influences of quaternary climatic changes on processes of soil development on desert loess deposits of the cima volcanic field california summary soils formed in loess are evidence of both relict and buried landscapes developed on pliocene to latest pleistocene basalt flows of the cima volcanic field in the eastern mojave desert california the characteristics of these soils change systematically and as functions of the age and surface morphology of the lava flow four distinct phases of soil development are recognized phase 1 weakly developed soils on flows less than 0 18 m y old phase 2 strongly developed soils with thick argillic horizons on 0 18 0 7 m y old flows phase 3 strongly developed soils with truncated argillic horizons massively impregnated by carbonate on 0 7 to 1 1 m y old flows and phase 4 degraded soils with petrocalcic rubble on pliocene flows a critical aspect of the development of stage 1 soils is the evolution of a vesicular a horizon which profoundly affects the infiltration characteristics of the loess parent materials laboratory studies show that secondary gypsum and possibly other salt accumulation probably occurred during the period of phase 1 soil development slight reddening of the interiors of peds from vesicular a horizons of phase 1 soils and presence of weakly developed b horizons indicates a slight degree of in situ chemical alteration however clay and fe oxide contents of these soils show that these constituents as well as carbonates and soluble salts are incorporated as eolian dust in contrast to phase 1 soils chemical and mineralogical analysis of argillic horizons of phase 2 soils indicate proportionally greater degrees of in situ chemical alteration these data the abundant clay films and the strong reddening in the thick argillic horizons suggest that phase 2 and phase 3 soils formed during long periods of time and periodically were subjected to leaching regimes more intense than those that now exist flow age data and soil stratigraphic evidence also indicate that several major loess deposition events occurred during the past 1 0 m y loess events are attributed to past changes in climate such as the pleistocene to holocene climatic change that periodically caused regional desiccation of pluvial lakes reduction of vegetational density and exposure of loose unconsolidated fine materials during times of warmer interglacial climates precipitation infiltrates to shallower depths than during glacial periods extensive saline playas which developed in the mojave desert during the holocene are a likely source of much of the carbonates and soluble salts that are accumulating at shallow depths both in phase 1 soils and in the formerly noncalcareous nongypsiferous argillic horizons of phase 2 and 3 soils

development of partial rock veneers by root throw in a subalpine setting rock veneers stabilize hillslope surfaces occur especially in areas of immature soil and form through a variety of process sets that includes root throw near westcliffe colorado usa data were collected from a 20 500 m transect on the east slope of the sangre de cristo mountains ages of pit mound complexes with rock fragments exposed at the surface by root throw ranged from recent freshly toppled tree to unknown complete tree decay calculations based on dimensions of the pit mound complexes estimated time of tree toppling sizes of exposed rock fragments and percentage rock covers at pit mound complexes as well as within the transect area indicate that recent rates of root throw have resulted in only partial rock veneering since late pleistocene deglaciation weathering of rock fragments prevents development of an extensive rock veneer and causes a balance achieved within an estimated 700 years between the rates of rock fragment exposure by root throw and clast disintegration by chemical reduction the estimated rate of rock fragment reduction accounts for part of the fluvial sediment yields observed for forested subalpine areas of western north america copyright 2005 john wiley sons ltd

chemostratigraphic correlation of the middle and upper proterozoic between the yanshan and shennongjia basins abstract this paper is concerned with the distribution of major elements transition elements ree sulphur isotopes and organic carbon in parts of the proterozoic of china lithophile and ore forming elements such as ba sr mn k v fe and cu are good chemical markers and are used for correlation in the yanshan basin the ba content is particularly high in red beds of several sections ba fe k mn v ca mg and organic carbon have provided useful data for correlation between the yanshan and shennongjia basins these elements reflect in varying degree widespread important geological events we propose several chemostratigraphic stages with divisions approximately at 1950 ma 1600 ma 1200 ma and 1000 ma these divisions correspond approximately to major time boundaries in the proterozoic of china 34s values for sulphur isotopes in proterozoic strata in china are between 13 and 27 ree patterns normalized to chondritic abundances for middle upper proterozoic rocks of china are similar to post archaean sedimentary rocks of australia they also show eu depletion and eu eu ratios between 0 6 and 0 8

flood geomorphology of arthurs rock gulch colorado paleoflood history abstract episodic late quaternary flooding is recorded by bouldery deposits and slackwater sediments along arthurs rock gulch an ephemeral stream west of fort collins colorado flood deposits consist of individual granodiorite and pegmatite boulders boulder bars and coarse overbank sediment that rest on erosional terrace segments along the channel we identified evidence for at least five flood in the lower two thirds of the 1 84 km 2 drainage basin flood deposits are differentiated by their position above the active channel weathering characteristics degree of boulder burial by colluvium amount of lichen cover and position with respect to terrace and colluvial deposits age estimates for the flood deposits are based on radiocarbon dating tree ring analyses and relative age criteria from four sites in the basin at least two floods occurred in the last 300 years a third flood is at least 5000 years old but likely younger than 10 000 yr bp and the two oldest floods occurred at least 40 000 years bp

the composition and evolution of the continental crust rare earth element evidence from sedimentary rocks the composition of the present day upper crust inferred from the uniformity of sedimentary rock r e e rare earth element patterns is close to that of granodiorite a revised andesite model is used to obtain total crustal composition the lower crust is the composition remaining assuming that the upper crust one third of the total is derived from intracrustal partial melting the upper crustal r e e pattern has pronounced eu depletion eu eu 0 64 the lower crustal pattern has eu enrichment eu eu 1 17 and the total crust has no eu anomaly relative to chondritic abundances the eu depletion in the upper crust is attributed to retention of eu in plagioclase in the lower crust because plagioclase is not stable below 40 km 10 kbar the anomaly is intracrustal in origin the archaean upper crust has a different r e e pattern to that of the present day upper crust being lower in total r e e and la yb ratios and lacking an eu anomaly these data are used to infer the archaean upper crustal composition which resembles that of the present day total crust except that ni and cr contents are higher the archaean crustal composition can be modelled by a mixture of tholeiites and tonalite trondhjemites the latter have steep light r e e enriched heavy r e e depleted patterns consistent with equilibration with garnet and hence probable mantle derivation there is little reason to suppose that the archaean lower crust was different in composition from the upper crust except locally where partial melting episodes occurred the r e e evidence is consistent with isotopic and geological evidence for a low continental growth rate in the early archaean a massive increase to about 70 of the total crust between about 3000 and 2500 ma b p and a slow increase until the present day the change from archaean to post archaean r e e patterns in the upper crust is not isochronous but is reflected in the sedimentary rock r e e patterns at differing times in different continents on the basis of a model composition for the mantle 36 of the potassium 30 of uranium 15 of lanthanum and 3 of ytterbium are concentrated in the present continental crust this enrichment is related to ionic size and valency differences from common mantle cations e g mg fe pre 3 9 ga b p crusts were obliterated by meteorite bombardment no geochemical evidence exists for primordial anorthositic sialic or mafic crusts

a distributed temperature index ice and snowmelt model including potential direct solar radiation hourly melt and discharge of storglaciaren a small glacier in sweden were computed for two melt seasons applying temperature index methods to a 30 m resolution grid for the melt component the classical degree day method yielded a good simulation of the seasonal patient of discharge but the pronounced melt induced daily discharge cycles were not captured modelled degree day factors calculated for every hour and each gridcell from melt obtained from a distributed energy balance model varied substantially both diurnally and spatially a new distributed temperature index model is suggested attempting to capture both the pronounced diurnal melt cycles and the spatial variations in melt due to the effects of surrounding topography this is accomplished by including a radiation index in terms of potential clear sky direct solar radiation and thus without the need for other data besides air temperature this approach improved considerably the simulation of diurnal discharge fluctuations and yielded a more realistic spatial distribution of melt rates the incorporation of measured global radiation to account for the reduction in direct solar radiation due to cloudiness did not lead to additional improvement in model performance

