radiocarbon dates and the late quaternary palaeogeography of the province of the eastern cape south africa abstract a total of 193 dates are listed from the eastern cape middle stone age hunter gatherers existed in the drakensberg prior to the rigours of cold climatic conditions after ca 22 000 bp these uplands were reoccupied under more favourable climatic conditions after ca 12 600 bp but were apparently abandoned between ca 6000 bp and 3000 bp hunter gatherer occupation throughout the holocene is indicated at lower altitudes with in migration of pastoralists ca 1800 bp in the fish river area and with iron age farmers entering coastal districts and adjacent river valleys from ca 1400 bp sand dunes accumulated in the holocene adjacent to the indian ocean flood plain development in the early holocene was succeeded by incision of rivers in the later holocene flood plain deposition began again in the southern drakensberg ca 1000 bp palynological studies evidence marked climatic oscillations around the late glacial holocene boundary with apparent stability at high altitude subsequent to 2700 bp

sand ramps in the golden gate highlands national park south africa evidence of periglacial aeolian activity during the last glacial abstract sand ramps have been identified in a side valley on the southern side of the little caledon river in the golden gate highlands national park free state south africa the site lies in the foothills of the northern drakensberg maluti mountains and this study aims to explore the potential of such deposits to add to the sparse palaeoenvironmental record of the region up to 11 m of aeolian sand banked against north facing slopes is exposed by fluvial incision through the deposits revealing interbedded fluvial lenses and palaeosols the region is currently devoid of significant aeolian sediment transport or deposition and supports well developed grassland vegetation these deposits testify to former conditions different from those of today which would have been characterised by depleted vegetation and a different wind and or climatic regime biogenic proxies are absent from the deposits but optically stimulated luminescence osl dating of the sediments reveals that they accumulated at intervals throughout much of the last glacial event from around 45 to 16 ka these dates are consistent with those of vegetation changes from palaeoecological sites elsewhere in the region and also with dated evidence for niche glaciation further south in the high drakensberg evidence from this study supports significant landscape changes in the drakensberg during the last glacial with the foothills in the region of golden gate highlands national park subject to aeolian processes under a periglacial environment

carbonates within a pleistocene glaciomarine succession yakataga formation middleton island alaska uplifted during the 1964 alaskan earthquake extensive intertidal flats around middleton island expose 1300 m of late cenozoic early pleistocene yakataga formation glaciomarine sediments these outcrops provide a unique window intooutershelfandupperslopestratathatareotherwiseburiedwithinthesoutheast alaska continental shelf prism the rocks consist of five principal facies in descending order of thickness i extensive pebbly mudstone diamictite containing sparse marine fossils ii proglacial submarine channel conglomerates iii burrowedmudstoneswithdiscretedropstonelayers iv boulderpavements whose upper surfaces are truncated faceted and striated by ice and v carbonates rich in molluscs bryozoans and brachiopods the carbonates are decimetre scale in thickness typically channellized conglomeratic event beds interpreted as resedimented deposits on the palaeoshelf edge and upper slope biogenic components originated in a moderately shallow ca 80 m relatively sediment free mesotrophic sub photicsetting thesecomponentsareamixture of parautochthonous large pectenids or smaller brachiopods with locally important serpulid worm tubes and robust gastropods augmented by sand size bryozoan and echinoderm fragments ice rafted debris is present throughout these cold water carbonates that are thought to have formed during glacial periods of lowered sea level that allowed coastal ice margins to advance near to the shelf edge such carbonates were then stranded during subsequent sea level rise productivity was enabled by attenuation of terrigenous mud deposition during these cold periods via reduced sedimentation together with active wave and tidal current winnowing near the ice front redeposition was the result of intense storms and possibly tsunamis these sub arctic mixed siliciclasticcarbonate sediments are an end member of the phanerozoic global carbonate depositional realm whose skeletal attributes first appeared during late palaeozoic southern hemisphere deglaciation

origin and evolution of lunettes on the high plains of texas and new mexico lunettes isolated dunes on the lee side of playa basins are common landforms on the southern high plains of northwest texas and eastern new mexico the dunes contain calcareous 15 40 caco3 sandy loam or loamy sand with minor amounts of sepiolite deposited 25 000 800014c yr b p and derived by deflation of lacustrine carbonate in the basins the dunes also contain low carbonate 0 15 caco3 sand or loamy sand that was deposited 25 000 15 000 yr b p and 8000 5000 yr b p and was derived by deflation that created the basins or deflated from sand deposited in the basins buried soils are common in the lunettes a bk profiles characterize soils formed in the calcareous sandy loam the sandy low carbonate sediments contain a bt profiles in the oldest sand of some dunes and a bw a bt or a btk in the early and middle holocene sand the dune stratigraphy combined with carbon isotope data derived from dated a horizons in lunettes suggests the following scenario for the southern high plains the lunettes began forming as low carbonate sand dunes in the late pleistocene as playa basins were formed or deepened by wind erosion the erosion repeatedly alternated with stability the environment probably was cool and dry but one or more cool and wet intervals 25 000 15 000 yr b p resulted in a rise in the water table and deposition of lacustrine carbonate in the deepest basins there may have been short departures toward warmer and probably toward drier conditions throughout this time episodically dry conditions 15 000 8 000 yr b p resulted in deflation of the carbonate and further dune construction by repeated accretion of calcareous sandy loam or loamy sand the low carbonate sand was deposited during widespread drought and deflation 8000 5000 yr b p the dunes have been largely stable in the late holocene

