first simultaneous and common volume observations of noctilucent clouds and polar mesosphere summer echoes by lidar and radar we present the results of first simultaneous and common volume observations of noctilucent clouds nlc and polar mesosphere summer echoes pmse by two ground based lidars and one vhf radar the measurements were performed at the alomar facility 69 n 16 e during the time period july 23 through august 18 1994 throughout this period nlc layers were observed by the lidars on four occasions during each of these four lidar observed nlc events pmse layers were also observed overhead by the radar these joint nlc pmse events divide into two distinct types 1 tightly coupled and 2 loosely coupled nlc and pmse layers in one of the events the pmse layer developed into a well defined double layer with only 0 8 km vertical separation while the lidar observed nlc layer matched closely in time and space the lower pmse sublayer within all four nlc pmse layers the wind speed increased sharply with increasing altitude with wind shears amounting to 0 03 s 1 and larger current theories can explain some of the observed layer features

first observations of polar mesosphere summer echoes in antarctica a 25 kw peak power 50 mhz radar was installed at the peruvian base on king george island antarctica 62 s in early 1993 a search for polar mesospheric summer echoes pmses was made during late january and early february of the first year of operation with negative results these results have been reported in the literature balsley et al 1993 1995 we report here results obtained during the austral summer of the second year 1994 of operation observations during the second year were begun earlier i e closer to the austral summer solstice pmses were observed during this period albeit the echoes were much weaker than what one would expect based on earlier poker flat radar results at a comparable latitude 65 n in the northern hemisphere a large and measurable asymmetry in pmse strength in the two hemispheres therefore exists we explain this asymmetry by postulating a difference in summer mesopause temperatures between the two hemispheres of 7 5 k this difference has been estimated using an empirical relationship between the variations of the poker flat pmse power as a function of temperature given by the mass spectrometer incoherent scatter extended msise 90 model

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

a constraint to the wisconsinan glacial history canadian arctic archipelago thick ice bearing permafrost is not observed today beneath the deeper channels of the central queen elizabeth islands canadian arctic archipelago analysis of a precision temperature log recently obtained at an offshore well near ellef ringnes island indicates that the thermal regime beneath the seabed is in equilibrium with today s marine environment if thick permafrost similar to that observed on land today had existed in the pleistocene in areas that are presently offshore then such permafrost must have started melting no later than 25000 years ago in order to allow the present thermal regime to evolve this suggests that the inter island channels must have been water filled at least by that date

last glacial maximum and deglaciation of devon island arctic canada support for an innuitian ice sheet abstract the extent and origin of quarternary glaciers in the queen elizabeth islands of arctic canada especially during the last glacial maximum lgm has been debated for well over a century no consensus has yet emerged and the spectrum of interpretations within the last decade is the broadest ever the glacial geology of devon island strongly supports the late wisconsinan innuitian ice sheet hypothesis during lgm the southeastern part of the queen elizabeth islands was covered by an ice sheet flowing from a centre or a divide centrally located in the archipelago another ice divide extended from the centre across devon island flow from the innuitian centre and convergent flow from devon island and probably also from cornwallis and bathurst islands sustained an ice stream in wellington channel ice was locally advancing to its lgm limit about 23 ka bp recession in the vicinity of the present coastline was underway by 10 ka bp and final ice remnants west of the present devon ice cap vanished about 8 ka bp the island bears the same two part landscape zonation as do other islands and peninsulas in the region these reflect a cold based core and warm based periphery at lgm

constraining landscape history and glacial erosivity using paired cosmogenic nuclides in upernavik northwest greenland high latitude landscape evolution processes have the potential to preserve old relict surfaces through burial by cold based nonerosive glacial ice to investigate landscape history and age in the high arctic we analyzed in situ cosmogenic 10 be and 26 al in 33 rocks from upernavik northwest greenland we sampled adjacent bedrock boulder pairs along a 100 km transect at elevations up to 1000 m above sea level bedrock samples gave significantly older apparent exposure ages than corresponding boulder samples and minimum limiting ages increased with elevation two isotope calculations 26 al 10 be on 20 of the 33 samples yielded minimum limiting exposure durations up to 112 k y minimum limiting burial durations up to 900 k y and minimum limiting total histories up to 990 k y the prevalence of 10 be and 26 al inherited from previous periods of exposure especially in bedrock samples at high elevation indicates that these areas record long and complex surface exposure histories including significant periods of burial with little subglacial erosion the long total histories suggest that these high elevation surfaces were largely preserved beneath cold based nonerosive ice or snowfields for at least the latter half of the quaternary because of high concentrations of inherited nuclides only the six youngest boulder samples appear to record the timing of ice retreat these six samples suggest deglaciation of the upernavik coast at 11 3 0 5 ka average 1 standard deviation there is no difference in deglaciation age along the 100 km sample transect indicating that the ice marginal position retreated rapidly at rates of 120 m yr 1

the physiography of high arctic cross shelf troughs abstract a comprehensive inventory of high arctic cross shelf troughs is compiled from international bathymetric chart of the arctic ocean ibcao bathymetric data v 3 0 the location of 75 cross shelf troughs is presented alongside a synthesis of their key physiographic characteristics and available glacial geological evidence the troughs are interpreted to have been occupied intermittently and eroded by marine terminating ice streams that traversed the shelf during at least one and often many quaternary full glacial periods considerable variation in cross shelf trough physiography exists in the high arctic trough lengths range between 35 and 1400 km widths from 12 to 260 km and maximum depths from 200 to 1000 m the longest cross shelf troughs extend through inter island channels on the beaufort sea queen elizabeth islands and barents kara sea margins the gradient of the upper slope beyond high arctic glacial troughs which ranges between 0 3 and 13 is shown to have a negative relationship with palaeo ice stream drainage basin area and trough length glacial sedimentary depocentres or trough mouth fans tmfs are inferred on the basis of bathymetric and where available seismic evidence to exist beyond the majority of high arctic cross shelf troughs evidence of shelf progradation or tmf development is absent from the slope beyond several high arctic troughs probably as a result of limited sediment supply to the margin and or sediment by passing of the upper slope on the south greenland continental margin it is likely that steep slopes prevented the development of significant glacial sedimentary depocentres beyond cross shelf troughs or that glacigenic debris has been removed from the upper slope by submarine slope failure

mid latitude noctilucent cloud observations by lidar regular zenith directed rayleigh lidar soundings at juliusruh 54 63 n 13 38 e in summer 1995 indicated the presence of overhead noctilucent clouds nlc during three nights in june for two of these nights nlc were also sighted visually near the northern horizon for one of the lidar observed nlc events temperature profiles were obtained immediately prior to the appearance of the nlc these show at 81 km a strong cooling of about 30 k within two hours the wind velocity and direction during the nlc events were inferred from daytime common volume mf radar wind measurements during the occurrence of the nlcs the interpolated mf radar wind was south westwards directed with velocities between 9 32 m s different from high latitudes nlcs can be observed by lidar at mid latitudes in total darkness therefore mid latitude observations hold the promise to allow a characterisation of nlc particle size distributions and particle densities even with comparatively simple multi color lidars

western frontal fault of the canyon range is it the breakaway zone of the sevier desert detachment geologic evidence developed from surface exposures demonstrates that the western frontal fault of the canyon range is a major structure representing the eastern breakaway zone of the sevier desert detachment the western frontal fault of the canyon range east of delta utah is a north trending west dipping low angle 18 24 normal fault that juxtaposes syntectonic conglomerates and large rock avalanches of the miocene oak city formation against footwall rocks that have been ductilely cataclastically and brittlely deformed the oak city strata dip variably to the east dips are shallow in eastern outcrops 5 15 steeper in central outcrops 20 60 and shallow in the western outcrops 10 20 in eastern exposures the shallow dips of the oak city formation 5 15 and the acute angle of 20 35 between the western frontal fault and oak city units limit past rotation of the fault to 15 the systematic variation in the dip of oak city units from east to west suggests that the western frontal fault probably flattens beneath present oak city outcrops linking the fault to the shallow reflector seen in the cocorp consortium for continental reflection profiling utah line 1 seismic line beneath the westernmost outcrops of the oak city formation upper plate movement is constrained by oak city clast compositions and rock avalanche lithologies fault geometry and lower plate reconstruction to a maximum of 6 7 km since oak city syntectonic deposition at 12 13 ma maximum upper plate displacement for the entire sevier desert detachment cannot be determined from these breakaway zone exposures

