late holocene activity of sherman and sheridan glaciers prince william sound alaska abstract two adjacent glaciers in the chugach mountains of south central alaska have markedly different histories on decadal to perhaps centennial timescales sheridan glacier has advanced and retreated hundreds of metres during the latest holocene its recent fluctuations have markedly altered local base level of sherman river which drains sherman glacier and flows into sheridan lake sheridan glacier advanced to its greatest extent during the little ice age raising base level of sherman river and inducing aggradation there of up to 17 m of sediment retreat of sheridan glacier formed a series of lakes that have coalesced as lower lake outlets have become available base level of sherman river has dropped resulting in the evacuation of substantial volumes of sediment from sherman river valley in about 2000 the terminus of sheridan glacier began to disintegrate retreat accelerated dramatically in 2010 by 2016 the glacier had retreated an average of 600 m from its 2010 terminus although some areas retreated up to 1 9 km and others did not retreat at all meanwhile sherman glacier continued a slow advance initiated by a rock avalanche that blanketed much of its ablation area in the 1964 alaska earthquake

holocene glacier fluctuations a global overview of glacier advances and retreats grouped by regions and by millennia for the holocene is compiled from previous studies the reconstructions of glacier fluctuations are based on 1 mapping and dating moraines defined by 14 c tcn osl lichenometry and tree rings discontinuous records time series and 2 sediments from proglacial lakes and speleothems continuous records time series using 189 continuous and discontinuous time series the long term trends and centennial fluctuations of glaciers were compared to trends in the recession of northern and mountain tree lines and with orbital solar and volcanic studies to examine the likely forcing factors that drove the changes recorded a general trend of increasing glacier size from the earlyemid holocene to the late holocene in the extra tropical areas of the northern hemisphere nh is related to overall summer temperature forced by orbitally controlled insolation the glaciers in new zealand and in the tropical andes also appear to follow the orbital trend i e they were decreasing from the early holocene to the present in contrast glacier fluctuations in some monsoonal areas of asia and southern south america generally did not follow the orbital trends but fluctuated at a higher frequency possibly triggered by distinct teleconnections patterns during the neoglacial advances clustered at 4 4e4 2 ka 3 8e3 4 ka 3 3e2 8 ka 2 6 ka 2 3e2 1 ka 1 5e1 4 ka 1 2e1 0 ka 0 7e0 5 ka corresponding to general cooling periods in the north atlantic some of these episodes coincide with multidecadal periods of low solar activity but it is unclear what mechanism might link small changes in irradiance to widespread glacier fluctuations explosive volcanism may have played a role in some periods of glacier advances such as around 1 7e1 6 ka coinciding with the taupo volcanic eruption at 232 5 ce but the record of explosive volcanism is poorly known through the holocene the compilation of ages suggests that there is no single mechanism driving glacier fluctuations on a global scale multidecadal variations of solar and volcanic activity supported by positive feedbacks in the climate system may have played a critical role in holocene glaciation but further research on such linkages is needed the rate and the global character of glacier retreat in the 20th through early 21st centuries appears unusual in the context of holocene glaciation though the retreating glaciers in most parts of the northern hemisphere are still larger today than they were in the early and or mid holocene the current retreat

late glacial to recent stratigraphy paleontology and sedimentary processes newfoundland continental slope and rise micropaleontology pollen sediment and 18o studies point to considerable variation in sedimentary processes and water mass characteristics on the northeast newfoundland slope and rise during late glacial and holocene time allochthonous shelf and upper slope foraminiferal species suggestive of turbidity current activity occur relatively frequently in rise sediments during a postglacial interval dated by extrapolation from a probable 9300 year old ash horizon a single late glacial turbidity current deposit involved a much larger volume of sediment than that noted for the earlier events and it appears to have originated primarily on the middle slope in conjunction with a widespread late glacial interval of fecal pellet deposition this larger event suggests an increased flux of material in the form of suspended particulate matter to the continental margin following the late wisconsinan glacial maximum oceanographic conditions during late glacial time appear to have stimulated the productivity of zoop

