the bering and okhotsk seas modern and past paleoceanographic changes and gateway impact abstract the high biological productivity and an efficient biological pumping in the subarctic pacific and adjacent seas make this region important to the modern carbon cycle and both modern and the past climate of the earth knowledge of the northern marginal seas of the pacific however is unsubstantial the bering sea is located between the pacific ocean and the arctic sea and plays an important role in ocean circulation involving balances of heat salt and various chemical properties thus it is necessary to unravel the geologic history of the bering sea as a gateway to the pacific and the arctic atlantic during the last 5 million years and beyond the okhotsk sea is considered a locus of north pacific intermediate water formation today the intermediate water formation is linked with seasonal sea ice cover diatom records from the okhotsk sea demonstrate that sea ice cover was distributed on the western side of the sea and the eastern part was open water during the last glacial maximum this configuration permitted a better ventilation of the glacial okhotsk sea through increased quantity of intermediate water presumably formed there at that time

controls of basement faults on the geometry and evolution of compressional basement involved structures foreland basement involved structures commonly occur in front of major fold thrust belts as irregular chains of uplifts the variation in the map and three dimensional 3 d geometries of individual structures and their mutual spatial and angular relationships are strongly suggestive of the influence of preexisting basement discontinuities three dimensional experimental models were constructed to determine the function of preexisting frontal and lateral discontinuities in determining the geometry of the structures the models consisted of two layers with stiff clay representing the basement and soft clay representing the sedimentary cover laser scanning and 3 d surface modeling were used to determine the map geometry to compare the models with examples of natural structures from the rocky mountain foreland in wyoming planar discontinuities result in doubly plunging structures terminating against a frontal fault with a linear trace sheep mountain anticline whereas intersecting fault sets with sharp or curved intersections result in trapdoor geometries grass creek anticline opposite dipping faults result in uplifted blocks with varying relief and orientations of the structures depending on the relative orientations of the two fault trends significant strike slip faulting along the frontal fault only occurs when the angle between the two fault trends exceeds 30 chains of structures show offsets or relay patterns commonly accompanied by changes in the orientations of adjacent structures the sage creek steamboat butte chains the hamilton dome wagonhound anticline chain the maverick springs circle ridge chain and the grass creek walker dome trend in the rocky mountain foreland are examples of these configurations these patterns suggest the influence of preexisting frontal or lateral discontinuities on the trends and locations of structures lateral discontinuities are either preexisting controlling the lateral extent of structures or form during deformation to accommodate the formation of structures formed along offset frontal faults preexisting lateral faults that penetrate the entire basement commonly result in surface lateral faults bounding the surface structures however reverse faults in the basement connected by buried lateral faults result in surface structures with overlaps between them a relay of reverse faults in the basement not connected by lateral faults may develop parallel or oblique structures with transfer zones between them the mapped geometries of the experimental models and the orientations of secondary faults provide predictive analogs that can be used in the interpretation of surface and subsurface structures

a 15 000 year paleoenvironmental record from meiji seamount far northwestern pacific late glacial and holocene hemipelagic sediments from meiji seamount in the far northwest pacific contain common to abundant planktonic and benthic foraminifera for ams 14c dating for stable isotope analysis and for interpreting paleoclimate change we present here chronostratigraphic faunal and geochemical results from a piston core which indicate that during glacial times as young as 14 000 yrs bp the northwest pacific sea surface salinity was at least as low as today effectively inhibiting convective overturn between 12 000 and 13 000 yrs ago after a major flux of ice rafting there is faunal and 18o evidence of an abrupt decrease in surface ocean salinity coincident with this event was an increase in biological productivity shown by higher fluxes of calcium carbonate organic carbon opal and greater abundances and lower 13o of the benthic foraminifera uvigerina oxygen isotope ratios in uvigerina and cibicidoides show step like decreases at about 13 000 14 000 11 000 10 000 and 6000 8000 yrs bp these events may be analogous to steps in the north atlantic 18o record during meltwater events if this interpretation is correct then the temperature and salinity history of the deep pacific lags that of the north atlantic by about 1000 yrs consistent with the transport time of deep water from the north atlantic to the north pacific

quantitative resolution of eolian continental crustal material and volcanic detritus in north pacific surface sediment proxy records of continental climate and atmospheric circulation provided by analyses of eolian continental material extracted from marine sediment have resulted in significant new information concerning the behavior of these climate systems on various timescales these studies however currently are limited to certain geographic areas because no chemical or physical extraction procedure provides an unambiguous separation of eolian continental crustal material from other contaminants like volcanic detritus we employ a combined analytical and statistical procedure in an effort to extract a more refined eolian signal from areas that may be affected by volcanic detritus bulk surface sediment samples from 33 locations in the north pacific were treated using a conventional sequential extraction procedure to remove the carbonate silica and oxyhydroxide components and the residue was analyzed by instrumental neutron activation analysis inaa for la ce sm eu yb lu hf sc and th q mode factor analysis of these data shows that 99 of the variance is explained by two end members which we interpret to be continental crustal material and volcanic detritus five least squares normative analysis models were evaluated to estimate the relative amount of these end members in each sample the continental crustal component was approximated using a fine grained fraction of china loess and bulk loess the volcanic component was approximated using the compositions of average kurile kamchatka volcanic material a median ocean drilling program odp leg 145 ash and a median kurile basalt the model based on average kurile kamchatka volcanic material and the fine loess fraction gives the most accurate results central and east pacific samples typically contain up to 100 of the eolian continental crustal component while samples near japan kamchatka and the aleutians contain a majority of volcanic detritus however the highly variable composition of volcanic material can result in systematic errors up to 25 in samples dominated by volcanic detritus the geographic distribution of the compositional end members is consistent with a continental dust source originating in asia and being diluted by ash from the volcanic arcs of the pacific rim this improved identification and resolution of the eolian continental component realized in this approach should permit paleoclimatic reconstructions to be developed from sediments in significant portions of the world that were previously precluded from analysis because of limitations with chemical or physical extraction procedures

climatic bisection of the last interglacial warm period in the polar north atlantic new multiproxy marine data of the eemian interglacial mis5e from the norwegian sea manifest a cold event with near glacial surface ocean summer temperatures 3 4 c this mid eemian cooling divided the otherwise relatively warm interglacial climate and was associated with widespread expansions of winter sea ice and polar water masses due to changes in atmospheric circulation and ocean stability while the data also verify a late rather than early last interglacial warm peak which is in general disharmony with northern hemisphere insolation maximum and the regional climatic progression of the early holocene the cold event itself was likely instrumental for delaying the last interglacial climate development in the polar north when compared with regions farther south such a climatic decoupling of the polar region may bear profound implications for the employment of eemian conditions to help evaluate the present and future state of the arctic cryosphere during a warming interglacial

causes and implications of the middle rare earth element depletion in the eolian component of north pacific sediment abstract previous studies clearly demonstrate that the detrital fraction of central north pacific sediment is derived almost exclusively from wind born particles from the arid and semi arid regions in asia these conclusions are based in part on trajectories observed for westerly wind systems and on a grainsize distribution for central north pacific sediment which can only be explained by eolian transport these observations have been verified by comparing the mineralogy neodymium isotopic composition and trace element geochemistry of the sediment with its asian source region however recent geochemical investigations consistently highlight compositional differences exemplified by a mree middle rare earth element depletion and a lower th sc ratio in eolian material extracted from north pacific sediment when compared to bulk china loess the continental analog of the eolian material these geochemical differences persist even when the bulk loess is subjected to the same extraction procedure here we present experiments demonstrating that these compositional differences are caused by a combination of grainsize fractionation during transport and partial dissolution of ree and th bearing phosphatic phases during the extraction procedure two bulk loess samples from china were separated into several different grain size fractions and a split of each fraction was subjected to the extraction procedure commonly used to isolate terrigenous material from marine sediment all extracted and unextracted sample pairs were analyzed for p th sc fe la ce sm eu yb and lu the amount of p removed by the extraction procedure correlates well with both the observed mree depletion and the decrease in th sc and is most pronounced in the finest grained samples these correlations strongly suggest that the extraction procedure dissolves inorganic phosphate phases which are rich in mrees and th a comparison of the compositions of the 2 3 mm loess size fractions with central north pacific sediment shows that both of these materials are identical

mechanical analysis of the geometry of forced folds a mechanical model of forced folding comprised of an anisotropic cover overlying displaced rigid basement blocks is used to investigate the influence of various parameters on theoretical fold form shape and dip of basement fault strength of basement cover contact and degree of anisotropy of the cover we show that the degree of anisotropy in the cover largely influences the geometry of the forelimb of the forced fold folds produced in isotropic cover display forelimbs that taper from large dip angles near the basement cover contact to low dip angles at the ground surface in contrast dips in the forelimbs of folds in anisotropic cover are nearly uniform with depth we show that the basement cover contact and the shape of the basement fault largely influence the geometry of the backlimb backlimb rotation occurs in cover welded to the basement and in cover underlying curved basement faults in addition the kinematic features of the theoretical folds are compared with the fold geometry generated by parallel kink and trishear models folds in isotropic cover overlying straight basement faults closely resemble the fold forms produced by the trishear kinematic model while fold forms in anisotropic cover more closely resemble folds produced by parallel kink geometric constructions

800 000 years of abrupt climate variability we constructed an 800 000 year synthetic record of greenland climate variability based on the thermal bipolar seesaw model our greenland analog reproduces much of the variability seen in the greenland ice cores over the past 100 000 years the synthetic record shows strong similarity with the absolutely dated speleothem record from china allowing us to place ice core records within an absolute timeframe for the past 400 000 years hence it provides both a stratigraphic reference and a conceptual basis for assessing the long term evolution of millennial scale variability and its potential role in climate change at longer time scales indeed we provide evidence for a ubiquitous association between bipolar seesaw oscillations and glacial terminations throughout the middle to late pleistocene

foreland basement involved structures basement involved structures commonly occur as long irregular chains of uplifts in foreland basins these structures commonly contain significant hydrocarbon accumulations with most major fields located on the broad crests of these structures the search for complex traps in deeper targets and in subthrust structures requires an improved understanding of the geometry and evolution of these structures characteristic features of basement structures include deformation zones within the sedimentary cover that dissipate significant fault slip and gently dipping frontlimbs and backlimbs fault slip in the basement is usually accommodated in the cover by a triangular widening upward deformation zone on the forelimb with the nature of deformation controlled primarily by the mechanical stratigraphy if the cover contains interlayered competent and incompetent units the incompetent units are characterized by significant penetrative deformation whereas the competent units are faulted after a relatively small amount of penetrative deformation depending on the competency contrast between the basement and cover the nature of basement and the physical conditions of deformation the deformation zone may also propagate downward into the basement gently dipping backlimb and frontlimb panels are related to movement of the hanging wall over synclinal and anticlinal bends in the major fault respectively many basement faults are characterized by a number of synclinal fault bends within the basement which result in long and gently dipping backlimbs forelimb panels are related to anticlinal bends that typically occur at the basement cover interface as well as at one or more locations in the sedimentary cover case studies of well constrained examples of structures from the bighorn and uinta basins and the central basin platform demonstrate the development of these characteristic features and their strong dependence on the mechanical stratigraphy these models and case studies will be useful in interpreting foreland basement structures in areas with poor or limited data

