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

mangrove forest evolution in a sediment rich estuarine system opportunists or agents of geomorphic change the majority of the world s mangrove forests occur on mostly mineral sediments of fluvial origin two perspectives exist on the biogeomorphic development of these forests i e that mangroves are opportunistic with forest development primarily driven by physical processes or alternatively that biophysical feedbacks strongly influence sedimentation and resulting geomorphology on the firth of thames coast new zealand we evaluate these two possible scenarios for sediment accumulation and forest development using high resolution sedimentary records and a detailed chronology of mangrove forest avicennia marina development since the 1950s cores were collected along a shore normal transect of known elevation relative to mean sea level msl activities for lead 210 pb 210 caesium 137 cs 137 and beryllium 7 be 7 and sediment properties were analysed with pb 210 sediment accumulation rates sars compensated for deep subsidence similar to 8 mm yr 1 used as a proxy for elevation gain at least four phases of forest development since the 1950s are recognized an old growth forest developed by the late 1970s with more recent seaward forest expansion thereafter excess 210pb profiles from the old growth forest exhibit relatively low sars near the top 7 12 mm yr 1 and bottom 10 22 mm yr 1 of cores separated by an interval of higher sars 33 100 mm yr 1 a general trend of increasing sar over time characterizes the recent forest biogeomorphic evolution of the system is more complex than simple mudflat accretion progradation and mangrove forest expansion surface elevation gain in the old growth forest displays an asymptotic trajectory with a secondary depocentre developing on the seaward mudflat from the mid 1970s two to ten fold increases in 210pb sars are unambiguously large and occurred years to decades before seedling recruitment demonstrating that mangroves do not measurably enhance sedimentation over annual to decadal timescales this suggests that mangrove forest development is largely dependent on physical processes with forests occupying mudflats once they reach a suitable elevation in the intertidal copyright c 2015 john wiley sons ltd

surface destabilisation by the invasive burrowing engineer mus musculus on a sub antarctic island abstract invasive species are known to have substantial trophic effects on ecosystems and ecosystem processes the invasion of the house mouse mus musculus onto sub antarctic islands has had a devastating effect on plants invertebrates and birds with substantial changes in ecosystem functions less well understood however are the nontrophic geomorphic effects of mice resulting from their burrowing activities we examined the extent of burrow construction by m musculus across an area of about 20 ha on marion island and the effects of burrows on water flow and sediment movement we recorded a density of 0 59 0 48 mean sd burrows m 2 with more burrows at lower altitudes and shallower slopes and twice the density in the solifluction risers 0 86 0 54 m 2 than the intervening terraces or treads 0 40 0 51 m 2 most burrows were dug horizontally into the slope and tended to extend about 20 cm deep before turning a very conservative estimate of sediment removed from burrows from this depth is 2 4 t ha 1 however taking into account more detailed data on burrow morphology based on excavations actual amounts may be closer to 8 4 t ha 1 average soil displacement rate for a single burrow measured over 5 days was 0 18 kg burrow 1 day 1 burrows acted as conduits for water and warmer air stones at burrow entrances were moved eight times farther by water 10 4 cm than those not associated with burrows similarly temperatures adjacent to burrow entrances were 4 1 c higher than sites 10 cm away together our data indicate that mice are having substantial deleterious and geomorphic effects on sub antarctic ecosystems through their burrowing with lower rates of mouse mortality resulting from warmer climates predicted under global climate models we can expect an increase in damage resulting from mouse activity

mapping surface mineralogy using imaging spectrometry abstract imaging spectrometry simultaneous measurement of spectra and images in up to hundreds of spectral channels or bands is a proven technology for identifying and mapping minerals based on their reflectance or emissivity signatures also known as hyperspectral imaging or hsi extraction of key spectral signatures from these data allows direct identification of iron minerals such as hematite goethite and jarosite in the visible near infrared vnir clays carbonates micas sulfates and other minerals in the short wave infrared swir and silicates and carbonates in the long wave infrared lwir the unique capability of imaging spectrometry to produce detailed maps of the spatial distribution of specific minerals mineral assemblages and mineral variability on the surface of earth makes it an ideal tool for enhanced geomorphic mapping case histories illustrate the use of hsi for characterizing and mapping active and relict geothermal hydrothermal systems and determining relations between mineralogy and derived landforms imaging spectrometry used in conjunction with complimentary datasets such as insar interferometric synthetic aperture radar light detection and ranging lidar or stereo photogrammetric derived digital elevation models dems provides a unique means of visualizing the spatial distribution and association of mineralogy with topography thus contributing to the understanding of the relations between geology and landscape and to improved interpretation of surface geologic processes

vegetation succession in deglaciated landscapes implications for sediment and landscape stability landscapes exposed by glacial retreat provide an ideal natural laboratory to study the processes involved in transforming a highly disturbed glacially influenced landscape to a stable diverse ecosystem which supports numerous species and communities large scale vegetation development and changes in sediment availability used as a proxy for paraglacial adjustment following rapid deglaciation were assessed using information from remote sensing delineation of broad successional vegetation cover types was undertaken using landsat satellite imagery covering a 22 year period to document the rate and trajectory of terrestrial vegetation development use of a space for time substitution in glacier bay national park alaska allowed back calculation of the age and stage of development of six catchments over 206 years the high accuracy 89 2 of the remotely sensed information used in monitoring successional change allowed detection of a high rate of change in vegetation classes in early successional stages bare sediment and alder in contrast later successional stages spruce and spruce hemlock dominated forest had high vegetation class retention and low turnover modelled rates of vegetation change generally confirmed the estimated rates of successional turnover previously reported these data when combined with the known influence of terrestrial succession on soil development and sediment availability suggest how physical and biological processes interact over time to influence paraglacial adjustment following deglaciation this study highlights the application of remote sensing of successional chronosequence landscapes to assess the temporal dynamics of paraglacial adjustment following rapid deglaciation and shows the importance of incorporating bio physical interactions within landscape evolution models 2014 the authors earth surface processes and landforms published by john wiley sons ltd

rock warming and drying under simulated intertidal conditions part ii weathering and biological influences on evaporative cooling and near surface micro climatic conditions as an example of biogeomorphic ecosystem engineering the way in which rocks and engineering materials heat up and dry out in the intertidal zone is of relevance to both weathering and ecology these behaviours can be measured in the laboratory under controlled conditions designed to replicate those occurring in the field previous studies have demonstrated differences in thermal behaviours between rock types and through time as a result of soiling in terrestrial environments but the influence of weathering and colonization on rock behaviours in the intertidal zone has not been previously assessed we measured the warming and drying of blocks of rock limestone and granite and marine concrete during low tide events simulated in the laboratory before and after a period of exposure eight months on rock platforms in cornwall uk as well as differences between the material types temperatures of control unexposed and field exposed blocks differed in the order of 1 to 2 c drying behaviours were also different after field exposure differences during the first few hours of exposure to air and heat were attributed to discolouration and albedo effects over longer periods of time changes in the availability of near surface pore water as a result of micro scale bioerosion of limestone and the development of bio chemical crusts on marine concrete observed using scanning electron microscopy sem are suggested as mechanisms enhancing and reducing respectively the efficiency of evaporative cooling the retention of moisture by epilithic biofilms may also influence thermal and drying behaviours of granite these observations represent one of the first examples of cross scalar biogeomorphic linkages in the intertidal zone the significance of the results for the subsequent efficiency of weathering and near surface micro climatic conditions experienced by colonizing organisms is discussed the involvement of microorganisms in the creation of more or less ecologically stressful conditions through the alteration of substratum geomorphic properties and behaviours is suggested as an example of biogeomorphic ecosystem engineering copyright 2011 john wiley sons ltd

zinc isotope systematics in snow and ice accretions in central european mountains abstract zinc zn pollution negatively affects human and ecosystem health we quantified atmospheric zn inputs at six remote mountain top locations in the czech republic central europe and used 66 zn isotope ratios to identify zn from different pollution sources the study sites were located at an elevation of approximately 1000 m near the state borders with germany and poland during two winter seasons 2009 2010 over 400 samples of vertical deposition snow and horizontal deposition ice accretions were collected zinc pollution levels were generally low zinc concentrations in snow and ice accretions were less than twice as high in the east compared to the west across the sites over 90 of zn was present in a weak acid soluble form zinc concentrations were 5 times higher in ice accretions which formed from small droplets originating in the basal cloud layer rich in pollutants than in snow in contrast droplets resulting in snow formation were larger and scavenged less pollution due to their smaller surface area 66 zn of pribram sphalerite west and smelter derived fly ash west were low 0 23 and 0 47 respectively olkusz sphalerite east had a higher 66 zn of 0 02 66 zn of snow ranged from 0 60 to 0 68 ice accretions had 66 zn between 0 67 and 0 14 at the three eastern sites 66 zn of ice accretions was lower than 66 zn of snow suggesting the presence of volatilized smelter derived or coal burning derived zn 66 zn of ice accretions at two of the three western sites was higher than 66 zn of snow different 66 zn values of snow and ice accretions from the same site reflected different pollution sources which may have been situated at different distances from the receptor site 66 zn of the soluble zn fraction was higher than 66 zn of the insoluble zn fraction possibly also indicating a different origin of these two zn fractions zinc isotope heterogeneity in the atmosphere of remote areas indicates that 66 zn can be a useful tool in pollution provenance studies

