detection of potential fields source boundaries by enhanced horizontal derivative method a high resolution method to image the horizontal boundaries of gravity and magnetic sources is presented the enhanced horizontal derivative ehd method the ehd is formed by taking the horizontal derivative of a sum of vertical derivatives of increasing order the location of ehd maxima is used to outline the source boundaries while for gravity anomalies the method can be applied immediately magnetic anomalies should be previously reduced to the pole we found that working on reduced to the pole magnetic anomalies leads to better results than those obtainable by working on magnetic anomalies in dipolar form even when the magnetization direction parameters are not well estimated this is confirmed also for other popular methods used to estimate the horizontal location of potential fields source boundaries the ehd method is highly flexible and different conditions of signal to noise ratios and depths to source can be treated by an appropriate selection of the terms of the summation a strategy to perform high order vertical derivatives is also suggested this involves both frequency and space domain transformations and gives more stable results than the usual fourier method the high resolution of the ehd method is demonstrated on a number of synthetic gravity and magnetic fields due to isolated as well as to interfering deep seated prismatic sources the resolving power of this method was tested also by comparing the results with those obtained by another high resolution method based on the analytic signal the success of the ehd method in the definition of the source boundary is due to the fact that it conveys efficiently all the different boundary information contained in any single term of the sum application to a magnetic data set of a volcanic area in southern italy helped to define the probable boundaries of a calderic collapse marked by a number of magmatic intrusions previous interpretations of gravity and magnetic fields suggested a subcircular shape for this caldera the boundaries of which are imaged with better detail using the ehd method

recent thermohaline trends of the atlantic waters inflowing to the mediterranean sea 1 a total of 5077 argo float profiles in the period 01 2002 05 2010 have been used to analyze salinity and temperature trends in the atlantic waters adjacent to the strait of gibraltar in order to identify the source of recent changes observed in the inflow to the mediterranean sea positive salinity trends of 0 038 0 009 year 1 and 0 013 0 003 year 1 have been found for the surface atlantic water and the eastern north atlantic central water respectively for temperature no significant trend is observed in the surface layer while positive trend of 0 05 0 02 c year is obtained for the thermocline waters the mediterranean water layer does not show any significant trend for the entire period but a switch from positive to negative trends is observed in year 2006 in contrast to previous findings these thermohaline variations are driven by intrinsic water masses changes instead of isopycnal vertical displacements probably related to an enhancement of the net freshwater losses in the area

3 d density modelling of underground structures and spatial distribution of salt diapirism in the dead sea basin a new compilation of bouguer gravity data stemming from airborne shipborne and terrestrial data set in the entire dead sea basin dsb was reinterpreted by applying 3 d density modelling that incorporated independent information on other geophysical researches allowing for regional and residual filtering in the gravity field carrying out curvature analysis and euler deconvolution of the combined gravity field 3 d density modelling enables us to detailed resolution of upper crustal structures from the southern to the northern subbasin below the saline dead sea 3 d gravity modelling led to the identification of three salt structures which are found beneath the sedom area the lisan peninsula and the dead sea in the vicinity of the western margin of the dead sea a salt diapir segment with a thickness of about 4 km has been identified at a top depth of about 2 km which has not been recognised by any other geophysical interpretations the thickness of the sedimentary infill overlying the basement in the dsb decreases from 14 km in the vicinity of the lisan peninsula to 8 km in the northern and the southern subbasins large negative gravity anomalies lower than 100 x 10 5 m s 2 observed in the dsb correspond with the spatial distribution of salt diapirism with an average density of 2 100 kg m 3 the shallower microearthquakes registered in the dsb are related to the movement of salt diapir in the dsb

long term surface temperature modeling of pluto abstract nasa s new horizons reconnaissance of the pluto system has revealed at high resolution the striking albedo contrasts from polar to equatorial latitudes on pluto as well as the sharpness of boundaries for longitudinal variations these contrasts suggest that pluto must undergo dynamic evolution that drives the redistribution of volatiles using the new horizons results as a template we explore the surface temperature variations driven seasonally on pluto considering multiple timescales these timescales include the current orbit 248 years as well as the timescales for obliquity precession peak to peak amplitude of 23 over 3 million years and regression of the orbital longitude of perihelion 3 7 million years these orbital variations create epochs of extreme seasons where one pole receives a short relatively warm summer and long winter while the other receives a much longer but less intense summer and short winter we use thermal modeling to build upon the long term insolation history model described by earle and binzel 2015 and investigate how these seasons couple with pluto s albedo contrasts to create temperature effects from this study we find that a bright region at the equator once established can become a site for net deposition we see the region informally known as sputnik planitia as an example of this and find it will be able to perpetuate itself as an always available cold trap thus having the potential to survive on million year or substantially longer timescales meanwhile darker low albedo regions near the equator will remain relative warm and generally not attract volatile deposition we argue that the equatorial region is a preservation zone for whatever albedo is seeded there this offers insight as to why the equatorial band of pluto displays the planet s greatest albedo contrasts

research note compact depth from extreme points a tool for fast potential field imaging we propose a fast method for imaging potential field sources the new method is a variant of the depth from extreme points which yields an image of a quantity proportional to the source distribution magnetization or density such transformed field is here transformed into source density units by determining a constant with adequate physical dimension by a linear regression of the observed field versus the field computed from the depth from extreme points image such source images are often smooth and too extended reflecting the loss of spatial resolution for increasing altitudes consequently they also present too low values of the source density we here show that this initial image can be improved and made more compact to achieve a more realistic model which reproduces a field consistent with the observed one the new algorithm which is called compact depth from extreme points iteratively produces different source distributions models with an increasing degree of compactness and correspondingly increasing source density values this is done through weighting the model with a compacting function the compacting function may be conveniently expressed as a matrix that is modified at any iteration based on the model obtained in the previous step at any iteration step the process may be stopped when the density reaches values higher than prefixed bounds based on known or assumed geological information as no matrix inversion is needed the method is fast and allows analysing massive datasets due to the high stability of the depth from extreme points transformation the algorithm may be also applied to any derivatives of the measured field thus yielding an improved resolution the method is investigated by application to 2d and 3d synthetic gravity source distributions and the imaged sources are a good reconstruction of the geometry and density distributions of the causative bodies finally the method is applied to microgravity data to model underground crypts in st venceslas church tovacov czech republic

