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1.
Features and Formation Mechanism of Faults and Potash-forming Effect in the Lop Nur Salt Lake, Xinjiang, China 总被引：4，自引：0，他引：4
LIU Chenglin WANG Mili JIAO Pengcheng LI Shude CHEN Yongzhi School of Environmental Sciences Peking University Beijing Institute of Mineral Resources Chinese Academy of Geological Sciences Beijing 《《地质学报》英文版》2006,80(6):936-943
1 Introduction The Lop Nur Salt Lake, located in the eastern part of the Tarim Basin, Xinjiang, China, has become a playa in the Quaternary. It is under the jurisdiction of Ruoqiang County, Xinjiang, being ~450 km east of Korla City, the capital of the Bayingolin Mongolian Autonomous Prefecture (Fig. 1), and 300 km south of the seat of Shanshan County. The geographic coordinates are 90o00'–91o30' E and 39o40'– 41o20' N. Field survey and drilling since 1995 have revealed an occurren… 相似文献
2.
侯马-运城盆地为晚新生代以来强烈下沉的盆地,现今却大面积遭受剥蚀,有悖于构造下沉接受沉积的常理。为探究其原因,在对侯马-运城盆地及邻区20多个黄土剖面进行野外测量及年代对比的基础上,选择运城盐湖北缘进行连续钻探,开展钻孔岩芯的粒度、磁化率、色度、烧失量及微量元素环境替代性指标分析,并进行光释光及磁性地层学综合定年,同时与前人在侯马-运城盆地的近50个钻孔进行了对比。结果表明,盐湖钻孔200 m岩芯代表了大约距今0.7 Ma以来的沉积。55~200 m深度（约距今0.2~0.7 Ma）岩芯反映受气候旋回影响为主的宽阔河湖沉积环境,指示侯马-运城盆地曾与邻近的渭河盆地、三门盆地连成浩瀚的汾渭古湖;55 m深度以上（约0.2 Ma以后）突然转为以河流相为主的沉积环境,这是由于三门峡谷河流溯源侵蚀贯通三门盆地,导致湖水下泄,使盆地发生大面积湖退,从长期沉积转向广泛剥蚀,并被S2以来黄土/古土壤披盖。研究区盆岭空间分布分析揭示,早期北东东向隆起-凹陷被晚期北北东向隆起-凹陷叠加,隆起叠加处构成较强抬升区（峨嵋台地等）,披盖不同时期的黄土或古土壤;凹陷叠加区则构成强烈沉降区,如运城盐湖因强烈下沉而封闭和咸化。其构造叠加可能与鄂尔多斯地块运动方式有关。距今约8 Ma前,青藏地块向东北方向与鄂尔多斯地块发生强烈碰撞,在来自青藏高原深部地幔流的配合下,可能使鄂尔多斯地块向东北方向移动,一方面使北东东向汾渭盆地进一步拉张;另一方面与华北克拉通构成右旋力偶,拉裂成北北东雁行排列的山西地堑系。两者于侯马-运城盆地叠加,形成隆起与凹陷的叠加构造地貌格局。 相似文献
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Bradley G. Johnson Martha Cary Eppes John A. Diemer Gonzalo Jiménez-Moreno Anthony L. Layzell 《Quaternary Research》2011,76(3):352-362
Geomorphic mapping in the upper Conejos River Valley of the San Juan Mountains has shown that three distinct periods of aggradation have occurred since the end of the last glacial maximum (LGM). The first occurred during the Pleistocene–Holocene transition (~ 12.5–9.5 ka) and is interpreted as paraglacial landscape response to deglaciation after the LGM. Evidence of the second period of aggradation is limited but indicates a small pulse of sedimentation at ~ 5.5 ka. A third, more broadly identifiable period of sedimentation occurred in the late Holocene (~ 2.2–1 ka). The latest two periods of aggradation are concurrent with increases in the frequency of climate change in the region suggesting that Holocene alpine and sub-alpine landscapes respond more to rapid changes in climate than to large singular climatic swings. Soil development and radiocarbon dating indicate that hillslopes were stable during the Holocene even while aggradation was occurring in valley bottoms. Thus, we can conclude that erosion does not occur equally throughout the landscape but is focused upslope of headwater streams, along tributary channels, or on ridge tops. This is in contrast to some models which assume equal erosion in headwater basins. 相似文献
