from greenhouse to icehouse organic walled dinoflagellate cysts as paleoenvironmental indicators in the paleogene abstract dinoflagellates are an important component of the extant eukaryotic plankton their organic walled hypnozygotic cysts dinocysts provide a rich albeit incomplete history of the group in ancient sediments building on pioneering studies of the late 1970s and 1980s recent drilling in the southern ocean has provided a wealth of new dinocyst data spanning the entire paleogene such multidisciplinary studies have been instrumental in refining existing and furnishing new concepts of paleogene paleoenvironmental and paleoclimatic reconstructions by means of dinocysts because dinocysts notably exhibit high abundances in neritic settings dinocyst based environmental and paleoclimatic information is important and complementary to the data derived from typically more offshore groups as planktonic foraminifera coccolithophorids diatoms and radiolaria by presenting case studies from around the globe this contribution provides a concise review of our present understanding of the paleoenvironmental significance of dinocysts in the paleogene 65 25 ma representing earth s greenhouse icehouse transition this episode holds the key to the understanding of extreme transient climatic change we discuss the potential of dinocysts for the reconstruction of paleogene sea surface productivity temperature salinity stratification and paleo oxygenation along with their application in sequence stratigraphy oceanic circulation and general watermass reconstructions

dinoflagellate cysts and mid oligocene chronostratigraphy in the central mediterranean region two new dinoflagellate cyst zones are proposed linking previously established zonal schemes for the eocene oligocene and oligocene miocene successions in the central mediterranean region the hystrichokolpoma pusillum hpu and chiropteridium lobospinosum clo interval zones are based on the contessa quarry and monte cagnero sections central italy and are correlated with previously established magnetostratigraphical and biostratigraphical schemes the base of the chattian is considered to correlate with chron cl0n in central italy the most distinct dinoflagellate cyst event associated with this chron is the first occurrence of distatodinium biffii marking the base of the distatodinium biffii dbi zone indirect evidence also suggests that the first occurrence of distatodinium biffii is above but close to the base of the chattian stage in its type area in northwest germany thus making it an important marker other possible markers for the base of the chattian are the last occurrence of areosphaeridium pectiniforme and the lowest acme of chiropteridium spp the latter may be related to the major mid oligocene sea level fall ta tb exxon supercycle boundary also considered to represent the base of the chattian and previously correlated with chron cl0n however in the contessa quarry section this dinoflagellate cyst event is associated with the older chron c11

late eocene to early oligocene dinoflagellate cysts from the priabonian type area northeast italy biostratigraphy and paleoenvironmental interpretation abstract marginal marine late eocene through early oligocene dinoflagellate cyst successions have been studied from the type area of the priabonian stage northeast italy the results allow the recognition of dinoflagellate zones previously defined in bio and magnetostratigraphically well calibrated pelagic sequences from central italy thus providing a first order correlation of the priabonian stage to the standard chronostratigraphic scale with unprecedented precision within this detailed biostratigraphic framework successive shifts in the composition of the dinoflagellate cyst assemblages are interpreted in terms of sea level and sea surface temperature sst fluctuations the evaluation of ecologically and sedimentary controlled changes in the composition of dinoflagellate cyst assemblages in combination with sequence stratigraphic analysis allows the reconstruction of third and fourth order sea level fluctuations the third order sea level fluctuations appear to correspond to exxon cycles ta4 1 4 5 the stratigraphically and palaeoenvironmentally important late eocene dinoflagellate cyst species glaphyrocysta priabonensis sp nov is formally described

radiocarbon chronology of the neolithic sites from the boreal zone of european russia and environmental changes based on the last proxy data this article discusses the possible correlation of the neolithisation of western europe with the environmental changes the database of the neolithic sites developed by the radiocarbon laboratory of the institute for history of material culture has been used in the assessment of the frequency of radiocarbon dated sites various isotopic methods have been used for the estimation of holocene environmental changes the comparative analysis reveals the correlation of maxima and minima in the distribution of radiocarbon dated sites with the fluctuations of lake level solar and cosmic ray activities oxygen isotopes and other environmental records

a glaciochemical survey of the summit region greenland spatial representativene ss and an understanding of controls on chemical species distribution are essential requirements of any significant ice core investigation snowpit studies provide an essential tool in this process in preparation for the central greenland deep drilling effort a series of snowpits was sampled in detail for oxygen isotopes major anions major cations total acidity and radionuclides the results of this sampling program are used to define 1 the chemical composition of the snow in the region 2 the input timing and spatial distribution of major chemical species 3 the potential dependence of

