abrupt change in slope causes variation in the deposit thickness of concentrated particle driven density currents abstract abrupt changes in slope occur frequently in some marine environments laterally confined laboratory experiments show that when dense surge like particulate flows travel over abrupt slope reductions their deposits may have an asymmetric bell shaped thickening near the break of slope this thickening is herein called a slope break deposit and is related to the change in kinetic energy of the flow slope break deposits are particularly pronounced under relatively high velocity flows in our experiments these are flows with high particle concentrations c 5 10 by volume silicon carbide moving down slopes steeper than 3 the experiments were designed such that currents generated by a lock exchange mechanism flowed down a slope variable slope angle onto a flat surface the bodies of the flows became thicker and slower just downstream of the slope break because the flow body slows very rapidly particles are dumped forming the slope break deposit the peak in sediment thickness of the slope break deposit is downstream of the break in slope because falling particles continue to move forward in the flow during settling the slope break deposits may be several tens of percent thicker than deposits from an equivalent flow in which no change in slope occurred the parameters of the slope break deposit correlate with slope angle change

the use of multifrequency and polarimetric sir c x sar data in geologic studies of bir safsaf egypt abstract bir safsaf within the hyperarid core of the sahara in the western desert of egypt was recognized following the sir a and sir b missions in the 1980s as one of the key localities in northeast africa where penetration of dry sand by radar signals delineates previously unknown sand buried paleodrainage valleys radar rivers of middle tertiary to quaternary age the bir safsaf area was targeted as a focal point for further research in sand penetration and geologic mapping using the multifrequency and polarimetric sir c x sar sensors analysis of the sir c x sar data from bir safsaf provides important new information on the roles of multiple sar frequency and polarimetry in portraying specific types of geologic units materials and structures mostly hidden from view on the ground and on landsat tm images by a relatively thin but extensive blanket of blow sand basement rock units granitoids and gneisses and the fractures associated with them at bir safsaf are shown here for the first time to be clearly delineated using c and l band sar images the detectability of most geologic features is dependent primarily on radar frequency as shown for wind erosion patterns in bedrock at x band 3 cm wavelength and for geologic units and sand and clay filled fractures in weathered crystalline basement rocks at c band 6 cm and l band 24 cm by contrast quaternary paleodrainage channels are detectable at all three radar frequencies owing among other things to an usually thin cover of blow sand the sir c x sar data investigated to date enable us to make specific recommendations about the utility of certain radar sensor configurations for geologic and paleoenvironmental reconnaissance in desert regions

the sir c x sar synthetic aperture radar system the spaceborne imaging radar c x band synthetic aperture radar sir c x sar was a joint united states german italian space agency imaging radar system successfully flown aboard the shuttle endeavor in april 1994 and again in september october 1994 the multifaceted sir c x sar represents a major technological step forward in radar remote sensing and is the first spaceborne multifrequency polarimetric sar the united states developed sir c operated at l and c band each with quad polarization the sir c antenna was an active phased array with the capability for electronic beam steering and multiple swath width illumination the german italian x sar operated at x band with a single polarization using a slotted waveguide antenna mechanically steerable in elevation sir c and x sar were designed to operate synchronously collecting data over common sites synchronously a total of 143 hours 93 terabits of sar data were recorded on tape

intertidal occurrence of mesoscale scours in the bay of bengal india and their implications abstract a kind of fairweather high energy mesoscale flute like scours is observed in the intertidal zone in chandipur at the northwestern corner of the bay of bengal india the scours are localized immediately in front of three sharp breaks within three contrasting environmental subzones their open ends point to the local slope directions that vary between adjacent subzones shapes and dimensions of the scours in association with a low intertidal bar vary subtly but significantly with bar height roller eddies caused by ephemeral hydraulic jumps provide a plausible explanation for their generation extended covering of rippled silt or very fine sand on the scoured intertidal flat denotes a rapid fall in depositional energy soon after scouring this is a consequence of submergence emergence tidal cycles occurrence of such mesoscale flute like scours in ancient tidal flats would provide positive help in recognizing palaeoreliefs such as bars there is however no reason for these scours to remain confined either to the sea margins or to the fairweather the prerequisites for their formation are a sharp change in gradient of the depositional substrate and a periodic or episodic sedimentation process possible analogues of such scours are cited from a few ancient sequences

