coarse grained sediment gravity flow facies in a large supraglacial lake near williams lake in the central interior of british columbia the fraser river exposes long sections of late pleistocene glaciolacustrine sediments selectively preserved within a bedrock trough the dominant facies types are thick normally graded gravels and sands that occupy steeply dipping multistorey channels up to 300 m wide and several tens of metres deep channels appear to have been simultaneously cut and filled by high density turbidity currents in a glacial lake floored by stagnant ice fining upward sediment gravity flow sequences up to 50 m thick may be the product of quasi continuous surging turbidity flows triggered by catastrophic meltwater discharges into the trough or retrogressive failure of ice cored sediments large scale post depositional deformation structures such as synclinal folds normal faults sedimentary dyke swarms and dewatering structures record gravitational foundering of sediment and pore water expulsion caused by the melt of underlying glacier ice melting of buried ice masses along the floor of the trough appears to have controlled the flow paths of turbidity currents by producing sub basins within the overlying sediment pile an idealized model of supraglacial lacustrine sedimentation is developed that may be applicable to other glaciated areas with similar bedrock topography

debris flows and debris torrents in the southern canadian cordillera in canada debris torrents also referred to as channelized debris flows occur in parts of british columbia alberta and the yukon at least 17 deaths and an estimated 100 million of damage to bridges and property can be attributed to this natural hazard the debris mainly comprises large boulders rock fragments gravel to clay sized material tree and wood mulch materials that accumulate in the mountain creeks to be susceptible to a debris torrent a creek must have a drainage area within a critical range a profile that is sufficiently steep an accumulation of debris and some form of triggering mechanism the most common triggering mechanism is an extreme water discharge which may result from a very intense rainfall or a temporary damming of the creek in western canada the resulting torrents involve masses of debris typically less than 50 000 m3 that travel down creeks at speeds between 3 and 12 m s several passive and active forms of mitigation can be used to reduce the impact of debris to

landsliding caused by pleistocene glacial lake ponding an example from central british columbia sections cut through the quaternary sediment fill of the fraser river valley in central british columbia provide evidence for large scale landsliding during pleistocene time especially notable are thick laterally extensive diamict beds consisting mainly of tertiary rock debris that occur near the base of glaciolacustrine sequences these beds were deposited by subaqueous debris flows during one or more periods of lake ponding when advancing pleistocene glaciers blocked the ancestral fraser river the association of diamict beds and glaciolacustrine sediments deposited during periods of glacier advance may indicate a genetic link between slope failure and lake filling these observations 1 demonstrate the adverse effects of high pore pressures on the stability of slopes underlain by poorly indurated tertiary rocks and 2 extend the known history of landslides involving these rocks back into the pleistocene key words landslides debris flows pleistocene glacial lake

active slide in tertiary bentonitic claystones upper hat creek british columbia potential exploitation of the 500 m thick coal deposit at upper hat creek british columbia required detailed investigation of the sequence of tertiary tuffaceous rocks surrounding the coal and the overlying surficial materials studies have shown that extensive bentonitic slide deposits partially cover the coal body on the west side of hat creek valley part of this area is currently active a translational debris slide of approximately 17 106 m3 volume and 2 km length is moving across the northwest boundary of the proposed pit into the valley bottom detailed field investigations complemented by laboratory testing have defined the basal plane of sliding and permitted a back analysis to be made from measured piezometric pressures the mobilized shear strength on the failure plane is calculated to be cr 0 which is largely in accord with laboratory test results slope stability in thick montmorillonite rich claystones siltstones is known to present difficulties as evidenced by the panama canal exc

