sediment motion and velocity in a glacier fed stream current understanding of coarse sediment transport e g threshold for motion travel length and virtual velocity in mountain rivers is still quite limited and even less is known about glacial streams however the hydrological characteristics of these systems strong daily discharge fluctuations high water turbidity pose challenges to the use of tracers to monitor bed sediment dynamics as tagged clasts are usually located after bedload events when flow stage has receded e g by means of portable antennas in the case of passive integrated transponders pit the use of stationary antennas still scarcely in use worldwide to detect pit tagged particles has potential advantages in glacier fed streams if water discharge is monitored continuously a stationary antenna provides real time data on the actual discharge at the moment of tracer particles passage this study focuses on incipient motion and virtual velocity of bed particles measured by a stationary antennas system in a steep mountain channel saldur river drainage area 18 6 km2 italian alps where significant daily discharge fluctuations and bedload transport occur as a result of a nivo glacial regime four stationary antennas were installed 50 m apart in the study reach a total of 629 pit tagged clasts were inserted in the studied reach between 2011 and 2014 ranging in size from 35 mm to 580 mm with an overall recovery rate of around 44 critical discharge for sediment entrainment was obtained by detecting the movement of tracers placed immediately upstream of antennas virtual velocity was derived by knowing distances between the antennas and travel time of tracers results on initiation of motion show that the relationship between the size of transported tracers and the discharge measured at the time clasts were passing the stationary antenna is very weak the influence of antecedent flows on incipient motion was thus investigated by dividing the highest discharge recorded between each pit deployment and the subsequent entrainment by the actual critical discharge at the time of movement ratio qmax qc results show that approximately 50 of tracers moved at qmax qc 1 2 and that 73 of tracers moved at qmax qc 1 5 therefore about 30 of tracers had to previously experience a discharge substantially greater than the one that actually mobilized them also coarser particles moved at higher qmax qc ratios suggesting that higher antecedent flows may be needed to destabilize bed clustering results on the virtual velocity of the pit tagged clasts employed in the field show that the virtual velocity turned out to be highly variable ranging from 101 to 10 5 m min 1 and weakly related to either particle size or flow discharge however virtual velocity was well correlated with the highest flow discharge experienced by each tracer normalized by a percentile of the flow duration curve this evidence further stresses the importance of flow history on sediment entrainment and transport finally the pros and cons of the deployed monitoring technology are discussed

hydraulics of subglacial supercooling theory and simulations for clear water flows 1 glaciohydraulic supercooling is a mechanism for accreting ice and sediment to the base of glaciers we extend existing models by reworking the spring hutter model for subglacial water flow in tubular conduits to allow for distributed water sheets our goal is to determine diagnostic features of supercooling relative to controlling variables results focus on along path water flow under time varying conditions with attention to ice accretion in and along subglacial overdeepenings we contrast simulations with constant recharge to diurnally varying recharge and expose behavior that cannot be inferred from simple models for example locations of simulated ice accretion differ from those found for steady state models even though total ice accretion remains comparable to field estimates downstream accretion influences upstream effective pressures that then modify the hydraulic gradient that drives water flow this modified gradient tends to inhibit additional accretion by increasing velocity and heat production via viscous dissipation during diurnal cycles accretion varies considerably in daytime viscous dissipation dominates the heat balance and ice melts in morning and evening when flow is rising or falling viscous dissipation is lower and accretion can proceed over nighttime the largest temperature depressions occur in the subglacial system but water flux is lowest and accretion rates are negligible we conclude by inferring that overdeepened glaciers with only clear water flows evolve toward stronger supercooling regimes rather than toward a dynamic equilibrium stabilizing feedbacks are unlikely to occur through glacier hydrology alone and other processes such as erosion sedimentation and sliding must play an important role

assessment of erosion and deposition in steep mountain basins by differencing sequential digital terrain models abstract digital elevation models dems built from repeated topographic surveys permit producing dem of difference dod that enables assessment of elevation variations and estimation of volumetric changes through time in the framework of sediment transport studies dem differencing enables quantitative and spatially distributed representation of erosion and deposition within the analyzed time window at both the channel reach and the catchment scale in this study two high resolution digital terrain models dtms derived from airborne lidar data 2 m resolution acquired in 2005 and 2011 were used to characterize the topographic variations caused by sediment erosion transport and deposition in two adjacent mountain basins gadria and strimm vinschgau venosta valley eastern alps italy these catchments were chosen for their contrasting morphology and because they feature different types and intensity of sediment transfer processes a method based on fuzzy logic which takes into account spatially variable dtms uncertainty was used to derive the dod of the study area volumes of erosion and deposition calculated from the dod were then compared with post event field surveys to test the consistency of two independent estimates results show an overall agreement between the estimates with differences due to the intrinsic approximations of the two approaches the consistency of dod with post event estimates encourages the integration of these two methods whose combined application may permit to overcome the intrinsic limitations of the two estimations the comparison between 2005 and 2011 dtms allowed to investigate the relationships between topographic changes and geomorphometric parameters expressing the role of topography on sediment erosion and deposition i e slope and contributing area and describing the morphology influenced by debris flows and fluvial processes i e curvature erosion and deposition relations in the slope area space display substantial differences between the gadria and the strimm basins while in the former erosion and deposition clusters are reasonably well discriminated in the latter characterized by a complex stepped structure we observe substantial overlapping erosion mostly occurred in areas that show persistency of concavity or transformation from convex and flat to concave surfaces whereas deposition prevailingly took place on convex morphologies less expected correspondences between curvature and topographic changes can be explained by the variable sediment transport processes which are often characterized by alternation of erosion and deposition between different events and even during the same event

disturbances in coarse bedload transport in a high mountain stream channel system western tatras poland abstract bedload transport measurements in the formerly glaciated chocholowski catchment located in the western tatras in poland were performed in the period 1975 to 2018 measurement of bedload displacement allowed to determine the role of bedload transport disturbances in both system connectivity and sediment transfer bedload transport occurred as many as triggered up to several times a year the longest distances were observed during rain on snow events between 12 m in headwaters and over 100 m in the fluvial valley bedload became activated along the entire length of the channel system 10 5 km every 2 to 5 years when the stream discharge exceeded 10 m3 s 1 with an average of 1 25 m3 s 1 in such situations bedload dynamics increased downstream and stream power was sufficient to overcome local barriers i e boulder and log steps downstream increases in bedload dynamics may become disturbed and inverted by sudden snowmelt and locally heavy rainfall these types of events caused the dynamics of bedload transport to be 190 to 320 greater in the upper part of the studied catchment and to decline in the downstream direction over a distance of 7 km to yield an attenuation effect the same pattern was observed in local tributaries where the dynamics of bedload transport were 200 higher in the upper part and attenuation was observed along a distance of 1 5 km in the downstream direction all events of this type cause seasonal disturbances in bedload transport however the greatest effect on bedload dynamics was produced by natural deforestation a 16 decrease in forest cover causes a fluvial system disequilibrium manifested in an intensification of hydro geomorphologic processes and formation of new landforms

antarctic peninsula mesoscale cyclone variability and climatic impacts influenced by the sam 1 the frequency of mesoscale cyclones in the western antarctic peninsula wap region during 1991 94 is correlated with the southern hemisphere annular mode sam index most strongly during winter and spring also during periods of positive sam index polarity there is a shift in the storm tracks to favor more east bound trajectories consistent with strengthening of circumpolar westerlies the presence of mesoscale cyclones is associated with positive near surface air temperature anomalies in the wap region year round largest during winter

southern ocean mesocyclones and polar lows from manually tracked satellite mosaics a new reference dataset of mesocyclone activity over the southern ocean has been developed from the manual analysis of high resolution infrared satellite mosaics for winter 2004 of the total 1735 mesocyclones which were identified and analyzed about three quarters were classified as being polar lows i e intense systems see rasmussen and turner 2003 the dataset includes mesocyclone track size associated cloud vortex type and background synoptic conditions maxima in track density were observed over the bellingshausen sea and around east antarctica and are highly correlated with cyclogenesis regions a comparison against quikscat and reanalyses wind characteristics shows that the reanalyses while capturing mesocyclone events tend to considerably underestimate their wind speed by up to 10 ms 1 this mesocyclone dataset is available as a reference for further analysis of mesocyclones and for the evaluation and development of cyclone tracking algorithms

