persistent millennial scale climatic variability over the past 25 000 years in southern africa abstract data from stalagmites in the makapansgat valley south africa document regional climatic change in southern africa in the late pleistocene and holocene a new tims u series dated stalagmite indicates speleothem growth from 24 4 to 12 7 ka and from 10 2 to 0 ka interrupted by a 2 5 ka hiatus high resolution oxygen and carbon stable isotope data suggest that postglacial warming was first initiated 17 ka was interrupted by cooling probably associated with the antarctic cold reversal and was followed by strong warming after 13 5 ka the early holocene experienced warm evaporative conditions with fewer c4 grasses cooling is evident from 6 to 2 5 ka followed by warming between 1 5 and 2 5 ka and briefly at ad 1200 maximum holocene cooling occurred at ad 1700 the new stalagmite largely confirms results from shorter holocene stalagmites reported earlier the strongest variability superimposed on more general trends has a quasi periodicity between 2 5 and 4 0 ka also present are weaker 1 0 ka and 100 year oscillations the latter probably solar induced given similarities to the antarctic records the proximate driving force producing millennial and centennial scale changes in the makapansgat record is postulated to be atmospheric circulation changes associated with change in the southern hemisphere circumpolar westerly wind vortex

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

point spread functions for interferometric imaging interferometric redatuming is a data driven method to transform seismic responses with sources at one level and receivers at a deeper level into virtual reflection data with both sources and receivers at the deeper level although this method has traditionally been applied by cross correlation accurate redatuming through a heterogeneous overburden requires solving a multidimensional deconvolution problem input data can be obtained either by direct observation for instance in a horizontal borehole by modelling or by a novel iterative scheme that is currently being developed the output of interferometric redatuming can be used for imaging below the redatuming level resulting in a so called interferometric image internal multiples from above the redatuming level are eliminated during this process in the past we introduced point spread functions for interferometric redatuming by cross correlation these point spread functions quantify distortions in the redatumed data caused by internal multiple reflections in the overburden in this paper we define point spread functions for interferometric imaging to quantify these distortions in the image domain these point spread functions are similar to conventional resolution functions for seismic migration but they contain additional information on the internal multiples in the overburden and they are partly data driven we show how these point spread functions can be visualized to diagnose image defocusing and artefacts finally we illustrate how point spread functions can also be defined for interferometric imaging with passive noise sources in the subsurface or with simultaneous source acquisition at the surface

glacier reconstruction and mass balance modelling as a geomorphic and palaeoclimatic tool the reconstruction of former mountain glaciers has long been used to examine the implications of rapid climate shifts for example at the last glacial interglacial transition and for evaluating asynchronous behaviour of mountain glaciers compared with mid latitude ice sheets during the late quaternary glacier reconstruction has also been used as a source of palaeoclimatic information based on the recognition of empirical relationships between glaciers and climate this paper reviews the application and implications of a recently revised method of glacier reconstruction carr and coleman 2007 based around glaciological principles of mass balance this study examines how this approach can be used to test geomorphological interpretations of former mountain glaciation and also to infer precipitation fields at sites of former glaciation sites of younger dryas niche and icefield glaciation in the british isles demonstrate how this method can verify interpretations of marginal glaciation and begin to understand the different behaviour of outlet glaciers within the same environmental regime examination of a site of former niche glaciation in southern africa demonstrates how glacier reconstruction may be used to infer annual and seasonal precipitation values and strongly supports the idea that winter precipitation in lesotho and se south africa was substantially greater than present day values during the last glacial cycle copyright 2010 john wiley sons ltd

holocene climatic variability indicated by a multi proxy record from southern africa s highest wetland the eastern lesotho highlands experience climate patterns distinct from those of surrounding lower altitude regions representing a niche environment with a unique biodiversity leading to well adapted but restricted vegetation this study explores changes in the holocene composition of diatoms and pollen at southern africa s highest altitude wetland mafadi 3390 m a s l the palaeoenvironmental record for mafadi wetland indicates fluctuations between cold wet conditions prevalent between 8140 and 7580 cal yr bp and between 5500 and 1100 cal yr bp and warmer drier periods between 7520 and 6680 cal yr bp and between 6160 and 5700 cal yr bp marked climatic variability is noted from 1100 cal yr bp with colder conditions at 150 kyr bp notably the first of these cold periods occurs soon after the northern hemisphere 8 2 kyr event while a second period of notably cold conditions occurs around 1100 cal yr bp variability exists between the moisture reconstructions presented in this study and those from adjacent lower altitude sites which is hypothesised to reflect variations in the strength and extent of the westerlies throughout the holocene

afromontane foragers of the late pleistocene site formation chronology and occupational pulsing at melikane rockshelter lesotho this paper provides a preliminary chronostratigraphic and palaeoenvironmental framework for the late pleistocene archaeological sequence at melikane rockshelter in mountainous eastern lesotho renewed excavations at melikane form part of a larger project investigating marginal landscape use by late pleistocene foragers in southern africa geoarchaeological work undertaken at the site supports in eld observations that melikane experienced regular often intensive input of groundwater via ssures in the shelter s rear wall this strong hydrogeological connection resulted in episodic disturbances of the sedimentary sequence exacerbated by other processes such as bioturbation despite this taphonomic complexity a robust chronology for melikane has been developed based on tightly cross correlated accelerator mass spectrometry ams 14 c with acid base wet oxidation stepped combustion abox sc pretreatment and single grain optically stimulated luminescence osl dating the results show that human occupation of melikane was strongly pulsed with episodes of late pleistocene occupation at w80 w60 w50 w46e38 and w24 ka at least three additional occupational pulses occurred in the holocene at w9 ka w3 ka and in the second millennium ad but these are dealt with only brie y in this paper implications of the late pleistocene pulsing for the colonisation of high elevations by early modern humans in africa ahead of dispersals into challenging landscapes beyond the continent are discussed

source characterization of near surface chemical explosions at safod a series of near surface chemical explosions conducted at the san andreas fault observatory at depth safod main hole were recorded by high frequency downhole receiver arrays in april 2005 these seismic recordings at depths ranging from the surface to 2 3 km constrain the shallow velocity and attenuation structure as well as the first order characteristics of the source forward modeling of the explosions indicates that a source consisting of combined explosion delayed implosion and second order moment tensor components corresponding to a distribution of vertical shear dislocations in the rock directly above the explosion is sufficient to characterize the generated seismic wave fields to first order grid searches over source parameters controlling the nonexplosive components allow for the quantification of distributed vertical shear above the source and the estimation of the moment and time delay of the implosive component relative to the explosion an estimated implosive to explosive moment ratio of 0 34 to 0 43 indicates a net static moment and positive macroscopic volume change

late quaternary glaciation in southern africa moraine ridges and glacial deposits at mount enterprise in the drakensberg of the eastern cape province south africa late quaternary moraines and diamictons containing striated clasts are described from near elliot in the drakensberg of south africa an equilibrium line altitude ela of 2109 m is suggested for the palaeoglacier associated with the innermost moraine this glacier was fed by a very extensive snowblow area and the ela may reflect the temperature precipitation wind ela rather than the temperature precipitation ela and be considerably below the regional ela mean annual air temperatures when glaciation occurred were probably at least 10 0 c below those of the present copyright 2001 john wiley sons ltd

spatial self organization in geomorphology from periodic bedforms and patterned ground to scale invariant topography a rich diversity of spatial order can be discerned in landforms and small scale features of landscapes with spatial order ranging in scale from 107 m to 10 2 m and in geometry from pronounced two dimensional periodicity to three dimensional scale invariance ripples of wind blown sand with their strikingly uniform spacing and mountainous topography with its fractal characteristics illustrate the range of geomorphic self organization patterns on the land surface are often very distinct easily observed and readily studied because of their accessibility and yet the systematic quantitative study of geomorphic self organization is only in its infancy it offers difficult challenges but also exceptional opportunities particularly for those versed in modern techniques used in studies of self organization in this overview diverse examples of spontaneous organization in geomorphic systems and recent pertinent studies are described starting with spatial structures that are generally most distinct and best understood they include 1 periodic structures that form on various substrates as water or air transports erodes and deposits sediments ripples and dunes meanders and bar pool topography of rivers and rhythmic shoreline features 2 polygonal patterns that result either from the growth cracks in such contrasting media as freezing lava and frozen ground or from freeze thaw alternations in soils 3 large scale periodic structures dictated by the deformation of magma or of the earth s crust linear arrays of evenly spaced volcanoes and sequences of alternating valleys and mountain ranges and 4 scale invariant structures revealed in drainage networks and topography

the cold climate geomorphology of the eastern cape drakensberg a reevaluation of past climatic conditions during the last glacial cycle in southern africa publisher elsevier articletitle the cold climate geomorphology of the eastern cape drakensberg a reevaluation of past climatic conditions during the last glacial cycle in southern africa journaltitle geomorphology articlelink http dx doi org 10 1016 j geomorph 2016 11 011 content type article copyright crown copyright 2016 published by elsevier b v all rights reserved

