soil weathering and accumulation rates of oxalate extractable phases derived from alpine chronosequences of up to 1 ma in age abstract in this study we compare newly developed chemical weathering data with previously published data from soils developed along two chronosequences of glacial deposits in the european alps and the rocky mountains wind river range usa by combining these chronosequences we are able to present a comprehensive dataset that represents a time period of 1 ma we describe weathering trends of important elements using a number of weathering indices e g k ca ti ratio the weathering index b of kronberg and nesbitt 1981 and the open mass transport function further we describe the accumulation of al fe si and mn oxyhydroxides including partially organic phases as a function of time and derive the corresponding accumulation rates we calculated pedogenetically formed oxyhydroxides using an approach based on immobile elements our study represents one of only a few studies that describe rates of soil chemical weathering over a period as long as 1 ma results show that rates of chemical weathering clearly decrease along the chronosequences with increasing age of the soils we find weathering rates are nearly four orders of magnitude lower in the 1 ma old soils than in the young soils our results suggest that the older soils may be reaching a steady state for these chemical properties in their present environments a power function best explains the measured time trends of the index b and k ca ti ratios in the soils the best time trend model for pedogenic weakly to poorly crystalline phases and the relative losses gains based on the open system mass transport function were obtained with an exponential decay model function in terms of the soil system the decreases in the accumulation rate of the oxyhydroxides appears to be influenced not only by the factor of time but by climate as well increased precipitation at higher altitudes slows the decrease in weathering rate over time thus our 1 ma chronosequences also become pedogenic gradients since we describe variations in soil properties along biogenic gradients

u pb dating of monazite and its application to geological problems monazite is an underutilized mineral in u pb geochronological studies of crustal rocks it occurs as an accessory mineral in a wide variety of rocks including granite pegmatite felsic volcanic a

igneous and tectonic evolution of the batchawana greenstone belt superior province a u pb zircon and titanite study u pb isotopic dating of zircon and titanite from all the major litho tectonic units of the batchawana belt an archean greenstone belt of the abitibi subprovince of the superior province in canada shows that the belt evolved during a period of about 60 ma between about 2730 and 2670 ma ago the earliest date of 2729 3 2 ma was found in a predominantly tholeiitic metavolcanic sequence the base of which is intruded by a tonalite dated at 2716 2 ma younger ages of 2720 10 ma 2709 2ma 2711 2ma 2701 2ma and 2698 2 ma date rocks at increasingly higher stratigraphic levels of a mixed tholeiitic calc alkalic metavolcanic sequence which is itself overlain by a thick succession of clastic metasedimentary rocks subsequent deformation of the supracrustal sequences produced isoclinal folding and culminated in metamorphism ranging from lower greenschist to amphibolite facies and anatexis related to the intrusion of syn to late tectonic plutons four phases of which have ages of 2678 4 2ma 2677

mineralogical evidence for eolian contribution to soils of late quaternary moraines wind river mountains wyoming usa abstract volcanic heavy minerals are found in the a and b horizons of soils on moraines of the western wind river mountains of wyoming volcanic minerals do not occur in the underlying moraine sediments derived from plutonic and metamorphic bedrock sources of the volcanics are the sedimentary rocks of the green river basin the presence of volcanic minerals in the green river basin and their patterns of distribution in the moraine soils indicate eolian sedimentation is an important factor of soil genesis in this region moraines affected by eolian sediments include the pinedale and temple lake indian basin type localities the presence of eolian sediments in both pinedale and holocene deposits suggests eolian addition is not simply a late glacial phenomenon but continues throughout postglacial time relations between eolian sediments and soil development must be accounted for when comparing soil development on moraine chronosequences in this and possibly all alpine regions of western north america

landscape evolution post lgm surface denudation and soil weathering processes from dickinson park mire wind river range wyoming usa abstract at mid latitudes the transition from the pleistocene to the holocene was characterised by distinct and partially abrupt climatic changes also during the holocene climatic perturbations with sometimes cold dry conditions have occurred how land surfaces and soil development processes in high mountains respond to these climatic oscillations is so far only poorly known we traced the responses of surfaces in the alpine settings of the wind river range wyoming us by using a large mire as natural archive this enabled us to reconstruct environmental conditions and ecosystem changes during the holocene in this montane area although adjacent moraine deposits display 10be exposure ages from the last glacial maximum up to mis16 or even older the accessible sediment deposits covered only the holocene via radiocarbon dating by applying a geoforensic approach and deriving sedimentation rates major climatic signals were detected a higher deposition and consequently erosion rate and thus a higher rate of geomorphic activity was measured for the known cold periods 9 4 10 2 ka bp 4 2 ka bp and 2 5 ka bp during the lia especially rapid aggradation of organic matter organic matter took place here rates of chemical weathering and soil formation seem to have been relatively low until about 5 6 ka bp but have since increased during the late holocene this would fit previous observations of increasing moisture conditions after the mid holocene aridity period in contrast to several other studies no clear signs of major disturbances erosion weathering during the 8 2 ka event could be observed together with the low levels of chemical weathering found here we do not see any evidence that the climate was more humid during this period compared to previous findings more humid conditions seemed to have returned earlier i e about 5 kyr bp in general this landscape displayed a patchy pattern of reaction to environmental changes as all events were not recorded in each mire profile

lichenometric and radiocarbon dating of holocene glaciation cordillera blanca peru hfeasurements of rliizocurpoii subgenus rliizocurpo r thalli on moraines the ages of which are constrained by six radiocarbon dates two pre colombian structures and one historically dated flood dep6sit indicate that lichenometry can be used to estimate the age of stabilization of glacial deposits that date to the last c 7 ka on the west side of the cordillera blanca perlj 8 40 9040 s 77 00 77 40 w the preliminary growth curve for subgenus rtiizocurpan resembles those derived for alpine areas in alaska and colorado and can be subdivided into an initial rapid phase of growth c 0 4 mm yr that lasts c 100 years a c 500 to 1000 year long phase of decelerating growth and a period of slow linear growth 0 016 mm yr that commences after c loo0 years size clustering of subgenus riiizocurpoir thalli supports a four fold subdivision of cirque moraines at altitudes between 4200 and 4650 m the oldest moraines stabilized between c 7000 and 6ooo bp and the three younger groups between c 3350 and 1600 bp between c 1250 and 400 bp and within the last 100 years this subdivision is supported by limiting radiocarbon dates from the cordillera blanca and from several cordilleras in southern peni and indicates that the holocene glacial chronology of the cordillera blanca is the most complete heretofore recognized in the tropical andes

superposed neoglacial and late pinedale wisconsinan tills titcomb basin wind river mountians western wyoming abstract late pinedale wisconsinan and neoglacial deposits mantle most valley floors above the timberlane in the wind river mountains although these tills are generally assigned ages by radiocarbon relative topographic position weathering characteristics and soil morphology they are rarely superposed this paper describes a sequence of moraines in titcomb basin where early neoglacial till now called indian basin till is superposed on a moraine of late pinedale age providing important information on relative ages for the two tills late pinedale deposits radiocarbon date at ca 8000 yr b p from bog bottom organic materials time of onset of neoglaciation is unknown while the termination of the indian basin advance is placed at ca 3000 yr b p differences in soil profile morphology particle size mineralogy and chemistry are described and discussed with respect to relative age assignment while profile morphology and particle size differences appear important in differentiating the two soils differences in clay mineral composition appear to have greater utility in discriminating post indian basin soils from post late pinedale soils

the labradorian orogeny in the grenville province eastern labrador canada two minor intrusions within the hawke river terrane in the grenville province eastern labrador have upper intercept u pb ages as follows i for a megacrystic intermediate dyke and ii 1622 3 ma for a pegmatite dyke the upper intercepts date time of emplacement and the lower intercepts 508 and 320 ma respectively record the timing of early paleozoic events in the region a third sample a sillimanite bearing pelitic gneiss from the paradise metasedimentary gneiss belt in the hawke river terrane yielded a range of ages between 1647 and 1627 ma from seven single zircon analyses the zircons in the metasedimentary gneiss are interpreted as detrital because of their variation in morphology the range of ages obtained and their extreme variation in u content a detrital origin implies that the sedimentary protolith must have been deposited after 1627 ma and is therefore not the same age as morphologically similar metasedimentary gneiss that occurs as enclaves within pre 1670 ma migmatized quartz d

