spatio temporal variability in suspended particulate matter concentration and the role of aggregation on size distribution in a coral reef lagoon this paper presents the concentration and size distribution of suspended particles in the south west coral reef lagoon of the island of new caledonia data are provided by filtration techniques optical backscattering obs measurements and in situ laser diffraction particle sizing the concentration of suspended particles increased from reef to land a bottom nepheloid layer occurred over the entire lagoon and was more distinct on the nearshore area small particles were more abundant in the bottom nepheloid layer than in the overlying water column the concentration of suspended particles showed more variability over space than over time conversely the particle size distribution of suspended particles showed more variability at a given location over a month time variability than at a given moment over the lagoon space variability analysis showed that aggregates represented a large fraction of suspended particles microscope visualization and chemical analysis of a sample suggest the inclusion of a transparent exopolymeric matrix the relative abundance of aggregates over suspended particle volume concentration was found to increase as the quantity of suspended particle decreased the spatial distribution of the relative abundance of aggregates suggests more aggregates proximal to coral reefs the high concentration of aggregates at low turbidity and the spatial distribution of the relative abundance infer that aggregation is induced by the presence of organic ligands unlike optical backscattering and light attenuation measurements that are size sensitive measurements of suspended particle concentration in situ laser diffraction particle sizing provides a relevant optical measurement of suspended particulate matter in such an aggregate dominated system

geochemistry reservoir characterization and hydrocarbon generation potential of lacustrine shales a case of yq 1 well in the yuqia coalfield northern qaidam basin nw china abstract ever since a breakthrough of marine shales in china lacustrine shales have been attracting by the policy makers and scientists organic rich shales of the middle jurassic strata are widely distributed in the yuqia coalfield of northern qaidam basin in this paper a total of 42 shale samples with a burial depth ranging from 475 5 m to 658 5 m were collected from the shimengou formation in the yq 1 shale gas borehole of the study area including 16 samples from the lower member and 26 samples from the upper member geochemistry reservoir characteristics and hydrocarbon generation potential of the lacustrine shales in yq 1 well were preliminarily investigated using the experiments of vitrinite reflectance measurement maceral identification mineralogical composition carbon stable isotope low temperature nitrogen adsorption methane isothermal adsorption and rock eval pyrolysis the results show that the shimengou shales have rich organic carbon averaged 3 83 which belong to a low thermal maturity stage with a mean vitrinite reflectance ro of 0 49 and an average pyrolytic temperature of the generated maximum remaining hydrocarbon tmax of 432 8 c relative to marine shales the lacustrine shales show low brittleness index averaged 34 9 but high clay contents averaged 55 1 high total porosities averaged 13 71 and great langmuir volumes averaged 4 73 cm 3 g unlike the marine and marine transitional shales the quartz contents and brittleness index bi values of the lacustrine shales first decrease then increase with the rising toc contents the kerogens from the upper member shales are dominant by the oil prone types whereas the kerogens from the lower member shales by the gas prone types the sedimentary environment of the shales influences the toc contents thus has a close connection with the hydrocarbon potential mineralogical composition kerogen types and pore structure additionally in terms of the hydrocarbon generation potential the upper member shales are regarded as very good and excellent rocks whereas the lower member shales mainly as poor and fair rocks in overall the shales in the top of the upper member can be explored for shale oil due to the higher free hydrocarbon amount s1 whereas the shales in the lower member and the upper member with the depths greater than 1000 m can be suggested to explore shale gas

influence of the tropics and southern westerlies on glacial interhemispheric asymmetry latitudinal variations in the location of the southern westerly wind belt have been associated with millennial scale climate variations during the last glacial period a reconstruction of sea surface temperatures off the southern coast of australia suggests that these climate variations also drove changes in the location of the oceanic subtropical front

southwest pacific deep water carbonate chemistry linked to high southern latitude climate and atmospheric co2 during the last glacial termination abstract a greater amount of co2 was stored in the deep sea during glacial periods likely via greater efficiency of the biologic pump and increased uptake by a more alkaline ocean reconstructing past variations in seawater carbonate ion concentration a major component of alkalinity enables quantification of the relative roles of different oceanic co2 storage mechanisms and also places constraints on the timing magnitude and location of subsequent deep ocean ventilation here we present a record of deep water inorganic carbon chemistry since the last glacial maximum lgm 19 23 ka bp derived from sediment core rr0503 83 raised from 1627 m in new zealand s bay of plenty the core site lies within the upper limit of southern sourced circumpolar deep water cdw just below the lower boundary of antarctic intermediate water aaiw we reconstruct past changes in bottom water inorganic carbon chemistry from the trace element and stable isotopic composition of calcite shells of the epibenthic foraminifer cibicidoides wuellerstorfi a record of co 3 2 co 3 2 co 3 2 i n s i t u co 3 2 saturation derived from the foraminiferal boron to calcium ratio b ca provides evidence for greater ice age storage of respired co2 and reveals abrupt deglacial shifts in co 3 2 i n s i t u of up to 30 mol kg 5 times larger than the difference between average lgm and holocene values the rapidity of these changes suggests the influence of changing water mass structure and atmospheric circulation in addition to a decrease in co2 content of interior waters

climatic records over the past 30 ka from temperate australia a synthesis from the oz intimate workgroup temperate australia sits between the heat engine of the tropics and the cold southern ocean encompassing a range of rainfall regimes and falling under the influence of different climatic drivers despite this heterogeneity broad scale trends in climatic and environmental change are evident over the past 30 ka during the early glacial period 30 22 ka and the last glacial maximum 22 18 ka climate was relatively cool across the entire temperate zone and there was an expansion of grasslands and increased fluvial activity in regionally important murray darling basin the temperate region at this time appears to be dominated by expanded sea ice in the southern ocean forcing a northerly shift in the position of the oceanic fronts and a concomitant influx of cold water along the southeast including tasmania and southwest australian coasts the deglacial period 18 12 ka was characterised by glacial recession and eventual disappearance resulting from an increase in temperature deduced from terrestrial records while there is some evidence for climatic reversals e g the antarctic cold reversal in high resolution marine sediment cores through this period the high spatial density of holocene terrestrial records reveals an overall expansion of sclerophyll woodland and rainforest taxa across the temperate region after 12 ka presumably in response to increasing temperature while hydrological records reveal spatially heterogeneous hydro climatic trends patterns after 6 ka suggest higher frequency climatic variability that possibly reflects the onset of large scale climate variability caused by the el nino southern oscillation

millennial scale variability in south east australian hydroclimate between 30 000 and 10 000 years ago abstract global climate variability during the late quaternary is commonly investigated within the framework of the bipolar seesaw pattern of asynchronous temperature variations in the northern and southern polar latitudes the terrestrial hydrological response to this pattern in south eastern australia is not fully understood as continuous high resolution well dated proxy records for the hydrological cycle in the region are sparse here we present a well dated highly resolved record of moisture balance spanning 30000 10000 calendar years before present 30 10 ka bp based on x ray fluorescence and organic carbon isotope 13com measurements of a sedimentary sequence from lake surprise in south eastern australia the data provide a locally coherent record of the hydrological cycle elevated si reflecting windblown quartz and clays and relatively high 13com indicate an extended period of relative aridity between 28 and 18 5 ka bp interrupted by millennial scale episodes of decreased si and 13com suggesting increased moisture balance this was followed by a rapid deglacial shift to low si and 13com at 18 5 ka bp indicative of wetter conditions we find that these changes are coeval with other records from south eastern australia and new zealand and use a monte carlo empirical orthogonal function approach to extract a common trend from three high resolution records our analyses suggest that drivers of the regional hydrological cycle have varied on multi millennial time scales in response to major shifts in global atmosphere ocean dynamics during the last glacial interglacial transition southern ocean processes were the dominant control on hydroclimate during glacial times via a strong influence of cold sea surface temperatures on moisture uptake and delivery onshore following the last deglaciation around 18 ka bp the southward migration of cold southern ocean fronts likely resulted in the establishment of conditions more like those of the present day millennial scale variability in records from the region is dominated by a persistent ca 2300 year periodicity consistent with other records across the southern hemisphere mid latitudes however this pervasive periodicity is not obviously linked to the bipolar seesaw and the mechanism remains equivocal

late quaternary productivity changes from offshore southeastern australia a biomarker approach reconstructions of primary productivity at low latitudes have been the focus of several studies to better understand how the export of nutrient rich intermediate southern ocean so waters influences productivity at these latitudes this was triggered by the general observation of minima in the planktonic foraminiferal delta c 13 values during deglaciations which was interpreted as an isotopic signal of intermediate so waters together with a concomitant increase in diatom productivity at some equatorial sites however the impact of these so waters on productivity at higher latitudes is not well constrained here we compare a high resolution planktonic foraminiferal delta c 13 record with total organic carbon and biomarker records for proboscia diatoms and haptophytes in marine sediments from offshore southeastern australia the planktonic foraminiferal delta c 13 record shows distinct minima during deglaciations and the marine isotope stage 4 3 transition tentatively suggesting that c 13 depleted so waters reached the coast of southeastern australia however it did not result in increased productivity during these periods instead the highest primary productivity period as indicated by total organic carbon and alkenone accumulation rates occurred during the last glacial maximum while proboscia diatoms mainly proliferated during interglacials and marine isotope stage 3 matching periods of increased diatom productivity in some sites of the eastern equatorial pacific our study suggests that increased primary productivity offshore southeastern australia was mainly due to stronger westerly winds during glacial periods while proboscia diatom productivity was probably controlled by the transport of silicic acid to this area

instruments for particle size and settling velocity observations in sediment transport in this paper we describe two sensors for measurement of particle size distribution and settling velocity distribution these measurements are critical to the correct estimation of the true sediment concentration in the field as well as to evaluating models for transport rates of sediments a multi angle measurement of laser scattering is made and inverted to obtain the particle size distribution since small angle scattering is relatively insensitive to particle composition the size distribution measurements are robust and do not require particle refractive index it is shown that with a knowledge of the size distribution true particulate volume concentration can be obtained unaffected in calibration by changes in particle size distribution the data from bottom boundary layer experiments using the instrument show the presence of temporal variability in size distribution associated with the strength of forcing of the boundary layer the importance of these observations lies in the implication that historical data acquired with single parameter optical or other sensors needs to be revisited in the second instrument analyzing the observation of size distributions during settling in a settling column produces settling velocity estimates in this case the history of concentration of each size class is examined to determine the settling velocity without invoking any assumptions of settling regime settling velocity data from a field experiment off the new jersey coast fit the model wf na 0 45 10 23 a 1 2 n

