two cryogenian glacial successions compared aspects of the sturt and elatina sediment records of south australia abstract two cryogenian glacial sequences the sturt and elatina occur within the adelaide rift complex s australia and are part of an 8 km thick succession recording rodinia fragmentation and subsequent passive margin development we compare and contrast these glacial successions presenting new data including detailed logged sections for both glacial sequences facies analysis reveals a total of six facies associations recording a range of glacial and glacially related processes these are a diamictite facies association ice proximal debris flows a sheet sandstone facies association fluvial deposits a flaser and rhythmically bedded facies association tidal flat a hummocky cross stratified sandstone facies association shoreface to offshore transition zone deposits and an underflow facies association recording offshore deposition a sixth facies association a ferruginous lonestone bearing siltstone is restricted to the top of the elatina formation and records rapid environmental amelioration and emergence from glaciation in the central flinders ranges the sturt succession commences with a glacial erosion surface ges which in agreement with previous workers was probably enhanced by rifting this ges is overlain in ascending order by the pualco tillite holowilena ironstone and wilyerpa formation with the warcowie dolomite member at the base of this latter formation a second ges is preserved within this latter unit and is overlain by a stratigraphic motif that records an alternation of offshore transition zone and offshore deposits significant base level falls within the wilyerpa formation are identified by fluvial deposits sitting disconformably upon offshore deposits in contrast within the elatina formation a single ges is proposed which defines the base of the formation the elatina formation is split into two informal members on the basis of analysis of sediment stacking patterns and the recognition of a sharp stratigraphic surface that divides the formation apart from a locally preserved basal diamictite the lower member consists of fluvial deposits whereas the upper member is dominated by a mixture of tidal flat sediments and debris flow deposits the boundary between these units is therefore interpreted as a hybrid surface recording tidal ravinement in some areas and a glacial advance in others deglaciation left contrasting deposits the sturt deglaciation culminated in deposition of black shale of the tindelpina shale member of the tapley hill formation seemingly as a sheet like deposit over the adelaide rift complex and beyond into the amadeus basin of central australia the elatina deglaciation meanwhile began first with deposition of the sixth facies association ferruginous dropstone bearing siltstone then proceeded with deposition of cap dolostone of the nuccaleena formation

stratigraphic architecture of the cenozoic succession in the mcmurdo sound region antarctica an archive of polar palaeoenvironmental change in a failed rift setting the victoria land basin forms part of the failed west antarctic rift and preserves a cenozoic succession up to 4 km thick that records the onset of cenozoic glaciation and the history of antarctic glaciation over the past 34 myr this succession is relevant both to investigations of modern climate change and to studies of long term palaeoclimate change in general this study provides a sedimentological and stratigraphic review of the victoria land basin succession based on analysis of several continuous drillcores acquired since the 1970s and supported by seismic stratigraphic analysis of a large array of seismic reflection data an array of fifteen lithofacies is recognized within the victoria land basin cenozoic succession including fossiliferous and diversely bioturbated mudrocks and diatomites texturally mature sandstones and conglomerates mixed mudstones and sandstones with dispersed gravel with restricted bioturbation and diamictites and associated lithologies these facies record a variety of marine glaciomarine proglacial and subglacial environments locally volcanic and volcaniclastic deposits are interbedded in the succession lithofacies are arranged in repetitive vertical stacking patterns depositional sequences that record glacial advance retreat cycles with attendant relative sea level changes seven varieties of depositional sequences stratigraphic motifs are recognized within the succession as a whole and interpreted to record a range of depositional settings from rifts unaffected by glacial ice motif 7 through varying degrees of glacial influence with abundant meltwater contributions motifs 6 to 3 to cold polar glaciated environments such as that of today motifs 2 and 1 overall there is a gradual trend upward through the succession from motif 7 at the base towards motif 1 at the top but the trend is not monotonic a significant conclusion of this work is that a record of dynamic climate and glacial conditions is preserved through the entire 34 myr period of the cenozoic icehouse at least in the victoria land basin intervals characterized by consistent stratigraphic style motifs are recognized throughout the victoria land basin succession these intervals are of 1 to 6 myr duration each containing numerous depositional sequences they are one to two orders of magnitude longer than glacial interglacial cycles and record periods during which environmental conditions varied in an internally consistent manner these intervals are considered to reflect convolutions of orbital parameters that remained stable for periods of 106 a and then switched to alternative configurations such intervals are directly analogous to 1 to 8 myr intervals characterized by glaciogenic strata that are preserved within the late palaeozoic of eastern australia among other areas and may be a recurring stratigraphic response to icehouse climate regimes through geological time

