subsurface architecture of the boulder creek critical zone observatory from electrical resistivity tomography the architecture of the critical zone includes the distribution thickness and contacts of various types of slope deposits and weathering products such as saprolite and weathered bedrock resting on solid bedrock a quantitative analysis of architecture is necessary for many model driven approaches used by pedologic geomorphic hydrologic or biologic studies we have used electrical resistivity tomography a well established geophysical technique causing minimum surficial disturbance to portray the subsurface electrical resistivity differences at three study sites green lakes valley gordon gulch betasso at the boulder creek critical zone observatory bcczo possible limitations of the technique are discussed interpretation of the specific resistivity values using natural outcrops pits roadcuts and drilling data as ground truth information allows us to image the critical zone architecture of each site green lakes valley 3700 masl a glacially eroded alpine basin shows a rather simple split configuration with coarse blockfields and sediments partly containing permafrost above bedrock the critical zone in gordon gulch 2650 masl a montane basin with rolling hills and betasso 1925 masl a lower montane basin with v shaped valleys is more variable due to a complex quaternary geomorphic history boundaries between overlying stratified slope deposits and saprolite were identified at mean depths of 3 0 2 2 m and 4 1 3 6 m in the respective sites the boundary between saprolite and weathered bedrock is deeper in betasso at 5 8 3 7 m compared with 4 3 3 0 m in gordon gulch in general the data are consistent with results from seismic studies but electrical resistivity tomography documents a 0 5 1 5 m shallower critical zone above the weathered bedrock on average additionally we document high lateral variability which results from the weathering and sedimentation history and seems to be a consistent aspect of critical zone architecture within the bcczo copyright 2013 john wiley sons ltd

thermal and impact histories of reheated group iva ivb and ungrouped iron meteorites and their parent asteroids the microstructures of six reheated iron meteoritesotwo iva irons maria elena 1935 fuzzy creek one ivb iron ternera and three ungrouped irons hammond babb s mill blake s iron and babb s mill troost s iron owere characterized using scanning and transmission electron microscopy electron probe microanalysis and electron backscatter diffraction techniques to determine their thermal and shock history and that of their parent asteroids maria elena and hammond were heated below approximately 700 750 c so that kamacite was recrystallized and taenite was exsolved in kamacite and was spheroidized in plessite both meteorites retained a record of the original widmanstitten pattern the other four which show no trace of their original microstructure were heated above 600 700 c and recrystallized to form 10 20 lm wide homogeneous taenite grains on cooling kamacite formed on taenite grain boundaries with their close packed planes aligned formation of homogeneous 20 lm wide taenite grains with diverse orientations would have required as long as approximately 800 yr at 600 c or approximately 1 h at 1300 c all six irons contain approximately 5 10 lm wide taenite grains with internal microprecipitates of kamacite and nanometer scale m shaped ni profiles that reach approximately 40 ni indicating cooling over 100 10 000 yr un decomposed high ni martensite a2 in taeniteothe first occurrence in ironsoappears to be a characteristic of strongly reheated irons from our studies and published work we identified four progressive stages of shock and reheating in iva irons using these criteria cloudy taenite m shaped ni profiles in taenite neumann twin lamellae martensite shock hatched kamacite recrystallization microprecipitates of taenite and shock melted troilite maria elena and fuzzy creek represent stages 3 and 4 respectively although not all reheated irons contain evidence for shock it was probably the main cause of reheating cooling over years rather than hours precludes shock during the impacts that exposed the irons to cosmic rays if the reheated irons that we studied are representative the iva irons may have been shocked soon after they cooled below 200 c at 4 5 gyr in an impact that created a rubblepile asteroid with fragments from diverse depths the primary cooling rates of the iva irons and the proposed early history are remarkably consistent with the pb pb ages of troilite inclusions in two iva irons including the oldest known differentiated meteorite blichert toft et al 2010

the effects of 10 to 160 gpa shock on the magnetic properties of basalt and diabase hypervelocity impacts within the solar system affect both the magnetic remanence and bulk magnetic properties of planetary materials spherical shock experiments are a novel way to simulate shock events that enable materials to reach high shock pressures with a variable pressure profile across a single sample ranging between 10 and 160 gpa here we present spherical shock experiments on basaltic lava flow and diabase dike samples from the osler volcanic group whose ferromagnetic mineralogy is dominated by pseudo single domain titano magnetite our experiments reveal shock induced changes in rock magnetic properties including a significant increase in remanent coercivity electron and magnetic force microscopy support the interpretation that this coercivity increase is the result of grain fracturing and associated domain wall pinning in multidomain grains we introduce a method to discriminate between mechanical and thermal effects of shock on magnetic properties our approach involves conducting vacuum heating experiments on untreated specimens and comparing the hysteresis properties of heated and shocked specimens first order reversal curve forc experiments on untreated heated and shocked specimens demonstrate that shock and heating effects are fundamentally different for these samples shock has a magnetic hardening effect that does not alter the intrinsic shape of forc distributions while heating alters the magnetic mineralogy as evident from significant changes in the shape of forc contours these experiments contextualize paleomagnetic and rock magnetic data of naturally shocked materials from terrestrial and extraterrestrial impact craters this article is protected by copyright all rights reserved

lake devlin and pinedale glacial history front range colorado abstract glacial lake devlin was an ice margin lake that formed during pinedale time when the north boulder creek valley glacier blocked the mouth of a tributary near the downvalley limit of glaciation the lake was about 2 km long and as much as 60 m deep and was fed by meltwater from small valley glaciers it accumulated sediment apparently without interruption for about 10 000 yr the inception of lake devlin between 23 500 and 21 000 yr b p provides a limiting date for the maximum expansion of pinedale ice because the lake could not form until the north boulder creek glacier had advanced to within 2 km of its downvalley limit the maximum lowering of timberline which occurred about 19 000 yr b p is assumed to coincide with the pinedale glacial maximum apparent timberline elevations determined from picea pinus pollen ratios suggest that ice front positions during the time between 23 000 and 19 000 yr b p may have been only slightly less extensive than at the pinedale maximum lake devlin drained catastrophically about 13 000 yr b p which was after ice had receded from the outlet area pinedale glaciation in the front range began about or after 30 000 yr b p and final deglaciation occurred between 15 000 and 12 000 yr b p

magnetic remanence in the murchison meteorite the murchison meteorite is a carbonaceous chondrite containing a small amount of chondrules various inclusions and matrix with occasional porphyroblasts of olivine and or pyroxene it also contains amino acids that may have served as the necessary components for the origin of life magnetic analyses of murchison identify an ultrasoft magnetic component due to superparamagnetism as a significant part of the magnetic remanence the rest of the remanence may be due to electric discharge in the form of lightning bolts that may have formed the amino acids the level of magnetic remanence does not support this possibility and points to a minimum ambient field of the remanence acquisition we support our observation by showing that normalized mineral magnetic acquisition properties establish a calibration curve suitable for rough paleofield determination when using this approach 1 2 of the natural remanence left in terrestrial rocks with trm and or crm determines the geomagnetic field intensity irrespective of grain size or type of magnetic mineral with the exception of hematite the same method is applied to the murchison meteorite where the measured meteorite remanence determines the paleofield minimum intensity of 200 2000 nt during and or after the formation of the parent body

spruce trees from a melting ice patch evidence for holocene climatic change in the colorado rocky mountains usa in september 2006 we found the remains of timber sized spruce trees picea engelmannii on the floors of melting ice patches at altitudes of 3465 3480 m in the mummy range of north central colorado the ice patches occupy northeast facing recesses in which windblown snow scoured from a tundra upland to the southwest accumulates deeply we hypothesize that the upland was timbered during the early to middle holocene dense forest vegetation intercepted snow preventing it from blowing to the recesses and allowing trees to become established there neoglacial cooling led to gradual deforestation of the upland renewed transport and deposition of snow by wind and death of the ice patch trees radiocarbon dates show that the trees died between 3860 15 and 3780 20 14c yr bp c 4200 cal yr bp the trunks show decay similar to that of historic log structures built above timberline during the late nineteenth and early twentieth centuries suggesting that they have been protected by ice for all but a