x sar interferometry first results repeat pass interferometry data were acquired during the first and second sir c x sar missions in april and october 1994 this paper presents the first results from x sar interferometry at four different sites the temporal separations were one day and six months at two sites the coherence requirements were met resulting in high quality interferograms a digital elevation model in ground range geometry has been derived the limitations of the x sar interferometry are discussed

surface deformation and coherence measurements of kilauea volcano hawaii from sir c radar interferometry the shuttle imaging radar c x synthetic aperture radar sir c x sar radar on board the space shuttle endeavor imaged kilauea volcano hawaii in april and october 1994 for the purpose of measuring active surface deformation by the methods of repeat pass differential radar interferometry observations at 24 cm l band and 5 6 cm c band wavelengths were reduced to interferograms showing apparent surface deformation over the 6 month interval and over a succession of 1 day intervals in october a statistically significant local phase signature in the 6 month interferogram is coincident with the pu u o o lava vent interpreted as deformation the signal implies centimeter scale deflation in an area several kilometers wide surrounding the vent peak deflation is roughly 14 cm if the deformation is purely vertical centered southward of the pu u o o caldera delays in the radar signal phase induced by atmospheric refractivity anomalies introduce spurious apparent deformation signatures at the level of 12 cm peak to peak in the radar line of sight direction though the phase observations are suggestive of the wide area deformation measured by global positioning system gps methods the atmospheric effects are large enough to limit the interpretation of the result it is difficult to characterize centimeter scale deformations spatially distributed over tens of kilometers using differential interferometry without supporting simultaneous spatially distributed measurements of refractivity along the radar line of sight studies of the interferometric correlation of images acquired at different times show that l band is far superior to c band in the vegetated areas even when the observations are separated by only 1 day these results imply longer wavelength instruments are more appropriate for studying surfaces by repeat pass observations

erosional and depositional patterns associated with the 1993 missouri river floods inferred from sir c and topsar radar data the missouri river floods of 1993 caused significant and widespread damage to the floodplains between kansas city and st louis immediately downstream of levee breaks flood waters scoured the bottoms as the floodwaters continued they spread laterally and deposited massive amounts of sand as crevasse splays on top of agricultural fields we explore the use of radar interferometry and backscatter data for quantitative estimation of scour and deposition for jameson island arrow rock bottoms and lisbon bottoms two bottoms that were heavily damaged during the floods and subsequently abandoned shuttle imaging radar c sir c l band 24 cm hh horizontally transmitted and horizontally received radar backscatter data acquired in october 1994 were used together with a distorted born approximation canopy scattering model to determine that the abundance of natural leafy forbs controlled the magnitude of backscatter for former agricultural fields forb areal density was found to be inversely correlated with thickness of sand deposited during the floods presumably because thick sands prevented roots from reaching nutrient rich moist bottoms soils using the inverse relationship a lower bound for the mass of sand added was found to be 6 3 million metric tons over the 17 km2 study area digital elevation data from topographic synthetic aperture radar topsar c band 5 6 cm interferometric observations acquired in august 1994 were compared to a series of elevation profiles collected on the ground vertical errors in topsar were estimated to range from 1 to 2 m providing enough accuracy to generate an estimate of total mass 4 7 million metric tons removed during erosion of levees and scour of the bottoms terrains net accretion of material to the study areas is consistent with the geologic record of major floods where sediment laden floodwaters crested over natural levees initially scoured into the bottoms and then deposited sands as crevasse splays as the flows spread out and slowed by frictional dissipation the addition of artificial levees to the missouri river system has undoubtedly enhanced flood damage although quantitative estimation of the degree of enhancement will require additional work