surface lowering of limestone pavement as determined by cosmogenic 36cl analysis determination of the rate and total amount of limestone pavement surface lowering is a critical issue in developing models of regional landscape change in limestone terrain erratic capped pedestals have frequently been used for this purpose but problems concerning definition and measurement of pedestal height and the absence of a secure timeframe for erratic emplacement have resulted in conflicting interpretations we have used cosmogenic 36cl to establish the emplacement age of erratic boulders and the total amount of pavement surface lowering at sites in northwest england since erratic emplacement at 17 9 ka the limestone pavement has been lowered by 22 45 cm average 33 10 cm assuming lowering was continuous although indicating some spatial heterogeneity the results contrast with earlier reported values based on the measurement of pedestal heights and inferred age for deglaciation we consider that changes in climate and the character and duration of regolith covers to have been important influences in promoting surface lowering it is argued that nivation chemical and mechanical snow related processes associated with several cool cold periods is likely to have played an important role in surface lowering complicating factors associated with surface lowering thickness and longevity of snow and regolith covers are identified but as yet cannot be quantified copyright 2012 john wiley sons ltd

depth and character of rock weathering across a basaltic hosted climosequence on hawai i using field observations and geochemical and digital terrain analyses we describe the structure and thickness of the regolith across a climosequence on the island of hawai i to gain insight into the relative roles of precipitation and the near surface hydrologic structure in determining weathering patterns in the wet portion of the climosequence where the long term water balance is positive the regolith thickness reaches an observed maximum of 40m and appears limited by the geomorphic base level of the landscape however even within this thick regolith distinct units of varying weathering intensity occur the vertical ordering of which largely reflects differences in the initial permeability structure of the basalt flows rather than a systematic decrease in weathering intensity downwards from the ground surface in the dry portion of the climosequence where the long term water balance is negative the regolith thickness is confined to 1m is highly dependent on the inferred permeability structure of the basalt flows and is independent of geomorphic base level weathering intensity also varies according to permeability structure and decreases in this thin regolith with distance beneath the ground surface the abrupt change in regolith depth and character that coincides with the transition from net positive to net negative long term water balance implies that small changes in precipitation rates around a neutral water balance result in large changes in the distribution and depth of weathering together our observations indicate that the distribution and depth of weathering in basalts and probably other lithologies might be best understood by considering how precipitation interacts with the complicated near surface permeability structure over regolith forming timescales to weather rock in the vadose zone 2013 john wiley sons ltd

the distinction between geomagnetic excursions and reversals summary two recent studies of the geomagnetic eld in the last 1 myr have found 14 excursions large changes in direction lasting 5 10 kyr each six of which are established as global phenomena by correlation between diierent sites the older picture of the geomagnetic eld enjoying long periods of stable polarity may not therefore be correct instead the eld appears to suier many dramatic changes in direction and concomitant reduction in intensity for 10 20 per cent of the time during excursions the eld may reverse in the liquid outer core which has timescales of 500 yr or less but not in the solid inner core where the eld must change by diiusion with a timescale of 3 kyr this timescale is consistent with the remarkably uniform duration of well dated excursions the disparity of dynamical timescales between the inner and outer cores a factor of 10 is consistent with the 10 excursions between full reversals

ultra rapid topographic surveying for complex environments the hand held mobile laser scanner hmls terrestrial laser scanning is the current technique of choice for acquiring high resolution topographic data at the site scale i e over tens to hundreds of metres for accurate volume measurements or process modelling however in regions of complex topography with multiple local horizons restricted lines of sight significantly hinder use of such tripod based instruments by requiring multiple setups to achieve full coverage of the area we demonstrate a novel hand held mobile laser scanning technique that offers particular promise for site scale topographic surveys of complex environments to carry out a survey the hand held mobile laser scanner hmls is walked across a site mapping around the surveyor continuously en route we assess the accuracy of hmls data by comparing survey results from an eroding coastal cliff site with those acquired by a state of the art terrestrial laser scanner tls and also with the results of a photo survey processed by structure from motion and multi view stereo sfm mvs algorithms hmls data are shown to have a root mean square rms difference to the benchmark tls data of 20 mm not dissimilar to that of the sfm mvs survey 18 mm the efficiency of the hmls system in complex terrain is demonstrated by acquiring topographic data covering 780 m2 of salt marsh gullies with a mean point spacing of 4 4 cm in approximately six minutes we estimate that hmls surveying of gullies is approximately 40 times faster than using a tls and six times faster than using sfm mvs 2013 the authors earth surface processes and landforms published by john wiley sons ltd

aeolian sand strip mobility and protodune development on a drying beach examining surface moisture and surface roughness patterns measured by terrestrial laser scanning ephemeral aeolian sand strips are commonplace on beaches their formation during high energy sand transport events often precedes the development of protodunes and their dynamics present interesting feedback mechanisms with surface moisture patterns however due to their temporary nature little is known of their formation mobility or the specifics of their interaction with beach surface characteristics similarly surface moisture has an important influence on sediment availability and transport in aeolian beach systems yet it is difficult to quantify accurately due to its inherent variability over both short spatial and temporal scales whilst soil moisture probes and remote sensing imagery techniques can quantify large changes well their resolution over mainly dry sand close to the aeolian transport threshold is not ideal particularly where moisture gradients close to the surface are large in this study we employed a terrestrial laser scanner to monitor beach surface moisture variability during a three and a half hour period after a rain event and investigated relationships between bedform development surface roughness and surface moisture our results demonstrate that as the beach surface dries sand transport increases with sediment erosion occurring at the wet dry surface boundary and deposition further downwind this dynamic structure dependent upon changing surface moisture characteristics results in the formation of a rippled sand strip and ultimately a protodune our findings highlight dynamic mobility relationships and confirm the need to consider transient bedforms and surface moisture across a variety of scales when measuring aeolian transport in beach settings the terrestrial laser scanner provides a suitable apparatus with which to accomplish this

equivalent monopole source of the geomagnetic south atlantic anomaly the south atlantic magnetic anomaly saa is an important feature of the present geomagnetic field in this paper we model the space time evolution of this anomaly over the past 400 years in terms of the resultant between a decrease of a global axial dipole and an increase of a virtual local monopole source certain characteristics of this evolution are investigated and some considerations are made in the light of a possible special state of the global geomagnetic field dynamical regime among the possible speculations one is made regarding the topography of the core mantle boundary cmb and its possible aspect beneath the saa region in terms of simple sinusoidal undulations met by the monopole source during its centennial motion

groundwater and river baseline quality using major trace elements organic carbon and sr pb o isotopes in a mediterranean catchment the case of the lower var valley south eastern france summary dissolved trace and major elements organic carbon and pb sr o isotopes have been investigated in surface and groundwater of the var river valley se france including alluvial conglomerate and limestone aquifers as well as surface water boxplots and cumulative frequency distribution diagrams define chemical characteristics of each water group and distinguish between natural and anthropogenic range of concentrations low concentration of trace elements statistical analysis of data and pb isotopic ratios demonstrate that the measured baseline quality is close to the natural background mainly influenced by water rock interaction pb and sr isotopes evidence specific primitive end members buffering these two elements through leaching late paleozoic rocks strongly depleted in u and rb since their formation arsenic undergoes geochemical processes such as sorption on clay minerals of the alluvial deposits sr isotopic ratios and high so 4 2 sr and li contents show that permo triassic sediments including evaporites strongly imprint surface waters and alluvial groundwaters limestone and conglomerate aquifers are mainly influenced by carbonate minerals but may be locally affected by evaporite dissolution high dissolved silica is also specific to conglomerate groundwaters limestone and conglomerate groundwaters are characterised by low and heterogeneous trace element compositions that may result from various residence times and rock compositions related to different sampling depth even if water quality is generally good for most of the investigated elements pollution by agricultural activity fertilisers and pesticides in the alluvial and some limestone groundwaters has been demonstrated by high no 3 and br contents br is suspected to originate from methyl bromide fertiliser in conglomerate aquifers no 3 contents may reach high levels probably due to both agriculture and residential waste pollution despite the industrialization in the low var valley no significant metallic contamination could be detected and therefore for trace elements given parameters min max and median values can be used as a baseline guide to detect future contamination

