首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 15 毫秒
1.
Prehistoric farmers in arid and semiarid ecosystems commonly used rock alignments to concentrate water and sediments on their fields. Previous research has emphasized the importance of runoff from organic matter‐rich uplands as a mechanism for soil nutrient replenishment. However, eolian inputs to these dryland ecosystems might also contribute substantially to mineral‐derived nutrient pools. We explored the relative importance of eolian deposition, prehistoric agriculture, and the presence of rock alignments on soil properties in a semiarid grassland in Arizona. Subsurface soils behind natural rock alignments are finer in texture than soils unbound by rock alignments, while subsurface soils behind agricultural rock alignments coarsen relative to unbound soils. Neither rock alignments nor estimated crop yields had detectable effects on mineral‐derived nutrient pools. In contrast, eolian deposition is an important source of soil mass and nutrients to modern soils. While dust deposition likely reduced soil heterogeneity across this landscape, it could have also contributed to the sustainability of prehistoric agriculture.  相似文献   

2.
Swelling behavior of clayey soils regarded as a hidden disaster, causes a great deal of damage in light hydraulic structures such as drinking water network, irrigation pipes or open canal linings through which water can easily leak and penetrate into soil during loading and unloading stages. Early identification during site investigation and laboratory testing is extremely important to ensure that the appropriate design strategy is adopted. The clay soils having swelling potential are generally found in arid and semi-arid regions, such as in the Şanlıurfa-Harran plain located in the southeast of Turkey. The problems associated with swelling clays occurred for the lightweight hydraulic structures constructed in Turkey have been met during the construction of irrigation structures in the scope of Southeast Anatolian Project as the Turkey’s greatest water resources project. Therefore, the identification of such soils and the assessment of their swelling potential parameters are necessary for hazard mitigation planning and land-use management. In this scope, extensive geotechnical study is executed for an investigation area. The samples were obtained from the Harran plain where many irrigation canal structures are constructed, and geotechnical study was performed on these samples. Atterberg limit tests often provide the basic field information to substantiate the soil’s swelling nature. The plasticity index (PI) and liquid limit (LL) values are also used extensively for classifying swelling soil and should always be determined during preliminary investigations. Because of this, LL and PI are assessed by using geographical information system (GIS)-based computer software, and LL and PI contour maps are created. Swelling percentages of the soil samples were carried out on both undisturbed and compacted soil samples by using direct methods. As a result of this extensive study, the values of swelling percentages determined for each location are used to obtain the swelling potential hazard map of the area by means of a GIS program. The results of GIS analyses for this area indicate that the analyses based on a lot of data introduce meaningful results for this study. It is expected that these maps will be a useful tool for planners and engineers in their efforts to achieve better land-use planning and to decide necessary remedial measures.  相似文献   

3.
Research on soil fertility is presented in the context of runoff agriculture, a venerable farming system that has been used for millennia in arid to semiarid regions, where water is a major limiting resource for crop production. The agroecology of runoff farming was studied with the Zuni to evaluate nutrient and hydrologic processes, management, maize productivity, and soil quality in some of the oldest recognized fields in the United States. This ancient Southwest agriculture has functioned without conventional irrigation or fertilization by tapping into biogeochemical processes in natural watersheds connected to fields. Carefully placed fields are managed on alluvial fans and other valley margin landforms to intercept runoff and associated sediment and organic debris transported from adjoining forested uplands. We report on research to evaluate and link nitrogen and phosphorus, two key nutrients for crop production, in watershed, soil, and crop components of this agroecosystem. Nutrient data have been collected by observational and experimental methods for each component and the transport of nutrients from watershed to field to maize. The condition of Zuni agricultural soils suggests that their knowledge and management of soils contributed to effective conservation. This study and others indicate the need for further long‐term monitoring and experimental research on watersheds, runoff processes, field soils, and crops across a range of arid to semiarid ecosystems. © 2007 Wiley Periodicals, Inc.  相似文献   