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通过对云南泸沽湖高分辨率沉积指标序列(硅藻、枝角类和孢粉)的对比分析,初步揭示了水生生物(硅藻、枝角类和水生孢粉)对末次冰盛期期间气候变化的快速响应过程.结果表明,硅藻群落组成首先响应末次冰盛期时期的开始变冷,枝角类滞后,水生孢粉则表现为渐进的响应过程.然而,泸沽湖沉积硅藻记录对末次冰期以来的短时间尺度气候快速变化的Heinrich和新仙女木事件并未有响应,揭示气候事件判别的准确性取决于指标直接响应气候的特征以及多指标的综合对比.综合西南季风区云南不同海拔湖泊沉积记录(硅藻、孢粉、摇蚊等)获得的2万年以来数据及序列表明,末次冰期千年尺度的气候突变事件( Heinrich 1、 B?lling/Aller?d暖期和新仙女木YD冷事件)在整个西南季风系统中都有反映,且气候事件变化区间及幅度存在区域差异,其根本原因是受不同气候系统、复杂地形(青藏高原)的制约. 相似文献
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DOREEN RÖßLER MATTHIAS MOROS WOLFRAM LEMKE 《Boreas: An International Journal of Quaternary Research》2011,40(2):231-241
Rößler, D., Moros, M. & Lemke, W. 2010: The Littorina transgression in the southwestern Baltic Sea: new insights based on proxy methods and radiocarbon dating of sediment cores. Boreas, 10.1111/j.1502‐3885.2010.00180.x. ISSN 0300‐9483. The Littorina transgression is one of the most pronounced environmental events in the Holocene history of the Baltic Sea. It changed the hydrographic system from the freshwater Ancylus Lake into the brackish‐marine Littorina Sea. Here, 18 cores from two western Baltic basins, Mecklenburg Bay and the Arkona Basin, were analysed. We show that, besides biological indicators, sedimentary organic carbon, C/N ratio, bulk δ13C isotope values and carbonate content display clearly the transition from Ancylus Lake to the Littorina Sea. The first appearances of benthic foraminifers, marine molluscs and ostracods represent the onset of brackish‐marine conditions in the bottom waters. Central Arkona Basin sediments display more abrupt shifts in geochemical parameters and microfossil records at the transition from Ancylus Lake to the Littorina Sea than those from Mecklenburg Bay. Mixing of reworked Ancylus material with Littorina Sea stage material was stronger in Mecklenburg Bay, resulting in less pronounced proxy parameter changes and older bulk material dates. Radiocarbon dating of both calcareous material (benthic foraminifers, mollusc shells) and bulk fractions at the transgression horizon shows large age discrepancies. Based on calcareous fossil dates it appears that marine waters began to enter Mecklenburg Bay c. 8000 cal. a BP. In the Arkona Basin the first marine signals are recorded approximately 800 years later, c. 7200 cal. a BP. This indicates a transgression pathway via the Great Belt into Mecklenburg Bay and then into the Arkona Basin. 相似文献
6.
