sea level fall and coastal water cooling during the late holocene in southeastern brazil based on vermetid bioconstructions abstract the relative sea level variation curve obtained by dating and leveling vermetid shells from northern santa catarina state 26 3 s presents fall trend during all the last 4 0 cal ka bp which matches previous results based on the same kind of indicator for the brazilian coast between 3 s and 28 s chemical and isotopic analyses of 50 vermetid bioconstructions from distinct localities of south southeastern brazilian coast indicate possible changes in the coastal water temperature these changes may have been caused by oscillations in the strength of brazilian coastal current which carries la plata plume northward being therefore responsible for the penetration of cold and less saline water masses in the study area this is a reasonable explanation for the scarcity of vermetid biolithites around 3 4 2 6 cal ka bp and 0 5 0 cal ka bp

the instability theory of drumlin formation and its explanation of their varied composition and internal structure despite their importance in understanding glaciological processes and constraining large scale flow patterns in palaeo glaciology there is little consensus as to how drumlins are formed attempts to solve the drumlin problem often fail to address how they are created from an initially flat surface in the absence of obvious cores or obstacles this is a key strength of the instability theory which has been described in a suite of physically based mathematical models and proposes that the coupled flow of ice and till causes spontaneous formation of relief in the till surface encouragingly model predictions of bedform height and length are consistent with observations and furthermore the theory has been applied to a range of subglacial bedforms and not just drumlins however it has yet to confront the myriad observations relating to the composition and internal structure of drumlins and this could be seen as a major deficiency this paper is a first attempt to assess whether the instability theory is compatible with the incredible diversity of sediments and structures found within drumlins we summarise the underlying principles of the theory and then describe and attempt to explain the main types of drumlin composition e g bedrock till glaciofluvial sediments and combinations thereof contrary to a view which suggests that the presence of some sedimentary sequences e g horizontally stratified cores is inconsistent with the theory we suggest that one would actually expect a diverse range of constituents depending on the inheritance of sediments that pre date drumlin formation the duration and variability of ice flow and the balance between erosion and deposition till continuity at the ice bed interface we conclude that the instability theory is compatible with and potentially strengthened by what is known about drumlin composition and as such offers the most complete and promising solution to the drumlin problem to date

path and variability of the agulhas return current the combined analysis of hydrographic kinematic and dynamic data collected during the 1997 1999 kapex cape of good hope experiments reveals a quasi stationary meandering pattern of the agulhas retroflection current east and upstream of the southwest indian ridge the current meanders between 38 s and 40 s in a spatially and temporally continuous fashion and has a core width of approximately full size image 1 k with an associated transport of full size image 1 k in the upper full size image 1 k peak surface velocities decrease from full size image 1 k near the agulhas retroflection to full size image 1 k around 32 e meander troughs northward extremes are found predominantly near 26 8 e 32 6 e and 38 9 e while crests southward extremes are located with high probability near 29 7 e 35 5 e and 42 9 e resulting in a typical wavelength of full size image 1 k cold eddies are shed along the northern boundary of the current from meander troughs into the recirculation regime between the agulhas current proper and the agulhas return current strongest cyclonic eddies are preferably shed in austral autumn the cyclonic eddies so formed propagate westward at an average phase speed of full size image 1 k with however a variability of at least the same magnitude subsequently the cyclones are absorbed by the next meander trough located upstream and to the west of the shedding trough

a high resolution 15 600 year pollen and microcharcoal record from the cederberg mountains south africa abstract the cederberg mountains western cape province south africa are located within the fynbos biome which exhibits some of the highest levels of species richness and endemism in the world the region s post glacial vegetation history however remains largely unknown presented here are high resolution pollen and microcharcoal records spanning the last 15 600 years obtained from the de rif rock hyrax midden from the driehoek valley of the central cederberg in this region previous pollen studies have shown muted variability in vegetation community composition during periods of globally marked climatic variability e g the last glacial interglacial transition in our record however significant changes in vegetation composition are apparent most notably they indicate a shift from ericaceous restioid fynbos present from 15 600 to 13 300 cal yr bp to a brief but prominent development of proteoid fynbos at the beginning of the holocene around 11 200 cal yr bp this vegetation shift is associated with increased moisture at the site and coincides with reduced fire frequency as indicated by the microcharcoal record at 10 400 cal yr bp there is a marked reduction in protea type pollen which is replaced by thicket characterised by dodonaea which became the dominant arboreal pollen type this shift was likely the result of a long relatively fire free period coupled with warmer and wetter climates spanning much of the early holocene a brief but marked decrease in water availability around 8500 8000 cal yr bp resulted in the strong decrease of dodonaea pollen the vegetation of the mid to late holocene is characterised by the increased occurrence of asteraceae and succulent taxa suggesting substantially drier conditions these data give unprecedented insight into the vegetation dynamics across a period of substantial rapid climate change and while they confirm the presence of fynbos elements throughout the last 15 600 years the results highlight significant fluctuations in the vegetation that were triggered by changes in both climate and fire regimes

drumlins carved by deforming till streams below the laurentide ice sheet the peterborough drumlin field 5000 km 2 is the largest in central canada and was formed during readvance of the laurentide ice sheet shortly after 13 000 b p morphometric analysis of 998 drumlins combined with study of 6921 borehole logs and downhole geophysical data has established the distribution of drumlin types and their stratigraphy along a 70 km flow line through the drumlin field in the north drumlins are spindle shaped composed of till resting directly on bedrock and were formed by deformation of till into low pressure zones in the lee of bedrock scarps eskers record subglacial drainage by channeled meltwaters flowing on bedrock to the south drift thickness increases and eskers are absent drumlins are larger and more ovoid and are composed of overridden proglacial and glaciolacustrine sediments overlain erosively by deformation till till is thin over drumlin crests and thick in interdrumlin swales and records subglacial cannibalization and mixing of overridden sediments the drumlin form is the product of erosion by streams of deforming till flowing in swales separating cores composed of older sediments systematic down field changes in drumlin shape and size can be related to decreased duration of subglacial deformation toward the limit of the readvance and increased thickness of preexisting sediments available for dissection by subglacial till streams absence of eskers in the central and southern parts of the drumlin field suggests that the ice base was drained by mass flow of the deforming substrate the substantial subsurface data available from the peterborough area indicate that drumlins are predominantly erosional in origin and are the geomorphological expression of a deforming subglacial bed below the margin of the laurentide ice sheet

holocene rainfall variability in southern chile a marine record of latitudinal shifts of the southern westerlies geochemical and clay mineral parameters of a high accumulation marine sediment core from the chilean continental slope 41 s provide a 7700 yr record of rainfall variability in southern chile related to the position of the southern westerlies we especially use the iron content measured with a time resolution of ca 10 yr on average of 14 caccelerator mass spectrometry dated marine sediments as a proxy for the relative input of iron poor coastal range and iron rich andean source rocks variations in this input are most likely induced by rainfall changes in the continental hinterland of the core position based on these interpretations we find a pronounced rainfall variability on multicentennial to millennial time scales superimposed on generally more arid conditions during the middle holocene 7700 to 4000 cal yr b p compared to the late holocene 4000 to present this variability and thus changes in the position of the southern westerlies are first compared to regional terrestrial paleoclimate data sets from central and southern chile in order to derive possible wider implications and forcing mechanisms of the holocene latitudinal shifts of the southern westerlies we then compare our data to ice core records from both tropical south america and coastal antarctica these records show similar bands of variability centered at ca 900 and 1500 yr comparisons of band pass filters suggest a close connection of shifts of the southern westerlies to changes within the tropical climate system the correlation to climate conditions in coastal antarctica shows a more complicated picture with a phase shift at the beginning of the late holocene coinciding with the onset of the modern state of el nin o southern oscillation system the presented data provide further evidence that the well known millennial scale climate variability during the last glacial continued throughout the holocene fl 2001 elsevier science b v all rights reserved

