late pleistocene colonization of north america from northeast asia new insights from large scale paleogeographic reconstructions advances in large scale paleogeographic reconstruction define physical and environmental constraints relevant to understanding the timing and character of the first colonization of the americas during the late pleistocene diachronic mapping shows continental glaciers coalesced in central canada during the last glacial maximum lgm 20 000 14 000 years ago while unglaciated refugia existed along the northwest coast the bering land bridge connected asia and north america until about 10 000 years ago when the two continents were separated by rising sea level this visual analysis from large scale synthesis of recent geological and environmental research establishes timelines for biotically viable colonization corridors connecting eastern beringia to southern north america and provides insights into probable paleoindian origins and subsistence strategies

landslide induced iron mobilisation shapes benthic accumulation of nutrients trace metals and ree fractionation in an oligotrophic alpine stream large alpine landslides that entrain substantial organic material below the water table and create suspended floodplains may have long term consequences for the mobilisation of redox sensitive elements such as fe into streamwaters in turn the cycling of iron in aquatic systems can influence the fate of nutrients alter primary productivity enhance accumulation of trace metals and induce fractionation of rare earth elements ree in this study we examine a reach of a pristine oligotrophic alpine stream bracketing a 30 year old landslide and explore the consequences of landslide induced fe mobilisation for aqueous geochemistry and the composition of benthic stream cobble biofilm elevated fe2 and mn in landslide zone stream waters reflect inputs of circumneutral groundwater from the landslide debris zone floodplain geochemical characteristics are consistent with reductive dissolution being a primary mechanism of fe2 and mn mobilisation stream cobble biofilm in the landslide zone is significantly p 0 01 enriched in poorly crystalline fe iii similar to 10 400 times background and mn similar to 15 150 times background 1 m hc1 extractable fe iii ab while the landslide zone accounts for less than similar to 9 of the total stream length we estimate it is responsible for approximately 60 80 of the stream s benthic biofilm load of poorly crystalline fe iii and mn biofilm fe iii precipitates are comprised mainly of ferrihydrite lepidocrocite and an organic fe species while precipitate samples collected proximal to hyporheic seeps contain abundant sheath structures characteristic of the neutrophilic fe ii oxidising bacteria leptothrix spp stream cobble fe iii rich biofilm is accumulating po43 similar to 3 30 times background and behaving as a preferential substrate for photosynthetic periphyton with benthic po chlorophyll a organic carbonim and total n all significantly positively correlated with fe iii ab and significantly elevated within the landslide zone p 0 01 p k edge xanes indicates p is associated with both ferric and ca phosphate minerals while sem edx elemental mapping of fe iii precipitates reveal strong spatial associations between p ca and fe cobble fe iii rich biofilm is also sorbing and accumulating multiple trace metals and ree within the landslide zone there are significant p 0 01 enrichments up to similar to 10 100 times background for most trace metals examined here and metals display significant positive linear correlations with fe iii ab on a log transformed basis stream cobble biofilm also exhibits distinct ree fractionation along the flow path with light ree la ce nd pr preferentially partitioning to the fe iii and mn rich biofilm within the landslide zone accumulation of po43 and trace metals in this relatively environmentally labile form may have implications for their bioavailability and downstream transport but further research is required to assess possible ecological consequences this study demonstrates the potential for large alpine landslides to encourage reach scale circumneutral fe mobilisation in adjacent streams thereby shaping multiple aspects of benthic stream geochemistry for many years after the landslide event itself c 2014 elsevier ltd all rights reserved

quaternary stratigraphy of the buried valleys of the lower red deer river alberta canada the quaternary fills of the buried valleys of southern alberta and saskatchewan have provided a wealth of information for the reconstruction of the glacial interglacial record of the western plains of canada and this paper reports on the previously unstudied stratigraphy of the buried calgary valley and its former tributaries in the lower red deer river area we attempt to differentiate empress group sediments which potentially relate to pre glacial interglacial interstadial and post glacial lake and river deposition using sedimentology stratigraphy and palaeoecology twenty nine stratigraphical logs indicate that empress group sediments have infilled a considerably large area of badlands and tributary coulees that once drained into the calgary valley located 15 km to the north of dinosaur provincial park radiocarbon dates of 52 4 ka 27 4 ka and 42 4 ka and glacially modified quartz grains suggest that at least some of the valley fills date to interglacial or interstadial periods and may be mid wisconsinan in age however outcrops of an older till overlying other valley fills suggest that the buried valleys were only partially excavated during interglacials interstadials and that older even pre glacial sediments could have survived subglacial channels recognisable on air photographs largely coincide with buried valley positions due to the preferential excavation of the quaternary sediment by meltwater and are filled with post glacial lake sediment from which a radiocarbon date of 16 ka bp was obtained pre glacial and glacial post glacial empress group sediments are lithologically indistinct but cover a large time span in southern alberta

controls on transport and fractionation of the rare earth elements in stream water of a mixed basaltic granitic catchment basin massif central france abstract we present rare earth element ree patterns of small streams from a catchment basin in the massif central france in order to characterize the individual fractionation stages for the dissolved ree from the source to the catchment outlet the upper part of the catchment is located on a basalt plateau followed downstream by deep and narrow valleys within granitic and orthogneissic bedrock basalt normalized 0 45 m filtered stream water has ree patterns slightly depleted in the light ree la sm lree on the basalt plateau close to the source followed by a continuous amplification of this lree depletion downstream at the same time also a negative ce anomaly develops in the adsorbed fraction of 0 45 m particles which has been isolated by leaching with 1 m hcl strontium and neodymium isotope ratios of stream water demonstrate that the dissolved ree are essentially of basaltic origin even in the lower granitic and gneissic part of the catchment mixing with gneiss or granite derived ree thus cannot explain the observed evolution of the ree patterns our data suggest that the ree of the 0 45 m particles in contrast to earlier studies we found no link between ree behavior and organic colloids or organic complexes this scenario is confirmed by a detailed analysis of the ree patterns at 3 stream confluences the results show that the ree do not behave conservatively during mixing at stream confluences but that the lree and ce are preferentially removed similarly to what has been observed at catchment scale our study thus underlines the importance of fe colloids for the transport and fractionation of the ree in stream water

evolution of the slave craton greenstone belts in the slave craton represent the episodic accumulation of volcanic and sedimentary rocks over as much as 200 m y in the western craton volcanic and sedimentary rocks were deposited between 2 81 and 2 60 ga on 2 9 3 1 ga sialic basement not tectonically juxtaposed with it deposition of 2 6 ga turbidite and conglomerate sequences across the entire slave craton was synchronous with or followed by the main phase of regional deformation and metamorphism at 2 6 2 58 ga and final stabilization of the craton

the role of seamount volcanism in crustal construction at the mid atlantic ridge 24 30 n an analysis of approximately 6000 km2 of sea beam swaths indicates that the floor of the median valley of the mid atlantic ridge mar between 24 30 n is strewn with near circular volcanoes we have identified 481 seamounts in the height range 50 650 m because many of the features which appear to be seamounts do not meet our criteria fully they have not been counted and our numbers are likely a minimum estimate of the population the large abundance of seamounts on the median valley floor indicates that seamount volcanism plays an important role in the accretionary processes at this section of the mar the summit height distribution of the mar seamount population is consistent with the exponential frequency size distribution model for off axis eastern pacific seamounts jordan et al 1983 smith and jordan 1987 the model parameters for the mar population yield an average of about 195 seamounts per one thousand square kilometers and a characteristic height of about 60 m shape statistics compiled from the 481 seamounts give parameters that are exactly the same or cover the same range in values as those obtained from a study of pacific seamounts in the height range 140 3800 m smith 1988 implying a universal control on seamount construction based on the volcanic morphology we identify 18 spreading segments along the ridge all except two contain a prominent axial volcanic ridge many of the seamounts identified are associated with the axial ridges from the sea beam swaths we infer that the ridges are composed of piled up seamounts and hummocky flows and interpret them to be the primary sites of crustal construction this style of volcanism contrasts strongly with that observed at the east pacific rise where seamounts are virtually absent at the spreading axis the construction of seamounts and hummocky flows may be directly related to the fact that the mar is fed by magma chambers that are limited in size and frequency we suggest that small magma pockets with slow eruption rates produce seamounts either from pipes or initial fissure eruptions that collapse to construct a single edifice small magma bodies with somewhat higher eruption rates produce hummocky fissure fed flows using buoyancy arguments the heights of the mar seamounts are related to the depth of the magma bodies we hypothesize that small magma bodies rise buoyantly to the base of the hydrothermally cooled brittle lid where they are trapped and then erupt if this hypothesis is correct the thickness of the brittle lid controls seamount height and the exponential distribution of seamount summit heights implies that the thickness of the brittle hd follows an exponential distribution in time and space with characteristic thickness 1 4 1 9 km if seamounts and hummocky flows are fed each from their own discrete magma body trapped at the brittle ductile transition then the lower crust of the mar will be made up of the products of a multitude of small plutons

bubble migration and coalescence during the solidification of basaltic lava flows the initial size distribution of gas bubbles in lava flows is modified by bubble rise and coalescence during post eruptive cooling and crystallization a simple model which computes the effects of rise and coalescence accounts for observed features and may provide a means whereby the initial bubble size distribution can be inferred a model lava flow of assumed thickness viscosity and volume percentage of gas bubbles is given an initial bubble size distribution bubbles coalesce due to differences in their relative rise velocities using a gravitational collection kernel the process may be modeled by numerical integration of the stochastic collection equation which yields the change in the number density spectrum of the population from the number densities of all pairs of bubbles and their probabilities of collision bubbles rise and coalesce within a fluid interior sandwiched between fronts of crystallization that advance inward from top and bottom bubbles that are overtaken by the crystallization f

u pb zircon geochronology of the yellowknife volcanic belt nwt canada new constraints on the timing and duration of greenstone belt magmatism volcanic and sedimentary rocks in the slave province collectively termed the yellowknife supergroup have long been considered to represent laterally continuous and correlative stratigraphically coherent homoclinal sequences correlation based on the lithologic analysis of certain distinctive units has been most intensely applied to the yellowknife volcanic belt in the southern slave province u pb zircon data for seven samples collected from within the belt are reported here the distinctiveness of the townsite formation a term applied to three lenticles of rhyodacitic to dacitic tuffs breccias and pillowed flows in comparison to the overlying and underlying tholeiitic basalts kam group has led to its use as a key marker unit for stratigraphic correlations and palinspastic restorations of offsets on proterozoic faults in the area a sample from each of the three segments was collected for u pb zircon geochronology in addition numerous thinner tuffaceous beds from the kam group were also dated

new radiocarbon dates for columbian mammoth and mexican horse from southern alberta and the lateglacial regional fauna abstract new radiocarbon dates on columbian mammoth mammuthus columbi and mexican horse equus conversidens specimens from southern alberta are 10 930 100 bp and 10 870 45 years bp respectively older than originally thought these specimens are reviewed in the light of 10 other sites in southern alberta that have yielded large mammal remains radiocarbon dated to about 11 000 bp thus the regional fauna includes at least 11 mammalian species this fauna was not restricted to the foothills but extended well onto the plains and may prove useful in correlating foothills terraces with those of the plains

geomorphic imprint of landslides on alpine river systems southwest new zealand an inventory of 846 mass movements mainly landslides in two alpine regions of southwest new zealand was created to explore the geomorphic impacts of slope failure processes on river channels and valley floors in total 213 i e 27 per cent of the slope failures descended to valley floors affecting the geomorphology of trunk channels catchment area ac 10 km2 and valley floors in recurring patterns a nominal classification system is introduced for characterizing a the physical contact nature between landslides and river channels and b the resulting geomorphic consequences for drainage although landslide area a is useful for estimating the length of channel directly impacted by debris it does not necessarily predict the direction of fluvial response or type of impact dominant persistent geomorphic imprints of bedrock landslides include channel occlusions and landslide dams in south westland and fiordland respectively differences in size distribution and geomorphic effects on river systems between the two study regions are attributed to bedrock geology tectonics and sediment flux although south westland rivers are more frequently affected by landslides disrupting long term effects such as blockage are more persistent in fiordland copyright 2005 john wiley sons ltd