a depositional record of deglaciation in a paleofjord late carboniferous pennsylvanian of san juan province argentina the role of catastrophic sedimentation the combination of high sediment supply rates and ample accommodation within fjords provides high resolution records of deglaciation ancient fjord fills provide the potential for three dimensional views of the evolution of depositional environments in response to changing sediment supply and base level through the deglacial process we describe the fill jejenes formation of a well exposed late carboniferous pennsylvanian glacial valley and its tributaries these deposits record the progressive marine flooding and infilling of topography by glacially derived sediments the geometry of the valley and its tributaries is controlled by the underlying lower paleozoic lithologies a deep valley with steep sides exists where the bedrock is massive limestones and a broader shallower valley exists where the bedrock is generally a fine grained olistostrome the valleys are locally floored with diamictites including both in situ tillites and remobilized diamictites in the trunk valley these are locally overlain by a small shallow water delta the major part of the valley fill consists of a 150 m thick mudstone dominated succession probably generated by plumes of glacial outwash containing numerous dropstones that decrease in abundance down the fjord the mudstones contain numerous thin sandstone and conglomerate turbidites that were supplied laterally via subaqueous gravel fans feeding in from the tributary valleys each of which has a distinctive clast suite related to the local subcrop the entire succession is overlain by 300 m of sandy turbidites of which the upper part includes large mass transport complexes intercalated within the succession in the trunk valley are structureless graded silty mudstones lacking dropstones but with abundant large wood fragments close to the steep western margin of the trunk valley each of these massive mudstones is underlain by a slump or debris flow locally containing meter scale blocks of ordovician limestone from the valley side we interpret these as a consequence of rockfalls from the steeper valley sides triggering debris flows on the subaqueous fjord slopes we suggest that large solitary waves were generated as the rockfalls entered the water traveling along the fjord and stripping vegetation from the shoreline large amounts of mud and silt were thrown into suspension during these events and subsequently settled from suspension to form the structureless graded beds these deposits and other mass flow deposits within the succession emphasize the potential importance of catastrophic sedimentation within deglacial successions

debris transport in a temperate valley glacier haut glacier d arolla valais switzerland hambrey m j goodsell becky glasser n f 2005 debris transport in a temperate valley glacier haut glacier d arolla valais switzerland journal of glaciology 51 172 pp 139 146

tidewater glacier beds insights from iceberg debris in kongsfjorden svalbard the sediment in icebergs offers an opportunity to sample the otherwise inaccessible beds of modern tidewater glaciers this paper presents a discussion of the benefits and problems of using iceberg debris to make inferences about the nature of the beds of modern tidewater glaciers as an example we present data obtained from icebergs calved from fast flowing tidewater glaciers in kongsfjorden svalbard sediment samples obtained from 12 icebergs show that clast rich muddy diamicton is the dominant facies although muddy gravel and mud are also present in some debris layers sediment texture and clast shape analyses indicate that most debris in the icebergs is of basal origin micro morphological analyses of thin sections of the diamicton also indicate pervasive deformation of the sediment although individual icebergs only represent small samples of the bed of a tidewater glacier and problems remain in linking iceberg sediments to their pre calving transport history beneath the glacier this method provides a potentially fruitful way of linking sediments to glacier dynamics

pleistocene variability of antarctic ice sheet extent in the ross embayment cores acquired by the andrill mcmurdo ice shelf project and 1b provide the basis for a new sedimentation model for glacimarine depositional sequences that reflect cyclic glacial interglacial fluctuations of a marine based ice sheet in the western ross embayment over the past 2 0 ma notwithstanding periodic erosion during advances of the ice sheet uncertainties inherent to the sedimentological interpretation and a limited number of chronological datums it is clear that subglacial to grounding zone sedimentation was dominant at the and 1b site during the late pleistocene with interglacials being represented only by thin intervals of ice shelf sediment each sequence is characterised by subglacial massive diamictite that pass upwards into glacimarine diamictites and mudstones this provides the first direct evidence that the marine based antarctic ice sheet has oscillated between a grounded and floating state at least 7 times in the ross embayment over the last 780ka implying a milankovitch orbital influence an unconformity in and 1b that spans most 200 kyr of the mid pleistocene transition is inferred to represent widespread expansion of a marine based ice sheet in the ross embayment at 0 8 ma prior to 1 0 ma interglacial periods are characterised by open water conditions at the drill site with high abundances of volcanoclastic deposits and occasional diatomaceous sediments these may have responded to precession 20 kyr or obliquity 40 kyr orbital control the occurrence of 6 7 m of phonolitic glass reworked from mt erebus in interglacial deposits beneath last glacial maximum till requires open ocean or ice shelf conditions in the western ross sea around the drill site within the past 250 ka and implies a ross ice shelf similar to or less extensive than today during marine isotope stage 7 or 5

pliocene pleistocene glaciomarine sedimentation in eastern prydz bay and development of the prydz trough mouth fan odp sites 1166 and 1167 east antarctica abstract lithostratigraphy grain sizes and down hole logs of site 1166 on the continental shelf and site 1167 on the upper slope are analyzed to reconstruct glacial processes in eastern prydz bay and the development of the prydz trough mouth fan in eastern prydz bay upper pliocene lower pleistocene glaciomarine sediments occur interbedded with open marine muds and grade upward into waterlaid tills and subglacial tills lower pleistocene sediments of the trough mouth fan consist of coarse grained debrites interbedded with bottom current deposits and hemipelagic muds indicating repeated advances and retreats of the lambert glacier amery ice shelf system with respect to the shelf break systematic fluctuations in lithofacies and down hole logs characterize the upper pliocene lower pleistocene transition at sites 1166 and 1167 and indicate that an ice stream advanced and retreated within the prydz channel until the mid pleistocene the record from site 1167 shows that the grounding line of the lambert glacier did not extend to the shelf break after 0 78 ma published ice rafted debris records in the southern ocean show peak abundances in the pliocene and the early pleistocene suggesting a link between the nature of the glacial drainage system as recorded by the trough mouth fans and increased delivery of ice rafted debris to the southern ocean