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

scale matters a multi resolution study of the determinants of patterned ground activity in subarctic finland abstract numerical studies of earth surface processes in relation to their environment are one of the central topics in physical geography however collinearity between explanatory variables and spatial autocorrelation can hinder the detection of key environmental correlates underlying response explanatory variables relationships identified by traditional regression methods moreover conclusions about the potential importance of environmental variables have generally made on analysis conducted only at one spatial scale resolution in this study a variation partitioning method provided a framework to obtain new insights into the relative roles of different factors determining patterned ground activity at multiple spatial resolutions the variation in the distribution of the sorted and non sorted patterned ground was decomposed into independent and joint effects of relief soil and spatial variables geographical location based on a multi resolution system of 1 ha 25 ha and 100 ha cells covering in total 100 km 2 of a subarctic landscape in northern finland the independent effects of relief and soil variables captured the largest fraction of the variation in the non sorted patterned ground distribution while relief had a major contribution for sorted patterned ground activity the independent effect of spatial autocorrelation on sorted patterned ground was higher than that on non sorted patterned ground however a considerable amount of variation in the distribution of both patterned ground types was accounted for by the joint effects of explanatory variables and may thus be causally related to two or all three groups of variables our analyses produced often contradicting results at different resolutions consequently this has substantial implications for the study of geomorphological systems since the choice of resolution can have a major effect on the inferences of analyses our results draw attention to the roles of resolution and spatial autocorrelation in the study of geomorphological systems

the southern oscillation index wave climate and beach rotation short embayed beaches bounded by headlands are a common feature along the southern and central coastline of new south wales australia many of these embayed beaches have experienced severe erosion at their southern end over the last decade previous studies have suggested that this erosion may be the result of an oscillatory medium term phenomenon known as beach rotation the present study was undertaken with the objectives of 1 establishing definitive links between the southern oscillation index soi wave climate and beach rotation and 2 determining the physical processes governing beach rotation data from two similar new south wales beaches were analysed using time series analysis techniques and image processing techniques using argus video images in this study the results indicate that the northern end of this type of beach accretes during el nino phases while the southern end erodes resulting in a net clockwise rotation of the beach the opposite occurs during la nina phases resulting in a net anti clockwise rotation of the beach the beach response at the northern and southern ends lags soi trend shifts by 3 and 17 months respectively waves are predominantly incident from the southeast during both el nino and la nina phases offshore wave height is positively correlated with the soi while offshore wave direction is negatively correlated with the soi on average the number of storms per year doubles from el nino to la nina based on these links between beach width fluctuations soi and incident wave conditions a conceptual model of beach rotation is presented the model describes the combinations of cross shore and longshore sediment transport and hydrodynamic processes that are expected to result in the observed clockwise and anti clockwise beach rotation during el nino and la nina phases respectively

generalities on static equilibrium bays abstract previous methods of determining the curved waterlines of bays which form on the coasts around the world have involved the logarithmic spiral this has been applied to unstable bays which could erode back to a limit termed static equilibrium for which the constant in the spiral could be related to the obliquity of the wave crests to the control line joining the upcoast headland to the downcoast extremity of the bay it is shown that this applies mainly to the shadow zone behind the upcoast headland and not to the full bay periphery and does not have a fixed centre a new method is proposed utilising arcs from the point of wave diffraction to the shoreline whose lengths and angles to the wave crest line are related to those of the control line data and curves are presented for the static equilibrium shape by which the stability can be tested they thus predict the waterline for the case of no sediment supply either from littoral drift or rivers debouching into the bay an indentation ratio can also be derived to test stability

geometrical aspects of sorted patterned ground in recurrently frozen soil a model for sorted patterned ground shows that some types arise from density driven rayleigh free convection that occurs during thawing of water saturated recurrently frozen soils the regularly spaced convection cells result in an uneven melting of the underlying ice front frost action causes stones to be upthrusted and to form in a pattern on the ground surface that mirrors the corrugation in the underlying ice front the implications of the water circulation direction in the cells on the sorting process are considered

shifting westerlies and precipitation patterns during the late pleistocene in southern africa determined using glacier reconstruction and mass balance modelling abstract south africa experiences a range of different climatic regimes and is thus an ideal region to investigate late pleistocene environmental and climate change however detailed quantifiable palaeoclimate data are sparse in the region in particular reliable palaeoclimatic data are essential to resolve ongoing controversies regarding temperature depression and moisture availability during glacial periods in the sub continent small glaciers close to the glaciation threshold are highly sensitive to changes in temperature and precipitation and are therefore ideal indicators of past climatic conditions during their existence this paper derives some of the first quantitative data on last glacial maximum lgm palaeoprecipitation in southern africa based on glacier reconstruction and mass balance modelling for the lesotho highlands the reconstruction of former glaciers and their dynamics enables the determination of glacier viability under specific climatic envelopes glacier reconstructions at five sites in the lesotho highlands yield palaeoglaciers with equilibrium line altitudes elas ranging from 3095 to 3298 m a s l and reconstructed steady state mass balance and flow dynamics are comparable with modern analogues topoclimatic factors are investigated with temperature radiation index modelling indicating that topographic shading was an important factor determining the existence of small glaciers in this region the occurrence of glaciation in the drakensberg during the lgm suggests a potential increase in precipitation and change in its seasonality such trends are likely associated with an increased frequency of westerly wave cold front disturbances due to the northward shift of pressure belts which would also increase precipitation as snow at higher altitudes the application of a high resolution climate model hadam3h to test this displays a change in the seasonal timing of precipitation during the last glacial cycle with a decrease in precipitation evident during the summer months this is likely to have had important implications for the mass balance and survival of small niche glaciers in the region with more precipitation falling during the spring winter autumn months as snow

near wellbore vsp imaging without overburden in seismic exploration a complex overburden can cause defocused and distorted seismic images of deeper target areas while in surface seismic imaging it is difficult to overcome this problem vertical seismic profile vsp borehole seismic imaging with its well oriented recording geometry has proven able to circumvent the overburden s detrimental impact recently vspnear wellboresaltflankimagingwithout knowledge of the overburden has shown encouraging results in this paper we introduce another method for a more common imaging purpose imaging near wellbore horizons without knowledge of the overburden a key component of ourmethodisareverseray tracingtechniquethatusesactual vspdirect wave traveltime picks and extrapolates through a local velocity model to obtain the direct wave traveltimes in the vicinity of the well the extrapolated traveltimes then serve as references for migration of the vsp reflected data from near wellbore horizons the merits of this method are that all source side effects such as shot position and triggeringtimestaticsareavoided anditcanefficientlyandrobustly imagethenear wellborehorizonsbecauseitdoesnotneedan estimated overburden velocity model prone to errors however the image is limited to a diamond shaped area around the well whose size is proportional to the vsp array a synthetic vsp experiment on the seg eage 2d overthrust modelshowsthatthismethod withalocalevenanestimated 1d velocity model effectively images structural features suchasdipdirectionanddiscontinuitiesofthenear wellbore horizons

modelling storm impacts on beaches dunes and barrier islands a new nearshore numerical model approach to assess the natural coastal response during time varying storm and hurricane conditions including dune erosion overwash and breaching is validated with a series of analytical laboratory and field test cases innovations include a non stationary wave driver with directional spreading to account for wave group generated surf and swash motions and an avalanching mechanism providing a smooth and robust solution for slumping of sand during dune erosion the model performs well in different situations including dune erosion overwash and breaching with specific emphasis on swash dynamics avalanching and 2dh effects these situations are all modelled using a standard set of parameter settings the results show the importance of infragravity waves in extending the reach of the resolved processes to the dune front the simple approach to account for slumping of the dune face by avalanching makes the model easily applicable in two dimensions and applying the same settings good results are obtained both for dune erosion and breaching

