time scale and conditions of weathering under tropical climate study of the amazon basin with u series the rio solimoes amazonas amazon river and its major tributaries have been analyzed for u series nuclides 238 u 234 u 230 th 226 ra disequilibria have been measured in the dissolved 0 2 lm as well as bed sands u series disequilibria are closely related to major and trace element compositions and therefore reflect elemental fractionation during chemical weathering moreover while the dissolved load records present day weathering suspended particles integrate the erosion his tory over much longer time scales 100 ka lowland rivers are characterized by long time scales of chemical erosion p100 ka result ing in a high weathering intensity moreover exchange between suspended particles and the dissolved load may explain the u series signature for these rivers by combining u series and pb isotopes in suspended particles we show that erosion in the rio madeira basin occurred as a multi step process whereby the pristine continental crust was eroded several hundreds of ma ago to produce sediments that have then been integrated in the cordillera by crustal shortening and are currently eroded in contrast recent erosion of a pristine crust is more likely for the rio solimoes amazonas 10 ka the suspended particles of the rivers draining the andes solimoes ama zonas madeira suggest time scales of weathering ranging between 4 and 20 ka this indicates that suspended particles transported by those rivers are not stored for long periods in the andean foreland basin and the tropical plain the sediments delivered to the ocean have resided only a few ka in the amazon basin 6 3 1 ka for the rio amazonas at obidos nevertheless a large fraction of the sediments coming out from the andes are trapped in the foreland basin and may never reach the ocean erosion in the andes is not operating in steady state u series systematics shows unambiguously that rivers are exporting a lot more sediments than predicted by steady state erosion and that is a consequence of soil destruction greater than production by relating this observation to the short time scales of weathering inferred for the andes a few ka it appears that the erosion regime has been recently perturbed resulting in high denudation rates a possible explanation would be the increase in precipitation less than 5 ka proposed by recent paleoclimatic studies our results indicate that erosion responds rapidly to high frequency climatic fluctuations

scaling nature of crustal susceptibilities scale invariant or self similar properties have been demonstrated for a wide range of geophysical processes and rock properties evidence from well logs and inferences from aeromagnetic field power spectra suggest that crustal susceptibility also shows this behaviour with a power spectrum proportional to the 4 power of the spatial frequency we examine two large susceptibility measurement data sets and find that they both support the scaling hypothesis

dating plio pleistocene glacial sediments using the cosmic ray produced radionuclides 10be and 26al we use the cosmic ray produced radionuclides 26al and 10be to date plio pleistocene glacial sediment sequences these two nuclides are produced in quartz at a fixed ratio but have different decay constants if a sample is exposed at the surface for a time and then buried by overburden and thus removed from the cosmic ray flux the 26al 10be ratio is related to the duration of burial we first attempted to date pre wisconsinan tills by measuring 26al and 10be in fluvial sediments beneath them and applying the method of burial dating which previous authors have used to date river sediment carried into caves this method however requires simplifying assumptions about the 26al and 10be concentrations in the sediment at the time of burial we show that these assumptions are not valid for river sediment in glaciated regions 26al and 10be analyses of such sediment do not provide accurate ages for these tills although they do yield limiting ages in some cases we overcome this difficulty by instead measuring 26al and 10be in quartz from paleosols that are buried by tills we use a more general mathematical approach to determine the initial nuclide concentrations in the paleosol at the time it was buried as well as the duration of burial this technique provides a widely applicable improvement on other means of dating plio pleistocene terrestrial glacial sediments as well as a framework for applying cosmogenic nuclide dating techniques in complicated stratigraphic settings we apply it to pre wisconsinan glacial sediment sequences in southwest minnesota and eastern south dakota pre wisconsinan tills underlying the minnesota river valley were deposited 0 5 to 1 5 ma and tills beneath the prairie coteau in eastern south dakota and adjacent minnesota were deposited 1 to 2 ma

energy histograms for the characterization of deep reflection seismic profiles summary we modified dohr s method and were able to establish trends of crustal reflectivity distribution four main types of crustal reflectivity depth histograms could be distinguished dohr s method was based on line drawings from which the total length of reflections was calculated for time distance frames along the profile in this paper we present a new method to derive such histograms automatically from the final stack tapes this allows an objective comparison of deep reflection seismograms from different crustal units and from different research groups it is shown that our energy histograms are consistent with earlier manually produced histograms and that the previous results can be reproduced first applications to dekorp and ktb data in germany are presented

