stratigraphy amino acid geochronology and correlation of quaternary sea level and glacial events broughton island arctic canada raised marine and glaciomarine terraces on broughton island record regional isostatic adjustments and eustatic sea level changes previous workers proposed three alternative glacial and sea level chronologies of the region these conflicts are resolved by the stratigraphic control provided by amino acid ratios d allo isoleucine l isoleucine in marine molluscs collected form cliff exposures amino acid ratios radiometric dates and relative weathering measurements on geomorphological features provide a basis for regional correlations based upon amino acid ratios the coastal sedimentary sequences all part of the broughton island formation can be subdivided into six units to which informal member names have been assigned these units delimit at least four glacial episodes during which local ice advanced around broughton island to the outer coast the youngest advance is correlative with deposits that are dated 54 000 bp and the absolute ages of older events have been estimated from minimum uranium s

enso and solar driven sub milankovitch cyclicity in the palaeogene greenhouse world high resolution pollen records from eocene lake messel germany the annually laminated oil shale from the eocene maar lake at messel germany provides unique palaeoenvironmental and palaeoclimatological information for the palaeogene greenhouse phase two palynological analyses of 6 3 and 70 kyr long records with a temporal resolution of 70 and 700 years respectively confirm vegetation and climate variability in the sub milankovitch range this variability clearly corresponds to cyclic climate fluctuations indicating the influence of solar activity and a millennial scale variability of the el nino southern oscillation also seen during the quaternary icehouse system this provides strong evidence of cyclic fluctuations in the sub milankovitch frequency band that represent a pervasive and persistent system not only of the quaternary icehouse but also throughout the entire neogene and the palaeogene greenhouse this is proof for the long term stability of the driving forces of natural climate change on earth fluctuations in the frequency of palynomorphs indicate cyclic short term quantitative changes in the composition of the vegetation these changes were related to precipitation and corresponding fluctuations of the lake level as well as to changes in pollen production transport and deposition supplementary material a complete list of variables and palynomorphs used for pollen diagrams and statistical analyses as well as additional time series analyses are available at https doi org 10 6084 m9 figshare c 3458778

holocene and pleistocene dissolution cycles in deep sea cores of baffin bay and davis strait palaeoceano graphic implications abstract calcium carbonate dissolution has been studied in several grab samples and piston cores from baffin bay and davis strait ranging in water depth from 200 to 2300 m the intensity of dissolution was determined from examining 1 the ratio of arenaceous to calcareous benthonic foraminifera 2 the ratio of benthonic to planktonic foraminifera 3 the relationships between the dissolution susceptible and dissolution resistant foraminifera 4 the degree of foraminiferal test fragmentation and 5 the relationships between plankton tows and the fauna in the surface sediments all core tops and grab samples from baffin bay surface sediments below 600 900 m water depth demonstrated intense dissolution of calcium carbonate sediments below 900 m were biogenic carbonate free indicating 100 foraminiferal loss due to dissolution possible causes of substantial undersaturation in calcium carbonate of baffin bay bottom water are very low temperatures and higher concentrations of carbon dioxide all cores also demonstrated intense dissolution during interglacial or interstadial isotope stages 1 3 5 7 and 9 similarities in planktonic foraminiferal assemblages suggested the presence of similar bottom water masses during these periods the preservation state of biogenic carbonate debris in glacial isotope stages 2 4 6 8 and 10 is similar to the assemblage found in the water at present

new palynology based astronomical and revised 40ar 39ar ages for the eocene maar lake of messel germany the annually laminated oil shale from the eocene maar lake at messel federal state of hessen germany provides unique paleoenvironmental data for a time interval of 640 ka during the paleogene greenhouse phase as a consequence of orbitally controlled changes in the vegetation in the vicinity of the lake the lacustrine laminites can now be astronomically tuned dating is based on the short eccentricity amplitude modulations of the regional pollen rain and their correlation to the astronomical la2010a la2010d solutions in combination with a revised 40ar 39ar age of a basalt fragment from a lapilli tuff section below the first lacustrine sediments depending on different newly suggested ages for the fish canyon sanidine used as monitor for neutron irradiation the age for the eruption at messel is between 48 27 0 22 and 48 11 0 22 ma this allows for the first time the exact correlation of a paleogene lacustrine sequence to the marine record in central europe the messel oil shale becomes now slightly older than previously assumed and includes the ypresian lutetian boundary that moves the base of the european land mammal age geiseltalian mp 11 into the lower eocene this opens a window for establishing an independent chronostratigraphic framework for paleogene terrestrial records and their correlation to the marine realm furthermore the study reveals that higher amounts of pollen from wet and thermophilous plants indicate less seasonal and more balanced precipitation and slightly higher temperatures during a well expressed eccentricity minimum

a glacio isostatic facies model and amino acid stratigraphy for late quaternary events in spitsbergen and the arctic strong early holocene crustal uplift over the spitsbergen archipelago reflects disappearance of an ice mass centred just north east of the archipelago and which decayed rapidly just after 10 000 bp after a maximum extension between 12 600 and 10 000 bp from the lithofacies distributions associated with these events a glacio isostatic facies model can be defined which combined with analyses of amino acid racemization provides a valuable stratigraphic method for correlating pre holocene glacio isostatic events these are correlated with events in greenland and both are contrasted with weichselian glacial events at the southern margins of the two great northern hemisphere ice sheets and with contemporary water mass changes in the north atlantic and norwegian sea the geographical variation in glacier response through time is explained by three principal climatic circulation patterns

latest quaternary and holocene paleoceanography of the eastern baffin island continental shelf canada benthic foraminiferal evidence foraminiferal zones radiocarbon ages on shells and corrected ages on pretreated organic sediment from four cores from the eastern baffin island continental shelf suggest a three stage deglacial to postglacial history late wisconsin to holocene the earliest sediments in the cores contain foraminiferal species elphidium excavatum cassidulina reniforme islandiella helenae indicative of distal glaciomarine environments that lasted at least several thousand years an oceanographic change about 8500 years ago is indicated by a melonis zaandamae zone in northern and central shelf cores collected from 200 800 m water depth the presence of m zaandamae in the north and its absence in the south suggest warmer and more saline postglacial water in northern baffin bay whose influence became diluted with cooler coastal meltwater as the current flowed south along the baffin island shelf sediments after 6000 years ago on the northern and central shelf are dominated by agglutinated foraminifera suggesting dis

the variability of baffin bay seafloor sediment mineralogy the identification of discrete glacial sediment sources and application to late quaternary downcore analysis quantitative x ray diffraction qxrd mineralogy of bedrock ice rafted and fluvial clasts 239 seafloor samples 2 mm and samples from two long piston cores were used to i define regional pa

ocean atmosphere responses to climatic change in the labrador sea pleistocene plankton and pollen records abstract pleistocene climate change is examined using proxy climatic records from oxygen isotope data calcareous and organic walled marine microfossils pollen and terrestrial spores deposited during the past 0 9 ma at odp site 646 in the labrador sea 500 km north of the present polar front paleotransfer functions applied to planktonic foraminiferal assemblages show relative increases in interglacial summer 3 7 and winter 3 5 temperatures and in winter salinity 0 5 2 for the past 0 4 ma but only two earlier intervals early stage 11 and stage 17 have changes of comparable magnitude coccolith and dinoflagellate cyst accumulation rates show that primary productivity is generally correlated with temperature and salinity changes at the start of interglacials these productivity peaks lag the ice volume changes by 2 4 ka dinocyst blooms seem to precede coccolith peaks reflecting the tolerance of opportunistic species for large variations in temperature and salinity peaks in pollen and spore abundance are strongly correlated with ice volume which controls the position and stability of the polar jet stream in addition to the northern extent of forest vegetation time series analysis was made of 7 oceanographic variables sst summer and winter surface salinity coccoliths dinocysts planktonic and benthic foraminifera and 5 other variables 18 pollen spores percent sand foraminiferal test fragmentation and reworked palynomorphs most variables showed significant power peaks at 100 ka and or at 41 ka however sea surface responses showed minor peaks at 26 and 16 ka and microfossil productivity also showed significant peaks at 68 ka the high latitude labrador sea records thus display large non linear regional responses to climate changes in addition to the effects of orbital insolation forcing at 41 and 23 ka