deepwater formation in the north pacific during the last glacial termination between approximately 17 500 and 15 000 years ago the atlantic meridional overturning circulation weakened substantially in response to meltwater discharges from disintegrating northern hemispheric glacial ice sheets the global effects of this reorganization of poleward heat flow in the north atlantic extended to antarctica and the north pacific here we present evidence from north pacific paleo surface proxy data a compilation of marine radiocarbon age ventilation records and global climate model simulations to suggest that during the early stages of the last glacial termination deep water extending to a depth of approximately 2500 to 3000 meters was formed in the north pacific a switch of deepwater formation between the north atlantic and the north pacific played a key role in regulating poleward oceanic heat transport during the last glacial termination

geochemical multielement signatures of glacial and interglacial facies of the okhotsk sea deepwater sediments during the past 350 kyr a response to global climate changes at the orbital and millennial scales the previously dated deepwater sediment core mr06 04 pc 7r length 1723 cm 350 kyr recovered from the central okhotsk sea os was analyzed for biogenic compounds and for 63 chemical elements using the inductively coupled plasma mass spectrometry method with a high resolution 1 cm 200 years a one box model with two main members and mathematical methods based on multielemental composition of sediments for the calculation of weight fractions at each time slice of two main types of geochemical facies that dominate during considerably diverse climatic periods glacial maxima and interglacial optima were proposed and tested this model can be applied to other analogous natural systems whose sedimentation is driven by two main types of geochemical facies the application of the developed model to the studied core revealed that variations of weight fractions of the typical interglacial and glacial geochemical facies in the sediments along the core depth named as warm and cold covariators respectively change synchronously with global and regional climate variability profiles of warm and inversed cold covariators coincide tightly and their values increase during warm marine isotope stages and substages and decrease during cold ones over the last 350 kyr millennial scale changes in covariators had occurred simultaneously with abrupt variability in the os productivity and sediment lithology and with millennial global climate variability some discrepancies in the warm and inversed cold covariators calculated using specific mathematical treatments revealed the episodic influence of volcanogenic matter presented in the core by visible tephra layers and cryptotephras

uranium removal in oceanic sediments and the oceanic u balance pore water uranium data from the nw atlantic ocean cariaco trench black sea and san clemente basin are used to calculate fluxes across the sediment water interface all samples were collected in situ and show depletions in pore water u relative to the overlying water concentration the uptake rate of u derived from pore water gradients reflects the redox environment with lowest fluxes 10 g cm 2 ky in oxic su ic sediments of the nw atlantic dominated by no 3 reduction and higher fluxes 25 70 g cm 2 ky in the anoxic sulfate reducing sediments of the cariaco trench black sea and san clemente basin the anoxic fluxes compare well with previous estimates based on solid phase data calculations indicate that the areally integrated removal of u into su ic hemipelagic sediments is of greater magnitude than that into anoxic sulfate reducing sediments these fluxes are discussed in the context of the oceanic u balance the removal of u in all oceanic sediments is estimated to account for about 65 of the riverine input and this sink plus removal of u in altered oceanic crust balances the most probable value for riverine input

preservation of elemental and isotopic source identification of sedimentary organic matter the amount and type of organic matter in the sediments of lakes and oceans contribute to their paleoenvironmental and paleoclimatological records only a small fraction of the initial aquatic organic matter survives destruction and alteration during sinking and sedimentation selective degradation modifies the character of the surviving small fraction of organic matter which becomes incorporated in bottom sediments organic matter alterations can continue to sub bottom depths of hundreds of meters corresponding to millions of years source and paleoenvironmental information nonetheless remains preserved in the molecular elemental and isotopic compositions of organic matter c n and 13c values of total organic matter in particular appear to retain paleoenvironmental information for multi myr time periods

growth folds above propagating normal faults abstract growth folds above the upper tips of normal faults are ubiquitous in extensional settings especially during the early phases of extension and in salt rich basins as slip accumulates on the underlying normal fault the geometry and size of the fold changes these changes reflect the dip throw displacement and propagation rate of the underlying normal fault as well as the thickness and rheology of the overlying cover these changes also have a marked impact on the architecture and distribution of synkinematic sediments as well as the styles of secondary deformation accommodating strain within the growing fold here we analyse a large dataset of natural and physically and numerically modelled growth folds to i characterise their diagnostic features ii investigate the controls on their geometry size and differences and iii describe how they grow with increasing extensional strain we demonstrate that larger fault throws and a thicker and weaker cover are associated with larger growth folds in contrast small fault throws as well as thin and strong brittle cover are associated with smaller growth folds we show that the geometry and size of growth folds vary through time the width and thus the wavelength of the fold is established relatively early during fold growth whereas fold amplitude increases gradually with increasing fault throw fold width and amplitude become increasingly similar during fold evolution until the fold is breached by the underlying normal fault we also derive a number of preliminary empirical relationships between readily observable structural and stratigraphic parameters in our dataset that may help estimate the geometry and size of poorly exposed i e in the field or imaged i e in the subsurface growth folds in addition we discuss how fault growth models i e constant length vs propagating may impact the three dimensional evolution of growth folds finally our work shows that growth folds are likely more common than previously thought for example although they are well documented in areas characterised by weak ductile cover strata and low strain rates our dataset illustrates that growth folds may also occur in brittle relatively strong rocks and in regions with high strain rates however the underlying controls on fold occurrence remain elusive

coccolithophore caco3 flux in the sea of okhotsk seasonality settling and alteration processes abstract coccolithophore fluxes were determined in the sea of okhotsk using samples from a 1 year experiment 12 august 1990 to 12 august 1991 with sediment traps at 258 and 1061 m depth a special study was made on coccolithus pelagicus using fragmentation and the degree of etching as indicators of transport mechanisms a corrosion index for c pelagicus is developed the coccolithophore flux pattern at 258 m depth was characterised by a strong seasonality with flux peaks during autumn 1990 late november to early december and spring 1991 march the assemblage consisted almost entirely of the two species c pelagicus and emiliania huxleyi during autumn coccolithophore transportation to 258 m depth mainly occurred within cylindrical fecal pellets and marine snow aggregates of silicoflagellates and through agglutination on tintinnids grazing caused severe fragmentation of coccoliths and disintegration of coccospheres marine snow aggregates contained many intact coccospheres of c pelagicus during spring coccolithophores were probably removed from the euphotic zone by the ballast effect of sinking diatoms the coccolithophore flux peak in spring occurred immediately after the ice had retreated from the trap station and the trapped assemblage included coccoliths of subtropical species these features indicate drifting from an ice free location to the south or east the coccolith and coccosphere flux at 1061 m was respectively 7 and 12 times lower than at 258 m depth and maximum fluxes were recorded 2 months later increasing carbonate dissolution from 258 to 1061 m depth is expressed in the coccolithophore caco 3 flux reduction of 82 and in the increasing percentage of etched coccoliths of coccolithus pelagicus from 32 to 90

rapid switches in subpolar north atlantic hydrography and climate during the last interglacial mis 5e plateauing just below early mis 5e values a planktonic d 18 o minimum during the cooling event indicates that marked freshening of the surface waters accompanied the cooling we suggest that switches in the subpolar gyre hydrography occurred during a warmer climate involving regional changes in freshwater fluxes balance and east greenland current influence in the study area the nature of these hydrographic transitions suggests that they are most likely related to large scale circulation dynamics potentially amplified by gis meltwater influences

large changes in seasonal sea ice distribution and productivity in the sea of okhotsk during the deglaciations changes in the surface environment of the central sea of okhotsk were reconstructed using tex86 paleothermometry facilitated by the bit index in order to investigate paleoenvironmental changes during the glacial interglacial cycles the core top tex86 derived temperature is the same as the present day summer sea surface temperature sst suggesting that tex86 records seasonal rather than annually averaged ssts in this region the tex86 record reveals 3 c lower summer sst during glacial maxima than during interglacial periods and significant warming during the deglaciations 15 10 ka and 136 130 ka this is consistent with previous inferences of more expanded and persistent seasonal sea ice during the glacial periods than the present day and its substantial retreat during the deglaciation timing of the deglacial warming also coincided with a distinct increase in coccolithophorid productivity suggesting a causal relationship between sea surface warming and coccolithophorid blooms during the deglaciations the relationship could reflect an increase in the supply of fresh and warm water from the amur river during deglaciation which significantly impacted hydrology by facilitating sea surface stratification which in turn promoted production of coccolithophids

strain variation with progressive deformation in basement involved trishear structures abstract basement involved structures associated with reverse vertical and normal faults commonly involve non parallel shear within a triangular deformation trishear zone located on the front limbs of the structures deformation within the trishear zone is characterized by shear gradients and an associated decrease in the dips of the beds in stratigraphically higher units geometric models suggest that the layer parallel strain within the trishear zone depends on the type of fault normal reverse or vertical the dip and throw of the fault the dip of the anticlinal or synclinal axial surfaces and the distance of any unit above the initial tip of the trishear zone located at the basement sediment contact at any given location reverse faults typically show increasing layer parallel shortening followed by decreasing layer parallel shortening and a transition to extension with increasing throw the transition from contraction to extension occurs at lower values of throw for stratigraphically lower units and also for faults with smaller dips vertical and normal faults exhibit increasing layer parallel extension of all units with increasing throw with larger extension for stratigraphically lower units experimental models suggest that the trishear zone can expand with increasing fault throw the strain within the trishear zones is accommodated largely by secondary faults which are rotated with progressive deformation the strain variations in the experiments closely mimic those predicted by the geometric models for reverse vertical and normal faults

synchronous climate anomalies in the western north pacific and north atlantic regions during the last 14 000 years abstract a peat cellulose 18 o record spanning around 14 000 years from the hani peat mire in northeastern china reveals several abrupt temperature anomalies in the period from the last deglaciation through the holocene the timing of these anomalies coincides well with the notable cooling events recorded respectively using the gisp2 ice core and ice rafted sediment of the north atlantic ocean such as the older dryas inter allerod younger dryas and the nine ice rafted debris events the results demonstrate that this repeating pattern of abrupt temperature deterioration is not limited to the north atlantic area at high latitude but also exists in the western north pacific region at middle latitude the synchronous temperature anomalies possibly are resulted from the joint effects of meltwater discharge into the north atlantic ocean and reduced solar activity in the period from around 8600 to 8200 cal yrs bp the hani peat record shows a broad 18 o peak that may reflect compound climate signals resulting from the two kinds of forcing factors the temperature drop related to reduced solar activity at around 8600 8250 cal yrs bp and the temperature anomaly attributed to the meltwater effect at around 8220 70 cal yrs bp this result may provide palaeo temperature evidence for existence of the sharp 8 2 k event in the western north pacific region in addition our results have revealed that in the period from the last deglaciation through the holocene the synchronous temperature anomalies before and after the 8 2 k event seem to be related to meltwater outflow and reduced solar activity respectively it is important that the all temperature anomalies whether because of reduced solar activity in the late holocene or from meltwater discharge in the early holocene are accompanied by an abrupt decline in the indian ocean summer monsoon and abrupt strengthening of the east asian summer monsoon it is likely that reduced solar activity and meltwater outflow appear to modulate earth system changes in the same direction the influences could be compounded reduced solar activity and meltwater outburst both appear to act as triggers for occurrence of the el nino phenomenon in the equatorial pacific ocean which may result in broad teleconnections between the temperature anomaly in the northern hemisphere and abrupt variation of the asian monsoon