southern hemisphere strong polar mesoscale cyclones in high resolution datasets mesoscale cyclones are small low pressure systems usually 500 km in radius that often appear embedded in synoptic structures these events can be weak and short lived or vigorous and destructive here we use an automatic tracking scheme to investigate two subsets of southern hemisphere mesoscale cyclones that are strong and have the potential to cause damage namely polar lows i e strong and short lived and explosive cyclones i e rapid intensification but not necessarily short lived a short climatology 2009 2012 is obtained by using high resolution 0 5 antarctic mesoscale prediction system amps mean sea level pressure the results show a significant improvement of spatial detail compared to the 0 75 resolution era interim dataset with a total count approximately 46 higher in amps the subset of mesoscale cyclones that are explosive is small with a total genesis number of about 13 that of polar lows in addition only about 1 of the polar lows are explosive suggesting that cyclones that undergo rapid intensification tend to become larger longer lived and hence are no longer regarded as polar lows mesoscale cyclones are more frequent in winter with a maximum concentration around the antarctic but also occurring as far north as tasmania and new zealand analysis of sensible heat flux and sea ice extent anomalies during the genesis days shows that there is a large spread of genesis points over both positive and negative flux anomalies in winter with a somewhat random pattern in the other seasons

short term geomorphological evolution of proglacial systems proglacial systems are amongst the most rapidly changing landscapes on earth as glacier mass loss permafrost degradation and more episodes of intense rainfall progress with climate change this review addresses the urgent need to quantitatively define proglacial systems not only in terms of spatial extent but also in terms of functional processes it firstly provides a critical appraisal of prevailing conceptual models of proglacial systems and uses this to justify compiling data on rates of landform change in terms of planform horizontal motion elevation changes and sediment budgets these data permit us to produce novel summary conceptual diagrams that consider proglacial landscape evolution in terms of a balance of longitudinal and lateral water and sediment fluxes throughout we give examples of newly emerging datasets and data processing methods because these have the potential to assist with the issues of i a lack of knowledge of proglacial systems within high mountain arctic and polar regions ii considerable inter and intra catchment variability in the geomorphology and functioning of proglacial systems iii problems with the magnitude of short term geomorphological changes being at the threshold of detection iv separating short term variability from longer term trends and v of the representativeness of plot scale field measurements for regionalisation and for upscaling we consider that understanding of future climate change effects on proglacial systems requires holistic process based modelling to explicitly consider feedbacks and linkages especially between hillslope and valley floor components such modelling must be informed by a new generation of repeated distributed topographic surveys to detect and quantify short term geomorphological changes

rare earth element concentrations and speciation in organic rich blackwaters of the great dismal swamp virginia usa concentrations of rare earth elements ree major inorganic solutes and dissolved organic carbon doc were measured in waters from the great dismal swamp in southeastern virginia including lake drummond ph 4 3 and its principal surface inflows and outflow concentrations of ree are high in the lake average nd 8 nmol kg and the acidic doc rich inflow and out flow waters i e nd 12 5 nmol kg in jericho washington ditch and 8 nmol kg in feeder ditch respectively the slightly acidic ph 6 6 4 inflow waters from west of the suffolk scarp that comprise the chief source of surface water flow into lake drummond exhibit lower ree concentrations nd 3 4 7 nmol kg great dismal swamp waters are all enriched in the middle rees compared to the light and heavy rees lree and hree when normalized to upper continental crustal ucc values rare earths are positively correlated to doc concentrations in great dismal swamp waters and inversely correlated with ph speciation calculations using a modified version of the well established humic ion binding model v predict that organic matter complexes are the predominant form of dissolved rees in great dismal swamp waters despite significant competition from aqueous fe and al for organic matter binding sites adsorptive cathodic stripping voltammetry acsv was employed using a previously developed competitive ligand equilibration approach that involved adding the o cresolphthalexon ocp ligand to directly investigate ree complexation with natural organic ligands in great dismal swamp waters although preliminary the results of the acs voltammetric titrations are consistent with dominance of organic matter complexes of rees in great dismal swamp waters the results of the speciation modeling and the voltammetric titrations all point towards control of dissolved rees in great dismal swamp waters by complexation of these heavy metals with natural organic matter

mesoscale cyclone activity over antarctica during 1991 2 near the antarctic peninsula a survey of mesoscale cyclogenesis near the antarctic peninsula has been carried out for 1991 based on digital satellite imagery collected at palmer station slightly higher cyclonic activity was found over the bellingshausen sea sector bss than in the weddell sea sector wss both sides were characterized by a pronounced formation maximum in summer and a minimum in winter comma clouds were the dominant vortex type and their average diameter was around 370 km trajectories show that many vortices in the bss move northeastward toward the drake passage with some of the most well developed moving north northeastward to the southern tip of south america bringing severe weather conditions to that area little systematic motion was noted over the wss the fraction of mesoscale cyclones with middle and or high cloud on the west side of the antarctic peninsula was much higher than on the east side these numerous and deep mesoscale cyclones are a consequence of the frequent outbreaks of cold air associated with synoptic scale cyclones that move cold air northward over the relatively warm bellingshausen sea with convective instability resulting this happens much less often in the wss where low level baroclinic instability and vortex stretching are the dominant formation mechanisms and air sea interaction is usually much less vigorous due to the stabilizing influence of the extended sea ice cover

diagenetic versus biotic accretionary mechanisms of bryozoan sponge buildups lower silurian anticosti island canada abstract lower silurian mud rich fenestrate bryozoan sponge buildups of anticosti island quebec canada display facies ranging from fenestrate bryozoan cementstone to crinoid and fenestrate bryozoan hash mudstone wackestone with distinctive polymud fabric sponge spicules and stromatactis these buildups consist of a massive core with thinner stratiform counterparts that show no significant compositional variation raising the question as to how such a deposit could have accreted these features are similar to those mentioned for many paleozoic carbonate mounds in particular the lower carboniferous waulsortian or waulsortian type mounds here the combination of petrographic fluorescence spectrometric and geochemical evidence carbon and oxygen stable isotopes rare earth elements yttrium shows that the accretionary mechanisms of the anticosti buildups were the results of marine cement precipitation near the sea floor for the fenestrate cementstone facies and of early calcification of sponge derived organic matter organogenic lithification within the sediment for the crinoid and fenestrate bryozoan hash mudstone wackestone facies thus the accretionary mechanisms of anticosti fenestrate bryozoan sponge buildups are essentially diagenetic and conventional mechanisms invoked for reef growth such as frame building or sediment trapping or binding based on the preserved fauna or flora do not constitute an appropriate explanation for such paleozoic mud rich buildups these conclusions may well shed light on the more general ongoing debate as to the origin and accretionary mechanisms of carbonate mudmounds

atmospheric patterns over the antarctic peninsula abstractusing clustering analysis for the sea level pressure field of the era interim reanalysis between 1979 and 2016 five synoptic pressure patterns have been obtained for the drake area and antarctic peninsula ap region 45 75 s 20 120 w and the resulting daily series has been made available to the scientific community the five patterns have been named according to their most important features as follows low over the weddell sea lws low over the amundsen and bellingshausen seas lab low over the drake passage ldp zonal flow over the drake passage zdp and ridge over the antarctic peninsula rap each atmospheric pattern is described after analyzing its development and evolution a frequency analysis shows that the five atmospheric patterns present a similar annual frequency but a large seasonal variability the transitions from one pattern to another tend to follow a cycle in which synoptic atmospheric waves are displaced eastward by a quarter wavelength four of the five atmosphe

