late quaternary palaeoenvironmental change in the year round rainfall zone of south africa derived from peat sediments from vankervelsvlei abstract due to the scarcity of natural archives for palaeoenvironmental studies the climatic evolution of south africa during the late quaternary remains the subject of considerable debate peat deposits provide excellent archives to investigate past environmental and climate variability vankervelsvlei a fen near the southern cape coast located 152 m above mean sea level within the year round rainfall zone of south africa is ideally suited to investigate past environmental changes in this region a 14 6 m long sediment sequence was retrieved from the fen from which 8 85 m of sediment have been analysed using a multi proxy approach this includes elemental macrofossil and micropalaeontological analyses as a novelty in palaeoenvironmental reconstruction in this region leaf wax n alkanes and their compound specific stable carbon and hydrogen isotopes were also investigated the chronology of the sequence is based on 13 radiocarbon ages and reveals a basal age of 37 430 1 570 1 710 cal bp the top of the investigated sequence has an age of 1 180 340 170 cal bp leaf wax n alkane abundances and their compound specific stable carbon and hydrogen isotopes as well as various in organic bio geochemical parameters indicate that the older section of the sequence 37 430 1 570 1 710 28 050 510 600 cal bp which is composed of strongly degraded peat represents a rather dry phase during mis 3 this is followed by a hiatus of around 20 000 years 28 050 510 600 to 8 360 730 810 cal bp reflecting the driest conditions during mis 2 by comparing to supra regional archives this is hypothesised to have resulted from a larger extension of the antarctic sea ice which caused an equatorward shift of the westerlies blocking the tropical easterlies and resulting in drier conditions along the south coast and the adjacent coastal platform during the early holocene the input of reworked soil into the depression and subsequently renewed peat formation from 6 820 305 365 cal bp to 1 180 340 170 cal bp in vankervelsvlei point to moister climatic conditions contraction of antarctic sea ice and a poleward shift of the westerlies during the holocene is consistent with this interpretation climatic driving forces are suggested to differ between centennial millennial and orbital time scales evapotranspirative enrichment through stronger winds is assumed to be the main driver on centennial to millennial time scale within this hydrological system however a combination of evapotranspiration and precipitation amount seems to be the most prominent driver on the orbital time scales

holocene palaeoclimates from peat stratigraphy macrofossil proxy climate records from three oceanic raised bogs in england and ireland quantified analyses of plant macrofossil remains have been made from three profiles of peat from raised bogs spanning a distance of 425 km from western ireland to northern england the reconstructed vegetation of each profile is related to changing bog surface wetness bsw and since the bogs are ombrotrophic these bsw changes are interpreted in terms of changing climate using age depth models based on a total of 49 radiocarbon dates a number of wetter and drier phases are identified and phase shifts to wetter and or cooler climates are defined prominent coincident changes to wetter conditions are dated in at least two of the profiles to ca 4400 4000 1750 1400 and 1000 cal bp and in all three profiles at 3200 2750 2350 2250 and around 700 cal bp these phases are related to proxy climate changes in other terrestrial data sets from northwest europe and a broad degree of synchroneity is demonstrated

flow of dense avalanches past obstructions one means of preventing areas from being hit by avalanches is to divert the flow by straight or curved walls or tetrahedral or cylindrical type structures thus there arises the question how a given avalanche flow is changed regarding the diverted flow depth and flow direction in this paper a report is given on laboratory experiments performed for gravity driven dense granular flows down an inclined plane obstructed by plane wall and tetrahedral wedge it was observed that these flows are accompanied by shocks induced by the presence of the obstacles these give rise to a transition from super to subcritical flow of the granular avalanche associated with depth and velocity changes it is demonstrated that with an appropriate shock capturing integration technique for the savage hutter theory the shock formation for a finite mass granular flow sliding from an inclined plane into a horizontal run out zone is well described as is the shock formation of the granular flow on either side of a tetrahedral protection structure

late quaternary paleotemperatures derived from a speleothem from cango caves cape province south africa abstract an oxygen isotope temperature record over a large part of the past 30 000 yr has been obtained for the southern cape province of south africa by combining data on the isotopic composition of a stalagmite from a deep cave with that of a confined groundwater aquifer in the same region results show that temperatures during the last glacial maximum were on average about 6 c lower than those today with peaks up to 7 c lower a detailed analysis of the past 5000 yr suggests multiple fluctuations with generally lower temperatures 1 2 c around 4500 and 3000 yr b p the carbon isotopic composition of the stalagmite indicates significant vegetation changes between the late pleistocene and today and also during the second half of the holocene

n alkan 2 one biomarkers as a proxy for palaeoclimate reconstruction in the mfabeni fen south africa abstract the sub tropical mfabeni fen is the only continuous coastal peat deposit that documents glacial and interglacial palaeoenvironmental conditions since the late pleistocene ca 47 cal kyr bp in southern africa published bulk geochemical biomarker and leaf wax 13c data along with palynology and stratigraphic studies of the mfabeni peat sequence render it an ideal record for testing new palaeoreconstruction proxies in this study we aimed to establish the proxy potential of n alkan 2 one n ket compounds by tracing their source origin and post depositional diagenetic change and if they preserve or not a robust palaeoenvironment signal that complements our understanding of palaeoclimatic variations in the mfabeni archive the most likely source for n kets is via microbial decarboxylation of n 1 alkanoic acids n fas and to a lesser degree oxidation of same chain length n alkanes n alks the n ket average chain length aclket and n c23 and c25ket precursor ratios displayed a statistical significant negative relationship with the n alk aquatic plant proxy paq suggesting the source of n kets to be submerged aquatic plants during waterlogged conditions that suppressed microbial activity during the ensuing anoxic conditions both the mid chain and long chain n ket precursor ratios displayed predominant water level fluctuation controls with temperature as a secondary regulator by comparing the n ket data with published environmental and climate reconstructions from the same core and with geomorphology and palynological studies of the mfabeni basin we conclude that the n kets show promise as a palaeoclimate proxy and can be used in conjunction with other biomarker proxies to reconstruct ancient hydrological changes in sub tropical peatlands