late holocene glacial activity at bromley glacier cambria icefield northern british columbia coast mountains canada retreating and downwasting glaciers in the british columbia coast mountains are exposing the remains of forests buried during holocene age glacial advances despite recent progress in discerning th

late holocene glacial history of the copper river delta coastal south central alaska and controls on valley glacier fluctuations abstract fluctuations of four valley glaciers in coastal south central alaska are reconstructed for the past two millennia tree ring crossdates on 216 glacially killed stumps and logs provide the primary age control and are integrated with glacial stratigraphy ages of living trees on extant landforms and historic forefield photographs to constrain former ice margin positions sheridan glacier shows four distinct phases of advance in the 530s to c 640s in the first millennium a d and the 1240s to 1280s 1510s to 1700s and c 1810s to 1860s during the little ice age lia the latter two lia advances are also recorded on the forefields of nearby scott sherman and saddlebag glaciers comparison of the sheridan record with other two millennia long tree ring constrained valley glacier histories from south central alaska and switzerland shows the same four intervals of advance these expansions were coeval with decreases in insolation supporting solar irradiance as the primary pacemaker for centennial scale fluctuations of mid latitude valley glaciers prior to the 20th century volcanic aerosols coupled atmospheric oceanic systems and local glacier specific effects may be important to glacier fluctuations as supplemental forcing factors for causing decadal scale differences between regions and as a climatic filter affecting the magnitude of advances

palaeooceanographic significance of bottom current fluctuations in the southern ocean hiatuses in the sedimentary record of the southern ocean are usually attributed to erosion by high velocity bottom currents1 3 to test for palaeoclimatic mechanisms which intensified bottom circulation however the timing of increases in bottom current velocity must be known as the sedimentary record of the period of initial erosion is lost within the hiatus the timing of increased velocity must be determined in cores which are adjacent to the axis of highest velocity4 5 in those cores the accumulation rates are reduced due to the current but a record of the period of initiation of scour is preserved as a zone of particle size winnowing of the fine fraction3 4 the timing of major episodes of bottom current intensification in the south australian basin for the past 4 5 myr are reported here for the first time and may be used to examine the role of palaeoclimatic fluctuations on bottom current intensity

response of deep ocean circulation to initiation of northern hemisphere glaciation 3 2 ma carbon isotopic records from benthic foraminifera are used to map patterns of deep ocean circulation between 3 and 2 million years ago the interval when significant northern hemisphere glaciation began the 18o and 13c data from four atlantic sites 552 607 610 and 704 and one pacific site 677 show that global cooling over this interval was associated with increased suppression of north atlantic deep water nadw formation however the relative strength of nadw production was always greater than is observed during late pleistocene glaciations when extreme decreases in nadw are observed in the deep north atlantic our data indicate that an increase in the equator to pole temperature gradient associated with the onset of northern hemisphere glaciation did not intensify deepwater production in the north atlantic but rather the opposite occurred this is not unexpected as it is the warm high salinity characteristic rather than the low temperature of thermocline waters that is critical to the deepwater formation process in this region today

elevation changes 1949 1995 of black rapids glacier alaska derived from a multi baseline insar dem and historical maps we have constructed a new digital elevation model dem of the 1995 surface of black rapids glacier a surge type glacier in the central alaska range using ers 1 2 repeat pass interferometry we isolated the topographic phase from three interferograms with contrasting perpendicular baselines numerous phase unwrapping errors caused by areas of poor coherence were corrected in all three interferograms using a novel iterative semi automated approach that capitalizes on the multi baseline nature of the dataset comparison of our dem with a 1949 us geological survey dem and with 1973 95 ground survey data shows the gradual return of black rapids glacier to a pre surge hypsometry following a surge in 1936 37 maximum elevation changes along the glacier center line in the ablation and accumulation areas are respectively 249 and 63 m 5 4 and 1 4 m a 1 maximum elevation changes of survey points at nearby locations are 4 9 m a 1 1975 84 and 0 5 ma 1 1975 85 center line thickening of 62 m between 1949 and 1995 1 4 m a 1 just above the loket tributary in the upper part of the ablation zone indicates dynamic thickening following the 1936 37 surge

