early and late holocene paleoenvironmental reconstruction of the pearl river estuary south china sea using foraminiferal assemblages and stable carbon isotopes abstract proxy reconstructions of estuarine evolution provide perspectives on regional to global environmental changes including relative sea level changes climatic changes and agricultural developments here we present a new benthic foraminiferal record along with 13c and c n and lithological data from a sediment core in the pearl river estuary lingding bay adjacent to the south china sea the core has relatively thick holocene sediments 40 m due to its location in the paleo valley of the pearl river the lithologic and foraminiferal record reveal an evolution in paleoenvironment from fluvial inner estuary to middle estuary between 11300 and 8100 cal a bp in response to rapid sea level rise 13c and c n data indicate high freshwater discharge from 10500 to 8100 cal a bp driven by a strong asian monsoon the middle holocene 8100 3300 cal a bp sediment is absent in the core due to subaqueous erosion resulting from the unique geomorphology of the pearl river delta in the late holocene from 3300 cal a bp to the present the lithology and foraminiferal assemblages suggest a further evolution from outer estuary middle estuary channel to middle estuary shoal resulting from deltaic progradation under stable relative sea levels in the last 2000 years 13c and c n values reveal the intensive development of agriculture coupled with the reduction of freshwater input derived from a weakening asian monsoon

pfs mex observations of the condensing co2 south polar cap of mars abstract the condensing co2 south polar cap of mars and the mechanisms of the co2 ice accumulation have been studied through the analysis of spectra acquired by the planetary fourier spectrometer pfs during the first two years of esa s mars express mex mission this dataset spans more than half a martian year from ls 330 to ls 194 and includes the southern fall season which is found to be extremely important for the study of the residual south polar cap asymmetry the cap expands symmetrically and with constant speed during the fall season the maximum extension occurs sometime in the 80 90 ls range when the cap edges are as low as 40 latitude inside hellas and argyre basins frost can be stable at lower latitudes due to the higher pressure values causing the seasonal cap to be asymmetric within the seasonal range considered in this paper the cap edge recession rate is approximately half the rate at which the cap edge expanded the longitudinal asymmetries reduce during the cap retreat and disappear around ls 145 two different mechanisms are responsible for co2 ice accumulation during the fall season especially in the 50 70 ls range here co2 condensation in the atmosphere and thus precipitation is allowed exclusively in the western hemisphere and particularly in the longitudinal corridor of the perennial cap in the eastern hemisphere the cap consists mainly of co2 frost deposits as a consequence of direct vapor deposition the differences in the nature of the surface ice deposits are the main cause for the residual south polar cap asymmetry results from selected pfs orbits have also been compared with the results provided by the martian general circulation model gcm of the laboratoire de meteorologie dynamique lmd in paris with the aim of putting the observations in the context of the global circulation this first attempt of cross validation between pfs measurements and the lmd gcm on the one hand confirms the interpretation of the observations and on the other hand shows that the climate modeling during the southern polar night on mars is extremely sensitive to the dynamical forcing

carbon dioxide snow storms during the polar night on mars 1 the mars orbiter laser altimeter detected clouds during the polar night on mars while these clouds are associated with topographic features and are clearly mountain wave clouds as suggest by pettengill and ford 2000 we suggest that they differ greatly from terrestrial mountain wave clouds uplift generated from flow over the mountains may initiate the clouds on both planets terrestrial wave clouds are generally compact features with sharp edges however we find that the relatively large mass of condensate on mars leads to diffuse clouds with snow tails that may extend many kilometers downwind from the mountain and even reach the surface both the observations and the simulations suggest substantial carbon dioxide snow precipitation in association with the underlying topography this precipitation deposits co2 dust and water ice to the surface and may lead to propagating geologic features in the martian polar regions

carbon dioxide ice clouds snowfalls and baroclinic waves in the northern winter polar atmosphere of mars 1 the formation of co2 ice clouds in the northern winter polar atmosphere of mars and their relation to baroclinic planetary waves which dominate local dynamics are studied using a general circulation model the simulation shows that clouds are formed at altitudes of up to 40 km and their occurrence correlates to a large degree with the cold phases of transient planetary waves ice particles formed up to 20 km can reach the surface in the form of snowfall in certain longitude regions while in others these particles likely sublimate in the lower warmer atmospheric layers the simulation suggests that about a half of the seasonal ice cap is created by co2 snow while the remaining half by direct condensation on the surface thus the occurrences of ice clouds and rates of deposition are closely linked to traveling planetary waves indicating the possibility for the reliable forecasts of co2 snow storms citation kuroda t a s medvedev y kasaba and p hartogh 2013 carbon dioxide ice clouds snowfalls and baroclinic waves in the northern winter polar atmosphere of mars geophys res lett 40 1484 1488 doi 10 1002 grl 50326

chronostratigraphic studies of sediments in the negev desert using amino acid epimerization analysis of land snail shells abstract the chronostratigraphy of mostly holocene sediments in the northern negev desert of israel was studied through amino acid epimerization analysis alloisoleucine isoleucine ratio a i of individual land snail shells and 14c analysis of bulk samples of land snail shells contained within the sediments analysis of 31 deposits shows a very strong correlation between a i and 14c age a i analyses indicate that age mixtures occur within all colluvial and in some fluvial deposits consequently radiocarbon dates of bulk samples which give an average age overestimate the time of deposition sedimentation rates were generally rapid in both fluvial and colluvial deposits colluviation shows a maximum in the early holocene and decreases progressively thereafter in accordance with the change in average rainfall accumulation of fluvial sediments shows a distinct mid holocene maximum and apparently relates to the interaction between variation in rainfall extent of bedrock exposure and vegetation density late holocene fluvial deposition may relate to agricultural activity the understanding of the chronology of sedimentation is dependent on an integrated approach employing amino acid epimerization analysis to study age variation within a layer and 14c analyses for establishment of an absolute chronology

initiation of the mekong river delta at 8 ka evidence from the sedimentary succession in the cambodian lowland abstract modern deltas are understood to have initiated around 7 5 9 ka in response to the deceleration of sea level rise this episode of delta initiation is closely related to the last deglacial meltwater events and eustatic sea level rises the initial stage of the mekong river delta one of the world s largest deltas is well recorded in cambodian lowland sediments this paper integrates analyses of sedimentary facies diatom assemblages and radiocarbon dates for three drill cores from the lowland to demonstrate holocene sedimentary evolution in relation to sea level changes the cores are characterized by a tripartite succession 1 aggrading flood plain to natural levee and tidal fluvial channel during the postglacial sea level rise 10 8 4 ka 2 aggrading to prograding tidal flats and mangrove forests around and after the maximum flooding of the sea 8 4 6 3 ka and 3 a prograding fluvial system on the delta plain 6 3 ka to the present the maximum flooding of the sea occurred at 8 0 0 1 ka 2000 years before the mid holocene sea level highstand and tidal flats penetrated up to 20 50 km southeast of phnom penh after a period of abrupt 5 m sea level rise at 8 5 8 4 ka the delta progradation then initiated as a result of the sea level stillstand at around 8 7 5 ka another rapid sea level rise at 7 5 7 ka allowed thick mangrove peat to be widely deposited in the cambodian lowland and the peat accumulation endured until 6 3 ka since 6 3 ka a fluvial system has characterized the delta plain and the fluvial sediment discharge has contributed to rapid delta progradation the uppermost part of the sedimentary succession composed of flood plain to natural levee sediments reveals a sudden increase in sediment accumulation over the past 600 1000 years this increase might reflect an increase in the sediment yield due to human activities in the upper to middle reaches of the mekong as with other asian rivers