sea ice conditions in the okhotsk sea during the last 550 kyr deduced from environmental magnetism 1 reconstructing past sea ice conditions in the okhotsk sea is important because sea ice conditions vary in response to global climate changes which in turn may affect global ocean circulation through intermediate water mass formation we conducted an environmental magnetic study of six cores from three stations in the central okhotsk sea to better understand temporal and spatial sea ice variations intercore correlations and age estimations are based mainly on geomagnetic paleointensity an oxygen isotope stratigraphy is available for one station magnetic susceptibility ms minima are accompanied by maxima in color b the ratio of the anhysteretic remanent magnetization susceptibility to saturation isothermal remanent magnetization karm sirm and the s ratio which indicates a higher proportion of biogenic to terrigenous magnetic components this reflects enhanced ocean productivity first order reversal curve diagrams and irm component analyses support the dominance of biogenic magnetite at ms minima in contrast color b karm sirm and s ratio values are low when ms is high which indicates an increased proportion of the terrigenous component that was probably transported as ice rafted debris ird for the southern two stations ird accumulation increased in glacial and deglacial periods which implies mobile sea ice conditions even in full glacials this was succeeded by extremely enhanced ocean productivity in early interglacials which suggests nearly ice free conditions for the northernmost station on the other hand ird accumulation was low in glacials and increased in early interglacials which indicates perennial sea ice coverage with little mobility in glacials succeeding ocean productivity enhancement was delayed compared to the southern stations

okhotsk sea ice coverage and kamchatka glaciation over the last 350ka evidence from ice rafted debris and planktonic δ18o high resolution records of ice rafted debris ird and oxygen isotope records spanning an e w trending transect across the okhotsk sea unravel the marine and terrestrial cryogenic history of ne siberia over the last 350 kyr ird predominantly dispersed basin wide by sea ice shows lowest fluxes during interglacial periods implying a reduced and seasonal sea ice coverage highest ird accumulation rates are observed during glacial and deglacial periods with a more extended but highly dynamic ice cover although being rather synchronous ird fluxes are on average higher in the western okhotsk sea than in the eastern part pointing to a persistent but mobile particle supplying sea ice cover even during full glacial conditions presumably less dense in the eastern parts mis 6 is exceptional in this respect asynchronous fluxes of ird which vary spatially reflect rapid paleoclimatic and paleo glaciomarine changes ird accumulation rates were by factor 2 3 higher during mis 6 as compared to the last glacial maximum and the ird depositional center shifted from the western okhotsk sea early mis 6 toward kamchatka late mis 6 synchronous to a distinct change in the ird mineral composition both the characteristic composition of late mis 6 ird originating from the sredinny mountain range of kamchatka and their significantly enhanced accumulation rates refer to intensified iceberg dispersal across the eastern part of the okhotsk sea at 138 ka 135 ka 129 ka and 128 ka bp this scenario affords the presence of extended mountain glaciers protruding down to sea level on the western side of kamchatka anomalously light planktonic stable oxygen isotopes during mis 6 3 termination ii and mis 5 5 5 4 suggest significant freshwater supply related to the westward drainage of kamchatka glaciers the intensified kamchatka glaciation observed during late mis 6 was repeated during mis 3 iceberg discharges into the eastern okhotsk sea are observed at 60 ka 51 ka 42 ka 38 ka 36 ka and 31 ka and may partly correspond to n atlantic heinrich events

geomagnetic relative paleointensity chronostratigraphy of sediment cores from the okhotsk sea abstract we conducted a paleomagnetic study of three piston cores from the central okhotsk sea to enable inter core correlation and age estimation using relative paleointensity of the geomagnetic field which can provide the basis for paleoceanographic studies in this area the cores are composed of diatom bearing dark olive gray silty clay magnetic overprints were generally removed by alternating field demagnetization of up to 10 mt magnetic properties reveal no evidence of reductive diagenesis or magnetite dissolution the anhysteretic remanent magnetization arm was used as a normalizer for relative paleointensity estimations because there is a smaller coherence between normalized intensity and the arm than with saturation isothermal remanent magnetization sirm depths of the three cores were converted to ages by correlating relative paleointensity variations with those from ocean drilling program site 983 which was selected as a target curve because of its higher resolution than the widely used sint 800 paleointensity stack the age at the bottom of the cores is estimated to be between 360 and 540 ka inter core correlation using relative paleointensity variations reveals that changes in magnetic properties such as magnetic susceptibility and magnetic mineral grain size are not synchronous between the northernmost site and the southern two sites despite their close proximity which indicates regional differences in paleoenvironmental variations associated with glacial interglacial changes nevertheless relative paleointensity variations among the three cores are mutually consistent and agree with other published paleointensity curves which indicates that our paleointensity records are not influenced significantly by lithological changes

northern hemisphere ice sheet responses to past climate warming during periods of glaciation the northern hemisphere was swathed by large ice sheets a review of ice sheet retreat during the last two deglaciations shows that land based ice sheets responded rapidly to rising summer insolation whereas marine based ice sheets underwent a delayed but more abrupt response

distribution and formation of okhotsk sea intermediate water an analysis of isopycnal climatological data 1 in order to clarify the distribution and formation of okhotsk sea intermediate water osiw an isopycnal climatological data set based on all of the available historical observations is developed and examined the isopycnal maps clearly show that there are two direct ventilation sources for osiw dense shelf water dsw with cold and fresh properties influenced by sea ice formation in the northwest shelf region and forerunner of soya warm current water fscw which has warm and saline properties originating in the japan sea the cold and fresh water extends southward from the northwest shelf to the shelf slope off sakhalin island it suggests that dsw is transported southward by the east sakhalin current the dsw enters the kuril basin and mixes with fscw and western subarctic water wsaw originating from the north pacific to form osiw the annual mean production rate of dsw estimated from the total volume of dsw over the shelf in spring and summer is 0 67 sv 1 sv 106 m3 s the annual mean volume transport of fscw is estimated to be 0 08 sv on the basis of its cross section area and the current speed assumption of isopycnal mixing yields a mixing ratio of 1 1 0 1 among dsw wsaw and fscw to form osiw we estimate the annual production rate of osiw to be 1 4 sv the corresponding osiw s renewal time is 7 years continued assumption of isopycnal mixing yields a mixing ratio of 0 6 0 4 between wsaw and osiw to form oyashio intermediate water oyiw

benthic foraminiferal δ13c and accumulation rates of organic carbon uvigerina peregrina group and cibicidoides wuellerstorfi the glacial to interglacial 13c records of the benthic foraminifera cibicidoides wuellerstorfi and the uvigerina peregrina group from deep sea cores cannot be adjusted by a generally valid constant the 13c values of the u peregrina group largely correlate with the accumulation rates of organic carbon suggesting a local habitat effect those of c wuellerstorfi vary independently with respect to the carbon flux and record fluctuations in the 13c of the ambient bottom water isotopic composition

reconstruction of surface water conditions in the central region of the okhotsk sea during the last 180 kyrs abstract core gc9a a 6 7 m long gravity core collected from the central region of the okhotsk sea during cruise yk0712 on r v yokosuka jamstec was used to reconstruct the changes in surface water conditions by measuring biogenic components biogenic opal caco3 total organic carbon and 15n of sediment organic matter of sediment samples the age of core gc9a was determined indirectly by graphic correlation comparing the b psychometric yellow blue chromaticness values with those of well dated core md01 2415 with complement to the tephra layer k3 50 ka the bottom age of core gc9a was estimated to be about 180 kyr therefore it provides the history of surface water conditions from mis 1 to mis 6 the biogenic opal caco3 and toc contents were high during the interglacial periods as expected indicating enhanced surface water production under warm climatic conditions this condition resulted from sufficient nutrient supply to the surface waters by active vertical mixing which was validated by low 15n values of the sediment organic matter in contrast surface water productivity was depressed during the colder glacial periods probably due to the expanded sea ice distribution and limited nutrient supply however the glacial sediments had moderately high 15n values indicating enhanced nitrate utilization resulting from the limited nutrient supply caused by strong stratification of the surface water high 15n values were also observed during the deglaciation which was attributed to the increased nitrate utilization during enhanced surface water productivity however the low 15n values during the glacial and deglacial periods may be attributed to the increased supply of terrestrial organic matter diatom production was primarily responsible for surface water paleoproductivity during the interglacial periods rather than coccolithophores however the succession of glacial to early deglacial coccolithophore production and late deglacial to interglacial diatom production was remarkable corresponding to the present day seasonal phytoplankton succession such an advanced coccolithophore production relative to diatom production might be attributed to the degree of nutrient availability associated with surface water conditions on the basis of variations in the 15n value finally the opal and toc contents decreased abruptly in conjunction with a gradual decrease in caco3 content from about 2 ka which seems to implicate a late holocene sudden decrease in paleoproductivity in the central region of the okhotsk sea according to the increase in 15n values during this interval nutrient availability appears to be poor which is likely attributed to the resumed strong stratification that occurred due to the southward shift of the aleutian low atmospheric pressure system

organic geochemical proxies of paleoceanographic paleolimnologic and paleoclimatic processes abstract organic matter constitutes a minor fraction of marine and freshwater sediments yet its important contribution to the sedimentary record can be used to reconstruct marine and continental paleoenvironments the organic matter content of sediments is the residue of past biota the amounts and types of organic matter present in sediments consequently reflect environmental conditions that impacted ecosystems at different past times general sources of the organic matter are inferred from bulk properties such as elemental compositions carbon and nitrogen stable isotope ratios rock eval pyrolysis data and organic petrography details of organic matter origins are refined by analyses of biomarker molecular compositions source changes are proxies for fluctuations in sea level oceanic surface currents and continental climates algal paleoproductivity rates are indicated by organic carbon mass accumulation rates and carbon and nitrogen stable isotopic compositions these parameters record past availability of nutrients and therefore are proxies of surface mixing in the oceans and amount of land runoff to lakes sea surface paleotemperatures are recorded by the number of carbon carbon double bonds in lipid biomarkers produced by marine algae larger proportions of the double bonds are proxies for the cooler surface waters that accompanied periods of global glaciation and intervals of enhanced upwelling the 13c and d values of plant organic matter record past concentrations of carbon dioxide in the atmosphere and changes in delivery of atmospheric moisture respectively diagenesis which causes the concentration and composition of organic matter in sedimentary settings to differ from those of the original biologically synthesized materials can bias organic geochemical paleoenvironmental records the magnitude of this potential source of misinformation must always be considered and evaluated comparison of multiple organic geochemical proxies of past conditions helps to compensate for the effects of diagenetic alterations and thereby to improve interpretations of paleoenvironmental change

the salinity temperature and δ18o of the glacial deep ocean we use pore fluid measurements of the chloride concentration and the oxygen isotopic composition from ocean drilling program cores to reconstruct salinity and temperature of the deep ocean during the last glacial maximum lgm our data show that the temperatures of the deep pacific southern and atlantic oceans during the lgm were relatively homogeneous and within error of the freezing point of seawater at the ocean s surface our chloride data show that the glacial stratification was dominated by salinity variations in contrast with the modern ocean for which temperature plays a primary role during the lgm the southern ocean contained the saltiest water in the deep ocean this reversal of the modern salinity contrast between the north and south atlantic implies that the freshwater budget at the poles must have been quite different a strict conversion of mean salinity at the lgm to equivalent sea level change yields a value in excess of 140 meters however the storage of fresh water in ice shelves and or groundwater reserves implies that glacial salinity is a poor predictor of mean sea level