研究过去气候快速变化能为当前极端气候分析和未来环境预测提供自然背景理解。亚洲季风在北半球乃至全球的第四纪气候变化中扮演着重要角色,其演化是全球气候变化背景下的典型区域响应。然而,不同地质载体及不同指标所记录的亚洲冬、夏季风变化存在着较大差异,产生差异的原因及受到的动力机制是值得深入研究的科学问题。渭河盆地位于黄土高原和古三门湖沉积交叠的区域,是研究第四纪亚洲季风演化的理想场所。在盆地西南部西安市户县和长安县获取了两个黄土沉积钻孔,户县ZZC孔长4 m,长安县XFC孔长3 m,两孔的年代均超过25 ka。通过两钻孔的粒度和元素地球化学等代用指标研究,对比分析不同指标对气候变化的敏感度差异,反演了末次冰盛期(LGM)以来的区域沉积环境变化,并尝试探讨该时期发生的气候突变事件及反映的季风强度变化。结果表明,两钻孔的平均粒径从LGM到中全新世逐渐变细,中全新世之后少许变粗,空间上表现出一致性,总体反映了末次冰盛期以来的冬季风强度演化;Ca/Ti反映了与季风降水相关的淋溶强度,从LGM到全新世暖期夏季风逐渐减弱,并记录了若干次气候快速变化。粒度和元素比值变化表明,渭河盆地沉积良好地记录了末次冰盛期至全新世的大幅冷干-暖湿波动及若干次持续时间较短的快速水文变化事件,主要是受到太阳辐射和冰量等因素调控的影响。由于渭河盆地有上千米的新生代沉积,未来开展高分辨率研究有望揭示不同时间尺度季风变化特征及其与区域和全球变化的联系。 相似文献
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The Stansbury shoreline, one of the conspicuous late Pleistocene shorelines of Lake Bonneville, consists of tufa-cemented gravel and barrier beaches within a vertical zone of about 45 m, the lower limit of which is 70 m above the modern average level of Great Salt Lake. Stratigraphic evidence at a number of localities, including new evidence from Crater Island on the west side of the Great Salt Lake Desert, shows that the Stansbury shoreline formed during the transgressive phase of late Pleistocene Lake bonneville (sometime between about 22,000 and 20,000 yr B.P.). Tufa-cemented gravel and barrier beaches were deposited in the Stansbury shorezone during one or more fluctuations in water level with a maximum total amplitude of 45 m. We refer to the fluctuations as the Stansbury oscillation. The Stansbury oscillation cannot have been caused by basin-hypsometric factors, such as stabilization of lake level at an external overflow threshold or by expansion into an interior subbasin, or by changes in drainage basin size. Therefore, changes in climate must have caused the lake level to reverse its general rise, to drop about 45 m in altitude (reducing its surface area by about 18%, 5000 km2), and later to resume its rise. If the sizes of Great Basin lakes are controlled by the mean position of storm tracks and the jetstream, which as recently postulated may be controlled by the size of the continental ice sheets, the Stansbury oscillation may have been caused by a shift in the jetstream during a major interstade of the Laurentide ice sheet. 相似文献
9.
Twenty‐seven 14C dates from alluvial deposits and soils exposed in modern arroyos near Zuni Salt Lake, New Mexico, provide evidence for past episodes of piedmont and valley entrenchment by low‐order ephemeral streams. We recognize two episodes of entrenchment at A.D. 900–1050 and A.D. 1300–1400 that correlate to other arroyo‐cutting events in the region. Episodes of piedmont and valley entrenchment are followed by approximately 200–300 years of aggradation until arroyos are filled and shallow flooding with expansive sedimentation returns, completing an alluvial cycle. Many alluvial cycles appear synchronous across much of the southern Colorado Plateau and are likely linked to changes in climate and flood regime. Flooding on small basin drainages near Zuni Salt Lake is related to the Southwest summer monsoon, a meteorological event that is poorly linked to El Niño. Alluvial cycles on small basin drainages affected indigenous floodwater farming by locally lowering water tables and reducing irrigable area during phases of entrenchment and contributed to the aggregation of Puebloan communities on the southern Colorado Plateau in the A.D. 1300s. © 2008 Wiley Periodicals, Inc. 相似文献
10.