episodic sedimentation on an early silurian storm dominated carbonate ramp becscie and merrimack formations anticosti island canada the 150 160 m thick lowermost silurian rhuddanian becscie and merrimack formations of anticosti island canada represent continuous deposition on a shallow open marine carbonate ramp several rock types are identified a laminated and homogenous mudstone b laminated and homogenous packstone c argillaceous mudstone and packstone d calcareous shale e laminated calcisiltite f medium to fine grained grainstone and g bio intraclastic rudstone these rock types are arranged into five distinct lithofacies lf1 calcareous mudstone shale lf2 laminated homogenous mudstone lf3 calcareous grainstone shale lf4 laminated mudstone grainstone and lf5 laminated calcisiltite grainstone the sequence reflects deposition on a low energy muddy carbonate to argillaceous ramp subject to short lived episodic high energy storms these events produced fining upwards storm units 5 80 cm thick or tempestites consisting of a sharp scoured base overlain by intra bioclastic rudstone grading upwards into medium grained grainstone finely laminated calcisiltite and mudstone or shale these are interbedded with low energy fairweather mudstones and calcareous shales deposition progressed from a carbonate mud dominated ramp in the becscie formation to an argillaceous mud dominated ramp in the merrimack formation lateral tempestite proximality trends and lithofacies distribution indicate that the anticosti basin deepened to the south east into the iapetus ocean and shallowed towards a sw ne orientated shoreline to the north west vertical tempestite proximality trends and lithofacies changes identify third order eustatic sea level changes after an initial deepening at the base of the formation a shallowing deepening event dominated the sequence several higher order fluctuations defined by lithofacies and tempestite proximality trends are superimposed on these changes the fluctuations identified with the aid of tempestite proximality trends are of an order of magnitude higher than those identified by either lithofacies or palaeontological methods

the modern calcifying sponge spheciospongia vesparium lamarck 1815 great bahama bank implications for ancient sponge mud mounds abstract modern calcified siliceous sponges from the great bahama bank living at water depth ranges of 2 to 5 m have been proposed as likely analogues for calcified sponges in upper jurassic sponge reefs e g southern germany or lower jurassic bioherms that consist of reddish spiculiferous limestones e g broccatello formation of the southern alps indeed sponge related calcification or siliceous sponge diagenesis in general is widely considered a key feature for the mechanisms of accretion and textural maturation in phanerozoic sponge mounds or spiculiferous carbonate mud mounds based on a revisit of the original sites on the great bahama bank nw of andros island the biostratonomy of the calcifying sponge spheciospongia vesparium lamarck 1815 was explored using the patterns of fluorescent dissolved organic matter fdom as revealed by the application of three dimensional excitation emission matrix eem fluorescence spectroscopy geochemical sampling distinguished between fdom that was extracted from sponge tissue and fdom that was intimately associated with caco 3 from particles due to sediment agglutination and authigenic caco 3 both obtained from the living sponge at the sediment surface and from the calcified sponge at the shallow subsurface from 5 to 10 cm of depth as expected the sponge tissue shows highest intensities for protein like fluorescence however from the surface to the subsurface there is a loss of such relatively pristine fluorescent material in the range of 70 humic like fluorescence that occurs associated with sponge tissue is relatively mature or aged thus it most probably represents seawater fdom taken up through active filter feeding relative to the sponge tissue material the fdom patterns associated with ca carbonates show much lower total fluorescence intensities by up to two orders of magnitude the agglutinated sedimentary carbonate particles from the surface pellets ooids grapestones exclusively show a relatively mature humic like fluorescence the deeper calcified parts of spheciospongia which represent a mixture of particles and authigenic caco 3 provided a fdom pattern that obviously combines the mature fdom pattern of particles with diagenetically fresh protein like and fulvic acid like fluorescence we conclude that shallow subsurface calcification of s vesparium correlates with the initial stage of sponge biomass humification such a mechanism of biomass transformation i e from biopolymers to geopolymers via degradation and condensation has also been suggested for the large scale development of carbonate sponge mud mounds therefore we consider the modern calcifying siliceous sponge s vesparium lamarck 1815 a potential pardigm to decipher in more detail the geologically important process of biomass induced calcification or organomineralisation with its subsequent effect of pore water fdom preservation and sediment lithification

depositional controls on lower carboniferous microbial buildups eastern midland valley of scotland in the eastern midland valley of scotland non skeletal carbonate buildup complexes are present in the charlestown main limestone brigantian a thin marine carbonate unit within a lower carboniferous basin fill otherwise dominated by fluvio deltaic sediments and volcanics the buildups are restricted geographically to west lothian and central fife and correspond to an area of reduced subsidence the burntisland high buildup geometry and local facies mosaics reflect the relative water depth and position on the burntisland high that because of its slight topographical relief and more distal position with respect to the location of fluvio deltaic systems became an area of increased carbonate productivity and hence a locus for buildup development away from the burntisland high in the fife midlothian low more monotonous argillaceous limestone facies of low energy and somewhat deeper water aspect accumulated buildup facies contain a diverse marine fauna and are characterized by peloidal clotted and homogeneous micrites interpreted as predominantly microbial in origin two types of buildup complex occur at charlestown vertically stacked tabular banks up to 2 m thick and 100 m wide form the western margin of an asymmetric buildup accumulation east of this margin a complex mosaic of isolated low relief buildups and inter buildup sediments was deposited skeletal sand shoals present within these inter buildup sediments indicate that high energy conditions prevailed during buildup growth in contrast at roscobie inter buildup sediments are of low energy aspect and buildup geometry is domical rather than tabular initiated in slightly deeper and calmer water on the flank of the burntisland high the roscobie buildups up to 15 m thick and 46 m wide accreted vertically rather than laterally as at charlestown and coalesced to form an elongate ridge shaped buildup complex

glacier melt runoff controls bedload transport in alpine catchments abstract research on factors affecting sediment regime in glacierized catchments under warming climates is still scarce despite its societal relevance in particular coarse bedload transport has never been quantitatively related to water runoff origin snowmelt vs glacier melt which provides important information on the role of different sediment sources glaciers vs hillslopes and channel bed drawing on data from multiple spatial and temporal scales in a paradigmatic alpine glacierized catchment we show that glacier melt flows play a key role in coarse sediment transport dynamics bedload concentration measured during glacier melt flows is up to 6 orders of magnitude larger than during snowmelt at the catchment scale and within the channel however minimal aggradation and degradation was detected over almost a decade in addition sedimentation rates at a hydropower weir inferred from flushing frequency during the last four decades are tightly associated to summer air temperature and not to precipitation trends and most of sediment export occurred in july august however sediment flushing frequency has been decreasing since the late 1990s despite very warm summers in the following decades collectively these findings indicate that sediment is dominantly sourced from within glacier covered areas and that transport rates are thus dictated by seasonal and multi annual glacial dynamics as glacier melt flows decrease due to ice mass loss our results suggest that for similar basins a progressive shift from supply limited driven by glacier activity to transport limited during rainfall induced events sediment transport will occur disrupting the current near equilibrium channel conditions

foehn winds link climate driven warming to ice shelf evolution in antarctica rapid warming of the antarctic peninsula over the past several decades has led to extensive surface melting on its eastern side and the disintegration of the prince gustav larsen a and larsen b ice shelves the warming trend has been attributed to strengthening of circumpolar westerlies resulting from a positive trend in the southern annular mode sam which is thought to promote more frequent warm dry downsloping foehn winds along the lee or eastern side of the peninsula we examined variability in foehn frequency and its relationship to temperature and patterns of synoptic scale circulation using a multidecadal meteorological record from the argentine station matienzo located between the larsen a and b embayments this record was further augmented with a network of six weather stations installed under the u s nsf larsen ice shelf system antarctica project significant warming was observed in all seasons at matienzo with the largest seasonal increase occurring in austral winter 3 71 c between 1962 1972 and 1999 2010 frequency and duration of foehn events were found to strongly influence regional temperature variability over hourly to seasonal time scales surface temperature and foehn winds were also sensitive to climate variability with both variables exhibiting strong positive correlations with the sam index concomitant positive trends in foehn frequency temperature and sam are present during austral summer with sustained foehn events consistently associated with surface melting across the ice sheet and ice shelves these observations support the notion that increased foehn frequency played a critical role in precipitating the collapse of the larsen b ice shelf