major features and forcing of high latitude northern hemisphere atmospheric circulation using a 110 000 year long glaciochemical series the greenland ice sheet project 2 glaciochemical series sodium potassium ammonium calcium magnesium sulfate nitrate and chloride provides a unique view of the chemistry of the atmosphere and the history of atmospheric circulation over both the high latitudes and mid low latitudes of the northern hemisphere interpretation of this record reveals a diverse array of environmental signatures that include the documentation of anthropogenically derived pollutants volcanic and biomass burning events storminess over marine surfaces continental aridity and biogenic source strength plus information related to the controls on both high and low frequency climate events of the last 110 000 years climate forcings investigated include changes in insolation of the order of the major orbital cycles that control the long term behavior of atmospheric circulation patterns through changes in ice volume sea level events such as the heinrich events massive discharges of icebergs first identified in the marine record that are found to operate on a 6100 year cycle due largely to the lagged response of ice sheets to changes in insolation and consequent glacier dynamics and rapid climate change events massive reorganizations of atmospheric circulation that are demonstrated to operate on 1450 year cycles changes in insolation and associated positive feedbacks related to ice sheets may assist in explaining favorable time periods and controls on the amplitude of massive rapid climate change events explanation for the exact timing and global synchroneity of these events is however more complicated preliminary evidence points to possible solar variability climate associations for these events and perhaps others that are embedded in our ice core derived atmospheric circulation records

special speleothems in cement grouting tunnels and their implications of the atmospheric co2 sink based on the analyses and comparisons of water chemistry stable carbon isotopes and deposition rates of speleothems the authors found that there are two kinds of speleothems in the tunnels at the wujiangdu dam site guizhou china namely the co2 outgassing type and the co2 absorbing type the former is natural as observed in general karst caves and the product of karst processes under natural conditions the latter however is special resulting from the carbonation of a cement grouting curtain and concrete due to the quick absorption of co2 from the surrounding atmosphere evidenced by the low co2 content in the air and the high deposition rate of speleothems as high as 10 cm a in the tunnels the contribution of the carbonation process to the sink of co2 in the atmosphere is important in the order of magnitude of 108 tons c a and should be taken into consideration in the study of the global carbon cycle because of the use of cement on a worldwide scale

holocene climate variability as reflected by mid european lake level fluctuations and its probable impact on prehistoric human settlements abstract a data set of 180 radiocarbon tree ring and archaeological dates obtained from sediment sequences of 26 lakes in the jura mountains the northern french pre alps and the swiss plateau was used to construct a holocene mid european lake level record the dates do not indicate a random distribution over the holocene but form clusters suggesting an alternation of lower and higher climatically driven lake level phases they provide evidence of a rather unstable holocene climate punctuated by 15 phases of higher lake level 11 250 11 050 10 300 10 000 9550 9150 8300 8050 7550 7250 6350 5900 5650 5200 4850 4800 4150 3950 3500 3100 2750 2350 1800 1700 1300 1100 750 650 cal bp and after 1394 ad a comparison of this mid european lake level record with the gisp2 polar circulation index pci record the north atlantic ice rafting debris ird events and the 14 c record suggests teleconnections in a complex cryosphere ocean atmosphere system correlations between the gisp2 pci the mid european lake level the north atlantic ird and the residual 14 c records suggest that changes in the solar activity played a major role in holocene climate oscillations over the north atlantic area

major calcareous nannofossil and foraminiferal events between the middle eocene and early miocene abstract the more significant biostratigraphic events during the time interval from beginning middle eocene to beginning miocene with special emphasis on the eocene oligocene boundary are discussed the microfossils considered are calcareous nannofossils planktic foraminifera and smaller and larger benthic foraminifera areas taken into account include particularly the caribbean trinidad barbados dsdp south atlantic sections cape basin site 360 walvis ridge sites 362a 363 angola basin site 364 the equatorial north atlantic dsdp site 354 and the southern alps possagno in the larger foraminifera the treatment is somewhat different with selected families and genera being considered for their distribution in the eastern and western hemisphere

greenland ice core signal characteristics an expanded view of climate change the last millenium of earth history is of particular interest because it documents the environmental complexities of both natural variability and anthropogenic activity we have analyzed the major ions contained in the greenland ice sheet project 2 gisp 2 ice core from the present to 674 a d to yield an environmental reconstruction for this period that includes a description of nitrogen and sulfur cycling volcanic emissions sea salt and terrestrial influences we have adapted and extended mathematical procedures for extracting sporadic e g volcanic events secular trends and periodicities found in the data sets finally by not assuming that periodic components signals were stationary and by utilizing evolutionary spectral analysis we were able to reveal periodic processes in the climate system which change in frequency turn on and turn off with other climate transitions such as that between the little ice age and the medieval warm period

