cratered cobbles in triassic buntsandstein conglomerates in northeastern spain an indicator of shock deformation in the vicinity of large impacts quartzite cobbles in lower triassic buntsandstein conglomerates from northeastern spain display unusual millimeter to centimeter sized circular craters commonly having central mounds and surrounded by radial fractures the conglomerates are also marked by intense fracturing down to microscopic scale these features have traditionally been attributed to tectonic compression and pressure dissolution at cobble contacts sections through the cratered cobbles reveal pervasive internal fracturing segments detached along concave spall fractures and zones marked by quartz grains with planar deformation features comparison with results of impact experiments on artificial conglomerates suggests that these features were produced by internal accelerations grain collisions and spallation related to shock wave propagation through inhomogeneous deposits the proximity of the outcrops to the azuara and proposed rubielos de la cerida impact structures suggests that shock deformation of conglomerates can provide an easily recognizable regional impact signature

rare slickenside kinematic indicator asymmetric elevations seen to be abundant on southern aksa beach mumbai india asymmetric elevations fig 1 are types of slickenside kinematic indicators doblas 1998 that form on fault planes as miniature roche moutonnees dzulynski and kotlarczyk 1965 and are sim ilar in geometry and mechanism of formation however asymmetric elevations have been used rarely as kinematic indicators possibly due to their rare occurrence we found abundant asymmetric elevations of

evolution of mica fish in mylonitic rocks abstract mineral fish are lozenge shaped porphyroclasts single crystals in a finer grained matrix which occur in ductile shear zones and which are commonly used as shear sense indicators mineral fish of biotite tourmaline k feldspar garnet hypersthene and quartz occur in mylonites but most common are white mica fish these mica fish can be subdivided into six morphological groups that develop by different mechanisms determined by different initial shapes and orientations the principal mechanisms of formation are intracrystalline deformation combined with rigid body rotation concomitant selective grain size reduction occurs by recrystallisation cataclastic separation pressure solution and diffusional mass transfer microboudinage has been proposed for the breakdown of large mica fish into smaller ones but many mica fish undergo shortening rather than extension along their long axes evidence is presented for an alternative process in which the tips of mica fish are isoclinally folded and then break off along the hinge of these microfolds all the presented fish shaped porphyroclasts or mineral fish have a specific shape preferred orientation with their long axis at a small antithetic angle with respect to the foliation they represent a special group of objects with a stable orientation due to flow partitioning into narrow shear bands

unusual radar echoes from the greenland ice sheet airborne radar images of part of the greenland ice sheet reveal icy terrain whose radar properties are unique among radar studied terrestrial surfaces but resemble those of jupiter s icy galilean satellites the 5 6 and 24 centimeter wavelength echoes from the greenland percolation zone like the 3 5 and 13 centimeter wavelength echoes from the icy satellites are extremely intense and have anomalous circular and linear polarization ratios however the detailed subsurface configurations of the galilean satellite regoliths where heterogeneities are the product of prolonged meteoroid bombardment are unlikely to resemble that within the greenland percolation zone where heterogeneities are the product of seasonal melting and refreezing

diagenetic origin for quartz pebble conglomerates the occurrence of quartz pebble conglomerates qpc in the rock record increases backward through time from the tertiary through the precambrian the positive correlation between qpc abundance and age is valid both for numbers of reported qpc and for qpc as a percentage of all conglomerate and at both the era and the period level qpc are usually interpreted as being due to intense chemical weathering protracted transport or sediment recycling but none of these can account for the age distribution of qpc which is the opposite of the global mass age distribution for sedimentary rocks precambrian and tertiary conglomerates with similar sources and sedimentology have vastly different clast populations nonquartzose clasts being much more abundant in the younger rocks comparison of the petrology of qpc and polymict conglomerates shows that qpc have consistently higher proportions of diagenetic secondary matrix and pressure solved grain contacts we conclude that diagenetic factors play an important role in qpc formation by preferentially destroying less durable clasts

structure and organization of the porma melange progressive denudation of a submarine nappe toe by gravitational collapse the porma melange is a unit up to 1 km thick underlying the forcada nappe in the variscan foreland of the iberian peninsula most of the porma melange consists of a highly deformed boudinaged sequence with extension values over 300 percent the boudins or melange blocks are the result of bed parallel extension in two perpendicular directions giving rise to equidimensional boudins in plan view choco late tablet structure in cross section view the boudins show different shapes rectan gular rhomboid triangular trapezoid or with arrowhead edges due to various combinations of extension and shear fractures both the provenance of the melange blocks mostly derived from the upper part of the bodon nappe that overlies the forcada nappe and flattening type strain ellipsoid shapes support the interpretation that hanging wall gravitational collapse of these nappes was the cause of the exten sional deformation the current distribution of the melange blocks from different nappe formations implies progressive unroofing of the nappe stack through subse quent submarine slumps the internal structure of the melange blocks depends on the degree of sediment lithification during slumping and illustrates the significance of the so called native and exotic blocks the source of most of the melange material shaly matrix and native blocks or boudins was the semilithified syntectonic sediments of the upper part of the bodon nappe which underwent brittle ductile deformation boudinage during slumping however a few and usually larger exotic blocks also came into the basin as individual slip blocks from competent well lithified formations originally located at the lower part of the nappe stack with higher shear resistance and less suitable for spreading thus the arrangement of major nappe fragments traditionally named klippes and showing sizes that may reach up to several kilometers does not agree with the geometric rules of thrusting and are reinterpreted as megablocks resulting from gravitational sliding during denudation of advancing nappes

tectonic implications and morphology of trapezoidal mica grains from the sutlej section of the higher himalayan shear zone indian himalaya abstractmicroscopic trapezoidal micas are reported from the sutlej section of the higher himalayan shear zone india and are attributed to an up dip top to southwest sense of brittle shear along c planes of preexisting ductile shear dipping northeast the longest margins of these trapezoids dip northeast and are oblique to either the c planes or their enveloping planes intragrain slips along cleavages aided their thrusting while the surrounding competent quartzofeldspathic minerals resisted it the cleavages of the trapezoids are parallel to their longest margins these cleavages the longest margins the overall asymmetry of trapezoid aggregates and the trails emanating from their corners are reliable indicators of brittle shear sense trails broken from the corners of developing trapezoids define both the p and the y shear planes subcircular stacks and triangular mineral grains are also possible variations of trapezoids some of the trapezoidal micas were products of ductile brittle deformation va

formation and maintenance of shear zones the processes that initiate and maintain prograde ductile shear zones are not well understood we have performed shear experiments 1 to 3 on a fine grained 100 150 m gneiss 59 quartz 28 plagioclase 13 aligned but not interconnected biotite to determine the evolution of deformation mechanisms that produce dramatic strain weakening and localization at conditions 1 5 gpa 800 c dot gamma 2 10 5 s where pure quartz aggregates deform homogeneously by dislocation creep initial yield occurs where stress concentrations at the tips of weak biotite grains produce semibrittle deformation in intervening quartz or plagioclase allowing local biotite interconnection by slip on 001 and initiating strain weakening after yield the interconnected biotites kink and thus strengthen but the highly strained parts of grains react to a fine grained mixed phase assemblage which deforms by grain size sensitive creep allowing further strain weakening and localization at 3 3 the strain and strain rate in the 100 m thick shear zone are 100 times that of the enclosing host rock similar to the localization observed in natural shear zones thus the processes that initiate strain localization are not necessarily the same as those that preserve the weak shear zone and once formed a shear zone may be permanently weakened

retrieving snowpack properties and accumulation estimates from a combination of sar and scatterometer measurements this study combines two satellite radar techniques low resolution c ku band scatterometer and high resolution c band synthetic aperture radar sar for glaciological studies in particular mass balance estimations three parameters expressing the mean backscattering and its dependency on azimuth and incidence angle are used to describe and classify the antarctic ice sheets backscattering behavior simple linear regression analyses are carried out between ground truth accumulation data and the sar backscattering coefficient along continuous profile lines from this we parameterize the accumulation rate separately for certain snow pack regimes we find that sar data can be used to map mass balance changes however only within limited areas applying this method therefore generally requires accurate ground truth for regional calibration together with additional information regarding mean air temperature or elevation this investigation focuses on the area of dronning maud land antarctica we present the first high resolution accumulation map based on sar data for the surrounding area of the epica deep ice core drilling site kohnen which is compared to reliable ground truth records as well as to a surface mass balance map interpolated from these at low resolution

internal reflecting horizons in spitsbergen glaciers a single pronounced internal reflecting horizon has been observed on radio echo sounding from over 30 glaciers in spitsbergen they are often present along the entire length of the glacier remaining at a fairly constant depth 100 200 m below the ice surface echo strength data from radio echo sounding have been used to obtain reflection coefficients for these horizons of between 15 and 25 db combined with results of ice core studies the possible causes of this internal layer are investigated the presence of water is found to be the most likely explanation indicating the existence at depth of a layer of temperate ice

insar elevation bias caused by penetration into uniform volumes natural media like cold land ice vegetation and dry sand are subject to a substantial penetration at microwave frequencies for such media the synthetic aperture radar sar phase center is located below the surface and consequently the surface elevation determined with sar interferometry insar is biased downward for infinitely deep uniform volumes the elevation bias is often equated with the penetration depth but in this paper it is shown that the two quantities generally differ the interferometric bias is approximately equal to the two way power penetration depth if the latter is small compared to the ambiguity height but for increasing penetration depth the bias approaches one quarter of the ambiguity height consequently no phase wrapping results even if the penetration depth exceeds the ambiguity height the ratio of the insar elevation bias to the ambiguity height depends only on the ratio of the penetration depth to the ambiguity height and the bias can be expressed in terms of the insar coherence magnitude which makes it possible to correct the insar surface elevation for the bias the volume depth can be considered infinite if it exceeds the penetration depth by a factor of two to five and if the surface scattering from the top and the bottom of the volume is negligible

