jebar bottom pressure torque and gulf stream separation abstract a diagnostic finite element barotropic ocean model has been used to simulate the mean circulation in the north atlantic with the inclusion of the joint effect of baroclinicity and relief jebar the gulf stream is found to separate at the correct latitude 35 n off cape hatteras results suggest that the jebar term in three key regions offshore of the separation point in the path of the main jet along the slope region of the north atlantic bight and in the central irminger sea is crucial in determining the separation point the transport driven by the bottom pressure torque component of jebar dominates the solution except in the subpolar gyre and is also responsible for the separation of the gulf stream excluding high latitudes in the deep water formation regions density variations in the upper 1000 m of the water column govern the generation of the necessary bottom pressure torque in our model examination of results from the world ocean circulation experiment community modelling

petrographic and geochemical analysis of caliche profiles in a bahamian pleistocene dune two caliche profiles from a pleistocene carbonate dune on san salvador island bahamas were examined by petrographic and geochemical analysis profile a is an immature buried caliche profile characterized by caliche pisolites a friable crust and abundant cerion profile b is a more well developed caliche profile at the top of the dune which contains abundant pisolites rhizomorphs laminated calcrete a breccia and abundant cerion geochemical changes in caliche profiles relative to the host rock are an increase in al2o3 fe2o3 and total organic carbon a decrease in mg and sr and a decrease in 13ccarb 18ocarb and 13corg the magnitude of these changes is probably a function of the duration of subaerial exposure and resultant colonization by dune plants and associated microflora abundance of calcified filaments and needle fibre crystals in profile a attests to the importance of microbial processes in the early development of caliche profiles biogenic structures are largely destroyed in profile b due to recrystallization but indirect evidence of biological activity is retained in the form of carbon isotope values

observed cross shelf flow induced by mesoscale eddies in the northern south china sea abstractcross shelf flow induced by mesoscale eddies has been investigated in the northern south china sea nscs using velocity observations from long ranger adcp moorings mesoscale eddies influe

the stable isotopic composition of modern soil carbonate and its relationship to climate the oxygen isotopic composition of modern soil carbonate is well correlated with the isotopic composition of local meteoric water the carbon isotopic cycle for co 2 in soils can be described in terms of the proportion of biomass using the c 4 photosynthetic pathway and the co 2 respiration rate of the soil at low soil respiration rates significant atmospheric co 2 mixing can occur in general the carbon isotopic composition of soil carbonate is related to the proportion of c 4 biomass present in soil but soils that freeze to the depth of carbonate formation often have a significant atmospheric component this suggests that freezing of the soil solution should be considered as another important mechanism for soil carbonate formation because of these relationships the isotopic composition of soil carbonate may be a paleoclimatic and paleoecologic indicator in cases in which diagenetic alteration has not occurred

clinoforms and clinoform systems review and dynamic classification scheme for shorelines subaqueous deltas shelf edges and continental margins abstract clinoforms are inclined and normally basinward dipping horizons developed over a range of spatial and temporal scales in both siliciclastic and carbonatic systems the study of clinoform successions underpins sequence stratigraphy and all efforts to reconstruct the relative partitioning of reservoir seal and source rocks along shoreline to basin floor profiles here we review clinoform research and propose a more systematic description and classification of clinoforms this is a crucial step to improve predictions of facies and lithology distribution within shoreline to continental shelf and abyssal plain successions together with the genesis drivers and dynamics of their constituent sedimentary units four basic clinoform types are here distinguished in delta shorelines lacustrine and marine environments on the basis of their overall spatial and temporal scale morphology outbuilding dynamic and geodynamic and depositional setting 1 2 delta scale clinoforms which in turns are sub divided into shoreline and delta scale subaqueous clinoforms 3 shelf edge clinoforms and 4 continental margin clinoforms delta scale clinoform sets are tens of metres high and typically represent 1 103 kyr with progradation rates ranging from 1 000 100 000 m kyr for shorelines and subaerial deltas to 100 20 000 m kyr for subaqueous deltas shelf edge clinoform sets are hundreds of metres high and are nucleated and accreted in 0 1 20 myr usual progradation rates of 1 100 m kyr by successive cross shelf transits of delta scale clinoforms continental margin clinoform sets are thousands of metres high hallmark key geodynamic crustal boundaries e g continent ocean transition and slowly prograde basinwards in ca 5 100 myr with typical rates of 0 1 10 m kyr as a consequence of the very different progradation rates and of the difficulty of large scale clinothems to backstep during transgressions shorelines are the most dynamic clinoforms with regards to position continental margins the least and shelf edges are intermediate shortly after a transgression therefore the four clinoform types may prograde synchronously along shoreline to abyssal plain transects forming compound clinoform systems during the subsequent regressive cycle however due to the dissimilarity in progradation rates different clinoform types will normally merge progressively with each other giving rise to hybrid clinoforms e g shelf edge deltas and fewer depositional breaks in slope are distinguished along a single shoreline to abyssal plain transect overall all clinoform systems are the result of the dynamic evolution of compound and hybrid clinoforms along a temporal and spatial continuum regulated by the cyclical backstepping of the smaller scale system within natural progradational retrogradational cycles of larger scale clinothem outbuilding all clinothem types may show either an accretionary active or draping passive style depending on the proximity to the sediment source draping clinothems are nearly always composed of condensed fine grained sediments while actively accreting clinothems can be composed of predominantly coarse grained i e reservoir forming or predominantly fine grained i e non reservoir lithotypes a novel hierarchical classification scheme for both recent and ancient clinoforms is here proposed consisting of 12 classes the four basic clinoform types delta scale shoreline delta scale subaqueous shelf edge and continental margin are sub divided into eight accretionary active and draping passive sub types 8 division each accretionary sub type is then sub divided into a sandstone prone and mudstone prone variant 12 division which can be at least tentatively predicted on the basis of the clinoform morphology even in the absence of direct stratigraphic logs

palaeoenvironmental significance of palustrine carbonates and calcretes in the geological record interest in palustrine carbonates and calcretes has increased over the last 20 years since they contain significant environmental information much of the work performed in this area has focused on either of two types of terrestrial carbonate palustrine carbonates or calcretes pedogenic and groundwater yet their simultaneous study shows there may be a gradual transition from one form to the other revealing the interplay between pedogenic sedimentary and diagenetic processes three main factors control the formation of these carbonates the position of the water table the host rock and the period of sub aerial exposure in pedogenic calcretes precipitation of carbonate takes places mostly in the vadose zone above the water table and within a previous host rock or sediment in groundwater calcretes the precipitation of carbonate also occurs within a previous host rock and around the groundwater table in palustrine carbonates however the precipitation of lime mud occurs in a lacustrine water body palustrine carbonates necessarily form on previous lacustrine mud whereas both types of calcretes may form on any type of sediment or soil the sub aerial exposure time needed to form palustrine carbonates may by relatively short even a season whereas pedogenic calcretes need more time several years to millions of years groundwater calcretes do not form on the topographic surfaces so there is no need of sub aerial exposure however stable surfaces favour the development of thick groundwater calcretes small fluctuations in the water table cause gradual transitions of these three types of terrestrial carbonates and the subsequent mixture of their characteristic features causing difficulties in the interpretation of these carbonates the formation of these carbonates is controlled by palaeoenvironmental factors both commonly form in semi arid climates arid climates are also suitable for calcretes but sub humid conditions are more suitable for palustrine carbonates more indications of climatic conditions may be obtained through the analysis of the d18o content of both calcretes and palustrine carbonates and from the depth of the horizon containing carbonate nodules in pedogenic calcretes vegetation is also important in the formation of these types of carbonates data on the prevailing vegetation can be obtained from the analysis of the micro and macrofabric as well as from the d13c signal of the primary carbonates which in pedogenic carbonates has also been used to estimate atmospheric pco2 during the phanerozoic these terrestrial carbonates are widely distributed on floodplains and distal areas of alluvial basins their presence and characteristics can be used as indicators of aggradation subsidence or accommodation rates and therefore as indicators of different tectonic regimes even though the study of these carbonates has notably increased in recent years much less is known about them than about marine carbonates presently there is much emphasis on obtaining a general model for sequence stratigraphy in terrestrial basins with a need to include the carbonates analysed in this paper