wavelet analysis of stratospheric gravity wave packets over macquarie island 1 wave parameters we describe a technique to detect gravity wave packets in high resolution radiosonde soundings of horizontal wind and temperature the vertical profiles of meridional and zonal wind speeds are transformed using the morlet wavelet and regions of high wind variance in height wavenumber space are identified as gravity wave packets application of the stokes parameter analysis to horizontal wind and temperature profiles of the reconstructed wave packets yields the wave parameters the technique was applied to twice daily radiosonde launches at macquarie island 55 s 159 e between 1993 and 1995 a strong seasonal cycle in the total wave variance was found with a maximum in winter the amount of wave energy propagating downward from the upper stratosphere also maximized in winter waves propagated predominately toward the southwest in winter but in summer propagation directions were approximately isotropic the intrinsic frequencies were close to the inertial frequency and the waves had inferred horizontal wavelengths of several hundred kilometers

geomorphic processes and remote sensing signatures of alluvial fans in the kun lun mountains china the timing of alluvial deposition in arid and semiarid areas is tied to land surface instability caused by regional climate changes the distribution pattern of dated deposits provides maps of regional land surface response to past climate change sensitivity to differences in surface roughness and composition makes remote sensing techniques useful for regional mapping of alluvial deposits radar images from the spaceborne radar laboratory and visible wavelength images from the french spot satellite were used to determine remote sensing signatures of alluvial fan units for an area in the kun lun mountains of northwestern china these data were combined with field observations to compare surface processes and their effects on remote sensing signatures in northwestern china and the southwestern united states geomorphic processes affecting alluvial fans in the two areas include aeolian deposition desert varnish and fluvial dissection however salt weathering is a much more important process in the kun lun than in the southwestern united states this slows the formation of desert varnish and prevents desert pavement from forming thus the kun lun signatures are indicative of the dominance of salt weathering while signatures from the southwestern united states are characteristic of the dominance of desert varnish and pavement processes remote sensing signatures are consistent enough in these two regions to be used for mapping fan units over large areas

overview of results of spaceborne imaging radar c x band synthetic aperture radar sir c x sar the spaceborne imaging radar c x band synthetic aperture radar sir c x sar was launched on the space shuttle endeavour for two ten day missions in the spring and fall of 1994 radar data from these missions are being used to better understand the dynamic global environment during each mission radar images of over 300 sites around the earth were obtained returning over a terabit of data sir c x sar science investigations were focused on quantifying radar s ability to estimate surface properties of importance to understanding global change and focused studies in geology ecology hydrology and oceanography as well as radar calibration and electromagnetic theory studies in addition the second flight featured an interferometry experiment where digital elevation maps were obtained by interfering data from the first and second shuttle flight and from successive days on the second flight sir c x sar data have been used to validate algorithms which produce maps of vegetation type and biomass snow soil and vegetation moisture and the distribution of wetlands developed with earlier aircraft data

overview of the spaceborne imaging radar c x band synthetic aperture radar sir c x sar missions abstract the spaceborne imaging radar c x band synthetic aperture radar sir c x sar the most advanced imaging radar system to have flown in earth orbit was carried in the cargo bay of the space shuttle endeavour in april and october 1994 sir c x sar simultaneously recorded data at three wavelengths l c and x bands 23 5 cm 5 8 cm and 3 1 cm respectively in addition the full polarimetric scattering matrix was obtained at l and c band over a variety of terrain and vegetation types scientists are using multifrequency polarimetric sir c x sar data in studies of geology hydrology ecology oceanography and radar remote sensing techniques the october sir c x sar flight also included acquisition of experimental repeat pass interferometry data which have been used to generate digital elevation models and to detect surface motions in volcanic tectonic and glacial terrains results from sir c x sar clearly show the increased value of using multiparameter and interferometric capabilities to characterize earth s surface and vegetation cover and to generate geophysical products compared with optical sensors or single channel radars alone

detection of sand covered geologic features in the arabian peninsula using sir c x sar data eolian sand covers a large part of the arabian peninsula the flow of eolian sand is ongoing and sand covers bedrock as well as fluvial features of the peninsula consequently there is a gap in the understanding of the geological processes shaping the region the extensive coverage of shuttle imaging radar sir c x sar data over the arabian peninsula has provided a new means of mapping sand obscured features the preliminary interpretation of the data has identified several sites where l band reveals sand covered geological structures and drainage channels that are not shown on published maps and are not traceable with more conventional methods the indications are that these radar data may lead to improving the geological and fluvial geomorphic understanding of the region

