precise single grain 40 ar 39 ar dating of a cold to warm climate transition in central europe recent advances in 40ar 39ar dating1 2 have made it possible to date individual k feldspar grains from pleistocene tephra a capability that greatly improves the reliability and temporal resolving power of the method here we apply these new techniques to the dating of a phonolite tephra from the east eifel volcanic field in west germany which is sandwiched between loess and palaeosol alfisol deposits and which was therefore erupted during the transition from a glacial to an interglacial period our age estimate for this transition is 215 4 kyr 1 which has important implications for the marine 18o timescale and for models of global climate change during the pleistocene the results show that single grain dating can detect and compensate for the large quantities of xenocrystic contaminants which are found in many tephra deposits this technique could be used to date the tephra layers found in marine sediment cores and the results could greatly enhance the reliability of the marine 18o timescale for more rigorous fourier analysis testing of the milankovitch hypothesis

late pleistocene time series of atmospheric and oceanic variables recorded in sediments from the subarctic pacific time series analyses of atmospheric and oceanic variables in a late pleistocene record from the northwest pacific show the complex relationship of the response of various segments of the climate system to changes in the earth s orbit most variance spectra of time series from this subarctic record contain frequency peaks with periods corresponding to at least one of the major orbital components of eccentricity obliquity or precession although the radiolarian faunal water mass assemblages have prominent spectral peaks with 41 000 year periods which are coherent with obliquity at this frequency only the transitional faunal assemblage contains variance focused at a frequency corresponding to the 100 000 year period of eccentricity three of these faunal time series also show variance concentrated at a frequency with a 20 000 year period these three time series are not coherent at a 20 000 year frequency with either of the dominant spectral peaks of precession they are coherent however with variations in the second harmonic of the obliquity cycle changes in obliquity apparently affect siliceous faunal abundances in the northwest pacific region of this high latitude site more than variations in eccentricity or precession maxima in the time series of quartz abundance occur during low values of eccentricity and high glacial ice volume because atmospheric winds serve as the major source of supply of quartz to the sediments at this site these high quartz values reflect increased aridity at the source region except for short periods during interglacials the characteristics of the surface waters in this region of the subarctic pacific during much of the last 460 000 years were similar to those which exist today in the sea of okhotsk the spectrum of winter sea surface temperature estimates derived from siliceous microfaunal abundances contains dominant frequency peaks at periods of 100 000 41 000 and 23 000 years which are coherent with eccentricity obliquity and precession respectively based upon the relationship of the subarctic front with the dominance of specific faunal asemblages the front was positioned south of its present day location throughout much of the late pleistocene

formal quaternary stratigraphy what do we expect and need at the start of my inqua career a reasonable target for the long term development of quaternary stratigraphy was the construction of a table that listed a number perhaps fewer than a dozen perhaps more of stages for each of the chief regions of the earth and which reliably indicated how these stages should be correlated from region to region a second target was to estimate ages for the stage boundaries finally some workers may have looked towards a series of global stages with the hope that these would be defined in their own region rather than in the alps for some researchers the target has not changed nor does its attainment appear much closer however there are now many whose requirement is that we create time series of environmental and climatic change with ever increasing temporal resolution along with correlation lines that are precise enough to permit global synoptic reconstruction funding for this research is justified partly on the grounds that it will give us increased confidence in our ability to forecast climatic change during the next century hence far from only being of academic interest long term planning of energy based economies indirectly depends upon it there is a danger that some excellent research by members of the inqua community becomes marginalized because the stratigraphic framework through which the research is communicated does not meet modern requirements oxygen isotope stratigraphy as it was quasi formalized by shackleton and opdyke 1973 and 1976 only applies to marine sediments containing foraminifera suitable for oxygen isotope analysis on the other hand there can be no doubt that as an informal standard means of communication oxygen isotope stratigraphy has been incredibly valuable even in settings where it is very hard to justify its use formal stratigraphy is intended to enable precise communication in research publications and in maps and i believe that in this regard there is more to be gained by improving correlation to the ocean oxygen isotope record than by working to define stage boundary stratotypes with continent scale utility

isotopic modeling of climatic oscillations implications for a comparative study of marine and ice core records a simple climate model of quaternary glaciations is combined with a simple isotopic model in order to study phase relationships between 18o records in deep sea cores and in ice cores power spectra of the model s climatic and isotopic variables show a dominant peak near 100 kyr 1 kyr 1000 years the continuous background of all paleoclimatic spectra smaller peaks at the orbital periodicities of 41 23 and 19 kyr and additional peaks at 14 7 13 11 5 10 4 and 9 5 kyr time lags between the model s isotopic profiles are highly variable ice core events identified as sharp maxima or minima can lead apparently homologous events in the marine record or lag them by a few thousand years this time domain instability of lags is due to the complexity of the power spectrum with its continuous component and large number of lines since the complex spectrum is present in both model and paleoclimatic data we expect lag relations in the data to be quite variable as well independent dating of ice cores is preferable therefore to dating by comparison with marine records absolute dating can be based on a combination of ice flow models and of accelerator mass spectroscopy time averaged cross spectra of independently dated isotopic profiles should be stable and should help us to understand the mechanisms which lead to internal climatic variability

periodicities of caco3cycles in the pliocene of sicily discrepancies with the quasi periods of the earth s orbital cycles a high resolution caco3 record in combination with a detailed magnetostratigraphy is presented for the rhythmically bedded marly sequence of the pliocene trubi formation on sicily italy magnetostratigraphic age calibration and subsequent spectral analysis of the variatrions in caco3 content yield a remarkably consistent discrepancy between the resulting periodicities and the corresponding quasi periods of the earth s orbital cycles this discrepancy can only be explained by assuming that ages assigned to polarity reversal boundaries in the geomagnetic polarity time scale lack sufficient precision a new polarity time scale is presented for the major part of the gilbert and gauss chron using the radiometrically dated gilbert gauss chron boundary at 3 40 ma as an age reference point and extrapolating an average quasi period of 21 7 kyr of the precession cycle as the periodicity of small scale colour annex caco3 cycles

late pleistocene to holocene environmental changes as recorded in the sulfur geochemistry of coastal plain sediments southwestern taiwan abstract a core drilled at san liao wan in the southwestern coastal plain of taiwan has been analyzed for total sulfur contents isotopic values as well as ratios of pyritic sulfur to organic carbon our results demonstrate a close relationship between late pleistocene sea level change and the proxies generated in this study the inorganic sulfur contents indicate that at our study site the holocene transgression started at 11 ka and remained under seawater for thousands of years until the late holocene corresponding to a depth of 20 m in the study core the uppermost 20 m of core shows relatively high total organic carbon toc and 34s of inorganic sulfur suggesting a transitional environment such as muddy lagoon or marsh before the site turned into a modern coastal plain in the lower part of the core at depths of 110 145 m corresponding ages of 12 30 ka low sulfur contents are recorded probably indicating fluvial sediments deposited during the oceanic isotope stage ois 2 a sea level lowstand the lower part of the core roughly within ois 3 records at least two transgressions although the transgressional signals may be somewhat obscured by subsequent weathering the reworked origin of organic matter reported in previous studies is confirmed by our organic sulfur data however the marine organic source was periodically dominant the modern high sulfate concentrations in pore water have no correlation to the other sulfur species in the sediments probably indicating that the sulfate migrated into the site subsequent to early diagenesis