the earthquake triggered rock avalanche of cui hua qin ling mountains p r of china the benefits of a lake damming prehistoric natural disaster abstract this paper deals with an investigation of cui hua rock avalanche in the qin ling mountains in the dong cha valley an eastern branch of taiyi river some 30 km south of xi an province of shaanxi p r of china the landslide originated on lithotectonic structures along seismic active fault systems its occurrence could be correlated with an earthquake in 780 bc that must have triggered the landslide due to a stabilizing human input the landslide area in front of the dammed tianchi lake became an area of settlement for native people of this area which used this rapidly geomorphologic changing system for their needs over the past 2780 years nowadays the lake is considered to be a reservoir for drinking water agriculture and a hydropower plant even more the deposit of the cui hua rock avalanche has become a touristic place for sightseeing and vacation

controls on early permian shelf deglaciation in the karoo basin of south africa abstract the late carboniferous to early permian glacigene dwyka group has at its top three types of transitions from diamictite to postglacial mudrock in the southern karoo the type 1 transition sequence consists of clast poor carbonate rich diamictite having a sharp contact with the overlying mudrocks this diamicton accumulated slowly by rain out and sediment gravity flow processes during sedimentation the polar ice front was stabilised by a possible ice shelf collapse of the ice shelf caused rapid ice margin retreat the type 2 transition sequence consists of clast poor diamictite with sandstone bodies overlain by mudrock with ice rafted debris or thin interbedded debris flow diamictites deposition of the diamictite facies occurred during oscillations of a subpolar ice front with short stable periods of surface melting of the ice resulting in the formation of small subaqueous outwash fans the type 3 transition sequence consists of bouldery diamictite interbedded with massive or sandstone bearing diamictite overlain by mudrock with ice rafted debris or thin interbedded debris flow diamictites the sequence represents highly unstable ice front conditions and fluctuating sea levels with periods of rapid deposition probably by collapsing ice streams climatic conditions may have alternated between polar and subpolar the type 1 transition sequence is predominant in the western part and the type 3 sequence in the eastern part of the karoo basin long term controls on deglaciation was climatic warming as gondwana drifted over the pole as well as changes in land sea configuration superimposed on these were local controls such as relative sea level changes presence of deformable substrate and meltwater production

the permo carboniferous dwyka formation of southern africa deposition by a predominantly subpolar marine ice sheet abstract the 800 m thick glacigene dwyka formation was deposited along the northern margin of the permo carboniferous dwyka basin which covered an area of approximately 2 10 6 km 2 in southwestern gondwana the palaeogeographic setting geochemical data of the mudrocks and diamictites and the palaeontology indicate marine conditions during sedimentation ice lobes from spreading centres in the north east and south coalesced in the basin to form an extensive ice cover from the westphalian to the late sakmarian lodgement rain out and subaqueous debris flow diamictons subaqueous and subglacial melt water sands suspended mud and turbidity current sands and silts accumulated in the dwyka basin sedimentation started on the continental shelf during a grounded ice sheet stage predominantly lodgement processes then a floating ice stage predominantly debris rain out and finally an ice sheet disintegration stage debris rain out sand fall out and suspension settling of mud the palaeogeographic setting presence of marine conditions in the basin and the scale of glaciation indicate deposition from a predominantly mid latitudinal marine ice sheet the overall characteristics of the glacial sequence are neither typical of a polar nor a temperate setting and for such ancient glaciations a subpolar setting with the presence of unstable ice shelves is suggested

late quaternary climatic changes and associated human responses during the last 45 000 yr in the eastern and adjoining western cape south africa abstract palaeoenvironmental evidence indicative of former climatic conditions in the eastern and adjoining western cape during the last 45 000 yr is presented and summarised interstadial conditions began before 43 000 bp but were succeeded by stadial conditions at 24 000 bp these climatic phases are designated the birnam interstadial and the bottelnek stadial after the type sites at which they were identified in the eastern cape the bottelnek stadial apparently equates with the last glacial maximum late glacial warming was apparent by 18 17 000 bp sea level rose markedly by 14 000 bp climatic oscillations marked the end of the late glacial the early holocene was drier than the late holocene and at least in the drakensberg there was marked aridity in the mid holocene human responses to these climatic events are briefly described

the polonez cove formation of king george island antarctica stratigraphy facies and implications for mid cenozoic cryosphere development the middle to late oligocene polonez cove formation exposed on south eastern king george island south shetland islands provides rare evidence of mid cenozoic west antarctic cryosphere evolution a revised lithostratigraphy and facies analysis and a review of the palaeoenvironmental significance of the formation are presented here the diamictite dominated basal member of the formation krakowiak glacier member records the presence and retreat of marine based ice on a shallow continental shelf five overlying members are recognized these consist of basaltic sourced sedimentary rocks and lavas and represent a variety of shoreface and shallow continental shelf environments in an active volcanic setting these units contain diverse reworked and ice rafted exotic clasts that become sparse towards the top of the formation suggesting a continuing but waning glacial influence new 40ar 39ar dates from interbedded lava flows indicate a late oligocene age 25 6 27 2 ma for the polonez cove formation but are slightly younger than skeletal carbonate sr isotope ages obtained previously 28 5 29 8 ma there is evidence for wet based subice conditions at the base of the polonez cove formation but no sedimentary facies to suggest substantial meltwater this may reflect a subpolar setting or may result from lack of preservation or a high energy depositional environment a northern antarctic peninsula south shetland islands provenance is probable for most non basaltic clasts but certain lithologies with possible origins in the transantarctic and ellsworth mountains also occur sparsely throughout the formation there is evidence to suggest that the presence of such far travelled clasts within subglacially deposited facies at the base of the formation reflects the advance of a local ice cap across marine sediments containing the clasts as ice rafted material the presence of these clasts suggests that extensive marine based ice drained into the southern weddell sea region and that a strong weddell sea surface current operated both before and during deposition of the polonez cove formation

