making diagenesis obey thermodynamics and kinetics the case of quartz cementation in sandstones from offshore mid norway calculation of the quantity and distribution of quartz cement as a function of time and temperature depth in quartzose sandstones is performed using a coupled dissolution diffusional transport precipitation model this model is based on the assumptions that the source of the silica cement is quartz surfaces adjoining mica and or clay grains at stylolite interfaces within the sandstones and the quantity of silica transport into and out of the sandstone by advecting fluids is negligible integration of the coupled mass transfer transport equations over geologically relevant time frames is performed using the quasi stationary state approximation results of calculations performed using quartz dissolution rate constants and aqueous diffusion coefficients generated from laboratory data are in close agreement with both the overall porosity and the distribution of quartz cement in the middle jurassic garn formation only after optimizing the product of the effective surface area and quartz precipitation rate constants with the field data when quartz precipitation rate constants are fixed to equal corresponding dissolution rate constants the effective surface area required to match field data depends on the choice of laboratory generated quartz rate constant algorithm and ranges from 0 008 cm 1 to 0 34 cm 1 in either case these reactive surface areas are 2 to 4 orders of magnitude lower than that computed using geometric models

quantification of holocene asian monsoon rainfall from spatially separated cave records abstract a reconstruction of holocene rainfall is presented for southwest china an area prone to drought and flooding due to variability in the east asian monsoon the reconstruction is derived by comparing a new high resolution stalagmite 18 o record with an existing record from the same moisture transport pathway the new record is from heshang cave 30 27 n 110 25 e 294 m and shows no sign of kinetic or evaporative effects so can be reliably interpreted as a record of local rainfall composition and temperature heshang lies 600 km downwind from dongge cave which has a published high resolution 18 o record wang y j cheng h edwards r l he y q kong x g an z s wu j y kelly m j dykoski c a li x d 2005 the holocene asian monsoon links to solar changes and north atlantic climate science 308 854 857 by differencing co eval 18 o values for the two caves secondary controls on 18 o e g moisture source moisture transport non local rainfall temperature are circumvented and the resulting 18 o signal is controlled directly by the amount of rain falling between the two sites this is confirmed by comparison with rainfall data from the instrumental record which also allows a calibration of the 18 o proxy the calibrated 18 o record provides a quantitative history of rainfall in southwest china which demonstrates that rainfall was 8 higher than today during the holocene climatic optimum 6 ka but only 3 higher during the early holocene significant multi centennial variability also occurred with notable dry periods at 8 2 ka 4 8 4 1 ka 3 7 3 1 ka 1 4 1 0 ka and during the little ice age this holocene rainfall record provides a good target with which to test climate models the approach used here of combining stalagmite records from more than one location will also allow quantification of rainfall patterns for past times in other regions

variability of arctic sea ice topography and its impact on the atmospheric surface drag over the polar oceans near surface atmospheric transport of momentum is strongly influenced by sea ice surface topography the latter is analyzed on the basis of laser altimeter data obtained during airborne campaigns between 1995 and 2011 over more than 10 000 km of flight distance in different regions of the arctic ocean spectra of height and spacing between topographic features averaged over 10 km flight sections show that typical values are 0 45 m for the mean height and about 20 m for the mean spacing nevertheless the variability is high and the spatial variability is stronger than the temporal one the total topography spectrum is divided into a range with small obstacles between 0 2 m and 0 8 m height and large obstacles 0 8 m results show that large pressure ridges represent the dominant topographic feature only along the coast of greenland in the central arctic the concentration of large ridges decreased over the years accompanied by an increase of small obstacles concentration and this might be related to decreasing multiyear ice the application of a topography dependent parameterization of neutral atmospheric drag coefficients reflects the large variability in the sea ice topography and reveals characteristic differences between the regions based on the analysis of the two spectral ranges we find that the consideration of only large pressure ridges is not enough to characterize the roughness degree of an ice field and the values of drag coefficients are in most regions strongly influenced by small obstacles

a one dimensional analytically based approach for studying poroplastic and viscous consolidation application to woodlark basin papua new guinea 1 in the study of sedimentary basin evolution consolidation of marine sediments has historically been characterized by applying variations on poroplastic theory however recent field evidence and models of deformation by pressure solution suggest that both poroplastic and viscous modes of compaction should be investigated when evaluating basin development to study the influence of poroplastic and viscous deformation on marine sediments we constructed a generic framework that incorporates the two modes of compaction into a numerical scheme analytical solutions for pressure development and porosity change based on both poroplastic and viscous theory were incorporated into this scheme and a characteristic height was determined to indicate the depth at which viscous deformation is initiated application of our framework to a site in woodlark basin papua new guinea and comparison of the simulated results to measured porosity data suggest that poroplastic deformation is the dominant mode of consolidation at the site and that lithologic strength is controlling the observed porosity profile two simulated scenarios based on different characteristic heights showed that while a full poroplastic model may be most appropriate to characterize compaction at the site viscous deformation may be a factor in developing the low porosities 26 to 40 observed below 590 m below seafloor as such although poroplastic deformation may be predominant in basins less than 1 km deep a combined poroplastic viscous model may be useful to address sediments which exhibit markedly low porosity at shallow depths

reevaluation of the oxygen isotopic composition of planktonic foraminifera experimental results and revised paleotemperature equations cultured planktonic foraminifera orbulina universa symbiotic and globigerina bulloides nonsymbiotic are used to reexamine temperature 18o relationships at 15 25 c relationships for both species can be described by linear equations equations for o universa grown under low light ll and high light hl share a slope of 4 80 0 21 c 1 with a hl ll offset of 0 33 due to symbiont photosynthetic activity the effect of co32 on o universa is 0 002 mol 1 kg 1 and is insensitive to temperature for g bulloides ontogenetic effects produce size related trends in temperature 18o whereby larger shells are enriched in 18o relative to smaller specimens the o universa temperature 18o relationships are more accurate than previously published equations for describing plankton tow data our equations do not explain planktonic core top data with the same precision but provide a good fit to benthic cibicidoides data below 10 c temperature 18o relationships for g bulloides provide good agreement with field data for this species from the northeast pacific

