the distribution and origin of dimethyldibenzothiophenes in sediment extracts from the liaohe basin east china abstract the distributions of dimethyldibenzothiophenes dmdbts the relationship between dmdbts and dimethylbiphenyls dmbps and the applications of dmdbts as maturity indicators in source rocks have been investigated in a set of 21 lacustrine shales from the eocene shahejie formation well sg1 in the western depression liaohe basin china all source rock samples are characterized by total organic carbon contents of 1 37 3 27 and type ii with minor type iii kerogen they were deposited in suboxic and brackish lacustrine environments and have maturities ranging from immature to mid mature the 3 3 dmbp isomer can potentially react to yield 4 6 dmdbt 2 6 dmdbt and 2 8 dmdbt by incorporating sulfur into biphenyl which may be supported by a strong positive correlation between the absolute concentration changes of 3 3 dmbp and those of 4 6 dmdbt 2 6 dmdbt plus 2 8 dmdbt the relative abundance of dmdbt isomers may be explained by the sulfur radical mechanism and are also controlled by steric hindrance and thermodynamic stability the 4 6 1 4 1 6 dmdbt ratio shows no regular trend with increasing maturity at the low stage and it should be used with caution as a maturity indicator for immature sediments however within the oil generation window the relative concentration of 4 6 dmdbt progressively increases with increasing maturity which can be explained by its higher thermodynamic stability relative to the 1 4 dmdbt isomer the 4 6 1 4 1 6 dmdbt ratio exhibits a linear increase with increasing thermal maturity of the sediments thus this ratio can be applied as an effective maturity indicator for source rocks within oil generation window

lower permian paleomagnetism of the tarim block northwestern china we collected 262 samples at 39 sites in three thick lower permian sections along the northwestern margin of the tarim block the lower permian sections are basalts interbedded with limestones or sandstones or shallow marine limestones and sandstones alone all with biostratigraphic age control alternating field af and thermal demagnetization experiments remove small secondary components and reveal characteristic magnetizations reversed directions consistent with the kiaman reversed interval similar directions between basalts sandstones and limestones a positive fold test and apparent polar wander and polarity changes recorded in underlying devonian sediments all attest to the primary nature of the remanence two paleomagnetic poles one from the limestone section 65 1 n 162 5 e k 128 a95 4 1 n 11 sites and the other from the two basalt sections 54 5 n 172 3 e k 66 a95 4 0 n 21 sites differ primarily in colatitude 8 1 6 5 suggesting a difference in magnetization age permian paleomagnetic poles from tarim siberia north china and south china all differ significantly suggesting substantial post permian relative motions

biomarker 17α h diahopane a geochemical tool to study the petroleum system of a tertiary lacustrine basin northern south china sea abstract relatively abundant c30 17 h diahopane has been detected in oils and rock extracts in the fushan depression a tertiary lacustrine basin of the northern south china sea c30 17 h diahopane c30 17 h diahopane c30 17 h hopane ratios di increase with increased burial depth of the source rocks di values of most oils from the upper unit e 2 l 3 1 of the third member of the eocene liushagang formation e2l3 in the huachang oil and gas field show a positive correlation with other molecular maturity indicators such as the dnr dimethylnaphthalene ratio mdr methyldibenzothiophene ratio 4 6 1 4 dmdbt 4 6 1 4 dimethyldibenzothiophene mpr methylphenanthrene ratios or the mpi 1 methylphenanthrene index the inflection of the di depth curve occurring at about 3200 m corresponds to 0 55 ro the oils of the huachang oil and gas field have higher di values than the extracts of in situ source rocks indicating the oils might be sourced from deeply buried source rocks two petroleum systems can be distinguished in the huachang field in terms of the relative concentration of diahopane and other maturity parameters the oils in the upper petroleum system consisting of the reservoirs in e 2 l 3 1 are mainly sourced from the e2l source rocks in the bailian sag and are characterized by relatively higher maturity higher oil and gas yields and lower contents of diahopane and oleananes the oils in the lower system consisting of middle e 2 l 3 2 and lower units e 2 l 3 3 of e2l3 have higher contents of diahopane higher contents of co2 gas and lower maturity and oil and gas yields the occurrence and geochemical characteristics of the petroleum system are mainly controlled by the double fault system in the huachang uplift the c30 17 h diahopane is an effective biomarker for oil source rock correlation oil oil correlation maturity assessment and petroleum system study in some terrestrial lacustrine basins

hydrological characteristics of the drainage system beneath a surging glacier a rare combination of natural circumstances permits assessment of current theories on water flow beneath glaciers outburst floods from the subglacial lake grimsvotn in iceland took place before during and after surging of skei ararjokull the glacier beneath which the outburst floods drain the observable drainage patterns associated with these floods show the different nature of the basal water conduit system of the glacier during surge and non surge phases during surge conditions basal water is dispersed slowly across the bed in a distributed drainage system but when the glacier is not surging water is transported rapidly through a system of tunnels

