sedimentation organic maturity and petroleum potential of the oligocene miocene oil shale deposits yayu basin southwestern ethiopia studies initiated in the search for domestic energy supplies for ethiopia have confirmed the presence of oil shales in the yayu basin this article presents some of the characteristics of these shales the basin is located in the southwest of ethiopia and consists of precambrian basement and cenozoic volcanic and sedimentary rocks three sedimentary successions reach a cumulative maximum thickness of 165 m 541 ft two oil shale horizons have been identified in the upper and lower sedimentary successions and reach a maximum thickness of 35 and 20 m 115 and 65 ft respectively sedimentation in the basin occurred in fluvial and lacustrine depositional environments the sandstone facies was deposited in a fluvial environment whereas the oil shale bearing sediments were deposited in a lacustrine environment algal amorphous materials and minor amounts of woody materials characterize the studied oil shales with botryococcus and pediastrum indicating a lacustrine environment the studied oil shales are characterized by high total organic carbon values up to 61 2 and s2 hydrocarbon generating potential values ranging from 10 78 to 119 07 hc g kg indicating excellent source rocks most of the oil shales are at the immature to early mature stage for hydrocarbon generation vitrinite reflectance measurements on the oil shale samples are less reliable because of the presence of abundant algal materials gas chromatogram results also indicate source rocks the yayu basin is estimated to have up to 1 billion metric tons of oil shale reserves

shallow sub surface stratigraphy of the ganga basin himalayan foreland present status and future perspectives the ganga basin in northern india is one of the world s largest fluvial basins and has attracted enormous attention from earth scientists across the globe with a view to understanding large river processes and landforms despite the scarcity of hydrological data from the ganga basin some important studies have been carried out in the last several decades however the unavailability of deep sections in this vast alluvial tract has always limited understanding of the sub surface stratigraphy of these plains during the last decade some important developments have taken place in integrating exposed cliff section data with the drill cores in pre defined transects and with targeted geophysical investigations additionally new areas of the basin have been studied for understanding landscape evolution including the effects of active tectonics this special issue of quaternary international highlights some of these developments from the stratigraphic archives of this large basin this collection of papers covers a wide gamut of subjects including terrace development in the frontal parts of the ganga basin resistivity based mapping of sub surface stratigraphy micromorphology of soils from plains drill core samples historical scale avulsion of large dynamic system such as the kosi active tectonics and landform development in southern ganga plains and finally some policy issues for management of dynamic river systems this introductory paper provides a background and present status of research in the ganga basin it attempts to summarise some of the recent research developments in the ganga basin research and highlights the unresolved issues some of which have been addressed through the contributions in this special issue

fluvial facies model of the ganga river sediments india abstract the river ganga flows from the northwest to the southeast following the lineaments developed in response to the himalayan tectonics ganga sediments show a large number of facies developments throughout the study area from hardwar to kachhla the active channel deposits are marked by the development of large scale facies in gravel and coarse sand small scale facies comprising fine sand silt and clay are developed in inactive channel deposits and overbank deposits the depositional model shows a progressive decrease in particle size thickness of units and scale of cross bedded sets from the lower to the upper parts of sequences as well as from upstream to downstream the sedimentation of the ganga basin is seasonally and tectonically controlled