displaced antarctic diatoms in vema channel sediments late pleistocene holocene fluctuations in aabw flow abstract displaced antarctic diatoms were identified and counted in a suite of 23 giant gravity cores from the east flank of the vema channel providing a semi quantitative index of late pleistocene holocene fluctuations in antarctic bottom water aabw flow twelve species of antarctic diatoms were counted and three of these nitzschia kerguelensis eucampia antarctica and coscinodiscus lentiginosus occur in sufficient quantity for statistically meaningful interpretations the number of diatom specimens per gram of carbonate free sediment was determined for core top last glacial maximum last interglacial and penultimate glacial maximum intervals antarctic diatoms are abundant in cores from depths in excess of 4100 m and disappear abruptly in core tops between approximately 4125 and 3975 m water depth no specimens of antarctic diatoms are present in cores shallower than 3744 m the top of this transition zone corresponds with the isotherms 1 9 c and the isopycnal 4 45 93 that hogg et al 1982 selected as a suitable reference level between northward and southward flow in the vema channel axis the sediments from the vema channel indicate no significant shallowing or deepening of this level during the glacial or interglacial intervals examined displaced antarctic diatoms are generally less abundant during glacial maxima than during interglacials downcore counts of displaced antarctic diatoms reveal two peaks of dramatically increased abundances at the isotopic stage 6 7 and 3 2 boundaries in other cores within the vema channel from below 3965 m late pleistocene hiatuses are common

earth s precession cycle and quaternary climatic change in tropical africa high abundances of the freshwater diatom melosira spp reflecting eolian input from dry lake beds in tropical africa occur in deep sea sediments of the equatorial atlantic at discrete times during the late quaternary1 2 we report here an approximately 260 kyr record of melosira accumulation in an equatorial atlantic sediment core and demonstrate significant influence of the earth s precessional cycle on the climate of tropical africa

astronomical theory of the pleistocene ice ages a brief historical review abstract this paper traces the evolution of the astronomical theory of the pleistocene ice ages from its origin in the work of adhemar and croll through its quantitative transformation in the hands of milankovitch to its current renaissance emphasis is given to the interplay between climatic theory and geologic observation from 1941 when milankovitch published his final version of the theory until the early 1970s most attempts to test the theory empirically were carried out in the time domain by comparing the geologic record of climate with predicted climate curves these attempts ran into serious difficulties particularly the inaccuracy of the geologic time scale and the ambiguity of climate predictions early attempts to evaluate the theory with simple radiation balance models appeared to indicate that the climatic response to secular changes in the orbit would be too small to be observed geologically but by the mid 1970s the advent of an improved time scale for pleistocene marine deposits and the availability of long closely sampled records made it possible to arrange generalized but unambiguous tests of the theory in the frequency domain by comparing orbital and climatic spectra these results decisively confirmed the idea that orbital variations significantly influenced the earth s climate during the pleistocene but they did not tell us how this influence was exercised the emphasis of current work has therefore shifted to the identification and quantitative modeling of physical mechanisms by which the climate system responds so dramatically to the predicted rather subtle changes in radiative boundary conditions

low temperature hydrothermal oil and associated biological precursors in serpentinites from mid ocean ridge abstract the origin of light hydrocarbons discovered at serpentinite hosted mid ocean hydrothermal fields is generally attributed to the abiogenic reduction of carbon di oxide by molecular hydrogen released during the progressive hydration of mantle derived peridotites these serpentinization by products represent a valuable source of carbon and energy and are known to support deep microbial ecosystems unrelated to photosynthesis in addition the pool of subsurface organic compounds could also include materials derived from the thermal degradation of biological material we re investigate the recently described relics of deep microbial ecosystems hosted in serpentinites of the mid atlantic ridge 4 6 n in order to study the ageing and hydro thermal degradation of the preserved biomass an integrated set of high resolution micro imaging techniques scanning electron microscopy high resolution transmission electron microscopy raman and fourier transform infra red microspectroscopy confocal laser scanning microscopy and scanning transmission x ray microscopy at the carbon k edge has been applied to map the distribution of the different organic components at the micrometer scale and to characterize their speciation and structure we show that biologically derived material containing aliphatic groups along with carbonyl and amide functional groups has experienced hydrothermal degradation and slight aromatization in addition aliphatic compounds up to c 6 c 10 with associated carboxylic functional groups wet the host bastite and the late serpentine veins crosscutting the rock these compounds represent a light soluble organic fraction expelled after biomass degradation through oxidation and thermal cracking the detected complex organic matter distribution recalls a typical petroleum system where fossil organic matter of biological origin maturates expelling the soluble fraction which then migrates from the source to the reservoir ecosystem hosting serpentinites can thus be seen as source rocks generating a net transfer of hydrocarbons and or fatty acids issued from oxidative processes and primary cracking reactions then migrating upward through the serpentine vein network this finally suggests that deep thermogenic organic compounds of biological origin can be a significant contributor to the organic carbon balance at and far below peridotite hosted hydrothermal fields

the geologic record of climatic change this paper reviews the principal results from paleoclimate studies and includes background material slanted toward climate modelers the inferred temperature history of the last 4 6 billion years indicates major changes in the components of the earth s climate system a secular change in global insolation receipt is due to a 20 30 increase in solar luminosity since the formation of the earth a co2 h2o greenhouse effect may have offset the lower luminosity during early earth history inferred fluctuations of global temperature have occurred over a broad range of time scales on time scales of 106 108 years paleogeographic factors e g continental drift and sea level changes have contributed significantly to temperature changes associated with transitions between nonglacial and glacial states preliminary modeling efforts indicate that additional factors e g co2 changes in atmospheric circulation must also be considered in order to explain the origin of nonglacial climates the origin of polar ice caps may result from ocean circulation changes that were caused by plate tectonic processes fluctuations of ice volume on a time scale of 10 105 years correlate with insolation variations caused by orbital perturbations feedback interactions within the land sea air ice system e g ocean circulation changes and bedrock dynamics have been responsible for a significant modulation of the orbital signal ice ages may be due to orbitally induced temperature changes superimposed on a global cooling of terrestrial origin