reconstruction of millennial changes in dust emission transport and regional sea ice coverage using the deep epica ice cores from the atlantic and indian ocean sector of antarctica continuous sea salt and mineral dust aerosol records have been studied on the two epica european project for ice coring in antarctica deep ice cores the joint use of these records from opposite sides of the east antarctic plateau allows for an estimate of changes in dust transport and emission intensity as well as for the identification of regional differences in the sea salt aerosol source the mineral dust flux records at both sites show a strong coherency over the last 150 kyr related to dust emission changes in the glacial patagonian dust source with three times higher dust fluxes in the atlantic compared to the indian ocean sector of the southern ocean so using a simple conceptual transport model this indicates that transport can explain only 40 of the atmospheric dust concentration changes in antarctica while factor 5 10 changes occurred accordingly the main cause for the strong glacial dust flux changes in antarctica must lie in environmental changes in patagonia dust emissions hence environmental conditions in patagonia were very similar during the last two glacials and interglacials respectively despite 2 4 c warmer temperatures recorded in antarctica during the penultimate interglacial than today 2 3 times higher sea salt fluxes found in both ice cores in the glacial compared to the holocene are difficult to reconcile with a largely unchanged transport intensity and the distant open ocean source the substantial glacial enhancements in sea salt aerosol fluxes can be readily explained assuming sea ice formation as the main sea salt aerosol source with a significantly larger expansion of summer sea ice in the weddell sea than in the indian ocean sector during the penultimate interglacial our sea salt records point to a 50 reduction of winter sea ice coverage compared to the holocene both in the indian and atlantic ocean sector of the so however from 20 to 80 ka before present sea salt fluxes show only very subdued millennial changes despite pronounced temperature fluctuations likely due to the large distance of the sea ice salt source to our drill sites

insolation values for the climate of the last 10 million years new values for the astronomical parameters of the earth s orbit and rotation eccentricity obliquity and precession are proposed for paleoclimatic research related to the late miocene the pliocene and the quaternary they have been obtained from a numerical solution of the lagrangian system of the planetary point masses and from an analytical solution of the poisson equations of the earth moon system the analytical expansion allows the direct determination of the main frequencies with their phase and amplitude numerical and analytical comparisons with the former astronomical solution ber78 are performed so that the accuracy and the interval of time over which the new solution is valid can be estimated the corresponding insolation values have also been computed this analysis leads to the conclusion that the new values are expected to be reliable over the last 5 ma in the time domain and at least over the last 10 ma in the frequency domain

climate and vegetation history from a 14 000 year peatland record kenai peninsula alaska abstract analysis of pollen spores macrofossils and lithology of an ams 14c dated core from a subarctic fen on the kenai peninsula alaska reveals changes in vegetation and climate beginning 14 200 cal yr bp betula expansion and contraction of herb tundra vegetation characterize the younger dryas on the kenai suggesting increased winter snowfall concurrent with cool sunny summers remarkable polypodiaceae fern abundance between 11 500 and 8500 cal yr bp implies a significant change in climate enhanced peat preservation and the occurrence of wet meadow species suggest high moisture from 11 500 to 10 700 cal yr bp in contrast to drier conditions in southeastern alaska this pattern may indicate an intensification and repositioning of the aleutian low al drier conditions on the kenai peninsula from 10 700 to 8500 cal yr bp may signify a weaker al but elevated fern abundance may have been sustained by high seasonality with substantial snowfall and enhanced glacial melt decreased insolation induced seasonality resulted in climatic cooling after 8500 cal yr bp with increased humidity from 8000 to 5000 cal yr bp a dry interval punctuated by volcanic activity occurred between 5000 and 3500 cal yr bp followed by cool moist climate coincident with neoglaciation tsuga mertensiana expanded after 1500 cal yr bp in response to the shift to cooler conditions

the geomorphologic evolution of the wilderness dune cordons south africa abstract the wilderness dune cordons consist of steep sided ridges up to 207 m high separated by coastal lakes they probably formed during the sea level highstands of the pleistocene interglacials three major dune cordons are developed there is an additional huge coalesced mass of older fossil dunes landward of these cordons forming hills up to 340 m high in places lying on the coastal platform 150 260 m generally locally 210 260 m the dunesand reaches thicknesses in excess of 300 m the cordons form by accretion of transgressive dunefields and large compound imbricate parabolic dunes an individual cordon can result from numerous phases of dune formation during periods of sea level highstand the dunes of the present interglacial are mostly accreting on top of the seaward cordon which was initiated during the last interglacial during the complex sea level history there have been numerous phases of dune building followed by coastal erosion that formed seacliffs in the dune cordons in some areas almost all the cordon was subsequently eroded away these fossil seacliffs form large steep seaward facing slopes parallel to the present coastline and form a major element in the morphology of the cordons trailing arms of parabolic dunes form another major topographic element oriented at 15 30 to the shoreline river erosion has altered the cordon morphology in places the geomorphology of the cordons is thus a function primarily of dune cordon construction accentuated by coastal erosion in the form of cliff cutting secondarily of dune morphology and thirdly of fluvial erosion the evolution of the cordons can be dated tentatively using palaeontologic stratigraphic and sediment dynamic data the seaward cordon formed during the eem and holocene a fairly reliable dating the middle cordon probably formed between 200 500 ka and the landward cordon probably formed between 600 900 ka the coalesced dune deposits lie inland of the cordons and are thus older this would place the minimum age of the younger coalesced dune deposits in the middle pleistocene about 1000 ka early miocene fossil plant remains in the knysna lignites which underlie the older coalesced dunes indicate their maximum possible age westerly winds dominated in the area for the past few million years

development and refinement of proxy climate indicators from peats peat especially from acidic mires bogs is a natural archive of past environmental change reconstructions of past climate from bogs commenced in the 19th century through examination of visible peat stratigraphy and later formed the basis for a postglacial climatic scheme widely used in northwest europe nevertheless misconceptions as to how bogs grow led to a 50 year lacuna in peat climate study before the concept of cyclic regeneration in bogs was refuted in recent decades research using proxy climate indicators from bogs has burgeoned a range of proxies for past hydrological change has been developed as well as use of pollen bog oaks and pines and other data to reconstruct past temperatures most of this proxy climate research has been carried out in northern europe but peat based research in parts of asia and north america has increased particularly during the last decade while research has also been conducted in australia new zealand and south america this paper reviews developments in proxy climate reconstructions from peatlands chronicles use of a range of palaeo proxies such as visible peat stratigraphy plant macrofossils peat humification testate amoebae and non pollen palynomorphs and explains the use of wiggle match radiocarbon dating and relationship to climate shifts it details other techniques being used increasingly such as biomarkers stable isotopes inorganic geochemistry and estimation of dust flux and points to new proxies under development although explicit protocols have been developed recently for research on ombrotrophic mires it must be recognised that not all proxies and techniques have universal applicability owing to differences in species assemblages mire formation topographic controls and geochemical characteristics

