multiple charcoal profiles in a scottish lake taphonomy fire ecology human impact and inference abstract sedimentary microscopic charcoal in lacustrine environments has received much attention although this has been concerned largely with the deposition of modern charcoal or with distributions through time based on single profiles lake sediments are dynamic entities however and the phenomenon of sediment focusing for example will lead to the redistribution of pollen spores and charcoal the process may not always result in greatly altered fossil assemblage in percentage terms but values for individual indicators or their absolute values may be affected strongly this is investigated using multiple microscopic charcoal profiles covering many thousands of years from black loch fife eastern scotland relative and absolute measures of charcoal depiction are considered as a prelude to discussion of microscopic charcoal taphonomy in the context of a small lake fire ecology and human impacts the charcoal measures concentrations influx and charcoal to pollen ratios all follow similar patterns though with very different numerical values two cores have charcoal influx values of similar orders of magnitude for much of the holocene whereas quantities in two other cores vary by a factor of 16 after 1000 cal bp the differences between influx measures for total pollen and charcoal indicate that focusing effects between the two indicators are dissimilar correlations with pollen and spore taxa are explored and demonstrate the problems of discrepant data between profiles charcoal pollen patterns for specific cultural periods are examined for one profile and they provide data suggesting that a direct fire vegetation relationship for the site is unproven the need to adopt a multi causal approach to inference is emphasised

electromagnetic images of modern and ancient subduction zones abstract one question frequently posed since the advent of plate tectonic theory is when did it begin correlations of zones of enhanced electrical conductivity with orogenic belts dated to half the age of the earth support the suggestion that plate tectonic processes have been in operation since at least the early proterozoic the causes for such zones are examined and whereas anomalies associated with modern and recent subduction collision systems can be readily explained an explanation for palaeozoic and proterozoic ones is more difficult correlation of geophysical characteristics associated with the trans hudson north america and svecofennian fen noscandia orogenic zones and consideration of the paleopole positions of those zones and the superior and slave provinces during the period 1 900 1 825 ga lead to the suggestion that a pan scandamerican orogenic zone was in existence at that time

succession of arboreal taxa during the late glacial in south eastern poland climatic implications abstract this paper presents and discusses vegetation changes between ca 14 910 and 11 620 cal bp which are recorded in the deposits of a small mire located in south eastern poland particular attention is paid to arboreal taxa changes in arboreal vegetation are reconstructed on the basis of pollen analysis including pollen accumulation rate par and analysis of plant macrofossils these being supported by radiocarbon chronology before the onset of the gi 1 warming 14 910 310 14 810 280 cal bp a mosaic of pinus and betula wood patches and or isolated stands of trees along with heliophilous juniperus thickets were dispersed within patches of herb steppe and tundra communities thermal amelioration at the gs 2 gi 1 transition ca 14 810 280 14 510 200 cal bp led to the spread of salix and to a lesser extent of tree birches betula pines pinus and hippophae rhamnoides in the light of par values from ca 14 550 210 cal bp there were open pine birch woodlands there which ca 14 270 160 cal bp turned into dense forests cold oscillations such as gi 1d gi 1c2 and gi 1b dated in the profile at ca 14 190 120 13 870 140 13 740 120 13 490 80 and 13 120 12 870 60 cal bp respectively are visible as declines in the par of arboreal taxa from ca 13 770 120 cal bp picea abies whose nearest glacial refugia were located in the western carpathians probably reached the site surroundings 50 n in the younger dryas gs 1 climate deterioration caused a decline in birch population in the first phase a slight retreat of forests and the simultaneous expansion of artemisia poaceae steppe communities and juniperus thickets the par values reflect a division of the younger dryas into two distinct phases an older phase more severe for tree populations probably due to longer and cooler winters and a younger phase with milder winters which begun ca 11 960 110 cal bp

petrogenesis of the late cretaceous northern alberta kimberlite province abstract at present 48 late cretaceous ca 70 88 ma kimberlitic pipes have been discovered in three separate areas of the northern alberta the mountain lake cluster the buffalo head hills field and the birch mountains field the regions can be distinguished from one another by their non archetypal kimberlite signature mountain lake or in the case of kimberlite fields primitive buffalo head hills to evolved birch mountains magmatic signatures the dominant process of magmatic differentiation is crystal fractionation and accumulation of olivine which acts as the main criteria to distinguish between primitive and evolved group i type kimberlite fields in the northern alberta this is important from the viewpoint of diamond exploration because the majority about 80 of the more primitive buffalo head hills kimberlites are diamondiferous whereas the more evolved birch mountains pipes are barren of diamonds for the most part petrographically the buffalo head hills samples are distinct from the birch mountains samples in that they contain less carbonate have a smaller modal abundance of late stage minerals such as phlogopite and ilmenite and have a higher amount of fresh coarse macrocrystal 0 5 mm olivine consequently samples from the buffalo head hills have the highest values of mgo cr and ni and have chemistries similar to those of primitive hypabyssal kimberlite in the northwest territories based on whole rock isotopic data the buffalo head hills k6 kimberlite has 87sr 86sr and end values similar to those of south african group i kimberlites whereas the birch mountains legend and phoenix kimberlites have similar end values between 0 and 1 9 but distinctly higher 87sr 86sr values 0 7051 0 7063 the lack of whole rock geochemical overlap between kimberlite and the freshest least contaminated mountain lake south pipe rocks reflects significant mineralogical differences and mountain lake is similar geochemically to olivine alkali basalt and or basanite intra field geochemical variations are also evident the k4 pipe buffalo head hills and xena and kendu pipes birch mountains are characterized by anomalous concentrations of incompatible elements relative to other northern alberta kimberlite pipes including chondrite normalized rare earth element distribution patterns that are less fractionated than the other kimberlite samples from the buffalo head hills and birch mountains the xena pipe has similar major element chemical signatures and high al clinopyroxene similar to or trending towards the mountain lake pipes in addition k4 and kendu have higher 87sr 86sr and lower end than bulk earth and plot in the bottom right quadrant of the nd sr diagram we suggest therefore that the k4 and kendu pipes contain a contribution from old lree enriched low sm nd lithosphere that is absent from the other kimberlites are affected by crustal contamination or both based on xenocryst populations the northern alberta kimberlite province mantle is dominated by carbonate saturated lherzolitic mantle higher levels of melt depletion characterize the buffalo head hills mantle sample despite high diamondiferous to barren pipe ratios in the buffalo head hills pipes mineral indicators of high diamond potential such as g10 garnet diamond inclusion composition chrome spinels and high sodium eclogitic garnet are rare

area selection for diamond exploration using deep probing electromagnetic surveying abstract previously proposed methods of area selection for diamond prospective regions have predominantly relied on till geochemistry airborne geophysics and or an appraisal of tectonic setting herein we suggest that a novel deep probing geophysical technique electromagnetic studies using the natural source magnetotelluric mt method can contribute to such an activity essentially diamondiferous regions must have 1 old lithosphere 2 thick lithosphere and 3 lithosphere that contains high concentrations of carbon deep probing mt studies are able to address all three of these the second and the third of these can be accomplished independently using mt but for the first the geometries produced from modelling the mt observations must be interpreted with appropriate interaction with geologists geochemists and other geophysicists examples are given from the slave and superior cratons in north america with a brief mention of an area of the rae craton and general speculations about possible diamondiferous regions

geophysical characterization of the azimuth 125 lineament with aeromagnetic data contributions to the geology of central brazil abstract this study analyzes a portion of the azimuth 125 lineament az 125 located in the brazilian states of goias and minas gerais based on its magnetic signature and previous studies in particular the determination of a chronology of events that shaped the az 125 lineament is the focus of this contribution geological provinces with highly economically valuable mineralizations occur along az 125 including the most important carbonatite and kimberlite complexes in brazil az 125 is the main structural feature associated with these complexes consisting of an extensive set of nw se oriented faults approximately 850 km long and 70 km wide however it is not mapped on geological maps at a regional scale as a continuous structural feature because it is not consistently visible on the surface or in satellite images magnetic signature characterizes the lineament as a set of linear features with regional continuity in the subsurface it is characterized by a higher magnetic susceptibility response that contrasts with the response exhibited by surrounding host rocks field data support geophysical data occasional outcrops resulting from active erosion reveal dikes formed by gabbroic rocks and diabase and define the az 125 lineament as a set of dikes of different ages other magnetic anomalies that occur along az 125 are associated with intrusive rocks from the goias and alto paranaiba alkaline provinces based on magnetic signatures and mapped igneous rocks chronology the az 125 is partitioned within the study area into three main systems called l1 l2 and l3 this subdivision in conjunction with the dates assigned to various basic dikes within the azimuth reveals that the evolution of the azimuth can be associated with three events the first event occurred during the brasiliano 950 520 ma the second event occurred during the gondwana fragmentation starting circa 180 ma the third event is related to the tectonomagmatic activity of the trindade plume 90 80 ma we posit that the l1 system includes the older dikes and the l3 system includes the youngest dikes the l2 system which is intersected by l3 is therefore of intermediate age the determination of a chronology of events that characterizes the segmented structure of the az 125 lineament here defined as l systems l1 l2 and l3 based on both geological and geophysical data and not yet reported in earlier scientific articles is the main contribution of this study