precrags and drumlin fields in finland abstract the paper deals with radially oriented moraine ridges precrags and other drumlins in finland their distribution and location in relation to ice lobes local topography and bedrock structure emphasis is given to precrag ridges whose occurrence in southwestern finland was only recently established as a result of more detailed quaternary geological mapping 1 20 000 and 1 100 000 the short review of drumlins is based both on recent drumlin studies and on those undertaken during past decades the size and shape of all these streamlined moraine ridges were studied morphologically the internal structure and material of moraines were determined by drilling and sampling in addition to seismic refraction sounding or ground probing radar surveys variations in the size shape and structure of precrags and drumlins are attributed to the dimensions of the moving continental ice mass and glacial activity in different parts of the country the orientation of the precrag ridges and the drumlin fields reflects local ice flow patterns during the late weichselian glaciation the precrag field and southwestern finland is evidently older than the other drumlin fields in finland and does not contain any other streamlined moraine ridges than precrags on the basis of the ice marginal formations and the glacial flow patterns the authors have inferred that the oldest precrag ridges originally developed in a cold based subglacial thermal zone at the time when the margin of the continental ice was probably still in estonia i e almost 200 km to the south the drumlin fields formed again under the warm based part of the ice sheet in a zone that extended for about 20 100 km inwards from the ice margin and situated in the middle of active ice lobes

hydroclimate in africa during the medieval climate anomaly the medieval climate anomaly mca is a recognized period of distinct pre industrial climate change with a core period of 1000 1200 ce the field of palaeoclimatology has made major progress over the past 15 years during which a great number of high and medium resolution case studies were published reconstructing climate change of the past millennia in many parts of the world regional data coverage has now reached a point which allows compiling palaeoclimate maps for well defined time intervals here we present hydroclimatic trend maps for the mca in africa based on 99 published study locations key hydroclimatic proxy curves are visualized and compared in a series of 16 correlation panels proxy types are described and possible issues discussed based on the combined mca dataset temporal and spatial trends are interpreted and mapped out three areas have been identified in africa in which rainfall seems to have increased during the mca namely tunisia western sahel and the majority of southern africa at the same time a reduction in precipitation occurred in the rest of africa comprising of nw and ne africa west africa eastern africa and the winter rainfall zone of south africa mca hydroclimate change in africa appears to have been associated with characteristic phases of ocean cycles as also supported by modern climate observations aridity in morocco typically coincides with the positive phase of the north atlantic oscillation nao whilst increased rainfall in the western sahel is often coupled to the positive phase of the atlantic multidecadal oscillation amo reduction in rainfall in the region gulf of aden southern red sea to eastern africa could be linked to a negative indian ocean dipole iod or a derived long term equivalent indian ocean cycle parameter the intertropical convergence zone itcz appears to have been shifted pole wards during the mca for both the january and july positions mca hydroclimate mapping revealed major data gaps in the sahara south sudan somalia central african republic democratic republic of congo angola northern mozambique zambia and zimbabwe special efforts are needed to fill these gaps e g through a dedicated structured research program in which new multiproxy datasets are created based on the learnings from previous african mca studies

rapid and quantitative major element analysis method for wet fine grained sediments using an xrf microscanner several types of x ray fluorescence xrf core scanners have been developed to fulfill the demands for high resolution rapid chemical analysis of wet sediment cores however their application to quantitative analysis has been hampered by the difficulty of evaluating the xrf absorption effect of water in a water film on the sediment surface and interstitial water within the sediments especially for lighter elements in this study we established a non destructive rapid high resolution and quantitative chemical analysis method for wet fine grained sediment samples using an xrf microscanner results of our experiments suggest that the degree of xrf absorption by the water film which develops on the wet sample surface covered with mylar film shows a clear positive correlation with the water content of the sediments under the measurement area a clear positive correlation also exists between the degree of xrf absorption by the interstitial water and the water content of the sediments under the measurement area we evaluated the xrf absorption by the thin water film using the relationship between the water content and thickness of the thin water film and the xrf absorption by the interstitial water using its relation with the water content the water content under the measurement area is estimated from the average transmitted x ray intensity that is measured on the same measurement area simultaneously with the measurement of xrf intensities the dry sample equivalent xrf intensities of major elements al si k ca ti and fe which are the xrf intensities of wet samples corrected for the xrf absorption by the thin water film and the interstitial water show better correlation with the major element concentrations determined by conventional xrf methods using this new method it is possible to measure the average water content and average concentrations of the 6 major elements simultaneously for a square area as small as 0 5 0 5 mm on the wet fine grained sediment within 6 min which is nearly ten times faster than the conventional xrf method

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

late holocene marine radiocarbon reservoir correction δr for the west coast of south africa in order to calibrate radiocarbon ages based on samples with a marine carbon component it is important to know the marine carbon reservoir correction or r value this study measured the r on both known age pre bomb marine shells and paired marine and terrestrial samples from two regions on the west coast of south africa the southwestern cape and namaqualand pooling the data by region produces r values that are similar enough to use a west coast weighted mean r of 146 85 14c years to correctly calibrate marine shell or mixed marine and terrestrial 14c ages there are however temporal differences in r throughout the holocene which we compare with proxy data for upwelling and sea surface temperatures

a critical review of mid to late holocene sea level fluctuations on the eastern brazilian coastline abstract the eastern coast of brazil is 7000 km long and has been the subject of systematic paleo sea level investigations for more than 35 years more than 1000 samples have been radiocarbon dated and paleo sea level trends have been determined for 14 coastal sectors these trends have in common a mid holocene sea level maximum pmt above present sea level and a subsequent fall to the present time the time and elevation of the pmt the time when relative sea level rose above present mean sea level and the nature of late holocene sea level fall can however differ significantly discrepancies are observed not only between neighboring coastal sectors but also between different studies in a same coastal sector this paper discusses all the key radiocarbon dated samples used to establish regional trends in relative sea level on the eastern coast of brazil it is concluded that although many of the key sea level indicators are imprecise in time and space there is widespread evidence 30 of the data set for a progressive decline possibly with uneven rates of relative sea level since the end of the pmt