Late Pleistocene and late Holocene lake highstands in the Pyramid Lake subbasin of Lake Lahontan, Nevada, USA 总被引：1，自引：0，他引：1
Shoreline geomorphology, shoreline stratigraphy, and radiocarbon dates of organic material incorporated in constructional beach ridges record large lakes during the late Pleistocene and late Holocene in the Pyramid Lake subbasin of Lake Lahontan, Nevada, USA. During the late Holocene, a transgression began at or after 3595 ± 35 14C yr B.P. and continued, perhaps in pulses, through 2635 ± 40 14C yr B.P., resulting in a lake as high as 1199 m. During the latest Pleistocene and overlapping with the earliest part of the Younger Dryas interval, a lake stood at approximately 1212 m at 10,820 ± 35 14C yr B.P. and a geomorphically and stratigraphically distinct suite of constructional shorelines associated with this lake can be traced to 1230 m. These two lake highstands correspond to periods of elevated regional wetness in the western Basin and Range that are not clearly represented in existing northern Sierra Nevada climate proxy records. 相似文献
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High-temporal resolution analyses of pollen, chironomid, and lake-level records from Lake Lautrey provide multi-proxy, quantitative estimates of climatic change during the Late-Glacial period in eastern France. Past temperature and moisture parameters were estimated using modern analogues and ‘plant functional types’ transfer-function methods for three pollen records obtained from different localities within the paleolake basin. The comparison of these methods shows that they provide generally similar climate signals, with the exception of the Bölling. Comparison of pollen- and chironomid-based temperature of the warmest month reconstructions generally agree, except during the Bölling. Major abrupt changes associated with the Oldest Dryas/Bölling, Alleröd/Younger Dryas, and the Younger Dryas/Preboreal transitions were quantified as well as other minor fluctuations related to the cold events (e.g., Preboreal oscillation). The temperature of the warmest month increased by ∼5°C at the start of Bölling, and by 1.5°-3°C at the onset of the Holocene, while it fell by ca. 3° to 4°C at the beginning of Younger Dryas. The comparative analysis of the results based on the three Lautrey cores have highlighted significant differences in the climate reconstructions related to the location of each core, underlining the caution that is needed when studying single cores not taken from deepest part of lake basins. 相似文献
13.
Benjamin J.C. Laabs David W. Marchetti Jeffrey S. Munroe Kurt A. Refsnider John C. Gosse Elliott W. Lips Richard A. Becker David M. Mickelson Brad S. Singer 《Quaternary Research》2011,76(2):272-284
Understanding the timing of mountain glacier and paleolake expansion and retraction in the Great Basin region of the western United States has important implications for regional-scale climate change during the last Pleistocene glaciation. The relative timing of mountain glacier maxima and the well-studied Lake Bonneville highstand has been unclear, however, owing to poor chronological limits on glacial deposits. Here, this problem is addressed by applying terrestrial cosmogenic 10Be exposure dating to a classic set of terminal moraines in Little Cottonwood and American Fork Canyons in the western Wasatch Mountains. The exposure ages indicate that the main phase of deglaciation began at 15.7 ± 1.3 ka in both canyons. This update to the glacial chronology of the western Wasatch Mountains can be reconciled with previous stratigraphic observations of glacial and paleolake deposits in this area, and indicates that the start of deglaciation occurred during or at the end of the Lake Bonneville hydrologic maximum. The glacial chronology reported here is consistent with the growing body of data suggesting that mountain glaciers in the western U.S. began retreating as many as 4 ka after the start of northern hemisphere deglaciation (at ca. 19 ka). 相似文献
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气象观测资料表明,在当前全球暖化背景下高海拔地区的增温速率更快,其气候对全球气候变化的响应更为敏感.但是,高海拔地区如何响应快速气候事件,由于古气候古环境重建资料在高海拔地区较少,这一问题还没有很好的回答.为此选择云南省高山湖泊错恰湖为研究对象(海拔约3960 m),分析了湖泊沉积岩芯(深度范围90~244 cm)中正构烷烃的分布特征,重建了末次冰消期(19000~9500 a B. P.)沉积物有机质来源的变化,进而推断古气候演变.在17800~17000 a B. P.,错恰湖有机质以陆源输入为主,水生贡献相对减少,气候以暖湿为主;在17000~15100 a B. P.,水生有机质的贡献的比例增加,气候以冷干为主;在15100~12700 a B. P.,湖泊沉积有机质的陆源贡献增加,水生贡献相对减少,气候相对暖湿;在12700~11400 a B. P.时段,湖泊沉积水生有机质来源相对增多,气候相对冷干.与其他区域和全球气候记录对比发现,错恰湖的沉积记录指示的气候变化事件,受高纬冰量以及北大西洋驱动的西南季风突变所影响,在末次冰消期记录的4个明显的千年尺度气候事件,在时间上与First warmth、 H1、 B-A和YD事件相对应.与云南地区其他湖泊记录对比发现,小型湖泊或高海拔湖泊对这些全球快速气候事件的响应更加敏感. 相似文献
16.