evaluation of amino acid racemization epimerization dating using radiocarbon dated fossil land snails the relation between age and amino acid epimer ratios alloisoleucine isoleucine a i of holocene land snails was quantitatively evaluated through 14 c and amino acid analysis of 33 samples from fluvial and colluvial sediments and rodent middens in the northern negev desert of israel a i is strongly correlated with 14 c ages in fluvial and rodent midden deposits r 0 95 and 0 94 respectively permitting age estimates from a i ratios with precisions of 700 and 660 yr the correlation is weaker in colluvial deposits r 0 74 and age estimates from a i ratios are correspondingly less precise 1580 yr this probably results from delayed burial which exposes the shells to intense radiation on the desert surface because of the generally strong relation between age and a i amino acid epimerization analysis of individual shells can be used to identify mixed age deposits and to reconstruct species chronologies from mixed age deposits

marine deposition and sea surface temperature changes during the last and present interglacials in the west coast of taiwan strait abstract in order to reconstruct the environmental and climatic conditions of the last and present interglacials this study has examined a 52 m long core obtained from a coastal embayment chang le on the west coast of taiwan strait the analyses of particle size distributions total carbon content organic carbon isotope ratios n alkane indices and alkenones from the core reveal two periods of marine transgression together with the radiocarbon and optically simulated luminescence dating analyses the environmental proxies indicate that the older marine sequence m1 was deposited during the period of rising sea level in the early to middle part of mis5e the younger marine sequence m2 was confirmed as a deposit formed during the stable sea level of the latter part of the present interglacial the shallow marine facies and the abundant alkenones from m2 suggest a deeper water environment under full marine conditions during the last interglacial the sub tidal to intertidal facies and weak appearance of alkenones in m1 imply a shallow water environment under weak marine influence because the site was close to upland landscape high input of terrigenous material for both periods is evident the alkenone based sea surface temperature sst reconstructions indicate that the sst during mis5e fluctuated slightly around 28 1 c which is about one degree higher than that of mis1 consistent with records from the northern coast of the south china sea the depositional conditions and the burial depths of the two marine sequences also provide hints for the local tectonic movements

numerical simulation of the winter polar wave clouds observed by mars global surveyor mars orbiter laser altimeter abstract in 1998 the mars orbiter laser altimeter revealed the presence of isolated or quasi periodic thick clouds during the martian polar night they are believed to be composed of co 2 ice particles and to be tilted against the wind direction a feature characteristic of vertically propagating orographic gravity waves to support that interpretation we present here numerical simulations with a two dimensional anelastic model of stratified shear flow that includes simple co 2 ice microphysics in some of the simulations presented the orography is an idealized trough with dimensions characteristic of the many troughs that shape the mars polar cap in others it is near the real orography in the polar night conditions our model shows that gravity waves over the north polar cap are strong enough to induce adiabatic cooling below the co 2 frost point from this cooling airborne heterogeneous nucleation of co 2 ice particles occurs from the ground up to the altitude of the polar thermal inversion although the model predicts that clouds can be present above 15 km only low altitude clouds can backscatter the laser beams of mola at a detectable level accordingly the shape of the laser echoes is related to the shape of the clouds at low level but do not necessarily coincide with the top of the clouds the model helps to interpret the cloud patterns observed by mola above an isolated orographic trough an isolated extended sloping cloud tilted against the wind is obtained the model shows that the observed quasi periodic clouds are due to the succession of small scale topographic features rather than to the presence of resonant trapped lee waves indeed the co 2 condensation greatly damps the buoyancy force essential for the maintenance of gravity waves far from their sources simulations with realistic topography profiles show the cloud response is sensitive to the wind direction when the wind is directed upslope of the polar cap on the one hand a large scale cloud modulated by small scale waves forms just above the ground on the other hand when the wind is directed downslope air is globally warmed and periodic ice clouds induced by small scale orography form at altitudes higher than 3 5 km above the ground in both cases a good agreement between the simulated echoes and the observed one is obtained according to our model we conclude that the observed clouds are quasi stationary clouds made of moving ice particles that successively grow and sublimate by crossing cold and warm phases of orographic gravity waves generated by the successive polar troughs we also find that the rate of ice precipitation is relatively weak except when there is a large scale air dynamical cooling

radio occultation measurements of forced atmospheric waves on mars mars global surveyor performed a series of radio occultation experiments in december 1998 resulting in 36 profiles of the neutral atmosphere in late northern spring ls 74 1 77 3 the measurements are confined in latitude 64 6 67 2 n and local time 0321 0418 but their distribution in longitude is fairly uniform we used least squares spectral analysis to characterize the zonal structure of the atmosphere and constructed longitude height cross sections of both temperature and geopotential zonal variations of temperature exceed 12 k near the surface but are much smaller 2 3 k at higher altitudes zonal variations of geopotential are 200 m throughout the vertical range of the measurements these patterns of temperature and geopotential appear to be stationary relative to the surface with little day to day variation within the 7 sol span of the measurements we relied heavily on mars general circulation models gcms for guidance in understanding these data stationary planetary waves are responsible for some aspects of the temperature and geopotential fields particularly at pressures exceeding 100 200 pa on the basis of strong similarities between a gcm simulation and the observations we conclude that the disturbance takes the form of a planetary wave train excited by alba patera the data also include the signature of non sun synchronous thermal tides which produce a pattern that appears to be stationary when sampled at fixed local time comparison between a gcm simulation and the measured geopotential field provides evidence for the presence of the resonantly enhanced diurnal wave 1 kelvin mode

quaternary aminostratigraphy of eolianite on lord howe island southwest pacific ocean abstract amino acid racemization aar dating of the eolianite on lord howe island is used to correlate several disparate successions and provides a geochronological framework that ranges from holocene to middle pleistocene time the reliability of the aar data is assessed by analysing multiple samples from individual lithostratigraphic units checking the stratigraphic order of the d l ratios and the consistency of the relative extents of racemization for a suite of seven amino acids three aminozones are defined on the basis of the extent of racemization of amino acids in land snails placostylus bivaricosus and whole rock eolianite samples aminozone a includes placostylus from modern soil horizons e g mean d l leucine ratio of 0 03 0 01 and whole rock samples from unconsolidated lagoonal and beach deposits 0 10 0 01 0 07 0 03 aminozone b includes placostylus 0 45 0 03 and whole rock samples from beach 0 48 0 01 and dune 0 45 0 02 0 30 0 02 units of the neds beach formation deposited during ois 5 the oldest aminozone c comprises placostylus recovered from paleosols 0 76 0 02 and whole rock eolianite samples 0 62 0 00 from the searles point formation which indicate the formation was likely deposited over several oxygen isotope stages ois during and prior to ois 7 these data support independent lithostratigraphic interpretations and are in broad agreement with u th ages of speleothems from the searles point formation and corals from the neds beach formation and with several tl ages of dune units in both formations the aar data reveal that eolianite deposition extends over a significantly longer time interval than previously appreciated and indicate that the deposition of the large dune units is linked to periods of relatively high sea level

the use of land snail shells in paleoenvironmental reconstruction fossil land snail shells constitute a valuable source of paleoenvironmental information for the quaternary they can be dated by a variety of methods including radiocarbon amino acid racemization and epimerization and perhaps also thu and esr the vast majority of paleoenvironmental studies based on land snail shells have examined the faunal composition of fossil assemblages from which a variety of paleoenvironmental characteristics such as biome temperature and moisture conditions have been reconstructed still there are a number of problems involved in using this approach and these are discussed shell morphology has occasionally been used to reconstruct such factors as rainfall and temperature stable isotope studies on quaternary land snails include analysis of 18o values of organic matter in the shells to reconstruct c4 plant distributions from which rainfall amounts can be inferred and analysis of 18o values of shell carbonate from which trends in the oxygen isotope composition of rainfall can be reconstructed stable carbon isotopes of shell carbonate have also been studied but their interpretation is not clear amino acid epimerization analysis dalloisoleucinel isoleucine ratios of land snail shells has been used for estimation of paleotemperatures some potential uses of land snail shells for paleoenvironmental reconstruction include the study of stable isotopes of h and n periodic growth lines and deposits of pedogenic carbonates on the shells