the application of cathodoluminescence to interpreting the diagenesis of an ancient calcrete profile a laterally extensive calcrete profile has been identified in the late asbian lower carboniferous shallow marine shelf limestones of the llangollen area north wales the upper surface of the profile is defined by a laterally discontinuous palaeokarstic surface and by laminated calcareous crusts which developed within the underlying limestone the profile contains a unique series of early pore filling vadose cements which only occur down to 1 m below the palaeokarstic surface cathodoluminescence reveals that these cements pre date the late pore filling meteoric phreatic cements which occur throughout local asbian lithologies a spar cement stratigraphy has been established for the calcrete profile subaerial vadose cements comprise two generations of non luminescent cement followed by a brightly luminescent generation which occasionally shows an acicular habit this needle fibre calcite represents the final stage of vadose cementation precipitation of vadose cements was contemporary with subaerial alteration and micritization of the limestone textures visible only with cathodoluminescence provide evidence of recurrent periods of fabric dissolution the most extensive phase of dissolution occurred immediately after the precipitation of the non luminescent subaerial vadose cements several different textures have been recorded each reflecting the morphology of a partially dissolved substrate dissolution textures are generally confined to the walls of the larger pores and to early brecciation fractures these probably acted as fluid pathways in the calcrete during early subaerial diagenesis much of the non marine micrite in the calcrete profile appears as needle fibre calcite under cathodoluminescence this acicular calcite was probably formed in response to localized supersaturation of meteoric pore fluids caused by periods of near surface evaporation since needle fibre luminescence is strongly variable these ambient conditions are not believed to have directly controlled the activator ion concentrations of cementing pore waters needle fibre calcite is considered to be a cement precipitate which has almost completely recrystallized to micrite probably during the late stages of subaerial diagenesis two generations of subaerial micrite which define a micrite stratigraphy have been distinguished under cathodoluminescence reconstructing the diagenetic history of this ancient calcrete profile has revealed that subaerial alteration was multistaged with many diagenetic processes acting simultaneously during a single phase of emergence

kalahari valley calcretes their nature origins and environmental significance abstract calcretes that form in non pedogenic settings have been widely reported in the geomorphological and geological literature yet they are still poorly understood in comparison with pedogenic varieties this may be because there are assorted types of non pedogenic calcretes often loosely referred to as groundwater calcretes but encompassing groundwater phreatic open valley or confined channel calcrete types forming within vadose and phreatic environments in different geomorphological settings relatively few studies have described the detailed petrological characteristics of such calcretes leading wright and tucker calcretes international association of sedimentologists reprint series 1991 vol 2 blackwell scientific publications oxford p 10 to suggest that much more work is needed to define the groundwater calcrete facies and to devise criteria for its recognition so that the various non pedogenic calcretes can be identified within the quaternary as well as further back in the geological record most descriptions of groundwater calcretes are highly generalistic and do not take into account the variability that may occur as a result of calcretes forming in different positions within a landscape and affected by separate controls thus the range of groundwater calcretes that exists now needs to be studied individually to identify patterns within the distinct types as a step towards expanding our knowledge of the variety of non pedogenic calcretes this paper describes the petrology micromorphology and mode of development of one of these types of calcrete namely that which forms within valley locations but not in definite fluvial channels late quaternary to holocene valley calcretes are described from various dry valleys mekgacha across the kalahari region of central botswana with the majority of samples collected from trunk and tributary valleys of the okwa samples have been analysed in thin section and under scanning electron microscope in order to determine the carbonate matrix type and calcrete micromorphology in general most samples consist of grains of quartzose kalahari sand cemented by fine crystalline often glaebular grain coating and pore filling micrite cement types are fairly consistent and not as micromorphologically variable as has been noted for other kalahari calcretes biological inputs are prevalent in many samples and include networks of calcified rootlets these characteristics reflect the fact that the calcretes formed in a relatively near surface environment with relatively high rates of evaporation

intraseasonal variability of cross slope flow in the northern south china sea abstractcross slope flow plays an important role in the exchange of material heat and momentum between the continental shelf and the open sea in the northern south china sea scs long period ob

variability of circulation induced by the separation of gaspe current in baie des chaleurs canada observational studies the observed variability of summer circulation in the baie des chaleurs bdc canada is found to be largely controlled by the intrusion separation processes of a coastal jet gaspe current gc at the bay entrance an analysis of hydrographic and current meter data showed that the mean counter wind cyclonic circulation in the bdc from spring to the beginning of the cooling season in 1991 was ascribed to the westward intrusion of the gc the forcing mechanism of the gc on the bdc was determined by the characteristics of the coastal jet separation under the intrusion regime the gc entered into the bdc along the north coast of the bay suppressed the local wind driven eastward currents and formed a cyclonic circulation in the bay under the separation regime gc mainly passed across the entrance of the bdc with the formation of an anticyclonic recirculation at the lee of the jet near the bay entrance and a weaker cyclonic circulation in the bay dynamics of the boundary current separation is utilized to reason the observed variability of flow field in the bdc

using two and three dimensional georadar methods to characterize glaciofluvial architecture abstract the threat of pollution in the shallow subsurface has led to an increasing need to understand how complex heterogeneities in gravel aquifers influence groundwater transport to characterize these heterogeneities we have conducted extensive two dimensional 2 d and three dimensional 3 d ground penetrating radar gpr or georadar surveys in two quarries within the rhine valley of northeastern switzerland the quarries comprised gravel and sand deposited in a proglacial braided river system that followed the maximum wurm stage glaciation after the surveys the terrace walls beneath the two study sites were photographed as they were being excavated by combining information extracted from the 2 and 3 d georadar images with the outcrop photographs it was possible to correlate georadar facies with the various glaciofluvial architectural elements the dominant elements were scour pools formed at or near the confluences of two stream channels and horizontally bedded and massive gravel sheets deposited during moderate to high water flow conditions and exposed during low flow conditions architectural elements were generally elongated parallel to the mean flow directions of the ancient river system variations in the strike of their long axes reflected lateral and vertical changes in the local flow direction time slices showed structural trends not evident on 2 d georadar images and photographs data interpretation was quicker more complete and less ambiguous when georadar facies analyses were based on a combination of georadar vertical profiles and time slices than when based on georadar vertical profiles alone

early carbonate diagenetic fabrics in the rhizosphere of late pleistocene aeolian sediments analysis of a range of aeolianite deposits from the western mediterranean roquetas in southern spain and campo de tiro in mallorca and the bahamas crab cay on san salvador island has shown that biota can be important in the diagenesis of deposits in the vadose zone and this may aid in the interpretation of palaeoenvironments particularly where pedogenic calcretes are absent this paper looks at how the growth of roots into dune sediments and the associated profusion of micro fauna and micro flora can have on a local scale a profound affect on the early diagenetic and sediment fabric these fabrics are affected at three levels 1 at the site of the former root 2 directly surrounding the root the peritrophic zone and 3 from the peritrophic zone to a few tens of centimetres from the former root

human induced calcretisation in anthropogenic soils and sediments field observations and micromorphology in a mediterranean climatic zone israel abstract for over a century the study of pedogenic calcrete and its formation focuses on natural processes disregarding the possible role of humans in its formation here we present field and micromorphological evidence from archaeological and modern sites in the eastern mediterranean region israel that indicate that some specific calcretes are human induced we demonstrate that anthropogenic affected calcrete differs from natural non human induced calcrete we show that the occurrence of the human induced calcrete is spatially limited and is associated with both macro and micro scale remnants and occasionally high content of organic material we propose an operative definition for anthropogenic calcretisation as the interference of humans with a component s that influence the formation of calcrete we assume that if present day calcretised environments will retain their calcretisation prone conditions for the next 5 10 millennia a distinct calcretic morphology could become a significant terrestrial formation this discovery can be particularly useful for evaluating past human impact on the environment adding a new archaeological set of research tools that should further be developed

stable carbon and oxygen isotope signatures of pedogenic needle fibre calcite abstract carbon and oxygen isotope compositions of the needle fibre calcite nfc from two soils observed in quarries villiers and savagnier in the swiss jura mountains are used to investigate the processes involved in the formation of these calcite crystals in pedogenic environments nfc occurs in soils with different macroscopic and microscopic morphologies three groups of microscopic morphologies are distinguished simple needles sn simple needles with overgrowths sno and simple needles with nanofibres snn nanofibres being either organic or mineral in nature these groups correspond to different stages in the formation and evolution of nfc evaluation of the 13c and 18o values of nfc and late calcite cements lcc in relationship to the composition of the carbonate host rock chr and 13cdic from the soil waters indicate that both nfc and lcc are precipitated in isotopic equilibrium with the soil waters similar 13c and 18o values of the elongated nfc and the rhombohedral calcite crystals of the lcc suggest that the precipitation of these different calcite habits is not due to changes in physicochemical conditions the growth of nfc crystals inside an organic mould formed by the fungal hyphae could explain the formation of calcite crystals in the shape of a needle in isotopic equilibrium with the local environment the comparison of the 13c and 18o signatures of the various nfc morphological groups suggests that they likely evolve in the soil solution from calcite crystals liberated during the degradation of fungal hyphae walls the nfc may be a proxy of the soil conditions temperature and vegetation during its precipitation and also an indicator of biogenic fungal activity

interpretation of late quaternary climate and landscape variability based upon buried soil macro and micromorphology geochemistry and stable isotopes of soil organic matter owl creek central texas usa abstract small basin floodplain buried soils formed in association with low order tributary streams are valuable archives of past climates but have not been studied extensively in central texas usa four buried soils exposed along owl creek within the larger brazos river drainage basin were examined using soil morphology and micromorphology optically stimulated luminescence osl dating soil characterization whole soil geochemical and stable isotope analyses of soil organic matter and pedogenic carbonate these buried soils provide a record of changes in paleoecological and paleo alluvial conditions spanning 14 ky morphological and geochemical differences between buried soils reflect changes in landscape attributable to climate with a distinct 5 increase in 13 c values of soil organic matter corresponding to the holocene onset and drier conditions paleoecological reconstructions coupled with depth to bk suggest possible amounts of erosion of 1 m for each of the buried soils compilation of the proxies presented shows evidence for a cooler and wetter late pleistocene climate followed by a warmer and drier climate dominating during the holocene