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

lower timberline in central colorado during the past 15 000 yr a 15 000 yr paleoenvironmental record at the elevation of lower timberline in central colorado suggests two major paleoclimatic changes during that interval 1 at 10 000 yr b p from cool moist conditions to warm moist conditions and 2 at 4 000 yr b p to warm dry conditions this sequence can be interpreted as a shift from precipitation predominantly originating from pacific winter storms before 10 000 yr b p to a predominantly monsoonal type regime lasting until 4 000 yr b p to the present pattern contemporaneity of higher upper timberline and lower lower timberline during the 10 000 to 4 000 yr b p interval is not contradictory but a result of changes in those circulation patterns

climatic controls of western u s glaciers at the last glacial maximum abstract we use a nested atmospheric modeling strategy to simulate precipitation and temperature of the western united states 18 000 years ago 18 ka the high resolution of the nested model allows us to isolate the regional structure of summer temperature and winter precipitation that is crucial to determination of the net mass balance of late pleistocene mountain glaciers in this region of diverse topography and climate modeling results suggest that climatic controls of these glaciers varied significantly over the western u s glaciers in the northern rocky mountains existed under relatively cold july temperatures and low winter accumulation reflecting anticyclonic easterly wind flow off the laurentide ice sheet in contrast glaciers that existed under relatively warmer and wetter conditions are located along the pacific coast south of oregon where enhanced westerlies delivered higher precipitation than at present between these two groupings lie glaciers that were controlled by a mix of cold and wet conditions attributed to the convergence of cold air from the ice sheet and moisture derived from the westerlies sensitivity tests suggest that for our simulated 18 ka climate many of the glaciers exhibit a variable response to climate but were generally more sensitive to changes in temperature than to changes in precipitation particularly those glaciers in central idaho and the yellowstone plateau our results support arguments that temperature depression generally played a larger role in lowering equilibrium line altitudes in the western u s during the last glacial maximum than did increased precipitation although the magnitude of temperature depression required for steady state mass balance varied from 8 18 c only the sierra nevada glaciers required a substantial increase in precipitation to achieve steady state mass balance while glaciers in the cascade range existed with decreased precipitation

evidence of early holocene glacial advances in southern south america from cosmogenic surface exposure dating cosmogenic nuclide surface exposure dating reveals that glaciers in southern south america 46 s advanced at ca 8 5 and 6 2 ka likely as a result of a northward migration of the southern westerlies that caused an increase in precipitation and or a decrease in temperature at this latitude the older advance precedes the currently accepted initiation of holocene glacial activity in southern south america by 3000 yr both of these advances are temporally synchronous with holocene climate oscillations that occurred in greenland and the rest of the world if there are causal links between these events then rapid climate changes appear to be either externally forced e g solar variability or are rapidly propagated around the globe e g atmospheric processes

timberline fluctuations and late quaternary paleoclimates in the southern rocky mountains colorado pollen and plant macrofossils from eight sedimentary basins on the west slope of the colorado rocky mountains document fluctuations in upper and lower timberline since the latest pleistocene by tracking climatically sensitive forest boundaries the moisture controlled lower timberline and the temperature controlled upper timberline paleoclimatic estimates can be derived from modern temperature and precipitation lapse rates pollen data suggest that prior to 11 000 yr b p a subalpine forest dominated by picea spruce and pinus pine grew 300 700 m below its modern limit the inferred climate was 2 5 c cooler and had 7 16 cm greater precipitation than today abies fir increased in abundance in the subalpine forest around 11 000 yr b p probably in response to cooler conditions with increased winter snow pollen and plant macrofossil data demonstrate that from 9000 to 4000 yr b p the subalpine forest occupied a greater elevational range than it does today upper timberline was 270 m above its modern limit suggesting that mean annual and mean july temperatures were 1 2 c warmer than today intensification of the summer monsoon coupled with increased summer radiation between 9000 and 6000 yr b p raised mean annual precipitation by 8 11 cm and allowed the lower limit of the subalpine and montane forests to descend to lower elevations the lower forest border began to retreat upslope between 6000 and 4000 yr b p in response to drier conditions and the upper timberline descended after 4000 yr b p when temperatures cooled to about 1 c warmer than today the modern climatic regime was established about 2000 yr b p when the summer precipitation maxima of the early and middle holocene were balanced by increased winter precipitation

patterns and timing of late quaternary faulting in the great basin province and relation to some regional tectonic features large scale surface faulting events each tens of kilometers long and involving more than a meter of displacement of late quaternary age have not been uniformly distributed but have been concentrated in subprovincial and smaller belts and areas within the great basin province furthermore faulting apparently has not been uniformly distributed over time the average recurrence interval of large scale faulting events on individual faults in the province is measured in thousands or tens of thousands of years in contrast to such long recurrence intervals in the central nevada and eastern california seismic belts large scale faulting events have occurred during the last 111 years in an apparently coherent sequential belt filling pulse of activity in which events were separated by only a few years or a few decades the questions are where are other pulses of large scale faulting likely to occur and what controls the localization of such belts and areas characterized by higher rates of faulting two examples of tectonic subprovinces that may play a role in delimiting smaller zones of faulting are the black rock carson sink zone of extension and the central nevada downwarp the central nevada seismic belt lies along the dividing line between these two subprovinces and the northwest margin of the black rock carson sink zone of extension coincides with the margin of a fingerlike belt of dense faulting in northwestern nevada

using soils as indicators of past slope instability in forested terrain kamienne mts sw poland abstract the kamienne mts in sw poland abound in geomorphic evidence for past landslides developed at the rhyolite sedimentary rock contact but it remains unknown when the displacements occurred the slopes generally have been stable in the last 200 years or so covered by historical records in this paper we use the presence of periglacial solifluction layers cover beds and soil characteristics as indicators of the status of hillslopes and relative age of landslides we follow an assumption that if landslides predate the holocene then solifluction layers should be present and soils within and outside landslide affected slopes should have similar characteristics allowing for differences caused by local factors cover beds are not expected to be associated with holocene landslides differences in the degree of soil development may be used to argue for different ages of some landslides within the holocene the absence of solifluction layers cannot always be regarded as the evidence of post pleistocene landsliding since such a layer is unlikely to have ever formed on densely jointed but otherwise strong rhyolite soil morphological properties particularly horizonation helped to establish the relative chronology of mass movement and to recognize both early to mid holocene and late holocene landslides soils are good relative dating tools and their usage does not necessarily require adherence to any particular soil classification system this is because morphological features of entire profiles provide more information than diagnostic properties used in these systems

late pleistocene and holocene seasonal temperatures reconstructed from fossil beetle assemblages in the rocky mountains abstract mutual climatic range mcr analysis was applied to 20 fossil beetle assemblages from 11 sites dating from 14 500 to 400 yr b p the fossil sites represent a transect of the rocky mountain region from northern montana to central colorado the analyses yielded estimates of mean july and mean january temperatures the oldest assemblage 14 500 yr b p yielded mean july values of 10 11 c colder than present and mean january values 26 30 c colder than present postglacial summer warming was rapid as indicated by an assemblage dating 13 200 yr b p with mean july values only 3 4 c cooler than modern by 10 000 yr b p several assemblages indicate warmer than modern mean summer and winter values by 9000 yr b p mcr reconstructions indicate that both summer and winter temperatures were already declining from an early holocene peak mean july values remained above modern levels and mean january values remained below modern levels until 3000 yr b p a series of small scale oscillations followed

