contributions of wind forcing waves and surface heating to sea surface height observations in the pacific ocean the dominant processes affecting sea surface height ssh variability observed by the topex poseidon altimeter vary regionally in the pacific baroclinic rossby waves equatorially trapped kelvin waves steric response to seasonal heating and the response to wind stress curl forcing are all important the steric response to surface heating dominates seasonal ssh variability in the subpolar gyre and the eastern subtropical gyre south of the kuroshio extension and south of 20 n in the eastern pacific the dominant contribution to ssh is from near annual period rossby waves to quantify the wave energy observed ssh was assimilated into a kinematic model of westward propagating waves these waves account for 70 of ssh variance between 10 s and 10 n but only 30 between 10 n and 30 n although wave energy in the eastern pacific is correlated with ssh anomalies at the equator the much larger wave energy in the western pacific is correlated with wind stress curl suggesting that the rossby waves there are locally forced in addition to these planetary waves the ocean response to wind forcing via ekman pumping is observed in several places specifically in the north equatorial current a quasi steady topographic sverdrup balance is detectable over most of the north pacific at latitudes as low as 10 15 n as well as in the south pacific where it is seen north of 50 s the decomposition of the ssh signal into propagating waves an ekman pumping response and sverdrup transport is consistent with the results from an isopycnal numerical model

seasonal fluctuations of the surface north equatorial countercurrent necc across the pacific basin 1 based on multisatellite derived sea surface current sea surface height anomaly and geostrophic current data the annual variability of the surface necc across the pacific basin is investigated inferred from the surface current data the necc axis east and west of the dateline moves northward along its pathway in the latter half of a year and the first half of a year respectively the sea surface height anomaly in the necc region and the meridional movement of necc are well reproduced by a linear wind driven first mode baroclinic rossby wave model model experiments by setting the phase speed of baroclinic rossby wave or the ekman pumping to zero in different regions are carried out to clarify the influence of rossby wave and local ekman pumping on the movement of necc east of the dateline both ekman pumping and rossby wave are important in determining the northward movement of the necc axis however the necc axis west of the dateline moves northward primarily due to the westward transmission of positive sea surface height anomalies or downwelling rossby waves that originate in the east of the dateline the local ekman pumping plays a minor role in controlling the migration of the necc axis west of the dateline

evidence of 550 year and 1000 year cyclicities in north atlantic circulation patterns during the holocene sedimentological colour data obtained from north atlantic deep sea sediment core neap15k pro vide a continuous climate record for the last 11500 yr with a mean sampling interval of 15 yr variations in sediment lightness a proxy for changes in north atlantic deep water nadw circulation are characterized by high frequency fluctuations with periodicities equivalent to 550 and 1000 yr as well as a 1600 yr cyclicity comparable to that reported in other studies of holocene climate cross spectral analysis suggests that the 550 yr and 1000 yr cyclical variations in nadw circulation were coherent with fluctuations in atmospheric con ditions over greenland where both these periodicities have been identified previously in the holocene gisp2 d18o record stuiver et al 1995 a similar statistical comparison provides evidence that high frequency 550 yr variability in nadw circulation patterns may have been linked to short term variations in atmospheric 14c values during the holocene in general nadw pro

mapping ocean observations in a dynamical framework a 2004 06 ocean atlas abstract this paper exploits a new observational atlas for the near global ocean for the best observed 3 yr period from december 2003 through november 2006 the atlas consists of mapped observations and derived quantities together they form a full representation of the ocean state and its seasonal cycle the mapped observations are primarily altimeter data satellite sst and argo profiles gcm interpolation is used to synthesize these datasets and the resulting atlas is a fairly close fit to each one of them for observed quantities especially the atlas is a practical means to evaluate free running gcm simulations and to put field experiments into a broader context the atlas derived quantities include the middepth dynamic topography as well as ocean fluxes of heat and salt freshwater the atlas is publicly available online www ecco group org this paper provides insight into two oceanographic problems that are the subject of vigorous ongoing research first regarding ocean circulation estimates

the role of ocean atmosphere reorganizations in glacial cycles abstract a case is made that glacial to interglacial transitions involve major reorganizations of the ocean atmosphere system such reorganizations constitute jumps between stable modes of operation which cause changes in the greenhouse gas content and albedo of the atmosphere only in this way can the rapidity of glacial terminations the hemispheric synchroneity and symmetry of mountain glaciation and the large polar air temperature and dustiness variations be accounted for if these reorganizations are driven in some fashion by orbitally induced seasonal insolation changes then the connection between insolation and climate is most likely through impacts of fresh water transport on the ocean s salinity distribution

geochemistry of the mesozoic bedded cherts of central baja california vizcaino cedros san benito implications for paleogeographic reconstruction of an old oceanic basin abstract in central baja california vizcaino peninsula and cedros and san benito islands two distinct radiolarian bedded chert sequences of late triassic and late jurassic lowermost cretaceous age can be differentiated on lithostratigraphic and geochemical criteria these bedded chert sequences are part of the conformable sedimentary cover of more or less dismembered ophiolites which are overthrusted by the san andres cedros volcanic arc system of middle late jurassic age major and trace elements permit paleogeographic zonation of the late jurassic lowermost cretaceous radiolarites lying conformably upon ophiolites considered as fragments of an oceanic basin floor which developed westward of the san andres volcanic arc progressive accretion of this oceanic basin floor along the continental margin is supported by the fact that the more distal radiolarian chert sequences belong to the lowermost structural units of this area

a census of tehuantepec and papagayo eddies in the northeastern tropical pacific 1 we use a 12 year 1992 2004 time series of satellite altimetry to characterize long lived wind generated anticyclonic eddies originating in the gulfs of tehuantepec and papagayo in the northeastern tropical pacific a total of 42 tehuantepec and 26 papagayo eddies were observed eddy merging usually of a tehuantepec papagayo pair was observed on 16 occasions on average the eddy season began in late october and lasted approximately 250 days until early july with 3 5 tehuantepec and 2 2 papagayo eddies formed each year minimum average eddy lifespan was 143 days and 84 days for tehuantepec and papagayo eddies respectively there was considerable interannual variability in eddy activity with greater fewer number of eddies more intense weaker eddies and a longer shorter eddy season during el nino la nina years eddy intensification was consistently observed at the east pacific rise

rare earth major and trace element composition of monterey and dsdp chert and associated host sediment assessing the influence of chemical fractionation during diagenesis abstract chert and associated host sediments from monterey formation and deep sea drilling project dsdp sequences were analyzed in order to assess chemical behavior during diagenesis of biogenic sediments the primary compositional contrast between chert and host sediment is a greater absolute sio2 concentration in chert often with final sio2 98 wt this contrast in sio2 and si al potentially reflects precursor sediment heterogeneity diagenetic chemical fractionation or both sio2 concentrations and si al ratios in chert are far greater than in modern siliceous oozes however and often exceed values in acid cleaned diatom tests compositional contrasts between chert and host sediment are also orders of magnitude greater than between multiple samples of the host sediment calculations based on the initial composition of adjacent host observed porosity reductions from host to chert and a postulated influx of pure sio2 construct a chert composition which is essentially identical to observed sio2 values in chert thus precursor heterogeneity does not seem to be the dominant factor influencing the current chert composition for the key elements of interest in order to assess the extent of chemical fractionation during diagenesis we approximate the precursor composition by analyzing host sediments adjacent to the chert the sio2 concentration contrast seems caused by biogenic sio2 dissolution and transport from the local adjacent host sediment and subsequent sio2 reprecipitation in the chert along with sio2 other elements are often added with respect to al to monterey and dsdp chert during silicification although absolute concentrations decrease the two monterey quartz chert nodules investigated in contrast to the opal ct and quartz chert lenses formed primarily by extreme removal of carbonate and phosphate thereby increasing relative sio2 concentrations dsdp chert formed by both carbonate phosphate dissolution and sio2 addition from the host manganese is fractionated during chert formation resulting in mno al 2 o 3 ratios that no longer record the depositional signal of the precursor sediment ree data indicate only subtle diagenetic fractionation across the rare earth series ce ce values do not change significantly during diagenesis of either monterey or dsdp chert eu eu decreases slightly during formation of dsdp chert la n yb n is affected only minimally as well during formation of one monterey opal ct chert lens ree al ratios show subtle distribution changes at gd and to a lesser extent near nd and ho ree compositional contrasts between diagenetic states of siliceous sediment and chert are of a vastly smaller scale than has been noted between different depositional environments of marine sediment indicating that the paleoenvironmental ree signature is not obscured by diagenetic overprinting

a recent sea ice retreat west of the antarctic peninsula satellite passive microwave data show a record decrease in sea ice extent in the bellingshausen sea from mid 1988 through early 1991 the change coincides with more southerly surface winds increased cyclonic activity and rising surface air temperatures which reached historic highs along the west coast of the antarctic peninsula in 1989 preceded by high ice cover in 1986 87 the retreat was most evident during summer in the formerly perennial sea ice field over the continental shelf ocean heat storage probably contributed to the persistence and coastal propagation of this anomaly

the effects of wind forcing and background mean currents on the latitudinal structure of equatorial rossby waves abstract the latitudinal structure of annual equatorial rossby waves in the tropical pacific ocean based on sea surface height ssh and thermocline depth observations is equatorially asymmetric which differs from the structure of the linear waves of classical theory that are often presumed to dominate the variability the nature of this asymmetry is such that the northern ssh maximum along 5 5 n is roughly 2 times that of the southern maximum along 6 5 s in addition the observed westward phase speeds are roughly 0 5 times the predicted speed of 90 cm s 1 and are also asymmetric with the northern phase speeds about 25 faster than the southern phase speeds one hypothesized mechanism for the observed annual equatorial rossby wave amplitude asymmetry is modification of the meridional structure by the asymmetric meridional shears associated with the equatorial current system another hypothesis is the asymmetry of the annually varying wind forcing which is stronger north of the equator a reduced g

