applications of organic geochemistry to paleolimnological reconstructions a summary of examples from the laurentian great lakes the organic matter content of lake sediments contains information that helps to reconstruct past environmental conditions evaluate histories of climate change and assess impacts of humans on local ecosystems the elemental isotopic and molecular compositions of organic matter buried in sediment provide evidence of the biota that have lived in a lake and its catchment area and they serve as proxies of organic matter delivery and accumulation sedimentary records from the north american great lakes provide examples of applications of organic geochemistry to paleolimnological reconstructions the records of these lakes date from retreat of the laurentide ice sheet around 12 ka include the mid holocene hypsithermal and show consequences of recent human changes low corg ntotal ratios indicate that most of the sediment organic matter in the great lakes is from algal production yet changes in biomarker molecule compositions also show that varying amounts of land plant organic matter have been delivered to the lakes elevated algal productivity that accompanies nutrient enrichments of lake waters is recorded as excursions to less negative 13c values in the organic matter of sediments that were deposited in the 1960s and 1970s increased organic carbon mass accumulation rates mirror the isotopic excursions in most parts of the great lakes accumulations of petroleum residues and pyrogenic polycyclic aromatic hydrocarbons in sediments identify fluvial and eolian delivery of organic matter components to different parts of the great lakes emerging applications of multiple and novel organic geochemical proxies to paleolimnological reconstructions are promising yet some potentially important measurements remain underutilized

empirical relationship between leaf wax n alkane δd and altitude in the wuyi shennongjia and tianshan mountains china implications for paleoaltimetry article i nfo estimating past elevation not only provides evidence for vertical movements of the earth s lithosphere but also increases our understanding of interactions between tectonics relief and climate in geological history development of biomarker hydrogen isotope based paleoaltimetry techniques that can be applied to a wide range of sample types is therefore of continuing importance here we present leaf wax derived n alkane d dwax values along three soil altitudinal transects at different latitudes in the wuyi shennongjia and tianshan mountains in china to investigate dwax gradients and the apparent fractionation between leaf wax and precipitation ewax p we findthatsoil dwax trackaltitudinal variationsof precipitation d along the three transects that span variable environment conditions and vertical vegetation spectra an empirical dwax altitude relation is therefore established in which the average dwax lapse rate of 2 27 0 38 100 m is suitable for predicting relative paleoelevation change relative uplift the application of this empirical gradient is restricted to phases in the mountain uplift stage whenthe atmospheric circulation had not distinctly changed and to when the climate was notarid anempirical dwax latitude altitudeformulaisalsocalculated dwax 3 483lat 0 0227alt 261 5 which gives the preliminary spatial distribution pattern of dwax in modern china meanvalue of ewax p intheextreme humid wuyimountainsisquite negative 154 compared to the humid shennongjia 129 and the arid but with abundant summer precipitation tianshan mountains 130 which suggests aridity or water availability in the growing season is the primary factor controlling soil sediment ewax p along the tianshan transects values of ewax p are speculated to be constant with altitude while along the wuyi and shennongjia transects ewax p are also constant at the low mid altitudes but become slightly more negative at high altitudes which could be attributed to overestimates of precipitation d or the vegetation shift to grass conifer additionally a reversal of altitude effect in the vertical variation of dwax was found in the alpine zone of the tianshan mountains which might be caused by atmospheric circulation change with altitude this implies that the paleo circulation pattern and its changes should alsobe evaluated whenstable isotope based paleoaltimetry is applied

a study of oxygen isotopic fractionation during bio induced calcite precipitation in eutrophic baldeggersee switzerland in order to better understand environmental factors controlling oxygen isotope shifts in autochthonous lacustrine carbonate sequences we undertook an extensive one year study march 1995 to february 1996 of water column chemistry and daily sediment trap material from a small lake in central switzerland comparisons between calculated equilibrium isotope values using the fractionation equation of friedman and o neil 1977 and measured oxygen isotope ratios of calcite in the sediment traps reveal that oxygen isotopic values of autochthonous calcite 18o are in isotopic equilibrium with ambient water during most of the spring and summer when the majority of the calcite precipitates in contrast small amounts of calcite precipitated in early spring and again in late autumn are isotopically depleted in 18o relative to the calculated equilibrium values by as much as 0 8 this seasonally occurring apparent isotopic nonequilibrium is associated with times of high phosphorous concentrations elevated ph 8 6 and increased co32 50 mol l in the surface waters the resulting weighted average 18o value for the studied period is 9 6 compared with a calculated equilibrium 18o value of 9 4 these data convincingly demonstrate that 18o of calcite are for the most part a very reliable proxy for temperature and 18o of the water

lake level and climate records of the last 90 ka from the northern basin of lake van eastern turkey abstract sedimentary geochemical and mineralogical analyses of the icdp cores recovered from the northern basin nb of lake van provide evidence of lake level and climatic changes related to orbital and north atlantic climate system over the last 90 ka high lake levels are generally observed during the interglacial and interstadial periods which are marked by deposition of varved sediments with high total organic carbon toc total inorganic carbon tic low detrital influx high ca f and high 18o and 13c values of authigenic carbonate during the glacial and stadial periods of 71 58 ka bp marine isotope stage 4 mis4 and end of last glaciation deglaciation 30 14 5 ka bp mis3 relatively low lake levels prevailed and grey homogeneous to faintly laminated clayey silts were deposited at high sedimentation and low organic productivity rates millennial scale variability of the proxies during 60 30 ka bp mis3 is correlated with the dansgaard oeschger d o and holocene abrupt climate events in the atlantic these events are characterized by laminated sediments with high toc tic ca fe 18o and 13c values the lake van nb records correlate well in the region with the climate records from the lakes zeribar and urmia in iran and the sofular cave in nw anatolia but are in general in anti phase to those from the dead sea basin lake lisan in the levant the relatively higher 18o values 0 to 0 4 for the interglacial and interstadial periods in the lake van nb section are due to the higher temperature and seasonality of precipitation and higher evaporation whereas the lower values 0 8 to 2 during the glacial and stadial periods are caused mainly by relative decrease in both temperature and seasonality of precipitation the high 18o values up to 4 2 during the younger dryas together with the presence of dolomite and low toc contents supports evaporative conditions and low lake level a gradual decrease in the 18o values from an average of 0 4 during the humid early holocene to an average of 3 5 during the more arid late holocene suggests an increasing contribution of winter precipitation the changes in the seasonality of precipitation in eastern anatolia are probably caused by changes in the temperatures of north atlantic and mediterranean and in the strength of siberian high

vegetation and climate changes during the last two glacial interglacial cycles in the western mediterranean a new long pollen record from padul southern iberian peninsula abstract a new sediment core from padul padul 15 05 provides a long and continuous sedimentary and paleoenvironmental record of the last 200 kyr here we present a detailed palynological study from this sedimentary sequence with new vegetation and paleoenvironmental data and a climatic interpretation for the last two climatic cycles from the southern iberian peninsula in the western mediterranean region pollen analysis from this core shows orbital scale vegetation oscillations mainly forced by precession and eccentricity pointing into insolation as the principal factor controlling vegetation changes at this latitude the last two glacial interglacial cycles from mis 6 to the present as well as stadial and interstadial phases are well represented and characterized by significant oscillations in mediterranean forest in the area but several differences with respect to other mediterranean long pollen records can be recognized some of these disparities between regions seem to be more related to different precipitation rates linked to the specific geographical features e g strong topographic relief than to latitudinal differences between the sites in addition a lake level reconstruction based on palynological data was developed and compared with the previous reconstruction from this record representing local environmental changes in the padul wetland that seems to be related to precipitation evapotranspiration balance and therefore to changes in regional climate conditions during glacial stadial conditions recorded by maxima in xerophytes the p e increased due to very low evapotranspiration resulting in high lake levels while during warmer interglacial interstadial phases except for the mis 5e mainly represented in this record by maxima in the mediterranean forest water level decreased as a result of high evapotranspiration exceeding precipitation input the comparison of the new padul 15 05 pollen record with the two previous palynological studies from padul shows significant differences mainly due to disagreements in the age control of the sequences this study shows that an accurate age depth model becomes essential when interpreting long paleoenvironmental and paleoclimate records

the effect of soil hydrology on the oxygen and hydrogen isotopic compositions of plants source water abstract many studies have demonstrated that the isotopic composition of plants source water is the main factor affecting the isotopic composition of tree rings because of soil hydrological processes soil water as the source water for plants may isotopically differ from precipitation that contains climatic information such as surface temperature this study addresses the effects of soil hydrological processes on the isotopic compositions of soil water and discusses how these effects affect interpretations of tree ring data in isotopic dendroclimatology we collected precipitation soil gas at two depths 20 and 50 cm and twigs from a maple tree acer saccharum on a biweekly basis during the growing season in 1997 1999 at hanover nh usa water was extracted from the twig samples by vacuum distillation all water samples were analyzed for both d and 18 o soil co 2 was extracted from soil gas and measured for the 18 o values and using the soil temperature and assuming isotopic equilibrium between co 2 and h 2 o we calculated the 18 o values of soil water comparisons among the isotopic time series of each type of sample indicate the following 1 the isotopic composition of soil water is much less variable than that of precipitation suggesting isotopic mixing between waters of different precipitation events 2 in early spring soil water at all depths is isotopically similar to winter precipitation but with time the surface soil water becomes progressively enriched in deuterium and 18 o due to infiltration of summer rain and enrichment through soil water evaporation 3 the influence of summer precipitation decreases with increasing depth and soil at 50 cm can only receive water from large storms 4 replacement of old soil water with new infiltrating water is dependent upon frequency and intensity of growing season precipitation and it is generally more efficient in a wet year than in a dry year 5 the tree we studied uses water mainly from near surface soil layers 6 the d 18 o relationship in twig water indicates that soil water has experienced isotopic enrichment by evaporation these results have important implications for selecting sites for paleoclimatic studies using isotopic data of tree rings

effects of aridity and vegetation on plant wax δd in modern lake sediments we analyzed the deuterium composition of individual plant waxes in lake sediments from 28 watersheds that span a range of precipitation d h vegetation types and climates the apparent isotopic fractionation ea between plant wax n alkanes and precipitation differs with watershed ecosystem type and structure and decreases with increasing regional aridity as measured by enrichment of 2 h and 18 o associated with evaporation of lake waters the most negative ea values represent signatures least affected by aridity these values were 125 5 for tropical evergreen and dry forests 130 for a temperate broadleaf

temperature and precipitation variability in eastern anatolia results from independent component analysis of lake van sediment data spanning the last 250 kyr bp abstract in this study we present the results of independent component analysis ica of previously published lake van data covering the last 250 kyr bp to shed light on the precipitation and temperature regime in eastern anatolia the data processed were the element intensities of ca fe k mn and si analyzed by xrf core scanner concentrations of toc and caco 3 content and b color reflectance from the ahlat ridge sediment record our analysis is based on application of ica on the data by changing the initial random unit vector several times and clustering possible independent components through average link agglomeration as components extracted by ica do not have a hierarchy mutual information which is a measure of information content between two random variables is used as a measure of similarity by which to select candidate components as a result we argue the independent component van ic8 which shows the highest similarity to the greenland 18 o record and visually similar to other regional temperature indicating data can be read as a proxy for temperature variability we also assert that the independent component van ic7 which has the highest similarity to b and visually similar to other regional precipitation proxies and with the lake level reconstruction from another sediment profile from lake van is a proxy of precipitation variability across the region our results show that the region s temperature approximately maps onto global records i e warm during interglacials and cold during stadials however the precipitation proxy reveals that the region was not dry or at least as wet as it is today during the end of the mis 6 and the lgm the mis 5e c and holocene were characterized by a wet period followed by dry intervals and dansgaard oeschger events are characterized as being warm and wet

the radiocarbon reservoir age of lake van eastern turkey abstract lake van is the largest soda lake in the world located on the east anatolian plateau in turkey its varved sediments provide an excellent archive of high resolution paleoclimate record for the near east varve counting and radiocarbon methods are therefore important dating techniques for investigating the lake van sedimentary paleoclimate record we have studied 4 56 m core vp0801 and 4 70 m core vp0807 long cores recovered from 80 m and 65 m water depths located in se and sw of lake van respectively the cores cover the last 8 4 ka and lithologically include three laminated sedimentary units from top to the bottom the units were dated 4 2 ka bp present 5 4 4 2 ka bp and older than 5 4 ka bp according to carbon nitrogen atomic c n values the uppermost unit contains mainly organic matter of biodegraded soil origin and the middle and lower units c3 type vascular land plant origin suggesting decreased precipitation during 4 2 ka to present we identified tephra layers previously dated by varve counting and used the varve ages to obtain age models for the cores we also obtained a total of eight accelerator mass spectrometry ams 14c dates from total organic carbon toc in the two cores close to the tephra layers comparison of the varve ages of the ams 14c dated samples with their corresponding ams 14c dates indicates large differences suggesting significant reservoir ages that range from 2 8 to 2 5 ka for 3 0 2 4 varve ka bp and from 2 8 to 3 3 ka for 8 0 5 9 varve ka bp the results suggest that the reservoir age of the organic matter increases with the varve age of the sediments this increase is mainly related to the rate of supply of dead carbon from the old carbonate rocks in the watershed of lake van which was relatively higher during 8 4 5 9 ka than during 3 0 2 4 ka bp because of the higher atmospheric precipitation and higher rate of biochemical weathering during the former period

