a chronology of holocene and little ice age glacier culminations of the steingletscher central alps switzerland based on high sensitivity beryllium 10 moraine dating abstract the amplitude and timing of past glacier culminations are sensitive recorders of key climate events on a regional scale precisely dating young moraines using cosmogenic nuclides to investigate holocene glacier chronologies has proven challenging but progress in the high sensitivity 10 be technique has recently been shown to enable the precise dating of moraines as young as a few hundred years in this study we use 10 be moraine dating to reconstruct culminations of the steingletscher a small mountain glacier in the central swiss alps throughout the holocene the outermost recorded positions of steingletscher most likely occurred in the early holocene and appear nearly synchronous with glacier culminations reported from other regions in the alps a late holocene position corroborates the evidence for a significant glacier advance of similar extent to that of the little ice age lia 3 kyr ago finally fourteen boulders from different moraines yield 10 be ages between 580 and 140 years with analytical precisions mostly 10 dating steingletscher advances during the lia because these lia 10 be ages are in stratigraphic order we tentatively distinguish four lia glacier culminations about 1470 ce 1650 ce 1750 ce and 1820 ce which are in good agreement with existing independent records during the lia in the swiss alps these findings illustrate the high potential of the 10 be moraine dating method to directly link paleo glacier chronologies to historical records and thus present day glacier evolution

detrital carbonate peaks on the labrador shelf a 13 7 ka template for freshwater forcing from the hudson strait outlet of the laurentide ice sheet into the subpolar gyre abstract the laurentide ice sheet lis was a large dynamic ice sheet in the early holocene the glacial events through hudson strait leading to its eventual demise are recorded in the well dated labrador shelf core md99 2236 from the cartwright saddle we develop a detailed history of the timing of ice sheet discharge events from the hudson strait outlet of the lis during the holocene using high resolution detrital carbonate ice rafted detritus ird 18o and sediment color data eight detrital carbonate peaks dcps associated with ird peaks and light oxygen isotope events punctuate the md99 2236 record between 11 5 and 8 0 ka we use the stratigraphy of the dcps developed from md99 2236 to select the appropriate r to calibrate the ages of recorded glacial events in hudson bay and hudson strait such that they match the dcps in md99 2236 we associate the eight dcps with h0 gold cove advance noble inlet advance initial retreat of the hudson strait ice stream hsis from hudson strait opening of the tyrrell sea and drainage of glacial lakes agassiz and ojibway the opening of foxe channel and retreat of glacial ice from foxe basin are represented by a shoulder in the carbonate data r of 350 years applied to the radiocarbon ages constraining glacial events h0 through the opening of the tyrell sea provided the best match with the md99 2236 dcps r values and ages from the literature are used for the younger events a very close age match was achieved between the 8 2 ka cold event in the greenland ice cores dcp7 8 15 ka bp and the drainage of glacial lakes agassiz and ojibway our stratigraphic comparison between the dcps in md99 2236 and the calibrated ages of hudson strait bay deglacial events shows that the retreat of the hsis the opening of the tyrell sea and the catastrophic drainage of glacial lakes agassiz and ojibway at 8 2 ka are separate events that have been combined in previous estimates of the timing of the 8 2 ka event from marine records sw iceland shelf core md99 2256 documents freshwater entrainment into the subpolar gyre from the hudson strait outlet via the labrador north atlantic and irminger currents the timing of freshwater release from the lis hudson strait outlet in md99 2236 matches evidence for freshwater forcing and lis icebergs carrying foreign minerals to the sw iceland shelf between 11 5 and 8 2 ka the congruency of these records supports the conclusion of the entrainment of freshwater from the retreat of the lis through hudson strait into the subpolar gyre and provides specific time periods when pulses of lis freshwater were present to influence climate

secondary palaeoremanence of tethyan sediments from the zanskar range nw himalaya summary palaeomagnetic investigations have been carried out on tethyan sediments from the nw zanskar range 33 9 n 76 5 e a total of 455 oriented samples from 41 sites were drilled from four stratigraphic units of middle cretaceous to early eocene age shillakong formation marpo limestone spanboth formation stumpata quartzarenite spanboth formation kong formation a characteristic remanence chrm could be isolated for 27 sites 254 specimens through detailed thermal and alternating field demagnetization and multicomponent analysis all the chrm directions identified are similar irrespective of geological age they fail the fold test and yield an overall in situ mean direction of d 336 6 i 39 6 with 95 5 9 and k 22 9 this corresponds to a palaeopole position at 66 5 n 323 5 e n pole isothermal remanence irm acquisition and thermal demagnetization of a saturation irm identify pyrrhotite as the dominant ferrimagnetic mineral and carrier of the chrm the pyrrhotite remanence is probably a thermoremanent magnetization acquired when the temperature of low grade metamorphism decreased below about 300 c the chrm directions are thus clearly secondary in origin and a negative conglomerate test carried out on the kong formation demonstrates that remanence acquisition post dates the early eocene the mean chrm inclination suggests that the remanence was acquired at about 20 n cooling events in the higher himalayan crystallines indicate an oligocene age for this remanence acquisition the mean chrm declination shows a counterclockwise rotation of 23 4 since remanence acquisition assuming remanence acquisition at about 30 myr ago a slight counterclockwise rotation of about 10 relative to the stable indian plate can be concluded this does not fit with the general pattern of palaeomagnetic results from neighbouring areas within the western syntaxis of the himalaya from which a clockwise rotation relative to the stable indian plate is expected for the zanskar range

paleolatitudes of the tibetan himalaya from primary and secondary magnetizations of jurassic to lower cretaceous sedimentary rocks the tibetan himalaya represents the northernmost continental unit of the indian plate that collided with asia in the cenozoic paleomagnetic studies on the tibetan himalaya can help constrain the dimension and paleogeography of greater india the indian plate lithosphere that subducted and underthrusted below asia after initial collision here we present a paleomagnetic investigation of a jurassic limestones and lower cretaceous volcaniclastic sandstones section of the tibetan himalaya the limestones yielded positive fold test showing a prefolding origin of the isolated remanent magnetizations detailed paleomagnetic analyses rock magnetic tests end member modeling of acquisition curves of isothermal remanent magnetization and petrographic investigation reveal that the magnetic carrier of the jurassic limestones is authigenic mag netite whereas the dominant magnetic carrier of the lower cretaceous volcaniclastic sandstones is detrital magnetite our observations lead us to conclude that the jurassic limestones record a prefolding remagnetiza tion whereas the lower cretaceous volcaniclastic sandstones retain a primary remanence the volcaniclastic sandstones yield an early cretaceous paleolatitude of 55 5 s 52 5 s 58 6 s for the tibetan himalaya suggesting it was part of the indian continent at that time the size of greater india during jurassic time cannot be estimated from these limestones instead a paleolatitude of the tibetan himalaya of 23 8 s 21 8 s 26 1 s during the remagnetization process is suggested it is likely that the remagnetization caused by the oxidation of early diagenetic pyrite to magnetite was induced during 103 83 or 77 67 ma the inferred paleolatitudes at these two time intervals imply very different tectonic consequences for the tibetan himalaya

cosmogenic 3he production rates from 39 n to 46 n latitude western usa and france the in situ production rate of cosmogenic 3he was determined in seven different olivine or pyroxene bearing rocks between the latitudes 39 n and 46 n the integrated production rate over the last 17 500 years is about 115 4 atoms gram yr for high latitude at sea level the variation in the integrated production rate between 2000 and 18 000 years is less than 30 and is probably on the order of 20 or less

cosmic ray labeling of erosion surfaces in situ nuclide production rates and erosion models a number of in situ cosmogenic radionuclides and stable nuclides have been measured in natural exposed rock surfaces with a view to study their in situ production and rock erosion rates 1 the in situ radionuclides can be used for a high resolution tomography of the erosional history of an exposed surface two stable nuclides 3he 21ne and five radionuclides 10be 26al 36cl 14c 39ar having half lives in the range of 300 1 5 106 yr half life are measurable in many rock types a prerequisite for the application of the in situ nuclides for the study of erosional histories of surfaces is a knowledge of their production rates under different irradiation conditions altitude latitude irradiation geometry and shielding relative nuclide production rates can be determined fairly accurately using the extensive available data on cosmic ray neutrons 2 absolute nuclide production rates cannot generally be predicted with any accuracy because of lack of data on excitation functions of nuclides unless some normalization is possible as was done in the case of several cosmic ray produced isotopes in the atmosphere 3 based on a recent natural calibration experiment in which erosion free surfaces exposed to cosmic radiation for 11 000 yrs were sampled the absolute production rates of 10be and 26al in quartz have been accurately estimated for mountain altitudes in sierra nevada 4 the absolute production rates of 10be and 26al in quartz can therefore be estimated fairly accurately for any given latitude and altitude some measurements of 14c in rocks of low erosion rate 5 similarly allow an estimate of its production rate attempts made to measure the in situ production rates of 3he in rocks have not yet led to a convergent production rate in view of the importance of knowing the production rates of isotopes of he ne and ar i present here theoretical estimates of their production rates based on available cross section data i discuss the information that can be extracted from the study of the in situ nuclides in rocks useful parameters characterizing the exposure history of a rock surface are 1 the effective surface exposure age and 2 the time averaged erosion rate the implications of these parameters for single and multiple nuclide studies are discussed in terms of the erosion models considered

paleomagnetic investigation of the early permian panjal traps of nw india regional tectonic implications abstract the 289 ma panjal traps of nw india kashmir are part of a series of rift related mafic suites abor sikkim etc that were erupted onto northern india present day coordinates around the same time as separation of the cimmerian blocks of qiangtang and sibumasu we report new data from only the second paleomagnetic investigation of this unit standard alternating field and thermal demagnetization methods were used to isolate characteristic magnetizations from seven outcrops at three locations within the kashmir valley nw india analysis of four sections 14 individual cooling units from close to srinagar that together form a tectonically coherent sequence spanning 3 km of stratigraphy yield a single component primary magnetization with a mean direction of dec 134 8 inc 55 3 95 8 9 k 21 0 an inclination only mean of 52 5 95 8 9 k 47 2 gives a paleolatitude of 33 s 5 a paleopole of 110 5 e 8 4 s a 95 10 7 is also calculated assuming the magnetization records a portion of the reverse polarity kiaman superchron the new result indicates extrusion of the panjal traps basalts at mid latitudes in the southern hemisphere by inference this constrains the location of central gondwana and informs debates related to cimmeria s detachment from gondwana