quantitative particle size microtextural and outline shape analyses of glacigenic sediment reworked by paraglacial debris flows particle size analysis and scanning electron microscopy have been used with some success to differentiate sediments sampled from varying geomorphological environments in the paraglacial environment however discrimination of paraglacially reworked deposits from in situ glacigenic deposits has proven to be problematic we consider till sediments that have been reworked by paraglacial debris flows and in situ unreworked parent material and apply a series of quantitative techniques in an attempt to discriminate samples from each environment initial analysis of particle size suggests some eluviation of fines from the debris flow reworked deposits but is of insufficient significance to allow reliable differentiation of geomorphological environment similarly although slight differences are identified in terms of quartz grain surface microtextures and quartz grain outline shape subsequent pca cluster and fourier analyses fail to reliably differentiate quartz grains from each geomorphological environment owing to high levels of intra sample heterogeneity this lack of apparent difference may arise from a lack of paraglacial process operation of significant magnitude or duration for a characteristic process imprint to emerge at this scale of observation accordingly further assessment of particle size and microtextural characteristics of glacial and paraglacial sediments may be most fruitful where sediments have been reworked over long distances moreover differentiating glacial from paraglacial deposits is likely to yield the most reliable results where rigorous statistical analyses are combined with a wide range of sedimentological and geomorphological techniques copyright 2008 john wiley and sons ltd

earthflows in the interior plateau southwest british columbia examples of large slow moving earthflows from the western part of the interior plateau zone of british columbia are discussed the larger examples exceeding 107 m3 the study provides a regional framework for previous site specific work on the geotechnical properties of earthflows in this region factors responsible for earthflow development are 1 low shear strength claystone shale and siltstone units within principally middle cretaceous to eocene sediments and volcanics 2 steep topographic gradients at the plateau margins plus availability of tributary valley incisions to provide lateral confinement of earthflow debris 3 sufficient moisture surplus at the plateau level to cause seasonal fluctuations in piezometric head both within and beneath earthflow debris so far work on the holocene record of movement suggests 1 relatively modest earthflow activity during the warm dry period of the first 3000 years or so of postglacial time 2 a post mazama maximum of movement probably correla

climate sensitivity implications for the response of geomorphological systems to future climate change climate sensitivity is defined as the equilibrium temperature response of the climate system to a doubling of atmospheric co2 levels from pre industrial levels despite three decades of debate in the climatological literature on the estimation and significance of climate sensitivity very little appears in the geomorphological literature on the implications of this for geomorphological systems this paper reviews the concept of climate sensitivity and applies its findings to an assessment of future landscape change in cold regions it is concluded that paraglacial processes will become the dominant mechanism of sediment transfer in currently glaciated catchments and that this period of sediment mobilization will be the last episode of major sediment movement for geological time periods there is a scientific consensus oreskes 2004 that the mean surface temperature of the earth has increased in recent decades and that the warming amounts to around 0 8 8c since the beginning of the twentieth century ipcc 2007 from this nasa goddard institute of space studies giss estimates that 2005 was the warmest year to date since reliable instrumental measurements become available although the world meteorological office wmo and climatic research unit cru place it just behind 1998 detection and attribution studies show that there is high probability at least 90 that this warming is largely the result of anthropogenic emissions of greenhouse gases ghg mainly co2 in the troposphere and that the amount and rate of warming lie outside of the range of natural variation and are unprecedented within the context of the holocene the last 11 000 years continued future warming is expected to have important consequences for a range of earth systems including the atmosphere cryosphere oceans hydrological systems and the biosphere and there are compelling reasons to expect increases in the magnitude and frequency of some natural hazards such as floods huntington 2006 droughts mason goddard 2001 and landslides e g fischer et al 2006 and increases in the intensity of tropical cyclones emanuel 2005 there are also concerns about the stability of several of the large ice sheets on earth e g overpeck et al 2006 as break up of these has the ability to impact upon global sea levels and regulate ocean currents given that climate is a major driver of many earth systems the rate nature and extent of future climate changes are important variables for understanding the future behaviour of geomorphological processes and the likely evolution of geomorphological systems as a result it is surprising that little appears in the geomorphological literature assessing climate sensitivity as a factor in landform and landscape evolution it is therefore the purpose of this paper to synthesize current understanding of climate sensitivity defined later and discuss briefly the implications of this for assessing the response of mountain geomorphological systems to future temperature rises metrics for climate change metrics are of interest to geomorphologists and other earth scientists modelling the response of earth systems to changes in climate as they provide a baseline measurement from which to calculate change the most widely used metric is the global mean surface temperature which is estimated by the hadcru hadley climatic research unit data set which excludes the polar regions or by the nasa giss assessment which extrapolates to the poles the warming of mean surface temperature is related theoretically and empirically to the idea of radiative forcing at the top of the atmosphere radiative forcing is measured in w m and can be defined as a measure of the influence a factor has in altering the balance of incoming and outgoing energy in the earth atmosphere system and is an index of the importance of the factor as a potential climate change mechanism ipcc 2001 despite this metric having been used by the ipcc assessment reports and adopted by from knight j harrison s eds periglacial and paraglacial processes and environments the geological society london special publications 320 257 265 doi 10 1144 sp320 16 0305 8719 09 15 00 the geological society publishing house 2009 policy makers there have been a number of challenges to its use the most credible challenge comes from the suggestion that a global heat budget measures the warming of the earth in a more complete way than the global mean surface temperature e g pielke 2003 in addition there are important uncertainties and limitations associated with the concept national academies of sciences 2005 especially as radiative forcing fails to account adequately with regional forcings such as by aerosols and land use changes that may have significant climatic effects at the local scale