a model of slope formation related to landslide activity in the eastern prealps austria abstract the rhenodanubian flysch zone of the eastern alps of austria is considered to be susceptible to landslides in the study area an undulating low mountain landscape of the eastern european prealps the flysch bedrock is superimposed by quaternary periglacial cover beds and loess both the petrography of the bedrock and the soil mechanical properties of quaternary sediments control the slope dynamics a database compiled for the study area comprises about 200 datasets on landslide and rock fall hazards it covers a time span between 1771 and 2007 and shows clusters between 1940 and 1943 1965 and 1966 1979 and 1982 as well as in 2006 the study analyses slope stability in the light of slope formation phases with respect to weathering erosion and geology furthermore geomorphological and soil geographical methods are combined with soil mechanical calculations the application of the concept of periglacial cover beds facilitates the distinction between holocene and pleistocene landforms and slide masses in the research area as a result the study shows that the properties of quaternary sediments and the occurrence of the densely bedded basal cover beds are responsible for landslide susceptibility the variable permeability in loess layers in contrast to that in the underlying basal cover beds consisting mainly of marls and clayey material is one of the fundamental controlling factors of mass movements in a temporal context it is evident that the stability of slopes in the study area is influenced by several phases of slope formation the synopsis of field survey morphometrical geotechnical as well as laboratory analyses and slope stability calculation gives evidence of five morphodynamic phases that partly reoccur in an alternating pattern after having passed all phases the stability of the slopes studied is increased because modified soil mechanical properties of the slide masses become important as a consequence the critical slope angle is raised by 3 5

chemical studies of l chondrites vi variations with petrographic type and shock loading among equilibrated falls to study compositional trends associated with open and closed system metamorphism and or shock induced heating of the l4 6 chondrite parent s we used icpms and rnaa to quantify 51 trace elements in 48 chemically representative fall samples with these data we used graphic and two multivariate statistical methods for examining evidence for compositional differences with respect to petrographic type and degree of shock loading comparisons of mildly shocked s1 s3 l5 and l6 suites 9 and 8 chondrites respectively yield no convincing statistical evidence for a difference in trace element content our multivariate comparisons show a difference on a model dependent basis but yield indeterminate results on a model independent basis compositionally suites of strongly shocked s4 s6 and mildly shocked l4 6 chondrites 26 and 19 samples respectively can be distinguished at statistically significant levels on both model dependent and independent bases in the strongly shocked suite contents of refractory lithophiles are higher and siderophiles and volatiles are lower than those of the mildly shocked suite at moderately p 0 05 to highly significant p 0 01 levels our studies suggest that chemical differences from vaporization and loss of volatiles along with metal silicate partitioning are present from extended cooling of shock heated bodies produced by intermittent impacts especially the massive impact s that disrupted the l chondrite parent s 500 ma ago

a soil chronosequence study of the reno valley italy insights into the relative role of climate versus anthropogenic forcing on hillslope processes during the mid holocene abstract relatively few soil chronosequences with good age control exist for late pleistocene and holocene deposits in the mediterranean region of europe yet surface soils and their young buried counterparts can provide meaningful information about the timing and processes of landscape response to external forcing such as climate or anthropogenic change here we present the results of a study that examines a well dated chronosequence of nineteen soil exposures in surficial deposits ranging in age from hundreds of years to hundreds of thousands of years located in the reno river valley near bologna italy the soil forming climate of the reno valley sits on a threshold between that which facilitates the accumulation of caco 3 and that which facilitates the translocation and formation of clay minerals and iron oxides once formed secondary iron oxides are relatively immobile in oxidizing conditions in the soil profile and therefore consistently record age trends with feo fed ratios decreasing predictably with soil age for all soils in the chronosequence the morphology of secondary carbonate accumulation and its depth of leaching also vary predictably with soil age but only for soils younger than about 12 000 years in these young soils horizons that contain secondary carbonate progress from relatively shallow stage i bk horizons in late holocene aged soils to deeper stage iii bk horizons in latest pleistocene aged soils in soils older than approximately 12 000 cal ybp however carbonate dissolution during wetter climates and the addition of colluvium and or dust to terrace surfaces become important factors in the preservation of carbonate in the profile and carbonate content is not predictable by age alone without significant depositional additions these older soils become decalcified pedogenic carbonate precipitated during drier climates is susceptible to dissolution during wetter periods as evidenced by discontinuous carbonate coatings on grains in some soils therefore overall measurable pedogenic carbonate content is spatially and temporally variable as a function of input of fresh carbonate and locally controlled soil moisture conditions particle size does not decrease predictably with soil age for reno valley soils and appears to be strongly influenced by parent material variability in younger soils and by dust additions in older soils our detailed examination of soil stratigraphy in the reno valley revealed evidence of significant aggradation of colluvium and tributary fans in the middle holocene between 6000 and 4000 ybp this aggradation pre dates bronze age agricultural expansion and appears to be instead attributable to the climate conditions of the middle holocene that have been documented elsewhere in italy for this time period this study demonstrates that late pleistocene and holocene surface soils in the mediterranean region of europe can effectively help elucidate rates and processes of landscape evolution

four dimensional analog and geometrical modeling of the hides anticline papua new guinea structure of a giant gas field the hides anticline in the papua new guinea fold belt is the core part of the papua new guinea liquified natural gas project that commenced production in 2014 yet little is known about its internal structure particularly at depth the structure of the upper 3 km 9843 ft is relatively well constrained from surface data recent development wells and poor quality two dimensional seismic data but the deep structure has been obscure seismic data and gravity modeling suggest an underlying large normal fault in basement forward geometrical modeling using movetm and four dimensional analog sandbox modeling under an x ray tomography scanner have greatly constrained the structural interpretation the modeling confirms the presence of the underlying basement normal fault and suggests that it was mildly inverted prior to the onset of pure compression deformation in the sedimentary section the main detachment level was just above basement approximately 8 10 km 5 6 mi beneath the surface but this ramped up at the basement fault creating an array of triangle zone faults through the overlying sedimentary section building the hides anticline the early inversion was instrumental in initiating a back thrust and hinterland verging tight fold in the mesozoic section including the source reservoir and seal deformation in the thick miocene carbonates at the surface was detached from that in the underlying reservoir along an upper cretaceous mudstone horizon that varies strongly in thickness such that the 2 4 km 6562 13 123 ft high mesozoic structure verges northeast and the overlying miocene structure verges southwest analog modeling shows that a ductile stratigraphy is required with slow strain rates of approximately 1 3 km m y 3281 9843 ft m y

aspect dependent soil saturation and insight into debris flow initiation during extreme rainfall in the colorado front range hydrologic processes during extreme rainfall events are poorly characterized because of the rarity of measurements improved understanding of hydrologic controls on natural hazards is needed because of the potential for substantial risk during extreme precipitation events we present field measurements of the degree of soil saturation and estimates of available soil water storage during the september 2013 colorado extreme rainfall event at burned wildfire in 2010 and unburned hillslopes with north and south facing slope aspects soil saturation was more strongly correlated with slope aspect than with recent fire history south facing hillslopes became fully saturated while north facing hillslopes did not our results suggest multiple explanations for why aspect dependent hydrologic controls favor saturation development on south facing slopes causing reductions in effective stress and triggering of slope failures during extreme rainfall aspect dependent hydrologic behavior may result from 1 a larger gravel and stone fraction and hence lower soil water storage capacity on south facing slopes and 2 lower weathered bedrock permeability on south facing slopes because of lower tree density and associated deep roots penetrating bedrock as well as less intense weathering inhibiting soil drainage

meteoric 10be clay and extractable iron depth profiles in the colorado front range implications for understanding soil mixing and erosion abstract analyzing meteoric 10be in soil profiles along with soil measurements such as pedogenic fe and clay content permits better understanding of meteoric 10be transport in soils soil formation and hillslope geomorphology this study presents meteoric 10be depth profiles from saprolite derived soil catenas sampled in the gordon gulch catchment colorado front range and from nearby c 130 and 15 ka glacial moraines we compare meteoric 10be data with more classically used soil analyses of clay and extractable iron fed content meteoric 10be and fed do not show consistent trends in the hillslope profiles meteoric 10be and clay concentrations however generally decrease with depth and highest concentrations of 10be in horizons coincide with highest clay concentrations soils at moraine sites are better developed than those on hillslopes and correlations of 10be fed and clay are stronger in gordon gulch south facing hillslopes display meteoric 10be bulges at depth and lower near surface concentrations compared to the declining profiles and higher near surface concentrations of north facing hillslopes the aspect differences imply that south facing hillslopes experience greater vertical mixing than north facing hillslopes and that greater lateral transport and erosion has occurred over the last 15 20 ka on south facing hillslopes relative to north facing hillslopes meteoric 10be depth profiles at moraine sites display bulge profiles with highest meteoric 10be concentrations in b horizons reflecting landform stability and pedogenic processes overall our data demonstrate that signatures of chemical weathering in soils fed and clay may or may not correlate to the meteoric 10be added through atmospheric deposition and that profile shape of meteoric 10be can provide insight into the relative contribution of vertical mixing and surface erosion in relation to catena location and aspect during hillslope evolution

