climate reconstruction for the holsteinian interglacial in eastern poland and its comparison with isotopic data from marine isotope stage 11 abstract sediments of palaeolakes located in eastern poland represent the holsteinian interglacial and the initial part of the succeeding saalian glaciation they consist of 55 m thick lake marl and calcareous gyttja deposits reconstruction of climate during this part of the pleistocene was carried out by the analyses of oxygen and carbon isotope ratios of carbonates palynological data al and ca content of sediments isotope ratios and palynological results give in some cases contradictory results 18o ratios from lake ossowka eastern poland indicate relatively cool conditions at the climatic optimum of the holsteinian interglacial low ratios may have been caused by increased precipitation that led to high stands of the lake level during the initial stages of the following glaciation the 18o and 13c ratios increased probably resulting from low water level and strong evaporation in cool and dry climate phases additionally high al contents indicate high allochthonous siliciclastic input high ca concentrations indicate autochthonous carbonate precipitation from the lake epilimnion the combined climate indicators for the holsteinian interglacial in eastern poland suggest that this temperate episode corresponds to marine isotope stage 11 mis 11 of the north atlantic comparison of the continental record from eastern poland with the marine record from the north atlantic separated by about 2500 km indicates that even small climatic changes can be identified in genetically different deposits documenting the global nature of pleistocene climate trends

source and origin of roxana silt and middle wisconsinan midcontinent glacial activity abstract thick roxana silt middle wisconsinan in central and southwestern illinois traditionally has been interpreted as loess derived from valley train deposits in the ancient mississippi river valley winters et al h a winters j j alford and r l rieck quaternary research 29 25 35 1988 recently suggested that the roxana was not directly related to glacial activity but was derived from sediment produced by increased shoreline and spillway erosion associated with a fluctuating ancestral lake michigan because 1 paleoenvironmental and paleohydrologic conditions inferred in the hypothesis are unlikely for a loess depositional system and 2 loess did not accumulate during late wisconsinan deglaciation under conditions similar to those hypothesized we suggest the hypothesis should be rejected roxana distribution suggests the major source was drainage from the upper mississippi river valley and variations in loess thickness in illinois can be explained by consideration of valley width depth orientation and postdepositional erosion tills in the headwaters region of the ancient mississippi drainage system in minnesota and wisconsin occur in the appropriate stratigraphic position and have colors and mineralogic compositions that suggest they could be the parent till of the roxana we believe a valley train source for thick roxana is most probable and urge continued consideration of middle wisconsinan glaciation in the upper great lakes area

carbon and oxygen isotope fractionations between aragonite and calcite of shells from modern molluscs carbon and oxygen isotope fractionations between calcite and aragonite were investigated by analyzing marine gastropods and bivalves that lived under temperate to tropical climates species that secrete both aragonite and calcite layers were studied to ensure similitude of changes in the isotopic composition of water in diet and in metabolic activity during shell growth aragonite and calcite layers from the adult parts of the shell were identified and mapped by using raman spectroscopy powder samples were obtained by micro drilling under a stereo microscope thirty six pairs of aragonite calcite samples were obtained from ten gastropod and five bivalve species biogenic aragonite is c 13 enriched by 0 95 0 81 and o 18 enriched by 0 37 0 65 relative to co existing biogenic calcite direction and magnitude of the carbon isotope fractionation are compatible with those already determined by using low temperature experimental approaches the observed oxygen isotope difference between biogenic aragonite and calcite is assigned to the difference similar to 0 4 parts per thousand in the acid fractionation factor values that must be taken into account during digestion of carbonate polymorphs at 90 degrees c it is concluded that biogenic calcium carbonate polymorphs precipitate close to but not in isotopic equilibrium with seawater therefore empirical oxygen isotope fractionation equations that were established on the basis of modern mollusc shells and ambient waters should be preferred for the calculation of aquatic paleotemperatures

ionospheric effects of the solar eclipse of march 9 1997 as deduced from gps data this paper presents data from first measurements of total electron content tec and its gradient during the solar eclipse of march 9 1997 obtained with the gps radio interferometer at irkutsk the interferometer consists of three receivers one turbo rogue snr 8000 and two ashtech z 12 located at the vertices of a triangle and spaced by about 3 5 km the measured tec variations are indicative of profound changes in the ion production process in the ionosphere attendant on the solar eclipse simultaneously in a large volume of space with a radius of at height 300 km at 300 km altitude the delay of a minimum value of tec with respect to the maximum phase of eclipse at 300 km altitude was about 10 min and the depression depth of tec growth varies from l 3 1016m 2 by analyzing the data on tec gradient variations one is led to conclude that the depression of tec growth during the eclipse is essentially independent of the longitude and of the latitude within the observation ranges 52 6 n and 104 11 e