4.
The arid area is one of the most concerned areas among the water resources researchers and economists. Northwest China will be an important developing region of China in the 21st century. Yaoba is a well-irrigation oasis within this arid area, which is located in the Alxa area west of the Helan Mountains and next to the Tengger desert in the east. It has contributed greatly to the local stock raising and agriculture since its development in 1970. However, the groundwater which the oasis depends on to survive has been getting salinized gradually and more serious in recent years.A comprehensive study was carried out using the methods of groundwater environment isotope analysis, lithofaci-es and palaeogeography, calculations of water-rock interaction and the existing form of chemical components in groundwater etc. It has been found that the salinization of groundwater is mainly caused by reinfiltration water solving the salt in soil which is deposited simultaneously with the sediments and accumulated in th  相似文献   

5.
膜下滴灌微区环境对土壤水盐运移的影响   总被引：1，自引：0，他引：1       下载免费PDF全文
基于膜下滴灌特有的"膜中"、"膜间"、"膜边"、"膜外"微区环境,利用2011—2013年田间对比试验方法获取的5 960个数据,运用柯布-道格拉斯模型,构建膜下滴灌环境土壤层次、灌水定额、土壤水分、气温、蒸发综合因素与土壤水盐关系及影响效应分析模型.结果表明,在气候干旱、蒸发强烈灌区,地膜覆盖与滴灌结合的地表介面灌溉形式下,土壤水盐具有水平方向由"膜中"向"膜边"地表裸露区定向迁移,垂直方向土壤水盐则由下向上层运移且趋于"膜外"边界积累的趋势,尤其是气温与蒸发因素交互作用,推进膜下滴灌土壤水盐在地膜覆盖与土壤裸露区域空间运移,研究结果进一步揭示了膜下滴灌"土壤水盐定向迁移"形成机理,为膜下滴灌土壤水盐地表排放模式应用提供了依据.  相似文献   

6.
在干旱、半干旱地区,水分是环境体系中最活跃的因素,植被对水分具有高度的依赖性,水分成为影响植物生存、生长发育的关键因素,对植被的稳定性生长与恢复重建具有极大的限制性。泾惠渠灌区位于陕西省关中平原中部,属大陆性半干旱气候区,该区降水时空分布不均,水资源短缺。从土壤水分的测试技术和土壤水分的动态变化研究方面进行综述,分析研究灌区2004～2007年四年土壤水分动态观测资料,得出研究区的土壤水分动态变化规律,同时简述水分有效性的研究进展,对提高农业干旱防御能力,制定节水灌溉计划,提高水分利用效率具有重要意义。  相似文献   

7.
The present study examines the geoarchaeological history of an oasis in Kharga Depression in central Egypt. El‐Deir is renowned for its Ptolemaic temple and Roman fortress on the road from former Hibis (Kharga) to the Nile Valley. During the survey, spring mounds and irrigation soils belonging to an ancient agricultural zone were discovered, and further documented by ceramics found on the site. Our methodology combines the geomorphological interpretation of landforms (especially yardangs) with ceramics and 14C‐dated charcoal to distinguish and date former agricultural areas in El‐Deir. The results show that the oasis experienced several phases of soil accretion and destruction through time. Playa sediments were deposited in the humid early Holocene and severely eroded by deflation before the onset of irrigated agriculture between Pharaonic and Persian times. Very fast vertical soil accretion occurred in the Ptolemaic period, but irrigation soils were later destroyed during the Roman period by a combination of wind deflation and flash floods (second to fourth century A.D.), suggesting a period of climate instability. The case of El‐Deir invites reevaluation of constructive agencies for the development of irrigated land and destructive agencies as limiting factors for the sustainability of agricultural practices in late antiquity.  相似文献   

8.
The occurrence and significance of biogenic opal in the regolith   总被引：1，自引：0，他引：1  
Jonathan   《Earth》2003,60(3-4):175-194
Biogenic opal produced by vascular plants, diatoms, and siliceous sponges have been found in soils and terrestrial sediments of all continents except Antarctica since the middle of the 19th century. The opal particles range in size from fine silt to fine sand. Almost all soils contain detectable opal up to levels of 2–3%, and a significant number contain values in excess of 5%. Even higher values have been found from soils and sediments of all continents in a wide range of soil types. The most important factor is poor soil drainage and seasonal to permanent water logging. This encourages the proliferation of silica producing organisms. Such conditions have been found in the soils and aquatic sediments of the monsoonal tropics, tropical rain forests, temperate forests, tropical savanna, tropical islands, semi-arid grasslands and savanna, and temperate woodland and grassland. The presence of a volcanic substrate also appears favourable in some cases, but is not necessary. Biogenic opal preferentially collects in the A horizon of soils and, to a lesser extent, in the B horizon. This preferential distribution facilitates identification of palaeosols in stacked soil sequences. Biogenic opal is also a component of windblown dust, even in arid environments. Biogenic opal is significant to regolith processes in a number of ways. Firstly, as in the case in marine environments, it is likely to be important in silica cycling and storage because of its greater lability compared to quartz. Secondly, dissolution and reprecipitation of opal A as opal CT or micro-quartz may play a role in cementation and silicification of regolith to form silica hardpans and silcrete. Thirdly, the organisms that form biogenic opal can have considerable palaeoenvironmental significance and be valuable in reconstructing regolith evolution. Finally, some forms of biogenic silica, in particular sponge spicules, can present a health hazard. Their high abundance in some soils and sediments needs to be considered when assessing the health implications of airborne dust.  相似文献   

