middle to late holocene palaeoenvironmental study of gialova lagoon sw peloponnese greece abstract the coastal areas of eastern mediterranean have long been the subject of research due to their rapid geomorphological changes but also because of their archaeological interest our study is focused on a shallow coastal lagoon of peloponnese gialova lagoon which for several years has attracted the scientific interest of archaeologists geomorphologists as well as sedimentologists gialova lagoon is located near the ancient city of pylos the kingdom of king nestor during the mycenaean period 1600 1100 bc the objectives of this study are a to reconstruct the middle to late holocene depositional environments of the lagoon and b to correlate our data to already existing publications in order to shed new light on the holocene evolution of the lagoon and the associated coastal palaeoenvironmental changes an 8 m deep vibracore was drilled and a multi proxy analysis was carried out on the sediment sequence including sedimentological grain size analysis and moment measures total organic carbon toc total nitrogen tn and total phosphorus tp high resolution geochemical xrf scanning and palaeontological micro and macro faunal analysis the chronological framework is based on five 14c datings forming the basis for an age depth model calculated using the oxcal software the radiocarbon dates from previous studies 6 cores 20 dates were also taken into account the data synthesis and interpretation provided robust and coherent indications regarding the palaeoenvironment shoreline changes and the rate of geomorphological changes of the coastal area of gialova lagoon as well as useful information about the palaeonvironmental and palaeoclimatic conditions that prevailed during the mycenaean period the interpretation reveal a transition from a shallow marine environment 6500 5800 yr b p to a brackish lagoonal 5800 3300 yr b p followed by a shift towards a freshwater marsh environment 3300 yr b p to present

sedimentary features of the seismo turbidites lake biwa japan abstract seismo turbidite layers are deposited at the foot of the steep slope of the half graben in which lake biwa has accumulated sedimentary studies especially of grain size distribution of selected turbidites provide excellent information for clarifying the distinctive features of general seismo turbidites development of the two constituent sublayers lower sandy sublayer and upper silt sublayer lack or limited appearances of traction indicating structures and characteristic grain size distribution in the two constituent sublayers are most remarkable and significant the characteristic grain size distribution features are coarse tail grading in a relatively thick sandy sublayer exceptionally rapid distribution grading through the thin boundary interval between the two sublayers height increase and fluctuation of the silt mode and high clay content brief discussion was made on the causes of these sedimentary features the need and importance of further comparative studies of various turbidites known triggering forces are emphasized

global chemical erosion during the last glacial maximum and the present sensitivity to changes in lithology and hydrology geographically based calculations for 18 000 years ago 18 ka and today were made to examine the potential effects on terrestrial chemical erosion of changes in lithology and hydrology on glacial interglacial timescales runoff fields were derived from general circulation model predictions of precipitation minus evaporation then global lithologic maps were prepared so that empirical relationships for runoff versus bicarbonate flux for different rock types could be used to calculate global chemical erosion rates assuming that significant chemical erosion does not occur beneath ice sheets we find that chemical erosion in ice free areas at 18 ka was only slightly greater than today this result arises because the amount of land covered by ice sheets is roughly compensated for by exposed shelf areas and because there is little difference in global runoff the small 20 increase in the global chemical erosion rate during glacial conditions is due to exposure on the shelves of a relatively high proportion of carbonates which weather faster than average data on glacial interglacial movements of the calcite compensation depth ccd are inconclusive but seem to indicate little change whereas even a 20 increase in the riverine bicarbonate flux should cause an observable deepening if the ccd did not indeed change then our predicted increase in the bicarbonate flux from land during glaciations would have to be accommodated by other means such as increased carbonate productivity about half of the observed decrease in atmospheric pco2 at 18 ka could be explained if increased silicate chemical erosion accompanied increased total chemical erosion in ice free areas consideration of the maximum possible effect of meltwater at ice margins leads to an 80 increase in the global chemical erosion rate at 18 ka such an increase would lead to a larger and faster drop in atmospheric pco2 but also to an excessive deepening of the global ccd this scenario seems unrealistic our results are contrary to interpretations of a much higher silicate chemical erosion rate during glaciations based on recently published records of quaternary marine sr isotopic ratios therefore if these records are indeed globally representative and entirely due to increased silicate chemical erosion as opposed to changes in source areas or hydrothermal inputs then other factors such as a shift in the global weathering regime which we do not explicitly consider here may be involved sensitivity tests show that considering spatial heterogeneities in lithology and runoff leads to lower predictions of global chemical erosion rates than what one would obtain by considering only global averages in a non spatially resolved calculation

geochemistry of daihai lake sediments inner mongolia north china implications for provenance sedimentary sorting and catchment weathering abstract to advance the understanding of sediment distribution catchment weathering hydraulic sorting and sediment provenance in a tectonically stable basin the geochemistry of surface sediment samples from daihai lake in north china is presented mud bulk sediments were analyzed for 10 major and 30 trace elements organic carbon and nitrogen and for 87sr 86sr ratios in silicate fraction acid insoluble ai and carbonates acid soluble as enrichment in fe2o3 cao mno mgo k2o and p2o5 and their positive correlation with al2o3 rb sr ratios and bivariate discrimination diagrams of k vs rb and th u vs th suggest low chemical weathering intensity under semiarid conditions in the daihai catchment accumulation of clays in deeper water sites by sedimentary sorting results in an evident distribution of sediment composition with the lake water depth although similar chondrite normalized ree rare earth element patterns of lake sediment samples with lree light rare earth element enrichment negative eu anomalies and an almost flat hree heavy rare earth element pattern may suggest similar sedimentary source rocks original sediment provenance can be recognized on the basis of their distinctive 87sr 86sr ai ratios and immobile th zr ti and nb trace element signature separating from weathering and sedimentary processes as well as from grain size effect

variation of rb sr ratios in the loess paleosol sequences of central china during the last 130 000 years and their implications for monsoon paleoclimatology abstract rb sr and magnetic susceptibility have been measured in the last interglacial glacial loess profiles at luochuan and huanxian central china a high degree of similarity between the parameters in both profiles suggests that variations of rb sr ratios in the sequence can be regarded as an indicator of east asian summer monsoon strength matching the rb sr record with the specmap 18o curve suggests that the rb sr ratio responds sensitively to changes of the east asian monsoon induced by global ice volume variation

the active main marmara fault abstract this paper presents selections from and a synthesis of a high resolution bathymetric sparker and deep towed seismic reflection data set recently acquired by the french ifremer r v le suroit in an e w deep trough that forms the northern half of the sea of marmara in nw turkey it includes the first high resolution complete bathymetric map of this area a single throughgoing dextral strike slip fault system which is the western continuation of the northern branch of the north anatolian fault cuts this trough lengthwise and joins the 1999 8 17 kocaeli earthquake fault with the 1912 8 09 arkoy murefte earthquake fault both of which display strike slip offset in its eastern one fourth the structure follows closely the northern margin of the deep trough whereas in the west it hugs its southern margin the eastern one fourth of the structure has a minor component of its displacement distributed across the deep trough owing to a possible original bend in the course of the dextral structure the present course of the north anatolian fault in the sea of marmara originated some 2 105 a ago by cutting across the older basin fabric generated by a dominant nne ssw extension before it began taking up major motion in the pliocene

the little ice age and medieval warm period in the sargasso sea sea surface temperature sst salinity and flux of terrigenous material oscillated on millennial time scales in the pleistocene north atlantic but there are few records of holocene variability because of high rates of sediment accumulation holocene oscillations are well documented in the northern sargasso sea results from a radiocarbondated box core show that sst was approximately 1 degree c cooler than today approximately 400 years ago the little ice age and 1700 years ago and approximately 1 degree c warmer than today 1000 years ago the medieval warm period thus at least some of the warming since the little ice age appears to be part of a natural oscillation 39 refs 4 figs 1 tab

detrital events and hydroclimate variability in the romanian carpathians during the mid to late holocene the romanian carpathians are located at the confluence of three major atmospheric pressure fields the north atlantic the mediterranean and the siberian despite its importance for understanding past human impact and climate change high resolution palaeoenvironmental reconstructions of holocene hydroclimate variability and in particular records of extreme precipitation events in the area are rare here we present a 7500 year long high resolution record of past climatic change and human impact recorded in a peatbog from the southern carpathians integrating palynological geochemical and sedimentological proxies natural climate fluctuations appear to be dominant until 4500 years before present yr bp followed by increasing importance of human impact sedimentological and geochemical analyses document regular minerogenic deposition within the bog linked to periods of high precipitation such minerogenic depositional events began 4000 yr bp with increased depositional rates during the medieval warm period mwp the little ice age lia and during periods of societal upheaval e g the roman conquest of dacia the timing of minerogenic events appears to indicate a teleconnection between major shifts in north atlantic oscillation nao and hydroclimate variability in southeastern europe with increased minerogenic deposition correlating to low nao index values by linking the minerogenic deposition to precipitation variability we state that this link persists throughout the mid to late holocene

the effect of snow on antarctic sea ice simulations in a coupled atmosphere sea ice model the effect of a snow cover on sea ice accretion and ablation is estimated based on the zero layer version sea ice model of semtner and is examined using a coupled atmosphere sea ice model including feedbacks and ice dynamics effects when snow is disregarded in the coupled model the averaged antarctic sea ice becomes thicker when only half of the snowfall predicted by the atmospheric model is allowed to land on the ice surface sea ice gets thicker in most of the weddell and ross seas but thinner in east antarctic in winter with the average slightly thicker when twice as much snowfall as predicted by the atmospheric model is assumed to land on the ice surface sea ice also gets much thicker due to the large increase of snow ice formation these results indicate the importance of the correct simulation of the snow cover over sea ice and snow ice formation in the antarctic our results also illustrate the complex feedback effects of the snow cover in global climate models in this study we have also tested the use of a mean value of 0 16 wm 1 k 1 instead of 0 31 for the thermal conductivity of snow in the coupled model based on the most recent observations in the eastern antarctic and bellingshausen and amundsen seas and have found that the sea ice distribution changes greatly with the ice becoming much thinner by about 0 2 m in the antarctic and about 0 4 m in the arctic on average this implies that the magnitude of the thermal conductivity of snow is of considerable importance for the simulation of the sea ice distribution an appropriate value of the thermal conductivity of snow is as crucial as the depth of the snow layer and the snowfall rate in a sea ice model the coupled climate models require accurate values of the effective thermal conductivity of snow from observations for validating the simulated sea ice distribution under the present climate conditions

