persistent millennial scale climatic variability over the past 25 000 years in southern africa abstract data from stalagmites in the makapansgat valley south africa document regional climatic change in southern africa in the late pleistocene and holocene a new tims u series dated stalagmite indicates speleothem growth from 24 4 to 12 7 ka and from 10 2 to 0 ka interrupted by a 2 5 ka hiatus high resolution oxygen and carbon stable isotope data suggest that postglacial warming was first initiated 17 ka was interrupted by cooling probably associated with the antarctic cold reversal and was followed by strong warming after 13 5 ka the early holocene experienced warm evaporative conditions with fewer c4 grasses cooling is evident from 6 to 2 5 ka followed by warming between 1 5 and 2 5 ka and briefly at ad 1200 maximum holocene cooling occurred at ad 1700 the new stalagmite largely confirms results from shorter holocene stalagmites reported earlier the strongest variability superimposed on more general trends has a quasi periodicity between 2 5 and 4 0 ka also present are weaker 1 0 ka and 100 year oscillations the latter probably solar induced given similarities to the antarctic records the proximate driving force producing millennial and centennial scale changes in the makapansgat record is postulated to be atmospheric circulation changes associated with change in the southern hemisphere circumpolar westerly wind vortex

finite difference technique for sh waves in 2 d media using irregular grids application to the seismic response problem summary the finite difference method is applied to compute the seismic response of 2 d inhomogeneous structures for sh waves a technique is proposed which uses an irregular grid a rectangular grid with varying grid spacing a geological structure may be composed of blocks of media inside of which velocity and density vary linearly in horizontal and vertical directions the technique allows better adjusted modelling of a medium and in numerical examples presented yields more efficient computations as compared to those with regular grids the technique is tested through comparison with a discrete wavenumber method as an example the seismic response of the sediment filled chusal valley carm region ussr is computed the numerical results are compared with observations

middle eocene lower oligocene calcareous nannofossil biostratigraphy and paleoceanographic implications from site 711 equatorial indian ocean abstract nannofossil data from odp site 711 equatorial indian ocean yield a set of consistent reliable biohorizons that form the basis of a revised calcareous nannofossil biostratigraphy for the low latitude eocene oligocene we discuss 31 biohorizons occurring over an 11 myr time interval which we correlate to previous magnetostratigraphic data calcareous nannofossils from the middle eocene through the lower oligocene of the studied section are characterized by moderately well preserved assemblages consisting largely of low latitude and cosmopolitan species a significant nannofossil dissolution interval is evidenced at the middle eocene climatic optimum meco we document a significant increase in late eocene nannoplankton exhibiting a eutrophic preference analysis of the assemblage suggests important changes in the equatorial oceanic regime just before the onset of the eocene oligocene transition eot that foreshadow the more dramatic climatic shift of the early oligocene

biogeographic gradients of middle eocene oligocene calcareous nannoplankton in the south atlantic ocean middle eocene oligocene calcareous nannoplankton have been analyzed quantitatively for eight dsdp and odp sites ranging from the equatorial zone to 65 s latitude in the south atlantic ocean there is a general decrease in calcareous nannoplankton species diversity from the middle eocene through the oligocene and species diversity also decreases towards the higher latitudes similar to findings of other studies the drop of the species diversity of calcareous nannoplankton across the eocene oligocene boundary is not drastic delineation of latitudinal distribution patterns of individual species or groups and r mode cluser analysis permit the classification of warm water taxa coccolithus formosus discoasters helicosphaerids and sphenoliths temperate water taxa coccoliths pelagicus cyclicargoliths floridanus group reticulofenestra bisecta reticulofenestra samodurovii reticulofenestra umbilica and cool water taxa chiasmoliths isthmolithus recurvus and reticulofenestra daviesii the abundance of warm water taxa plummets whereas the abundance of cool water taxa sharply increases across the eocene oligocene boundary at the middle and high latitude sites reflecting a profound cooling event in these areas polar ordination and similarity analyses reveal that steep latitudinal biogeographic gradients had been established at least by the middle eocene the gradient greatly increases near the eocene oligocene boundary indicating more severe and permanent cooling at the high latitudes the biogeographic gradient data of this study conflict with the widely accepted inference from the oxygen isotopic data that the thermal gradients between mid latitudes and high latitudes are low or nearly flat for the paleogene oceans lower surface water salinities in the high latitudes may have lowered the 18o values of the planktonic microfossils but apparently did not have significant effect on latitudinal distribution patterns of calcareous nannoplankton which offers an independent means for estimating latitudinal thermal gradients

late oligocene climatic changes evidence from calcareous nannofossils at kerguelen plateau site 748 southern ocean abstract palaeoecological changes in nannofossil assemblages in the southern ocean during oligocene times are examined through high resolution quantitative analyses of samples from ocean drilling program odp site 748 kerguelen plateau we quantitatively characterized the palaeoecological preference of groups of species and compared their general trends with those determined at maud rise odp sites 690 and 689 persico d villa g 2004 eocene oligocene calcareous nannofossils from maud rise and kerguelen plateau antarctica palaeoecological and palaeoceanographic implications marine micropaleontology 52 153 179 we then attempt a correlation between the main assemblage variation and sea surface temperature sst changes in the southern ocean at this time relatively stable cool conditions are interpreted to have persisted from earliest to late oligocene times when an increase in abundance of temperate water taxa is recorded both at maud rise and kerguelen plateau before the mi 1 event this reveals a climatic event that probably involved both sites and which is comparable to that indicated by the global oxygen isotope curve miller k g wright j d fairbanks r g 1991 unlocking the ice house oligocene miocene oxygen isotopes eustasy and margin erosion journal of geophysical research 96 6829 6848 zachos j pagani m sloan l thomas e billups k 2001 trends rhythms and aberrations in global climate 65 ma to present science 292 686 693 in the uppermost oligocene at site 689 the temperate water taxa index temperate temperate cool 100 increases from 25 2 ma similarly at site 748 the temperate water taxa index indicates an increase in sst in the late oligocene from about 26 5 ma at the base of chron c8n 2n which is offset by about 1 m y between the two areas the reason for this time difference can probably be found in the location of site 748 with respect to site 689 and in the palaeoceanographic setting taking into account that site 748 lies north of a deep water passage that separates kerguelen plateau from antarctica and north of the present day front of the antarctic circumpolar current the presence of warm water taxa exclusively at site 748 corroborates this hypothesis