pattern analysis of seismic records the three steps in automated analysis of seismic records are trace matching event detection and seismic zoning our algorithm matches traces by comparing sequences of peaks on neighboring traces and edits pairs of peaks identified as similar for consistency in trend across and down the record by combining connected pairs we obtain laterally coherent events of varying quality which divide a record into zones that may have lithologic significance these zones can be obtained automatically by applying cluster analysis to seismic attributes and other discriminating properties of these events on common shot gathers from a four fold survey in saskatchewan canada the coherent events which we detected this way are consistent with those recognized visually and are associated with clear formation boundaries strong reflections correspond to events detected with high confidence and the seismic zones show good correlation among shot records high detection confidence and good correlation indicate that the app

empirical mode skeletonization of deep crustal seismic data theory and applications seismic skeletonization is a pattern recognition technique used to decompose reflection seismic data into events or reflectors and their seismic attributes and to store the results in an event file for an analysis toward seismic interpretation the extraction of instantaneous frequency from the event file for any statistical analysis of the seismic attribute analysis is currently not possible thus precluding the complete parameterization of the reflected seismic wave field in terms of its decomposition products empirical mode decomposition of reflection seismic data has uniquely addressed the question of computing the instantaneous frequency from its decomposition products using the hubert transform although the decomposition products of the seismic skeletonization and the empirical mode decomposition are conceptually different they share a common link to the primitive features of the seismic waveforms in this paper we introduce a new decomposition technique empirical mode skeletonization that combines the features of both seismic skeletonization and empirical mode decomposition by this process it is now possible to subject the reflection seismic data to an analysis that could include a parameterization of the reflected wave field we apply the new technique to a segment of seismic line 1 of the lithoprobe slave northern cordillera lithosphere evolution snorcle transect to extract event oriented instantaneous frequency attributes and also to analyze the decomposition products for any scaling behavior of the reflected wave field

steady state reach scale theory for radioactive tracer concentration in a simple channel floodplain system 1 a steady state analytical model is presented for reach scale variation in the concentration of a decaying radioactive tracer associated with sediment particles that regularly pass through an off channel floodplain the floodplain is represented as a series of well mixed sediment reservoirs that continually exchange sediment with the channel the model allows for tributary input and valley wide aggradation or degradation tracer concentration depends on the upstream boundary concentration the tracer and sediment load floodplain geometry and the rates of in floodplain tracer production and or decay the theory predicts relatively modest down channel change in the concentration of long lived isotopes but implies that significant change may occur for 1 tracers with a short enough half life such as 14c or 2 floodplains with sediment residence times that are large enough for cosmogenic production or meteoric fallout to increase tracer concentration in the down valley direction the profiles are shown to be strongly dependent on the grain size distributions of both the sediment load and the floodplain the results imply that down channel 14c profiles have the potential to constrain holocene bed material loads in systems with sufficient storage the theory concisely describes the general importance of a floodplain for modifying in situ produced cosmogenic tracer concentration and can also characterize floodplain importance for fallout radioisotopes i e 10be 210pb or 7be or organic 14c

chemical weathering and atmospheric soil co2 uptake in the andean and foreland amazon basins abstract this study is a geochemical investigation of the andean and foreland basins of the amazon river at high spatial and time resolution carried out within the framework of the hybam research program hydro geodynamics of the amazon basin monthly sampling was carried out at 27 gauging stations located in the upper tributaries of the amazon basin from north to south the napo maranon ucayali madre de dios beni and mamore rivers the aim of this paper is to estimate the present day chemical weathering rate cwr as well as the flux of co 2 consumption from total and silicate weathering in the andes and foreland amazon basins and to discuss their distribution as a function of geomorphic and structural parameters based on the forward method the napo and other ecuadorian basins present high silicate weathering rates in comparison with the other basins we confirm that the maranon and ucayali rivers control the amazon hydrochemistry due to the presence of salt rocks and carbonates in these basins the madre de dios beni and mamore basins do not contribute much to the amazon dissolved load this north to south cwr gradient can be explained by the combination of decreasing weatherable lithology surface and decreasing runoff rates from the north to the south the foreland part of the basins or mountain lowland transition accounts for nearly the same proportion of the amazon silicate chemical weathering and carbonate chemical weathering fluxes as the andean part this result demonstrates the importance of the sediment accumulation areas in the amazon basin weathering budget and can be explained by the occurrence of a higher temperature the deposition of fresh sediments from andean erosion and a higher sediment residence time than in the upper part of the basin with a total co 2 consumption rate of 744 10 3 moles km year 1 and a silicate co 2 consumption rate of 300 10 3 moles km year 1 the upper amazon river andes foreland part is the most intense part of the amazon basin in terms of atmospheric co 2 consumption by weathering processes it is an important co 2 sink by weathering processes but accounts for only somewhat more than half of the co 2 consumption by silicate weathering of the amazon basin this result points out the importance of the lowland part of the basin in the inorganic c silicate budget the upper amazon accounts for 2 4 of the world s silicate co 2 consumption which is the same proportion as for the southern and southern east himalaya and tibetan plateau

