discriminating between subglacial and proglacial lake sediments an example from the danischer wohld peninsula northern germany subglacial lakes are common features of contemporary ice masses however they are rarely identified in the geological record this is due to the difficulty in discriminating between subglacial and proglacial lake sediments a proglacial origin is typically preferred as the simplest explanation we hypothesise that numerous deposits currently interpreted to record proglacial lake sedimentation may actually have a subglacial origin here we try and find ways of distinguishing proglacial from subglacial lake sediments by investigating three sites along the danischer wohld peninsula northern germany which have been interpreted to record both proglacial and subglacial sedimentation we identify two major phases of ice activity and associated lake formation during the late weichselian glaciation 1 proglacial lake formation at 23 ka in front of the advancing baltic ice stream this lake was subsequently overridden and the sediments glaciotectonised as ice continued to advance to its maximum extent 2 retreat of ice back into the baltic basin at 19 ka and formation of a proglacial lake that persisted for 4 ka we suggest that subglacial lake activity may have occurred at two of the sites between 23 and 19 ka this is based on the presence of aggrading sediment deposits characterised by stratified laminated diamictons and interbedded tabular to channelized sorted sediments the juxtaposition of relatively undeformed waterlain sediment and subglacial till absence of glaciotectonic thrusting and folding or of fining coarsening successions and the geomorphic association with tunnel valleys to the south of the study area the style of sedimentation and deformation provided the greatest insight into the discrimination of proglacially vs subglacially deposited glaciolacustrine sediments the luminescence signal palaeodose distributions also offers a potentially powerful means of fingerprinting sediment transport pathways of young glacial systems

horizontal lamination and the sequence of bed phases and stratification under upper flow regime conditions two forms of horizontal laminae have been produced under upper flow regime conditions in a flume by deposition on a plane bed and on low in phase waves upper plane bed laminae consist of approximately equal numbers of fining upward fu and coarsening upward cu textural laminae heavy minerals when present are typically within or form cu laminae in horizontal laminae formed under low in phase waves fu laminae may predominate and are significantly thicker than cu laminae heavy minerals are associated with the tops of some fu laminae and are absent from cu laminae deposits aggraded on plane beds and low in phase waves both display low angle 13 14 upstream grain imbrication upper plane bed horizontal laminae are attributed to the effects of the burst sweep cycle on local bedload transport bursts form fu laminae and sweeps form cu laminae some fu laminae in in phase wave deposits are thought to form with downstream migration of bed waves on which sand size decreases from trough to crest heavy minerals are concentrated in the tops of these fu laminae due to their enrichment on the crests of the migrating bed waves other fu and cu laminae in in phase wave deposits probably formed by the action of bursts and sweeps as on upper plane beds a sequence of bed phases and stratification formed under upper flow regime conditions is described based on the observations here combined with descriptions from the literature with increasing flow strength the gradual sequence of bed phases is 1 plane bed 2 low relief downstream migrating inphase waves increasing in amplitude and wavelength with increasing flow strength 3 stationary in phase waves 4 upstream migrating including breaking wave antidunes the sequence of stratification formed under these bed phases is 1 upper plane bed horizontal lamination 2 in phase wave horizontal lamination to in phase wave foreset cross laminae 3 in phase wave drape laminae 4 antidune backset cross laminae

rapid deposition of sand and gravel mixtures downstream of a negative step the role of matrix infilling and particle overpassing in the process of bar front accretion an experimental flow channel was used to investigate the rapid deposition of sand and gravel mixtures downstream of a negative step hydraulic processes give rise to the quasi simultaneous accumulation of openwork gravels matrix filled contact framework and dilated framework gravels the resultant structure is analogous to a bar front in gravel bed streams flow conditions were non uniform but steady in time whereas open and closed gravel fabrics are usually interpreted as representing deposition from unsteady flows for example a varying discharge regime consideration of the percentage of sand in the deposits indicated that in terms of packing the sediments may be considered as a simple binary mixture with partial framework dilation occurring with sand percentages in excess of c 32 despite dilation for sand percentages less than 50 structural stability of the foreset gravels was maintained so that the bar front exhibited a distinct brinkpoint and a planar slip face at the angle of initial yield which made an angular contact with the base of the flume for sand percentages in excess of 80 individual gravel clasts were completely supported by sand the original structural stability was lost so that the bar front eroded by reverse currents assumed a tangential contact with the flume base below the angle of initial yield the brinkpoint was rounded and indistinct in addition to altering the bar front slope increasing the quantity of sand in the bed sediments had a major influence on the dip of gravel particles on the foresets in all experimental runs a surface sand seal with openwork gravels beneath developed upstream of the brinkpoint the mechanics of sand seal formation require further investigation however an overpassing mechanism was noted to be very important in sorting gravel particles rolling over the brinkpoint a published mathematical model describing the overpassing mechanism was found to be appropriate to the present experimental observations