coupling of late orogenic tectonics and secondary pyrrhotite remanences towards a separation of different rotation processes and quantification of rotational underthrusting in the western himalaya northern india abstract the total amount of crustal shortening within the indian plate includes straight forward and rotational shortening the complex tectonic history of the western himalaya impedes a direct observation of rotational shortening between india and its northern margin a combination of palaeomagnetic results and tectonic structures along a 300 km nw se section from nw zanskar 33 9 n 76 5 e to malari 30 0 n 79 6 e in northern india enable a separation of rotations on different scales correction of the observed rotations and quantification of uniform rotational shortening new palaeomagnetic results from metacarbonates of the tethyan himalaya in sarchu losar and spiti and earlier studies from nw zanskar and malari reveal a characteristic remanent magnetisation carried by pyrrhotite unblocking spectrum 250 330 c negative fold tests 99 level indicated remanence acquisition after the main folding of the himalaya the formation of pyrrhotite during thermal events t 200 c suggests a remanence acquisition related to exhumation and cooling temperatures of about 200 300 c indicate a thermochemical remanence acquisition with an eohimalayan age dated in two areas by 40k 39ar techniques on illites the resulting rotation angles in respect to stable india show an anomalous counterclockwise rotation in nw zanskar and a trend of decreasing clockwise rotations to the se these variations may be attributed to meso scale 100 km tectonic features and oroclinal bending for the first time block rotations with respect to stable india are separated into local meso scale and regional significant ones after elimination of local and meso scale effects using structural analysis of late orogenic features modelled rotations due to oroclinal bending were subtracted regionally significant rotations of 0 20 clockwise are interpreted to be caused only by uniform rotational underthrusting

cambrian stratigraphy of kashmir and its boundary problems abstract the biostratigraphy of the cambrian of kashmir based on trilobite assemblage zones and trace fossils has been attempted faunal gaps occur in lower part of lower cambrian upper lower cambrian lower middle cambrian and upper part of upper cambrian in the lower cambrian cruziana rusophycus and redlichia zones in the middle cambrian solenopleura tonkinella tonkinella anomocare anomocare bailiella and bolaspidella zones and in the upper cambrian chuangia and dikelocephalites zones are recognized the position of intrasystem boundaries is also discussed while the various taxa have lithological preferences and are not necessarily found in a continuous sequence an attempt has been made to interpret the ranges of different genera the affinities of the fauna with that of other cambrian basins of the world are discussed it is concluded that the bulk of the fauna is of a cosmopolitan nature

chronology of the late weichselian glaciation in the bohemian forest in central europe abstract a glacial chronology based on in situ produced 10 be surface exposure dating of moraines in the bohemian forest central europe was established eleven exposure ages obtained for moraine boulders in the prasilske lake and laka lake valleys czech republic were complemented by 10 be ages from kleiner arbersee germany recalculated according to recently calibrated production rates in the northern hemisphere the glacial phases in the bohemian forest occurred during the last glacial maximum around 24 1 2 5 23 6 2 4 21 8 2 0 and 19 5 2 1 ka following phases of local glaciation occurred during the northern hemisphere deglaciation period around 16 ka and 14 ka the last indicated phase may correlate with older dryas the glacial chronology of the bohemian forest is in agreement with local glaciation chronologies in the giant mts krkonose mts and the eastern alps

palaeomagnetism of cretaceous to tertiary sediments from southern tibet evidence for the extent of the northern margin of india prior to the collision with eurasia abstract palaeomagnetic studies have been carried out on mid cretaceous to latest palaeocene sediments from the tethyan himalaya on the northern margin of the indian plate near the localities of gamba 28 3 n 88 5 e and duela 28 0 n 89 2 e in southern tibet a total of 61 sites more than 700 cores have been sampled mainly from limestones zongshan formation jidula formation member ii zongpu formation sandstones jidula formation member iii and graywackes gamba group member ii with ages well defined from detailed lithological and biostratigraphic analyses carriers of characteristic remanences are magnetite in limestones and graywackes and hematite in sandstones reliable palaeodirections were obtained from 35 sites 356 specimens positive fold tests antiparallel normal and reverse polarities a northward trend of the palaeolatitudes with decreasing age and absence of any metamorphic overprint indicate a primary origin for the characteristic remanences the results have been compared with expected palaeodirections according to available data for the indian subcontinent based on its present day geometry the late maastrichtian sites fourteen sites 156 specimens and the middle late palaeocene sites fourteen sites 113 specimens yield palaeolatitudes of 5 7 s and 4 0 n for the sampling localities in southern tibet respectively these palaeolatitudes are much further north than expected and imply that crustal shortening between the tethyan himalaya and the indian shield since the time of india eurasia collision has occurred on the order of 1500 km at the longitude of gamba duela comparison of our observed palaeolatitudes with palaeolatitudes for the lhasa block during cretaceous and palaeocene times indicate that initial contact of the northern indian margin with the lhasa block was already established at 65 60 ma with suturing completed at about 55 50 ma

reconstructing greater india paleogeographic kinematic and geodynamic perspectives abstract key in understanding the geodynamics governing subduction and orogeny is reconstructing the paleogeography of greater india the indian plate lithosphere that subducted since tethyan himalayan continental collision with asia here we discuss this reconstruction from paleogeographic kinematic and geodynamic perspectives and isolate the evolution scenario that is consistent with all three we follow recent constraints advocating a 58 ma initial collision and update a previous kinematic restoration of intra asian shortening with a recently proposed model that reconciles long debated large and small estimates of indochina extrusion our new reconstruction is tested against paleomagnetic data and against seismic tomographic constraints on paleo subduction zone locations the resulting restoration shows 1000 1200 km of post collisional intra asian shortening leaving a 2600 3400 km wide greater india from a paleogeographic sediment provenance perspective eocene sediments in the lesser himalaya and on undeformed india may be derived from tibet suggesting that all greater indian lithosphere was continental but may alternatively be sourced from the contemporaneous western indian orogen unrelated to india asia collision a quantitative kinematic paleomagnetic perspective prefers major cretaceous extension and a greater india basin opening within greater india but data uncertainty may speculatively allow for minimal extension finally from a geodynamic perspective assuming a fully continental greater india would require that subduction rates close to 20 cm yr was driven by a down going lithosphere crust assemblage more buoyant than the mantle which seems physically improbable we conclude that the greater india basin scenario is the only sustainable one from all three perspectives we infer that old pre collisional lithosphere rapidly entered the lower mantle sustaining high subduction rates whilst post collisional continental and young greater india basin lithosphere did not inciting the rapid india asia convergence deceleration 8 myr after collision subsequent absolute northward slab migration and overturning caused flat slab subduction tibetan shortening arc migration and arc volume decrease

late glacial and holocene 10be production rates for western norway we present a new regional calibration of the 10be production rate from two well dated surfaces insouthern norway a rock avalanche with 14c dated wood and a precisely dated younger dryas moraine c

marine magnetic anomalies palaeomagnetism and the drift history of gondwanaland abstract the results of palaeomagnetic surveys of mesozoic and tertiary rocks from gondwanaland can be reconciled with the results of modelling the evolution of oceanic floors from analyses of marine magnetic anomalies previous inconsistencies were mainly due to errors apparent in the australian cenozoic palaeomagnetic data an alternative tertiary apparent polar wander path apwp has been constructed from an analysis of all published laterite and weathered profile data palaeomagnetic results for africa antarctica australia india madagascar and south america are compared for rotations corresponding to marine magnetic anomalies 16 22 28 34 and m1 and for fit india has been selected as the reference continent since it provides the most detailed apwp having drifted about 50 of latitude since breakup

quaternary landscape development alluvial fan chronology and erosion of the mecca hills at the southern end of the san andreas fault zone abstract quantitative geomorphic analysis combined with cosmogenic nuclide 10 be based geochronology and denudation rates have been used to further the understanding of the quaternary landscape development of the mecca hills a zone of transpressional uplift along the southern end of the san andreas fault in southern california the similar timing of convergent uplifts along the san andreas fault with the initiation of the sub parallel san jacinto fault suggest a possible link between the two tectonic events the ages of alluvial fans and the rates of catchment wide denudation have been integrated to assess the relative influence of climate and tectonic uplift on the development of catchments within the mecca hills ages for major geomorphic surfaces based on 10 be surface exposure dating of boulders and 10 be depth profiles define the timing of surface stabilization to 2 6 5 6 1 3 ka qyf1 surface 67 2 5 3 ka qvof2 surface and 280 24 ka qvof1 surface comparison of 10 be measurements from active channel deposits qac and fluvial terraces qt illustrate a complex history of erosion sediment storage and sediment transport in this environment beryllium 10 catchment wide denudation rates range from 19 9 3 2 to 149 22 5 m ma and demonstrate strong correlations with mean catchment slope and with total active fault length normalized by catchment area the lack of strong correlation with other geomorphic variables suggests that tectonic uplift and rock weakening have the greatest control the currently measured topography and denudation rates across the mecca hills may be most consistent with a model of radial topographic growth in contrast to a model based on the rapid uplift and advection of crust

the timing of india asia collision onset facts theories controversies abstract the timing of initial collision between india and asia has remained controversial for half a century this paper attempts to review this crucial and hotly debated argument describing first the different methods used to constrain the age of collision and discussing next the rationale results inferences and problems associated with each we conclude that stratigraphy represents the best direct way to unravel collision chronology other methods focusing on the magmatic metamorphic or paleomagnetic record provide additional fundamental constraints but cannot provide a robust direct estimate of collision onset initial collision in the central eastern himalaya is dated directly at the middle paleocene 59 1 ma by the abrupt change in sediment provenance recorded in trench settings the quasi synchronous unconformities documented along both tethyan passive margin of india and active margin of asia from tibet to zanskar ladakh confirm that orogeny was underway at the close of the paleocene 56 ma well before the disappearance of marine seaways in the himalaya during the early middle eocene 50 45 ma sedimentary evolution and provenance changes in marine to fluvio deltaic successions are recorded synchronously within error from the western to the central eastern himalaya failing to provide conclusive evidence for diachronous collision these coherent observations are hard to reconcile with three widely cited hypotheses invoking either paleogene arc continent collision or late cretaceous ophiolite obduction or the protracted existence of a greater india basin which are all not favored after discussing the geological evidence critically point by point a scenario no more complex than the one involving solely the passive continental margin of india and the active continental margin of asia is needed to explain the geological evolution of the nascent himalaya the collision between the tethys himalaya and the transhimalayan arc trench system does represent the collision between india and asia because the yarlung zangbo ophiolite is the forearc basement of the asian active margin its obduction onto india could not have preceded the initial closure of neo tethys ophiolite obduction began when collision began in the middle paleocene