abrupt increase in greenland snow accumulation at the end of the younger dryas event the warming at the end of the last glaciation was characterized by a series of abrupt returns to glacial climate the best known of which is the younger dryas event1 despite much study of the causes of this event and the mechanisms by which it ended many questions remain unresolved1 oxygen isotope data from greenland ice cores2 4 suggest that the younger dryas ended abruptly over a period of about 50 years dust concentrations2 4 in these cores show an even more rapid transition 20 years this extremely short timescale places severe constraints on the mechanisms underlying the transition but dust concentrations can reflect subtle changes in atmospheric circulation which need not be associated with a large change in climate here we present results from a new greenland ice core gisp2 showing that snow accumulation doubled rapidly from the younger dryas event to the subsequent preboreal interval possibly in one to three years we also find that the accumulation rate change from the oldest dryas to the bo11ing allerod warm period was large and abrupt the extreme rapidity of these changes in a variable that directly represents regional climate implies that the events at the end of the last glaciation may have been responses to some kind of threshold or trigger in the north atlantic climate system

the flickering switch of late pleistocene climate change polar ice contains a unique record of past climate variations previous greenland ice cores have documented relatively warm interstadial periods during the last glaciation and short centuryscale returns to colder conditions during the glacial to interglacial warming see for example ref 1 these climate features have also been observed to varying degrees in ocean sediment cores2 4 and terrestrial pollen and insect records5 7 here we report electrical conductivity measurements from a new greenland ice core which confirm these previous observations and also reveal a hitherto unrecognized mode of rapid climate variation fluctuations in ice conductivity on the scales of 5 20 years reflect rapid oscillations in the dust content of the atmosphere this flickering between two preferred states would seem to require extremely rapid reorganizations in atmospheric circulation

late holocene variability of upper north atlantic deep water temperature and salinity 1 magnesium calcium ratios in benthic foraminifera cibicidoides pachyderma from a sediment core on the laurentian slope 1854 m exhibit strong millennial scale fluctuations during the past 4000 years we convert these data to seawater paleotemperatures using a new monospecific linear equation results suggest that the temperature of upper north atlantic deep water dominated by labrador seawater today has varied by at least 2 c during the late holocene millennial scale coolings coincide with previously identified periods of increased drift ice and regional glacier advances including the little ice age paired oxygen isotope measurements indicate that salinity and perhaps density were reduced during the cold periods we discuss possible mechanisms for transmitting this cold fresh signal from surface waters to intermediate depths our reconstructed late holocene ranges in upper north atlantic deep water properties greatly exceed those of the instrumental record and imply that large changes may be yet to come

differentiating glacio eustacy and tectonics a case study involving dinoflagellate cysts from the eocene oligocene transition of the pindos foreland basin nw greece in an attempt to discriminate between tectonically induced sea level changes and glacio eustacy the ekklissia and arakthos sections epirus nw greece are examined applying dinocyst palynology sedimentology and magnetostratigraphy the sections located in the pindos foreland basin both comprise the transition from pelagic limestones to hemipelagic silty clays and turbidite sandstones reflecting the onset of flysch sedimentation as a result of the pindos thrust activity despite an overall tectonic overprint relative changes of sea level can be reconstructed using i continental marine palynomorph ratios ii relative abundance of inshore and offshore dinoflagellate cysts and iii taxa indicative of relatively cold and warm sea surface temperature that can be calibrated against the global polarity time scale gpts increased fluxes of marginal marine and continental palynomorphs coincide with colder periods on a third order scale which thus appear to be related to glacio eustatic trends in sea level the larger scale is attributed to the increasing effect of tectonics and acts on a second order scale

comparison of oxygen isotope records from the gisp2 and grip greenland ice cores recent results1 2 from the greenland ice core project grip summit ice core suggest that the climate in greenland has been remarkably stable during the holocene but was extremely unstable for the time period represented by the rest of the core spanning the last two glaciations and the intervening eemian inter glacial here we present the complete oxygen isotope record for the greenland ice sheet project 2 gisp2 core drilled 28 km west of the grip core we observe large rapid climate fluctuations throughout the last glacial period which closely match those reported for the grip core however in the bottom 10 of the cores spanning the eemian interglacial and the previous glacia tion there are significant differences between the two records it is possible that ice flow may have altered the chronological sequences of the stratigraphy for the bottom part of one or both of the cores considerable further work will be necessary to evaluate the likelihood of this and the extent to which it will still be possible to extract meaningful climate information from the lowest sections of the cores