oceanic eddy formation and propagation southwest of taiwan 1 oceanic eddies are active and energetic southwest of taiwan the formation and propagation of eddies in this area were investigated using 17 year satellite altimeter data cyclonic eddies ces and anticyclonic eddies aces often coexisted but there were more ces than aces generated during the period from october 1992 to october 2009 aces were stronger and in general lived longer than ces aces occurred more often in winter than in other seasons while ces were more frequent in summer compared with the direct local wind forcing the kuroshio path variability appears to be a dominant factor for eddy formation in this area a conceptual model of an eddy kuroshio interaction is proposed in summer there exists an outflow northwest of luzon island and the kuroshio likely leaps across the luzon strait to the north of the outflow and left of the kuroshio axis ces are often formed which in turn induce aces to the west of ces in winter under the influence of northeasterly monsoon the kuroshio current loop kcl appears southwest of taiwan more frequently than in other seasons and aces are frequently shed from the kcl most of the aces propagate westward and as a result ces are often spun up to the east of the aces the surface south china sea outflow in summer and the kcl in winter are however likely related to the monsoons therefore the indirect effects of monsoon winds are also evident in the seasonal variations of eddy occurrence

oxygen and carbon isotopic composition of quaternary meteoric carbonates from western and southern europe their role in palaoenvironmental reconstruction abstract the relationship between environmental conditions and the 18 o and 13 c values of soil and groundwater carbonates in europe is poorly understood consequently the use of the isotopic composition of these carbonate palaeoclimatic indicators in european sedimentary sequences is restricted in this study we examine the 18 o and 13 c values of soil and groundwater carbonates from western and southern europe in western europe there is no relationship between carbonate 18 o values and carbonate 13 c values the 18 o values of soil carbonate appears to be driven by temperature whilst the 13 c value of soil and groundwater carbonate reflects the persistent dominance of c 3 vegetation in this region during the quaternary the 18 o and 13 c values of soil carbonates from spain and crete show a strong degree of co variance suggesting that they are being controlled by the same environmental factor this is suggested to be aridity 18 o values are controlled by soil moisture evaporation whilst 13 c value is controlled by soil moisture degassing vegetation abundance and possible c 3 c 4 vegetation inputs the paper concludes by highlighting the fact that although currently under utilised the 18 o and 13 c values of soil and groundwater carbonates have a huge potential for providing important palaeoenvironmental information from sites across europe

separation of tidal and subtidal currents in ship mounted acoustic doppler current profiler observations a simple method is developed to analyze current measurements obtained from a moving platform the need for this is motivated by the now common use of the ship mounted acoustic doppler current profiler adcp to acquire absolute velocity data during an oceanographic survey of a given region the full potential of this new measurement technique is severely hindered when the presence of high frequency phenomena e g tidal or inertial motions prevents a clear visualization of the lower frequency current structure of interest our analysis method is based on a spatial interpolation scheme using arbitrary functions that allows for the tidal current time variability which then permits the tide induced motions to be subtracted from the adcp data to yield the subtidal current field the method also allows nearby moored and drifter current measurements if available to be combined with the shipboard adcp observations in a single analysis to obtain the best description of the tidal and subtidal currents to illustrate this method we present results from the analysis of adcp data taken during oceanographic surveys in two different continental shelf regions the east china sea and the amazon shelf a 5 day conductivity temperature depth ctd and adcp survey was made in the east china sea near the mouth of the yellow sea during january 1986 there the currents were essentially barotropic and dominated by the semidiurnal tide the adcp derived cotidal chart for the m2 12 42 hours component agrees well with existing charts derived empirically from sea level observations or from regional numerical models the adcp derived steady flow is also consistent with the observed density field and indicates little flow in or out of the yellow sea and a transport of about 1 sv toward the tsushima strait two ctd adcp surveys lasting 21 and 23 days were conducted over the amazon shelf during march and may 1990 simultaneously moored current observations were also obtained at three locations along a cross shelf array 200 km north of the amazon river mouth for a common period of at least 2 months february 12 to april 13 over the shelf tidal and subtidal currents were comparable in magnitude our analysis indicates that the tidal currents were essentially barotropic semidiurnal and polarized in the cross shelf direction increasing in magnitude toward the inner shelf where current values of more than 2 m s are common the adcp derived steady currents were aligned in the along shelf direction and strongly influenced by the north brazil current nbc during both adcp surveys the northwestward flowing nbc was transporting more than 2 sv over the shelf at depths shallower than 100 m

depositional characteristics and processes of alongslope currents related to a seamount on the northwestern margin of the northwest sub basin south china sea this study infers from 2d seismic data the presence of a seamount related deep water contourite depositional system located on the northwestern margin of the northwest sub basin of the south china sea alongslope aligned erosive features and contourite drifts developed in water depths between 1000 and 1500 m on the present seafloor a moat formed north of the seamount as a result of bottom current intensification after being deflected by an obstacle morphology indicating a major eastward flowing current due to the coriolis deflection an elongated mounded drift developed to the north of the moat and a modest plastered drift to the south onlapping the north side of the seamount bottom currents away from the seamount are less or minimally intensified generating contourite channels and furrows over the drift to the north of the moat combined with the known oceanographic setting the bottom currents could belong to the anticyclonic south china sea intermediate water circulation from the seismic data the architecture of contourite deposits during progressive burial of the seamount is documented the first appearance of contourite channels in seismic unit 1 is inferred to be the onset of the contourite depositional system which could be traced back to the early late miocene the following aggradational pattern of this system from the base of seismic unit 2 onwards indicates relatively enhanced and stable south china sea intermediate water circulation occurring on the northwestern margin of the northern south china sea subsequently the behaviour and depositional processes of bottom currents upstream and downstream the seamount are discussed the depositional model suggests that a complex contourite channel system will replace the former moat drift system once the seamount is buried finally our findings may provide new challenges for investigating the south china sea cenozoic palaeoceanography which are helpful to understand the sedimentary dynamic processes related to the south china sea deepwater circulation c 2014 elsevier b v all rights reserved

two layer model on the branching of the kuroshio southwest of kyushu japan observations suggest that a separation branch of the kuroshio appears southwest of kyushu japan the observed density and surface current fields clearly show a separation branch in autumn however the separation branch disappears in winter and spring when the relatively homogeneous structure develops due to the intense surface cooling a scenario generating a separation branch is examined using simple two layer model the northward kuroshio along the shelf slope turns to the east abruptly and leaves the shelf slope around tokara strait a hump local increase of the upper layer thickness is made by the lower layer flow impinging on the bottom slope this hump extends to the shallow shelf region due to the combined effect of advection and dissipation of the upper layer thickness then the cross isobath flow that is the separation branch appears around the hump when the thin upper layer obstructs the advection process in winter and spring a separation branch disappears moreover the separation branch disappears when a small damping coefficient is used

mesoscale eddies cases study at xisha waters in the south china sea in 2009 2010 analyzing the observed currents at xisha 110 3899 degrees e 17 1038 degrees n during may 2009 to may 2010 it is found that the kinetic energy has significant mesoscale variability and each peak responds to large positive negative ocean surface current curl caused by mesoscale eddies compared the kinetic energy with the wind stress work and the pressure work it is also found that the barotropic pressure work which is mainly contributed by the sea surface height ssh corresponding to the mesoscale eddies behaves like the kinetic energy the contribution of the mesoscale eddies to the kinetic energy can be up to 90 sometimes and reach deep level every time using the satellite altimeter data the paths of mesoscale eddies contributing to the kinetic energy variability are traced back in the winter half of the year the mesoscale eddies propagating along the northern south china sea shelf or across the basin from the west of the philippines toward xisha arrive at xisha influencing the kinetic energy in the summer half of the year the mesoscale eddies are mainly from the south which were shed from the vietnam coast current and the cause for eddy shedding may be related to the relaxation of the ekman transport anomalies

dynamically active areas in the south china sea detected from topex poseidon satellite altimeter data abstract topex poseidon t p altimeter measurements from december 1992 to april 1998 were processed to study the sea surface height ssh variation in the south china sea scs patterns of variance of the ssh deviations from the four year 1993 1996 mean show that there are three high variation areas in the deep basin the first is at the northern basin west of luzon island 16 18 n 117 119 e the second is at the center of the scs 14 16 n 113 5 114 5 e and the third is off the central vietnam coast 12 13 n 110 112 e from empirical orthogonal function eof analysis we found that the variations of these three active areas are dominated by annual cycles but out of phase the first two areas have the highest ssh in june and the lowest ssh in december the third one off the vietnam coast has the highest ssh in february and the lowest ssh in august the eof analysis also reveals that the variation of ssh in the scs has a response to el nino events

