on the role of rossby wave breaking in the quasi biennial modulation of the stratospheric polar vortex during boreal winter the boreal winter stratospheric polar vortex is more disturbed when the quasi biennial oscillation qbo in the lower stratosphere is in its easterly phase eqbo and more stable during the westerly phase wqbo this so called holton tan effect hte is known to involve rossby waves rws but the details remain obscure this tropical extratropical connection is re examined in an attempt to explain its intra seasonal variation and its relation to rossby wave breaking rwb reanalyses in isentropic coordinates from the national center for environmental prediction climate forecast system for the 1979 2017 period are used to evaluate the relevant features of rwb in the context of waveguide wave mean flow interaction and the qbo induced meridional circulation during eqbo the net extratropical wave forcing is enhanced in early winter with 25 increase in upward propagating prws of zonal wavenumber 1 wave 1 rwb is also enhanced in the lower stratosphere characterized by convergent anomalies in the subtropics and at high latitudes and strengthened waveguide in between at 20 40 n 350 650 k in late winter rwb leads to finite amplitude growth which hinders upward propagating prws of zonal wavenumber 2 and 3 wave 2 3 during wqbo rwb in association with wave 2 3 is enhanced in the upper stratosphere wave absorption mixing in the surf zone reinforces a stable polar vortex in early to middle winter a poleward confinement of extratropical waveguide in the upper stratosphere forces rwb to extend downward around january a strengthening of upward propagating wave 2 3 follows and the polar vortex response switches from reinforcement to disturbance around february thus a sign reversal of the hte in late winter

tectonic wedging blueschist metamorphism and exposure of blueschists are they compatible tectonic wedging is currently deforming rocks along the westernmarginofthecentralvalleyofcalifornia structuralrelations in the strata of the mesozoic great valley group fore arc basin indicatethatearlierphasesofwedgingwerecoevalwithsubduction and accretion of the franciscan complex to the west the presentday geometry of tectonic wedging is incompatible with blueschist metamorphism in the franciscan complex because the detachment for the wedge system would have prevented the transport of accretionary wedge materials to great depth we propose a sequence of tectonic events that reconciles these tectonic processes franciscan subduction and metamorphism began at 165 ma and great valley group deposition began in the tithonian shortening affected great valley group rocks in the hauterivian barremian and may havecoincidedwithagapinblueschistmetamorphisminthefranciscan major uplift of franciscan blueschist relative to the unmetamorphosed great valley group rocks began in the albian cenomanian this uplift was accommodated along an east dipping extensional fault system between the franciscan complex and the structurally overlying coast range ophiolite and great valley group movement on this fault system caused the western side of thefore arcbasintosubside resultinginuninterrupteddeposition ofgreatvalleygroupsedimentsfromthecenomaniantothecampanian maastrichtian the youngest exposed blueschists in the franciscan were metamorphosed at 80 90 ma uplift of blueschist relativetogreatvalleygrouprocksmusthavebeencompleteprior todevelopmentofthepresentstyleofeast vergenttectonicwedging this style of deformation probably began between the maastrichtian and paleocene resulting in exhumation and deformation of bothfranciscanandgreatvalleygrouprocks thedevelopmentof wedging was coincident in part with the shallowing of subduction dip and voluminous frontal accretion of the coastal belt of the franciscan

birth death and resurrection the life cycle of suprasubduction zone ophiolites 1 suprasubduction zone ssz ophiolites display a consistent sequence of events during their formation and evolution that suggests that they form in response to processes that are common to all such ophiolites this sequence includes the following 1 birth which entails the formation of the ophiolite above a nascent or reconfigured subduction zone this stage is typically characterized by the eruption of arc tholeiite lavas and the formation of layered gabbros and sheeted dike complex 2 youth during which is continued melting of refractory asthenosphere depleted during birth occurs in response to fluid flux from the subducting slab with extensional deformation of the older plutonic suite eruption of refractory lavas and the intrusion of wehrlite pyroxenite 3 maturity with the onset of semistable arc volcanism typically calc alkaline as the subduction zone matures and stabilizes and the intrusion of quartz diorite and eruption of silicic lavas and 4 death which is the sudden demise of active spreading and ophiolite related volcanism which in many cases is linked to collision with an active spreading center and the onset of shallow underthrusting of the buoyant spreading axis expressed as dikes and lavas with oceanic basalt compositions that crosscut or overlie rocks of the older suites 5 resurrection with emplacement by obduction onto a passive margin or accretionary uplift with continued subduction the early stages 1 3 may be diachronous and each stage may overlap in both time and space the existence of this consistent progression implies that ophiolite formation is not a stochastic event but is a natural consequence of the ssz tectonic setting

behavior of planetary waves before and after stratospheric sudden warming events in several phases of the equatorial qbo almost a thousand stratospheric sudden warming ssw events are obtained through long time integrations with a simple global circulation model and a statistical analysis based on such a large number of samples is made to investigate behavior of planetary waves before and after ssw events depending on the phase of the equatorial quasi biennial oscillation qbo an idealized zonal momentum forcing to mimic a phase of the qbo is imposed under a perpetual winter condition and eight phases of the qbo wind forcing are examined for 8 10 800 day datasets some systematic dependence on the phase of the qbo wind forcing is seen in the anomaly of the eliassen palm ep flux in the winter hemisphere both in the 10 800 day average and in the composites for ssw events the composite analysis shows that before ssw events the upward ep flux in the troposphere and midlatitude lower stratosphere as well as the equatorward flux above the tropopause is larger in the westerly forcing runs than in the easterly forcing runs after ssw events the upward ep flux in the troposphere is still larger in the westerly forcing runs correlation associated with the differences among ssw events that occurred in each run is significantly positive between the magnitude of the warming and the planetary wave activity flux before all the events in qbo wind forcing in the stratosphere but only in the easterly forcing runs in the troposphere

the last interglacial glacial cycle in ne fennoscandia a nearly continuous record from sokli finnish lapland abstract boreholes from the sokli basin in finnish lapland have recovered a unique sequence of diamicts interlayered with fine grained sediments that are rich in fossils the diamicts are interpreted as till beds deposited by the fennoscandian ice sheet the fine grained intercalations seem to represent a series of warm stages that include one interglacial and three interstadials the interglacial is characterized by a mixed taiga pollen assemblage and corresponds to a distinct diatom gyttja bed the interstadials show progressively colder floras from open birch forest to arctic forest limit to shrub tundra their sediments comprise gyttja interlayered with wood and sand interstadial 1 sands grading into sandy gyttja interstadial 2 and sands overlain by laminated silt and clay interstadial 3 the interstadial 2 and 3 deposits are underlain by diamict and are interpreted as deglaciation sequences silts with a tundra pollen assemblage separate the interglacial and interstadial 1 deposits luminescence dating evidence indicates that the interglacial bed most probably represents the nw european mainland eemian interglacial marine isotope stage mis 5e the interstadial 1 2 and 3 deposits are tentatively correlated with the early weichselian brorup and odderade interstadials and an interstadial of middle weichselian age respectively mis 5c 5a and 3 respectively the correlation implies that the easternmost part of the ice divide zone of the fennoscandian continental ice sheet was deglaciated during part of mis 3

present day temperatures in northern scandinavia during the last glaciation scandinavia is generally considered to have been covered extensively with ice throughout marine isotope stages mis 4 2 between 75 and 10 ka here we present evidence for ice free warm conditions in the central area of the scandinavian glaciations during mis 3 our multiproxy data obtained from a lacustrine sequence in northern fin land reveal not only significant response in the northeastern sector of the scandinavian ice sheet to warming during the early part of mis 3 but also indicate rapid climate warming to present day temperatures in this ice free period new climate model simulations for interstadial conditions in mis 3 confirm the high mean july temperatures northeast of the scandinavian ice sheet in response to the high insolation values and the presence of the ice sheet during mis 3

chronology and paleoenvironment of marine isotope stage 3 from two high elevation speleothems austrian alps abstract a new high resolution stable isotope record from the alpine kleegruben cave 2165 m central alps is presented this record largely duplicates a previously reported speleothem record from this site high precision u series thermal ionization mass spectrometry dates constrain the growth history of this new sample 56 48 ka to the marine isotope stage mis 3 both stalagmites reveal highly similar variations in o isotopes that can be directly compared to o isotope variability associated with dansgaard oeschger interstadials recorded in the greenland ice cores greenland interstadials gis based on the new record we refine our previous age assignments of the gis during this time interval i e gis 15b at 55 7 ka gis 15a at 55 3 ka onset mid point of the prominent gis 14 at 54 5 yr and onset of gis 12 at 48 ka the overall uncertainties associated with these ages are 0 1 0 3 ka the timing of these dansgaard oeschger interstadials is within 0 2 ka of the newly proposed grip sfcp04 timescale the age data for both kleegruben stalagmites demonstrate that liquid water was at least seasonally present in the shallow sub surface allowing calcite precipitation to continue even during stadials of mis 3 given the present day low temperature 2 4 c we propose that these unusual speleothems formed in a karst system overlain by a warm based glacier

isotope calibrated greenland temperature record over marine isotope stage 3 and its relation to ch4 large temperature variations on millennial time scales in greenland characterised the last ice age abrupt warmings known as dansgaard oeschger do events can be traced in the 18oice record of greenland ice cores however it has been shown that 18oice is not a direct temperature proxy measurements of the isotopic composition of gases trapped in the ice can be used to calibrate the paleothermometer here we present a continuous temperature record based on high resolution 15n measurements and firn model studies it covers a sequence of 9 do events 9 17 during the time period from 38 to 64 kyr bp for which temperature changes of 8 to 15 c were estimated the difference between the modern and the glacial 18oice t relationship can be explained by a combination of source temperature changes and changes in the annual distribution of precipitation a detailed comparison of the temperature evolution with reconstructions of the atmospheric methane ch4 concentration shows that ch4 rises lag temperature increases at the onset of do events by 25 to 70 yr within data resolution the strong correlation between greenland temperature and ch4 on millennial and submillennial time scales suggests that variations on these time scales were probably of hemispheric extent