combined use of relative and absolute dating techniques for detecting signals of alpine landscape evolution during the late pleistocene and early holocene article i nfo a combination of three relative and two absolute numerical dating techniques applied on nine soil profiles in an alpine environment located in val di rabbi trentino northern italy was used to improve the investigation methodology of alpine sites in response to climate change and to reconstruct the chronology of late pleistocene and early holocene landscape evolution the degree of podzolisation clay mineral evolution and the element mass balances of each site were investigated furthermore the stable fraction of the soil organic matter som was extracted with 10 h2o2 and 14 c dated the age of the organic residues was compared with the age of charcoal fragments found in one of the studied soils and with the age of rock boulders obtained by surface exposure dating sed with cosmogenic 10 be numerical dating and weathering characteristics of the soils showed a fairly good agreement and enabled a relative and absolute differentiation of landscape elements the combination of 14 c dating of som and sed indicated that deglaciation processes in val di rabbi were already far advanced by around 14000 cal bp and that glacier oscillations affected the highest part of the region until about 9000 cal bp the development of clay minerals is time dependent and reflects weathering intensity we found a close link between secondary clay minerals like smectite or vermiculite and soil age as obtained by the dating of the organic residues after the h2o2 treatment calculated element mass balances strongly correlated with the ages derived from 14 c measurements old soils have lost a major part of base cations up to 75 compared to the parent material fe and al which indicates a continuous high weathering intensity results of the chemical and mineralogical analyses were in good agreement with numerical dating techniques showing the dynamics of an alpine landscape within a relatively small area the combination of relative and absolute dating techniques is a promising tool for the reconstruction of landscape history in high elevation alpine areas on siliceous substrates

magnetic anisotropy of hed and martian meteorites and implications for the crust of vesta and mars abstract we investigate the petrofabric of crustal rocks from mars and vesta through the measurement of the anisotropy of the magnetic susceptibility ams of achondrites previous data are integrated with new measurements to obtain a dataset that provide macroscopic information about the magnetic fabric of 41 meteorites of the howardite eucrite diogenite clan hed falls only and 16 martian meteorites the interpretation takes into account the large contribution of paramagnetism to the magnetic susceptibility of these meteorites we use a model that allows the computation of the anisotropy degree of the population of ferromagnetic grains and provides a quantitative proxy for the degree of shape preferential orientation of these grains in hed and martian meteorites the results also provide quantitative information about the shape of the magnetic fabric prolate oblate in hed achondrites the ductile feni grains are sensitive strain recorders and our magnetic fabric data provide the first quantitative insights to the strain history of the crustal rocks of vesta most hed achondrites are breccias but display a strong and spatially coherent magnetic anisotropy indicating that intense deformation of feni grains took place after brecciation the average fabric of eucrites howardites is oblate i e the texture is foliated whereas the fabric of diogenites is more neutral the howardite results suggest the existence of an isotropic fraction of ferromagnetic minerals that can be ascribed to the presence of carbonaceous chondrite clasts that have preserved their original magnetic fabric in this hypothesis howardites have an intensity of petrofabric very similar to eucrites and diogenites thermal metamorphism itself possibly impact related plus lithostatic compaction occurring after brecciation appears as the best candidate to explain the observed petrofabric in eucrites and diogenites whereas compaction by hypervelocity impacts may be reponsible for the fabric of howardites martian meteorites may still possess their primary magmatic fabric among martian meteorites basaltic shergottites and nakhlites display an oblate fabric foliated texture with only limited variations among each group olivine phyric shergottites have a neutral fabric that points to a different petrogenesis nakhlites have weaker fabric intensity than shergottites the fabric intensity is comparable to what is classically observed in terrestrial volcanic and plutonic rocks

pro glacial soil variability and geomorphic activity the case of three swiss valleys soils in pro glacial areas are often approached from a chronosequence viewpoint in the chronosequence approach the objective is to derive rates of soil formation from differences in properties between soils of different age for this reason in chronosequence studies soils are sampled in locations that are assumed geomorphically stable and that have different age as a result these studies do not necessarily yield a complete view of soil variability in pro glacial areas and may miss important relations between geomorphology and soil development in this contribution we present new soil observations from three closely related pro glacial areas in switzerland these observations were intended to get closer to a complete view of soil variability and to assess impacts from factors other than time on soil development about 40 soils were visited in each pro glacial valley in a combined design convenience sampling scheme and described in the field linear modelling was used to assess effects of time and topographic factors on soil properties the time since glacial retreat turned out to rarely explain more than half of the variation in soil properties and a linear model combining effects of time and topographic variables explained typically about half of the variation in each pro glacial valley models differed and were not transferable between valleys apparently time and the present day shape of the landscape combined are insufficient information to accurately predict soil properties field evidence points to the importance of the geomorphic history and regime of the valleys as a reason for this copyright c 2014 john wiley sons ltd

on the efficiency of shock magnetization processes abstract the acquisition of remanent magnetization caused by hypervelocity impacts may be a major contribution to the remanent magnetization of planetary surfaces and meteorites in this paper we investigate the properties of shock remanent magnetization srm and in particular the relative efficiency of this phenomenon with respect to thermoremanent magnetization trm a parameter of interest for the understanding of the magnetic signatures of impact basins on extraterrestrial bodies we imparted shock remanent magnetization on basalt and microdiorite samples using laser shock in controlled magnetic field shock modeling indicates a pressure range of 0 6 1 5 gpa for our experiments the results confirm that the srm is parallel to the ambient magnetic field srm increases linearly with the ambient field in the 1 2500 t range the intensity of srm is independent of the angle between the shock direction and the direction of the ambient field the coercivity spectrum of srm is shifted towards lower values compared to the coercivity spectra of trm and isothermal remanent magnetization for the two studied lithologies the efficiency of srm versus trm acquisition is 17 for the basalt and is 36 for the microdiorite this efficiency depends on the magnetic mineralogy and increases with decreasing coercivity the rather high efficiency values that we obtained show that a significant remanent magnetization can be acquired by the crust during an hypervelocity impact on a planetary surface in the presence of an ambient field

experimental shock metamorphism of terrestrial basalts agglutinate like particle formation petrology and magnetism hypervelocity impacts occur on bodies throughout our solar system and play an important role in altering the mineralogy texture and magnetic properties in target rocks at nanometer to planetary scales here we present the results of hypervelocity impact experiments conducted using a two stage light gas gun with 5 mm spherical copper projectiles accelerated toward basalt targets with similar to 6 km s 1 impact velocities four different types of magnetite and titanomagnetite bearing basalts were used as targets for seven independent experiments these laboratory impacts resulted in the formation of agglutinatelike particles similar in texture to lunar agglutinates which are an important fraction of lunar soil materials recovered from the impacts were examined using a suite of complementary techniques including optical and scanning electron microscopy microraman spectroscopy and high and low temperature magnetometry to investigate the texture chemistry and magnetic properties of newly formed agglutinate like particles and were compared to unshocked basaltic parent materials the use of cu projectiles rather than fe and ni projectiles avoids magnetic contamination in the final shock products and enables a clearer view of the magnetic properties of impact generated agglutinates agglutinate like particles show shock features such as melting and planar deformation features and demonstrate shock induced magnetic hardening two to seven fold increases in the coercivity of remanence b cr compared to the initial target materials and decreases in low field magnetic susceptibility and saturation magnetization

effect of shock on the magnetic properties of pyrrhotite the martian crust and meteorites 1 we performed planar shock recovery experiments on natural pyrrhotite at pressures up to 6 9 gpa we find that high field isothermal remanent magnetization in pyrrhotite is demagnetized up to 90 by shock due to preferential removal of low coercivity components of magnetization contrary to static experiments we do not observe complete demagnetization post shock permanent changes in magnetic properties include increasing saturation isothermal remanent magnetization bulk coercivity and low temperature memory and changes in squareness of hysteresis these changes are consistent with an increase in the volume fraction of single domain grains the lack of magnetic anomalies over large martian impact basins is not expected to be solely due to shock demagnetization of the crust we find that pyrrhotite bearing rocks and meteorites can retain records of martian magnetic fields even if shocked to pressures approaching 7 gpa however some paleointensity techniques may underestimate this field