orthorhombic fault fracture patterns and non plane strain in a synthetic transfer zone during rifting lennard shelf canning basin western australia abstract a complex series of faults occur within transfer zones normal to the wnw trending rifted northern margin of the canning basin western australia these zones controlled basinal fluid flow and the formation of some carbonate hosted mississippi valley type zn pb deposits along the basin margin during devonian to carboniferous rifting the study area has a regional fault geometry similar to a synthetic overlapping transfer zone surface and underground mapping in this transfer zone combined with 3d modelling indicate the faults and related extension fractures have an orthorhombic geometry the orthorhombic fault fracture mesh developed in response to three dimensional non plane strain in which the intermediate finite extension magnitude was non zero pre mineralisation marine calcite fill in the fault fracture mesh indicates that it formed early in the deformation history later deformation that overprints the zn pb mineralisation and fault fracture mesh was associated with a different maximum extension direction and this modified and reactivated the faults with both dip slip and oblique slip movement and tilting of earlier structures the orthorhombic geometry is not observed at a regional scale 10 10 km indicating probable scale dependant behaviour this study indicates that this transfer zone developed either by 1 strain partitioning with synchronous strike slip structures and adjacent zones of non plane extension or 2 by a component of non plane extension sub parallel to the basin margin followed by subsequent transtensional overprint of the system preferred model synthetic overlapping transfer zones are inferred to be key regions where orthorhombic fault geometries may develop

gps tec technique for observation of the evolution of substorm particle precipitation 1 one of the signatures of magnetospheric substorms is the precipitation of high energy particles into the high latitude ionosphere in this paper we introduce a new method of tracking substorm particle precipitation using gps total electron content tec and provide some preliminary observations of precipitation signatures from application of this method using tec measurements from several gps receivers we examined particle precipitation signatures associated with two separate substorm events 4 october 2008 and 29 october 2008 and monitored the expansion of the high energy precipitation regions with a higher temporal and spatial resolution than previously available for each event we have observed tec signatures associated with substorm particle precipitation along 20 to 25 separate gps raypaths from up to 7 gps receivers located in the canadian arctic this is in addition to particle injection signatures found in cluster satellite data and precipitation signatures in ground based riometer data signature timing on different raypaths from different stations indicates a mainly northward tailward expansion of the precipitation injection region with a smaller westward azimuthal component for the events studied by applying a triangulation method we also calculated propagation velocity of the precipitation boundary in regions covered by our gps receivers for each substorm expansion velocity ranged from 0 3 2 km s northward and 0 1 km s westward and tended to decrease in magnitude at higher latitudes

a study of secondary pyrite deformation and calcite veins in safod damage zone with implications for aseismic creep deformation mechanism at depths 3 km abstract previous studies of the san andreas fault damage zone samples from the san andreas fault observatory at depth safod have identified a variety of tectonic microstructures including pressure solution cleavage calcite sealed fractures vein fabric and pyrite and anhydrite hydrothermal fracture sealing understanding the deformation provenance of the damage zone rocks and operative deformation mechanism s based on preserved microstructures provide insight into overall deformation behavior of the entire seismogenic zone in the creeping section of this transform fault we analysed the deformation of hydrothermal secondary pyrite in connection with network of calcite veins in a sample of foliated ultracataclasites bordering the actively creeping southwestern deforming zone sdz using sem ebsd and cl microscopy the results show that calcite veins associated with the pressure solution cleavage are crosscut by the secondary pyrite deformed under a range of p t conditions relatively undeformed secondary pyrite is found sealing implosion microbreccia our review of previously available data indicates that the damage zone rocks may represent a collage of structural and compositional domains from both locked and creeping sections of the saf this interpretation together with results of this study suggest that weak clay frictional deformation mechanism s is likely to be the predominant aseismic creep mechanism at depths below the safod

observational facts in revealing a close relation between acoustic gravity waves and midlatitude spread f the main purpose of this paper is to provide observational phenomena which show a close relation between acoustic gravity waves agws and blurred traces of hf doppler shifts this relationship is regarded as observational evidence of a close connection of agws with midlatitude spread f msf analyzed with six years of hf doppler records it is found that the frequency shift traces often become very blurred after local sunset and this kind of echo is reasonably assumed to be caused by ionospheric irregularities namely spread f in most of the cases these blurred echoes follow leading agws generally the periods of agws were in a range of 15 30 mins and the doppler frequency shifts were around or greater than 0 5 hz roughly equivalent to the amplitude of agw about 30 50 m s usually during local night when there were agws with larger amplitudes indicated by a frequency shift up to 0 5 hz and above the blurred echoes followed or overlapped them these phenomena lasted for hours in general then weakened gradually with the wavelike echoes still existing or having ceased of course this is not always the case in a few instances clear wavelike disturbances solely are without accompanying blurred echoes or blurred echoes occurred with only small amplitude waves ahead however it should be stressed that such exceptions were quite few statistics show that 23 5 of the total night time records were with blurred traces and 96 of blurred traces were accompanied with agws in this paper some typical examples are provided for different background such as typhoon volcano eruption and other situations whenever agws appeared these observations can be regarded as evidence of agws having a seeding role in exciting msf