influence of tectonism and climate on lithofacies distribution and sandstone and conglomerate composition in the archean beaulieu rapids formation northwest territories canada abstract the 0 2 1 km thick archean beaulieu rapids formation is a late orogenic tectonically controlled sedimentary sequence overlying the beaulieu river volcanic belt unconformably on the west and bordering the major n trending beniah lake fault on the east local porphyry stocks characteristic of late orogenic successions were emplaced along strike of the fault four lithofacies comprise the beaulieu rapids formation 1 the 20 320 m thick conglomerate i 2 the 10 305 m thick siltstone sandstone 3 the 20 120 m thick conglomerate ii and 4 the 40 320 m thick quartz rich sandstone lithofacies stacking displays two distinct large scale fining upward sequences represented by the 300 375 m thick conglomerate i and sandstone siltstone sequence a and the 300 400 m thick conglomerate ii and quartz rich sandstone sequence b fining upward sequences a bounding unconformity and the beniah lake fault are compelling indicators of tectonic influence on sedimentation conglomerate i was deposited by debris flows traction currents and sheetfloods on the proximal medial and distal portions of alluvial fans or fan deltas respectively the overlying siltstone sandstone contains two distinct lithological units a sandstone dominated unit formed from fluvial dune migration and overbank deposition in a sandy braidplain setting with scattered ponds whereas sedimentary structures in the siltstone dominated unit are consistent with lacustrine deposition a second phase of tectonic uplift produced sequence b conglomerate ii was deposited in a proximal braided stream setting characterized by abundant longitudinal gravel bars the quartz rich sandstone developed from dune migration on a sandy braidplain mineralogy and textures reflect high sediment influx limited transport distance local sources and climatic influence clast populations in conglomerate indicate a prevalent mafic volcanic source whereas sandstones contain prominent quartz av 76 with subordinate feldspar 13 and lithic fragments 11 the disparity between clast and sandstone composition is a function of chemical weathering typical of a humid climate source areas are restricted to the mafic dominated beaulieu river volcanic belt the 2 8 ga gneisso plutonic sleepy dragon complex and fault related porphyry stocks the humid weathering aggressive archean climate was responsible for destroying labile minerals and lithic fragments in proximal source rocks rich in plagioclase accounting for the high quartz component in the sandstones the beaulieu rapids formation is similar to modern strike slip basins that form along major fault zones in terms of basin geometry faulted and unconformable contacts lithological units and sedimentary facies stacking and organization fault controlled basins of this nature commonly develop during the last stage of terrane accretion on archean cratons

paradigms and proboscideans in the southern great lakes region usa abstract thirteen new chronometric dates for illinois proboscideans are considered in relation to well dated pollen records from northeastern and central illinois these dates span an interval from 21 228 to 12 944 cal bp when compared to pollen spectra it is evident that mammut americanum inhabited spruce picea and black ash fraxinus nigra forest during the bolling allerod 14 700 12 900 cal bp and early younger dryas 12 900 11 650 cal bp chronozones both mammuthus jeffersonii and mammuthus primigenius inhabited spruce dominated open woodland during the oldest dryas chronozone while m primigenius persisted in a forest of predominantly black ash during the allerod chronozone a newly discovered specimen from lincoln il clarifies the taxonomic distinction between m primigenius and m jeffersonii hitherto a paradigm of proboscidean succession during the full to late glacial periods was based on the vegetation succession of steppe tundra like vegetation to spruce forest to spruce deciduous forest the presumed proboscidean succession was that of cold dry steppe adapted m primigenius succeeded by more mesic tolerant m jeffersonii that in turn was succeeded by the wet forest adapted m americanum reported data do not support this view and indicate a need for re evaluation of assumptions of proboscidean ecology and history e g the environmental tolerances and habits of m primigenius in regions south of 55 n and its dynamic relationship with other proboscidean taxa

rare earth elements ree and yttrium in stream waters stream sediments and fe mn oxyhydroxides fractionation speciation and controls over ree y patterns in the surface environment we have collected 500 stream waters and associated bed load sediments over an 400 km 2 region of eastern canada and analyzed these samples for fe mn and the rare earth elements ree y in addition to analyzing the stream sediments by total digestion multi acid dissolution with metaborate fusion we also leached the sediments with 0 25 m hydroxylamine hydrochloride in 0 05 m hcl to determine the ree y associated with amorphous fe and mn oxyhydroxide phases we are thus able to partition the ree into dissolved 0 45 lm labile hydroxylamine and detrital sediment fractions to investigate ree fractionation and in particular with respect to the development of ce and eu anomalies in oxygenated surface environments surface waters are typically lree depleted la sm nasc ranges from 0 16 to 5 84 average 0 604 n 410 where the ree are normalized to the north america shale composite have strongly negative ce anomalies ce ce nasc ranges from 0 02 to 1 25 average 0 277 n 354 and commonly have positive eu anomalies eu eu nasc ranges from 0 295 to 1 77 average 0 764 n 84 in contrast the total sediment have flatter ree y patterns relative to nasc la sm nasc ranges from 0 352 to 1 12 average 0 778 n 451 and are slightly middle ree enriched gd yb nasc ranges from 0 55 to 3 75 average 1 42 most total sediments have negative ce and eu anomalies ce ce nasc ranges from 0 097 to 2 12 average 0 799 and eu eu nasc ranges from 0 39 to 1 43 average 0 802 the partial extraction sediments are commonly less lree depleted than the total sediments la sm nasc ranges from 0 24 to 3 31 average 0 901 n 4537 more mree enriched gd yb nasc ranges from 0 765 to 6 28 average 1 97 and ce and eu anomalies negative and positive are more pronounced the partial extraction recovered on average 20 of the fe in the total sediment 80 of the mn and 21 29 of the rees ce 19 and y 32 comparison between rees in water partial extraction and total sediment analyses indicates that rees y in the stream sediments have two primary sources the host lithologies i e mechanical dispersion and hydromorphically transported the labile fraction furthermore eu appears to be more mobile than the other ree whereas ce is preferentially removed from solution and accumulates in the stream sediments in a less labile form than the other rees y despite poor statistical correlations between the rees y and mn in either the total sediment or partial extractions based on apparent distribution coefficients and the ph of the stream waters we suggest that either sediment organic matter and or possibly d mno2 feooh are likely the predominant sinks for ce and to a lesser extent the other ree in the stream sediments

mammoths in our midst the proboscideans of anza borrego desert state park southern california usa abstract anza borrego desert state park abdsp has an exceptional proboscidean fossil record the remains of gomphotheriidae and elephantidae span over 10 ma and encompass over eighty productive sites the most numerous of the proboscideans are the mammoths significant specimens include one of the youngest gomphotherium and the most complete skeleton of mammuthus meridionalis in north america over 6 km of fossiliferous sediments spans the miocene pliocene and pliocene pleistocene boundaries and provides a continuous record of changing environments over 550 taxa of aquatic and terrestrial plants marine and lacustrine invertebrates and marine fresh water and terrestrial vertebrates are represented present are both asian and south american immigrant mammals m meridionalis and m columbi m imperator regionally co existed here a specimen from the diablo formation extends the temporal range of gomphotherium in north america nearly one million years into the middle blancan

camel fossils from gravel pits near edmonton and vauxhall and a review of the quaternary camelid record of alberta camelid remains are known from several quaternary palaeontological localities in alberta yet most specimens are undescribed in the literature specimens reported here comprise a large sample of the known camelid record from the province and provide further insight into the record of quaternary megafauna of western canada remains from the edmonton area include specimens pre and post dating the last glacial maximum lgm whereas remains from the vauxhall area are post lgm a metapodial fragment of a giant camel originally described as titanotylopus from the edmonton area is likely from earlier in the pleistocene or late pliocene camelid remains are not overly abundant in alberta but are widely distributed having been recovered from several sites across the province a new radiocarbon date of 11 280 40 14c years bp on a radioulna of camelops cf c hesternus represents only the fourth direct age assessment of a quaternary camelid from alberta radiocarbon data may suggest linkages to patterns of ext

magmatic processes at superfast spreading mid ocean ridges glass compositional variations along the east pacific rise 13 23 s major and minor element analyses of 496 natural volcanic glass samples from 141 locations along the superfast spreading 150 mm yr east pacific rise epr 13 23 s and near ridge seamounts comprise 212 chemical groups we interpret these groups to represent the average composition of individual lava flows or groups of closely related flows groups slightly enriched in k2o t morb are distributed variably along the axis in contrast to the galapagos spreading center where t morb are extremely rare this result is consistent with the interpretation that t morb magmas arise from low melting temperature k rich heterogeneities in the subaxial epr mantle the galapagos spreading center which is migrating to the west in an absolute reference frame is underlain by mantle previously processed and depleted in the t morb component during melting events giving rise to earlier epr magmas excluding t morb there are nearly monotonic twofold increases in k ti and k p of axial lavas from 23 s to 13 s from 22 s to 17 s these gradients correlate with isotopic ratios but north of 17 s there is a reversal of isotopic gradients indicating recent decoupling of the isotopic and minor element ratios in the subaxial mantle a strong southward increase in degree of differentiation for approximately 200 km north of the large offset at 20 7 s correlates with a gradient in bathymetry consistent with previous interpretations that this offset is propagating to the south samples from recently abandoned ridges associated with this dueling propagator mainly carry the distinctive evolved fractionation signatures of rift propagation suggesting that propagating rift tips have been abandoned preferentially to failing rift tips glass compositional variations south of this offset are consistent with rift failure on the southern limb within 40 km of the offset and possibly also south of 22 s the latter region may be affected by deformation accompanying northward growth of the easter microplate near ridge seamounts on the pacific plate between 18 19 s comprise two distinct populations those aligned approximately parallel to the spreading direction are extremely variable in major element composition but consistently enriched in sr relative to nearby axial lavas smaller seamounts aligned approximately parallel to the direction of absolute plate motion are uniformly depleted in minor elements and sr relative to axial lavas the degree of differentiation of axial lavas between 18 19 s can be related to the structural development of the rift axis and or vigor of hydrothermal activity of individual segments glass compositional variations indicate that magmatic segmentation occurs on several different scales at the superfast spreading rate of this area primary magmatic segmentation mainly reflects mantle source variations the boundaries of which correlate with the largest physical offsets in the rise axis between the easter microplate and garrett transform zone a secondary magmatic segmentation defined by the along axis continuity of similar parental magma compositions or liquid lines of descent occurs with a length scale varying from 11 to 185 km with an average of 69 57 1 km the boundaries of these segments mainly occur at overlapping spreading centers all first second and third order physical offsets correspond to secondary magmatic segment boundaries but some secondary magmatic segment boundaries also occur at small fourth order ridge axis discontinuities the secondary magmatic segments define the length scale of mantle melting variations mainly variations in extent of melting but not the scale of melt extraction processes that feed the axis this scale must be smaller than that of the secondary magmatic segments and probably corresponds to the length scale of fourth order physical discontinuities along axis there is a good positive correlation of average secondary magmatic segment length with spreading rate for four well sampled areas varying from 20 to 150 mm yr secondary magmatic segments also become more variable in axial length with increasing spreading rate the average lengths of secondary magmatic segments are smaller than those predicted by gravitational instability considerations at all spreading rates superposed on the axial magmatic segmentation are variations reflecting subaxial magmatic temperature defined by extent of magmatic differentiation which bears little systematic relation to physical or other kinds of magmatic segmentation at 13 23 s the length scale of this variation is 217 60 1 km approximately corresponding to the wavelength of rolls in the gravity field observed off axis taken together the various kinds and scales of magmatic variations observed for this superfast spreading ridge suggest that regional temperature of the upwelling asthenosphere magma supply to the axis and crustal magmatic temperature reflect independent regionally decoupled processes

a miocene island arc volcanic seamount the takashibiyama formation shimane peninsula sw japan abstract the miocene volcanic complex of the takashibiyama formation consists largely of subalkali subaqueous basalt to andesite lavas and andesite to dacite subaqueous volcaniclastic flow deposits most of subaqueous lavas are moderately to intensely brecciated with rugged rough surfaces and ramp structures similar to subaerial block lava volcaniclastic flow deposits commonly include basalt to andesite lava fragments and or pyroclastic materials and are similar in internal features to debris flow and turbidite deposits subaqueous block lavas and minor pillow lavas form volcanic piles above the vents being flanked or covered with volcaniclastic flow deposits each volcanic pile is several kilometers wide and several hundred meters thick and overlaps one after another as the major eruptive center migrates from time to time thus the volcanic complex comprises three or more superimposed volcanic piles which are intruded by basalt to andesite dikes and sills and are underlain by mafic to intermediate large hypabyssal to plutonic bodies hydrothermal alteration occurs in places but especially concentrates in the lower part of the volcanic complex after the cessation of opening of the japan sea the volcanic complex started to erupt in a middle bathyal environment on the japan sea side and became emergent as it grew to a thickness over 1500 m during 4 m y under a n s trending horizontal compressional stress it is a volcanic seamount probably in a typical island arc setting

