Cosmogenic radionuclide dating of glacial landforms in the Lahul Himalaya,northern India: defining the timing of Late Quaternary glaciation

The timing of glaciation in the Lahul Himalaya of northern India was ascertained using the concentrations of cosmogenic ¹⁰Be and ²⁶Al from boulders on moraines and drumlins, and from glacially polished bedrock surfaces. Five glacial stages were identified: Sonapani I and II, Kulti, Batal and Chandra. Of these, cosmogenic exposure ages were obtained on samples representative of the Batal and Kulti glacial cycles. Stratigraphical relationships indicate that the Sonapani I and II are younger. No age was obtained for the Chandra glacial advance. Batal Glacial Stage deposits are found throughout the valley, indicating the presence of an extensive valley glacial system. During the Kulti Stage, glaciers advanced ca. 10 km beyond their current positions. Moraines produced during the Batal Stage, ca. 12–15.5 ka, are coeval with the Northern Hemisphere Late‐glacial Interstadial (Bølling/Allerød). Deglaciation of the Batal Glacial Stage was completed by ca. 12 ka and was followed by the Kulti Glacial Stage during the early Holocene, at ca. 10–11.4 ka. On millennial time‐scales, glacier oscillations in the Lahul Himalaya apparently reflect periods of positive mass‐balance coincident with times of increased insolation. During these periods the South Asian summer monsoon strengthened and/or extended its influence further north and west, thereby enhancing high‐altitude summer snowfall. Copyright © 2001 John Wiley & Sons, Ltd.     

Style and timing of glaciation in the Lahul Himalaya,northern India: a framework for reconstructing late Quaternary palaeoclimatic change in the western Himalayas

This paper presents a revised glacial chronology for the Lahul Himalaya and provides the most detailed reconstruction of former glacier extents in the western Himalayas published to date. On the basis of detailed geomorphological mapping, morphostratigraphy, and absolute and relative dating, three glaciations and two glacial advances are constrained. The oldest glaciation (Chandra glacial stage) is represented by glacially eroded benches and drumlins (the first to be described from the Himalaya) at altitudes of >4300 m and indicates glaciation on a landscape of broad valleys that had minimal fluvial incision. The second glaciation (Batal glacial stage) is represented by highly weathered and disssected lateral moraines and drumlins representing two phases of glaciation within the Batal glacial stage (Batal I and Batal II). The Batal stage was an extensive valley glaciation interrupted by a readvance that produced superimposed bedforms. Optically stimulated luminescence (OSL) dating, indicates that glaciers probably started to retreat between 43400 ± 10300 and 36900 ± 8400 yr ago during the Batal stage. The Batal stage may be equivalent to marine Oxygen Isotope Stage 4 and early Oxygen Isotope Stage 3. The third glaciation (Kulti glacial stage), is represented by well-preserved moraines in the main tributary valleys that formed due to a less-extensive valley glaciation when ice advanced no more than 12 km from present ice margins. On the basis of an OSL age for deltaic sands and gravels that underlie tills of Kulti age, the Kulti glaciation is younger than 36900 ± 8400 yr ago. The development of peat bogs, having a basal age of 9160 ± 70 ¹⁴C yr BP possibly represents a phase of climatic amelioration coincident with post-Kulti deglaciation. The Kulti glaciation, therefore, is probably equivalent to all or parts of late Oxygen Isotope Stage 3, Stage 2 and early Stage 1. Two minor advances (Sonapani I and II) are represented by small sharp-crested moraines within a few kilometres of glacier termini. On the basis of relative weathering, the Sonapani advance is possibly of early mid-Holocene age, whereas the Sonapani II advance is historical. The change in style and extent of glaciation is attributed to topographic controls produced by fluvial incision and by increasing aridity during the Quaternary. © 1997 John Wiley & Sons, Ltd.     

Dendrochronological reconstruction of snow avalanche activity in the Lahul Himalaya,Northern India

Mass wasting and avalanche events substantially impact the landscape morphology and consequently human habitation throughout the Himalaya. There is, however, a paucity of snow avalanche documentation for the region. The application of dendrochronologic research methods introduces a sensitive approach to document the recurrence of snow avalanche events in a region where historical records are either non-existent or difficult to access. An exploratory dendrochronologic study was undertaken in the Lahul Himalaya of Northern India during the summer of 2006. Included within the fieldwork was an assessment of avalanche track morphology to enable identification of the slope characteristics that might be associated with an increase in avalanche activity. Thirty-six trees growing on the Ratoli avalanche track were sampled. The oldest tree was a Cedrus deodara with a pith date of 1950. A tree-ring-derived avalanche response curve highlights four avalanche events that occurred from 1972 to 2006. The successful scientific results based on the application of the method used provide the basis for local planners to quantify slope failure hazards in forested areas throughout the western Himalaya.     