a new geomagnetic polarity time scale for the late cretaceous and cenozoic we have constructed a magnetic polarity time scale for the late cretaceous and cenozoic based on an analysis of marine magnetic profiles from the world s ocean basins this is the first time since heirtzler et al 1968 published their time scale that the relative widths of the magnetic polarity intervals for the entire late cretaceous and cenozoic have been systematically determined from magnetic profiles a composite geomagnetic polarity sequence was derived based primarily on data from the south atlantic anomaly spacings in the south atlantic were constrained by a combination of finite rotation poles and averages of stacked profiles fine scale information was derived from magnetic profiles on faster spreading ridges in the pacific and indian oceans and inserted into the south ariantic sequence based on the assumption that spreading rates in the south atlantic were smoothly varying but not necessarily constant a time scale was generated by using a spline function to fit a set of nine age calibration points

tropospheric rivers a one year record and a possible application to ice core data the morphology of tropospheric rivers has been examined for the period june 1991 may 1992 from atmospheric specific humidity and wind velocity data vertically integrated water vapor flux vectors are subjected to harmonic analysis and the high frequency components periods less than 3 days show large amplitude values in the north atlantic north pacific south atlantic south indian ocean and south pacific plus small amplitude occurrences in the red sea arabian sea region in the december february season in june august the latter is replaced with a large amplitude monsoon related region over south east asia maximum intensities increase slightly in altitude with latitude the correspondence between rivers frontal boundaries and storm tracks is noted sometimes rivers originating over the north pacific cross north america and reach greenland while at other times they pass polewards over the north atlantic raising the possibility that water vapor involved in ice core formation may have evaporated from surface water bodies with different temperature and salinity characteristics changes in oxygen isotope variations at a point may therefore reflect changes in the dynamics of tropospheric rivers in addition to local temperature changes

high resolution alkenone sea surface temperature variability on the north icelandic shelf implications for nordic seas palaeoclimatic development during the holocene the palaeoceanography of the northern icelandic shelf for the holocene period was reconstructed from alkenone indices measured in core jr51 gc35 this contains a continuous record of holocene sedimentation spanning 0 10 2 cal kyr bp with a resolution of 20 yr cm we have identified a general holocene cooling trend that has superimposed millennial scale oscillations of 28c their timing is in close agreement with the timing of glacier advances in northern iceland for the later half of the holocene the alkenone sea surface temperature sst record from jr51 gc35 correlates with proxy data for the strength of nadw formation recorded in cores south of iceland this is interpreted as evidence of a close connection existing between north icelandic sea surface temperatures and the north atlantic meridonal overturning circulation the timing of the millennial scale sst variability in our core off north iceland is found to be out of phase or anti phased with the sst variability of a record in the eastern nordic seas md952011 this suggests that the evolution of holocene climate in the nordic seas was more complex than previously proposed and it is likely to be caused by differential responses of the irminger and norwegian currents and modulated by changes in atmospheric circulation analogous to the north atlantic oscillation

integrated stratigraphy of the oligocene pelagic sequence in the umbria marche basin northeastern apennines italy a potential global stratotype section and point gssp for the rupelian chattian boundary the oligocene represents an important time period from a wide range of perspectives and includes significant climatic and eustatic variations the pelagic succession of the umbria marche apennines central italy includes a complete and continuous sequence of marly limestones and marls with volcaniclastic layers that enable us to construct an integrated stratigraphic framework for this time period we present here a synthesis of detailed biostratigraphic magnetostratigraphic and chemostratigraphic studies along with geochronologic results from several biotite rich volcaniclastic layers which provide the means for an accurate and precise radiometric calibration of the oligocene time scale from this study the interpolated ages for the rupelian chattian stage boundary located in the upper half of chron 10n at meter level 188 in the monte cagnero section and corresponding to the o4 o5 planktonic foraminiferal zonal boundary are 28 36 ma paleomagnetic interpolation 28 27 0 1 ma direct radioisotopic dating and 27 99 ma astrochronological interpolation these ages appear to be slightly younger than those reported in recent chronostratigraphic time scale compilations the monte cagnero section is a potential candidate for defining the chattian global stratotype section and point gssp and some reliable criteria are here proposed for marking the rupelian chattian boundary according to international union of geological sciences iugs recommendations