solidification and morphology of submarine lavas a dependence on extrusion rate the results of recent laboratory experiments with wax extruded beneath relatively cold water may be extrapolated to predict the surface morphology of submarine lavas as a function of the extrusion rate and melt viscosity the experiments with solidifying wax indicated that the surface morphology was controlled by a single parameter the ratio of the time taken for the surface to solidify and a time scale for lateral flow for submarine basalts a solution of the cooling problem which is dominated by conduction in the lava but convective heat transfer in the water and estimates of lava viscosities place this parameter within the empirically determined pillowing regime over a wide range of extrusion rates this result is consistent with the observation that pillow basalts are the most common products of submarine eruptions smoother surfaces corresponding to the various types of submarine sheet flows are predicted for sufficiently rapid extrusions of basaltic magma still higher eruption rates in regions of low topographic relief may produce submarine lava lakes minimum emplacement times can be calculated for submarine volcanic constructs of a single lava flow type

the slave province a distinct archean craton the slave province is a relatively small late archean craton that exhibits distinctive rock associations and structures by comparison with the much larger superior province differences are evident in i the abundance of sedimentary versus volcanic rocks and of felsic versus mafic volcanic rocks ii the greater evidence for sialic basement iii the higher proportion of more evolved potassium rich granite iv the type setting and timing of gold and base metal mineralization and v a regional zonation of gold deposits that seems to be a unique feature of the slave province contrasts in structure are also significant the large scale linear belts and boundaries sutures that characterize the superior province have no obvious counterpart in the slave province despite some similarities with other archean cratons the distinct features of the slave province are important for they imply that no single archean craton should be used to develop a universal paradigm for the genesis and tectonic evol

lava flows from a mid 1980s submarine eruption on the cleft segment juan de fuca ridge a series of lava flows with a total volume of 0 05 km3 were erupted in the mid 1980s along 17 km of the northern cleft segment of the juan de fuca ridge observations from camera tows and submersible dives show that the new flows are all similar in appearance and consist entirely of pillow lava with a mixture of smooth and striated surface textures suggesting a relatively uniform eruption rate approaching 1 m3 s at point source vents the flows vary in size from small patches to large steep sided ridges and were probably erupted from a dike intruded along the ridge axis because they are aligned along a linear fissure graben system observations at north cleft show that the physical appearance of new flows changes more rapidly than previously realized and that earlier qualitative dating of young lavas based on sediment cover and glassy surface texture were probably overestimates by an order of magnitude sediment accumulation on the lavas is quite variable and locally surprisingly substantial mainly due to hydrothermal deposits that formed while the lava flows were cooling biological vent communities photographed on the new flows in 1989 show that vent animals can colonize new vent sites rapidly but that warm water was still venting only in a few places nonvent animals are much slower to colonize the new flows and rates of colonization observed at north cleft may be useful for making improved age estimates of young 10 years lava flows elsewhere the north cleft eruption represents about 2 of the estimated average annual volcanic output along the global mid ocean ridge implying that many other submarine eruptions are occurring undetected

description of fossil muskoxen and relative abundance of pleistocene megafauna in central alberta significant work has gone into describing ice age faunas from alberta but relatively little work has been dedicated to understanding the actual structure of quaternary faunal assemblages in the province development of such a data set is necessary to fully understand differences in faunal assemblages that existed before and after the last glacial maximum and may eventually provide an important historical perspective for understanding the impact of large scale ecosystem disturbance muskoxen fossils from central alberta were examined to differentiate specimens of bootherium and ovibos those remains along with other fossils of pleistocene megafauna collected from gravel deposits near edmonton were used to examine patterns of relative abundance from both pre and postglacial maximum time periods relative abundance for genera of pleistocene megafauna was calculated using the number of individual specimens nisp from 11 individual localities i e gravel pits in central alberta preglacial localities with statistically significant numbers of specimens n 30 are dominated by horse equus mammoth mammuthus and bison bison are common but other megafauna such as jefferson s ground sloth megalonyx jeffersoni and yesterday s camel camelops hesternus are comparatively rare current data for the postglacial fauna indicate a shift in which bison becomes the most abundant large herbivore on the landscape a pattern observed in other parts of north america

a single late wisconsin laurentide glaciation edmonton area and southwestern alberta the absence of igneous and metamorphic clasts of canadian shield origin in the saskatchewan gravels and sands preglacial valley fills in seven active gravel pits studied over a 5 yr period coupled with 29 radiocarbon dates 21 300 42 910 yr b p suggest that laurentide glaciation prior to the late wisconsin did not reach the edmonton area on the basis of edmonton9s elevation 670 m above sea level asl compared to higher regional elevations to the south calgary 1060 m asl and maps of the retreat pattern of late wisconsin laurentide ice which we equate approximately with advance pattern it is likely that large areas of higher elevation in alberta south and west of edmonton only underwent the late wisconsin event not multiple glaciations

dental variation in the molars of mammuthus columbi var m imperator proboscidea elephantidae from a mathis gravel quarry southern texas abstract a large sample n 149 of mammuthus columbi molars was excavated from a gravel quarry of rancholabrean north american land mammal age nalma near mathis san patricio county in southern texas this attritional assemblage which also includes xenarthra equidae camelidae cervidae and bovidae was recovered from fluvial point bar deposits standard mammoth dental measurements and metrics enamel thickness plate width plate number and lamellar frequency from a minimum of 25 individuals vary widely the number of plates in the tooth pn is the most reliable measurement in the identification of the molar to the species level enamel thickness and lamellar frequency suggest that the mathis sample represents a local population of mammuthus columbi that approaches molar morphologies found in irvingtonian nalma populations usually placed in m imperator

variation in peperite textures associated with differing host sediment properties peperites formed by mixing of magma and wet sediment are well exposed along punta china baja california mexico where two sills intrude a section of lava flows limestones and volcaniclastic rocks irregular lobes and dikes extend from the sills several meters into host sediments including highly comminuted flow top breccias lithic lapilli tuff breccias and shelly micrites whereas intrusive contacts with lava flows are sharp and planar where one sill intruded both coarse grained volcaniclastic rock and fine grained limestone textural differences between the hosts produced strikingly different styles of peperite blocky masses of the basaltic intrusions up to 1 m in size were dispersed for distances up to 3 m into host lithic lapilli tuff breccias the blocks consequently underwent in situ fragmentation as they were rapidly quenched the high degree of dispersion resulted from steam explosions as the magma enveloped pockets of water in the coarse grained permeable host elutriation of fine grained material from vertical pipes in tuff breccia above the lower sill provides evidence for meter scale fluidization of the host the contact zone between the basaltic magma and the shelly micrite host resembles a mixture of two viscous immiscible fluids fluidal peperite intrusion occurred behind a stable vapor film which entrained lime mud particles and carried them off grain by grain as magma advanced into the host thin section scale elutriation pipes formed microglobular peperite represents a frozen example of a fuel coolant interaction fci between basaltic magma and fluidized micrite host the intimate intermixing of magma and host at the submillimeter level is attributed to fluid instabilities developed along the magma vapor host interface such intimate intermixing of magma and water bearing fragmental debris is commonly a precursory step toward explosive hydrovolcanism

a new look at the stratigraphy of the yellowknife supergroup at yellowknife n w t implications for the age of gold bearing shear zones and archean basin evolution based on recent detailed mapping a revised stratigraphic column is proposed for the rocks of the archean yellowknife supergroup in the yellowknife greenstone belt the mafic volcanic rocks of the kam formation previously thought to represent the oldest supracrustal rocks of the belt overlap remnants of an earlier volcanic sedimentary sequence here referred to as the octopus formation as its enormous thickness makes it too unwieldy to be described as a single formation the kam formation is raised to group status and subdivided into four formations it is proposed that the kam group should replace the beaulieu group in the yellowknife area the chan formation at the base of the kam group consists of multiple gabbroic intrusions that were emplaced into a carapace of pillowed flows the intrusions locally resemble sheeted mafic dyke complexes in phanerozoic ophiolites thought to represent evidence for sea floor spreading the crestaurum formation which overlies the chan formation is characterized b

a felsic dyke swarm formed under the sea the archean hunter mine group south central abitibi belt quebec canada an extensive rhyolitic dyke swarm has intruded subaqueous pyroclastic deposits iron formations hyaloclastite breccias and lava flows of the 2730 ma hunter mine group hmg in the south central part of the archean abitibi belt quebec the dyke swarm has a minimum width of 500 m and can be traced perpendicular to the section for 2 4 km based on crosscutting relationships chilled margins quartz content and colour five distinct dyke generations have been established each dyke generation has several magmatic pulses as indicated by parallel rows of columnar joints absence of brecciation between parallel rows suggests extremely brief intervals between magma pulses the central parts of most dykes display inverted v shaped patterns of columnar joint convergence inferred to indicate differential cooling during the late stages of dyke propagation the dykes commonly display delicate spherulites suggesting rapid cooling solidification temperatures between 400 and 600 c and penecontemporaneous devitrification quartz feldspar aggregates in the groundmass have locally developed microgranophyric textures large spherulites near the chilled margins probably formed at temperatures below 400 c percolation of abundant water throughout the dyke complex is suggested by ubiquitous prominent chilled dyke margins development of a chilled margin 500 m along one dyke suggests that water percolated at least 500 m below the water rock interface because the dykes intruded subaqueous pyroclastic deposits of similar composition dyke emplacement below the sea floor is inferred interstratification of pillowed flows and brecciated pillowed flows containing rhyolite fragments at the top of the 4 5 km thick sequence indicates that the central felsic complex probably never emerged during its evolutionary history supporting the contention that the felsic dyke complex was emplaced beneath the archean sea floor

major ion chemistry of the yarlung tsangpo brahmaputra river chemical weathering erosion and co2 consumption in the southern tibetan plateau and eastern syntaxis of the himalaya the yarlung tsangpo brahmaputra river drains a large portion of the himalaya and southern tibetan plateau including the eastern himalayan syntaxis one of the most tectonically active regions on the globe we measured the solute chemistry of 161 streams and major tributaries of the tsangpo brahmaputra to examine the effect of tectonic climatic and geologic factors on chemical weathering rates specifically we quantify chemical weathering fluxes and co2 consumption by silicate weathering in southern tibet and the eastern syntaxis of the himalaya examine the major chemical weathering reactions in the tributaries of the tsangpo brahmaputra and determine the total weathering flux from carbonate and silicate weathering processes in this region we show that high precipitation rapid tectonic uplift steep channel slopes and high stream power generate high rates of chemical weathering in the eastern syntaxis the total dissolved solids tds flux from the this area is greater than 520 tons km 2 yr 1 and the silicate cation flux more than 34 tons km 2 yr 1 in total chemical weathering in this area consumes 15 2 10 5 mol co2 km 2 yr 1 which is twice the brahmaputra average these data show that 15 20 of the total co2 consumption by silicate weathering in the brahmaputra catchment is derived from only 4 of the total land

comparative volcanology of small axial eruptive centers in the mark area we describe selected examples of small volcanic features identified during ocean drilling program odp site surveys in the mark area for which additional observations and sample data have been obtained by manned submersible and or drilling based on both morphologic relations and similarities in chemistry and petrography serocki volcano the site of bare rock drilling on odp legs 106 and 109 appears to be a flat topped megatumulus a large rootless vent developed on a lava flow originating from an adjacent cone located above the true eruptive fissure a linear set of five apparent volcanic centers on the east side of the median valley the eastmark cones differ from one another in morphology and degree of tectonic degradation they formed at different times and from different vents but all were localized by damming of the flows against the steep walls of the linear valley containing them the two northernmost features are probably megatumuli at the terminal ends of lava flows descending the valley walls the other three vents are cones with breached craters and probably were more recently erupted in situ the snakepit hydrothermal area is located near the highest and widest part of a 35 km long ridge that appears to be a major relatively young fissure eruption the associated lavas are among the geochemically most primitive in the mark area but have their counterparts in several subsets of lavas associated with serocki volcano in spite of the morphologic contrasts and large geographic separation between the two features we conclude that a volcano like form geographic proximity and conformance to a linear geometry do not guarantee compositional or temporal coherence nor is the alignment of apparent volcanic centers a reliable guide to underlying tectonic patterns the chemistry and petrography of the serocki and eastmark basalts resemble older adjacent lavas and also conform to subtle along ridge variations this and the relatively old appearance of their flow surfaces indicate that these lavas represent the waning stage of an older magmatic event the more recent eruptions in the snakepit area seem to reflect a renewed influx of the same relatively primitive and presumably hotter magma that initiated the serocki eruptions residual pockets of this hotter magma in the shallow crust may provide the heat that drives the present hydrothermal system