does the holton tan mechanism explain how the quasi biennial oscillation modulates the arctic polar vortex idealized experiments with the whole atmosphere community climate model waccm are used to explore the mechanism s whereby the stratospheric quasi biennial oscillation qbo modulates the northernhemispherewintertimestratosphericpolarvortex overall theeffectofthecriticallineemphasized in the holton tan mechanism is less important than the effect of the mean meridional circulation associated with qbo winds for the polar response to the qbo more specifically the introduction of easterly winds at the equator near 50 hpa 1 causes enhanced synoptic scale eliassen palm flux epf convergence in the subtropics from 150 to 50 hpa which leads to the subtropical critical line moving poleward in the lower stratosphere and2 createsabarriertoplanetarywavepropagationfromsubpolarlatitudestomidlatitudesin the middle andupper stratosphere e g less equatorwardepf near 508n whichleads to enhancedplanetary wave convergence in the polar vortex region these two effects are mechanistically distinct while the former is relatedtothesubtropicalcriticalline thelatterisduetothemeanmeridionalcirculationofthe qbo allof these effects are consistent with linear theory although the evolution of the entire wind distribution is only quasi linear because induced zonal wind changes cause the wave driving to shift and thereby positively feed back on the zonal wind changes finally downward propagation of the qbo in the equatorial stratosphere upper stratospheric equatorial zonal wind and changes in the tropospheric circulation appear to be less important than lower stratospheric easterlies for the polar stratospheric response overall an easterly qbo wind anomaly in the lower stratosphere leads to a weakened stratospheric polar vortex in agreement with previous studies although not because of changes in the subtropical critical line

deformation history of the yolla bolly terrane at leech lake mountain eastern belt franciscan subduction complex california coast ranges the roles of volume loss coaxial versus noncoaxial flow and blueschist exhumation in subduction related accretionary wedges are still poorly understood in our study at leech lake mountain in the eastern belt of the franciscan subduction complex we focus on these subjects in the specific example of the franciscan the tectonic significance of the boundary between the eastern and central belts remains controversial the leech lake mountain area in northern california is situated immediately above this boundary and therefore appears to be of crucial importance for understanding aspects of the tectonic evolution of the franciscan the structural development at leech lake mountain is characterized by three deformational events d2 produced the regional cleavage s2 during blueschist facies metamorphism d2 is the only entirely ductile deformation event and was associated with accretion related internal stacking within the yolla bolly terrane the s2 cleavage is folded by f3 folds which are overturned to the west spacing of a related s3 cleavage is generally at the decimeter scale but locally is spaced at the centimeter scale the s2 and s3 cleavages and f3 folds are overprinted by tight to open f4 folds at the decimeter to map scale map scale f4 folds are largely upright whereas small scale f4 folds are either upright or overturned to the east our finite strain analysis relates deformed lengths to original lengths in the rock and thus provides an absolute reference frame which allows us to detect deformation related volume changes absolute finite strain data from 20 samples support earlier studies indicating that the development of the moderately dipping s2 cleavage was accompanied by pronounced volume loss averaging 36 the directions of the principal finite strain axes are scattered therefore we calculated a tensor average of the data the principal stretches of the tensor average are s x s y s z 1 06 0 91 0 66 indicating that the accumulation of ductile strain was characterized by subvertical shortening which was largely compensated for by volume loss and not by orthogonal extension evidence for noncoaxial deformation in our samples is limited indicating that the accumulation of ductile strain was largely coaxial our preferred tectonic interpretation is that accretion and blueschist facies metamorphism of the yolla bolly terrane at leech lake mountain occurred during d2 under an almost coaxial deformation regime during and after d2 the rocks were considerably exhumed and were telescoped by d3 top to the west out of sequence thrusts at shallow crustal levels in the leech lake mountain area d3 thrusting juxtaposed the eastern and central belts along the red mountain fault and cut out the lower tectonic units of the eastern belt the difference in the degree of peak metamorphism between the eastern and central belts is modest indicating that displacement at the red mountain fault was not large we propose that d3 out of sequence thrusts attenuated the metamorphic and stratigraphic section across the entire franciscan and overlying great valley forearc the final d4 event produced large scale folds all three events resulted from horizontal shortening there is no evidence for a major phase of horizontal extension which might have aided exhumation of the eastern belt blueschists modest tectonic exhumation was due to vertical ductile shortening during d2

early mis 3 glacial lake evolution ice marginal retreat pattern and climate at sokli northeastern fennoscandia lake development at sokli northern finland is traced through the analysis of diatoms and other siliceous micro fossils in a 2 meter thick minerogenic laminated clay silt deposit dated to the early part of marine isotope stage mis 3 fluctuating water levels and changes in lake extent depicted by the siliceous micro fossil record together with lithology suggest that an important part of the sediment sequence was deposited in a glacial lake the proxy based glacial lake evolution is tested using a digital elevation model and geomorphologic evidence including eskers dated to the early mis 3 tulppio interstadial at sokli despite the apparent ice dammed nature of the lake the sediment is relatively rich in fossils and there are limited signs of re deposition of older fossil material the siliceous micro fossil record together with data from other proxies previously analysed in the same sediment samples provides a coherent picture of past environmental changes around the sokli site this is most probably due to the sheltered position of the coring site in a lake embayment quantitative climate reconstructions based on the diatom record show mean july air temperatures as high as present day values at sokli and the temperature ranges indicated by the diatom record are in agreement with temperature reconstructions based on chironomids the position of sokli in the northeastern portion of the central area of the scandinavian glaciations and the northern retreat pattern implies that an important part of eastern fennoscandia was deglaciated during the early mis 3 warming event

source characterization and ground motion modeling of the 1892 vacaville winters earthquake sequence california a sequence of several earthquakes in april 1892 produced significant damage in the towns of winters dixon allendale and vacaville along the boundary between the southwestern sacramento valley and northern coast ranges of california the largest event occurred on 19 april 1892 with a maximum modified mercalli intensity of ix and was assigned a moment magnitude m of 6 5 based on felt area these earthquakes occurred within a zone of active crustal shortening accommodated by postulated blind thrust faults seismotectonic and structural analyses are used to evaluate the depth geometry and segmentation of thrust faults that were the probable sources of the 1892 earthquake sequence synthetic ground motion modeling demonstrates that rupture of a 17 km long segment of the thrust fault system can produce the magnitude and distribution of intensities documented from anecdotal accounts of the 19 april 1892 earthquake including probable directivity effects east of the range front integrated structural and seismotectonic analyses also are used to interpret the role of inferred geometric segment boundaries in arresting the 19 april 1892 earthquake rupture and the subsequent occurrence of the 21 april 1892 aftershock

role of the quasi biennial oscillation in the downward extension of stratospheric northern annular mode anomalies using the jra 55 reanalysis datasets and radiosonde observations the impact of the quasi biennial oscillation qbo on the downward extension of stratospheric northern annular mode nam signals in its positive and negative phases positive and negative nam hereafter is examined the results show that the average number of days per month on which stratospheric negative nam signals extend downward into the troposphere is more than twice as large during the easterly phase of the qbo eqbo as those during the westerly phase of the qbo wqbo the increasing likelihood of downward extension of stratospheric negative nam signals during the eqbo is related to three factors enhanced upward wave 1 fluxes entering the stratosphere anomalous poleward wave fluxes below 100 hpa and eqbo induced residual circulation it is also revealed that the eqbo induced subtropical tropospheric easterly anomalies lead to positive height anomalies over the subtropical north atlantic which are amplified by transient eddies and maintained by convection these subtropical positive height anomalies further stimulate an anomalous wave train forcing subpolar positive height anomalies over the euro atlantic sector and enhancing wave 1 over the pacific the eqbo could also induce positive height anomalies in the tropical troposphere and these anomalies are related to convection and vertical motion the positive height anomalies can induce anomalous poleward propagating waves forcing negative height anomalies over the north pacific at mid high latitudes and the enhancing wave 1 fewer stratospheric positive nam signals extend downward into the troposphere during the eqbo than during the wqbo with mechanisms similar to those of negative nam

chironomid inferred air temperatures from lateglacial and holocene sites in north west europe progress and problems abstract non biting midges insecta diptera chironomidae are now widely recognised as powerful biological proxies for inferring past climatic change in this paper the response of chironomid assemblages to lateglacial and holocene climatic change from sites in scotland and norway is discussed analyses have shown that midge assemblages have responded to major and minor climatic fluctuations during the last 15 000 yr such as the aegelsee oscillation gerzensee oscillation and younger dryas in the lateglacial and the thermal optimum little ice age and cooling events at 8 2 and 2 0 cal ka bp in the holocene in an attempt to quantify these and other climatic fluctuations a chironomid mean july air temperature inference model based on a modern calibration set of 109 lakes in norway and svalbard has been developed the 3 component weighted averaging partial least squares inference model performs well with a root mean squared error of prediction of 0 90 c and a maximum bias of 0 59 c both based on leave one out cross validation which is lower than chironomid temperature inference models developed in canada switzerland and finland however while temperature inference models perform well in the lateglacial the more subtle climatic changes of the holocene are more difficult to reconstruct because the likely temperature changes are close to the limits of the prediction errors of the existing models to address this problem future work is required to refine and develop the calibration set by further improving taxonomic resolution by adding more lakes to the calibration set and by investigating the influence of other environmental variables on chironomid distributions and abundances