9.
A number of archeological features, including in‐filled irrigation canals of uncertain prehistoric age, occur within the Holocene floodplain of the Salt River at Phoenix, Arizona. In the first attempt to date irrigation‐canal sediments using luminescence methods, we obtained age estimates of 1640 ± 190 yr B.P. (1σ) (multi‐aliquot or MA) and 1621 ± 95 yr B.P. (post‐IR single‐aliquot‐regenerative‐dose or SAR) for a single sample from the base of the oldest canal‐infilling deposits (all IR‐PSL ages reported in this article are in calendar years before A.D. 2001). For the remaining canal samples, weighted mean luminescence ages of 819 ± 45 yr (MA) and 826 ± 32 yr (post‐IR SAR) were obtained. Thus from photonic dating we can resolve the first and last phases of canal use at this Phoenix site: initiation at ca. 1600 years ago and final use at ca. 800 years ago. These results demonstrate the power of SAR luminescence sediment dating to enhance our understanding of prehistoric irrigation‐canal development and usage here and elsewhere in the world. © 2004 Wiley Periodicals, Inc.  相似文献   

10.
This study is an attempt to contribute to the data set of granulometric studies of sediments by measuring the sedimentary structure and texture, along with statistical parameters, of cold and arid lake systems. The palaeolake sequence along the River Indus on the western fringe of the Tibetan Plateau in Ladakh sector was selected in order to shed light on depositional environmental changes within the lake from post‐last glacial maximum to 5 ka. The River Indus was blocked by Lamayuru dam burst during the deglaciation, after the Last Glacial Maximum (LGM) and the subsequent increase in water level led to the formation of the Saspol–Khalsi palaeolake. This lake was ca 55 km in length, extending from Nimo to Khalsi, had a surface area of 370 km2 and was in existence until 5 ka. Two sections (Saspol and Khalsi) separated by an aerial distance of 35 km show a similar trend in sediment character due to their deposition in the same lake system. Grain‐size studies show a polymodal nature of sediments for both of the sections. However, sediments of the lower/downstream section (Khalsi) show a poorer degree of sorting, and coarser grain size and high energy depositional condition as compared with the sediments of Saspol section (positioned upstream) due to the location of the sections within the lake system. It was noted that, in high‐altitude arid regions, the sedimentological characteristics of large‐sized valley lakes may vary greatly, horizontally as well as vertically, owing to local stream input, inflow intensity from the catchment, outflow velocity of water channels, lithology and valley widths at the different sites.  相似文献   

11.
Chronological, sedimentological and geochemical analyses of a clastic infill from Kelly Hill Cave (5K1), Kangaroo Island, document a palaeoenvironmental record that spans from the Late Pleistocene to the middle Holocene. We AMS radiocarbon‐dated bone collagen and U–Th‐dated speleothem to determine that fossiliferous sediments were deposited between >20 ka and 7 ka ago. Most of the 15 sedimentary layers are dominated by sand‐ and silt‐sized quartz that is physically and geochemically comparable with surface soils in the Kelly Hill area. Late Pleistocene and Last Glacial Maximum strata are represented primarily by homogeneous, poorly sorted quartz‐rich sediments that contain little organic matter, but include a thin layer composed largely of silt‐sized clay pellets that resemble sediments deflated from playa lakes. Microstructures observed in petrographic slides indicate that, with the exception of one layer, all sediments experienced little reworking once deposited in the cave. Some layers display pedogenic microstructures such as redeposited clays and opaline silica infilling that indicate postdepositional modification; that is, cave‐floor soil development. Overlying Holocene‐aged sediments also consist mainly of quartz but have much greater organic matter content. Some of these sediments have been strongly influenced by re‐precipitated organic matter that appears to have been transported into the cave via vadose drip water. The presence of dissolved organic matter in soil/vadose waters suggests a high vegetation density and acidic soils, which are congruent with the more equitable climatic conditions characteristic of the Holocene. The sediments described here provide a valuable palaeoenvironmental record that will facilitate future interpretation of associated vertebrate fossils.  相似文献   