legacy impacts of acid sulfate soil runoff on mangrove sediments reactive iron accumulation altered sulfur cycling and trace metal enrichment abstract the off site impacts of iron rich acidic runoff from drained acid sulfate soils ass on the geochemistry of estuarine sediments are relatively poorly constrained in this study we examine the geochemistry of intertidal zone mangrove sediments and porewaters from an estuarine tributary that received 15 20 years of acute ass drainage compared to adjacent control sites mixing of acidic iron rich ass drainage waters with circumneutral ph estuarine waters drove precipitation of fe iii floc and has led to significant localized accumulation of reactive fe species fer 1 m hcl and citrate buffered dithionite extracts up to 4200 mol g 1 as well as significantly elevated porewater fe2 1000 m in ass impacted sediments x ray diffraction indicates that goethite lepidocrocite and ferrihydrite are important fe iii minerals in surficial sediments at ass impacted sites the abundant fer is shifting the equilibrium of reduced inorganic sulfur ris mineral formation pathways towards accumulation of s 0 and acid volatile sulfide avs species and is buffering porewater s ii to low concentrations in contrast ris speciation at the control sites is dominated by pyrite scr and porewater s ii is present some porewater metals i e al mn cu cr are significantly elevated at sites proximal to the source of ass drainage compared to control sites abundant fer also provides a substrate for sorption and accumulation of metals and correspondingly there is significant relative enrichment of reactive metal fractions 1 m hcl extractable in sediments at the ass impacted sites with al mn u cu cr ni this study demonstrates that ass drainage which causes accumulation of reactive fe in mangrove environments can substantially influence sediment biogeochemistry by altering reduced inorganic sulfur cycling and enhancing the availability of some trace metals

field relations u pb geochronology and sm nd isotope geochemistry of the point lake greenstone belt and adjacent gneisses central slave craton n w t canada data from the point lake area central slave craton suggest an intimate tectonic and paleogeographic association between volcano sedimentary supracrustal rocks and adjacent gneisses granite plutons and orthogneisses yield u pb zircon crystallization ages ranging from ca 3230 to 2818 ma numerous mafic dykes cut the gneisses and two have been dated by u pb zircon geochronometry at 2673 3 and 2690 3 ma ages similar to those of volcanic rocks in the point lake greenstone belt although high strain zones form the greenstone gneiss in most places a structural repetition of granite about 4 km east of keskarrah bay is cut by numerous mafic dykes and apparently overlain depositionally by pillow basalt mafic volcanic and plutonic rocks from point lake have initial 2 7 ga end values ranging from about 2 2 to 6 3 significantly lower than the depleted mantle at that time the nd data suggest either derivation from a more isotopically evolved reservoir or assimilation of crust similar to the granit

the role of the early tertiary ulukisla basin southern turkey in suturing of the mesozoic tethys ocean the maastrichtian late eocene ulukisla basin is representative of the tectonic and sedimentary evolution of prominent early tertiary basins in central anatolia including the tuzgolu and arkisla basins the ulukisla basin overlies an ophiolitic melange of late cretaceous age between the bolkar carbonate platform to the south and the nigde kirsehir metamorphic massif to the north the basin stratigraphy records successive phases of transgression subsidence volcanism evaporite deposition deformation and uplift subsidence curves are consistent with an extensional or transtensional basin origin terminated by uplift the ulukisla basin includes a thick succession c 2 km of upper paleocene lower eocene basaltic to andesitic submarine pillow lavas lava flows volcaniclastic rocks and intercalated limestones whole rock xrf chemical analysis indicates a within plate origin with a marked subduction influence believed to be inherited rather than contemporaneous the ulukisla basin formed after late cretaceous ophiolite and melange emplacement and ended with late eocene emergence deformation and onset of oligo miocene non marine deposition we propose that late cretaceous ophiolite and melange emplacement reflect initial ocean basin closure this was followed by a long period c 30 ma of microcontinental adjustment including possible strike slip palaeorotation and suture tightening during which the early tertiary ulukisla basin developed possible driving forces were regional slab pull of a relict subduction zone or oblique diachronous convergence suture tightening was complete by late eocene time marked by collisional deformation and regional uplift

controls on valley width in mountainous landscapes the role of landsliding and implications for salmonid habitat a fundamental yet unresolved question in fluvial geomorphology is what controls the width of valleys in mountainous terrain establishing a predictive relation for valley floor width is critical for realizing links between aquatic ecology and geomorphology because the most productive riverine habitats often occur in low gradient streams with broad floodplains working in the oregon coast range western united states we used airborne lidar to explore controls on valley width and couple these findings with models of salmon habitat potential we defined how valley floor width varies with drainage area in a catchment that exhibits relatively uniform ridge and valley topography sculpted by shallow landslides and debris flows in drainage areas 0 1 km 2 valley width increases as a power law function of drainage area with an exponent of 0 6 consequently valley width increases more rapidly downstream than channel width exponent of 0 4 as derived by local hydraulic geometry we used this baseline valley width drainage area function to determine how ancient deep seated landslides in a nearby catchment influence valley width anomalously wide valleys tend to occur upstream of and adjacent to large landslides while downstream valley segments are narrower than predicted from our baseline relation according to coho salmon habitat potential models broad valley segments associated with deep seated landsliding resulted in a greater proportion of the channel network hosting productive habitat because large landslides in this area are structurally controlled our findings indicate a strong link between geologic properties and aquatic habitat

new field and laboratory evidence for the origin of hyaloclastite flows on seamount summits new field observations with the submersible alvin and photographic evidence from a study of the summits of seamounts near the east pacific rise show that hyaloclastite deposits occur commonly hyaloclastite outcrops were found on six volcanoes at depths from 1240 to 2500 m these new observations plus laboratory study of new hyaloclastite specimens extend the results of previous studies most of the hyaloclastite samples are of hydrovolcanic eruptive origin but a few show evidence of a predominantly sedimentary origin primarily from morphology we identify several vent areas from which hyaloclastite presumably erupted the surface appearance of the hyaloclastite deposits varies with distance to these vents leading us to propose a facies model for deep sea hyaloclastites on seamount summits hyaloclastites of hydromagmatic origin exhibit weak normal grading and bedding parallel alignment of platy shards they consist of blocky sliver and fluidal basalt glass shards and lithics in a matrix that contains pelagic sediment the shards themselves are remarkably free of even the tiniest crystals and are usually chemically homogeneous we propose that the shards form mainly by cooling contraction granulation but cannot rule out the possibility of limited steam explosivity hyaloclastites are closely associated with submarine pahoehoe and we propose that a very rapid eruption rate promoting clastic dominated versus flow dominated eruptive behavior is the dominant control on hyaloclastite formation we propose that shard formation occurs during submarine lava fountaining gravitational instability of the resulting slurry of shards sea water and possibly steam causes gravity flow that carries the shards outward from the vent further field and modelling studies are needed to test these ideas and more quantitatively constrain the ascent mechanism eruption dynamics and deposition of deep sea hyaloclastites

chemical denudation and silicate weathering in himalayan glacier basins batura glacier pakistan original article can be found at http www sciencedirect com science journal 00221694 copyright elsevier b v doi 10 1016 s0022 1694 02 00036 7 full text of this article is not available in the uhra

lithofacies of deep marine basalts emplaced on a jurassic backarc apron baja california mexico basalts of the mid jurassic gran canon formation cedros island mexico were emplaced on a volcani clastic apron in a deep marine backarc basin elongate pillows and lava tubes as well as paleocurrent data from the volcaniclastic apron indicate a southward regional paleoslope away from the island arc source basalts emplaced on relatively proximal parts of the apron are nearly entirely pillowed and have thick flow units with mega pillows basalts on distal parts of the apron about 15 to 20 km down paleo current are dominated by pillow fragment breccias flow foot rubble and individual lava flows are generally thin with small pillows suggesting that the distal ends of lava flows erupted upslope are represented these distal flow fronts however are interstratified with features that typically form close to a vent including thick massive to mega pillowed lavas and lava tubes up to 8 m in diameter it is inferred that a fissure or system of fissures extended from the arc into the backarc basin

pleistocene mammals of the edmonton area alberta part i the carnivores late pleistocene fossils have been recovered sporadically in the edmonton area in central alberta for many years but there has been little work in determining their age fossils from quarries in north saskatchewan river terraces and buried valley gravels are recognized as late pleistocene mid wisconsinan and early holocene taxa and numerous 14c dates on mammalian remains now support the assessment the mammalian fauna consists of at least 16 taxa including mostly grazing herbivores but also three carnivores canis cf canis lupus gray wolf arctodus simus giant short faced bear and panthera leo atrox pleistocene lion the carnivores are first records for the region and arctodus is a first record for alberta

morphology and distribution of lava flows on mid ocean ridges a review abstract both pillow lavas and sheet flows are important features of oceanic volcanism at mid ocean ridges submersible surveys of the neovolcanic zone and off axis areas of these complex seafloor volcanic terrains conducted during the past two decades have uncovered a wide array of basaltic surface forms with pillow basalts displaying bulbous spherical and elongate tubular patterns and sheet flows exhibiting smooth lobate rippled wrinkled ropy whorly hackly and jumbled configurations the genesis of pillow lavas and sheet flows appears to be coupled to variations of spreading rates within the plate boundary zone while pillow lavas predominate at slow spreading centers i e mid atlantic ridge sheet flows prevail along the active volcanic zones at intermediate i e galapagos rift and juan de fuca ridge fast and superfast i e east pacific rise spreading centers yet both types of flows are present at each setting the distribution of pillow lavas and sheet flows along a ridge segment is related to the topographic gradient of the ridge axis hence the formation of sheet flows tends to be favored by the development of topographic highs between ridge segment boundaries where the crustal lid is thinnest and rifting directly taps the underlying magma chamber fissure eruptions here release copious amounts of surface fed fluid lavas which decrease in volume down the topographic gradient away from the bathymetric high of the ridge segment lava flows become more distal and channelized thereby fostering greater concentrations of tube fed pillow flows toward the segment boundaries the type of lava flow morphologies encountered at any specific site on the seafloor is contingent upon the effusion rate cooling rate and slope as demonstrated by laboratory simulations

morphological and sedimentological characteristics of the neogene submarine coherent lavas and hyaloclastites in southwest hokkaido japan abstract the neogene formations in southwest hokkaido japan are mostly composed of submarine volcanic products such as submarine coherent lavas and hyaloclastites associated with feeder dikes this paper presents criteria for recognition of submarine effusion products through description of the morphological and sedimentological characteristics of coherent lavas such as pillow lobes sheet flow lava lobes and pseudo pillow lavas and hyaloclastites and feeder dikes and a small amount of associate pyroclastic rocks

seamount formation and associated caldera complex and hydrothermal mineralization in ancient oceanic crust troodos ophiolite cyprus abstract the inter graben zone between the solea and mitsero grabens in the northern part of the troodos ophiolite cyprus displays igneous tectonic and physiographic features that are characteristic of seamount volcanism at modern oceanic spreading centers in this zone the 200 m high alestos hill volcanic edifice consisting of pillow lavas with preserved lava tubes and cone sheet intrusions is interpreted to have developed as a seamount fed by a late stage off axis shallow level gabbroic pluton that was intrusive into young oceanic crust concentric cone sheet intrusions and associated faults and shear zones in and around the alestos hill seamount collectively form a seafloor caldera complex which probably formed during the extrusion of lavas and subsequent cauldron subsidence over the gabbroic pluton the ene trending elongated massive sulfide ore deposit formation in the alestos memi area represents a focused upflow zone for hydrothermal fluids driven by the same off axis gabbroic intrusion responsible for formation of the alestos hill seamount the ene trending and up to 150 m wide alestos memi fault zone dissects the elongated ore body in a dextral sense and might have provided a high permeability conduit in the upper crust for upwelling hydrothermal flow at the time of magmatism the geometry of this fault zone and its kinematic relations with a n s striking alestos forest normal fault in the west are suggestive of its transfer fault origin reminiscent of mineralized transfer faults found at the mid atlantic ridge the active tag hydrothermal mound with massive sulfide deposits that is located on a small volcanic dome 3 km off axis and along a transfer fault in the trans atlantic geotraverse tag area at 26 n provides a modern analogue for the alestos hill seamount and associated faulting and mineralization in the ancient oceanic crust of the troodos ophiolite these findings indicate that off axis magmatism played a major role in crustal accretion hydrothermal alteration and ore mineralization during the late stage evolution of the troodos ophiolite

