a jokulhlaup near sondre stromfjord west greenland and some effects on the ice sheet margin description de la vidange d un lac marginal par un tunnel sous glaciaire les 19 et 20 aout 1984

ammonite and inoceramid bivalve extinction patterns in cretaceous tertiary boundary sections of the biscay region southwestern france northern spain cretaceous tertiary boundary sections located in the biscay region of southwestern france and northern spain are among the most complete of all known land based sequences across this boundary new collections of ammonites and inoceramid bivalves from five localities show quite distinct extinction patterns for these two groups of characteristic cretaceous molluscs from eight to ten ammonite species extend into the latest cretaceous and possibly to the boundary in contrast inoceramid bivalve diversity gradually diminished from a minimum of six species in the early maastrichtian to zero at the beginning of the late maastrichtian when they were replaced by the cryptic pteriomorph tenuipteria extinction of typical inoceramids well before the end of the maastrichtian is supported by data from other regions indicating that it was a global rather than local phenomenon

theoretical contemporary observational and palaeo perspectives on ice sheet hydrology processes and products publisher elsevier articletitle theoretical contemporary observational and palaeo perspectives on ice sheet hydrology processes and products journaltitle earth science reviews articlelink http dx doi org 10 1016 j earscirev 2016 01 010 content type article copyright copyright 2016 elsevier b v all rights reserved

astronomical duration of polarity chron c31r lower maastrichtian cyclostratigraphy of odp site 762 indian ocean and the contessa highway section gubbio italy the duration of polarity chron c31r is estimated with a cyclostratigraphic approach two sites are investigated odp site 762 indian ocean and the contessa highway section gubbio italy cyclostratigraphic analysis is performed on greyscale variations site 762 and magnetic susceptibility variations contessa section both sites reveal an astronomical control of the sedimentation highlighted by the identification of all the orbital periodicities cyclostratigraphic signals are tuned on 405 ka eccentricity cycles extracted from the la04 astronomical solution in both sites cycle counting gives an estimate of the duration of polarity chron c31r of about 2 09 0 03 ma

on the clague mathews relation for jokulhlaups in the empirical study of jokulhlaups the peak discharge q max and water volume drained by the ice dammed lake during the floods v t appear to follow a power law relation q max kv t b where k are b are constants determined from field data first identified by clague and mathews 1973 this relation is a useful reference for predicting flood magnitude but its physical origin remains unclear here we develop the theory that connects it to contemporary models for simulating the flood hydrograph we explain how the function q max f v t arises from nye s 1976 theory of time dependent water flow in a subglacial channel coupled to a lake and we describe how discharger volume data record the monotonically increasing form of this function so long as the lake is not emptied in the floods the grimsvotn jokulhlaups present an example where because of partial draining of the lake agreement between the model derived f and data is excellent it is documented that other lake systems drain completely but we explain how the exponent b 2 3 observed for them collectively is due primarily to a scaling effect related to their size modified by other factors such as the flood initiation process

proglacial lakes character behaviour and geological importance proglacial lakes are ubiquitous within the quaternary record and can provide exceptional breadth and depth of palaeoenvironmental information present deglaciation is increasing the number and size of proglacial lakes around the world this study provides a synthesis of knowledge on proglacial lake character and behaviour and critically evaluates the importance of proglacial lakes from a geological perspective we show how ice marginal or ice contact lakes and other distal proglacial lakes can be distinguished from each other by geomorphological sedimentological chemical and biological characteristics the key controls on proglacial lake geomorphology and sedimentology are outlined and discussed proglacial lakes can exacerbate mountain glacier and ice sheet margin ablation via mechanical and thermal stresses but very large lakes can moderate summer air temperatures and relatively retard summer ice ablation proglacial lakes interrupt meltwater flux and are very efficient sediment traps hydrological routing and consequent geomorphological activity can be radically modified by sudden drainage of proglacial lakes and resultant glacial lake outburst floods exceptionally large proglacial lake drainages affected global ocean circulation and global climate during the quaternary overall analyses of proglacial lakes can provide a valuable insight into i patterns character and behaviour of mountain glaciers ice sheets and glaciations and ii the impacts of past present and future deglaciation

jokulhlaup initiation by ice dam flotation the significance of glacier debris content ice dam flotation is a commonly described mechanism for the initiation of jokulhlaups catastrophic floods from ice dammed lakes but predictions of the critical lake depth required for flotation often differ from the actual lake depth at which flotation occurs glacier debris content is identified as an insufficiently recognized variable in ice dam flotation it is demonstrated that high debris contents could suppress flotation and thereby affect the timing mechanism and magnitude of catastrophic lake drainage events the density of the part of the glacier forming the ice dam rather than pure ice density is the key to predicting ice dam flotation

reorganization of deep ocean circulation accompanying a late cretaceous extinction event deep ocean circulation may be a significant factor in determining global climate1 5 increases in the flux of warm saline waters from low to high latitudes would enhance the poleward transport of heat and thus help maintain the warm conditions at high latitudes typical of globally warm greenhouse periods but controversy exists1 2 as to whether the ocean s thermohaline circulation can transport enough heat to bring about the temperature distributions of these times such as the mid cretaceous and early eocene here we present stable isotope records of ocean temperature and salinity that indicate that bottom waters in late cretaceous oceans of the southern hemisphere became cooler and less saline at the same time about 70 myr ago as widespread biotic changes3 6 8 these findings support the idea that changes in deep ocean circulation can act as a climate switch

oxygen and carbon isotope stratigraphy of the palaeogene and cretaceous limestones in the bottaccione gorge and the contessa highway sections umbria italy we have made oxygen and carbon isotope measurements on limestone samples of albian to eocene age recovered from the bottaccione gorge section in the umbrian apennines central italy additional measurements have been made on topmost maastrichtian and palaeocene sediments from the adjacent contessa highway section our data from the bottaccione gorge show 13c maxima at the cenomanian turonian boundary and during the palaeocene as well as a pronounced 13c minimum 7 metres above the clay layer at the k t boundary our data from the contessa highway show a 13c minimum 9 metres above the k t boundary clay these minima are probably diagenetic artifacts in the bottaccione gorge there is evidence for a hiatus in the early middle eocene the palaeocene of the bottaccione gorge appears to have been affected by slumping or faulting in addition to the diagenetic overprinting giving a spurious 13c recovery after the k t boundary the contessa highway section appears to be more complete the coniacian maastrictian is characterized by relatively stable 13c values our data indicate an increase in 18o and therefore possible cooling across the cretaceous tertiary boundary in both the bottaccione and contessa highway sections

obstacle marks produced by flow around stranded ice blocks during a glacier outburst flood jokulhlaup in west greenland the effects of glacier ice block grounding on the morphology and sedimentology of proglacial fluvial outwash were examined during a glacier outburst flood or jokulhlaup near sondre stromfjord west greenland observations made during and after the 1987 jokulhlaup both on the surface of an ice contact delta and within a confined valley sandur plain provided information about the formation of ice block obstacle marks and the significance of these bedforms for sandur morphology and sedimentology flow directions determined from obstacle mark morphology have been used successfully to chart flow direction changes on the falling limb of the jokulhlaup maximum flow depths for scour around stranded ice blocks may be given by 0 5 0 9 times the diameter of the ice block as estimated from the depth of scour the height of the obstacle shadow or the extent of ice block meltout sediments minimum flow depths can be represented by the height of the obstacle shadow above the mean bed level the internal composition of the shadow indicates the ability of the flow to transport various sizes of material into the lee of obstacles ice block obstacle marks within the distal portion of the sandur initiated waning stage channel change proximal and lateral erosion around stranded ice blocks extended downstream from the ice block forming chute channels which then captured waning stage flows resulting in significant bar incision with associated deposition of lobate or deltaic deposits it is suggested that ice block obstacle marks are important in terms of channel morphology channel morphological change and their usefulness as palaeohydrological indicators

a study of ablation variations on the tongue of hintereisferner austrian alps austria here we discuss the interpretation of detailed ablation measurements on the tongue two profiles are considered one along the glacier axis and one across the glacier tongue at the crossing an energybalance station was operated providing the necessary meteorological data at all stakes the albedo was measured several times with a simple light weight instrument described separately in the appendix the absorption of solar radiation was calculated for all stake positions taking into account local albedo slope aspect and shading effects it appears that the differences in ablation can be explained almost entirely by the differences in surface albedo both along and across the glacier tongue

observed runoff jokulhlaups and suspended sediment load from the greenland ice sheet at kangerlussuaq west greenland 2007 and 2008 this study fills the gap in hydrologic measurements of runoff exiting a part of the greenland ice sheet gris the kangerlussuaq drainage area west greenland the observations are of value for obtaining knowledge about the terrestrial freshwater and sediment output from part of the gris and the strip of land between the gris and the ocean in the context of varying ice sheet surface melt and influx entering the ocean high resolution stage discharge and suspended sediment load show a decrease in runoff of approx 25 and in sediment load of approx 40 from 2007 to 2008 in response to a decrease in the summer accumulated number of positive degree days during the 2007 and 2008 runoff season joekulhlaups are observed at kangerlussuaq drained from an ice dammed lake at the margin of the gris

ice dammed lake drainage in west greenland drainage pattern and implications on ice flow and bedrock motion ice dammed lakes drain frequently in greenland but the impacts of these events differ between sites here we study the quasi cyclic behavior of the 40 km2 lake tininnilik in west greenland and its impact on ice flow and crustal deformation data reveal rapid drainage of 1 83 0 17 km3 of water in less than 7 days in 2010 leading to a speedup of the damming glacier and an instantaneous modeled elastic bedrock uplift of 18 6 0 1 mm confirmed by an independent lake side gps record since ice dammed lakes are common on greenland our results highlight the importance of including other sources of surface loading in addition to ice mass change when assessing glacial isostatic adjustment or elastic rebound using geodetic data moreover the results illustrates a linkage between subglacial discharge and ice surface velocity important for assessing ice flux and thus mass balance in a future warming climate