marine debris flows late precambrian tillites of the avalonian cadomian orogenic belt abstract correlative late precambrian strata of the avalonian cadomian orogenic cycle deposited after 670 and before 550 ma are now widely dispersed around the margins of the north atlantic these contain several prominent diamictite horizons long interpreted as tillites within thick turbidite successions associated with volcanic horizons the granville formation of the armorican massif in normandy france contains many pebby mud diamicite beds up to 20 m thick that have been interpreted as glaciogenic regionally the granville formation occurs within the lowest part of the upper brioverian supergroup which consists of several kilometres of turbidites and volcanogenic rocks at granville diamictites can be traced along striked into deformed and intermixed graded conglomerates and mudstones diamictites are identified as debris flows generated on a submarine slope by the emplacement of gravel turbidites on a mud substrate and their mixing during downslope slumping a glacial influence cannot be identified in north america the conception group of the avalon peninsula newfoundland canada contains nearly 4 km of turbidites with a conformable sequence of diamictites the gaskiers formation near its base massive and crudely stratified diamicite beds the diamictite successions of the granville and gaskiers formations provide significant data regarding facies types associations and the geometry of resedimented diamictite sequences in deep marine basins along active plate margins similar deposits at the same tectonic stratigraphic horizon occur in new england and africa this paper emphasizes the difficulty of identifying a direct glacial influence on diamictite sedimentation in such settings and the need for a sedimentological reappraisal of other supposed late precambrian tillites preserved in orogenic belts this is a necessary first step prior to modelling late precambrian paleoclimates

geochemical characteristics and depositional environments of cherts and associated rocks in the franciscan and shimanto terranes abstract analyses of 122 jurassic cretaceous rock samples from the franciscan terrane california and 24 cretaceous samples from the shimanto terrane southwest japan show that the cherts and associated rocks accompanied by pillow basalts are enriched in fe and mn which may have been derived from hydrothermal activities the results of the fraction analyses for terrigenous basaltic hydrothermal and biogenic end members in the franciscan rocks show that hydrothermal emanations caused iron and manganese enrichment in the rock samples and played an important role in the formation of siliceous rocks vertical variations of the hydrothermal fraction and tio2 normalized values for hydrothermal elements such as fe mn ni zn y and pb show a possibility that the bedded cherts of the franciscan terrane were deposited in a hydrothermal field on or near some active oceanic ridge for more than 30 ma and were a remnant slice of oceanic crust added to the north american continent on the other hand from the field occurrences and vertical variations of tio2 normalized values of hydrothermal elements the shimanto rocks are inferred to have been deposited in a hemipelagic environment such as marginal and inter arc basins

on the southerly extent of the antarctic circumpolar current in the southeast pacific a front at 67 s in the bellingshausen sea at 85 w is shown to be part of the antarctic circumpolar current acc and the southernmost zone of concentrated eastward transport at that longitude the front lies 6 south of the polar front at 88 w and 3 north of the continental water boundary the front is continuous to the east through drake passage where it forms a southern branch of the polar front for which reason we have named it the southern polar front data from a towed profiling ctd were able to distinguish the polar front from the southern polar front even though they were only 0 5 apart thus the width of the acc south of the polar front varied considerably about a third of the transport of the acc also lay south of the polar front with 15 sv carried by the southern polar front alone at 85 w distinguishing features of the southern polar front were a water mass boundary associated with a zone of concentrated baroclinic flow and a surface salinity minimum these features also have been found at the greenwich meridian at 53 s so the southern polar front can be traced round at least a quarter of the globe to the west of the bellingshausen sea both eltanin data and the fine resolution antarctic model show that the aac is at its narrowest at 145 w where its southern boundaries lie as far north as 56 s at this longitude the acc meets the topographic barrier of the pacific antarctic ridge to conserve potential vorticity the current is forced to make a southward loop as it crosses the ridge and the current broadens dramatically the flow remains broad until forced to sharpen by the constriction of drake passage a similar broadening of the acc is seen where it crosses the southwest indian ridge south of africa at 30 e here it remains broad until it encounters the kerguelen plateau thus the eastern boundaries of both the weddell and ross gyres are determined by where the acc crosses midocean ridges

sources of sediment found in sea ice from the western arctic ocean new insights into processes of entrainment and drift patterns 1 the geochemical fingerprint of entrained fe oxide mineral grains in arctic ocean sea ice is used to determine precise sources of this sediment this approach substantiates the importance of the laptev sea as a source of sea ice and even the presence of russian ice in the beaufort sea off alaska fe oxide grains from the laptev sea were found in floes in the beaufort sea chukchi borderland and central arctic ocean demonstrating the importance of sea ice in distributing itself throughout the arctic ocean and the potential of transporting sediment from russian rivers to north american shelves banks island shelf is the most important source of sediment sampled from ice floes in the beaufort sea northern chukchi sea and chukchi borderland area although most of the entrained sediment fits the criteria for suspension freezing in shallow water the presence of winter polynyas with offshore winds and not the size of shallow areas appears to be the critical factor for sea ice entrainment seven of the 18 ice floes sampled contained fe oxide grains from more than one source area the two most common sources that are found in the same ice floes are banks island and the laptev sea multiple sources in ice floes suggest that either mingling of fragmented ice floes occurs or that a source area containing grains from both these sources has yet to be located the addition of fine sand sized windblown sediment is not thought to be significant

permian radiolarian faunas from thailand and their paleogeographic significance abstract chert and fine grained clastic rocks in thailand contain rich permian radiolarian faunas we have discriminated eight radiolarian assemblages in these rocks pseudoalbaillella bulbosa upper carboniferous to lowermost permian gzhelian to asselian pseudoalbaillella simplex lowermost permian asselian pseudoalbaillella lomentaria lower permian asselian to sakmarian pseudoalbaillella scalprata lower permian sakmarian follicucullus monacanthus middle permian wordian follicucullus porrectus upper middle to lowermost upper permian capitanian to lower wuchiapingian neoalbaillella ornithoformis upper permian wuchiapingian and neoalbaillella optima upper permian changsingian assemblages in stratigraphic order these radiolarians have a potential to contribute to understanding the history of the paleotethys based on the radiolarian biostratigraphy and lithological characteristics lower to lower upper permian radiolarian bearing cherts are thought to have been deposited in a pelagic environment in a deep basin far from land the uppermost permian radiolarian bearing cherts however reveal differences in their depositional environments in northern thailand the uppermost permian to middle triassic radiolarian chert was deposited in a pelagic basin while in eastern thailand the uppermost permian chert and the conformably overlying clastic rocks show a change in depositional environment across the p t boundary from a deep pelagic or hemipelagic to shallow seas in the triassic

late holocene cyclic glaciomarine sedimentation in a subpolar fjord of the south shetland islands antarctica and its paleoceanographic significance sedimentological geochemical and paleontological evidence the glaciomarine sedimentary record of the fjord head collins harbor in maxwell bay south shetland islands west antarctica a large marine calving embayment contains repeating couplets of organic rich massive diamicton and organic poor stratified diamicton the massive diamicton is characterized by high total organic carbon toc content and carbon to nitrogen c n ratios and was deposited in a cold climate regime by iceberg rafted sedimentation from coastal fast ice in which algal plants as well as gravels were entrained the stratified diamicton is characterized by low toc content and c n ratios and was formed in a warmer climate regime when the flux of icebergs was suppressed but turbid meltwater discharge continued to produce lamination when the meltwater discharge decreased in cold climatic conditions and resultant phytoplankton productivity was reduced due to the increased sea ice coverage ice rafting from shorefast sea ice might have played a major role in entraining benthic algae as well as loads of sand and gravel along the coastal area resulting in an increased c n ratio and gravel content in the massive diamicton accelerator mass spectrometry ams radiocarbon analyses conducted on well preserved calcite shells were used to construct a chronology for the past 3000 years fluctuations in toc are recorded approximately four cycles over this time period with the average duration of a cooling cycle being 500 years these cycles may be correlative with the high frequency 550 yr variability in reduced circumpolar deep water cdw on the west antarctic peninsula shelf because a decrease in cdw may be related to reduced deep water production in the north atlantic during colder periods as demonstrated for glacial intervals throughout the pleistocene

temperate glacimarine varves an example from disenchantment bay southern alaska abstract the sediment record of disenchantment bay southern alaska a large marine calving embayment contains distinctive annual deposits each year a glacimarine couplet forms with a clast rich stratified to massive diamicton deposited in winter by intense iceberg rafting and a summer meltwater deposit of thinly laminated mud and turbidite sand beds although iceberg rafting occurs throughout the year coarse debris is deposited in high concentrations and forms diamicton only during the winter because of minimal fine sediment from meltwater discharges and a longer residence time of icebergs in the bay due to winter fjord circulation and meteorological factors when meltwater discharge commences in summer laminated mud with dropstones is deposited spring and fall conditions are recorded a transitional phases between winter and summer by clast poor diamictons average sediment accumulation rates calculated from varve thicknesses range from 48 cm yr 3 4 km from hubbard glacier at the head of the bay to 14 cm yr 15 km away sediment accumulation rates estimated from 210pb dating of core sediments are in the same range deposits from the 1986 russell fiord outburst flood are identified from anomalously high 210pb activities in sediments indicating an alternative sediment source to disenchantment bay glacimarine varves are a dating tool for the barren proximal sediments commonly deposited near calving glacier termini they yield paleoclimatic information because they are a product of both glacial ice in the sea and laminated sediments deposited from significant melt water discharge found in a temperate to subpolar climate