middle eocene to late oligocene antarctic glaciation deglaciation and southern ocean productivity during the eocene oligocene transition earth cooled significantly from a greenhouse to an icehouse climate nannofossil assemblages from southern ocean sites enable evaluation of paleoceanographic changes and hence of the oceanic response to antarctic ice sheet evolution during the eocene and oligocene a combination of environmental factors such as sea surface temperature and nutrient availability is recorded by the nannofossil assemblages of and can be interpreted as responses to the following changes a cooling trend started in the middle eocene was interrupted by warming during the middle eocene climatic optimum and by short cooling episodes the cooling episode at 39 6 ma preceded a shift toward an interval that was dominated by oligotrophic nannofossil assemblages from 39 1 to 36 2 ma we suggest that oligotrophic conditions were associated with increased water mass stratification low nutrient contents and high efficiency of the oceanic biological pump that in turn promoted sequestration of carbon from surface waters which favored cooling after 36 2 ma we document a large synchronous surface water productivity turnover with a dominant eutrophic nannofossil assemblage that was accompanied by a pronounced increase in magnetotactic bacterial abundance this turnover reflects a response of coccolithophorids to changed nutrient inputs that was likely related to partial deglaciation of a transient antarctic ice sheet and or to iron delivery to the sea surface eutrophic conditions were maintained throughout the oligocene which was characterized by a nannofossil assemblage shift toward cool conditions at the eocene oligocene transition finally a warm nannofossil assemblage in the late oligocene indicates a warming phase

acoustic modes of propagation in the borehole and their relationship to rock properties acoustic waveform measurements in boreholes have important applications in fracture hydrology and radioactive waste disposal but ambiguities in existing interpretation techniques remain a problem we have addressed the problem by using residue theory to predict the relative excitation of various modes contained in experimental waveforms a plane geometry model involving a layer of fluid between two elastic half spaces is shown to provide velocity dispersion curves for propagating modes that are very similar to those for the fluid filled borehole we use the plane geometry model to illustrate the effects of the confined borehole fluid on surface and body waves traveling along the borehole in the elastic solid we also computed excitation functions for some of the lowest order symmetric modes calculated the time domain response of the trapped modes following the shear head waves and compared them to waveforms recorded in boreholes through several homogeneous formations the insight into the mode composit

new stratigraphical results and significance of reworking based on nannofossil foraminiferal and sedimentological records in the lower tertiary sequence from the northern isparta angle eastern mediterranean abstract this study presents new stratigraphical data on the sediments of the lower tertiary sequence outcropping in the northern isparta angle southwest anatolia these data which are based on field observations foraminifera and nannofossil studies and sedimentological findings contribute to the paleoenvironmental and structural interpretations reworking of fossils that was neglected in previous work is an important factor for understanding and clarifying the early tertiary geological evolution of the region this investigation particularly focuses on the significance of reworking in the stratigraphic record the early tertiary unconformity bounded unit consist of two transitional lithofacies varying from marine clastics to carbonates the first lithofacies mainly composed of clastics whereas the second contains carbonate dominated sediments the lower tertiary sequence unconformably overlies an irregular surface composed of ophiolitic rocks deep marine bedded cherts and carbonates of early mesozoic age mesozoic carbonates and marine clastics and carbonates of late cretaceous age the unit is unconformably overlain by lower miocene marine clastics both the unconformity and tectonic relationships between the eocene and lower miocene sequences are seen in the northern study area these exposures are proof of pre miocene erosion and post miocene deformation in this study two nannofossil interval zones np12 and np13 were identified from fine grained clastics and carbonates according to benthic foraminifera and nannofossil contents the formation is early eocene ypresian in age the percentages of reworked older fossils range from 75 in the lower levels to 15 in the higher levels of the lower tertiary sequence this study demonstrates that detailed analyses of fossil reworking are needed in order to obtain more reliable results the evidence of strong reworking plant traces biostratigraphical and sedimentological data indicate that a single cycle of early eocene sedimentation occurred in a shallow to open marine depositional environment becoming shallower as time progressed the obtained data indicate a marine transgression from north to south in the northern part of the isparta angle during eocene time

stratigraphy and palaeoenvironment of the lower middle oligocene units in the northern part of the western taurides incesu area isparta turkey abstract this study describes the stratigraphic and palaeoenvironmental significance of the lower middle oligocene sediments based on the fauna from the delikarkasi formation and the microflora from the incesu formation of the incesu area northern part of the western taurides isparta province turkey in the area the oligocene sediments show a regressive succession which begins with the limestones of the delikarkasi formation indicating marine conditions followed by conglomerates sandstones and coaly mudstones of alluvial and fluvial shallow marine continental origin a well preserved foraminiferal assemblage including nummulites intermedius nummulites vascus and halkyardia maxima proves an early oligocene age for the delikarkasi formation due to palynological markers such as boehlensipollis hohli slowakipollis hippophaeoides dicolpopollis kockelii magnolipollis neogenicus ssp minor plicapollis pseudoexcelsus caryapollenites simplex and intratriporopollenites instructus the incesu formation which concordantly rests on the delikarkasi formation may be assigned to the early middle oligocene from the palynomorph assemblage three zones have been recognised according to abundance of species zone 1 is characterized by predominance of c simplex and momipites punctatus and rarely presence of tricolpate and tricolporate pollen zone 2 consists mainly of inaperturopollenites dubius leiotriletes maxoides ssp maximus verrucatosporites favus verrucatosporites alienus and infrequently marine dinoflagellate cysts zone 3 is characterized by a high percentage of ferns such as echinatisporis chattensis and polypodiaceoisporites saxonicus the presence of marine dinoflagellate cysts like apectodinium sp and cleistosphaeridium sp back mangrove elements such as acrostichum aureum and lepidocaryoid palms e g longapertites discordis longapertites punctatus and longapertites psilatus in the sediments of the incesu formation imply coastal or near coastal conditions terrestrial palynomorphs in more inland settings were transported by running water towards the sea conifers are represented by poorly preserved and rare pollen grains of pityosporites cathayapollis and piceapollis which may have been transported by wind in this study the terrestrial climate of the incesu formation is also discussed on the basis of the coexistence approach method the climate was warm at the coast over 20 c as evidenced by a aureum and lepidocaryoid palms whereas there was a mean annual temperature of 17 2 17 4 c must be assumed for the upland environment s