environmental interpretation of fossil insect assemblages from mis 5 at ziegler reservoir snowmass village colorado abstract organic rich lake sediments from a trench exposed at the ziegler reservoir fossil site near snowmass village colorado yielded a sequence of 27 insect fossil assemblages spanning the time interval from about 125 to 77 ka the assemblages appear to represent mis 5e 5c 5b and 5a a total of 99 taxa were identified mostly beetles the fossils represent the oldest known pleistocene insect faunas from high elevation in the rocky mountains and document a series of climatic oscillations from full interglacial to stadial and interstadial environments accompanied by changes in regional biological communities the mis 5e fauna indicates summer temperatures similar to modern values with winter temperatures 5 7 c cooler than today regional climates cooled somewhat by mis 5c and during mis 5b summer temperatures were 5 6 c colder than modern values summer temperatures recovered to near modern levels during early mis 5a and cooled by 1 2 c at its end although winter temperatures were apparently above modern levels the indication of milder but wetter winters strengthened by the inclusion of species found today only in the pacific northwest region suggests conditions that may have led to increased snowpack at high elevations in this part of the rocky mountains linked with the onset of mis 4 glaciation

new pollen and beetle analyses at the mary jane site colorado evidence for late glacial tundra conditions analyses of fossil pollen and beetles from a late pinedale peat deposit from the upper fraser river colorado allow a reassessment of previously published paleoenvironmental evidence from the site between 13 800 and at least 12 600 yr b p the environment was an open tundra indicative of a cold dry climate scattered spruce trees were probably present at the site by the end of the record ca 12 300 yr b p

tracing hydrologic flow paths in a small forested watershed using variations in 87sr 86sr ca sr ba sr and δ18o 1 natural variations in 87sr 86sr ca sr ba sr and 18o were used to investigate changing hydrologic flow paths during storm events in an 11 8 ha first order watershed of the hubbard brook experimental forest throughfall soil water and stream water were sampled during several storm events and a single snowmelt event throughfall had 87sr 86sr ca sr and 18o values that were distinct from other water types soil water was highly variable in composition but could be separated into three distinct elevation zones in the watershed with 87sr 86sr and ba sr both increasing with elevation in the watershed changes in 87sr 86sr ba sr and 18o of stream water during storm events yielded complementary information about watershed hydrologic flow paths traditional hydrograph separation using 18o values indicated that new water was only a small component of storm flow 9 18 whereas 87sr 86sr and ba sr ratios indicated that shallow subsurface flow soil water contributed significantly to storm flow in amounts up to 40 depending on soil moisture conditions

new data for late pleistocene pinedale alpine glaciation from southwestern colorado abstract new cosmogenic surface exposure ages of moraine crest boulders from southwestern colorado are compared with published surface exposure ages of boulders from moraine complexes in north central colorado and in west central fremont lake basin wyoming 10be data sets from the three areas were scaled to a single 10be production rate of 5 4 at g yr at sea level and high latitude slhl which represents the average 10be production rate for two high altitude mid latitude sites in the western united states us and austria multiple nuclide ages on single boulders indicate that this 10be production rate yields ages comparable to those calculated with a commonly used 36cl production scheme the average age and age range of moraine crest boulders on terminal moraines at the southwestern colorado and wyoming sites are similar indicating a retreat from their positions 16 8 36cl ka cosmogenic ages in this paper are labeled 10be or 36cl ka or just ka when both 10be or 36cl ages are being discussed radiocarbon ages are labeled 14c ka calibrated radiocarbon are labeled cal ka and calendar ages are labeled calendar ka errors 1 associated with ages are shown in tables radiocarbon ages were calibrated using the data of hughen et al science 303 2004 202 this suggests a near synchronous retreat of pinedale glaciers across a 470 km latitudinal range in the middle and southern rocky mountains hypothetical corrections for snow shielding and rock surface erosion shifts the time of retreat to between 17 2 and 17 5 10be ka at pinedale wyoming and between 16 3 and 17 3 36cl ka at hogback mountain colorado

metal mobility due to storm events on an impacted hillslope in palmerton pa abstract water samples were collected continuously from perennial springs on a hillslope impacted by historical metal deposition to study the hydrologic and geochemical behavior of a watershed during storm events and assess the natural attenuation of metals in soil water samples were collected throughout storm hydrographs for inorganic chemistry analyses and a sequential extraction was performed on watershed soil samples despite 30 a of natural attenuation at the site zn is mobilized into streamwater during storm events with concentrations ranging from 18 to 452 g l while cd and pb concentrations in water samples remained relatively constant zn concentration increased corresponding with the peak in the hydrograph indicating this metal is being released from adsorption sites located in an unsaturated zone that is temporarily inundated during storm events zinc is held on exchangeable water and acid soluble sites and in the reducible fraction further indicating zn may be released as a result of the downward movement of water through the soil profile equilibrium geochemical modeling predicts zn desorption with a decrease in ph which may occur as a result of site re vegetation the long legacy of metal emissions from a historical smelting operation will continue to limit the attenuating ability of this site

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

soil geomorphology present dilemmas and future challenges abstract understanding the manner in which landscapes change is still a major challenge for geomorphologists recent work has shown quite convincingly that landscape evolution occurs during relatively short periods of intense adjustment followed by longer periods of stability the challenge is to determine the way in which such change occurs and the factors which control the changes this paper by using a number of specific examples from a variety of environments suggests that many of these issues may be resolved by adopting an integrative approach involving soil information as well as geomorphological concepts

experimental modelling of tectonics erosion sedimentation interactions in compressional extensional and strike slip settings tectonically controlled landforms develop morphologic features that provide useful markers to investigate crustal deformation and relief growth dynamics in this paper we present results of morphotectonic experiments obtained with an innovative approach combining tectonic and surface processes erosion transport and sedimentation coupled with accurate model monitoring techniques this approach allows for a qualitative and quantitative analysis of landscape evolution in response to active deformation in the three end member geological settings compression extension and strike slip experimental results outline first that experimental morphologies evolve significantly at a short time scale numerous morphologic markers form continuously but their lifetime is generally short because erosion and sedimentation processes tend to destroy or bury them for the compressional setting the formation of terraces above an active thrust appears mainly controlled by narrowing and incision of the main channel through the uplifting hanging wall and by avulsion of deposits on fan like bodies terrace formation is irregular even under steady tectonic rates and erosional conditions terrace deformation analysis allows retrieving the growth history of the structure and the fault slip rate evolution for the extensional setting the dynamics of hanging wall sedimentary filling appears to control the position of the base level which in turn controls footwall erosion two phases of relief evolution can be evidenced the first is a phase of relief growth and the second is a phase of upstream propagation of topographic equilibrium that is reached first in the sedimentary basin during the phase of relief growth the formation of triangular facets occurs by degradation of the fault scarp and their geometry height becomes stationary during the phase of upstream propagation of the topographic equilibrium for the strike slip setting the complex morphology of the wrench zone composed of several interacting fault segments enhances the interactions with the drainage network because of the widening of the main fault zone toward the surface a significant amount of distributed deformation is observed along the wrench zone locally where two terminations of fault segments interact less than a quarter of the far field displacement can remain measurable using fault offsets leading to a systematic underestimation of the real fault slip rate these different experimental examples illustrate the great potential of the approach coupling deformation mechanisms and erosion transport sedimentation processes to investigate qualitatively and quantitatively the morphotectonic evolution of tectonically controlled landscapes