new evidence for complex climate change in mis 11 from hoxne suffolk uk the climatic signal of marine isotope stage mis 11 is well documented in marine and ice sheet isotopic records and is known to comprise at least two major warm episodes with an intervening cool phase terrestrial records of mis 11 though of high resolution are often fragmentary and their chronology is poorly constrained however some notable exceptions include sequences from the maar lakes in france and tenaghi philippon in greece in the uk the hoxnian interglacial has been considered to correlate with mis 11 new investigations at hoxne suffolk provide an opportunity to re evaluate the terrestrial record of mis 11 at hoxne the type hoxnian interglacial sediments are overlain by a post hoxnian cold temperate sequence the interglacial sediments and the later temperate phase are separated by the so called arctic bed from which cold climate macroscopic plant and beetle remains have been recovered the later temperate phase was deposited during an episode of boreal woodland and is associated with the artefacts a diverse vertebrate fauna and molluscs new amino acid geochronological data and biostratigraphical considerations suggest that the post hoxnian sequence correlates with late substages of mis 11 the paper further investigates the correlation of the sequence at hoxne with the palynological sequences found elsewhere in europe and adjacent offshore areas

hydrological factors in the interpretation of stable isotopic proxy data present and past a european perspective in the context of this paper stable isotopic proxies are those preserving directly or via known or calculable fractionation factors a record of 18o 16o and or 2h 1h in the water which contributed to their growth suitable proxies include amongst others tree ring cellulose bone phosphate lake sediment minerals and speleothem fluid inclusions a principal aim of studying isotopic proxies is to gain more information about past climates through a knowledge of how rainfall isotope compositions have changed over time however converting back from proxy to rainfall is not necessarily straightforward because however well the isotopic fractionation due to proxy growth or formation is understood a variety of modifying processes may have intervened between this and the actual rainfall events three main reservoirs of environmental water may contribute to the isotopic compositions of terrestrial proxy indicators surface waters soil moisture and groundwater each of these can in principle be isotopically modified compared to rainfall in the locality this review examines these effects and how they may change under different european climate types at the present day it is concluded that while groundwater isotopic compositions typically represent closely the bulk composition of rainfall under a variety of climatic regimes soil and particularly lake waters require detailed study if their isotope systematics are to be adequately understood the review also finds that to a large extent the present is the key to the past in terms of recharge processes during the late pleistocene though glaciation may have had profound isotopic consequences in certain areas while a more general aridity led to the apparent absence of recharge in most areas for much of the late devensian

isotopic and geochemical composition of marl lake waters and implications for radiocarbon dating of marl lake sediments radiocarbon dates on organic and calcareous fractions of sediment cores from marl lakes may yield anomalous ages due to the assumption of a constant hardwater correction factor along the sediment sequence a study of eight marl lakes in southern ontario that are actively precipitating calcium carbonate was conducted in order to assess those isotopic and aqueous geochemical parameters in modern lakes that may be utilized to estimate the history and extent of variations in the hardwater effect along such sediment sequences results show an increase in the 13c composition of lake dic dissolved inorganic carbon as approach to isotopic equilibrium with atmospheric co2 occurs differences in the extent to which this equilibrium is established also appear responsible for observed differences in the 14c activity of dic between lakes of as much as 20 pmc percent modern carbon these variations have been related to the relative residence times of water in each lake by examination of their corresponding seasona

the midlatitude ionosphere during the total solar eclipse of march 9 1997 the total solar eclipse of march 9 1997 was visible from some regions of china mongolia and east siberia during 0045 0130 ut the eclipse coincided with a relatively long geomagnetically quiet period during the total solar eclipse the observations included oblique incidence ionograms recording also measurement the total electron content along specified directions to the visible global positioning system satellites and the doppler sounding on various hf ray paths over the region under consideration were carried out this paper presents results derived from studying the spatial pattern of midlatitude ionospheric response to this eclipse on the basis of a numerical simulations calculations have been executed using a model for ionosphere plasmasphere coupling comparison of model results with data of all measurements showed a good qualitative and quantitative agreement it is shown that by and large the behavior of the ionosphere during the eclipse manifests itself as a short lasting l hour rearrangement to nighttime conditions with the ion flow directed downward from the plasmasphere as a rise of the f2 layer maximum by about 20 km and as a twofold increase in electron density at the height of the maximum during the eclipse s totality phase the electron temperature decreases by 200 400 k while the ion temperature drops only slightly it is found that changes in the spatial distribution of electron density along the hf ray paths during the eclipse give rise to variations of doppler frequency shift with amplitudes of about 1 hz and a duration of about 120 min the findings reported in this paper do not validate the hypothesis that solar eclipses generate atmospheric gravity waves and associated traveling ionospheric disturbances