energy balance and deformation mechanisms of duplexes abstract a duplex consists of a series of imbricate faults that are asymptotic to a roof thrust and a floor thrust depending on the final orientations of the imbricate faults and the final position of the branch lines a duplex may be hinterland dipping foreland dipping or an antiformal stack the exact geometry depends on various factors such as the initial dimensions of the individual slices horses their lithology the amount of displacement normalized to size of horse on each fault and the mechanics of movement along each fault the energy required in duplex formation can be determined by calculating the total work involved in emplacing each horse this is given by where w t w p w b w g w i wp is the work involved in initiating and propagating a fracture wb is the work involved in basal sliding which may be frictional or some form of ductile flow wg is the work done against gravity during the emplacement of the horse and wi is the work involved in the internal deformation of the horse by calculating and comparing these work terms it is possible to predict the conditions under which the different types of duplexes will form normally the development of a hinterland dipping duplex is most likely however if deformation conditions are favorable displacements on individual imbricate faults may be very large compared to the size of the horses leading to the formation of either antiformal stacks or foreland dipping duplexes

structural evolution of connecting splay duplexes and their implications for critical taper an example based on geometry and kinematics of the canyon range culmination sevier belt central utah abstract critical taper in an evolving orogenic wedge can be maintained by structural thickening in the back of the wedge this is often achieved by folding and uplift of pre existing large internal thrust sheets by the continued growth and or reactivation of duplexes in the hinterland the growth of a blind imbricate complex off a lower thrust provides another mechanism for folding a higher thrust individual splays in a blind imbricate complex may have fault propagation folds and or fault bend folds associated with them if the splays reach the overlying thrust they serve as connecting splays between the lower thrust floor and the upper thrust roof thereby forming a connecting splay duplex csd this type of duplex geometry requires periodic reactivation of the pre existing roof thrust the canyon range thrust in central utah is an internal thrust that is folded into an overturned antiform synform pair and overrides its own synorogenic conglomerates the same conglomerates are infolded into the core of the synform and preserve critical timing information regarding the history of folding and thrust reactivation the folding is caused by the development of a footwall antiformal stack in the core of the canyon range antiformal culmination the geometry and timing relationships suggest that the structure grew as a csd regional timing relationships suggest that the growth of the csd and reactivation of the thrust took place during the later part of the evolution of the orogenic wedge and may have helped the wedge maintain critical taper during thrusting in the external fold and thrust belt

revision of the nw laurentide ice sheet implications for paleoclimate the northeast extremity of beringia and arctic ocean sedimentation abstract for the past half century reconstructions of north american ice cover during the last glacial maximum have shown ice free land distal to the laurentide ice sheet primarily on melville and banks islands in the western canadian arctic archipelago both islands reputedly preserve at the surface multiple laurentide till sheets together with associated marine and lacustrine deposits recording as many as three pre late wisconsinan glaciations the northwest corner of banks island was purportedly never glaciated and is trimmed by the oldest and most extensive glaciation banks glaciation considered to be of matuyama age 780 ka bp inside the limit of banks glaciation younger till sheets are ascribed to the thomsen glaciation pre sangamonian and the amundsen glaciation early wisconsinan stade the view that the western canadian arctic archipelago remained largely ice free during the late wisconsinan is reinforced by a recent report of two woolly mammoth fragments collected on banks and melville islands both dated to 22 ka bp these dates imply that these islands constitute the northeast extremity of beringia a fundamental revision of this model is now warranted based on widespread fieldwork across the adjacent coastlines of banks and melville islands including new dating of glacial and marine landforms and sediments on dundas peninsula southern melville island ams 14 c dates on ice transported marine molluscs within the most extensive laurentide till yield ages of 25 49 ka bp these dates require that late wisconsinan ice advanced northwestward from visount melville sound excavating fauna spanning marine isotope stage 3 laurentide ice that crossed dundas peninsula 300 m asl coalesced with melville island ice occupying liddon gulf coalescent laurentide and melville ice continued to advance westward through m clure strait depositing granite erratics at 235 m asl that require grounded ice in m clure strait as do streamlined bedforms on the channel floor deglaciation is recorded by widespread meltwater channels that show both the initial separation of laurentide and melvile ice and the successive retreat of laurentide ice southward across dundas peninsula into viscount melville sound sedimentation from these channels deposited deltas marking deglacial marine limit forty dates on shells collected from associated glaciomarine rhythmites record near synchronous ice retreat from m clure strait and dundas peninsula to north central victoria island 11 5 ka bp along the adjacent coast of banks island deglacial shorelines also record the retreat of laurentide ice both eastward through m clure strait and southward into the island s interior the elevation and age 11 5 ka bp of deglacial marine limit there is fully compatible with the record of ice retreat on melville island the last retreat of ice from mercy bay northern banks island previously assigned to northward retreat into m clure strait during the early wisconsinan is contradicted by geomorphic evidence for southward retreat into the island s interior during the late wisconsinan this revision of the pattern and age of ice retreat across northern banks island results in a significant simplification of the previous quaternary model our observations support the amalgamation of multiple till sheets previously assigned to at least three pre late wisconsinan glaciations into the late wisconsinan this revision also removes their formally named marine transgressions and proglacial lakes for which evidence is lacking erratics were also widely observed armouring meltwater channels originating on the previously proposed never glaciated landscape an extensive late wisconsinan laurentide ice sheet across the western canadian arctic is compatible with similar evidence for extensive laurentide ice entering the richardson mountains yukon farther south and with the innuitian ice sheet to the north widespread late wisconsinan ice in a region previously thought to be too arid to sustain it has important implications for paleoclimate ice sheet modelling arctic ocean ice and sediment delivery and clarifying the northeast limit of beringia

transgressions rethinking beringian glaciation abstract the purpose of this investigation is to encourage a fresh look at pleistocene beringia heretofore flooding of bering strait has been cited as the only barrier to migration with marine sea transgressions being a sea gate that closed off migration during glacial interstadials and interglaciations however the possibility exists that glacial advances were also barriers with marine ice transgressions being an ice gate that closed off migration during glacial stadials and glacial maxima this possibility proceeds from the marine ice transgression hypothesis mith which states that marine ice sheets form on the broad arctic continental shelf of northern hemisphere continents when sea ice thickens grounds and domes in shallow water and then transgresses landward as continental ice sheets and seaward as floating ice shelves hughes 1987 landward transgression is onto coastal lowlands during pleistocene glaciations a marine ice sheeet extending from spitsbergen to greenland may have transgressed the circumpolar continental landmass at its lowest and narrowest gap central beringia and calved into the pacific ocean four models of beringian glaciation are presented based on the distinction between marine glaciation and highland glaciation central beringia was glaciated only in highlands in the traditional model hopkins et al 1982 was also glaciated by a self sustaining ice shelf floating over the deep ocean basins of the bering sea in the model by grosswald and vozovik 1984 was glaciated by a marine ice sheet that covered highlands the continental shelf and supplied the ice shelf in a model for maximum pleistocene glaciation and was glaciated by a marine ice sheet in the chukchi sea that merged with highland glaciers transgressed the continental shelf of the western bering sea and calved into the southern bering sea along the edge of the continental shelf in a model for the last glaciation field tests are suggested to assess the viability of these four models the first model is already established for highland glaciation in alaska but less established in siberia the last model should be the easiest to evaluate for marine glaciation the last model limits human migration across the beringian land bridge to brief intervals between stadials and interstadials of the last glaciation cycle when both the ice gate and the sea gate were opened to human migration this model can influence the sea change now underway among quaternary scientists studying peopling of the americas based on the archaeological linguistic and ethnic diversity among native american populations