diagenetic history of cambrian quartzarenites ras dib zeit bay area gulf of suez eastern desert egypt abstract in the northern corner of the el zeit range 370 m of sandstone overlie precambrian granite and underlie cretaceous marine strata the sandstones include the marine lower cambrian araba formation and the overlying dominantly fluvial upper cambrian naqus formation the framework compositions of both sandstones are almost entirely quartz with trace amounts of muscovite k feldspar and heavy minerals up to 21 oversize pores some filled with younger cements attest to extensive dissolution loss of detrital grains because the final mineralogical maturation of these quartzarenites reflects diagenesis they are diagenetic quartzarenites during burial diagenesis the introduction of up to 8 quartz cement inhomogeneously distributed mean 3 was followed by local pore occluding calcite cement which halted compaction sandstones without calcite cement underwent additional mechanical and chemical compaction sufficient to develop sutured quartz grain contacts and reduce porosity 27 these events were followed by 1 extensive dissolution loss of carbonate cement detrital feldspars micas and heavy minerals 2 formation of local patches of kaolinite mean 3 and 3 formation of extensive iron oxide cements including specular hematite these features suggest extensive invasion by oxidizing meteoric water the timing of this event can only be dated as post cambrian and pre cenomanian some outcrop samples contain pore occluding gypsum cement or mixtures of gypsum and halite sr87 sr86 ratios of four samples of gypsum cement have values 0 7079 and 0 7085 that indicate miocene and slightly younger seawater evaporites were evidently leached by modern meteoric water from nearby outcrops of miocene and younger marine evaporite bearing strata transported in surface and ground water to the topographically low terrain where the cambrian sandstones crop out and reprecipitated by evaporation initial primary porosity 45 was reduced to 27 by compaction in sands with minor quartz cement compaction ceased where calcite was precipitated subsequent dissolution of some calcite cement and unstable detrital grains generated considerable secondary porosity

application of geomorphic indices to address the foreland himalayan tectonics and landform deformation matiali chalsa baradighi recess west bengal india abstract in the himalayan foreland basin of the tista jaldhaka system of north bengal the presence of main boundary thrust mbt and himalayan frontal thrust hft along an e w direction has been reanalysed in the context of tectonic instability especially along the 17 93 km stretch of the kurti river it is a small rain fed stream that originated in the piedmont zone near the samsing scarp lineament trending e w this work discusses in detail the control of active matiali chalsa and baradighi faults that has been determined by the river morphometric aspects deformed landform as terraces and the valley incision mechanism over time we document not only the fault scarps as mbt near matiali and hft near chalsa but also decipher the baradighi fault as a local manifestation of tectonism with well exposed scarps a ramp anticline synformal zone i exists between the northernmost part of the matiali scarp mbt and towards the south near the chalsa scarp hft however to the south of chalsa lies another depression zone synformal zone ii that extends up to the baradighi scarp exposed in the left eastern side of kurti river changes in geomorphic indices such as long profile analysis drainage basin asymmetry hypsometric curve valley floor width to height ratio vfwh concavity index transverse topographic symmetry factor and sinuosity index along the kurti river have been evaluated uplift erosion cycle with valley incision between the mbt hft and hft baradighi fault scarp connotes that the foreland tectonics emerged to be the recent evolutionary phases in the tecto morphological study

folding of boudinaged layers abstract the boudinage structure in the vaddo area in sweden developed during an early isoclinal folding during a second deformation which deformed the axial surfaces and the limbs of the isoclinal folds the shapes of boudins were variously modified the resulting structures include folding of the individual boudins into half waves a tile like piling up of straight or gently folded boudins and arrangement of straight boudins in a herring bone pattern similar structures have been produced experimentally in soft models containing boudins of different competencies the relative importance of the different physical parameters which contribute towards the development of the various structures is examined in particular the experiments showed that when the competence contrast between the boudin and the host material was rather small the shape of the boudins was modified by a second deformation into trapezoidal forms often with flame shaped projections at the edges from an analysis of the experimental and natural structures a set of criteria has been formulated which can be used to identify structures formed by superposed deformations and to give an approximate idea of the competence contrast between the boudin and the host rock during the second deformation

simulation of the supersar multi azimuth synthetic aperture radar imaging system for precise measurement of three dimensional earth surface displacement the supersar imaging system a novel multi azimuth synthetic aperture radar sar system capable of detecting earth surface deformation in three dimensions from a single satellite platform has recently been proposed in this paper we investigate the feasibility of detecting precise 3 d surface displacement measurements with the supersar imaging system using a point target simulation from this simulation we establish both a relationship between the interferometric sar phase and the across track displacement and a relationship between the multiple aperture interferometry phase and the along track displacement based on the supersar imaging geometry the theoretical uncertainties of the supersar measurement are analyzed in the across and along track directions and the theoretical accuracy of the 3 d displacement measurement from the supersar system is also investigated according to both the decorrelation and the squint and look angles in the case that the interferometric coherence is about 0 8 and that five effective looks are employed the theoretical 2 d measurement precision values are about 3 67 and 6 35 mm in the across and along track directions respectively and the theoretical 3 d measurement precision values for 3 d displacement are about 4 05 4 56 and 3 45 mm in the east north and up directions respectively the result of this study demonstrates that the supersar imaging system is capable of measuring the 3 d surface displacement in all directions with subcentimeter precision

tracking subpixel scale sastrugi with advanced land imager high radiometric resolution imagery from the advanced land imager ali can detect the spatial reflectance variations associated with sastrugi snow dunes on ice sheets this is shown in theory by considering the appropriate snr ratio of ali as compared with eight bit optical sensors and in practice with multitemporal ali imagery comparison of ali imagery spanning 7 5 months also shows that the reflectance pattern associated with sastrugi can persist over this interval offering the potential of their use for measuring ice sheet velocity in uncrevassed regions

kinematic history of the narragansett basin massachusetts and rhode island constraints on late paleozoic plate reconstructions the formation of the narragansett basin of rhode island and massachusetts and the polyphase deformation geometry of the pennsylvanian age basin sediments can be explained by collision and strike slip interactions between an avalonian microcontinent the european north american plate and the african plate during the late paleozoic sinistral movement between an avalonian microcontinent and the european north american plate resulted in formation of pull apart basins subsequently africa moved toward north america along an east west trending dextral megashear zone and collided with the eastern margin of southern north america the narragansett basin is located on the avalonian microcontinent near the suture with the north american continent and in the transition zone between the megashear and the collision tectonic regimes the basin shape stratigraphy and sedimentary relationships can be explained by the coalescence of two composite grabens which formed at different times the thicker northern graben is only affected by one deformation whereas the southern graben shows evidence of four distinct phases of postrifting deformation the first two coaxial folding deformations of the basin sediments are attributed to the closure of the basin complex during collision of africa and north america the third and fourth deformations are interpreted as sinistral r riedal and dextral shears respectively associated with the east west trending megashear system a prograde barrovian metamorphic front started in the western portion of the southern graben slightly after the first deformation and migrated northward and eastward where it is synchronous with the second deformation

estimation of glacier ice extinction using long wavelength airborne pol insar in the recent years there has been increased interest in using synthetic aperture radar sar to study and monitor glaciers and ice sheets for glaciological and climate change research this paper describes the estimation of ice extinctions through the modeling of polarimetric interferometric sar pol insar coherences as a combination of a surface contribution from the snow firn interface and wind induced sastrugi features and a volume response ground to volume scattering ratios derived from a novel polarimetric decomposition are used in conjunction with pol insar coherence magnitudes to invert the extinction of the ice layer the inversion is performed for experimental airborne pol insar data at l band and p band acquired by the german aerospace center s dlr e sar system over the austfonna ice cap in svalbard norway as part of the 2007 icesar campaign extinction dependences on frequency and glacier facie are investigated and validation is performed comparing ground penetrating radar data to sar backscatter and extinction values best extinction results are obtained at shallow incidence angles with small wavenumbers and for low ground to volume scattering ratios for swath areas in mid range to far range accuracies of 25 in extinction are anticipated when averaging over 100 effective looks for a four baseline inversion constraining solutions to vertical wavenumbers of 0 01 kz 0 1 to allow inversion using single baseline pol insar the proposed model is of limited complexity suggested extensions for a more realistic scattering scenario include incorporating multiple englacial ice scattering layers and improving the way multiple baselines are combined

meso scale flanking structure and micro scale push up structure within migmatitic biotite granite peninsular gneissic complex southern india