lithoprobe crustal reflection cross section of the southern canadian cordillera 1 foreland thrust and fold belt to fraser river fault seismic reflection data from the south central canadian cordillera covering the interval from the easternmost metamorphic core complexes near arrow lakes to the fraser river fault system along the fraser river reveal a highly reflective and complex crust the base of the crustal reflectivity interpreted as the reflection moho is clearly delineated by a continuous sharp boundary that is essentially planar and slopes uniformly over a distance of 250 km from about 12 0 s in the east to about 10 5 s in the west this virtual lack of relief at the base of the crust contrasts sharply with surface structures that involve 25 km or more of structural relief some of these surface structures can be readily correlated to structures that are outlined by the reflection data and that can be followed into the middle and lower crust even though part of this area was subjected to large amounts of eocene extension the crust is not divisible into transparent upper and reflective lower layers as it is in parts of the u s cordillera three structural culminations the monashee complex the vernon antiform and the central nicola horst are interpreted on the basis of the reflection configuration and the surface geological relationships to have formed initially during jurassic to eocene compression and then to have been modified and exposed during early and middle eocene extension an example of a compressional structure observed on the profiles is the monashee decollement which can be traced from the surface westward into the lower crust extension is manifested along a variety of normal faults including the regionally extensive low angle okanagan valley eagle river fault system moderately dipping faults such as the columbia river and slocan lake faults and high angle faults such as the quilchena creek and coldwater faults both jurassic to eocene compressional shear zones and early to middle eocene extensional shear zones are listric into the lower crust or moho under the intermontane belt

beryllium isotope geochemistry in tropical river basins abstract the distributions of beryllium 9 and beryllium 10 in rivers within the orinoco and amazon basins have been examined to extend our understanding of their geochemical cycles and to develop their use both in geochronometry and in studying erosional processes beryllium 9 the stable isotope is weathered from mineral lattices before entering the riverine dissolved or exchangeable phase the cosmogenic radioisotope 10be t 1 2 1 5 myr is produced primarily in the atmosphere and is brought into riverine systems via rainfall in dissolved or exchangeable form it may be used to examine the processes which affect beryllium partitioning between the dissolved and particulate phases ancillary data such as major ion distributions provide a basis for selecting regions in which riverine chemistry is dominated by a single geochemical process allowing examination of its effects on be distributions in isolation analyses of 9be in dissolved and suspended material from rivers with a wide range of chemical compositions indicate that its geochemistry is primarily controlled by two major factors 1 1 its abundance in the rocks of the watershed and 2 2 the extent of its adsorption onto particle surfaces the relative importance of these parameters in individual rivers is determined by the extent of interaction with flood plain sediments and the riverine ph this understanding of 9be geochemistry forms a basis for examination of the geochemical cycling of 10be in rivers which are dominated by interaction with sediments the riverine concentration of dissolved 10be is far lower than that in the incoming rainwater indicating that a substantial proportion of it is retained within the soils of the basin or is adsorbed onto riverine particles however in acidic rivers in which the stable dissolved be concentration is determined by the be level in the rocks of the drainage basin dissolved 10be has essentially the same concentration as in precipitation these observations imply that the soil column in such regions must be saturated with respect to 10be and that the ratio of the inventory to the flux does not represent an age as may be the case in temperate latitudes but rather a residence time