subglacial sedimentary features in late palaeozoic sedimentary rocks central victoria australia abstract a section of late palaeozoic diamictite in the bacchus marsh formation in central victoria southeastern australia contains 1 1 striated boulders with long axes tilted up glacier 2 2 layers of pebbles lacking evidence of water sorting 3 3 thin sheets and lenses of sandstone 4 4 slab like and contorted sandstone bodies cut by closely spaced step fractures 5 5 thin slabs of rhythmically bedded siltstone and claystone the boulders indicate that the diamictite was deposited by lodgement beneath moving wet based glacial ice the sandstone sheets and lenses indicate periods of rapidly increasing subglacial water pressure and the deformed sandstone bodies indicate flow of some of the newly deposited diamicton in response to shear imparted by the overlying ice the pebble layers probably formed as a moving carpet of clasts close to the controlling obstacle size of the glacier during deposition from a layer of mobile subsole debris which then halted these features indicate changes in subglacial conditions that may have led to surging behaviour by the glacier the model of pebble layer formation allows an estimate of ice sliding velocity during layer formation and thus provides a method of quantifying one aspect of ice behaviour for a pre pleistocene glacier

criteria for the recognition of salt pan evaporites layered evaporites can accumulate in 1 ephemeral saline pans 2 shallow perennial lagoons or lakes and 3 deep perennial basins criteria for recognizing evaporites deposited in these settings have yet to be explicitly formulated the characteristics of the ephemeral saline pan setting have been determined by examining eight holocene halite dominated pans salt pans and their deposits marine and non marine from the u s mexico egypt and bolivia these salt pans are typified by alternating periods of flooding resulting in a temporary brackish lake evaporative concentration when the lake becomes saline and desiccation which produces a dry pan fed only by groundwater the resulting deposits consist of alternating layers millimetres to decimetres of halite and mud the layers of halite are characterized by 1 vertical and horizontal cavities rounded crystal edges and horizontal truncation surfaces due to dissolution during flooding 2 vertical chevrons and cornets grown syntaxially on the bottom during the saline lake stage 3 halite cements overgrowths and euhedral cavity linings and disruption of layering into metre scale polygons produced during the desiccation stage the muddy interbeds are characterized by displacive growth of halite during the desiccation stage immediately below the surface of the pan the halite layers are matured by repeated episodes of dissolution and diagenetic crystal growth this results in porous crusts with patches of chevron and cornet crystals truncated by dissolution clear diagenetic halite cement and internal sediment these layers of mature halite closely resemble the patchy cloudy and clear textures of ancient halite deposits holocene salt pans are known to cover thousands of square kilometres and cap halite deposits hundreds of metres thick so they are realistic models for ancient evaporites in scale e g permian salado formation of new mexico texas which preserves many primary salt pan features

late quaternary lunette dune sedimentation in the southwestern kalahari desert south africa luminescence based chronologies of aeolian activity abstract through the application of luminescence dating techniques great advances have recently been made in the understanding of the late quaternary histories of many dryland regions including southern africa here this work has largely applied optical dating to sediments from the extensive linear dune systems which dominate the kalahari region of the central southern african interior relatively little attention has been given to localised aeolian accumulations such as lunette dunes despite their wide distribution over many parts of the region in particular the arid southwest kalahari to redress this we consider the palaeoenvironmental significance of pan margin lunettes and investigate the timing of lunette dune development in the southwest kalahari through the application of optical dating to sediments from lunette dunes associated with four closed basins pans ages show that localised aeolian activity occurred frequently throughout the past 18 ka indicating that the factors controlling lunette sedimentation are markedly different from those determining regional linear dune development it is proposed that the mechanisms controlling sediment supply to lunette dunes are controlled at both the regional and local pan specific scales by factors such as groundwater levels where pans support more than one discrete lunette the time since any individual lunette crest received significant accumulations of sediment increases with distance away from the pan margin outer and inner lunette sequences may be chronologically disparate features inner lunette formation may arise in response to modifications to the local atmospheric boundary conditions by the presence of large downwind outer lunette features or by shifts in sediment supply

the sedimentary record of drifting ice early wisconsin sunnybrook deposit in an ancestral ice dammed lake ontario canada abstract outcrops of pebbly mud diamict at scarborough in southern ontario canada the so called sunnybrook till are associated with the earliest incursion of the laurentide ice sheet lis into mid continent north america some 45 000 years ago the sunnybrook is a blanket like deposit containing deepwater ostracodes and occurs conformably within a thick 100 m succession of deltaic and glaciolacustrine facies that record water depth changes in a large proglacial lake contextual evidence associated facies sedimentary structures deposit geometry and landforms indicates a low energy depositional setting in an ice dammed ancestral lake ontario in which scouring by floating ice masses was an important process u shaped iceberg cut scours with lateral berms up to 7 m deep occur on the upper surface of the sunnybrook and are underlain by sub scour structures that extend several meters below the scour base ice rafted concentrations of clasts clast layers grooved surfaces formed by floating ice glissading over a muddy lake floor soft sediment striations and melanges of sand and mud mixed by grounding ice keels ice keel turbates are present and are all well known from modern cold environments the wider significance of this depositional model is that the lis margin lay east of scarborough and did not overrun southern ontario this finding is in agreement with recent data from the erie basin of canada ohio and indiana where deposits formerly correlated with the sunnybrook and thus implying an extensive early wisconsin ice sheet are now regarded as illinoian a speculative hypothesis is proposed that relates deposition of the sunnybrook and two younger deposits of similar sedimentology to surge like instabilities of the southern lis margin