improving predictions of swash dynamics in xbeach the role of groupiness and incident band runup abstract in predicting storm impacts on sandy coasts possibly with structures accurate runup and overtopping simulation is an important aspect recent investigations stockdon et al 2014 palmsten and splinter 2016 show that despite accurate predictions of the morphodynamics of dissipative sandy beaches the xbeach model roelvink et al 2009 does not correctly simulate the individual contributions of set up and infragravity and incident band swash to the wave run up in this paper we describe an improved numerical scheme and a different way of simulating the propagation of directionally spread short wave groups in xbeach to better predict the groupiness of the short waves and the resulting infragravity waves the new approach is tested against field measurements from the delilah campaign at duck nc and against video derived runup measurements at praia de faro a relatively steep sandy beach compared to the empirical fit by vousdoukas et al 2012 the xbeach model performs much better for more extreme wave conditions which are severely underestimated by existing empirical formulations for relatively steep beaches incident band swash cannot be neglected and a wave resolving simulation mode is required therefore in this paper we also test the non hydrostatic wave resolving model within xbeach for runup and overtopping against three datasets results for a high quality flume test show non hydrostatic xbeach predicts the run up height with good accuracy maximum deviation 15 a case with a very shallow foreshore typical for the belgian coast at wenduine was compared against detailed measurements overall the model shows correct behavior for this case finally the model is tested against a large number 551 of physical model tests of overtopping from the clash database for relatively high overtopping discharges the non hydrostatic xbeach performs quite well with increasing accuracy for increasing overtopping rates however for relatively low overtopping rates of less than 10 20 l m s the model systematically underestimates measured overtopping rates

dissolved gas paleotemperatures and 18o variations derived from groundwater near uitenhage south africa abstract under the near ideal hydrologic conditions provided by the uitenhage artesian aquifer reliable estimates of paleotemperatures were obtained by measurement of the dissolved n2 and ar in groundwater confidently dated in the range 28 000 yr b p to the present using 14c the mean annual air temperature in this area during the last glaciation is calculated to have been on average 5 1 2 c lower than during the holocene the change in the 18 o 16 o ratio of the groundwater corrected for changes in ocean water amounted to 0 4 per c

pleistocene periglacial imprinting on polygenetic soils and paleosols in the sw italian alps abstract because of extensive pleistocenic glaciations which erased most of the previously existing soils slope steepness and climatic conditions favoring soil erosion most soils observed in the alps and in other mid latitude mountain ranges have developed during the holocene or late glacial period however in few sites particularly in the outermost sections of the alpine range pleistocene glaciers covered only small and scattered surfaces and ancient soils could be preserved for long periods on stable surfaces in many cases these soils retain good memories of quaternary periglacial activity which have never been characterized on the alpine range based on both geomorphological and pedological interpretations this work aims to investigate these environments providing therefore new evidences to support paleoclimate reconstructions on the alps we described and sampled soils on stable surfaces in the upper tanaro valley ligurian alps southwestern piemonte italy the sampling sites were between 600 and 1600 m a s l under present day lower montane ostrya carpinifolia montane fagus sylvatica forests or montane heath grazed grassland on quartz rich substrata the surface morphology often showed strongly developed fossil periglacial morphologies such as large scale patterned ground blockfields blockstreams or solifluction sheets the soils preserved in such quaternary periglacial landforms normally showed stratification of different layers units separated by structural discontinuities evidencing different depositional settings and different pedogenic development degree a strong cryogenic granulometric sorting characterized all the observed soils paleosols with silt enriched horizons and lateral differentiation of sand and stone rich parts and fine enriched ones organic matter was irregularly distributed at depth as a result of past cryoturbation compact and dense layers with strong platy lenticular structural aggregation wedge casts and large scale cryoturbations were described below fixed depths in all soil profiles thus surface morphology and soil properties suggest the presence of permafrost during cold pleistocene phases with two main active layer thicknesses at 60 120 and 100 160 cm depths respectively

the late quaternary of the lesotho highlands southern africa preliminary results and future potential of ongoing research at sehonghong shelter abstract previous archaeological and palaeoenvironmental work relating to the late quaternary of the lesotho highlands southern africa is reviewed emphasis is placed upon the region s importance for the investigation of late pleistocene hunter gatherer settlement subsistence systems and of the transition from middle msa to later stone age lsa technologies the paper then reports on the re excavation of sehonghong rock shelter in 1992 and provides an improved radiocarbon chronology for the site and initial results of the analysis of the late pleistocene and holocene assemblages recovered of particular importance is the identification of assemblages transitional between msa and lsa stoneworking techniques but a re assessment of the existing industrial subdivisions of the later stone age of southern africa may also be supported by the sehonghong sequence the palaeoenvironmental potential of the extensive faunal and botanical assemblages recovered is stressed especially given the limited extent of previous palaeoenvironmental work in lesotho the importance of the lesotho highlands for investigating differences in site use and subsistence strategies through the late pleistocene and the holocene is emphasized within an overall aim of testing previously proposed models of resource exploitation under glacial and interglacial conditions

annually re forming miniature sorted patterned ground in the high drakensberg southern africa an analysis of miniature sorted circles and polygons provides the first detailed assessment of sorted patterned ground from a southern african alpine region pattern dimensions and particle sorting were determined from two sites in the high drakensberg although the sorted patterns in the high drakensberg are somewhat polygenetic in developmental origin they are primarily frost induced miniature sorted patterned ground below 3200 m a s l on the drakensberg plateau develops annually during the winter months and disintegrates towards summer the development of miniature sorted patterns within five to six weeks demonstrates the effect of regular freeze thaw cycles at higher altitudes in the drakensberg 1997 by john wiley sons ltd

two dimensional time dependent hurricane overwash and erosion modeling at santa rosa island abstract a 2dh numerical model which is capable of computing nearshore circulation and morphodynamics including dune erosion breaching and overwash is used to simulate overwash caused by hurricane ivan 2004 on a barrier island the model is forced using parametric wave and surge time series based on field data and large scale numerical model results the model predicted beach face and dune erosion reasonably well as well as the development of washover fans furthermore the model demonstrated considerable quantitative skill upwards of 66 of variance explained maximum bias 0 21 m in hindcasting the post storm shape and elevation of the subaerial barrier island when a sheet flow sediment transport limiter was applied the prediction skill ranged between 0 66 and 0 77 in a series of sensitivity tests in which several hydraulic forcing parameters were varied the sensitivity studies showed that the variations in the incident wave height and wave period affected the entire simulated island morphology while variations in the surge level gradient between the ocean and back barrier bay affected the amount of deposition on the back barrier and in the back barrier bay the model sensitivity to the sheet flow sediment transport limiter which served as a proxy for unknown factors controlling the resistance to erosion was significantly greater than the sensitivity to the hydraulic forcing parameters if no limiter was applied the simulated morphological response of the barrier island was an order of magnitude greater than the measured morphological response

micromorphological criteria for discriminating subglacial and glacimarine sediments evidence from a contemporary tidewater glacier spitsbergen abstract sedimentological and micromorphological evidence is presented from four sites within st jonsfjorden western spitsbergen sedimentological and geomorphological evidence is used to distinguish sites comprising undisturbed glacimarine sediments from glacially over ridden glacimarine sediments and subglacial diamicts impregnated thin sections are used to define associations of micromorphological characteristics that allow diamicts formed under these different conditions to be discriminated in situ glacimarine deposits display winnowed textures dropstone structures and distinct vertical orientations of sand grains whilst subglacial conditions result in structures indicative of deformation under moderate to high stress regimes these criteria may help to determine the origin of ancient and quaternary diamicts of questionable subglacial or glacimarine origin

till as a glacial tectomict its internal architecture and the development of a typing method for till differentiation abstract till has been studied for over a century yet still a clear understanding of the mechanics of deposition and or emplacement of till eludes us tills in the past have been generally subdivided into sediments formed in various sub environments of the glacial system as such it has been generally agreed that tills can be separated in terms of these types based on various attributes such as clast fabric increasingly such separation into various sub types of till has become however highly debatable and tenuous based upon the use of micromorphology and a greater in depth appreciation of the internal architecture of till it has become apparent that previously established classifications of till are erroneous micromorphology reveals that deposition and or emplacement of tills is a complex tectonic process such that lodgement melt out and flow tills as previously defined do not appear to exist rather a new term better describes tills as glacial tectomicts by using micromorphology in establishing the presence of sets of microstructures a statistical method is introduced that permits differentiation of tills from other diamictons the implications for this new understanding of tills allied to statistical typing is considerable in terms of till formation glacial stratigraphy and understanding glacial environments in terms of stress histories porewater transmission subglacial deformation mechanics till rheological phase changes and the timeline of till formation