on the unsteady separation intrusion of the gaspe current and variability in baie des chaleurs modeling studies a numerical model has been used to study separation intrusion of an unsteady baroclinic coastal jet the gaspe current gc and its impact on dynamics and thermodynamics of the baie des chaleurs bdc gulf st lawrence canada the model has 2 layers with primitive equation dynamics and an embedded bulk mixed layer ml model it is forced with observed atmospheric fluxes as well as the gc the simulations show that the variability in the baie des chaleurs is controlled by the characteristics of the unsteady gc separation intrusion on the basis of the dynamic and vorticity balance analyses it is found that the separation is related to the adverse pressure gradient force which is induced by the ageostrophic terms in the momentum equations and to local vorticity intensification due to the inertial effect in the flow the simulations demonstrate characteristics of unsteady separation the presence of separation in an accelerating current as well as in a linear current with strong deceleration when momentum advection is neglected gives new insight into the mechanisms of unsteady boundary current separation unsteady separation or intrusion occurrence depends on the magnitude of the gc transport as well as its rate and duration of deceleration or acceleration the gc intrusion generates cyclonic circulation in the bdc prevailing westerly winds reduce the cyclonic circulation inside the bay but have little effect on separation intrusion near the entrance the gc either intrudes along the coastline attachment or after separation reattachment increasing vertical shear of the gc and offshore movement of the gc axis reduces the tendency to separate the finding of an asymmetric response of gc separation intrusion to symmetric gc forcing explains the monthly mean features seen in observations taken in the bay

facies and ground penetrating radar characteristics of coarse grained beach deposits of the uppermost pleistocene glacial lake algonquin ontario canada the lithofacies of the uppermost pleistocene ca 11 800 to 10 400 14 c yr bp cold temperate coarse grained beach deposits of lake algonquin the precursor of the present lake huron of north america have been studied and interpreted based on analogous features of modern beaches from the same region ice foot and ice cementation develop during winter but unlike arctic beaches ice related sedimentary features are seldom if ever preserved in the pleistocene and recent deposits of the great lakes instead the deposits retain the typical characteristics of wave dominated pure gravel and mixed sand and gravel beaches there including the classical subdivision of infill zone swash zone sand run imbricated zone coarse flat clast zone and coastal dunes these zones form a regular succession on the surface of many modern beaches however they seldom occur as quasi complete vertical successions in older deposits in the studied uppermost pleistocene deposits the various components are separated vertically by erosional contacts bounding surfaces readily recognizable on working faces of large sand and gravel pits and mappable in the subsurface by ground penetrating radar the lithofacies are sufficiently diagnostic to allow recognition of depositional settings and the lithofacies architecture allows the deciphering of important geological events such as i local input of fluvial material onto the shoreface where it was partially reworked by waves and moved onto the beachface ii occurrence of major storm events and iii repeated rapid transgressions and regressions typical of the glacial lake precursors of the modern great lakes

winter eddy genesis in the eastern south china sea due to orographic wind jets abstract generation of mesoscale eddies in the eastern south china sea scs in winters during august 1999 to july 2002 is studied with a reduced gravity model it is found that the orographic wind jets associated with the northeast winter monsoon and the gaps in the mountainous island chain along the eastern boundary of the scs can spin up cyclonic and anticyclonic eddies over the scs results suggest that direct wind forcing could be an important generation mechanism for the rich eddy activity in the scs and that to simulate this mechanism the resolution of the wind forcing has to be high enough to resolve the local wind jets induced by orographic effects

pedogenic carbonates on precambrian silicate rocks in south india origin and paleoclimatic significance abstract calcrete in alfisols on precambrian silicate rocks is studied here in an attempt to reconstruct paleorainfall trends in semiarid south india facies of observed carbonate accumulation are pseudomycelium calcrete nodules nodular horizons hardpan and laminar horizons based on geochemical and sr isotope tracing we relate the presence of calcrete to local geologic conditions within the precambrian basement notably discrete ca rich metamorphic outcrops and rule out eolian input micromorphologic analysis reveals a multi stage origin of the calcretes involving soil colluvial geochemical and biologic processes mostly in vadose environments preliminary u th ages of 190 200 ka obtained on calcrete nodules suggest a major phase of ca release rock weathering and precipitation during marine oxygen isotope stage 7 the calcrete thus indicates fairly stable semiarid conditions at the 200 ky time scale despite fluctuations around an annual rainfall average close to current values 700 mm the stability of the western ghats barrier as a shield to the southwest monsoon explains the long term average stability of the pedoclimatic environment in the rainshadow zone the radiometric ages suggest that weathering may occur massively at discrete intervals of geologic history during spikes of humidity in the paleoclimatic record the rest of the time is spent recycling and redistributing the products of weathering incrementally at landscape scale within seasonal cycles of a relatively stable semi arid climate dating the calcrete therefore does not equate with dating the soil but instead the residence times of nodules in a dynamic soil system in which different constituents have different turnover rates

sediment dynamics driven by contour currents and mesoscale eddies along continental slope a case study of the northern south china sea abstract based upon 3 d seismic reflection data published drill core studies oceanographic observations and numerical modelling this study identifies a small scale contourite depositional system that is locally confined by canyons slope failures erosional terraces and erosional slopes on the jianfeng slope northern south china sea 1500 to 2300 m water depth possible oceanic driving mechanisms for the spatial heterogeneity in sedimentation and erosion within the quaternary deposits in this complex slope system are investigated numerical simulations show that the quasi steady south china sea deep water circulation which affects the study area is characterised by low velocities maximum 4 cm s with a slight modulation by tides 1 cm s this quasi steady deep water thermohaline circulation is able to keep sediment particles in suspension rather than to erode seafloor sediment the bottom hydrodynamic regime becomes energetic when mesoscale eddies horizontal scale of 10 to 100 km approach our modelling study indicates that both surface and bottom mesoscale eddies are essential to account for the spatial heterogeneity in sedimentation pattern along the northern south china sea continental slope according to simulation the eddy front contains the highest flow velocity over a mesoscale eddy cycle 45 days exceeding the threshold for resuspension of unconsolidated sediment 15 cm s as a consequence massive resuspension is produced at various sites and redistributed by sub mesoscale horizontal scale of 1 to 10 km circulations originated from an eddy topography interaction in contrast to the surrounding areas which are subject to erosional forcing for a relatively long part 7 of an eddy cycle both the locally confined drift and a further upstream large elongated mounded drift experience little erosion

calcretes from a palaeosinkhole in jurassic palaeokarst subbetic southern spain abstract calcretes have been recognized in the bottom of a palaeokarstic sinkhole etched into early jurassic carbonates from the subbetic southern spain these are 3 to 10 cm thick and they show an internal structure in which three units can be distinguished the lower unit is composed of alternate irregular bands of unfossiliferous micrite and sparry calcite in the micrite several features point out the activity of endolithic microorganisms as fungi and bacteria the middle unit which has a laminated structure with palisade calcite spar and some vadose silt is interpreted as a speleothem and finally the upper unit shows calcrete pisoids and rhizocretions the isotope ratio analysis gives results in which 13 c ranges from 10 1 to 10 9 and 18 o ranges from 5 7 to 7 0 these values are very similar to those from palaeosols of other ages and localities which is an important argument favouring emersion stages with continental deposition in an island with an arid or semi arid climate nevertheless these calcretes outcrop in association with a palaeokarstic relief reflecting wet climate before the calcrete formation

mineralogical geochemical and isotopic characteristics of quaternary calcretes in the adana region southern turkey implications on their origin abstract calcretes are widespread and form as nodular columnar tubular fracture infill laminated hardpan and conglomeratic crust in the adana region x ray powder diffractometry xrd scanning electron microscopy and energy dispersive analyses sem edx and differential thermal analysis thermal gravimetry dta tg reveal that calcretes and their host rock mudstones are composed predominantly of calcite and smectite respectively the other minerals determined in the samples are palygorskite quartz and feldspar palygorskite is a minor component of the calcretes the inductively coupled plasma atomic emission spectroscopy icp aes analyses reveal that the calcrete samples are characterized by high cao and loi values whereas the host rock mudstones contain relatively high values of sio 2 al 2 o 3 fe 2 o 3 and mgo the cross plots of sio 2 al 2 o 3 cao sio 2 cao mgo and cao fe 2 o 3 show positive and negative correlations their gradual change is due to the degree of the progressive calcretization causing mudstone replacement the 18 o and 13 c values range from 3 8 to 5 7 mean 4 4 and from 7 7 to 10 0 mean 8 6 pdb respectively which are consistent with values of pedogenic calcretes reported in the literature from worldwide sites the 18 o values indicate formation from meteoric water either by replacement or precipitation at estimated temperatures from 21 to 23 c the 13 c values are typical for pedogenic calcretes reflecting development under the c3 dominated vegetation cover and semiarid or seasonally arid climatic conditions

