a new record of holocene climate change from the bottom sediments of lake baikal abstract detailed siliceous microfossil records diatoms and chrysophyte cysts from the bdp 93 2 borehole with resolution of ca 30 120 years were obtained from lake baikal sediments to test the sensitivity of the lake baikal system to minor climate changes during the holocene our new results demonstrate that the subboreal period is characterized by the highest accumulations of diatom frustules and chrysophyte cysts in lake baikal sediments the siliceous microfossil record suggests that the holocene climatic optimum in this interior part of asia corresponds to the subboreal period 2 5 4 5 ka and not to the atlantic period 4 6 6 ka although quite different from holocene reconstructions for the european part of eurasia the holocene sedimentary record from lake baikal shows good correlation with palynological and soil climatic records from southeast siberia and mongolia where similar responses of the terrestrial biosphere are also documented a distinctive monospecific lamina of synedra acus diatom species coincident with the maximum of chrysophyte cyst accumulation during the subboreal period argues for the possible short term changes of the trophic state of lake baikal from oligotrophic with a cold water diatom assemblage to eutrophic with a thermophilic monospecific diatom flora comparison of diatom and cyst responses provides a key to distinguishing the humidity from temperature response in future studies of high resolution records of lake baikal

response of lake baikal ecosystem to climate forcing and pco2 change over the last glacial interglacial transition abstract the 13 c record of total organic carbon in the lake baikal core bdp 93 2 over the last glacial interglacial transition shows remarkable correlation with atmospheric co 2 fluctuations and the negative isotopic shift of 3 5 4 in response to the global increase in paleo p co 2 level with rapid evolution of the lake baikal carbon cycle from full glacial to full interglacial modes however the p co 2 signal in the baikal 13 c sedimentary organic matter is inundated by the basin wide productivity signal in the holocene the baikal diatom abundance record as a paleotemperature proxy lags behind the gisp2 ice core 18 o temperature proxy record by ca 1 ka possibly reflecting the response time of the baikal ecosystem to major climatic transitions there is no lag associated with the pronounced younger dryas cooling however suggesting a different forcing mechanism with a short response time for this abrupt climatic event in continental interior asia the phase difference observed between the diatom abundance and 13 c proxies in lake baikal core bdp 93 2 suggests their independent responses to different forcing mechanisms further justifying their importance for paleoclimate reconstructions from lake baikal records

climate and vegetation changes around lake baikal during the last 350 000 years abstract we conducted particle size and pollen analyses on two cores extracted from lake baikal to investigate the response of vegetation to climate change and to assess the differences in vegetation changes between the northern and southern regions of lake baikal over the last 350 kyr vegetation changes in the lake baikal region corresponded well to the fluctuations in median particle size which are indicators of the climate changes in this region forest which was mainly composed of pinus and picea spread widely during the interglacials interstadials of mis 9 7 5 and 1 and open forest or desert covered most areas during the glacial stadial substages however the responses of vegetation to climate changes differed between the northern and southern regions generally vegetation expansion was restricted around the northern region during the interglacial substages equivalent to mis 9 3 7 5 and 5 5 forest spread widely around both the northern and southern regions however sparsely vegetated poor desert open forest covered the northern region during mis 5 3 and 5 1 while forest extended around the southern region in these substages moreover during glacial periods open forest composed mainly of artemisia chenopodiaceae amarantaceae betula and alnus covered the southern region while poor desert open forest covered the northern region these different vegetation responses are considered to have been caused by the geographical characteristics of the regions i e the mountains around the northern region and the plains around the selenga river in the southern region

an alternative to exotic spore or pollen addition in quantitative microfossil studies uncertainties in availability and formulation of exotic microfossils e g lycopodium spp eucalyptus spp to be added to microfossil preparations may be resolved by the use of plastic microspheres 25 0 1 0 m which are unaffected by standard pollen preparative treatments koh hcl hf acetolysis and organic solvents the microspheres are sensitive to strongly oxidizing treatments e g schulze s reagent h2o2 h2so4 reflux for diatom preparation but can be added following digestion of organic material preparation of microsphere suspensions in a suitable electrolyte e g nacl formic acid water permits calibration by coulter counter of suitable dilutions e g 5000 100 ml 1 for delivery by tipet volumetric flasks the uniformity and distinctive appearance of the microspheres not only facilitate recognition but also provide a constant reference for both size 25 m and volume 8180 m3 as well as a reference standard for computerized microfossil scanning the microspheres are inert