from source to sink a new perspective on the past dynamics of the murray canyon group from benthic foraminiferal communities abstract we present fossil benthic foraminiferal assemblage data from marine sediment core ss02 06 gc2 located in the abyssal plain of the murray canyon group offshore south australia the sedimentological characteristics indicate the presence of turbidite deposits showing classical bouma like sequences dated between 40 and 12 cal ka bp these results confirm the previous interpretation of the observed large deep water holes in the abyssal area where the core was sampled as being gouged by surges of high energy turbidity currents the presence of good indicator taxa and unique assemblages occupying specific bathymetric depths allows the determination of the source origin of the sediments making the turbidites three distinct faunal groups are found 1 mostly shelf species 2 mostly bathyal species and 3 mostly abyssal species in the sediment core these groups present a quasi systematic succession with nearly all bouma like sequences starting with the dominance of bathyal species in the coarse grained base followed by the dominance of shallow species in the silty part and finally with abyssal species in the clays to explain such phenomena turbidites triggered by mixed hyperpycnal hypopycnal flow processes and turbidity currents during periods of river floods are considered for the first time within the murray canyon group they are mostly related to periods of increased fluvial discharges during wet phases in the murray darling basin

southern ocean seasonal temperature and subtropical front movement on the south tasman rise in the late quaternary 1 the subtropical front stf marking the northern boundary of the southern ocean has a steep gradient in sea surface temperature sst of approximately 4c over 0 5 of latitude presently in the region south of tasmania the stf lies nominally at 47s in the summer and 45s in the winter we present here sst reconstructions in a latitudinal transect of cores across the south tasman rise southeast of australia during the late quaternary sst reconstructions are based on two paleotemperature proxies alkenones and faunal assemblages which are used to assess past changes in sst in spring and summer the north south alignment in core locations allows reconstruction of movement of the stf over the last 100 ka surface water temperatures during the last glaciation in this region were 4c colder than today additional temperature changes greater in magnitude than 4c seen in individual cores can be attributed to changes in the water mass overlying the core site caused by the movement of the front across that location during the penultimate interglacial sst was 2c warmer and the stf was largely positioned south of 47s movement of the stf to the north occurred during cool climate periods such as the last marine isotope stages 3 and 4 in the last glaciation the front was at its farthest north position becoming pinned against the tasmanian landmass it moved south by 4 latitude to 47s in summer during the deglaciation but remained north of 45s in spring throughout the early deglaciation after 11 ka b p inferred invigoration of the east australia current appears to have pushed the stf seasonally south of the east tasman plateau until after 6 ka b p when it achieved its present configuration

the last termination in the central south atlantic lake sediments and peat deposits from two basins on nightingale island 37 degrees s in the tristan da cunha archipelago south atlantic have been analyzed the studies were focused on the time period 16 2 10 0 cal ka bp determined by 36 c 14 dates from the two sequences a wide variety of proxies were used including pollen and diatom analyzes biogenic silica content c and n analyzes stable isotopes c 13 and n 15 elemental concentrations and magnetic susceptibility measurements to detect environmental changes that can be related to shifts of the circulation belts of the southern ocean in addition climate model simulations were carried out we find that the sediments are underlain by a 2 cal ka bp long hiatus possibly representing a dried out lake bed the climate simulations corroborate that the area might have been exposed to arid conditions as a consequence of the heinrich i event in the north and a southward displacement of the itcz the development on the island after 16 2 cal ka bp is determined by the position of the subtropical front stf and the southern hemisphere westerlies shw the period 16 2 14 75 cal ka bp was characterized by varying influence from shw and with stf situated south of tristan da cunha ending with a humidity peak and cooler conditions the stable conditions 14 7 14 1 cal ka bp with cool and fairly arid conditions imply that stf and shw were both north of the islands during the first part of the antarctic cold reversal the most unstable period 14 1 12 7 cal ka bp indicates incessant latitudinal shifts of the zonal circulation perhaps related to climate variability in the northern hemisphere and bipolar seesaw mechanisms as the strength of the atlantic meridional overturning circulation amoc varied at 12 7 cal ka bp the holocene warming began with a gradually drier and warmer climate as a result of a dampened amoc during the younger dryas cooling in the north with itcz stf and shw being displaced southwards peak warming seems to have occurred in the earliest part of the holocene but this period was also characterized by humidity shifts possibly an effect of retraction and expansion phases of shw during amoc variations in the north c 2015 elsevier ltd all rights reserved less

eight glacial cycles from an antarctic ice core the antarctic vostok ice core provided compelling evidence of the nature of climate and of climate feedbacks over the past 420 000 years marine records suggest that the amplitude of climate variability was smaller before that time but such records are often poorly resolved moreover it is not possible to infer the abundance of greenhouse gases in the atmosphere from marine records here we report the recovery of a deep ice core from dome c antarctica that provides a climate record for the past 740 000 years for the four most recent glacial cycles the data agree well with the record from vostok the earlier period between 740 000 and 430 000 years ago was characterized by less pronounced warmth in interglacial periods in antarctica but a higher proportion of each cycle was spent in the warm mode the transition from glacial to interglacial conditions about 430 000 years ago termination v resembles the transition into the present interglacial period in terms of the magnitude of change in temperatures and greenhouse gases but there are significant differences in the patterns of change the interglacial stage following termination v was exceptionally long 28 000 years compared to for example the 12 000 years recorded so far in the present interglacial period given the similarities between this earlier warm period and today our results may imply that without human intervention a climate similar to the present one would extend well into the future

a review of the australian new zealand sector of the southern ocean over the last 30ka aus intimate project the australia new zealand region of the southern ocean is influenced by several of the major global water masses of the oceans and is the prime entry point for cold deep waters into the pacific basin during the last glacial there was increased sea ice extent around antarctica as far north as 55 s as well as increased iceberg presence inferred from ice rafted debris evidence from microfossil assemblages suggests that sea surface temperatures sst were up to 7 c cooler consistent with recent estimates of cooling for new zealand derived from glacier modelling and other terrestrial proxies the subtropical front stf subantarctic front saf and polar front pf had migrated north except where the position of the fronts were controlled bathymetrically despite the potential for iron fertilisation by increased dust input into the ocean during the glacial there is limited evidence for higher total biological productivity in the pacific sector of the southern ocean the altered oceanic circulation during the glacial also decreased nutrients in the surface waters and affected the outgassing of co 2 this contributed to an increased storage of co 2 in the deep waters and lowering of the carbonate lysocline during the deglaciation sea ice retreat and sst increased rapidly at 18 ka roughly synchronous with the reinvigoration of deep water circulation in the southern ocean and the release of co 2 stored in the deep waters the gradient in carbon isotopes 13 o benthic between antarctic intermediate water aaiw and lower circumpolar deep water lcdw was greatest at the start of the deglaciation suggesting that the aaiw ventilation preceded lcdw ventilation or there was a significant change in air sea fractionation of 13 o benthic there was a slight enrichment in 18 o planktic decrease in ssts and a reduction in intermediate and deep water circulation between 14 and 12 5 ka bp during the antarctic cold reversal acr coincident with glacier advances in the new zealand southern alps and other terrestrial records of cooling following the acr there was a second more minor release of deep water co 2 most likely related to reinvigoration of north atlantic deep water nadw from 10 ka onwards the modern intermediate and deep water circulation was established air temperatures and ssts reached a maximum in the early holocene with the stf located at its most southerly position and there was a widespread retreat of antarctic ice sheets to their modern position a decline to modern sst and air temperatures in the mid to late holocene followed while millennial cycles overprinted on the sst and 18 o planktic records may be the result of subtle changes in the position and strength of the westerly winds during the holocene

the role of biophysical cohesion on subaqueous bed form size biologically active fine grained sediment forms abundant sedimentary deposits on earth s surface and mixed mud sand dominates many coasts deltas and estuaries our predictions of sediment transport and bed roughness in these environments presently rely on empirically based bed form predictors that are based exclusively on biologically inactive cohesionless silt sand and gravel this approach underpins many paleoenvironmental reconstructions of sedimentary successions which rely on analysis of cross stratification and bounding surfaces produced by migrating bed forms here we present controlled laboratory experiments that identify and quantify the influence of physical and biological cohesion on equilibrium bed form morphology the results show the profound influence of biological cohesion on bed form size and identify how cohesive bonding mechanisms in different sediment mixtures govern the relationships the findings highlight that existing bed form predictors require reformulation for combined biophysical cohesive effects in order to improve morphodynamic model predictions and to enhance the interpretations of these environments in the geological record

in situ estimations of the density and porosity of flocs of varying sizes in a submarine canyon abstract this paper introduces a new method to estimate in situ floc density and porosity of three particle size classes 0 45 10 10 63 and 63 250 m lisst 100 and catnet a novel on board filtration system of nested filters were used to measure suspended particle volume and mass concentrations of 32 and 3 size classes respectively two field experiments were conducted in 2004 and 2006 in the head region of gaoping submarine canyon gpsc to test this method in each experiment ctd and lisst 100 profiling and simultaneous water sampling were carried out on board r v ocean research iii in 2004 the water samples were filtered in the laboratory after the cruise using traditional methods catnet was used in 2006 and the seawater filtration was done on board assuming the observed suspended particles were all flocs composed of primary particles with assumed density of 2 65 g cm 3 and interstitial water with assumed density of 1 025 g cm 3 we estimated the volume of primary particles the volume difference between flocs measured from lisst 100 and primary particles is the interstitial pore space in flocs subsequently the porosity of a floc particle is the ratio of the volume of the interstitial pore space to that of the floc particle results for 2004 show erroneous values of estimated floc porosities which do not appear in 2006 the major difference is that the seawater was filtered immediately on board using catnet in 2006 after removing erroneous data related to after cruise filtering the averaged floc porosity and density in the three grain size classes were 47 0 64 0 85 9 and 1 89 1 61 1 25 g cm 3 respectively there is a trend that larger particles have lower density which is supported by literature the temporal variations of floc density and porosity of all three particle size groups were larger in the surface than near the bottom of the submarine canyon this vertical variability resulted from flocculation and biogenic processes in the surface of the coastal ocean and the terrestrial source of the gaoping river floc density is an important physical parameter to evaluate the settling flux of suspended sediments in estuarine and marine environments this approach provides direct in situ floc bulk densities of different grain size classes which has advantages over conventional methods