long term observations of the arctic mesosphere with the mst radar at poker flat alaska in this report we summarize the results of 22 months of observations of arctic mesosphere echoes with the 50 mhz radar at poker flat alaska operation with a partially complete system began in february 1979 and has continued on a nearly continuous basis to the present time the altitude range of the mesospheric echoes obtained during this period shows a pronounced seasonal variation during summer months the mesospheric echoes are relatively continuous in time and extend from about 80 to 100 km with an unexpectedly strong peak in signal to noise ratio at about 85 km in contrast in nonsummer months mesospheric echoes are less intense and occur at lower altitudes in the range from 55 to 80 km these lower altitude nonsummer echoes are observed primarily during daytime hours when energetic auroral particle precipitation as determined by the poker flat 30 mhz riometer is present

late wisconsinan glaciation of southern eureka sound evidence for extensive innuitian ice in the canadian high arctic during the last glacial maximum abstract southern eureka sound was originally proposed as the centre of an innuitian ice sheet in the canadian high arctic at the last glacial maximum lgm based largely on the pattern of holocene emergence this paper focuses on the glacial geological evidence for such an ice sheet in the region granite dispersal trains and ice moulded bedrock record regional westward flow of warm based ice into eureka sound from se ellesmere island regional ice was coalescent with local ice domes on inter fiord peninsulas marine limit in the form of raised deltas beaches and washing limits formed during deglaciation of the regional ice throughout southern eureka sound marine limit dates 9 2 ka bp indicating that ice commenced retreat during the early holocene ice divides were located along the highlands of central ellesmere and axel heiberg islands from which ice inundated eureka sound flowing north and south along the channel regional radiocarbon dates on marine limit show that deglaciation occurred in two steps initial break up and radial retreat of ice from eureka sound to the inner fiords was rapid and preceded stabilisation along adjacent coastlines and at fiord heads two step deglaciation is also reflected in differences in glacial geomorphology between the inner and outer parts of many fiords a prominent belt of fiord head glaciogenic landforms long proposed to mark the last glacial limit is re interpreted to record initial stabilisation of ice margins due predominantly to bathymetric control

critical taper model of fold and thrust belts and accretionary wedges the fold and thrust belts and submarine accretionary wedges that lie along compressive plate boundaries are one of the best understood deformational features of the earth s upper crust although there is considerable natural variation among the many fold and thrust belts and accretionary wedges that have been recognized and explored several features appear to be universal in cross section fold and thrust belts and accretionary wedges occupy a wedge shaped deformed region overlying a basal detachment or decollement fault the rocks or sediments beneath this fault show very little deformation the decollement fault characteristically dips toward the interior of the mountain belt or in the case of a submarine wedge toward the island arc the topography in contrast slopes toward the toe or deformation front of the wedge deformation within the wedge is generally dominated by imbricate thrust faults verging toward the toe and related fault bend folding two north american fold and thrust belts that exhibit these features are shown in figure 1 neither of these two examples is tectonically active today the southern canadian fold and thrust belt was active during the late jurassic and cretaceous 150 100 ma whereas the southern appa lachians were deformed during the late carboniferous to permian alle ghenian orogeny 300 250 ma figure 2 shows two examples that are currently active the taiwan fold and thrust belt produced by the sub duction of the eurasian plate beneath the philippine sea plate suppe 1981 1987 and the barbados accretionary wedge produced by the sub

evidence for ice clouds causing polar mesospheric summer echoes we compare 22 temperature height profiles derived from falling sphere experiments with simultaneous 50 mhz mesospheric radar echoes obtained during the middle atmosphere co operation summer in northern europe campaign in the summer of 1987 above andenes norway common features of these observations are as follows 1 more than 80 of the echoes occur at temperatures below 140 k and more than two thirds of the bottommost echo maxima appear at temperatures that deviate less than 5 from 140 k 2 we can find no significant correlation between the echo strength or the echo occurrence probability and the local temperature once it is below 140 k 3 the echoes are not symmetrically distributed around the mesospheric temperature minimum but there are clearly more echoes below than above the temperature minimum equivalently while the local temperature at the height of the bottommost echoes is about 140 k it is much lower at the height of the topmost echoes we compare the height range of the observed polar mesospheric summer echo returns with the height range that can be inferred for an ice cloud from the observed temperature profile by means of a simple stationary nucleation sedimentation model for reasonable values of the height integrated ice particle nucleation rate of about 3 107 m 2 s 1 and for a water molecule mixing ratio at the bottom of the ice cloud of 0 1 to 1 0 ppmv we find excellent agreement between the height range within which the ice particles may exist and the height range from which mesospheric echoes are seen for example in 17 out of the 22 individual observations reasonable values for the water vapor mixing ratio can be found such that the height of the strong bottommost echo corresponds to within the resolution of the radar to the bottom height of our model ice cloud if our height estimates are correct and the observations are representative our results yield a somewhat smaller water vapor mixing ratio in the summer mesosphere at high latitudes compared to what has been measured at midlatitudes

glacier dynamics and paleoclimatic change during the last glaciation of eastern ellesmere island canada a 300 km transect along the east coast of ellesmere island fills a major gap in the late quaternary data base of the canadian high arctic the last glacial maximum lgm is marked by prominent moraines and meltwater channels that terminate within 30 km of modern ice margins shells in glaciomarine deposits collected beyond the lgm indicate deglaciation by more extensive ice prior to 35 ka bp more than 60 14c dates from glaciomarine sediments provide a chronology for past ice dynamics during the lgm to the north while many areas remained ice free due to severe aridity several glaciers remained in contact with the sea until 7 1 ka bp farther south most glaciers reached the coast and significantly infilled several fiords this southward increase in glacier extent is due to larger glacial catchment basins and increased precipitation towards storm tracks in northern baffin bay the earliest dates on deglaciation along the transect range from 8 1 to 7 7 ka bp initial retreat was controlled by the exten

more on deep glacial erosion by continental ice sheets and their tongues of distributary ice high latitude intracontinental seaways occupy great troughs carved by broad tongues of inland ice as it debouched to deep marine water such troughs occur in glaciated coasts but not in stable nonglaciated ones where ice flowed along the walls of troughs whose adjacent uplands held local glaciers the walls simulate alpine troughs with faceted spurs and submarine hanging tributary valleys where uplands were not glaciated trough walls are unbreached where ice flowed across them coasts are digitate in low relief in the northeastern sector of the laurentide ice sheet large glacial grooves converge toward the gulf of boothia prince regent inlet lancaster sound avenue of egress to open sea suggesting that it was an exit for inland ice which shaped it to its present form the subduction pacific coast of the americas is mostly harborless in nonglaciated latitudes but in southern chile and british columbia it is dissected a circular gravity high 2800 km across is concentric with the area covered by the laurentide ice sheet abyssal glacial silts are voluminous enough to account for an average of 100 150 m of erosion over the area covered by the laurentide ice sheet

comment holocene palaeoceanographic changes in barrow strait canadian arctic foraminiferal evidence t r gregory c w smart m b hart g masse l l vare and s t belt 2010 journal of quaternary science 25 903 910

case of the phantom foredeep early cretaceous in west central utah a reconstruction of the structure in west central utah shows that a major foredeep with sedimentary deposits possibly as thick as 6 km now eroded probably existed at the present site of the sevier desert during early cretaceous time and conceivably during late jurassic time concurrent emplacement and erosion of the canyon range thrust sheet provided the load and sediment much like the willard paris thrust sheet did for the better documented early cretaceous foredeep in northern utah and eastern idaho the onset of major thrusting in western utah may have been as early as callovian or as late as albian a 50 m y time span

glaciomarine sedimentation in disraeli fiord high arctic canada abstract disraeli fiord represents a glaciomarine environment unique to the north coast of ellesmere island featuring floating glacier tongues multi year landfast sea ice and a strongly stratified water body which results from enclosure of the fiord by ward hunt ice shelf it is a very low energy depositional environment even at sites proximal to glaciers sediment enters the fiord by interflow and is deposited through suspension settling ice rafting is precluded by the year round sea ice cover sedimentation rates in the inner fiord since about 7000 yrs b p are estimated to be 5 10 cm ka a reflection of the limited sediment influx from the cold based glaciers which contact the fiord changes in sediment structure through the holocene reflect changes in the rate and process of sediment input as well as changes in fiord circulation all of which relate to regional climate during deglaciation early holocene sedimentation rates were orders of magnitude greater than at present subglacial meltwater was the dominant source of inflow with sediment transported in turbid plumes as over or interflow and deposited through suspension settling this is supportive of other studies indicating that a pronounced climatic amelioration led to warm based glaciers at this time

noctilucent clouds and wave dynamics observations at sondrestrom greenland rayleigh lidar measurements of the arctic summer stratosphere and mesosphere have been conducted routinely since 1994 at the sondrestrom atmospheric research facility near kangerlussuaq greenland 67 0n 50 9w between 1994 and 1996 seventeen separate events of noctilucent clouds nlcs as well as corresponding stratospheric wave structure have been observed we present in this study two main results 1 the occurrence of persistent quasi monochromatic wave structure in the stratosphere having observed vertical wavelengths of 8 to 12 km and observed temporal periods of approximately 2 3 hours and 2 evidence that the strength of such lower altitude waves may be associated with the overall strength of the observed nlc volume backscatter coefficient