biostratigraphy and magnetostratigraphy of the cretaceous tertiary sopelana section basque country remarkably thick sequences of upper cretaceous and lower tertiary sediments outcrop on the northern coast of the basque country we have sampled the well exposed section along the sopelana beach over 150 m spanning roughly from middle maastrichtian 71 ma to lower paleocene 66 ma for both biostratigraphic and magnetostratigraphic studies thermal demagnetization of 400 specimens revealed both normal and reversed recent overprints unblocked below 200 c and both normal and reversed characteristic directions at higher temperatures 200 450 c in the grey limestones 350 550 c in the redder marls and limestones thermal and af demagnetization and monitoring of weak field susceptibility are consistent with some form of titano magnetite as the main carrier of magnetization 259 demagnetization diagrams yielded two nearly antipodal clusters of directions which are still polluted by some 20 remaining recent overprint the overall mean direction in stratigraphic coordinates is d 356 i 51 3 consistent with what is expected for eurasia at ktb time magnetic stratigraphy outlines a succession of eight polarity intervals and is rather straightforward except for two highly complex zones 52 to 40 m and 28 to 26 m below the ktb where the magnetic polarity appears to flip at an unreasonable rate biostratigraphic check allows unambiguous assignment of several chrons with the recognition of the gansserina gansseri abathomphalus mayaroensis globigerina eugubina eoglobigerina edita e pseudobulloides and e trinidadensis zones the magnetostratigraphic section therefore begins in chron 31r and ends in 29n further detailed study of the complex zones reveals that specimens there have a distinct magnetic behaviour susceptibility increases beyond 400 c indicating instability and mineralogical change intensities are higher than elsewhere and more scattered and a higher unblocking temperature higher coercivity magnetic component is uncovered this component which is absent from the rest of the section could be an early chemical remagnetization indeed the complex zones contain larger amounts of chlorite a sign of more intense diagenesis we have therefore discarded samples showing this anomalous behaviour and have retained only the 223 samples where demagnetization was achieved by 450 c the thicker lower complex zone reduces to a reversed chron which we propose to correlate with 30r we have identified an extra short reversed event within chron 30n for which independent support is found in dsdp sites 524 and 577a and possibly in gubbio finally the high sedimentation rate section at sopelana 25 m ma in the maastrichtian 7 m ma in the danian displays one of the best resolved on land magnetostratigraphies around ktb time the two complex zones of early remagnetization form an echo which may have been generated some 100 kyr after deposition of the sediments the ktb itself occurs approximately halfway to 3 5 up 29r in terms of time

some comments on climatic reconstructions from ice cores drilled in areas of high melt poor consideration has been given in many arctic circum polar ice core studies to the effect of summer snow melt on chemistry stable isotope concentrations and time scales many of these corps are drilled close to the firn line where melt is intense some come from below the firn line where accumulation is solely in the form of super imposed ice in all cases seasonal signals are reduced or removed and in some time gaps develop during periods of excessive melting which situate the drill site in the ablation zone consequently cross correlations of assumed synchronous events among the cores are invalid so that time scales along the same cores differ between authors by factors of over 2 many so called climatic signals are imaginary rather than real by reference to published analyses of cores from the superimposed ice zone on devon ice cap koerner 1970 and meighen ice cap koerner and paterson 1974 it is shown how melt affects all the normally well established ice core proxies and leads to their misinterpretation despite these limitations the cores can give valuable low resolution records for all or part of the holocene they show that the thermal maximum in the circum polar arctic occurred in the early holocene this maximum effected negative balances on all the ice caps and removed the smaller ones cooler conditions in the second half of the holocene have caused the regrowth of these same ice caps

jokulhlaup ice dammed lake outburst flood impact within a valley confined sandur subject to backwater conditions kangerlussuaq west greenland abstract this paper examines the controls on the morphology and sedimentology of a valley confined proglacial outwash plain or sandur in west greenland subject to glacial outburst floods jokulhlaups jokulhlaup flow conditions observed during a recent 1987 flood are linked to sandur sedimentology and morphological change backwater effects over the distal sandur resulted in a reduction of stream power despite increasing discharge bar units were typically large bar front advance of 60 m during 1987 jokulhlaup occurred prior to waning stage bar dissection by chute channels channel change was confined to the distal sandur due to the greater erodibility of the finer grained bars a temporary zone of sediment storage prevailed at the transition between free flowing and ponded flood waters until flood powers increased during waning flood stage as backwater effects were removed extension of pre existing high relief amplitude bars within the distal sandur records sedimentation related to at least eight jokulhlaups whilst lower relief amplitude proximal sandur sediments provide a composite record of the last high stage jokulhlaup flows backwater conditions during jokulhlaups have increased the rapidity of spatial variation of grain sizes and fluvial facies types complex within event sediment reworking and routing is generated by the onset and break up of backwater effects the role of local topography is therefore crucial when interpreting the sedimentary record of former proglacial channels potentially subject to jokulhlaups this study may prove useful in identifying the presence of flood cycles within palaeo fluvial systems in both formerly glaciated and non glaciated areas

an analysis of eemian climate in western and central europe on the basis of 31 pollen diagrams and additional data for botanical macrofossils an analysis is made of the last interglacial eemian climatic history in western and central europe the main tool for this analysis is the climatic indicator species method only selected woody species are used for the quantification of data partial climatic range diagrams are presented for abies alba acer monspessulanum acer tataricum buxus sempervirens tilia tomentosa the problem of time correlation and pollen zonation of the eemian is discussed the climatic analysis itself is based on an improved version of the indicator species method in this version not every site is analysed for its climatic values instead maps and tables on the migrational history of hedera ilex buxus abies and species of acer tilia and abies are the basis for climatic maps showing respectively january and july isotherms for the periods of the corylus zone e4a and the carpinus zone e5 it is concluded that mean january temperatures were as much as 3 c higher at amsterdam the netherlands than at present and mean temperatures in july were 2 c higher however the thermal maximum in winter was later zone e5 than the summer thermal maximum zone e4a winter temperatures changed parallel to rise and fall of global sea level precipitation changes are more difficult to estimate in the first part of the eemian precipitation must have been relatively low but from zone e4b onward it increased to higher values reaching 800 mm and probably substantially more in zones e5 and e6 hence the eemian climate was in its beginning relatively more contintental and later from e4b onward more oceanic however as compared with the holocene the eemian climate was generally speaking more oceanic

subglacial jokulhlaup deposition jotunheimen norway abstract the aim of this paper is to discuss the origin of a linear boulder deposit near the mjolkedalsbreen jotunheimen norway subglacial fluvial deposition is suggested by palaeoflow indicators showing flow directions uphill along the axis of a ridge like deposit and the close association of this deposit with an ice contact boulder delta peak discharges of repeated jokulhlaups from the former ice dammed ovre mjolkedalsvatn were estimated at 1188 m3 s 1 using evidence derived from the proglacial jokulhlaup routeway former ice tunnel dimensions and flow conditions associated with the ridge like deposit were derived from a simple pipe flow equation flow velocities of 9 8 11 6 m s 1 and shear stresses of 1440 2018 n m2 were reconstructed for a tunnel less than 3 m in average height and 45 m wide such flows would have been capable of transporting boulders of greater than 3 m in diameter as traction load and material of gravel cobble size in suspension material of this size has been deposited downflow as an ice contact delta linear ridges of boulder gravel with up slope gradients found in association with ice contact deposits in other formerly glaciated areas may similarly be of jokulhlaup origin

the holocene sedimentary history of the kangerlussuaq fjord valley fill west greenland abstract west greenland has been intensively studied to reconstruct and better understand past relative sea level changes and deglacial history this study extends these efforts by linking sea level and deglacial history to the sedimentary infill successions of kangerlussuaq fjord and associated landward valleys based on published and new land and sea based geophysical data radiocarbon dates and geological observations we have characterized the infill and reconstructed the sedimentation history during the holocene based on a revised sea level curve and data presented in this paper we defined three depositional phases phase i 7000 yr bp is represented by dominant glaciomarine deposition associated with a tide water glacier system as the greenland ice sheet gis continued to retreat it became land based during phase ii 7000 1500 yr bp two separate depocenters formed keglen delta depocenter arose from a temporary stabilization phase of the gis and prograded rapidly over the glaciomarine deposits of phase i further inland proglacial lake formation and subsequent sedimentary infill associated with the ongoing gis retreat is represents the second depocenter the watson river connected both depocenters by a flood plain which transferred sediment from the gis to the keglen delta ongoing sea level fall due to glacio isostastic uplift combined with a gradually cooler and dryer climate resulted in terrace formation along the watson river flood plain around 4000 yr bp the gis margin reached its most landward location and began to advance to its present location the final phase phase iii

long mis 5e 3 environmental history of a paleolake in central poland recorded in the succession from kublowo abstract one of the longest above 7 m thick uninterrupted eemian vistulian weichselian pollen successions in poland is known from kublowo central poland the huge importance of this succession is manifested in the possibility of study the evolution of the lake environment under the influence of changing from interglacial to glacial climatic conditions the reconstruction of the environmental changes at kublowo and its surroundings show the short climate fluctuations and a detailed picture of the natural conditions prevailing in central poland central europe during the period from approximately 126 000 to 55 000 years bp based on the results of multi proxy analysis four lacustrine stages linked with a higher water level and three boggy stages low water level of evolution of the kublowo paleolake were observed the pollen diagram from kublowo reveals a succession of eighteen local pollen assemblage zones k1 k18 l paz the k1 to k7 lpaz zones record the interglacial succession correlated with the eemian the next pollen zones k8 to k18 are linked with the vistulian the pollen sequence shows between the eemian interglacial mis 5e and the last glaciation second stadial of the plenivistulian mis 4 3 four cold intervals that are interpreted as stadial phases herning rederstall schalkholtz and ebersdorf separated by three temperate intervals interstadials brorup odderade and oerel in the studied sediments 25 species of subfossil cladocera were identified and ten zones of fauna development were distinguished the unique feature of this profile is the good preservation of above 100 000 year old cladocera remains and a high diversity of species which are primarily littoral the middle and late eemian were periods convenient to cladocera development due to high temperatures high water levels high trophy and occurrence macrophytes a deterioration of fauna living conditions started in the late eemian and next took place in the vistulian cold events the results of isotopic and geochemical analyses of organic matter from kublowo have enabled the reconstruction of varying environmental conditions and the origin of organic matter the organic carbon content toc changes from 1 to 40 and is closely related to climatic conditions during the eemian the amount of toc systematically increased the lowest values are recorded in the coldest periods during the herning rederstall and schalkholz stadials the c n atomic ratio fluctuates from 13 to 34 and the highest values occur in the brorup interstadial the values of 13 c change from 27 9 to 12 9 and 15 n values oscillate between 1 6 and 5 3

palaeocene oceans and climate an isotopic perspective abstract the early cenozoic was a time of climatic and oceanographic transition from the cretaceous greenhouse world to the icehouse world of the neogene 18 o measurements shed light on ocean temperature and possible polar ice fluctuations during this interval while 13 c measurements monitor fluctuations in ocean productivity deep water circulation and atmospheric co 2 the major features from 18 o analysis of the early cenozoic are general cooling of surface waters with some evidence for transient cooling across the k t boundary surface water temperatures were at a cenozoic maximum in the early eocene whereas deep waters cooled then warmed during the palaeocene the 13 c of bulk carbonates is at a minimum at the start of the cenozoic due to the profound crisis in ocean surface water productivity associated with the extinctions of marine plankton at the cretaceous tertiary boundary thereafter 13 c values increase in bulk carbonates as well as planktonic and benthonic foraminifera to their cenozoic maximum in the late palaeocene c 60 ma after which time they again decrease over an interval of c 4 5 m y to a cenozoic low in the early eocene the increase in 13 c values characteristic of the palaeocene period is probably related to a combination of increasing surface water productivity and accelerated burial of organic carbon conversely the decline in 13 c into the early eocene is probably related to a decrease in ocean productivity and a deceleration in the rate of organic carbon burial benthic 13 c comparisons suggest that deep waters appear to have been predominantly formed in the high southern latitudes with the exception of a short lived interval near the palaeocene eocene boundary possibly associated with a transient climatic anomaly the late palaeocene thermal maximum the thermal change of palaeocene deep waters may be related to the changing productivity of surface waters by controlling atmospheric co 2 flux in a similar way to that proposed for the control of the pleistocene glacial cycles