microfracturing and microporosity in shales shales are ubiquitous rocks in sedimentary basins where their low permeability makes them efficient seals for conventional oil and gas reservoirs and underground waste storage repositories waste waters co2 nuclear fuels moreover when they contain organic matter they form source rocks for hydrocarbons that may escape towards a more porous reservoir during burial a process referred to as primary migration and when the hydrocarbons cannot escape these rocks can be exploited as oil or shale gas reservoirs while the presence of fractures at the outcrop scale has been described the existence of fractures at smaller scales their link with microporosity the mechanisms that created them their persistence over geological times and their effect on the petrophysical properties of shales represent scientific challenges for which drillings in various sedimentary basins over the past decades may hold timely key data here we review and synthetize the current knowledge on how microfractures and micropores in shales can be imaged and characterized and how they control their anisotropic mechanical properties and permeability one question is whether such microfractures when observed in outcrops or in drilled core samples extracted from boreholes are related to decompaction and do not exist at depth another question is whether veins observed in shales represent microfractures that were open long enough to have acted as flow paths across the formation the mechanisms of microfracture development are described some have an internal origin fracturing by maturation of organic matter dehydration of clays while others are caused by external factors tectonic loading importantly the amount of microfracturing in shales is shown to depend strongly on the content in 1 organic matter and 2 strong minerals the nucleation of microfractures depends on the existence of mechanical heterogeneities down to the nanometer scale their propagation and linkage to create a percolating network will depend on the presence of heterogeneities at the meso to macro scales such percolating microfracture networks could control both the long term sealing capabilities of cap rocks and the further propagation of hydraulic fracturing cracks finally possible areas of research for describing the mechanism of microfracture formation in greater detail and how this impacts the transport and mechanical properties of shales are also discussed

high latitude forcing of diatom productivity in the southern agulhas plateau during the past 350 kyr the hydrography of the indian atlantic ocean gateway has been connected to high latitude climate dynamics by oceanic and atmospheric teleconnections on orbital and suborbital timescales a wealth of sedimentary records aiming at reconstructing the late pleistocene paleoceanography around the southern african continent has been devoted to understanding these linkages most of the records are however clustered close to the southern south african tip with comparatively less attention devoted to areas under the direct influence of frontal zones of the southern ocean south atlantic here we present data of the composition and concentration of the diatom assemblage together with bulk biogenic content and the alkenone based sea surface temperature sst variations for the past 350 kyr in the marine sediment core md02 2588 approximately 41 s 26 e recovered from the southern agulhas plateau variations in biosiliceous productivity show a varying degree of coupling with southern hemisphere paleoclimate records following a glacial interglacial cyclicity ecologically well constrained groups of diatoms record the glacial interglacial changes in water masses dynamics nutrient availability and stratification of the upper ocean the good match between the glacial maxima of total diatoms concentration chaetoceros spores abundance and opal content with the maximum seasonal cover of antarctic ice and the atmospheric dust records points to a dominant southern hemisphere forcing of diatom production suborbital variability of sst suggests rapid latitudinal migrations of the subtropical front and associated water masses over the southern agulhas plateau following millennial contractions and expansions of the subtropical gyres warmings of the upper ocean over site md02 2588 during terminations iv to i occurred earlier than that in the antarctic vostok which is indicative of a northern hemisphere lead our multiparameter reconstruction highlights how high latitude atmospheric and hydrographic processes modulated orbital highs and lows in primary production and sst as triggered by northward transport of si eolian dust input and latitudinal migrations of frontal zones

a laboratory evaluation of the laser in situ scattering and transmissometery instrument using natural sediments abstract the lisst laser in situ scattering and transmissometery instrument was designed by sequoia scientific to measure the particle size distributions and concentrations of sediment suspensions in the field environment to understand the lisst s performance with natural sediments from a variety of marine sources several experiments were performed to compare the lisst s results to traditional sieving filtering and weighing techniques the lisst was able to correctly locate the peak of a unimodal particle size distribution and resolve the two peaks of a bimodal distribution if they are separated by at least 1 for sediment sizes of 5 to 250 m unlike a single frequency scattering sensor for sediment concentration which require sediment size specific calibration constants the lisst is able to accurately measure sediment concentration with a single calibration constant for varying size distributions within the size range of 5 to 250 m the lisst was also found to adequately represent the particle volumetric size distribution for two different samples from marine environments

sediment dynamics during wet and dry storm events on the tet inner shelf sw gulf of lions abstract the importance of short term processes such as floods and storms on sediment delivery and reworking on the tet inner shelf was investigated the tet inner shelf is a small event dominated system located in the south western part of the gulf of lions the expected sedimentary scenario in this environment is that fluvial sediment should be deposited on the prodelta and later dispersed around the shelf and slope by wave and current reworking during storms this paper investigates differences in inner shelf sediment dynamics between storm events occurring during usual river discharges and those occurring during river floods waves current velocities near bottom water turbidity bottom sediment grain size and sea floor erosion accretion were concurrently measured at 28 m water depth on the tet inner shelf from november 2003 to march 2004 two major storms took place on 4 december 2003 and 21 february 2004 and two moderate storms occurred on 8 december 2003 and 14 march 2004 the two major storms displayed similar wave characteristics maximum significant wave height h s 7 m peak period t p 12 s and wave direction around 90 the main environmental differences during the two major storm events correspond to the amount of sediment discharged from the tet river about 2 10 4 t of sediment was delivered by the river during the 4 december flood wet storm and less than 5 10 2 t during the 21 february storm dry storm sediment dynamics were quite similar during the storm events resuspension caused by waves and sediment advection towards the southeast due to near bottom shelf currents were the dominant sedimentary processes the result was a bottom sediment erosion of several centimetres at the study site during both the wet and dry events the main differences between the wet and dry events arose after the storm immediately after the peak of the wet storm sediment supplied by the tet river and probably from other rivers was deposited around the river mouth a few days later during a moderate storm this unconsolidated sediment was resuspended transported offshore and deposited on the inner shelf in contrast a moderate storm which occurred some days after the dry february storm caused bottom erosion on the inner shelf because no fresh sediment was available on the shallower area the results from this study indicate that the tet inner shelf at 28 m water depth is mainly a bypass zone for sediment that is transported s se towards the middle outer shelf and slope although ephemeral sediment deposits may be favoured by the sediment supplied from flood events sediment transport across the shelf from the river to the slope follows a complex multi step pattern that needs to be addressed using a multi event approach

suspended particulate matter dynamics and aggregate sizes in a high turbidity area measurements of aggregate size suspended particulate matter spm concentration and current velocity have been carried out in the belgian coastal zone southern north sea two stations were situated in the coastal turbidity maximum zone another station was located more offshore at the edge of this turbidity maximum the data have been collected using a lisst 100 obs sensors water samples and a bottom mounted adcp turbulence kolmogorov microscale has been modelled for the same period using a 3d numerical model the results show that the size of the aggregates is significantly smaller in the coastal turbidity maximum area the processes responsible for the occurrence of smaller aggregate size in the coastal zone compared with the more offshore location are the higher turbulence the smaller time available for the aggregates to grow up to an equilibrium size the higher deposition of mud resulting in a break up of the floes and the lower availability of organic matter which may limit the size of the floes c 2006 elsevier b v all rights reserved

sticky stuff redefining bedform prediction in modern and ancient environments the dimensions and dynamics of subaqueous bedforms are well known for cohesionless sediments however the effect of physical cohesion imparted by cohesive clay within mixed sand mud substrates has not been examined despite its recognized influence on sediment stability here we present a series of controlled laboratory experiments to establish the influence of substrate clay content on subaqueous bedform dynamics within mixtures of sand and clay exposed to unidirectional flow the results show that bedform dimensions and steepness decrease linearly with clay content and comparison with existing predictors of bedform dimensions established within cohesionless sediments reveals significant over prediction of bedform size for all but the lowermost clay contents examined the profound effect substrate clay content has on bedform dimensions has a number of important implications for interpretation in a range of modern and ancient environments including reduced roughness and bedform heights in estuarine systems and the often cited lack of large dune cross sets in turbidites the results therefore offer a step change in our understanding of bedform formation and dynamics in these and many other sedimentary environments

sea surface temperatures around the australian margin and indian ocean during the last glacial maximum abstract we present new last glacial maximum lgm sea surface temperature sst maps for the oceans around australia based on planktonic foraminifera assemblages to provide the most reliable sst estimates we use the modern analog technique the revised analog method and artificial neural networks in conjunction with an expanded modern core top database all three methods produce similar quality predictions and the root mean squared error of the consensus prediction the average of the three under cross validation is only 0 77 c we determine lgm sst using data from 165 cores most of which have good age control from oxygen isotope stratigraphy and radiocarbon dates the coldest sst occurred at 20 500 1400 cal yr bp predating the maximum in oxygen isotope records at 18 200 1500 cal yr bp during the lgm interval we observe cooling within the tropics of up to 4 c in the eastern indian ocean and mostly between 0 and 3 c elsewhere along the equator the high latitudes cooled by the greatest degree a maximum of 7 9 c in the southwest pacific ocean our maps improve substantially on previous attempts by making higher quality temperature estimates using more cores and improving age control