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

morphotectonic evolution of triangular facets and wine glass valleys in the noakoh anticline zagros iran implications for active tectonics article i nfo the noakoh anticline is located in kermanshah province and is part of the simply folded belt of zagros boundaries of 97 triangular facets and 67 wine glass w g valleys which formed on anticline limbs were delineated using quickbird satellite imagery the strata dip d area a base length bl topographic slope s of facets the maximum width m outlet width o and ratio of maximum width to outlet width w index of w g valleys were analysed in detail noakoh anticline was subdivided into 9 tectonic zones on the basis of dip topographic slopes and width of limbs results show that there are strong positive corre lations between means of d bl and s bl pairs poor positive correlations exist between means of d a and s a pairs among w g valley metrics the w index has strong relations with d and s parameters based on the results steep facets with long bases and well developed w g valleys with narrow outlets and wide upper parts are associated with more rotated limbs having steep slopes facets on the northeastern slope have more forest cover micro organism activity karstic features and soil cover whereas facets on relatively drier southwestern slope are characterized by physical weathering processes and minor karstic landforms this study demonstrates that apart from tectonic activity as a major control on the morphometry of facets and valleys climate and slope aspect have also acted as secondary factors on the development of the studied landforms

release transport and attenuation of metals from an old tailings impoundment abstract the oxidation of sulfide minerals from mine wastes results in the release of oxidation products to groundwater and surface water the abandoned high sulfide camp tailings impoundment at sherridon manitoba wherein the tailings have undergone oxidation for more than 70 a was investigated by hydrogeological geochemical and mineralogical techniques mineralogical analysis indicates that the unoxidized tailings contain nearly equal proportions of pyrite and pyrrhotite which make up to 60 wt of the total tailings and which are accompanied by minor amounts of chalcopyrite and sphalerite and minute amounts of galena and arsenopyrite extensive oxidation in the upper 50 cm of the tailings has resulted in extremely high concentrations of dissolved so4 and metals and as in the tailings pore water ph 1 m thick geochemical modeling and mineralogical analysis indicate that the hardpan layer consists of secondary melanterite rozenite gypsum jarosite and goethite the minerals indicated mainly control the dissolved concentrations of so4 fe ca and k the highest concentrations of dissolved metals are observed directly above and within the massive hardpan layer near the water table at a depth of 4 m most metals and so4 sharply decline in concentration although dissolved concentrations of metals and so4 decrease below the water table these concentrations remain elevated throughout the tailings with up to 60 600 mg l 1 fe and 91 600 mg l 1 so4 observed in the deeper groundwater during precipitation events surface seeps develop along the flanks of the impoundment and discharge pore water with a geochemical composition that is similar to the composition of water directly above the hardpan these results suggest that shallow lateral flow of water from a transient perched water table is resulting in higher contaminant loadings than would be predicted if it were assumed that discharge is derived solely from the deeper primary water table the abundance of residual sulfide minerals the depletion of aluminosilicate minerals in the upper meter of the tailings and the presence of a significant mass of residual sulfide minerals in this zone after 70 a of oxidation suggest that sulfide oxidation will continue to release acid metals and so4 to the environment for decades to centuries

the loch lomond readvance on the isle of mull scotland glacier reconstruction and palaeoclimatic implications geomorphological mapping of mull provides evidence for an icefield 143 km2 in area flanked by six corrie glaciers with a total area of ca 13 km2 the absence of lateglacial periglacial features shorelines and pollen sites from the area occupied by this readvance together with radiocarbon dating of shell fragments confirm that it occurred during the loch lomond younger dryas stade the thickness of glacigenic deposits within the area of the readvance is attributed to reworking of paraglacial sediments up valley continuity of recessional moraines indicates that the ice remained active and near to equilibrium during retreat consistent with slow warming following the coldest part of the stade reconstructed equilibrium line altitudes elas imply vigorous snow blowing by westerly winds and are consistent with a general southwestwards decline in elas across the scottish highlands an ela of 250 m was calculated for the mull icefield using an ablation accumulation balance ratio abr approach palaeotemperature and palaeoprecipitation estimates were derived by calculating a theoretical regional ela from meteorological data and assuming that the combination of temperature and precipitation implied by the theoretical ela approximates conditions at 250 m on mull during the loch lomond stade the result indicates a mean july sea level temperature of 5 7 0 5 c and a mean annual precipitation at 250 m of ca 2700 3800 mm best estimate 3200 mm indicating higher precipitation totals than at present owing to more vigorous atmospheric circulation copyright 2002 john wiley sons ltd

neoproterozoic sulfur isotope variation in australia and global implications abstract seven sulfur isotope stages are apparent in australian neoproterozoic sections 1 from 840 ma to the sturtian glaciation 700 ma 34ssulfate varied little 19 to 17 5 and 34ssulfide ranged from 20 to 23 2 the sturtian glaciation was followed by 3 a rise in 34ssulfide to an average of 30 seen also in china namibia and canada and in 34ssulfate at least to 26 and possibly to 45 the sharp rise in 34s of all sulfur fractions sulfate sulfide and organic leads us to speculate that sulfide depleted in 34s was deposited on the abyssal plain and that residual sulfate enriched in 34s remained beneath a stagnant ice covered ocean during the sturtian glaciation and was brought to the shallow continental margin during the post glacial transgression 4 34ssulfide and 34ssulfate fall from 640 to 607 ma 34ssulfate down to 17 probably from oxygen excess through massive organic carbon burial which causes weathering of sulfide depleted in 34s continental sulfide and previously deposited sulfide on the abyssal plain 5 the oxic environment of the marinoan 605 595 ma glaciation minimises sulfate reduction unlike the sturtian so that 34ssulfate is unvarying 6 the post glacial environment has sulfide depleted in 34s average 34ssulfide

on the geochemical evolution of sedimentary rocks the average major element compositions of clastic sedimentary rock assemblages i e carbonates evaporites and iron formations not considered for various times in earth history archean early proterozoic late proterozoic phanerozoic are reported based largely on the compilations of f l schwab uncertainties in the averages are considerable there is little evidence of secular change in the average composition of sedimentary rocks during post archean times such data do not support the idea of a gradual change in composition of the upper continental crust from mafic to felsic composition trace element patterns in sedimentary rocks particularly ree and th distributions support the idea of constancy of upper crustal composition during the post archean the average composition of archean clastic sedimentary rocks differs significantly from the post archean average being enriched in na mg and ca and depleted in si and k such differences are consistent with the archean upper crust having a more mafic composition than post archean upper crust the trace element data further support this idea it is noted that the average composition of post archean clastic sedimentary rocks predicts to within a factor of 1 2 the composition of the exposed continental crust for the elements si al fe k mg and ti the abundances of ca and na are depleted in the sedimentary rocks due to the fact that the compositions of carbonates evaporites and seawater were not considered the average composition of archean clastic sedimentary rocks does not compare favourably with an independent estimate of archean upper crust composition being enriched in si k and depleted in ca fe mg and ti such a comparison indicates that the archean upper crust may have had a more felsic major element composition than previously thought