a review of glacier outburst floods in iceland and greenland with a megafloods perspective the very largest glacier outburst floods have been termed megafloods given their volume and peak discharge that definition might be revised because those floods have become understood due to their distinctive and pervasive landscape impacts at least three floods in iceland can be categorized as megafloods since they produced impressive bedrock canyons and giant fluvially transported boulders glacier lake outburst floods glofs in greenland might also have megaflood type attributes given the enormous lake volumes drained we therefore here present the first review of glacier outburst floods in greenland sites isvand russell glacier kuannersuit glacier lake tininnilik two unnamed lakes near amitsulooq ice cap and iluliallup tasersua base camp lake lake hullett qorlortorssup tasia imaersartoq tordenso north midternaes and an outlet glacier of the a p olsen ice cap overall megaflood type landscape impacts in iceland tend to be best preserved and most easily identified inland although there has also been extensive offshore sedimentation there are very few reported impacts of glacier outburst floods in greenland in greenland ice dam failure causes frequent flooding compared to the volcanically triggered floods in iceland and this combined with the proximity of the greenland glacier lakes to the coast means that most proglacial channels in greenland are flood hardened and most landscape impact is likely to be offshore in estuaries and fjords future floods with megaflood type attributes will occur in iceland induced by volcanic activity in greenland they will be induced by extreme weather and rapid ice melt any potential landscape impact of these future floods remains open to question

isotope and cladocera data and interpretation from the eemian optimum and postoptimum deposits kaliska palaeolake central poland during the eemian optimum calcareous gyttja and lake marl accumulated the characteristic feature of calcareous gyttja is an occurrence of fragments of diatoms and plants while in lake marl they are absent in the carbonate rich deposits no cladocera remains are preserved based on the results of stable isotope analyses of carbonates the eight isotopic horizons is were defined and characterised in the studied deposits 15 species of subfossil cladocera were identified and 6 zones of fauna development were distinguished the defined cladocera species are similar to ones known from the other eemian site in poland the faunal taxa indicate the low trophy status of the lake initially followed by an increase to eutrophic status the cladocera and isotopic compositions suggest that the hornbeam zone e5 was a period of higher density of macrophytes as well as of an increase of biological activity associated with the low water level the fluctuations of the isotopic curves caused by a shallowing of the basin and a change of sediment lithology are characteristic for the spruce zone e6 the palaeolake transformed into a peatbog during the pine zone e7 during the early vistulian renewed carbonate accumulation and cladocera development took place indicating the repeated reservoir existence

effects of glacier retreat on the outbursts of goesvatnet southwest spitsbergen svalbard effects of the retreat of gasbreen south spitsbergen svalbard on the evolution of the ice dammed lake goesvatnet are shown for the period 1899 1991 the retreat and lowering of the damming ice masses have changed not only the sotred lake volume the lake geometry and the elevation slope and length of the subglacial outlet tunnel but also the frequency and magnitude of ourburst floods of goesvatnet for the estimation of peak discharges of outburst floods we computed an unbiased regression equation related to the progressive enlargement of subglacial tunnels using lake volume data and peak discharge data from the literature the derived equation is very similar to the original form of the clague mathews formula and answers the question why this formula has worked well in many cases peak discharges of goesvatnet in various years were estimated by means of the derived equation effects of the changed lake geometry as well as the changed length and slope of the subglacial outlet tunnel on the discharge during outbursts will be discussed by means of the nye clarke model observation of an out burst of goesvatnet in summer 1991 indicates that the outbursts may have been triggered by pressure decrease in the subglacial outlet tunnel increased discharge whereas flotation of the ice dam can be excluded

perturbation at the sea floor during the paleocene eocene thermal maximum evidence from benthic foraminifera at contessa road italy abstract detailed analyses of the benthic foraminiferal assemblages extracted with the cold acetolyse method together with high resolution geochemical and mineralogical investigations across the paleocene eocene p e boundary of the classical succession at contessa road western tethys allowed to recognize and document the paleocene eocene thermal maximum petm interval the position of the benthic extinction event bee and the early recovery of benthic faunas in the aftermath of benthic foraminiferal extinction the stratigraphical interval spanning the p e boundary consists of dominantly pelagic limestones and two prominent marly beds benthic foraminifera indicate that these sediments were deposited at lower bathyal depth not deeper than 1000 1500 m the carbon isotope excursion cie interval is characterized by high barite abundance with a peak at the base of the same stratigraphic interval indicating a complete although condensed record of the early cie a succession of events and changes in the taxonomic structure of benthic foraminifera has been recognized that may be of use for supra regional stratigraphic correlation across the p e boundary interval the composition of the benthic foraminiferal assemblages dominated by infaunal taxa indicates mesotrophic and changing conditions on the sea floor during the last 45 kyr of the paleocene the bee occurs at the base of the cie within the lower marly bed and it is recorded by the extinction of several deep water cosmopolitan taxa then the lysocline ccd rose and severe carbonate dissolution occurred preservation deteriorated the faunal density and simple diversity dropped to minimum values and a peak of glomospira spp has been observed stress tolerant and opportunistic groups represented mainly by bi and triserial taxa dominate the low diversity post extinction assemblages indicating a benthic foraminiferal recovery under environmental unstable conditions probably within a context of sustained food transfer to the bottom a three phase pattern of faunal recovery is recognizable at first the lysocline ccd started to descend and then recovered small sized bulimina oridorsalis umbonatus and tappanina selmensis rapidly repopulated the severely stressed environment later on siphogenerinoides brevispinosa massively returns dominating the assemblage together with other buliminids nuttallides truempyi and anomalinoides sp 1 finally a marked drop in abundance of s brevispinosa is followed by a bloom of the opportunistic and recolonizer agglutinated pseudobolivina that for the first time is recorded within the main cie a second interval of dissolution but less severe than the previous one has been recognized within the upper marly bed uppermost part of the main cie interval and it is interpreted as a renewed less pronounced shoaling of the lysocline ccd that interrupted the recovery of benthic faunas this further rise likely represents a response to persistent instability of ocean geochemistry in this sector of the tethys before the end of the cie in the cie recovery and post cie intervals the composition of the benthic foraminiferal assemblages suggests mesotrophic and unstable conditions at the sea floor according to the geochemical proxy for redox conditions the deposition of the petm sediments at contessa road occurred in well oxygenated waters leading out a widespread oxygen depletion as major cause of the bee changing oceanic productivity carbonate corrosivity and global warming appear to have played a much more important role in the major benthic foraminiferal extinction at the p e boundary

mass extinctions and sea level changes abstract review of sea level changes during the big five mass extinctions and several lesser extinction events reveals that the majority coincide with large eustatic inflexions the degree of certainty with which these eustatic oscillations are known varies considerably thus the late ordovician and end cretaceous extinctions are associated with unequivocal major regressions demonstrated from numerous widespread regions in contrast the multiple high frequency sea level changes reported for the frasnian famennian crisis based on the supposed depth preferences of conodont taxa have little support from sequence stratigraphic analyses which reveals the interval to be one of highstand the end permian mass extinction has long been related to a severe first order lowstand of sea level newell n d 1967 revolutions in the history of life geol soc am spec pap 89 63 91 based primarily on the widespread absence of latest permian ammonoid markers but field evidence reveals that the interval coincides with a major transgression newell s hypothesis that marine extinctions are related to shelf habitat loss during severe regression remains tenable for the end guadalupian and end triassic extinction events but not for other crises rapid high amplitude regressive transgressive couplets are the most frequently observed eustatic changes at times of mass extinction with the majority of extinctions occurring during the transgressive pulse when anoxic bottom waters often became extensive the ultimate cause of the sea level changes is generally unclear a glacioeustatic driving mechanism can only be convincingly demonstrated for the end ordovician and end devonian events at other times it is speculated that they may relate to the widespread regional doming and subsequent collapse caused by the impingement of superplumes and ultimate eruption on the base of the lithosphere

extinction dissolution and possible ocean acidification prior to the cretaceous paleogene k pg boundary in the tropical pacific abstract biotic perturbations and changes in ocean circulation during the maastrichtian stage of the latest cretaceous raise questions about whether the biosphere was preconditioned for the end cretaceous mass extinction of calcareous plankton a brief acme of inoceramid clams at 71 ma on shatsky rise in the tropical north pacific was followed by their extinction during the mid maastrichtian event at 70 1 ma associated with an abrupt warming of deep waters this was later followed by an interval of intense dissolution beginning 67 8 ma at odp site 1209 2387 m the late maastrichtian dissolution interval was initially gradual and is characterized by a low planktic benthic p b ratio highly fragmented planktic foraminifera mostly an absence of larger taxa low abundances of smaller taxa extremely low planktic foraminiferal numbers and low planktic foraminiferal and nannofossil species richness a partial recovery in carbonate preservation and calcareous plankton simple diversity began 250 kyr prior to the k pg boundary associated with the incursion of a younger more enriched 13c deep water mass although total abundances of planktic foraminifera in the sediment remained a tiny fraction of their earlier maastrichtian values a second brief dissolution event occurred 200 kyr before the boundary evidenced by renewed increase in planktic fragmentation but without a decrease in p b ratio our data show that changing deep water masses coupled with reduced productivity and associated decrease in pelagic carbonate flux was responsible for the first 1 6 myr dissolution interval while deccan traps volcanism may have caused surface ocean acidification 200 kyr prior to the k pg mass extinction event

periodic drainage of ice dammed lakes as a result of variations in glacier velocity previous discussions of the catastrophic drainage of ice dammed lakes have centred on mechanisms where characteristics of the lake are crucial to drainage initiation for example dam flotation or tunnel formation at a critical lake depth this paper describes a mechanism for lake drainage where drainage initiation depends on the characteristics of the glacier and is independent of the characteristics of the lake prediction of this mechanism must be based on glacier dynamics whereas the mechanisms most commonly discussed previously are best predicted primarily on the basis of lake evolution an ice dammed lake at the margin of the glacier solheimajokull in southern iceland was observed to drain rapidly into the sub or englacial drainage system supplying water and debris to the bed or interior of the glacier geomorphological evidence suggests that the lake drains and refills periodically discharging up to 13300 m3 of water into the glacier hydrological system the depth of the maximum lake is insufficient to cause either flotation of the ice margin or tunnel opening by plastic deformation of the ice and we suggest that sudden drainage is related to ice bed separations associated with specific glacier flow states rather than to a critical lake depth threshold this mechanism of lake drainage has implications for conditions at the glacier bed for the development of basal ice and for the entrainment of debris into the glacier as well as for the prediction of potentially hazardous catastrophic drainage events and jokulhlaups from ice dammed lakes keywords ice dammed lakes glacier hydrology basal ice jokulhlaup