a multiproxy study of the ocean atmospheric forcing and the impact of sea level changes on the southern cape coast south africa during the holocene abstract a multiproxy approach focusing on biological proxies was undertaken to determine the influence of sea level changes along the southern cape coast and the variability of water masses over the central agulhas bank region during the holocene a 30 47 m sedimentary core extracted from the coastal lake eilandvlei shows continuous deposition for the last 9000 years microfossils were classified based on salinity and habitat diatoms were further defined by their temperature preferences as either warm or cold water species the composition of the assemblages is strongly linked to fluctuations in marine inflow into the system and the extent of freshwater inputs to the lake as recorded at the core site paleoproductivity improved during periods of equatorward migration of the westerlies notably from 5800 to 5000 cal yr b p when surface water mixing increased spectral analysis revealed periodicities associated with solar cycles namely gleissberg and de vries the system remained predominantly marine and submerged in response to an early mid holocene transgression until 4700 cal yr b p when sea level fluctuations and landscape modification restricted marine incursions modified the exposed landscape and shifted the system toward a lagoon state this multiproxy record provides insights into oceanic exchanges surface water conditions and the mechanisms that govern them during the holocene

holocene paleo climatic record from the south african namaqualand mudbelt a source to sink approach variations in the sediment input to the namaqualand mudbelt during the holocene are assessed using an integrative terrestrial to marine source to sink approach geochemical and sr and nd isotopic

holocene climate in the atlantic sector of the southern ocean controlled by insolation or oceanic circulation abstractthe holocene climate of the southern ocean is not well un derstood mainly because of the lack of high resolution reconstruc tions of ocean surface properties here we present a 12 500 yr long decadal scale record of holocene sea surface temperatures and sea ice presence from the polar front of the east atlantic southernocean the record shows gradual climate change with no abruptneoglacial cooling and an unprecedented late holocene warming the dominant forcing factor appears to be precessional insolation northern hemisphere summer insolation correlates to at least theearly to middle holocene climate trend spectral analysis revealscentennial scale cyclic climate changes with periods of 1220 1070 400 and 150 yr the record shows good correlation to east ant arctic ice cores and to climate records from south georgia andbunger oasis however the record shows out of phase behaviorwith regard to climate records from the western antarctic penin sula and the peru chile current such behavior hints at a climaticdivide through patagonia the drake passage and between westand east antarctica keywords southern ocean paleoclimate diatoms modern analogtechnique holocene insolation antarctic polar front introductionthe holocene climate variability has received less attention thanthe more dramatic changes during the last glacial period the holoceneis generally assumed to be a stable interglacial period when climatechanges in the north atlantic are transmitted to the rest of the worldthrough a strong thermohaline circulation imbrie et al 1992 thelarge uctuations of the last glacial period appear to continue into thisinterglacial although in a subdued manner bond et al 2001 the southern ocean has received even less attention than the highnorthern latitudes oceanic records are few and coarse they generallydisplay a warm early holocene followed by cooling labracherie etal 1989 pichon et al 1992 hodell et al 2001 similar to northatlantic climate e g koc and jansen 1994 high resolution recordsare restricted to antarctic ice cores which mostly display little climatevariability during the holocene jouzel et al 2001 an exception isthe taylor dome deuterium record in which the holocene appears tobe split by an abrupt cooling event ca 5 5 5 ka steig et al 1998 this cooling appears to t the late holocene global cooling trend por ter 2000 as a nonlinear response from the climate system to insolationchanges demenocal et al 2000 hodell et al 2001 high resolution holocene records available for southern oceanclimate reconstruction are rarely from the antarctic circumpolar cur rent proper e g domack et al 2001 stenni et al 2001 lamy et al 2002 with the exception of a multiproxy approach to holocene cli mate that includes a high resolution description of lithic fragments hodell et al 2001 we present data from site tn057 17 near the polar front in theeast atlantic southern ocean it is based on quantitative estimates ofsummer sea surface temperature ssst and sea ice presence sip utilizing the down core variability of diatom assemblages the recordshows good correlation to antarctic ice cores but a gradual change inphase relationships during the early holocene the record shows anin phase relationship with the ross sea region ice cores during thelate holocene the record shows an in phase relationship with the eastantarctic region ice cores antarctic polar frontthe antarctic polar front apf fig 1 is an important climateboundary in terms of air sea uxes and the heat and salt budgets ofthe oceans at the surface the apf is a steep sea surface temperaturegradient while the subsurface expression is the southern limit for sub duction of cold fresh antarctic surface water below warmer and moresaline subantarctic surface water orsi et al 1995 globally the apfcould be the southern limit of synchrony with northern hemisphereclimate broecker 1996 the apf is subject to large spring and sum mer blooms of diatoms fischer et al 2002 and achieves the largestbiogenic sedimentation rates of the diatom ooze belt of the southernocean burckle and cirilli 1987 it is these high sedimentation ratesof diatomaceous oozes and the sensitivity of diatoms especially to lightand temperature that make sites in the apf region suitable for pro ducing high resolution records of climate change

holocene climate change in southernmost south africa rock hyrax middens record shifts in the southern westerlies abstract south africa s southern coastal margin is recognised as being a highly dynamic climatic region that plays a critical role in both regional and global atmospheric and oceanic circulation dynamics our understanding of the past dynamics of this system however has been limited by the number and nature of datasets available that can be used to infer changes in key climatic parameters in the region in this paper we present new high resolution 13c and 15n data from two independently dated rock hyrax procavia capensis middens from seweweekspoort in south africa s groot swartberg mountains these data provide information regarding both past vegetation and hydroclimatic change and allow a regional integration of available data that explore the long term dynamics of mid latitude circulation systems in the african sector of the southern hemisphere combined a negative relationship is apparent between temperature and humidity in this area of the southern cape and these changes can for the first time be clearly linked to variations in antarctic sea ice extent and shifts in the southern westerly storm track this dynamic is particularly evident between 5 and 7 cal kbp when a reduction in sea ice extent and a southward shift of the westerlies are manifested regionally by increased temperatures and a phase of marked aridity

abrupt cooling of antarctic surface waters and sea ice expansion in the south atlantic sector of the southern ocean at 5000 cal yr b p antarctic surface waters were warm and ice free between 10 000 and 5000 cal yr b p as judged from ice rafted debris and microfossils in a piston core at 53 s in the south atlantic this evidence shows that about 5000 cal yr b p sea surface temperatures cooled sea ice advanced and the delivery of ice rafted detritus ird to the subantarctic south atlantic increased abruptly these changes mark the end of the hypsithermal and onset of neoglacial conditions they coincide with an early neoglacial advance of mountain glaciers in south america and new zealand between 5400 and 4900 cal yr b p rapid middle holocene climate changes inferred from the taylor dome ice core antarctica cooling and increased ird in the north atlantic and the end of the african humid period the near synchrony and abruptness of all these climate changes suggest links among the tropics and both poles that involved nonlinear response to gradual changes in northern hemisphere insolation sea ice expansion in the southern ocean may have provided positive feedback that hastened the end of the hypsithermal and african humid periods in the middle holocene