late labradorian metamorphism and anorthosite granitoid intrusion cape caribou river allochthon grenville province labrador evidence from u pb geochronology in the cape caribou river allochthon ccra metaigneous and gneissic units occur as a shallowly plunging synform in the hanging wall of the grand lake thrust system glts a grenvillian structure that forms the boundary between the mealy mountains and groswater bay terranes the layered rocks of the ccra are cut by a stockwork of monzonite dykes related to the dome mountain suite and by metadiabase amphibolite dykes that probably form part of the ca 1380 ma mealy swarm the mafic dykes appear to postdate much of the development of subhorizontal metamorphic layering within the lower parts of the ccra the uppermost least metamorphosed units of the ccra the north west river anorthosite metagabbro and the dome mountain monzonite suite have been dated at 1625 6 and 1626 2 ma respectively an amphibolite unit that concordantly underlies the anorthosite metagabbro and is intruded discordantly by monzonite dykes has given metamorphic ages of 1660 3 and 1631 2 ma granitoid gneisses that form the

chronology of pleistocene glacial advances in the central rocky mountains the distribution and ages of moraines in the wyoming type localities for pre pinedale rocky mountain glacial deposits are not well known through morphostratigraphic mapping river terrace longitudinal profile analysis and tephrochronology we place the age of sacagawea ridge moraines in the dinwoody lakes type area at about 660 ka outwash and river terrace deposits in the bull lake type area previously considered to be sacagawea ridge are actually older by one or two glacial cycles in the bull lake type locality 15 individual moraines are divided into 4 groups on the basis of relative age criteria using 36cl 10be cosmogenic dating of boulders the two older groups must be 130 ka the younger groups are given age ranges of 130 to 100 ka and 120 to 95 ka a terrace along wind river can be morphostratigraphically traced to the youngest of these moraine groups 36cl dating of boulders on the terrace provides an age range of 125 to 100 ka the combined relative age and cosmogenic nuclide chronology is consistent with previously published evidence from yellowstone national park demonstrating that mountain glaciers advanced not only prior to and during the later portion of marine isotope stage 6 but also during marine isotope stage 5d in contrast with some other areas of the rocky mountains we found no evidence for advances during marine isotope stage 4 at bull lake pinedale moraines that have a 36cl 10be age range of 23 to 16 ka suggest that glacial advances were limited to the later part of marine isotope stage 2 a river terrace that can be traced to these moraines has an age range of 23 to 16 ka a possible glacial advance during early marine isotope stage 2 is indicated by a river terrace whose age range is estimated by incision rate modeling at 46 to 28 ka but no moraines were identified along wind river there are eight terrace levels capped with outwash that are older than sacagawea ridge although the terraces are the record of early to middle pleistocene climatic cycles there are no correlative moraines preserved at the land surface

labradorian and grenvillian crustal evolution of the goose bay region labrador new u pb geochronological constraints major initial crust formation in the northeastern grenville province of labrador occurred during the labradorian orogeny 1710 1620 ma prior to re deformation in the grenvillian orogeny between 10

rates of soil development from four soil chronosequences in the southern great basin abstract four soil chronosequences in the southern great basin were examined in order to study and quantify soil development during the quaternary soils of all four areas are developed in gravelly alluvial fans in semiarid climates with 8 to 40 cm mean annual precipitation lithologies of alluvium are granite gneiss at silver lake granite and basalt at cima volcanic field limestone at kyle canyon and siliceous volcanic rocks at fortymile wash ages of the soils are approximated from several radiometric and experimental techniques and rates are assessed using a conservative mathematical approach average rates for holocene soils at silver lake are about 10 times higher than for pleistocene soils at kyle canyon and fortymile wash based on limited age control holocene soils in all four areas appear to develop at similar rates and pleistocene soils at kyle canyon and fortymile wash may differ by only a factor of 2 to 4 over time spans of several millennia a preferred model for the age curves is not linear but may be exponential or parabolic in which rates decrease with increasing age these preliminary results imply that the geographical variation in rates within the southern great basin mojave region may be much less significant than temporal variation in rates of soil development the reasons for temporal variation in rates and processes of soil development are complexly linked to climatic change and related changes in water and dust erosional history and internally driven chemical and physical processes

gis based weights of evidence modelling of rainfall induced landslides in small catchments for landslide susceptibility mapping landslide susceptibility mapping is a vital tool for disaster management and planning development activ ities in mountainous terrains of tropical and subtropical environments in this paper the weights of evidence modelling was applied within a geographical information system gis to derive landslide susceptibility map of two small catchments of shikoku japan the objective of this paper is to evaluate the importance of weights of evidence modelling in the generation of landslide susceptibility maps in relatively small catchments having an area less than 4 sq km for the study area in moriyuki and monnyu catchments northeast shikoku island in west japan a data set was generated at scale 1 5 000 relevant thematic maps representing various factors e g slope aspect relief flow accumulation soil depth soil type land use and distance to road that are related to landslide activity were generated using field data and gis techniques both catchments have homogeneous geology and only consist of cretaceous granitic rock thus bedrock geology was not considered in data layering during gis analysis success rates were also estimated to evaluate the accuracy of landslide suscepti bility maps and the weights of evidence modelling was found useful in landslide susceptibility mapping of small catchments

abrupt increase in greenland snow accumulation at the end of the younger dryas event the warming at the end of the last glaciation was characterized by a series of abrupt returns to glacial climate the best known of which is the younger dryas event1 despite much study of the causes of this event and the mechanisms by which it ended many questions remain unresolved1 oxygen isotope data from greenland ice cores2 4 suggest that the younger dryas ended abruptly over a period of about 50 years dust concentrations2 4 in these cores show an even more rapid transition 20 years this extremely short timescale places severe constraints on the mechanisms underlying the transition but dust concentrations can reflect subtle changes in atmospheric circulation which need not be associated with a large change in climate here we present results from a new greenland ice core gisp2 showing that snow accumulation doubled rapidly from the younger dryas event to the subsequent preboreal interval possibly in one to three years we also find that the accumulation rate change from the oldest dryas to the bo11ing allerod warm period was large and abrupt the extreme rapidity of these changes in a variable that directly represents regional climate implies that the events at the end of the last glaciation may have been responses to some kind of threshold or trigger in the north atlantic climate system

two high precision u pb zircon ages for the sudbury nickel irruptive two independent u pb zircon ages were measured using norite samples from the north and south ranges of the sudbury nickel irruptive ages of and ma were obtained with a probability of fit within experimental error of 51 and 57 respectively previous determinations by the rb sr whole rock method gave ages between about 1700 and 2000 ma with errors of the order of 100 ma the difference in precision is inherent in the two methods zircons from the norite are highly radiogenic and almost concordant whereas rb sr whole rock ages are determined by very small increments in radiogenic 87sr the two zircon ages have completely different discordia so that all simple models for lead loss by continuous diffusion can be excluded

pedogenic gradients for iron and aluminum accumulation and phosphorus depletion in arctic and alpine soils as a function of time and climate pedogenically significant chemical extracts of iron aluminum and phosphorus are related mainly to time in chronosequences from baffin island canadian arctic the alpine sierra nevada and wind river range western united states the alpine khumbu glacier area himalaya nepal and the alpine southern alps new zealand based on the accumulation index for fe and al and the depletion index for p in each region the following ranking of chemical pedogenic development is obtained southern alps khumbu glacier area wind river range sierra nevada coastal baffin island inland baffin island the ranking mainly follows regional climate with the greatest accumulation and depletion to the warmest and wettest environment and the least accumulation and depletion in the coldest and driest environment