late pliocene vegetation and climate of the lake baikal region southern east siberia reconstructed from palynological data abstract palynomorphs from a palaeomagnetically dated late pliocene sediment core 3 6 2 35 ma reflect highly variable climatic conditions and repeated expansion of steppe and boreo alpine vegetation mixed coniferous forests picea tsuga pinus with associated broadleaved taxa quercus corylus ulmus tilia were affected by dry and cold intervals already between 3 48 and 3 39 ma peak records of non arboreal pollen types and spores including subarctic boreo alpine selaginella selaginoides evidence advances of open vegetation which can be correlated to glacial marine oxygen isotope stages a cooling trend occurred from 3 15 ma to 2 5 ma documented by cold dry intervals and increased fluctuations of picea and pinus around 3 2 9 ma the palaeoclimate variation pattern shifted towards cold dry and warm moist oscillations cooling strengthened after 2 89 ma and severely restricted tsuga development cool and oligotrophic limnic conditions are documented by abundant gonyaulax dinoflagellate cysts in the interval 2 65 2 57 ma due to decreasing precipitation extensive areas with open steppe and rock steppe vegetation became permanently established after 2 62 ma dry conditions became a dominant environmental factor in the baikal region coeval in time with the red clay loess shift in northern china this climatic transition can be explained as a consequence of major intensification of northern hemisphere glaciation around 2 75 ma evidenced by marine records of ice rafted debris

temporal changes in the phytoplankton community of the southern basin of lake baikal over the last 24 000 years recorded by photosynthetic pigments in a sediment core abstract photosynthetic pigments and other indicators of phytoplankton were analyzed in a dated undisturbed sediment core obtained from the southern basin of lake baikal to reveal temporal changes in the phytoplankton community in the lake through the last glacial post glacial transition the sedimentation age of the core spans the last 24 14c ka chlorophyll a its derivatives carotenoids and total organic carbon toc started to increase after 15 14c ka and the onset of biogenic silica occurred at 10 14c ka this indicated that the post glacial growth of diatoms was preceded by that of other phytoplankton groups in the record of the pigments and toc a temporary decrease was observed in the period 11 5 10 5 14c ka corresponding to the younger dryas cold period the similarity found between the depth profiles of pyropheophytin a and steryl chlorin esters formed through predation of phytoplankton by zooplankton and that of toc suggested the important contribution of fecal pellets to sedimentary organic matter in the lake

glaciers and meltwater flux to lake baikal during the last glacial maximum abstract maximal 3d ice extent during mis 2 around lake baikal has been reconstructed using glacial landforms in the field aerial photos satellite images and gis analysis this regional glacial maximum is correlated 18 kyr bp with the global lgm based on available 14 c dates cosmogenic 10 be exposure ages correlation of lakeshore moraines with two raised shorelines and the ird record in lake sediments total ice area was 13 000 km 2 and ice volume 2000 km 3 1800 km 3 in water equivalent ice distribution was controlled by topography and ice fields with valley glaciers spreading to adjacent depressions locally ice caps with outlet glaciers existed averaged regional ela is estimated to be 1290 240 m with the ela depression at approximately 1340 m more acceptable regional scenario of the lgm precipitation reduction by 25 50 implies that summer temperature decreased by 6 12 c along with an increased solid fraction in precipitation up to 85 there were primary climatic controls for glaciation meltwater supply as a strong controller of lgm water budget 60 of total water input to the lake is estimated to have been from 6 4 to 9 0 km 3 yr 1 7 9 times less than present day river input preliminary balance estimation shows that during full glacial stage lake baikal was overflowing with the angara river output as 4 9 km 3 yr 1 and with lake level close to that today lake level drop down to the depth of 40 m is recorded by geological and geophysical evidence perhaps explaining the abrupt increase in effective evaporation in the lake watershed at the start of mis 2 24 18 ky bp