albedo matters understanding runaway albedo variations on pluto abstract the data returned from nasa s new horizons reconnaissance of the pluto system show striking albedo variations from polar to equatorial latitudes as well as sharp longitudinal boundaries pluto has a high obliquity currently 119 that varies by 23 over a period of less than 3 million years this variation combined with its regressing longitude of perihelion 360 over 3 7 million years creates epochs of super seasons where one pole is pointed at the sun at perihelion thereby experiencing a short relatively warm summer followed by its longest possible period of winter darkness in contrast the other pole experiences a much longer less intense summer and a short winter season we use a simple volatile sublimation and deposition model to explore the relationship between albedo variations latitude and volatile sublimation and deposition for the current epoch as well as historical epochs during which pluto experienced these super seasons our investigation quantitatively shows that pluto s geometry creates the potential for runaway albedo and volatile variations particularly in the equatorial region which can sustain stark longitudinal contrasts like the ones we see between tombaugh regio and the informally named cthulhu regio

convection in a volatile nitrogen ice rich layer drives pluto s geological vigour the volatile ice filled basin informally named sputnik planum is central to pluto s geological activity this ice layer is organized into cells or polygons and it is now shown that convective overturn in a several kilometre thick layer of solid nitrogen can explain both the presence of the cells and their great width nasa s new horizons spacecraft has revealed fascinating details of the surface of pluto including a vast ice filled basin known as sputnik planum which is central to pluto s geological activity much of the surface of sputnik planum consisting mostly of nitrogen ice is divided into irregular polygons that are tens of kilometres in diameter and whose centres rise tens of metres above their sides two papers in this issue of nature analyse new horizons images of this polygonal terrain both conclude that it is continually being resurfaced by convection but arrive at contrasting models for the process alexander trowbridge et al report a parameterized convection model in which the nitrogen ice is vigorously convecting ten or more kilometres thick and about a million years old william mckinnon et al from the new horizons team show that sluggish lid convective overturn in a several kilometre thick layer of solid nitrogen can explain both the presence of the cells and their great width the vast deep volatile ice filled basin informally named sputnik planum is central to pluto s vigorous geological activity1 2 composed of molecular nitrogen methane and carbon monoxide ices3 but dominated by nitrogen ice this layer is organized into cells or polygons typically about 10 to 40 kilometres across that resemble the surface manifestation of solid state convection1 2 here we report on the basis of available rheological measurements4 that solid layers of nitrogen ice with a thickness in excess of about one kilometre should undergo convection for estimated present day heat flow conditions on pluto more importantly we show numerically that convective overturn in a several kilometre thick layer of solid nitrogen can explain the great lateral width of the cells the temperature dependence of nitrogen ice viscosity implies that the ice layer convects in the so called sluggish lid regime5 a unique convective mode not previously definitively observed in the solar system average surface horizontal velocities of a few centimetres a year imply surface transport or renewal times of about 500 000 years well under the ten million year upper limit crater retention age for sputnik planum2 similar convective surface renewal may also occur on other dwarf planets in the kuiper belt which may help to explain the high albedos shown by some of these bodies

shallow stratigraphic drilling applied in hydrocarbon exploration of the nordkapp basin barents sea abstract the nordkapp basin is a late palaeozoic rift basin characterised by numerous salt diapirs the salt was deposited in the late carboniferous early permian and has been remobilised several times upper palaeozoic and mesozoic sediments filled in the basin and were uplifted by salt diapirism in the early middle triassic late jurassic late cretaceous and tertiary regional uplift and erosion in the early tertiary and extensive glacial erosion in the late pliocene pleistocene removed up to 1200 m of the mesozoic and cenozoic strata and left them heavily tilted and truncated around the salt diapirs only covered by a thin sheet of glacial sediments during much of the triassic and jurassic the nordkapp basin was a large marine embayment open to the ocean in the southwest this allowed deposition of potential hydrocarbon source rocks in anoxic basins during transgressive periods in the triassic and late jurassic coastal processes improved the reservoir quality of upper triassic to middle jurassic sands during regressive periods one exploration well within the basin and three wells surrounding the basin have produced oil shows but no commercial discoveries have been made so far during the review period of the present paper an exploration well encountered oil and gas in triassic sandstones in the southwestern segment of the basin this is the first direct indication of a mature oil producing source rock in the nordkapp basin and will be important for future exploration of the basin

magnetic expression of salt diapir related structures in the nordkapp basin western barents sea high resolution aeromagnetic surveys in the nordkapp basin western barents sea demonstrate the capability of modern high resolution aeromagnetic surveys to provide an efficient and promising tool for mapping features related to salt diapirism salt diapirs are clearly visible by a small low amplitude negative round to ellipsoidal magnetic pattern this pattern coincides with shallow sedimentary layers deformed by the rising salt during active and passive diapirism the dimensions of these features coincide in shape and size with those interpreted on gravity and seismic surveys

the ch4 cycles on pluto over seasonal and astronomical timescales abstract pluto s surface is covered in numerous ch4 ice deposits that vary in texture and brightness as revealed by the new horizons spacecraft as it flew by pluto in july 2015 these observations suggest that ch4 on pluto has a complex history involving reservoirs of different composition thickness and stability controlled by volatile processes occurring on different timescales in order to interpret these observations we use a pluto volatile transport model able to simulate the cycles of n2 and ch4 ices over millions of years by assuming fixed solid mixing ratios we explore how changes in surface albedos emissivities and thermal inertias impact volatile transport this work is therefore a direct and natural continuation of the work by bertrand et al 2018 which only explored the n2 cycles results show that bright ch4 deposits can create cold traps for n2 ice outside sputnik planitia leading to a strong coupling between the n2 and ch4 cycles depending on the assumed albedo for ch4 ice the model predicts ch4 ice accumulation 1 at the same equatorial latitudes where the bladed terrain deposits are observed supporting the idea that these ch4 rich deposits are massive and perennial or 2 at mid latitudes 25 70 forming a thick mantle which is consistent with new horizons observations in our simulations both ch4 ice reservoirs are not in an equilibrium state and either one can dominate the other over long timescales depending on the assumptions made for the ch4 albedo this suggests that long term volatile transport exists between the observed reservoirs the model also reproduces the formation of n2 deposits at mid latitudes and in the equatorial depressions surrounding the bladed terrain deposits as observed by new horizons at the poles only seasonal ch4 and n2 deposits are obtained in pluto s current orbital configuration finally we show that pluto s atmosphere always contained over the last astronomical cycles enough gaseous ch4 to absorb most of the incoming lyman flux