surge propagation constrained by a persistent subglacial conduit bakaninbreen paulabreen svalbard glacier surges tend to be initiated in relatively small regions then propagate down glacier up glacier and or across glacier the processes controlling patterns and rates of surge propagation however are incompletely understood in this paper we focus on patterns of surge propagation in two confluent glaciers in svalbard and examine possible causes one of these glaciers bakaninbreen surged in 1985 95 the surge propagated 7 km down glacier but did not cross the medial moraine onto the other glacier paulabreen when paulabreen surged between 2003 and 2005 the surge wave travelled several km down glacier but its lateral boundary stayed very close to the medial moraine the confluent glaciers formerly extended into a fjord and bathymetric mapping and historical observations show that an active subglacial conduit has existed between bakaninbreen and paulabreen since at least the early 20th century the existence of a persistent subglacial conduit below the medial moraine was confirmed when we entered and mapped a nye channel at the confluence of bakaninbreen and paulabreen we argue that the conduit acts as a barrier to surge propagation if pressurized water below one branch of the glacier system reaches the conduit water can be readily evacuated preventing its propagation into the other branch

karakoram glacier surge dynamics quincey d j braun m glasser n f bishop m p hewitt k luckman a 2011 geophysical research letters 38 article number l18504

climatic and geometric controls on the global distribution of surge type glaciers implications for a unifying model of surging financial support was provided by the conocophillips lundin northern area program project crios

contrasting patterns of early twenty first century glacier mass change in the himalayas glaciers are among the best terrestrial climate indicators an important water resource in mountains1 2 and a major contributor to global sea level rise3 4 in the hindu kush karakoram himalaya region hkkh a paucity of appropriate glacier data has prevented a comprehensive assessment of current regional mass balance5 however there are indirect evidences of a complex pattern of glacial responses5 8 in reaction to heterogeneous climate change signals9 here we provide the first coherent data set of detailed glacier thickness changes over the hkkh during 2003 2009 by combining satellite laser altimetry and a global elevation model in the eastern central and south western parts of the hkkh glacier wastage is widespread with regional thinning rates up to 0 66 0 09 m a 1 in the jammu kashmir region conversely in the karakoram glaciers are close to balance with only a slight thinning of 0 07 0 04 m a 1 regionally averaged thinning rates under debris mantled ice are similar to those of clean ice despite insulation by debris covers the 2003 2008 specific mass balance for our hkkh study region is 0 21 0 05 m a 1 water equivalent we significantly less negative than the global average of 0 7 m a 1 we for glaciers and ice caps4 10 this difference is mainly an effect of the balanced glacier mass budget in the karakoram the corresponding hkkh sea level contribution is 0 035 0 009 mm a 1 amounting to 1 of the present day sea level rise11 our 2003 2008 mass budget of 12 8 3 5 gt a 1 is more negative than recent satellite gravimetry based estimates of 5 6 gt a 1 over 2003 2010 ref 12 for the mountain catchments of the indus and ganges basins13 the glacier imbalance contributes 3 5 and 2 0 respectively to the annual average river discharge13 and up to 10 for the upper indus basin14

the duration of the active phase on surge type glaciers contrasts between svalbard and other regions many glaciers in svalbard and in other glacierized areas of the world are known to surge however the time series of observations required to assess the duration of fast motion is very restricted data on active phase duration in svalbard come from aerial photographs satellite imagery field surveys and airborne reconnaissance evidence on surge duration is available for eight svalbard ice masses varying from 3 to 1250 km 2 worldwide active phase duration is recorded for less than 50 glaciers few observations are available on high polar ice masses the duration of the active phase is significantly longer for svalbard glaciers than for surge type glaciers in other areas from which data are available in svalbard the active phase may last from 3 to 10 years by contrast a surge duration of 1 2 years is more typical of ice masses in northwest north america iceland and the pamirs ice velocities during the protracted active phase on svalbard glaciers are considerably lower than those for many surge type glaciers in these other regions mass is transferred down glacier more slowly but over a considerably longer period svalbard surge type glaciers do not exhibit the very abrupt termination of the active phase over periods of a few days observed for several alaskan glaciers the duration of the active phase in svalbard is not dependent on parameters related to glacier size the quiescent phase is also relatively long 50 500 years for svalbard ice masses detailed field monitoring of changing basal conditions through the surge cycle is required from surge type glaciers in svalbard in order to explain the significantly longer length of the active phase for glaciers in the archipelago which may also typify other high polar ice masses the finding that surge behaviour in the form of active phase duration shows systematic differences between different regions and their environments has important implications for understanding the processes responsible for glacier surges

the sedimentary architecture of outburst flood eskers a comparison of ground penetrating radar data from bering glacier alaska and skeiðararjokull iceland we present ground penetrating radar gpr profiles that reveal the sedimentary architecture of an esker deposited during a surge associated outburst flood at the bering glacier alaska the wide up flow end of the esker contains a transition from large backset beds to large foreset beds interpreted to reflect composite macroform development in an enlarged part of the conduit by contrast the narrow down flow portion of the esker is dominated by plane beds interpreted to have been deposited where the conduit was constricted and the flow was faster a previously studied outburst esker at skeidararjokull iceland has a similar morphology and stratigraphic architecture this suggests that outburst floods generate distinct depositional signatures in eskers both in terms of morphology and sedimentary architecture identification of these distinct signatures in ancient eskers will help assess the paleohydraulic conditions under which ancient eskers formed and by extension the nature of meltwater drainage systems beneath the laurentide and eurasian ice sheets