eocene oligocene paleoceanographic changes in the stratotype section massignano italy clues from rock magnetism and stable isotopes 1 we have conducted high resolution paleomagnetic and rock magnetic studies in addition to stable isotope analyses of the massignano sedimentary section which is the global stratotype section and point gssp for the eocene oligocene boundary our research builds upon the many past studies of the massignano section in seeking to understand the timing and nature of the paleoenvironmental variations that occurred during the transition for the earth s climate system from greenhouse to icehouse the new paleomagnetic results provide a refined magnetostratigraphy of the section and new age for the eocene oligocene boundary at 33 7 ma abrupt and large alternations in magnetic concentration composition and grain sizes that occur in the high resolution rock magnetic record are interpreted to be the result of rapid bimodal shifts in deep sea circulation that affect sediment sources or transport we speculate that currents flowing through the gateway between the atlantic and indo pacific oceans may have turned on and off as the gateway was progressively closing resulting in the deposition of two different assemblages of magnetic minerals at massignano finally stable isotope 18o and 13c data collected on ostracod valves also suggest significant changes in sea bottom circulation in the neo tethys ocean at and about 2 m y before the eocene oligocene boundary

middle eocene late oligocene climate variability calcareous nannofossil response at kerguelen plateau site 748 a major deterioration in global climate occurred through the eocene oligocene time interval characterized by long term cooling in both terrestrial and marine environments during this long term cooling trend however recent studies have documented several short lived warming and cooling phases in order to further investigate high latitude climate during these events we developed a high resolution calcareous nannofossil record from odp site 748 hole b for the interval spanning the late middle eocene to the late oligocene 42 to 26 ma the primary goals of this study were to construct a detailed biostratigraphic record and to use nannofossil assemblage variations to interpret short term changes in surface water temperature and nutrient conditions the principal nannofossil assemblage variations are identified using a temperate warm water taxa index twwt from which three warming and five cooling events are identified within the middle eocene to the earliest oligocene interval among these climatic trends the cooling event at 39 ma cooling event b is recorded here for the first time variations in fine fraction 18o values at site 748 are associated with changes in the twwt index supporting the idea that significant short term variability in surface water conditions occurred in the kerguelen plateau area during the middle and late eocene furthermore odp site 748 calcareous nannofossil paleoecology confirms the utility of these microfossils for biostratigraphic paleoclimatic and paleoceanographic reconstructions at southern ocean sites during the paleogene

responses of calcareous nannofossil assemblages mineralogy and geochemistry to the environmental perturbations across the paleocene eocene boundary in the venetian pre alps responses of calcareous nannofossil assemblages mineralogy and geochemistry to the environmental pertubartions across the paleocene eocene boundary in the venetian pre alps

late quaternary sea level change in south africa abstract a late quaternary sea level curve for south africa is presented on the basis of new and published data from a range of sea level indicators and a variety of locations available evidence suggests that sea level in south africa broadly follows that described from the caribbean but that deviations occur during sea level highstands during the last interglaciation oxygen isotope stage 5 and the late holocene coastal emergence produced higher sea levels in south africa than those identified in the caribbean during the same time intervals this is tentatively ascribed to predicted lithospheric deformation in continental margin settings

9000 years of sea level change along the southern african coastline abstract beachrocks are good indicators of sea level stillstands on microtidal coastlines and data for this sea level curve is mainly based on dating a series of holocene beachrocks and planation episodes on the southeast african coastline sea level reached its present level along the southern african coastline at ca 6500 bp sea level then rose depositing a series of beachrocks at an elevation of 2 75 m this mid holocene sea level highstand persisted for a period of 2500 years with a 3 5 m stillstand dated at 4480 bp being the highest sea level reached during the holocene in post holocene sea level optimum times a regression occurred lowering sea level to its present level at 3880 bp and down to 2 m at approximately 3000 bp subsequently sea level rose to 1 5 m at 1610 bp and attained its present level at about 900 bp the mid holocene sea level highstand appears to have resulted from a combination of isostatic emergence and the steric expansion of seawater relating to warmer ocean temperatures associated with the holocene hypsithermal event on the eastern agulhas bank

holocene dynamics of the salt fresh groundwater interface under a sand island inhaca mozambique abstract the configuration of coastal groundwater systems in southeast africa was strongly controlled by the holocene sea level changes with an early holocene transgression 15 m 10 000 5000 cal bp and two assumed high stand events in the middle and late holocene with levels higher than the present the fluctuation of the salt fresh groundwater interface under inhaca island in mozambique during the holocene has been studied using an adapted version of the numerical code sutra s aturated u nsaturated tra nsport in this study small scale variations such as tidal effects have not been considered a number of transient simulations were run with constant boundary conditions until the steady state condition was reached in order to study the sensitivity of response time salt fresh interface position and thickness of the transition zone to different parameters such as hydraulic conductivity porosity recharge and dispersivity a 50 increase in horizontal hydraulic conductivity yields a rise in the location of the interface of 15 m while an increase in recharge from 8 to 20 of mean annual precipitation map causes a downward shift in the interface position of 40 m a full transient simulation of the holocene dynamics of the salt fresh groundwater interface showed a response time of several hundred years with a duration sensitive to porosity hydraulic conductivity and recharge and a position determined by the recharge rate and the hydraulic conductivity dispersivity controls the thickness of the transition zone in this non tidal model physical processes such as changes in recharge and or the sea level may cause rapid shifts in the interface position and affect the thickness of the transition zone

precessional forcing of nutricline dynamics in the equatorial atlantic climate control of nutricline depth in the equatorial atlantic can be monitored by variations in the abundance of the phytoplankton species florisphaera profunda a conceptual model based on in situ evidence associates high abundances of f profunda with a deep nutricline and low abundances with a shallow nutricline a 200 000 year record of f profunda relative abundances obtained from a deep sea core sited beneath the region of maximum equatorial divergence at 10 w has 52 percent of its variance centered on the 23 000 year precessional band cross spectral analysis between the signals of f profunda and sea surface temperature independently derived from zooplankton species shows their 23 000 year cycles to be coherent and nearly in phase abundance minima of f profunda coincide with times of december perihelion whereas abundance maxima coincide with june perihelion these relations indicate that nutricline dynamics in the divergence region of the equatorial atlantic are controlled by variations in the tropical easterlies forced by the precessional component of orbital insolation on time scales greater than 10 000 years