millennial to decadal scale paleoenvironmental change during the holocene in the palmer deep antarctica as recorded by particle size analysis 1 a record of holocene paleoenvironmental variability from the antarctic peninsula has been produced using sediment cores from site 1098 gathered on ocean drilling project leg 178 the results provide an accurate and continuous record of biotic and sedimentologic responses to holocene environmental change holes 1098b and 1098c were used to produce the first ultrahigh resolution record of grain size variability for the past 13 000 years we utilized samples every 2 5 cm at 3 5 yr cm 1 which involved the analysis of 1466 samples from two holes at the site particle size was measured on uniform suspensions of dispersed particles using a laser diffraction method the particles are mainly grains of silt 65 85 and clay 15 35 size the analyses revealed that in most intervals biotic particles in the form of diatom frustules mostly spores dominate the silt component which is inversely reflected by magnetic susceptibility ms in intervals of the core that deviate from this relationship it was found that the ms signal correlated with medium to fine or coarse silt that was dominated by terrigenous rather than a biogenic diatom component spectral analyses of the variability in clay and medium fine silt content over the last 9000 calendar years reveal cycles of 1800 400 200 100 70 60 and 50 years the analyses revealed that particle size specifically medium fine silt is an excellent proxy for environmental change in the palmer deep region such changes may be forced by solar variability the 200 and 400 year cycles lunar tidal changes the 1800 year cycles and an as yet undetermined multidecadal forcing phenomena that operates in the se pacific sector of the southern ocean

sediments in arctic sea ice implications for entrainment transport and release despite the arctic sea ice cover s recognized sensitivity to environmental change the role of sediment inclusions in lowering ice albedo and affecting ice ablation is poorly understood sea ice sediment inclusions were studied in the central arctic ocean during the arctic 91 expedition and in the laptev sea east siberian arctic region expedition 1992 results from these investigations are here combined with previous studies performed in major areas of ice ablation and the southern central arctic ocean this study documents the regional distribution and composition of particle laden ice investigates and evaluates processes by which sediment is incorporated into the ice cover and identifies transport paths and probable depositional centers for the released sediment in april 1992 sea ice in the laptev sea was relatively clean the sediment occasionally observed was distributed diffusely over the entire ice column forming turbid ice observations indicate that frazil and anchor ice formation occurring in a large coastal polynya provide a main mechanism for sediment entrainment in the central arctic ocean sediments are concentrated in layers within or at the surface of ice floes due to melting and refreezing processes the surface sediment accumulation in central arctic multi year sea ice exceeds by far the amounts observed in first year ice from the laptev sea in april 1992 sea ice sediments are generally fine grained although coarse sediments and stones up to 5 cm in diameter are observed component analysis indicates that quartz and clay minerals are the main terrigenous sediment particles the biogenous components namely shells of pelecypods and benthic foraminiferal tests point to a shallow benthic marine source area apparently sediment inclusions were resuspended from shelf areas before and incorporated into the sea ice by suspension freezing clay mineralogy of ice rafted sediments provides information on potential source areas a smectite maximum in sea ice sediment samples repeatedly occurred between 81 n and 83 n along the arctic 91 transect indicating a rather stable and narrow smectite rich ice drift stream of the transpolar drift the smectite concentrations are comparable to those found in both laptev sea shelf sediments and anchor ice sediments pointing to this sea as a potential source area for sea ice sediments in the central arctic ocean sea ice clay mineralogy is significantly different from deep sea clay mineral distribution patterns the contribution of sea ice sediments to the deep sea is apparently diluted by sedimentary material provided by other transport mechanisms

altimeter derived surface circulation in the large scale ne pacific gyres part 1 seasonal variability abstract the seasonal variability of sea surface height ssh and currents are defined by analysis of altimeter data in the ne pacific ocean over the region from central america to the alaska gyre the results help to clarify questions about the timing of seasonal maxima in the boundary currents as explained below the long term temporal mean of the ssh values must be removed at each spatial point to remove the temporally invariant and large signal caused by the marine geoid we refer to the resulting ssh values which contain all of the temporal variations as the residual ssh our main findings are 1 the maximum surface velocities around the boundaries of the cyclonic alaska gyre the alaska current and the alaska stream occur in winter at the same time that the equatorward california current is weakest or reversed forming the poleward davidson current the maximum surface velocities in the california current occur in summer these seasonal maxima are coincident with the large scale atmospheric wind forcing over each region 2 most of the seasonal variability occurs as strong residuals in alongshore surface currents around the boundaries of the ne pacific basin directly connecting the boundaries of the subpolar gyre the subtropical gyre and the equatorial current system 3 seasonal variability in the surface velocities of the eastward north pacific current west wind drift is weak in comparison to seasonal changes in the surface currents along the boundaries 4 there is an initial appearance next to the coast and offshore migration of seasonal highs and lows in ssh alongshore velocity and eddy kinetic energy eke in the alaska gyre similar to the previously described seasonal offshore migration in the california current 5 the seasonal development of high ssh and poleward current residuals next to the coast appear first off central america and mainland mexico in may june prior to their appearance in the southern part of the california current in july august and their eventual spread around the entire basin in november december similarly low ssh and equatorward transport residuals appear first off central america and mexico in january february before spreading farther north in spring and summer 6 the maximum values of eke occur when each of the boundary currents are maximum

secondary detachments within carbonates of the saraburi group triassic khao khwang fold and thrust belt thailand abstract permian limestones of the saraburi group in central thailand deformed during the triassic indosinian orogeny exhibit detachments formed in response to the following variations in lithology thin shale beds within a limestone sequence massive limestone overlaying well bedded limestone massive limestone overlying interbedded limestones and shales within well bedded limestones thin shales interbedded with limestones overlying limestones where shales are present the decoupling of layers is similar to examples previously described in the literature from outcrop and analogue models however more unusually detachments are also present within limestone units while detachment folds are typically developed above a basal weak unit usually salt or shale in the study area is an example developed entirely within well bedded limestones instead of flow of the weak unit into the core of the fold room problems in the core of the fold are accommodated by pressure solution parallel to bedding thrusts small fault propagation folds and intense folding variations in structural style are largely influenced by the spacing intensity of bedding limestone clay content and the efficiency of pressure solution during deformation and the presence absence and thickness of interbedded shales a ductile detachment zone is developed between well bedded limestones and overlying massive limestones the detachment zone separates highly folded sequence dominated by steep dips from a weakly folded sequence dominated by gentle dips pressure solution processes and variability in pressure solution intensity related to clay content play a very strong role in accommodating the difference in deformation styles across the detachment

glaciomarine sedimentation and palaeo glacial setting of maxwell bay and its tributary embayment marian cove south shetland islands west antarctica abstract high resolution 3 5 khz and multi channel seismic profiles and piston cores were collected from maxwell bay and its tributary embayment marian cove in the south shetland islands antarctica during the korea antarctic research program 1992 93 and 1995 96 to elucidate the glaciomarine sedimentation processes and recent glacial history of the area seismic data from maxwell bay reveal a rugged bay margin and flattened basin floor covered with well stratified hemipelagic muds on the base of slope acoustically transparent debris flows occur indicating downslope resedimentation of glaciomarine sediments despite the subpolar and ice proximal settings of marian cove the seafloor is highly rugged with a thin sediment drape suggesting that much of the area has been recently eroded by glaciers sediment cores from the cove penetrated three distinct fining upward lithofacies 1 basal till in the lower part of the core accumulated just seaward of the grounding line of the tidewater glacier 2 interlaminated sand and mud in the middle part deposited in ice proximal zone by a combination of episodic subglacial meltwater inflow and iceberg dumping and 3 pebbly mud in the upper part deposited in ice distal zone by both surface meltwater plume and ice rafting from the glacier front a reconstruction of the glacial history of these areas since the late glacial maximum shows an ice sheet filling maxwell bay in late wisconsin time and grounding of the tidewater glacier in marian cove until about 1300 yr bp

understanding sibumasu in the context of ribbon continents abstract well described ribbon continent collision belts and modern examples with 2d seismic coverage particularly zealandia provide analogues for the permo triassic development of sibumasu two key parameters for the ribbon continents are their width and how rifting developed which in turn impact the structural metamorphic igneous and stratigraphic development of ribbon continents in ways that make them significantly different from the collisional development of major continents key characteristics of the tectonics of sibumasu are 1 a tendency towards basin inversion during the late triassic and possibly early jurassic and mixed thick skinned and thin skinned style deformation 2 extensional collapse around 215 ma is an important feature of sibumasu particularly in northern thailand and probably other areas too 3 slab delamination and extension related decompression melting were probably important mechanisms for generating granites in addition to crustal thickening 4 metamorphism is relatively high temperature lower pressure

oceanographic and physiographic controls on modern sedimentation within antarctic fjords physical oceanographic data and modern surface sediments were collected from eleven fjords along the western side of the antarctic peninsula and south shetland islands surface sediment samples 62 were analyzed for texture and total organic carbon content the distribution of biogenic and terrigenous facies within the fjords is controlled by bay geometry and oceanographic regime climate plays a secondary role but along with ice drainage basin size controls the rate of terrigenous supply to the glacial marine environment specifically fjords along the danco coast and palmer archipelago with a high length to width ratio tend to have bottom sediments that are arenaceous where ice rafted sediment is released preferentially at the head of the fjord biogenic facies are favored where the bay geometry is complex where such complexity exists separate oceanographic regimes develop that lead to separation of terrigenous and biogenic sediments processes of interflow mid and deep water turbid cold tongues and coriolis deflection produce terrigenous facies along the inner fjord and western edges of a fjord system warm outer bay waters tend to develop a stable eddy circulation pattern that favors the productivity of phytoplankton in the surface layers outer bays are therefore floored with organic rich siliceous muds and ice rafted material only in the south shetland islands is melt water input significant enough to generate estuarine circulation within the fjord but here strong bottom currents result in arenaceous bottom sediments with no biogenic facies ice rafted diamictons are produced proximal to the edges of small tide water glaciers in the south shetlands the facies relationships established in this study provide a strong reference for paleoclimatic studies that utilize downcore measurements of texture and organic carbon