a review of the thermal maturity and hydrocarbon potential of the mancos and lewis shales in parts of new mexico usa abstract this study reviews specific public geochemical data mainly toc and rock eval pyrolysis parameters of the mancos shale and the lewis shale located in an area to the south of the san juan basin new mexico both shale formations are immature within the study area proper and surrounding acreage maturity increases in a southeastern direction within the study area and is the only location where the mancos shale has thermogenic gas generating potential the quality of the organic matter kerogen reported for the mancos and the lewis shales is mostly of type iii gas prone with type ii being less dominant the thicknesses of both the mancos and lewis shales are adequate to generate and store large volumes of natural gas in the thermally mature areas the study area is also faulted which may provide opportunities for natural fracturing to have formed furthermore silt and sand layers within the mancos shale could provide permeability pathways for the gas in a similar fashion to the lewis shale in the san juan basin the part of the study area that belongs to the albuquerque basin contains thick sections of the mancos shale but at great depths 13 000 ft or 4 km however it might be possible to find prospective areas near the margins of the basin particularly if there is an active hydrologic system that operates close to the shale that may be responsible for late stage biogenic gas generation

interhemispheric anti phasing of rainfall during the last glacial period abstract we have obtained a high resolution oxygen isotopic record of cave calcite from caverna botuvera 27 13 s 49 09 w southern brazil which covers most of the last 36 thousand years ka with an average resolution of a few to several decades the chronology was determined with 46 u th ages from two stalagmites tests for equilibrium conditions show that oxygen isotopic variations are primarily caused by climate change we interpret our record in terms of meteoric precipitation changes hence the variability of south american monsoon sam intensity the oxygen isotopic profile broadly follows local insolation changes and shows clear millennial scale variations during the last glacial period with amplitudes as large as 3 but with smaller centennial scale shifts 1 during the holocene the overall record is strikingly similar to but strongly anti correlated with a number of records from the northern hemisphere we compared our record to other precisely dated contemporaneous records from hulu cave eastern china minima in 18o wet periods intense sam at our site are synchronous with maxima in 18o dry periods weak east asian monsoon eam in eastern china within precise dating errors and vice versa this anti phased precipitation relationship between two low latitude locations may be interhemispheric in extent based on comparison with records from other sites precipitation anti phasing may be related to north south shifts in the mean position of the intertropical convergence zone itcz and asymmetry in hadley circulation in two hemispheres associated not with seasonal changes as observed today but with millennial scale climate shifts the millennial scale atmospheric see saw patterns that we observe could have important controls and feedbacks on climate within hemispheres because of water vapor s greenhouse properties

comparison of oxygen isotope records from the gisp2 and grip greenland ice cores recent results1 2 from the greenland ice core project grip summit ice core suggest that the climate in greenland has been remarkably stable during the holocene but was extremely unstable for the time period represented by the rest of the core spanning the last two glaciations and the intervening eemian inter glacial here we present the complete oxygen isotope record for the greenland ice sheet project 2 gisp2 core drilled 28 km west of the grip core we observe large rapid climate fluctuations throughout the last glacial period which closely match those reported for the grip core however in the bottom 10 of the cores spanning the eemian interglacial and the previous glacia tion there are significant differences between the two records it is possible that ice flow may have altered the chronological sequences of the stratigraphy for the bottom part of one or both of the cores considerable further work will be necessary to evaluate the likelihood of this and the extent to which it will still be possible to extract meaningful climate information from the lowest sections of the cores

climatic evolution in the australian region over the last 94 ka spanning human occupancy and unveiling the last glacial maximum abstract the quaternary is well known for being a period of the geological record that saw significant and alternating climatic fluctuations here we concentrate on the last 94 millennia that saw australia and its surrounding seas undergo significant environmental changes importantly also it is during that this period of time includes the arrival and settlement of humans in australia following on from marine isotopic stage 4 mis4 that saw over the period of 71 59 ka bp a significant eustatic sea level drop 100 m low sea surface temperatures as well as glacial conditions on land australia experienced wet conditions again but eventually progressively entered into a glacial phase by then humans had arrived on this large continent and later the megafauna progressively became extinct this paper describes in detail the climate over this period based principally on the high resolution record of two marine sediment cores located offshore of the southern australian margin and that are then compared with known events on land as well as other deep sea cores particular emphasis is placed on the period that spans the last glacial maximum lgm the extent of which thus far had been poorly defined in the australian region emphasis is placed on the period from 34 to 14 ka to demonstrate that 1 the lgm defined here as the period 24 to 18 ka was not always extremely dry and cold and 2 that people were able to live in inland australia as water existed in places despite generally cold conditions we also show using a series of ten maps at 2 ka intervals over the 34 14 ka period the waxing and waning of oceanic fronts such as the subtropical and subantarctic fronts link sea surface temperatures sst with periods of glacial expansion in the australian alps and tasmania as well as the south island of new zealand and the extent of the leeuwin current down to south of australia aeolian dust was transported at sea over the main core site from 26 to 18 ka period pointing to arid conditions in australia but this period was punctuated by two significant reductions in dust transport to both core sites coinciding with a retreat of the subantarctic front away from the australian southern coastline and slight sst shifts for a few centuries at 24 and 22 21 ka bp at the peak of the cold phase from 23 to 18 4 ka summer sst were of the order of 9 c below that experienced during the middle of the holocene at about 6 ka bp a similar temperature drop was also experienced offshore the northwestern corner of western australia periglacial activity dates for the australian mainland and tasmania pool around 22 ka on either side of the 24 ka event the chain of lakes in the willandra lakes retained water and human activity was registered in the area elsewhere in australia water was present to sustain human populations during the cold and dry times it is postulated here that northern australia was at times quite wet especially during mis4 the cessation of the lgm is set on 18 4 ka from offshore southern australia as confirmed for the deep sea cores by several proxies and more likely at 18 ka inland finally we document that it took two millennia for glacial conditions to end in the australian region as registered in our deep sea core records well after the lowest global sea level 20 6 and 20 ka respectively started to rise there is also evidence of another very cold period determined on the australian mainland tasmania and the south island of new zealand centred around 27 ka after which time warmer conditions occurred before the start of the lgm this is matched with our deep sea records with very cold conditions and changes in oceanographic conditions

interhemispheric atlantic seesaw response during the last deglaciation the asynchronous relationship between millennial scale temperature changes over greenland and antarctica during the last glacial period has led to the notion of a bipolar seesaw which acts to redistribute heat depending on the state of meridional overturning circulation within the atlantic ocean here we present new records from the south atlantic that show rapid changes during the last deglaciation that were instantaneous within dating uncertainty and of opposite sign to those observed in the north atlantic our results demonstrate a direct link between the abrupt changes associated with variations in the atlantic meridional overturning circulation and the more gradual adjustments characteristic of the southern ocean these results emphasize the importance of the southern ocean for the development and transmission of millennial scale climate variability and highlight its role in deglacial climate change and the associated rise in atmospheric carbon dioxide

geomorphic tectonic control of sediment discharge to the ocean the importance of small mountainous rivers analysis of data from 280 rivers discharging to the ocean indicates that sediment loads yields are a log linear function of basin area and maximum elevation of the river basin other factors controlling sediment discharge e g climate runoff appear to have secondary importance a notable exception is the influence of human activity climate and geology on the rivers draining southern asia and oceania sediment fluxes from small mountainous rivers many of which discharge directly onto active margins e g western south and north america and most high standing oceanic islands have been greatly underestimated in previous global sediment budgets perhaps by as much as a factor of three in contrast sediment fluxes to the ocean from large rivers nearly all of which discharge onto passive margins or marginal seas have been overestimated as some of the sediment load is subaerially sequestered in subsiding deltas before the proliferation of dam construction in the latter half of this century rivers

millennial scale ice rafting events and hudson strait heinrich like events during the late pliocene and pleistocene a review abstract various types of abrupt millennial scale climate variability such as dansgaard oeschger and heinrich events characterized the last glacial period over the last decade a number of studies demonstrated that such millennial scale climate variability was not limited to the last glacial but inherent to quaternary climate here we review the occurrence and origin of millennial ice rafting events in the north atlantic during the late pliocene and pleistocene last 3 4 ma with a special focus on north atlantic hudson strait hs heinrich like events we show that heinrich layers 5 4 2 and 1 in marine sediment cores from across the north atlantic all bear the organic geochemical fingerprint of the hudson area using this framework and combining previously published results detailed investigations into the organic and inorganic chemistry of ice rafted debris ird found across the north atlantic demonstrate that prior to mis 16 650 ka ird in the north atlantic did not originate from the hudson area of northern canada the signature of this early ird is distinctly different compared to that of hs heinrich layers rather ice rafting events during the late pliocene and early pleistocene predominantly emanated from the calving of the greenland and fennoscandian ice sheets and possibly minor contributions from local ice streams from the north american and british ice sheets compared to north atlantic hs heinrich events these early pleistocene ird events had a limited impact on surface water characteristics in the north atlantic north atlantic hs heinrich like events first occurred during mis 16 at the same time the dominant frequency in silicate rich ird accumulation shifted from the obliquity 41 ka to a 100 ka frequency across the north atlantic iceberg survivability or a change in iceberg trajectory likely did not control this change in ird regime these results lend further support for the existing hypothesis that an increase in size thickness of the laurentide ice sheet controls the occurrence of north atlantic hs heinrich events favoring an internal dynamic mechanism for their occurrence

a 550 ka record of aeolian activity near north west cape australia inferences from grain size distributions and bulk chemistry of se indian ocean deep sea sediments abstract the terrigenous fraction of sediments from a deep sea sediment core recovered from the northwestern western australian continental slope offshore north west cape se indian ocean reveals a history of western australian climate throughout the last 550 ka end member modelling of a data set of grain size distributions n 438 of the terrigenous sediment fraction allows to interpret the record in terms of aeolian and fluvial sediment deposition both related to palaeo environmental conditions in the north west cape area the data set can be best described by two aeolian end members and one fluvial one changes in the ratio of the two aeolian end members over the fluvial one are interpreted as aridity variations in northwestern western australia these grain size data are compared with bulk geochemical data obtained by xrf scans of the core log ratios of the elements zr fe and ti ca which indicate a terrigenous origin corroborate the grain size data we postulate that the mid to late quaternary near north west cape climate was relatively arid during the glacial and relatively humid during the interglacial stages owing to meridional shifts in the atmospheric circulation system opposite to published palaeo environmental records from the same latitude 20 s offshore chile and offshore namibia the australian aridity record does not show the typical southern hemisphere climate variability of humid glacials and dry interglacials which we interpret to be the result of the relatively large land mass of the australian continent which emphasises a strong monsoonal climatic system