climate zones on pluto and charon abstract we give an explanatory description of the unusual climate zones on pluto that arise from its high obliquity mean 115 and high amplitude 12 of obliquity oscillation over a 2 8 million year period the zones we describe have astronomically defined boundaries and do not incorporate atmospheric circulation for such a high mean obliquity the lines of tropics greatest latitudes where the sun can be overhead cycle closer to each pole than does each arctic circle which in turn cycle nearly to the equator as a consequence in an astronomical context pluto is more predominantly tropical than arctic up to 97 of pluto s surface area can experience overhead sun when the obliquity cycle is at its minimum of 103 at this same obliquity phase most recently occurring 0 8 myr ago 78 of pluto s surface experienced prolonged intervals without sunlight or arctic winter and corresponding arctic summer the intersection of these climate zones implies that a very broad range of pluto s latitudes spanning 13 77 in each hemisphere 75 of the total surface area are both tropical and arctic while some possible correlations to these climate zones are suggested by comparison with published maps of pluto and charon yielded by the new horizons mission in this work we present a non physical descriptive analysis only for example the planet wide dark equatorial band presented by stern et al 2015 science 350 292 299 corresponds to pluto s permanent diurnal zone in this zone spanning latitudes within 13 of the equator day night cycles occur each pluto rotation 6 4 days such that neither arctic winter nor arctic summer has been experienced in this zone for at least 20 million years the stability of this and other climate zones may extend over several gyr temperature modeling shows that the continuity of diurnal cycles in this region may be the key factor enabling a long term stability for the high albedo contrast between tombaugh regio adjacent to the dark cthulhu regio earle et al 2017 icarus special issue submitted all names are informal charon s synchronous alignment with pluto dictates that both bodies in the binary pair have the same climate zone structure but any effects on charon s morphology may be limited if volatile transport there is minimal or absent cold trapped methane rich volatiles on top of its water ice surface may be responsible for forming charon s dark red north polar cap grundy et al 2016b and we note the most concentrated area of this feature resides almost entirely within the permanent polar zone above 77 latitude where the sun never reaches the overhead point and arctic seasons have been most consistently experienced over at least tens of millions of years pluto is not alone among bodies in the kuiper belt and uranian satellites in having high obliquities overlapping tropical and arctic zones and latitude bands that remain in a continuous diurnal cycle over long terms

cenozoic erosion and sedimentation in the western barents sea abstract seismic reflection data and well logs are used to interpret cenozoic sedimentary environments in the south western barents sea using volumetric calculations and compaction trend analysis the cenozoic erosion and sedimentation rates have been quantified marine environments ranging from neritic to bathyal water depths dominated the southern barents sea during the late palaeocene at the palaeocene eocene boundary a southwards progradation commenced along the uplifted and eroded loppa and stappen highs during the early eocene to mid miocene sedimentation continued in the intracratonic basins as well as along the newly established continent ocean boundary in the embryonic northern norwegian greenland sea substantial erosion occurred on the westernmost margin particularly on the stappen high during this time interval in the mid miocene during a period of relative lowstand of sea level a system of lowstand fans was deposited west of the stappen high later a pronounced progradation of the shelf edge commenced during the mid miocene to late pliocene the shelf edge prograded between 20 and 40 km during the mid pliocene to early pleistocene the barents sea and adjacent land areas were uplifted a fluvial glaciofluvial drainage system developed on the continental shelf resulting in pronounced erosion there and very high sedimentation rates on the continental margin during the last 0 8 ma several large glaciations on the barents sea shelf proper have resulted in overdeepened troughs and high sedimentation rates at the continental shelfbreak and on the continental slope the overall cenozoic erosion varies spatially as well as temporally in the svalbard area close to 3 km of rocks have been eroded since the oligocene the same amount or more was eroded from the stappen high during the palaeocene and early neogene in the south western areas during the eocene mid miocene erosion occurred along the margin in addition the loppa high and adjacent areas served as sediment source areas during the late pliocene and pleistoncene the average erosion in the south western barents sea amounted to about 600 m erosion was greater in the south east than to the west and north and was more extensive where the former glacial ice streams had flowed

pluto s global surface composition through pixel by pixel hapke modeling of new horizons ralph leisa data abstract on july 14th 2015 nasa s new horizons mission gave us an unprecedented detailed view of the pluto system the complex compositional diversity of pluto s encounter hemisphere was revealed by the ralph leisa infrared spectrometer on board of new horizons we present compositional maps of pluto defining the spatial distribution of the abundance and textural properties of the volatiles methane and nitrogen ices and non volatiles water ice and tholin these results are obtained by applying a pixel by pixel hapke radiative transfer model to the leisa scans our analysis focuses mainly on the large scale latitudinal variations of methane and nitrogen ices and aims at setting observational constraints to volatile transport models specifically we find three latitudinal bands the first enriched in methane extends from the pole to 55 n the second dominated by nitrogen continues south to 35 n and the third composed again mainly of methane reaches 20 n we demonstrate that the distribution of volatiles across these surface units can be explained by differences in insolation over the past few decades the latitudinal pattern is broken by sputnik planitia a large reservoir of volatiles with nitrogen playing the most important role the physical properties of methane and nitrogen in this region are suggestive of the presence of a cold trap or possible volatile stratification furthermore our modeling results point to a possible sublimation transport of nitrogen from the northwest edge of sputnik planitia toward the south

interpretation of regional aeromagnetic data by the scaling function method the case of southern apennines italy a complex aeromagnetic anomaly in southern apennines italy is analysed and interpreted by a multiscale method based on the scaling function we use multiscale methods allowing analysis of a potential field along ridges which are lines defined by the position of the extrema of the field at the considered scales the method developed and applied in this paper is based on the study of the scaling function of the total magnetic field it allows recovering of source parameters such as depth and structural index the studied area includes a pleistocene volcanic structure mt vulture whose intense dipolar anomaly is superimposed on a longer wavelength regional anomaly the interpretation of ridges of the modulus of the analytic signal at different altitude ranges allows recognition of at least three distinct sources between about 5 km and 20 km depth their interpretation is discussed in light of borehole data and other geophysical constraints a reasonable geological model for these sources indicates the presence of intrusions probably linked to the past activity of mt vulture

methane distribution on pluto as mapped by the new horizons ralph mvic instrument abstract the data returned from nasa s new horizons spacecraft have given us an unprecedented detailed look at the pluto system new horizons ralph mvic multispectral visible imaging camera is composed of 7 independent ccd arrays on a single substrate among these are a red channel 540 700 nm near infrared channel 780 975 nm and narrow band methane channel 860 910 nm by comparing the relative reflectance of these channels we are able to produce high resolution methane equivalent width based on the 890 nm absorption band and spectral slope maps of pluto s surface from these maps we can then quantitatively study the relationships between methane distribution redness and other parameters like latitude and elevation we find pluto s surface to show a great diversity of terrains particularly in the equatorial region between 30 n and 30 s latitude methane equivalent width also shows some dependence on elevation while spectral slope shows very little