mid dinantian waulsortian buildups in the dublin basin ireland abstract the sedimentary history and biostratigraphic setting of waulsortian carbonate buildups of the feltrim limestone formation late courceyan to early chadian within the dublin basin are described there is no unique precursor or successor facies to this formation and the massive waulsortian banks are composed predominantly of peloidal skeletal wackestones and lime mudstones with packstones near the tops of banks these banks form tabular bodies of moderate relief and are interbedded with thin shales and argillaceous crinoidal limestones of inter bank facies in the southwest of the basin inter bank facies are rare and the bank facies have abundant stromatactis cavities and uniquely at roselawn a fauna of rugose corals all buildups in the dublin basin have phase c and or d component assemblages of lees and miller 1985 and are interpreted as accumulating in moderately shallow water depths near or within the photic zone isopachs for the feltrim limestone formation show a ne sw trending axial depocentre where the waulsortian facies is in excess of 400 m thickness deposition appears to have taken place on this double sided ramp in a manner similar to the model of lees 1982 for belgium and southern britain soft sediment deformation such as large scale slumping shale injections and water escape structures not previously recorded from these rocks is widespread the upper surface of the feltrim limestone formation is fissured and displays a prominent erosion surface termination of waulsortian facies deposition and influx of terrigenous sediment was caused by rapid uplift attributed to chadian tectonism however eustatic sea level fall cannot be ruled out as a partial cause of the demise of the waulsortian

antarctic peninsula ice sheet evolution during the cenozoic era the antarctic peninsula region is currently undergoing rapid environmental change resulting in the thinning acceleration and recession of glaciers and the sequential collapse of ice shelves it is important to view these changes in the context of long term palaeoenvironmental complexity and to understand the key processes controlling ice sheet growth and recession in addition numerical ice sheet models require detailed geological data for tuning and testing therefore this paper systematically and holistically reviews published geological evidence for antarctic peninsula ice sheet variability for each key locality throughout the cenozoic and brings together the prevailing consensus of the extent character and behaviour of the glaciations of the antarctic peninsula region major contributions include a downloadable database of 186 terrestrial and marine calibrated dates an original reconstruction of the lgm ice sheet and a new series of isochrones detailing ice sheet retreat following the lgm glaciation of antarctica was initiated around the eocene oligocene transition in east antarctica palaeogene records of antarctic peninsula glaciation are primarily restricted to king george island where glacigenic sediments provide a record of early east antarctic glaciations but with modification of far travelled erratics by local south shetland island ice caps evidence for neogene glaciation is derived primarily from king george island and james ross island where glaciovolcanic strata indicate that ice thicknesses reached 500 850 m during glacials this suggests that the antarctic peninsula ice sheet draped rather than drowned the topography marine geophysical investigations indicate multiple ice sheet advances during this time seismic profiling of continental shelf slope deposits indicates up to ten large advances of the antarctic peninsula ice sheet during the early pleistocene when the ice sheet was dominated by 40 kyr cycles glacials became more pronounced reaching the continental shelf edge and of longer duration during the middle pleistocene during the late pleistocene repeated glacials reached the shelf edge but ice shelves inhibited iceberg rafting the last glacial maximum lgm occurred at 18 ka bp after which transitional glaciomarine sediments on the continental shelf indicate ice sheet retreat the continental shelf contains large bathymetric troughs which were repeatedly occupied by large ice streams during pleistocene glaciations retreat after the lgm was episodic in the weddell sea with multiple readvances and changes in ice flow direction but rapid in the bellingshausen sea the late holocene epoch was characterised by repeated fluctuations in palaeoenvironmental conditions with associated glacial readvances however this has been subsumed by rapid warming and ice shelf collapse during the twentieth century

modeling channelized and distributed subglacial drainage in two dimensions 1 we present a two dimensional glacier drainage system model glads that couples distributed and channelized subglacial water flow distributed flow occurs through linked cavities that are represented as a continuous water sheet of variable thickness channelized flow occurs through rothlisberger channels that can form on any of the edges of a prescribed unstructured network of potential channels water storage is accounted for in an englacial aquifer and in moulins which also act as point sources of water to the subglacial system solutions are presented for a synthetic topography designed to mimic an ice sheet margin for low discharge all the flow is accommodated in the sheet whereas for sufficiently high discharge the model exhibits a channelization instability which leads to the formation of a self organized channel system the random orientation of the network edges allows the channel system geometry to be relatively unbiased in contrast to previous structured grid based models under steady conditions the model supports the classical view of the subglacial drainage system with low pressure regions forming around the channels under diurnally varying input water flows in and out of the channels and a rather complex spatiotemporal pattern of water pressures is predicted we explore the effects of parameter variations on the channel system topology and mean effective pressure the model is then applied to a mountain glacier and forced with meltwater calculated by a temperature index model the results are broadly consistent with our current understanding of the glacier drainage system and demonstrate the applicability of the model to real settings

novel development in fluorescence microscopy of complex organic mixtures application in petroleum geochemistry abstract new data on the spectral fluorescence properties of complex organic mixtures derived from organic rich sediments and from fossil fuels are presented both the spectral ranges of the bitumen fractions including extractable hydrocarbons and polar compounds and the factors governing the spectral characteristics of complex organic mixtures are established the data provide rapid means of determining qualitatively an abundance or low concentration of saturates of highly alkylated aromatics and of condensed aromatic systems in such entities as extractable organic matter kerogen migrated hydrocarbons and liptinite macerals the implication of the data to petroleum geochemistry is discussed

the impact of a changing southern hemisphere annular mode on antarctic peninsula summer temperatures since the mid 1960s rapid regional summer warming has occurred on the east coast of the northern antarctic peninsula with near surface temperatures increasing by more than 2 degrees c this warming has contributed significantly to the collapse of the northern sections of the larsen ice shelf coincident with this warming the summer southern hemisphere annular mode sam has exhibited a marked trend suggested by modeling studies to be predominantly a response to anthropogenic forcing resulting in increased westerlies across the northern peninsula observations and reanalysis data are utilized to demonstrate that the changing sam has played a key role in driving this local summer warming it is proposed that the stronger summer westerly winds reduce the blocking effect of the antarctic peninsula and lead to a higher frequency of air masses being advected eastward over the orographic barrier of the northern antarctic peninsula when this occurs a combination of a climatological temperature gradient across the barrier and the formation of a fohn wind on the lee side typically results in a summer near surface temperature sensitivity to the sam that is 3 times greater on the eastern side of the peninsula than on the west sam variability is also shown to play a less important role in determining summer temperatures at stations west of the barrier in the northern peninsula similar to 62 degrees s both at the surface and throughout the troposphere this is in contrast to a station farther south similar to 65 degrees s where the sam exerts little influence

fulvic acid like organic compounds control nucleation of marine calcite under suboxic conditions intracrystalline organic compounds enclosed within in situ precipitated marine microcrystalline calcite automicrite might represent either an inclusion or the catalyst of such precipitation we use evidence from a lower cretaceous deep water carbonate mound to show 1 the original source 2 the degree of condensation 3 the redox conditions involved and 4 the catalytic role of natural organic matter for the precipitation of automicrite fluorescence spectrometry of the intracrystalline organic fraction extracted from these carbonates identifies a marine fulvic acid like organic compound with a low degree of polycondensation this finding points to a temporal correlation of the initial stage of geopolymer formation with the precipitation of automicrite furthermore the rare earth element ree distribution patterns in the mineral show a consistent positive ce anomaly suggesting an episode of reductive dissolution of iron manganese oxyhydroxides during automicrite formation in general a relative enrichment of middle weight rees is observed resulting in a convex distribution pattern typical for e g phosphate concretions or humic acid material by merging the results of spectrometry and ree geochemistry we thus conclude that the marine calcite precipitation was catalyzed by marine fulvic acid like compounds during the early stages of humification under suboxic conditions this indicates that humification driven by the presence of a benthic biomass is more important for calcite authigenesis than any site specific microbial metabolism the neoproterozoic rise of carbonate mounds supports this hypothesis there is molecular evidence for early metazoan divergence then but not for a major evolutionary episode of microorganisms