multiple expansions of c4 plant biomass in east asia since 7 ma coupled with strengthened monsoon circulation the expansion of plants using the c4 photosynthetic pathway is one of the most prominent changes in the global ecosystem during the cenozoic era a significant late miocene expansion is well documented however the existence and cause of subsequent expansions are still not clear owing in part to the lack of long continuous climate vegetation records here we present two high resolution carbon isotope time series covering the past 7 m y derived from eolian deposits on the chinese loess plateau the data indicate three intervals of significant c4 plant expansions within the semiarid monsoonal region of east asia ca 2 9 2 7 ma 1 3 0 9 ma and 0 6 ma present these expansions covary with strengthened east asian summer monsoon circulation we conclude that in east asia large scale late miocene c4 c3 vegetation changes in semiarid areas have been primarily driven by warm seasonal precipitation and temperature variations associated with changes in monsoon circulation

evolution of the eastern tropical pacific through plio pleistocene glaciation a tropical pacific climate state resembling that of a permanent el nino is hypothesized to have ended as a result of a reorganization of the ocean heat budget 3 million years ago a time when large ice sheets appeared in the high latitudes of the northern hemisphere we report a high resolution alkenone reconstruction of conditions in the heart of the eastern equatorial pacific eep cold tongue that reflects the combined influences of changes in the equatorial thermocline the properties of the thermocline s source waters atmospheric greenhouse gas content and orbital variations on sea surface temperature sst and biological productivity over the past 5 million years our data indicate that the intensification of northern hemisphere glaciation 3 million years ago did not interrupt an almost monotonic cooling of the eep during the plio pleistocene sst and productivity in the eastern tropical pacific varied in phase with global ice volume changes at a dominant 41 000 year obliquity frequency throughout this time changes in the southern hemisphere most likely modulated most of the changes observed

astronomical forcing of the east asian monsoon mirrored by the composition of pliocene south china sea sediments abstract high precision major and minor element records of pliocene core intervals from ocean drilling program odp site 1145 located in the northern part of the south china sea were generated at a 5 cm approximately 2 kyr resolution from the geochemical data distinct proxies those indicating changes in detrital matter provenance as well as those indicating productivity variations could be derived both the terrigenous input to the northern south china sea k si and variations in productivity ba al show a response to insolation forced monsoon variability while the fluvial input k si responds to changes in the summer monsoon productivity increases as documented by ba enrichments seem to reflect variations in winter monsoon intensity a stronger winter monsoon may have increased nutrient availability via dust input and or upwelling phenomena according to our geochemical proxy records summer and winter monsoons are approximately 180 out of phase this may imply forcing of the winter monsoon through southern hemisphere summer insolation maxima the k si ratio shows a linear correlation with the la90 1 0 5 northern hemisphere summer insolation record and has therefore been used to create an astronomical timescale for the investigated sediments of odp site 1145 carbonate contents and corresponding color reflectances display 41 and 100 kyr cycles we propose that these do not reflect glacial cycles but are rather the result of an interference signal of dilution by fluvial and eolian terrigenous material and carbonate production burial flux a sudden onset of gradual changes in sediment composition occurs after 3 0 ma this is also documented by an increase in sedimentation rates and may be caused by enhanced fluvial input from the pearl river due to intensified weathering rates on the asian continent this may be linked to tectonic processes around the himalayan tibetan complex and its consequences regarding land sea heating and atmospheric circulation

airborne observations of summer thinning of multiyear sea ice originating from the lincoln sea to better understand recent changes of arctic sea ice thickness and extent it is important to distinguish between the contributions of winter growth and summer melt to the sea ice mass balance in this study we present a lagrangian approach to quantify summer sea ice melt in which multiyear ice myi floes that were surveyed by airborne electromagnetic thickness sounding within nares strait during summer were backtracked using satellite imagery to a region in close proximity 3 20 km to spring ice thickness surveys carried out in the lincoln sea typical modal total myi thicknesses including 0 4 m snow ranged between 3 9 and 4 7 m in the lincoln sea during april ice only modal thicknesses were between 2 2 and 3 0 m in nares strait during august total thinning including snow and ice was 1 3 0 1 m including 0 4 0 09 m of snow melt and 0 9 0 2 m of ice melt this translates to a seasonal net heat input of 305 69 mj m2 262 60 mj m2 for ice only and seasonal net heat flux of 57 13 w m2 45 10 w m2 for ice only which is unlikely to be explained by solar radiation fluxes alone furthermore our approach provides an improvement on traditional ice mass balance buoy estimates because it integrates melt over larger spatial scales where melt can be highly variable due to differential melt experienced between melt ponds bare ice hummocks and ridges

temporal variability in the northern arabian sea oxygen minimum zone omz during the last 225 000 years the northern arabian sea is one of the few regions in the open ocean where thermocline water is severely depleted in oxygen the intensity of this oxygen minimum zone omz has been reconstructed over the past 225 000 years using proxies for surface water productivity water column denitrification winter mixing and the aragonite compensation depth acd changes in omz intensity occurred on orbital and suborbital timescales lowest o2 levels correlate with productivity maxima and shallow winter mixing precession related productivity maxima lag early summer insolation maxima by 6 kyr which we attribute to a prolonged summer monsoon season related to higher insolation at the end of the summer periods with a weakened or even non existent omz are characterized by low productivity conditions and deep winter mixing attributed to strong and cold winter monsoonal winds the timing of deep winter mixing events corresponds with that of periods of climatic cooling in the north atlantic region

surface roughness of baltic sea ice small medium and large scale measurements of sea ice surface roughness were carried out in the baltic sea over a 3 year period a clear relationship was found between the rms height and correlation length of baltic sea ice in most cases the surface correlation function was close to exponential the logarithm of rms height showed a linear dependence on that of measured distance similarly the correlation length was in many cases linearly dependent on the measured distance this dependence on length suggests that ice surface roughness could be characterized as a fractal

coupled fluid flow and sediment deformation in margin scale salt tectonic systems 2 layered sediment models and application to the northwestern gulf of mexico 1 in paper 1 we described a methodology to model coupled fluid flow and deformation in composite salt and siliciclastic tectonic systems and investigated their compaction and overpressuring behavior prior to and during continental margin scale gravitational spreading compaction driven darcy fluid flow in clastic sediments is coupled through the effective pressure to their frictional plastic yield and mechanical deformation viscous flow of the underlying salt is independent of fluid pressure paper 1 presented prototype models that are limited to single uniform sediment lithologies either sandstone type or shale type that undergo mechanical and volumetric viscous compaction in this paper we present models with layered sandstone type and shale type lithologies designed to better approximate the more complex stratigraphy of the gulf of mexico our natural example a first set of models demonstrates that layered lithologies can produce fluid pressure regimes similar to those observed in sedimentary basins we then introduce an improved formulation of viscous compaction that includes a stronger dependence on porosity and depth used as proxy for temperature thereby more effectively self limiting viscous compaction a second set of models with the improved viscous compaction formulation demonstrates that the onset of gravity spreading is mainly controlled by overpressuring in the landward end of the salt basin and that resulting shortening in the distal part is partly accommodated by horizontal compaction models with moderately high fluid pressure best reproduce conditions considered to have been necessary for large scale gravitational spreading in the northwestern gulf of mexico which led to the formation of the perdido fold belt