abrupt environmental changes within a late holocene lacustrine sequence south of the marmara sea lake manyas n w turkey possible links with seismic events abstract a coring campaign in lake manyas kus golu on the southern coast of the sea of marmara turkey has provided insights into basin infilling processes during the upper 11 metres of the sedimentary record combined sedimentary features between 5 and 4 m depth have been explained by a seismite a brittle mixed layer uniquely rich in seeds and ostracod valves was widely detected at 4 m downcore this has been interpreted as being the result of a seiche either through a salt inundation linked to a tsunami in the sea of marmara the large scale scenario or a local hydrothermal fluid discharge the small scale scenario ostracod valves which are usually not preserved in lake manyas sediment are either incorporated here as tsunami debris providing a spatially averaged snapshot of the regional assemblage or are locally preserved following a temporary geochemical hydrochemical change of the water of unknown duration but probably several decades the brittle mixed layer overlies cracks resulting from the direct effects of the seismic shock wave on slightly compacted sediment at around 964 cm depth palynological and particle size analyses indicate a change from backswamp to open lacustrine conditions the end of the backswamp has been correlated with a decrease in the level of the sea of marmara from 4000 to 3000 2800 yr ago uncal caused by regional tectonic movements an age depth model is presented based on two ams radiocarbon dates on the palynological detection of the end of the beysehir occupation phase 130 cm above the event and on maximal sedimentation accumulation rates obtained by radionuclide analyses the entire study sequence covers the last 4300 yr the paper examines the possibility of an early byzantine age for the seismic event this may have been the historical event at ad 460 that destroyed cyzicus the ancient erdek 20 km north of the lake and various villages in the interior and was felt widely in the then known world other possibilities include various local and regional events in that same period the early byzantine tectonic paroxysm and the large earthquake in ad 447 that affected the entire sea of marmara region

milankovitch theory of ice ages hypothesis of ice sheet linkage between regional insolation and global climate abstract j d hays j imbrie and n j shackleton 1976 science 194 1121 1132 showed that the astronomical theory explained many features of late quaternary ice age climates but they did not specify the physical mechanisms involved here it is proposed that interlocked variations of ice sheet heat sinks in both polar hemispheres amplified and transmitted milankovitch summer half year insolation changes a version of the astronomical theory between 45 and 75 n into the globally synchronous climate changes recorded in geologic records it is suggested that late quaternary ice sheets had terrestrial components grounded above sea level melting margins fluctuations controlled by climate and marine components grounded below sea level drained largely by ice streams limited melting margins fluctuations controlled primarily by sea level and secondarily by climate interior surface elevations coupled to downdraw through ice streams northern hemisphere ice sheets were largely marine with minor melting margins in the arctic and terrestrial with major melting margins in the midlatitudes west antarctic and peripheral east antarctic ice was marine based and lacked melting margins because of their geographic array these terrestrial and marine components formed an ice sheet system whose variations were coupled on a global scale milankovitch summer isolation changes near midlatitude northern hemisphere melting margins controlled most variations of this system because advance or retreat of melting margins initiated concurrent eustatic sea level change such sea level change afforded the critical interlocking mechanism between terrestrial and marine components because it forced simultaneous expansion or contraction of marine margins in both polar hemispheres this initiated an amplifying feedback loop among all marine components and influenced interior downdraw through ice streams arctic summer insolation change was less important because northern melting margins were relatively minor its greatest influence was on surface ablation of ice streams that controlled interior downdraw this affected eustatic sea level and activated global linkage of marine sectors by analogy with present day antarctica late quaternary ice sheets were enormous planetary heat sinks due to their reflective and radiative surface characteristics it is suggested that the effectiveness of these ice sheet heat sinks varied with their areal extent and interior surface elevation thus it is postulated that concurrent growth or decay of these interlocked ice sheet heat sinks in both polar hemispheres served as the global amplifier of regional milankovitch summer insolation

biomarker determination as a provenance tool for detrital carbonate events heinrich events fingerprinting quaternary glacial sources into baffin bay sedimentary deposits associated with heinrich events are anomalously rich in detrital carbonate off hudson strait the dominant carbonate is calcite whereas at distal sites in the north atlantic dolomite is dominant more diagnostic a significant source for dolomite is its outcrop at the northern end of baffin bay where major ice streams from the laurentide innuitian and greenland ice sheets converged the provenance of samples containing detrital carbonate mainly dolomite from a core in baffin bay has been confirmed using organic geochemistry to distinguish between alternative sources based upon the thermal maturity of organic matter in carbonates of the source region the core contained five distinct carbonate units dating between 14 and 51 cal ka bp and indicates significant ice stream instability associated with iceberg calving and significant volumes of meltwater the exact temporal relationship to heinrich events is not yet clear a long mid wisconsin interval 38 to 22 cal ka bp devoid of detrital carbonate suggests a major reduction in ice extent at high northern latitudes the core samples yield thermally sensitive biomarker ratios comparable to those from laurentian carbonates in the canadian arctic islands but unlike those from north greenland identifying the former region as their provenance however a late holocene sample from off newfoundland shows a stronger affinity with greenland 2007 elsevier b v all rights reserved

palynological evidence for prolonged cooling along the tunisian continental shelf following the k pg boundary impact abstract the cretaceous palaeogene k pg boundary mass extinction event is related to major global environmental changes resulting from a large extraterrestrial impact organic walled cyst producing marine dinoflagellates dinocysts survived the k pg mass extinction relatively unscathed making them ideally suited for reconstructing these environmental changes so far one of the best dinocyst records available is from the k pg boundary global stratotype section and point gssp at el kef nw tunisia there the dinocyst record shows major fluctuations across the boundary likely reflecting strong responses to environmental changes these fluctuations have so far not been confirmed by other studies therefore in this study we performed a high resolution marine palynological study on a closely spaced sample set from the elles section some 75 km south of el kef in order to generate a palaeoenvironmental and palaeoclimatic record across the k pg boundary to allow verification and refinement of earlier reported environmental changes to better constrain the reconstructions based on qualitative biotic proxies we employed the quantitative sea surface temperature proxy tex86 unfortunately the tex86 proxy record of the studied section is compromised because of post depositional oxidation however the diverse dinocyst assemblages at elles show strong fluctuations similar to the el kef record therefore confirming the earlier recorded signals showing rapid regionally consistent changes these records imply that the latest cretaceous was characterized by a gradual cooling trend and the onset of relative sea level fall within the immediate post extinction interval in the first thousands of years after the impact dinocyst assemblages reveal multiple incursions of higher latitude dinocyst species implying repeated pulses of cooling these results signify that the earliest danian climatic and environmental conditions were relatively unstable across the tunisian shelf