aminostratigraphic correlation and geochronology of two quaternary loess localities central mississippi valley abstract amino acid epimeric aile ile values from terrestrial molluscs are used to define and correlate three aminozones in loess sequences exposed across the central mississippi valley in arkansas and tennessee three superposed aminozones are defined at wittsburg quarry arkansas primarily using aile ile values from total hydrolysates of the gastropod genus hendersonia peoria loess aile ile 0 07 0 01 roxana silt 0 14 0 02 and a third loess 0 28 0 06 loess units at wittsburg quarry can be correlated on lithologic characteristics eastward across the mississippi valley to the old river section near memphis tennessee however only one loess unit is fossil bearing peoria loess aile ile 0 05 at that section radiocarbon analyses of charcoal from the upper roxana silt ca 26 000 to 29 000 yr old and mollusc shell carbonate from the basal roxana silt ca 39 000 yr old are used to calibrate amino acid epimeric data for the central mississippi valley these data applied to the apparent parabolic kinetic model of r m mitterer and n kriausakul 1989 quaternary science reviews 8 353 357 suggest an illinoian 120 000 yr age for the third loess in the central mississippi valley that is correlative with part of the loveland loess in illinois and iowa

reasons for the low sedimentation and slow progradation in the pearl river delta southern china during the middle holocene abstract holocene sea level rise monsoonal discharge and human activity have been the main drivers for the evolutionary history of asian deltas in theory when sea level ceased to rise in around 7000 cal a bp deltas should have started to prograde seawards however previous studies revealed that the progradation of modern deltas was initially very slow and more importantly sediment accumulation within central deltaic basins was exceptionally low between 7000 and 4000 cal a bp in order to investigate the main reasons for such slow progradation and low sedimentation during the middle holocene this study reconstructed the sedimentary history of the head area of the pearl river delta the results show marine transgression from 9500 to 7500 cal a bp followed by marine regression starting from 7500 to 4000 cal a bp in response to sea level change during the latter period sedimentation was concentrated in the head area the amount of sediment entering the central basin was significantly reduced this limited amount of sediment was spread thinly across the wide deltaic basin a portion of it could have been transported out into the south china sea by the strong tidal currents resulting in an exceptionally low sedimentation in the central basin however in locations adjacent to former present islands locally supplied sediment helped sedimentation to continue from 7500 to 4000 cal a bp by about 4000 cal a bp the deltaic shoreline advanced into the central basin this period saw an increase of human activity that caused soil erosion and sediment supply leading to a marked increase in sedimentation rate active land reclamations also helped the acceleration of shoreline advance this sedimentary evolution model in the pearl river delta mirrors those of other deltas in the monsoonal asia

a census of eddy activities in the south china sea during 1993 2007 1 numerous mesoscale eddies occur each year in the south china sea scs but their statistical characteristics are still not well documented a pacific basin wide three dimensional physical biogeochemical model has been developed and the result in the scs subdomain is used to quantify the eddy activities during the period of 1993 2007 the modeled results are compared with a merged and gridded satellite product of sea level anomaly by using the same eddy identification and tracking method on average there are about 32 9 2 4 eddies predicted by the model and 32 8 3 4 eddies observed by satellite each year and about 52 of them are cyclonic eddies the radius of these eddies ranges from about 46 5 to 223 5 km with a mean value of 87 4 km more than 70 of the eddies have a radius smaller than 100 km the mean area covered by these eddies each year is around 160 170 km2 equivalent to 9 8 of the scs area with water depths greater than 1000 m linear relationships are found between eddy lifetime and eddy magnitude and between eddy vertical extent and eddy magnitude showing that strong eddies usually last longer and penetrate deeper than weak ones interannual variations in eddy numbers and the total eddy occupied area indicate that eddy activities in the scs do not directly correspond to the el nino southern oscillation events the wind stress curls are thought to be an important but not the only mechanism of eddy genesis in the scs

the role of sea level rise monsoonal discharge and the palaeo landscape in the early holocene evolution of the pearl river delta southern china abstract the early holocene history of the pearl river delta is reconstructed based on a series of sediment cores obtained from one of the main palaeo valleys in the basin sedimentary and microfossil diatom analyses combined with radiocarbon dating provide new evidence for the interactions between sea level rise antecedent topography and sedimentary discharge changes within the deltaic basin since the last glacial these new records show that river channels of last glacial age incised down to c 40 m into an older possibly mis5 age marine sequence which forms the floor of the deltaic basin and exists primarily at c 10 m 15 m below present mean sea level rapid postglacial sea level rise flooded the incised valleys by the beginning of the holocene and prior to c 9000 cal years bp marine inundation was largely confined within these incised valleys the confined available accommodation space of the incised valleys combined with strong monsoon driven freshwater high sediment discharge and a period of rapid rising sea level meant that sedimentation rates were exceptionally high towards c 8000 cal years bp as sea level rose to about 5 m marine inundation spilled out of the incised valleys and the sea flooded the whole deltaic basin as a result the mouth of the pearl river was forced to retreat to the apex of the deltaic basin water salinity within the basin increased markedly as the previously confined system dispersed across the basin and the sedimentation changed from fluvial dominated to tidal dominated sea level continued to rise albeit at a much reduced rate between 8000 and 7000 cal years bp and deltaic sedimentation was concentrated around the apex area of the basin during the last 7000 cal years bp the delta shoreline moved seawards and the sedimentary processes changed gradually from tidal dominated to fluvial dominated

holocene sea level history of the northern coast of south china sea abstract this study has collected and analyzed seven sediment cores from the pearl river delta from which 16 new and high quality sea level index points are generated using a new approach this study has also re checked and re calibrated the previously published sea level data from china s southeast coast with corrections made for tectonic subsidence and sediment compaction factors these sea level data indicate a rise of relative sea level from 49 3 0 8 m to the present height between 10 500 and 7000 cal a bp this sea level history is similar to those recorded from other far field locations and ice volume equivalent sea level models the early to early middle holocene sea level history in the study area shows a phase of accelerated rise at a rate increasing rapidly from 16 4 6 1 mm a at 10 500 cal a bp to 33 0 7 1 mm a at 9500 cal a bp this phase was followed by a period of rapid decrease in the rate of sea level rise to 8 8 1 9 mm a at 8500 cal a bp and 1 7 1 3 mm a at 7500 cal a bp during the past 7000 years the relative sea level in the study area changed very little this new and complete history of holocene sea level change supports the following findings 1 no obvious higher than present sea level highstand in the holocene is found from the northern south china sea 2 certain proportion of the effects of the predicted glacial isostatic adjustment were cancelled out by the effects of the weak upper mantle viscosity in the study area 3 meltwater pulse 1b likely exists spanning into the early holocene 4 there are significant misfit between sea level data and glacial isostatic adjustment models and a revision to the existing ice melting history for the early holocene is possibly needed

rainfall in the negev desert during the middle holocene based on 13c of organic matter in land snail shells abstract analysis of stable carbon isotope ratios 13 c 12 c of organic matter in land snail shells is used to infer middle holocene rainfall amounts in the negev desert by reconstructing the distribution of c 4 plants in the family chenopodiaceae the organics are derived from the diet of the snails which consists of plant material and are enriched in 13 c where c 4 plants are present a survey of modern plant communities indicates that in areas receiving 300 mm mean annual rainfall nearly all plant communities consist of c 3 species only no c 4 chenopodes whereas in areas under 230 mm rainfall most plant communities contain one or more c 4 chenopode species in between is a transition zone consisting of a mosaic of both pure c 3 and mixed c 3 c 4 plant communities isotopic results for fossil land snails indicate a consistent geographic pattern throughout the middle holocene from ca 6500 to 3000 yr b p with the transition zone located ca 20 km south of its present position this implies a near doubling of rainfall within this region as compared to present

