paleoseismic evidence of a giant medieval earthquake in the eastern himalaya we present here the results of a paleoseismic investigation carried across a 10 m high fault scarp at panijhora village west bengal in northeastern india accelerator mass spectrometer analyzed 14c radiocarbon age constraints from six detrital charcoal samples ranging between 1688 b c and a d 1152 are consistent with the great medieval earthquake of a d 1255 that is interpreted to have produced a minimum observed fault slip of 5 m in the trench exposure recalibration of radiocarbon ages from previous studies at harmutty nameri and marha in the eastern himalaya using bayesian statistical analyses further substantiates the possibility that the a d 1255 earthquake might have ruptured the himalayan front over a length of 800 km from 85 87 to 93 76 e longitudes

segmentation of the himalayan megathrust around the gorkha earthquake 25 april 2015 in nepal abstract we put the 25 april 2015 earthquake of nepal mw 7 9 into its structural geological context in order to specify the role of the segmentation of the himalayan megathrust the rupture is mainly located nw of kathmandu at a depth of 13 15 km on a flat portion of the main himalayan thrust mht that dips towards the n ne by 7 10 the northern bound of the main rupture corresponds to the transition towards a steeper crustal ramp this ramp which is partly coupled during the interseismic period is only locally affected by the earthquake the southern bound of the rupture was near the leading edge of the lesser himalaya antiformal duplex and near the frontal footwall ramp of the upper nawakot duplex the rupture has been affected by transversal structures on the western side the judi lineament separates the main rupture zone from the nucleation area on the eastern side the gaurishankar lineament separates the 25 april 2015 rupture from the 12 may 2015 mw 7 2 rupture the origin of these lineaments is very complex they are probably linked to pre himalayan faults that extend into the indian shield beneath the mht these inherited faults induce transverse warping of the upper lithosphere beneath the mht control the location of lateral ramps of the thrust system and concentrate the hanging wall deformation at the lateral edge of the ruptures the mht is therefore segmented by stable barriers that define at least five patches in central nepal these barriers influence the extent of the earthquake ruptures for the last two centuries the 1833 mw 7 6 earthquake was rather similar in extent to the 2015 event but its rupture propagated south westwards from an epicentre located ne of kathmandu the patch south of kathmandu was probably affected by at least three earthquakes of mw 7 that followed the 1833 event a few days later or 33 years 1866 event mw 7 2 later the 1934 earthquake mw 8 4 had an epicentre 170 km east of kathmandu may have propagated as far as kathmandu and jumped the gaurishankar lineament this combined structural approach and earthquake study allows us to propose that the mht in the central eastern himalaya is segmented by stable barriers that define barrier type earthquake families however for each individual earthquake within a family the rupture histories could be different furthermore the greatest earthquakes could have broken the barriers and affected the patches of several families the concept of a regular recurrence of characteristic earthquakes is therefore misleading to describe the succession of himalayan earthquakes

carnian norian biomagnetostratigraphy at silicka brezova slovakia correlation to other tethyan sections and to the newark basin correlations of upper triassic magnetic stratigraphies from tethyan sections have been hampered by difficulties with conodont biostratigraphy and taxonomy and discontinuous sedimentation particularly in the hallstatt limestones of turkey and austria the magnetic stratigraphy and conodont biostratigraphy from the upper carnian to upper norian limestones exposed at silickabrezova slovakia can be correlated to other tethyan sections and to the continental succession in the newark basin the resulting correlations help to resolve some of the apparent discrepancies in existing conodont zonations and result in a revised correlation to north american terrestrial vertebrate and palynological zones the correlations imply that the norian rhaetian boundary lies within newark polarity zone e17r at v207 ma the carnian norian boundary lies close to the base of newark polarity zone e7r at v226 ma this implies durations for the norian and rhaetian stages of 19 myr and 7 myr respectively 2002 elsevier science b v all rights reserved

primary surface ruptures of the great himalayan earthquakes in 1934 and 1255 it is unclear where plate boundary thrusts generate giant rather than great earthquakes along the himalayas the source sizes and recurrence times of large seismic events are particularly uncertain since no surface signatures were found for those that shook the range in the twentieth century here we challenge the consensus that these events remained blind and did not rupture the surface we use geomorphological mapping of fluvial deposits palaeo seismological logging of river cut cliffs and trench walls and modelling of calibrated 14c ages to show that the mw 8 2 bihar nepal earthquake on 15 january 1934 did break the surface traces of the rupture are clear along at least 150 km of the main frontal thrust fault in nepal between 85 50 and 87 20 e furthermore we date collapse wedges in the sir valley and find that the 7 june ad 1255 earthquake an event that devastated kathmandu and mortally wounded the nepalese king abhaya malla also ruptured the surface along this stretch of the mega thrust thus in the past 1 000 years two great earthquakes 679 years apart rather than one giant eleventh century ad event contributed to the frontal uplift of young river terraces in eastern nepal the rare surface expression of these earthquakes implies that surface ruptures of other reputedly blind great himalayan events might exist the recurrence times of great himalayan earthquakes are difficult to assess because they rarely rupture the surface field mapping and 14c dating of offset fluvial deposits are used to identify two great himalayan quakes that ruptured the surface along the main plate boundary fault in ad 1255 and 1934

timing of recovery from the end permian extinction geochronologic and biostratigraphic constraints from south china four volcanic ash beds bracket the early middle triassic boundary as defined by conodont biostratigraphy in a stratigraphic section in south china high precision u pb dates of single zircons allow us to place the early to middle triassic olenekian anisian boundary at 247 2 ma magnetic reversal stratigraphy allows global correlation the new dates constrain the early triassic interval characterized by delayed biotic recovery and carbon cycle instability to 5 m y this time constraint must be considered in any model for the end permian extinction and subsequent recovery

geomorphological evidence of holocene climatic change from northwest ellesmere island canadian high arctic proxy data from the northern coast of ellesmere island are used to reconstruct holocene palaeoclimate and appear to corroborate the ice core record from the canadian and greenland high arctic despite some regional variation geomorphological evidence indicates that deglaciation was associated with a marked climatic amelioration in the late pleistocene early holocene 10 ka bp this contrasts with glaciers on the south side of grant land mountains which started to retreat at 7 5 ka bp perhaps due to significant differences in glacioclimatic regime and the influence of the arctic ocean indicators of sea ice conditions on northern ellesmere island suggest that the early holocene was a period of considerable open water radiocarbon dates on driftwood collected from behind the north coast ice shelves suggest that the ice shelves formed during a mid holocene climatic deterioration geomorphic evidence shows that the ice shelves are presently breaking up and melting in response to recent warming glaciers hav

global correlation of the radiolarian faunal change across the triassic jurassic boundary precise comparison of the change in radiolarian faunas 3 5 m above a u pb zircon dated 199 6 0 3 ma tuff and approximately coincident with a negative 13 c anomaly in the queen charlotte islands b c canada with inuyama japan sequences indicates that major global changes occurred across the triassic jurassic t j boundary nearly 20 genera and over 130 rhaetian species disappeared at the end of the triassic the index genera betraccium and risella disappear and the final appearance of globolaxtorum tozeri livarella valida and pseudohagiastrum giganteum sp nov are also diagnostic for the end of the triassic the low diversity hettangian survival fauna immediately above the boundary is composed mainly of small primitive spumellarians with spongy or irregularly latticed meshwork and rod like spines and new genera charlottea udalia and parahsuum s l first appear in the lowest hettangian in both localities irrespective of different sedimentation rates and sedimentary environments such as shelf to upper slope queen charlotte islands and deep sea below carbonate compensation depth ccd inuyama radiolarians show a similar turnover pattern at the t j boundary