field experiments on the transport of rock fragments by animal trampling on scree slopes qualitative observations in an area with steep scree slopes in turkey suggested that trampling by goats and sheep may contribute significantly to the downslope movement of rock fragments in these environments therefore a series of field experiments was set up to determine the rate of rock fragment transport caused by trampling the experimental results allowed the calculation of a unit displacement distance from each trampling experiment which may then be used to extrapolate the measured transport rates over longer time periods and larger areas although such extrapolations should be interpreted with great caution the results demonstrate that trampling contributes significantly to rock fragment transport in such environments as calculated yearly displacement distances are equal to or higher than those reported in the literature for other geomorphic processes the observed travel distance distributions are not well described by a negative exponential distribution trampling causes a weak downslope sorting the coarsest clasts move farther but has a significant effect on vertical sorting and is one of the factors which can explain the layered structure of the scree slopes in the area

sedimentary evidence of landscape and climate history since the end of mis 3 in the krkonose mountains czech republic abstract a sedimentary core recovered from the cirque basin of labsk d l valley 1039 m a s l in the krkonose mountains reflects the environmental history for approximately the last 30 000 years analyses of magnetic susceptibility carbon content pollen assemblages and macrofossil data in a 15 m thick sediment sequence provide the first continuous record of lateglacial and holocene vegetation history in sudetes region of the czech republic the succession of sedimentary units in the lower part of the core suggests that the cirque was ice free before the onset of the last glaciation at the beginning of marine isotope stage 2 highly variable climate prevailed during this period with cold conditions culminating about 18 cal ka bp cold climates persisted until the lateglacial period evidenced by an identified warming and subsequent cooling event correlated with the younger dryas period sparse treeless vegetation dominated in the catchment area at that time the sequence of interrupted thinly laminated silts reflects the retreat and temporary readvance of a local glacier in the cirque during 12 5 10 8 cal ka bp subsequently the alpine treeline ecotone gradually shifted above the cirque floor palaeoclimatic conditions in the early holocene fluctuated strongly whereas since 5 1 cal ka bp conditions have been more stable pollen based climate reconstructions suggest significant cooling at around 9 8 9 3 7 7 7 5 and 4 0 3 3 cal ka bp spruce forests have dominated the site since 5 0 cal ka bp when the vegetation became similar to the modern one two phases of increased sedimentation were identified within the holocene culminating about 9 2 7 5 cal ka bp and 5 8 5 5 cal ka bp sediment yield was as high as 2 4 mm yr 1 during the period reflecting environmental changes during the atlantic sub boreal transition

evaluation of image analysis methods used for quantification of particle angularity angularity is an important parameter in the characterization of particle morphology that is used to interpret the transport history of particles in sedimentary deposits in the past visual classification using silhouette charts was widely used to determine particle angularity but this approach is subjective and time consuming with advances in modern image analysis techniques and low cost software packages it is possible to rapidly quantify particle angularity more objectively than using visual classification methods this study re examines the performance of three existing image analysis methods and one new image analysis procedure applied to six rock and sediment samples that were visually different in angularity to facilitate comparison between the angularity results measurements were reduced to rankings for each aggregate sample these results show that the four image analysis methods rank the angularity of the samples differently and that none rank the mean angularity index in the same order as the angularity ranking using visual classification therefore further research is needed to develop an image analysis method that can quantify the angularity of sedimentary particles more precisely

geomorphological and sedimentary evidence of probable glaciation in the jizerske hory mountains central europe abstract the jizerske hory mountains in the czech republic have traditionally been considered to be a highland that lay beyond the limits of quaternary glaciations recent work on cirque like valley heads in the central part of the range has shown that niche glaciers could form during the quaternary here we report geomorphological and sedimentary evidence for a small glacier in the pytlacka jama hollow that represents one of the most enclosed valley heads within the range shape and size characteristics of this landform indicate that the hollow is a glacial cirque at a degraded stage of development boulder accumulations at the downslope side of the hollow probably represent a relic of terminal moraines and the grain size distribution of clasts together with micromorphology of quartz grains from the hollow indicate the glacial environment of a small glacier this glacier represents the lowermost located such system in central europe and provides evidence for the presence of niche or small cirque glaciers probably during pre weichselian glacial periods the glaciation limit 1000 m asl and paleo ela 900 m asl proposed for the jizerske hory mountains implies that central european ranges lower than 1100 m asl were probably glaciated during the quaternary

a glacial lake outburst flood associated with recent mountain glacier retreat patagonian andes harrison s glasser n f winchester v haresign e warren c jansson k 2006 a glacial lake outburst flood associated with recent mountain glacier retreat patagonian andes the holocene 16 4 pp 611 620 sponsorship nerc grant ner b s 2002 00282 carnegie trust for the universities of scotland