the chemical evolution of a travertine depositing stream geochemical processes and mass transfer reactions this field study focuses on quantitatively defining the chemical changes occurring in falling spring creek a travertine depositing stream located in alleghany county virginia the processes of co sub 2 outgassing and calcite precipitation or dissolution control the chemical evolution of the stream the observed chemical composition of the water was used with the computerized geochemical model wateqf to calculate aqueous speciation saturation indices and co sub 2 partial pressure values mass balance calculations were performed to obtain mass transfers of co sub 2 and calcite reaction times estimated from stream discharge were used with the mass transfer results to calculate rates of co sub 2 outgassing and calcite precipitation between consecutive sampling points the stream which is fed by a carbonate spring is supersaturated with respect to co sub 2 along the entire 5 2 km flow path outgassing of co sub 2 drives the solution to high degrees of supersaturation with respect to calcite metabolic uptake of co sub 2 by photosynthetic plants is insignificant because the high supply rate of dissolved carbon dioxide and the extreme agitation of the stream at waterfalls and rapids causes a much greater amount of inorganic co sub 2 outgassing to occur calcite precipitation is kinetically inhibited until near the crest of amore 20 m vertical waterfall calcite precipitation rates then reach a maximum at the waterfall where greater water turbulence allows the most rapid escape of co sub 2 physical evidence for calcite precipitation exists in the travertine deposits which are first observed immediately above the waterfall and extend for at least 1 0 km below the falls net calcite precipitation occurs at all times of the year but is greatest during low flow conditions in the summer and early fall less

eocene and early oligocene micropaleontology and paleoenvironments in se umbria italy a detailed study based on calcareous nannofossils and planktonic and benthic foraminifera has been carried out on five sections in the scaglia group of the umbrian region visso and cascia areas central italy these sections are characterized by continuous pelagic sedimentation and are constituted mainly of marls marly limestones and limestones of early eocene to early oligocene age calcareous turbidites with shallow water skeletal debris discharged from the latium abruzzi carbonate platform are interbedded within the pelagic sequences the biostratigraphic study based on calcareous nannofossils and planktonic foraminifera confirmed the continuous succession of standard events and revealed some new ones these results allow us to refine the biostratigraphic resolution with a very good correlation between calcareous nannofossil and planktonic foraminiferal zonations the major features and events recognized are the early middle eocene boundary zones p9 p10 is characterized by the first occurrence fo of hantkeninids by abundant thick walled globigerinatheka g senni and by spinose acarininids a decrease has been noted in planoconvex morozovellids and an increase of low spired subbotinids the benthic assemblage shows a great variability with an increase in the zone p11 of the large heterolepa and cibicidoides this is an event of worldwide significance in the calcareous nannofossils the fo of nannotetrina sp was used to define the lower boundary of zone cp13 instead of n fulgens because poor preservation prevented identification at the specific level the fo of reticulofenestra umbilica marking the lower boundary of zone cp14 occurs in the upper part of zone p11 the zone p13 was recognized indirectly because of the absence of the index species orbulinoides beckmanni the base of the zone is close to the fo of turborotalia cerroazulensis and is defined by an increase of catapsydrax sp and by the last occurrence lo of acarinina bullbrooki the top of the zone is defined by an increase of the high spired subbotinids of the s corpulenta group and the disappearance of morozovella spinulosa the middle late eocene boundary zones p14 p15 is characterized by the extinction of the spinose acarininids and of the smooth walled planorotalites from zone p13 to zone p15 there is a replacement in the benthic assemblages in fact pleurostomella heterolepa and anomalinoides capitata characterize these zones bolivinids become abundant and uvigerinids appear around the p14 p15 boundary the late eocene is characterized by an increase of subbotinids with abortive chambers and of the turborotalia cerroazulensis lineage hantkeninids and cribohantkeninids are rare particularly c inflata the fo of istmolithus recurvus has been noted at the base of zone p16 within this zone globigerinatheka index and turborotalia cunialensis coexist the lo of g index is associated with a strong decrease of representatives of the genus globigerinatheka at the same level of the lo of g index the coeval extinctions of discoaster barbadiensis and discoaster saipanensis are noted just above this level within zone p17 the lo of t cerroazulensis lineage t cocoaensis and t cunialensis has been recognized the eocene oligocene boundary is defined by planktonic foraminifera at the extinction level of hantkeninids and cribrohantkeninids shortly following that of the t cerroazulensis group