spatiotemporal heterogeneity of the palaeoecological record in a large temperate palaeolake sur southwest slovakia comparison of pollen macrofossil and geochemical data abstract aquatic macrophytes living within shallow lakes are particularly sensitive to climate change and fluctuations in water depth in the dabubian lowland of southwestern slovakia sediments from the large shallow palaeolake named sur provide a unique opportunity to reconstruct changes in water depth to analyse succession within local aquatic and terrestrial vegetation here we used a multi core multi proxy approach macrofossils pollen and geochemistry in order to reconstruct water depth changes and its influence on aquatic and terrestrial vegetation succession during the holocene additionally we also consider how heterogeneity in proxy data varied across time and space using particular macrophyte taxa found in the macrofossil assemblage which have specific water depth requirements our results demonstrate changes in water depth created a long term mosaic of vegetation succession in the early holocene aquatic macrophytes suggest the water column was high 100 cm during the middle holocene water depths decreased creating mosaics of aquatic succession by ca 4200 cal yr b p terrestrialization had occurred in the former lake area regional vegetation succession was likely more influenced by the presence of fluvial sands and or by low precipitation and high evaporation rates which delayed the expansion of temperate trees and favoured pinus until 8850 cal yr b p macrofossils exhibit the lowest temporal variation among all proxies which suggests a rather stable macrophyte community when water depth was high pollen data show very low spatial variation given by the size of the accumulation basin which reflects regional pollen rain higher spatial variation was observed in the geochemistry and macrofossil data compared to the pollen data which could be the result of different mosaics of aquatic plants local dispersion of propagules or changes in sediment types we conclude that changes in water depth were not homogenous but rather heterogeneous in space and time

landslide susceptibility revealed by lidar imagery and historical records seattle washington abstract light detection and ranging lidar data were used to visually map landslides headscarps and denuded slopes in seattle washington four times more landslides were mapped than by previous efforts that used aerial photographs the mapped landforms landslides headscarps and denuded slopes were created by many individual landslides the spatial distribution of mapped landforms and 1308 historical landslides show that historical landslide activity has been concentrated on the mapped landforms and that most of the landslide activity that created the landforms was prehistoric thus the spatial densities of historical landslides on the landforms provide approximations of the landforms relative susceptibilities to future landsliding historical landslide characteristics appear to be closely related to landform type so relative susceptibilities were determined for landslides with various characteristics no strong relations were identified between stratigraphy and landslide occurrence however landslide characteristics and slope morphology appear to be related to stratigraphic conditions human activity is responsible for causing about 80 of historical seattle landslides the distribution of mapped landforms and human caused landslides suggests the probable characteristics of future human caused landslides on each of the landforms the distribution of mapped landforms and historical landslides suggests that erosion of slope toes by surface water has been a necessary condition for causing seattle landslides human activity has largely arrested this erosion which implies that landslide activity will decrease with time as hillsides naturally stabilize however evaluation of glacial age analogs of areas of recent slope toe erosion suggests that landslide activity in seattle will continue for the foreseeable future

kimberlite exploration at serra da canastra province brazil kimberlite and lamproite pipes are the only economically significant source rocks forming primary diamond deposits brazil the world s seventh largest diamond producer has all of its production from alluvial deposits the quest for a primary deposit has continued over several decades with very few positive results to that end airborne magnetic data from the serra da canastra diamondiferous province was used to identify kimberlite signatures serra da canastra is located in the central portion of the brazilian province in a low magnetic latitude region the main tectonic feature of the area is a northwest southeast major crustal fracture zone that extends for more than 3000 km within the territory the interpretation strategy was based on joint analysis of analytic signal and euler deconvolution a selected kimberlite target should typically have a roughly circular analytic signal anomaly coincident with a depth 0 200 m and structural n 2 constrained euler solution the proposed approach led to rec

chironomid inferred holocene temperature changes in the south carpathians romania we present a holocene summer air temperature reconstruction based on fossil chironomids from lake brazi 1740 m a s l a shallow mountain lake in the south carpathians summer air temperature rec

rich fen development in ce europe resilience to climate change and human impact over the last ca 3500 years here for the first time in se poland we document the long term development of a rich fen and assess its sensitivity to climate change and human impacts over the last ca 3500 years our results are based on a high resolution continuous plant macrofossil remains mollusc and pollen record complemented by geochemical mineral magnetic and physical characterisation and radiocarbon dating from bagno serebryskie rich fen located in se poland based on the palaeoecological data we distinguished five stages of wet habitat conditions 5000 3300 2800 2150 1600 1100 750 230 150 10 cal yr bp and five dry periods at ca 3300 2800 2150 1600 1100 750 230 150 10 to 64 cal yr bp the pollen and geochemistry records particularly pb show that the first human activity in the study area occurred ca 3200 cal yr bp and increased markedly from 500 cal yr bp affecting local plant development including the population size of cladium mariscus our study has shown that despite human impact drainage fire bagno serebryskie peatland has hosted rare presently protected species such as cladium mariscus for hundreds of years we conclude that in common with ombrotrophic bogs rich fen ecosystems can provide a reliable source of palaeoclimatic and palaeohydrological data our study also shows that a large peatland 376 ha can be as sensitive a palaeohydrological archive as smaller mires

subducting oceanic crust the source of deep diamonds inclusions of majoritic garnet in diamonds from the jagersfontein kimberlite formed at unusually great depths of 250 to 500 km in the asthenosphere and transition zone the original host rocks were derived from a much shallower basaltic eclogitic source the presence of negative eu anomalies in all majoritic garnets requires a crustal origin thereby linking these very deep diamond sources to subducting oceanic crust the carbon isotope values 13c of the host diamonds fall within a narrow range at 20 which is fundamentally different from the broad range 24 to 2 and bimodal distribution of carbon isotopes of jagersfontein diamonds that formed in the shallower lithosphere this indicates that majoritic garnet bearing diamonds at jagersfontein inherited their light carbon isotopic composition directly from organic matter contained in a subducting slab these diamonds were likely formed by direct conversion from graphite well within the diamond stability field

the geometry of the iapetus suture zone in central ireland deduced from a magnetotelluric study abstract the crustal geometry of the iapetus suture zone isz in central ireland is inferred from an electrical resistivity model derived from broadband and long period magnetotelluric measurements along a 200 km long nnw sse profile the model highlights an undulating high conductivity layer of thickness 10 15 km and resistivity 2 5 m at middle to lower crustal depths interpreted as sulphide bearing graphitic sediments deposited between the converging continents of laurentia and avalonia during the closure of the iapetus ocean the sediments underwent sinistral transpressional deformation during convergence and movements along the faults transported the sediments to depths of 5 10 km forming the u shaped conductor beneath the centre of the profile correlative with the inferred location of the iapetus suture zone two high resistivity blocks identified above the u shaped conductor are interpreted as caledonian granite bodies and likely relate to late caledonian igneous activity

deep electrical structure of northern alberta canada implications for diamond exploration geophysical studies of upper mantle structure can provide constraints on diamond formation teleseismic and magnetotelluric data can be used in diamond exploration by mapping the depth of the lithosphere asthenosphere boundary studies in the central slave craton and at fort a la corne have detected conductors in the lithospheric mantle close to or beneath diamondiferous kimberlites graphite can potentially explain the enhanced conductivity and may imply the presence of diamonds at greater depth petrologic arguments suggest that the shallow lithospheric mantle may be too oxidized to contain graphite other diamond bearing regions show no upper mantle conductor suggesting that the correlation with diamondiferous kimberlites is not universal the buffalo head hills in alberta host diamondiferous kimberlites in a proterozoic terrane and may have formed in a subduction zone setting long period magnetotelluric data were used to investigate the upper mantle resistivity structure of this region magnetotell

geophysical methods for kimberlite exploration in northern canada in 1991 the discovery of diamondiferous kimberlite in canada s northwest territories nwt precipitated the largest mineral staking rush in north america and sparked a remarkable exploration effort which extended across northern canada thirteen years later two diamond mines with estimated annual productions of 1 billion can are in operation a third is in permitting and several other projects are approaching development ekati mine operated by bhp billiton since 1998 produced 4 8 million carats from 4 2 million tons of ore in 2003 while the nearby diavik diamond mine yielded 2 7 million carats from 1 0 million tons of ore during the same period when diavik has achieved full production in 2004 canada will account for 15 of global diamond output by value the exploration programs which created this new industry relied heavily upon the efficient application of complementary geophysical techniques this paper overviews geophysical exploration methods currently used in diamond exploration in northe

late glacial and early holocene development of lakes in northeastern poland in view of plant macrofossil analyses the late glacial history of the development of seven extant or former now sediment filled lakes in northeastern poland was investigated based on high resolution plant macrofossil analyses and ams radiocarbon dating according to palaeobotanical data and ams dating the accumulation of organic sediments began during the bolling period the bottom sediments of all studied lakes contain plant macrofossils typical of late glacial vegetation such as betula nana dryas octopetala potamogeton filiformis and potamogeton alpinus the first plants to occur in the lakes were chara sp p filiformis and batrachium sp the late glacial sediments included rarely encountered macrofossils of sphagnum teres at the beginning of the holocene the water level in the studied northeastern polish lakes decreased significantly this was manifested in a change in the type of sediment transformation of small lakes into peatland in places and expansion of typical indicator plants of shallow waters

nd isotopic evidence for crustal recycling in the ca 2 0 ga subsurface of western canada sm nd isotopic data are presented for 23 drill core samples from five aeromagnetically and geochronologically u pb zircon distinct domains of the precambrian basement of northern alberta the domains in question are the taltson 1 96 1 94 ga buffalo head 2 32 1 99 ga chinchaga 2 19 2 09 ga ksituan 1 99 1 90 ga and nova 2 81 ga these domains are truncated to the north and south by the great slave lake shear zone and the snowbird tectonic zone respectively initial end values are 5 0 to 9 7 for the taltson 0 2 to 6 3 for the buffalo head 0 6 to 1 8 for the chinchaga 1 8 to 2 1 for the ksituan and 5 6 for the nova crustal residence model ages fall in the 2 5 2 8 ga range the nd isotopic signatures may be viewed in terms of mixing a minimum of 10 archean continental crust with a depleted mantle component speculations on the tectonic history of the basement domains in question involve the assembly of archean crustal nuclei to form the buffalo head chinchaga composite domain a