a record of holocene summer climate from a canadian high arctic ice core melt layers in ice cores are formed by melting on the snow pack surface which produces water that percolates down and refreezes in the colder snow layers below melt layers are distinguished by their bubble texture because more ice forms in the snow pack in warm summers than in cool summers the changing concentration with depth of melt layers in snow pits1 2 and ice cores3 5 is an indicator of past summer climate here we report on studies of melt layers in two canadian high arctic surface to bedrock ice cores although changes in elevation of the drill site owing to isostatic depression and uplift may contribute up to 40 of the total climatic signal recorded in the melt layers we interpret their varying concentrations in terms of changing summer temperatures over the past 10 000 years the warmest summers occurred 8 10 kyr ago and the coldest only 150 years ago the summers over the past 100 years have been the warmest for more than 1 000 years but are still not as warm as those of the early holocene the melt layer record is in broad agreement with geological records of glacier retreat during the holocene6 8 indicating that these data also contain information of regional significance

the mass balance of circum arctic glaciers and recent climate change the sum of winter accumulation and summer losses of mass from glaciers and ice sheets net surface mass balance varies with changing climate in the arctic glaciers and ice caps excluding the greenland ice sheet cover about 275 000 km2of both the widely glacierized archipelagos of the canadian norwegian and russian high arctic and the area north of about 60 n in alaska iceland and scandinavia since the 1940s surface mass balance time series of varying length have been acquired from more than 40 arctic ice caps and glaciers most arctic glaciers have experienced predominantly negative net surface mass balance over the past few decades there is no uniform recent trend in mass balance for the entire arctic although some regional trends occur examples are the increasingly negative mass balances for northern alaska due to higher summer temperatures and increasingly positive mass balances for maritime scandinavia and iceland due to increased winter precipitation the negative mass balance of most arctic glaciers may be a response to a step like warming in the early twentieth century at the termination of the cold little ice age arctic ice masses outside greenland are at present contributing about 0 13 mm yr 1to global sea level rise

low latitude and southern hemisphere origin of anisian triassic bedded chert in the inuyama area mino terrane central japan paleomagnetic and paleontologic studies of middle triassic to earliest jurassic radiolarian bedded chert in the inuyama area southern mino terrane of central japan have shown that the chert was deposited in an equatorial region with a paleolatitude between 10 n and 10 s and in particular the lower to middle anisian chert depositional basin was situated in the southern hemisphere the chert has four characteristic components of remanent magnetization the highest blocking temperature component carried by hematite shows positive fold and reversal tests and is regarded as the primary remanent magnetization acquired just after deposition the other three components are interpreted as a present field overprint and two postfolding remagnetizations the absolute tilt corrected inclinations of the primary component are less than 20 for all the samples of middle triassic to earliest jurassic age with the mean inclination of the lower to middle anisian chert being 11 0 4 3 paleomagnetic polarity reversals observed for the lower to middle anisian chert are well correlated with those of the european triassic sections under paleontologic age constraints using radiolarians and conodonts provided that the anisian chert in inuyama was deposited in the southern hemisphere this conclusion illuminates the paleogeographic evolution of the chert bearing accretionary complexes not only in japan but along the eastern margin of asia as well

biostratigraphy interpretations of oppel s zones abstract zones like those of oppel and hedberg s oppel zone are commonly interpreted as rock units delimited temporally a more restricted view is that they are rock units empirically defined by bioevents that occur in the same order in all sections methods used by oppel and definitions proposed by hedberg are reviewed to assess their adequacy for definition of biostratigraphic units and their ability to support temporal inferences although they are usually interpreted as chronostratigraphic units oppel defined his zones in stratigraphic space without temporal reference in contrast hedberg required that bioevents for his oppel zone should be approximately isochronous across their distribution but provided no operational way to identify such bioevents neither author clearly indicated how boundaries should be defined recourse to a principle of biosynchroneity to support inferences that stratigraphically ordered bioevents are temporal markers conflicts with knowledge of the biogeographies of modern taxa evolutionary theory explains why some bioevents occur in the same stratigraphic order but does not support the inference that they are isochronous events since its inception biostratigraphy has focused on ordered classifications like those of oppel stratigraphic codes should allow for a complementary category of biofacies zones that reflect depositional environments and are not constrained to occur in a particular order

holocene paleoclimatology of the queen elizabeth islands canadian high arctic abstract a wide variety of evidence reflecting in different ways the changing climate of the queen elizabeth islands during the holocene is reviewed all proxies pertain to summer conditions many sources of information provide weak or equivocal paleoclimatic signals but a general pattern of events can be discerned temperatures in the early to mid holocene were highest comparable with or higher than temperatures prevailing for much of this century although much evidence points to a mid holocene thermal maximum there is also considerable evidence that conditions were warmer in the early holocene possibly related to orbitally induced radiation anomalies the apparent mid holocene thermal maximum may reflect lags in the response of the environment and of some proxies in recording paleoclimatic conditions more direct indices point to warmest conditions in the early holocene before 7500 bp temperatures declined from 3000 bp culminating in exceptionally low temperatures from 100 400 bp this may have been the coldest period of the entire holocene resulting in glacier advances to post glacial maximum positions the period since 1925 has witnessed a pronounced increase in temperature leading to negative mass balances on glaciers and ice sheets throughout the archipelago this period is the warmest for at least 1000 years and perhaps for several thousand years modern climate in the queen elizabeth islands may thus be characteristic of the early to mid holocene and atypical of conditions which prevailed for much of the last few thousand years

well documented travel history of mesozoic pelagic chert in japan from remote ocean to subduction zone the mino tanba belt in southwest japan a segment of the cordilleran type orogenic chain of jurassic east asia is composed mainly of a middle upper jurassic subduction accretion complex in which triassic and lower jurassic bedded radiolarian cherts occur as large allochthonous units structurally interlayered with middle upper jurassic clastic rocks high resolution microfossil conodont and radiolaria research has identified very low average sedimentation rates of about 0 5 g cm 1000 yr in the chert units similar to those of modern pelagic sediments accumulated in open ocean environments judging from the low average sedimentation rate high purity of biogenic silica long duration of continuous deposition 50 m y and wide along strike extent 1000 km the bedded radiolarian cherts in the mino tanba belt are best understood as ancient pelagic sediments that accumulated in open ocean environments accordingly the alleged origin in smaller marginal basins is untenable upward lithologic change from bedded chert to overlying siliceous mudstone in the uppermost portion of chert sequences suggests the gradual landward approach of the oceanic plate toward a trench the tectonic interlayering of these cherts and coarse grained terrigenous elastics is a secondary feature that was added through duplexing underplating in the subduction zone on the basis of the primary stratigraphy and field occurrence of triassic bedded chert in the mino tanba belt newly proposed are an idealized oceanic plate stratigraphy and a generalized travel history of a cordilleran type bedded chert from its birth at a mid oceanic ridge to its demise at a subduction zone

mass balance of devon ice cap canadian arctic interferometric synthetic aperture radar data show that devon ice cap dic northern canada is drained through a network of 11 glacier systems more than half of all ice discharge is through broad flows that converge to the southeast of the ice cap and these are grounded well below sea level at their termini a calculation of the ice cap mass budget reveals that the northwestern sector of dic is gaining mass and that all other sectors are losing mass we estimate that a 12 489 km 2 section of the main ice cap receives 3 46 0 65 gt of snowfall each year and loses 3 11 0 21 gt of water through runoff and 1 43 0 03 gt of ice through glacier discharge altogether the net mass balance of dic is 1 08 0 67 gt a 1 this loss corresponds to a 0 003 mm a 1 contribution to global sea levels and is about half the magnitude of earlier estimates

area change of glaciers across northern ellesmere island nunavut between 1999 and 2015 using a variety of optical satellite scenes this study quantifies the change in the areal extent of 1773 glaciers across northern ellesmere island between 1999 and 2015 our results show that the regional ice coverage decreased by 1705 3 km 2 over the 16 year period a loss of 5 9 ice shelves had the greatest losses relative to their size of 42 4 glaciers feeding into ice shelves reduced in area by 4 7 while tidewater glaciers reduced in area by 3 3 marine terminating glaciers with floating ice tongues reduced in area by 4 9 and 19 of these 27 ice tongues disintegrated causing these glaciers to retreat to their grounding lines land terminating glaciers lost 4 9 of their 1999 area including the complete loss of three small ice caps 2 our study highlights the high sensitivity of the ice cover of northern ellesmere island to recent climate warming and the continued losses that are likely to occur in the future in particular the ice masses most susceptible to further losses are marine terminating glaciers with floating termini and small land terminating ice caps at low elevations