the anatomy of a deep water mud mound complex to the southwest of the dinantian platform in derbyshire uk an elongate waulsortian mud mound complex developed at dovedale on a ramp to the southwest of a developing carbonate platform in derbyshire during chadian early visean times the complex occupied an area of approximately 6 km2 and grew to a maximum relief of 80 m with longitudinal and transverse valleys developed near the southern margin five mound associated facies have been identified mound core mound flank fine mound flank coarse intermound fine and intermound coarse the mound core facies is a massive skeletal wackestone with comminuted sponge debris foraminifera ostracodes and crinoid debris set in a matrix of clotted micrite the mound flank sediments display moderately inclined bedding surfaces while the mound flank fine contains sponge debris the mound flank coarse is dominated by articulated crinoid columnals and includes algal encrusted micritized intraclasts and coarse peloids the well bedded intermound fine facies is bituminous and micritic while the intermound coarse facies is composed of skeletal peloidal intraclast grainstones which locally contain calcified algae although the fauna is diverse the density of colonization by metazoans was low and the supply of macrofossil debris modest the clotted micrite texture is interpreted as the product of micro organisms which precipitated and trapped fine grained sediment the mud mound complex is dominated by the bathymetric assemblages b and c proposed by lees hallet hibo which on their model of the belgian waulsortian indicate depths of between 220 and 280 m intercalation of assemblages b c and c d on the northern margin of the complex is interpreted as the result of local storm disturbance a deep water drift is postulated to explain the nw se alignment of the complex which probably fitted the export model of bosence rowlands quine beneath the sediment surface phreatic flow eroded unlithified sediments and developed interconnected cavities which were filled by cement and sediment relatively eariy mound instability triggered the opening of fissures which filled with crinoid debris peloids indurated lithoclasts and micrite

bedload pulses in a hydropower affected alpine gravel bed river abstract this study investigated the sediment resupply and transport dynamics at the upper drau river upstream of lienz eastern tyrol austria due to a hydropower plant a 24 km long river reach of this alpine gravel bed river is under residual flow conditions although sediment is still resupplied into the reach through many active torrents and tributaries as a result sediment deposition in the residual flow reach intensified hence increasing maintenance efforts to stabilize this river section and ensure flood protection in combination with a new sediment management program a continuous bedload monitoring system was installed 2 km downstream of the residual reach in 2001 to support the development of adapted sediment management strategies the surrogate bedload monitoring system consists of 16 impact plate geophones installed over a 17 m wide cross section the unprecedented 15 year dataset of high resolution bedload intensity revealed a complex process of gravel storage and intermittent resupply from the residual reach allowing the authors a detailed analysis of frequently occurring bedload pulses these transport features are triggered by increased discharges during floods in the residual reach and created pronounced anticlockwise bedload hysteresis or with a temporal shift to the event peak caused distinct shifts in the bedload activity downstream bedload pulses produce very high bedload fluxes while in transit tend to increase bedload flux in the post event phase and can alter and reduce the upstream sediment storage leading to a lowering of bedload availability for future pulses the observed time lags between main discharge events and the arrival of the macro pulses are correlated with mean water discharge during pulse propagation thus enabling a prediction of the pulse arrival at the monitoring station solely based on the hydrograph in combination with the hydrological setup of the reach the observed bedload pulse time lags allowed an estimation of pulse velocities in the range 0 002 0 05 m s 1

interpretation of recent southern hemisphere climate change climate variability in the high latitude southern hemisphere sh is dominated by the sh annular mode a large scale pattern of variability characterized by fluctuations in the strength of the circumpolar vortex we present evidence that recent trends in the sh tropospheric circulation can be interpreted as a bias toward the high index polarity of this pattern with stronger westerly flow encircling the polar cap it is argued that the largest and most significant tropospheric trends can be traced to recent trends in the lower stratospheric polar vortex which are due largely to photochemical ozone losses during the summer fall season the trend toward stronger circumpolar flow has contributed substantially to the observed warming over the antarctic peninsula and patagonia and to the cooling over eastern antarctica and the antarctic plateau

sediment export transient landscape response and catchment scale connectivity following rapid climate warming and alpine glacier recession abstract in the face of rapid climate warming rapid glacier recession should lead to a marked increase in the spatial extent of the paraglacial zone in glaciated drainage basins the extent of the paraglacial zone has been well established to be transient but there are very few studies of this transient response and what it means for sediment export there is good reason to expect that glacier recession could increase basin scale sediment connectivity as sediment becomes less dependent on glacier surface transport proglacial streams are more able to migrate laterally than subglacial streams and so access sediment for transport and glacier debuttressing may aid the development of gullies that can dissect moraines and so aid hillslope to proglacial zone connectivity by using records of the flushing of hydroelectric power installations we were able to develop a record of coarse sediment sand and gravel export from a basin with a rapidly retreating valley glacier the haut glacier d arolla from 1977 to 2014 modelling suggested that these data could only be partially controlled by transport capacity implying an important role for sediment supply and potentially for the influence of changing sediment connectivity indeed there was evidence of the effects of glacial debuttressing upon gullying processes and hence a possible increase in the ease of connection of upstream basins to the proglacial area more recently we were able to show possible temperature control on sediment export which may only have become apparent because of the progressive development of better sediment connectivity however whilst rapid glacier recession should result in theory in a progressive increase in connectivity of sediment sources to the basin outlet the supply to capacity ratio does not increase continually with glacier recession until maximum capacity is reached we identified two possible examples of why first gullying was also accompanied by the sediment accumulation at the base of moraines that was too coarse to be transported by the proglacial stream maintaining disconnection of the upper basins second the sediment capacity ratio appeared to be elevated during periods of more rapid retreat and we attribute this to the importance of a continued supply of unworked glacial till before fluvial reworking and sorting of freshly exposed sediment increased the resistance of sediment to entrainment and hence export rates thus the transient geomorphic response of glaciated basins to glacier recession may involve negative feedbacks that can reduce the extent to which increases in connectivity elsewhere in the basin lead to increased sediment export

landslide response to climate change in permafrost regions abstract rapid permafrost thaw in the high latitude and high elevation areas increases hillslope susceptibility to landsliding by altering geotechnical properties of hillslope materials including reduced cohesion and increased hydraulic connectivity this review synthesizes the fundamental processes that will increase landslide frequency and magnitude in permafrost regions in the coming decades with observational and analytical studies that document landslide regimes at high latitudes and elevations we synthesize the available literature to address five questions of practical importance which can be used to evaluate fundamental knowledge of landslide process and inform land management decisions to mitigate geohazards and environmental impacts after permafrost thaws we predict that landslides will be driven primarily by atmospheric input of moisture and freeze thaw fracturing rather than responding to disconnected and perched groundwater melting permafrost ice and a plane of weakness between ground ice and the active layer transition between equilibrium states is likely to increase landslide frequency and magnitude alter dominant failure styles and mobilize carbon over timescales ranging from seasons to centuries we also evaluate potential implications of increased landslide activity on local nutrient and sediment connectivity atmospheric carbon feedbacks and hazards to people and infrastructure last we suggest three key areas for future research to produce primary data and analysis that will fill gaps in the existing understanding of landslide regimes in permafrost regions these suggestions include 1 expand the geographic extent of english language research on landslides in permafrost 2 maintain or initiate long term monitoring projects and aerial data collection and 3 quantify the net effect on the terrestrial carbon budget

the effects of low magnitude flow conditions on bedload mobility in a steep mountain stream abstract the transport of coarse material strongly controls the stability and evolution of mountain fluvial systems but despite this bedload dynamics are not yet fully understood especially in mountain streams in this sense particular attention was paid on the bedload magnitude volume expressed at event scale and on the long term while few studies were focused on when and how the transport of the coarse material occurs the aim of this work was to investigate the bedload mobility in the rio cordon a mountain stream characterized by cascade and step pool morphologies with a rough streambed here the critical conditions for initiation of motion transport distance and virtual velocity expressed by the coarse streambed material were assessed and their relationships with hydraulic forcing conditions and grain size were analyzed to this end a monitoring program based on bedload tracing was maintained over 7 years allowing to analyze the bedload mobility during persistent high frequency low magnitude flow conditions to investigate the bedload mobility 250 tracers were released between 2011 and 2012 and their propagation along study site was monitored until 2018 overall 14 tracer inventories were realized determining 1697 tracer localizations during the study period the bedload dispersion resulted well described by the peak discharge magnitude qp qp and p c while no significant relationships were observed with duration of competent flow tover and effective runoff volume er transport distance and tracer grain size were negatively correlated whereas virtual velocity increased with increasing particle size in this sense the propagation velocity seems to be affected by the high frequency flows that on the one hand triggered mobilization of the coarser tracers only through limited and impulsive events and on the other hand favored a slowdown on the finer particles due to bedforms disturbance compared to other study sites the rio cordon exhibited accentuated threshold conditions with lower transport distance and virtual velocity confirming that steep mountain streams are generally influenced by a reduced transport efficiency due to protruding bedforms and macro roughness that cause a pronounced energy dissipation interestingly such condition seems to have progressively reduced from under to near bankfull flows the results were compared to the bedload mobility observed in the rio cordon during 1993 1998 enabling to quantitatively assess how the bedload dispersion varied between a setting of stable armouring layer with protruding bedforms 2012 2018 and a partial alteration of these 1993 1998 an evident difference was observed in terms of transport distance while critical conditions did not significantly change lastly the long term bedload tracing investigation highlighted that a certain legacy on the transport efficiency was produced by the persistent high frequency flow conditions over the study period a general decrease of transport distance was observed that could be explained by a progressive stabilization of streambed material previous studies suggested that such condition can be interrupted by high magnitude low frequency floods