the occurrence and distribution of phenylnaphthalenes terphenyls and quaterphenyls in selected lacustrine shales and related oils in china abstract phenylnaphthalenes phns terphenyls trps quaterphenyls qtps and triphenylbenzenes were identified by the use of authentic standards in gc ms analysis phenyl derivatives of fused ring polycyclic aromatic hydrocarbons phpahs and polyphenyls pphs were observed in selected lacustrine shales and related oils from the tarim liaohe and bebuwan basins in china all isomers of phenylnaphthalene and terphenyl were observed in these oils the more stable 2 phn and m trp p trp isomers are predominant among phenylnaphthalenes and terphenyls respectively the effect of maturity on the distribution patterns of phenylnaphthalenes and terphenyls in a set of lacustrine shales from the liaohe basin east china was investigated the depth trends of three currently used maturity indicators were investigated analysis was based on the relative abundance of phenylnaphthalene and terphenyl isomers namely phnr 2 phn 1 phn trp1 p trp o trp and trp2 m trp p trp o trp in lacustrine shales from well s202 in the liaohe basin east china the indicators increase slightly with relatively great deviations within low to intermediate maturation stages and then increase abruptly in high maturity stages therefore they are not suitable maturity indicators for lacustrine source rocks in this study an alternative thermal maturity indicator defined as p trp m trp was proposed it exhibits a uniform increase with increasing maturity and is probably a more suitable indicator for use in maturity assessment in lacustrine source rocks and related oils this study broadens the current understanding of the occurrence and distribution of phpahs and pphs in sedimentary organic matter of various origins

seismotectonic and refraction seismic investigations in the border region between the eastern alps and the pannonian basin focal solutions of four strong earthquakes and p signals of twenty four smaller shocks of the active mur murz valley the semmering pass and the vienna basin an equivalent slip rate of 0 03 this feature agrees with the model of a subsiding pannonian basin an equivalent slip rate of 0 03 cm year is roughly estimated from earthquake data 1903 1978 this rate does not include the creep rate but it gives an idea of the magnitude of speed of geological processes in this area

glacier surge propagation by thermal evolution at the bed bakaninbreen southern svalbard began a prolonged surge during 1985 in 1986 an internal reflecting horizon on radio echo sounding data was interpreted to show that the position of the surge front coincided with a transition between areas of warm unfrozen and cold frozen bed ground penetrating radar lines run in 1996 and 1998 during early quiescence show that the basal region of the glacier is characterized by a strong reflection interpreted as the top of a thick layer of sediment rich basal ice down glacier of the present surge front features imaged beneath the basal reflection are interpreted as the bottom of the basal ice layer the base of a permafrost layer and local ice lenses this indicates that this region of the bed is cold up glacier of the surge front a scattering zone above the basal reflection is interpreted as warm ice there is no evidence for this warm zone down glacier of the surge front nor do we see basal permafrost up glacier of it thus as in early surge phase the location of the surge front is now at the transition between warm and cold ice at the glacier bed we suggest that the propagation of the front is associated with this basal thermal transition throughout the surge because propagation of the front occurs rapidly and generates only limited heat basal motion during fast flow must have been restricted to a thin layer at the bed and occurred by sliding or deformation localized at the ice bed interface

topographic controls on the surging behaviour of sabche glacier nepal 1967 to 2017 abstract using a combination of landsat pleiades and corona satellite imagery from 1967 to 2017 we map changes in the terminus position ice surface velocity and surface elevation of sabche glacier and report the first observations of surging behaviour in central nepal our observations show that sabche glacier surged four times over the last 50 years the three most recent surges occurred at 10 to 11 year cycles which is one of the shortest surge cycles ever recorded detailed analysis of the most recent surge 2012 onwards indicates that the glacier advanced 2 2 km and experienced maximum velocities of 1 6 0 10 m day 1 during this surge there was a surface elevation gain at the terminus of up to 90 6 19 m a 1 with a corresponding surface lowering of between 10 6 19 and 60 6 19 m a 1 3 km up glacier of the terminus this transfer of mass amounted to a volume of 2 7 107 0 1 107 m3a 1 sabche glacier is the first surge type glacier to be observed in the central himalayas but this is consistent with a previous global analysis which indicates that surge type glaciers should exist in the region we hypothesise that the surge is at least partially controlled by subglacial topography whereby a major subglacial overdeepening and constriction 3 km up glacier of the terminus provides resistance to glacier flow from the accumulation area to the ablation area this overdeepening appears to store mass until a threshold is crossed after which the glacier flows out of the subglacial depression and rapidly surges over a bedrock lip and down the valley thus whilst the surges are likely to be facilitated by subglacial processes e g changes in subglacial hydrology and or basal thermal regime the topographic setting of the glacier appears to be modulating both the timing and duration of each surge

evaluation of existing and new methods of tracking glacier terminus change acknowledgements the authors thank two anonymous reviewers for constructive comments that helped to improve the manuscript this research was financially supported by j m l s phd funding from uk natural environment research council grant no ne i528742 1