higher himalayan shear zone sutlej section structural geology and extrusion mechanism by various combinations of simple shear pure shear and channel flow in shifting modes the higher himalayan shear zone hhsz in the sutlej section reveals 1 top to sw ductile shearing 2 top to ne ductile shearing in the upper and the lower strands of the south tibetan detachment system stdsu stdsl and 3 top to sw brittle shearing corroborated by trapezoid shaped minerals in micro scale in the proposed extrusion model of the hhsz the e1 phase during 25 19 ma is marked by simple shearing of the upper sub channel defined by the upper strand of the main central thrust mctu and the top of stdsu as the lower and the upper boundaries respectively subsequently the e2a pulse during 15 14 ma was characterized by simple shear pure shear and channel flow of the entire hhsz finally the e2b pulse during 14 12 ma observed simple shearing and channel flow of the lower sub channel defined by the lower strand of the main central thrust mctl and the top of the stdsl as the lower and the upper boundaries respectively the model explains the constraints of thicknesses of the stdsu and the stdsl along with spatially variable extrusion rate and the inverted metamorphism of the hhsz the model predicts 1 shear strain after ductile extrusion to be maximum at the boundaries of the hhsz which crudely matches with the existing data the other speculations that cannot be checked are 2 uniform shear strain from the mctu to the top of the hhsz in the e1 phase 3 fastest rates of extrusion of the lower boundaries of the stdsu and the stdsl during the e2a and e2b pulses respectively and 4 variable thickness of the stdsl and rare absence of the stdsu non parabolic shear fabrics of the hhsz possibly indicate heterogeneous strain the top to sw brittle shearing around 12 ma augmented the ductile extruded rocks to arrive a shallower depth the brittle ductile extension leading to boudinage possibly did not enhance the extrusion

higher himalayan shear zone zanskar indian himalaya microstructural studies and extrusion mechanism by a combination of simple shear and channel flow thin section studies of the zanskar shear zone zsz rocks reveal a top to sw and subsequent primary and secondary top to ne ductile shearing brittle ductile and brittle extensions top to sw brittle shear steep normal faulting and fracturing in the proposed two phase model of ductile extrusion of the higher himalayan shear zone hhsz a top to sw simple shearing during 22 18 ma was followed by a combination of top to sw simple shear and channel flow at 18 16 ma the second phase simulates a thin zsz characterized by a top to ne shearing the channel flow component ceased around 16 ma the extruding hhsz entered the brittle regime but the top to sw shearing continued until perturbed by faults and fractures variation in the extrusion parameters led to variable thickness of the zsz shear strain after the extrusion is presumably maximum at the boundaries of the hhsz and falls towards the base of the zsz which crudely matches with the existing data the other predictions 1 spatially uniform shear strain after the first stage 2 fastest extrusion rate at the base of the zsz and 3 a lack of continuation of the zsz along the himalayan trend are not possible to validate due to paucity of suitable data non parabolic shear fabrics of the zsz indicate their heterogeneous deformation

numerical modelling of clast rotation during soft sediment deformation a case study in miocene delta deposits a numerical model for a rotated clast in a sedimentary matrix is presented quantifying the deformation in associated soft sediment deformation structures all the structures occur in a southwards prograding deltaic sequence within the miocene ingering formation deposited at the northern margin of the fohnsdorf basin eastern alps austria debris flow and pelitic strata contain boudins pinch and swell structures ptygmatic folds rotated top to s reverse faults and rigid clasts developed under different stress conditions within the same layers the deformation around a 24 10 cm trapezoid shaped rigid clast resembling the clast geometry in metamorphic rocks has been modelled using a 2d finite element modelling software under the chosen initial and boundary conditions the rotational behaviour of the clast mainly depends on the proportions of pure and simple shear best fitting results were attained with a dominantly pure shear deformation 65 85 with stretching parallel and shortening normal to the bedding in this specific model set up the initial sedimentary thickness is reduced by 30 explained by stretching due to sediment creeping and compaction the high amount of pure shear deformation proposed is compatible with the observed layer parallel boudinage and pinch and swell structures rotated faults and ptygmatic folds were caused by the minor component of bedding parallel simple shear

channel flow extrusion model to constrain dynamic viscosity and prandtl number of the higher himalayan shear zone constraining magnitudes of mechanical and thermo mechanical parameters of rocks and shear zones are the important goals in structural geology and tectonics talbot in j struct geol 21 949 957 1999 such parameters aid dynamic scaling of analogue tectonic models ramberg in gravity deformation and the earth s crust in theory experiments and geological applications 2nd edn academic press london 1981 which are useful to unravel tectonics in further details schultz ela and walsh in j struct geol 24 247 275 2002 the channel flow extrusion of the higher himalayan shear zone hhsz higher himalaya can be explained by a top to s sw simple shear i e the d2 deformation in combination with a pressure gradient induced flow against gravity presuming its newtonian incompressible rheology with parallel inclined boundaries the viscosity of this shear zone along a part of the himalayan chain through india nepal and bhutan is estimated to vary widely between 1016 and 1023 pa s and its prandtl number pr within 1021 1028 the estimates utilized ranges of known thickness 6 58 km of the hhsz that of its top subzone of ductile shear of normal shear sense stdsu 0 35 9 4 km total rate of slip of its two boundaries 0 7 131 mm year 1 pressure gradient 0 02 6 kb km 1 density 2 2 3 1 g cm 3 and thermal diffusivity 0 5 10 6 2 1 10 6 m s 2 along the orogenic trend considering most of the parameters specifically for the sutlej section india the calculated viscosity and the prandtl number pr of the hhsz are deduced to be 1017 1023 pa s and pr 1022 1028 the upper limits of the estimated viscosity ranges are broadly in conformity with a strong tibetan mid crust from where a part of the hhsz rocks extruded on the other hand their complete ranges match with those for its constituent main rock types and partly with those for the superstructure and the infrastructure the estimated mechanical and thermo mechanical parameters of the hhsz will help to build dynamically scaled analogue models for the himalayan deformation of the d2 phase

near n s paleo extension in the western deccan region india does it link strike slip tectonics with india seychelles rifting this is the first detailed report and analyses of deformation from the w part of the deccan large igneous province dlip maharashtra india this deformation related to the india seychelles rifting during late cretaceous early paleocene was studied and the paleostress tensors were deduced near n s trending shear zones lineaments and faults were already reported without significant detail an e w extension was envisaged by the previous workers to explain the india seychelles rift at 64 ma the direction of extension however does not match with their n s brittle shear zones and also those faults sub vertical ne sw nw se and few n s we report and emphasize in this work slickenside bearing fault planes brittle shear zones and extension fractures in meso scale enabled us to estimate the paleostress tensors directions and relative magnitudes the field study was complemented by remote sensing lineament analyses to map dykes and shear zones dykes emplaced along pre existing n s to ne sw nw se shears fractures this information was used to derive regional paleostress trends a nw se ne sw minimum compressive stress in the oldest kalsubai subgroup and a n s direction for the younger lonavala wai and salsette subgroups were deciphered thus a nw ne to n s extension is put forward that refutes the popular view of e w india seychelles extension paleostress analyses indicate that this is an oblique rifted margin field criteria suggest only ne sw and nw se with some n s strike slip faults brittle shear zones we refer this deformation zone as the western deccan strike slip zone wdsz the observed deformation was matched with offshore tectonics deciphered mainly from faults interpreted on seismic profiles and from magnetic seafloor spreading anomalies these geophysical findings too indicate oblique rifting in this part of the w indian passive margin we argue that the seychelles microcontinent separated from india only after much of the dlip erupted further studies of magma rich passive margins with respect to timing and architecture of deformation and emplacement of volcanics are required

use of c band ground penetrating radar to determine backscatter sources within glaciers the question of penetration of synthetic aperture radar sar signals at c band frequency into polar glaciers is addressed by comparing ground penetrating radar gpr and sar backscatter signatures profiles of the kongsvegen glacier svalbard were obtained with a c band gpr the received signal is converted to the equivalent radar cross section using the standard radar equation thus mapping the effective scattering sources within the glacier at this frequency the depth of the observed scattering sources is greatest in the superimposed ice where layers are clearly seen to a depth of approximately 14 m the very high scattering properties of the upper firn layers preclude layers deeper than approximately 6 m from being imaged integrating the radar cross sections over the depth gives a single backscatter value that we compare with the backscatter coefficient scattering cross section per unit area of the processed sar data for the same profile the comparison indicates that for coincidentally acquired gpr and sar data the radar cross section measured by the gpr does represent the features that contribute to the sar signal

heterogeneity and lithotype distribution in ancient deep sea canyons point lobos deep sea canyon as a reservoir analogue abstract an evolution and history of filling is proposed for an exceptionally exposed ancient deep sea canyon on a paleocene oblique slip tectonic margin which on a number of scales reveals successive phases of canyon activity the quantitative methods adopted for this study make it of direct use to modellers as an example of reservoir heterogeneity in an ancient canyon fill where facies distribution from boreholes can be scaled up to reconstruct the reservoir using the methods outlined in this paper the point lobos submarine canyon near carmel in california provides a complete cross section of an ancient canyon with a fill which displays a whole range of channel morphologies and laterally extensive coverage of the internal architecture of associated conglomerate packages and related debris flows this paper presents quantitative documentation of the canyon fill sediments and canyon wide fill packages on scales which vary from bed to bed analysis reflecting processes in operation during individual events to canyon wide analysis reflecting the overall evolution of the canyon the northern and southern canyon margins are both exposed and the paleocene fill onlaps the subvertical canyon wall the canyon was incised into cretaceous granodiorite the fill comprises five thick sequences which correspond to five successive phases of sediment deposition within the canyon each sequence typically consists of resedimented conglomerates that are stacked and channelised with a vertical architecture which resembles that of subaerial braided stream deposits these are overlain by channelised turbidite sandstones interbedded with intraformational conglomerates and mud chip breccias these in turn are overlain by mudstones and shales which are commonly slumped and disturbed published classification schemes that show the range of deep water facies were found insufficient to describe the point lobos canyon fill methods were developed for recording the lithologic proportions of the fill twenty three lithotypes were defined which show the variation in the sedimentary units and a range of processes are proposed to explain each lithotype these methods produced a quantitative database of lithologic proportions for the canyon fill over 80 of the fill comprises sandstone and conglomerate conglomerate is more common near the canyon margins mud and silt comprise the other 20 of the canyon fill predominantly as laterally extensive slumped packages which cap the coarser sequences the distribution of these lithotypes within the fill was found to have a cyclicity with five cycles of sedimentation recorded and lateral transport of material from the canyon walls a primary feature

