geometry and regional significance of neoproterozoic cadomian structures of the narcea antiform nw spain the narcea antiform is located at the hinterland to foreland transition of the variscan belt in the nw of the iberian massif it consists of an antiformal stack of fault propagation folds that developed in the hanging wall of allochthonous thrust sheets during the first variscan deformation event in the palaeozoic rocks the neoproterozoic narcea slates formation cropping out in the core of the narcea antiform records a cadomian deformation event that formed large asymmetric nw vergent folds with related axial planar cleavage developed in the lower greenschist facies these folds are truncated by the lower cambrian angular unconformity lower cambrian conglomerates contain pebbles with predepositional microstructures that are widespread in the underlying neoproterozoic rocks the narcea antiform provides valuable information concerning major tectonic cadomian events the large scale near recumbent cadomian folds developed between 560 and 540 ma top to the nw kinematics can be deduced for the cadomian plate convergence transverse to the variscan convergence in present coordinates it was followed shortly afterwards by large displacements along the northern gondwana margin that resulted in its accretion alongside the essentially undeformed neoproterozoic rocks of the central iberian zone before early cambrian times

melatroctolite anorthositic gabbro complex cumberland rhode island petrology origin and regional setting an igneous complex exposed in cumberland rhode island is one of a series of mafic intrusions that outline a northeast trending lineament extending from the preston gabbro in connecticut to the boston massachusetts area the age of these intrusions is not well constrained but appears to be between 620 and 370 m y b p the mafic complex in northern rhode island consists of a small body of melatroctolite adjacent to a much larger body 1 km2 of anorthositic gabbro the contact between the two rock types is not exposed but inclusions of anorthositic gabbro and large cumulophyric crystal aggregates identical to the gabbro occur in the melatroctolite the latter rock is composed of 49 olivine fo63 32 titaniferous magnetite 15 plagioclase an59 ab40 or1 and minor ilmenite and aluminum spinel the plagioclase in the melatroctolite occurs as tabular cumulophyric crystal aggregates 0 2 cm 0 5 cm in a matrix of and often including finer grained 3 mm olivine and titaniferous magnetite the tabular plagioclase aggregates are oriented to give the rock a weak foliation the gabbroic rocks are composed of a framework of thin tabular 1 0 cm 0 2 cm cumulus plagioclase identical in composition to that in the melatroctolite interstitial volumes in the gabbro are filled by ca pyroxene zoned overgrowths on the plagioclase and smaller amounts of olivine fo57 52 magnetite ilmenite and apatite the prominent igneous lamination and parallel but weak rhythmic layering in the gabbro are not parallel to the lamination in the melatroctolite but the rocks have been subjected to one and possibly two episodes of deformation faulting and rotation accompanying these deformations may explain the fact that the two foliations are not parallel or the relatively weak lamination in the melatroctolite may have formed during postcumulus flow compositionally the gabbroic rocks range from a high alumina gabbro 19 5 a12o3 to anorthositic gabbro 25 a12o3 a porphyritic chilled margin locality on the northern edge of the gabbro contains plagioclase phenocrysts an61 as much as 8 cm across and oriented parallel to the contact in a finer grained 0 5 mm groundmass of plagioclase and altered ferromagnesiaia minerals the mineralogy whole rock chemistry cumulus textures and igneous laminations indicate that the melatroctolite and anorthositic gabbro are genetically related igneous rocks this evidence together with the presence of the gabbroic inclusions in the melatroctolite indicates that the two rocks formed simultaneously by gravitational settling of olivine titaniferous magnetite and cumulophyric plagioclase olivine aggregates whereas discrete plagioclase crystals did not sink the fine grained ground mass of the marginal gabbro sample is thought to represent the parent magma on the basis of the composition an61 and planar orientation of the plagioclase phenocrysts the calculated density of the proposed parent magma is 2 66 g cc at 1250 c and 1 atm which is between that of plagioclase 2 63 and the plagioclase olivine aggregates 2 68 as would be required the crystal settling occurred slowly enough to permit unzoned adcumulus overgrowths to completely fill the interstices in the melatroctolite according to magnetite ilmenite pairs in the melatroctolite and gabbro the final equilibration between these two minerals took place at 950 c 100 c and a fo2 of 10 12 5 1 0

deep water facies processes and models a review and classification scheme for modern and ancient sediments abstract a review of previous work on modern and ancient deep water facies processes and models is presented with a new classification scheme involving 40 distinct facies related to 15 conceptually distinct facies groups these facies are fixed points in a spectrum of facies generated in a process continuum from resedimentation processes through semi permanent bottom currents to pelagic settling in essence the scheme is descriptive of the sedimentary attributes of sediments although it is designed to aid interpretation of possible sediment transport deposition processes the classification scheme is three tier with facies classes groups and constituent facies and is hierarchical to allow flexibility in its use there are seven facies classes with classes a e defined largely on the basis of grain size differences class f on the basis of internal organization and class g on composition the facies classes are class a gravels muddy gravels gravelly muds and pebbly sands with 5 gravel grade class b sands with 80 sand grade and 80 mud 40 silt and 0 20 sand class e muds and clays with 95 mud grade for the purpose of large scale mapping or reconnaissance fieldwork either the level of facies classes or groups may be appropriate whereas for more detailed sedimentology the more detailed facies level will be necessary

a new satellite derived glacier inventory for western alaska glacier inventories provide the baseline data to perform climate change impact assessment on a regional scale in a consistent and spatially representative manner in particular a more accurate calculation of the current and future contribution to global sea level rise from heavily glacierized regions such as alaska is much needed we present a new glacier inventory for a large part of western alaska including kenai peninsula and the tordrillo chigmit and chugach mountains derived from nine landsat thematic mapper scenes acquired between 2005 and 2009 using well established automated glacier mapping techniques band ratio because many glaciers are covered by optically thick debris or volcanic ash and partly calve into water outlines were manually edited in these wrongly classified regions during post processing in total we mapped 8830 glaciers 0 02 km2 with a total area of 16 250 km2 large parts of the area 47 are covered by a few 31 large 100 km2 glaciers while glaciers less than 1 km2 constitute only 7 5 of the total area but 86 of the total number we found a strong dependence of mean glacier elevation on distance from the ocean and only a weak one on aspect glacier area changes were calculated for a subset of 347 selected glaciers by comparison with the digital line graph outlines from the us geological survey the overall shrinkage was 23 between 1948 57 and 2005 09

correlation scales of digital elevation models in developed coastal environments accuracy of digital elevation models dems often depends on how features of different spatial scales are represented scale dependence is particularly important in low gradient coastal environments where small vertical errors can affect large areas and where representation of fine scale topographic features can influence how dems are used for modeling inundation it is commonly observed that different types of dems represent larger coarse scale topographic features similarly but differ in how they represent smaller finer scale features the spatial scale dependence of dem accuracy can be quantified in terms of the correlation scale c the spatial wavelength above which models agree with spectral coherency 0 5 and below which they differ we compare cross spectral analyses of the gdem2 and srtm global dems with 14 572 lidar derived elevations along transects in diverse coastal environments of new york city both global dems have positive bias relative to lidar ground elevations but bias and uncertainty of gdem2 8 1 m 7 6 m are significantly greater than those of srtm 1 9 m 3 6 m cross spectral coherency between gdem2 and the lidar dem begins to roll off at scales of 3 km while coherency between srtm and the lidar dem begins to roll off at scales of 1 km the correlation scale below which coherency with lidar attains a signal to noise ratio of 1 is 1 km for gdem2 and 0 5 km for srtm closely matching the divergence scales where the surface roughness of the land cover exceeds the roughness of the underlying terrain

superimposed folding and w sn vein type mineralisation in the central iberian zone associated with late variscan oroclinal buckling a structural analysis from the regoufe area portugal abstract the cantabrian orocline is a major orocline that bends the variscan belt of western europe despite a wealth of studies its timing and relationship with the late variscan folding stages in the iberian massif are still debated this study provides an integrated structural analysis of the variscan fold generations and associated w sn bearing vein systems within the southern central iberian zone regoufe portugal giving insight into their kinematic relationship with oroclinal buckling two superimposed fold generations with mutually parallel steep to vertical fold axes have been identified isoclinal f 1 folds with e w striking axial planes formed during coaxial shortening and are spatially localised f 3 folds with nw se axial planes are associated with late variscan transpressional deformation and constrain the structural outline of the major folds temporal and kinematic considerations indicate that vertical axis asymmetric f 3 folding corresponds with the expected deformation style within the southern limb of the cantabrian orocline the regoufe area is characterised by two types of w sn vein type mineralisation granite hosted hydrothermal quartz veins show a concentric distribution and are associated with the stress regime during granite emplacement the vein system within the metasedimentary host rock however is emplaced along a regional subhorizontal cross fold joint system this cross fold joint system developed orthogonal to the subvertical f 3 fold axes and is interpreted to be coeval with oroclinal buckling these results impact the understanding of i the relative significance and geometry of the main deformation stages in the iberian massif reconciling the timing and kinematics of f 3 regional folding with oroclinal buckling and ii the kinematic relationship between late to postorogenic deformation and w sn vein type mineralisation

the impact of misregistration on srtm and dem image differences abstract image differences between shuttle radar topography mission srtm data and other digital elevation models dems are often performed for either accuracy assessment or for estimating vegetation height across the landscape it has been widely assumed that the effect of sub pixel misregistration between the two models on resultant image differences is negligible yet this has not previously been tested in detail the aim of this study was to determine the impact that various levels of misregistration have on image differences between srtm and dems first very accurate image co registration was performed at two study sites between higher resolution dems and srtm data and then image differences srtm dem were performed after various levels of misregistration were systematically introduced into the srtm data it was found that 1 misregistration caused an erroneous and dominant correlation between elevation difference and aspect across the landscape 2 the direction of the misregistration defined the direction of this erroneous and systematic elevation difference 3 for sub pixel misregistration the error due solely to misregistration was greater than or equal to the true difference between the two models for substantial proportions of the landscape e g greater than 33 of the area for a half pixel misregistration and 4 the strength of the erroneous relationship with aspect was enhanced by steeper terrain spatial comparisons of dems were found to be sensitive to even sub pixel misregistration between the two models which resulted in a strong erroneous correlation with aspect this misregistration induced correlation with aspect is not likely specific to srtm data only we expect it to be a generic relationship present in any dem image difference analysis