a cosmogenic 10be chronology for the local last glacial maximum and termination in the cordillera oriental southern peruvian andes implications for the tropical role in global climate abstract resolving patterns of tropical climate variability during and since the last glacial maximum lgm is fundamental to assessing the role of the tropics in global change both on ice age and sub millennial timescales here we present a10be moraine chronology from the cordillera carabaya 14 3 s a sub range of the cordillera oriental in southern peru covering the lgm and the first half of the last glacial termination additionally we recalculate existing 10be ages using a new tropical high altitude production rate in order to put our record into broader spatial context our results indicate that glaciers deposited a series of moraines during marine isotope stage 2 broadly synchronous with global glacier maxima but that maximum glacier extent may have occurred prior to stage 2 thereafter atmospheric warming drove widespread deglaciation of the cordillera carabaya a subsequent glacier resurgence culminated at 16 100 yrs followed by a second period of glacier recession together the observed deglaciation corresponds to heinrich stadial 1 hs1 18 000 14 600 yrs during which pluvial lakes on the adjacent peruvian bolivian altiplano rose to their highest levels of the late pleistocene as a consequence of southward displacement of the inter tropical convergence zone and intensification of the south american summer monsoon deglaciation in the cordillera carabaya also coincided with the retreat of higher latitude mountain glaciers in the southern hemisphere our findings suggest that hs1 was characterised by atmospheric warming and indicate that deglaciation of the southern peruvian andes was driven by rising temperatures despite increased precipitation recalculated 10be data from other tropical andean sites support this model finally we suggest that the broadly uniform response during the lgm and termination of the glaciers examined here involved equatorial pacific sea surface temperature anomalies and propose a framework for testing the viability of this conceptual model

summer temperature fluctuations in southwestern china during the end of the lgm and the last deglaciation abstract we present a sub centennial resolution summer temperature record from the se tibetan plateau tiancai lake sw china 3900 m a s l derived from a chironomid stratigraphy covering the last c 19 5 ka the record highlights the interaction between tropical and high latitude climate forcing through the changes in atmospheric circulation during the last deglaciation the scale of the last glacial maximum lgm cooling is consistent with other tropical mountain regions at c 5 c and a rapid recovery of temperatures at 19 0 ka is related to changes in adiabatic lapse rates at the end of the glaciation the overall pattern of change shows that north atlantic deglaciation climate events the heinrich 1 and younger dryas cooling events and the bolling allerod warm period are all recorded but the influence of the events decline as the deglaciation progresses we relate these patterns to north atlantic deep water ventilating the southern ocean and to the consequent movements of the intertropical convergence zone itcz in the indian ocean basin as transmitted through changes in the southern mid latitude circulation

antarctic deglacial pattern in a 30 kyr record of sea surface temperature offshore south australia 1 comparison of ice cores from greenland and antarctica shows an asynchronous two step warming at these high latitudes during the last termination however the question whether this asynchrony extends to lower latitudes is unclear mainly due to the scarcity of paleorecords from the southern hemisphere new data from a marine core collected off south australia 36s allows a detailed reconstruction of sea surface temperatures over the last termination this confirms the existence of an antarctic type deglacial pattern and shows no indication of cooling associated with the northern hemisphere yd event the sst record also provides a new comparison with the more extensive paleoclimatic data available from continental australia this shows a strong climatic link between onshore and offshore records for australia and to southern hemisphere paleorecords we also show a progressive sst drop over the last 6 5 kyr not seen before for the australian region citation calvo e c pelejero p de deckker and g a logan 2007 antarctic deglacial pattern in a 30 kyr record of sea surface temperature offshore south australia geophys res lett 34 l13707 doi 10 1029 2007gl029937

asynchronous marine terrestrial signals of the last deglacial warming in east asia associated with low and high latitude climate changes a high resolution multiproxy record including pollen foraminifera and alkenone paleothermometry obtained from a single core dg9603 from the okinawa trough east china sea ecs provided unambiguous evidence for asynchronous climate change between the land and ocean over the past 40 ka on land the deglacial stage was characterized by rapid warming as reflected by paleovegetation and it began ca 15 kabp consistent with the timing of the last deglacial warming in greenland however sea surface temperature estimates from foraminifera and alkenone paleothermometry increased around 20 19 kabp as in the western pacific warm pool wpwp sea surface temperatures in the okinawa trough were influenced mainly by heat transport from the tropical western pacific ocean by the kuroshio current but the epicontinental vegetation of the ecs was influenced by atmospheric circulation linked to the northern high latitude climate asynchronous terrestrial and marine signals of the last deglacial warming in east asia were thus clearly related to ocean currents and atmospheric circulation we argue that i early warming seawater of the wpwp driven by low latitude insolation and trade winds moved northward via the kuroshio current and triggered marine warming along the ecs around 20 19 kabp similar to that in the wpwp and ii an almost complete shutdown of the atlantic meridional overturning circulation ca 18 15 kabp was associated with cold heinrich stadial 1 and delayed terrestrial warming during the last deglacial warming until ca 15 kabp at northern high latitudes and hence in east asia terrestrial deglacial warming therefore lagged behind marine changes by ca 3 4 ka

settling velocity and mass settling flux of flocculated estuarine sediments new formulations are presented for the settling velocity and mass settling flux the product of settling velocity and sediment concentration of flocculated estuarine mud physics based formulae for these are developed based on assumptions of a two class floc population microflocs and macroflocs in quasi equilibrium with the flow the settling velocities of microflocs and macroflocs are related to floc size and density via the kolmogorov microscale as a function of turbulent shear stress and sediment concentration including height dependence and floc density dependence coefficients in the formulae are calibrated against an existing large data set of in situ observations of floc size and settling velocity from northern european estuaries various measures of performance show that the resulting formulae achieve an improved level of agreement with data compared with other published prediction methods the new formulae with the original calibration coefficients perform well in tests against independent measurements made in two estuaries

the last glacial termination a major puzzle of paleoclimatology is why after a long interval of cooling climate each late quaternary ice age ended with a relatively short warming leg called a termination we here offer a comprehensive hypothesis of how earth emerged from the last global ice age a prerequisite was the growth of very large northern hemisphere ice sheets whose subsequent collapse created stadial conditions that disrupted global patterns of ocean and atmospheric circulation the southern hemisphere westerlies shifted poleward during each northern stadial producing pulses of ocean upwelling and warming that together accounted for much of the termination in the southern ocean and antarctica rising atmospheric co2 during southern upwelling pulses augmented warming during the last termination in both polar hemispheres

paleocean circulation during the last deglaciation a bipolar seesaw hughen et al 1998 have documented that during the first 200 years of younger dryas time the 14c content of atmospheric co2 increased by 50 and that during the remainder of this 1200 year duration cold event it steadily declined the initial increase in 14c c was likely the result of a reduction in the atlantic s conveyor circulation however were the subsequent radiocarbon decline due to the rejuvenation of this potent heat pump then it is difficult to understand why the climate conditions in the northern atlantic basin remained cold throughout the younger dryas modeling exercises by stocker and wright 1996 mikolajewicz 1998 and schiller et al 1998 show that if the conveyor is terminated the transfer of radiocarbon into the deep sea shifts to the southern ocean thereby stabilizing the atmospheric 14c c ratio paleoclimatic evidence from the antarctic continent suggests that this model based scenario might have been played out in the real world while the younger dryas cooling has been documented in many places around the world including new zealand denton and hendy 1994 sowers and bender 1995 using their 18o in o2 based correlation between the ice core 18o in ice records for antarctica and greenland have demonstrated that in antarctica the younger dryas was a time of maximum warming the point of this paper is that the steep rise in 18o rise in antarctic ice which commenced close to the onset of the younger dryas might have been caused by heat released to the atmosphere in response to an increase in deep sea ventilation in the southern ocean

the influence of a salt wedge intrusion on fluvial suspended sediment and the implications for sediment transport to the adjacent coastal ocean a study of the lower brazos river tx usa abstract the brazos river is second only to the mississippi river in terms of sediment load discharged to the gulf of mexico gom this study focused on the interaction between a salt wedge and suspended sediment in the lower brazos river and the implications for sediment export to the coastal ocean salinity and turbidity optical backscatter sensor data with depth swath bathymetry and chirp sub bottom profiling data were collected from 2007 to 2012 over various river discharge stages sampling locations included the lower most 15 km river reach and the coastal ocean proximal to the mouth results indicated that during low to moderate river discharges a salt wedge was present in the lower river but absent during elevated fluvial discharge quantitative analysis showed the salt wedge within the river modulated sediment export to the gom by trapping sediment along the lower most 9 km reach within this reach the trapped sediment formed a decimeter thick mud layer observed in the chirp and bathymetric data at elevated fluvial discharges the salt wedge was no longer observed in the river and the lower river reach transitioned from depositional to erosional based on the observations and analysis from this study a fluvial discharge threshold where the salt wedge is not present in the river and sediment export to the coastal ocean was maximized was estimated this threshold has been met or exceeded only 10 of time since the 1960s these conditions imply that sediment transport to the coastal ocean is highly variable and occurs during irregular pulsed events this study highlights how estuarine conditions at the river mouth can impact terrestrial material flux to the coastal ocean

in situ particle size spectra and density of particle aggregates in a dredging plume abstract an in situ laser particle sizer the lisst 100 was used to describe the spatial variation of beam attenuation coefficient in situ particle size spectra and aggregate densities in a dredging plume in the sound oresund between denmark and sweden the results proved that the above mentioned parameters varied significantly within the investigated length of the plume approximately 2 km it is shown how the small single primary particles aggregate and change the in situ particle size spectra into a slightly better sorted and coarser size distribution and at the same time how the mean density of particles aggregates decreases significantly this shift in the state in which the particles exist in the water effectively changes the optical response of the mass of particles suspended in the water it is shown that adequate correlations between mass concentrations and beam attenuation coefficients can only be obtained if parameters describing the in situ quality and state of the mass of particles e g standard deviation of the size spectra and volume concentration is included in the regression from the spatial variation in mean density and in situ particle size it was possible to calculate the spatial difference in settling velocity it was found that the difference in settling velocity was only about a factor of 1 7 because increasing in situ particle size was counter balanced by decreasing mean density furthermore the time scale of flocculation within the plume was found to be in the order of 50 min

