contemporary rates of chemical denudation and atmospheric co2 sequestration in glacier basins an arctic perspective this paper presents new estimates of solute fluxes from five high arctic glacier basins in svalbard these estimates are combined with data from two other glacier basins to assess the effectiveness of chemical denudation on svalbard and to estimate rates of temporary or transient co2 drawdown we use a solute provenance model to partition solutes into marine aerosol atmospheric and crustal components and to estimate their annual fluxes crustally derived solute fluxes are equivalent to a mean chemical denudation rate of 350 meq m 2 a 1 for svalbard range 160 560 meq m 2 a 1 which lies within the global range of 94 4200 meq m 2 a 1 for 21 glacier basins in the northern hemisphere and is close to the continental average of 390 meq m 2 a 1 specific annual discharge is the most significant control upon chemical denudation in the glacierized basins and basin lithology is an important secondary control with carbonate rich and basaltic lithologies currently showing the greatest chemical denudation rates estimates of transient co2 drawdown are also directly associated with specific annual discharge and rock type on svalbard transient co2 drawdown lies in the range 110 3000 kg c km 2 a 1 whilst the range is 110 13000 kg c km 2 a 1 for the northern hemisphere glacial data set transient co2 drawdown is therefore usually low in the svalbard basins unless carbonate or basalt rocks are abundant the analysis shows that a large area of uncertainty in the transient co2 drawdown estimates exists due to the non stoichiometric release of solute during silicate hydrolysis silicate hydrolysis is particularly non stoichiometric in basins where the extent of glacierization is high which is most probably an artefact of high flushing rates through ice marginal and subglacial environments where k feldspars are undergoing mechanical comminution copyright 2000 john wiley sons ltd

erosion rates in and around shenandoah national park virginia determined using analysis of cosmogenic 10be we use cosmogenic 10be analysis of fluvial sediments and bedrock to estimate erosion rates 104 105 year timescale and to infer the distribution of post orogenic geomorphic processes in the blue ridge province in and around shenandoah national park virginia our sampling plan was designed to investigate relationships between erosion rate and lithology mean basin slope basin area and sediment grain size fifty nine samples were collected from a variety of basin sizes inferred erosion rates for the medium sand fraction of all fluvial samples from all lithologies range from 3 0 to 21 m my the area weighted mean erosion rate for single lithology basins in the park is 12 2 m my single lithology erosion rate ranges for fluvial samples are granite 7 0 to 20 m my metabasalt 3 8 to 21 m my quartzite 3 8 to 15 m my and siliciclastic rocks 5 2 to 15 m my multilithology basins erode at rates between 3 0 16 m my the shenandoah river basin 3305 km2 is eroding at 6 6 m my bedrock erosion rates range from 1 8 to 11 m my across all lithologies with a mean of 6 5 4 3 m my grain size specific 10be analysis of four samples showed no consistent trend of concentration with grain size cosmogenic analysis of bedrock and sediment from the shenandoah national park area allows us to speculate about why some parts of the appalachian mountains erode more slowly and some more rapidly overall it appears that steep drainage basins erode more rapidly than gently sloped basins climate and lithology may also influence basin scale rates of erosion as suggested by the difference in average erosion rates east and west of the divide and the difference between the erosion rates of quartzite and granite dominated basins data are conflicting in regards to the evolution of relief over time analyses made of exposed bedrock along ridgelines suggest that such rock is eroding either more slowly than adjacent drainage basins susquehanna river shenandoah national park region or at similar rates great smoky mountains providing a mechanism for growing relief at the scale of individual ridgelines however considering relief on a landscape or physiographic province scale by comparing erosion rates of the highlands versus the lowlands suggests that relief of the range as a whole is either steady or very slowly decreasing over multi millennial timescales the presence of significant erosion rate slope relationships negates a broad hackian view of the landscape because there is not uniform erosion across this landscape the aspect erosion rate and slope erosion rate relationships present in the shenandoah area suggest that the landscape is not fully adjusted to rock strength