the source of the canary current in fall 2009 1 the source of the canary current has been inferred from an inverse box model applied to the hydrographic data of a survey carried out in 2009 in the northeast subtropical gyre 29 37 n 9 24 w the portugal current is observed between 13 5 and 14 8 w at 37 n carrying 1 8 0 4 sv southward this current presumably merges with the eastward transport of the azores current system and partly contributes to the mediterranean inflow and partly to the northward recirculation of the azores current through the gulf of cadiz the azores current system is located in the meridional range 33 50 36 25 n at 24 50 w this system transports eastward 7 2 0 5 sv in the thermocline layers and 1 1 0 8 sv at intermediate layers the azores current intermediate water mass has the highest portion of sub arctic intermediate water saiw in the region while the azores countercurrent intermediate waters mass is mainly mediterranean water the canary current extends from 22 25 to 18 50 w at 29 n the westernmost position ever observed this current transports southward 6 2 0 6 sv in the thermocline layers and 2 0 0 8 sv in the intermediate layers this intermediate flow shows a relative maximum of oxygen and a relative minimum in nutrient concentration indicating the presence of saiw the study concludes that at least in fall 2009 the canary current extends to the intermediate waters n 27 9220 approximately 1600 dbar and that azores current feeds the canary current at surface and intermediate layers

basin geometry and salt diapirs in the flinders ranges south australia insights gained from geologically constrained modelling of potential field data abstract the adelaide basin in australia is a complex of late neoproterozoic to early cambrian rift and sag basins which was inverted during the cambro ordovician delamerian orogeny the deposition of evaporitic sediments during the earliest stage of basin development in the late neoproterozoic willouran age played a major role in the subsequent tectonic evolution of the basin previous studies have shown that early mobilization vertical transport and withdrawal of the evaporites influenced the sedimentation during the late neoproterozoic and early cambrian the evaporites also influenced deformation during the inversion of the basin and the development of the delamerian fold and thrust belt however the control exerted by basement structures in the deposition of the evaporitic beds and the role of these tectonic structures in the later inversion of the basin have been poorly constrained in this work we use a combination of published and original geological observations along with the interpretation of potential field datasets total magnetic intensity and bouguer anomaly data to better constrain the geology of the basin at depth we construct two and a half dimensional forward models of the potential field data along selected profiles across the adelaide basin these models are constrained by the geology at the surface drill hole data and measured petrophysical properties specific gravity and magnetic susceptibility we achieved the best fit between observed and modelled potential fields with a model favouring thick skinned deformation where the diapirs are not randomly distributed but located directly above basement penetrating normal faults furthermore these normal faults were probably active during the sedimentation of the late neoproterozoic and early cambrian sediments and underwent partial or total inversion during the cambro ordovician delamerian orogeny mobilisation and withdrawal of the evaporites was therefore initiated and facilitated by the extension coeval with the opening of the basin and continued during the subsequent delamerian orogeny

salt diapirs of the southwest nordkapp basin analogue modelling the geometry and evolution of the salt diapirs in the southwestern segment of the nordkapp basin sw nkb were interpreted on reflection seismic data reflection seismic profiles were used to build

physical state and distribution of materials at the surface of pluto from new horizons leisa imaging spectrometer abstract from earth based observations pluto is known to be the host of n2 ch4 and co ices and also a dark red material very limited spatial distribution information is available from rotational visible and near infrared spectral curves obtained from hemispheric measurements in july 2015 the new horizons spacecraft reached pluto and its satellite system and recorded a large set of data the leisa spectro imager of the ralph instruments are dedicated to the study of the composition and physical state of the materials composing the surface in this paper we report a study of the distribution and physical state of the ices and non ice materials on pluto s illuminated surface and their mode and degree of mixing principal component analysis as well as various specific spectral indicators and correlation plots are used on the first set of 2 high resolution spectro images from the leisa instrument covering the whole illuminated face of pluto at the time of the new horizons encounter qualitative distribution maps have been obtained for the 4 main condensed molecules n2 ch4 co h2o as well as for the visible dark red material based on specific spectral indicators using either the strength or the position of absorption bands these 4 molecules are found to indicate the presence of 3 different types of ices n2 rich ch4 co ices ch4 rich co n2 ices and h2o ice the mixing lines between these ices and with the dark red material are studied using scatter plots between the various spectral indicators ch4 is mixed at the molecular level with n2 most probably also with co thus forming a ternary molecular mixture that follows its phase diagram with low solubility limits the occurrence of a n2 rich ch4 rich ices mixing line associated with a progressive decrease of the co ch4 ratio tells us that a fractionation sublimation sequence transforms one type of ice to the other forming either a n2 rich ch4 rich binary mixture at the surface or an upper ch4 rich ice crust that may hide the n2 rich ice below the strong ch4 rich h2o mixing line witnesses the subsequent sublimation of the ch4 rich ice lag left behind by the n2 co sublimation n spring summer or a direct condensation of ch4 ice on the cold h2o ice s autumn the weak mixing line between ch4 containing ices and the dark red material and the very sharp spatial transitions between these ices and this non volatile material are probably due to thermal incompatibility finally the occurrence of a h2o ice red material mixing line advocates for a spatial mixing of the red material covering h2o ice with possibly a small amount intimately mixed in water ice from this analysis of the different materials distribution and their relative mixing lines h2o ice appears to be the substratum on which other ices condense or non volatile organic material is deposited from the atmosphere n2 rich ices seem to evolve to ch4 dominated ices possibly still containing traces of co and n2 as n2 and co sublimate away the spatial distribution of these materials is very complex the high spatial definition of all these composition maps as well as those at even higher resolution that will be soon available will allow us to compare them with pluto s geologic features observed by lorri panchromatic and mvic multispectral imagers to better understand the geophysical processes in action at the surface of this astonishingly active frozen world

improved salt imaging in a basin context by high resolution potential field data nordkapp basin barents sea abstract the seismic imaging of salt diapirs in the nordkapp basin gave rise to considerable problems in defining their shape and volume independent information was added by integrating the interpretation with high resolution gravity and magnetic data we developed a novel iterative workflow separated into sub categories sediments salt structures basement and moho distinctions between the sources of the anomalies from different depths was achieved by utilizing the different decay characteristics of gravity gravity gradiometry and high resolution magnetic anomalies the workflow was applied to the southern part of the nordkapp basin it started with the sedimentary model derived from seismics populated with measured densities and magnetic susceptibilities and a starting model for the base salt the residual after the removal of this model was interpreted in terms of a crustal model including flexural isostatic calculations for the moho with the sedimentary load the residual after the removal of crustal and early sedimentary model was used to tune the salt model as these major and minor modelling steps depend on each other an iterative process was applied to stepwise improve the density and magnetic susceptibility model the first vertical gradient of gravity and the magnetic field were found to give most information about the cap rock of the diapirs the improvement in salt imaging integrated with results from controlled source electromagnetic and magneto telluric modelling is shown for the salt diapir uranus where a well terminated in the salt constrains the minimum of the depth to base salt