the evolution of pleistocene climate a time series approach abstract in the later part of the pleistocene variations in global ice volume have been dominated by an approximate 100 000 year cycle analysis of 2 myr long oxygen isotope record from an equatorial pacific core indicates that this is true only for the last 900 000 years prior to this time the amplitude of the 100 000 year cycle is much reduced as is the variance of all oscillations with periods greater than 60 000 years based on results of time series analysis of this 2 myr long record the pleistocene glacial cycles can be divided into three sections 1 the late pleistocene 0 900 kyr b p where the variations in the isotope record are dominated by the 100 000 year cycle 2 the middle pleistocene 900 1450 kyr b p in which low frequency components are not as important as in the later period of the pleistocene and 3 the early pleistocene late pliocene 1450 2000 kyr b p where general reductions of importance at all frequencies is seen as compared to the later intervals recent modeling efforts which describe variations in global ice volume show that the dominant low frequency component observed in the late pleistocene can result from different time constants for the rate of glacial growth and decay in response to variations in the earth s orbital parameters it is hypothesized that during the early pleistocene the rate of growth and decay of glaciers were more similar and that continental erosion by successive glacial advances lowered the land surface in areas of ice cap formation to below sea level when the ice caps became marine based more rapid decay of the ice became possible

stable isotope data and depositional environments in the late quaternary arctic ocean there has been much speculation about the history of the arctic ocean particularly its response to the late quaternary climatic fluctuations1 8 as a result considerable data have been gathered from arctic ocean sediment cores to reconstruct glacial and interglacial arctic ocean palaeoenvironments8 9 but even with these data the reconstructions and the correlations with the quaternary chronostratigraphy have been unsatisfactory mainly because of the lack of detailed stratigraphical data such as those provided by stable oxygen isotope stratigraphy10 here we present stable isotope records from arctic ocean sediment cores which can be correlated convincingly with corresponding data from the north atlantic together with lithostratigraphical data they provide new evidence on arctic ocean history in relation to global late quaternary climatic fluctuations

a strategy for frequency spectra of quaternary climate records the paleoclimatic variability at frequencies ranging from 10 4 cycle per year cpy to 10 5 cpy is investigated using a set of four deep sea cores from the atlantic pacific and indian oceans dominant features are the presence of orbital frequencies corresponding to mean periods of 117 7 43 6 24 9 and 19 3 kyr these are statistically significant according to such advanced spectral tools as blackman tukey maximum entropy and the highly efficient thomson technique however the main purpose of this paper is methodological describing the statistical analyses of time series with modern methods in order to stress their relative power advantages and disadvantages the more advanced statistical methods confirm the coincidence of the dominant periods in the deep sea cores and those in the astronomical elements including combination tones three frequency bands of high paleoclimatic variability centred at 15 4 13 and 10 8 kyr are indeed also detected these two last periods are very close to those predicted by the climatic non linear model of ghil and le treut and found by pestiaux et al and yiou et al

high resolution stratigraphy in late pleistocene holocene sediments of the vema channel abstract twenty five giant gravity cores ggc were obtained from the southwest flank of the rio grande rise in the summer of 1980 and were analyzed for time slice interpretations of the late pleistocene paleoceanography of the southwestern atlantic the cores span a depth interval of 1430 4148 m encompassing each of the principal deep water masses the suite of cores contains a continuous depositional record of the past 150 000 200 000 years from calcium carbonate oxygen isotope carbon 14 and biostratigraphic analyses it is possible to determine the precision in core to core correlation which is obtainable within this region of relatively low accumulation rates 0 5 2 0 cm 10 3 yrs calcium carbonate analyses were performed on each of the 25 cores at 1 cm sampling intervals using a technique that yields an analytical precision of 0 25 the carbonate curves show glacial interglacial amplitudes of typically 10 30 caco3 higher frequency amplitudes of 2 5 are also present both the glacial interglacial and the higher frequency carbonate signals can be correlated from core to core over the entire depth interval of the transect and are essentially synchronous based on independent stratigraphic control provided in selected cores by 18o 14c and biostratigraphic analyses despite the low sedimentation rates within this particular region we obtain a precision in core to core correlation of 1000 2000 yrs over the late pleistocene holocene these high resolution studies from the vema channel have important implications for interpreting the effects of bioturbation on a given stratigraphic sequence modeling the effects of bioturbation on the abundance and isotopic records of the benthonic foraminifera planulina wuellerstorfi suggests that for the region of the vema channel rio grande rise invalid stratigraphic and paleoceanographic interpretations may result if abundance variations in this species are ignored the results of these analyses show that it is possible to generate detailed stratigraphies in regions that have not previously been selected for high resolution studies solely because of relatively low accumulation rates of sediments our results indicate that carbonate analyses in some regions may provide a distinct advantage over 18o analyses because of the ease of analysis and high precision for identifying low amplitude high frequency fluctuations which can be correlated from core to core at the same time independent stratigraphic control via 18o or 14c is essential to verify whether this technique of carbonate curve matching is valid

strong evidence of high frequency sub milankovitch orbital forcing by amplitude modulation of milankovitch signals abstract high frequency sub milankovitch signals have occasionally been recognised in the sedimentary record but their interpretation is yet controversial the transmission of most information involves modulating the original signal transmission in the geological sense is the process of changing the astronomical signal into insolation climate and finally the observed sediment modulated signals may contain different frequencies from the original and the former can sometimes be recognised more easily than the original ones thus sedimentary cycles belonging to the high frequency band could be interpreted as a possible modulation of the astronomical milankovitch signals to check this possibility a detailed spectral analysis was carried out on a selected marl limestone and limestone jurassic succession in which high frequency signals in the sub milankovitch range with a persistent peak at 13 14 kyr were recognised relationships between frequencies of the registered peaks suggest that the sedimentation pattern is caused by the amplitude modulation am of the milankovitch forcing in am the amplitude of a carrier frequency is modulated according to the value of a signal the spectrum of the resulting am signal is composed of three frequencies the frequency of the carrier and two side tones but the carrier and one side tone may be suppressed without destroying the information the information remains in the other side tone usually the one with the highest frequency this version of am is called single sideband carrier suppressed ssbcs for milankovitch forcing the implication is that the signals are not transmitted as added up sinusoidal signals but both the short eccentricity and the obliquity signals affect the sedimentation pattern by am of the precession signal which is the carrier frequency the sub milankovitch peaks registered in the succession studied reveal the ssbcs am of the original milankovitch signals with the ssbcs frequencies being highly significant in the estimated power spectra after applying conservative tests assuming underlying red noise

quaternary fluctuations in the northern hemisphere trade winds and westerlies the mass accumulation rate and grain size of the total colian component isolated from pelagic sediment in two north pacific cores piston core kk75 02 under the prevailing westerlies and deep sea drilling project site 503 beneath the trade winds have been used to evaluate changes in the intensity of atmospheric circulation and source area aridity over the past 700 000 yr the eolian grain size a direct indicator of wind intensity fluctuates at periodicities similar to those calculated for the earth s orbital parameters of precession obliquity and eccentricity both sites display greater variability in wind intensity prior to 250 000 yr ago eolian accumulation rates an indicator of source area aridity fluctuate at periodicities similar to those of the glacial interglacial cycles lower eolian accumulation rates during colder glacial times most likely reflect increased glacial age humidity at central asian and central american source areas