chert geochemistry depositional setting stratigraphic and structural significance for the permian nong pong formation khao khwang fold and thrust belt saraburi thailand abstract the deepwater chert shale limestone tuff permian nong pong formation npf of the saraburi group is a major unit within the triassic indosinian orogeny khao khwang fold and thrust belt kkftb whether the npf was deposited in a continental margin or ocean basin remains uncertain and impacts structural sedimentary and stratigraphic interpretations of the kkftb this study investigates chert geochemistry from a 60 m section of the formation near muak lek town to determine its depositional environment radiolarian fauna from the chert beds includes follicucullus porrectus rudenko probable late guadalupian late middle permian indicating the npf is time equivalent to adjacent carbonate platform deposition khao khwang and khao khad formations high ratios of sio2 sio2 al2o3 fe2o3 and fe al mn plots indicate a biogenic origin radiolarians sponge spicules for the cherts far from a hydrothermal source trace element ratios for u th sc th and sr ba and ce anomalies in the nasc normalized ree distribution are ambiguous and range between shallow to deep ocean basin and continental margin settings major elements analysis of cherts show 1 high ratios of sio2 sio2 al2o3 fe2o3 range 0 60 0 82 0 76 average 2 al al fe mn range 0 67 0 82 and 3 average mno tio2 0 14 the mno tio2 and al2o3 al2o3 fe2o3 ratio 100 fe2o3 sio2 vs 100 al2o3 sio2 and fe2o3 100 sio2 vs al2o3 100 sio2 diagrams indicate deposition on a continental margin the lan cen versus al2o3 al2o3 fe2o3 discrimination diagram indicates a pelagic continental margin setting combined geochemical structural and sedimentary facies analyses suggests the npf was deposited in a deep marine normal fault bounded basin on a rifted ribbon continent margin where carbonate platforms grew on structural highs

diatom distribution in southern ocean surface sediments atlantic sector implications for paleoenvironmental reconstructions abstract a study of 230 surface sediment samples collected in the atlantic sector of the southern ocean between the southernmost weddell sea and the subtropical zone documents the modern distribution of diatoms revealing patterns of paleoenvironmental significance estimations of diatom valves per gram dry sediment display numbers of 50 200 106 in the zone of high opal burial located between the mean position of the winter sea ice edge and the polar front and maximum values of greater than 200 106 in the near shore sedimentary basins off the antarctic peninsula lowest diatom concentrations and assemblages strongly affected by dissolution were encountered in the weddell basin despite alteration of the diatom assemblages prior to their incorporation into the sediment record the biogeographic distribution and the abundance pattern of most of the 35 studied diatom species shows a close relationship with the surface hydrography water temperature these relationships can be used to estimate past surface water temperatures based on statistical treatments of the assemblages or on simple relations of species occurrences in the geological record another close link occurs between the distribution of sea ice and sea ice related diatoms

new data on the indosinian orogeny from central thailand the main aspects of the geosynclinal and orogenic evolution of the petchabun foldbelt in central thailand are described this area was previously thought to be deformed by the indosinian triassic orogeny the new data show that the main orogenic event in thailand can be dated post lower permian pre uppermost permian evidence is given that paleotethys closed on thai territory during this orogenic event the known upper triassic deformations in northern thailand are supposed to be strictly intracontinental and therefore of minor importance

impact of assimilating bottom pressure anomalies from grace on ocean circulation estimates 1 the impact of assimilating global ocean bottom pressure obp information from the gravity recovery and climate experiment grace gravity anomalies on the circulation estimate was investigated for this an estimate of the ocean circulation is being inferred by extending the 50 year long german part of the estimating the circulation and climate of the ocean gecco ocean synthesis into recent years the assimilation system is an improved version of the previous gecco optimization which now includes a sea ice model has enhanced resolution on a truly global domain including the arctic ocean by analyzing differences to a synthesis that additionally assimilated obp the grace data was found to provide complementary information to standard ocean data sets including satellite altimetry when assimilated although in principle standard ocean data sets include the obp information the reason why this cannot be extracted is the much larger prior errors for hydrographic and altimeter data in comparison to obp data owing to the fact that only the former two need to include the unresolved eddy signal the largest impact of gravity data is found to be on the barotropic circulation particularly in the subtropical gyres and the polar latitudes remaining differences between the simulated and observed obp information are associated with meridional stripes in the grace gravity maps and with the leakage of terrestrial hydrological information into the ocean additional differences close to the continental boundaries are related to the self attraction and loading processes that are not included in the models

structure of the sibumasu indochina collision central thailand a section through the khao khwang fold and thrust belt abstract mainland se asia is composed of a number of continental fragments and volcanic arcs separated by oceanic suture zones which were accreted to the growing asian continent during the triassic indosinian orogeny the evolution of this orogeny has always been quite controversial indeed the effects of this orogeny in thailand have often been interpreted without considering the detailed tectonic evolution of the portion of the indochina block s margin formed by khao khwang platform area of the saraburi group in central thailand this area is unusual because 1 an extensive area representing a thin skinned fold and thrust belt is well exposed due to quarrying and 2 the fold and thrust belt displays a series of e w and wnw ese striking thrusts and associated folds that are not easily explained in the context of the traditional interpretation where the terranes have been accreted broadly along n s striking collisional zones detailed structural observations in numerous quarries around highway 21 in a 13 km long dip direction traverse have revealed that overall the thrust belt is composed of several large thrusts with an approximately northwards transport direction in the southern part of the area south verging structures are present although the dominant structural trend is northwards verging interference structures and late strike slip faults indicate there is more than one phase of structural development present

hydrothermal chert and associated siliceous rocks from the northern pacific their geological significance as indication od ocean ridge activity adachi m yamamoto k and sugisaki r 1986 hydrothermal chert and associated siliceous rocks from the northern pacific their geological significance as indication of ocean ridge activity sediment geol 47 i25 148 analyses of 42 cretaceous rock samples from deep sea drilling project dsdp leg 32 in tile northern pacific show that chert and porcellanite are enriched in fe mn p cu ba mo ni and pb relative to both triassic biogenic cherts of central japan and cretaceous dsdp cherts of leg 62 the iron enrichment up to 6 68ve fe20 as total iron is most prominent in chert immediately overlying basal basah which is the only chert free of radiolarians and veined by megaquartz containing many fluid inclusions chemical features characterized by a low ratio for a1 ai fe mn and ai z tio 2 and a high ratio for total fe2oj tio 2 mno tio 2 and mo tio 2 as well as petrological evidence indicatc that the cherts formed in an intense submarine hydrothermal environment on or near the cretaceous japanese spreading center which separated the kula plate from the pacific plate the spreading rate of the cretaceous japanese spreading center estimated from the chemical composition of the cherts was about 3 7 cm r i the rate is comparable to that inferred from the geomagnetic data

development of the khao khwang fold and thrust belt implications for the geodynamic setting of thailand and cambodia during the indosinian orogeny abstract the indosinian orogeny in thailand is often viewed as having developed between strongly linear terranes which today trend approximately n s the terranes were subsequently disrupted by later tectonics particularly nw se trending cenozoic strike slip faults the ene wsw to ne sw striking thrusts and folds in the khao khwang platform area of the saraburi group on the sw margin of the indochina terrane are not easily explained in the context of this traditional view reversal of the clockwise rotation shown to have affected the block north of the mae ping fault zone only enhances the e w orientation of structures in the fold and thrust belt and moves the belt further east towards cambodia one solution for the trend that fits better with regional understanding from hydrocarbon exploration of the khorat plateau is that the indochina terrane was actually a series of continental blocks separated by permian rifting during the early triassic the early stages of collision south china cathaysian terrane collision with vietnam indochina resulted in the amalgamation of disparate blocks that now form the indochina terrane by closure along the rifts at the same time or following on from the collision there was closure of the back arc area between indochina and the sukhothai zone the rift basins were thrusted and inverted during the early stages of the indosinian orogeny and only underwent minor reactivated when later sibumasu collided with sukhothai zone indochina terrane margin during the late triassic the scenario described above requires the presence of a minor e w trending suture in nw cambodia evidence for this suture is suggested by the presence of permo triassic calc alkaline volcanism

inheritance of jurassic rifted margin architecture into the apennines neogene mountain building a case history from the lucretili mts latium central italy the western lucretili mts in the central apennines latium italy have been recently re mapped in great detail and are the subject of combined stratigraphic sedimentological and structural investigations in this paper we present a new stratigraphic interpretation of the jurassic paleogeography of western lucretili mts where a rift derived intrabasinal paleo high of the alpine tethys has been identified for the first time by means of facies analysis and biostratigraphic dating recognised facies associations combined with dated stratigraphic sections allow to define the morphology of the structural paleo high and to identify the associated gravity driven deposits olistoliths accumulated in the surrounding basin furthermore we investigated the modes of interaction between jurassic extensional structures and the subsequent contractional patterns developed during the tertiary mountain building in detail the role played during apennines tectonics by the paleo escarpments bounding the paleo high and by the surrounding olistoliths has been analysed the paleo escarpments either acted as focussing features for ene directed frontal thrust ramp localisation and were offset with small shortening amounts or reactivated as nne striking high angle transpressional faults or preserved the original geometries as a result of variable orientation of paleo escarpments with respect to the neogene compressive stress field with ene oriented sigma1 newly formed ene striking tear faults connect these either inherited or neo formed discontinuities this complex stratigraphic and structural pattern is substantially different from the previous interpretations of this portion of the central apennines based on a hypothesised layer cake stratigraphy deformed by neo formed neogene thrusts this contribution strengthens the importance of integrating facies analyses and structural investigations to detect the influence of pre orogenic structures on compressive structural patterns in an area where commercial seismic lines are not available and cannot help in reconstructing the subsurface geometries