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

glacially derived shallow marine gold placers of the cape yakataga district gulf of alaska abstract economic gold bearing coastal sediment of holocene age 10 ka occurs along the gulf of alaska coastal margin from cape yakataga in the west to icy bay in the east a distance of 50 km deposits have been worked since 1898 and total production since then is about 15 000 ounces gold is recovered from discontinuous sheets of ruby garnet rich beach sand exposed at low tide along the high energy storm dominated coastline similar auriferous sand facies are also present within raised marine terraces cut across outwash fans along the narrow mountainous coastal margin the area has been uplifted by glacio isostatic rebound following the last glacial maximum and by high magnitude earthquakes the area lies along the collision zone between the north american and pacific plates study of uplifted and well exposed late cenozoic strata the glaciomarine yakataga formation that outcrop along the coastal margin confirms this succession as the source of placer gold the yakataga formation records the rapid accumulation of over 6 km of gold bearing glaciomarine sediments in a rapidly subsiding forearc basin these strata have in turn been uplifted as coastal mountains and eroded by glaciers the white river glacier and yakataga glacier drainage basins can be identified as the principal source of detrital gold along the yakataga coastline auriferous beach sediment is the product of westward reworking of glacial outwash from the white and yakataga rivers and is accompanied by a well defined downcurrent reduction in the size and number of gold particles

evidence of glacial abrasion in the calingasta uspallata and western paganzo basins mid carboniferous of western argentina abstract evidence of glacial abrasion is present in the basal part of the carboniferous section of the calingasta uspallata and paganzo western argentina where subglacial and proximal glacial marine diamictites with pebbly dropstone shales constitute the dominant facies association intraformational striated pavements are exposed in the hoyada verde and leoncito formations of the calingasta uspallata basin marine invertebrate fossils levispustula zone in associated shales indicate a mid carboniferous age for both units a single layer striated boulder pavement is superbly exposed in the hoyada verde formation local a axis clast imbrication in the underlying bouldery diamictite and strong parallel striae on the flattened upper surfaces of boulders indicate a subglacial origin for the pavement paleo ice flow directions have an nne ssw strike the leoncito intraformational pavement is shaped on bioturbated fine grained sandstones with plant remains glacial striations are straight and parallel with subcircular cross sections dome like features are present in the surface which is covered in turn by a sandy bouldery diamictite four striated surfaces are present in the western paganzo basin three of them pavements at the san juan river valley loma de los piojos and agua hedionda are developed on basement rocks they contain parallel to subparallel striations nailhead striations crescentic gouges impact marks and furrows the pavements are overlain by thin up to 1 5 m laterally discontinuous diamictite beds with striated clasts some of them bullet shaped paleo ice flow directions are n ne directed an intraformational pavement is also present at the san juan river valley section it is carved on the top of the basal diamictite and exhibits furrows probably caused by subglacial soft sediment grooving the dispersion of paleo ice flow directions in the calingasta uspallata and paganzo basins indicates i regional slopes toward the north into a brackish water embayment and northwest into the open marine conditions ii glacial erosion by ice grounded below sea level and confined to the margins of the basins

a model for striated boulder pavement formation on glaciated shallow marine shelves an example from the yakataga formation alaska abstract laterally extensive striated boulder pavements crop out within glaciomarine diamicts of the early pleistocene yakataga formation on middleton island alaska boulder pavements consist of planes of one clast thickness with faceted upper surfaces showing consistently oriented striation directions cropping out over several kilometers along strike clasts do not have the preferred long axis alignment nor the characteristic bullet shape of boulders transported at a glacier base and deposited by lodgement processes in most cases pavements identify the planar bounding surfaces of thick up to 100 m tabular units of fossiliferous muddy diamict deposited by the settling of fine grained sands and muds from suspension together with ice rafted debris in water depths between 20 and 250 m diamict facies both underlying and overlying the pavements contain abundant unabraded macro and microfossils and show no evidence of deformation by subglacial shear processes pavements appear to have originated as boulder lag surfaces produced by wave and tidal current winnowing of diamict on relatively shallow bank areas during episodes of relative sea level lowering lags were subsequently overridden and abraded by a grounding ice shelf the glacially abraded pavements are thought to record the repeated expansion of a partially floating ice shelf to the edge of the gulf of alaska continental shelf during the early pleistocene recognition of boulder pavements formed in this manner may help establish the former presence of ice shelves whose depositional record remains enigmatic

the athabasca fluting field alberta canada implications for the formation of large scale fluting erosional lineations abstract current drumlin and fluting hypotheses centred on processes of formation erosion and deposition by subglacial deformation accretion by lodgement glacial erosion and meltwater erosion and deposition rarely receive comprehensive field testing this paper documents the morphology internal structure and landscape associations of the athabasca fluting field alberta and discusses how well these characteristics are explained by postulated fluting forming processes fluting hypotheses are comprehensively tested by this approach and their rejection or acceptance are firmly based on field observation and knowledge of processes using multiple criteria fluting is shown to be erosional and not to be a product of pervasive subglacial deformation or accretion by lodgement morphology landscape associations bed truncation plus glaciofluvial lags and gravel on fluting ridges are inferred to support erosion by meltwater intact primary bedding synsedimentary faults and injection structures very close to the landsurface showing no sign of shear deformation are used to reject erosion by subglacial deformation fluting is shown to be closely associated with tunnel channels and indicates that these channels were overtopped by broad floods that formed the fluting field and eroded anabranching tracts over the length of the alberta plains prior to fluting formation sequences with melt out and lodgement till conduit sediment and boulder lags record net deposition over an extended time period diapirism prior to fluting formation marks a period of extreme pressure gradients which are related to bed separation following fluting formation there was only minimal landscape modification dominated by glaciofluvial and glaciolacustrine deposition not glacial processes this progression is presented as evidence for two very different glacial regimes separated by a short period with diapirism and extensive landscape modification by meltwater erosion we note that the study area was glaciated only once during the late wisconsinian and it follows that glacial sedimentation and landscape modification were confirmed to this single glacial episode