12.
On the basis of site investigation and sample collection of petroleum contaminants in the soil-water-crop system in the Shenyang-Fushun sewage irrigation area, the physical-chemical-biological compositions of the unsaturated zone is analyzed systematically in this paper. At the same time, the degradation kinetics of residual and aqueous oils is determined through biodegradation tests. The studies show that dominant microorganisms have been formed in the soils after long-term sewage irrigation. The microorganisms mainly include bacteria, and a few of fungus and actinomycetes.After a 110-days‘ biodegradation test, the degradation rate of residual oil is 9.74%--10.63%, while the degradation rate of aqueous oil reaches 62.43 %. This indicates that the degradation rate of low-carbon aqueous oil is higher than that of highcarbon residual oil. In addition, although microbial degradation of petroleum contaminants in soils is suitable to the firstorder kinetics equation, the half-lives of aqueous oil, No. 20 heavy diesel and residual oil in the surface soils (L2-1, S1-1 and X1-1) are 1732 h, 3465 h and 17325 h, respectively.  相似文献   

13.
银北地区土壤盐渍化形成机理与模拟研究   总被引：1，自引：1，他引：1  
银北地区位于干旱、半干旱气候带,降水稀少,蒸发强烈,导致本地区土壤盐渍化严重。近年来,由于黄河来水量的逐年减少,引黄灌溉不能满足农业灌溉需求,逐渐开始开采利用地下水。由于银北地区浅层地下水矿化度较高,利用地下水灌溉可能引起次生土壤盐渍化。本文运用PHREEQC模型软件模拟灌溉水与土壤之间的相互作用过程,探讨了土壤盐渍化的形成机理。通过模拟分析得到以下结论:(1)地表水和地下水联合运用是解决银北灌区土壤盐渍化的关键,不同地区采取不同的混合比例,可以实现水资源的高效利用。(2)银北地区灌溉淋洗期间存在蒸发浓缩叠代在2~4次,说明存在轻微蒸发。(3)INVERSE模拟结果说明,银北地区灌溉淋洗期间存在轻微蒸发,水相和固相的相互作用,石膏、白云岩和盐岩溶解,Na 、Ca2 和Mg2 吸附交换,渠水下渗转化为地下水;非灌水期地下水通过毛细管作用强烈蒸发,水相和固相的相互作用,石膏、白云岩和盐岩沉淀,Na 、Ca2 和Mg2 解吸附,使有害盐分氯化物、硫酸盐存留在土壤层中,形成土壤盐渍化。  相似文献   

14.
Loboi Swamp is a 1·5 km2 freshwater wetland situated near the equator in the Kenya Rift Valley. The climate is semi‐arid: precipitation is ≈ 700 mm year?1, and evapotranspiration is ≈ 2500 mm year?1. Some of the wetland water is currently used for irrigation. An interdisciplinary study was conducted on the geology, hydrology, pedology and biology of the wetland to determine its origin and history and to assess its longevity under present hydrological conditions. Sedimentary records from two piston cores (1·8 and 4 m long) indicate that the present wetland developed during the late Holocene on a low‐relief alluvial plain. Floodplain deposits (sandy silts) are capped with wetland sediments (organic‐rich clay and peat), which began to form at ≈ 700 BP. The swamp is dominated by Typha domingensis Pers. (≈ 80%) and floating Cyperus papyrus L. (20%). It is fed by warm springs (T ≈ 35 °C; pH ≈ 6·4–6·9) emanating from grid faults of the rift floor. Water compositions suggest that sources are dominated by shallow meteoric water, with little contribution from deeper geothermal fluids. Siderite concretions in the floodplain silts reflect the Fe‐reducing conditions that developed as the surface became submerged beneath the water table. The pollen record captured both local and more regional vegetation, showing the prevailing dry rift valley climate despite development of the wetter conditions on the valley floor. The diatom record also suggests a dramatic change in local hydrology. The combined biological records of this semi‐arid wetland indicate an abrupt change to wetter conditions, most probably as a result of a regional change in climate. Rift tectonics provided accommodation space, maintained the wetland at or below the water table and enabled spring recharge. The size of the modern wetland has been reduced by about 60% since 1969, which suggests that the system may now be under hydrological stress due to anthropogenic impacts from land‐use change.  相似文献   