preliminary analysis of shuttle radar laboratory srl 1 data to study aeolian features and processes in april 1994 the shuttle radar laboratory srl 1 obtained quad polarization data in l band spl lambda 24 cm and c band spl lambda 5 6 cm and vv polarized data in x band spl lambda 3 cm preliminary analyses show that radar backscatter coefficients spl sigma sup 0 can be used to map the aerodynamic roughness parameter z sub 0 over large areas from orbit as demonstrated by comparisons with measurements of z sub 0 obtained in the field although all wavelengths and polarizations show fairly good correlations with z sub 0 r 0 78 l band hv shows the best relationship r 0 81 this result has potential use in regional studies of sand and dust transport modeling atmospheric circulation and general climate studies srl images of aeolian landforms were also studied including dunes sand sheets and wind streaks dunes in the stovepipe wells area of death valley were clearly visible on l band hv images but not detected on c band images in the same area l band penetrated a sand sheet to reveal a buried fault scarp l band images in namibia showed the classic linear dunes near gobabeb and also revealed previously undetected sets of cross dunes wind streaks were imaged in several areas including namibia where streaks are associated with the impact crater roter kamm these features enable mapping of near surface wind patterns

analysis of active lava flows on kilauea volcano hawaii using sir c radar correlation measurements precise eruption rates of active pahoehoe lava flows on kilauea volcano hawaii have been determined using spaceborne radar data acquired by the space shuttle imaging radar c sir c a coastal site downslope from the pu9u o9o vent was imaged once per day on each of the four days of october 7 10 1994 day to day decorrelation due to resurfacing was determined by interferometric combination of the data at 15 m resolution over a wide area on successive days new lava resurfaced 335700 m 2 368775 m 2 and 356625 m 2 assuming an average pahoehoe flow thickness of 50 cm a mean effusion rate for this period is approximately 2 m 3 s the radar observations show persistent surface activity at each site rather than downslope migration of coherent lava flows

cyclic deposits and hummocky cross stratification of probable storm origin in upper cretaceous rocks of the cape sebastian area southwestern oregon abstract cyclic deposits containing hummocky cross stratification occur in the upper part of the cape sebastian sandstone of bourgeois 1980 a shallow marine transgressive sandstone of late cetaceous age on the southern oregon coast the cycles average 1 6 m in thickness and consist where complete of a lower hummocky cross stratified sandstone a middle planar and ripple bedded sandstone with a shale bed in its middle part and an upper bioturbated sandstone noteworthy features of the hummocky cross stratification include the presence of depositional domes in addition to scoured depressions the absence of significant bedform migration and the presence of a small proportion of dip angles greater than the angle of repose 34 in addition to the large proportion of low 15 deg dip angles the lower stratified fining upward part of the cycle up to the top of the shale bed is interpreted as having accumulated under conditions of initially great but gradually decreasing current velocity and deposition rate the currents probably had a strong oscillatory component and the depositional event is inferred to have been a storm the part of the planar and ripple bedded sandstone above the shale bed was probably deposited during relatively fair weather after the storm but before re establishment of a normal benthic fauna the bioturbated sandstone is interpreted to have been deposited during fair weather or during minor storms separated by long intervals of fair weather

marine to fluvial transition proterozoic upper rewa sandstone maihar india abstract the proterozoic upper rewa sandstone in central india is generally interpreted as entirely marine a detailed study in maihar madhya pradesh however reveals upward transition from marine to fluvial through a mixed facies association also bearing eolian imprints facies associations differ in stratal geometry and arrangement palaeocurrent direction and pattern as well as in grain size and sorting the fine grained marine association is dominated by tidal sheet deposits with characteristic rhythmic changes in thickness and style of cross stratification and their packages as well as local evidence of current reversals subordinate beach deposits are also present the major palaeocurrent direction is highly consistent and westward the coarse grained often granule rich sandstones of the fluvial association are embodied by four facies correlatable with flow stages and relative bed shear these braided stream deposits are preserved in vertical stacks of tabular sandbodies in response mainly to basin subsidence the palaeocurrent pattern is unimodal and northwestward but its dispersion covers 180 the rocks are poorly sorted and at places incorporate sand clasts although they are virtually mud free and mineralogically mature as in two other associations the medium to fine grained sandstones at the intermediate interval between the marine and fluvial associations are of distinct lensoid geometry they incorporate representatives from the previous two associations as well as translatent strata interdune erg deposits and possibly aeolian cross strata consequently the palaeocurrent pattern is polymodal with a spread over 270 an overall coarsening up trend in the fluvial part and thinning up trend in the tidal part imply progradation in spite of evidence of basin subsidence a high rate of sediment discharge from a perennial river system in a humid climate is suggested