shipborne electromagnetic measurements of antarctic sea ice thickness we present a study of antarctic sea ice thickness estimates made using a shipborne geonics em31 electromagnetic em instrument based on both 1d and 3d models apparent conductivities measured in the vertical coplanar vcp geometry are shown to be the measured quantity most sensitive to changes in the height of the instrument above seawater an analysis of the effect of instrument orientation on the measured vcp apparent conductivity shows that the effects of pitch and roll on the calculated sea ice thickness can be neglected except in the case of very thin sea ice because only a single quadrature component of the magnetic field is measured at a single frequency interpretation of shipborne em31 data must necessarily be based on very simple models for a typical sea ice bulk conductivity of 60 ms m a uniform half space model representing conductive seawater is appropriate for interpretation of vcp em31 measurements over level sea ice up to 2 5 m thick for thicker more conductive sea ice the interpretation model must account for the effect of the finite sea ice conductivity simultaneous acquisition of em data at several frequencies and or transmitter receiver geometries permits interpretation of the data in terms of multilayered models a synthetic example shows that 1d inversion of single frequency in phase and quadrature data from two transmitter receiver geometries can yield reliable estimates of sea ice thickness even when the ice contains thin highly conductive brine layers our 3d numerical model calculations show that smoothing the measured response over the system footprint means that the sea ice thickness recovered over multidimensional sea ice structures via half space inversion of apparent conductivity data yields a highly smoothed image of the actual keel relief the dependence of footprint size on the height of the system above seawater results in the interpreted sea ice thicknesses being dependent on the deployment height of the instrument sea ice thickness data acquired using an em31 equipped with a hardware processing module can be transformed to apparent conductivity and then inverted assuming a conductive half space model for em system heights 4 5 m above seawater corresponding to large altitude and or thick sea ice inversion assuming a conductive half space model yields an improved estimate of the true sea ice thickness compared to that obtained using the processing module however the noise level in the estimated depth to seawater is relatively large 0 1 m in comparison with typical antarctic sea ice thicknesses and thickness estimates made using the shipborne system may be significantly in error over thin ice

characteristics of sea ice thickness and snow depth distributions of the summer landfast ice in lutzow holm bay east antarctica sea ice observations have been conducted on board icebreaker shirase as a part of the scientific programs of the japanese antarctic research expedition we summarize these to investigate spatial and interannual variability of ice thickness and snow depth of the summer landfast ice in lutzow holm bay east antarctica electromagnetic inductive observations which have been conducted since 2000 provide total thickness distributions with high spatial resolution a clear discontinuity which separates thin first year ice from thick multi year ice was observed in the total thickness distributions in two voyages comparison with satellite images revealed that such phenomena reflected the past break up of the landfast ice within 20 30 km from the shore total thickness as well as snow depth decrease toward the shore this is due to the snowdrift by the strong northeasterly wind video observations of sea ice thickness and snow depth were conducted on 11 voyages since december 1987 probability density functions derived from total thickness distributions in each year are categorized into three types a thin ice thick ice and intermediate type such interannual variability primarily depends on the extent and duration of the successive break up events

sedimentary features of seismoturbidites triggered by the 1983 and older historical earthquakes in the eastern margin of the japan sea abstract both mass failure deposits and turbidites are widely distributed in the epicentral area of the 1983 earthquake mw 7 9 in the eastern margin of the japan sea this basin is semi enclosed with no active conduits for the entrance of coarse detrital sediments seismic reflection surveys and sediment cores reveal that mass failure deposits which are distributed on the continental slopes merge into turbidites in the basin plain hence the mass wasting process is a major transportation process in this region one gravity core gh93 816 was recovered from the southeastern margin of the japan basin close to the epicentral area of the 1983 japan sea earthquake sedimentological results show that five turbidite beds are intercalated in the top 68 cm of the column occurrence of the b tm tephra at the depth of 68 71 cm indicates that these turbidite beds were developed during the last 1000 years the high 137cs concentration in the top 20 cm of the core implies that the uppermost turbidite bed was deposited after 1954 based on these age limits for the top and the bottom of the studied interval we estimate the recurrence intervals of turbidites as 160 330 years we suggest that these turbidites were generated by submarine slides which were triggered by the 1983 and older historical earthquakes in this region these seismoturbidites are characterized by amalgamated beds irregular structure sequences grain size breaks fluctuations abrupt changes in composition within bed and variable composition among beds from these features we infer that deposition resulted from a series of turbidity currents associated with multiple or line sources for example multiple shallow slides that were regionally initiated by the same earthquake the sedimentary features described herein may be useful as criteria for identifying modern seismoturbidites in other settings as well as seismoturbidites in the geologic record however further study is needed for the distinction of this type of turbidites from other types e g tempestites reflected turbidites

morphotectonic development of the marmara region abstract the marmara region of northwest turkey covers the marmara sea basin and the surrounding lands in the region morphologically different areas may be distinguished the marmara sea basin is a structural depression the land to the north is known as the thrace kocaeli peneplain a flatland elevated above a horst this may be referred to as the istanbul horst bounded by two strike slip fault zones which define the structural boundaries of two sea basins the black sea in the north and the marmara sea in the south the southern boundary fault is part of the north anatolian transform fault zone nafz which cuts through the region in the e w direction and extends to the aegean sea region the land to the south of the marmara sea is a plateau about 300 to 800 m high known as the bursa balikesir plateau it has a rather rugged topography represented by nw and ne trending ridges separated by depressions the ridges and the depressions correspond to horsts and grabens respectively the data reveal that the marmara region has passed through the following morphotectonic evolution together with the surrounding region it suffered a long period of denudation between the oligocene and the end of the late miocene which formed a regionwide peneplain the n s extensional regime followed this phase and began to produce a horst graben system and thus fragmented the peneplain the flat lying erosional surfaces have been elevated above the horsts later the nafz reached the marmara region in the initial stage it affected nw anatolia extensively as a wide right lateral shear regime this has evolved and through time the present narrow fault zone has developed the major morphological difference between the regions to the north and the south of the marmara sea basin is mainly related to the nafz as a plate boundary it formed a barrier to the n s extension saving the northern sector from the effect of the extension the southern region has gradually elevated to much higher altitudes

environmental changes based on multi proxy analysis of core sediments in lake aktas turkey preliminary results abstract a sediment core covering the last millennium from lake aktas a shallow alkaline soda lake in the northeast anatolian highland of turkey was studied for pollen and physical and chemical proxies to reconstruct past climate change the sediments were dated by ams radiocarbon dating of bulk organic carbon among arboreal pollen ap from around 930 years ago dominant trees were pinus sylvestris picea orientalis abies betula fagus and quercus ap exceeded nap non arboreal pollen in this time whereas the opposite is the case in a pollen trap in the same region collecting the pollen for one year in 2015 2016 the comparison of modern and fossil pollen influx indicates that in that period trees were more widely distributed around the lake than today where steppe vegetation now prevails inferred causes for the disappearance of trees are anthropogenic impacts and climatic change towards more continental conditions the results also identify the onset of the little ice age in the ne anatolian highland of turkey

non residual sr of the sediments in daihai lake as a good indicator of chemical weathering abstract the rb sr ratio of lake sediments has been demonstrated to be a potential indicator of chemical weathering by increasing work however rb and sr in lake sediments are derived from both chemical weathering and physical erosion rb and sr of different forms in lake sediments may record different environmental processes and information in this study the variation patterns of rb and sr of different forms in sediments of daihai lake were investigated the results show that rb and sr of different forms display noticeably different variation patterns due to their different sources and associated environmental processes using the rb sr ratios of bulk lake sediments to reflect chemical weathering is not accurate the non residual sr of the sediments without detrital carbonates representing the sr leached from the catchment can be used as an index of chemical weathering because the weathering of sr minerals is very sensitive to climate change and the non residual sr content of the sediment is determined more by sr2 influx than by the physicochemical conditions of lake water the correspondence between the non residual sr and tic toc in daihai lake also indicates that the non residual sr of the sediments is a good indicator of chemical weathering in the catchment

plateau uplift forcing climate change around 8 6 ma on the northeastern tibetan plateau evidence from an integrated sedimentary sr record abstract the uplift of the northern tibetan plateau tp has long been regarded as one of major factors accounting for both the enhanced process of aridification recorded in central asia and the shifts in the asian monsoonal circulations that are known to have occurred at approximately 8 ma until now there have been few sedimentary records reported on which can directly and in an integrated fashion shed light on the region s tectonic and climate regimes this can be largely attributed to the fact that the influence exerted by the presence of source materials and subsequent sedimentary sorting in this tectonically active region would be likely to bias significantly any paleoclimatic interpretation of silicate derived proxies based on detailed investigations of strontium sr distributions revealed by multi step leaching in a fluvial sequence from the linxia basin which includes paleosols we reconstructed the long term late miocene regional climatic and environmental changes likely to have occurred on the northeastern tp from 12 1 to 5 2 ma we investigated sr related proxies in two typical paleosol profiles to constrain sr mobility in paleosol weathering and thus to further prompt the interpretation of sr related proxies along the whole section we would suggest that carbonate derived sr concentrations and sr ca ratios are suitable proxies for tracing regional climate change associated with weathering and pedogenesis together they exhibit weakened chemical weathering intensity and pedogenesis at 8 6 ma the concomitant appearance of immature sediments through poor sedimentary sorting revealed by silicate derived rb sr 87 sr 86 sr and eu anomaly eu eu alongside a sharp increase in sedimentation rates noted at this time suggests that it was indeed tectonic uplift that principally controlled the dramatic climatic and environmental changes this multi proxy record of concomitant tectonic uplift and climate change in the linxia basin provides direct geological evidence for uplift driven climate change in the northeastern tp region

late pleistocene to holocene sedimentary fills of the cinarcik basin of the sea of marmara a giant rv marion dufresne piston core md01 2425 recovered from the 1276 m deep cinarcik basin of the sea of marmara documents characteristics of deep basin sedimentation influenced by large scale gravity controlled mass wasting processes and associated turbidite deposition during the late pleistocene to holocene a visual lithological description of the core reveals twenty major seismoturbidite layers 20 cm thick intercalated in hemipelagic type fine grained calcareous and slightly siliceous clays the thickness and frequency of the sesimoturbidite layers deposited during the lacustrine period prior to 12 3 cal ka bp is much greater than during the holocene marine period the sedimentary processes during deposition of seismoturbidites in the basin have been determined in this study using a combination of grain size parameters often the seismoturbidites show strong grain segregation with a sharp boundary between a coarse lower and a homogeneous upper part the traction carpet deposits formed at the base of a turbulent suspension and were produced in the lower coarse grained part whereas the homogeneous upper part was deposited by uniform suspensions following bedload deposition

late holocene coastal depositional environments and climate changes in the gulf of corinth greece multidisciplinary studies in coastal systems of the eastern mediterranean region have proven to be excellent tools in understanding paleoenvironmental paleoecological and paleoclimatic changes th

asian summer monsoonal variations during the holocene revealed by huguangyan maar lake sediment record abstract high resolution records of summer monsoonal evolution in the holocene are essential to paleoclimate reconstruction but are hard to obtain here we provide a continuous well dated high resolution record from huguangyan maar lake located in the west pacific climate regime multi proxies including chlorophyll a toc sr rb ratio and magnetic susceptibility have been used to reconstruct the monsoon variations in the holocene higher chlorophyll a values are related with stronger summer monsoon and vice versa high temporal resolution radiocarbon dating enables us to divide summer monsoon evolution stages summer monsoon in zhanjiang area was strongest in the early holocene but began to decline at 6080 yr bp and weakened substantially since about 3600 yr bp the transition around 6080 yr bp supported by our high resolution dating lags the previous estimates by 1700 years the decreasing summer solar radiation at 30 n through the holocene is probably responsible for gradually weakened summer monsoon the anti phased co variation of summer monsoon intensity and enso activity throughout the holocene suggests that they could be interlinked driven together by solar radiation at orbital scale