the composition and internal structure of drumlins complexity commonality and implications for a unifying theory of their formation investigation of drumlins is significant to both glaciology and palaeoglaciology but the sheer diversity of their composition and internal structure is often cited as a major obstacle towards a satisfactory unifying explanation of their formation this paper presents the first systematic survey of the vast literature on this subject with the aim of concisely summarising observations and identifying any emergent patterns or commonality that theories of drumlin formation should be able to explain results confirm that investigations are often limited by availability of suitable sediment exposures 40 of studies report data from 5 drumlins and 44 do not specify sample size although borehole data and geophysical techniques can alleviate this problem however it is clear that the constituents of drumlins are incredibly diverse in terms of their composition e g a range of lithologies clast shapes sizes and fabrics structure e g sediments that are sorted homogeneous surface conformable unconformable and evidence of deformation e g ranging from pervasive to non pervasive limited to absent despite this diversity our review leads us to suggest that drumlin composition can be simplified to five basic types i mainly bedrock ii part bedrock part till iii mainly till iv part till part sorted sediments and v mainly sorted sediments this is a potentially significant step in that it reduces the oft cited complexity of drumlin composition and provides a more realistic goal for theories or numerical models of drumlin formation to target the various types can occur within the same drumlin field which leaves us with two possible implications for drumlin formation 1 different types of drumlin are formed seeded by different processes despite being morphologically similar equifinality investigation of drumlin composition may therefore reveal diagnostic processes explanations for these different types of drumlin and we argue that bedrock drumlins are an example 2 a single process occurs across large parts of the ice bed interface to create drumlinised terrain in a variety of sediments investigation of drumlin composition may in this case simply reflect pre existing sediments but importantly the way in which the drumlin forming mechanism modifies is modified by them we argue that the latter simpler explanation applies to all other types of drumlin excluding purely bedrock forms and conclude that the diversity in drumlin composition is no obstacle to a single unifying theory

a north to south transect of holocene southeast atlantic continental margin sediments relationship between aerosol transport and compound specific δ13c land plant biomarker and pollen records 1 we examined near surface late holocene deep sea sediments at nine sites on a north south transect from the congo fan 4 s to the cape basin 30 s along the southwest african continental margin contents distribution patterns and molecular stable carbon isotope signatures of long chain n alkanes c27 c33 and n alkanols c22 c32 are indicators of land plant vegetation of different biosynthetic types which can be correlated with concentrations and distributions of pollen taxa in the same sediments calculated clusters of wind trajectories and satellite aerosol index imagery afford information on the source areas for the lipids and pollen on land and their transport pathways to the ocean sites this multidisciplinary approach on an almost continental scale provides clear evidence of latitudinal differences in lipid and pollen composition paralleling the major phytogeographic zonations on the adjacent continent dust and smoke aerosols are mainly derived from the western and central south african hinterland dominated by deserts semi deserts and savannah regions rich in c4 and cam plants the northern sites congo fan area and northern angola basin which get most of their terrestrial material from the congo basin and the angolan highlands may also receive some material from the chad region very little aerosol from the african continent is transported to the most southerly sites in the cape basin as can be expected from the present position of the phytogeographic zones the carbon isotopic signatures of the n alkanes and n alkanols both become isotopically more enriched in 13c from north to south the results of the study suggest that this combination of pollen data and compound specific isotope geochemical proxies can be effectively applied in the reconstruction of past continental phytogeographic developments

multiphase late quaternary aeolian sediment accumulation in western south africa timing and relationship to palaeoclimatic changes inferred from the marine record abstract extensive aeolian deposits exist along the western margin of south africa from cape town through to the namib sand sea and represent a significant palaeoenvironmental archive recording millennial scale patterns of regional and hemispheric environmental change to establish the timing of dune development this study applies optically stimulated luminescence osl dating techniques to the aeolian features of the west coast in total 35 samples were obtained from six dune cores along a north south transect extending from elands bay 32 26 s 18 14 e to kleinsee 29 14 s 16 59 e ages from these dunes exhibit five distinct peaks suggesting phases of activity deposition at 4 5 16 24 30 33 43 49 and 63 73 ka the spatial and temporal extent of the data have allowed for correlations to be made with evidence from marine cores from the southeast atlantic and a more coherent regional environmental history to be developed results suggest that 1 environmental changes in this region are strongly linked to variations in wind strength and atmospheric circulation systems during the late quaternary and 2 luminescence ages from aeolian deposits cannot necessarily be equated with periods of increased aridity with other factors such as wind strength and sediment supply being of critical importance

structure and diagenesis of recent algal foraminifer reefs fernando de noronha brazil abstract the volcanic island of fernando de noronha in the south atlantic is fringed by an emergent algal ridge rising from a subtidal volcanic or eolianite foundation the ridge and adjacent reef flat result from aggradation by skeletal growth mainly crustose coralline algae and foraminifer homotrema rubrum and deposition of volcanic gravel extending landward as beachrock the aggrading units involve sand filled skeletal and gravel frameworks with the detrital sediment representing about two thirds of the reef volume distribution of radiocarbon dates suggests combined effect of marine abrasion and seaward progradation after an initial upward growth rate of 1 m 500 years prior to 3000 years b p at present the ridge and reef flat are undergoing considerable diagenetic alteration pervasive generation of mg calcite micrite cement occurring simultaneously with bioerosion and deposition of new carbonate fabric produces dense and texturally complex reefrock this early lithification is taking place in an extremely turbulent wave swept environment and its upper limit extends several meters above the intertidal zone

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

late holocene oceanic variability in the southern benguela region driven by interplay of upwelling fluvial discharge and agulhas leakage the southern benguela upwelling system near the st helena bay has been proposed to be affected by various factors while few investigations about the late holocene oceanic conditions has been carr

the distribution of carbonate eolianite abstract carbonate eolianite forms distinctive coastal landforms on many mid latitude continents and islands numerous studies of extensive continental and smaller island deposits in both hemispheres have shown the eolianites are predominantly pleistocene in age the coorong coastal plain of south australia contains the world s longest record of eolianite deposition revealing that major phases of carbonate accumulation occurred during interglacial and some interstadial sea level highstands throughout the quaternary similarly the well studied eolianite islands of bermuda and the bahamas record a close match between dune accretion and sea level highstands since the middle pleistocene several other eolianite deposits appear to have formed at least partially during glacial periods the glacial age deposits are eolian reworked relict shelf or coastal sediments or remnants of former highly mobile coastal dunes sourced from low sea level shorelines the distribution and bioclastic composition of large scale eolianite deposits suggests carbonate production on shallow shelves and banks is the ultimate control on the formation of eolianite the bulk of the carbonate comprising those eolianites is heterozoan being produced where there is low terrigenous sediment input in dominantly temperate cool water and subtropical carbonate provinces quaternary cyclical movements of sea level have also controlled the form and rate of coastal carbonate deposition with repeated pulses of sedimentation during highstands forming laterally coalesced vertically stacked or composite dune successions major unconformities within the deposits are marked by paleosols which record hiatuses in coastal sedimentation in several regions major eolianite units overlie coastal deposits of terrigenous sediment those successions suggest that the trend towards aridity and reduction in the supply of terrigenous sediment to shelves during the quaternary has enhanced the production of carbonate and the deposition of eolianite

