character of hearwaters adjustment to base level drop investigated by digital modeling using a computer model written for dynamic river profile modeling snow and slingerland 1987 long term profile adjustments to constant rate base level lowering tectonic block uplift have been simulated with varied conditions of outflow discharge 10 and 100 m3 s sediment diameter 0 1 0 4 and 2 0 mm and sediment load concentrations of 1200 and 400 ppm by weight tweleve sets of initially graded profile data cover all possible combinations of the variables each modeled stream has been subjected to each of three base level drop rates 0 1 1 0 and 10 0 mm yr for 10 000 years of model time modeled histories of headwaters erosional response differ in two ways the first is length of lag time of response characterized by a period of quiescence in erosion at the headwaters prior to the channel steepening sufficiently for erosion to commence at this upstream point variations in discharge and sediment concentration affect the lag time of response in all cases the second variable aspect of response is the relative magnitude of eventual headwaters erosion the main control is the drop rate a high drop rate yields a low relative magnitude whereas a low drop rate yields a high relative magnitude of response the rate of base level drop also controls to what degree the other controlling variables of discharge sediment concentration and sediment diameter affect the eventual magnitude of headwaters erosion rates of trunk stream and headwaters erosion indicate that 21 out of 36 of the modeled stream systems attain a condition approximating parallel profile erosion after 10 000 years some examples notably those with low power to erode and high imposed drop rates exhibit headwaters erosion rates that continue to be well below rates of base level lowering creating profile steepening with no apparent time limit

improved age estimates for the white river and bridge river tephras western canada new 14c ages date the eruptions that produced the white river and bridge river tephras two important holocene marker beds in western canada the 14c ages were obtained on trees in growth position buried in coarse tephra and a pyroclastic flow near the source vents the mean calendric age of the white river eruption based on four 14c ages is 1147 cal years bp calibrated years approximately equivalent to calendric years or ad 803 the 2 age range obtained from the two most precise 14c ages is 1014 1256 cal years bp or ad 694 936 the mean age of the bridge river eruption determined both from i the single most precise outer ring 14c age and ii the weighted mean of six outer ring 14c ages is 2360 cal years bp or 411 bc 2 age range 2349 2704 cal years bp or 755 400 bc

a model of late quaternary landscape development in the delaware valley new jersey and pennsylvania abstract in the delaware valley of new jersey and eastern pennsylvania the late quaternary history of colluviation fluvial adjustment and soil formation is based on the ages of pre wisconsinan soils and glacial deposits which are indicated by feld relationships and inferred from mid latitude climate changes indicated by marine oxygen isotope records the area is divided into four terranes characterized by sandstone gneiss slate and carbonate rocks since the last pre wisconsinan glaciation 130 ka inferred to be late illinoian each terrane responded differently to chemical and mechanical weathering during the sangamon interglacial stage 130 75 ka in situ weathering is inferred to have occurred at rates greater than transportation of material which resulted in the formation of deep highly weathered soil and saprolite and dissolution of carbonate rocks cold climatic conditions during the wisconsinan on the other hand induced erosion of the landscape at rates faster than soil development upland erosion during the wisconsinan removed pre wisconsinan soil and glacial sediment and bedrock to produce muddy to blocky colluvium grezes litees and alluvial fans on footslopes fluvial gravel and overlying colluvium in the delaware valley both buried by late wisconsinan outwash are inferred to represent episodes of early and middle wisconsinan 75 25 ka upland erosion and river aggradiation followed by river degradation and colluvium deposition early middle wisconsinan colluvium is more voluminous than later colluvium despite colder possibly permafrost conditions during the late wisconsinan 25 10 ka extensive colluviation during the early and middle wisconsinan resulted from a longer 50 kyr generally cold interval of erosion with a greater availability of easily eroded pre wisconsinan surficial materials on uplands than during the late wisconsinan after recession of late wisconsinan ice from its terminal position soil formation and landscape stability were delayed until the holocene by a lingering cold climate slope erosion colluvium and alluvial fan deposition and eolian sedimentation late quaternary erosion in the delaware valley was dominated by glacial and periglacial processes during glacial stages during the warm interglacial stages soils developed on a more stable landscape these souls were easily colluviated by periglacial erosion during periods of intermittent cold climate

glacier change of the columbia icefield canadian rocky mountains 1919 2009 we determined length area elevation and volume change of the columbia icefield using interprovincial boundary commission survey maps from 1919 eight sets of aerial photographs from 1948 to 1993 and satellite data from 1999 to 2009 over the period 1919 2009 glaciers on average retreated 1150 34 m and shrank by 2 4 0 2 km 2 total area loss was 59 6 1 2 km 2 23 5 and mean elevation change was 49 25 m w e resulting in a total volume loss of 14 3 2 0 km 3 w e large outlet glaciers experienced the greatest absolute ice loss while small detached glaciers lost the most relative length and area thinning rates of debris covered ice were 30 60 lower than those for clean ice all glacier changes were significantly correlated with each other p 0 01 with r values ranging from 0 54 to 0 82 temperature is correlated with length and area change over periods lagged 1 5 years p 0 05 and with elevation and volume change over periods lagged 9 18 years p 0 05 precipitation is correlated with glacier change over periods lagged 1 10 years p 0 05

8000 year old wood from the athabasca glacier alberta several wood fragments of pinus sp dated at 8230 80 and 8000 90 years bp and abies sp were recovered from the snout of the athabasca glacier this wood derived from an unknown source up valley indicates that the glacier was less extensive than at present during the hypsithermal and that an area up valley of the present snout was tree covered ca 8000 8300 years bp

appalachian piedmont landscapes from the permian to the holocene abstract between the potomac and susquehanna rivers and from the blue ridge to the fall zone landscapes of the piedmont are illustrated for times in the holocene late wisconsin early miocene early cretaceous late triassic and permian landscape evolution took place in tectonic settings marked by major plate collisions permian arching and rifting late triassic and development of the atlantic passive margin by sea floor spreading early cretaceous erosion proceeded concurrently with tectonic uplift and continued after cessation of major tectonic activity atlantic outer continental shelf sediments record three major erosional periods 1 late triassic early jurassic 2 late jurassic early cretaceous and 3 middle miocene holocene the middle miocene holocene pulse is related to neotectonic activity and major climatic fluctuations in the piedmont upland the holocene landscape is interpreted as an upland surface of low relief undergoing dissection major rivers and streams are incised into a landscape on which the landforms show a delicate adjustment to rock lithologies the fall zone has apparently evolved from a combination of warping faulting and differential erosion since late miocene the periglacial environment of the late wisconsin and earlier glacial epochs resulted in increased physical erosion and reduced chemical weathering even with lowered saprolitization rates geochemical modeling suggests that 80 m or more of saprolite may have formed since late miocene this volume of saprolite suggests major erosion of upland surfaces and seemingly contradicts available field evidence greatly subdued relief characterized the early miocene time near the end of a prolonged interval of tropical morphogenesis the ancestral susquehanna and potomac rivers occupied approximately their present locations in early cretaceous time local relief may have been as much as 900 m and a major axial river draining both the piedmont and appalachians flowed southeast past baltimore the late triassic landscape was influenced by rift basin development streams drained into a hydrologically closed basin no through flowing rivers seem to have been present a limestone escarpment along the blue ridge may have existed as a consequence of a semi arid climate the permian may have been a time of himalayan like mountains and mountain glaciers streams and glaciers generally flowed southwest and west

water geochemistry controlled by carbonate dissolution a study of the river waters draining karst dominated terrain guizhou province china concentrations of major ions and sr and sr isotopic compositions of two major river systems wujiang river and yuanjiang river in karst dominated regions and during winter were measured the rivers and their tributaries have high total dissolved solid concentrations with tz ranging from 2 1 to 6 3 meq l which are significantly higher than that of the global river average calcium and hco3 followed by mg2 and so42 dominate the chemical composition of major ions in the river waters both na k and cl si account for 5 10 of the cations and anions respectively the waters of the wujiang river have high sr2 concentrations and lower 87sr 86sr ratios 0 7077 0 7110 while those of the qingshuijiang river one of two major tributaries of the yuanjiang river system show higher sr isotopic ratios 0 7090 0 7145 and low sr concentrations the lithology and geography of the river basins largely control the chemical and isotopic compositions of these rivers analyses of the stoichiometry of the river waters show that the water chemistry is controlled by carbonate dissolution by both carbonic and sulfuric acid especially of the wujiang river and suggest an origin of sulfate mainly from atmospheric input because of coal combustion and or oxidation of sulfide minerals in the catchments we identify three main weathering sources limestone dolomite and silicates chemical and sr isotopic composition of wujiang river waters are characterized mainly by limestone weathering while those of the qingshuijiang river waters mainly by dolomite and silicate weathering chemical weathering rates of carbonate and silicate are estimated and the results indicate that the chemical weathering rates of carbonate in the catchments are remarkably high significantly higher than most large rivers it is considered that presence of sulfuric acid in the rock weathering overuse of land and deterioration of vegetation are most likely the key factors responsible for the high weathering rates of carbonate in the catchments