investigation of the tectonics of the main marmara fault by means of deep towed seismic data abstract we report a study of the active principal deformation zone pdz of the main marmara fault mmf in the sub basins of the sea of marmara by means of deep towed seismic pasisar as well as multi beam bathymetry data collected by ifremer s r v le suroit in september 2000 our main objective is to investigate the active deformation within the uppermost sedimentary layers with a much higher resolution than hitherto has been available to the west of the sea of marmara the pdz is located along the southern flank of the tekirdag basin where the sediments are affected by steep reverse faults dipping toward the north e w strike slip faults are also observed in the central part of the tekirdag basin and thrusting occurs along its n50 trending margin we interpret these structures in terms of a slight clockwise rotation in the basin north of the pdz to the east the pdz enters the central basin and follows a steep scarp along the southern flank of a tectonic depression the scarp consists of an en echelon fault system with a normal component these faults are combined with small parallel anticlines and synclines that extend along the southern portion of the depression the northern scarp of the depression is made of a mixed system of faults with both normal and reverse components associated with anticlines and synclines these faults are best interpreted as right lateral strike slip faults with a vertical component that is dominantly normal these faults and the sigmoid shape of the depression are compatible with a clockwise rotation above the pdz this recent tectonic structure appears to be superimposed over a pre existing graben that is now essentially deactivated the pdz continues eastwards out of the central basin as a n50 e trending nw verging thrust system toward the kumburgaz basin that is located on a restraining bend of the pdz this shortening zone consists of two main n60 e trending branches the northern one is more pronounced and composed of two successive restraining bends the southern branch is smoother and forms a gently curved connection between the two segments of the pdz this suggests that the pdz migrates southward to cut through this restraining bend further east the pdz enters the cinarcik basin along its northern scarp active deformation observed on the pasisar profiles along the 290 trending eastern portion of this scarp consists of n110 5 trending dextral strike slip faults connecting short segments of active n130 140 normal faults that control elongated depocenters along the southern flank of the cinarcik basin the e w izmit fault enters the basin from the east pasisar data confirm the extension of the izmit strike slip fault into the cinarcik basin and the large development of normal faulting along the southern flank of the basin some of the normal faulting observed here may be related to horse tail termination of the izmit fault while most of it is the expression of strain partitioning

late glacial to mid holocene palaeoclimate development of southern greece inferred from the sediment sequence of lake stymphalia ne peloponnese abstract the sedimentary sequence of lake stymphalia ne peloponnese for the first time sheds light on the palaeoclimate development of southern greece from 15 to 5 ka bp new geochemical data based on high resolution x ray fluorescence scanning provide in situ and continuous analysis of predefined element suites on split core surfaces variations of elements over time were assessed constructing correlation matrices based on the calculation of pearson correlation coefficients the element suite includes al si k ca ti mn fe zn rb sr and zr a major result includes that changes in element behaviour are related to hydrological changes in the catchment precipitation lake level status and evaporation insolation solar activity and are ultimately driven by climate major trends shifts in elemental ratios correspond to the climate development in the eastern mediterranean region based on correlation of rb sr reflecting wet dry climates with foraminiferal proxies of marine core lc21 from the southern aegean sea and the stable oxygen isotope record of soreq cave israel the bolling allerod the younger dryas and the 8 2 ka cold event were identified

storm wave reactivation of a submarine landslide submarine landslides move large amounts of sediment and are often hazardous to offshore installations marine surveying techniques effectively define landslide locations and geometries for example refs 1 4 in various underwater geological settings including deltas fjords and earthquake prone areas1 5 movement rates and mechanics are generally inferred from indirect evidence such as cable breaks and damage to sea floor structures for example refs 6 8 but actual measurements of landslide behaviour are sparse using bottom deployed pressure sensors tiltmeters and accelerometers we have collected data on sea floor landslide reactivation involving sediment collapse and remoulding on the submarine slopes of the huanghe delta china the sensors were emplaced into sea floor clayey silts on 4 october 1987 and recovered on 16 october after the passage of three severe storms

the sea of marmara a plate boundary sea in an escape tectonic regime abstract the sea of marmara is dissected by two major fault systems the first consists of two east west striking transtensional boundary faults and a number of secondary faults subparallel to them the second is made up of ne sw trending subvertical strike slips and their conjugates oriented nw se that offset the first system these fault systems segment the deep marmara sea into 5 blocks that are either rhomboidal lazy z or wedge shaped three of these blocks may be interpreted as pull apart basins characterized by transtension while the other two sill areas which separate the basins are transpressional push up structures the blocks are subjected to rapid episodic subsidence but they also undergo pervasive vertical motions and possible rotations relative to one another the sedimentary column above the acoustic basement mapped within the sea of marmara can be divided into 3 seismic units a folded and truncated pre transform unit and two syn transform units the lower thick syn transform unit exhibits 3 distinct seismic facies a well stratified basin fill facies cut by subvertical growth faults a push up facies with a contorted or chaotic internal configuration and a slump facies the observed neotectonic and sedimentary regimes result from compressional movement between eurasia and africa which has led to major dextral transform movements along the north anatolian fault zone escape tectonics and from the fact that this fault zone splinters into two overlapping right stepping oblique master faults at the eastern and western border of the sea of marmara respectively

magnetic susceptibility evidence of monsoon variation on the loess plateau of central china during the last 130 000 years the magnetic susceptibility of loess and paleosols in central china represents a proxy climate index closely related to past changes of precipitation and vegetation and thus to summer monsoon intensity time series of magnetic susceptibility constructed for three loess paleosol sequences in the southern part of the chinese loess plateau document the history of summer monsoon variation during the last 130 000 yr they correlate closely with the oxygen isotope record of stages 1 to 5 in deep sea sediments soils were forming during intervals of strong summer monsoon whereas loess units were deposited at times of reduced monsoon intensity the chinese loess paleosol sequence can thus be viewed as a proxy record of asian monsoon variability extending over the last 2 5 myr

deep sea tsunami deposits in the eastern mediterranean new evidence and depositional models the tsunami wave induced by the collapse of the santorini caldera after the bronze age minoan eruption 3500 bp produced turbidites and large volume mega turbidites in the abyssal plains of the ionian sea as well as on the floor of small basins of the mediterranean and calabrian ridges characterized by the so called cobblestone topography since the first discovery in 1978 a holocene mud layer which has been termed homogenite and which typically shows a graded interval at its base has been identified and correlated in over 50 deep sea cores recovered in the eastern mediterranean four types of homogenite can be distinguished each related to a particular depositional setting 1 a closed cobblestone these are from a few decimetres to several metres thick pelagic turbidites of local provenance exclusively found at the bottom of small sized ponded basins of the mediterranean and calabrian ridges a debris flow may be present at the base of the turbidite where the vertical relief of the basins is over 200 m 2 b abyssal plain a 10 to 20 m thick megaturbidite recorded in the ionian and sirte abyssal plains the source area is the african continental margin possibly the continental shelf it can be easily identified as a transparent acoustic layer that shows recent deformation across the deformation front of the mediterranean ridge accretionary prism the volume of the minoan homogenite in the ionian abyssal plain has been calculated at a minimum of 11 km3 3 c open cobblestone this type is exclusively found on the outer slope of the mediterranean ridge near the deformation front unlike types a and b the base of the turbidite here is erosional instead of depositional this homogenite has been deposited in small basins and occasionally on topographic highs of the mediterranean ridge by the up slope flow of turbidity currents of african provenance that formed the abyssal plain deposit type b 4 d a fourth depositional model has been identified homogenites present in deep anoxic basins of the mediterranean ridge this setting is substantially similar to type a but the vertical relief of the basin is much higher up to 800 m and the deposition occurs in high density anoxic brines which modify the settling rate and hence the resulting sedimentological characters

deep sea tsunami deposits triggered by the explosion of santorini 3500 y bp eastern mediterranean abstract the collapse of the santorini caldera after the catastrophic eruption of the bronze age 3500 y bp caused a tsunami wave that had catastrophic effects in the ionian basin including its deepest parts pelagic turbidites of local origin were deposited on the bottom of small perched basins of the southern calabrian western and central mediterranean ridges type a homogenite whereas a megaturbidite of distal origin presumably triggered by the tsunami wave hitting the shoreline of the sirte gulf was deposited on the ionian and sirte abyssal plains extending eastwards as far as the western herodotous trough depositing a thick acoustically transparent layer type b homogenite three core transects crossing the deformation front of the mediterranean ridge are presented and discussed a fourth transect of giant piston cores was collected on the abyssal plains located to the south of the mediterranean ridge all those to the west of the collision zone contain the holocene homogenite with a thickness in excess of 20 m whereas the cores taken from the herodotous abyssal plain east of the collision zone are devoid of the homogenite sedimentological analyses were performed on the only giant core that penetrated the sandy base of the homogenite and the underlying pelagic sediments of late pleistocene last glacial age the african provenance of this typical type b homogenite is corroborated by shallow water fauna derived from the north african shelf no sedimentological characteristics peculiar to tsunamiites are observed in the deep sea homogenite of the eastern mediterranean

mid to late holocene indian winter monsoon variability from a terrestrial record in eastern and southeastern coastal environments of sri lanka the southeastern coastal plain of sri lanka contains holocene sediment archives representing the winter monsoon variability because this region is protected from both summer monsoon and cyclonic rainfall chemical biological mineralogical and physical climate proxies were studied in sediment cores extracted from three different coastal estuaries and lagoons situated on the southeastern coast to derive winter monsoon variability these cores displayed minimum influence of sea level related changes in sediments clay normalized proxy records suggest intervals of aridity from 7300 to 6750 semi aridity from 6250 to 4600 yr bp and aridity from 4000 to 3000 and 1100 to 500 cal yr bp with a short wet interval from 6500 to 6250 cal yr bp and a wet interval from 3000 to 1500 yr bp our results match the timing of previously published climate events for holocene variations in the indian summer monsoon wavelet analysis of the detrended climate proxy records identify significant periodicities at 2

the north anatolian fault within the sea of marmara a new interpretation based on multi channel seismic and multi beam bathymetry data abstract we analyze 2200 km of multi channel seismic reflection profiles that have become recently available in the sea of marmara this analysis benefits from the recent acquisition of multi beam bathymetric data covering the axial portion of the northern basins we conclude that the northern sea of marmara is at present cut by an active continuous strike slip fault system that we call the marmara fault it links the 270 izmit portion of the northern branch of the north anatolian fault to the east of the sea to the 245 ganos fault to the west the marmara fault itself consists of two main parts the western one is a single 80 km long fault it follows a 265 direction that differs by 20 from the direction of the ganos fault at its northeastern extremity it turns toward the northern margin of the cinarcik basin this western part of the fault is seismically quite active the eastern part is more complex it extends over 65 km in a 280 direction there is thus a 10 clockwise rotation with respect to the 270 izmit fault strand that should result in a slight extensional component within the eastern cinarcik basin this part of the marmara fault has two parallel branches 10 km apart the northern one near the foot of the northern slope the southern one near the foot of the southern slope a shortening zone occupies the northwestern corner of the cinarcik basin and much of the adjacent eastern central high and separates the northern branch from the western one the southern branch on the other hand may cross the eastern central high along a narrow 280 valley the data we have provide no definitive evidence on which of these two branches carries most of the motion the establishment of the present trace of the fault through the marmara basin is contemporaneous with a recent phase of deposition of deep giant ripples parallel to the bathymetric slope contours and adjacent to the turbidites basin deposits the base of these deep basins sedimentary deposits is marked by a widespread erosional unconformity below which lies a gently folded sedimentary sequence that may consist of shallow thrace basin deposits