pollen distribution in the marine surface sediments of the mudbelt along the west coast of south africa abstract the distribution of pollen in marine surface sediments offshore of the west coast of south africa has been investigated to aid in the interpretation of marine pollen records of onshore vegetation changes a transect of sediment surface pollen samples retrieved from the namaqualand mudbelt from just south of the orange river mouth 29 s to st helena bay 33 s indicates distinctive pollen spectra reflecting vegetation communities on the adjacent continent pollen concentration increases southwards partly in relation to greater pollen productivity due to higher biomass and density of fynbos vegetation and of sedimentary processes and low pollen concentrations consequent to dilution with silt and clay from the orange river the distribution of specific pollen taxa suggests that the orange river is a major contributor of pollen to the northern mudbelt declining southwards while the pollen distribution in the central mudbelt is largely attributable to seasonal inputs of pollen from offshore berg winds and local ephemeral namaqualand rivers the typical fynbos elements dominate in the southern mudbelt indicating a pollen source mainly in the fynbos vegetation types these conclusions support a companion analysis of fossil pollen records of two marine sediment cores from the northern and southern mudbelt respectively this study demonstrates that pollen records from marine sediment cores in the namaqualand mudbelt have the potential to be a tool to reconstruct palaeovegetation on the adjacent continent however to better reconstruct the palaeoclimate of south africa and fully understand the relations between terrestrial and marine deposits more marine surface sediments along the western coast of south africa as well as more terrestrial surface sediments need to be studied

sea ice as the glacial cycles climate switch role of seasonal and orbital forcing a box model of the coupled ocean atmosphere sea ice and land ice climate system is used to study glacial interglacial oscillations under seasonally and orbitally varying solar forcing the dominant 100 kyr oscillation in land ice volume has the familiar sawtooth shape of climate proxy records and to zeroth order it does not depend on the seasonal and milankovitch forcing the sea ice controls via its albedo and insulating effects the atmospheric moisture fluxes and precipitation that enable the land ice sheet growth this control and the rapid growth and melting of the sea ice allow the sea ice to rapidly switch the climate system from a growing ice sheet phase to a retreating ice sheet phase and to shape the oscillation s sawtooth structure a specific physical mechanism is proposed by which the insolation changes act as a pacemaker setting the phase of the oscillation by directly controlling summer melting of ice sheets this mechanism is shown to induce deglaciations during periods of lower summer insolation superimposed on the 100 kyr are the linear milankovitch forced frequencies of 19 23 and 41 kyr the transition from 41 kyr glacial cycles to 100 kyr cycles one million years ago may be explained as being due to the activation of the sea ice switch at that time this would be the case if sea ice extent was more limited during the warmer climate of the early pleistocene

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

ultra long distance littoral transport of orange sand and provenance of the skeleton coast erg namibia abstract quantitative provenance analysis based on high resolution bulk petrography and heavy mineral data on beach and dune sands integrated with detrital zircon geochronology and chemical analyses of pyroxene garnet and staurolite demonstrates that sand derived from the orange river is carried by powerful and persistent longshore currents as far as northern namibia and southern angola 1750 km north of its mouth this is the longest cell of littoral sand transport documented so far compositional forward modeling indicates that 80 of dune sand in the skeleton coast is orange derived the remaining 20 being supplied by slow erosion of the damara orogen chiefly via the swakop river a decrease in basaltic rock fragments and pyroxene with relative enrichment in garnet staurolite tourmaline and other metamorphic minerals north of walvis bay indicates that only one third of beach sand in the 350 km dune free gap between the namib and skeleton coast ergs is orange derived the remaining two thirds being supplied largely by the swakop river draining the damara orogen although volcanic gravel becomes dominant in beaches of the skeleton coast north of the uniab mouth detritus from cretaceous etendeka lavas accounts for only 4 of beach sand reflecting limited sand generation in the arid catchment contributions from the kunene river to either dune or beach sands is ruled out indicating that gem diamonds found in placer deposits along the coast of namibia are all derived from the orange river

contrasting evolution of sea surface temperature in the benguela upwelling system under natural and anthropogenic climate forcings we present alkenone derived sea surface temperature sst records from three marine cores collected within the southern benguela upwelling system bus spanning the last 3 ka the sst evolution over the last 3 millennia is marked by aperiodic millennial scale oscillations that broadly correspond to climatic anomalies identified over the north atlantic region the bus sst data further suggest cooling and warming trends opposite to the temperature evolution in the moroccan upwelling region and in antarctica in contrast the last decades are marked by a cooling of unprecedented magnitude in both the benguela and moroccan upwelling systems which is not observed in the antarctic record these contrasted responses in atlantic upwelling systems triggered by natural and anthropogenic forcings shed light on how different climatic mechanisms are mediated by ocean atmosphere interactions and transmitted to the geological records of past and present climate changes citation leduc g c t herbert t blanz p martinez and r schneider 2010 contrasting evolution of sea surface temperature in the benguela upwelling system under natural and anthropogenic climate forcings geophys res lett 37 l20705 doi 10 1029 2010gl044353

holocene climate evolution in the high latitude southern hemisphere simulated by a coupled atmosphere sea ice ocean vegetation model the holocene climate is simulated in a 9000 yr long transient experiment performed with the ecbilt clio vecode coupled atmosphere sea ice ocean vegetation model this experiment is forced with annually varying orbital parameters and atmospheric concentrations of co2 and ch4 the objective is to study the impact of these long term forcings on the surface temperature evolution during different seasons in the high latitude southern hemisphere we find in summer a thermal optimum in the mid holocene 6 3 ka bp with temperatures locally 3 degrees c above the preindustrial mean in autumn the temperatures experienced a long term increase particularly during the first few thousand years the opposite trend was simulated for winter and spring with a relatively warm southern ocean at 9 ka bp in inter up to 3 5 degrees c above the preindustrial mean and a warm continent in spring 3 degrees c followed by a gradual cooling towards the present these long term temperature trends can be explained by a combination of 1 a delayed response to orbital forcing with temperatures lagging insolation by i to months owing to the thermal inertia of the system and 2 the long memory of the southern ocean this long memory is related to the storage of the warm late winter spring anomaly below the shallower summer mixed layer until next winter sea ice plays an important role as an amplifying factor through the ice albedo and ice insulation feedbacks our experiments can help to improve our understanding of the holocene signal in proxies for instance the results suggest that in contrast to recent propositions teleconnections to the northern hemisphere appear not necessarily to explain the history of southern hemisphere temperature changes during the holocene

sources transport and deposition of terrestrial organic material a case study from southwestern africa abstract southwestern africa s coastal marine mudbelt a prominent holocene sediment package provides a valuable archive for reconstructing terrestrial palaeoclimates on the adjacent continent while the origin of terrestrial inorganic material has been intensively studied the sources of terrigenous organic material deposited in the mudbelt are yet unclear in this study plant wax derived n alkanes and their compound specific 13c in soils flood deposits and suspension loads from regional fluvial systems and marine sediments are analysed to characterize the origin of terrestrial organic material in the southwest african mudbelt soils from different biomes in the catchments of the orange river and small west coast rivers show on average distinct n alkane distributions and compound specific 13c values reflecting biome specific vegetation types most notably the winter rainfall associated fynbos biome of the southwestern cape in the fluvial sediment samples from the orange river changes in the n alkane distributions and compound specific 13c compositions reveal an overprint by local vegetation along the river s course the smaller west coast rivers show distinct signals reflecting their small catchment areas and particular vegetation communities marine surface sediments spanning a transect from the northern mudbelt 29 s to st helena bay 33 s reveal subtle but spatially coherent changes in n alkane distributions and compound specific 13c indicating the influence of orange river sediments in the northern mudbelt the increasing importance of terrigenous input from the adjacent western coastal biomes in the central mudbelt and contributions from the fynbos biome to the southern mudbelt these findings indicate the different sources of terrestrial organic material deposited in the mudbelt and highlight the potential the mudbelt has to preserve evidence of environmental change from the adjacent continent