geologic time series from deep sea sediments time scales and distortion by bioturbation abstract in order to evaluate the time and frequency domain characteristics of geologic time series obtained from deep sea sediments two important problems must be considered first an accurate time scale must be established for the sediment records to be studied an accurate time scale is a basic requirement for such techniques as spectral and cross spectral analysis secondly the distortion of a geologic time series by sedimentation processes such as bioturbation must be considered if inferences are to be made about the mechanisms controlling climatic and oceanographic processes reflected in the geologic record recently it has been suggested that the periodic components in paleoclimatic records which can be related to variations in the earth s orbital parameters can be used as a means for providing very detailed control for late pleistocene sediment sections a time scale is estimated by tuning an individual frequency component in a climate record to an orbital parameter the tuning procedure commonly uses the technique of bandpass filtering which removes all frequency components except the one equivalent to an orbital parameter and then adjusting the geologic time scale so that the filtered record and orbital record align since bandpass filtering will produce a periodic record from any data set a question is raised as to the circularity of this tuning approach a series of numerical experiments using synthetic time series are used to determine if the tuning of a geologic record artificially induces improved correlation and increased periodic character in a climatic record these experiments indicate that the tuning does not artificially induce these effects thus it is suggested that the careful use of orbital tuning provides a powerful means of defining a geologic time scale the degree to which bioturbation distorts a paleoclimatic record is studied by comparing the spectra of oxygen isotopic records obtained from cores with sedimentation rates ranging from 1 to 12 cm 1000 yr 1 it is shown that the systematic change in the variance spectra of these records that is predicted by models of bioturbation cannot be observed for sedimentation rates greater than 2 cm 1000 yr 1 this can be explained in part if bioturbation is a function of sedimentation rates if this is the case then bioturbation must proceed to depth of tens to hundreds of centimeters however it seems likely that the degree to which bioturbation alters the climate signal preserved in deep sea sediment cores has been overestimated

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

patterns of pervasive shear strain near the boundaries of the la ronge domain inner trans hudson orogen western canadian shield abstract the saskatchewan segment of juvenile paleoproterozoic crust inner trans hudson orogen reindeer zone is widely regarded as a nw dipping stack of litho structural domains the metavolcanic metasedimentary la ronge domain lrd whose least deformed portion has the geological map pattern of an archean greenstone belt is underlain by metasedimentary rocks of the kisseynew domain and overlain by migmatitic rocks of the rottenstone domain in easily accessible parts of lrd boundary walls the horizontal patterns of tangential boundary parallel strain accumulated under peak metamorphic conditions are investigated utilizing the strain patterns and recently published reflection seismic profiles we estimated the direction and derived the sense of tangential shear strain components on various horizontal scales in all parts of boundary walls investigated the dip shear has the sense of ductile thrusts but the strike shear sense varies with position on scales ranging from 100 m to 10 km the regional persistence of thrust shear in both lrd walls accords with tectonic scenarios of protracted horizontal convergence of juvenile crust after initial collision between the archean superior and hearne continents the patterns of strike shear on the other hand are difficult to reconcile with indentation hypotheses or counter clockwise oroclinal rotation

fourier stratigraphy spectral gain adjustment of orbital ice mass models as an aid in dating late neogene deep sea sediments orbital tuning has become an important means of dating deep sea sediments of pliocene pleistocene age one approach is to generate a template simulating ice mass history based on milankovitch forcing for comparison with a given 18o record to obtain a template that closely mimics a given 18o record we propose the following steps 1 generate a preliminary template based on a simple ice mass model 2 find the fourier matrix for this model 3 find the fourier matrix for the 18o record to be tuned if necessary adjust preliminary sedimentation rate so that maxima appear at the correct spectral lines 4 import the spectral power distribution from the matrix of the record into the matrix of the template while preserving phase of template and 5 generate the new template from the gain adjusted template matrix the record should now show optimum coherency with the template over the appropriate interval the efficiency of this method fourier matrix conjugation in producing hybrid templates is illustrated using four examples 1 testing the stacked record of prell et al 1986 for constant sedimentation rate 2 testing the date of 790 ka of the brunhes matuyama boundary in ontong java plateau ocean drilling program hole 805c berger et al 1993a 3 testing the age scale for a core from the norwegian sea containing meltwater events jansen 1989 and 4 checking the age model of ocean drilling program site 677 shackleton et al 1990 for internal consistency the template shows just where the given age models have optimum coherency with the selected orbital model and where in the record discrepancies arise

periodicities in natural remanent magnetization and palaeoclimatic records detected by walsh spectra the time series consisting of nonsinusoidal natural remanent magnetization nrm and palaeoclimatic variations for the past two million years have been spectrally examined by using a new walsh transform technique the results show statistically significant periodicities at 95 confidence level of approximately 92 000 years 43 000 years and 21 000 years in the ensemble spectra of the nrm intensity mineralogic variations these nrm periodicities are remarkably close to the well known milankovitch cycles the ensemble spectra of palaeoclimatic records reveal only 41 000 years statistically significant 95 periodicity corresponding to the obliquity cycle the study suggests that nrm variations in deep sea sediments probably are more sensitive recorders of palaeoclimatic memory than the oxygen isotope variations

periodicities of palaeomagnetic intensity and palaeoclimatic variations a walsh spectral approach abstract the walsh power spectral technique has been applied to the non sinusoidal palaeoclimatic thegloborotalia menardii climatic curve and palaeomagnetic intensity variation records of the last 1 2 myr the analysis reveals in the case of palaeomagnetic variations statistically significant peaks at 90 confidence level centered around 150 60 and 24 kyr the palaeoclimatic spectrum however indicates only two significant peaks of 60 and 24 kyr the identical periodicities in both the phenomena may suggest a causal link between the geomagnetic intensity variations and climatic changes

an automatic orbital tuning method for paleoclimate records the recognized linkage of climatic events to the earth s orbital variations has provided the basis for establishing time scales of pleistocene climatic records most of the classic orbital tuning methods developed so far however need visual judgements to add new time control points into the climatic records thus being time consuming and hindering the construction of high resolution climatic time series in this study we propose to use the dynamic optimization method to overcome the shortcomings with this technique the additional time control points can be automatically added into the climatic records and a best age for each of the climatic data can be calculated results of a case study conducted on the baoji loess section show that the automatic orbital tuning method can lead to a much better agreement of climatic time series with theoretical changes in the orbital elements relative to the classic ones