time response of the water table and saltwater transition zone to a base level drop 1 this paper investigates the effect of a drainage base level drop on the groundwater system in its vicinity using theoretical analysis simulations and field data we present a simple and novel method for analyzing the effect of a base level drop by defining two characteristic times that describe the response of the water table and the transition zone between the fresh and saline water the dead sea was chosen as a case study for this process because of the lake s rapid level drop rate during a continuous lake level drop the discharge attains a constant value and the hydraulic gradient remains constant we describe this new dynamic equilibrium and support it by theoretical analysis simulation and field data using theoretical analysis and sensitivity tests we demonstrate how different hydrological parameters control the response rate of the transition zone to the base level drop in some cases the response of the transition zone may be very rapid and in equilibrium with the water table or alternatively it can be much slower than the water table response as is the case in the study area

calcareous nannofossils as paleoproductivity indicators in upper cretaceous organic rich sequences in israel abundant and diverse calcareous nannofossil assemblages were found in organic rich carbonate sequences which accumulated in a campanian maastrichtian upwelling belt along the southeastern tethys the sequences studied represent the inner shallower and the outer deeper parts of the upwelling belt the paleoenvironmental significance of selected nannofossil taxa and their utility in productivity reconstruction was established by comparing their distribution to foraminifera and dinocyst based productivity profiles based on the calcareous nannofossil assemblages a high productivity group and a low productivity group of species were determined the distribution of these groups agrees well with the dinocyst and foraminifera based productivity curves and hence can be used to record paleoproductivity changes the ratio between the high productivity and low productivity nannofossil groups the nannofossil index of productivity nip is proposed here as a productivity proxy that can be utilized in reconstructing basinal productivity development a quantitative analysis of the nannofossil assemblages indicates that their abundance and diversity increase towards the open sea in the outer and less productive part of the upwelling belt in the inner and more productive part of the upwelling belt the nannofossils assemblages become less abundant and less diverse relative to those of the open marine environment micula decussata and watznaueria barnesae are common to abundant in most samples m decussata becomes more abundant in poorly preserved samples on the other hand the distribution of w barnesae matches better with intermediate productivity levels

cross well seismic modeling with inclusion of tube waves and tube wave related arrivals 1 cross well seismic data often contain strong tube waves and tube wave related arrivals due to the effects of the presence of two boreholes a basic requirement for accurate cross well seismic modeling and data processing is inclusion of these events we use a 2 d velocity stress variable grid finite difference parallel code for efficient cross well field data modeling with inclusion of the two perforated cased boreholes the synthetics resemble the field observations in terms of arrival times not only on p and s waves but also on tube waves and tube wave related secondary arrivals generated by perforations in the receiver and source wells this study demonstrates that including boreholes into the modeling scheme can distinguish tube wave related events on seismograms to better assist data analysis and to guide data processing and interpretation

radiometric time scale for the upper eocene and oligocene based on k ar and rb sr dating of volcanic biotites from the pelagic sequence of gubbio italy several samples of unaltered volcanic biotite were recovered from five biostratigraphically and magnetostratigaphically controlled bentonite horizons in the continuous upper eocene oligocene pelagic carbonate sequence of gubbio northern italy k ar and rb sr dates on these samples offer a unique opportunity to calibrate with closely spaced points the late paleogene biostratigraphic and magnetostratigraphic time scales until now time scales have been constructed by interpolating between less certain and more widely spaced data points our combined k ar and rb sr dates are here used to calibrate the following five stratigraphic levels from top to bottom level 5 upper part of globorotalia opima opima planktonic foraminiferal zone upper part of indistinct np23 np24 nannoplankton zone and cp18 nannoplankton zone bottom of magnetic anomaly 9n 28 0 0 3 ma level 4 globigerina ampliapertura and cassigerinella chipolensis zone lower part of np23 zone and bottom of cp18 zone upper part of anomaly 12r 32 0 0 8 ma level 3 pseudohastigerina micra zone upper part of np21 and cp16b zones top of anomaly 13n 35 4 0 4 ma level 2 upper part of globigerinatheka semiinvoluta zone upper part of np18 and cp15a zones top of magnetic anomaly 16n 36 0 0 4 ma level 1 lower part of g semiinvoluta zone between zones np18 and np19 middle part of zone cp15a upper part of anomaly 17n 36 4 0 3 ma from these data the interpolated age for the much debated eocene oligocene boundary is 35 7 ma with a 2 standard deviation uncertainty of 0 4 ma

calcareous nannofossil changes in response to the spreading of the south china sea basin during eocene oligocene abstract numerous models have been proposed to constrain the process of the south china sea formation yet the paleogene paleoenvironmental researches are hindered by the paucity of long continuous well dated geological records in this work eocene to oligocene nannofossil biostratigraphy and assemblage changes in a sediment section from the northern south china sea were studied to shed light on these issues we established an age model to confine the studied section between 40 and 22 ma based on 17 calcareous nannofossil datum levels the age model enabled to date the most prominent seismic reflector t60 centered at 26 8 ma a regional tectonic event interpreted as corresponding to the ridge jump event in the early phase of south china sea spreading changes in nannofossil abundance and assemblage compositions imply continuous transgression and deepening of water depth from the late eocene to early miocene during the late eocene the studied area was a neritic sea with relatively eutrophic conditions supporting abundant r lockeri group and c pelagicus from 34 ma to 27 ma during the oligocene the earlier neritic environment was replaced by relative warm and oligotrophic conditions in a shallow sea as indicated by higher concentration of c floridanus sphenolithus spp and helicosphaera spp since 26 ma pelagic conditions prevailed small reticulofenestra

synthetic reconstructions of southern african environments during the last glacial maximum 21 18kyr and the holocene altithermal 8 6kyr abstract the pash database has been assembling palaeoclimatic data from the southern hemisphere for a number of years the southern african sector now contains more than 100 records spanning the last 200 000 years a number of these relate to the last glacial maximum and holocene altithermal which represent the two most recent extremes in global temperatures syntheses of these records have permitted the preparation of preliminary palaeoenvironmental maps for the two intervals the results provide insights into probable changes in atmospheric circulation as temperatures across the subcontinent rose by 6 7 c these changes are in agreement with a present day model which has been developed to explain short term variations in southern african climate the results presented here should assist in calibrating models developed to predict future climate change