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

last interglacial and early glacial circulation in the northern north atlantic ocean abstract studies of marine records from the northwestern european shelf and the northern north atlantic suggest that last interglacial environments were less stable in this area than in the mid latitude atlantic the influx of atlantic water masses to the northern north atlantic was generally higher and the meridional temperature gradient was steeper during the last interglaciation than during the holocene strong north south sea surface temperature gradients during the early weichselian indicate a generally low influx of atlantic water to the northern north atlantic even during interstades

processes controlling the advance and retreat of sea ice in the sea of okhotsk using defense meteorological satellite program dmsp special sensor microwave imager ssm i sea ice data and meteorological data we investigate processes controlling the advance and retreat of sea ice in the sea of okhotsk for this investigation we apply a new algorithm to the ssm i data which is capable of calculating ice concentration and distinguishing sea ice types this algorithm is confirmed by comparison with national oceanic and atmospheric administration noaa advanced very high resolution radiometer avhrr imagery our investigations show that there exists a locality for the areas of new ice formation and the ice formation near the ice edge always occurs as a recovery after sea ice has retreated suddenly we also reveal that the speed of ice edge advance fairly coincides with that predicted by 2 of the geostrophic wind furthermore there exists a good correspondence between the times when the overall advance and retreat of ice cover begin and the decrease and increase of air temperature begin we conclude that the advance of the ice cover in the sea of okhotsk occurs primarily through ice advection by wind and that the interannual variation in the maximum sea ice extent can be interpreted by that in wind and air temperature conditions

garzon massif basement tectonics structural control on evolution of petroleum systems in upper magdalena and putumayo basins colombia abstract the garzon massif is an active laramide style basement uplift flanked by the upper magdalena valley umv and the putumayo basin in this paper we use new gravity magnetic well and seismic data for the first geophysical interpretation of the garzon massif the garzon algeciras fault has been previously interpreted as a right lateral strike slip fault the new seismic well and gravity data demonstrates that the garzon fault is also a low angle 12 17 andean age fault thrusting precambrian basement 10 17 km northwestward over miocene sediments of the umv in a prospective footwall anticline the new geophysical data as well as previous field mapping were used to produce the first gravity and magnetic maps and retrodeformable structural cross section of the northern garzon massif the new model distinguishes for the first time distinct episodes of thin skinned and thick skinned deformation in the garzon massif the model indicates approximately 43 km of early to middle miocene shortening by thin skinned imbricate thrusting contemporaneous with the uplift of the nearby southern central cordillera 9 16 ma and the main hydrocarbon expulsion event for the umv and putumayo basin this was followed by at least 22 km of late miocene 3 6 ma thick skinned andean shortening and 7 km of uplift on the symmetrical garzon thrust and a se verging basement thrust fault zone the andean uplift interrupted and exposed the hydrocarbon migration pathways to the putumayo basin 3 d volume fracture analysis was used for the first time in this paper together with the first seismic and well data published for the topoyaco and miraflor structures to test closure models for the topoyaco foothills intense fracturing is observed in the topoyaco basement monocline from the near surface to depths of over 3 5 km the high level of fracturing permitted freshwater flushing and oil biodegradation and hydrocarbon escape in contrast the miraflor 1 well located just southwest of the topoyaco block tested light gravity oil and is sealed from groundwater flushing and biodegradation by a backthrust

reconstruction of paleoproductivity in the sea of okhotsk over the last 30 kyr 1 marine and terrestrial derived biomarkers alkenones brassicasterol dinosterol and long chain n alkanes as well as carbonate biogenic opal and ice rafted debris ird were measured in two sediment cores in the sea of okhotsk which is located in the northwestern pacific rim and characterized by high primary productivity down core profiles of phytoplankton markers suggest that primary productivity abruptly increased during the global meltwater pulse events 1a about 14 ka and 1b about 11 ka and stayed high in the holocene spatial and temporal distributions of the phytoplankton productivity were found to be consistent with changes in the reconstructed sea ice distribution on the basis of the ird this demonstrates that the progress and retreat of sea ice regulated primary productivity in the sea of okhotsk with minimum productivity during the glacial period the mass accumulation rates of alkenones caco3 and biogenic opal indicate that the dominant phytoplankton species during deglaciation was the coccolithophorid emiliania huxleyi which was replaced by diatoms in the late holocene such a phytoplankton succession was probably caused by an increase in silicate supply to the euphotic layer possibly associated with a change in surface hydrography and or linked to enhanced upwelling of north pacific deep water index terms 1050 geochemistry marine geochemistry 4835 4850 1055 geochemistry organic geochemistry 4267 oceanography general paleoceanography keywords okhotsk sea paleoproductivity sediment citation seki o m ikehara k kawamura t nakatsuka k ohnishi m wakatsuchi h narita and t sakamoto 2004 reconstruction of paleoproductivity in the sea of okhotsk over the last 30 kyr paleoceanography 19 pa1016

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

experimental models of transfer zones in rift systems transfer zones in rift basins are classified into convergent divergent and synthetic based on the relative dip directions of adjacent faults within the transfer zone experimental models were constructed to determine the geometry evolution and fault patterns associated with each of these transfer zones in addition basement faults with initially approaching laterally offset and overlapping geometries were modeled the models consisted of two layers with stiff clay representing basement and soft clay representing the sedimentary cover laser scanning and three dimensional surface modeling were used to determine the map geometry to compare the models with examples of natural structures the experimental models showed many similarities with conceptual models but also showed more details and a few significant differences typically divergent transfer zones are narrower than convergent transfer zones for the same initial spacing between basement faults the differences between the different initial fault configurations approaching laterally offset or overlapping are the degree of interaction of the secondary faults the amount of overlap between the fault zones and in some cases the width of the transfer zone the main faults propagate laterally and upward and curve in the direction of dip of the faults so that the faults curve toward each other in convergent transfer zones away from each other in divergent transfer zones and in the same direction in synthetic transfer zones a primary difference with schematic models is the significant component of extensional fault propagation folding drape folding accompanied by secondary faulting within the sedimentary cover especially in the early stages of fault propagation therefore all three types of transfer zones are characterized by significant folding and related variations in the shapes of structures the transfer zones are marked by a progressive change in relief from the footwall to the hanging wall resulting in a saddle shaped geometry the hanging walls of the faults are marked by a gentle flexure or rollover into the fault with the amount of flexure increasing with fault throw away from the fault tip the geometries and fault patterns of the experimental structures match some of the observations in natural structures and also provide predictive analogs for interpretation of surface and subsurface structures and the delineation of structural traps in rift basins

glacial age hydrography of the far northwest pacific ocean stable isotope data on benthic foraminifera from more than 30 cores on the northern emperor seamounts and in the okhotsk sea are synthesized in paleohydrographic profiles spanning the depth range 1000 4000 m holocene core top benthic foraminiferal 18o and 13c data are calibrated to modern hydrographic properties through measurements of 13c of co2 and 18o of seawater cibicidoides stable isotope ratios are close to the 13c and equilibrium 18o of seawater whereas uvigerina 18o and 13c are variably offset from cibicidoides glacial maximum 13c of cibicidoides displays a different vertical profile than that of the holocene when results are adjusted by 0 32 to account for the secular change in 13c during the last glacial maximum the data coincide with the modern seawater and foraminiferal curves deeper than 2 km however at shallower depths 13c gradually increases by as much as 1 above the modern value furthermore above 2 km the benthic 18o decreases by 0 5 these results are consistent with a benthic front at 2 km in the north pacific see herguera et al 1992 but they differ from interpretations based on trace metal data which indicate a source of nutrient depleted deep water during glaciation the isotopic data suggest that during glaciation there was a better ventilated watermass at intermediate depths in the far northwestern pacific it was relatively fresher than deep waters there and deep waters were as nutrient rich as today

assessment and calibration of tex86 paleothermometry in the sea of okhotsk and sub polar north pacific region implications for paleoceanography abstract we measured tex86 indices in surface sediments and sediment cores from marginal seas and open ocean sites in the north pacific to test the accuracy of tex86 paleothermometry in the region application of the global core top tex 86 l and tex 86 h calibrations in the sea of okhotsk and northern north pacific sub polar region results in over and under estimations of tex86 derived ssts in surface sediments in deep ocean and coastal areas respectively further challenges apparent in applying tex 86 l and tex 86 h in late quaternary sediment cores from the okhotsk sea mr06 04 pc7 and northwestern pacific mr00 k03 pc1 are unrealistically warm holocene mean annual reconstructed temperatures tex 86 l and excessively cold glacial temperatures tex 86 h compared with other high latitude records and climate models application of a calibration based on a sub set of deep tex 86 h in the glacial period in the okhotsk sea core mr06 04 pc7 however a regional comparison of okhotsk sea and sub polar surface sediment tex 86 l values with observational sea water temperatures at different seasons and water depths reveals that an optimized positive correlation is obtained with summer sub surface temperatures august 20 m depth the unique hydrographic setting of the okhotsk sea region likely exerts a strong control on the ecology of gdgt producers assumed to be primarily be marine thaumarchaeota resulting in highly season and depth specific export production and a distinct regional gradient in surface sediment tex86 values when our new regional tex 86 l calibration is applied to the sediment cores tex 86 l and alkenone u 37 k temperature estimates overlap in the holocene and tex 86 l produces plausible lgm to holocene temperature reconstructions our study provides a region specific calibration and confirms the importance of acquiring local calibration equations to optimize tex86 paleothermometry for specific regions and ocean basins

the role of pre existing discontinuities in the development of extensional faults an analog modeling perspective abstract several mountainous regions are currently affected by syn or post orogenic active extension we investigate how a newly formed normal fault interacts with structures inherited from a previous contractional phase to this end we use analog models that adopt an innovative technique for performing a precut that mimics such inherited structures into a clay layer this clay layer is laid on top of a master fault simulated by two rigid blocks sliding along an inclined plane we carry out six experiments with variously oriented precuts and compare the results with those obtained in a reference isotropic experiment all other conditions are identical for all seven realizations fault evolution is monitored by taking closely spaced snapshots analyzed through the digital image correlation method we find that the upward propagation of the normal fault can be either accelerated or decelerated depending on the presence of a precut and its orientation such precuts can also promote or inhibit the formation of bending moment faults these interactions between master fault and precut also affect the shape of the fault related syncline anticline pair

tectonic evolution of the intra uplift vigodi gugriana khirasra netra fault system in the seismically active kachchh rift basin india implications for the western continental margin of the indian plate abstract the e w striking kachchh rift basin krb at the western continental margin of indian plate is located in the northern part of gujarat state india krb has undergone polyphase deformation owing to changing stress field since late triassic we establish the kinematic framework along the nw striking intra uplift vigodi gugriana khirasra netra fault system vgknfs located at the western part of the krb the vgknfs consists of 0 25 50 km long sub parallel striated reactivated dip slip faults a total of 1150 fault slip data consisting of fault planes and striations attitude were recorded from 66 sites including a single site with systematic joints slip sense of faults was determined by documenting kinematic indicators paleostress analysis was carried out using win tensor t tecto faultkin and sg2ps to compare and validate the results the chi square statistical analysis was undertaken to evaluate how relevant are paleostress analysis results to the present day compressional stress field geophysical investigations were conducted at selected sites using ground penetrating radar gpr to understand the shallow subsurface geometry and trace the continuity of faults buried below patchy alluvial cover 15 17 m long 2d gpr cross sections were recorded across faults using monostatic antenna of 200 mhz frequency two major deformation events d1 and d2 are determined in the present study the extension event d1 shows w and nw nnw extension during late triassic to late cretaceous it occurred during the rift phase of krb in response of the break up of gondwanaland the latest event d2 shows nne ne compression from late cretaceous up to the present it is interpreted to have developed during post rift inversion phase induced by collision of the indian plate with the eurasian plate at 55 ma