1976-2017年青藏高原可可西里盐湖面积动态变化及成因分析 总被引：1，自引：0，他引：1
青藏高原湖泊是全球气候变化的敏感指示器。近56年来,可可西里地区气候呈显著暖湿化趋势,其中气温上升速率为0.33℃·（10a）-1（R=0.746,P<0.01）,降水增加速率为23.4mm·（10a）-1（R=0.422,P<0.01）。近40年来,盐湖面积总体呈增大趋势,其中,1976-2011年溃堤前盐湖面积以1.63 km2·a-1的速率扩大,溃堤后以8.51 km2·a-1的速率持续扩大。总体来看,近40多年来,盐湖面积先后经历了缓慢增大（1976-2011年）→急剧增大（2012-2013年）→稳定增大（2014-2017年）三个阶段。盐湖面积前期缓慢扩大的主要原因是可可西里地区气候暖湿化的结果,而后期面积急剧扩大的主要原因是因为2011年9月15日盐湖上游的卓乃湖溃堤,导致下游的3个湖泊（库赛湖、海丁诺尔湖和盐湖）串连成一体;冰川和冻土融水可能是引起可可西里盐湖面积扩张的原因,但并非主要原因。后期盐湖面积还将呈稳定增大趋势。盐湖面积扩大导致盐湖湖水淡化,周边草地受到淹没破坏的面积不断扩大,这种变化不仅对其周边草地生态环境产生破坏,还可能对可可西里周边重大工程设施产生不利影响。鉴于盐湖面积今后还将持续增大,并对其周边重大工程设施产生不利影响。因此,应用多源卫星资料对盐湖进行长期持续的跟踪观测仍将是相关政府部门关注的重点。 相似文献
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Lake Emma, which no longer exists because of a mining accident, was a tarn in a south-facing cirque near the headwaters of the Animas River in the San Juan Mountains of southwestern Colorado. During the Pinedale glaciation, this area was covered by a large transection glacier centered over the Lake Emma region. Three radiocarbon dates on basal organic sediment from Lake Emma indicate that by ca. 15,000 yr B.P. this glacier, one of the largest in the southern Rocky Mountains, no longer existed. Twenty-two radiocarbon dates on Picea and Abies krummholz fragments in the Lake Emma deposits indicate that from ca. 9600 to 7800 yr B.P., from 6700 to 5600 yr B.P., and at 3100 yr B.P. the krummholz limit was at least 70 m higher than present. These data, in conjunction with Picea:Pinus pollen ratios from both the Lake Emma site and the Hurricane Basin site of J. T. Andrews, P. E. Carrara, F. B. King, and R. Struckenrath (1975, Quaternary Research 5, 173–197) suggest than from ca. 9600 to 3000 yr B.P. timberline in the San Juan Mountains was higher than present. Cooling apparently began ca. 3000 yr B.P. as indicated by decreases in both the percentage of Picea pollen and Picea:Pinus pollen ratios at the Hurricane Basin site (Andrews et al., 1975). Cooling is also suggested by the lack of Picea or Abies fragments younger than 3000 yr B.P. at either the Lake Emma or the Hurricane Basin site. 相似文献
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ATLE NESJE SVEIN OLAF DAHL HENRIETTE LINGE COLIN K. BALLANTYNE DANNY MCCARROLL EDWARD J. BROOK GRANT M. RAISBECK FRANCOISE YIOU 《Boreas: An International Journal of Quaternary Research》2007,36(3):227-239
Blockfields, weathering boundaries and marginal moraines have been mapped along a longitudinal transect from northern Andøya to Skånland in northern Norway. The degree of rock-surface weathering above and below glacial trimlines, clay-mineral assemblages and surface exposure dating based on in situ cosmogenic 10 Be have been used to reconstruct the vertical dimensions and timing of the Last Glacial Maximum (LGM) of the Scandinavian Ice Sheet in this region. The cosmogenic exposure dates suggest that the lower blockfield boundary/trimline along the Andøya-Skånland transect represents the upper limit of the Late Weichselian ice sheet, with an average surface gradient of c . 9.5 m/km. The surface exposure dates from Andøya pre-date the LGM, suggesting that the LGM ice sheet did not reach mountain plateaux at northwest Andøya. The results thus support evidence from lake sediment records that the northern tip of Andøya was not covered by the Scandinavian Ice Sheet during the LGM. 相似文献