sensitivity of circumpolar deep water transport and ice shelf basal melt along the west antarctic peninsula to changes in the winds circumpolardeepwater cdw can be found near the continental shelfbreak around most of antarctica advection of this relatively warm water up to 28c across the continental shelf to the base of floating ice shelves is thought to be a critical source of heat for basal melting in some locations a high resolution 4 km regional ocean sea ice ice shelf model of the west antarctic peninsula wap coastal ocean was used to examine the effects of changes in the winds on across shelf cdw transport and ice shelf basal melt increases and decreases in the strength of the wind fields were simulated by scaling the present day winds by a constant factor additional simulations considered effects of increased antarctic circumpolar current acc transport increased wind strength and acc transport increased the amount of cdw transported onto the wap continental shelf but did not necessarily increase cdw flux underneath the nearby ice shelves the basal melt underneath some of the deeper ice shelves actually decreased with increased wind strength increased mixing over the wap shelf due to stronger winds removed more heat from the deeper shelf waters than the additional heat gained from increased cdw volume transport the simulation results suggest that the effect on the wap ice shelves of the projected strengthening of the polar westerlies is not a simple matter of increased winds causing increased or decreased basal melt a simple budget calculation indicated that iron associated with increased vertical mixing of cdw could significantly affect biological productivity of this region

maturation thermique et histoire de l enfouissement et de la generation des hydrocarbures du bassin de l archipel de mingan et de l ile d anticosti canada carbonate platform sequences of anticosti island and the mingan archipelago are early ordovician to early silurian in age with the exception of the macasty formation the sequences are impoverished in dispersed organic matter which is chiefly composed of zooclasts zooclast reflectances suggest that the upper ordovician and silurian sequences outcropping on anticosti island are entirely in the oil window but that the lower to middle ordovician beds of the mingan archipelago and their stratigraphic equivalents in the subsurface of most of anticosti island belong to the condensate zone only the deeper sequences of the southwestern sector of anticosti island are in the diagenetic dry gas zone the maximum depth of burial of sequences below now eroded silurian to devonian strata increases from 2 3 km on southwestern anticosti island to 4 5 km in the mingan archipelago a late upwarp of the precambrian basement likely allowed deeper erosion of the paleozoic strata in the vicinity of the mingan archipelago t

geomorphic implications of subglacial drainage configuration rates of basal sediment evacuation controlled by seasonal drainage system evolution abstract although basal sediment evacuation by subglacial meltwater is widely assumed to dominate the sediment budget of most temperate glaciers and ice caps its potential influence for glacial geomorphic processes and landforms has largely been overlooked in the glacial literature data collected at haut glacier d arolla switzerland during the 1998 ablation season are used to test theoretical predictions that subglacial drainage configuration should exert a primary control on rates of basal sediment evacuation by subglacial meltwater seasonal evolution of the subglacial drainage system enables observation of sediment evacuation from both distributed and channelised drainage systems daily suspended sediment load exhibits an extreme nonlinear increase with respect to discharge between winter and summer periods which correspond to periods of predominantly distributed and channelised subglacial drainage respectively these results suggest that subglacial drainage configuration should significantly impact upon a rates of subglacial erosion and debris production b the nature of debris transport and the proportion of sediment in glacial versus fluvioglacial transport pathways and c rates and styles of ice marginal sedimentation in contrast to their distributed counterparts channelised drainage configurations are predicted to encourage subglacial erosion through the removal of basal sediment from the ice bedrock interface and with the exception of supraglacial transport will discourage sediment transport by alternative glacial mechanisms direct sedimentation at the glacier margin may therefore be reduced resulting in smaller moraines despite an overall increase in sediment production an appreciation of the coupling between glacier hydrology and geomorphic processes suggests new frameworks for the understanding of rates and styles of glacial erosion sediment transfer and deposition and the complex geomorphology of ice marginal environments

holocene southern ocean surface temperature variability west of the antarctic peninsula the antarctic peninsula is currently one of the fastest warming locations on earth but its long term variability has remained unclear amelia shevenell and colleagues now use the tex86 proxy a palaeothermometer that tracks membrane lipids of the marine picoplankton crenarchaeota to show that a long term cooling of about 4 c occurred in waters near the tip of antarctic peninsula over the past 12 000 years this is consistent with orbitally controlled changes in insolation shorter term variability in temperature seems to have been strongly influenced by the position of the westerly winds this work suggests that the present influence of the el nino southern oscillation system on the antarctic peninsula is a relatively recent phenomenon dating to the late holocene the antarctic peninsula is currently one of the fastest warming locations on earth but its long term variability has remained unclear this study uses tex86 sea surface temperature proxy evidence to show that a long term cooling of about 3 4 c occurred in waters near the tip of the antarctic peninsula over the past 12 000 years consistent with orbitally controlled changes in insolation shorter term variability in temperature at the antarctic peninsula appears to have been strongly influenced by the position of westerly winds the present influence of the el nino southern oscillation system on the antarctic peninsula may have arisen only during the late holocene the disintegration of ice shelves reduced sea ice and glacier extent and shifting ecological zones observed around antarctica1 2 highlight the impact of recent atmospheric3 and oceanic warming4 on the cryosphere observations1 2 and models5 6 suggest that oceanic and atmospheric temperature variations at antarctica s margins affect global cryosphere stability ocean circulation sea levels and carbon cycling in particular recent climate changes on the antarctic peninsula have been dramatic yet the holocene climate variability of this region is largely unknown limiting our ability to evaluate ongoing changes within the context of historical variability and underlying forcing mechanisms here we show that surface ocean temperatures at the continental margin of the western antarctic peninsula cooled by 3 4 c over the past 12 000 years tracking the holocene decline of local 65 s spring insolation our results based on tex86 sea surface temperature sst proxy evidence from a marine sediment core indicate the importance of regional summer duration as a driver of antarctic seasonal sea ice fluctuations7 on millennial timescales abrupt sst fluctuations of 2 4 c coincide with globally recognized climate variability8 similarities between our ssts southern hemisphere westerly wind reconstructions9 and el nino southern oscillation variability10 indicate that present climate teleconnections between the tropical pacific ocean and the western antarctic peninsula11 strengthened late in the holocene epoch we conclude that during the holocene southern ocean temperatures at the western antarctic peninsula margin were tied to changes in the position of the westerlies which have a critical role in global carbon cycling9 12