differential insect and mammalian response to late quaternary climate change in the rocky mountain region of north america abstract of the 200 beetle species identified from rocky mountain late pleistocene insect faunal assemblages 23 are no longer resident in this region none of the 200 species is extinct in contrast to this only 8 of 73 identified mammal species from rocky mountain late pleistocene assemblages are no longer resident in the rockies and 12 species are now extinct since both groups of organisms are highly mobile it would appear that their responses to the large scale fluctuations of climate associated with the last 125 000 years have been considerably different most strikingly contrasting with the insects there are no mammals in the rocky mountain late pleistocene fossil record that are found exclusively today in the pacific northwest pnw region the pnw does have a distinctive modern mammalian fauna but only one of these keen s myotis has a fossil record outside the pnw region in the eastern and central united states no modern pnw vertebrate species have been found in any rocky mountain fossil assemblages based on these data it appears that there has been little or no mammalian faunal exchange between the pnw region and the rocky mountains during the late pleistocene or holocene this is in stark contrast to the fossil beetle record where pnw species are a substantial component in many faunas right through to the late holocene

grouping and migration of surface faulting and variations in slip rates on faults in the great basin province abstract nonuniformity of the occurrence of large slip events producing surface ruptures on seismogenic faults and variations in slip rate probably characterize seismogenic faulting in the great basin province western united states examples include the grouping of faulting events along the lost river fault idaho changes in tilt rates of the east range and cortez mountains nevada extension of slip along a fault on the northwest flank of the humboldt range nevada and migration or shifting of slip back and forth from one fault to another along subparallel range front faults in dixie valley nevada

revised age of deglaciation of lake emma based on new radiocarbon and macrofossil analyses abstract previous radiocarbon ages of detrital moss fragments in basal organic sediments of lake emma indicated that extensive deglaciation of the san juan mountains occurred prior to 14 900 yr b p carrara et al 1984 paleoecological analyses of insect and plant macrofossils from these basal sediments cast doubt on the reliability of the radiocarbon ages subsequent accelerator radiocarbon dates of insect fossils and wood fragments indicate an early holocene age rather than a late pleistocene age for the basal sediments of lake emma these new radiocarbon ages suggest that by at least 10 000 yr b p deglaciation of the san juan mountains was complete the insect and plant macrofossils from the basal organic sediments indicate a higher than present treeline during the early holocene the insect assemblages consisted of about 30 bark beetles which contrasts markedly with the composition of insects from modern lake sediments and modern specimens collected in the lake emma cirque in which bark beetles comprise only about 3 of the assemblages in addition in the fossil assemblages there were a number of flightless insect species not subject to upslope transport by wind indicative of coniferous forest environments these insects were likewise absent in the modern assemblage

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

the compositional evolution of meso and neoproterozoic carbonate rocks abstract petrochemical data on meso and neoproterozoic riphean and vendian carbonates from the urals and siberia suggest that upper riphean carbonate rocks differ from both older and younger equivalents in their lower dolomite limestone and higher strontium abundance it is suggested that the directional increase in the ca content of the earth s sedimentary shell results from the hydrothermal interaction of seawater with oceanic basalts manifest in a progressive reduction of dolomite formation throughout geological history superimposed cyclical variation in dolomite limestone may reflect secular changes in the rate of co 2 introduction into the atmosphere in particular the relative low dolomite limestone ratio seen in upper riphean carbonates may reflect low p co 2

soil geomorphology the linkage of pedology and surficial processes geologists have made significant contributions to the discipline of pedology however until recently direct contributions came largely prior to 1935 as exemplified by those of powell and shaler during the late 19th century tandarich et al 1987 during much of the twentieth century geology and pedology have generally evolved along nearly separate pathways re integration of the two disciplines began slowly in the late 1950s and early to middle 1960s through the research and publications of ruhe 1956 1960 1964 richmond 1962 and morrison 1964 1965 1967 richmond s and morrison s research has provided much of the basis for the use of soils in the study of the stratigraphy of quaternary deposits in the western u s a birkeland 1984 the soil stratigraphic unit the geosol is a key component of the methodology developed by morrison geosols are presumed to have formed only during soil forming intervals interglacial or interstadial periods when climatic conditions were deemed optimal for rapid soil development recognition of soil stratigraphic units as geosols automatically conferred climatic as well as stratigraphic significance to buried soils this approach may have great utility in regions at higher latitudes that were characterized by extremes of climatic fluctuation during the qua ternary catt 1986 with little or no soil development during cold climate intervals a rather different approach involving the use of soils has been adopted by geoscientists conducting geomorphological research during the mid to late 1960s studies by researchers such as balster daniels hawley gile parsons and yaalon focussed on the nature of the relationships linking soils and landscape elements in many respects the philisophical approach to soil geomorphic research emphasized in the studies of these scientists strongly reflected the intellectual impact of jenny 1941 on the science of pedology this philosophy also strongly influenced the research of birkeland and following publication of birkeland s important textbook pedology weathering and geomorphological research 1974 a dramatic increase in the use of pedology in the geosciences occurred as researchers focussed on the study of landscape evolution in our view this emerging marriage of pedology and studies of surficial processes provides a critical framework for both the study of soil genesis and the study of evolution of and or stability of landscape elements

modeling the shape and evolution of normal fault facets facets formed along the footwalls of active normal fault blocks display a variety of longitudinal profile forms with variations in gradient shape degree of soil cover and presence or absence of a slope break at the fault trace we show that a two dimensional process oriented cellular automaton model of facet profile evolution can account for the observed morphologic diversity the model uses two dimensionless parameters to represent fault slip progressive rock weathering and downslope colluvial soil transport driven by gravity and stochastic disturbance events the parameters represent rock weathering and soil disturbance rates respectively scaled by fault slip rate both can be derived from field estimated rate coefficients in the model s transport limited regime slope gradient depends on the ratio of disturbance to slip rate with a maximum that represents the angle of repose for colluvium in this regime facet evolution is consistent with nonlinear diffusion models of soil mantled hillslope evolution under the weathering limited regime bedrock becomes partly exposed but microtopography helps trap some colluvium even when facet gradient exceeds the threshold angle whereas the model predicts a continuous gradient from footwall to colluvial wedge under transport limited behavior fully weathering limited facets tend to develop a slope break between footwall and basal colluvium as a result of reduced transport efficiency on the rocky footwall slope to the extent that the model provides a reasonable analogy for natural facets its behavior suggests that facet profile morphology can provide useful constraints on relative potential rates of rock weathering soil disturbance and fault slip

degree day glacier mass balance modelling with applications to glaciers in iceland norway and greenland a degree day glacier mass balance model is applied to three glaciers in iceland norway and greenland for which detailed mass balance measurements are available over a period of several years model results are in good agreement with measured variations in the mass balance with elevation over the time periods considered for each glacier in addition the model explains 60 80 of the year to year variance in the elevation averaged summer season mass balance measurements on the glaciers using a single parameter set for each glacier the increase in ablation on the glaciers due to a warming of 2 c is predicted to range from about 1 m w e year 1 at the highest elevations to about 2 5 m w e year 1 at the lowest elevations predicted changes in the winter balance measured between fixed date are relatively small except at the lowest elevations on the icelandic and norwegian glaciers where the winter balance is significantly reduced equilibrium line altitudes are raised by 200 300 m on the icelandic and norwegian glaciers except at the highest elevations the winter balance of the icelandic and norwegian glaciers is predicted to decrease even if the warming is accompanied by a 10 increase in the precipitation no firm evidence of a climate related variation in the degree day factors or in the temperature lapse rate on the same glacier could be found the model furthermore reproduces large variations in the mass balance with elevation and from year to year on each glacier using the same parameter set we assume therefore that these parameters will not change significantly for the climate scenarios considered here

late pleistocene glacial equilibrium line altitudes in the colorado front range a comparison of methods abstract six methods for approximating late pleistocene pinedale equilibrium line altitudes elas are compared for rapidity of data collection and error rmse from first order trend surfaces using the colorado front range trend surfaces computed from rapidly applied techniques such as glaciation threshold median altitude of small reconstructed glaciers and altitude of lowest cirque floors have relatively high rmses 97 186 m because they are subjectively derived and are based on small glaciers sensitive to microclimatic variability surfaces computed for accumulation area ratios aars and toe to headwall altitude ratios thars of large reconstructed glaciers show that an aar of 0 65 and a thar of 0 40 have the lowest rmses about 80 m and provide the same mean ela estimate about 3160 m as that of the more subjectively derived maximum altitudes of pinedale lateral moraines rmse 149 m second order trend surfaces demonstrate low elas in the latitudinal center of the front range perhaps due to higher winter accumulation there the mountains do not presently reach the ela for large glaciers and small front range cirque glaciers are not comparable to small glaciers existing during pinedale time therefore pleistocene ela depression and consequent temperature depression cannot reliably be ascertained from the calculated ela surfaces