composition and origin of ash zones from marine isotope stages 3 and 2 in the north atlantic abstract the composition and distribution of four north atlantic ash zones from the faroe islands margin is presented including the widespread north atlantic ash zone ii naaz ii 52 53 ka bp and three mainly basaltic ash zones here referred to as the faroe marine ash zones fmaz i ca 15 4 14 c ka bp ii ca 23 14 c ka bp also referred to as the fugloyarbanki tephra and iii ca 33 14 c ka bp one core from the south east labrador sea was also analysed naaz ii was found in all investigated cores indicating very large eruption events in the early marine isotope stage mis 3 detailed investigations of naaz ii in high resolution cores show that two separate layers can be distinguished a lower mixed alkalic basalt and rhyolitic layer and an upper predominantly tholeiitic basalt tephra the main component of the basaltic fmaz ii was found in all cores from the faroe island margin and the labrador sea indicating that this tephra is the most widespread tephra from mis 2 in the north atlantic discovered so far we discuss the possibility to use these tephra layers for exact correlations between marine records and land sections such as the greenland ice cores and terrestrial records on the european mainland

two paradigms of baroclinic wave life cycle behaviour two idealized baroclinic wave 6 life cycles examined here suggest a framework of opposite extremes a in which to view the behaviour of real synoptic scale disturbances in middle latitudes and b in which to interrelate the synoptic and wave theoretic viewpoints using the saturation propagation saturation sps picture of wave 6 life cycle behaviour the two life cycles dented by lc1 and lc2 are higher resolution versions of the simmons hoskins basic and anomalous cases showing strong and weak late decay of eddy kinetic energy eke they illustrate in varying degrees two extreme types of behaviour here disignated anticyclonic and cyclonic and epitomized by strongly contrasting upper air trough behaviour anticyclonic behaviour dominates the late stages of lc1 and is characterized by backward tilted thinning troughs being advected anticyclonically and equatorward as in the commoner cases of planetary scale mid stratospheric rossby wave breaking cyclonic behaviour dominates lc2 and is characterized by forward tilted broadening troughs wrapping themselves up cyclonically and poleward producing major cut off cyclones in high latitudes these morphologies are visualized by upper air maps of potential temperature on the nominal tropopause defined as a constant potential vorticity surface some atmospheric mid latitude disturbances examined here using the same visualization applied to operational analyses show the same two extreme types of trough behaviour together with intermediate cases the sps picture is re examined using eliassen palm and refractive index cross sections it is shown in particular by reference to a wave activity theorem of haynes that the late stages of lc2 can be looked upon as a remarkably clear and morphologically novel large amplitude counterpart of the nonlinear reflection scenario of rossby wave critical layer theory the late stages of lc1 by constrast look more akin to an nonlinear critical layer absorption scenario lc2 exhibits region of largely undular pv contours adjacent to a nonlinear of irreversiby deformen pv contous in the latter region pv rearrangement and hence absorption of rossby wave activity has largely ceased this accounts for the more persistent ekee in the lc2 case

late quaternary ice sheet history of northern eurasia the maximum limits of the eurasian ice sheets during four glaciations have been reconstructed 1 the late saalian 140 ka 2 the early weichselian 100 80 ka 3 the middle weichselian 60 50 ka and 4 the late weichselian 25 15 ka the reconstructed ice limits are based on satellite data and aerial photographs combined with geological field investigations in russia and siberia and with marine seismic and sediment core data the barents kara ice sheet got progressively smaller during each glaciation whereas the dimensions of the scandinavian ice sheet increased during the last ice age the barents kara ice sheet attained its maximum size as early as 90 80 000 years ago when the ice front reached far onto the continent a regrowth of the ice sheets occurred during the early middle weichselian culminating about 60 50 000 years ago during the late weichselian the barents kara ice sheet did not reach the mainland east of the kanin peninsula with the exception of the nw fringe of taimyr a numerical ice sheet model forced by global sea level and solar changes was run through the full weichselian glacial cycle the modeling results are roughly compatible with the geological record of ice growth but the model underpredicts the glaciations in the eurasian arctic during the early and middle weichselian one reason for this is that the climate in the eurasian arctic was not as dry then as during the late weichselian glacial maximum

tropospheric precursors of anomalous northern hemisphere stratospheric polar vortices regional extratropical tropospheric variability in the north pacific and eastern europe is well correlated with variability in the northern hemisphere wintertime stratospheric polar vortex in both the ecmwf reanalysis record and in the whole atmosphere community climate model to explain this correlation the link between stratospheric vertical eliassen palm flux variability and tropospheric variability is analyzed simple reasoning shows that variability in the north pacific and eastern europe can deepen or flatten the wintertime tropospheric stationary waves and in particular its wavenumber 1 and 2 components thus providing a physical explanation for the correlation between these regions and vortex weakening these two pathways begin to weaken the upper stratospheric vortex nearly immediately with a peak influence apparent after a lag of some 20 days the influence then appears to propagate downward in time as expected from wave mean flow interaction theory these patterns are influenced by enso and october eurasian snow cover perturbations in the vortex induced by the two regions add linearly these two patterns and the quasi biennial oscillation qbo are linearly related to 40 of polar vortex variability during winter in the reanalysis record

mis 3 mammoth remains from sweden implications for faunal history palaeoclimate and glaciation chronology the distribution of low arctic megafaunal remains in time and space from the area previously covered by the scandinavian ice sheet sis suggests the presence of breeding mammoth populations in the circum baltic region during the time interval from 44 to 26 ka ago the transport history of 30 mammoth teeth and bones from southern and north central sweden was estimated and the remains were subjected to osteological analyses and 14c dating oxygen isotope analyses of tooth enamel indicate a palaeoclimate considerably more homogenous than that experienced in sweden today showing moderate north south gradients in the d18o value of precipitation and temperature in general the results support the model of restricted ice sheet distribution during the second half of the middle weichselian the clear discrepancy in the inferred absence of glaciation in the central swedish uplands and the baltic basin as evidenced by the swedish mammoth data versus the danish osl based glaciation chronology in the period from 40 to 30 ka ago is discussed in the light of radiocarbon calibration and glacial dynamics r 2007 published by elsevier ltd less

reappraisal of hypothetical franciscan thrust wedging at coalinga implications for tectonic relations along the great valley flank of the california coast ranges 1 correlation of the character and orientation of seismic reflectors imaged on profiles across the coalinga anticline with known surface geology indicates that local franciscan thrust wedging favored for past geodynamic interpretations of the 1983 coalinga earthquake is an untenable hypothesis the inference that a subhorizontal detachment surface of simple shear is present beneath the anticline is consequently unnecessary and unlikely in view of the coherent areal pattern of wrench folding within the southern diablo range elsewhere along the structural front of the california coast ranges at the western flank of the great valley interpretations of similar thrust wedging based in part on analogy with supposed structural relations at coalinga are equally questionable in a wider context the seismogenic behavior of blind thrust and reverse faults in california cannot be interpreted with the invalid concept of thrust wedging at coalinga as a guiding template for geotectonic interpretations

seasonal evolution of the qbo induced wave forcing and circulation anomalies in the northern winter stratosphere diagnostics of wave mean flow and wave wave interactions in isentropic coordinates are analysed regarding the mechanisms that govern the holton tan effect hte whereby the tropical quasi biennial oscillation qbo modulates the northern winter stratospheric polar vortex we find a clear seasonal evolution of a qbo modulation of rossby waves and linear and nonlinear wave interactions along with multiple mechanisms at work in early winter when the lower stratospheric qbo is easterly there is enhanced upward stationary planetary wave activity in the subtropical to midlatitude lower stratosphere these upward propagating waves are first refracted towards the zero wind line approximately one month later poleward propagating wave anomalies appear at midlatitudes as a result of nonlinear wave interactions the enhanced upward wave propagation appears to be due to a combination of the qbo influence on the latitudinal location of the zero wind line and the increased midlatitude baroclinicity associated with the qbo induced meridional circulation this is further aided by a gradual poleward shift over the winter of the middle stratospheric waveguide refracting waves poleward the associated wave breaking weakens the polar vortex and drives a stronger meridional circulation throughout the lower to middle stratosphere contributing to the high latitude warming it is additionally found that in late winter the modified high latitude waveguide associated with the weaker polar vortex consequently reduces upward propagating transient planetary waves at high latitudes whilst simultaneously enhancing upward propagating synoptic waves at midlatitudes this highlights the need to view the hte and its mechanisms as an evolving phenomenon throughout the winter

the nature of mis 3 stadial interstadial transitions in europe new insights from model data comparisons 15 abrupt warming transitions perturbed glacial climate in greenland during marine isotope stage 3 mis 3 60 27 ka bp one hypothesis states that the 8 16 degrees c warming between greenland stad