weakening of gneiss surfaces colonized by endolithic lichens in the temperate climate area of northwest italy a role of lithobionts in geomorphological processes is increasingly argued but the spatio temporal scale of their impact is largely unexplored in many ecosystems this study first characterizes in the temperate zone northwest italy the relationships between lithobiontic communities including endolithic lichens and the hardness of their siliceous rock substrate villarfocchiardo gneiss the communities are characterized on humid and xeric quarry surfaces exposed for decades and natural outcrops exposed for centuries in terms of lichen and microbial constituents using a combined morphological and molecular approach and with regard to their development on and within the gneiss a lichen species belonging to acarosporaceae polysporina sarcogyne acarospora group needing taxonomic revision chasmoendolithically colonizes both the humid and xeric quarry surfaces on which epilithic cyanobacterial biofilms and epilithic pioneer lichens respectively occur light and electron microscopic observations show the development of the endolithic thalli within rock microcracks and the hyphal penetration along crystal boundaries down to depths of 1 to 3 mm more pronounced within the humid surfaces such colonization patterns are likely related to biogeophysical deterioration while no chemical alteration characterizes minerals contacted by the endolithic lichen by contrast on natural outcrops where the endolithic colonization is negligible a reddish rind below epilithic lichens indicates chemical weathering processes schmidt hammer measurements highlight that the endolithic lichens deeply affect the hardness of the gneiss down to 60 with respect to fresh controls and surfaces only colonized by cyanobacteria exerting a significantly higher weakening effect with respect to the associated epilithic lithobionts the phenomenon is more remarkable on humid than on xeric quarry surfaces and natural outcrops where epilithic lichens are likely involved in long term hardening processes supporting surface stabilization endolithic lichens are thus active biogeomorphological agents at the upper millimetric layer of siliceous rocks in temperate areas exerting their weakening action during the early decade scaled stages of surface exposure copyright 2015 john wiley sons ltd

the role of biological weathering in periglacial areas a study of weathering rinds in south iceland the importance of biogeochemical processes in the morphogenic system of periglacial environments has been underestimated for decades weathering rind studies help to characterise and quantify biogeochemical weathering over time experiments using fungi strains isolated from basaltic boulders allow one to decipher biological weathering a historical approach using heterochronous moraines provides the opportunity to follow the life of weathering rinds and helps to build a chronology of dominant processes of weathering during the first century of exposure it appears that exfoliation of weathering rinds commonly observed on boulders is the result of a combination of both biogeochemical and physical processes

estimating ages of late quaternary stream terraces from analysis of weathering rinds and soils rates of growth of rock weathering rinds and rates of changes of soil morphologic and chemical properties that are calibrated at sites of known ages produce powerful tools for estimating ages of geomorphic surfaces particularly when materials datable by conventional methods are not widespread sequences of latest quaternary stream terraces from the south island of new zealand are ideally suited for application of these calibrated age techniques because climate and source materials for terrace deposits are internally consistent within two regions west land and marlborough modal and mean thicknesses of weathering rinds formed in surface cobbles of torlesse graywacke provide age estimates for latest pleistocene and holocene stream terraces in marlborough with uncertainties estimated at 5 to 40 modal rind thickness of subsurface cobbles provides age estimates for latest quaternary westland sites with uncertainties of 10 to more than 50 few dated soils are available to constrain rates of soil development in westland and marlborough furthermore soils were sampled from only one pedon on each surface morphologic data however provide least squares age estimates for westland sites with uncertainties typically greater than 100 and the calibration data can further bracket likely soil ages to less than 50 uncertainty the regression data from marlborough are less reliable but profile index ratios help bracket ages to at least 50 distributions of oxalate extractable fe and ai and total major element concentrations allow age estimates for westland and marlborough soils with uncertainties estimated at 15 to 50 despite these uncertainties the three techniques combine to provide age estimates with the high resolution needed to examine details of fault slip rates or stream downcutting the calibration data and weathering rates used herein are applicable only to the new zealand region studied although similar calibrated age techniques should provide high resolution dating in many other regions such techniques are particularly useful when multiple approaches are available to provide independent cross checks

a porosity related diffusion model of weathering rind development abstract a model of weathering rind growth is proposed based on the study of andesite cobbles sampled from a modern floodplain and four fluvial terraces 0 20 130 290 and 660 ka in central japan the times elapsed since each of the above ages can be assumed to be the weathering periods the 0 ka rocks are not visibly weathered the 20 ka rocks have an alteration layer with white or brown colours and a mean thickness of 0 7 mm on their surface the 130 290 and 660 ka rocks have brown weathering rinds with average thicknesses of 3 6 mm based on the measurements of physical and mechanical properties throughout from the rock surface to the interior weathering rinds are divided into two bands the outer brown band is characterized by ferric hydroxides which experienced both oxidization and leaching the inner band is formed by leaching alone of alkalis alkaline earths the inner border of this band is located at the position where vickers hardness numbers start decreasing with decreasing depth the thickness of each band was determined from its physical and mechanical properties the results show that brown band thickness l i is a function of time however total thickness of the two bands i e total weathering rind thickness l i ii is also controlled by initial rock porosity n their relationships are represented by diffusive equations l i dt 1 2 0 0283 t 1 2 and l i ii dt 1 2 0 0431 exp 0 4287 n t 1 2 these findings indicate that rind characterization and original rock porosity should be taken into consideration when weathering rind thickness is used as a dating tool