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

palynological evidence for late and postglacial environmental change in central colorado abstract a sediment core recovered from lost park 39 17 30 n 105 32 30 w elevation 3079 m provides palynological evidence for postglacial vegetational and environmental change in the central front range of colorado pine spruce woodland was the dominant vegetation type throughout the 12 000 yr long record nonarboreal taxa however showed substantial changes from 11 800 to 9100 14 c yr b p high artemisia levels suggest steppe vegetation indicative of a climate cooler than that at present with an annual precipitation regime dominated by winter moisture the pollen spectra of this interval resemble modern spectra at two sites within colorado and wyoming comparisons of modern climatic data suggest that lost park may have experienced winter temperatures 3 to 3 5 c colder than those at present and monthly winter precipitation levels 3 5 cm higher than those at present during this late glacial time lower artemisia coupled with increases in poaceae pollen suggest a shift to warmer conditions dominated by summer monsoon precipitation around 9100 14 c yr b p increased charcoal occurrences between 6000 and 4000 14 c yr b p may suggest the onset of drier summer conditions that would be expected with a waning summer monsoon circulation at that time since 1800 14 c yr b p a resurgence in artemisia pollen suggests a return to relatively cool and or dry conditions similar to the present climate

climate at the equilibrium line of glaciers the relationships between temperature precipitation and radiation on glacier equilibrium lines are investigated using 70 glaciers for which the mass balance and meteorological observations have been carried out for sufficiently long periods it is found that the characteristic climate at glacier equilibrium lines can be described using the summer 3 months temperature in a free atmosphere annual total precipitation and the sum of global and long wave net radiation all of these are measured at or very near the equilibrium line altitudes then it is shown how the shift of the equilibriumline will occur as a result of a climatic change finally the effect of the shift of the equilibrium line on the annualmean specific mass balance is analytically derived and compared with observations the present results make it possible to identify the altitudes in climate models where glacierization should begin and to evaluate the mass balance changes as a result of possible future changes in the climate

application of principal component analysis on chemical data for reservoir correlation a case study from cretaceous carbonate sedimentary rocks saudi arabia a new method is presented to identify chemostratigraphic zones by applying principal component analysis pca and interpret geological boundaries based on principal component pc curves pc data were calculated using icp oes inductively coupled plasma optical emission spectrometry and icp ms inductively coupled plasma mass spectrometry with data acquired for 50 chemical elements in the range na u in the present study a total of 832 core and cuttings samples were analyzed from four wells penetrating the cretaceous wasia formation southeastern saudi arabia the conventional workflow involves plotting profiles for elements and elemental ratios with 250 to 300 profiles produced for each study section with so many variables to consider it is a challenging and time consuming process to produce chemostratigraphic frameworks requiring expert knowledge of chemostratigraphy by utilizing only a few pc curves as opposed to element or ratio profiles it is easier for non experts to identify correlative boundaries pc parameters reflect changes in more than one group of elements and summarize geological changes for example in this study pc2 parameter values relate to changes in depositional redox conditions a close association was revealed between boundaries identified using pc and ones from an existing conventional chemostratigraphic study on the same wells for example pc zone e1 3 relates to the conventional c3 1b the fact that some pc and conventional chemostratigraphic boundaries do not always coincide e g conventional boundaries c2 1 c2 2 and c2 2 c2 3 exist within pc zone e2 1 means that the integrated correlation scheme is of higher resolution if these techniques were employed in isolation

soils and geomorphic evolution of bedrock facets on a tectonically active mountain front western sangre de cristo mountains new mexico abstract soil profiles colluvial stratigraphy and detailed hillslope morphology are key elements used for geomorphic interpretations of the form and long term evolution of triangular facets on a 1200 m high tectonically active mountain front the facets are developed on precambrian gneisses and tertiary volcanic and plutonic rocks along a complexly segmented active normal fault zone in the rio grande rift of northern new mexico the detailed morphologies of 20 to 350 m high facets are defined by statistical and time series analyses of 40 field transects that were keyed to observations of colluvium bedrock microtopography and vegetation the undissected parts of most facets are transport limited hillslopes mantled with varying thicknesses 0 1 to 1 m thick of sand and gravel colluvium between generally sparse 10 30 bedrock outcrops facet soils range from a thin 0 2 m weakly developed soils with cumulic silty a or transitional a b epipedons above cox horizons in bedrock or colluvium to b deep 0 5 1 m moderately to strongly developed profiles containing thick cambic bw and or argillic bt horizons that commonly extend into highly weathered saprolitic bedrock the presence of strongly weathered profiles and thick colluvium suggests that rates of colluvial transport and hillslope erosion are less than or equal to rates of soil development over at least a large part of the holocene the catenary variation of soils and colluvium on selected facet transects indicate that the degree of soil development generally increases and the thickness of colluvium decreases upslope on most facets this overall pattern is commonly disrupted on large facet hillslopes by irregular secondary soil variations linked to intermediate scale 20 60 m long concave slope elements these features are interpreted to reflect discontinuous transport and erosion of colluvium down slope below bedrock outcrops the degree of weathering in subsurface bedrock commonly increases more systematically upslope on most facets than colluvial soils this pattern is consistent with an increase in age with height on these fault generated facet hillslopes the characteristic range of internal variation in soils and colluvial deposits on a given facet also varies greatly among facets with differing overall morphologies and external environments deep cumulic soils and thick colluvium occur consistently on steep 30 high and relatively undissected facets above the narrow central sections of fault segments much thinner and less weathered colluvium and soils overlie saprolitic bedrock at shallow depths on low highly dissected gently sloping 20 facets above complex fault segment boundaries parametric and nonparametric analyses of variance indicate that these large scale contrasts in facet morphology correlate primarily with a few facet subgroups related in decreasing importance to variations in range front faulting bedrock lithology and piedmont dissection or aggradation these factors are related to facet morphology drainage evolution and hillslope soil stratigraphy in a general geomorphic model for fault generated facets in this model segmentation related changes in the geometry and or rates of faulting most strongly affect facet size slope gradient the thickness of colluvium and soil development and drainage patterns facets of varying heights have similar hillslope forms at the same position on the range front these characteristic morphologies are established under prevailing tectonic and nontectonic conditions on facets as bedrock is initially exposed from beneath alluvial covered fault scarps above a height threshold of 15 35 m