hydrothermal venting and basin evolution devonian south china constraints from rare earth element geochemistry of chert this paper presents rare earth element ree geochemistry of siliceous deposits from which hydrothermal activity and basin evolution are elucidated in the late devonian in the yangshuo basin south china where siliceous deposits widely occurred as nodular chert in the deep water limestones and bedded chert interbeded with tuffaceous chert in the early late devonian both nodular and bedded cherts are characterized by very low la abundances avg 2 07 and 2 49 ppm respectively intermediate negative ce anomalies ce ce avg 0 69 and 0 61 slight to intermediate positive eu anomalies eu eu avg 1 33 and 1 57 and low to intermediate shale normalized lan ybn values avg 0 86 and 0 52 and intermediate lan cen values avg 1 61 and 1 72 these suggest both nodular and bedded cherts formed in the open marine basin of south china rather than in the intracontinental rift basin as previously assumed with involvement both with seawaters as indicated by intermediate negative ce anomalies and generally lree depleted patterns and hydrothermal vent fluids as indicated by convex less lree depleted patterns with apparent positive eu anomalies in comparison with nodular and bedded chert the tuffaceous chert has the highest la abundances avg 17 11 ppm similar ranges of ce anomalies avg 0 63 and lan cen values avg 1 77 but lower lan ybn values avg 0 48 and no apparent positive eu anomalies avg 0 97 this suggests that the tuffaceous fallouts were also significantly modified by the hydrothermal fluid and seawater rapid spatial variations of eu eu values and degree of lree depletions in the studied basin are recognized characterizing a spatially differential hydothermal activity that is not well discriminated by major element features such a difference in hydrothermal activity is interpreted as having been related to the intensity and depth of syndepositional tectonic activity reconciling the structural pattern unraveled by stratigraphic packages d 2005 elsevier b v all rights reserved

bottom pressure signature of annual baroclinic rossby waves in the northeast tropical pacific ocean the annual cycle in bottom pressure pb in the northeast tropical pacific ocean ntpo is studied focus is on a zonal section along 12 n between 105 w and 145 w that is characterized by a strong annual cycle in sea level from satellite altimetry estimates of pb from the gravity recovery and climate experiment grace a state estimate produced by the estimating the circulation and climate of the ocean ecco consortium and a linear rossby wave model lrwm are used the grace ntpo pb annual cycle shows amplitudes as large as 1 cm water equivalent the grace data also evidence westward propagation that is consistent with the behavior of long mode 1 rossby waves at this latitude with phase increasing from east to west at a rate of 0 34 m s 1 the ecco and lrwm pb estimates corroborate the notion that grace reveals the pb signature of annual rossby waves driven by interior wind stress curl and possibly damped by frictional processes results have implications for attempts to constrain global ocean mass using a single point mooring

depositional setting and paleoenvironment of an alatoconchid bearing middle permian carbonate ramp sequence in the indochina terrane abstract a middle permian carbonate sequence at khao somphot in the south of the khao khwang platform has been measured and analyzed this sequence is characterized by prolific fossil content and large bizarre alatoconchid bivalves nine major microfacies types are differentiated and consist of algal foram facies fusuline facies alatoconchid facies lime mudstone wackestone facies laminated bindstone facies fine grained cortoid grainstone facies coral biostrome facies crinoidal packstone facies and carbonate breccia conglomerate facies laminated bindstone lime mudstone with fenestral fabric and algal foram facies represent loferites deposited in a restricted intertidal zone of an inner ramp fusuline grainstone and cortoid grainstone facies indicate sand shoals of an inner ramp the fusuline wackestone packstone and alatoconchid facies were deposited in a subtidal below fair weather wave base environment in the mid ramp the crinoidal facies which overlies collapse breccia possibly accumulated during transgression in the deeper part of the mid ramp storm deposits are prevalent throughout as thin accumulates and as alatoconchid floatstone rudstone coquinite layers and are common in mid ramp setting the khao khwang platform probably evolved from a rimmed platform in the early permian to a ramp in the middle permian the general trend of 13c composition from both brachiopod shell and rock matrix from the lower part of the study section wordian is significantly high moreover the 13c signature from this interval is up to 8 vpdb which suggests high productivity on the tropical tethyan shelf of the indochina terrane an abrupt negative shift in 13c in the late wordian and late capitanian indicating significant changes in paleoenvironment productivity and the carbon cycle is probably contemporaneous with the kamura event recorded from sediments of the mid panthalassa ocean in japan and elsewhere related to global cooling and a sea level lowstand

geodynamic evolution of loei and phetchabun regions does the discovery of detrital chromian spinels from the nam duk formation permian north central thailand provide new constraint abstract the discovery of the chromian spinel detritus in sandstones from the permian nam duk formation phetchabun region confirms that the siliciclastic part of this formation is related to the erosion of a mountain belt caused by compressional deformation the question discussed is whether this detritus is derived from an older orogen exposed today in the region of loei east of the nam duk basin or it is from a mountain belt which evolved during permian times in the west nan uttaradit region in the first case the nam duk formation would represent the passive continental margin sequence of the indochina craton and in the second case it would be part of the sedimentary wedge associated with the compressional deformation and subsequent uplift to the erosional level during middle to upper permian of a rising mountain belt further in the west in this contribution arguments in favour of the second scenario are discussed the region close to the nan uttaradit suture zone shows evidence of compressional deformation and subsequent uplift to an erosional level in the permian when the chromian spinel detritus was deposited in the nam duk formation

direct measurements of upper ocean currents and water properties across the tropical pacific during the 1990s abstract meridional sections of upper ocean zonal currents potential temperature and salinity are estimated at ten longitudes from 143 e to 95 w using conductivity temperature depth and acoustic doppler current profiler data from 172 synoptic sections taken in the tropical pacific between 138 e and 86 w mostly in the 1990s data reduction is carried out in a potential isopycnal and mixed layer framework to preserve a sharp pycnocline a mixed layer water property extrema and velocity extrema mean zonal currents potential temperatures and salinities are produced at each longitude the seasonal cycles of these fields are also estimated as well as a simple el nino southern oscillation enso cycle zonal sections along the equator are also presented properties of the near equatorial zonal currents including transports temperatures and salinities are estimated separately from the synoptic sections the seasonal cycles of these quantities and their correlations with the southern oscillation index are investigated the work is distinguished from most existing literature in that direct estimates of zonal velocity are combined with contemporaneous temperature and salinity data allowing trans pacific estimates of near equatorial current transports and properties including those of the northern branch of the south equatorial current the new guinea coastal undercurrent and the equatorial undercurrent

the origin of massive diamicton facies by iceberg rafting and scouring scoresby sund east greenland almost 90 of 39 m of core material recovered from scoresby sund and the adjacent east greenland shelf is massive diamicton interpreted to be formed predominantly by the release of iceberg rafted debris and reworking by iceberg scouring there is also likely to be a contribution from suspension settling of fines derived from glaciofluvial sources model calculations suggest that the 14c derived holocene sedimentation rate of 0 1 0 3 m 1000 yr 1 in scoresby sund can be accounted for mainly by iceberg rafting of debris a further 4 of core material is of gravel or coarse sand lenses interpreted to reflect iceberg dumping of debris intensive iceberg scouring which reworks sea floor sediments is observed on acoustic records from over 30 000 km2 of the scoresby sund fiord system and the adjacent east greenland shelf 69 72 n and 75 n the rate of iceberg production from greenland ice sheet outlet glaciers and iceberg drift tracks on the shelf suggests that iceberg rafting and scouring may be important over a significant proportion of the 500 000 km2 area above the shelf break the relatively extensive modern occurrence of massive diamicton formed by iceberg rafting and scouring together with suspension settling of fines suggests that it may also be a significant facies in the glacier influenced geological record the recognition in the geological record of the massive diamicton facies described above may also indicate the former presence of fast flowing ice sheet outlet glaciers

models of glaciomarine sedimentation and their application to the interpretation of ancient glacial sequences abstract this paper argues that glaciomarine environments can be regarded as special glacially influenced types of continental margin environments e g continental shelf slope rise and basin plain knowledge of the stratigraphic architecture and typical sedimentary sequences of non glacial margins is becoming well known but remains limited for those that have been glacially modified the principal influences on sedimentation in these environments relate to the glacial sediment input controlled by relief of basin margin glacier thermal regime and ice flow dynamics and depositional environments influence of traction currents substrate relief and proximity to nearby ice margins typical ranges of sedimentation rates can be established for glacially influenced continental margin environments and these may provide a framework for ancient sequences starvation of sediment supply to glacially influenced continental margins is common the nature of sub ice shelf sedimentation a model that has been applied to many ancient glacial sequences is critically reviewed the significance of such sedimentation in the rock record has probably been exaggerated because of oversimplistic interpretations of diamictite sequences existing process models of glaciomarine sedimentation derived from study of modern environments are sometimes difficult to employ in investigation of ancient sedimentary sequences because simple lithofacies criteria and typical vertical profiles are not available to aid in interpretation in addition compositional data emphasized by many workers for distinguishing glaciomarine from continental glacial diamict ite s frequently fingerprint sediment source and not mode of deposition the importance of facies analysis methods for isolating depositional environments is illustrated by three examples of ancient glaciomarine sequences these are the early proterozoic gowganda formation 2 3 ga of northern ontario canada the late proterozoic port askaig formation 670 ma of scotland and ireland and the late cenozoic yakataga formation 20 ma to recent of the gulf of alaska these examples illustrate the significance of detailed genetic studies of ancient glacial rocks in the interpretation of palaeogeographic and tectonic settings diamictite units in ancient glaciomarine sequences cannot be easily interpreted in terms of climatic or ice advance retreat cycles because of the varied controls on diamict accumulation and diamictite preservation in marine basins