remote sensing of floodplain geomorphology as a surrogate for biodiversity in a tropical river system madre de dios peru the complex floodplains of large rivers offer a striking example of how geomorphology by dictating patterns in the frequency and duration of soil saturation and surface flooding influences ecosystem structure and function this study draws on multiple sources of data from remote sensing together with ground observations and water sampling to distinguish floodplain ecosystems in the madre de dios river a tributary of the amazon river in peru this remote tropical river meanders across sub andean alluvial deposits in a tectonically active region and creates floodplain surfaces of varying ages including terraces that are above the reach of present day river floods data from landsat etm optical multispectral jers 1 l band radar and the shuttle radar topography mission c band interferometric digital elevation models were integrated in an object oriented image analysis approach to distinguish five classes of floodplain vegetation vegetation classes generally correspond with successional age and reflect the activity of the riverine meander belt stage data for the river show erratic fluctuations and an annual range exceeding 8 m but the maximum depth of floodplain inundation varied from 1 m close to the river to approximately 0 1 m on more elevated terraces the major ion composition of standing waters on the floodplain during the dry season indicated the importance of emergence of local groundwater in maintaining saturated soils particularly further from the river where backswamp vegetation is distinct and includes palm swamps thus a hydrological continuum exists from deep but sporadic river inundation near the river to constant soil saturation by groundwater emergence in distal backswamps reflecting the geomorphological origin and age of the floodplain deposits this hydrogeomorphic continuum results in fundamental ecological differences the exceptionally rich biodiversity of the sub andean region may be ascribed in part to the enhanced biodiversity associated with fluvial geomorphological features and thus conservation planning must account for the diverse landforms created by fluvial dynamics

the hf isotopic composition of ferromanganese nodules and crusts and hydrothermal manganese deposits implications for seawater hf we present hf and pb isotopic data and chemical compositions of the outermost layers of marine ferromanganese deposits of different types hydrogenous and hydrothermal with a worldwide distribution the hf isotopic compositions display a broad range and refine previously reported regional differences as follows atlantic ocean hf 4to 2 indian ocean hf 2to 4 pacific ocean hf 3to 10 the most radiogenic hf isotopic compositions in the pacific samples are for hydrothermal manganese deposits that also have low 207pb204pb demonstrating that this signature reflects a contribution from hydrothermal venting of hf leached from oceanic volcanic rocks rather than from riverine inputs volcanic ash or eolian dust hafnium concentrations in the deposits increase from 20 ppb to 20 ppm with decreasing hf the hf and pb isotopic compositions for ferromanganese crusts define an apparent mixing trend between literature values of average continental crust and morb the range in hf for ferromanganese crusts is narrower than it is for 206pb204pb compared to the differences in isotopic composition of the sources of hf and pb this is consistent with hf having a longer residence time than pb the concentration of hf in ferromanganese crusts has been found to co vary with growth rate and inversely correlates with hf isotopic compositions hf isotope ratios may be used to determine not only the source of hf but possibly the source of fe and mn measurements of hf and hf concentrations in nodule tops bottoms and associated sediments show that the hf of nodules is sensitive to sedimentary oxic and sub oxic diagenetic processes and thus most nodules may not reliably reflect the isotopic composition of hf in seawater

reconstruction of dems from ers 1 2 tandem data in mountainous area facilitated by srtm data a new approach is presented in this paper to produce digital elevation model dem in mountainous areas with steep slope using ers 1 2 tandem data in order to reduce the impact of phase errors on the interferometric synthetic aperture radar insar generated dem an external dem such as that from shuttle radar topography mission srtm is utilized in this approach the proposed algorithm includes two steps the first step is to model and remove phase trends with a linear regression analysis before converting phase to height the second step is to filter unreliable height points before interpolating the dem from the insar height map the critical points are the following 1 determining the one to one correspondence between the interferogram and the srtm dem before knowing the insar derived elevation values and 2 estimating the elevation range of every pixel from srtm dem to solve the first problem an iteratively geocoding algorithm is performed a dem interpolation error model solves the second one for insar data processing the srtm dem is not only usable for modeling systematic phase errors but also for filtering gross height errors the experiments in zhangbei and the three gorges areas in china show that our approach has improved the accuracy of the resulting dems significantly without any ground control points

comparison of new and existing global digital elevation models aster g dem and srtm 3 1 a new global elevation dataset known as g dem based on the aster satellite imagery will be released in late 2008 g dem will be the best freely available global digital elevation model dem at a horizontal resolution of 1 arc second we assess the quality of g dem in comparison with 3 arc second srtm dem the best current global elevation dataset basic geomorphometric parameters elevation slope and curvature were examined for a pre release version of g dem and srtm dem for western japan g dem has fewer missing cells than srtm dem particularly in steep terrain also g dem gives smoother and more realistic representations of lowlands valleys steep slopes and mountain ridges whereas srtm dem includes many local spikes and holes and tends to overestimate valley floor elevation and underestimate ridge elevation g dem will be commonly used in geoscientific studies because of its higher resolution fewer missing data and better topographic representation than srtm dem

the tectonic significance of dikes of irregular fold like shape the effects of postemplacement deformation on originally nonplanar dikes were tested experimentally and compared to field data from the rainy lake zone ontario canada where irregular fold like structures are observed the analyses reveal that two processes are responsible for the irregular dike geometries first dikes intrude with varying orientations as they propagate across layers with rheology contrasts thus developing nonplanar profiles second with postemplacement ductile deformation dikes that are more competent than the host rocks are folded and refracted in variable amounts with the amount depending on the initial dike geometry the heterogeneities in the host and the regional strain deformed dikes and veins are often used as kinematic markers to evaluate regional tectonics using methods that generally assume that veins had planar walls prior to deformation the experimental results indicate that caution should be taken when using this approach and they provide criteria to distinguish between intrusive and deformation structures in intensely deformed areas where distinction between the two is not readily apparent

late precambrian series and structures in the navalpino variscan anticline central iberian peninsula the navalpino anticline is a major variscan structure in the central iberian zone of spain three lithological groups are defined in the pre ordovician rocks of this anticline the rifean or lower vendian extremeno dome group is unconformably overlain by the upper vendian ibor navalpino group this latter group presents two different facies separated by a nw se trending synsedimentary fault the lower cambrian valdelacasa group unconformably overlies both the extremeno dome and the ibor navalpino groups

new u pb ages for early ordovician magmatism in central spain felsic orthogneisses occur widely in the ollo de sapo domain of the central iberian zone most of which were previously considered to represent a precambrian basement to the palaeozoic sequences of this domain however new u pb dating across the berzosa riaza shear zone sierra de guadarrama central spain indicates an early ordovician age for the most representative types of orthogneisses in the eastern part of the ollo de sapo domain dated rocks include the volcaniclastic cardoso gneiss 480 2 ma from the low medium grade hanging wall the riaza gneiss 468 8 16 ma mylonitic granite in the berzosa riaza shear zone three types of leucogneiss buitrago gneiss 488 8 10 ma megacrystic granite 482 11 14 ma aplitic vein and 482 8 9 ma gneissic leucogranite and the la morcuera granitic augen gneiss 477 4 ma in the high grade footwall the new age of the cardoso gneiss brackets to the mid late arenig the so called early ordovician sardic unconformity characteristic of the central iberian zone these new ages suggest that the broadly coeval volcanism and plutonism were closely associated with the sardic events and that these orthogneisses were part of a felsic magmatic belt which extended along the ollo de sapo domain of the central iberian zone this magmatic belt is interpreted to have been active during the early ordovician break up of the peri gondwanan margin of the iapetus ocean

probing the mechanical properties of seismically active crust with space geodesy study of the coseismic deformation due to the 1992 mw7 3 landers southern california earthquake 1 the coseismic deformation due to the 1992 m w 7 3 landers earthquake southern california is investigated using synthetic aperture radar sar and global positioning system gps measurements the ers 1 satellite data from the ascending and descending orbits are used to generate contiguous maps of three orthogonal components east north up of the coseismic surface displacement field the coseismic displacement field exhibits symmetries with respect to the rupture plane that are suggestive of a linear relationship between stress and strain in the crust interferometric synthetic aperture radar insar data show small scale deformation on nearby faults of the eastern california shear zone some of these faults in particular the calico rodman and pinto mountain faults were also subsequently strained by the 1999 m w 7 1 hector mine earthquake i test the hypothesis that the anomalous fault strain represents essentially an elastic response of kilometer scale compliant fault zones to stressing by nearby earthquakes fialko et al 2002 the coseismic stress perturbations due to the landers earthquake are computed using a slip model derived from inversions of the insar and gps data calculations are performed for both homogeneous and transversely isotropic half space models the compliant zone model that best explains the deformation on the calico and pinto mountain faults due to the hector mine earthquake successfully predicts the coseismic displacements on these faults induced by the landers earthquake deformation on the calico and pinto mountain faults implies about a factor of 2 reduction in the effective shear modulus within the similar to 2 km wide fault zones the depth extent of the low rigidity zones is poorly constrained but is likely in excess of a few kilometers the same type of structure is able to explain high gradients in the radar line of sight displacements observed on other faults adjacent to the landers rupture in particular the lenwood fault north of the soggy lake has likely experienced a few centimeters of left lateral motion across 1 km wide compliant fault zone having the rigidity reduction of more than a factor of 2 the inferred compliant fault zones are interpreted to be a result of extensive damage due to past earthquakes

quartzite development in early palaeozoic nearshore marine environments quartzites are especially characteristic of proterozoic and cambro ordovician shallow marine strata whereas equivalent age fluvial deposits are commonly arkosic the absence of land vegetation in the pre silurian influenced weathering processes and styles of fluvial deposition it may also have had an impact on shallow marine sedimentation two field studies from the english channel region are presented to investigate the processes leading to quartzite formation on alderney nearshore marine and fluvial facies occur interbedded on a metre scale and are interpreted to represent deposition on the lower reaches of an alluvial plain and in beach and upper shoreface environments the marine and fluvial sandstones display marked differences in textural and mineralogical maturity pointing to a process of sediment maturation by the destruction of feldspar and labile grains at the shoreline at erquy fully mature marine quartzites occur bounded above and below by alluvial deposits via sharp or erosional surfaces and are interpreted to represent high energy storm and tidally influenced lower shoreface and inner shelf deposits a model for quartzite development is proposed where under a cool climate frequent storms in un vegetated tectonically rejuvenated uplands provided an abundance of arkosic sand to fluvial basins and clastic shorelines the model proposes that the marine basins were subject to high wave energies frequent storm events and tidal currents these were conditions conducive to transforming arkosic sand to quartz rich sand by the attrition of feldspar at the shoreline and in the shallow marine environment on sediment burial further feldspar destruction occurred during diagenesis the proposed model highlights the potential for a step change in sediment maturity to occur at the shoreline in early palaeozoic depositional systems tracts