morphological and chemical characteristics of soil catenas on pinedale and bull lake moraine slopes in the salmon river mountains idaho abstract morphological and chemical properties of soils developed on moraines of granitic composition and forested with lodgepole pine in bear valley idaho change significantly with age and slope position soil development on pinedale and bull lake moraine slopes of similar curvature and steepness was assessed at the summits shoulders backslopes and footslopes of both catenas and at the toeslope of the bull lake catena many soil properties show trends in development with both age and slope position these properties include clay content clay film development color plagioclase weathering and dithionite citrate extractable iron fed the degree of development of all these properties is greater on the bull lake catena relative to that on the pinedale catena this trend reflects increased soil development with age on both catenas development of soil properties is commonly highest at the footslope or toeslope sites and minimum at the backslope site downslope changes are attributed to both colluviation and pedogenic processes including sorting of sediments during downslope transport greater accumulation of eolian materials transported to downslope sites by surface processes and greater in situ weathering of mineral grains at the footslope and toeslope sites

adjustments by the charwell river new zealand to uplift and climatic changes major climatic changes and rapid local and regional tectonic movements were common in new zealand during the late quaternary and caused a diversity of adjustments in the drainage basin and piedmont reaches of the charwell river which are separated by the hope fault the onset of semi arid frigid climates during the latest pleistocene probably greatly increased hillslope sediment yields in a periglacial environment and the piedmont reach aggraded as much as 42 m on top of a broad strath with the return of humid mesic climates in the holocene sediment yields decreased as dense forests again mantled the slopes and the piedmont reach degraded as mush as 81 m dating of eleven cut and strath terraces by radiocarbon calibrated weathering rind measurements on greyawake cobbles shows the degradation rates varied greatly during the last 14 ka 1 ka 1000 yr initial degradation rates of 4 m ka 1 increased to 30 m ka 1 by 6 ka ago during a mid holocene climatic optimum since 4 ka ago degradation rates have been only 1 2 m ka 1 comparable to uplift rates in the piedmont reach inferred from marine terrace studies and the river is again cutting a broad strath each broad strath represents equilibrium conditions attained by this powerful stream during interglacial times despite episodes of being overwhelmed by climatically induced sediment yield increases during full glacial climates and having to maintain a long term degradation rate equal to the uplift rate the 75 81 m of degradation since formation of the latest pleistocene fill terrace tread is the sum of the amount of late pleistocene valley floor aggradation and the amount of regional uplift that occurred between the estimated times of major strath formation at about 30 and 0 ka the 39 m of tectonically induced degradation below the pre aggradation strath is sufficiently large that post 30 ka uplift may have doubled holocene degradation rates each of the eleven degradation terraces represents pauses of a few centuries in holocene downcutting brief equilibrium conditions were attained by streambed armoring and concurrent growth of riparian plants both processes progressively increased hydraulic roughness and the shear stresses needed to entrain streambed materials occasional floods possibly from rare cyclones derived from tropical moisture sources destroyed streambed armor and channel downcutting was renewed thus the formation of eleven equilibrium terraces can be accounted for without postulating additional tectonic perturbations or secular climatic changes

mass balance and equilibrium line altitudes of glaciers in high mountain environments abstract the mass balance characteristics of glaciers in high mountain environments complicate the relationship between glacier equilibrium line altitudes elas and climatic variables such as precipitation and air temperature therefore methods of ela reconstruction employed in low relief environments are commonly not applicable in high mountains or require some modification we review the concept of the ela with reference to the mass balance of a range of glacier types found in high mountain regions we examine the applicability of several commonly used methods of ela reconstruction for different glacier types and propose some general principles to guide the choice of appropriate methods

late quaternary glaciation of costa rica the highest peaks of costa rica 9 15 9 36 n were glaciated during the late quaternary attesting to a significantly cooler climate in central america than today during the last local glacial maximum llgm an ice cap 35 km2 in extent covered the highest peaks of the cordillera de talamanca around cerro chirripo and around cerros de la muerte and kamuk 5 and 2 km2 of ice existed respectively in chirripo national park three moraine groups define three glacial stages the talamanca stage extends to 3040 m and represents the last local glacial maximum chirripo stage moraines reach elevations of 3300 m and talari stage moraines formed at 3300 and 3420 m former equilibrium line altitudes elas were 3500 m 3600 m and 3620 m respectively cirque floor elevations of 3260 m at cerro kamuk suggest a lower pre llgm ela radiosonde data from san jose place the modern 0 c isotherm at 5000 m which suggests a late quaternary ela depression of 1500 m which is consistent with a temperature reduction at chirripo of 8 9 c during the llgm some of this cooling may be attributable to a steeper lapse rate associated with a drier atmosphere possibly due to a more restricted position of the intertropical convergence zone decreased yearly convection or more frequent incursion of polar air masses

deglaciation and postglacial timberline in the san juan mountains colorado abstract lake emma which no longer exists because of a mining accident was a tarn in a south facing cirque near the headwaters of the animas river in the san juan mountains of southwestern colorado during the pinedale glaciation this area was covered by a large transection glacier centered over the lake emma region three radiocarbon dates on basal organic sediment from lake emma indicate that by ca 15 000 yr b p this glacier one of the largest in the southern rocky mountains no longer existed twenty two radiocarbon dates on picea and abies krummholz fragments in the lake emma deposits indicate that from ca 9600 to 7800 yr b p from 6700 to 5600 yr b p and at 3100 yr b p the krummholz limit was at least 70 m higher than present these data in conjunction with picea pinus pollen ratios from both the lake emma site and the hurricane basin site of j t andrews p e carrara f b king and r struckenrath 1975 quaternary research 5 173 197 suggest than from ca 9600 to 3000 yr b p timberline in the san juan mountains was higher than present cooling apparently began ca 3000 yr b p as indicated by decreases in both the percentage of picea pollen and picea pinus pollen ratios at the hurricane basin site andrews et al 1975 cooling is also suggested by the lack of picea or abies fragments younger than 3000 yr b p at either the lake emma or the hurricane basin site

fault behavior and characteristic earthquakes examples from the wasatch and san andreas fault zones paleoseismological data for the wasatch and san andreas fault zones have led to the formulation of the characteristic earthquake model which postulates that individual faults and fault segments tend to generate essentially same size or characteristic earthquakes having a relatively narrow range of magnitudes near the maximum analysis of scarp derived colluvium in trench exposures across the wasatch fault provides estimates of the timing and displacement associated with individual surface faulting earthquakes at all of the sites studied the displacement per event has been consistently large measured values range from 1 6 to 2 6 m and the average is about 2 m on the basis of variability in the timing of individual events as well as changes in scarp morphology and fault geometry six major segments are recognized along the wasatch fault on the basis of the most likely number of surface faulting events 18 that have occurred on segments of the wasatch fault zone during the past 8000 years an average recurrence interval of 400 666 years with a preferred average of 444 years is calculated for the entire zone geologic data on the distribution of slip associated with prehistoric earthquakes and slip rates along the south central segment of the san andreas fault suggest that the m 8 1857 earthquake is a characteristic earthquake for this segment comparisons of earthquake recurrence relationships on both the wasatch and san andreas faults based on historical seismicity data and geologic data show that a linear constant b value extrapolation of the cumulative recurrence curve from the smaller magnitudes leads to gross underestimates of the frequency of occurrence of the large or characteristic earthquakes only by assuming a low b value in the moderate magnitude range can the seismicity data on small earthquakes be reconciled with geologic data on large earthquakes the characteristic earthquake appears to be a fundamental aspect of the behavior of the wasatch and san andreas faults and may apply to many other faults as well