orbit related long term climate cycles revealed in a 12 myr continental record from lake baikal quaternary records of climate change from terrestrial sources such as lake sediments1 2 and aeolian sediments3 4 in general agree well with marine records5 6 but continuous records that cover more than the past one million years were essentially unavailable until recently when the high sedimentation rate site of lake baikal was exploited1 2 7 8 because of its location in the middle latitudes lake baikal is highly sensitive to insolation changes9 and the entire lake remained uncovered by ice sheets throughout the pleistocene epoch making it a valuable archive for past climate here we examine long sediment cores from lake baikal that cover the past 12 million years our record reveals a gradual cooling of the asian continental interior with some fluctuations spectral analyses reveal periods of about 400 kyr 600 kyr and 1 000 kyr which may correspond to milankovitch periods reflecting orbital cycles our results indicate that changes in insolation were closely related to long term environmental variations in the deep continental interior over the past 12 million years

paleoenvironmental proxy records from lake hovsgol mongolia and a synthesis of holocene climate change in the lake baikal watershed abstract here we discuss paleoenvironmental evolution in the baikal region during the holocene using new records of aquatic diatom and terrestrial vegetation changes from hovsgol mongolia s largest and deepest lake we reconcile previous contradictory baikal timescales by constraining reservoir corrections of ams dates on bulk sedimentary organic carbon synthesis of the holocene records in the baikal watershed reveals a northward progression in landscape vegetation changes and an anti phase behavior of diatom and biogenic silica proxies in neighboring rift lakes in lake baikal these proxies appear to be responsive to annual temperature increases after 6 ka whereas in lake hovsgol they respond to higher precipitation runoff from 11 to 7 ka unlike around lake baikal warmer summers between 6 and 3 5 ka resulted in the decline not expansion of forest vegetation around lake hovsgol apparently as a result of higher soil temperatures and lower moisture availability the regional climatic proxy data are consistent with a series of 500 yr time slice holocene gcm simulations for continental eurasia our results allow reevaluation of the concepts of the holocene optimum and a maximum of the asian summer monsoon as applied to paleoclimate records from continental asia

depositional and tectonic framework of the rift basins of lake baikal from multichannel seismic data recent multichannel seismic reflection data from lake baikal located in a large active continental rift in central asia image three major stratigraphic units totaling 3 5 to 7 5 km thick in four subbasins a major change in rift deposition and faulting between the oldest and middle rift units probably corresponds to the change from slow to fast rifting in early pliocene time inferred from on land studies a minor modification of fault patterns characterizes the youngest unit a brief comparison of the basins of lake baikal with those of the east african rift system highlights differences in structural style that can be explained by differences in age and evolution of the surrounding basement rocks

a new age model for the sediment cores from academician ridge lake baikal based on high time resolution ams 14c data sets over the last 30 kyr paleoclimatic and environmental implications abstract we constructed a new age model based on high time resolution 14 c data sets from three sediment cores from academician ridge lake baikal for reconstruction of environmental and biological changes in southern siberia during the last ca 30 kyr we used 14 c ages of total organic carbon toc for the model because terrestrial plant residues and biogenic carbonate were not observed in the sediments for accurate dating and age models based on 14 c ages of toc the freshwater 14 c reservoir effect and the effect of dead carbon from land derived organic materials must be estimated in this study we estimated the correction factor for these effects to be 2100 90 yr on the basis of a key layer the 14 c plateau caused by changes in the atmospheric 14 c concentration during the younger dryas yd cooling event the new age scale along with the toc mass accumulation rate mar toc and stable carbon isotope ratio in the sediment cores clearly indicate a rapid decrease in lake productivity and reduced influx of terrestrial organic materials into the lake during the yd 12 8 11 6 cal ka bp productivity was high mar toc up to 19 7 mg cm 2 kyr in and around lake baikal during 9 3 6 4 cal ka bp holocene climate optimum moreover paleoproductivity changes during the last ca 30 kyr in and around the lake baikal were clearly associated with fluctuations in the east asian monsoon intensity as inferred from the 18 o record from sanbao and hulu caves china during the late quaternary wang et al 2008 nature 451 1090 1093

high resolution record of northern hemisphere climate extending into the last interglacial period high resolution record of northern hemisphere climate extending into the last interglacial period