facies architecture and sequence stratigraphy in glacially influenced basins basic problems and water level glacier input point controls with an example from the quaternary of ontario canada abstract sequence architecture is controlled by two fundamental factors the water level relative to the depositional surface which controls accommodation space and the points or areas of sediment injection which control how this space is filled in relative water level accommodation space and injection points normally vary together and various genetic terms are used to define systems tracts but in glacially influenced basins accommodation space is controlled not only by water level but also by the glacier injection points are similarly dually controlled by water level and by the terminus of the glacier during high lake levels the injection point of the glacier may be underwater at the base of the slope genetic terms like highstand and lowstand therefore are meaningless in successions controlled by sediment input points which are independent of water levels and accommodation space distinct water level and glacier input point systems can occur side by side the water level system controlled by lake level or sea level the glacier input point system controlled by the position of the subaqueous glacier front and both can form juxtaposed systems passing laterally into each other a bewildering and incompatible terminology is needed if the terms of genetic sequence stratigraphy are used for both water level and glacier input point systems because the sedimentary injection points and sequence boundaries of the two systems fluctuate out of phase with one another sequences developed by movement of the glacier are completely independent of those controlled by water levels if genetic sequence stratigraphy is applied to a basin with both lake level and glacier input point systems then each needs separate genetic terminologies to describe them which leads only to confusion however descriptive sequence stratigraphy allostratigraphy can be readily applied to successions like the quaternary of lake ontario we therefore suggest that genetic sequence terms be discarded and simpler allostratigraphic terminology used in glacially influenced basins

towards realistic aquifer models three dimensional georadar surveys of quaternary gravel deltas singen basin sw germany abstract understanding sedimentary heterogeneities has nowadays become crucial for sophisticated aquifer management the methods used so far for aquifer characterization e g pump test coring analysis cannot provide the needed resolution for a sufficient prediction of the subsurface properties e g sudicky 1986 this calls for the application of the outcrop analogue approach to aquifers e g macfarlan et al 1994 aigner 1995 in this project we used georadar ground penetrating radar or gpr to acquire the subsurface information for high resolution three dimensional images and radar facies mapping of glaciolacustrine delta sediments in the singen basin sw germany a three dimensional reconstruction of sedimentary heterogeneities for a detailed aquifer characterisation becomes possible by combining gpr profiling and outcrop information a case study is presented showing a complex three dimensional architecture of a quaternary gravel body consisting of the following three types of architectural elements 1 glaciolacustrine delta foresets 2 erosional surfaces with scour pool fills and 3 horizontal glaciofluvial gravel sheets although this seems a relatively simple architectural inventory the three dimensional georadar profiling shows considerable internal heterogeneities the radar data are interpreted following the seismic stratigraphic approach i e the delineation of radar facies types and of radar sequences the three dimensional heterogeneities are visualized by means of time slices 3 d block or chair diagrams or series of radar facies maps

jet efflux deposits of a subaqueous ice contact fan glacial lake rinteln northwestern germany abstract the coarse grained ice contact porta subaqueous fan delta complex was deposited in glacial lake rinteln at the margin of the saalian ice sheet that advanced south of the weser chains nw germany the ice proximal depositional system was up to 15 km long and 10 km wide the present study deals with ice proximal subaqueous fan deposits which are interpreted as products of a subcritical plane wall outflow jet that periodically passed into a supercritical jet with hydraulic jump the proximal facies assemblage consists of the coarse clast supported gravelly deposits of a hyperconcentrated high density effluent and of related cohesionless debris flows attributed to the conduit or immediate proximal jet outflow zone of flow establishment the intermediate facies assemblage attributed to the outflow jet proximal zone of flow transition is dominated by normally graded and cross stratified gravels with scour structures at their bases these gravels were deposited by a high density effluent capable of forming mouthbar like features these deposits pass downcurrent into an assemblage of planar parallel stratified and planar and trough cross stratified sands and pebbly sands partially interpreted as antidunes with abundant scour structures and intercalated layers of fine sand silt and silty mud attributed to the jet distal zone of flow transition the distal facies assemblage consists of trough cross stratified sands and pebbly sands and is attributed to the outflow jet proximal zone of established flow the sedimentary succession as a whole has wedge shape geometry with a gentle fan shaped inclination of the bedding from the southeast to the southwest repeated vertical alternations of supercritical and subcritical deposits and muddy interlayers can be attributed to temporary fluctuations in the meltwater outflow whereas the overall upward fining of the succession indicates a net decline of meltwater discharges

glacial lake outburst erosion of the grand valley michigan and impacts on glacial lakes in the lake michigan basin abstract geomorphic and sedimentologic evidence in the grand valley which drained the retreating saginaw lobe of the laurentide ice sheet and later acted as a spillway between lakes in the huron and erie basins and in the michigan basin suggests that at least one drainage event from glacial lake saginaw to glacial lake chicago was a catastrophic outburst that deeply incised the valley analysis of shoreline and outlet geomorphology at the chicago outlet supports j h bretz s hypothesis of episodic incision and lake level change shoreline features of each lake level converge to separate outlet sills that decrease in elevation from the oldest to youngest lake phases this evidence coupled with the presence of boulder lags and other features consistent with outburst origin suggests that the outlets were deepened by catastrophic outbursts at least twice the first incision event is correlated with a linked series of floods that progressed from huron and erie basin lakes to glacial lake saginaw to glacial lake chicago and then to the mississippi the second downcutting event occurred after the two rivers advance of the lake michigan lobe outbursts from the eastern outlets of glacial lake agassiz to glacial lake algonquin are a possible cause for this period of downcutting at the chicago outlets