a chironomid based reconstruction of late glacial summer temperatures in the southern carpathians romania late glacial and early holocene summer temperatures were reconstructed based on fossil chironomid assemblages at lake brazi retezat mountains with a joint norwegian swiss transfer function providing an important addition to the late glacial quantitative climate reconstructions from europe the pattern of the late glacial temperature changes in lake brazi show both similarities and some differences from the ngrip 18o record and other european chironomid based reconstructions our reconstruction indicates that at lake brazi 1740 m a s l summer air temperature increased by 2 8 c at the oldest dryas bolling transition gs 2 gi 1 and reached 8 1 8 7 c during the late glacial interstade the onset of the younger dryas gs 1 was characterized by a weak 1 c decrease in chironomid inferred temperatures similarly at the gs 1 holocene transition no major changes in summer temperature were recorded in the early holocene summer temperature increased in two steps and reached 12 0 13 3 c during the preboreal two short term cold events were detected during the early holocene between 11 480 11 390 and 10 350 10 190 cal yr bp the first cooling coincides with the preboreal oscillation and shows a weak 0 7 c temperature decrease while the second is characterized by 1 c cooling both cold events coincide with cooling events in the greenland ice core records and other european temperature reconstructions

timing of glaciation during the last glacial cycle evaluating the concept of a global last glacial maximum lgm abstract it has long been known that mountain glaciers and continental ice sheets around the globe reached their respective maximum extent at different times during the last glacial cycle often well before the global last glacial maximum lgm c 23 19 ka which is formally defined by peaks in global sea level and marine oxygen isotope records however there is increasing evidence from around the world that it was not only mountain glaciers which were asynchronous with the global lgm but also some regions of the large continental glaciers the barents kara ice sheet in northern eurasia together with a majority of ice masses throughout asia and australasia reached their maximum early in the last glacial cycle a few thousand years before the global lgm period the east antarctic ice sheet also reached its maximum extent several millennia before the global lgm in numerous mountainous regions at high mid and low latitudes across the world glaciers reached their maximum extent before marine isotope stage mis 2 in mis 5 4 and 3 this is in contrast to most sectors of the laurentide ice sheet the cordilleran ice sheet the se sector of the fennoscandinavian ice sheet and the alpine ice sheet in central europe which appear to have reached their maximum close to the global lgm in mis 2 the diachronous maximum extents of both mountain glaciers and continental ice sheets during the last glacial cycle means that the term and acronym last glacial maximum lgm has limited chronostratigraphical meaning when correlating glacial deposits and landforms

palaeomagnetic constraints on formation of the mianwali reentrant trans indus and western salt range pakistan abstract successions of lower to lower middle cambrian upper permian to upper triassic and lower tertiary carbonates and arenites have been sampled in five sections representative of the three main segments of the mianwali reentrant in the trans indus salt range northern pakistan i e the southern khisor range the northern surghar range and the western salt range comparison of primary and secondary magnetization directions with the indian apwp demonstrates the secondary origin of the mianwali reentrant and shows a pattern of rotations which varies in sense and magnitude along the reentrant with the main structural trends data from the trans indus and western salt range and published early cambrian early permian and late tertiary palaeomagnetic results from the southern salt range and the potwar plateau show that the hazara arc underwent a 20 45 counterclockwise rotation relative to the indian shield a contrasting clockwise rotation over about 45 has recently been established for thrust sheets in the opposing eastern limb of the western himalayan syntaxis i e for the panjal nappe 1 and the riasi thrust sheet 2 these palaeomagnetically established rotations conform with the about 75 azimuthal change in structural trend along the syntaxis and support crawford s 3 suggestion that the salt range was originally in line with the northwestern himalaya the salt range front prograded and moved southwards as part of the hazara arc thrust sheet detached from basement along the evaporitic salt range formation the mianwali reentrant originated through obstruction of the southwards advancing thrust sheet by moulding around basement topography of the northwest oriented sarghoda ridge

remagnetization of carbonate rocks in southern tibet perspectives from rock magnetic and petrographic investigations netherlands organization for scientific research nwo with a rubicon grant 825 15 016 institute for rock magnetism irm at the university of minnesota instruments and facilities program of nsf erc starting grant 306810 nwo vidi 864 11 004

form flow interactions of an aeolian saucer blowout airflow patterns through a saucer blowout are examined from wind speed and direction measurements made during a chinook wind event the blowout long axis is oriented east west with a broad depositional apron on the east side wind directions during the event rotated from south westerly to westerly permitting an assessment of oblique and axis parallel flows results show that airflow passing over the windward rim of the saucer blowout expands and decelerates leading to flow separation and a small re circulation zone on sheltered lee slopes near the deflation basin airflow re attaches to the blowout surface and accelerates up to a small opening in the east rim where it can be up to 50 faster than on the windward edge beyond the downwind rim the airflow expands and decelerates and sand is deposited onto a broad apron similar to coastal trough blowouts the degree of airflow steering and acceleration along the deflation basin is determined by the angle of incidence between the approach wind and the long axis of the blowout as the angle of incidence increases wind speed accelerates at 0 3 m above the surface of the deflation basin and the degree of airflow steering increases overall a two fold process is identified where south westerly flows have greater potential for eroding the deflation basin while westerly flows have greater potential for evacuating sand from within the blowout visual observations indicate that sand eroded from the deflation basin during south westerly flows is re distributed to adjacent zones of low wind speed until axis parallel winds evacuate the sand through the opening in the east rim morphometric changes since 1994 indicate that the blowout morphology has remained relatively constant suggesting a persistent interplay between oblique and axis parallel wind erosion events collectively these findings indicate that the angle of approach winds is an important control on saucer blowout morphodynamics copyright 2009 john wiley sons ltd

evolution of the subglacial hydrologic system beneath the rapidly decaying cordilleran ice sheet caused by ice dammed lake drainage implications for meltwater induced ice acceleration abstract a positive correlation between ice dammed lake drainage and ice acceleration at antarctic ice sheets ais and land terminating sections of the greenland ice sheet gris has been implicated in enhanced ice sheet decay however the paucity of direct measurements at the ice sheet bed restricts our understanding of subglacial drainage system evolution in response to transient water inputs we present evidence that two meltwater corridors on the former bed of the thin 600 m at last glacial maximum over the interior plateaus of british columbia and rapidly decaying cordilleran ice sheet cis were generated subglacially in response to the drainage of an ice dammed lake and operated as canals tunnel channels geomorphological ground penetrating radar gpr and electrical resistivity tomography ert data reveal a simple event sequence that includes initial propagation of a broad at least 2 5 km wide floodwave inefficient drainage from an ice dammed lake over relatively short 3 24 km zones at the corridor heads that collapsed into efficient canals large up to 0 25 2 5 km wide channels incised down into the sediment bed and up into the ice downglacier canal formation on the southern fraser plateau involved synchronous along the full canal length system development including elements of headward erosion and plunge pool formation our data suggest that ice dammed lake drainage beneath a rapidly decaying thin ice mass that has an efficient antecedent drainage network is not conducive to large scale ice acceleration these data may aid better assessment of the role of ice dammed lake drainage on the dynamics of former as well as contemporary ice sheets

a primitive clupeomorph from the albian loon river formation northwest territories canada foreyclupea loonensis gen et sp nov is described from the early middle albian loon river formation of the northwest territories canada the only specimen of the new species was originally described as a part of an enigmatic taxon erichalcis arcta in 1975 which was assigned to the clupeomorpha since then e arcta has proven to be a composite taxon made up of clupeomorph and non clupeomorph specimens the non clupeomorph material was redescribed as a euteleostei incertae sedis and retained the species name described herein is the fossil clupeomorph specimen originally assigned to erichalcis arcta as in other members of the superorder clupeomorpha the ventral margin of the body in the specimen is covered with spiny scutes and the supratemporal commissural sensory canal passes through the parietals along with these diagnostic characters the new taxon also shows primitive traits of the basal members of the group including a medioparietal skull roof unfused halves of the neural spines of the a

the indus tsangpo suture zone in ladakh northwest himalaya further palaeomagnetic data and implications abstract a total of 81 samples 244 specimens from upper cretaceous indus molasse and middle to upper cretaceous dras flyschoids of the indus tsangpo suture zone in ladakh northwest himalaya has been studied by thermal demagnetization methods both formations showed a characteristic magnetization component indicative for equatorial to low northern palaeolatitudes of acquisition similar palaeolatitudes have been obtained before from secondary magnetization components of early tertiary age in the ladakh intrusives and in the tibetan sedimentary series of central nepal the present characteristic components are interpreted likewise as secondary magnetizations which stabilized between 50 and 60 m y ago during greater india s collision with asia s southern margin the dras flyschoids show another magnetic component which in case of primary origin indicates acquisition at a low southern palaeolatitude if correct this interpretation supports recent suggestions for late cretaceous obduction of an island arc on greater india s northern margin

cirque form and development in romania allometry and the buzzsaw hypothesis abstract a complete inventory of the 631 glacial cirques in romania and adjacent ukraine shows that they are scale specific and develop allometrically extending in length more rapidly than they deepen shape changes with size horizontal dimensions are around 700 m vertical around 300 m on each quantitative measure they form a single unimodal population with limited variation in size on a logarithmic scale cirque axial gradients 15 33 are appropriate to occupation by rotationally flowing glaciers lake basins are more common 26 on granitic rocks compared with 10 6 of all cirques geology also affects vertical dimensions and gradients the relation between subjective five grades and objective measures of cirque development is shown by an r 2 of 62 when grade is predicted from maximum gradient minimum gradient and plan closure cirques larger in horizontal dimensions have better grades cirque floors cover around 28 of cirque map area larger cirques and nested inner and outer cirques are common in ranges that rose well above the snowline and are associated with more extensive more symmetrical glaciation and more cols in size and shape romanian cirques are similar to those in england and wales they are similar in some respects to those in part of the british columbia coast mountains except for smaller vertical dimensions they may have developed only in the last few glaciations mountain ranges can be ranked by degree of glacial modification and symmetry of glaciations the buzzsaw hypothesis is applicable only in the cores of the higher ranges elsewhere summit surfaces that are essentially preglacial survive

rotational overthrusting of the northwestern himalaya further palaeomagnetic evidence from the riasi thrust sheet jammu foothills india abstract thermal demagnetization results 316 samples are presented for the tertiary succession of the riasi thrust sheet jammu foothills northwestern himalaya primary and secondary magnetization directions of murree group red beds miocene to upper eocene sampled northeast of jammu indicate for this part of the riasi thrust sheet a clockwise rotation over about 45 with respect to the indian shield since late eocene early miocene time this accords with clockwise rotations of similar magnitude observed in the panjal nappe and the krol belt and is interpreted as representative for the northwestern himalaya results from the western part of the kalakot inlier sampled northwest of jammu i e basal murree claystone middle eocene and carbonate from the subathu group lower middle to lower eocene indicate an aberrant 20 25 counterclockwise rotation which is of local importance only available observations on rotation of himalayan thrust sheets with respect to the indian shield indicate that the himalayan arc has formed through oroclinal bending this supports powell and conaghan s and veevers et al s model of greater india with large scale intracontinental underthrusting along the main central thrust beneath the tibetan plateau minimal magnitudes of underthrusting of 550 km in the krol belt and 650 km in the thakkhola region are concluded palaeolatitude observations herein and in 1 agree with absolute positioning of the indian plate based on india africa relative movement data fixed to a hotspot frame in the atlantic ocean and with palaeolatitude observations from dsdp cores on the indian plate collision related secondary magnetic components observed both to the north and to the south of the indus tsangpo suture zone show palaeolatitudes between the equator and 7 n comparison of both datasets indicates that initial contact between greater india and south central asia had been established in the hindu kush karakorum region by about 60 ma ago whereas eastwards progressive suturing had advanced to the lhasa block segment of the indus tsangpo suture zone before 50 ma ago