the medina wrench a key to the kinematics of the central and eastern mediterranean over the past 5 ma the medina wrenth in the central mediterranean is a transform fault connecting the plate collision in northwest africa and northern sicily with that occurring at the aegean plate boundary south of greece the more than 800 km long crescent shaped wrench zone is currently seismically quiet but exhibits major deformation since 5 ma within a belt 30 100 km wide it forms the southern boundary of two microplates moving eastward with respect to africa and europe a simple plate rotation model constrained by recent paleomagnetic data indicates that a continental iblean microplate and a hybrid continental oceanic ionian microplate separated along the malta escarpment have rotated anticlockwise by 11 and 12 respectively around poles in southern italy these rotations involved some 100 km of dextral eastward movement relative to africa of the ionian basin north of the medina wrench since 5 ma combining the published 26 clockwise rotation of the peloponnesus and northwest half of the aegean with the 12 anticlockwise rotation of the ionian microplate results in a a 99 agreement between the length of the seismic benioff zone beneath greece and the total convergence of the microplates and b an average rate of convergence across the aegean plate boundary southwest of the peloponnesus of 6 6 1cm a 1 since the miocene relative motion between microplates in a collision zone thus may be as much as 6 times faster than convergence between the major plates which spawned them and they can be considered rigid to the first order over the time span involved

last glacial interglacial vegetation and environmental dynamics in southern siberia chronology forcing and feedbacks abstract radiocarbon dated pollen and diatom records from lake kotokel in southern siberia help to reconstruct the environmental history of the area since 47 kyr bp pollen spectra composition and reconstructed biome scores suggest predominance of a tundra steppe vegetation and variable woody cover 5 20 between 47 and 30 kyr bp indicating generally a harsh and unstable climate during this interval conventionally regarded as the interstadial within the last glacial the short term climate amelioration episodes in the glacial part of the records are marked by the peaks in taiga and corresponding minima in steppe biome scores and appear synchronously with the hemispheric temperature and precipitation changes recorded in the greenland ice cores and chinese stalagmites transition to full glacial environments occurred between 32 and 30 kyr bp the interval at 30 24 kyr bp was probably the driest and coldest of the whole record as indicated by highest scores for steppe biome woody coverage

palaeoenvironmental history of lake baikal during the last 23000 years abstract a sediment core recovered from lake baikal was studied in an attempt to elucidate the palaeoenvironmental history of an intra continental lake under the control of last glacial to post glacial climatic fluctuations the lake conditions were characterised by subdued primary production and increased turbidity conditions during the last glacial maximum terrestrial vegetation and the development of soil layers were reduced in the drainage areas the deglaciation suggested by increased terrigenous sand influx and biological productivity took place at around 18 000 yr b p responding to the increased insolation in the northern hemisphere high latitude the onset of wet and warm conditions at ca 12 000 yr b p brought on a maximum of aquatic production and forestal expansion between 7 000 and 6 000 yr b p since 5 000 yr b p enhanced blooming of diatoms has occurred due to an increased nutrient supply and dissolved silica input into the lake

vegetation response in the southern lake baikal region to abrupt climate events over the past 33calkyr abstract we reconstructed vegetation changes and fire events in the southern lake baikal region over the past 33 cal kyr using a sediment core from the buguldeika saddle southern lake baikal to examine vegetation response to past short term climate variations herbs such as artemisia and asteraceae were dominant just before the last glacial maximum lgm low pollen accumulation rates pars with little herb pollen indicate sparse herbaceous vegetation cover during the lgm picea expanded after the bolling interval suggesting expansion of riparian areas and shrub alnus rapidly increased during the following allerod interval abies and pinus subgen haploxylon began to increase at the beginning of the holocene and pinus subgen diploxylon has been highly dominant since the middle holocene the vegetation change after the lgm is similar to that from other sites in the lake baikal region but the responses to short term climate events are pronounced fluctuations in herb elements and vegetation cover as indicated by the par correspond to the younger dryas yd cooling event the decline in the par and increase in herb taxa were remarkable at the beginning of the yd but larix and picea trees were distributed in river valleys near lake baikal in the latter half the rapid expansion of betula and artemisia following frequent fires in the early holocene may have been in response to the 8 2 cal ka bp cooling event from these findings the southern lake baikal region including the selenga river basin may possibly have been more sensitive than other parts of the region to abrupt climate changes