characteristics of coarse grained sequences deposited in nearshore wave dominated environments examples from the miocene of south west oregon the conglomeratic sandstone of the sandstone of floras lake miocene is a superbly exposed example of a coarse grained sequence deposited in a high energy storm wave dominated shallow marine environment the features of the unit suggest deposition on a shoreface in proximity to a fluvial source distinguishing characteristics include amalgamated hummocky stratified sandstone low angle cross stratified conglomerate beds lenticular conglomerate beds tabular conglomerate beds high angle scours trough cross bedded sandstone organic rich beds and burrows of several sizes these features are interpreted in terms of their depths of deposition generation by fair weather storm and or flood processes and as indicators of relative rates of sedimentation the unit records complex interaction of tectonic wave fluvial and tidal processes relative depth changes indicated in the sequence probably reflect changes in the balances between sediment supply basin subsidence and eustatic sea level changes wave processes are manifest in the presence of structures deposited both above and below fair weather wave base deposition and reworking by chaotic seas associated with local storms and by long period swell associated with distant storms may be indicated by the interbedding of amalgamated hummocky stratified sandstone and conglomerate beds the effects of the lateral migration of a fluvial source with time are reflected by the changing nature and apparent rates of supply of sediments deposited in the nearshore zone tidal processes are manifest largely as superimposed features on wave and current generated structures biogenic structures are an important clue to the rates and frequencies of all these processes the conglomeratic sandstone was deposited on a high energy tectonically active continental margin similar to the present setting of the southern oregon coast it was deposited at varying depths in a subsiding basin during a time of world wide sea level rise the sequence provides an opportunity for the study of coarse grained nearshore marine sediments and the delineation of the interaction of various processes during deposition detailed sedimentologic and palaeoecologic analysis provides insight into the nature of storm and flood processes that are difficult to observe in the modern environment

facies flow and bedform patterns across a storm dominated inner continental shelf proterozoic kaimur formation rajasthan india abstract a comprehensive sedimentation model for an epeiric sea useful for further comparison and prediction is derived crom the proterozoic kaimur formation rajasthan india facies analysis of a steadily regressive shale quartz arenite sequence documents the patterns of flow sediment transport and deposition from beach to offshore across a storm dominated gently sloping

sir c x sar observations of rain storms abstract the spaceborne imaging radar c x band synthetic aperture radar observations of rain storms are the first multipolarization and multifrequency observations of precipitation from space in addition to numerous often dramatic images of severe weather systems obtained by forming a synthetic aperture in the usual side looking attitude several data takes were performed while the radar antennas were parallel to the ground and the radar beams were pointing at nadir these opportunities coincided with the passage of the shuttle over tropical cyclone odille in the southern indian ocean during the first flight and over typhoon seth in the western pacific during the second flight the resulting observations or more appropriately the resulting measurements demonstrate for the first time the capability of a spaceborne multifrequency multipolarization microwave radar system to quantify precipitation rates to detect hydrometeor phase and to classify rain type

radarclinometry of the sand seas of africa s namibia and saturn s moon titan abstract radarclinometry is a powerful technique for estimating heights of landforms in synthetic aperture radar sar images of planetary surfaces in particular it has been used to estimate heights of dunes in the sand seas of saturn s moon titan lorenz r d and 39 colleagues 2006 science 312 724 727 in this work we verify the technique by comparing dune heights derived from radarclinometry to known topography of dune fields in the namib sand sea of western africa we compared results from three different image grid spacings and found that 350 m pixel the same spacing at which the cassini radar data was processed is sufficient to determine dune height for dunes of similar morphometry to those of the namib sand sea at this grid spacing height estimates derived from radarclinometry are largely representative of though may underestimate by as much as 30 or overestimate by as much as 40 true dune height applying the technique to three regions on titan we estimate dune heights of 45 180 m and dune spacings of 2 3 3 3 km obtaining accurate heights of titan s dunes will help to constrain the total organic inventory on titan