song hong red river delta evolution related to millennium scale holocene sea level changes abstract the song hong red river delta occurs on the northwest coast of the south china sea its evolution in response to holocene sea level changes was clarified on the basis of sedimentary facies and 14 radiocarbon dates from the 40 m long duy tien core from the delta plain and using previously reported geological geomorphological and archaeological data the delta prograded into the drowned valley as a result of early holocene inundation from 9 to 6 cal kyr bp as sea level rise decelerated the sea level highstand at 2 3 m from 6 to 4 cal kyr bp allowed widespread mangrove development on the delta plain and the formation of marine notches in the ha long bay and ninh binh areas during sea level lowering after 4 cal kyr bp the former delta plain emerged as a marine terrace and the delta changed into the present tide and wave influenced delta with accompanying beach ridges delta morphology depositional pattern and sedimentary facies are closely related to holocene sea level changes in particular falling sea level at 4 cal kyr bp had a major impact on the evolution of the song hong delta and is considered to be linked to climate changes

role of stationary and transient waves in co2 supersaturation during northern winter in the martian atmosphere revealed by mgs radio occultation measurements the martian atmosphere which mainly consists of carbon dioxide co2 is characterized by extremely low temperatures that cause co2 gas to freeze and dry ice to form to date temperatures below the co2 saturation temperature which can be attributed to the effects of atmospheric waves have been observed in the polar winter and in the mesosphere using data from mars global surveyor mgs radio occultation measurements we investigated the role of large scale atmospheric waves including stationary and transient waves at northern high latitudes in winter on co2 supersaturation a distinct longitudinal dependence of co2 supersaturation was observed at altitudes higher than the pressure level of 200 400 pa where a stationary wave with a wave number of 2 whose temperature amplitude had minima at 30 100 pa lowered the background temperature to a level close to the co2 saturation temperature however the stationary wave alone was not sufficient to cause co2 supersaturation additional temperature disturbances caused by transient waves namely superposition of both waves had a significant role in co2 supersaturation the longitudinal dependence of the occurrence of co2 supersaturation revealed by our study might affect the longitudinal distribution of co2 snowfall and the formation of the seasonal polar ice cap

evolution status of the distal mud deposit associated with the pearl river northern south china sea continental shelf abstract the sedimentary characteristics of distal mud deposits a product of along shore transport of river discharged suspended sediment contain information on their different evolutionary stages in the present study the distal mud associated with the pearl river southern china is investigated using the data sets obtained from seabed sediment sample analysis shallow geophysical survey and 210pb dating the results indicate that although the mud deposit in consideration occupies an area of more than 8000 km2 the thickness is small with a young age i e

sedimentary facies and holocene progradation rates of the changjiang yangtze delta china abstract the changjiang yangtze river one of the largest rivers in the world has formed a broad tide dominated delta at its mouth during the holocene sea level highstand three boreholes cm97 js98 and hq98 were obtained from the changjiang delta plain in 1997 1998 to clarify the characteristics of tide dominated delta sediments and architecture based on sediment composition and texture and faunal content core sediments were divided into six depositional units in ascending order they were interpreted as tidal sand ridge prodelta delta front subtidal to lower intertidal flat upper intertidal flat and surface soil deposits the deltaic sequence from the prodelta deposits to the delta front deposits showed an upward coarsening succession overlain by an upward fining succession from the uppermost part of the delta front deposits to the surface soil thinly interlaminated to thinly interbedded sand and mud sand mud couplets and bidirectional cross laminations in these deposits show that tide is the key factor affecting the formation of changjiang deltaic facies sediment facies and their succession combined with ams 14c dating revealed that isochron lines cross unit boundaries clearly and delta progradation has occurred since about 6000 to 7000 years bp when the rising sea level neared or reached its present position the average progradation rate of the delta front was approximately 50 km kyear over the last 5000 years the progradation rate however increased abruptly ca 2000 years bp going from 38 to 80 km kyear the possible causes for this active progradation could have been an increase in sediment production in the drainage basin due to widespread human interference and or decrease in deposition in the middle reaches related to the channel stability caused by human activity and climatic cooling after the mid holocene

wave energetics of the southern hemisphere of mars abstract an assessment of the energetics of transient waves in the southern hemisphere of mars is presented using the mars analysis correction data assimilation macda dataset v1 0 and the eddy kinetic energy equation the dataset is divided into four representative periods covering the summer and winter solstices a late fall period and an early spring period for three mars years spring eddies are the most intense with eddies during the fall being less intense due to a marginally more stable mean temperature profile and reduced recirculation of ageostrophic geopotential fluxes compared to the spring eddy kinetic energy during winter is reduced in intensity as a result of the winter solstitial pause in wave activity and eddy kinetic energy during the summer is limited baroclinic energy conversion acts as a source in fall and spring but disappears during the winter as a result of a stabilized vertical temperature profile barotropic energy conversion acts as both a source and a sink of eddy kinetic energy being most positive during the solstitial pause eddies take a northwest to southeast track across the southern highlands in the fall but have a more zonal track in the spring due to stronger eddy kinetic energy advection wave energetics is less intense in the southern compared to the northern hemisphere as a result of a shallower baroclinically unstable vertical profile

an early holocene sea level jump and delta initiation 1 early holocene sea level change controlled the evolution of clastic coastal depositional systems radiocarbon dated borehole cores obtained from three incised valley fill systems in asia changjiang song hong and kiso river record very similar depositional histories especially between about 9000 and 8500 cal bp sedimentary facies changes from estuarine sand and mud to shelf or prodelta mud suggest that the marine influence in the incised valleys increased during this period in addition large decreases in sediment accumulation rates occurred a sea level jump causes an estuarine system and its depocenter to move rapidly landward it is possible that the final collapse of the laurentide ice sheet accompanied by catastrophic drainage of glacial lakes at approximately 8500 cal bp caused such a jump the jump was followed immediately by a period of decelerated sea level rise that promoted delta initiation

delta initiation and holocene sea level change example from the song hong red river delta vietnam abstract delta initiation and subsequent delta growth were investigated by using radiocarbon dated borehole cores from the song hong red river delta vietnam the sediments underlying the present delta plain record three depositional systems since the last glacial maximum fluvial estuarine and deltaic in ascending order the landward part of the initial delta was characterized by an active tide influenced accumulation of sandy sediments the seaward part of the initial delta is composed of muddy prodelta and seafloor sediments that accumulated slowly radiocarbon ages of molluscan shells and organic materials suggest that the transition from estuary to delta occurred at approximately 8500 cal years bp the transition was induced by deceleration of the postglacial sea level rise which was coeval with the delta initiation the stacking pattern of the delta system is very different from that of the estuary system the sediments of the estuary that developed during the rapid rise in sea level between 11000 and 8500 cal years bp display a retrogradational stacking pattern forming a thick transgressive systems tract on the other hand aggradational as well as progradational stacking with clinoform architecture characterized the delta system between 8500 and 6500 cal years bp as the sea level continued its slow rise progradation has been dominant during the last 6500 years because the cessation of sea level rise resulted in little accommodation being added the results of this study are similar to those for other major delta systems such as the changjiang and the ganges brahmaputra deltas despite large differences in sediment discharge tectonics basin size and coastal environment this implies that the postglacial sea level rise and the change in the rise rate markedly influenced the evolution of depositional systems at river mouths