rock weathering processes and landform development in the sor rondane mountains antarctica abstract field observations of weathering processes and the related landforms combined with laboratory analyses of weathering products permit a synthetic evaluation of late cenozoic weathering environments in the sor rondane mountains antarctica an arid upland characterized by low temperatures and strong winds rates and character of weathering depend mainly on moisture availability and the bedrock geology under the humid weathering regime that occurs only locally around the margin of the present sheet frequent diurnal freeze thaw cycles in summer cause relatively rapid rock fragmentation most of the mountains are situated in the arid weathering regime under which rock breakdown is very slow unless the rock contains plenty of salts salt weathering becomes more intensive and extensive with exposure age as a result of salt accumulation in rock eventually producing soils as small as fine silt size lack of clay mineralization even in weathered rocks having been exposed above the ice sheet prior to 4 ma ago indicates that hydrolysis or carbonation of rock minerals has been insignificant during the past 4 ma the final products of weathering are due mainly to salt action and reflect the parent lithology resistant fine grained granite forms strongly oxidized tors carved with tafoni or fields of mushroom like boulders overlying the fractured bedrock less resistant rocks like biotite gneiss and amphibolite produce stone pavements underlain by saline silty soils up to 30 40 cm thick the thickness of which corresponds to the maximum thaw depth

reconstruction of ice conditions in the northern chukchi sea during recent centuries geochemical proxy compared with observed data abstract this paper presents the first results of the quantitative reconstruction of ice conditions in the arctic based on a comparison of the data for periods of meteorological observations with variations in the chemical compositions of the sediments accumulated during the same times the biogenic elements br ca and sr and some redox sensitive as and fe elements are the most informative for the reconstruction of changes in ice conditions with positive correlations and the lithogenic elements k and ti are predominantly negatively correlated the reconstruction results for the last 300 400 years of average annual air temperature anomalies for all cores in general terms coincide with the reconstruction for the northern hemisphere the common features of all reconstructions are low temperatures during the little ice age lia and a rapid warming in the middle of the 19th century and in the last decades of the 20th and first decades of the 21st centuries the results of the reconstruction of the duration of the ice free period generally coincide with the temperature changes for the last two centuries although for lia there is an inverse correlation between the variations in temperature and the duration of the ice free period a possible reason for this may be changes in the structure of the surface currents in the chukchi sea and the northern part of the bering sea because of which the inflow of warm and freshened waters through the bering strait to the arctic increased occasionally

rock weathering by the lichenlecidea auriculata in an arctic alpine environment scanning electron microscopy reveals that lecidea auriculata penetrates rock surfaces detaching incorporating and expelling flakes of rock measurements on an age sequence of moraine ridges illustrate changes in the extent and intensity of weathering over time a minimum rate of surface lowering 0 0012 mm a 1 is 25 to 50 times faster than weathering due to other processes in the same area the spatial pattern of weathering is influenced by the narrow ecological range of the species surface rocks on dry exposed sites are probably weathering much more rapidly than those in adjacent damp hollows and beneath snowpatches

microbial trace fossil formation biogenous and abiotic weathering in the antarctic cold desert in the antarctic cold desert ross desert the survival of the cryptoendolithic microorganisms that colonize the near surface layer of porous sandstone rocks depends on a precarious equilibrium of biological and geological factors an unfavorable shift of this equilibrium results in death and this may be followed by formation of trace fossils that preserve the characteristic iron leaching pattern caused by microbial activity similar microbial trace fossil may exist in the geological record if life ever arose on early mars similar processes may have occurred there and left recognizable traces