daytime e region field aligned irregularities observed during a solar eclipse the driving mechanism of the midlatitude field aligned irregularities fais has been in dispute for many years the experimental observations were carried out during the solar eclipse of 22 july 2009 in wuhan china to study the possibility of the wave driven irregularities a high frequency coherent scatter radar was used to detect the e region irregularities an ionosonde was applied to record the trace of gravity waves in ionosphere the e region fais occurred at the end of the solar eclipse with fluctuant doppler at the same time the oscillations on the fes maximum reflecting frequency of es curve and in the doppler velocity of the echoes from the es layer were also recorded the data analysis and comparison show that the gravity waves and the fais occurred at the same time with the in phase variations in amplitude and phase thus the solar eclipse and the gravity waves may play important roles in the occurrence of the irregularities a schematic diagram of one period gravity wave is used to explain the possible gravity wave driven mechanism and the doppler fluctuation in the irregularities the daytime fai in midlatitude is a rare phenomenon even in the condition of solar eclipse there are only four cases of the e region fais observed during a solar eclipse including our observations the unique feature of our observations is the synchronized oscillations in the irregularities and in the es layer which will help address the outstanding question of the source of the midlatitude e region fais

palaeoclimate interpretation of stable isotope data from lake sediment archives the isotope composition of authigenic and biogenic carbonates and diatom silica are commonly used as palaeoclimate proxies from lake sediments this article reviews the controls on the isotope composition of lacustrine skeletal and non skeletal deposits and illustrates how stable isotope studies contribute to an understanding of changes in temperature precipitation patterns evaporation and the carbon cycle it highlights the differences in the palaeoclimate potential of a wide range of lakes ranging from open to closed lake basins a large number of the case histories but not all are drawn from studies of temperate lakes from europe large closed lake systems in the tropics and elsewhere lose water predominantly through evaporation and contain sediments with variable and generally high 18o values fluctuations in the isotope composition of authigenic or biogenic minerals are mainly a function of long term changes in the precipitation evaporation ratio in contrast small open lakes which have a degree of through flow typically contain sediments with 18o values that vary by no more than a few these variations are generally ascribed to variations in temperature or the isotope composition of precipitation p from which either an annual or seasonally specific signal can be gained these types of lakes are common in northern europe and at high altitudes the interpretation of isotope data from a lacustrine succession requires a knowledge of the local processes that might control and modify the signal their effects need to be quantified and a robust calibration using the modern lake system is necessary to establish the relationship between the measured signal the isotopic composition of the host waters and climate

lacustrine molluscan carbonates an interspecific approach toward the understanding of palaeoenvironmental conditions during the holsteinian interglacial mis 11 using δ18o and δ13c abstract stable isotope geochemistry is a well known tool for the investigation of palaeoclimate the application of this methodology to molluscan carbonate materials has increasingly receiving more attention in recent decades stimulating the development of numerous environmental reconstructions among the different habitats and shell species investigated so far the freshwater are the ones that have received least attention the scarcity of systematic studies on lacustrine and riverine molluscan species considerably limits the use of these remains to reconstruct the environmental conditions of inland palaeontological and archaeological sequences the present study focuses on bithynia tentaculata a freshwater species abundant in the european quaternary fossil record the aim of the research is to validate the use of oxygen 18o and carbon stable isotopes 13c of this species as palaeoenvironmental proxies for this purpose shells and opercula from stratigraphic sequences of three palaeolakes in eastern poland formed during the holsteinian interglacial mis 11 are analysed the intercorrelation between b tentaculata and two other molluscan species together with good agreement with the pollen record reveal that 18o and 13c are suitable indicators of water temperature and humidity levels for lacustrine environments these results pave the way for using b tentaculata in further palaeoclimatic reconstructions

pre wisconsinan glacial stratigraphy chronology and paleomagnetics of west central wisconsin detailed evaluation of pedogenic geologic and paleomagnetic properties has enabled the identification of several pre wisconsinan stratigraphic units in west central wisconsin the older unit is the pierce formation consisting of the hersey member which contains gray calcareous loam textured till and the kinnickinnic member which contains rhythmically bedded lacustrine sediments deposited in a complex network of proglacial lakes paleomagnetic and pedogenic data from the pierce formation suggest that the hersey member was deposited during either the emperor reversed event or the matuyama reversed polarity epoch and that deposition of the kinnickinnic member spanned either the emperor brunhes or the matuyama brunhes boundary 460 000 or 730 000 b p during pre illinoian time the younger pre wisconsinan unit is the river falls formation which contains a reddish brown sandy clay loam textured till and associated sand and gravel soil profile development and regional correlation indicate that this unit is illinoian in age these results contradict previously published studies which suggested that tills of the hersey member and the river falls formation were deposited by the same wisconsinan ice advance and that no pre wisconsinan sediment is present in western wisconsin