facies and provenance analysis of upper carboniferous to lower permian fan sequences at a convergent plate margin using phyllosilicates heavy minerals and rock fragments erbendorf trough f r g the erbendorf trough is a narrow permo carboniferous graben in the northeast bavarian crystalline basement at the saxothuringian moldanubian plate edge its elastic and volcanic rocks reflect a complex story of alluvial fan progradation and retreat unit i precambrian gneissic bedrock is followed by units ii to v a wet mixed fan debris stream flows braided streams peat swamps organic lake units vi to x reflect a retrogradational dry fan braided streams calcretes flood plain deposition with tuffaceous interbeds units xi to xii are acid extrusive rocks the uppermost part hydrothermally altered and units xiii to xiv denote a progradational dry fan the wet fan at the base is characterized by a predominance of illite stable to intermediate heavy mineral associations zircon and garnet and a clast community pointing to medium pressure metamorphic rocks in the variscan nappe the following dry fan contains various 14 a phyllosilicates besides white mica its heavy mineral suite contains more labile constituents apatite and amphibole gneissic pebbles accompany those from acid volcanic and plutonic rocks the volcanogenic rocks contain expandable 14 a phyllosilicates formed by devitrification anatase and brookite dominate the heavy minerals tio2 associated with phosphate indicates hydrothermal alteration of host rock whereas detrital tio2 and a high ztr zircon tourmaline rutile index reflect paleosol formation as shown at the wet dry fan boundary fan progradation occurred under semi arid conditions with kaolinization and formation of illite partly detrital and a moderately stable heavy mineral association apatite dominated owing to the kaolinization only quartz bearing gneisses were preserved the facies succession reflect the evolution from a fault bordered basin with various fan sections proximal vs distal preserved into a caldera like volcanotectonic depression regionally the grain size intervals reflect a passage from recycled orogen into a transitional arc which accords with the late variscan horizontal gliding of the moldanubian plate over the saxothuringian plate and basement uplift proximal to this suture

superposed hercynian and cadomian orogenic cycles in the ossa morena zone and related areas of the iberian massif polyphase ductile deformation and metamorphism in the ossa morena zone of the iberian massif are related to a complex evolution including two major tectonothermal episodes of cadomian late proterozoic to early cambrian and hercynian age middle to late paleozoic petrological structural and geochronological data attest to a number of tectonic episodes in the 620 480 ma interval the model presented for this orogeny comprises stages of volcanic arc generation backarc extension tectonic inversion crustal thickening and cratonization in an andean type continental margin the hercynian cycle began in the early paleozoic with episodes of continental rifting orogenic events occurred in the 390 300 ma interval and affected both the cadomian basement which was heterogeneously reworked and overprinted and the paleozoic cover hercynian regional metamorphism was generally of low grade high pressure assemblages and thermal domes developed locally and were related to subduction and late extensional events the geodynamic model proposed for the cadomian and hercynian orogenies and the correlation with comparable areas from pre mesozoic massifs elsewhere in western europe account for the geodynamic scenarios that drove the fate of cadomian terranes

comment on paleozoic reactivation structures in the appalachian ouachita marathon foreland far field deformation across pangea by j craddock d malone r porter j compton j luczaj a konstantinou j day and s johnston earth science reviews 169 2017 1 34

phosphate lu hf geochronology abstract igneous metamorphic and biogenic apatite contains lu and hf in proportions that make this mineral suitable for dating by the 176lu 176hf method we present a new method for separation of lu and hf from apatite that involves a single extraction column step for hf and a second exchange column step for lu this procedure allows rapid sample processing prior to analysis by mc icp ms results from the igneous gardiner skaergaard and khibina intrusions indicate that the closure temperature for the lu hf isotopic system in apatite is relatively high the lu hf isochron age of 60 ma for the skaergaard intrusion east greenland is older than the generally accepted emplacement age but does not appear to be a product of mixing a centimeter sized apatite from the otter lake area grenvillian province yields high and variable 176lu 177hf ratios showing that metamorphic apatite may in some cases allow for mono mineral dating the most important application of the method is undoubtedly its potential use for dating sedimentary formations although we find biogenic apatite in porous matrix highly susceptible to post depositional resetting of the lu hf isotopic system the preservation of a near depositional age for a shark tooth from the impermeable london clay and recent work on crystalline authigenic phosphorites earth planet sci lett 201 2002 203 show the lu hf system to be a promising tool for direct dating of sedimentary formations

evaluation of tandem x elevation data for geomorphological mapping and interpretation in high mountain environments a case study from se tibet china abstract digital elevation models dems are a prerequisite for many different applications in the field of geomorphology in this context the two near global medium resolution dems originating from the srtm and aster missions are widely used for detailed geomorphological studies particularly in high mountain environments these datasets are however known to have substantial disadvantages beyond their posting i e data gaps and miscellaneous artifacts the upcoming tandem x dem is a promising candidate to improve this situation by application of state of the art radar technology exhibiting a posting of 12 m and less proneness to errors in this study we present a dem processed from a single tandem x cossc scene covering a study area in the extreme relief of the eastern nyainqentanglha range southeastern tibet the potential of the resulting experimental tandem x dem for geomorphological applications was evaluated by geomorphometric analyses and an assessment of landform cognoscibility and artifacts in comparison to the aster gdem and the recently released srtm 1 dem detailed geomorphological mapping was conducted for four selected core study areas in a manual approach based exclusively on the tandem x dem and its basic derivates the results show that the self processed tandem x dem yields a detailed and widely consistent landscape representation it thus fosters geomorphological analysis by visual and quantitative means allowing delineation of landforms down to footprints of 30 m even in this premature state the tandem x elevation data are widely superior to the aster and srtm datasets primarily owing to its significantly higher resolution and its lower susceptibility to artifacts that hamper landform interpretation conversely challenges toward interferometric dem generation were identified including i triangulation facets and missing topographic information resulting from radar layover on steep slopes facing toward the radar sensor ii low coherence values on leeward slopes iii decorrelation effects over water bodies and iv challenges for phase unwrapping in settings of strong topographic contrasts there is however a high probability that these drawbacks can be overcome by applying multiple interferograms exhibiting different perpendicular baselines as planned for the generation of the final tandem x dem product

evaluation of aster gdem and srtm and their suitability in hydraulic modelling of a glacial lake outburst flood in southeast tibet the resolution and accuracy of digital elevation models dems can affect the hydraulic simulation results for predicting the effects of glacial lake outburst floods glofs however for the tibetan plateau high quality dem data are often not available leaving researchers with near global freely available dems such as the advanced spaceborne thermal emission and reflection radiometer global digital elevation model aster gdem and the shuttle radar topography mission data srtm for hydraulic modelling this study explores the suitability of these two freely available dems for hydraulic modelling of glofs our study focused on the flood plain of a potentially dangerous glacial lake in southeastern tibet to evaluate the elevation accuracy of aster gdem and srtm and their suitability for hydraulic modelling of glofs the elevation accuracies of aster gdem and srtm were first validated against field global position system gps survey points and then evaluated with reference to the relatively high precision of 1 50 000 scale dem dem5 constructed from aerial photography moreover the dem5 aster gdem and srtm were used as basic topographic data to simulate peak discharge propagation as well as flood inundation extent and depth in the hydrologic engineering center s river analysis system one dimensional hydraulic model results of the three dem predictions were compared to evaluate the suitability of aster gdem and srtm for glof hydraulic modelling comparisons of aster gdem and srtm each with dem5 in the flood plain area show root mean square errors between the former two as 15 4 m and between the latter two as 13 5 m although srtm overestimates and aster gdem underestimates valley floor elevations both dems can be used to extract the elevations of required geometric data i e stream centre lines bank lines and cross sections for flood modelling however small errors still exist in the cross sections that may influence the propagation of peak discharge the flood inundation extent and mean water depths derived from aster gdem predictions are only 2 2 larger and 2 3 m deeper than that of the dem5 predictions whereas the srtm yields a flood zone extent 6 8 larger than the dem5 prediction and a mean water depth 2 4 m shallower than the dem5 prediction the modelling shows that in the absence of high precision dem data aster gdem or srtm dem can be relied on for simulating extreme glofs in southeast tibet copyright 2011 john wiley sons ltd

neoproterozoic cambrian synsedimentary magmatism in the central iberian zone spain geology petrology and geodynamic significance petrographic geochemical and field studies in low grade metamorphic areas ciudad rodrigo hurdes sierra de gata domain crhsg central western spain show that neoproterozoic lowermost cambrian series in the central iberian zone ciz record two kinds of provenance sources including 1 detrital material derived from recycled orogens and 2 a cadomian coeval juvenile contribution that governs their isotopic signature evidence of magmatism contemporaneous with neoproterozoic cambrian sedimentation is provided by the presence of coherent massive volcanic rocks metabasalts metaandesites and metarhyolites volcaniclastic shales sandstones conglomerates and breccias the appearance of volcanogenic lithic fragments and crystals mixed in different proportions with siliciclastic constituents and also present within calcareous components in the sedimentary succession reinforces this evidence although most of the selected volcanic and volcaniclastic samples appear to show tholeiitic affinity some of them display calc alkaline affinity different trace element ratios such as sm nd nb yb and ta yb suggest a magmatic evolution in the same tectonic setting the geochemical results reported here support the existence of an active geodynamic setting as a direct contributor to the synsedimentary and magmatic content of the neoproterozoic lowermost cambrian successions in the ciz in particular the relatively high end t values and the high range of f sm nd ratios are consistent with an active margin during the neoproterozoic early cambrian the existence of tectonic activity is also confirmed by the presence of synsedimentary deformation and volcanic rocks all of these traits favour a geodynamic model in which the iberian cadomian segment represented in the ciz would have been part of an active northern margin of gondwana with an associated magmatic arc and related basins during neoproterozoic lower cambrian times a proposed link between the ossa morena and the central iberian zones might account for late cadomian pull apart basins developed on both sides of the magmatic arc sharing the same scenario and involving similar magmatic activity during the neoproterozoic cambrian transition

