天山乌鲁木齐河源末次冰期冰川沉积光释光测年   总被引：6，自引：5，他引：1  

曾兰华  欧先交  陈嵘  赖忠平 《冰川冻土》2019,41(4):761-769

乌鲁木齐河源地区是中国冰川遗迹保存最丰富、地貌最典型的区域之一,是根据冰川遗迹重建第四纪冰川历史的理想地区。大量的研究工作以及技术测年结果也使其成为试验冰川沉积光释光（optically stimulated luminescence,OSL）测年可行性的理想地点。共采集了6个冰碛及上覆黄土样品用于光释光测年。提取38~63 μm的石英颗粒,运用SAR-SGC法测试等效剂量。各种检验表明测试程序是适用的。通过地貌地层关系、重复样品、已有年代的对比等方法,检验该地冰川沉积OSL测年的可行性。结果表明,OSL年代结果与地貌地层新老关系非常吻合,与已有的其他测年技术的年代结果也具可比性,表明这些样品的OSL信号在沉积之前晒退较好,OSL年代是可信的。冰川观测站侧碛垄的OSL年代为14.8±1.2 ka;9号冰川支谷口附近冰碛的OSL年代为13.5±1.1 ka和17.2±1.3 ka;上望峰冰碛的OSL年代为20.1±1.6 ka。综合OSL年代结果与此前其他测年结果,这几套冰碛垄形成于深海氧同位素MIS 2阶段应该是比较统一的认识。上望峰冰碛上覆黄土的OSL年代（10.5±0.8 ka）也印证了该结论。OSL年代指示上望峰冰碛对应于末次冰期最盛期,冰川观测站和9号冰川支谷谷口冰碛对应于晚冰期。下望峰冰碛的OSL年代为36.3±2.8 ka,对应于MIS 3阶段。下望峰冰碛的形成时代,仍有待更多沉积学以及测年工作进一步确定。  相似文献   

The Retreat of Tien Shan Glaciers (Kyrgyzstan) Since the Little Ice Age Estimated from Aerial Photographs, Lichenometric and Historical Data   总被引：2，自引：0，他引：2  

Olga Solomina  Roger Barry  Maria Bodnya 《Geografiska Annaler: Series A, Physical Geography》2004,86(2):205-215

The retreat of 293 glaciers in the Tien Shan Mountains (Kyrgyz Republic) from their maximum extent during the Little Ice Age (LIA) is estimated using aerial photographs from 1980 to 1985 and maps at a scale of 1:25000, constructed during period 1956–1990. Two indices of changes are used: the linear distance from the glacier terminus to its Little Ice Age moraine and the difference in absolute elevation of the terminus and the moraine. Historical information about the front positions of glaciers in the 1880s to the 1930s was used as an indirect control of remote sensing data. The age of moraines in key regions was estimated by lichenometry. On average, Tien Shan glaciers have retreated by 989 ± 540 m since the LIA maximum. Their front elevations (dh) rose by 151 ± 105 m. These changes are similar to changes observed in the Alps and western Norway, Pamir‐Alay and Koryak plateau, but greater than in east Siberia over the same interval. Differences between four regions in Tien Shan (northern, western, inner, central) are generally small, though in the northern Tien Shan the glacier retreat and frontal rise are more prominent (1065 ± 479 m and 215 ± 140 m, respectively).  相似文献   

Constraints on paleolake levels,spillways and glacial lake history,north-central Ontario,Canada     

Shawn R. Slattery  Peter J. Barnett  Darrel G. F. Long 《Journal of Paleolimnology》2007,37(3):331-348

The recognition of ice-marginal deltas constructed during the formation of the Nakina II moraine and a previously unrecognized spillway, in the vicinity of Longlac, northern Ontario, indicates that existing concepts of ancestral lake level history and drainage systems in the Lake Superior–Lake Nipigon region is inadequate. Based on isostatically corrected digital elevation maps, ice-marginal deltas of the Nakina II moraine probably formed at the level of glacial Lake Minong, most likely Minong III, and not glacial Lake Nakina as has been commonly suggested. In addition, the presence of a spillway near Longlac indicates that lake water drained southward through the Mullet Outlet–Pic River system immediately following ice-marginal retreat from the Nakina II moraine and not eastward as previously proposed. Architectural-element analysis of exposures within the spillway indicates hyperconcentrated outbursts of meltwater produced thick channel-fill elements during flood conditions with peak-velocities exceeding 3 m/s. Subsequent retreat of ice from the Pic River valley to the east, may have allowed waters of Lake Agassiz, Lake Barlow–Ojibway, or both, to drain into post-Minong lake levels in the Lake Superior basin. These findings place major constraints on previously proposed concepts of northeastern or eastern outlets of Lake Agassiz.  相似文献   