strontium in rainwater from israel sources isotopes and chemistry abstract eighteen rain samples from israel have been analyzed for their chemical composition and87sr 86sr ratios the sr isotopic ratios lie in the range 0 7078 and 0 7092 and the sr concentrations vary from 1 10 4 to 9 10 4 meq sr l soluble salts in rainwater are inherited from three major natural sources seaspray recent marine minerals and mineral dust eroded from rock outcrops and soil a mixing model is formulated to apply the chemical composition of rain cl and sr2 and its isotopic87sr 86sr ratio for the identification and estimation of the sr sources all the samples fall within the mixing space predicted by the model for the three end members mentioned above the data indicate that the most important non seaspray source contributing dissolved salts to the rains in israel comprises a mixture of senonian to eocene chalk and its weathering products and recent marine minerals from local and imported sources most of the samples 67 contain 50 or more non seaspray sr i e sr dissolved from dust or recent marine minerals whereas 56 of the samples display87sr 86sr ratios lower than 0 7090 the rest represent mixtures of seaspray and recent marine minerals

tracing the transport of anthropogenic lead in the atmosphere and in soils using isotopic ratios the isotopic composition of lead in aerosols and soils in israel is used to characterize the sources of anthropogenic lead in the region to ascertain the isotopic composition of natural rock derived lead in specific areas and to determine rates of anthropogenic lead migration in soils the isotopic composition of lead currently emitted from cars in israel 206pb207pb 1 115 2 is controlled by alkyl lead produced in france and germany in addition to petrol lead two more sources of anthropogenic lead can be detected in sampled aerosols the first one has low concentrations of lead 4 ng m3 and 206pb207pb 1 157 and is most likely lead emitted in turkey that traveled across the eastern mediterranean basin the second type of aerosols contains a mixture of lead emitted in several countries including turkey greece and ukraine 206pb207pb value of 1 155 1 160 pb 20 30 ng m3 anthropogenic lead is more accessible for acid leaching than natural lead therefore it is more labile in the soil the isotopic composition of lead in the acid leached fraction of near road soil profiles record the histor of alkyl lead emission in the country based on changes in the isotopic composition of lead with soil depth it is estimated that anthropogenic lead migrates into the soil at approximately 0 5 cm y a soil profile from a relatively remote area is less contaminated by anthropogenic lead and displays a different distribution of lead isotopic values with depth the isotopic composition of lead suggests that natural lead in soils developed on carbonate bedrock is derived from clays either from the rock esidue the clay fraction in the carbonate bedrock or from airborne clay but not from lead released from the carbonate fraction in the rock

technology and geomorphology are improvements in data collection techniques transforming geomorphic science in recent years technological developments have revolutionized our ability to collect data in geomorphology enhanced data collection not only enables us to provide deeper answers to a wider range of fundamental questions about the earth s surface but also encourages us to pose new questions this paper considers in more detail the relationships between science technology and the development of geomorphological tools and techniques reviews the spectrum of tools and techniques now available to geomorphologists and critically assesses what impact new technologies are having on geomorphology it focuses on the role of technology in biogeomorphology and weathering research and how it is advancing theoretical empirical and applied dimensions of these growing sub fields of geomorphology five areas of important technological development are reviewed remote sensing dating geophysical techniques field and laboratory based analysis and sensing of physical and chemical characteristics and field and laboratory based analysis of biological properties there is good evidence that taken together technological developments are revolutionizing geomorphology through opening the doors to better cross scalar investigations blurring the boundaries between laboratory field and computer model and facilitating cross disciplinary and democratized research

accuracy constraints of terrestrial lidar data for soil erosion measurement application to a mediterranean field plot abstract applications of terrestrial laser scanning tls to measure soil erosion are yet limited although this topographic mapping method allows for large area coverage with high resolution and reliable precision however restricting factors are accurate and stable references for multi temporal change detection and adverse scanning geometries at agricultural fields the plot is usually situated on gentle slopes provoking low viewing angles of the scanning device onto the surface which inherits the risk of high data noise in this study tls is exploited from a high tripod to measure soil erosion at an andalusian hillslope 2 1000 m2 in the mediterranean sediment yield reveals discontinuous pattern and tls is a promising method to quantify these surface changes a stable reference system is defined resulting in multi temporal registration accuracy better than 7 mm further an mm accurate calibration plot 60 m2 is designed to evaluate scan geometry and radiometry i e incidence angle footprint and intensity in dependence of distance related errors a lookup table is determined to correct systematic errors of the field data the andalusian field plot is captured during a winter season and during single precipitation events estimated erosion rates amount 10 and 2 4 t ha 1 respectively surface changes with magnitudes larger 1 5 cm are reliably measured tls can be implemented to estimate soil erosion with cm resolution if errors are carefully accounted for

use of isotope ratios to assess sources of pb and zn dispersed in the environment during mining and ore processing within the orlovka spokoinoe mining site russia element concentrations element ratios and pb and zn isotope data are reported for different geologic samples barren and ore bearing granites and host rocks technogenic products ore concentrates and tailings and biologic samples lichens and birch leaves from the orlovka spokoinoe mining district eastern transbaikalia russia with the aim to trace the sources of pb and zn at a local level within the mining site lichens and birch leaves were used as receptors of contamination within the mining site pb zr and zn zr values indicated pb and zn enrichment relative to host rocks zn isotope data of 15 geologic and 11 lichen samples showed different zn isotopic signatures with the total range for the geologic suite of 0 4 to 1 2 and for lichens of 0 4 to 1 4 in 66zn relative to lyon jmc zn standard the source of isotopically heavy zn within the orlovka spokoinoe mining site could be potentially associated with long range atmospheric aerosols that also contributed pb to the studied mining site our results demonstrated that zn isotopes might be used as new tools for zn source assessment

geochemistry and water dynamics ii trace metals and pb sr isotopes as tracers of water movements and erosion processes abstract a dynamic scheme for water movements over a flood in a small watershed was proposed in a previous paper ben othman d luck j m tournoud m g 1997 geochemistry and water dynamics application to short time scale flood phenomena in a small mediterranean catchment i alkalis alkali earths and sr isotopes chem geol 140 9 28 based on major alkali alkali earth trace elements and sr isotopes in the present paper metal contents and pb isotope data are reported for the same samples and compared to natural and anthropogenic local sources analysed for this purpose water treatment plants have stable 206 pb 204 pb but show relatively large 207 pb 204 pb variations presumably related to yet unidentified industrial pb sources some cu zn rich chemicals used extensively on vineyards have unradiogenic 206 pb 204 pb around 17 7 local rains sampled over two years show roughly similar low values pb from rocks is variable and more radiogenic 206 pb 204 pb 18 8 22 8 except for the first hours trace element concentrations in the dissolved load are similar to or slightly higher than those observed over the year and similar to other moderately anthropogenic areas shiller a m boyle e a 1987 variability of dissolved trace metals in the mississippi river geochim cosmochim acta 51 3273 3277 for pb 0 05 0 45 nm zn 10 75 nm and cd 0 03 0 18 nm dissolved u and co show simple variations correlated to carbonate related to local natural sources most trace elements in the particulate load are strongly correlated lead isotopes in the dissolved and particulate loads show ranges over the flood again similar to those observed over the year 206 pb 204 pb 17 9 18 3 implying the same sources the very good alignments observed in 207 pb 204 pb and 208 pb 204 pb vs 206 pb 204 pb diagrams especially for the particulate are interpreted as mixing phenomena generally pb isotopic signature of the dissolved load is less radiogenic than the particulate indicating differences in sources or proportions and absence of isotopic equilibration with respect to the time of transfer pb isotopes shift regularly with time away from the road runoff endmember towards more radiogenic values the strong negative correlation between pb isotopes in the particulate load and sr isotopes in the dissolved load observed for the first time in a small watershed probably reflects the local coupling between mechanical and chemical erosion respectively