holocene glaciation and climate evolution of baffin island arctic canada abstract lake sediment cores and cosmogenic exposure ce dates constrain the pattern of deglaciation and evolution of climate across baffin island since the last glacial maximum lgm ce dating of erratics demonstrates that the northeastern coastal lowlands became ice free ca 14 ka as the laurentide ice sheet lis receded from its lgm margin on the continental shelf coastal lakes in southeastern baffin island started to accumulate sediment at this time whereas initial lacustrine sedimentation was delayed by two millennia in the north reduced organic matter in lake sediment deposited during the younger dryas chron and the lack of a glacial readvance at that time suggest cold summers and reduced snowfall ice retreated rapidly after 11 ka but was interrupted by a widespread readvance of both the lis and local mountain glaciers 9 6 ka cockburn substage a second readvance occurred just before 8 ka during a period of unusually cold summers corresponding to the 8 2 ka cold event in the greenland ice sheet most local glaciers were behind their present margins before 7 ka and in some instances much earlier although the foxe dome of the lis continued to slowly retract toward the present day barnes ice cap throughout the holocene pollen in lake sediments is rare and dominated by exotic sources prior to 12 ka subsequently grass tundra became established followed by modern tundra vegetation ca 8 ka with subtle changes in pollen assemblages in the late holocene lake primary productivity peaked in the early holocene before terrestrial vegetation or marine surface waters reached their apparent thermal maxima lacustrine marine and glacial proxies all reflect significant late holocene cooling the onset of neoglaciation is well dated in lacustrine records at ca 6 ka with intensification after 2 5 ka the expansion of local glaciers during the little ice age represents the most extensive advance since 7 ka we suggest that the replacement of atlantic surface waters by cold low salinity arctic ocean water coupled with the steady reduction of summer insolation resulted in a significant positive sea ice feedback that produced a larger late holocene summer temperature depression over the baffin region than in the pacific sector of the arctic

global radiolarian zonation for the pliensbachian toarcian and aalenian jurassic radiolarians from 220 samples in queen charlotte islands b c williston lake b c east central oregon baja california sur southern spain austria slovenia turkey oman japan and argentina were studied in order to construct global zonation for the pliensbachian toarcian and aalenian stages well preserved faunas from continuous stratigraphic sections in queen charlotte islands provide the most detailed record for this time interval and all collections are tied to north american ammonite zones or assemblages collections from nearly all other areas lack independent dating except for early toarcian carbon isotope dating in slovenia and late aalenian ammonites in spain a database of 197 widely distributed updated taxonomic species was used to construct a unitary association ua zonation for the interval a global sequence of 41 uas was obtained for the top of the sinemurian to the base of the bajocian the first and the last uas represent the late sinemurian and the early bajocian respectively the remaining 39 uas were merged into nine zones four early pliensbachian one late pliensbachian one early toarcian one middle late toarcian and two aalenian according to prominent radiolarian faunal breaks and ammonite data the new zones are the canutus tipperi katroma clara zone latest sinemurian earliest pliensbachian zartus mostleri pseudoristola megaglobosa hsuum mulleri trillus elkhornensis and gigi fustis lantus sixi zones early pliensbachian eucyrtidiellum nagaiae praeparvicingula tlellensis zone late pliensbachian napora relica eucyrtidiellum disparile zone early toarcian elodium pessagnoi hexasaturnalis hexagonus zone middle and late toarcian higumastra transversa napora nipponica zone early aalenian and mirifusus proavus transhsuum hisuikyoense zone late aalenian these zones can be correlated worldwide and link previously established ua zonations for the hettangian sinemurian and the middle to upper jurassic the new zonation allows high resolution dating in the studied interval and provides a solid basis for analyzing faunal turnovers and the paleobiogeography of jurassic radiolarians

influence of the changing lunar orbit on the astronomical frequencies of pre quaternary insolation patterns the sensitivity of the frequencies of the earth s orbital elements involved in the astronomical theory of paleoclimates obliquity and climatic precession to the earth moon distance and consequently to the length of the day and to the dynamical ellipticity of the earth is investigated for the last billions of years but the new frequencies have been computed for the last 440 million years only a time interval over which data and a model of the earth were available moreover we consider only the impact of the changing precessional parameter assuming that the fundamental frequencies of the planetary motion are steady at the geological time scale under such hypotheses the shortening of the earth moon distance and of the length of the day back in time induces a shortening of the fundamental astronomical periods for obliquity and precession a shortening that is larger for longer periods

paleomagnetism of triassic and jurassic red bedded chert of the inuyama area central japan a paleomagnetic study was conducted on triassic and jurassic red bedded chert from the inuyama area central japan paleomagnetic specimens were collected from single chert beds at nine sites within mesoscopic 1 5 m folds whose ages were determined by radiolarian fossils progressive thermal demagnetization experiments were conducted and three of the four magnetization components provided tectonic implications component d unblocking temperature of 560 680 c from six sites passes the fold test with the mesoscopic folds paleolatitude was estimated as 12 3 15 6 n or s 19 0 10 5 n or s and 25 7 16 7 n or s for 237 ma 223 5 ma and 210 ma respectively in the case of northern latitude a northward migration of 5 6 9 cm yr is estimated between 237 ma and 210 ma with no significant latitudinal migration from 210 ma to 160 ma component c unblocking temperature of 350 530 c has normal polarity and is thought to have been acquired as a chemical remanent magnetization carried by magnetite which was acquired as synfolding magnetization with the sakahogi synform the magnetization is considered to have been acquired through heating in the accretionary wedge during the cretaceous normal superchron 120 5 83 5 ma component b unblocking temperature of 200 350 c has reversed polarity and is thought to have been acquired as a thermoviscous remanent magnetization after the bending of the sakahogi synform the most probable period of the magnetization acquisition is between c27r and c24r 58 63 ma after the emplacement of late cretaceous granitic batholiths

high resolution multispectral techniques for mapping former little ice age terrestrial ice cover in the canadian high arctic abstract multispectral classification approaches were applied to high resolution aster 15 m and etm 30 m imagery for the purpose of developing new techniques for mapping recently deglaciated lia perennial ice cover in the canadian arctic four areas in the queen elizabeth islands with dissimilar surficial geology and diverse topographic complexity were selected to test the efficacy of both sensors for mapping these subtle landscape features automated classification band calculation methods were found to be most effective on quartzitic sandstone and siliceous crystalline bedrock whereas semi automated supervised classification techniques were most successful on substrates comprised primarily of carbonate lithologies aster s superior spatial resolution yielded higher accuracies in topographically complex areas however etm was more effective over a wider variety of substrate lithologies and topographic settings with a mean overall accuracy of 91 mean statistic 0 71 compared to 87 mean statistic 0 60 for aster

late holocene environmental conditions in coronation gulf southwestern canadian arctic archipelago evidence from dinoflagellate cysts other non pollen palynomorphs and pollen boxcore 99lssl 001 68 0958 n 114 1868 w 211 m water depth from coronation gulf represents the first decadal scale marine palynology and late holocene sediment record for the southwestern part of the northwest passage the record was studied for organic walled microfossils dinoflagellate cysts non pollen palynomorphs pollen terrestrial spores and sediment characteristics 210 pb 137 cs and three accelerator mass spectrometry 14 c dates constrain the chronology three prominent palaeoenvironmental zones were identified during the interval ad 1470 1680 zone i the climate was warmer and wetter than at present and environmental conditions were more favourable to biological activity and northward boreal forest migration with reduced sea ice and a longer open water growing season the interval ad 1680 1940 zone ii records sea ice increase and generally cool polar conditions during the little ice age during ad 1940 2000 zone iii organic microfossils indicate an extended open water season and decreased sea ice with suggested amelioration surpassing that of zone i although more marine studies are needed to place this record into an appropriate context the succession from ameliorated zone i to cooler sea ice influenced conditions zone ii and finally to 20th century warming zone iii corresponds well with several terrestrial climatic records from the neighbouring mainland and victoria island and with lower resolution marine records to the west copyright 2011 john wiley sons ltd