dust response to seasonal atmospheric forcing proxy evaluation and calibration eolian grain size and flux were measured on samples from 11 arabian sea sediment traps deployed 200 1250 km offshore the timing of increased grain size is coincident with the onset of strong summer monsoon winds and dust storm activity over the arabian peninsula and middle east data spanning a full annual cycle show that eolian grain size is highly correlated with barometric pressure r 0 91 and wind speed r 0 84 enabling calibration of the downcore record in terms of these primary meteorological variables eolian flux is highly correlated with organic carbon flux r 0 80 both increase 6 8 weeks after the grain size increase and summer monsoon onset this lag and the low correlation between eolian grain size and eolian flux r 0 36 likely result from the differential sinking rates of large and small dust particles in the surface waters as well as biological scavenging associated with monsoon induced productivity marily to aridity and vegetation cover at the source and 3 that grain size is primarily a function of atmospheric transport capacity these findings are based on statistical relation ships linking dust flux to glacial interglacial climate change 5 o and grain size to biological indicators of wind driven upwelling such relationships are well documented and have provided a reasonably robust framework for interpreting the downcore dust record rea 1994 provides an excellent overview however direct evaluation of links between at mospheric dynamics dust aerosols and deep sea sediments in the modem environment are needed to better understand

the roughness of natural terrain a planetary and remote sensing perspective we examine the various methods and parameters in common use for quantifying and reporting surface topographic roughness it is shown that scale dependent roughness parameters are almost always required though not widely used we suggest a method of standardizing the parameters that are computed and reported so that topographic data gathered by different workers using different field techniques can be directly and easily intercompared we illustrate the proposed method by analyzing topographic data from 60 different surfaces gathered by five different groups and examine the information for common features we briefly discuss the implications of our analysis for studies of planetary surface roughness lander safety and radar remote sensing modeling and analysis

southern hemisphere forcing of pliocene δ18o and the evolution of indo asian monsoons monsoon phase relationships consistent with direct orbital forcing across the entire indo asian region including marine and terrestrial proxies from the chinese loess plateau the south china sea and the arabian sea strong pliocene summer and winter monsoons were in phase with one another strengthened at obliquity minima and precession minima the summer monsoon was also strengthened at precession maxima yielding a semiprecession spectral signal strong pliocene monsoons at orbital extremes indicate a direct response to fast physics processes including sensible heating and cooling of the asian landmass and for the summer monsoon the export of latent heat from the southern indian ocean as northern hemisphere ice volume grew into the pleistocene the timing of strong winter and summer monsoons drifted apart becoming influenced by the combined effects of fast physics and slow physics ice volume variables the phase of strong winter monsoons shifted toward ice maxima and the phase of strong summer monsoons shifted toward ice minima

development of east asian summer monsoon environments in the late miocene radiolarian evidence from site 1143 of odp leg 184 abundant radiolarians are preserved in the relatively complete upper miocene section of odp site 1143 three radiolarian zones rn6 rn7 and rn8 are recognized on the basis of diartus petterssoni total range in rn6 6 7 ma variations in the abundance of radiolarians especially pyloniid forms radiolarian flux and species diversity are good proxies of upwelling which similar to today s was likely driven by summer monsoons these radiolarian paleomonsoon proxies indicate that the east asian summer monsoon first initiated close to the middle late miocene boundary at similar to 12 11 ma and reached a maximum strength at similar to 8 24 ma therefore the initiation of the east asian summer monsoon was likely earlier than the first indian monsoon which appeared similar to 8 myr ago c 2003 elsevier b v all rights reserved

relation between eurasian snow cover snow depth and the indian summer monsoon an observational study abstract satellite derived snow cover data for 22 yr and snow depth data for 9 yr over eurasia have been analyzed to reexamine the possible relation of snow with the indian summer monsoon in contrast to the previous studies that use snow cover averaged over all of eurasia as a single number the frequency of occurrence of snow at each grid point over eurasia is correlated with the indian summer monsoon rainfall thus specific geographical regions over eurasia that are responsible for the well known inverse relationship between eurasian snow cover and indian monsoon rainfall are delineated it is found somewhat surprisingly that western eurasia is the only geographical region for which a significant inverse correlation exists between winter snow cover and subsequent summer monsoon rainfall however composites for high and low snow cover over eurasia show spatially homogeneous large scale patterns of snow cover and surface temperature anomalies winters of high and low snow cover for eurasia are found t

stress state interpretation in light of pressure solution creep numerical modelling of limestone in the eastern paris basin france abstract this paper presents an interpretation of the present stress state in the eastern paris sedimentary basin france based on considerations that regard the long term limestone rheology a comprehensive stress profile was acquired in this region and it was determined that the minimum horizontal stress in an argillite layer is much larger than that in the under and overlying stiffer limestone layers while the major horizontal stress seems almost insensitive to lithology in a previous study the genesis of this intriguing stress state was modelled by considering the limestone to be elastic however the calculation implied the use of unrealistic mechanical characteristics for this rock extremely low long term elastic modulus and poisson s ratio from the study it was concluded that some dissipative viscous process of unknown origin might be at work in the limestone herein we propose that the deformation micro mechanism that is responsible for this time dependent behaviour is pressure solution creep psc we show that this hypothesis is mechanically realistic by adapting an existing model of psc which is based on the description of mass transfer within grain to grain contacts dissolution diffusion and precipitation we deduce a set of long term rheological characteristics for the limestone and use them in the numerical model of the stress genesis in the paris basin the results show that psc is a possible explanation for the present stresses and total strains in this region the fact that limestone should be considered as visco elastic over geological time scales with a viscosity ranging between 10 17 and 10 21 pa s and not as purely elastic is at the core of this work although it is probably ubiquitous in nature psc is notoriously difficult to assess in the laboratory thus our effort of coupling small scale processes in a quantitative manner to large scale deformation and in situ measurements provides a useful tool for gaining insight into the role of psc in the long term behaviour of carbonated rocks and its effect on sedimentary basin evolution