active tectonics around almaty and along the zailisky alatau rangefront this is the author accepted manuscript the final version is available from wiley via http onlinelibrary wiley com doi 10 1002 2017tc004657 abstract

near global validation of the srtm dem using satellite radar altimetry abstract this paper reports the results of a near global validation of the srtm dem dataset using a unique database of completely independent height measurements derived from satellite altimeter echoes primarily gathered by ers 1 these heights are obtained using a rule based expert system which identifies each echo as 1 of 11 different characteristic shapes and selects the optimal retracking algorithm to obtain best range to surface the results of this comparison which includes over 54 million altimeter derived heights show generally very good agreement with the srtm data with global statistics for mean difference of 3 m and a standard deviation of 16 m quantitative validation results are given for each continent and are summarised here mean difference m standard deviation of differences m africa 1 86 15 62 australia 1 09 11 49 eurasia 2 54 16 09 north america 3 15 15 18 south america 12 22 18 51 global 3 60 16 16 a range of examples are included to illustrate key findings of this work and to indicate synergistic applications of these two datasets currently being studied including the potential for forest canopy measurement

new lu hf and pb pb age constraints on the earliest animal fossils abstract the neoproterozoic doushantuo formation south china preserves a unique assemblage of early multicellular fossils and overlies rocks which are thought to have formed during an ice age of global extent the age of this formation is thus critical for understanding the important biological and climatic events that occurred towards the end of the proterozoic eon until now direct dating of sedimentary formations such as the doushantuo has been difficult and associated with large uncertainties here we show that dating of doushantuo phosphorites by a novel lu hf dating method and conventional pb pb geochronometry independently yield ages of 584 26 ma and 599 3 4 2 ma respectively these ages are in agreement with bio and chemostratigraphical observations and show that the doushantuo animal remains predate diverse ediacaran fossil assemblages making them the oldest unambiguous remains of metazoans currently known furthermore the pb pb age for the post glacial doushantuo rocks suggests that the neoproterozoic glaciation in china might predate glacial rocks in eastern north america commonly associated with the younger marinoan of two major neoproterozoic glaciations the combination of lu hf and pb pb dating shows considerable potential for dating other phosphorite successions and future application of these methods could therefore provide further constraints on proterozoic biological and environmental history

comparative mass balance of volcanic edifices at the southern volcanic zone of the andes between 33 s and 46 s volcano edifice volume calculations are presented for 65 volcanoes of the 1400 km long chilean southern volcanic zone svz as a basic step in subduction zone mass budgets volume calculations are performed in a geographical information system that integrates digital elevation models based on of shuttle radar topography mission as well as aster gdem topographic data landsat satellite images and geological maps the method of volume calculation is straightforward for isolated morphologically well defined stratovolcanoes uncertainties increase for volcanic edifices that formed on pre existing rugged terrain for multi phase eruptive centers as well as for eroded edifices a revised segmentation of the arc is used to describe the spatial volume distribution of extruded magma along the svz and to discuss controlling tectonic factors peak volumes between arc and back arc are offset by 400 km the total volcanic extrusion is in the range of 10 13 km3 km ma major differences between the svz and the central american subduction system are notable with regard to volcano density and maximum volumes

which dem is best for analyzing fluvial landscape development in mountainous terrains abstract regional studies of fluvial landforms and long term quaternary landscape development in remote mountain landscapes routinely use satellite derived dem data sets the srtm and aster dems are the most commonly utilised because of their longer availability free cost and ease of access however rapid technological developments mean that newer and higher resolution dem data sets such as alos world 3d aw3d and tandem x are being released to the scientific community geomorphologists are thus faced with an increasingly problematic challenge of selecting an appropriate dem for their landscape analyses here we test the application of four medium resolution dem products 30 m srtm aster aw3d 12 m tandem x for qualitative and quantitative analysis of a fluvial mountain landscape using the dades river catchment high atlas mountains morocco this landscape comprises significant dem remote sensing challenges notably a high mountain relief steep slopes and a deeply incised high sinuosity drainage network with narrow canyon gorge reaches our goal was to see which dem produced the most representative best fit drainage network and meaningful quantification to achieve this we used arcgis and stream profiler platforms to generate catchment hillshade and slope rasters and to extract drainage network channel long profile and channel slope and area data tandem x produces the clearest landscape representation but with channel routing errors in localised high relief areas thirty metre dems are smoother and less detailed but the aw3d shows the closest fit to the real drainage network configuration the tandem x elevation values are the closest to field derived gps measurements long profiles exhibit similar shapes but with minor differences in length elevation and the degree of noise smoothing with aw3d producing the best representation slope area plots display similarly positioned slope break knickpoints with modest differences in steepness and concavity indices but again best represented by aw3d collectively our study shows that despite the higher effective resolution of tandem x 12 m the aw3d 30 m data performs strongly across all analyses suggesting that it currently offers the greatest potential for regional mountain geomorphological analyses

fracture cleavage in the duluth complex northeastern minnesota an unusual cleavage is developed in troctolitic rocks of the late precambrian duluth complex in northeastern minnesota it is localized in a zone 250 m wide and it is parallel to the axes of gentle folds in rhythmic banding the rocks show no textural signs of ductile deformation and the cleavage is defined by fractures that are fairly straight and evenly spaced but on a fine scale somewhat irregular multiple anastomosing and locally crosscutting textures indicate a purely extensional mode of development cleavage refraction across interfaces of bands of different composition is common serpentine coats the fracture surfaces and suggests that fluids were present to produce this alteration during formation of cleavage the geological relationships and serpentinization suggest conditions of cleavage formation of 1 5 1 8 kb and 350 to 500 c the presence of extensional fractures indicates that cleavage formation involved crack propagation at high fluid pressures the absence of shear fractures or ductile deformation features and the nature of the cleavage refraction indicate that differential stresses were low localization of the cleavage seems to be due to the presence of a structure probably a dike below the layered intrusive rocks this could have served to localize stresses and reactive fluids at high pressure during a late stage of continental rifting

modification of a rare earth element deposit by low temperature partial melting during metamorphic overprinting norra karr alkaline complex southern sweden abstract rare earth elements play a crucial role in modern technologies and are necessary for a transition to a green economy potentially economic deposits of these elements are typically hosted in minerals such as monazite bastnasite and eudialyte a complex na ca fe zr silicate mineral with cl making these prime targets for geological research globally rare earth mineral deposits commonly show evidence of polyphase development and mineralisation processes which need to be better understood to improve exploration strategies the norra karr alkaline complex sweden contains a globally significant deposit of rare earth elements hosted in the mineral eudialyte in this study we focussed on eudialyte crystals in undeformed cross cutting pegmatoid veins from norra karr in order to determine their age we refined an established micromilling method to enable sampling of minerals rich in rare earth elements for precise analysis of major and trace elements nd isotope ratios and sm nd geochronology down to a scale of

paleozoic evolution of the armorica plate on the basis of paleomagnetic data new paleomagnetic data support the contention that armorica and gondwana formed a coherent block until ordovician time however by early devonian time armorica collided with the north american northern european assembly to form the old red continent and the collision itself was responsible for the acadian orogeny not for the earlier taconic orogeny as postulated previously the carboniferous collision of gondwana with the old red continent subsequently formed pangaea and produced the appalachian hercynian orogeny

integrating historical topographic maps and srtm data to derive the bathymetry of a tropical reservoir this paper proposes a cheap and fast method for est imating the bathymetry of hydroelectric reservoirs brazil has more than 30 l arge hydroelectric reservoirs with volume exceeding one billion cubic meters the hydroelectric sector is responsible for 97 of energy generation being the largest hydroele ctric park in the world these dams however cause a series of environmental social an d economic impacts which need to be monitored among the variables affecting the env ironmental impact posed by reservoirs depth has a key role because it acts on the aquatic system hydrodynamics reservoir depth distribution the bathymetry is al so a fundamental factor controlling physical chemical and biological properties of the system in brazil the acquisition of bathymetric information for the large reservoirs h owever is not a simple task because 1 most of the topographic maps available in the ar ea covered by the lake have very small scale 1 100 000 and smaller 2 larger char ts are property of the hydropower companies and are classified 3 the size of the re servoirs prevent the use of bathymetric surveys due the challenge therefore is how to comb ine the use of low precision topographic charts from the period previous to rese rvoir filling srtm data to obtain a bathymetric map which could be used for planning echo bathymetric missions so as reducing both cost and time of data acquisition and processing

evaluation of aster gdem2 srtmv3 0 alos aw3d30 and tandem x dems for the peruvian andes against highly accurate gnss ground control points and geomorphological hydrological metrics abstract we present an analysis for peru of the vertical accuracy and derived geomorphological parameters of three freely available digital elevation models dems with 30 m grid sizes and one commercially available 12 m dem aster gdem2 srtmv3 0 hereafter called srtm3 alos world 3d aw3d30 and 12 m tandem x their elevation values were compared against values measured with a dual frequency trimble 5800 global navigation satellite systems gnss receiver with two antennas in static relative positioning a total of 139 ground control points gcps with elevations of up to 4334 m above sea level asl were obtained from four topographically contrasting regions along the flat arid coast the semi dry andes and the amazon rainforest the combined results of the four areas showed that the residuals of aster gdem2 had a root mean square error rmse of 6 907 m srtm3 5 113 m and aw3d30 6 246 m for the two areas where tandem x was investigated a rmse of 1 666 m was obtained when considering each area individually of the three 30 m dems srtm3 performed best in all areas while aster gdem2 was always performing worst the standard deviation sd of the residuals of aster gdem2 and aw3d30 varied much more between the four study areas than the sd of srtm3 and tandem x it was possible to establish linear correlations with r2 0 95 between the gnss measured and dem derived elevation values for all areas and all dems which can be used to correct aster gdem2 and aw3d30 for peru no relationship was found between absolute elevation and residuals slope angle of 15 however correlated to much higher residuals for srtm3 and aw3d30 whereas a constant increase in residual correlated to a constant increase in slope angle for tandem x in general the highest residuals corresponded to the highest slope classes a comparison of absolute elevation values and slope angles of selected areas between aster gdem2 and srtm3 as well as between aw3d30 and srtm3 showed in all cases more deviation from true values in areas with steeper slopes this effect seems independent of vegetation the presence of buildings however severely affected performance of aster gdem2 for some areas aw3d30 suffered from mismatch between adjacent scenes and horizontal and oblique stripping an analysis of drainage networks showed that all three 30 m dems were capable of producing a similar number of strahler orders total number of channels minimum and maximum channel length and accumulative channel length all dems produced accurate networks in the upper reaches of the catchments but suffered in flat areas such as wide fluvial valleys and sink filled areas aster gdem2 in particular produced parallel river channels and unnatural short cuts our results agreed well with those of other studies elsewhere around the world and showed that i the vertical error is much less than those officially reported for all dems ii slope is the most determinant factor in dem accuracy we conclude that srtm3 delivers the most stable performance in almost all tests and is therefore the dem of choice for landscape analysis in peru tandem x 12 m performed very well in our elevation accuracy test and could become a worthy successor to srtm3