quaternary dinoflagellate cysts in the arctic ocean potential and limitations for stratigraphy and paleoenvironmental reconstructions abstract the arctic ocean is a siliciclastic depositional environment which lacks any rock forming biogenic calcareous and siliceous components during large parts of its quaternary history these hemipelagic sediments are nevertheless suitable for the study of organic walled microfossils of which the fossil remains of dinoflagellates dinoflagellate cysts are the most important group dinoflagellate cysts have become an important tool in paleoceanography of the high northern latitudes but their potential for quaternary biostratigraphy has remained largely unexplored dinoflagellate cysts are the dominant marine palynomorph group which is more continuously present in the marginal seas e g barents sea bering sea than in the arctic ocean itself throughout the quaternary most species have long stratigraphic ranges are temporary absent and show abundance variations on glacial interglacial timescales of the more than 30 taxa recorded only habibacysta tectata and filisphaera filifera became extinct in the pleistocene the highest persistent occurrence of h tectata at ca 2 0 ma and the top of f filifera acme at ca 1 8 ma can be used for supra regional stratigraphic correlation between the arctic ocean and adjacent basins these events corroborate a slow sedimentation rate model for the quaternary section on the central lomonosov ridge but a combination of different methods will have to be applied to provide a detailed chronostratigraphy the occurrence of cysts of phototrophic dinoflagellates in certain stratigraphic intervals on lomonosov ridge supports published evidence of episodic opening of the multiyear arctic sea ice cover during the quaternary probably related to a stronger inflow of atlantic water this contradicts the hypothesis of a permanently ice covered central arctic ocean in the quaternary

recognition of cyclic and non cyclic environmental changes in the mediterranean pliocene a palynological approach the interval between 2 8 and 2 3 ma b p from the south italian singa section has been investigated for its dinoflagellate cyst and sporomorph contents in order to facilitate palaeoenvironmental interpretation the following curves are derived from the data the ratios sporomorphs dinoflagellate cysts protoperidinioid gonyaulacoid dinoflagellate cysts warm cold water indicating dinoflagellate cysts inner neritic oceanic dinoflagellate cysts outer neritic oceanic dinoflagellate cysts and the reworked dinoflagellate cysts per gram of sediment furthermore the already available 18o curve has been used calibration of changes in the sporomorph dinoflagellate ratio against the computed astronomical insolation curve leads to an improved age assessment for the section frequency analysis on the curves shows the 23 41 and 100 ka frequency components to be most important phase and amplitude differences between the filtered 23 41 and 100 ka frequency components are used for environmental interpretation the 23 ka frequency band is best explained by changes in runoff induced transport the 41 ka frequency components are classified in a group with short response time to orbital forcing and a group with longer response time those signals having a short response time are attributed to local precipitation induced changes in runoff those signals having a longer response time are mainly attributed to changes in global temperature and to a lesser extent to changes in global ice volume finally longer term cyclic and non cyclic changes are mainly attributed to temperature and sea level variation

late quaternary sedimentation in baffin bay baffin bay is a small ocean basin that connects the arctic and atlantic oceans the adjacent continental shelves have been extensively reworked during quaternary glaciation the shelf break generally lies between 200 and 500 m the continental slope passes directly into the abyssal plain of baffin bay basin without any major submarine canyon deep sea fan system being present except for a large smooth sediment apron in northern baffin bay on the basis of over 50 piston cores six quaternary sediment facies are distinguished from detrital mineralogy reflected in colour and sediment texture facies a b and c are predominantly ice rafted or are debris flow deposits each with a distinct mineralogy facies d is turbidites and bottom current sorted sands silts and muds facies e is hemipelagic sediment facies f consists of sediments ranging from slumps through debris flow deposits to fine grained turbidites with a distinctive provenance in northern baffin bay these sediment facies appear to be part

deformation around a rising diapir modeled by creeping flow past a sphere a new experimental method for determining the pattern of flow and three dimensional progressive finite deformation of fluid elements in low reynolds number re viscous flow has been applied to creeping flow past a rigid sphere falling in a cylinder this is intended as a model analogue of natural rock deformation associated with magmatic and solid state diapirs rising through ductile crust the kinematics of finite strain in such analogue experiments may give useful information on the development of natural structures the experiment and a new method for quantifying the progressive finite deformation of fluid volumes in the transparent newtonian test fluid used sgm36 are discussed in detail the progressive finite deformation of fluid flowing along specific streamlines passing the sphere appears to be complex and largely a function of the initial distance of fluid volumes and the particular streamlines which they follow from the flow axis the progressive deformation history in the material surrounding a rising spherical diapir is characterized by progressive flattening and rotation of material above and progressive stretching below the sphere the results compare favorably with the external strain pattern associated with post tectonic mesozonal diapiric intrusions

pollen distribution in recent marine sediments eastern canada analysis of 90 samples from coastal and continental shelf areas off eastern canada between 42 and 69 n shows that quaternary pollen and spores are present in recent marine muds throughout this region pollen and spore concentrations range from 50 000 to 100 grains per cm3 and they decrease both offshore as a function of distance from vegetation sources and northwards as a function of lower vegetation density north of the summer arctic frontal zone isopercentage contours show that maximum relative abundances of most palynomorphs occur in marine sediments adjacent to their regions of highest vegetation representation onshore however pinus and picea pollen tend to increase in percentage abundance with distance offshore presence of these tree pollen in marine sediments off baffin island implies that wind transport is an important pathway by which bisaccate pollen types enter the ocean in addition to fluvial transport q mode factor analysis shows that four major factors account for 89 of the variance amo

a dinoflagellate cyst record for the last 0 7 ma from the rockall plateau northeast atlantic ocean organic walled dinoflagellate cyst analysis of samples previously used to establish a high resolution oxygen and carbon isotope stratigraphy for the last 0 7 ma in the northeastern atlantic is detailed data from hole 552a leg 81 of the deep sea drilling project drilled on the western flank of the rockall plateau reveal peaks of dinoflagellate cyst recovery relatable with isotope stages 1 11 13 and 17 cysts most prersistently present include the oceanic impagidinium species nematosphaeropsb labyrinthea ostenfeld reid and the ubiquitous operculodinium centrocarpum deflandre cookson wall the results offer a correlation between the oceanic oxygen isotope stratigraphy and the dinoflagellate cyst record the potential for further correlation with the extensive quaternary marine sequences of the continental shelf around the british isles is explored the dinoflagellate cyst signal is an important factor in understanding oceanographic changes both at the surface and at depth

multiple deglaciations of the hudson bay lowlands canada since deposition of the missinaibi last integlacial formation abstract the stratigraphic record in the james and hudson bay lowlands indicates that the sequence of glacial events at the geographical center of the 12 6 10 6 km 2 laurentide ice sheet may have been more complex than hitherto imagined isoleucine epimerization ratios of in situ and transported shells recovered from till and associated marine and fluvial sediments cluster into at least 4 discrete groups two alternative explanations of the data are offered of which we strongly favor the first hypothesis 1 setting the age of the last interglacial marine incursion the bell sea at 130 000 yr b p results in a long term average diagenetic temperature for the lowlands of 0 6 c using this temperature enables us to predict the age of shells intermediate in age between the last interglaciation and the incursion of the tyrrell sea 8000 yr ago between these two interglacial marine inundations hudson bay is predicted to have been free of ice along its southern shore about 35 000 75 000 and 105 000 yr ago based on amino acid ratios from shells occurring as erratics in several superimposed tills and fluvial sediments these results suggest 1 that traditional concepts of ice sheet build up and decay must be reexamined 2 that high sea levels may have occurred during the wisconsin glaciation and 3 that a critical reappraisal is required of the open ocean 18 o record as a simple indicator of global ice volume an alternative hypothesis 2 is also examined it is based on the assumption that the 35 000 yr old deposits calculated on the basis of hypothesis 1 date from the last interglaciation this in effect indicates that the missinaibi formation commonly accepted as sediments of the last interglaciation are about 500 000 yr old and that the effective diagenetic temperature in the lowlands during approximately the last 130 000 yr has been close to 6 c we argue for rejection of this alternative hypothesis