variegated glacier alaska usa a century of surges a 1995 surge of variegated glacier alaska usa is discussed in the context of its six 20th century predecessors especially the previous surge in 1982 83 which was studied in detail the average time between surge initiations is 15 years the 1995 surge was considerably weaker than its predecessors having a single phase or at most a very weak second phase the 1995 surge confirms that there is a seasonal cycle with surge initiation in winter and termination in the first part of the melt season and a correlation between weather and both surge termination date and surge extent two days of record high temperature correlated with the termination of the 1995 surge the most obvious issue is the absence of a strong second surge phase as there was in the 1982 83 surge culminating in a surge extent more in line with that of the predecessors this is considered in the light of a simple criterion for surge initiation and re initiation which depends upon the evolving basal shear stress

flow thermal structure and subglacial conditions of a surge type glacier temperature measurements in a subpolar surge type glacier reveal a distinctive thermal structure associated with the boundary between the ice reservoir and receiving areas in the receiving area the glacier is cold based but bottom temperature has increased as much as 0 5 c between 1981 and 1982 and the basal heat flux is roughly 10 times the expected geothermal flux water percolation through permeable subglacial material is the probable energy source deformation of the substrate could destroy this drainage system and trigger a surge

alkylbiphenyls and alkyldiphenylmethanes as indicators of petroleum biodegradation abstract gas chromatographic mass spectrometric analyses of alkylbiphenyls and alkyldiphenylmethanes have been performed on a series of crude oils reservoired in the gippsland basin australia as well as in some marine coastal sediments contaminated with a condensate changes in the isomeric distribution of the alkylbiphenyls and alkyldiphenylmethanes with increasing biodegradation were investigated the relative abundance and distributions of the isomers were found to change significantly with increasing biodegradation isomers with the 4 substituent s generally increase in abundance relative to isomers that lack this feature thus alkylbiphenyl and alkyldiphenylmethane isomeric distributions are useful indicators of the extent of petroleum biodegradation in reservoirs and surface sediments it is suggested that geosynthetic processes and or relative susceptibilities of certain isomers to microbial attack can account for changes in the isomeric distribution of these components with increasing biodegradation significant differences in the relative abundances of the methylbiphenyls are apparent and are probably due to variations in the conditions that the petroleum had been subjected to in the two contrasting environments

extractable organic material in fault zones as a tool to investigate frictional stress abstract the detection of a frictional heating signature is an attractive but elusive way to measure frictional stress on exhumed faults with no evidence of melting we present a new paleothermometer for fault zones that utilizes the thermal maturity of extractable organic material to determine the maximum frictional heating experienced by the fault because there are no retrograde reactions in these organic systems maximum heating is preserved we investigate the punchbowl fault an ancient strand of the san andreas fault in southern california according to the methylphenanthrene index for thermal maturity there is no differential heating between the fault and off fault samples indicating that the fault did not get hotter than the surrounding rock during slip additionally the thermal maturity of the rocks falls within the range of heating expected from the bounds on burial depth and time and adds some constraint to the burial depth range simple heating models indicate that the fault must have had either 1 an extremely low shear stress during slip 2 an active slipping zone thicker than 1 mm or 3 earthquakes smaller than m6 to lack a differential heating signature after 44 km slip

fast glacier flow ice streams surging and tidewater glaciers fast flowing glaciers are unusual but important jakobshavns glacier in western greenland illustrates this point figure 1 considered to be the world s fastest glacier its maximum observed flow rate measured in midsummer near the floating terminus is 8360 m yr 1 lingle et al 1981 except for a tidal influence near the terminus the flow is believed to be fairly steady bindschadler 1984

geometric evolution and ice dynamics during a surge of bakaninbreen svalbard bakaninbreen svalbard started surging in 1985 and developed a steep surge front where fast moving ice impinged on stagnant non surging ice this front which was 20 25 m high in 1985 became a steep and heavily crevassed fcature about 60 m high the surge continued through 1986 95 annual surge front propagation rate was 1 0 1 8 km a 1 during 1985 89 this rate dropped considerably during 1989 95 and the front became less steep front propagation occurred largely by longitudinal compression and vertical extension of the ice and the effects of over riding appear minor ice velocities were slowe than the average propagation rate of the front the surge affected bakanin breen in four zones upper region where extensiv e flow fast propagation rates and negative vertical strain occurred resulting in widespread crevassing and stranded blocks tens of metres above the post surge ice surface 2 mid glacier region where initial strong compression was associated with ice thickening which started before the arrival of the surge front horizontal strain rates were very low but vertical strain rates were up to 300 mm d 1 as the front passed the horizontal velocity increased and about 500 m behind it became extensive negative vertical strain and ice down draw occurred as ice vclocities dropped 3 surge front where ice velocity w as high but vertical strain remained positive associated with compression 4 lower region below the front where only compression occurred resulting in the formation of a fore bulge a thickening of the ice of up to 50 m above pre surge levels the fore bulge affected the whole 1 7 km below the now halted surge front the glacier has not advanced ba kaninbreen s surge was characterized by a long active phase approximately 10 years low ice velocities and low basal shear stresses compared to glaciers in lower latitudes and an indistinet surge termination