global environmental changes preceding the cretaceous tertiary boundary early late maastrichtian transition stable carbon oxygen and strontium isotope data from maastrichtian planktic and benthic foraminifera from southern high latitude ocean drilling program sites 690 750 and 761 reveal major changes in climate and ocean chemistry during the early to late maastrichtian transition some 4 to 6 m y prior to the cretaceous tertiary k t boundary the 18o results suggest accelerated cooling resulting in the lowest marine temperatures of the late cretaceous the late maastrichtian rise in the seawater 87sr 86sr ratio begins at the time of this change and suggests increased rates of continental weathering and or runoff the 13c values show a negative shift of 0 5 followed by a positive shift of 1 these 13c fluctuations may reflect change in deep water chemistry with cooling variation in reduced carbon storage in coastal areas caused by eustatic sea level fluctuation and increased surface water productivity these findings contradict the common representation of stable and climatically equable environmental conditions in the latest cretaceous before the k t boundary event

a critical evaluation of carbon isotope stratigraphy and biostratigraphic implications for late cretaceous global correlation abstract climate variability is driven by a complex interplay of global scale processes and our understanding of them depends on sufficient temporal resolution of the geologic records and their precise inter regional correlation which in most cases cannot be obtained with biostratigraphic methods alone chemostratigraphic correlation based on bulk sediment carbon isotopes is increasingly used to facilitate high resolution correlation over large distances but complications arise from a multitude of possible influences from local differences in biological diagenetic and physico chemical factors on individual 13c records that can mask the global signal to better assess the global versus local contribution in a 13c record it is necessary to compare numerous isotopic records on a global scale as a contribution to this objective this paper reviews bulk sediment 13ccarb records from the late cretaceous in order to identify differences and similarities in secular 13c trends that help establish a global reference 13c record for this period the study presents a global scale comparison of twenty 13c records from sections representing various palaeo latitudes in both hemispheres and different oceanic settings from the boreal tethys western interior indian ocean and pacific ocean and with various diagenetic overprinting the isotopic patterns are correlated based on independent dating with biostratigraphic and paleomagnetic data and reveal good agreement of the major isotope events despite offsets in absolute 13c values and variation in amplitude between the sites these differences reflect the varying local influences e g from depositional settings bottom water age and diagenetic history whereas the concordant patterns in 13c shifts might represent 13c fluctuations in the global seawater dissolved inorganic carbon the latter is modulated by variations in organic matter burial relative to re mineralization in the global scale formation of authigenic carbonate and in partitioning of carbon between organic carbon and carbonate sinks these variations are mainly controlled by changes in climate and eustasy additionally some globally synchronous shifts in the bulk 13ccarb records could result from parallel variation in the contribution of authigenic carbonate to the sediment formation of these cements through biologically mediated early diagenetic processes is related to availability of oxygen and organic material and thus can be globally synchronized by fluctuations in eustasy atmospheric and oceanic oxygen levels or in large scale oceanic circulation because the influence of early diagenetic cements on the bulk 13ccarb signal can but need not be synchronized chemostratigraphy should not be used as a stand alone method for trans continental correlation and especially minor isotopic shifts have to be interpreted with utmost care nevertheless the observed consistency of the 13c correlations confirms global scale applicability of bulk sediment 13c chemostratigraphy for the late cretaceous including sediments that underwent lithification and burial diagenesis such as the sediments from the himalayan and alpine sections limitations arise from increased uncertainties 1 in sediments with very low carbonate content 2 from larger 13c variability in sediments from very shallow marine environments 3 from unrecognized hiatuses or strong changes in sedimentation rates and 4 in sections with short stratigraphic coverage or with few biostratigraphic marker horizons the combination of chemostratigraphy with biostratigraphy and magnetostratigraphy substantially increases the precision and temporal resolution of inter regional correlations and helps overcome problems that arise from differences in biostratigraphic schemes facies or provincialism of key fossils by using an iterative approach to stepwise increase precision of the correlations isochroneity of first and last occurrences of marker species versus chemostratigraphy is tested which helps to improve biostratigraphic zonations to assess zonal boundary ages and to identify useful criteria for defining late cretaceous stage boundaries many of which are still not formally defined the presented correlations indicate a consistent position for most planktic foraminifer zonal boundaries relative to corresponding isotope shifts during the mid cretaceous sea level high whereas diachroneity appears to be more pronounced during the late campanian and maastrichtian global sea level fall a similar pattern is observed for trans continental consistency in the 13c shifts graphic correlation of isotopic shifts magnetostratigraphic and biostratigraphic events among the compared sections is used to detect hiatuses or relative changes sediment accumulation rates and visualizes consistency or offsets of individual biostratigraphic markers relative to chemo and magnetostratigraphy finally an attempt of a global average 13c stack is presented for the turonian through maastrichtian

the link between glacier velocity and the drainage of ice dammed lakes comment on a paper by knight and tweed the interesting suggestion by knight and tweed 1991 that a link exists between glacier velocity changes and the filling and draining of a marginal ice dammed lake at solheimajokull southern iceland is examined the main problem lies not with plausibility but with a lack of field data to substantiate the argument some pertinent hydrological glaciological and meteorological data from the area are presented here many of which do not entirely support certain inferences and observations made in their paper it is shown that this very small lake is likely to have limited quantitative significance in the operation of the glacio hydrological or solute and sediment transfer systems in this basin further specific difficulties include the absence of crucial observations on glacier velocity variations and the precise timing and pattern of lake drainage in relation to such velocity changes the lack of evidence for a significant relationship between precipitation receipt and ice velocity here a component of the knight and tweed 1991 proposition and the occurrence of the lake drainage event in a rain free period contrary to the authors suggestion the opportunity is also taken to correct some incidental errors

maastrichtian molluscan biostratigraphy and extinction patterns in a cretaceous tertiary boundary section exposed at zumaya spain ammonites and inoceramid bivalves were stratigraphically collected from lower and upper maastrichtian units in continuous exposure along the seacoast near zumaya spain three ammonite teilzones can be recognized 1 a lower zone correlative with parts of the globotruncana ganserri planktonic foram zone and characterized by numerous inoceramids among three different species as well as pachydiscus neubergicus a noded baculites polyptychoceras sipho and hauericeras renbda 2 a middle zone that has no inoceramids but that has pachydiscus fresvillensis and p neubergicus and is correlative with the lower parts of the abathomphalus mayaroensis zone planktonic foram and 3 an upper zone that has p colligatus and is correlative with the upper parts of the a mayaroensis zone these three teilzones may be the basis for a tethyan facies wide ammonite zonation of the maastrichtian the four main components of the fossil record at the zumaya section show differing range characteristics with respect to the cretaceous tertiary k t boundary exposed in this section the inoceramids disappear at the top of the lower maastrichtian except for the small enigmatic form tenuipteria which has a restricted range in the uppermost levels of the cretaceous ammonites range upward to levels approximately 10 m below the boundary most larger planktonic forams and many nannofossil species disappear within several centimetres of the boundary echinoid fossils range up to and possibly across the k t boundary the zumaya section is thus characterized by apparently nonsynchronous or graded extinctions of most of its fossil content

mechanisms of remanent magnetization acquisition in marl and limestone alternations case study upper cretaceous chron 31 30 sopelana basque country abstract the marl and limestone m l alternations of the cretaceous tertiary section in sopelana in the basque country provide a good example of two chemical magnetizations which have been acquired at different times a detailed study was conducted on a core which contained an unusual paleomagnetic record in the vicinity of chron 30 r the magnetic polarity switches far more rapidly than expected from the reversal time scale a 10 cm sampling interval provided on average six samples in each m l couplet that was identified from a curve of carbonate content the lithostratigraphic nrm pattern is related to the lithology the intervals three to four m l couplets along which the contrast in the carbonate content between the limestone beds and the marly layers is low 20 are characterized in normal polarity intervals by the expected nrm in the limestone beds and a reverse or blurred nrm in the marly layers the dominant magnetic carrier in this complex zone is diagenetic hematite whereas titanomagnetite was identified below this interval the characteristics of the detrital minerals indicate an erosion of a mature landscape dominance of weathered ilmenite probably related to deformation in the pyrenees diagenetic hematite is characterized by two families the first microgranular size only tenths of a micrometre is present in all the samples and is interpreted as a very early chemical remanent magnetization crm acquired in the oxic zone that probably extended over a few decimetres below the sediment surface the second is restricted to the marly layers of intervals with large carbonate content contrasts in the m l couplets the grains in this family are larger very fine some micrometres in size and carry a reverse or blurred polarity in a normal polarity zone it is proposed that this chemical remagnetization was acquired during the circulation of oxygenated fluids the timing for this process is at least 2 m y after deposition and more likely 7 m y the second diagenetic family grew at least 90 m below the seafloor and its distribution shows that the marly layers in intervals with large contrasts in the carbonate content between the marls and the limestones were preferential drains along which circulation was favoured this suggests that although the porosity was still high 40 60 the diagenetic evolution in the m l alternations was already being expressed by different physical properties limestone beds and marly layers in intervals with low carbonate content contrasts in the m l couplets were impermeable to fluid circulation and the early diagenetic crm signal has been preserved in contrast marls in intervals with a large carbonate content contrast in the m l couplets were sites of later diagenesis and their early crm was overprinted by another magnetization

magnetic stratigraphy applied to synsedimentary slumps turbidites and basin analysis the scaglia limestone at furlo italy the previously studied italian scaglia sections at gubbio and moria consist entirely of pelagic limestone and marl by contrast the furlo section is characterized by synsedimentary slump folds and slide masses in the lower portion cenomanian coniacian and by intercalation of white calcarenitic turbidites in the upper part campanian paleocene demagnetization to 20 mt and 350 c or higher reveals a single stable direction after removal of an initial low coercivity component despite the stratigraphic complications the pattern of polarity zones clearly matches gubbio and the sea floor anomalies the abrupt faunal break at the end of the cretaceous was located and foram zonation shows that the very base of the paleocene is missing sedimentation rate determinations based on the magnetic polarity zonation have clarified the origin of stratigraphic complications in the furlo paleocene most samples were taken from pelagic beds but ten samples from calcarenitic turbidites yielded directions indistinguishable from those of adjacent pelagic beds detailed sampling of a turbidite 33 cm thick confirmed that this lithology is an accurate recorder of the geomagnetic field synsedimentary slumps range from coherent slide blocks with undeformed bedding to smoothly curving folds indicating flow of very soft sediment coherent slide blocks show declinations rotated by tens of degrees away from the typical regional direction but their inclinations are unaffected soft sediment slump folds yield typical regional directions indicating resetting of the remanent magnetization after deformation using stratigraphic structural and paleomagnetic data it is possible to identify in the lower part of the section a basal nonslumped unit overlain by seven slump units with various characteristics inter layered with four units of pelagic sediments which were deposited on older slump units but which themselves were not affected by synsedimentary slumping this paper emphasizes the value of paleomagnetic stratigraphy as a tool in detailed studies of sedimentology stratigraphy and basin analysis

