玉龙山东麓更新世冰川作用   总被引：34，自引：7，他引：27  

赵希涛  李铁松 《冰川冻土》1999,21(3):242-248

利用１：１００００地形图和航空照片,对玉龙山东麓更新世冰川作用遗迹进行了调查和填图。据冰川与冰水沉积物的钙质胶结物和冰湖相钙板的ＥＳＲ测年结果,初步划分４次冰期,即０．７￣０．６Ｍａ ＢＰ的玉龙冰期。其中最早一次冰期为规模较大的山麓冰川,后２次冰期为规模较大的山谷冰川。  相似文献   

地外撞击诱发的气候循环和新冰期的形成     

王世杰  欧阳自远  肖志峰 《地球科学》1999,24(6):568-572

考虑全球反照率随温度的变化,利用零维能量平衡模式,对撞击能量与其诱发的气候循环和注期形成之间的关系进行了计算模拟研究,当撞击坑的直径大于１５￣２０ｋｍ,全球气温在１ａ的时间里会产生快速的降温,降温幅度取决于撞击能量的大小,大约不到１００ａ的时间,下降趋势逐渐减缓,全球气温缓慢上升,并稳定在２５０Ｋ,如果没有 别的因素影响喧一平衡温度将会存在较长一段时间。有可能导致地球上冰期气候的形成结合新生代以来  相似文献   

Glacial–interglacial changes in Subantarctic sea surface temperature and δO-water using foraminiferal Mg     

Tracy A. Mashiotta  David W. Lea  Howard J. Spero 《Earth and Planetary Science Letters》1999,170(4):113-432

Laboratory culturing experiments with living Globigerina bulloides indicate that Mg/Ca is primarily a function of seawater temperature and suggest that Mg/Ca of fossil specimens is an effective paleotemperature proxy. Using culturing results and a core-top Neogloboquadrina pachyderma calibration, we have estimated glacial–interglacial changes in sea surface temperature (SST) using planktonic Mg/Ca records from core RC11-120 in the Subantarctic Indian Ocean (43°S, 80°E) and core E11-2 in the Subantarctic Pacific Ocean (56°S, 115°W). Our results suggest that glacial SST was about 4°C cooler in the Subantarctic Indian Ocean and 2.5°C cooler in the Subantarctic Pacific. Comparison of SST and planktonic δ¹⁸O records indicates that changes in SST lead changes in δ¹⁸O by on average 1–3 kyr. The glacial–interglacial temperature change indicated by the Subantarctic Mg/Ca records suggests that temperature accounts for 40–60% of the foraminiferal δ¹⁸O change. We have used the Mg/Ca-based SST estimates and δ¹⁸O determinations to generate site-specific seawater δ¹⁸O records, which suggest that seawater δ¹⁸O was on average 1‰ more positive during glacial episodes compared with interglacial episodes.  相似文献   

Near-field hydro-isostasy: the implementation of a revised sea-level equation   总被引：2，自引：0，他引：2  

Glenn A. Milne  Jerry X. Mitrovica  & James L. Davis 《Geophysical Journal International》1999,139(2):464-482

  相似文献   

Subglacial sediment production and snout marginal ice uplift during the late ablation season of a temperate valley glacier     