high time resolution ams 14c data sets for lake baikal and lake hovsgol sediment cores changes in radiocarbon age and sedimentation rates during the transition from the last glacial to the holocene abstract high time resolution 14 c dating of lake baikal sediment cores indicates negative and positive anomalies of calculated linear sedimentation rate lsr 1 1 and 35 6 cm ka respectively during the period of climate transition from the last glacial to holocene the timing of the lake baikal apparent lsr anomalies is consistent with that of the changes in the atmospheric radiocarbon concentration 14 c during younger dryas rapid cooling event 14 c dating of lipids in the lake baikal surface sediments revealed that the sources of sedimentary lipids were different in each basin in the northern basin of lake baikal the 14 c age of total lipids from the surface sediment 4 0 14 c ka was found to be older than that of toc 1 6 14 c ka by contrast the 14 c age of total lipids in the southern basin was younger than that of the toc by ca 0 7 3 0 ka in the lake hovsgol sediment cores ages of the main lithologic boundaries during the last glacial interglacial transition were estimated based on new 14 c data sets toc concentration in the cores started to rapidly increase at 13 8 0 3 14 c ka at the base of the basinwide finely laminated layer deposited during bolling allerod the base of the layer diatomaceous mud corresponds to the end of younger dryas event 10 6 0 1 14 c ka

muted climate variations in continental siberia during the mid pleistocene epoch the large difference in carbon and oxygen isotope data from the marine record between marine oxygen isotope stage 12 mis 12 and mis 11 spanning the interval between about 480 and 380 kyr ago has been interpreted as a transition between an extremely cold glacial period and an unusually warm interglacial period with consequences for global ice volume sea level and the global carbon cycle1 2 3 4 the extent of the change is intriguing because orbital forcing is predicted to have been relatively weak at that time5 here we analyse a continuous sediment record from lake baikal siberia which reveals a virtually continuous interglacial diatom assemblage a stable littoral benthic diatom assemblage and lithogenic sediments with interglacial characteristics for the period from mis 15a to mis 11 from about 580 to 380 kyr ago from these data we infer significantly weaker climate contrasts between mis 12 and 11 than during more recent glacial interglacial transitions in the late pleistocene epoch about 130 to 10 kyr ago for the period from mis 15a to mis 11 we also infer an apparent lack of extensive mountain glaciation

lake baikal record of continental climate response to orbital insolation during the past 5 million years the sedimentary record of biogenic silica from lake baikal in south central siberia suggests that this region of central asia was impacted by two major cooling episodes at 2 8 to 2 6 and 1 8 to 1 6 million years ago the spectral evolution of this continental interior site parallels the evolutionary frequency spectra for various marine oxygen isotope records in the baikal record the 41 000 year obliquity cycle is particularly strong from 1 8 to 0 8 million years ago variance in the 100 000 year eccentricity band increases during the past 0 8 million years the expected precession frequency of 23 000 years is highest during the past 400 000 years the modulation of the predicted 23 000 and 41 000 year insolation forcing by the 100 000 and 400 000 year eccentricity bands indicates that the transfer of variance from the precession and obliquity frequencies to the eccentricity part of the spectrum occurred in the eurasian continental interior as well as in tropical and high latitude ocean sites

late pleistocene and holocene vegetation and climate records from lake kotokel central baikal region abstract climatically driven late pleistocene and holocene vegetation changes were reconstructed based on pollen records from the sediments of lake kotokel and cheremushka bog located on the eastern shore of lake baikal the described paleoenvironmental record has higher resolution than records collected from lake baikal and unites individual events identified in prior studies of bottom and onshore cores remarkable shifts in landscapes and expansions of index plants are as follows forest tundra and or forest steppe landscape with birch spruce artemisia and poaceae prevailed at ca 50 25 14 c kyr bp tundra and or steppe vegetation dominated by artemisia and poaceae was typical for the last glacial maximum the expansion of shrub birch and willow occurred at ca 15 5 14 c kyr bp two peaks of spruce expansion at ca 47 5 42 4 14 c kyr bp karginian time and at ca 14 5 13 ka bolling allerod warm intervals suggest that the condition were more humid than today a slight increase in artemisia at ca 11 10 5 14 c kyr bp 13 12 ka was indicative of the younger dryas event an expansion of birch forests with fir at ca 12 6 4 ka suggests higher humidity the currently dominant scots and siberian pine forests with birch expanded since 6 4 ka