geochemical and isotopic composition of groundwater in the complex terminal aquifer in southwestern tunisia with emphasis on the mixing by vertical leakage the complex terminal ct confined aquifer of the djerid basin southwestern tunisia was studied using major ion concentrations and stable isotope contents in order to 1 investigate the changes on its hydrodynamic functioning due to the long term over pumping and the large scale flood irrigation practices 2 determine the principal mineralization processes of its fossil groundwater and 3 examine the mode of recharge of this aquifer and whether it contains part of modern hydrological regime the observed geochemical patterns indicated that the main mineralization processes affecting the ct groundwater water rock interactions and mixing the native na cl and cl so4 ca na waters resulting from the dissolution of halite and gypsum and from pyrite oxidation interacted with those of the underlying and the overlying aquifers without changing their chemical facies stable isotope data provided evidences about upward and downward leakage into the ct aquifer and their relationships with anthropogenic activities they demonstrated that the long term over pumping of the ct aquifer which contributed to the loss of its potentiometric pressure favored the upward leakage of the artesian deep groundwater along parts of the major faults moreover the large scale flood irrigation practices in the oases domain which ensured the recharge of the shallow water table by return flow enhanced the downward leakage toward the ct aquifer

glacier fluctuation and tree ring records for the last millennium in the canadian rockies tree ring series and records of alpine glacier fluctuations provide complementary evidence to reconstruct decade to century climate fluctuations over the last millennium in the canadian rockies tree line ring width chronologies in this area are temperature sensitive and long ca 900 years series from sites adjacent to bennington and athabasca glaciers show synchronous declines in ring width during the periods ca 1170 1180 1280 1290 1330 1350 1430 1450 1530 1540 1690 1705 and 1810 1825 a d the latter two events are replicated in many shorter tree ring chronologies and immediately precede the two major periods of moraine development ca 1700 1725 and 1825 1875 a d during the little ice age dendrochronological dating of glacially overridden trees 0 5 1 0 km upvalley of 18th century maximum positions indicate that robson and peyto glaciers were advancing between 1150 and 1350 a d during the earliest phase of the little ice age in the canadian rockies available tree ring data suggest that the level and pattern of climate variability during the 18th and 19th centuries extends back over the last milennium it is also hypothesised that glaciers attained their maximum holocene extent during the little ice age because of the interaction between these decade to century scale fluctuations and the progressive long term decline of incoming summer solar radiation in the northern hemisphere over the last 10 000 years

regolith residence time and the concept of surface age of the piedmont peneplain the common upland weathering profile on foliated metamorphic rocks on the appalachian piedmont between alabama and maryland includes a 50 cm 1 m thick clay rich soil b horizon over 10 20 m of saprolite the saprolite retains the volume fabric and structure of the underlying parent rock but has lost about one third of the mass of the parent rock where the saprolite is thickest beneath upland drainage divides those divides are of loow slope and relief the flatness of the piedmont drainage divides provides the appearance of a planation surface of accordant summits or peneplain i interpret this flatness to be the result of three active processes volume reduction during compaction of saprolite into soil loss of mass in dissolved solids draining the soil b horizon and loss of mass from the soil surface by erosion of clay size particles the cumulative effects of these upland processes are to convert saprolite into soil to limit soil thickness and residence time and to limit the age of the oldest residual soils on the surface this results in a continual lowering of the piedmont peneplain surface this interpretation is corroborated by evidence of topographic inversion of fluvial gravels since the miocene near the fall line study of baseflow dissolved solids draining piedmont basins indicates a minimum rate of saprolite production of about 4 m ma 1 this minimum rate of production near the fall line is less than the estimated rate of surface lowering and saprolite consumption during the late tertiary and quaternary periods of topographic inversion measurement of cosmogenic 10be inventories in two 15 20 mores of piedmont upland regolith indicate a minimum residence time of residual soil and saprolite of about 1 ma this indicates a possible maximum rate of saprolite production and erosion of about 20 m ma 1 using the best available evidence therefore the typical piedmont upland regolith has a residence time of between 1 and 5 ma residence times may not be the same everywhere and ages may vary systematically across the surface the geomorphic evidence of topographic inversion and similar regolith profiles in other humid temperate and tropical regions strongly suggests that production and removal of piedmont saprolite has been an ongoing quaternary process and that most of the piedmont regolith is significantly younger than 5 ma independent geophysical evidence suggests that the rate of uplift probably involving tilting of parts of the piedmont blue ridge and valley and ridge has averaged between 5 and 20 m ma 1 through the cenozoic

strontium isotope and sequence stratigraphy of the miocene kirkwood formation southern new jersey we use sr isotope stratigraphy to correlate the miocene kirkwood formation of the new jersey coastal plain to the geomagnetic polarity time scale gpts and to ascertain the age of miocene depositional sequences sr isotope stratigraphy confirms diatom biostratigraphy which delineates three kirkwood sequences corresponding to east coast diatom zone ecdz 1 ecdz 2 and ecdz 6 of andrews 1988 sr isotope age estimates of the lowermost sequence ecdz 1 range from 19 2 to 22 6 ma 0 5 m y the middle sequence ecdz 2 ranges from 15 5 to 17 4 ma 0 5 m y a disconformity within ecdz 2 at the belleplain state forest borehole and the wildwood 198a well separates it into two sequences with a possible hiatus from 17 to 16 ma sr isotope age estimates of the upper kirkwood sequence ecdz 6 are not as certain and range from 11 5 to 13 6 ma 0 8 ma a shorter age range of 12 2 13 6 ma for this sequence is supported by its assignment to the d stauracanthus silicoflagellate subzone sedimentation rates were as high as 40 m per million years during deposition of the kirkwood formation suggesting possible tectonic influences on depositional history the timing of lower to middle miocene sequence boundaries from the new jersey coastal plain compares well with other indicators of sea level change including oxygen isotopes miller and others 1991b the global sea level record of haq and others 1987 and the offshore new jersey sequence boundaries of greenlee and others 1992 thus both tectonic and eustatic changes influenced miocene depositional history of the new jersey coastal plain

mathematical modeling of graded river profiles numerical modeling of the longitudinal profiles of rivers at grade is accomplished using the basic equations of open channel flow sediment transport equations and empirical relations for downstream variation in flow discharge sediment discharge sediment caliber and channel width only in some cases are the computed stream profiles fit exactly by any one of the commonly supported mathematical function analogs to graded profile form exponential logarithmic or power function but in most cases any of these functions can provide a fit with a degree of error smaller than would be noted in treating field data profiles dominated by spatial change in fluid and sediment discharge are distinctly power functions while profiles dominated by sediment size reduction are not necessarily exponential in form other important controls on profile shape are the degree of downstream width change in response to increasing discharge and the general range of sediment size a dynamic model of a river s approach to grade

glacial and periglacial erosion of the appalachians abstract the marine 18 o record indicates that the first ice advance into the appalachians equivalent to that of the late wisconsin occurred in the pliocene at about 2 4 ma only periodic localized glacial and periglacial activity occurred in the northern appalachians from 2 33 to 0 85 ma after 0 85 ma middle to late pleistocene eight out of ten glaciations covered the northern appalachians and brought periglacial conditions to the southern appalachians during the last 850 000 years glaciation extended to the late wisconsin limit within the appalachians for 15 of the time and extended to the early wisconsin limit just north of the appalachians for 25 of the time pleistocene glacial erosion of the appalachians of 120 200 m is necessary to account for the estimated volume of pleistocene ocean sediment derived from the appalachians and the estimated volume of pliocene pleistocene glaciogenic ocean sediment derived from the entire laurentide ice sheet this amount of glacial erosion occurring over the maximum expectable duration of pliocene pleistocene ice cover of 247 000 years yields glacial erosion rates from 0 5 0 8 m ka 1 such depths of erosion by thick warm based ice streams were localized in the lowlands and estuaries of the northern appalachians in the maritimes the presence of thin cold based ice caused minimal erosion of uplands periglacial landforms and tundra boreal forest were distributed throughout the appalachian highlands and the northern coastal plain during the glacial maxima periglacial erosion of 0 15 0 30 m ka 1 near the ice in pennsylvania decline to 0 1 0 2 m ka 1 in the southern piedmont each cold period almost completely renewed the regolith by eroding slopes and filling valleys the cumulative effect of the eight to ten major cold events could have produced as much as a few ten s of meters of periglacial ridge top lowering during the pleistocene both estimated glacial and periglacial erosion rates greatly exceed estimated current fluvial erosion rates therefore glacial and periglacial processes should be considered the dominant processes in shaping the present appalachian landscape the northern appalachians may be evolving towards a form where the landscape provides just the shape necessary to permit the least work conveyance of the ice across the region during glacial maxima the southern appalachians may be evolving towards a form where the landscape provides just the hillslope form necessary to transport the debris provided by periglacial conditions

does altonian drift exist in pennsylvania and new jersey abstract from new jersey to southwestern new york altonian colluvium and fluvial gravel have been recognized beneath woodfordian drift but the existence of altonian till near or beyond the woodfordian border has not been demonstrated reworking of weathered materials by woodfordian ice has produced some drift with an altonian appearance soil criteria applied without regard for parent material differences have been incorrectly used to infer an altonian age for illinoian deposits that have a redbed provenance the currently mapped distribution of altonian till and the occurrence of undisturbed illinoian deposits within areas of inferred altonian ice cover are incompatible with the behavior of ice sheets