tracing the 1271 1246 ma central scandinavian dolerite group mafic magmatism in fennoscandia u pb baddeleyite and hf isotope data on the moslatt and borgefjell dolerites between 1271 and 1246 ma dolerite dykes and sills of the central scandinavian dolerite group intruded into the fennoscandian shield during three distinct magmatic pulses they are distributed around five large magmatic complexes extending from sweden to western finland and record large scale intracratonic tensional stress coeval plutonism is observed in the westernmost terrane of the sveconorwegian orogen in southern norway but differs in the sense of a bimodal character and uncertain fennoscandian ancestry of the host terrane we report a u pb baddeleyite age of 1269 12 ma for a gabbronoritic member of an e trending set of dykes called the moslatt dolerites near lake vattern in southern sweden much farther to the south than any previously known central scandinavian dolerite group rock a similar age of approximately 1275 ma is obtained for a meta dolerite sheet in the borgefjell basement window in the scandinavian caledonides in mid norway the initial epsilon hf values for these two dykes are 3 9 and 10 1 respectively and correspond to the range of values for other occurrences of the central scandinavian dolerite group 4 7 to 10 3 they add to the evidence that the central scandinavian dolerite group is characterized by more positive epsilon values depleted source than other mafic proterozoic suites in fennoscandia these results extend the distribution of c 1270 1245 ma mafic magmatism in fennoscandia particularly when accounting for significant caledonian shortening the central scandinavian dolerite group and coeval bimodal magmatism in s norway may represent distal magmatic events related to a mesoproterozoic subduction along the western margin of fennoscandia rather than hotspot mantle plume activity as previously suggested

high resolution topography along surface rupture of the 16 october 1999 hector mine california earthquake mw 7 1 from airborne laser swath mapping in order to document surface rupture associated with the hector mine earthquake in particular the area of maximum slip and the deformed surface of lavic lake playa we acquired high resolution data using relatively new topographic mapping methods we performed a raster laser scan of the main surface breaks along the entire rupture zone as well as along an unruptured portion of the bullion fault the image of the ground surface produced by this method is highly detailed comparable to that obtained when geologists make particularly detailed site maps for geomorphic or paleoseismic studies in this case however for the first time after a surface rupturing earthquake the detailed mapping is along the entire fault zone rather than being confined to selected sites these data are geodetically referenced using the global positioning system thus enabling more accurate mapping of the rupture traces in addition digital photographs taken along the same flight lines can be overlaid onto the precise topographic data improving terrain visualization we demonstrate the potential of these techniques for measuring fault slip vectors

ediacaran palaeozoic tectonic evolution of the ossa morena and central iberian zones sw iberia as revealed by sm nd isotope systematics abstract sm nd isotopic analyses of palaeozoic sedimentary and igneous rocks in the southwest iberian massif western end of the european variscan belt are presented in order to unravel its complex poly orogenic evolution during the closure of the rheic ocean and the amalgamation of pangea the gondwanan margin in southwest iberia sw iberia is subdivided into the ossa morena and central iberian zones separated by the badajoz cordoba shear zone which represents a cryptic suture zone between these terranes the relationships between these terranes and between units preserved within the suture zone e g the sierra albarrana group during the palaeozoic and neoproterozoic are controversial sm nd isotopic studies of representative sedimentary sequences covering the entire pre variscan record of the ossa morena and central iberian zones show very similar characteristics from the uppermost ediacaran onwards these data indicate that their accretion to one another must have been completed by the late neoproterozoic ediacarin that time an event assigned to cadomian orogeny and that they never separated substantially from each other since that time the sm nd isotopic composition of the sierra albarrana group metasedimentary rocks is similar to that of the pre cadomian sequences of the ossa morena zone serie negra suggesting derivation from a common source the common provenance of the palaeozoic sequences in the two zones is identical to that of the pre cadomian serie negra of the ossa morena zone which in accordance with the data presented herein and published u pb zircon data indicates a west african affinity

origin of meso proterozoic post collisional leucogranite suites kaokoveld namibia constraints from geochronology and nd sr hf and pb isotopes leucocratic granites of the proterozoic kaoko belt northern namibia now preserved as meta granites define a rock suite that is distinct from the surrounding granitoids based on their chemical and isotopic characteristics least evolved members of this 1 5 1 6 ga old leucogranite suite can be distinguished from ordinary calc alkaline granites that occur elsewhere in the kaoko belt by higher abundances of zr y and ree more radiogenic initial end values and unradiogenic initial 87sr 86sr the leucogranites have high calculated zircon saturation temperatures mostly 920 c for least fractionated samples suggesting that they represent high temperature melts originating from deep crustal levels isotope data i e endi 2 3 to 4 2 demonstrate that the granites formed from different sources and differentiated by a variety of processes including partial melting of mantle derived meta igneous rocks followed by crystal fractionation and interaction with older crustal material most fractionation corrected nd model ages tdm are between 1 7 and 1 8 ga and only slightly older than the inferred intrusion age of ca 1 6 ga indicating that the precursor rocks must have been dominated by juvenile material epsilon hf values of zircon separated from two granite samples are positive 11 and 13 and hf model ages 1 5 and 1 6 ga are similar to the u pb zircon ages again supporting the dominance of juvenile material in contrast the hf model ages of the respective whole rock samples are 2 3 and 2 4 ga demonstrating the involvement of older material in the generation of the granites the last major tectonothermal event in the kaoko belt in the proterozoic occurred at ca 2 0 ga and led to reworking of mostly 2 6 ga old rocks however the presence of 1 6 ga post collisional granites reflects addition of some juvenile mantle derived material after the last major tectonic event the results suggest that similar a type leucogranites are potentially more abundant in crustal terranes but are masked by afc processes in the case of the kaoko belt it is suggested that this rock suite indicates a yet unidentified period of mantle derived crustal growth in the proterozoic of south western africa

analysis and characterization of the vertical accuracy of digital elevation models from the shuttle radar topography mission 1 the first near global high resolution digital elevation model dem of the earth has recently been released following the successful shuttle radar topography mission srtm of 2000 this data set will have applications in a wide range of fields and will be especially valuable in the earth sciences prior to widespread dissemination and use it is important to acquire knowledge regarding the accuracy characteristics in this work a comprehensive analysis of the vertical errors present in the data set and the assessment of their effects on different hydrogeomorphic products is performed in particular the work consisted of 1 measuring the vertical accuracy of the data set in two areas with different topographic characteristics 2 characterizing the error structure by comparing elevation residuals with terrain attributes 3 assessing a wavelet based filter for removing speckle and 4 assessing the effects of vertical errors on hydrogeomorphic products and on slope stability modeling the results indicate that in the two sites relief has a strong effect on the vertical accuracy of the srtm dem in the high relief terrain large errors and data voids are frequent and their location is strongly influenced by topography while in the low to medium relief site errors are smaller although the hilly terrain still produces an effect on the sign of the errors speckling generates deviations in the drainage network in one of the investigated areas but the application of a wavelet filter proved to be an effective tool for removing vertical noise although further fine tuning is necessary vertical errors cause differences in automatically extracted hydrogeomorphic products that range between 4 and 1090

simulating the surface waters of the amazon river basin impacts of new river geomorphic and flow parameterizations this paper describes the impacts of new river geomorphic and flow parameterizations on the simulated surface waters dynamics of the amazon river basin three major improvements to a hydrologic model are presented 1 the river flow velocity equation is expanded to be dependent on river sinuosity and friction in addition to gradient forces 2 equations defining the morphological characteristics of the river such as river height width and bankfull volume are derived from 31 622 measurements of river morphology and applied within the model 3 1 km resolution topographic data from the shuttle radar topography mission srtm are used to provide physically based fractional flooding of grid cells from a statistical representation of sub grid scale floodplain morphology the discharge and floodplain inundation of the amazon river is simulated for the period 1968 1998 validated against observations and compared with results from a previous version of the model these modifications result in considerable improvement in the simulations of the hydrological features of the amazon river system the major impact is that the average wet season flooded area on the amazon mainstem for the period 1983 1988 is now within 5 of satellite derived estimates of flooded area whereas the previous model overestimates the flooded area by about 80 the improvements are a consequence of the new empirical river geomorphologic functions and the srtm topography the new formulation of the flow velocity equation results in increased river velocity on the mainstem and major tributaries and a better correlation between the mean monthly simulated and observed discharge copyright 2007 john wiley sons ltd