the january 2018 to september 2019 surge of shisper glacier pakistan detected from remote sensing observations abstract this study analysed the actively surging shisper glacier in the karakoram region of pakistan using earth observation data from landsat 8 oli and planet images changes in the surface glacier velocity supraglacial moraines and debris cover were assessed using landsat 8 data at monthly time steps from january 2018 to may 2019 high resolution data from planet labs was used to precisely detect the snout advance and ice dammed lake expansion downstream cross section profiles of the valley were generated using a moderate resolution digital elevation model to assess the inundation in the event of rapid ice dammed lake drainage correlation image analysis software working on the principle of normalized cross correlation was used to generate time series monthly surface velocity profiles for shisper glacier manual digitization at 1 30000 scale was used to delineate supraglacial moraines and supraglacial debris cover the glacier surface velocity profiles indicate that the ablation zone of the glacier continues to be in an active surge phase resulting in advance of the snout and expansion of the ice dammed lake surface glacier velocities are as high as 48 m d 1 between 18 december 2018 and 8 may 2019 the glacier snout advanced at 6 m d 1 with a total overall advance of 860 m the lake formed due to damming of an outflow stream from mochowar glacier expanded to its maximum area 29 69 ha in may 2019 before drainage started on 23 june 2019 our estimates indicate that the peak discharge in case of rapid drainage could vary between 5033 m3 s 1 and 6167 m3 s 1 and potentially affect infrastructure downstream

is there a single surge mechanism contrasts in dynamics between glacier surges in svalbard and other regions 1 during the 1990s monacobreen a 40 km long tidewater glacier in svalbard underwent a major surge we mapped the surge dynamics using ers synthetic aperture radar images differential dual azimuth interferometry and intensity correlation tracking a series of 11 three dimensional 3 d velocity maps covering the period 1991 1997 show a months long initiation and years long termination to the surge with no indication of a surge front travelling downglacier during the surge the front of the glacier advanced 2 km the velocity and derived strain rate increased by more than an order of magnitude and maximum ice flow rates measured during 1994 were 5 m d 1 the spatial pattern of both velocity and strain rate was remarkably consistent and must therefore be controlled by spatially fixed processes operating at the glacier bed we combine these results with those published in the literature to construct a typical svalbard glacier surge cycle and compare this to surge dynamics of glaciers from other cluster regions especially those of variegated glacier in alaska the strong contrast in dynamics suggests that there exist at least two distinct surge mechanisms

subglacial basins their origin and importance in glacial systems and landscapes closed topographic basins are found beneath contemporary ice masses and within the footprint of former ice masses in all glaciated regions we present the first integrated review of subglacial basin occurrence and formation and the implications of such basins for glaciological processes and the evolution of landscape our purpose is to motivate research in areas where understanding of basin origin and process significance is weak basins on the order of 10 102 m deep and 102 103 m long are produced by glacial erosion of subglacial rock and or sediment and are known as overdeepenings outlet and valley glaciers can overdeepen their beds far below sea level or local fluviatile base level larger basins typically in ice sheet contexts may have a pre glacial usually tectonic origin subglacial basins are important glaciologically because they require ice water and sediment to ascend an adverse subglacial slope in order to exit the glacial system the efficiency of which is dependent upon the gradient of the adverse slope and that of the ice surface basins thus influence subglacial drainage system morphology and transmissivity the thickness and distribution of basal ice and sediment layers and the mechanisms and dynamics of ice flow adverse gradients that exceed 11 times that of the ice surface may even permit the formation of subglacial lakes we speculate that in comparison to ice masses with few or no subglacial basins those with numerous or very large basins may respond to climatic changes with unexpected vigour in addition erosion rates and transport pathways of water and sediment through the glacial system and the expression of these processes in the sediment and landform record may be unexpectedly complex further our review shows that in a warming climate ice masses resting on adverse slopes will be vulnerable to rapid and potentially catastrophic retreat new lakes in subglacial basins exposed by mountain glacier retreat will present an increasing hazard and subglacial lakes may drain catastrophically on even longer time scales we speculate that the glacial excavation and post glacial filling of basins in mountainous regions should contribute importantly to climate related changes in isostasy and relief although the controls on overdeepening and their influence on other glacial and landscape processes remain uncertain we hypothesise that overdeepened glacial systems reflect an equilibrium ice bed geometry that maximises the efficiency of ice discharge improved understanding of overdeepening processes especially overdeepened bed hydrology is therefore necessary to understand fully the dynamic behaviour of valley and outlet glaciers and thus the fate of earth s largest ice masses

effects of bedrock lithology and subglacial till on the motion of ruth glacier alaska deduced from five pulses from 1973 2012 a pulse is a type of unstable glacier flow intermediate between normal flow and surging using landsat mss tm and etm imagery and feature tracking software a time series of mostly annual velocity maps from 1973 to 2012 was produced that reveals five pulses of ruth glacier alaska peaks in ice velocity were found in the 1981 1989 1997 2003 and 2010 approximately every 7 years during these peak years the ice velocity increased 300 from approximately 40 m yr to 160 m yr and occurred in an area of the glacier underlain by sedimentary bedrock based on the spatio temporal behavior of ruth glacier during the pulse cycles we suggest the pulses are due to enhanced basal motion via deformation of a subglacial till the cyclical nature of the pulses is theorized to be due to a thin till with low permeability that causes incomplete drainage of the till between the pulses followed by eventual recharge and dilation of the till these findings suggest care is needed when attempting to correlate changes in regional climate with decadal scale changes in velocity because in some instances basal conditions may have a greater influence on ice dynamics than climate