pliocene variations in the position of the antarctic convergence in the southwest atlantic middle to late pliocene 4 1 1 9 ma variations in the positions of surface water masses and migrations of the polar front in the southwest atlantic are inferred from a factor analysis of radiolarian assemblages from dsdp site 514 faunal results suggest that surface water masses underwent progressive cooling as the polar front zone pfz advanced northward during the latest gilbert to late gauss chron the late gilbert chron 4 12 3 86 ma was the waning phase of a mid gilbert warm interval northern subantarctic surface water prevailed between 4 12 and 3 97 ma indicative of surface water temperatures warmer than those during the succeeding pliocene a long term sea surface cooling trend began between 3 97 and 3 86 ma which moved the pfz northward and closer to site 514 bringing cooler southern subantarctic surface waters to the site this movement northward of cooler surface waters is inferred to be related to the initial growth of sea ice and ice shelves throughout regions of west antarctica which were deglaciated or unglaciated during the prior warming interval of the gilbert chron a major late gilbert early gauss chron increase in the production of antarctic bottom water aabw resulted in an erosional or nondepositional hiatus at site 514 spanning 3 86 to 3 18 ma increased aabw activity at this time is linked to continued growth of expansive ice shelves and sea ice in the west antarctic region in the east antarctic margin and possibly in the marine embayments of east antarctica decreased aabw production led to a 3 2 ma resumption of sedimentation at site 514 and elsewhere in the southern ocean antarctic surface water assemblages above the hiatus 3 18 3 16 ma suggest that the pfz first passed over site 514 during the 3 86 3 18 ma interval of the hiatus following this initial invasion of antarctic surface waters between 3 16 and 2 94 ma the pfz retreated to a position near or south of the site this slight retreat of the pfz with a corresponding decrease in aabw activity is possibly related to a significant reduction in the area of shelf and sea ice as grounded ice expanded in the west antarctic region we interpret the widespread global enrichment of 18o at approximately 3 2 ma to be partially related to a cooling of surface waters the production of cooler bottom waters and an expansion of west antarctic ice volume associated with its grounding phase between 3 5 and 2 7 ma based on surface water mass migrations at site 514 the west antarctic ice volume increased significantly slightly prior to or at approximately 3 2 ma decreased between 3 14 and 2 7 ma and then increased by 2 67 ma to a more stable configuration with a volume at least as great as that at 3 2 ma during the late gauss 2 94 2 47 ma four northward advances of the pfz led to the migration of antarctic surface waters over the site by 2 67 ma and continued dominance of antarctic surface water through the remainder of the pliocene we suggest that this permanent change from subantarctic to antarctic surface water mass dominance was linked indirectly to the initial growth of northern hemisphere ice and a reduction of sea level we propose a model of simultaneous northern and southern hemisphere ice volume growth induced by interhemisphere positive feedback which is responsible for the major late gauss advance of antarctic surface waters and the global enrichment of 18o at 2 5 ma