from source to sink preserving the cosmogenic 10be derived denudation rate signal of the bolivian andes in sediment of the beni and mamore foreland basins abstract the denudation rate signal of the bolivian andes as measured by cosmogenic 10 be in sediment is preserved in the floodplain of adjacent foreland basins even though these basins store the sediment for thousands of years this conclusion is drawn from comparing published andean source area denudation rates with new cosmogenic 10 be data as measured in the floodplains of the large beni and mamore basins for the entire beni basin including the sediment producing andes and the vast flooded plains of the foreland the cosmogenic nuclide derived denudation rate is 0 45 0 06 mm yr while that of the mamore basin is 0 55 0 19 mm yr by comparison the respective andean source areas erode at averaged rates of 0 37 0 06 mm yr upper beni and at 0 56 0 09 mm yr upper mamore we notice a decrease in variability of denudation rate with increasing spatial scale as small scale processes are averaged out sediment mixing within the floodplain damps scatter of nuclide derived denudation rates picked up in the source area on the temporal scale a remarkable agreement between cosmogenic nuclide derived rates averaging over a few kiloyears with those from fission track dating averaging over millions of years seems to suggest that cosmogenic nuclide derived denudation rates capture the long term erosional characteristics of the mountain belt the sum of these observations suggests that any sample collected along a river traversing a floodplain will yield the denudation rate of the source area this finding opens the unique possibility of constraining cosmogenic nuclide derived paleo sediment budgets for these large basins as the long term spatially averaged denudation rate signal of the sediment producing area is preserved in sedimentary archives

the fluvial geochemistry and denudation rate of the guayana shield in venezuela colombia and brazil abstract the guayana shield is composed of early to mid precambrian igneous and metamorphic basement rocks with a quartzitic platform cover the complete absence of limestones and evaporites allows a clear chemical expression in the stream data of the primary weathering of the basement in a humid tropical environment total erosion rates are extremely slow 10 m m y with equal contributions from the dissolved and suspended loads however the former is largely silica with ratios of si to total cation equivalents si tz ranging to in excess of three weathering is complete to kaolinite and gibbsite i e the environment is one of active laterisation with a penetration rate of the weathering front into the fresh substrate about twice the denudation rate in basins of relatively homogeneous lithology rb sr isochrons constructed from the river data agree with the whole rock ages from the drainages thus all the common refractory rb containing minerals k feldspar mica are completely dissolved the thick lateritic regolith that is accumulating as a result of this intense weathering is a common relict feature on other southern hemisphere shields in the absence of active tectonics or greatly accelerated mechanical erosion the weathering rates of these basement rocks must be quite insensitive to environmental change

the dependence of meteoric 10be concentrations on particle size in amazon river bed sediment and the extraction of reactive 10be 9be ratios abstract concentrations of meteoric 10 be extracted from detrital amazon river sediment are strongly particle size dependent such grain size dependency presents a formidable obstacle to routine applications of meteoric cosmogenic 10 be to basin wide erosion studies in this study we explore means to eliminate these grain size effects in bedload from rivers of the amazon basin by measuring 10 be 9 be ratios after selective chemical extraction of reactive authigenic phases these phases mainly comprise fe mn hydr oxides that are the main carriers of 9 be and 10 be we explore the distribution of 10 be and its stable 9 be counterpart between these phases and the partitioning of be into remaining silicate fractions this extraction procedure was carried out on bedload samples comprising the three main tectonic units of the amazon basin namely the andes the guyana and brazilian shields and the central amazonian lowlands for all samples extracted 10 be concentrations show a strong decrease with increasing particle size with up to 20 times more 10 be extracted from the finest analyzed 10 be concentrations mostly to subsequent dilution by quartz in coarse bedload however when normalized to stable 9 be concentrations that are also extracted from reactive phases grain size effects are effectively removed and the resulting reactive 10 be 9 be ratio is uniform for all particle sizes the reactive 10 be 9 be ratio thus offers important advantages over methods employing single meteoric 10 be concentrations such that this ratio can now be developed as quantitative tracer for earth surface processes