applications of quaternary geology to assess fault activity palmdale area california u s a abstract quaternary geologic investigations are routinely applied in california to assess the time of last fault displacement for purposes of engineering mitigation and regional planning this is exemplified by investigations for a 400 ha housing tract at palmdale california where several photolineaments were trenched to determine their origin some lineaments coincide with known or suspected traces of the san andreas fault and with two nearby second order faults other lineaments proved to be previously unknown faults or cultural features holocene faults designated as active by california legislation were identified on the basis of the age and apparent offset of seven quaternary morphostratigraphic units the units were correlated and relatively dated based on degree of surface dissection terrace slope angle elevation above modern drainage radiocarbon assay and relative soil profile development morphostratigraphic unit age ranges are estimated by correlation with soil profiles dated elsewhere in california and by inferred association with the marine oxygen isotope stage chronology the potential for earthquake induced ground rupture is mitigated by appropriate setbacks avoidance for habitable structures and by engineering design

tyrrhenian sea tephrochronology of the oxygen isotope record for the past 60 000 years abstract a chronology of the marine oxygen isotope record of the past 60 ka is proposed by correlating eight marine ash layers with terrestrial volcanic deposits dated by the 14c and or k ar methods detailed oxygen isotope analyses were made on the planktonic foraminifera of three cores collected in the central tyrrhenian sea the origin of the ash layers was determined by major and trace elements analyses then the major pyroclastic terrestrial deposits were sampled and analysed in order to provide land sea correlations two ash layers occurred during the warm event that followed the first step of the deglaciation and which was dated at 12 6 0 5 ka b p another ash layer is present near the last glacial maximum that we have dated at 17 5 0 3 ka b p during isotopic stage 3 five ash layers were recognized and dated which allowed us to assign ages to the isotopically light oxygen peaks warmer interstadials at 31 1 5 ka and 33 4 1 6 ka denekamp at 37 5 2 ka hengelo and successively at 49 2 ka 52 4 2 2 ka 57 2 2 ka and 60 5 2 2 ka moershoofd complex

certain aspects of radiolarian data as evidence of the paleoenvironment abstract different aspects of the ecology and biogeography of radiolarians are considered as a means of interpreting the paleoenvironment the quantitative and spatial distribution of radiolarians in the sediments of the world ocean are discussed including differences between marine and oceanic thanatocoenoses relations between species and high rank associations of radiolarians and fluctuation of climate areal changes of some species with time etc

tephrochronology of the western gulf of mexico for the last 185 000 years abstract tephra in 31 piston cores from the western gulf of mexico and 7 piston cores from the equatorial pacific were analyzed by electron microprobe six ash layers in the western gulf of mexico were easily distinguished by tio2 feo and cao contents and correlated by geochemistry in order to determine the distribution pattern for each ash layer correlation by geochemistry is an easier more accurate method than biostratigraphic correlation some of the tephras were miscorrelated by biostratigraphy the six tephras were dated by geochemical identification in a piston core with oxygen isotope stratigraphy and the ages are y5 30 000 yr b p y6 65 000 yr b p y8 84 000 yr b p x2 110 000 yr b p w1 136 000 yr b p and w2 185 000 yr b p data from this study corroborated correlations of the y8 tephra in the western gulf of mexico with the d layer in the eastern equatorial pacific ocean none of the other five layers in the gulf of mexico however were found in the pacific ocean the limited distribution of the y5 y6 x2 and w2 ash layers close to mexico indicates possible sources in mexico tephra from the late pleistocene la primavera pumice in mexico however does not correlate with the marine tephra

the last interglacial ocean the final effort of the climap project was a study of the last interglaciation a time of minimum ice volume some 122 000 yr ago coincident with the substage 5e oxygen isotopic minimum based on detailed oxygen isotope analyses and biotic census counts in 52 cores across the world ocean last interglacial sea surface temperatures sst were compared with those today there are small sst departures in the mid latitude north atlantic warmer and the gulf of mexico cooler the eastern boundary currents of the south atlantic and pacific oceans are marked by large sst anomalies in individual cores but their interpretations are precluded by no analog problems and by discordancies among estimates from different biotic groups in general the last interglacial ocean was not significantly different from the modern ocean the relative sequencing of ice decay versus oceanic warming on the stage 6 5 oxygen isotopic transition and of ice growth versus oceanic cooling on the stage 5e 5d transition was also studied in most of the southern hemisphere the oceanic response marked by the biotic census counts preceded led the global ice volume response marked by the oxygen isotope signal by several thousand years the reverse pattern is evident in the north atlantic ocean and the gulf of mexico where the oceanic response lagged that of global ice volume by several thousand years as a result the very warm temperatures associated with the last interglaciation were regionally diachronous by several thousand years these regional lead lag relationships agree with those observed on other transitions and in long term phase relationships they cannot be explained simply as artifacts of bioturbational translations of the original signals

african monsoons an immediate climate response to orbital insolation the croll milankovitch astronomical theory of climate1 3 has received strong support from the evidence of a linear climatic forcing by obliquity and precession although nonlinearity had to be assumed for eccentricity4 5 moreover interglacials have appeared to be controlled by the orbital insolation6 although a phase shift of 6 000 5 000 yr is seen between an astronomical climate index and terrestrial climate indicators dominated by the northern ice sheet dynamics climate proxy data of low latitudes are less directly dependent on the ice sheets here it is shown that during the past 464 000 yr african monsoons signalled by the east mediterranean sapropels were heaviest always and only when a northern summer monsoon index computed from the orbital variation of insolation reached maximum values this occurred during all the interglacials but also twice during glacial periods thus tropical aridity is not the single climatic pattern of glacial periods an immediate terrestrial climate response to orbital variations of insolation is established

astronomical theory of paleoclimates and the last glacial interglacial cycle in the 19th century croll and pilgrim stressed the importance of severe winters as a cause of quaternary ice ages later on mainly during the first half of the 20th century koppen spitaler and milankovitch regarded high winter and low summer insolation as favoring glaciation after koppen and wegener related the milankovitch new radiation curve to penck and bruckner s subdivision of the quaternary there was a long lasting debate whether or not such changes in the insolation can explain the quaternary glacial interglacial cycles in the 1970s with the improvements of radiometric dating and of acquiring and interpreting the long continuous geological records with the advent of computers and with the development of more sophisticated astronomical and climate models the astronomical theory and in particular its milankovitch version were revived over the last 5 years most geological astronomical and climatological obstacles have been overcome and the causal role of the orbital variations in long term variation of climate is taken almost universally for granted models of different categories of complexity from conceptual ones to 3 d atmospheric general circulation models and 2 d time dependent models of the whole climate system have now been astronomically forced in order to test the physical reality of the astronomical theory for example experiments with both low and high resolution gcms show that the increased seasonality at 9 000 bp leads to intensified summer monsoon circulation of africa and southern asia on the other hand seasonal models for simulating the transient response of the climate system to astronomical forcing are also developed and the output of these most recent modeling efforts compares favorably with data of the past 400 000 years accordingly the model predictions for the next 100 000 years are used as a basis for forecasting how climate would evolve when forced by orbital variations in the absence of anthropogenic disturbances the long term cooling trend which began some 6 000 years ago will continue for the next 5 000 years this first temperature minimum will be followed by an amelioration around 15 000 ap after present by a cold interval centered al 23 000 ap and by a major glaciation at around 60 000 ap