dendrohydroclimate reconstructions of july august runoff for two nival regime rivers in west central british columbia lengthy records of river discharge are necessary to comprehensively assess the long term connection between synoptic climate forcings and nival regime systems in british columbia a regional multispecies network of tree ring width and ring density chronologies was built for west central british columbia with the intention of dendrohydrologically extending short runoff records in this area extended records of july august mean discharge anomalies for the skeena and atnarko rivers were reconstructed back to ad 1660 low flow events represented during the late 1600s early 1700s and late 1800s lie beyond those experienced during the recent instrumental period for these basins the documentation of extreme events of this magnitude necessitates consideration when planning for future water resources in this region supplementary dendroclimatic reconstructions of the winter pacific north american pna pressure anomaly pattern and records of mean summer temperature and end of winter snow water equivalent were also constructed these ancillary climate records provide insight into the long term climate drivers of annual discharge dynamics within these nival basins correlation and wavelet analyses confirm the persistent relationship of synoptic climate regimes described by the southern oscillation index nino 3 4 pacific decadal oscillation and pna indices on runoff in west central british columbia copyright 2012 john wiley sons ltd

interhemispheric atlantic seesaw response during the last deglaciation the asynchronous relationship between millennial scale temperature changes over greenland and antarctica during the last glacial period has led to the notion of a bipolar seesaw which acts to redistribute heat depending on the state of meridional overturning circulation within the atlantic ocean here we present new records from the south atlantic that show rapid changes during the last deglaciation that were instantaneous within dating uncertainty and of opposite sign to those observed in the north atlantic our results demonstrate a direct link between the abrupt changes associated with variations in the atlantic meridional overturning circulation and the more gradual adjustments characteristic of the southern ocean these results emphasize the importance of the southern ocean for the development and transmission of millennial scale climate variability and highlight its role in deglacial climate change and the associated rise in atmospheric carbon dioxide

accuracy of cosmogenic ages for moraines analyses of all published cosmogenic exposure ages for moraine boulders show an average age range of 38 between the oldest and youngest boulders from each moraine this range conflicts with the common assumption that ages of surface boulders are the same as the age of the landform the wide spread in boulder ages is caused by erosion of the moraine surface and consequent exhumation of fresh boulders a diffusion model of surface degradation explains the age range and shows that a randomly sampled small set of boulders n 3 7 will always yield a lower age limit for the moraine the model indicates that for identical dating accuracy six to seven boulders are needed from old and tall moraines 40 000 100 000 yr 50 100 m initial height but only one to four boulders from small moraines 20 000 100 000 yr 10 20 m by following these guidelines the oldest obtained boulder age will be 90 of the moraine age 95 probability this result is only weakly sensitive to a broad range of soil erosion rates our analysis of published boulder ages indicates that 3 of all moraine boulders have prior exposure and 85 of these boulders predate the dated moraine

age and significance of core complex formation in a very curved orogen evidence from fission track studies in the south carpathians romania abstract twenty four new zircon and apatite fission track ages from the getic and danubian nappes in the south carpathians are discussed in the light of a compilation of published fission track data a total of 101 fission track ages indicates that the getic nappes are generally characterized by cretaceous zircon and apatite fission track ages indicating cooling to near surface temperatures of these units immediately following late cretaceous orogeny the age distribution of the danubian nappes presently outcropping in the danubian window below the getic nappes depends on the position with respect to the cerna jiu fault eocene and oligocene zircon and apatite central ages from the part of the danubian core complex situated southeast of this fault monitor mid tertiary tectonic exhumation in the footwall of the getic detachment while zircon fission track data from northwest of this fault indicate that slow cooling started during the latest cretaceous the change from extension getic detachment to strike slip dominated tectonics along the curved cerna jiu fault allowed for further exhumation on the concave side of this strike slip fault while exhumation ceased on the convex side the available fission track data consistently indicate that the change to fast cooling associated with tectonic denudation by core complex formation did not occur before late eocene times i e long after the cessation of late cretaceous thrusting core complex formation in the danubian window is related to a larger scale scenario that is characterized by the nnw directed translation followed by a 90 clockwise rotation of the tisza dacia block due to roll back of the carpathian embayment this led to a complex pattern of strain partitioning within the tisza dacia block adjacent to the western tip of the rigid moesian platform our results suggest that the invasion of these southernmost parts of tisza dacia started before the late eocene i e significantly before the onset of miocene age rollback and associated extension in the pannonian basin

a palaeomagnetic reconnaissance of kashmir northwestern himalaya india abstract thermal demagnetization studies of 800 palaeozoic and lower mesozoic samples mainly carbonates from 14 localities in kashmir showed four magnetic components a a recent field component of normal polarity and large intensity b a middle to late tertiary secondary component of large intensity and of reversed and normal polarity which indicates clockwise rotation of central and eastern kashmir over approximately 45 with respect to peninsular indo pakistan c primary magnetic components of triassic late permian early carboniferous siluro ordovician and middle to early ordovician age the triassic and late permian components show a 20 30 cumulative counterclockwise offset with respect to the indo pakistan apparent polar wander path apwp this indicates a post middle to late triassic counterclockwise rotational movement of kashmir over 65 75 with respect to peninsular indo pakistan d a component of low inclination and predominantly east west declination which is observed only in rocks of pre panjal traps age a secondary origin associated with extrusion of the panjal traps flows is surmised but could not be established beyond doubt alternatively this component may be related to the regional foliation the triassic and late permian primary component directions are predominantly of normal polarity this suggests a pre punjabian late permian upper age limit for the permo carboniferous kiaman reversed polarity interval which is earlier than the early to late tatarian limit observed in the u s s r

exhumation of the danubian nappes system south carpathians during the early tertiary inferences from kinematic and paleostress analysis at the getic danubian nappes contact abstract a detailed kinematic study based on the analysis of brittle structures combined with a description of structures in the adjacent foredeep allows for the definition of three major tectonic episodes during the late cretaceous tertiary evolution of the central part of the south carpathians following middle cretaceous and older orogenic phases the first tectonic event that affected the studied area was a late cretaceous nnw sse oriented contraction which led to the final major emplacement of the danubian and getic nappes during the paleogene early miocene an extension event induced rapid exhumation of the danubian units leading to the formation of large normal faults dipping towards both the foreland and the hinterland this extension together with dextral rotation of the south carpathians around the western corner of the moesian platform allows for the ne ward movement of the internal continental blocks with respect to the foreland platforms in the late miocene e ward translation of the internal south carpathians units with respect to the moesian platform was accommodated through a large scale e w oriented strike slip corridor within the south carpathians the general paleogene early miocene ne to e ward rotation and the late miocene e ward translation of the rhodopian fragment allowed for the accommodation of roll back and contraction taking place in the east carpathians

10be exposure age chronology of the last glaciation in the krkonose mountains central europe abstract a new chronology of the last glaciation is established for the krkonose giant mountains central europe based on in situ produced 10be in moraine boulders exposure ages and schmidt hammer rebound values obtained for terminal moraines on the northern and southern flank of the mountains suggest that the oldest preserved moraines represent early phases of the last glacial maximum lgm large moraines at the outlet of the snowy cirques niezne kotly and in the middle part of the upa ob i d l trough were deposited around 21 ka while a series of smaller moraines above the lgm deposits represent readvances that occurred no later than 18 1 0 6 ka 15 7 0 5 ka 13 5 0 5 ka and 12 9 0 7 ka an exposure age of 13 8 0 4 ka obtained for protalus ramparts at the foot of the upska jama cirque headwall indicates that glaciers advanced only in north to east facing cirques during the lateglacial the last glacier fluctuation was synchronous with the younger dryas cold event the timing of local glacier advances during the last glacial episode correlates with the late weichselian glacier phases in the alps and in the bavarian bohemian forest

cretaceous paleomagnetic results from western tibet and tectonic implications we present paleomagnetic results obtained from samples collected in the summer of 1989 along a 1000 km traverse between yecheng xinjiang and shiquanhe tibet in the western qinghai xizang plateau along 80 e longitude during this field trip 480 paleomagnetic cores in jurassic to tertiary limestones and sandstones were drilled at 49 sites 400 were measured isothermal remanent magnetization analysis indicates the existence of high coercivity minerals and thermal rather than alternating field demagnetization was found to be more efficient in isolating paleomagnetic directions the characteristic magnetization has rather low unblocking temperatures 250 560 c in most limestone samples and higher unblocking temperatures 400 c 680 c in the sandstone samples about half of the measured samples show the present geomagnetic field or aberrant directions the remainder display stable multicomponent magnetizations the stable characteristic magnetizations indicate 1 a probable jurassic remagnetization 2 a cretaceous 120 80 ma magnetization which passes a fold test yielding a mean pole at 66 2 n 245 0 e a95 5 1 n 14 sites and 3 a large scatter of tertiary directions which may be due to tectonic problems and or remagnetization in the sampling zone the cretaceous paleodirections from aksaichin and longmuco 11 sites on the qiangtang north tibet block are very similar to those from shiquanhe three sites on the lhasa south tibet block separated by 300 km this suggests that the north and south tibet blocks formed a single unit at least as early as the cretaceous comparing our results with previous paleomagnetic work on the tibetan plateau it is found that the paleolatitude of 10 6 5 1 obtained from this study for a reference at domar 33 75 n 80 4 e is close to that 9 6 2 8 obtained by achache et al 1984 and lin and watts 1988 from the takena formation 110 100 ma in the lhasa region 30 n 91 e in addition it appears that the southern margin of the tibetan blocks i e eurasia occupied an e w trending position at about 7 6 n latitude paleodeclination differences between the western and eastern tibetan blocks suggest internal deformations of the plateau at different scales from 1 to 1000 km according to differences in paleomagnetic declinations the arcuate shape of the blocks would have been partly acquired after the collision