chronosequence development and soil variability from a variety of sub alpine post glacial landforms and deposits in the southeastern san juan mountains of colorado abstract surficial processes acting on post glacial alpine and sub alpine landscapes vary at small temporal and spatial scales and are thus often difficult to conceptualize in the context of large scale landscape evolution models soils developing in this setting can thus provide valuable information about landform genesis sedimentology and age relatively few post glacial chronosequences have been examined in these settings however particularly for the variety of landforms and parent materials that exist within alpine and sub alpine environments here we examine a chronosequence of relatively young post glacial landforms with varying parent materials and climate histories we dug and described 39 soil pits in the upper conejos river valley of colorado on a variety of deposits and landforms including alluvial fans terraces colluvium glacial till and terminal moraines and compared soil properties with radiocarbon ages from the area our results suggest that some typical chronosequence soil properties e g ph structure color do not correlate with time over short time scales however extractable iron ratios feo fed show a relatively strong correlation with age across late pleistocene and holocene time scales and maximum profile clay content shows a weak but statistically significant relationship with age both of these trends are stronger when examined across a single parent material differences in initial parent material texture and dust inputs seem to be the most significant complicating factors over post glacial time scales soil property development through time is most inconsistent in cumulic alluvial fan soils this observation may indicate that alluvial fans are more responsive to sub basin scale processes as opposed to fluvial terraces that are more likely respond to processes active across the entire basin these differences would explain why stratigraphically similar alluvial fans are mantled by soils with varying development nonetheless horizonation clay content and extractable iron ratios provide a useful tool for correlating young deposits assigning ages and interpreting the geomorphic history of complex post glacial environments

shock induced metallic iron nanoparticles in olivine rich martian meteorites magnetic anomalies observed by the mars global surveyor mission are attributed to crustal remanence snc shergotty nakhla chassigny meteorites are likely samples of the martian crust and are amenable to mineralogical and magnetic measurements essential to the understanding of the origin of magnetic anomalies the recently discovered chassignite nwa 2737 and lherzolitic shergottite nwa 1950 display unusual magnetic characteristics that argue for a different magnetic carrier than the oxides and sulfides previously invoked in snc meteorites nwa 2737 the second member of the chassignite group is a dunite with unusually dark brown olivines and large magnetic susceptibility while chassigny contains green olivines and is nearly a pure paramagnet dark olivines are also found in nwa 1950 a lherzolitic shergottite which has singular magnetic properties when compared with other shergottites the dark olivine color is due to the presence of fe and feni metal nanoparticles identified both by tem and by magnetic measurements their size distribution encompasses the superparamagnetic to single domain transition at 30 k 10 nm range and explains the magnetic properties of the bulk rocks the formation of these nanoparticles is attributed to heating during the shock events that affected nwa 2737 and nwa 1950 the production of metal particles by shock induced reduction of olivine has been invoked on surfaces deprived of atmosphere but never observed on earth or mars therefore metal formed by shock in the heavily cratered noachian crust is a possible carrier for crustal magnetic remanence widespread surface formation of metal nanoparticles could provide the precursor for the oxidized particles goethite hematite observed in the martian soils c 2007 elsevier b v all rights reserved

magnetic properties of a freshly fallen ll ordinary chondrite the bensour meteorite abstract a comprehensive rock magnetic magnetic anisotropy and paleomagnetic study has been undertaken in the brecciated ll6 bensour ordinary chondrite a few months only after its fall on earth microscopic observations and electronic microprobe analyses indicate the presence of ni rich taenite tetrataenite and rare co rich kamacite tetrataenite is the main carrier of remanence magnetization and anisotropy measurements were performed on mutually oriented 125 mm 3 sub samples a very strong coherent susceptibility and remanence anisotropy is evidenced and interpreted as due to the large impact responsible for the post metamorphic compaction of this brecciated material and disruption of the parent body we show that the acquisition of remanent magnetization postdates metamorphism on the parent body and predates the entering of the meteorite in earth s atmosphere three components of magnetization could be isolated a soft coherent component is closely related to the anisotropy of the meteorite and is interpreted as a shock remanent magnetization acquired during the same large impact on the parent body two harder components show random directions at a few mm scale this randomness is attributed either to the formation mechanism of tetrataenite or to post metamorphic brecciation all components are likely acquired in very low t to null ambient magnetic field as demonstrated by comparison with demagnetization behavior of isothermal remanent magnetization two other ll6 meteorites kilabo and st mesmin have also been studied for comparison with bensour

toward a robust normalized magnetic paleointensity method applied to meteorites abstract we propose a new paleointensity method based on normalization by isothermal remanent magnetization derivative vs alternating field rem method it provides an estimate of the absolute paleointensity with an uncertainty of about a factor two contrary to methods using normalization by total isothermal remanent magnetization or anhysteretic magnetization it is applicable to multicomponent magnetizations artificial or natural isothermal remanent magnetizations can be recognized and relaxation of natural remanent magnetization can be taken into account it is applicable for magnetizations carried by magnetite feni alloys and pyrrhotite the rem method is of particular interest to estimate paleointensities in meteorites as these materials are often characterized by complex multicomponent magnetization of various origins impact magnetization thermoremanence isothermal remanent magnetization and metastable magnetic minerals not suitable for thellier experiments however like other paleointensity methods the rem method underestimates the true paleointensity for meteorite samples with magnetizations that are heterogeneous on spatial scales below the sampling scale for l ordinary chondrites an upper limit of 1 t is proposed for the paleofield tentative paleofield estimates in the 0 05 0 5 t range are proposed for ll ordinary chondrites which is much lower than previous results the first paleofield estimates for rumuruti chondrites indicate the presence of magnetic fields around 6 t during the last major impact on their parent body aubrites and hed achondrites paleofields of at least 10 t may suggest the existence of a dynamo field during the cooling of their parent body results from martian meteorites are scattered between 1 and 24 t and may represent the crustal magnetic field of the planet after dynamo shutdown carbonaceous chondrites provide contrasting results with possible evidence of strong field mt processes that clearly require additional studies

shock metamorphism of ordinary chondrites a revised petrographic classification of progressive stages of shock metamorphism of ordinary chondrites is proposed six stages of shock s1 to s6 are defined based on shock effects in olivine and plagioclase as recognized by thin section microscopy the characteristic shock effects of each shock stage are s1 unshocked sharp optical extinction of olivine s2 very weakly shocked undulatory extinction of olivine s3 weakly shocked planar fractures in olivine s4 moderately shocked mosaicism in olivine s5 strongly shocked isotropization of plagioclase maskelynite and planar deformation features in olivine and s6 very strongly shocked recrystallization of olivine sometimes combined with phase transformations ringwoodite and or phases produced by dissociation reactions s6 effects are always restricted to regions adjacent to melted portions of a sample which is otherwise only strongly shocked in stages s3 to s6 localized melting results from stress and temperature peaks which locally deviate from the equilibration shock pressure due to differences in shock impedance these melting effects are a opaque melt veins shock veins b melt pockets with interconnecting melt veins c melt dikes and d troilite metal deposits in fractures based on a critical evaluation of data from shock recovery experiments a shock pressure calibration for the six shock stages is proposed which defines the s1 s2 s2 s3 s3 s4 s4 s5 and s5 s6 transitions at 5 5 10 15 20 30 35 and 45 55 gpa respectively whole rock melting and formation of impact melt rocks or melt breccias occurs at about 75 90 gpa the symbol for the shock stage may be used in combination with the symbol for the petrologic type to abbreviate the complete classification of a chondrite e g h5 s3 we propose this new shock classification and pressure calibration system to replace previous systems which are out of date with respect to the pressure calibration nominally restricted to l chondrites and based on incomplete and in part illdefined sets of shock effects we have classified seventy six ordinary chondrites using the new classification system and conclude the following 1 1 shock effects and the sequence of progressively increasing degrees of shock metamorphism are very similar in h l and ll groups differences in the frequency distribution of shock stages are relatively minor e g l chondrites appear to have the largest fraction with stages s5 and s6 this suggests that the collisional histories of the h l and ll parent bodies were similar 2 2 petrologic type 3 chondrites are deficient in stages s4 to s6 and with increasing petrologic type the frequency of stages s4 to s6 increases we suggest that the more porous and volatile rich type 3 chondrites are subject to melting at a lower shock pressure than the nonporous chondrites of higher petrologic type volatiles trapped in pores cause shock induced dispersal of the shocked and melted material into small particles which are not expected to survive as meteorites 3 3 stage s3 is the most abundant in nearly all petrologic types 4 4 at shock pressures in excess of about 35 gpa s5 and s6 4he and 40ar are almost completely lost pressures below 10 gpa s1 and s2 do not cause noble gas losses