spatial variability and hydrologic evolution of australian lake basins analogue for pleistocene hydrologic change and evaporite formation abstract processes evident in basins across hydrologic gradients from humid to arid regions today provide analogues for systems that may have operated in some individual basins during periods of past hydrologic change thus lakes in humid regions today with low salinity sedimentary facies and with morphology controlled largely by wave action may closely resemble past lacustral pluvial phases experienced in zones which today are relatively arid and saline conversely playas controlled today by groundwater and in some cases subject to defletion may resemble those arid and dune building stages experienced by basins in sub humid regions today as they underwent glacial age desiccation in any such sequence of spatial or temporal gradients from humid to more arid conditions the frequency of basin filling and drying modulates the rate of evaporitive loss of interstitial waters from the exposed basin surface this in turn controls the salinity evolution of the interstitial and local groundwaters the notion of closed systems for terminal lakes while satisfactory for analysis of surface water budgets is quite inapplicable to the evolution of brines where surfacewater groundwater exchange during the high salinity drying stages becomes a controlling factor affecting all salt budgets in these systems evaporites may only be preserved when the sub surface waters have evolved to salinites near saturation for the salts concerned if sub surface waters are frequently diluted by surfacewater groundwater exchange evaporites will not be preserved in the record even though the surface system appears hydrologically closed the process of interstitial water evolution which controls efflorescence deflation and salt weathering exerts a dominating influence on basin geomorphic expression as well as on hydrochemical fractionation

maximum extent and dynamic behaviour of the last british irish ice sheet west of ireland a complete reconstruction of the last british irish ice sheet biis is hindered by uncertainty surrounding its offshore extent and dynamic behaviour this study addresses this problem by reconstructing the depositional history of four sediment cores taken from a series of sinuous glacigenic sediment ridges on the continental shelf west of ireland we present new geomorphic sedimentary and micropaleontological data that record a maximum westward biis extent that was at least 80 km farther offshore from any previous estimates the data suggests that a large ice shelf formed over parts of the shelf prior to retreat this new data increases the areal extent of grounded biis ice by 6700 km2 from previous estimates which represents a 3 increase in the irish sector of the ice sheet three new ams radiocarbon dates demonstrate for the first time that the biis advanced to the shelf edge during last glaciation late midlandian late devensian with ice advance onto the porcupine bank occurring after 24 720 260 yr cal bp deglaciation was complete by 19 182 155 yr cal bp thus constraining biis occupation over the porcupine bank to less than 5500 years estimated retreat rates of marine terminating ice across the shelf range from 70 to 180 myr 1

geomorphological significance of ontario lacus on titan integrated interpretation of cassini vims iss and radar data and comparison with the etosha pan namibia abstract ontario lacus is the largest lake of the whole southern hemisphere of titan saturn s major moon it has been imaged twice by each of the cassini imaging systems imaging science subsystem iss in 2004 and 2005 visual and infrared mapping spectrometer vims in 2007 and 2009 and radar in 2009 and 2010 we compile a geomorphological map and derive a hydrogeological interpretation of ontario lacus based on a joint analysis of iss vims and radar sar datasets along with the t49 altimetric profile acquired in december 2008 the morphologies observed on ontario lacus are compared to landforms of a semi arid terrestrial analog which resembles titan s lakes the etosha pan located in the owambo basin namibia the etosha pan is a flat floored depression formed by dissolution under semi arid conditions of a surface evaporitic layer calcretes controlled by groundwater vertical motions we infer that ontario lacus is an extremely flat and shallow depression lying in an alluvial plain surrounded by small mountain ranges under climatic conditions similar to those of terrestrial semi arid regions channels are seen in the southern part of ontario lacus in vims and radar data acquired at a 2 years time interval their constancy in location with time implies that the southern portion of the depression is probably not fully covered by a liquid layer at the time of the observations and that they most probably run on the floor of the depression a shallow layer of surface liquids corresponding to the darkest portions of the radar images would thus cover about 53 of the surface area of the depression of which almost 70 is located in its northern part these liquid covered parts of the depression where liquid ethane was previously identified are interpreted as topographic lows where the alkanofer raises above the depression floor the rest of the depression and mostly its southern part is interpreted as a flat and smooth exposed floor likely composed of a thick and liquid saturated coating of photon absorbing materials in the infrared this hypothesis could explain its dark appearance both in the infrared and radar data and the persistence of channels seen on the depression floor over the time shorelines are observed on the border of ontario lacus suggesting past high stand levels of the alkanofer table the analogy with the etosha pan suggests that ontario lacus depression developed at the expense of a soluble layer covering the region dissolution of this layer would be controlled by vertical motions of the alkanofer table over the time during flooding events liquid hydrocarbons covering the depression floor would dissolve the surface layer increasing progressively the diameter of the depression on geological timescales during drought episodes liquid hydrocarbons of the underground alkanofer would evaporate leading to crystallization of evaporites in the pores and at the surface of the substratum and to the formation of the regional soluble layer the presence of specific landforms lunette dunes or evaporites is compatible with such evaporitic regional settings alternatively but not exclusively the surface soluble layer might have formed by accumulation on the ground of soluble compounds formed in the atmosphere