moraine formation in northwestern ontario product of subglacial fluvial and glaciolacustrine sedimentation long arcuate stratified end moraines in northwestern ontario may represent major and rapid sedimentation events in glacial lake agassiz rapid lowering of the lake or lift of a marginal ice dam m

quaternary glaciations of northern europe this paper presents the outcome of a workshop held in berlin in february 2009 concerned with current research on the glacial history of northern europe including the british isles the methodologies presently used to resolve this topic are outlined particular attention is given to new analytical methods deriving from high resolution remote imaging of glacial terrain both on land and on the sea bed key new stratigraphic sections higher resolution results from conventional geochronological methods like radiocarbon and more recently developed technologies such as luminescence and cosmogenic radionuclide dating the relationships between the results derived from these two methods are discussed in further detail along with possible explanations for these differences an outline of a most likely glacial history of the scandinavian and british and irish ice sheets is presented along with possible links to global climate change as represented by the marine isotope mis record tentative evidence for glaciation is identified in mis 22 16 12 10 8 6 4 and 2 and correlations of phases within the last glaciation are also explored for both the scandinavian and british and irish ice sheets the results show that the character and extent of glaciation in different parts of the region are not synchronous and much more geochronological work is required before regional correlations can be established with confidence

sedimentological and deformational criteria for discriminating subglaciofluvial deposits from subaqueous ice contact fan deposits a pleistocene example ireland a pit located near ballyhorsey 28 km south of dublin eastern ireland displays subglacially deposited glaciofluvial sediments passing upwards into proglacial subaqueous ice contact fan deposits the coexistence of these two different depositional environments at the same location will help with differentiation between two very similar and easily confused glacial lithofacies the lowermost sediments show aggrading subglacial deposits indicating a constrained accommodation space mainly controlled by the position of an overlying ice roof during ice bed decoupling these sediments are characterized by vertically stacked tills with large lenses of tabular to channelized sorted sediments the sorted sediments consist of fine grained laminated facies cross laminated sand and channelized gravels and are interpreted as subglaciofluvial sediments deposited within a subglacial de coupled space the subglaciofluvial sequence is characterized by glaciotectonic deformation structures within discrete beds triggered by fluid overpressure and shear stress during episodes of ice bed recoupling clastic dykes and folds the upper deposits correspond to the deposition of successive hyperpycnal flows in a proximal proglacial lake forming a thick sedimentary wedge erosively overlying the subglacial deposits gravel facies and large scale trough bedding sand are observed within this proximal wedge while normally graded sand beds with developed bedforms are observed further downflow the building of the prograding ice contact subaqueous fan implies an unrestricted accommodation space and is associated with deformation structures related to gravity destabilization during fan spreading normal faults this study facilitates the recognition of subglacial submarginal depositional environments formed in part during localized ice bed coupling episodes in the sedimentary record the sedimentary sequence exposed in ballyhorsey permits characterization of the temporal framework of meltwater production during deglaciation the impact on the subglacial drainage system and the consequences on the irish sea ice stream flow mechanisms

autogenic response of fluvial deltas to steady sea level fall implications from flume tank experiments flume tank experiments on fluvial deltas conducted with constant fall of relative sea level rate a 0 constant sediment discharge q s and constant water discharge q w reveal a built in geomorphic process that inevitably causes valley incision autoincision after the beginning of the sea level fall and forms paired stream terraces on the abandoned alluvial slope despite steady sea level fall deltas aggrade without major incision until the autoincision threshold is attained at which time the aggradational regime is replaced by a degradational one results of the experiments imply that multiple valley incision and terrace formation can occur as an autogenic response of the depositional system to steady forcing by constant sea level fall changes of a q s and q w or changes in river energy are not required to account for these geomorphic events the understanding of the autogenic response when combined with the theory of shoreline autoretreat provides an alternative view of the geomorphic development of fluviodeltaic systems during base level fall

a methodology to reconstruct small and short lived ice dammed lakes in the appalachians of southern quebec abstract previous studies on the deglaciation of the appalachians of southern quebec reconstructed only the most extensive ice dammed lakes and the most stable glaciolacustrine water levels they only used the best developed shoreline features and thus were not able to reconstruct small or short lived ice dammed lakes both being characterized by a weak development of their features we propose a methodology to reconstruct glacial lakes which follows three main steps 1 the mapping of shoreline features generally the best developed ones as in previous studies 2 the delineation of the former shoreline for each water level by also considering the less well developed shoreline features which were found during field surveys designed as a function of the presumed shoreline position and 3 the mapping of the maximum extension of the water plane which includes the location of the former ice dam and of the former glacial lake spillway in southern quebec small ice dammed lakes were numerous and important because they shaped the geomorphology of the region during the deglaciation they are thus among the key components of a deglaciation model for this area