snow mapping in alpine regions with synthetic aperture radar active microwave sensors can discriminate snow from other surfaces in all weather conditions and their spatial resolution is compatible with the topographic variation in alpine regions using data acquired with the nasa airsar in the otztal alps in 1989 and 1991 the authors examine the usage of synthetic aperture radar sar to map snow and glacier covered areas by comparing polarimetric sar data to images from the landsat thematic mapper obtained under clear conditions one week after the sar flight the authors found that sar data at 5 3 ghz c band can discriminate between areas covered by snow from those that are ice free however they are less suited to discrimination of glacier ice from snow and rock the overall pixel by pixel accuracies 74 from vv polarization alone with topographic information 76 from polarimetric sar without any topographic information and 79 from polarimetric sar with topographic information are high enough to justify the use of sar as the data source in areas that are too cloud covered to obtain data from the thematic mapper this is especially true for snow discrimination where accuracies exceed 80 because mapping of a transient snow cover during a cloudy melt season is often difficult with an optical sensor the airsar survey was carried out in summer during a heavy rainstorm when the snow surfaces were unusually rough even better results for snow discrimination can be expected for mapping in the spring when snow is usually smoother

himalayan inverted metamorphism constrained by oxygen isotope thermometry inverted metamorphic field gradients are preserved in two amphibolite facies metapelitic sequences forming the crystalline core zone of the himalayan orogen in the sutlej valley nw india in the high himalayan crystalline sequence hhcs metamorphic conditions increase upwards from the staurolite zone at the base through the kyanite in and sillimanite in isograds finally to reach partial melting conditions at the top the structurally lower lesser himalayan crystalline sequence lhcs shows a gradual superposition of garnet in staurolite in and kyanite sillimanite in isograds although phase equilibria constraints imply inverted temperature field gradients in both units garnet biotite garb rim thermometry indicates final equilibration at a nearly uniform temperature around t 600 c across these sequences the p t path and garnet zoning data show that this apparent lack of thermal field gradient is mainly the consequence of a resetting of the garb equilibria during cooling in order to constrain peak temperature conditions 20 samples along the studied section have been analysed for oxygen isotope thermometry the isotopic fractionations recorded by quartz garnet and quartz aluminosilicate mineral pairs indicate temperatures consistent with phase equilibria and p t path constraints for metamorphic peak conditions together with barometry results based on net transfer continuous reactions the oxygen isotope thermometry indicates peak conditions characterized by 1 a temperature increase from t 570 to 750 c at a nearly constant pressure around p 800 mpa from the base to the top of the hhcs unit 2 a temperature increase from t 610 to 700 c and a pressure decrease from p 900 to 700 mpa from the base to the top of the lhcs metapelites oxygen isotope thermometry thus provides the first quantitative data demonstrating that the himalayan inverted metamorphism can be associated with a complete inversion of the thermal field gradient across the crystalline core zone of this orogen

jointing and fracture interactions in middle eocene chalks near beer sheva israel abstract this study presents some observations on jointing and fracture interaction in synclinal middle eocene chalks horsha formation near beer sheva israel three joint sets occur in an outcrop set 344 n16 w developed first and was followed by sets 028 and 062 each set reflects a different fracture mechanism joint spacing and fracture length were investigated in set 028 but there did not appear to be any correlation between the two parameters the mean spacings in two layers 30 cm and 60 cm thick range closely between 23 16 cm and 26 19 cm suggesting independence of joint spacing from bed thickness in set 028 log probability plots of joint lengths from these two layers suggest an approximate lognormal distribution the mean joint lengths are 82 2 cm 56 8 cm and 64 1 cm 44 0 cm in the thicker and thinner beds respectively statistically the length populations in the two beds are considered to be significantly distinguishable implying that the mean fracture lengths show some dependence on layer thickness joint sets that reflect different fracture mechanisms show differences in intensity and in style of fracture termination terminations between parallel joints of the same set are differentiated from interactions between joints of different sets at acute angles in joints of set 028 various crack terminations are classified into seven styles there is on the average a visible interaction every 120 cm along joints of set 028 interactions between sets 0 28 and 344 induce secondary fractures which are identifiable as three style groups the most frequently induced secondary fractures are either subparallel or subperpendicular to the two sets the sum length of the secondary cracks in an interaction zone does not seem to be akin to the lengths of the parent joints especially puzzling interactions between sets 028 and 344 are triple junctions and complex triple junctions defined by these fractures interactions between sets 028 and 0 62 result in rhomboid structures at acute angles ranging between 18 and 51 evidently these structures are the product of extension and no shear offsets are visible along the fractures characteristically some of these rhomboids are being subdivided into smaller structures by the same sets

modeling multifrequency pol insar data from the percolation zone of the greenland ice sheet the analysis of data from an airborne synthetic aperture radar sar campaign in the percolation zone of greenland revealed an interferometric coherence undulation behavior with respect to vertical wavenumber which cannot be explained with existing models we propose a model extension that accounts for scattering from distinct layers below the surface simulations show that the periodicity of the coherence undulation is mainly driven by the vertical distance between dominant subsurface layers while the amplitude of the undulation is determined by the ratio between scattering from distinct layers and scattering from the firn volume we use the model to interpret quad pol sar data at x c s l and p bands the inferred layer depths match layer detections in ground based radar data and in situ measurements we conclude that in the percolation zone scattering from subsurface layers has to be taken into account to correctly interpret sar data and demonstrate the potential to retrieve geophysical information about the vertical subsurface structure

boudinage in multilayered rocks under layer normal compression a theoretical analysis abstract this paper presents a dynamic analysis of boudinage in multilayers of alternate brittle and ductile layers under layer normal compression based on the mode of fracturing of individual brittle layers boudinage is classified into three types tensile fracture boudinage type 1 shear fracture boudinage type 2a and extensional shear fracture boudinage type 2b the layer thickness ratio t r t b t d and the strength ratio f t 2 e between the brittle and the ductile units are the principal physical factors determining the type of boudinage type 1 boudinage develops rectangular boudins and occurs when t r is low f is high 0 8 in contrast type 2a boudinage takes place when t r is high 8 5 or f is low a r of all the types of boudins is inversely proportional to layer thickness ratio t r however type 1 and type 2 boudins have contrasting aspect ratios which are generally greater and less than 1 respectively

spatial gradients in snow layering and 10 m temperatures at two epica dronning maud land antarctica pre site survey drill sites

single and multipolarimetric p band sar tomography of subsurface ice structure in this paper first results concerning the characterization of the subsurface of ice sheets and glaciers through single and multipolarization synthetic aperture radar sar tomography tomosar are illustrated to this aim the processing of data acquired in the framework of the european space agency icesar 2012 campaign is discussed icesar 2012 was conceived so as to support the secondary objectives of the future earth explorer mission biomass which will be a sar instrument with media penetration capabilities due to the use of the p band frequency in this regard a tomographic study of ice was motivated by the fact that cryospheric remote sensing is of fundamental importance in order to understand more in depth the morphology and the dynamic processes regulating ice sheets the main objective of the tomographic experiment of the campaign herein discussed was indeed to assess the capability of p band sar to retrieve any information about ice subsurface structure imaging has been achieved through tomosar techniques applied to airborne multibaseline data acquired in the southwest of greenland different imaging approaches are compared and the main results achieved are presented it is found that scattering in the upper layers of glacial subsurface can be achieved up to an extent of about 20 60 m conditional on the different types of glaciological zone observed moreover clear morphological structures have been found beneath the ice surface at one of the investigated sites

the depth of penetration in antarctic firn at 10 ghz measurements taken by an x band pulse radar system in east antarctica in 1987 were analyzed to determine the depth of penetration of radar energy in polar firn a minimum estimate of the penetration depth at 10 ghz for the cold and dry polar plateau region is approximately 4 7 m spatial variations in the amount of signal penetration were observed and are related to latitude surface elevation and mean annual temperature the amount of signal penetration and its spatial variation are important factors that should be considered when processing datasets from microwave remote sensing systems that operate in the polar regions

radar interferometry and its application to changes in the earth s surface geophysical applications of radar interferometry to measure changes in the earth s surface have exploded in the early 1990s this new geodetic technique calculates the interference pattern caused by the difference in phase between two images acquired by a spaceborne synthetic aperture radar at two distinct times the resulting interferogram is a contour map of the change in distance between the ground and the radar instrument these maps provide an unsurpassed spatial sampling density 100 pixels km 2 a competitive precision 1 cm and a useful observation cadence 1 pass month 1 they record movements in the crust perturbations in the atmosphere dielectric modifications in the soil and relief in the topography they are also sensitive to technical effects such as relative variations in the radar s trajectory or variations in its frequency standard we describe how all these phenomena contribute to an interferogram then a practical summary explains the techniques for calculating and manipulating interferograms from various radar instruments including the four satellites currently in orbit ers 1 ers 2 jers 1 and radarsat the next chapter suggests some guidelines for interpreting an interferogram as a geophysical measurement respecting the limits of the technique assessing its uncertainty recognizing artifacts and discriminating different types of signal we then review the geophysical applications published to date most of which study deformation related to earthquakes volcanoes and glaciers using ers 1 data we also show examples of monitoring natural hazards and environmental alterations related to landslides subsidence and agriculture in addition we consider subtler geophysical signals such as postseismic relaxation tidal loading of coastal areas and interseismic strain accumulation we conclude with our perspectives on the future of radar interferometry the objective of the review is for the reader to develop the physical understanding necessary to calculate an interferogram and the geophysical intuition necessary to interpret it