pliocene pleistocene radiolarian events and magnetostratigraphic calibrations for the tropical indian ocean johnson d a schneider d a nigrini c a canlet j p and kent d v 1989 pliocene pleistocene radiolarien events and magnetostratigraphic calibrations for the tropical indian ocean micropaleontol 14 33 64 a composite of four piston cores from the central indian basin and adjacent ninetyeast ridge has yielded a continuous magnetobiostratigraphic reference section for most of the pliocene and the pleistocene 0 0 4 5 ma we identified thirty three radiolarian events first or last occurrences and precisely correlated each event to the neogene geomagnetic polarity time scale thirteen of these events are based on revised taxonomic studies of the genera anthocyrtidium and pterocorys some events show significant departures from synchroneity five of the radiolarian first appearances and seven of the last appearances are time transgressive by 0 4 m y or greater we here propose a revised eleven fold radiolarian zonation for the pliocene pleistocene using zonal boundaries defined by events which are easily recognized and are demonstrably synchronous in the tropical indo paciflc the sequence of faunal and floral events reported in this paper will allow high resolution biostratigraphic correlations within the tropical indian ocean however the same sequence of events is not necessarily applicable to other tropical or extratropical regions

unravelling patterns of reworking in lowstand shelf deposits using amino acid racemisation and radiocarbon dating abstract amino acid racemisation calibrated by radiocarbon dating liquid scintillation and accelerator mass spectrometry has provided a chronostratigraphic framework in which to evaluate the later quaternary evolution of mollusc rich carbonate sediments on the outer continental shelf of new south wales australia three vibracores cores 112 vc 130 112 vc 121 and 112 vc 134 from the outer continental shelf in present water depths of 123 139 and 150 m respectively each contain alternating successions of pedogenically unmodified fine grained mixed quartz carbonate sand and densely packed mollusc dominated sediments set in a matrix of carbonate sand the extent of racemisation for several amino acids and radiocarbon dates on the shallow water molluscs pecten fumatus and placamen placidium reveals the presence of sediments deposited during three successive glacial maxima i e stages 8 6 and 2 of the marine oxygen isotope record three chronostratigraphically distinct aminozones oxygen isotope stages 8 6 and 2 are identified in core 134 samples in cores 121 and 130 record only two aminozones collectively stages 6 and 2 amino acid racemisation indicates that fossil molluscs with background radiocarbon results are in fact significantly beyond the range of radiocarbon dating by analogy with other deposits from southern australia a thin veneer of early holocene fine calcareous sand occurs at the top of each core all three cores reveal varying degrees of reworking of fossil molluscs which is not immediately apparent on the basis of lithostratigraphy or biostratigraphy reworking of macrofossils is more pronounced closer to the inferred location of the palaeoshoreline of pleistocene glacial maxima

continental climate response to orbital forcing from biogenic silica records in lake baikal changes in insolation caused by periodic changes in the earth s orbital parameters provide the primary forcing for global ice ages1 6 but it is not clear to what extent the climates in continental interiors are controlled directly by regional variations in insolation and to what extent they are driven instead by the highly nonlinear response of the oceans and ice sheets here we investigate this question using the record of biogenic silica in lake baikal as a proxy for climate change in this high latitude mid continental region we find a good correlation between this record and that of marine oxygen isotopes4 over the past 250 kyr the baikal record exhibits both a strongly nonlinear component manifested in a 100 kyr periodicity and weaker direct insolation components manifested in the 41 kyr obliquity and 23 and 19 kyr precession orbital cycles these results show that even though extreme continental climates such as this are influenced directly by insolation variations they are dominated by the nonlinear rhythm of the oceans and ice sheets

towards a high resolution global deep sea chronology for the last 750 000 years abstract variations in the ratio of 18 o 16 o as measured in shells of marine calcareous microfossils are primarily dominated by changes in global ice volume hence these variations provide a set of global time lines in deep sea sediments it is likely that the timing of major changes in oxygen isotope values is strongly influenced if not controlled by variations in the geometry of the earth s orbit since the variation of orbital parameters can be accurately calculated the opportunity exists for transforming this orbital chronology into a geological chronology through careful correlation of oxygen isotope records in a set of deep sea cores from the sub antarctic south atlantic and equatorial pacific we have assembled a composite isotopic section spanning the last 750 000 years with an average sedimentation rate of 2 3 cm 1000 years a new chronology for this time period was developed by adjusting the ages of the oxygen isotope stage boundaries in this composite section so as to extend the consistent phase relationships that exist between variations in oxygen isotope ratios and changes in obliquity and precession during the last 300 000 years to the entire 750 000 year record previously identified difficulties in phase locking precession with the filtered isotopic signal between 365 000 and 465 000 years b p have been resolved with the recognition that precessional variations have an average period of 19 000 years and not 23 000 years during this interval since this new age model yields the best match between variations in obliquity and precession and their corresponding frequency components in the oxygen isotope record we believe that it presents the most accurate chronology yet developed for deep sea sediments with this new age model providing the time control power spectral analyses of south atlantic and sub antarctic chemical and biotic indices show that there is a strong tendency for variance to be concentrated at frequencies corresponding to periods of 100 000 41 000 and 23 000 years

orbital frequencies in radiolarian assemblages of the central indian ocean implications on the indian summer monsoon radiolarian distribution in surface sediments and its relationships with overlying surface oceanography provided impetus for down core faunal variation related to changes in monsoon intensity due to the earth s orbital eccentricity in the geologic past in present study a high resolution t 4 75 ka radiolarian distribution for the last 485 ka in a core aas 2 3 from the central indian ocean basin revealed orbital and sub orbital cycles relationships between temporal distribution of 1 high salinity pyloniids and didymocyrtis 2 low salinity spongodiscids and spongaster 3 transitional euchitoniids and 4 southern anthocyrtidium assemblages and the orbital forcing etp i e the normalized sum of the earth s eccentricity tilt and precession and the may july insolation were analyzed spectral analyses revealed significant cycles of pyloniids 400 126 95 54 41 31 23 19 17 and 15 ka spongaster 95 41 29 23 19 17 and 15 ka euchitoniids 126 95 51 31 21 18 and 17 ka and anthocyrtidium 400 69 41 31 23 19 and 15 ka cross spectral analysis between pyloniids and etp suggested coherent pyloniid cycles lagging etp by 9 ka at 100 ka eccentricity while both were in phase 2 ka at 41 ka tilt and 23 ka precession cycles coherent spongaster cycles led etp by 38 ka at 100 ka eccentricity 15 ka at 41 ka tilt 5 ka at 23 ka precession cycles coherent anthocyrtidium cycles led etp by 14 ka at 100 ka eccentricity 10 ka at 31 ka tilt and were in phase at 41 ka tilt as well as 23 and 19 ka precession cycles similarly a radiolarian monsoon index defined as the normalized sum of pyloniids didymocyrtis spongodiscids spongaster euchitoniids and anthocyrtidium pdssea led etp at 54 and 23 ka cycles while both were nearly in phase at 41 31 and 15 ka cycles coherent pdssea cycles led insolation during may july at 8 s core site at 23 ka precession lagged 100 54 and 29 ka cycles and were in phase at 41 ka tilt and 15 ka sub orbital cycles the results suggest that radiolarian assemblages exhibit proxy monsoon cycles due to the earth s orbital eccentricity at 400 126 and 95 ka tilt at 54 41 and 31 ka next to precession at 23 19 and 17 ka as well as insolation forcings at the core site during the late quaternary