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

seafloor features delineate late wisconsinan ice stream configurations in eastern parry channel canadian arctic archipelago abstract multibeam imagery and 3 5 khz sub bottom profiles acquired from ccgs amundsen between 2003 and 2013 by arcticnet and the ocean mapping group at the university of new brunswick provide information on seafloor features geology bathymetry and morphology in eastern parry channel and the adjoining large channels in the canadian arctic archipelago together these include peel sound barrow strait lancaster sound wellington channel prince regent inlet admiralty inlet and navy board inlet those data are in part complemented by high resolution single channel seismic reflection profiles acquired by the geological survey of canada in the 1970s and 1980s and by sediment cores that provide chronological and depositional information the occurrence and pattern of streamlined mega scale ridge and groove lineations msgls indicate that these waterways were occupied by glacial ice streams in the past chronological information from marine and adjoining terrestrial areas suggests a long history of glacial events ranging in time from early pleistocene to late wisconsinan seafloor morphology and msgl trends together with terrestrial ice flow patterns indicate that ice streams flowed into barrow strait from peel sound and wellington channel and ice streams in prince regent admiralty and navy board inlets flowed northward into and eastward along lancaster sound recession of the ice stream westward along parry channel occurred 16 cal ka bp to 10 8 cal ka bp thick ice contact sediments deposited by a late ice advance from prince regent inlet constitute the seabed across a large area of western lancaster sound timing for that late ice advance appears to be bracketed between the 11 5 cal ka bp lift off of the eastern parry ice stream north of prince leopold island and the 10 0 cal ka bp deglaciation of prince regent inlet seafloor morphology and lineation trends suggest that ice delivered by the ice stream in peel sound was the westernmost tributary to the ice stream occupying lancaster sound during the late wisconsinan glaciation bathymetric data and msgls indicate that the ice stream emanating from m clintock channel flowed westward

cosmogenic 10be and 26al ages for the last glacial maximum eastern baffin island arctic canada a chronology for the last glacial maximum based on cosmogenic exposure dating in the pangnirtung fjord area eastern baffin island arctic canada is at odds with many decades of land based glacial stratigraphic research most previous chronologies focused primarily on relative weathering criteria and suggested that ice extent was restricted during the late wisconsinan ca 24 8 ka in contrast by directly dating glacial features we conclude that late wisconsinan ice was far more extensive than previously believed there are 36 gneissic boulders and 8 samples of ice molded gneissic bedrock that yield late wisconsinan 10 be and 26 al exposure ages for the last glaciation of pangnirtung fjord the prominent duval moraines which were previously interpreted to represent a significant early wisconsinan 100 60 ka ice advance on southern cumberland peninsula were actually deposited between 24 and 9 ka two boulders from a raised glaciomarine delta stratigraphically related to the duval moraines date to about 10 ka two recessional moraines and striated bedrock along pangnirtung fjord as well as erratics on the floor of the kolik river valley a tributary to pangnirtung fjord indicate that deglaciation began between 12 and 9 ka in situ produced 10 be and 26 al abundances indicate that ice filled pangnirtung fjord for about 15 k y either continuously or intermittently prior to 10 ka which is compatible with 14 c chronologies for adjacent cumberland sound thus our data support other recent studies that suggest the northern and southern margins of the laurentide ice sheet were generally in phase during the latest wisconsinan contrary to earlier interpretations

first wind shear observation in pmse with the tristatic eiscat vhf radar c american geophysical union reprinted with permission article also available at source https doi org 10 1002 2016ja023080

an investigation of measured temperature profiles and vhf mesosphere summer echoes at midlatitudes during the summers of 1992 and 1994 experiments were conducted in germany 52 n to investigate the region of the summer mesopause in connection with mesospheric summer echoes mse mse form in layers and are associated with dramatically enhanced radar scattering cross sections furthermore since the summer mesopause is characterized by very low temperatures it has been proposed that mse layers are related to the presence of subvisible ice particles parallel measurements were made using the sounding system sousy vhf radar and rayleigh lidar radar observations showing mse signatures are presented together with accompanying temperature profiles obtained from the lidar data generally the ambient temperatures in the summer mesosphere at midlatitudes are above that required to create ice crystals however the presence of waves can reduce the temperature our observations show this to be the case in particular during one of the mse events two long period inertia gravity waves were observed these waves had estimated local periods of 6 and 8 hours with accompanying vertical wavelengths of 10 and 15 km respectively we find a good correlation between the locations of the calculated temperature minima and the observed mse layers furthermore the temperature minima were generally below the saturation temperature for water vapor lending support to the supposition that the backscatter is connected with the presence of ice particles

timing of deformation in overthrust belt and foreland of idaho wyoming and utah a review of the timing and displacement evidence of the major structures of the western wyoming overthrust belt and foreland shows there is a progression in thrust displacement apparent duration of motion and palinspastic position of thrust traces from west to east those toward the west moved farther for an apparently longer period of time and are more widely spaced in their restored positions than those toward the east however average thrust velocities are all on the order of 0 5 0 5 cm yr 0 2 in yr foreland events are in part synchronous with thrust belt events and had an effect on them although dating precision varies widely on major normal faults present evidence does not contradict the generally held view that all normal faults postdate the youngest thrusting

the late quaternary environmental evolution of marine arctic canada barrow strait to lancaster sound abstract a marine sediment core from the east central canadian arctic archipelago core 86027 154 74 22 01 n 89 51 26 w 329 m water depth studied by a multiproxy approach lithostratigraphy biogeochemistry micropalaeontology dinoflagellate cysts other non pollen palynomorphs benthic and planktonic foraminifera ostracods and encompassing 14 ams 14 c dates provides valuable insights into regional deglacial to holocene palaeoenvironments six palaeoenvironmental zones are recognized based on prominent changes in the litho and biostratigraphy the waterlain diamicton of zone i records immediate deglaciation being derived from lift off and calving of previously grounded glacial ice though deglacial timing is complicated by the sparsity of dating materials and the portlandia effect age depth model extrapolation places deglaciation at 11 54 cal ka bp zone ii 11 5 11 0 cal ka bp represents a distinct progression from initially ice proximal to increasingly ice distal conditions interrupted by an interval of pervasive sea ice 11 4 11 2 cal ka bp noteworthy biological activity commences in zone iii 11 0 9 7 cal ka bp with a prominent signal of planktonic foraminifera neogloboquadrina pachyderma this likely signifies penetration of deeper atlantic derived water through the central canadian arctic archipelago upon deglaciation facilitated by the greater glacioisostatically induced water depths 80 m and implies separation of laurentide and innuitian ice sheets by 11 0 cal ka bp zone iv 9 7 7 2 cal ka bp records ameliorated biologically favourable conditions with reduced seasonal sea ice accompanied by high microfossil species diversity and the presence of subpolar taxa zone v 7 2 6 5 cal ka bp signals the exclusion of atlantic derived water concomitant with increasing sea ice simultaneously representing the termination of the dynamic deglacial to early holocene environments zones i iv conditions similar to modern typified by uniform sediment characteristics present day microfossil assemblage structures and sparse benthic foraminifera were established by 5 6 cal ka bp zone vi