collaborative effects of acidithiobacillus ferrooxidans and ferrous ions on the oxidation of chalcopyrite abstract in recent decades the bioleaching of chalcopyrite has been successfully developed and employed in copper hydrometallurgy understanding the decomposition mechanism of chalcopyrite is also of great significance for environmental remediation because the microbial oxidation of metal sulfides in mining waste and outcrop rocks commonly causes serious environmental contamination this study investigates the influence of acidithiobacillus ferrooxidans a ferrooxidans and added fe2 ions on the oxidation of chalcopyrite the results show that a ferrooxidans and added fe2 ions can collaboratively promote the recovery of cu from chalcopyrite in the bioleaching system with added fe2 ions a ferrooxidans prefer to oxidize soluble fe2 ions rather than decompose chalcopyrite to acquire energy which inhibits the release of cu at the first stage but enhances the growth of a ferrooxidans after reacting for 18 days however the produced fe3 ions greatly promote decomposition and release more cu than the bioleaching system free of fe2 which remained in the rest experiments both the oxidation of chalcopyrite and the release of cu in the bioleaching system are greater than what occurs in the chemical leaching system chalcocite covellite bornite and elemental sulfur were identified as intermediate products and a sulfur transforming route of s2 s22 sn2 s0 so32 so42 can be recognized by x ray photoelectron spectroscopy as the principle end product jarosite covered the chalcopyrite grains and consequently inhibited further oxidation it is noteworthy that the released cu2 ions barely suppressed the growth of a ferrooxidans because they tended to be enriched only in extracellular polymeric substance eps while fe3 ions could be found on both the cell surfaces and the eps which implies a potential mechanism for the survival of cells in a high cu2 solution collectively an integrated model of chalcopyrite oxidation collaborated by both chemical and microbial oxidation has been proposed to elucidate the bioleaching mechanisms and to give a perspective on its hydrometallurgical and environmental applications

geochemical and mineralogical aspects of sulfide mine tailings abstract tailings generated during processing of sulfide ores represent a substantial risk to water resources the oxidation of sulfide minerals within tailings deposits can generate low quality water containing elevated concentrations of so 4 fe and associated metal loid s acid generated during the oxidation of pyrite fes 2 pyrrhotite fe 1 x s and other sulfide minerals is neutralized to varying degrees by the dissolution of carbonate oxy hydroxide and silicate minerals the extent of acid neutralization and therefore pore water ph is a principal control on the mobility of sulfide oxidation products within tailings deposits metals including fe iii cu zn and ni often occur at high concentrations and exhibit greater mobility at low ph characteristic of acid mine drainage amd in contrast hydr oxyanion forming elements including as sb se and mo commonly exhibit greater mobility at circumneutral ph associated with neutral mine drainage nmd these differences in mobility largely result from the ph dependence of mineral precipitation dissolution and sorption desorption reactions cemented layers of secondary oxy hydroxide and hydroxy sulfate minerals referred to as hardpans may promote attenuation of sulfide mineral oxidation products within and below the oxidation zone hardpans may also limit oxygen ingress and pore water migration within sulfide tailings deposits reduction oxidation redox processes are another important control on metal loid mobility within sulfide tailings deposits reductive dissolution or transformation of secondary oxy hydroxide phases can enhance fe mn and as mobility within sulfide tailings production of h 2 s via microbial sulfate reduction may promote attenuation of sulfide oxidation products including fe zn ni and tl via metal sulfide precipitation understanding the dynamics of these interrelated geochemical and mineralogical processes is critical for anticipating and managing water quality associated with sulfide mine tailings