expanded late wisconsinan ice cap and ice sheet margins in the western queen elizabeth islands arctic canada abstract recent mapping of surficial geology and geomorphology in the western canadian high arctic melville and eglinton islands together with new radiocarbon dates acquired from ice contact raised marine sediments document expanded late wisconsinan ice limits for the northwest laurentide ice sheet and the western innuitian ice sheet an extension of the northwestern margin of the laurentide ice sheet onto eglinton island is proposed based on evidence from till containing erratics derived from the canadian shield and a pattern of meltwater channels indicating ice retreat offshore into m clure strait expansion of the western melville island ice cap part of the western lowland sector of the innuitian ice sheet to its offshore late wisconsinan limit was facilitated by coalescence with the laurentide ice sheet whose buttressing allowed thickening to occur estimates of ice extent and thickness 500 m of the western melville island ice cap are in agreement with high marine limits 70 m asl lateral and proglacial meltwater channels moraines and glaciomarine glaciolacustrine and glaciofluvial deposits indicate radial retreat of the western melville island ice cap onto central highlands after 13 0 cal ka bp older marine limit shorelines on southern eglinton island 13 6 cal ka bp are broadly synchronous with the early and rapid deglaciation of other areas formerly glaciated by the northwestern laurentide ice sheet to the southeast and southwest 14 2 13 6 cal ka bp the collapse of the northwest laurentide ice sheet in m clure strait beginning at 14 2 cal ka bp in addition to prior inferred thinning opens the possibility that it made a significant contribution to meltwater pulse 1a

evidence for a great medieval earthquake 1100 a d in the central himalayas nepal the himalayan orogen has produced three thrust earthquakes with moment magnitude m w 7 8 to 8 5 during the past century yet no surface ruptures associated with these great earthquakes have been documented here we present paleoseismic evidence from east central nepal that since 700 a d a single earthquake ruptured the frontal thrust fault at 1100 a d with a surface displacement of 17 5 3 meters and a lateral extent and size that could have exceeded 240 kilometers and m w 8 8 respectively ruptures associated with m w

seismotectonic perspectives on the himalayan arc and contiguous areas inferences from past and recent earthquakes abstract spread over countries including pakistan india nepal bhutan and china the himalayan mountain chain the most spectacular result of the indo eurasian plate collision is a locus of destructive earthquakes past earthquakes from this region have impacted vast swathes of frontal himalaya and stretches of alluvial plains south of the range front risk from future earthquakes has increased considering the burgeoning population and an ever expanding built environment in the region while considerable ambiguities exist on the locations ruptures and sizes of the earthquakes during the first half of the last millennium 1255 1344 and 1505 ce those during the latter half 1803 and 1833 ce are quite well documented all reported from the central himalayan segment comprising eastern nepal kumaun and garhwal while dormancy prevailed in the central segment in the intervening period the himalayan arc elsewhere witnessed three large great earthquakes in the last century namely 1905 kangra mw 7 8 1934 bihar nepal mw 8 2 and 1950 upper assam mw 8 6 the last one being the largest intra continental earthquake in the recorded history the april 25 gorkha nepal earthquake mw 7 8 located in the central seismic gap terminated the period of low level seismic productivity that followed the 1950 event the himalayan arc and its contiguous regions are now being investigated using various tools including paleoseismology quite understandably the interpretations and tectonic models do not always converge given the diverse quality and type of data the data from variously sized modern day earthquakes sourced in the diverse structural settings of the himalaya provide better constraints on the source properties of the himalayan earthquakes the source complexity and diversity is a striking point of interest for the post 1950 events and at least some of them seem to deviate from the generally accepted model of great ruptures on a shallow dipping detachment a prime example of such anomalies is the 2005 kashmir earthquake mw 7 6 sourced on an out of sequence thrust the sources of the 1991 uttarkashi mw 6 8 1999 chamoli mw 6 6 and the 2015 gorkha nepal mw 7 8 earthquakes all in the central himalayan segment are attributed to the ramp flat on the down dip part of the main himalayan thrust mht in contrast the 2011 sikkim mw 6 9 and the 2016 imphal mw 6 7 earthquakes are intraplate events sourced within the subducting slab source models of modern day earthquakes 1991 2016 discussed in this paper bring out this plurality of mechanisms expected of a complex subduction cum collisional boundary this review presents the status of current seismotectonic understanding of the himalaya from the analyses of significant earthquakes from the past as well as recent events with a focus on the central himalayan segment

late cretaceous orbitally paced carbon isotope stratigraphy from the bottaccione gorge italy abstract a refined astronomical tuning of the upper albian lower campanian is proposed from the bottaccione reference section gubbio central italy long term eccentricity cycles filtered from a high resolution 13c record were tuned to the highly stable 405 kyr cycles of the new la2010 astronomical solution for the earth s orbital elements the achieved orbital tuning provides a new precise and accurate age model for dating biostratigraphic magnetostratigraphic and carbon isotope events through a 23 myr long record cycles of 8 0 4 7 3 4 and 2 4 myr modulate the entire 13c record thus extending their detection from the cenozoic to 100 ma and represent primary and stable long term oscillation modes of earth s climate ocean system although an ultimate driver of these long term periodicities is lacking we speculate that specifically the periodicity at 4 7 myr represents a homologue of the present eccentricity grand cycles evolved by the chaotic behaviour of solar system planets during the mesozoic the long term periodicities potentially reflect an unexplored expression of the low frequency response of the carbon cycle to global biogeochemical dynamics of major nutrients particularly phosphorus associated with modulation of inputs to the ocean in turn triggered by high order marine transgressions and formation of highly productive shelf seas this very long term eccentricity control modulated by periodic low energy cycles is suggested to play a crucial role in carbon cycling controlling a chain of climate sensitive global biogeochemical processes on the earth finally these grand cycles provide a potential tool for geological correlation and provide a robust constraint for accurate calculation of the orbital evolution of the solar system

carbon isotope record of the early jurassic toarcian oceanic anoxic event from fossil wood and marine carbonate lusitanian basin portugal thetoarcianoceanicanoxicevent oae intheearlyjurassic 183maago wascharacterizedbywidespreadnear synchronous deposition of organic rich shales in marine settings as well as perturbations to several isotopic systems characteristically two positive carbon isotope excursions in a range of materials are separated by an abrupt negative shift carbon isotope profiles from toarcian fossil wood collected in england and denmark have previously been shown to exhibit this large drop 7 i n 13 c values interpreted as due to an injection of isotopically light co2 into the ocean atmosphere system however the global nature of this excursion has been challengedonthebasisofcarbon isotopedatafromnektonicmarinemolluscs belemnites whichexhibitheavierthanexpectedcarbonisotope values here we present new data principally from fossil wood and bulk carbonate collected at centimetre scale from a hemipelagic section at peniche coastal portugal this section is low in organic carbon average toc 0 5 and the samples should not have suffered significant diagenetic contamination by organic carbon of marine origin the carbon isotope profile based on wood shows two positive excursions separated by a large and abrupt negative excursion which parallels exactly the profile based on bulk carbonate samples from the same section albeit with approximately twice the amplitude 8 in wood versus 3 5 in carbonate these data indicate thatthe negative carbon isotope excursion affected the atmosphereand by implication the global ocean as well the difference in amplitude between terrestrial organic and marine carbonate curves can be explained by greater water availability in the terrestrial environment during the negative excursion for which there is independent evidence from marine osmiumisotope records and plausibly changes in atmospheric co2 content for which independent evidence is also available the peniche succession is also notable for the occurrence of re deposited sediments their lowest occurrence coincides with the base of the negative excursionandtheirhighestoccurrencecoincideswithitstop thus slopeinstabilityandsedimentsupplycouldhavebeenstronglylinked to the global environmental perturbation an association that may misleadingly simulate the effects of sea level fall