dinoflagellate cyst stratigraphy of the eocene oligocene transition in central italy abstract eight dinoflagellate cyst zones based on the massignano and monte cagnero sections in central italy provide high resolution control for the eocene oligocene e o transition most of these zones have been recognized in the time equivalent contessa highway section and are calibrated against previously established magneto and biostratigraphies the invasion of the mediterranean area by several higher latitude dinoflagellate taxa marks the e o boundary as characterized by the last occurrence of the hantkeninids planktic foraminifers calibrated against a horizon just above the youngest normal polarity event within chron c1 3r quantitative and qualitative dinoflagellate events across the e o boundary allow the recognition of warmer and cooler successive intervals of sea surface temperature in addition to apparent sea level fluctuations our data indicate that latest eocene warm conditions and a sea level highstand were rapidly replaced by short term cooler conditions and a lowstand across the e o boundary horizon following a shortterm warmer interval and a highstand during the earliest oligocene a second cool and lowstand episode occurred this cool interval was of greater magnitude and duration than the one at the e o boundary horizon and may correspond to the globally recognized cooling event reported from the basal part of chron c1 3n

bartonian to priabonian dinoflagellate cyst biostratigraphy and paleoenvironments of the m karcha section in the southern tethys margin rif chain northern morocco abstract palynological analyses were performed on the eocene sediments of the m karcha section which is located in the taza region structural tsoul unit eastern external rif northeastern morocco the palynological content of this section is composed essentially of well preserved and diverse dinoflagellate cyst assemblages allowing detailed taxonomic determinations age assignments biostratigraphic correlations and paleoenvironmental interpretations other palynomorphs such as spores pollen grains and foraminiferal linings are rare and therefore not taxonomically determined up to the genus level 131 dinoflagellate cyst species were identified age assignments are based on dinocyst bioevents considered previously as potential biostratigraphic markers of the bartonian and priabonian including the lowest occurrences los of glaphyrocysta semitecta impagidinium dispertitum rhombodinium perforatum cooksonidium capricornum stoveracysta ornata stoveracysta sp 2 of brinkhuis and biffi 1993 and lo and highest occurrence ho of schematophora speciosa the quantitative palynological analyses based mainly on dinoflagellate cysts through the m karcha section revealed an inner neritic generally lagoon environment with a low productivity alternated with short episodes of the open marine influence

late eocene oligocene magnetostratigraphy and biostratigraphy at south atlantic dsdp site 522 upper eocene to lowest miocene sediments recovered at deep sea drilling project dsdp site 522 in the south atlantic ocean allow direct calibration of magnetostratigraphy and calcareous plankton biostratigraphy the results from site 522 show that the eocene oligocene boundary occurs in the reversed interval of magnetic chron c13 c13r and that the oligocene imiocene boundary probably occurs in the upper part of chron c6c

eocene to oligocene dinoflagellate cysts from the tattofte section western external rif northwestern morocco biostratigraphy paleoenvironments and paleoclimate abstract the palynological analysis of the eocene oligocene succession from the tattofte section in the western external rif northwestern morocco reveals the presence of well preserved and diverse assemblage rich in dinoflagellate cysts dinocysts qualitative analyses especially of the dinocysts differentiate the individual stages of the deposits while quantitative analyses permit paleoenvironmental and paleoclimatic interpretations we assign the lower part of the tattofte section to the middle eocene lutetian and bartonian and its upper part to the upper oligocene chattian and define a hiatus spanning the late eocene priabonian and early oligocene rupelian the dinocyst marker events used for the biostratigraphic interpretations include the first and last occurrences of marker species such as batiacasphaera compta castellodinium compactum cerebrocysta bartonensis distatodinium biffii distatodinium paradoxum distatodinium ellipticum enneadocysta arcuata homotryblium floripes hystrichokolpoma bullatum impagidinium velorum lentinia serrata pentadinium imaginatum rhombodinium spinula saturnodinium perforatum and ynezidinium brevisulcatum as well as the chiropteridium spp acmes and we equate the chattian with the dinocyst distatodinium biffii zone of brinkhuis et al 1992 changes in the relative abundances of selected dinocyst groups spores and pollen lead to the distinction from oldest to youngest of four marine environments 1 marginal marine to coastal inner neritic under relatively warm water during the middle eocene 2 outer neritic to oceanic during a transgressive regime in the early chattian 3 fluctuating restricted to open marine in the middle chattian and 4 shallow coastal to open marine due to sea level fall at the top of the section in the latest chattian suggested by the chiropteridium spp acmes the acmes of selected thermophilic dinocyst taxa such as polysphaeridium spp and homotryblium spp suggest warm water marine conditions which may be related to the middle eocene climatic optimum meco and late oligocene warming

dinoflagellate cyst record of the eocene oligocene boundary succession in flysch deposits at leluchow carpathian mountains poland

