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991.
岩溶发育的气候条件是决定碳酸盐岩油气田储集空间和运移通道类型的主要因素,溶缝和溶洞是古潮湿环境下塔里木盆地奥陶系碳酸盐岩岩溶发育的产物。通过对塔里木盆地北缘奥陶系碳酸盐岩古风化壳岩溶发育特征的调查与分析,掌握了溶缝与溶洞的发育分布规律,认为溶洞与裂缝并不是孤立分布的,溶洞与周边有成因联系的影响带(裂缝密集发育带)一起共同组成一个有机的缝洞系统,从而构成了良好的缝洞型储集层。将溶洞与裂缝有机的结合起来,建立了碳酸盐岩风化壳储集体的非均质分布模型—— 缝洞型油气藏结构模式,并提出将裂缝和溶洞比较集中的彼此互相连通的区域作为油元来研究,有利于从宏观上认识缝洞型油气藏的实质。   相似文献   
992.
塔里木盆地轮南地区中奥陶统油气富集条件   总被引:3,自引:0,他引:3  
旷红伟  彭德堂  李楠 《地质力学学报》2001,7(2):161-166,103
本文从地层沉积出发,结合地震资料综合解释,简要论述了塔里木盆地轮南地区中奥陶统的油气富集条件,指出轮南地区中奥陶统沉积相带控制了碳酸盐岩储层的分布,生、储、盖条件基本配套,圈闭形成的时间与烃源岩形成的时间一致,有形成岩性油气藏的可能性。   相似文献   
993.
冲绳海槽北部CSH1岩芯地层与碳酸盐沉积特征   总被引:4,自引:1,他引:3  
对冲绳海槽北部CSH1岩芯地层及岩芯碳酸盐含量的分析表明,该岩芯记录了氧同位素3期以来的碳酸盐沉积特征,其碳酸盐沉积类型属于“大西洋型”。进一步研究表明,溶解作用对该区域碳酸盐沉积变化的影响作用不大;引起本区域碳酸盐变化的主要因素为非钙质物质的稀释作用,其中陆源物质的稀释作用可能控制了碳酸盐沉积的整体特征,而火山物质则对局部层位的沉积起到了显著作用;钙质生物生产力的变化对碳酸盐沉积的整体变化有一定的影响。  相似文献   
994.
16ka以来青海湖湖相自生碳酸盐沉积记录的古气候   总被引:33,自引:1,他引:32  
研究了青海湖沉积物碳酸盐的组成、来源及其同湖水物理化学性质的关系,建立了文石饱和指数同温度和湖水Mg/Ca比值(可指示盐度)的关系,利用碳酸盐的组成探讨了青海湖16ka B.P.以来的古气候环境演化过程。结果表明,青海湖沉积碳酸盐大都是自生的,16ka B.P.以来沉积碳酸盐以文石为主。文石的高含量时段同暖湿气候相对应,低含量则同冷干气候相对应。15.2ka B.P.为末次冰期盛冰阶进入晚冰期的界限,晚冰期气候的冷暖波动频繁,幅度较小,13.4-13ka B.P.,11.6-12ka B.P.和11-10.4ka B.P.之间的冷颤动分别相当于老仙女木、中仙女木和新仙女木事件,12-13ka B.P.和11.6-11ka B.P.之间的暖期则分别对应于博令和阿勒罗得暖期。全新世初期(10.4-10ka B.P.)白云石含量的突然增高和文石的消失,可能同淡水快速补给前期盐度较高的湖水有关,反映了全新世开始时气温和降水的增加具有突变性的特点。全新世大暖期的鼎盛期,即6.7ka B.P.左右时湖水的盐度较低。6.7-4ka B.P.为气候转型过程中的冷暖和干湿的快速波动期。4ka B.P.以后碳酸盐含量急剧降低,气候逐步向冷干化方向发展。  相似文献   
995.
云冈石窟地区云冈组上段砂岩中碳酸盐胶结物的含量普遍在10%以上,其主要矿物成分为含铁方解石和含铁白云石。在碳酸盐胶结物化学风化过程中发生的化学反应包括碳酸盐矿物溶解、Fe2+ 离子氧化及Fe3+ 离子水解,以及石膏、泻利盐、水碳镁石、球碳镁石等矿物结晶。水、砂岩中裂隙和层理发育、大气污染等是影响碳酸盐胶结物化学风化的主要外因。碳酸盐胶结物化学风化引发了多种文物病害,对云冈石窟的文物价值造成严重破坏。   相似文献   
996.
997.
We introduce a new representation of coupled solute and water age dynamics at the catchment scale, which shows how the contributions of young runoff waters can be directly referenced to observed water quality patterns. The methodology stems from recent trends in hydrologic transport that acknowledge the dynamic nature of streamflow age and explores the use of water age fractions as an alternative to the mean age. The approach uses a travel time‐based transport model to compute the fractions of streamflow that are younger than some thresholds (e.g., younger than a few weeks) and compares them to observed solute concentration patterns. The method is here validated with data from the Hubbard Brook Experimental Forest during spring 2008, where we show that the presence of water younger than roughly 2 weeks, tracked using a hydrologic transport model and deuterium measurements, mimics the variation in dissolved silicon concentrations. Our approach suggests that an age–discharge relationship can be coupled to classic concentration–discharge relationship, to identify the links between transport timescales and solute concentration. Our results highlight that the younger streamflow components can be crucial for determining water quality variations and for characterizing the dominant hydrologic transport dynamics.  相似文献   
998.