The Loch Lomond Readvance on the Isle of Skye,Scotland: Glacier reconstruction and palaeoclimatic implications

Geomorphological mapping of southern Skye indicates evidence for a single readvance of locally-nourished glaciers. These comprised a major icefield that occupied c. 155 km² of the main mountain area, a small icefield c. 10 km² in extent in the Kyleakin hills and ten corrie glaciers with a total area of c. 16 km². The absence of Lateglacial pollen sites, shorelines and periglacial features within the limits of local glaciation implies a Loch Lomond Readvance age for this glacial event. The area-weighted mean equilibrium line altitude (ELA) of the reconstructed Loch Lomond Readvance glaciers (319 m) conforms with a regional eastwards rise in ELAs that indicates dominant westerly airstreams during the Loch Lomond Stadial. An easterly decline in ELAs across the former icefields is interpreted in terms of easterly transfer of snow across ice-sheds by westerly winds, though the altitudes of corrie glacier ELAs suggest that the dominant snow-bearing winds were southerlies. Calculations based on the area-weighted mean ELA for the major icefield (308 m) indicate a stadial mean July sea-level temperature of c. 6 °C. The anomalously low gradients of certain former icefield outlet glaciers are attributed to deformation of subglacial sediment, an effect that may vitiate the assumption of linear ablation/accumulation gradients in the calculation of former ELAs for reconstructed glaciers.     

Solute dynamics of meltwater of Gangotri glacier,Garhwal Himalaya,India

The present study investigates solute dynamics of meltwater of Gangotri glacier system in terms of association of different chemical compounds with the geology of the area. In the meltwater, the presence of cations varied as c(Mg²⁺) > c(Ca²⁺) > c(Na⁺) > c(K⁺), while order of concentration of anions has been c(HCO₃ ⁻) > c(SO₄ ²⁻) > c(Cl⁻) > c(NO₃ ⁻) in years 2003 and 2004. The magnesium and calcium are found as the dominant cations along with bicarbonate and sulphate as dominant anions. The high ratios of c(Ca²⁺ + Mg²⁺)/total cations and c(Ca²⁺ + Mg²⁺)/c(Na⁺ + K⁺) indicate that the meltwater chemistry of the Gangotri glacier system catchment is mostly controlled by carbonate weathering. Attempts are made to develop rating curves for discharge and different cations. Sporadic rise in discharge without corresponding rise in concentration of most of cations is responsible for their loose correlation in a compound valley glacier like Gangotri glacier.     

Late quaternary glacial history of the South Orkney Plateau, Antarctica

Piston cores from the South Orkney Plateau penetrated overcompacted diamictons in water depths of up to 250 m. Detailed textural and petrological analyses of these diamictons indicate that they are basal tills. Seismic records from the plateau show a widespread surface of glacial erosion and provide additional evidence of an ice cap grounded to a depth of 250 m. Piston cores from the slope of the plateau penetrated diatomaceous muds resting directly on poorly sorted muds with very little to no biogenic material. The ice-rafted debris in these glacial-marine sediments is composed almost exclusively of material derived from the South Orkney Islands. This implies deposition beneath an ice shelf as opposed to iceberg rafting. In contrast, diatomaceous muds contain relatively abundant exotic iceberg-rafted material and reflect a glacial-maritime setting similar to that of today. The sharp contact separating diatomaceous surface sediments from basal tills and sub-ice shelf deposits indicates that the ice cap and ice shelf retreated from the plateau rapidly. Radiocarbon dates for diatomaceous muds from a glacial trough on the plateau indicate that the ice cap and ice shelf retreated from the plateau prior to 6000 to 7000 years ago. The homogeneity of surficial diatomaceous sediments suggests that sea ice conditions over the plateau have not changed radically since that time.     