mechanical models for correlation of ring fracture eruptions at pantelleria strait of sicily with glacial sea level drawdown recent k ar dating of eruptions at pantelleria a peralkaline volcanic island in the strait of sicily shows a correlation between eruption of pantellerite lavas from caldera ring fractures and low stands of sea level as determined from 18o stratigraphy post caldera pantellerite lavas associated with an 114 ky old caldera erupted along the ring fracture zone during a major low stand of sea level at about 67 ka the most recent episode of lava flow emplacement began about 20 ky ago during the last glacial maximum magma vented along the ring fault of a 45 ky old caldera from fractures radial to the caldera and along faults formed by intracaldera trapdoor uplift two mechanical models based on elasticity theory are presented to explain the correlation of post caldera ring fracture eruptions at pantelleria with lowering of sea level a simple analysis of a bending circular plate of thickness t r and radius r representing the magma chamber roof block shows that tensile stress is concentrated by a factor of 0 75r 2 t 2 at the lower perimeter of the plate when sea level drops stress changes may be even greater ift r is effectively less than the stratigraphic thickness due to layering of rocks in the roof block calculated stress changes due to a 100 m drawdown of sea level are similar in magnitude to stresses associated with dike propagation more realistic model geometries including different chamber shapes a conical volcanic edifice and sea level drawdown beyond the surface projection of the magma chamber were tested using the boundary element method lowering sea level generates a horizontal tensile stress above the chamber even when sea water is removed outboard of the magma chamber for some chamber geometries the magnitude of the tensile stress maximum is greater than the 1 mpa pressure of the 100 m of removed water and is of the right order of magnitude for dike propagation dikes initiated by the change of the stress field may originate and propagate along fractures inboard of the chamber margin the magnitudes of tensile maxima along the top of the chamber decrease as original sea level is moved outboard of the chamber margin and as the chamber thickness decreases when the depth to the top of the magma chamber reaches a critical value dependent on chamber geometry the propagation of dikes to the surface is inhibited

late quaternary climatic changes on the southwestern balearic slope western mediterranean isotopic faunal and mineralogical relationships abstract we report the results of a research on the carbonate mineralogy planktonic foraminifera distribution and oxygen and carbon isotope composition of g bulloides in hemipelagic carbonate oozes of the southwestern balearic slope western mediterranean to contribute to the understanding of climatic and ecological variations during the last quaternary interglacial glacial cycle and their influences on the carbonate sedimentary processes of the western mediterranean oxygen isotope stages 1 2 and 3 have been identified and correlated to those established in tyrrhenian cores the carbon isotope records display several anomalies which are explained by productivity variations and diagenetic processes pelagic carbbonates low mg calcite and aragonite and detrital minerals quartz high mg calcite and dolomite display variations that are climate related pelagic carbonates increase during warm intervals while intense low mg calcite dissolution and greater quantities of detrital minerals are found in colder intervals our results suggest that the carbonate distribution of the western mediterranean correlates to the reported from the atlantic ocean nevertheless the molar mgco3 content in low mg calcite disagree to the established temperature relationship in other oceans

paleoclimatic implications of u series dates for lake sediments and travertines in the arava rift valley israel abstract the sayif travertines and lacustrine limestones cropping out in the northern arava valley a region of extreme aridity have been dated by the 230 th 234 u disequilibrium method the consistency between the stratigraphic position and the apparent ages at each of the sampling sites strongly supports the reliability of the ages most of the ages fall within two clusters that are coincident with ages representative of oceanic oxygen isotope stages 5 and 7 the colder intervening stage 6 was not a period of substantial travertine formation during the warmer global episodes of isotopic stages 5 and 7 the arid south of israel apparently was considerably wetter than at present

climatostratigraphic scheme of the black sea pleistocene and its correlation with the oxygen isotope scale and glacial events abstract new evidence from the asov sea black sea region shows that after the cobb mountain magnetic event 1 1 myr there were 8 saline water events with mediterranean molluscs penetrating into the asov sea five times farther than the western manych strait and 7 or 10 cold freshwater events during the freshening phase the caspian sea molluscan fauna penetrated into the black sea each time the caspian mollusc assemblage was characterized by a new species of didacna thus some 18 20 bioclimatostratigraphic units can be distinguished in the asov sea black sea section for the last 1 myr their numerical age is estimated by some dozen thermoluminescence dates and 12 magnetic polarity datum planes the karangatian s lato corresponds to the interval 300 000 50 000 yr the uzunlarian to 580 000 300 000 yr and the chaudian to 1 100 000 600 000 yr the karangatian and tyrrhenian marine terraces correspond to marine isotope stages 5 and 7 the uzunlarian and milazzian to stages 11 15 and the chaudian and sicilian to stages 16 28 the number and ages of glacial interglacial cycles in continental europe are identical to the climatic cycles in the black sea and mediterranean

nonlinear response in the global climate system evidence from benthic oxygen isotopic record in core rc13 110 the milankovitch theory of climate change predicts that variations of the climate system should match the dominant frequencies of the orbital forcing in the 41 and 23 kyr 1 frequency bands such a linear theory would predict that the amplitude variations of the climate response in these bands should match amplitude variations in orbital forcing here we compare amplitude variations of the marine oxygen isotope record with orbital forcing in these bands over the last 700 000 years and find systematic changes through time we express these amplitude mismatches as variations in the glacial response time a measure of the climate system s sensitivity to orbitally induced insolation changes variations in the glacial response time occur in all frequencies bands without strong concentration of variance in any given band and have a red spectrum with larger variations at the longer periods the response time is coherent with 18o at periods of 100 and 41 kyr which suggests that the variations in glacial response time in part reflect internal feedback mechanisms of the global climate system the phase relationship between the estimated glacial response time and the 18o ice volume record is very different at these two frequencies which suggests at least two separate feedback mechanisms the first mechanism enhances the 100 000 year climate cycle by increasing rates of change during major glacial terminations candidates for this feedback include lithospheric depression and rebound enhanced ice calving from large marine based ice sheets and possibly others a second set of mechanisms which is detected in the response to the 41 000 year orbital cycle of earth s obliquity accelerates ice growth events and slows glacial melting some models which include feedbacks between ice sheets sea ice and deep ocean temperatures predict early rapid ice growth followed by slower growth and this general feature is consistent with our analysis while we can not at present identify the specific feedbacks leading to asymmetry of growth and decay rates at different frequency bands the finding of this ice growth acceleration mechanism in the 41 000 year frequency band suggests that high latitude processes where insolation varies most strongly at this rhythm may be involved our finding of systematic changes in climate sensitivity has implications for orbitally tuned chronologies in pleistocene sediments instead of a constant phase shift within a frequency band between orbital forcing and glacial response as has been assumed in the past we suggest a variable phase the largest changes in age estimates for isotopic events are at the glacial terminations which in our chronology are as much as 3500 years older that estimated previously