iceberg drop dump and grounding structures from pleistocene glacio lacustrine sediments scotland abstract dropstone dump and grounding structures resulting from the melt out of debris contained in floating and grounded icebergs are described from a pleistocene ice marginal glacio lacustrine sequence in scotland dropstones display bending penetration rucking and complete rupture of stratum occurring beneath them and onlap above them with the degree of deformation varying as a function of the size shape and axial disposition of the clast and of the sediment type into which they fell dump structures are conical mounds of gravel or diamict formed by the break up and overturning of dirt laden icebergs and the consequent release of large quantities of debris to the lake floor grounding structures are caused by the grounding of icebergs the down warping of underlying lake floor se iment and the subsequent in situ melt out of contained debris to form isolated troughs of diamict

tectonic geomorphology of marine terraces santa barbara fold belt california uplifted marine terraces are common landforms in coastal regions where active tectonics are an important component of landscape evolution such as along the coastal stretches of southern california the pattern and elevation of shoreline angles on active folds provide information about rates of uplift and fold growth which is important for defining tectonic models a particularly impressive succession of marine terraces are developed across the santa barbara fold belt sbfb in southern california which comprises an east west linear zone of active folds and mostly blind faults on the coastal piedmont and in the santa barbara channel the fold belt is characterized by several flights of emergent late pleistocene marine terraces uplifted and preserved on the flanks of active anticlines at several locations along the fold belt the first emergent marine terrace is numerically dated by methods that include uranium series dating on terrace corals 14 c dating on terrace shells and detrital charcoal optically stimulated luminescence of marine terrace sands and oxygen isotopic signatures 18 o of mollusks individual marine terraces have as many as four ages using up to three different dating methods providing confidence in terrace chronology ages of higher terraces are estimated assuming a constant rate of uplift for a particular flight of the 31 terraces 22 formed during a time of falling sea level with 9 forming at or near marine oxygen isotope stage mis 3 or 5 highstands ages and rates of uplift of the first emergent terrace vary systematically from west younger and higher to east older and lower the first emergent marine terraces in the westernmost sbfb are approximately 45 ka mis 3 and the rate of local surface uplift is 2 m k y in the central part of the belt first emergent terraces date to 60 70 ka mis 5 and uplift rates decrease to 1 2 m k y first emergent marine terraces preserved in the easternmost fold belt range from 70 ka to 105 ka mis 5 with rates of local surface uplift of 0 5 m k y lower rates of uplift in the eastern end of the fold belt result from the mis 5 terrace being tilted down into the carpinteria syncline rates of vertical uplift in the western end of the fold belt are about six times higher than previously reported suggesting the seismic hazard is also greater

glacimarine processes at grounding line fans and their growth to ice contact deltas abstract grounding line fans originate from subglacial and basal stream tunnels at grounding lines of glaciers terminating in a marine environment during melt seasons discharge forms a turbulent jet beyond the efflux over the initial zone of flow establishment in the jet it may remain in contact with the sea floor for up to 13 4 d d tunnel diameter along a runout distance if velocity is constant plug flow in this zone deposits marine outwash sediment commonly having chaotic texture and graded and welded contacts texture may vary rapidly because of discharge pulses and the jet may move laterally to produce sheet or cut and fill geometries imbricate gravel is deposited near the efflux then farther out are sheet or weakly channelized finer grained gravels and sands in some instances a migrating barchanoid bar forms at the detachment zone and forms large scale trough cross beds beyond the detachment zone the turbulent jet becomes vertical and sediment cascades from it in a veil this sediment is added to by flows from continuous failures of bed load sediment in the detachment zone resulting deposits are interstratified sediment gravity flows and thick coarse end members of cyclopsams the jet changes to a plume when inertial forces become less than buoyancy forces turbulent vorticies within the jet can re entrain particles into a buoyant plume the plume remains vertical although continuously spreading until reaching neutral buoyancy fan depocentres have been observed to accumulate at over 10 6 m 3 a 1 in temperate glacial areas eventually at quasi stable grounding lines fans may aggrade to sea level to form ice contact deltas at incipient deltas when the delta plain is intertidal coarse sediment is redistributed to the prodelta with each tidal cycle intense prodelta rhythmites mark the transition of a fan into a delta