uk 37 temperature estimates from eemian marine sediments in the southern coast of hainan island tropical china abstract this study concerns high resolution sea surface temperature sst changes for the eemian interglacial period reconstructed from the southern coast of hainan island china the lower marine unit in the sediment core is composed of monotonous mud 31 m thick dated to be from the eemian interglacial period or lower part of marine isotope stage 5 mis 5 determined by optically stimulated luminescence osl the high sedimentation rate and the richness of organic matter and marine fossils provide good opportunity for the study of palaeo environments in the northern margin of the south china sea scs sediment grain size foraminifer sediment color index and long chain alkenone were used to reveal the near shore sedimentary environments and temperature at millennial scale specifically a high resolution uk 37 sst record was reconstructed for the eemian interglacial period the new evidence in northwestern margin of scs shows that the maximum value of sst during the eemian interglacial is approximately 29 c and the lowest is 26 5 c the trend of decreasing sst from 29 c throughout the marine sequence is consistent with the variations in sediment grain size reflecting the cooling trend of sst and sea level lowering tendency during the last interglacial period this new eemian sst result agrees with other records in the region of scs showing a coherent descending trend but spatial heterogeneity exists in timing and amplitude the insolation changes might be the main force for initiating the sst evolution during the penultimate interglacial period

a multi year survey of dynamics near the surface in the northern hemisphere of mars short period baroclinic waves and dust storms abstract baroclinic waves figure prominently in the dynamics of the northern hemisphere of mars and extensive observations by the viking landers and two atmospheric sounders on mars global surveyor have revealed many of their basic properties however previous investigations considered these data sets individually so that their cumulative value is not fully appreciated we have re examined these data to extract new information about the dynamics near the surface at mid to high northern latitudes by applying the same method of spectral analysis to each type of observation we derive a uniform multi year characterization of basic elements of martian weather this survey documents the time evolution of baroclinic waves among modes with different periods and zonal wave numbers we devote particular attention to a recurring wave 3 mode which is distinguished by its capacity to initiate regional dust storms in the topographic basins of the northern hemisphere our results include a detailed case study that shows how the intermittence of this mode and the strong zonal modulation of its amplitude influence the timing and location of these distinctive flushing dust storms more generally we find that the properties of the wave 3 mode are largely the same whenever it appears and that its intermittence plays an important role in the annual dust cycle

records of the mid brunhes event in chinese loess paleosol sequences abstract the mid brunhes event mbe was a climatic transition characterized by warmer temperatures smaller ice volume and higher sea levels during interglacials since marine oxygen isotope stage mis 11 data from numerous long term sedimentary sequences indicate that the mbe was expressed throughout the whole earth surface however conflicting evidence in terrestrial sequences from middle high latitudes of the northern hemisphere mean that the event s existence and global synchronicity are a matter of debate to address this problem we investigated the mbe signal in paleoclimate records from the chinese loess plateau clp higher magnetic susceptibility since s5 in the luochuan yimaguan and lingtai sections and since s4 in the jingyuan and xijin sections indicate that east asian summer monsoon easm precipitation strongly affected the central clp since mis 13 but exerts a relatively weak influence on the northwestern clp until mis 11 during the past 800 kyr from mis 13 to mis 11 shrinkage of the northern hemisphere ice sheet resulted in northward movement of the intertropical convergence zone and elevated sea level an 25 m sea level rise could have caused the coastline of the asian continent to shift northwestward by 50 100 km these changes induced extension of easm domain areas into the northwestern clp from the central clp the response to the mbe in loess paleosol sequence of the clp was expressed by variations in the geographic extent of easm domain areas rather than changes in the easm intensity the mbe emerged at mis 11 in the clp and was globally synchronous

forced waves in the martian atmosphere from mgs tes nadir data abstract we have analyzed the temperature retrievals from mars global surveyor mgs thermal emission spectrometer tes nadir spectra to yield latitude height resolved maps of various atmospheric forced wave modes as a function of season for a full mars year among the isolated wave modes is the zonal mean time mean temperature which we used to derive zonal mean zonal winds and stationary wave quasi geostrophic indices of refraction diagnostic of their propagation the diurnal kelvin wave was isolated in the data with results roughly consistent with models wilson and hamilton 1996 j atmos sci 33 1290 1326 the s 1 and s 2 stationary waves were found to have significant amplitude in ducts extending up the winter polar jets while the s 3 stationary wave was found to be confined to near the surface the s 1 stationary wave was found to have little phase tilt with height during northern winter but significant westward phase tilt with height in the southern winter this indicates that the wave carries heat poleward slightly more than that found in barnes et al 1996 j geophys res 101 12 753 12 776 the s 1 stationary wave is likely the dominant mechanism for eddy meridional heat transport for the southern winter we noted that the phase of the s 2 stationary wave is nearly constant with time but that the s 1 stationary wave moved 90 of longitude from fall to winter and back in spring in the north while interannual variability is not yet addressed overall these results provide the first comprehensive benchmark for forced waves in mars s atmosphere against which future atmospheric models of mars can be compared

holocene hydrological and sea surface temperature changes in the northern coast of the south china sea abstract in order to reconstruct the holocene environmental history of a coastal site in the northern south china sea this study analysed the organic carbon isotope ratios 13corg and alkenone unsaturation ratios uk 37 from a 36 5 m long sediment core drilled at seabed in the mouth region of the pearl river estuary and generated a coupled hydrological and temperature record this record reveals changes of monsoon induced sediment discharge and sea surface temperature of the holocene in four stages in stage i the site was under fluvial conditions prior to postglacial marine transgression stage ii saw an increase of sea surface temperature from c 23 0 c to 27 0 c associated with a strengthened summer monsoon from c 10 350 to 8900 cal years bp this was also a period of rapid sea level rise and marine transgression during which the sea inundated the palaeo incised channel i e the lower part of the t shape accommodation space created by the rising sea in these 1500 years fluvial discharge was strong and concentrated within the channel and the high sedimentation rate 11 8 mm year was very close to the rate of sea level rise in the subsequent 2000 years stage iii sea level continued to rise and the sea flooded the broad seabed above the palaeo incised channel resulted in fluvial discharge spreading thinly across the wide accommodation space and a much reduced sedimentation rate 1 8 mm year sea surface temperature in this stage reached 27 3 c initially but dropped sharply to 26 1 c towards c 8200 cal years bp the final stage covers the last 7000 years and the site was under a stable sea level sedimentation in this stage varied a little but averaged at 1 8 mm year whilst fluvial discharge and sea surface temperature didn t change much two short periods of hydrological and temperature change were observed which are related to the climatic cooling events of c 4200 cal years ago and the little ice age

radio occultation measurements of transient eddies in the northern hemisphere of mars 1 we have characterized the behavior of transient eddies in the northern hemisphere of mars through analysis of radio science rs occultation data from mars global surveyor mgs the weather in the lowest scale height above the surface at 55 n 80 n is dominated by shallow eastward moving baroclinic eddies distinguished by their intensity and coherence the vertical structure of these eddies is fully resolved by the rs measurements which also yield unique estimates of the near surface meridional winds implied by geostrophic balance we identified and characterized the most prominent eddies through space time analysis of rs measurements of geopotential height at 610 pa a few kilometers above the surface eddy activity appears as well defined modes with zonal wave numbers 1 3 and variations in the amplitudes of these modes tend to be anticorrelated so that a large amplitude in one mode is often accompanied by a small amplitude in the others the wave number and period of the dominant mode shift at intervals of 30 50 sols eddy winds near the surface vary distinctively with season in response to changes in eddy amplitude and zonal wave number the meridional winds peak sharply in two seasonal windows one in early to middle autumn and the other in middle to late winter separated by a lull around winter solstice comparisons with previous results reveal close connections with the transient eddies observed by the viking landers and with distinctive southward moving frontal dust storms observed by the mgs mars orbiter camera