geological applicability of critical wedge thrust belt models critical wedge models for foreland thrust belts although popular paradigms for thrust mechanics also predict definite progressive changes within the orogenic belt the most important constraint on critical wedge models is the need for deformation of the interior of the wedge when new sheets are accreted to its front well dated foreland thrust belts have sequential formation of new thrust sheets in the front of the belt thus they also require continued superimposed deformation within the wedge geologic mapping and fabric studies provide evidence of only minor later intra wedge shortening severely reducing the acceptability of an accreting critically tapered wedge model to apply critically tapered wedge models to foreland fold and thrust belts one must relax requirements for constant wedge strengths and basal sliding laws the wedge will need to strengthen after initial thrust emplacement and the fault zones will probably need to progressively weaken it is most likely that critical wedge models which apply well to accretionary wedges do not apply in simple ways to foreland fold and thrust belts

cenozoic and mesozoic structure of the eastern basin and range province utah from cocorp seismic reflection data cocorp seismic reflection data collected from the eastern basin and range in west central utah provide information on cenozoic extensional tectonics mesozoic thrusting and their interrelationships those data show a series of remarkably continuous low angle reflectors that extend more than 120 km perpendicular to strike and can be traced as deep as 15 20 km over that distance none of these events are significantly cut by any high angle normal faults a major detachment beneath the sevier desert can be traced from a surface zone of normal faulting to a depth of 12 15 km with a regional apparent westward dip of 12 tentative correlation of upper and lower plate events suggests 30 60 km of extensional displacement on this detachment whether this structure is a reactivated mesozoic thrust is uncertain west steepening splays off the end of the detachment reach depths of 20 km and may represent a major mesozoic ramp or zones of distributed ductile shearing during extension some events are interpreted to be mesozoic thrusts of which at least one beneath the house range has been reactivated during the cenozoic the snake range decollement dips gently east and has a sense of cenozoic displacement opposite to that of other cenozoic detachments farther east deep events are most numerous beneath the east side of the sevier desert where they occur to depths of 30 km at the top of or perhaps partly within the anomalously low velocity upper mantle

stratigraphy and palaeoecology of a possible interglacial site northernmost ellesmere island canada an extensive stratigraphic section at cape alfred ernest on the wootton peninsula northwest ellesmere island contains six lithofacies which appear to record two glacial phases separated by an organic layer 1 a lower massive gravel records a pre ice advance outwash phase 2 massive fine grained sediments record a period of non glacial marine deposition when sea level was higher than present 3 a massive diamicton records the advance of ice across the site 4 intermediate stratified beds record supraglacial and proglacial outwash and include an organic layer 5 massive diamicton grading down valley to stratified diamicton and then massive sheared diamicton overlain by laminated fine grained sediments with dropstones recording the last late wisconsinan glaciation 6 upward coarsening sands and gravels record proglacial outwash and grade to raised marine deltas radiocarbon dates of 39270 640 and 51000 yr bp were obtained on samples from the organic layer by accelerator mass spectrometry and conventional radiocarbon dating respectively palaeoecological data suggest that the organics accumulated in a wet sedge meadow environment when the climate was warmer than present stratigraphic considerations suggest that the organic layer represents an interglacial interval which if valid indicates that the site constitutes the northernmost interglacial stratigraphy in the canadian arctic alternatively the organic layer may date to plio pleistocene times

bedrock morphology reveals drainage network in northeast baffin bay a subglacial drainage network underneath the paleo ice sheet off west greenland is revealed by a new compilation of high resolution bathymetry data from melville bay northeast baffin bay this drainage network is an indicator for ice streaming and subglacial meltwater flow toward the outer shelf repeated ice sheet advances and retreats across the crystalline basement together with subglacial meltwater drainage had their impact in eroding overdeepened troughs along ice stream pathways these overdeepenings indicate the location of a former ice sheet margin the troughs inherit characteristics of glacial and subglacial meltwater erosion most of the troughs follow tectonic weakness zones such as faults and fractures in the crystalline bedrock many of these tectonic features correspond with the orientations of major fault axes in the baffin bay region the troughs extend from the present sub glacial fjord systems at the greenland coast and parallel modern outlet glacier pathways the fast flowing paleo ice streams were likely accelerated from the meltwater flow as indicated by glacial landforms within and along the troughs the ice streams flowed along narrow tributary troughs and merged to form large paleo ice streams bedded in the major cross shelf troughs of melville bay apart from the troughs a rough seabed topography characterises the bedrock and we see a sharp geomorphic transition where ice flowed onto sedimentary rock and deposits

glacial advances and stratigraphy in otto fiord and adjacent areas ellesmere island northwest territories hvitland and svartfjeld peninsulas have been glaciated at least two or three times since the late pliocene the earliest recognized glaciation is constrained by amino acid ratios on in situ pelecypods from marine sediments stratigraphically overlying till in otto fiord high amino acid ratios suggest that the shells may be pliocene and related to recently discovered late pliocene hvitland beds at white point the same samples yielded finite radiocarbon ages in the 30 2 34 8 ka bp range which cautions against their acceptance a second mid quaternary glaciation is suggested by intermediate amino acid ratios from in situ pelecypods and shell bearing till covering coastal uplands along nansen sound during the last glaciation the peninsula was covered by coalesced ice caps with glacial tongues descending tributary valleys and extending into the fiords deglaciation of a tributary valley in outer otto fiord proceeded before 11 6 ka bp and before 9 1 ka bp in mid otto fiord but major ice margins remained a

including strain data in balanced cross sections abstract almost all published balanced cross sections include cleaved and or strained rocks and may therefore violate the requirement that bed lengths and formation areas are preserved between undeformed and deformed states knowledge of distortions presence and type of cleavage and overprinting relations in poly deformed segments are necessary to define area changes related to volume loss strike elongation and poly deformation work in the southern and central appalachians has shown variation in structural complexity and changing deformation styles both along and across the thrust belt this necessitates separate treatment of individual sheets during balancing regions of little or no interstratal slip pinning points should be chosen for each thrust sheet and each fold strain in the sheet in external sheets where deformation intensity increases towards thrusts pin points should be back limb inflection points in intermediate and internal sheets where cleavage is approximately coeval with folding pin points should be at fold hinges where cleavage and strain are heterogeneously developed throughout a stratigraphic sequence a line length balance using massive relatively uncleaved beds e g knox group southern appalachians can be used as a basis for restoring the section unstraining of deformed layers given strain data and cleavage trajectories for individual thrust sheets provides line lengths and formation areas which can be fitted to the key bed of the undeformed section cleavages which partially or fully postdate folding indicate continued shortening in the thrust wedge and modify earlier pinning points in upper sheets these cleavages and poly deformed segments are difficult to restore as strain data are generally scarce in the metamorphosed internal thrust sheets

strain variation in thrust sheets across the sevier fold and thrust belt idaho utah wyoming implications for section restoration and wedge taper evolution abstract although strain in fold and thrust belts is typically inhomogeneous on the largest scale strain within thrust sheets shows regular patterns the strain which is a quantitative measure of the deformation of any thrust sheet is independent of the translation of the sheet the internal deformation can be represented by a deformation profile the change in shape during thrusting of a fault perpendicular line which can then be used to unstrain the sheet during restoration in cross section balancing deformation profiles in well studied thrust sheets show regular geometric patterns and compatibility constraints can be used to minimize the data needed to define the profiles in other sheets from the geometry of deformation profiles and direct field observations the most important component of internal deformation of thrust sheets in many fold and thrust belts is early layer parallel shortening lps this can be removed in a straightforward manner during restoration and significantly affects the geometry i e taper of the restored section original basin wedge taper may have important implications for the mechanical evolution of fold and thrust belts thus changes in original basin taper resulting from strain removal may affect significantly the way in which we interpret the evolution of a fold and thrust belt in an area