stable isotope based paleoaltimetry abstractthe quantitative estimation of paleoaltitude has become an increasing focus of earth scientists because surface elevation provides constraints on the geodynamic mechanisms operating in mountain belts as well as the influence of mountain belt growth on regional and global climate the general observation of decreasing 18o and 2h values in rainfall as elevation increases has been used in both empirical and theoretical approaches to estimate paleoelevation these studies rely on the preservation of ancient surface water compositions in authigenic minerals to reconstruct the elevation at the time the minerals were forming in this review we provide a theory behind the application of stable isotope based approaches to paleoaltimetry we apply this theory to test cases using modern precipitation and surface water isotopic compositions to demonstrate that it generally accords well with observations examples of the application of paleoaltimetry techniques to himalaya tibet and the andes are discussed

biomarker reconstruction of the early eocene paleotopography and paleoclimate of the northern sierra nevada we reconstruct ancient temperature and elevation gradients across the early eocene 52 49 ma northern sierra nevada california united states using organic molecular proxies that record atmospheric and ground level effects of topography paleoelevation was determined by reconstructing the change in the hydrogen isotopic composition of precipitation d precip and mean annual temperature t gdgt glycerol dialkyl glycerol tetraethers from the isotopic composition of fossil angiosperm leaf n alkanes and the distribution of microbially produced soil tetraethers preserved in leaf bearing sediments organic molecular data produce equivalent range scale d n alkane and channel t gdgt paleoelevation estimates that show the northern sierra nevada was a warm 6 8 c warmer than modern high elevation 2 km and moderate to low relief landscape at the eocene climatic optimum modern northern sierra nevada topography likely refl ects post paleocene reduction of mean surface elevation and late cenozoic increases in relief

empirical relationships between elevation and the stable isotope composition of precipitation and surface waters considerations for studies of paleoelevation change a compilation of 68 studies from throughout many of the world s mountain belts reveals an empirically consistent and linear relationship between change in elevation and change in the isotopic composition of precipitation along altitudinal transects the isotopic composition of precipitation decreases linearly with increasing elevation in most regions of the world except in the himalayas and at elevations 5000 m there are no significant differences in isotopic lapse rates from most regions of the world 0 28 permil 100 m except at the extreme latitudes where isotopic lapse rates are higher given information on past changes in the isotopic composition of precipitation preserved in pedogenic or authigenic minerals this global isotopic lapse rate can be used to place numerical constraints on the topo graphic development of some ancient mountain belts or plateaus there are many complicating factors that can confound interpretation of paleoel evation change based on stable isotopes and many of these are unique to specific mountain belts or time periods relevant to all stable isotope based paleoelevation change studies is the temperature dependent isotope fractionation between a pedo genic or authigenic mineral and the water from which it forms in cases where isotopic proxy minerals are sampled from localities where temperature will change simulta neously with elevation change the apparent change in the isotopic composition of precipitation may be dampened by several permil this suggests that samples taken from the rainshadow side of an emerging orographic barrier may be more likely to preserve isotopic changes resulting from mountain uplift than samples taken from atop a rising mountain range or plateau

a 600 000 year long continental pollen record from lake van eastern anatolia turkey abstract lake van is the fourth largest terminal lake in the world 38 5 n 43 e volume 607 km 3 area 3570 km 2 maximum water depth 460 m extending for 130 km wsw ene on the eastern anatolian high plateau turkey the sedimentary record of lake van partly laminated obtains a long and continuous continental sequence that covers multiple interglacial glacial cycles promoted by the potential of the sedimentary sequence for reconstructing the paleoecological and paleoclimate development of the near east a deep drilling operation was carried out in 2010 supported by the international continental scientific drilling program icdp the 219 m long continental pollen record presented here is based on a well dated composite profile drilled on the so called ahlat ridge in water depth of 360 m encompassing the last 600 000 years it is the longest continuous continental pollen record of the quaternary in the entire near east and central asia obtained to date the glacial interglacial cycles and pronounced interstadials are clearly reflected in the vegetation development based on millennial scale time resolution in general the glacial stadial vegetation is characterized by dwarf shrub steppe and desert steppe whereas the climax vegetation of past interglacials can be described as oak steppe forest similar to the present interglacial in this sensitive semi arid region between the black caspian and mediterranean seas by comparing the lake van pollen record with other western asian and southern european long continental pollen sequences as well as marine and ice core records the regional variability of the climate signals is also discussed

paleomagnetism of lake van sediments chronology and paleoenvironment since 350 ka abstract in the framework of the paleovan project a high resolution paleomagnetic and rock magnetic study was carried out on a 149 m sedimentary sequence recovered from ahlat ridge in the deepest part of the lake van eastern turkey icdp site 5034 2 high sedimentation rates average 30 cm ka allow high resolution measurements of natural remanent magnetization nrm magnetic susceptibility anhysteretic remanence arm and hence of anhysteretic susceptibility arm over the last 350 ka the carrier of the remanence is detrital titanomagnetite largely from volcanic sources based on the similarity of magnetite grain size of tephra layers and the other lacustrine lithologies observed in a plot of the versus arm bulk magnetic parameters often covary with paleoclimatic signals in the lake van sediments a correlation exists between variations of and arm intensity and glacial interglacial marine isotopic stages as well as dust flux and temperatures observed in ice cores from greenland and antarctica the quality of the paleomagnetic record is compromised by weak nrm intensities as well as by the presence of tephra and turbidites throughout the sequence nonetheless a correlation is observed between the relative paleointensity rpi record based on nrm arm and the calibrated piso rpi stack that supports the independently derived age model for the site

late holocene high resolution multi proxy climate and environmental records from lake van eastern turkey abstract we present the multi proxy records of centennial scale climate and environmental changes over the last 3 5 ka from a varved sediment core in lake van eastern turkey the multi proxy analyses include ostracod counts xrf elemental total organic toc and inorganic carbon c n elemental and stable isotopes for the age model of the core we use radionuclide 210pb and 137cs analysis and varve counting large differences between accelerator mass spectrometry ams radiocarbon dates from toc and varve ages indicate reservoir ages of 1 2 3 8 ka calbp average sedimentation rate for the last 170 years top 75 mm of the core ranges between 0 42 and 0 54 mm yr according to 210pb dating multi proxy parameters show that lake van experienced more arid conditions during the 3 5 1 6 ka calbp than those during the last 1 6 ka bp 16 periods of alternating cold dry and warm wet intervals with 100 350 years duration are observed over the last 3 5 ka the lake van climate records are conformable with the lake nar and the sofular speleothem records as well as the european historical climate periods including roman warm period rwp dark age cold period dacp medieval warm period mwp and little ice age lia indicating teleconnections with the north atlantic system human influence is reflected by high detrital influx in the last 700 years

petroleum seepages and impregnations in great britain abstract this paper documents 173 occurrences of surface petroleum seepages and impregnations in great britain a brief description is given of the seven main areas where they are found the descriptions range from pore fillings of bitumen to steady flows of oil and gas the principal areas in which seepages are found are as follows the orcadian basin of north east scotland the midland valley of scotland the flanks of the pennines the welsh borderlands cornwall the dorset coast of the wessex basin and the south eastern weald stratigraphically the seepages range from caledonide basement to holocene peat the principal sources for the petroleum are devonian oil shales orcadian basin carboniferous shales and coals midland valley pennines welsh borderlands devon and cornwall and the liassic wessex and wealden basins several anomalous seepages are recorded from welsh and scottish basement there are three clearly defined styles in which the seepages occur many are found where permeable carrier beds unconformably overlie impermeable basement around the margins of basins orcadian basin midlands carboniferous basin others are fault related especially in the wessex and wealden basins the seepages in the cornish tin mines are best explained as sourced from the culm series and drawn by the convective flow of connate waters into the thermal chimneys of the granite intrusions

lake van deep drilling project paleovan a complete succession of the lacustrine sediment sequence deposited during the last 600 000 years in lake van eastern anatolia turkey was drilled in 2010 supported by the international continental scientific drilling program icdp based on a detailed seismic site survey two sites at a water depth of up to 360 m were drilled in summer 2010 and cores were retrieved from sub lake floor depths of 140 m northern basin and 220 m ahlat ridge to obtain a complete sedimentary section the two sites were multiple cored in order to investigate the paleoclimate history of a sensitive semi arid region between the black caspian and mediterranean seas this introductory paper provides background information of the deep drilling project and an overview of the studies presented in this special volume by the paleovan science team dealing with chronology paleomagnetism paleoenvironmental proxies geophysical and petrophysical investigations as well as pore water and fluid transport

cyclostratigraphic studies of sediments from lake van turkey based on their uranium contents obtained from downhole logging and paleoclimatic implications a deep drilling campaign was performed at lake van turkey to enhance the understanding of the paleoenvironmental conditions of the middle east cores were collected and the sediments are mainly composed of clayey silts and tephra deposits spectral gamma ray data were acquired 0 210 m below lake floor and the uranium data were used for cyclostratigraphic studies to estimate the sedimentation rates and the time of deposition detection and analysis of climate cycles require continuous sedimentation and cannot be applied to these sediments which include numerous tephra layers therefore these layers were removed and a synthetic log was created cumulative thickness of the tephra 50 m remaining lacustrine sediments 160 m high amplitudes were detected and correlated to milankovic cycles their evolution was analyzed using the sliding window technique the sedimentation rates varied from 22 to 33 cm ka in the upper section the sediments between the lake floor and a depth of 210 m were deposited over a period of 587 ka our results agree with core interpretations e g correlation of total organic carbon with marine isotope stages which suggest a time span of deposition of 600 ka high frequency cycles were detected and correlated with interstadials from the north greenland 18o record for the past 75 ka the two datasets agreed closely we conclude that climate signals even on sub milankovic scale are imprinted in uranium of these sediments and cyclostratigraphic methods are applicable if event layers are subtracted from the sediment record

spatial distribution and controlling factors of stable isotopes in meteoric waters on the tibetan plateau implications for paleoelevation reconstruction abstract debates persist about the interpretations of stable isotope based proxies for the surface uplift of the central northern tibetan plateau these disputes arise from the uncertain relationship between elevation and the 18 o values of meteoric waters based on modern patterns of isotopes in precipitation and surface waters we present a large river water data set 1 340 samples covering most parts of the tibetan plateau to characterize the spatial variability and controlling factors of their isotopic compositions compared with the amount weighted mean annual oxygen isotopic values of precipitation we conclude that river water is a good substitute for isotopic studies of precipitation in the high flat e g elevation 3 300 m interior of the tibetan plateau in the mean annual timescale we construct for the first time based on field data contour maps of isotopic variations of meteoric waters 18 o d and d excess on the tibetan plateau in the marginal mountainous regions of the plateau especially the southern through eastern margins the 18 o and d values of river waters decrease with increasing mean catchment elevation which can be modeled as a rayleigh distillation process however in the interior of the plateau northward increasing trends in 18 o and d values are pronounced and present robust linear relations d excess values are lower than the marginal regions and exhibit distinct contrasts between the eastern 8 12 and western

facies characterization based on physical properties from downhole logging for the sediment record of lake van turkey abstract lake van turkey is the 4th largest terminal lake in the world and is located at a key position for climatic reconstruction the icdp project paleovan is a deep drilling campaign initiated in the summer of 2010 to enhance the understanding of paleoclimatic and paleoenvironmental conditions in the middle east for a period of 550 000 years multiple coring of two sites northern basin and ahlat ridge at a water depth of up to 360 m has been performed the sedimentary record is mainly composed of clayey silts and tephra deposits that were supplied by four volcanic sources 1 the suphan volcano located on the northern shore 2 the nemrut volcano 15 km west of the westernshore 3 the incekaya volcano on the southwestern shore and 4 intralake eruptive centers the dominant chemical composition of the volcanic sources is known from studies of land deposits high quality downhole logs have been acquired from both sites to construct a continuous lithological profile 180 m of downhole logging data from the ahlat ridge have been analyzed by cluster analysis to improve the differentiation of the sediments two elemental intensity profiles from x ray fluorescence core scanning calcium and zirconium performed on the composite profile core material were added to the cluster analysis five cluster units were derived and transformed into three tephra and two clayey silt units to compare the two clayey silt units with the composite profile from the visual core description vcd that showed 15 lithological units the composite profile was classified into two major groups of lacustrine sediments banded clayey silts interpreted as glacial deposits and laminated clayey silts interpreted as interglacial deposits despite this simplification no correlation between the two clayey silt units derived from cluster analysis and the banded and laminated clayey silts could be found the following reasons are proposed a the comparability of the datasets was limited by significant depth shifts of up to 2 5 m between the composite profile based on the vcd and the downhole measurements in hole 2d of the ahlat ridge b a correlation was difficult to ascertain from the vertical resolution of the downhole logging data and the extremely detailed core description in mm scale c mixed signals were obtained because of prevailing thin layers and intercalations of different lithotypes and d cluster analysis was difficult to perform because the contrast within the input data is too low possibly background sedimentation to distinguish between glacial and interglacial deposits tephra units are characterized by contrasting properties and differ mainly in their magnetic susceptibility spectral gamma ray components uranium thorium and potassium and xrf intensities of calcium and zirconium tephra units have been linked to the dominant volcanic composition of the deposited tephra layers and partly to the volcanic sources depth trends are derived with prevailing basaltic deposits in the bottom part 128 m 210 m below lake floor and are gradually outweighed by the highly differentiated dacitic and rhyolitic trachytic products towards the top of the record