synrift stratigraphic geometry in a transfer zone coarse grained delta complex miocene pohang basin se korea the gojusan fan delta is a coarse grained delta complex on the western margin of the miocene pohang basin se korea the deposits consist of five facies associations fa alluvial fan conglomerates fa i shallow marine mouthbar sandstones fa ii fluvial and mouth bar conglomerates fa iii gilberttype foreset conglomerates fa iv and hemipelagic mudstones fa v different facies associations characterize the northern central and southern parts of the delta complex to the north fa iv is laterally juxtaposed with fa i or the basement with scarp derived breccias along the contact centrally and to the south fa i is laterally juxtaposed with fa ii with an abrupt facies change and local inliers of basement rocks along the contact early alluvial fan and mouth bar deposits are overlain by the topset fa iii and truncated by the foreset fa iv of a gilbert type delta in the central part of the fan delta complex whereas fa ii passes transitionally upward into fa iii in the south with the latter extending basinward into a gently inclined shoal water delta front gilbert type and shoal water geometries are therefore developed in the same delta complex the composite delta geometry is interpreted as reflecting 1 its development near an extensional transfer zone where the hangingwall relief was variable over short distances along strike and 2 the operation of intrabasinal faults this interpretation contrasts with previous studies that viewed the delta complex as having formed along a pull apart basin margin

anatomy of a subaqueous ice contact fan and delta complex middle pleistocene north west germany this paper presents a detailed analysis of the high resolution facies architecture of the middle pleistocene porta subaqueous ice contact fan and delta complex deposited on the northern margin of glacial lake weser northwest germany a total of 10 sand and gravel pits and more than 100 wells were examined to document the complex facies architecture the field study was supplemented with a ground penetrating radar survey and a shear wave seismic survey all collected sedimentological and geophysical data were integrated into a high resolution three dimensional geological model for reconstructing the spatial distribution of facies associations the porta subaqueous fan and delta complex consist of three fan bodies deposited on a flat lake bottom surface at the margin of a retreating ice lobe the northernmost fan complex is up to 55 m thick 6ae2 km wide and 6ae5 km long the incipient fan deposition is characterized by high energy flows of a plane wall jet very coarse grained highly scoured jet efflux deposits with an elongate plan shape indicate a high froude number probably 5 these jet efflux sediments are deposited in front of a large 3ae2 km long up to 1ae2 km wide and up to 25 m deep flute like scour indicating the most proximal erosion and bypass area of the jet that widens and deepens with distance downstream to the region of maximum turbulence approximately five times the conduit diameter evidence for subsequent flow splitting is given by the presence of two marginal gravel fan lobes deposited in front of 1ae 3t o 2ae5 km long flute like scours that are 0ae8 to 1 km wide and 7 to 20 m deep in response to continued aggradation small jets developed at the periphery of these bar like deposits and filled in the low areas adjacent to the original superelevated regions locally raising the depositional surface and characterized by large scale trough cross stratified sand and pebbly sand the incision of an up to 1ae2 km wide and up to 35 m deep channel into the evolving fan is attributed to a catastrophic drainage event probably related to a lake outburst and lake level fall in the range of 40 to 60 m at the mouth of this channel highly scoured jet efflux deposits formed under hydraulic jump conditions during flow expansion subsequently gilbert type deltas formed on the truncated fan margin recording a second lake level drop in the range of 30 to 40 m these catastrophic lake level falls were probably caused by rapid ice lobe retreat controlled by the convex up bottom topography of the ice valley

deglaciation lake levels and meltwater discharge in the lake michigan basin abstract the deglacial history of the lake michigan basin including discharge and routing of meltwater is complex because of the interaction among 1 glacial retreats and re advances in the basin 2 the timing of occupation and the isostatic adjustment of lake outlets and 3 the depositional and erosional processes that left evidence of past lake levels in the southern part of the basin a restricted area little affected by differential isostasy new studies of onshore and offshore areas allow refinement of a lake level history that has evolved over 100 years important new data include the recognition of two periods of influx of meltwater from lake agassiz into the basin and details of the highstands gleaned from sedimentological evidence major disagreements still persist concerning the exact timing and lake level changes associated with the algonquin phase approximately 11 000 bp a wide variety of independent data suggests that the lake michigan lobe was thin unstable and subject to rapid advances and retreats consequently lake level changes were commonly abrupt and stable shorelines were short lived the long held beliefs that the southern part of the basin was stable and separated from deformed northern areas by a hinge line discontinuity are becoming difficult to maintain numerical modeling of the ice earth system and empirical modeling of shoreline deformation are both consistent with observed shoreline tilting in the north and with the amount and pattern of modern deformation shown by lake level gauges new studies of subaerial lacustrine features suggest the presence of deformed shorelines higher than those originally ascribed to the supposed horizontal glenwood level finally the lake michigan region as a whole appears to behave in a similar manner to other areas both local other great lakes and regional u s east coast that have experienced major isostatic changes detailed sedimentological and dating studies of field sites and additional development of geophysical models offer hope for reconciling the field data with our understanding of earth rheology