soil development in till of various ages in northeastern pennsylvania abstract eleven well drained soils formed in till parent materials of varying ages in northeastern pennsylvania were studied to determine changes in the soils with time four profiles three lackawanna and one bath were formed in woodfordian till 15 000 yr b p and two leck kill were formed in altonian till 28 000 75 000 yr b p in these soils the extractable iron oxide extractable aluminum oxide and kaolinite contents increase with age as do the total clay and fine total clay ratio with increasing age the maximum accumulation of these constituents is found deeper in the profile the extractable silicon oxide distribution is constant with depth but it decreases in overall amount with time gibbsite is found only in small amounts in the a horizon of altonian soils but occurs throughout the profile of pre wisconsinan soils although only in small amounts in general differences were found in these soils which separated them into three groups representing varying degrees of soil development a regression equation was derived to predict the age of soils formed from the altonian till based on a clay accumulation index value for soils of known woodfordian and holocene ages the equation log y 1 80 0 992 log x best fit the data with an r 2 value of 0 913 using this equation a mean age of 41 000 yr was calculated for the altonian soils this date was used to derive a second equation to predict ages for pre wisconsinan soils the equation with the highest r 2 value 0 934 was log y 1 81 0 998 log x dates for soils developed in the white deer till and the laurelton till of the pre wisconsinan stage were calculated to be 86 000 and 91 000 yr b p respectively these dates fall within ages estimated for the sangamon interglaciation and thus would appear to be too young for pre sangamonian materials the probable reason for the too young age is that the c horizon material of the pre wisconsinan soils was weathered and did not provide an accurate estimate of clay accumulation for the prediction equation

the holocene history of the columbia icefield canada abstract the columbia icefield is the largest icefield in the canadian rockies and feeds eight major glaciers that drain to three different oceans previous glacier studies have focused on athabasca and saskatchewan glaciers primarily due to their easy access this paper reviews evidence of the holocene history from all eight glaciers maximum holocene glacier extent was during the little ice age lia with dating based mainly on minimum tree ring estimates from trees growing on the moraines or from trees scarred tilted or killed by the glaciers the lia maximum advance was during the 19th century at athabasca 1843 4 dome 1846 saskatchewan 1862 and castleguard 1271 and detrital wood from lateral moraines at columbia ca 0 8 0 7ka two overridden stumps at columbia glacier indicate a previously unidentified advance ca 1500 a d these four phases of lia coincide with major reductions in summer temperatures reconstructed at the icefield there are also undated pre 1600 possibly pre lia moraines at kitchener glacier less extensive neoglacial glacier events are documented by an in situ forest bed buried by the saskatchewan glacier ca 2 90 3 4 ka equivalent to the peyto advance and stumps buried by till ca 4 2ka at boundary glacier detrital wood recovered from till at columbia glacier indicates at least one glacier advance ca 2 0 2 2ka till exposed between the bridge river and mazama tephras at stutfield glacier includes detrital wood dating 2 22 2 70 ka that possibly indicates a glacier advance immediately prior to the bridge river tephra regional paleoenvironmental data indicate warmer conditions and higher treelines in the early holocene detrital wood washed out of dome and athabasca glaciers indicates trees were present in these valleys ca 6 7 and 9ka upvalley of present glacier snouts evidence from castleguard cave indicates upstream entrances below the present icefield were probably ice free ca 9 5ka indicating the icefield was much reduced in extent at that time the detrital wood may represent wood killed and reworked by limited glacier advances from the icefield far upstream of present glacier fronts at these times

neoglacial history of robson glacier british columbia as glaciers in the canadian rockies recede glacier forefields continue to yield subfossil wood from sites overridden by these glaciers during the holocene robson glacier in british columbia forme

stratigraphy petrography and correlation of late cenozoic middle atlantic coastal plain deposits implications for late stage passive margin geologic evolution regional chronostratigraphic correlation of middle atlantic upper coastal plain and fall zone fluvial deposits long thought to represent the updip proximal facies of a well dated post oligocene marine sequence in the salisbury embayment remains incomplete in part because of the paucity of biostratigraphic data petrography based lithostratigraphic correlations provide an opportunity to extend age control present in downdip marine deposits updip to fluvial deposits thus establishing the means for a regional chronostratigraphic correlation previous stratigraphic studies in new jersey delmarva southern maryland virginia and the central appalachian piedmont are linked by a crucial sequence of fluvial deposits at the head of chesapeake bay here petrography based lithostratigraphic correlations demonstrate 1 late oligocene late miocene susquehanna river dominated polygenetic quartzose fluvial aggradation bryn mawr formation 2 pliocene heterolithic but quartz dominated fluvial terrace and alluvial fan deposition perryville formation 3 pliocene early pleistocene paleo delaware hudson river dominated lithic and feldspathic rich fluvial aggradation pensauken formation and 4 the initiation of estuarine conditions turkey point beds by early pleistocene time these results are synthesized to propose a new late cenozoic regional chronostratigraphic correlation and depositional history for the salisbury embayment the correlation elucidates a complex interaction between passive margin isostasy tectonics eustasy and sediment source

neoglaciation in the southern coast mountains of british columbia chronology prior to the late neoglacial maximum moraine stratigraphy and morphology radiocarbon dates from klinaklini franklin tiedemann gilbert and bridge glaciers and related information from elsewhere in the coast mountains are used to construct a chronology for glacier fluctuations the garibaldi phase of glacier expansion 6000 5000 14c years bp at the end of the early holocene xerothermic interval is indicated by overridden tree stumps the mid neoglacial tiedemann advance 3300 1900 14c years bp is represented by moraines till and meltwater sediments at three glaciers but only tiedemann glacier attained its greatest holocene extent at this time late neoglacial expansion commenced before 900 14c years bp and continued without notable interruption until glaciers achieved their maximum post pleistocene expansion during the eighteenth and nineteenth centuries evidence for the garibaldi and tiedemann events is scarce within the coast mountains because of the more extensive late neoglacial advance however correlative advances have been

sea level changes an integrated approach sea level changes an integrated approach in october 1985 sepm sponsored a four day conference entitled sea level changes an integrated approach the purpose of the conference was to provide a forum for an interdisciplinary exchange of ideas on sea level changes and to provide an opportunity for integrating various types of evidence in approaching unresolved issues the conference was successful in bringing together scientists from industry academia and government representing all of the major geosciences disciplines presentations of many new papers plus significant releases of data that were previously held proprietary provided fertile ground for discussion this much cited volume represents the best of the material presented at the conference includes the early vail chart

age of the crowfoot advance in the canadian rocky mountains a glacial event coeval with the younger dryas oscillation a suite of sediment core samples was recovered from two lakes crowfoot and bow lakes that are adjacent to the crowfoot moraine type locality to identify and radiocarbon date sediments related to the crowfoot advance the crowfoot moraine system widely recognized throughout northwestern north america represents a glacial advance that is post wisconsin and pre mazama tephra in age an interval of inorganic sediments bracketed by accelerator mass spectrometry radiocarbon ages of ca 11 330 and 10 100 sup 14 c yr b p is associated with the crowfoot moraine the crowfoot advance is therefore approximately synchronous with the european younger dryas cold event ca 11 000 10 000 sup 14 c yr b p furthermore the termination of the crowfoot advance also appears to have been abrupt these findings illustrate that the climatic change responsible for the european younger dryas event extended beyond the northern atlantic basin and western europe equilibrium line altitude ela depressions associated with the crowfoot advance are similar to those determined for the little ice age advance whereas younger dryas ela depressions in europe significantly exceed little ice age ela depressions 26 refs 3 figs 1 tab

chemical characteristics of groundwater in parts of mountainous region alvand hamadan iran eighty seven groundwater samples have been collected from a mountainous region alvand iran for hydrochemical investigations to understand the sources of dissolved ions and assess the chemical quality of the groundwater most water quality parameters are within world health organization acceptable limits set for drinking water the least mineralized water is found closest to the main recharge zones and the salinity of water increased towards the north of the basin the most prevalent water type is ca hco3 followed by water types ca no3 ca cl ca so4 and mg hco3 the ca no3 water type is associated with high nitrate pollution agricultural and industrial activities were associated with elevated level of no3 mineral dissolution weathering of evaporites dominates the major element hydrochemistry of the area chemical properties of groundwater in alvand region are controlled both by natural geochemical processes and anthropogenic activities

the influence of bedrock geology on knickpoint development and channel bed degradation along downcutting streams in south central indiana geologic controls on knickpoint development and the mechanics of channel bed degradation were eluci dated by comparison of downcutting streams in south central indiana developed in lithologically homoge neous carbonate units and layered siliciclastic strata knickpoints formed in a single lithologic unit are stepped each step consists of a knickpoint face and tread the height of each step is equal to and controlled by bed thickness spatially knickpoints in homogeneous terrain are limited to jointed strata that dip 1 upstream or 2 downstream at angles less than the channel gradient knickpoints observed in lithologically layered strata are characterized by a single step in which resistant jointed rocks overlie and protect weaker units total knickpoint relief is influenced by thickness of the weaker strata knickpoints in layered siliciclastic strata are spatially limited to bedrock reaches produced by differential rates of channel incision knickpoint distribution is also influenced by joint

late tertiary floral assemblage from upland gravel deposits of the southern maryland coastal plain a diverse flora has been discovered in a dark clay lens in upland gravel in southern maryland near brandywine more than 49 taxa have been identified in the assemblage which includes leaves seeds fruits pollen and a taxodium bald cypress trunk the vegetation is dominated by deciduous trees and vines four taxa are now absent from north america but survive elsewhere one is extinct a late miocene age and warm temperate climate are inferred from the flora the clay lens probably represents a cutoff distributary in the extensive braided stream system that covered the area and is unique in maryland similar dark clays have been described from miocene sands and gravels in new jersey the brandywine flora is the first direct evidence of the miocene age of part of the fluvial upland deposits of maryland on the basis of the age inferred from the flora the brandywine deposit is correlated with the st marys formation or the eastover formation which are upper miocene shelly marine units south and southeast of brandywine