intermediate and deep water mass distribution in the pacific during the last glacial maximum inferred from oxygen and carbon stable isotopes intermediate ocean circulation changes during the last glacial maximum lgm in the north pacifi ch ave been linked with northern hemisphere climate through airesea interactions although the extent and the source of the variability of the processes forcing these changes are still not well resolved the ventilated volumes and ages in the upper wind driven layer are related to the wind stress curl and surface buoyancy fluxes at mid to high latitudes in the north pacific in contrast the deeper thermohaline layers are more effectively ventilated by direct atmosphere sea exchange during convective formation of subantarctic mode waters samw and antarctic intermediate waters aaiw in the southern ocean the precursors of pacific intermediate waters piw in the north pacific results reported here show a fundamental change in the carbon isotopic gradient between intermediate and deep waters during the lgm in the eastern north pacific indicating a deepening of nutrient and carbon rich waters these observations suggest changes in the source and nature of intermediate waters of southern ocean origin that feed piw and enhanced ventilation processes in the north pacific further affecting paleoproductivity and export patters in this basin furthermore oxygen isotopic results indicate these changes may have been accomplished in part by changes in circulation affecting the intermediate depths during the lgm 2010 elsevier ltd all rights reserved

contrasting ocean changes between the subpolar and polar north atlantic during the past 135 ka variations in the poleward directed atlantic heat transfer was investigated over the past 135 ka with special emphasis on the last and present interglacial climate development eemian and holocene both interglacials exhibited very similar climatic oscillations during each preceding glacial terminations deglacial ti and tii like ti also tii has pronounced cold warm cold changes akin to events such as h1 bolling allerod and the younger dryas but unlike ti the cold events in tii were associated with intermittent southerly invasions of an atlantic faunal component which underscores quite a different water mass evolution in the nordic seas within the eemian interglaciation proper peak warming intervals were antiphased between the nordic seas and north atlantic moreover inferred temperatures for the nordic seas were generally colder in the eemian than in the holocene and vice versa for the north atlantic a reduced intensity of atlantic ocean heat transfer to the arctic therefore characterized the eemian requiring a reassessment of the actual role of the ocean atmosphere system behind interglacial but also glacial climate changes key points reduced amoc during the eemian ba yd type warming cooling in termination 1 and 2 comparison of glacial inceptions reveals present climate status

precession phasing offset between indian summer monsoon and arabian sea productivity linked to changes in atlantic overturning circulation results from transient climate modeling experiments indicate an in phase relationship between insolation forcing and indian summer monsoonal precipitation this is in contrast to high resolution radioisotopically dated speleothem oxygen isotope 18o records of china which showed that east asian monsoon maxima lag northern hemisphere peak summer insolation by 2 700 years while an approximately 8 000 year time lag was derived from late pleistocene records of arabian sea sediments here we evaluate the precession phase of the arabian sea signal by comparing a new high resolution productivity and oxygen minimum zone omz intensity record from the arabian sea over the past 450 000 years with the results of a transient climate modeling experiment that includes glacial bound ice volume variations the well established tuning technique between radioisotopically dated north atlantic cold events and the occurrence of deep dwelling planktonic foraminifera in the arabian sea for the last glacial cycle was used to extend the arabian sea chronology independent of orbital tuning cross spectral analysis over the last 224 000 years reveals that arabian sea productivity maxima lag precession minima by 6 900 200 years i e in close agreement with previous reconstructions also our climate modeling simulations are in accord with previous studies indicating an in phase relationship between precession minima and maximum summer monsoon intensity we argue that the summer monsoon is most likely not the main driver of changes in arabian sea biological productivity and omz intensity at the precession frequency band but that changes in the intensity of the atlantic meridional overturning circulation amoc have played the prominent role in controlling the nutrient delivery into the euphotic layer of the northern indian ocean and hence the amount of primary productivity and intensity of the oxygen minimum zone in the arabian sea such a mechanism explains the large precession related time lag between minimum precession and maximum productivity and omz conditions in the arabian sea since intensified amoc occurred during precession maxima

inverse modeling for possible rather than unique solutions abstract despite the implementation of several kinematic and mechanical models for fault related folding and the incorporation of structural uncertainty in geological models structural modeling is still too deterministic the current focus is on forward modeling of a unique fit we show the application of trishear inverse modeling global optimization and markov chain monte carlo mcmc methods to a clay model of basement involved compressional faulting from which we know both total and incremental deformation global optimization and mcmc methods provide a range of possible models rather than a unique fit total inversions give an average of the model s deformation while incremental inversions are more physically related to the model s evolution global optimization identifies the full range of possible models while mcmc characterizes expected parameter values and their uncertainties structural inversions without sound geology are meaningless a robust stratigraphy geomorphic markers mesoscopic structures analogue and mechanical modeling can all greatly improve the inversions

glacial to interglacial fluctuations in productivity in the equatorial pacific as indicated by marine barite an empirical correlation between marine barite baso4 accumulation rate in core top sediment samples from two equatorial pacific transects at 140 w and 110 w and the estimated primary productivity of the overlying water column were used to evaluate glacial to interglacial changes in productivity fluctuations in barite accumulation rates down core indicate that during glacial periods of the past 450 000 years the productivity in the central and eastern equatorial pacific was about two times that during intervening interglacial periods this result is consistent with other evidence that productivity was high in the eastern and central equatorial pacific during the last glacial

trishear kinematic modeling of extensional fault propagation folding we present a new non linear 2 d numerical trishear model that is capable of modeling both symmetrical and asymmetrical trishear zones and a strain prediction approach based on the velocity field within the trishear zone a simple relationship exists between the shape factor r of the velocity field the hanging wall apical angle and footwall apical angle the implication of this relationship is that when dealing with a real deformed state cross section one can measure the hanging wall and footwall apical angles to determine the r value to specify the velocity field within the trishear zone for either the forward modeling or restoration the new trishear model can accurately reproduce the geometry of two experimental clay models and an extensional fault propagation fold from the gulf of suez predicted strain is greatest directly above the fault tip and decreases with distance from the fault tip as in the experimental models greater strain occurs in the hanging wall because of the greater velocity gradient there whereas the footwall is much less intensely deformed consequently secondary faulting and fracturing if present should be better developed along the fault tip line or in the hanging wall the orientation of fractures or minor faults can be predicted from the strain ellipses calculated from the trishear velocity field

contribution of aeolian dust in japan sea sediments estimated from esr signal intensity and crystallinity of quartz 1 late quaternary hemipelagic sediments in the japan sea contain aeolian dust from east asia which potentially records past variations in the asian monsoon and the westerly jet however extracting information about aeolian dust from japan sea sediments is difficult because the sediments also contain detrital material from the japanese islands here we present a method for extracting the aeolian dust components from japan sea hemipelagic sediments using provenance analysis of different size fractions hemipelagic sediments of the japan sea can be described by a combination of two populations characterized by lognormal grain size distributions with different median grain sizes which are called the coarser 2 15 m and the finer 10 m populations we characterized these populations on the basis of provenance analyses using the electron spin resonance esr signal intensity and crystallinity of quartz the results suggest that quartz in the coarser population has been mostly supplied from northern china and siberia northeastern china by aeolian transport whereas quartz in the finer population has been dominantly supplied by rivers draining the japanese islands

subsurface structural interpretation by applying trishear algorithm an example from the lenghu5 fold and thrust belt qaidam basin northern tibetan plateau abstract the application of trishear algorithm in which deformation occurs in a triangle zone in front of a propagating fault tip is often used to understand fault related folding in comparison to kink band methods a key characteristic of trishear algorithm is that non uniform deformation within the triangle zone allows the layer thickness and horizon length to change during deformation which is commonly observed in natural structures an example from the lenghu5 fold and thrust belt qaidam basin northern tibetan plateau is interpreted to help understand how to employ trishear forward modelling to improve the accuracy of seismic interpretation high resolution fieldwork data including high angle dips dragging structures thinning hanging wall and thickening footwall are used to determined best fit trishear model to explain the deformation happened to the lenghu5 fold and thrust belt we also consider the factors that increase the complexity of trishear models including a fault dip changes and b pre existing faults we integrate fault dip change and pre existing faults to predict subsurface structures that are apparently under seismic resolution the analogue analysis by trishear models indicates that the lenghu5 fold and thrust belt is controlled by an upward steepening reverse fault above a pre existing opposite thrusting fault in deeper subsurface the validity of the trishear model is confirmed by the high accordance between the model and the high resolution fieldwork the validated trishear forward model provides geometric constraints to the faults and horizons in the seismic section e g fault cutoffs and fault tip position faults intersecting relationship and horizon fault cross cutting relationship the subsurface prediction using trishear algorithm can significantly increase the accuracy of seismic interpretation particularly in seismic sections with low signal noise ratio

concentration vertical flux and remineralization of particulate uranium in seawater abstract concentrations and fluxes of particulate u were measured throughout the water column at several locations in the atlantic and pacific oceans with in situ filtration systems and sediment traps the results indicate that dissolved u is fixed to particles in surface seawater organic matter appears to be the carrier phase formation of particulate authigenic u below the surface waters could not be detected authigenic u is remineralized within the bathypelagic layers at the open ocean sites studied in the panama basin an upwelling area with high biological productivity remineralization of authigenic u in the deep water column was not observed the rate of remineralization of authigenic u in the deep sea is insufficient to produce a measurable concentration gradient between surface and deep waters within the mixing time of the oceans formation of authigenic u in the water column in areas such as the panama basin is not a significant sink for u on an ocean wide basis

how do horizontal frictional discontinuities affect reverse fault propagation folding abstract the development of new reverse faults and related folds is strongly controlled by the mechanical characteristics of the host rocks in this study we analyze the impact of a specific kind of anisotropy i e thin mechanical and frictional discontinuities in affecting the development of reverse faults and of the associated folds using physical scaled models we perform analog modeling introducing one or two initially horizontal thin discontinuities above an initially blind fault dipping at 30 in one case and 45 in another and then compare the results with those obtained from a fully isotropic model the experimental results show that the occurrence of thin discontinuities affects both the development and the propagation of new faults and the shape of the associated folds new faults 1 accelerate or decelerate their propagation depending on the location of the tips with respect to the discontinuities 2 cross the discontinuities at a characteristic angle 90 and 3 produce folds with different shapes resulting not only from the dip of the new faults but also from their non linear propagation history our results may have direct impact on future kinematic models especially those aimed to reconstruct the tectonic history of faults that developed in layered rocks or in regions affected by pre existing faults

numerical modeling of trishear fault propagation folding in contrast to kink band migration modeling methods trishear numerical models produce fault propagation folds with smooth profiles and rounded hinges modeled fold hinges tighten and converge downward within a triangular zone of distributed deformation which is focused on the fault tip such features have been reported from field studies and are also seen in analogue models of compressional deformation however apart from its initial application to laramide folds little quantitative work has been undertaken on trishear fault propagation folding in other settings in addition no study has been undertaken into the growth strata which might be associated with such structures this paper uses an equivalent velocity description of the geometric model of trishear together with models of erosion and sedimentation to investigate trishear fault propagation folding of both pregrowth and growth strata the trishear model is generalized to include a variety of fault propagation to slip ratios and fault propagation from a flat decollement the models show continuous rotation of the forelimb with the characteristic development of cumulative wedges within growth strata when total slip on a structure is high the model predicts overturned pregrowth and growth strata during the initial stages of deformation beds in the forelimb thicken but later thin when they become steep or overturned the effect of variations in fault propagation to slip ratios on two dimensional finite strain in the models is assessed by the use of initially circular strain markers high fault propagation to slip p s ratios lead to narrow zones of high finite strain while lower p s ratios lead to more ductile deformation and broader zones of high strain in all cases hanging wall anticlines and footwall synclines originate as early ductile folds which are later cut by the propagating fault modeled structures are compared with natural examples