reconstruction of environmental conditions of eemian palaeolake at studzieniec central poland on the basis of stable isotope and cladocera analyses abstract the results of isotopic and cladocera investigations of the eemian lacustrine sediments of studzieniec palaeolake central poland are presented the 12 m thick section contains silty sands and clayey silts on the bottom then gyttja and organic silts and peat in the upper part based on the results of stable isotope analysis of carbonates the 11 isotopic horizons is were defined and characterised results of isotopic analysis correlated with cladocera and pollen data enabled reconstruction of varying environment conditions the environmental changes were caused by a transition from the glaciation to the interglacial period expressed by a significant decrease in 18 o is 3 a warming of climate characterised by a positive trend in 18 o is 3 6 an increase of biological activity noted as very high positive values of 13 c above 7 is 7 the fluctuations of the isotopic values at the upper part of the section probably point to a shallowing of the lake due to sedimentary infill is 9 10 in the studied deposits 23 species of the subfossil cladocera were identified and seven zones of faunal development were distinguished the studzieniec palaeolake was sufficiently a shallow reservoir the cladocera composition indicates the initial oligotrophic status of the lake and then its subsequent increase and the periods of higher density of macrophytes during the interglacial optimum the low frequency of cladocera remains in carbonate rich deposits may be caused by a state of preservation of faunal assemblages or the fast rate of sediment accumulation

danian faunal succession planktonic foraminiferal response to a changing marine environment planktonic foraminiferal evolution following the cretaceous tertiary boundary extinction event is marked by a series of events in which one assemblage is rapidly replaced by another this pattern is characteristic of a highly changing pelagic environment the observed changes in the planktonic foraminifera may be related to long term changes in oceanic productivity that persisted for about the first 2 m y of the danian

inoceramid extinction in the gubbio basin northeastern apennines of italy and relations with mid maastrichtian environmental changes abstract a detailed study of five representative maastrichtian sections of deep water pelagic limestones in the umbria marche apennines of italy shows that inoceramids became extinct synchronously throughout this region some 3 5 ma before the cretaceous tertiary boundary the decline and disappearance of these bivalves are immediately preceded by two closely spaced peak abundance zones and are linked with an important change in environmental conditions during the mid maastrichtian period as is indicated by modifications in the 13c composition of sea water and variations in planktonic foraminiferal assemblages the restoration of stable environmental conditions after this biotic crisis took about half a million years in this region excursions of the 13c signal contemporaneous to the extinction of inoceramids in other maastrichtian basins throughout the world i e basque country and southern oceans indicate that these bivalves were extremely sensitive to environmental changes however accurate magneto and biostratigraphic correlations between the italian basque and southern hemisphere sections unambiguously indicate that the extinction of inoceramids was widely diachronous throughout the world of as much as 4 ma

ice dammed lake drainage cools and raises surface salinities in a tidewater outlet glacier fjord west greenland the drainage of ice dammed lakes in the form of outburst floods in greenland is detected regularly by remote sensing and these events are expected to occur more frequently in a warmer climate however their impact on ice sheet stability and neighboring water bodies is still unknown in this interdisciplinary study we investigate lake drainages from the greenland ice sheet into a west greenland fjord by analyzing simultaneous time series of satellite observations and direct hydrographic measurements of temperature and salinity in the fjord satellite images show that in general lake drainages have occurred quasiperiodically during the last decade a particular sequence of drainage events was observed by satellite in 2009 and was analyzed together with the first direct hydrographic observations signs of ice dammed lake drainages were observed by a downstream mooring located just below the intertidal zone the release of freshwater occurred at the fjord subsurface at a tidewater outlet glacier the downstream in water sequence of property changes in relation to these drainage events was observed as an almost immediate decrease in surface layer temperature 2 c followed within a week by the arrival of a high saline pulse 5 units with elevated salinity lasting for several days during the passage during lake drainages large amounts of relatively warm and saline intermediate water are brought to the near surface layers by entrainment processes near the glacier front and this influences the hydrography of the fjord but also impacts the ecosystem through upwelling of nutrient rich intermediate water

stable climatic conditions in central germany during the last interglacial stable isotopic data from the high resolution limnic sequence in the opencast mine at grobern central germany confirm the relatively stable climate of the last interglacial deduced from pollen analyses after significant warming during the transition from the saalian to the eemian stable warm climatic conditions set in once the climatic optimum was reached in the course of biozones e4 to e5 from the middle of biozone e6b a gradual temperature decrease can be observed reaching a minimum at the start of biozone e7 the division of the early weichselian glacial in central germany into two stadials herning rederstall and two interstadials brorup odderade is also documented by the findings copyright 2000 john wiley sons ltd

hydrologic and geomorphic effects of temporary ice dammed lake formation during jokulhlaups glacial outburst oods jokulhlaups occur frequently in glaciated environments and the resultant ooding causes geomorphic change and in some instances damage to local infrastructure during some jokulhlaups oodwater is stored temporarily in ice marginal locations in july 1999 a linearly rising jokulhlaup burst from solheimajokull iceland during this remarkable event subglacial oodwater pooled transiently in two relict ice dammed lake basins before draining suddenly back into solheimajokull the signi cance of such rapid formation and attendant drainage of temporary ice dammed lakes during jokulhlaups has not been addressed consequently this paper i assesses the hydrologic and geomorphic effects of temporary ice dammed lake formation caused by lake basin retro lling and ii discusses the impact and signi cance of transient retro lling under jokulhlaup conditions pre and post ood eldwork at solheimajokull enabled the impact and signi cance of lake basin retro lling to be assessed field evidence demonstrates that the july 1999 jokulhlaup had an unusually rapid rise to peak discharge resulting in subglacial oodwater being purged to ice marginal locations the propensity for temporary retro lling was controlled by rapid expulsion of oodwater from solheimajokull coincident with locations suitable for oodwater storage floodwater inundated both ice marginal lake basins permitting signi cant volumes of sediment deposition coarse grained deltas prograding from the ice margin and boulders perched on scoured bedrock provide geomorphic records of sudden retro lling the depositional characteristics of lake basin deposits at solheimajokull are similar to jokulhlaup sediments documented in proglacial settings elsewhere however their depositional setting and association with ice marginal landforms is distinctive findings suggest that temporary ice dammed lake formation and drainage has the capacity to alter the shape of the ood hydrograph especially if drainage of a temporary lake is superimposed on the original jokulhlaup deposits associated with lake basin retro lling have a long term preservation potential that could help to identify temporary ice dammed lake formation in modern and ancient glacial environments copyright 2003 john wiley sons ltd

professor mathews outburst floods and other glaciological disasters misfortunes befalling the granduc mining operation near stewart british columbia stimulated professor mathews influential scientific contributions on subglacial hydrology a series of violent fl

the significance of multiple causes and coincidence in the geological record from clam clusters to cretaceous catastrophe specific causes of unusual events recorded in the geological record are commonly difficult to distinguish and isolate in some instances event strata contain features that cannot be explained by a single causal mechanism unicausal hypotheses when applied to complex problems can lead to the misidentification misinterpretation and force fitting of observations great expectations syndrome the close timing or temporal overlap of significant events although statistically improbable on short time scales becomes possible on long time scales event coincidence may occur on a wide range of scales from local to global on the local scale a multiple event interpretation is offered for both the concentration and clustering of bivalves at specific levels within the upper cretaceous bearpaw formation of southern alberta for this example the relative timing of fluctuations in benthic substrate texture oxygen concentration abundance of planktotrophic larvae and degree of sea floor scouring was crucial

a 35 myr record of helium in pelagic limestones from italy implications for interplanetary dust accretion from the early maastrichtian to the middle eocene we have determined the helium concentration and isotopic composition of a suite of early maastrichtian through middle eocene pelagic limestones in the italian apennines the results provide a 35 myr record of the implied flux of extraterrestrial 3he which is a proxy for the accretion rate of interplanetary dust particles idps our measurements show that the 3he flux was fairly constant in the maastrichtian except for possible minor increases factor of two or less from 70 5 ma to 68 ma and at 66 ma which probably reflect transient increases in the accretion rate of asteroidal and or cometary idps we find no evidence for an increase in idp accretion at or immediately before the k t boundary implying that the k t impact was not associated with enhanced solar system dustiness this observation precludes the possibility that the k t impactor was a member of a major comet shower and is more consistent with impact of a lone comet or asteroid our data suggest a 2 to 4 fold increase in idp accretion between 57 and 54 ma followed by a factor of three decrease over an 4 myr period in the early to middle eocene the duration and magnitude of this variability is inconsistent with previous observations attributed to a shower of long period comets and is more likely the result of collisions in the asteroid belt and or kuiper belt in the entire 35 myr record we find no evidence for major enhancements of the idp accretion rate of the type expected from comet showers our results in combination with earlier 3he measurements do not support models that predict recurrent comet showers with periods of 38 myrs if there is a periodicity in the cratering record that is caused by periodic modulation of the oort cloud it is not evident in the apennine sediment data along with the 3he measurements we also obtained 4he concentrations which record temporal changes in the flux or composition of terrigenous matter the most significant change in 4he occurs in the last 4 myrs of the cretaceous over which the concentration of 4he in the detrital component rises by 300 this rise tracks a strong increase in the seawater 87 sr 86 sr ratio suggesting a globally significant change in the composition of continental detritus delivered to the oceans possibly arising from increased continental weathering

faunal turnover at the end of the cretaceous in the north pacific region implications from combined magnetostratigraphy and biostratigraphy of the maastrichtian senpohshi formation in the eastern hokkaido island northern japan abstract a combined magnetostratigraphic and biostratigraphic study has been performed on the maastrichtian senpohshi formation in eastern hokkaido island northern japan which is an approximately 1300 m thick section mainly composed of hemipelagic mudstone the identification of magnetic polarity was possible at 51 horizons whereby four magnetozones were recognized these magnetozones were correlatable to geomagnetic polarity chrons c31r to c30n suggesting that the age of the senpohshi formation is spanning from middle to upper part of the maastrichtian ca 69 67 ma the magnetostratigraphy of the senpohshi formation established in this study enables a direct age correlation to the maastrichtian successions in other regions thus this detailed chronology of the formation contributes to paleontological studies of the maastrichtian in the north pacific region for instance this magnetostratigraphic age assessment implies the following 1 the stratigraphic range of the ammonite pachydiscus flexuosus contains polarity chrons from the lower part of c31r to the lower part of c31n 2 the first occurrence fo of the calcareous nannofossil nephrolithus frequens in the north pacific region is correlatable to polarity chron c30n or below and 3 the fo of the bivalve inoceramus awajiensis is located within polarity chrons from c31r to the upper part of c31n this suggests that the inoceramid extinction event in the north pacific region might have occurred during polarity chrons from c31r to the upper part of c31n ca 70 5 67 8 ma which is 2 3 5 0 myr prior to the cretaceous paleogene boundary the trend of the maastrichtian faunal turnover in the north pacific is well consistent with those of other regions brings a new evidence for understanding the global faunal turnover in the maastrichtian just before cretaceous paleogene mass extinction

a new cycle of jokulhlaups at russell glacier kangerlussuaq west greenland jokulhlaups in 2007 and 2008 from an ice dammed lake at the northern margin of russell glacier west greenland marked the onset of a renewed jokulhlaup cycle after 20 years of stability we present a record of successive ice dammed lake drainage events and associated ice margin dynamics spanning 25 years robust calculations of lake volumes and peak discharges are made based on intensive field surveys and utilizing high spatial resolution orthophotographs of the lake basin and ice margin these data enable identification of controls on the behaviour of the ice dammed lake and provide the first field based examination of controls on jokulhlaup magnitude and frequency for this system we find that russell glacier jokulhlaups have a much higher peak discharge than predicted by the clague mathews relationship which we attribute to an unusually short englacial subglacial routeway and the presence of a thin ice dam that permits incomplete sealing of jokulhlaup conduits between lake drainage events additionally we demonstrate that the passage of jokulhlaups through an interlinked system of proglacial bedrock basins produces significant attenuation of peak discharge downstream we highlight that improved understanding of jokulhlaup dynamics requires accurate information about ice dammed lake volume and ice proximal jokulhlaup discharge