review of major shale dominated detachment and thrust characteristics in the diagenetic zone part i meso and macro scopic scale there is considerable variability in the thickness structure and macroscopic deformation style within shale prone major thrust zones which also impacts the structural style in the overlying and sometimes the underlying section the properties and percentages of clay minerals and percentages of organic material quartz and calcite affect fault zone weakness and behaviour the distribution of competent units within a shale prone zone can also significantly affect fault zone architecture even over short strike distance of 10s to 100s of metres other influences include high pore fluid pressures and associated veins deformation of the fault zone may disrupt the original principal displacement zones and force them to relocate including switching lithologies calcite veins can become concentrated locally in the fault zone and become a focus of fault zone weakness we still need many more descriptions of shale prone fault zones to understand the potential variations in thrust sheet structural style caused by differences in shale detachment characteristics the variations in structural style in the hanging walls of shale detachments are broad and range between the sledge runner style in many appalachian examples and the extensive closely spaced imbricate style of the osen roa detachment southern norway such contrasts are related to several factors including thrust sheet mechanical stratigraphy thickness of the overburden lateral continuity of the detachment detachment mechanical properties composition pore fluid pressures presence absence of higher level detachments and strain rate in many structural locations and at many scales shale prone sequences will pile up to produce over thickened masses cleavage duplexes s c fabrics duplexes imbricates pseudo duplexes and vein formation can all contribute to the thickening at nested scales a mixture of brittle and solution diffusion processes overall cause the affected unit to exhibit flow like characteristics while the broad principles are now well established considerable work remains to be done understanding the full range of structural geometries associated with shale detachments what factors regarding the nature of the detachments affect overlying structural styles rates of deformation and the controls on deformation mechanisms within the thrust zones

complex structure of an upper level shale detachment zone khao khwang fold and thrust belt central thailand abstract shale detachment zones have been previously described as largely mobile in character however increasing resolution of seismic images and understanding of these zones suggest brittle deformation may have a significant role in their deformational behaviour and in the deformation of overlying fold and thrust belts dependence on seismic imaging and other indirect and low resolution study methods has resulted from the lack of outcropping shale detachment zones both active and ancient for detailed study however a newly described upper level detachment zone in a shale unit in the khao khwang fold and thrust belt in central thailand is exceptionally well exposed we use detailed structural analysis to investigate deformational mechanisms of this ancient exhumed detachment zone as an analogue to active modern day examples through detailed field mapping we were able to construct multiple cross sections through the detachment zone these cross sections were subdivided into structural domains which display an increase in density and complexity of deformational structures folds faults and heterogeneity of their orientations toward the thrust at the base of the detachment zone contrasting strain rates in zones of continuous discontinuous deformation result from contrasting rock competencies through the sections we conclude that the fault damage zone in this study constitutes an upper level detachment and is potentially analogous to those in active collisional fold and thrust belts it displays mixed brittle ductile deformation and a complex three dimensional anastomosing fault system

ice sheet extent of the antarctic peninsula region during the last glacial maximum lgm insights from glacial geomorphology we present marine geological and geophysical data for the antarctic peninsula that call for a larger ice sheet reconstruction during the last glacial maximum lgm than suggested by previous studies such glacial reconstructions are important for quantifying post lgm sea level rise and providing boundary conditions for general circulation models megascale glacial lineations on the continental shelf surrounding antarctica provide documentation for grounded ice that was streaming swath bathymetry data nbp02 01 reveal lineations in each of the major glacial troughs except for smith trough which features grooves and bedrock drumlins 0 5 3 km spacing 1 20 elongation ratios on crystalline bedrock we place the maximum extent of ice at the seaward limit of the lineations at or near megascale glacial lineations imaged in this study and other areas surrounding antarctica including the ross sea pine island bay have a consistent morphology with elongation ratios of 80 1 and spacings of 200 600 m mode of 300 m in contrast lineations bundles canals et al 2000 in the gerlache boyd trough exhibit larger spacing 1 5 km and the upstream portions 7 km are carved directly into bedrock rather than till as suggested by previously unpublished air gun 120 hz seismic data these features have yet to be dated however they are believed to have been active during the lgm radiocarbon dates in glaciomarine sediments foraminifera and organic matter from seven glacial troughs indicate that megascale glacial lineations were formed during the lgm other geomorphic features such as the grounding zone wedge in the northwestern weddell sea formed when the ice sheet was retreating the initial retreat of the grounded ice from the outer shelf occurred by 18 500 cal yr b p the inner shelf was mostly ice free by 13 000 cal yr b p this is significantly earlier than numerical models which suggest antarctic deglaciation began at 12 000 cal yr b p this also suggests the peninsula area contributed to global sea level rise associated with meltwater pulse mwp 1a

modeling the growth and decay of the antarctic peninsula ice sheet a model of the growth and decay of the antarctic peninsula ice sheet during the last glacial interglacial cycle is used to identify the main controls on ice sheet behavior using as input glaciological assumptions derived by w f budd and i n smith 1982 annals of glaciology 3 4249 bedrock topography isostatic compensation and mass balance relationships the model is driven by sea level change over the last 40 000 yr in association with assumed changes in the rate of melting beneath ice shelves an ice sheet dome over 3 5 km thick grows on the offshore shelf and straits west of the antarctic peninsula and reaches a maximum at 18 000 yr b p collapse begins at 14 000 yr b p but becomes rapid and continuous after 10 000 yr b p the present stable ice cover is achieved at 6500 yr b p ice growth and decay are characterized by thresholds which separate periods of steady state from periods of rapid transition the thresholds usually relate to topography tests show that ice sheet behavior is most sensitive to sea level change basal marine melting and accumulation and is less sensitive to isostasy spatial variation in accumulation calving rates and ice flow parameterization tests of the model against field evidence show good agreement in places as well as discrepancies which require further work o

lithofacies types and vertical profile models an alternative approach to the description and environmental interpretation of glacial diamict and diamictite sequences abstract increased knowledge of modern glacial depositional environments has resulted in rapidly evolving classifications of glacial tills these are based to a large degree on theoretical considerations of likely depositional processes the classifications are sophisticated and more advanced than the establishment of simple field criteria whereby individual till facies can be identified in quaternary and pre quaternary successions this situation is compounded in many quaternary terrains by the continued description of tills in terms of laboratory derived analytical data only reflecting a traditional interest in stratigraphic correlation rather than reconstruction of depositional environment detailed sedimentological logging of lithofacies is rarely undertaken there is thus considerable confusion as to what is being described or sampled when analytical data are presented for many pleistocene tills the same remarks apply to pre pleistocene tillites a lithofacies code is presented here for the rapid description and visual appraisal of field sequences or drill cores containing unconsolidated diamicts or lithified diamictites the term till is not used as it has a strict genetic definition referring to direct aggregation and deposition by glacier ice use of a four part code in conjunction with codes already published for fluvial sediments allows fundamental field properties to be depicted independent of genetic terminology and provides a firm basis for subsequent environmental interpretation and analytical work the value of this approach is illustrated by comparing a representative suite of vertical profiles of diamict assemblages deposited by modern grounded glaciers with a classic late pleistocene glacigenic sequence at scarborough bluffs ontario

a computer interfaced sedigraph for modal size analysis of fine grained sediment a system has been developed allowing the direct storage on disc of size data from the x ray scanning settling tube sedigraph 5000et processing of the cumulative percentage data output to produce smooth frequency curves is described this allows rapid 15 min and precise m 0 1o discrimination of size modes peak heights median and silt and clay percentages of fine grained sediments an example of a mud turbidite is given showing systematic changes in bulk and modal properties not visible by eye lack of size segregation in the 1 m thickness of this turbidite shows that it may have been deposited from a highly concentrated flow rather than from a dilute waning turbidity current such flows may explain ungraded poorly graded muddy sediments also known as homogenites unifites or megaturbidites by other authors

equatorially trapped rossby waves in the presence of meridionally sheared baroclinic flow in the pacific ocean topex poseidon altimeter data are analyzed for the 8 5 year period november 1992 to may 2001 to investigate the sea surface height ssh and geostrophic velocity signatures of quasi annual equatorially trapped rossby waves in the pacific the latitudinal structures of ssh and both components of geostrophic velocity are found to be asymmetric about the equator across the entire pacific with larger amplitude north of the equator the westward phase speeds are estimated by several different methods to be in the range 0 5 0 6 m s 1 these observed characteristics are inconsistent with the classical theory for first vertical first meridional mode equatorially trapped rossby waves which predicts a phase speed of about 0 9 m s 1 with latitudinally symmetric structures of ssh and zonal velocity and antisymmetric structure of meridional velocity the observations are even less consistent with the latitudinal structures of ssh and geostrophic velocity components for other modes of the classical theory the latitudinal asymmetries deduced here have also been consistently observed in past analyses of subsurface thermal data and altimeter data and have been variously attributed to sampling errors in the observational data a superposition of multiple meridional rossby wave modes asymmetric forcing by the wind and forcing by cross equatorial southerly winds in the eastern pacific we propose a different mechanism to account for the observed asymmetric latitudinal structure of low frequency equatorial rossby waves from the free wave solutions of a simple 1 5 layer model it is shown that meridional shears in the mean equatorial current system significantly alter the potential vorticity gradient in the central and eastern tropical pacific the observed asymmetric structures of sea surface height and geostrophic velocity components are found to be a natural consequence of the shear modification of the potential vorticity gradient the mean currents also reduce the predicted westward phase speed of first meridional mode rossby waves improving consistency with the observations