tectonic controls on distribution and stratigraphy of the cryogenian rapitan iron formation northwestern canada paleogeographic data indicate that the neoproterozoic rapitan group accumulated in two spatially related silled basins during the first mid neoproterozoic glacial episode ca 711 ma yet the controls on glaciation reason for basin development spatio temporal relationships among stratigraphic units and constraints on iron formation deposition and distribution in this region and globally at this time have not been adequately explained the lack of a coherent understanding of the group s regional stratigraphy has been a significant barrier to deciphering the geologic history of this critically important succession based on new stratigraphic data and incorporating the results of a related geochemical study the rapitan group accumulated in tectonically complex sub basins of a young rift zone the spatial and temporal dynamics of these sub basins controlled the grain size volume and distribution of detrital sediment predominantly turbidites and diamictites deposited during two glacially influenced episodes with ice cover during an interglacial episode the rotated exposed upper surfaces of newly displaced rift blocks directed drainage away from basin margins precluding significant clastic sediment delivery and subaqueous margins of outboard tilted fault blocks acted as sills that isolated local bottom water allowing the accumulation of an entirely hydrogenous succession jaspilitic and hematitic iron formation two strike parallel normal faults that strongly controlled basin margin development are prominent thrust faults in the present day orogen syndepositional activity of strike normal transfer faults segmented the basins along their length as reflected in pronounced along strike variations in the presence absence thickness and composition of the three stratigraphic units mt berg sayunei and shezal formations and in the presence or absence of iron formation locally 100 m thick top of sayunei formation differential subsidence in actively rifting basins was essential for deposition of rapitan type iron formation but glaciation although coeval with rapitan group accumulation was not a strong control the timing of the onset of glacially influenced sediment deposition in the closely spatially related rapitan similar to 711 ma and mount harper groups similar to 717 ma in northwestern laurentia differs by 6 m y arguing for diachronous sturtian glaciation both locally and globally c 2016 elsevier b v all rights reserved

an antarctic stratigraphic record of stepwise ice growth through the eocene oligocene transition earth s current icehouse phase began 34 m y ago with the onset of major antarctic glaciation at the eocene oligocene transition changes in ocean circulation and a decline in atmospheric greenhouse gas levels were associated with stepwise cooling and ice growth at southern high latitudes the antarctic cryosphere plays a critical role in the ocean atmosphere system but its early evolution is still poorly known with a near field record from prydz bay antarctica we demonstrate that antarctic ice growth was stepwise and had an earlier onset than previously suggested prydz bay lies downstream of a major east antarctic ice sheet drainage system and its sedimentary records uniquely constrain the timing of ice sheet advance onto the continental shelf we investigated a detrital record extracted from three ocean drilling program drill holes within a new depositional and chronological framework spanning the late eocene to early oligocene ca 36 33 ma the chemical index of alteration cia and the s index calculated from the major element geochemistry of bulk samples yielded estimates of chemical weathering intensities and mean annual temperature on the east antarctic continent we document evidence for late eocene mountain glaciation along with transient warm events at 35 8 34 8 ma from 34 4 ma associated with the eocene oligocene transition precursor 18o excursion glaciers advanced into prydz bay coincident with a decline in chemical weathering and temperature we conclude that antarctic continental ice growth commenced with the eocene oligocene transition precursor glaciation during a time of subantarctic surface ocean cooling and a decline in atmospheric pco2 these results call for dynamic high latitude feedbacks that are currently poorly represented in earth system models and emphasize the need for additional near field glacio sedimentological high latitude sea surface temperature and pco2 records across the eocene oligocene transition

middle pleistocene glacier behaviour in the mediterranean sedimentological evidence from the pindus mountains greece detailed sedimentological analyses of diamicton sequences in two areas of the pindus mountains greece indicate multiple episodes of glacier advance and retreat during cold stages of the middle pleistocene these glacial sequences represent some of the most southerly in europe and are important archives of regional and global climate change the pindus glaciers were relatively small by world standards and would have been highly responsive to changes in air temperature and precipitation on mount tymphi at least three phases of glacier advance are recorded within deposits assigned to the skamnellian stage mis 12 further north on mount smolikas a thick multiple diamicton sequence records evidence for multiple glacier advances during both the skamnellian stage and the vlasian stage mis 6 these records highlight the dynamic nature of glacier behaviour in the mediterranean mountains during the middle pleistocene and provide new evidence for unstable cold stage climates

some aspects of the geochemistry provenance and palaeoclimatology of the torridonian of nw scotland geochemical data mostly from mudstones are used in an attempt to investigate some aspects of the palaeoclimatology and provenance of the torridonian succession in nw scotland the basal part of the stoer group which has been interpreted as glaciogenic is thought to have formed in a warm arid setting the presence of oscillation ripples and desiccation cracks in mudstones containing isolated clasts is thought to preclude their interpretation as ice rafted debris some aspects of the major element geochemistry of the stoer group mudstones suggest deposition in an environment with little weathering but chemical weathering is inhibited in both frigid and arid settings and sedimentological evidence favours the latter the stoer group mudstones are enriched in mg ca and na relative to the torridon group samples which are much closer in composition to an average shale estimate paas the cr and ni contents of the stoer mudstones are significantly higher than those of the torridon group samples there is however no evidence that enrichment in these elements was due to contamination with volcanic material like that of the stac fada member the scourian basement appears to be an adequate source of the ni and cr in the stoer group sediments th sc ratios are higher in the torridon than in the stoer mudstones this difference is interpreted as indicating that the stoer mudstones were largely derived from local archaean sources but that the torridon group mudstones incorporated materials from a much wider provenance including younger and recycled materials evidence from rare earth elements also provides evidence for different source terrains for the stoer and torridon groups the torridon group mudstones are more weathered have a higher ree content and display a more prominent eu anomaly lower value for eu eu than do the stoer samples these results support evidence from th sc ratios that the torridon group was derived from a more varied recycled and granite rich terrain than the stoer much of which appears to have relatively local provenance the geochemistry of mudstones can shed considerable light on problems of provenance and palaeoclimatology because many useful trace elements tend to be concentrated in such fine grained rocks and some aspects of their major element chemistry may be related to climatic factors

