seismic and geoelectric evidence for collisional and extensional events in the fennoscandian shield implications for precambrian crustal evolution extensive deep seismic and electromagnetic sounding programs have resulted in tens of deep refraction seismic profiles normal incidence reflection profiles several hundred magnetotelluric soundings and several magnetovariational array observations results are compiled into four maps 1 moho depth 2 thickness of the lower crustal high velocity layer vp 7 km s 3 depth to the upper interface of the high velocity layer and 4 distribution of upper and middle crustal electrical conductors the moho depth is approximately 40 km in the archaean domain and varies between 40 and 65 km in the svecofennian domain most of the thickness variation 0 24 km is concentrated in the lower crustal high velocity layer electrically the crust is formed of several rather homogeneous either resistive or conductive blocks that are bounded by upper and middle crustal conductive zones the cratonized archaean crust experienced an extensional phase during which a thin mafic lower crustal high velocity layer was produced in association with mafic dykes 2 2 2 1 ga and well conducting volcanogenic and metasedimentary belts 2 5 2 0 ga the moho of the archaean domain was consequently reformed in the early proterozoic major thickening of the crust 50 65 km occurred when a svecofennian island arc and the archaean craton collided the svecofennian orogeny 1 76 1 9 ga resulted in a collage of metasedimentary rocks squeezed between crustal blocks of the island arc the internal terrane boundaries are seen as good reflectors and or inclined or vertical conductors that extend at least to the middle crust the thick high velocity 7 km s lower crust is a combination of mafic lower crust of the island arc crustal blocks and mafic additions from either delamination of the lithosphere after the collision or from a period of late svecofennian subduction the collisional boundary is also preserved as a discontinuous conductive zone between the archaean and svecofennian domains the thickened crust was subsequently thinned to 42 km along e w striking zones during an extensional period characterized by the intrusion of anorogenic rapakivi granitoid batholiths coeval mafic dykes and gabbro anorthosite bodies 1 6 1 5 ga the crust of the central part of the shield has since remained virtually intact

la icp ms analysis of pressed powder pellets to luminescence geochronology abstract laser ablation inductively coupled plasma mass spectrometry la icp ms is applied to determining the concentrations of radioactive isotopes 87 rb 232 th 234 u and 238 u in soil samples from lake baikal russia for an annual dose estimation for luminescence dating after an examination of pellet making procedures the dried sediments were pressed into pellets the concentrations of radioisotopes were successfully measured taking the national institute of standards and technology standard glass srm 610 from nist as an external standard reference material to convert the signal intensity to a concentration when the laser ablation setting is chosen to send a significant amount of material to the mass spectrometer e g the repetition frequency of 20 hz and spot diameter of 140 m a very small quantity of 234 u 10 ppb order could be measured and the resultant concentration agreed with the result obtained by conventional alpha spectrometry analyses radioisotopes along with other major elements measurable by la icp ms can be measured quickly on fine grained sediments e g lake and deep sea sediments of small quantity by the simple procedure proposed here

cyclic climate and vegetation change in the late miocene of western bulgaria abstract a late miocene paludal to lacustrine sequence from a carbonate basin in nw bulgaria staniantsi basin is analysed displaying up to 27 rhythmically bedded sedimentary cycles in the lower part of the sequence the cycles consist of alternating autochthonous brown coal and marls containing diverse mollusc assemblages the upper part of the sequence is characterized by alternating dark to light grey clays and calcareous silts a palynomorph record comprising 163 samples is analysed by statistical means to reconstruct vegetation changes the coexistence approach is used to calculate quantitative palaeoclimate records for 6 parameters the studied section displays hierarchical cyclicity patterns longer term cycles possibly related to eccentricity period 100 kyr are present in the palynomorph record and show climate changes of warmer wetter and cooler drier periods in combination with frequency oscillations of thermophilous elements short term cycles most probably related to precession period 21 7 kyr are expressed by alternations of brown coal and marl shell beds and show cyclic change in peat forming vegetation related to oscillations of the groundwater level as a triggering mechanism wetter warmer and drier cooler climate phases related to orbital precession are probable in addition sections sampled at high resolution display small scale climate and vegetational variability as is shown by the analysis ferns were an important component of the peat forming vegetation while outside the mire a wetland vegetation consisting of pioneers and a mixed mesophytic forest with evergreen shrubs existed an oligo to mesotrophic slightly alkaline lake became repeatedly established with a diverse mollusc fauna and a dense hydrophytic vegetation with characean meadows in the upper part of the section a spreading of herbaceous vegetation is observed also known from other contemporaneaous palynomorph records in bulgaria and surrounding areas the increase of asteraceae in the upper part of the section combined with a marked decrease in woody taxa points to an opening of habitats and a decrease in mean annual precipitation this trend is paralleled by the mollusc fauna which yields several terrestrial partly xerophilous taxa

time variation in coarse materials from lake bottom sediments and secular paleoclimatic change variations in the percentage of materials coarser than 4 5 phi in sediment from lake biwa are closely related to global climatic change and are indicative of large fluctuations in sediment discharge into the lake coarse materials increased markedly during the interglacials postglacial and last interglacial periods the variations also are linked with solar insolation and have distinct periods of about 20 000 and 40 000 years which correspond to the periods of the obliquitical and processional parameters periods of 60 000 and 120 000 years are major in the variations

oxygen isotope calibration of the onset of ice rafting and history of glaciation in the north atlantic region we report here that dsdp site 552a cored with the hydraulic piston corer on the west flank of rockall bank recovered an undisturbed sequence of alternating white deep sea carbonate oozes and dark coloured layers that are rich in glacial debris oxygen isotope analysis of the sequence together with detailed nannofossil and palaeomagnetic stratigraphy shows that the first major horizon of ice rafting occurred at about 2 4 myr and was preceded by a minor pulse of ice rafting at about 2 5 myr the carbon isotope record shows that the site has been bathed by a water mass of similar characteristics to present day north atlantic deep water at least since 3 5 myr

insolation values for the climate of the last 10 million years new values for the astronomical parameters of the earth s orbit and rotation eccentricity obliquity and precession are proposed for paleoclimatic research related to the late miocene the pliocene and the quaternary they have been obtained from a numerical solution of the lagrangian system of the planetary point masses and from an analytical solution of the poisson equations of the earth moon system the analytical expansion allows the direct determination of the main frequencies with their phase and amplitude numerical and analytical comparisons with the former astronomical solution ber78 are performed so that the accuracy and the interval of time over which the new solution is valid can be estimated the corresponding insolation values have also been computed this analysis leads to the conclusion that the new values are expected to be reliable over the last 5 ma in the time domain and at least over the last 10 ma in the frequency domain

delamination of eclogitized lower crust control on the crust mantle boundary in the central fennoscandian shield abstract the crustal structure of the central part of the fennoscandian shield is dominated by a high velocity lower crust hvlc vp 7 3 7 5 km s at the depth of 40 63 km in an area of ca 400 km 600 km formed in the palaeoproterozoic svecofennian orogen at 1 91 1 87 ga in the area of the hvlc the moho is deeper than 50 km and attains depths of up to 63 km in eastern finland at the archaean proterozoic boundary zone we suggest that the present moho dates back to late svecofennian time and was determined by delamination of high density eclogitized lower crust after tectonic collisional thickening of crust densities deduced from seismic and gravity data suggest a very small or completely lacking density contrast between lower crust and uppermost mantle new geological evidence from kimberlite hosted garnet xenocrysts supports the presence of a garnet population with compositions in agreement with crustal eclogitic garnets in addition small clinopyroxene garnet mineral aggregates microxenoliths show omphacitic clinopyroxene compositions therefore the presence of eclogites in the high velocity lower crust is implied although the eclogite proportion as estimated from seismic velocity data is only a few percent in the present hvlc with results on near incidence and wide angle seismic studies and geological and geochemical data on heat producing elements we modeled the svecofennian collision and the thermal evolution of the crust to provide temperature constraints for the delamination model the constructed thermal model simulates the genesis of svecofennian synkinematic at 1 89 1 88 ga and postkinematic 1 88 1 87 ga granitoids as well as the general metamorphic grade of the surface rocks and lower crustal xenoliths moreover the narrow distribution of the ages of the svecofennian mafic ultramafic magmatism ca 1 89 1 87 ga dispersed around the hvlc area is explained by the homogeneous warming of the lithosphere the conditions of lower crustal delamination were estimated with a rayleigh taylor convective instability model constrained with lower crustal and upper mantle rheological data delamination of a lower crustal eclogite layer 5 30 km thick takes place in about 7 50 ma if the rock dynamic viscosity is 1 1021 pa s it requires temperatures of 1000 c in the lower crust and upper mantle in the svecofennian crust such temperatures were attained at about 1860 1850 ma i e after the orogenic peak we conclude that the moho of the hvlc area was controlled by delamination of a ca 5 10 km thick layer of high density lowermost crust into the mantle such a density controlled process may have controlled the moho depth also in other proterozoic shield areas