a pliocene shoaling basaltic seamount ba volcanic group at rakiraki fiji abstract at rakiraki in northeastern viti levu the pliocene ba volcanic group comprises gently dipping pyroxene phyric basaltic lavas including pillow lava and texturally diverse volcanic breccia interbedded with conglomerate and sandstone three main facies associations have been identified 1 the primary volcanic facies association includes massive basalt flows and sills pillow lava and related in situ breccia pillow fragment breccia autobreccia in situ hyaloclastite peperite 2 the resedimented volcaniclastic facies association consists of bedded monomict volcanic breccia and scoria lapilli rich breccia 3 the volcanogenic sedimentary facies association is composed of bedded polymict conglomerate and breccia together with volcanic sandstone and siltstone mudstone facies pillow lava and coarse hyaloclastite breccia indicate a submarine depositional setting for most of the sequence thick massive to graded beds of polymict breccia and conglomerate are interpreted as volcaniclastic mass flow deposits emplaced below wave base well rounded clasts in conglomerate were reworked during subaerial transport and or temporary storage in shoreline or shallow water environments prior to redeposition red oxidised lava and scoria clasts in bedded breccia and conglomerate also imply that the source was partly subaerial the facies assemblage is consistent with a setting on the submerged flanks of a shoaling basaltic seamount the coarse grade and large volume of conglomerate and breccia reflect the high supply rate of clasts and the propensity for collapse and redeposition on steep palaeoslopes the clast supply may have been boosted by vigorous fragmentation processes accompanying transition of lava from subaerial to submarine settings the greater proportion of primary volcanic facies compared with resedimented volcaniclastic and volcanogenic sedimentary facies in central and northwestern exposures near rakiraki indicates they are more proximal than those in the southeast towards viti levu bay the proximal area coincides with one of two zones where nw se trending mafic dykes are especially abundant and it is close to several small dome like intrusions of intermediate and felsic igneous rocks the original surface morphology of the volcano is no longer preserved though the partial fan of bedding dip azimuths in the south and east and the wide diameter exceeding 20 km are consistent with a broad shield

esr dating of pleistocene fossil teeth from alberta and saskatchewan teeth collected from pleistocene surficial sediments in southeastern alberta and western saskatchewan have been dated by electron spin resonance esr the dates generally agree with the previously

geology of tok island korea eruptive and depositional processes of a shoaling to emergent island volcano detailed mapping of tok island located in the middle of the east sea sea of japan along with lithofacies analysis and k ar age determinations reveal that the island is of early to late pliocene age and comprises eight rock units trachyte i unit p i unit p ii trachyandesite 2 7 0 1 ma unit p iii trachyte ii 2 7 0 1 ma trachyte iii 2 5 0 1 ma and dikes in ascending stratigraphic order trachyte i is a mixture of coherent trachytic lavas and breccias that are interpreted to be subaqueous lavas and related hyaloclastites unit p i comprises massive and inversely graded basaltic breccias which resulted from subaerial gain flows and subaqueous debris flows a basalt clast from the unit derived from below trachyte i has an age of 4 6 0 4 ma unit p ii is composed of graded and stratified lapilli tuffs with the characteristics of proximal pyroclastic surge deposits the trachyandesite is a massive subaerial lava ponded in a volcano tectonic depression probably a summit crater a pyroclastic sequence containing flattened scoria clasts unit p iii and a small volume subaerial lava trachyte ii occur above the trachyandesite suggesting resumption of pyroclastic activity and lava effusion afterwards shallow intrusion of magma occurred producing trachyte iii and trachyte dikes

the pliocene seamount series of la palma canary islands a pliocene submarine series of alkali basaltic pillow lavas hyaloclastites and breccias a a sheeted dike swarm b and a basal suite of gabbro and ultramafic rocks c from la palma canary islands is interpreted as a cross section through an uplifted seamount this series has been tilted to its present orientation of 50 230 plunge and azimuth probably by upwarping due to intrusions in the central portion of the island the basal plutonic complex c also includes intrusives coeval with up to 2000 m of younger subaerial alkali basaltic lavas unconformably overlying the submarine series the plutonic suite c is overlain abruptly by more than 1800 m of sills b 0 4 1 m thick on average with minor screens of lavas and breccias extrusives a form a 1750 m thick sequence of pillow lavas breccias and hyaloclastites the clastic rocks increase in abundance upward and are of four main types 1 breccias consisting of partly broken pillows formed nearly in situ 2 heterolithologic pillow fragment breccias 3 hyaloclastites composed dominantly of highly vesicular lapilli and ash sized shards the latter thought to have formed by near surface explosive eruptions and been subsequently transported downslope by mass flows 2 and 3 being interpreted to have been resedimented and 4 pillow scoria breccias from the upper 700 m of the extrusive section consisting of amoeboidal highly vesicular pillows and lava stringers and local bombs probably formed by cracking and bleeding of gas rich expanding pillow lava and some shallow submarine subaerial lava fountaining the extrusive series is chemically and mineralogically crudely zoned with the most differentiated rocks metatrachytes and mugearites at the base and most picritic lavas occurring near the top of the series subsequent to emplacement the entire extrusive and intrusive series has been hydrothermally altered the lower part to greenschist and the upper part to smectite zeolite facies mineral assemblages the la palma succession combined with evidence from surface studies of seamounts suggests that seamounts are formed by intrusive and extrusive processes in approximately equal portions the nature of eruptive clastic and depositional mechanisms changes drastically during growth of a seamount if the critical depth for major magmatic degassing is surpassed and especially if magmatic explosive processes can occur at very shallow water depth the critical depth depending on magma and thus volatile composition changes in slopes of a seamount influence depositional processes based on these factors at least three major depositional sites develop as a seamount grows summit flank and apron facies nonexplosive extrusive processes prevail in the deep water stage dominantly producing pillow lavas 75 these consist of individual pillow volcanoes up to 200 m high with large pillows near the base and decreasing pillow size toward the top of a volcano pillow breccias and pillow fragment breccias comprise approximately 20 of this facies the deep water flank and apron facies are characterized by debris flow deposits with possibjy rather dense matrix material the shallow water shoaling stage is reached when the seamount top reaches the critical depth for drastic increase in exsolution of magmatic volatiles about 800 m for the alkali basaltic seamount of la palma resulting in formation of mainly clastic rocks 70 in situ pillow rind breccias and scoriaceous amoeboidal breccias and pillows are formed in the summit regions of the seamount by repeated expansion and leaking of frothy pillow lava possibly by lava fountaining resedimented heterolithologic pillow fragment breccias lapilli breccias and hyaloclastites are deposited on the flanks and aprons of the seamount pillow lavas comprise 30 of these deposits

ree fractionation during granite weathering and removal by waters and suspended loads sr and nd isotopic evidence very few studies deal with ree rare earth element mobility within the system soil soil solution streamwater in this article we try to characterize the fractionation and the migration of the ree in a granite derived soil system located in a small catchment of the vosges mountains icp ms and tims measurements were performed on both solid samples fresh granite soil and suspended load of the stream and waters soil solutions springwater and streamwater to determine their respective ree concentrations and sr and nd isotopic compositions the paas normalized ree pattern of the bedrock is characterized by a strong depletion in hree heavy ree and a negative eu anomaly 0 46 similarly the granite normalized ree distribution patterns of the soil samples show hree depletions that become more important with decreasing depth the correlative behavior between p2o5 th and ree with depth indicates that besides apatite other phosphate minerals such as monazite are the most important phases controlling the th and ree budget in the soil profile on the other hand at greater depth zircon seems to be another important mineral phase controlling especially the hree enrichment as shown by the positive relationship between zr content and the yb ho ratio different grain size fractions show similar ree distribution patterns and are only weakly fractionated compared with bulk soil sample however the finest fraction 0 20 m is more enriched in sr and ree suggesting a stronger concentration of ree carrying minerals in this fraction the suspended and dissolved load of the stream show as a whole an enrichment in hree if compared with the granite or with the different soil samples however compared with the uppermost soil samples the suspended load is significantly more enriched in hree its ree distribution pattern is more similar to that of the finest fraction of the deeper soil sample and to the fresh granite thus most probably the ree of the suspended load originated from a source with ree characteristics found in the deep soil horizons this source might have been situated in the uppermost soil profile which is actually ree depleted the weathering process can be compared with a leaching experiment where the waters correspond to the leachate and the soil to the residual phase of the granite the sr isotope data indicate that the suspended load originates from the finest soil fraction the sr and nd isotopic data of the suspended load suggest that it contains up to 3 sr and nd from apatite and up to 97 from feldspar most of the sr and nd in the waters originate from apatite leaching or dissolution

in situ hydroclastic fragmentation of subaqueous ponded lavas new senator caldera abitibi greenstone belt quebec canada abstract subaqueous ponded lavas have been recognized within the structure of the new senator caldera in the blake river group of the abitibi greenstone belt quebec canada sub vertical to near vertical dips of extrusive volcanic facies within the southern sector of the caldera permit the identification of the internal architecture of an archean subaqueous volcanic complex detailed facies analyses of the dominantly mafic sequences have shown two localities with atypical primary volcanic structures and facies inconsistent with those observed at modern subaqueous mafic seamounts combined with the use of facies specific geochemical analyses a coherent model for the two localities accounting for all observed volcanic structures and features has been developed mapping completed at a scale of 1 100 at localities 1 and 2 reveals a series of sub parallel to parallel hyaloclastite rich horizons separating aphanitic to medium grained ponded units several primary volcanic structures are observed within the hyaloclastite horizons and are identified as pillowed forms cigar forms and v shaped structures ponded units range in thickness from 2 5 to 5 m with the exception of one unit which is approximately 30 m thick in central portions this thick unit is medium grained and has a sub ophitic texture units at locality 1 strike approximately nw while those at locality 2 strike ene several families of mafic dykes cross cut locality 1 and trend e w and nne both volcaniclastic and effusive facies have similar compositions affinities and trace and rare earth element signatures all facies have a tholeiitic affinity range in composition from basalt to andesite and have morb type trace and rare earth element signatures locality 1 appears slightly more evolved than locality 2 with later dykes and a late sill being the most evolved facies volcanic facies at localities 1 and 2 are consistent with subaqueous ponded lavas bounding synvolcanic structures and volcanic facies validate this interpretation and indicate these ponded lavas are hosted within a large synvolcanic depression at the summit of a mafic shield complex primary volcanic structures within hyaloclastite horizons formed via in situ fragmentation when water entered the system as ponded lavas began to cool water entered the system through synvolcanic fractures and encountered semi molten pockets of lava leading to hydroclastic fragmentation of the lavas v shaped and cigar structures formed during more energetic events and changed laterally into pillowed forms as energy dissipated from the system

synchrotron based p k edge xanes spectroscopy reveals rapid changes of phosphorus speciation in the topsoil of two glacier foreland chronosequences phosphorus p is a crucial element for life on earth and the bioavailability of p in terrestrial ecosystems which is dependent on the soil p stock and its speciation may limit ecosystem productivity and succession in our study for the first time a direct speciation of soil p in two glacier foreland chronosequences has been conducted using synchrotron based x ray absorption near edge structure xanes spectroscopy the chronosequences are located in the forefields of hailuogou glacier gongga shan china and damma glacier swiss alps the age since deglaciation of the investigated soils ranges from 0 to 120 years at hailuogou and from 15 to 700 years at damma differences in climate conditions cooler at damma in contrast to hailuogou precluding the establishment of forest in advanced ecosystem succession stages and in the chemical composition of the parent material result in different soil contents of total p and fe al oxyhydroxides which are much smaller at damma than at hailuogou nevertheless both chronosequences show similar trends of their topsoil p status with increasing soil age our study reveals a rapid change of topsoil p speciation in glacier retreat areas already during initial stages of pedogenesis initially dominating bedrock derived apatite p and al bound p is depleted fe bound p and particularly organically bound p is accumulated organic p strongly dominates in the topsoil of the mature soils outside the proglacial area of damma glacier age 700 3000 years and already 50 years after deglacation in the topsoil of the retreat area of hailuogou glacier a key factor for the change in topsoil p speciation is the establishment of vegetation resulting in soil organic matter som accumulation as well as accelerated soil acidification and apatite dissolution by organic acids which are produced by som degrading micro organisms mykorrhiza fungi and plant roots particularly the succession of grassland to forest seems to accelerate the transformation of topsoil p from apatite p into organic p the conceptual model developed by walker and syers 1976 to explain long term millennial changes of p speciation availability and turnover in soils and terrestrial ecosystems seems to be valid to describe short term changes of p speciation and p availability in proglacial topsoils already within a century of initial soil formation because the apatite depleted topsoil horizons in the young proglacial soils are shallow the change of topsoil p speciation should not seriously affect p availability and the p acquisition strategy of adult trees whose roots can easily access apatite containing c horizons in contrast p acquisition strategies of fungi micro organisms and plants confined to the topsoil probably change from apatite dissolution to mineralization of organic p already within 3000 years in a proglacial ecosystem succession from bare soil to grassland damma glacier chronosequence or even within 100 years in a proglacial ecosystem succession to forest hailuogou glacier chronosequence c 2013 elsevier ltd all rights reserved