characteristics and genetic mechanism of the cuihua rock avalanche triggered by a paleo earthquake in northwest china abstract the cuihua rock avalanche 30 km south of xi an china is located within a marvelous geological landscape and was triggered by an ancient paleo earthquake the area is mainly characterized by cliffs stone seas and a dammed lake shuiqiu pool with a total area of 5 105 m2 and a volume of 1 8 107 m3 field investigations historical records dating methods and typical seismic profiles indicated that its occurrence could be correlated with an earthquake in 780 bc that most likely triggered the landslide the results also showed that a the formation of the rock avalanche was associated with high steep slope created by lifting of qinling mountain and cutting of rock fractures and b the high steep slope and several preferred structural planes play an important role in controlling the slope instability based on conjectures the failure process of the rock avalanche can be divided into four stages the preliminary stage the starting up stage the accelerating stage and the accumulating stage

a holocene late pleistocene aeolian record from lunette dunes of the western free state panfield south africa the greatest concentration of pans in southern africa occurs in the western free state province south africa a feature of many free state pans is their fringing lunettes located on the southern

evidence for a glacial origin of neoproterozoic iii striations at oaibaccannjar ga finnmark northern norway the origin of the famous late precambrian striated pavement at oaibaccannjar ga bigganjargga northern norway remains controversial most investigators have accepted a glacial formation but some prefer a soft sediment mechanism however a newly discovered c 2 5 mm thick zone of brecciation under rare polished striations indicates a hard substrate during formation and thus a glacial origin for the striations other points indicating that the striations formed in a hard substrate are 1 the striated platform in the veidnesbotn formation is c 150 ma older than the overlying diamictite smalfjord formation having been buried to c 2 5 km depth cementation should have started before smalfjord times 2 the marked irregularity of the sub smalfjord formation palaeotopography on skjaholmen 3 the presence of rounded veidnesbotn formation boulders in the diamictite above the striations imprints of clasts appearing to lie across the striations are re interpreted as relicts of mud flakes within the veidnesbotn formation which were cut across and quarried out during pavement formation the origin of the overlying diamictite tillite vs debris flow is not constrained by the presence of glacial striations and most probably was deposited some time after striation formation

intertidal boulder pavements in the northeastern gulf of alaska and their geological significance abstract striated boulder pavements consisting of planar concentrations of clasts having striated upper surfaces are a common feature of glacigenic deposits but their origin is not well understood laterally extensive pavements are currently forming in the intertidal zone west of icy bay in the gulf of alaska pavements comprise armoured layers of interlocking boulders one clast thick that have been eroded from underlying outcrops of late cenozoic glaciomarine diamictites they originate essentially as lag surfaces along a high energy storm dominated mesotidal shoreline boulder pavements are either flat or show a nucleated plan form where successively smaller boulders have been accreted around a large core boulder nucleation imparts a hummocky surface topography to the pavements and suggests that some form of size sorting of clasts has occurred packing is promoted by repeated tamping of the clast lag by floating masses of glacier ice which become grounded across the intertidal zone at low tide repeated abrasion of the pavement surface by debris contained within ice blocks produces smooth flattened clast upper surfaces and short randomly oriented striations data from icy bay can be used to constrain the origin of laterally extensive boulder pavements exposed in late cenozoic glaciomarine sediments on middleton island the significance of such pavements in the geologic record is that they form along erosional unconformities and may identify sequence boundaries

geomorphic evidence for late quaternary environmental change from the eastern great karoo margin south africa abstract the eastern margins of the great karoo south africa represent a transition zone between the semi arid shrublands of the karoo to the west and the moister grasslands of the east for this reason the surficial sediments and younger geomorphic features of the area might reliably be expected to record evidence for environmental change particularly with regard to the precipitation record and phases of greater aridity as the boundary of the karoo migrated in response to climate change during the late quaternary the high altitude catchment on which we report here is situated on the inland flank of the upwarped south african great escarpment which here forms the stormberg range the catchment is unique in that a number of geomorphic features have within their structure preserved evidence of aeolian fluvial and colluvial processes which were active in the past we present evidence from a variety of depositional landforms and sedimentary deposits that suggests that late quaternary climates in the eastern karoo have been both moister and significantly more arid than at present as well as displaying a greater seasonality in rainfall

assessment of a catastrophic rock avalanche in the west mongolian altai mountains abstract a giant rock avalanche that resulted in the formation of a dammed lake was discovered during geological mapping in the valley of the dund tsenkher gol river munhkhairkhan soum western mongolian altai field and satellite data worldview 2 and sentinel 1 were used to obtain a geomorphological description of the landslide and a 3d geometric reconstruction of the rock avalanche with deposits exceeding 14 million cubic meters in volume the rock avalanche is one of the largest catastrophic landslides in the world the rock avalanche was controlled by tectonic setting the slope instability was favored by the presence of nw se and ne sw trending fault systems steep foliation and morphology the rock avalanche was likely triggered by an earthquake related to the activity of the tolbonuur and hovd faults although the area is sparsely populated the settlement of munhkhairkhan soum is threatened by rockfalls or even by rock avalanches that could be triggered by future earthquakes along these faults