facies and cyclicity of the late permian bainmedart coal measures in the northern prince charles mountains macrobertson land antarctica the late permian bainmedart coal measures form part of the permo triassic amery group which crops out in the beaver lake area of the northern prince charles mountains macrobertson land antarctica the exposed strata are believed to have formed in graben or half graben sub basins on the western edge of the lambert graben a major failed rift system sedimentological analysis has revealed that these rocks formed in alluvial environments in which swiftly flowing rivers of low sinuosity represented by facies a1 and a2 flowed northward down the axis of the basin and were associated with waterlogged floodbasin and peat forming wetlands facies b1 b4 a third facies association comprising facies c1 c3 interpreted as the deposits of lake floor and delta environments is exclusively developed within a distinctive fine grained interval here named the dragon s teeth member the proportion of association b facies within the succession increases markedly above the level of the dragon s teeth member at about 300 m above the base of the formation flat low angle and undulatory bedding structures preserved within channel deposits are suggestive of sediment deposition in flow conditions which were often critical or supercritical presence of massive and chaotic intervals of sandstone further implies some deposition from high concentration aqueous flows alluvial channel bodies show evidence of incision into underlying substrates both during initiation and at later stages in channel belt construction the lack of interfingering between channel deposits and coals suggests that thick peats formed only in areas and at times of minimal clastic sediment supply analysis of well developed cyclicity within the coal measures suggests that the dominant control on sequence architecture was climatic related to precessional milankovitch fluctuations of c 19 kyr periodicity cycles began abruptly with the deposition of coarse grained material in high energy alluvial channels which contracted with time in response to changes in water supply rainfall upper parts of cycles are dominated by finer grained sediments and then coal indicative of progressively reduced coarse sediment input tectonic processes overprinted this pattern at least once during the period of sediment accumulation to form the dragon s teeth member

long period astronomically forced terrestrial carbon sinks abstract sequestration of organic matter by peat accumulation constitutes a primary sink for carbon in the global carbon cycle the processes that control the formation and storage of peat at geological time scales are poorly understood but are of a non solved issue of fundamental importance for understanding the global climate system we analyzed a 7 million years long terrestrial record of late oligocene age from the as pontes basin in northern spain which demonstrates that minima in the 405 kyr and 2 4 myr eccentricity cycles play a key role in peat formation such nodes exhibit reduced precession amplitudes thus avoiding extremes in seasons and seasonal contrast for a prolonged period of time in the as pontes basin this orbital configuration is associated with a decrease in siliciclastic sedimentation and enhanced peat formation feedbacks between equilibrium landscapes and ecosystem stability will lead to a deceleration of weathering and erosion rates in catchment areas and to minimum and stable sediment flux along the sediment routing system mid latitude peat burial could contribute to disturb the carbon cycle by removing atmospheric carbon at times of minimum eccentricity

depositional environments and tectonic controls on the coal bearing lower to middle jurassic yan an formation southern ordos basin china the ordos basin of north central china is well known for vast energy resources this nonmarine interior basin developed on the north china korean platform following the late triassic indochina orogeny and for a time contained a large freshwater lake prior to being uplifted into its present form at the close of the mesozoic lower to middle jurassic coal occurs in the fluviolacustrine yan9an formation along the southern margin of the basin in the huanglong coalfield in the northeast part of the field the formation ranges from 0 to 180 m in thickness and is divided into five fining upward members each representing a regressive transgressive lacustrine cycle low sulfur high volatile bituminous coal is complexly distributed in the lowest member of the yan9an formation deposition of this member was influenced by two tectonic events that controlled coal occurrence first regional uplifts were produced by the late triassic indochina orogeny and left as highlands on the pre yan9an triassic land surface in the lowest member coal beds thin toward and pinch out against these highlands second syndepositional tectonism of the jurassic through cretaceous yanshan orogeny created a series of northeast trending folds that were topographically expressed as evolving highs and lows swamps and resulting peat accumulation preferentially occupied the subsiding paleodepressions because of the tectonic influence on peat accumulation coal beds thin and merge toward anticlines and thicken and split toward synclines in addition coal quality is documented to be less variable along a northeast trend than along a northwest trend

high resolution terrestrial record of orbital climate forcing in coal pre quaternary terrestrial climate records in which time has been calibrated using astronomical cycles are with the exception of lacustrine proxies poorly represented in the geological record this omission is a significant gap in our knowledge of ancient climate systems here we present new evidence of orbital periodicities in an 18 3 m thick late paleocene coal and conclude that coal has the potential to provide continuous time calibrated terrestrial climate data spectral analysis of changes in the relative proportions of vitrinite to inertinite two environmentally sensitive coal macerals reveals several characteristic frequencies some of which display evidence of amplitude modulation every five to six cycles combining this observation with depositional time limitations derived from present day rates of carbon accumulation in mires we interpret the characteristic frequencies as resulting from precession and obliquity and their influence on oxidation and decay using the inferred precession component of the data to derive an internal time scale we estimate that the wyodak coal was deposited over a period of 414 k y with a long term carbon sequestration rate of 29 g m 2 yr 1 the identification of an internal astronomical time scale in coal is an important step toward realizing the potential for coal to extend our high resolution knowledge of earth s terrestrial climate back to the formation of the first peat deposits at 360 ma

the heartbeat of the oligocene climate system a 13 million year continuous record of oligocene climate from the equatorial pacific reveals a pronounced heartbeat in the global carbon cycle and periodicity of glaciations this heartbeat consists of 405 000 127 000 and 96 000 year eccentricity cycles and 1 2 million year obliquity cycles in periodically recurring glacial and carbon cycle events that climate system response to intricate orbital variations suggests a fundamental interaction of the carbon cycle solar forcing and glacial events box modeling shows that the interaction of the carbon cycle and solar forcing modulates deep ocean acidity as well as the production and burial of global biomass the pronounced 405 000 year eccentricity cycle is amplified by the long residence time of carbon in the oceans

disentangling the control of tectonics eustasy trophic conditions and climate on shallow marine carbonate production during the aalenian oxfordian interval from the western france platform to the western tethyan domain the objective of this work is to improve our understanding of the processes controlling changes in the architecture and facies of intracontinental carbonate platforms we examined the facies and sequence stratigraphy of aalenian to oxfordian limestones of western france seventy seven outcrop sections were studied and thirty one sedimentary facies identified in five depositional environments ranging from lower offshore to backshore platform evolution was reconstructed along a 500 km cross section twenty two depositional sequences were identified on the entire western france platform and correlated with european third order sequences at the biozone level demonstrating that eustasy was the major factor controlling the cyclic trend of accommodation the tectonic subsidence rate was computed from accommodation measurements from the aalenian to the oxfordian in key localities tectonism controlled the sedimentation rate and platform architecture at a longer time scale tectonic subsidence triggered the demise of carbonate production at the bathonian callovian boundary while the uplift made possible the recovery of carbonate platform from caen to le mans during the mid oxfordian topography of the paleozoic basement mainly controlled lateral variations of paleodepth within the western france platform until the mid bathonian a synthesis of carbonate production in the western tethyan domain at that time was conducted stages of high carbonate production during the bajocian bathonian and the middle to late oxfordian are synchronous with low 13c high eccentricity intervals and rather dry climate promoting 1 evaporation and carbonate supersaturation and 2 oligotrophic conditions periods of low carbonate production during the aalenian and from the middle callovian to early oxfordian correlate with high 13c and low eccentricity intervals characterized by wet climate and less oligotrophic conditions such conditions tend to diminish growth potential of carbonate platforms this work highlights the importance of climate control on carbonate growth and demise at large scale in western tethyan epicontinental seas

sandstone type uranium deposits in the ordos basin northwest china a case study and an overview abstract this paper provides a comprehensive review on studies of sandstone type uranium deposits in the ordos basin northwest china as the second largest sedimentary basin the ordos basin has great potential for targeting sandstone type u mineralization the newly found and explored dongsheng and diantou sandstone type uranium deposits are hosted in the middle jurassic zhilou formation a large number of investigations have been conducted to trace the source rock compositions and relationship between lithic subarkose sandstone host rock and uranium mineralization an optical microscopy study reveals two types of alteration associated with the u mineralization chloritization and sericitization some unusual mineral structures with compositional similarity to coffinite have been identified in a secondary pyrite by sem these mineral phases are proposed to be of bacterial origin following high resolution mapping of uranium minerals and trace element determinations in situ moreover geochemical studies of ree and trace elements constrained the mechanism of uranium enrichment displaying lree enrichment relative to hree trace elements such as pb mo and ba have a direct relationship with uranium enrichment and can be used as index for mineralization the source of uranium ore forming fluids and related geological processes have been studied using h o and c isotope systematics of fluid inclusions in quartz veins and the calcite cement of sandstone rocks hosting u mineralization both h and o isotopic compositions of fluid inclusions reveal that ore forming fluids are a mixture of meteoric water and magmatic water the c and s isotopes of the cementing material of sandstone suggest organic origin and bacterial sulfate reduction bsr providing an important clue for u mineralization discussion of the ore genesis shows that the greenish gray sandstone plays a crucial role during processes leading to uranium mineralization consequently an oxidation reduction model for sandstone type uranium deposit is proposed which can elucidate the source of uranium in the deposits of the ordos basin based on the role of organic materials and sulfate reducing bacteria we discuss the mechanism of uranium deposition responsible for the genesis of these large sandstone type uranium deposits in this unique sedimentary basin

crustal structures of eastern fennoscandia the area of the eastern fennoscandian shield is quite well covered by deep seismic sounding profiles most of which were shot in the last ten years in general the velocities of the seismic waves in the crust increase continuously with depth but intense reflections also indicate the presence of distinct velocity boundaries the velocities of the refracted waves in the various profiles resemble each other but the depths to the boundaries vary considerably low velocity zones were found in the uppermost crust along most of the profiles the eastern karelia profiles also exhibited large low velocity zones in the lower part of the crust high velocity bodies found in the uppermost crust in eastern fennoscandia are thought to be associated with mafic intrusions and mafic metavolcanic rocks the depth to the moho shows considerable lateral variation and deep depressions in this boundary are thought to be connected with large fracture zones high pn wave velocities of about 8 5 km s are in many cases associated with these depressions

