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241.
A study of sedimentary processes and sediment yields in a high arctic meromictic lake (Lake C2, Taconite Inlet, Northern Ellesemere Island, Canada) was undertaken from May 1990 through August 1992 to understand the links between climatic controls, hydrology, and the laminated sediment record preserved in the lake. Understanding the relationships between processes and the sediment record is critical for interpreting the climatic significance of the laminated sediments in a region where high resolution climate proxy records are quite limited.Sediment transport to Lake C2 is dominated by fluvial processes. During the early part of the melt season slushflows transport sediment to the lake surface. Subsequently, suspended sediment is delivered to the lake by the main inlet stream and distributed lakeward by a plume emanating the main inlet channel. Due to the strong density stratification of the water column the plume distributes sediment downlake by overflows and interflows in the epilimnion. In general, overflows are generated by lower discharge events whereas interflows penetrate to the halocline during high discharge with increased suspended sediment concentration.Sediment trap analysis demonstrates that suspended sediment transport and deposition responds to diurnal through annual changes in stream discharge. Seasonal and annual sediment trap yields agree with average accumulation rates determined from varve thickness measurements and cumulative suspended sediment discharge from the main inlet stream indicating a close link between climatological, hydrological, and sedimentological controls and varve deposition.This is the fourth in a series of papers published in this issue on the Taconite Inlet Lakes Project. These papers were collected by Dr R. S. Bradley. 相似文献
242.
新疆盐湖卤水成分及其成因 总被引:15,自引:0,他引:15
根据野外考察和室内研究资料,论述了新疆盐湖的概况,卤水主要和次要成分,盐湖的水化学类型。探讨了盐湖卤水化学成分的来源和集散特点。 相似文献
243.
N. I. Andreev I. S. Plotnikov N. V. Aladin 《International Journal of Salt Lake Research》1992,1(1):111-116
Data are presented on the composition and biomass of the Aral Sea zooplankton in August and October, 1989. As salinity gradually
increased, a decrease in zooplankton species composition occurred at a salinity of 25–30 g L−1. Because the Aral has now divided into two water-bodies, the zooplankton communities in these lakes have begun to conform
with their individual hydrological and biological regimes. 相似文献
244.
论述了冰期与间冰期的气候变化与海平面升降的关系以及冰期与间冰期的古地貌,全面系统地阐述了上海地面沉降之后的地质环境,并提出了控制地面沉降的5条建议。 相似文献
245.
层序地层学方法及其在陆相湖盆研究中的应用 总被引:29,自引:2,他引:29
针对中国中、新生代陆相湖盆的特征,从沉积盆地的构造和边缘背景对海相层序地层的影响出发,讨论了湖水面相对变化、沉积物供给、气候等对湖相层序地层的控制作用,明确指出两种背景条件具有本质差异,海相层序地层学方法不能简单套用于内陆盆地分析。 相似文献
246.
247.
Analysis of the influence of Taihu Lake and the urban heat islands on the local circulation in the Yangtze Delta 总被引:6,自引:0,他引:6
The influences of human activities on regional climate and weather are tremendous. The re-gional temperature and the distributing of wind field are influenced, whereas the precipitation in-tensity and the spatial and temporal distribution of the precipita… 相似文献
248.
249.
The results of the geochemical investigation on bulk sediment fromthree cores collected in Albano crater lake (Central Italy) are reported, andthe main markers of the palaeoenvironmental changes in the last 26ka are discussed. The sediment of Lago Albano consists of greysilt and mud, and is made of volcanogenic, calcareous, siliceous and organicmaterial. Some tephra layers provide a chronological framework for thesequence. The chemical features of the sediments are strongly impacted by theAlban Hills volcanism (Roman volcanic area), but there are also strong changesof organic/inorganic matter ratios, owing to variations in biologicalproductivity and terrigeous supply from the catchment. Six chemostratigraphiczones record the main steps of the transition from the cold and dry climate ofGlacial Maximum to the warmer and more humid Holocene climate. The most usefulgeochemical indices are: biogenic silica, CO2, Br and organiccontent (OM) for biological productivity; Al, Y, CIA (Chemical Index ofAlteration), Al/Rb, Ti/Zr and Y/Al ratios for terrigenous clasticmaterial; OM/Al ratio for organic/terrigenous ratio; S/Fe andMo/Fe ratios and Authigenic U for redox diagenetic conditions of the lakesediment. The geochemical records agree rather well with those of thelithological and paleomagnetic studies, and despite the information obtainedare less detailed than those acquired by the study of biological remains, thepalaeoenvironmental significance inferred is consistent. A comparison of thechemostratigraphic results of Lago Albano with those obtained on coevalsediments from Central and Southern Italy lakes supports the role of thegeochemical investigation as important complement to more sophisticatedtechniques in the palaeoenvironmental reconstructions. 相似文献
250.
Michael F. Rosenmeier David A. Hodell Mark Brenner Jason H. Curtis Jonathan B. Martin Flavio S. Anselmetti Daniel Ariztegui Thomas P. Guilderson 《Journal of Paleolimnology》2002,27(1):117-131
Stratigraphic shifts in the oxygen isotopic (18O) and trace element (Mg and Sr) composition of biogenic carbonate from tropical lake sediment cores are often interpreted as a proxy record of the changing relation between evaporation and precipitation (E/P). Holocene 18O and Mg and Sr records from Lakes Salpetén and Petén Itzá, Guatemala were apparently affected by drainage basin vegetation changes that influenced watershed hydrology, thereby confounding paleoclimatic interpretations. Oxygen isotope values and trace element concentrations in the two lowland lakes were greatest between ~ 9000 and 6800 14C-yr BP, suggesting relatively high E/P, but pollen data indicate moist conditions and extensive forest cover in the early Holocene. The discrepancy between pollen- and geochemically-inferred climate conditions may be reconciled if the high early Holocene 18O and trace element values were controlled principally by low surface runoff and groundwater flow to the lake, rather than high E/P. Dense forest cover in the early Holocene would have increased evapotranspiration and soil moisture storage, thereby reducing delivery of meteoric water to the lakes. Carbonate 18O and Mg and Sr decreased between 7200 and 3500 14C-yr BP in Lake Salpetén and between 6800 and 5000 14C-yr BP in Lake Petén Itzá. This decline coincided with palynologically documented forest loss that may have led to increased surface and groundwater flow to the lakes. In Lake Salpetén, minimum 18O values (i.e., high lake levels) occurred between 3500 and 1800 14C-yr BP. Relatively high lake levels were confirmed by 14C-dated aquatic gastropods from subaerial soil profiles ~ 1.0–7.5 m above present lake stage. High lake levels were a consequence of lower E/P and/or greater surface runoff and groundwater inflow caused by human-induced deforestation. 相似文献