glaciation and the evolution of the canadian high arctic landscape the canadian arctic islands represent a tertiary fluvial landscape developed on a contiguous landmass subsequently fractured by block faulting nonetheless some theoretical models invoke pervasive high latitude ice sheets and continue to misattribute the faulted landscape to glacially scoured river valleys quaternary fieldwork on northern ellesmere island suggests that these models are inappropriate for high latitude ice sheets and should be abandoned if there was ever a regional ice sheet over arctic canada it likely occurred on a prefaulted contiguous landmass that had a more temperate climate than at present possibly during the late tertiary after block faulting the marine channels permanently prevented the ice from inundating the landscape it once crossed tectonics and not climate have led to a fundamental change in glacial style this block faulting also may have played a role in terminating the late tertiary boreal forest to 80 n by establishing cold marine channels that diminished the continentality of the once contiguous landmass for a thorough understanding of the canadian arctic landscape future research should determine the continuity between the tertiary and quaternary paleoenvironments the unknown ages of the fiords and interisland channels are of primary importance

upper jurassic lower cretaceous morrison and cedar mountain formations ne utah nw colorado relationships between nonmarine deposition and early cordilleran foreland basin development abstract sedimentologic stratigraphic and petrologic analysis of the upper jurassic lower cretaceous morrison and cedar mountain formations of utah and colorado provides information on the timing and nature of early cordilleran foreland basin development the morrison formation can be subdivided into three depositional facies assemblages 1 lower progradational shallow marine lacustrine fluvial and eolian facies deposited during oxfordian kimmeridgian retreat of the stump sundance sea 2 a middle assemblage containing sandy gravelly braided fluvial deposits which are overlain by meandering fluvial channel and overbank facies and 3 an upper assemblage of laterally stable low sinuosity fluvial channel facies deposited during tithonian early neocomian time the upper part of this assemblage shows evidence of alteration and early diagenesis related to development of an early cretaceous unconformity the overlying cedar mountain formation is subdivided into two facies assemblages 1 the neocomian buckhorn conglomerate was deposited by northeast trending sandy gravelly braided rivers that were incised into the underlying morrison formation 2 an upper assemblage containing laterally stable low sinuosity fluvial channel facies deposited during late neocomian albian time the base of the unit contains a thick calcrete zone that formed during an unconformity following buckhorn deposition morrison and cedar mountain formation sandstones contain three petrofacies a feldspar rich lower morrison petrofacies qmflt 70 19 11 and chert rich upper morrison and buckhorn cedar mountain petrofacies qmflt 54 5 41 and 69 4 27 respectively sandstone composition and paleocurrent data indicate a cordilleran source area composed of proterozoic paleozoic and mesozoic sedimentary rocks the morrison formation and buckhorn conglomerate were deposited in the back bulge depozone of the late jurassic cordilleran foreland basin system and onlapped a flexural forebulge located in central utah late neocomian eastward migration of the forebulge uplifted areas in eastern utah producing an unconformity while the foredeep in central utah underwent flexural subsidence the upper part of the cedar mountain formation represents overfilling of the foredeep and deposition above the forebulge

role of shear in development of the helvetic fold thrust belt of switzerland the geometric features of the helvetic nappes of the alps show intense internal deformation set up predominantly by simple shear during nappe transport the nappes are bounded by thrusts that parallel incompetent layers and ramp upward stratigraphically across competent units in the direction of tectonic transport stratal layering is oblique to nappe boundaries thrust surfaces formed after ductile shear zones developed in underlying pre triassic gneissic basement the broad zone of shearing narrowed down as deformation increased to form zones of intense shear and ultimately to form thrust faults contraction along competent layers obliquely inclined to shear surfaces produced buckle folds the geometry of these folds was modified by further shearing as their normal limbs became aligned in the extension field of the strain ellipse for simple shear producing normal faults

magnetostratigraphic chronology of cretaceous to eocene thrust belt evolution central utah usa the axhandle basin in central utah is a piggyback basin that formed above the gunnison thrust system the basin contains 1 km of upper cretaceous to eocene strata of the north horn and lower flagstaff limestone formations a significantly more exact chronology based on magnetic polarity stratigraphy has been developed for the basin filling strata the new data provide a detailed temporal framework for the interpretation of the depositional and tectonic evolution of the basin during chrons 33 21 75 49 ma tectonic subsidence curves and stratigraphie relations along the eastern basin margin define two episodes of motion on the gunnison thrust system the majority of tectonic shortening on the system occurred between 83 75 ma and caused widespread non deposition within the axhandle basin a second episode of motion in detail comprising of four separate periods of backthrusting occurred between 70 60 ma the canyon range pavant and nebo thrust sheets were emplaced 30 50 km to the west of the axhandl

history of the sevier orogenic wedge in terms of critical taper models northeast utah and southwest wyoming problems with applying critical taper models to ancient orogenic wedges are overcome in the late cretaceous late paleocene sevier orogenic wedge in utah and wyoming by a symptomatic approach in which wedge behavior is inferred from the time space distribution of thrust faulting erosion and synorogenic sediment accumulation in association with the orogenic wedge in turn the causes of wedge behavior are interpreted in terms of features that are known about the sevier wedge such as the locations of major decollements and the lithologic constituents of major thrust sheets from coniacian through late paleocene time 35 m y basement and cover rocks in the sevier wedge were shortened by 100 km in three major and one minor events an overall eastward progression of thrusting was punctuated by several episodes of out of sequence and hinterland vergent thrusting over the long term wedge taper was controlled by internal wedge strength initial taper and changes in the durability of the upper surface of the wedge and its internal lithostratigraphy critical taper was maintained by the offsetting effects of basement duplexing in the rear of the wedge and forward imbrication at the front of the wedge while the basal decollement was mainly in basement rocks the wedge was highly tapered and thrust spacing was relatively close 15 km beginning ca 75 ma the basal decollement ramped upward and eastward into weak cambrian shale and jurassic salt thrust spacing increased to 25 45 km and wedge taper decreased drastically the highly tapered rear part of the wedge carried strong basement rocks above moderately weak mylonitic and cataclastic decollements whereas the frontal lower taper part of the wedge carried sedimentary rocks above extremely weak salt and shale decollements through time internal strength of the wedge decreased as it incorporated an increasing proportion of sedimentary rocks the thrust belt was able to advance eastward in spite of its decreasing internal strength and decreasing taper because the basal decollement of the wedge also became weaker through time both by strain softening beneath the rear of the wedge and by propagating along extremely weak rocks beneath the front of the wedge provenance data from associated synorogenic conglomerates indicate that the durability of the upper surface of the wedge probably increased over the long term history of the sevier wedge as an increasing proportion of the erosional surface became occupied by resistant precambrian quartzite and basement rocks this would have had the effect of decreasing the rate of erosion through time and maintaining a steeper surface slope which would have helped the wedge to remain at critical to supercritical taper the sevier wedge also exhibits several shorter term 10 km and 3 was subjected to regional erosion marked by major unconformities that ultimately caught up with tectonic thickening and caused the wedge to stall this cyclicity is attributed to the need for wedges to become supercritical before they can propagate forward over large distances and a lag time between wedge thickening and uplift and wedge erosion erosion eventually catches up to the rate of uplift the wedge stalls and the locus of deformation shifts to the rear of the wedge in order to rebuild taper this analysis suggests that orogenic wedges continually deform and find a way to maintain taper sufficient to allow forward propagation as long as a sufficient push from the rear exists the actual taper value may change substantially through time as lithostratigraphy internal strength upper surface durability and presence absence of weak potential stress guides conspire to maintain a critical taper

