Pervasive autocorrelation of the chemical index of alteration in sedimentary profiles and its palaeoenvironmental implications     

SHANGBIN XIAO  WEIGUO LIU  ANCHUN LI  SHOUYE YANG  ZHONGPING LAI 《Sedimentology》2010,57(2):670-676

The chemical index of alteration has been used widely for reconstruction of the palaeoclimate. However, the mechanisms and environmental factors controlling the chemical index of alteration of sediments are not yet fully understood. In this study, autocorrelations of the chemical index of alteration in nine sedimentary profiles, from both the land and the sea, spanning different geological times, are discussed. The sediments of these profiles have different origins (dust, fluvial or ocean sediments) and are from various climate situations and sedimentary environments. Autocorrelations of chemical index of alteration series are ubiquitously evident in all profiles. It is suggested here that autocorrelations may be caused by post‐depositional changes such as persistent weathering and diagenesis. As a result, the chemical index of alteration may not reflect climatic conditions during the time of sediment deposition. This study strongly recommends the confirmation of the reliability and veracity of the chemical index of alteration before it is adopted to evaluate the weathering degree of parent rocks and to reconstruct the past climate. Significant autocorrelations in loess profiles were specifically observed, suggesting that the existing understanding of loess deposition in terms of climate conditions requires re‐examination, and that previous reconstructions of rapid climate changes (for example, in centennial‐millennial scales) should be treated with caution.  相似文献   

甘肃花牛山喷流沉积型金银铅锌矿床控矿因素与找矿前景分析   总被引：2，自引：0，他引：2  

杨建国  翟金元  杨宏武  王小红  谢春林  王兴安  任秉琛 《大地构造与成矿学》2010,34(2)

花牛山银铅锌矿床过去大多研究者认为其形成与印支期花岗岩有关。但矿床地质特征、矿化类型及成矿年代学研究表明,花牛山银铅锌矿床是中元古代晚期古火山喷流沉积作用的产物。本文在分析论述矿区喷流沉积型贵重-有色金属系列矿化成矿作用特点和成矿规律的基础上,系统归纳总结了矿床主要控矿因素与找矿标志。并按照层控找矿思路,结合地质及物探工作资料,指出了今后开展接替资源勘查的找矿靶区。  相似文献   

陕西旬北地区钠长石岩与热水沉积成矿     

高荣虎  刘利民  唐永忠 《陕西地质》2010,28(1):18-24

近年来,旬北铅锌矿集区发现了长达近百公里的铅锌矿带及钠长石岩带,铅锌矿多顺层整合产在以志留系为主的细碎屑岩中,沉积特征明显,含矿层内热水沉积岩发育,围岩蚀变不明显,矿体下部钠长石岩发育,底板多见铁碳酸盐岩,矿层内常见热水沉积微晶硅质岩,矿石多具块状、层状、层纹状构造。热水沉积可能是铅锌矿主要成矿方式,成矿物质来自盆下深处。  相似文献   

Multiscale analysis of geomorphological and geological features in high resolution digital elevation models using the wavelet transform   总被引：3，自引：0，他引：3  

Michael KalbermattenDimitri Van De Ville  Pascal TurbergDevis Tuia  Stéphane Joost 《Geomorphology》2012,138(1):352-363

  相似文献   

利用地震波多参数组合预测沉积微相研究   总被引：1，自引：0，他引：1  

梁桂蓉  黄晓红  赵宪生 《地震研究》2004,27(3):252-255

对渤海油田多井沉积微相的速度与密度参数随深度的变化规律分析后,应用主振幅参数与波阻抗参数的组合预测了该油田沉积微相的横向分布,通过与井的沉积微相对比表明,该预测沉积微相的方法是可行的。  相似文献   

Experimental catchments in the Pampa biome: Database on hydrology in grasslands and eucalyptus plantations in subtropical Brazil     

José Miguel Reichert  José Carlos de Deus Junior  Norton Borges Junior  Rosane Barbosa Lopes Cavalcante 《水文研究》2021,35(8):e14285

The introduction of exotic, fast-growing forest species in the Pampa biome (Southern Grasslands) is a controversial topic, considering the potential effect on water and soil resources. This repository contains hydrologic data (rainfall, discharge and turbidity) collected since 2011 in three small (≤1.1 km²), paired experimental catchments of the “Ponta da Canas” site, in the Pampa biome in subtropical Brazil. Two catchments are predominantly covered with eucalyptus plantations, and one with livestock-grazing degraded grassland. For each catchment, the collected data include 10-min resolution rainfall, streamflow, and turbidity (except for one of the eucalyptus catchments), automatically recorded in 10-min intervals. In each catchment, rainfall is measured with an automatic tipping-bucket rain gauge; stream depth is determined with a pressure transducer at the spillway, and a rating curve is used to estimate discharge; and turbidity is measured with a turbidimeter. The collected data are being used to understand water balance and sediment production under the distinct land uses, to improve forest management, and comply with State legislation.  相似文献   