high resolution palaeomagnetic study of late pleistocene sediments from baffin bay first results the detailed palaeomagnetic study of core 85027016 collected in central baffin bay confirms the occurrence of anomalous directions in the depositional remanent magnetization previously observed in the upper part of the pleistocene sequence chronology and sedimentation rates are discussed on the basis of new 14c ages 18o isotopic stratigraphy and palaeoclimatic arguments provided by other works two successions of anomalous inclinations are recorded between 15 000 and 30 000 years bp preceded by long period secular variations the possible occurrence of geomagnetic excursions in this region is discussed in considering contemporaneous high resolution palaeomagnetic records of the northern hemisphere

glacial terminations in the oxygen isotope record of deep sea cores hypothesis of massive antarctic ice shelf destruction abstract glacial terminations i and ii in the deep sea core foraminiferal oxygen isotope ratios though not similar in form are each characterized by a short interval of about 3 ka during which a large negative change occurred in the ratios after correcting for temperature effects we estimate that each change was equivalent to a glacial disintegration capable of causing a 50 60 m eustatic sea level rise in the termination i interval 16 13 ka b p the estimated equivalent sea level rise is much larger than that suggested by the best evidence of deglacial ice loss from the laurentide ice sheet which is thought to dominate pleistocene glacial ice volume changes moreover in termination ii about 125 ka b p the estimated equivalent sea level rise is much larger than that inferred from the stratigraphy of coral reefs and beaches on new guinea and other locations which suggests quite high sea levels for 10 ka prior to this termination to reconcile these severely conflicting lines of evidence we propose that the rapid negative isotope ratio changes were largely caused by the disintegration of massive floating antarctic ice shelves which masqueraded as land ice in the oceanic isotope ratios but which contributed no sea level change we propose that such shelves were formed when oceanic circulation changes in the north atlantic under glacial conditions greatly reduced the formation of relatively warmer north atlantic deep water and its injection into circumpolar antarctic regions and that the shelves disintegrated rapidly with the resumption of large scale formation of this deep water and its input into the antarctic we find that high sea levels in the 125 135 ka b p interval prior to termination ii which imply very little northern ice then are well supported by dated coral reef stratigraphy although these ages were not accepted by the climap study of the last interglacial ocean minimal northern ice volumes at that time imply that strong milankovitch summer insolation is not always required for northern deglaciation a promising additional deglacial mechanism is the prolonged viscous depression of the crust beneath the laurentide ice sheet combined with atmospheric oceanic circulation factors

oceanic mechanisms for amplification of the 23 000 year ice volume cycle situated adjacent to the largest northern hemispher ice sheets of the ice ages the mid latitude north atlantic ocean has an important role in the earth s climate history it provides a significant local source of moisture for the atmosphere and adjacent continents forms a corridor that guides moisture bearing storms northward from low latitudes and at times makes direct contact along its shorelines with continental ice masses evidence of major ice ocean air interactions involving the north atlantic during the last 250 000 years is summarized outflow of icebergs and meltwater initially driven by summer insolation over the ice sheets affects midlatitude ocean temperatures summer heat storage winter sea ice extent and global sea level these oceanic responses in turn influence the winter moisture flux back to the ice sheets as well as ablation of land ice by calving spectral data indicate that the oceanic moisture and sea level feedbacks in part controlled by glacial melt products amplify milankovitch insolation forcing of the volumetrically dominant mid latitude ice sheets at the 23 000 year precessional cycle

palynostratigraphy and chronostratigraphy of baffin bay deep sea cores climatostratigraphic implications abstract palynostratigraphic considerations and 14c dates ams accelerator mass spectrometry on foraminifera samples from piston cores suggest sedimentation rates as high as ca 8 11 cm ka in deep baffin bay during the late pleistocene throughout this interval baffin bay experiences rigorous conditions and probably the extension of a dense sea ice cover unfavourable to phytoplanktonic productivity the dinocyst microflora indicates only brief episodes of higher productivity related to arctic conditions and to moderately low salinites ca 30 31 the abundance of reworked pre quaternary palynomorphs in the deposits is interpreted as a response to glacial and glacio marine activity in the northernmost areas surrounding baffin bay the dinocyst stratigraphy spanning approximately over the last ice age ca 100 ka reveals that baffin bay constituted a confined basin isolated from the north atlantic ocean prior to the present interglacial

postglacial sequence stratigraphy of lake melville labrador abstract in lake melville labrador the quaternary glacimarine sediments reflect a single retreat phase of the laurentide ice sheet during the early holocene based on extensive airgun and high resolution seismic surveys sediment deposits are subdivided into thirteen units that are associated with glacial paraglacial and postglacial styles of deposition their distribution patterns reflect paleo positions of a retreating ice margin during the period between 10 000 and 9000 years before present formation of paraglacial deltas during the early to mid holocene 6 9 ka and postglacial tidal influenced deposition during the late holocene

neodymium isotopes in planktonic foraminifera a record of the response of continental weathering and ocean circulation rates to climate change the neodymium nd isotope composition of ancient seawater is a potentially useful tracer of changes in continental inputs and ocean circulation on timescales of a few ka here we present the first nd isotope record for seawater using sedimentary foraminifera cleaned using standard oxidative reductive techniques the data along with mn ca ratios suggest that cleaned foraminifera provide a reliable record of nd in seawater and hold out the prospect of using nd in foraminifera to examine changes in seawater that accompany glacial interglacial climatic cycles the principal potential problem to be overcome with the use of forams as records of trace elements in ancient seawater is their diagenetic fe mn coatings these contain large amounts of nd and other trace elements but can be cleaned off using highly reducing reagents mn ca ratios for the majority of the cleaned sedimentary foraminifera analysed here lie within the range 10 100 mol mol that has yielded success in studies of transition elements in forams mass balance modelling suggests that for residual mn ca ratios 100 mol mol nd added to the foram in the coating will never shift the measured nd isotope composition significantly away from the seawater value acquired by the foram test in the water column additionally nd concentrations measured in cleaned sedimentary foraminifera are comparable with those for a modern sample that has never encountered diagenetic fluids finally core top planktonic foraminifera for two sites have nd isotope compositions that are identical to local surface seawater the data we present here for labrador sea forams over the past 2 5 m y are interpreted in terms of changes in the seawater isotopic composition the data show a pronounced shift from end values of 12 to 19 in the period 2 5 1 5 ma this change is interpreted to result from the initiation of northern hemisphere glaciation and the increased derivation of labrador sea nd via ice rafting from archaean terranes in central canada in combination with stable isotope and foraminiferal relative species abundance data the new nd data are consistent with the surface hydrography of the labrador sea being dominated by a fluctuating balance between cold polar waters containing unradiogenic nd and warm subtropical waters containing more radiogenic nd the major change in labrador sea nd that is observed in the past 2 5 ma can on its own account for the change in the nd isotope composition of north atlantic deep water over the same time period