a model for sandstone compaction by grain interpenetration abstract the compaction of an idealized sandstone is described quantitatively in terms of its stress temperature history and the microstructure of its monomineralic load bearing grain cement framework the model relationship is developed from simple energy and volume balance considerations although chemistry mineral pore fluid and transport diffusion fluid flow play major roles in most diagenetic processes they do not appear explicitly in this mechanical model for grain interpenetration in sandstones for a model sandstone at compaction equilibrium the only quantity determined uniquely by the ambient stress and temperature is its burial constant equal to the ratio of its grain cement contact diameter to the separation of its grain centers the burial constant determines what the maximum porosity can be whether primary or secondary sandstones with identical burial constants may have very different grain interpenetrations and minus cement porosities depending on the amount of supporting cement and the time of its emplacement supporting load bearing cement increases the effective intergrain contact area thereby increasing a sandstone s resistance to compaction supporting cement usually preserves more pore space than it occupies this is in direr contrast to passive non lo d bearing cement which may destroy even more effective pore space than its solids occupy the removal of passive cement increases porosity but the removal of supporting cement initiates further compaction and causes porosity to decrease with sufficient supporting cement primary porosity can retain economic values to great depths model predictions are uniformly consistent with available observational data on quartzose sandstones agreement among data from geographically diverse sandstone reservoirs ranging in age from jurassic to pleistocene suggests that compaction equilibrium is reached in times that are short on the geological time scale and that age is not a factor in the compaction of sandstones

biological markers and their carbon isotopes as an approach to the paleoenvironmental reconstruction of nansha area south china sea during the last 30 ka paleoenvironmental changes over the last 30 ka have been documented for the nansha area south china sea from the biomarkers and their carbon isotopic composition of 314 sediment samples from core 17962 the concentrations of marine lipids indicate that the paleoceanographic and paleoclimatic conditions were not stable in the nansha area during the last glacial period the accumulation rates of c37 alkenones and c30 alkyl diols show that marine paleoproductivity was higher during the last glaciation than in the holocene and correlate well with those of terrestrial biomarkers simultaneous variations in accumulation rates of marine biomarkers and terrigenous long chain compounds during the last glacial period suggest that this enhancement of marine productivity was caused by an increase in terrestrial nutrient supply from the sunda shelf the stable carbon isotopic composition of terrigenous long chain compounds such as n alkanes 13 c 28 6 34 2 n alkanoic acids 13 c 27 1 31 8 and n alkanols 13 c 26 6 35 3 indicates that these compounds were derived from c3 plants and the surrounding area of southern south china sea was not dry during the last glacial 2002 elsevier science ltd all rights reserved

strain variations and three dimensional strain factorization at the transition from the southern to the central appalachians abstract the transition between the southern and the central appalachian foreland thrust system is a region subjected to at least two non coaxial deformations where typical two dimensional analyses such as cross section balancing or plane strain retro deformation cannot be applied three dimensional factorization can simulate the non coaxial strain history simulation results for compaction and layer parallel shortening lps were compared to finite strains of 16 quartz arenite samples from the tuscarora sandstone successful simulations indicate in the southern appalachians 30 35 total compaction by volume loss including a 4 5 9 e w horizontal shortening during lithification and 5 lps along 150 330 by plane strain or axial symmetric flattening in the central appalachians 30 35 total compaction by volume loss including a 3 7 n s horizontal shortening during lithification and 10 lps along 120 300 by plane strain or axial symmetric flattening in the transition zone 30 compaction by volume loss including a 3 e w horizontal shortening during lithification 5 southern lps along 150 330 by axial symmetric flattening and 5 10 central shortening along 130 or 140 by plane strain or axial symmetric flattening at 10 to the normal central trend from the simulations horizontal shortening in the southern appalachians during lithification in the mississippian was greater than the later alleghanian deformation this shortening probably represents a very early lps developed in unlithified sand that required less deviatoric stress to deform than did the cemented quartz arenites during later tectonic deformation also the oblique and weaker central tectonic lps in the transition zone probably represents behavior at the limits of central appalachian deformation finally the lps simulations indicate that axial symmetric flattening oblate strain is more successful than plane strain as the representative behavior so caution is recommended in assuming plane strain as the dominant strain behavior in orogenic forelands

combined observations of arctic sea ice with near coincident colocated x band c band and l band sar satellite remote sensing and helicopter borne measurements in this study we compare colocated near coincident x c and l band fully polarimetry sar satellite images with helicopter borne ice thickness measurements acquired during the norwegian young sea ice 2015 n ice2015 expedition in the region of the arctic ocean north of svalbard in april 2015 the air borne surveys provide near coincident snow plus ice thickness surface roughness data and photographs this unique data set allows us to investigate how the different frequencies can complement one another for sea ice studies but also to raise awareness of limitations x band and l band satellite scenes were shown to be a useful complement to the standard sar frequency for sea ice monitoring c band for lead ice and newly formed sea ice identification this may be in part be due to the frequency but also the high spatial resolution of these sensors we found a relatively low correlation between snow plus ice thickness and surface roughness therefore in our dataset ice thickness cannot directly be observed by sar which has important implications for operational ice charting based on automatic segmentation

development of the east asian summer monsoon evidence from the sediment record in the south china sea since 8 5 ma 128 samples from ocean drilling program odp site 1143 in the southern south china sea were analyzed for grain size clay minerals biogenic opal content and quartz in order to reconstruct changes in east asian monsoon climate since 8 5 ma an abrupt change of terrigenous mass accumulation rate mar clay mineral assemblage median grain size and biogenic opal mar about 5 2 ma suggests that between 8 5 5 2 ma the source of terrigenous sediment was mainly in the region of surface uplift and basaltic volcanism in southern vietnam a simple model of east asian summer monsoon evolution was based on the clay feldspar ratio kaolinite chlorite ratio and biogenic opal mar the summer monsoon has two periods of maximum strength at 8 5 7 6 ma and 7 1 6 2 ma subsequently there was a relatively stable period at 6 2 3 5 ma continued intensification about 3 5 2 5 ma and gradually weakening after 2 5 ma since i ma the monsoon has intensified with remarkable high frequency and amplitude variability simultaneous increase in sedimentation rates at odp sites 1143 1146 and 1148 as well as in mar of terrigenous materials quartz feldspar and clay minerals at odp site 1143 at 3 5 2 5 ma may be the erosional response to both global climatic deterioration and the strengthening of the east asian summer monsoon after about 3 4 ma c 2006 elsevier b v all rights reserved