accelerator dating of a mixed assemblage of late pleistocene insect fossils from the lamb spring site colorado abstract fossil insects from the late glacial deposits at the lamb spring archaeological site near denver colorado are relatively abundant and diverse providing considerable paleoecological data for the site the late pleistocene insect fauna from the site comprises 72 identified taxa principally beetles however the fauna presented an interpretive problem because it contained a mixture of prairie and alpine tundra species this was initially considered to be the result of a mixing of faunal elements during the climatic transition of late glacial times a no modern analog fauna accelerator dating of insect fossil specimens from the two ecological groups helped resolve the paleoecological problem fossil specimens of the prairie associated species were dated at 17 850 550 yr b p while specimens of the tundra associated species yielded an age of 14 500 500 yr b p these dates reveal that what appeared to be an ecological mixing was probably a taphonomic problem wherein full glacial age fossils were probably reworked into latest wisconsin sediments while both faunal assemblages reflect climatic conditions substantially colder than present initial results suggest that the full glacial fauna represents a cold dry grassland or steppe environment while the younger fauna suggests moister and more tundra like conditions

a four component mixing model for water in a karst terrain in south central indiana usa using solute concentration and stable isotopes as tracers the study area lies in a highly karstified carbonate terrain in south central indiana sinkholes conduits and caves form large secondary pathways for the subsurface flow as a result the discharge from a main emergence point for the subsurface flow system the orangeville rise quickly responds to the storm events and shows wide variations in flow rate water chemistry and stable isotopic compositions these responses are attributed to the mixing of water in secondary pathways in the study area recharge occurs through the thick mantled karst plain and the sinkhole plains and the role of soil layer and epikarst in the recharge process is of great importance rain dic 2 hco3 mg l 13cdic 7 soil water dic 544 hco3 mg l 13cdic 14 7 epikarstic water dic 224 hco3 mg l 13cdic 13 6 and phreatic diffuse flow water dic 299 hco3 mg l 13cdic 11 8 generally showed unique and constant dissolved inorganic carbon dic and 13cdic values over time using dic and 13cdic as tracers a four component mixing model was established for the karstic flow system by constructing the discharge hydrograph separation curves the mixing ratio of each component rain 10 6 soil 3 1 epikarstic 52 3 and phreatic 34 0 water was determined for the orangeville rise discharge over the testing period of 104 h after the storm event of 10 4 90 vadose water occupied 55 4 of spring discharge and this demonstrates the importance of the unsaturated zone especially the epikarst in the karstic flow systems

late pleistocene climate inferred from the reconstruction of the taylor river glacier complex southern sawatch range colorado abstract ice surface topography of a late pleistocene glacier complex herein named the taylor river glacier complex trgc was reconstructed on the basis of detailed mapping of glacial landforms combined with analyses of aerial photos and topographic maps during the last glacial maximum lgm the trgc covered an area of 215 km 2 and consisted of five valley or outlet glaciers that were nourished by accumulation in cirques basins and or upland ice fields equilibrium line altitudes elas for the glaciers of the trgc were estimated using the accumulation area ratio method assuming that ratio to be 0 65 0 05 elas thus derived ranged from about 3275 to 3400 m with a mean of 3340 60 m a degree day model ddm was used to infer the climatic significance of the lgm ela with no appreciable differences in precipitation with respect to modern climate the ela implies that mean summer temperatures during the lgm were 7 6 c cooler than today the ddm was also used to determine the temperatures required to maintain steady state mass balances for each of the reconstructed glaciers the required reductions in summer temperature vary little about a mean of 7 1 c the sensitivity of these results to slight 25 changes assumed for lgm precipitation are less than 0 5 c even under an lgm climate in which precipitation is assumed to be substantially different 50 than the present mean summer temperatures must be on the order of 7 0 to 8 5 c lower to depress equilibrium lines to lgm altitudes the greater sensitivity of the ela to changes in temperature suggests that glaciation in the region was driven more by decreases in summer temperature rather than increases in precipitation

geochemical response to variable streamflow conditions in contaminated and uncontaminated streams 1 seasonal variations in stream inorganic geochemistry are not well documented or understood we sampled two mining impacted and two relatively pristine streams in western montana over a 12 month period collecting samples every 4 weeks with supplemental sampling at least weekly during spring runoff we analyzed all samples for dissolved operationally defined as 0 2 m and total recoverable concentrations generally the trace elements al as cu fe mn and zn did not correlate linearly with streamflow while the major elements e g ca k and mg did suspended sediment total recoverable metals and h followed clockwise hysteresis rotations driven by short term flushing events during the very early stages of spring runoff mining impacted sites had higher concentrations of many trace elements than did relatively pristine sites one of the mining impacted sites exhibited strong geochemical responses to spring rain events in the basin the results underscore the need to sample streams frequently during changing hydrologic and climatic conditions in order to accurately monitor surface water quality and to determine solute and particulate loads both contaminant and noncontaminant

topographic expression of active faults in the foothills of the northern apennines abstract active faults that rupture the earth s surface leave an imprint on the topography that is recognized using a combination of geomorphic and geologic metrics including triangular facets the shape of mountain fronts the drainage network and incised river valleys with inset terraces we document the presence of a network of active high angle extensional faults collectively embedded in the actively shortening mountain front of the northern apennines that possess unique geomorphic expressions we measure the strain rate for these structures and find that they have a constant throw to length ratio we demonstrate the necessary and sufficient conditions for triangular facet development in the footwalls of these faults and argue that rock type exerts the strongest control the slip rates of these faults range from 0 1 to 0 3 mm yr which is similar to the average rate of river incision and mountain front unroofing determined by corollary studies the faults are a near surface manifestation of deeper crustal processes that are actively uplifting rocks and growing topography at a rate commensurate with surface processes that are eroding the mountain front to base level

a sulfur isotope study of pyrite genesis the mid proterozoic newland formation belt supergroup montana abstract different generations of sedimentary pyrite from the mid proterozoic newland formation usa have been analysed for their sulfur isotopic compositions the results indicate bacterial sulfate reduction as the pyrite forming process the 34 s values for early diagenetic pyrite around 14 are in contrast to dominantly more positive values for many other middle proterozoic units a progressive reduction of sulfate availability during diagenesis can be recognized by an increase in 34 s content rayleigh distillation as well as through detailed petrographic observations contemporaneous seawater had a sulfur isotopic ratio between 14 and 18 as measured from sedimentary barite within the unit

holocene glacier variations of blaisen hardangerjokulen central southern norway abstract a 1 m deep gully section 460 m beyond the maximum little ice age marginal moraines of blaisen hardangerjokulen central southern norway revealed alternations of minerogenic and organic sediments the geographical geological settings of the dated section provides a unique on off signal of holocene glacier fluctuations of blaisen lithostratigraphy sediment characteristics and radiocarbon dates from the study section indicate one period of glacier re advance between the late preboreal deglaciation of the inland ice sheet and 8660 100 yr b p a grey sand layer 56 57 cm below the surface is interpreted to be of fluvial colluvial origin and is radiocarbon dated to about 7700 yr b p at 48 cm below the surface a bluish grey sand silt layer is radiocarbon dated to 7590 12 yr b p 6560 6240 b c and interpreted to be glaciofluvial origin a minor glacier oscillation postdates 1130 70 yr b p 810 990 a d the medieval little ice age glacier advance of blaisen beyond its modern extent occurred after 1040 60 yr b p 960 1030 a d calculations of the modern and little ice age equilibrium line altitudes elas on hardangerjokulen suggest an ela depression of ca 130 m during the little ice age maximum