postglacial vegetational history of tonquin pass british columbia a pollen and macrofossil study of peat sediments in tonquin pass british columbia provides the oldest dated record of vegetational and climatic changes in the middle canadian rockies paleoecological interpretation of these events dated by tephrochronology and radiocarbon dating is facilitated by comparisons with other regional pollen profiles late wisconsin ice receded from tonquin pass prior to 10 000 years bp by 9700 years bp a pinus contorta forest with an understory dominated by ferns had colonized the area the climate of this period was cool and moist following this interval was a brief episode 9000 8040 years bp of haploxylon pine dominance during which the climate became colder a long warm period beginning by 8040 years bp was characterized by desiccation of local meadows and fens and invasions of these areas by trees principally picea dated fossil picea and abies logs from alpine bogs within jasper national park document that timberlines had advanced beyond present limits by 8770 years b

fluvial terraces of the lower susquehanna river abstract fluvial terraces of the lower susquehanna river offer a unique opportunity to investigate the late stage geologic and geomorphic evolution of the u s atlantic passive margin petrography and elevation distinguish and provide a basis for correlation of two groups of terraces the upland terraces and lower terraces through the piedmont newark basin and great valley downstream correlation to dated upper coastal plain and fall zone fluvial deposits relative weathering and soil profile development characteristics establish terrace age upland terraces tg1 tg2 and tg3 middle to late miocene strath terraces 80 to 140 m above the present channel occur only along the piedmont reach they are underlain by unstratified texturally mature quartz dominated roundstone diamictons lower terraces qtg qt1 qt6 pliocene and pleistocene strath and thin aggradational terraces within 45 m of the present channel are underlain by stratified and unstratified texturally and compositionally immature sand gravel and pebbly silt terrace age and longitudinal profiles suggest complex interactions among relative base level long term flexural isostatic processes climate and river grade our model for terrace genesis requires the susquehanna river to attain and maintain a characteristics graded longitudinal profile over graded time for the u s atlantic margin we propose that straths are continually cut along this graded profile during periods of relative base level stability achieved by slow steady isostatic continental uplift acting in concert with eustatic rise change in an external modulating factor such as eustatic fall or climate change results in fluvial incision and subsequent genesis of strath terraces longitudinal profiles of lower susquehanna river terraces which converge at the river mouth diverge through the piedmont and reconverge north of the piedmont contrast with their hypothesized original concave up profiles progressive and cumulative flexural upwarping of the atlantic margin accounts for terrace profile deformation suggesting flexural isostasy as a first order regional deformation mechanism these results offer new interpretations of terrace age correlation and geologic significance that require modification of previous studies suggesting uplifted or anticlinically warped peneplains on the u s atlantic margin

western canadian glaciers advance in concert with climate change circa 4 2 ka 1 disparate climate proxies from the northern hemisphere record a climate event at 4 2 3 8 ka here we show that glaciers throughout the mountain ranges of western canada advanced at about this time this conclusion is based on 1 new and previously reported radiocarbon ages on in situ stumps logs branches and soils exposed by recent retreat in glacier forefields and 2 clastic rich sediment intervals in cores retrieved from four montane lakes these glacier and lacustrine data indicate a period of several decades to century length when climate conditions cool summers wet winters or both favoured glacier nourishment and advance across western canada

climatic impact on isovolumetric weathering of a coarse grained schist in the northern piedmont province of the central atlantic states the possible impact of periglacial climates on the rate of chemical weathering of a coarse grained plagioclase muscovite quartz schist has been determined for a small watershed near baltimore maryland the isovolumetric chemical weathering model formulated from the geochemical mass balance study of the watershed shows that the weathering front advances at a velocity of 9 1 m m y if the modern environmental parameters remain the same back through time however recent surficial geological mapping demonstrates that periglacial climates have impacted the area such an impact significantly affects two key chemical weathering parameters the concentration of co2 in the soil and groundwater moving past the weathering front depending upon the assumptions used in the model the rate of saprolitization varies from 2 2 to 5 3 m m y the possible impact of periglacial processes suggested by the chemical weathering rates indicates a need to reconsider theories of landscape evolution as they apply to the northern piedmont province of the mid atlantic states i suggest that from the late miocene to the present that the major rivers have become incised in their present locations this incision has enhanced groundwater circulation and chemical weathering such that crystalline rocks beneath interfluvial areas remain mantled by saprolite and the saprolite mantle has been partially stripped as periglacial conditions alternate with humid temperate conditions

geochemical and quality assessment of groundwater of marand basin east azarbaijan province northwestern iran the chemical analysis of 83 water wells in the marand area azarbaijan province nw of iran was evaluated to determine the hydrogeochemical processes and ion concentration background in the region over the entire area the dominated hydrochemical types are ca mg so4 cl ca so4 na cl and ca mg hco3 based on the total hardness the softness of the groundwater is determined according to electrical conductivity ec and sodium adsorption ratio sar the most dominant classes are c3 s1 c3 s2 c4 s2 and c2 s1 the major ion concentrations are below the acceptable level for drinking water the groundwater salinity hazard is medium to high but the na hazard is low to medium with regard to irrigation water the quality is low to medium so a drainage system is necessary to avoid the increase of toxic salt concentrations

geochemistry characterization of groundwater in an agricultural area of razan hamadan iran this study was conducted to evaluate factors regulating groundwater quality in an area with agriculture as main use thirty groundwater samples have been collected from razan area hamadan iran for hydrochemical investigations to understand the sources of dissolved ions and assess the chemical quality of the groundwater the chemical compositions of the groundwater are dominated by na ca2 hco3 cl and so42 which have been derived largely from natural chemical weathering of carbonate gypsum and anthropogenic activities of fertilizer s source the production of so42 has multiple origins mainly from dissolution of sulphate minerals oxidation of sulphide minerals and anthropogenic sources the major anthropogenic components in the groundwater include na cl so42 and no3 with cl and no3 being the main contributors to groundwater pollution in razan area

a record of appalachian denudation in postrift mesozoic and cenozoic sedimentary deposits of the u s middle atlantic continental margin abstract the complex interplay between source terrain uplift basin subsidence paleoclimatic shifts and sea level change left an extensive sedimentary record in the contiguous offshore basins of the u s middle atlantic margin salisbury embayment baltimore canyon trough and hatteras basin isopach maps of 23 postrift lower jurassic to quaternary a allostratigraphic units coupled with a revised stratigraphic framework reveal that tectonism by regulating sediment supply accumulation rate dominated the interplay of forcing mechanisms tectonic pulses are evidenced by abruptly accelerated sediment accumulation marked latitudinal shifts in the location of depocenters and regional changes in lithofacies relatively rapid tectonic subsidence during the early and middle jurassic history of the basins may have enhanced sediment accumulation rates beginning in the late jurassic however subsidence rates decreased significantly though occasional short pulses of subsidence may have effected relative sea level rises sea level change heavily influenced the distribution and redistribution of sediments one they reached the basins and paleoclimate regulated the relative abundance of carbonates and evaporites in the basins we conclude that source terrains of the central appalachian highlands were tectonically uplifted intensely weathered and rapidly eroded three times since the late triassic 1 early to middle jurassic aalenian to callovian 2 mid early cretaceous barremian and 3 late cenozoic middle miocene intervals of tectonic quiescence following these three tectonic pulses provided conditions suitable for the formation of regional erosion surfaces geomorphic features commonly reported to characterize the central appalachian highlands this series of three irregularly spaced tectonic quiescent cycles does not however match the traditional four cycle concept of post triassic appalachian peneplanation

identification and evolution of hydrogeochemical processes in the groundwater environment in an area of the palar and cheyyar river basins southern india the palar and cheyyar river basins in tamil nadu state of southern india are characterised by different geological formations and groundwater is the major source for domestic agricultural and other water related activities hydrogeochemical studies were carried out in this area with the objective of identifying the geochemical processes and their relation to groundwater quality groundwater samples were collected once a month from 43 groundwater wells in this area from january 1998 to july 1999 sampling procedures and chemical analysis were carried out as per the standard methods chemical data are used for mathematical calculations and graphical plots to understand the chemical process and its relation to the groundwater quality the chemical composition of groundwater in the central part of the study area mainly depends on the recharge from lakes and the river which is explained by a mixing mechanism in addition weathering of silicate minerals controls the concentration of major ions such as sodium calcium magnesium and potassium in the groundwater of this area further the activity ratios indicate that the groundwater is in equilibrium with kaolinite smectite and montmorrillonite the reverse ion exchange process controls the concentration of calcium magnesium and sodium in hard rock formations and dissolution of carbonate minerals and accessory minerals is the source of ca and mg in addition to cation exchange in the sedimentary formations in general the chemical composition of the groundwater in this area is influenced by rock water interaction dissolution and deposition of carbonate and silicate minerals ion exchange and surface water interactions

holocene glacier fluctuations in the canadian cordillera alberta and british columbia abstract although the record of holocene glacier fluctuations in british columbia and alberta is still very fragmentary much recent progress has been made in their study dating of end moraines has been supplemented by studies of lateral moraine stratigraphy and dating of glacially overridden organic matter upstream of end moraines dates from sites close to contemporary glaciers indicate that ice had retreated to about its present limits before 10 ka bp prior to deposition of mazama tephra a minor pre hypsithermal readvance the crowfoot advance left deposits in the rockies and the interior of british columbia the earliest known neoglacial advances occurred 5 6 ka bp in the coast mountains and shortly after 4 ka bp in the rockies an advance culminating ca 4 3 ka bp has been reported from bugaboo glacier while evidence of another advance culminating in the period ca 2 5 1 8 ka bp the tiedemann advance is reported from more than one site following a recession the little ice age expansion the cavell advance began shortly after 900 bp this advance culminated in most cases in the 18th or 19th centuries the crowfoot tiedemann and little ice age advances were apparently of roughly the same magnitude the latter was most extensive in most cases but at several sites crowfoot moraines lie slightly farther downvalley than little ice age moraines during the present century ice fronts have generally retreated particularly rapidly in the period 1920 1950 a d although rates of retreat have decreased in the last three decades and some glaciers have readvanced slightly