aureole deformation by flattening around a diapir during in situ ballooning the cannibal creek granite the cannibal creek granite a foliated pluton within a strongly deformed aureole shows several diagnostic features of a diapir the intensity of the aureole deformation diminished away from the contact the aureole foliation is continuous with that of the granite and forms closed elliptical trend lines and the contact metamorphic minerals are synkinematic with regard to the aureole foliation the pluton deformed its aureole in three stages involving initially brittle then ductile and finally brittle deformation styles initial intrusion of a low strength magma stoped kinked and flexed aside its overburden crystallization of the magma prevented further rise and it ballooned and deformed its aureole evidently entirely by ductile bulk shortening perpendicular to the contact this the major stage of aureole deformation records no evidence of vertical movement of the pluton or of progressive simple shear along its margin during this stage the magma may have been theologically a high strength bing

palaeocene eocene paratropical floral change in north america responses to climate change and plant immigration the initial eocene thermal maximum ietm at c 55 ma represents a period of rapid global warming that lasted less than 200 ka the response of vegetation to such an event and particularly warm adapted highly diverse vegetation types is poorly understood using pollen floral clay mineral and stable carbon isotope analyses of sediments from the upper tuscahoma formation on the eastern us gulf coast eastern mississippi and western alabama we document paratropical floral changes across the palaeocene eocene boundary from the wahalak 2 and lower harrell cores data indicate strong changes in the abundance of kaolinite that correlate with changes in relative abundance of native pollen taxa there is no evidence for a transient extra tropical flora on the us gulf coast that may characterize the ietm immigration and extinction are not associated with this event instead early eocene plant immigration occurs in pulses and therefore is not associated directly with climate change during the ietm the two cores share the same regional species pool but compositional differences are stronger between cores than they are either through changes in environment increased soil erosion or chemical weathering or through the introduction of non native plants our data suggest that vegetation change across the palaeocene eocene boundary is not a single event but rather a sequence of cascading events

late quaternary chronostratigraphic framework of deep baffin bay glaciomarine sediments from high resolution paleomagnetic data 1 the late quaternary baffin bay sediments provide exclusive records of greenland innuitian and laurentide ice sheet margin activities as well as information about the arctic and northern atlantic ocean linkages through the canadian arctic archipelago because of specific oceanographic conditions foraminiferal 18o stratigraphies and radiocarbon ages fail to provide reliable chronologies here we propose an original chronostratigraphy spanning the last glacial cycle based on high resolution paleomagnetic investigations on a 741 cm long core hu2008 029 016pc raised from the deep central baffin bay near odp site 645 two major difficulties were encountered 1 the high frequency occurrence of rapidly deposited layers related to short ice sheet margin events e g ice surges and 2 the magnetic grain size variability physical and magnetic mineralogical properties were used to screen out unreliable magnetic sediment layers the obtained relative paleointensity rpi proxy matches reference paleomagnetic stacks and regional records moreover the resulting record depicts two major excursions which were assigned to the laschamp and the norwegian greenland sea events it has thus been possible to derive a robust 115 ka chronology for the cored sequence we concluded that even under such a dynamic sedimentary regime magnetic properties of the sediments can provide a reliable chronostratigraphy together with information on sedimentary processes

late quaternary stratigraphy and paleoecology of northwest labrador sea abstract sedimentological study of 20 piston cores from the northwestern labrador sea shows that thin bedded distal turbidites are important constituents of the quaternary strata on the continental slope and rise sedimentation on the outer shelf ca 500 900 m is dominated by ice rafting and hemipelagic deposition detailed study of two outer shelf cores reveals a stratigraphic record extending to oxygen isotopic stage 9 studies of foraminifera and dinoflagellates show that subarctic surface waters penetrated into the northern labrador sea during the early middle glacial stages and pollen data indicate that northward advection of warm air masses occurred at the same time microfossil data indicate that late glacial stages were characterized by year around sea ice cover and arctic surface water and by the dominance of cold dry arctic air masses transitions from glacial to interglacial stages are marked by the presence of low salinity melt water these data support models which postulate that open water in the labrador sea played an important role in supplying moisture to laurentide and greenland ice sheets

surface sediment dinoflagellate cysts from the hudson bay system and their relation to freshwater and nutrient cycling abstract surface sediment samples from the hudson bay system were analysed in order to examine the role of key regulators of arctic marine productivity light and nutrients as affected by freshwater stratification and sea ice cover on the spatial distribution and production of dinoflagellate cysts total cyst fluxes vary from 0 2 10 6 to 30 6 10 6 cysts m 2 a 1 with the highest values observed in eastern hudson bay a total of 24 cyst taxa representing 11 genera of five orders were identified and distribution maps of the most common taxa have been produced this is the first record of echinidinium aculeatum echinidinium karaense cf echinidinium delicatum islandinium brevispinosum selenopemphix quanta cysts of protoperidinium americanum cysts of cf biecheleria sp and polarella glacialis in the hudson bay system dinoflagellate cyst assemblages show distinct spatial patterns revealing three compositional domains eastern hudson bay western central hudson bay and hudson strait the eastern domain is characterised by a dominance of autotrophic cysts of pentapharsodinium dalei whereas the western central domain is characterised by autotrophic operculodinium centrocarpum with some contribution by heterotrophic polykrikos sp var arctic morphotype and polykrikos spp sites from hudson strait are distinguished by an overwhelming prevalence of heterotrophic protoperidiniaceae cysts mainly islandinium minutum and have the highest values of sedimentary biogenic silica used as a proxy for diatom productivity sediment geochemical tracers are used as proxies for freshwater inputs lignin and its biomarkers and nitrate availability nitrogen isotopes and sea ice concentrations derived from passive microwave data as a proxy for light availability sea ice regulated length of the dark season has a negligible influence on the proportion and production of heterotrophic dark adapted versus autotrophic light dependent dinoflagellate cysts perhaps due to the location of our study area on the southern fringe of the arctic instead cyst populations in hudson bay are primarily regulated by vertical stratification and nitrate availability while in hudson strait the pivotal mechanism constitutes food availability

pliocene paleoclimatic reconstruction using dinoflagellate cysts comparison of methods the application of quantitative and semiquantitative methods to assemblage data from dinoflagellate cysts shows potential for interpreting past environments both in terms of paleotemperature estimates and in recognizing water masses and circulation patterns estimates of winter sea surface temperature wsst were produced by using the impagidinium index ii method and by applying a winter temperature transfer function tfw estimates of summer sea surface temperature ssst were produced by using a summer temperature transfer function tfs two methods based on a temperature distribution chart act and actpo and a method based on the ratio of gonyaulacoid protoperidinioid specimens g p wsst estimates from the ii and tfw methods are in close agreement except where impagidinium species are sparse ssst estimates from tfs are more variable the value of the g p ratio for the pliocene data in this paper is limited by the apparent sparsity of protoperidinioids which results in monotonous ssst estimates of 14 26 c the act methods show two biases for the pliocene data set taxonomic substitution may force matches yielding incorrect temperature estimates and the method is highly sensitive to the end points of species distributions dinocyst assemblage data were applied to reconstruct pliocene sea surface temperatures between 3 5 2 5 ma from dsdp hole 552a and odp holes 646b and 642b which are presently located beneath cold and cool temperate waters north of 56 n our initial results suggest that at 3 0 ma wssts were a few degrees c warmer than the present and that there was a somewhat reduced north south temperature gradient for all three sites it is likely that sssts were also warmer but by an unknown perhaps large amount past oceanic circulation in the north atlantic was probably different from the present