eolian sand and loess deposits indicate west northwest paleowinds during the late pleistocene in western wisconsin usa our study adds to the quaternary history of eolian systems and deposits in western wisconsin usa primarily within the lower chippewa river valley thickness and textural patterns of loess deposits in the region indicate transport by west northwesterly and westerly winds loess is thickest and coarsest on the southeastern flanks of large bedrock ridges and uplands similar in some ways to shadow dunes in many areas sand was transported up and onto the western flanks of bedrock ridges as sand ramps presumably as loess was deposited in their lee long linear dunes common on the sandy lowlands of the chippewa valley also trend to the east southeast small depressional blowouts are widespread here as well and often lie immediately upwind of small parabolic dunes finally in areas where sediment was being exposed by erosion along cutbanks of the chippewa river sand appears to have been transported up and onto the terrace treads forming cliff top dunes luminescence data indicate that this activity has continued throughout the latest pleistocene and into the mid holocene together these landforms and sediments paint a picture of a locally destabilized landscape with widespread eolian activity throughout much of the postglacial period

latitudinal dependence of the ionospheric response to solar eclipse of 15 january 2010 1 the ionospheric responses to the solar eclipse of 15 january 2010 in the equatorial anomaly region have been investigated by three vertical incidence and seven oblique incidence ionosondes arranged along the meridian from geomagnetic latitudes 18 n to 30 n in eastern china though the solar eclipse occurred later in the evening the eclipse effect on electron density and reflection height of ionospheric f2 layer was clearly observed the study of the eclipse lag the time lag between the occurrence of the eclipse maximum obscuration and the occurrence of the maximum depletion of fof2 with latitude indicates it increased with f2 layer altitude results suggest also that this eclipse enhanced the prereversal enhancement an unusual peak occurred after the maximum reduction in fof2 and this was observed by all our ionosondes the following f2 layer plasma density increase was considered to be caused by the increased westward electric field

optical ages on loess derived from outwash surfaces constrain the advance of the laurentide ice sheet out of the lake superior basin usa abstract we present textural and thickness data on loess from 125 upland sites in west central wisconsin which confirm that most of this loess was derived from the sandy outwash surfaces of the chippewa river and its tributaries which drained the chippewa lobe of the laurentide front during the wisconsin glaciation mis 2 on bedrock uplands southeast of the widest outwash surfaces in the chippewa river valley this loess attains thicknesses 5 m osl ages on this loess constrain the advance of the laurentide ice from the lake superior basin and into west central wisconsin at which time its meltwater started flowing down the chippewa drainage the oldest mar osl age 23 8 ka from basal loess on bedrock agrees with the established but otherwise weakly constrained regional glacial chronology basal ages from four other sites range from 13 2 to 18 5 ka pointing to the likelihood that these sites remained geomorphically unstable and did not accumulate loess until considerably later in the loess depositional interval other osl ages from this loess taken higher in the stratigraphic column but below the depth of pedoturbation range to nearly 13 ka suggesting that the chippewa river valley may have remained a loess source for several millennia

sea surface water temperatures over the period 1884 1983 reconstructed from oxygen isotope ratios of a bivalve mollusk shell arctica islandica southern north sea although climate system modeling cannot be imagined without long sea surface temperature sst records observational data is spatiotemporally incomplete and inhomogeneous prior to about 1950 moreover almost no high resolution sst proxies exist from temperate and boreal marine settings here we present a temporally equidistant high resolution sst proxy record of the southern north sea during the period 1884 1983 calculated from oxygen isotope ratios 18oaragonite of arctica islandica l a bivalve mollusk shell arctica islandica produces daily growth increments which enable precise intraannual dating the growing season of specimens from about 25 m water depth upper well mixed layer of the ocean started in february and ended in september observational coads etc and 18oaragonite derived sst data during february through september compare well to each other especially after 1950 apart from similar overall sst trends we found north atlantic oscillation type cycles of 7 9 years in our proxy sst record and in various different instrumentally determined sst chronologies no vital effects exist so that 18oaragonite ratios determined across the shell i e throughout lifetime of the studied specimen reflect ambient water temperatures that occurred during shell growth results of our study demonstrate that a islandica provides long independent and high resolution sst proxy chronologies from higher latitudes such records can complement and further validate observational sst data and help improving climate system models