gps tec variations in the polar cap ionosphere solar wind and imf dependence this statistical study examines the solar wind dependence of total electron content tec variations arising from mesoscale tens to hundreds of kilometers structuring of the polar cap ionosphere six years of tec measurements were collected from five high data rate global positioning system gps receivers of the canadian high arctic ionospheric network chain from which high resolution magnetic local time latitude maps of tec variation occurrence rate and amplitude were created ionosonde radars were used to identify tec variations arising from ionization of the e and f region ionospheres statistical tec maps were examined as a function of solar wind and interplanetary magnetic field imf measurements statistical results showed that occurrence rate of tec variations was highest in localized dayside regions with exact local time and latitude of peak occurrence depending primarily on the dayside coupling rate of the solar wind and magnetosphere as well as imf orientation and magnitude in the y z plane occurrence of tec variations throughout the polar cap increased with solar wind magnetosphere coupling rate and imf magnitude the solar wind dependence of occurrence rate largely reflected the location and rate of dayside magnetic reconnection and subsequent particle precipitation and polar cap convection amplitudes of tec variations were largest around noon and increased throughout the polar cap with increased solar wind magnetosphere coupling rate these statistical results improve upon the existing observational picture of the polar ionosphere and will potentially facilitate development of models and techniques for mitigating impacts of the polar ionosphere on navigation signals and communication links

three dimensional ionospheric tomography of post seismic perturbations produced by the denali earthquake from gps data summary the coupling between the solid earth and its atmosphere is responsible for vertically propagating infrasonic waves generated by seismic surface waves these pressure waves are amplified as they propagate upward and produce perturbations of ionospheric electron density the electron density perturbations above california due to the seismic surface waves generated by the denali earthquake on 2002 november 3 have been imaged from gps data by a tomographic method the integrated electron content along gps ray paths presents a noise level that is lower in the acoustic wave frequency band than in the gravity wave frequency band therefore the filtered gps data from californian networks are inverted for a tomographic reconstruction of electron density perturbations in the acoustic frequency band the inversion is properly resolved only in a small number of areas due to the geometry of gps ray paths in these areas a wave propagating upward at 1 2 0 3 km s 1 and horizontally at 4 1 km s 1 is observed with a timing consistent with an infrasonic wave generated by the path of seismic surface waves the discrepancies between the observed electron density perturbation structure and the expected infrasonic wave can be explained by the poor resolution of the inverse problem or by a simple model of interactions between the neutral wave and the plasma future development of dense gps networks and the advent of the galileo system will overcome the resolution problems and allow us to relate ionospheric perturbations to the seismic signal such a relation can be used to constrain the source and propagation of seismic waves as well as upper atmosphere characteristics

storm time observations of plasmasphere erosion flux in the magnetosphere and ionosphere plasmasphere erosion carries cold dense plasma of ionospheric origin in a storm enhanced density plume extending from dusk toward and through the noontime cusp and dayside magnetopause and back across polar latitudes in a polar tongue of ionization we examine dusk sector 20 mlt plasmasphere erosion during the 17 march 2013 storm dst 130 nt using simultaneous magnetically aligned direct sunward ion flux observations at high altitude by van allen probes rbsp a at 3 0 re and at ionospheric heights 840 km by dmsp f 18 plasma erosion occurs at both high and low altitudes where the subauroral polarization stream flow overlaps the outer plasmasphere at 20 ut rbsp a observed 1 2e12 m 2 s 1 erosion flux while dmsp f 18 observed 2e13 m 2 s 1 sunward flux we find close similarities at high and low altitudes between the erosion plume in both invariant latitude spatial extent and plasma characteristics