the genesis ascent and emplacement of the northern arran granite scotland implications for granitic diapirism integrated structural and petrological data are used to trace the evolution of the northern arran coarse granite during the latter stages of its ascent and its emplacement structural analysis of the aureole of the granite suggests that it rose as a single body of magma which is confirmed by petrological data during its ascent the pluton intersected the downward dipping limb of an existing synform refolding and displacing it upward to form a concentric or rim synform this direct evidence of vertical displacement of the country rocks confirms that the pluton is a diapir diapiric ascent was permitted by a reduction in wall rock viscosity and hence viscous drag forces on the pluton aided by heat loss due to crystallization during ascent most of the deformation within the aureole can be attributed to ascent of the pluton the early rim synform is overprinted by flattening strains and faulting caused by in situ radial expansion which represents the ultimate evolution of a diapiric body the final shape of the pluton is determined by inhomogeneous deformation of the aureole which is partly controlled by pre existing faults

multivariate analysis and quantitative paleoecology of benthic foraminifera in surface and late quaternary shelf sediments northern canada abstract benthic foraminifera in surface sediments from northeastern canada and the beaufort shelf were studied to determine the quantitative relationship between recent assemblage distributions and modern water depth temperature and salinity factor analysis shows that 7 factor assemblages account for 92 of the variance between samples multiple linear regression shows that different factors are significantly related to water depth august bottom water temperature or salinity multiple correlation coefficients for depth temperature and salinity are 0 94 0 72 and 0 92 respectively labrador fjords contain arenaceous faunas dominated by eithersaccammina atlantica andreophax fusiformis or byeggerella advena regression analysis shows that thesaccammina reophax factor is most strongly related to salinity theeggerella factor is related to depth and temperature a fauna dominated bytrochammina nana andbuliminella elegantissima is correlated with warm deep water in davis strait calcareous assemblages dominated byelphidium excavatum orcassidulina reniforme are found in arctic bays and shelf areas these factor assemblages are strongly related to temperature and depth cassidulina is also related to salinity anislandiella helenae fauna on the inner labrador shelf is strongly correlated with depth and salinity anonionellina labradorica fauna in deep shelf basins is closely related to salinity the multiple regression model for the sea bed data estimates water depth august bottom water temperature and salinity within confidence limits of 67 m 1 3 c and 1 0 paleoecological transfer functions were used to quantify environmental changes recorded by the foraminifera in two piston cores on a transect across the labrador shelf paleo depth estimates obtained from the core data produce relative sea level curves which are similar in shape to theoretical curves for this region paleo salinity and temperature estimates for offshore core 12 show that the change from a postglacialnonionellina fauna to a late glaciale excavatum fauna is accompanied by a decrease of about 2 in salinity and 4 c in temperature paleoecological estimates for fjord core 111 show that the change from a modernsaccammina reophax fauna to a mid holocenei helenae fauna corresponds to a salinity increase of 3 5 and temperature increase of 1 2 c

short term fluctuations in vegetation and phytoplankton during the middle eocene greenhouse climate a 640 kyr record from the messel oil shale germany the palaeogene was the most recent greenhouse period on earth especially for the late palaeocene and early eocene several superimposed short term hyperthermal events have been described including extremes such as the palaeocene eocene thermal maximum major faunal and floral turnovers in the marine and terrestrial realms were recorded in association with these events high resolution palynological analysis of the early middle eocene maar lake sediments at messel near darmstadt germany provides an insight into the dynamics of a climax vegetation during the middle eocene greenhouse climate in a time span without significant climatic excursions numerical techniques like detrended correspondence analysis and wavelet analysis have been applied to recognize cyclic fluctuations and long term trends in the vegetation through a time interval of approximately 640 kyr based on the numerical zoning of the pollen diagram three phases in the development of the vegetation may be distinguished throughout these phases the climax vegetation did not change substantially in qualitative composition but a trend towards noticeably less humid conditions probably in combination with a drop of the water level in the lake may be recognized a shift in algal population from the freshwater dinoflagellate cyst messelodinium thielepfeifferae to a dominance of botryococcus in the uppermost part of the core is interpreted as a response to changes in acidity and nutrient availability within the lake time series analyses of pollen assemblages show that variations in the milankovitch range of eccentricity obliquity and precession can be distinguished in addition fluctuations in the sub milankovitch range are indicated this demonstrates that floral changes during steady depositional conditions in the middle eocene of messel were controlled by orbital forcing

late quaternary pollen transport processes western north atlantic data from box models cross margin and n s transects abstract surface pollen assemblages in coastal and neritic sediments of the western north atlantic compare well with eastern north american vegetation zones and late quaternary pollen in marginal marine sediments clearly correlate with changes in terrestrial vegetation and paleoclimates in contrast offshore assemblages are strongly affected by differential adaptation of pollen to long distance transport by wind and water marine pollen transport processes were studied by measuring air and water inputs to a coast shelf box model and by study of surface samples from cross margin transects in three different climatic and oceanographic regions at approximately 38 45 and 55 n latitude the box model shows that aerial transport is the main process by which pollen moves across the continental margin off nova scotia two clear seabed distribution patterns were found betula quercus and herb pollen decrease rapidly offshore in abundance grains per cubic centimetre and in relative abundance percentage pinus and picea have abundance peaks on the continental margin but percentages increase further offshore distributions of the main pollen and spore taxa were compared for late wisconsinan glacial oxygen isotopic stage 2 12 28 ka terminal pleistocene 10 12 ka and holocene sediments at 5 continental margin and 3 deep sea sites the largest changes were found in percentages of pinus picea and herb pollen during the late wisconsinan glacial and terminal pleistocene intervals at subpolar latitudes these data can be related to shifts in paleo vegetation winds and hydrology that accompany global climate change

paleoenvironments of the last interglacial in northwest north atlantic region and adjacent mainland canada abstract the paleoenvironmental conditions that prevailed in the northwest north atlantic regions and adjacent mainland canada during the last interglacial are documented through lithostratigraphical and paleontological data in terrestrial sections and marine cores with special reference to the deep sea records that allow global correlations based on their isotopic stratigraphy the onshore paleovegetational data and the offshore planktonic faunal and algal records demonstrate much warmer than present terrestrial and marine environments during the climate optimum of the last interglacial sensu stricto isotopic substage 5e optimal conditions persisted in surface water of the labrador sea during the early glacial inception isotopic substage 5e 5d transition when extensive ice masses developed over arctic canada a deterioration of sea surface temperature in labrador sea followed the maximum 18 o peak of isotopic substage 5d during the later part of stage 5 climatic conditions similar to the present prevailed over southeastern canada and a recurrent warming is recorded in south central labrador sea fluctuating ice volumes in the canadian arctic led to episodic dilution of surface water masses in baffin bay and the eastern labrador sea and subarctic conditions apparently prevailed in nearshore environments of baffin island despite an ice marginal context