quantifying glacial moraine age denudation and soil mixing with cosmogenic nuclide depth profiles 1 glacial boulders and soils on moraines are often dated to quantify the timing of glaciations and or rates of chemical weathering in moraine chronosequences a common assumption is that moraine crest erosion and soil mixing are unimportant however several studies suggest moraine denudation may be substantial we evaluate the magnitude of moraine denudation and soil mixing in the pinedale 21 ka and bull lake 140 ka moraines at fremont lake wyoming united states using cosmogenic nuclide depth profiles and a numerical model of moraine erosion and nuclide production and decay depth profiles indicate mixing of the surface layer from 40 to 60 cm depth age constraints from depth profile dating of cosmogenic nuclides result in ages of 17 24 ka for the pinedale moraine and 70 127 5 ka for the bull lake moraine these ages are comparable to ages based on the lal and chen approach which uses a sample from the mixed layer and the unmixed layer however the lal and chen approach is difficult to apply in real environments as the mixing depth needs to be determined independently we find our best fit model based ages for the bull lake moraine are younger than independent age constraints from boulder exposure dating due to incomplete mixing exposure age constraints from boulders are more straightforward for moraines than ages based on depth profile dating finally we find that moraine crests do significantly erode and are mixed suggesting that previous weathering and dust accumulation rate studies on moraines provide minimum estimates for these processes

alluvial fan sediments and surface ages resulting from differing climatic and tectonic conditions in star valley wyoming usa abstract alluvial fans occur in all climatic and tectonic environments however most descriptions of fan features and sediments have focused on arid and semiarid regions this paper describes the sediments and soil ages on 63 alluvial fans in a subhumid climate mean annual precipitation of 45 52 cm ssurgo soil data were merged with geologic and topographic data in the arcmap gis platform to develop a series of maps showing variations across fan surfaces in sediment textures and surface stability ages particle size data percent cobble and percent total gravel from the upper 150 cm of sediments cluster into six textural groups that are aligned along a trend of decreasing gravel percentage decreasing stream capacity and decreasing cobble percentage decreasing stream competency the groups of higher cobble and gravel percentages extend from fan apex to toe in both the shallow 100 cm depth layers with groups of lower cobble and gravel percentage occurring along fan margins in the shallow

the deglaciation of the americas during the last glacial termination this paper reviews current understanding of deglaciation in north central and south america from the last glacial maximum to the beginning of the holocene together with paleoclimatic and paleoceanographic data we compare and contrast the pace of deglaciation and the response of glaciers to major climate events during the global last glacial maximum glgm 26 5 19 ka average temperatures decreased 4 to 8 c in the americas but precipitation varied strongly throughout this large region many glaciers in north and central america achieved their maximum extent during the glgm whereas others advanced even farther during the subsequent heinrich stadial 1 hs 1 glaciers in the andes also expanded during the glgm but that advance was not the largest except on tierra del fuego hs 1 17 5 14 6 ka was a time of general glacier thickening and advance throughout most of north and central america and in the tropical andes however glaciers in the temperate and subpolar andes thinned and retreated during this period during the bolling allerod interstadial b a 14 6 12 9 ka glaciers retreated throughout north and central america and in some cases completely disappeared many glaciers advanced during the antarctic cold reversal acr 14 6 12 9 ka in the tropical andes and patagonia there were small advances of glaciers in north america central america and in northern

soil catenas on pinedale and bull lake moraines willow lake wind river mountains wyoming abstract soils in coarse grained tills on pinedale about 20 000 years old and bull lake about 140 000 years old moraines show significant variaton with slope position and age soils on the pinedale moraine are mostly non calcareous typic cryoborolls with a bw c profiles that thicken considerably downslope these soils are weakly developed due to their youth and to the unstable steep up to 24 highly convexo concave slopes soils on the bull lake moraine are mostly argic cryoborolls with a bt c profiles these soils are more strongly developed than soils at similar positions on the pinedale moraine because the bull lake moraine is older and has less steep up to 16 more gently curved slopes the soils on the bull lake moraine contain more clay a higher proportion of pedogenic clay more weathered stones and more free sesquioxides erosion and dry conditions at the convex summit and shoulder sites on the bull lake moraine have resulted in thin soils with minimal argillic horizons these soils are only slightly more strongly developed than soils at analogous sites on the much younger pinedale moraine in contrast at the concave sites in downslope positions the soils on the bull lake moraine are much more strongly developed than analogous soils on the pinedale moraine slow deposition of weathered material probably transported by creep has acted concurrently with pedogenesis to form soils with thick homogeneous argillic horizons the relationship between hillslope curvature and soil properties on both moraines is shown by significant correlations between soil properties and the second derivative of the hillslope profile this relationship is probably due primarily to the interaction of soil formation and soil creep

late quaternary vegetation and climate of the wind river range wyoming abstract sediments from rapid lake document glacial and vegetation history in the temple lake valley of the wind river range wyoming over the past 11 000 to 12 000 yr radiocarbon age determinations on basal detrital organic matter from rapid lake 11 770 710 yr b p and temple lake 11 400 630 yr b p bracket the age of the temple lake moraine suggesting that the moraine formed in the late pleistocene this terminal pleistocene readvance may be represented at lower elevations by the expansion of forest into intermontane basins 12 000 to 10 000 yr b p vegetation in the wind river range responded to changing environmental conditions at the end of the pleistocene following deglaciation alpine tundra in the temple lake valley was replaced by a pinus albicaulis parkland by about 11 300 14 c yr b p picea and abies established by 10 600 14c yr b p grew with pinus albicaulis in a mixed conifer forest at and up to 100 m above rapid lake for most of the holocene middle holocene summer temperatures were about 1 5 c warmer than today by about 5400 14 c yr b p pinus albicaulis and abies became less prominent at upper treeline because of decreased winter snowpack and higher maximum summer temperatures the position of the modern treeline was established by 3000 14 c yr b p when picea retreated downslope in response to neoglacial cooling

cosmogenic 36cl and 10be ages of quaternary glacial and fluvial deposits of the wind river range wyoming we measured cosmogenic 36 cl in 56 samples from boulders on moraines and fluvial terraces in the vicinity of the wind river range wyoming we also measured 10 be in 10 of the same samples most of the 10 be ages were in good agreement with the 36 cl ages indicating that rock surface erosion rates were very low the oldest moraine investigated the type sacagewea ridge site yielded only a limiting minimum age of 232 ka the oldest moraines in the type bull lake complex also could be constrained only to 130 ka the main sequence of type bull lake moraines yielded age distributions indicating deposition within the intervals 130 to 100 ka and 120 to 100 ka the best estimates are closer to the upper limits of these ranges and associated uncertainties are in the range of 10 to 15 these uncertainties could permit deposition in either marine isotope stage 6 or stage 5d we found no evidence of glacial deposits dating to marine isotope stage 4 both bull lake age moraines from fremont lake on the opposite side of the wind river range and boulders on a fluvial terrace above the wind river gave age distributions very similar to that of the second oldest bull lake advance ca 130 to 100 ka the distribution of boulder ages for pinedale moraines at bull lake indicated deposition between 23 and 16 ka nearly identical to the distribution of 10 be ages previously reported for the type pinedale moraines at fremont lake

tectonic and metamorphic events in the westernmost grenville province central ontario new results from high precision u pb zircon geochronology the u pb isotopic ages of metamorphic zircons from deformed amphibolitized metadiabase dykes and associated unstrained anatectic pegmatites have been determined to constrain the times of postdyke ductile flow related recrystallization and deformation samples from the central gneiss belt of the grenville province in the southern georgian bay region provide a means of linking areas formed during common episodes of ductile flow three zircon fractions from one attenuated dyke in the moon river domain gave identical concordant ages of 1062 1065 and 1064 2 ma while those from another gave identical concordant ages of 1052 1051 and 1050 2 ma for the time of metamorphism zircons from a folded dyke from the go home domain gave identical concordant ages of 1049 1047 and 1046 2 ma while a single overgrowth fragment from an unstrained anatectic pegmatite in the fold hinge gave a concordant age of 1047 2 ma as if folding metamorphic zircon growth and postfolding pegmatite are part of the same proc