deglaciation chronology and paleoclimate of the pieciu stawow polskich roztoki valley high tatra mountains western carpathians since the last glacial maximum inferred from 36cl exposure dating and glacier climate modelling abstract exposure dating of abraded bedrock surfaces below glacial trimlines in the pieciu stawow polskich roztoki valley using cosmogenic 36 cl has been applied to determine the deglaciation chronology in the study area nineteen rock samples yielded ages between 21 5 and 9 5 ka the spatial distribution of ages provides evidence of progressive downwasting of glaciers within the study area dates of exposure indicate that the onset of ice volume decrease occurred no later than 21 5 ka this provides evidence that the local maximum glaciation occurred in accordance with the global last glacial maximum lgm the first period of deglaciation in the study area was completed around 18 ka further significant loss of ice volume is confirmed between 15 and 13 ka the spatial distribution of chronological data within the pieciu stawow polskich valley indicates post lgm readvances of glaciers around 17 ka and 12 ka using the glacier modelling and paleoclimate proxies from the study area the early late glacial glacier had been stable with a 9 10 c decrease in temperature and 30 50 lower precipitation in relation to modern conditions the subsequent advance took place with temperatures 6 7 c lower and 10 30 less precipitation the timing of the readvances is nearly synchronous with late glacial advances in the european alps southern carpathians and anatolian peninsula this suggests synchronicity of major climatic fluctuations across central europe and the northern margin of the mediterranean basin

deglaciation constraints in the parâng mountains southern romania using surface exposure dating cosmogenic nuclide surface exposure ages have been widely used to constrain glacial chronologies in the european regions this paper brings new evidence that the romanian carpathians sheltered mountain glaciers in their upper valleys and cirques until the end of the last glaciation twenty four 10be surface exposure ages were obtained from boulders on moraine crests in the central area of the par ng mountains southern carpathians exposure ages were used to constrain the timing of the deglaciation events during the late glacial the lowest boulders yielded an age of 13 0 1 1 1766 m and final deglaciation occurred at 10 2 0 9 ka 2055 m timing of the late glacial events and complete deglaciation reported in this study are consistent with and confirm previously reported ages of deglaciation within the carpathian and surrounding european region

the himalayan arc large scale continental subduction oroclinal bending and back arc spreading abstract palaeomagnetic results from the himalayan arc and southern tibet compared with simulated apparent polar wander paths for the indian plate show a consistent pattern of rotations of the himalayan arc relative to the indian shield varying gradually from 45 clockwise in the northwestern himalaya to slightly counterclockwise in the lhasa region this pattern is consistent with continental underthrusting of greater india beneath the tibetan plateau since the early miocene over at least 650 km at the longitude of western nepal and oroclinal bending since the latest miocene available palaeomagnetic observations support the steady state model for the formation of the himalayan arc with refinements as follows 1 collision between greater india s northern boundary and southern asia occurred at equatorial latitudes with progressive suturing from palaeocene in the northwestern himalaya until early eocene in the eastern himalaya 2 continuing convergence and indentation of greater india into southern asia over about 2000 km up to the early miocene resulted in southeastward extrusion of indochina and 3 neogene counterclockwise rotational underthrusting of greater india along the main central thrust with pliocene quaternary oroclinal bending of the himalayan arc

a palaeomagnetic reconnaissance of northeastern baluchistan pakistan a total of 560 samples from three areas in northeastern baluchistan the southern sulaiman range the central loralai range and the northern kirthar range were analyzed using thermal demagnetization techniques thirteen formations of late palaeozoic to early tertiary age were studied palaeomagnetically inclinations of the obtained results show a general affinity with the indian apparent polar wander path deviating declinations from the loralai range indicate a clockwise rotation over 50 with respect to the indian shield secondary magnetization components probably of late palaeocene to early eocene age were consistently present in the samples from the kirthar range and the sulaiman range but were not observed in samples from the loralai range acquisition of these components is attributed to crustal upwarping during the palaeocene which is tentatively related to initial collision of continental indo pakistan with an island arc off south central asia the baluchistan data support recent palaeomagnetic results from the indus tsangpo suture zone in ladakh nw himalaya which indicate that such an initial collision took place at very low northern palaeolatitudes

ordovician magnetostratigraphy a correlation of global data palaeomagnetic studies where primary magnetizations are established from well dated rocks have been compiled to construct a magnetostratigraphic time scale for the ordovician period an excellent correlation of magnetozones is observed between independent studies of the baltic and south siberian platform sequences supplemental datasets from other continents concur with the baltic and siberian polarity data early ordovician times were mainly characterized by a reverse field rapid reversals then occurred during llanvirn and llandeilo times late ordovician times were dominated by a normal polarity field some gaps remain in the polarity record notably for late caradoc early ashgill and mid tremadoc times

revised deglaciation history of the pietrele stânisoara glacial complex retezat mts southern carpathians romania abstract although geomorphological evidences of quaternary glaciations of the southern carpathians were extensively studied and discussed the limited number of chronological studies resulted in poor and controversial knowledge on the age of glaciations and deglaciation of the area we use new and recalculated in situ produced 10be surface exposure ages of glacial landforms to shed light on the age of the maximum glacial extent and the glacier oscillations during the last deglaciation process on the northern side of the retezat mountains according to our data the maximum ice extent documented by preserved moraines occurred around 21 0 1 5 0 8 ka coincident with the global last glacial maximum lgm the deglaciation process during the lateglacial was characterized by two glacial advances at 18 6 0 8 0 9 and 16 3 0 6 0 6 ka inferred stabilization date of the penultimate glacial stage at 15 2 0 8 0 7 ka was closely followed by the abrupt warming at the onset of the bolling allerod documented by a local chironomid based temperature reconstruction the last small glacier advance was dated to 13 5 0 4 0 5 ka these recessional readvance phases agree with other european glacial chronologies

the last glacial termination a major puzzle of paleoclimatology is why after a long interval of cooling climate each late quaternary ice age ended with a relatively short warming leg called a termination we here offer a comprehensive hypothesis of how earth emerged from the last global ice age a prerequisite was the growth of very large northern hemisphere ice sheets whose subsequent collapse created stadial conditions that disrupted global patterns of ocean and atmospheric circulation the southern hemisphere westerlies shifted poleward during each northern stadial producing pulses of ocean upwelling and warming that together accounted for much of the termination in the southern ocean and antarctica rising atmospheric co2 during southern upwelling pulses augmented warming during the last termination in both polar hemispheres

magmatism and metamorphism in the ladakh himalayas the indus tsangpo suture zone abstract ladakh india provides a complete geological section through the northwestern part of the himalayas from kashmir to tibet within this section the magmatic metamorphic and geotectonic evolution of the northern himalayan orogeny has been studied using petrographic geochemical and isotope analytical techniques the beginning of the himalayan cycle was marked by large basaltic extrusions panjal trap of permian to lower triassic age at the northern margin of the gondwana continent indian shield these continental type tholeiitic basalts were followed by a more alkaline volcanism within the triassic to jurassic lamayuru unit of the gondwana continental margin lower jurassic to cretaceous oceanic crust and sediments ophiolitic melange s s accompany the triassic to cretaceous flysch deposits within the indus tsangpo suture zone the major structural divide between the indian shield high himalaya and the tibetan platform so far no relic of paleozoic oceanic crust has been found subduction of the tethyan oceanic crust during upper jurassic and cretaceous time produced an island arc represented by tholeiitic and calc alkaline volcanic rock series dras volcanics and related intrusives accompanied by volcaniclastic flysch deposits towards the tibetan continental margin subsequent to the subduction of oceanic crust large volumes of calc alkaline plutons trans himalayan or kangdese plutons intruded the tibetan continental margin over a distance of 2000 km and partly the dras island arc in the ladakh region the collision of the indian shield and tibetan platform started during the middle to upper eocene and caused large scale still active intracrustal thrusting as well as the piling up of the himalayan nappes the tectonically highest of these nappes is built up of oceanic crust and huge slices of peridotitic oceanic mantle spongtang klippe in the high himalayas the tectonic activity was accompanied and outlasted by a barrovian type metamorphism that affected triassic sediments of the kashmir nun kun synclinorium up to kyanite staurolite grade and the deeper seated units up to sillimanite grade cooling ages of micas are around 20 m y muscovite and 13 m y biotite towards the indus tsangpo suture zone metamorphism decreases with no obvious discontinuity through greenschist prehnite pumpellyite to zeolite grade remnants of possibly an eo himalayan blueschist metamorphism have been found within thrust zones accompanying ophiolitic melange in the suture zone

cosmocalc an excel add in for cosmogenic nuclide calculations as dating methods using terrestrial cosmogenic nuclides tcn become more popular the need arises for a general purpose and easy to use data reduction software the cosmocalc excel add in calculates tcn production rate scaling factors using lal stone dunai and desilets methods topographic snow and self shielding factors and exposure ages erosion rates and burial ages and visualizes the results on banana style plots it uses an internally consistent tcn production equation that is based on the quadruple exponential approach of granger and smith 2000 cosmocalc was designed to be as user friendly as possible although the user interface is extremely simple the program is also very flexible and nearly all default parameter values can be changed to facilitate the comparison of different scaling factors a set of converter tools is provided allowing the user to easily convert cut off rigidities to magnetic inclinations elevations to atmospheric depths and so forth because it is important to use a consistent set of scaling factors for the sample measurements and the production rate calibration sites cosmocalc defines the production rates implicitly as a function of the original tcn concentrations of the calibration site the program is best suited for be 10 al 26 he 3 and ne 21 calculations although basic functionality for cl 36 and c 14 is also provided cosmocalc can be downloaded along with a set of test data from http cosmocalc googlepages com

contributions and unrealized potential contributions of cosmogenic nuclide exposure dating to glacier chronology 1990 2010 abstract this paper reviews the application of cosmogenic nuclide exposure dating to glacier chronology exposure dating of glacial landforms has made an outsize impact on this field because the technique filled an obvious need that had already been recognized by glacial geologists by now hundreds of studies have used cosmogenic nuclide exposure dating to date glacial deposits and in fact it is rare to find a study of glacial geology or glacier chronology or any paleoclimate synthesis that makes use of such studies that does not involve exposure dating these developments have resulted in major contributions to glacier chronology and paleoclimate in particular i reconstructing antarctic ice sheet change ii establishing the chronology of late pleistocene and holocene glacier change in mountain regions where it was previously unknown iii establishing the broad chronological outlines of mountain glaciations prior to the last glacial maximum and iv gaining insight into subglacial erosional processes through the observation that many glaciated surfaces preserve cosmogenic nuclide inventories from long past ice free periods as well as the present one an important potential future contribution will be the application of the large data set of exposure dated glacier chronologies to better understand global and regional climate dynamics during lateglacial and holocene millennial scale climate changes however this contribution cannot be realized without significant progress in two areas i understanding and accounting for geologic processes that cause apparent exposure ages on glacial landforms to differ from the true age of the landform and ii minimizing systematic uncertainties in exposure ages that stem from cosmogenic nuclide production rate estimates and scaling schemes at present there exists an enormous data set of exposure ages on glacial deposits but these data cannot be used to their full potential in paleoclimate syntheses due to an inadequate understanding of geologic scatter and production rate uncertainties the intent of this paper is to highlight this situation and suggest some strategies for realizing this potential