plio pleistocene ice volume antarctic climate and the global δ18o record we propose that from 3 to 1 million years ago ice volume changes occurred in both the northern and southern hemispheres each controlled by local summer insolation because earth9s orbital precession is out of phase between hemispheres 23 000 year changes in ice volume in each hemisphere cancel out in globally integrated proxies such as ocean 18 o or sea level leaving the in phase obliquity 41 000 years component of insolation to dominate those records only a modest ice mass change in antarctica is required to effectively cancel out a much larger northern ice volume signal at the mid pleistocene transition we propose that marine based ice sheet margins replaced terrestrial ice margins around the perimeter of east antarctica resulting in a shift to in phase behavior of northern and southern ice sheets as well as the strengthening of 23 000 year cyclicity in the marine 18 o record

quantitative roughness characterization of geological surfaces and implications for radar signature analysis stochastic surface models are useful for analyzing in situ roughness profiles and synthetic aperture radar sar images of geological terrain in this paper two different surface models are discussed surfaces with a stationary random roughness conventional model and surfaces with a power law roughness spectrum fractal model in the former case it must be considered that for short profiles l 200l sub 0 the measured values of rms height s and correlation length l may be significantly smaller than the intrinsic values s sub 0 and l sub 0 in the latter case rms height and correlation length depend on the profile length l and the surface is better characterized by slope and offset of the roughness spectrum which are independent of l the sensitivity of the sar signature to variations in surface roughness parameters is evaluated by means of theoretical scattering models for smoother geological surfaces such as most arid terrain types single scattering is dominant which means that the roughness parameters can be determined from sar data using comparatively simple algorithms multiple scattering processes on rough surfaces such as a a lava and variations of the local incidence angle due to large scale terrain undulations make the retrieval of roughness parameters by means of inverse modeling much more complex field data of surface roughness indicate that rougher geological surfaces may be in the diffractal regime at higher radar frequencies in which the scattering characteristics deviate significantly from the patterns observed for stationary surfaces on the basis of surface and scattering models recently published observations of roughness data and radar signatures from volcanic alluvial and arid surfaces are examined

high resolution elemental records from the south china sea and their paleoproductivity implications 1 the biogenic related elements ca sr ba p cd scavenged al and ti were analyzed by inductively coupled plasma mass spectrometry icp ms and inductively coupled plasma atomic emission spectrometry icp aes for core ns93 5 from the west slope of the south china sea terrestrial input as estimated from the accumulation of ti was higher during glacials than during interglacials carbonate accumulation rates are inversely related to those of terrestrial input suggesting higher production of calcareous phytoplankton during interglacials the accumulation patterns of authigenic sr ba p and cd match that of carbonate further indicating higher calcareous phytoplankton production during interglacials scavenged al and excess sio2 which is related to biogenic opal exhibit higher accumulation rates during glacials and correspond with changes in terrestrial input this indicates that terrestrial input driven is important to siliceous phytoplankton production but not for calcareous phytoplankton production as calcareous phytoplankton is the dominant component of the biogenic sediments in the south china sea particularly during interglacials previous inference of higher productivity in the south china sea during glacials based on only the biogenic opal proxy needs to be reconsidered

geochemistry of the surface sediments of the sulu and south china seas abstract the chemical and mineralogical composition of the surface sediments of the sulu sea a deep hydrographically restricted basin in the indonesian archipelago and the neighbouring area of the south china sea have been examined the aim of the study was to characterize the geochemistry of the sediments of the isolated oxygen deficient basin and to compare them with sediments at equivalent water depths outside the basin as a prelude to a further study of the response of the composition of the sediments to oceanographic changes including possible anoxia during the last glacial maximum the concentrations of most of the chemical constituents in the surface sediments along four transects change markedly with water depth in the sulu sea ss and the south china sea scs thus caco 3 decreases from around 60 by weight in the shallowest samples 800 1000 m to around a few percent in the deepest sample at 4203 m in the scs where the ccd lies at around 4000 m in the ss however the ccd lies much deeper so that the caco 3 contents are still approximately 40 at 4500 m depth organic c also decreases with depth in both basins from values of around 1 2 in the shallowest samples to less than 1 in the deepest samples the ratios of si mg na k co cr cu ni pb rb y zr and zn to al all decrease with increasing water depth because of the change in mineralogy and sediment texture with water depth the p al is higher in shallower water in both areas because of the higher abundance of detrital phosphorite or phosphatized limestone in these sediments the sr al ratio is also higher in shallower water reflecting the supply of aragonitic shell debris from the shallow banks and shelves around the basin the ba al ratio has a maximum at 2000 m depth in the scs due to higher primary production in overlying surface waters whereas it is uniformly low in the ss manganese is also enriched at intermediate water depths in both the ss and the scs because of the presence of oxyhydroxides and this also produces a slight enrichment in mo in the same samples because of their association in this authigenic phase the concentration of i and the i c organic ratio decreases with water depth in both areas due to the higher abundance of fresh marine organic matter at the shallow water sites which scavenges proportionally more i from sea water finally the 13 c organic values tend to decrease irregularly with increasing water depth probably reflecting a higher contribution of terrestrial organic matter in deeper water a discriminant analysis of the full data set reveals that compared with the scs samples the oxygen deficient ss sediments have higher caco 3 contents lower n and s contents and lower i c organic ba al fe al k al pb al rb al ti al v al y al and zn al ratios these contrasts are brought about by the different depths of the ccd differences in the nature of the organic matter and different types of aluminosilicate detritus in the two areas although the i c organic ratios are slightly but significantly lower in the ss which may be due to the low dissolved oxygen contents of the waters of this basin the mn and mo contents and other minor elements that respond significantly to ambient bottom water oxygen levels are not significantly different in the ss and the scs moreover the organic c contents are also indistinguishable in the two areas hence the low bottom water oxygen levels in the ss do not lead to higher organic carbon contents in the surface sediments the composition of sediments in contact with waters having even lower oxygen concentrations should be evaluated in order to conduct a more definitive test of the effect of low oxygen conditions on carbon preservation comparison of glacial interglacial sediment sections from this area must take particular care to separate the effects of source variations on those potentially caused by low oxygen levels

molecular biomarker record of sea surface temperature and climatic change in the south china sea during the last 140 000 years the d 18 oa ndd 18 c isotopic composition of globigerinoides ruber the concentration of c37 alkenones n nonacosane and n hexacosan 1 ol and the populations of coccolith species in core 17961 2 have been used to characterize the climatic changes which occurred in the south china sea scs during the last climatic cycle the relative composition of diand triunsaturated c37 alkenones the u k index has been used to estimate the variation in sea surface temperatures the concentrations of the terrigenous markers n nonacosane and n hexacosan 1 ol have allowed to infer changes in continental water dynamics during the glacial and interglacial times the stratigraphic record of these compounds has shown that the influence of continental waters i e the molengraaff river and restricted water circulation in scs gave rise to a marginal system of higher but slower response to climatic change both in terminations i and ii the change from glacial to interglacial conditions involves a considerable reduction of continental water input into this semi enclosed system the high resolution study of the biomarker proxies in termination i has shown that the sst increase lagged about 2 3 ky the d 18 o isotopic decrease of cibicidoides wuellerstorfi probably the sst increase corresponds to the period of the sunda shelf inundation onset 1999 elsevier science b v all rights reserved