pb and sr isotopic compositions of snowpack from quebec canada inferences on the sources and deposition budgets of atmospheric heavy metals elemental concentrations of al ba cd cu mg mn pb rb sr and zn as well as pb and sr isotopic compositions were determined in samples of snowpack obtained along two main transects from the province of quebec canada one north south between 47 n and 55 n 1994 and the other within the st lawrence valley 1997 median enrichment factors relative to upper crustal abundances for cd cu mn pb and zn for all samples range from 300 to 42 000 and are indicative of an anthropogenic origin pb isotope ratios for snow samples retrieved in 1994 are highly variable 206pb 207pb 1 148 to 1 193 and are characterized by the most radiogenic sr isotope values 87sr 86sr 0 710 in contrast the pb and sr isotope results for 1997 snow samples collected along the st lawrence valley below latitude 47 n yield the most radiogenic pb isotope ratios 206pb 207pb 1 180 to 1 190 and 87sr 86sr ratios between 0 708 and 0 710 the former indicate that the atmospheric pollution in this region of quebec is dominated by a mixture of anthropogenic emissions from u s 206pb 207pb 1 20 and canadian 206pb 207pb 1 15 sources pb isotope ratios 206pb 207pb 1 160 to 1 180 for 1997 samples collected north of latitude 47 n indicate input of an additional anthropogenic component possibly that of eurasian pollution being transported over the high arctic during the winter season a comparison of the pb isotope results between lichens and snow samples from identical sample locations indicate that these either overlap along st lawrence valley or are significantly different north south transect the latter discrepancy may be attributed to either 1 different time scales for the integration of the atmospheric signal months for snow vs years for lichens 2 recording of the atmospheric signal at substantially different altitudes or 3 the presence of an important local point source of atmospheric pollution annual depositional budgets have been estimated for pb cd zn cu and mn and average values g km 2 yr 1 are 1500 130 196 000 1900 and 6400 respectively compared to previous depositional fluxes 1993 1994 estimated from adjacent regions in north america those reported here are slightly lower with the exception of mn and zn the nondecrease in depositional fluxes of mn may be attributed to combustion of mn bearing fossil fuels by automotive vehicles the exact cause for the elevated annual depositional values for zn however remains enigmatic

visual dating of rockfall scars in larix decidua trees dating past mass wasting with growth disturbances in trees is widely used in geochronology as the approach may yield dates of past process activity with up to subannual precision past work commonly focused on the extraction of increment cores wedges or stem cross sections however sampling has been shown to be constrained by sampling permissions and the analysis of tree ring samples requires considerable temporal efforts to compensate for these shortcomings we explore the potential of visual inspection of wound appearance for dating purposes based on a data set of 217 wood penetrating wounds of known age inflicted to european larch larix decidua mill by rockfall activity we develop guidelines for the visual noninvasive dating of wounds including i the counting of bark rings ii a visual assessment of exposed wood and wound bark characteristics such as the color and weathering status of wounds and iii the relationship between wound age and tree diameter a characterization of wounds based on photographs randomly selected from the data set reveals that young wounds typically can be dated with high precision whereas dating errors gradually increase with increasing wound age while visual dating does not reach the precision of dendrochronological dating we clearly demonstrate that spatial patterns of and differences in rockfall activity can be reconstructed with both approaches the introduction of visual dating approaches will facilitate fieldwork especially in applied research assist the conventional interpretation of tree ring signals and allow the reconstruction of geomorphic processes with considerably fewer temporal and financial efforts

geomagnetic jerks as chaotic fluctuations of the earth s magnetic field 1 the geomagnetic field is chaotic and can be characterized by a mean exponential time scale after which it is no longer predictable it is also ergodic so time analyses can substitute the more difficult phase space analyses taking advantage of these two properties of the earth s magnetic field a scheme of processing global geomagnetic models in time is presented to estimate fluctuations of the time scale here considering that the capability to predict the geomagnetic field is reduced over periods of geomagnetic jerks we propose a method to detect these events over a long time span this approach considers that epochs characterized by relative minima of fluctuations in time scale i e those periods when a geomagnetic field is less predictable are possible jerk occurrence dates we analyze the last 400 years of the geomagnetic field covered by the gufm1 model to detect minima of fluctuations i e epochs characterized by low values of the time scale most of the well known jerks are confirmed through this method and a few others have been suggested finally we also identify some short periods when the field is less chaotic more predictable than usual naming these periods as steady state geomagnetic regime to underline their opposite behavior with respect to jerks

the role of rock surface hardness and internal moisture in tafoni development in sandstone the development of cavernous weathering features such as tafoni remains poorly understood in particular the roles played by internal moisture and case hardening remain unclear in this study electric resistivity tomography ert has been used to map moisture distribution within inner walls of tafoni developed in sandstone and an equotip device used to measure rock surface hardness as a proxy measure of the degree of weathering and case hardening seven large tafoni in the golden gate highlands national park south africa varying in size and degree of development have been monitored a dynamic relationship between surface hardness degree of weathering and internal moisture regimes has been found we propose a new conceptual model which illustrates the complex interaction between case hardening and internal moisture and suggests a new direction for cavernous weathering research copyright 2011 john wiley sons ltd

paleomagnetism and the nature of the geodynamo records of direct observations of the earth s magnetic field cover less than a ten millionth ofthe known lifetime of the field thus our knowledge of several geomagnetic phenomena critical to our understanding of the geodynamo must come firom the paleomagnetic record a combination of substantial advances during the past decade or so both in dynamo theory previously the domain of the mathematician and in paleomagnetism previously the domain of the geologist has led to provocative models of the earth s magnetic field and a better understanding of the geodynamo

information content and k entropy of the present geomagnetic field abstract concepts of information theory are applied to global models of the geomagnetic field b of the last century the temporal behavior of information content suggests that b is in a chaotic state with characteristic times close to those of its westward drift and of the convective overturn in the outer core and the secular variation shows a comparable characteristic time of predictability the main implication of these results is the suggestive hypothesis that a possible geomagnetic reversal or excursion is currently in progress

mechanism for geomagnetic polarity reversals recent studies of old magnetic observations1 and the seismic velocity of the lower mantle2 suggest that at least part of the geomagnetic secular variation is driven by temperature anomalies in the solid mantle3 in particular a patch of flux of opposite sign to that expected for a dipole field occurs beneath southern africa it has intensified throughout the twentieth century by a process that is believed to be flux expulsion associated with a particularly hot part of the lowermost mantle and is drifting westwards a similar patch lies beneath south america here i show that the present fall in the dipole moment is directly related to the intensification and southward movement of these patches and suggest the fall occasionally leads to polarity reversal the almost linear increase in the frequency of polarity reversals that has occurred since the cretaceous quiet interval is attributed to the growth of the hot patch of mantle presently under southern africa

dissolution rates of subsoil limestone in a doline on the akiyoshi dai plateau japan an approach from a weathering experiment hydrological observations and electrical resistivity tomography abstract this study aims at estimating the controlling factors for the denudation rates of limestone which often forms solution dolines on karst tablelands our approaches include 1 electrical resistivity tomography ert to reveal shallow subsurface structures and hydrological settings 2 automated monitoring of volumetric water content in soil profiles and manual measurements of subsurface co2 concentrations and soil water chemistry and 3 a field weathering experiment using limestone tablets with the micro weight loss technique for determining current denudation rates the field experiment and monitoring were carried out over 768 days from 2009 2011 at four sites with varying topographic and hydrological conditions along the sideslope of a doline on the akiyoshi dai karst plateau in sw japan the installation depths of the limestone tablets were 15 cm or 50 cm below the slope surface the soil moisture conditions varied site by site water saturated conditions continued for 40 50 of the whole experimental period at 50 cm depth of upper and middle sites while only 0 10 of the experimental period was water saturated at the other sites chemical analysis revealed that the soil water was chemically unsaturated with calcite for all the sites spatial differences in concentrations of co2 in soil pore air were statistically less significant the denudation rates of the buried limestone tablets were 17 7 21 9 mg cm 2 a 1 at the upper and middle slopes where the soil was water saturated for a long time after precipitation the lowest denudation of 3 9 mg cm 2 a 1 was observed on lower slopes where soil was not capable of maintaining water at a near saturation level even after precipitation statistical analysis revealed that the denudation rates of the tablets were strongly controlled by the duration for which soil pores were saturated by water the conditions defined here are degrees of water saturation greater than 97 electrical resistivity tomography indicated that areas with high soil moisture conditions were located at the deeper zone on the lower slopes and the bottom of the doline where denudation would be faster