ocean circulation and iceberg discharge in the glacial north atlantic inferences from unmixing of sediment size distributions variability in iceberg discharge and deep ocean circulation in the north atlantic during the last glacial period is inferred from the grain size distribution and trace elemental composition of terrigenous sediments in a deep sea core taken on reykjanes ridge south of iceland end member modeling of the grain size distributions is used to unmix the signals of varying bottom current speed and iceberg discharge the size distribution within the silt fraction appears to be influenced by both factors based on th sc la relationship we established that during the ice rafted detritus events continental material of likely greenlandic origin increased to 87 and that bottom current derived material contains to 40 mid oceanic ridge fines probably of icelandic origin our results have important implications for the use of silt grain size as an indicator for paleocurrent speed in the glacial north atlantic we show that reconstructions of variations in bottom current speed based on the raw grain size data are opposite to inferences from the unmixed record the latter indicates that deep water convection decreased during periods of enhanced iceberg discharge which is in general agreement with paleoceanographic reconstructions of the north atlantic

late holocene dynamics of sea surface temperature and terrestrial hydrology in southwestern africa southwest africa is an important region for paleo climatic studies being influenced by both tropical and temperate climate systems and thus reflecting the interplay of variable controls the aim of this study was to unravel the interaction of sea surface temperature sst changes in the southernmost benguela upwelling system with precipitation changes in south africa s winter rainfall zone wrz during the late holocene therefore a marine sediment core from the southernmost benguela upwelling system was investigated to reconstruct climate changes in this region for the past 2000 years grain size and geochemical analyses were conducted to reconstruct changes in fluvial sediment discharge and weathering intensity while sst changes were estimated using alkenone paleo thermometry results show that the southernmost benguela behaves distinctly in comparison with the rest of the benguela system reflecting amplified sst changes decreasing ssts accompanied increasing river discharge during times of increas

quaternary sea level changes and aeolianites in the fernando de noronha archipelago northeastern brazil abstract finite and directional sea level indicators were found in the fernando de noronha archipelago brazil showing that in the mid to late holocene the sea level was similar to present and had been stable for at least the preceding 500 years this sea level behaviour is different from that observed in the nearest continental coast of northeastern brazil suggesting a slight sinking of the archipelago relative to the mainland the caracas formation that corresponds to the conspicuous aeolianites found on the archipelago was subdivided into two chronological units i and ii unit i is pleistocene formed before 50 000 bp and could correspond to an interglacial stage unit ii was formed during the holocene and was built up over the period from 10 700 to 5700 bp meaning that the sand dunes were transgressive and formed during the postglacial sea level rise prior to a mid holocene maximum at 7000 5000 bp

experimental observations on fungal diagenesis of carbonate substrates 1 carbonate substrates dolomites and limestones are susceptible to fungal attack that results in significant microbial diagenesis of these substrates in a 15 day experimental study fungi growing in petri dishes from airborne spores attacked petrographic thin sections and chips prepared from the dolomites of terwagne formation visean bocahut quarry at avesnes sur helpe northern france and limestones of the morrone di pacentro formation lower cretaceous italy the analyses of the fungal material samples of mycelia thin sections and chips under optical microscopy scanning electron microscope sem energy dispersive x ray edx x ray diffraction xrd raman spectroscopy and stable isotopes c and o revealed an extensive fungally induced diagenesis the results indicate strong diagenesis and biomineral neomorphism neo dolomite glushinskite weddellite whewellite and possibly struvite as well as intense substrate de micritization and micritization with oxalates grain bridging and cementation open space filling formation of intergranular and intragranular porosity and permeability enhancement advanced stages of diagenesis were characterized by dissolution and replacement of original minerals by new substrates produced by fungal biomineralization the formation of new substrates on the original attacked surfaces produced microscale stratification stable isotope analysis of fungal biomineralized material and of attacked and unattacked chip surfaces revealed marked differences in their isotopic signatures the c and o isotopes of biomineralized material within the fungal mass were fractionated differently as compared to the signature measured in the original and unattacked surfaces in sedimentary cycles such microbially modified isotopic signature of carbonate substrates may be used to define microbial events and consequently whether certain types of diagenesis were produced by microbial interaction the finding of neo dolomite formed during fungi dolomite substrate interaction suggests the possibility of sedimentary dolomite recycling in a fungal microenvironment the results of this experimental study confirm the significant role of fungi in reshaping carbonate substrates and forming new biominerals in the natural environment

high and low latitude climate control on the position of the southern peru chile current during the holocene 1 we reconstructed changes of temperature salinity and productivity within the southern peru chile current during the last 8000 years from a high resolution sediment core recovered at 41 s using alkenones isotope ratios of planktic foraminifera biogenic opal and organic carbon paleotemperatures and paleosalinities reached maximum values at 5500 years ago and thereafter declined to modern values whereas paleoproductivity continuously increased throughout the last 8000 years we ascribe these long term holocene trends primarily to latitudinal shifts of the antarctic circumpolar current acc the concurrence with shifts in the position of the southern westerlies points to a common response of atmospheric and oceanographic circulation patterns off southern chile millennial to centennial scale fluctuations of paleotemperatures and paleosalinities on the other hand lag displacements in the position of the southern westerlies but reveal a significant correlation to short term temperature changes in antarctica indicating a high latitude control of the acc at these timescales

holocene tectonic uplift of the st peter and st paul rocks equatorial atlantic consistent with emplacement by extrusion abstract st peter and st paul rocks spspr are emergent portions of a peridotitic mass within the st paul fracture zone of the equatorial mid atlantic ridge where local seismicity is dominated by strike slip mechanisms we used subtidal red algae in living position death assemblages in intertidal conglomerates and marine terraces as sea level markers the highest deposits correspond to a marine terrace with a shoreline angle at 8 1 m asl that formed ca 6400 6200 cal yr bp after correction for the sea level changes derived by glacioisostatic modelling ams and radiometric 14 c age measurements on the holocene sea level markers indicate emergence during the last 6600 a at a minimum average rate of 1 5 mm a we propose that uplift resulted from peridotite emplacement by extrusion rather than volcanic activity or fault slip with the implication that the ridge has been subject to compression during the holocene