Geomorphological evidences of post-LGM glacial advancements in the Himalaya: A study from Chorabari Glacier,Garhwal Himalaya,India

Field geomorphology and remote sensing data, supported by Optical Stimulated Luminescence (OSL) dating from the Mandakini river valley of the Garhwal Himalaya enabled identification of four major glacial events; Rambara Glacial Stage (RGS) (13 ± 2 ka), Ghindurpani Glacial Stage (GhGS) (9 ± 1 ka), Garuriya Glacial Stage (GGS) (7 ± 1 ka) and Kedarnath Glacial Stage (KGS) (5 ± 1 ka). RGS was the most extensive glaciation extending for ~6 km down the valley from the present day snout and lowered to an altitude of 2800 m asl at Rambara covering around ~31 km² area of the Mandakini river valley. Compared to this, the other three glaciations (viz., GhGS, GGS and KGS) were of lower magnitudes terminating around ~3000, ~3300 and ~3500 m asl, respectively. It was also observed that the mean equilibrium line altitude (ELA) during RGS was lowered to 4747 m asl compared to the present level of 5120 m asl. This implies an ELA depression of ~373 m during the RGS which would correspond to a lowering of ~2°C summer temperature during the RGS. The results are comparable to that of the adjacent western and central Himalaya implying a common forcing factor that we attribute to the insolation-driven monsoon precipitation in the western and central Himalaya.     

Late quaternary glacial history of George VI Sound area, West Antarctica

During the last glacial maximum in West Antarctica separate ice caps developed on Alexander Island and on Palmer Land, became confluent in George VI Sound, and discharged northward from latitude 72° S. Radiocarbon (>32,000 yr) and amino acid (approximately 120,000 yr) age determinations on shell fragments (Hiatella solida) found in basal till suggest a Wisconsin age for the glaciation that incorporated them. The pattern of ice flow differed from that deduced for this area in the CLIMAP reconstruction. Following the maximum stage, there was a stadial event when outlet valley glaciers flowed from smaller ice caps into George VI Sound. More widespread recession permitted the George VI ice shelf to deposit Palmer Land erratics on eastern Alexander Island before isostatic recovery raised them to final elevations of about 82 m. The ice shelf may have been absent at about 6500 yr B.P., when large barnacles (Bathylasma corolliforme) were living in the sound. Small glaciers readvanced to form at least two terminal moraines before the ice shelf re-formed and incorporated the barnacle shells into its moraine on Alexander Island. The shells gave a ¹⁴C age (corrected for Antarctic conditions) of about 6500 yr B.P. and an amino acid ratio consistent with a Holocene age. Valley glaciers readvanced over the ice-shelf moraine before oscillations of both valley glaciers and the ice shelf led to the formation of the present sequence of contiguous ice-cored moraines, probably during the Little Ice Age. Such oscillations may represent a climatic control not yet observed in the dry valleys of Victoria Land, the only other part of Antarctica studied in detail for glacier fluctuations.     

Reconstruction of the Past Climate From Tree Rings Over Western Himalaya, India

RECONSTRUCTION OF THE PAST CLIMATE FROM TREE RINGS OVER WESTERN HIMALAYA, INDIA     

Late quaternary glacial stades in the Cordillera Central,Colombia, based on glacial geomorphology,tephra–soil stratigraphy,palynology, and radiocarbon dating

Using data from glacial geomorphology, tephra–soil stratigraphy and mineralogy, palynology, and radiocarbon dating, a sequence of glacial and bioclimatic stades and interstades has been identified for the last ca. 50000 yr in the Ruiz-Tolima massif, Cordillera Central, Colombia. Six Pleistocene cold stades separated by warmer interstades occurred: before 48000, between 48000 and 33000, between 28000 and 21000, from ≥16000 to ca. 14000, ca. 13000–12400, and ca. 11000–10000 yr BP. Although these radiocarbon ages are minimum-limiting ages obtained from tephra layers on top of tills, the tills are not significantly older because most are bracketed by dated tephra sets in measured stratigraphic sections. Two minor moraine stages likely reflect glacier standstill during cold intervals ca. 7400 yr BP and slightly earlier. Finally, glaciers readvanced between the seventeenth and nineteenth centuries. In contrast to the ice-clad volcanoes of the massif, ca. 34 km² in area above an altitude of ca. 4800 m, the ice cover expanded to 1200 km² during the Last Glacial Maximum (LGM) and was still 800 km² during Late-glacial time (LGT). Glacier reconstructions based on the moraines suggest depression of the equilibrium line altitude (ELA) by ca. 1100 m during the LGM and 500–600 m during LGT relative to the modern ELA, which lies at ca. 5100 m in the Cordillera Central. Glaciers in this region apparently reached their greatest extent when the climate was cold and wet, e.g. during stades corresponding to Oxygen Isotope Stage 3; glaciers were still expanding during the LGM ca. 28000–21000 yr BP, but they shrank considerably after 21000 yr BP because of greatly reduced precipitation. © 1997 John Wiley & Sons, Ltd.     