soil catenas to estimate ages of movements on normal fault scarps with an example from the wasatch fault zone utah usa trenches excavated across fault scarps on a 13 ka delta surface at brigham city utah usa document four types of soil catena phenomena first the relict summit soil is eroded at the scarp crest and its components incorporated into the accumulating colluvial wedge at the scarp base second the pre faulting soil weakens laterally as it is traced scarpward beneath the colluvial wedge from a relict position beyond the scarp toe third soils developed on individual colluvial wedges and on the underlying pre faulting surface merge downslope to form a cumulative soil profile at the scarp toeslope fourth soil horizons thicken downslope probably due to the combined affect of more available moisture water infiltration and sediment accumulation two soil catenas were used to evaluate the applicability of a continuity approach to paleoearthquake dating by which percentages of total development time represented by each soil at a fault scarp footslope could be estimated the continuity approach sets total soil development at the scarp footslope including any buried pre faulting soil plus the sum development of all colluvial wedge soils corrected by a slope factor f equal to total soil development at the scarp summit soil development was characterized by profile development index pdi and pedogenic clay parameters using facies models to estimate parent material values for genetically different colluvial units and recognizing inherited soil components in colluvial wedges as parent material properties the f slope factor used to correct colluvial wedge soils for development attributable to slope position rather than age was checked by using a nearby fluvial scarp as an independent control our soil data when compared to independent age estimates imply that rates of soil development have not been constant over the last 13 ka at brigham city but rather were considerably higher than average between 13 ka and 8 3 ka higher rates are probably due to a relatively high influx of eolian dust during the late pleistocene to early holocene following the lowering of lake bonneville a large paleolake in the western usa these variable rates of soil development preclude using the continuity approach for paleoearthquake dating at brigham city however promising results showing that generally consistent f factors can be calculated for fault and fluvial scarps leave open the possibility that in areas where soil development rates have been relatively constant over the time period in question the continuity approach may be a broadly applicable method for paleoearthquake dating

quaternary soils and dust deposition in southern nevada and california eoliandustconstitutesmuchofthepedogenic material in late pleistocene and holocene soils of many arid regions of the world comparisonofthecompositionsand influx rates of modern dust with the eolian component of dated soils at 24 sites in southern nevada and california yields informationon 1 thecompositionandinflux rate of dust in late pleistocene and holocene soils 2 paleoclimate and its effects on the genesis of aridic soils especially with regard to dustfall events 3 the timing and relative contribution of dust from playa sources versus alluvial sources and 4 the effects of accumulation of dust in soil horizons the 2mmfractionsofaandbhorizons of soils formed on gravelly alluvial fan deposits in the study area are similar to moderndustingrainsize contentofcaco3and salt majoroxides andclaymineralogy thus they are interpreted to consist largely of dust the major oxide compositions of the shallow soil horizons are nearly identical to that of the modern dust but the compositions of progressively deeper horizons approachthatoftheparentmaterial theclay mineralogyofmoderndustatagivensiteis similar to that of the av horizons of nearby holocene soils but is commonly different from the mineralogies of deeper soil horizonsandoftheavhorizonsofnearbypleistocenesoils theseresultsareinterpretedto indicate that dust both accumulates and is transformed in av horizons with time changes in soil accumulation rates provide insights into the interplay of paleoclimate dustsupply andsoil formingprocesses modern dust deposition rates are more than large enough to account for middle and late holocene soil accumulation rates at nearly all sites however the early holocene soil accumulation rates in areas near late pleistocene pluvial lakes are much higher than modern rates and clearly indicate a dust deflation and deposition event that caused rapid formation offine grained shallow soil horizons on uppermost pleistocene and lower holocene deposits we interpret late pleistocene soil accumulation rates to indicate that dust deposition rates were low during this period but that increased effective moisture during the late wisconsinan favored translocation of clay andcaco3fromnearthesurfacetodeeper inthesoilprofile pre latepleistocenerates are very low in most areas mainly due to a pedogenic threshold that was crossed when accumulations of silt clay and caco3 began to inhibit the downward transport of eolian material but in part due to erosion

geomorphology and quaternary stratigraphy the roles of morpho litho and allostratigraphy abstract the subdivision and ordering of quaternary sediments and landforms is very often based on geomorphology quaternary landforms such as moraines river terraces palaeoshorelines and indeed any other landform can be arranged and ordered in time based on their relative position in the landscape morphostratigraphy is the subdivision of sedimentary units primarily on the basis of surface form whilst surface form is often used as a criterion for separating sedimentary units morphostratigraphy also usually incorporates lithological criteria to aid stratigraphical subdivision and morpho and lithostratigraphy are often interlinked in quaternary science however another approach allostratigraphy has increasingly been applied to subdivide and order quaternary sediment landforms allostratigraphy uses discontinuities to subdivide sedimentary successions allostratigraphy enables lateral variations in lithology to be included within the same stratigraphical unit furthermore it enables lithologically similar sediments stacked on top of each other to be divided into separate units based on discontinuities this paper examines the applications of morpho litho and allostratigraphy to subdivide sediment landform assemblages and critically reviews their role in quaternary stratigraphy

rates and processes of soil development on quaternary terraces in cajon pass california field and laboratory analyses of soils on 11 well dated fluvial terraces spanning the past 0 5 m y demonstrate that a threshold governs changes in several morphological and chemical characteristics of increasingly older soils correlations with respect to time among iron species soil morphology and soil silt and clay demonstrate that the chronosequence at cajon pass reflects primarily an evolutionary largely time dependent trend and does not reflect differences in external factors such as climate most of the soil development on holocene terraces of the cajon pass area is due to physical incorporation of eolian dust and organic material into initially very permeable gravels this process decreases soil permeability and is conducive for an increase in the magnitude of chemical weathering latest pleistocene and older pleistocene soils have developed clay and authigenic iron oxide rich b horizons at the expense of organic matter rich a horizons and color b horizons as the extent of chemical weathering has increased this conversion of the soil from a noncolloidal system to a much more colloidal system takes place over a relatively short period of time 4 000 yr and is herein defined as a type of pedologic threshold in the cajon pass area the attainment of the threshold and subsequent development of the argillic b horizon of soils on latest pleistocene terraces occurred during the holocene thus the absence of argillic horizons in soils on holocene terraces is attributable to simply their younger age rather than to the pleistocene to holocene climatic change the threshold is a function of several variables including influx rate of eolian dust and initial soil permeability therefore the time required to attain the threshold will vary in chronose quences characterized by geomorphic or geographic settings that are different from conditions found in cajon pass

holocene and latest pleistocene alpine glacier fluctuations a global perspective abstract alpine glacier fluctuations provide important paleoclimate proxies where other records such as ice cores tree rings and speleothems are not available about 20 years have passed since a special issue of quaternary science reviews was published to review the worldwide evidence for holocene glacier fluctuations since that time numerous sites have been discovered new dating techniques have been developed and refined climatic hypotheses have been proposed that contribute to a better understanding of earth s climate system this special volume includes 12 papers on holocene and latest pleistocene alpine glacier fluctuations that update the seven review papers from 1988 major findings of these 12 papers include the following many but certainly not all alpine areas record glacier advances during the younger dryas cold interval most areas in the northern hemisphere witnessed maximum glacier recession during the early holocene with some glaciers disappearing although a few sites yield possible evidence for advances during the 8 2 ka cooling event in contrast some alpine areas in the southern hemisphere saw glaciers reach their maximum post glacial extents during the early to middle holocene in many parts of the globe glaciers reformed and or advanced during neoglaciation beginning as early as 6 5 ka neoglacial advances commonly occurred with millennial scale oscillations with many alpine glaciers reaching their maximum holocene extents during the little ice age of the last few centuries although the pattern and rhythm of these glacier fluctuations remain uncertain improved spatial coverage coupled with tighter age control for many events will provide a means to assess forcing mechanisms for holocene and latest pleistocene glacial activity and perhaps predict glacier response to future impacts from human induced climate change