provenance and thermal history of the franciscan accretionary complex constraints from zircon fission track thermochronology the franciscan accretionary complex of california contains large belts of sediments that were subducted to depths of 10 to 30 km metamorphosed under high pressure and low temperature conditions and later returned to the surface reconnaissance zircon fission track ft data 21 samples place constraints on the sedimentary provenance thermal history and or exhumation history of various franciscan units in a transect across the northern coast ranges through mendocino pass metagraywacke samples from the valantine springs formation of the franciscan eastern belt experienced maximum temperatures tmax ranging from 250 to 310 c zircon ft and previously reported apatite ft data indicate that parts of the western eastern and eastern central belts cooled at about 100 70 ma from 300 c to 100 c considering the low paleogeothermal gradient of roughly 9 c km during franciscan subduction these rocks were apparently uplifted and exhumed from 30 to 10 km depth at this time one sample from the eyler mountain sequence in the northwestern diablo range similarly shows tmax 310 c and major cooling at 100 70 ma this uplift and exhumation may have reflected accelerated accretion at the base as well as the front of the franciscan wedge accompanied by extensional thinning at shallower levels as a result of massive sediment influx into the franciscan trench from the sierra nevada magmatic arc in the northern coast ranges the western part of the central belt and the coastal belt experienced lower tmax probably 200 c and retain source area detrital zircon ft ages burnt hills terrane samples in the diablo range also experienced tmax 230 c and retain detrital ages the detrital single grain age patterns from these areas are compatible with those expected from the sierra nevada magmatic arc and its country rocks this is consistent with derivation of franciscan sediments from arc terranes in california and provides no particular suggestion that these parts of the franciscan are highly allochthonous paleogene coastal belt sandstones also yield detrital ages compatible with derivation from the sierra nevada but also include early tertiary zircon populations compatible with reconstructions suggesting these sandstones were sourced partly from the idaho batholith

tectonic wedging along the rear of the offshore taiwan accretionary prism abstract the structural geometry kinematics and density structure along the rear of the offshore taiwan accretionary prism were studied using seismic reflection profiling and gravity modeling deformation between the offshore prism and forearc basin at the point of incipient collision and southward into the region of subduction has been interpreted as a tectonic wedge similar to those observed along the front of mountain ranges this tectonic wedge is bounded by an east dipping roof thrust and a blind west dipping floor thrust an east dipping sequence of forearc basin strata in the hanging wall of the roof thrust reaches a thickness in excess of 4 km near the tip of the interpreted tectonic wedge section restoration of the roof sequence yields an estimate of 4 km of shortening which is small compared with that inferred in the collision area to the north based on the variation in distance between the apex of the prism and the island arc previous studies propose that either high angle normal faulting or backfolding has exhumed the metamorphic rocks along the eastern flank of the central range in the collision zone on land to better constrain the initial crustal configuration we tested 350 crustal models to fit the free air gravity anomaly data in the offshore region to study the density structure along the rear of the accretionary prism in the subduction and initial collision zones before the structures become more complex in the collision zone on land the gravity anomaly observed in the region of subduction 20 2 n can be modeled with the arc basement forming a trenchward dipping backstop that is overlain by materials with densities in the range of sedimentary rocks near the point of incipient collision 20 9 n however the free air gravity anomaly over the rear of the prism is approximately 40 mgal higher compared with the region of subduction and requires a significant component of high density crustal rocks within the tectonic wedge these results suggest that the forearc basement may be deformed along the rear of the prism associated with the onset of collision but not in the subduction region further to the south

northern hemisphere winter circulation associated with the north atlantic oscillation and stratospheric polar night jet the interannual variability of the atmospheric winter circulation as characterized by the geopotential height at 500 hpa and temperature at 850 hpa associated with the north atlantic oscillation nao and stratospheric polar night jet pnj is examined it is suggested that the wintertime atmospheric circulation related to the nao index can be separated into two different modes of variability one is a regional mode characterized by a meridional dipole type pattern in the 500 hpa geopotential height anomaly field over the atlantic region the other having more zonal structure extends over wider region of the northern hemisphere this is also related to the lower stratospheric polar night jet air temperature near the surface over the eastern part of the eurasian continent is more closely correlated with the above mentioned hemispheric mode of variability than the regional nao

internal variability of the troposphere stratosphere coupled system simulated in a simple global circulation model internal variability of a troposphere stratosphere coupled system is investigated in a series of numerical experiments with a simple global circulation model under a perpetual winter condition in order to examine the relative importance of forced planetary waves in the interaction with the zonal mean zonal flow and baroclinic disturbances amplitude of a sinusoidal surface topography of zonal wavenumber 1 or 2 is swept as an experimental parameter 1000 day integrations are performed for 110 combinations of the external parameters intraseasonal variability of the extratropical winter stratosphere in the parameter sweep experiment of the zonal wavenumber 1 topography is classified into four regimes dependent on the topographic amplitude i a nearly radiative equilibrium state ii small undulations of the polar vortex iii intermittent breakdowns of the polar vortex or occurrence of stratospheric sudden warming events and iv a usually weak and warm state of the polar vortex the behavior of planetary waves in the stratosphere is characterized by linear propagation in regime i and by quasi linear or weakly nonlinear wave mean flow interaction in regime ii in regimes iii and iv on the other hand it is in a highly nonlinear state reflecting the occurrence of sudden warming events and the usually distorted polar vortex respectively the northern hemisphere winter stratosphere corresponds to regime iii in the intraseasonal variations while the southern counterpart is close to regime ii a lag correlation analysis shows that the dynamical linkage between the stratosphere and the troposphere is also dependent on the regimes the vertical linkage is primarily the upward control in regime i planetary waves are generated by nonlinear interaction of baroclinic disturbances in the troposphere and propagate into the stratosphere in regime ii stratospheric variations are largely confined in the stratosphere although planetary waves are generated in the troposphere the linkage in regime iii on the other hand is inevitably two way planetary wave variability has upward influence from the troposphere to the stratosphere as well as the zonal mean zonal wind shows preconditioning in the troposphere before stratospheric sudden warming events downward propagation of signals to the upper troposphere are also seen in the zonal mean temperature in high latitudes it is higher than normal at the final stage of the sequence of sudden warming events the linkage is also two way in regime iv

propagation of the arctic oscillation from the stratosphere to the troposphere geopotential anomalies ranging from the earth s surface to the middle stratosphere in the northern hemisphere are dominated by a mode of variability known as the arctic oscillation ao the ao is represented herein by the leading mode the first empirical orthogonal function of low frequency variability of wintertime geopotential between 1000 and 10 hpa in the middle stratosphere the signature of the ao is a nearly zonally symmetric pattern representing a strong or weak polar vortex at 1000 hpa the ao is similar to the north atlantic oscillation but with more zonal symmetry especially at high latitudes in zonal mean zonal wind the ao is seen as a north south dipole centered on 40 45 n in zonal mean temperature it is seen as a deep warm or cold polar anomaly from the upper troposphere to 10 hpa the association of the ao pattern in the troposphere with modulation of the strength of the stratospheric polar vortex provides perhaps the best measure of coupling between the stratosphere and the troposphere by examining separately time series of ao signatures at tropospheric and stratospheric levels it is shown that ao anomalies typically appear first in the stratosphere and propagate downward the midwinter correlation between the 90 day low pass filtered 10 hpa anomaly and the 1000 hpa anomaly exceeds 0 65 when the surface anomaly time series is lagged by about three weeks the tropospheric signature of the ao anomaly is characterized by substantial changes to the storm tracks and strength of the midtropospheric flow especially over the north atlantic and europe the implications of large stratospheric anomalies as precursors to changes in tropospheric weather patterns are discussed

normal faulting at convergent plate boundaries mylonitic extensional fabrics in the franciscan subduction complex in del puerto canyon california revisited 1 using a strain and rotation analysis we tested the hypotheses that top east mylonitic extensional structures in the uppermost franciscan subduction complex in del puerto canyon california accomplished exhumation of the franciscan blueschists we found no evidence of strongly noncoaxial deformation instead our data indicate overall coaxial deformation in the proposed zone of mylonitic extensional deformation there are no extensional strains moderate vertical shortening occurred without horizontal extension and was compensated by modest deformation related volume loss there is also no strain gradient toward and within the proposed shear zone therefore the results of our work indicate that mylonitic extensional structures in del puerto canyon do not exist overall we conclude that there is no currently identifiable structure adjacent to or within the franciscan in california that could have accommodated large scale horizontal extension exhumation of the franciscan blueschists was mainly achieved by erosion of an emergent forearc high our strain results and published data are also inconsistent with the development of a supercritically tapered franciscan wedge that ultimately should have triggered normal faulting strain magnitudes are low despite the relatively long residence time of the rocks in the accretionary wedge from this we infer that strain rates were low and that the wedge material flowed with a relatively high viscosity therefore ductile flow probably was not fast enough to form a supercritically tapered franciscan wedge

tectonic evolution of the jurassic cretaceous great valley forearc california implications for the franciscan thrust wedge hypothesis interpretation of seismic reflection data and restoration of depositional geometries of cretaceous forearc basin strata in the northwest great valley of california provide important controls on structural reconstructions of the western margin of the sacramento valley and northern coast ranges monoclinal eastward dips of great valley group strata and fault systems striking northwest southeast which are features proposed as evidence for a west dipping blind great valley franciscan sole thrust and related backthrusts instead are expressions of bedding geometry that resulted from folding of the paskenta and related synsedimentary normal faults depositional onlap and a major structural stratigraphic discontinuity the discontinuity separates east dipping aptian and younger great valley group strata from beds of lower great valley group and coast range ophiolite that were deformed and erosionally or structurally truncated by mid cretaceous time dip divergence imaged between the supracrop and subcrop of the discontinuity is not unique to the ancient great valley forearc but is also observed in modern forearc basins advocates of the franciscan thrust wedge model have also proposed that west dipping shingled patterns of seismic events imaged beneath the sacramento valley are imbricate thrust slices of the great valley group this hypothesis however is incompatible with borehole potential field and seismic refraction data that characterize the sacramento valley basement as ophiolitic seaward dipping reflections in the ophiolitic basement of the sacramento valley are analogous to layering developed in the oceanic crust of volcanic rifted margins or generated along midocean ridges thus late stage tectonic mechanisms are not required to interpret a forearc that owes much of its present day bedding architecture to processes coeval with deposition thickening of the great valley group stratigraphic section valanginian turonian in the hanging walls of the paskenta elder creek and cold fork fault zones combined with attenuation or complete omission of preextensional units including the coast range ophiolite and geometric evidence based on seismic reconstructions suggest that these faults are jurassic cretaceous normal faults that developed in a submarine setting down structure views of the great valley outcrop belt simplify otherwise complex map relations and portray the paskenta and related faults as half graben bounding faults that accommodated significant northwestward tectonic transport of hanging wall rocks it is significant that these faults sole into the coast range fault an enigmatic forearc structure that juxtaposes rocks of the franciscan complex blueschists with rocks of the coast range ophiolite and great valley group that have sustained only zeolite grade metamorphism discovery of jurassic cretaceous crustal scale extension in the great valley forearc suggests that a significant part of coast range fault related attenuation developed early in the history of the subduction complex