macroforms large bedforms and rhythmic sedimentary sequences in subglacial eskers south central ontario implications for esker genesis and meltwater regime abstract eskers of south central ontario were deposited in closed subglacial conduits which were continuous main conduits this interpretation is supported by the intimate association of eskers with an anastomosing network of tunnel channels relatively continuous esker ridges minimal post formational disturbance of esker sediments intercalation of till and stratified sand and gravel diapiric folding at an esker core low variability in palaeocurrent direction and upslope flow paths down esker trends in clast lithology roundness and sphericity indicate continuous conduits with sediment supply by subglacial deformation of adjacent material into the conduits melt out of sediment from the conduit walls and fluvial resedimentation esker ridge morphology is attributed to synchronous erosion transportation and deposition along the main conduits such that ridge discontinuities are primarily explained as zones of non deposition during esker formation composite pseudoanticlinal and oblique accretion avalanche bed macroforms are identified gravel facies within these macroforms were deposited from fluidal flows or hyperconcentrated dispersions progradation of macroforms or migration of constituent large bedforms through the main conduits may have temporarily blocked constricted portions of those conduits and acted as possible internal autogenic controls on sediment availability and flow resistance the location of macroforms within conduits was primarily controlled by conduit geometry and sediment availability and later by feedback between macroform and conduit geometries sand and gravel units alternate rhythmically in vertical section rhythmicity is interpreted as a response to episodic flood flows controlled by seasonal changes in water supply but not necessarily representing annual events fans beads anabranched reaches and extended hummocky deposits are intimately associated with the main esker ridges they are interpreted in terms of subglacial cavities and localized flotation zones connected to the main conduits during flood events in phase wave structures are the products of hydraulic jumps in hyperconcentrated flood flows at flow expansions into swells within the main conduits into cavities connected to the main conduits or at a grounding line esker ridges record only the most powerful flood events whereas fans and beads record flow events in finer detail being primarily depositional reservoirs laterally fining deposits record the waning stages of conduit operation

asynchronous glacier dynamics during the antarctic cold reversal in central patagonia abstract we present 14 new 10be cosmogenic nuclide exposure ages quantifying asynchronous readvances during the antarctic cold reversal from glaciers in the baker valley region of central patagonia we constrain glacier and ice dammed palaeolake dynamics using a landsystems approach concentrating on outlet glaciers from the eastern northern patagonian icefield npi and monte san lorenzo msl soler glacier npi produced lateral moraines above lago bertrand from 15 1 0 7 to 14 0 0 6 ka when it dammed the drainage of lago general carrera buenos aires through rio baker at a bedrock pinning point at this time soler glacier terminated into the 400 m deseado level of the ice dammed palaeolake later calluqueo glacier msl deposited subaerial and subaqueous moraines in the salto valley near cochrane at 13 0 0 6 ka these moraines were deposited in an ice dammed palaeolake unified through the baker valley lago chalenko 350 m asl the salto valley glaciolacustrine landsystem includes subaqueous morainal banks ice scoured bedrock glacial diamicton plastered onto valley sides perched delta terraces kame terraces ice contact fans palaeoshorelines and subaerial push and lateral moraines boulders from the subaqueous salto moraine became exposed at 12 1 0 6 years indicating palaeolake drainage these data show an asynchronous advance of outlet glaciers from the northern patagonian icefield and monte san lorenzo during the antarctic cold reversal these advances occurred during a period of regional climatic cooling but differential moraine extent and timing of advance was controlled by topography and calving processes

delayed and sustained remote triggering of small earthquakes in the san jacinto fault region by the 2014 mw 7 2 papanoa mexico earthquake we apply a move max matched filter method to detect heightened seismicity triggered in the san jacinto fault sjf zone by the 2014 mw 7 2 papanoa mexico earthquake the move max matched filter detects 5 4 and 1 7 times the number of earthquakes in the southern california seismic network catalog and those detected by the matched filter method respectively the seismicity rate increases significantly 3 5 hr after the passage of the teleseismic waves and persists above the background level for about 1 week this observation of delayed triggering may imply that dynamic stresses had initiated a time dependent advance to failure or a secondary process a highly active triggered patch is located 10 km west of the sjf near anza on a previously unmapped fault focal mechanisms and a best fit plane suggest a normal fault perpendicular to the sjf the unmapped fault may indicate higher seismic hazard in the surrounding areas if a large earthquake nucleated around the anza seismic gap

deposition in an esker bead and fan complex lanark ontario canada abstract a glaciofluvial landform complex comprising a single esker ridge proximally multiple ridges and beads in the middle section and a complex of ridges and fans distally is mapped and described we present detailed successions in the associated sediment showing sedimentary structure grain size and palaeocurrent estimates sediment in the esker is mainly coarse grained and varies from boulders with a fine sand matrix deposited at maximum discharges to diamicton interpreted as a product of ice pressing under low discharges early stage deposition in the esker at high flow was from suspension and bed load intermediate stage deposition was mainly from bed load and late stage deposition was from hyperconcentrated suspension the esker rests in a bedrock channel which functioned as a nye channel prior to esker formation the channel surface carries a variety of fluvial erosional marks short distributary ridges of the ridges and beads complex contain mainly cobbles and boulders but beads are mainly in sand with rapid down flow fining and change in sedimentary structure faulting and overfolding of bead sediment suggest a subglacial origin deposition of the esker fan complex was highly variable in space and time down fan sedimentary changes with transitions from gravel to cross laminated fine sand in a few tens of metres indicate rapid loss in competence fan location lateral to the esker indicates a broadening of the zone of subglacial meltwater with time deposition from suspension and steep sided scours are interpreted to result from deposition and erosion by hyperconcentrated flows a model of underflows with submerged hydraulic jumps spilling laterally from the esker tunnel into subglacial cavities explains the morphological and sedimentary characteristics of the fans detailed analysis of small scale fining upwards sequences in the fans and beads indicates deposition by a large number of flow events these events are explained by glacier hydraulics whereby periodic separation of the glacier from its bed caused water with a high suspended sediment concentration to spill out from the esker tunnel into adjacent subglacial cavities evolution of the subglacial drainage system indicates a complexity of subglacial sedimentation near to a grounding line which is not readily apparent from observations at modern glaciers terminating in relatively deep water