Tree establishment on bars in low‐order gravel‐bed mountain streams     

Isabelle Charron  Edward A. Johnson  Y. E. Martin 《地球表面变化过程与地形》2011,36(11):1522-1533

In many large alluvial rivers, trees often recruit and survive along laterally accreted sediments on bars. This produces a gradient of tree ages and composition with distance from the active channel. However, in low‐order, gravel‐bed mountain streams, such as the stream investigated in this study, it is suggested that vertical accretion results in sediment deposition patterns on bars that are often highly patchy. Consequently, tree species and ages are also heterogeneously distributed, rather than having distinct linear or arcuate banding patterns with distance from the channel. In addition, overall age patterns of trees on these bars follow the distribution of floods, with numerous young trees and few older trees. Recruitment is fairly continuous on these bars and is not correlated with high water years, suggesting that even flows close to bankfull levels are capable of transporting fine sediment to the bars on which trees establish. This pattern of sediment deposition/erosion and the resulting tree recruitment and survival seem to be a result of valley confinement and the lack of lateral accretion in these smaller, mountainous channels. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

Relative importance of dust inputs and aquatic biological production as sources of lake sediments in an oligotrophic lake in a semi‐arid area     

Luis A. Oseguera  Javier Alcocer  Gloria Vilaclara 《地球表面变化过程与地形》2011,36(3):419-426

The dustfall (DF) and mass sedimentation rate (MSR) in Lake Alchichica, Central Mexico, were studied from June 2006 to June 2008. DF ranged between 0·11–0·93 g m^?2 d^?1 in the warm and rainy season and 0·54–1·21 g m^?2 d^?1 in the cold and dry season. MSR varied from 0·52–2·40 g m^?2 d^?1 in the stratification season to 1·14–5·07 g m^?2 d^?1 in the circulation season. The timing of the highest fluxes of DF and MSR is most likely a product of several factors coinciding during the cold and dry season: (a) availability of dust sources and the presence of strong winds (>7·5 m s^?1) in the DF case, and (b) the circulation period of the lake and the availability of nutrients in the MSR case. As expected, the DF in Alchichica was high and similar to that found in other arid and semi‐arid areas. However, the MSR was higher than that reported for other oligotrophic lakes. Particles captured in the aerial traps consisted mainly of detrital minerals; in contrast, particles found in the water traps were mostly biogenic and, to a lesser extent, detrital minerals. The MSR was one to seven times higher than the DF. In spite of the oligotrophic status of Lake Alchichica, the large size of the settled phytoplankton (autochthonous, waterborne) is what leads to the high MSR, which surpasses the DF (allochthonous, airborne) derived from whirlwinds originating in easily eroded terrains that are characteristic of arid/semi‐arid areas. Our results indicate that caution must be taken in considering that the DF amount measured through DF collectors located at the lake shore does actually represent the DF entering into the lake. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

Geology as a control on landslides on the Isle of Wight: an overview     

G.O. Jenkins  C. Foster  P.M. Hopson 《Proceedings of the Geologists' Association. Geologists' Association》2011,122(5):906-922

The Cretaceous and Palaeogene sedimentary rocks that crop out on the Isle of Wight are highly prone to landsliding and the island offers an important field laboratory wherein to investigate a number of the different types of failure. Many of these landslides represent a significant engineering hazard, with several urban areas requiring remedial work and planning constraints (e.g. The Undercliff and Seagrove Bay) to aid development. Previous studies have thoroughly investigated the major landslides in the Undercliff area around Ventnor and presented a mechanism for that massive failure. This overview of the landslides throughout the Isle of Wight by the British Geological Survey was completed as part of the multidisciplinary survey of the surface geology, structure, geophysical response and offshore interpretations of the island between 2007 and 2010. The survey has collected new observational data on the extensive coastal landslides, as well as the distribution, nature and mechanism of failure of the lesser-studied inland examples.  相似文献   

江西潭坑铅锌（银）矿床特征及成因分析     

徐顺国 《火山地质与矿产》2011,(1):29-36

江西省潭坑铅锌（银）矿区位于北武夷铅锌银成矿带内,本文系统阐述了矿区地质和矿床特征,并对矿床的成因进行了探讨。认为本区铅锌（银）矿床,经历了火山喷发沉积和后期热液充填两大成矿期,与次火山岩体（流纹斑岩）有密切的关系,属次火山热液矿床。  相似文献