palaeomagnetic results from the tibetan sedimentary series of the manang area north central nepal summary the remanent magnetization of palaeozoic and mesozoic carbonates from the tibetan sedimentary series tss of the manang area north of the annapurna range north central nepal has been investigated the tss forms part of the tectonic unit between the indian eurasian plate boundary in the north and the main central thrust mct in the south apart from a present field direction three remanence components have been separated a normal polarity post folding remanence negative fold test is carried by pyrrhotite the core corrected mean direction for five sites with 47 specimens from silurian devonian rocks is decl 312 9 incl 58 3 95 17 6 k 19 8 the origin of this component is not understood a more precisely determined reversed polarity post folding remanence 99 per cent negative fold test is also carried by pyrrhotite the core corrected mean direction for 12 sites with 229 specimens from carboniferous triassic rocks is decl 196 4 incl 65 9 95 3 2 k 183 one site of lower carinan age shows in addition to the pyrrhotite component a second stable remanence direction carried by magnetite the fold test is 99 per cent positive and there is a high probability that the remanence is of detrital origin the bedding corrected direction for one site with 40 specimens is decl 334 3 incl 54 1 95 4 2 k 30 2 palaeolatitude 34 6 s the direction of the magnetite component coincides with other triassic palaeodirection data from the literature and the inclination suggests a palaeoposition of the tss at the northern margin of india at this time the northern extent of india in the triassic cannot be reconstructed from the data because of the strong anticlockwise rotation 48 of stable india since this time the inclination of the reverse polarity pyrrhotite component is 19 steeper than expected from the maximum northern position of the area this suggests a regional northward tilt along the mct which is supported by steep inclinations found in other areas declination data for the reverse polarity pyrrhotite component and for the magnetite component deviate clockwise from expected values for the area by 23 34 calculated from the indian apwp utilizing klootwijk conaghan powell s 1985 rotational underthrusting model the minimum magnitude of continental underthrusting between the tss and stable india at the longitude of central nepal 84 e has been calculated from the declination of our reverse polarity pyrrhotite component a possible range of 520 1100 km results from consideration of different tectonic models

paleoenvironments during younger dryas early holocene retreat of the greenland ice sheet from outer disko trough central west greenland paleoenvironments during the late younger dryas through early holocene retreat of the greenland ice sheet from the outer shelf in the disko trough system of central west greenland were investigated via lithofacies foraminifera dinocysts and sediment provenance analyses in radiocarbon dated sediment cores from the upper slope jr175 vc35 and outer shelf jr175 vc20 and hu2008029 070cc core data show that the ice margin retreated rapidly from the outer shelf by calving beginning by 12 2k cal a bp under cold paleoceano graphic conditions with up to 11 months of sea ice ice retreat into disko bugt was well underway by 10 9k cal a bp enhanced ice sheet ablation in disko bugt and elsewhere along the west greenland coast is inferred from cold glacial marine conditions associated with high sedimentation rates between 10 9 and 9 5k cal a bp on the outer shelf glacial marine conditions are recorded on the outer shelf until 7 8k cal a bp detrital carbonate bearing sediments rich in 2 mm clasts deposited between 11 6 and 10 6k cal a bp indicate that icebergs calved from northern baffin bay ice margins were melting and releasing sediments along west greenland while the greenland ice sheet margin was retreating into disko bugt copyright 2013 john wiley sons ltd

rapid vegetation response to lateglacial and early holocene climatic fluctuation in the south carpathian mountains romania abstract high resolution pollen conifer stomata and plant macrofossil analyses of two glacial lake sediments 1740 and 1990 m a s l are used to reconstruct lateglacial lg and early holocene eh vegetation and tree line changes in the retezat mountains our results show that during the lg tree line was between 1750 and 1800 m a s l formed by larix decidua pinus mugo and picea abies early lg spread to high altitudes suggests refugia of these tree species in the mountain the younger dryas cooling resulted in regional steppe tundra expansion but tree line position and composition showed little change the abundance of trees and shrubs decreased at 1740 m a s l but species richness increased with the arrival of pinus cembra our data support climate model hindcasts for only modest decrease in accumulated growing season heat at mid high altitudes regionally the pollen records suggest enhanced aridity and seasonality in the eh tree line reached 2000 m a s l higher than today by 11 100 cal yr bp p mugo p cembra p abies established around the upper lake suggesting rapid increase in summer temperatures the eh maximum of l decidua between 11 200 10 600 cal yr bp was connected to high summer insolation high altitude expansion of abies alba between 10 600 10 300 cal yr bp suggested summer mean temperatures 2 8 c higher then today in comparison with other mountain sites in europe lg interstadial tree line was at similar altitude in the s alps and 350 m higher in the pirin mountains lg tree line fluctuation had similar low amplitude in the se alps retezat and pirin mts suggesting relatively weak influence of the north atlantic thermohaline circulation changes on growing season temperatures

a review of indian phanerozoic palaeomagnetism implications for the india asia collision abstract an overview is presented of the indian apparent polar wander path apwp for the phanerozoic and in particular for post late palaeozoic times this apwp is compiled on basis of data available at october 1981 from peninsular and extrapeninsular indo pakistan and from dsdp cores from the indian plate one of the more important and newly recognized features of this apwp is a large scale triassic jurassic loop this loop indicates a changeover from a late palaeozoic early mesozoic northwards and counter clockwise rotational movement with greater india reaching moderately low southern latitudes into a southwards and clockwise rotational movement during the early to middle jurassic recognizable likewise in apwp s from other gondwana continents this loop reflects the opening of the neotethys studies of extrapeninsular regions up to and north of the indus tsangpo suture zone have shown wide spread presence of magnetic overprints which delineate two regionally confined age groups younger overprints 20 40 m y predominate in the more external thrust zones older overprints 50 60 m y in contrast are found in the more internal zones both north and south of the indus tsangpo suture zone the latter are interpreted to reflect a late phase of relaxation in the early tertiary collision of greater india with south central asia or off shore island arcs which occurred at equatorial to low northern palaeolatitudes 0 10 n subsequent northwards movement over 2500 3000 km or more and impingement of greater india into southern asia resulted into large scale underthrusting of greater india along the main central thrust beneath southern tibet and to clockwise rotation of thrust units in the western himalaya a discrepancy between indian palaeomagnetic data and results available todate from southern tibet is discussed

chronology of the last glacial cycle in the european alps chronological data for glacier advances in the european alps between the last interglacial eemian and the holocene are summarised 115 to 11 ka during this time glaciers were most extensive extending tens of kilometres out onto the forelands between 30 and 18 ka that is synchronous with the global ice volume maximum of marine isotope stage mis 2 evidence for ice expanding to just past the mountain front for an earlier major glacier advance comes from swiss sites where advances have been luminescence dated to mis 5d 100 ka and mis 4 70 ka up to now no such evidence has been found in the eastern alps by 18 ka more than 80 of the late wurmian ice volume had gone subsequently glaciers readvanced reaching into the upper reaches of the main valleys during the lateglacial gschnitz stadial which likely occurred around 17 ka with final moraine stabilisation no later than 15 4 ka the link of the egesen stadial with the younger dryas climate deterioration is supported by exposure ages from four sites as well as minimum limiting radiocarbon dates from bogs within former glacier tongue areas key questions on the spatial and temporal variability of ice extents throughout the last glacial cycle have yet to be answered copyright 2008 john wiley sons ltd

expression of the younger dryas cold event in the carpathian mountains ukraine past glacial activity in the ukrainian carpathian mountains is characterized by cirques glacial valleys and moraine ridges at altitudes between 1350 and 1850 m a s l although the geomorphology of this area was extensively studied the deposition time of these glacial forms and specifically the moraines was never determined we surveyed and mapped the geomorphology of the pozhezhevs ka glacial valley which is part of the charnogora ridge we used surface exposure dating and developed a data base of this area using remote sensing and geographic information system to understand the timing and nature of glacial event in the eastern carpathian mountains well developed continuous lateral frontal moraines cross the valley floor at 1400 m a s l ten sandstone boulders were sampled from one of these to determine the deposition time of the moraine samples were prepared at the glasgow university cosmogenic nuclide laboratory and analyzed at the suerc ams laboratory surface exposure ages were calculated using the cronus earth online 10be exposure age calculator our exposure ages for nine samples ukr 2 to ukr 10 range from 11 0 0 4 10be ka to 14 5 0 5 10be ka one sample ukr 1 produced no current and thus no exposure age is available the mean deposition time for the moraine ranges from 12 4 0 3 to 12 9 0 3 10be ka depending on choice of surface erosion and snow cover these results provide the first direct indication using surface exposure dating of a possible glacier response in the ukrainian carpathian mountains to a cold event contemporary with the younger dryas yd together with exposure ages from other mountain ranges across europe the new data provide direct chronological evidence for a widespread expression of the yd cold event outside the main ice margin limits left by the former scandinavian ice sheet

a new articulated freshwater fish clupeomorpha ellimmichthyiformes from the horseshoe canyon formation maastrichtian of alberta canadathis article is one of a series of papers published in this special issue on the theme albertosaurus horseshoeichthys armaserratus gen et sp nov clupeomorpha ellimmichthyiformes sorbinichthyidae is described from the horseshoe canyon formation maastrichtian albertosaurus bonebed locality alberta canada horseshoeichthys armaserratus is classified as an ellimmichthyiform based on the following characters the presence of a sixth infraorbital with a sensory canal that leads to the fifth infraorbital absence of a supraorbital bone subrectangular predorsal scutes parietals in contact with each other at the midline and two supramaxillae the specimen is classified in the sorbinichthyidae family as it has abdominal ribs articulating in pits on the centra posterior spines on predorsal scutes and absence of a median spine on predorsal scutes a new genus and species is proposed based on the presence of anteriorly y shaped mesethmoid supraorbital subrectangular predorsal scutes with coarse rounded serrae on the posterior margin and a large anterior projection scales with serrae on the ci

a new greenland ice core chronology for the last glacial termination 1 we present a new common stratigraphic timescale for the north greenland ice core project ngrip and grip ice cores the timescale covers the period 7 9 14 8 kyr before present and includes the bolling allerod younger dryas and early holocene periods we use a combination of new and previously published data the most prominent being new high resolution continuous flow analysis cfa impurity records from the ngrip ice core several investigators have identified and counted annual layers using a multiparameter approach and the maximum counting error is estimated to be up to 2 in the holocene part and about 3 for the older parts these counting error estimates reflect the number of annual layers that were hard to interpret but not a possible bias in the set of rules used for annual layer identification as the grip and ngrip ice cores are not optimal for annual layer counting in the middle and late holocene the timescale is tied to a prominent volcanic event inside the 8 2 kyr cold event recently dated in the dye 3 ice core to 8236 years before a d 2000 b2k with a maximum counting error of 47 years the new timescale dates the younger dryas preboreal transition to 11 703 b2k which is 100 150 years older than according to the present grip and ngrip timescales the age of the transition matches the gisp2 timescale within a few years but viewed over the entire 7 9 14 8 kyr section there are significant differences between the new timescale and the gisp2 timescale the transition from the glacial into the bolling interstadial is dated to 14 692 b2k the presented timescale is a part of a new greenland ice core chronology common to the dye 3 grip and ngrip ice cores named the greenland ice core chronology 2005 gicc05 the annual layer thicknesses are observed to be log normally distributed with good approximation and compared to the early holocene the mean accumulation rates in the younger dryas and bolling periods are found to be 47 2 and 88 2 respectively