sedimentary facies and depositional architecture of ice contact glaciomarine systems abstract the characteristics of ice contact glaciomarine systems are reviewed based on a range of weichselian and holocene examples from the fjordal basins in norway and svalbard these depositional systems occur as large morphological ridges end moraines including push moraines which are coarse grained and show large scale foreset bedding the paper addresses some of the major problems with regard to the recognition classification and stratigraphic analysis of these systems the ice proximal glaciomarine systems are classified here into three categories 1 ice contact submarine fans 2 ice contact deltas and 3 glaciofluvial deltas this classification integrates morphological and sedimentological criteria and renders these glaciomarine systems not only easier to recognize in the stratigraphic record but also possible to compare with common non glacial deltaic systems the emphasis is on the criteria for the recognition of the ice contact glaciomarine systems i e ice contact fans and ice contact deltas and their discrimination from common gilbert type deltas and fan deltas the review further focuses on ice contact glaciomarine systems as highly sensitive recorders of glacier dynamics and climatic fluctuations it is shown that both the periods of ice front stability and changes in the ice front position as well as the magnitude and rate of those changes are all recorded in the ice contact depositional system the sedimentary record further reflects glacio isostatic sea level changes and local palaeogeography a new conceptual model is suggested which places these ice contact glaciomarine systems in a dynamic stratigraphic context the model integrates sedimentary facies and their depositional architecture in an allostratigraphic framework and is meant to be a guide for the analysis of the sedimentary record of ice contact systems

sequence analysis of early saalian glacial lake deposits nw germany evidence of local ice margin retreat and associated calving processes abstract this paper presents a detailed analysis of high resolution facies architecture of glaciolacustrine ice margin deposits which formed at the southern margin of the scandinavian ice shield the ice margin depositional systems are characterised by coarse grained deltas and subaqueous fans which are formed by stacked transgressive regressive sequences recording an overall lake transgression interrupted by minor short term lake level falls the delta complexes at the northern margin of glacial lake rinteln are thought to reflect a relatively stable position of the ice margin in front of the weser chains mountain ridges the onset of delta progradation probably represents a halt in ice advance and a related high sediment supply period the sedimentary facies and depositional architecture resemble those of nonglacial gilbert type deltas except for the deposition of glacial debris the main delta progradation is recorded from the highstand systems tract when high meltwater and sediment discharge occurred during the melt season a forced regression during opening of outlets led to the formation of subaerially exposed sequence boundaries and the erosion of the highstand systems tract deeply incised channels incised valleys were filled during the subsequent transgression at the eastern lake margin subaqueous fan deposits reflect an unstable ice front that was rapidly retreating and subject to periodic calving which resulted in the generation of floating icebergs dumping ice rafted debris and ploughing into subaqueous fan deposits the rapid retreat of this eastern ice margin is interpreted to result from the overall lake level rise the fan stacking pattern and bulk geometry were determined by the ice front fluctuations the shifting of meltwater outlets and the short term lake level fluctuations depositional processes reflect the character of sediment supply and distance from the ice margin ice proximal upper fan deposits are characterised by coarse grained gravel deposited by debris flows that document continuous discharge slump and slide deposits are related to steep depositional slopes the mid fan contains basinward fining and thinning deposits of quasi steady and surge type high and low density turbidity currents indicating more ice distal and periodic deposition the outer fan deposits mainly consist of surge type low density turbidites and glacial debris dumped by icebergs the forcing parameters governing the development of depositional sequences in both delta and fan settings were lake level fluctuations sediment yield rates and physiography the depositional sequences were deposited on a time scale of seventh and eighth order high frequency cycles 101 102 years in this short time span lake level fluctuations were on the order of 120 m therefore accommodation space was largely controlled by lake level and subsidence can be ignored