multiscale analysis of potential fields by a ridge consistency criterion the reconstruction of the bishop basement summary we use a multiscale approach as a semi automated interpreting tool of potential fields the depth to the source and the structural index are estimated in two steps first the depth to the source as the intersection of the field ridges lines built joining the extrema of the field at various altitudes and secondly the structural index by the scale function we introduce a new criterion called ridge consistency in this strategy the criterion is based on the principle that the structural index estimations on all the ridges converging towards the same source should be consistent if these estimates are significantly different field differentiation is used to lessen the interference effects from nearby sources or regional fields to obtain a consistent set of estimates in our multiscale framework vertical differentiation is naturally joint to the low pass filtering properties of the upward continuation so is a stable process before applying our criterion we studied carefully the errors on upward continuation caused by the finite size of the survey area to this end we analysed the complex magnetic synthetic case known as bishop model and evaluated the best extrapolation algorithm and the optimal width of the area extension needed to obtain accurate upward continuation afterwards we applied the method to the depth estimation of the whole bishop basement bathymetry the result is a good reconstruction of the complex basement and of the shape properties of the source at the estimated points

basins fractures and volcanoes global cartography and topography of pluto from new horizons abstract the 2015 new horizons flyby has produced the first high resolution maps of morphology and topography of pluto and charon the most distant objects so mapped global integrated mosaics of pluto were produced using both lorri framing camera and mvic line scan camera data showing the best resolution data obtained for all areas of the illuminated surface 78 of the body a unique feature of the pluto imaging data set is the observation of terrains illuminated only by light scattered from atmospheric haze allowing us to map terrains in the southern hemisphere that would otherwise have been in darkness mvic 4 color data were combined with the panchromatic map to produce full color global maps digital elevation models dems over 42 of pluto were produced using combinations of mvic hemispheric scans and lorri mosaics from which slopes at scales of 1 km can be determined pluto can be divided into regions each with distinct topographic signatures corresponding with major physiographic terrain types large areas of pluto are comprised of low relief moderately cratered plains units deeply pitted and glaciated plains east of sputnik planitia are elevated 0 7 km the most dominant topographic feature on pluto is the 1200 by 2000 km wide depression enclosing the bright sputnik planitia ice sheet the surface of which is 2 5 to 3 5 km deep relative to the rim and 2 km deep relative to the mean radius the partial ring of steep sided massifs several of which are more than 5 km high along the western margins of sputnik planitia produce some of the locally highest and steepest relief on pluto with slopes of 40 50 the second major topographic feature is a complex eroded ridge trough system 300 400 km wide and at least 3200 km long extending north to south along the 155 meridian this enormous structure has several kilometers of relief it may predate the large impact event forming the basin though some post sputnik planitia deformation is evident the large depressed partially walled plain hyecho palus lies due southwest of sputnik planitia near the center of hyecho palus lie the circular constructional edifices wright and piccard montes wright mons rises 4 5 km above these plains with a central depression 4 5 km deep whereas piccard mons best observed in haze light rises 5 5 km above the plains but has a bowl shaped central depression 5 5 km below the plains for a total relief of up to 11 km the greatest observed on pluto both of these features are interpreted as constructional volcanic in nature additional prominent topographic features include a 2 3 km high and 600 km wide dome centered on the illuminated iau pole and the amoeboidal plateaus of bladed terrains in the equatorial region which rise 2 5 km above local terrains and are the highest standing geologic units on the encounter hemisphere the mean elevations in the integrated dem for the two radio occultation areas are consistent with the 5 6 km difference in elevation as determined independently by the radio experiment and a limb profile near the egress point confirms the presence of elevated bladed terrains in that area local relief of 3 5 km at massifs troughs and pits supports conclusions that the icy shell of pluto is relatively rigid numerous examples of topographic control of ice or frost deposition occur across pluto including the distinct coloration of the polar dome the elevated terrains of eastern tombaugh regio and along the ridge trough system where ridge tops and fossae rims are covered in different ices than at lower elevations the topographic hypsogram of pluto s encounter hemisphere is strongly bimodal due to the large sputnik planitia depression otherwise the topographic signature of pluto is controlled by deviations from the otherwise dominant low plains including elevated bladed terrain plateaus and the depressed volcanic province including wright and piccard montes

the geology of pluto and charon through the eyes of new horizons nasa s new horizons spacecraft has revealed the complex geology of pluto and charon pluto s encounter hemisphere shows ongoing surface geological activity centered on a vast basin containing a thick layer of volatile ices that appears to be involved in convection and advection with a crater retention age no greater than 10 million years surrounding terrains show active glacial flow apparent transport and rotation of large buoyant water ice crustal blocks and pitting the latter likely caused by sublimation erosion and or collapse more enigmatic features include tall mounds with central depressions that are conceivably cryovolcanic and ridges with complex bladed textures pluto also has ancient cratered terrains up to 4 billion years old that are extensionally faulted and extensively mantled and perhaps eroded by glacial or other processes charon does not appear to be currently active but experienced major extensional tectonism and resurfacing probably cryovolcanic nearly 4 billion years ago impact crater populations on pluto and charon are not consistent with the steepest impactor size frequency distributions proposed for the kuiper belt

observed glacier and volatile distribution on pluto from atmosphere topography processes simulations of the levels of nitrogen methane and carbon monoxide over thousands of years confirm the existence of a nitrogen glacier in sputnik planitia pluto s deepest basin tanguy bertrand and francois forget have developed a model for volatile transport on pluto and use it to simulate the evolution of n2 ch4 and co on the dwarf plant over tens of thousands of earth years the model predicts n2 ice accumulation in the deepest low latitude basin and the threefold increase in atmospheric pressure that has been observed to occur since 1988 this points to atmospheric topographic processes as the origin of the prominent equatorial n2 glacier known as sputnik planitia formerly sputnik planum this is one of four papers on the geology of sputnik planitia in this issue of nature in news views amy barr puts these latest contributions into context pluto has a variety of surface frosts and landforms as well as a complex atmosphere1 there is ongoing geological activity related to the massive sputnik planitia glacier mostly made of nitrogen n2 ice mixed with solid carbon monoxide and methane2 covering the 4 kilometre deep 1 000 kilometre wide basin of sputnik planitia1 3 near the anti charon point the glacier has been suggested to arise from a source region connected to the deep interior or from a sink collecting the volatiles released planetwide1 thin deposits of n2 frost however were also detected at mid northern latitudes and methane ice was observed to cover most of pluto except for the darker frost free equatorial regions2 here we report numerical simulations of the evolution of n2 methane and carbon monoxide on pluto over thousands of years the model predicts n2 ice accumulation in the deepest low latitude basin and the threefold increase in atmospheric pressure that has been observed to occur since 19884 5 6 this points to atmospheric topographic processes as the origin of sputnik planitia s n2 glacier the same simulations also reproduce the observed quantities of volatiles in the atmosphere and show frosts of methane and sometimes n2 that seasonally cover the mid and high latitudes explaining the bright northern polar cap reported in the 1990s7 8 and the observed ice distribution in 20152 the model also predicts that most of these seasonal frosts should disappear in the next decade