comment on lightning as a geomorphic agent on mountain summits evidence from southern africa by knight and grab 2014 insights into the possible effect of lightning strikes on rock breakdown are presented by knight and grab 2014 from a summit area in the lesotho highlands based on their findings the authors challenge the association of angular debris with frost shattering and use this as a platform for directing critique against palaeo geomorphic studies while the lightning strike data are not questioned directly here the palaeo environmental context within which the paper is set the portrayal of former findings and the assumptions regarding weathering mechanisms in lesotho are commented on frost shattering is the centre of knight and grab s weathering critique but contrary to that stated in their text none of the cited authors invoke this process in lesotho other weathering processes that are speculated upon are not specific to cold climates either and thus cannot be used in support of their argument in terms of debris and block distribution lightning will not account for the preferential location of relict blocks and debris below the summits on south facing slopes or for the extensive valley floor accumulations that are documented in lesotho knight and grab also falsely portray former studies by implying that palaeo environmental inferences in the area are drawn from block origin or morphology alone when the climatic signatures were derived from integrated assessments in a palaeo context the relative contribution of lightning to debris production under dryer and colder conditions when convective thunderstorm activity in the highlands was likely reduced is also questioned the weathering context as well as the critique that knight and grab direct at other studies on relict landforms is thus shown as inappropriate

modelling infragravity motions on a rip channel beach a non linear shallow water wave model operating on the time scale of wave groups is compared with measurements of infragravity motions on a rip channel beach to verify the model concepts and assess the model performance the measurements were obtained during the rip current experiment ripex in concert with the steep beach experiment sbe performed at sand city monterey bay ca during the spring of 2001 the nearshore bathymetry was made up of shore connected shoals incised by relatively narrow rip channels spaced approximately 125 m apart the comparison considers a 20 day period during which significant changes in both the offshore wave climate and nearshore bathymetry occurred the temporal variation in infragravity conditions during the experiment is strong with computational results typically explaining 70 to 80 of the observed infragravity motions within the nearshore in contrast to the temporal variation the alongshore spatial variation in infragravity intensity during the experiment is generally weak even though the underlying bathymetry shows strong depth variations model computations suggest preferential coupling between the computed edge wave motions and the quasi periodic bathymetry is present a prerequisite for strong spatial variability however the infragravity field is dominated by cross shore infragravity motions which are only weakly coupled to the quasi periodic bathymetry resulting in a weak alongshore variability of the total infragravity motions

shoreline dynamics and beach rotation of artificial embayed beaches abstract artificially embayed beaches are an increasingly common environment in retreating and urban coasts the study of embayed beaches usually focuses on the concept of some equilibrium configuration of the shoreline caused by the wave approach and the location of protection structures but detailed studies of their shoreline dynamics are scarce the study reported herein monitored the shoreline dynamics of three artificial embayed beaches in barcelona city during a three year period using an argus video system to examine the behaviour of the emerged beach in order to assess the main factors affecting the shoreline and to analyze the processes causing beach rotation at different time scales the length and degree of protection of the three beaches were different and so were their morphological behaviours two of the beaches presented a general retreating trend with rapid abrupt displacements of the shoreline caused by oblique wave incidence during storm events and to the effects of beach nourishment after nourishment slower changes at the beaches determined beach evolution which was also influenced by the formation of long lasting megacusps the third beach the most protected one showed an accretionary trend no formation of megacusps and episodes of beach rotation related to the gradual recovery of the beach after storm events it is concluded that factors controlling the evolution of barcelona city beaches are associated with both natural processes and man induced actions resulting in a more complex pattern than would be expected for small embayed beaches beach rotation appears as a key process for understanding the morphodynamics of embayed beaches it occurs as a fast response to storms but also as a medium term adaptation of the shoreline configuration to morphological changes in the beach or to the recovery of a more stable orientation after storm events and man made changes in the beach orientation resulting from nourishment or sand relocation

the two step shape and timing of the last deglaciation in antarctica the two step character of the last deglaciation is well recognized in western europe in greenland and in the north atlantic for example in greenland a gradual temperature decrease started at the bolling b around 14 5 ky bp spanned through the allerod a and was followed by the cold younger dryas yd event which terminated abruptly around 11 5 ky bp recent results suggest that this ba yd sequence may have extended throughout all the northern hemisphere but the evidence of a late transition cooling is still poor for the southern hemisphere here we present a detailed isotopic record analyzed in a new ice core drilled at dome b in east antarctica that fully demonstrates the existence of an antarctic cold reversal acr these results suggest that the two step shape of the last deglaciation has a worldwide character but they also point to noticeable interhemispheric differences thus the coldest part of the acr which shows a temperature drop about three times weaker than that recorded during the yd in greenland may have preceded the yd antarctica did not experienced abrupt changes and the two warming periods started there before they started in greenland the links between southern and northern hemisphere climates throughout this period are discussed in the light of additional information derived from the antarctic dust record

defining modern day area altitude balance ratios aabrs and their use in glacier climate reconstructions abstract with the increasing use of digital elevation models in palaeo glacier reconstructions and the availability of freeware spreadsheets the area altitude balance ratio aabr and balance ratio br methods are becoming increasingly used in palaeo glacier reconstruction for estimating equilibrium line altitudes ela and subsequently deriving quantitative estimates of palaeo climate while there are many data detailing contemporary accumulation area ratios there are still only a few studies that have established from contemporary environments aabr br ratios publicly available glacier mass balance world glacier monitoring service us geological survey and norwegian water directorate and spatial extent datasets provided the basis for this research from a time series of mass balance regressing specific net balance against ela allows the zero net balance ela to be identified once the zero balance ela is established the glacier hypsometry above and below the ela is defined the aabr br is calculated by using the right hand side the following aabr b n a b b n a c z a c a a c z a b a a b where b nab and b nac are the net mass balance gradients in the ablation and accumulation zones respectively z a c and z a b are the area weighted mean altitudes of the accumulation and ablation areas respectively and a ac and a ab are the areas of the accumulation and ablation areas respectively aabrs are calculated for a suite of glaciers located across a range of climatic zones and glacier types with antarctica being excluded the following representative aabrs are found a global aabr 1 75 0 71 mid latitude maritime 1 9 0 81 high latitude 2 24 0 85 north america west coast 2 09 0 93 north america eastern rockies 1 11 0 1 canadian arctic 2 91 0 35 svalbard 2 13 0 52 western norway 1 5 0 4 european alps 1 59 0 6 central asia 1 75 0 56 kamchatka 3 18 0 16 this study provides an empirically derived dataset characterising aabr ratios which may be used for ela estimation in palaeo glacier reconstructions and for palaeo climate quantification

morphological response to storms in an embayed beach having limited sediment thickness abstract the morphological response of a wave dominated embayed beach to large storms was investigated via field data collection and numerical simulation hydrodynamic and morphological field data collected in haeundae beach facing sse in the south eastern corner of korea were analysed during the southerly storm waves i e almost shore normal direction the upper part sediments of the beach were eroded and redistributed to the surf zone meanwhile easterly storm waves transported sediment from east to west resulting in coastline advancement in the west and retreat in the east in order to investigate the morphological response of the beach with limited sediment availability under storm conditions the numerical model xbeach was used with the assumption of unlimited sediment availability the southerly storms led to overestimation of sediment transports and unrealistic erosion and deposition patterns in the middle part of the beach in contrast the model results with the option of sediment layer thickness showed good agreement with the erosion and deposition patterns analysed from field data this suggests that sediment availability can be one of the key factors in determining the morphological response in a wave dominated embayed beach where sediment supply from neighbouring beaches or rivers is limited

a 3000 year high resolution stalagmitebased record of palaeoclimate for northeastern south africa high resolution stable isotope variations and growth structure analyses of the last three millennia of a 6600 year stalagmite record at cold air cave makapansgat valley south africa are presented growth layers which are measurable over the last 250 years are shown to be annual the correlation between the width of growth layers and precipitation is strongly positive changes in 18o and 13c are positively correlated and inversely correlated to changes in the colour of the growth layers in the stalagmite variations in colour are directly correlated with mean annual temperature dark colouration is the product of increased temperature and mobilization of organic matter from the soil and is associated with wetter summers and enhanced growth of c4 grasses darker colouring and enriched 18o and 13c reflect a warmer wetter environment whereas lighter colouring and depleted isotopic values are indicative of cooler drier conditions the dominant episode in the 3000 year record is the cool dry 500 year