ice keel seabed features in marine channels of the central canadian arctic archipelago evidence for former ice streams and iceberg scouring abstract the study area lies within the central part of the canadian arctic archipelago a region that was covered by the laurentide ice sheet during the late wisconsinan glaciation and earlier multibeam imagery from widely spaced transects indicates the presence of linear groove and ridge features on the seabed at several localities in peel sound franklin strait northern larsen sound and within m clintock channel these lineations resemble features in antarctica and in several formerly glaciated regions that have been interpreted to be sole marks emplaced beneath fast flowing ice streams based on these analogies a similar origin is inferred for the lineations on the channel floors within the study area the lineations are oriented parallel to the channel axes and margins they occur on all transects within the bathymetrically deeper area at the junction of franklin strait and peel sound northward in peel sound they occur extensively on the western and central transects and more locally on the eastern transect their north south orientation is normal to that of glacial flow features on somerset island and most of eastern prince of wales island which border peel sound to the east and west respectively the trend of the lineations is northeasterly parallel to the channel axis in franklin strait and mainly northerly in larsen sound and m clintock channel elsewhere the seabed imagery commonly displays scours of various sizes and orientations created by the keels of icebergs seabed sediments revealed by 3 5 khz sub bottom profiles are interpreted to consist primarily of ice contact sediments that in part are thinly mantled by draped water lain sediments the age of the lineations has not been established possibly their formation was coincident with an ice stream in the m clintock channel eastern victoria island region which formed an ice shelf in viscount melville sound that grounded on southern melville and byam martin islands at ca 10 4 9 6 14 c ka bp alternatively they could result from later glacial events

thrust tectonics and the deep structure of the pakistan himalaya the systematic restoration of thrust systems provides a powerful constraint on the deep structure of orogenic belts a balanced cross section through the imbricated upper crust of the indian plate in the footwall to the main mantle thrust of the western himalaya restores to a minimum width of 730 km the implicit shortening being in excess of 470 km this requires the himalaya and southern tibetan region to be underlain by a wedge of indian crust however a full appraisal of gross crustal structure awaits deep seismic control

pliocene warmth polar amplification and stepped pleistocene cooling recorded in ne arctic russia understanding the evolution of arctic polar climate from the protracted warmth of the middle pliocene into the earliest glacial cycles in the northern hemisphere has been hindered by the lack of co

vhf radar echoes observed in the summer and winter polar mesosphere over andoya norway the mobile sousy vhf 53 5 mhz radar has been operated on a campaign basis on the island of andoya in northern norway 69 17 n 16 01 e with the aim of investigating the backseattering structures and dynamics of the polar middle atmosphere since november 1983 during winter the occurrence of mesospheric echoes at altitudes from 50 to 90 km is strongly correlated with radio wave absorption events measured with a riometer on 32 5 mhz individual structures are observed for up to 8 hours and in general appear as thin layers separated by 3 5 km with typical maximum signal to noise ratios snrs of 5 25 db many of these are related to variations in the background wind produced by long period gravity waves and tidal period motions and in as much are similar to mesospheric layers at middle and low latitudes in summer the echo region is largely restricted to a height interval from 75 to 95 km with 80 of the echoes occurring in the 80 to 93 km height range and on average it has a distinct maximum in snr near 86 km in the 83 to 91 km height region echoes are detected almost continuously with a minimum occurrence rate of 85 there is a low correlation 0 26 between echo strength and absorption many of the weaker echoing regions those with snrs up to 30 db are related to the background wind shear spectral analysis of time series of both snr and zonal velocity for a period of 9 days reveals 54 24 12 and 8 hour components with the 12 hour component dominating strong bursts in backscattered power tend to occur in the late afternoon and early morning hours so they coincide with the time of maximum westward velocity of the semidiurnal tide this suggests that the bursts are due to an increase in the turbulent intensity produced by dynamical instability of this mode layers consistent with dynamically unstable upward propagating inertio gravity waves are also often observed to move down through the 93 to 80 km height range thus dynamical instability of the semidiurnal tide and long period gravity waves appears to play a major role in determining much of the structure observed in the backscatter region however the strongest summer polar mesopause echoes those with peak snrs greater than 30 db while showing modulation due to the background winds often show no clear relation to the background wind shear this supports the view that the production mechanism of the very strong snrs associated with this layer is different in character from that of winter echoes observed in the polar mesosphere by vhf radars and to those mesospheric layers observed at mid latitudes using the same technique

marine transgression shoreline emergence evidence in seabed and terrestrial ground temperatures of changing relative sea levels arctic canada precise temperatures to depths of several hundred meters have been measured in abandoned petroleum exploration wells in coastal and offshore areas of the canadian arctic in these regions changes in relative sea level during the quaternary have left a strong thermal signature on deep ground temperatures surface temperature changes of the order of 10 20 k accompanied shoreline emergence due to uplift in some regions and marine transgression due to eustatic changes in sea levels in others classical analytic techniques are used to demonstrate that these anomalous features are a direct consequence of recent changes in sea level in coastal areas of the queen elizabeth islands modelling of the large near surface temperature depth gradients and the distinct curvature in the measured profiles yield emergence times in general agreement with dates taken from emergence curves the analysis suggests that surface temperatures of these coastal areas were 16 19 k higher than at present from the late wisconsinan until emergence in the holocene suggesting either marine conditions for this period or glacial ice cover with basal temperatures near the pressure melting point in contrast at two offshore wells on the beaufort shelf analyses of the negative temperature depth gradients below the seabed and profile curvature yield times of marine transgression generally consistent with the published sea level curve for the area the analyses suggest that surface temperatures of some present offshore areas were 10 16 k lower than today s sea bottom temperatures from the late wisconsinan until marine transgression in the holocene the characteristic ground temperature profiles measured in such arctic areas provide independent evidence for the relative changes in sea level indicated by proxy data it is especially valuable for these areas where there is little historical record and from which datable material such as shells driftwood and pumice fragments may be scarce or ambiguous these effects may not be observable in temperate areas because of the smaller contrast in sea bottom and terrestrial temperatures

lidar observations of ice crystals associated with noctilucent clouds at middle latitudes lidar observations at aberystwyth 52 4 n 4 1 w have shown layers of enhanced backscatter at heights just below the mesopause during four nights in late june and early july 1993 the characteristics of these layers and their association with noctilucent clouds indicate that they are comprised of ice crystals an examination is made of the temperature prior to the formation of a layer the rates of descent of layers and their integrated backscatter coefficients the results are discussed in terms of the size of the crystals giving rise to backscatter the ambient water mixing ratio and the equivalent water vapour represented by these crystals

unusual rates and patterns of holocene emergence ellesmere island arctic canada substantial postglacial emergence up to 150 m characterizes the canadian high arctic following the last glacial maximum across northern ellesmere island rapid emergence is not observed during the early stages of deglaciation as it is in other parts of arctic canada rather the curves show an interval of slow emergence c 1 m per century during initial ice retreat this is attributed to a slow rate of glacial rebound that was countered by a similar rate of eustatic sea level rise normally isobases drawn on postglacial shorelines define broad cells of uplift that mimic centres of former maximum ice thickness however isobases on the 8 ka bp shoreline surveyed throughout northern ellesmere island indicate more complex patterns of crustal uplift that seem in congruent with reported ice thicknesses on west central ellesmere island the isobases 110 150 m asl trace a plunging ridge aligned with geological structure across an area considered to have had minimal ice cover during the last glacial maximum the ridge may record an important structural influence associated with the geologically youthful sverdrup basin collectively this evidence cautions against the view that postglacial emergence has a universally predictable signature solely portraying former ice loads

quaternary history of axel heiberg island bordering nansen sound northwest territories emphasizing the last glacial maximum the landscape of northeastern axel heiberg island records an erosional history since the neogene whereas the glacial and sea level history relate to late wisconsinan glaciation during the last glacial maximum northeastern axel heiberg island was covered by glaciers emanating from local and regional sources local ice caps expanded from highlands on axel heiberg island across the coastal slope a trunk glacier flowed northward out of eureka and flat sounds into nansen sound and reached northernmost axel heiberg island radiocarbon ages on marine shells suggest that the last glacial maximum was attained along the coast after 29 ka bp and extensive deglaciation was taking place by 10 3 ka bp the postglacial marine limit rises continuously from 78 m above sea level near the entrance to nansen sound to 158 m above sea level at the mouth of eureka sound showing greatest glacioisostatic loading to the south