an automated algorithm for dating annually laminated sediments using x ray radiographic images with applications to lake van turkey lake nautajarvi finland and byfjorden sweden abstract annually laminated varved sediments in marine and lake basins are important archives for paleoenvironmental and paleoclimatic reconstructions especially with their property to provide a continuous chronology in this study we introduce a new approach for counting laminae using both digital and analogue x ray radiographic images the requirement for the method is that the resolution of the image is higher than the minimum lamina thickness so that the measurement interval should be at least one third of the minimum lamina thickness in our method 8 bit or 16 bit grey scale radiographic images are scaled to grey scale values between 0 and 1 and every maximum and minimum peaks corresponding to seasonal lamination are defined along the sediment core the algorithm counts laminae rather than varves thus allowing control on estimation of more reliable age models detected peaks are summed cumulatively along the core length using a step determined by the annual lamina number of the varve using the algorithm we provide test examples from the varved sediments of the lake nautajarvi in finland byfjorden in sweden and lake van in eastern turkey and compare our results with previously dated levels in the cores there are good agreements between the varve counting results of our study and the previous studies except for the ages from the lower part of the lake van core corresponding to a time interval between ca 7000 and 8000 bp for which there is ca 1000 year difference between the two sets of results this difference might be the result of under counting of varves in the previous studies

late eocene oligocene high relief paleotopography in the north central tibetan plateau insights from detrital zircon u pb geochronology and leaf wax hydrogen isotope studies

hydrogen isotope ratios of recent lacustrine sedimentary n alkanes record modern climate variability abstract hydrogen isotope ratios were measured on n alkanes n c12 to n c31 extracted from recent lake surface sediments along a n s european transect to test if modern climate variability is recorded in these biomarkers d values of the n alkanes are compared to d values of meteoric water from the iaea gnip database spanning a range from 119 in northern sweden to 41 in southern italy to lake water d values and to mean annual temperatures varying between 2 0 c in the north and 13 7 c in the south d values of the short chained n alkanes n c12 to n c20 excluding algal derived n c17 and n c19 are higher in the north and lower in the south the isotopic fractionation e for hydrogen between meteoric water and the short chained n alkanes is increasing from n to s by more than 100 and is significantly correlated to mean annual temperature for n c16 and n c18 this suggests that these n alkanes may originate from a different source in the northern lakes possibly due to petroleum contamination or are synthesized using a different biochemical pathway the n c17 and n c19 alkanes of algal origin the n c21 and n c23 alkanes originating from water plants and the long chain n alkanes n c25 n c27 n c29 and n c31 of terrestrial origin clearly correlate with d values of meteoric water lake water and mean annual temperature indicating that they excellently record the d value of meteoric water the mean hydrogen isotope fractionation ec17 w of 157 sd 13 between n c17 and meteoric water is fairly constant over the wide range of different climates and lake environments suggesting only minor influence of environmental factors on this biochemical fractionation this suggests that d values of n c17 are suitable to reconstruct the isotopic composition of source water the mean fractionation between the long chain n alkanes and water is 128 sd 12 the mean difference of 31 between both e values is likely due to evaporative enrichment of deuterium in the leaf water if this is the only influence on the enrichment the difference between the d values of terrestrial and aquatic compounds might be suitable to reconstruct terrestrial evapotranspiration of the lake environment

paleovan international continental scientific drilling program icdp site survey results and perspectives lake van is the fourth largest terminal lake in the world volume 607 km 3 area 3570 km 2 maximum depth 460 m extending for 130 km wsw ene on the eastern anatolian high plateau turkey the sedimentary record of lake van partly laminated has the potential to obtain a long and continuous continental sequence that covers several glacial interglacial cycles ca 500 kyr therefore lake van is a key site within the international continental scientific drilling program icdp for the investigation of the quaternary climate evolution in the near east paleovan as preparation for an icdp drilling campaign a site survey was carried out during the past years we collected 50 seismic profiles with a total length of similar to 850 km to identify continuous undisturbed sedimentary sequences for potential icdp locations based on the seismic results we cored 10 different locations to water depths of up to 420 m multidisciplinary scientific work at positions of a proposed icdp drill site included measurements of magnetic susceptibility physical properties stable isotopes xrf scans and pollen and spores this core extends back to the last glacial maximum lgm a more extended record than all the other lake van cores obtained to date both coring and seismic data do not show any indication that the deepest part of the lake tatvan basin ahlat ridge was dry or almost dry during past times these results show potential for obtaining a continuous undisturbed long continental palaeoclimate record in addition this paper discusses the potential of paleovan to establish new results on the dynamics of lake level fluctuations noble gas concentration in pore water of the lake sediment history of volcanism and volcanic activities based on tephrostratigraphy and paleoseismic and earthquake activities c 2009 elsevier ltd all rights reserved

helium radon and hydrothermal circulation associated with the carnmenellis radiothermal granite of southwest england the carnmenellis granite of southwest england has higher than average radioelement concentrations and a heat flow greater than 100 mw m 2 more than twice the united kingdom average measurements were made of 4he concentrations and 222rn activities in surface waters over the granite and its immediate host rocks high values greater than 48 ppb 4he 160 c min 222rn for either or both gases are interpreted as indicating discharge of groundwater from the upwelling limbs of hydrothermal convection cells 4he has a spatial distribution which agrees well with the observed variations of heat flow within the pluton but 222rn is also influenced by lithology and depth of groundwater flow although the distribution of convection cells is partly determined by the presence of nw se faults there is close similarity with theoretical models of groundwater circulation it is concluded that 4he and 222rn surveys provide a simple but effective method for mapping areas of modern hydrothermal activity

different altitude effect of leaf wax n alkane δd values in surface soils along two vapor transport pathways southeastern tibetan plateau abstract here we present 76 hydrogen isotope values for leaf wax derived n alkanes d wax being the abundance weighted average d values of c 29 and c 31 n alkanes in surface soils along two vapor transport pathway transects running across the southeastern tibetan plateau tp the first is the south himalayan sh transect with an altitude range of 1660 5050 m above sea level and representing the southern himalayan air mass and the second a combination of the zayu bomi zb altitude 1468 4800 m and bayi lhasa bl altitude 3050 4970 m transects together representing the brahmaputra yarlung zangbo river valley air mass d wax values and their relation to altitude did exhibit some variability nonetheless altitude was the predominant factor in determining soil d wax values with a lapse rate of 2 2 100 m r 2 0 78 n 76 based on overall soil d wax values despite changes in precipitation amount relative humidity rh and vegetation type furthermore our e wax rw values the isotopic fractionation between the d wax and d values of river water d rw remained approximately constant at 104 5 ranging between 99 and 110 confirming that the relation between altitude and isotopic hydrology river water and precipitation controls the n alkane d wax altitudinal gradients for all of the sample localities in the southern himalaya sh and the southern tp this endorses the efficacy of using d wax to reconstruct paleoelevation along the sh transect soil d wax values varied from 151 to 264 with an altitudinal lapse rate of 2 4 100 m r 2 0 84 n 32 this was due to the significant change in altitude over short distances along the zb transect soil d wax values varied from 174 to 263 with a lower lapse rate of 1 9 100 m r 2 0 68 n 29 the altitudinal lapse rate was 3 3 100 m above 3000 m r 2 0 63 n 19 and 1 35 100 m below 3000 m r 2 0 64 n 10 in the lower sub transect the latitudinal effect significantly counteracted the altitude effect along the bl transect soil d wax values varied from 205 to 244 with an altitudinal lapse rate of 1 4 100 m r 2 0 74 n 15 the lower lapse rate for soil d wax reflects a combination of local continental and altitudinal effects the differences we observed in soil d wax altitudinal lapse rates along the two vapor transport pathways imply that they are affected by subtle local environmental conditions moisture sources latitude and topography this should be considered fully during any reconstruction of paleoelevation

reactive plasticity for clays application to a natural analog of long term geomechanical effects of nuclear waste disposal abstract long term changes in mechanical properties of clays induced by heating are investigated based on findings at orciatico site of natural analog of nuclear waste disposal to quantify the extent of such changes a chemo thermo plastic model for illitization and re smectitization of clays int j plast 2000 is used the model is an extension of cam clay model identification of parameters is presented for the material from one peripheral borehole where temperatures developed in clay near the contact were in the analogy range short term heating experiments on previously thermally unaffected specimens were used to identify thermal softening characteristics apparent maximum past precompression stress was determined throughout the borehole hypothetical history of the clay in the borehole including pre loading heating cooling and mineralogical reaction was reconstructed and the apparent maximum past precompression stress data were used to identify the characteristics of chemical softening function describing the long term clay transformations

refining the interpretation of lacustrine carbonate isotope records implications of a mineralogy specific lake van case study abstract oxygen and carbon isotope 18o and 13c data from bulk carbonates are widely applied proxies for temperature the precipitation evaporation ratio and productivity in lacustrine palaeohydrology and palaeoclimatology in case of the terminal and alkaline lake van however previous studies have shown that bulk oxygen isotope compositions are in disagreement with other proxies when interpreted in a conventional manner similarly the reports on the nature and the timing and site of carbonate precipitation in lake van are inconsistent this study provides evidence on the mineralogy x ray powder diffraction analysis scanning electron microscope imaging confocal raman microscopy electron microprobe analysis and isotope composition 18o and 13c of non skeletal carbonate minerals in a lake van sedimentary profile spanning the last ca 150 kyr carbonate phases present in the sediment include aragonite low mg calcite and calcian dolomite dolomite forms as an early diagenetic phase and occurs episodically in high concentrations driving the bulk isotope record towards the higher dolomite 18o and varying 13c values aragonite and low mg calcite precipitate in the surface water and are present in the sediments in varying amounts relative aragonite to calcite content for dolomite poor samples ar ar cc of 93 to 41 wt in an attempt to explain this variation we revised a precipitation model based on annually laminated sediments containing both aragonite and calcite spatially separated in light and dark coloured laminae respectively according to our model spring calcite precipitation under close to freshwater conditions is followed by evapoconcentration driven aragonite precipitation in late summer the precipitation of these carbonate polymorphs from chemically differing surface waters i e freshwater influenced and evapoconcentrated leads to distinctly different oxygen and carbon isotope signatures between sedimentary penecontemporaneous aragonite and calcite the 18o and 13c values of aragonite relative to calcite are significantly higher by several per mille than inferred from aragonite calcite fractionation factors alone suggesting that the generalised assumption of sedimentary coeval calcite and aragonite precipitating from water with the same isotopic composition is flawed the here proposed revised hydrologically separated carbonate precipitation model is not only taking i differences in the isotopic fractionation between carbonate minerals into account but also ii considering the hydrological conditions and the processes favouring the precipitation of a given mineral and ultimately controlling its isotopic composition if mixed mineralogies are present this mineralogy specific approach has the potential of refining environmental reconstructions and reconciling apparently equivocal interpretations of different proxy records

millennial to orbital scale variations of drought intensity in the eastern mediterranean abstract millennial to orbital scale rainfall changes in the mediterranean region and corresponding variations in vegetation patterns were the result of large scale atmospheric reorganizations in spite of recent efforts to reconstruct this variability using a range of proxy archives the underlying physical mechanisms have remained elusive through the analysis of a new high resolution sedimentary section from lake van turkey along with climate modeling experiments we identify massive droughts in the eastern mediterranean for the past four glacial cycles which have a pervasive link with known intervals of enhanced north atlantic glacial iceberg calving weaker atlantic meridional overturning circulation and dansgaard oeschger cold conditions on orbital timescales the topographic effect of large northern hemisphere ice sheets and periods with minimum insolation seasonality further exacerbated drought intensities by suppressing both summer and winter precipitation