ground penetrating radar images of selected fluvial deposits in the netherlands ground penetrating radar gpr surveys have been carried out in order to characterise reflection patterns and to assess the method s potential for imaging palaeofluvial sediments in the mass rhine former confluence area in the southern netherlands the results show that the deposits of meandering braided and transitional river types produce characteristic radar facies representative examples of each of these river types were selected where the gpr data could be directly correlated with sedimentary information derived from exposures and detailed drilling and geomorphological data could be supplied individual channels may be distinguished by the radar facies of their fills the floodplains of the different river types also show a characteristic radar facies in gpr data from the meander floodplain parallel dipping reflections represent point bar structures while irregular intersecting small channel patterns that alternate with parallel continuous reflections are more typical in the braid plain a transitional river type shows characteristics of both of these types typical examples of gpr sections recorded in each of the different fluvial palaeoenvironments are presented in an interpretative radar facies chart

genesis of palygorskite and calcretes in pliocene eskisehir basin west central anatolia turkey abstract calcretes are common in the eskisehir province and occur as powder nodules tubes fracture infills and hard laminated crusts they are white in color and developed in the near surface setting of the pliocene reddish brown mudstones calcrete profiles consist mainly of isolated calcrete occurrences within mudstone palygorskite occurs generally as a beige colored layer in the mudstone and also as a minor component in the calcretes the calcrete nodules are roughly spherical to ellipsoidal in shape with diameters of 3 to 20 cm and are composed mainly of micrite locally recrystallized to microsparite and sparite detrital quartz and feldspar float in the micritic groundmass circumgranular cracks crumbly fractures and rhizoliths are also present xrd analyses indicate that calcrete samples are comprised mainly of calcite accompanied by small amounts of palygorskite quartz feldspar smectite chlorite and locally accessory illite and amphibole the sem tem images indicate that palygorskite fibers formed singly as bundles knitted and or matted aggregates either covering calcite crystals or smectite aggregates or as a meniscus cement between smectite flakes the latter are precipitated from meteoric water flushed through the open pore system of the sediments close to the surface based on the sem images palygorskite is presumed to have formed authigenically by direct precipitation in the vadose zone of a lacustrine environment following precipitation of calcite the 13c and 18o values of calcite indicate calcretization from meteoric soil water in an arid environment enrichment of ba sr ni and lree relative to mree hree and a negative eu anomaly reflect the fractionation of feldspar and amphibole in the parent mudstone the palygorskite associated with calcretes and mudstone was precipitated from alkaline water rich in si al fe and mg having mg rich character with a structural formula of si7 94al0 06o20mg2 96al0 99fe0 31 oh 2 oh2 4ca0 12k0 01 nh2o the required elements were derived from ophiolitic melange and volcanic units

abiogenic growth of needle fiber calcite in spring towers at shiqiang yunnan province china abstract at shiqiang china there are spring towers up to 4 m high and 3 m in diameter that are formed of porous gray to orange to brown bedded limestones that have a multistage diagenetic history the walls of many cavities in these limestones are covered with hypocoatings and or needle fiber calcite nfc that formed during the last stage of diagenesis where present the hypocoatings are 10 m thick appear homogeneous and typically lie under the nfc mats the nfc is divided into nanofibers rods 1 m long 75 100 nm diameter composite fibers bundles of 2 to 16 rods each rod 300 400 nm in diameter up to 25 m wide and 100 m long pyramid fibers pyramid shape with 4 to 6 sides up to 25 wide at base tapering to point up to 100 m long and ribbon fibers blade shape 2 4 m wide 1 m thick up to 100 m long many crystals are highly ornate with epitaxial overgrowths that display elements of skeletal and or dendritic growth the wall covering nfc mats are formed of one crystal type or any combination of different crystal types with or without epitaxial overgrowths precipitation of needle fiber calcite known from a diverse array of geological settings throughout the world is commonly linked to fungi or other biogenic processes in the shiqiang spring towers however no fungi were found with the nfc and only scattered microbes and minor amounts of exopolysaccharides were associated with some of the nfc in some pores the nfc crystals appear to have been precipitated from fluids that were highly saturated with respect to calcite as a result of evaporation the calcium probably came from rainwater groundwater via capillary action and or dissolution of the calcite framework whereas evaporation was mediated by solar radiation and or the wind available evidence indicates that the nfc found in the spring deposits at shiqiang were a late diagenetic product that probably formed through abiogenic precipitation

lacustrine and palustrine facies in the bembridge limestone late eocene hampshire basin of the isle of wight southern england abstract the carbonate lake system represented by the late eocene bembridge limestone formation isle of wight southern england comprises two main facies lacustrine and palustrine these facies are arranged vertically in transgressive regressive cycles corresponding to a model of carbonate lakes of low gradient and fluctuating margins with extensive palustrine fringes these lakes developed in a coastal plain of limited relief where two paleogeographical domains predominate a lacustrine domain is represented in northern and eastern sections in the isle of wight by cycles representing upward passage from central lacustrine sub facies marl marly limestone through marginal lacustrine sub facies biomicrite to sub facies indicative of exposure brecciated nodular limestone a palustrine domain predominant in west wight is represented by a predominantly pedogenic palustrine facies with clotted peloidal to ooidal textures and some intercalated laminated laminar calcrete horizons within the pedogenic facies textures have evolved from those of unaltered biomicrites through clotted peloidal to dense ooidal to open ooidal textures a third domain developed in close geographical proximity to more saline waters is represented by gypsiferous lake margin facies found in north wight in which microlenticular gypsum developed post depositionally as a result of evaporation following subaerial sediment exposure in the lacustrine domain there appears to be an association between cyclicity and changes in base sea level reflecting a likelihood that the lakes were part of a paralic coastal plain complex with distal marine connections alternatively the cyclicity might have developed as a result of the alternation of wetter and drier climatic periods

submarine erosional troughs in the northern south china sea evidence for early miocene deepwater circulation and paleoceanographic change abstract the paleoceanography of the south china sea scs is poorly understood although recent cruises and an odp expedition leg 184 have provided a useful general framework here we report previously unrecognized multi km scale sedimentary structures consisting of coupled ridges and troughs within the early miocene strata using high resolution 3d seismic data from the northern scs margin the troughs are interpreted as linear and or arcuate erosional features which truncate the underlying strata they range in orientation from e w in the southern part of the study area to nearly ne sw in the northwestern part of the study area the spacing of erosional troughs varies from less than 0 1 km in the southern part to more than 3 km in the northern part and they are about 50 1500 m in width with a relief of 10 90 m the erosional troughs are parallel to the regional strike of the early miocene slope of the northern scs from their internal geometry context regional distribution and most importantly their orientation relative to the paleo slope gradient at the time of their formation it is argued that they formed due to the action of bottom currents linked to the broader paleo circulation regime in the basin we infer that the paleo bottom currents intruding from the pacific flowed along the northern scs slope resulting in the occurrence of localized erosional troughs as deep water masses impinged on and interacted with the sea floor topography this study provides new insights into the early miocene paleoceanography of the scs and demonstrates the utility of 3d seismic data to enhance our understanding of paleo bottom current circulation regimes

an analysis of the current deflection around dongsha islands in the northern south china sea based on the in situ data and adcp observation in fall it is found that a northeastward current at inter middle level flows on the northern south china sea nscs continental shelf this current flows almost along the isobaths and it deflects from the isobaths veering toward deep water when flowing over the dongsha islands geographic currents derived from the climatologic hydrography data woa01 and absolute dynamic topography adt data confirm the deflection of the northeastward current on nscs continent a fine resolution regional ocean model which can well reproduce the large scale circulation in the nscs is used to analyze the dynamic about the deflection the vorticity term balances shows that jebar joint effect of baroclinicity and relief drives the water column to depart from the isobaths to the east of the dongsha islands the isopycnal is almost orthogonal to the isobaths the joint effect of the topographic and the baroclinic effect supplies negative vorticity and drives the water column to deflect from the isobaths and veer to deeper water momentum analysis along the stream line shows that when the sea water flows around the dongsha islands the pressure gradient along the isobath pushes the sea water to accelerate and then the coriolis force orthogonal to the isobath increases and overcomes the corresponding pressure gradient which drives the water deflected from the isobath toward the deep sea citation wang d q wang w zhou s cai l li and b hong 2013 an analysis of the current deflection around dongsha islands in the northern south china sea j geophys res oceans 118 490 501 doi 10 1029 2012jc008429