the petroleum generation potential and effective oil window of humic coals related to coal composition and age abstract a worldwide data set of more than 500 humic coals from the major coal forming geological periods has been used to analyse the evolution in the remaining hydrogen index hi and total quality index qi generation potentials with increasing thermal maturity and the effective oil window oil expulsion window all samples describe hi and qi bands that are broad at low maturities and that gradually narrow with increasing maturity the oil generation potential is completely exhausted at a vitrinite reflectance of 2 0 2 2 ro or tmax of 500 510 c the initial large variation in the generation potential is related to the original depositional conditions particularly the degree of marine influence and the formation of hydrogen enriched vitrinite as suggested by increased sulphur and hydrogen contents during initial thermal maturation the hi increases to a maximum value himax similarly qi increases to a maximum value qimax this increase in hi and qi is related to the formation of an additional generation potential in the coal structure the decline in qi with further maturation is indicating onset of initial oil expulsion which precedes efficient expulsion liquid petroleum generation from humic coals is thus a complex three phase process i onset of petroleum generation ii petroleum build up in the coal and iii initial oil expulsion followed by efficient oil expulsion corresponding to the effective oil window efficient oil expulsion is indicated by a decline in the bitumen index bi when plotted against vitrinite reflectance or tmax this means that in humic coals the vitrinite reflectance or tmax values at which onset of petroleum generation occurs cannot be used to establish the start of the effective oil window the start of the effective oil window occurs within the vitrinite reflectance range 0 85 1 05 ro or tmax range 440 455 c and the oil window extends to 1 5 2 0 ro or 470 510 c for general use an effective oil window is proposed to occur from 0 85 to 1 7 ro or from 440 to 490 c specific ranges for himax and the effective oil window can be defined for cenozoic jurassic permian and carboniferous coals cenozoic coals reach the highest himax values 220 370 mg hc g toc and for the most oil prone cenozoic coals the effective oil window may possibly range from 0 65 to 2 0 ro or 430 to 510 c in contrast the most oil prone jurassic permian and carboniferous coals reach the expulsion threshold at a vitrinite reflectance of 0 85 0 9 ro or tmax of 440 445 c

a late quaternary sedimentary record of steryl alkyl ethers from offshore southeastern australia steryl alkyl ethers saes have been reported from marine sediments ranging from holocene to lower cretaceous and their production has been linked to upwelling of cold nutrient rich water however the lack of continuous stratigraphic records for them has complicated validation of the precise connection of their production sedimentary distribution and survival to climatic conditions here we report an sae record that spans the last ca 135 ka from a core taken offshore southeastern australia in the murray canyons group region the saes are composed predominantly of c 27 c 30 steroid moieties with one or two double bonds ether bound to c 10 c 11 alkyl moieties some of the saes are identical to those reported in marine sediments whereas others have not been identified previously they do not exhibit any systematic change in distribution over the past 110 ka but sediments older than 110 ka possess a different assemblage with a higher amount of constituents containing a c 11 alkyl moiety the sae accumulation rate increases rapidly during glacial episodes and for intervals characterized by a sharp decline in sea surface temperature the results suggest that saes may be related to marine eukaryotes that thrive when there is an influx of cold deep waters in the murray canyons group region likely triggered by stronger westerlies over southeastern australia forcing deeper water to reach the surface during glacials

bipolar seesaw in the northeastern tropical atlantic during heinrich stadials two sst records based on mg ca of g ruber pink from the continental slope off west africa at 15 n and 12 n shed new light on the thermal bipolar seesaw pattern in the northeastern tropical atlantic during periods of reduced atlantic meridional overturning circulation amoc associated with heinrich stadials h1 to h6 the two records indicate that the latitudinal position of the bipolar seesaw s zero anomaly line between cooling in the north and warming in the south gradually shifted southward from h6 to h1 a conceptual model is presented that aims to provide a physically consistent mechanism for the southward migration of the seesaw s fulcrum the conceptual model suggests latitudinal movements of the intertropical convergence zone driven by a combination of orbital forced changes in the meridional temperature gradient within the realm of the hadley cell and the expansion of the northern hemisphere cryosphere as a major factor

low latitude hydrological cycle and rapid climate changes during the last deglaciation sea surface temperature and oxygen isotopic records from two well dated indian ocean cores covering the last deglaciation show the occurrence of two periods of increased salinity along the route of warm surface water transport from the indian to the atlantic ocean one between 18 and 14 5 ka and the other during the younger dryas our results imply that during these periods salt accumulated in the tropical atlantic creating favorable conditions for an abrupt resumption of the thermohaline circulation and abrupt northern hemisphere warming furthermore we suggest that the observed pattern of millennial climate variability during the last glacial and deglaciation resulted from the interaction between the relatively slow rhythm of expansion and decay of the northern hemisphere ice sheets and el nino southern oscillation variability through changes in the position of the intertropical convergence zone this interaction generated an oscillator with millennial time response that operated at times of sufficient northern hemisphere ice sheets extent

the dynamical subtropical front 1 the southern ocean subtropical front stf is thought to play a key role in the global climate system theory suggests that the latitude of the stf regulates the volume of saline agulhas leakage into the atlantic ocean from the indian here we use satellite sea surface temperature sst and sea surface height ssh data to study the physical characteristics of the stf water mass boundary we find that the strong currents in this region do not align with the surface water mass boundary therefore we provide a new climatology for these currents which we define as the dynamical stf dstf the dstf is the eastward extension of the western boundary current in each basin and is characterized by strong sst and ssh gradients and no seasonal cycle at the center of each basin it merges with the sub antarctic front on the eastern side of basins the stf surface water mass boundary coincides with a separate region of multiple sst fronts we call this the subtropical frontal zone stfz the fronts in the stfz have a large seasonal cycle and no ssh signature despite lying close to the same water mass boundary the dstf and stfz are completely unrelated we therefore suggest the term stf only be used when referring to the surface water mass boundary when studying the strong currents on the western side of basins the term dstf is more relevant and similarly the term stfz better describes the region of enhanced sst gradients towards the east

sediment resuspension flocculation and settling in a macrotidal estuary national natural science foundation of china 40876043 papd fund china scholarship council 2010832427 mel young scientist visiting fellowship melrs0938

palaeoenvironmental change in tropical australasia over the last 30 000 years a synthesis by the oz intimate group the tropics are the major source of heat and moisture for the australasian region determining the tropics response over time to changes in climate forcing mechanisms such as summer insolation and the effects of relative sea level on exposed continental shelves during the last glacial period is an ongoing process of re evaluation we present a synthesis of climate proxy data from tropical australasia spanning the last 30 000 years that incorporates deep sea core coral speleothem pollen charcoal and terrestrial sedimentary records today seasonal variability is governed largely by the annual migration of the inter tropical convergence zone itcz influencing this region most strongly during the austral summer however the position of the itcz has varied through time towards the end of marine isotope stage mis 3 conditions were far wetter throughout the region becoming drier first in the south universally cooler land and sea surface temperature sst were characteristic of the last glacial maximum with drier conditions than previously although episodic wet periods are noted in the fluvial records of northern australia the deglacial period saw warming first in the coral sea and then the indonesian seas with a pause in this trend around the time of the antarctic cold reversal c 14 5 ka coincident with the flooding of the sunda shelf wetter conditions occurred first in indonesia around 17 ka and northern australia after 14 ka the early holocene saw a peak in marine sst to the northwest and northeast of australia modern vegetation was first established on indonesia then progressively south and eastward to ne australia flores and the atherton tablelands show a dry period around 11 6 ka steadily becoming wetter through the early holocene the mid late holocene was punctuated by millennial scale variability associated with the el nino southern oscillation this is evident in the marine coral speleothem and pollen records of the region

assessment of organic richness and hydrocarbon generation potential of raniganj basin shales west bengal india abstract high energy prices and severe energy shortage has led shale gas to become the focus of study and exploration in many countries india like many other countries around the world with shale gas potential recognizes the strategic importance of developing its shale gas resources for the purpose of shale gas assessment the authors have selected sixty six borehole shale samples of different formations from different parts of raniganj basin west bengal india rock eval pyrolysis and total organic carbon toc analysis and petrographic characterization of the shales were carried out shales from barakar lower permian barren measures upper permian and raniganj formation upper permian are marked by good to excellent toc content input of type iii organic matter and are capable of generating oil and thermogenic gas upon thermal cracking igneous intrusives dykes and sills in the formations occurring in and around the areas of sitarampur si and kulti ku in western part of the basin might have resulted in cooking of the shales increasing their maturities estimated vitrinite reflectance vro as indicated by the barren measures shales of shallow depths from the above mentioned areas majority of the samples are marked by low oxygen index oi values

sediment trapping of turbidity maxima in the changjiang estuary abstract sediment trapping in the turbidity maxima tm is highly variable in different estuaries or at different times in the same estuary how related processes influence the tm behavior and its structure has not yet been completely clear here we present moored and shipboard observations in the 2008 flood and dry seasons in the lower reaches of the changjiang estuary where the deepwater navigation channel was still under construction the excavation of the pristine mouth bar has caused the saline wedge to move upstream resulting in new tm zones the magnitude and extent of the tm are strongly seasonal under the influence of distinct sediment processes the tm appears as a high concentration undercurrent in the flood season whereas they occur as a low concentration sediment cloud over the water column in the dry season the hyperpycnal flow can be formed by flocculation settling and the sediment cloud can be caused primarily by resuspension the sediment trapping in the tm occurs more often during accelerating and decelerating ebb tides when the bed stress is small but the flow is highly accelerating and decelerating sediment resuspension and deposition at these tidal reversals can be induced by the growing and decaying flow spirals respectively therefore the diversity of the tm may be associated with density stratification accelerating flows flocculation or generally the interaction between stratified flows and cohesive sediments