texture and mineralogy of sediments from the ganges brahmaputra meghna river system in the bengal basin bangladesh and their environmental implications the bengal basin bangladesh represents one of the most densely populated recent floodplains of the world the sediment flux through the basin is one of the highest on a global scale a significant portion of this sediment load find its sink in the basin itself because of its lower elevation and frequent flooding the textural mineralogical and chemical nature of the sediments thus have an important bearing on the environmental quality of the basin as well as for the bay of bengal

characteristics of gps tec variations in the polar cap ionosphere this paper presents statistical characteristics occurrence rate amplitude and frequency of low frequency 100 mhz variations in total electron content tec observed in the polar cap ionosphere tec variations were primarily associated with mesoscale tens to hundreds of kilometers ionization structures and were observed by five global positioning system gps receivers over a 6 year period 2009 2014 the altitude of ionization structures was estimated by using colocated ionosonde radars high data rate receivers combined with broad spatial coverage of multisatellite tec measurements provided high resolution magnetic local time latitude maps of tec variation characteristics which were examined as a function of solar cycle and season these high resolution maps improve upon the current observational picture of mesoscale structuring in the polar cap and provide accurate links to particular magnetospheric source regions occurrence of tec variations was consistently highest in dayside regions mapping to low latitude and plasma mantle boundary layers while largest amplitude tec variations were observed in dayside regions close to the polar cusp and lower latitudes around midnight occurrence and amplitude of tec variations increased significantly during the ascending phase of the solar cycle independent of solar wind conditions while seasonal statistics showed highest dayside occurrence and amplitude in winter months lowest in summer and highest nightside occurrence and amplitude around equinox a surprising result in the frequency distributions of tec variations was discrete frequencies of about 2 and 4 mhz which appeared to originate from regions corresponding to the plasma mantle immediately poleward of the polar cusp

middle and low latitude ionosphere response to 2015 st patrick s day geomagnetic storm this paper presents a study of the st patrick s day storm of 2015 with its ionospheric response at middle and low latitudes the effects of the storm in each longitudinal sector asian african american and pacific are characterized using global and regional electron content at the beginning of the storm one or two ionospheric positive storm effects are observed depending on the longitudinal zones after the main phase of the storm a strong decrease in ionization is observed at all longitudes lasting several days the american region exhibits the most remarkable increase in vertical total electron content vtec while in the asian sector the largest decrease in vtec is observed at low latitudes using spectral analysis we were able to separate the effects of the prompt penetration of the magnetospheric convection electric field ppef and of the disturbance dynamo electric field ddef on the basis of ground magnetic data concerning the ppef earth s magnetic field oscillations occur simultaneously in the asian african and american sectors during southward magnetization of the b z component of the interplanetary magnetic field concerning the ddef diurnal magnetic oscillations in the horizontal component h of the earth s magnetic field exhibit a behavior that is opposed to the regular one these diurnal oscillations are recognized to last several days in all longitudinal sectors the observational data obtained by all sensors used in the present paper can be interpreted on the basis of existing theoretical models