submarine volcaniclastic rocks in this chapter we are concerned with underwater volcaniclastic eruptions and products as well as pyroclastic flows and debris generated on land and transported by mass flowage into the sea submarine fallout deposits derived from land based eruptions are treated in chapter 7 clastic materials redistributed as mass flows or turbidity currents originating from the rapid build up of tephra and epiclastic volcanic debris along coastal parts of volcanoes are also discussed in various places throughout the text e g chap 13

taxonomic overview and tusk growth analyses of ziegler reservoir proboscideans abstract at an altitude of 2705 m in the colorado rockies usa the ziegler reservoir fossil site gives a rare look at a high elevation ecosystem from the late pleistocene especially mis 5 of north america remains of more than four mammoths and about 35 mastodons dominate the macrofossil assemblage mammoth remains are attributed to mammuthus columbi and mastodon remains are referred to the well known continent wide mammut americanum mastodon remains occur within and between several lake margin slump deposits their deposition must therefore have occurred as events that were to some degree separate in time we treat the mastodon assemblage in each stratigraphic unit as a source of information on environmental conditions during the lives of these individuals mastodon mandibular tusks are abundant at the site and represent both males and females from calves to full grown adults this study presents the first attempt to use microct thin section and isotope records from mandibular tusks to reconstruct features of life history we recognize an up section trend in 18o profiles toward higher values suggestive of warmer temperatures throughout this sequence mastodon growth histories show low mean sensitivities suggestive of low levels of environmental stress this work helps frame expectations for assessing environmental pressures on terminal pleistocene populations

quaternary geochronology and distribution of mammuthus on the colorado plateau there are 41 known localities containing mammoth remains from the colorado plateau 24 in arizona 12 in utah 3 in new mexico and 2 in colorado of the 41 localities 13 32 arizona and utah only have yielded radiometric dates sup 14 c and u th 10 77 of these have been the result of the authors investigations the four youngest radiocarbon dates produce a weighted average date of approximately 11 270 plus minus 65 yr b p the youngest directly aged mammoth remains on the colorado plateau mammoth remains are recovered predominantly in alluvial regimes in addition to alcove cave and spring deposits no direct association of mammuthus and the clovis hunters has been reported from the colorado plateau dietary intake recorded in dung remains included predominantly graminoids in addition to various woody shrubs and trees that currently grow at higher elevations on the colorado plateau

archean mafic dyke swarms near the cameron river and beaulieu river volcanic belts and their implications for tectonic modelling of the slave province northwest territories three dense swarms of archean mafic dykes which intrude the beaulieu river and cameron river volcanic belts and adjacent granitoid terranes of the sleepy dragon complex and meander lake complex in the southern slave province all contain clusters of multiple parallel sided sheeted dykes none of the swarms can be convincingly modelled as being part of an ophiolite assemblage the 3 km by 20 km step9nduck dyke complex comprising about 350 mainly metabasaltic to meta gabbroic dykes separated by screens of granitoid gneiss 2750 ma represents profuse mafic magmatism in the meander lake complex dense dyke swarms within the cameron river belt fed the lavas and are an integral part of the volcanic stratigraphy all basaltic magmas represented by the volcanic belts and the dyke sets are predominantly mantle derived fractionated tholeiites nd isotope geochemistry indicates that they were all contaminated by archean sialic material isotopic systematics are satisfied by mixing of depleted mantle and varying proportions of sleepy dragon type crust the dyke swarms in the sleepy dragon complex and the step9nduck swarm record extensional events in archean continental crust possibly they are subsurface equivalents of now eroded flood basalts that signalled the activity of mantle plumes during archean times this hypothesis is consistent with magmatic underplating of continental lithosphere and with extensive involvement of continental material

sea floor lava fields on the east pacific rise a seabeam and seamarc i survey of a seamount group located several kilometres west of the axis of the east pacific rise epr at lat 9 53 n defines the existence of a large submarine lava field at the base of one of the volcanoes mib the field must be relatively young with respect to the surrounding terrain because lavas lap up against the base of mib seamount obscuring older erosional terrain and extend out over the faulted sedimented terrain of the flank of the epr volcanic cones within the lava field are aligned with the strike of fault scarps that are buried by the lavas mib seamount is characterized by a large well developed caldera and we suggest that the lava field was created during a recent volcanic episode when magmas migrated laterally away from the seamount9s reservoir along preexisting faults parallel to the ridge axis the withdrawal of magmas from the mib reservoir into the flanking parasitic eruptive plumbing system created the lava field and deflated the seamount summit this event contributed to the development of the mib caldera draining of shallow level magma chambers under seamounts by pressure controlled basal flank eruptions that form lava fields is an important mechanism for the development of seamount morphology

vertebrate paleontology and the alleged ice free corridor the meat of the matter abstract the existence of a full glacial ice free corridor through western alberta has been argued for many years it has been assumed to have existed notwithstanding a near total lack of evidence by many in the north american archeological community as a means of explaining the occurrence of early man south of the ice in early postglacial time in the last 15 years much has been done to fill the knowledge gap including theories on alternate routes but there is still no consensus quaternary vertebrate fossils from alberta accompanied by numerous radiocarbon dates with a clear gap between 21 ka bp and at least 11 6 ka bp now suggest that alberta was overridden by ice during an extensive late wisconsinan glaciation therefore a full glacial ice free corridor could not have existed however much of the province could have served as a migration route northward and southward both before and after late wisconsinan glaciation the preglacial passage could not have been a corridor because numerous megafaunal remains and conifer wood from numerous localities with finite dates from ca 43 ka to 21 ka bp indicate extensive ice free conditions similarly a late pleistocene corridor critically appraised from the standpoints of vertebrate paleontology and archeology is irrelevant because by the time human migrants arrived in southern alberta less than 11 ka bp the ice had been in retreat for well over 1000 years relative to human influx the continuing use of the term corridor with its connotation of a narrow or restricted passage seems inappropriate

mammalian faunal dynamics in late pleistocene alberta canada abstract as a conduit for the passage of faunal and human species into the new world the much abused concept of the so called ice free corridor has served its purpose the corridor concept has had an important bearing on discussions of zoogeography and paved the way for hypotheses about the recolonization of north america by mammalian species from asia alberta situated along the eastern slopes of the western cordillera adjacent to the northern great plains was long considered the ideal route for late pleistocene migrations into the north american heartland yet a temporal hiatus in the large suite of bone and wood dates from central alberta indicates that no corridor existed during the full glacial from about 22 000 to 12 000 bp dna isotopic and other studies of equids bovids cervids ursids mustelids and others confirm that animals flowed through alberta except during full glaciation the mid wisconsinan fauna in alberta indicates movements from both south and north reflecting the absence of ice sheets during that interval migrations during the last glacial maximum were precluded because the cordilleran and laurentide ice masses had coalesced to close the corridor finally with the postglacial reopening of the passage late surviving proboscideans muskoxen horses camels and lions facing imminent extinction may have formed a northwesterly bound megafaunal vanguard simultaneously a thriving population of moose and wapiti drove southward from beringia towards the mid continent

magma water interactions in subaqueous and emergent basaltic in the subaqueous growth and emergence of a basaltic volcano clasts are formed by one or a combination of 1 explosive release of magmatic volatiles 2 explosive expansion and collapse of steam formed at magma water contact surfaces 3 explosive expansion of steam following enclosure of water in magma or entrapment of water close to magma and 4 cooling contraction these processes named respectivelymagmatic explosivity contact surface steam explosivity bulk interaction steam explosivity andcooling contraction granulation can be enhanced by mutual interaction and feedback the first three explosive processes are limited at certain water depths hydrostatic pressures and become increasingly vigorous at shallower levels the depth of onset of magmatic explosivity depends largely on juvenile volatile content it is up to 200 m for tholeiitic magmas and up to 1 km for alkalic magmas at the depth where formation of clastic deposits becomes predominant over effusion of lavas magmatic explosivity is subordinate to steam explosivity as a clast forming process the upward transition to accumulation of dominantly clastic deposits is not simply related to the onset of substantial exsolution of magmatic volatiles and can occur without it contact surface explosivity commonly requires initiation by a vigorous impact between magma and water and although no certain depth limit is known likelihood of such explosivity decreases rapidly with depth clast generation by bulk interaction explosivity appears to be restricted to depths much shallower than that of the critical pressure of water which in sea water is at about 3 km cooling contraction granulation can occur in any depth of water but at shallow levels may be replaced by contact surface explosivity during continuous eruption under water tephra can be ejected and deposited within a cupola of steam such that rapid quenching does not occur emergent volcanoes are characterized by distinctive steam explosive activity that results primarily from a bulk interaction between rapidly ascending magma and a highly mobile slurry of clastic material water and steam the water gets into the vent by flooding across or through the top of the tephra pile and violent explosions cease when this access is sealed the eruptions during emergence of surtsey and capelinhos typify the distinctive explosive activity the style and controls of which are different from those of maar volcanoes

climatic and tectonic influences on fan deltas and wave to tide controlled shoreface deposits evidence from the archaean keskarrah formation slave province canada the 2 6 ga keskarrah formation located in the central slave province northwest territories canada is a late orogenic tectonically controlled sedimentary sequence that developed under unusual climatic and depositional conditions the formation is adjacent to the crustal scale north trending beniah lake fault and overlies the 3 15 ga augustus granite the 2 69 2 7 ga mafic volcanic peltier formation and the turbiditic contwoyto formation unconformably principal lithofacies in the keskarrah formation include conglomerate sandstone and siltstone sandstone the conglomerate lithofacies represents coalescing gravelly streamflow dominated fan deltas adjacent to topographic highs up section quartz rich arenites and quartz arenites of the sandstone lithofacies are interpreted to be shallow water shoreface deposits influenced by wave action and tides the overlying feldspathic litharenites of the siltstone sandstone lithofacies are consistent with a lower shoreface to proximal offshore environment dominated by wave and tide interaction tidal influence in both sandstone dominated lithofacies is inferred from the presence of mudstone laminae between bedforms and on foresets of cross beds as well as from abundant reactivation surfaces with local mudstone drapes intense chemical weathering during the archaean resulting from elevated atmospheric co2 levels higher temperatures and moist climatic conditions played an important role in the development of quartz rich arenites that appear to be first cycle deposits few lithic fragments and feldspar grains are preserved due to in situ host rock weathering chemical weathering during transport and wave and tide action hydraulic sorting and abrasion in the shoreface environment contributed to the continued breakdown and transport of labile minerals increased proportions of lithic fragments in sandstone beds of the conglomerate lithofacies are the result of shorter transport distances from source areas to the depositional environment abundant conglomerate with up to 4 m large granitic boulders derived from the adjacent augustus granite and mafic clasts from the peltier formation indicate high relief and fault related uplift and subsidence the intimate association of fan deltas and wave and tide influenced shallow marine deposits in association with quartz rich sandstones forming in a high relief area make the keskarrah formation remarkable in the rock record

green lake landslide and other giant and very large postglacial landslides in fiordland new zealand abstract green lake landslide is an ancient giant rock slide in gneiss and granodiorite located in the deeply glaciated fiordland region of new zealand the landslide covers an area of 45 km 2 and has a volume of about 27 km 3 it is believed to be new zealand s largest landslide and possibly the largest landslide of its type on earth it is one of 39 known very large 10 6 10 7 m 3 and giant 10 8 m 3 postglacial landslides in fiordland discussed in the paper green lake landslide resulted in the collapse of a 9 km segment of the southern hunter mountains slide debris moved up to 2 5 km laterally and 700 m vertically and formed a landslide dam about 800 m high impounding a lake about 11 km long that was eventually infilled with sediments geomorphic evidence supported by radiocarbon dating indicates that green lake landslide probably occurred 12 000 13 000 years ago near the end of the last otira glaciation the landslide is described and its geomorphic significance age failure mechanism cause and relevance in the region are discussed in relation to other large landslides and recent earthquake induced landslides in fiordland the slope failure occurred on a low angle fault zone undercut by glacial erosion and was probably triggered by strong shaking mm ix x associated with a large m 7 5 8 earthquake on the alpine fault c 80 km to the northwest geology was a major factor that controlled the style and size of green lake landslide and in that respect it is significantly different from most other gigantic landslides future large earthquakes on the alpine fault in fiordland are likely to trigger more very large and giant landslides across the region causing ground damage and devastation on a scale that has not occurred during the last 160 years with potentially disastrous effects on towns tourist centres roads and infrastructure the probability of such an event occurring within the next 50 years may be as high as 45