what drives the southward drift of sea ice in the sea of okhotsk abstract the sea of okhotsk is the southernmost sea ice zone with sizable ice it is widely believed that the prevailing northwesterly wind and the southward east sakhalin current esc are the two main factors that drive the southward drift of sea ice however the relative contributions of these factors have not been understood in this paper by using the current and ice drift data measured with the moored acoustic doppler current profiler a 3 d ocean model simulation objective analysis data of the wind and satellite sea ice data we examine to what degree and how the ice drift is determined by the wind and ocean current from a linear regression of the observed ice drift ocean current and wind the wind forced component of the ice drift was best fitted when sea ice is assumed to move with a speed of 1 6 of the geostrophic wind with a turning angle of 17 6 to the left of the wind such a relationship was adopted as the wind drift component for all sea ice pixels detected from special sensor microwave imager data for the ocean forced component of the ice drift we adopted the current at 20 m depth from a numerical model simulation that reproduces well the esc and its variability we then evaluated the sea ice drift over 46 54 n during 1998 2005 for the southward drift of sea ice the contribution of the wind component is found to be larger than the oceanic component although the ocean contribution becomes larger typically comparable to the wind contribution near the coast and in the northern region where the esc is stronger we estimated the average annual cumulative southward ice transport to be 3 0 0 9 10 11 m 3 at 53 n this ice transport is comparable to the annual discharge of the amur river the ratio of wind to oceanic components in the transport is estimated to be 1 2 1 8 we also conducted ice drift simulations based on the modeled current velocity and the assumed wind drift of 1 5 geostrophic wind with a turning angle of 15 to the left the simulations reproduce well the ice drift north of 47 n but not south of 47 n likely due to the poor representation of the current system at the latter underevaluation of the wind factor near the ice edges and the neglect of ice formation and melt

structural analysis and miocene to present tectonic evolution of a lithospheric scale transcurrent lineament the sciacca fault sicilian channel central mediterranean sea abstract seismo stratigraphic and structural analysis of a large number of multichannel seismic reflection profiles acquired in the northern part of the sicilian channel allowed a 3 d reconstruction of a regional ns trending transfer zone which displays a transcurrent tectonic regime and that is of broad relevance for its seismotectonic and geodynamic implications it is constituted of two major transcurrent faults delimiting a 30 km wide mostly undeformed basin the western fault capo granitola does not show clear evidence of present day tectonic activity and toward the south it is connected with the volcanic area of the graham bank the eastern fault sciacca is structurally more complex showing active deformation at the sea floor particularly evident along the nerita bank the sciacca fault is constituted of a master and splay faults compatible with a right lateral kinematics sciacca fault is superimposed on an inherited weakness zone a mesozoic carbonate ramp which borders to the east a 2 5 km thick plio quaternary basin and that was reactivated during the pliocene a set of scaled claybox analogue models was carried out in order to better understand the tectonic processes that led to the structural setting displayed by seismic data tectonic structures and uplift subsidence patterns generated by the models are compatible with the 3 d model obtained from seismic reflection profiles the best fit between the tectonic setting deriving from the interpretation of seismic profiles and the analogue models was obtained considering a right lateral movement for the sciacca fault nevertheless the stress field in the study area derived from gps measurements does not support the present day modelled right lateral kinematics along the sciacca fault moreover seismic events along this fault show focal mechanisms with a left lateral component we ascribe the slip change along the sciacca fault from a right lateral transcurrent regime to the present day left lateral kinematics to a change of principal horizontal stress direction starting from late pliocene

the signature of river and wind borne materials exported from patagonia to the southern latitudes a view from rees and implications for paleoclimatic interpretations abstract riverine and wind borne materials transferred from patagonia to the sw atlantic exhibit a homogeneous rare earth element ree signature they match well with the ree composition of recent tephra from the hudson volcano and hence this implies a dominance of material supplied by this source and other similar andean volcanoes due to the trapping effect of proglacial and reservoir lakes the larger patagonian rivers deliver to the ocean a suspended load with a slightly modified andean signature that shows a ree composition depleted in heavy rees in this paper we redefine patagonia as a source of sediments which is in contrast with other sources located in southern south america quaternary sediments deposited in the northern and to a lesser extent in the southern scotia sea and most of the dust in ice cores of east antarctica have ree compositions very similar to the loess from buenos aires province and to patagonian eolian dust however we rule out buenos aires province as a holocene major source of sediments similarly to buenos aires loess a proximal facies it is likely that the ree compositions of most sediment cores of the scotia sea and antarctica reflect a distal transport of dust with an admixed composition from two main sources a major contribution from patagonia and a minor proportion from source areas containing sediments with a clear upper crustal signature e g western argentina or from bolivia s altiplano evidence indicates that only during the last glacial maximum patagonian materials were the predominant sediment source to the southern latitudes

a late eemian aridity pulse in central europe during the last glacial inception how do ice ages begin it s an obvious question to ask as we enjoy the relative luxury of an interglacial but a hard one to answer a look at past transitions may give some clues as to how this period will one day come to an end a climate reconstruction based on sediments found beneath a lake in the eifel mountains in germany provides evidence of an extreme climate event lasting 468 years right at the end of the last interglacial dust storms aridity bushfires and the loss of trees associated with a warm climate coincided with a southward shift of the warm waters of the north atlantic drift in terms of insolation the rate of delivery of the sun s radiation to earth conditions then were similar to those we have now investigating the processes that led to the end of the last interglacial period is relevant for understanding how our ongoing interglacial will end which has been a matter of much debate see for example refs 1 2 a recent ice core from greenland demonstrates climate cooling from 122 000 years ago3 driven by orbitally controlled insolation with glacial inception at 118 000 years ago4 5 6 7 8 here we present an annually resolved layer counted record of varve thickness quartz grain size and pollen assemblages from a maar lake in the eifel germany which documents a late eemian aridity pulse lasting 468 years with dust storms aridity bushfire and a decline of thermophilous trees at the time of glacial inception we interpret the decrease in both precipitation and temperature as an indication of a close link of this extreme climate event to a sudden southward shift of the position of the north atlantic drift the ocean current that brings warm surface waters to the northern european region the late eemian aridity pulse occurred at a 65 n july insolation of 416 w m 2 close to today s value of 428 w m 2 ref 9 and may therefore be relevant for the interpretation of present day climate variability

a radiometric calibration of the specmap timescale the astronomical theory of climate change asserts that earth s climate is affected by changes in its orbit which vary the seasonal and latitudinal distribution of solar radiation this theory is the basis of the orbitally tuned specmap timescale a key constraint for this important chronology was the mid point of the penultimate deglaciation initially dated to 127 000 years ago recent work suggests this event may be considerably older casting doubt on the astronomical theory the specmap timescale and the accuracy of orbitally tuned chronologies difficulties with u th coral dating of sea level events have impeded progress on this problem because most corals are not closed systems here we use a new approach to u th dating that corrects for open system behavior and produces a sea level curve of sufficient resolution to confidently correlate with specmap over the last 240 000 years permitting a reassessment of both this critical chronology and a central tenet of climate change theory high precision ages for 24 oxygen isotope events provide a 240 000 year chronology for marine 18o records that is independent of orbital tuning assumptions although there appear to be significant differences between the radiometric and orbitally tuned timescales near the lastglacial maximum and at the marine isotope stage 7 6 boundary a comparison of radiometric and specmap ages for identical isotope events suggest that the specmap timescale is quite accurate and that its errors were in general overestimated despite suborbital complexity orbital cyclicity is clearly evident in our record high amplitude sea level oscillations at periods greater than 20 000 years are very close in phase to summer insolation in the northern hemisphere although sea level changes cannot be uniquely tied to a specific season or latitude of insolation forcing the simplest explanation is that long period high amplitude sea level change is linked to northern hemisphere insolation forcing these results validate the principles of orbital tuning and suggest such timescales are generally robust

fault patterns associated with extensional fault propagation folding abstract extensional fault propagation drape folds are a common type of structure in rift basins and a number of oil and gas fields produce from these structures the detailed geometry and trap volumes are dependent on the relationship between the basement faults and the overlying folds and associated secondary faults in the sedimentary cover experimental models were used to study the 3 d geometry and secondary fault patterns of drape folds associated with single faults and two or more intersecting faults two layer clay models consisting of stiff and soft clay were used to model the deformation zones in the basement and sedimentary cover respectively extension on single basement faults normal to the direction of extension results in the development of a deformation zone with expanding width in which the fault density initially increases and then remains approximately constant extension on terminating faults results in conical drape folds with faults oblique to the fold axis along the propagating tip basement faults oblique to the direction of extension are characterized by oblique secondary faults along the boundaries of the deformation zone which curve into a direction normal to the extension direction in the center trapdoor fault geometries associated with two or more intersecting faults result in a triangular uplift with maximum relief at the apex the difference in relief between the flanks and the apex is greatest in the case of propagating basement faults en echelon secondary faults initiate on the flanks and extend into the apex area curving into orientations that are closer to normal to the regional direction of extension the width of the fault zone and the total fault length increase with increasing extension the fault density initially increases and then remains approximately constant with increasing extension

glacial to deglacial ventilation and productivity changes in the southern okhotsk sea abstract as a source region of north pacific intermediate water the okhotsk sea plays an important role in the ventilation of the north pacific to understand the detailed oceanographic changes in this marginal sea since the last glaciation we studied decadal to centennial scale proxy records from new sediment cores from the southwestern okhotsk sea glacial to holocene 14 c records of benthic foraminiferal shells suggested enhanced ventilation in the okhotsk sea during the early deglacial period between 18 and 15 ka corresponding to heinrich event 1 although the 14 c reconstruction has considerable uncertainties the okhotsk sea may have acted as a source for vigorous ventilation of the subarctic pacific during this period caco 3 preservation events appear to be better explained by the ventilation history of the okhotsk sea than by coccolithophores and foraminifera production caco 3 preservation started to improve during 18 to 15 ka and pronounced peaks in the caco 3 content corresponded to the bolling allerod 15 to 13 ka and preboreal 11 5 to 10 ka warm periods diatom and coccolithophore productivity remained low in the okhotsk sea throughout the glacial to deglacial periods different from the situation in the open subarctic pacific where high productivity was observed during the bolling allerod period after the preboreal period biogenic opal gradually increased and 15 n decreased in the southern okhotsk sea suggesting that productivity was enhanced by a relaxation of the nitrate limitation

active normal faulting beneath a salt layer an experimental study of deformation patterns in the cover sequence scaled experimental models show that the presence of a viscous layer such as salt facilitates the development of extensional forced folds above active normal faults the geometries of the extensional forced folds and their associated secondary fault patterns depend on the thickness and viscosity of the viscous layer the thickness of the cover sequence the strength and ductility of the cover sequence and the magnitude and rate of displacement on the underlying master normal fault increasing the thickness of the viscous layer and the cohesive strength and ductility of the overburden enhances the decoupling between the deep and shallow deformation alternatively increasing the viscosity of the viscous layer the thickness of the overburden and the magnitude and rate of displacement on the master normal fault reduces the decoupling between the deep and shallow deformation enhanced decoupling facilitates the formation of broad extensional forced folds and the development of detached secondary faults both near and far from the master normal faults the model predicted deformation patterns closely resemble those observed in the gulf of suez the haltenbanken area of offshore norway and the jeanne d arc basin of the grand banks offshore southeastern canada