quantitative analysis of sea ice draft 1 methods for stochastic modeling this paper seeks to develop a robust set of tools for estimating the stochastic properties of sea ice drafts five parameters are estimated along with their formal uncertainties mean draft rms topographic variation characteristic length fractal dimension and normalized skewness these provide an objective basis for terrain classification a recent 10 km by 10 km upward looking submarine sonar survey serves as a test case data profiles are compared with synthetic profiles generated from the statistical parameters estimated from the data these provide a means of qualitatively assessing the success of the stochastic model at characterizing the principal morphological properties in general the comparisons are good providing confidence in the applicability and versatility of the stochastic model a few exceptions are notable but these also provide valuable insight into our understanding of the morphology of sea ice draft

coupled mechanical and chemical processes in engineered geothermal reservoirs with dynamic permeability abstract a model is developed to represent mechanical strain stress enhanced dissolution and shear dilation as innately hysteretic and interlinked processes in rough contacting fractures the model is incorporated into a numerical simulator designed to examine permeability change and thermal exchange in chemically active and deformable fractured reservoirs a candidate engineered geothermal reservoir system egs is targeted the mechanistic model is able to distinguish differences between the evolution of fluid transmission characteristics of 1 small scale closely spaced fractures and 2 large scale more widely spaced fractures alternate realizations of fracture frequency and scale exhibiting identical initial bulk permeability lead to significantly different conclusions regarding permeability evolution and thermal drawdown within the reservoir reactivation primarily through mechanical shear of pervasive large scale fractures is shown capable of causing both hydraulic and thermal short circuiting small variations in fracture scale impact the balance between the efficiency of thermal transfer and the rate of fluid circulation stress enhanced chemical dissolution initially at equilibrium within the reservoir may be reactivated as fractures are forced out of equilibrium during hydraulic fracturing at the conditions examined 250 c reservoir with 70 c injection however shear dilation exerts dominant control over changes to permeability heterogeneity in permeability generated from a normal distribution of fracture spacing impacts thermal breakthrough times at the withdrawal well as well as withdrawal rates for the given conditions spatial variability over 1 order of magnitude leads to a reduction of 10 in withdrawal rates compared to a spatially uniform system permeability is a strongly dynamic property and at geothermal conditions is influenced by the full suite of thmc interactions

oxygenation changes in the deep western arabian sea during the last 190 000 years productivity versus deepwater circulation 1 fluctuations in the abundance of selected foraminiferal indicator species and diversity allowed the reconstruction of changes in deepwater oxygenation and monsoon driven organic matter fluxes in the deep western arabian sea during the last 190 kyr times of maximum surface production coincide with periods of intensified sw monsoon as shown by the abundance of globigerina bulloides and enhanced carbonate corrosion benthic ecosystem variability in the deep arabian sea is not exclusively driven by variations in monsoonal upwelling and related organic matter supply to the seafloor but also by changes in deepwater ventilation deepening of the base of the oxygen minimum zone omz below 1800 m water depth is strongly coherent on the precessional band but lags proxies of sw monsoon strength by 4 to 6 kyr the out of phase relationship between omz deepening and maximum sw monsoon strength is explained by temporal changes in the advection of oxygen rich deepwater masses of north atlantic and antarctic origin this process affected the remineralization and burial efficiency of organic matter in the deep arabian sea resulting in the observed phase lag between maximum monsoon strength and organic carbon preservation

palaeo climate reconstruction from stable isotope variations in speleothems a review abstract speleothems are now regarded as valuable archives of climatic conditions on the continents offering a number of advantages relative to other continental climate proxy recorders such as lake sediments and peat cores they are ideal materials for precise u series dating yielding ages in calendar years thereby circumventing the radiocarbon calibration problems associated with most other continental records stable isotope studies in speleothems have shifted away from attempting to provide palaeo temperature reconstructions to the attainable goal of providing precise estimates for the timing and duration of major o isotope defined climatic events characterised by high signal to noise ratios e g glacial interglacial transitions dansgaard oeschger oscillations the 8200 year event unlike the marine records speleothem data sets are not tuned and their independent chronology offers opportunities to critically assess leads and lags in the climate system that in turn can provide important insights into forcing and feedback mechanisms improved procedures for the extraction and measurement of stable isotope ratios in fluid inclusions trapped in speleothems are likely to provide in the near future a much enhanced basis for the quantitative interpretation of o isotope ratios in speleothem calcite the latter developments open up once again the tantalising prospect of palaeo temperature estimates but more importantly perhaps provide a direct test for a new generation of general circulation models whose hydrological cycles will incorporate the water isotopes the literature is reviewed briefly to provide for the reader a sense of the current state of the art and to provide some pointers for future research directions

comparison of the sea ice thickness distribution in the lincoln sea and adjacent arctic ocean in 2004 and 2005 results of helicopter borne electromagnetic measurements of total ice plus snow sea ice thickness performed in may 2004 and 2005 in the lincoln sea and adjacent arctic ocean up to 868 n are presented thickness distributions south of 848 n are dominated by multi year ice with modal thicknesses of 3 9 m in 2004 and 4 2 m in 2005 mean thicknesses 4 67 and 5 18 m respectively modal and mean snow thickness on multi year ice amounted to 0 18 and 0 30 m in 2004 and 0 28 and 0 35 m in 2005 there are also considerable amounts of 0 9 2 2 m thick first year ice modal thickness mostly representing ice formed in the recurring refrozen lincoln polynya results are in good agreement with ground based electromagnetic thickness measurements and with ice types demarcated in satellite synthetic aperture radar imagery four drifting buoys deployed in 2004 between 868 n and 84 58 n show a similar pattern of a mean southward drift of the ice pack of 83 18 km between may 2004 and april 2005 towards the coast of ellesmere island and nares strait the resulting area decrease of 26 between the buoys and the coast is larger than the observed thickness increase south of 848 n this points to the importance of shear in a narrow band along the coast and of ice export through nares strait in removing ice from the study region