phenyldibenzofurans and phenyldibenzothiophenes in marine sedimentary rocks and hydrothermal petroleum abstract the phenyl derivatives of dibenzo b d furan and dibenzo b d thiophene so far not reported in geological samples have now been identified in some sedimentary rocks bitumen and hydrothermal petroleum through a comparison of their retention times and mass spectra with those of authentic standards all four possible positional isomers were detected for each phenyldibenzo b d furan phdbf and phenydibenzo b d thiophene phdbt their elution sequence is 1 4 2 and 3 phenyldibenzo b d furan and 1 4 2 and 3 phenyldibenzo b d thiophene on apolar stationary phases in contrast to phenyldibenzofurans the distributions of the thiophene series is controlled mainly by the organic matter maturity in the most mature samples 4 2 and 3 phdbts prevail over 1 phdbt while less mature samples contain mainly 4 phdbt or 1 phdbt and 2 3 phdbts occur at comparable concentrations however in samples of low maturity in addition to the phenyldibenzo b d thiophene c 18 h 12 s series other structural isomers of c 18 h 12 s possessing very similar mass spectra were detected these are likely to be either naphthylbenzo b thiophenes and or phenylnaphtho b thiophenes phdbfs and phdbts are likely to be intermediate products in the formation of more condensed heterocyclic polycyclic aromatic compounds like triphenyleno 1 12 bcd thiophene and triphenyleno 1 12 bcd furan and benzobisbenzofurans and benzobisbenzothiophenes which are commonly detected in geological samples

monitoring surging glaciers of the pamirs central asia from space the evolution of surging glaciers of the pamirs central asia has been studied using repeat remote sensing surveys in the institute of geography russian academy of sciences since the early 1970s we use images obtained from national resurs f satellites 1972 91 as well as landsat 7 and terra 1999 2006 to provide a basis for monitoring of surging glaciers aimed at developing their inventory studying the causes and mechanisms of surges and examining the timing and extent of glacial catastrophes the inventory from the early 1990s allows identification of 215 glaciers with a dynamically unstable regime we discovered 51 surging glaciers up until 2006 10 more surges had occurred we use stereoscopic deciphering and photogrammetric processing of consecutive satellite images to study the morphology and ice velocity changes of several compound surging glaciers we analyze the results of monitoring of bivachny and oktyabr sky glaciers from 1972 to 1991 and sugran glacier from 1972 to 2006 two surges of sugran glacier occurred during this time an internal surge in 1976 80 and a surge with glacier tongue advance as far as 4 5 km in 2000 05 the role of damming in compound glacier systems is examined satellite based monitoring is now the only method for obtaining initial information about the state and fluctuations of such glaciers

characteristics of the last five surges of lowell glacier yukon canada since 1948 field observations aerial photographs and satellite images are used to reconstruct the past surges of lowell glacier yukon canada since 1948 based on the timing of terminus advances a total of five surges occurred over this time each with a duration of 1 2 years the time between successive surges ranged from 12 to 20 years and appears to have been shortening over time the relatively short advance and quiescent phases of lowell glacier together with rapid increases in velocity during surges suggest that the surging is controlled by a hydrological switch the 2009 10 surge saw ablation area velocities increase by up to two orders of magnitude from quiescent velocities and the terminus increase in area by 5 1 km 2 and in length by up to 2 85 km this change in area was the smallest since 1948 and follows the trend of decreasing surge extents over time this decrease is likely driven by a strongly negative surface mass balance of lowell glacier since at least the 1970s and means that the current town site of haines junction is very unlikely to be flooded by damming caused by any future advances of the glacier under the current climate regime

the galloping glacier trots decadal scale speed oscillations within the quiescent phase a 28 year record of annual surface speeds has revealed oscillations with a period of roughly 12 years during the quiescent phase of black rapids glacier alaska u s a the original galloping glacier these oscillations are hypothesized to be the manifestation of slowly propagating waves of till failure and till healing with at least the second cycle being initiated by the anomalous advance of a tributary glacier observations support the idea that such dynamics may have occurred but are not conclusive in the conceptual model describing the mechanisms of till failure and healing temporal variations in longitudinal stress gradients are proposed to be more important in causing till failure than temporal variations in effective pressure

a surge of bualtar glacier karakoram range pakistan a possible landslide trigger bualtar glacier karakoram range northern pakistan surged during the spring and early summer of 1987 this followed a major episode of three landslides which impacted part of the glacier ablation zone on 30 31 july 1986 in may 1987 surface velocities of 7 m d 1 were measured at one profile down glacier from the landslide deposits where in 1986 velocities were an order of magnitude less surface and hydrological characteristics of the glacier in and down glacier from the landslide deposit were also indicative of surge like behavior in 1987 and a return to pre surge conditions by 1988