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

a 19 5 kyr vegetation history from the central cederberg mountains south africa palynological evidence from rock hyrax middens abstract in arid and semi arid areas such as southern africa rock hyrax procavia capensis middens represent an exceptionally valuable source of late quaternary palaeoenvironmental information pollen and stable isotope data derived from two rock hyrax middens extracted from de rif in the cederberg mountains of the southwestern cape casts new light on climatic changes that occurred across the last glacial interglacial transition lgit and the holocene 19 5 0 7 cal kbp and how the region s vegetation responded to these changes significant changes in vegetation community composition would be expected in response to environmental changes characteristic of the contrast between glacial and interglacial climates however the pollen assemblages in general indicate that mountain fynbos remained dominant throughout the record and that most of the pollen taxa exhibited only muted frequency variations this finding could be considered to be inconsistent with indications of marked climatic variations recorded in the stable isotope records for the same midden an analysis of the geological setting and the bioclimatic affinities of the taxa suggest that the explanation for this inconsistency may lie in the dominating influence of sandstone substrates and the relative resilience of mountain fynbos vegetation to climate change

characteristics of the surface boundary layer important to the development of red tide on the southern namaqua shelf of the benguela upwelling system the southern namaqua shelf north of the cape columbine upwelling center is particularly prone to red tide two influences of the surface boundary layer on the development of red tide in this area were investigated the dynamics of the upper mixed layer in determining phytoplankton community composition and the role of mesoscale circulation in bloom concentration and transport two survey periods 18 february 11 march 2000 and 13 30 march 2001 are reported during which red tide dominated by the dinoflagellate gyrodinium zeta formed in the area a high degree of concordance between characteristics of stratification and groupings of phytoplankton demonstrated the importance of the upper mixed layer in determining species or life form selection and development ordination of across shelf phytoplankton samples revealed a consistent banded pattern created by a wind induced upwelling plume tending to isolate a nearshore zone from an offshore domain thereby creating an area of retention on the coastal side of the plume favoring development of dinoflagellate blooms the appearance of red tide was clearly associated with increasingly stratified conditions driven by alongshore flow from the north following periods of wind relaxation and consequent reversal of surface currents the southern benguela upwelling system forms part of one of four major eastern boundary current regions of the world ocean here a range of dinoflagellate species is responsible for toxic or otherwise harmful blooms pitcher and calder 2000 these blooms often referred to as red tides are common during the latter part of the upwelling season when the wind moderates and insolation is still strong causing seasonal stratification to increase their accumulation inshore and the formation of red tide is thought to be driven by synoptic weather patterns which dictate the across shelf and alongshore movement of blooms pitcher et al 1995 pitcher and boyd 1996 red tide has therefore been closely related to the prevailing winds of the region which govern most hydrodynamic processes on the continental shelf pitcher et al 1998 these observations are considered to reflect the consequences of two important influences of the surface boundary layer on the development of red tide the dynamics of the upper mixed layer in determining species selection and development and the role of mesoscale circulation in bloom retention and advection in the southern benguela three upwelling centers may be distinguished all of which coincide with a narrowing of the shelf the namaqua 30us cape columbine 33us and cape peninsula 34us upwelling centers fig 1 the region to the north of the cape columbine cell is particularly susceptible to red tide formation and its negative impacts and a historical perspective of faunal mortalities associated with red tides in this region is given by cockcroft et al 2000 here topographic and bathymetric features alter current patterns and mixing regimes features considered important in the development of red tide the shelf broadens to the north of columbine favoring stratification and stability of the water column airborne radiometer studies within this region have identified upwelling off cape columbine and along the coast north of dwarskersbos jury 1985 taunton clark 1985 under conditions of upwelling an equatorward coastal jet is formed off the columbine headland but wind stress shear promotes clockwise circulation within st helena bay jury 1985 thereby favoring retentive nearsurface circulation patterns within the region holden 1985 penven et al 2000 alongshore variability of flow considered to play a dominant role in driving the southward advection of phytoplankton blooms is thought to be associated with barotropic flow inshore generated by coastally trapped waves over the southern namaqua shelf with periods of 3 to 6 d lamberth and nelson 1987

distribution of major elements in atlantic surface sediments 36 n 49 s imprint of terrigenous input and continental weathering 1 numerous studies use major element concentrations measured on continental margin sediments to reconstruct terrestrial climate variations the choice and interpretation of climate proxies however differ from site to site here we map the concentrations of major elements ca fe al si ti k in atlantic surface sediments 36 n 49 s to assess the factors influencing the geochemistry of atlantic hemipelagic sediments and the potential of elemental ratios to reconstruct different terrestrial climate regimes high concentrations of terrigenous elements and low ca concentrations along the african and south american margins reflect the dominance of terrigenous input in these regions single element concentrations and elemental ratios including ca e g fe ca are too sensitive to dilution effects enhanced biological productivity carbonate dissolution to allow reliable reconstructions of terrestrial climate other elemental ratios reflect the composition of terrigenous material and mirror the climatic conditions within the continental catchment areas the atlantic distribution of ti al supports its use as a proxy for eolian versus fluvial input in regions of dust deposition that are not affected by the input of mafic rock material the spatial distributions of al si and fe k reflect the relative input of intensively weathered material from humid regions versus slightly weathered particles from drier areas high biogenic opal input however influences the al si ratio fe k is sensitive to the input of mafic material and the topography of andean river drainage basins both ratios are suitable to reconstruct african and south american climatic zones characterized by different intensities of chemical weathering in well understood environmental settings

holocene changes in the position and intensity of the southern westerly wind belt the position and intensity of the southern westerly wind belt varies seasonally as a consequence of changes in sea surface temperature during the austral winter the belt expands northward and the wind intensity in the core decreases conversely during the summer the belt contracts and the intensity within the core is strengthened reconstructions of the westerly winds since the last glacial maximum however have suggested that changes at a single site reflected shifts throughout the entire southern wind belt 1 4 here we use sedimentological and pollen records to reconstruct precipitation patterns over the past 12 500 yr from sites along the windward side of the andes precipitation at the sites located in the present core and northern margin of the westerlies is driven almost entirely by the wind belt 5 and can be used to reconstruct its intensity rather than varying coherently throughout the holocene epoch we find a distinct anti phasing of wind strength between the core and northern margin over multi millennial timescales during the early holocene the core westerlies were strong whereas the northern margin westerlies were weak we observe the opposite pattern in the late holocene as this variation resembles modern seasonal variability we suggest that our observed changes in westerly wind strength can best be explained by variations in sea surface temperature in the eastern south pacific ocean chile is ideally located to reconstruct past variability of the southern westerly wind belt sww as the sww almost entirely controls precipitation on the western side of the andes in southern south america with an extreme northsouth

evidence for holocene sea level change at verlorenvlei western cape south africa abstract a series of sediment cores extracted from what is today a large freshwater coastal lake verlorenvlei has been sub sampled radiocarbon dated and subjected to a range of palaeoenvironmental techniques in particular pollen analysis sedimentology and geochemistry a mid late holocene higher sea level is evident in the cores indicating the rapidity with which sea level change can occur and invoke other forms of environmental response following a hiatus in sedimentation most probably around 3800 bp the marine conditions at the site were replaced by fresh water as the dominant hydrological and ecological influence laminated organic sediments in some of the cores suggest that around 300 years ago a fresh water lake characterised verlorenvlei since then the picture revealed by high resolution palynology is one of progressive levels of human disturbance both in and around the study area sedimentological and palaeoecological analyses of additional cores from the vlei two from the distal inland and one from the proximal coastal end of the system serve further to elucidate the precise nature of sea level change in the late holocene and facilitate the construction of a refined holocene sea level curve for the region environmental changes in the late holocene are shown to be especially dynamic

modelling holocene relative sea level observations from the caribbean and south america abstract holocene data from the caribbean and the atlantic coast of south america have been critically assessed and a subset of the best quality data are presented these data cover a large north south geographic extent and display a distinct spatial variation we make the first comparisons of this data set to predictions based on a realistic model of glaciation induced sea level change with the main aims of understanding the cause of the observed spatial trend and estimating a eustatic signal for the holocene the spatial variation is dominated by the influence of the ice and ocean mass redistribution on sea level change with the ice induced effect dominating the observed north south trend a best fitting model is applied to estimate a holocene eustatic signal from the observations we find that the model corrected data are consistent with a relatively rapid rise of 7 8 mm yr in the early holocene with a marked reduction in this rate around 7 cal kyr bp from this time until present the model corrected data suggest that the volume of mass transfer between ice sheets and oceans was no more than 1 m eustatic sea level equivalent