classification of poorly sorted sedimentary rocks abstract the classification and nomenclature of sandstones has evolved over the years into a system which is now generally accepted as standard however no equivalent system exists for the poorly sorted sedimentary rocks which include grain sizes from clay to gravel a descriptive classification is proposed based on an earlier system but using updated nomenclature and lithological fields such a scheme is needed to clearly define lithological terms currently used in the description of sedimentary sequences

permian diamictites in northeastern asia their significance concerning the bipolarity of the late paleozoic ice age despite a lack of detailed sedimentologic analyses diamictites in the middle permian atkan formation were previously interpreted as glaciomarine and glacially influenced marine deposits this interpretation allowed this unit to play a prominent role in paleoclimatic and biogeographical reconstructions associated with presumed bipolar glaciation during the late paleozoic ice age lpia in this sense the lpia is considered to be a close analog to bipolar glaciation and climate change during the cenozoic here results are presented that challenge the glacigenic interpretation for these strata and negate interpretations of the bipolar nature of the lpia the 400 to 1500 m thick atkan formation was deposited in back arc basins associated with activity of the okhotsk taigonos volcanic arc along the leading edge of pangea as it drifted across the north polar circle the occurrence of tuffs volcanic clasts and glass shards indicate derivation from a nearby arc cooling and solidification of some clasts during sedimentation is suggested by the occurrence of clasts with embayments and protrusions that extend into the surrounding matrix clasts with columnar like jointing and alteration of the matrix surrounding some clasts ca tims dating of tuff zircons indicate a late capitanian age which is consistent with fossils within the strata bedded diamictites deposited as debrites dominate these diamictites which occur as tens of m thick downlapping packages that thicken then thin upward were deposited as prograding and abandoning sediment gravity flow fans chaotic and folded strata formed as slumps graded sandstones and conglomerates were deposited as turbidites and mudstones were deposited as mudflows low density turbidites and hemipelagic deposits striated clasts and outsized clasts piercing bedding were not observed in the study area strata above and below the atkan formation contain abundant graded beds and deep water trace fossils indicating deposition as turbidites the combination of debrites turbidites slumps volcanic grains clasts glass and tuffs and an absence of glacigenic indicators suggest that atkan strata were deposited in deep water basins associated with the development of the volcanic arc rather than due to glacial activity these findings are significant as they require reconsideration of current views of lpia glaciation and suggest that ice sheets were limited to gondwana

glacigenic and associated marine sediments in the weddell sea fjords of spitsbergen and the barents sea a review abstract studies of glacigenic and associated marine sediments in the weddell sea fjords of spitsbergen and barents sea show that during periods of limited glacial coverage interstadials large amounts of material may be brought into the sea mainly by meltwater the major load is deposited relatively close to the icefront 1 at times of maximum glacial extent grounded ice extends onto the shelf with the shelf edge as the outer limit and land and inner shelf areas are eroded main glacial depositional sites are then the outer shelf and shelf edge the sedimentary environment outside an ice shelf is characterized by low clastic supply mainly deposited from icebergs due to low turbidity and a supply of nutrient rich water biogenic matter accumulates leading to a glaciomarine sequence rich in bioclastics sea level lowering results in grounding and seaward expansion of the ice shelf subsequent eustatic rise causes the grounded ice to float deglaciation and sea level rise reduces clastic input to the shelves glacial sediments are reworked and carbonates may accumulate forming tillite carbonate sequence e g late precambrian break up of marine ice sheets such as the barents sea ice sheet seems to have taken place stepwise in response to eustatic rise and climatic changes

development of sediment landform associations at cold glacier margins dry valleys antarctica hambrey m j fitzsimons s j 2010 development of sediment landform associations at cold glacier margins dry valleys antarctica sedimentology 57 3 857 882 michael hambrey is corresponding author sponsorship marsden fund of new zealand university of otago research committee nerc grant no ner a s 2000 01256

neogene fjordal sedimentation on the western margin of the lambert graben east antarctica neogene glacial sedimentation east antarctica

neogene glacial record from the sirius group of the shackleton glacier region central transantarctic mountains antarctica neogene glacigenic strata collectively referred to as the sirius group are widely distributed throughout the transantarctic mountains the group is particularly well exposed near the head of shackleton glacier 858109 to 858409s on roberts massif and at bennett platform these deposits are critical for examining the nature of former ice flow from the east antarctic ice sheet into the ross embayment the sirius group rests on a glacially grooved and striated pavement named herein the shackleton erosion surface the sub sirius group surface on roberts massif was of low relief and glaciogenic sediment was deposited on it as a sheet of uniform thickness at bennett platform stratigraphic sections attain a thickness of 110 m thick and are subdivided into the shackleton glacier formation maximum thickness 98 m and the overlying bennett platform formation 44 m separated by an unconformity a third older lithified diamictite containing wood fragments occurs as clasts within these formations and as boulders in the modern lateral moraines of shackleton glacier the dominant facies massive diamict is interpreted primarily as lodgement till other facies indicate glaciofluvial and glaciolacustrine deposition facies associations suggest deposition either by sliding temperate or by polythermal glaciers under much warmer conditions than those of today widespread large and small scale faulting has affected the sirius group and underlying rocks to the extent that inland exposures are over 500 m higher than those to the north over a distance of 30 km thus at the time of deposition of the sirius group the mountains were probably lower and the ice sheet was much thinner