holocene and latest pleistocene fluctuations of stutfield glacier canadian rockies the holocene and late glacial history of fluctuations of stutfield glacier are reconstructed using moraine stratigraphy tephrochronology and dendroglaciology stratigraphic sections in the lateral moraines contain tills from at least three glacier advances separated by volcanic tephras and paleosols the oldest pre mazama till is correlated with the crowfoot advance dated elsewhere to be younger dryas equivalent a neoglacial till is found between the mazama tephra and a paleosol developed on the bridge river tephra a log dating 2400 bp from the upper part of this till indicates that this glacier advance correlated with the peyto advance culminated shortly before deposition of the bridge river tephra radiocarbon and tree ring dates from overridden trees exposed in moraine sections indicate that the initial cavell little ice age lia advance overrode this paleosol and trees after a d 1271 three subsequent phases of the cavell advance were dated by dendrochronology the maximum glacier extent occurred in the mid 18th century predating 1743 on the southern lateral although ice still occupied and tilted a tree on the north lateral in 1758 subsequent glacier advances occurred ca 1800 1816 and in the late 19th century the relative extent of the lia advances at stutfield differs from that of other major eastward flowing outlets of the columbia icefield which have maxima in the mid late 19th century this is the first study from the canadian rockies to demonstrate that the large morphologically simple lateral moraines defining the lia glacier limits are actually composite features built up pro gressively but discontinuously over the holocene and contain evidence of multiple holocene and crowfoot age gla cier advances resume la stratigraphie des moraines la tephrochronologie et la dendroglaciologie des moraines ont servi a recons truire les fluctuations a l holocene et au cours de l histoire glaciaire tardive du glacier stutfield les sections stratigra phiques dans les moraines laterales contiennent des tills d au moins trois avancees glaciaires separees par des tephras volcaniques et des paleosols le plus ancien le till pre mazama est correle a l avancee crowfoot dont on a determine l ge ailleurs comme etant un equivalent du dryas recent un till de l epoque neo glaciaire se retrouve entre le tephra mazama et un paleosol developpe sur le tephra de bridge river un billot date 2400 bp provenant de la partie supe rieure de ce till indique que cette avancee glaciaire correlee a l avancee de peyto a culmine peu de temps avant la deposition du tephra de bridge river des datations au 14 c et des series chronlogiques provenant d arbres recouverts puis exposes dans des sections de moraine indiquent que l avancee cavell initiale petit ge glaciaire a chevauche ce paleosol et les arbres apres l an 1271 la dendrochronologie a permis la datation de trois phases subsequentes de l avancee cavell l etendue glaciaire maximale eut lieu au milieu du 18e siecle avant 1743 sur le cote sud bien que la glace fut encore presente sur le cote nord et y ait bascule un arbre en 1758 des avancees glaciaires subsequentes ont eu lieu vers 1800 1816 et vers la fin du 19e siecle l etendue relative des avancees du petit ge glaciaire a stutfield differe de celles d autres glaciers majeurs du champ de glace columbia s ecoulant vers l est et qui ont eu leur maxi mum dans la deuxieme moitie du 19e siecle cette etude est la premiere provenant des rocheuses canadiennes a de monter que les grandes moraines laterales morphologiquement simples definissant les limites du glacier au petit ge glaciaire sont en fait des elements composites developpes progressivement mais de facon discontinue tout au cours de l holocene et qu elles contiennent des evidences d avancees glaciaires multiples d ge holocene et crowfoot

assessment of groundwater quality for irrigation purposes and identification of hydrogeochemical evolution mechanisms in pengyang county china groundwater is an important water source for agricultural irrigation in penyang county some traditional methods such as irrigation coefficient sodium adsorption ratio total alkalinity total salinity and total dissolved solids were employed to assess groundwater quality in this area in addition an improved technique for order preference by similarity to ideal solution model was applied for comprehensive assessment the origin of major ions and groundwater hydrogeochemical evolution was also discussed groundwater in penyang county contains relative concentrations of dominant constituents in the following order na ca2 mg2 k for cations and hco3 so42 cl co32 for anions groundwater quality is largely excellent and or good suggesting general suitability for agricultural use calcite and dolomite are found saturated in groundwater and thus tend to precipitate out while halite fluorite and gypsum are unsaturated and will dissolve into groundwater during flow groundwater in the study area is weathering dominated and mineral weathering carbonate and silicate minerals and ion exchange are the most important factors controlling groundwater chemistry

evidence for a neoglacial advance of the boundary glacier banff national park alberta direct evidence for an early neoglacial advance in the canadian rocky mountains is presented radiocarbon dates from buried peat and tree remains at boundary glacier suggest limiting dates for this advance of between 3800 and 4200 years bp these data from boundary glacier are consistent with previously published dates for the onset of the neoglacial and an early neoglacial advance

palynological evidence for late miocene pliocene and early pleistocene climate changes in the middle u s atlantic coastal plain abstract palynomorph assemblages from eight geologic formations in the middle atlantic coastal plain ranging in age from latest miocene to early pleistocene have been interpreted in terms of terrestrial paleoclimates the data suggest that a warm temperate to subtropical climate warmer than at present prevailed at the close of the miocene and the beginning of the pliocene at that time there was little or no temperature gradient within the study area 36 30 to 39 n this warm period was followed by a warm temperate interval in virginia and north carolina with temperatures probably not very different from those of today although a slight warming trend probably occurred during the deposition of the colerain beach member of the chowan river formation a definite cool interval is indicated by the presence of spruce pollen in the bacons castle formation of virginia this interval is interpreted to have begun about 2 3 2 4 ma or possibly slightly later simultaneous with the cooling that has been recorded in deep sea cores of the north atlantic ocean and in the pre tiglian of western europe this was followed by a warmer than present period that may be correlated with the tiglian of the latest pliocene finally palynological data from the cape may formation of new jersey suggest that a warm temperate warmer than at present climate prevailed during the early pleistocene

ancient channels of the susquehanna river beneath chesapeake bay and the delmarva peninsula three generations of the ancestral susquehanna river system have been mapped beneath chesapeake bay and the southern delmarva peninsula closely spaced seismic reflection profiles in the bay and boreholes in the bay and on the southern delmarva peninsula allow detailed reconstruction of each paleochannel system the channel systems were formed during glacial low sea level stands and each contains a channel fill sequence that records the subsequent transgression the trunk channels of each system are 2 to 4 km wide and are incised 30 to 50 m into underlying strata they have irregular longitudinal profiles and very low gradients within the chesapeake bay area the three main stem channels diverge from the head of the bay toward the southeast the channels are rarely coincident although they commonly intersect all three main channels pass beneath the southern delmarva peninsula forming an age progression from north oldest to south youngest beneath the peninsula and from east oldest to west youngest beneath chesapeake bay southward progradation of the tip of the delmarva peninsula during interglacial high sea level stands caused southward migration of the mouth of the bay so that the next generation of channels were incised progressively further towards the southwest the youngest paleochannel is clearly of late wisconsinan age about 18 ka and the intermediate one appears to be late illinoian in age or about 150 ka the age of the oldest paleochannel is not well constrained but it is in the range of about 200 to 400 ka the three paleochannel systems imply a dynamic coastal plain environment and at least two previous generations of the chesapeake bay both the chesapeake bay and the southern delmarva peninsula have changed considerably in the past half million years

identification of hydrogeochemical processes and pollution sources of groundwater resources in the marand plain northwest of iran the main aims of the present study are to identify the major factors affecting hydrogeochemistry of groundwater resources in the marand plain nw iran and to evaluate the potential sources of major and trace elements using multivariate statistical analysis such as hierarchical clustering analysis hca and factor analysis fa to achieve these goals groundwater samples were collected in three sampling periods in september 2013 may 2014 and september 2014 and analyzed with regard to ions e g ca2 mg2 na and k hco3 so4 2 cl f and no3 and trace metals e g cr pb cd mn fe al and as the piper diagrams show that the majority of samples belong to na cl water type and are followed by ca hco3 and mixed ca na hco3 cross plots show that weathering and dissolution of different rocks and minerals ion exchange reverse ion exchange and anthropogenic activities especially agricultural activities influence the hydrogeochemistry of the study area the results of the fa demonstrate that 6 factors with 81 7 of total variance are effective in the overall hydrogeochemistry which are attributed to geogenic and anthropogenic impacts the hca categorizes the samples into two clusters samples of cluster c1 which appear to have higher values of some trace metals like pb and as are spatially located at the eastern and central parts of the plain while samples of cluster c2 which express the salinization of the groundwater are situated mainly westward with few local exceptions

reconstruction of holocene changes in alpine vegetation and climate in the maligne range jasper national park alberta abstract pollen macrofossil logs and needles and oxygen isotope data from tree rings are presented for three alpine bog sites in the maligne range of the canadian rockies organic sedimentation at the watchtower site began prior to ca 9500 14 c yr b p and by 8770 yr b p timberlines were at least 100 m above present levels the two pollen records are dominated by pinus and subsequent changes in timberlines are inferred from pollen ratio data abies pinus and from macrofossils the recovered records indicate two periods of high hypsithermal timberlines ca 8800 7500 and 7200 5200 yr b p separated by a short interval ca 7300 7400 yr b p when timberline approached modern levels after ca 4500 yr b p timberlines have been similar to or lower than present reaching minimum values in the last 500 yr 18 o determinations from the cellulose of samples of 5 or 10 annual rings cut from contemporary picea englemannii at timberline show strong correlations with mean annual temperatures at jasper isotopic determinations from hypsithermal age logs recovered from sites above present timberline indicate mean annual temperatures were at least 0 5 c warmer ca 8060 and 8770 yr b p than at present at the watchtower site data from logs at the maligne pass site suggest that temperatures were about 1 2 and 1 6 c warmer ca 6000 and 5300 yr b p estimates of temperature from the pollen ratio data are more conservative and suggest maximum differences of ca 1 0 c in july temperatures over the last 8000 yr