can stable isotopes ride out the storms the role of convection for water isotopes in models records and paleoaltimetry studies in the central andes abstract globally changes in stable isotope ratios of oxygen and hydrogen o 18 and d in the meteoric water cycle result from distillation and evaporation processes isotope fractionation occurs when air masses rise in elevation cool and reduce their water vapor holding capacity with decreasing temperature as such o 18 and d values from a variety of sedimentary archives are often used to reconstruct changes in continental paleohydrology as well as paleoaltimetry of mountain ranges based on 234 stream water samples we demonstrate that areas experiencing deep convective storms in the eastern south central andes 22 28 s do not show the commonly observed relationship between o 18 and d with elevation these convective storms arise from intermontane basins where diurnal heating forces warm air masses upward resulting in cloudbursts and raindrop evaporation especially at the boundary between the tropical and extra tropical atmospheric circulation regimes where deep convective storms are very common 26 to 32 n and s the impact of such storms may yield non systematic stable isotope elevation relationships as convection dominates over adiabatic lifting of air masses because convective storms can reduce or mask the depletion of heavy isotopes in precipitation as a function of elevation linking modern or past topography to patterns of stable isotope proxy records can be compromised in mountainous regions and atmospheric circulation models attempting to predict stable isotope patterns must have sufficiently high spatial resolution to capture the fractionation dynamics of convective cells

biomarker seasonality study in lake van turkey the endorheic lake van in eastern anatolia turkey is the world s largest soda lake and it is an important site in paleoclimate studies to understand past continental conditions in western asia in order to gain further insights into the biomarker signatures in lake van s sediments we have analyzed particulate material in sediment traps deployed between august 2006 and july 2007 the biomarkers used were long chain alkenones lcas c37 c39 haptophyte lipids isoprenoid glycerol dialkyl glycerol tetraethers gdgts archaea membrane lipids and pigments chlorins and fucoxanthin the biomarker fluxes indicate a strong seasonality in export primary productivity and the phytoplankton community structure the highest total mass and organic carbon fluxes were found in summer coupled to strong stratification while the lowest mass fluxes occurred in winter at the time of water column mixing with increasing temperatures in early spring phytoplankton export productivity grew coupled with an increase of total mass flux and organic carbon which might be associated to enhanced nutrient input from snowmelt runoff the percentage of c37 4 shows some correspondence with observed seasonal changes in lake van s stratification structure we also evaluated the potential applicability of molecular temperature proxies derived from archaea and haptophyte lipids the use of the tex86 proxy was precluded by low gdgt abundances estimated lca temperatures were consistent with temperatures in the photic zone but no seasonality changes were observed despite the wide annual temperature range measured at lake van 2011 elsevier ltd all rights reserved

a model for the tectonic evolution of south cornwall a stratigraphy for south cornwall is combined with an analysis of the chronology of thrust nappe emplacement the resulting model suggests that northward overthrusting of nappes of flysch and olistostrome ophiolite and continental basement is related to the closure of an oceanic basin in south cornwall involving southward subduction throughout the devonian the subsequent continental collision between the normannian high and part of laurentia occurred in the upper devonian with deformatian continuing until late carboniferous times

the annual particle cycle in lake van turkey abstract the varved sediments of lake van provide a high quality continental archive of seasonal to decadal scale climate variability in order to read the natural record modern varve formation was studied on the basis of 1 remotely sensed total suspended matter tsm rs concentrations 2 time series of particle flux and water temperatures and 3 turbidity temperature and oxygen profiles tsm rs validated by contemporaneous water column sampling shows great temporal and lateral variations whitings and turbidity plumes from 2006 to 2009 sequential sediment traps recorded high particle fluxes during spring and fall medium fluxes during summer and almost zero flux during winter the mean total mass flux of 403 mg m 2 day 1 comprised 33 seasonally up to 67 calcium carbonate 7 aquatic organic matter 6 biogenic opal and 54 detrital minerals the caco 3 fluxes are controlled by river discharge precipitation and snowmelt during spring by high productivity during summer and by river discharge precipitation before snowfall starts and mixing during fall in november 2007 an anomalously high caco 3 flux occurred as a result of a warm water surface supersaturated with calcite coinciding with an anomalous runoff event the results demonstrate that the couplets of light and dark laminae in the short sediment cores are true varves representing spring summer fall and winter conditions respectively consequently varve formation can be linked to the seasonal climate pattern providing a calibration that can be used to interpret the partially varved paleo record of lake van and related environmental processes

altitudinal shift in stable hydrogen isotopes and microbial tetraether distribution in soils from the southern alps nz implications for paleoclimatology and paleoaltimetry abstract the southern alps are an ideal locality for studying patterns of isotopic fractionation associated with orographic precipitation we have evaluated whether altitudinal change is reflected in the stable hydrogen isotopic composition 2 h of stream water plant stem water and leaf wax lipids n alkanes from living plants and soils as well as in soil temperature samples were collected along an altitudinal transect from the windward side of the southern alps to lake hawea in the rain shadow the results indicate that 2 h values of stem water overlap with stream water demonstrating a gradual decrease with elevation that complied with modeled rayleigh distillation reflecting an isotopic lapse rate of 18 0 1 1 1 km leaf and soil n alkanes shared similar 2 h values and were 2 h depleted relative to stem stream waters the values for soil n alkanes indicated an isotopic lapse rate of 21 8 2 0 1 km consistent with precipitation data and long term observations mbt cbt derived soil temperature values based on the relative distribution of microbial tetraether lipids were similar to midsummer temperature observations displaying an elevational decrease rate of 5 6 1 5 1 c km consistent with regional and global observations the results indicate that sedimentary lipid 2 h and microbial tetraether temperature estimates captured altitudinal trends in the isotopic composition of precipitation and mean temperature and further support their application in the reconstruction of past climate and surface uplift histories however notable differences in isotopic composition and temperature estimates between in situ soils and those with downslope transport of material emphasize the importance of facies analysis when interpreting past systems

hydrogen isotope ratios of terrestrial leaf wax n alkanes from the tibetan plateau controls on apparent enrichment factors effect of vapor sources and implication for altimetry abstract empirical evidence suggested that the altitudinal dependence of hydrogen isotope ratios of leaf wax n alkanes d wax can be used to estimate paleoaltitudinal changes however the application of d wax based paleoaltimetry remains difficult as the impacts of evaporative transpirative and biosynthetic processes on hydrogen isotope fractionations in changing environments and the influence of likely changing water vapor sources are not well explored for this study we sampled stream waters soils and plant leaves along two transects spanning large gradients of altitude precipitation amount vapor source temperature and vegetation type on the tibetan plateau tp d values of stream water as an approximation for d p soil water d sw and plant leaf water d lw as well as leaf wax n alkanes were measured in order to quantify isotopic fractionations in the formation of leaf waxes most interestingly we found a strong negative correlation between the evapotranspirative enrichment of leaf water against precipitation e lw p which combines the effects of soil evaporation and leaf transpiration and the biosynthetic hydrogen isotope fractionation e wax lw which describes isotopic enrichment between leaf wax and leaf water the relationship yields a steady apparent isotopic enrichment factor e wax p between leaf wax and precipitation which is independent from climatic parameters and has an average value of 107 26 for grasses monocotyledons and 77 22 for trees dicotyledons since the terrestrial n alkanes especially n c 27 and n c 29 in sediments are derived from trees and grasses the likely change of the vegetation type in the uplift of mountains can change the isotopic estimates by about 30 which corresponds to an altitudinal change of 1600 m we therefore suggest that hydrogen isotope ratio of sedimentary n c 31 alkane which is mainly derived from grasses might be better proxies to reconstruct paleoaltitudes our large dataset of d wax from trees and grasses that aimed to mirror the variability of environmental factors over geological time frames showed the lapse rates were significant but much smaller than in previous studies most importantly our result demonstrated that the lapse rate significantly differed for both transects p 0 0068 i e 0 87 0 71 100 m r 2 0 28 p 0 2841 n 6 and 2 28 0 82 100 m r 2 0 34 p 0 0135 n 17 for indian monsoon and westerly dominated areas respectively this suggests that different moisture sources might strongly affected the observed lapse rates in consequences altitude reconstructions are strongly complicated in areas with likely changing air masses like the tibetan plateau

seismic stratigraphy of lake van eastern turkey more than 1500 km of multi channel seismic reflection profiles combined with icdp international continental scientific drilling program drilling data provide important insights into the stratigraphic evolution of lake van eastern turkey three major basins tatvan northern and the deveboynu basins comprise the main lake basin and are separated by morphological highs ahlat ridge and northern ridge moreover ne sw faults parallel to the general tectonic lineament of the area dominate the entire basin and are in charge of creating graben and half graben structures well developed prograding deltaic sequences on top of the basement were recognized by seismic stratigraphy analysis most likely they formed during the initial flooding of lake van 600 ka the tatvan basin sediments are dominated by mass flow deposits of various origins alternating with undisturbed lacustrine sediments including distinct tephra layers faulting along the tatvan basin margins may have triggered margin wide slope failures ahlat ridge started to form between ca 340 ka 290 ka since then ahlat ridge was sheltered from major mass flows due to its elevation hence slow lacustrine sedimentation has prevailed throughout lake history on ahlat ridge which was the location of the main drill site during the icdp several lake level fluctuations are evident on the eastern slope area but the deep basins were permanently covered by water a significant lake level low stand ca 600 ka bp was found at 610 m below present lake level the setting of the lake changed at about 30 ka tectonic activity appears to have waned significantly as the mass transport deposition decreased across the tatvan basin while normal undisturbed lacustrine sedimentation prevailed a different setting is found in the northern basin from ca 90 ka to present especially due to the strong influx of mostly volcaniclastic turbidites causing sedimentation rates to be about 3 5 times higher drill site 1 than at site 2 ahlat ridge

leaf wax stable isotopes from northern tibetan plateau implications for uplift and climate since 15 ma abstract the growth of tibetan plateau is considered to have played a key role during the evolution of asian climate our understanding of the relationship between the plateau growth and asian climate changes is limited however due to the scarcity of well dated sedimentary sequences that could provide parallel information of the evolution of elevation and climate here we report a high resolution time series record of the stable hydrogen isotopic composition of leaf wax n alkanes d n alk from a continuous neogene stratigraphic sequence 15 1 8 ma from the qaidam basin on the northern tibetan plateau these data are used to reconstruct the isotopic composition of meteoric waters d m and subsequently applied to interpret the history of paleotopography and climate in qaidam our results indicate four stages in the evolution of hydrology in the qaidam basin in stage i 15 ma to 10 4 ma d m gradually decreases from 24 9 to 75 5 synchronous with a period of active tectonism the estimated topographic growth of 2 1 0 3 km is comparable to the height of qaidam basin relative to the foreland hexi corridor we note that c 3 plants were dominant in this region since the miocene we take this as independent evidence that this area was mountainous before the c 4 expansion in late miocene and pliocene d m variability in subsequent stages appears to be related to shifts in dry and moist conditions and independent of topographical changes a conclusion supported by other independent climatic records on the tibetan plateau high d m values in stage ii 10 4 ma to 6 9 ma are related to severe aridity and stage iii 6 9 ma to 4 1 ma is marked by low d m values suggestive of moist conditions related to the strengthening east asia summer monsoon high d m values in stage iv 4 1 ma to 1 8 ma reflect a climate drier than the present

soil n alkane δd vs altitude gradients along mount gongga china the altitude effect on the isotopic composition of precipitation and its application to paleoelevation reconstruction using authigenic or pedogenic minerals have been intensively studied however there are still no studies on variations in biomarker d along altitude transects to investigate its potential as a paleoelevation indicator although it has been observed that d of higher plant lipid may record changes in precipitation d dp here we present d values of higher plant derived c27 c29 and c31n alkanes from surface soil along the eastern slope of mount gongga china with great changes in physical variables and vegetation over a range from 1000 to 4000 m above sea level the weighted mean d values of these n alkanes dwax show significant linear correlations with predicted dp values r2 0 76 with an apparent isotopic enrichment ewax p of 137 9 indicating that soil dwax values track overall dp variation along the entire altitudinal transect leaf dwax is also highly correlated with mountain altitude by a significant quadratic relationship r2 0 80 evapotranspiration is found declining with altitude potentially lowering dwax values at higher elevations however this evapotranspiration effect is believed to be largely compensated by the opposing effect of vegetation changes resulting in less varied ewax p values over the slope transect this study therefore confirms the potential of using leaf dwax to infer paleoelevations and more generally to infer the d of precipitation