the hf isotope composition of global seawater and the evolution of hf isotopes in the deep pacific ocean from fe mn crusts this paper presents a revised chemical purification method of hf for the measurement of hf isotope ratios of fe mn crusts on a new generation of double focusing multiple collector plasma source mass spectrometer mc icp ms by measuring surface scrapings of hydrogenetic fe mn crusts distributed over the three major ocean basins the present day hf isotope distribution of oceanic deep water is assessed in detail the results show an ehf provinciality correlated with those of other radiogenic isotope tracers such as nd and pb in agreement with previous studies this supports the use of hf isotopes as tracer of element source provenance and water masses fe mn crusts display the same present day hf nd isotope array as given before for mn nodules the smaller isotopic variability of hf compared with nd may either be caused by a more efficient mixing of hf than nd in the ocean due to a longer residence time or may be a consequence of a systematically more radiogenic hf than nd isotope signature delivered to the oceans by weathering of continental crust a hf isotope time series was measured on crust va13 2 to assess the hf isotope compositions of the central pacific deep water over the past 26 ma no consistency is observed between the hf and pb isotope time series in contrast hf and nd isotope time series display similar patterns which are however apparently offset by 2 ma prior to 14 ma differential diffusion of hf and nd does not explain this offset the smaller amplitude in the hf isotope variations compared with the nd isotopes rather argues for more efficient mixing of hf in the ocean we suggest that both isotope systems have responded in a similar way to the processes affecting the dissolved radiogenic isotope composition of pacific deep water during this time interval the parallel increase in ehf and end observed between 14 and 3 ma may probably be attributed to the increased inputs of hf and nd into the central pacific ocean derived from the weathering of the pacific islands arcs over the past 3 ma an increased aeolian continental input derived from asia most likely caused negative shifts in end and ehf recorded by va13 2 the fact that hf and nd isotope compositions plot along the present day array for fe mn crusts and mn nodules over the entire past 26 ma suggests that aeolian supply of hf to the pacific ocean has been a long term important feature

petrochronology based on ree minerals monazite allanite xenotime apatite ree minerals monazite xenotime and allanite are ree1 minerals sensu stricto because lanthanides la lu and yttrium are critical constituents in them apatite does not require ree but because it contains substantial ree in many rocks it is included in this review all four minerals also host unusually high radionuclide concentrations notably th and u forming the basis of their utility as geochronometers this quartet of accessory minerals is playing an increasingly important role in petrochronology because they provide ways to link robust spot ages to petrogenetic p t conditions so can lend petrogenetic context to chronology based on other minerals part i of this review assembles the basic requisites prior to integrative petrochronologic analysis individual characteristics of the four ree minerals are addressed first i e their crystal chemistry and stability relations thermobarometers and trace element geochemistry used for tracing petrogenesis are discussed next and finally their chronology is summarized part ii presents case studies to highlight the specific strengths of ree minerals used to resolve the dynamics of a broad range of processes from diagenetic to magmatic conditions finally a brief section at the end outlines a few of the current challenges and promising perspectives for future work to introduce the four ree minerals in style let us recall the origins of their names the three phosphates have well respected greek grandparents and allanite has solid scottish roots yet of all four of them show idiosyncracies in etymology or type material apatite had long puzzled naturalists as it shows great chemical and physical variability and can resemble other minerals once properly identified abraham gottlieb werner named it apatite his reasoning referred to the greek root and giving the precise latin translation decipio taken literally both mean i deceive or i mislead which sounds like an apt confession from this mineral for having fooled

ediacaran to cambrian oceanic rocks of the gondwana margin and their tectonic interpretation in tectonic maps of variscan europe allochthonous pieces of cadomian basement clearly stand out with their predominant metabasic to ultrabasic elements the so called exotic terranes with ophiolites most of these domains are observed in basements of the central iberian allochthone the south armorican domain the nappe structures of the french massif central the saxothuringian zone and the bohemian massif similar relics can be recognized in many alpine basement areas and correlations with supposedly more autochthonous basements such as the ossa morena zone and the central iberian basement can be envisaged all of these relics are thought to represent the interrupted trace of a former continuous or discontinuous structure characterized by the presence of ocean derived proto rheic rock suites these can be interpreted as pieces of former magmatic arcs of ediacaran to cambrian age accreted to the gondwana margin which later were scattered as allochthonous units during the variscan plate tectonic processes the presence of similar rock suites of ordovician age in the alpine realm is explained by the accretion of exotic china derived basements and their collision with the gondwana margin during the opening of the rheic ocean

burial rates during prograde metamorphism of an ultra high pressure terrane an example from lago di cignana western alps italy abstract estimation of burial rates and duration of prograde metamorphism of ultra high pressure uhp rocks t 590 630 c p 2 7 2 9 gpa of the zermatt saas ophiolite from lago di cignana italy may be made through combined lu hf and sm nd garnet geochronology in conjunction with petrologic estimates of the prograde p t path we report a lu hf garnet omphacite whole rock isochron age of 48 8 2 1 ma from the uhp locality at lago di cignana which stands in contrast to the sm nd age of 40 6 2 6 ma amato et al earth planet sci lett 171 1999 425 438 obtained from the same sample and mineral material the sm nd and lu hf ages as well as other ages determined on metamorphic garnet zircon and white mica amato et al earth planet sci lett 171 1999 425 438 mayer et al eur union geosci 10 1999 abstr 809 rubatto et al contrib mineral petrol 132 1998 269 287 dal piaz et al int j earth sci 90 2001 668 684 from lago di cignana and elsewhere in the zermatt saas ophiolite lie within a range of 50 38 ma which we interpret to encompass the duration of prograde metamorphism and possibly the duration of garnet growth the difference in measured sm nd and lu hf ages from cignana can be accounted for by expected core to rim variations in lu hf sm and nd the measured yttrium content in garnet which may be a proxy for lu is highest in garnet core and lowest in the mineral rim generally following a profile that is predicted by rayleigh fractionation preferential enrichment of lu in the core produces a lu hf age that is weighted toward the older garnet core sm nd ages as predicted by rayleigh fractionation of sm and nd during garnet growth however reflect later grown garnet as compared to lu hf ages the difference in sm nd and lu hf ages from a single sample should therefore be a minimum estimate for the duration of garnet growth and prograde metamorphism so long as sm nd and lu hf blocking temperatures were not exceeded for a long period of time based on the 12 myr duration of prograde garnet growth estimated in this study burial rates for rocks at lago di cignana were on the order of 0 23 0 47 cm yr these values correlate with continuous shortening rates of 0 4 1 4 cm yr between the european plate and the african adriatic promontory between 50 and 38 ma which is on the order of that calculated for plate velocities from plate reconstructions suggesting that the zermatt saas ophiolite may have remained well coupled to the down going slab to uhp conditions

the nature and origin of titaniferous magnetite rich layers in the upper zone of the bushveld complex a review and synthesis the occurrence and geologic relationships of ti magnetite layers indicate that their genesis is intimately related to fractional crystallization processes that were responsible for the formation of their silicate host rocks the exact mechanism by which these oxide rich layers form is however still debated most recent models recognize that precipitation of copious quantities of ti magnetite is triggered by episodic increases in f sub o 2 but the process whereby this occurs is not well understood the nature and occurrence of ti magnetite rich layers in the bushveld complex is reviewed and the requirements of any satisfactory genetic model are outlined the formation and subsequent textural evolution of ti magnetite layers is believed to have taken place as follows 1 favorable conditions for the precipitation of large quantities of ti magnetite were created by a lengthy period of fractional crystallization that resulted in the concentration of large amounts of fe ti and v in the residual magma 2 large scale in situ bottom crystallization of plagioclase resulted in a marked increase in the total fe content and density of the immediately surrounding melt which collected as a dense layer on the bottom of the magma chamber this dense fe ti v enriched liquid did not mix with the overlying magma and formed a stagnant layer from which copious amounts of ti magnetite may have crystallized 3 crystallization of ti magnetite is controlled by the fe 2 o 3 feo ratio of the liquid and is a function of f sub o 2 temperature and the f sub h 2 o f sub h 2 ratio the fe 2 o 3 content of the liquid will also increase during the crystallization of ilmenite and fe super 2 bearing silicates clinopy roxene pigeonitc and fayalitic olivine the h 2 o content of the residual liquid will also be increased by the fractionation of anhydrous silicate phases 4 a complex interplay of these factors resulted in the precipitation of relatively large amounts of ti magnetite required for the development of ore rich layers the bulk of the ti magnetite formed by in situ bottom crystallization the nucleation and growth of magnetite within the stagnant layer and gravitative settling of these crystals over a short distance on the order of meters may have augmented the growth of the layers 5 variations in the relative proportions of coexisting oxide and silicate phases may be related to differences in concentrations and diffusion rates of ions in the liquid immediately above the crystallizing layer this resulted in differences in the rates of nucleation and growth of individual phases 6 precipitation of abundant magnetite lowered the density of the stagnant layer until it reached that of the overlying magma the two liquids then mixed thus terminating the cycle of magnetite layer formation and marking a return to silicate dominated fractionation 7 the ore rich layers originally consisted of ti magnetite crystals and variable amounts of silicate crystals which contained a certain amount of interstitial residual liquid densification of these layers and expulsion of significant amounts of this liquid were accomplished by annealing at high subsolidus temperatures possibly augmented by the addition of suitable material from interprecipitate liquids 8 variations in f sub o 2 during subsolidus cooling resulted in the development of a wide range of ulvoespinel and ilmenite microintergrowths

despeckling srtm and other topographic data with a denoising algorithm abstract noise in topographic data obscures features and increases error in geomorphic products calculated from dems dems produced by radar remote sensing such as srtm are frequently used for geomorphological studies they often contain speckle noise which may significantly lower the quality of geomorphometric analyses we introduce here an algorithm that denoises three dimensional objects while preserving sharp features it is free to download and simple to use in this study the algorithm is applied to topographic data synthetic landscapes srtm topsar and the results are compared against using a mean filter using lidar data as ground truth for the natural datasets the level of denoising is controlled by two parameters the threshold t that controls the sharpness of the features to be preserved and the number of iterations n that controls how much the data are changed the optimum settings depend on the nature of the topography and of the noise to be removed but are typically in the range t 0 87 0 99 and n 1 10 if the threshold is too high noise is preserved a lower threshold setting is used where noise is spatially uncorrelated e g topsar whereas in some other datasets e g srtm where filtering of the data during processing has introduced spatial correlation to the noise higher thresholds can be used compared to those filtered to an equivalent level with a mean filter data smoothed by the denoising algorithm of sun et al sun x rosin p l martin r r langbein f c 2007 fast and effective feature preserving mesh denoising ieee transactions on visualisation and computer graphics 13 925 938 are closer to the original data and to the ground truth changes to the data are smaller and less correlated to topographic features furthermore the feature preserving nature of the algorithm allows significant smoothing to be applied to flat areas of topography while limiting the alterations made in mountainous regions with clear benefits for geomorphometric analysis in areas of mixed topography the results of denoising on the derived flow accumulation and slope maps particularly when compared to the results of mean filtering demonstrate the usefulness of the algorithm in fields such as hydrological modelling and landslide prediction