re examining pluton emplacement processes discussion in a recent review paterson fowler 1993 showed decreasing away from the pluton as discussed by gughow estimated volumes of displaced wall rock are lielmo 1993b smaller than pluton volumes and how the widths of laboratory experiments indicate that rocks behave as strain aureoles around natural plutons are considerably power law fluids with exponents n between 2 5 and 5 narrower than in models of diapirs where spheres rise hansen carter 1982 kirby 1983 wilks carter through newtonian fluids cruden 1988 schmeling et 1990 the power law exponent n of a viscous fluid is a al 1988 they then argued that mechanisms other than measure of the sensitivity of its viscosity stress or ductile flow of the wall rocks were necessary to account strain role for n 1 newtonian fluid the viscosity is for these observations although i accept that several constant for any strain rate for n 1 the fluid softens mechanisms may act simultaneously and change in imwith increased strain rate the strain rate dependency of portance as plutons are emplaced i argue here that i the viscosity of power law fluids has important effects on the displaced volumes of wall rocks may be underestithe velocity and flow patterns of the ambient fluid mated because of difficulties in assessing the shape and around rising spheres or diapirs and therefore the size of the three dimensional flow cell in the wall rocks width of their strain aureoles crochet et al 1984 caused by pluton emplacement and more importantly kawase moo young 1986 weinberg podladchikov ii the narrow strain aureoles may result from diapiric in press in the following discussion the difficulties in rise of plutons through power law rocks and or result determining the volumes of rock displaced by diapir from the effects of thermal softening of the wall rocks emplacement are first considered the effect which several field studies have measured the width of the power law rocks might have on the width of the strain strain aureole caused by pluton emplacement see gugaureole is then discussed and finally the possible effects lielmo 1993a paterson fowler 1993 and references of thermal softening of the wall rocks by the diapir are therein the measured width depends on three main examined factors i the finite strain of the wall rocks which depends on the velocity field imposed by the diapir this in turn depends on the diapir s mechanism and depth of rock volumes displaced by diapirs emplacement and on the rheology and physical boundaries of its wall rocks the longer a rock volume is paterson fowler 1993 studied horizontal shortensubmitted to a particular strain rate velocity field the ing in strain aureoles around plutons and then integrated larger is its strain the velocity of flow decreases with shortening to three dimensions around plutons of differdistance from the contact of rising spheres so that ent shapes the amount of shortening they obtained for strains have to accumulate a long time to be distinguishseveral natural examples only accounted for about 30 able from any background strain ii late deformation of the volume of the plutons they argued that this will mask the strain aureoles of pre tectonic plutons volume difference implies that other mechanisms such while interference with regional tectonic strains will as doming of the roof stoping assimilation and rigid affect the width of the aureoles of syn tectonic plutons translation of wall rock must have operated at the same guglielmo 1993b iii the measurable width of the time as viscous flow of the wall rock aureole depends on distinguishing the strain due to the however this discrepancy may largely be due to pluton from regional strains of any age paterson difficulties in measuring small pluton related strains fowler 1993 this distinction becomes increasingly beyond the obvious strain aureole and difficulties in more difficult as strains are spread over larger volumes determining the shape of the flow cell around the pluton the width of the strain aureole around a rising sphere depends on the power law exponent n of the country current address research school of earth sciences anu act rocks it is widest in newtonian fluids and narrows as n 6200 canberra australia increases however even in the case of rocks with high n

an early eocene sphagnum bog at schoningen northern germany a thin local seam in the early eocene lignite succession of the opencast mine schoningen sudfeld lower saxony northern germany revealed pollen and spore assemblages of low diversity they are characterized by an abundance of sphagnum type spores especially tripunctisporis and fern and lycopod spores together with the common occurrence of pollen of ericaceae restionaceae and droseraceae well preserved fragments of sphagnum leaves are common and loricae of habrotrocha like bdelloid rotifers have been recorded occasionally we reconstruct an ombrogenous domed peat bog maintained by prolific growth of sphagnum in association with a rich fern cover oligotrophic and acidophilic plants as well as insectivorous plants indicating severe nutrient deficiency this resembles in many respects an eocene equivalent of a quaternary high latitude sphagnum bog in view of the significant amount of restionaceae pollen however it appears more similar to southern hemisphere restionad bogs the total lack of a waterlogged layer in the highly permeable substrate strongly argues in favour of a purely rain fed ombrogenous peat bog the required high precipitation in combination with frequent wildfires as evidenced by the abundance of charcoal however suggests a highly stressed hydrological cycle under an alternating wet dry climate close to the alleged early eocene climatic optimum eeco

elements d une climatostratigraphie du pleistocene moyen et tardif dans l est du canada par l analyse palynologique et isotopique du forage 84 030 003 mer du labrador the piston and gravity cores 84 030 003 collected in the southern labrador sea have been sampled for detailed palynological and isotopic analyses the 18o record on foraminifera neogloboquadrina pachyderma left coiling indicates a stratigraphy spanning isotopic stages 8 to 1 i e over ca 300 000 years the isotopic record allows the calculation of a mean sedimentation rate of approximately 5 cm ka the pollen and spore contents of the sediments are low the low pollen influxes generally less than 1 grain cm2 per year and the dominance of pinus suggest aeolian transport over long distances with southwest northeast to south southwest north northeast trends dinoflagellate cyst concentrations are relatively low indicating a low regional phytoplanktonic productivity the assemblages are however diversified they reflect influences from the north atlantic drift and from the labrador current the occurrence of warm temperate to tropical impagidinium species in deposits suggests an almost permanent

controls on sedimentation and vegetation in an eocene pull apart basin prinz von hessen germany evidence from palynology tectonically controlled lakes may experience a complex history of deposition and subsidence which can influence their ecology and environment to correlate controls on sedimentation with changes in vegetation within a small pull apart basin at grube prinz von hessen hessen germany during paleogene greenhouse conditions 47 core samples were analysed palynologically the lower eocene succession includes 34 m of clastic sediments overlain by 54 m of massive mudstone finely laminated bituminous claystone and lignite a fluvial lacustrine and a profundal deep lake facies association are distinguished statistical analysis of the diverse and well preserved palynoflora reveals five distinct associations throughout the sedimentary record there is a strong correlation between major changes in vegetation and lithology which were controlled mainly by changes in humidity together with tectonic activity which led to lake basin subsidence and a rise in lake level based on the association of pollen and spores which are typical for the lower eocene it can be shown that the basin is older than previously assumed supplementary material a complete list of variables and palynomorphs used for pollen diagrams and statistical analyses as well as their abundance percentages is available at https doi org 10 6084 m9 figshare c 4108016

stratigraphic classification of ancient lakes balancing tectonic and climatic controls lakes and lake deposits present two fundamental paradoxes 1 modern lakes are vastly complicated but the rock records of lakes are relatively simple extensive observations reveal three distinct facies associations of common and widespread occurrence these are referred to here as fluvial lacustrine fluctuating profundal and evaporative facies associations 2 most explanations of modern and ancient lakes attribute their nature to climate but neither modern lake parameters lake size depth and salinity nor the character of ancient lake strata thickness extent lithology correlate with measured or inferred climatic humidity we propose that it is the relative balance of rates of potential accommodation mostly tectonic with sediment water fill mostly a function of climate that controls lake occurrence distribution and character lake basins may be termed overfilled balanced fill or underfilled depending on the balance between these rates we conclude that climate and tectonics exert coequal influence on lake deposits at both mesoscales 1 m to hundreds of meters and macroscales hundreds to thousands of meters