evolution of palaeolake environment in poland during the eemian interglacial based on oxygen and carbon isotope data from lacustrine carbonates abstract the results of oxygen and carbon stable isotope investigations of eight eemian lacustrine sediments from poland are presented the values of 18o changed from ca 11 to 1 and 13c values oscillated between 3 5 and 7 0 the isotopic record correlated well with pollen cladoceran and diatom data the evolution of the palaeolakes in poland was reconstructed the palaeolakes originated during the final phase of the wartanian late saalian glaciation the 18o and 13c values of that time reflect the input of detrital carbonates into the basins the boundary between the glaciation and the interglacial period is expressed by a significant decrease in 18o and 13c values during the early eemian a positive trend in 18o values confirms the gradual climatic changes the eemian optimum is characterized by constant 18o and 13c values during the early vistulian weichselian glaciation the palaeolake declined the varying 18o values likely reflect frequent changes in water balance between precipitation and evaporation associated with an influence of marine circulation the fluctuations of the isotopic curves in the upper parts of the successions the post optimum were caused by a shallowing of the basin by infilling with sediments the observed shifts in the isotopic curves are due to the proximity of the baltic sea and earlier strong oceanic influences

periodic lake peatland shifts under the eemian and early weichselian climate changes in central europe on the basis of multi proxy studies abstract long term palaeoecological sequences dated to the eemian interglacial and weichselian glaciation are crucial for understanding cyclic climate changes and ecosystem responses this article presents a multi proxy palaeobotanical zoological and geochemical study considering variable aspects of the eemian early weichselian lake mire succession in central poland the investigated sequence collected from a former small kettle hole revealed many ecosystem alterations i e warm stages led to the terrestrialisation of the lake whereas stadial coolings to its reappearance hence we examined whether i the eemian warming influenced the ecological succession of the lake ii lakes which reappeared during the herning and rederstall stadial coolings developed alike and iii the beginning of peatland functioning interglacial or interstadial had an impact on further plant succession the results show that thermal amelioration during the eemian interglacial supported domination of tetraedron minimum and pediastrum boryanum var boryanum which contributed to the sedimentation of bituminous shales the expansion of salvinia natans in the final stage of lake existence middle eemian was probably a result of the mild climate characterised by the lack of late spring frosts algae in contrast to cladocera revealed bipartition of the herning and rederstall stadials older sections were colder younger warmer however geochemical and isotopic data point to the very low productivity of the lakes during those stadials the lake that existed during the herning stadial revealed very low taxonomical diversity of cladocera whereas that during the rederstall was characterised by relatively high diversity of this group during the late eemian and brorup interstadial rich fens with some oligotrophic patches with sphagnum sp developed this study revealed that small water bodies due to their very local character and often uniqueness of palaeo records may be a very valuable source of information about climate and palaeoecology of different groups of organisms during the eemian interglacial and the weichselian glaciation

an integrated structure from motion and time lapse technique for quantifying ice margin dynamics fine resolution topographic data derived from methods such as structure from motion sfm and multi view stereo mvs have the potential to provide detailed observations of geomorphological change but have thus far been limited by the logistical constraints of conducting repeat surveys in the field here we present the results from an automated time lapse camera array deployed around an ice marginal lake on the western margin of the greenland ice sheet fifteen cameras acquired imagery three times per day over a 426 day period yielding a dataset of 19 000 images from these data we derived 18 point clouds of the ice margin across a range of seasons and successfully identified calving events ranging from 234 to 1475 m2 in area and 815 8725 m3 in volume induced by ice cliff undercutting at the waterline and the collapse of spalling flakes low ambient light levels locally reflective surfaces and the large survey range hindered analysis of smaller scale ice margin dynamics nevertheless this study demonstrates that an integrated sfm mvs and time lapse approach can be employed to generate long term 3 d topographic datasets and thus quantify ice margin dynamics at a fine spatio temporal scale this approach provides a template for future studies of geomorphological change

controls on the sedimentology of an ice contact jokulhlaup dominated delta kangerlussuaq west greenland abstract this paper characterises the sedimentary impact of a glacial outburst flood or jokulhlaup on an ice contact delta topset at russell glacier kangerlussuaq west greenland rapid drainage of an ice dammed lake in july 1987 generated a jokulhlaup with a peak discharge of 1300 m3 s 1 which drained across a 500 m wide 200 m long delta top into a proglacial lake the delta topset comprises boulder clusters ice block obstacle marks with relief of up to 4 m and is graded to lake levels up to 6 m higher than those during typical non jokulhlaup conditions the delta top was dissected by the 1987 jokulhlaup causing a fan shaped extension of the delta front by 30 m surface grain size on the delta decreases rapidly away from the main flood flow direction reflecting rapid downstream reduction in sediment transport capacity the 1987 jokulhlaup was predominantly fluidal and turbulent and had peak stream powers of 2846 w m 2 proximally and

reply to comments on 6000 year climate records in an ice core from the hoghetta ice dome in northern spitsbergen fujii y and 10 others 1990 6000 year climate records in an ice core from the hoghetta ice dome in northern spitsbergen ann glaciol 14 85 89

eemian and vistulian weichselian paleoenvironmental changes a multi proxy study of sediments and mammal remains from the ławy paleolake eastern poland abstract the eemian vistulian developmental history of the awy paleolake eastern poland has been studied by analysing records of micro pollen cladocera ostracoda macrofossils molluscs mammal remains the lithological record and radiocarbon dating from a 5 30 m sediment core at awy in the paterebo stream valley well preserved mammal fossil remains accompanied by organic deposits have also been investigated the results of the multi proxy analyses suggest explicitly that the climate was the main driving force of the changes in terrestrial and aquatic ecosystems and in the geomorphological processes in the catchment however we propose that the water level fluctuations were also an important factor in the modification of the aquatic assemblages pollen cladocerans molluscs and ostracods from awy indicate the existence of a small shallow well vegetated paleolake during the warm eemian climate optimum in the final phase of the eemian the lake was transformed into a mire in the early vistulian the variable hydrological conditions were the main driver force for the development of the study area finally the existence of the basin at awy was closely associated with periodic coexistence of limnic telmatic and river environments

palaeoecological investigations and 230th u dating of eemian interglacial peat sequence of banzin mecklenburg western pomerania ne germany abstract a novel occurrence of an eemian interglacial peat was identified in 2011 in a short lived outcrop of the nel pipeline trench near the village of banzin germany the profiles are situated in a shallow kettle hole within the undulated landscape of the saalian glaciation the distribution of dominantly till lithofacies in the banzin area confirms the regional trend of saalian tills with a locally higher abundance of cretaceous clasts in the banzin kettle at a depth of 2 2 m lies a 0 5 m thick strongly compressed eemian peat layer the buried eemian peat layer is deformed by ice wedge pseudo morphological and mega crack structures indicating a strong periglacial influence during weichselian stadial phases the post eemian sequence is subdivided into three units beginning with a mixture of aeolian and gelifluction deposits which are also modified by cryostructures the top of the banzin sequence is covered by a 0 5 m thick colluvisol layer of redeposited humic loam from the late weichselian holocene the uppermost unit suggests that solifluction processes occurred in the last few hundred years likely driven by intensive anthropogenic influence limnic sedimentation began during the late saalian period in a landscape characterized by herbaceous vegetation and heliophytes during the latest interval of saalian deglaciation shallow waters of the basin most likely attained a depth below 3 m and were abundant in calcium carbonate the beginning of eemian interglacial peat accumulation mis 5e is characterized by a dominance of light birch forests followed by pine the ensuing optimum climate was dominated by the encroachment of oak forests and then hazel oak forest and sedimentation ceased in the basin during this phase at the climatic optimum pz iii iv the eemian peat included remains of ceratophyllum submersum and species of higher temperature requirements the banzin basin gradually became shallower and overgrown until the closing of its open water at the end of phase iii iva the lack of cladocera species composition in the eemian sequence proves isolated conditions of a shallow reservoir we present the first results from ne germany for eemian peat bog samples dated by the u th disequilibrium method 230 th u using leachate alone l l and total sample dissolution tsd analytical techniques isochron corrected 230 th u ages of 118 8 10 ka l l and 121 9 13 ka tsd were obtained both 230 th u dates 118 121 ka obtained using two different techniques confirm the biostratigraphical classification into the eemian interglacial

a comparison of two recent jokulhlaups from an ice dammed lake sondre stromfjord west greenland the hydro graphs of two jokulhl aups resulting from the sudden drainage of an ice d ammed lake in west greenland in 1984 and 1987 are compared the first flood had a similar peak discharge to the second but drained only two thi rds of the total volume of the 1987 event which amounted to 32 36 x 106 m3 in 36 h calcula tions based on the lake refill time suggest that it drains every 2 3 years but that peak flows may be variable from flood to flood the timing of the joku lhlaups in relation to the melt season may reflect variations of water pressure within the subglacial drainage networks and changes in the

outburst floods from glacier dammed lakes the effect of mode of lake drainage on flood magnitude published accounts of outburst floods from glacier dammed lakes show that a significant number of such floods are associated not with drainage through a tunnel incised into the basal ice the process generally assumed but rather with ice marginal drainage mechanical failure of part of the ice dam or both non tunnel floods are strongly correlated with formation of an ice dam by a glacier advancing from a tributary drainage into either a main river valley or a pre existing body of water lake or fiord for a given lake volume non tunnel floods tend to have significantly higher peak discharges than tunnel drainage floods statistical analysis of data for floods associated with subglacial tunnels yields the following empirical relation between lake volume v and peak discharge qp qp 46v0 66 r2 0 70 when qp is expressed in metres per second and v in millions of cubic metres this updates the so called clague mathews relation for non tunnel floods the analogous relation is qp 1100v0 44 r2 0 58 the latter relation is close to one found by costa 1988 for failure of constructed earthen dams this closeness is probably not coincidental but rather reflects similarities in modes of dam failure and lake drainage we develop a simple physical model of the breach widening process for non tunnel floods assuming that 1 the rate of breach widening is controlled by melting of the ice 2 outflow from the lake is regulated by the hydraulic condition of critical flow where water enters the breach and 3 the effect of lake temperature may be dealt with as done by clarke 1982 calculations based on the model simulate quite well outbursts from lake george alaska dimensional analysis leads to two approximations of the form qp vqf hi 0 where q 0 5 to 0 6 hi is initial lake depth 0 is lake temperature and the form of f hi 0 depends on the relative importance of viscous dissipation and the lake s thermal energy in determining the rate of breach opening these expressions along with the regression relations should prove useful for assessing the probable magnitude of breach type outburst floods