dynamics of the last four glacial terminations recorded in lake van turkey abstract a well dated suite of lake van climate proxy data covering the last 360 ka documents environmental changes over 4 glacial interglacial cycles in eastern anatolia turkey the picture of cold and dry glacials and warm and wet interglacials emerging from pollen organic carbon authigenic carbonate content elemental profiling by xrf and lithological analyses is inconsistent with classical interpretation of oxygen isotopic composition of carbonates pointing to a more complex pattern in lake van region detailed analysis of glacial terminations allows for the constraining of a depositional model explaining different patterns observed in all the proxies we hypothesize that variations in relative contribution of rainfall snowmelt and glacier meltwater recharging the basin have a very important role for all sedimentary processes in lake van lake level of glacial lake van predominantly fed by snowmelt was low the water column was oxic and carbonates precipitating in the epilimnion recorded the light isotopic signature of inflow during terminations increasing rainfall and significant supply of mountain glaciers meltwater contributed to lake level rise increased rainfall enhanced density gradients in the water column and hindered mixing leading to development of bottom water anoxia carbonates precipitating during terminations show large fluctuations in their isotopic composition full interglacial conditions in lake van are characterized by high or slowly falling lake level rainfall and snowmelt feed the lake but due to re established mixing the isotopic composition of authigenic carbonates is heavier and closer to that of evaporation influenced lake water than that of runoff representing snowmelt and atmospheric precipitation

modis imagery of turbid plumes in san diego coastal waters during rainstorm events abstract data of normalized water leaving radiance nlw obtained from the moderate resolution imaging spectroradiometer modis on the aqua satellite at spatial resolution of 250 m band 1 centered at 645 nm and 500 m band 4 at 555 nm are used to study turbid plumes in coastal waters of southern california during rainstorm events in winter of 2004 2005 our study area includes san diego coastal waters which extend approximately 25 km offshore between point loma and 10 km south of the us mexican border these waters are influenced by terrigenous input of particulate and dissolved materials from san diego and tijuana watersheds and non point sources along the shore optimum threshold values of satellite derived normalized water leaving radiances at both wavebands were established for distinguishing the plume from ambient ocean waters these threshold values were determined by searching for a maximum correlation between the estimates of satellite derived plume area calculated using a broad range of nlw values and the environmental variables characterizing rainfall river discharge wind and tides a correlation analysis involving the amount of precipitated water accumulated during a storm event over the san diego and tijuana watersheds was selected as the basis for final determinations of the optimum threshold nlwthr and subsequent calculations of the plume area by applying this method to a sequence of modis imagery we demonstrate the spatial extent and evolution of the plume during rainstorm events under various conditions of precipitation river discharge wind forcing and coastal currents

can sedimentary leaf waxes record d h ratios of continental precipitation field model and experimental assessments abstract d h ratios of leaf waxes d wax derived from terrestrial plants and preserved in lake sediments can provide important information on past continental hydrology ideally d wax can be used to reconstruct precipitation d h ratios d p which is a well established paleoclimate proxy however many other factors such as vegetation and relative humidity rh also affect d wax variation how the combination of these factors affects sedimentary d wax is unclear here we use a transect of 32 lake surface sediments across large gradients of precipitation relative humidity and vegetation composition in the southwestern united states to study the natural factors affecting sedimentary d wax d values of c 28 n alkanoic acids show significant correlation with d p values r 2 0 76 with an apparent isotopic enrichment of 99 8 indicating that sedimentary d wax values track overall d p variation along the entire transect leaf waxes produced by plants grown under controlled conditions rh 80 60 40 show a small increase in d h ratios as rh decreases consistent with prediction from the craig gordon model however the isotopic effect of rh on d wax along the natural transect is partially countered by the opposing influence of vegetation changes the correlation between d wax and d p values is significantly higher r 2 0 84 in the drier portions of the transect than in the wetter regions r 2 0 64 this study suggests that d h ratios of sedimentary leaf waxes can be used as a proxy for precipitation d variations with particularly high fidelity in dry regions although more studies in other regions will be important to further test this proxy

hydrogen isotopic compositions along a precipitation gradient of chinese loess plateau critical roles of precipitation evaporation and vegetation change as controls for leaf wax δd abstract the hydrogen isotopic compositions d of long chain plant leaf waxes can reflect changes of continental hydrology and thus have been increasingly utilized for paleoclimate reconstruction one of the unresolved major issues is whether variations of leaf wax d dwax signals along a precipitation gradient reflect changes of precipitation d precipitation amount and or evapo transpiration this ambiguity limits our interpretation of dwax in geological records as well as the quantitative reconstruction of paleohydrological variability here we systematically investigated d of soil water and waxes extracted from soil and plant leaves in the chinese loess plateau clp and its surrounding areas along a precipitation gradient with mean annual precipitation map varying from 140 mm to 676 mm the results showed that while the variation of modeled precipitation d has no significant correlation with map soil water d soil dwax and individual plant dwax exhibit negative correlations with map in relatively arid areas the d values of soil water and plant leaf waxes are significantly more positive due to much lower precipitation relative to evapo transpiration suggesting that effective precipitation p e ratio has played a crucial role in the d enrichment of soil and plant leaf waxes in this region while parallel decreasing trends in dwax are found along the increase of precipitation gradient among dominant plants including artemisia spp aster hispidus stipa bungeana and cleistogenes squarrosa in the region with similar slopes the large d offsets between plant groups suggest that plant type is an important factor in controlling plant hydrogen isotope fractionations our results indicate that dwax preserved in paleosols can be used to infer past conditions of water availability in arid and semi arid inland regions but with a mechanism that is different from the influence of amount effect in humid areas moreover vegetation changes should be constrained by independent paleobotanical data before monsoon related paleohydrology in the clp and its surrounding areas can be quantitatively reconstructed using the plant wax d proxy

modern sedimentary analogues and integrated monitoring to understand varve formation in the mediterranean lake montcortes central pyrenees spain abstract varved sediments provide unique opportunities to carry out high resolution paleoclimatic and paleoenvironmental reconstructions with accurate time control to better interpret the sediment record it is necessary to understand the physical chemical and biological factors that influence varve formation and preservation we explored the link between the annual limnological cycle and current varve deposition in the oligotrophic hard water lake montcortes central pyrenees the varves of this lake consist of couplets of dark organic and light calcareous laminae a two year limnological monitoring 10 2013 10 2015 combined with a sediment trap study were conducted at monthly resolution limnological and sedimentological measurements were compared with meteorological data although the lake was considered meromictic in the first limnological studies we documented total mixing of the water column both winters in spite of this long periods of stratification and hypolimnetic anoxia create suitable conditions for varve formation and preservation sediment deposition followed a clear seasonal pattern related to biological processes in the euphotic zone during summer and fall calcite precipitation was favored by high calcite saturation indices and enhanced primary production that promoted relatively high ph values as a result of co2 uptaking there was considerable variability in the amount of calcite deposition between years which was linked to seasonal temperature differences in addition calcite crystal sizes and diatom fluxes showed seasonal patterns related to calcite saturation index and changes in water stratification which in turn were also related to temperature variability seasonal sedimentation patterns were strongly linked to primary producers and especially sensitive to temperature shifts it results in a clear seasonal signal and varve formation we compared our results with previous sedimentological interpretations of the varved record of this lake this study improves the interpretation of lake montcortes sediment record extending back several millennia

fracture detection and groundwater flow characterization using he and rn in soil gases manitoba canada abstract surveys of the distribution and migration of he and rn were carried out in the well characterized granitic terrane of the aecl underground research laboratory url manitoba as part of a joint aecl research united kingdom department of the environment and united states department of energy research initiative the investigations were designed to determine whether concentrations of he and rn in soil gases could be used to identify locations of groundwater recharge and discharge from bedrock fractures the results obtained indicate that subsurface transport of he and possibly rn in this setting appears to be controlled largely by the groundwater flow system in the bedrock release of dissolved gases near the ground surface causes soil gas anomalies which reflect discharge from the deeper flow system in the recharge area of the deep groundwater flow system at the url site he abundances are close to the atmospheric level but the discharge area of the deep flow system is characterized by significant he anomalies up to 0 5 ppm above atmosphere levels for rn the recharge area has broadly distributed high concentrations probably caused by local rn production in u rich overburden while the discharge area has only localized concentrations of rn which are not at the same location as the he anomalies the general nature of the groundwater flow regime in both areas is reflected in the presence and distribution of the soil gas anomalies in addition major fractures in bedrock which act as preferential groundwater flow paths have been located from soil gas anomalies even when obscured by overburden of variable thickness and character the distribution of he in soil gas appears to be most representative of groundwater recharge and discharge conditions in the granitic rock while rn may be useful for locating specific channels where more rapid groundwater discharge is occurring from deep fracture zones

222rn and co2 soil gas geochemical characterization of thermally altered clays at orciatico tuscany central italy abstract the physical properties of clay allow argillaceous formations to be considered geological barriers to radionuclide migration in high level radioactive waste isolation systems as laboratory simulations are short term and numerical models always involve assumptions and simplifications of the natural system natural analogues are extremely attractive surrogates for the study of long term isolation the clays of the orciatico area tuscany central italy which were thermally altered via the intrusion of an alkali trachyte laccolith represent an interesting natural model of a heat source which acted on argillaceous materials the study of this natural analogue was performed through detailed geoelectrical and soil gas surveys to define both the geometry of the intrusive body and the gas permeability of a clay unit characterized by different degrees of thermal alteration the results of this study show that gas permeability is increased in the clay sequences subjected to greater heat input from the emplacement of the orciatico intrusion despite the lack of apparent mineral and geotechnical variations these results which take into consideration long time periods in a natural large scale geological system may have important implications for the long term safety of underground storage of nuclear waste in clay formations

hydrogen isotope ratios of lacustrine sedimentary n alkanes as proxies of tropical african hydrology insights from a calibration transect across cameroon abstract hydrogen isotope values d of sedimentary aquatic and terrestrial lipid biomarkers originating from algae bacteria and leaf wax have been used to record isotopic properties of ancient source water i e precipitation and or lake water in several mid and high latitude lacustrine environments in the tropics however where both processes associated with isotope fractionation in the hydrologic system and vegetation strongly differ from those at higher latitudes calibration studies for this proxy are not yet available to close this gap of knowledge we sampled surface sediments from 11 lakes in cameroon to identify those hydro climatological processes and physiological factors that determine the hydrogen isotopic composition of aquatic and terrestrial lipid biomarkers here we present a robust framework for the application of compound specific hydrogen isotopes in tropical africa our results show that the d values of the aquatic lipid biomarker n c17 alkane were not correlated with the d values of lake water carbon isotope measurements indicate that the n c17 alkane was derived from multiple source organisms that used different hydrogen pools for biosynthesis we demonstrate that the d values of the n c29 alkane were correlated with the d values of surface water i e river water and groundwater which on large spatial scales reflect the isotopic composition of mean annual precipitation such a relationship has been observed at higher latitudes supporting the robustness of the leaf wax lipid d proxy on a hemispheric spatial scale in contrast the d values of the n c31 alkane did not show such a relationship but instead were correlated with the evaporative lake water d values this result suggests distinct water sources for both leaf wax lipids most likely originating from two different groups of plants these new findings have important implications for the interpretation of long chain n alkane d records from ancient lake sediments in particular a robust interpretation of palaeohydrological data requires knowledge of the vegetation in the catchment area as different plants may utilise different water sources our results also suggest that the combination of carbon and hydrogen isotopes does help to differentiate between the metabolic pathway and or growth form of organisms and therefore the source of hydrogen used during lipid biosynthesis

calcite precipitation in lake constance chemical equilibrium sedimentation and nucleation by algae1 seasonal shifts in calcium carbonate solution equilibria in the limnetic zone of lake constance were documented between 1981 and 1983 except during mixing times lake water was supersaturated with respect to calcite epilimnetic supersaturation maxima were closely related to changes in ph sedimentation of calcium from the lower boundary of the euphotic zone to the lake bottom was also assessed the daily sedimentation flux for calcium during the season varied over three orders of magnitude differences in the calcium content of sediments trapped at various depths were insignificant sedimentation rates of titanium were used as tracers for the fluxes of calcium bound on allochthonous elastic material lacustrine calcite precipitation 39 49 of the total sedimentation rate was obtained by subtracting fluxes of allochthonous ca from the rates of total ca sedimentation calcium supersaturation maxima were not in phase seasonally with maximum fluxes of autochthonous ca instead calcite precipitation was associated with the occurrence of stephanodiscus hantzschii fragilaria crotonensis asterionella formosa chlorella sp pandorina morum and mougeotia thylespora indicating that calcite formation was triggered by heterogeneous nucleation induced by certain algal species autochthonous formation and subsequent precipitation of calcium carbonate is an important process in the carbon and calcium cycling in many hard waters through coprecipitation calcium carbonates affect nutrient budgets rossmann 1980 rossknecht 1980 murphy et al 1983 and by adsorption they remove dissolved organic carbon doc from the water suess 1970 chave and suess 1970 otsuki and wetzel 1972 hence several studies have focused on the formation reactions settling processes and deposition of caco in lakes cf