infilling of the younger kathmandu banepa intermontane lake basin during the late quaternary lesser himalaya nepal a sedimentological study the kathmandu and banepa basins central nepal are located in a large syncline of the lesser himalayas the older kathmandu lake evolved during the pliocene and early pleistocene the younger kathmandu lake which is the focus of this study is infilled with late quaternary sediments three formations arranged in stratigraphical order the kalimati gokarna and thoka formations formed during the infilling stage of this lacustrine basin structural and textural sedimentological analyses a chemical survey across the basin and mineralogical investigations of fine grained sediments form the basis of this palaeogeographical study the basin under investigation was covered by a perennial freshwater lake before 30 000 yr bp the lake was infilled with alluvial and fluvial sediments delivered mainly from the mountains north of the basin a fairly low gradient was favourable for the formation of diatomaceous earths carbonaceous mudstones and siltstones which were laid down in the centre of the lake and in small ponds towards the basin edge lacustrine sediments gave way to deltaic deposits spread across the delta plain crevasse splays and anastomosing rivers mainly delivered suspended load for the widespread siltstones and mudstones the proximal parts of the alluvial fluvial sedimentary wedge contain debris flows that interfinger with fine grained floodplain deposits three highstands of the water level 30 000 yr bp 28 000 19 000 yr bp 11 000 4000 yr bp have been recognised in the sedimentary record of the younger kathmandu lake in the late quaternary second order water level fluctuations are assumed to be triggered by local processes damming by tectonically induced landslides first order water level fluctuations are the result of climatic changes copyright 2003 john wiley sons ltd

traditional soil particle sphericity roundness and surface roughness by computational geometry definitions of soil particle sphericity roundness and roughness have existed since at least the 1930s in the 1950s charts of typical sphericity and roundness values were developed to alleviate tedious manual determination they allowed users to classify particles by visual comparison to typical particles possessing ranges of sphericity and roundness the original definitions and somewhat subjective chart methods are still widely used today this paper describes robust numerical methods based on computational geometry to determine precisely the traditional values from two dimensional images of particles statistical methods including locally weighted regression and k fold cross validation were used to discretise a mean particle surface and thereby quantify and remove roughness the paper details the algorithms for identifying particle corners and fitting circles to them for computation of roundness conclusions are also drawn regarding the most appropriate definition for particle sphericity from among f

assessing automated image analysis of sand grain shape to identify sedimentary facies gran dolina archaeological site burgos spain abstract gran dolina is a cave sierra de atapuerca spain infilled by a 25 m thick sedimentary record divided into 12 lithostratigraphic units that have been separated into 19 sedimentary facies containing early and middle pleistocene hominin remains in this paper an automated image analysis method has been used to study the shape of the sedimentary particles since particle shape is interpreted as the result of sedimentary transport and sediment source this study can provide valuable data about the sedimentological mechanism of sequence formation the shape of the sand fraction in 73 samples from gran dolina site and sierra de atapuerca was analyzed using the malvern morphologi g3 an advanced particle characterization tool in this first complete test we used this method to the published sequence of gran dolina defined previously through field work observations and geochemical and textural analysis the results indicate that this image analysis method allows differentiation of the sedimentary facies providing objective tools to identify weathered layers and measure the textural maturity of the sediments channel facies have the highest values of circularity and convexity showing the highest textural maturity of particles on the other hand terra rossa and debris flow samples show similar values with the lowest particle maturity

particle size scales and classification of sediment types based on particle size distributions review and recommended procedures this paper provides a review of different particle size scales size class terminology and particle size distribution textural classification schemes which are widely used in sedimentology geomorphology soil science aquatic ecology and civil engineering it is concluded that a revised system of size class nomenclature based on the udden 1898 and wentworth 1922 schemes provides the most logical and consistent framework for use with sediments and a wide range of other particulate materials a refined scheme is proposed which has five first order size classes boulder gravel sand silt and clay each of which has five second order subdivisions with limits defined at one phi intervals the scheme is simple and intuitively easy to understand the paper also provides a review of previous schemes that have been proposed to describe and classify sediments on the basis of the proportions of gravel sand and mud or sand silt and clay using trigons also termed ternary diagrams many of these schemes do not have a logical basis and provide limited or uneven resolution new gravel sand and mud and sand silt and clay classification systems are proposed that are both more logical and provide greater discriminatory power than previous schemes they are therefore more suitable for use in environmental and forensic investigations a new microsoft excel program freely available to download from http www kpal co uk allows rapid classification of sediments based on the proportions of gravel sand and mud and sand silt and clay proportions and graphical comparison of the data for different sample groups