from sumatra 2004 to tohoku oki 2011 the systematic gps detection of the ionospheric signature induced by tsunamigenic earthquakes the recent tsunamigenic earthquake in tohoku 11 march 2011 strongly affirms one more time after the sumatra event 26 december 2004 the necessity to open new paradigms in oceanic monitoring detection of ionospheric anomalies following the sumatra tsunami demonstrated that ionosphere is sensitive to the tsunami propagation observations supported by modeling proved that tsunamigenic ionospheric anomalies are deterministic and reproducible by numerical modeling via the ocean neutral atmosphere ionosphere coupling mechanism in essence tsunami induces internal gravity waves propagating within the neutral atmosphere and detectable in the ionosphere most of the ionospheric anomalies produced by tsunamis were observed in the far field where the tsunami signature in the ionosphere is clearly identifiable in this work we highlight the early signature in the ionosphere produced by tsunamigenic earthquakes and observed by gps measuring the total electron content close to the epicenter we focus on the first hour after the seismic rupture we demonstrate that acoustic gravity waves generated at the epicenter by the direct vertical displacement of the source rupture and the gravity wave coupled with the tsunami can be discriminated with theoretical support we illustrate the systematic nature of those perturbations showing several observations nominally the ionospheric perturbation following the tsunamigenic earthquakes in sumatra on 26 december 2004 and 12 september 2007 in chile on 14 november 2007 in samoa on 29 september 2009 and the recent catastrophic tohoku oki event on 11 march 2011 based on the analytical description we provide tracks for further modeling efforts and clues for the interpretation of complex and thus often misleading observations the routine detection of the early ionospheric anomalies following the rupture highlights the role of ionospheric sounding in the future ocean monitoring and tsunami detection

ionospheric remote sensing of the denali earthquake rayleigh surface waves 1 using the global positioning system we have detected ionospheric disturbances associated with the long period rayleigh waves from the 2002 denali earthquake ms 7 9 the dense california gps networks allowed us to map the ionospheric perturbations and to compute the group velocity with a high spatial resolution above the pacific coasts due to a low sampling rate a large error in the velocity determination remains nonetheless it demonstrates that bi static remote sensing measurements of seismic waves with gps networks can be performed monostatic measurements with a dedicated satellite could possibly be used to record in the ionosphere surface waves originating from large earthquakes such a space based remote sensing of the local group velocity of rayleigh surface waves would effectively complement the seismic networks for high resolution global tomography of the earth s lithosphere

morphological features of ionospheric response to typhoon couplings between the ionosphere and meteorological events have been studied widely however most of them are individual case studies or correlation analyses and few are aiming at the full morphological features of the ionospheric response processes in this paper complete records of 24 strong typhoons from 1987 to 1992 were collected and comparison was made with corresponding ionospheric hf doppler shift data the main purpose of the present work is to find the temporal evolution of these responses and their common features by the merit of the continuities of hf doppler shift observation in time on the basis of the statistical analyses this paper reveals the common features of ionospheric responses to typhoon a summary of these characteristics is as follows 1 during the existing time of a typhoon there are almost always medium scale traveling ionospheric disturbances tids in the ionosphere especially when a strong typhoon is landing or near the coast of a mainland 2 these tids show quite clear periodicity and their periods vary with time and gradually grow longer 3 after sunset the wavelike disturbances with large magnitudes often excite the midlatitude spread f 4 the intense typhoon can cause the wavelike records of the doppler shift to show the s shaped echo tracing which means that the amplitudes of those waves are sufficiently large and 5 the sunrise like phenomena often appear in nonsunrise time during the period the typhoon exists the phenomena mentioned above are generally in agreement with the linear propagation theories of the acoustic gravity waves agws in the atmosphere a typhoon is surely one of the important ground sources of the wavelike disturbances in troposphere this source is very effective especially when a typhoon is landing on or near a mainland coast of course the morphological details of the ionospheric response to typhoon can by no means be completely identical every time in this study except for tids that almost always appear during all the typhoon events the other common features are not seen every time however we are certain that the phenomena summarized above are statistically the manifestation of the ionospheric response to typhoon since they appear much more frequently during periods influenced by typhoon