effect of precipitation regime on δ d values of soil n alkanes from elevation gradients implications for the study of paleo elevation we measured dd values of long chain n alkanes isolated from 30 surface soil samples along two elevation transects on the tibetan plateau differing in precipitation regime and water source the east asian monsoon precipitation dominates the wetter regime on the eastern slope from 1230 to 4300 m of gongga shan on the eastern tibetan plateau precipitation from the polar westerlies dominates the drier region on the slope from 1900 to 5000 m in the west kunlun shan on the northwestern tibetan plateau the decrease in dd value with elevation in the wetter region greatly exceeded that in drier region by 1 9 0 1 100 m and 1 4 1 0 100 m respectively the apparent fractionation between leaf wax and precipitation ewax p values in the wetter region ca 164 were more negative than those in drier region ca 125 above 3200 m we also measured dd values in leaves of six common living trees values from 287 to 193 from gongga shan ranging from about 2900 4200 m the abundance weighted average values of the nalkanes ddwax show a strong reverse correlation with sample source elevation r 2 0 78 for soils from 2 0 85 for soils from west kunlun shan above 3200 m suggesting that n alkane ddwax faithfully records the precipitation dd and that the isotopic altitude effect of precipitation controls ddwax altitudinal gradients in the mountains the data show a fairly strong monotonic dependency of n alkane dd values on elevation for the eastern plateau but a complex relationship between n alkane dd values and elevation for the northwestern plateau the ddwax values at sites below 3200 m from the kunlun shan area exhibit an unexpected positive correlation with elevation the study confirms the potential for using sediment ddwax values to reconstruct paleo elevation in wetter regions but suggests caution in applying the approach to dry regions our results also show it is essential to consider the intricacy of the pattern of atmospheric circulation and water sources and their influence on the lapse rate of dd values with elevation

assessing paleohydrologic controls on the hydrogen isotope compositions of leaf wax n alkanes in chinese peat deposits abstract the high concentrations of lipid biomarkers in peat and the close relation between peatland development and hydrological conditions merit further assessment of the paleohydrological proxy potential of the 2h 1h ratio of leaf wax n alkanes 2halk in peat deposits in the context of the dynamics of the east asian summer monsoon detailed investigation of modern processes is an important way to improve our understanding of the controls on 2halk records from chinese peat deposits this review first synthesizes the results of investigations of modern processes in the dajiuhu peatland of central china complemented by results from other peatlands and nearby non peatland sites to evaluate how the 2h 1h ratio changes from source water to leaf water and then to lipids in leaf waxes and ultimately to peat deposits the results reveal that the precipitation 2h values and the peatland plant types are the two major factors that control the 2halk signals preserved in peat at dajiuhu comparison of results from holocene 2halk sequences from other chinese peat deposits illustrates how peat 2halk values respond to paleoclimate changes on centennial to millennial timescales throughout the east asian summer monsoon region finally proposed incubations of peat forming plants in controlled chambers that could assess the response of plant 2halk values to environmental stresses are described as an example responses of the compound specific biomarker 2h and 13c values of sphagnum the dominant plant in the dajiuhu peatland could provide important information on the symbiotic relation between sphagnum and microbes it is expected that experiments such as these that combine the carbon and hydrogen isotope compositions of multiple lipids will yield important new insights into the responses of peatland ecosystems to climate changes

paleoaltimetry of the tibetan plateau from d h ratios of lipid biomarkers abstract the past elevation of the land surface provides a unique constraint on the underlying lithospheric structure during mountain and plateau formation development of new paleoaltimetry techniques that can be applied to a wide variety of sample types is therefore of continuing importance this study evaluates organic substrates that preserve the d ratio of surface waters as a new approach to reconstruct paleoaltimetry we measured the hydrogen isotope composition of n alkanes from epicuticular plant waxes preserved in lacustrine deposits to reconstruct the d of precipitation in cenozoic basins that have been elevated as part of the tibetan plateau n alkane d and carbonate 18 o inferred water compositions from the eocene miocene lunpola basin and miocene hoh xil basin plot near or at enriched values relative to the global meteoric water line as expected for evaporative lakewater and leafwater systems that have the same precipitation source n alkane d based water compositions are nearly identical to the minimum carbonate 18 o based values demonstrating that plant wax d is minimally affected by evaporation compared to lacustrine calcite 18 o this agreement strongly supports the presence of similar precipitation isotopic compositions in both archives despite different isotope systems source water reservoirs archive materials modes of incorporation and diagenetic processes paleoelevations for each basin and time period were calculated from precipitation isotope ratios using the isotope altitude relationship derived from both a simple thermodynamic model and modern precipitation sampling from the plateau region our new results from the hoh xil basin suggest 1700 to 2600 m of uplift may have occurred some time between the late eocene and early miocene the timing of this uplift is consistent with late oligocene compressional deformation of the hoh xil basin and northward growth of the tibetan plateau however the calculated uplift is not a unique solution from the paleoisotope data because of uncertainties in eocene and miocene moisture sources and isotope gradients for the northern plateau our results demonstrate the utility of lipid based estimates of paleoelevation and expand the types of deposits amenable to paleoaltimetry analysis

gas migration through water saturated fractured rock results of a gas injection test abstract the generation of gases and possible development and migration of a gas phase at depth in groundwater saturated fractured rock has become an important aspect of assessing the performance and safety of radioactive waste disposal sites to study gas phase migration in this environment helium gas was injected at constant pressure through an access borehole into an inclined fracture zone at a depth of about 40 m in the granitic lac du bonnet batholith southeastern manitoba canada the gas flow rate arrival time and pattern of distribution of gas at the surface were monitored by soil gas surveys gas flow rate increased from 5 to 20 l min 1 over the 11 day period of the test indicating removal of water from the flow paths breakthrough of injected gas at the surface was detected within 2 days two areas of high concentrations of gas discharge were observed within 40 m of the injection borehole indicating gas transport through near vertical fractures a larger area of trace he concentrations was detected 200 m away indicating transport along the fracture zone the field results were compared with predictions of a simple analytical model derived from braester and thunvik 1983 good agreement was found when the influence of fracturing in the bedrock and a low permeability overburden and excess porosity due to non uniformity of fracture apertures were included in the model the model was then used to estimate and map the relative hydraulic conductivities of individual gas flow paths in the fractured rock

varves in lake sediments a review abstract downcore counting of laminations in varved sediments offers a direct and incremental dating technique for high resolution climatic and environmental archives with at least annual and sometimes even seasonal resolution the pioneering definition of varves by de geer 1912 had been restricted to rhythmically deposited proglacial clays one century later the meaning of varve has been expanded to include all annually deposited laminae in terrestrial and marine settings under favourable basin configurations and environmental conditions limnic varves are formed due to seasonality of depositional processes from the lake s water column and or transport from the catchment area subsequent to deposition of topmost laminae the physical preservation of the accumulating varved sequence requires the sustained absence of sediment mixing for example via wave action or macrobenthic bioturbation individual sub laminae in varved lake sediments typically express contrasting colours always differ in terms of their organic chemical and or mineralogical compositions and often also differ with regard to grain size various predominating climatic and depositional conditions may result in clastic biogenic or endogenic incl evaporitic varved sediments and their mixtures to reliably establish a varve chronology the annual character of laminations needs to be determined and verified in a multidisciplinary fashion sources and influences of possible errors in varve chronologies are best determined and constrained by repeated varve counts and by including radioisotopes and correlation with historically documented events a well established varve chronology greatly enhances the scientific value of laminated limnic archives by securely anchoring the wealth of multi proxy palaeoenvironmental information in the form of time series for multidisciplinary investigations applications of varved records are discussed with special reference to advances since the 1980s these span fields like calibrating radiometric dating methods reconstructing past changes of the earth s magnetic field or detecting fluctuations in solar forcing once a varve chronology is established it can be applied to precisely date events like volcanic ash layers earthquakes or human impact as well as short and long term climate temperature precipitation wind hydroclimatic conditions or flooding and environmental changes eutrophication pollution due to their exceptional high temporal resolution and in combination with their robust and accurate internal time scale in calendar years annually laminated sediments can be regarded as one of the most precious environmental archives on the continents these records are necessary to extend temporally limited instrumental records back in time as such they have societal relevance with regard to risk assessments related to natural hazards arising from e g flooding or volcanic eruptions

characterization and disequilibrium cases of radioelements in some syrian hot waters the radioactive and physical characteristics of syrian hot waters were studied the concentration of uranium its daughters and the 234u 238u activity ratios in the hot waters were measured by gamma and alpha ray spectroscopy the 234u 238u activity ratios showed that uranium in syrian hot waters are in an equilibrium state some anomalous observations of these ratios were explained by former leaching of the uranium from cretaceous phosphates by underground water also the results showed that the temperature of the studied hot waters was independent of the contained radioelements the temperature of hot waters is explained by the passing of these waters near the hot spot or by the relationship between the geological deposit of the aquifer rocks and the waters rather than the contents of the radioelements

climate change vegetation history and landscape responses on the tibetan plateau during the holocene a comprehensive review abstract numerous studies of changes in the climate vegetation and landscape responses of the tibetan plateau tp during the holocene have been published in recent decades however several conflicting interpretations are evident within these studies and a comprehensive review of the topic is needed to reconcile them and thus to provide an improved understanding of the history and forcing mechanisms of holocene environmental changes within the region here we review the evidence for changes in climate temperature precipitation moisture vegetation and landscape attributes glacier and eolian activity on the tp during the holocene our main conclusions are as follows 1 the patterns of holocene mean annual temperature change on the tp remain controversial however an early to middle holocene summer temperature maximum is evident which coincided with high summer insolation and a strengthening of the indian summer monsoon ism this suggests that the summer land sea thermal gradient impacted by the temperature of the tp may be an important factor driving orbital scale ism changes 2 lake level records indicate an optimum in moisture conditions on the southwestern sw tp in the early holocene while on the northeastern ne tp the optimum occurred in the middle to late holocene this out of phase or anti phased relationship may be linked to the role of the ism in dominating precipitation on the sw tp while the westerlies and east asian summer monsoon dominated the precipitation on the ne tp 3 most of the lake sediment based stable isotope records 18o and leaf wax d exhibit a pattern similar to that of stalagmite 18o records from monsoonal asia reflecting the dominance of large scale patterns of atmospheric circulation rather than localized moisture changes reflected by lake level records 4 a synthesis of pollen records reveals that the extent of forest was maximal in the mid holocene while from the early holocene onwards alpine steppe shrunk and alpine meadow and desert gradually expanded 5 evidence of glacier advance increased slightly during the early holocene decreased during the mid holocene and then increased substantially after 3 ka bp 6 the integrated ages of eolian sand and loess from the ne tp reveal that eolian activity intensified during the early and late holocene site inter comparisons reveal that regional climate change played a major role in modulating changes in vegetation and other landscape attributes overall producing holocene climate reconstructions for the entire tp remains a major challenge even though much progress has been made further improvements in terms of the spatial coverage of high resolution paleoclimatic records with robust chronological control and a deeper understanding of the specific climatic significance of several climatic proxies will facilitate an improved understanding of how the monsoon and the westerlies interacted and their impacts on vegetation and landscape changes on the tp

major crustal reflectors beneath sw england strong wide angle reflection events were detected during a crustal seismic experiment carried out in sw britain in 1979 three crustal reflectors have been identified referred to as rl r2 and r3 rl lies at a depth of about 8 km and appears to be restricted to the interior of the granite batholith underlying sw england the nature of this reflector is unknown r2 is a mid crustal reflector lying at a depth of 10 15 km and interpreted as rising gradually northwards it coincides locally with the base of the granite as predicted by gravity modeling but extends well beyond the northern limit of the granite body it is suggested that r2 may represent a major thrust of late variscan age r3 is the deepest reflector identified and lies at a depth of 27 30 km r3 is interpreted as the base of the crust and its computed depth is in close agreement with the local depth to the moho derived from an earlier seismic experiment in sw britain

controls on cyclic formation of quaternary early diagenetic dolomite the origin of sedimentary dolomite and the factors that control its formation within the geological record remain speculative in most models dolomite formation is linked to evaporative conditions high water temperature increasing mg ca ratio increasing alkalinity and high amounts of biomass here we challenge these archetypal views by documenting a case example of quaternary dolomite which formed in lake van at constantly low temperature 4 c and without direct control of the latter conditions dolomite occurs within highstand sediments related to suborbital climate variability dansgaard oeschger cycles we propose that dolomite precipitation is a product of a microbially influenced process triggered by ecological stress resulting from reventilation of the water sediment interface independently from the validity of this hypothesis our results call for a reevaluation of the paleoenvironmental conditions often invoked for early diagenetic dolomite rich intervals within sedimentary sequences and for caution when interpreting time series of subrecent lacustrine carbonates

profiling interactions between the westerlies and asian summer monsoons since 45 ka insights from biomarker isotope and numerical modeling studies in the qaidam basin