sea level changes and depositional environments in the izmit gulf eastern marmara sea during the late glacial holocene period abstract offshore and onshore stratigraphic studies together with high resolution shallow seismic reflection profiling and multibeam bathymetric mapping were carried out in the western and central part of the izmit gulf these studies indicate that the izmit gulf was a lacustrine environment as part of the marmara lake during the late glaciation and early deglaciation until 12 kyr bp when the marmara basin was inundated by the mediterranean waters correlation of 14 c dated onshore and offshore stratigraphic units in the western izmit gulf indicates that generally coarse late glacial sediments overlie a marked erosional surface formed during the low water level of the marmara lake these coarse sediments are succeeded by 10 4 7 kyr bp old transgressive and by late holocene post transgression mud units the bathymetry and sub bottom chirp profiles clearly show that the paleoshoreline of the gulf was located at 85 m having been controlled by the bedrock sill depth of the canakkale strait another paleoshoreline observed at 65 m on the northern margin of the western izmit and karamursel basins was probably formed during the younger dryas sea level stillstand the shelf areas during this time were colonized by bioherms which were subsequently drowned and disappeared after a further rise of the sea level the presence of a 65 m marine paleoshoreline in the karamursel basin indicates that the sill restricting this basin to the west was much deeper than its present 55 m level and was located further south the golcuk basin restricted by a 38 m sill to its west was probably not flooded by marine waters until 9 kyr bp

the 9 2 ka event in asian summer monsoon area the strongest millennial scale collapse of the monsoon during the holocene numerous holocene paleo proxy records exhibit a series of centennial millennial scale rapid climatic events unlike the widely acknowledged 8 2 ka climate anomaly the likelihood of a significant climate excursion at around 9 2 cal ka bp which has been notably recognized in some studies remains to be fully clarified in terms of its magnitude and intensity as well as its characteristics and spatial distributions in a range of paleoclimatic records in this study a peat sediment profile from the dajiuhu basin in central china was collected with several geochemical proxies and a pollen analysis carried out to help improve understanding of the climate changes around 9 2 cal ka bp the results show that the peat development was interrupted abruptly at around 9 2 cal ka bp when the chemical weathering strength decreased and the tree pollen declined this suggests that a strong drier regional climatic event occurred at around 9 2 cal ka bp in central china which was in turn probably connected to the rapid 9 2 ka climate event co developing worldwide in addition based on the synthesis of our peat records and the other holocene hydrological records from asian summer monsoon asm region we further found that the 9 2 ka event probably constituted the strongest abrupt collapse of the asian monsoon system during the full holocene interval the correlations between asm and the atmospheric 14c production rate the north atlantic drift ice records and greenland temperature indicated that the weakened asm event at around 9 2 cal ka bp could be interpreted by the co influence of external and internal factors related to the changes of the solar activity and the atlantic meridional overturning circulation amoc

disentangling late quaternary climatic and seismo tectonic controls on lake mucubaji sedimentation merida andes venezuela abstract lake mucubaji is a moraine dammed lake crossed by the bocono fault in the merida andes venezuela four long piston cores up to 8 m long and 24 short gravity cores 0 6 to 0 8 m long were collected to study the sedimentary fill of the lake lithostratigraphy magnetic susceptibility organic and inorganic contents and 14 c ages permit lateral correlations between the cores and with an emerged part of the former larger lacustrine basin fill the cored succession spans the last 16 000 years several abrupt changes in sediment texture and composition are ascribed to depth and surface modifications together with soft sediment disturbances they are related to the seismo tectonic activity of the bocon fault shock induced phenomena slumps seiche effects liquefaction and co seismic scarps four major earthquakes indicate a mean minimum recurrence interval of 1200 years which is consistent with trench data obtained from a neighbouring active trace of the bocono fault system despite the seismo tectonic imprint a general post lgm climatic trend can be traced and correlated with northern hemisphere global evolution in particular for the last 13 000 years

seasonal evolution of an ice shelf influenced fast ice regime derived from an autonomous thermistor chain ice shelves strongly interact with coastal antarctic sea ice and the associated ecosystem by creating conditions favorable to the formation of a sub ice platelet layer the close investigation of this phenomenon and its seasonal evolution remains a challenge due to logistical constraints and a lack of suitable methodology in this study we characterize the seasonal cycle of antarctic fast ice adjacent to the ekstrom ice shelf in the eastern weddell sea we used a thermistor chain with the additional ability to record the temperature response induced by cyclic heating of resistors embedded in the chain vertical sea ice temperature and heating profiles obtained daily between november 2012 and february 2014 were analyzed to determine sea ice and snow evolution and to calculate the basal energy budget the residual heat flux translated into an ice volume fraction in the platelet layer of 0 18 0 09 which we reproduced by a independent model simulation and agrees with earlier results manual drillings revealed an average annual platelet layer thickness increase of at least 4 m and an annual maximum thickness of 10 m beneath second year sea ice the oceanic contribution dominated the total sea ice production during the study effectively accounting for up to 70 of second year sea ice growth in summer an oceanic heat flux of 21 w m 2 led to a partial thinning of the platelet layer our results further show that the active heating method in contrast to the acoustic sounding approach is well suited to derive the fast ice mass balance in regions influenced by ocean ice shelf interaction as it allows subdiurnal monitoring of the platelet layer thickness

a rb sr record of catchment weathering response to holocene climate change in inner mongolia variation in the rubidium to strontium rb sr ratio of the loess palaeosol sequences has been proposed to reflect the degree of pedogenesis and weathering in the northwestern region of china to characterize the rb sr ratio of the dissolved loads of a single catchment we analysed a 12 08 m sediment core from daihai lake in inner mongolia north china dating control was provided by 210pb 137cs and ams 14c sequential extraction experiments were conducted to investigate the concentrations of rb and sr on various chemical fractions in the lake sediments down core variation in the rb sr ratios provides a record of holocene weathering history from 9 to 3 5 ka bp accelerated chemical weathering was experienced throughout the daihai catchment under mainly warm and humid conditions and this reached a maximum at c 5 ka bp however weathering was reduced between c 8 25 and 7 90 ka bp which may reflect the global 8 2 ka cooling event after c 2 5 ka bp increased rb sr ratios with higher frequency of fluctuations indicate reduced weathering within the daihai catchment the highest rb sr ratios in the little ice age lake sediments indicate the weakest phase of holocene chemical weathering resulting from a marked reduction in sr flux into the basin the rb sr record also shows an enhancement of chemical weathering under today s climate but its intensity is less than that of the medieval warm period increased rb sr in lake sediment corresponding to reduced catchment weathering is in striking contrast to rb sr decrease in the glacial loess layers in the loess palaeosol sequence copyright 2005 john wiley sons ltd

panigarh cave stalagmite evidence of climate change in the indian central himalaya since ad 1256 monsoon breaks and winter southern jet depressions abstract variations in petrography stable isotopes reflectance and luminescence along the central growth axis of a 14 5 cm stalagmite from panigarh cave indicate cooler and slightly wetter conditions in the himalayan foothills of northern india during the little ice age lia which lasted from ad 1489 1889 based on deposition of calcite and ad 1450 1820 based on rapid changes in 18o values conditions were warmer and drier during the preceding medieval climate anomaly mca and also in the post lia periods as evidenced by deposition of aragonite a review of currently existing stalagmite and other proxy data from south and east asia reveals a broad spatial pattern in precipitation over south and east asia during the lia with northern areas showing generally increased precipitation and southern areas reduced precipitation during the mca and after the lia the records suggest this pattern was reversed weaker ism during the lia brought drought conditions to the core ism area but triggered more monsoon breaks that brought higher precipitation to the himalayas at the same time the weaker ism may also have pushed more depressions along the path of the southern winter jet which brought more winter precipitation to the himalayas and therefore a lia wetter in our study area

hydrology in the sea of marmara during the last 23 ka implications for timing of black sea connections and sapropel deposition 1 sediments deposited under lacustrine and marine conditions in the sea of marmara hold a late quaternary record for water exchange between the black sea and the mediterranean sea here we report a multiproxy data set based on oxygen and strontium isotope results obtained from carbonate shells major and trace elements and specific organic biomarker measurements as well as a micropaleontological study from a 14c dated sediment core retrieved from the sea of marmara pronounced changes occurred in 18o and 87sr 86sr values at the fresh and marine water transition providing additional information in relation to micropaleontological data organic biomarker concentrations documented the marine origin of the sapropelic layer while changes in n alkane concentrations clearly indicated an enhanced contribution for organic matter of terrestrial origin before and after the event when compared with the black sea record the results suggest that the black sea was outflowing to the sea of marmara from the last glacial maximum until the warmer bolling allerod the first marine incursion in the sea of marmara occurred at 14 7 cal ka b p however salinification of the basin was gradual indicating that black sea freshwaters were still contributing to the marmara seawater budget after the younger dryas which is associated with a high input of organic matter of terrestrial origin both basins were disconnected resulting in a salinity increase in the sea of marmara the deposition of organic rich sapropel that followed was mainly related to enhanced primary productivity characterized by a reorganization of the phytoplankton population

large arctic temperature change at the wisconsin holocene glacial transition analysis of borehole temperature and greenland ice sheet project ii ice core isotopic composition reveals that the warming from average glacial conditions to the holocene in central greenland was large approximately 15 c this is at least three times the coincident temperature change in the tropics and mid latitudes the coldest periods of the last glacial were probably 21 c colder than at present over the greenland ice sheet

geology and major and trace element chemistry of late archean weathering profiles in the fortescue group western australia implications for atmospheric po2 abstract we have identified two thick weathering profiles between flows of the mt roe basalt unit of the fortescue group in the pilbara area of western australia the age of weathering is constrained by u pb zircon dating to lie between 2765 and 2715 ma the profiles herein referred to as the mt roe 1 and 2 paleosols were mapped in detail for 1500 m and 760 m along strike respectively samples were collected along traverses across both profiles where they were well developed and well exposed the profiles which may be structurally offset parts of the same weathering horizon have well developed upper sericite zones 1 15 m thick these grade downward into chlorite rich zones which are chemically and physically heterogeneous the chlorite zones grade downward into unweathered basalts the mt roe 1 profile is overlain by 2 6 m of bedded probably lacustrine sediments these in turn are covered by succeeding lava flows evidence of a surficial origin for the paleosols includes mud cracks ripple marks and rip ups of the paleosol material in the post paleosol sediments soft sediment deformation and probable dewatering structures are present along the paleosol sediment contact the mt roe 2 profile is overlain directly by the succeeding lava flow with little or no intervening sediments some brecciation and pillowing is observed along the base of the overlying basalt flow in both cases probably due to emplacement of lava into a shallow lake or onto wet soil in the sericite zones of both profiles nearly all of the fe mn mg and zn and a substantial fraction of the ca pb na ni and si have been leached the chlorite zones have elevated fe pb ni and zn contents and appear to be repositories of elements lost from the sericite zone al ti zr and th were immobile in the mt roe 1 paleosol and are concentrated by factors of 2 5 2 6 over the unweathered basalt v u and cr were also nearly immobile major element and trace element data indicate that weathering took place under conditions of low atmospheric oxygen k is strongly enriched toward the upper contact of the sericite zone and was introduced during post weathering metasomatism together with rb and sr na and ca are also enriched near the top of each profile and small amounts of each may have been introduced during regional low grade metamorphism of the hamersley basin at 2168 10 ma