shuttle imaging radar sir c x sar reveals near surface properties of the south patagonian icefield shuttle imaging radar c x band synthetic aperture radar sir c x sar views of the south patagonian icefield in southern chile and argentina demonstrate the ability of spaceborne multiparameter radar to detect climatically driven intra annual changes in the snow and ice conditions on glaciers the sir c x sar system aboard space shuttle endeavor acquired images during two 11 day missions in april and october 1994 the radar signatures of differing snow and ice conditions are distinctive and homogeneous over large areas of the ice fields the signatures are characterized mainly by 1 backscatter amplitude levels 2 relative amplitudes of the c and l bands wavelengths of 5 7 and 24 cm respectively and 3 polarization properties indicative of volumetric or surface scattering the radar signatures are interpreted by correlating the radar characteristics with elevation of the snow and ice surfaces and with changes in the meteorological conditions we are able to define four radar glacier zones zone a a relatively dry snow zone with dominant c band returns zone b a moderately wet snow zone with dominant l band returns zone c a wet snow zone with weak returns in all bands and zone d bare ice and or heavily crevassed surfaces with strong returns in all bands the spatial changes in the radar glacier zones between april and october are consistent with colder temperatures recorded in october producing drier snow conditions at lower elevations than in april

atmospheric limitations to repeat track radar interferometry in its recent radar imaging mission the shuttle imaging radar satellite sir c devoted three days to repeat track interferometry we have analyzed the data from a test site in the mojave desert of california although good topography 10 m on 21 m postings was obtained most of the error was caused by turbulent water vapor in the lower atmosphere spatial structure of 6 km and all smaller sizes was observed the rms one way time delay was found to be 0 24 cm essentially identical results were obtained at two wavelengths 24 and 5 7 cm

preliminary observations of volcanoes with the sir c radar the two flights of the shuttle imaging radar sir c x sar in april and october 1994 provided a wealth of new image data over many of the world s volcanoes including 13 of the 15 international decade volcanoes a first look at these data shows that mapping of remote volcanoes e g nyiragongo and nyamuragira in africa will now be easier especially when aided by the collection of multi parameter radar data over better known analogous volcanoes such as kilauea hi the utility of the radar to identify different types of lava flows is shown for fernandina volcano galapagos islands growth of mudflow deposits lahars that were emplaced on mount pinatubo philippines during the six months between the two missions is also illustrated additionally interferometric radar data were collected over several active volcanoes the potential uses of these data for topographic mapping and ground deformation studies are discussed

linear dunes on titan and earth initial remote sensing comparisons thousands of dunes found in cassini radar images of the equatorial regions of titan a moon around saturn are similar in size and morphology to linear dunes on earth we present remote sensing images of terrestrial analogues to the dunes on titan obtained by landsat and radar both at considerably higher resolution than are available at titan that provide information about dune landforms and processes dunes are generally dark to radar indicating smooth surfaces and signal absorbing materials but at certain incidence angles dune surfaces can reflect the radar signal and lead to a bright return linear dunes on titan and earth diverge around topographic obstacles creating teardrop patterns that indicate mean direction of wind flow and sand transport when sand supply or wind conditions change in linear dune fields such as behind an obstacle or near the margin of the dune field dunes disappear change size and spacing or change dune type these comparisons of features on titan and earth provide a better understanding of the global sand transporting wind directions sand properties and supply and the nature of the underlying substrate on titan

real time observations of southern ocean wave fields from the shuttle imaging radar during the april and october 1994 flights of the space shuttle endeavour c band synthetic aperture radar sar signal was acquired and processed in real time into ocean wave images and two dimensional image spectra by an on board processor the image spectra were transmitted to the ground as they were acquired during 20 days of observations spanning the two missions over 100000 spectra were collected these data provide the first truly synoptic directional measurements of the southern ocean wave field with additional processing estimates of ocean wavelength and propagation direction were extracted from the spectra during the october mission daily comparisons of these estimates with wave model predictions were made available at a world wide web site the authors describe the computations performed by the processor and the real time data flow and ground processing in addition they summarize and interpret some gross characteristics of the processor observed real time wave field from the april and october missions