constraints on carbon accumulation rate and net primary production in the lopingian late permian tropical peatland in sw china article i nfo during the permian peatland as represented in extensive coal deposits was a major component of the global carbon cycle carbon storage in peatland is a balance between decay and net primary production npp which in turn are sensitive to variations in the concentration of atmospheric co2 and o2 to evaluate peatland carbon storage and npp during the lopingian a period thought to be characterised by higher atmospheric o2 and co2 than modern levels spectral analyses of geophysical data from a 15 1 m thick lopingian upper permian coal in southwestern china were conducted to define the time frame of temporal carbon accumulation in tropical peatland the result shows that the mineral matter content ash yield of the coal was possibly influenced by 123 ka eccentricity 35 6 ka obliquity and 21 2 ka precession milankovitch periodicities using this timeframe and an understanding of carbon loss during coalification the lopingian tropical peatland carbon accumulation rate is calculated to be 61 1 73 0 g c m 2 yr which is expected to correspond to a npp of 611 1460 g c m 2 yr respectively a comparison between the predicted pennsylvanian late carboniferous npp and modern values indicates that the permian npp calculated is consistent with geochemical and paleobotanical models supporting a proposal that productivity was mainly controlled by temporal atmospheric o2 and co2 levels

comparison of crustal structure along dss profiles in se fennoscandia summary main features of the crustal structure of the karelian and svecofennian provinces are discussed on the basis of data obtained from deep seismic sounding dss profiles across the se fennoscandian shield the data show that in the ancient karelian province the crust is thinner about 40 km the average velocity is lower about 6 4kms l and the moho boundary is a sharp discontinuity which produces strong reflections the high velocity layer in the lower crust if it exists at all is thin in the younger svecofennian province crustal thickness averages about 45 km with a velocity of 6 6 6 8 km s the reflectivity of the moho is usually weak and a high velocity layer with velocities greater than 7 km s is ubiquitous in the lower crust high velocities in the lower crust and upper mantle are found in deep moho areas beneath the younger granitic intrusions gothian complex and vyborg rapakivi granites the crust is thinner than on average

orbital tuning and correlation of 1 7 m y of continuous carbon storage in an early miocene peatland peatland is an important terrestrial carbon reservoir that contains 25 of soil carbon and accounts for 25 38 of natural methane emissions most of this carbon is contained in postglacial boreal peat our understandingof the carbon cycle within this reservoir and its links to the atmosphere is therefore restricted to periods of 1 m y spectral analysis of varying lignite color reveals that 120 m of early miocene lignite from the gippsland basin australia contains a 1 7 m y record of orbitally paced climate oscillations dominated by the response to obliquity use of the regular orbital signal indicates that the average long term rate of peatland carbon accumulation recorded in the lignite is 27 5 g m 2 yr 1 this rate is constant over periods of 100 k y and is independent of shorter term 10 k y fluctuations in climate and hydrology matching the lignite record to the theoretical insolation curve indicates that the lignite formed between 22 5 and 20 8 ma contemporaneous long term changes in lignite color and the 1 3 c 1 2 c ratios of marine foraminifera may relate to changing peatland methane flux and thus point to a link between terrestrial and marine carbon dynamics

eurobridge 95 deep seismic profiling within the east european craton abstract the eurobridge deep seismic sounding dss profile is a key component of a europrobe project to examine palaeoproterozoic processes of continental collision and crustal accretion its purpose is to establish the deep lithospheric structure of the east european craton between the exposed proterozoic and archaean complexes of the baltic and ukrainian shields in 1994 a dss experiment was recorded across the baltic sea from vastervik sweden to shventoji lithuania we report on eurobridge 95 the first onshore stage of the seismic profile it is 280 km long recorded from nw to se on the lithuanian part of the east european platform traversing the proterozoic west lithuanian granulite domain wlg and east lithuanian belt el terranes explosive shots of up to 1000 kg tnt were detonated at 10 shotpoints sp01 sp10 at intervals of about 30 km arrivals were recorded at 76 3 component seismograph stations with an average station spacing of 3 5 km providing high quality records a 11th shot of 3000 kg sp00 was fired in the baltic sea close to gotland raytracing analysis of refracted and reflected p waves has been used to determine a 2 dimensional seismic velocity model for the crust and uppermost mantle below eurobridge 95 the thickness of the phanerozoic sedimentary cover decreases from 2 2 km in the north west near the baltic sea coast to 0 4 km at the south east end of the profile near the lithuania belarus border crust in the north west and central part of profile consists of two major layers with a thickness of about 44 km increasing to 50 km and three layers in the south east crystalline upper crust is about 20 km thick thinning in the south east with p wave velocities of 6 0 6 3 km s a very weak low velocity zone with a velocity contrast of 0 1 0 2 km s occurs at 8 13 km depth below the north west and central part of the profile only lower crust exhibits velocities of commonly 6 5 6 9 km s and thickens to the south east with p wave velocities up to 7 0 km s in the deepest parts crystalline crust is characterised by low velocity gradients and small velocity contrasts at most seismic boundaries major lateral changes in crustal velocity structure at all depths can be spatially correlated with the wlg el boundary determined from near surface geological information very strong reflections from the moho boundary are observed the mantle p wave velocity immediately below the crust is 8 2 8 35 km s a reflector in the lower lithosphere at a depth of almost 70 km was found below lithuania reflectivity modelling of the gotland shot data suggests that this interface is absent offshore where mantle velocities are lower the dss model supports the interpretation of the wlg and el as terranes of proterozoic age forming part of fennoscandia later modification of crustal structure may have occurred possibly by a mantle heating episode centred on the baltic sea area

orbital forcing in pliocene pleistocene mediterranean lacustrine deposits dominant expression of eccentricity versus precession abstract milankovitch forcing of climate is expressed in the sedimentary record as lithological cycles that can have one or more of four typical periods related to precession 21 kyr obliquity 41 kyr and eccentricity 100 and 400 kyr in several mediterranean continental successions striking differences in the expression of particularly precession and eccentricity appear we present the results of an additional lower pliocene lacustrine succession from lupoaia southern romania and compare the cyclic expression in this lignite siliciclastic basin in detail with the time equivalent lignite carbonate basin of ptolemais northern greece the middle pleistocene lignite siliciclastic basin of megalopolis southern greece and the miocene carbonate clay basin of orera north eastern spain it appears that carbonate basins dominantly express precession while siliciclastic basins dominantly express eccentricity in their lithological cycles this can be explained by a more linear response to insolation forcing in carbonate basins than in siliciclastic basins alternatively it can be explained by the low amplitude of 100 kyr eccentricity at the times the carbonate sections were deposited this reduced 100 kyr amplitude was caused by minima in the 2 35 myr eccentricity cycle that co occurred with the deposition in both carbonate basins finally the expression of 100 kyr eccentricity appears to be independent of glacial cyclicity

pollen record and integrated high resolution chronology of the early pliocene dacic basin southwestern romania an integrated stratigraphic study has been performed on four early pliocene fssections in the western dacic basin including the long reference section of lupoaia based on the integration of mediterranean nannoplankton assemblages the regional lignite stratigraphy records of large and small mammals large climatic fluctuations according to pollen grains and climatostratigraphic relationships at the european scale it has been possible to establish a magnetostratigraphic correlation of the different sections to the geomagnetic polarity time scale gpts this correlation suggests that all normal episodes of the early pliocene from thvera to cochiti chrons are recorded hence the complete pollen record covers an almost continuous time span from about 5 33 to 4 30 ma in addition the regional dacian romanian stage boundary in the dacic basin is located in the nunivak c3n 3n episode with an age of 4 55 0 05 ma our chronologic calibration combined with high resolution pollen data results in a detailed record of paleoclimate in which the 100 kyrs and 400 kyrs eccentricity cycles are clearly identified

crustal structure of the baltic shield based on off fennolora refraction data abstract since the early 1960s deep seismic sounding experiments have been carried out on the baltic shield in this study we will mainly concentrate on the results obtained from two international profiles sveka and baltic carried out in finland in 1981 and 1982 results from these profiles are shown and discussed and compared with those obtained from the fennolora and from the other recent refraction profiles of the baltic shield in fennoscandia according to the results from sveka and baltic and average crustal velocity is 6 6 6 7 km s which is rather high several distinct reflection boundaries have been found within the crust in the lower part of the crust a high velocity layer with a p wave velocity of 7 0 7 5 km s has been found in some cases in addition the results indicate that the crustal structure has a clear block like character different blocks being separated from each other by deep fractures the crustal thickness in the baltic shield is about 45 km on average whereas around the ladoga bothnian bay zone in central finland it is about 10 km thicker than this thus there is a large scale depression in the moho boundary in the central part of the baltic shield

polar lows over the gulf of alaska in conditions of reverse shear abstract the formation of two polar lows over the gulf of alaska are studied using observations taken during the ocean storms field experiment synoptic scale and mesoscale analyses were constructed using noaa p 3 aircraft flight level and radar data and drop windsonde profiles in addition to conventional data sources the synoptic scale analyses show that polar low development occurred in a low level mesoscale baroclinic zone near the center of a mature occluded synoptic scale low pressure system the disturbances propagated along the zone in the reverse shear sense i e in the direction opposite to the thermal wind within the zone the mesoscale analysis reveals a boundary layer jet of 38 m s 1 on the cold side of the baroclinic zone accompanying the leading polar low indirect evidence suggests that a sawyer eliassen secondary circulation was present polar low development occurred in the region of a frontogenetical geostrophic deformation convective activity was not prominent during the growth p

tectono magmatic control on vertical dip slip basement faulting an example from the fennoscandian shield vertical dip slip basement faults play an important role in the evolution and structuring of the earth s crust the proterozoic anorogenic rapakivi anorthosite setting of the fennoscandian shield in southern finland exhibits a widespread pattern of vertical dip slip basement faults that are deeply eroded the porkkala mantsala pm fault located c 30 km w of helsinki is part of a system of crustal lineaments that closely follows the outcrop pattern of mid late proterozoic anorogenic crustal elements such as basic dyke swarms the outline of rapakivi granites and remnants of sediment filled grabens these lineaments are formed by low grade dip slip faults that overprint svecofennian shear zones structural analysis of the pm fault supports an interpretation in terms of reactivation of a high grade ductile wrench zone successive stages of brittle deformation visible in as well the pm fault and the obbnas granite demonstrate that brittle deformation in the pm fault is coeval with the intrusion of the anorogenic obbnas rapakivi granite based on the spatial and temporal relationship of anorogenic magmatism and block faulting a genetic relationship is proposed