stable isotopic compositions of recent freshwater cyanobacterial carbonates from the british isles local and regional environmental controls recent 50 years old freshwater cyanobacterial carbonates from diverse environments streams lakes waterfalls throughout britain and ireland were analysed for their stable carbon and oxygen isotope compositions the mean 18o value of 5 9 pdb for river and stream data represents calcite precipitation in equilibrium with the mean oxygen isotopic composition of precipitation in central britain 7 5 smow assuming a mean water temperature of 9 c the mean 18o of lake data 4 5 pdb is statistically different reflecting the effects of residence time and or variations in the oxygen isotopic composition of rainfall carbon isotopes have wide variations in both fluviatile and lake data sets 3 to 12 pdb these variations are principally controlled in the fluviatile samples by contribution of isotopically light soil zone carbon relative to isotopically heavier carbon from limestone aquifer rock dissolution lake samples have the heaviest carbon isotope values reflecting a trend toward isotopic equilibrium between atmospheric co2 and aqueous hco 3 we infer that isotopic compositions of ancient cyanobacterial carbonates should also record environmental information although the effects of stabilization and diagenesis on primary 18o values will need careful consideration primary carbon isotope compositions should be well preserved although in marine samples values will be buffered by the isotopic composition of aqueous marine bicarbonate

autogenic incision and terrace formation resulting from abrupt late glacial base level fall lower chippewa river wisconsin usa abstract a paucity of research exists regarding the millennial scale response of inland alluvial streams to abrupt base level fall studies of modern systems indicate that over short time scales the response is a diffusion like process of upstream propagating incision in contrast evidence from the lower chippewa river lcr located in the upper midwest of the usa suggests that autogenic controls operating over time scales of several millennia can overwhelm diffusion resulting in incision that is prolonged and episodic during the last glacial maximum the lcr drained the chippewa lobe of the laurentide ice sheet to the glacial upper mississippi river umr as a meltwater stream it aggraded and filled its valley with glacial outwash as did its largest tributaries which were also meltwater streams its nonglacial tributaries aggraded too filling their valleys with locally derived sediment during deglaciation the umr incised at least twice abruptly lowering the lcr s base level 15 m at 16 ka or earlier and an additional 40 m at ca 13 4 ka each of these base level falls initiated incision of the lcr led by upstream migrating knickpoints the propagation of incision has however been a lengthy process the optically stimulated luminescence osl ages of terrace alluvium indicate that by 13 5 ka incision had advanced up the lcr only 15 km and by 9 ka only 55 km the process has also been episodic resulting in the formation of fill cut terraces inferred from gpr surveys and exposures of terrace alluvium that are younger and more numerous in the upstream direction autogenic increases in sediment load and autogenic bed armoring the result of periodic tributary stream rejuvenation and preferential winnowing of fines by the incising river may have periodically caused knickpoint migration and incision to slow and possibly stop allowing lateral erosion and floodplain formation to dominate a decline in sediment flux from stabilizing incised tributary stream systems would have led to renewed knickpoint migration and incision when floods of sufficient magnitude to breach the channel armor occurred minimal floodplain development along the upper section of the present day lcr along with the channel morphology of an unstable wandering gravel bed river immediately downstream from it suggest that the river is still responding to the base level falls that happened many millennia ago the autogenic controls on the lcr s response to umr incision are a direct consequence of the thick fills of noncohesive sediment that accumulated in its valley and the valleys of its tributary streams during the late wisconsinan making the lcr a prime example of a former proglacial river that remains a paraglacial fluvial system

rapid hydrological changes during the holocene revealed by stable isotope records of lacustrine carbonates from lake igelsjon southern sweden a holocene sediment sequence from lake igelsjon south central sweden was studied by stable oxygen and carbon isotope analyses of different carbonate components the deposit which covers the time span from ca 11 500 cal bp to the present was laid down in a small kettle hole lake the hydrological balance of which is presently dominated by groundwater flow isotopic records obtained on bulk carbonates originating mainly from summer produced calcitic algal encrustations exhibit several rapid shifts of more than 2parts per thousand likely reflecting pronounced hydrological variations corresponding isotopic data obtained on calcitic gastropod opercula from parts of the profile show subdued responses to major climatic shifts probably related to an extended calcification season the isotopic records were complemented by studies of modern isotope hydrology and our interpretations are based on a simplistic climate hydrology model in which variations in groundwater generation within the lake catchment produce changes in groundwater level and related adjustments of lake level and surface volume ratio of the basin during the ice free season assumed periods of decreased lake volume in a relatively dry climate low lake level are characterised by enrichment in o 18 and c 13 resulting from increased evaporation inflow ratio and atmospheric equilibration respectively in clear contrast to this situation intervals of more humid climatic conditions give rise to increased lake volume high lake level possibly surface over flow and relatively depleted isotopic ratios relatively humid conditions which may correlate to a wide spread cooling event recorded by various proxies across the north atlantic region are indicated by distinct isotopic shifts at ca 8300 and 8000 cal bp bracketing a period of o 18 depletion the period between ca 8000 and 4000 cal bp was characterised by relatively dry and stable climatic conditions whereas the subsequent part of the holocene experienced a more humid and variable climate following marked and coherent depletions in o 18 and c 13 at ca 4000 cal bp c 2002 elsevier science ltd all rights reserved less