first southern hemisphere common volume measurements of pmc and pmse 1 using rayleigh lidar and mesosphere stratosphere troposphere radar at davis antarctica 68 6 s during the 2005 2006 austral summer we obtained the first southern hemisphere common volume measurements of polar mesospheric clouds pmc and polar mesosphere summer echoes pmse pmc were observed with 6 probability during 349 hours of lidar observations pmse were simultaneously observed during 70 of the pmc events the mean centroid altitudes of simultaneous pmc and pmse were 83 97 0 10 km and 85 31 0 14 km respectively the altitude difference 1 3 km is comparable to earlier boreal common volume measurements both phenomena show clear diurnal variations in altitude and occurrence pmc had a unimodal local time occurrence distribution which peaked 4 6 hours after solar midnight pmse were most prevalent at this time but had a secondary occurrence peak 6 hours after solar noon when pmc were absent we explain the altitude time distributions of pmc and pmse in terms of the thermal structure of the mesopause region determined using measurements from the aura satellite

late cretaceous paleocene synorogenic sedimentation and kinematic history of the sevier thrust belt northeast utah and southwest wyoming integration of cross cutting structural relationships overlapping sedimentary units new conglomerate provenance data and radiometric and palynological dates provides a basis for reinterpretation of the distribution and timing of late cretaceous through paleocene thrust faulting in the northeast utah southwest wyoming part of the sevier thrust belt these data indicate a general eastward progression of deformation that was punctuated by local out of sequence and hinterlandward verging events provenance data delimit a sequential restoration of a regional cross section the principal thrust systems in northeast utah and southwest wyoming are the willard ogden crawford absaroka and hogsback thrusts the willard is the westernmost structurally highest and oldest of the thrusts it carries a unique section of thick proterozoic sedimentary rocks as well as paleozoic rocks and was folded during displacement on younger thrust systems the next youngest thrust system is the ogden which comprises several basement rooted imbricate thrusts that together form a large antiformal stack with a structural culmination in the wasatch range growth of the wasatch culmination took place during coniacian through paleocene time contemporaneous with sequential displacement on the frontal crawford absaroka and hogsback thrusts total shortening in this part of the thrust belt was 100 km and structural relief of 25 km developed in the area of the wasatch culmination during coniacian through paleocene time thrusting followed an overall eastward progression that was interrupted by local out of sequence and hinterlandward verging events several episodes of synchronous displacement on two or more thrusts can be demonstrated shortening occurred in three main episodes the first episode 89 84 ma involved 33 km of shortening on the crawford thrust and its footwall imbricates approximately 19 km of structural relief on the basement cover contact developed in the area of the wasatch culmination the second episode 84 62 ma with a break between 75 69 ma involved 30 km of shortening mainly on the absaroka thrust and development of an additional 6 km of structural relief in the culmination the third episode of shortening 56 50 ma took place on the hogsback thrust involved 21 km of horizontal shortening and produced no significant increase in structural relief in the culmination long term rates of shortening ranged between 3 0 mm yr and 6 6 mm yr these three episodes of shortening produced three large accumulations of synorogenic conglomerate totaling 3 km in thickness the henefer formation and echo canyon and weber canyon conglomerates were deposited during crawford thrusting the evanston formation was deposited during and after absaroka thrusting and the lower conglomeratic part of the wasatch formation was deposited during and after hogsback thrusting most of the sediment in these synorogenic units however was derived from repeated uplift of the willard thrust sheet and from the eastern flank of the wasatch culmination in the rear part of the thrust belt only local minor accumulations were derived from the frontal ramp anticlines sediment accumulation and structural deformation were generally out of phase periods of regional shortening and uplift were marked by development of unconformities and sediment bypassing to distal parts of the foreland basin periods of structural inactivity were marked by accumulation of aerially widespread braided river conglomerate on top of the thrust belt one exception to this pattern is the henefer echo canyon weber canyon conglomerate deposit which contains evidence of progressive deformation in close proximity to the tip of the crawford thrust comparison of the sequential restoration with the late cretaceous subsidence history and isopach patterns in the distal foreland basin of western wyoming demonstrates that the principal controls on regional subsidence and sediment supply were the growth and erosion of the wasatch culmination growth of the duplex beneath the culmination may have been a means of maintaining critical taper in the thrust wedge

basement cover relations sevier orogenic belt northern utah precambrian crystalline basement and sedimentary cover rocks were deformed within a regional anticline in the wasatch range of northern utah during the cretaceous to early tertiary sevier orogeny this regional fold had a complex uplift and deformation history and is an imbricated ramp anticline that marks the transition to basement involved deformation large scale thrusting and folding within the basement cored anticline produced about 60 shortening and most of the slip on thrusts within the anticline was transferred into slip on frontal thrusts of the idaho utah wyoming thrust belt a network of ductile deformation zones ddz9s accommodated heterogeneous internal deformation of the basement and cleavage minor folds and vein arrays accommodated internal deformation of the sedimentary cover kinematics of internal deformation are consistent between basement and cover rocks in most areas and vary systematically with structural position recording early layer parallel shortening localized layer parallel shear and minor detachment of the cover and later fanning of structures during large scale folding ddz sets with opposite shear senses accommodated bulk coaxial flattening perpendicular to cleavage away from major thrust faults and ddz9s with consistent shear sense produced simple shear near major thrusts cleavage intensifies and refracts and minor folds tighten in the cover near major thrusts and glide horizons vein arrays record principal extension down the dip of cleavage minor extension parallel to the regional fold axis and differential displacements at high angles to fold axes slip on basement ddz9s produced about 5 to 20 bulk shortening subparallel to the basement cover contact shortening in the cover ranges from about 5 to 30 in most areas but reaches 65 near imbricate thrusts and along glide horizons reflecting heterogeneous simple shear principal extension is down the dip of cleavage and minor extension parallels local fold axes consistent with the geometry of mesoscopic structures

duplex structures and imbricate thrust systems geometry structural position and hydrocarbon potential duplexes and imbricate thrust systems form some of the most complex hydrocarbon traps in overthrust belts the geometry of a duplex is controlled by the ramp angle thgr and height hr the final spacing between adjacent thrusts a prime and the relative displacements on them d1 d2 for constant thgr and hr three different classes are recognized 1 independent ramp anticlines and hinterland sloping duplexes 2 true duplexes and 3 overlapping ramp anticlines imbricate thrust systems consist of several thrust faults each of which loses displacement upsection and eventually dies out by progressively transferring its displacement to a fold at its tip or by distributing it among several splays hybrid duplexes are ormed from systems of fault propagation folds that are subsequently carried over ramps so they have a more complex geometry and a greater structural relief these different types of thrust systems occur as outcrops and prospect scale structures and they define the regional structural styles of most fold and thrust belts second and third order duplexes and imbricate thrust systems occur in specific structural positions such as footwalls hanging walls and frontal zones of major thrust ramps and in cores of major anticlines several types of duplexes and imbricate thrust systems form important hydrocarbon traps examples include the system of independent anticlines of the turner valley and highwood oil and gas fields the hinterland sloping duplex consisting of the chestnut ridge sandy ridge system of the ben hur oil field the partly overlapping anticlines of the waterton and savanna creek gas fields and the completely overlapping anticlines of the rose hill oil field

thrust timing growth of structural culminations and synorogenic sedimentation in the type sevier orogenic belt western united states most of the regional shortening in the type area of the sevier orogenic belt in central utah was accommodated by displacement on the canyon range neocomian aptian pavant aptian albian paxton cenomanian campanian and gunnison late campanian paleocene thrust systems inception of each thrust system generated synorogenic sediment associated with frontal thrust tip anticlines or triangle zones and older thrust sheets that were elevated above major ramps farther toward the hinterland the sevier culmination a large antiformal duplex cored by crystalline basement rocks developed during paxton and gunnison thrusting west of and structurally beneath the canyon range and pavant thrusts growth of the sevier culmination was coeval with reactivation of the canyon range and pavant thrust systems and produced a second culmination in proterozoic lower cambrian rocks in the canyon range these structural highs provided much of the sediment to the adjacent foreland basin from late cenomanian to late paleocene time and may have helped to maintain critical taper in the thrust belt