rapid northward shift of the indian monsoon on the tibetan plateau at the end of the little ice age variations in the indian monsoon im and westerlies ws significantly affect the climate on the tibetan plateau tp and have widespread ecological and socioeconomic impacts on the whole of asian society so far however the rate and magnitude of changes in the im have still remained unclear here we report for the first time that the im rapidly shifted northward at the end of the little ice age lia we used sediment proxies for humidity and moisture sources from the taro co lake which is located in the transition zone between the ws and im our comprehensive survey of climate records for the tp and its peripheral mountain ranges revealed that the northern boundary of the im i e the southern boundary of the ws lay along the southern slope of the gandise range 29 5 n in the late lia in contrast it passed quickly over the gandise range by at least 1 5 in latitude at the end of the lia our results suggest that this rapid climatic shift was potentially triggered by the counteracting effects of blocking by the tp and its marginal orography which hindered the northward movement of the im and the pulling thermal gradient of the tp

decoupled evolution of nd and sr isotopes in the continental crust and the mantle nd and sr isotopes evolve independently in clastic sedimentary rocks and the continental crust as a whole because sr is recycled preferentially from the continents to the mantle as a result the differentiation age of the mantle inferred from sr isotopes and the mean rb sr age of the continental crust are younger than their true ages

physical structural and isotopic characteristics and growth processes of fast sea ice in lutzow holm bay antarctica a sea ice ocean study was conducted off queen maud land and enderby land antarctica from 1990 to 1991 by the japanese antarctic research expedition observations of multiyear land fast sea ice were made in lutzow holm bay over a period of 2 years to determine the snow and ice characteristics and ice growth processes the snow depth in the bay reached large values of 1 0 to 1 5 m during the winter season at offshore locations from the analysis of ice thickness measurements it is confirmed that the fast ice with deep snow cover grew little in winter but substantially thickened during the summer months on the basis of ice core structure salinity and stable isotopic composition we conclude that the summer growth was caused by upward growth at the top of the ice to which snow ice and superimposed ice formation contribute these processes were the primary contributors to sea ice growth and characteristics only where the snow accumulation was large in areas of low snow accumulation there was no surface growth superimposed ice formation on sea ice in antarctica has not been reported previously evidence for snow cover melting which is a prerequisite for superimposed ice formation was also found

late pleistocene holocene evolution of the northern shelf of the sea of marmara abstract chirp sub bottom profiling multibeam bathymetric mapping and a combination of faunal and isotopic analysis of molluscs and foraminifera in sediment cores on the northern shelf of the sea of marmara som provide evidence of sea level excursions water exchanges between the adjacent mediterranean and black seas and oscillating salinity over the last 160 ka bp during the marine isotope stages mis 2 mis 3 mis 4 and mis 6 the som disconnected from the mediterranean sea and evolved into a lake during mis 1 mis 5 and mis 7 the som reconnected and became salty once again sapropels formed shortly after each invasion of mediterranean saltwater observed in our cores concurrent suboxic dysoxic conditions prevailed over quite shallow substrates on the shelf ancient shorelines are pervasive at 85 m on the northern shelf and in the region of prince islands coincident with the elevation of the modern bedrock sill in the canakkale dardanelles strait at times when global eustatic sea level dropped below this sill the surface of the som stabilized at its outlet and freshened thus this particular shoreline is interpreted as the edge of the most recent som lake that existed from about 75 ka bp to 12 ka bp the freshening is observed in very light 6 values of 18 o measured on freshwater molluscs and the complete absence of foraminifera two brief lacustrine episodes during mis 5 suggest that the level of the canakkale outlet might have been as shallow as 50 m in the past a likelihood supported by submerged terraces along its margins bounding the modern central channel and the presence of an euryhaline biofacies in unit l4 1 corresponding to mis 5b 18 o profiles and carbon 14 dating show that salinification of the som and the blossoming of bioherms evolved rapidly after the latest connection with the mediterranean at 12 ka bp however freshening proceeded more slowly once the connection was severed

application of allochthonous organic carbon and phosphorus forms in the interpretation of past environmental conditions organic matter in sediments for instance carbon nitrogen and phosphorus can be used to reconstruct the paleoecological and pollution history of lakes and their catchment basins in this paper the contents of allochthonous organic carbon allochthonous oc and autochthonous organic carbon autochthonous oc in sediment cores taken from wuliangsuhai lake and daihai lake in northern china are quantified by using a binary model and phosphorus forms in the sediment cores from the two lakes are extracted by sequential extraction techniques the results indicate that the palaeoenvironment and paleoclimate of daihai lake and its catchment basin in the recent 250 years can be well reconstructed based on the content of allochthonous oc the climate was relatively humid and warm in the period of 1865 2005 while relatively dry and cold in the period of 1765 1865 the sedimentary information of allochthonous oc in the 22 42 cm portion of the sediment cores in daihai lake corresponds to the final cold fluctuation of the little ice age that occurred since the middle holocene the difference of phosphorus forms in the sediment cores between the two lakes indicates that phosphorus input to the lakes and the correlation between phosphorus forms and distribution and the changes of environment are influenced by the eutrophication mechanisms and environmental conditions of the two lakes

linkage between lake xingkai sediment geochemistry and asian summer monsoon since the last interglacial period in this study we present the element geochemical data of core xk08 a2 drilled from lake xingkai khanka northeast china the study aims to examine the changes of sediment provenance and geochemical composition in response to asian summer monsoon variability since the last interglacial period major elemental analyses on lacustrine samples and sand samples from lake xingkai and the surrounding sandy ridges in northeast china indicate that their abundance varied in relatively narrow ranges the samples had only undergone the primary stage of chemical weathering similar ti al and k al ratios between the lacustrine samples from lake xingkai and the loess paleosol samples in north china were observed which suggests that they come from broadly similar desert sources due to the significant dependence on grain size and influence of sediments recycling chemical index of alteration of the lacustrine sediments could not be regarded as sensitive indicators of source regions weathering on the glacial interglacial timescale alternatively the geochemical proxies of the lacustrine sediments could be linked to the asian summer monsoon through the development of runoff and physical erosion in the catchment weakened asian summer monsoon caused more fine particles transported to the lake basin by reduced runoff in the last glacial period in contrast coarser and less weathered detritus are transported into the lake accompanying strengthened asian summer monsoon during the warm periods

sediments in palaeo notches potential proxy records for palaeoclimatic changes in antarctica abstract many climatic proxy materials such as ice cores coastal and lacustrine sediments and abandoned penguin rookeries have been used to study palaeoclimatic changes and the palaeoenvironmental evolution of antarctica in this paper we report another geological record well preserved sedimentary sequences in the palaeo notches in marine terraces of fildes peninsula king george island based upon grain size distribution and microtexture geochemical element compositions and radiocarbon dating we identified the sediments in one palaeo notch as lacustrine sediments most likely deposited in a small palaeo lake from these data we inferred that between 4000 and 3000 yr b p a moderate chemical weathering occurred and the climate was warmer and more humid than present in good agreement with the findings from other climatic proxy materials we believe that the sediments in palaeo notches provide another reliable proxy material for studying the palaeoclimate and the palaeoenvironment in antarctica

flood and earthquake disturbance of 210pb geochronology lake anterne nw alps dating recent lake sediment records yielding disturbed 210pb profiles has been a problem of wide interest in palaeoclimatic and palaeoseismic studies over the last few centuries when applied to an alpine lake sedimentary record a high resolution sedimentological study reveals that the 210pb profile is disturbed by the occurrence of single event deposits triggered by two different mechanisms flood events deposits and gravity reworking removing disturbed layers from the 210pb profile yields a logarithmic depth activity relationship using a simple 210pb decay model cfcs provides an assessment of mean accumulation rate of continuous sedimentation as opposed to event linked sedimentation the correlation of the thickest four gravity reworked deposits with historically known earthquakes permits both validation and refinement of the age depth relationship this refinement highlights variations in accumulation rate consistent with post little ice age climatic variations

submarine earthquake geology along the north anatolia fault in the marmara sea turkey a model for transform basin sedimentation abstract the submerged portions of the north anatolia fault system beneath the marmara sea were studied with high resolution multibeam bathymetry subbottom profiling and sediment cores the major objectives were to learn about the seismic and tectonic history of the fault from the stratigraphic record at a scale similar to paleoseismic studies on land and to develop tools for submarine earthquake geology that can be applied to fault controlled basins in general we focused on holocene sediment in several marmara sea basins of different sizes the approach was to test whether 1 the depocenters of the larger basins contain a record of all historic ms 7 earthquakes within the marmara sea region 2 the small transform basins record earthquakes that rupture through them 3 vertical and strike slip holocene deformation can be quantified and 4 the effects of an earthquake generally includes both primary structural features due to rupture of the sea floor such as strata offset scarps and tilting as well as secondary effects due to shaking such as mass wasting and gravitational flows we found evidence of earthquakes that we correlate with historic events in 181 ad 740 ad 1063 ad 1343 ad 1509 ad 1766 ad 1894 ad and 1912 ad the geologic evidence is primarily from those basins adjacent to the rupture as inferred from historic data this suggests that coseismic deformation of the sea floor along the rupture is a critical factor in the sedimentary record we propose a qualitative sedimentation model that relates this coseismic deformation to mass wasting of the slope scour of the basin floor seiche motions and homogenite deposition frequent earthquake activity sheds sediments from the flanks contributes to the much thicker sediment on the basin floor and decreases the likelihood of sediment failures in response to normal marine gravity driven processes the surveying techniques and approaches used have therefore the potential of documenting earthquake ruptures of fault segments and to extend the earthquake record far before the known history thus improving hazard evaluations and the fundamental understanding of earthquake process

submarine fault scarps in the sea of marmara pull apart north anatolian fault implications for seismic hazard in istanbul earthquake scarps associated with recent historical events have been found on the floor of the sea of marmara along the north anatolian fault naf the marmarascarps cruise using an unmanned submersible rov provides direct observations to study the fine scale morphology and geology of those scarps their distribution and geometry the observations are consistent with the diversity of fault mechanisms and the fault segmentation within the north marmara extensional step over between the strike slip ganos and izmit faults smaller strike slip segments and pull apart basins alternate within the main step over commonly combining strike slip and extension rapid sedimentation rates of 1 3 mm yr appear to compete with normal faulting components of up to 6 mm yr at the pull apart margins in spite of the fast sedimentation rates the submarine scarps are preserved and accumulate relief sets of youthful earthquake scarps extend offshore from the ganos and izmit faults on land into the sea of marmara our observations suggest that they correspond to the submarine ruptures of the 1999 izmit mw 7 4 and the 1912 ganos ms 7 4 earthquakes while the 1999 rupture ends at the immediate eastern entrance of the extensional cinarcik basin the 1912 rupture appears to have crossed the ganos restraining bend into the sea of marmara floor for 60 km with a right lateral slip of 5 m ending in the central basin step over from the gulf of saros to marmara the total 1912 rupture length is probably about 140 km not 50 km as previously thought the direct observations of submarine scarps in marmara are critical to defining barriers that have arrested past earthquakes as well as defining a possible segmentation of the contemporary state of loading incorporating the submarine scarp evidence modifies substantially our understanding of the current state of loading along the naf next to istanbul coulomb stress modeling shows a zone of maximum loading with at least 4 5 m of slip deficit encompassing the strike slip segment 70 km long between the cinarcik and central basins that segment alone would be capable of generating a large magnitude earthquake mw 7 2 other segments in marmara appear less loaded