10be and 9be in marine sediments and their potential for dating using sequential leaching experiments we have measured the fraction of the cosmogenic isotope 10be half life 1 5 my and its stable isotope 9be co extracted with the following phases in marine sediments exchangeable calcium carbonate fe and mn oxyhydroxides organic opal and detrital the extraction of the authigenic phases typically release 70 of the 10be but only 40 of the 9be in order to test its potential for dating marine sediments we have measured the authigeniccally associated 10be 9be in 17 surface sediment samples from different ocean basins the observed spatial variability which appears to be influenced by proximity to continental input of 9be precludes the general and precise applications of leached 10be 9be for dating however the relatively constant value observed in surface sediments over large areas of the pacific indian and southern atlantic oceans shows considerable promise for approximate dating of open oceans sediments in order to test temporal variability a profile of the authigenically associated 10be 9be ratio has been measured in the independently dated central pacific core rc12 65 the observed variation in 10be 9be over the past nine my is approximately twice that expected on the basis of 10be decay alone several possible explanations for such behavior and their potential consequences for the use of leached 10be 9be for dating are discussed

non pegmatitic deposits of beryllium mineralogy geology phase equilibria and origin non pegmatitic occurrences of be minerals constitute a diverse set of geologic environments of considerable mineralogical and petrological interest they currently provide the majority of the world s be ore and emeralds and they contain the greatest resource of these commodities of the approximately 100 be minerals known see chapter 1 by grew appendix a most occur in hydrothermal deposits or non pegmatitic igneous rocks where their distribution varies systematically with the setting and origin table 1 fig 1 view this table table 1 beryllium minerals in non pegmatitic deposits formulas use and occurrence 1 figure 1 chemography of the principal solid phases in the beo al2o3 sio2 h2o f2o 1 bash system with the projected positions of helvite group and alkali be silicates also shown are generalized fields for some of the major types natural of occurrences cf table 1 fig 4 see text for discussion beryllium minerals are best known from geologic systems associated with felsic magmatism they also occur in a variety of settings that lack evident igneous associations environments range from the surface to the deep crust and host rocks range from feldspathic to carbonate to ultramafic in composition genetically related igneous rocks are felsic and share low calcium and high f contents but are diverse in composition setting and origin compositions range from strongly peraluminous to peralkaline and can be silica undersaturated beryllium minerals also occur in metamorphic and basinal environments and are redistributed by surface processes table 2 summarizes the types and significance of major groups of occurrences by their lithologic associations figure 2 shows the global distribution of some important examples and regional belts for most types at least one example has been described in some detail and can be used to help evaluate general patterns however

skeletons and fractals a statistical approach to deep crustal seismic data processing and interpretation abstract coherent seismic reflection events are identified using seismic skeletonization an automatic pattern recognition technique in which waveforms are parameterized such that the attributes of each event are identified and stored in a relational database or event file this new approach to seismic interpretation allows statistical analyses of the attributes including estimation of scaling laws for reflectivity observed on deep seismic data and development of new filtering techniques based on characteristics such as dip and reflection event length applications of the technique to deep crustal reflection data sets from the alberta basement transect of the lithoprobe project assist interpretation in areas that lack surface outcrop or other means of relating reflections from the deep crust to the surface

regolith production and transport at the susquehanna shale hills critical zone observatory part 2 insights from meteoric 10be 1 regolith mantled hillslopes are ubiquitous features of most temperate landscapes and their morphology reflects the climatically biologically and tectonically mediated interplay between regolith production and downslope transport despite intensive research few studies have quantified both of these mass fluxes in the same field site here we present an analysis of 87 meteoric 10be measurements from regolith and bedrock within the susquehanna shale hills critical zone observatory ssho in central pennsylvania meteoric 10be concentrations in bulk regolith samples n 73 decrease with regolith depth comparison of hillslope meteoric 10be inventories with analyses of rock chip samples n 14 from a 24 m bedrock core confirms that 80 of the total inventory is retained in the regolith the systematic downslope increase of meteoric 10be inventories observed at ssho is consistent with 10be accumulation in slowly creeping regolith 0 2 cm yr 1 regolith flux inferred from meteoric 10be varies linearly with topographic gradient determined from high resolution light detection and ranging based topography along the upper portions of hillslopes at ssho however regolith flux appears to depend on the product of gradient and regolith depth where regolith is thick near the base of hillslopes meteoric 10be inventories at the north and south ridgetops indicate minimum regolith residence times of 10 5 3 7 and 9 1 2 9 ky respectively similar to residence times inferred from u series isotopes in ma et al 2013 the combination of our results with u series derived regolith production rates implies that regolith production and erosion rates are similar to within a factor of two on ssho hillcrests