landform characterization using geophysics recent advances applications and emerging tools abstract this paper presents an overview of the strengths and limitations of existing and emerging geophysical tools for landform studies the objectives are to discuss recent technical developments and to provide a review of relevant recent literature with a focus on propagating field methods with terrestrial applications for various methods in this category including ground penetrating radar gpr electrical resistivity er seismics and electromagnetic em induction the technical backgrounds are introduced followed by section on novel developments relevant to landform characterization for several decades gpr has been popular for characterization of the shallow subsurface and in particular sedimentary systems novel developments in gpr include the use of multi offset systems to improve signal to noise ratios and data collection efficiency amongst others and the increased use of 3d data multi electrode er systems have become popular in recent years as they allow for relatively fast and detailed mapping novel developments include time lapse monitoring of dynamic processes as well as the use of capacitively coupled systems for fast non invasive surveys em induction methods are especially popular for fast mapping of spatial variation but can also be used to obtain information on the vertical variation in subsurface electrical conductivity in recent years several examples of the use of plane wave em for characterization of landforms have been published seismic methods for landform characterization include seismic reflection and refraction techniques and the use of surface waves a recent development is the use of passive sensing approaches the use of multiple geophysical methods which can benefit from the sensitivity to different subsurface parameters is becoming more common strategies for coupled and joint inversion of complementary datasets will once more widely available benefit the geophysical study of landforms three cases studies are presented on the use of electrical and gpr methods for characterization of landforms in the range of meters to 100 s of meters in dimension in a study of polygonal patterned ground in the saginaw lowlands michigan usa electrical resistivity tomography was used to characterize differences in subsurface texture and water content associated with polygon swale topography also a sand filled thermokarst feature was identified using electrical resistivity data the second example is on the use of constant spread traversing cst for characterization of large scale glaciotectonic deformation in the ludington ridge michigan multiple cst surveys parallel to an 60 m high cliff where broad 100 m synclines and narrow clay rich anticlines are visible illustrated that at least one of the narrow structures extended inland a third case study discusses internal structures of an eolian dune on a coastal spit in new zealand both 35 and 200 mhz gpr data which clearly identified a paleosol and internal sedimentary structures of the dune were used to improve understanding of the development of the dune which may shed light on paleo wind directions

geochemistry of dissolved and suspended loads of the seine river france anthropogenic impact carbonate and silicate weathering this study focuses on the chemistry of the seine river system one of the major rivers in europe and constitutes the first geochemical investigation of both suspended and dissolved loads of this river the seine river drains a typical mesozoic cenozoic sedimentary basin the paris basin constituted of limestones mixed or interbedded with terrigenous sediments derived from the paleoreliefs bordering the mesozoic and cenozoic seas in the context of quantifying the global influence of carbonate and silicate weathering on atmospheric co2 consumption the seine river offers the possibility of examining weathering rates in a flat sedimentary environment under temperate climatic conditions one of the major problems associated with the seine river as with many temperate rivers is pollution we propose in this paper 2 approaches in order to correct the dissolved load of the seine river for anthropogenic inputs and to calculate weathering rates of carbonates and silicates the first uses the dissolved load of rivers and tries to allocate the different solutes to different sources a mixing model based on elemental ratios is established and solved by an inversion technique the second approach consists in using the suspended load geochemistry under steady state conditions we show that the geochemistry of suspended sediments makes it possible to estimate the amount of solutes released during the chemical weathering of silicates and thus to calculate weathering rates of silicates the total dissolved load of the seine river at paris can be decomposed into 2 of solutes derived from natural atmospheric sources 7 derived from anthropogenic atmospheric sources 6 derived from agriculture 3 derived from communal inputs and 82 of solutes derived from rock weathering during high floods the contribution of atmospheric and agriculture inputs predominates the weathering rate of carbonates is estimated to be 48 t km2 yr 25 mm 1000 yr only 10 of carbonates are transported in a solid form the rest being transported in solution co2 consumption by carbonate weathering approaches 400 103 mol km2 yr in the seine river at paris about 2 3 mg l of dissolved cations are found to originate from the chemical weathering of silicates by taking dissolved silica into accounts the total dissolved load derived from silicate weathering is about 6 7 mg l this value is minimal because biological uptake of silica probably occur in the seine river the chemical weathering rate of aluminosilicates is estimated to be 2 t km2 yr the ratio of physical over chemical weathering of silicates range between 1 and 3 and the total chemical and physical erosion rates of sedimentary silicates are about 2 3 mm kyr the co2 consumption by silicate weathering 15 24 103 mol km2 yr and is independent of dissolved silica concentration silicate consumption is thus 20 times less than carbonate consumption in the paris basin compared to the neighboring granitic areas the sedimentary region drained by the seine river has 2 to 3 times lower co2 consumption rates we attribute this difference to the cation depleted nature of the seine basin aluminosilicates which are of sedimentary origin at a world scale the chemical denudation rates found for the seine basin are very low and comparable to those given for tropical lowland rivers draining silicates such as the rivers of the congo and amazon basins in spite of huge climatic differences we attribute this similarity to the low mechanical denudation that characterizes these two types of regions

trends in publications in fluvial geomorphology over two decades a truly new era in the discipline owing to recent technological revolution abstract trends in the field of fluvial geomorphology have been reviewed by a number of authors who have emphasized the dramatic change occuring in the field in the last two decades of the twentieth century largely as a result of technological advances nevertheless no prior authors have systematically compiled data on publications in fluvial geomorphology over a long period and statistically analyzed the resulting data set in this contribution we present a quantitative analysis of fluvial geomorphology papers published in the twenty two year period 1987 2009 in five journals of the discipline with a more specific focus on geomorphology and earth surface processes and landforms espl identifying authorships geographic origin of authors and spatial and temporal scales covered we also documented the tools employed demonstrating the transformation of the field with the emergence of new tools over this period and conducted a cluster to highlight links between tools and a set of factors country of author s origin journals time and spatial and temporal scales of the 1717 papers published in the five journals during this period the results showed an increased diversity in the nationality of the first author mainly when dealing with present time scale and channel feature our data show a significant change in methods used in the field as a result of the increase in data availability and new sources of information from remote sensing ground airborne and satellite clearly a new era in knowledge production is observed since 2000 showing the emergence of a second period of active quantification and an internationalization of the fields

investigating a damaging buried sinkhole cluster in an urban area zaragoza city ne spain integrating multiple techniques geomorphological surveys dinsar dems gpr ert and trenching abstract this contribution analyses a complex sinkhole cluster buried by urban elements in the mantled evaporite karst of zaragoza city ne spain where active subsidence has caused significant economic losses 0 3 million euro the investigation conducted after the development of the area has involved the application of multiple surface and subsurface techniques a detailed map of modern surface deformation indicates two active coalescing sinkholes whereas the interpretation of old aerial photographs reveals the presence of two additional dormant sinkholes beneath human structures that might reactivate in the near future dinsar differential interferometry synthetic aperture radar displacement data have limited spatial coverage mainly due to high subsidence rates and surface changes re pavement and the electrical resistivity tomography ert and trenching investigations were severely restricted by the presence of urban elements nonetheless the three techniques consistently indicate that the area affected by subsidence is larger than that defined by surface deformation features the performance of the ground penetrating radar gpr technique was adversely affected by the presence of highly conductive and massive anthropogenic deposits but some profiles reveal that subsidence in the central sector of one of the sinkholes is mainly accommodated by sagging the stratigraphic and structural relationships observed in a trench dug across the topographic margin of one of the sinkholes may be alternatively interpreted by three collapse events of around 0 6 m that occurred after 290 yr bp or by progressive fault displacement combined with episodic anthropogenic excavation and fill average subsidence rates of 6 6 mm yr and 40 mm yr have been calculated using stratigraphic markers dated by the radiocarbon method and historical information respectively this case study illustrates the need of conducting thorough investigations in sinkhole areas during the pre planning stage including a geomorphic approach a sound geomorphic model is essential for the proper design of the site investigation the interpretation of the data and application of effective mitigation measures once sinkhole areas are developed urban elements largely restrict the applicability and performance of multiple techniques substantially decreasing the feasibility and benefit effort ratio of the investigations