geoelectric structure of the proterozoic wopmay orogen and adjacent terranes northwest territories canada magnetotelluric mt soundings were made along a transect in northern canada crossing the proterozoic wopmay orogen fort simpson basin and adjacent parts of the slave craton and the nahanni terrane the results are used to define the geoelectric structure and constrain the crustal and lithospheric structure and evolution across the wopmay orogen geoelectric strikes at crustal depths average n34 e and are interpreted to be related to transcurrent faulting that occurred during late distal collisions at the western margin of the orogen weak two dimensionality in the fort simpson basin is interpreted to be due to the sedimentary rocks in the basin at longer periods geoelectric strikes across the wopmay orogen rotate from n43 e at uppermost mantle penetration to n62 e at a depth of 100 km the uppermost mantle strikes are interpreted to be due to ductile shearing linked to the transcurrent faulting in the overlying crust the deeper strikes may be caused by shearing at the base of the present day lith

automated landslide mapping using spectral analysis and high resolution topographic data puget sound lowlands washington and portland hills oregon abstract landslide inventory maps are necessary for assessing landslide hazards and addressing the role slope stability plays in landscape evolution over geologic timescales however landslide inventory maps produced with traditional methods aerial photograph interpretation topographic map analysis and field inspection are often subjective and incomplete the increasing availability of high resolution topographic data acquired via airborne light detection and ranging lidar over broad swaths of terrain invites new automated landslide mapping procedures we present two methods of spectral analysis that utilize lidar derived digital elevation models of the puget sound lowlands washington and the tualatin mountains oregon to quantify and automatically map the topographic signatures of deep seated landslides power spectra produced using the two dimensional discrete fourier transform and the two dimensional continuous wavelet transform identify the characteristic spatial frequencies of deep seated landslide morphologic features such as hummocky topography scarps and displaced blocks of material spatial patterns in the amount of spectral power concentrated in these characteristic frequency bands highlight past slope instabilities and allow the delineation of landslide terrain when calibrated by comparison with detailed independently compiled landslide inventory maps our algorithms correctly classify an average of 82 of the terrain in our five study areas spectral analysis also allows the creation of dominant wavelength maps which prove useful in analyzing meter scale topographic expressions of landslide mechanics past landslide activity and landslide modifying geomorphic processes these results suggest that our automated landslide mapping methods can create accurate landslide maps and serve as effective objective and efficient tools for digital terrain analysis

gis based landslide susceptibility mapping using analytical hierarchy process and bivariate statistics in ardesen turkey comparisons of results and confirmations abstract the ardesen area is prone to landslides because of the climate conditions geologic and geomorphologic characteristics of the region as in previous years in 2001 due to heavy rainfall there were many landslides resulting in damage and human casualties there is still a great danger of further landslides in the region therefore it is vitally important to prepare a landslide susceptibility map of the region in this study the analytical hierarchy process ahp the statistical index wi and weighting factor wf methods were used to produce and later compare three susceptibility maps for this purpose thematic layers including landslide inventory lithology weathering slope aspect land cover distance to stream drainage density and distance to road were used in this study area 98 of landslides occurred in highly or completely weathered units lithology weathering land cover and slope data layers were found to be important factors in the study area to confirm the practicality of the three susceptibility maps were compared with a landslide activity map containing 16 active landslide zones the outcome was that the active landslide zones do not completely fit into the high and very high susceptibility classes but 81 3 of these landslide zones fall into the high and very high susceptibility zones of the ahp method while this is 62 5 in the case of wi method and 68 8 with the wf method in spite of the results obtained in this study the development of a susceptibility map is usually determined by the needs and available resources the results showed that the ahp method gave a more realistic picture of the actual distribution of landslide susceptibility than the wi and wf methods

holocene development of a peatland southern quebec a spatio temporal reconstruction based on pachymetry sedimentology microfossils and macrofossils this study examines the relationships between allogenic and autogenic processes during the holocene development of a southern quebec bog local vegetation surface moisture and peat accumulation were independently reconstructed from palaeoecological data microfossils macrofossils loss on ignition and radiocarbon dating and sedimentological analyses conducted on seven profiles the observed successional stages from pond to marsh rich fen poor fen then bog represents a typical hydrosere the early wetland development provides an obvious illustration of the facilitation model each community modified the hydrological conditions by means of peat accumulation which then favoured the onset of the succeeding stage no direct link is evidenced between vegetation moisture and peat accumulation while all of them clearly reveal the initial influence of minerotrophic groundwater supply notably the decrease in this allogenic influence is reflected by the increasing asynchrony of local vegetation change th

digital terrain modelling a review of hydrological geomorphological and biological applications the topography of a catchment has a major impact on the hydrological geomorphological and biological processes active in the landscape the spatial distribution of topographic attributes can often be used as an indirect measure of the spatial variability of these processes and allows them to be mapped using relatively simple techniques many geographic information systems are being developed that store topographic information as the primary data for analysing water resource and biological problems furthermore topography can be used to develop more physically realistic structures for hydrologic and water quality models that directly account for the impact of topography on the hydrology digital elevation models are the primary data used in the analysis of catchment topography we describe elevation data sources digital elevation model structures and the analysis of digital elevation data for hydrological geomorphological and biological applications some hydrologic models that make use of digital representations of topography are also considered

on two dimensional interpretation of magnetotelluric soundings summary the paper presents the views of the 2 d interpretation of magnetotelluric mt data that are characteristic of the russian magnetotelluric school discussing the strategy of 2 d interpretation of mt data we have to answer three questions in decreasing order of importance these questions are as follows 1 which field mode is more sensitive to the near surface and deep structures that are the targets of mt surveys 2 which field mode is more robust to the 3 d evects caused by real geological bodies 3 which field mode is more susceptible to the static shift induced by nearsurface inhomogeneities we examine the transverse magnetic tm and transverse electric te modes of the 2 d magnetotelluric field and show that they satisfy the principle of information complementarity 1 while the tm mode is more sensitive to the near surface structures the te mode may be more sensitive to the deep structures 2 while the tm mode is more robust to the 3 d evects caused by conductive structures the te mode may be more robust to the 3 d evects caused by resistive structures and 3 while the tm mode is more susceptible to the static shift the te mode may be almost undistorted thus the gaps left by one mode can be filled by another mode if so the most comprehensive and reliable information on the conductivity of the earth s interior can be obtained using both modes i e the transverse and longitudinal mt curves the general scheme of this bimodal mt inversion is rather simple the transverse curves provide details of near surface structures e g in the sediments and allow one to evaluate the lithosphere resistance and outline the deep conductive faults while the longitudinal curves help one to detect the conductive zones in deep layers of the lithosphere and in the asthenosphere an eycient two level algorithm for the bimodal mt inversion realizing this scheme is suggested as an illustration the paper presents the geoelectrical model of the kirghiz tien shan constructed by means of the bimodal mt inversion

suitability of lidar point density and derived landform curvature maps for channel network extraction this study uses landform curvature as an approach for channel network extraction we considered a study area located in the eastern italian alps where a high quality set of lidar data was available and where channel heads and related channel network were mapped in the field in the analysis we derived 1 m dtms from different ground lidar point densities and we used different smoothing factors for the landscape curvature calculation in order to test the suitability of the lidar point density and the derived curvature maps for the recognition of channel network this methodology is based on threshold values of the curvature calculated as multiples 1 3 times of the standard deviation of the curvature our analyses suggested that i the window size for curvature calculations has to be a function of the size of the features to be detected ii a coarse ground lidar point density could be as useful as a finer one for the recognition of main channel network features and iii rougher curvature maps are not optimal as they do not explore a sufficient range at which features occur while smoother curvature maps overcome this problem and are more appropriate for the extraction of surveyed channels copyright 2010 john wiley sons ltd

electromagnetic images of crustal structures in southern and central canadian cordillera data from more than 400 magnetotelluric soundings made since the early 1980 s in the canadian cordillera over a 300 000 km2 area between 49 and 53 5 n are used to image qualitatively regional three dimensional crustal variation in electrical conductivity by means of phase maps phase frequency sections and maps of resistivity at depth two hundred of the soundings were acquired as part of lithoprobe southern canadian cordillera transect activities and their locations were coordinated with the seismic reflection and refraction experiments the lower crust has a generally pervasive low resistivity 1 100 m throughout the cordillera west of the foreland belt within this canadian cordilleran regional conductor the magnetotelluric data reveal both two dimensional structures with highest conductivities along the coast belt and omineca belt and three dimensional variation along geological strike this conductor mapped over a volume in excess of 106 km3 is most probably caused by fluids saline wat

response of a spring fed fen ecosystem in central eastern europe nw romania to climate changes during the last 4000 years a high resolution multi proxy reconstruction we document the long term development of a spring fed fen assessing its sensivity to climate changes over the last ca 4000 years our investigation is based on high resolution continuous plant macrofossil remains and mollusc records complemented by pollen geochemical analysis and radiocarbon dating of valea morii located in the feleac hills transylvanian depression in nw romania central eastern europe based on our palaeocological data we have distinguished three stages of wet habitat conditions two stages between 4000 and 2450 cal yr bp and one in the last 800 cal yr bp and one dry stage between ca 2450 and 800 cal yr bp these local habitat conditions appear to reasonably reflect regional climate characteristics high resolution analysis of two replicated cores documented a mostly comparable pattern of local plant and mollusc succession and stable isotope values from ca 500 cal yr bp the appearance of c mariscus during the last two centuries may be related to increased wetness and associated active caco3 precipitation which allowed this plant to colonise the spring fed fen studied however it can be not excluded that the occurrence and spread of a cladium mariscus population at this site during the last two centuries might have been partly favoured by the warming of the climate after the little ice age the potential of carbonate oxygen stable isotope values as an indicator of major trends in climatic change both temperature and humidity in mountain spring fed fen deposits is shown carbon isotopes in the carbonates were found to be useful in reconstruction of changes in vegetation soil development and the dissolution of bedrock carbonates primarily as a reaction to changes in climate humidity