the influence of vegetation on debris flow initiation during extreme rainfall in the northern colorado front range we explored regional influences on debris flow initiation throughout the colorado front range colorado usa by exploiting a unique data set of more than 1100 debris flows that initiated during a 5 day rainstorm in 2013 using geospatial data we examined the influence of rain hillslope angle hillslope aspect and vegetation density on debris flow initiation in particular we used a greenness index to differentiate areas of high tree density from grass and bare soil the data demonstrated an overwhelming propensity for debris flow initiation on south facing hillslopes however when the debris flow density was analyzed with respect to total rainfall and greenness we found that most debris flows occurred in areas of high rainfall and low tree density regardless of hillslope aspect these results indicate that present day tree density exerts a stronger influence on debris flow initiation locations than aspect driven variations in soil and bedrock properties that developed over longer time scales

shock experiments with the h6 chondrite kernouve pressure calibration of microscopic shock effects shock recovery experiments were carried out on samples of the h6 chondrite kernouve at shock pressures of 10 15 20 25 30 35 45 and 60 gpa and preheating temperatures of 293 k low temperature experiments and 920 k high temperature experiments using a calculated equation of state of kernouve pressure pulse durations of 0 3 to 1 2 s were estimated the shocked samples were investigated by optical microscopy to calibrate the various shock effects in olivine orthopyroxene oligoclase and troilite the following pressure calibration is proposed for silicates 1 undulatory extinction of olivine gpa 2 weak mosaicism of olivine from 10 15 gpa to 20 25 gpa 3 onset of strong mosaicism of olivine at 20 25 gpa 4 transformation of oligoclase to diaplectic glass completed at 25 30 gpa low temperature experiments and at 20 25 gpa high temperature experiments 5 onset of weak mosaicism in orthopyroxene at 30 35 gpa low temperature experiments and at 25 30 gpa high temperature experiments and 6 recrystallization or melting of olivine starting at 45 60 gpa low temperature experiments and at 35 45 gpa high temperature experiments and completed above 45 60 gpa in the high temperature experiments troilite displays distinct differences between the samples shocked at low and high temperatures in the low temperature experiments the following effects can be observed in troilite 1 undulatory extinction up to 25 gpa 2 twinning up to 45 gpa 3 partial recrystallization from 30 to 60 gpa and 4 complete recrystallization 35 gpa whereas in the high temperature experiments troilite shows 1 complete recrystallization from 10 up to 45 gpa and 2 melting and crystallization above 45 gpa localized shock induced melting is observed in samples shocked to pressures 15 gpa in the high temperature experiments and 30 gpa for the low temperature experiments in the form of feni metal and troilite melt injections and intergrowths and as pockets and veins of whole rock melt obviously the onset and abundance of shock induced localized melting strongly depends on the initial temperature of the sample

soil stratigraphic techniques in the study of soil and landform evolution across the southern alps new zealand the southern alps lie along the convergent pacific indian plate boundary geomorphically distinct eastern axial and western regions reflect the east west gradient in tectonic uplift 1 to 10 mm a 1 and precipitation 600 to 10 000 mm a 1 the eastern region is divided into front ange and basin and range subregions soil sequence studies on terraces established temporal contrasts in pedogenesis within and between eastern and western regions encompassing entisols inceptisols and spodosols on late pleistocene and early holocene terraces dystrochrepts are persistent soils in the eastern region and aquods in the western region these soil sequences are used in the interpretation of relative soil age stratigraphy and erosion history in hill and mountain drainage basins of the eastern and western regions in the subhumid to humid eastern front range subregion simple soil forms occur as catenary sequences and there is little evidence of erosion following the destruction of forests in the last millenium mollisols are dominant in the subhumid and dystrochrepts in humid areas respectively soil debris mantle regoliths date from the early holocene and are still developing on slopes the soil pattern on mountain slopes in the humid eastern basin and range subregion is a complex array of simple eroded composite and compound soils this pattern has resulted from erosion following forest destruction within the last millenium the oldest surface or buried forest soils are dystrochrepts dating from the late pleistocene to early holocene wind erosion of these low fertility soils contributes to the loessial sediments in which younger soils have formed in the western region soil patterns and soil stratigraphy indicate continous instability with a complex pattern of highly leached shallow orthents and bedrock outcrops on slopes the soils are eroded from slopes within 2 ka these contrasts in soil development and erosion periodicity in the eastern and western regions of the southern alps parallel the east west contrasts in erosion rates of ca 1 10 mm a 1

a comparison of mineralogical techniques and potassium adsorption isotherm analysis for relative dating and correlation of late quaternary soil chronosequences abstract the utility of potassium adsorption isotherm analysis kia for relative dating and correlation of soil chronosequences was assessed by a comparison with some widely used mineralogical techniques the soils studied near detroit michigan are brown 10yr calcareous entisols developed in holocene 4 ka floodplain sediments and inceptisols and alfisols with redder 7 5yr 5yr cambic and argillic b horizons formed on late pleistocene 14 5 12 4 ka fluvial terraces fluvial paleochannels and paleoshorelines beach ridges of proglacial lakes the soils show a positive linear correlation between soil age and clay content depth of carbonate leaching and fe oxide accumulation in contrast the duration of soil formation is too short for variations in heavy mineral frequencies to discriminate soil age reliably scanning electron microscopy shows that chemical weathering stage is indicated by progressive etching and pitting of calcite apatite and amphibole with increasing soil age k isotherms are linear or slightly curvilinear indicating that ion exchange is dominant over specific adsorption a statistically significant linear correlation between k distribution constant and soil age attributed to progressive weathering of mica suggests that kia is useful for relative dating of genetically related soils once a well dated chronosequence is established kia produces results comparable to or better than mineralogical techniques however soil morphology and a clay redness index are more effective than mineralogical and chemical techniques for interchronosequence correlation

origin of glossic horizons in cryalfs of the eastern rocky mountains usa abstract cryalfs are the predominant suborder along the eastern front of the rocky mountains from northern nm through mt and into alberta approximately 50 of the cryalfs in the western usa contain a glossic horizon defined as a degraded argillic horizon containing properties of both an e and a bt horizon using the nrcs database we examined 257 cryalf soil series 79 of which contain a glossic horizon the glossic horizon occurs at an average depth of 32 cm and averages 24 cm thick the glossic horizon is most commonly an e bt with textures similar to the e above and bt below waxy or glossy argillans are common as well as clay enriched nodules and seams laboratory data are available for only 10 cryalf pedons containing a glossic horizon based on these data the glossic horizon contains an average of 24 clay 1 0 clay cec7 0 6 organic c a cation exchange capacity of 19 cmolc kg soil 85 base saturation and a ph of 5 6 several theories for the origin of the glossic horizon were considered from a weight of evidence approach the glossic horizon in cryalfs of the rocky mountains may be attributed to an input of eolian silt which creates a lithologic discontinuity and a mid holocene 5000 yr bp to present lowering of treeline containing the strongly podzolizing species picea engelmannii and abies lasiocarpa although glossic horizons are common in upper montane soils now containing lodgepole pine pinus contorta they are uncommon in lower montane soils supporting lodgepole and ponderosa pinus ponderosa pines

an impact origin for the foliation of chondrites abstract the origin of the foliation of ordinary chondrites is addressed through the study of the anisotropy of magnetic susceptibility ams of these meteorites based on a database of 295 different meteorites including 35 achondrites hed and snc ams is a reliable proxy for preferred orientation in ordinary chondrites moreover the intensity of magnetic anisotropy is constant over a given chondrite the intensity of l chondrite petrofabric evaluated by means of ams measurements and shock stage determined independently by microscopic observation of shock features in silicates appear to be positively correlated this suggests that the oblate petrofabric in l chondrites is shock induced the inverse correlation between porosity and ams intensity suggests that hypervelocity impacts compacted and lithified an originally loose material causing the deformation of metallic fe ni grains ll and h ordinary chondrites cannot be studied as easily as l chondrites tetrataenite in ll chondrites affects the ams in an unpredictable way and shape anisotropy due to the strong susceptibility of h chondrites imposes strong constraints on sample shape our limited dataset for carbonaceous chondrites is compatible with a shock induced foliation model the very low degrees of ams in rumuruti chondrites testify that surprisingly the easily deformable fe sulfides in these chondrites show almost no deformation suggesting that sulfidation is a secondary phenomenon that occurred after the major impacts on the rumuruti parent body the weak magnetic anisotropy of martian meteorites implies that no significant macroscopic deformation took place during the severe impacts suffered by these rocks which is explained by the weak initial porosity and high compressive strength of these igneous products