landsat based inventory of glaciers in western canada 1985 2005 abstract we report on a glacier inventory for the canadian cordillera south of 60 n across the two western provinces of british columbia and alberta containing 30 000 km2 of glacierized terrain our semi automated method extracted glacier extents from landsat thematic mapper tm scenes for 2005 and 2000 using a band ratio tm3 tm5 we compared these extents with glacier cover for the mid 1980s from high altitude aerial photography for british columbia and from landsat tm imagery for alberta a 25 m digital elevation model dem helped to identify debris covered ice and to split the glaciers into their respective drainage basins the estimated mapping errors are 3 4 and arise primarily from seasonal snow cover glaciers in british columbia and alberta respectively lost 10 8 3 8 and 25 4 4 1 of their area over the period 1985 2005 the region wide annual shrinkage rate of 0 55 a 1 is comparable to rates reported for other mountain ranges in the late twentieth century least glacierized mountain ranges with smaller glaciers lost the largest fraction of ice cover the highest relative ice loss in british columbia 24 0 4 6 occurred in the northern interior ranges while glaciers in the northern coast mountains declined least 7 7 3 4

nature and timing of quaternary glaciation in the himalayan tibetan orogen abstract much effort has been made in recent years to define the timing and extent of quaternary glaciation throughout the himalayan tibetan orogen these studies are challenging because of the logistical and political inaccessibility of the region and the inherent problems associated with the application of numerical dating techniques nevertheless the studies are providing abundant evidence for significant glacial advances throughout the last several glacial cycles and are beginning to accurately define the extent and timing of glaciation in selected regions studies are showing that himalayan tibetan glaciers in arid regions during the last glacial cycle reached their maximum extent early in the cycle and that global last glacial maximum glacier advances were significantly less extensive however along the more monsoonal influenced greater himalaya there is increasing evidence to suggest that glaciation was more extensive later in the last glacial cycle but this has yet to be fully assessed in addition the new studies are showing that throughout most himalayan tibetan regions significant glacier advances occurred during the lateglacial and early holocene with minor advances in some regions during the mid holocene the still relatively poor chronological control in the himalayan tibetan orogen however makes it difficult to construct correlations across the region and with regions elsewhere in the world this in turn makes it hard to assess the relative importance of the different climatic mechanisms that force glaciation across the himalayan tibetan orogen and to quantify paleoclimate change in this high altitude subtropical region the lateglacial and holocene glacial records however are particularly well preserved in several himalayan tibetan regions glacial successions such as these have the greatest potential to be examined in detail using newly developing numerical dating and geomorphic and sedimentologic methods to derive high resolution terrestrial records of glaciation that will help in paleoclimatic reconstruction for high altitude subtropical regions

endostromatolites from permafrost karst yukon canada paleoclimatic proxies for the holocene hypsithermal a remarkable biogenic calcite precipitate forms carpets of finely laminated 1 mm diameter columns lining fissures within limestone bedrock in the permafrost regions of the northern yukon this material endostromatolite for its laminated morphology and growth hidden within the carbonate rock is ubiquitous within limestone terrains of the arctic and grew during the early holocene hypsithermal dissolution on the interior fissure faces is accompanied by biomineralization of the opposing faces a previously unrecognized weathering process in permafrost regions occurrence is restricted to outcrops with a southern orientation in permafrost regions in this case from the ogilvie mountains northern yukon growth occurs in water saturated talik during periods of permafrost degradation during insolation maxima their enriched 13c values 1 7 to 11 4 are generated in a methanogenic environment during anaerobic degradation of soil derived organic carbon a paleotemperature signal extracted from the 18o

holocene glacier fluctuations in alaska abstract this review summarizes forefield and lacustrine records of glacier fluctuations in alaska during the holocene following retreat from latest pleistocene advances valley glaciers with land based termini were in retracted positions during the early to middle holocene neoglaciation began in some areas by 4 0 ka and major advances were underway by 3 0 ka with perhaps two distinct early neoglacial expansions centered respectively on 3 3 2 9 and 2 2 2 0 ka tree ring cross dates of glacially killed trees at two termini in southern alaska show a major advance in the ad 550s 720s the subsequent little ice age lia expansion was underway in the ad 1180s 1320s and culminated with two advance phases respectively in the 1540s 1710s and in the 1810s 1880s the lia advance was the largest holocene expansion in southern alaska although older late holocene moraines are preserved on many forefields in northern and interior alaska tidewater glaciers around the rim of the gulf of alaska have made major advances throughout the holocene expansions were often asynchronous with neighboring termini and spanned both warm and cool intervals suggesting that non climatic factors were important in forcing these advances however climatic warming appears to have initiated most rapid iceberg calving retreats large glaciers terminating on the forelands around the gulf of alaska may have had tidewater termini early in the holocene but have progressively become isolated from the adjacent ocean by the accumulation and subaerial exposure of their own sediments