new tectonic divisions of the grenville province southeast canadian shield on the basis of geological geophysical and geochronological data the grenville province has been divided into three first order longitudinal belts the parautochthonous belt pb allochthonous polycyclic belt apb and allochthonous monocyclic belt amb these are set apart by three first order tectonic boundaries the grenville front gf allochthon boundary thrust abt and monocyclic belt boundary zone mbbz the belts are subdivided into terranes based on internal lithological character the gf separates the archean to proterozoic foreland northwest of the orogen from reworked equivalents to the southeast continuous at the scale of the orogen its main characteristic is that of a crustal scale contraction fault the pb although less clearly identified along the length of the orogen in most places represents upgraded and tectonically reworked rocks of the adjacent foreland the boundary between the pb and the apb to the southeast the abt is most clearly delineated in the eastern half of the province it is the locus of major crustal delamination along which high grade mostly middle proterozoic polycyclic terranes were tectonically transported northwest toward and onto the pb the amb comprises two separate areas underlain by the wakeham supergroup and what is currently known as the grenville supergroup respectively its basal contact the mbbz is a decollement zone of variable kinematic significance between older polycyclic rocks and tectonically overlying monocyclic rocks this first order zonation implies a tectonic polarity to the grenville province superimposed on which are second order features evident from contrasting tectonic styles and radiometric ages these characteristics are consistent with a diachronous or oblique collisional model for the grenville orogen

holocene glacier fluctuations in the american cordillera abstract in many areas of the american rocky mountains colorado wyoming utah idaho montana cascade range washington oregon and the sierra nevada california radiocarbon ages suggest that ice receded to near present limits before 10 ka bp a pre altithermal readvance or stillstand left moraines ca 1 3 km beyond and ca 50 300 m below present glacier margins at one locality on glacier peak in washington these deposits are perhaps dated to the early holocene but in general these deposits are probably at least 10 ka old glacial advances during the altithermal ca 8 to 5 ka bp elsewhere are rare radiocarbon evidence for altithermal glacial advances in the colorado front range is questionable the earliest radiocarbon dated neoglacial advances occurred about 5 ka bp in the washington cascades moraines and related deposits believed to be of early neoglacial age i e 5 to 3 ka bp elsewhere are poorly dated for example moraines believed to date to the early neoglacial in colorado triple lakes and wyoming temple lake are actually late pleistocene age based on radiocarbon ages derived from lake sediments at the type localities although relative age data i e lichens rock weathering soils from many areas suggest a three fold neoglacial sequence little supporting radiocarbon evidence is available however tephrochronology distinguishes three neoglacial advances near mount rainier in washington in most mountain ranges of the western united states fresh unweathered sharp crested moraines usually adjacent to present ice margins or near headwalls in empty cirques date to the little ice age of the last several centuries however detailed photographic or other historical records of glacial fluctuations during the last century are rare and detailed mass balance studies rarer still whether or not pre little ice age glacial fluctuations in the american cordillera are synchronous must await better radiometric dating of local moraine sequences

continental glacier meltwater contributions to late summer stream flow and water quality in the northern wind river range wyoming usa the wind river range in wyoming contains more than 60 glaciers that are part of the headwaters for the wind missouri green colorado and snake columbia river systems continental glacier lies on the crest of the northern wind river range and covers approximately 2 5 km2 with meltwater flowing into west torrey creek and the wind river discharge measurements of upper continental glacier meltwater were made in august 2012 and 2014 water samples were collected in 2014 for the analysis of stable isotopes field parameters and 23 trace elements this study demonstrated that continental glacier meltwater accounted for a mean of 32 91 8 4 of torrey creek flow and 4 11 18 38 of wind river flow as measured above red creek for august 2012 and 2014 scaling of these results to all perennial snow and ice in the upper torrey creek basin yielded an estimate of 82 70 contribution to torrey creek flow and 10 32 of wind river flow above red creek during august glacier meltwater contributions versus snow melt to torrey creek based on 18o ratios ranged from 81 05 to 82 70 of flow with a mean of 81 88 1 17 for august 2014 continental glacier meltwater accounted for 89 99 of nitrate nitrite and 34 83 of total phosphorus loading to torrey creek in august 2014 the ph of the snow and glacier meltwater was less than 6 0 likely the result of nitrate nitrite and other atmospheric deposition finally analysis of trace elements showed distinct differences between water sources

holocene paleolakes of lake canyon colorado plateau paleoclimate and landscape response from sedimentology and allostratigraphy middle and late holocene paleoclimate can be inferred from lake level fluctuations recorded in the sediment of two fresh groundwater controlled paleolakes in lake canyon southeast utah the record from lake canyon contributes proxy climate data for the region as well as insight into climate controls on sedimentation the paleolakes were formed immediately upcanyon of side stream confluences where disproportionately large volumes of alluvium were focused into the bedrock canyon excellent exposure allows a depositional facies model to be developed and allostratigraphic units to be defined a facies based proxy for the past shoreline position is applied to the allostratigraphy and radiocarbon based chronostratigraphy to produce a record of lake level through time that is corroborated by diatom proxy data the earliest known lake formed during an episode of aggradation that began just before 5180 14 c yr b p and an arroyo cutting event drained the lake before 3050 14 cy r b p the lake canyon record for the past 3 k y is composed of wet dry cycles that have a periodicity of 520 yr matching cycles resolved by the regional tree ring record and the timing of the medieval warm period and little ice age lake level rose after 420 14 c yr b p and aggradation continued until an advancing arroyo headcut drained the upper lake in a d 1915 fluvial and lacustrine aggradation in lake canyon accompanied shifts to wetter climate when sediment stored in upper reaches of the drainage basin was delivered to the canyon whereas arroyo cutting in the canyon is more a function of sediment supply and internal complex response mechanisms than dry climate conditions correlation with other records is hindered by differences in resolution and the influence of local controls on alluvial stratigraphy the lake canyon record confirms that episodes of high flood frequency in holocene time have been wetter overall but not all wet periods have been marked by high flood frequency

proterozoic anorogenic magmatism and its orogenic connections there is a major belt of proterozoic so called anorogenic igneous rocks that extends from the baltic shield through southern greenland and eastern canada to southern usa all rocks are situated within a zone of 1 9 1 6 ga arc accretionary orogens that consist of juvenile mantle derived material especially accretionary prism sediments that provided the fertile source for abundant granitic crustal melts there were two main periods of formation of the anorogenic rocks 1 76 1 55 ga rocks are mainly rapakivi granites and rhyolites that formed about 60 200 ma after the last compressional events in the svecofennian ketilidian and penokean orogens the time lag being caused by the slow thermal relaxation of thickened lower crust that had commonly been depleted by the extraction of earlier granitic crustal melts 1 45 1 4 ga anorogenic rocks are mainly rhyolites and peraluminous granites in central southern usa and anorthosites in eastern canada that formed in the continental margin of the grenvillian ocean the subduction of which led to the grenville orogen these anorogenic igneous rocks formed in extensional regimes during the formation and breakup of a 1 5 ga supercontinent

precise cosmogenic 10be measurements in western north america support for a global younger dryas cooling event the inner titcomb lakes moraine in the wind river mountains wyoming has been dated with a precision of 5 using accelerator mass spectrometric measurements of cosmogenic 10be in surface samples from nine boulders resting on its crest the age of this moraine is 11 4 0 5 to 13 8 0 6 ka the range in age is due to the uncertainty in the 10be production rate and uncertainties in rock erosion rate and shielding of cosmic rays by snow additional exposure ages on bedrock and boulder surfaces that are stratigraphically younger and older than the inner titcomb lakes moraine conform with this age the exposure ages of the inner titcomb lakes moraine overlap the north atlantic younger dryas event 12 8 0 2 to 11 5 0 3 ka

a computational approach to quaternary lake level reconstruction applied in the central rocky mountains wyoming usa abstract sediment based reconstructions of late quaternary lake levels provide direct evidence of hydrologic responses to climate change but many studies only provide approximate lake elevation curves here we demonstrate a new method for producing quantitative time series of lake elevation based on the facies and elevations of multiple cores collected from a lake s margin the approach determines the facies represented in each core using diagnostic data such as sand content and then compares the results across cores to determine the elevation of the littoral zone over time by applying the approach computationally decisions are made systematically and iteratively using different facies classification schemes to evaluate the associated uncertainty after evaluating our assumptions using ground penetrating radar gpr we quantify past lake elevation changes precipitation minus evapotranspiration p et and uncertainty in both at lake of the woods and little windy hill pond wyoming the well correlated r 0 802 0 002 reconstructions indicate that water levels at both lakes fell at 11 300 8000 5500 and 4700 1600 cal yr bp when p et decreased to 50 to 250 mm yr differences between the reconstructions are typically small 10 24 mm yr since 7000 cal yr bp and the similarity indicates that our reconstruction method can produce statistically comparable paleohydrologic datasets across networks of sites