late glacial vegetation and climate oscillations on the southeastern tibetan plateau inferred from the lake naleng pollen profile we present a late glacial pollen record 17 700 to 8500 cal yr bp from a lake naleng sediment core lake naleng is located on the southeastern tibetan plateau 31 10 n 99 75 e 4200 m along the upper tree line variations in the summer monsoon are evident from shifts in vegetation that correspond to late glacial climate trends from other monsoon sensitive regions alpine steppe was recorded between 17 700 and 14 800 cal yr bp indicating low effective moisture at the study site expansion of alpine meadows followed by advances in the position of tree line around lake naleng suggest that climate became warmer and wetter between 14 800 and 12 500 cal yr bp probably representing an enhancement of the asian monsoon climatic cooling and reduced effective moisture are inferred from multivariate analysis and the upward retreat of tree line between 12 500 and 11 700 cal yr bp the timing and nature of these shifts to warm wet and then cold dry climatic conditions suggest that they correspond to the bolling allerod and younger dryas intervals abies betula forests representing warm and moist conditions spread during the early holocene

topography of closed depressions scarps and grabens in the north tharsis region of mars implications for shallow crustal discontinuities and graben formation abstract using viking orbiter images detailed photoclinometric profiles were obtained across 10 irregular depressions 32 fretted fractures 49 troughs and pits 124 solitary scarps and 370 simple grabens in the north tharsis region of mars these data allow inferences to be made on the shallow crustal structure of this region the frequency modes of measured scarp heights correspond with previous general thickness estimates of the heavily cratered and ridged plains units the depths of the flat floored irregular depressions 55 175 m fretted fractures 85 890 m and troughs and pits 60 1620 m are also similar to scarp heights thicknesses of the geologic units in which these depressions occur which suggests that the depths of these flat floored features were controlled by erosional base levels created by lithologic contacts although the features have a similar age both their depths and their observed local structural control increase in the order listed above which suggests that the more advanced stages of associated fracturing facilitated the development of these depressions by increasing permeability if a ground ice zone is a factor in development of these features as has been suggested our observation that the depths of these features decrease with increasing latitude suggests that either the thickness of the ground ice zone does not increase poleward or the depths of the depressions were controlled by the top of the ground ice zone whose depth may decrease with latitude deeper discontinuities are inferred from fault intersection depths of 370 simple grabens assuming 60 dipping faults that initiate at a mechanical discontinuity in tempe terra and alba patera and from the depths of the large flat floored troughs in tempe terra the frequency distributions of these fault intersection and large trough depths show a concentration at 1 0 1 6 km depth similar to data obtained for syria sinai and lunae plana the consistency of these depth data over such a large region of western mars suggests that a discontinuity or a process that transcends local and regional geology is responsible for the formation of these features if this discontinuity is represented by the base of the cryosphere its uniform depth over 55 of latitude suggests that the cryosphere did not thicken poleward alternatively the concentration of depths at 1 0 1 6 km may represent the upper level of noneruptive dike ascent lateral dike propagation of mars which is controlled by gravity and atmospheric pressure and magma and country rock characteristics and was probably controlled in part by ground ice fault intersection depths in the north tharsis region locally extend down to a depth of 5 7 km the depth data between 2 and 3 km are attributed to the discontinuity at the interface of megaregolith and basement or to the upper limit of noneruptive dike ascent of magma with a high volatile content intersection depths greater than 3 km which were found at alba patera may be due to the megaregolith basement discontinuity which was buried and depressed by volcanic loading or to the upper level of noneruptive dike ascent of magma with a low volatile content the near absence of narrow simple grabens with fault initiation depths less than 0 6 1 0 km in this study area as well as in most of western mars suggests that this depth represents the minimum depth that normal faults can initiate at shallower depths tension cracks or joints would form instead this hypothesis is supported by the application of the griffith failure criterion to this minimum depth of normal fault initiation which suggests that shallow crustal materials have a tensile strength of 2 4 mpa throughout most of western mars in close agreement with previous estimates of tensile strength of martian basaltic rock