production of cosmogenic radionuclides at great depth a multi element approach abstract for the last two decades in situ produced cosmogenic nuclides are increasingly applied in earth sciences to quantify surface processes in parallel significant reduction of the analytical uncertainties linked to advances in accelerator mass spectrometry ams allows more precise measurements however among all the published works on cosmogenic nuclides only few studies are dedicated to a better understanding of their production systematic or to a better constrain of the physical parameters involved in their production thus an approach to investigate in situ produced cosmogenic nuclides 10 be 26 al and 36 cl along a single 11 meter long core drilled from the surface and composed of carbonates and quartzose conglomerates has been launched these measurements have been used to quantify muon induced productions based on natural samples for each studied nuclide contrary to the current most oftenly used calculation of muon induced production parameters which are based on irradiation experiments at discrete energies productions based on natural samples are considering the entire energy range of particles reaching the ground surface the evolution of 36 cl concentrations with depth needs to agree with those parameters deduced from 10 be and 26 al data this is optimized when considering a fast muon induced 36 cl production contribution and a spallation production rate at sea level high latitude slhl of 42 0 2 0 atoms 36 cl g ca 1 a 1 1 sigma uncertainty

first evidence of in situ eemian sediments on the high plateau of evian northern alps france implications for the chronology of the last glaciation a 2 m profile of organic sediments interbedded between two tills was taken from the evian high plateau at hameau de maravant 860 m a s l haute savoie western alps france pollen plant macrofossils and insect remains were used to reconstruct the local palaeoenvironment which consisted of a moss and carex mire surrounded by a dense abies and picea mixed forest pollen and macrofossil data indicate that this peat layer was deposited at the end of the eemian interglacial the lower till should therefore be assigned to the penultimate glaciation and the upper till to the maximum extent of the rhone glacier during the wurm a comparison of the results with previous studies carried out in the geneva area and other alpine valleys has yielded a detailed reconstruction of the past fluctuations of the rhone glacier 1 a first early lower wurmian advance reaching the region around lyon 2 a subsequent retreat of ice 3 a second moderate readvance restricted to the surroundings of geneva followed by a final deglaciation a continuous lacustrine sequence has been obtained from the nearby roseire peat bog 890 m a s l pollen and radiometric results show the establishment of a former palaeolake during the upper pleniglacial probably before ca 22 450 850 cal years bp thus implying that the high plateau was ice free from that time these new data appear to suggest that the maximal extension of the rhone glacier occurred prior to the last glacial maximum ois 2 and according to a well documented geomorphological context probably during the lower wurmian pleniglacial

late pleistocene glacial chronology of the pietrele valley retezat mountains southern carpathians constrained by 10be exposure ages and pedological investigations abstract the southern carpathians are located in the transition zone between mediterranean and continental climates and constituted the major areas of ice accumulation in the carpathians during pleistocene glaciations an absolute glacial chronology had not yet been established in this study we constrain the glacial history of the pietrele valley in the retezat mountains located in the southern carpathians and find that the timing of the late wurmian glacial advance is asynchronous to global climate records likely reflecting changes in moisture availability in the area the former ice extent of two major glacial advances m1 or lolaia glacial advance and m2 or capra judele glacial advance in the valley was reconstructed based on mapping and surveying of glacial features field relations and different pedological weathering indicators of till imply that the m1 glacial advance occurred well before the global last glacial maximum lgm its deposition during the penultimate glaciation is unlikely no boulders suitable for exposure dating were found on m1 moraines seventeen exposure ages show that the moraines of the maximum late wurmian m2 glacial advance were abandoned around 16 1 1 6 ka another late glacial advance m3 or stevia advance occurred during the younger dryas chron as constrained by two exposure ages we suggest that the glacial advance that occurred during the time of the global lgm was less extensive than the m2 glacial advance and the deposits were overrun by the lateglacial m2 glacier as we found no field evidence of glacial deposits between the m1 and the m2 moraines we explain this obvious asynchronity of the local late wurmian ice extent with that of global records of ice accumulation with increased aridity in the carpathians during the global lgm due to a lower sea level the reconstructed late pleistocene equilibrium line altitude ela shows a distinct increase in the trend from the alps and the bavarian forest to the carpathians in comparison to the modern ela this finding supports the high aridity in the study area during the late pleistocene two distinct lateglacial moraines were deposited during times of reported colder and wetter climatic conditions around the north atlantic heinrich events h0 and h1

climatic implications of cirque distribution in the romanian carpathians palaeowind directions during glacial periods the many glacial cirques in the mountains of romania indicate the distribution of former glacier sources related to former climates as well as to topography in the transylvanian alps southern carpathians cirque floors rise eastward at 0 714 m km 1 and cirque aspects tend ene confirming the importance of winds from some westerly direction there is a contrast between two neighbouring ranges the fa ga ras where the favoured aspect of cirques is ene and the iezer where the tendency is stronger and to nne this can be explained by the iezer mountains being sheltered by the fa ga ras which implies precipitation bearing winds from north of west at times of mountain glaciation palaeoglaciation levels also suggest winds from north of west which is consistent with aeolian evidence from pleistocene dunes yardangs and loess features in the plains of hungary and south western romania in northern romania including ukrainian maramures the influence of west winds was important but sufficient only to give a northeastward tendency in cirque aspects this gave stronger asymmetry than in the transylvanian alps as the northward solar radiation incidence tendency in these marginally glaciated mountains was less diluted by wind effects cirque floors in northern romania are lower also in northeast facing cirques in general cirque aspects result from several factors and the mean tendency is not downwind but is displaced from poleward by wind and by minor effects copyright 2010 john wiley sons ltd

a geomagnetic polarity timescale for the permian calibrated to stage boundaries the reverse polarity kiaman superchron has strong evidence for at least three or prob ably four normal magnetochrons during the early permian normal magnetochrons are during the early asselian base ci1r 1n at 297 94 0 33 ma late artinskian ci2n at 281 24 2 3 ma mid kungurian ci3n at 275 86 2 0 ma and roadian ci3r an at 269 54 1 6 ma the mixed polarity illawarra superchron begins in the early wordian at 266 66 0 76 ma the wordian capitanian interval is biased to normal polarity but the basal wuchiapingian begins the beginning of a significant reverse polarity magnetochron lp0r with an overlying mixed polarity interval through the later lopingian no significant magnetostratigraphic data gaps exist in the permian geomagnetic polarity record the early cisuralian magnetochrons are calibrated to a succession of fusulinid zones the later cisuralian and guadalupian to a conodont and fusulinid biostratigraphy and lopingian magnetochrons to conodont zonations age calibration of the magnetochrons is obtained through a bayesian approach using 35 radiometric dates and 95 confidence intervals on the ages and chron durations are obtained the dating control points are most numerous in the gzhelian asselian wordian and changhsingian intervals this significant advance should provide a framework for better correlation and dating of the marine and non marine permian

a new species of sorbinichthys teleostei clupeomorpha ellimmichthyiformes from the late cretaceous of morocco a new species of ellimmichthyiform fish represented by three specimens has been recovered from deposits of the akrabou formation of morocco the new species is described in the existing genus sorbinichthys family sorbinichthyidae as sorbinichthys africanus sp nov closely related to the type species sorbinichthys elusivo the ellimmichthyiformes is an extinct order of clupeomorph fishes that includes both freshwater and marine species ranging from the early cretaceous through the eocene sorbinichthys elusivo is known from cenomanian deposits of the eastern mediterranean tethys lebanon whereas the new species is possibly early turonian but more probably late cenomanian in age from the western tethys eastern morocco at lower taxonomic levels the assemblage from the akrabou formation has a primarily tethyan composition exemplified by the genus sorbinichthys whereas supra generic taxa found there include groups with trans atlantic e g sorbinichthyidae macrosemiidae or near cosmopolitan

timing of glacier advances and climate in the high tatra mountains western carpathians during the last glacial maximum during the last glacial maximum lgm long valley glaciers developed on the northern and southern sides of the high tatra mountains poland and slovakia chlorine 36 exposure dating of moraine boulders suggests two major phases of moraine stabilization at 26 21 ka lgm i maximum and at 18 ka lgm ii the dates suggest a significantly earlier maximum advance on the southern side of the range reconstructing the geometry of four glaciers in the sucha woda panszczyca mlynicka and velicka valleys allowed determining their equilibrium line altitudes elas at 1460 1460 1650 and 1700 m asl respectively based on a positive degree day model the mass balance and climatic parameter anomaly temperature and precipitation has been constrained for lgm i advance modeling results indicate slightly different conditions between northern and southern slopes the n s ela gradient finds confirmation in slightly higher temperature at least 1 c or lower precipitation 15 on the south facing glaciers during lgm i the precipitation distribution over the high tatra mountains indicates potentially different lgm atmospheric circulation than at the present day with reduced northwesterly inflow and increased southerly and westerly inflows of moist air masses

high resolution mapping of glacial landforms in the north alpine foreland austria abstract in this study results from traditional field mapping were merged with precise elevation information from airborne lidar light detection and ranging surveys morphological and sedimentological data provide new results from the austrian eastern part of the salzach piedmont glacier during times of and shortly after the last glacial maximum lgm the variations in meltwater discharge had a major impact on the development of glacial landforms in areas with high meltwater supply erosional or debris reworking processes play a major role represented by drainage channels drumlins and kettled low relief hummocky moraine with low slope angles low discharge areas are associated with distinct depositional forms such as high relief end moraines up to 30 m and hummocky moraine averaging 20 m with high slope angles isolated conical kames may reach heights up to 45 m fluvial activity is supposed to rise towards the end of the glacial cycle causing high melting rates and comprehensive debris reworking the formation of terminal lakes and associated widespread inorganic lake clays are the last deposits within the study area before the salzach glacier completely receded to its main valley the survey of glacial landforms through the combination of field mapping and high resolution dem derived from airborne lidar missions gives precise information on transport and deposition during the last glacial cycle of the eastern salzach glacier piedmont lobe