petrography micromorphology and genesis of holocene pedogenic calcrete in al jabal al akhdar sultanate of oman abstract holocene pedogenic calcrete nodules occur within quaternary terra rossa soil that fills shallow phytokarst cavities in the permian triassic carbonate sequence of al jabal al akhdar in the sultanate of oman they are preferentially clustered around plant roots and are almost wholly formed of calcite holocene pedogenic calcrete nodules developed within a mediterranean like climate that is characterized by intermittent wet and dry seasons petrographic examination revealed that the host terra rossa soil is partially calcitized and that the calcrete nodules consist of smaller coalesced diffused and or discrete granular nodules the latter consist of several types of rhizoliths floating in a groundmass formed of micrite and microspar as well as spar to a lesser extent several textures of calcrete groundmass are recognized the most common is partially neomorphosed micrite three types of rhizoliths are recognized root moulds root casts and petrified calcified root tissues the latter were developed by mimic replacement of the tissue cells by cytomorphic calcite sem investigation of the calcite forming the calcrete nodules revealed that it consists of closely stacked sheets formed of calcareous nanoglobules agglutinated by eps and entombed calcareous microbial fossils which indicate a biogenic origin the calcareous nature of the bedrock climatic conditions and prevalence of biological activities of microorganisms associated with the plant root system in the host soil have significantly controlled the development and texture of these nodules the relative abundance of scalenohedral calcite within the calcrete groundmass is attributed to the impact of mg ions and organic compounds it has been concluded that the studied pedogenic calcrete is a type of freshwater terrestrial thrombolitic microbialite this study may help improve the understanding of the palaeoenvironmental conditions of analogue fossil calcretes

the role of fungal biomineralization in the formation of early carboniferous soil fabrics paleosols in the lower carboniferous limestones of south wales commonly contain needle fibre calcite which is an unusual form of calcite recently shown to form by the calcification of fungal hyphae in present day soils the needle fibre calcite occurs in two associations in the paleosols as coatings on sediment grains and as rhizocretions the former can be compared with the microbial grain coatings of quaternary calcretes the latter represent the sites of fungal coats on roots and are interpreted as probable ectomycorrhizae a symbiotic fungal sheath root association these findings suggest that biomineralization was important in the formation of soil fabrics during the carboniferous as it is in present day soils

a new form of needle fiber calcite produced by physical weathering of shells needle fiber calcite is a common crystal form in soils and sediments from diverse environmental settings and it has been used as evidence of a specific soil development either past or present however it can have either a physicochemical or a biological origin and its ubiquity prevents straightforward use as an environmental proxy in this paper we present a new form of needle fiber calcite derived neither from biologically mediated mineralization in the soil nor from physicochemical precipitation this needle fiber calcite is monocrystalline and prismatic and is associated with the physical weathering of mytilus edulis linnaeus bivalve shells found in soils from anthropic shell middens located on the northern coast of the beagle channel argentina the effects of freeze thaw cycles can be observed in the local soils and would be responsible for the release of the calcite crystals that make up the outer layer of the shell in this respect the new form of needle fiber calcite would be specific for this process in anthropogenic soils in cold climates and could provide information on past climatic conditions

bedform and stratification characteristics of some modern small scale washover sand bodies washover sand bodies commonly develop along microtidal coastlines in beach barrier island or spit settings wave runup usually in conjunction with an abnormally high water level may overtop the most landward berm of the beach and the foredune crest if one exists to produce overwash and subsequent runoff across the more landward subaerial surface two main elements of the resulting deposit are the washover fan and runoff channel newly formed small scale washover deposits were examined along the outer banks north carolina near pt mugu california and at presque isle lake erie pennsylvania the fans were formed in response to unidirectional landward transport and the runoff channels in response to unidirectional flow usually in a landward direction but sometimes in shore parallel then seaward direction where overwash carried across the fan surface and entered a pond or lagoon a small scale delta microdelta developed in this case the washover fan consisted of two subfacies the wetted but subaerial part of the fan and the subaqueous washover delta flow associated with the development of the fan and runoff channel produced distinctive sets of bedforms and internal stratification high velocity discontinuous surges moving across the fan surface resulted in the development of a plane bed and subhorizontal to low angle landward dipping planar stratification which comprised the major part of the fan similarly rhomboid forms were produced by high velocity sheet flow across the fan surface where flow carried into a standing body of water delta type foreset strata developed for this case the lateral structural sequence was subhorizontal planar stratification merging landward into landward dipping delta tabular foreset strata in the runoff setting where flow became channelized and continuous both upper flow and lower flow regime currents were typical upper flow regime bedforms included antidunes standing waves and plane beds the most commonly observed lower flow regime bedforms included microdelta like bars low amplitude bars linguoid ripples and sinuous crested current ripple trains the sets of sedimentary structures comprising modern washover sand bodies provide criteria for the identification of similar deposits in ancient sediments and for more specific interpretation of the environment

development of asian monsoon revealed by marked ecological shift during the latest miocene in northern pakistan carbon isotopes from soil carbonate1 4 and soil organic matter5 6 yield palaeoecological information because the carbon in the soil carbonate forms in isotopic equilibrium with local soil co2 refs 1 7 the isotopic composition of which is in turn determined by local plant cover siwalik group sediments in northern pakistan contain a well exposed palaeosol record spanning the past 18 myr here we report on stable carbon isotope results from associated pedogenic carbonate which indicate a dramatic ecological shift from to dominated floodplain biomass beginning 7 4 7 0 myr ago the earlier c3 floodplain biomasses were probably mainly composed of trees and shrubs whereas c4 grasslands dominated in the plio pleistocene oxygen isotopes also exhibit a shift in the latest miocene probably corresponding to a major climate change which may have induced the forest to grassland transition this dramatic ecological shift in the latest miocene may mark the inception or a marked strengthening of the asian monsoon system

paleosols of late pennsylvanian cyclic strata new mexico cyclically deposited siliciclastic and carbonate rocks of the late pennsylvanian virgilian holder formation of south central new mexico were deposited on a narrow shelf between the pedernal uplift and the orogrande basin in the dry canyon area sacramento mountains shelf to basin palaeotopography is indicated by onlapping beds and primary dips calcareous alteration zones are developed on the tops of major carbonate units these detailed studies confirm earlier interpretations that alteration zones represent subaerial exposure events and provide new evidence for and further documentation of a paleosol environment the paleosols contain 1 rhizoliths 2 tangential needle fibres of calcite 3 five types of alveolar texture 4 upward oriented ribbon spar 5 brownish and clear isopachous spar 6 blackened grains 7 random needle fibres of calcite 8 coated grains 9 micritized grains 10 glaebules 11 desiccation cracks 12 possible microcodium and 13 well developed laminated crusts isopachous cements upward oriented cements which mark the former tops of capillary fringes dark colour and shallow depth of penetration of rhizoliths less than 1 m indicate significant paleosol formation in waterlogged hydromorphic and drier conditions pennsylvanian palaeohydrogeology of the system is reflected in the type of paleosol alteration paleosols developed on subtidal strata and paleosols which drape tens of metres of palaeotopography indicate cyclic sedimentation was not controlled by delta lobe switching local tectonic up and down movement would be an unlikely mechanism to explain the repeated tens of metres of relative sea level fluctuation eustatic sea level fluctuations induced by late pennsylvanian gondwana glaciation probably were of the correct magnitude and frequency to have caused the holder cycles

geochemical constraints on the origin of enigmatic cemented chalks norfolk uk very hard cemented chalk stacks and crusts found locally in the upper part of the cretaceous chalk of north norfolk uk are related to solution features the solution features mainly pipes and caves formed after deposition of the overlying middle pleistocene wroxham crag probably by routing of sub glacial or glacial melt waters derived from late pleistocene glaciers new geochemical particularly stable isotope data shows that cementation of the chalks although related spatially to the solution features was not caused by glacier derived waters the carbon isotope composition of the chalk cements is typically around 9 5 indicative of biologically active soils moreover the oxygen isotope compositions of the cements around 5 are incompatible with water 18 o values much below 9 to 10 which probably precludes isotopically negative glacier derived water as resulting palaeo temperatures are below zero taken together the isotope data suggest chalk cementation occurred under interglacial conditions similar to the present dissolved calcium carbonate for cementation came from dissolution of reworked chalk in overlying mis 12 glacial tills

optically stimulated luminescence osl dating of loessic sediments and cemented scree in northwest england optically stimulated luminescence osl dates are reported for silts and very fine sands believed to be loessic sediments from northwest england at three sites loessic sediments were initially interpreted as primary aeolian deposits and at two other sites as loess incorporated into the matrix of cemented scree however the results of osl dating indicate a more complex pattern of accumulation than originally hypothesized and have prompted reconsideration of these materials whatever the process es and underlying cause s it is evident that significant amounts of soil erosion occurred on the limestone uplands earlier than previously thought all but one of the ages fall entirely within the holocene period and suggest that these deposits contain reworked rather than primary loess four of the five sites are characterized by non gaussian dose distributions and consequently equivalent doses have been estimated using a range of appropriate age models the implications of differences in the ages derived f