Timing of Late Quaternary glaciations in the Himalayas of northern Pakistan     

Benedict W. Richards  Lewis A. Owen  Edward J. Rhodes 《第四纪科学杂志》2000,15(3):283-297

Optically stimulated luminescence dating of Late Quaternary glaciogenic sediments was undertaken in critical areas of the Himalayas of northern Pakistan in order to examine the timing of glaciation. The dates demonstrate that several glaciations occurred during the last glacial cycle. In Swat, the Grabral 2 Stade and the Kalam I Stade were dated at ca. 77 ka and ca. 38 ka, respectively. The error on the former date is large and it is conceivable that the moraines may have formed during the early part of Oxygen Isotope Stage 3 rather than during Oxygen Isotope Stage 4. The Kalam I Stade, however, clearly represents a glaciation during Oxygen Isotope Stage 3. The oldest moraines and those at the lowest altitude in the Indus valley at Shatial have an age of ca. 60 ka. These also relate to a major glacial advance during Oxygen Isotope Stage 3. A younger series of moraines, the Jalipur Tillite, and glaciofluvial sands at Liachar in the Indus valley, and moraines at Rampur–Tarshing have ages of ca. 27 ka, ca. 21–23 ka and ca. 15 ka, respectively. These dates show that glaciers also occupied parts of the Indus valley during Oxygen Isotope Stage 2. These dates and the morphostratigraphy show that glaciation in the Pakistani Himalaya was more extensive during the early part of the last glacial cycle and that the local last glacial maximum in Pakistan was asynchronous with the maximum extent of Northern Hemisphere ice sheets. Copyright © 2000 John Wiley & Sons, Ltd.  相似文献   

Glacier response to climatic change during the Loch Lomond Stadial and early Flandrian: Geomorphological and palynological evidence from the Isle of Skye,Scotland     

Douglas I. Benn  J. John Lowe  Michael J. C. Walker 《第四纪科学杂志》1992,7(2):125-144

The deglaciation of Skye at the close of the Loch Lomond Stadial is assessed on the basis of detailed geomorphological mapping and pollen-stratigraphic correlations. It is concluded that deglaciation proceeded in two distinct stages. The first was marked by numerous glacier stillstands and readvances, while uninterrupted retreat and local glacier stagnation occurred during the second and final stage. The pollen evidence indicates that the first stage was well advanced before the marked thermal improvement at the start of the Flandrian, and it is inferred that initial glacier retreat occurred in response to a decline in precipitation in the later part of the Loch Lomond Stadial. The first stage of glacier retreat continued into the early Flandrian, during which climatic amelioration was interrupted briefly. Final deglaciation appears to have occurred rapidly in response to sustained temperature increases. The collective evidence also indicates spatial variations in the timing of deglaciation, which appear to reflect differences in glacier morphology.  相似文献   

Variations of southeast Vatnajökull ice cap (Iceland) 1650–1900 and reconstruction of the glacier surface geometry at the Little Ice Age maximum          下载免费PDF全文

Hrafnhildur Hannesdóttir  Helgi Björnsson  Finnur Pálsson  Guðfinna Aðalgeirsdóttir  Snævarr Guðmundsson 《Geografiska Annaler: Series A, Physical Geography》2015,97(2):237-264

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CHANGES IN MORPHOLOGY AT THE MARGIN OF THE GREENLAND ICE SHEET (LEVERETT GLACIER), IN THE PERIOD 1943–1992: A QUANTITATIVE ANALYSIS     

FRANK G. M. VAN TATENHOVE 《地球表面变化过程与地形》1996,21(9):797-816

Changes in ice-marginal morphology near Leverett glacier, a small outlet glacier at the western margin of the Greenland ice sheet, are determined from a photogrammetrical analysis. To be able to compare two datasets from subsequent years with measurements at different coordinates, kriging was used for interpolation. In this study the kriging standard error is used to evaluate the relative accuracy of the resulting maps. Aerial photographs of 1943, 1968 and 1985 were compared. In the period 1943–1968 an area of 0.2 × 10⁶ m² was deglaciated. Approximately 1.1 × 10 m³ of material is deposited in this area. The southern part of the deglaciated area is characterized by ice-cored moraines, while moraines without ice core were formed in the north. Differences in depositional products reflect differences in meltwater activity and probably ice-marginal thermal regime. During deglaciation a small proglacial sandur decreased in altitude by 3.2 ± 0.1 m. From the early 1970s Leverett glacier advanced over a previously deglaciated area. During this advance, small ice-marginal accumulations were incorporated and eroded by the advancing glacier. Erosion products were for a substantial part stored in the proglacial sandur. About 1.2 ×10⁵ m² of the northern part of an ice-cored moraine complex decreased in altitude by −3.6 ± 0.1 m from 1943 to 1968 and over 2.7 × 10⁴ m² by −2.7 ± 0.1 m during 1968–1985. The spatial patterns of altitude change were analysed in relation to topomorphological parameters as exposition and slope angle and areas occupied by lakes. The estimated energy used to melt the subsurface ice of the ice-cored moraine is 1.4–2.2 W m² (1943–1968) and 1.0–1.6 W m² (1968–1985). These values are 30–50 times larger than the geothermal heat flux. For the expected average debris concentration of the ice core (< 10 per cent by volume) the deviation of the surface energy balance forced by climate change will be small and encompass an insignificant part of the total estimated energy used for melting.  相似文献   