interpretation of s waves generated by near surface chemical explosions at safod a series of near surface chemical explosions conducted at the san andreas fault observatory at depth safod were recorded by high frequency downhole receiver arrays in separate experiments in november 2003 and may 2005 the 2003 experiment involved 100 kg shots detonated along a 46 km long line hole ryberg line centered on safod and recorded by 32 three component geophones in the pilot hole between 0 8 and 2 0 km depth the 2005 experiment involved 36 kg shots detonated at parkfield area seismic observatory paso stations at 1 8 km offset recorded by 80 three component geophones in the main hole between the surface and 2 4 km depth these data sample the downgoing seismic wavefield and constrain the shallow velocity and attenuation structure as well as the first order characteristics of the source using forward modeling on a velocity structure designed for the near field both observed p and s wave energy for the paso shots are identified with the travel times expected for direct and or reflected phases larger offset recordings from shots along the hole ryberg line reveal substantial sv and sh energy especially southwest of safod from the source as indicated by p to s amplitude ratios the generated sv energy is interpreted to arise chiefly from p to s conversions at subhorizontal discontinuities this provides a simple mechanism for often observed low p to s amplitude ratios from nuclear explosions in the far field as originating from strong near field wave conversions online material figures of observed and synthetic seismogram record sections snapshots of synthetic wavefields and models of crustal structure

deformation of laminated silt loam due to repeated freezing and thawing cycles the effect of repeated freezing and thawing cycles on an experimentally produced laminated silt loam was studied with the purpose of obtaining more insight into the genesis of macro and microstructures observed in the loessic formations of northwestern europe the laminated silt loam was subsequently subjected to 18 cycles of alternate freezing and thawing the minimum temperature recorded after 11 days of frost was 7 c at a depth of 5 cm and 4 c at 29 cm the underlying sediments compact loam except its upper part and sand always remained unfrozen the experiment reproduced a seasonal superficially frozen ground new structures and microfabrics in the form of vesicles platy structures shear planes and micro undulations were created by ice segregation and thawing mechanical stress and subsequent frost creep the impact of the freezing and thawing cycles is very strong all the laminae being deformed or broken judging by the abundance and the diversity of the structures created freezing is a more important process than simple drying without frost as is evidenced by the range in temperature chosen for the experiment and the low number of cycles these structures do not necessarily require severe climatic conditions to develop unlike frost cracks or ice wedge casts they could develop in winter conditions similar to those present today in the french southern alps

near surface soil displacement in sorted circles resolute area cornwallis island canadian high arctic lines of dowels originally inserted vertically to depths of 100 and 200 mm in generally fine grained soil across sorted circles were repeatedly surveyed over a 3 year period measurements of dowel

effects of storm clustering on beach dune evolution abstract impacts of storm clustering on beach dune morphodynamics were investigated by applying the state of the art numerical model xbeach to formby point sefton coast uk the adopted storm cluster was established by analysing the observed winter storms from december 2013 to january 2014 using a storm threshold wave height the first storm that occurred during this period is regarded as exceptionally intense and the occurrence of such a cluster of events is very unusual a 1d model was setup for the highly dynamic cross shore at formby point after initial calibration of the model parameters against available post storm profile data the model was used for the simulation of the storm cluster it was assumed that no beach recovery occurred between adjacent storms due to the very short time intervals between storms as a result the final predicted post storm profile of the previous storm was used as the pre storm profile of the subsequent storm the predicted evolution during each storm was influenced by the previous storms in the cluster due to the clustering effect the bed level change is not proportional to the storm power of events within the cluster as it would be in an individual storm case initially the large storm events interact with the multi bared foreshore enabling the subsequent weaker storms to influence the upper beach and lower dune system this results in greater change at the dune toe level also during less severe subsequent storms it is also shown that the usual water level threshold used to define dune erosion is over predicted by about 1 m for extreme storm conditions the predicted profile evolution provides useful insights into the morphodynamic processes of beach dune systems during a storm cluster using formby point as an example which is very useful for quantifying the clustering effects to develop tools for coastal management

the predictability of cross shore bed evolution of sandy beaches at the time scale of storms and seasons using process based profile models deterministic and probabilistic profile models have been compared with hydrodynamic and morphodynamic data of laboratory and field experiments on the time scale of storms and seasons the large scale laboratory experiment is a pure 2d case and offers and ideal test case for cross shore profile models as disturbing alongshore non uniformities are absent the field experiments are performed at the egmond site the netherlands during the eu coast3d project and represent storm time scale oct nov 1998 as well as seasonal time scale conditions may 1998 sep 1999 the objective of the paper is to present information of coastal processes on these time scales and to assess the predictive capabilities coastal process based profile models with respect to hydrodynamics and morphodynamics at sandy beaches on the time scales of storms and seasons profile models can quite accurately errors smaller than 10 represent the cross shore significant wave height distribution in the surf zone if the wave breaking model is properly calibrated the wave breaking coefficient should be a function of local wave steepness and bottom slope for most accurate results profile models can reasonably represent the cross shore and longshore currents undertow in a pure 2d case and in 3d field conditions profile models including cross shore mixing effects and breaker delay effects do not produce better predictions of the longshore and cross shore current velocities profile models using default settings can quite reasonably simulate the behaviour of the outer and inner bars on the storm time scale the behaviour of the beach cannot be modelled with sufficient accuracy on the storm time scale profile models can reasonably simulate the post storm onshore bar migration provided that the near bed orbital velocities and wave asymmetry related sand transport are represented in a sufficiently accurate way using non linear wave theories profile models cannot simulate the beach recovery processes on the post storm time scale because these essentially 3d processes are not sufficiently known to be included in the models profile models using default settings cannot simulate the behaviour of the outer and inner bars and the beach on the seasonal time scale the behaviour of the outer bar on the seasonal time scale can only be represented properly after tuning using measured bed profiles the simulation of the inner bar and beach morphology on the seasonal time scale could not be improved by tuning

synthetic reconstructions of southern african environments during the last glacial maximum 21 18kyr and the holocene altithermal 8 6kyr abstract the pash database has been assembling palaeoclimatic data from the southern hemisphere for a number of years the southern african sector now contains more than 100 records spanning the last 200 000 years a number of these relate to the last glacial maximum and holocene altithermal which represent the two most recent extremes in global temperatures syntheses of these records have permitted the preparation of preliminary palaeoenvironmental maps for the two intervals the results provide insights into probable changes in atmospheric circulation as temperatures across the subcontinent rose by 6 7 c these changes are in agreement with a present day model which has been developed to explain short term variations in southern african climate the results presented here should assist in calibrating models developed to predict future climate change

dynamics of periglacial sorted circles in western spitsbergen a working hypothesis for the development and maintenance of sorted circles which are finegrained soil domains delineated by borders of coarser material involves clast motion relative to soil and intermittent circulatory motion of soil in the active layer the hypothesis is compatible with the observed size regularity sorting microtopography surface soil motion vegetation cover and subsurface organic carbon content of soil patterns studied in spitsbergen theoretical considerations of buoyancy driven convection suggest that intermittent convection of thawed soils is plausible and that the requisite bulk density decrease with depth arises naturally from moisture gradients that develop during the thaw consolidation of ice rich soils these considerations also help in understanding the dependence of sorted circles on soil characteristics and on moisture moreover they point to the possible use of sorted patterns as paleoclimatic indicators based on the expected relation between pattern size and active layer depth

last glacial maximum and hypsithermal in the southern hemisphere abstract a synthesis of the two contrasting climates of the upper quaternary in the southern hemisphere based on continental geological indicators suggests that the antarctic anticyclone is the most important climatic system in the hemisphere according to glaciological and oceanographic studies the antarctic anticyclone covered an area in the lgm that was double of that during the hypsithermal this phenomenon produced a consequent shifting of the climatic belts by approximately 10 of latitude to the north in the lgm and a migration to the south during the hypsithermal oceanic and continental anticyclones were active systems in shaping climates in south america australasia and southern africa these structures were enhanced throughout the lgm provoking generalized droughts and weakened at the hypsithermal permitting more rains in tropical latitudes the results presented here were obtained by integrating our own results with regional and continental syntheses of other authors the paleoclimatic proposals are amply validated by more than 1500 dates in the four continents geological and geomorphological features such as dunefields paleosols fluvial terraces and lake levels were the main tools employed in the work

