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281.
Sediments of the western part of the Valjevo-Mionica basin (Serbia) were examined both geochemically and mineralogically to explain, on the basis of their sedimentologicai characteristics, the causes of changes in their qualitative and quantitative composition. A total of 62 samples obtained from the drillhole at depths up to 400 m was investigated. Using correlation of the obtained data, six geochemical zones were defined, two of which being specially distinguished by their mineralogical, geochemical and sedimentological characteristics. The first one, upper zone A, consists of banded marlstones interbedded with clay and oil shales and is characterized by presence of analcite and searlesite. These minerals and very high contents of Na20 indicate sedimentation in alkaline conditions with increased salinity in arid climate. That provided pronounced water stratification, as well as higher bioproductivity in the basin and sedimentary organic matter preservation. Therefore, the zone A sediments are characterized by high organic matter contents of the type which provides good potential for production of liquid hydrocarbons. Another specific zone, zone F, contains sediments with very high MgO, K2O and Li concentrations. Their geochemical correlation, as well as almost complete absence of illite in this zone, indicates the presence of interstratified clay mineral type illite-saponite (lithium-bearing Mg-smectite).  相似文献   
282.
王子龙  付强  姜秋香  王湘浩 《水文》2016,36(3):6-10
积雪是陆地水文循环以及大气过程的重要组成部分,它调节了陆地和大气之间的能量交换,对下垫面的能量收支平衡与水热迁移起重要作用。在介绍积雪特性参数确定方法及积雪水热运移规律的基础上,对国内外现有积雪模型进行了分类和总结,并指出未来在积雪特性参数化方案、数值模拟计算、尺度转换等方面还应进行更深入的研究。  相似文献   
283.
The Lower Ordovician Shirgesht Formation in central Iran is composed of siliciclastic and carbonate rocks deposited in diverse coastal and marine shelfal environments (tidal flat, lagoon, shoreface, offshore-shelf and carbonate ramp). Five facies associations contain diverse ichnofossil assemblages that show distinct proximal to distal trends formed in a wide range of physical-chemical conditions. The ethological groups of trace fossils in the Shirgesht Formation reflect a gradient of depositional stress conditions across a wave-influenced shoreline and shelf. Deposits of wave-influenced environments make up a significant component of the geological record of shallow marine settings, and the ability to determine paleoenvironments in detail in such successions is critical for reconstruction of depositional histories and sequence-stratigraphic interpretation.The Cruziana ichnofacies of the study shows highly diverse suites that record the establishment of a benthic community under stable conditions and a long-term colonization window. The Skolithos ichnofacies recognized is a low diversity opportunistic ichnocommunity suite that resulted from colonization after tempestite deposition in a stressed environment. The strata record an onshore to offshore replacement of the Cruziana ichnofacies (with abundant feeding traces of deposit-feeders) by the Skolithos ichnofacies (dominated by suspension-feeders and predators). A transitional zone between the two ichnofacies coincides with the offshore-transition/distal lower-surface deposits. The distribution of ichnofacies, the diversity and range of ethological characteristics reflected by the ichnogenera, and the wide range of wave-dominated coastal facies demonstrate the potential to use individual trace fossils and ichnofacies for significantly refined palaeoenvironmental analysis of wave-dominated coastal settings, particularly in Ordovician successions.  相似文献   
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广西油麻坡钨钼矿床地质特征及成因探讨   总被引:1,自引:1,他引:0  
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287.
Three tracing tests from the same injection point executed at low, medium, and high water levels in the karst aquifer near Tianshengan village, Lunan Stone Forest, Yunnan Province, China, have revealed the basic properties of underground water flow. They showed the general directions of water flows; tracer concentrations were observed at six successive points allowing for the calculation of apparent dominant flow velocities at these sections towards the Dalongtan karst spring. For the high water level, the discharge between single sections was between two and 10 times greater than that at low water level. For the medium water level, the flow velocity at different sections was between 1.4 and 3.7 times faster than that at low water level; and for high water level, it was between 1.3 and 2.7 times faster than that at medium water level. The fastest water flow appeared at the first section (23 cm/s at medium water level); and the slowest (0.6 cm/s at low water level) appeared where water flow must cross the Tianshengan fault (north–south direction), and later, a layer of 20–30 m thickness of quartz sandstone and shale clay-stones. It was also possible to calculate the recovery of the tracer for point 4, Dakenyan, where discharge was measured. At the medium water level, 50% of the injected tracer was detected a half-day after its first appearance and at low water level after more than 3 days. The previously published research illustrates the transport velocities of possible contaminants and their solubilities in water at different hydrological conditions.  相似文献   
288.
Cockroach as the Earliest Eusocial Animal   总被引:2,自引:1,他引:1  
<正>A completely preserved cockroach Sociala perlucida gen.et sp.nov.(Blattida:Socialidae fam.nov.)is described from the Mesozoic(Albian Early Cretaceous)amber of Archingeay in France.It is categorized within the new family Socialidae,originating from the Mesozoic cockroach family Liberiblattinidae,and representing the sister group to the most basal known eutermite families.Numerous direct and indirect morphological evidence(such as a unique narrow body and pronotum with reduced coloration,legs without carination and with numerous sensillar pitts(forelegs)as adaptations to life in nests analogical to the living termitophillous species; enlarged head,long palps for communication,a general venation modified in a direction towards termites (subcosta and radial vein[R]approximated,R branches approximated,simplified,cross-veins reduced),and possibly also the development of the breaking forewing sutura for detaching wings after marriage flight),suggest its eusocial mode of life.Thus,the first eusociality originated within cockroaches,prior to giving birth to termites; termites and Cryptocercus are not directly related.The group of eusocial cockroaches makes termite morphotaxon polyphyletic,but also in this case,the erection of a new order for mastotermites(including Cratomastotermitidae)and/or the inclusion of eusocial,morphological cockroaches within termites appears counterproductive,thus an example of such a general exception to the taxonomical procedure is provided.  相似文献   
289.
The huge, up to 40-50 cm long bivalves, Lithiotis, Cochlearites and Lithioperna, which dominated within “Lithiotis” facies (sensu – Fraser et al., 2004 with lit-erature cited therein), are most significant representa-tives of buildup-maker of shallow marine/lagoonal bivalve mounds (reefs) in numerous places of Tethyan- Panthalassa margins during Pliensbachian-Early Toar-cian times. The distribution of Lithiotis-facies bivalves from Western (Spain, Italy) and Middle Europe (Slo-venia, Croatia, Albania) trough north Africa (Morocco) and Arabian Peninsula (Oman, Arabian Emirates) up to Timor Island, Himalaya Mts (Nepal, China) and west-ern margin of both Americas (USA, Peru) indicates world-wide, rapid expansion of such Lithiotis-type bivalves (Leinfelder et al., 2002; Fraser et al., 2004; Krobicki et al., 2008). The Early Jurassic migration routes were connected both with break-up of Pangea and oceanic circulation, which facilitated high speed of distribution of larva’s of such oyster-like bivalves.  相似文献   
290.
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