late cretaceous orbitally paced carbon isotope stratigraphy from the bottaccione gorge italy abstract a refined astronomical tuning of the upper albian lower campanian is proposed from the bottaccione reference section gubbio central italy long term eccentricity cycles filtered from a high resolution 13c record were tuned to the highly stable 405 kyr cycles of the new la2010 astronomical solution for the earth s orbital elements the achieved orbital tuning provides a new precise and accurate age model for dating biostratigraphic magnetostratigraphic and carbon isotope events through a 23 myr long record cycles of 8 0 4 7 3 4 and 2 4 myr modulate the entire 13c record thus extending their detection from the cenozoic to 100 ma and represent primary and stable long term oscillation modes of earth s climate ocean system although an ultimate driver of these long term periodicities is lacking we speculate that specifically the periodicity at 4 7 myr represents a homologue of the present eccentricity grand cycles evolved by the chaotic behaviour of solar system planets during the mesozoic the long term periodicities potentially reflect an unexplored expression of the low frequency response of the carbon cycle to global biogeochemical dynamics of major nutrients particularly phosphorus associated with modulation of inputs to the ocean in turn triggered by high order marine transgressions and formation of highly productive shelf seas this very long term eccentricity control modulated by periodic low energy cycles is suggested to play a crucial role in carbon cycling controlling a chain of climate sensitive global biogeochemical processes on the earth finally these grand cycles provide a potential tool for geological correlation and provide a robust constraint for accurate calculation of the orbital evolution of the solar system

origin and dynamics of fe and mn sedimentary layers in lake baikal remobilization and accumulation of iron and manganese were measured by porewater and sediment core analyses at six contrasting sedimentary environments of lake baikal with bulk sedimentation rates varying between 0 8 and 0 02 mm year 1 the results allow for the distinction between two types of fe and mn diagenesis in areas of relatively high sedimentation and in regions of low sedimentation rates in the first case only small fe mn enrichments near the sediment water interface were observed in the central and southern basins at the high sediment flux area near the selenga delta and in maloe more strait massive sedimentary layers enriched in fe and mn were found within the upper 15 25 cm of the sediments exclusively in northern baikal and in the underwater academician ridge which are characterized by low sedimentation rates and deep sulfate penetration depths in the porewaters the mn content in the enriched layers ranged from 10 5 mol cm 2 at the sites near the selenga delta up to 10 2 mol cm 2 at academician ridge the accumulation times for the enriched fe mn layers calculated from the size of the fe and mn oxide pools and the diffusive fluxes into the enriched zones also varied by a factor of 1000 they ranged from a few years near the selenga delta to several thousand years for the sites at academician ridge and northern baikal these values were generally congruent with the sediment age of the accumulation zones calculated from sedimentation rates these findings have significant implications for paleolimnological studies iron and manganese dynamics at sites with high sedimentation rates is dominated by allochthonous input which is only partially dissolved close to the sediment surface in contrast the massive fe mn sedimentary layers at sites of slow sedimentation are of autochthonous origin slow dissolution and reprecipitation maintain their constant position with respect to the sediment surface and prevent burial as long as the sedimentation regime remains constant buried fe mn sedimentary layers widespread in lake baikal may therefore serve as general indicators for low sedimentation rates and as specific proxies for sudden changes in the sediment regime d 2004 elsevier b v all rights reserved

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

the moho depth distribution in fennoscandia and the regional tectonic evolution from archean to permian times abstract from a variety of seismic refraction and reflection profiling results a new detailed moho depth map for the fennoscandian part of the baltic shield has been compiled a complementary crystalline crustal thickness map was compiled for denmark the skagerrak sea offshore western norway and adjacent areas where sedimentary strata reach maximum thicknesses of 10 km and even more these maps are discussed in relation to tectonic evolution and crustal ages of fennoscandia seismic velocities bouguer gravity and seismicity areas deviating from the proposed age thickness relationships are the kola peninsula archean and the oslo rift permian the average crustal thickness in the former area is around 44 km while the latter area is associated with a moho elevation of 3 5 km maximum crustal thicknesses in excess of 50 km have been found in southwestern and central finland and correlate with a crust of proterozoic age the caledonides of western norway do not exhibit as elsewhere a crustal root sub moho p n and s n seismic velocities are relatively small in that area and bouguer gravity values are strongly negative intracrustal p velocity variations do not seem to reflect geological age or specific tectonic features although the seismicity is moderate in fennoscandia most of the earthquake activity and in particular the largest earthquakes are confined to areas where the crustal thinning is most pronounced

long term climato limnological oscillation during the past 2 5 million years printed in lake baikal sediments the physical properties of long sediment cores bdp96 obtained from the academician ridge of lake baikal eastern siberia show that the changes in the climato limnological environment of the continental interior during the past 2 5 m y clearly reflected global climatic change oscillation in water content and grain size which are closely related to biogenic productivity coincides with marine 18o variation the values for water content and grain size are large during interglacial periods and small during glacial periods milankovitch parameters were also imprinted in the sediments over the past 2 5 m y a 400 ky period as well as a 100 ky period due to eccentricitical parameters is found in addition to other orbital parameter a 40 ky period of obliquitical and a 20 ky period of precessional parameter this indicates that change in solar insolation was closely related to long term variations in climato limnological regime in this area

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 precision u pb zircon age calibration of the global carboniferous time scale and milankovitch band cyclicity in the donets basin eastern ukraine 1 high precision id tims u pb zircon ages for 12 interstratified tuffs and tonsteins are used to radiometrically calibrate the detailed lithostratigraphic cyclostratigraphic and biostratigraphic framework of the carboniferous donets basin of eastern europe chemical abrasion of zircons use of the internationally calibrated earthtime mixed u pb isotope dilution tracer and improved mass spectrometry guided by detailed error analysis have resulted in an age resolution of 0 05 or 100 ka for these carboniferous volcanics this precision allows the resolution of time in the milankovitch band and confirms the long standing hypothesis that individual high frequency pennsylvanian cyclothems and bundles of cyclothems into fourth order sequences are the eustatic response to orbital eccentricity 100 and 400 ka forcing tuning of the fourth order sequences in the donets basin to the long period eccentricity cycle results in a continuous age model for the middle to late pennsylvanian moscovian kasimovian ghzelian strata of the basin and their record of biological and climatic changes through the latter portion of the late paleozoic ice age detailed fusulinid and conodont zonations allow the export of this age model to sections throughout euramerica additional ages for mississippian strata provide among the first robust radiometric calibration points within this subperiod and result in variable lowering of the base ages of its constituent stages compared to recent global time scale compilations

models of crustal anatexis in volcanic rifts applications to southern finland and the oslo graben southeast norway summary crustal anatexis in volcanic rifts is discussed in terms of a 1 d numerical model incorporating lithospheric extension emplacement of hot mafic magma at crustal levels various crustal compositions and pre rift conditions only the volume of melt generated by anatexis is considered crustal melt segregation transport and emplacement at higher levels are not included we find that under a broad range of conditions influx of mafic magma to the crust is required for substantial anatexis to take place and once this stops silicic magmatism dies out rapidly in many rifts the observed change in type of magmatism from predominantly mafic to silicic during rifting is probably more due to a diminishing potential for mafic magmas to ascend though the crust than to an actual halt in mafic melt generation at depth this has important implications where melt production rates are used to analyse the formation of volcanic rifts and margins when influx of mafic magmas takes place over a finite period of time they may be focused in the depth region where the potential for anatexis is largest and in some cases more anatexis can occur than by instantaneous emplacement of the entire mafic body our results support the idea that the 1 6 gyr old rapakivi granites in southern finland were formed by anatexis of an intermediate to felsic svecofennian crust provided a mantle thermal anomaly of 200 250 c existed beneath finland the seismically observed 10 km thick magmatic underplated body could have produced the exposed silicic rocks which are on average 2 3 km thick in the oslo graben in southeast norway where the thickness of magmatic underplating is also about 10 km the amount of rock produced by anatexis is poorly constrained but appears to be between 1 and 2 km provided the pre rift crustal thickness in the graben was 35 40 km or more and heat was transported to crustal levels more eyciently than is feasible by conventional stretching models the model predicts melt volumes in agreement with these estimates we propose that secondary convection within the narrow graben could have contributed to the high heat transport eyciency finally a conspicuous feature of the southern finland magmatic region as well as the oslo graben is the large discrepancy between stretching factors derived from analysing dyke intrusions and faulting finland b 1 001 oslo graben b 1 05 and by using variations in crustal thickness finland b 2 oslo graben b 1 7 2 a possible explanation for this diverence may be that when large volumes of mafic rocks cause crustal anatexis the partially molten crust becomes very weak and acts as a barrier for stress propagation evectively isolating the upper crust from further deformations this could add to the thermal weakening of the ductile lower crust due to the influx of hot mafic magmas this hypothesis could be tested by investigating a large number of magmatic rifts combined with development of new rheological models of the lithosphere including the evects of underplating and anatexis