last glacial sea surface temperatures and sea ice extent in the southern ocean atlantic indian sector a multiproxy approach 1 on the basis of the quantitative study of diatom radiolarian and planktic foraminiferal assemblages we estimated summer sea surface temperature ssst and sea ice extent at 50 sediment core localities in the atlantic and western indian sector of the southern ocean to reconstruct the last glacial environment at the glamap 18 to 15 ka equal to 21 500 to 18 000 calendar cal years bp and epilog 19 5 to 16 0 ka equal to 23 000 to 19 000 cal years bp time slices stratigraphic identification of the time slices was accomplished by a combination of ams 14c measurements benthic isotope and siliceous microfossil abundance records while the ssst estimates reveal greater surface water cooling than reconstructed by climap 1981 reaching a maximum in the area of the present subantarctic zone the sea ice reconstruction indicates that climap overestimated the expansion of the antarctic sea ice field especially for austral summer during winter the sea ice field was expanded by 60 70 compared to the present last glacial summer sea surface isotherms indicate a northward shift of the zonal bands of the antarctic circumpolar current and a relative expansion of the cold water realm south of the subantarctic front by 5 in latitude this coincides with a northward displacement of the zone of enhanced biogenic silica deposition and iceberg occurrence as a result of northward expansion of antarctic cold waters and a relatively small displacement of the subtropical front thermal gradients were steepened during the last glacial in the area of the present subtropical front the northward displacement of antarctic cold waters and the related deflection of southern ocean waters along the eastern boundary of south america may have resulted in a weakened cold water route across the drake passage in contrast the transport of warm and salty surface water from the indian into the atlantic ocean via the warm water route was not blocked allowing continuous but reduced import of heat into the south atlantic

a late quaternary pollen sequence from mfabeni peatland south africa reconstructing forest history in maputaland abstract this paper documents a continuous 44 000 yr pollen record derived from the mfabeni peatland on the maputaland coastal plain a detailed fossil pollen analysis indicates the existence of extensive podocarpus abundant coastal forests before 33 000 cal yr bp the onset of wetter local conditions after this time is inferred from forest retreat and the development of swampy conditions conditions during the last glacial maximum 21 000 cal yr bp are inferred to have been colder and drier than the present as evidenced by forest retreat and replacement of swampy reed sedge communities by dry grassland forest growth and expansion during the holocene altithermal 8000 6000 cal yr bp indicates warm relatively moist conditions previous records from maputaland have suggested a northward migration of podocarpus forest during the late holocene however we interpret a mid holocene decline in podocarpus at mfabeni as evidence of deforestation forest clearance during the mid holocene is supported by the appearance of morella serrata suggesting a shift towards more open grassland savanna possibly due to burning these signals of human impact are coupled with an increase in acacia indicative of the development of secondary forest and hence disturbance

influence of agulhas forcing of holocene climate change in south africa s southern cape this paper analyses a series of high quality continuous records from southeastern africa to study the spatiotemporal patterning of holocene hydroclimatic anomalies in the region results indicate dominant frequencies of variability at millennial time scales and a series of anomalies broadly common to all records of particular interest data from the southern cape coast exhibit periods of wetter drier conditions that are out of phase with the sites less than 150 km away in the adjacent interior but in phase with sites in tropical regions over 1000 km to the northeast to explain such spatial patterns and gradients we propose that the agulhas current may be a critical vector by which tropical climatic signals are propagated along the littoral zone exerting a dominant highly localized influence on near coastal environmental conditions limitations in the data available do not allow for a detailed examination of the climatic dynamics related to these phenomena but this paper highlights a series of avenues for future research to clarify the spatial extent and stability of the patterns observed

limiting stress states in granular avalanches the savag e hutter theory for granular avalanches assumes that the granular material is in either of two limiting stress states depending on whether the motion is convergent or divergent at transitions between convergent and divergent regions ajump in stress occurs which necessarily implies that there is ajump in the ava lanche velocity and or its thickness in this paper a regularization scheme is used which smoothly switches from one stress state to the other and avoids the generation of such singular surfaces the resulting algorithm is more stable than previous numerical meth ods but shocks can still occur during rapid convergence in the run out zone results are presented from two di mensional calculations on complex geometry which illustrate that some necking features observed in laboratory experiments can be explained by the regu larized savage rutter model

late quaternary dynamics of southern africa s winter rainfall zone abstract variations in the nature and extent of southern africa s winter rainfall zone wrz have the potential to provide important information concerning the nature of long term climate change at both regional and hemispheric scales positioned at the interface between tropical and temperate systems southern africa s climate is influenced by shifts in the intertropical convergence zone the westerlies and the development and position of continental and oceanic anticyclones over the last glacial interglacial cycle substantial changes in the amount and seasonality of precipitation across the subcontinent have been linked to the relative dominance of these systems central to this discussion has been the extent to which the region s glacial climates would have been affected by expansions of antarctic sea ice equatorward migrations of the westerlies more frequent intense winter storms and an expanded wrz this paper reviews the developing body of evidence pertaining to shifts in the wrz and the evolution of ideas that have been presented to explain the patterns observed dividing the region into three separate axes along the western and southern margins of the continent and across the interior into the karoo and the kalahari a range of evidence from both terrestrial sites and marine cores is considered and potential expansions of the wrz expansions are explored despite the limitations of many of the region s proxy records a coherent pattern has begun to develop of a significantly expanded wrz during phases of the last glacial period with the best documented being between 32 17 ka while more detailed inferences will require the recovery and analysis of longer and better dated records this synthesis provides a new baseline for further research in this key region

climate variability at the southern boundaries of the namib southwestern africa and atacama northern chile coastal deserts during the last 120 000 yr abstract in this study we present grain size distributions of the terrigenous fraction of two deep sea sediment cores from the se atlantic offshore namibia and from the se pacific offshore northern chile which we unmix into subpopulations and which are interpreted as coarse eolian dust fine eolian dust and fluvial mud the downcore ratios of the proportions of eolian dust and fluvial mud subsequently represent paleocontinental aridity records of southwestern africa and northern chile for the last 120 000 yr the two records show a relatively wet last glacial maximum lgm compared to a relatively dry holocene but different orbital variability on longer time scales generally the northern chilean aridity record shows higher frequency changes which are closely related to precessional variation in solar insolation compared to the southwestern african aridity record which shows a remarkable resemblance to the global ice volume record we relate the changes in continental aridity in southwestern africa and northern chile to changes in the latitudinal position of the moisture bearing southern westerlies potentially driven by the sea ice extent around antarctica and overprinted by tropical forcing in the equatorial pacific ocean