how a sphagnum fuscum dominated bog changed into a calcareous fen the unique holocene history of a slovak spring fed mire mires develop by autogenic succession from more groundwater fed to more rainwater fed this study describes a similar development in the early holocene followed by a reverse development in the middle and late holocene pollen macrofossil and testate amoeba analyses show that the site started as a minerotrophic open fen woodland after 10 700 cal a bp autogenic succession led to the accumulation of at least 1 m of sphagnum fuscum peat around 9000 cal a bp as climate could no longer sustain a stable water regime the bog desiccated and a fire broke out the fire removed part of the peat layer and as a consequence relative water levels rose leading to the establishment of a wet minerotrophic swamp carr after 600 cal a bp rapid peat accumulation with calcareous tufa formation resumed as a result of anthropogenic deforestation and hydrological changes in the catchment and resulting increased groundwater discharge

proterozoic tectonic accretion and growth of western laurentia results from lithoprobe studies in northern alberta the western canadian shield of northern alberta is composed of a series of continental slivers that were accreted to the margin of the archean rae hinterland ca 1 9 2 0 ga preserving a unique record of continental evolution for the interval 2 1 2 3 ga this part of laurentia owes its preservation to the accretionary style of tectonic assembly south of the great slave lake shear zone which contrasts with indentation escape processes that dominate the paleoproterozoic record farther north the buffalo head and chinchaga domains form the central core of this region comprising a collage of ca 2325 2045 ma crustal elements formed on an archean microcontinental edifice and similar age crust is preserved as basement to the taltson magmatic zone the distribution of magmatic ages and inferred collision and subduction zone polarity are used to indicate closure of intervening oceanic basins that led to magmatism and emplacement of continental margin arc and collisional belts that formed from ca 1998 to1900

the late quaternary environmental history of batorliget n e hungary abstract a sedimentary sequence extending back into the last glacial has been obtained from batorliget marsh in n e hungary reconstruction of the environmental history of the region using the techniques of pollen analysis molluscan analysis and geochemistry has revealed an important late quaternary refugium during the last glacial a refugium for temperate flora and fauna existed within a landscape dominated by coniferous forest predominantly made up of pinus and picea the lateglacial postglacial transition at 10 000 yr b p resulted in a dramatic shift from coniferous but also including betula woodland to deciduous woodland following the lateglacial postglacial transition a highly diverse woodland became established in the early postglacial accompanied by an equally diverse molluscan assemblage this diversity remained throughout the early postglacial although the types present within the woodland changed a number of times at c 7000 yr b p anthropogenic disturbance resulted in the destruction of the mixed forest and the development of agricultural land the importance of this region as a refugial area both in the lateglacial and early postglacial is discussed and the influence that it had on the postglacial development of the fauna and flora of northeastern hungary is reviewed

origin of a boreal birch bog woodland and landscape development on a warm low mountain summit at the carpathian pannonian interface we analysed two peat cores of late glacial origin from a bog woodland in the male karpaty mts sw slovakia using plant macrofossil pollen peat chemistry and charcoal analyses to trace local successional patterns regional vegetation development and occurrence of rare species

the effect of land plants on weathering rates of silicate minerals abstract land plants and their associated microbiota directly affect silicate mineral weathering in several ways by generation of chelating ligands by modifying ph through production of co2 or organic acids and by altering the physical properties of a soil particularly the exposed surface areas of minerals and the residence time of water in laboratory experiments far from equilibrium 1 mm oxalate a strong chelator of al has a negligible effect on the dissolution rate of alkali feldspars but some effect on calcic feldspars and olivine by analogy to oxalate the overall effect of organic ligands on the weathering rate of silicate minerals in nature is likely to be small except perhaps in microenvironments adjacent to roots and fungal hyphae the effect of ph on silicate mineral dissolution rate depends on ph below ph 4 5 the rate increases with decreasing ph in the circumneutral region the rate is ph independent and at ph values above around 8 the rate increases with increasing ph vegetation should thus cause an increase in weathering rate through the ph effect only where the ph is below 4 5 as an overall generalization the effect of plants on weathering rate through changes in soil solution chemistry is probably small for granitic rocks it may be greater for more mafic rocks it is the release of ca and mg from mafic rocks that has the greatest influence on the global co2 budget the effect of changes in soil physical properties on weathering rate can be major by binding fine particles plants can greatly increase weathering rates in areas of high physical erosion where erosion rates are lower the effect of plants is less clear on long timescales plants may decrease chemical weathering by binding secondary products and isolating unweathered minerals from meteoric water a major unknown in estimating the effect of the advent of land plants on weathering rates is the nature thickness particle size distribution permeability of the regolith on the pre silurian continents the indirect effect of vegetation through changing the regional distribution of precipitation may be as important as the direct effects

landslide inventory maps new tools for an old problem landslides are present in all continents and play an important role in the evolution of landscapes they also represent a serious hazard in many areas of the world despite their importance we estimate that landslide maps cover less than 1 of the slopes in the landmasses and systematic information on the type abundance and distribution of landslides is lacking preparing landslide maps is important to document the extent of landslide phenomena in a region to investigate the distribution types pattern recurrence and statistics of slope failures to determine landslide susceptibility hazard vulnerability and risk and to study the evolution of landscapes dominated by mass wasting processes conventional methods for the production of landslide maps rely chiefly on the visual interpretation of stereoscopic aerial photography aided by field surveys these methods are time consuming and resource intensive new and emerging techniques based on satellite airborne and terrestrial remote sensing technologies promise to facilitate the production of landslide maps reducing the time and resources required for their compilation and systematic update in this work we first outline the principles for landslide mapping and we review the conventional methods for the preparation of landslide maps including geomorphological event seasonal and multi temporal inventories next we examine recent and new technologies for landslide mapping considering i the exploitation of very high resolution digital elevation models to analyze surface morphology ii the visual interpretation and semi automatic analysis of different types of satellite images including panchromatic multispectral and synthetic aperture radar images and iii tools that facilitate landslide field mapping next we discuss the advantages and the limitations of the new remote sensing data and technology for the production of geomorphological event seasonal and multi temporal inventory maps we conclude by arguing that the new tools will help to improve the quality of landslide maps with positive effects on all derivative products and analyses including erosion studies and landscape modeling susceptibility and hazard assessments and risk evaluations

potential field signatures of buried precambrian basement in the western canada sedimentary basin an internally consistent levelled compilation of magnetic data is derived for alberta and northeastern british columbia with bouguer gravity data this compilation is used to refine the definition of precambrian basement domains within the western canada sedimentary basin magnetic data are draped at a constant distance above the mapped basement surface to reduce the effects of varying magnetic source depths automated interpretation methods that effectively map outlines of magnetic sources are used to characterize the internal structure of the domains and to aid in their delineation the basement domain map thus derived differs from previous interpretations in the extension of domains further to the southwest due mainly to the availability of new public domain magnetic data and the more precise definition of domain boundaries based on the magnetic source location maps the nahanni hottah chinchaga thorsby vulcan and kiskatinaw domains are weakly magnetic and characterized by magnetic sources tha

vegetation and environmental responses to climate forcing during the last glacial maximum and deglaciation in the east carpathians attenuated response to maximum cooling and increased biomass burning the carpathian mountains were one of the main mountain reserves of the boreal and cool temperate flora during the last glacial maximum lgm in east central europe previous studies demonstrated lateglacial vegetation dynamics in this area however our knowledge on the lgm vegetation compo sition is very limited due to the scarcity of suitable sedimentary archives here we present a new record of vegetation fire and lacustrine sedimentation from the youngest volcanic crater of the carpathians lake st anne lacul sf ana szent anna tto examine environmental change in this region during the lgm and the subsequent deglaciation our record indicates the persistence of boreal forest steppe vegetation with pinus betula salix populus and picea in the foreland and low mountain zone of the east carpathians and juniperus shrubland at higher elevation we demonstrate attenuated response of the regional vegetation to maximum global cooling between 22 870 and 19 150 cal yr bp we find increased regional biomass burning that is antagonistic with the global trend increased regional fire activity suggests extreme continentality likely with relatively warm and dry summers we also demonstrate xerophytic steppe expansion directly after the lgm from 19 150 cal yr bp and regional increase in boreal woodland cover with pinus and betula from 16 300 cal yr bp plant macrofossils indicate local 950 m a s l establishment of betula nana and betula pubescens at 15 150 cal yr bp pinus sylvestris at 14 700 cal yr bp and larix decidua at 12 870 cal yr bp pollen data furthermore support population genetic inferences regarding the regional presence of some temperate deciduous trees during the lgm fagus sylvatica corylus avellana fraxinus excelsior our sedimentological data also demonstrate intensified aeolian dust accumulation between 26 000 and 20 000 cal yr bp

magnetotelluric imaging beneath the taiwan orogen an arc continent collision 1 the taiwan orogen has formed since the late miocene by oblique collision between the luzon volcanic arc on the philippine sea plate and the eurasian continental margin this oblique collision has produced an orogen that decreases in age from north to south and permits study of the temporal evolution of an arc continent collision these factors make taiwan a favorable location to study the process of arc continent collision the first long period magnetotelluric mt measurements were recorded in taiwan as part of the taiwan integrated geodynamics research taiger project in 2006 7 measurements were made at 82 sites on three transects across south central and north taiwan that span the breadth of the orogen and cross all major tectonic boundaries robust remote reference processing of the mt time series data resulted in high quality soundings that were modeled in both 2 and 3 dimensions these mt models support predictions of lithospheric deformation i e thick skinned tectonics beneath the central ranges in south and central taiwan but are inconsistent with predictions of orogen scale thin skinned models the mt resistivity model for northern taiwan is consistent with dewatering of the subducting philippine slab and with deformation described by the subducting indenter tectonic model modeling the taiger mt data has definitively shown that conductive and seismically active crustal structures exist to 30 km beneath the orogen these conductive regions interpreted as interconnected fluid map pervasive zones of collisional deformation that are lithospheric in scale