facies and architecture of a carboniferous grounding line system from the guandacol formation paganzo basin northwestern argentina abstract new outcrops of middle carboniferous glacigenic deposits found in the guandacol formation western paganzo basin are described in this paper the study locality of los pozuelos creek northwestern argentina includes coarse grained diamictites rhythmites laminated pebbly mudstones and shales that represent an expanded column of the gondwanic glaciation in this region thirteen lithofacies recorded at the measured section have been grouped into three facies associations facies association i is composed of coarse grained massive and stratified diamictites lithofacies dmm dms dmg dcs laminated siltstones with dropstones fld and interstratified sandstones and mudstones fl sr these rocks represent both tillites and resedimented diamictites closely associated to small water bodies where laminated siltstones with dropstones and stratified sandstones and mudstones were deposited facies association ii comprises couplets of matrix supported thinly bedded diamictites dmld and laminated mudstones with dropstones fld this facies association results from the combination of three different processes subaqueous cohesionless debris flows coeval rainout of ice rafted debris and settling of fine grained particles from supension finally facies association iii is made up of laminated mudstones without dropstones thin marl levels and scarce fine to very fine grained sandstones this assemblage clearly suggests sedimentation in a deep marine environment below the wave base the architecture of the glacigenic deposits has been investigated using photomosaic panels the geometry of the depositional bodies and facies suggest that los pozuelos creek outcrops exhibit a well preserved three dimensional example of a grounding line system in particular three different subenvironments of a morainal bank were interpreted a bank front a bank core and a bank back the bank front assemblage is characterized by coarse grained mainly resedimented diamictites grading laterally to prograding clinoforms composed of interbedded matrix supported thinly bedded diamictite and mudstones the bank core assemblage is formed by a stacking of coarse grained diamictites where at least five major erosional surfaces bounding four multistory diamictite bodies can be recognized finally the bank back assemblage corresponds to discontinuous intervals of striated lodgement till and coarse grained resedimented diamictites showing important post depositional deformation the retrogradational stacking of the morainal banks indicate an overall glacial retreat and a glacioeustatic sea level rise erosional surfaces at the base of each morainal bank suggest intervening short term episodes of ice advance the new data presented here confirm the existence of true tillites in western paganzo basin and suggest several at least four pulses of glacial advance and retreat during the namurian glaciation in the region and permit a more refined interpretation of the glacial deposits in the huaco area

drumlin evolution and ice sheet oscillations along the ne atlantic margin donegal bay western ireland abstract satellite imagery of donegal bay northwestern ireland reveals two streamlined subglacial bedform sets produced during the late devensian glaciation ca 22 000 15 000 yrs b p the first bedform set trends northeast southwest and records fast ice flow from inland ice domes onto the eastern atlantic continental shelf the second bedform set trending east west crosscuts and partially reorientates the first morphological and sedimentary evidence show that the second set corresponds to the last phase of fast ice flow drumlinization in northwestern ireland morphological characteristics of the donegal bay drumlin field and sedimentary characteristics of the mullinasole drumlin donegal bay support a two stage interpretation of drumlin evolution these are the following 1 deposition of glaciomarine mud and diamict facies at a tidewater glacier margin stratified diamicts record debris flow events and sediment reworking this facies sequence is erosionally truncated 2 deposition of subglacial diamict and sand facies recording ice readvance and drumlinization drumlinization sediment streamlining reflects ice mass balance destabilization episodic fast ice flow and ice marginal oscillation and may be correlated with millennial time scale climate changes in the circum north atlantic

ams c 14 dating of deglacial events in the irish sea basin and other sectors of the british irish ice sheet sedimentary sequences deposited by the decaying marine margin of the british irish ice sheet biis record isostatic depression and successive ice sheet retreat towards centres of ice dispersion radiocarbon dating by accelerator mass spectrometry ams of in situ marine microfaunas that are commonly associated with these sequences constrain the timing of glacial and sea level fluctuations during the last deglaciation enabling us to evaluate the dynamics of the bus and its response to north atlantic climate change here we use our radiocarbon dated stratigraphy to define six major glacial and sea level events since the last glacial maximum 1 initial deglaciation may have occurred 18 3 kyr c 14 bp along the northwestern irish coast in agreement with a deglacial age of similar to 22 cl 36 kyr bp for southwestern ireland ice retreated to inland centres and areas of transverse moraine began to form across the north irish lowlands 2 channels cut into glaciomarine deglacial sediments along the western irish sea coast are graded to below present sea level identifying a fall of relative sea level rsl in response to isostatic emergence of the coast 3 marine mud that rapidly infilled these channels records an abrupt rise in global sea level of 10 15 m similar to 16 7 c 14 kyr bp that flooded the irish sea coast and may have triggered deglaciation of a marine based margin in donegal bay 4 intertidal boulder pavements in dundalk bay indicate that rsl similar to 15 0 c 14 kyr bp was similar to present 5 a major readvance of all sectors of the biis occurred between 14 and 15 kyr 14 c bp which overprinted subglacial transverse moraines and delivered a substantial sediment flux to tidewater ice sheet margins this event the killard point stadial indicates that the bus participated in heinrich event 1 6 subsequent deposition of marine muds on drumlins 12 7 c 14 kyr bp indicates isostatic depression and attendant high rsl resulting from the killard point readvance these events identify a dynamic biis during the last deglaciation as well as significant changes in rsl that reflect a combination of isostatic loading and eustatic changes in global sea level c 2005 elsevier ltd all rights reserved

characteristics of late quaternary activity along the southern border fault zone of weihe graben basin abstract the weihe graben basin located in the centre of shaanxi china is a tectonic depression on the southern border of ordos massif a subtectonic unit in the sino korean paraplatform in the light of new information exhibited from geological mapping on the scale of 1 50 000 the active history and the feature of the southern border fault zone of weihe graben basin have been researched the fault zone may be subdivided into two segments the piedmont fault of huashan mt in the east sector and the northern border fault of qinling mts in the west sector the research shows that new activity of the piedmont fault of huashan mt is obvious since the late quaternary a great number of relics of earthquake deformation such as the newest fault scarps bedrock fractures loess crevices landslides and mountain creep are distributed along this fault and its two flanks this fault is most likely the causative fault zone of the huaxian great earthquake in 1556 m 8 the analysis of two palaeoseismic profiles shows the earthquake recurrence interval is 2000 2500 years for the huashan mt piedmont fault whereas 2000 4000 years for the northern border fault of qinling mts