trace elements in organic and iron rich surficial fluids of the boreal zone assessing colloidal forms via dialysis and ultrafiltration on site size fractionation of about 40 major and trace elements te was performed on waters from boreal small rivers and their estuaries in the karelia region of north west russia around the vetreny belt mountain range and in paanajarvi national park northern karelia samples were filtered in the field using a progressively decreasing pore size 5 m 2 5 3 m 0 22 0 45 m 100 kda 10 and 1 kda by means of frontal filtration and ultrafiltration uf techniques and employing in situ dialysis with 10 and 1 kda membranes followed by icp ms analysis for most samples dialysis yields a systematically higher factor of 2 3 proportion of colloidal forms compared to uf nevertheless dialysis is able to provide a fast and artefact free in situ separation of colloidal and dissolved components similar to previous studies in european subarctic zones poor correlation of iron concentration with that of organic carbon oc in ultra filtrates and dialysates reflect the presence of two pools of colloids composed of organic rich and fe rich particles all major anions and silica are present as dissolved species or solutes passing through the 1 kda membrane size separation ultrafiltration experiments show the existence of larger or smaller pools of colloidal particles different for each of the considered elements the effect of rock lithology acidic versus basic on the colloidal speciation of te is seen solely in the increase of fe and some accompanying te concentrations in catchment areas dominated by basic rocks compared to granitic catchments neither the ultrafiltration pattern nor the relative proportions of colloidal versus truly dissolved te are affected by the lithology of the underlying rocks within 10 uncertainty the two colloidal 10 kda 0 22 m and 1 10 kda and the truly dissolved 1 kda pools show no difference in percentage of te distribution between two types of bedrock lithology the same conclusion is held for organic and fe rich waters in contrast landscape context analysis demonstrated slight dominance for most te affected by uf of large size colloids 10 kda 0 22 m in rivers and streams and small size colloids and truly dissolved fractions in swamp stagnant surface waters this supports the existence of two pathways of colloids formation during the plant litter degradation in wetland zones and at the redox front in river riparian zone

iron oxide precipitate in seepage of groundwater from a landslide slip zone orange precipitate was collected at the mouth of groundwater drainage tubes from the kumanashi landslide slip zone in toyama prefecture northwest japan data from xrf x ray diffraction and mossbauer spectroscopy determined the precipitate as hydrous ferric oxide hfo bearing multi elements such as phosphorous silica calcium etc the occurrence of hfo may indicate an oxidation of ferrous iron in the percolated groundwater from the slip zone moreover the precipitate iron should be mobilized with groundwater circulation from the slip zone whose reducing condition was determined by the iron speciation on the same type of landslide profiles within the study area in previous studies the hfo precipitate may be considered as a secondary reliable indicator to locate the seepage of a slip zone on surface especially for a landslide newly investigated under wet warm climate

mid ocean ridge eruptive vent morphology and substructure evidence for dike widths eruption rates and evolution of eruptions and axial volcanic ridges high resolution side scan sonar data of mid atlantic ridge mar inner valley floor axial volcanic ridges reveal details of their architectural elements we develop quantitative models for basaltic eruptions from dikes and compare the predicted products of these eruptions with the observed morphologic features inhibition of gas exsolution lack of magma disruption and hydrothermal effects combine to decrease the rise speed of magma in submarine dikes and enhance cooling leading to more rapid centralization of eruptions along the widest places in the dike dikes are predicted to initially feed eruptions from fissure vents producing lines of hummocky ridges centralization of activity to several adjacent vents produces chains of hummocky bulbous mounds and can enhance the effusion rate at a single vent to produce small seamounts the widest dikes are predicted to produce smooth flows up to several kilometers in length which should pond in adjacent lows edifice sizes predicted on the basis of volume fluxes and flow lengths implied by the widths of dikes observed on the seafloor in iceland and in ophiolite complexes are in quantitative agreement with the dimensions of observed features each ridge is made up of the products of a variety of these individual dike emplacement and extrusive events involving various dike widths cooling times and eruption durations on the basis of typical mar spreading rates about one dike emplacement event would be expected every 40 years since not all dikes reach the surface the actual mean interval between eruptions will exceed this mar dikes should solidify between average dike emplacement events dike emplacement events are more frequent on the east pacific rise epr and thus new dikes are more likely to reoccupy the sites of incompletely solidified older dikes differences between the morphology of the mar axial volcanic ridge and the sheet flow dominated epr are attributed to on average wider dikes erupting with greater frequency along the epr

two stage vesiculation in the cohassett flow of the grande ronde basalt south central washington the cohassett flow in south central washington is considered a possible host for a nuclear waste repository at the hanford site and is being investigated as part of the basalt waste isolation project the cohassett flow of the grande ronde basalt contains two vesicular zones separated by 24 m of dense sparsely vesicular basalt the vesicular zones represent accumulations of upward migrating bubbles sequentially frozen in by the downward passage of the upper solidification front the separation of the two zones suggests a hiatus in the exsolution of aqueous vapor from the lava the flow top vesicular zone formed during and immediately following emplacement of the flow from vapor bubbles nucleated during ascent and eruption whereas the internal vesicular zone formed after emplacement from bubbles apparently nucleated at the lower solidification front homogeneous nucleation of vapor was probably initially driven by large oversaturation pressures in the erupting lava after emplacement heterogeneous nucleation of vapor was probably initiated by crystallization in the margins of the flow

iron geochemical zonation in a tidally inundated acid sulfate soil wetland abstract tidal inundation is a new technique for remediating coastal acid sulfate soils cass here we examine the effects of this technique on the geochemical zonation and cycling of fe across a tidally inundated cass toposequence by investigating toposequence hydrology in situ porewater geochemistry solid phase fe fractions and fe mineralogy interactions between topography and tides exerted a fundamental hydrological control on the geochemical zonation redistribution and subsequent mineralogical transformations of fe within the landscape reductive dissolution of fe iii minerals including jarosite kfe3 so4 2 oh 6 resulted in elevated concentrations of porewater fe2 30 mmol l 1 in former sulfuric horizons in the upper intertidal zone tidal forcing generated oscillating hydraulic gradients driving upward advection of this fe2 enriched porewater along the intertidal slope subsequent oxidation of fe2 led to substantial accumulation of reactive fe iii fractions up to 8000 mol g 1 in redox interfacial tidal zone sediments these fe iii precipitates were poorly crystalline and displayed a distinct mineralisation sequence related to tidal zonation schwertmannite fe8o8 oh 6so4 was the dominant fe mineral phase in the upper intertidal zone at mainly low ph 3 4 this was followed by increasing lepidocrocite feooh and goethite feooh at circumneutral ph within lower intertidal and subtidal zones relationships were evident between fe fractions and topography there was increasing precipitation of fe sulfide minerals and non sulfidic solid phase fe ii in the lower intertidal and subtidal zones precipitation of fe sulfide minerals was spatially co incident with decreases in porewater fe2 a conceptual model is presented to explain the observed landscape scale patterns of fe mineralisation and hydro geochemical zonation this study provides valuable insights into the hydro geochemical processes caused by saline tidal inundation of low lying cass landscapes regardless of whether inundation is an intentional strategy or due to sea level rise

submarine volcanism eruption styles products and relevance to understanding the host rock successions to volcanic hosted massive sulfide deposits the increasing hydrostatic pressure of the water column with increasing water depth in subaqueous environments limits the ability of superheated volatiles to expand instantaneously against the ambient pressure explosive submarine eruptions are only likely in water depths less than 1 km and generally less than 500 m thus refuting models of highly explosive very deep water calderas popularly proposed as the host volcanic centers for the kuroko volcanic hosted massive sulfide vhms deposits of japan large volumes of blocky breccias can be produced by quench fragmentation during submarine lava eruptions and such deposits may have been mistaken for pyroclastic deposits in many cases in the past pyroclastic debris may occur in the host rock successions of some vhms deposits and may even be very voluminous however facies characteristics and theoretical constraints indicate that these are usually the products of mass flow deposition from shallow water or basin margin volcanic centers the maximum water depths for submarine explosive eruptions coincide approximately with the minimum pressures and water depths required to prevent boiling of mineralizing hydrothermal fluids in the stockwork before the fluids reach the sea floor the key elements in evaluating the prospectivity of ancient volcanic successions for vhms deposits appear to be deep water sediments and lavas or shallow intrusions in an extensional basin setting pyroclastic debris in many cases at least appears to be an accidental externally introduced component there is little evidence that explosive submarine calderas are essential as host volcanic centers to vhms deposits

chemical weathering and lithologic controls of water chemistry in a high elevation river system clark s fork of the yellowstone river wyoming and montana seasonal analyses of surface water geochemistry were conducted in the clark s fork of the yellowstone watershed to determine whole rock weathering rates the clark s fork of the yellowstone is a high elevation catchment with distinct bedrock lithologies using dissolved solute concentrations and stream flow data we calculated cation denudation rates of 119 g m 2 yr 1 65 900 eq ha 1 yr 1 for carbonate rich sedimentary rocks 16 6 g m 2 yr 1 8200 eq ha 1 yr 1 for andesitic volcanics and 9 8 g m 2 yr 1 5300 eq ha 1 yr 1 for granitic gneisses ca na ratios indicate that chemical weathering of disseminated calcite in granitic rocks contributes to the total solute load in these subcatchments removal of this c 2100 eq ha 1 yr 1

interpretation of the relations between massive pillowed and brecciated facies in an archean submarine andesite volcano amulet andesite rouyn noranda canada abstract the amulet andesite formation in the archean terrain of rouyn noranda p q consists of 19 flows distinguished by variations in phenocryst content and vesicularity and by the presence of concentric contraction fractures detailed mapping of flows revealed the presence of three main facies 1 massive facies 2 pillowed facies and 3 foreset bedded brecciated facies the massive facies consists of 50 massive lava overlain by pillow lava and or pillow breccia the pillowed facies consists of 50 pillows in some flows the pillowed facies contains a thin sheet of massive lava at the base of the flow facies 2a generally massive lava fills braided channels 10 50 m wide facies 2b facies 2c consists of pillows and large irregular megapillows determination of the flow direction shows that facies 1 is proximal facies 2 distal the foreset bedded facies 3 consists of alternating thin 1 2 m lobes of massive lava pillow lava and broken pillow breccia it makes up flows 16 19 at the top of the sequence flow m a unit entirely composed of massive lava is ponded against flows 9 and 10 we interpret the growth of the amulet andesite volcano in the light of new work on ocean floor basalt and on the 1969 1973 mauna ulu eruption the feeding fissure was located in the area of massive facies at the beginning of eruptions lava spread laterally as a sheet flood flow massive base of facies 2a but rapidly became channelized the pillow lava and in particular the facies 2b 2c and 3 are considered as the subaqueous equivalents of tube fed pahoehoe flow m probably represents a lava lake shallowing upward of the sequence during the built up of the volcano is indicated by increasing vesicularity of the flows and by an upward increase of the proportion of broken pillow breccia this increase is gradual from flow 1 to flow 15 but abrupt from flow 15 to 16 19

the bell lake group and anton complex a basement cover sequence beneath the archean yellowknife greenstone belt revealed and implicated in greenstone belt formation u pb zircon and monazite geochronology indicates the presence of a 2 93 ga basement anton complex and 2 8 ga cover sequence bell lake group beneath the 2 70 to 2 72 ga kam group of the yellowknife greenstone belt in the southern slave province the bell lake group comprises remnants of a quartzite rhyolite banded iron formation succession the ages of detrital zircons from the quartzite unit constrain its deposition to be younger than 2 92 and range up to 3 7 ga u pb ages for gneisses beneath the bell lake group are in excess of 2 93 ga and they are locally overlain by the quartzite the contact between the tholeiitic to calc alkaline kam group and the bell lake group is poorly exposed and equivocal approximately 6 km higher in the section the ranney chert a felsic volcaniclastic layer separates 2 70 2 72 ga tholeiitic to calc alkaline upper kam group rocks from a lower tholeiitic section containing sheeted dike complexes zircons from the ranney chert yield pb pb ages ranging from 2 72