青藏高原现代最大冰原区第四纪冰川作用   总被引：2，自引：1，他引：1  

易朝路  李孝泽  屈建军 《冰川冻土》2003,25(5):491-497

普若岗日冰原是青藏高原最大的冰原,总面积达400km².野外观察表明,从现代冰舌前端开始向山外有5套终碛垄和侧碛垄系列,分别称之为冰碛垄Ⅰ、Ⅱ、Ⅲ、Ⅳ和Ⅴ.根据地貌位置、地层关系、相对风化程度、风的改造程度和覆盖在有冰川漂砾的戈壁上的沙子的电子自旋共振(ESR)年代,并与中国西部山地第四纪冰川数值年代比较,这些冰碛垄分别形成于现代冰川、小冰期、新冰期、末次冰期晚阶段和早阶段.冰碛垄V中的花岗岩漂砾散布于距山前6km以内的山麓平原,说明在第四纪晚期冰原西坡的古冰川虽到达山麓平原,但未能与邻近山地古冰川相连形成统一大冰盖.  相似文献   

A locally calibrated,late glacial 10Be production rate from a low-latitude,high-altitude site in the Peruvian Andes     

《Quaternary Geochronology》2015

Well-dated records of tropical glacier fluctuations are essential for developing hypotheses and testing proposed mechanisms for past climate changes. Since organic material for radiocarbon dating is typically scarce in low-latitude, high-altitude environments, surface exposure-age dating, based on the measurement of in situ produced cosmogenic nuclides, provides much of the chronologic information on tropical glacier moraines. Here, we present a locally calibrated ¹⁰Be production rate for a low-latitude, high-altitude site near Quelccaya Ice Cap (∼13.95°S, 70.89°W, 4857 m asl) in the southeastern Peruvian Andes. Using an independent age (12.35 +0.2, −0.02 ka) of the late glacial Huancané IIa moraines based on thirty-four bracketing radiocarbon ages and twelve ¹⁰Be concentrations of boulders on the moraines, we determine a local production rate of 43.28 ± 2.69 atoms gram⁻¹ year⁻¹ (at g⁻¹ yr⁻¹). Reference ¹⁰Be production rates (i.e., production rates by neutron spallation appropriate for sea-level, high-latitude sites) range from 3.97 ± 0.09 to 3.78 ± 0.09 at g⁻¹ yr⁻¹, determined using scaling after Lal (1991) and Stone (2000) and depending on our assumed boulder surface erosion rate. Since our boulder surface erosion rate estimate is a minimum value, these reference production rates are also minimum values. A secondary control site on the Huancané IIIb moraines suggests that the ¹⁰Be production rates are at least as low as, or possibly lower than, those derived from the Huancané IIa moraines. These sea-level, high-latitude production rates are at least 11–15% lower than values derived using the traditional global calibration dataset, and they are also lower than those derived from the late glacial Breque moraine in the Cordillera Blanca of Peru. However, our sea-level, high-latitude production rates agree well with recently published, locally calibrated production rates from the Arctic, New Zealand, and Patagonia. The production rates presented here should be used to calculate ¹⁰Be exposure ages in low-latitude, high-altitude locations, particularly in the tropical Andes, and should improve the ability to compare the results of studies using ¹⁰Be exposure-age dating with other chronological data.  相似文献   

The glacial landsystem of a tropical glacier: Charquini Sur,Bolivian Andes          下载免费PDF全文

Jakub Małecki  Harold Lovell  Wojciech Ewertowski  Łukasz Górski  Tomasz Kurczaba  Beata Latos  Michał Miara  Dorota Piniarska  Jacek Płocieniczak  Tomasz Sowada  Marcin Spiralski  Anna Warczachowska  Antoine Rabatel 《地球表面变化过程与地形》2018,43(12):2584-2602

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