climatic and sea level controls on late quaternary eolian activity on the agulhas plain south africa abstract located at the interface between the temperate westerly and sub tropical climate systems south africa s winter rainfall zone wrz is a key location in understanding late quaternary atmospheric circulation dynamics inactive eolian deposits in the wrz comprising pan fringing lunette and coastal dunes were investigated to establish their depositional ages and utility as paleoenvironmental indicators the resulting optical luminescence chronology reveals episodic lunette accretion at 60 000 45 000 yr 12 000 13 000 yr 2800 2600 yr 1200 yr and episodes of lunette and coastal dune accretion on the agulhas plain are temporally distinct reflecting differing fundamental controls on their activity comparisons to previously published data also reveal that the lunettes differ in age from more ancient coastal eolianites lunette deposition is asynchronous between locations reflecting the topographic and hydrological setting of the individual pans in near coastal settings with limited surface recharge lunette accretion appears to be at least partially controlled by sea level induced changes in groundwater levels those pans with more significant surface recharge particularly from fluvial systems may produce less ambiguous paleoenvironmental records with pan status more strongly reflecting regional hydrological conditions lunette orientation is indicative of strong westerly winds during both the pleistocene and holocene lunette accretion would have been promoted by reduced on shore moisture transport during the summer months enhancing rainfall seasonality such conditions would have been promoted by increased continentality as the agulhas bank was exposed during low sea level stands

ice sheets and sea level of the last glacial maximum this paper outlines the general issues regarding ice sheets and sea level of the last glacial maximum lgm which formed the basis of an epilog project workshop papers in this special issue of quaternary science reviews provide a comprehensive assessment of these issues from the perspective of geological reconstructions of ice sheet extent records of sea level change ice sheet modelling geophysical models of glacial isostatic adjustment and geochemical proxies of ice volume this new assessment has substantially narrowed the uncertainties in the total changes in ice sheets and sea level and their proxies suggesting a net decrease in eustatic sea level at the lgm ranging from 120 to 135 m r 2001 elsevier science ltd all rights reserved

late quaternary peat accumulation in southern africa abstract it is suggested that the accumulation of peat deposits and other organic sediment may be a clue to the timing of moister periods in the late quaternary climatic history of southern africa data presented from 26 sites across the sub continent point to two periods during which organic sedimentation commenced suggesting a moister late pleistocene and a period during the mid late holocene when conditions also became more conducive to peat formation owing to the confusing and conflicting nature of other palaeoenvironmental information organic sediment accumulation chronologies seem to provide additional insight into the environmental history of southern africa and the implications of this are discussed

unravelling extrinsic and intrinsic factors of the early palaeozoic diversification of blastozoan echinoderms abstract the subphylum blastozoa represents more than one third of the early palaeozoic echinoderm fauna a comprehensive database including all records of blastozoans was built to provide quantitative analyses of palaeogeography and diversity patterns and processes for the 10 classes currently included in this subphylum during the early palaeozoic the global pattern of taxonomic diversity shows two peaks during the cambrian series 3 and the late ordovician intervals in cambrian times the high taxonomic diversity seems to be related with a high turnover rate and a high endemicity of blastozoan genera whereas in ordovician times the rise in diversity is associated with a low endemicity and a low turnover rate the gradual increase of ordovician diversity can be explained by the progressive geographic extension of blastozoan genera onto most palaeocontinental margins associated to the long term gradual sea level rise this global pattern is subdivided into local trends to compare the relative influence of regional distributional patterns blastozoans occurred mainly on gondwanan and laurentian margins during the cambrian in both ordovician and silurian times blastozoans colonised different provinces characterised by varied latitudinal position and environmental conditions the laurentian province was mainly located in the equatorial latitudes temperate to warm waters mainly carbonate platforms and both the northwestern peri gondwanan and asian provinces in the intermediate to high latitudes temperate to cold water mainly siliciclastic environments after the hirnantian mass extinction blastozoans finally recovered chiefly on laurentian margins where climate and environmental conditions were probably more favourable the two diversification events recorded for blastozoans in the early palaeozoic concerned two distinct evolutionary faunas cambrian evolutionary fauna vs palaeozoic evolutionary fauna they were driven by distinct processes even if the ordovician diversification had indeed started during the middle furongian with a medium origination event difference in processes might be related to the evolution of global environmental climatic conditions coupled with the position of continental masses

a review of lower and middle palaeozoic biostratigraphy in west peninsular malaysia and southern thailand in its context within the sibumasu terrane abstract fossils from the cambrian to devonian rocks of southern thailand the langkawi islands mainland kedah perlis north perak and central west peninsular malaysia are listed and reviewed and their stratigraphy and correlation reassessed the hitherto anomalous record of the trilobite dalmanitina from malaysia is reviewed and found to be of latest ordovician hirnantian age rather than lower silurian age as previously reported and is considered a probable synonym of the widespread mucronaspis mucronata a new stratigraphical nomenclature is erected for part of the langkawi mainland kedah and perlis area successions in which the term setul limestone which stretched from the ordovician to the devonian is abandoned and replaced by the middle ordovician kaki bukit limestone the late ordovician and early silurian tanjong dendang formation the silurian mempelam limestone and the early devonian timah tasoh formation all underlying the paraconformity with the late devonian langgun red beds there was a single depositional basin in the generally shallow water and cratonic areas of southern thailand langkawi and mainland kedah and perlis in contrast to the deeper water basin of north perak only silurian rocks are dated with certainty within another basin in central west malaysia near kuala lumpur which were also cratonic and shallow water although to the east in west pahang there are basal devonian deeper water sediments with graptolites the area is reviewed in its position within the sibumasu terrane which in the palaeozoic also included central and northern thailand burma myanmar and southwest china part of yunnan province

the little ice age in the southern hemisphere in the context of the last 3000 years peat based proxy climate data from tierra del fuego the so called little ice age lia of the 15th to 19th centuries ad is well attested from much of europe and from some other parts of the northern hemisphere it has been attributed to solar forcing associated with reduced solar activity notably during the sporer maunder and dalton solar minima although other causes have also been proposed and feature strongly in recent papers detection of the lia in some proxy climate records from the southern hemisphere is less clear leading to suggestions that the lia was perhaps not a global phenomenon resolving this issue requires more data from the southern hemisphere we present proxy climate data plant macrofossils peat humification covering the past three millennia from an ombrotrophic mire peat bog in tierra del fuego southern south america but focus our discussion on the period traditionally associated with the lia during parts of this time the mire surface was apparently relatively dry compared with much of its 3000 year record it was report