sea ice growth in ongul strait antarctica a two year study was conducted on the growth processes of sea ice in ongul strait antarctica routine measurements of snow depth and ice thickness were made and sea ice cores were collected to assess their structure temperature and salinity the snow depth varied from 0 to about 1 m in the winter months the growth rate is higher in bare ice regions than in snow covered regions however over the year the ice thickness itself is lower in the bare ice regions than in the snow covered regions sea ice in the snow covered regions increased in thickness in spring rather than in winter due to the formation of snow ice and by ice formation related to the melting of snow cover

high resolution record of paleoclimate since the little ice age from the tibetan ice cores climate changes during the little ice age were studied based on oxygen isotope values 18o measured from ice cores recovered on and nearby the qinghai tibetan plateau three cold periods have been identified and are supported by three widely existing moraine ridges formed during the little ice age importantly the amplitude of the three cold periods differ in the cores studied in the dunde ice core the coldest period occurred in the 17th century while it occurred in the 19th century in the guliya ice core all the ice cores recovered from the tibetan plateau and nearby regions show strong climatic warming in the 20th century

late miocene early pleistocene climate change in the mid latitude westerlies and their influence on asian monsoon as constrained by the k al ratio record from drill core ls2 in the tarim basin abstract in order to study the evolution of westerly mid latitude winds we analyzed k al records from lacustrine and fluvial sediments of drill core ls2 in the eastern tarim basin for which the sedimentary record is continuous and well dated back to the late miocene by magnetostratigraphy the k al ratio obtained from drill core ls2 may be a proxy index for precipitation amounts in the tarim basin k al ratios from drill core ls2 indicate that precipitation increased gradually in the tarim basin from 7 24 6 34 ma with a brief but rapid decrease from 6 708 6 702 ma climate became increasingly arid beginning at 5 68 ma we attribute these paleoclimatic changes in the tarim basin in western china to 1 global phenomena such as the expansion of global ice volume and 2 regional forcings such as the growth of the tibetan plateau and the retreat of the paratethys ocean expansion of global ice volume and uplift of the tibetan plateau migrated westerlies southward which results in the transport of moisture to the south and east of the plateau and enhanced the aridification of western china the retreat of the paratethys ocean may have further exacerbated the lack of water vapor the change of westerly winds in the late miocene early pliocene may have influenced east asian climate on the basis of comparison climatic indices from these two regions

holocene climate development on the central tibetan plateau a sedimentary record from cuoe lake abstract we present a climate record for central tibet spanning the time between 10500 and 1600 cal years bp from a 5 3 m long sediment core from cuoe lake the analyses show that high sr concentration high toc content high c n ratio and enriched 13c of lake sediments corresponded to stronger chemical weathering high productivity high lake level and warmer wetter climate and vice versa as revealed by the variations of these proxies the climatic evolution during this period can be divided into five stages and several substages these are a cold dry stage before 10140 cal years bp a transition stage from 10140 to 8560 cal years bp an optimum stage warm wet from 8560 to 5750 cal years bp a cool dry stage from 5750 to 4000 cal years bp a transition stage from 4000 to 3000 cal years bp and a drying up stage after 3000 cal years bp these changes are presumably reflections of variations in indian monsoon intensity which according to that interpretation should have been enhanced from 8560 cal years bp slightly weakened after 5750 cal years bp and gradually diminished since 3000 cal years bp in this region

considering lacustrine erosion records and the de ploey erosion model in an examination of mountain catchment erosion susceptibility and precipitation reconstruction reconstruction of paleo precipitation can provide an insight into past climate and precipitation de ploey et al 1995 presents a highly simplified erosion equation to consider precipitation and erosion susceptibility this empirical model allows estimation of total precipitation and erosion susceptibility across a range of catchment characteristics including catchment area slope elevation vegetation cover and when limited catchment or meteorological data is available the presented study tests the de ploey equation using dated lacustrine records of catchment soil deposition both spatially and temporally the objective is to examine the de ploey equation s ability and efficiency in reconstructing past long term precipitation using sedimentological parameters the erosion susceptibility factor is described as a black box value by de ploey et al 1995 this research unravels the erosion susceptibility variable identifying it to change spatially and temporally according to precipitation vegetation cover and composition the extent of tree establishment across the catchment total lacustrine deposition and geochemical signatures in the archive calculation of the erosion sustainability variable and it s use within the de ploey erosion equation illustrate a reconstruction of an indicative mean annual precipitation and erosion susceptibility change over the recent period 100 years

deterioration of perennial sea ice in the beaufort gyre from 2003 to 2012 and its impact on the oceanic freshwater cycle time series of ice draft from 2003 to 2012 from moored sonar data are used to investigate variability and describe the reduction of the perennial sea ice cover in the beaufort gyre bg culminating in the extreme minimum in 2012 negative trends in median ice drafts and most ice fractions are observed while open water and thinnest ice fractions 0 3 m have increased attesting to the ablation or removal of the older sea ice from the bg over the 9 year period monthly anomalies indicate a shift occurred toward thinner ice after 2007 in which the thicker ice evident at the northern stations was reduced differences in the ice characteristics between all of the stations also diminished so that the ice cover throughout the region became statistically homogenous the moored data are used in a relationship with satellite radiometer data to estimate ice volume changes throughout the bg summer solid fresh water content decreased drastically in consecutive years from 730 km3 in 2006 to 570 km3 in 2007 and to 240 km3 in 2008 after a short rebound solid fresh water fell below 220 km3 in 2012 meanwhile hydrographic data indicate that liquid fresh water in the bg in summer increased 5410 km3 from 2003 to 2010 and decreased at least 210 km3 by 2012 the reduction of both solid and liquid fresh water components indicates a net export of approximately 320 km3 of fresh water from the region occurred between 2010 and 2012 suggesting that the anticyclonic atmosphere ocean circulation has weakened

a silicate weathering mechanism linking increases in marine 87sr 86sr with global glaciation the 87sr 86sr ratio of sea water is generally regarded as a proxy for the rate of chemical weathering of the continents interpretation of the 87sr 86sr record in marine limestones requires an understanding of how changes in this quantity are linked to climate and tectonic events a connection between the strontium isotope record and the extent of global glaciation has been proposed1 8 but without a well established mechanism glaciation may influence marine 87sr 86sr by changing global riverine sr fluxes that is rock weathering rates and or 87sr 86sr ratios that is relative mineral weathering rates here we investigate how the 87sr 86sr release from silicate weathering is affected by glaciation using the sr isotope systematics of granitoid soils on alpine glacial moraines in the wind river range wyoming we observe a negative correlation between the 87sr 86sr ratio of exchangeable sr in soils and the soil age indicating that the 87sr 86sr ratio of sr released in the early stages of weathering is significantly higher than in later stages we estimate that this mechanism can increase global riverine 87sr 86sr by an average of 0 0002 during periods of glacial interglacial cycling when superimposed on long term trends controlled by tectonic processes2 7 9 10 this shift can account for the correlation between the rate of change of marine 87sr 86sr and the intensity of glaciation over at least the past 10 myr

turbidites as records of intense palaeoearthquakes in lake biwa japan abstract some 20 turbidites were collected in the uppermost 3 m of surface sediments in lake biwa southwest japan these turbidites correlate in age to historical earthquakes that caused severe loss of lives and property near lake biwa the age of each turbidite was estimated precisely based on sedimentation rate by weight and the age of tephra markers below the turbidites the magnitudes and epicentres of major historical earthquakes during the last 1300 years are available from historical documents empirical equations relating intensity distance to the epicentre and magnitude enable us to calculate the ground shaking at lake biwa from these historical earthquakes earthquakes having intensity stronger than grade iv l on the japan meteorological agency jma earthquake scale that is 44 gal acceleration at lake biwa all coincide with the turbidite ages this intensity is apparently the lower threshold for turbidity current initiation in lake biwa

roles of sorting and chemical weathering in the geochemistry and magnetic susceptibility of xiashu loess east china abstract uncertainties in paleoenvironmental interpretations for traditional chemical analysis of bulk samples result from different grain size sub populations of sediments containing variable distributions of elements and minerals therefore it is important to understand the elemental and mineral distribution in different grain sizes in determining the quantitative relationship between chemical weathering and climatic change we sieved a series of xiashu loess samples into three sub populations of different grain sizes 45 m respectively and then analyzed each population for rubidium rb strontium sr rare earth elements and magnetic susceptibility in comparison with elemental concentrations of bulk samples clay mineralogy and illitic crystallinity our results show that distinct elemental distributions and magnetic susceptibilities for different grain size sub populations are controlled by sorting and or chemical weathering although we also suggest that the xiashu loess may have the same provenance as the central chinese loess maximum concentrations of rb and fine grained magnetic minerals in the less than 2 m sub population coupled with our finding of maximum sr in the larger than 45 m fraction indicate that sr was lost during chemical weathering grain size sub population analysis is therefore an effective method for extracting paleoenvironmental information because individual sub populations show minimal variations in initial rb sr ratios compared to bulk analysis of all sizes together furthermore a negative correlation between rb sr ratios and sr concentrations for the r 2 0 97 may indicate that clay is a sensitive indicator of intensity of chemical weathering and is an ideal sub population for determining rb sr ratios but not for magnetic susceptibility

late holocene paleoenvironmental changes inferred from manasbal lake sediments kashmir valley india abstract paleoclimate investigations and reconstruction using the lake sediment cores of kashmir valley have been rarely attempted the basin is influenced by indian summer monsoon westerlies and the local katabatic winds in the present study an 80 cm undisturbed sediment core was retrieved from the manasbal lake situated in north western himalaya sediments were dated using 14c method and the age depth model indicated a depositional history extending from 3345 yrs bp to the present grain size major and trace elements toc om contents c n ratio and diatom assemblages were applied to reconstruct the paleoenvironmental changes around the area the a cn k diagram displays that the weathering intensity of the manasbal lake sediments are moderate to highly weathered and the sediments have been derived from nearby and mixed source origin several wet and cold phases were identified during 3300 yrs bp to 2500 yrs bp and 1800 yrs bp to 1300 yrs bp due to intense precipitation reflect high lake level these wet phases are marked by higher sand and silt content c n ratio and high allochthonous input with less abundance of diatom species clay om toc contents and high cia values consequently low lake level and dry and cold period from 3345 yrs bp to 3300 yrs bp and 2500 yrs bp to 1800 yrs bp is observed these inferences are corroborated with the trace elemental ratios cia and cwi data our data indicate that the westerlies and localised katabtic winds rather than the indian summer monsoons played a major role in controlling the past climate around the manasbal lake kashmir valley