latest pleistocene and holocene glacier fluctuations in western canada we summarize evidence of the latest pleistocene and holocene glacier fluctuations in the canadian cordillera our review focuses primarily on studies completed after 1988 when the first comprehensive review of such evidence was published the cordilleran ice sheet reached its maximum extent about 16 ka and then rapidly decayed some lobes of the ice sheet valley glaciers and cirque glaciers advanced one or more times between 15 and 11 ka by 11 ka or soon thereafter glacier cover in the cordillera was no more extensive than at the end of the 20th century glaciers were least extensive between 11 and 7 ka a general expansion of glaciers began as early as 8 4 ka when glaciers overrode forests in the southern coast mountains it culminated with the climactic advances of the little ice age holocene glacier expansion was not continuous but rather was punctuated by advances and retreats on a variety of timescales radiocarbon ages of wood collected from glacier forefields reveal six major periods of glacier advance 8 59 8 18 7 36 6 45 4 40 3 97 3 54 2 77 1 71 1 30 ka and the past millennium tree ring and lichenometric dating shows that glaciers began their little ice age advances as early as the 11th century and reached their maximum holocene positions during the early 18th or mid 19th century our data confirm a previously suggested pattern of episodic but successively greater holocene glacier expansion from the early holocene to the climactic advances of the little ice age presumably driven by decreasing summer insolation throughout the holocene proxy climate records indicate that glaciers advanced during the little ice age in response to cold conditions that coincided with times of sunspot minima priority research required to further advance our understanding of late pleistocene and holocene glaciation in western canada includes constraining the age of late pleistocene moraines in northern british columbia and yukon territory expanding the use of cosmogenic surface exposure dating techniques using multi proxy paleoclimate approaches and directing more of the research effort to the northern canadian cordillera

a case study on geochemical anomaly identification through principal components analysis supplementary projection abstract based on a case study in which a single geochemical anomaly was located in the vicinity of an abandoned mine in central portugal a recursive methodology for anomaly background separation was developed this methodology relies on the supplementary projection of each of the samples taken from a subset of anomaly candidates onto the axes provided by principal components analysis of the background subset the concept of anomaly intensity defined by the average of the distances from the original to the supplementary projections is the basis for final anomaly identification

drumlins subglacial meltwater floods and ocean responses drumlins and erosional marks in bedrock give evidence for broad subglacial meltwater floods that have discharge rate estimates of about 10 6 m 3 s similar discharge rates are obtained for other late glacial catastrophic floods the total volume of meltwater that is thought to have formed the livingstone lake saskatchewan drumlin field is estimated at 8 4 x 10 4 km 3 this volume is equivalent to a eustatic rise of 0 23 m in global sea level meltwater release and roughly contemporaneous formation of drumlin fields in north america and europe could have involved several metres of sea level rise in a few years the implications of such floods for the generation of myths and the interpretation of the oxygen isotopic record of the oceans are discussed high meltwater discharges are of potential importance to the generation of a lid of cold fresh water over the north atlantic and its effects on late glacial climate

quaternary climates and sea levels of the u s atlantic coastal plain uranium series dating of corals from marine deposits of the u s atlantic coastal plain coupled with paleoclimatic reconstructions based on ostracode marine and pollen continent data document at least five relatively warm intervals during the last 500 000 years on the basis of multiple paleoenvironmental criteria we determined relative sea level positions during the warm intervals relative to present mean sea level were 7 5 meters at 188 000 years ago 7 5 1 5 meters at 120 000 years ago 6 5 3 5 meters at 94 000 years ago and 7 3 meters at 72 000 years ago the composite sea level chronology for the atlantic coastal plain is inconsistent with independent estimates of eustatic sea level positions during interglacial intervals of the last 200 000 years hydroisostatic adjustment from glacial interglacial sea level fluctuations lithospheric flexure and isostatic uplift from sediment unloading due to erosion provide possible mechanisms to account for the discrepancies alternatively current eustatic sea level estimates for the middle and late quaternary may require revision

new accelerator mass spectrometry radiocarbon ages for the mazama tephra layer from kootenay national park british columbia canada charcoal fragments recovered from the mazama air fall tephra layer in cores from dog and cobb lakes kootenay national park british columbia yielded accelerator mass spectrometry ages of 6720 70 and 6760 70 14c years bp respectively these two new ages together with other previously published radiocarbon ages on charcoal and twig fragments from mazama air fall deposits indicate that the climactic eruption of mount mazama occurred 6730 40 14c years bp

high eustatic sea level during the middle pliocene evidence from the southeastern u s atlantic coastal plain the middle pliocene approximately 3 5 2 5 ma was a period of global warmth preceding the growth of major northern hemisphere ice sheets the authors report on eustatic sea level for the middle pliocene based on microspaleontologic study of marine deposits of the duplin formation of south carolina and north carolina the duplin was deposited during a middle pliocene marine transgression that formed the orangeburg scarp a prominent wave cut geomorphic paleoshoreline of the southeastern u s atlantic coastal plain they concluded that 1 the scarp in south carolina was formed mostly during the middle pliocene 3 5 3 0 ma 2 eustatic sea level was about 35 plus minus 18 m higher than modern sea level the scarp has been uplifted about 50 65 m since the middle pliocene and 3 ocean water temperatures along eastern north america were warmer when the scarp was formed that they are at present

identification of probable groundwater paths in the amargosa desert vicinity in this study the hydrogeochemical program phreeqc was used to determine the chemical speciation and mineral saturation indices sis of groundwater in the vicinity of the proposed high level nuclear waste repository at yucca mountain nevada usa in turn these data were used to interpret the origin and recharge mode of groundwater to elucidate the mechanisms of flow and transport and to determine potential sources of groundwater contamination phreeqc was run to determine aqueous dissolved species and minerals that would be in equilibrium with the study area s groundwater selected major ions associated si f and ca na ion exchange were then examined using the multivariate statistical methods of principal component factor analysis and k means cluster analysis analysis of dissolved ion concentrations sis and ca na ion exchange allows simultaneous consideration of arithmetic raw concentrations and logarithmic si ion exchange variables that describe the hydrochemical system and therefore can provide further insight into the system s behavior the analysis indicates that the dominant processes and reactions responsible for the hydrochemical evolution in the system are 1 evaporative concentration prior to infiltration 2 carbonate equilibrium 3 silicate weathering reactions 4 limited mixing with saline water 5 dissolution precipitation of calcite dolomite and fluorite and 6 ion exchange principal component factor analysis and k means cluster analysis of factor scores allow the reduction of dimensions describing the system and the identification of hydrogeochemical facies and the processes that defined and govern their evolution statistical analysis results indicate that the northern west face and southern yucca mountain groundwater is fresh water with low concentrations of ca2 mg2 cl ca2 na 2 and caf2 the fortymile wash groundwater is dilute the carbonate signature is shown in the ash meadows and death valley waters with high fluorite si finally the crater flat stripped hills and skeleton hills are dominated by ca na ion exchange mg and ca the hydrochemical and statistical analyses showed three main groundwater signatures or hydrochemical processes indicating groundwater evolution potential flowpaths and recharge areas the flowpaths are the trace of the amargosa river the trace of fortymile wash and its convergence with the amargosa river this appears to represent not just a groundwater flow path but traces of surface runoff infiltration as well

holocene glacier activity in the british columbia coast mountains canada abstract the coast mountains flank the pacific ocean in western british columbia canada subdivided into the southern pacific ranges central kitimat ranges and northern boundary ranges the majority of large glaciers and icefields are located in the boundary and pacific ranges prior descriptions of the holocene glacial history of this region indicate the holocene was characterized by repeated episodes of ice expansion and retreat recent site specific investigations augment our understanding of the regional character and duration of these events in this paper previously reported and new radiocarbon evidence is integrated to provide an updated regional assessment the earliest evidence of glacier expansion in the coast mountains comes from the boundary ranges at 8 9 and 7 8 ka and in the pacific ranges at 8 5 8 2 ka with the latter advance corresponding to an interval of rapid global climate deterioration although generally warm and dry climates from 7 3 to 5 3 ka likely limited the size of glaciers in the region there is radiocarbon evidence for advances over the interval from 7 3 to 6 0 and at 5 4 5 3 ka in the pacific ranges following these advances glaciers in the pacific ranges expanded down valley at 4 8 4 6 4 4 4 0 3 5 2 6 1 4 1 2 and 0 8 0 4 ka while glaciers in boundary ranges were advancing at 4 1 4 0 3 7 3 4 3 1 2 8 2 3 1 7 1 1 and 0 8 0 4 ka after 0 4 ka it appears that most glaciers in the coast mountains continued to expand to attain their maximum holocene extents by the early 18th to late 19th centuries this enhanced record of holocene glacier activity highlights the temporal synchrony in the coast mountains individual expansion events in the mid to late holocene broadly correspond to intervals of regional glacier activity reported in the canadian rocky mountains in alaska and on high elevation volcanic peaks in washington state

