian Tyennan unconformity. Cambrian volcanics at Licola and unusual features of the Melbourne Zone sequence indicate that Tyennan continental crust extends north as basement to the central Victorian portion of the Lachlan Fold Belt. In contrast, adjacent parts of the Lachlan Fold Belt in Victoria contain conformable sea‐floor sequences that span the Early Cambrian to Late Ordovician, with no evidence of either Cambrian deformation or underlying continental basement. The block of Tyennan continental crust beneath central Victoria—the Selwyn Block—is fundamentally different, and has influenced temporal and spatial patterns of sedimentation, deformation, metamorphism and plutonism. Palaeogeographical reconstructions suggest that the block was a submarine plateau that lay outboard of the Australian craton, upon which a condensed Ordovician sequence was deposited. The sequence above the Selwyn Block unconformity at Waratah Bay is similar to widespread post‐Tyennan sediments in western Tasmania. During Late Ordovician and Early Silurian deformation, the Selwyn Block protected much of the overlying sedimentary sequence. Instead, shortening was focused into the Stawell and Bendigo Zones to the west. These zones were sandwiched between the Selwyn Block and the Australian craton in a ‘vice’ scenario reminiscent of some Appalachian orogenic events. The region above the Selwyn Block was downwarped adjacent to the overthrust Bendigo Zone as a foreland deep, into which a conformable clastic wedge of sediment was deposited in Late Ordovician to Devonian time, prior to final Middle Devonian deformation. The Selwyn Block includes the Cambrian calc‐alkaline Licola and Jamieson Volcanics that are correlated with the Tasmanian Mt Read Volcanics. In Victoria, these form a basement high controlling the unusual down‐cutting thrusts in the overlying Melbourne Zone and explaining the major structural vergence reversal between the Melbourne and Tabberabbera Zones. The Selwyn Block has exerted some control on the timing, chemistry and distribution of post‐orogenic granites, and on central Victorian gold mineralisation. Reactivated faults in the block influenced deposition, and continue to control the deformation of the portions of the Otway and Gippsland Basins that lie above it. 相似文献
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Recharge to the Quaternary aquifers beneath the Northern Adelaide Plains was estimated to be 3.9 x 106 m3/year using the environmental tritium concentration of water samples taken from suitably sited boreholes. Recharge to the Tertiary aquifers was estimated to be 0.4 x 106m3/year, by the same isotopic techniques. These results may be compared with a total recharge by leakage through the beds of streams which cross the plain, estimated by the South Australian Department of Mines to be 6.4 x 106 m3/year. 相似文献
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本文对“第33次南极科考—海洋六号航次”在乔治王岛南侧、象岛西侧海域内通过箱式取样获得的表层沉积物样品进行了硅藻组成和分布特征的研究。主要统计了硅藻丰度、简单分异度、属种组成等, 并结合沉积物粒度数据进行分析, 结果表明乔治王岛南侧站位丰度和分异度高于象岛西侧站位, 最高丰度达到1.96×106壳/g。丰度的差异分布可能主要与洋流有关, 别林斯高晋海表层洋流带入充足营养盐导致乔治王岛南侧站位硅藻繁盛, 而威德尔海涡流底层水影响下的象岛西侧站位则难以沉降保存包括硅藻壳体在内的细小沉积颗粒。各站位硅藻组成的差异主要体现在海冰相关种分布不均和半咸水种类繁盛情况等, 前者可能与漂浮海冰控制的时间长短有关, 而后者与淡水输入等综合环境因素有关。 相似文献
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