models of glaciomarine sedimentation and their application to the interpretation of ancient glacial sequences abstract this paper argues that glaciomarine environments can be regarded as special glacially influenced types of continental margin environments e g continental shelf slope rise and basin plain knowledge of the stratigraphic architecture and typical sedimentary sequences of non glacial margins is becoming well known but remains limited for those that have been glacially modified the principal influences on sedimentation in these environments relate to the glacial sediment input controlled by relief of basin margin glacier thermal regime and ice flow dynamics and depositional environments influence of traction currents substrate relief and proximity to nearby ice margins typical ranges of sedimentation rates can be established for glacially influenced continental margin environments and these may provide a framework for ancient sequences starvation of sediment supply to glacially influenced continental margins is common the nature of sub ice shelf sedimentation a model that has been applied to many ancient glacial sequences is critically reviewed the significance of such sedimentation in the rock record has probably been exaggerated because of oversimplistic interpretations of diamictite sequences existing process models of glaciomarine sedimentation derived from study of modern environments are sometimes difficult to employ in investigation of ancient sedimentary sequences because simple lithofacies criteria and typical vertical profiles are not available to aid in interpretation in addition compositional data emphasized by many workers for distinguishing glaciomarine from continental glacial diamict ite s frequently fingerprint sediment source and not mode of deposition the importance of facies analysis methods for isolating depositional environments is illustrated by three examples of ancient glaciomarine sequences these are the early proterozoic gowganda formation 2 3 ga of northern ontario canada the late proterozoic port askaig formation 670 ma of scotland and ireland and the late cenozoic yakataga formation 20 ma to recent of the gulf of alaska these examples illustrate the significance of detailed genetic studies of ancient glacial rocks in the interpretation of palaeogeographic and tectonic settings diamictite units in ancient glaciomarine sequences cannot be easily interpreted in terms of climatic or ice advance retreat cycles because of the varied controls on diamict accumulation and diamictite preservation in marine basins

a comparison of clast fabric and shape in late precambrian and modern glacigenic sediments abstract northeastern svalbard contains a well preserved glacigenic sequence of vendian late precambrian age in which terrestrial lacustrine intertidal and marine glacial facies are represented diamictite facies are of two main types massive and weakly to strongly bedded diamictite field appearance and relationships with other facies however provide insufficient information to allow a clear interpretation of the precise mode of glacial deposition by combining this information with data concerning the fabric of clasts in modern glacigenic sediments where the mode of glacial deposition is better known a wider understanding of the processes of glacial deposition in vendian time is obtained several diamictite samples were interpreted to be of lodgement tillite facies and material o water laid and glacigenic sediment flow origin was also recorded clast shape analyses indicate that most glacial debris was transported at least for a time at the glacier bed little angular supraglacial debris was present implying that the ice mass was of ice cap or ice sheet dimensions with few subaerial rock exposures clast shape in the late precambrian deposits was not useful in distinguishing between the variety of lithofacies derived from basally transported glacial material too few systematic studies of clast striation in modern glacigenic sediments are yet available for this criterion to be helpful in distinguishing between tillite facies lithofacies analysis together with clast fabric and shape studies provide useful and complementary lines of evidence concerning the ode of deposition of ancient diamictite sequences an understanding of the depositional processes and patterns of modern glacial sedimentation provides a fundamental framework for such studies