sediment production and delivery in the amazon river basin quantified by in situ produced cosmogenic nuclides and recent river loads we use cosmogenic nuclide derived denudation rates from in situ produced 10 be in river sediment to determine sediment production rates for the central amazon river and its major tributaries recent developments have shown that this method allows calculating denudation rates in large depositional basins despite intermediate sediment storage with the result that fluxes of the sediment producing hinterland can now be linked to those discharged at the basins outlet in rivers of the central amazonian plain sediment of finer grain sizes 125 500 m yields a weighted cosmogenic nuclide derived denudation rate of 0 24 0 02 mm yr that is comparable to the integrated rate of all main andean draining rivers 0 37 0 06 mm yr which are the beni napo mamore ucayali and maranon rivers coarser grained sediment 500 m of central amazonian rivers is indicative of a source from the tectonically stable cratonic headwaters of the guyana and brazilian shields for which the denudation rate is 0 01 0 02 mm yr respective sediment loads can be calculated by converting these cosmogenic nuclide derived rates using their sediment producing areas for the amazon river at obidos a sediment production rate of 610 mt yr results non andean source areas contribute only 45 mt yr a comparison with published modern sediment fluxes shows similarities within a factor of 2 with an average gauging derived sediment load of 1000 mt yr at obidos for example we attribute this similar trend in cosmogenic versus modern sediment loads first to the absence of long term deposition within the basin and second to the buffering capability of the large amazon floodplain the buffering capability dampens short term high amplitude fluctuations climatic variability in source areas and anthropogenic soil erosion by the time the denudation rate signal of the hinterland is transmitted to the outlet of the basin

stable runoff and weathering fluxes into the oceans over quaternary climate cycles the effect of glacial interglacial cycles on surface weathering rates has been unclear a beryllium based proxy for weathering shows minimal variations in the input of silicate weathering products to the oceans for the past two million years

10be study of rapid erosion in taiwan cosmogenic 10be was measured using accelerator mass spectrometry in soils and sediments to study the erosion of taiwan which has the highest denudation rate in the world the river sediments in taiwan have very low 10be concentrations around 5 million atoms per gram about 145 the world wide average this is the direct consequence of its high sediment yield of more than 1000 mg cm2 yr 70 times the world average combining these values we found that for taiwan as a whole the 10be output to the sea only slightly exceeds the input from the rain a situation typical of many areas around the world therefore even in this example of extremely rapid erosion 10be seems to remain a useful indicator for erosion status the total 10be inventory found in a soil profile from a geologically stable area is at least 18 of the maximum possible inventory the minimum age thus estimated for the soil is 0 11 ma in reasonable agreement with estimates from other means the maximum erosion rate for this area thus estimated is at most 0 14 mg cm2 yr four orders of magnitude slower than the average value observed for taiwan we also demonstrate that the shelf sediments around taiwan have received the admixing of a 10be rich component from the ocean and would give a poor estimate for material eroded from taiwan

the movement of indian monsoon depressions by interaction with image vortices near the himalayan wall it is argued that a simple explanation for the westward propagation of indian monsoon depressions imds is the interaction of the depression vortex with the himalayan wall this interaction can be modelled by simulating an imd as a point vortex in a horizontal plane at 850 hpa and invoking image vortices behind the barrier solenoidal flows associated with the image vortices allow the boundary conditions at the himalayas to be met and cause the imd vortex to propagate parallel to the barrier toward the west this simple model is tested against propagation speeds for observed imds the histogram of observed propagation speed normalised by the point vortex model prediction has a mean of 1 08 and standard deviation of 0 68 the model also explains the observed intensification of flow on the himalayan side of the imd which is a key process in enhancing rainfall to the indo gangetic plain in the monsoon season

skeletonization of aeromagnetic data skeletonization is a syntactic pattern recognition method that is applied to gridded data to produce an automatic line drawing with an associated event catalog previous implementations of skeletonization have been tailored for seismic data here we modify that technique to render it more suitable for other types of gridded data with particular emphasis on aeromagnetic maps a modification from previous schemes is the use of a two pass approach to reduce the effects of an otherwise problematic directional bias that discriminates against events oriented parallel to columns of the grid the method can be used effectively for filtering aeromagnetic data on the basis of strike direction event linearity event amplitude and polarity it is based on the delineation of peak trough pairs cycles which are traced throughout the grid to form contiguous events cycles and events are characterized by attributes that include amplitude polarity and pulse width events are further characterized by length average strike direction and linearity the event attributes are stored in a catalog thus enabling one to perform attribute based analysis and data filtering we illustrate our algorithm using two regional aeromagnetic examples from different parts of the canadian shield the first from the great slave lake shear zone is dominated by linear anomaly trends produced by faults and mafic dikes the second from the manicouagan region of northeastern quebec contains abundant subcircular and arcuate anomaly patterns caused by large intrusive complexes and a meteorite impact structure