paleoseismological evidence of surface faulting along the northeastern himalayan front india timing size and spatial extent of great earthquakes the similar to 2500 km long himalayan arc has experienced three large to great earthquakes of m w 7 8 to 8 4 during the past century but none produced surface rupture paleoseismic studies have been conducted during the last decade to begin understanding the timing size rupture extent return period and mechanics of the faulting associated with the occurrence of large surface rupturing earthquakes along the similar to 2500 km long himalayan frontal thrust hft system of india and nepal the previous studies have been limited to about nine sites along the western two thirds of the hft extending through northwest india and along the southern border of nepal we present here the results of paleoseismic investigations at three additional sites further to the northeast along the hft within the indian states of west bengal and assam the three sites reside between the meizoseismal areas of the 1934 bihar nepal and 1950 assam earthquakes the two westernmost of the sites near the village of chalsa and near the nameri tiger preserve show that offsets during the last surface rupture event were at minimum of about 14 m and 12 m respectively limits on the ages of surface rupture at chalsa site a and nameri site b though broad allow the possibility that the two sites record the same great historical rupture reported in nepal around a d 1100 the correlation between the two sites is supported by the observation that the large displacements as recorded at chalsa and nameri would most likely be associated with rupture lengths of hundreds of kilometers or more and are on the same order as reported for a surface rupture earthquake reported in nepal around a d 1100 assuming the offsets observed at chalsa and nameri occurred synchronously with reported offsets in nepal the rupture length of the event would approach 700 to 800 km the easternmost site is located within harmutty tea estate site c at the edges of the 1950 assam earthquake meizoseismal area here the most recent event offset is relatively much smaller 2 5 m and radiocarbon dating shows it to have occurred after a d 1100 after about a d 1270 the location of the site near the edge of the meizoseismal region of the 1950 assam earthquake and the relatively lesser offset allows speculation that the displacement records the 1950 m w 8 4 assam earthquake scatter in radiocarbon ages on detrital charcoal has not resulted in a firm bracket on the timing of events observed in the trenches nonetheless the observations collected here when taken together suggest that the largest of thrust earthquakes along the himalayan arc have rupture lengths and displacements of similar scale to the largest that have occurred historically along the world s subduction zones

a new procedure for gridding elevation and stream line data with automatic removal of spurious pits abstract a morphological approach to the interpolation of regular grid digital elevation models dems from surface specific elevation data points and selected stream lines is described the approach has given rise to a computationally efficient interpolation procedure which couples the minimization of a terrain specific roughness penalty with an automatic drainage enforcement algorithm the drainage enforcement algorithm removes spurious sinks or pits yielding dems which may be used to advantage in hydrological process studies the drainage enforcement algorithm has also been found to significantly increase the accuracy of dems interpolated from sparse but well chosen surface specific elevation data moreover it facilitates the detection of errors in elevation data that would not be detected by more conventional statistical means and forms a sound physical basis for cartographic generalization

review and revision of cenozoic tropical planktonic foraminiferal biostratigraphy and calibration to the geomagnetic polarity and astronomical time scale planktonic foraminifera are widely utilized for the biostratigraphy of cretaceous and cenozoic marine sediments and are a fundamental component of cenozoic chronostratigraphy the recent enhancements in deep sea drilling recovery multiple coring and high resolution sampling both offshore and onshore has improved the planktonic foraminiferal calibrations to magnetostratigraphy and or modified species ranges this accumulated new information has allowed many of the planktonic foraminiferal bioevents of the cenozoic to be revised and the planktonic foraminiferal calibrations to be reassessed we incorporate these developments and amendments into the existing biostratigraphic zonal scheme in this paper we present an amended low latitude tropical and subtropical cenozoic planktonic foraminiferal zonation we compile 187 revised calibrations of planktonic foraminiferal bioevents from multiple sources for the cenozoic and have incorporated these recalibrations into a revised cenozoic planktonic foraminiferal biochronology we review and synthesize these calibrations to both the geomagnetic polarity time scale gpts of the cenozoic and astronomical time scale ats of the neogene and late paleogene on the whole these recalibrations are consistent with the previous work however in some cases they have led to major adjustments to the duration of biochrons recalibrations of the early middle eocene first appearance datums of globigerinatheka kugleri hantkenina singanoae guembelitrioides nuttalli and turborotalia frontosa have resulted in large changes in the durations of biochrons e7 e8 and e9 we have introduced upper oligocene zone o7 utilizing the biostratigraphic utility of paragloborotalia pseudokugleri for the neogene period major revisions are applied to the fohsellid lineage of the middle miocene and we have modified the criteria for recognition of zones m7 m8 and m9 with additional adjustments regarding the globigerinatella lineage to zones m2 and m3 the revised and recalibrated datums provide a major advance in biochronologic resolution and a template for future progress of the cenozoic time scale

thirty seven year mass balance of devon ice cap nunavut canada determined by shallow ice coring and melt modeling 1 in april may 2000 eight boreholes were drilled to 15 20 m depth on the devon ice cap 137cs activity profiles of each borehole showed a peak count rate at depth that is associated with fallout from atmospheric thermonuclear weapons testing in 1963 snow firn and ice densities were measured at each core site and were used to estimate the average pattern of mass balance across the accumulation zone of the ice cap over the period 1963 2000 the average mass balance across the entire ice cap for the period 1960 2000 was also estimated using a degree day model driven by data derived from on ice temperature sensors and long term measurements at resolute bay best fitting degree day factors were determined for different sectors of the ice cap by comparing model output with repeated annual mass balance measurements made along two transects koerner 1970 the results suggest that the ice cap has lost 1 6 km3 water per year equivalent to a mean net mass balance of approximately 0 13 m we a 1 estimates of the mean mass balance for individual drainage basins reveal regions of positive and negative mass balance that are consistent with remotely sensed observations of advancing and retreating ice cap margins respectively

on glacial inception and orography abstract there is no doubt that orography plays a crucial role in the initiation of ice sheets mass balance observations on glaciers in high mountain and polar climates show that the specific balance varies first of all with altitude the height mass balance feedback hmb feedback is the most effective process to turn local ice caps into big ice sheets here a study is presented on the processes that determine the strength of the hmb feedback this is done by carrying out a set of integrations with a numerical ice sheet model for a bounded domain and a sinusoidally varying bed shape results are analysed for different wavenumbers and amplitudes it turns out that the relative importance of the geometric effect higher mountains allow earlier glacierisation and the ice mechanical effect dependence of ice flow on the bed slope varies significantly with wavenumber and amplitude with regard to full glaciation of the domain this implies that for a given wavenumber there is a preferred amplitude that is the drop in the equilibrium line altitude needed to initiate full glaciation has a minimum

geochronological constraints on post extinction recovery of the ammonoids and carbon cycle perturbations during the early jurassic abstract this paper presents the first quantitative study of the early jurassic recovery of ammonoids after the end triassic mass extinction based on detailed u pb id tims isotope dilution thermal ionization mass spectrometry geochronology from ash bed zircons placed within a clear phylogenetical and biochronological framework at the subzonal and species level this study was triggered by the discovery of a rich peruvian succession of ammonites deposited concomitantly with an unusually large number of ash beds two major phases of rediversification are observed during the psiloceras spelae and angulaticeras zones that correspond to positive peaks in the 13corg curve providing a possible link between biodiversity and the global carbon cycle in the case of the post extinction recovery the development of the earliest hettangian ammonites occurs within the genus psiloceras which begins with the occurrence of p spelae and then explodes into worldwide development of smooth psiloceratids of the psiloceras planorbis group s l this rapid biodiversification likely occurred less than 100 ka after the end triassic crisis the genus psiloceras occupied all the possible ecological niches worldwide from the pacific deep waters to the nw european shallow deposits and also in some rare tethyan occurrences like at germig in tibet this global dispersion allowed the differentiation of the group in several major phyla the schlotheimiidae discamphiceratinae arietitidae and lytocerataceae which were the roots of all other jurassic and cretaceous ammonites