P. Perolo  M. Bakker  C. Gabbud  G. Moradi  C. Rennie  S.N. Lane 《地球表面变化过程与地形》2019,44(5):1117-1136

Sediment export from glaciated basins involves complex interactions between ice flow, basal erosion and sediment transfer in subglacial and proglacial streams. In particular, we know very little about the processes associated with sediment transfer by subglacial streams. The Haut Glacier d'Arolla (VS, Switzerland) was investigated during the summer melt season of 2015. LiDAR survey revealed positive surface changes in the ablation zone, indicating glacier uplift, at the end of the morning during the period of peak ablation. Instream measures of sediment transport showed that suspended load and bedload responded differently to diurnal flow variability. Suspended load depended on the availability of fine material whereas bedload depended mainly on the competence of the flow. Interpretation of these results allowed development of a conceptual model of subglacial sediment transport dynamics. It is based upon the mechanisms of clogging (deposition) and flushing (transport/erosion) in sub-glacial channels as forced by diurnal flow variability. Through the melt season, the glacier hydrological response evolves from being buffered by glacier snow cover with a poorly developed subglacial drainage system to being dominated by more rapid ice melt with a more hydraulically efficient subglacial channel system. The resultant changes in the shape of diurnal discharge hydrographs, and notably higher peak flows and lower base flows, causes sediment transport to become discontinuous, with overnight clogging and late morning flushing of subglacial channels. Overnight clogging may be sufficient to reduce subglacial channel size, creating temporarily pressurized flow and lateral transfer of water away from the subglacial channels, leading to the late morning glacier surface uplift. However, without further data, we cannot exclude other hypotheses for the uplift. © 2018 John Wiley & Sons, Ltd.  相似文献   

Ice cap erosion patterns from bedrock 10Be and 26Al,southeastern Tibetan Plateau     

Ping Fu  Arjen P. Stroeven  Jonathan M. Harbor  Jakob Heyman  Clas Hättestrand  Marc W. Caffee 《地球表面变化过程与地形》2019,44(4):918-932

Quantifying glacial erosion contributes to our understanding of landscape evolution and topographic relief production in high altitude and high latitude areas. Combining in situ ¹⁰Be and ²⁶Al analysis of bedrock, boulder, and river sand samples, geomorphological mapping, and field investigations, we examine glacial erosion patterns of former ice caps in the Shaluli Shan of the southeastern Tibetan Plateau. The general landform pattern shows a zonal pattern of landscape modification produced by ice caps of up to 4000 km² during pre-LGM (Last Glacial Maximum) glaciations, while the dating results and landforms on the plateau surface imply that the LGM ice cap further modified the scoured terrain into different zones. Modeled glacial erosion depth of 0–0.38 m per 100 ka bedrock sample located close to the western margin of the LGM ice cap, indicates limited erosion prior to LGM and Late Glacial moraine deposition. A strong erosion zone exists proximal to the LGM ice cap marginal zone, indicated by modeled glacial erosion depth >2.23 m per 100 ka from bedrock samples. Modeled glacial erosion depths of 0–1.77 m per 100 ka from samples collected along the edge of a central upland, confirm the presence of a zone of intermediate erosion in-between the central upland and the strong erosion zone. Significant nuclide inheritance in river sand samples from basins on the scoured plateau surface also indicate restricted glacial erosion during the last glaciation. Our study, for the first time, shows clear evidence for preservation of glacial landforms formed during previous glaciations under non-erosive ice on the Tibetan Plateau. As patterns of glacial erosion intensity are largely driven by the basal thermal regime, our results confirm earlier inferences from geomorphology for a concentric basal thermal pattern for the Haizishan ice cap during the LGM. © 2018 John Wiley & Sons, Ltd.  相似文献   

Reconstructing ice-flow fields from streamlined subglacial bedforms: A kriging approach     

Felix S. L. Ng  Anna L. C. Hughes 《地球表面变化过程与地形》2019,44(4):861-876

The orientation of several landforms, e.g. drumlins, flutes, crag-and-tails, and mega-scale glacial lineations, records the direction of the overlying ice flow that created them. Populations of such features are used routinely to infer former ice-flow patterns, which serve as the building blocks of reconstructions of palaeo ice-sheet evolution. Currently, the conceptualisation of flow patterns from these flow-direction records is done manually and qualitatively, so the extractable glaciological information is limited. We describe a kriging method (with Matlab code implementation) that calculates continuous fields of ice-flow direction, convergence, and curvature from the flow-direction records, and which yields quantitative results with uncertainty estimates. We test the method by application to the subglacial bedforms of the Tweed Valley Basin, UK. The results quantify the convergent flow pattern of the Tweed Palaeo-Ice Stream in detail and pinpoint its former lateral shear margins and where ice flowed around basal bumps. Ice-flow parameters retrieved by this method can enrich ice-sheet reconstructions and investigations of subglacial till processes and bedform genesis. © 2018 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd.  相似文献   