sedimentary evidence of late holocene human activity in the pearl river delta china this study examines the sedimentary evidence of human activities during the last 4000 years in the pearl river deltaic area the analyses are focused on indentifying agricultural signatures present in the sedimentary record and establishing the timing of a change from a simple rice based agriculture to a more advanced diverse agriculture the examination is based on modern sediment and plant samples and a sediment core collected from the deltaic area the analyses include particle size and diatom analysis to determine the environmental conditions that were associated with the period of human activities organic carbon isotope ratios and major metal elements reveal an expansion in commercial crop production and metal smelting in the pearl river delta area about 2000 years ago the input of organic matter from introduced sugarcane a c4 plant elevates the bulk organic carbon isotope values in the estuarine sediments above that represented by other common agricultural crops in the study area including rice banana and lotus which are all c3 plants the increase in bulk organic isotopic value coincides with the rise in the concentration of copper iron and lead in the sedimentary sequence suggesting a wider use of metal tools these results indicate that advanced agriculture started about 2000 years ago as an expansion in human population took place in the area this record also provides sedimentary evidence that help ascertain the timing and type of human activities that are linked to subsequent land reclamation on the deltaic plain resulting in rapid shoreline advancement in the last 2000 years copyright 2010 john wiley sons ltd

the solsticial pause on mars 1 a planetary wave reanalysis large scale planetary waves are diagnosed from an analysis of profiles retrieved from the thermal emission spectrometer aboard the mars global surveyor spacecraft during its scientific mapping phase the analysis is conducted by assimilating thermal profiles and total dust opacity retrievals into a mars global circulation model transient waves are largest throughout the northern hemisphere autumn winter and spring period and almost absent during the summer the southern hemisphere exhibits generally weaker transient wave behaviour a striking feature of the low altitude transient waves in the analysis is that they show a broad subsidiary minimum in amplitude centred on the winter solstice a period when the thermal contrast between the summer hemisphere and the winter pole is strongest and baroclinic wave activity might be expected to be strong this behaviour here called the solsticial pause is present in every year of the analysis this strong pause is under represented in many independent model experiments which tend to produce relatively uniform baroclinic wave activity throughout the winter this paper documents and diagnoses the transient wave solsticial pause found in the analysis a companion paper investigates the origin of the phenomenon in a series of model experiments

sediment retention at the changjiang sub aqueous delta over a 57 year period in response to catchment changes the growth of a river delta system is controlled mainly by fluvial sediment discharge and sediment retention in the deltaic areas in the present study we attempt to define a sediment retention index r and its relation to the deposition rate of the delta based upon two assumptions that the amount of the sediment that escapes from the deltaic areas qe is stationary with minor fluctuations and that there is a linear relationship between the deposition rate averaged over the sub aqueous delta dav and the deposition rate at accretion sites within the delta dr the changes in the accretion erosion patterns of the changjiang sub aqueous delta during the period of 1951 2007 in response to river sediment discharge changes are analyzed the results show that the sediment retention index can be related to the deposition rate of the sub aqueous delta the spatial temporal distribution pattern of the deposition rate reveals the behaviour of sediment retention of a delta system for the changjiang sub aqueous delta fluvial sediment discharge data together with pb 210 based deposition rates provide useful information on sediment retention changes in the sediment retention index and the accretion erosion patterns of the sub aqueous delta have taken place in response to river input changes in order to improve our understanding of the processes associated with estuarine sediment retention sediment cores with sufficient spatial coverage may be collected and analyzed to establish accurate qe r and dav dr relationships in combination with numerical modeling of sediment transport these relationships form a basis for the analysis of sediment retention mechanisms

amino acid geochronology resolution and precision in carbonate fossils changes in indigenous proteins preserved in carbonate skeletons can be used to estimate the time elapsed since death of the organism racemization the most widely used reaction in amino acid geochronology refers to the inversion of l amino acids to their d configuration for the protein amino acid l isoleucine racemization occurs about only one of the two chiral carbon atoms this reaction epimerization proceeds from an initial dl ratio near zero to an equilibrium ratio of about 1 30 the reaction rate is controlled primarily by temperature and to a lesser degree by the nature of the proteins themselves a variable related to taxonomy and the extent of protein degradation analyzing monospecific samples minimizes the taxonomic variable the resolving power of dl ratios as relative age indices is a function of the reaction rate degree of natural variability and analytical uncertainty natural variability is defined as the spread in ratios in five well preserved shells of the same age from a single stratum and is primarily related to taxonomy it can range from 20 or more in taxa of low reliability to 1 in taxa of greatest integrity 5 to 10 is to be expected analytical uncertainty within a single laboratory is relatively insignificant amounting to no more than 2 but interlaboratory comparisons suggest caution in comparing ratios determined at different laboratories or by different techniques sampling appropriate portions of a shell is essential to minimize variability in dl ratios site temperature exerts the greatest control on reaction rate hence resolving power for tropical sites 25 c age differences 1 ka can be resolved within the holocene and ca 5 to 10 ka for older samples as the rate decreases equilibrium is attained after 150 to 300 ka the reaction rate is substantially lower at mid latitude sites ca 10 c where equilibrium requires about 2 ma and resolution within the last glacial cycle is no better than 10 to 20 ka arctic sites 10 c show almost no measurable racemization within the holocene and in extreme cases even within the last 100 ka equilibrium is not attained in 10 ma the extent of amino acid racemization epimerization in carbonate fossils provides chronological information for the critical time period beyond radiocarbon dating dl ratios can be used directly as relative age indices and with suitable calibration can provide reasonable estimates of absolute age and or effective diagenetic temperature improving the accuracy of racemization based age estimates requires a better understanding of racemization kinetics in carbonate systems

reconstruction of holocene monsoon history from the pearl river estuary southern china using diatoms and carbon isotope ratios this study employs a multiproxy approach in the reconstruction of holocene monsoon history from sedimentary sequences obtained from the pearl river estuary southern china a set of modern surface sediment samples were collected within and outside the estuary and a sediment core was obtained from the mouth of the estuary a range of modern environmental variables were recorded including water salinity summer winter and annual average and water depth the diatom results show a good relationship with water salinity with marine diatoms dominating the more distal samples from outside the main estuary and freshwater diatoms dominating the proximal samples influenced by higher freshwater flux this pattern is matched by the bulk organic carbon isotopes the isotope values vary between 21 1 0 3 0 for samples from the fully marine environment between 23 2 0 8 and 23 7 0 8 for samples from the mid to outer estuary brackish water environment and less than 24 7 1 3 for samples from the inner estuary close to the freshwater sources similarly the c n ratios vary from below 7 0 6 in the marine end members to over 14 8 3 0 in the freshwater end members both the diatom and carbon data from the sediment core reveal a significant increase in freshwater flux from 8500 cal yr bp resulting from the enhanced summer monsoon regime in early holocene the strength of freshwater flux reached its highest between 7500 and 6000 cal yr bp in the last 6000 years freshwater flux decreased towards present reflecting a gradual weakening of the summer monsoon