ionospheric gps total electron content tec disturbances triggered by the 26 december 2004 indian ocean tsunami 1 tsunami ionospheric disturbances tids of the 26 december 2004 mw 9 3 sumatra earthquake are detected by the total electron content tec of ground based receivers of the global positioning system gps in the indian ocean area it is found that the tsunami waves triggered atmospheric disturbances near the sea surface which then traveled upward with an average velocity of about 730 m s 2700 km hr into the ionosphere and significantly disturbed the electron density within it results further show that the tids which have maximum height of about 8 6 17 2 km periods of 10 20 min and horizontal wavelengths of 120 240 km travel away from the epicenter with an average horizontal speed of about 700 km hr 190 m s in the ionosphere

ionospheric ripples excited by superimposed wave fronts associated with rayleigh waves in the thermosphere 1 coseismic ionospheric disturbances cids associated with the 2011 tohoku earthquake off the pacific coast mw 9 0 tohoku eq were examined using total electron content and seismic wave data a faster cid propagated at 3 0 km s only in the west southwest while a slower cid propagated concentrically at 1 2 km s or slower from the tsunami source area taking the propagation speed and oscillation cycle into account the faster cid was associated with a rayleigh wave but the slower cid was associated with an acoustic or gravity wave the north south asymmetry of the cid associated with the rayleigh wave suggests that the rayleigh wave did not act as a point source of the acoustic wave because a point source propagating in all directions must produce symmetric cid in all directions therefore a superimposed wave front of acoustic waves was excited by the rayleigh wave and produced the north south asymmetry of the faster cid due to the magnetic inclination effect which is different from a well known north south asymmetry of cid excited at the epicenter on the other hand above and south of the tsunami source area the cid with a period of 4 min was excited by a point source located at the tsunami source area because atmospheric waves propagating from a point source produce north south asymmetry in the resulting cid

discriminating the tectonic and non tectonic contributions in the ionospheric signature of the 2011 mw7 1 dip slip van earthquake eastern turkey 1 it has previously been suggested that ionospheric perturbations triggered by large dip slip earthquakes might offer additional source parameter information compared to the information gathered from land observations based on 3d modeling of gps and glonass derived total electron content signals recorded during the 2011 van earthquake thrust intra plate event mw 7 1 turkey we confirm that coseismic ionospheric signals do contain important information about the earthquake source namely its slip mode moreover we show that part of the ionospheric signal initial polarity and amplitude distribution is not related to the earthquake source but is instead controlled by the geomagnetic field and the geometry of the global navigation satellite system satellites constellation ignoring these non tectonic effects would lead to an incorrect description of the earthquake source thus our work emphasizes the added caution that should be used when analyzing ionospheric signals for earthquake source studies

th pb and u pb dating of ore stage calcite and paleozoic fluid flow thorium 232 lead 208 and uranium 238 lead 206 radiometric ages for ore stage calcite show that mississippi valley type mvt ore deposits can form in distinct tectonic settings an age of 251 11 million years for the jumbo mine in kansas united states is in agreement with other ages for mvt deposits in the midcontinent of north america the similarity of ages of these deposits supports the concept that they formed in response to fluid flow during the late paleozoic alleghenian ouachita orogeny an age of 351 15 million years for twelve mile bore and bloodwood kapok deposits in australia indicates that these mvt ores were deposited in a rifting environment

gps total electron content variations associated with a polar cap arc 1 we report an example of total electron content tec variations using global positioning system gps measurements associated with a polar cap arc detected by an all sky imager and ionosonde at a polar cap station during the transit of the arc gps signals along the arc length showed an increase of 2 tec units whereas gps signals perpendicular to the arc showed only an increase of 0 3 tec units this indicates that the gps tec variations associated with a polar cap arc are dependent on the geometry of the gps raypaths with respect to the arc ionosonde measurements confirm that this arc was an e region feature at 110 km with peak electron density of 5 4 1011 el m3 estimated speed of the arc using a gps triangulation method was about 300 m s