early cretaceous tectonic rejuvenation of an early jurassic margin in the central apennines the mt cosce breccia abstract evidence for an extension dominated tectonic phase in the late early cretaceous has been identified for the first time at mt cosce in the narni ridge 60 km n of rome central apennines as a result of geological mapping there the umbria marche sabina pelagic succession overlies shallow water carbonates calcare massiccio formation hettangian the mt cosce area represents a jurassic pelagic carbonate platform basin system the inheritance of early jurassic tethyan rifting hosting a remarkable stratigraphic unit named the mt cosce breccia this is a sedimentary breccia bearing clasts of calcare massiccio and of pelagic units and forming sparse to laterally continuous outcrops which rests unconformably on the horst block calcare massiccio the polygenic breccia is chaotic and displays heterometric clasts made of rocks not younger than the early cretaceous white pebbly mudstones with radiolarian and calpionellid rich maiolica formation elements and a maiolica type matrix the lithoclasts were clearly sourced locally and represent formations from the calcare massiccio to the jurassic basinal and condensed pelagic carbonate platform units the age of the polygenic breccias is assigned to the middle barremian due to the youngest age detected within the clasts the occurrence of hedbergella cf h luterbacheri in the matrix and calcareous nannofossils the unconformity and breccia indicate an episode of exhumation of an original jurassic paleoescarpment tract that had by then been buried by the lower part of the maiolica formation the clasts were sourced from the exhumed vestiges of the jurassic onlap wedge hangingwall basin succession the peritidal pre rift substrate and its condensed drape pelagic carbonate platform type deposits as a product of escarpment rejuvenation erosion and displacement along an early cretaceous fault

westward motion of mesoscale eddies abstract since the pioneering work of nof the determination of the westward drift of mesoscale eddies under the planetary beta effect has been a recurrent theme in mesoscale oceanography and several different formulae have been proposed in the literature here recpatiulation is sought and within the confines of a single layer model a generalized formula is derived although it is similar to nof s the present formula is established from a modified definition and with fewer assumptions it also recaptiulates all other formulae for the one layer model and applies to a wide variety of situations including cases when the vortex develops a wake of rossby waves or undergoes axismmetrization following the derivation of the formula a physical interpretation clarifies the migration mechanism which can be divided between a self induced propulsion and a reaction from the displaced ambient fluid numerical simulations with primitive and geostrophic equations validate the formula for a variety of length sc

seasonal temperature variation below the thermocline detected by argo floats 1 strong seasonal temperature variation below the thermocline is detected by argo profiling floats the variation is associated with a long baroclinic rossby wave the results of this study show that seasonal signals can be captured at 1000 2000 dbar not only in basin boundary regions or deep convection regions but also in the interior ocean a clear westward propagation signal is observed the phase speed is of the same order as a theoretically derived speed below the thermocline the first mode of empirical orthogonal function analysis of potential density variations in the strong signal region shows a clear seasonal variation even in the middle layer the amplitude of the temperature anomaly is 0 05 0 12 c at 1200 dbar which is equivalent to the annual standard deviation from the woa01 these results are obtained using the dense spatial and temporal distributions provided by the argo observations

anomalously low al2o3 tio2 values for archean cherts from the pilbara block western australia possible evidence for extensive chemical weathering on the early earth geochemical sedimentological and mineralogical features of 3 0 ga archean cherts and intercalated bifs from the pilbara block western australia were studied chert layers that are well exposed at point samson 20 km north northeast of roebourne consist of various types of chert white light gray chert brownish yellow chert gray chert dark gray chert massive black chert and light gray chert the cherts other than brownish yellow chert consist mostly of microcrystalline quartz with a minor amount of fine silicate minerals and carbonates the brownish yellow chert is characterized by a high concentration of goethite most cherts contain thin layers characterized by high concentrations of ti bearing minerals such as rutile anatase fe ti aggregates and fine tio2 grains accordingly al2o3 tio2 values in some samples are very low 1 0 indicating that these samples contain more tio2 than al2o3 this geochemical feature is attributed mainly to the supply of detrital materials with high ti bearing minerals to the site of deposition because the ti bearing minerals are generally associated with detrital quartz and zircon ti enriched detrital materials are possibly formed by al ti fractionation during 1 extensive chemical weathering or 2 hydrothermal alteration of the source rocks in the first hypothesis which we prefer it is suggested that low ph values 4 of meteoric waters accelerated the decomposition of rock forming minerals and prevented precipitation of dissolved al3 such low ph values of meteoric waters could have been attributed to more violent volcanic activities issuing acid materials e g h2s and hcl and or a higher concentration of atmospheric co2 in the archean than today

global observations of large oceanic eddies 1 ten years of sea surface height ssh fields constructed from the merged topex poseidon t p and ers 1 2 altimeter datasets are analyzed to investigate mesoscale variability in the global ocean the higher resolution of the merged dataset reveals that more than 50 of the variability over much of the world ocean is accounted for by eddies with amplitudes of 5 25 cm and diameters of 100 200 km these eddies propagate nearly due west at approximately the phase speed of nondispersive baroclinic rossby waves with preferences for slight poleward and equatorward deflection of cyclonic and anticyclonic eddies respectively the vast majority of the eddies are found to be nonlinear

stratigraphy of deformed permian carbonate reefs in saraburi province thailand kilometre scale thrusts affect the stratigraphic order of the sedimentary rocks that form the khao khwang platform in central thailand the effect of these thrusts requires detailed analysis to unravel the original distribution of the sedimentary units and their associated facies the khao khwang platform comprises three carbonate dominated units identified previously as the phu phe khao khad and khao khwang formations these carbonates are intercalated with clastic mixed siliciclastic and carbonate sequences the sap bon pang asok and nong pong formations the palaeogeography of the area prior to the indosinian orogeny is poorly known and has herein been investigated by combining structural reconstructions microfacies and biostratigraphy in the saraburi area a stratigraphic model for the yakhtashian midian carbonate platform palaeogeography using the well developed exposed sections of the khao khwang platform located in the saraburi province of thailand is presented this has revealed the presence of several separate carbonate platforms dominated by four major middle permian facies peritidal platform interior algal reef and basin slope which are dated using foraminifera and algae this model integrates recent structural studies and considers their impact on the present day distribution of the facies in terms of platform development using biostratigraphy and detailed microfacies analysis supplementary material characteristic images of the six facies high resolution stratigraphic logs a timescale correlation chart and a table detailing the common fossils identified in this study are available at https doi org 10 6084 m9 figshare c 3861796

weighing the ocean using a single mooring to measure changes in the mass of the ocean 1 combining ocean and earth models we show that there is a region in the central pacific ocean where ocean bottom pressure is a direct measure of interannual changes in ocean mass with a noise level for annual means below 3 mm water equivalent and a trend error below 1 mm yr we demonstrate this concept using existing ocean bottom pressure measurements from the region from which we extract the annual cycle of ocean mass amplitude 8 5 mm peaking in late september which is in agreement with previous determinations based on complex combinations of global data sets this method sidesteps a number of limitations in satellite gravity based calculations but its direct implementation is currently limited by the precision of pressure sensors which suffer from significant drift development of a low drift method to measure ocean bottom pressure at a few sites could provide an important geodetic constraint on the earth system citation hughes c w m e tamisiea r j bingham and j williams 2012 weighing the ocean using a single mooring to measure changes in themass ofthe ocean geophys res lett 39 l17602 doi 10 1029 2012gl052935

distinguishing subglacial till and glacial marine diamictons in the western ross sea antarctica implications for a last glacial maximum grounding line analyses of lithology stratigraphy and tephra from marine sediment cores collected from the western ross sea during cruises eltanin 32 and 52 and deep freeze 80 and 87 indicate that subglacial till does not extend to the continental shelf edge subglacial till occurs as the lowest unit in most cores landward south of approximately 74 s while seaward of approximately 74 s the lowest diamicton units are glacial marine diamictons glacial marine diamictons are distinguished from subglacial tills by the presence of higher and more variable total organic carbon content downcore distinct tephra layers stratification higher diatom and foraminifera abundances higher sand content and radiocarbon dates in chronological order downcore sand sized tephra layers from two cores on the outer continental shelf are interpreted as single eruptive events one likely to have been derived from the mount melbourne volcano and the other from the pleiades volcano radiocarbon dates from sediment above and below the tephra layer in one of these cores df87 32 show that deposition indicative of open water conditions occurred between 22 and 26 ka in the western ross sea

structural and fluid evolution of saraburi group sedimentary carbonates central thailand a tectonically driven fluid system abstract a stable isotopic study focused on calcite cements vein fill calcite and various bioclasts was conducted on variably deformed and thrusted lower and middle permian carbonates of the saraburi group samples were collected in quarry faces across 3 areas in the saraburi lopburi region of central thailand stable isotope crossplots carbon and oxygen using texture aware isotope samples defined variable but related fluid cement histories which are tied to regional burial and then orogenic overprints driven by the indosinian triassic orogeny this was followed by telogenetic overprints driven by late cenozoic uplift the studied carbonates were deposited along the western margin of the indochina block where they were deposited as isolated calcareous algal sponge and fusilinid rimmed platforms on highs bound by extensional faults the platform areas passed laterally and vertically into more siliciclastic dominated sequences deposited in somewhat deeper waters within probable fault bound lows regional post depositional mesogenetic fluid rock re equilibration of the isotope values in ongoing calcite precipitates occurred until the matrix permeability was occluded via compaction and pressure solution this regional burial regime was followed by collision of the indochina and sibumasu blocks during the indosinian triassic blocks which drove a set of structurally focused thrust plane related increasingly warmer set of fluids through the studied sequences the final diagenetic overprint seen in the isotopic values of the latest calcite cements occurs in a telogenetic uplift setting driven by cenozoic tectonics and isostatic uplift integration of isotope data with its structural setting establishes a clear separation in fluid events related to two time separate tectonic episodes its fluid chemistry defines the permo triassic closure of the paleotethys and its subsequent reactivation during the tertiary collision of india and asia the c o covariant plot fields in the permian carbonates of central thailand are so distinct that it is possible to use their signatures to separate burial from meteoric cements in drill cuttings and hence recognise equivalent subsurface unconformities and likely zone of porosity development in possible buried hill plays in thailand