glacier velocities across the central karakoram optical matching of aster advanced spaceborne thermal emission and reflection radiometer satellite image pairs is used to determine the surface velocities of major glaciers across the central karakoram the aster images were acquired in 2006 and 2007 and cover a 60 120 km region over baltoro glacier pakistan and areas to the north and west the surface velocities were compared with differential global position system gps data collected on baltoro glacier in summer 2005 the aster measurements reveal fine details about ice dynamics in this region for example glaciers are found to be active over their termini even where they are very heavily debris covered the characteristics of several surge type glaciers were measured with terminus advances of several hundred meters per year and the displacement of trunk glaciers as surge glaciers pushed into them this study is the first synthesis of glacier velocities across this region and provides a baseline against which both past and future changes can be compared

a general theory of glacier surges we present the first general theory of glacier surging that includes both temperate and polythermal glacier surges based on coupled mass and enthalpy budgets enthalpy in the form of thermal energy and water is gained at the glacier bed from geothermal heating plus frictional heating expenditure of potential energy as a consequence of ice flow enthalpy losses occur by conduction and loss of meltwater from the system because enthalpy directly impacts flow speeds mass and enthalpy budgets must simultaneously balance if a glacier is to maintain a steady flow if not glaciers undergo out of phase mass and enthalpy cycles manifest as quiescent and surge phases we illustrate the theory using a lumped element model which parameterizes key thermodynamic and hydrological processes including surface to bed drainage and distributed and channelized drainage systems model output exhibits many of the observed characteristics of polythermal and temperate glacier surges including the association of surging behaviour with particular combinations of climate precipitation temperature geometry length slope and bed properties hydraulic conductivity enthalpy balance theory explains a broad spectrum of observed surging behaviour in a single framework and offers an answer to the wider question of why the majority of glaciers do not surge

tsivat basin conduit system persists through two surges bering piedmont glacier alaska the 1993 1995 surge of bering glacier alaska occurred in two distinct phases phase 1 of the surge began on the eastern sector in july 1993 and ended in july 1994 after a powerful outburst of subglacial meltwater into tsivat lake basin on the north side of weeping peat island within days jokulhlaup discharge built a 1 5 km 2 delta of ice blocks 25 30 m buried in outwash by late october 1994 discharge temporarily shifted to a vent on weeping peat island where a second smaller outburst dissected the island and built two new sandar during phase 2 which began in spring 1995 and ended within five months continuous discharge issued from several vents along the ice front on weeping peat island before returning to the tsivat basin surge related changes include a five to six fold increase in meltwater turbidity the redirection of supercooled water in two ice contact lakes and an increase in the rate of glaciolacustrine sedimentation u s geological survey aerial photos by austin post show large ice blocks in braided channels indicating excessive subglacial discharge in a similar position adjacent to weeping peat island during the 1966 1967 surge during the subsequent three decades of retreat the location of ice marginal subglacial discharge vents remained aligned on a linear trend that describes the position of a persistent subglacial conduit system the presence of a major conduit system possibly stabilized by subglacial bedrock topography is suggested by 1 high level subglacial meltwater venting along the northern side of weeping peat island during the 1966 1967 surge 2 persistent low level discharge between surges and 3 the recurrence of localizing meltwater outbursts associated with both phases of the 1993 1995 surge

identification and characteristics of surge type glaciers on novaya zemlya russian arctic we present a comprehensive new inventory of surge type glaciers on the novaya zemlya archipelago using high resolution up to 4 m satellite imagery from 1976 77 hexagon 1989 landsat tm 2001 landsat etm and 2006 aster a total of 692 glaciers and their forelands were observed for glaciological and geomorphological criteria indicative of glacier surging e g looped moraines heavy surface crevassing surface potholes thrust block moraines concertina eskers this enabled the identification of 32 potential surge type glaciers compared with four previously identified representing 4 6 of the total but 18 by glacier area we assess the characteristics of surge type glaciers surge type glaciers are statistically different from non surge type glaciers in terms of their area length surface slope minimum elevation mid range elevation and terminus type they are typically long median length 18 5 km large median area 106 8 km 2 outlet glaciers with relatively low overall surface slopes median slope 1 7 and tend to terminate in water marine or lacustrine they are predominantly directed towards and located in the more maritime western region of the russian arctic and we suggest that surge occurrence might be related to large and complex catchment areas that receive increased delivery of precipitation from the barents sea