pressure solution deformation of the purgatory conglomerate rhode island u s a quantification of volume change real strains and sedimentary shape factor abstract pressure solution has caused substantial volume redistribution within the purgatory conglomerate from rhode island material has been removed from quartzite cobble surfaces parallel to the fold axes and mostly redeposited as fibrous pressure shadows at the long axis terminations of the cobbles in the hinges of folds 23 of the mean cobble volume has been removed and in highly deformed and overturned fold limbs up to 55 volume reduction has occurred the initial cobble shape and orientation can be measured at an undeformed locality and the deformation path can be easily deduced thus these are real cobble volume reductions apparent volume losses initial shapes not removed range from 70 to 89 real strains for cobbles axial ratios ranging from 1 0 65 0 38 to 1 0 47 0 15 have values of e x e y e z which range from 0 20 11 to 0 37 42 respectively depending on structural position the conglomerate itself has been extended parallel to the fold axes e r but the extension is not recorded by the cobble shapes

diagenetic quartzarenite and destruction of secondary porosity an example from the middle jurassic brent sandstone of northwest europe significant amounts of feldspar have been dissolved from middle jurassic sandstone oil reservoirs in the north sea northwest europe during burial diagenesis sandstones of the middle jurassic brent group become increasingly quartzose with increasing burial depth at statfjord field 2500 m depth sandstones are arkose to subarkose at hutton field 3050 m depth they are subarkose to quartzarenite and at lyell field 3500 m depth sandstones are typically quartzarenite in spite of extensive feldspar dissolution the abundance of secondary porosity due to feldspar dissolution is similar for all fields averaging 2 9 of the total rock volume thus far more feldspar has been dissolved than is recorded as secondary porosity the limit on preservation of secondary porosity may be largely the effect of the mechanical strength of the rock an excessive number of large secondary pores lowers the rock strength below the point at which the rock can withstand overburden stress thus causing collapse of some of the secondary pores

high resolution ice sounding radar measurements of ice thickness over east antarctic ice sheet as a part of chinese national antarctic research expedition this paper presents the ice thickness fine resolution internal reflecting horizons irhs and distinct bottom topography measurements of chinese kunlun station and grove mountains antarctica derived from sounding these glaciers with a high resolution radar to enable the development of next generation ice sheet models we need information on irhs bottom topography and basal conditions to this end we performed measurements with the progressively improved ice sounding radar system currently known as the high resolution ice sounding radar developed by the key laboratory of electromagnetic radiation and sensing technology of institute of electronics chinese academy of sciences beijing china we processed the collected data using focused synthetic aperture radar sar algorithm named the modified range migration algorithm using curvelets and the modified nonlinear chirp scaling algorithm to improve radar sensitivity and reduce along track surface clutter representative results from selected transects indicate that we successfully sounded 3 km thick ice with a fine resolution of 0 75 m in this paper we provide a brief description of the radar system discuss the focused sar processing algorithms and provide sample results to demonstrate the successful sounding of the ice sheet in antarctica

recent fluctuations in the extent of the firn area of austfonna svalbard inferred from gpr in spring during 2004 07 we conducted ground penetrating radar gpr measurements on the austfonna ice cap svalbard with the original aim of mapping the thickness and distribution of winter snow here we further exploit the information content of the data and derive a multi year sequence of glacier facies distribution that provides valuable spatial information about the total surface mass balance smb of the ice cap beyond the usually evaluated winter balance we find that following an initial decrease in the extent of the firn area 2003 04 the firn line lowered within two subsequent years by 40 100m elevation in the north and west and 150 230 m in the south and east of the ice cap corresponding to a lateral expansion of the firn area along the profiles by up to 7 3 and 13 3 km respectively the growth of the firn area is in line with stake measurements from etonbreen that indicate a trend towards less negative smb over the corresponding period

velocity structure flow instability and mass flux on a large arctic ice cap from satellite radar interferometry satellite radar interferometry allows calculation of the ice surface velocity distribution throughout the largest ice cap in the eurasian arctic austfonna in eastern svalbard data on ice cap velocity structure show strong spatial variations observed in unprecedented detail ice cap drainage basins have clearly defined fast flowing units with marked shear margins at the surface associated with troughs in the subglacial bedrock identified from 60 mhz ice penetrating radar interferometric measurements show that the velocity structure in most ice cap drainage basins remained stable over a 2 year period unexpectedly however in the basin where surface velocities were the highest on the ice cap at 140 m yr 1 in winter 1992 the flow rate had halved by winter 1994 a time series of visible band landsat imagery shows that this basin was relatively inactive between 1973 and 1991 but had a distinctly disturbed surface in 1993 this flow instability was initiated after summer 1991 and is likely to be a glacier surge or mini surge demonstrating the increasing diversity of motion events revealed by radar interferometry mass flux through this basin calculated using ice velocity and thickness data was 0 1 km 3 yr 1 in 1992 an increase of up to two orders of magnitude over that prior to flow instability calculated balance velocity is an order of magnitude less than the interferometrically derived velocity implying that the flow rates observed for the fast flowing unit cannot be sustained under the present climate c 1999 elsevier science b v all rights reserved

s c mylonites two types of foliations are commonly developed in mylonites and mylonitic rocks a s surfaces related to the accumulation of finite strain and b c surfaces related to displacement discontinuities or zones of relatively high shear strain there are two types of s c mylonites type i s c mylonites described by berthe et al typically occur in deformed granitoids they involve narrow zones of intense shear strain which cut across mylonitic foliation type ii s c mylonites described here have widespread occurrence in quartz mica rocks involved in zones of intense non coaxial laminar flow the c surfaces are defined by trails of mica fish formed as the result of microscopic displacement discontinuities or zones of very high shear strain the s surfaces are defined by oblique foliations in the adjacent quartz aggregates formed as the result of dynamic recrystallization which periodically resets the finite strain clock these oblique foliations are characterized by grain elongations alignments of segments of the grain boundary enveloping surfaces and by trails of grains with similar c axis orientations examples of this aspect of foliation development in mylonitic rocks are so widespread that we suggest the creation of a broad class of s c tectonites and a deviation from the general tradition of purely geometric analysis of foliation and time relationships kinematic indicators such as those discussed here allow the recognition of kilometre scale zones of intense non coaxial laminar flow in crustal rocks and unambiguous determination of the sense of shear

mineral fish their morphological classification usefulness as shear sense indicators and genesis mineral fish are sheared and commonly asymmetric mineral grains or clusters of grains this work reports 11 sub types of mineral fish showing a top to se sense of ductile shearing in the karakoram metamorphic complex kmc the mineral fish are of three broad geometries sigmoid lenticular and parallelogram reliable senses of shear are indicated by the overall asymmetry and inclination of mineral fish on the other hand the true shear sense is not always indicated by either the orientations of their cleavage planes or those of the individual grains in composite mineral fish the ranges of local orientations of single sigmoid mineral fish that include the lower values 23 in the kmc indicate their extensive ductile shearing the studied mineral fish were products of a range of deformation mechanisms including homogeneous deformation simple shear intra granular slip crystal plastic deformation fracturing and synthetic shearing additionally some examples might have undergone duplex slips and a few nucleated and grew either prior to or during the top to se shearing

phase boundary mobility in naturally deformed high grade quartzofeldspathic rocks evidence for diffusional creep abstract grain shape fabrics and optical microstructures of some quartzofeldspathic rocks deformed under upper amphibolite facies conditions in the southwestern grenville province ontario canada suggest that quartz and feldspar have accommodated intracrystalline plastic strains by both diffusional and dislocation creep in these rocks quartz and feldspar form polycrystalline domains separated by gently curved and locally cuspate phase boundaries whose morphology is similar in certain respects to the phase boundary morphology of rocks annealed experimentally under hydrostatic stress conditions in the naturally deformed rocks however phase boundary cusps consistently point along the foliation and parallel to the mineral fibre lineation i e in directions of inferred finite extension which implies that phase boundary motion and cusp formation occurred during deformation optical microstructures in feldspar and crystallographic preferred orientations in quartz are consistent with the accommodation of some intracrystalline plastic strains by dislocation creep however the morphology of quartz feldspar phase boundaries cannot be explained by either dislocation creep or static annealing alone we propose that phase boundary motion resulted from a diffusion assisted process involving dissolution at foliation parallel quartz feldspar phase boundaries mass transfer over length scales of the order of feldspar domain size 200 m or greater and precipitation at quartz feldspar phase boundary cusps this study extends the range of natural deformation conditions under which diffusional creep has been identified in quartzofeldspathic rocks it also has important implications for the natural rheological behavior of the mid and lower continental crust

viscous dissipation pattern in incompressible newtonian simple shear zones an analytical model an analytical model of shear heating in an inclined simple shear zone with newtonian rheology under a reverse shear sense and an upward resultant pressure gradient is presented neglecting a number of secondary factors the shear heat is expressed as a function of the total slip rates at the boundaries pressure gradient dip and thickness of the shear zone and density viscosity and thermal conductivity of the rock a quartic temperature profile develops with a point of maximum temperature near the bottom part of the shear zone in general the profile is parabolic if pressure gradient vanishes leading to a couette flow the profile attains a bell shape if there is no slip at the boundaries i e a true pouseille flow the present model of shear heating is more applicable in subduction channels and some extruding salt diapirs where the rheology is newtonian viscous and pressure gradient drives extrusion