the mendel formation evidence for late miocene climatic cyclicity at the northern tip of the antarctic peninsula abstract a detailed description of the newly defined mendel formation is presented this late miocene 5 9 5 4 ma sedimentary sequence with an overall thickness of more than 80 m comprises cyclic deposition in terrestrial glacigenic glaciomarine and marine environments subglacial till was deposited by a thick grounded antarctic peninsula ice stream advancing eastwards through the prince gustav channel crossing the northernmost part of present day james ross island with most of the material carried actively at the base of the warm based glacier the form of the prince gustav channel originated before the late miocene and its present glacial over deepening resulted in multiple grounded glacier advances during the neogene and quaternary the sea prograded from the east and the glacier margin became buoyant building a small ice shelf below and in front of which glaciomarine and marine sediments were deposited these sedimentary deposits are composed of material that was transported mostly by small glaciers and subsequently by the floating ice shelf and by calving icebergs towards the open sea these environmental and glaciological conditions differ strongly from the present cold based local glaciers of james ross island and the antarctic peninsula these changes were triggered by the global sea level fluctuation connected with climatic changes due to antarctic ice sheet build up and decay this reveals late miocene obliquity driven cyclicity with a 41 ka period the mendel formation sedimentary sequence is comprised of at least two glacial periods and one interglacial period sea level rise at the northern tip of the antarctic peninsula between glacial lowstand and interglacial highstand was more than 50 m during the late miocene and was followed by a subsequent sea level fall of at least the same magnitude the presence of well preserved articulated pectinid bivalves support interglacial open sea conditions the re deposition of palaeontological material was shown to be important for the mendel formation reworked pectinid shells revealed an open marine interglacial condition in this part of the antarctic peninsula during the early to mid miocene 20 5 17 5 ma unfortunately relevant sedimentary deposits have not been found on land

working with broken agents exploring computational 2d morphometrics for studying the post depositional history of potsherds abstract the study of size and shape of ceramic fragments is a common approach used for unraveling the depositional and post depositional history of archaeological assemblages similar to sediment particles the size and shape of a potsherd are altered under conditions of abrasion breakage or weathering occurring during or after deposition which can be the product of both human and non human agents thus the analysis of dimensional and morphological changes of fragments not only points towards specific post depositional processes but can also shed light on the nature of human interaction with broken pottery by coupling a traditional sedimentological framework for shape description and a computational approach to 2d morphometrics in this paper we present a quick reproducible and accurate method for studying the alteration of shape and size of potsherds three main shape descriptors i e sphericity roundness and convexity were tested on a combination of experimental and early neolithic potsherds in northwest romania from contexts where the conditions of fragment alteration were known or could be safely inferred in addition potsherds from an early neolithic pit discovered at c linesti oas d mbul sfintei m rii satu mare county romania were analysed for determining the pit infilling process and understanding the extent of the interaction between humans and broken pots results from morphometric tests show the reliability of the computational technique and shape descriptors for identifying different conditions of alteration of potsherds the analysis of the romanian assemblages provide insight into post depositional processes showing downslope movement as the main mechanism behind the infilling of the pit at c linesti oas d mbul sfintei m rii in addition the potsherds possessed a high level of erosion and fragmentation highlighting a long span of human interaction with broken materials at this site during early neolithic times

mid carboniferous deglaciation of the protoprecordillera argentina recorded in the agua de jaguel palaeovalley abstract the agua de jaguel formation near uspallata mendoza province argentina was deposited within a palaeovalley along the southeastern margin of the calingasta uspallata basin adjacent to the protoprecordillera the basal glacigenic sequence of the formation was deposited in the serpukhovian early bashkirian near the beginning of the late palaeozoic ice age the sequence is composed of diamictite conglomerate sandstone and mudrock and records four depositional stages within a palaeofjord 1 morainal bank deposition by a wet based tidewater glacier 2 glacial retreat succession where ice retreated up the fjord out of the immediate area allowing iceberg deposition of dropstones and dump deposits 3 continued glacial retreat with ice receding onto land allowing a shoreface to develop within the palaeovalley and 4 transgression across the shoreface and resumption of iceberg deposition the thickness and facies of this succession are similar to deposits within modern alaskan fjords housing temperate tidewater glaciers comparison of the agua de jaguel formation with alaskan fjords indicates that sequence stratigraphy used for low latitude deposits must be applied with caution as glacimarine ice retreat within a fjord produces strata surfaces that are easily misidentified as flooding surfaces resulting from changes in water depth likewise the transgression during stage 4 is significant as it indicates a rise in sea level that occurred during glaciation of the protoprecordillera thus suggesting that the transgression between stages 3 and 4 was not driven by input of glacial meltwater additionally the sediment geochemistry suggests that the bottom waters of the palaeovalley were anoxic which may help explain the absence of bioturbation in the sequence as well as in other ancient glacimarine palaeovalleys the deglaciation succession and transgression are also recorded in the nearby hoyada verde and tramojo formations so it is proposed that all three formations record one glacial event in the protoprecordillera overlying fluvial and shallow marine strata in the agua de jaguel hoyada verde and tramojo formations show no indication of continued glaciation in the protoprecordillera following stage 4 and equivalent strata the deglaciation succession of the agua de jaguel formation affirms the emerging concept that the late palaeozoic ice age was characterized by alpine glaciers ice caps and small ice sheets that were not massive enough to have driven eustatic fluctuations of 100 m as previously understood and that ice never covered westernmost gondwana during later lpia events

a new depositional model for ice shelves based upon sediment cores from the ross sea and the mac robertson shelf antarctica we document the similarity of depositional facies occurring in gravity cores recovered from two disjunct regions of the antarctic continental shelf the ross sea and the mac robertson shelf the facies sequence model is represented in two cores one collected during the 1995 1 cruise of the r v nathaniel r palmer core nbp95 tc 18 and the other collected by the rsv aurora australis during cruise 149 in 1995 core 149 39gc38 both cores show a succession of facies indicative of ice shelf retreat during the late pleistocene to holocene transition distinct lithofacies range in thickness from a few tens of cm to 1 m and consist of from bottom to top a coarse granulated sandy mud laminated silt and clay structureless silly clay poorly sorted sandy siliceous mud and siliceous mud and ooze these facies represent the passage of distinct depositional regimes across the core sites including sub ice shelf beneath a basal debris zone sub ice shell distal to a debris zone calving line transition and open marine this facies model represents an advance in our understanding of glacial marine stratigraphy for the antarctic continental shelf and will provide the basis for more realistic palaeoglacial reconstructions