progressive arcward contraction of a mesozoic tertiary fore arc basin southwestern sacramento valley california the modern sacramento valley intermontane basin is the successor to a deformed mesozoic tertiary fore arc basin based on analysis of seismic reflection profiles drill hole data and surface mapping we propose a model for progressive arcward contraction of the fore arc basin in the rumsey hills region southwestern sacramento valley beginning in cretaceous and continuing episodically through cenozoic time we present our interpretation in the form of a kinematically restorable forward model the major tectonic and depositional events include 1 mid cretaceous or older shortening of fore arc basin strata along imbricate west dipping thrust faults 2 erosion of the deformed fore arc strata 3 onlap of cenomanian and younger fore arc strata onto deformed older strata and crystalline sierran basement 4 renewed shortening in latest cretaceous to early tertiary accommodated by delamination of upper cretaceous strata from the mid cretaceous angular unconformity tectonic wedging and west directed backthrusting 5 erosion of the deformed upper cretaceous strata and deposition of the eocene capay formation 6 uplift and east directed shortening from eocene to late neogene with local erosion of the capay formation over the ancestral rumsey hills 7 uplift of the northern coast ranges beginning ca 3 4 ma and deposition of the pliocene pleistocene tehama formation in the western sacramento valley as a syntectonic molasse and 8 fault propagation folding of the tehama formation beginning ca 0 5 1 0 ma with the exception of quaternary shortening progressive arcward contraction of the western basin margin occurred during east dipping subduction and plate convergence beneath western california the deformation of the ancestral sacramento valley fore arc basin is analogous to arcward contraction of the tobago trough in the lesser antilles arc trench system and suggests that tectonic wedging may be a relatively common process in the evolution of fore arc regions late quaternary shortening has occurred in a transpressional setting and suggests a continuity in structural style despite a change in plate boundary kinematics from convergence to transpression during the past 3 5 m y

crustal structure of the ancestral northwestern california forearc region from seismic reflection imaging implications for convergent margin tectonics abstract analysis of a suite of 2 d seismic reflection profiles reveals that the northwestern sacramento valley and eastern coast range foothills northern california are underlain by a system of blind west dipping thrust faults homoclinally east dipping and folded mesozoic marine forearc strata exposed along the western valley margin define the forelimbs of northeast vergent fault propagation folds developed in the hanging walls of the thrusts exhumed coherent blueschists of the accretionary complex and attenuated remnants of the ophiolitic forearc basement presently exposed in the eastern coast ranges are in the hanging wall of the blind thrust system and have been displaced from their roots in the footwall deep east dipping magnetic reflectors in the footwall of the thrust system may be fragments of sheared serpentinized and attenuated ophiolitic basement restoration of slip on the thrusts suggests that the coast range fault which is the exposed structural contact between the coherent blueschists and attenuated ophiolite originally dipped east and is associated with the east dipping magnetic reflectors in the footwall this interpretation of the reflection data is consistent with previous inferences about the deep structure in this region and supports a two stage model for blueschist exposure in the eastern coast ranges 1 blueschist exhumation relative to the forearc basin by attenuation of the ophiolitic basement along the east dipping coast range fault system in late cretaceous 2 blueschists attenuated ophiolite and forearc strata all were subsequently uplifted and folded in the hanging wall of the blind thrust system beginning in latest cretaceous early tertiary the blind thrust system probably rooted in and was antithetic to the east dipping subduction zone beneath the forearc region active transpressional plate motion in western california is locally accommodated in part by reactivation of blind thrust faults that originally developed during the convergent regime

zooming in on frozen bed patches scale dependent controls on fennoscandian ice sheet basal thermal zonation in this paper we explore geomorphological evidence allowing a first order reconstruction of the extent and pattern of frozen bed conditions under the last fennoscandian ice sheet we mapped relict landscapes i e glacial landforms and subaerially developed ground surfaces predating the last ice sheet and marking sustained frozen bed conditions at four different spatial scales at the ice sheet scale relict landscapes are most abundant between the last glacial maximum ice divide and the elevation axis of the scandinavian mountain range the location of frozen bed zones was mainly a function of dispersal centre location low surface temperatures and small strain heating and small ice thickness over the eastern flank of the mountain range at the mesoscale 260 360 km map area the pattern of relict surfaces is governed by inward cutting ice stream erosion topographical control was weak but relation to flow pattern was strong with the major frozen bed zone located where ice flow was strongly divergent at the regional scale 40 65 km map area in hilly terrain topographical control was strong with relict surfaces only appearing above a plane dipping in the up ice direction at the local scale 12 14 km map area control by topography was likewise strong but the detailed boundary pattern was irregular with specific landforms occurring both up and down ice of frozen patches

the last interglacial glacial cycle in fennoscandia abstract the climate and glacier fluctuations during the last interglacial glacial cycle in fennoscandia seem to correspond roughly in time with the climate fluctuations recorded in france germany holland however the climate in fennoscandia was considerably colder and the coldest phases are recorded as periods with glacier fluctuations admittedly the exact age and amplitudes of some fluctuations are still much debated

the last interglacial glacial cycle mis 5 2 re examined based on long proxy records from central and northern europe abstract current multi proxy studies on a long sediment sequence preserved at sokli n finland i e in the central area of fennoscandian glaciations are drastically changing classic ideas of glaciations vegetation and climate in northern europe during the late pleistocene the sediments in the sokli basin have escaped major glacial erosion due to non typical bedrock conditions in this review the sokli record is compared in great detail with other long proxy records from central temperate and northern boreal europe these comprise the classic records of la grande pile e france and oerel n germany and more recently obtained records from horoszki duze e poland and lake yamozero nw russia the focus of the review is on pollen lithology and macrofossil and insect based temperature inferences the long records are further compared with recent proxy data from nearby terrestrial sites as well as with the rapidly accumulating high resolution proxy data from the ocean realm the comparison allows a re examination of the environmental history and climate evolution of the last interglacial glacial li g cycle mis 5 2 it shows that environmental and climate conditions during mis 5 ca 130 70 ka bp were distinctly different from those during mis 4 2 ca 70 15 ka bp mis 5 is characterized by three long forested intervals broadly corresponding to mis 5e 5c 5a both in temperate and northern boreal europe these mild periods were interrupted by two short relatively cold and dry intervals mis 5d and 5b with mountain centered glaciation in fennoscandia millennial scale climate events were superimposed upon these longer lasting climate fluctuations the time interval encompassing mis 4 2 shows open vegetation it is characterized by two glacial maxima mis 4 and 2 with sub continental scale glaciation over northern europe and dry conditions in strongly continental eastern european settings high amplitude climate oscillations of millennial duration characterized the climate variability of mis 3 mild climate conditions in early mis 3 caused large scale deglaciation of the fennoscandian ice sheet and ice free conditions with betula dominated vegetation including tree birch persisted over large parts of fennoscandia possibly interrupted by glaciation during major part of mis 3 till ca 35 ka bp overall mis 5 was mostly mild with warmest or peak interglacial conditions at the very start during mis 5e mis 4 2 was mostly cold with most extreme or peak glacial conditions in the closing phase during mis 2 this points to a subdivision of the last climate cycle into an early overall mild interglacial half and a late overall cold glacial half each with duration of ca 50 ka this review also shows that the climate variability in central and northern europe during the li g cycle was mostly in degrees of continentality with major shifts in winter temperature and precipitation values summer temperatures on the other hand remained largely unchanged it points to the waxing and waning of sea ice over the north atlantic ocean as a possible characteristic feature of the late pleistocene the present compilation based on long terrestrial sequences high resolution multi proxy data from the oceans and quantified paleo climate data strongly favors a definition of entire marine oxygen isotope stage 5 as the last interglacial similar as in the original marine stratigraphy and the stratigraphy at la grande pile in france the proxy based climate data places the start of the last glacial at the base of mis 4 and the northwest european pleniglacial it shows that the division between the eemian mis 5e and the early weichselian mis 5d a is not useful as not relevant from a climate point of view