the nitrogen cycles on pluto over seasonal and astronomical timescales abstract pluto s landscape is shaped by the endless condensation and sublimation cycles of the volatile ices covering its surface in particular the sputnik planitia ice sheet which is thought to be the main reservoir of nitrogen ice displays a large diversity of terrains with bright and dark plains small pits and troughs topographic depressions and evidences of recent and past glacial flows outside sputnik planitia new horizons also revealed numerous nitrogen ice deposits in the eastern side of tombaugh regio and at mid northern latitudes these observations suggest a complex history involving volatile and glacial processes occurring on different timescales we present numerical simulations of volatile transport on pluto performed with a model designed to simulate the nitrogen cycle over millions of years taking into account the changes of obliquity solar longitude of perihelion and eccentricity as experienced by pluto using this model we first explore how the volatile and glacial activity of nitrogen within sputnik planitia has been impacted by the diurnal seasonal and astronomical cycles of pluto results show that the obliquity dominates the n2 cycle and that over one obliquity cycle the latitudes of sputnik planitia between 25 s 30 n are dominated by n2 condensation while the northern regions between 30 n and 50 n are dominated by n2 sublimation we find that a net amount of 1 km of ice has sublimed at the northern edge of sputnik planitia during the last 2 millions of years it must have been compensated by a viscous flow of the thick ice sheet by comparing these results with the observed geology of sputnik planitia we can relate the formation of the small pits and the brightness of the ice at the center of sputnik planitia to the sublimation and condensation of ice occurring at the annual timescale while the glacial flows at its eastern edge and the erosion of the water ice mountains all around the ice sheet are instead related to the astronomical timescale we also perform simulations including a glacial flow scheme which shows that the sputnik planitia ice sheet is currently at its minimum extent at the northern and southern edges we also explore the stability of n2 ice deposits outside the latitudes and longitudes of the sputnik planitia basin results show that n2 ice is not stable at the poles but rather in the equatorial regions in particular in depressions where thick deposits may persist over tens of millions of years before being trapped in sputnik planitia finally another key result is that the minimum and maximum surface pressures obtained over the simulated millions of years remain in the range of milli pascals and pascals respectively this suggests that pluto never encountered conditions allowing liquid nitrogen to flow directly on its surface instead we suggest that the numerous geomorphological evidences of past liquid flow observed on pluto s surface are the result of liquid nitrogen that flowed at the base of thick ancient nitrogen glaciers which have since disappeared

enhancement and sharpening the migration images of the gravity field and its gradients potential field migration represents a rapid technique for imaging the subsurface based on gravity data however migration transformation usually produces a smooth and unfocused image of the targets due to the diffusive nature of the potential fields in this paper we introduce a method of the migration image enhancement and sharpening based on the application of the hybrid focusing stabilizer which combines the edge preserving smoothing filter with the minimum support functional the method is based on the model resolution matrix of the migration operator we also improve the migration image with a novel target oriented migration method the developed method of migration image enhancement and sharpening is illustrated by synthetic model studies and case studies the case study involves imaging the full tensor gravity gradient data collected in the nordkapp basin of the barents sea

overburden deformation patterns and mechanisms of salt diapir penetration in the central graben north sea abstract active and passive diapirism control the deformation and geometry of hydrocarbon traps in the overburden and a more detailed understanding of this process will help reservoir prediction and hydrocarbon recovery cores studies of seven central graben diapirs indicate zechstein salt penetrated late cretaceous chalk by extreme tectonic thinning with high angle 70 to bedding normal faulting tensile fracturing and pressure solution attenuation of the chalk significantly weakens the overburden allowing buoyancy forces to dome up the overburden doming created enough topography for downslope sliding of chalk slabs on slip planes parallel to bedding or in the case of the kyle diapir for chaotic debris flows of lithified chalk significant extensional bedding parallel faults and slump folds are developed within palaeocene shale on the diapiric flanks inter granular slip in unconsolidated clastic material was probably the dominant deformation mechanism diapirs have penetrated the palaeocene clastic sediments by maintaining topographic relief so that unlithified sediment continually slid off the crest producing translated intact rafts up to several tens of metres in thickness

concept of effective density key to gravity depth determinations for sedimentary basins the gravity anomaly observed over a layered sedimentary basin is close to that calculated over a basin with the same configuration and depth but filled by homogeneous sediments with density equal to the effective weighted average density of the real layered basin therefore it is possible to calculate the effective density contrast of a basin from the residual gravity anomaly over it if the depth of the basin is known at least at one point assuming a mathematical function for density depth dependence an expression for the gravity depth dependence using the infinite slab bouguer formula can be developed this expression makes it possible to calculate the depth of a basin or an isopach map from gravity data an exponential function and a new hyperbolic density depth function and their gravity depth functions are analyzed and implemented for determining the depths of basins from gravity data for the san jacinto graben california and the tucson basin southern arizona the hyperbolic functions are m

magnetic susceptibility of mesozoic and cenozoic sediments off mid norway and the role of siderite implications for interpretation of high resolution aeromagnetic anomalies abstract the study was designed to examine lithological and stratigraphic variations in magnetic susceptibility of the mesozoic and parts of the cenozoic sedimentary succession in petroleum exploration areas offshore norway and investigate the source of the susceptibility the study includes measurements of more than 6 km core from exploration wells and shallow drill sites with main focus on the northern north sea norwegian sea area considerable variation in susceptibility is detected and includes 1 average higher susceptibility in the finer grained lithologies and lowest susceptibility in mineralogically mature sandstones 2 relatively high susceptibility in upper jurassic cretaceous shaly sequences 3 provenance controls on susceptibility in triassic jurassic coarse clastic sediments 4 in all exploration wells positive correlation of high susceptibility to diagenetic siderite cementation the siderite cemented beds and nodules are of particular importance in controlling the susceptibility distribution in the dark shale units susceptibility log patterns from different sediment environments are also exemplified and can tentatively be divided into four types of patterns reflecting combinations of dispersed and concentrated mineral sources of susceptibility magnetic laboratory measurements verify presence of both paramagnetic and ferrimagnetic components in samples with high susceptibility values and with a dominance of the induced magnetisation