small scale structure of the geodynamo inferred from oersted and magsat satellite data the geodynamo in the earth s liquid outer core produces a magnetic field that dominates the large and medium length scales of the magnetic field observed at the earth s surface1 2 here we use data from the currently operating danish oersted3 satellite and from the us magsat2 satellite that operated in 1979 80 to identify and interpret variations in the magnetic field over the past 20 years down to length scales previously inaccessible projected down to the surface of the earth s core we found these variations to be small below the pacific ocean and large at polar latitudes and in a region centred below southern africa the flow pattern at the surface of the core that we calculate to account for these changes is characterized by a westward flow concentrated in retrograde polar vortices and an asymmetric ring where prograde vortices are correlated with highs and retrograde vortices with lows in the historical 400 year average magnetic field4 5 this pattern is analogous to those seen in a large class of numerical dynamo simulations6 except for its longitudinal asymmetry if this asymmetric state was reached often in the past it might account for several persistent patterns observed in the palaeomagnetic field7 8 9 10 we postulate that it might also be a state in which the geodynamo operates before reversing

lead and its isotopes in the sediment of three sites on the lebanese coast identification of contamination sources and mobility abstract lead concentrations and isotopic composition of sediment samples collected from three sites within the lebanese coastal zones were measured at akkar dora and selaata akkar is located far from any direct source of contamination while dora and selaata receive urban and industrial wastes respectively low pb concentrations 6 16 g g 1 were detected in the akkar sediments and high concentrations of pb 70 101 g g 1 were detected in the dora sediments measuring stable isotope ratios of pb makes it possible to identify the principal sources of pb in the akkar sediments as pb emitted from gasoline combustion and pb originating from natural sources on the other hand pb stable isotopic ratios in dora sediments indicate that they are more highly influenced by anthropogenic sources isotopic pb ratios in the selaata deposits where pb concentrations range between 5 and 35 g g 1 have an exceptional radiogenic signature for marine sediments 1 25 60 after 24 h of extraction and that the extracted pb is less radiogenic than the residual pb

solubilities of al pb cu and zn in rain sampled in the marine environment over the north atlantic ocean and mediterranean sea chemical processes controlling the dissolved and particulate phase distribution of crustal al and noncrustal metals pb cu and zn appear to differ in marine precipitation sampled over the north atlantic ocean and mediterranean sea dissolved al appears to be in equilibrium with a trivalent al salt at rainwater ph 80 of the total pb cu and zn concentrations are delivered to the surface oceans in the dissolved form for a corresponding ph range al solubility varies from 60 over the wider observed ph range of 3 5 to 6 9 the solubilities of pb cu zn and al are highly variable the use of mean trace metal solubilities for the assessment of dissolved atmospheric trace metal wet deposition fluxes and their effects on surface ocean biogeochemistry should be constrained by taking into account rainwater ph in future estimates in global models

correlating river terrace remnants using an equotip hardness tester an example from the mino river northwestern iberian peninsula abstract this paper describes a new method to distinguish river terrace levels based on clast hardness and degree of weathering measured with an equotip hardness tester the technique was applied to a series of terraces on the mino river in the northwestern iberian peninsula where the lack of suitable material high degree of weathering and intense iron cementation precluded routine dating detailed mapping demonstrated that terrace sediments occupy a range of altitudes that make assignment to a specific terrace and or correlation between levels difficult statistical analysis of the equotip hardness data from quartzite clasts using k means clustering allowed four probable terrace levels to be identified a series of t tests generally supported these groupings a fifth lowermost terrace level was not included in the analysis because of limited exposure above a reservoir clast hardness and degree of terrace weathering were generally consistent with progressive river downcutting the occurrence of faulted sediments however suggested that terrace elevations were modified locally by post depositional tectonic movements which may explain why probable younger terraces in some sectors of the mino river are at higher elevations than older terraces in adjacent sectors the equotip tester helped to resolve stratigraphic uncertainties and to assign deposits to specific terrace levels and was found to be a useful tool to distinguish and correlate river terraces

contrasting weathering and climate regimes in forested and cleared sandstone temples of the angkor region comparative assessment of stone weathering intensities and bioclimatic conditions was conducted at four temples located in cleared and forested sites of the angkor park based on similar protocols four thousand sculpted lotus petals carved in the same grey sandstone were categorized by using two customized scales of weathering intensity and climate monitoring was conducted from december 2008 to november 2009 whereas 70 of the sandstone lotus petals are almost completely destroyed by mechanical weathering in cleared areas 74 of petals located in forested environments appear to be totally free of mechanical weathering and are only affected by superficial biochemical weathering ambient conditions are also contrasting with the magnitude of the diurnal surface temperature and relative humidity ranges being three times higher at cleared sites than in wooded areas as wetting drying cycles are the driving force of sandstone decay at angkor causal links are suggested between weathering and climate regimes in wooded areas the microclimate is buffered by the forest and the associated lithobionts which maintain constant humidity levels reduce thermal stresses at the stone surface and induce a slow biochemical weathering regime in cleared areas direct exposure to sunshine and monsoon rains induces pronounced wetting drying cycles conducive to swelling shrinking movements and other potential processes provoking the rapid mechanical decay of the sandstone even if local damage can be caused by tree roots the forest cover and the associated lithobionts obviously play an overall protective role additionally microtopographical factors related to architectural designs and post building events probably explain intra site and between site minor differences in the amount of sandstone decay by influencing key factors such as the water residence time at the stone surface last the contrasting weathering regimes in forested and cleared sites are but a trend for besides overwhelming mechanical weathering chemical weathering is also operative at cleared sites as indicated by salt efflorescences and ferric oxidation copyright 2012 john wiley sons ltd

investigations into the relationship between changes in internal moisture regimes and rock surface deterioration in cavernous sandstone features cavernous features commonly develop in sandstone but their development over time remains enigmatic it has been suggested that moisture movements within the rock mass play a key role in the location development and dynamics of cavernous features in this research the role of internal moisture movement is tested through monitoring moisture and surface deterioration dynamics in april 2008 and april 2009 within two large cavernous features mega tafoni in the golden gate highlands national park south africa gghnp data are presented from surveys of internal moisture using electrical resistivity tomography ert surface moisture using a protimeter and deterioration using surface hardness as recorded with an equotip as a proxy for surface deterioration across five 2 45 m long transects in addition a high resolution temperature record is presented to assess the influence of micro climates within the caverns the results indicate consistency in the gross spatial pattern of moisture flow within the rock mass over a one year period but significant changes in mean moisture contents and in the fine detail of moisture patterning some noticeably weakened areas had developed within the central parts of the cavernous features often linked to wetter subsurface conditions supporting the theory that core softening is a main driver of cavernous feature formation however in some areas surface hardening is also found to be associated with wetter subsurface conditions supporting the theory that case hardening is a main driver of cavernous feature formation in addition the presence of well established biofilms suggests an even more complex interaction between moisture surface development and biological activity a model is presented therefore which integrates this paradox by proposing a non linear relationship between moisture dynamics facilitation of biofilm formation and deterioration within cavernous features

asian provenance of glacial dust stage 2 in the greenland ice sheet project 2 ice core summit greenland samples of dust from the greenland ice sheet project 2 gisp2 ice core summit greenland dated within marine isotope stage 2 between 23 340 and 26 180 calendar years b p around the time of the coldest local last glacial temperatures have been analyzed to determine their provenance to accomplish this we have compared them with approximately coeval aeolian sediments mostly loesses sampled in possible source areas psas from around the northern hemisphere the 5 m grain size fraction of these samples was analyzed on the basis that it corresponds to the atmospheric dust component of that time and locale which was sufficiently fine grained to be transported over long distances on the basis of comparison of the clay mineralogy and sr nd and pb isotope composition with ice dust and psas and assuming that we have sampled the most important psas we have determined that the probable source area of these gisp2 dusts was in eastern asia the dust was not derived from either the midcontinental united states or the sahara two more proximal areas that have been suggested as potential sources based on atmospheric circulation modeling except for a brief period during an interstadial when dust transport was exceptionally low for glacial times and had a mineralogical composition indicative of a slightly more southern provenance the source area of the dust did not change significantly during times of variably higher fluxes of dust with larger mean grain size or lower fluxes of dust with smaller mean grain size this includes the high dust period that correlates with the heinrich 2 period of major iceberg discharge into the north atlantic variable wind strengths must therefore be invoked to account for these abrupt and significant changes in dust flux and grain size

quantifying the rate and depth dependence of bioturbation based on optically stimulated luminescence osl dates and meteoric 10be both the rate and the vertical distribution of soil disturbance modify soil properties such as porosity particle size chemical composition and age structure all of which play an important role in a soil s biogeochemical functioning whereas rates of mixing have been previously quantified the nature of bioturbation s depth dependence remains poorly constrained here we constrain for the first time the relationship between mixing rate and depth in a bioturbated soil in northeast queensland australia using a novel method combining osl optically stimulated luminescence ages and meteoric beryllium 10 10be inventories we find that the best fit mixing rate decreases non linearly with increasing soil depth in this soil and the characteristic length scale of 0 28 m over which the mixing coefficient decays is comparable to reported rooting depth coefficients in addition we show that estimates of surface mixing rates from osl data are highly dependent on erosion rate and that erosion rate must be constrained if accurate mixing rates are to be quantified we calculate surface diffusion like mixing coefficients of 1 8 10 4 and 2 1 10 4 m2 yr 1 for the studied soil for two different estimates of soil erosion 2014 the authors earth surface processes and landforms published by john wiley sons ltd