high resolution holocene record in the southeastern bay of biscay global versus regional climate signals abstract core ks10b north east atlantic 43 50 n 2 03 w water depth 550 m was recovered at a location of high sediment deposition and hence includes a high resolution palaeoclimatic record for the southeastern bay of biscay over the last 9000 cal yr bp the effect of global and regional climatic forcing factors e g orbital forcing north atlantic oscillation nao and their subsequent control on water temperature sea level hydrology and continental influence were investigated by studying planktic and benthic foraminiferal faunas 150 m sedimentology and stable isotopes results indicate probable episodic long term incursions of the warm and salty iberian poleward current ipc into the bay of biscay during the holocene by the intermittent presence of subtropical globigerinoides ruber in the otherwise temperate fauna these incursions seem to be triggered by negative nao like conditions our data show five main climatic periods which are in general agreement with the literature data on the climatic variability in the north atlantic and the iberian peninsula the early holocene 9000 7400 cal yr bp is characterized by low sea level significant downslope transport eutrophic benthic settings and high surface water productivity these environmental characteristics are probably due to the general wet and warm climate under a prevailing negative nao increasing precipitation and river runoff and favouring the incursion of the ipc into the bay of biscay the climatic optimum appears between 7400 and 6000 cal yr bp under a generally positive nao index in the following 6000 3500 cal yr bp surface water cooling is matching a steep decline of the northern hemisphere summer insolation meanwhile benthic settings are changing progressively towards present day trophic conditions the time interval from 3500 to 1800 cal yr bp encompasses the iberian roman humid period characterized by warm and humid conditions and increasing primary production under a prevailing negative nao index the last 1800 years were characterized by stable cool conditions reflecting a change towards a positive nao state

millennial scale pulsebeat of glaciation in the southern alps of new zealand abstract we undertook geomorphological mapping in conjunction with 10be surface exposure dating in a previously unstudied sector of the left lateral moraine sequence of the ice age pukaki glacier in the southern alps of new zealand the mapping and dating approach enabled the identification of six distinct moraine belts that were formed during maxima of glacier extent during the last glaciation the chronology implies that ice recession occurred during northern hemisphere heinrich stadials while expansion occurred between heinrich stadials the ages of the moraine belts identified here are 44 000 1000 yrs 41 800 1100 yrs 36 450 940 yrs 26 730 740 yrs 20 030 460 yrs and 18 000 400 yrs this moraine chronology is consistent with previous dating results from other sectors of the pukaki moraine sequence except that the c 44 000 yr old moraine belt has not previously been detected elsewhere in the pukaki moraines collectively with previously published 10be chronologies from the pukaki glacier and the adjacent ohau glacier valley the results demonstrate that there were several millennial scale episodes of ice advance to full glacial extent and subsequent ice recession during marine isotope stages 3 and 2 this millennial scale pulsebeat of oscillations of the pukaki and ohau glaciers in sympathy with the north atlantic heinrich episodes is further emphasized by rapid ice recession in the southern alps early in the last glacial termination coeval with the onset of heinrich stadial 1 hs 1 in the northern hemisphere that this pattern is widespread in mid latitudes of the southern hemisphere is highlighted by similar chronologies of glacier variation for andean ice lobes in the chilean lake district of south america

synchronous volcanic eruptions and abrupt climate change 17 7 ka plausibly linked by stratospheric ozone depletion glacial state greenhouse gas concentrations and southern hemisphere climate conditions persisted until 17 7 ka when a nearly synchronous acceleration in deglaciation was recorded in paleoclimate proxies in large parts of the southern hemisphere with many changes ascribed to a sudden poleward shift in the southern hemisphere westerlies and subsequent climate impacts we used high resolution chemical measurements in the west antarctic ice sheet divide byrd and other ice cores to document a unique 192 y series of halogen rich volcanic eruptions exactly at the start of accelerated deglaciation with tephra identifying the nearby mount takahe volcano as the source extensive fallout from these massive eruptions has been found 2 800 km from mount takahe sulfur isotope anomalies and marked decreases in ice core bromine consistent with increased surface uv radiation indicate that the eruptions led to stratospheric ozone depletion rather than a highly improbable coincidence circulation and climate changes extending from the antarctic peninsula to the subtropics similar to those associated with modern stratospheric ozone depletion over antarctica plausibly link the mount takahe eruptions to the onset of accelerated southern hemisphere deglaciation 17 7 ka

seasonal variation of sediment deposition in the hudson river estuary abstract during and following the spring freshet rapid rates of sediment deposition were observed in the hudson river estuary side scan sonar surveys and sediment coring studies revealed a large amount of spatial variability in sedimentation within the estuary and a distinct seasonal progression during the freshet sediment was deposited in the seaward reaches of the estuary in the two month period after the freshet this sediment was eroded and sedimentation occurred 10 30 km further landward at the estuarine turbidity maximum etm zone the thickness of the new freshet deposit was as great as 40 cm in the etm indicating intense trapping and rapid deposition the location of this depocenter corresponded to a frontal zone where water column observations and modeling studies have indicated enhanced sediment trapping the mass of the new deposits was estimated at 300 000 metric tons during both 1998 and 1999 with similar spatial distributions in 1998 the estimated fluvial input was 560 000 metric tons significantly greater than the 120 000 metric tons estimated for 1999 thus the mass of the observed deposits appear to be more influenced by the redistribution of sediment within the estuary due to seasonal variations in erosion deposition conditions rather than by the direct input of sediment from the watershed

the effect of chemical pretreatment of sediment upon foraminiferal based proxies 1 paleoceanographic studies routinely combine different foraminiferal proxies i e weight abundance trace metal and stable isotope measurements into a cohesive narrative the application of chemical treatment to disaggregate ocean sediments in the most efficient way to isolate the fossils of foraminifera from the other sediment components is dictated by the time available and the material used yet few studies have aimed to test both the physical and geochemical effects associated with such practices in this study we use samples with different sedimentological characteristics i e varying percentages of caco3 and of terrigenous material to test the impact upon these proxies of three processing methods and a control 1 no chemicals contol run 2 soaking in sodium hexametaphosphate calgon 3 soaking in hydrogen peroxide and 4 soaking in a sodium pyrophosphate the samples were analyzed for faunal abundance shell weight stable isotope 18o 13c and trace metal mg ca geochemistry for four species of planktonic foraminifera globigerina bulloides globigerinoides ruber globorotalia inflata and globorotalia menardii results show that apart from the calgon solution the values of faunal abundance shell weight mg ca and stable isotopes are similar irrespective of the cleaning treatment utilised and therefore warrant cross comparison of results obtained with different preparation techniques the use of calgon in pretreatment shows statistically different values for only foraminiferal shell weight

mass settling flux of fine sediments in northern european estuaries measurements and predictions abstract this study describes a new flocculation model which was based entirely on observations of settling floc spectra and turbulent shear stresses acquired primarily from a series of in situ experiments conducted in several european estuaries the synthesis identified that the key components which best quantitatively describe a floc population are the changes in the macrofloc 160 m and microfloc settling velocities ws macroem and ws microem together with how the suspended matter is distributed across each floc sub population spm ratioem the ws macroem algorithm displayed an increase in settling velocity at low shear stresses due to flocculation enhanced by shear and floc disruption at higher stresses for the same concentration the transition being a turbulent shear stress of about 0 36 n m 2 the combination of the three algorithms into a single equation to predict mass settling flux msf em estimated the total flux of the 157 measured floc samples with a cumulative error 1 and 5 mm s 1 were both in error by an average of 86 and 41 respectively a concentration settling parameterisation and the van leussen techniques under predicted the total cumulative flux by 35 and 38 respectively furthermore the analysis indicated that the various existing methods all incurred high predictive errors at times under estimating by over 70 as concentration levels rose in close proximity to the bed the findings of this study demonstrate the new manning floc settling velocity mfsv empirical model has flexibility in adapting to a wide range of both turbulent shear stress and suspended sediment concentration estuarine conditions

insights into subtropical australian aridity from welsby lagoon north stradbroke island over the past 80 000 years abstract terrestrial sedimentary archives that record environmental responses to climate over the last glacial cycle are underrepresented in subtropical australia limited spatial and temporal palaeoenvironmental record coverage across large parts of eastern australia contribute to uncertainty regarding the relationship between long term climate change and palaeoecological turnover including the extinction of australian megafauna during the late pleistocene this study presents a new high resolution calibrated geochemical record and numerical dating framework from welsby lagoon a wetland from north stradbroke island that records key periods of late pleistocene environmental change single grain optically stimulated luminescence and radiocarbon dating are integrated into a bayesian age depth model for the sedimentary sequence spanning marine isotope stage mis 5 to the present scanning micro x ray fluorescence xrf and bulk sediment xrf assays are used to infer past dust dynamics with changes in the abundance of silica and potassium interpreted as proxies for aridity across local and regional sources variations in dust flux were contemporaneous with hydrological change concordant with changes in vegetation cover on the island and relate to deflation events at major dust source regions on the australian continent the welsby lagoon record supports the notion of a variable mis4 within which an increased dust flux 71 67 ka may be indicative of drier climate additionally the record also shows a lower dust flux through the last glacial maximum lgm than is evident in other australian aeolian records however this low lgm flux is attributed to the wetland s evolution rather than a reduction in total dust flux

timing of millennial scale climate change in antarctica and greenland during the last glacial period a precise relative chronology for greenland and west antarctic paleotemperature is extended to 90 000 years ago based on correlation of atmospheric methane records from the greenland ice sheet project 2 and byrd ice cores over this period the onset of seven major millennial scale warmings in antarctica preceded the onset of greenland warmings by 1500 to 3000 years in general antarctic temperatures increased gradually while greenland temperatures were decreasing or constant and the termination of antarctic warming was apparently coincident with the onset of rapid warming in greenland this pattern provides further evidence for the operation of a bipolar see saw in air temperatures and an oceanic teleconnection between the hemispheres on millennial time scales