the deep crust beneath the trans european suture zone from a multiscale magnetic model we present a 3 d interpretation of the deep magnetic sources beneath the main geological structure of central eastern europe the trans european suture zone tesz we used a multiscale analysis of aeromagnetic data based on a multiscale data set generated by upward continuation of the european and mediterranean magnetic project data set from 5 to 100 km altitude we also computed the multiscale total gradient t of the multiscale field both of the multiscale data sets allow us to discriminate the main crustal contributions to the field at various scales and we showed that at large altitudes the field is dominated by the sole effect of the tesz the multiridge geometric method was very useful in studying the complex features of the main crustal interfaces either shallow or deep the interpreted interfaces are largely agreement with geological models based on seismic surveys and in some cases complete the models out of the analyzed region in order to estimate the deepest source depths in the tesz region we applied the multiridge method to the large scales 50 100 km altitude obtaining a set of singular points at depths ranging between 35 and 40 km considering the heat flow trend and the geological models around the tesz area we found a meaningful correspondence among the location of the estimated singular points and the most abrupt variations and complex morphology features of the moho boundary the multiridge estimates are consistent with known structural information and can be used for a 3 d representation of the moho depth along the tesz

the rapid formation of sputnik planitia early in pluto s history modelling suggests that the icy region on pluto known as sputnik planitia formed shortly after charon did and has since been stable with its latitude corresponding to a minimum in annual solar illumination and its longitude determined by tidal forces from charon douglas hamilton et al present modelling data that imply that pluto s sputnik planitia basin may be an ice cap rather than the product of an impact their data suggest that the feature formed shortly after pluto s largest satellite charon did and has since been stable with its latitude corresponding to a minimum in annual solar illumination over its orbital precession period of about a million years and its longitude determined by tidal forces from charon this is one of four papers on the geology of sputnik planitia in this issue of nature in news views amy barr puts these latest contributions into context pluto s sputnik planitia is a bright roughly circular feature that resembles a polar ice cap it is approximately 1 000 kilometres across and is centred on a latitude of 25 degrees north and a longitude of 175 degrees almost directly opposite the side of pluto that always faces charon as a result of tidal locking1 one explanation for its location includes the formation of a basin in a giant impact with subsequent upwelling of a dense interior ocean2 once the basin was established ice would naturally have accumulated there3 then provided that the basin was a positive gravity anomaly with or without the ocean true polar wander could have moved the feature towards the pluto charon tidal axis on the far side of pluto from charon2 4 here we report modelling that shows that ice quickly accumulates on pluto near latitudes of 30 degrees north and south even in the absence of a basin because averaged over its orbital period those are pluto s coldest regions within a million years of charon s formation ice deposits on pluto concentrate into a single cap centred near a latitude of 30 degrees owing to the runaway albedo effect this accumulation of ice causes a positive gravity signature that locks as pluto s rotation slows to a longitude directly opposite charon once locked charon raises a permanent tidal bulge on pluto which greatly enhances the gravity signature of the ice cap meanwhile the weight of the ice in sputnik planitia causes the crust under it to slump creating its own basin as has happened on earth in greenland5 even if the feature is now a modest negative gravity anomaly it remains locked in place because of the permanent tidal bulge raised by charon any movement of the feature away from 30 degrees latitude is countered by the preferential recondensation of ices near the coldest extremities of the cap therefore our modelling suggests that sputnik planitia formed shortly after charon did and has been stable albeit gradually losing volume over the age of the solar system

past epochs of significantly higher pressure atmospheres on pluto abstract pluto is known to have undergone thousands of cycles of obliquity change and polar precession these variations have a large and corresponding impact on the total average solar insolation reaching various places on pluto s surface as a function of time such changes could produce dramatic increases in surface pressure and may explain certain features observed by new horizons on pluto s surface including some that indicate the possibility of surface paleo liquids this paper is the first to discuss multiple lines of geomorphological evidence consistent with higher pressure epochs in pluto s geologic past and it also the first to provide a mechanism for potentially producing the requisite high pressure conditions needed for an environment that could support liquids on pluto the presence of such liquids and such conditions if borne out by future work would fundamentally affect our view of pluto s past climate volatile transport and geological evolution this paper motivates future more detailed climate modeling and geologic interpretation efforts in this area

global albedos of pluto and charon from lorri new horizons observations abstract the exploration of the pluto charon system by the new horizons spacecraft represents the first opportunity to understand the distribution of albedo and other photometric properties of the surfaces of objects in the solar system s third zone of distant ice rich bodies images of the entire illuminated surface of pluto and charon obtained by the long range reconnaissance imager lorri camera provide a global map of pluto that reveals surface albedo variegations larger than any other solar system world except for saturn s moon iapetus normal reflectances on pluto range from 0 08 1 0 and the low albedo areas of pluto are darker than any region of charon charon exhibits a much blander surface with normal reflectances ranging from 0 20 0 73 pluto s albedo features are well correlated with geologic features although some exogenous low albedo dust may be responsible for features seen to the west of the area informally named tombaugh regio the albedo patterns of both pluto and charon are latitudinally organized with the exception of tombaugh regio with darker regions concentrated at the pluto s equator and charon s northern pole the phase curve of pluto is similar to that of triton the large moon of neptune believed to be a captured kuiper belt object kbo while charon s is similar to that of the moon preliminary bond albedos are 0 25 0 03 for charon and 0 72 0 07 for pluto maps of an approximation to the bond albedo for both pluto and charon are presented for the first time our work shows a connection between very high albedo near unity and planetary activity a result that suggests the kbo eris may be currently active

uxo detection by multiscale potential field methods the choice of an effective interpretative methodology in terms of management costs timing reliability safety and efficiency is a key issue for the identification of unexploded ordnance uxo among geophysical methods magnetometry plays an important role in detection and interpretation of uxo objects we present a study aimed at the identification and characterization of buried uxo in rohoznik slovakia by a multiscale analysis on high resolution magnetic data the area is located close to a former army shooting range and is characterized by several buried uxo when a uxo hits the ground but does not explode the impact causes a re organization of the magnetic domains within the armature shock demagnetization due to shock demagnetization the object gets a magnetization oriented in the direction of the actual earth magnetic field furthermore the elongated shape of the uxo of rohoznik causes their anomalies to be oriented along the longitudinal axis of the projectiles our multiscale analysis was performed through methods such as depth from extreme points dexp and the multi ridge method the upward continuation employed by these two methods allowed reducing the influence of the high frequency noise related to non uxo buried iron objects also the use of high order derivatives in the multiscale approach decreased interference effects related to close by sources and avoided any pre filtering our approach was first validated on a test site located close to rohoznik where unexplored projectiles were buried with different orientations at a known depth then we focused on the real data of the former army shooting range for all our analyses we employed a structural index value of 2 5 which was estimated through the scaling function analysis and the derivative euler deconvolution algorithm both the dexp and multi ridge depth estimation methods proved to be effective and rapid with respect to more expensive and time consuming methods such as inversion our analysis revealed average depths for the analysed uxos matching rather well with what was found by subsequent excavations with a maximum discrepancy of a few decimetres