the last reconnection of the marmara sea turkey to the world ocean a paleoceanographic and paleoclimatic perspective during the late glacial marine isotope stage 2 the marmara sea transformed into a brackish lake as global sea level fell below the sill in the dardanelles strait a record of the basin s reconnection to the global ocean is preserved in its sediments permitting the extraction of the paleoceanographic and paleoclimatic history of the region the goal of this study is to develop a high resolution record of the lacustrine to marine transition of marmara sea in order to reconstruct regional and global climatic events at a millennial scale for this purpose we mapped the paleoshorelines of marmara sea along the northern eastern and southern shelves at cekmece prince islands and imrali using data from multibeam bathymetry high resolution subbottom profiling chirp and ten sediment cores detailed sedimentologic biostratigraphic foraminifers mollusk diatoms x ray fluorescence geochemical scanning and oxygen and carbon stable isotope analyses correlated to a calibrated radiocarbon chronology provided evidence for cold and dry conditions prior to 15 ka bp warm conditions of the bolling allerod from 15 to 13 ka bp a rapid marine incursion at 12 ka bp still stand of marmara sea and sediment reworking of the paleoshorelines during the younger dryas at 11 5 to 10 5 ka bp and development of strong stratification and influx of nutrients as black sea waters spilled into marmara sea at 9 2 ka bp stable environmental conditions developed in marmara sea after 6 0 ka bp as sea level reached its present shoreline and the basin floors filled with sediments achieving their present configuration

carbonate versus silicate weathering in the raikhot watershed within the high himalayan crystalline series the major element and sr isotope geochemistry of surface waters bedrock and river sands was investigated in the raikhot watershed within the high himalayan crystalline series hhcs in northern pakistan mass balance calculations of mineral weathering contributions to the dissolved flux of ions from the watershed indicate that 82 of the hco 3 flux is derived from the weathering of carbonate minerals and only 18 is derived from silicate weathering even though the bedrock is predominantly quartzofeldspathic gneiss and granite with only 1 carbonate in the watershed this study demonstrates the importance of trace amounts of bedrock carbonate in controlling the water chemistry of glacial watersheds we suggest that the flux of sr with a high 87 sr 86 sr ratio in the major himalayan rivers may be derived in large part from weathering of trace amounts of calcite within the largely silicate hhcs models that use the flux of radiogenic sr from the himalayas as a proxy for silicate weathering rates may therefore overestimate the amount of co 2 consumption due to silicate weathering in the himalaya

the wet little ice age recorded by sediments in huguangyan lake tropical south china abstract although temperature decreased in a similar trend in many regions around the word during the little ice age lia the reconstructed humidity is remarkably different from region to region the precipitation history during the lia is poorly understood as compared to the temperature history in tropical south china in this study a sediment core with a length of 117 5 cm was recovered in the central part of huguangyan lake in tropical south china total organic carbon toc total nitrogen tn inorganic carbon ic and non residual strontium sr were analyzed at approximately 1 cm intervals to study the regional precipitation changes during the lia generally sr containing minerals are sensitive to chemical weathering which is dominated by the precipitation in tropical south china thus the non residual sr in huguangyan sediments can be used as an indicator of precipitation changes which is also verified by the downcore variations of toc tn and ic in huguangyan lake the non residual sr correlated positively with toc and tn but negatively with ic in the sediment profile toc tn ic and the non residual sr jointly demonstrated a wet period from ad 1500 to 1750 which corresponds to the lia coincidently both the total solar irradiance tsi and northern hemisphere temperature have the lowest values between ad 1500 and 1750 over the past millennium therefore the wet lia in tropical south china was most likely caused by the low solar irradiation during the lia the low solar irradiation likely resulted in the decrease of the northern hemisphere temperature which weakened the intensity of the east asian summer monsoon easm and synchronously moved the north edge of the asian summer monsoon southward leading to an increase in the precipitation in tropical south china

black sea impact on the formation of eastern mediterranean sapropel s1 evidence from the marmara sea abstract water exchange between the black sea and the mediterranean sea has been a major focus of the paleohydrography of the eastern mediterranean glacial melt water released from the black sea is a potential factor in the formation of sapropel s1 an organic rich sediment layer that accumulated during the early holocene a high resolution study done on sediments from the marmara sea the gateway between the mediterranean and the black sea sheds light on the holocene exchange processes past sea surface temperature and sea surface salinity sss were derived from stable oxygen isotope ratios 18o of foraminiferal calcite and alkenone unsaturation ratios uk 37 heavy 18o values and high sss in the marmara sea suggest absence of low salinity water from the black sea during s1 the comparison with data from the levantine basin and southern aegean sea outlines gradients of freshening in the eastern mediterranean sea whereby the major sources of freshwater were closer to the levantine basin it is thus concluded that the black sea was not a major freshwater source contributing to formation of s1 given the absence of a low salinity layer the deposition of organic rich sediments corresponding to s1 in the marmara sea is likely the result of the global transgression and the concomitant re organization of biogeochemical cycles leading to enhanced productivity as shown by globigerina bulloides

paleoenvironmental shifts spanning the last 6000 years and recent anthropogenic controls inferred from a high altitude temperate lake anchar lake nw himalaya integrating multiproxy results geochemistry mineral magnetism grain size and c n ratio variability supported by 14c ams dating obtained from a 1 4 m sediment core retrieved from high altitude

effects of land use and climate change on erosion intensity and sediment geochemistry at lake lehmilampi finland this paper aims to evaluate the possible relationships between erosion intensity and changes in climate and land use during the past 5 5 cal k years at lake lehmilampi eastern finland in this st

abnormal rb sr ratio in lacustrine sediments of qaidam basin ne qinghai tibetan plateau a significant role of aeolian dust input abstract the rb sr ratio is an important indicator of weathering intensity in both lacustrine and loess sediments because of the inertness of the rb element and the activity of the sr element during the weathering process generally the environmental interpretation of rb sr ratio proxy in lacustrine sediments is contrary to that in the loess paleosol sequence it shows a negative correlation between the rb sr ratio and chemical weathering intensity in lacustrine sediments but shows a positive pattern in the loess paleosol sequence however in this study we investigated the rb sr ratio of a lacustrine core isl1a from qarhan salt lake qsl in eastern qaidam basin qb and found the rb sr ratio indicated a positive correlation with regional precipitation this pattern is similar to that of the loess paleosol sequence rather than the lacustrine sediments according to grain size statistics and the comparison of rb sr ratio with other proxies halite and calcite contents grain size and f values of grain size discriminant function we preliminarily proposed that the abundant input of aeolian materials transported by the strong northwest wind cause these unexpected rb sr ratio fluctuations in the isl1a core the comparison between background rb and sr elemental data of relevant regions and these of the core indicated the aeolian origin of rb sr ratio in the lacustrine sediments and the rb and sr elemental composition probably represents the geochemical characteristics of the dust source area the sr nd isotopic composition indicates that the erosive paleo lake strata in western qb could be the origin of aeolian materials in lacustrine sediments in the qsl as well as the loess deposits in dulan county qinghai lake basin and xining basin the regional correlation between proxies of the isl1a core and other aeolian records also supports the aeolian origin of detrital input in the core finally we propose that the origin of the detrital input must be distinguished before the rb sr ratio is applied as a weathering intensity proxy in lacustrine sediments especially in arid basins

asymmetric slip partitioning in the sea of marmara pull apart a clue to propagation processes of the north anatolian fault between 1939 and 1999 the north anatolian fault naf experienced a westward progression of eight large earthquakes over 800 km of its morphological trace the 2000 km long north anatolian transform fault has also grown by westward propagation through continental lithosphere over a much longer timescale 10 myr the sea of marmara is a large pull apart that appears to have been a geometrical mechanical obstacle encountered by the naf during its propagation the present paper focuses on new high resolution data on the submarine fault system that forms a smaller pull apart beneath the northern sea of marmara between two well known strike slip faults on land izmit and ganos faults the outstandingly clear submarine morphology reveals a segmented fault system including pull apart features at a range of scales which indicate a dominant transtensional tectonic regime there is no evidence for a single continuous purely strike slip fault this result is critical to understanding of the seismic behaviour of this region of the naf close to istanbul additionally morphological and geological evidence is found for a stable kinematics consistent both with the long term displacement field determined for the past 5 myr and with present day anatolia eurasia motion determined with gps however within the sea of marmara region the fault kinematics involves asymmetric slip partitioning that appears to have extended throughout the evolution of the pull apart the loading associated with the westward propagation process of the naf may have provided a favourable initial geometry for such a slip separation

1822 earthquake triggered homogenite in lake le bourget nw alps high resolution textural signatures of an earthquake induced historical homogenite layer are presented as well as its 3d distribution this homogeneous deposit is correlated with the ad 1822 event vii viii msk intensity the main historical earthquake of the french outer alps using 210pb dating and historical chronicles during this earthquake a violent lake water oscillation was reported seiche effect in the present study we discuss the influence of lake water oscillations during earthquake induced subaqueous slide through a pluridisciplinary analysis of subbottom sediments including high resolution seismic sidescan sonar and short gravity coring

direct effects of co2 and temperature on silicate weathering possible implications for climate control a critical uncertainty in models of the global carbon cycle and climate is the combined effect of organic activity temperature and atmospheric co2 on silicate weathering here we present new dissolution rates of anorthite and augite which indicate that silicate weathering in organic rich solutions is not directly affected by soil co2 but is very sensitive to temperature apparently co2 accelerates silicate weathering indirectly by fertilizing organic activity and the production of corrosive organic acids the weathering dependencies highlight the ability of silicate weathering to act as a global thermostat and damp out climate change when used as input in steady state carbon cycle and climate models

sedimentary basin evolution gravity flows volcanism and their impacts on the formation of the lower cretaceous oil shales in the chaoyang basin northeastern china abstract no detailed research has been carried out on the oil shales that are interbedded with gravity flow deposits and volcaniclastic rocks in the third member of the jiufotang formation in order to study the impact of basin evolution gravity flows and volcanism on oil shale formation petrology sedimentology sequence stratigraphy organic geochemistry and elemental geochemistry were used to characterise the oil shales extensional tectonic subsidence is suggested as the controlling factor for basin evolution the predominant maceral in the oil shales is sapropelinite suggesting organic matter was derived from mainly aquatic organism especially algae element indices u cu mo zn sr ba th g g zr g g and the chemical index of alteration cia show that the water conditions during deposition of the oil shales were anoxic and brackish with little terrigenous detrital input and a cold and dry palaeoclimate gravity flows were accompanied by the input of terrestrial detritus and a degree of oxygenation of the bottom waters reducing oil shale formation volcanic eruptions ejected intermediate acidic ashes not only leading to climate cooling but also either enhancing algal blooms by a fertilisation effect due to minor volcanic ash input or inhibiting algal blooms by a poisoning effect due to major volcanic ash input there is synchronicity between the occurrence of rifting gravity flows volcanism and earthquakes the best periods for oil shale formation were during intermissions between tectonic movement when there were few gravity flows volcanic eruptions or earthquakes high bioproductivity and lake expansion along with an anoxic environment were the main controlling factors for high quality oil shale formation there is a series of oil shale bearing rift basins formed in northeastern china that share a similar geological setting so this research provides a useful example for future resource exploration of coeval oil shales in northeastern china