enhancement and hf doppler observations of sporadic e during the solar eclipse of 22 july 2009 1 the sporadic e es frequently emerging in midlatitude during summer is a very special layer in the ionosphere and its formation mechanism is different to from that of other layers the total solar eclipse of 22 july 2009 provided a very unique opportunity to study the relationship of es and solar radiation during the solar eclipse day and the days before and after the vertical incidence ionosonde was located in wuhan to record the ionograms for this event two oblique incidence high frequency radio systems were used to record the waves from wuhan to suzhou and from wuhan to huaian the enhancement of es during the eclipse period was observed in the vertical and oblique incidence ionograms the quasi periodic fluctuations in the critical frequency and doppler frequency shift curves indicated the possible existence of the gravity waves which may be responsible for the es enhancement however we find that the enhancement occurred earlier than the appearance of gravity waves and consider that there may be other mechanisms which contribute to the observed enhancement in the ionosphere a hypothesis is put forward that the cooling effect of the lunar shadow induced powerful airflow from the northern and southern limits of the shadow toward its center which accelerated the irregularities in es to produce the large scale doppler shift in the reflected waves and form the meridional windshear both the windshear and the gravity waves may affect the es layer and increase the electron concentration many observed phenomena are in accordance with this

signature of the 29 march 2006 eclipse on the ionosphere over an equatorial station 1 this study documents some results of the effect of the 29 march 2006 eclipse on the ionosphere over ilorin nigeria longitude 4 57 e latitude 8 53 n dip 4 1 s an equatorial station in the west african region the maximum obscuration of the eclipse at this station was 99 percent and it occurred before midday true height electron density profile analysis below the f2 peak was employed in the study the effect on the e and f1 layers was a drastic decrease in electron density with maximum decrease percentages of 60 and 68 for the e and f1 layers respectively a decrease in fof2 began at about 1 hour 20 min after those in the lower layers had started variation of electron density with height showed that the decrease in the electron density occurred through out the e and f1 heights at about the same time while that of the f2 region began at lower heights and extended progressively toward the peak of electron density height of the layer the recovery in the e and f1 layers has already reached an advanced stage before the effect of the eclipse got to the maximum in the f2 region a major departure of hmf2 from the normal variation was observed and discussed

nighttime ionospheric enhancements induced by the occurrence of an evening solar eclipse 1 the solar eclipse on 15 january 2010 traversed asia and completed its travel on the shandong peninsula in china at sunset two vertical incidence ionosondes at wuhan and beijing and the oblique incidence ionosonde network in north china were implemented to record the ionospheric response to the solar eclipse following the initial electron density decrease caused by the eclipse the ionosphere was characterized by a strong premidnight enhancement and a subsequent ionospheric decay and a 10 h later postmidnight enhancement neither geomagnetic disturbance occurred during the eclipse day nor did obvious nighttime peak appear for the 10 day mean of the f2 layer critical frequency fof2 the electron density profilogram of the beijing ionosonde indicates that the two enhancements were the result of the plasma flux downward from the top ionosphere possibly due to the steep decrease of the ionospheric electron density and plasma temperature during the solar eclipse the two dimensional differential fof2 maps present the regional variations of the nighttime electron density peaks and decay both the pre and postmidnight enhancements initially appeared in a belt almost in parallel with the eclipse track and then drifted southward the different magnitudes of greatest eclipse in the umbra and outside tend to account for the different occurrence times of the plasma flux the ionospheric decay following the premidnight enhancement is also considered as a consequence of the eclipse shade

stable isotope composition of the holsteinian mis 11 freshwater snail valvata piscinalis o f muller 1774 from eastern poland and its palaeoenvironmental implications stable oxygen and carbon isotope investigations were conducted on shells of the freshwater gastropod valvata piscinalis from palaeolake deposits of holsteinian age marine isotope stage 11 from eastern poland the isotope record of this species was used for the first time as an archive of environmental conditions for selected lakes between the protocratic stage and the post optimum period of the interglacial the lowest 18o and 13c values of 8 1 and 12 1 respectively were recorded in the picea alnus zone at ortel krolewski palaeolake the sparse vegetation and low productivity of that time are reflected in the relatively low 13c values the first significant increase of temperature was recorded in the taxus zone i e an increase in 18o the higher temperature influenced the expansion of macrophytes which stimulated enhanced photosynthesis similar mean 18o values in the taxus and pinus larix zones imply no distinct temperature change v piscinalis populations from ossowka hrud and roskosz palaeolakes record variations in lake productivity during the climatic optimum of the interglacial carpinus abies zone the 18o values of that time are relatively high up to 4 5 and reveal no significant differences between the lakes decreases of the oxygen isotope values in the szymanowo lake reflect post optimum cooling