systematic variations in xenocryst mineral composition at the province scale buffalo hills kimberlites alberta canada abstract the buffalo hills kimberlites define a province of kimberlite magmatism occurring within and adjacent to proterozoic crystalline basement termed the buffalo head terrane in north central alberta canada the kimberlites are distinguished by a diverse xenocryst suite and most contain some quantity of diamond the xenocryst assemblage in the province is atypical for diamondiferous kimberlite including an overall paucity of mantle indicator minerals and the near absence of compositionally subcalcic peridotitic garnet g10 the most diamond rich bodies are distinguished by the presence of slightly subcalcic chromium rich garnet and the general absence of picroilmenite with the majority forming a small cluster in the northwestern part of the province barren and near barren pipes tend to occur to the south with increasing proximity to the basement structure known as the peace river arch niobian picroilmenite compositionally restricted low to moderate cr peridotitic garnet and megacrystal titanian pyrope occur in kimberlites closest to the arch major element data for clinopyroxene and trace element data for garnet from diamond rich and diamond poor kimberlites suggests that metasomatism of lithospheric peridotite within the diamond stability field may have caused destruction of diamond and diamond source rocks proximal to the arch were the most affected

gravimetric study of a potential mineral deposit in the itapororoca region brazil a semi detailed gravity survey was carried out over an area of 650 km 2 localized in the eo neoproterozoic coastal zone of paraiba state where 548 new gravity stations were added to the existing database gravity measurements were made with a lacoste and romberg model g meter with a precision of 0 04 mgal the altitude was determined by barometric levelling with a fixed base achieving a 1 2 m measure of uncertainty corresponding to an overall accuracy of 0 24 mgal for the bouguer anomaly the residual bouguer map for a 7th degree regional polynomial showed a circumscribed negative anomaly coincident with a localized aero magnetic anomaly and with hydrothermally altered outcrops near the city of itapororoca the 3d gravity modelling constrained by geologic mapping was interpreted as a low density fractured and or altered material with a most probable volume of approximately 23 km 3 extending to about 8 500 m depth this result is in accordance with a volcanic body associated with hydrothermal processes accompanied by surface mineralization evidence which may be of interest to the mining industry

rapid vegetation response to lateglacial and early holocene climatic fluctuation in the south carpathian mountains romania abstract high resolution pollen conifer stomata and plant macrofossil analyses of two glacial lake sediments 1740 and 1990 m a s l are used to reconstruct lateglacial lg and early holocene eh vegetation and tree line changes in the retezat mountains our results show that during the lg tree line was between 1750 and 1800 m a s l formed by larix decidua pinus mugo and picea abies early lg spread to high altitudes suggests refugia of these tree species in the mountain the younger dryas cooling resulted in regional steppe tundra expansion but tree line position and composition showed little change the abundance of trees and shrubs decreased at 1740 m a s l but species richness increased with the arrival of pinus cembra our data support climate model hindcasts for only modest decrease in accumulated growing season heat at mid high altitudes regionally the pollen records suggest enhanced aridity and seasonality in the eh tree line reached 2000 m a s l higher than today by 11 100 cal yr bp p mugo p cembra p abies established around the upper lake suggesting rapid increase in summer temperatures the eh maximum of l decidua between 11 200 10 600 cal yr bp was connected to high summer insolation high altitude expansion of abies alba between 10 600 10 300 cal yr bp suggested summer mean temperatures 2 8 c higher then today in comparison with other mountain sites in europe lg interstadial tree line was at similar altitude in the s alps and 350 m higher in the pirin mountains lg tree line fluctuation had similar low amplitude in the se alps retezat and pirin mts suggesting relatively weak influence of the north atlantic thermohaline circulation changes on growing season temperatures

holocene forest dynamics in northwestern romnania pollen analyses and ams radiocarbon measurements were carried out on peat deposits from the former crater lake preluca tiganului located in a mid altitude area of the gutaiului mountains nw romania in order to reconstruct the postglacial vegetation history at the lateglacial holocene transition the open vegetation was replaced by forest suggesting a fast response to climatic warming the rapid expansion of pinus betula and later picea may be due to their existence in the area during the lateglacial at approximately 11 250 cal yr bp the dense forest was composed primarily of ulmus and some picea betula and pinus a small population of ulmus might also have survived in the area during the lateglacial at 10750 cal yr bp quercus tilia and fraxinus followed by corylus at c 10200 cal yr bp expanded significantly in the forest the delay of approximately 550 years in their establishment as compared to the expansion of ulmus was probably due to their immigration from more distant localities

replicability and variability of the recent macrofossil and proxy climate record from raised bogs field stratigraphy and macrofossil data from bolton fell moss and walton moss cumbria england replication of results is a basic tenet of science but in palaeoecology this is very time consuming and the signal is subject to noise the derivation of proxy climate signals from ombrotrophic peat was carried out originally using samples from open peat faces where the stratigraphic relationships could be easily observed now that such sections are rare and often degraded there is a need to demonstrate that data can be replicated from core profiles ten short cores taken from two adjacent bogs have been analysed for macrofossils and show a coherent series of changes which are also similar to previous profiles from the same sites it is concluded that variation between profiles is slight and less than observations of present vegetation mosaics might suggest recommendations for a standard approach to fieldwork on raised bogs that emphasises the utility of subfossil pool layers are proposed and the need for a secure chronology is stressed 1998 john wiley sons ltd

lithoprobe s impact on the canadian diamond exploration industrythis article is one of a series of papers published in this special issue on the theme lithoprobe parameters processes and the evolution of a continent earth sciences sector contribution 20070261 lithoprobe contribution 1479 lithoprobe aided and will continue to guide diamond exploration in canada via a number of diverse ways and at scales from cratons to individual ore bodies specific transects outlined the domainal nature geometry and age relations of crust subjacent mantle and diamond bearing roots in unusually rich detail for cratonic settings such as those of the superior and slave cratons as well as pericratonic shield settings such as those of the sask craton and buffalo hills terrane the superior and slave examples of craton construction by multiple underthrust layers as inferred from structural geometries observed in lithoprobe seismic and magnetotelluric surveys remain the clearest resolved to date the first definition of the sask craton occurred 10 15 years ago and helped fuel the diamond industry s ongoing revision of clifford s rule for exploration so as to include targets in proterozoic shield settings main lithoprobe transect results and supporting geoscience studies have helped to demonstrate the

deep electrical structure of the northern cascadia british columbia canada subduction zone implications for the distribution of fluids long period magnetotelluric data have been used to image the deep electrical structure of the cascadia subduction zone in british columbia canada zones of elevated electrical conductivity were found in both the forearc and backarc regions and are interpreted as a consequence of the fluid release from subducting slab a shallow zone of high conductivity beneath vancouver island is likely due to fluids that are trapped above the subducting plate east of this structure is a conductive 0 03 s m forearc mantle wedge that also exhibits low seismic velocities and may be serpentinized a free fluid phase is required to account for this enhanced conductivity elevated conductivities are observed in the upper mantle throughout the backarc 0 01 s m and strongly support the hypothesis of a shallow convecting asthenosphere this enhanced upper mantle conductivity can be explained by either hydrogen ion diffusion in olivine minerals or by a few percent partial melting 4

magnetotellurics along the fennoscandian long range profile summary estimates of magnetotelluric transfer functions along the fennoscandian long range fennolora profile are presented and discussed in relation to the major lithotectonic subdivisions of the swedish part of the baltic shield none of the transfer functions are found to be consistent with a one dimensional earth structure thereby making a quantitative interpretation difficult however the geological units are found to display characteristic differences in the obtained transfer functions and in some areas a quantitative interpretation can be justified the most interesting structure indicated is a low resistive 4 am crustal structure of lateral extension more than 150 km centred around the skellefte ore district a minimum thickness for this structure of 15 km is inferred

uav based remote sensing of the super sauze landslide evaluation and results unmanned aerial vehicles uavs equipped with digital compact cameras can be used to map landslides quickly and at a high ground resolution images taken by a radio controlled mini quad rotor uav of the super sauze france landslide have been used to produce a high resolution ortho mosaic of the entire landslide and digital terrain models dtms of several regions the uav capability for imaging fissures and displacements on the landslide surface has been evaluated and the subsequent image processing approaches for suitably georectifying the data have been assessed for super sauze horizontal displacements of 7 to 55 m between a high resolution airborne ortho photo of may 2007 and a uav based ortho mosaic of october 2008 have been measured fixed areas of persistent deformation have been identified producing fissures of different distributions and orientations comparable to glacial crevasses and relating directly to the bedrock topography the uav has demonstrated its capability for producing valuable landslide data but improvements are required to reduce data processing time for the efficient generation of ortho mosaics based on photogrammetric dtms in order to minimise georeferencing errors