mobilization of coarse surface layers in gravel bedded rivers by finer gravel bed load 1 additions of sand to gravel beds greatly increase the mobility and flux of gravel however it is not known how additions of finer gravel to coarser gravel beds will affect the mobility of bed material here we examine the effect of fine gravel pulses on gravel bed material transport and near bed flow dynamics in a series of flume experiments bed material refers exclusively to sediment in the channel prior to the pulse introduction the observations indicate that fine sediment pulses tend to migrate downstream in low amplitude waves as the waves pass over the gravel bed the interstitial pockets in the bed material surface fill and coarse gravel particles are entrained this increases bed material transport rates and causes a distinct shift from a selective mobility transport regime where particles coarser than the bed material median 8 mm make up 30 of the load to an equal mobility transport regime where bed materials coarser than 8 mm and finer than 8 mm are transported in equal proportions the only possible source for this coarser bed load material is the sediment bed suggesting that portions of the coarse surface layer are being mobilized observations of near bed velocity and turbulence suggest that fine gravel pulses cause fluid acceleration in the near bed region associated with a reduction in the level of turbulence produced at the sediment boundary this accelerated fluid at the bed increases drag exerted on coarse surface layer particles promoting their mobilization our findings suggest that in general finer bed sediment not just sand can mobilize coarser sediment and that expressions for the influence of sand on bed mobility need to be generalized on the basis of grain ratios

automated monitoring of subglacial hydrological processes with ground penetrating radar gpr at high temporal resolution scope and potential pitfalls kulessa b a d booth a hobbs and a l hubbard 2008 automated monitoring of subglacial hydrological processes with ground penetrating radar gpr at high temporal resolution scope and potential pitfalls geophysical research letters 35 24 l24502

rocky shoreline deposits in the lower silurian upper llandovery telychian chicotte formation anticosti island quebec the upper llandovery telychian chicotte formation is a regionally extensive crinoid rich unit exposed in the south central part of anticosti island in the gulf of st lawrence the chicotte encrinites represent an inner ramp crinoidal sand shoal complex about 80 m thick that prograded over deeper middle to outer ramp facies of the underlying jupiter formation in response to a long term sea level fall the typical depositional unit in the chicotte formation is a metre scale subtidal cycle indicating that higher frequency sea level changes were also present metre scale cycles are typically characterized by coarsening upward locally cross bedded encrinitic material capped by a sharp erosional surface these bounding surfaces change progressively upsection from simple planar to low relief scalloped erosional surfaces to complex polyphase surfaces formed by distinct but superimposed erosional events three dimensional paleomorphological features with local relief up to 50 m associated with erosional sur

expanded reef rock textural classification and the geologic history of bryozoan reefs the wide range of colony forms assumed by bryozoans results in a greater variety of bryozoan reef carbonate rock types than can be accommodated within present classifications consequently the currently used textural classification is expanded to include several new reef rock categories branchstone cruststone globstone lettucestone shellstone immediately applicable to bryozoan reefs those in the early paleozoic were small mounds largely cruststones and bindstones accompanied later by globstones and lettucestones a very few similar mounds live today others many larger in the mid and late paleozoic were branchstones and bafflestones in some cases so sediment rich as to appear mostly as floatstones with interspersed rudstones to micstones

linking danube river activity to alpine ice sheet fluctuations during the last glacial ca 33 17 ka bp insights into the continental signature of heinrich stadials abstract offshore archives retrieved from marine lacustrine environments receiving sediment from large river systems are valuable quaternary continental records in the present study we reconstruct the danube river activity at the end of the last glacial period based on sedimentological mineralogical and geochemical analyses performed on long piston cores from the north west black sea margin our data suggest that the danube river produced hyperpycnal floods throughout the ca 33 17 ka period four main periods of enhanced danube flood frequency each of 1 5 3 kyr duration are recorded at ca 32 5 30 5 ka equivalent to the first part of heinrich stadial hs 3 at ca 29 27 5 ka equivalent to greenland stadial 4 at ca 25 3 23 8 ka equivalent to hs 2 and at ca 22 3 19 ka based on mineralogical and geochemical data we relate these events to enhanced surface melting of the alpine ice sheet ais that covered 50 000 km2 of the danube watershed at the last glacial maximum lgm our results suggest that i the ais growth from the inner alps to its lgm position in the northern alpine foreland started from ca 30 5 ka ended no later than ca 25 3 ka and was interrupted by a melting episode ca 29 27 5 ka ii the ais volume drastically decreased from ca 22 3 to 19 ka as soon as summer insolation energy at the ais latitude increased and iii hss strongly impacted the ais mass balance through enhanced summer surface melt this together with evidence of severely cool winters and the rapid expansion of sea ice in the north atlantic implies strong seasonality in continental europe during stadials

do archean chemical sediments record ancient seawater rare earth element patterns rare earth elements ree concentrations of archean and proterozoic chemical sediments are commonly used as proxies to study secular trends in the geochemistry of precambrian seawater in addition similarities in the ree signatures of archean chemical sediments and modern seawater have led researchers to argue that some archean rocks originated as biochemical precipitates i e microbial carbonates in shallow marine e g peritidal environments however terrestrial waters including river water and groundwater also commonly exhibit ree fractionation patterns that resemble modern seawater here we present the seawater like ree data for ground

morphological changes in alpine rivers following the end of the little ice age abstract this work investigates the channel changes of alpine rivers from the end of the little ice age 1850s to the 1950s with the aim to determine the possible role of climatic variations occurred in this period before the onset of anthropic pressures i e dams check dams bank protections and gravel mining the research was conducted on 17 river catchments of south tyrol northern italy glaciated and unglaciated a multitemporal gis analysis approach was adopted to assess the morphological changes in terms of channel width and pattern from three different sources i austrian cadastral map 1858 ii maps from the italian institute of military geography 1917 1925 and iii two aerial photo sets taken in 1945 and 1954 the analysed river network a total of 480 km was subdivided into 162 morphologically homogeneous reaches 76 confined 81 partly confined and 5 unconfined with lengths ranging from 630 to 5500 m slope from 0 3 to 24 and drained area from 20 to 4000 km 2 the statistical relationships among morphological changes and reach and basin scale factors were analysed by univariate and multivariate methods and the relationships between width changes and 36 controlling factors were explored using principal component analysis the variability in width and morphological pattern changes were very pronounced between and within single rivers highlighting the value of such a large data set overall the analysed rivers varied their morphological pattern mostly exhibiting a shift from multithread transitional to single thread patterns but unchanged planform types were also common variations in channel width varied substantially among the analysed rivers which featured narrowing slightly prevailing and widening the least common as well as many cases of very limited changes channel width variations appear statistically although weakly related to some morphometric variables and significant differences emerge comparing glaciated vs unglaciated basins climate related variations glacier dynamics and channel disturbance frequency are argued to be the dominant factors that affected channel variations

interpreting temperature information from ice cores along the antarctic peninsula era40 analysis 1 analysis of era40 temperature and accumulation data suggests that annual mean isotopic fluctuations due to temperature change will be geographically very variable across the peninsula isotopic variations of 0 4 at james ross island 0 9 at dyer and 1 3 at gomez are all likely to indicate an identical magnitude of temperature change the reduction in the magnitude of the isotopic signal in the north and east is due to climatically dependent synoptic covariance between temperature and accumulation whilst in the west and south seasonal covariance amplifies the isotopic temperature signal additionally we show that the relationship between accumulation and temperature is rather weak in the north east regions but is stronger in the central and southerly regions therefore isotopes may record 11 to 30 of the variance in annual mean temperatures in the north east 75 in central regions and 70 in the south this study enables physically based reconstructions of peninsula climate based on multi core analysis citation sime l c g j marshall r mulvaney and e r thomas 2009 interpreting temperature information from ice cores along the antarctic peninsula era40 analysis geophys res lett 36 l18801 doi 10 1029 2009gl038982

flume and field based calibration of surrogate sensors for monitoring bedload transport bedload transport assessment is important for geomorphological engineering and ecological studies of gravel bed rivers bedload can be monitored at experimental stations that require expensive maintenance or by using portable traps which allows measuring instantaneous transport rates but at a single point and at high costs and operational risks the need for continuously measuring bedload intensity and dynamics has therefore increased the use and enhancement of surrogate methods this paper reports on a set of flume experiments in which a japanese acoustic pipe and an impact plate have been tested using four well sorted and three poorly sorted sediment mixtures additional data were collected in a glacierized high gradient andean stream estero morales using a portable bunte type bedload sampler results show that the data provided by the acoustic pipe which is amplified on 6 channels having different gains can be calibrated for the grain size and for the intensity of transported sediments coarser than 9 mm r2 0 93 and 0 88 respectively even if the flume based calibration is very robust upscaling the calibration to field applications is more challenging and the bedload intensity could be predicted better than the grain size of transported sediments r2 0 61 and 0 43 respectively the inexpensive impact plate equipped with accelerometer could be calibrated for bedload intensity quite well in the flume but only poorly in the field r2 0 16 and could not provide information on the size of transported sediments