vegetation pattern and sedimentation changes in the context of the lateglacial climatic events case study of staroje lake eastern belarus abstract a lake sediment core collected from the staroje lake southeastern belarus reveals significant changes of the terrestrial and limnic environmental during the lateglacial and early holocene in the periglacial zone of the late weichselian glaciation the combination of lithological loss on ignition palaeobotanical pollen non pollen palynomorphs diatoms and isotopic 18o 13c 14c proxy parameters was applied for the reconstruction of the vegetation pattern and sedimentation regime the lateglacial pre interstadial gs 2 vegetation was dominated by mineral soil pioneers with scattered occurrence of pinus and betula an interstadial gi 1 dominated by pinus forest with increasing representation of open ground species since approximately 13 500 cal bp and lateglacial stadial gs 1 with recurring opening of the vegetation pattern with scattered tree patches including those of picea presence of pinus stomata confirms the local origin of this plant since the pre interstadial starting from the holocene birch later accompanied by other deciduous species ulmus alnus quercus corylus took over in the local vegetation structure isotopic records 18o 13c obtained on bulk carbonates as well as diatom data exhibit several shifts reflecting variations both in terrestrial and limnic environment distinct negative excursion of 18o curve recorded during the first half of the gi 1 event suggests intensive groundwater discharge accompanied by active transportation of detrital carbon in to the basin limited basin productivity is also indicated by lithological and diatom records since approximately 13 700 cal bp sedimentation regime in the lake stabilised and productivity of the basin started to increase in positive correlation with loi data a considerable decrease in 18o values punctuated by a rapid jump in the middle of the interval was recorded during the gs 1 stadial and could be associated with the deterioration of the environmental regime and degradation of the soil layer increasing erosion activity alongside the rising input of detrital carbonates into the basin the water table was low as indicated by diatom data recovery of the environmental regime preceded the gs 1 holocene boundary as is seen in lithostratigraphical and isotopic data during the early holocene stable isotopes show several episodes with altered levels suggesting instability of the environmental regime most probably related with the global climatic alterations

tropical upper tropospheric potential vorticity intrusions during sudden stratospheric warmings abstractthe intrusion of lower stratospheric extratropical potential vorticity into the tropical upper troposphere in the weeks surrounding the occurrence of sudden stratospheric warmings ssws is examined the analysis reveals that ssw related pv intrusions are significantly stronger penetrate more deeply into the tropics and exhibit distinct geographic distributions compared to their climatological counterparts while climatological upper tropospheric and lower stratospheric utls pv intrusions are generally attributed to synoptic scale rossby wave breaking it is found that ssw related pv intrusions are governed by planetary scale wave disturbances that deform the extratropical meridional pv gradient maximum equatorward as these deformations unfold planetary scale wave breaking along the edge of the polar vortex extends deeply into the subtropical and tropical utls in addition the material pv deformations also reorganize the geographic structure of the utls waveguide which alters where synopti

recognition of a santonian submarine canyon great valley group sacramento basin california implications for petroleum exploration and sequence stratigraphy of deep marine strata seismic stratigraphic and outcrop interpretation of santonian campanian portions of the great valley group in the north central sacramento basin california reveal the presence of a large north south oriented submarine canyon named after an overlying town williams canyon appears to have been cut during the middle santonian and filled during the late santonian and early campanian approximately 85 80 ma this fossil canyon is more than 100 km in length ranges from 12 to 22 km in width and contains compacted sedimentary fill with a maximum thickness of 1 5 km over its mapped extent williams canyon is comparable in scale to the paleogene gorges of the sacramento basin stratigraphic relations indicate active folding locally during the turonian santonian and probable structural control on the location of the canyon regional correlations showing uplift and regression along the northern basin margin synchronous with transgression of the eastern basin margin during canyon incision suggest that tectonic tilting of the basin initiated cutting of williams canyon whereas the role of eustatic sea level change appears to have been negligible delineation of williams canyon clarifies geometries of outcropping and subsurface strata because some of the canyon fill previously has been correlated to older strata and canyon boundaries locally have been misinterpreted as faults over most of its areal extent the sequence boundary associated with canyon incision is characterized by facies associations that do not conform to widely cited sequence stratigraphic models of deep marine deposits suggesting that such models are oversimplified combination trapping geometries created by williams canyon cut and fill represent an untested gas exploration play

temperature patterns over the past eight centuries in northern fennoscandia inferred from sedimentary diatoms establishing natural climate variability becomes particularly important in remote polar regions especially when considering questions regarding higher than average warming we present a high resolution record of temperature variability for the past 800 yr based on sedimentary diatoms from a treeline lake in finnish lapland the bsizer multiscale smoothing technique is applied to the data to identify significant features in the record at different temporal levels the overall reconstruction shows relatively large multi centennial temperature variability with a total range of about 0 6 0 8 c at millennial scales the temperatures exhibit a statistically significant long term cooling trend prior to industrialization t 0 03 c century at the centennial timescale three warm time intervals were identified around ad 1200 1300 terminal phase of the medieval warm period mwp 1380 1550 and from 1920 until the present pronounced coolness occurred between ad 1600 and 1920 indicative of the little ice age lia at the decadal level certain shorter term climate excursions were revealed the warmest 10 30 yr nonoverlapping periods occurred in ad 1220 1250 1470 1500 and 1970 2000 respectively the classic events of mwp and lia are evident in our record as is also the 20th century warming

the role of gravitational potential energy in active deformation in the southwestern united states in orogenic belts intrinsic buoyancy and extrinsic boundary forces act on the continental lithosphere determining the relative importance of these forces is fundamental to understanding the dynamics of continental deformation in the western united states estimates of gravitational potential energy show that given available constraints on rheology buoyancy forces are sufficient to produce the wide variety of rates and styles of observed deformation including absence of deformation this underscores the importance of gravitational potential energy for deformation in orogenic belts

drumlinised glaciofluvial and glaciolacustrine sediments on the smaland peneplain south sweden new information on the growth and decay history of the fennoscandian ice sheets during mis 3 abstract dug trenches in sediment cored drumlins on the smaland peneplain southern sweden occurring intermixed with rock cored drumlins revealed sedimentary successions and facies suggesting that the core sediments were primarily deposited proglacially both in glaciolacustrine settings as delta front and more distal deeper water sediments and as glaciofluvial braidplain sediments from the relationship between the drumlin sorted sediment cores and their surficial drape by a till carapace it is concluded that erosion was the main drumlin forming process here reshaping the original sediment morphology into streamlined landforms after which a more or less thick traction till was deposited over the eroded and or deformed ice bed interface drumlin formation probably took place during the last deglaciation over the area the drumlin core sediments in 14 excavated trenches were dated by optically stimulated luminescence osl most retrieved ages fall into two distinct groups both within marine isotope stage 3 c 60 30 ka when plotted as mean osl ages for each site all but two sites fall either into an older age group c 48 56 ka seven sites or into a younger age group c 28 38 ka five sites these age intervals correlate well with the suggested time spans for the ristinge and klintholm ice advances in denmark by ice flowing from the baltic basin westwards terminating in fan shaped patterns these interstadial ice advances in the southwestern sector of the fennoscandian ice sheet give rise to enigmatic questions on the physics and mechanics of ice sheet build up and decay especially as palaeoenvironmental data for northern fennoscandia suggest widespread ice free conditions within roughly the same time fame as the recorded ice advances in the south

pollen based palaeoclimate reconstructions over long glacial interglacial timescales methodological tests based on the holocene and mis 5d c deposits at sokli northern finland palaeoclimatic reconstructions over long glacial interglacial timescales present major methodological challenges as calibration methods based on modern climate and vegetation patterns may yield biased reconstructions from non analogue palaeoclimates such as severely continental glacial periods in this work we present pollen based summer temperature reconstructions based on holocene and early weichselian marine isotope stages mis 5d c deposits at sokli northern finland we attempt to improve the robustness of reconstructions of continental palaeoclimates by using two calibration sets with one located in the region surrounding the fossil site and another in a more continental region in northwestern russia we assess the reliability of the reconstructions by estimating the compositional fit between fossil and calibration samples and by comparison with independent plant macrofossil based reconstructions we find the fossil samples to fit the extra regional high continentality calibration set better during the early holocene and mis 5d c especially in mis 5d c however even the high continentality calibration set fits the fossil samples poorly compared to the fit achieved in the mid and late holocene thus our results highlight the problem of finding applicable calibration data for pre holocene periods we finally discuss the relative strengths and vulnerabilities of different calibration methods in reconstruction of non analogue palaeoclimates copyright 2013 john wiley sons ltd

radioisotopic and biostratigraphic age relations in the coast range ophiolite northern california implications for the tectonic evolution of the western cordillera the coast range ophiolite cro in northern california includes two distinct remnants the elder creek ophiolite is a classic suprasubduction zone ophiolite with three sequential plutonic suites layered gabbro wehrlite pyroxenite quartz diorite a mafi c to felsic dike complex and mafi c felsic volcanic rocks the entire suite is cut by late mid oceanic ridge basalt morb dikes and overlain by ophiolitic breccia the stonyford volcanic complex sfvc comprises three volcanic series with intercalated chert horizons that form a submarine volcano enclosed in sheared serpentinite structurally below this seamount are melange blocks of cro similar to elder creek u pb zircon ages from plagiogranite and quartz diorites at elder creek range in age from 165 ma to 172 ma u pb zircon ages obtained from cro melange blocks below the sfvc are similar 166 172 ma 40 ar 39 ar ages of alkali basalt glass in the upper sfvc are all younger at 164 ma radiolarians extracted from chert lenses intercalated with basalt in the sfvc indicate that the sedimentary strata range in age from bathonian unitary association zone 6 6 of baumgartner et al 1995a near the base of the complex to late callovian to early kimmeridgian unitary association zones 8 10 in the upper part the sfvc sedimentary record preserves evidence of a major faunal change wherein relatively small sized polytaxic radiolarian faunas were replaced by very robust oligotaxic nassellarian dominated faunas that included praeparvicingula spp we suggest that cro formation began after the early middle jurassic 172 180 ma collision of an exotic or fringing arc with north america and initiation of a new or reconfi gured east dipping subduction zone the data show that the cro formed prior to the late jurassic nevadan orogeny probably by rapid forearc extension above a nascent subduction zone we infer that cro spreading ended with the collision of an oceanic spreading center ca 164 ma coincident with the oldest high grade blocks in the structurally underlying franciscan assemblage we further suggest that the classic nevadan orogeny represents a response to spreading center collision with shallow subduction of young lithosphere causing the initial compressional deformation and with a subsequent change in north american plate motion to rapid northward drift j2 cusp causing sinistral transpression and transtension in the sierra foothills these data are not consistent with models for late jurassic arc collision in the sierra foothills or a back arc origin for the cro