bog burst in the eastern netherlands triggered by the 2 8 kyr bp climate event the nature and cause of the so called 2 8 kyr bp event have been a subject of much debate peat sequences have provided much of the evidence for this event but the process link between climate and peatland response is not well understood multiproxy high resolution analysis of a core from bargerveen in the eastern netherlands based on pollen non pollen palynomorphs testate amoebae and geochemistry identified an abrupt shift from relatively dry to extremely wet conditions radiocarbon based wiggle match dating wmd and biostratigraphy based on the pollen record show that this shift in local hydrology occurred around 2800 cal yr bp we interpret an erosional hiatus lasting up to 950 years immediately prior to this as the effect of a bog burst after excessive rainfall this phenomenon was not limited to our sampling location but occurred over a large part of the former bargerveen peat at the hiatus contains microfossils that reflect temporary eutrophication as a consequence of local fires and secondary decomposition because of increased drainage after the erosion event our data show how detailed multiproxy analyses can elucidate the past response of peatlands to changing climate and suggest that the climatic change in northwest europe at this time caused major non linear disruption to these ecosystems

early holocene succession of vegetation and molluscs in lake jaczno east central europe abstract here we present results of high resolution palaeoecological studies of the organic deposits accumulated in lake jaczno located in the north eastern poland plant macrofossils and malacological analyses complimented by radiocarbon dating ams were undertaken to reconstruct early holocene succession of the pioneer wetland plants and molluscs in the lake ecosystem numerous presence of charcoal pieces 1 mm and fungal remains sclerotia in the peat layer accumulated on the mineral ground document dry habitat what coincides with warm and dry climate conditions in the early holocene recorded in this part of europe change to lacustrine environment documented by accumulation of the carbonate gyttja on the highly decomposed peat layer took place ca 10 500 cal yr bp the current morphology of lake jaczno in which several basins can be distinguished suggests that different age of sediments accumulated at the bottom part at our sampling sites might result from different sizes of the buried dead ice blocks and their heterochronous final melting the first aquatic plants that appeared in lake jaczno were chara sp ceratophyllum demersum and nymphaea alba the appearance of cladium mariscus in lake jaczno ca 9400 cal yr bp was synchronous with the substantial spread of this plant in this region which coincided with increased climate humidity the first molluscan species that colonized the lake ecosystem were gyraulus crista and bithynia tentaculata species living on macrophytes and valvata piscinalis typical for habitats characterized by a thick layer of plant detritus

responses of terrestrial ecosystems to dansgaard oeshger cycles and heinrich events a 28 000 year record of environmental changes from se hungary abstract according to the findings of a complex sedimentological geochemical malacological and pollen study implemented on a core sequence of an alkaline lake feher lake interstadials in the se great hungarian plain were characterized by increased boreal woodland cover during marine isotope stage 2 mis 2 29 700 14 500 cal bp these interstadials were dated to 26 420 27 970 23 185 24 880 and 18 810 20 770 cal bp and correlate well with the dansgaard oeschger do interstadials 2 and 3 and the post lgm warm interval seen in the greenland ice core oxygen isotope records intervening cold phases on the other hand were found between 24 880 26 420 and 20 770 23 185 cal bp correlating with heinrich event 2 and the lgm these data overall confirm that millennial scale climate variability during marine isotope stage 2 had profound effect on the terrestrial ecosystems in the continental interior of se europe leading to periodic boreal woodland expansions and contractions and wildfires

buried proterozoic foredeep under the western canada sedimentary basin electromagnetic studies of the precambrian basement beneath the western canada sedimentary basin in alberta indicate a narrow linear conductivity anomaly spatially correlated with a strong positive magnetic feature the red deer high the conductor is located below sedimentary cover near the top of the crystalline basement and has limited depth extent we propose that this anomalous feature represents graphitic metasedimentary rocks in the euxinic flysch facies of a proterozoic foredeep sequence the strong magneticanomalyresultsfromanassociatedironformationdepositedontheouterrampofthe foredeep this model explains the geophysical anomalies has analogues on the exposed shield and is consistent with the timing deformation history and known geology of the precambrian basement

a proxy record of late holocene climate change from may moss northeast england quantitative reconstruction of changes in mire surface wetness has been used to reconstruct proxy climate from an upland ombrotrophic blanket mire on the north york moors in northeast england may moss testate amoebae plant macrofossil and humification analyses were carried out for six peat profiles transfer functions are used to generate estimates of water table levels from the testate amoebae stratigraphy which complement the semi quantitative indications of changing surface wetness provided by plant macrofossil and humification analysis 14c dates provide the chronology for the stratigraphy differences were encountered between ams 14c dates on pure sphagnum remains and radiometric dates on bulk peat from the same horizon which perhaps arise from the heterogeneity of peat replicate palaeoecological analysis of adjacent cores identifies consistency within testate amoebae and plant macrofossil stratigraphies and reveals a strong agreement between the water table level proxies the record of hydrological changes at sites across may moss are in synchrony and so climate change is the most likely cause of the moisture fluctuations changes to a wetter or cooler climate were identified cal ad 260 540 ca ad 550 650 cal ad 670 980 ca ad 1350 1450 cal ad 1400 1620 and ca ad 1700 1800 periods with a drier or warmer climate precede all of these wet shifts with particularly dry periods between cal ad 650 860 and 690 980 and between cal ad 1290 1410 and 1400 1620 copyright 2001 john wiley sons ltd

integrated teleseismic studies of the southern alberta upper mantle this paper presents results from a teleseismic experiment conducted across the hearne province in south central alberta data from an array of nine portable broad band seismographs deployed along a 500 km nw se array have been supplemented with recordings from two canadian national seismograph network stations p wave delay times from 293 earthquakes have been inverted for upper mantle velocity structure below the array the recovered model reveals high velocities beneath much of the southern hearne province to depths of 200 250 km which are interpreted as deep seated lithospheric structure contrary to recent tectonic models these results suggest that the hearne lithosphere has remained intact in particular it appears unlikely that evidence for extensive lower crustal melting derives from lithospheric delamination however the results admit the possibility that high mantle conductivity as revealed in magnetotelluric studies originates through small volumes of connected hydrous minerals or other c

evaluation of landslide reactivation a modified rainfall threshold model based on historical records of rainfall and landslides abstract this study proposes a modification of the conventional threshold model for assessing the probability of rainfall induced landslide reactivation the modification is based on the consideration that exceedance of a pre determined rainfall threshold is a necessary but not sufficient condition to reactivate a landslide the proposed method calculates the probability of reactivation as a function of the probability of exceedance of a pre determined rainfall threshold as well as the probability of occurrence of a landslide after such exceedance the data for the calculation were obtained from historical records of landslides and rainfall the method was applied to two complex landslides san donato and la salsa involving fine grained debris in the southern section of the apennine foredeep the minimum rainfall threshold triggering landslide reactivation on the two slopes was determined by examining rainfall patterns during the 180 days preceding the slide events for the san donato and la salsa landslides the minimum triggering threshold consists of rainfall events lasting 15 days with cumulated rainfall exceeding 150 and 180 mm respectively based on hydrological and statistical analyses the annual probabilities of exceeding the thresholds were estimated to be 0 38 and 0 25 respectively during the period from 1950 to 1987 the minimum threshold was exceeded 14 times and four reactivations occurred at san donato whereas the threshold was exceeded 10 times and three reactivations occurred at la salsa hence the probabilities of landsliding after exceedance of the minimum rainfall threshold are 4 14 and 3 10 respectively finally annual reactivation probabilities were calculated to be 0 11 and 0 08 respectively the reliability of the minimum rainfall threshold was tested by i simulating variations in the stress strain behavior of the slopes as a result of fluctuations in the water table from normal to extreme values and ii analyzing the results of continuous multi year monitoring of pore pressure and rainfall variations on a slope composed of dominantly fine grained debris

tectonic setting of the taltson magmatic zone at 1 92 0 ga a granitoid based perspective the paleoproterozoic taltson magmatic zone is one of the key tectonic features of western laurentia the existing tectonic model for the belt envisions its formation by subduction of oceanic crust beneath a continental margin followed by direct collision between formerly separate crustal blocks we tested this model by comparing the large geochemical and isotopic database available for taltson magmatic zone granitoids with similar databases for phanerozoic granitoid suites from different tectonic environments the comparison reveals that the early granitoid suite of the taltson magmatic zone which had been ascribed to the subduction phase of orogenesis lacks the mantle signature apparent in granitoids of phanerozoic continental margin arc settings instead both early and late suites appear to have an intracrustal origin similar to mesozoic and cenozoic granitoids of the cordilleran interior of western north america which formed in the distant hinterland of a convergent plate margin in light of thes

persistent homology on lidar data to detect landslides abstract landslides can result in loss of lives cause damage to property infrastructure utilities and residential structures and can block transportation routes landslide inventory maps can provide spatial temporal information about past and recent landslides and are used for analysis to create models that can characterize susceptibility as such these maps are considered an essential source for risk management tasks in this paper we propose a persistent homology method applied on lidar derived digital terrain model data to detect landslides for landslide inventory maps in testing the hypothesis that persistent homology a method for computing topological features of a space at different resolutions can be used to accurately detect landslides we applied the method on lidar derived digital terrain models to detect shapes and patterns that are indicative of landslide surface expressions we validated our test results by comparing them to currently available landslide inventory maps for selected locations in pennsylvania oregon colorado and washington the results show a different performance for each state the accuraces were 0 79 0 71 0 53 0 69 and 0 77 for five study areas variations in performance are linked to varying surface roughness between different types of landslides their size shape ages composition and a possible history of reactivations of landslides that would further pronounce surface expressions to overcome some of these challenges that may hinder performance of our method we recommend that other datasets containing landslides be considered as additional nth order dimensions beyond the spatial and elevation dimensions inherent in topographic datasets