tectonics global changes in sea level and their relationship to stratigraphical sequences at the us atlantic continental margin of geological the principal factors that control the extent of seas through geological time are vertical movements of the lithosphere and global changes in sea level the relative height of the sea surface determines the facies and the thickness of sediments that can accumulate in a sedimentary basin backstripping studies show that the primary factors affecting the subsidence of rifted sedimentary basins are thermal contraction following heating and thinning of the lithosphere at the time of rifting and sedimentary loading factors such as compaction palaeobathymetry erosion and global sea level changes also contribute but their combined affects are small compared to those of thermal contraction and sedimentary loading simple models have been constructed which combine the effects of sedimentary loading and thermal contraction with those of compaction sub aerial erosion and global changes in sea level in the models it was assumed that the lithosphere was heated and thinned by stretching at the time of rifting sedimentary loading occurs by flexure of a lithosphere that progressively increases its flexural rigidity with age following rifting and that sediment compaction and bathymetry change across a basin but do not vary significantly with geological time furthermore different assumptions were made on the magnitude of curves of global sea level changes and the relationship between denudation rate and regional elevation the models show that tectonics in the form of thermal contraction of the lithosphere and flexure and slowly varying global changes in sea level can explain a number of the stratigraphic features of the us atlantic continental margin in this paper some of the implications of these results are examined for studies of a sea level changes through geological time and b the maturation history of continental margin basins

recent glacier advances in the premier range british columbia aerial photography 1948 1985 and field investigations are used to reconstruct recent ice front fluctuations for 27 glaciers size range 0 63 17 9 km2 in the premier range british columbia rapid rates of frontal recession between ca 1930 and the mid fifties were followed by glacier readvance at many sites culminating in the 1973 1976 period when 90 of the monitored ice fronts were either advancing 68 or stable maximum downvalley advance was about 0 5 km median 90 m and 14 glaciers formed new terminal or lateral moraine ridges between 1970 and 1985 nine of these postdate 1976 one is dated to the 1980 1981 winter using tree rings the glacial advance is attributed to significant mass balance changes inferred from periods of increased winter precipitation ca 1951 1976 and low summer temperatures 1954 1968 measured at valemount warmer summers and reduced winter precipitation after 1976 account for the slight recession of ice fronts from maximum downvalley positions in the last few years

summer temperatures in the canadian rockies during the last millennium a revised record we present a significant update to a millennial summer temperature reconstruction 1073 1983 that was originally published in 1997 utilising new tree ring data predominantly picea engelmannii the reconstruction is not only better replicated but has been extended 950 1994 and is now more regionally representative calibration and verification statistics were improved with the new model explaining 53 of may august maximum temperature variation compared to the original 39 of april august mean temperatures the maximum latewood density data which are weighted more strongly in the regression model than ringwidth were processed using regional curve standardisation to capture potential centennial to millennial scale variability the reconstruction shows warm intervals comparable to twentieth century values for the first half of the eleventh century the late 1300s and early 1400s the bulk of the record however is below the 1901 1980 normals with prolonged cool periods from 1200 to 1350 and from 1450 to the late 19th century the most extreme cool period is observed to be in the 1690s these reconstructed cool periods compare well with known regional records of glacier advances between 1150 and the 1300s possibly in the early 1500s early 1700s and 1800s evidence is also presented of the influence of solar activity and volcanic events on summer temperature in the canadian rockies over the last 1 000 years although this reconstruction is regional in scope it compares well at multi decadal to centennial scales with northern hemisphere temperature proxies and at millennial scales with reconstructions that were also processed to capture longer timescale variability this coherence suggests that this series is globally important for the assessment of natural temperature variability over the last 1 000 years

calendar dated early little ice age glacier advance at robson glacier british columbia canada dendrochronological studies at robson and bennington glaciers have provided the first calendar dating of an early little ice age glacier advance in north america dates derived from in situ stumps indicate that robson glacier began over riding forest between c ad 1142 and 1150 and continued until at least ad 1350 the highest rates of glacier advance c 3 8 m yr 1 occurred between ad 1214 and 1261 based on a series of kill dates from in situ stumps between c ad 1142 1214 and 1261 1350 rates were somewhat lower at c 2 2 5 m yr 1 this glacier advance terminated upvalley of the little ice age maximum position of robson glacier and there is no evidence at this site for glacial events between ad 1350 and 1783 however two smaller glaciers in the robson area and the main tongue of small river glacier have outermost little ice age moraines that date from the first decades of the ad 1700s all glaciers examined in the mount robson area have several well developed moraines dating from the period c

experimental study of knickpoint and longitudinal profile evolution in cohesive homogeneous material a series of experiments were conducted in homogeneous bedrock to study knickpoint and longitudinal profile evolution knickpoints are created by successive drops in base level which simulate intermittent uplift channel morphology and flow characteristics vary systematically along a knickpoint reach as the knickpoint lip is approached width decreases but depth velocity and bottom shear stress increase as a result knickpoints are rapidly destroyed through the process of 1 knickpoint replacement and 2 subsequent knickpoint inclination knickpoint replacement consists of two morphologically distinct erosional reaches the knickpoint face below the knickpoint lip which decreases in slope and an incising reach above the knickpoint lip which increases in slope knickpoint replacement is a significant process in the evolution of knickpoints in homogeneous bedrock within experimental limits this study supports the notion that knickpoints do not undergo parallel head ward retreat in homogeneous bedrock given intermittent uplift except in those possible cases of extensive and pervasive bedrock jointing only the erosional sediment transport discontinuity above the knickpoint is developed in cohesive sediments below the knickpoint a steep bedrock channel slope low sediment load and rapid decrease in grain size of sediment load preclude development of the aggradational sediment transport discontinuity knickpoint evolution can be characterized by three general models parallel retreat replacement and inclination these models are based on the following criteria within the knickpoint reach 1 relationship between bottom shear stress 0 and critical shear stress needed to initiate motion c 2 nature of the bed load transport discontinuities and 3 spatial variability of bedrock resistance to fluvial erosion

quaternary stratigraphy and sea level history of the u s middle atlantic coastal plain abstract middle atlantic inner continental shelf stratigraphic studies document a regional late pleistocene fossiliferous mud deposit from northern new jersey to cape lookout north carolina seismic reconnaissance and detailed stratigraphic analyses reveal the nature of the mud termed unit q2 on the maryland inner continental shelf extensive amino acid relative age determinations from the single genus mulinia combined with additional amino acid analyses from onshore deposits having radiometric dates for calibration indicate an age range for unit q2 corresponding to oxygen isotope stage 5 ostracode assemblages delineate four distinct climatic episodes in unit q2 enabling correlation of the zones in q2 to the deep sea isotopic record of climatic fluctuations substages in stage 5 late stage 5 is represented on the maryland shelf by the 6 meter thick mud of unit q2 deposited in an open shelf environment at slightly depressed sea levels relative to substage 5e late stage 5 sea levels including sea level minima can be estimated for the mid atlantic coastal plain by direct measurement of the altitudes of ostracode zone boundaries offshore and from peak transgressive facies in correlative deposits onshore late stage 5 sea levels determined from the inner shelf and adjacent nearshore facies on the atlantic coast comprise the most complete sea level history for stage 5 yet proposed some recent revisions of glacioeustatic sea level models advocate slightly higher sea levels during late stage 5 substage 5c in particular than originally estimated from uplifting reef tracts and support sea levels higher than estimates from deep sea isotopic records the sea level record from the maryland inner continental shelf confirms these recent estimates in an area of minimal tectonism and adds sea level minima estimates for substages 5d and 5b offshore a more complete record of stage 5 is preserved than in onshore deposits which are limited to peak transgressive facies discrepancies in correlation among emerged coastal plain facies therefore become resolvable within the context provided by the shelf stratigraphy

the little ice age in the canadian rockies abstract this paper reviews the evidence and history of glacier fluctuations during the little ice age lia in the canadian rockies episodes of synchronous glacier advance occurred in the 12th 13th early 18th and throughout the 19th centuries regional ice cover was probably greatest in the mid 19th century although in places the early 18th century advance was more extensive glaciers have lost over 25 of their area in the 20th century selective preservation of the glacier record furnishes an incomplete chronology of events through the 14th 17th centuries in contrast varve sequences provide continuous annually resolved records of sediments for at least the last millennium in some highly glacierized catchments such records have been used to infer glacier fluctuations evaluation of recent proxy climate reconstructions derived from tree rings provides independent evidence of climate fluctuations over the last millennium most regional glacier advances follow periods of reduced summer temperatures reconstructed from tree rings particularly ca 1190 1250 1280 1340 1690s and the 1800s reconstructed periods of higher precipitation at banff alberta since 1500 are 1515 1550 1585 1610 1660 1680 and the 1880s glacier advances in the early 1700s the late 1800s and in places the 1950 1970s reflect both increased precipitation and reduced summer temperatures negative glacier mass balances from 1976 to 1995 were caused by decreased winter balances the glacier fluctuation record does not contain a simple climate signal it is a complex response to several interacting factors that operate at different timescales evaluation of climate proxies over the last millennium indicates continuous variability at several superimposed timescales dominated by decade century patterns only the 19th century shows a long interval of sustained cold summers this suggests that simplistic concepts of climate over this period should be abandoned and replaced with more realistic records based on continuous proxy data series the use of the term lia should be restricted to describing a period of extended glacier cover rather than being used to define a period with specific climate conditions