19.
《Quaternary Science Reviews》2003,22(8-9):823-837
Some syntheses of lake-level data for the Last Glacial Maximum (LGM) in East Africa (10°N and 30°S, East of 25°E) show apparently wetter conditions than present for some basins, whereas palaeovegetation reconstruction indicates a generally dry climate. PMIP GCM simulations for the LGM support both scenarios for this region when run under different boundary conditions. Here, we compare three new records from lakes in the data-poor southern part of East Africa; Lake Malawi, Lake Massoko, and Lake Rukwa. We also re-assess previously published lake-level data and apply a salinity transfer function to the diatom record from Lake Manyara. Our results show that in contrast to previous interpretations, these lakes were at least as low as today at the LGM and are thus in agreement with the palaeovegetation data. Relative drought across East Africa is best simulated by GCMs that use computed SSTs rather than the higher CLIMAP values. Lower SSTs and the presence of the Northern Hemisphere ice sheets must have been dominant over any monsoon precipitation rise caused by astronomically induced summer insolation enhancement in the southern African tropics. 相似文献
20.
Alexandra Raab Martin Melles Glenn W. Berger Birgit Hagedorn Hans-Wolfgang Hubberten 《Quaternary Science Reviews》2003,22(21-22):2267-2283
The extent of the Barents-Kara Sea ice sheet (northern Europe and Russia) during the Last Glacial Maximum (LGM), in Marine Isotope Stage (MIS) 2 is controversial, especially along the southern and northeastern (Russian High Arctic) margins. We conducted a multi-disciplinary study of various organic and mineral fractions, obtaining chronologies with 14C and luminescence dating methods on a 10.5 m long core from Changeable Lake (4 km from the Vavilov Ice Cap) on Severnaya Zemlya. The numeric ages indicate that the last glaciation at this site occurred during or prior to MIS 5d-4 (Early Middle Weichselian). Deglaciation was followed by a marine transgression which affected the Changeable Lake basin. After the regression the basin dried up. In late Middle Weichselian time (ca 25–40 ka), reworked marine sediments were deposited in a saline water body. During the Late Weichselian (MIS 2), the basin was not affected by glaciation, and lacustrine sediments were formed which reflect cold and arid climate conditions. During the termination of the Pleistocene and into the Holocene, warmer and wetter climate conditions than before led to a higher sediment input. Thus, our chronology demonstrates that the northeastern margin of the LGM Barents-Kara Sea ice sheet did not reach the Changeable Lake basin. This result supports a modest model of the LGM ice sheet in northern Europe determined from numeric ice sheet modelling and geological investigations. 相似文献