beryllium 10 dating of the duration and retreat of the last pinedale glacial sequence accurate terrestrial glacial chronologies are needed for comparison with the marine record to establish the dynamics of global climate change during transitions from glacial to interglacial regimes cosmogenic beryllium 10 measurements in the wind river range indicate that the last glacial maximum marine oxygen isotope stage 2 was achieved there by 21 700 700 beryllium 10 years and lasted 5900 years ages of a sequence of recessional moraines and striated bedrock surfaces show that the initial deglaciation was rapid and that the entire glacial system retreated 33 kilometers to the cirque basin by 12 100 500 beryllium 10 years

soil geomorphic analysis of late pleistocene glacial sequences in the mcgee pine and bishop creek drainages east central sierra nevada california abstract late pleistocene glacial sequences at mcgee pine and bishop creeks in the east central sierra nevada are resolvable into distinct relative age groups on the basis of soil development the weathering of surface and subsurface clasts and geomorphic criteria the data differentiate moraines from tioga and tahoe glaciations at mcgee creek and tioga tahoe and pre tahoe post sherwin glaciations at pine and bishop creeks no moraines from a tenaya glaciation are differentiated by the data perhaps because the soil geomorphic methods are not sensitive enough to resolve small age differences between moraines the lack of fine age resolution is probably due to a combination of factors including 1 slow rates of soil development 2 low amounts of atmospheric dust added to the soils 3 the susceptibility of crest soils to erosion and 4 the susceptibility of footslope soils to burial by colluvium age resolution is improved by evaluating soils at both the moraine crests and the relatively wetter footslope sites and by basing age assignments on a combination of macro and micromorphologic soil properties the disintegration of subsurface clasts and parameters of surface clast weathering

use of soil catena field data for estimating relative ages of moraines soils at the crests of moraines are commonly used to estimate the relative ages of moraines however for various pedologic and geomorphic reasons soil development at crest sites may not truly reflect the time since moraine formation for example some crest soils on moraines of greatly different age are similar in morphology and development soil catena data for soils at several sites aligned downslope from the crest can greatly improve on the usefulness of soil data for estimating moraine ages for this purpose the authors use the weighted mean catena profile development index which condenses field data for all of the soils in each catena into a single value

late quaternary stratigraphy and geochronology of the western killpecker dunes wyoming usa abstract new stratigraphic and geochronologic data from the killpecker dunes in southwestern wyoming facilitate a more precise understanding of the dune field s history prior investigations suggested that evidence for late pleistocene eolian activity in the dune field was lacking however luminescence ages from eolian sand of 15 000 yr as well as folsom 12 950 11 950 cal yr b p and agate basin 12 600 10 700 cal yr artifacts overlying eolian sand indicate the dune field existed at least during the latest pleistocene with initial eolian sedimentation probably occurring under a dry periglacial climate the period between 13 000 and 8900 cal yr b p was characterized by relatively slow eolian sedimentation concomitant with soil formation erosion occurred between 8182 and 6600 cal yr b p on the upwind region of the dune field followed by relative stability and soil formation between 5900 and 2700 cal yr b p the first of at least two latest holocene episodes of eolian sedimentation occurred between 2000 and 1500 yr followed by a brief 500 yr episode of soil formation a second episode of sedimentation occurring by at least 700 yr may coincide with a hypothesized medieval warm period recent stabilization of the western killpecker dunes likely occurred during the little ice age 350 100 yr b p the eolian chronology of the western killpecker dunes correlates reasonably well with those of other major dune fields in the wyoming basin suggesting that dune field reactivation resulted primarily due to departures toward aridity during the late quaternary similar to dune fields on the central great plains dune fields in the wyoming basin have been active under a periglacial climate during the late pleistocene as well as under near modern conditions during the latest holocene

precise u pb ages for grenvillian and pre grenvillian thrusting of proterozoic and archean metamorphic assemblages in the grenville front tectonic zone canada while the position of the grenville front is placed at a structural feature associated with the onset of high grade rocks when approached from the north the time of first metamorphism in these rocks is in general pre grenvillian and highly variable at killarney amphibolite to granulite grade rocks were metamorphosed lineated and foliated to their present front parallel configuration mainly by 1453 6 ma north of north bay amphibolite grade migmatites have been subjected to a pre 2650 ma metamorphism granulite grade gneisses south of the grenville front near val d or record a 2640 ma metamorphic event south of chibougamau mafic enclaves in tonalite south of the front were converted to migmatitic amphibolite at about 2680 to 2690 ma in central labrador a 1650 ma foliated granite is present south of the grenville front and at least some of the banding is this old at the atlantic coast granulite facies metamorphism in front parallel gneisses predates a 1790 1662 ma deformation in contrast each of these areas shares a near common age of second metamorphism that is variable in degree and accompanies nw directed thrusting or crustal loading near killarney on georgian bay titanite records an episode of 977 2 ma partial resetting the degree of which increases with distance into the grenville province here grenvillian deformation where present is manifest as feldspar porphyroclastic fabric with strong se plunging lineations near north bay archean pegmatites in the grenville front zone were similarly deformed at 988 10 ma and strongly rodded ductile amphibolite underwent late melting to produce postlineation tonalite in which new zircon tips grew at 987 2 ma a 991 4 ma cooling age for titanite in this melt is analytically identical to the zircon growth age hence rapid cooling occurred south of chibougamau new zircons grew in high pressure coronite in response to tectonic loading at 995 6 ma and in central labrador melt pods that developed in 1650 granites in response to thrusting record a zircon new growth age of 995 2 ma titanite in the granitic host rock has an analytically identical age of 992 4 ma again indicating rapid cooling this second event is recorded by 28 titanite and zircon analyses for samples up to 225 km apart that record a 1651 5 ma to 988 5 ma two age mixing line grenville resetting at about 1037 19 ma in the grenville front zone on the labrador coast is indicated but major thrusting is pre 1662 ma u pb isotopic results indicate that the grenville front zone is characterized along its length by partially reset u pb systems high pressure assemblages local melting and rapid cooling crustal loading and shearing with lead loss related to mechanically induced recrystallization and local heat that was rapidly terminated by rebound and cooling are required

surface reconstruction and derivation of erosion rates over several glaciations 1 ma in an alpine setting sinks canyon wyoming usa at middle to high latitudes many alpine valleys have been shaped by glaciers associated with periods of pleistocene glaciation present glaciated valleys are characterised by broadened valley floors and u shaped cross sections continuously formed by glacial activity from initially v shaped fluvial cross sections sinks canyon wind river range usa is a glaciated valley characterised by a typical u shaped cross section containing till from several glacial advances over a range of at least 1 ma the morphostratigraphic records indicate a fourfold difference in ice surface elevation between the youngest and oldest glacial periods which is not easily explained by the present day valley topography to assess possible evolution scenarios of sinks canyon we modelled the palaeovalley topography using a geographic information system gis filtering technique in combination with temporal reference points from relative and numerically dated glacial deposits ice thicknesses were calculated using the shallow ice approximation in our model the valley became shallower and the topography smoother with increasing years back in time the results suggest that valley topography with ages between 640 and 1000 ka can clearly be distinguished from the present day topography surfaces with ages of 130 200 ka attributable to mis 6 bull lake glaciation still could be discerned from present day topography but with relatively high uncertainties the method did not work for topography less than 100 ka or older than 1 ma erosion depths were calculated using the differences between present day elevation and the modelled surfaces calculated erosion rates were within the range of reference values for glacial erosion 0 001 to 1 mm a 1 glacial erosion appears to have removed 0 52 to 0 72 mm a 1 of rock within a time frame of 1 ma assuming 200 ka of aggregated glacial flow if the glacial occupation was longer or the impact of fluvial erosion was not negligible as assumed then the calculated rate is lower if the model assumes a less extended time of glacial flow 100 ka the rate exceeds 1 mm a 1 the method used for surface reconstruction and erosion rates calculation is highly dependent on i the reliability of the temporal anchor points and ii the assumption of physical glacier conditions basal shear stress