controls on cu mineralization in central part of the kerman porphyry copper belt se iran constraints from structural and spatial pattern analysis abstract the sarduiyeh area in the central part of the kerman porphyry copper belt kpcb se iran contains numerous cu deposits and prospects this area is bound by e w trending major faults which show the northern and southern borders of fault duplex minor faults first second or third orders were identified in three trends of nw n s and ne analysis of the fault kinematics data revealed an extensional fault duplex pattern for this area in this fault zone cu deposits are associated with faults that have a special trend this proposed kinematic model for evolution of sarduiyeh extensional fault duplex emphasizes that the main cu deposits in the sarduiyeh area are located within the dilatational zones related to nw se trending normal faults in this study the spatial pattern analysis conducted by fry fractal fracture density and buffer zones methods support the conceptual model of district scale mechanism of structural controls on final emplacement of cu deposits this investigation of sarduiyeh cu mineralization revealed that the nw se trending faults are effective in localization of cu mineralization in the central part of kpcb

the relationship of strain and preferred orientation of phyllosilicate grains in rocks a review abstract the calculation of strain from the preferred orientation of platy phyllosilicate grains taking strain to be homogeneous is surprisingly often successful from a pragmatic point of view although numerous theoretical objections to this procedure can be and have been raised for the calculation to succeed the original distribution of mica or clay mineral grains must be known or assumed the usual assumption that the starting distribution was random and therefore nearly uniform implies that the strain history of pelitic sediments is taken to start when the watery sediment was last stirred by waves or bioturbation or if it was laid down in still anoxic waters from the moment of first deposition it therefore includes compaction as part of the strain history which is usually neglected by structural geologists originally random distribution of clay flake orientations has been observed in recently deposited sediments in many instances and has been theoretically explained in various ways exceptions probably exist but their frequency has not been estimated biologically disturbed sediments may be brought nearer to a state of random orientation of clay flakes than they were at deposition with the exception of whole beds or concretions in which pores are early filled with cement mudrocks are almost always compacted by the weight of later deposits the strain so induced is axially symmetric about the vertical and thus about the pole of the bedding planes compaction acts on soft unconsolidated rocks but may continue with increasing overburden on rocks strengthened by cementation and by increasing interlocking of grains tectonic deformation may start early before the rock is fully compacted or it may begin only much later and the mechanisms of deformation increase in complexity with the increasing temperature and hydrostatic stress of deeper burial up to a certain level of mild metamorphism however phyllosilicate grains seem to be rather permanent if not as mineral species then at least by preservation of their constituent sheets of silica tetrahedra given this permanence the mechanisms of rock deformation whether intergranular slip cataclasis or dissolution and reprecipitation and various intragranular processes in the non phyllosilicate matrix hardly matter as far as the recording of strain is concerned even a certain amount of stress solution at especially heavily loaded points of the phyllosilicate grains themselves does not destroy their value as strain markers as long as the dissolved material is disposed of mainly by crystallographically continuous overgrowth on existing grains the same holds for local dissolution of phyllosilicates in portions of old grains that have become thermodynamically unstable by bending widespread irregular or random nucleation and growth of newly nucleated phyllosilicate grains at intermediate or high grades of metamorphism can reduce the reliability of the strain record and so can domainal structure of the deformed rock if both the volume fraction of phyllosilicate grains and the intensity of total strain differ sharply from one domain to another if distinct domains are not equant and have themselves a strong preferred orientation of shape nevertheless rocks containing an anastomosing network of zones rich in phyllosilicate grains as slates and other deformed mudrocks commonly do have in many cases been found to have average preferred orientations of mica or chlorite which if used to estimate the strain give results similar to those obtained from independent strain markers in the same rocks thus the most significant verification of the usefulness of strain estimates by measurement of preferred orientation is the mutual confirmation with independently determined strain the limit to such verification is the rarity of strain markers so that the coexistence of two independent ones is exceptionally rare for this reason however it is important to make full use of the orientation of phyllosilicate grains where they are available the alternative to have no strain measurements at all causes structural geologists to miss potential information

seasonal and short term variability of multifrequency polarimetric radar backscatter of alpine terrain from sir c x sar and airsar data signatures of glaciated and ice free areas were analyzed from polarimetric sar data at c l and p band and single polarization x band data the data base includes an airsar scene from june 25 1991 and sir c x sar images from april and october 1994 srl 1 and srl 2 acquired over the high alpine test site o spl uml tztal in austria the environmental conditions were different at the time of the three experiments ground measurements meteorological observations and backscattering modeling are the basis for interpreting the backscattering signatures seasonal differences are due mainly to the presence or absence of snow and due to changes of its properties short term variations of snow conditions can be monitored at c and x band for unglaciated areas the surface roughness has a dominant influence on backscattering in all seasons the dependence of the mean backscattering and correlation coefficients on the incidence angle was analyzed spectral and depolarization ratios and the magnitude of the hhvv correlation coefficient were selected as components of the multidimensional feature vector for studying the target separability good separability was found between the accumulation and ablation areas on the glaciers whereas on ice free areas the dominance of surface roughness limits the discrimination of different surface types short term variations of backscattering have significant impact for the classification of accumulation and ablation areas on glaciers as verified by comparisons with field data

quantitative kinematic flow analysis from the main central thrust zone nw himalaya india implications for a decelerating strain path and the extrusion of orogenic wedges quantitative kinematic indicators from the main central thrust zone mctz in the nw himalaya have been used to characterize the type of flow during deformation different generations of tension gashes have been rotated by variable angles with respect to the mylonitic foliation forming associated fringe folds these record the late stage brittle ductile flow and reveal that a strong pure shear component of deformation occurred throughout the mctz to characterize earlier deformation increments fabrics from highly deformed quartz ribbons were analyzed well developed shape and lattice preferred orientation patterns show a systematic change of the glide systems and suggest inverted palaeotemperatures within the mctz investigations of the c axes patterns reveal a strong asymmetry at the top of the mctz whereas the samples from the base of the mctz show almost perfectly symmetrical type i crossed girdles deformation within the mctz probably started close to simple shear flow at higher temperatures which progressively became a more general shear during cooling and ended in a pure shear dominated flow during the final stages of brittle ductile deformation i e a decelerating strain path using the higher himalaya crystalline as an example a kinematic model for the extrusion of crustal wedges above major thrust zones is suggested

single baseline polarimetric sar interferometry examines the application of single baseline polarimetric sar interferometry to the remote sensing and measurement of structure over forested terrain for this a polarimetric coherent scattering model for vegetation cover suitable for the estimation of forest parameters from interferometric observables is introduced discussed and validated based on this model an inversion algorithm which allows the estimation of forest parameters such as tree height average extinction and underlying topography from single baseline fully polarimetric interferometric data is addressed the performance of the inversion algorithm is demonstrated using fully polarimetric single baseline experimental data acquired by dlr s e sar system at l band

interferometric estimation of three dimensional ice flow using ascending and descending passes satellite radar interferometry sri provides an important new tool for determining ice flow velocity interferometric measurements made from a single track direction are sensitive only to a single component of the three component velocity vector observations from along three different track directions would allow the full velocity vector to be determined a north south looking synthetic aperture radar sar could provide these observations over large portions of the globe but not over large areas of the polar ice sheets the authors develop and demonstrate a technique that allows the three component velocity vector to be estimated from data acquired along two track directions ascending and descending under a surface parallel flow assumption this technique requires that there are accurate estimates of the surface slope which are also determined interferometrically to demonstrate the technique the authors estimate the three component velocity field for the ryder glacier greenland their results are promising although they do not have yet ground truth data with which to determine the accuracy of their estimates

inclined transpression in the neka valley eastern alborz iran three major nappes in the neka valley in the eastern alborz mountains of iran allow the cimmerian to present convergence following the oblique collision between iran and the southern margin of eurasia this work reports the identification of an inclined transpression zone recognized by field investigations and strain analyses of the geometries of formations and detailed mesoscopic structural analyses of multiple faults folds and a cleavage the main structures encountered include refolded recumbent asymmetric fold nappes highly curved fold hinges in a transpression zone that dips 37 to the nw between boundaries thrusts striking from n050 to n060 the angle the angle between the zone boundary and direction of horizontal far field shortening is about 80 the north west and south east boundaries of this zone coincide with the haji abad thrust and the shah kuh thrust respectively fold axes generally trend ne sw and step to both right and left as a result of strike slip components of fault displacements strain analyses using fry s method on macroscopic ooids and fusulina deformed into oblate ellipsoids indicate that the natural strain varies between 2 1 and 3 14 the estimated angle between the maximum instantaneous strain axis isamax and the transpression zone boundary is between 6 and 20 the estimated oblique convergence angle therefore ranges between 31 and 43 the average kinematic vorticity number wk is 0 6 in a zone of sinistral pure shear dominated inclined triclinic transpression these results support the applicability of kinematic models of triclinic transpression to natural brittle ductile shear zones