circulation in the south china sea during summer 2000 as obtained from observations and a generalized topography following ocean model 1 on the basis of the recently obtained hydrographic data in the south china sea the improved princeton ocean model with a generalized topography following coordinate system is used to study the circulation in the region during summer 2000 several sensitivity experiments are carried out to achieve reasonable model parameters for the south china sea scs it is shown from the resting stratification experiments that the generalized topography following coordinate scheme is better than the standard sigma grid scheme for reducing the pressure gradient errors the combination of sea surface height anomaly derived from topex poseidon and numerical results with both diagnostic and semidiagnostic simulations provides a consistent circulation pattern for the scs in august and the main circulation features can be summarized as follows 1 there is a notable anticyclonic warm eddy southeast of vietnam with a horizontal scale of 300 km and there is a cyclonic cold eddy the simultaneous existence of these cold and warm eddies is one of the important circulation characteristics in the scs during summer 2000 2 a secondary cold eddy is found east of vietnam 3 the northwestern part of the scs is dominated by an anticyclonic circulation system 4 there is also a secondary warm eddy southwest off the luzon island 5 a cyclonic eddy is found west off the borneo island 6 a western intensification phenomenon obviously occurs in the scs the dynamical mechanisms of the above mentioned circulation pattern in the scs are the interaction between the wind stress and bottom topography and the joint effect of baroclinicity and relief

interpretations of the jebar term abstract in diagnostic calculations of the ocean s circulation the so called jebar joint effect of baroclinicity and relief term may induce a significant depth average current field as has been noted in the oceanographic literature here we present two consistent interpretations of this term in the equation governing the vorticity of the depth averaged current a topographic vortex stretching term proportional to the dot product of depth averaged velocity and the depth gradient arises we show that jebar corrects this term by removing the contribution of the geostrophic flow referenced to the bottom which cannot generate topographic vortex stretching in the evolution equation for the vorticity of the depth integrated flow a bottom torque term is present we show that the jfbar term discussed above enters here as a contribution to the bottom torque emphasizing the role of jebar as a forcing term we also show that when a diagnostic calculation is formulated completely in terms of the transport str

separation of a midlevel density current from the bottom of a continental slope the high salinity water flowing out of the mediterranean sea descends to mid depths in the density stratified ocean continues as a narrow jet along the iberian continental slope and intermittently detaches large scale eddies called meddies this process is important because it maintains the relatively high mean salinity of a major water mass the mediterranean intermediate water in the north atlantic our simplified model of this jet consists of a moving layer with intermediate density 2 sandwiched between motionless layers of density 1 2 the inshore anticyclonic portion of the midlevel jet in the 2 water rests on an inclined bottom the continental slope whereas the cyclonic offshore portion rests on the density interface of the stagnant deep 3 layer an inviscid steady and finite amplitude longwave theory is used to show that if the cross stream topographic slope increases gradually in the downstream direction then the 2 jet is deflected off the bottom slope and onto the upper density interface of the 3 layer the computed magnitude of this separation effect is such as to produce an essentially free jet which is removed from the stabilizing influence of the continental topography it is therefore conjectured that time dependent effects baroclinic instability will produce further amplification causing an eddy to detach seaward from the branch of the jet remaining on the slope

mesoscale dongsha cyclonic eddy in the northern south china sea by drifter and satellite observations 1 near the center of the northern south china sea nscs the dongsha atoll is situated on the continental slope that runs from taiwan to hainan a mesoscale cyclonic eddy south or southwest of dongsha seems to appear annually and has been identified as the dongsha cyclonic eddy dce historical drifter 1988 2005 and satellite altimeter 2000 2005 data were adopted to study the variations to and characteristics of the dce some typical features were derived such as mean tangential speed of 20 cm s moving speed of 8 km d i e 9 cm s eddy size of 22 103 km2 center sea surface lowering height difference dif of 6 cm and angular velocity of 9 d mean tangential speeds of 12 16 cm s in late spring and summer are slower than those of 16 31 cm s in winter and early spring moving speeds are of the order of the rossby wave at nscs latitudes variations in the time series of eddy size and dif are generally similar and show a positive linear relation between them the dce starts near dongsha and moves southwestward along the continental slope at a depth of 1000 2000 m the eddy peaks with maximum eddy size and dif when reaching 114 e and then diminishes south of hainan because of trapping of the underwater bay formed by the continental slope the dce typically exists 1 2 times per year and lasts 1 3 months roughly 90 of observed dces formed in winter or spring a unique dce was identified in the summer of 2000 and lasted for over 4 months its birth was associated with typhoon kai tak the positive linear relationship between eddy size and dif in this case was unique before reaching 114 e and then returned to the typical relationship of other dces the dif of this unique dce attained the highest of 24 cm right at the climax longitude according to avhhr and seawifs images such a dce is associated with a core of which sea surface temperature is 2 c lower and chlorophyll a concentration is 0 1 mg m3 higher than those of surrounding seas migration of the dce may be linked to tuna fish farms in the nscs

the ground penetrating radar facies and architecture of a paleo spit from huangqihai lake north china implications for genesis and evolution abstract a paleo spit is identified from huangqihai lake in north china and proposed as a classic example for investigating the influence of lake level changes and storms on the construction of these bodies ground penetrating radar gpr data collected with a 400 mhz antenna are used together with sedimentologic observations from trenches to define the facies and sedimentary architecture of the spit six types of radar surface both depositional and erosional were identified radar facies bounded by radar surfaces were interpreted from reflection characteristics and termination patterns eight different radar facies were identified in the profiles and we assign these to three groups inclined horizontal and irregular the whole barrier spit system comprises spit bar and salt marsh units distinguished using gpr profiles linked radar and sedimentologic data are used to develop a model for spit bar evolution the spit was formed during a cycle of lake level change spanning 200 years the characteristics of the different building blocks washover lobes sheets and swash laminated sands within the spit bar unit and their depositional regimes are defined and interpreted based on the known lake evolution during the holocene a relative chronological framework is presented two storms in the 1880s and 1960s may have played an important role in building the spit bar

wettability decay in an oil contaminated waste mineral mixture with dry wet cycles the dependency of soil particle wettability on soil water content implies that soils subjected to drying wetting cycles become wettable with wetting and water repellent with drying while this has been demonstrated widely the results are contradictory when water repellent soils are subjected to a sequence of cycles added to this past wettability measurements were seldom done in batches of samples collected from the field at natural or dry water contents with little appreciation that slight particle size variations different drying wetting histories and fabric as required by different wettability measurement methods may alter the results this note presents soil particle wettability soil water content relations by means of an index test following staged drying and wetting paths over a period of 8 months for an untreated oil contaminated anthropogenic soil a mixture of slag coal particles fly ash and mineral particles from barry docks uk a site formally used for oil storage which is to be remediated and redeveloped for housing the results revealed a decrease in the water repellency and increasing mineralization and bacterial activity with the wetting and drying cycles

ground penetrating radar for high resolution mapping of soil and rock stratigraphy ground penetrating radar is a technique which offers a new way of viewing shallow soil and rock conditions the need to better understanding overburden conditions for activities such as geochemical sampling geotechnical investigations and placer exploration as well as the factors controlling groundwater flow has generated an increasing demand for techniques which can image the subsurface with higher resolution than previously possible the areas of application for ground penetrating radar are diverse the method has been used successfully to map ice thickness water depth in lakes bedrock depth soil stratigraphy and water table depth it is also used to delineate rock fabric detect voids and identify karst features the effective application of the radar for the high resolution definition of soil stratigraphy and fractures in bedrock is highlighted the basic principles and practices involved in acquiring high quality radar data in the field are illustrated by selected case histories one example demonstrates how radar has been used to map the bedrock and delineate soil horizons to a depth of more than 20 m two case histories show how radar has been used to map fractures and changes of rock type to 40 m range from inside a mine another case history demonstrates how radar has also been used to detect and map the extent of groundwater contamination the corroboration of the radar results by borehole investigations demonstrates the power and utility of the high resolution radar method as an aid for interpolation and extrapolation of the information obtained with conventional coring programmes with the advent of new instrumentation and field procedures the routine application of the radar method is becoming economically viable and the method will see expanded use in the future

energetic topographic rossby waves in the northern south china sea abstracttopographic rossby waves trws are reported to make a significant contribution to the deep ocean current variability on the northern south china sea nscs continental slope trws with pe

boundary current separation in a quasigeostrophic eddy resolving ocean circulation model abstract the response of a rectangular flat bottom eddy resolving quasigeostrophic ocean to a steady double gyre wind stress is studied to assess the sensitivity of the solutions to a partial slip lateral boundary condition in which tangential stress is proportional to tangential velocity the constant of proportionality has limiting values of zero and infinity corresponding to free slip no stress and no slip conditions respectively seven numerical solutions corresponding to the values 0 0 2 0 3 5 5 0 6 5 8 0 and 100 0 are obtained which span the free slip and no slip limits significant qualitative changes in the time mean behavior of the solutions are observed to occur with increasing these changes include a gradual retreat of the separation points of the western boundary currents in the subtropical and subpolar gyres a dramatic reduction in the basin integrated reservoirs of mean and eddy kinetic energy a weakening of bottom dissipation and its replacement by lateral dissipat

paleosols in shallow marine carbonate sequences abstract shallow water carbonate sequences in the geological record commonly exhibit numerous exposure surfaces reflecting emersion of sediment due to progradation processes and sealevel oscillations some ancient platform sequences contain hundreds of such surfaces associated with paleosols fossil soils typically calcretes a wide range of macro and microstructures are associated with these calcretes which are reviewed profile types and stages in profile development can be defined the nature of the exposure surface and associated paleosols can be used to identify the nature of the prevailing climate although hydromorphic effects related to marine flooding of the platforms can modify the paleosols a potentially important use of paleosols is to define the nature of sequence boundaries several studies have identified sets of paleosols with varying maturities reflecting changes in rates of accommodation space creation during sealevel rises and falls