lichenometric dating science or pseudo science the popular technique of estimating ages of deposits from sizes of lichens continues despite valid criticism and without agreement on range of utility treatment of error and methods of measurement sampling and data handling a major source of error is the assumption that the largest lichen s colonized soon after deposition and will survive indefinitely recent studies on lichen mortality suggest that this assumption is untenable meanwhile the use of growth curves constructed from independently dated substrates is problematic for many reasons but this has not prevented the publication of baseless claims of accuracy and ages that are extrapolated well beyond data experiments indicate that numeric lichenometric ages are not reliable and in general do not advance the cause of quaternary science there are a few studies suggesting reliability and indeed there may be cases where lichens and growth curves actually provide realistic numerical ages but it cannot be foretold which lichen assemblages will provide good ages and which bad ages the logical conclusion is that no assumption of good ages can be made and that it is folly to assign numerical ages to a deposit on the basis of lichen sizes

glacial stratigraphy of stough creek basin wind river range wyoming abstract multiparameter relative age ra techniques identify four post pinedale morphostratigraphic units in each of three cirque valleys tributary to stough creek basin wind river range wy soil development lichenometry boulder weathering characteristics and the geomorphic relations among morphostratigraphic units indicate glacial deposits here correspond to the sequence previously described in the temple lake valley arct alp res 6 1974 301 cirque deposits in stough creek basin correspond to the temple lake alice lake black joe and gannett peak alloformations gsa abs prog 32 2000 a 16 10 be ages from moraine boulders and polished striated bedrock assoc am geogr annu mtg abs 2000 155 support recent numeric age estimates from temple lake and titcomb basin that indicate the temple lake alloformation corresponds to the younger dryas climate episode geogr phys quat 41 1987 397 geology 23 1995 877 science 268 1995 1329 gsa abs prog 31 1999 a 56 soils described from pinedale recessional deposits here represent the first systematic description of pinedale alpine deposits in the wrr

late holocene paleoclimate and treeline fluctuation in wyoming s wind river range usa this study presents evidence for treeline advance in the central rocky mountains united states between 1800 and 800 cal yr bp this evidence was generated by systematic survey sampling and acc

evolution of soil erosion rates in alpine soils of the central rocky mountains using fallout pu and δ13c abstract data from soil chronosequences have been widely used to quantify soil formation and weathering rates but are less used to determine erosion rates and the stabilisation of moraines over time we hypothesise that soil erosion rates on moraine hillslopes decrease over time as soils evolve and slopes stabilise we selected a sequence of moraines in the wind river range central rocky mountains to study these processes over time moraine ages were based on 10be surface exposure dating of moraine boulders quantitative soil erosion and accumulation rates along slopes with similar exposures lengths and gradients were determined from profile patterns of 239 240pu radionuclides we used stable carbon isotopes 13 c in relation with the total soil organic carbon soc content for qualitative information about soil erosion the 10be boulder exposure ages revealed that the moraines were deposited during the younger dryas and the pre bolling allerod episodes of the late pleistocene the morphology of the soils suggests a complex history of development and shows that both erosion and aeolian deposition have affected the soils the 239 240pu measurements revealed that erosion rates strongly decrease with time as soils develop a weakly developed soil cambisol is found on the youngest moraine 11 8 ka that exhibits an erosion rate depending on the calculation procedure in the range of 260 to 520 t km 2 a 1 with time the erosion rate rapidly decreases to almost zero presumably as a full vegetation cover develops bioturbation and or dust influx is increasingly obvious with increasing age of the soils as evidenced by the comparison of 13 c and soc the mass balance of the oldest soil 15 8 ka indicates that the slopes have reached a geomorphological stability with little or no net erosion aeolian influx appears to be the primary factor to account for mass changes in the oldest soil

revised quaternary glacial succession and post lgm recession southern wind river range wyoming usa abstract we present here a more complete cosmogenic chronology of pleistocene glacial deposits for the wind river range wyoming usa fifty one new and thirty nine re calculated 10be and 26al exposure ages from sinks and north fork canyons stough basin cirque of the towers and the temple lake valley allow us to more tightly constrain the timing and sequence of glacial alloformations in the southern portion of the range moraines diamicts and bedrock exposures here have previously been correlated with as many as five pleistocene and four holocene glacial events exposure ages from pleistocene alloformations associated with trunk glaciers in sinks canyon and north fork canyon generally confirm earlier age estimates cosmogenic radionuclide crn 10be and 26al ages from moraines and striated bedrock surfaces previously mapped as pinedale correspond to mis2 while boulder exposure ages from moraines mapped as bull lake correspond generally to mis5 mis6 geomorphic data from a moraine previously mapped as younger pre sacagawea ridge appears to correspond most closely to the sacagawea ridge glacial episode mis 16 but the uncertainty of a single 10be exposure age suggests the unit could be as young as mis 10 or as old as mis 18 boulders from a diamict on table mountain previously reported as older pre sacagawea ridge yield two 10be exposure ages that suggest the presence of early pleistocene glacial activity here possibly older than 1 2 ma mis 30 bedrock exposure ages within sinks canyon suggest the pinedale valley glacier had retreated from the floor of sinks canyon to above popoagie falls by ca 15 3 ka cirque glaciers in stough basin appear to have retreated behind their riegels by ca 16 ka which suggests the cirque glaciers were decoupling across their riegels from the valley glaciers below at this time prior to their readvance to form lateglacial moraines new 10be boulder exposure ages from moraines previously correlated to the temple lake and alice lake allostratigraphic units in the cirques of stough basin and cirque of the towers show general equivalence to the stadial event just prior to the onset of the bolling interstadial 17 5 14 7 ka and to the intra allerod cold period younger dryas stadial phase 13 9 11 7 ka respectively from this evidence the temple lake alloformation of the wind river mountains now should correspond to the intimate gs 2 1a oldest dryas stadial event while the alice lake alloformation should correspond to the intimate gs 2 stadial iacp younger dryas thus we consider that evidence no longer exists for early to mid holocene glacial events in the southern wind river range

soil formation rates on silicate parent material in alpine environments different approaches different results abstract high mountain soils develop in particularly sensitive environments consequently deciphering and predicting what drives the rates of soil formation in such environments are a major challenge in terms of soil production or formation from chemical weathering the predominating perception for high mountain soils and cold environments is often that the chemical weathering portion of soil development is temperature inhibited often to the point of non occurrence several concepts exist to determine long term rates of soil formation and development we present three different approaches 1 quantification of soil formation from minimally eroded soils of known age using chronosequences known surface age and soil thickness sast 2 determination of soil residence times srt and production rates through chemical weathering using un stable isotopes e g 230 th 234 u activity ratios and 3 a steady state approach using cosmogenic isotopes e g 10 be for each method data from different climate zones and particularly from high mountains alpine environment are compared the sast and steady state approach give quite similar results for alpine environments european alps and the wind river range rocky mountains usa using the srt approach soil formation rates in mountain areas but having a temperate climate do not differ greatly from the sast and steady state approaches independent of the chosen approach the results seem moderately comparable soil formation rates in high mountain areas alpine climate range from very low to extremely high values and show a clear decreasing tendency with time very young soils have up to 3 4 orders of magnitude higher rates of development than old soils 10 5 to 10 6 yr this apparently is a result of kinetic limits on weathering in regions having young surfaces and supply limits to weathering on old surfaces due to the requirement for chemical weathering to occur soil production rates cannot be infinitely high consequently a speed limit must exist in the literature this limit has been set at about 320 to 450 t km 2 a our results from the sast approach show however that in alpine areas soil formation easily reaches rates of up to 800 2000 t km 2 a these data are consistent with previous studies in mountain regions demonstrating that particularly young soils intensively weather even under continuous seasonal snowpack and thus that the concept of temperature controlled soil development soil forming intervals in alpine regions must be reconsidered