mineral accumulations induced by biological activity on granitic rocks in qinghai plateau china fragments of weathered granitic rocks from the kunlun shan qinghai plateau china were investigated to elucidate the influence of biotic crusts on the breakdown of granitic rocks in an alpine environment scanning electron microscopy with energy dispersive system and x ray diffractometry were used to describe the nature and properties of mineral accumulations on the rock surface results showed that organic salts such as calcium oxalate and calcium formate are associated with aspicilia caesiocinera nyl ex malbr arnold caloplaca sp xanthoria elegans link th fr and lecidea plana lahm nyl secondary accumulations of 2 i clays minerals are found in a caesiocinera while oxides of manganese are associated with x elegans coatings of goethite iron oxides are believed to form from biological activity associated with the presence of hyphae and rodlet structures on the flakes calcium oxalate crystallizes into several morphologies such as druse hexagonal plates and lenticular containing between 20 and 48 per cent calcium by weight calcium formate and iron oxide goethite occur together in the form of red desert varnish observed black coatings contain as much as 37 per cent manganese and 22 per cent iron clay accumulations have plate like morphology and contain c 2 1 silicon to aluminium contents we argue that organic acids from the activities of biotic crusts contribute to the breakdown of granitic rocks fungi accelerate the breakdown of granitic rocks through the growth of fungal hyphae along the 001 cleavage planes in primary chloritic minerals copyright c 2003 john wiley sons ltd

climatic significance of glacier retreat and rockglaciers re assessed in the light of cosmogenic dating and weathering rind thickness in claree valley brianconnais french alps recent advances in geochronology provide opportunities to identify the glacial and periglacial sequences in mountain area in this paper we focus on the upper durance catchment southern french alps in the claree valley where no absolute chronological benchmark was defined glacial remnants and periglacial features were investigated integrated within a chronological scenario thanks to relative weathering rind thickness and absolute cre technique dates we find evidence of the existence of a late glacial valley glacier that has never been reported before then the upper valleys became ice free during a period corresponding to the early holocene climate optimum whereas two sequences of cirque glaciation are identified during the second half of the holocene we also show evidence of three main generations of rockglaciers which also mainly developed during the second half of the holocene probably at the end of the subboreal period the location and the altitudes of rockglaciers are strongly dependent on the geomorphic setting especially the location of the sediment sources hence complicating their palaeo climatic interpretations

effect of porosity on the increase in weathering rind thicknesses of andesite gravel abstract factors affecting the increase in weathering rind thickness i e weathering rates were investigated using andesite gravel in fluvial terrace deposits with a known emergence time the time between the age of each terrace formation 20 130 290 and 660 ka and the present was assumed to be the weathering period three zones were classified from measurements of the vickers hardness number vhn across weathering rinds from the rock surface to the inner fresh part 1 zone i the outermost brown layer which has low vhn values of 10 to 80 gf m2 2 zone ii the inner gray layer which has increasing vhn values 100 to 500 gf m2 with increasing depth 3 the innermost fresh part which has large vhn values of 500 gf m2 in this paper zones i and i ii are defined as the brown layer and the weathering rind respectively diffusion theory was applied to the relationship between the thickness of the brown layer or the weathering rind and time weathering periods the results show that the thickness of the brown layer depends mainly on time whereas the thickness of the weathering rind is controlled by the porosity of the host rock as well as time consequently rocks with higher porosity have thicker weathering rinds than brown layers

relative surface age dating of rock glacier systems near holar in hjaltadalur northern iceland schmidt hammer rebound values and photogrammetric measurements of surface displacement were used to date two active polymorphic high altitude and two relict monomorphic low altitude rock glaciers near holar in hjaltadalur trollaskagi peninsula northern iceland 65 40 n 19 00 w both low altitude rock glaciers are of late weichselian or preboreal origin ca 10 3 9 2 k yr bp with minor later reshaping until the early neoglacial period vatnsdalur i ca 5 2 k yr bp both high altitude rock glaciers consist of an upper lobe overriding a lower lobe corresponding to initiation during different cool phases the initiation of the lower lobes can possibly be attributed to the gh 8 2 event 8 6 8 0 k cal yr bp they reached their terminal position at the end of the vatnsdalur i stage the upper lobes of the high altitude rock glaciers were initiated sometimes between the vatnsdalur i but substantially before the vatnsdalur ii ca 3 0 3 2 k yr bp stages and underwent modification during each following holocene glacier expansion episode culminating the last time in the little ice age thus it is suggested that similar looking rock glaciers occurring elsewhere in the trollaskagi peninsula may have a similar complex history therefore they may not be seen as rather simple landforms developed during the little ice age copyright 2007 john wiley sons ltd