greater india basin hypothesis and a two stage cenozoic collision between india and asia cenozoic convergence between the indian and asian plates pro duced the archetypical continental collision zone comprising the himalaya mountain belt and the tibetan plateau how and where india asia convergence was accommodated after collision at or be fore 52 ma remains a long standing controversy since 52 ma the two plates have converged up to 3 600 35 km yet the upper crustal shortening documented from the geological record of asia and the himalaya is up to approximately 2 350 km less here we show that the discrepancy between the convergence and the shortening can be explained by subduction of highly extended continental and oceanic indian lithosphere within the himalaya be tween approximately 50 and 25 ma paleomagnetic data show that this extended continental and oceanic greater india promontory resulted from 2 675 700 km of north south extension between 120 and 70 ma accommodated between the tibetan himalaya and cratonic india we suggest that the approximately 50 ma india asia collision was a collision of a tibetan himalayan microconti nent with asia followed by subduction of the largely oceanic greater india basin along a subduction zone at the location of the greater himalaya the hard india asia collision with thicker and contiguous indian continental lithosphere occurred around 25 20 ma this hard collision is coincident with far field deforma tion in central asia and rapid exhumation of greater himalaya crys talline rocks and may be linked to intensification of the asian monsoon system this two stage collision between india and asia is also reflected in the deep mantle remnants of subduction imaged with seismic tomography

in situ produced 10be measurements at great depths implications for production rates by fast muons in situ cosmogenic 10be values have been used to investigate a brazilian quartz vein from the surface to a depth of 15 m at depths greater than 1000 g cm2 deep enough for neutron induced reactions to be insignificant there is only a slight decrease in 10be concentration with increasing depth our results are consistent with deep production of 10be by a mechanism presumably induced by fast muons with an attenuation length of 5300 950 g cm2 and a contribution of 0 65 0 25 to the total surface production results are compared with values from the literature and implications of this re evaluation are discussed

the last deglaciation of the southeastern sector of the scandinavian ice sheet the scandinavian ice sheet sis was an important component of the global ice sheet system during the last glaciation but the timing of its growth to or retreat from its maximum extent remains poorly known we used 115 cosmogenic beryllium 10 ages and 70 radiocarbon ages to constrain the timing of three substantial ice margin fluctuations of the sis between 25 000 and 12 000 years before the present the age of initial deglaciation indicates that the sis may have contributed to an abrupt rise in global sea level subsequent ice margin fluctuations identify opposite mass balance responses to north atlantic climate change indicating differing ice sheet sensitivities to mean climate state

paleomagnetism and microtextures reveal neohimalayan deformation pattern in the northwestern tethys himalaya abstract the india asia collision produced the himalayan orogenic belt the kinematics of crustal blocks within the orogenic belt can shed insights into the tectonic processes related with the continental collision we report a combined study of paleomagnetism and microtextures from the zhongba microterrane northwestern tethys himalaya the zhongba microterrane is located in the southwestern part of tibet a total of 71 samples collected from permian formations yield a distinct remanent component carried by pyrrhotite which failed fold tests compared with the apparent polar wander path of india it is suggested that this overprint component is acquired recently 10 0 ma and a 16 clockwise rotation is also indicated microtextures from several localities show e w directed shear together with reported gps observations and clockwise rotations a bookshelf style deformation pattern associated with strike slip faulting is proposed for the neohimalayan tectonics in the tethys himalaya bookshelf style rotation of small blocks coordinated by strike slip faults is not only a practical model to absorb the crustal shortening caused by the convergence of the indian eurasian plate but also an important way for the escape of the tibetan plateau to the southeast

a stratigraphic framework for abrupt climatic changes during the last glacial period based on three synchronized greenland ice core records refining and extending the intimate event stratigraphy due to their outstanding resolution and well constrained chronologies greenland ice core records provide a master record of past climatic changes throughout the last interglacial glacial cycle in the north atlantic region as part of the intimate integration of ice core marine and terrestrial records project protocols have been proposed to ensure consistent and robust correlation between different records of past climate a key element of these protocols has been the formal definition and ordinal numbering of the sequence of greenland stadials gs and greenland interstadials gi within the most recent glacial period the gs and gi periods are the greenland expressions of the characteristic dansgaard oeschger events that represent cold and warm phases of the north atlantic region respectively we present here a more detailed and extended gs gi template for the whole of the last glacial period it is based on a synchronization of the ngrip grip and gisp2 ice core records that allows the parallel analysis of all three records on a common time scale the boundaries of the gs and gi periods are defined based on a combination of stable oxygen isotope ratios of the ice 18o reflecting mainly local temperature and calcium ion concentrations reflecting mainly atmospheric dust loading measured in the ice the data not only resolve the well known sequence of dansgaard oeschger events that were first defined and numbered in the ice core records more than two decades ago but also better resolve a number of short lived climatic oscillations some defined here for the first time using this revised scheme we propose a consistent approach for discriminating and naming all the significant abrupt climatic events of the last glacial period that are represented in the greenland ice records the final product constitutes an extended and better resolved greenland stratotype sequence against which other proxy records can be compared and correlated it also provides a more secure basis for investigating the dynamics and fundamental causes of these climatic perturbations

the greenland ice core chronology 2005 15 42 ka part 1 constructing the time scale the greenland ice core chronology 2005 gicc05 is extended back to 42 ka b2k before 2000 ad i e to the end of greenland stadial 11 the chronology is based on independent multi parameter counting of annual layers using comprehensive high resolution measurements available from the north greenland ice core project ngrip these are measurements of visual stratigraphy conductivity of the solid ice electrolytical melt water conductivity and the concentration of na c a 2 s o 4 n o 3 n h 4 a n uncertainty estimate of the time scale is obtained from identification of uncertain annual layers which are counted as 0 570 5 years the sum of the uncertain annual layers the so called maximum counting error of the presented chronology ranges from 4 in the warm interstadial periods to 7 in the cold stadials the annual accumulation rates of the stadials and interstadials are on average one third and half of the present day values respectively and the onset of the greenland interstadials 2 3 and 8 based on 20 year averaged d 18 o

intermontane basin development in the past 4 myr in the north west himalaya the through the combined use of magnetic polarity stratigraphy with fission track dating of volcanic ashes a new chronology spanning 4 myr has been developed for the intermontane basin of kashmir in the northwestern himalaya

the glacial history of the dinaric alps montenegro abstract large areas of montenegro were glaciated during the pleistocene this paper presents evidence from the massifs of central montenegro including durmitor and sinjajevina moracke planine maganik prekornica and vojnik glacial deposits have been subdivided on the basis of morphostratigraphy and soil weathering and 31 u series ages from cemented tills provided a geochronological framework the largest glaciation occurred before 350 ka when a series of conjoined ice caps over the massifs of central montenegro covered a total area of nearly 1500 km 2 these formed during mis 12 and correspond with the largest skamnellian stage glaciations in greece to the south later middle pleistocene glaciations occurred during the penultimate glacial cycle correlating with the vlasian stage in greece mis 6 when ice caps covered an area of 720 km 2 over central montenegro there is also geochronological evidence of glacial deposits dating from the interval between mis 12 and mis 6 before the interglacial complex of mis 7 this glaciation appears to have been very similar in extent to that which occurred during mis 6 the last glacial cycle in central montenegro was characterised by valley and cirque glaciers covering a total area of 49 km 2 it is very likely that glaciers have been present in the mountains of central montenegro during every glacial cycle since a small glacier still survives today the smaller glaciers of the last glacial cycle are likely to have been associated with summer temperatures that were warmer than those of earlier cold stages the striking contrast in the extent and thickness of ice cover during the cold stages of the pleistocene has an important bearing on the geomorphological and biological evolution of the balkans

glaciation in the rila mountains bulgaria during the last glacial maximum abstract relict glacial landform complexes have been studied in the mountains of the central balkan peninsula since the end of the 19th century since their existence was proved for the first time by cvijic various authors have debated the number of glacial phases as well as their age at present the problem of age determination is being solved by the application of the new methods for numerical dating this paper is a detailed study of the maximum glaciation in the rila massif which is the highest mountain in bulgaria and in the whole balkan peninsula the application of cosmogenic nuclide dating 10be on moraine samples confirmed that the largest extent of former glaciers that left moraine deposits was around the time of the last glacial maximum most probably the maximum extent occurred in two phases the first around the beginning and the second around the end of the lgm 24 23 ka bp and 18 16 ka bp respectively separated by a retreat phase during the coldest but also driest phase of the glacial stage the gis processed calculations on the basis of field evidence of the former glacier extent and the preliminary calculations of the equilibrium line altitude ela through the accumulation ablation ratio aar method show that the ela during the lgm had quite small differences throughout the rila massif from about 2150 to 2200 m a s l in the nw to about 2250 2290 m in the se despite the considerable differences in terminal moraine depositional altitudes from 1150 to 2000 m a s l this is due to both the complicated pattern in the directions of moisture supply and to the influences of local topography

the extent and chronology of cenozoic global glaciation abstract the quaternary is synonymous with extensive glaciation of earth s mid and high latitudes although there were local precursors significant glaciation began in the latest eocene ca 35 ma in eastern antarctica it was followed by glaciation in mountain areas through the miocene in alaska greenland iceland and patagonia later in the pliocene e g in the bolivian andes and possibly in tasmania and in the earliest pleistocene e g in the alps new zealand iceland and greenland today evidence from both the land and the ocean floors demonstrates that the major continental glaciations outside the polar regions rather than occurring throughout the 2 6 ma of the quaternary were markedly restricted to the last 1 ma 800 ka or less marine isotope stage mis 22 ca 870 880 ka included the first of the major worldwide events with substantial ice volumes that typify the later pleistocene glaciations i e mis 16 12 10 6 4 2

insights into continental temperatures in the northwestern black sea area during the last glacial period using branched tetraether lipids abstract in the continental realm continuous quantitative temperature reconstructions spanning the last glacial are rare especially in central and eastern europe here we provide a reconstruction from the northwestern black sea catchment spanning 40 to 9 ka bp from a study of the relative distribution of branched glycerol dialkyl glycerol tetraethers brgdgts in black sea lacustrine sediments first the origins of brgdgts are discussed the comparison of geochemical proxies from the same core supports a dominant terrestrial origin for brgdgts during the last glacial and a strong decrease in the soil derived brgdgt proportion toward the holocene since the lowering of soil vs lacustrine derived brgdgts is prone to bias the temperature signal that is reconstructed using a soil calibration a correction for in situ production is applied the corrected signal is compared to independent discrete temperature records from the study area the brgdgt temperature relative evolution reconstructed in this work provides additional insight regarding millennial scale climate variability in central and eastern europe notably the imprints of heinrich event cold spells and lateglacial climatic oscillations are consistent with other regional paleorecords from the northern hemisphere

variable responses of western u s glaciers during the last deglaciation cosmogenic 10 be exposure ages from moraines in the wallowa mountains oregon identify two maximal late pleistocene glaciations at 21 1 6 0 4 ka and 17 0 6 0 3 ka and a minor glacial event at 10 2 6 0 6 ka our new high resolution chronology integrated with other well dated glacial records from the western united states demonstrates sub stantial differences in the synoptic responses of western u s glaciers to climate forcing associated with the global last glacial maximum and subsequent millennial scale events originating in the north atlantic region these variable synoptic glacier responses identify large changes in the relative contributions of regional to global controls on the climate of the western united states that accompanied the deglaciation