the antarctic ice sheet during the last glacial maximum and its subsequent retreat history a review abstract an emerging body of evidence from studies of the last glacial interglacial cycle suggests that the east and west antarctic ice sheets have not advanced and retreated in concert the west antarctic ice sheet advanced to the outer shelf in most regions during the last glacial maximum lgm the retreat from the shelf commenced shortly after the lgm and continued into the late holocene the west antarctic ice sheet in ross and amundsen seas slid across a deforming bed at least during the final phases of extended glaciation this implies that at this time the ice sheet had a low profile differences in the number and locations of grounding zone wedges and smaller grounding zone features from trough to trough imply that individual west antarctic ice sheet ice streams retreated episodically details concerning the expansion retreat and behavior of the east antarctic ice sheet eais are more sparse the picture emerging is that the eais did not expand to the continental shelf edge during the lgm rather it achieved a maximum extent of a mid shelf position in some locations while in other areas the ice terminus was situated near its present location the timing of retreat along sectors within the eais appears diachronous and in places occurred prior to the lgm the antarctic peninsula shelf contained considerably more ice during the lgm than previously proposed the results presented in this paper support more recent published ice sheet models that call for greater contributions of melting ice from west antarctica including the antarctic peninsula to the post glacial rise in sea level

a synoptic decomposition of rainfall over the cape south coast of south africa a synoptic climatology is derived for the cape south coast region of south africa by application of the self organizing map som technique the som is applied to average daily low level circulation fields as represented by sea level pressure anomalies for the period 1979 2011 this coastal region receives rainfall all year round with slight peaks during march april and with more pronounced peaks during august and october november the synoptic forcing responsible for this annual multi modal rainfall distribution is identified and the relative contribution of different synoptic types to the annual rainfall is quantified ridging high pressure systems contribute to 46 of the annual rainfall while tropical temperate troughs contribute 28 cut off lows cols co occurring with ridging highs and tropical temperate troughs are associated with 16 of the annual rainfall total the contribution of ridging high pressure systems decreases from south to north whilst the opposite is true for tropical temperate troughs cols ridging high pressure systems and tropical temperate troughs are associated with the march april rainfall peak while cols are largely associated with the august rainfall peak ridging high pressure systems and to a lesser extent tropical temperate troughs are responsible for the october peak observed along the coast while the november peak over the adjacent interior regions is associated with cols that occur in combination with the tropical temperate troughs during this month

reconstructing the antarctic ice sheet at the last glacial maximum abstract a reconstruction of the antarctic ice sheet at the last glacial maximum lgm constrained by geologic data shows expansion across continental shelves accompanied by little inland change this added peripheral ice volume contributed 14 m to the lowering of eustatic sea level at the lgm of the total expansion one third took place in east antarctica and two thirds in west antarctica

relationship between antarctic sea ice and southwest african climate during the late quaternary here we compare late quaternary southwest african climate records from the west coast of southern africa published winter rainfall and trade wind intensity records from a core off the coast of namibia to records of antarctic sea ice extent this comparison reveals coherent changes between antarctic sea ice extent and the southwest african winter rain region since 45 k y b p with enhanced winter rainfall and trade wind vigor during periods of increased sea ice presence we propose an oceanic and atmospheric coupling between antarctic sea ice and the winter rainfall zone of southwest africa that may lead to increased desertification in the region if global warming persists

the evolution of coastal barrier systems a case study of the middle late pleistocene wilderness barriers south africa abstract barrier systems contain lengthy but complex records of long term environmental fluctuations the wilderness embayment south africa contains a system of shore parallel barriers reaching up to 200 m above modern sea level this study reports the results of chronological topographical both on and off shore sedimentological and micromorphological analyses within the wilderness embayment sixty one new luminescence ages from sixteen sites in unconsolidated dunes and three separate barriers are presented which when combined with previously published luminescence ages from the area provide a high resolution chronological framework for the emplacement and evolution of the barrier system the preserved barriers have been constructed within at least the last two glacial interglacial cycles with notable phases between 241 221 ka 159 143 ka 130 120 ka 92 87 ka and post 6 ka multiple phases of barrier construction occurred during sea level highstands with sediment deposition on each individual barrier occurring over at least two interglacials holocene evolution of the system sheds light on earlier events with dune preservation occurring only during early regression from the mid holocene highstand tectonic stability at wilderness allowed glacio eustatically formed shorelines to occupy similar positions on multiple occasions this in conjunction with a relatively humid climate and a well vegetated landscape enabled deflated sediment from beaches to form dunes which stacked upon each other to form an extensive and complex vertical accretionary sequence repeated erosion and recycling of pre existing barriers as well as barrier construction on what is currently the off shore platform during still stands in sea level regressional cycles when sea levels dropped below ca 50 m from the present day has added to the complexity of the preserved terrestrial barrier record the wilderness barrier system contrasts with barriers developed elsewhere in the world where higher rates of crustal uplift have allowed preservation of a more complete and more widely spaced palaeorecord this research also shows the utility of integrating off shore topography as revealed by bathymetry with terrestrial topographic data for the better understanding of the evolution of palaeo coastlines and the preserved dune record found on present day coastal plains local variation in the topography of the continental shelf at wilderness has generated spatial and temporal complexity within the sedimentary records of individual barriers as well as having a significant influence on preservation

geochemical records of palaeoenvironmental controls on peat forming processes in the mfabeni peatland kwazulu natal south africa since the late pleistocene the mfabeni peatland is the only known sub tropical coastal fen that transcends the last glacial maximum lgm this ca 10 m thick peat sequence provides a continuous sedimentation record spanning from the late pleistocene to present basal age c 47 kcal yr bp we investigated the paleaeoenvironmental controls on peat formation and organic matter source input at the mfabeni fen by 1 exploring geochemical records mass accumulation rate total organic carbon carbon accumulation rate delta c 13 delta n 15 and c n ratio to delineate primary production organic matter source input preservation and diagenetic processes and 2 employ these geochemical signatures to reconstruct the palaeoenvironmental conditions and prevailing climate that drove carbon accumulation in the peatland we established that the mfabeni peat sediments have undergone minimal diagenetic alteration the peat sequence was divided into 5 linear sedimentation rate lsr stages indicating distinct changes in climate and hydrological conditions isr stage 1 c 47 to c 32 2 kcal yr bp predominantly cool and wet climate with c4 plant assemblages interrupted by two short warming events lsr stage 2 c 32 2 to c 27 6 kcal yr bp dry and windy climate followed by a brief warm and wet period with increased c4 sedge swamp vegetation lsr stage 3 c 27 6 to c 20 3 kcal yr bp initial cool and wet period with prevailing c4 sedge plant assemblage until c 23 kcal yr bp then an abrupt change to dry and cool glacial conditions and steady increases in c3 grasses lsr stage 4 c 203 to c 10 4 kcal yr bp continuation of cool and dry conditions and strong 0 grassland signature until c 15 kcal yr bp after which precipitation increases lsr stage 5 c 10 4 kcal yr bp to present characterised by extreme fluctuations between pervasive wet and warm to cool interglacial conditions with intermittent abrupt millennial scale cooling drying events and oscillations between c3 and c4 plant assemblages in this study we reconstructed a high resolution record of local hydrology bulk plant assemblage and inferred climate since the late pleistocene which suggest an anti phase link between southern african and the northern hemisphere most notably during heinrich 5 to 2 and younger dryas events