three dimensional numerical modeling of deltaic depositional sequences 1 influence of the rate and magnitude of sea level change abstract a three dimensional numerical model of deltaic deposition is used to investigate the influence of sea level changes on delta development and sequence variability results illustrate the three dimensional morphology of key stratal surfaces and architecture of stratal units systems tracts and highlight the importance of the rate and magnitude of sea level change in controlling the evolution of deltaic depositional sequences high rates of sea level fall lead to the development of a limited number of major incised channels that focus sediment supply to a few elongate finger like forced regressive lobes separated by large areas of nondeposition in contrast low rates of sea level fall cause only minor channel incision which occurs late during sea level fall as a result sediment is supplied more uniformly to the delta front leading to an attached laterally continuous forced regressive apron during lowstand and subsequent sea level rise the delta morphology and internal geometry are strongly controlled by the rate of rise high rates lead to i poorly developed lowstand wedges that are drowned early ii high magnitude transgressions and iii the late development of maximum flooding surfaces the stratigraphy developed during sea level rise is also strongly influenced by the incised valley system created during the preceding sea level fall if deep major valleys developed that captured most of the sediment supply the resultant stratigraphy has well developed lowstand wedges that are flooded relatively late during sea level rise even within a single delta systems tracts and key stratal surfaces show three dimensional variability and two dimensional sections often lack significant elements of the stratigraphy as a result analysis of two dimensional sections can often lead to miscorrelation and erroneous interpretations of the controlling processes

ages and stratigraphical architecture of late miocene deposits in the lorca basin betics se spain new insights for the salinity crisis in marginal basins unlike most neogene basins of the betic cordillera where the salinity crisis is dated to the messinian a contradictory tortonian dating was proposed for evaporites of the lorca basin as a consequence complex structural models have been proposed in the literature to explain this discrepancy in the timing of evaporites in order to integrate the lorca basin into the geological context of the western mediterranean domain during the late miocene new sedimentological and stratigraphical studies coupled with new dating were performed which allow us to propose a messinian age for both diatomite bearing deposits and evaporites of the lorca basin these new ages challenge the idea of a tortonian salinity crisis in the lorca basin three main events of base level drop were evidenced during the messinian each event is correlated with successive steps of basin restriction shallow salina evaporites were deposited after a base level fall during the messinian before a final base level drop which led to the entire exposure of the basin this last exposure is interpreted as coeval with the deposition of first evaporites and halite in the deep mediterranean basins the reflooding which allowed the deposition of brackish deposits and a short lived marine incursion occurred at the end of the messinian base level drops occurred during eustatic falls amplified by the gradual uplift of the betic cordillera the exhumation of the tercia ridge along the strike slip alhama de murcia fault system during the messinian probably favoured the gradual restriction of the basin a discussion on correlations of main unconformities between several neogene basins of the betics is proposed suggesting a similar structural evolution at the regional scale

pulsed iceberg delivery driven by sturtian ice sheet dynamics an example from death valley california the kingston peak formation is a cryogenian sedimentary succession that crops out in the death valley area california usa it is widely accepted to record pre glacial conditions kp1 followed by two glaciations of pan global extent the older sturtian kp2 to kp3 and younger marinoan glaciation kp4 in the type area the kingston range detailed facies analysis of the sturtian succession reveals that a basal diamictite unit and an upper boulder conglomerate were deposited by proglacial subaqueous sediment gravity flows an olistostrome unit punctuating the succession is interpreted to result from tectonically induced downslope mobilization during isostatic rebound triggered by significant ice meltback focussing on strata onlapping the olistostrome this article provides insight into the processes of glacial re advance following an intra sturtian glacial minimum the first 50 m of strata above the olistostrome are thinly bedded turbidites that are devoid of lonestones a trend towards thicker graded beds upsection in concert with the gradual appearance and then abundance of lonestones testifies to the influence of ice rafting and to the resumption of a direct ice sheet influence upon sedimentation stratigraphic organization into thickening and coarsening upward bedsets over a multi metre scale reveals a subaqueous gravity flow dominated succession composed of a spectrum of high to low density turbidites with thick graded boulder conglomerates at intervals the finer grained facies assemblage is heterolithic current ripple cross laminated sandstones intercalated with shales that bear delicate granule to pebble sized dropstones in abundance intervals of dropstone bearing and dropstone free strata are attributable to dynamic oscillation of the ice margin in the hinterland integrating palaeocurrent data with observations from neighbouring outcrop belts allows a detailed palaeogeographic map of the eastern death valley area to be compiled for the first time

particle over passing on depth limited gravel bars an experimental channel is used to examine the transport of mixed sand and gravel bedload over the crestal platform of hump back bars and along the top of planar gravel sheets hydraulic processes result in the simultaneous transport of cobbles and pebbles over a static closely packed bed consisting of like sized and finer particles for prescribed conditions flat upper stage plane sand beds develop over the crestal location with pebbles rolling easily over the sandy bed at the brinkpoint flow separation ensures effective segregation of the gravel from the sand over the slip face the deposition rate of the sand is insufficient to fill fully the interstices within the gravel foresets before rapid deposition of gravel further advances the bed form consequently distinctive vertical assemblages of open work and closed contact framework gravels could be generated as another bar migrates over and preserves the initial structure in respect to the observed mechanisms of sorting over the bars a mathematical expression is developed to explain the critical conditions allowing coarse particle mobility over planar sand or gravel beds under upper stage plane bed conditions on the crestal platform the model then is used to ascertain whether the depositional environment ascribed to certain facies in the bunter pebble beds described in a recent publication is appropriate given the distinctive facies assemblages generated in this experiment and the known hydrodynamic control of the particle segregation process