lithofacies types and vertical profile models an alternative approach to the description and environmental interpretation of glacial diamict and diamictite sequences abstract increased knowledge of modern glacial depositional environments has resulted in rapidly evolving classifications of glacial tills these are based to a large degree on theoretical considerations of likely depositional processes the classifications are sophisticated and more advanced than the establishment of simple field criteria whereby individual till facies can be identified in quaternary and pre quaternary successions this situation is compounded in many quaternary terrains by the continued description of tills in terms of laboratory derived analytical data only reflecting a traditional interest in stratigraphic correlation rather than reconstruction of depositional environment detailed sedimentological logging of lithofacies is rarely undertaken there is thus considerable confusion as to what is being described or sampled when analytical data are presented for many pleistocene tills the same remarks apply to pre pleistocene tillites a lithofacies code is presented here for the rapid description and visual appraisal of field sequences or drill cores containing unconsolidated diamicts or lithified diamictites the term till is not used as it has a strict genetic definition referring to direct aggregation and deposition by glacier ice use of a four part code in conjunction with codes already published for fluvial sediments allows fundamental field properties to be depicted independent of genetic terminology and provides a firm basis for subsequent environmental interpretation and analytical work the value of this approach is illustrated by comparing a representative suite of vertical profiles of diamict assemblages deposited by modern grounded glaciers with a classic late pleistocene glacigenic sequence at scarborough bluffs ontario

the gowganda formation in the southern part of the huronian outcrop belt ontario canada stratigraphy depositional environments and regional tectonic significance abstract the early proterozoic huronian supergroup of the north shore of lake huron comprises a lower part that is largely of continental origin and a more widespread dominantly marine upper succession the gowganda is the lowest formation of the upper huronian in the southern part of the huronian outcrop belt it is in conformable but commonly erosional contact with the underlying serpent formation the basal part of the gowganda formation unit 1 is stratified diamictites boulder and cobble orthoconglomerates and subordinate thin turbiditic sandstones these rocks are largely resedimented but glaciogenic the basal diamictite complex is overlain by unit 2 a thick argillite formed in deep water during a period of glacial retreat unit 3 begins with a discontinuous glaciomarinite this is overlain by resedimented boulder and cobble conglomerates that pass up into sandy turbidites down to basin movements on syn sedimentary north trending normal faults led to deposition of coarsening upward wedges of eastward transported debris there is a thick stratified diamictite complex at the top of unit 3 in the eastern part of the study area it includes a 50 m thick argillite the diamictite complex is overlain by a series of coarsening upward sequences formed by prograding deltas these comprise unit 4 of the gowganda formation the lowest deltaic sequence includes a thick diamictite in the east and a more widespread thin diamictite in its upper part the glaciogenic and resedimented nature of the rocks at the base of the gowganda formation suggests that basin deepening was tectonic rather than due to eustatic sea level rise glaciation in the huronian supergroup may have been initiated by uplift of rift shoulders and propagated by influx of marine waters into the interior of the continent the regional extent of the gowganda formation its unconformable relationship with older huronian rocks in the north and its largely resedimented nature all indicate an episode of regional subsidence possibly after continental separation similar tectonic and climatic events have been postulated for early proterozoic rocks of southeastern wyoming and possibly elsewhere lending support to earlier correlations based mainly on stratigraphic similarities glaciogenic diamictites are present above the breakup unconformity in many early and late proterozoic successions suggesting a possible causative relationship

remedial measures for debris flows at the agassiz mountain institution british columbia on the evening of january 23 1982 a debris flow having an estimated volume of 11 000 m3 occurred in a stream channel on the south slope of mount agassiz adjacent to the mountain institution of the