parent material and chemical weathering in alpine soils on mt mansfield vermont usa we compared the elemental composition of soil and bedrock samples to determine the extent of chemical weathering and the nature of the soil parent material in alpine soils on vermont s highest summit previously it was unclear whether these soils formed through weathering of bedrock glacial till or eolian sediment or solely through the accumulation of organic matter in eighteen profiles no evidence was found to indicate that soils have developed in glacial till despite evidence that the mountain was completely inundated by the laurentide ice sheet in contrast results strongly support the theory that pedogenesis in this environment involves in situ bedrock weathering under a thickening blanket of acidic organic litter weathering indices reveal an increase in weathering intensity upwards from the bedrock and trends of normalized rare earth elements demonstrate a strong similarity between bedrock and soil samples leaching has concentrated less mobile elements such as al cr la p pb and ti in soil horizons and removed mobile elements such as co fe k mg mn si and zn x ray diffraction reveals that chlorite which is present in all bedrock samples and some saprolites has weathered completely from upper soil horizons and that hydrobiotite vermiculite kaolinite gibbsite and goethite have formed in the soil ratios of immobile elements ce cr nb ta ti y and zr in soil and bedrock samples are however notably different furthermore the moderately mobile trace elements cu mo and sr are actually more abundant in soil than in bedrock and soil concentrations of zr are up to an order of magnitude greater than in bedrock samples together these data argue for at least a modest eolian influx which may have arrived during the regression of lake vermont during the latest pleistocene or from an outwash source in the immediate post glacial period similarly increased ca and na concentrations in soil samples may signify modern deposition of dust bearing ca from agricultural fields and na from roads

concentration discharge relationships during an extreme event contrasting behavior of solutes and changes to chemical quality of dissolved organic material in the boulder creek watershed during the september 2013 flood during the week of september 9 15 2013 about 44 cm of rain fell across boulder county colorado usa representing a very rare precipitation event the resultant stream flows corresponded to an extreme event not seen since the historical flood of 1894 for the boulder creek critical zone observatory bcczo this event provided an opportunity to study the effect of extreme rainfall on solute concentration discharge relationships and biogeochemical processes we measured weathering derived lithologic solutes ca mg na k and si and dissolved organic carbon doc concentrations at two sites on boulder creek during the recession of peak flow we also isolated four distinct fractions of dissolved organic matter dom for chemical characterization at the upper and lower sites all solutes had their highest concentration at peak flow at the upper site which represented a mostly forested catchment the concentrations of lithologic solutes decreased slightly during flood recession in contrast doc and k concentrations decreased by a factor of three at the lower site within the urban corridor concentration of lithologic solutes decreased substantially for a few days before rebounding whereas the doc and k concentrations continued to decrease additionally we found spatiotemporal trends in the chemical quality of dom that were consistent with a limited reservoir of soluble organic matter in surficial soils becoming depleted and deeper layers of the critical zone contributing dom during the flood recession overall these results suggest that despite the extreme flood event concentration discharge relationships were similar to typical snowmelt periods in this rocky mountain region

contemporary geochemical composition and flux of aeolian dust to the san juan mountains colorado united states 1 dust deposition in the rocky mountains may be an important biogeochemical flux from upwind ecosystems seasonal winter spring dust mass fluxes to the san juan mountains during the period from 2004 to 2008 ranged from 5 to 10 g m 2 with individual deposition events reaching as high as 2 g m 2 dust deposited in the san juan mountains was primarily composed of silt and clay sized particles indicating a regional source area the concentrations of most major and minor elements in this dust were similar to or less than average upper continental crustal concentrations whereas trace element concentrations were often enriched in particular dust collected from the san juan mountain snowpack was characterized by enrichments of heavy metals including as cu cd mo pb and zn the mineral composition of dust partially explained dust geochemistry however based on results of a sequential leaching procedure it appeared that trace element enrichments were associated with the organic and not the mineral fraction of dust our observations show that the dust derived fluxes of several nutrients and trace metals are substantial and because many elements are deposited in a mobile form could be important controls of vegetation soil or surface water chemistry the flux measurements reported here are useful benchmarks for the characterization of ecosystem biogeochemical cycling in the rocky mountains

exploring weathering and regolith transport controls on critical zone development with models and natural experiments the architecture of the critical zone including mobile regolith thickness and depth to the weathering front is first order controlled by advance of a weathering front at depth and transport of sediment at the surface differences in conditions imposed by slope aspect in the gordon gulch catchment of the boulder creek critical zone observatory present a natural experiment to explore these interactions the weathering front is deeper and saprolite more decayed on north facing than on south facing slopes simple numerical models of weathering front advance mobile regolith production and regolith transport are used to test how weathering and erosion rates interact in the evolution of weathered profiles as the processes which attempt are being made to mimic are directly tied to climate variables such as mean annual temperature the role of quaternary climate variation in governing the evolution of critical zone architecture can be explored with greater confidence

experimental shock metamorphism of the l4 ordinary chondrite saratov induced by spherical shock waves up to 400 gpa abstract we carried out shock experiments on macroscopic spherical samples of the l4 ordinary chondrite saratov natural shock stages s2 s3 using explosively generated spherical shock waves with maximum peak pressures of 400 gpa and shock induced temperatures 800 c up to several thousands c the evolution of shock metamorphism within a radius of the spherical samples was investigated using optical and scanning electron microscopy microprobe and magnetic analyses as well as mossbauer spectroscopy and x ray diffraction techniques petrographic analyses revealed a shock induced formation of three different concentric petrographic zones within the shocked samples zone of total melting i zone of partial melting ii and zone of solid state shock features iii we found a progressive pressure induced oxidation of fe ni metal whose degree increased with increasing shock peak pressure the amount of feo within zone i increased the factor of 1 4 with respect to its amount in the unshocked saratov sample this suggests that within zone i about 70 wt of the initial metallic iron was oxidized whereas magnetic analyses showed that about 10 wt of it remained intact this strongly supports the hypothesis that in addition to oxidation a migration of metallic iron from the central heavily shocked zone i toward less shocked peripheral zone took place as well likely through shock veins where metallic droplets were observed magnetic analyses also showed a shock induced transformation of tetrataenite to taenite within all shocked subsamples resulting in magnetic softening of these subsamples decrease in remanent coercivity these results have important implications for extraterrestrial paleomagnetism suggesting that due to natural impact processes the buried crustal rocks of heavily cratered solid solar system bodies can have stronger remanent magnetism than the corresponding surface rocks

weathering mineralogical evolution and soil organic matter along a holocene soil toposequence developed on carbonate rich materials a toposequence of holocene soils located between 1100 2400 m asl in the italian alps served as the basis for the following analyses the weathering of limestone and dolomite the calculation of mass balances understanding the formation of pedogenic fe and al the determination of soil mineral and clay mineral reactions and transformation and the measurement of accumulation and stabilisation mechanisms of soil organic matter leaching of carbonates is most intense at the lower elevations although calcite and dolomite have a higher solubility at low temperatures the pco2 in the soil is higher at lower elevations and weathering is driven mainly by carbonic acids at higher elevations organic acids appear to determine the mineral transformations and weathering reactions to a greater extent this suggests that two very different weathering regimes carbonic and organic acid weathering exist along the toposequence the transformation of mica into vermiculite is the main process in both the clay and fine earth fraction weathering of silicate minerals started even before the carbonates had been completely removed from the soils the transformation mechanisms of silicate minerals in the a and o horizon at higher elevations was at least as intensive as that at the climatically warmer sites the neoformation of pedogenetic clays at climatically cooler sites was slightly greater than that at the warmer sites however the formation rate of secondary fe and al phases was more pronounced at lower elevation which means that this process seemed to be driven dominantly by carbonic acid weathering of primary minerals soil organic matter som abundance in the mineral soil is nearly 15 kg m2 at all sites and surprisingly no climate driven effect could be detected in general the preservation and stabilisation of som was due to poorly crystalline al and fe phases and vermiculite regardless of some variations in the composition of the parent material varying calcite dolomite ratio