younger dryas to early holocene paleoclimate in cantabria n spain constraints from speleothem mg annual fluorescence banding and stable isotope records abstract the younger dryas yd stadial represents the most abrupt climate change of the earth s recent history thus understanding its causes and different local responses is relevant for quaternary paleoclimatology we present a speleothem high resolution proxy record of the lateglacial to early holocene paleoclimate of the cantabrian cordillera n spain a strategic location to evaluate the influence of north atlantic events such as the yd on south western europe fluorescence lamination growth rate stable isotope and mg records from stalagmite sir 1 were dated using an age depth model constrained by u th dates and annual lamina counting the yd is recorded as a prominent positive 13c excursion whose chronology 12 95 0 14 to 11 62 0 16 ka and shape closely agree with the gs 1 stadial as defined in greenland ice supporting the event synchronicity in both areas a colder and drier yd climate limited soil productivity and dripwater availability leading to higher 13c and mg reduced growth rate and virtually absent fluorescence lamination the early yd record until 12 5 ka reflects increasing aridity whereas the late yd from 12 2 ka on shows the opposite trend at the yd boundaries temperature changes influenced the mg record by modifying the mg partition into calcite however this effect was superseded by major changes in dripwater mg ca linked to rainfall variations during the early holocene the arnero sierra was forested and had a relatively warm and humid seasonal climate indicated in sir 1 by higher growth rates lower 13c and mg and well developed fluorescent lamination similar to other high resolution stalagmitic records of the cordillera from 8 5 to 8 0 ka sir 1 reflects a temporary trend of increasing aridity

factors controlling floc settling velocity along a longitudinal estuarine transect a 147 km longitudinal transect of flocculated cohesive sediment properties in san francisco bay sfb was conducted on june 17th 2008 our aim was to determine the factors that control floc settling velocity along the longitudinal axis of the estuary the inssev lf video system was used to measure floc diameters and settling velocities at 30 stations at a distance of 0 7 m above the estuary bed floc sizes d ranged from 22 m to 639 m and settling velocities ws ranged between 0 04 mm s 1 and 15 8 mm s 1 during the longitudinal transect nearbed turbulent shear stresses throughout the transect duration were within the 0 2 0 5 pa range which typically stimulates flocculation growth the individual d ws floc density plots suggest the suspended sediments encountered throughout sfb were composed of both muddy cohesive sediment and mixed sediments flocs mass weighted population mean settling velocity wsmass ranged from 0 5 mm s 1 to 10 mm s 1 the macrofloc and microfloc demarcation at 160 m sub populations demonstrated parameterised settling velocities which spanned nearly double the range of the sample mean settling velocities wsmean the macroflocs tended to dominate the suspended mass up to 77 of the ambient suspended solid concentration ssc from san pablo bay to carquinez strait the vicinity of the turbidity maximum zone microfloc mass was particularly significant typically 60 100 of the ssc in the northern section of south bay and most of central bay the transect took eleven hours to complete and was not fully synoptic during slack tide larger and faster settling flocs deposited accounting for most of the longitudinal variability the best single predictor of settling velocity was water velocity 39 min prior to sampling not suspended sediment concentration or salinity resuspension and settling lags are likely responsible for the lagged response of settling velocity to water velocity the distribution of individual floc diameters and settling velocities indicates that floc density for a given floc diameter varies greatly a small portion a few percent of suspended sediment mass in sfb is sand sized and inclusion of sand in flocs appears likely fractal theory for cohesive sediment assumes that there is a single primary particle size that flocculates which is not the case for these types of mixed sediment flocs the wide variability in the physical biological and chemical processes which contribute to flocculation within sfb means that spatial floc data is required in order to accurately represent the diverse floc dynamics present in the bay system the importance in determining accurate estimates of floc density has been highlighted by the sfb data as these provide the basis for realistic distributions of floc dry mass and the mass settling flux across a floc population however although video floc sampling devices can produce the various floc property trends observed in sfb good survey practice is still paramount one can see that if the sampling coverage i e data collection frequency is poor this could lead to potential mis interpretations of the data and only limited conclusions may be drawn from such a restricted survey for example a limited survey i e only 3 stations compared to the 10 stations in the full survey in south bay produces an under estimate in both the macrofloc sscmacro distribution by a factor of four and the wsmacro by a factor of two to develop sediment transport numerical models for sfb high quality floc size and settling data are needed to understand and simulate the depositional qualities of both suspended cohesive sediment and mixed sediments in san francisco bay this study has shown that the most pragmatic solution is a physically based approach whereby the detailed flocs d vs ws spectra are parameterised in terms of their macrofloc and microfloc properties this aids in model calibration whilst retaining more of the dynamical aspects of the floc populations all forms of flocculation are dynamically active processes therefore it is important to also include both ssc and turbulence functions together with the floc data

heinrich events massive late pleistocene detritus layers of the north atlantic and their global climate imprint 1 millennial climate oscillations of the glacial interval are interrupted by extreme events the so called heinrich events of the north atlantic their near global footprint is a testament to coherent interactions among earth s atmosphere oceans and cryosphere on millennial timescales heinrich detritus appears to have been derived from the region around hudson strait it was deposited over approximately 500 250 years several mechanisms have been proposed for the origin of the layers binge purge cycle of the laurentide ice sheet jokulhlaup activity from a hudson bay lake and an ice shelf buildup collapse fed by hudson strait to determine the origin of the heinrich events i recommend 1 further studies of the timing and duration of the events 2 further sedimentology study near the hudson strait and 3 greater spatial and temporal resolution studies of the layers as well as their precursory intervals studies of previous glacial intervals may also provide important constraints

comparison of organic uk 37 texh86 ldi and faunal proxies foraminiferal assemblages for reconstruction of late quaternary sea surface temperature variability from offshore southeastern australia several proxies have been developed to reconstruct past sea surface temperature sst but different proxies may reflect temperatures of different seasons and each proxy is characterized by certain uncertainties therefore a multiproxy approach is preferred to precisely reconstruct sst here we reconstruct sst of the ocean offshore southeastern australia murray canyons area for the last 135 ka using three independent organic proxies texh86 based on glycerol dialkyl glycerol tetraethers gdgts uk 37 based on alkenones and ldi based on long chain diols in addition to foraminiferal faunal assemblages the organic proxy records show similar trends with the highest temperature 21 c for uk 37 and texh86 and 25 c for ldi during the last interglacial and lowest temperature 8 c for texh86 10 c for uk 37 and 12 c for ldi during the last glacial maximum however the differences in absolute sst estimates obtained by the organic proxies varied over time with differences of up to 9 c between ldi and texh86 the seasonal sst reconstructions based on the modern analogue of foraminiferal assemblages also show similar trends as the organic proxies with highest temperatures during the last interglacial 23 c for the warmest month sst 20 c for mean annual and 18 c for the coolest month and lowest temperature during the last glacial maximum 14 c for the warmest month 11 c for mean annual and 9 c for the coolest month down core comparison between the reconstructed ssts of the organic and inorganic proxies shows that ldi inferred temperatures compare well with the temperature of the warmest month texh86 with the temperature of the coolest month and uk 37 with mean annual temperature an increase in texh86 sst estimates relative to those of other proxies during deglaciations and interglacials suggests that either winter temperatures rapidly warmed possibly due to an invigoration of the leeuwin current over the core site or there was a change in the growth season of the thaumarchaeota the source organism of gdgts our study shows the benefits of a multiproxy approach in the interpretation of sst proxies leading to a more robust knowledge of past ocean temperature changes

observations of distribution and flocculation of suspended particulate matter in the minjiang river estuary china abstract in this study we described the distribution pattern of suspended particulate matter spm and its influencing factors in the waters around the minjiang river estuary further we investigated the flocculation process of spm and its underlying mechanism in the study area the objectives were achieved using water temperature salinity turbidity fluorescence and particle size distribution of spm data measured in august 2009 as influenced by dilution from the minjiang river water the water column structure was significantly stratified in the estuary with an obvious thermocline and halocline the turbidity was relatively low in the surface water ssc 15 mg l fluorescence was high up to 10 l l in the surface water which was markedly lower and more uniform in the lower water layer the total volume concentration and particle size of the spm in the upper water layer were significantly higher than those of the lower water layer the in situ particle size frequency distribution of spm markedly changed in the different water layers whereas the dispersed particles were fine with little difference in frequency distribution the mean effective density of spm was generally 3 in the surface and benthic water and the values were slightly higher in the benthic water layer than in the surface water layer with a significant increase in the middle water layer the significant differences between the distribution trends of the total volume concentration and water turbidity were controlled by the size distribution of spm the concentration distribution of spm was mainly influenced by source re suspension and thermocline among other factors flocs widely occurred in the study area and the flocculation mechanism of spm varied in the different water layers in the upper water layer intense biological activity promoted the formation of stable macroflocs in the benthic water layer the biological activity was limited the flocculation of sediment particles was mainly caused by physico chemical attraction of inorganic particles and the hydrodynamic conditions and high settling velocity were also unfavourable to the formation of macroflocs

southern ocean wind response to north atlantic cooling and the rise in atmospheric co2 modeling perspective and paleoceanographic implications 1 a recent study found enhanced upwelling rates in the southern ocean during the last glacial termination that coincided with the deglacial warming in antarctica and the rise in atmospheric co2 they hypothesized that the intensification of southern hemisphere midlatitude westerlies the presumed cause of the increased wind driven upwelling was triggered by an initial cooling within the glacial north atlantic whose influence was then communicated to the southern midlatitudes through an atmospheric teleconnection in this study we explore the viability of the above hypothesis using a modeling strategy focusing on the atmospheric teleconnection in simulations where north atlantic cooling was applied the model intertropical convergence zone shifted southward and westerlies and wind stress over southern ocean increased by as much as 25 while the perennial westerly anomalies occur over the entire southern ocean they are strongest over the south pacific during the austral winter when the wind stress anomalies were applied to an earth system model incorporating interactive marine biogeochemistry atmospheric co2 rises between 20 and 60 ppm depending on the biological response we thus confirm the viability of the proposed atmospheric teleconnection hypothesis the teleconnection appears to involves two distinct steps first the north atlantic cooling shifts the intertropical convergence zone southward weakening the southern branch of the hadley circulation and second how the altered hadley circulation in turn modifies the structure of midlatitude westerlies in the south pacific via the former s influence on the southern hemisphere subtropical jet this study underscores the control of the northern hemisphere has on southern midlatitude westerlies mediating by tropical circulation in contrast to past paleoclimate hypotheses that the magnitude and position of the southern midlatitude westerlies was controlled by global mean temperature our results do not preclude other potential mechanisms for affecting southern ocean ventilation in particular through oceanic pathways