meltwater chemistry and solute export from a greenland ice sheet catchment watson river west greenland summary solute export from the greenland ice sheet gris to coastal regions around greenland is likely to increase in the future as a consequence of increasing icemelt production here we present hydrochemical characteristics solute and major ion exports and chemical denudation rates for 2007 2010 for the watson river sector of the gris that drains into the fjord kangerlussuaq the hydrochemistry is dominated by ca2 and hco3 with a relatively high molar k na ratio of 0 6 0 1 typical for meltwaters draining a gneissic lithology low molar ca2 na and mg2 na ratios indicate that weathering of disseminated carbonates contributes less than silicate weathering to the chemical composition the solute export varied between 33 103 2009 and 61 103 tons 2010 showing that increasing discharge leads to increasing solute export at the catchment scale deviations between ion yield estimates derived from use of discharge weighted and mean daily concentrations methods were generally less than 5 indicating that the choice of method is of less importance the chemical denudation rates ranged between 36 and 56 meq m 2 per year which are lower than previous records from glacierized catchments however when normalized by discharge the denudation rates are comparable to other arctic sites when extrapolating the results from the watson river catchment to the entire greenland for 2007 2010 the solute export from greenland meltwater varied between 7 1 106 and 7 8 106 tons whilst the major ion export was between 6 4 106 and 7 3 106 tons dissolved fe a potential biolimiting nutrient for primary productivity in the north atlantic had annual export rates from greenland between 15 103 and 52 103 tons

chasma boreale mars topographic characterization from mars orbiter laser altimeter data and implications for mechanisms of formation 1 chasma boreale a large reentrant in the north polar cap of mars is distinct in scale detailed topography and orientation from the spiraling troughs that characterize the majority of the polar cap we use new high resolution mars orbiter laser altimeter mola data and mars orbiter camera moc and viking images of the chasma region to assess hypotheses of origin of chasma boreale these hypotheses include formation by glacial flow and ablation by eolian processes such as katabatic winds and sublimation by outflow of meltwater or by a combination of two or more of these processes we find that these new data support initial formation by outflow of meltwater with later modification by katabatic winds and sublimation on the basis of our analysis we suggest a possible scenario in which outflow has occurred in several stages the outflow appears to have begun near an enclosed depression at the head of the chasma meltwater migrated within and below the ice down the regional slope and eventually broke out to the surface removal of material by melting caused subsidence and erosion of the polar deposits forming the chasma which has subsequently undergone modification by eolian and sublimation processes the outflow deposited most of its sediment in the form of a lobe that stratigraphically overlies the polygonal plains mapped at the mouth of the chasma and scoured some of the circumpolar sediment mantle in the surrounding region the lowest portions of the north polar basin received the rest of the sediment as a deposit a few meters thick mola data also reveal evidence for similar events of smaller magnitude elsewhere on the margins of the polar cap

short term discharge and suspended sediment fluctuations in the proglacial skeldal river north east greenland the summer discharge pattern of the skeldal river which drains a 560 km2 partly glacierized catchment in north east greenland is dominated by diurnal oscillations reflecting variations in the melt rate of snow and ice in the basin superimposed on this diurnal pattern are numerous short lived discharge fluctuations of irregular periodicity and magnitude the larger fluctuations are described and attributed to both rainfall events and periodic collapse of the glacier margin damming flow from beneath the skelbrae glacier other minor fluctuations are less readily explained but are associated with changes in the channelized and distributed reservoirs and possibly temporary blockage of subglacial conduits caused by ice melt with subsequent damming fluctuations in suspended sediment concentration ssc are normally associated with discharge fluctuations although examples of transient flushes were observed where marked increases in ssc occurred in the absence of corresponding discharge variations a strong relationship between the event discharge increase and event ssc increase for rainfall induced events was established but no such relationship existed for non rainfall induced events there is some evidence for an exhaustion effect in the ssc patterns both at the event time scale and as the month proceeds a mean suspended sediment load of 1765 0 26 t day 1 was estimated for the study period which would be equivalent to a suspended sediment yield of 732 4 t km 2 year 1 copyright 2001 john wiley sons ltd

effects of ice front collapse and flood generation on a proglacial river channel near kangerlussuaq sondre stromfjord west greenland river discharge measurements downstream of the russell glacier near kangerlussuaq sondre stroomfjord west greenland revealed the occurrence of short term discharge fluctuations during the 1991 melt season frontal ice cliff collapse results in temporary river damming producing initial decreases in discharge and subsequent sudden flood peaks on dam failure fluctuations are less than two hours in duration with a maximum discharge fluctuation magnitude of 50 m 3 s 1 double that of normal ablation controlled diurnal fluctuations as such these events are exceeded in magnitude only by periodic jokulhlaups resulting from the drainage of an ice dammed lake further up glacier the concentration of discharge fluctuations at the beginning of the melt season the large number of ice blocks within the flow and the confinement of flows between ice block levees all add to the effectiveness of these events in terms of channel erosion and sediment transport

glacier advance ice marginal lakes and routing of meltwater and sediment russell glacier greenland the ice sheet margin at russell glacier west greenland advanced 7 m a 1 between 1968 and 1999 as the ice advanced over moraine ridges small changes in position caused major changes in the routing of proglacial water and sediment these included changes in the distribution of ice marginal lakes in the periodic drainage of ice dammed lakes in the routing and sediment content of meltwater draining into the proglacial zone and in the release of sediment from the moraines by erosion and mass movements proglacial hydrology and sediment flux appear to be controlled not simply by glacier mass balance but by evolving ice marginal geomorphology which must be accounted for in palaeoenvironmental interpretation of proglacial sediments

paleogene magnetic stratigraphy in umbrian pelagic carbonate rocks the contessa sections gubbio the umbrian sequence of pelagic carbonate rocks provides an opportunity for precise correlation between paleogene biostratigraphy and geomagnetic polarity history the red to pink paleocene to middle eocene scaglia rossa limestone the varicolored upper eocene scaglia variegata limestone and the gray green oligocene scaglia cinerea marlstone form a 250 m thick continuous exposure in the contessa valley near gubbio italy magnetostratigraphic lithostratigraphic and biostratigraphic investigations in three sections covering the entire paleogene have confirmed and dated the geomagnetic reversal sequence for most of this period the ferromagnetic mineral in the scaglia cinerea is magnetite and af demagnetization to peak fields of 20 mt is sufficient to define the characteristic remanent magnetization the scaglia variegata and pink scaglia rossa samples contain an additional hematite component which is very pronounced in dark red paleocene scaglia rossa samples changes of magnetic mineralogy take place in these limestones during heating especially above 500 c however thermal demagnetization is effective in isolating the characteristic remanence vectors which form almost antipodal clusters of directions representing normal and reversed polarities the directions are rotated counterclockwise partly due to post oligocene tectonism paleontological zonations of planktic foraminifera and calcareous nannofossils were hampered by poor preservation but the major epoch and stage 29 as in the gubbio bottaccione section paleocene eocene just above anomaly 25 eocene oligocene between anomalies 13 and 15 oligocene miocene just below anomaly 6c these correlations require slight modifications to previous conclusions on paleogene sea floor spreading rates

bioturbation inoceramid extinction and mid maastrichtian ecological change notable among the biological changes of the middle part of the maastrichtian age was a major pulse of extinction among inoceramid bivalves analysis of the distribution of inoceramid shell fragments suggests that the population of burrowing organisms increased across the same stratigraphic interval that the bivalve population decreased a global reorganization of ocean circulation that resulted in cooler better oxygenated bottom waters is proposed as an explanation for the observed changes in the deep sea other observations regarding the mid maastrichtian are consistent with this hypothesis

synsedimentary slides and bedding formation in apennine pelagic limestones abstract jurassic to lower tertiary pelagic carbonates in the umbria marches apennines of northern peninsular italy are well bedded and synsedimentary submarine slide deposits are common bedding planes were formed by pressure solution during compaction where original rhythmic alternations in clay content were present bedding formed along the clay rich horizons where the original sediments were uniform stylolitic pseudobedding approximately marks paleohorizontal even where true bedding departs from paleohorizontal because of the presence of soft sediment folds deformational facies observed in synsedimentary slides are compared to a conceptual model of a bedding plane glide with a longitudinal sequence of four deformational facies 1 the slide scar where section is missing may be identified if biostratigraphic or magnetostratigraphic zones are missing 2 the stretched rear of the slide is thinned and shows extensional shear joints and sedimentary boudinage 3 the transported but undeformed main body of the slide may be identified paleomagnetically if it has been rotated and the basal shear surface may show deformational structures 4 the shortened front of the slide commonly shows on a small scale the ramp thrusts and folds typical of foreland fold and thrust belts the state of induration of the sediments at the time of movemen is shown by their theological behavior in areas of major subsea relief slides may have moved far enough for the distal parts to lose their coherence and all the transitional stages from a slide to a pebbly mudstone can be identified

biostratigraphic and magnetostratigraphic intercalibration of latest cretaceous and paleocene depositional sequences from the deep water basque basin western pyrenees spain abstract latest cretaceous late maastrichtian and paleocene depositional sequences from the deep water basque basin have been calibrated with published 1 2 and newly acquired magnetostratigraphic data sequences mostly consist of hemipelagic marls and limestones and their relative ages are well constrained with planktic foraminifera they accumulated during a phase of tectonic tranquillity and reduced clastic input into the basin and therefore they can be attributed to eustatic sea level changes with reasonable confidence on the basis of the planktic foraminifera zonation a good match has been observed previously between the depositional sequences of the basque basin and specific sea level cycles of the 1988 version of the exxon global cycle chart gcc 3 here a new attempt at correlation using their respective magnetostratigraphic data has failed to confirm such a match the disagreements observed may indicate that for the studied interval 1 the current planktic foraminifera biostratigraphy lacks the necessary level of resolution to ensure synchrony between sequences of different basins and or 2 the magnetostratigraphy of the gcc needs to be revised whatever the case the new findings lend support for some criticism on the use of the gcc for interregional correlations

magnitude and frequency in proglacial rivers a geomorphological and sedimentological perspective abstract proglacial fluvial sedimentary systems receive water from a variety of sources and have variable discharges with a range of magnitudes and frequencies little attention has been paid to how these various magnitude and frequency regimes interact to produce a distinctive sedimentary record in modern and ancient proglacial environments this paper reviews the concept of magnitude and frequency in relation to proglacial fluvial systems from a geomorphic and sedimentary perspective rather than a hydrological or statistical perspective the nature of the meltwater inputs can be characterised as low magnitude high frequency primarily controlled by ablation inputs from the source glacier or high magnitude low frequency primarily controlled by exceptional inputs the most important high magnitude low frequency inputs are catastrophic outburst floods often referred to by the term jokulhlaup icelandic for glacier burst glacier surges are an additional form of cyclical variation impacting the proglacial environment which briefly alter the volumes and patterns of meltwater input the sedimentary consequences of low magnitude high frequency discharges are related to frequent variations in stage the greater directional variability that sediment will record and the increased significance of channel confluence sedimentation in contrast the most significant characteristics of high magnitude low frequency flooding include the presence of large flood bars and mid channel jokulhlaup bars hyperconcentrated flows large gravel dunes and the formation of ice block kettle hole structures and rip up clasts glacier surges result in a redistribution of low magnitude high frequency processes and products across the glacier margin and small floods may occur at the surge termination criteria for distinguishing magnitude and frequency regimes in the proglacial environment are identified based on these major characteristics studies of quaternary proglacial fluvial sediments are used to determine how the interaction of the various magnitude and frequency regimes might produce a distinctive sedimentary record consideration of sandur architecture and stratigraphy shows that the main controls on the sedimentary record of proglacial regions are the discharge magnitude and frequency regime sediment supply the pattern of glacier advance or retreat and proglacial topography a model of sandur development is suggested which shows how discharge magnitude and frequency in combination with sandur incision and aggradation controlled by glacier advance and retreat can control sandur stratigraphy