terrestrial environments during mis 11 evidence from the palaeolithic site at west stow suffolk uk abstract multidisciplinary investigations of the sequence at beeches pit west stow suffolk uk have a direct bearing the age of the hoxnian interglacial and its correlation with the continental holsteinian and with the global marine record at this site glacial deposits till and outwash gravels referable to the anglian lowestoft formation fill a subglacial channel cut in chalk bedrock above these glacial deposits a series of interglacial sediments occurs consisting of limnic tufaceous and colluvial silts lacking pollen but rich in shells ostracods and vertebrates lower palaeolithic flint artefacts of acheulian character have also been recovered including refitting examples charred material is abundant at certain horizons and many of the bones have been burned several discrete areas of burnt sediment are interpreted as hearths the molluscan fauna comprises some 78 taxa and includes species of considerable zoogeographical and biostratigraphical importance the land snail assemblage from the tufa consists of woodland taxa with no modern analogue including species that are either extinct e g zonitoides sepultus or which no longer live in britain e g platyla polita p similis neniatlanta pauli this is also the type locality of retinella lyrodiscus skertchlyi which belongs to a subgenus of zonitid land snail now living only on the canary islands there are indications from this fauna the lyrodiscus biome that the climate was wetter and perhaps warmer than the present day the vertebrate fauna is also noteworthy with species of open habitats such as rabbit oryctolagus cf cuniculus and of closed forest such as squirrel sciurus sp and garden dormouse eliomys quercinus present at different times the occurrence of southern thermophiles such as aesculapian snake zamenis longissimus indicates temperatures warmer than those of eastern england today the upper levels include much material reworked from the interglacial sediments although there is clear faunal evidence for climatic deterioration both the molluscan and vertebrate faunas suggest correlation of the interglacial sediments with the hoxnian uranium series dates from the tufa 455 ka bp tl dates from burnt flints 414 30 ka bp and a range of amino acid racemization data all support correlation of this interglacial with mis 11 however four osl dates from sand beneath the interglacial sequence yield a mean age of 261 31 ka bp far younger than all other age determinations and far younger than implied by the biostratigraphy archaeologically the site is unusual in showing prolonged human occupation within closed deciduous forest and evidence for controlled use of fire in a lower palaeolithic context biostratigraphical correlations with other lower palaeolithic sites support the suggestion that acheulian and clactonian industries both occurred in southern britain during the same substage of the hoxnian although not necessarily at precisely the same time the characteristics of the mis 11 interglacial in britain are discussed in the light of evidence from beeches pit and elsewhere

abrupt climate events 500 000 to 340 000 years ago evidence from subpolar north atlantic sediments subpolar north atlantic proxy records document millennial scale climate variations 500 000 to 340 000 years ago the cycles have an approximately constant pacing that is similar to that documented for the last glacial cycle these findings suggest that such climate variations are inherent to the late pleistocene regardless of glacial state sea surface temperature during the warm peak of marine isotope stage 11 mis 11 varied by 0 5 to 1 c less than the 4 to 4 5 c estimated during times of ice growth and the 3 c estimated for glacial maxima coherent deep ocean circulation changes were associated with glacial oscillations in sea surface temperature

an aminostratigraphy for the british quaternary based on bithynia opercula aminostratigraphies of quaternary non marine deposits in europe have been previously based on the racemization of a single amino acid in aragonitic shells from land and freshwater molluscs the value of analysing multiple amino acids from the opercula of the freshwater gastropod bithynia which are composed of calcite has been demonstrated the protocol used for the isolation of intra crystalline proteins from shells has been applied to these calcitic opercula which have been shown to more closely approximate a closed system for indigenous protein residues original amino acids are even preserved in bithyniid opercula from the eocene showing persistence of indigenous organics for over 30 million years geochronological data from opercula are superior to those from shells in two respects first in showing less natural variability and second in the far better preservation of the intra crystalline proteins possibly resulting from the greater stability of calcite these features allow greater temporal resolution and an extension of the dating range beyond the early middle pleistocene here we provide full details of the analyses for 480 samples from 100 horizons 75 sites ranging from late pliocene to modern these show that the dating technique is applicable to the entire quaternary data are provided from all the stratotypes from british stages to have yielded opercula which are shown to be clearly separable using this revised method further checks on the data are provided by reference to other type sites for different stages including some not formally defined additional tests are provided by sites with independent geochronology or which can be associated with a terrace stratigraphy or biostratigraphy this new aminostratigraphy for the non marine quaternary deposits of southern britain provides a framework for understanding the regional geological and archaeological record comparison with reference to sites yielding independent geochronology in combination with other lines of evidence allows tentative correlation with the marine oxygen isotope record