on eustatic sea level history last glacial maximum to holocene abstract this paper addresses the question of the magnitude and time dependence of the globally averaged eustatic rise of sea level that occurred subsequent to the time of last glacial maximum lgm at approximately 21 000 calendar years before present through the analysis of relative sea level rsl histories predicted by a realistic mass conserving and gravitationally self consistent theory of postglacial sea level change it is demonstrated that there are preferred oceanic locations at which this eustatic function is well approximated by local sea level history one such location is the island of barbados in the caribbean sea a site from which a coral based record exists that extends from mid holocene to lgm because of the sea level ambiguity that is inherent to coral based records however it is important that the global ice equivalent eustatic sea level curve inferred on the basis of the barbados data be tested against observations at other locations from which similarly extensive records are also available but which are derived on the basis of sea level indicators which are not subject to the ambiguities inherent to corals it is shown that when the eustatic function employed in the global theoretical model is tuned so as to enable the model to fit the barbados observations where the maximum relative sea level rsl depression is assumed to be near 120 m then the theory misfits the record from the sunda shelf in the indonesian archipelago as well as the record from j bonaparte gulf in northern australia both of these recently published records appear to constrain the lgm low stand of rsl to a value above 120 m the implications of these results for interpretation of the long coral derived records from the huon peninsula of papua new guinea and the island of tahiti are also discussed

morphometry of the eocene nannofossil reticulofenestra umbilicus lineage and its biochronological consequences abstract morphometruc measurements of eocene and early oligocene reticulofenestrids from dsdp site 523 in the south atlantic show that a 90 size increased led to the appearance of reticulofenestra umbilicus this increase occurred between about 45 2 ma and 42 9 ma the attempts made to recognize r umbilicus during this period of change as a distinct subpopulation among the reticulofenestrid assemblages did not yield any tenable conclusions however using a lower size limit of 14 m for recognition of the r umbilicus morphovariant resulted in an easily identified first appearance event which occurred during chron 19r at an age of about 44 4 44 5 ma from a morphometric point of view the two morphovariants r hillae and r umbilicus could not be distinguished as two distinct subpopulations the oligocene assemblages show markedly smaller 10 central opening placolith length ratios as compared to the eocene forms but for several reasons it seems difficult to use this decrease biostratigraphically

groundwater lens dynamics of atoll islands a variable density groundwater model is used to analyze the effects of various controls on the size of the freshwater lens the structure of the transition zone and the propagation of tidal fluctuations in a two layer atoll island groundwater system modeling results indicate that mixing of fresh water and saltwater occurs primarily as a result of oscillating vertical flow due to tidal fluctuations and depends to a lesser extent on transverse dispersion along the dominantly horizontal recharge discharge path of flow the controls on the amount of mixing are 1 the accumulated vertical distance which increases with tidal range and is restricted by vertical permeabilities and 2 vertical longitudinal dispersion comparison of cross sectional simulations of atoll islands using nontidal and tidal models shows that the nontidal model must use artificially high values of transverse dispersivity to compensate for the lack of tidally driven vertical mixing processes although the tidal model has high computational requirements it can be used to calibrate vertical permeabilities and is best suited for problems dealing with groundwater resource evaluations hydrologic events and hydrologic processes the limitations of the nontidal model are that it cannot be used for calibration of vertical permeabilities and will not realistically simulate those cases in which transition zones are thick or recharge low

shocked quartz from the late eocene impact evidence from massignano italy this paper reports the discovery of shocked quartz grains within a well dated upper eocene marlstone at the massignano outcrop ancona italy the shocked quartz reaches a maximum concentration of 1 6 0 4 grains per cubic centimetre of bulk rock a modest ir anomaly is also coincident with the shocked quartz and together they strongly support an impact origin moreover this impact layer has a precise interpolated radiometric age of 35 7 0 4 ma although impact evidence found throughout the world indicates that at least two large impacts did occur during this time the actual number timing and environmental effects of these impact events remain unclear the late eocene was a critical time in earth history because of significant climatic biotic and environmental crises

biotic signals from nannoflora across the iridium anomaly in the upper eocene of the massignano section evidence from statistical analysis abstract strong evidence for a major late eocene impact including an iridium rich layer and shocked quartz has been found in the massignano section central italy stratotype of the eocene oligocene boundary quantitative calcareous nannofossils analyses have been performed and classical and multivariate statistical techniques have been applied to assess the paleonvironmental effect of this impact on the nannoflora abundance patterns indicate 1 a warming episode just above the iridium layer 2 a subsequent slight cooling trend probably related to the global cooling during late eocene to early oligocene 3 marked fluctuations in the trophic resources and an increase in near shore taxa in the upper part of the interval 4 increase in low nutrient taxa in biotite rich layers just above the iridium level possibly related to lowered productivity linked to volcanic activity all these signals appear most likely to be the result of long term climatic changes rather than to short term effects of extraterrestrial impact in addition cluster analysis was performed on the assemblage data this delineated similarities among different taxa and grouped samples with similar assemblages several groups related to temperature trophic and unknown preference conditions have been distinguished a consistent difference in the abundances of the taxa and in their correlation has been detected between samples above and below the iridium level this change appears to be related to two important sedimentary features which are found in the interval above the iridium occurrence 1 the presence of biotite rich layers linked to increasing volcanism and 2 a conspicuous color transition from reddish to greenish related to changes in sedimentary environments e g variations in trace element abundance these environmental changes rather than the impact may have affected the nannoflora assemblages

insights into late quaternary calcareous nannoplankton assemblages under the theory of statistical analysis for compositional data abstract the investigation of changes in abundance of calcareous nannofossil associations is fundamental for palaeoclimatic and palaeoceanographic reconstructions in general since the number of recognised species is high the numerical and graphical treatments of the data play an important role to validate hypotheses about the influence of physico chemical factors on the quality of past environments as reflected by changes in abundance moreover the application of multivariate procedures may be useful for improving interpretation of the overall data structure calcareous nannofossil associations analysed in this work are related to core gns84 c106 collected in the gulf of salerno campania southern italy under a national interdisciplinary research programme aimed at recognising the impact of natural events on biological communities during the last 20 kyr biplot analysis of compositional data was applied to indicate the presence of subcompositions or in other words to identify strong relationships among a limited number of species that can be interpreted from a palaeoenvironmental point of view this investigation was followed by the application of simplicial principal component analysis with the aim of determining from a numerical point of view the laws for describing and modelling the behaviour of the species involved in these subcompositions in this work all statistical methods were applied by taking rigorously into account the sample space of compositional data i e data matrices whose rows sum to 100 from a general point of view the results obtained related to the detection of new parameters to be used for monitoring the quality of the past environment have encouraged us to promote the application of statistical methodologies that take into account the correct sample space for compositional data in this context inferential applications and modelling can be developed under a correct theoretical framework