ice volume and subglacial topography for western canadian glaciers from mass balance fields thinning rates and a bed stress model abstracta method is described to estimate the thickness of glacier ice using information derived from the measured ice extent surface topography surface mass balance and rate of thinning or thickening of the ice column shear stress beneath an ice column is assumed to be simply related to ice thickness and surface slope as for an inclined slab but this calculation is cast as a linear optimization problem so that a smoothness regularization can be applied assignment of bed stress is based on the flow law for ice and a mass balance calculation but must be preceded by delineation of the ice flow drainage basin validation of the method is accomplished by comparing thickness estimates to the known thickness generated by a numerical ice dynamics model once validated the method is used to estimate the subglacial topography for all glaciers in western canada that lie south of 60 n adding the present ice volume of each glacier gives the estimated total volume as 2320 km3 equivalent to 5 8 mm of sea leve

bottom current speed in the vema channel recorded by particle size of sediment fine fraction abstract the particle size distribution of the carbonate free silt fraction was determined in forty two core top samples from the east flank of the vema channel in order to allow comparison of the mean particle size with near bottom current speed based on nearby ctd and current meter observations the silt mean particle size fluctuates insignificantly between 1450 3950 m but coarsens markedly below 4000 m under antarctic source bottom currents the top of the zone of coarse sizes approximates the top of lower circumpolar water lcpw at 4000 m the steep gradient to coarsest sizes in the axis of the channel marks the transition to antarctic bottom water aabw the vertical profile of mean particle size on the east flank correlates in general respects with the vertical velocity gradient in the channel axis although the core sites on the east flank are as far as 200 miles from the current meter arrays nevertheless this relationship is used to infer that the non carbonate particle sizes deposited on the east flank of the channel may be an indication of bottom current speed and therefore the mean size is used to reconstruct profiles of mean current speed for three time slices 18 120 and 140 ka b p during glacial isotopic stages 2 and 6 the particle sizes deposited on the east flank of the channel are characterized by finer sizes at nearly all depths and the zone of coarse sizes corresponding to lcpw and aabw deepens during interglacial isotopic stage 5e the particlesize profile is very similar to the modern profile however lcpw and aabw appear to be deeper than at present the finer particle sizes deposited at nearly all depths during glacial periods indicates that the velocity of deep circulation in the atlantic was reduced in response to the ice ages deep circulation during isotopic stage 5e closely resembled modern circulation however aabw production rates may have been less that at present

pacific caco3 preservation and δ18o since 4 ma paleoceanic and paleoclimatic implications the pliocene pleistocene history of caco3 preservation in the central equatorial pacific is reconstructed from a suite of deep sea cores and is compared to fluctuations in global ice volume inferred from 18o records the results are highlighted by 1 a strong covariation between caco3 preservation and ice volume over 104 to 106 year time scales 2 a long term increase in ice volume and caco3 preservation since 3 9 ma demonstrated by a deepening of the lysocline and the carbonate critical depth 3 a dramatic shift to greater caco3 preservation at 2 9 ma 4 distinctive ice volume growth and caco3 preservation events at 2 4 ma which are associated with the significant intensification of northern hemisphere glaciation 5 a mid pleistocene transition to 100 kyr cyclicity in both caco3 preservation and ice volume and 6 a 600 kyr brunhes dissolution cycle superimposed on the late pleistocene glacial interglacial 100 kyr cycles caco3 preservation primarily reflects the carbonate chemistry of abyssal waters and is controlled by long term 106 year and short term 104 to 105 year biogeochemical cycling and by distinct paleoclimatic events we attribute the long term increase in caco3 preservation primarily to a fractionation of caco3 deposition from continental shelf to ocean basin and secondarily to a gradual rise in the riverine and glaciofluvial flux of ca on shorter time scales the fluctuations in caco3 preservation slightly lag ice volume fluctuations and are attributed to climatically induced changes in the circulation and chemistry of pacific deep water