distribution and dispersal pattern of suspended particulate matter in maxwell bay and its tributary marian cove in the south shetland islands west antarctica abstract water property casting data spm and ctdt have been obtained from ice influenced fjords maxwell bay and marian cove in the south shetland islands antarctica to describe the configuration of turbid meltwater plumes in detail and to elucidate the dispersal pattern of the plumes in the areas of the primary sediment pathways only ice contact processes are unique in ice influenced fjords the effect of glaciofluvial discharges has been overwhelmed by the influences of subglacial discharge and ice front melting fluvial discharge from side entry glaciers that commonly end on land and or supraglacial discharge from ice surface are however more responsible for the overflow plumes in maxwell bay and marian cove subglacial meltwater discharge which is almost always in the form of vertically rising buoyant jets is considered rare active glaciofluvial and or supraglacial input from marian cove causes most suspended particulate matter to be concentrated near the mid point of maxwell bay thus even though closer to fjord head trunk glaciers spm concentration in collins bay is comparatively low largely due to clean tidewater glaciers and absence of meltwater streams around collins bay strong bottom current flowing along the continental shelf off the south shetland islands may import and export sediment from the outside of maxwell bay influencing the distribution of bottom sediment as well as benthic community

rare earth major and trace elements in chert from the franciscan complex and monterey group california assessing ree sources to fine grained marine sediments abstract rare earth element ree major and trace element analyses of 77 samples from the mesozoic franciscan complex and miocene monterey group of california usa indicate that magnitudes of the ce anomaly ce ce and total ree abundances sree in these rocks are controlled dominantly by a the amount of included metalliferous material b the amount of direct terrigenous input and c the overall burial rate the relative importance of these individual processes varies across an ocean basin in such a way that ree relative fractionations and sree correspond with its depositional environment our conclusions are supported by an extensive review of published ree data from various river coastal open ocean and ridge influenced waters as well as terrigenous pelagic and metalliferous sediment the chert sequences record deposition in spreading ridge open ocean basin and continental margin environments the relative importance of metalliferous and terrigenous influences and the role of scavenging from seawater may be estimated from a sample s inferred depositional distance km from the spreading ridge the major element chemistry and the stratigraphie context the ce ce values are low 0 29 in the vicinity of spreading ridges and trend to successively higher 1 values with decreasing metalliferous and increasing terrigenous influences other ree indicators ree lu n la n eu eu also respond to metalliferous and terrigenous influences near the spreading ridge chert ree appears determined by burial rate while shale ree responds to metalliferous abundance in open ocean and continental margin environments ree is controlled by sediment exposure time and therefore is related inversely to burial rate ree data are consistent with the major elements fe2o3 mno and al2o3 in reflecting the respective metalliferous and terrigenous sources p2o5 and cao do not vary with ce ce in any environment but cao shows a weak negative correlation with ree trace element trends e g v cr cu ge si rb sr y th u in general can similarly be accounted for in the context of depositional position relative to metalliferous and terrigenous inputs rees in chert appear less affected by post depositional processes than either major or trace elements indicating that rees are better tools for paleoceanographic or tectonic reconstructions that are based on chert chemistry this work complements recent efforts to elucidate the factors determining large scale ree distributions in marine sediments and has direct bearing on previous attempts to use the ce anomaly in older rocks and sediments as a recorder of secular variations and anoxic events in the overlying water column

ensemble prediction and intercomparison analysis of grace time variable gravity field models precise measurements of the earth s time varying gravitational field from the nasa deutsches zentrum fur luft und raumfahrt gravity recovery and climate experiment grace mission allow unprecedented tracking of the transport of mass across and underneath the surface of the earth and give insight into secular seasonal and subseasonal variations in the global water supply several groups produce these estimates and while the various gravity fields are similar differences in processing strategies and tuning parameters result in solutions with regionally specific variations and error patterns this study examined the spatial temporal and spectral variations between the different gravity field products and developed an ensemble gravity field solution from the products of four such analysis centers the solutions were found to lie within a certain analysis scatter regardless of the local relative water height variation and the ensemble model is clearly seen to reduce the noise in the gravity field solutions within the available scatter of the solutions

interannual to decadal variability in the bifurcation of the north equatorial current off the philippines satellite altimeter sea surface height ssh data from the past 17 yr are used to investigate the interannualto decadal changes in the bifurcation of the north equatorial current nec along the philippine coast the nec bifurcation latitude migrated quasi decadally between 108 and 158n with northerly bifurcations observed in late 1992 1997 98 and 2003 04 and southerly bifurcations in 1999 2000 and 2008 09 the observed necbifurcationlatitudecanbeapproximatedwellbythesshanomaliesinthe128 148nand1278 1308ebox east of the mean nec bifurcation point using a 1 layer reduced gravity model forced by the ecmwf reanalysis wind stress data the authors find that the ssh anomalies in this box can be simulated favorably to serve as a proxy for the observed nec bifurcation with the availability of the long term reanalysis wind stress data this helps to lengthen the nec bifurcation time series back to 1962 although quasi decadal variability was prominent in the last two decades the nec bifurcation was dominated by changes with a 3 5 yr period during the 1980s and had low variance prior to the 1970s these interdecadalmodulationsin the characteristics of the nec bifurcation reflect similar interdecadal modulations in the wind forcing field over the western tropical north pacific ocean although the nec bifurcation on interannual and longer time

sedimentation on the ross sea continental shelf antarctica abstract glacial marine sedimentation has prevailed throughout most of the early glacial history of the ross sea region however since late miocene to early pliocene time the west antarctic ice sheet has advanced onto the continental shelf perhaps several times glacial troughs of the western ross sea may also have formed at this time these glacial troughs border outlet glaciers of the east antarctic ice sheet a widespread lodgement till facies was deposited during this glacial advance holocene retreat of this expanded ice sheet left no conspicuous meltwater record so decoupling of the ice sheet from the seafloor rather than rapid melting is implied modern glacial sediment is far less prevalent than biogenic sediment and reworked glacial sediment except in coastal areas adjacent to small ice shelves and ice tongues little or no debris is being transported beyond the calving line of the ross ice shelf siliceous mud and ooze occurs in the western ross sea where surface circulation is most vigorous and warm deep waters up well this siliceous sediment along with terrigenous silt and clay blankets the seafloor below approximately 300 m water depth most of the ross sea continental shelf is deeper than this surface sediments on shallow banks and coastal platforms have clearly been reworked by marine currents the most vigorous bottom current activity occurs in those areas where geostrophic currents impinge onto the shelf debris flows and turbidity currents are also important in eroding and redistributing glacial sediments on the shelf terrigenous silt and clay are more abundant in surface sediment than basal till the source of this silt and clay is problematic the most plausible sources being onshore transport of suspended sediment by impinging currents and subglacial meltwater input

rare earth element patterns of the central indian basin sediments related to their lithology rare earth element ree concentrations have been determined in terrigenous siliceous nodule barren and nodule bearing calcareous and red clay from the central indian basin the bulk distribution of ree and in particular the relative cerium fractionation in these surface sediments has been studied in relation to bottom water conditions ree fractionations within a single depositional environment are found to be characteristic for each sediment type with flat shale normalized patterns associated with terrigenous sediments positive ce anomalies with siliceous sediments negative ce and positive eu anomalies with calcareous sediments and lree depleted patterns with pelagic red clays there is no relation of any ree fractionation to bottom water redox conditions our results indicate that the ree signatures in marine sediments are not only related to depositional setting but also to the lithological variations and surficial diagenetic processes therefore these further constraints on understanding ree behaviour indicate that ree fractionations for paleotectonic and paleoredox reconstructions should be used with caution

evidence from southern ocean sediments for the effect of north atlantic deep water flux on climate evidence from southern ocean sediments for the effect of north atlantic deep water flux on climate

late holocene advance of the collins ice cap king george island south shetland islands radiocarbon dates of incorporated moss indicate advance of the collins ice cap on fildes peninsula king george island after 650 cal yr bp ad 1300 broadly contemporaneous with the little ice age as defined in europe during that time the glacier extended less than 400 500 m beyond its present day margin moreover radiocarbon data indicate that this was the most extensive advance of the last 3500 cal years prior to 650 cal yr bp the ice must have been at or behind its present position furthermore the data indicate that climate conditions prior to the late holocene advance may have been similar to or possibly warmer than today

an origin for laminated glacimarine sediments through sea ice build up and suppressed iceberg rafting laminated glacimarine sediments are observed in visual core logs and x radiographs from scoresby sund and nansen fjord east greenland they are mostly underlain and overlain by massive or stratified glacimarine diamicton dmm or dms which is a product of iceberg delivery of heterogeneous debris and in scoresby sund reworking by deep drafted iceberg keels the laminated sediments are ams radiocarbon dated to two cold periods since the last late weichselian deglaciation the younger dryas stadial milne land stadial in east greenland and the little ice age during cold climatic events multiyear shorefast sea ice sikussak formed in these fjords and trapped the icebergs fine grained laminated muds fl were deposited in scoresby sund when the flux of icebergs was suppressed but turbid meltwater continued to provide some sediment flux to the fjord systems varying through time to produce laminations in nansen fjord thinner and often massive mud layers fm resulted from shorter intervals of sea ice cover with no ice rafting stratified diamicton layers dms which alternate with mud deposition to produce a laminated unit probably represent intervening times of more open conditions with iceberg rafting in scoresby sund foraminifera are either absent from the laminated unit or begin to appear towards the end of its deposition the absence of both benthic and planktonic foraminifera also suggests that multiyear sea ice was covering the core sites there is no evidence of macrofaunal activity and bioturbation is absent from the laminated sediments satellite data show that multiyear shorefast sea ice is present in several areas of the high arctic today and this traps icebergs calved from interior ice cap drainage basins thus the process of laminated glacimarine sediment formation is likely to be applicable to a number of areas of the modern and quaternary arctic