Neotectonic Control on the Geomorphic Evolution of the Gangotri Glacier Valley, Garhwal Himalaya

The paper records evidences of neotectonic activities in the Gangotri glacier valley that are found to be responsible for the present-day geomorphic set-up of the area since the last phase of major glaciation. Geomorphological features indicate the presence of a large glacier in the valley in the geological past. Prominent planar structures present in the rocks were later on modified into sets of normal faults in the present-day Himalayan tectonic set-up giving rise to graben structures. The block nearest the snout is traversed by the NW-SE trending Gaumukh fault. A number of terraces mark the entrenchment of Bhagirathi River in this part. The contrasting drainage morphometric parameters of two sides of the valley and asymmetric recessional patterns of the tributary glaciers further document movement along the fault. The distribution and orientation of debris fans also seem to be controlled by neotectonic activity. The neotectonic activity that followed the process of deglaciation has brought the glacially carved, wide U- shaped valley in contact with the present-day fluvially incised narrow and relatively deep valley. The wider segments have become sites of active deposition of glacially eroded debris. The low gradient and excessive filling has resulted in the river attaining a braided nature in these segments.     

The Holocene glacial history of Lyngshalvöya, northern Norway: chronology and climatic implications

Up to four nested Neoglacial moraines occur in front of glaciers on Lyngshalvöya. Lichenometric measurements at 21 glaciers demonstrate that these represent five episodes of glacier expansion, one of which predated the Little Ice Age. Lichenometric, dendrochronological and historical evidence indicates that the oldest Little Ice Age moraines date to the mid-18th century, and the youngest to A.D. 1910-30. At nine small glaciers the A.D. 1910-30 moraine represents the Neoglacial maximum; only larger glaciers were more extensive in the 18th century. It is inferred that conditions for glacier growth were less favourable in the 18th century than in A.D. 1880–1910 because of low winter snowfall. Comparison of the relative magnitude of 18th- and 20th-century advances on Lyngshalvöya with those of southern Norway suggests that the diminished winter precipitation was due to the southerly location of the North Atlantic oceanic polar front in the 18th century, which resulted in a reduction in winter cyclonic activity in northern Scandinavia but in an increase in snowfall farther south.     

喜马拉雅山珠穆朗玛峰北坡绒布冰川消融速率特征分析

根据1959年和2009年在喜马拉雅山珠穆朗玛峰北坡绒布冰川获得的冰川消融数据, 分析了该冰川消融速率变化特征.结果表明: 1) 在珠峰绒布冰川表碛覆盖区, 表碛厚度随海拔升高而降低. 2) 不同厚度表碛下的冰川消融速率差别较大; 当表碛厚度>8.5 cm时, 消融速率随表碛厚度的增加而减小; 促进冰川消融的表碛厚度阈值大于5 cm. 3) 从冰川消融速率的空间分布看, 绒布冰川大部分区域的消融速率<20 mm·d^-1, 最大消融速率出现在海拔5 400~5 450 m处. 4) 绒布冰川消融速率受表碛厚度和气温综合影响, 低海拔处表碛太厚, 高海拔处气温较低, 冰川消融在上述两海拔处均受抑制, 冰川消融速率较小; 在中海拔处, 表碛相对较薄, 气温相对较高, 冰川消融速率最大; 冰川日均消融速率与日均正积温正相关. 5) 喜马拉雅山南坡冰川消融速率大于北坡冰川消融速率.     

Geology,structural and exhumation history of the Higher Himalayan Crystallines in Kumaon Himalaya,India

The crystallines in the Kumaon Himalaya, India are studied along Goriganga, Darma and Kaliganga valleys and found to be composed of two high-grade metamorphic gneiss sheets i.e. the Higher Himalayan Crystalline (HHC) and Lesser Himalayan Crystalline (LHC) zones. These were tectonically extruded as a consequence of the southward directed propagation of crustal deformation in the Indian plate margin. The HHC and its cover rocks i.e. the Tethyan Sedimentary Zone (TSZ) are exposed through tectonic zones within the hinterland of Kumaon Himalaya. The HHC records history of at least one episode of pre-Himalayan deformation (D₁), three episodes of Himalayan deformation (D₂, D₃, D₄). The rocks of the HHC in Kumaon Himalaya are thoroughly transposed by D₂ deformation into NW-SE trending S_m (S₁+S₂). The extent of transposition and a well-developed NE-plunging L₂ lineation indicate intense strain during D₂ throughout the studied portion of the HHC. Ductile flow continued, resulting in rotation of F₁ and F₂ folds due NE-direction and NW-SE plunging F₃ folds within the HHC. The over thickened crystalline was finally, superimposed by late-to-post collisional brittle-ductile deformation (D₄) and exposed the rocks to rapid erosion.     