eocene oligocene calcareous nannofossils from maud rise and kerguelen plateau antarctica paleoecological and paleoceanographic implications abstract the evolution of the southern ocean climate during the late eocene late oligocene interval is examined through high resolution quantitative calcareous nannofossil analyses on samples from the southern ocean sections on maud rise and kerguelen plateau we determined the abundance patterns of the counted species to clarify the biostratigraphy which we correlated with high resolution magnetostratigraphy roberts a p bicknell s j byatt j bohaty s m florindo f harwood d m 2003a magnetostratigraphic calibration of southern ocean diatom datums from the eocene oligocene of kerguelen plateau ocean drilling program sites 744 and 748 in florindo f cooper a k o brien p a eds antarctic cenozoic palaeoenvironments geologic record and models palaeogeogr palaeoclimatol palaeoecol 198 145 168 florindo f roberts a p in press eocene oligocene magnetobiochronology of odp sites 689 and 690 maud rise weddell sea antarctica geol soc am bull and used this data to interpret paleoceanographic changes through the late eocene to late oligocene percentage plots of the individual species compared with r mode principal component and cluster analysis results allowed us to divide the assemblages into three groups temperate water taxa cool water taxa and no temperature affinity taxa we attempt correlations between these paleoecological groups and the major sea surface temperature sst variations with tectonic and paleoceanographic changes in the southern ocean during the late eocene the nannofossil assemblage data reveal that there were several minor sst decreases coolings from 36 to 34 ma before the eocene oligocene e o boundary a sharp cooling event dated at 33 54 ma earliest oligocene occurred about 160 kyr after the e o boundary which is dated at 33 7 ma relatively stable cool conditions are interpreted to persist until the latest oligocene when an increase in abundance of temperate water taxa which corresponds to an antithetical decrease in abundance of cool water indicators is recorded on the basis of our dating the opening of the drake passage allowing shallow water circulation began by 33 54 ma at the latest while the establishment of deep water connections through the tasmanian gateway occurred at 33 ma as suggested by exon et al proc odp init rep 189 2001 1

major shifts in calcareous phytoplankton assemblages through the eocene oligocene transition of tanzania and their implications for low latitude primary production a high resolution record of exceptionally well preserved calcareous nannofossil assemblages from tanzania is marked by two key transitions closely related to the climatic events of the eocene oligocene transition eot the first transition at similar to 34 0 ma precedes the first positive shift in delta o 18 and coincides with a distinct interval of very low nannofossil abundance and a cooling in sea surface temperatures sst the second at similar to 33 63 ma is immediately above the eocene oligocene boundary eob and is associated with a significant drop in nannofossil diversity both transitions involve significant reductions in the abundance of holococcoliths and other oligotrophic taxa these changes in calcareous phytoplankton assemblages indicate 1 a widespread and significant perturbation to the low latitude surface ocean closely tied to the eob 2 a potential role for reduced carbonate primary production at the onset of global cooling and 3 a significant increase in nutrient availability in the low latitude surface ocean through the eot

refining the eustatic sea level curve since the last glacial maximum using far and intermediate field sites the eustatic component of relative sea level change provides a measure of the amount of ice transferred between the continents and oceans during glacial cycles this has been quantified for the period since the last glacial maximum by correcting observed sea level change for the glacio hydro isostatic contributions using realistic ice distribution and earth models during the last glacial maximum lgm the eustatic sea level was 125 5 m lower than the present day equivalent to a land based ice volume of 4 6 4 9 107 km3 evidence for a non uniform rise in eustatic sea level from the lgm to the end of the deglaciation is examined the initial rate of rise from ca 21 to 17 ka was relatively slow with an average rate of ca 6 m ka 1 followed by an average rate of ca 10 m ka 1 for the next 10 ka significant departures from these average rates may have occurred at the time of the younger dryas and possibly also around 14 ka most of the decay of the large ice sheets was completed by 7 ka but 3 5 m of water has been added to the oceans since that time

astronomic calibration of the late eocene early oligocene massignano section central italy we present an astronomically tuned polarity timescale for the late eocene early oligocene based on a cyclic limestone marls sedimentary succession exposed at massignano italy gssp for the eocene oligocene boundary here we applied spectral analysis techniques to the high resolution magnetic susceptibility record the results provide clear evidence of a regular and cyclic signal that allows us to discard a stochastic mechanism as controlling these fluctuations conversely these outcomes reveal the presence of stable and notable periodicities that are in tune with those associated with orbital forcing through a cyclostratigraphic analysis of the rhythmic sedimentary alternations and combination with the results of time series analysis of the proxy record we refine the late eocene portion of the gpts through astronomical tuning of the rhythmic sedimentary alternations to recent astronomically calculated variations of earth s orbit we recalibrated the polarity boundaries ages and the main stratigraphic events recognized throughout the sedimentary record among these an age of 33 714 ma is proposed for the e o boundary

crosswell seismic applications for improved reservoir understanding abstract crosswell seismic cs technology provides a high resolution image of the subsurface between two nearby wells crosswell seismic data can reach frequencies greater than 1000 hz which makes the technology applicable to many reservoir development challenges in hydrocarbon exploration and production studies that require high resolution applications of crosswell seismic data range from structural and stratigraphic interpretation to reservoir monitoring and enhanced oil recovery eor when integrated with rock physics crosswell seismic data can be used in reservoir characterization studies which potentially could be used for enhancing the resolution of rock properties derived from 3d surface seismic data to that of crosswell resolution in addition velocity models obtained from crosswell seismic data can be used to better predict event locations in microseismic data processing

environmental magnetic record of paleoclimate change from the eocene oligocene stratotype section massignano italy 1 a high resolution environmental magnetic study of the massignano section italy global stratotype section and point for the eocene oligocene boundary has been performed to test whether a clear magnetic signature associated with climatic change is recognizable in this record our results reveal the existence of alternating intervals with high and low magnetic mineral concentrations similar to the pattern of rock magnetic property variations observed from an environmental magnetic study of the ciros 1 sediment core from antarctica these results suggest that an external forcing mechanism drove the sedimentary response to global climate change prior to the major oi 1 cooling event at the eocene oligocene boundary