late holocene glacier expansion in the cariboo and northern rocky mountains british columbia canada abstract castle creek glacier in the cariboo mountains of british columbia remained close to its little ice age limit for most of the past 1500 years without significant recession until the 20th century this conclusion is based on radiocarbon dated detrital and in situ plant material overrun by the glacier and the sedimentary record from informally named on off lake which received clastic sediments only when castle creek glacier crossed a hydrologic divide 330 m upvalley of the little ice age limit plant macrofossils recovered from the transition between basal inorganic silt and overlying organic silty clay in a sediment core from the lake indicate that the glacier first retreated behind the divide ca 10 92 9 70 ka ages of 8 97 8 61 and 5 58 5 53 ka on detrital wood from the glacier s forefield may record earlier advances but the first unequivocal evidence of glacier expansion is from an overridden stump with an age of 4 96 4 45 ka continuous accumulation of gyttja within on off lake however indicates that castle creek glacier did not cross the hydrologic divide at any time during the first half of the holocene glacigenic sediments began to accumulate in the lake between 2 73 and 2 49 ka indicating that castle creek glacier expanded beyond the hydrologic divide at that time a coincident advance is also recorded in the northern rocky mountains of british columbia at kwadacha glacier which overran a vegetated surface at 2 69 2 36 ka clastic sedimentation in on off lake ceased soon after the bridge river volcanic eruption 2 70 2 35 ka indicating that castle creek glacier retreat to a position upvalley of the divide at that time sedimentation resumed before 1 87 1 72 ka when the glacier advanced again past the hydrologic divide following a second retreat castle creek glacier advanced across the divide a final time at ca 1 54 1 42 ka the snout of the glacier remained less than 330 m upvalley of the little ice age moraine until the early twentieth century when annual moraines indicate rapid frontal recession to a position upvalley of the hydrologic divide these data collectively indicate that glaciers in the cariboo mountains of british columbia nearly achieved their all time holocene limits as early as 2 73 2 49 ka and climatic conditions in the early 20th century abruptly ended a 1500 year period favoring glacier expansion

neoglacial glacier fluctuations in the canadian rockies abstract the little ice age was the most extensive neoglacial glacier advance in the canadian rockies evidence of earlier less extensive neoglacial glacier advances is based on wood recovered from several glacier forefields wood flushed out of athabasca glacier 7550 8230 yr b p three dates and dome glacier 6120 6380 yr b p two dates indicates that forests occurred upvalley of present glacier termini during the hypsithermal detrital logs from peyto 14 dates saskatchewan 3 dates robson 3 dates and yoho 1 date glaciers plus in situ slumps at peyto and robson glaciers have yielded 14 c dates between 2490 and 3300 yr b p 12 dates between 2800 and 2990 this wood is derived from sources at or upvalley from present glacier termini and represents forests overridden by glaciers between ca 3100 and 2500 yr b p treeline was higher than present immediately prior to this advance this advance which did not extend beyond the little ice age maximum position is designated the peyto advance and correlated with the tiedemann advance in western british columbia earliest little ice age advances at peyto and robson glaciers are dated ca 800 600 yr b p at positions ca 500 m upvalley from little ice age limits

disequilibrium profile of the potomac river near washington d c a result of lowered base level or quaternary tectonics along the fall line longitudinal profiles of major rivers in maryland and virginia are generally closely adjusted to the resistance of the rocks over which they flow but they all show major discontinuities at or just above the fall line the amount of discrepancy at the fall line between the actual profiles and the projection of the profiles of the upstream reaches increases from about 27 m at the james river to about 50 m at the susquehanna river at the potomac river it is about 45 m detailed study of the terraces along the potomac in the piedmont above washington d c suggests that the discontinuity in longitudinal profile is the result of quaternary downcutting in response to a lowered base level changes in base level during sea level fluctuations in the pleistocene must have been an important factor but strong circumstantial evidence suggests that the discontinuities in river profiles may in part be due to differential uplift of the piedmont with respect to the coastal plain along a zone of flexure or distributed faulting near the fall line

a chronology of pliocene sea level fluctuations the u s middle atlantic coastal plain record abstract the sequence of marine and marginal marine silts and sands of the u s middle atlantic coastal plain preserves a relatively complete record of pliocene sea level highstands a general chronology for the deposition of these units has been developed previously from studies of the microfossil biostratigraphy complemented by a limited number of paleomagnetic and radiometric dates within this broad temporal framework it is currently difficult to assign ages to individual transgressive events with a resolution much better than 0 5 ma the age model proposed here attempts to refine the depositional history of the atlantic coastal plain by correlation with the more continuous deep ocean record the model assigns probable ages to the pliocene transgressions onto the atlantic coastal plain based on evidence for sea level highstands inferred from high resolution deep ocean 18 o records at least five major transgressive regressive events can be correlated with presumed eustatic fluctuations the temporal resolution for the timing of the transgressive events is greatly improved over that of the biostratigraphy alone many aspects of the proposed chronology require verification by more detailed field study but it is offered as a testable working hypothesis

determining the factors controlling the chemical composition of groundwater using multivariate statistics and geochemical methods in the xiqu coal mine north china studying the hydrogeochemical processes that control groundwater quality in different aquifers helps to identify the sources of inrush water into coal mines in this paper 65 mine water samples were collected from xiqu coal mine during 2016 and 2017 to determine the hydrogeochemical processes and controlling factors of mine water using hydrochemical methods and multivariate statistical analysis the mine water is acidic to alkaline in nature the dominant anions in the mine water are so42 and hco3 and cations were dominated by ca2 na and mg2 the dominant hydrochemical facies of groundwater were so4 na ca and so4 ca mg water types based on multivariate statistical analysis four principal components and two clusters were obtained concentrations of so42 showed significant positive correlations with ca2 mg2 fe2 and fe3 and strong negative correlations with hco3 and ph the mine water chemistry was dominated by the oxidation of iron bearing sulfide minerals cation exchange and the dissolution of silicate carbonate and sulfate minerals in addition human activities such as agriculture are also likely to have influences groundwater chemistry at the mine site

genesis of soils and landscapes in the ridge and valley province of central pennsylvania abstract the characteristics and properties of the soils on the ridge tops footslopes and adjacent limestone valley areas in the ridge and valley of central pennsylvania have been strongly influenced by their parent material and geomorphic history the ridge top soils have developed in sandstone colluvium which mantles sandstone residuum the upper part of the original residual ridge top soil was truncated during late wisconsinan time and then covered with local colluvium or it was cyroturbated these sandstone parent materials have been stable since the late wisconsinan and have sandy skeletal dystrochrepts and haplorthods developed in them the haplorthods are minor soils and are associated with local concentrations of coniferous vegetation during the late wisconsinan the sandstone colluvium also moved downslope and was mixed with bedrock and residual material from shale and limestone and deposited on the footslope over a pre wisconsinan soil developed in older colluvium or limestone residuum the footslope surface colluvial soils vary in texture and drainage because of their parent material their location in discharge areas and fragipan development the age of the brown surface colluvium is considered late wisconsinan and the age of the pre wisconsinan buried soils is not known the buried soil s bright red rubified color and argillic horizon indicate a much greater degree of soil development than noted in the brown surface colluvium and its age may be correlated with isotope stage 6 the soils developed at the surface in the colluvium are mainly ultisols although some poorly drained soils particularly in limestone material are alfisols the ultisols are parent material ultisols and the poorly drained alfisols have a high base status in their parent material or were recharged with bases from the groundwater the soils of the limestone valleys are developed in residuum the residuum accumulated from the insoluble residues after the caco 3 was leached from the bedrock if the residuum is thick 2 to 3 m the soils date back many hundreds of thousands of years but are still classified as hapludalfs in addition to being old the surface of the hapludalfs has been modified by periglacial truncation and the addition of eolian materials these processes have given the upper 50 cm of the hapludalfs a late wisconsinan age but the bulk of the b horizon is many thousands of years older eolian material has also been added to the ridge top soils as well as the colluvial soils the mineralogy of all the soils in this landscape including the buried paleosols does not show significant clay mineral weathering this appears anomalous considering the degree of oxidation of the buried paleosols and the limestone soils and their estimated age

neoglacial 3000 years till and flutes at saskatchewan glacier canadian rocky mountains formed by subglacial deformation of a soft bed understanding the processes that deposit till below modern glaciers provides fundamental information for interpreting ancient subglacial deposits a process deposit landform model is developed for the till bed of saskatchewan glacier in the canadian rocky mountains the glacier is predominantly hard bedded in its upper reaches and flows through a deep valley carved into resistant palaeozoic carbonates but the ice margin rests on a thick 6 m soft bed of silt rich deformation till that has been exposed as the glacier retreats from its little ice age limit reached in 1854 in situ tree stumps rooted in a palaeosol under the till are dated between ca 2900 and 2700 yr bp and record initial glacier expansion during the neoglacial sedimentological and stratigraphic observations underscore the importance of subglacial deformation of glaciofluvial outwash deposited in front of the advancing glacier and mixing with glaciolacustrine carbonate rich silt to form a soft bed the exposed till plain has a rolling drumlinoid topography inherited from overridden end moraines and is corrugated by more than 400 longitudinal flute ridges which record deformation of the soft bed and fall into three genetically related types those developed in propagating incipient cavities in the lee of large subglacial boulders embedded in deformation till and those lacking any originating boulder and formed by pressing of wet till up into radial crevasses under stagnant ice a third type consists of u shaped flutes akin to barchan dunes these wrap around large boulders at the downglacier ends of longitudinal scours formed by the bulldozing of boulders by the ice front during brief winter readvances across soft till pervasive subglacial deformation during glacier expansion was probably facilitated by large boulders rotating within the soft bed glacioturbation