pradip k bose a dedication like most parts of the world serious sedimento logical research in india started only in the 1960s prior to that time very few earth scientists showedmuch interest in sedimentology prof pradip k bosewas one of the few workers who initiated seriousscientific study of the sedimentary rocks in india pradip bose was born on january 2 1942 in howrahin west bengal and obtained his early educationduring the depression time in a rural school histertiary education in geology was at jadavpuruniversity kolkata and he earned his ph d degreein 1967 he joined punjab university as a post doctoral fellow thereafter he shifted to jadavpuruniversity as a lecturer in the year 1970 and began hisserious research efforts in sedimentology with anothergreat indian sedimentologist the late prof sukomalchanda in his retirement pradip bose is still veryactively associated with the same university prof bose made significant contributions inresolving major geological problems based on high resolution field studies petrography elementary geo chemistry and fossil evidence within the domain ofsedimentary geology pradip has a rare quality ofviewing body fossils trace fossils and sediment in abroader way as inseparable parts of a single entity hehas shown remarkable versatility in process relatedhigh resolution facies analysis of diverse kinds ofdepositional regimes with an outstanding ability todeal with the products of widely varied palaeoenvir onments tide and wave dominated shelf bose 1982 bose et al 1988a b 1997a bose and chaud huri 1990 chakraborty and bose 1990 1992a deep

mapping of glacial motion and surface topography of hielo patagonico norte chile using satellite sar l band interferometry data the first topographic and ice motion maps of the northwestern flank of hielo patagonico norte hpn northern patagonia icefield in chile were produced using satellite synthetic aperture interferometric radar data acquired by nasa s spaceborne imaging radar c instrument in october 1994 the topographic map has a io m vertical precision with a 30 m horizontal spacing which should be sufficient to serve as a reference for monitoring future mass changes of the icefield the ice motion map is accurate to within 4 mm d or 1 ma the radar derived surface topography and ice velocity are used to estimate the ice discharge from the accumulation area of four outlet glaciers and the calving flux and mass balance of glaciar san rafael the results demonstrate the use of sar interferometry for monitoring glaciological parameters on a spatial and temporal scale unattainable by any other means

interferometric radar observations of glaciar san rafael chile interferometric radar observations of glaciar san rafael chile were collected in october 1994 by nasa s spaceborne imaging radar c sir c at both l 24 cm and c band frequency 5 6 cm with vertical transmit and receive polarization the c band data did not yield good geophysical products because the temporal coherence of the signal was significantly reduced after 24 h the l band data were however successfully employed to map the surface topography of the icefield with a 10 m uncertainty in height and measure ice velocity with a precision of 4 mm d 1 or 1 4 ma 1 the corresponding error in strain rates is 0 05 a 1 at a 30 m horizontal spacing the one dimensional interferometric velocities were subsequently converted to horizontal displacements by assuming a flow direction and complemented by feature tracking results near the calving front the results provide a comprehensive view of the ice flow dynamics of glaciar san rafael the glacier has a core of rapid flow 4 5 km in width and 3 5 in average slope surrounded by slowermoving ice not by rock ice velocity is 2 6 m d 1 or 0 95 km a 1 near the equilibrium line altitude 1200 m increasing rapidly before the glacier enters the narrower terminal valley to reach 17 5 m d 1 or 6 4 km a 1 at the calving front strain rates are dominated by lateral shearing at the glacier margins 0 4 0 7 a 1 except for the terminal valley section where longitudinal strain rates average close to 1 a 1 this spectacular longitudinal increase in ice velocity in the last few kilometers may be a fundamental feature of tidewater glaciers