the messinian salinity crisis new seismic evidence in the west sardinian margin and eastern sardo provencal basin west mediterranean sea abstract we processed and interpreted a newly acquired geophysical dataset ws10 project integrated with vintage seismic profiles to study the evolution of the sardinian passive margin of the sardo provencal basin the most prominent features of the area of study are a consequence of the messinian salinity crisis msc which produced a thick salt layer in the deep basin complex halokinetic tectonics deformed the overlying messinian upper unit uu and the pliocene quaternary pq sediments sometimes also bending the sea bottom a thinner autochthonous salt in the uu suggests at least one further low stand during the late msc the messinian erosional surface mes separates the erosional truncation of the pre messinian sedimentary sequence from the overlaying plio pleistocene sequence with a clear angular discordance which almost completely masks possible earlier erosional events the mes is present across the middle and upper slopes of the sardinian margin and can be easily recognized down to the lower slope where it interfingers with the messinian evaporites which gradually thicken basinward we propose a correlation between the main erosional surface of the lower slope and the salt layer recognized in the uu as a consequence of a falling stage during the last part of the msc the seismic profiles now available along the west sardinian margin provide novel and crucial information to correlate the messinian depositional units in the deep basin with those present in the lower continental slope and with the erosional surface of the middle and upper slopes our data and interpretation highlight the main units of the messinian trilogy and further internal sequences that are probable related to cyclic fluctuations during their deposition

the pluto system initial results from its exploration by new horizons the pluto system was recently explored by nasa s new horizons spacecraft making closest approach on 14 july 2015 pluto s surface displays diverse landforms terrain ages albedos colors and composition gradients evidence is found for a water ice crust geologically young surface units surface ice convection wind streaks volatile transport and glacial flow pluto s atmosphere is highly extended with trace hydrocarbons a global haze layer and a surface pressure near 10 microbars pluto s diverse surface geology and long term activity raise fundamental questions about how small planets remain active many billions of years after formation pluto s large moon charon displays tectonics and evidence for a heterogeneous crustal composition its north pole displays puzzling dark terrain small satellites hydra and nix have higher albedos than expected

quasi synoptic transport budgets and water mass transformation in the azores gibraltar strait region during summer 2009 abstract we describe the circulation patterns in the azores gibraltar strait region north eastern atlantic during the 2009 caibox cruise on the basis of hydrographic and direct current velocity measurements this study offers new data for a region where importation of central waters subpolar and subtropical modes of eastern north atlantic central water and exports of mediterranean water are strongly related to large scale dynamics in the north atlantic ocean azores current mediterranean water system the description is backed up quantitatively by the results of a box inverse model which was used to obtain absolute water mass transport values consistent with thermal wind equations and with conservation of volume salt and heat the contributions of water masses were determined in an extended optimum multiparameter analysis from a quasi synoptic point of view providing detail in addition to volume salt and heat transport the surface subsurface large scale current system in the region consists of the azores current 13 1 2 5 sverdrup sv 1 sv 10 6 m 3 s 1 the azores counter current 5 2 2 1 sv the portugal current 4 5 1 4 sv and the canary current 7 1 1 1 sv broadly speaking central waters are imported into the caibox region at a rate of 1 6 0 9 sv and mediterranean water is exported at a rate of 1 5 0 4 sv the downwelling of central waters west of gibraltar strait was quantified at 1 1 sv not all this volume participates in mw formation but 0 8 sv of entrained central waters of which 0 5 sv are from central waters of subpolar origin and 0 3 sv from subtropical central waters of the 4 9 sv of subtropical central waters advected by the azores current about 0 7 sv would reach the gulf of cadiz region either to take part in central water entrainment or to flow across the gibraltar strait as part of the atlantic inflow to the mediterranean sea

seismic interpretation and characterization of anhydrite caprocks in the tromso basin sw barents sea abstract the origin of anhydrite caprocks found in many evaporite basins is currently under debate existing models in the literature for anhydrite formation include rotated stratigraphic layering rotated crestal caprock and diagenetic anhydrite in this work we interpret high quality 2d seismic reflection data to understand the processes associated with anhydrite caprock formation our study focuses on anhydrite caprock formation in the tromso basin which represents one of several underexplored salt basins in the arctic we use well log data and seismic stratigraphic as well as seismic attribute analyses to characterize the anhydrite layers associated with salt diapirs our results reveal that the anhydrite layers are high amplitude reflections at the crests which are often found close to the seabed and lateral caprocks on the flanks of salt diapirs a third class of anhydrite layers is folded faulted and boudinaged intrasalt stringers encased by the salt diapirs lateral caprocks in the tromso basin are formed in response to rotated crestal caprock failure the crestal caprocks are secondary in origin occur at shallow depths and are formed as insoluble residues from the dissolution of halite by the ingress of basinal fluids into the tops of diapirs anhydrite stringers or floaters originate from tectonic related multi dimensional salt flow salt diapirs in the tromso basin are associated with varied anhydrite caprocks their formation cannot be fully explained using a single model our work demonstrates from seismic reflection data the occurrence of caprock events that formed progressively on the flanks of salt diapirs due to local folding

focusing iterative migration of gravity gradiometry data acquired in the nordkapp basin barents sea abstract geological interpretation based on gravity gradiometry data constitutes a very challenging problem rigorous 3d inversion is the main technique used in quantitative interpretation of the gravity gradiometry data an alternative approach to the quantitative analysis of the gravity gradiometry data is based on 3d smooth potential field migration this rapid imaging approach however has the shortcomings of providing smooth images since it is based on direct integral transformation of the observed gravity tensor data another limitation of migration transformation is related to the fact that in a general case the gravity data generated by the migration image do not fit the observed data well in this paper we describe a new approach to rapid imaging that allows us to produce the density distribution which adequately describes the observed data and at the same time images the structures with anomalous densities having sharp boundaries this approach is based on the basic theory of potential field migration with a focusing stabilizer in the framework of regularized scheme which iteratively transfers the observed gravity tensor field into an image of the density distribution in the subsurface formations the results of gravity migration can also be considered as an a priori model for conventional inversion subsequently we demonstrate the practical application of migration imaging using both synthetic and real gravity gradiometry data sets acquired for the nordkapp basin in the barents sea

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

stable asymmetric ice belts in an energy balance model of pluto abstract in this paper we analyze a latitude dependent energy balance model with two dynamic ice lines between the north and south poles and consider results for a range of parameter values of which some may pertain to pluto our analysis shows that for any albedo contrast there exist stable ice line equilibria where the northern and southern edges are not symmetric about the equator in particular stable asymmetric ice belts can be found within the latitude ranges defined by sputnik planitia on pluto however we find that an ice belt with northern and southern edges defined by the northern and southern boundaries of sputnik planitia would be flowing to a symmetrical configuration for the parameter values used in this study