varve formation in the gulf of california insights from time series sediment trap sampling and remote sensing the varved sediments that accumulate in the central gulf of california guaymas and carmen basins provide a record that allows for the resolution of annual to decadal scale climate variability in this region time series sediment trapping combined with remotely sensed observations of sea surface temperature avhrr and color czcs have been used to examine the mechanism of varve formation in the central gulf sst and surface pigment concentration records for both the mainland and baja sides of the gulf display similar seasonal trends high temperatures and low pigment concentrations occur synchronously on both sides of the central gulf from june through to october in association with the 1991 92 el nino warm temperatures persist in the central gulf until december low ssts typically occur from december through may with high pigment concentrations marking the period from november through april the summer early fall june october is a time of high terrigenous and biogenic sediment fluxes during this time of year the total flux is dominated by eolian transported lithogenic material and dark laminae are deposited during this period during el nino years high terrigenous fluxes may extend into winter light laminae represent deposition from november through may during which time biogenic material dominates the total sediment flux high opal fluxes beginning in november are attributed to seasonal cooling of surface water and upward mixing of nutrients true upwelling conditions do not develop in the gulf until late winter spring during this time the total flux is still dominated by opal but the magnitude of the flux is reduced this may be an artifact of phytoplankton grazing and not lower production rates

lipids of aquatic organisms as potential contributors to lacustrine sediments ii abstract the relationship between the lipid composition of organisms in the water column of an eutrophic lake and the lipid composition of underlying sediments previously examined for n alkanols and steroids is now reported for hydrocarbons ketones and carboxylic acids the n c7 alkane and alkenoic acids from two primary sources are rapidly metabolized in the water column and surficial sediment bacterial biomarkers including hopenes and i ai branched fatty acids were detected in the photosynthetic bacterial layer occurring just above the sediment water interface within the sediment the apparent conversion of free n alkanes alkan 2 ones and hydroxy acids to the corresponding bound form is noted microbiological oxidation of n alkanes to alkan 2 ones is supported by the detection of the intermediate alkan 2 ols with a distribution similar to that of the ketones the geochemistry of sediment deposited c 1900 prior to biological study of the site was interpreted from stable biomarkers and the diagenetic changes recognised in the study of contemporary deposition a qualitative difference in algal input to the older sediment is inferred from the low 7 sterol content and presence of 2 6 10 trimethyl 7 3 methylbutyl dodecane however there was still significant dinoflagellate input as indicated by the presence of 4 methylsterols a difference in higher plant input to the older sediment indicated from the n alkane alkene and triterpenoid ketone distributions is consistent with the recent development of tree cover

holocene sedimentology of hypersaline lake urmia northwestern iran abstract a limnogeological expedition examined the sedimentary record of lake urmia one of the world s largest saline lakes located in a tectonically active arid intermontane plateau in northwestern iran near the cradle of western civilization lake urmia resembles the great salt lake u s a in many respects of morphology water chemistry and sediments the present lake area is about 5000 km 2 shallow 8 12 m and a perennial sodium chloride sulfate system 22 salts high resolution 3 5 khz seismic profiles show morphological relicts from a desiccation playa phase buried below only a few meters of sediments from lacustral phases in places around the deeper areas the lake floor is not smooth but covered with mounds aligned in prevailing current directions these are erosional relicts rather than bioherms sediments comprise aragonite chemical precipitates fecal pellet sands detrital clayey muds thin aragonite crusts oolites various gypsum types and occurrences of dolomite in peripheral areas organic matter characteristic of the present shorelines is not preserved at depth in basinal areas piston cores up to 6 m long penetrated a holocene sequence of hypersaline facies with laminated aragonite fecal pellet muds and bottomed in a playa mudflat facies with central gypsiferous muds and marginal terrigenous to dolomitic muds preliminary radiocarbon and pollen analyses suggest a playa stage prior to 9000 yr b p with saline lake deposition in a cool arid climate from 9000 to 7500 yr b p higher energy facies prevailed in a shallow saline lake and since then present day saline environments have persisted with evidence of numerous second order water level fluctuations the preliminary results suggest a lake system out of phase with north african and some other middle eastern lakes

sedimentary evolution and environmental history of lake van turkey over the past 600 000 years the lithostratigraphic framework of lake van eastern turkey has been systematically analysed to document the sedimentary evolution and the environmental history of the lake during the past ca 600 000 years the lithostratigraphy and chemostratigraphy of a 219 m long drill core from lake van serve to separate global climate oscillations from local factors caused by tectonic and volcanic activity an age model was established based on the climatostratigraphic alignment of chemical and lithological signatures validated by 40ar 39ar ages the drilled sequence consists of ca 76 lacustrine carbonaceous clayey silt ca 2 fluvial deposits ca 17 volcaniclastic deposits and 5 gaps six lacustrine lithotypes were separated from the fluvial and event deposits such as volcaniclastics ca 300 layers and graded beds ca 375 layers and their depositional environments are documented these lithotypes are i graded beds frequently intercalated with varved clayey silts reflecting rising lake levels during the terminations ii varved clayey silts reflecting strong seasonality and an intralake oxic anoxic boundary for example lake level highstands during interglacials interstadials iii caco3 rich banded sediments which are representative of a lowering of the oxic anoxic boundary for example lake level decreases during glacial inceptions iv caco3 poor banded and mottled clayey silts reflecting an oxic anoxic boundary close to the sediment water interface for example lake level lowstands during glacials stadials v diatomaceous muds were deposited during the early beginning of the lake as a fresh water system and vi fluvial sands and gravels indicating the initial flooding of the lake basin the recurrence of lithologies i to iv follows the past five glacial interglacial cycles a 20 m thick disturbed unit reflects an interval of major tectonic activity in lake van at ca 414 ka bp although local environmental processes such as tectonic and volcanic activity influenced sedimentation the lithostratigraphic pattern and organic matter content clearly reflect past global climate changes making lake van an outstanding terrestrial archive of unprecedented sensitivity for the reconstruction of the regional climate over the last 600 000 years

δd values of individual n alkanes from terrestrial plants along a climatic gradient implications for the sedimentary biomarker record abstract the compound specific hydrogen isotope composition d of sedimentary n alkanes is increasingly used as a palaeoclimate proxy to explore the origin of the hydrogen isotope signal of n alkanes from higher terrestrial plant biomass in sedimentary organic matter of small lakes we have analysed the n alkane composition and d values of 31 plant biomass samples birch betula beech fagus oak quercus alder alnus hornbeam carpinus and myrtle myrtus as well as non stomata containing sphagnum cladonia and moss from 14 sites along a climatic gradient from northern finland to southern italy eleven of the sites were previously investigated for the n alkane d values in adjacent lake sediments and are compared to the leaf wax n alkane d values the distribution of terrestrial n alkanes in lake sediments was not found to be characteristic of the dominant vegetation around the lake evidently n alkane distributions within the same species at different sites were found to be variable these findings complicate the use of certain n alkane distributions in sediments as a palaeoenvironmental indicator d values of plant biomass n alkanes show a significant positive correlation with the precipitation d values biomass n alkane d values are in general less negative than the associated sedimentary n alkanes of terrestrial origin possibly due to the stronger evapotranspiration during the summer when sampling took place this suggests that n alkanes in leaves show seasonal variations and the sedimentary organic matter receives the lighter isotope signal of the autumn when most leaves are incorporated into the sediment the variability of the d values from non stomata containing plants is much higher than for broadleaf trees since stomata can regulate water loss through evapotranspiration the average chain length acl of n alkanes from deciduous tree leaves increases from north to south with increasing acl the hydrogen isotopic fractionation e between source water and n alkanes also increases our results prove that terrestrial n alkane d values record the d value of precipitation modified by the amount of isotope enrichment in the leaf water due to plant anatomy stomata vs no stomata and site specific meteorological conditions such as evapotranspiration relative humidity and soil moisture therefore terrestrial n alkanes in lake sediments can deliver information on changes in these parameters over geological timescales in lake sediments where aquatic n alkanes such as n c 17 record the lake water d value the isotopic difference between terrestrial and aquatic n alkanes could therefore be used to reconstruct changes in evapotranspiration

a synthesis of hydrogen isotope variability and its hydrological significance at the qinghai tibetan plateau abstract hydrogen isotope ratios of sedimentary biomarkers are known to record the climatic variability in terrestrial and marine environments however there is still a lack of calibration studies that can quantitatively retrace the driving forces especially at the tibetan plateau here we elaborate the actual influence of environmental parameters such as temperature evapotranspiration salinity and biosynthetic fractionation on d values of n alkanes we measured hydrogen isotope values d of n alkanes in recent sediment and plant samples as well as d values of different water sources lake and inflow water precipitation as well as leaf root and soil water from six tibetan lakes along a 10 spanning longitudinal transect covering an aridity gradient as expected the deuterium record can be used to distinguish two water pools at the plateau i precipitation water which supplies water for the lake inflow and terrestrial plants and ii enriched lake water having a clear evaporative signal based on significant correlations of the source water and d values of n alkanes d of alkane n c 23 record the lake water isotope composition and track the evaporative enrichment of the lake system in contrast d of alkane n c 29 can be used to retrace the isotope composition of the inflow displaying the integrated rainfall signal in the vegetation period modified by soil and leaf water evaporation while temperature changes are less pronounced across the tibetan transect the isotopic difference between c 23 and c 29 could potentially be used as a proxy to reconstruct effective moisture precipitation minus evaporation areas with lower precipitation amounts and higher evaporation rates are characterized by higher d c 23 c 29 values this relationship is more pronounced in regions with mean annual precipitation below 350 mm even in contrasting environments the application of the d proxies is very promising combining other tibetan studies it is possible to present a comprehensive picture of the usage of compound specific hydrogen isotopes of n alkanes on the tibetan plateau

modern seasonality in lake challa kenya tanzania and its sedimentary documentation in recent lake sediments from november 2006 to january 2010 a sediment trap that was cleared monthly was deployed in lake challa a deep stratified freshwater lake on the eastern slope of mt kilimanjaro in southern kenya geochemical data from sediment trap samples were compared with a broad range of limnological and meteorological parameters to characterize the effect of single parameters on productivity and sedimentation processes in the crater basin during the southern hemisphere summer november march when the water temperature is high and the lake is biologically productive nondiatom algae calcite predominated in the sediment trap samples during the long rain season march may a small amount of organic matter and lithogenic material caused by rainfall appeared this was followed by the cool and windy months of the southern hemisphere winter june october when diatoms were the main component indicating a diatom bloom initiated by improvement of nutrient availability related to upwelling processes the sediment trap data support the hypothesis that the light dark lamination couplets which are abundant in lake challa cores reflect seasonal delivery to the sediments of diatom rich particulates during the windy months and diatom poor material during the wet season however interannual and spatial variability in upwelling and productivity patterns as well as el nino southern oscillation enso related rainfall and drought cycles exert a strong influence on the magnitude and geochemical composition of particle export to the hypolimnion of lake challa

effect of lake evaporation on δd values of lacustrine n alkanes a comparison of nam co tibetan plateau and holzmaar germany compound specific hydrogen isotope ratio values of lacustrine n alkanes from two contrasting ecosystems the semiarid to arid nam co central tibet and the humid holzmaar germany were compared in order to assess whether or not these environmental conditions are recorded in the isotopic signatures of biomarkers increased evaporation of lake water at nam co is recorded by the n alkanes of aquatic origin hence isotopic enrichment results in a di erence between terrestrial and aquatic n alkanes in the opposite direction 68 from that known for humid climate conditions 30 predominating at holzmaar based on this isotopic di erence between terrestrial and aquatic n alkanes evaporation to inflow ratio e i values were estimated and suggest that the isotopic di erence is indicative of the general hydroclimatic characteristics of a lake system moreover the comparison with e i values calculated with actual stable water isotope data showed that the dd values of aquatic and terrestrial lacustrine n alkanes serve as a proxy for the relative isotopic di erences between lake and inflow waters and can be used to assess the proportion of water undergoing evaporation relative to the inflow and thus to reconstruct the lake water balance in the past 2008 published by elsevier ltd

alkenone distribution in lake van sediment over the last 270 ka influence of temperature and haptophyte species composition abstract fossil long chain alkenones have been used for several decades to reconstruct past ocean surface water temperatures and gained recent interest as a paleotemperature proxy for continental lake settings however factors besides temperature can affect alkenone distributions in haptophyte algae and alkenone compositions can differ between haptophyte species alkenone biosynthesizing haptophyte algae are genetically much more diverse in lakes than in the marine realm and species level variations in alkenone compositions could have implications for alkenone paleothermometry here we performed a paired analysis of alkenone distributions and haptophyte species compositions using ancient dna in up to 270 ka old sediments of lake van in turkey to reveal a possible species effect on fossil alkenone distributions and paleotemperature estimates the same predominant haptophyte in lake van today prevailed also since the last 100 ka however a calibration of alkenone paleotemperature especially in the oldest analyzed intervals is complicated due to a more complex haptophyte species composition predominated by a haptophyte lvhap 6 which is phylogenetically different from sequences recovered from currently existing lakes including lake van and from haptophyte species existing in culture the predominance of lvhap 6 coincided with the presence of alkenone mec38 3 and relatively high mec37 3 4 2 4 and mec38 4 5 ratios 3 0 uk37 index values in the sediment core over the last 270 ka reflect relative changes in past temperature and are additionally linked to haptophyte species composition a sustained period of high salinity as indicated by pore water salinity measurements could potentially have triggered the succession of haptophytes as sources of alkenones in lake van