high precision u pb zircon geochronology of the late triassic chinle formation petrified forest national park arizona usa temporal constraints on the early evolution of dinosaurs the triassic successions of the colorado plateau preserve an important record of vertebrate evolution and climate change but correlations to a global triassic framework are hampered by a lack of geochronological control tuffaceous sandstones and siltstones were collected from the upper triassic chinle formation exposed in the petrified forest national park arizona usa within a refined stratigraphic context of 31 detailed measured sections u pb analyses by the isotope dilution thermal ionization mass spectrometry id tims method constrain maximum depositional ages for nine tuffaceous beds and provide new insights into the depositional history of the chinle fluvial system the base of the blue mesa member of the chinle formation is placed at ca 225 ma and the top of the petrified forest member is placed at 208 ma or younger bracketing an 280 m thick section that spans nearly the entire norian stage of the late triassic estimated sediment accumulation rates throughout the section reflect extensive hiatuses and or sediment removal by channel erosion the new geochronology for the chinle formation underscores the potential pitfalls of correlation of fluvial units based solely on lithostratigraphic criteria a mid norian age ca 219 213 ma for the distinctive sonsela conglomeratic sandstone bed constrains the adamanian revueltian land vertebrate faunachron boundary our new data permit a significant time overlap between the lower chinle sequence and the dinosauromorph rich ischigualasto formation of northwestern argentina near contemporaneity of the trans american deposits and their faunal similarities imply that early dinosaur evolution occurred rapidly across the americas

crust and upper mantle structure along the dss baltic profile in se finland summary the 430 km long dss baltic profile in se finland runs through the rapakivi intrusion the svecokarelian geosynclinal complex including the ladoga bothnian bay zone and the archean basement complex a brief description of field operations in 1982 is presented record sections of p and s waves were used for the interpretations a starting model was constructed by inverse methods and improved by dynamic ray tracing modelling three blocks are indentified on the cross section from sw to ne these are the southern associated with the rapakivi massif depth to moho m about 40 km the central ladoga bothnian bay zone with m of approximately 55 60 km and the northern archean crystalline basement with m about 40 45 km the average crustal velocity is 6 6 6 7 kms the crustal structure along the baltic profile is compared with the surrounding dss profiles finnish sveka and soviet kern tulos and ladoga profiles the eastern border of the ladoga bothnian bay zone was located and specific features of the crust and uppermost mantle along the profile area are discussed

crustal and uppermost mantle velocity structure of northern eurasia along the profile quartz the velocity structure of the crust and uppermost mantle beneath the dss profile quartz in northwestern russia is determined using a linearized seismic tomography scheme the analysis is performed on the northern 2200 km of the profile spanning from the kola peninsula the timan pechora basin and the uralian fold belt to the west siberian basin refracted and reflected phases recorded from 28 chemical and two nuclear shot points are analyzed the inversion technique allows determination of the p wave velocity structure and estimation of the depth of the crust mantle discontinuity resolution analysis shows that the upper crustal structure and sections of the lower crust and uppermost mantle are well resolved the modeled velocity and crustal thickness anomalies are confirmed by the resulting structure of the resolution matrix poorer ray coverage in parts of the lower crust and most sections of the uppermost mantle limits their resolvable structures a thick over 10 km high velocity block vp 7 0 km sec in the lower crust of the precambrian beneath the kola peninsula crustal thinning and a wide range of compressional velocities in the sedimentary basin structures and a significant crustal root beneath the uralian fold belt 42 to 45 km moho depth with high lower crustal velocities exceeding 7 0 km sec were identified in the tectonic structure of northwestern eurasia

influence of climate and hydrology on carbon in an early miocene peatland abstract our understanding of the hydrodynamic response of peatland to climate change is restricted to the holocene which confines our knowledge of the fundamental controls on this important carbon reservoir to recent sedimentary successions to understand the interaction of peatland hydrodynamics climate and the carbon cycle on longer time scales a 95 4 m record from lower miocene lignite from the gippsland basin australia is considered 13 c and colour records for the lignite were created by analysing samples every 0 1 m solid state 13 c nmr results indicate that lignite colour is related to the relative abundance of aliphatic carbon the lack of a direct correlation between colour and 13 c demonstrates that the 13 c signal has not been significantly influenced by the diagenetic processes that produce the colour an offset correlation occurs between 13 c and colour with the degree of offset decreasing from 4 5 m at the base to about 0 m at the top this offset is considered to represent a zone of surface influence that extends up to 20 m below the peat surface using numerical modelling we demonstrate that this zone of surface influence and its gradual decline in thickness could arise as a consequence of enhanced fluid flow in regions of high tensile stress within the unconfined peat body the removal of lignin and its derivatives from the zone of surface influence will be favoured by cooler drier periods with lower sea level and high hydraulic gradients across the peatland therefore in the early miocene this peatland acted as a carbon source during global cooling

seismic velocity structure across the fennoscandia sarmatia suture of the east european craton beneath the eurobridge profile through lithuania and belarus

proterozoic extensional tectonics of the central fennoscandian shield results from the baltic and bothnian echoes from the lithosphere experiment a three dimensional crustal structure of the bothnian sea is deduced from the near vertical reflection data of the crosscutting lines 1 6 7 and c of the babel baltic and bothnian echoes from the lithosphere experiment for this study the common depth point stacked sections have been migrated with a velocity 6 5 km s and displayed as stacked envelope sections to show their enhanced large scale crustal structures the seismic sections show listric shear zones which dip toward se and flatten at major detachment zones 35 40 km and 48 km in depth the detachment zones are associated with changes in p wave velocity from 6 8 km s to 7 0 km s and from 7 4 km s to 8 2 km s and coincide with the middle and lower crustal boundary and the moho boundary respectively the geometry and crosscutting relationship of the detachment zone are well developed on the e w directed line 7 from where the moho detachment zone can be interpreted as to be younger different shear zone systems operated in the parallel n s directed lines 1 and 6 and therefore it is not easy to correlate crustal structures between lines 1 and 6 in the thinned southern part of study area the lower crust has a highly reflective lamellar structure and a strongly reflective subhorizontal moho increased reflectivity of the lower crust is attributed to stretching and mafic underplating of the crust associated with the subjotnian diabase dykes and rapakivi magmatism in the upper crust the rapakivi granite and diabase association is characterized by a rather transparent area within which strong reflections mimic graben and horst structures the distribution of the bimodal association seems to be controlled by the low angle listric shear zones the spatial distribution of outcropping lithologies combined with deeply penetrating shear zones suggests a simple shear extensional deformation the first stage of deformation which concentrated in the upper and middle crust records the collapse of the overthickened svecofennian crust the second stage involving the entire crust may record either the continuation of the postcollisional collapse or a separate anorogenic extensional period the seismic structures predict major post svecofennian deformation faulting and tilting in the central fennoscandian shield the extensional tectonics operating in the fennoscandian shield in the proterozoic is comparable to modern extensional tectonics

new chronology of the best developed loess paleosol sequence of hungary capturing the past 1 1 ma implications for correlation and proposed pan eurasian stratigraphic schemes abstract in this paper we are presenting a revised chronology of the best developed longest 100 m lps in hungary dating back 1 1 ma borehole udvari 2a it is based on a non tuned age depth model built on the position of the matuyama brunhes boundary jaramillo and olduvai subchrons furthermore on the assignment of formerly recorded uninterpreted geomagnetic reversals in both chrons other chronometric tools ams 14c dating biostratigraphy tephrostratigraphy yielding absolute ages and or ensuring validation of these were also used records of a middle pleistocene gastropod index fossil neostyriaca corynodes 400 140 ka facilitated verification of ages between mis 10 and mis 6 multiple age control points at 15 25 27 45 120 191 362 430 670 780 900 990 1070 ka were established for the last ca 1 1 ma the resulting chronology is the best resolved independent one so far among danubian basin lpss in light of our data the s3 s4 units were fused as s3 in all serbian and some romanian sites and re correlated with mis 9 the results also point to a misassignment of the s5 units at these sites to mis 13 15 leading to erroneous conclusions regarding paleoclimatic conditions and cyclicity in our new stratigraphic scheme these s5 paleosols were taken to represent the s4 paleosol and recorrelated with mis 11 finally an ideal stratigraphic column dating back 1 1 ma for sw hungary was constructed and correlated with the chinese loess paleosol sequence of xifeng and the benthic oxygen isotope record down to mis 31

loess stratigraphy in central china abstract the loess deposits in central china record world wide climate changes of the last 2 5 ma numerous climatic oscillations are marked by alternating loess and soil units with continuous coverage of the matuyama and brunhes epochs magnetic susceptibility of the deposits correlates closely with the oxygen isotope record of the deep sea sediments and provides an independent measure of climate and time the key marker bed of the chinese loess sequence is the paleosol s5 the time equivalent of the mid brunhes oxygen isotope stages 13 14 and 15 it marks a prolonged interval of warm humid climate lasting from approximately 615 to 470 thousand years ago several episodes of river downcutting coincide with deposition of the exceptionally thick loess units l1 oceanic oxygen isotope stages 2 to 4 l2 stage 6 l5 stage 12 l6 stage 16 l9 stage 22 l15 stage 38 about 1 15 ma and ws4 about 2 3 ma these erosional events are interpreted as a result of episodic uplift of the loess plateau the deposition of the earliest loess layers between 2 5 and 2 3 ma ago marks a first order shift from warm and humid environments toward harsh continental steppes comparable to those of the middle and late pleistocene little if any lithologic or paleontologic changes were noted within or above the olduvai magnetozone so that the proposed plio pleistocene boundary at approximately 1 65 ma has no lithostratigraphic and biostratigraphic representation in the chinese loess series comparison with the deep sea drilling program core 552a in the north atlantic and with the santerno river section near bologna shows that the occurrence of the earliest loess in china coincides with the timing of the first significant ice rafting in the north atlantic and with the appearance of cold water foraminifers in the marine deposits of northern italy an extension of the stage system of the oxygen isotope signal extended back to the gauss matuyama boundary is proposed

