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RAÚL DE LA HORRA Ma ISABEL BENITO JOSE LÓPEZ‐GÓMEZ ALFREDO ARCHE JOSÉ F. BARRENECHEA JAVIER LUQUE 《Sedimentology》2008,55(6):1849-1873
The Late Permian (Wuchiapingian) Alcotas Formation in the SE Iberian Ranges consists of one red alluvial succession where abundant soil profiles developed. Detailed petrographical and sedimentological studies in seven sections of the Alcotas Formation allow six different types of palaeosols, with distinctive characteristics and different palaeogeographical distribution, to be distinguished throughout the South‐eastern Iberian Basin. These characteristics are, in turn, related to topographic, climatic and tectonic controls. The vertical distribution of the palaeosols is used to differentiate the formation in three parts from bottom to top showing both drastic and gradual vertical upwards palaeoenvironmental changes in the sections. Reconstruction of palaeoenvironmental conditions based on palaeosols provides evidence for understanding the events that occurred during the Late Permian, some few millions of years before the well‐known Permian‐Triassic global crisis. 相似文献
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Pyroclastic deposits exposed in the caldera walls of Santorini Volcano (Greece), contain several prominent horizons of coarse-grained andesitic spatter and cauliform volcanic bombs. These deposits can be traced around most of the caldera wall. They thicken in depressions and are intimately associated with ignimbrite and co-ignimbrite lithic lag breccias. They are interpreted as a proximal facies of pyroclastic flow deposits. Evidence for a flow origin includes the presence of a fine-grained pumiceous matrix, flow deformation of ductile spatter clasts, exceedingly coarse grain sizes several kilometres from any plausible vent, imbrication of flattened spatter clasts, intimate interbedding with normal pyroclastic flow deposits and the presence of inversely graded basal layers. The deposits contain hydrothermally altered, rounded lithic ejecta including gabbro nodules. The andesitic ejecta and the fine matrix are typically moderately to poorly vesicular indicating that magmatic gas had a subordinate role in the eruptive process. The andesitic clasts contain abundant angular lithic inclusions and some clasts are themselves formed of pre-existing agglutinate. We propose that these eruptions occurred when external water gained access to the vents, causing large-scale explosions which formed pyroclastic flows rich in coarse, semifluid but poorly vesicular ejecta. We postulate that large volumes of coarse pyroclastic ejecta and degassed lava accumulated in a deep crater prior to being disrupted by these large explosions to form pyroclastic flows. 相似文献
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CL de Moor SJ Johnston A Brandão RA Rademeyer JP Glazer LB Furman 《African Journal of Marine Science》2015,37(3):285-311
The waters off South Africa's coastline boast a rich mix of commercially fished species. Quantitative assessments of these marine resources have developed from simple methods first applied in the 1970s, to models that encompass a wide range of methodologies. The more valuable resources have undergone regular assessments in recent decades, with frequencies closely related to the management approach employed for each fishery. Many of these assessments form the operating models used to simulation-test candidate management procedures. This paper provides a comprehensive review of the assessments of 11 of the most important fisheries resources in South Africa. Some assessments use simple biomass dynamics models, whereas others are a hybrid of age- and length-based models, each designed to model the specific characteristics of the resource and fishery concerned. Many of the assessments have been disaggregated by species/stock and/or area as related multispecies/stock/ distribution hypotheses have arisen. This paper explores the similarities and differences in the data available and the methods applied. The review indicates that, whereas the status of three of these resources cannot be estimated reliably at present, the status of six resources is considered to be reasonable to good, whereas that of abalone Haliotis midae and West Coast rock lobster Jasus lalandii remains poor. 相似文献
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主要论述了以浙江省 CORS 系统为基础,综合运用GNSS 空间定位技术、计算机技术、通讯技术、网络技术等现代技术,对可能由地表位移引起的地质灾害进行实时监测、预警和形变分析,建立地质灾害监测预警系统的设计思路和实现过程。 相似文献
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A re-evaluation of the threat status of New Zealand's marine invertebrates was undertaken in 2009, following earlier review of New Zealand's Threat Classification System and subsequent refinement of the national criteria for classifying threat of extinction to New Zealand's flora and fauna. Sufficient information was available to enable 295 marine invertebrate taxa to be fully evaluated and assigned to a national threat category. The 10 taxa at most risk of extinction (‘nationally critical’) were the giant seep clam Calyptogena sp., the primitive acorn barnacle Chionelasmus crosnieri, O'Shea's vent barnacle Volcanolepas osheai, the stalked barnacle Ibla idiotica, the four-blotched umbrella octopus Cirroctopus hochbergi, the roughy umbrella octopus Opisthoteuthis chathamensis, the giant squid Idioteuthis cordiformis, the large-egged polychaete Boccardiella magniovata and two gravel maggots, Smeagol climoi and Smeagol manneringi. The key threatening processes identified for marine invertebrates were fishing and land-use associated impacts such as sedimentation. We identified no taxa that had improved in threat status as a result of past or ongoing conservation management action, nor any taxa that had worsened in threat status because of known changes in their distribution, abundance or rate of population decline. We evaluated a small fraction of New Zealand's marine invertebrate fauna for their threat status. Many taxa remain ‘data deficient’ or unlisted. In addition to the most threatened taxa, we recommend these taxa and their habitats as priorities for further survey and monitoring. 相似文献
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川滇交界地区地壳结构及现代地壳活动模式 总被引：6，自引：0，他引：6
根据地球物理异常及大地测深资料探讨川滇交界地区的地壳深部构造背影及地壳结构特征,并综合多方面的研究资料,以两板块碰撞、青藏高原窿升为构造背景,以川滇菱形断块运动为基本模式,全面系统地揭示川滇交界面区的现代地壳活动性。从地壳运动图象中可以清楚地看到断块差异性活动是现代地壳活动主要形式。 相似文献
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井点降水是一种方便易行的降水方式,在黄河湿地承台施工中较好地解决了基坑开挖基坑涌水、流沙现象的发生。 相似文献
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以绿沸石、硅藻土、膨润土、牡蛎壳为主要原材料,包衣机制粒后马弗炉焙烧制成绿沸石-硅藻土(GZD)、绿沸石-膨润土(GZB)、绿沸石-牡蛎壳(GZO)等3款球状氨氮吸附材料。探究造孔剂-粘结剂配比、物料配比、焙烧温度、焙烧时间对污水中氨氮的吸附量和材料散失率的影响,通过吸附动力学、吸附等温线、氨氮去除率、材料散失率试验探讨其吸附机理。并设计了简易装置,用实际河道水样对比分析了3款复合材料与块状绿沸石原矿对氨氮的吸附效果和重复利用次数,对处理效果最佳的GZD中的主要材料绿沸石和硅藻土进行了SEM和XRF表征。结果表明:GZD的氨氮吸附效果最佳,制备条件为造孔剂、粘结剂、绿沸石、硅藻土的质量比为1.2﹕5﹕9﹕1;在500℃下焙烧3 h;GZD对氨氮的吸附符合准二级动力学,用Freundlich等温线比Langmuir等温线更适合描述其吸附过程;GZD对实际河道水样进行5次吸附再生后仍具有明显效果。 相似文献
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