synchronisation of palaeoenvironmental records over the last 60 000 years and an extended intimate event stratigraphy to 48 000 b2k the intimate protocol for the correlation of marine ice core and terrestrial records is here updated reflecting recent developments in palaeoclimate research originally focussed on last glacial to interglacial transition lgit 22 000 11 500 years b p the intimate group has now extended its study period back to 60 000 years as a first step the intimate event stratigraphy has now been extended to include 8000 48 000 b2k based on a combined ngrip and grip isotope profile against a gicc05 chronology and key tephra horizons from iceland and continental european volcanic sources in this lead article of this intimate special issue we introduce some of the recent achievements of the intimate community and discuss the challenges associated with extending the intimate approach back in time focussing in particular on the chronological problems inherent in comparing different proxy records the intimate approach has thus far been limited predominantly to the north atlantic and australasian regions and we also discuss the potential to extend the intimate protocol beyond these regions

the application of c isotope measurements to the identification of the sources of c in diamonds a review abstract in the past decade the isotopic compositions of c in 600 inclusion bearing diamonds have been determined such analyses have revealed the following isotopic characteristics 1 peridotitic diamonds which typically contain garnet chromite olivine and or orthopyroxene inclusions with refractory compositions high mg cr have 13 c values predominantly between 10 and 1 with a sharp peak in the distribution near 5 2 eclogitic diamonds which commonly contain inclusions of omphacitic clinopyroxene cr poor pyrope and or eclogitic accessory minerals such as rutile kyanite coesite or sanidine have 13 c values between 34 and 3 with a smaller peak near 5 3 the isotopic compositions obtained for suites of diamonds from individual occurrences are in general unique and do not resemble the range and distribution obtained by amalgamating the diamond isotope data from a number of localities 4 isotopic zoning patterns and heterogeneities are found in some diamonds cores of coated diamonds tend to be depleted in 13 c relative to the rims and within single octahedral diamonds 13 c variations of nearly 6 have been reported because expected c isotope fractionations at mantle temperatures are small attempts to model the full range of diamond isotope values through fractionating a homogeneous mantle c source have been unsuccessful nevertheless fractionation is probably responsible for some of the observed variation in 13 c values two other models have also been proposed to account for the diamond characteristics outlined above the primordial model suggests that the range and distribution of c isotope compositions are inherited from primordial c in the mantle which has an inhomogeneous isotopic composition such as that found in meteorites the subduction model suggests that subducted crustal c is the source of c in diamonds as organic and inorganic c compounds in the crust exhibit a range of 13 c values similar to that observed in diamonds this paper reviews the c isotope characteristics of diamonds and compares the models which have been proposed to explain the origins of these characteristics

the influence of partial melting on the electrical behavior of crustal rocks laboratory examinations model calculations and geological interpretations abstract the complex electrical impedance of a granulite has been determined over the frequency range 10 1 to 105 hz at temperatures between 600 and 1200 c at normal pressure and different oxygen fugacities in the stability field of magnetite the impedance spectroscopic is measurements are compared with the results of melting experiments performed under the same experimental conditions and with the same rock sample as the is measurements a strong increase in the electrical conductivity of about one and a half orders of magnitude is observed during partial melting this increase is explained by the formation of an interconnected network of melt the wetting of the grain surfaces starts slightly above the solidus however complete interconnection of the network is detected at higher temperatures 1070 c and hence higher melt fractions 10 vol this is explained by deviations from the equilibrium fabric of the partially molten sample with a modified brick layer model mblm the electrical conductivity is calculated as a function of the observed melt portion this model is valid if the melt forms a complete interconnected network at the grain boundaries the electrical conductivity at different temperatures was modeled using the results of the melting experiments and the mblm melt 10 s m with ea melt 1 ev solid 0 01 s m with ea solid 1 4 ev the results of the laboratory examinations were applied to different crustal regions where partially molten rocks are assumed to exist the same mblm is used to estimate the melt fraction that is necessary to explain the high conducting zones hczs observed in the crust beneath the andean orogen the pyrenees and the tibetan plateau at least 14 4 and 4 vol of interconnected melt are necessary to produce the observed conductivity respectively the actual amount of melt should be higher due to perturbation problems and melt trapped in pockets

geochemistry of peat over kimberlites in the attawapiskat area james bay lowlands northern canada abstract the james bay lowlands which is the se part of the hudson bay lowlands canada and within the paleozoic limestone terrane is covered mostly by peatlands peat samples were examined in the attawapiskat area a region of discontinuous permafrost where more than 19 kimberlite pipes have been found beneath a cover of peat 2 4 m thick and quaternary sediments up to 20 m thick of tyrell sea clay beds and glacial tills pore water at a depth of 40 cm in the peat has a consistently low ph the compositions of peat show spatial variation with the distribution of kimberlites suggesting that they are influenced by the underlying rocks even through there are thick layers of tills and sediments between the bedrocks and peat however elevated concentrations of pathfinder elements of kimberlites in bulk peat samples and aa5 leach are not necessarily directly above kimberlites the diffused metal anomalies around kimberlites are attributed to the dissolution precipitation of secondary phases carbonates and fe o oh in acidic and reduced waters in peat and the movement of waters through peat this pilot study suggests that peat compositions do reflect the underlying bedrock compositions for kimberlite exploration a geochemical survey of peat is useful to discriminate concealed kimberlites from other anomalies defined by geophysical and other techniques however such a geochemical survey is not suitable for delineating the shapes of the concealed kimberlites due to broad dispersed anomalies

landslide erosion controlled by hillslope material landslide erosion is a primary control of landscape relief a wide ranging analysis of landslide geometry shows that soil based landslides are generally less voluminous than landslides that involve the failure of bedrock and provides refined metrics for estimating the volume of a landslide from the area of the failure

a high resolution magnetotelluric survey of the iapetus suture zone in southwest scotland summary magnetic variation mv surveys show a 40 km wide zone of high electrical conductivity in the middle crust extending across the southern uplands of scotland from the north sea to galloway a new magnetotelluric mt survey across the conductor in galloway was designed to improve the resolution of structure in the depth range 1 15 km and at the same time assess the improvement in resolution that could be achieved in a practical situation by optimizing data acquisition processing analysis and modelling a 40 km long profile was measured doubled for part of its length at a separation of 1 km with a typical site spacing of 2 km or less it was supplemented by shorter parallel and orthogonal lines giving a total of 40 sites galvanic distortion models involving regional 2 d structures gave poor fits to the impedance tensors both for the array as a whole and for individual sites confirming the picture from induction arrow maps that many sites were influenced by 3 d structures on scales of a few kilometres and upwards other indicators of the electrical strike regional and local mv measurements the spatial structure of the groom bailey regional impedance phase and of the rotated off diagonal phase gave values more in agreement with the geological strike of n52 e which was adopted as the most appropriate coordinate system into which to resolve the data the mt impedances were accordingly rotated into directions n38 w tm and n52 e te and inverted using the 2 d code of rodi mackie the investigation explored the sensitivity of the outcome to a wide range of starting model resistivities and roughness parameters and to different data subsets the te mode data were insensitive to structural detail and the best fit achieved was unacceptable suggesting the influence of structure outside the plane of the section the tm mode data could be fitted satisfactorily by varying the model roughness and gave the best control on the geometry of the conductive bodies forward modelling showed that the model generated from the tm mode also fitted the mv data adequately the inversion resolved the conductive zone into distinct blocks with edges matching faults mapped in the surface geology the leadhills fardingmullach and orlock bridge faults and the moffat valley lineament in the resistivity image the faults are vertical structures disrupting other features to a depth of 15 km which agrees with the view that although they originated as thrusts they were reactivated by strike slip motion during oblique closure of the iapetus ocean within some of the blocks are highly conductive regions no more than 4 km wide the most likely explanation is graphite or other metallic mineralization localized in shear zones

electromagnetic images of the trans hudson orogen the north american central plains anomaly revealed magnetotelluric studies of the trans hudson orogen over the last two decades prompted by the discovery of a significant conductivity anomaly beneath the north american central plains nacp from over 300 sites yield an extensive database for interrogation and enable three dimensional information to be obtained about the geometry of the orogen from southern north dakota to northern saskatchewan the nacp anomaly is remarkable in its continuity along strike testimony to along strike similarity of orogenic processes where bedrock is exposed the anomaly can be associated with sulphides that were metamorphosed during subduction and compression and penetratively emplaced deep within the crust of the internides of the orogen to the boundary of the hearne margin a new result from this compilation is the discovery of an anomaly within the upper mantle beginning at depths of 80 100 km this lithospheric mantle conductor has electrical properties similar to those for the central slave craton mantle conductor

partial melting below the magmatic arc in the central andes deduced from geoelectromagnetic field experiments and laboratory data abstract magnetotelluric and geomagnetic deep soudings in northern chile revealed a pronounced high conductivity zone hcz below the western cordillera which constitutes the present magmatic arc with active volcanism of the south american continental margin conductivities in the range of 1 s m are observed the anomalously high conductivities in a broad depth range from approximately 20 km to at least 60 km are interpreted in terms of partial melting other geophysical observations such as a zone of low seismic velocities lvz at similar depths high heat flow values 100 mw m2 and a pronounced negative anomaly in the residual gravity field are also considered impedance spectroscopic laboratory experiments up to and in the temperature range of partial melting were performed under controlled oxygen fugacities at sub solidus temperatures electrical behavior is described by defect electrons with an activation energy of 1 34 ev and a conductivity of 2 5 ms m at 900 c model calculations using a modified brick layer model mbl were compared with experimental observations a good agreement between calculations and experiments is achieved with an electrical resistivity of the melt phase of 7 s m at 1250 c assuming an activation energy of 1 ev the same mbl model is used to calculate melt proportions beneath the western cordillera between 14 and 27 vol of interconnected melt are necessary to explain the observed hcz the stability of the melt rich crust is explained by a dynamic melting crystallisation behavior during crustal anatexis and by magma filled dikes