response of the mediterranean and dead sea coastal aquifers to sea level variations 1 the present study examines the response of groundwater systems to expected changes in the mediterranean sea rise of 1cm yr and dead sea levels decline of 1 m yr a fast response is observed in the dead sea coastal aquifer exhibited both in the drop of the water levels and in the location of the fresh saline water interface no such effect is yet observed in the mediterranean coastal aquifer as expected numerical simulations using the feflow software show that the effect of global sea level rise depends on the coastal topography next to the shoreline a slope of 2 5 is expected to yield a shift of the interface by 400 m after a rise of 1m 100 years whereas a vertical slope will yield no shift reduced recharge due to climate change or overexploitation of groundwater also enhances the inland shift of the interface

characteristics of shocked quartz in late eocene impact ejecta from massignano ancona italy clues to shock conditions and source crater the microstructure and optical properties of shocked quartz discovered in a distal ejecta horizon of the stratigraphically continuous upper eocene section at massignano italy have been investigated in detail the microstructural observations confirm the impact origin of the shocked quartz grains and reveal that the optically visible planar lamellae are well preserved amorphous to partially recrystallized planar deformation features refractive index measurements of shocked quartz and analysis of the orientation and thickness of planar deformation features indicate shock pressures of 10 to 26 gpa at ambient preshock temperature altogether the characteristics of shocked quartz from massignano imply a nonporous quartz rich near surface rock as its source popigai russia is favored as the source crater because of the presence of compact quartzites in its preimpact cover

export production of coccolithophores in an upwelling region results from san pedro basin southern california borderlands a seven month long time series sediment trap project was carried out in san pedro basin southern california borderlands in order to evaluate the response of calcareous nannoplankton to seasonal hydrographic changes this region is periodically influenced by upwelling particularly during the spring and early summer the highest fluxes of both whole coccospheres and individual coccoliths occurred during winter january february a period when the fluxes of diatoms and planktic foraminifera were low the highest coccolithophore fluxes were recorded in the mid february with 860 106 coccoliths m 2 day 1 8 106 whole coccospheres m 2 day 1 and 80 mg of coccolith carbonate m 2 day 1 coccolith carbonate fluxes in january and february account for most of the total carbonate fluxes measured during this period the season of maximum coccolithophore production in this region winter is correlated with weak stratification of the upper water column low total primary production low nutrient contents and low temperatures emiliania huxleyi and florisphaera profunda are the two most abundant species in this region while e huxleyi displays no distinct seasonal changes in flux f profunda shows a clear preference for cold low nutrient water conditions and low light levels helicosphaera spp flux is positively correlated to the total coccosphere fluxes and is indicative of high coccolithophore productivity

modes of seawater intrusion during transgressions analytical methods and numerical experiments are used to study salinization of groundwater in response to sea level rise the system that is studied involves a saturated porous medium with an inclined upper surface the upper surface is progressively inundated during sea level rise to simulate transgression the landward migration of the shoreline four modes of seawater intrusion are distinguished 1 horizontal intrusion for slow transgression and a relatively high permeability substrate 2 vertical intrusion by seawater fingering for fast transgression and a sand silt substrate 3 vertical intrusion by diffusion for fast transgression and a low permeability clay substrate 4 vertical intrusion by combined diffusion and low salinity fingering for fast transgression and a clay layer at the seafloor overlying an aquifer these four modes are characterized by the development of very distinctive transition zones between the fresh and salt groundwater domains an analytical expression is derived for the critical transgression rate which separates horizontal mode 1 from dominantly vertical modes 2 4 intrusion for modes 3 and 4 salinization significantly lags behind sea level rise the results are consistent with observations of fossil fresh brackish groundwater beneath many continental shelves and shallow seas

multicomponent heterovalent chromatography in aquifers modelling salinization and freshening phenomena in field conditions abstract analysis of hydrochemical data using diagrams and the geochemical transport model phreeqc confirmed that for the argos plain aquifer and for other heterogeneous confined alluvial coastal aquifers in greece the variation of water qualities along a flow path has basically a chromatographic origin due to seawater intrusion and freshening processes additionally calcite precipitation dolomite and gypsum dissolution take place intense fertilization and overexploitation of the area resulted in degradation of the groundwater quality by high amounts of nitrate ions and increased salinization the main physical factor affecting groundwater quality in this area is the cation exchange capacity that is calculated to be 4 3 meq 100 gr 1 good adaptation of the transport model to the field data showed that the model can be used to predict the freshening process after an artificial recharge hence in a first stage for cl there is a continuous decrease to the initial fresh water concentrations corresponding to about 1 1 5 pores volumes that should have been shifted through the aquifer while for both cations ca 2 and mg 2 this decrease is even lower and leads to concentrations lower than that of the initial fresh water complete restoration of the aquifer requires a great amount of recharge water that should be transported through the aquifer and corresponds to 32 pores volumes

identification of a holocene aquifer lagoon system using hydrogeochemical data abstract the hydrogeochemical characteristics of the cabo de gata coastal aquifer southeastern spain were studied in an attempt to explain the anomalous salinity of its groundwater this detritic aquifer is characterised by the presence of waters with highly contrasting salinities in some cases the salinity exceeds that of seawater multivariate analysis of water samples indicates two groups of water g1 and g2 group g1 is represented in the upper part of the aquifer where the proportion of seawater varies between 10 and 60 whilst g2 waters taken from the lower part of the aquifer contain 60 70 seawater in addition hydrogeochemical modelling was applied which reveals that the waters have been subject to evaporation between 25 and 35 there was a good agreement between the modelled results and the observed water chemistry this evaporation would have occurred during the holocene in a coastal lagoon environment the resulting brines would have infiltrated into the aquifer and due to their greater density sunk towards the impermeable base the characteristics of this water enabled us to reconstruct the interactions that must have occurred between the coastal aquifer and the lagoon and to identify the environmental conditions that prevailed in the study area during the middle holocene