discriminating glacier thermal and dynamic regimes in the sedimentary record abstract this paper provides a description and evaluation of the sedimentary facies and environments associated with a range of glacier thermal and dynamic regimes with additional consideration given to the tectonic context new and previously published data are evaluated together and are presented from modern terrestrial and marine glacial sedimentary environments in order to identify a set of criteria that can be used to discriminate between different glacier thermal regimes and dynamic styles in the sedimentary record sedimentological data are presented from a total of 28 glaciers in 11 geographical areas that represent a wide range of contemporary thermal dynamic and topographic regimes in the context of landsystems representatives from terrestrial environments include temperate glaciers in the european alps patagonia new zealand the cordillera blanca peru cold glaciers in the dry valleys of antarctica and the antarctic peninsula region and polythermal valley glaciers in svalbard northern sweden the yukon and the khumbu himal nepal the glaciomarine environment is illustrated by data from cold and polythermal glacier margins on the east antarctic continental shelf and from a polythermal tidewater glacier in svalbard along with general observations from temperate glaciers in alaska these data show that temperate glacial systems particularly in high relief areas are dominated by rockfall and avalanche processes although sediments are largely reworked by glaciofluvial processes debris in polythermal glaciers is both thermally and topographically influenced in areas of moderate relief debris is mainly of basal glacial origin and the resulting facies association is dominated by diamicton in high relief areas such as the himalaya the debris load in polythermal glaciers is dominated by rockfall and avalanche inputs resulting in extensive accumulations of sandy boulder gravel cold glaciers are dominated by basal debris entrainment but sediments are little modified from the source materials which are typically sandy boulder gravel from older till and sand from glaciofluvial glaciolacustrine and aeolian sources similar facies associations but with different facies geometry and thickness occur in equivalent glaciomarine settings application of these concepts can aid the interpretation of glacier thermal regime and hence palaeoclimate in quaternary and ancient glacial systems

neoproterozoic ice sheets and olistoliths multiple glacial cycles in the kingston peak formation california the kingston peak formation is a diamictite bearing succession that crops out in the death valley region california usa an exceptionally thick 1 5 km outcrop belt in its type area the kingston range provides clear insights into the dynamics of mid cryogenian sturtian ice sheets in laurentia seven detailed logs allow the lateral and vertical distribution of facies associations to be assessed we recognize 1 diamictite facies association ice proximal glacigenic debris flows 2 lonestone bearing facies association ice marginal hemipelagic deposits and low density gravity flows with iceberg rafting 3 pebble to boulder conglomerate facies association ice proximal cogenetic glacigenic debris flows and high density turbidites 4 megaclast facies association olistostrome and hemipelagic sediments subject to ice rafting and 5 interbedded heterolithics facies association low density turbidites and hemipelagic deposits the stratigraphic motif allows three glacial cycles to be inferred across the range ice minimum conditions interrupting the kingston peak succession are associated with the development of an olistostrome complex succeeded by a thick accumulation of boulder conglomerates deposited during ice readvance the data testify to a strong glacial influence on sedimentation within this ancient subaqueous succession and to highly dynamic ice sheet behaviour with clear glacial cycles during the sturtian glaciation

standardizing texture and facies codes for a process based classification of clastic sediment and rock abstract proposed here is a universally applicable texturally based classification of clastic sediment that is independent from composition cementation and geologic environment is closely allied to process sedimentology and applies to all compartments in the source to sink system the classification is contingent on defining the term clastic so that it is independent from composition or origin and includes any particles or grains that are subject to erosion transportation and deposition modifications to folk s 1980 texturally based classification that include applying new assumptions and defining a broader array of textural fields are proposed to accommodate this the revised ternary diagrams include additional textural fields that better define poorly sorted and coarse grained deposits so that all end members gravel sand and mud size fractions are included in textural codes revised textural fields or classes are based on a strict adherence to volumetric estimates of percentages of gravel sand and mud size grain populations which by definition must sum to 100 the new classification ensures that descriptors are applied consistently to all end members in the ternary diagram gravel sand and mud according to several rules and that none of the end members are ignored these modifications provide bases for standardizing vertical displays of texture in graphic logs lithofacies codes and their derivatives hydrofacies hydrofacies codes are nondirectional permeability indicators that predict aquifer or reservoir potential folk s 1980 ternary diagram for fine grained clastic sediments sand silt and clay size fractions is also revised to preserve consistency with the revised diagram for gravel sand and mud standardizing texture ensures that the principles of process sedimentology are consistently applied to compositionally variable rock sequences such as mixed carbonate siliciclastic ramp settings and the extreme ends of depositional systems

glaciar leon chilean patagonia late holocene chronology and geomorphology harrison s glasser n f winchester v haresign e warren c duller g a t bailey r ivy ochs s jansson k kubik p 2008 glaciar leon chilean patagonia late holocene chronology and geomorphology the holocene 18 4 pp 643 652 sponsorship nerc university of st andrews american alpine club british geomorphological research group dudley stamp memorial trust royal scottish geographical society quaternary research association carnegie trust for the universities of scotland