paleoclimatic implications of pedogenic carbonates in holocene soils of the gangetic plains india abstract this study attempts to reconstruct the holocene climatic history of the indo gangetic plains based on micromorphological characteristics and stable isotope composition of calcretes in a soil chronoassociation between the ramganga and rapti rivers the calcrete from the b2 horizon of older soils qgh4 qgh5 6500 13 500 year bp consists of septaric and irregularly shaped nodules of dense micrite and diffused needles associated with the illuvial clay pedofeatures fabric of the calcretes of older soils show inclusion of soil constituents and precipitation of carbonates in between weathered layers of micas formation of this calcrete took place during the pedogenesis in an arid to semi arid climate that also influenced vegetation and c4 type biomass such as chenopodium and typha angustata spread in the area a change to warm and humid phase at 6500 year bp led to dissolution and reprecipitation of the calcretes this led to the formation of blocky crystals and needles of calcite in voids and coarsening of the fabric in the lower horizons the vegetation pattern also changed to woodland with anogeissus and tecomella spp the younger soils bp show secondary carbonate accumulation associated mainly along the voids in lower parts of the profiles these are relatively coarse textured with little or no inclusion of soil constituents this coarse grained calcrete results from capillary rise from a fluctuating water table in a sub humid climate similar to present carbon and oxygen isotope data suggest that the formation of pedogenic carbonate in old soils qgh4 and qgh5 by evapotranspiration during arid to semi arid climate in the upper horizons the carbonates are depleted in 13c as their formation was influenced by the sparse vegetation and low soil respiration rate in the lower horizons the carbonates show enrichment of 13c due its extensive dissolution reprecipitation during the humid climate the younger soils showed the enrichment of 13c in their calcretes and support their formation from fluctuating shallow groundwater table the oxygen isotope values similar to that of meteoric water of the area indicate calcrete precipitation in equilibrium with the soil water

a giant submarine creep zone as a precursor of large scale slope instability offshore the dongsha islands south china sea a giant submarine creep zone exceeding 800 km2 on the continental slope offshore the dongsha islands south china sea is investigated using bathymetric and 3d seismic data tied to borehole information the submarine creep zone is identified as a wide area of seafloor undulations with ridges and troughs the troughs form nw and wnw trending elongated depressions separating distinct seafloor ridges which are parallel or sub parallel to the continental slope the troughs are 0 8 4 7 km long and 0 4 to 2 1 km wide the ridges have wavelengths of 1 4 km and vertical relief of 10 30 m slope strata are characterised by the presence of vertically stacked ridges and troughs at different stratigraphic depths but remaining relatively stationary in their position the interpreted ridges and troughs are associated with large scale submarine creep and the troughs can be divided into three types based on their different internal characters and formation processes the large scale listric faults trending downslope below mtd 1 and horizon t0 may be the potential glide planes for the submarine creep movement high sedimentation rates local fault activity and the frequent earthquakes recorded on the margin are considered as the main factors controlling the formation of this giant submarine creep zone our results are important to the understanding of sediment instability on continental slopes as a the interpreted submarine creep is young or even active at present and b areas of creeping may evolve into large scale slope instabilities as recorded by similar large scale events in the past

the structure and development of foredunes on a locally prograding coast insights from ground penetrating radar surveys norfolk uk the internal structure of coastal foredunes from three sites along the north norfolk coast has been investigated using ground penetrating radar gpr which provides a unique insight into the internal structure of these dunes that cannot be achieved by any other non destructive or geophysical technique combining geomorphological and geophysical investigations into the structure and morphology of these coastal foredunes has enabled a more accurate determination of their development and evolution the radar profiles show the internal structures which include foreslope accretion trough cut and fill roll over and beach deposits foredune ridges contain large sets of low angle cross stratification from dune foreslope accretion with trough shaped structures from cut and fill on the crest and rearslope foreslope accretion indicates sand supply from the beach to the foreslope while troughs on the dune crest and rearslope are attributed to reworking by offshore winds bounding surfaces between dunes are clearly resolved and reveal the relative chronology of dune emplacement radar sequence boundaries within dunes have been traced below the water table passing into beach erosion surfaces these are believed to result from storm activity which erodes the upper beach and dunes in one example at brancaster a dune scarp and erosion surface may be correlated with erosion in the 1950s possibly the 1953 storm results suggest that dune ridge development is intimately linked to changes in the shoreline with dune development associated with coastal progradation while dunes are eroded during storms and where beaches are eroding a stable coast provides more time for dune development resulting in higher foredune ridges a model for coastal dune evolution is presented which illustrates stages of dune development in response to beach evolution and sand supply in contrast to many other coastal dune fields where the prevailing wind is onshore on the north norfolk coast the prevailing wind is directed along the coast and offshore which reduces the landward migration of sand dunes

the biogenic origin of needle fibre calcite needle fibre calcite is one of the most ubiquitous habits of calcite in vadose environments caves deposits soil pores etc its origin either through inorganic indirect or direct biological processes has long been debated in this study investigations at 11 sites in europe africa and central america support arguments for its biogenic origin the wide range of needle morphologies is the result of a gradual evolution of the simplest type a rod this rod is the elementary brick which by aggregation and welding builds more complex needles the absence of cross welded needles implies that they are welded in a mould or under a longitudinal and unidirectional constraint before being released inside the soil pores the difference between the lengthening of the needles and the c axis can be explained by the existence of needles observed under a scanning electron microscope in organic sleeves which can act as a mould during rod growth complex morphologies with epitaxial outgrowths on straight rods cannot have grown entirely inside organic microtubes they must result from soil diagenesis after the release of straight rods in a soil free medium whisker crystals are interpreted as the result of growth and coalescence of euhedral crystals on a rod rhomb chains are considered to be the consequence of successive epitaxial growth steps on a needle during variations in growth conditions isotopic signatures for needle fibre calcite vary from 16 63 to 1 10 and from 8 63 to 2 25 for 13c and 18o respectively the absence of high 18o values for needle fibre calcite precludes a purely physicochemical origin evaporative for this particular habit of calcite as epitaxial growth cannot precipitate in the same conditions as initial needles needle fibre calcite stable isotopic signatures should be used with caution as a proxy for palaeoenvironmental reconstructions in addition it is suggested that the term needle fibre calcite should be kept for the original biogenic form the other habit should be referred to as epitaxial forms of needle fibre calcite

a holocene calcrete from north yorkshire england implications for interpreting palaeoclimates using calcretes glacial gravels of late devensian dimlington stadial age 26 000 13 000 years bp at west tanfield north yorkshire england have been cemented by carbonate rich solutions to produce a strongly indurated calcrete horizon the low mg cements occur as drusy spar needle fibres alveolar septal structures micrite and micropinnacles indicative of vadose zone cementation some complex pore partition structures attributed to precipitation along meniscus films also occur these partitions separate air dominated and water dominated microenvironments of the vadose zone the abundance of vadose fabrics shows that the accumulation is not a groundwater calcrete in addition much of the carbonate appears to have been precipitated by biological mediation carbon and oxygen isotopic data suggest that the carbonate did not form as a result of freezing as has been suggested for some arctic soil carbonates the pollen history of the area since the devensian suggests that this calcrete precipitated at low temperatures this contrasts with widely reported occurrences of calcrete in soils of hot arid or semi arid regions and suggests that palaeo calcretes should not be used as absolute palaeoclimatic indicators the unusual occurrence albeit localized of a thick calcrete under a cool and wet climate probably reflects the well drained nature of the gravels the abundance of caco3 as limestone clasts in the gravel and a high degree of biological activity beneath a forest cover which created a local environment favouring carbonate precipitation

proxy records of holocene storm events in coastal barrier systems storm wave induced markers abstract extreme storm events in the coastal zone are one of the main forcing agents of short term coastal system behavior as such storms represent a major threat to human activities concentrated along the coasts worldwide in order to better understand the frequency of extreme events like storms climate science must rely on longer time records than the century scale records of instrumental weather data proxy records of storm wave or storm wind induced activity in coastal barrier systems deposits have been widely used worldwide in recent years to document past storm events during the last millennia this review provides a detailed state of the art compilation of the proxies available from coastal barrier systems to reconstruct holocene storm chronologies paleotempestology the present paper aims i to describe the erosional and depositional processes caused by storm wave action in barrier and back barrier systems i e beach ridges storm scarps and washover deposits ii to understand how storm records can be extracted from barrier and back barrier sedimentary bodies using stratigraphical sedimentological micro paleontological and geochemical proxies and iii to show how to obtain chronological control on past storm events recorded in the sedimentary successions the challenges that paleotempestology studies still face in the reconstruction of representative and reliable storm chronologies using these various proxies are discussed and future research prospects are outlined