the mealy dykes labrador petrology age and tectonic significance the mealy dykes constitute a major olivine diabase swarm in the mealy mountains grenville province labrador the dykes intrude anorthosites and monzonites of the mealy mountains complex and outcrop over an area of at least 4000 km2 the swarm strikes east northeast and may constitute the largest group of unmetamorphosed diabase dykes in the grenville province the mealy dykes are moderately iron rich olivine tholeiites typically nonporphyritic thick dykes have coarse grained interiors that show some fractionation but variations in bulk chemical composition are relatively modest olivine fo47 fo27 plagioclase cores an63 an47 rims an47 an30 and low ca augite are the principal silicate minerals coexisting magnetite and ilmenite suggest that solidus temperatures were about 980 c and that subsolidus oxide re equilibration continued to near 530 c or perhaps lower a whole rock rb sr errorchron age for the mealy dykes yielded 1380 54 ma sr1 0 7028 0 0002 which within precision estimates i

cryogenic disturbance and pedogenic lag effects as determined by the profile developmental index the styggedalsbreen glacier chronosequence norway abstract a chronosequence with a terminal moraine dating to the mid eighteenth century is found at the norwegian glacier styggedalsbreen patches of sorted polygonal ground nets with varying degrees of activity occur along the chronosequence with activity decreasing with distance from the ice margin soil development was studied along the chronosequence in three differently aged terrain units 1 recently deglaciated i e 20 30 yr 2 deglaciated ca a d 1930 and 3 deglaciated between a d 1836 and 1867 within each similarly aged terrain unit pedogenesis was investigated in regards to three different categories of decreasing disturbance regimes 1 polygon centers 2 polygon borders and 3 relatively stable nonpolygonal ground physical soil properties along with the use of a soil development index i e pdi show significant differences in pedogenic development between the three different categories of disturbance within similarly aged terrain units the relatively stable nonpolygonal soils have thicker horizons and so higher pdi values as compared to the soils of sorted polygons suggesting that soil properties show the intensity of disturbance significant variations of pdi values were also observed with distance from the ice margin within decades of deglaciation and subsequent pedogenic development surficial a horizons obtained the highest index values over that of bw and c horizons suggesting developmental history is most represented in surficial horizons on very recently developed soils these findings suggest that soil indices are useful geochronological tools on young landscapes and can be used to explore the pedogenic heterogeneity found across the landscape resulting from disturbance processes

decoding potential effects of climate and vegetation change on mineral weathering in alpine soils an experimental study in the wind river range wyoming usa abstract climate change and a related increase in temperature particularly in alpine areas force both flora and fauna to adapt to the new conditions these changes should in turn affect soil formation processes the aim of this study was to identify possible consequences for soils in a dry alpine region with respect to weathering of primary minerals and leaching of elements under expected vegetation and climate changes to achieve this a field empirical approach investigating an altitudinal sequence was used in combination with laboratory weathering experiments simulating several scenarios the study sites are located in sinks canyon and stough basin of the wind river range wyoming usa the following sites from moist to dry with increasing temperature along the sequence were investigated 10 soil profiles typic haplocryoll in a tundra ecotone 10 soil profiles ustic haplocryoll in a pine fir forest and 20 soil profiles ustic argicryoll in sagebrush all soils developed on granitoid moraines soil mineralogy was analysed using cathodoluminescence and x ray diffraction this revealed that biotite and plagioclase were both weathered to smectite while plagioclase also weathered to kaolinite cooler wetter altitude dependent conditions promoted weathering of primary minerals furthermore the soils of the tundra and forest zone exhibited a higher acidity and more organic carbon in a series of wet laboratory batch experiments materials from topsoils a horizons and subsoils b horizons in each ecotone were examined alone or in combination with other samples in a first step aqueous extracts of the topsoil samples were generated in batch reactors and analysed for the main ions in a second and a third step the topsoil extracts were reacted with the subsoil samples of the same ecotone and with the subsoil samples of the ecotones at higher altitude the total duration of these batch experiments was 1800 h and the solutes were measured using icp oes and ion chromatography dissolved ca mg and k were mainly controlled by the chemical weathering of oligoclase k feldspar and biotite with increasing altitude the total concentrations of ca mg and k in the aqueous extracts decreased the relative ionic contribution from k decreased while the ionic contribution from ca increased climate change warming changed precipitation potentially will reduce weathering intensity soil acidity and the content of organic carbon an altitudinal shift in vegetation due to climate change seems to affect the ionic composition of the soil solution in the case of a shift from forest to sagebrush and tundra to forest or sagebrush the relative contribution from k would increase at the expense of ca we hypothesise that k will play an important role in future biogeochemical cycles under the assumptions of climate warming and subsequent vegetation shifts to higher altitudes

carbonate and elemental accumulation rates in arid soils of mid to late pleistocene outwash terraces southeastern wind river range wyoming usa an important result of the past few decades of soil geomorphic research is the awareness of the major role of dust and related carbonate precipitates in arid soils the temporal evolution of soils developed on outwash terraces is still a matter of debate particularly regarding the type of evolution progressive evolution and constant rates vs complex and or interval accumulation rates progressive or regressive evolution possible soils on a chronosequence of outwash terraces just outside and downstream of canyon mouths of the wind river range usa were analysed for carbonate accumulation organic carbon and poorly crystalline pedogenetic oxyhydroxides stocks and pathways of chemical weathering the soils and their carbonate stocks in the fine earth fraction 2 mm can be used as a relative dating tool and appear to correlate with regional glacial chronostratigraphy pinedale c 20 ky bull lake with two different units around 160 and 260 ky and sacagawea ridge c 660 ky carbonate stocks of soils on these terraces increase with increasing soil age but at generally decreasing rates a quasi steady state situation however was not reached before 1 my the time split approach showed that caco3 accumulation rates were the highest during marine isotope mis cold stages 2 13 g caco3 m2 y presumably due to a sparse vegetation cover during mis2 pinedale and 8 lower bull lake compared to organic carbon c 8 10 kg corg m2 the inorganic carbon stocks of the fine earth fraction were much higher c 60 kg cinorg m2 although the dominant pedogenic process here appears to be carbonate accumulation chemical weathering and elemental leaching also are significant weathering data were obtained using immobile elements and rare earth elements ree as tracers chemical weathering and related leaching were particularly notable for na originating from plagioclase in addition pedogenetic al and mn oxyhydroxides accumulate 220 and 32 g m2 respectively after 660 ky these form at relatively low rates however when compared to moister and cooler conditions at higher altitudes in the wind river range due to the dry climate under which the terrace soils formed annual precipitation 32 cm yr 1 weakly crystalline and amorphous fe oxyhydroxide is rapidly transformed into crystalline forms hematite over time consequently the stocks of weakly crystalline and amorphous fe oxyhydroxide was significantly lower in the 660 ky soils 50 g m2 than in the holocene soils 1000 g m2 the development of soils on quaternary outwash terraces in this region is controlled through the rates of aeolian influx over time as modified by glacial interglacial climate variations rather than by moisture availability consequently carbonate accumulation rates in these soils are influx limited rather than moisture limited

crustal evolution in eastern labrador constraints from precise u pb ages abstract new u pb ages for rocks of eastern labrador complement previous u pb dates for the grenville and makkovik provinces and substantiate the following conclusions eastern labrador consists of two distinct crustal blocks that are different in age as well as magmatic metamorphic and structural overprint the northern block includes archaean to lower proterozoic basement rocks 1900 ma and two distinct episodes of rhyolitic volcanism at 1860 and 1807 ma high grade metamorphism deformation and anatexis affected this block between 1860 and 1760 ma ago makkovikian orogeny the southern block comprises the trans labrador batholith and the various terranes of the grenville province in contrast to the northern region the southern block shows no proof for the existence of continental crust older than 1710 ma this suggests that large amounts of juvenile material were added between 1710 and 1630 ma ago as dated by a large series of precise rock ages at least towards its end this crust forming event was associated with high grade metamorphism deformation and anatexis labradorian orogeny the 1710 1630 ma period of activity was followed by three distinct phases of anorogenic plutonism causing the emplacement of pegmatites 1500 ma a widespread suite of cotonitic metagabbros michael gabbro 1426 ma and granitic syenitic bodies 1296 ma during the grenvillian orogeny the region achieved its present structural configuration including the emplacement of granitoid plutons the structurally highest regions the mealy mountains and the hawke river terranes were thrust over the lake melville terrane and part of the groswater bay terrane and they were only marginally affected by grenvillian metamorphism the more deeply buried lake melville and groswater bay terranes however were significantly modified during tectonothermal events at 1030 ma and 980 960 ma respectively