tree ring dated little ice age histories of maritime glaciers from western prince william sound alaska tree ring studies at 13 glacier forefields in western prince william sound show little ice age glacial fluctuations were strongly synchronous on decadal timescales cross dated glacially overrun trees at eight sites indicate ice margins advanced in the early late twelfth through thirteenth centuries and middle seventeenth to early eighteenth centuries little ice age tree ring dates of 22 moraines at 13 glaciers show two main periods of stabilization the earlier of these in the first decades of the eighteenth century overlaps with the second period of glaciers overrunning trees and marks culmination of this middle little ice age expansion stabilization of moraines on nine of the study forefields in the latter part of the nineteenth century delineates a third interval of little ice age glacial advance the detailed little ice age record from land terminating glaciers in western prince william sound is consistent on a timescale of decades with four other tree ring dated glacial histories from across the northern gulf of alaska this coastal northeastern pacific glacial record reveals the structure of the little ice age in the region and provides a strong basis for comparison with other proxy climate records spanning the past 1000 years

deep circulation changes in the south atlantic ocean response to initiation of northern hemisphere glaciation particle size statistics coarsest 1 percentile and mean of the nonbiogenic silt fraction of samples from deep sea drilling project sites 514 516a 517 518 and 548 were used to infer relative changes in paleospeed of deep water masses in the atlantic ocean during the late pliocene initiation of northern hemisphere glaciation grain size statistics were integrated with previous studies of geochemical and faunal assemblages to examine how climatic forcing regulates deepwater mass paleospeed and stratification on the basis of between site comparison of particle size the late pliocene was divided into four intervals of deepwater activity 3 2 to 2 9 ma 2 9 to 2 6 ma 2 6 to 2 5 ma and 2 5 to 2 3 ma with pulses of increased paleospeed occurring at 3 15 3 10 2 85 2 7 2 6 and 2 4 ma except for a brief increase in paleospeeds at 3 1 ma the first time interval is characterized by low inferred antarctic bottom water aabw paleospeed corresponding to depleted 13c and enriched 18o values in all but the shallowest core enriched 13c and depleted 18o values in the shallowest core correspond to coarse grain sizes and are inferred to represent a deep and intense antarctic intermediate water aaiw the expansion of aabw and aaiw precludes a significant north atlantic deep water nadw incursion to 30 s at this time the interval from 2 9 to 2 6 ma is dominated by climatic cooling and an influx of deep waters originating in the north atlantic the introduction of significant volumes of mediterranean outflow water mow as demonstrated by increased inferred paleospeed at site 548 and an expanding glaciation beginning at 2 9 ma resulted in increased paleospeed and an expansion of nadw in the south atlantic a pulse of increased inferred paleospeed at 2 7 ma resulted in the temporary deepening of nadw to the depth of site 518 presently 3944 m from 2 9 to 2 6 ma aabw velocity remained low but aaiw deepened and intensified the 2 6 to 2 5 ma interval represents the retreat of deep water originating in the north atlantic from the depth of site 518 to the depth of site 517 presently 2963 m increased inferred paleospeed at site 518 corresponds with depleted 13c values and a northward shift in the polar front thus suggesting the reintroduction of circumpolar water to the depth of site 518 and the establishment of a deepwater stratification similar to today s a continuing trend toward a modern stratification continued into the latest time interval 2 5 2 3 ma as inferred deepwater paleospeed at all depths increased in response to the formation of extensive northern hemisphere ice sheets