axial and off axial heterogeneity of basaltic rocks from the east pacific rise at 12 35 n 12 51 n and 11 26 n 11 30 n surface ship operations and 40 submersible dives have provided a large amount of field observations and rock samples from two segments of the epr at 12 35 n 12 51 n and at 11 26 n 11 30 n and from four adjacent seamounts centered at less than 18 km from the rise axis the basaltic samples show a great variety of morphological features and a diversity in the proportions of early formed mineral phases and chemical composition there is no correlation between lava flow morphology geological settings and compositions based on mineral and compatible element composition these basalts were classified into three types the least evolved olivine basalts and highly phyric plagioclase basalts type a have high fo87 89 high mg 66 70 and high ni 100 contents the most evolved plagioclase olivine basalts with or without pyroxene type b and c have relatively low fo78 86 low mg 55 65 and low ni 60 100 ppm contents simple crystal fractionation 3 18 accounts for some of the observed compositional range however based on their incompatible element contents the above basalts are divided into three groups the various types a to c are found in each group depleted basalts with low k ti 0 04 0 15 ratios low zr 100 ppm and low nb 0 4 ppm contents undepleted basalts with the highest k ti 0 25 0 46 zr 150 170 ppm and nb 8 16 ppm contents and the transitional basalts having compositions between these two extremes these three basaltic groups occur within limited portions of the axial graben and its limbs in areas of less than 10 km in length and less than 3 4 km in width near 12 43 n 12 51 n on the epr similar volcanic diversity in a more limited area 3 km2 is observed on off axial seamounts and other constructional features centered up to 6 and 18 km from the rise axis depleted and undepleted melts are believed to have been formed during sequential batch melting of a composite mantle the transitional basalts probably result from a mixing of depleted and undepleted liquids which have undergone variable degrees of crystal fractionation two distinct mantle sources are distinguishable by their incompatible element contents and their susceptibility to melting we suggest that a lherzolitic mantle with minerals having a variable behavior under partial melting constitutes this type of composite mantle indeed clinopyroxene enriched in incompatible elements will be consumed at an earlier stage of melting than the olivine plus orthopyroxene eruption of compositionally distinct magma batches in close proximity on axial and off axial structures implies periods of quiescence between successive magmatic stages and cycles

underwater faunal assemblages radiocarbon dates and late quaternary vertebrates from cold lake alberta and saskatchewan canada late quaternary faunal remains from three underwater settings in cold lake alberta and saskatchewan canada include at least 13 vertebrate taxa consistent with assemblages that post date the last glacial maximum lgm seven new radiocarbon dates range from 10350 40 yr bp to 161 23 yr bp and provide insight into the post lgm biotic history of east central alberta and west central saskatchewan the presence of an essentially modern large mammal biota is suggested for the mid holocene and possibly earlier if the absence of extinct or extirpated taxa in association with late pleistocene bison at the ab sk site is meaningful taphonomically some of the remains suggest deposition in open environments during the holocene possibly when lake levels were lower the recovery of late quaternary faunal remains from a present day lacustrine setting is novel and suggests that similar records may occur in other lakes in western canada including those in areas with scarce quaternary vertebrate records

recognizing distinct portions of seamounts using volcanic facies analysis examples from the archean slave province nwt canada abstract archean volcanic rocks in the mafic dominated ca 2 66 2 69 ga point lake and beaulieu river belts slave province northwest territories are significant in demonstrating the facies that characterize specific portions of pillow volcanoes or seamounts irrespective of tectonic setting three distinct localities mapped in detail display facies consistent with 1 proximal deep water 2 medial to distal deep water and 3 medial shallow water seamount settings the proximal facies in the point lake belt include a 55 m thick non vesicular pillowed sequence cut by numerous mafic dykes and sills dykes contain multiple chilled margins indicating successive magma pulses which contributed to edifice construction abundant feeder conduits in addition to the absence of fragmental facies and vesicles are typical of the central deep water portion of seamounts where growth is initiated the medial to distal deep water facies in the point lake belt are represented by a 30 80 m thick assemblage of disorganized pillow breccia and pillowed and massive flows with 5 27 vesicularity massive non vesicular hyaloclastite intermingled with sedimentary material fluidal peperite in addition to thin shale units interstratified with pillow breccia and hyaloclastite indicate that sedimentation and volcanism were contemporaneous an increase in fragmental units and vesicularity relative to the proximal deep water facies is suggestive of the medial to distal part of a seamount in shallower water bedded tuffs laterally along strike with massive flows are the results of turbidity current deposition immediately following localized subaqueous eruptions a medial shallow water seamount setting is represented in the beaulieu river belt by a 5 85 m thick sequence of vesicular lobate pillowed and massive flows stratified pillow breccia and hyaloclastite and mafic dykes vesicularity ranges from 21 49 in pillowed flows 5 40 in massive flows and 20 35 in pillow breccia and hyaloclastite stratified pillow breccia developed along steep flow fronts in shallow water whereas bedded hyaloclastite formed during reworking and redeposition of autoclastic hyaloclastite on seamount flanks in shallow water the volcanic facies associations in the study areas are analogous to those of modern seamounts associated with the mid atlantic ridge and east pacific rise as well as mesozoic cenozoic seamounts in the canary islands fiji southwest japan the sea of japan and cyprus volcanological studies in the point lake and beaulieu river volcanic belts and subsequent comparisons with phanerozoic analogues demonstrate the manner in which distinct portions of ancient seamounts can be recognized in similar archean terranes

a review of quaternary proboscideans from alberta canada here we present a summary of the largest museum collection of quaternary proboscideans known from alberta housed at the royal alberta museum the 378 specimens reported here come from localities across the province highlighting the broad distribution of proboscideans in southwestern canada during the late pleistocene despite the isolated nature of most individual specimen records the cumulative record provides a broad sense of the chronologic distribution of late pleistocene proboscideans in a large portion of southwestern canada new and summary radiocarbon data indicate that the sparse record of pre lgm mastodon mammut americanum is limited to 40 700 3000 yr bp suggesting a pattern of pre lgm extirpation previously observed at more northern latitudes mammoths mammuthus spp occur in greater numbers and have a more lengthy late pleistocene record characterized by a temporal gap related to the last glacial maximum lgm

accretion of japanese island arcs and implications for the origin of archean greenstone belts the present day region of arc arc collision between the izu bonin arc and mainland japan honshu arc in the western pacific called the izu collision zone or icz provides a useful kinematic model for the development of many archean greenstone belts the compositional assemblage thermal structure and structural style of the crust in the icz are very similar to those inferred for many archean greenstone belts in both cases thick young and flaky arc crust with a high heat flux is in collision with another crustal block the icz has resulted in the imbrication of very thick slices of crust and associated sediments juxtaposed against older accretionary prisms many archean greenstone belts show similar geological features and we suggest that the incremental imbrication of the crust was a common tectonic style in some archean convergent margins

geology and geochemistry of an archean mafic dike complex in the chan formation basis for a revised plate tectonic model of the yellowknife greenstone belt an archean mafic dike complex in the chan formation at the base of the mafic volcanic section of the yellowknife greenstone belt consists of multiple metagabbro dikes and sills separated by screens of pillowed mafic volcanic rocks which are cut by a younger postvolcanic metadiabase dike swarm field relationships and geochemical characteristics are compatible with a comagmatic origin for the metagabbro and metavolcanic rocks that were fed through and deposited on an older rift related supracrustal sequence of the dwyer group the synvolcanic metagabbro dikes have extended the strike length of the volcanic section by at least 100 the mafic rocks of the chan formation are geochemically similar to mid ocean ridge basalt possibly with a minor subduction zone component preliminary end values for metagabbroic rocks are consistent with the derivation of magmas predominantly from a normal depleted mantle source the chan formation is interpreted to have formed in a marginal basin like setting adjacent to

stratigraphic and geochronologic contexts of mammoth mammuthus and other pleistocene fauna upper missouri basin northern great plains and rocky mountains u s a abstract mammoth fossils and other pleistocene vertebrates from the upper missouri basin in the northern plains and rocky mountains of the western interior of north america have been dated to the late pleistocene and are associated with wisconsinan deposits mammoth remains have also been found in older stratigraphic contexts for example mammuthus columbi and other fossils from the doeden locality are in pre wisconsinan terrace gravels along the yellowstone river the deposits are likely illinoian or sangamonian faunas that appear to be associated with the wisconsinan interstadial before the last glacial maximum are found in intermountain valleys and mountain settings the merrell locality blacktail cave natural trap cave and on the plains in both glaciated and unglaciated regions box creek wibaux gravel pit localities containing faunas dated to the time interval from about the last glacial maximum to the end of the younger dryas chronozone late wisconsinan include the youngest fossil bearing strata at merrell blacktail cave natural trap cave deposits at sheep rock spring indian creek machaffie false cougar cave shield trap cave and mammoths found at sun river glendive colby and the deer creek drainage

morphometric study of pillow size spectrum among pillow lavas measurements of h and v dimensions in the horizontal and vertical directions of pillows exposed in vertical cross section were made on 19 pillow lavas from the azores cyprus iceland new zealand tasmania the western usa and wales the median values of h and v plot on a straight line that defines a spectrum of pillow sizes having linear dimensions five times greater at one end than at the other basaltic toward the small size end and andesitic toward the large size end the pillow median size is interpreted to reflect a control exercised by lava viscosity pillows erupted on a steep flow foot slope in lava deltas can however have a significantly smaller size than pillows in tabular pillowed flows inferred to have been erupted on a small depositonal slope indicating that the slope angle also exercised a control pipe vesicles generally abundant in the tabular pillowed flows and absent from the flow foot pillows have potential as a paleoslope indicator pillows toward the small size end of the spectrum are smooth surfaced and grew mainly by stretching of their skin whereas disruption of the skin and spreading were important toward the large size end disruption involved increasing skin thicknesses with increasing pillow size and pillows toward the large size end are more analogous with toothpaste lava than with pahoehoe and are inferred from their thick multiple selvages to have taken hours to grow pseudo pillow structure is also locally developed an example of endogenous pillow lava growth that formed intrusive pillows between normal pillows is described from sicily isolated pillow like bodies in certain andesitic breccias described from iceland were previously interpreted to be pillows but have anomalously small sizes for their compositions it is now proposed that they may lack an essential attribute of pillows namely the development of bulbous forms by the inflation of a chilled skin and are hence not true pillows para pillow lava is a common lava type in the flow foot breccias it forms irregular flow sheets that are locally less than 5 cm thick and failed to be inflated to pillows perhaps because of an inadequate lava supply rate or too high a flow velocity

american mastodon extirpation in the arctic and subarctic predates human colonization and terminal pleistocene climate change existing radiocarbon 14c dates on american mastodon mammut americanum fossils from eastern beringia alaska and yukon have been interpreted as evidence they inhabited the arctic and subarctic during pleistocene full glacial times 18 000 14c years b p however this chronology is inconsistent with inferred habitat preferences of mastodons and correlative paleoecological evidence to establish a last appearance date lad for m americanum regionally we obtained 53 new 14c dates on 36 fossils including specimens with previously published dates using collagen ultrafiltration and single amino acid hydroxyproline methods these specimens consistently date to beyond or near the 50 000 y b p limit of 14c dating some erroneously young 14c dates are due to contamination by exogenous carbon from natural sources and conservation treatments used in museums we suggest mastodons inhabited the high latitudes only during warm intervals particularly the last interglacial marine isotope stage mis 5 when boreal forests existed regionally our 14c dataset suggests that mastodons were extirpated from eastern beringia during the mis 4 glacial interval 75 000 y ago following the ecological shift from boreal forest to steppe tundra mastodons thereafter became restricted to areas south of the continental ice sheets where they suffered complete extinction 10 000 14c years b p mastodons were already absent from eastern beringia several tens of millennia before the first humans crossed the bering isthmus or the onset of climate changes during the terminal pleistocene local extirpations of mastodons and other megafaunal populations in eastern beringia were asynchrononous and independent of their final extinction south of the continental ice sheets

late quaternary vertebrates and the opening of the ice free corridor with special reference to the genusbison abstract the ice free iorridor opened physically in early deglaciation after 14 ka bp but at first was not necessarily passable in an ecological sense one way to gauge the timing of its ecological opening is to establish a chronology for the arrival of immigrant animal species the bison have excellent potential because of the abundance of their remains late pleistocene and early holocene bison finds from western canada north to the peace river area extend the known database and provide new insights bison of southern appearance referable tob bison antiquus were present as far north as the peace river region until about 10 ka bp bison populations in western canada apparently underwent a rapid change at that time such that barely 500 years later bison of northern appearance referable tob bison occidentalis were established the rapidity and pervasiveness of this change seem to defy an evolutionary explanation rooted in punctuated equilibrium or phenotypic change and could indicate a sudden population influx through the newly opened corridor thus far no late glacial bison in western canada have been dated in excess of 11 5 ka bp with the possible exception of material from empress alberta if a steppe tundra was established before that time the absence of bison with either southern or northern affinities seems inexplicable outburst floods have undoubtedly removed part of the record by scouring gravel fills from valleys but it is doubtful that they completely obliterated the fossil record of a gregarious herbivore such as the bison

late pleistocene northward dispersing bison antiquus from the bighill creek formation gallelli gravel pit alberta canada and the fate of bison occidentalis late pleistocene bison skeletal remains from the gallelli gravel pit in the bighill creek formation at calgary alberta document at least two individuals including the largest postglacial bison r