forward and reverse shear environments during polar low genesis over the northeast atlantic abstractthe synoptic and subsynoptic environments associated with polar low genesis are examined ambient pre polar low environments are classified as forward or reverse shear conditions based on the angle between the thermal and mean wind forward shear environments are associated with a synoptic scale ridge over scandinavia featuring a zonally oriented baroclinic zone extending throughout the troposphere with a wind speed maximum at the tropopause similar to typical midlatitude cyclogenesis concurrent wavelike development occurs both in the lower and upper troposphere along the baroclinic zone and the mean propagation direction is eastward parallel to isolines of sea surface temperature reverse shear environments exhibit a distinctly different structure and are characterized by a trough over scandinavia associated with a synoptic scale occluded cyclone the genesis area exhibits strong cold air advection on its right hand side and polar low development occurs on the warm side of an intense low le

filtering of milankovitch cycles by earth s geography abstract earth s land sea distribution modifies the temperature response to orbitally induced perturbations of the seasonal insolation we examine this modification in the frequency domain by generating 800 000 yr time series of maximum summer temperature in selected regions with a linear two dimensional seasonal energy balance climate model previous studies have demonstrated that this model has a sensitivity comparable to general circulation models for the seasonal temperature response to orbital forcing on land although the observed response in the geologic record is sometimes significantly different than modeled here differences attributable to model limitations and feedbacks involving the ocean atmosphere cryosphere system there are several results of significance 1 in mid latitude land areas the orbital signal is translated linearly into a large 10 c seasonal temperature response 2 although the modeled seasonal response to orbital forcing on antarctica is 6 c the annual mean temperature effect

magnetostratigraphy based astronomical tuning of the early pliocene lacustrine sediments of ptolemais nw greece and bed to bed correlation with the marine record continental deposits from the early pliocene lacustrine ptolemais basin in nw greece display rhythmical alternations of lignite and marl beds three parallel sections from this area are studied using magnetostratigraphy and cyclostratigraphy the presence of the greater part of the gilbert chron enables the recognition of astronomical periodicities in the succession especially the precessional influence is evident as it determines the lithological cycles the continental ptolemais composite section is correlated to the most recent astronomical time scale and thus to the marine reference section the rossello composite from sicily c g langereis f j hilgen the rossello composite a mediterranean and global reference section for the early to early late pliocene earth planet sci lett 104 1991 211 225 on a bed to bed scale it is concluded that lignite corresponds to an insolation minimum beige layer in the rossello composite and marl to an insolation maximum grey layer in the rossello composite this implies a precipitation increase during insolation maxima in early pliocene continental greece 1998 elsevier science b v all rights reserved

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

eccentricity forcing of pliocene early pleistocene climate revealed in a marine oxygen isotope record milankovitch theory that climate is controlled by variations in the earth s orbital parameters has gained wide acceptance for its ability to account for two climate cycles a 23 kyr cycle that is phase locked to the precession driven insolation cycle and a 41 kyr cycle that is phase locked to the obliquity driven insolation cycle1 6 but explaining the observed 100 kyr climate cycle in terms of milankovitch theory especially for the late pleistocene ice age cycle remains controversial in spite of a strong correlation with the 100 kyr cycle in the earth s orbital eccentricity5 one problem is that eccentricity affects insolation mainly by modulating the precession cycle its direct contribution to radiation change is too small 0 1 to effect the observed climate change directly5 7 another is the absence of a late pleistocene ice volume cycle in oxygen isotope records to match the 404 kyr component of the eccentricity cycle5 8 here we examine an oxygen isotope record spanning the interval 1 2 to 5 2 million years ago before the late pleistocene ice age regime we find 404 kyr and 100 kyr climate cycles which are coherent with eccentricity and which have amplitudes that are similar to the coexisting 23 kyr cycle analysis of these low frequency cycles suggests that they originate through an asymmetrical response mechanism that preferentially introduces variance into the climate system from the warmer portions of the eccentricity modulated precession cycle our data thus support eccentricity s role in the origin of low frequency oxygen isotope cycles before the late pleistocene ice age

a new local magnitude scale for the finnish seismic network abstract a total of 1259 synthesized wood anderson recordings from 216 local and regional earthquakes were used to establish a new ml scale for finland the hypocentral distances of the events range from 25 to 1940 km and the reported magnitudes from 1 to 4 the attenuation function log a0 in richter s original definition of ml magnitudes and station corrections for the eleven stations used in this study were determined by a multiple linear regression analysis the shape of the attenuation function was modelled by two parametric forms the bilinear function log a0 f was described in terms of a frequency dependent anelastic attenuation and a geometrical spreading with separate rates for sg and lg domains the log a0 function comprised a single geometrical spreading term and a frequency independent anelastic attenuation term the results are as follows loga0 f 1 27log r 0 00041f0 36r 0 36 s for r 350 km loga0 f 0 83log r 0 00041f0 36r 1 48 s for 350 km loga0 f 1 42log r 0 00008r 0 15 s for r 1900 km where r is hypocentral distance in kilometers f is frequency hz and s is station correction the absolute levels of the attenuation functions were adjusted so that at 60 km the log a0 and log a0 10 hz curves equal the revised log a0 for southern california a correction was determined to accommodate the use of vertical seismograms in the ml formula the logarithm of the horizontal h to vertical z shear wave amplitude ratio was found to be distance dependent log h z 0 00009r the difference in magnitudes computed from the above distance correction functions was less than 0 1 units the frequency independent form is preferred as it is simple to apply in routine bulletin work the new ml scale can be written as ml f log a 0 00017r 0 15 s for r 350 km where a is the synthesized wood anderson amplitude mm measured from the vertical component seismogram

a numerical modeling study of mesoscale cyclogenesis to the east of the korean peninsula numerical simulations and the analysis of observational data are employed to understand the mesoscale cyclogenesis in a polar airstream that occurred over the sea to the east of the korean peninsula on 28 29 january 1995 the observational analysis shows that a mesoscale low develops over the southeastern east sea japan sea on 29 january 1995 satellite imagery also indicates that a meso b scale vortex forms on the lee side of the northern korean mountain complex kmc which is located in the northern korean peninsula and that a meso a scale cyclone develops over the southeastern east sea at a later time the mesoscale cyclone forms in the lower troposphere with strong baroclinicity and cyclonic circulation under the influence of an upper level synoptic scale cold vortex numerical simulation has captured major features of the observed cyclogenesis very well the cyclogenesis occurs in a progressive manner basically four distinctive stages of the cyclogenesis are identified 1 first a surface pressure trough forms on the lee side of the kmc under a northwesterly synoptic scale flow that is deflected anticyclonically over the kmc 2 second the lee trough deepens further into a strong convergence zone and a meso b scale vortex 3 next the meso b scale vortex develops into a meso a scale vortex as the vortex and the trough begin to move southeastward from the lee of the kmc 4 finally the surface trough deepens into a closed low and the meso a scale vortex becomes collocated with this deepening surface low to form a meso a scale cyclone over the southeastern east sea several sensitivity experiments are performed to isolate the effects of a topography warmer sea surface diurnal thermal forcing and latent heat release during stages 1 and 2 it is found that the kmc and low level baroclinicity are responsible for generating the strong lee trough and vortex during stage 3 the development of the meso a scale vortex is brought on by the tilting of horizontal vorticity and vertical stretching in a synopticscale cyclonic circulation in the final stage the condensational heating plays the key role for the development of the meso a scale cyclone under the influence of an upper level synoptic scale cold vortex the presence of the warm sea surface is found to be a necessary condition for the development of a polar air convergence zone and the mesoscale cyclone it is also found that the low level baroclinicity is essential for the present case of mesoscale cyclogenesis

mineral magnetic record of the chinese loess and paleosols variations in the magnetic susceptiblity of the chinese loess and its interbedded paleosols correlate strikingly well with the deep sea oxygen isotope record low susceptibility values are found for the loess layers and high values are found for the soil horizons two interpretative models have been advanced to account for these magnetic variations both of these models discount any significant in situ formation of magnetite during soil forming periods instead they infer relative concentration of detrital or atmospheric magnetite at these times we critically examine the assumptions made in these models and on the basis of some new mineral magnetic data and fromalized magnetic flux calculations offer an alternative explanation of the loess magnetic record our model identifies pedogenic formation of magnetite as the major contributor to the high magnetic susceptibility of the paleosols the formation and preservation of this pedogenic magnetite is dependent on soil froming conditions and hence reflects the regional climate

conceptual models for short eccentricity scale climate control on peat formation in a lower palaeocene fluvial system north eastern montana usa fluvial systems in which peat formation occurs are typified by autogenic processes such as river meandering crevasse splaying and channel avulsion nevertheless autogenic processes cannot satisfactorily explain the repetitive nature and lateral continuity of many coal seams compacted peats the fluvial lower palaeocene tullock member of the fort union formation western interior williston basin montana usa contains lignite rank coal seams that are traceable over distances of several kilometres this sequence is used to test the hypothesis that peat formation in the fluvial system was controlled by orbitally forced climate change interacting with autogenic processes major successions are documented with an average thickness of 6 8 m consisting of ca 6 m thick intervals of channel and overbank deposits overlain by ca 1 m thick coal seam units these major coal seams locally split and merge time stratigraphic correlation using a cretaceous palaeogene boundary event horizon several distinctive volcanic ash fall layers and the c29r c29n magnetic polarity reversal shows consistent lateral recurrence of seven successive major successions along a 10 km wide fence panel perpendicular to east south east palaeo flow the stratigraphic pattern complemented by stratigraphic age control and cyclostratigraphic tests suggests that the major peat forming phases resulting in major coal seams were driven by 100 kyr eccentricity related climate cycles two distinct conceptual models were developed both based on the hypothesis that the major peat forming phases ended when enhanced seasonal contrast at times of minimum precession during increasing eccentricity intensified mire degradation and flooding in model 1 orbitally forced climate change controls the timing of peat compaction leading to enhancement of autogenic channel avulsions in model 2 orbitally forced climate change controls upstream sediment supply and clastic influx determining the persistence of peat forming conditions at the scale of the major successions model 2 is supported because interfingering channel sandstones do not interrupt lateral continuity of major coal seams