impact of lake level change on deep water renewal and oxic conditions in deep saline lake van turkey 1 changes in the hydrological regime of the saline closed basin lake van a large deep lake in eastern turkey resulted in a lake level increase by about 2 m between 1988 and 1995 followed by a 1 5 m decrease until 2003 and a relatively constant lake level thereafter based on measurements of transient tracers sulfur hexafluoride cfc 12 3h 3he 4he ne dissolved oxygen light transmission conductivity temperature depth profiles and thermistor data we investigate the implications associated with lake level fluctuations for deep water renewal and oxygenation our data suggest that deep water renewal was significantly reduced in lake van between 1990 and 2005 this change in mixing conditions resulted in the formation of a more than 100 m thick anoxic deep water body below 325 m depth apparently the freshwater inflows responsible for the lake level rise between 1988 and 1995 decreased the salinity of the surface water sufficiently that the generation of density plumes during winter cooling was substantially reduced compared to that in the years before the lake level rise significant renewal and oxygenation of the deep water did not occur until at least 2005 although by 2003 the lake level was back to almost the same level as in 1988 this study suggests that short term changes in the hydrological regime resulting in lake level changes of a couple of meters can lead to significant and long lasting changes in deep water renewal and oxic conditions in deep saline lakes

systematic review of geochemical data from thermal springs gas vents and fumaroles of southern italy for geothermal favourability mapping abstract in recent years two research projects specifically conceived by italian institutions of research to promote the implementation of the use of geothermal energy in southern italy has allowed the review of most data on chemical and isotopic compositions of natural thermal manifestations in the territory of italy two large databases one for thermal springs and co2 rich springs and a second one for fumarolic condensates and associated gas phase have been produced and are available on line with data spanning in time from the early 70 s to the present we have used those data after careful evaluation of the quality and reliability of them to produce correlation diagrams and isodistribution maps of some relevant geochemical geothermal parameters such as pco2 in thermal springs co2 and 13c in co2 of gas phases 3he 4he ratio and he in this way we have been able to delimit the areal patterns of thermal anomalies potentially related with geothermal reservoirs the cross correlation among the many parameters 40 selected has allowed the overview on the circulation of fluids at shallow crust in one of the most active tectonic boundary of the earth between the african and the eurasian continents shallow circulation of hot fluids is particularly active in the roman comagmatic province the neapolitan area and sicily both at etna aeolian archipelago and pantelleria island in the sicily channel where active geothermal systems are already known whose areal extension is probably much larger than what envisaged at present the geothermometric evaluation of data has not allowed to clearly identity new areas apart from those already known but nevertheless some areas in the inner apennines as well as sicily and sardinia have shown anomalous 3he 4he values that point to the presence of mantle fluids located inside the crust being most of active volcanic islands likely much smaller than the thermal anomaly they are associated with a futuristic perspective of utilizing geothermal fluids off shore is suggested moreover the database and the proposed maps can be a useful tool both scientific community and stakeholders to perform geothermal favourability maps and to identify potential new areas interesting from a geothermal perspective

evolution of colpan barrier and lagoon complex lake van turkey sedimentological and hydrological approach abstract the northeastern coast of the lake van eastern anatolia turkey is exposed to energetic waves inducing large sediment transport rates intense wave activity on coastal environment shows the shaping impact on the shoreline either erosional or depositional processes sedimentation is characterized by gravelly beaches spit formation and barrier lagoon complex colpan barrier and lagoon complex forming the subject of this study occurred in these swashed environmental conditions this study aims to introduce formation and evolution of the colpan barrier and lagoon complex and to assess the future development of the coastal area around the lake van characteristics of barrier sediments as shape size provenance sedimentary structures and palaeocurrent directions are determined with field investigations smooth flattened and rounded polygenetic sediments compose the barrier drifted to the shoreline with coastal processes as wave and longshore currents colpan barrier was created a lagoon completely isolated from lake van this wetland constitutes a habitat for some animals and plants with relatively dilute water than sodic lake van s water level fluctuation is an important element for the constructive and destructive processes for the barrier and lagoon complex

elevation dependent changes in n alkane δd and soil gdgts across the south central andes abstract surface uplift of large plateaus may significantly influence regional climate and more specifically precipitation patterns and temperature sometimes complicating paleoaltimetry interpretations thus understanding the topographic evolution of tectonically active mountain belts benefits from continued development of reliable proxies to reduce uncertainties in paleoaltimetry reconstructions lipid biomarker based proxies provide a novel approach to stable isotope paleoaltimetry and complement authigenic or pedogenic mineral proxy materials in particular outside semi arid climate zones where soil carbonates are not abundant but soil organic matter has a high preservation potential here we present d values of soil derived n alkanes and mean annual air temperature mat estimates based on branched glycerol dialkyl glycerol tetraether brgdgt distributions to assess their potential for paleoelevation reconstructions in the southern central andes we analyzed soil samples across two environmental and hydrological gradients that include a hillslope 26 28 s and a valley 22 24 s transect on the windward flanks of central andean eastern cordillera in nw argentina our results show that present day n alkane d values and brgdgt based mat estimates are both linearly related with elevation and in good agreement with present day climate conditions soil n alkanes show a d lapse rate d of 1 64 100 m r 2 0 91 p 0 01 at the hillslope transect within the range of d lapse rates from precipitation and surface waters in other tropical regions in the andes like the eastern cordillera in colombia and bolivia and the equatorial and peruvian andes brgdgt derived soil temperatures are similar to monitored winter temperatures in the region and show a lapse rate of t 0 51 c 100 m r 2 0 91 p 0 01 comparable with lapse rates from in situ soil temperature measurements satellite derived land surface temperatures at this transect and weather stations from the eastern cordillera at similar latitude as a result of an increasing leeward sampling position along the valley transect lapse rates are biased towards lower values and display higher scatter d 0 95 100 m r 2 0 76 p 0 01 and t 0 19 c 100 m r 2 0 48 p 0 05 despite this higher complexity they are in line with lapse rates from stream water samples and in situ soil temperature measurements along the same transect our results demonstrate that both soil n alkane d values and mat reconstructions based on brgdgts distributions from the hillslope transect d 1 64 100 m r 2 0 91 p 0 01 and t 0 51 c 100 m r 2 0 91 p 0 01 track the direct effects of orography on precipitation and temperature and hence the combined effects of local and regional hydrology as well as elevation

δ18o and δd of streamwaters across the himalaya and tibetan plateau implications for moisture sources and paleoelevation reconstructions abstract this study presents new 18o and d data from 191 streams across the himalaya and tibetan plateau to better constrain the spatial variability of stable isotopes in modern precipitation over this region moisture penetrating into the southeastern tibetan plateau is predominantly derived from monsoonal airmasses originating from the bay of bengal and transported into the eastern himalayan syntaxis along the brahmaputra river progressive rainout during orographic lifting and cooling results in clear relationships between 18o and d and catchment hypsometric elevation on the plateau margin however monsoonal derived moisture is progressively mixed with central asian airmasses in more western and northern parts of the tibetan plateau as a result predicted isotope elevation relationships that are based on empirical lapse rates or thermodynamic models of the isotopic evolution of an airmass produce large 1 3 km misfits between measured and predicted catchment elevations for much of the tibetan plateau including some areas directly north of the central himalayan crest this suggests that changes in the 18o or d of paleoprecipitation on the central and southwestern tibetan plateau may reflect surface uplift along moisture transport pathways or changes in the penetration of monsoonally derived moisture rather than regional surface uplift histories

an abrupt wind shift in western europe at the onset of the younger dryas cold period the younger dryas cold reversal during the last glacial termination is one of the most abrupt climate change events observed in the northern hemisphere analyses of varved lake sediments from western germany suggest that storminess in the north atlantic region increased within a single year at this time providing a mechanistic link between a decrease in the meridional overturning circulation and western european cooling the younger dryas cooling 12 700 years ago is one of the most abrupt climate changes observed in northern hemisphere palaeoclimate records1 2 3 4 annually laminated lake sediments are ideally suited to record the dynamics of such abrupt changes as the seasonal deposition responds immediately to climate and the varve counts provide an accurate estimate of the timing of the change here we present sub annual records of varve microfacies and geochemistry from lake meerfelder maar in western germany providing one of the best dated records of this climate transition5 our data indicate an abrupt increase in storminess during the autumn to spring seasons occurring from one year to the next at 12 679 yr bp broadly coincident with other changes in this region we suggest that this shift in wind strength represents an abrupt change in the north atlantic westerlies towards a stronger and more zonal jet changes in meridional overturning circulation alone cannot fully explain the changes in european climate6 7 we suggest the observed wind shift provides the mechanism for the strong temporal link between north atlantic ocean overturning circulation and european climate during deglaciation

discrimination of holocene tephra units in lake van using mineral magnetic analysis abstract detailed magnetic analysis of the four sediment cores from lake van eastern turkey dating back to 9 4 cal ka bp were carried out for discriminating and correlating tephras and laminated sediments in four different cores six tephra units t0 t1 t2 t3 t4 and t5 with distinct magnetic properties were identified in the cores the tephra units are characterized by ferrimagnetic material with a grain size in the pseudo single domain psd range there is no significant correlation between magnetic susceptibility peaks of the different tephra units except for the tephra t1 and t2 on the contrary arm profiles show significant correlations as remanent magnetization indicators the tephra units t1 and t2 have a higher magnetic susceptibility and a higher intensity of remanent magnetization and finer grain size than the other tephra units the results suggest that there is a clear difference between the magnetic properties of the different tephra units and the lake sediments our findings show that also differential deposition of volcanic material including magnetic mineral occurs during the transport with distance from the volcanic source

whitings a sedimentologic dilemma whitings drifting clouds of water milky because of suspended carbonate have been claimed to originate from either the action of bottom feeding fish or direct precipitation of calcium carbonate five cruises during different seasons were made to the great bahama bank to collect data pertinent to the controversy measurements of particulate concentrations average 10 mg liter with a maximum of 20 mg liter of carbonate sediment suspended in whiting water compared with an average of 1 5 mg liter for clear water outside the whitings the particles are dominantly acicular aragonite but mg calcite composes as much as 20 percent of some whitings sedimentation rates measured with fixed and drifting sediment traps were as great as 34 g m 2 hr sediment suspended in whitings aggregated into silt and sand size fioccules and settled to the bottom of settling tanks within six hours even on a rocking ship sediment in artificial whitings created by stirring sediment from the bottom with a shrimp trawl settled to the bottom in about the same time natural whitings on the other hand were never observed to dissipate because sedimentation from whitings occurs at rates sufficient to cause dissipation of the whitings within six hours we conclude that the natural whitings are continually replenished by direct precipitation the search for fish in whitings utilized sidescan sonar and fathometer imaging shrimp trawls rotenone remote video and direct scuba observation these methods and 25 years of casual observations leading to this study indicate that fish are not involved in the formation of most bahamian whitings several whitings were found over rocky or sandy bottoms where there was no mud available for fish to suspend the distance of these whitings from areas of muddy bottom precluded their having been made elsewhere by fish stable carbon and oxygen isotopic analyses and delta 14 c activity are interpreted to indicate that the suspended sediment in whitings contains some precipitated calcium carbonate and is not merely bottom sediment stirred into suspension estimates indicate that the amount of new carbonate produced in whitings on the great bahama bank is substantially higher than that arising from algal production consequently the amount of sediment transported to deep water may be much greater than previously thought

the structure of sw cornwall and its bearing on the emplacement of the lizard complex six phases of deformation can be recognized in the devonian metasediments to the n of the lizard complex the first two phases d 1 d 2 show a variety of orientations and styles but with a general n or nw vergence these phases while respresenting regional deformation events are considerably modified by the emplacement of the lizard complex there is a general increase in intensity of both d 1 and d 2 structures towards the lizard boundary this is accompanied by variation in the orientation of both early phases of deformation leading to a variety of interference patterns domains of oblique f 1 folds with axes trending n s are developed in the rocks immediately to the ne and nw of the lizard and are considered to have formed by differential nnw directed thrusting of slabs of the complex during the early regional deformation d 2 produced discrete shear zones ahead and below the lizard rocks and may have resulted from the gravitational collapse of the d 1 nappes the d 3 deformation post dates the lizard emplacement being related to the cornubian batholith subsequent phases represent essentially post batholith and hence post lizard emplacement deformation