bedload hysteresis in a glacier fed mountain river sediment transport during flood events often reveals hysteretic patterns because flow discharge can peak before counterclockwise hysteresis or after clockwise hysteresis the peak of bedload hysteresis in sediment transport has been used in the literature to infer the degree of sediment availability counterclockwise and clockwise hysteresis have been in fact interpreted as limited and unlimited sediment supply conditions respectively hysteresis has been mainly explored for the case of suspended sediment transport but it was rarely reported for bedload transport in mountain streams this work focuses on the temporal variability of bedload transport in an alpine catchment saldur basin 18 6 km2 italian alps where bedload transport was monitored by means of an acoustic pipe sensor which detects the acoustic vibrations induced by particles hitting a 0 5m long steel pipe runoff dynamics are dominated by snowmelt in late spring early summer mostly by glacier melt in late summer early autumn and by a combination of the snow and glacier melt in mid summer the results indicate that hysteretic patterns during daily discharge fluctuations are predominantly clockwise during the snowmelt period likely due to the ready availability of unpacked sediments within the channel or through bank erosion in the lower part of the basin on the contrary counterclockwise hysteresis tend to be more frequent during late glacier melting period possibly due to the time lag needed for sediment provided by the glacial and peri glacial area to be transported to the monitoring section however intense rainfall events occurring during the glacier melt period generated predominantly clockwise hysteresis thus indicating the activation of different sediment sources these results indicate that runoff generation processes play a crucial role on sediment supply and temporal availability in mountain streams

mesozoic lower jurassic red stromatactis limestones from the southern alps arzo switzerland calcite mineral authigenesis and syneresis type deformation the broccatello lithological unit lower jurassic hettangian to lower parts of upper sinemurian near the village of arzo southern alps southern switzerland is a mound shaped carbonate deposit that contains patches of red stromatactis limestone within the largely bioclastic broccatello unit the stromatactis limestone is distinguished by its early diagenetic cavity system a relatively fine grained texture and an in situ assemblage of calcified siliceous sponges various demosponges and hexactinellids a complex shallow subsurface diagenetic pathway can be reconstructed from sediment petrography in combination with comparative geochemical analysis carbon and oxygen isotopes trace and rare earth elements ree y this pathway includes organic matter transformation aragonite and skeletal opal dissolution patchy calcification and lithification sediment shrinkage sagging and collapse partial ree remobilization and multiple sediment infiltration these processes occurred under normal marine essentially oxic conditions and were independent from local recurring syn sedimentary faulting it is concluded that the stromatactis results from a combination of calcite mineral authigenesis and syneresis type deformation the natural stromatactis phenomenon may thus be best explained by maturation processes of particulate polymer gels expected to form in fine grained carbonate sediments in the shallow subsurface conditions favorable for the evolution of stromatactis appear to be particularly frequent during drowning of tropical or subtropical carbonate platforms

soluble humic substances from in situ precipitated microcrystalline calcium carbonate internal sediment and spar cement in a cretaceous carbonate mud mound albian carbonate mud mound limestones exposed near iraneta northern spain show a fabric and particle specific fluorescence intense fluorescence is restricted to in situ precipitated microcrystalline automicritic fabrics calcified demosponges and coralline sponges intermediate intensity derives from micritized bioclasts pellets and a rim of marine bladed cement most invertebrate skeletons late diagenetic equant cement and crosscutting zones of dolomitization are weakly to nonfluorescent internal microcrystalline sediment allomicrite and red algae debris have variable fluorescence correlation between rock fluorescence and soluble humic substances was evaluated from 3 g of automicrite allomicrite and cement time resolved laser induced fluorescence spectroscopy trlfs with ultra short pulses on two extracrystalline fractions naoh soluble and two intracrystalline fractions hcl soluble and naoh soluble showed that most of the soluble humic substances of automicrite are within the crystals but conversely are significantly enriched on outer surfaces of allomicrite spar cement is close to detection limits fluorescence lifetimes are in the range of 0 5 2 ns and 3 5 6 ns we conclude that precipitation of automicrite took place during oxidative organic matter diagenesis i e during condensation reactions of degradation products of marine biopolymers by contrast allomicrite formed by skeletal breakdown followed by ingestion organic coating and reingestion during deposit feeding a humic substance based model of marine polymer gels represents a new approach for the understanding of ancient polygenetic carbonate muds so typical of phanerozoic mud mounds in deeper water settings

sediment sources spatiotemporal variability and rates of fluvial bedload transport in glacier connected steep mountain valleys in western norway erdalen and bodalen drainage basins abstract contemporary fluvial bedload transport rates are still very difficult to measure and as a result of this in many sites only quantitative data on suspended and solute transport are included in sediment budget studies carried out for defined drainage basin systems the presented analysis of fluvial bedload dynamics in different defined subsystems of the glacier connected erdalen 79 5 km 2 and bodalen 60 1 km 2 drainage basins in the steep fjord landscape of western norway provides insights into i detectable relevant sediment sources ii instream channel storage of bedload material iii spatiotemporal variability and controls of bedload transport rates and bedload yields and iv the absolute and relative importance of fluvial bedload transport within the sedimentary budgets of these steep cold climate mountain valleys rockfalls snow avalanches stream channel bank erosion and fluvial transfers through small tributaries draining slope systems are relevant sediment sources for fluvial bedload transport in the main stream channels whereas the main outlet glaciers in both drainage basins are not of importance as all bedload material delivered directly from these outlet glaciers is trapped within proglacial lakes narrow valleys within both drainage basin systems are characterized by a higher intensity of slope channel coupling and display higher rates of sediment supply from slopes into the main stream channels than wider valleys snow avalanches are the most important sediment source in erdalen whereas fluvial transfers through small tributaries followed by snow avalanches are most important in bodalen longer term instream channel storage is not of great importance in the steep bodalen drainage basin but currently plays an important role within the erdalen drainage basin which is characterized by a stepped longitudinal main valley bottom profile favoring deposition of bedload material within less steep main channel reaches the mean annual bedload yields 2010 2013 are 2 4 t km 2 y 1 for the entire erdalen and 13 3 t km 2 y 1 for the entire bodalen drainage basin which are comparably low values for steep and partly glacierized drainage basin systems because of supply limited conditions the intensity of fluvial bedload transport is generally much more related to the availability of sediments than to channel discharge fluvial bedload transport accounts for about one third of the total fluvial transport and accordingly plays an important role within the sedimentary budgets of both drainage basin systems

a model study of circumpolar deep water on the west antarctic peninsula and ross sea continental shelves abstract transport of relatively warm nutrient rich circumpolar deep water cdw onto continental shelves around antarctica has important effects on physical and biological processes however the characteristics of the cdw along the shelf break as well as what happens to it once it has been advected onto the continental shelf differ spatially in the present study high resolution 4 5 km regional models of the ross sea and the west antarctic peninsula coastal ocean are used to compare differences in cdw transport the models compared very well with observations from both regions examining the fluxes not only of heat but also of a simulated dye representing cdw shows that in both cases cdw crosses the shelf break in specific locations primarily determined by the bathymetry but eventually floods much of the shelf the frequency of intrusions in marguerite trough was ca 2 3 per month similar to recent mooring observations a significant correlation between the along shelf break wind stress and the cross shelf break dye flux through marguerite trough was observed suggesting that intrusions are at least partially related to short duration wind events the primary difference between the cdw intrusions on the ross and west antarctic peninsula shelves is that there is more vigorous mixing of the cdw with the surface waters in the ross sea especially in the west where high salinity shelf water is created the models show that the cdw moving across the antarctic peninsula continental shelf towards the base of the ice shelves not only is warmer initially and travels a shorter distance than that advected towards the base of the ross ice shelf but it is also subjected to less vertical mixing with surface waters which conserves the heat available to be advected under the ice shelves this difference in vertical mixing also likely leads to differences in the supply of nutrients from the cdw into the upper water column and thus modulates the impacts on surface biogeochemical processes