the kaituri drumlin and drumlin stratigraphy in the kangasniemi area finland abstract the kangasniemi research area is part of the extensive pieksamaki drumlin field situated in central finland the most common drumlin types in the kangasniemi area are rock cored drumlinoids drumlin shields and till cored drumlins these landforms are composed of sandy till showing well developed fissility shear planes and a range of stratified structures till fabrics in the drumlins are strongly oriented and indicate changes in ice flow that occurred during drumlin formation the drumlins were formed in the late phase of the weichselian glaciation under a quick and strong southeasterly ice flow the drumlins in the kangasniemi area are mainly the result of deposition during ice flow accumulation of material occurred around rock or till cores ice flow erosion had only an effect on the uppermost part of the drumlins a clear example of the material accumulation is the onion shaped structure of the kaituri drumlin

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

late holocene environments at verlorenvlei western cape province south africa abstract evidence on late quaternary palaeoenvironments of the western and southwestern cape of south africa has facilitated detailed reconstructions mainly for the mountains where organic sediment accumulation has been favoured by relatively humid climates on the lowlands particularly those of the west coast region the search for sites traditionally regarded as suitable for the accumulation of sediments containing preserved fossil pollen has commenced only more recently this area of the western cape province has however provided quaternary scientists with a rich archaeological record that has yet to be tested against independent lines of palaeoecological evidence a sequence of sediments which have accumulated in what is today a large freshwater coastal lake verlorenvlei has been sampled at grootdrift 15 km inland of the coast a series of seven sediment cores was extracted during 1991 and three of these have now been sub sampled radiocarbon dated and subjected to a range of palaeoenvironmental techniques in particular pollen analysis sedimentology and geochemistry three pollen diagrams are presented which reveal the vegetation history of both the immediate grootdrift environment and the wider catchment during several periods over the last 5500 years a mid holocene higher sea level is evident in two of the cores which were examined for pollen throughout their length the surrounding area appears at this time to have been somewhat more arid than today following a hiatus in sedimentation some time after 4300 bp the marine conditions at the site disappear and are replaced by fresh water as the dominant hydrological and ecological influence around the time of colonial occupation of the region some 300 years ago lacustrine conditions prevailed at grootdrift and greater moisture availability is indicated in the catchment during the last 300 years the picture revealed by high resolution palynology of the third core is one of progressive levels of human disturbance both in and around the verlorenvlei evidence from a textural and geochemical analysis of the sediments is consistent with the interpretation based on fossil pollen the implications of this information are examined against the archaeology and palaeoecology of several cave sites in the vicinity of the vlei the consistency apparent in the range of types of evidence suggests that some reliance can be placed on the mid late holocene palaeoenvironmental reconstruction at verlorenvlei the paper thus provides insight into the nature of the complex interactions between late holocene climate change sea level fluctuation vegetation change vlei hydrology and human activity in the western cape coastal region

cortex a shipboard xrf scanner for element analyses in split sediment cores abstract the cortex corescanner texel is a non destructive xrf system for the logging of split sediment cores it is a seaworthy instrument that remains active during heavy weather conditions the scanner produces reliable counts for k to sr highly correlated with concentrations measured with atomic absorption spectrometry aas the option to scan al si and elements heavier than sr is in preparation a core section of 1 m can be scanned at 2 cm intervals within an hour a maximum resolution of 1 mm can be achieved at present each region and sedimentary environment requires separate calibration in the nearby future the generator settings will be standardized which may result in the development of a standard calibration procedure because of the high resolution of its semi quantitative records the cortex is a useful tool for detailed time series analysis inter core correlation and shipboard analysis

holocene variability in climate and oceanic conditions in the winter rainfall zone of south africa inferred from a high resolution diatom record from verlorenvlei

hydrographic variability in the st helena bay region of the southern benguela ecosystem cross shelf distributions of temperature salinity water masses and dissolved oxygen in st helena bay revealed substantial vertical and seasonal variations in the surface layers nearshore and offshore temperature and salinity patterns differed with bay scale variability linked to upwelling dynamics and coastal processes while the offshore region was influenced by solar insolation spectral analysis revealed that an annual signal prevailed at most stations and corroborated contrasting patterns between the offshore and nearshore regions with phase differences suggesting shoreward propagation of the offshore temperature signal the shelf was dominated by modified upwelled water muw and subantarctic mode water samw which comprised the primary source of upwelled water clear zonation of muw was evident across the shelf resulting from seasonal variations in locations of the oceanic and bifurcated shelf break fronts dynamics within st helena bay consistently differed from those further offshore due to the influences of the shelf break front cape columbine upwelling plume and cyclonic recirculation which appeared to be associated with an intraannual signal with a periodicity of 3 4 months persistent hypoxia in the bottom waters suggested the occurrence of a permanent reservoir of low oxygen water low seasonal shoreward and offshore expansion of low occurred throughout the upwelling season with maximum extent reached during summer and autumn due to the coupled effects of advection and local phytoplankton decay while wind mixing ventilated the water column at nearshore stations in winter and the onset of upwelling during spring introduced oxygen richer water from further offshore hypoxia persisted in the center of the bay

holocene vegetation history and palaeoenvironments at klaarfontein springs western cape south africa several sedimenit cores ai ounid the coastal lake of verlorenvlei westem cape have thus far revealed important details of the development of this semi arid winter rainfall environment during the late quatemary complex interplay between climate change sea level fluctuation and human activities have characterized the verlorenvlei record and suggests that these environments have been subject to high degrees of disturbance over time however due to the discontiniuous nature of the sedimentary record the holocene record has remained fragmentary investigation of a 6 in vibracore sequence at klaarfontein 32 25 26 s 18 29 40 e an artesian spring site some 18 km inland of eland s bay facilitates a more complete holocene palaeoenivironmental reconstruction pollen concentrations in 37 spectra distributed through the 6 m core vary with organic content but at all depths are stufficient to facilitate interpretation of vegetation history and reveal a high degree of dynamism in the local and regional enviro

new oceanic proxies for paleoclimate environmental variables such as temperature and salinity cannot be directly measured for the past such variables do however influence the chemistry and biology of the marine sedimentary record in a measurable way reconstructing the past environment is therefore possible by proxy such proxy reconstruction uses chemical and biological observations to assess two aspects of earth s climate system the physics of ocean atmosphere circulation and the chemistry of the carbon cycle early proxies made use of faunal assemblages stable isotope fractionation of oxygen and carbon and the degree of saturation of biogenically produced organic molecules these well established tools have been complemented by many new proxies for reconstruction of the physical environment these include proxies for ocean temperature mg ca sr ca 44ca and ocean circulation cd ca radiogenic isotopes 14c sortable silt for reconstruction of the carbon cycle they include proxies for ocean productivity 231pa 230th u concentration nutrient utilization cd ca 15n 30si alkalinity ba ca ph 11b carbonate ion concentration foraminiferal weight zn ca and atmospheric co2 11b 13c these proxies provide a better understanding of past climate and allow climate model sensitivity to be tested thereby improving our ability to predict future climate change proxy research still faces challenges however as some environmental variables cannot be reconstructed and as the underlying chemistry and biology of most proxies is not well understood few proxies have been applied to pre pleistocene times another challenge for future research only by solving such challenges will proxies provide a full understanding of the range of possible climate variability on earth and of the mechanisms causing this variability