paleoseismic evidence of great surface rupture earthquakes along the indian himalaya 1 toward understanding the relationship between strain accumulation and strain release in the context of the mechanics of the earthquake and mountain building process and quantifying the seismic hazard associated with the globes largest continental thrust system we describe the late quaternary expression and paleoseismic evidence for great surface rupture earthquakes at six sites along the himalayan frontal thrust hft system of india our observations span a distance of 250 km along strike of the hft uplifted and truncated fluvial terrace deposits resulting from the holocene displacements on the hft are preserved along canyons of the ghaggar markanda shajahanpur and kosi rivers dividing the elevation of the bedrock straths at each site by their ages yields estimates of the vertical uplift rate of 4 6 mm yr which when assumed to be the result of slip on an underlying thrust dipping at 20 45 are equivalent to fault slip rates of 6 18 mm yr or shortening rates of 4 16 mm yr trench exposures reveal the hft to fold and break late holocene surface sediments near the cities and villages of chandigarh kala amb rampur ganda lal dhang and ramnagar radiocarbon ages of samples obtained from the displaced sediments indicate surface rupture at each site took place after a d 1200 and before a d 1700 uncertainties attendant to the radiocarbon dating currently do not allow an unambiguous definition of the capping bound on the age of the displacement at each site and hence whether or not the displacements at all sites were contemporaneous trench exposures and vertical separations measured across scarps at rampur ganda lal dhang and ramnagar are interpreted to indicate single event displacements of 11 38 m dividing the observed single event vertical components of displacement by the estimated longer term uplift rates indicates 1330 3250 or more years should be required to accumulate the slip sufficient to produce similar sized displacements surface rupture appears to not have occurred during the historical 1905 kangra mw 7 7 1934 bihar nepal mw 8 1 and 1950 assam mw 8 4 earthquakes which also occurred along the himalayan front yet we observe clear evidence of fault scarps and displacements in young alluvium and progressive and continued offset of fluvial terrace deposits along the hft we suggest on this basis and the size and possible synchroneity of displacements recorded in the trenches that there exists the potential for earthquakes larger than recorded in the historical record and with the potential to rupture lengths of the hft greater than the 250 km we have studied

glacier change on axel heiberg island nunavut canada historical records are valuable for assessing glacier change in the canadian high arctic ommanney s 1969 detailed inventory of axel heiberg island glaciers based on photography from 1958 59 has been revisited converted into digital format and compared to glacier extents mapped from 1999 2000 satellite imagery our results show that the island wide ice coverage decreased by 15 92 km 2 in the 42 year period a loss of 2 if the contributions to ice advance of only three surging glaciers are removed then the island wide ice loss approaches 60 km 2 furthermore it is notable that 90 of ice masses smaller than 0 2 km 2 disappeared entirely during the 42 year study period an observation confirmed by field studies successful predictions from the original inventory are highlighted and the likely mechanisms driving the observed advances and retreats are discussed

biostratigraphic and radiometric age data question the milankovitch characteristics of the latemar cycles southern alps italy the combination of age diagnostic fossils in platform carbonates geometrical relationships with coeval basinal successions and single zircon u pb ages from volcaniclastic layers in basinal deposits constrain the age of a cyclic succession in the interior of the latemar platform to a narrow time span in the middle triassic with a duration shorter than 5 m y precession induced milankovitch band sea level oscillations are therefore excluded as controls for most of the 600 platform cycles reported from latemar statistical evaluation and graphic space time analyses of cycle stacking patterns alone may therefore not allow an unambiguous recognition of milankovitch frequencies in ancient platform carbonates

on a flawed conclusion that the 1255 a d earthquake ruptured 800 km of the himalayan frontal thrust east of kathmandu a reexamination of the observations and analysis recently reported to conclude that an 800 km section of the himalayan frontal thrust ruptured in 1255 a d shows that the conclusion is flawed and without merit because of misinterpretations of trench logs and incorrect interpretation of radiocarbon statistics

flow dynamics and iceberg calving rates of devon ice cap nunavut canada the surface velocity field of devon ice cap nunavut canada was mapped using interferometric synthetic aperture radar insar ascending european remote sensing satellite 1 and 2 ers 1 2 tandem mode data were used for the western and southeast sectors and 3 day repeat pass ers 1 imagery for the northeast sector speckle tracking procedures were used with radarsat 1 imagery to obtain surface velocities over the terminus of belcher glacier a major calving front where decorrelation between ers data occurred the insar data highlight a significant contrast in ice flow dynamics between the east and west sides of the ice cap ice movement west of the main north south divide is dominated by relatively uniform sheet flow but three fast flowing outlet glaciers that extend 14 23 km beyond the ice cap margin also drain this region several outlet glaciers that extend up to 60km inland from the eastern margin drain the eastern side of the ice cap the dominant ice flow regimes were classified based on the relationship between the driving stress averaged over a length scale often ice thicknesses and the ratio of surface velocity to ice thickness the mapped distribution of flow regimes appears to depict the spatial extent of basal sliding across the ice cap this is supported by a close relationship between the occurrence of flow stripes on the ice surface and flow regimes where basal sliding was found to be an important component of the glacier motion iceberg calving rates were computed using measured surface velocities and ice thicknesses derived from airborne radio echo sounding the volume of ice calved between 1960 and 1999 was estimated to be 20 5 4 7 km 3 or 0 57km 3 a 1 approximately 89 of this loss occurred along the eastern margin the largest single source is belcher glacier which accounts for 50 of the total amount of ice calved

astronomical cycle origin of bedded chert a middle triassic bedded chert sequence inuyama japan abstract astronomical forcing is one of the main drivers of climate change and astronomical cyclicity recorded in sediments provides a clue to understand the dynamics of the global climate system bedded cherts consist of rhythmic alternations of chert and shale beds although previous studies have hypothesized that the origin of bedded chert is related to astronomical cycles e g fischer 1976 hori et al 1993 conclusive proof remains elusive to explore this possibility we established a continuous high resolution lithostratigraphy of middle triassic bedded chert in central japan the average duration of each chert shale couplet is 20 kyr similar to that of the precession cycle spectral analysis of a bed number series of thickness variations in chert beds was performed assuming that each chert shale couplet represents a 20 kyr precession cycle the results reveal cycles involving approximately 200 20 5 and 2 3 beds corresponding to periodicities of approximately 4000 400 100 and 40 60 kyr respectively by further assuming that the 20 bed cycle represents a 405 kyr eccentricity cycle of constant and stable periodicity we converted the bed number series to a time series spectral analysis of the time series revealed distinct periodicities of 3600 117 97 and 38 kyr in addition to 405 kyr besides 3600 kyr these periodicities agree well with the 120 95 and 37 kyr periodicities for eccentricity cycles and the obliquity cycle during the triassic moreover we detected amplitude modulation of the approximately 100 kyr cycle of thickness variations in chert beds with a 405 kyr periodicity which may correspond to amplitude modulation of 100 kyr climatic precession cycle with the 405 kyr periodicity the approximately 3600 kyr periodicity described above and 1800 kyr periodicity manifested as the amplitude modulation of the 405 kyr cycle are correlated to present day long term eccentricity cycles of 2400 and 4800 kyr evolved by chaotic behavior of solar planets collectively these similarities in the periodicities of dominant cycles their hierarchy and the nature of amplitude modulation of cycles in chert bed thickness with those of astronomical cycles strongly support the hypothesis that the sedimentary rhythm of bedded chert is paced by astronomical cycles thereby indicating the potential of bedded chert as a template for a mesozoic cyclostratigraphy

comment on the organic carbon isotopic and paleontological record across the triassic jurassic boundary at the candidate gssp section at ferguson hill muller canyon nevada usa by ward et al 2007