holocene climate variability although the dramatic climate disruptions of the last glacial period have received considerable attention relatively little has been directed toward climate variability in the holocene 11 500 cal yr b p to the present examination of similar to50 globally distributed paleoclimate records reveals as many as six periods of significant rapid climate change during the time periods 9000 8000 6000 5000 4200 3800 3500 2500 1200 1000 and 600 150 cal yr b p most of the climate change events in these globally distributed records are characterized by polar cooling tropical aridity and major atmospheric circulation changes although in the most recent interval 600 150 cal yr b p polar cooling was accompanied by increased moisture in some parts of the tropics several intervals coincide with major disruptions of civilization illustrating the human significance of holocene climate variability c 2004 university of washington all rights reserved

complexity of holocene climate as reconstructed from a greenland ice core glaciochemical time series developed from summit greenland indicate that the chemical composition of the atmosphere was dynamic during the holocene epoch concentrations of sea salt and terrestrial dusts increased in summit snow during the periods 0 to 600 2400 to 3100 5000 to 6100 7800 to 8800 and more than 11 300 years ago the most recent increase and also the most abrupt coincides with the little ice age these changes imply that either the north polar vortex expanded or the meridional air flow intensified during these periods and that temperatures in the mid to high northern latitudes were potentially the coldest since the younger dryas event

reconstructing holocene shore displacement and stone age palaeogeography from a foredune sequence on ruhnu island gulf of riga baltic sea abstract holocene shore displacement and the palaeogeography of late mesolithic and late neolithic settlements on ruhnu island gulf of riga were reconstructed using foredune sequence luminescence dating sedimentological data supported by ground penetrating radar analysis and gis based landscape modelling the foredune ridges consist of very well to well sorted fine to medium grained aeolian sand and are underlain by seaward dipping foreshore sediments the studied sequence of 38 ridges was formed between 6 91 0 58 ka and 2 54 0 19 ka ago and represents a period of falling relative sea level foredune plain progradation with average rates of 0 3 0 6 m per year was controlled by isostatic land uplift which caused a continuous withdrawal of shorelines to lower elevations the dated foredune succession was used to reconstruct the coastal palaeogeography of the island palaeogeographical reconstructions show that during two phases of late mesolithic habitation at ca 7 2 cal ka bp and 6 2 cal ka bp seal hunters settled the coastal zone of ruhnu island based on tool material and pottery type they could have originated from saaremaa island which according to palaeoreconstruction of the gulf of riga was located approximately 70 km northwest of ruhnu island during the late mesolithic later signs of human occupation radiocarbon dated to ca 4 7 cal ka bp were from the centre of the island hundreds of metres away from the shore at about 8 m above its contemporary sea level this late neolithic habitation shows a clearly different pattern than earlier coastal settlement and suggests a shift in subsistence strategy towards agriculture and animal husbandry

dripping into unsaturated rock underground excavations literature review and geologic and hydrogeologic setting description a literature review of dripping in underground constructions in deep unsaturated geologic media was performed as part of a phased study the objective is to develop and test a formulation that can be used for studying unsaturated flow through rough multi segmented fractures with emphasis on predicting dripping initiation time geologic and hydrogeologic setting for the yucca mountain ym and its exploratory studies facility which is the site where the model will be tested are described

timing and nature of the deepening of the tasmanian gateway 1 tectonic changes that produced a deep tasmanian gateway between australia and antarctica are widely invoked as the major mechanism for antarctic cryosphere growth and antarctic circumpolar current acc development during the eocene oligocene e o transition 34 33 ma ocean drilling program odp leg 189 recovered near continuous marine sedimentary records across the e o transition interval at four sites around tasmania these records are largely barren of calcareous microfossils but contain a rich record of siliceous and organic walled marine microfossils in this study we integrate micropaleontological sedimentological geochemical and paleomagnetic data from site 1172 east tasman plateau to identify four distinct phases a d in the e o tasmanian gateway deepening that are correlative among odp leg 189 sites phase a prior to 35 5 ma minor initial deepening characterized by a shallow marine prodeltaic setting with initial condensation episodes phase b 35 5 33 5 ma increased deepening marked by the onset of major glauconitic deposition and inception of energetic bottom water currents phase c 33 5 30 2 ma further deepening to bathyal depths with episodic erosion by increasingly energetic bottom water currents phase d 30 2 ma establishment of stable open ocean warm temperate oligotrophic settings characterized by siliceous carbonate ooze deposition our combined evidence indicates that this early oligocene tasmanian gateway deepening initially produced an eastward flow of relatively warm surface waters from the australo antarctic gulf into the southwestern pacific ocean this proto leeuwin current fundamentally differs from previous regional reconstructions of eastward flowing cool water e g a proto acc during the early oligocene and thereby represents an important new constraint for reconstructing regional to global scale dynamics for this major global change event