chemostratigraphic resolution of widespread reducing conditions in the southwest pacific ocean during the late paleocene abstract paleogene strata throughout much of the southwest pacific is comprised of thick successions of fine grained siliceous to calcareous sediments however during the late paleocene the south pacific experienced widespread deposition of organic rich and 13corg enriched sediments that are recorded in the waipawa formation and the correlative waipawa organofacies the mechanisms responsible for the elevated input and preservation of organic matter are still poorly understood using a multi proxy chemostratigraphic approach we assess paleoceanographic conditions including paleo redox states and paleo productivity of the waipawa formation eight key sections from the east coast basin new zealand were sampled and analysed for multi element geochemistry and bulk pyrolysis sedimentological stratigraphic and chemostratigraphic evidence indicates the south pacific underwent an abrupt regression event during the late paleocene resulting in on shelf erosion and or bypassing of continental sourced sediments from the shelf into deeper waters the change in sediment delivery further increased nutrients and terrestrial organic matter loading to the site of deposition coeval excursions in ti zr and rb sr indicate a shift to an aluminosilicate dominated sediment supply resulting in a modest increase in marine productivity that cannot account for the anomalous organic matter enrichment changes in the hydrogen index show a transition from terrestrial to mixed terrestrial marine organic matter occurred during the late paleocene in which high concentration of type ii iii kerogens were buried and preserved in association with enhanced water column reducing conditions in deep marine settings elevated concentrations of redox sensitive trace elements e g u mo fe s are consistent with alternating phases of dysoxic to oxic conditions suggesting an expansion of an oxygen minimum zone enhancing preservation and delivery of organic matter to the seafloor leading to the subsequent burial and preservation of organic matter within anoxic sediments these new data provide insight into the depositional conditions and the petroleum potential of prospective source rocks in this basin using an integrated organic and inorganic geochemical approach to refine our knowledge of the depositional environment and paleoceanographic changes in shelfal to bathyal marine sediments of the late paleocene

abrupt environmental changes during the last 30 kyr in the southern margin of the taklimakan desert a record from an oasis abstract the taklimakan desert the largest sand sea in china is one of the most important sources of dust in the world millennial scale abrupt climate changes during the last glacial and holocene periods occurred in the region however these records remain poorly understood because dating eolian lacustrine and fluvial sediments and establishing reliable environmental proxies are challenging in this setting here we use accelerator mass spectrometry ams grain size and rb sr ratios of bulk sediments from an oasis sequence in the taklimakan desert while some 14c dates results are not in the stratigraphic order most of them can be grouped in four age groups during the last glacial we infer that reversals of radiocarbon age based on total organic carbon toc was controlled by organic carbon oc input from the regional carbon pool we selected 14c dates from the four age groups to develop an age depth model for a basin wide chronology peaks in a cumulative probability curve of radiocarbon dates with high rb sr ratios and fine mean grain sizes reveal four wet periods during the last glaciation and one wetter warmer period during the holocene the regional moisture variability appears to be influenced by the asian summer monsoon and mid latitude westerlies the holocene wetter warmer period facilitated human occupation of the oasis

chemical weathering since the little ice age recorded in lake sediments a high resolution proxy of past climate because of the different geochemical behaviour of rubidium and strontium in earth surface processes variations of the rb sr ratios in lake sediments were used as a geochemical proxy of chemical weathering and past climate in a single watershed low magnetic susceptibility low caco3 low sr concentration and hence high rb sr ratio in the lake sediments indicate weak chemical weathering under a cold but wet climate during the little ice age lia in the closed daihai lake watershed the concordant change in both sr and caco3 concentrations with 18o values in the dunde ice core suggests that weak chemical weathering during the wet lia was controlled by air temperature after the lia however precipitation played a dominant role in chemical weathering copyright 2001 john wiley sons ltd

a rb sr record of the weathering response to environmental changes in westerly winds across the tarim basin in the late miocene to the early pleistocene the long term record of lacustrine deposits in the tarim basin seems to provide a record of climate influenced by westerly winds to characterize the evolution of westerly winds we analyzed concentrations of rb v zn sc and sr for the drill core ls2 from lop nor in the eastern tarim basin the rb sr ratio in lacustrine deposits depends primarily on the sr element activity during weathering after the influence of source provenance has been removed we assume that with such a correction the rb sr ratio is controlled by precipitation which depends on moisture transport by westerly winds to the tarim basin the rb sr ratio displays a large amplitude oscillation that generally follows a pattern similar to that of pollen and ostracod assemblages which support the inference that rainfall amount affects the rb sr ratio and in turn suggests that it may serve as an index of precipitation that was transported by westerly wind all these climatic proxies obviously changed since the late miocene suggesting stronger aridification that may be attributed to a latitudinal shift in westerly winds since the late miocene a southward migration of westerly winds which then transported more moisture to the southern and eastern parts of the tibetan plateau agrees with modeling results and the geological record during that time this event may be causally related to the expansion of the northern hemisphere ice and or regional tectonic uplift of high mountains around the tarim basin

mineralogy and geochemistry of the holocene lacustrine sediments in nam co tibet abstract the carbonates clays and major chemical compositions of lacustrine sediments in nam co lake were examined by x ray diffraction scanning electron microscopy and chemical analysis carbonates include monohydrocalcite mhc first report from china and in a high altitude lake low mg calcite and traces of dolomite mhc in nam co is developed in water 1 8 g l with high mg ca molar ratios 10 03 15 03 high ph 8 04 9 72 and the presence of bacteria algae diatom and ostracoda illite and mg chlorite provide a strong evidence for physical weathering in the holocene most ca and sr in sediments originate from carbonates as the molar ratios of ca and co32 are all less than 1 and the curve of sr is very similar to that of ca however most of the mg fe and rb are from clays the lake water shifted from a fresh water environment to an evaporative alkaline environment by 2 06 cal ka bp there was a depositional event that the depositional rate changed from 0 134 to 1 639 mm a at about 2 cal ka bp

simulating magnetic susceptibility profiles in loess as an aid in quantifying rates of dust deposition and pedogenic development abstract magnetic susceptibility profiles z in loess sequences reflect a combination of two climatically modulated processes dust deposition and pedogenic development prominent soils with high values for example likely reflect periods of slow dust deposition and warm wet conditions favorable for rapid chemical weathering to refine our understanding of the climate records contained in loess we develop a numerical model as a tool for exploring quantitatively the integrated record of the temporal variation in rates of loess aggradation and soil development contained in profiles in our model the aggrading loess is pedogenically altered in a reactive zone near the ground surface the strength of the signal is dictated by both the depth dependent intensity of pedogenic processes and the rate of dust accumulation which dictates the total time a loess parcel spends in the near surface reactive zone the model can accommodate both pedogenic production of magnetically susceptible minerals and arrival of magnetically susceptible grains as eolian dust to explore the model performance and develop a sense of time and length scales implicit in profiles we first examine simple synthetic cases with idealized steady and cyclic climatic forcing reported profiles in three chinese loess sequences at varying distances from the western china dust source are then modeled in two illustrative ways i by imposing a specific dust deposition rate history that is proportional to the dust accumulation rate history reported from western pacific deep sea cores allowing the time variation of pedogenic rates to be calculated directly from profiles and ii by imposing both dust accumulation and pedogenic rate histories that are independently scaled by the deep sea 18 o history which reflects global climate cycles to which regional climate forcing is linked we find that the zone of pedogenic activity is roughly 0 5 1 0 m thick both deposition rate and pedogenic intensity have varied dramatically over the last 140 000 yr the age structure of the luochuan loess sequence is best fit by driving the model with the 18 o record and environmental conditions must have been anomalously favorable for pedogenesis during isotope stage 3 at all three sites finally we advocate the assembly of a variety of data types at a suite of sites within any loess field that taken together will better constrain the temporal and spatial patterns of climatically modulated deposition and pedogenic processes

late quaternary transition from lacustrine to a fluvio lacustrine environment in the north western nam co tibetan plateau china abstract holocene sediments from a 9 m high outcrop at the gangyasang qu s entry into lake nam co on the south eastern tibetan plateau were studied in a multiproxy approach the lowermost part of the section is of early holocene age and consists of varved sediments deposited in a proglacial lake geomorphological investigations of fossil beach ridges and fossil cliff lines in the littoral zone of nam co indicate a late pleistocene lake level high of 29 m above the present level a warming is visible in ostracode rich silts deposited after 9 6 ka bp an ostracode based transfer function estimates a lake level 28 m higher than today from this time until about 5 2 ka bp a late pleistocene lake level high was accompanied by an increase in lake size causing nam co to overflow into the lower course of gangyasang qu where a bay with slack water conditions formed between 4 2 and 1 3 ka bp the lake level was approximately 10 m higher than today the progradation of the gangyasang qu delta into nam co and the decreasing lake level shifted the study site into a fluvio lacustrine environment the sandy character and relatively low numbers of ostracode valves in the topmost sediments indicate increased fluvial activity possibly due to a temporary increase in flood frequency this facies lasted at least until 1 3 ka bp when the lake level of nam co dropped again and the river incised more than 10 m into the underlying fluvio lacustrine and lacustrine sediments

7000 year record of lake level change on the northern great plains a high resolution proxy of past climate mineralogical and paleobotanical characteristics of the sedimentary fill in a shallow saline lake in southeastern alberta indicate that drought intervals are aperiodic and that climatic extremes unprecedented in historic time occurred earlier during the holocene when century long intervals of repeated intense droughts alternated with long periods when droughts were rare low water intervals signifying periods of drought are recorded by carbonate rich laminae containing abundant plant fossils indicative of hypersalinity in contrast highstands of relatively fresh water outlining moist periods are represented by massive silicate rich sediment with lower numbers of halophytic indicators

contained reflected turbidity currents from the middle ordovician cloridorme formation quebec canada an alternative to the antidune hypothesis the parautochthonous cloridorme formation is a syn orogenic flysch succession that was deposited in an elongate foredeep basin as mainly lower middle fan outer fan and basin floor deposits the basin floor deposits about 1 5 km thick are confined to members 1 2 and 1 and are characterized by graded thick 1 10 m mud rich calcareous greywacke beds previously interpreted as deposits of concentrated muddy unidirectional turbidity currents that locally generated backset antidune lamination in internally stratified flows the dominant flow directions were from east to west but west to east transport also occurred as seen in the orientation of ripples climbing ripples flutes consistently overturned flames and grain imbrication we believe that the flows that deposited these thick calcareous greywacke beds reversed by roughly 180 one or more times during deposition of the lower sandy part of the beds flow reversals are consistent with the sharp grain size breaks and mud partings within sandy divisions measurement of grain fabric relative to stratification in the most celebrated antidune bedforms indicates flow from west to east thus the bedforms were produced by west to east migration of megaripples not by the upcurrent migration of antidunes the thick muddy beds were deposited by large volume muddy flows that were deflected and reflected from the side slopes and internal topographic highs of a confined basin floor much like the contessa and similar beds of the italian apennines large quantities of suspended mud were ponded above the irregular basin floor and settled to produce the thick silty mudstone caps seen on each bed because of their mode of emplacement we propose that these beds be called contained turbidites