the effects of dissolution precipitation creep on quartz fabrics within the purgatory conglomerate rhode island abstract quartz crystallographic preferred orientation cpo patterns are most commonly a result of deformation by dislocation creep we investigated whether dissolution precipitation creep dpc a process that occurs at lower differential stresses and temperatures may result in cpo in quartz the purgatory conglomerate is part of the se narragansett basin where strain intensity increases from west to east and is associated with top to the west transport and folding during the alleghanian orogeny within the purgatory conglomerate dpc led to quartz dissolution along cobble surfaces perpendicular to the shortening direction and quartz precipitation in overgrowths at the ends of the cobbles strain shadows parallel to the maximum extension direction quartz c axis orientations as revealed by electron backscatter diffraction ebsd methods were random in all analyzed domains within the cobbles and strain shadows irrespective of the intensity of strain or metamorphic grade of the sample quartz dissolution probably occurred exclusively along the cobbles margins leaving the remaining grains unaffected by dpc the fact that quartz precipitated in random orientations may indicate that the strain shadows were regions of little or no differential stress

determination of pressure solution shortening in sandstones abstract a new method for the determination of pressure solution shortening in sandstones uses the geometry of grain to grain interpenetrations and grains truncated against solution surfaces these features are used to construct plots from which the magnitude and direction of the pressure solution shortening can be determined using simulated pressure solution deformation of artificial and natural grain populations the new method is shown to correctly assess a variety of coaxial and non coaxial shortenings although primarily intended to determine shortening the method can also quantify extension related to growth of beards or overgrowths during pressure solution application of the method to naturally deformed quartz arenite samples shows that pressure solution shortening of up to 26 occurred during compaction and 22 during layer parallel shortening

postdepositional modification of uraninite bearing quartz pebble conglomerates from the quirke ore zone elliot lake ontario petrographic observations backscattered electron imagery spatial resolution or 0 1 mu m and semiquantitative energy dispersive electron microprobe analysis indicate that postdepositional modification of the uraniferous conglomerates occurred in three stages the first involved complete fluid mediated leaching of fe from detrital ilmeno magnetite grains and mobility of u th rare earth elements y po 4 super 2 and sio 2 uraninite was replaced by coffinite u th sio 4 and quartz detrital monazite was dissolved and slightly altered to urano thorite th u sio 4 u reacted with tio 2 derived from detrital grains to form composite grain aggregates composed of brannerite approximately uti 2 o 6 and other alteration products and coffinite together with a y rare earth elements u phosphate precipitated in the matrix the next stages involved the precipitation of the secondary pyrite and the occlusion of the conglomerate pore space by secondary quartz and sericite the most probable eh ph fields for the ground waters involved in postdepositional modification are low to moderate eh and slightly acid ph for ilmeno magnetite leaching and low eh and near neutral ph for pyrite precipitation both inferred eh ph fields fall within the thermodynamic stability fields of uraninite and coffinite in which uranium solubilities are low phosphate dissolved from monazite and apatite could have enhanced uranium solubility at the higher inferred eh values conclusion that neither the deposition nor the preservation of detrital uraninite can logically be used to draw conclusions about the oxygen content of the precambrian atmosphere at approximately 2 350 m y ago modified journal abstract

structural pattern and emplacement mechanism of the neka valley nappe complex eastern alborz iran the neka valley nappe complex is exposed in the south of gorgan county in the eastern alborz fold and thrust belt we use the results of a regional survey of the structural data and their patterns to interpret the mechanisms that emplaced the unmetamorphosed nappes in the foreland fold and thrust belt of the alborz mountains most of the strain magnitudes are low in the study area but increase slightly towards what are probably their proximal ends strain ellipsoid is dominantly oblate with xy aligned along and across the belt or the nappe complex the average kinematic vorticity number w k 0 6 which indicates most of the strain partitioning resulted in a general shear most of flinn s k values and the stretch along the shear plane values are lower than 1 structural indicators such as orthogonal extensional joints pinch and swell structures anastomosing cleavages and listric normal and growth faults developed by push from the rear large scale thrust complexes with opposed dips such as triangle zones as well as k and values 1 are compatible with the shear flow diverging distally and streamlines expected of the rear compression emplacement mechanism together with a later minor brittle deformation these major ductile strains appears to provide a general model suitable for the emplacement of the nappes studied in a thin skinned fold and thrust belt where the sedimentary cover strata shortened and imbricated in the upper crust

imaging the internal structure of an alpine glacier via l band airborne sar tomography in this paper we report results from the analysis of 3 d l band airborne synthetic aperture radar sar acquisitions acquired in march 2014 over the mittelbergferner glacier austrian alps during the european space agency esa campaign alptomosar the campaign included coincident in situ measurements of snow and ice properties and ground penetrating radar gpr data acquired at 600 and 200 mhz over a total length of 18 km radar data were acquired by repeatedly flying an l band sar along an oval racetrack at an altitude of about 1300 m over the glacier such that two data stacks from opposite views are obtained data from all passes were coherently combined to achieve 3 d resolution capabilities resulting in the generation of 3 d tomographic sar tomosar cubes where each voxel represents l band radar reflectivity from a particular location in the 3 d space at a spatial resolution on the order of meters tomosar cubes were finally corrected to account for wave propagation velocity into the ice which was a necessary step to associate the observed features with their geometrical location hence enabling a direct comparison to gpr data the tomosar cubes show the complexity of the glacier subsurface scattering most areas are characterized by surface scattering in proximity of the ice surface plus a complex pattern of in depth volumetric scattering beneath and scattering at the ice bedrock interface various subsurface features observed in gpr transects at 200 mhz clearly showed up in tomosar sections as well particularly firn bodies crevasses layer transitions and bedrock reflection down to 50 m below the ice surface

a rare microstructure trapezoid shaped aggregate of fine grained minerals a curved fault plane passes from lower middle part of the snap up to the upper right corner within recrystallized very fine grained aggregate of quartz white arrows chlorites red arrows and other clay minerals near the upper right side of the photo a trapezoidal aggregate yellow broken ellipse is discernible at a single side of the fault a much smaller trapezoid with more straight margins is also visible adjacent to the fault plane trapezoids have rarely been described as a shape fabric e g fig 2 18 of trouw et al 2010 mukherjee 2012 2013a and have been interpreted as a thrust slices in microscale in shear zones precipitation of syn tectonic chlorite parallel to shear planes in the pre existing quartzose veins indicates a late stage reactivation of the thrust under low grade pt conditions

v pull apart microstructures a new shear sense indicator abstract granitoids deformed in a low grade shear zone show conspicuous development of asymmetric pull apart microstructures in feldspars characterized by v shaped gaps between the separated fragments v pull aparts they occur beside active shear planes and result from rigid body rotation of one fragment relative to the other the shear sense in the adjacent flow surface can be easily determined through the asymmetry normally shown by v pull aparts where the fracture wall at a lower angle to the shear plane indicates which fragment has rotated synthetically to the adjacent shearing another diagnostic feature is the foliation deflection that occurs adjacent to the rotated fragment the v shaped gaps are infilled by recrystallized quartz mica aggregates showing quartz c axis patterns indicative of strong participation of crystal plastic processes in these domains evidence of crack seal by precipitation c axes parallel to the direction of separation have also been found the rigid body rotation indicated by these microstructures worked as a mechanism of removal of protruding porphyroclast edges enabling the smoothing of the shear planes rigid body rotation should operate in circumstances where other mechanisms such as dissolution or crystal plasticity did not succeed in eliminating undulations along the shear planes

a three component scattering model for polarimetric sar data an approach has been developed that involves the fit of a combination of three simple scattering mechanisms to polarimetric sar observations the mechanisms are canopy scatter from a cloud of randomly oriented dipoles evenor double bounce scatter from a pair of orthogonal surfaces with different dielectric constants and bragg scatter from a moderately rough surface this composite scattering model is used to describe the polarimetric backscatter from naturally occurring scatterers the model is shown to describe the behavior of polarimetric backscatter from tropical rain forests quite well by applying it to data from nasa jet propulsion laboratory s jpls airborne polarimetric synthetic aperture radar airsar system the model fit allows clear discrimination between flooded and nonflooded forest and between forested and deforested areas for example the model is also shown to be usable as a predictive tool to estimate the effects of forest inundation and disturbance on the fully polarimetric radar signature an advantage of this model fit approach is that the scattering contributions from the three basic scattering mechanisms can be estimated for clusters of pixels in polarimetric sar images furthermore it is shown that the contributions of the three scattering mechanisms to the hh hv and vv backscatter can be calculated from the model fit finally this model fit approach is justified as a simplification of more complicated scattering models which require many inputs to solve the forward scattering problem

circular polarization radar properties of high altitude ice western kunlun shan and central andes full polarization synthetic aperture radar images of high altitude glaciers and ice fields in the western kunlun shan of tibet and the central andes near santiago chile made with the shuttle imaging radar display regions with circular polarization ratios c in excess of unity the mountainous topography at both locales allows reconstruction of the angular scattering behavior the behavior is very similar to that displayed by greenland s percolation zone glaciologic evidence from the tibetan site confirms ice pipes and lenses embedded in the firn which have been identified as the scatterers producing c 1 in greenland this demonstrates that the cold snow percolation facies radar signature exists outside of greenland the greenland radar behavior had been suggested as an analogue for that of the icy galilean satellites we like previous workers find that the near nadir backscatter is too specular to be considered analogous to that of the jovian moons we also present a crevasse region in tibet that exhibits c 1 and a possible detection of the ice substrate of a rock covered glacier in the andes