late pleistocene nutrients and sea surface productivity in the south china sea a record of teleconnections with northern hemisphere events surface nutrient variations during the last 200 000 years have been reconstructed based on the cd ca ratios in the tests of planktonic foraminifera neogloboquadrina dutertrei and the biogenic opal content from two gravity cores retrieved from the northern and northwestern parts of the south china sea scs the cd ca ratios obtained from n dutertrei in recent sediments from fourteen box cores distributed over the scs basin reflect present nutrient levels in the overlying surface waters areas with relatively high cd ca values in the surface sediments are in the region of high chlorophyll a in the northern south china sea near the dongsha islands consistent with previous observation high values of cd ca found in sediments east of vietnam and east of the nansha islands may be a result of increased nutrients due to local upwelling induced by the summer monsoon core 17940 2 raised from the northern continental slope of the scs exhibits exceptional high sedimentation rates 25 85 cm kyr for the last 35 kyr the cd ca ratios in this core are relatively higher during the periods of late d 18 o stage 3 and the mid holocene core 17950 2 with an average sedimentation rate of 5 cm kyr offers a continuous long record back to d 18 o stage 7 in general cd ca values in the downcore records are higher during interglacials and progressively increase as the interglacials proceed values peak around the times of optimum climate conditions and correlate with periods of increased opal wt correlations in the interval of overlap between the two records support the interpretation that variations in cd ca ratios in core 17940 2 are not an individual signal but can be replicated of special interest in this study is the tentative correlation between cd ca peaks in the scs record and the timing of iceberg discharge events heinrich events in the north atlantic mass accumulation rate mar of opal data from core 17950 2 indicate high surface productivity during glacial intervals corresponding to oxygen isotope stages 6 4 and 2 the increase in surface productivity during glacials from the northern scs is contemporaneous with an intensified winter monsoon as recorded by the terrestrial loess deposits the agreement with wind strength recorded in the loess plateau from mainland china supports the

calibration of water granite interaction with pressure solution in a flow through fracture under confining pressure fluid mineral interaction has an irreversible impact on the fracture permeability evolution in the life span of deep geological reservoirs to investigate the impact a preliminary study on water granite interaction in an undeformable fracture under confining pressure is conducted a 1 d flow and reactive transport model is therefore developed and validated against the experimental data in yasuhara et al appl geochem 26 12 2074 2088 2011 the model takes free face dissolution on pore walls as well as enhanced dissolution at asperity contacts into account together with a nested well equipped geochemical system the simulation is implemented by fem based simulator opengeosys with a plugin module of iphreeqc for speciation calculation after calibration the predictions of effluent element concentrations are in good agreement with the measurements the study indicates the high effluent concentrations arise from enhanced mineral dissolution at asperity contacts pressure solution at anorthite contacts may not take effect under experimental conditions because of the high level energy barrier to interpenetration and al bearing secondary minerals such as gibbsite may be formed in the current near equilibrium aqueous system the sensitivity analysis suggests that contact area ratio is a paramount parameter in determining the surface reactivity and reactive surface area at contacts

porosity and consolidation limits of sediments and gassmann s elastic wave equation the elastic framework properties of sediments relate to porosity porosity relates to the state of consolidation of sediments the full range of quasi static elastic moduli vs porosity behavior can be incorporated into gassmann s 1951 equations i review the atterberg 1911 limits to establish a basis for discussing the precompaction porosity 0 which corresponds approximately to the atterberg plastic limit this porosity is about 0 36 0 40 for sands and sandstones the ratio of the dry frame moduli to the effective mineral moduli is 1 0 i incorporate this ratio into gassmann s equations which operate from 0 0 when sediments have a solid elastic frame for s 0 when sediments no longer have a solid elastic frame gassmann s equations reduce to reuss 1929 isostress average for the solid fluid mixture

quantifying the evolution of soil fabric during shearing using scalar parameters the packing density of a soil is typically described in terms of the scalar parameters void ratio specific volume or porosity within a critical state soil mechanics framework the response of a sand is considered to depend on its state that is the combination of void ratio and effective stress when soil is considered from a particle scale perspective the packing density is often described using the coordination number cn that is the average number of contacts per particle using particles with simple geometries discrete element method dem simulations photoelastic tests and experiments on analogue soils e g glass ballotini have all demonstrated a correlation between cn and mechanical response this study investigates whether these correlations apply to real soils using direct measurement of the fabric via micro computed tomography micro ct a variety of scalar fabric descriptors was measured during the triaxial compression of both intact and reconstituted reigate sand samples while ea

a renewed look at calcite cement in marine deltaic sandstones the brent reservoir heather field northern north sea uk wireline and seismic acoustic impedance imaging show that the marine part of the clastic brent group reservoir in the heather field northern north sea contains much calcite cement in the flank parts of the structure the non marine ness formation and crest parts of the structure contain negligible calcite cement this localised calcite cement has led to relatively poor reservoir performance since first oil in 1978 although a new suite of wells has boosted production with plans to keep the field active until 2030 understanding the origin and distribution of calcite cement would help the development of more realistic reservoir models and boost production rates through optimum well location we have thus used a suite of techniques including standard point counting sem eds mineralogy bse microscopy fluid inclusion thermometry and stable isotope analysis to develop new and improved models of calcite distribution calcite seems to have attributes of both early and late diagenetic cement 30 to 40 intergranular volume in calcite cemented beds seems to support pre compactional growth but high temperature fluid inclusions and the presence of primary oil inclusions suggests late growth much calcite may have developed early but it seems to have recrystallized and possibly undergone redistribution at close to maximum burial or had a late growth event calcite cement probably originated as marine derived micrite bioclasts or early marine cement but adopted the isotopic characteristics of high temperature growth as it recrystallized quartz grains have corroded outlines in calcite cemented areas with one sample with 79 calcite cement displaying signs of nearly total replacement of quartz grains by calcite the flank localisation of calcite remains to be explained although it could be due to primary depositional factors early diagenetic loss of calcite from crestal regions or late diagenetic loss of calcite from crestal regions controversially the growth of calcite seems to be associated with quartz dissolution although the geochemical and petrophysical cause of this remains obscure diagenetic loss of quartz from sandstones cannot easily be explained by conventional modelling approaches and yet seems to be an important phenomenon in heather sandstones