modern glacier characteristics as a basis for inferring former climates with particular reference to the loch lomond stadial abstract studies of the mass balance of modern glaciers have indicated that the equilibrium line altitude ela is the most critical parameter in the link between glaciers and climate average accumulation on a glacier includes components derived from direct precipitation on the glacier surface as well as wind drifting and avalanching of snow and approximates closely to accumulation at the equilibrium line ablation is most usefully predicted by mean summer temperature and there is a close non linear relationship between accumulation and mean summer temperature at the equilibrium line following discussion of methods of reconstructing former glaciers and calculating their equilibrium line altitudes the application of the above relationships to the loch lomond readvance glaciers of highland britain is considered and an outline of the precipitation pattern and the mean summer temperature of the loch lomond stadial is given

sedimentary sequences at sani top lesotho highlands southern africa detailed examination of sediments retained in two north facing cirques south of sani top latitude 29 30 s longitude 29 2 e has been undertaken as a contribution to the late quaternary history of highland lesotho the sediments are exposed by gullies incised through the deposits nine sections are discussed in detail inorganic sediments matrix supported diamictons and derived orange gravels as well as organic dark clays and peats are present eight dated organic samples range in age from 13490bp currently the oldest organic carbon date from highland lesotho to 2310 bp the sedimentary sequences are interpreted to present a sequence of late quaternary events with climatic implications

the use of vsp techniques for fault zone characterization an example from the san andreas fault vertical seismic profiling vsp technology is increasingly being used in the fields of earthquake seismology and tectonics this is motivated in part by the growing number of oil field microseismic monitoring surveys but more so by projects that involve drilling deep wells for monitoring crustal activity at depth examples of these projects are the san andreas fault observatory at depth safod the nankai trough seismogenic zone experiment the gulf of corinth rift laboratory and the taiwan chelungpu fault drilling project and other projects by the international continental and ocean drilling programs icdp and iodp these projects require instrumentation and surveying in deep and possibly hot borehole environments with higher resolution than surface seismic data images from 2d and 3d vsp data contribute to better characterization and interpretation of complex reservoirs at smaller scales the location of receivers in the low noise borehole environment yields higher signal to noise ratios higher

patterned ground by rainstorm erosion on the colorado plateau utah this short notice deals with the effect of highly intensive rainstorms more than 25 mm h or 8 mm 10 min on bare surfaces producing cones and needles of earth up to 12 cm in cryptogamic surface layers of canyonlands national park by splash erosion and widespread stone stripes resembling periglacial features on the steeper slopes up to more than 40 by rainwash in the areas of red canyon and bryce canyon national park a large amount of coarse material can be moved within a very short time and the surface patterns survive at least for several months

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

development of miniature sorted patterned ground following soil erosion in east falkland south atlantic miniature sorted patterned ground features nets and stripes occur at an elevation of ca 35 m in the l antioja valley east falkland the features have developed following recent soil erosion and display many of the characteristics associated with the operation of frost related processes in regolith materials the patterns are currently active and indicate that in cool oceanic climates the distribution of frost sorted patterns is controlled by the presence of bare ground on suitable regolith rather than by altitude

characteristics and palaeoenvironmental significance of relict sorted patterned ground drakensberg plateau southern africa abstract relict large sorted periglacial circles are described from the drakensberg plateau of southern africa morphological and sedimentological data for three populations of patterns occurring on high summit 3400 m a s l interfluves are presented the patterns range between 85 and 904 cm in diameter with centres encircled by primary and in some cases secondary borders patterns are sorted to maximum depths of 85 cm or more with borders occupying trough like depressions to a depth of 26 cm although it is found that contemporary freeze to 40 cm depth still permits some cryogenic activity within smaller patterns it is argued that the larger patterns are degrading owing to limited moisture and freeze duration and intensity the paper provides a literature summary of contemporary environmental parameters from 10 northern hemisphere localities where active relict large periglacial patterns occur findings suggest that patterns over 80 cm in diameter develop where the maat is 1 6 c or less it is demonstrated that the drakensberg palaeo maat reached such low temperatures during the lgm it is thus argued that the patterns developed during the lgm and that smaller varieties became reactivated during holocene cold phases the relict sorted circles provide confirmation for late quaternary permafrost above 3400 m a s l in southern africa the results further suggest pronounced palaeo climatic environmental variation over short spacial scales over southern africa s high plateau

the late quaternary glaciation of africa a regional synthesis abstract there are numerous mountain ranges in africa which carry evidence of quaternary glaciation though few have glaciers now and these are rapidly disappearing the best studied sites are in east africa and ethiopia in east africa the three highest mountains kilimanjaro kenya and the rwenzori each have evidence of 3 5 major glaciations dating back to an estimated 400 000 bp one of which is dated to the last glacial maximum lgm by radiocarbon or cosmogenic radionucleide crn methods two other mountains have similar large moraine systems inferred to date to the lgm in ethiopia three mountains have clear evidence of glaciation and on two of them radiocarbon dates give minimum ages which suggest that these are lgm features in north africa the atlas and other groups of mountains have evidence of glaciation but in the absence of any dating it is unclear whether these sites were glaciated at the lgm although geomorphic features resembling moraines and protalus ramparts have been described from the drakensberg mountains south africa it is still unclear whether these features indicate glaciation and can be attributed to the lgm thus although circumstances for fieldwork on african mountains are very difficult in many cases investigations for more than a century provide an extensive picture of quaternary glaciation in some cases there has been an increasingly detailed mapping of field evidence and the first crn dates were carried out recently thus improving the global picture considerably particularly in east africa and ethiopia there is sufficiently reliable field information to make useful estimates of equilibrium line altitude changes at the provisionally identified lgm but this age needs confirmation by further crn dating by making some hypothetical assumptions inferences can be drawn that indicate a temperature lowering of 5 6 c during the lgm elsewhere in africa further field surveys are required

a reevaluation of coastal embayment rotation the dominance of cross shore versus alongshore sediment transport processes collaroy narrabeen beach southeast australia 1 over 30 years of wave and beach survey data at collaroy narrabeen beach in southeast australia are analyzed to investigate the extent to which shoreline variability within this coastal embayment is dominated by shoreline oscillations due to cross shore sediment exchange or shoreline rotations due to alongshore exchange between the beach s extremities offshore wave data are derived from both buoy measurements and era 40 reanalysis data eof analysis of the monthly shoreline data suggests that the dominant mode of shoreline variability 60 of variability is an onshore offshore sediment exchange that is greater at the more exposed northern end of the beach than at the predominantly sheltered southern end this mode is primarily associated with variability in wave energy storms which by the nature of the wave climate of this region chiefly occurs from the south southeast the secondary mode of shoreline variability 26 of variability is a rotational signal between either end of the beach which coincides with 24 of the offshore wave climate shifting between the south southeast and east as well as changes in the wave period and wave energy storms a distinct annual cycle is identified in this rotation signal it is concluded that alongshore sediment transport processes associated with embayment rotation is more subtle than previously thought and a refined conceptual model of coastal embayment variability in this region is presented highlighting the dominance of cross shore sediment exchange processes

quaternary glaciations in the rio mendoza valley argentine andes in the rio mendoza valley five pleistocene drifts and one holocene drift are distinguished by multiple relative age criteria including surface rock weathering development of rock varnish moraine morphology soil profile development and stratigraphic relationships several absolute ages suggest a preliminary chronology during the oldest uspallata glaciation a system of valley glaciers flowed 110 km from the andean drainage divide and 80 km from cerro aconcagua to terminate at 1850 m drift of this ice advance is older than a widespread tephra dated by fission track at 360 000 36 000 yr during the punta de vacas advance ice terminated at 2350 m while during the subsequent penitentes advance the glacier system ended at 2500 m a travertine layer overlying penitentes drift has u series age of 24 200 2000 yr b p the distribution of horcones drift which is inferred to represent the last glacial maximum delimits an independent ice stream that flowed 22 km down horcones valley to 2750 m a later readvance almacenes reached 3250 m confluencia drift is considered to be neoglacial in age and extends downvalley to 3300 m the moraine sequence is compared with those studied by caviedes 1972 along rio aconcagua on the chilean flank of the andes