sulfide oxidation and distribution of metals near abandoned copper mines in coastal environments prince william sound alaska usa abstract the oxidation of sulfide rich rocks mostly leftover debris from cu mining in the early 20th century is contributing to metal contamination of local coastal environments in prince william sound alaska analyses of sulfide water sediment precipitate and biological samples from the beatson ellamar and threeman mine sites show that acidic surface waters generated from sulfide weathering are pathways for redistribution of environmentally important elements into and beyond the intertidal zone at each site volcanogenic massive sulfide deposits composed of pyrrhotite and or pyrite chalcopyrite sphalerite with subordinate galena arsenopyrite and cobaltite represent potent sources of cu zn pb as co cd and hg the resistance to oxidation among the major sulfides increases in the order pyrrhotite sphalerite chalcopyrite pyrite thus pyrrhotite rich rocks are typically more oxidized than those dominated by pyrite the pervasive alteration of pyrrhotite begins with rim replacement by marcasite followed by replacement of the core by sulfur fe sulfate and fe al sulfate the oxi dation of chalcopyrite and pyrite involves an encroachment by colloform fe oxyhydroxides at grain margins and along crosscutting cracks that gradually consumes the entire grain the complete oxidation of sulfide rich samples results in a porous aggregate of goethite lepidocrocite and amorphous fe oxyhydroxide enclosing hydrothermal and sedimentary silicates an inverse correlation between ph and metal concentrations is evident in water data from all three sites among all waters sampled pore waters from ellamar beach gravels have the lowest ph 3 and highest concentrations of base metals to 25 000 g l which result from oxidation of abundant sulfide rich debris in the sediment high levels of dissolved hg to 4100 ng l in the pore waters probably result from oxidation of sphalerite rich rocks the low ph and high concentrations of dissolved fe al and so4 are conducive to precipitation of interstitial jarosite in the intertidal gravels although pore waters from the intertidal zone at the threeman mine site have circumneutral ph values small amounts of dissolved fe2 in the pore waters are oxidized during mixing with seawater resulting in precipitation of fe oxyhydroxide flocs along the beach seawater interface at the beatson site surface waters funneled through the underground mine workings and discharged across the waste dumps have near neutral ph 6 7 7 3 and a relatively small base metal load however these streams probably play a role in the physical transport of metalliferous particulates into intertidal and offshore areas during storm events somewhat more acidic fluids to ph 5 3 occur in stagnant seeps and small streams emerging from the beatson waste dumps amorphous fe precipitates in stagnant waters at beatson have high cu 5 2 wt and zn 2 3 wt concentrations that probably reflect adsorption onto the extremely high surface area of colloidal particles conversely crystalline precipitates composed of ferrihydrite and schwertmannite that formed in the active flow of small streams have lower metal contents which are attributed to their smaller surface area and therefore fewer reactive sorption sites seeps containing precipitates with high metal contents may contribute contaminants to the marine environment during storm induced periods of high runoff preliminary chemical data for mussels mytilus edulis collected from beatson ellamar and threeman indicate that bioaccumulation of base metals is occurring in the marine environment at all three sites

catastrophic lake drainage within the homathko river basin british columbia three distinct phenomena related to sudden lake drainage which occurred in a restricted area within the southern coast mountains of british columbia are described i moraine breaching by solita

late pleistocene subaerial debris flow facies of the bow valley near banff canadian rocky mountains a thick late pleistocene sequence comprising multiple beds of massive diamict facies resting on outwash gravels occurs along the bow river near banff alberta diamicts have a simple sheet like geometry which dip downvalley at between 5 and 10 with largely conformable bedding contacts the sediments are strongly bimodal in texture consisting of clasts supported by a silty sand matrix prolate clasts show a weak a axis alignment parallel and transverse to the trend of the bow valley with a weak imbrication clasts of soft sediment are common the diamict sequence has a maximum thickness of 30 m infills the valley floor over an area of approximately 12 km2 and buries a channelled topography cut on the surface of underlying outwash gravels abandoned braided channels veneered by windblown sand containing volcanic tephra dated at 6600 yr bp occur on the infill surface diamict facies were emplaced as subaerial debris flows derived by the mixing and remobilization of large volumes of outwash and glaciolacustrine sediment orientation data from clasts and a few basal grooves indicate that debris was derived upvalley and from adjacent valleyside slopes a major episode of debris flow sedimentation may have been triggered by the abrupt drainage of lakes in tributary valleys as the bow valley glacier retreated downslope resedimentation of large volumes of sediment resulted in braided river aggradation downstream along the bow river and can be dated to between 12 000 and 10 000 yr bp similar conditions probably occurred during deglaciation throughout the canadian cordillera and many other alpine areas where poorly sorted late glacial debris flow facies have been mistaken for tills deposited directly by glaciers the late glacial setting identified in this paper provides a basis of comparison with ancient continental glacial facies preserved in areas of active tectonism and high relief