morphogenesis and microstructure of concrete derived calthemites distributions of calcareous calthemite deposits have been widely documented but depositional processes and the architecture of their internal fabrics are not well understood these concrete degradation products from a case study area in western canada have external morphologies comparable to calcite speleothems formed in natural limestone caves but the internal microstructural architecture and mineralogy are markedly different the mineralogy consists of mostly calcite with secondary halite and minor percentages of trona and portlandite a novel morphogenetic model explains depositional processes resulting in calcareous crusts that follow fractures of an overlying concrete surface and how sufficient structural integrity provided by the internal architecture supports attachment areas of tubular soda straws interiors of these multi cm crusts consist of curvilinear calcite laminae arrayed as sub parallel walls compartmentalizing water gas interfaces along variously interconnected conduits and basin form chambers overall porosities of 40 60 or more are prevalent in contrast to 1 associated with externally similar drapery form crusts deposited within natural limestone caves several calcite fabrics new to calthemite deposits are described including dendritic shrubs that coalesce into concentric growth rings along central canals of soda straws

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

millennial scale storminess variability in the northeastern united states during the holocene epoch for the purpose of detecting the effects of human activities on climate change it is important to document natural change in past climate1 in this context it has proved particularly difficult to study the variability in the occurrence of extreme climate events such as storms with exceptional rainfall1 previous investigations have established storm chronologies using sediment cores from single lakes2 3 4 5 6 7 8 but such studies can be susceptible to local environmental bias here we date terrigenous inwash layers in cores from 13 lakes which show that the frequency of storm related floods in the northeastern united states has varied in regular cycles during the past 13 000 years 13 kyr with a characteristic period of about 3 kyr our data show four peaks in storminess during the past 14 kyr approximately 2 6 5 8 9 1 and 11 9 kyr ago this pattern is consistent with long term changes in the average sign of the arctic oscillation9 suggesting that modulation of this dominant atmospheric mode may account for a significant fraction of holocene climate variability in north america and europe

arctic dinoflagellate migrations mark the strongest oligocene glaciations here we report on mid oligocene globally synchronous arctic dinoflagellate migration events calibrated against chron c9n we show that sudden appearances and marked abundance increases of the arctic taxon svalbardella at lower and middle latitudes coincide with the oi 2b benthic d 18 o glacial episode dated as ca 27 1 ma these unprecedented migrations are taken to indicate anomalously strong surface water cooling during oi 2b time in turn associated with strong concomitant antarctic ice sheet growth and sea level lowering we estimate the duration of these unique svalbardella migrations and the associated episode of profound cooling as 500 k y our records suggest a close link between this distinct oligocene glaciation episode strong sea level fall and the classic lower upper oligocene or rupelian chattian boundary dating this boundary as ca 27 1 ma

changes in atmospheric circulation and ocean ice cover over the north atlantic during the last 41 000 years high resolution continuous multivariate chemical records from a central greenland ice core provide a sensitive measure of climate change and chemical composition of the atmosphere over the last 41 000 years these chemical series reveal a record of change in the relative size and intensity of the circulation system that transported air masses to greenland defined here as the polar circulation index pci and in the extent of ocean ice cover massive iceberg discharge events previously defined from the marine record are correlated with notable expansions of ocean ice cover and increases in pci during stadials without discharge events ocean ice cover appears to reach some common maximum level the massive aerosol loadings and dramatic variations in ocean ice cover documented in ice cores should be included in climate modeling

the alps with little ice evidence for eight holocene phases of reduced glacier extent in the central swiss alps glacially deformed pieces of wood organic lake sediments and clasts of reworked peat have been collected in front of alpine glaciers since ad 1990 the palaeoglaciological interpretation of these organic materials is related to earlier phases of glacier recession surpassing that of today s shrunken glaciers and to tree growth and peat accumulation in the valleys now occupied by the glaciers glacial transport of the material is indicated by wood anatomy incorporated silt sand and gravel particles missing bark and deformed treerings a total of 65 samples have been radiocarbon dated so far and clusters of dates provide evidence of eight phases of glacier recession 9910 9550 9010 7980 7250 6500 6170 5950 5290 3870 3640 3360 2740 2620 and 1530 1170 calibrated years bp allowing for the timelag between climatic fluctuations glacier response and vegetation colonization these recession phases may lag behind climatic changes by 100 200 years