post miocene fluctuations of antarctic bottom water paleospeed in the southwest atlantic ocean abstract a gap in the falkland escarpment serves as the primary channel through which antarctic bottom water aabw flows into the argentine basin from the georgia basin the particle size distributions of the biogenic free silt fraction in four cores near the falkland gap and the hiatus frequency at water depths greater than 4000 m throughout the southern ocean are used to infer post miocene aabw paleospeed analysis of aabw paleocirculation indicates episodes of increased bottom current speeds at 5 3 4 5 4 0 3 5 3 3 3 1 2 5 2 3 2 0 1 5 and 1 0 ma these fluctuations in inferred paleospeed are compared to both northern and southern hemisphere paleoceanographic and paleoclimatic events in order to examine the response of bottom water circulation to post miocene climates during the early gilbert middle matuyama 5 3 1 5 ma southern hemisphere climatic events provided the primary forcing mechanisms on aabw activity the model invoked involves increased salinity and overturn of weddell shelf water in response to increased sea ice formation during cold episodes from the late matuyama after 1 5 ma to present fluctuations in warm deep water resulting from northern hemisphere climatic evolution may have been the predominant factor influencing aabw paleospeed these episodes of increased bottom current activity may correlate to periods of mudwave migration in the argentine basin during the past 5 ma the mudwave fields consist of silty siliceous clays deposited in response to enhanced sediment supply and fast moving currents in the interior basin we speculate that the periods of enhanced bottom water activity may have been responsible for major episodes of mudwave growth that began since the late oligocene and have persisted into the holocene

expansion of alpine glaciers in pacific north america in the first millennium a d radiocarbon ages and lichen dated moraines from 17 glaciers in coastal and near coastal british columbia and alaska document a widespread glacier advance during the first millennium a d glaciers at several sites began advancing ca a d 200 300 based on radiocarbon dated overridden forests the advance is centered on a d 400 700 when glaciers along an 2000 km transect of the pacific north american cordillera overrode forests impounded lakes and deposited moraines the synchroneity of this glacier ad vance and inferred cooling over a large area suggest a regional climate forcing and to gether with other proxy evidence for late holocene environmental change during the me dieval warm period and little ice age provide support for millennial scale climate variability in the north pacific region

the sedimentology and geomorphology of rock avalanche deposits on glaciers this article describes and compares the deposits of four large landslides on two glaciers in alaska using field mapping and remote sensing digital image analysis is used to compare the sedimentological characteristics of nearly 200 000 individual surface blocks deposited by three landslides at black rapids glacier in 2002 the debris sheets of one of the three landslides on black rapids glacier and a landslide emplaced on sherman glacier in 1964 are also investigated the three landslides on black rapids glacier have undergone little post depositional modification by glacier flow whereas the sherman glacier landslide has been transported supraglacially up to ca 1k m over the past 46 years the three debris sheets on black rapids glacier have coarse blocky rims at their distal edges and all four debris sheets have longitudinal flowbands characterized by differences in texture and produced by shearing within the moving debris elongated blocks are parallel to flow except at the perimeter of the debris sheets where they are aligned more perpendicular to flow blocks on the sherman glacier debris sheet have been reoriented by glacier flow the matrix shows no systematic differences with depth or distance from the source however it appears to become coarser over a time scale of decades due to weathering