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

shock metamorphism of carbonaceous chondrites abstract we have studied shock effects in carbonaceous chondrites using optical microscopy of thin sections and find that our petrographic classification of progressive shock metamorphism in ordinary chondrites can also be applied to carbonaceous chondrites we find that sixty nine carbonaceous chondrites can be assigned to four shock stages si to s4 largely on the basis of shock effects in olivine the least shocked chondrite groups are cm2 and co3 thirty six out of thirty eight members are classified as shock stage s1 differences between the mean shock levels of certain groups of chondrites e g co3 and cv3 are probably due to stochastic differences in the sampling of their parent bodies however there is an overall tendency for the mean shock level of carbonaceous chondrites and ordinary chondrites to increase with increasing petrologic type that may reflect real differences in the shock level of near surface materials on their parent bodies caused by intrinsic variations in the chemical and physical properties of these materials petrologic type 2 and 3 chondrites are more porous and richer in volatiles than types 4 to 6 the greater porosity of types 2 3 causes higher post shock temperatures and melting at lower pressures and the higher volatile contents ensure that strongly shocked material is more readily dispersed on release from high pressure we suggest that type 2 3 material shocked above 20 30 gpa normally escapes from the parent asteroids and forms particles that are too small to survive as meteorites in the cv3 group there is a correlation between the degree of chondrule flattening and the intensity of shock metamorphism analogous to that discovered in ordinary chondrites by sneyd et al 1988 suggesting that shock rather than static overburden pressure is responsible for chondrule flattening we infer that the correlations are due to collapse of pores under shock pressures of at least 5 10 gpa and that shock is an important process affecting many physical properties of type 2 4 chondrites

estimating peak currents at ground lightning impacts using remanent magnetization 1 the impact of lightning is permanently recorded in struck material by a secondary magnetization called lightning induced remanent magnetization lirm we introduce an original rock magnetic method based on alternating field demagnetization to define both the geometry and the intensity of the peak lightning magnetic field it also provides positive evidence than a material has effectively been struck on a schoolyard tree struck by lightning we were able to locate the impact to within a few centimeters to prove that it was a vertical negative current and to estimate a peak current intensity of 99 7 ka this value is 14 ka higher than the one provided by meteorage lightning detection network and offers an independent calibration

assessing volumetric strains and mass balance relationships resulting from biotite controlled weathering implications for the isovolumetric weathering of the boulder creek granodiorite boulder county colorado usa abstract an important process often cited in the development of saprock and saprolite is the isovolumetric weathering of granitic bedrock evidence for isovolumetric weathering includes the observation that the texture of the granitic protolith often remains recognizable in its weathered products in contrast to the above often cited view we present results from a study of two sites located on the 1 65 ga boulder creek granodiorite near boulder colorado usa in which weakly chemically altered saprock derived from tonalitic and granodioritic tonalitic bedrock records volumetric strains on the order of 7 6 8 5 and 7 9 8 2 respectively we show that dilation is likely due to the alteration of biotite to vermiculite during the early stages of weathering and is associated with an expansion normal to the 001 cleavage of 40 theoretical calculations of volumetric strains based on the modal biotite present in the protolith support such an interpretation

erosion rates of alpine bedrock summit surfaces deduced from in situ 10be and 26al we have measured the concentration of in situ produced cosmogenic 10be and 26al from bare bedrock surfaces on summit flats in four western u s mountain ranges the maximum mean bare bedrock erosion rate from these alpine environments is 7 6 3 9 m my 1 individual measurements vary between 2 and 19 m my 1 these erosion rates are similar to previous cosmogenic radionuclide crn erosion rates measured in other environments except for those from extremely arid regions this indicates that bare bedrock is not weathered into transportable material more rapidly in alpine environments than in other environments even though frost weathering should be intense in these areas our crn deduced point measurements of bedrock erosion are slower than typical basin averaged denudation rates 50 m my 1 if our measured crn erosion rates are accurate indicators of the rate at which summit flats are lowered by erosion then relief in the mountain ranges examined here is probably increasing we develop a model of outcrop erosion to investigate the magnitude of errors associated with applying the steady state erosion model to episodically eroding outcrops our simulations show that interpreting measurements with the steady state erosion model can yield erosion rates which are either greater or less than the actual long term mean erosion rate while errors resulting from episodic erosion are potentially greater than both measurement and production rate errors for single samples the mean value of many steady state erosion rate measurements provides a much better estimate of the long term erosion rate

magnetic characterization of the new magnetic mineral tetrataenite and its contrast with isochemical taenite abstract taenite with 48 57 ni is magnetically soft but when transformed via atomic ordering below 320 c it becomes the new magnetic mineral tetrataenite with considerable magnetic hardness and other distinctive magnetic properties tetrataenite is ubiquitous in chondrite meteorites occurring as discrete grains as a clear taenite rim and in the etched cloudy zone measured remanent coercivities range from 30 mt in appley bridge ll4 to 600 mt in some bjurbole l4 chondrules this range suggests a considerable variation in tetrataenite properties that might be related to degree of order size and properties of the ordered regions possible shock induced effects and other causes including the initial grain size particularly in the cloudy zone tetrataenite is characterized during heating to the apparent curie point near 550 c and taenite is characterized during subsequent cooling to room temperature this record is possible because of the large magnetic anisotropy contrasts between tetrataenite and taenite and the fact that heating to the apparent curie point destroys the magnetic anisotropy of tetrataenite thereby allowing a taenite cooling record failure to recognize the presence of tetrataenite can result in considerable misinterpretation of thermomagnetic analysis since the curve shapes for tetrataenite and taenite can be different magnetic hysteresis loops thermomagnetic curves coercivity temperature curves and saturation remanence thermal demagnetization curves provide unquestionable records of two vastly different magnetic materials classical magnetic techniques can be used to monitor the progress of disordering of the tetrataenite during isothermal annealing magnetic hysteresis loop measurements of a bjurbole chondrule at 488 c clearly record the magnetic parameter changes associated with disordering because of the large coercivity and other distinctive properties tetrataenite exerts significant control on the bulk magnetic properties of meteorites regardless of its volumetric significance paleofield estimates to date have not considered the role of tetrataenite and should therefore be accepted with caution

magnetic properties of the ll5 ordinary chondrite chelyabinsk fall of february 15 2013 here we characterize the magnetic properties of the chelyabinsk chondrite ll5 s4 w0 and constrain the composition concentration grain size distribution and mineral fabric of the meteorite s magnetic mineral assemblage data were collected from 10 to 1073 k and include measurements of low field magnetic susceptibility v0 the anisotropy of v0 hysteresis loops first order reversal curves m spectroscopy and x ray microtomography the rem and rem 0 paleointensity protocols suggest that the only magnetizations recorded by the chondrite are components of the earth s magnetic field acquired during entry into our planet s atmosphere the chelyabinsk chondrite consists of light and dark lithologies fragments of the light lithology show logv0 4 57 0 09 s d n 135 while the dark lithology shows 4 65 0 09 n 39 where v0 is in 10 9 m 3 kg 1 thus chelyabinsk is three times more magnetic than the average ll5 fall but is similar to a subgroup of metal rich ll5 chondrites paragould aldsworth bawku richmond and l ll5 chondrites glanerbrug knyahinya the meteorite s room temperature magnetization is dominated by multidomain feni alloys taenite and kamacite no tetrataenite is present however below approximately 75 k remanence is dominated by chromite the metal contents of the light and dark lithologies are 3 7 and 4 1 wt respectively and are based on values of saturation magnetization

integrating soils and geomorphology in mountains an example from the front range of colorado soil distribution in high mountains reflects the impact of several soil forming factors soil geomorphologists use key pedological properties to estimate ages of quaternary deposits of various depositional environments estimate long term stability and instability of landscapes and make inferences on past climatic change once the influence of the soil forming factors is known soils can be used to help interpret some aspects of landscape evolution that otherwise might go undetected the front range of colorado rises from the plains of the colorado piedmont at about 1700 m past a widespread dissected tertiary erosion surface between 2300 and 2800 m up to an alpine continental divide at 3600 to over 4000 m pleistocene valley glaciers reached the western edge of the erosion surface parent rocks are broadly uniform granitic and gneissic climate varies from 46 cm mean annual precipitation map and 11 jc mean annual temperature mat in the plains to 102 cm and 4 jc respectively near the range crest vegetation follows climate with grassland in the plains forest in the mountains and tundra above 3450 m soils reflect the bioclimatic transect from plains to divide a bw or bt bk or k grassland to a e bw or bt c forest to a bw c tundra corresponding soil ph values decrease from 8 to less than 5 with increasing elevation the pedogenic clay minerals dominant in each major vegetation zone are smectite grassland vermiculite forest and 1 0 1 8 nm mixed layer clays tundra within the lower forested zone the topographic factor aspect results in more leached colder soils with relatively thin o horizons well expressed e horizons and bt horizons alfisols on n facing slopes whereas soils with thicker a horizons less developed or no e horizons and bw or bt horizons mollisols are more common on s facing slopes the topographic factor in the tundra results in soil patterns as a consequence of wind redistributed snow and the amount of time it lingers on the landscape an important parent material factor is airborne dust which results in fine grained surface horizons and if infiltrated contributes to clay accumulation in some bt horizons the time factor is evaluated by soil chronosequence studies of quaternary deposits in tundra upper forest and plains grassland few soils in the study area are 10 000 years old in the tundra 100 000 years old in the forest and 2 million years old in the grassland stages of granite weathering vary with distance from the continental divide and the best developed is grus near the sedimentary granitic rock contact just west of the mountain front grus takes a minimum of 100 000 years to form