interplay between folding and ductile shearing in the proterozoic crust of the muskoka parry sound region central ontario grenville gneiss of the central georgian bay region was subjected to ductile deformation that produced narrow mylonite zones as well as three sets of superimposed folds differing greatly in structural signature size and orientation some mylonite zones are concordant to gneissosity and are repeatedly folded others cut gneissosity and postdate the folding gneissosity was generated as a regionally subhorizontal feature either by crustal thinning or like the early mylonite zones by low angle reverse shearing an attempt is made to account for the initially subhorizontal gneissosity the mylonite zones and the folds in a regime of large scale reverse shearing that strikes parallel to the grenville front upright northwest southwest to north south buckle folds dominate the map pattern and are subperpendicular to the reverse grenville front boundary fault these set 2 folds cannot be attributed to reverse simple shearing but require a large component of east west compression such stress could have been

late quaternary biostratigraphy and paleotemperatures of the red sea and the gulf of aden based on planktonic foraminifera and pteropods abstract the quantitative distributions of planktonic foraminifera and pteropods were analyzed in seven red sea cores and two deep sea cores from the gulf of aden and off sokotra island biostratigraphic intervals were distin guished corresponding to oxygen isotope stages 1 5 in the red sea and stages 1 3 in the gulf of aden the faunal assemblages demonstrate that in the red sea hydrological conditions changed significantly during the late quaternary especially at the last glacial maximum when water exchange at the bab el mandeb straits was at a minimum and at the pleistocene holocene boundary at the end of deglaciation water exchange renewal and pluvial conditions resulted in surface salinity decrease and stable stratification which was followed by a rise in planktonic fauna abundance and stagnation of bottom waters the more constant composition of rather cold water subtropical faunal assemblages in the gulf of aden during the last 40 000 50 000 yrs points to more stable hydrological parameters and to local upwelling or influx of arabian upwelling waters during the last stadial mean annual sea surface temperatures fell by at least 5 c compared to the present in the central part of the red sea and by 3 5 c in the western gulf of aden

mediterranean quaternary sapropels an immediate response of the african monsoon to variation of insolation abstract in the subsurface of the east mediterranean sea eleven discrete basin wide organic rich black sapropels were deposited during the last 465 000 years they are dated by oxygen isotopic chronostratigraphy the most recent sapropel has been shown to be the consequence of heavy nile river summer floods due to increased monsoonal summer precipitation over ethiopia and not of scandinavian ice sheet meltwater influx into the east mediterranean sea as was previously believed while most sapropels were deposited during interglacials two thick sapropels formed during glacial periods as shown by their position in the oxygen isotopic stratigraphy and by their pollen record in core rc9 181 the new evidence presented here is that the sapropel sequence in this core including the two glacial sapropels correlates on a one to one basis with the highest values of an index of insolation on top of the atmosphere the concept of this index derives from an analysis of the african monsoon process the index variation is computed for the last 465 000 years from the caloric northern summer insolation in the tropical latitudes controlled by variations of the earth s orbital parameters it is conjectured that this index might be linked through the climate system to the monsoonal precipitation which in africa produces the nile river summer flood

pyloniid stratigraphy a new tool to date tropical radiolarian ooze from the central tropical indian ocean pyloniid stratigraphy a faunal abundance variation stratigraphic tool similar to cycladophora davisiana stratigraphy employed at high latitudes is found to work well for tropical radiolarian ooze the relationship between the spatial distribution of 25 modern radiolarian groups in surface sediments and monsoonal surface salinity from the central indian ocean is analyzed among them pyloniids exhibit the potential to serve in the same way as the c davisiana stratigraphy down core temporal variation of pyloniids in a sediment core is compared with i the sum of the earth s orbital eccentricity axial tilt and precession etp ii solar insolation at the core site 8 s and 65 n and iii the specmap 18o stratigraphy the multi taper mtm spectral analysis of pyloniids for the last 485 ka in a core aas 2 3 reveals significant climatic cycles at the eccentricity 100 ka tilt 41 ka and precession 23 ka bands cross spectral analyses suggest coherent 90 pyloniid cycles lag both the etp and june insolation 65 n by 9 ka at 100 ka eccentricity and are almost 2 ka in phase with 41 ka tilt and 23 ka precession cycles coherent pyloniid cycles lag specmap 18o by 14 ka at 41 ka tilt and 6 ka at 23 ka precession while they lag insolation at the core site by 7 ka at 100 ka lead 18 ka at 41 ka and show in phase relation with 23 ka cycles marginal lead of 10 ka by etp and insolation over pyloniids at 100 ka eccentricity and in phase relation at 41 ka tilt and 23 ka precession cycles suggest pyloniids variation could be used as a tool to derive age models in tropical radiolarian ooze during the late neogene quaternary

late quaternary sedimentation in the eastern arctic basin stratigraphy and depositional environment abstract the late quaternary history of the arctic basin is poorly known because most sediment cores seemed to have accumulated very slowly based on magnetostratigraphy on the order of one to a few millimeters per thousand years two short sediment cores from the eurasian basin of the arctic ocean have now been dated by means of o and c isotopic ratios the o isotope stratigraphy suggests that these sediments accumulated much faster on the order of one to four centimeters per thousand years than in the central arctic ocean the cores penetrated sediments belonging to isotope stages 1 3 and allow a detailed description of the depositional environment under the arctic ice cover during the last ice age and the ensuing climatic warm interval

direct land sea correlations in the last interglacial complex isotopic and pollen analyses of an eastern atlantic core permit the first direct correlation of substages 5e and 5c of the marine climatostratigraphical system with the eemian and st germain i respectively of the classical grande pile pollen sequence north east france the vegetational sequences during the warm intervals of the last interglacial complex 125 000 75 000 yr bp indicate that climatic deterioration occurred late on the mid european continent after the initiation of glaciation over continental masses in high latitudes