特提斯喜马拉雅白垩纪层序地层分析

白垩纪是新特提斯演化过程中一个极其重要的阶段,其沉积蕴涵着新特提斯早期演变的丰富信息。在对典型剖面进行层序地层分析的基础上,结合前人的研究成果,笔者分别对特提斯喜马拉雅沉积带南、北两亚带白垩系进行较为详细的露头层序地层学研究,在沉积南带识别出为24个三级层序、5个层序组(亚二级层序)、2个二级层序(中层序),在北亚带识别出22个三级层序、5个层序组(亚二级层序)、2个二级层序(中层序)。特提斯喜马拉雅早白垩世层序地层总体表现为海进的退积序列,反映了特提斯洋壳的扩张阶段;晚白垩世层序地层总体表现为海退的进积序列,反映了特提斯洋盆地持续收缩和长期海平面逐步下降的过程,应是洋壳俯冲阶段的产物。整个白垩纪显示出一次极其明显的海水进退旋回,是特提斯洋从扩张到收缩这一演化过程的客观反映。由对层序特征、沉积特征及古生物特征等的分析所得出的特提斯喜马拉雅在白垩纪的海水进退规程,与同期的全球海平面的变化基本一致。     

Geomorphological and pedological investigations on the glacial history of the Kali Gandaki (Nepal Himalaya)

In semi-arid orographic left tributaries of the Kali Gandaki at the northern and western flank of the Nilgiri Himal, glacio-geomorphological and pedological investigations were carried out on prehistoric moraines. Geomorphological relief analysis was derived from other literature and the own fieldwork of the author. The resulting glacial chronology was used as benchmark to explore the limits of different pedological dating methods regarding the degree of soil development. These methods are based on iron fractionation, total element contents and particle size distribution. In general the different glacial stages are mirrored correctly in the relative graduation of soil development. The ratio of well crystallised pedogenic iron-oxides to the total iron content and the ratio fine clay to total clay are most suitable, because they are almost independent from existing changes in the lithological composition. The total element based weathering indices are less suitable, because they react highly sensitive to the geology dependent shift to higher carbonate content. Most of the grain size based weathering indices are inapplicable because of the typically high textural variability within till deposits.     

Environmental history of southern Patagonia unravelled by the seismic stratigraphy of Laguna Potrok Aike

Laguna Potrok Aike, located in southernmost Patagonia (Argentina, 52°S) is a 100 m deep hydrologically closed lake that probably provides the only continental southern Patagonian archive covering a long and continuous interval of several glacial to interglacial cycles. In the context of the planned ‘International Continental Scientific Drilling Program’ initiative ‘Potrok Aike Maar Lake Sediment Archive Drilling Project’, several seismic site surveys that characterize in detail the sedimentary subsurface of the lake have been undertaken. Long sediment cores recovered the material to date and calibrate these seismic data. Laguna Potrok Aike is rimmed steeply, circular in shape with a diameter of ∼3·5 km and is surrounded by a series of subaerial palaeoshorelines, reflecting varying lake-level highstands and lowstands. Seismic data indicate a basinwide erosional unconformity that occurs consistently on the shoulder of the lake down to a depth of −33 m (below 2003 ad lake level), marking the lowest lake level during Late Glacial to Holocene times. Cores that penetrate this unconformity comprise Marine Isotope Stage 3-dated sediments (45 kyr bp ) ∼3·5 m below, and post-6800 cal yr bp transgressional sediments above the unconformity. This Middle Holocene transgression following an unprecedented lake-level lowstand marks the onset of a stepwise change in moisture, as shown by a series of up to 11 buried palaeoshorelines that were formed during lake-level stillstands at depths between −30 and −12 m. Two series of regressive shorelines between ∼5800 to 5400 and ∼4700 to 4000 cal yr bp interrupt the overall transgressional trend. In the basin, mound-like drift sediments occur after ∼6000 cal yr bp, documenting the onset of lake currents triggered by a latitudinal shift or an increase in wind intensity of the Southern Hemispheric Westerlies over Laguna Potrok Aike at that time. Furthermore, several well-defined lateral slides can be recognized. The majority of these slides occurred during the mid-Holocene lake-level lowering when the slopes became rapidly sediment-charged because of erosion from the exposed shoulder sediments. Around 7800 and 4900 cal yr bp , several slides went down simultaneously, probably triggered by seismic shaking.