holocene sea level fluctuations inferred from the evolution of depositional environments of the southern langebaan lagoon salt marsh south africa a holocene sea level curve is constructed from the facies distribution and radiocarbon ages of sediment recovered from the distal southern salt marsh of langebaan lagoon on the southwest coast of south africa calibrated radiocarbon analyses of an oyster rich bioclastic gravel indicate that the flandrian transgression flooded the lagoon to 0 3 m above present day levels by 6750 years ago 6 8 ka organic matter and shell material dated in distal lagoonal sediments indicate that sea level returned to present day levels by 4 9 ka and have since remained within 61 m of present day levels bleached shell and a hiatus in sedimentation suggest an approximate 1 m sea level lowstand between 2 5 and 1 8 ka changes in the macrobenthos assemblage since 1 5 ka that include the loss of the oysterostrea atherstonei razor clamsolen capensis brown musselarcuatula capensis and periwinkleoxystele variegata reflect loss of hard substrate decreased tidal flow velocities as reworked sands prograded into the southern la

three agulhas rings observed during the benguela current experiment a field program to study the circulation of the benguela current and its extension into the southeastern atlantic ocean has completed the survey and instrument deployment phase we report here new observations of three agulhas rings north and west of cape town south africa three mesoscale anticyclonic rings initially identified by means of topex poseidon altimetry were surveyed with expendable bathythermographs conductivity temperature depth oxygen profiles direct current measurements from a lowered acoustic doppler current profiler a hull mounted acoustic doppler current profiler and satellite tracked surface drifters characteristics of the rings are presented and their origins are discussed two are typical agulhas rings surveyed at different times after their generation the third agulhas ring has an anomalous water mass structure whose most likely origin is the subtropical front

holocene and deglacial ocean temperature variability in the benguela upwelling region implications for low latitude atmospheric circulation 1 mg ca analyses of g bulloides and abundances of n pachyderma left coiling from ocean drilling program odp leg 175 hole 1084b in the benguela coastal upwelling system document lower sea surface temperatures during the last glacial maximum lgm younger dryas mid holocene and little ice age in the southeastern atlantic taking into consideration the possible effects of differential carbonate dissolution the mg ca data indicate younger dryas temperatures 2 3 c cooler than those of the early holocene and lgm temperatures 4 5 c cooler than those of the early holocene the cool interval during the deglacial period at hole 1084b matches the timing of younger dryas shifts in cariaco basin and greenland ice sheet records and that of a nearby alkenone record comparison of mid holocene cooling at hole odp1084b with other high resolution records of holocene and last deglacial sea surface temperatures from the tropical atlantic implies consistent basin wide changes in atmospheric circulation a brief period of 1 5 2 c cooling between 17 8 and 17 2 ka if related to heinrich event 1 is consistent with a previously hypothesized tropical origin of all heinrich climate change events

holocene geochronology of a continentalshelf mudbelt off southwestern africa the holocene lithostratigraphy and geochronology of sediments on an inner continental shelf mud belt off the west coast of southern africa is presented based on a study of seven large gravity cores numerous grab samples and two vibracores two distinctive sections of the mudbelt have been identie ed the northern section is associated with the orange river prodelta and is dominated by laminated clay rich sediments while the southern section off namaqualand is associated with more homogeneous muds ams radiocarbon ages of 31 samples from these cores are problematic due to the absence of expected modern material at the sediment ocean interface and numerous age reversals and inconsistencies in some of the cores possible mechanisms to explain the apparently anomalously old surface and near surface samples are suggested most likely expla nations appear to lie in a combination of sediment retrieval problems the periodic loss of e ne particulate organic carbon from within the water column the sampling of possible relic sediments and most likely of all the incorporation into the sediments of 14 c depleted terrigenous organic matter the age reversals are especially evident in the laminated sediments and the entrainment of old carbon from the terrestrial source of these sediments is offered as the most parsimonious explanation stable carbon isotope analyses and a single lumi nescence age support the contention that radiocarbon date inconsistencies are a consequence of terrestrial inputs of carbon which is non contemporaneous with the actual time of sedimentation in studies of offshore accumulations of terrigenous material the marine derived organic fraction may therefore prove a more reliable measure of radiocarbon chronology

holocene climatic optimum in southwest africa evidence from the marine clay mineral record abstract sediment composition grain size and clay mineral record of a high resolution sediment core from the continental slope off namibia was investigated to gain information on the deposition of terrigenous matter in this part of the southwest african continental margin during the last 18 k y the depositional processes involved are fluvial input by the kunene river and eolian input from the namib and kalahari deserts each supplying characteristic mineral suites during low sea level erosion of the exposed shelf yields additional material the amount of eolian or fluvial matter depends on the strength of the transport process which is a function of aridity or humidity of the source area thus allowing paleoclimatic interpretations arid conditions prevailed during a low sea level from 18 to 15 ka and unconsolidated shelf sediment was mobilized and supplied to the slope by short distance transport by southerly winds a dramatic increase in the accumulation of terrigenous sediment is recorded from 15 to 10 ka without major changes in sediment composition which is attributed to increased runoff of the kunene river and fluvial erosion of shelf sediments this period coincides with a strengthening of the monsoonal system during a precessional minimum which is observed in numerous sites in central africa and indicates an intensified influence of the monsoon at the kunene headwaters a distinct shift in clay mineralogy towards river derived material marks a second period of increased river runoff during high sea level from 9 to 5 ka indicating maximum humidity in the source area from 6 to 5 ka this corresponds to the holocene climatic optimum observed in the arid belts of northern africa the present balance between fluvial and eolian input was reached approximately at 4 ka

influence of tropical easterlies in southern africa s winter rainfall zone during the holocene abstract south africa s southwestern cape occupies a critical transition zone between southern hemisphere temperate winter and tropical summer moisture bearing systems in the recent geological past it has been proposed that the relative influence of these systems may have changed substantially but little reliable evidence regarding regional hydroclimates and rainfall seasonality exists to refine or substantiate the understanding of long term dynamics in this paper we present a mid to late holocene multi proxy record of environmental change from a rock hyrax midden from katbakkies pass located along the modern boundary between the winter and summer rainfall zones derived from stable carbon and nitrogen isotopes fossil pollen and microcharcoal these data provide a high resolution record of changes in humidity and insight into changes in rainfall seasonality whereas previous work concluded that the site had generally experienced only subtle environmental change during the holocene our records indicate that significant abrupt changes have occurred in the region over the last 7000 years contrary to expectations based on the site s location these data indicate that the primary determinant of changes in humidity is summer rather than winter rainfall variability and its influence on drought season intensity and or length these findings are consistent with independent records of upwelling along the southern and western coasts which indicate that periods of increased humidity are related to increased tropical easterly flow this substantially refines our understanding of the nature of temperate and tropical circulation system dynamics in sw africa and how changes in their relative dominance have impacted regional environments during the holocene