unconformity bounded stratigraphic units ubsus in an italian alluvial plain area recognizing and dating abstract we studied the coastal zone of the tavoliere di puglia plain puglia region southern italy with the aim to recognize the main unconformities and therefore the unconformity bounded stratigraphic units ubsus salvador 1987 1994 forming its quaternary sedimentary fill recognizing unconformities is particularly problematic in an alluvial plain due to the difficulties in distinguishing the unconformities that bound the ubsus so far the recognition of ubsus in buried successions has been made mostly by using seismic profiles instead in our case the unavailability of the latter has prompted us to address the problem by developing a methodological protocol consisting of the following steps i geological survey in the field ii draft of a preliminary geological setting based on the field survey results iii dating of 102 samples coming from a large number of boreholes and some outcropping sections by means of the amino acid racemization aar method applied to ostracod shells and 14c dating filtering of the ages and the selection of valid ages iv correction of the preliminary geological setting in the light of the numerical ages definition of the final geological setting with ubsus identification of a hypothetical or attributed time range htr or atr for each ubsu the former very wide and subject to a subsequent modification the latter definitive v cross checking between the numerical ages and or other characteristics of the sedimentary bodies and or the sea level curves with their effects on the sedimentary processes in order to restrict also the hypothetical time ranges in the attributed time ranges the successful application of aar geochronology to ostracod shells relies on the fact that the ability of ostracods to colonize almost all environments constitutes a tool for correlation and also allow the inclusion in the same unit of coeval sediments that differ lithologically and paleoenvironmentally the treatment of the numerical ages obtained using the aar method required special attention the first filtering step was made by the laboratory rejection criteria a and b then the second filtering step was made by testing in the field the remaining ages among these in fact we never compared an age with a single preceding and or following age instead we identified homogeneous groups of numerical ages consistent with their reciprocal stratigraphic position this operation led to the rejection of further numerical ages that deviate erratically from a larger homogeneous age population which fits well with its stratigraphic position rejection criterion c after all of the filtering steps the valid ages that remained were used for the subdivision of the sedimentary sequences into ubsus together with the lithological and paleoenvironmental criteria the numerical ages allowed us in the first instance to recognize all of the age gaps between two consecutive samples next we identified the level in the sedimentary thickness that is between these two samples that may represent the most suitable ubsu boundary based on its lithology and or the paleoenvironment the recognized units are i coppa nevigata sands nea htr mis 20 14 atr mis 17 16 ii argille subappennine asp htr mis 15 11 atr mis 15 13 iii coppa nevigata synthem nvi htr mis 13 8 atr mis 12 11 iv sabbie di torre quarto stq htr mis 13 9 1 atr mis 11 v amendola subsynthem mlm1 htr mis 12 10 atr mis 11 vi undifferentiated continental unit uci htr mis 11 6 2 atr mis 9 3 7 1 vii foggia synthem tgf atr mis 6 viii masseria finamondo synthem tpf atr upper pleistocene ix carapelle and cervaro streams synthem rpl subdivided into ixa incoronata subsynthem rpl1 htr mis 6 3 atr mis 5 3 ixb marane la pidocchiosa castello subsynthem rpl3 atr holocene x masseria inacquata synthem naq atr holocene the possibility of recognizing and dating quaternary units in an alluvial plain to the scale of a marine isotope stage constitutes a clear step forward compared with similar studies regarding other alluvial plain areas where quaternary units were dated almost exclusively using their stratigraphic position as a result they were generically associated with a geological sub epoch instead our method allowed a higher detail in the timing of the sedimentary processes for example mis 11 and mis 5 5 deposits have been recognized and characterized for the first time in the study area highlighting their importance as phases of sedimentation

vertical seismic profiling vertical seismic profiling is one of the rapidly developing areas of geophysical technology for exploring in mature basins the measurement basically involves recording the total upgoing and downgoing seismic wave fields propagating through a stratigraphic section by means of geophones clamped to the wall of a drilled well

links between climate and sea levels for the past three million years the oscillations between glacial and interglacial climate conditions over the past three million years have been characterized by a transfer of immense amounts of water between two of its largest reservoirs on earth the ice sheets and the oceans since the latest of these oscillations the last glacial maximum between about 30 000 and 19 000 years ago approximately 50 million cubic kilometres of ice has melted from the land based ice sheets raising global sea level by approximately 130 metres such rapid changes in sea level are part of a complex pattern of interactions between the atmosphere oceans ice sheets and solid earth all of which have different response timescales the trigger for the sea level fluctuations most probably lies with changes in insolation caused by astronomical forcing but internal feedback cycles complicate the simple model of causes and effects

late and postglacial sea level changes in the kattegat the consequences to different coastal aquifers on the islands zealand and anholt abstract fluctuations in sea level influence the condition of coastal groundwater aquifers in this paper the palaeo hydrology of anholt and part of zealand and its dependence on the sea level history of kattegat will be analyzed the late and postglacial sea level changes in kattegat are outlined and the consequences analyzed for late and postglacial ice movement and for two different coastal aquifers a simple unconfined aquifer at the island anholt and a complex confined limestone aquifers around roskilde on zealand data are presented which provide a description of how sea level changes have influenced and formed the island anholt this geological history can be used to provide information on the development of the salt fresh groundwater interface under a sand island the center of anholt was covered by the sea at 6 ka and has now an ideal ghyben herzberg freshwater lens this means that the present equilibrium between the saltwater and freshwater has been established in less than 6000 years limestone aquifers on zealand show no ideal ghyben herzberg freshwater lens detailed 3 d mapping of a study area around roskilde and isefjord has revealed how low sea levels around 50 30 ka cause development of karst structures and deep erosion channels in the limestone later filled with high permeable sand and gravel these channels drain the groundwater to subsea springs working as natural pumps resulting in a freshwater lens much thinner than the equilibrium

the age of the popigai impact event and its relation to events at the eocene oligocene boundary ages ranging from the late cretaceous 65 myr to the oligocene 29 myr have been reported for the 100 km diameter popigai impact structure1 2 on the anabar shield central siberia these ages3 4 5 6 7 8 overlap the timing of several possible impact related features including the cretaceous tertiary and eocene oligocene stratigraphic boundaries the north american tektites9 and the recently reported occurrences of an iridium anomaly and shocked quartz in late eocene deposits in northern italy10 here we report age determinations of several popigai impact melt rocks using the 40ar 39ar step heating technique to constrain the age of the impact event our results are consistent with a late eocene impact age of 35 7 0 2 myr 2 coincident in time with the impact deposits found in italy as this age is also similar to that of the north american tektites which have been associated with the chesapeake bay impact structure in the eastern united states11 12 13 there seem to have been at least two large and essentially contemporaneous impacts during the late eocene