sea level and climate change at the southern cape coast south africa during the past 4 2 kyr abstract south african coastal lake sediments provide an excellent opportunity to investigate environmental changes such as sea level and climate variability during the holocene period in this study we present a sediment record from the coastal lake groenvlei located in the southern cape region which is part of south africa s year round rainfall zone in order to improve the understanding of palaeoenvironmental changes in this region we provide a high resolution multi proxy data set derived from geochemical mineralogical isotopic and granulometric analyses the age depth model is based on 14c and 210pb dating and reveals a basal age of 4210 200 120 cal bp differences in the mineralogical composition of deposited carbonates reflect changes in the past lake water chemistry probably caused by variations in both sea level and climate compared to the present mostly drier conditions and a greater marine influence due to a higher sea level are inferred for the period between 4210 and 2710 cal bp however the record also indicates the occurrence of short humid phases during this time which were probably associated with heavy rainfall events a transition layer was deposited between 2710 and 1210 cal bp probably as a result of reworking of sediment during this time the lake passed through a major change finally turning into a freshwater system from at least 1210 cal bp until the present our data indicate that the marine influence on the lake decreased due to a lower sea level and climate became generally more humid after 1210 cal bp probably resulting in a greater lake internal and external bioproductivity based on a comparison with other palaeoenvironmental studies from south africa our record suggests a prevailing winter rainfall seasonality at the southern cape coast between 4210 and 2710 cal bp and a stronger influence of summer rainfall from 1210 cal bp onwards

evidence for progressive holocene aridification in southern africa recorded in namibian hyrax middens implications for african monsoon dynamics and the african humid period abstract presented here are stable nitrogen isotope data from a rock hyrax procavia capensis middens from northwestern namibia that record a series of rapid aridification events beginning at ca 3800 cal yr bp and which mark a progressive decrease in regional humidity across the holocene strong correlations exist between this record and other terrestrial and marine archives from southern africa indicating that the observed pattern of climate change is regionally coherent combined these data indicate hemispheric synchrony in tropical african climate change during the holocene with similar trends characterising the termination of the african humid period ahp in both the northern and southern tropics these findings run counter to the widely accepted model of direct low latitude insolation forcing which requires an anti phase relationship to exist between the hemispheres the combined dataset highlights 1 the importance of forcing mechanisms influencing the high northern latitudes in effecting low latitude climate change in africa and 2 the potential importance of solar forcing and variations in the earth s geomagnetic shield in determining both long term and rapid centennial scale climate changes identifying a possible mechanism for the variations marking the ahp termination in both the southern and northern tropics

late quaternary palaeoenvironments of the winter rainfall zone of southern africa palynological and sedimentological evidence from the agulhas plain abstract south africa s winter rainfall zone is a climatically sensitive region lying at the interface of the earth s temperate and sub tropical climatic systems its seasonally arid climate has generally prevented the preservation of long and organic rich sedimentary deposits producing a spatially limited and temporally biased quaternary record this paper seeks to address this issue further and develop a fuller understanding of the wider climatic changes in this region during the late quaternary modern climatic data does not support the definitions of the winter rainfall zone presented in previous syntheses and this factor amongst others may explain difficulties in resolving the palaeoenvironmental record in this region we present palaeoenvironmental evidence from the agulhas plain an area marginal to the modern winter rainfall zone cored sedimentological and palynological records from two pans are integrated with previously reported records of aeolian activity providing evidence for phases of enhanced aridity and humidity during the late quaternary the record is fragmentary which may reflect the cycling of sediment between the pans and their accompanying lunette dunes lacustrine sedimentary sequences dating to c 33 ka 47 ka provide evidence for enhanced humidity consistent with evidence in the winter and year round rainfall zones increased humidity is also recorded from c 2 ka following drier conditions than the present c 2 7 2 5 ka palynological evidence supports the sedimentological interpretations of pan water status and offers rare insights into the nature of the region s unique fynbos vegetation during the late pleistocene

timing of the last glacial maximum from observed sea level minima during the last glacial maximum ice sheets covered large areas in northern latitudes and global temperatures were significantly lower than today but few direct estimates exist of the volume of the ice sheets or the timing and rates of change during their advance and retreat here we analyze four distinct sediment facies in the shallow tectonically stable bonaparte gulf australia each of which is characteristic of a distinct range in sea level to estimate the maximum volume of land based ice during the last glaciation and the timing of the initial melting phase we use faunal assemblages and preservation status of the sediments to distinguish open marine shallow marine marginal marine and brackish conditions and estimate the timing and the mass of the ice sheets using radiocarbon dating and glacio hydroisostatic modelling our results indicate that from at least 22 000 to 19 000 calendar years before present land based ice volume was at its maximum exceeding today s grounded ice sheets by 52 5 x 10 exp 6 cu km a rapid decrease in ice volume by about 10 percent within a few hundred years terminated the last glacial maximum at 19 000 250 years

molecular proxies for paleoclimatology we summarize the applications of molecular proxies in paleoclimatology marine molecular records especially are proving to be of value but certain environmentally persistent compounds can also be measured in lake sediments loess deposits and ice cores the fundamentals of this approach are the molecular parameters the compound abundances and carbon hydrogen nitrogen and oxygen isotopic contents which can be derived by the analysis of sediment extracts these afford proxy measures which can be interpreted in terms of the conditions which control climate and also reflect its operation we discuss two types of proxy those of terrigenous and those of aquatic origin and exemplify their application in the study of marine sediments through the medium of ten case studies based in the atlantic mediterranean and pacific oceans and in antarctica the studies are mainly for periods in the present the holocene and particularly the last glacial interglacial but they also include one study from the cretaceous the terrigenous proxies which are measures of continental vegetation are based on higher plant leaf wax compounds i e long chain circa c30 hydrocarbons alcohols and acids they register the relative contributions of c3 vs c4 type plants to the vegetation in the source areas the two marine proxies are measures of sea surface temperatures sst the longer established one u37k is based on the relative abundances of c37 alkenones photosynthesized by unicellular algae members of the haptophyta the newest proxy tex86 is based on c86 glycerol tetraethers gdgts synthesized in the water column by some of the archaeal microbiota the crenarchaeota