do periglacial landscapes evolve under periglacial conditions polar and alpine periglacial areas are traditionally regarded as necessarily submitted to very efficient frost driven processes that control the holocene and ongoing geomorphic activity during the last decade the validity of this academic view has been increasingly questioned among the international scientific community the search for the real past and present processes responsible for landform evolution in cold nonglaciated areas is based mainly on more and more refined monitoring protocols relying upon sophisticated equipment to assess the representativeness and significance of monitoring data collected in restricted sites it appears necessary however to widen the perspective by adopting a twofold multiscale approach as proposed in the present paper 1 in space by integrating various scales from the general slope system to the bioclimatic nanoenvironment and 2 in time by taking into account the landscape history from tertiary inherited features to recent process changes induced by the contemporary warming reintegrating the historical approach should help both to place the ongoing processes within a succession and or combination of interoperating processes and to avoid misinterpretations of features considered wrongly as emblematic of frost action overall both the historical and monitoring approaches tend to reduce the geomorphic efficiency of frost derived processes instead the role of noncold related processes such as chemical thermal biogenic and rainfall induced ones is being emphasized of special interest would be an interdisciplinary discussion between geomorphologists and various disciplines of biological sciences including biochemistry and ecology studying processes of primary successions

endolithic microorganisms in the antarctic cold desert in the frigid desert of the antarctic dry valleys there are no visible life forms on the surface of the soil or rocks yet in certain rock types a narrow subsurface zone has a favorable microclimate and is colonized by microorganisms dominant are lichens of unusual organization they survive not by physiological adaptation to lower temperatures but by changing their mode of growth being able to grow between the crystals of porous rocks their activity results in mobilization of iron compounds and in rock weatherning with a characteristic pattern of exfoliation this simple ecosystem lacks both higher consumers and predators

fungal weathering of basaltic rocks in a cold oceanic environment iceland comparison between experimental and field observations this paper presents evidence for strong biochemical weathering of basaltic outcrops induced by fungal communities in a cold environment weathering rind formation is considered to be a consequence of the biological activity comparisons between in vitro experiments and in situ observations allow a characterization of fungi effects on rocks and help to define the place of these microorganisms in the cold environment weathering chain it is concluded that biological weathering is chronologically the first process of weathering probably leading to the subsequent expression of cryogenic processes information presented here suggests the need for reconsideration of the traditional frost driven morphogenetic system normally considered for sub polar areas

from climatic to global change geomorphology contemporary shifts in periglacial geomorphology periglacial geomorphology developed in the 1940s 1960s as a branch of climatic geomorphology focusing first on quaternary studies and palaeoenvironmental reconstructions then on current geomorphi

mcgee till oldest glacial deposit in the sierra nevada california and quaternary evolution of the rangefront escarpment abstract the mcgee till is an early pleistocene glacial diamict as thick as 50 m preserved over an area of 1 65 km2 on a relict low relief pliocene plateau that stands 900 m higher than mouths of its bounding canyons on the rangefront of the sierra nevada although recognized 90 years ago as the oldest till in the sierra its age and relation to the next oldest sierran till have remained uncertain even controversial this contribution seeks to clarify both the mcgee till consists predominantly of grussy boulders and sandy granular matrix derived largely from a distinctive cretaceous granodiorite that walls mcgee creek canyon 4 8 km to the south the till rests directly upon two different basaltic units that yield 40ar 39ar ages of 2 8 and 2 6 ma and show little or no evidence of preglacial erosion the basalts preserve a minimum of 165 255 m of relief on steep slopes that existed around the plateau margins at the time of their eruption mcgee creek consists of two segments a north directed reach that confined the glacier that deposited the till and now diverging at a right bend just upvalley from the till a northeast flowing reach that was incised later the base of the mcgee till is at 3160 m elevation on the present day rim of mcgee creek 610 m above the bend the base of the 130 ka tahoe till mis 6 is at 2550 m elevation directly downslope from the mcgee till and at 2300 m at the rangefront mouth of the canyon s northeast reach the base of the 900 866 ka sherwin till mis 22 is at 2400 m at the nearby rangefront mouth of rock creek as the canyons were cut to nearly modern depths before the sherwin glaciation the high perched mcgee till is probably older than 2 ma and possibly close in age to the 2 6 ma basalt it overlies growth in rangefront relief since about 3 0 2 5 ma owes to normal slip on the hilton creek and round valley faults east of mcgee mountain as well as to the 767 ka collapse of long valley caldera to its north