characteristics of beaver ponds on deltas in a mountain environment many beaver ponds in the rocky mountains that have been described in the literature are in channel ponds that are relatively small and short lived this paper describes floodplain beaver ponds on low gradient deltas in glacial finger lakes in glacier national park montana these ponds are distinctly larger probably fed by hyporheic flow and stable and long lived ponds examined were with one exception 44 years old glacial discharge is present in each valley where beaver ponds occupy low gradient deltas and this discharge likely sustains pond water level over the course of the summer as glaciers recede and disappear deltaic beaver ponds dependent on hyporheic flow may be negatively affected copyright 2012 john wiley sons ltd

time variations of the earth s magnetic field from daily to secular variations in time of the earth s natural magnetic field have a frightfully wide spectrum ranging over more than 20 orders of magnitude they extend from well over 103 hz where they merge into the radioelectric noise spectrum to probably more than 100 m y in rough summary the higher frequencies stem from external sources in the ionosphere and above into the magnetosphere whereas the longer periods arise from internal sources primarily fluid motions in the core at depths in excess of 2900 km methods for separating external and internal signals have been available since the time of gauss 1 838 but the accuracy the space distribution and the time duration of available data are often not sufficient to unambiguously solve the problem for all types of variations although periods shorter than 1 yr should clearly be assigned to external sources the extent to which the spectra of the external and internal parts overlap is the subject of recent debate and progress currie 1966 1 968 proposed that there was little overlap and a cutoff of 3 7 yr a long debated l l yr contribution due to the solar cycle was clearly demonstrated by currie 1973a courtillot le mouei 1976a b and alldredge 1976 and the cutoff period was thus rejected to at least 20 yr the situation seemed to be confused again when courtillot et al 1978a provided evidence for sharp impulses of 1 yr duration i n the internal so called secular variation the debate that followed over the reality of brief internal events is one of the topics addressed in this review we first provide a short historical account of successive discoveries

expansion rate and geometry of floating vegetation mats on the margins of thermokarst lakes northern seward peninsula alaska usa investigations on the northern seward peninsula in alaska identified zones of recent 50 years permafrost collapse that led to the formation of floating vegetation mats along thermokarst lake margins the occurrence of floating vegetation mat features indicates rapid degradation of near surface permafrost and lake expansion this paper reports on the recent expansion of these collapse features and their geometry is determined using geophysical and remote sensing measurements the vegetation mats were observed to have an average thickness of 0 57 m and petrophysical modeling indicated that gas content of 1 5 5 enabled floatation above the lake surface furthermore geophysical investigation provides evidence that the mats form by thaw and subsidence of the underlying permafrost rather than terrestrialization the temperature of the water below a vegetation mat was observed to remain above freezing late in the winter analysis of satellite and aerial imagery indicates that these features have expanded at maximum rates of 1 2 m yr 1 over a 56 year period including the spatial coverage of floating thermokarst mats increases estimates of lake area by as much as 4 in some lakes copyright 2011 john wiley sons ltd

transformative geomorphic research using laboratory experimentation abstract laboratory experiments in geomorphology is the theme of the 46th annual binghamton geomorphology symposium bgs while geomorphic research historically has been dominated by field based endeavors laboratory experimentation has emerged as an important methodological approach to study these phenomena employed primarily to address issues related to scale and the analytical treatment of the geomorphic processes geomorphic laboratory experiments can result in transformative research several examples drawn from the fluvial and aeolian research communities are offered as testament to this statement and these select transformative endeavors often share very similar attributes the 46th bgs will focus on eight broad themes within laboratory experimentation and a diverse group of scientists has been assembled to speak authoritatively on these topics featuring several high profile projects worldwide this special issue of the journal geomorphology represents a collection of the papers written in support of this symposium

a multi method investigation of temperature moisture and salt dynamics in tafoni tafraoute morocco despite numerous investigations and theoretical models tafoni weathering is still not fully understood largely because of limited data available on temperature moisture and salt regimes we investigated tafoni developed in granite in the tafraoute region morocco through an exploratory two week multi method field campaign temperatures were measured with ibuttons and by means of infrared thermography moisture distribution and progress were captured with handheld moisture sensors and with drilled in ibuttons salts were analysed in drill dust samples from different positions and rock depths the results derived from very different techniques mutually support one another salts and moisture are concentrated near the base of the investigated tafoni probably due to a saturated pore water body around the base of rock tors salts are accumulated close to the rock surface in tafoni but not on the surrounding rock surfaces a clear correlation was found between moisture and salt contents within a tafone areas of higher humidity also display increased salt concentration near the surface the temperature humidity records allied with ionic analyses suggest that sodium sulfate dominates and is likely to undergo frequent phase changes from thenardite to mirabilite and vice versa two pathways of salt transport in and around tafoni are assumed based on the data infiltration with rainfall on the top and around tors and boulders and capillary rise from saturated pore water bodies to the surface copyright 2015 john wiley sons ltd

geochemistry and water dynamics application to short time scale flood phenomena in a small mediterranean catchment we report major trace elements and sr isotope data for water samples taken regularly during a four day long september flood of a mediterranean river the vene herault s france the objective is to combine all these data into a dynamic model that describes the origin s and movements of waters and their loads this river drains the runoff from a small mainly carbonate partly karstified watershed with miocene and jurassic lithologies the watershed is also impacted by both agricultural and urban activities both the dissolved and the particulate loads were analyzed concentrations of the dissolved components show major remobilization of almost all elements during the first few hours of the flood water treatment plants and aerosol scavenging followed by a sharp concentration decrease some major species return to their previous summer values ca hco3 while others reach low background levels na k cl s04 some trace elements rb sr cs show similar behaviour but ba appears somewhat unaffected trace element concentrations and ratios define two main periods three in the suspended particulate matter ratios do not allow distinguishing between the three main sources for the dissolved load in the first period miocene jurassic water treatment plants but clearly show the jurassic karst influence later on the 87sr 86sr of the suspended particulate matter is more variable and more radiogenic than in the dissolved phase variations in concentration ratios and sr isotope composition in particulates indicate the large and variable contribution of miocene silicates with some carbonate however there is a need for another component with rb sr higher than bedrocks internal or external to the watershed possibly due to differential erosion dissolved ca and mg fluxes during the flood were calculated at 0 26 ton and 0 029 ton km2 respectively even though the carbonate nature of the watershed restricts variability in sr isotope composition in the dissolved load we distinguish several endmembers seawater marine rain miocene marls jurassic limestones water treatment plants and possibly another attributable to fertilizers combined with major and trace element variations sr isotope fluctuations indicate time varying proportions of different water endmembers at the outflow and suggest a general dynamic model based on pca principal component analysis a 3d representation allows to visualize the geochemical evolution of the vene waters in particular sr isotopes clearly indicate that the inflow of karstic waters during the flood was not continuous but occurred as a series of marked oscillations between flowing waters with chemical signature of miocene lithologies and increasing flushes of deeper waters that interacted with jurassic lithologies

arctic rockwall retreat rates estimated using laboratory calibrated ert measurements of talus cones in longyeardalen svalbard holocene rockwall retreat rates quantify integral values of rock slope erosion and talus cone evolution here we investigate holocene rockwall retreat of exposed arctic sandstone cliffs in longyear

how persistent is the present trend of the geomagnetic field to decay and possibly to reverse abstract recent studies provide evidence for a possible imminent change of polarity or an excursion of the geomagnetic field in this paper we explore the possibility that the present trends are persistent looking at the behaviour of some physical quantities of the recent geomagnetic field with particular attention to the last century analysis of the mean square value of the field over the last 400 years shows a linear decay that if extrapolated will be zero in around 1000 years while if we extrapolate the field over antarctica it will go to zero in around 300 years the information content of the geomagnetic field has been decaying from around 1690 but began to decrease more rapidly at around 1775 and even more rapidly after 1900 an intermittent synchronicity between the exponential field decay and the increase latitudinal speed of the south geomagnetic pole with similar decaying or growing timescales can be interpreted as evidence for a present persistent turbulence of the geomagnetic field from this work it emerges that the present situation is likely to persist further into the future probably for another century but longer predictions are not possible