nonlinear relation of the arctic oscillation with the quasi biennial oscillation a nonlinear principal component analysis nlpca is applied to a set of monthly mean time series from january 1956 to december 2007 consisting of the arctic oscillation ao index derived from 1 000 hpa geopotential height anomalies poleward of 20 n latitude and the zonal winds observed at seven pressure levels between 10 and 70 hpa in the equatorial stratosphere to investigate the relation of the ao with the quasi biennial oscillation qbo the nlpca is conducted using a new compact neural network model the nlpca modeling of the dataset of the ao index and qbo winds offers a clear picture of the relation between the two oscillations in particular the phase of covariation of the oscillations defined by the two nonlinear principal components of the dataset progresses with a predominant 28 4 month periodicity this predominant cycle is modulated by an 11 year cycle the variation of the ao index with the qbo phase also shows that the average ao index is positive when the westerly qbo phase descends past 30 hpa and conversely the average ao index is negative when the easterly qbo phase descends past 30 hpa this relationship is evident during the boreal cold season from november to april but non existent during the boreal warm season from may to october

a multi proxy study of holocene lake development lake settlement and vegetation history in central ireland stratigraphical investigations geomorphological mapping and diatom plant macrofossil and pollen analyses were undertaken in and around two lakes in central ireland to establish correlations between changes in lake conditions and catchment vegetation throughout the holocene similar investigations of an adjacent mire reveal early holocene changes in lake level and area the palaeoecological data show high correlations related to variations in lake depth and area catchment vegetation type organic inputs and trophic status catchment scale deforestation is gradual and occurs through the bronze and the iron ages and the construction of a crannog in the early medieval period seventh century ad appears to be associated with a widespread increase in deforestation and mixed agriculture in the catchment both pollen and plant macrofossils suggest that one of the crannogs was used for crop storage in addition to domestic and any other activities in the early to middle holocene similarities in the proxy data appear to be climatically driven through changing lake levels and areal extent whereas the later holocene record is clearly dominated by anthropogenic changes within the catchment and the construction of crannogs in the lakes the advantages of combining multi proxy indicators of lake hydroecology with the vegetation record are illustrated

model studies of the interannual variability of the northern hemisphere stratospheric winter circulation the role of the quasi biennial oscillation a series of experiments are described that examine the sensitivity of the northern hemisphere winter evolution to the equatorial quasi biennial oscillation qbo the prime tool for the experiments is a stratosphere mesosphere model the model is integrated over many years with the modelled equatorial winds relaxed towards observed values in order to simulate a realistic qbo in experiment a the equatorial winds are relaxed towards singapore radiosonde observations in the height region 16 32 km in contrast to previous modelling studies the holton tan relationship warm cold winters associated with easterly westerly qbo winds in the lower stratosphere is absent however in a second experiment run b in which the equatorial winds are relaxed towards rocketsonde data over the extended height range 16 58 km a realistic holton tan relationship is reproduced a series of further studies are described that explore in more detail the sensitivity to various equatorial height regions and to the bottom boundary forcing the experiments suggest that the evolution of the northern hemisphere winter circulation is sensitive to equatorial winds throughout the whole depth of the stratosphere and not just to the lower stratospheric wind direction as previously assumed

fennoscandian palaeoglaciology reconstructed using a glacial geological inversion model the evolution of ice sheet configuration and flow pattern in fennoscandia through the last glacial cycle was reconstructed using a glacial geological inversion model i e a theoretical model that formalises the procedure of using the landform record to reconstruct ice sheets the model uses mapped flow traces and deglacial melt water landforms as well as relative chronologies derived from cross cutting striae and till lineations as input data flow trace systems were classified into four types i time transgressive wet bed deglacial fans ii time transgressive frozen bed deglacial fans iii surge fans and iv synchronous non deglacial event fans using relative chronologies and aggregation of fans into glaciologically plausible patterns a series of ice sheet configurations at different time slices was erected a chronology was constructed through correlation with dated stratigraphical records and proxy data reflecting global ice volume geological evidence exists for several discrete ice sheet configurations centred over the scandinavian mountain range during the early weichselian the build up of the main weichselian fennoscandian ice sheet started at approximately 70 ka and our results indicate that it was characterised by an ice sheet with a centre of mass located over southern norway this configuration had a flow pattern which is poorly reproduced by current numerical models of the fennoscandian ice sheet at the last glacial maximum the main ice divide was located overthe gulf of bothnia a major bend in the ice divide was caused by outflow of ice to the northwest over the lowest part of the scandinavian mountain chain widespread areas of preserved pre late weichselian landscapes indicate that the ice sheet had a frozen bed core area which was only partly diminished in size by inward transgressive wet bed zones during the decay phase

a compilation of western european terrestrial records 60 8 ka bp towards an understanding of latitudinal climatic gradients terrestrial records of past climatic conditions such as lake sediments and speleothems provide data of great importance for understanding environmental changes however unlike marine and ice core records terrestrial palaeodata are often not available in databases or in a format that is easily accessible to the non specialist as a consequence many excellent terrestrial records are unknown to the broader palaeoclimate community and are not included in compilations comparisons or modelling exercises here we present a compilation of western european terrestrial palaeo records covering entirely or partially the 60 8 ka intimate time period the compilation contains 56 natural archives including lake records speleothems ice cores and terrestrial proxies in marine records the compilation is limited to include records of high temporal resolution and or records that provide climate proxies or quantitative reconstructions of environmental parameters such as temperature or precipitation and that are of relevance and interest to a broader community we briefly review the different types of terrestrial archives their respective proxies their interpretation and their application for palaeoclimatic reconstructions we also discuss the importance of independent chronologies and the issue of record synchronization the aim of this exercise is to provide the wider palaeo community with a consistent compilation of high quality terrestrial records to facilitate model data comparisons and to identify key areas of interest for future investigations we use the compilation to investigate western european latitudinal climate gradients during the deglacial period and despite of poorly constrained chronologies for the older records we summarize the main results obtained from nw and sw european terrestrial records before the lgm

quasi biennial modulation of the southern hemisphere stratospheric polar vortex observations reveal that the wintertime southern hemisphere stratospheric polar vortex is modulated by the phase of the equatorial quasi biennial oscillation qbo the high latitude southern stratosphere is shown to be slightly colder throughout the winter and the final warming occurs later when the qbo is in its west phase during may october the modulation of winds by the qbo is confined to midlatitudes at the edge of the polar vortex the difference between west and east phase composites of zonal mean wind during november at the time of the final warming in the southern hemisphere exceeded 14 ms 1 this difference is very similar to that in january in the northern hemisphere while northern hemisphere qbo effects are optimized using equatorial winds near 40 hpa southern hemisphere effects are best seen using 25 hpa winds

development of an eemian mis 5e interglacial palaeolake at sokli n finland inferred using multiple proxies a 12 m long lacustrine record from sokli n finland was analyzed for diatoms non pollen palynomorphs macrofossils pollen and geochemistry in order to reconstruct the development of a high latit

early cretaceous transition from nonaccretionary behavior to strongly accretionary behavior within the franciscan subduction complex 1 during subduction at the franciscan trench beginning at 170 160 ma and continuing to the present marine sedimentary and lesser volcanic rocks have been underthrust accreted and metamorphosed to form the franciscan accretionary wedge the south fork mountain schist sfms forms the eastern margin and structural top of the wedge and so was apparently the first unit of substantial size to accrete into the franciscan new u pb ages of detrital zircons and 40ar 39ar ages of metamorphic white micas indicate that the sfms accreted surprisingly late in the time span of franciscan subduction probably at ca 123 ma at least parts of the valentine spring formation and yolla bolly terrane accreted soon thereafter therefore accretion of the sfms apparently marks a fundamental transition from virtually nonaccretionary behavior to strongly accretionary behavior in the franciscan forearc about 75 of modern forearcs are nonaccretionary so recognition of an early nonaccretionary period is consistent with modern examples the franciscan mafic high grade exotic blocks and related very small slabs which yield ca 132 to 169 ma metamorphic ages are the only well documented rock record of the early 40 m y long nonaccretionary period and represent very sparse accretion during that interval the transition into an accretionary regime at ca 123 ma was essentially synchronous with the end of the late jurassic early cretaceous magmatic lull in the sierra nevada magmatic arc with the waning of early cretaceous faulting and warping within the great valley forearc basin and possibly with changes in motion vectors of the pacific and farallon plates