defining a 3 dimensional trishear parameter space to understand the temporal evolution of fault propagation folds abstract the application of trishear in which deformation occurs in a triangular zone in front of a propagating fault tip is often used to understand fault related folding a key element of trishear in comparison to kink band methods is that non uniform deformation within the triangle zone allows the layer thickness and length to change during deformation by varying three controlling parameters independently trishear propagation slip ratio trishear apical angle and fault dip we construct a three dimensional parameter space to demonstrate the variability of resultant geometry feasible with trishear we plot published natural examples in this parameter space and identify two clusters and show that the most applicable typical trishear propagation slip ratio is 2 to 3 while the trishear apical angle varies from 30 to 100 we propose that these findings can help estimate the best fit parameters for natural structures we then consider the temporal evolution of specific geometric examples and factors that increase the complexity of trishear including 1 fault dip changes and 2 pre existing faults to illustrate the applicability of the parameter space and complex trishear models to natural examples we apply our results to a sub surface example from the qaidam basin in northern tibetan plateau

fold related faults in the syrian arc belt of northern egypt abstract late cretaceous early tertiary syrian arc folds in northern egypt include both inversion and non inversion folds these folds are well exposed in northern sinai and the northern eastern desert but exist in the subsurface in the northern western desert in northern sinai the maghara yelleg and halal inversion folds are 45 50 km long similar size inversion folds with opposite vergence exist in the subsurface in the northern western desert and include the kattaniya mubarak alamein razzak and matruh basin folds smaller non inversion compressional folds include the falig and meneidret el etheili folds in northern sinai as well as the abu gharadig anticline in the subsurface in the northern western desert among others detailed surface and subsurface structural mapping made use of the excellent exposures and good 2d and 3d seismic data and led to the identification of the fault patterns of the inversion and non inversion syrian arc folds inversion folds have fault patterns that differ from the backlimb to the forelimb the backlimbs are pervasively dissected by long nw se oriented normal faults that were formed by the regional stress field on the contrary the forelimbs of inversion folds as well as the two limbs of non inversion folds are affected by the local stress in the folded areas and are dissected by three shorter fault sets a set of hinge transverse normal faults and two conjugate sets of hinge oblique faults that have oblique slip the hinge oblique faults dominate the steeper limbs of asymmetric non inversion folds

intensified deep pacific inflow and ventilation in pleistocene glacial times the production of cold deep waters in the southern ocean is an important factor in the earth s heat budget1 the supply of deep water to the pacific ocean is presently dominated by a single source the deep western boundary current east of new zealand here we use sediment records deposited under the influence of this deep western boundary current to reconstruct deep water properties and speed changes during the pleistocene epoch in physical and isotope proxies we find evidence for intensified deep pacific ocean inflow and ventilation during the glacial periods of the past 1 2 million years the changes in throughflow may be directly related to an increased production of antarctic bottom water during glacial times possible causes for such an increased bottom water production include increasing wind strengths in the southern ocean or an increase in annual sea ice formation leaving dense water after brine rejection and thereby enhancing deep convection we infer also that the global thermohaline circulation was perturbed significantly during the mid pleistocene climate transition between 0 86 and 0 45 million years ago

changes in detrital input ventilation and productivity in the central okhotsk sea during the marine isotope stage 5e penultimate interglacial period abstract by presenting benthic foraminifera isotope profiles and bulk geochemical composition of core sediments we offer a mutiproxy reconstruction of the central okhotsk sea oceanography between 130 to and 115 kyr related to the marine isotopic stage 5e mis 5e sediments from the site mr0604 pc7a have been compared with paleo sea surface temperatures and other records this multiparameter approach allowed to recognize three periods for mis 5e evolution characterized by variations in marine productivity and bottom oxygenation these variations have been ultimately associated with the production of okhotsk sea intermediate water and the presence or absence of nutrient contribution from the pacific deep water into central okhotsk sea aeolian input reconstructed by th sc ratio indicates higher values during the mis 6 and mis 5d compared with the mis 5e eu values indicate an input of detrital material from kurile islands and east kamchatka during the late mis 5e absent during the early mis 5e and glacial periods

what do we learn from peaks of uranium and of manganese in deep sea sediments abstract uranium and manganese are two redox sensitive trace elements with complementary behavior under anoxic conditions u is immobile while reduced mn is dissolved in pore water of sediments uranium diffuses from sea water into reducing sediments and is enriched there the depth of the reducing layers and the sediment accumulation rate determine the enrichment of authigenic uranium on the contrary mn is dissolved in the reducing sediment sections diffuses in pore water and forms peaks of mn oxide as soon as oxygen is available thus the profiles of both mn and authigenic u record the depth of the redoxcline during periods of oxygen limitation in the sediments estimates of the depth of incorporation of uranium during the last glacial were derived for several cores at localities in the atlantic numerical modeling of the redoxcline as a function of the oxygen content of the water column and of the flux of organic matter to the sediments constrains these values during periods of extreme shallow redoxcline depths burn down of organic matter and deepening of the redoxcline during the holocene may have significantly altered the organic matter and uranium signals of glacial sediments at present day conditions sediments accumulating at rates smaller than 2 cm ky 1 may have lost the u signals peaks of manganese are then the only reliable record for a less ventilated sediment column in the past

comparative fem and dem modeling of basement involved thrust structures with application to sheep mountain greybull area wyoming abstract basement involved fold and thrust systems have been widely studied in several locations through field and seismic investigations however our understanding of the geometries of the faults that drive folding and the mechanical conditions within the resulting folds is still limited simulations run using the finite element and discrete element methods have great potential to help determine the mechanical evolution of structures at all scales both methods have been employed to explore the structural evolution of the laramide age sheep mountain anticline located in the eastern bighorn basin of wyoming both sets of simulations are constrained by experimental and well log data and use the same size model domain and mechanical stratigraphy the underlying basement sediment boundary was deformed by a set of prescribed displacements the results of the two simulations are geometrically similar and match previous field based interpretations of the sheep mountain fold to the first order stresses calculated by the two methods were also very similar thus verifying the mechanical comparison differences in the geometric details however provide important perspectives on the capabilities of the two methods for example the major faults producing the sheep mountain fold develop slightly higher dips in the dem simulation than the fem simulation yielding a better match with published interpretations the crest of the anticline is characterized by distributed thinning of shallow strata in the fem simulation and by local extensional faulting in the dem simulation neither simulation reproduced the north south fold splay observed in the field suggesting that this minor feature results from preexisting structure or 3d effects not modeled here

physical modeling of deformation patterns in monoclines above oblique slip faults abstract many basement involved fault related folds are thought to form by reactivation of pre existing faults although oblique slip is expected on such structures it is often difficult to identify because the underlying faults are blind paleomagnetic records are ambiguous and mesoscopic deformation patterns in the associated monoclines are often incompletely exposed or difficult to interpret this study seeks to establish a relationship between oblique slip on a basement reverse fault and the deformation patterns in the overlying folded rock layers using scaled physical models of wet clay overlying a rigid basement we create a suite of laramide style folds over basement faults with variable obliquity precise displacements and strains on the surface of the clay are recorded using close range photogrammetry we use these measurements to predict deformation patterns that we would expect to find in analogous natural structures the results of our models show that there are three general strain zones that form in monoclines that form above oblique slip faults the upper hinge region of the monocline is dominated by extension the lower hinge region by contraction and the middle of the fold limb is dominated by shear strains the boundaries of these three zones as well as the magnitude of strain in each of the zones vary with the amount of oblique slip and fault throw deformation should be dominated by joints and extensional faults in the extensional zone by contractional faults and cleavage in the contractional zone and may contain extensional contractional or strike slip faults along with joints and cleavage arranged in riedel style geometries in the shear strain dominated zone at fault obliquities above 45 there is significant overlap of the different strain zones and deformation patterns in these regions can consequently be very complex involving reactivation or overprinting of earlier structures or the formation of mixed mode structures displacements on the surface of our model monoclines suggest that previous paleomagnetic interpretations of vertical axis rotations on natural monoclines may need to be re evaluated although such rotations increase with increasing fault obliquity the magnitude of these rotations will vary significantly with position across a monocline

deformation and secondary faulting associated with basement involved compressional and extensional structures experimental clay modeling is used to study the geometry and evolution of deformation zones formed above basement faults the nature of deformation is compared for reverse faults dipping 30 45 and 60 vertical faults and normal faults dipping 60 and 75 basement faulting results in the formation of a sheared triangular deformation zone that widens upward in the cover units most of the deformation is focused within a central zone of secondary faults which propagate upward and eventually break through the entire section basal units exhibit steeper dips and higher fault densities whereas stratigraphically higher units exhibit gentler dips and lower fault densities the width of the deformation zone is generally greater for reverse faults with low dips the anticlinal axial surface typically dips in the same direction as the synclinal axial surface for low to moderate angle reverse faults however the axial surfaces dip in opposite directions for vertical faults and normal faults particle paths suggest a convex upward rotation within the deformation zone suggesting transfer of material across the extension of the master fault reverse faults are associated with secondary faults with reverse and thrust separations vertical faults are associated with mostly vertical and reverse secondary faults whereas normal faults are generally associated with normal separation of most secondary faults therefore the nature of secondary faults varies with structural position possibly within the same layer these results provide some key insights that are useful in the interpretation of macroscopic surface and subsurface basement involved structures

environmental change in the sea of okhotsk during the last 1 1 million years on the basis of two sedimentary records from the central sea of okhotsk we reconstruct the closely coupled glacial interglacial changes in terrigenous flux marine productivity and sea ice coverage over the past 1 1 myr the correspondance of our sedimentary records to the china loess grain size record china loess particle timescale chiloparts suggests that environmental changes in both the sea of okhotsk area and in se asia were closely related via the siberian atmospheric high pressure cell during full glacial times our records point to a strong siberian high causing northerly wind directions the extension of the sea ice cover and a reduced amur river discharge deglacial maxima of terrigenous flux were succeeded by or synchronous to high productivity events marine productivity was strengthened during glacial terminations because of an effective nutrient utilization at times of enhanced water column stratification and high nutrient supply from fluvial runoff and sea ice thawing during interglacials se monsoonal winds prevailed analogous to today s summer situation of a pronounced mongolian heat low and a strong hawaiian high strong freshwater discharge induced by high precipitation rates in the amur drainage area and a seasonally reduced and mobile sea ice cover favored marine productivity although being considerably lower than during the terminations and a lowered flux of ice rafted detritus