ergodicity of the recent geomagnetic field the geomagnetic field is a fundamental property of our planet its study would allow us to understand those processes of earth s interior which act in its outer core and produce the main field knowledge of whether the field is ergodic i e whether time averages correspond to phase space averages is an important question since if this were true it would point out a strong spatio temporal coupling amongst the components of the dynamical system behind the present geomagnetic field generation another consequence would be that many computations usually undertaken with many difficulties in the phase space can be made in the conventional time domain we analyse the temporal behaviour of the deviation between predictive and definitive geomagnetic global models for successive intervals from 1965 to 2010 finding a similar exponential growth with time also going back in time at around 1600 and 1900 by using the gufm1 model confirms the same findings this result corroborates previous chaotic analyses made in a reconstructed phase space from geomagnetic observatory time series confirming the chaotic character of the recent geomagnetic field with no reliable prediction after around 6 years from definitive values and disclosing the potentiality of estimating important entropic quantities of the field by time averages although more tests will be necessary some of our analyses confirm the efforts to improve the representation of the geomagnetic field with more detailed secular variation and acceleration

the use of the schmidt hammer and equotip for rock hardness assessment in geomorphology and heritage science a comparative analysis rapid field based measurements of rock hardness are of use in investigating many geomorphological and heritage science problems several different methods are now available for taking such measurements but little work has been done to assess their comparability and strengths and weaknesses we review here the capabilities of two types of schmidt hammer classic n type and silver schmidt bl type alongside two types of equotip standard type d and piccolo for investigating rock hardness in relation to rock weathering on various types of sandstone and limestone as well as basalt and dolerite whilst the two schmidt hammers and the two equotips show comparable results when tested at 15 individual sites interesting differences are found between the equotip and schmidt hammer values which may reveal information about the nature of weathering on different surfaces operator variance is shown to be an issue in particular for the equotip devices which also exhibit higher variability in measurements and necessitate larger sample sizes carborundum pre treatment also has varying effects on the data collected depending on the nature of the surface studied the equotip devices are shown to be particularly useful on smaller blocks and in situations where edge effects may affect schmidt hammer readings we conclude that whilst each device contributes to geomorphological research they do not necessarily produce comparable information indeed using schmidt hammer and equotip in combination and looking at any differences in results may provide invaluable insights into the structure of the near surface zones and the nature of weathering processes copyright 2010 john wiley sons ltd

connection between south mediterranean climate and north african atmospheric circulation during the last 50 000 yr bp north atlantic cold events abstract high resolution clay mineralogical analyses were performed on sediment deposited during the last 50 000 yr in the alboran sea odp site 976 the clay mineral record is compared with pollen assemblages and with annual precipitation pann and mean temperatures of the coldest month mtco reconstructed with the modern analog technique mat enhanced contribution of palygorskite a typical wind blown clay mineral characterizes the north atlantic cold climatic events coeval development of the semi arid vegetation artemisia rich associated with a drastic fall of reconstructed precipitations and temperatures suggest cold and arid continental conditions in the west mediterranean area during north atlantic cold events the clay mineral association especially the palygorskite content and the illite to kaolinite ratio indicate western morocco as one of the major source of the clay size fraction during the north atlantic cold events the maximum abundance of artemisia associated with the presence of argania pollen both indicate morocco as the main origin for pollen during these cold periods the comparison of these pollen and clay mineral specific features allows us to pinpoint western morocco as the dominant source of wind blown particles during north atlantic cold events these specific mineralogical composition and palynological assemblages reveal enhanced aridity over north africa and intensification of winds favouring dust erosion and transport from north africa toward the alboran sea during the north atlantic cold events according to atmospheric models such a meridian transport 1 likely results from the development of strong and stable anticyclonic conditions over the tropical atlantic and north africa similar to today s summer meteorological configuration and 2 implies a northward position of the westerly winds during north atlantic cold events finally the synoptic situation over the west mediterranean during the north atlantic cold events is compared with the north atlantic oscillation nao suggesting that during the cold atlantic events weather regimes over europe and north africa may have been systematically shifted towards a positive nao situation

confirming geomorphological interpretations based on portable osl reader data portable optically stimulated luminescence osl readers are increasingly being used in geomorphological and archaeological investigations but information regarding data reproducibility and the reliability of interpretations based on portable osl reader data has not yet been presented to the wider geomorphological community this letter addresses these two issues by returning to grabben gullen creek in the southeastern australian tablelands where we remeasure a sediment profile that was first measured by other researchers 3 years earlier we also compare portable osl reader data measured on sediment interpreted to have been deposited in swampy meadow wetlands and flood alluvium settings with data measured on known swampy meadow and flood deposits our data show that portable osl reader data are reproducible moreover we confirm the earlier interpretation that stratigraphies commonly exposed in southeastern australian tablelands valley bottoms reflect pre european swampy meadow wetlands and flood alluvium copyright 2015 john wiley sons ltd

log jams and avulsions in the san antonio river delta texas the san antonio river delta sard texas has experienced two major avulsions in the past 80 years and a number of other historical and holocene channel shifts the causes and consequences of these avulsions one of which is ongoing were examined using a combination of fieldwork geographic information system gis analysis and historical information to identify active semi active and paleochannels and the sequence of shifting flow paths through the delta the role of deposition patterns and antecedent morphology large woody debris jams and tectonic influences were given special attention sedimentation in the sard is exacerbated by tectonic effects channel aggradation is ubiquitous and superelevation of the channel bed above the level of backswamp areas on the floodplain is common this creates ideal setup conditions for avulsions and stable cohesive fine grained banks favor avulsions rather than lateral migration flood basins between the alluvial ridges associated with the aggraded channels exist but avulsions occur by re occupation of former channels found within or connected to the flood basins large woody debris and channel blocking log jams are common and sometimes displace flow from the channel triggering crevasses however a large recurring log jam at the site of the ongoing avulsion from the san antonio river into elm bayou is not responsible for the channel shift rather narrow laterally stable channels resulting from flow splits lead to accumulation of wood some aspects of the sard avulsion regime are typical of other deltas while others are more novel these includes avulsions involving tributaries and subchannels within the delta as well as from the dominant channel tectonic influences on delta backstepping and on channel changes within the delta avulsions as an indirect trigger for log jam formation as well as vice versa and maintenance of a multi channel flow pattern distinct from classic anastamosing or distributary systems copyright 2012 john wiley sons ltd

comparison of electronic and mechanical schmidt hammers in the context of exposure age dating are q and r values interconvertible application of schmidt hammer exposure age dating shd to landforms has substantially increased in recent years the original mechanical schmidt hammer records r rebound values although the newly introduced electronic schmidt hammer silverschmidt facilitates greatly improved data processing it measures surface hardness differently recording q velocity values that are not a priori interconvertible with r values this study is the first to compare the performance of both instruments in the context of field based exposure age dating with a particular focus on the interconvertibility of r values and q values the study was conducted on glacially polished pyroxene granulite gneiss jotunheimen southern norway results indicate that mean q values are consistently 8 10 units higher than mean r values over the range of values normally encountered in the application of shd to glacial and periglacial landforms a convenient conversion factor of 10 units may therefore be appropriate for all but the softest rock types close to the technical resolution of the instruments the electronic schmidt hammer should therefore be regarded as a useful complement and potential replacement for the mechanical schmidt hammer conversion of published r values data to q values requires however careful control and documentation of instrument calibration copyright 2014 john wiley sons ltd

trace element and pb isotope variability during rainy events in the nw mediterranean constraints on anthropogenic and natural sources abstract rain samples collected over the period 1995 1999 on the french mediterranean coast have been analyzed for their trace elements and pb isotopic compositions both in the dissolved and particulate loads our results show that metal enrichment factors ef relative to upper erodable crust are high for cu pb zn and cd and comparable to values reported about 10 years ago for north western mediterranean rains overall unradiogenic pb isotopic compositions indicate the still visible influence of french gasoline lead on both dissolved and particulate loads this influence is also seen on aerosols although more variable the examination of air mass trajectories allows us to distinguih the pb isotopic signatures of main sources in particular marseille north italy north africa rains collected and analyzed sequentially show intra rain variations for metal contents metal ef and pb isotopes which may also be related to the main paths and altitudes of the air masses metal efs and pb isotopic data on rains from southern france in the late 1990s are similar to recent data published on french aerosols or sediments which are interpreted as reflecting the phasing out of leaded gasoline in the atmosphere