sedimentary responses to holocene sea level change in a shallow marine environment of southern china abstract this study has examined how the sedimentary processes in the prevalent non deltaic coastal marine environments along the southeast coast of china have responded to sea level change and other environmental drivers during the holocene three sediment cores collected from a shallow marine embayment of the lantau island hong kong on the northern coast of the south china sea were analyzed the results of particle size total organic carbon content organic carbon and nitrogen ratios organic carbon stable isotope ratios abundance of alkenones and radiocarbon dating of these cores have helped reconstruct the sedimentary history of this site this history shares the similarity in sedimentary processes within the deltaic environment for the early holocene because palaeo incised channels exist in both environments the first 1500 years of deposition involved rapid channel infill caused by the rapidly rising sea level and strong monsoon driven discharge this was followed by a period of decelerated sedimentation under strong marine influence as the sea flooded the wide accommodation space in the subsequent two millennia major differences between the two environmental settings occur in the past 7000 years vertical accretion was seen in the non deltaic coastal environment whilst lateral shoreline advance was the dominant process in the deltaic basin the progressively slowing down in sedimentation rate in the non deltaic site during the middle and late holocene was caused by the reduced monsoon discharge intensified disturbance from tropical cyclone activity and coastal currents

traveling waves in the martian atmosphere from mgs tes nadir data abstract we have characterized the annual behavior of martian atmospheric traveling waves in the mgs tes data set from the first two martian years of mapping there is a high degree of repeatability between the two years they are dominated by strong low zonal wavenumber waves with high amplitudes near the polar jets strongest in late northern fall and early northern winter the m 1 waves have amplitudes up to about 20 k are vertically extended and occasionally extend even into the tropics periods for m 1 range from 2 5 to 30 sols much weaker waves were identified in the south with amplitudes less than about 3 5 k traveling waves with m 2 and m 3 are also seen but their amplitudes are typically limited to less than 4 k and are generally more confined near the surface in the north they are more evident in fall and spring rather than winter solstice which is clearly dominated by m 1 waves some evidence of storm tracks has been identified in the data with accentuated weather related temperature perturbations near longitudes 200 to 320 e for both the southern and northern hemispheres near latitude 65 at the surface some evidence was also found for a sharpening of longitudinal gradients into what may be frontal systems ep flux divergences show the waves extracting energy from the zonal mean winds when the m 1 waves were strongest decelerations of the zonal jet of order 30 m s sol were measured above 1 scale height the waves extract energy from the jet predominately through barotropic processes but their character is overall mixed barotropic baroclinic inertial instabilities may exist at altitude on the equatorward flanks of the polar jets and marginal stability extends through to the tropics this may explain the coordination of the tropical behavior of the waves with that centered along the polar jet consistent with the ideas expressed in wilson et al 2002 geophys res lett 29 1684 and similar to those in barnes et al 1993 j geophys res 98 3125 3148 throughout the year there exist large regions with the meridional gradient of pv less than zero but they are strongest near winter solstice poleward of the winter jet the regions of instability reach the surface equatorward they do not these regions satisfying a necessary criterion for instability likely explain the genesis of the waves and perhaps also their bimodal character between surface faster waves and altitude slow m 1 waves

the mars observer laser altimeter investigation the primary objective of the mars observer laser altimeter mola investigation is to determine globally the topography of mars at a level suitable for addressing problems in geology and geophysics secondary objectives are to characterize the 1064 nm wavelength surface reflectivity of mars to contribute to analyses of global surface mineralogy and seasonal albedo changes to assist in addressing problems in atmospheric circulation and to provide geodetic control and topographic context for the assessment of possible future mars landing sites the principal components of mola are a diode pumped neodymium doped yttrium aluminum garnet laser transmitter that emits 1064 nm wavelength laser pulses a 0 5 m diameter telescope a silicon avalanche photodiode detector and a time interval unit with 10 ns resolution mola will provide measurements of the topography of mars within approximately 160 m footprints and a center to center along track foot print spacing of 300 m along the mars observer subspacecraft ground track the elevation measurements will be quantized with 1 5 m vertical resolution before correction for orbit and pointing induced errors mola profiles will be assembled into a global 0 2 deg x 0 2 deg grid that will be referenced to mars center of mass with an absolute accuracy of approximately 30 m other data products will include a global grid of topographic gradients corrected individual profiles and a global 0 2 deg x 0 2 deg grid of 1064 nm surface reflectivity

an evolutionary model for the holocene formation of the pearl river delta china this paper reconstructs the evolutionary history of the pearl river delta over the last 9000 years and investigates land sea interaction in a large deltaic complex which formed under the influence

late quaternary land snails from the north coast of jamaica local extinctions and climatic change abstract analysis of the land snail faunas and chronology 14c and amino acid epimer ratios of six late quaternary deposits from a site on the north coast of jamaica provides a basis for reconstruction of local extinction events and their relation to paleoclimate paleotemperature estimates are derived from epimerization rates at an interior site and indicate an average holocene late last glacial temperature difference of c 4 5 c size variation in land snails indicates relatively dry conditions during the late last glacial and moist conditions in the late holocene followed by drier conditions beginning sometime during the last millennium the rich faunas of the latter half of the last glacial are represented today at the same site by only a relatively few remnant species two major periods of extinction are identified during latest last glacial to early holocene time a number of species became locally extinct probably due to increased temperatures many survive today in the cooler interior of the island extensive extinctions occurred again during the last millennium these apparently resulted largely from habitat disturbance by man a similar pattern of late holocene extinctions has also been documented for vertebrates on other tropical islands and is also thought to result from human disturbance

amino acid racemization of fossil bone abstract a study of aspartic acid racemization in different fractions of 51 fossil bones of various ages shows that the collagen rich fractions do manifest increasing d aspartic acid contents with increasing age no such correlation exists for the fractions rich in non collagenous proteins more collagen rich samples particularly from bones in older sites are needed to verify the generality of this trend

the significance of large sediment supply active tectonism and eustasy on margin sequence development late quaternary stratigraphy and evolution of the ganges brahmaputra delta abstract borehole data from the ganges brahmaputra delta system unveil an intriguing late quaternary history controlled by immense sediment discharge tectonics and eustasy sea level first intersected a major portion of the lowstand surface 10 000 11 000 cal yr bp marking the onset of sediment trapping and delta growth despite rapid sea level rise 1 cm yr sediment load was sufficient to maintain relative shoreline stability during this time by 7000 cal yr bp accommodation was quickly infilled with slowed sea level rise leading to upstream channel migration and widespread dispersal of sands this forced coastal progradation along the western delta front where the ganges was situated and much of the river s fine grained discharge bypassed the subaerial delta and formed a prograding deltaic clinoform on the shelf concurrently brahmaputra sediments were sequestered to an inland tectonic basin thus starving the adjacent shoreline and leading to transgression along the eastern delta by 5000 cal yr bp the two rivers had migrated or changed course to discharge along the eastern delta shoreline which began to prograde into what is now the modern river mouth estuary present delta configuration appears to have developed by 3000 cal yr bp evolution of the tectonically active ganges brahmaputra g b system reveals important similarities and differences with other deltas overall facies succession follows that of basic models progressing from an alluvial valley to coastal marine delta front to a prograding subaerial delta plain however the timing thickness and controls of these deposits differ immense sediment discharge from the ganges and brahmaputra rivers allowed initial delta growth 2000 3000 yr earlier than the global average despite debouching onto a canyon incised high energy margin subsequently a thick 50 m transgressive systems tract was formed during the early holocene phase of delta aggradation contrasting with extensive shoreline retreat documented along most margins highstand progradation of coastal and shelf sequences ensued by the middle holocene but subsiding inland basins also favored accumulation of a thick to 40 m highstand sequence in the lower floodplains unlike many other delta systems subsidence in the subaerial g b delta is not dominated by compaction but rather by plate driven tectonic processes that generate rates up to 4 mm year overall the huge sediment load tectonic subsidence major seismic events and a nearshore canyon system have led to widespread sediment dispersal and sequence formation across the subaerial delta shelf and deep sea bengal fan throughout the late quaternary