the arctic oscillation signature in the wintertime geopotential height and temperature fields the leading empirical orthogonal function of the wintertime sea level pressure field is more strongly coupled to surface air temperature fluctuations over the eurasian continent than the north atlantic oscillation nao it resembles the nao in many respects but its primary center of action covers more of the arctic giving it a more zonally symmetric appearance coupled to strong fluctuations at the 50 hpa level on the intraseasonal interannual and interdecadal time scales this arctic oscillation ao can be interpreted as the surface signature of modulations in the strength of the polar vortex aloft it is proposed that the zonally asymmetric surface air temperature and mid tropospheric circulation anomalies observed in association with the ao may be secondary baroclinic features induced by the land sea contrasts the same modal structure is mirrored in the pronounced trends in winter and springtime surface air temperature sea level pressure and 50 hpa height over the past 30 years parts of eurasia have warmed by as much as several k sea level pressure over parts of the arctic has fallen by 4 hpa and the core of the lower stratospheric polar vortex has cooled by several k these trends can be interpreted as the development of a systematic bias in one of the atmosphere s dominant naturally occurring modes of variability

large shifts in vegetation and climate during the early weichselian mis 5d c inferred from multi proxy evidence at sokli northern finland abstract for decades detailed studies on early weichselian deposits have been made in central europe in contrast these studies are rare in fennoscandia in northern europe we here integrate an extensive multi proxy data set obtained on sediments of mis 5d c age that form part of a long sediment record preserved at sokli in northern finland we make a detailed interpretation of the vegetation and depositional history for mis 5d c using pollen macrofossils diatoms and other siliceous microfossils insect remains and sediment characteristics and combine these data with recently published estimates on july temperatures based on chironomids and selected plant indicator species in order to make inferences of paleo climate regimes the fossil record obtained on the seven meter thick mis 5d c deposit at sokli is exceptionally rich in species due to the large variety of habitats associated with an overall fluvial depositional environment a braided river system flanked by steppe tundra vegetation is inferred for mis 5d mean july temperatures of at least 12 14 c are indicated by chironomids and plant indicator species and are in agreement with the presence of conifers and birch trees as recorded by macrofossils the reconstructed environmental conditions suggest strong continental climate conditions at sokli during mis 5d the gradual infilling of an oxbow lake and subsequent return to stream channel deposition is traced in great detail in the overlying gyttja and gravelly sediment of mis 5c age the terrestrial pollen and plant macrofossil record from the gyttja shows the establishment of birch forest followed by the spread of pine and then spruce rich plant indicator species assemblages indicate that the boreal environment at sokli during mis 5c experienced july temperatures several degrees higher than the present day value of 13 c the high summer temperatures and presence of larch suggest more continental conditions more open vegetation returned at sokli during late mis 5c and was followed by glaciation by the fennoscandian ice sheet mis 5b despite the major differences in zonal vegetation types during mis 5d c differences in reconstructed july temperatures are minor and suggest that winter temperatures combined with precipitation values mostly determined the stadial interstadial climate variability the most compelling conclusion from our study is that forest development during mis 5c was remarkably similar to that recorded for the eemian mis 5e and holocene interglacials at the high latitude site sokli and also to that inferred from mis 5c sediments on the northern european mainland our results question the definition of mis 5c in the terrestrial record of europe as an interstadial interval of the last glacial cycle and suggest inclusion of mis 5c together with the eemian mis 5e in an interglacial complex

new radiocarbon dates from finnish mammoths indicating large ice free areas in fennoscandia during the middle weichselian new radiocarbon dates from finnish subfossil mammoth material mammuthus sp transported by glacial ice range in age from ca 32000 to ca 22500 yr bp these results suggest that there was a larger ice free area in fennoscandia during the middle weichselian than previously assumed in addition two dates are also presented for bones found in clay with a different transport history copyright 1999 john wiley sons ltd

cenozoic microfossils in northern finland local reworking or distant wind transport abstract allochthonous cenozoic microfossils have been reported from late pleistocene lake and mire host sediments across an area of 30 000 km2 in northern finland two main groups of microfossils are recognised palaeogene marine diatoms silicoflagellates and ebridians that include taxa from around the time of the palaeocene eocene thermal maximum and pliocene to early pleistocene freshwater diatoms the presence of these microfossils has been regarded as evidence that eocene marine and late neogene freshwater sediments formerly existed on the shield surface both groups have been referred to frequently in reconstructions of the sea level tectonic and erosion history of the northern fennoscandian shield the questions raised by the presence of allochthonous cenozoic microfossils in northern finland are however strongly resonant of the debate over the biota origin and age of the pliocene sirius group in antarctica where competing hypotheses have been put forward of local deposition and reworking versus distant wind transport of marine diatoms from the continental shelf this review explores alternative origins for the allochthonous cenozoic microfossils in northern finland local reworking of palaeogene marine sediments during pleistocene glaciation is unlikely as no source rocks of palaeogene age are known from the shield surface or from surrounding sedimentary basins in the baltic and white sea moreover at all sites except akanvaara the marine diatom taxa cover wide age ranges and occur only as minor components in diatom assemblages that are dominated by quaternary freshwater taxa local reworking of pliocene pleistocene freshwater diatoms is however compatible with the widespread survival of pre pleistocene deep weathering although no in situ or unmixed ice rafted pliocene pleistocene lacustrine sediment has yet been found an alternative origin for the marine palaeogene microfossils by distant wind transport is proposed in this hypothesis palaeogene diatomites on the barents sea shelf were exposed to deep glacial and fluvioglacial erosion during the pliocene and early pleistocene and in low sea level stages of the middle and late pleistocene intense wind action acting on comminuted mudstones on outwash plains carried dust including microfossils into northern fennoscandia to be deposited by rain out in lakes and wetlands this material may have been later further recycled by glacial and meltwater transport and more localised wind action processes that also may help to account for the distribution of eemian marine diatoms well beyond eemian shorelines the distant wind transport hypothesis implies that the presence of marine palaeogene diatoms on the shield surface in northern finland cannot be regarded as vestiges of former marine sediments and so do not constrain the tectonic and geomorphic history of the northern fennoscandian shield in the cenozoic

early holocene glacial lakes and ice marginal retreat pattern in labrador ungava canada abstract the existence of glacial lakes naskaupi mclean minto melezes and wapussakatoo during the deglaciation of labrador ungava canada was recognized at the end of 1950s however glacial lakes have seldom been included in regional reconstructions to constrain the outline of successive ice margins during the glacial retreat in labrador ungava reconstruction of the ice flow succession in labrador ungava has often primarily focused on till lineation systems these reconstructions often depict a late glacial ice dispersal center situated over central labrador ungava more recent studies on glacial geomorphology including meltwater features however suggest that north central labrador ungava exhibited cold based conditions at least during the latest deglaciation cold based conditions inhibit basal sliding and formation of landforms except for meltwater traces such as meltwater channels glacial lake shorelines and deltas this situation implies that meltwater traces are the main source of information when reconstructing the spatial retreat pattern during a cold based deglaciation evidence presented in this study such as glacial lake shorelines fossil deltas and spillway and drainage channels in north central labrador ungava indicates the existence of numerous previously unmapped glacial lakes the mapped glacial lake features are synthesized to a reconstruction of several glacial lake stages which in turn are used to constrain the late glacial ice margin retreat pattern over the inferred cold based areas of north central labrador ungava a total of 26 glacial lakes 65 sub stages existed during the deglaciation of labrador ungava these lakes were impounded along the southern margin of the shrinking ice sheet the required damming ice margins indicate that the last ice remnant of the laurentide ice sheet in labrador ungava was situated over the southern ungava bay and the adjacent southern shore

sensitivity of the boreal winter circulation in the middle atmosphere to the quasi biennial oscillation in maecham5 simulations the polar vortex in the northern hemisphere exhibits high intraseasonal and interannual variability which to some degree may be controlled by the quasi biennial oscillation qbo in the tropical stratosphere here we analyze the qbo signal in the northern hemisphere polar vortex in a model simulation using the general circulation model maecham5 middle atmosphere european center hamburg model which simulates the qbo as an internal mode of variability composites have been computed for the westerly and easterly qbo phases from early winter to late winter november december december january and january february of a 50 year experiment containing 20 complete qbo cycles this method identifies tropical and midlatitude patterns in wind and temperature that are related to the secondary meridional circulation of the qbo extending towards the winter pole in the tropics significant qbo signature is observed in the mesosphere up to 0 05 hpa only in early winter and mainly in the easterly qbo phase forced by the parameterized gravity waves mean flow interaction at high latitudes maecham5 shows a significantly warmer colder polar stratosphere in the easterly westerly qbo phase at 30 hpa accompanied by a weaker stronger polar vortex in the late winter months from december to february december to january in the easterly westerly phase of the qbo in early winter there is no significant change in temperature and zonal mean zonal wind in the polar stratosphere the analysis of ep fluxes shows a different behavior between qbo phases with changes in the waveguide wave propagation occurs upwards and polewards in the easterly qbo phase at 30 hpa while waves are refracted equatorward in the westerly phase no relationship has been found between the tropical qbo and the final warming at the end of the boreal winter

the early and middle weichselian interstadials in the central area of the scandinavian glaciations abstract in the central parts of the scandinavian glaciations in norway sweden and finland there are a number of early weichselian sites with fresh water sediments which by comparison with sites further south can be correlated with either the brorup or odderade interstadials few of these sites can with any certainty be correlated with just one of the two in northern jutland and at thecoast of south western norway there are early weichselian marine sediments some of those in norway having been interpreted as interstadial middle weichselian fresh water sediments have only been found in denmark and southern sweden whereas marine sediments occur in northern jutland and at the coast in norway in the same areas as the early weichselian marine sediments most of the middle weichselian sites must be referred to as representing an interstadial complex as a close correlation with the five interstadials identified in northwest germany and the netherlands is not possible a close correlation has been made between the fluctuations in the deep sea oxygen isotope curve and the weichselian history in scandinavia the justification for which is discussed