upper cenozoic history of the labrador sea baffin bay and the arctic ocean a paleoclimatic and paleoceanographic summary foraminifera palynomorphs and stable isotopes in planktonic foraminifera have been studied in piston cores from the northern labrador sea southern baffin bay and the alpha ridge region of the central arctic ocean foraminifera in cores from the labrador sea and southern baffin bay show glacial interglacial 18o values similar to those reported from the norwegian and greenland seas in contrast to the eastern north atlantic ocean however peaks of subarctic foraminifera and dinoflagellates in the western north atlantic cores show that relatively warm atlantic surface water continued to flow into the northern labrador sea during the early glaciation growth phases of isotopic stages 2 4 6 and 8 boreal and subarctic pollen suggest that warm atlantic air flowed into the northern labrador sea and baffin bay during the ice sheet growth phases the advection of warm air masses and the presence of open waters during the summer probably provided moisture for the growth of the laurentide innuitian and greenland ice sheets isotopic and microfossil records in arctic cores can also be tentatively correlated with major high latitude north atlantic glacial interglacial events magnetostratigraphic palynological and amino acid dating however shows that sedimentation on the alpha ridge has been very slow during the past 0 73 m y therefore events of less than 20 000 years duration cannot be clearly discerned interpretation of pre pleistocene paleoenvironments is further limited by the sparseness of calcareous and siliceous microfossils

palaeoclimate of baffin bay from 300 000 year record of foraminifera dinoflagellates and pollen several different models1 5 have attempted to relate quaternary marine and terrestrial records of ice sheet growth in the north atlantic region the models are derived from either discontinuous terrestrial records including marine fossils in raised shorelines1 2 or from deep sea calcareous microfossils3 4 this study correlates arctic marine and terrestrial data directly by comparing 18o foraminiferal dinoflagellate and pollen records from a core taken in baffin bay the core contains an almost continuous sequence of sediments deposited during isotope stages 1 10 subarctic foraminifera and atlantic dinoflagellates in early isotope stages 2 4 6 and 8 show that subarctic water entered southern baffin bay before the glacial maxima boreal subarctic pollen suggest that atlantic air flowed into baffin bay during the ice sheet growth phases these data support models which postulate that open water in the labrador sea had an important role in supplying moisture to laurentide and greenland ice sheets

report of 1st discussion group the last interglacial in high latitudes of the northern hemisphere terrestrial and marine evidence abstract the paleoclimatic informations preserved at some selected sites from high northern latitudes correlative with the last interglacial maximum of isotopic substage 5e have been compiled on a hemisphere scale the mapped compilation reveals much warmer climate conditions on average than present in both terrestrial and marine environments and indicates a northward shift of subpolar and boreal bioclimatic zones the data also suggest that temperature and precipitation gradients were significantly different than those of the holocene with particularly efficient latitudinal and eastward transport of warm air masses the paleoenvironmental and paleoclimate trends through the last interglacial sensu lato isotopic stage 5 are more difficult to assess because the chronostratigraphical framework is poorly constrained nevertheless the data suggest important regionalism in the climatostratigraphical trends in particular the large amplitude climatic cyclicity that characterizes the last interglacial of europe is barely observed elsewhere moreover by the end of the last interglacial isotopic substage 5a conditions slightly cooler than present are recorded in western europe while relatively warm conditions similar to today apparently prevailed in circumpolar regions adjacent to the north atlantic despite the onset of ice growth the last interglacial provides paleosynoptic situations unlike those of the present that may contribute to understanding interactions within the environmental system on a hemispheric scale there is however an imperative need for uniformization of data sets and for more accurate chronological control on regional scales

land ocean correlations during the last interglacial glacial transition baffin bay northwestern north atlantic a review abstract evidence from terrestrial sections ice cores and marine cores are reviewed and used to develop a scenario for environmental change in the area of the extreme northwest north atlantic during marine isotope stages 5 and 4 the critical physical link between the landbased glacial chronology and marine events in baffin bay is the presence of carbonate rich drift along the baffin bay coast of bylot island and a detrital carbonate facies facies b in baffin bay sediments cores from baffin bay labrador sea can be dated by means of oxygen isotope variations and by peaks in the abundance of volcanic glass shards one occurrence of facies b is dated between late stage 5 and stage 4 and we correlate this event with the eclipse glaciation of bylot island and the ayr lake stade of the foxe glaciation of baffin island kogalu aminozone in contrast on west greenland amino acid racemization evidence suggests that the greenland ice sheet developed throughout stage 4 and reached a maximum in stage 3 svartenhuk advance 40 ka the oxygen isotope record in the devon island ice cap northwest baffin bay indicates that baffin bay was largely open during marine isotope stage 5 analyses of shallow water molluscan and foraminiferal assemblages deep water foraminifera pollen from iand sections and deep sea cores and dinoflagellates from marine cores indicate that interglacial conditions prevailed during much of the stage 5 4 glaciation

re examining pluton emplacement processes abstract previous pluton emplacement studies have attempted to explain how space is made during pluton emplacement in fact the only means of making space during emplacement of mantle derived magmas in the crust are 1 lowering the moho or 2 outward displacement of the earth s surface other pluton emplacement mechanisms are material transfer processes mtps that do not increase the volume of the crust one frequently cited mtp for emplacement of concentrically zoned and ballooning plutons is ductile flow of wall rocks around the plutons the expected structures and total strains near such plutons are dependent on the three dimensional pluton shape the width of the deforming aureole whether the pluton is a piercing or non piercing diapir and in the latter case the number of body radii the pluton travels we have re examined a few such plutons and calculated the amount of material transfer caused by ductile flow in no case is more than 40 and in most cases only 15 35 of the required material transfer accommodated by wall rock flow the contact aureoles around these plutons are too narrow and or strains too low indicating that the plutons are predominantly discordant bodies with narrow 0 1 0 4 pluton radii concordant aureoles a comparison of strains in natural contact aureoles and those made in mechanical models of diapirs indicates that natural strains are at least an order of magnitude less than model strains we suggest that the similarities between models of diapiric ascent of spherical bodies and concentrically zoned plutons are superficial because the models are too simplistic instead we argue that the ascent and emplacement of magmas require multiple near field and far field mtps these mtps will show gradients with depth distance from the magma and with time rates of near field mtps must be rapid whereas far field rates are probably nearer to long term average rates of orogenic processes

geochemical and palynological sea level proxies in hemipelagic sediments a critical assessment from the upper cretaceous of the czech republic geochemical and palynological records are presented for an expanded turonian coniacian hemipelagic succession in the central bohemian cretaceous basin a high resolution stratigraphic framework is provided by biostratigraphy and organic carbon stable isotope 13corg chemostratigraphy a short term 100 kyr sea level curve has been derived from high resolution transgressive regressive maxima shore proximity data established from basin wide sediment geometries the viability of geochemical and palynological parameters as potential sea level proxies is tested against this independently derived sea level record elemental chemostratigraphy is demonstrated to offer a reliable means of identifying medium to long term 0 4 2 4 myr sea level trends manganese maxima are associated with periods of high sea level and troughs with intervals of low sea level falling mn contents accompany regression and rising values transgression major transgressive events associated with medium term sea level change are marked by sharp increases in ti al ratios but short term 100 kyr sea level cycles are not consistently identified long term 13corg variation and dinoflagellate cyst species richness are positively correlated and show similarities to the sea level curve baseline trends have a cycle duration close to the 2 4 myr long eccentricity cycle dinocyst species richness closely follows short term changes in sea level with marked increases in dinocyst diversity coincident with most short term flooding events periods of rapid sea level rise caused an influx of a more diverse outer shelf assemblage into the study area together with the addition of shallower water species some of which may have been transported into the central basin by hypopycnal flows changes in the proportion and abundance of peridinioid dinoflagellate cysts principally palaeohystrichophora infusorioides were controlled principally by changing nutrient levels proximity proxies derived from geochemical and palynological data are not always consistent with the independent sea level model this exemplifies the need to understand all factors influencing elemental geochemical and palynological proxies before making simplistic sea level interpretations