present day lunette sediment cycling at witpan in the arid southwestern kalahari desert abstract witpan is a pan depression in the southwestern kalahari desert the pan fringing lunette dune has a number of notable characteristics a highly active crest the lower lunette pediment is cemented and the lower lunette supports a highly developed and active gully system geomorphological and sedimentological considerations are used to evaluate the interaction of wind and water in shaping contemporary lunette processes it is considered that like other pans in the area groundwater activity influences pan floor sediment availability and transport that the present highly sea sonal climatic regime permits the interaction of aeolian transport of sediment to the dune and its return to the pan floor by water during storm events creating a cycling process favoured by sedimentary properties that promote surface runoff

sedimentology and chronology of the advance and retreat of the last british irish ice sheet on the continental shelf west of ireland the last british irish ice sheet biis had extensive marine terminating margins and was drained by multiple large ice streams and is thus a useful analogue for marine based areas of modern ice sheets however despite recent advances from investigating the offshore record of the biis the dynamic history of its marine margins which would have been sensitive to external forcing s remain inadequately understood this study is the first reconstruction of the retreat dynamics and chronology of the western marine terminating margin of the last late midlandian biis analyses of shelf geomorphology and core sedimentology and chronology enable a reconstruction of the late midlandian history of the biis west of ireland from initial advance to final retreat onshore five ams radiocarbon dates from marine cores constrain the timing of retreat and associated readvances during deglaciation the biis advanced without streaming or surging depositing a bed of highly consolidated subglacial traction till and reached to within 20 km of the shelf break by 24 000 cal bp ice margin retreat was likely preceded by thinning grounding zone retreat and ice shelf formation on the outer shelf by 22 000 cal bp this ice shelf persisted for 2500 years while retreating at a minimum rate of 24 m yr and buttressing a 150 km long 20 km wide bathymetrically controlled grounding zone a large 150 km long arcuate flat topped grounding zone wedge termed here the galway lobe grounding zone wedge glgzw was deposited below this ice shelf and records a significant stillstand in biis retreat geomorphic relationships indicate that the biis experienced continued thinning during its retreat across the shelf which led to increased topographic influence on its flow dynamics following ice shelf break up and grounding zone retreat past the glgzw at this stage of retreat the western biis was comprised of several discrete asynchronous lobes that underwent several readvances sedimentary evidence of dilatant till deposition suggests that the readvances may have been rapid and possibly associated with ice streaming or surging the largest lobe extended offshore from galway bay and deposited the galway lobe readvance moraine by 18 500 cal bp further to the north an ice lobe readvanced at least 50 km offshore from killary harbour possibly by 15 100 cal bp the existing chronology currently does not allow us to determine conclusively whether these readvances were a glaciodynamic internally driven response of the ice sheet during deglaciation or were climatically driven following the 18 500 cal bp readvance the galway lobe experienced accelerated eastward retreat at an estimated rate of 113 m yr

lunette dunes in the northeast cape south africa as geomorphic indicators of palaeoenvironmental change abstract three lunette dunes occur on the southern shore of a pan on the farm buffelsfontein above the great escarpment in the northeastern part of the eastern cape province south africa the two inner lunettes are formed of silt and clay and the third of fine sand the location of these dunes is anomalous as lunette dunes are rare in the wetter parts of the southern african subcontinent the two inner lunette dunes lie along the downwind margin of a present day pan while the third lunette is associated with the margin of a large palaeopan the morphometry of the buffelsfontein pan lunette dune series was investigated using aerial photography and field surveys sedimentological and geochemical techniques were applied to investigate the lunette and pan floor sediments and to assist in the elucidation of processes responsible for the development of the lunettes sedimentological differences in the pan fringing lunettes suggest two very different sediment sources related to changing geomorphic conditions possibly since the last glacial maximum the pan lunette complex offers a unique opportunity to quantify these changes as local rainfall records are available for the past 100 years

origin and morphology of barchan and linear clay dunes in the shuhongtu basin alashan plateau china abstract clay dunes are characterized by a relatively high content of silt and clay and are typically developed on the lee side margin of closed basins in arid and semi arid areas although they are widely distributed aeolian landforms on earth little is known about their development and distribution in asia our field investigations have identified for the first time the occurrence of clay dunes in the alashan plateau north china the clay dunes occur in three isolated lowland areas of the suhongtu sht basin and their morphologies barchans hooked barchans asymmetrical barchans and linear or seif dunes differ substantially from those of the well studied clay dunes in australia africa and north america these differences could be mainly attributed to the asymmetrical bimodal wind regime prolonged drought and sediment physical properties which indicate that dunes of any type can be formed in sand silt or clay based on the known evolution of the sht paleo lake basin and regional climate change we infer that the landscape of modern clay dunes in the desert of the alashan plateau does not predate mis 5 and probably formed during the late holocene analyses of grain size distributions and the contents of trace and rare earth elements combined with geomorphological characteristics indicate that the source sediments of the clay dunes are mainly local cretaceous tertiary and quaternary red fluvial lacustrine mudstone and sediments while the ultimate source is the weathered and denuded products of granitoids of the east altay mountains comparison of the morphology and alignment of the clay dunes with the prevailing wind pattern tends to support tsoar s 1984 model of the transition in dune shape from barchans to seif or linear dunes during 2003 2013 the seif or linear dunes of the sht basin migrated laterally and elongated northeastward at rates of about 2 4 m yr and 16 20 m yr respectively