dynamics of the north american ice sheet complex during its inception and build up to the last glacial maximum the north american ice sheet complex played a major role in global sea level fluctuations during the late quaternary but our knowledge of its dynamics is based mostly on its demise from the last glacial maximum lgm a period characterised by non linear behaviour in the form of punctuated ice margin recession episodic ice streaming and major shifts in the location of ice divides in comparison knowledge of the pre lgm ice complex is poorly constrained largely because of the fragmentary nature of the evidence relating to ice sheet build up in this paper we explore the inception and growth of ice 120 20 ka using a glacial systems model which has been calibrated against a large and diverse set of data relating to the deglacial interval we make use of calibration data prior to the lgm but its scarcity introduces greater uncertainty which is partly alleviated by our large ensemble analysis results suggest that following the last interglaciation oxygen isotope stage ois 5e the ice complex initiated over the north eastern canadian arctic and in the cordillera within a few thousand years it then underwent rapid growth to an ois 5 maximum at 110 ka 5d and covered 70 of the area occupied by the lgm ice cover although only 30 by volume an ois 5 minimum is modelled at 80 ka 5a before a second phase of rapid growth at the start of ois 4 which culminated in a large ice complex at 65 ka almost as large as at the lgm subsequent deglaciation was rapid maximum modelled sea level contribution of 16 cm per century and resulted in an ois 3 minimum between ca 55 60 ka thereafter the ice complex grew towards its lgm configuration interrupted by several phases of successively less significant mass loss our results support and extend previous inferences based on geological evidence and reinforce the notion of a highly dynamic pre lgm ice complex e g with episodes of 10 s m of eustatic sea level equivalent in 50 but even the thin ois 5 ice sheets exhibit fast flow features several 1000 m a 1 in major topographic troughs notwithstanding the severe limitations imposed by the use of the shallow ice approximation we note that most fast flow features generated prior to the lgm correspond to the location of known ice streams during deglaciation i e in major topographic troughs and over soft sediments at the southern and western margins moreover the modelled flux of these ice streams sensu lato appears to be non linearly scaled to ice sheet volume i e there is no evidence that decay phases were associated with significantly increased ice stream activity this hypothesis requires testing using a model with higher order physics and future modelling would also benefit from additional pre lgm constraints e g dated ice free margin positions to help reduce and quantify uncertainties

canada and the world glacier inventory this paper reviews the origins of the world glacier inventory program and canada s participation it tracks the program of the canadian federal government from its initiation to its demise today progress is geared towards the international glims and globglacier programs to which scientists from several canadian universities are making contributions achievements during the past decade towards providing data on canada s glacierized areas in the arctic and in western canada are documented

paleomagnetism of red cherts a case study in the inuyama area central japan this study is an attempt to isolate and identify the primary magnetization in red cherts red chert samples from a middle triassic sequence in the inuyama area 35 4 n 137 0 e central japan have a multicomponent magnetization which is delineated by thermal demagnetization two of the components have high coercivity and high blocking temperatures one is carried by hematite and the other by magnetite the former was concluded to be the primary magnetization for two reasons 1 it predates intraformational folding and 2 it records geomagnetic reversals the other component which accounts for the dominant part of natural remanent magnetization was probably acquired at a time long after the deposition two paleomagnetic results were drawn from the middle triassic red chert sequence 1 the mean inclination of the samples in the sequence was 1 4 6 8 therefore the paleolatitude amounts to 0 7 3 4 in contrast to the paleolatitude expected from the paleopole of eurasian continent which is about 70 and 2 the magnetostratigraphy of this sequence indicates that two geomagnetic epochs in the middle triassic are considerably longer more than several million years than the average of those in the cenozoic

changes in late neoglacial climate inferred from former equilibrium line altitudes in the queen elizabeth islands arctic canada regional scale spatial variation in the change in equilibrium line altitude ela trend surface in the queen elizabeth islands qei arctic canada between the little ice age lia and 1960 corresponds to empirical orthogonal functions eofs representing specific patterns of summer climate variability found in the modern record extreme warm 1953 1962 and cold 1965 1974 decades in the modern record were used as modern analogues of climatic conditions during the early twentieth century and the lia respectively because of the minimal influence of precipitation during both extreme decades temperature is the variable upon which the fluctuation of the ela is dependent hence the ela h pattern describes the spatial pattern of change in sat across the qei between the lia and 1960 this pattern is consistent with the primary mode of variability of mean summer surface air temperature sat in the modern record ie eof 1 1949 2002 the positive negative phase of which is strongly in place during th

an extended organic carbon isotope record across the triassic jurassic boundary in the queen charlotte islands british columbia canada abstract new lithologic and organic carbon isotope data are presented for the triassic jurassic boundary section at kennecott point queen charlotte islands british columbia canada the previously reported late norian to earliest hettangian record is extended by over 130 m and three new isotopic features are revealed the record now shows a negative offset in baseline carbon isotope values from approximately 29 in the late norian to 31 in the hettangian this offset is accompanied by the previously reported 2 negative excursion at the triassic jurassic boundary and a 5 positive excursion in the early hettangian there is a significant long term negative isotopic trend in the hettangian interval of the section which may be due to camp volcanism the positive excursion is attributed to a decline in bio calcification as well as changes in microbial ecology both related to the mass extinction at the triassic jurassic boundary

factors influencing the basal temperatures of a high arctic polythermal glacier a number of glaciers in the canadian high arctic are composed primarily of cold ice but the ice at or near their beds reaches the pressure melting point pmp in the ablation zone past modelling studies have suggested that the basal temperatures of some of these glaciers reach the pmp where they should not indicating that they are not in thermal equilibrium with present day surface air temperatures to investigate the possible reasons for thermal disequilibria in such glaciers a two dimensional ice temperature model was used to simulate the inferred thermal characteristics of john evans glacier ellesmere island results indicate that while surface refreezing and historical ice thickness changes have had a warming effect upon basal ice temperatures supraglacial meltwater reaching the glacier bed provides the single most critical heat source for explaining the apparent thermal disequilibrium between present day inferred ice bed temperatures and those modelled under present day boundary conditions

a 70 million year astronomical time scale for the deep sea bedded chert sequence inuyama japan implications for triassic jurassic geochronology abstract the astronomical time scale ats has provided high resolution geochronology however the early mesozoic ats is still under construction partly due to the lack of continuous pelagic sequences of the early mesozoic here we present ca 70 myr long ats constructed from the early mesozoic deep sea bedded chert sequence exposed in the inuyama area central japan the sedimentary rhythms of bedded chert display a full range of climatic precession related cycles 20 kyr cycle as a chert shale couplet and 100 405 2000 to 4000 and 10 000 kyr cycles as chert bed thickness variation the newly established ats inuyama ats is tuned by 405 kyr eccentricity cycle and is anchored at the end triassic radiolarian extinction level as 201 4 0 2 ma this inuyama ats gives ages consistent with the radiometric ages projected to the inuyama deep sea sequence using biostratigraphy and carbon isotope stratigraphy the inuyama ats provides the age constraints for the triassic and jurassic stage boundaries which support the long norian option of muttoni et al 2004 because the deep sea bedded chert sequence covers a long time interval before the cretaceous the ats for the bedded chert will serve as a template for the astrochronology of mesozoic and older ages

changes in late neoglacial perennial snow ice extent and equilibrium line altitudes in the queen elizabeth islands arctic canada changes in late neoglaical climate resulted in extensive modification of arctic terrestrial ice cover a substantial reduction in terrestrial ice cover in the queen elizabeth islands qei following the little ice age lia ad 1250 1900 is indicated by widespread light toned patches of poorly vegetated terrain extending back to the modern ice mass these patches display abrupt outer margins trimlines which record the former position and maximum extent of perennial snow ice and in many cases mark the former equilibrium line altitude ela trimlines surrounding terrain formerly covered by lia perennial snow ice were mapped using multispectral clas sification approaches applied to high resolution satellite imagery elas were reconstructed from trimlines associ ated with former perennial snow ice produced by long term snowline lowering between the end of the lia and 1960 the area of terrestrial ice in the qei decreased by 37 62 387 km 2 most of this reduction 94 occurred in the eastern qei where the majority of the ice exists today however a 100 reduction in ice cover occurred on many of the western islands by 1960 an effect largely controlled by the subtle topography of these islands the reconstructed lia ela trend surface was used with the 1960 mapped elas to calculate spatial variations in the change in height h of the ela trend surface throughout the qei during the first half of the twentieth century ela h between the lia and 1960 reveal a high degree of local variability in the mountainous regions ranging from 0 to 600 m however a strong regional scale pattern of change is shown over the qei as a whole