Continental weathering plays a dominant role in regulating the global carbon cycle, soil chemistry and nutrient supply to oceans. The CO2-mediated silicate weathering acts as a major CO2 sink, whereas sulphuric acid-mediated carbonate dissolution releases CO2 to the atmosphere–ocean system. In this study, dissolved major ions and silica concentrations of two tropical (Damodar and Subarnarekha) river systems from India have been measured to constrain the type and rate of chemical weathering for these basins. The total dissolved solids (TDS) of these rivers, a measure of total solute supply from all possible sources, are about 2–3 times higher than that of the global average for rivers. Mass balance calculations involving inverse modelling estimate that 63 ± 11% of total cations are derived from rock weathering, of which 27 ± 7% of cations are supplied through silicate weathering. The sulphide-S concentrations are estimated by comparing the water chemistry of these two rivers with that of a nearby river (Brahmani) with similar lithology but no signatures of sulphide oxidation. The outflows of Damodar and Subarnarekha rivers receive 17% and 55% of SO4 through sulphide oxidation, respectively. The sulphide oxidation fluxes from the ore mining areas, such as upper Damodar (0.52 × 109 mol/yr) and lower Subarnarekha (0.66 × 109 mol/yr) basins, are disproportionally (~9 times) higher compared to their fractional areal coverage to the global drainage area. The corresponding CO2 release rate (2.84 × 104 mol/km2/yr) for the Damodar basin is lower by five times than its CO2 uptake rate (1.38 × 105 mol/km2/yr). The outcomes of this study underscore the dominance of sulphide oxidation in controlling the dissolved chemical (cationic and sulphur) fluxes.  相似文献   
999.
Recently, evapotranspiration has been hypothesized to promote the secondary formation of calcium carbonate year‐round on tree islands in the Everglades by influencing groundwater ions concentrations. However, the role of recharge and evapotranspiration as drivers of shallow groundwater ion accumulation has not been investigated. The goal of this study is to develop a hydrologic model that predicts the chloride concentrations of shallow tree island groundwater and to determine the influence of overlying biomass and underlying geologic material on these concentrations. Groundwater and surface water levels and chloride concentrations were monitored on eight constructed tree islands at the Loxahatchee Impoundment Landscape Assessment (LILA) from 2007 to 2010. The tree islands at LILA were constructed predominately of peat, or of peat and limestone, and were planted with saplings of native tree species in 2006 and 2007. The model predicted low shallow groundwater chloride concentrations when inputs of regional groundwater and evapotranspiration‐to‐recharge rates were elevated, while low evapotranspiration‐to‐recharge rates resulted in a substantial increase of the chloride concentrations of the shallow groundwater. Modeling results indicated that evapotranspiration typically exceeded recharge on the older tree islands and those with a limestone lithology, which resulted in greater inputs of regional groundwater. A sensitivity analysis indicated the shallow groundwater chloride concentrations were most sensitive to alterations in specific yield during the wet season and hydraulic conductivity in the dry season. In conclusion, the inputs of rainfall, underlying hydrologic properties of tree islands sediments and forest structure may explain the variation in ion concentration seen across Everglades tree islands. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   
1000.
Despite the importance of tropical ecosystems for climate regulation, biodiversity, water and nutrient cycles, only a few Critical Zone Observatories (CZOs) are located in the tropics. Among these, most are in humid climates, while very few data exist for semi-arid and sub-humid climates, due to the difficulty of estimating hydro-geochemical balances in catchments with ephemeral streams. We contribute to fill this gap by presenting a meteorological and hydro-geochemical dataset acquired at the Mule Hole catchment (4.1 km2), a pristine dry deciduous forest located in a biosphere reserve in south India. The dataset consists of time series of variables related to (i) meteorology, including rainfall, air temperature, relative humidity, wind speed and direction, and global radiation, (ii) hydrology, including water level and discharge at the catchment outlet, (iii) hydrogeology, including manual (monthly) and/or automated (from 15 min to hourly) groundwater levels in nine piezometers and (iv) geochemistry, including suspended sediment content in the stream and chemical composition of rainfall (event based), groundwater (monthly sampling) and stream water (storm events, 15 min to hourly frequency with an automatic sampler). The time series extend from 2003 to 2019. Measurement errors are minimized by frequent calibration of sensors and quality checks, both in the field and in the laboratory. Despite these precautions, several data gaps exist, due to occasional access restriction to the site and instrument destruction by wildlife. Results show that large seasonal and interannual variations of climatic conditions were reflected in the large variations of stream flow and groundwater recharge, as well as in water chemical composition. Notably, they reveal a long-term evolution of groundwater storage, suggesting hydrogeological cycles on a decadal scale. This dataset, alone or in combination with other data, has already allowed to better understand water and element cycling in tropical dry forests, and the role of forest diversity on biogeochemical cycles. As tropical ecosystems are underrepresented by Critical Zone Observatories, we expect this data note to be valuable for the global scientific community.  相似文献   
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