15.
The Qarun Lake in the Faiyum Oasis (Egypt) provides a unique record of Holocene environmental and climate change in an arid area largely devoid of fossil proxy records. Multiple lithological, palaeontological and geochemical proxies and 32 radiocarbon dates from the 26‐m‐long core FA‐1 provide a time series of the lake's transformation. Our results confirm that a permanent lake appeared in the Holocene at c. 10 cal. ka BP. The finely laminated lake sediments consist of diatomite, in which diatoms and ostracods together with lower concentrations of ions indicate a freshwater environment at the end of the early and middle Holocene. This freshwater supply was closely associated with regular inflows of the Nile water during flood seasons, when the Intertropical Convergence Zone (ITCZ) migrated northwards in Africa, although it has probably never reached the Faiyum Oasis. Local rainfall, possibly connected with a northern atmospheric circulation, may have been important during winter. Several phases in the lake's evolution are recognized, represented by oscillations between deep open freshwater conditions during more humid climate and shallow fresh to brackish water during drier episodes. After a long freshwater phase, the lake setting has become more brackish since c. 6.2 cal. ka BP as indicated by diatoms and increasing contents of evaporite ions in the sediment. This clearly shows that since that time the lake has occasionally become partly desiccated. This is a result of reduced discharge of the Nile. In the late Holocene the lake was mostly brackish and then gradually turned into a saline lake. This natural process was interrupted about 2.3 cal. ka BP when a man‐made canal facilitated water inflow from the Nile. The examined FA‐1 core can be used as a reference age model of climate change in the Holocene and its impact on the development and decline of ancient civilizations in northeastern Africa.  相似文献   

16.
The imbalance between incoming and outgoing salt causes salinization of soils and sub-soils that result in increasing the salinity of stream-flows and agriculture land. This salinization is a serious environmental hazard particularly in semi-arid and arid lands. In order to estimate the magnitude of the hazard posed by salinity, it is important to understand and identify the processes that control salt movement from the soil surface through the root zone to the ground water and stream flows. In the present study, Malaprabha sub-basin (up to dam site) has been selected which has two distinct climatic zones, sub-humid (upstream of Khanapur) and semi-arid region (downstream of Khanapur). In the upstream, both surface and ground waters are used for irrigation, whereas in the downstream mostly groundwater is used. Both soils and ground waters are more saline in downstream parts of the study area. In this study we characterized the soil salinity and groundwater quality in both areas. An attempt is also made to model the distribution of potassium concentration in the soil profile in response to varying irrigation conditions using the SWIM (Soil-Water Infiltration and Movement) model. Fair agreement was obtained between predicted and measured results indicating the applicability of the model.  相似文献   

17.
为了探明耕地-荒地-海子系统中不同类型水分的运移转化规律,在2018-2019年典型时期对系统内具有代表性的采样点进行水样采集,分析了不同时期内不同水体的δ18O变化特征,并利用二端元混合模型和土壤水动力学方法计算了不同类型水分转化贡献率。结果发现：①在灌溉期,82%的灌溉水储存于1 m土体中,18%的灌溉水通过渗漏补给了耕地地下水,渠系灌溉水通过地下侧向径流给耕地地下水贡献了76%。②灌溉水和降雨对耕地地下水平均贡献率为94%和6%;耕地地下水和降雨对荒地地下水的平均贡献率为71%和29%;荒地地下水和降雨对海子的平均贡献率为43%和57%。③渠系灌溉水通过侧向径流贡献给耕地地下水的水量基本全部迁移给了荒地地下水,地下水迁移转化是由渠系水侧向径流触发的。④灌后5 d,耕荒地交界土层0~40 cm存在饱和-非饱和侧向补给;灌后15 d和30 d,耕地和耕荒地交界处的地下水向根区40~60 cm、土层80 cm以及100 cm补给水分;灌后30 d,耕地中的灌溉水水分消失。⑤在非灌溉期,荒地地下水和海子耗水较多,应给海子补给水分。  相似文献   