POLYNOMIAL AND POWER FUNCTIONS FOR GLACIAL VALLEY CROSS-SECTION MORPHOLOGY     

L. ALLAN JAMES 《地球表面变化过程与地形》1996,21(5):413-432

An empirical evaluation of glacial trough cross-section shape is performed on seven vertical cross-sections in three Sierra Nevada valleys glaciated during the late Quaternary. Power and second-order polynomial functions are fitted by statistical regression. Power functions are very sensitive to subtle valley-bottom topographic features and require precise specification of the valley-bottom-centre location. This dependency is problematic given under-representation of valley bottoms by conventional contour-sampling methods, and the common alteration of valley-bottom morphology by non-glacial processes. Power function exponents vary greatly in response to these and other non-genetic factors and are not found to be reliable indicators of overall valley morphology. Second-order polynomials express overall valley shape in a single robust function. They are applied to both bedrock- and sediment-floored glacial valleys with negligible statistical bias except where side-slopes are stepped or convex-upward or where valley form is asymmetrical. They can describe alluviated or severely eroded valleys, and can objectively identify indi-vidual components of polymorphic valleys, because valley bottom and centre locations need not be specified. Mathematical expressions of parameters useful for geomorphic measurements and glaciological modelling are analytically derived from the polynomials as functions of the three polynomial coefficients. These parameter equations provide estimates of valley side-slopes, mean and maximum depth, midpoint location, width, area, boundary length, form ratio and symmetry.  相似文献   

Moraine-dammed glacial lake changes during the recent 40 years in the Poiqu River Basin, Himalayas     

XiuJuan Zhang  ShiYin Liu  Li Liu 《寒旱区科学》2015,7(6):654-665

Glacier retreat is not only a symbol of temperature and precipitation change, but a dominating factor of glacial lake changes in alpine regions, which are of wide concern for high risk of potential outburst floods. Of all types of glacial lakes, moraine-dammed lakes may be the most dangerous to local residents in mountain regions. Thus, we monitored the dynamics of 12 moraine-dammed glacial lakes from 1974 to 2014 in the Poiqu River Basin of central west Himalayas, as well as their associated glaciers with a combination of remote sensing, topographic maps and digital elevation models (DEMs). Our results indicate that all monitored moraine-dammed glacial lakes have expanded by 7.46 km² in total while the glaciers retreated by a total of 15.29 km² correspondingly. Meteorological analysis indicates a warming and drying trend in the Nyalam region from 1974 to 2014, which accelerated glacier retreat and then augmented the supply of moraine-dammed glacial lakes from glacier melt. Lake volume and water depth changed from 1974 to 2014 which indicates that lakes Kangxico, Galongco, and Youmojanco have a high potential for outburst floods and in urgent need for continuous monitoring or artificial excavation to release water due to the quick increase in water depths and storage capacities. Lakes Jialongco and Cirenmaco, with outburst floods in 1981 and 2002, have a high potential risk for outburst floods because of rapid lake growth and steep slope gradients surrounding them.  相似文献   

末次盛冰期以来长江河口段河道演变研究综述   总被引：2，自引：0，他引：2  

曹光杰  王建  屈贵贤 《地球科学进展》2006,21(10):1039-1045

末次盛冰期以来,由于海面发生大幅度的变化,长江河口段经历了深切古河谷形成—古河谷充填—三角洲发育的河床演变过程。海陆相互作用是河口段河道演变的主要影响因素。综合分析了对河口段河道研究的成果,着重对长江河口段古河谷的形成与充填、最大海侵以来的河床演变、古河谷的沉积层序与沉积相及研究的方法进行了综述。过去对古河谷宏观的趋势研究及单个钻孔的研究较多,宏观与微观结合的不够,专门研究古河谷河形的成果很少。今后应注重宏观与微观研究的结合;根据系列钻孔剖面,分析、恢复古河谷河型;根据河型、沉积物特征等,估算古长江流速、流量;加强高分辨率研究、定性与定量研究相结合,探讨环境变化与河道演变的关系和规律。  相似文献