distribution and transport processes of lithogenic material from the amur river revealed by the sr and nd isotope ratios of sediments from the sea of okhotsk abstract primary productivity is very high in the sea of okhotsk most likely because of terrigenous input from the amur river that includes dissolved matter and suspended matter to reveal the transport and deposition processes of the fluvial materials in the northwestern continental shelf of the sea of okhotsk the sr and nd isotopes of the detritus in the surface sediments and suspended matter were investigated the regional variations of the radiogenic isotopes indicate that the detritus in the continental shelf has three main sources amur river detritus with a high 87 sr 86 sr ratio 0 711 0 715 and relatively low e nd value 7 6 to 7 3 volcanic detritus derived from the okhotsk chukotka volcanic belt to the north of the okhotsk sea with a low 87 sr 86 sr ratio 0 703 and high e nd value 7 to 8 and detritus from the sedimentary rocks north of sakhalin island with a high 87 sr 86 sr ratio 0 709 0 710 and low e nd value 10 2 to 9 2 the results indicate that the amur river detritus is dispersed across the northwestern continental shelf and further transported southward along the east coast of sakhalin while flowing out of the shelf around the northeast coast of sakhalin island the coarse grained detritus from the north region of sakhalin island is distributed only in the narrow region of the shallow depth area and is not transported to the shelf slope the amur river detritus flowing out of the shelf is mixed with the okhotsk chukotoka volcanic material transported from the northern area of the okhotsk sea by the okhotsk sea intermediate water osiw the transport processes of the amur river detritus in this area are supported by previous studies of turbidity that indicated that the dense shelf water dsw entrains resuspended sedimentary particles on the northwestern continental shelf and transports them to the osiw

characteristic of subionospheric vlf perturbations associated with winter lightning around japan 1 the vlf signature of ionospheric perturbations trimpis associated with winter lightning around japan has been investigated during a three month observation december 2000 to february 2001 the absence of observed optical phenomena mesospheric optical emissions such as sprites in the hokuriku area sea of japan side indicates that the period was not extremely active in lightning as compared with the previous winter hobara et al 2001 based on vlf subionospheric observation at moshiri hokkaido and maizuru near kyoto for two vlf transmitter signals nwc australia and npm hawaii we have found the following 1 lightning discharges are found not only on the japansea side but also on the pacific side although more lightning was observed on the pacific side of japan the trimpi occurrence rate is more enhanced over the sea of japan 2 trimpis tend to occur only when the lightning activity is enhanced 3 trimpi occurrence rate shows no particular diurnal variation 4 there is no significant difference in the trimpi occurrence rate between and cg discharges 5 the intensity of scattered signal with respect to the unperturbed wave is in most case ranging from 15 to 25 db these characteristics are discussed in terms of meteorological and lightning conditions

polyphase transpressional development of a nne striking basement cored anticline in the xining basin northeastern qinghai tibetan plateau the xiaoxia anticline is a basement cored fold in the northeastern qinghai tibetan plateau it formed during the middle late cenozoic in a nne orientation oblique to prevailing wnw striking thrusts in the surrounding region the fold lies within the fault bounded xining basin which has behaved as a clockwise rotating and internally deforming block during the mid late tertiary proterozoic crystalline basement rocks and jurassic cretaceous cenozoic terrestrial sediments exposed within the fold record three separate oblique slip deformation events as determined by cross cutting generations of faults and folds the modern xiaoxia anticline developed by 1 outward directed thrusting on the two fold limbs and 2 oblique slip thrusting on closely spaced minor nne striking faults that caused distributed uplift and passive shear folding of the sedimentary cover within the fold core tilted and thrusted river terraces on the flanks of the xiaoxia anticline dated by optically stimulated luminescence and electron spin resonance indicate that folding has continued into the late quaternary post 45 5 5 5 ka and therefore may still be active today the development of the xiaoxia anticline appears to be best explained in the context of the kinematic evolution of the xining basin s bounding strike slip faults formation of the xiaoxia anticline demonstrates that partitioned transpression in an evolving transpressional setting can invert intra montane basins and produce basement cored folds thereby contributing to regional plateau uplift

a stratigraphic framework for abrupt climatic changes during the last glacial period based on three synchronized greenland ice core records refining and extending the intimate event stratigraphy due to their outstanding resolution and well constrained chronologies greenland ice core records provide a master record of past climatic changes throughout the last interglacial glacial cycle in the north atlantic region as part of the intimate integration of ice core marine and terrestrial records project protocols have been proposed to ensure consistent and robust correlation between different records of past climate a key element of these protocols has been the formal definition and ordinal numbering of the sequence of greenland stadials gs and greenland interstadials gi within the most recent glacial period the gs and gi periods are the greenland expressions of the characteristic dansgaard oeschger events that represent cold and warm phases of the north atlantic region respectively we present here a more detailed and extended gs gi template for the whole of the last glacial period it is based on a synchronization of the ngrip grip and gisp2 ice core records that allows the parallel analysis of all three records on a common time scale the boundaries of the gs and gi periods are defined based on a combination of stable oxygen isotope ratios of the ice 18o reflecting mainly local temperature and calcium ion concentrations reflecting mainly atmospheric dust loading measured in the ice the data not only resolve the well known sequence of dansgaard oeschger events that were first defined and numbered in the ice core records more than two decades ago but also better resolve a number of short lived climatic oscillations some defined here for the first time using this revised scheme we propose a consistent approach for discriminating and naming all the significant abrupt climatic events of the last glacial period that are represented in the greenland ice records the final product constitutes an extended and better resolved greenland stratotype sequence against which other proxy records can be compared and correlated it also provides a more secure basis for investigating the dynamics and fundamental causes of these climatic perturbations

a high resolution absolute dated late pleistocene monsoon record from hulu cave china oxygen isotope records of five stalagmites from hulu cave near nanjing bear a remarkable resemblance to oxygen isotope records from greenland ice cores suggesting that east asian monsoon intensity changed in concert with greenland temperature between 11 000 and 75 000 years before the present yr b p between 11 000 and 30 000 yr b p the timing of changes in the monsoon as established with 230th dates generally agrees with the timing of temperature changes from the greenland ice sheet project two gisp2 core which supports gisp2 s chronology in this interval our record links north atlantic climate with the meridional transport of heat and moisture from the warmest part of the ocean where the summer east asian monsoon originates

evolution of fault patterns in clay experiments abstract the evolution of systems of strike slip faults from a single fault to intricate patterns is examined here in a series of clay experiments in the experiments plates of clay are loaded laterally under constant strain rate in plane strain with continuous monitoring of the stresses the experiments indicate that an individual fault appears as a linear trace about 1 mm in length that grows by in plane propagation of one or both ends next the fault evolves by out of plane propagation and interacts and coalesces with other subparallel faults this process generates a crooked nonlinear fault which at this point usually ceases to grow younger faults developing close to the older fault may cross and displace it the fault pattern in a sample changes in nature during a single run the early pattern is either domainal or conjugate depending on the initial fault distribution the second stage is usually domainal when subparallel faults develop close to each other during the final stage young faults cross old ones and generate conjugate patterns the relation between rheology and growth mechanisms of the faults is discussed faults in brittle elastic solids grow by out of plane propagation into zones of reduced normal stress whereas many of the faults in the present experiments grow by in plane propagation this propagation direction and the fault pattern evolution is interpreted here as indicating relaxation of nonuniform stresses at the proximity of the faults it is further argued that stress relaxation may be applicable to faulting of rocks in the upper crust

ice rafted debris ird based sea ice expansion events during the past 100 kyrs in the okhotsk sea abstract ice rafted debris ird from sediment traps surficial sediments and sediment cores were investigated in order to reconstruct the extent history of sea ice cover during the last 100 kyrs in the okhotsk sea the seasonal ird buried into the sediments during and just after sea ice melting in spring consists of silt and sand size terrigenous particles the spatial distribution of ird within surficial sediments clearly corresponds to the extent of sea ice coverage sea ice expanded to a maximum extent during the glacial periods although sea ice cover was not perennial the okhotsk sea sea ice expansion osie events which are recognized by millennial scale abrupt peaks of ird content have occurred 13 times during the past 100 kyrs these events were amplified during the glacial periods a significant modification of the polar atmospheric circulation in the northern hemisphere is a key process in explaining these osie events

experimental models of extensional forced folds we have used single layer and multilayer clay models to study the development of forced folds above normal faults our modeling results show that the deformation patterns associated with extensional forced folding depend on the dip of the underlying normal fault and the presence of layer parallel detachments in single layer clay models extensional forced folds are upward widening monoclines anticlinal axial surfaces dip in the same direction as underlying master normal faults and synclinal axial surfaces dip in the opposite direction of master normal faults most secondary faults are upward steepening normal faults if master normal faults are steeply dipping however many secondary normal faults become high angle reverse faults at shallow depths the propagation and linkage of secondary faults into through going normal faults terminates the development of extensional forced folds more folding occurs prior to fault linkage if the master normal fault is steeply dipping rather than gently dipping most dipping beds and secondary faults are preserved in the hanging walls of the through oing normal faults in multilayer clay models with layer parallel detachments extensional forced folds are also upward widening monoclines slip on the lowest detachment laterally transfers extension induced by normal faulting and forced folding from the master normal fault to the detachment edge slip on overlying detachments accommodates minor thickness changes associated with upward widening of the fold secondary faults include low angle normal faults near the anticlinal axial surface minor thrust faults near the synclinal axial surface and high angle normal faults above the detachment edge the model predicted deformation patterns are similar to those of extensional forced folds from the gulf of suez and offshore norway this similarity suggests that our modeling results apply to extensional forced folds and can provide guidelines for interpreting field well and seismic data

stable isotope and lithologic evidence of late glacial and holocene oceanography of the northwestern pacific and its marginal seas abstract stable isotopes geochemical lithological and micropaleontological results from cores from the far northwest fnw pacific and the okhotsk and bering seas are used to reconstruct the regional environment for the last glaciation the deglacial transition and the holocene 18 o records of planktonic foraminifera of the region show two light shifts during deglacial time provoked by the freshening of the surface water and climate warming these north pacific terminal events t1anp and t1bnp with ages of 12 500 and 9300 yr b p respectively occur almost simultaneously with two episodes of accelerated glacier melting around the north atlantic along with the isotopic shifts the caco 3 content in regional sediments increased abruptly 1a and 1b carbonate peaks probably due to changes of productivity and pore water chemistry of surface sediments organic matter and opal concentration increased during the transition between t1anp and t1bnp events in the sediments of the fnw pacific and the southern part of the bering sea and opal content increased in the holocene in the bering and okhotsk seas 13 c records of cores from the okhotsk and bering seas and the fnw pacific do not contradict the hypothesis of increased intermediate water formation in the region during glaciation during deglaciation accumulation of the coarse terrigenous component decreased in sediments of the bering sea and the fnw pacific before the t1anp event probably as a result of rising sea level and opening of the bering strait

evolution and demise of the last interglacial warmth in the subpolar north atlantic detailed faunal isotopic and lithic marine records provide new insight into the stability and climate progression of the last interglacial period marine isotope stage mis 5 which peaked approximately 125 000 years ago in the eastern subpolar north atlantic at the latitude of ireland interglacial warmth of the ice volume minimum of substage 5e mis 5e lasted 10 000 years 10 ka and its demise occurred in two cooling steps the first cooling step marked the end of the climatic optimum which was 2 3 ka long minor ice rafting accompanied each cooling step the second larger step encompassing cold events c26 and c25 was previously identified in the northwestern atlantic approximately 41c of cooling occurred between peak interglacial warmth and c25 and the region experienced an additional temporary cooling of at least 1 21c during c24 a cooling event associated with widespread ice rafting in the north atlantic beginning with c24 mis 5 was characterized by oscillations of at least 1 21c superimposed on a generally cool baseline the results of this study imply that the marine climatic optimum of the last interglacial was shorter than previously thought the finding that the eastern subpolar north atlantic cooled significantly before c24 reconciles terrestrial evidence for progressive climate deterioration at similar and lower latitudes with marine conditions our results also demonstrate a close association between modest ice rafting cooling and deep ocean circulation even during the peak of mis 5e and in the earliest stages of ice growth