ionospheric disturbances triggered by the 11 march 2011 m9 0 tohoku earthquake 1 an earthquake of magnitude 9 0 occurred near the east coast of honshu tohoku area japan producing overwhelming earth surface motions and inducing devastating tsunamis which then traveled into the ionosphere and significantly disturbed the electron density within it hereafter referred to as seismotraveling ionospheric disturbances stids the total electron content tec derived from nationwide gps receiving networks in japan and taiwan is employed to monitor stids triggered by seismic and tsunami waves of the tohoku earthquake the stids first appear as a disk shaped tec increase about 7 min after the earthquake occurrence centered at about 200 km east of the epicenter near the west edge of the japan trench fast propagating disturbances related to rayleigh waves quickly travel away from the epicenter along the main island of japan with a speed of 2 3 3 3 km s accompanied by sequences of concentric circular tec wavefronts and followed by circular ripples close to a tsunami speed of about 720 800 km h that travel away from the stid center these are the most remarkable stids ever observed where signatures of rayleigh waves tsunami waves etc simultaneously appear in the ionosphere

rayleigh wave signature in ionograms induced by strong earthquakes 1 after the magnitude 9 0 earthquake off the pacific coast of tohoku near the east coast of honshu japan which occurred on 11 march 2011 an unusual multiple cusp signature mcs was observed in ionograms at three ionosonde stations across japan to investigate the general characteristics of mcss we examined ionograms obtained during the period 1957 to 2011 from five ionosonde stations in japan after earthquakes with a seismic magnitude of 8 0 or greater a total of 43 such earthquakes occurred after 1957 as recorded in the database of the united states geological survey mcss were observed in 8 of 43 earthquakes allowing us to investigate the specific conditions of mcs appearance the appearance of mcss at different epicentral distances exhibits traveling characteristics at a velocity of 4 0 km s which is in the range of rayleigh waves there is a 7 min offset in delay time after the earthquake at each epicentral distance in the travel time diagram this offset is consistent with the propagation time of acoustic waves from the ground to the ionosphere launched by rayleigh waves mcss in ionograms provide a snapshot of vertical disturbances induced by a wave because the sweep time for the whole ionospheric echo traces is much shorter than the propagation time of acoustic waves the vertical scale of the disturbances is 10 30 km which corresponds to an acoustic wave period of 20 50 s at ionospheric heights

large amplitude gps tec variations associated with pc5 6 magnetic field variations observed on the ground and at geosynchronous orbit large amplitude variations in gps total electron content tec at pc5 6 6 67 mhz frequencies have been observed using a high data rate global positioning system gps receiver of the canadian high arctic ionospheric network tec variations with peak to peak amplitudes of 2 7 tec units 1 tecu 1016 el m 2 were observed over a 2 5 h period in the postnoon sector on 9 september 2011 during a period of high auroral activity within a moderate geomagnetic storm tec observations were from the sanikiluaq nunavut 56 54 n 280 77 e gps receiver located in the auroral region over this same time period compressional pc5 6 magnetic field variations were observed by the geosynchronous goes 13 magnetometer and the ground based sanikiluaq magnetometer goes 13 has a northern magnetic footprint in close proximity to sanikiluaq cross correlation analysis indicates that magnetic field and tec variations were possibly linked no natural hazards or nuclear explosions capable of exciting tec perturbations were reported on this day using a triangulation technique involving tec measurements of multiple gps satellites the propagation velocity of tec variations in the ionosphere was also calculated this calculation revealed two distinct events lower frequency 0 9 mhz tec variations that propagated westward consistent with the westward propagation of compressional pc5 waves observed by goes 13 and 15 satellites and higher frequency 3 3 mhz tec variations that propagated southward this is the first report of variations in ionospheric tec linked to satellite observations of pc5 6 ulf waves