stony meteorite porosities and densities a review of the data through 2001 in this review we summarize the data published up to december 2001 on the porosity and density of stony meteorites these data were taken from 925 samples of 454 different meteorites by a variety of techniques most meteorites have densities on the order of 3 to 4 g cm 3 with lower densities only for some volatile rich carbonaceous meteorites and higher densities for stony irons for the vast majority of stones porosity data alone cannot distinguish between different meteorite compositions average porosities for most meteorite classes are around 10 though individual samples can range as high as 30 porosity unbrecciated basaltic achondrites appear to be systematically less porous unless vesicles are present the measured density of ordinary chondrites is strongly controlled by the amount of terrestrial weathering the sample has undergone with porosities steadily dropping with exposure to the terrestrial environment a theoretical grain density based on composition can model pre weathered porosities the average model porosity for h and ll chondrites is 10 while l chondrite model porosities average only 6 a statistically significant difference

timing and warmth of the last interglacial period new u series evidence from hawaii and bermuda and a new fossil compilation for north america abstract the timing and duration of the last interglacial period have been controversial with some studies suggesting a relatively short duration that is orbitally forced and others suggesting a long duration that is at most only partly related to orbital forcing new high precison thermal ionization mass spectrometric tims u series ages of last interglacial corals from hawaii and bermuda test these competing hypotheses waimanalo formation corals from slowly uplifting oahu hawaii range in age from 134 to 113 ka with most ages between 125 and 115 ka combined with published u series ages from nearby lanai the data suggest a long last interglacial period that may have occurred from 136 to at least 115 ka the results indicate that orbital forcing may not have been the only control on ice sheet growth and decay because sea level would have been high at times of relatively low northern hemisphere summer insolation on tectonically stable bermuda deposits from the 200 ka penultimate interglacial period 120 ka peak last interglacial period and 80 ka late last interglacial period high sea stands have been newly dated fossil corals on bermuda are derived from patch reefs that likely were catch up responses to sea level rise it is expected that u series ages of last interglacial corals on bermuda should overlap with but not be as old as the range of corals on oahu last interglacial corals on bermuda give a range of 125 113 ka which supports this hypothesis a large number of emergent marine deposits on hawaii bermuda and along coastal north america have now been dated to the last interglacial period both oahu and bermuda have marine invertebrate faunas with a number of extralimital southern species of mollusks suggesting warmer than present waters during the last interglacial period warmer waters are also suggested for last interglacial localities around most of north america from florida to canada and greenland and baja california to alaska these observations are consistent with similar warm water faunas of last interglacial age reported from japan the mediterranean basin and western australia it is likely that significant changes in ocean currents took place during the last interglacial period with a movement of relatively warm waters to higher latitudes than is the case today

reconstruction of quaternary landscape formation as a tool to understand present geomorphological processes in the eastern prealps austria abstract the rhenodanubian flysch of the n vienna forest is composed of various layers of sandstones marly shales calcareous marls and clay schists covered by quaternary periglacial cover beds and loess deposits there is a characteristic sequence of slope evolution during the quaternary seven main phases are related to pleistocene processes and two stages reflect the most recent geomorphodynamic processes phases of erosion redeposition sedimentation and soil formation demonstrate stages of activity and stability under varying climatic conditions on the basis of pedological and geomorphological investigations it is possible to differentiate pleistocene and holocene sediments and processes in particular the distribution of periglacial cover beds loess and modern soils allows the reconstruction of the undisturbed pleistocene slope and sediments the sequence of slope formation causes a distinct spatial distribution of quaternary sediments and solid rock at the present land surface in consequence the influence of quaternary landscape formation significantly influences slope stability conditions in the study area this applies to the specific composition of the basal periglacial cover bed in the study area it often consists of densely bedded marls and sandstone and is therefore impermeable which can induce mass movements in the study area loess deposits frequently slide on top of the basal periglacial cover bed and form a susceptible pre requisite for the occurrence of landslides in the study area

late quaternary loess in northeastern colorado part i age and paleoclimatic significance loess in eastern colorado covers an estimated 14 000 km 2 and is the westernmost part of the north american midcontinent loess province stratigraphic studies indicate there were two periods of loess deposition in eastern colorado during late quaternary time the first period spanned ca 20 000 to 12 000 14 c yr b p ca 20 14 ka and correlates reasonably well with the culmination and retreat of pinedale glaciers in the colorado front range during the last glacial maximum the second period of loess deposition occurred between ca 11000 and 9000 14 c yr b p this interval may be holocene or may correlate with a hypothesized younger dryas glacial advance in the colorado front range sedimentologic mineralogic and geochemical data indicate that as many as three sources could have supplied loess in eastern colorado these sources include glaciogenic silt derived from the colorado front range and two bedrock sources volcaniclastic silt from the white river group and clays from the pierre shale the sediment sources imply a generally westerly paleowind during the last glacial maximum new carbon isotope data combined with published faunal data indicate that the loess was probably deposited on a cool steppe implying a last glacial maximum july temperature depression relative to the present of at least 5 6 c overall loess deposition in eastern colorado occurred mostly toward the end of the last glacial maximum under cooler and drier conditions with generally westerly winds from more than one source

aeolian dust contribution to the formation of alpine soils at amdo northern tibetan plateau abstract the tibetan plateau has one of the largest distributions of alpine meadow in the world due to the cold climate and dominance of physical weathering conditions coarse or massive debris prevails thus pedogenesis is controlled by both the temperature and parent material in this study the alpine soils gelic cambisol at altitudes of 4768 4980 m in the amdo zone of the northern tibetan plateau were investigated we found that the parent materials throughout the alpine soil profiles were rich in clayey and silty minerals here we focused on the origin of the soil forming materials of alpine meadows we examined the grain size distribution mineral compositions trace element concentrations and sr nd isotopic compositions of the alpine soils and their potential source materials in various grain size fractions based on a comparison of many fingerprints our results indicated that a red clay rich bed at the bottom of the alpine soil profile is a residual paleo weathering crust nevertheless the parent materials in the alpine soils did not have a clear inherited relationship with the weathering products of the in situ bedrock correspondingly we confirmed that the parent materials in the alpine soils have an aeolian origin the alluvial sediments and widespread beach and lacustrine delta sediments in the amdo zone are the main source of alpine soil materials however it was not clear whether sediments are the main source of aeolian dust aeolian dust with a short transport distance is one of the main components 300 m of alpine soils had a local origin i e from adjacent bedrock outcrops in contrast long range transport of dust had a minor role in the formation of alpine soils in the region investigated the aeolian dust began accumulating in the middle holocene on the tibetan plateau one positive effect of aeolian processes is that the aeolian dust accretion is a source of parent materials and nutrients for alpine soils

elucidating the role of vegetation in the initiation of rainfall induced shallow landslides insights from an extreme rainfall event in the colorado front range more than 1100 debris flows were mobilized from shallow landslides during a rainstorm from september 9 13 2013 in the colorado front range with the vast majority initiating on sparsely vegetated south facing terrain to investigate the physical processes responsible for the observed aspect control we made measurements of soil properties on a densely forested north facing hillslope and a grassland dominated south facing hillslope in the colorado front range and performed numerical modeling of transient changes in soil pore water pressure throughout the rainstorm using the numerical model we quantitatively assessed interactions among vegetation rainfall interception subsurface hydrology and slope stability results suggest that apparent cohesion supplied by roots was responsible for the observed connection between debris flow initiation and slope aspect results suggest that future climate driven modifications to forest structure could substantially influence landslide hazards throughout the front range and similar water limited environments where vegetation communities may be more susceptible to small variations in climate

revised ages for tuffs of the yellowstone plateau volcanic field assignment of the huckleberry ridge tuff to a new geomagnetic polarity event 40 ar 39 ar ages were determined on the three major ash flow tuffs of the yellowstone plateau volcanic field in the region of yellowstone national park in order to improve the precision of previously determined ages total fusion and incremental heating ages of sanidine yielded the following mean ages huckleberry ridge tuff 2 059 0 004 ma mesa falls tuff 1 285 0 004 ma and lava creek tuff 0 639 0 002 ma the huckleberry ridge tuff has a transitional magnetic direction and has previously been related to the reunion normal polarity subchron dating of the reunion event has been reviewed and its ages have been normalized to a common value for mineral standards the age of the huckleberry ridge tuff is significantly younger than lava flows of the reunion event on re union island supporting other evidence for a normal polarity event younger than the reunion event