microstructural and mineral analysis on the fault gouge in the coseismic shear zone of the 2008 m w 7 9 wenchuan earthquake the 2008 m w 7 9 wenchuan earthquake formed two coseismic surface rupture zones with the trend of n35 e known as the beichuan yingxiu rupture and the pengguan rupture the beichuan yingxiu rupture is the principle one with abundant fault gouge development along its length in the exploratory trench at the saba village along the beichuan yingxiu rupture the new fault gouge zone is only 3 mm wide which suggests that fault slip was constrained in a very narrow zone in this study we thus carried out detailed microstructural and mineral component analysis on the oriented fault gouge samples from the saba exploratory trench to understand their features and geological implication the results show that different microstructures of localized brittle deformation can be observed in the fault gouges including y shear r1 shear r2 shear p shear as well as tension fracture bookshelf glided structure and so on these microstructures are commonly recognized as the product of seismic fault slipping furthermore within the area between two parallel y shears of the fault gouge a few of microstructures of distributed ductile deformations were developed such as p foliation elongation and asymmetrical trailing structure of detrital particles the microstructure features of fault gouges implicate the thrust movement of the fault during the wenchuan earthquake in addition the fault gouge has less quartz and feldspar and more clay than the surrounding rocks which indicates that some quartz and feldspar in the surrounding rocks were transformed into clay whereas the fault gouge has more illite and less illite montmorillonite mixed layers than the surrounding rocks which shows that the illite montmorillonite mixed layer was partly converted into illite due to temperature increasing induced by coseismic fault slipping friction also being affected partly by the chemical action of solutions such microstructures features and mineral component changes recorded the information of fault slip and provide criterions for discussing the genesis of fault gouge and recognition of the direction of fault movement

structural analysis of nalagarh lobe nw himalaya implication of thrusting across tectonic edge of nw limb of nahan salient himachal pradesh india the main boundary fault mbf convex towards southwest forms the leading edge of the nahan salient near the southern end of an oblique ramp a lobe shaped physiographic front named in this work as nalagarh lobe has developed across nw limb of salient the lobe has formed across the mbf that separates the hanging wall lower tertiary dharmsala rocks from the footwall upper tertiary siwalik rocks and overlying quaternaries in front of lobe thrust fault splays splay 1 and splay 2 and associated tectonic fabrics have developed within the late pleistocene fan deposit structural elements developed across the front of nalagarh lobe are analysed with reference to evolution of lobe an unweathered 15 m high hanging wall or wedge top forms the uplifted and rejuvenated bedrock fault scarp of the mbf below the mbf the fan deposit has underthrust along splay 1 later the splay 2 formed within fan deposit near south of splay 1 geometry of the overturned limb of tight to isoclinal fault propagation fold formed on splay 2 plane suggests that the fold formed by normal drag produced by intermittent fault slips along splay 2 the displacement along splay 2 offset the marker bed to 1 m by which some clasts rotated parallel to the traces of brittle axial planes of fold the variable fold geometry and style of deformation are analysed along length of thrust splays for 5 km it is revealed that the lobe is bounded by transverse thrust faults along its nw and se margins the geometry of salient and oblique ramp suggests that the transverse thrust faults and associated transverse folds formed by right lateral displacement along the nw limb of the salient marking the northern margin of the intermontane piggyback basin of pinjaur dun the mbf is interpreted to be an out of sequence thrust that has brought up the lower tertiary dharmsala rocks over the late pleistocene fan deposit the geometry of lobe and its bounding transverse faults suggest that faults are intimately associated with the kinematics of the transition between the nahan salient and kangra recess the transition is a transfer zone forming a long pre himalayan lineament across which the stratigraphic set of the tethys and lesser himalaya is different the study suggests that the lateral ramp on the main himalayan thrust does not exist beneath the apex and also beneath the se limb of the salient in the sub himalayan region this ramp should be present only beneath near end point of sw limb of the nahan salient

polarimetric decomposition over glacier ice using long wavelength airborne polsar in recent years there has been increased interest in using synthetic aperture radar sar to study and monitor glaciers and ice sheets for glaciological and climate change research however due to the medium s complexity sar backscattering from ice remains poorly understood including the relative importance of scattering from surface and volume layers and also dependences on frequency and glacier zone extreme weather conditions can result in quickly changing surface conditions influencing backscatter signatures while leaving the underlying volume of interest unchanged surface and volume components must thus be separated in order to infer information regarding the properties of the ice volume this paper describes a three component scattering model to decompose polarimetric sar polsar images of glacier ice total backscatter is modeled as the incoherent summation of surface volume and sastrugi wind induced feature components the proposed model adapts and extends the freeman and durden decomposition for an ice volume scenario in which the volume is a dielectric medium forms of the model for both random and oriented volumes are considered and a new oriented sastrugi component is introduced which is able to explain backscatter behavior between different winter scenes validation is performed with airborne polsar data at l and p band collected using the e sar system of the german aerospace center over the austfonna ice cap in svalbard norway as part of the icesar campaign

grain boundary migration microstructures in a naturally deformed quartzite abstract in this study several grain scale microstructures are presented that are thought to demonstrate the migration direction of once mobile grain boundaries in a naturally deformed quartzite an analysis is presented of the sense of migration of the boundaries and the characteristics of the patterns of relative grain growth and shrinkage grain boundary migration seems to be correlated with the relative crystallographic orientations of neighbouring grains for the quartz quartz grain boundaries and the pattern of preferred grain growth is roughly symmetrical about the mica foliation plane

the internal inclusion trail geometries preserved within a first phase of porphyroblast growth the inclusion trail geometry within a first phase of porphyroblast growth can differ significantly from that preserved by further enlargement because the porphyroblast forms a rigid mass up against which the rock preferentially strains during ensuing events the geometry of the first overgrown inclusion trails is affected by their primary orientation including any pre existing curvature combined with any heterogeneous rotation of this foliation about the developing stretching lineation this can impact the apparent timing of foliation intersection inflection axes preserved within porphyroblasts fias that nucleated during the development of a sub horizontal foliation but is readily resolved 3 d computer analysis of sigmoidal inclusion trails reveals that the asymmetry method for fia determinations is unaffected by the cut location relative to the porphyroblast core significantly perfect spiral inclusion trail geometries can be produced from a sigmoidal shape in cuts up 30 away from the fia therefore since fias in most porphyroblasts bear no relation to matrix structures there is a 17 chance that thin sections cut relative to the foliation lie within 30 of a fia and could contain such an apparent spiral fias maintain consistent trends for the first phase of porphyroblast growth accompanying horizontal bulk shortening but may vary in plunge fias have sub horizontal plunges for porphyroblasts nucleating during gravitational collapse but may vary in trend for all periods of porphyroblast regrowth the data available indicates that fias remain consistently trending and sub horizontal until the relative direction of plate motion causing orogenesis changes

pressure solution deformation of the purgatory conglomerate from rhode island pressure solution is the dominant mechanism for the alleghenian age deformation of pennsylvanian quartzite conglomerates from the narragansett basin rhode island this deformation is accompanied by inter cobble rotation and occurred at low metamorphic grades no microscopic evidence for internal penetrative deformation of cobbles in the conglomerate is observed three major pressure solution features are characteristic of this conglomerate adjacent cobbles show indentation relationships with no change in quartz fabrics within the individual cobbles insoluble material is concentrated between cobbles in mutual contact both in the matrix and within the outer margins of the cobbles quartz overgrowths are found at the long axis terminations of the cobbles many other pressure solution features are discussed these features remain recognizable after subsequent metamorphism review of other studies suggests that pressure solution may well be a common conglomerate deformation mechanism during early deformati

penetration depths inferred from interferometric volume decorrelation observed over the greenland ice sheet radar interferometry provides a novel way to study the subsurface of glaciers interferometric correlation since the two complex images that comprise the interferogram have slightly different incidence angles at each point on the ground a decorrelating phase noise with statistics related to the scattering medium is present in the interferogram the amount of surface decorrelation is increased by volume scatter the larger the vertical extent of the scatterers contributing to the radar echo the greater the decorrelation will be by modeling this effect the authors can estimate radio wave penetration depths within the upper layers of the glacier or ice sheet observations of the greenland ice sheet using ers data yield penetration depths one way 1 e point for power that range from 12 to 35 m due to the contribution of volume scatter the critical interferometer baseline is decreased and the authors find for the greenland data the baseline must be restricted to be less than 300 m the authors also compare penetration depths measured within the dry snow zone with those found in the percolation zone and coastal areas they find that as expected the rocky coastal areas evidence minimal penetration interestingly the penetration depths that the authors measure in the percolation zone spl sim 23 m indicate a large degree of volume scatter which is contrary to earlier results that found the scattering in the percolation zone dominated by structures in the first few meters this discrepancy may be due to unmodeled scattering behavior or the radar return may indeed include significant contributions from scatterers far beneath the surface

first demonstration of airborne sar tomography using multibaseline l band data in synthetic aperture radar sar interferometry the phase differences between two different sensor positions are used to estimate the terrain topography although it is possible in this way to find a three dimensional 3d surface representation the distribution of the different scatterers in the height direction at a fixed range and azimuth position remains unknown contrary to this tomographic techniques enable a real geometric resolution capability in the height direction and introduce new possibilities for many applications and inversion problems even misinterpretations in sar images caused by layover and foreshortening effects can be solved by the tomographic processing in this paper the successful experimental realization of polarimetric airborne sar tomography is demonstrated for the first time the authors present the concept of aperture synthesis for tomographic imaging for the case of a multibaseline imaging geometry and discuss the constraints arising from the limited number of flight tracks they propose a method for reduction of the height ambiguities associated to the irregular and undersampled spatial distribution of the imaging positions finally they address the experimental requirements for polarimetric airborne sar tomography and show experimental results using a multibaseline data set acquired in l band by dlr s experimental sar e sar of a test site near oberpfaffenhofen germany