morphometric evaluation of papanasam and manimuthar watersheds parts of western ghats tirunelveli district tamil nadu india a gis approach a morphometric analysis was carried out to describe the topography and drainage characteristics of papanasam and manimuthar watersheds these watersheds are part of western ghats which is an ecologically sensitive region the drainage areas of papanasam and manimuthar watersheds are 163 and 211 km2 respectively and they show patterns of dendritic to sub dendritic drainage the slope of both watersheds varied from 0 to 59 and 0 to 55 respectively moreover the slope variation is chiefly controlled by the local geology and erosion cycles each watershed was classified as a fifth order drainage basin the stream order of the basin was predominantly controlled by physiographic and structural conditions the increase in stream length ratio from lower to higher order suggests that the study area has reached a mature geomorphic stage the development of stream segments is affected by rainfall and local lithology of the watersheds

on the use of high resolution topographic data as a proxy for seismic site conditions vs30 an alternative method has recently been proposed for evaluating global seismic site conditions or the average shear velocity to 30 m depth v s 30 from the shuttle radar topography mission srtm 30 arcsec digital elevation models dems the basic premise of the method is that the topographic slope can be used as a reliable proxy for v s 30 in the absence of geologically and geotechnically based site condition maps through correlations between v s 30 measurements and topographic gradient here we evaluate the use of higher resolution 3 and 9 arcsec dems to examine whether we are able to resolve v s 30 in more detail than can be achieved using the lower resolution srtm data high quality dems at resolutions greater than 30 arcsec are not uniformly available at the global scale however in many regions where such data exist they may be employed to resolve finer scale variations in topographic gradient and consequently v s 30 we use the u s geological survey earth resources observation and science eros data center s national elevation dataset ned to investigate the use of high resolution dems for estimating v s 30 in several regions across the united states including the san francisco bay area in california los angeles california and st louis missouri we compare these results with an example from taipei taiwan that uses 9 arcsec srtm data which are globally available the use of higher resolution ned data recovers finer scale variations in topographic gradient which better correlate to geological and geomorphic features in particular at the transition between hills and basins warranting their use over 30 arcsec srtm data where available however statistical analyses indicate little to no improvement over lower resolution topography when compared to v s 30 measurements suggesting that some topographic smoothing may provide more stable v s 30 estimates furthermore we find that elevation variability in canopy based srtm measurements at resolutions greater than 30 arcsec are too large to resolve reliable slopes particularly in low gradient sedimentary basins

the formation of pangea abstract the making of pangea is the result of large scale amalgamation of continents and micro continents which started at the end of the neoproterozoic with the formation of gondwana as pieces were added to gondwana on its south american antarctica and australia side ribbon like micro continents were detached from its african and south chinese side cadomia in the late neoproterozoic avalonia and hunia in the ordovician galatia in the devonian and cimmeria in the permian cadomia was re accreted to gondwana but the other ribbon continents were accreted to baltica north china laurussia or laurasia finding the origin of these numerous terranes is a major geological challenge recently a global plate tectonic model was developed together with a large geological geodynamic database at the lausanne university covering the last 600 ma of the earth s history special attention was given to the placing of gondwana derived terranes in their original position using all possible constraints we propose here a solution for the variscan terranes another paper deals with the altaids the galatian super terrane was detached from gondwana in the devonian during the opening of paleotethys and was quickly separated into four sub terranes that started to by pass each other the leading terranes collided at the end of the devonian with the hanseatic terrane detached from laurussia in the carboniferous gondwana started to impinge onto the amalgamated terranes creating the variscan chain and the pangean super continent east of spain paleotethys remained opened until the triassic subducting northward under laurasia roll back of the paleotethyan slab triggered the collapse of most of the european variscan orogen which was replaced by series of permian rifts some of them becoming oceanized back arc basins during the triassic major force changes at the pangean plate limits at the end of the triassic provoked its break up through the opening of the proto caribbean central atlantic alpine tethys oceanic seaways

fans and fan deltas precursors to the armorican quartzite ordovician in western iberia the armorican quartzite lower ordovician is a very extensive sandstone body found throughout a large part of iberia and brittany similar quartzites are present in north africa and elsewhere in iberia it generally lies unconformably on a thick folded late precambrian to cambrian turbidite sequence the complexo xisto grauvaquico cxg but there are some places where the quartzite has a conformable relationship with the underlying cxg where conformable the whole succession shows varied facies sequences including i a regressive mud sand sequence as a precursor to the main quartzite development ii submarine fan sediments of the cxg passing up into slope and then shallow marine facies or iii fluvially influenced breccio conglomerates of a marginal fan delta passing up into shallow marine sediments the inferred development of alluvial fans associated with fan deltas prograding into shallow marine environments implies steep slopes and the likelihood that faulting controlled some of the uplift the mozaic pattern of differential uplift and subsidence throughout the region suggests that the cxg was affected by local block movements rather than by regional folding the presence of upstanding blocks during the initial sedimentation of the armorican quartzite suggests that the quartz sand might have been derived from multiple sources dispersed throughout the area rather than from sources along a single shoreline at the margin of the depositional area

multidisciplinary constraints on the cadomian compression and early cambrian extension in the iberian chains ne spain abstract this paper presents a multidisciplinary approach stratigraphic sedimentologic structural and mineralogic to document the evidences for cadomian and earliest cambrian tectonic processes recorded in the iberian chains which were strongly overprinted during variscan and alpine deformation episodes the contact of the neoproterozic paracuellos group and the lower cambrian bambola formation is commonly identifiable by the presence of a distinct erosive unconformity related to the onset of alluvial plain sequences or associated with synsedimentary faults a meso structural analysis of the deformation recorded in the paracuellos slates reveals the existence of an earlier slaty cleavage s 1n overprinted by variscan contractional structures some of them related to positive inversion of pre variscan normal faults the comparative geometrical study with structures observed in the bambola formation essentially a single nw se to n s striking cleavage s 1c is not conclusive about the record of the cadomian orogeny however micro scale deformation associated with the earliest cleavage is much more intense in the paracuellos slates in addition the metamorphic grade and the pressure conditions of the lower cambrian anchizonal shales contrast with the neoproterozoic epizonal slates both observations are consistent with a cadomian contractional deformation associated with a low grade intermediate pressure metamorphism absent in the overlying rocks postdating both processes stratigraphically marked by a tectono thermal discontinuity located at the paracuellos bambola contact the onset of the lowermost cambrian bambola formation is accompanied by strong palaeogeographic transformations in the sedimentary basin including i a sharp relative sea level fall leading to deposition of alluvial plain sediments and ii an increase in sedimentation rates and tectonically induced subsidence at fault bounded depressions all these changes together with the presence of normal or transtensional faults at the base of bambola formation point to an earliest cambrian extensional regime similar to that described for other neighbouring post cadomian basins

ice loss rates at the northern patagonian icefield derived using a decade of satellite remote sensing abstract we use a satellite based survey of glacier surface elevation changes speeds and surface melt conditions between 2000 and 2011 to quantify mass loss from the northern patagonian icefield npi chile a history of ice elevation change is found by differencing aster digital elevation models dems relative to a void filled version of the dem collected by the shuttle radar topography mission srtm in february 2000 thinning rates have accelerated at lower elevations while above the equilibrium line altitude ela recent thinning rates are not significantly different from those observed in previous studies a volumetric change of 4 06 0 11 km 3 yr is found by summing surface elevation changes over all glaciers in the npi this is regarded as a lower bound because volume loss due to frontal retreat and sub aqueous melting is not included this volume change is converted to a mass loss of 3 40 0 07 gt yr taking into account density differences above and below the equilibrium line we find that the npi is providing at least 0 009 0 0002 mm yr to ongoing sea level change in agreement with previous estimates sub pixel offset tracking of aster image pairs is used to produce glacier displacements over intervals typically ranging from 6 days to 18 months the first whole icefield composite velocity map is presented the terminus of the san rafael glacier on the western side of the npi sustained a peak calving front speed of 19 7 1 2 m day for 7 days in the austral fall of 2007 passive microwave observations indicate that the surface of the accumulation basin of the glacier was wet during this period of rapid motion suggesting that the fast speed may be a consequence of a rise in sub glacial water pressure sourced from melt or rainwater making its way to the glacier bed and reducing basal friction several other outlet glaciers including the benito and hpn1 glaciers on the isolated western side of the icefield accelerated while thinning between 2007 and 2011 marked acceleration also occurred after 2007 at the front of the san quintin glacier the largest outlet glacier of the npi the paucity of thickness measurements at the outlet glaciers means it is impossible to accurately gauge the mass flux of the icefield and thus give a full estimate of the mass balance

the 2010 mw 7 8 mentawai earthquake very shallow source of a rare tsunami earthquake determined from tsunami field survey and near field gps data 1 the mw 7 8 october 2010mentawai indonesia earthquake was a tsunami earthquake a rare type of earthquake that generates a tsunami much larger than expected based on the seismicmagnitude itproducedalocallydevastatingtsunami withrunupcommonlyinexcess of 6 m we examine this event using a combination of high rate gps data from instruments located on the nearby islands and a tsunami field survey the gps displacement time series are deficient in high frequency energy and show small coseismic displacements 16 m our modeling results show that the combination of the small gps displacements and large tsunami can only be explained by high fault slip at very shallow depths far from the islands and close to the oceanic trench inelastic uplift of trench sediments likely contributed to the size of the tsunami recent results for the 2011 mw 9 0 tohoko oki earthquake have also shown shallow fault slip but the results from our study which involves a smaller earthquake provide much stronger constraints on how shallow the rupture can be with the majority of slip for the mentawai earthquake occurring at depths of 6 km this result challenges the conventional wisdom that the shallow tips of subduction megathrusts are aseismic and therefore raises important questions both about the mechanical properties of the shallow fault zone and the potential seismic and tsunami hazard of this shallow region