taku glacier alaska u s a on the move again active deformation of proglacial sediments taku glacier is one of the few glaciers in alaska u s a that has advanced over the last century 7 km since 1890 this advance slowed substantially during the past decade but in summer 2001 the glacier terminus began to readvance at a rate of 30 cm d 1 the advance produced dramatic proglacial sediment deformation up to 200 m in from of the terminus two to three large bulges and several secondary bulges developed in the proglacial sediments as a result of glacial compression along a 1 km wide portion of the terminus the bulge nearest the terminus was 10 m high and 65 m wide the middle bulge 7 m high advanced at 15 cm d 1 and the distal bulge 3 m high and 50 m wide at 9 cm d 1 crenulations and prominent fractures developed in the overlying vegetation layer the frontal lobes of the bulges were steep and overlaid a shear zonc where sediments were being thrust up and over the ground surface ice proximal push moraines 1 10 m high formed along much of the 9 km wide terminus although deformation was minimal at some locations

a 420 000 year record of cyclicity in oceanic and atmospheric processes from the eastern equatorial pacific samples from the upper portion of a cyclic pelagic carbonate sediment sequence in deep sea drilling project dsdp hole 503b 4 0 n 95 6 w are the first group to be analyzed for paleoceanographic and paleoclimatic proxy indicators of ice volume deep ocean and surface water circulation and atmospheric circulation in order to resolve the complex origin of the cyclicity temporal resolution is taken from the 18o time scale most other parameters are calculated in terms of their mass flux to the seafloor caco3 percent in the sediments fluctuates in the well known pacific pattern and is higher during glacial times the fluxes of opal and organic carbon have patterns similar to each other and show a variability of a factor of 2 5 to 4 the longer organic carbon record shows flux maxima during both glacial and interglacial times the accumulation patterns of both opal and organic carbon suggest that the variability in surface water productivity and or seafloor preservation of those materials is not simply correlated to glacial or interglacial periods eolian dust fluxes are greater during interglacial periods by factors of 2 to 5 indicating that eolian source regions in central and northern south america were more arid during interglacial periods the record of eolian grain size provides a semiquantitative estimation of the intensity of the transporting winds the eolian data suggest more intense atmospheric circulation during interglacial periods opposite to the anticipated results we interpret this observation as recording the southerly shift of the intertropical convergence zone to the latitude of hole 503b during glaciations

post miocene disconformities and paleoceanography in the atlantic sector of the southern ocean abstract the magnetostratigraphy and biostratigraphy of 166 islas orcadas piston cores in the atlantic sector of the southern ocean reveal disconformities in the sedimentary record which are attributed to bottom current erosion the hiatus frequency as a function of water depth reveals both shallow erosion by circumpolar deep water cdw and deep erosion by antarctic bottom water aabw the post miocene history of erosion by both bottom currents is delineated by analysis of areal and temporal fluctuations of hiatus frequency erosion by cdw caused disconformities on the maud rise astrid ridge indian antarctic ridge scotia sea and islas orcadas rise the shallow disconformities increased in frequency and size from 4 0 to 1 0 ma with two periods of distinctly widespread disconformities from 5 5 to 4 5 ma and 2 5 to 1 5 ma after 1 0 ma the frequency and extent of the hiatuses decreased erosion by aabw caused disconformities in the weddell abyssal plain argentine basin and through a narrow conduit in the south sandwich basin downstream from the bullard fracture zone the deep disconformities increased in frequency and size from 4 5 to 5 0 ma 3 5 to 4 0 ma and from 1 0 to 2 5 ma after 1 5 ma the frequency and extent of hiatuses decreased fluctuations in hiatus frequency are consistent with results of a similar study in the southeast indian ocean and may be correlated with paleoceanographic events southern ocean cooling and possible re establishment of the west antarctic ice sheet and fringing ice shelves at 4 3 3 5 ma was accompanied by increased aabw and cdw activity the formation expansion of the northern hemisphere ice sheets at 2 5 3 0 ma resulted in a decrease in aabw velocity and was accompanied by increased cdw activity both deep and shallow bottom currents increased in velocity during the late matuyama chron 2 0 1 5 ma as a result of antarctic cooling after 1 0 ma however the frequency and extent of shallow and deep hiatuses was reduced and the modern extent of hiatuses is the lowest within the post miocene