maastrichtian foraminiferal and paleoceanographic changes on milankovitch timescales milankovitch scale alternations in maastrichtian hemipelagic strata from ocean drilling program hole 1050c blake nose provide a natural experiment of paleoceanography and foraminiferal paleoecology in a tropical subtropical greenhouse ocean cycles are 30 50 cm thick and thought to reflect the 21 kyr precessional cycle high planktic 18o values are correlated with high planktic but low benthic 13c values indicating that cooler and or more saline surface waters were associated with higher productivity high productivity intervals are also characterized by high ca concentrations enrichment in feldspar and kaolinite and high relative abundance of heterohelix spp globigerinelloides spp and laeviheterohelix glabrans conversely low productivity intervals have low planktic 18o values high fe and ti concentrations enrichment in quartz illite and chlorite and relative increases in globotruncana spp and pseudoguembelina spp potential forcing mechanisms for observed covariation include cyclic variation in water column stratification variation in continental nutrient fluxes and changes in the intensity of upwelling

eemian lake development hydrology and climate a multi stratigraphic study of the hollerup site in denmark abstract a classic northwest european open section with lacustrine eemian sediments hollerup has been studied with respect to sedimentology geochemistry stable isotopes diatoms and mineral magnetic analyses and correlated by geochemistry and diatoms to a previously pollen analysed section by andersen 1965 this correlation has enabled the section to be related to muller s 1974 tentative eemian absolute chronology and shows that the hollerup eemian sediments appear to cover c 11 000 yr our studies show that the onset of the eemian was characterized by a major lake level rise followed by an almost 3000 yr long period of high but oscillating lake levels it is argued that the latter part of this period of highly maritime climate can be defined as the eemian climatic optimum this period was interrupted by a few hundred years long phase of low lake level coinciding with the immigration of spruce followed by medium high lake levels the next c 3500 yr coinciding with the carpinus pollen zone seem to have been characterized by fairly humid and mild conditions although slightly more arid than during the preceding optimum the carpinus period ended with a more than 1000 yr long gradual lake level fall and this period of lake level change concurring with the transition into the pinus pollen dominated period terminated with an extreme low lake level event this 300 500 yr long arid phase coincides with a distinct peak in pine pollen and was followed by higher but slightly oscillating lake levels in a cooler climate the end of the eemian seems to have been characterised by a gradual cooling until almost pure clastic sedimentation and a marked expansion of herb pollen grains mark the onset of the weichselian based on regional correlations to other european terrestrial and north atlantic marine proxy records we argue that the distinct hydrologic and climatic events displayed in the hollerup record were possibly caused by a combination of sea level changes changes in the hydrologic cycle and changing oceanic circulation patterns the latter two may have been triggered by the opening and closure of the baltic sea white sea connection the initial build up of continental ice sheets and the first major impacts of meltwater induced freshwater in key areas for thermohaline circulation

reaction of lake environment on the climatic cooling transition from the eemian interglacial to early vistulian on the basis of solniki palaeolake sediments ne poland abstract results of cladocera and organic matter analyses from the eemian lake deposits in solniki ne poland are presented we focused on the reaction of the lake s environment to progressive cooling reflected in the changes of the organic matter and the cladocera community approximately 3 m of sediments accumulated from the optimum of the eemian interglacial e5 to the early vistulian ev2 were analyzed results of analyses of organic matter correlated with cladocera data enabled a reconstruction of varying environmental conditions and geneses of organic matter the organic carbon content is closely related to climatic conditions the lowest values are recorded in the coldest periods during the ending of the eemian interglacial and the herning stadial of the early vistulian the highest ones occur unexpectedly in the eemian post optimum at the end of the spruce phase and at the beginning of the pine phase during the eemian optimum e5 biodiversity of cladocera species was maximal 17 but the frequency of specimens was low at the end of the optimum e5 an improvement of living conditions more optimal for various ecological groups of cladocera took place algae remained a significant component of organic matter the early eemian post optimum e6 is characterized as a period of the high number of zooplankton species the highest frequency as well as biodiversity at that time probably a higher water level and an optimal temperature formed very favorable conditions for the fauna development during this period maximal values of toc tn and the slight increase of c n ratio suggest a higher primary productivity with a small supply of organic matter of terrestrial origin coexistence of two species of the family bosminidae and maximum values of 15 n suggest a high trophy mesotrophy high resolution and detailed analyses of the lake sediments accumulated during the pollen zone e7 allowed to identity a few minor environmental fluctuations recorded in varied cladocera frequency toc and c n ratio in the final period of the eemian interglacial and in the early vistulian herning stadial a drastic reduction in frequency of cladocera and the features of om the lowest amounts of toc and tn and the highest value of c n reflect the decline of lake conditions and a lack of both primary production and aquatic vegetation in the lake during the amersfoort interstadial a renewed bioproduction and slightly supply of terrestrial plants in organic matter as well as revitalize zooplankton took place

palaeoecological investigations and 230 th u dating of the eemian interglacial peat sequence from neubrandenburg hinterste muhle mecklenburg western pomerania ne germany abstract the eemian interglacial sequence was explored in the gravel pit neubrandenburg hinterste muhle near neubrandenburg ne germany the sequence is situated in a former kettle hole depression between underlying late saalian till s str warthe covered by a late weichselian till today still visible a 3 m long and max 2 m wide profile is located on the edge of the former eemian depression the limnic sedimentation began during the late saalian in a landscape characterized by open herbaceous vegetation cool clear and calcium carbonate rich lake water dominated inhabited by characeae that indicates a presence of stonewort meadows most typical of waters up to 10 m in depth the beginning of the eemian interglacial succession was characterized by a dominance of scarce birch forest followed by pine forest the beginning of the mesocratic phase of the eemian was characterized by the appearance of warm climate indicators and by the development of thermophilic forest communities dominated by oak forest with the appearance of warm climate indicators the ensuing climate optimum was defined by the encroachment of hazel oak forest and later by mixed deciduous forest limnic sedimentation ceased in the basin during this phase and the end of predominantly limnic conditions is marked by a decrease in the frequency of aquatic plants and an increase in the amount of brown mosses during the interglacial optimum mixed forests reigned this phase bears a record of oligotrophication leading to transition mire and raised bog and the aquatic plants vanished the depression gradually became shallower and was overgrown by a forest cover during the telocratic phase of the eemian communities with pine birch and fir spread the end of the interglacial was characterized by a disappearance of the riparian forest and a sporadic appearance of reedswamp plants at the beginning of the early weichselian a deterioration of climatic conditions resulted in the formation of widespread heaths on acid soils and trees disappeared in the studied basin the water level fluctuated the hinterste muhle sequence shows the development of a small kettle hole lake and its transformation to an overgrowing mire including terrestrialization processes during the eemian interglacial the u th data obtained for five samples from the upper part of the studied profile which have been analyzed by the tsd technique has yielded an age of 116 13 10 kyr this date reflects the classification into the second half of the eemian interglacial and the early weichselian for the upper part of peat formation

the maastrichtian record from shatsky rise northwest pacific a tropical perspective on global ecological and oceanographic changes we present new isotopic and micropaleontological data from a depth transect on shatsky rise that record the response of the tropical pacific to global biotic and oceanographic shifts during the mid maastrichtian results reveal a coupling between the upper ocean characterized by a weak thermocline and low to intermediate productivity and intermediate waters during the earliest maastrichtian oxygen and neodymium isotope data suggest a significant contribution of relatively warm intermediate water from the north pacific isotopic shifts through the early maastrichtian suggest that this warmer water mass was gradually replaced by cooler waters originating in the southern ocean although the cooler water mass remained dominant through the remainder of the maastrichtian it was displaced intermittently at shallow intermediate depths by north pacific intermediate water the globally recognized mid maastrichtian event similar to 69 ma manifested by the brief appearance of abundant inoceramid bivalves over shallow portions of shatsky rise is characterized by an abrupt increase similar to 2degrees 3degrees c in sea surface temperatures a greater flux of organic matter out of the surface ocean and warmer similar to 4degrees c intermediate waters results implicate simultaneous changes in surface waters and the sources distribution patterns of intermediate water masses as an underlying cause for widespread biotic and oceanographic changes during mid maastrichtian time

changes of water level in the eemian palaeolake at imbramowice sw poland based on isotopic and cladoceran data abstract isotopic and cladoceran investigations of eemian mis 5e lake sediments from imbramowice sw poland allow us to reconstruct the environmental conditions especially changes of water level and trophic status during the early and middle eemian interglaciation we analyzed the sediments from 6 5 to 11 0 m depth in a core provided by mamakowa 1989 the upper 6 5 m had insufficient carbonates and cladoceran contents for analyses the analyzed section consists of sandy and organic silts at the bottom followed by gyttja characterized by increasing caco 3 content measured 18 o values oscillate from ca 9 to 4 and 13 c from 3 5 to above 6 based on stable isotope analyses of carbonates we define and characterize eight isotopic horizons is we identify 26 taxa of subfossil cladocera and seven zones clz of faunal development probably the greatest depth of the lake occurred with pollen zone e2 shallowing then took place during pollen zones e2 e3 gradual warming is observed and expressed through a positive trend in both 18 o and 13 c values pollen zone e4 is characterized by frequent changes of water level during the eemian interglaciation excluding the initial phase of lake evolution the lake was meso eutrophic and eutrophic with high phytoplankton productivity

the origin of major incisions within the pleistocene deposits of the north sea a seismic survey to resolve the geometry of major incisions within the upper pleistocene has been run over an area of 1600 km2 in the mid north sea twelve separate incisions have been identified ranging up to 5 km wide and 25 km long with incised depths from 100 to 350 m deposits categorised into four recurring types infill the incisions to form a flat sea bed the surveyed features are comparable to others widely found beneath the northern continental shelves and lowlands of europe asia and america such incisions have a similar range of sizes and shapes were cut during at least three separate periods in the pleistocene and are down cut into substrates of various lithologies ranging from precambrian to pleistocene in age the major incisions are believed to be the product of a singular mechanism the outburst of intra ice sheet lakes forming jokulhlaup plunge pools except for late stage hollow infills which have interglacial temperate deposits the incision infills are periglacial the former deposits are similar to the sediments accumulating in the present day bathymetric enclosed deeps such as the lambay deep and devil s hole found on continental shelves it is suggested that the enclosed deeps are large kettle holes which resulted from the thawing of ice formerly buried in the incision infills