identification and interpretation of azimuthally varying crustal reflectivity with an example from the southern canadian cordillera a new approach to seismic interpretation seismic skeletonization is used to analyze crustal reflection data by identifying numbers of reflection events their lengths their energies and their dips with respect to azimuths of recorded profiles application of the method to crustal reflection data in the southern canadian cordillera demonstrates strong directional dependence of crustal reflectivity with persistent trends at 025 040 205 220 085 095 265 275 115 125 295 305 and 140 160 320 340 these trends are visible in both the upper and lower crust and may be related to regional structural trends further applications of the technique particularly in different tectonic regions may allow categorization of seismic patterns and cataloguing of signatures for complex reflection data in a manner similar to seismic stratigraphy and structural patterns in stratified rocks

fractals in deep crustal seismic reflection profiles application of a syntactic pattern recognition technique seismic skeletonization to deep crustal seismic reflection data allows attributes such as energies lengths and dips to be associated with individual reflection events some of these attributes exhibit fractal properties e g the relationship between seismic event lengths and their spatial distribution throughout the crust this approach provides a new technique to analyse complex geometry on seismic reflection data

delineation of surfaces by skeletonization application to interpretation of 3d seismic reflection and georadar data volumes a new 3 d skeletonization technique based on a four cycle correlation allows automatic event detection and mapping of surfaces in any 3 d volume of reflection seismic data interpretation results are comparable to those derived using conventional 3 d interpretation packages furthermore a product of skeletonization is a surface file containing a variety of seismic attributes for each identified surface that can be accessed for detailed statistical analysis

a test of the cosmogenic 10be meteoric 9be proxy for simultaneously determining basin wide erosion rates denudation rates and the degree of weathering in the amazon basin we present an extensive investigation of a new erosion and weathering proxy derived from the 10be meteoric 9be stable ratio in the amazon river basin this new proxy combines a radioactive atmospheric flux tracer meteoric cosmogenic 10be with 9be a trace metal released by weathering results show that meteoric 10be concentrations 10be and 10be 9be ratios increase by 30 from the andes to the lowlands we can calculate floodplain transfer times of 2 30 kyr from this increase intriguingly however the riverine exported flux of meteoric 10be shows a deficit with respect to the atmospheric depositional 10be flux most likely the actual area from which the 10be flux is being delivered into the mainstream is smaller than the basin wide one despite this imbalance denudation rates calculated from 10be 9be ratios from bed load suspended sediment and water samples from amazon rivers agree within a factor of 2 with published in situ 10be denudation rates erosion rates calculated from meteoric 10be measured from depth integrated suspended sediment samples agree with denudation rates suggesting that grain size induced variations in 10be are minimized when using such sampling material instead of bed load in addition the agreement between erosion and denudation rates implies minor chemical weathering intensity in most amazon tributaries indeed the be specific weathering intensity calculated from mobilized 9be comprising reactive and dissolved fractions that are released during weathering is constant at approximately 40 of the total denudation from the andes across the lowlands to the amazon mouth therefore weathering in the amazon floodplain is not detected

a stochastic view of lower crustal fabric based on evidence from the ivrea zone despite its complicated history the ivrea zone is considered to be a representative surface exposure of extended continental crust we have digitized two standard 1 25 000 geological maps from this area and evaluated their structural statistics because of the subvertical orientation of the ivrea zone these maps can be considered as small scale cross sections through the lower continental crust the autocorrelation functions of the digitized lithologies measured from these maps show a clear self similar or fractal rather than a gaussian or deterministic trend we found that an anisotropic von karman correlation function with an aspect ratio around 4 and a hurst number of 0 3 corresponding to a fractal dimension of 2 7 matches the observed data our results represent an explicit confirmation of previous indirect evidence for the fractal nature of lithospheric heterogeneities and provide the means to construct realistic crustal scale seismic models of ivrea type lower continental crust