climate at the equilibrium line of glaciers the relationships between temperature precipitation and radiation on glacier equilibrium lines are investigated using 70 glaciers for which the mass balance and meteorological observations have been carried out for sufficiently long periods it is found that the characteristic climate at glacier equilibrium lines can be described using the summer 3 months temperature in a free atmosphere annual total precipitation and the sum of global and long wave net radiation all of these are measured at or very near the equilibrium line altitudes then it is shown how the shift of the equilibriumline will occur as a result of a climatic change finally the effect of the shift of the equilibrium line on the annualmean specific mass balance is analytically derived and compared with observations the present results make it possible to identify the altitudes in climate models where glacierization should begin and to evaluate the mass balance changes as a result of possible future changes in the climate

debris ridges along the southern drakensberg escarpment as evidence for quaternary glaciation in southern africa considerable geomorphological work has been undertaken on periglacial and possible glacial landforms found in the eastern lesotho highlands however the origin of several of these landforms remains controversial and differences in opinion concerning their original process mechanisms and associated climatic implications is unresolved debris ridges were recently found on south facing slopes along the tsatsa la mangaung and leqooa ranges in the southern drakensberg the objective is to use a variety of approaches to test a number of possible hypotheses to their origin these include an analysis of topographic and spatial positioning geomorphology sedimentology ams dating and palaeo climatological extrapolations a variety of possible geomorphological process origins for particular deposits are tested against the results of the above mentioned approaches the possible origins considered include debris flows water flow pronival ramparts seasonal perennial snow patches glacial moraine permanent glacier ice and variations in landscape denudation i e erosional remnant e g valley fill the results support the contention that the ridges are moraines which relate to the former presence of small glaciers

migration based location of seismicity recorded with an array installed in the main hole of the san andreas fault observatory at depth safod summary we present the principles of a recently developed event location procedure and its application to seismicity recorded in the main borehole of the san andreas fault observatory at depth safod the basic idea of the location approach is the backpropagation of the recorded wavefield along rays using a gaussian beam type weighting factor in the case of a sufficient number of receivers the intersection of these rays results in a distinct maximum at the corresponding hypocentre location we have applied this technique to data recorded with an 80 level three component 3c receiver array in the safod main hole and we have located a number of events in the vicinity of the fault system a modification of the location algorithm also allowed the precise location of one of the so called target events which are the subject of recent drilling activities as well as ongoing research at safod we summarize the principles of the location method and the performed processing steps provide estimates of the uncertainties for the target event location and test the robustness of the location using six different 3 d velocity models furthermore we discuss the event locations in comparison with borehole logging data and coincident seismic reflection images and we also show identified events with highly correlated waveforms

on the application of static equilibrium bay formulations to natural and man made beaches crenulate shaped bays are common features found all around the world the most widely used formulation for representing this kind of bay is the parabolic approach proposed by hsu and evans institution of civil engineers proc london england 87 1989 556 who suggested a methodology to test and predict the stability of static equilibrium shapes in natural and man made bays based on an analytical model of null drift current and using an empirical approach a modified methodology is proposed the new procedure is able to locate the downcoast starting point of the static equilibrium beach from which the parabolic plan form of hsu and evans is valid this methodology is applied with good results to different natural and man made beaches along the atlantic and mediterranean coasts of spain including tombolo shaped beaches

clastic polygonal networks around lyot crater mars possible formation mechanisms from morphometric analysis polygonal networks of patterned ground are a common feature in cold climate environments they can form through the thermal contraction of ice cemented sediment i e formed from fractures or the freezing and thawing of ground ice i e formed by patterns of clasts or ground deformation the characteristics of these landforms provide information about environmental conditions analogous polygonal forms have been observed on mars leading to inferences about environmental conditions we have identified clastic polygonal features located around lyot crater mars 50 n 30 e these polygons are unusually large 100 m diameter compared to terrestrial clastic polygons and contain very large clasts some of which are up to 15 metres in diameter the polygons are distributed in a wide arc around the eastern side of lyot crater at a consistent distance from the crater rim using high resolution imaging data we digi tised these features to extract morphological information these data are compared to existing terrestrial and martian polygon data to look for similarities and differences and to inform hypotheses concerning possible formation mechanisms our results show the clastic polygons do not have any morphometric features that indicate they are similar to terrestrial sorted clastic polygons formed by freeze thaw processes they are too large do not show the expected variation in form with slope and have clasts that do not scale in size with polygon diameter however the clastic networks are similar in network morphology to thermal contraction cracks and there is a potential direct martian analogue in a sub type of thermal contraction polygons located in utopia planitia based upon our observations we reject the hypothesis that polygons located around lyot formed as freeze thaw polygons and instead an alternative mechanism is put forward they result from the infilling of earlier thermal contraction cracks by wind blown material which then became compressed and or cemented resulting in a resistant fill erosion then leads to preservation of these polygons in positive relief while later weathering results in the fracturing of the fill material to form angular clasts these results suggest that there was an extensive area of ice rich terrain the extent of which is linked to ejecta from lyot crater

potential of 3 d vertical seismic profiles to characterize seismogenic fault zones the potential of a 3 d vertical seismic profile vsp to improve resolution of seismogenic plate interfaces was explored with synthetic modeling the 3 d vsp modeled is at a proposed site for a 1 to 1 5 km deep open hole that provides background for riser drilling three dimensional vsp images could resolve 30 60 m spaced reflective horizons in a costa rican subduction zone it can record a great amount of high fidelity s wave data to invert for physical properties directions of strain and pore pressure above and below the plate interface fault a 6 km 12 km grid of shots with a surface ship will illuminate a 4 km 7 km area of the plate interface fault zone with a high data density acquisition adds 5 to 9 days to drill ship time on site and a shooting ship seismic image resolution falls between that of borehole information and 3 d surface ship seismic images a multiple kilometer 3 d volume of high fidelity s wave data is an exceptional addition not available with other techniques

vertical seismic wave gradiometry application at the san andreas fault observatory at depth abstractwe have developed vertical seismic wave gradiometry vswg to estimate velocity impedance and attenuation structure in the vicinity of boreholes using borehole array waveforms of check shot explosions near the borehole head we have extended wave gradiometry wg theory from a purely local relation of the wavefield and wavefield spatial gradient to one that incorporated the ray ansatz over the length of the borehole for a traveling wave in a vertically inhomogeneous medium we checked the ray assumption against acoustic full wave synthetic seismograms and it was found to yield robust measures of the medium velocity anelastic attenuation and impedance structure trade off but in cases of high anelastic attenuation realistic bounds can be placed on the seismic impedance that effectively constrains the average attenuation we have applied these methods to data collected at the san andreas fault observatory at depth borehole in central california in 2005 and we found that the wg velocity estimat

evaluation of wave runup predictions from numerical and parametric models abstract wave runup during storms is a primary driver of coastal evolution including shoreline and dune erosion and barrier island overwash runup and its components setup and swash can be predicted from a parameterized model that was developed by comparing runup observations to offshore wave height wave period and local beach slope because observations during extreme storms are often unavailable a numerical model is used to simulate the storm driven runup to compare to the parameterized model and then develop an approach to improve the accuracy of the parameterization numerically simulated and parameterized runup were compared to observations to evaluate model accuracies the analysis demonstrated that setup was accurately predicted by both the parameterized model and numerical simulations infragravity swash heights were most accurately predicted by the parameterized model the numerical model suffered from bias and gain errors that depended on whether a one dimensional or two dimensional spatial domain was used nonetheless all of the predictions were significantly correlated to the observations implying that the systematic errors can be corrected the numerical simulations did not resolve the incident band swash motions as expected and the parameterized model performed best at predicting incident band swash heights an assimilated prediction using a weighted average of the parameterized model and the numerical simulations resulted in a reduction in prediction error variance finally the numerical simulations were extended to include storm conditions that have not been previously observed these results indicated that the parameterized predictions of setup may need modification for extreme conditions numerical simulations can be used to extend the validity of the parameterized predictions of infragravity swash and numerical simulations systematically underpredict incident swash which is relatively unimportant under extreme conditions