astrochronology of the early turonian early campanian terrestrial succession in the songliao basin northeastern china and its implication for long period behavior of the solar system abstract the first complete early turonian early campanian lacustrine succession has been recovered from the sk i south sk is borehole in the songliao basin slb northeastern china we conducted a detailed cyclostratigraphic study of natural gamma ray gr log thorium th log and magnetic susceptibility ms data from this core spectral analysis of the upper quantou formation k 2 q 3 4 qingshankou formation k 2 qn yaojia formation k 2 y and lower nenjiang formation k 2 n 1 2 reveals a hierarchy of meter to decameter scale cycling in the data the wavelength ratios of the cycles in these stratigraphic units are 20 5 2 1 corresponding with those of milankovitch cycle periods of 405 kyr long eccentricity 100 kyr short eccentricity 37 kyr obliquity 20 kyr precession indicating astronomical control on sedimentation an astronomical time scale ats was established by tuning interpreted 405 kyr cycles to a 405 kyr orbital eccentricity target curve and to four sims u pb zircon radioisotope ages this absolute ats provides precise numerical ages for stratigraphic boundaries biozones geological and geophysical events and serves as a basis for correlation of strata and events between marine and terrestrial systems the ages of the c33r c34n geomagnetic polarity boundary in k 2 n 2 and three short reversal events in k 2 y are estimated as 83 633 ma 84 819 84 862 ma 84 982 85 092 ma and 85 240 85 629 ma respectively long period amplitude modulations in the obliquity and eccentricity bands of the 405 kyr tuned gr th series provide strong evidence that long period orbital forcing influenced climate change and depositional processes in the slb the extracted amplitude modulations provide evidence that the orbits of earth and mars were not in secular resonance and were undergoing chaotic interactions during this time although the modulations do not match those of recent astronomical models

petrogenesis of the post kinematic magmatism of the central finland granitoid complex ii sources and magmatic evolution the 188 187ga post kinematic granitoids of the central finland granitoid complex cfgc provide a key geochemical link to understanding granite formation in paleoproterozoic orogenic and post orogenic terrains thickness of the crust and intra crustal differentiation processes played an important role in the formation of three granitoid types that shortly followed the peak of the svecofennian orogeny in the eastern cfgc pyroxene bearing plutons with c type geochemical affinities predominate these were formed from a mixture of low to moderate degree partial melts 30 of mafic mantlederived basaltic 49 sio2 source rocks and partial melts of pre existing mafic granulite lower crust at depth in the western cfgc high silica iron rich fluorite bearing plutons with a type granite characteristics predominate a higher thermal gradient thinner upper and lower crust and significantly more shallow moho depth resulted in higher proportions of crustal melts 03 0 4v s 0 1 02 in the eastern cfgc incorporated into the partial melts of a mafic mantle derived source a geochemical model focusing on the j and honkajoki plutons of the post kinematic suite is presented constraining the nature of the source rock s the degree of partial melting proportions of partial melts and fractionation processes involved

long periodic variations in the earth s obliquity and their relation to third order eustatic cycles and late neogene glaciations abstract evolutive spectra of four high resolution climatic proxy records reveal that the spectral power in the obliquity frequency band increases during five well defined intervals in the last 5 3 million years these intervals correspond to periods of high amplitude variations in the tilt obliquity of the earth s axis connected with a 1 2 myr cycle and to sea level lowstands of third order eustatic cycles in the haq et al 1987 curve this implies that the development of major plio pleistocene glaciations proceeded episodically and that third order cycles are glacio eustatically controlled in at least two of these intervals sinistrally coiled neogloboquadrinids entered the mediterranean at times of glacial periods one interval starts around 2 8 ma and is characterized by the first occurrence of n atlantica s another interval begins at the plio pleistocene boundary around 1 8 ma and is characterized by the common occurrence of sinistrally coiled n pachyderma also during the late miocene third order cycles correlate well with the 1 2 myr cycle of obliquity a significant drop in the third order eustatic curve starting at the tortonian messinian boundary for instance coincides with a period of high amplitude variations in the obliquity time series connected with the 1 2 myr cycle

shallow lacustrine carbonate microfacies document orbitally paced lake level history in the miocene teruel basin north east spain results are presented of a detailed carbonate petrographic study of an upper miocene lacustrine mixed carbonate siliciclastic succession in the teruel basin spain with the aim of constraining lake level variability at different stratigraphic scales regular alternations of red to green mudstone and lacustrine limestone termed the basic cycle reflect lake level variations at the metre scale in an earlier study the basic cycle was shown to be controlled by the climatic precession cycle petrographic analysis made it possible to distinguish two main carbonate microfacies groups characteristic of very shallow transient and shallow permanent lake environments respectively in addition to the basic cyclicity the microfacies analysis reveals lake level variations on a larger scale as a consequence the astronomical forcing hypothesis of the cyclicity in the cascante section is explored further a climate modelling study of orbital extremes indicates that high lake levels could relate to enhanced net winter precipitation and runoff during precession minima consistent with mediterranean geological data using this phase relationship an astronomical tuning of the cycles is established starting from astronomical ages of magnetic reversal boundaries subsequently successive basic cycles are correlated to precession minima the tuning reveals an identical number of basic cycles in the cascante section as precession related sapropel cycles in the deep marine succession at monte dei corvi italy corroborating the precessional control of the basic cycles at cascante lake level highstands in the large scale cycle identified by the microfacies analysis relate to maxima in both the ca 100 and 405kyr eccentricity cycles again consistent with mediterranean geological data subtraction of the identified astronomically related lake level variations from the palaeoenvironmental record at cascante indicates a shift to deeper and more permanent lacustrine environments in the upper half of the section the cause of this shift remains unclear but it may be linked to tectonics non astronomical climate long period astronomical cycles or autogenic processes 2008 the authors journal compilation 2008 international association of sedimentologists

time scale controversy accurate orbital calibration of the early paleogene 1 timing is crucial to understanding the causes and consequences of events in earth history the calibration of geological time relies heavily on the accuracy of radioisotopic and astronomical dating uncertainties in the computations of earth s orbital parameters and in radioisotopic dating have hampered the construction of a reliable astronomically calibrated time scale beyond 40 ma attempts to construct a robust astronomically tuned time scale for the early paleogene by integrating radioisotopic and astronomical dating are only partially consistent here using the new la2010 and la2011 orbital solutions we present the first accurate astronomically calibrated time scale for the early paleogene 47 65 ma uniquely based on astronomical tuning and thus independent of the radioisotopic determination of the fish canyon standard comparison with geological data confirms the stability of the new la2011 solution back to 54 ma subsequent anchoring of floating chronologies to the la2011 solution using the very long eccentricity nodes provides an absolute age of 55 530 0 05 ma for the onset of the paleocene eocene thermal maximum petm 54 850 0 05 ma for the early eocene ash 17 and 65 250 0 06 ma for the k pg boundary the new astrochronology presented here indicates that the intercalibration and synchronization of u pb and 40ar 39ar radioisotopic geochronology is much more challenging than previously thought

world peat occurrence and the seasonality of climate and vegetation abstract the climatic controls on present day peat formation are examined in order to develop a uniformitarian tool for refining paleoclimate studies and to create a retrodictive model for the coals of the geologic record a peat database has been compiled for the world and the resulting patterns are compared with aspects of precipitation and temperature drawn from a gridded data set precipitation continuity through the annual cycle is important for biologic productivity in the terrestrial realm it is expressed in terms of the number of months with average precipitation above 40 mm temperature is limiting at higher latitudes where the potential growing season may be defined by the number of months with mean temperature exceeding 10 c a map predicting the growing season has been constructed from these rainfall and temperature statistics which compares very well with actual vegetation persistence through the year as measured directly from satellite instruments however biologic production will not result in peat accumulation unless groundwater levels are maintained through the growing season our peat prediction map therefore shows the percentage of time that precipitation occurs during the potential growing season present day peat accumulations are well predicted by this map

occurrence of analcime in the middle jurassic coal from the dongsheng coalfield northeastern ordos basin china abstract this paper describes the occurrence of significant authigenic analcime naalsi2o6 h2o in the middle jurassic coal from the northeastern ordos basin and discusses its origin twelve coal samples from borehole zk31 19 in the dongsheng coalfield were collected and analyzed the coals are characterized by a low medium ash yield high volatile matter and low sulfur contents the major element oxides in the studied coals are mostly at similar or much lower concentrations compared to the averages for chinese coals similarly most trace elements are depleted or in concentrations close to the respective averages for world low rank coals based on seredin dai s classification the rey rare earth elements and y in the coal mainly display n and h type distribution patterns with no ce and eu anomalies coal sample zk31 19 12 from the lower zhiluo formation contains analcime up to 23 wt with a high na2o concentration of 1 23 both on a whole coal basis the analcime occurs as lath as subhedral granular crystals in fissures or pores and as anhedral crystals in the organic matrix furthermore significant analcime has also been observed by sem in coal from the upper yan an formation sample zk31 19 10 which mainly occurrs as anhedral crystals no evidence of analcime forming from precursors of volcaniclastic material alkali zeolites or other silicates was detected therefore it is deduced that the analcime in the studied coals formed by authigenic precipitation the na2o content in the studied coal seams displays a vertical variation different from that of the ash yield ad and those of the detrital dominated elements such as sio2 al2o3 tio2 zr nb and th indicating a different origin of na compared with other detrital materials of terrigenous origin combined with the evidence of the obvious na peak in authigenic amorphous material and gypsum mineral by sem it can be inferred that the source of na may derive from the fluids the paleoclimatic change from subtropical warm and humid to semi arid and arid hot during the deposition period of the yan an to the zhiluo formation may provide favorable conditions for analcime authigenesis leading to its abundant precipitation in the lower zhiluo formation and its limited occurrence in the upper yan an formation such paleoclimatic change is also significant for the u mineralization in the lower zhiluo formation