distal mud deposits associated with the pearl river over the northwestern continental shelf of the south china sea abstract continental shelf mud deposits represent an important archive of the holocene earth history such deposits are usually associated with large rivers that transport a large quantity of suspended sediment the pearl river has formed a distal shore parallel holocene mud deposit on the northwestern continental shelf of the south china sea investigations into its spatial distribution and evolutionary history are necessary for an improved understanding of such sedimentary systems seabed sediment sampling in situ tidal cycle measurements seismic survey and the associated data analyses reveal that the distal mud deposit associated with the pearl river occupies an area of approximately 8 87 10 3 km 2 with a modern deposition rate of 1 27 to 5 66 mm yr 1 evidence from sediment balance environmentally sensitive components sediment transport processes and regional shelf circulation patterns indicates that the pearl river is a major sediment source for the mud deposit this distal mud deposit represents an initial stage of its development the fining upward pattern and the negative skewness values in the layer are indicative of the pearl river influence and the 210 pb age is younger than 10 2 yr the main body of the holocene deposit of the region is not related directly to the modern pearl river sediment for most of the holocene periods the pearl river has been trapping the sediment to fill its extensive estuarine waters and therefore the formation of the distal mud is a recent event a regional characteristic is that the timing of the formation of distal muds associated with large rivers depends on the estuarine morphological evolution and the quantity of sediment discharge

transient eddies in the southern hemisphere of mars 1 mars global surveyor is providing the first observations of transient eddies in the southern hemisphere of mars we derive basic properties of the traveling eddies that appear in midwinter ls 134 148 through analysis of radio occultation measurements at 67 70 s latitude the dominant mode has a period of 2 solar days and a zonal wavenumber s 3 strong zonal variations in eddy amplitude signal the presence of a possible storm zone at 150 330 e longitude within this longitude band the eddies achieve peak amplitudes at the 300 pa pressure level of 7 k in temperature and 10 15 m s 1 in meridional wind speed the minimum temperature associated with the eddies is 2 k colder than saturation of co2 close to the threshold where nucleation and growth of new ice particles can occur a simulation by a mars general circulation model produces traveling eddies that closely resemble the observations

the huanghe yellow river and changjiang yangtze river deltas a review on their characteristics evolution and sediment discharge during the holocene abstract today asian rivers play an important role in delivering sediment from the land to the oceans however past sediment discharge before human activities modified the landscape is not well known and is estimated to have been roughly one third to one half of the present level chinese rivers have been strongly influenced by human activities and their sediment discharge has changed over the last 6000 years for the study of the long term human impact on rivers and catchment basins chinese rivers provide excellent examples because continuous historical records are available here the characteristics evolution and sediment discharge during the holocene of the deltas of two large chinese rivers huanghe yellow river and changjiang yangtze river are summarized the huanghe and changjiang deltas are different with respect to coastal environments water and sediment discharge the pattern of development of the delta lobe thickness of holocene sediments and basal topography of the incised valleys formed during the last glacial period the huanghe delta is characterized by a high concentration of sediment huge sediment discharge thin holocene deltaic sediments a lateral delta lobe shift and a steep longitudinal profile in its lower reaches the changjiang delta is characterized by a large water discharge a large interseasonal water level change a tide dominated coastal environment continuous seaward progradation with isolated river mouth sand bodies thick holocene sediments and a deep incised valley formed during the last glacial period based on the sediment volume of prograding deltaic sediments over the last 6000 years the sediment discharge of huanghe 1000 years ago is estimated to have been 1 10 8 tons year 1 10 of the present level an abrupt increase occurred at ca 1000 years ago as a consequence of human activities on the loess plateau especially involving cultivation and deforestation moreover the estimated sediment load of huanghe at sanmenxia station prior to 1000 years was 2 7 4 0 10 8 tons year or about 20 15 25 of the present level our recent study estimated that the sediment discharge of changjiang before 2000 years bp was ca 2 4 10 8 tons year total sediment discharge of both rivers before 2000 years bp is estimated to have been 3 4 10 8 tons year or only about 20 of the present level moreover the total sediment load to the lower reaches is estimated to have been 5 6 10 8 tons year or one fourth the present level

holocene evolution of the song hong red river delta system northern vietnam abstract the song hong red river delta located on the western coast of the gulf of bac bo tonkin in the south china sea formed as a result of the song hong sediment discharge throughout the holocene the river s sedimentary basin upstream from the delta plain is not large the delta plain comprises emerged tidal mangrove flats formed during the sea level highstand at 2 3 m 6 4 cal kyr bp and a beach ridge strandplain with straight to lobate beach ridges on the landward and seaward sides of the delta plain respectively the delta affords us the opportunity to examine river mouth morphodynamics comprehensively in relation to sediment discharge and sea level changes in this paper we describe the holocene evolution of the song hong delta system and the river mouth morphodynamics on the basis of seven sediment cores each 30 70 m long taken from the delta plain during 1999 2001 and 101 radiocarbon dates obtained from the core sediments sediments from the seven cores consisting of incised valley fills since the last glacial maximum can be divided in ascending order into fluvial sediments composed of gravelly sand and mottled clay tide influenced estuarine sediments containing shell and wood fragments and deltaic sediments composed of tide influenced sand and mud deposits in which the contents of sand and wood fragments increase upward by applying sequence stratigraphic concepts a transgressive surface can be identified at the gravelly sand mottled clay boundary and the maximum flooding surface can be identified at the estuarine deltaic sediments boundary the lowstand systems tract transgressive systems tract and highstand systems tract record 15 15 9 and 9 0 cal kyr bp respectively during the past 9 kyr the majority of the sediment discharged by the song hong accumulated in the incised valley and enhanced progradation at the river mouth the river mouth prograded from the bay head toward the gulf and its morphology changed from funnel shaped 9 6 cal kyr bp to straight 6 2 cal kyr bp and finally to lobate 2 0 cal kyr bp the morphological change from a funnel shaped to straight coast is interpreted to have been closely related to a hydrologic regime shift from a tide dominated bay head setting to a wave influenced open coast setting the cessation of the sea level rise at 6 cal kyr bp may have played only a small role in the change of river mouth morphology because the progradation rate decelerated from 22 to 4 m yr instead of accelerating at that time the river mouth morphodynamic change from straight to lobate was largely caused by an increase in the song hong sediment discharge from 17 27 9 2 cal kyr bp to 49 million t yr 2 0 cal kyr bp as a result of anthropogenic deforestation along the upper reaches of the song hong

further observations of regional dust storms and baroclinic eddies in the northern hemisphere of mars abstract we have investigated the near surface meteorology in the northern hemisphere of mars through detailed analysis of data obtained with mars global surveyor in january august 2005 the season in the northern hemisphere ranged from midsummer through winter solstice of mars year my 27 we examined composite wide angle images from the mars orbiter camera and compiled a catalog of the dust storms that occurred in this interval as in previous martian years activity in the northern hemisphere was dominated by regional flushing dust storms that sweep southward through the major topographic basins most frequently in acidalia planitia we also used atmospheric profiles retrieved from radio occultation experiments to characterize eddy activity near the surface at high northern latitudes there are strong correlations between the two sets of observations which allowed us to identify three factors that influence the timing and location of the regional dust storms 1 transitions among baroclinic wave modes which strongly modulate the intensity of meridional winds near the surface 2 storms zones which impose strong zonal variations on the amplitude of some baroclinic eddies and 3 stationary waves which further modulate the wind field near the surface the flushing dust storms ceased abruptly in midautumn possibly in response to source depletion co 2 condensation a shift in the period of the baroclinic eddies and changes in the tidal wind field near the surface our results extend the meteorological record of the northern hemisphere substantiate the findings of previous investigations and further illuminate the climatic impact of baroclinic eddies