slow surge of trapridge glacier yukon territory canada 1 trapridge glacier a polythermal surge type glacier located in the st elias mountains yukon territory canada passed through a complete surge cycle between 1951 and 2005 air photos 1951 1981 and ground based optical surveys 1969 2005 are used to quantify the modifications in flow and geometry that occurred over this period yearly averaged flow records suggest that the active phase began 1980 and lasted until 2000 the average velocity in the central area of the glacier went from 16 m yr 1 in 1974 to 39 m yr 1 in 1980 it peaked at 42 m yr 1 in 1984 and remained above 25 m yr 1 until 2001 over that interval the flow decelerated by steps in 4 year pulses after a particularly vigorous acceleration in 1997 1999 the glacier gradually slowed to presurge velocities in 2005 the flow was less than 9 m yr 1 digital elevation models are generated by stereographic analysis of air photos for 1951 1970 1972 1977 and 1981 these models are updated annually using ground based survey data and a novel implementation of bayesian kriging over the course of the surge the front of active ice advanced 450 m and the glacier area increased by 10 with an associated thinning of the ice the previous surge of trapridge glacier starting before 1939 and ending before 1951 led to a terminus advance of 1 km comparison of the two surges suggests that the 1930s surge started with a slow progression similar to what we observed in the 1980s and 1990s and switched to a faster flow mode after 1941 this second phase was never attained in the recent surge probably owing to a lack of mass

changes in ice front position on greenland s outlet glaciers from 1992 to 2007 1 previous studies in greenland show that retreat of tidewater glaciers may be linked to recent increases in ice loss raising greenland s contribution to sea level rise we examined ice front changes of 203 tidewater glaciers land terminating glaciers and glaciers terminating with ice shelves to understand greenland glacier behavior over three periods 1992 2000 2000 2006 and 2006 2007 we observed synchronous ice sheet wide increases in tidewater retreat during 2000 2006 relative to 1992 2000 coinciding with a 1 1 c increase in mean summer temperature at coastal weather stations rates of retreat for the southeast and east slowed during 2006 2007 when temperatures were slightly cooler than the 2000 2006 average our work suggests that regional greenland tidewater retreat responds strongly to climate change with higher temperatures corresponding to increasing retreat and helps confirm a link between ice thickness velocity and ice front position

glacier surface velocities in alpine terrain from optical satellite imagery accuracy improvement and quality assessment the worldwide retreat of mountain glaciers has important consequences for the water food and power supply of large and densely populated areas in south and central asia successful mitigation of the hydrological impacts on societies as well as assessing glacier related hazards require large scale monitoring of glacier dynamics however detailed glaciological data from the asian highlands are lacking due to its size and difficult accessibility we have applied a novel technique for precise orthorectification co registration and sub pixel correlation of advanced spaceborne thermal emission and reflection radiometer aster satellite imagery to derive surface velocities of himalayan glaciers our approach allows for the correction of offsets due to attitude effects and sensor distortions as well as elevation errors if a digital elevation model dem from the shuttle radar topography mission srtm was used for orthorectification after post processing the error on the displacements is on the order of 2 4 m per correlation translated into annual velocities this error is reduced increased when the correlated images are more less than a year apart through application of a filtering procedure and several quality tests the consistency of the results is validated to provide confidence in the remotely sensed velocity measurements despite the lack of ground control this novel approach allows fast easy and economically viable acquisition of detailed glaciological data in areas of difficult access and provides a means for large scale monitoring of glaciers in high mountainous terrain

glacier surge mechanism 1982 1983 surge of variegated glacier alaska the hundredfold speedup in glacier motion in a surge of the kind the kind that took place in variegated glacier in 1982 1983 is caused by the buildup of high water pressure in the basal passageway system which is made possible by a fundamental and pervasive change in the geometry and water transport characteristics of this system the behavior of the glacier in surge has many remarkable features which can provide clues to a detailed theory of the surging process the surge mechanism is akin to a proposed mechanism of overthrust faulting

slight mass gain of karakoram glaciers in the early twenty first century the mass balance of hindu kush karakoram himalaya glaciers has been debated partly because of a severe lack of observations from the region an analysis of the regional mass balance of karakoram glaciers by comparison of digital elevation models from 1999 to 2008 reveals a small glacier mass gain in the area

repeated catastrophic valley infill following medieval earthquakes in the nepal himalaya geomorphic footprints of past large himalayan earthquakes are elusive although they are urgently needed for gauging and predicting recovery times of seismically perturbed mountain landscapes we present evidence of catastrophic valley infill following at least three medieval earthquakes in the nepal himalaya radiocarbon dates from peat beds plant macrofossils and humic silts in fine grained tributary sediments near pokhara nepal s second largest city match the timing of nearby m 8 earthquakes in 1100 1255 and 1344 c e the upstream dip of tributary valley fills and x ray fluorescence spectrometry of their provenance rule out local sources instead geomorphic and sedimentary evidence is consistent with catastrophic fluvial aggradation and debris flows that had plugged several tributaries with tens of meters of calcareous sediment from a higher himalayan source 60 kilometers away

tributary glacier surges an exceptional concentration at panmah glacier karakoram himalaya four tributaries of panmah glacier have surged in less than a decade three in quick succession between 2001 and 2005 since 1985 13 surges have been recorded in the karakoram himalaya more than in any comparable period since the 1850s ten were tributary surges in these ten a full run out of surge ice is prevented but extended post surge episodes affect the tributary and main glacier the sudden concentration of events at panmah glacier is without precedent and at odds with known surge intervals for the glaciers interpretations must consider the response of thermally complex glaciers at exceptionally high altitudes and of high relief to changes in a distinctive regional climate it is suggested that high altitude warming affecting snow and glacier thermal regimes or bringing intense short term melting episodes may be more significant than mass balance change