sea ice surface roughness estimates from airborne laser scanner and laser altimeter observations in fram strait and north of svalbard we present sea ice surface roughness estimates i e the standard deviation of relative surface elevation in the arctic regions of fram strait and the nansen basin north of svalbard acquired by an airborne laser scanner and a single beam laser altimeter in 2010 we compare the scanner to the altimeter and compare the differences between the two survey regions we estimate and correct sensor roll from the scanner data using the hyperbolic response of the scanner over a flat surface measurement surveys had to be longer than 5 km north of svalbard and longer than 15 km in fram strait before the statistical distribution in surface roughness from the scanner and altimeter became similar the shape of the surface roughness probability distributions agrees with those of airborne electromagnetic induction measurements of ice thickness the ice in fram strait had a greater mean surface roughness 0 16m vs 0 09m and a wider distribution in roughness values than the ice in the nansen basin an increase in surface roughness with increasing ice thickness was observed over fast ice found in fram strait near the coast of greenland but not for the drift ice

climatically linked oscillations in arabian sea denitrification over the past 1 m y implications for the marine n cycle water column and core top 15n data show that arabian sea denitrification produces large nitrogen isotopic enrichments that are regionally recorded with fidelity in the sediments these results facilitate interpretation of a 1 m y 15n record for ocean drilling program site 722b on the owen ridge in terms of climatically linked oscillations in denitrification at the major orbital periods as at present denitrification was greatest during interglacial periods and apparently was not active during most glacial intervals cross spectral analysis of 15n with foraminiferal 18o global climate sea level index and lithogenic grain size monsoon strength index suggests forcings by changes in hydrography and productivity acting through the extent and intensity of the oxygen minimum zone the data suggest that denitrification may be an internal forcing mechanism for climate change during major glacial interglacial transitions through influence on marine n inventory and atmospheric co2 however compensation or amplification may occur from other sinks sediment denitrification or sources nitrogen fixation

parameterization of arctic sea ice surface roughness for application in ice type classification statistics of arctic sea ice surface roughness have been investigated in order to improve classification of ice thickness regimes the data consist of surface roughness and thickness profiles acquired simultaneously by helicopter borne laser altimetry and electromagnetic induction sounding five thickness classes were identified using the modal thickness as a criterion for each class the statistical properties of the surface roughness profiles were analyzed a classification algorithm was designed which assigns profiles to the thickness classes on the basis of a set of selected statistical roughness parameters the algorithm was applied to profiles of different lengths best results were obtained for 2 km long profiles for which it was possible to discriminate well between thick first year and multi year ice and to distinguish these classes from thinner ice the classification rule was tested on data obtained under winter and summer conditions the results suggest that statistical surface roughness properties are different for thinner and thicker ice classes however individual thin ice classes cannot be discriminated on the basis of the selected roughness parameters the mass balance of sea ice is one of the key parameters in studies of the cryosphere accurate knowledge of this quantity is of fundamental importance for climate and ocean models as well as for quantifying past and future changes satellite remote sensing can be used to estimate the lateral dimension of the sea ice cover however ice thickness cannot be derived directly from satellite data so estimates of the mass balance are difficult as sea ice is found in remote regions field campaigns are difficult and costly in addition ground based thickness measurements can only be carried out on local and regional scales indirect methods to determine the mass balance of sea ice from remote sensing are therefore crucial this study presents an analysis of the surface roughness relative to level ice thickness the level ice thickness rather than the mean thickness is analyzed as it represents the prevailing thickness along a profile assuming that for sufficiently long profiles the length of the level ice sections in the profile is greater than the length of the deformed ice sections we take this value as representative of different ice types as defined by the world meteorological organiza tion s sea ice nomenclature wmo 1989 level ice thick ness is estimated from the observed modal thickness roughness in our context is determined by undulations of surface height over the entire profile comprising both smaller undulations on level ice and deformation features such as ridges and rubble the question is addressed whether different ice types can be discriminated in an analysis of the surface roughness properties goff 1995 derived a method for stochastic modelling of sea ice draft he generated synthetic draft profiles from a set of statistical parameters estimated from upward looking submarine sonar data and compared these profiles to observed data we take the positive results of his comparison as a motivation to investigate whether the roughness properties of surface profiles described by a set of statistical parameters are characteristic for different ice types the work focuses on the roughness of the top side only as this property affects measurements from air and space borne sensors such as radar and laser

pervasive pressure solution transfer in a quartz sand the kinetics of deformation of a quartz aggregate by pervasive pressure solution can be under certain conditions of temperature and grain size strongly dependent upon the diffusivity of silica into the grain to grain contacts an analysis of the factors affecting this key parameter and less well constrained in the analysis of the problem of rock deformation by pressure solution is presented this analysis is based on recent advances on studying silica surfaces and particularly on the existence of a silica gel layer on the silica surfaces undergoing dissolution by reinvestigating the electroviscous effect occurring at the grain to grain contact the present analysis shows that the diffusivity of silica at the grain to grain contacts is likely to be relatively similar to that in the bulk pore water maybe 1 order of magnitude smaller but not more this contradicts the previous work by rutter 1976 which has been the key reference used in many subsequent papers to justify an extremely low value for the diffusivity of silica at the grain to grain contacts 5 orders of magnitude smaller than the diffusivity of silica in free water this finding has dramatic implications concerning the deformation rate of quartz sands and sandstones by pressure solution in sedimentary basins with regard to 1 the limiting step affecting the kinetics of the process diffusion of the solute or dissolution precipitation chemistry and 2 the existence of a thermodynamic equilibrium state when deformation by pressure solution occurs over geological timescales a poroviscoplastic model is used to describe deformation associated with pervasive pressure solution transfer in quartz sands this model is shown to be consistent with the current state of knowledge of the surface chemistry of silica in addition the comparison between this model and both laboratory and field data is rather good

orbital insolation forcing of the indian monsoon a motor for global climate changes abstract both modern and ancient indian summer monsoons are driven by transequatorial pressure differences directly coupled with the insolation difference between the northern and southern subtropical hemispheres a high resolution record of upwelling and dust flux from the western arabian sea resembles an insolation based indian summer monsoon index this index and the observed monsoonal climate variations share major elements on the orbital obliquity and precessional band with the specmap marine oxygen isotope record representing global ice volume the long term evolution of the index mirrors almost exactly the insolation changes at 65 n showing that the forcing of low latitude climate variability has a structure similar to that of the insolation forcing in the high northern latitudes moreover insolation forcing in the low latitudes directly controls atmospheric processes in the african indian and asian monsoon being responsible for a huge amount of transequatorial water vapour and therefore latent heat transport millennial scale variability of the monsoonal climate is concentrated at periodicities near 1100 1450 1750 and 2300 years these cycles are not strictly periodic but occur in bands with specific activity phases and amplitude increases during warm stages and interstadials for the 1100 and 1750 yr cycles whereas the 1450 yr cycle dominates the cold intervals