a contemporary winter ground thermal profile in the lesotho highlands and implications for active and relict soil frost phenomena a 2 m deep ground thermal pro le is constructed from temperature data collected over the winter and spring of 2000 at 3220 m a s l near the thabana ntlenyana summit 3482 m in lesotho southern africa the zero isotherm is found to have penetrated to 0 16 m soil depth ground remained frozen at 0 05 m for a total of 79 days and for shorter periods at 0 02 m and 0 10 m diurnal freezing and thawing is restricted to the upper 0 10 m and conforms to the observed depth of active micro patterned ground found in the region holocene temperature depressions projected along the thermal pro le can account for freezing down to 0 45 to 0 65 m deeper sorting to 1 m evident from relict patterned ground near the logger site corresponds to at least a 2 5 c temperature depression and such landforms are evidently pre holocene projections indicate a seasonal freezing depth exceeding 2 m during the pleistocene last glacial maximum although the existence of permafrost appears unlikely copyright 2003 john wiley sons ltd

holocene palaeoenvironments inferred from a sedimentary sequence in the tsoaing river basin western lesotho abstract the paper presents a sedimentological palynological and phytolith record from a 13 m deep holocene sedimentary sequence located in the tsoaing river valley southwestern lesotho six conventional radiocarbon and two ams dates provide a relatively high resolution holocene record for the sedimentary sequence ranging from ca 12 000 to 4000 years bp pollen is absent in the upper section but present in the lower 2 m confirming terminal pleistocene holocene conditions reported in previous published pollen and charcoal records from the region the absence of pollen in the upper layers of ca 9000 years bp and younger suggests that conditions over southwestern lesotho throughout much of the holocene was typified by a seasonal climate that prevented long term preservation of plant remains although other plant material like robust spores microscopic charcoal and phytoliths withstood oxidation sedimentological and phytolith results suggest that the period from ca 8600 to 8450 years bp experienced rapid environmental change towards drier conditions phases of chemical disintegration with organic input including local swamp phytoliths are suggested at ca 7000 years bp and again after 4500 years bp

analysis of a blockstream in the northern lesotho drakensberg southern africa abstract blockstreams are found in many mountain ranges worldwide and can be considered as an expression of the interplay between upslope sediment supply and transport limited capacity of slope sediment systems in mountain settings blockstreams have been most commonly described as periglacial landforms whose development and internal morphology reflect active layer processes and where the landforms are not active under present climatic conditions in the maloti drakensberg mountain range of eastern lesotho southern africa several blockstreams have been identified but their age evolution and relationships to climatic conditions are largely not known this study maps and analyses the properties of one large blockstream in the maloti drakensberg using field measurement techniques including schmidt hammer relative exposure age dating of blockstream boulders results show that the blockstream is a relict feature but debris may have been derived from several sources including from periglacial slope activity the presence of arcuate flow lobes within the main body of the studied blockstream attests to phases of slope driven boulder movement possibly controlled by active layer processes and cryoturbation or by slip at the base of the sediment body driven by seasonal water availability relative age data from schmidt hammer analysis suggest that different parts of the blockstream may have different ages and or sources by comparison with blockstreams elsewhere in the maloti drakensberg it is likely that it is of late quaternary and probably of local last glacial maximum age but younger holocene phases of activity cannot be excluded

morphodynamics of structurally controlled headland bay beaches in southeastern brazil a review abstract this paper presents a comprehensive review on the interaction between hydrodynamic processes beach morphology and sedimentology at large scale coastal behaviour along the coastline of santa catarina between laguna and sao francisco island a microtidal east coast swell environment with headland and bay geomorphologies the parabolic bay shape equation has proven to be a convenient and practical tool for studying the stability of the headland bay beaches tombolos and salients in santa catarina the beaches exhibit different patterns of sediment removal as a function of the degree of beach curvature in highly curved beaches there is a well developed shadow zone and a range of morphodynamic conditions from a sheltered low energy beach adjacent to the downdrift headland to a high energy exposed beach on the straight end of the headland bay beach the less curved beaches instead tend to show more uniform behaviour since they are directly exposed to incident waves there is no obvious relationship between average wave height and mean grain size showing the importance of sediment source to characterize the sedimentary distribution patterns in the study area the analysis of beaches showed that beach morphodynamics and sequence profiles for a bay headland coast in a microtidal east coast environment is a function of geological inheritance e g distance between headlands and orientation nearshore and inner shelf morphology coastal plain morphology and sediment source and hydrodynamic factors wave conditions oceanic wave exposure and relative tidal range

reconstructing the transport history of glacigenic sediments a new approach based on the co variance of clast form indices abstract two indices are used to describe the aggregate shape and roundness characteristics of glacially transported clasts the c40 index the percentage of clasts with c a ratios 0 4 and the ra index the percentage of very angular and angular clasts in a sample analysis of the between and within sample co variance of these indices provides a powerful tool for discriminating actively and passively transported clasts in glacigenic deposits use of these indices is illustrated in an analysis of the form characteristics of clasts from lateral and frontal moraines at storbreen jotunheimen these fall between those of actively transported clasts in basal till low c40 and ra values and those of unmodified frost weathered clasts high c40 and ra values both indices decline down moraine within sample analyses of clast shape demonstrates that these aggregate clast form gradients reflect changes in the relative proportions of actively and passively transported debris on the moraines rather than progressive modification of actively transported clasts these analyses also indicate that actively transported clasts form the dominant component of the moraines particularly near the former glacier terminus further applications of the approach developed here are suggested

climate and material controls on periglacial soil processes toward improving periglacial climate indicators one of the distinguished efforts of a l washburn was to reconstruct mean annual air temperature using periglacial features as climate indicators this paper reviews existing periglacial indicators and proposes a strategy to improve their thermal resolution based on recent periglacial process studies with a focus on solifluction and thermal contraction cracking and associated landforms structures landforms resulting from solifluction reflect both the depth subjected to freeze thaw and the thickness of frost susceptible soils the thickness of a solifluction structure can be used to infer the dominant freeze thaw regime and minimum seasonal frost depth ice wedge pseudomorphs have limited potential as a climate indicator because 1 they mainly reflect extreme winter temperatures 2 their thermal thresholds depend on the host material and 3 they need to be distinguished from frost wedges of other origin produced under different thermal and or material conditions monitoring studies of currently active ice wedges suggest that ice wedge cracking requires a combination of low temperature and large temperature gradients in the frozen active layer further field monitoring of periglacial processes and their controlling factors under various climate conditions and in various materials are needed however to improve the resolution of periglacial paleoclimate indicators

recognition and palaeoclimatic implications of late quaternary niche glaciation in eastern lesotho geomorphic evidence of former glaciation in the high drakensberg of southern africa has proven controversial with conflicting glacial and non glacial interpretations suggested for many landforms this paper presents new geomorphological sedimentological and micromorphological data and glacier mass balance modelling for a site in the leqooa valley eastern lesotho preserving what are considered to be moraines of a former niche glacier that existed during the last glacial maximum lgm the geomorphology and macro sedimentology of the deposits display characteristics of both active and passive transport by glacial processes however micromorphological analyses indicate a more complex history of glacial deposition and subsequent reworking by mass movement processes the application of a glacier reconstruction technique to determine whether this site could have supported a glacier indicates a reconstructed glacier equilibrium line altitude ela of 3136 m a s l and palaeoglacier mass balance characteristics comparable with modern analogues reflecting viable if marginal glaciation radiocarbon dates obtained from organic sediment within the moraines indicate that these are of lgm age the reconstructed palaeoclimatic conditions during the lgm suggest that snow accumulation in the drakensberg was significantly higher than considered by other studies and has substantial relevance for tuning regional climate models for southern africa during the last glacial cycle copyright 2009 john wiley sons ltd

controls on basalt terrace formation in the eastern lesotho highlands abstract the objective of this study is to ascertain the relative importance of lithological controls and geomorphological processes in the development of drakensberg basalt terraces various hypotheses for terrace formation are considered including geological controls macroscale geomorphology and climatic geomorphological controls the variations in strength and relative age differences for scarp surface exposures on two slopes of varying aspect are determined so that a comparison can be made between various scarp outcrops and relative rates of weathering scarp outcrops were measured for their rock mass strength rock surface roughness and percentage lichen cover the ethylene glycol test was performed on prepared rock samples to determine susceptibility to tensional breakup a satellite image depicting the distribution of late lying contemporary snow was used to assist in the construction of topo climatic linkages with scarp terrace localities findings show that terraces are most common on southeast facing aspects and coincide with the major joint strike direction lithological factors are thus considered the primary control to such terrace development it is suggested that a different set of geomorphological processes operates on various slope altitudinal and slope orientational positions at any given time