18.
为了探明耕地-荒地-海子系统中不同类型水分的运移转化规律,在2018-2019年典型时期对系统内具有代表性的采样点进行水样采集,分析了不同时期内不同水体的δ18O变化特征,并利用二端元混合模型和土壤水动力学方法计算了不同类型水分转化贡献率。结果发现:①在灌溉期,82%的灌溉水储存于1 m土体中,18%的灌溉水通过渗漏补给了耕地地下水,渠系灌溉水通过地下侧向径流给耕地地下水贡献了76%。②灌溉水和降雨对耕地地下水平均贡献率为94%和6%;耕地地下水和降雨对荒地地下水的平均贡献率为71%和29%;荒地地下水和降雨对海子的平均贡献率为43%和57%。③渠系灌溉水通过侧向径流贡献给耕地地下水的水量基本全部迁移给了荒地地下水,地下水迁移转化是由渠系水侧向径流触发的。④灌后5 d,耕荒地交界土层0~40 cm存在饱和-非饱和侧向补给;灌后15 d和30 d,耕地和耕荒地交界处的地下水向根区40~60 cm、土层80 cm以及100 cm补给水分;灌后30 d,耕地中的灌溉水水分消失。⑤在非灌溉期,荒地地下水和海子耗水较多,应给海子补给水分。  相似文献   

19.
Science-based management of shallow-water habitats is limited by information on the spatial distribution of properties of sediments. This limitation in part stems from the lack of an adequate model or system to classify and delineate subaqueous soil types (sediments). Present classification systems are inadequate because the existing paradigm does not actually consider them as “soils” but merely as “sediments”. Field observations suggest that these sediments could be better understood as “soils”, and the present paradigm could be modified to incorporate a new one—a pedological paradigm. We propose the application of a pedological paradigm for subqueous soils of subtidal habitats to develop ecological interpretations of subaqueous soil types and apply an inventory of subaqueous soil resources for management of estuarine shallow-water habitats. *** DIRECT SUPPORT *** A01BY074 00009  相似文献   

20.
Although pedogenic barite has been documented in many modern soils and palaeosols, no actualistic studies on its formation have been reported. Because barite is stable over the entire range of pressure and temperature of the Earth's crust, it preserves reliable data about the original environment in which it formed. Pedogenic barite and barite‐bearing soils have been used as indicators of landscape stability, environmental conditions, climate and microbial acti‐vity. This study compares field data, micromorphology and stable isotope geochemistry of a barite‐bearing palaeosol from the Morrison Formation (Jurassic) and a modern analogue soil in south‐central Texas, USA. Morrison barite‐bearing palaeosols are over‐thickened cumulic palaeosols that developed in subaerially exposed lacustrine sediments during an extended lake contraction event. Lateral facies relationships document changes in hydrology and duration of episaturated conditions (perched water table above the Btg horizons) that correspond to differences in barite nodule morphology and abundance. Barite precipitation occurred at a redox boundary higher on the landscape after organic matter was completely oxidized. Sulphur isotope data indicate that the initial source of sulphur was soil organic matter. Meteoric water is the likely source of oxygen for the sulphate. Barium sourced from weathering feldspars and clays. The modern analogue displays similar catenary relationships, redox features and micromorphological characteristics compared to the Morrison palaeosols, suggesting that similar pedogenic processes led to barite precipitation. Synthesized data suggest that conditions favourable to barite‐bearing soil formation are low‐gradient basins that have received feldspar‐rich sediments (i.e. volcanically influenced basins), soils that developed near salt domes, soils that developed in exposed wetland or lacustrine sediments and coastal plain deposits. When studied in a well‐documented palaeogeographic context, barite‐bearing soils are valuable to palaeoclimate, palaeoenvironmental and palaeohydrological studies. Combined with regional interfluve palaeosols, barite‐bearing palaeosols may document temporal changes in drainage, surface stability, and accommodation consistent with sequence boundaries/maximum flooding surfaces and climate changes.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号