effects of karoo ferrar volcanism and astronomical cycles on the toarcian oceanic anoxic events early jurassic abstract one of the most profound environmental changes in the mesozoic took place during pliensbachian toarcian early jurassic including oceanic anoxia toarcian oceanic anoxic event t oae the t oae is thought to have been caused by increased atmospheric co 2 triggered by karoo ferrar volcanism this idea however remains debated primarily due to uncertainties in their age constraints of the relevant sedimentary sequences to examine their temporal relationships herein we provide the astronomical time scale of the lower jurassic deep sea bedded chert sequences from the pelagic panthalassa superocean which are exposed in the inuyama area central japan a 405 kyr tuned astrochronology anchored to the end triassic extinction as 201 4 0 2 ma ikeda and tada 2013 allows us to constrain the ages of two black bedded cherts t oae1 and t oae2 the ages of these t oaes overlap u pb ages of karoo volcanic rocks t oae in the european region is also synchronous with the karoo ferrar volcanism based on radiolarian and ammonite biostratigraphic correlation these temporal relationships support the potential impact of karoo ferrar volcanism on t oaes on a global scale on the other hand the onset of t oaes occur at the maxima of 40 kyr 100 kyr and 405 kyr cycles of chert thickness variation the termination of t oaes and the recovery to oxic conditions in pelagic ocean coincide with the minima of 40 kyr 100 kyr and 405 kyr cycles of chert thickness moreover the termination of final black chert and grey chert deposition coincide with the minima of 1800 kyr cycles of chert thickness these temporal relationships imply that orbital scale productivity cycles were important in controlling the onset and termination of t oaes through the carbon cycle dynamics which have been already amplified by karoo ferrar volcanism

high resolution ammonite and carbon isotope stratigraphy across the triassic jurassic boundary at new york canyon nevada the triassic jurassic boundary is generally considered as one of the major extinctions in the history of phanerozoic the high resolution ammonite correlations and carbon isotope marine record in the new york canyon area allow to distinguish two negative carbon excursions across this boundary with different paleoenvironmental meanings the late rhaetian negative excursion is related to the extinction and regressive phase the early hettangian 13corg negative excursion is associated with a major floristic turnover and major ammonite and radiolarian radiation the end triassic extinction early jurassic recovery is fully compatible with a volcanism triggered crisis probably related to the central atlantic magmatic province the main environmental stress might have been generated by repeated release of so2 gas heavy metals emissions darkening and subsequent cooling this phase was followed by a major long term co2 accumulation during the early hettangian with development of nutrient rich marine waters favouring the recovery of productivity and deposition of black shales

rapid wastage of alaska glaciers and their contribution to rising sea level we have used airborne laser altimetry to estimate volume changes of 67 glaciers in alaska from the mid 1950s to the mid 1990s the average rate of thickness change of these glaciers was 0 52 m year extrapolation to all glaciers in alaska yields an estimated total annual volume change of 52 15 km 3 year water equivalent equivalent to a rise in sea level sle of 0 14 0 04 mm year repeat measurements of 28 glaciers from the mid 1990s to 2000 2001 suggest an increased average rate of thinning 1 8 m year this leads to an extrapolated annual volume loss from alaska glaciers equal to 96 35 km 3 year or 0 27 0 10 mm year sle during the past decade these recent losses are nearly double the estimated annual loss from the entire greenland ice sheet during the same time period and are much higher than previously published loss estimates for alaska glaciers they form the largest glaciological contribution to rising sea level yet measured

a 9 myr cycle in cenozoic δ13c record and long term orbital eccentricity modulation is there a link abstract the 65 myr long cenozoic carbon isotope record 13 c of zachos et al 2001 2008 documents a strong long term cycle with a mean pseudoperiodicity close to 9 myr this cyclicity modulates the 2 4 myr eccentricity cycle amplitude hinting at a possible link between long term astronomical and geological variations some phase shifts between 9 myr 13 c and astronomical cycles suggest that additional processes e g tectonics contribute to these long term carbon cycle variations the strong response of 13 c to long term eccentricity periods 9 myr 2 4 myr 400 kyr supports the hypothesis that the long time residence of carbon in the oceans amplifies lower frequency or dampens higher frequency orbital variations additionally the strong expression of low amplitude 9 myr eccentricity cycle in the 13 c record could be explained by energy transfer process from higher to lower frequency cycles and all eccentricity components modulate the carrier climatic precession cycles finally the paleocene eocene thermal maximum petm 55 9 ma event which corresponds to a pronounced 13 c negative excursion is situated within a strong decrease in the most prominent 9 myr 13 c cycle hinting at a link between accelerated rates in 13 c variations and the petm this specific 9 myr 13 c cycle seems to be amplified by non orbital mechanisms in atmosphere continent ocean system such as previously suggested methane release from gas hydrate and volcanism

panthalassic oceanic anoxia at the end of the early triassic a cause of delay in the recovery of life after the end permian mass extinction abstract fossil data show that the recovery of life after the end permian mass extinction occurred in the anisian early middle triassic the process by which oceanic environments recovered from anoxia after the end permian event is uncertain to determine the timing of known recovery stages the nature of oceanic redox conditions and the health of cyanobacterial plankton populations this study analyses conodonts and organic molecules from siliceous claystones and cherts from accretionary complexes in japan that span the upper lower triassic to the lowermost middle triassic conodonts indicate that the study section ranges from upper olenekian to anisian and includes the olenekian anisian boundary an increase in polycyclic aromatic hydrocarbons probably derived from algae dominated organic matter and a decrease in methylhopane index 2 methylhopane hopane a measure of cyanobacterial activity are present in end olenekian black chert pristane phytane ratios a measure of redox conditions in all stratigraphic units are lower than 1 indicating the prevalence of deep sea anoxia during the late olenekian to anisian high concentrations of dibenzothiophene an index of anoxic depositional environments high sulphur carbon ratios and high organic carbon contents are present in two upper olenekian intervals and at the end of the upper olenekian suggesting development of anoxic deep water one of the anoxic events in the end of the upper olenekian coincided with decreased radiolarian diversity this implies that anoxic deep water in the panthalassic ocean reached intermediate water depths at the end of the early triassic killing marine organisms including radiolaria this event may be related to the delay in the recovery of life and environments after the end permian mass extinction

timing of recovery from the end permian extinction geochronologic and biostratigraphic constraints from south china comment and reply reply bucher et al s comment 2007 1 questioned the validity of our 247 2 ma age estimate for the early middle triassic olenekian anisian o a boundary based on a comparison of recent data from lower guandao section presented by us lehrmann et al 2006 2 with preliminary data reported from

deep sea record of impact apparently unrelated to mass extinction in the late triassic the 34 million year my interval of the late triassic is marked by the formation of several large impact structures on earth late triassic impact events have been considered a factor in biotic extinction events in the late triassic e g end triassic extinction event but this scenario remains controversial because of a lack of stratigraphic records of ejecta deposits here we report evidence for an impact event platinum group elements anomaly with nickel rich magnetite and microspherules from the middle norian upper triassic deep sea sediment in japan this includes anomalously high abundances of iridium up to 41 5 parts per billion ppb in the ejecta deposit which suggests that the iridium enriched ejecta layers of the late triassic may be found on a global scale the ejecta deposit is constrained by microfossils that suggest correlation with the 215 5 mya 100 km wide manicouagan impact crater in canada our analysis of radiolarians shows no evidence of a mass extinction event across the impact event horizon and no contemporaneous faunal turnover is seen in other marine planktons however such an event has been reported among marine faunas and terrestrial tetrapods and floras in north america we therefore suggest that the manicouagan impact triggered the extinction of terrestrial and marine organisms near the impact site but not within the pelagic marine realm