isotope signature of the younger dryas and two minor oscillations at gerzensee switzerland palaeoclimatic and palaeolimnologic interpretation based on bulk and biogenic carbonates oxygen and carbon isotope ratios in the carbonate of benthic ostracodes pseudocandona marchica and molluscs pisidium ssp were measured across the transitions bordering the younger dryas chronozone in littoral lacustrine cores from gerzensee switzerland the specific biogenic carbonate records confirm the major shifts already visible in the continuous bulk carbonate oxygen isotope record 18occ if corrected for their vital offsets oxygen isotope ratios of pisidium and juvenile p marchica both formed in summer are almost identical to 18occ this bulk carbonate is mainly composed of encrustations of benthic macrophythes chara ssp also mainly produced during summer adult p marchica which calcify in winter show consistently higher 18o larger shifts across both transitions and short positive excursions compared with the summer forms especially during early preboreal despite such complexity the 18o of adult p marchica probably reflects more accurately the variations of the 18o of former lake water because during winter calcification temperatures are less variable and the water column isotopically uniform the difference between normalised 18o of calcite precipitated in winter to that formed in summer can be used to estimate the minimum difference between summer and winter water temperatures in general the results indicate warmer summers during the late allerod and early preboreal compared with the younger dryas altogether the isotopic composition of lake water 18ol and of the dissolved inorganic carbonate 13cdic reconstructed from adult pseudocandona marchica as well as the seasonal water temperature contrasts indicate that the major shifts in the 18o of local precipitation at gerzensee were augmented by changes of the lake s water balance with relatively higher evaporative loss occurring during the allerod compared with the younger dryas it is possible that during the early preboreal the lake might even have been hydrologically closed for a short period we speculate that such hydrologic changes reflect a combination of varying evapotranspiration and a rearrangement of groundwater recharge during those climatic shifts

climate and environment during the younger dryas gs 1 as reflected by composite stable isotope records of lacustrine carbonates at torreberga southern sweden climatic and environmental changes during the younger dryas stadial gs 1 and preceding and following transitions are inferred from stable carbon and oxygen isotope records obtained from the sediments of ancient lake torreberga southern sweden event gs 1 is represented in the sediment sequence by 3 5 m of clay containing lacustrine carbonates of various origins comparison of isotopic records obtained on mollusc shells ostracod valves and chara encrustations precipitated during specific seasons of the year supports estimates of relative changes in both lake water and mean annual air temperatures variations in soil erosion rates can also be estimated from a simple isotope mass balance model to separate allochthonous and autochthonous carbonate contributions to the bulk carbonate content of the sediments the well known rapid climatic shifts characterising the last termination in the north atlantic region are clearly reflected in the isotopic data as well as longer term changes within gs 1 following maximum cooling shortly after the allerod younger dryas gi 1 gs 1 transition a progressive warming and a slight increase in aquatic productivity is indicated at the younger dryas preboreal gs 1 pb transition mean annual air temperature rapidly increased by more than 5 c and summer lake water temperature increased by ca 12 c the subsequent preboreal oscillation is characterised by an increase in soil erosion and a slight decrease in mean annual air temperature these results are in harmony with recent findings about large scale climate dynamics during the last termination copyright 1999 john wiley sons ltd

changes of shell microstructural characteristics of cerastoderma edule bivalvia a novel proxy for water temperature abstract shells of bivalves potentially provide an excellent archive for high resolution paleoclimate studies however quantification of environmental variables specifically water temperature remains a very challenging task here we explore the possibility to infer water temperature from changes of microstructural characteristics of shells of the common cockle cerastoderma edule the size and elongation of individual microstructural units i e prisms in the outer shell layer of seven three to five year old specimens collected alive from the intertidal zone of the north sea near texel the netherlands and schillig germany were measured by means of automatic image processing growth patterns circatidal ciralunidian and fortnightly increments and lines shell oxygen isotope values and mark and recovery experiments were used to place the shell record in a precise temporal context irrespective of the locality and ontogenetic age size and elongation of the prisms increased non linearly with water temperature small 0 12 0 05 m 2 and round prisms elongation 2 42 0 31 were formed at temperatures of ca 10 c late april whereas larger 0 33 0 11 m 2 and more elongated prisms 3 26 0 28 occurred during hot summer ca 22 c no clear cut or consistent correlation existed between microstructural characteristics and growth rate as well as a variety of other environmental variables such as salinity chlorophyll a and turbidity based on these findings a model was constructed from three shells at texel that enables reconstruction of water temperature with a precision of 1 7 1 0 c from prism size and elongation sst 9 02 17 25 p s 1 10 p e this model was successfully tested at four shells from schillig the new temperature proxy can be of particular interest for paleoclimate studies in nearshore settings when non recrystallized c edule shells are available future studies are required to verify our findings and check if other species with the same and different microstructures show similar relationships with water temperature