inclusions in diamonds from the k14 and k10 kimberlites buffalo hills alberta canada diamond growth in a plume analyses of mineral inclusions carbon isotopes nitrogen contents and nitrogen aggregation states in 29 diamonds from two buffalo hills kimberlites in northern alberta canada were conducted from 25 inclusion bearing diamonds the following paragenetic abundances were found peridotitic 48 eclogitic 32 eclogitic websteritic 8 websteritic 4 ultradeep 4 and unknown 4 diamonds containing mineral inclusions of ferropericlase and mixed eclogitic asthenosphericwebsteritic and eclogitic websteritic mineral associations suggests the possibility of diamond growth over a range of depths and in a variety of mantle environments lithosphere asthenosphere and possibly lower mantle eclogitic diamonds have a broad range of c isotopic composition d 13 c y21 x to y5x peridotitic websteritic and ultradeep diamonds have typical mantle c isotope values d 13 c y4 9 x av except for two 13 c depleted peridotitic d 13 c y11 8 x y14 6 x and one 13 c depleted websteritic diamond d 13 c y11 9 x infrared spectra from 29 diamonds identified two diamond groups 75 are nitrogen free type ii or have fully aggregated nitrogen defects type iab with platelet degradation and low to moderate nitrogen contents av 330 ppm n 25 have lower nitrogen aggregation states and higher nitrogen contents f30 iab 1600 ppm n the combined evidence suggests two generations of diamond growth type ii and type iab diamonds with ultradeep peridotitic eclogitic and websteritic inclusions crystallised from eclogitic and peridotitic rocks while moving in a dynamic environment from the asthenosphere and possibly the lower mantle to the base of the lithosphere mechanisms for diamond movement through the mantle could be by mantle convection or an ascending plume the interaction of partial melts with eclogitic and peridotitic lithologies may have produced the intermediate websteritic inclusion compositions and can explain diamondsofmixedparageneses andtheoverlapinc isotopevaluesbetweenparageneses strongdeformationandextremelyhigh nitrogen aggregation states in some diamonds may indicate high mantle storage temperatures and strain in the diamond growth environment a second diamond group with type iaa iab nitrogen aggregation and peridotitic inclusions crystallised at the base of the cratonic lithosphere all diamonds were subsequently sampled by kimberlites and transported to the earth s surface crown copyright d 2004 published by elsevier b v all rights reserved

the largest prehistoric landslide in northwestern slovakia chronological constraints of the kykula long runout landslide and related dammed lakes abstract this study deals with the chronology of the largest long runout landslide in the northwesterrn part of the western flysch carpathians kysucke beskydy mts slovakia despite the impossibility of using direct radiocarbon dating method time constraints for the evolution of the landslide were determined on the basis of the dating of various sedimentological geomorphological elements situated on and adjacent to the landslide body the results show that the landslide evolved between 10 3 and 9 0 ka 14 c bp i e in the wider transitional phase between the late glacial lg and the holocene the main mass movement activity took place at the turn of the younger dryas preboreal chronozones whereas retrogressive activity continued up to the preboreal boreal transition radiocarbon dating together with pollen analysis and sedimentology of landslide dammed palaeolakes and colluvial peat bogs revealed almost continuous holocene palaeogeographical records between 10 3 and 3 3 ka 14 c bp periods of enhanced sediment supply to the reservoirs in 9 9 9 0 8 4 8 2 6 9 6 5 and 4 5 ka 14 c bp correlate well with palaeogeomorphic and palaeohydrological records from nearby polish carpathians the study confirms that the lg holocene transition represented a favourable period for the evolution of large landslides not only in glaciated high mountain areas but also in medium high mountains of central europe

using multi proxy palaeoecology to test a relict status of refugial populations of calcareous fen species in the western carpathians the distribution pattern of relict and specialised species in calcareous fens was revealed to be non stochastic with ancient fens harbouring more of these species than younger ones this phenomenon could be caused by long lasting in situ survivals over millennia but direct palaeoecological evidence is lacking we addressed the question whether at least some ancient calcareous fens indeed retained open fen patches throughout the holocene using a palaeoecological approach involving proxies with different taphonomies pollen vascular plants bryophytes molluscs we identified three old fens in the western carpathians where several postglacial relict species have recently been found and we reconstructed their histories with respect to sedimentary processes vegetation structure and dynamics of relict species the development at all the sites started with a semi open fen community dominated by sedges and brown mosses the site with the highest recent number of relict species was reconstructed to harbour open patches continually since the late glacial to the present including the middle holocene when open fen patches were restricted by contrast at the site with the lowest recent number of relict species a large sedimentary hiatus suggested peat mineralisation or erosion that prevented the survival of light demanding species at all the sites characteristic snails of european glacial periods occurred during fen initiation but disappeared around the early middle holocene transition the probability of a relict species being present in a modern fen community increases with fen age but it also depends on the continual existence of open fen patches and peat accumulation throughout the middle holocene

charcoal fragments in surface samples following a fire and the implications for interpretation of subfossil charcoal data abstract following an uncontrolled fire in an area of heathland in sw england surface samples were taken from selected positions charcoal concentrations charcoal pollen ratio and size class frequencies were measured and the data from burned unburned and forest areas are compared charcoal concentrations show distinct variability between closely spaced samples but despite this differences are shown between the burned and unburned areas selected size classes are suggested as being appropriate for distinguishing between burned and unburned areas in palaeoecological studies while in need of replication these data should provide a basis for further studies of this type

the historical development of the magnetic method in exploration the magnetic method perhaps the oldest of geophysical exploration techniques blossomed after the advent of airborne surveys in world war ii with improvements in instrumentation navigation and platform compensation it is now possible to map the entire crustal section at a variety of scales from strongly magnetic basement at regional scale to weakly magnetic sedimentary contacts at local scale methods of data filtering display and interpretation have also advanced especially with the availability of low cost high performance personal computers and color raster graphics the magnetic method is the primary exploration tool in the search for minerals in other arenas the magnetic method has evolved from its sole use for mapping basement structure to include a wide range of new applications such as locating intrasedimentary faults defining subtle lithologic contacts mapping salt domes in weakly magnetic sediments and better defining targets through 3d inversion these new applications have increased the method s utility in all realms of exploration in the search for minerals oil and gas geothermal resources and groundwater and for a variety of other purposes such as natural hazards assessment mapping impact structures and engineering and environmental studies

geomorphons a pattern recognition approach to classification and mapping of landforms abstract we introduce a novel method for classification and mapping of landform elements from a dem based on the principle of pattern recognition rather than differential geometry at the core of the method is the concept of geomorphon geomorphologic phonotypes a simple ternary pattern that serves as an archetype of a particular terrain morphology a finite number of 498 geomorphons constitute a comprehensive and exhaustive set of all possible morphological terrain types including standard elements of landscape as well as unfamiliar forms rarely found in natural terrestrial surfaces a single scan of a dem assigns an appropriate geomorphon to every cell in the raster using a procedure that self adapts to identify the most suitable spatial scale at each location as a result the method classifies landform elements at a range of different spatial scales with unprecedented computational efficiency a general purpose geomorphometric map an interpreted map of topography is obtained by generalizing allgeomorphons to a small number of the most common landform elements due to the robustness and high computational efficiency of the method high resolution geomorphometric maps having continental and even global extents can be generated from giga cell dems such maps are a valuable new resource for both manual and automated geomorphometric analyses in order to demonstrate a practical application of this new method a 30 m cell 1 geomorphometric map of the entire country of poland is generated and the features and potential usage of this map are briefly discussed the computer implementation of the method is outlined the code is available in the public domain

quantitative analysis of land surface topography land surface topography significantly affects the processes of runoff and erosion a system which determines slope aspect and curvature in both the down slope and across slope directions is developed for an altitude matrix also the upslope drainage area and maximum drainage distance are determined for every point within the altitude matrix a fortran 66 program performs the analysis

mid holocene charcoal stratigraphy fire history and palaeoecology at north gill north york moors uk abstract small peat mires are a favourable medium for the preservation of charcoal records that can be correlated more precisely with past fire history as part of multi proxy palaeoecological studies the north york moors upland has many suitable peat deposits with a well researched palaeoenvironmental history that offer the potential for high precision palaeofire studies we have examined the charcoal and pollen stratigraphy at the north gill site at a range of spatial and temporal resolutions for the mid holocene period between about 7k and 4 5k radiocarbon years ago in an individual core three size class charcoal records large small and microscopic reflect the scale and location of local fire events although the micro charcoal curve contains a background regional signal of about 10 of the charcoal pollen ratio most micro charcoal is generated locally and deposited close to its source at the site scale spatial comparison of four cores shows a variable relationship between tree pollen and micro charcoal concentrations which is an index of the size and intensity of local fire phases individual fires cannot be distinguished fine resolution sampling at the millimetre scale resolves major burning phases into discrete sub phases that may reflect the effects of individual fires at this fine temporal scale this multi scale research indicates that detailed charcoal stratigraphies at varying resolutions are capable of interpretation in terms of local regional and intermediate fire history

magnetotelluric and teleseismic study across the snowbird tectonic zone canadian shield a neoarchean mantle suture 1 the snowbird tectonic zone stz is a fundamental boundary within canada s western churchill province one of the world s largest yet poorly known fragments of archean crust geophysical data from a collocated magnetotelluric and teleseismic transect across the northeastern segment of the stz provide an image of its subsurface geometry and indicate that it may have been previously mislocated the model suggests that 1 the stz has played a major role in the neoarchean assembly and paleoproterozoic reworking of the western canadian shield 2 it was reactivated in a manner comparable to other crustal scale features such as the kapuskasing zone of the superior province canada and the redbank thrust of the arunta block central australia and 3 it juxtaposes mantle blocks with contrasting geophysical properties revealing a lithosphere scale overlap of the leading edges of the rae and hearne domains the stz thus records plate interactions in the neoarchean comparable in scale with that of modern orogenic belts