the effect of varying acquisition parameters on the interpretation of sir c radar data the virunga volcanic chain abstract in 1994 the spaceborne imaging radar experiment c sir c acquired five data takes with different acquisition parameters over the virunga volcanic chain zaire changes in incidence angle 20 0 48 1 look direction west and east looking and pulse bandwidth 10 mhz 20 mhz and 40 mhz affect the geologic interpretations drawn from these data we examine differences in spatial distortion of features near the summit of nyiragongo volcano finding that opposite look direction data are helpful in interpreting volcanic features such as the shape of small craters in areas of high relief the relative brightness of lava flows and vegetation change and actually reverse for different wavelengths and polarizations although l band data are best for mapping the outline of the flows c and x band cross polarization data show differences in backscatter intensity between and within flows in addition our ability to discriminate lava flows and vents from surrounding vegetation is strongly influenced by pulse bandwidth resolution and angle of incidence pulse bandwidth is the most important parameter in mapping small topographic features such as volcanic cones and a set of particularly thick flows on the flanks of karisimbi volcano these examples illustrate important considerations of the tradeoffs and priorities in acquisition parameters for future missions such as envisat as well as potential pitfalls for interpretation of existing data

setulfs modern and ancient formative mechanism preservation bias and palaeoenvironmental implications abstract setulfs or inverted flutes both in growth stage and in fossilized state are addressed here this account resolves the long standing questions about their formative mechanism depositional prerequisites and preservation bias as well as their palaeoenvironmental implications these structures were observed to grow by accretion of wind deflated sand in the lee of miniscule obstructions in the littoral supralittoral transition zone a little above the high water mark on top of a partially emerged bar at chandipur eastern india pseudopellets of crabs and scarce chips of microbial mat create the obstructions as shells might also do in the case of other modern analogs reported from essentially similar environmental conditions moisture on the beach sand limited the lifting power of the wind so that even miniscule obstructions could have a well developed wake zone at their lee side resulting in localized accumulation of a small ridge of sand extending downwind from the obstruction setulfs arrested under microbial mats were also found in chandipur on the seaward fringe of a shallow marsh encircled by a spit like those in growth stage these mat covered setulfs also had their tapering ends directed landward as the wind was directed onshore during the period of observation fossilized setulfs in swarms are also described here from two neoproterozoic formations in india viz the sonia sandstone and the upper bhander sandstone in both the cases setulfs are preserved in well sorted sandstones and are associated with planar laminae profound wave ripples bifurcated parting lineations infrequent rill marks and local swarms of current crescents on bedsurfaces additionally recorded fossil setulfs are found in association with inversely graded translatent strata crinkled adhesion laminae patches of impact ripples and isolated small sets of alternate grain flow and grain fall cross strata of aeolian origin this suggests preservation in the high littoral supralittoral zone as in case of all known modern setulf occurrences the palaeowind direction derived from the ancient setulfs conforms in orientation to that recorded from other aeolian structures in the strata supporting their wind deflation origin although shells and biogenic pellets were altogether absent from these neoproterozoic rocks microbial mat curls and fragments had presumably been abundantly present in the proterozoic high littoral supralittoral zone to facilitate formation of setulfs pertinently many microbial mat related features are present within both the siliciclastic formations studied in polished sections some of the studied proterozoic setulfs reveal the existence of crinkled carbonaceous lamina covers that signify microbial mat growth on top of them an a priori assumption is that microbial mats must have enhanced the preservation potential of these delicate structures which would otherwise be extremely unlikely to be preserved the seeming preference of fossil setulf occurrences from the proterozoic early palaeozoic time is most likely due to a lack of burrowers and grazers that would devastate the protective microbial mat later in the phanerozoic these observations suggest that swarms of setulfs are in general wind sculpted and their presence in the rock record prefers palaeoenvironment interpretration as a high littoral supralittoral transition zone and also stands as proxy records of syn depositional microbial mat growth

cassini radar images at hotei arcus and western xanadu titan evidence for geologically recent cryovolcanic activity 1 images obtained by the cassini titan radar mapper radar reveal lobate flowlike features in the hotei arcus region that embay and cover surrounding terrains and channels we conclude that they are cryovolcanic lava flows younger than surrounding terrain although we cannot reject the sedimentary alternative their appearance is grossly similar to another region in western xanadu and unlike most of the other volcanic regions on titan both regions correspond to those identified by cassini s visual and infrared mapping spectrometer vims as having variable infrared brightness strengthening the case that these are recent cryovolcanoes citation wall s d et al 2009 cassini radar images at hotei arcus and western xanadu titan evidence for geologically recent cryovolcanic activity geophys res lett 36 l04203 doi 10 1029 2008gl036415