a debris flow triggered by the breaching of a moraine dammed lake klattasine creek british columbia a very large debris flow of unusual origin occurred in the basin of klattasine creek southern coast mountains british columbia between june 1971 and september 1973 the flow was triggered by the sudden release of up to 1 7 106 m3 of water from a moraine dammed lake at the head of a tributary of klattasine creek water escaping from the lake mobilized large quantities of unconsolidated sediment in the valley below and thus produced a debris flow that travelled in one or more likely several surges 8 km downvalley on an average gradient of 10 to the mouth of the stream here the flow deposited a sheet of coarse bouldery debris up to about 20 m thick which temporarily blocked homathko river slumps slides and debris avalanches occurred on the walls of the valley both during and in years following the debris flow several secondary debris flows of relatively small size have swept down klattasine creek in the 12 14 years since klattasine lake drained

sedimentology and clast fabric of subaerial debris flow facies in a glacially influenced alluvial fan abstract a large alluvial fan 2 km2 constructed between 11 000 and 7000 years b p at the mouth of cinquefoil creek in interior british columbia canada is identified as glacially influenced debris flow dominated the fan was rapidly constructed during and immediately after deglaciation when large volumes of glacial debris were resedimented downslope fans of this type are widespread in the glaciated portion of the north american cordillera diamict facies deposited as debris flows account for 48 of the fan volume sheetflodd gravels 37 and other facies 15 diamicts show three facies types crudely bedded facies containing rafts of soft sediment that are attributed to downslope collapse and mixing of heterogeneous glacial deposits these occur within the core of the fan massive and weakly graded inverse to normal diamict facies derived from the downslope flow of weathered volcanic bedrock occur within a well defined bed that can be traced across the entire fan the occurrence of weakly graded facies as lateral equivalents to massive facies within the same bed implies the partial development of turbulent high velocity streams within a viscous debris flow moving over a slope of 6 clast fabrics in these facies show weakly clustered a axes dipping up and downslope comparable to other debris flows and lahars the cinquefoil fan its internal structure and facies provides a good modern analogue for ancient diamictite sequences deposited in areas of active uplift rifting and glaciation

clast orientation in mount st helens debris flow deposits north fork toutle river washington abstract clast orientation measurements were made at 11 sites on mount st helens lahar deposits along the north fork of the toutle river washington schmidt nets show that fabrics tend to be unimodal though relatively weak a quantitative comparison of the fabrics with those reported for basal tills and smaller debris flows was made using the eigenvalue method which calculates eigenvectors v1 the axis of maximum concentration v3 the axis of minimum concentration in effect the pole to the preferred plane of the long axes and their respective measures of strength s1 and s3 the s1 and s3 values were significantly weaker than those of basal tills but were similar to those of small debris flows the lahar fabrics could e distinguished from those of the latter however by the orientation of the v1 and v3 eigenvectors first the lahar v1s showed a statistically significant preference for an upstream dip whereas the v1s of the small flows displayed no dip preference second the mean absolute difference between the v1 azimuth and the local flow direction was significantly larger than that for the small flows indicating a greater tendency for transverse orientations in the lahar fabrics particularly those of clast supported samples third the mean v1 dip of the lahar fabrics was significantly greater than that of the small debris flows fourth the mean v3 dip of the lahar fabrics was significantly lower than that of the sma l flows indicating a significantly steeper dip of the preferred plane of the long axes particularly in the matrix supported samples the lahar fabrics could also be distinguished from those of basal tills by means of the v1 and v3 orientations the results suggest that clast fabric may be a more useful property for characterizing debris flow sedimentology than has been previously assumed