mapping recent lava flows at westdahl volcano alaska using radar and optical satellite imagery field mapping of young lava flows at aleutian volcanoes is logistically difficult and the utility of optical images from aircraft or satellites for this purpose is greatly reduced by persistent cloud cover these factors have hampered earlier estimates of the areas and volumes of three young lava flows at westdahl volcano including its most recent 1991 1992 flow we combined information from synthetic aperture radar sar images with multispectral landsat 7 data to differentiate the 1991 1992 flow from the 1964 flow and a pre 1964 flow and to calculate the flow areas 8 4 9 2 and 7 3 km 2 respectively by differencing a digital elevation model dem from the 1970 1980s with a dem from the shuttle radar topography mission srtm in february 2000 we estimated the average thickness of the 1991 1992 flow to be 13 m which reasonably agrees with field observations 5 10 m lava flow maps produced in this way can be used to facilitate field mapping and flow hazards assessment and to study magma supply dynamics and thus to anticipate future eruptive activity based on the recurrence interval of recent eruptions and the results of this study the next eruption at westdahl may occur before the end of this decade

lu hf apatite geochronology of mafic cumulates an example from a fe ti mineralization at smalands taberg southern sweden abstract we have employed lu hf apatite chronology to determine the age of a magnetite rich melatroctolite in southern sweden known as the smalands taberg fe ti ore deposit the melatroctolite is poor in incompatible elements and minerals forming at more advanced stages of differentiation which precludes the use of minerals baddeleyite zircon titanite or apatite commonly used for dating the emplacement of igneous rocks enclaves of leucogabbro in the melatroctolite have ree patterns parallel with the host melatroctolite and identical initial hf and nd isotope compositions these characteristics are conclusive evidence for a common parental magma the leucogabbro is a slightly more evolved facies that underwent limited fractionation of olivine and titanomagnetite the two major mineral phases in the melatroctolite apatite and plagioclase separated from the leucogabbro plus a whole rock sample define a lu hf isochron with a slope corresponding to an age of 1204 3 1 8 ma this result is close to the lower age boundary previously reported for this magmatic event comprising dolerites syenites and granites the lu hf apatite chronometer merits attention as a new tool in generating accurate and precise ages for igneous silica undersaturated rocks that may be difficult to date with traditional techniques

the isotopic composition of yb and the precise and accurate determination of lu concentrations and lu hf ratios by isotope dilution using mc icpms 1 we report yb isotopic data for the purpose of accurately correcting measurements of lu and lu hf ratios during multicollector inductively coupled plasma mass spectrometer mc icpms analysis the yb isotopic ratios agree with recent results of chu et al 2002 and amelin and davis 2004 when corrected for mass fractionation to the same reference values protocols for lu measurement involving simultaneous subtraction of yb interference and application of a fractionation correction based on yb are described it is shown that lu concentrations and lu hf ratios determined by mc icpms using this methodology are more precise and potentially more accurate than results based on analysis of lu by thermal ionization mass spectrometry tims a number of mc icpms lu hf isotopic analyses of standard rocks and other geological samples previously analyzed by tims are presented these document reproducibility of lu hf within 0 2 where most discrepancies can be assigned to the unknown lu mass fractionation during tims analysis

late ediacaran skeletal body fossil assemblage from the navalpino anticline central spain mineralized fossils have been described from late ediacaran rocks all over the world and have been interpreted as the first metazoans capable of secreting a mineralized skeleton among these early biomineralizers the tubular cloudina has a cosmopolitan distribution it often occurs in association with other mineralizing organisms such as sinotubulites and namacalathus which show a more restricted and seemingly non overlapping distribution many aspects of the biology of these organisms remain poorly known in particular the structure and composition of the ecosystems they formed part of here we report a diverse fossil assemblage from the ibor group of villarta de los montes of the central iberian zone spain the assemblage includes the first material of sinotubulites baimatuoensis from spain which is found in association with cloudina hartmanae and cloudina carinata also found are small tubular fossils and a flask shaped form comparable to protolagena among previously described assemblages of late ediacaran skeletal fossils the villarta assemblage unique in europe most closely compares to that from the dengying formation of south china

spatial variability of iron oxides in soils from brazilian sandstone and basalt abstract iron oxides as goethite gt and hematite hm are key minerals to better understand the soil landscape relationships soil samples were collected at three stages of landscape dissection from the geological formations of vale do rio do peixe sandstone and serra geral basalt in the western paulista plateau wpp brazil both iron oxides were quantified by x ray diffraction xrd and diffuse reflectance spectroscopy drs and the results were subjected to geostatistical analysis in order to assess the usefulness of drs for characterizing the spatial variability in gt and hm the prevalence and spatial variability of hm and gt in the soils were governed by the sandstone basalt lithological contrast and landscape dissection iron oxides in the clay fraction exhibited high spatial variability over a large area and can be robust indicators of geological diversity and landscape dissection in pedoenvironments with low or high contents of iron oxides goethite had the highest spatial variability based on the spatial pattern of the differences between drs and xrd estimates the saturated red color in soil made drs less useful for quantifying hm in environments with high iron oxide contents the maps indicate the sensitivity of xrd and drs techniques to represent hm and gt spatial variability patterns gt was more sensitive to landscape dissection while hm sensitive to lithology thus the drs technique is efficient in characterizing the spatial variability of these soil oxides in large areas even considering the complex relations between soil and landscape

changes in erosion and ocean circulation recorded in the hf isotopic compositions of north atlantic and indian ocean ferromanganese crusts abstract high resolution hf isotopic records are presented for hydrogenetic fe mn crusts from the north atlantic and indian oceans bm1969 from the western north atlantic has previously been shown to record systematically decreasing nd isotopic compositions from about 60 to 4 ma at which time both show a rapid decrease to unradiogenic nd composition thought to be related to the increasing influence of nadw or glaciation in the northern hemisphere during the oligocene north atlantic hf became progressively less radiogenic until in the mid miocene 15 ma it reached 1 it then shifted gradually back to an hf value of 3 at 4 ma since when it has decreased rapidly to about 1 at the present day the observed shifts in the hf isotopic composition were probably caused by variation in intensity of erosion as glaciation progressed in the northern hemisphere ferromanganese crusts ss663 and 109d are from about 5500 m depth in the indian ocean and are now separated by 2300 km across the mid indian ridge they display similar trends in hf isotopic composition from 20 to 5 ma with the more northern crust having a composition that is consistently more radiogenic by 2 hf units paradoxically during the last 20 ma the hf isotopic compositions of the two crusts have converged despite increased separation and subsidence relative to the ridge a correlatable negative excursion at 5 ma in the two records may reflect a short term increase in erosion caused by the activation of the himalayan main central thrust changes to unradiogenic hf in the central indian ocean after 5 ma may alternatively have been caused by the expanding influence of nadw into the mid indian basin via circum antarctic deep water or a reduction of pacific flow through the indonesian gateway in either case these results illustrate the utility of the hf isotope system as a tracer of paleoceanographic changes capable of responding to subtle changes in erosional regime not readily resolved using other isotope systems

apatite in igneous systems apatite is a minor but ubiquitous mineral in most igneous rocks although the modal proportion of apatite in common rocks is generally low it can reach high concentrations in enclaves cumulates and other rocks of low abundance i e rocks that constitute a small volume of the crust and mantle e g nelsonites the presence of apatite in most rocks is due not only to its low solubility in naturally occurring melts and aqueous solutions but also to the limited ability of common rock forming minerals to accept the amount of phosphorus that occurs in most rocks into their structure in this paper we will discuss some aspects of the occurrence texture composition physical chemistry and petrogenetic significance of apatite in felsic rocks i e andesite to rhyolite and their plutonic analogs in mafic i e basalts and related rocks and plutonic analogs and ultramafic rocks of the earth s crust and mantle fluorapatite is by far the most common member of apatite family found in igneous rocks however most natural fluorapatite contains some chlorine and hydroxyl as well and these constituents can attain high concentrations in some cases the other halogens bromine and iodine also occur in apatite but their concentrations are much lower than chlorine and fluorine many cations commonly substitute for calcium and phosphorus in apatite however they rarely reach concentrations that warrant the definition of a separate mineral species apatite can be described by the general formula a5 xo4 3z following sommerauer and katz lehnert 1985 the a site accommodates large cations e g ca2 sr2 pb2 ba2 mg2 mn2 fe2 ree3 eu2 cd2 na pan and fleet ch 2 in this volume and comprises two sites that exhibit vii fold

accuracy and resolution of shuttle radar topography mission data 1 we assess the accuracy and resolution of topography data provided by the shuttle radar topography mission srtm through spectral comparisons with the national elevation dataset ned and a high resolution laser data set of the 1999 hector mine earthquake rupture we find that srtm and the ned are coherent for wavelengths greater than 200 m however the spatial resolution of the ned data is superior to the srtm data for wavelengths shorter than 350 m likely due to the application of a boxcar filter applied during final srtm processing stages from these results a low pass filter decimation algorithm can be designed in order to expedite large area srtm applications

segmented curved faults the example of the balduini thrust zone northern apennines italy abstract meso and micro structural studies of the well exposed balduini thrust northern apennines italy indicate that the structure formed during a single folding event contemporaneous with diagenesis and is a zone comprising curved en echelon fault segments the geometry of each segment is arcuate with pure compression at one end and right lateral displacement along the other the thrust developed during the tortonian within a single mud rich formation the upper eocene upper oligocene scaglia cinerea but rheological variations within the unit led to differences in deformation style zones of scaly fabric are discontinuous and calcite veins vary in abundance the mesoscopic morphology of the veins and the distribution of calcium carbonate along the formation indicate variations in the distribution of fluids at the time of deformation which affected both diagenesis and the structural response of the material systematic variations of mechanical properties within the thickness of the scaglia cinerea formation account for the curvature of the propagating thrust together with the heterogeneity of the stress field the confinement of the arcing thrust to this single weak unit lead to repeated initiation of new fractures and hence segmentation of the propagating thrust geometric analysis of the calcite veins and their microscopic characters suggests that hydrofracturing was involved with the scaglia cinerea formation experiencing high fluid pressure followed by rapid water expulsion the balduini thrust is therefore an example of a fluid driven refracted compound shear zone the analysis presented here provides insights into the three dimensional arrangement of fault zones and fluid migration patterns during regional faulting