geocarbsulf a combined model for phanerozoic atmospheric o2 and co2 abstract a model for the combined long term cycles of carbon and sulfur has been constructed which combines all the factors modifying weathering and degassing of the geocarb iii model berner r a kothavala z 2001 geocarb iii a revised model of atmospheric co2 over phanerozoic time am j sci 301 182 204 for co2 with rapid recycling and oxygen dependent carbon and sulfur isotope fractionation of an isotope mass balance model for o2 berner r a 2001 modeling atmospheric o2 over phanerozoic time geochim cosmochim acta 65 685 694 new isotopic data for both carbon and sulfur are used and new feedbacks are created by combining the models sensitivity analysis is done by determining 1 the effect on weathering rates of using rapid recycling rapid recycling treats carbon and sulfur weathering in terms of young rapidly weathering rocks and older more slowly weathering rocks 2 the effect on o2 of using different initial starting conditions 3 the effect on o2 of using different data for carbon isotope fractionation during photosynthesis and alternative values of oceanic 13c for the past 200 million years 4 the effect on sulfur isotope fractionation and on o2 of varying the size of o2 feedback during sedimentary pyrite formation 5 the effect on o2 of varying the dependence of organic matter and pyrite weathering on tectonic uplift plus erosion and the degree of exposure of coastal lands by sea level change 6 the effect on co2 of adding the variability of volcanic rock weathering over time berner r a 2006 inclusion of the weathering of volcanic rocks in the geocarbsulf model am j sci 306 in press results show a similar trend of atmospheric co2 over the phanerozoic to the results of geocarb iii but with some differences during the early paleozoic and for variable volcanic rock weathering lower co2 values during the mesozoic atmospheric oxygen shows a major broad late paleozoic peak with a maximum value of about 30 o2 in the permian a secondary less broad peak centered near the silurian devonian boundary variation between 15 and 20 o2 during the cambrian and ordovician a very sharp drop from 30 to 15 o2 at the permo triassic boundary and a more or less continuous rise in o2 from the late triassic to the present

airborne dual doppler observations of an intense frontal system approaching the pacific northwest coast airborne doppler radar data collected off the pacific northwest coast by a noaa wp 3d orion aircraft over an 8 h period on 8 december 1993 during the coastal observations and simulations with topography experiment reveal the mesoscale structure of an intense frontal system while it was well offshore and as it approached within 20 km of the oregon coastline during the offshore stage a portion of the narrow coldfrontal rainband was characterized by deep convective cores pseudo dual doppler analyses characterize the kinematic and precipitation structure of the deep convection pseudo dual doppler analyses describe the subsequent evolution of the narrow cold frontal rainband as it approached to within 20 km of the oregon coast deformation of the frontal zone appeared to cause the dissipation of one of three precipitation cores contained within the dual doppler area the precipitation cores and the strong convergence zone associated with the front conformed to some degree to the shape of the coastline near cape blanco oregon as the front neared the coast changes in the prefrontal flow that occurred as the front approached the coast were qualitatively consistent with theoretical and numerical studies of upstream orographic influence comparison of pseudo dual doppler derived velocity profiles with idealized numerical model calculations suggests that the nearshore evolution of the frontal rainband was significantly affected by an upstream influence of the coastal orography

structure and environment of polar mesocyclones over the northeastern part of the sea of japan abstractpolar mesocyclones pmcs are mesoscale cyclonic vortices that develop poleward of the main polar front the sea of japan is one region where pmcs frequently occur during winter in this paper the general characteristics of the structure and environment of pmcs that form over the northeastern part of the sea of japan and move southward are examined using composite analysis and numerical simulation the composite analyses show that the synoptic scale environment of the pmcs is characterized by a zonal temperature gradient at lower levels and a trough accompanied by cold air at upper levels these elements of the environmental field form a reverse shear the mesoscale structure of the pmcs exhibits characteristics of baroclinic development while it is also accompanied by condensational heating the numerical simulation in which the composite fields are used for the initial and boundary conditions successfully reproduces a realistic pmc in this numerical simulation the mesoscale structures are al

20 myr of eccentricity paced lacustrine cycles in the cenozoic ebro basin abstract long period orbital forcing is a crucial component of the major global climate shifts during the cenozoic as revealed in marine pelagic records a complementary regional perspective of climate change can be assessed from internally drained lake basins which are directly affected by insolation and precipitation balance the ebro basin in northeastern iberia embraces a 20 myr long continuous sedimentary record where recurrent expansions and retractions of the central lacustrine system suggest periodic shifts of water balance due to orbital oscillations in order to test climatic orbital forcing a key piece of the basin the los monegros lacustrine system has been analyzed in detail the cyclostratigraphic analysis points to orbital eccentricity as pacemaker of short to long term lacustrine sequences and reveals a correlation of maxima of the 100 kyr 400 kyr and 2 4 myr eccentricity cycles with periods of lake expansion a magnetostratigraphy based chronostratigraphy of the complete continental record allows further assessing long period orbital forcing at basin scale a view that challenges alternate scenarios where the stratigraphic architecture in foreland systems is preferably associated to tectonic processes we conclude that while the location of lacustrine depocenters reacted to the long term tectonic driven accommodation changes shorter wavelenght oscillations of lake environments still million year scale claims for a dominance of orbital forcing we suggest a decoupling between tectonic supply driven clastic sequences fed from basin margins and climatic base level driven lacustrine sequences in active settings with medium to large sediment transfer systems

multiple polar mesocyclones over the japan sea on 11 february 1997 abstract the characteristics and development mechanism of four meso scale polar mesocyclones m pcs which appeared as a vortex train over the japan sea from 0000 to 1700 utc on 11 february 1997 are studied by means of observational analyses and numerical simulations these four m pcs were first observed at 0000 utc along the southern edge of a meso scale cloud system that looked like an occluded extratropical cyclone in a japanese geostationary meteorological satellite 5 gms 5 infrared satellite image detailed evolutionary processes of these m pcs were described based on satellite and radar images the horizontal scales of these m pcs were on the order of 100 km and the spatial intervals between their centers were about 200 km their lifetimes were around 10 h the occlusion like features of the meso scale cloud system and the synoptic situation prior to the development of these m pcs are examined by using regional objective analysis ranal data of the japan meteorological agency jma in o

electromagnetic studies in the fennoscandian shield electrical conductivity of precambrian crust abstract electromagnetic em investigations of the 1980s in the fennoscandian baltic shield produced an unique and unified em data set studies include regional investigations by the magnetovariational mv method with large lateral sampling distance investigations of anomalous conductivity structures by magnetotelluric mt soundings and other em and electrical methods audio mt soundings d c dipole dipole and vlf resistivity profilings with shorter sampling distance and studies of the near surface conductivity by airborne em surveys the variety of methods provide an ability to map efficiently crustal conductivity structures from a regional scale of hundreds of kilometres down to local details of some metres in the anomalous structures the precambrian of the fennoscandian shield is characterized by roughly nw se directed elongated belts of conductors which separate more resistive crustal blocks the latter serve as transparent windows through which to probe deep electrical structure and belts of conductors as tectonic markers of ancient orogenic zones including 1 the kittila vetrenny poyas conductor 2 the lapland granulite belt and inari pechenga imandra varzuga conductors 3 the archaean proterozoic boundary conductor and 4 the southern finland conductor the conductive belts orogenic conductors indicate places where crustal masses collided and were finally sealed together enhanced conductivity in the orogenic conductors is caused primarily by an electronic conducting mechanism in graphite and sulphide bearing metasedimentary rocks estimations of the lower crustal conductivity indicate a laterally heterogeneous lower crust in the fennoscandian shield archaean lower crust seems to be in general more resistive than the early proterozoic lower crust of the karelian and svecofennian domains the lower crust in the southwestern part of the svecofennian domain and in the sveconorwegian domain seems to be more resistive than in the central part of the svecofennian domain

tempo and scale of late paleocene and early eocene carbon isotope cycles implications for the origin of hyperthermals abstract the upper paleocene and lower eocene are marked by several prominent 1 carbon isotope 13c excursions cie that coincide with transient global warmings or thermal maxima including the paleocene eocene thermal maximum petm the cie which are recorded mainly in marine sedimentary sequences have also been identified in continental sequences occurred episodically and yet appear to be paced or triggered by orbital forcing to constrain the timing and scale of the cie relative to long term baseline variability we have constructed a 4 52 million year myr long high resolution 3 kyr bulk sediment carbon isotope record spanning the lower eocene to upper paleocene c25r c24n from a pelagic sediment section recovered at odp site 1262 in the southeast atlantic this section which was orbitally tuned utilizing high resolution core log physical property and geochemical records is the most stratigraphically complete upper paleocene to lower eocene sequence recovered to date time series analysis of the carbon isotope record along with a high resolution fe intensity record obtained by xrf core scanner reveal cyclicity with variance concentrated primarily in the precession 21 kyr and eccentricity bands 100 and 400 kyr throughout the upper paleocene lower eocene in general minima in 13c correspond with peaks in fe i e carbonate dissolution both of which appear to be in phase with maxima in eccentricity this covariance is consistent with excess oceanic uptake of isotopically depleted carbon resulting in lower carbonate saturation during periods of high eccentricity this relationship includes all late paleocene and early eocene cie confirming pacing by orbital forcing the lone exception is the petm which appears to be out of phase with the 400 kyr cycle though possibly in phase with the 100 kyr cycle reinforcing the notion that a mechanism other than orbital forcing and or an additional source of carbon is required to account for the occurrence and unusual scale of this event