a 300 kyr record of aridity and wind strength in southwestern africa inferences from grain size distributions of sediments on walvis ridge se atlantic abstract the terrigenous fraction of sediments recovered from walvis ridge se atlantic ocean reveals a history of southwestern african climate of the last 300 kyr end member modelling of a data set of grain size distributions n 428 results in three end members the two coarsest end members are interpreted as eolian dust the third end member as hemipelagic mud the ratio of the two eolian end members reflects the eolian grain size and is attributed to the intensity of the se trade winds trade winds were intensified during glacials compared to interglacials changes in the ratio of the two eolian end members over the hemipelagic one are interpreted as variations in southwestern african aridity late quaternary southwestern african climate was relatively arid during the interglacial stages and relatively humid during the glacial stages owing to meridional shifts in the atmospheric circulation system during glacials the polar front shifted equatorward resulting in a northward displacement of the zone of westerlies causing increased rainfall in southwestern africa the equatorward shift of the polar front is coupled with an increase of the meridional pressure gradient leading to enhanced atmospheric circulation and increased trade wind intensity

increased atmospheric dust deposition during the neoglacial in a boreal peat bog from north eastern canada abstract dust deposition in north eastern canada was estimated from the geochemical signature of a boreal peat bog from the james bay lowlands the rare earth elements and other lithogenic elements as well as nd isotopes were measured by q icp ms icp oes and mc icp ms respectively along a 4 20 m peat core covering the last 7000 years a principal component analysis performed on the geochemical dataset shows that rees display the same chemical behavior as other lithogenic elements such as al and ti which suggests that they are immobile in the peat column and can be used as tracers of dust deposition after 4000 cal yr bp peaks in dust deposition associated with greater variability in testate amoebae assemblages and plant macrofossil composition as well as a change in nd values are observed between 7000 and 4100 cal yr bp the nd values varied from 36 to 29 while they gradually increased from 4100 cal yr bp until 1500 cal yr bp suggesting proportionally less dust from local source s is deposited in favor of more regional source s from 1500 cal yr bp nd values remained relatively stable around 15 and 12 most of the dust peaks correspond to documented cold and dry periods likely linked to intrusion of arctic air masses a migration of the polar front might explain the more frequent intrusion of arctic air masses in the region and the greater variability in the lg2 record over the last 4000 years

postglacial climate change record in biomarker lipid compositions of the hani peat sequence northeastern china abstract the peat sequence at hani in northeastern china accumulated over the past 16 cal kyr in a percolation mire in which rain water and ground water seeped through the peat system the molecular compositions of n alkanes n alkanols and n alkanoic acids extracted from the hani peat sequence reveal different responses to the progressive evolution of climate and changes in the nature of the peat forming vegetation long chain length components that originate from the waxy coatings of subaerial vascular plants dominate the n alkane distributions throughout the hani peat sequence the paleoclimate integrity of these biomarker molecules appears to be well preserved most of the n alkanol distributions are similarly dominated by long chain components that indicate their origins from subaerial plants in contrast n alkanoic acid distributions are dominated by secondary components that record the importance of post depositional microbial activity in this peat sequence which evidently can be extensive in a percolation mire elevated n alkane paq values and c23 c29 ratios which are both molecular proxies for water loving plants record an especially moist local climate in the bolling allerod 14 5 to 12 9 ka younger dryas 12 9 to 11 5 ka and pre boreal 11 5 to 10 5 ka portions of the hani peat sequence depressed paq values and c23 c29 ratios and larger n alkane average chain length values indicate that the holocene climatic optimum 10 5 to 6 ka was a period of warmer climate with lower effective precipitation which contrasts with evidence of wetter climates in most of east asia

sea level and deep water temperature changes derived from benthic foraminifera isotopic records we show that robust regressions can be established between relative sea level rsl data and benthic foraminifera oxygen isotopic ratios from the north atlantic and equatorial pacific ocean over the last climatic cycle we then apply these regressions to long benthic isotopic records retrieved at one north atlantic and one equatorial pacific site to build a composite rsl curve as well as the associated confidence interval over the last four climatic cycles our proposed reconstruction of rsl is in good agreement with the sparse rsl data available prior to the last climatic cycle we compute bottom water temperature changes at the two sites and at one southern indian ocean site taking into account potential variations in north atlantic local deep water 18o our results indicate that a last glacial maximum lgm enrichment of the ocean mean oxygen isotopic ratio of 0 95 is the lowest value compatible with unfrozen deep waters in the southern indian ocean if local deep water 18o did not increase during glacials with respect to present such a value of the lgm mean ocean isotopic enrichment would impose a maximum decrease in local bottom water 18o at the north atlantic site of 0 30 during glacials

pressure coefficient in dam break flows of dry granular matter abstractthe propagation of dry granular flows such as rock and snow avalanches can be described by depth averaged models different from classical shallow water equations these models take into account the anisotropy of normal stresses inside the flowing pile through using an earth pressure coefficient in the pressure term a new regularization function for calculating the pressure coefficient in the savage hutter type models at the early stages of dam break flows and collapses is proposed in such circumstances the flow lines are significantly curved with respect to the basal surface and a special treatment of the earth pressure coefficient is required for obtaining a satisfactory agreement with experimental data the comparison between numerical simulations and laboratory experimental data shows an apparent improvement in describing the early stages of dam break waves over rough beds the comparison with experiments over smooth bed surface exhibits minor evidence of improvement nonetheless in this

sea surface temperature fluctuations during the holocene off the south coast of africa implications for terrestrial climate and rainfall models of southern african palaeoclimate implicate surface atmospheric circulation anoma lies as forcing large scale changes during the late quaternary the available proxy data are insufficient to test the models since they provide information about temperature and rainfall rather than surface circulation a conceptual model is proposed which links coastal ocean temperatures with atmospheric circulation and allows a history of surface circulation to be inferred from sea temperature data a holocene sea surface temperature sst record was constructed by measuring the oxygen isotope composition of marine mollusc shells preserved in an archaeological cave deposit on the coast of the eastern agulhas bank southern africa radiocarbon dating of individual shells allowed definition of the timing and timespan of events in the record by serially sampling along the growth axis of each shell information was obtained about intra annual variability as well as millennial scale trends during the early holocene th