upper regime parallel lamination as the result of turbulent sediment transport and low amplitude bed forms a series of laboratory experiments has been carried out in which parallel laminated deposits were produced from an upper regime plane bed the laminae had thicknesses of a few mm and could be traced continuously over distances up to the length and width of the depositional area 0 3 m by 1 5m fluctuations in bed elevation were measured both during deposition and at equilibrium much of the bed fluctuation occurs at time scales that are too long to be due directly to turbulence as most theories for lamina formation would require we suggest instead that extremely low amplitude bed forms are present even on apparently flat beds and that the migration of these bed forms produces laterally continuous lamination all the lamination produced in the laboratory experiments was normally graded using high speed photography it was observed that the normal grading results from rapid deposition of a layer of loosely packed coarse sand several grain diameters thick followed by the slow sieving out of a well packed surface layer of finer sand the initial deposition is the result of small scale turbulent fluctuations in boundary shear stress the sieving out that follows results in a smooth surface whose low friction coefficient temporarily inhibits further deposition we term this process glazing the alignment of small scale turbulent scour and fill structures along the paths traced by migrating bedform troughs produces laterally continuous parallel lamination

detection and modeling of rayleigh wave induced patterns in the ionosphere 1 global positioning system gps allows the detection of ionospheric disturbances associated with the vertical displacements of most of the major shallow seismic events we describe a method to model the time and space distributions of rayleigh wave induced total electron content tec patterns detected by a dense gps array we highlight the conditions for which a part of the ionospheric pattern can be directly measured at teleseismic distance and above the epicenter in particular a satellite elevation angle lower than 40 is a favorable condition to detect rayleigh wave induced ionospheric waves the coupling between the solid earth and its atmosphere is modeled by computing the normal modes of the solid earth atmosphere system we show the dependency of the coupling efficiency on various atmospheric conditions by summation of the normal modes we model the atmospheric perturbation triggered by a given earthquake this shows that a part of the observation is a rayleigh induced radiation pattern and therefore characteristic of the seismic rupture through atmosphere ionosphere coupling we model the ionospheric perturbation after the description of the local geomagnetic field anisotropic effects we show how the observation geometry is strongly affecting the radiation pattern this study deals with the related data for two earthquakes with far field and near field observations using the japanese gps network geonet after the 12 may 2008 wenchuan earthquake china and after the 25 september 2003 tokachi oki earthquake japan respectively waveforms and patterns are compared with the observed tec perturbations providing a new step toward the use of ionospheric data in seismological applications

gps detection of ionospheric perturbations following the january 17 1994 northridge earthquake sources such as atmospheric or buried explosions and shallow earthquakes producing strong vertical ground displacements are known to produce pressure waves that propagate at infrasonic speeds in the atmosphere at ionospheric altitudes low frequency acoustic waves are coupled to ionospheric gravity waves and induce variations in the ionospheric electron density using global positioning system gps data recorded by the permanent gps network operating in southern california we computed ionospheric electron content time series for several days preceding and following the january 17 1994 mw 6 7 northridge earthquake we observe an anomalous signal beginning several minutes after the earthquake with time delays that increase with distance from the epicenter the signal frequency and phase velocity are consistent with results from numerical models of atmospheric ionospheric acoustic gravity waves excited by seismic sources as well as previous electromagnetic sounding results we believe that these perturbations are caused by the ionospheric response to the strong ground displacement associated with the northridge earthquake

evolution of miocene fluvial environments eastern potwar plateau northern pakistan the miocene pliocene siwalik group records changing fluvial environments in the himalayan foreland basin the nagri and dhok pathan formations of this group in the eastern potwar plateau northern pakistan comprise relatively thick tens of metres sandstone bodies and mudstones that contain thinner sandstone bodies metres thick and palaeosols thick sandstone bodies extend for kilometres normal to palaeoflow and are composed of large scale stratasets storeys stacked laterally and vertically adjacent to each other sandstone bodies represent single or superimposed braided channel belts and large scale stratasets represent channel bars and fills channel belts had widths of km bankfull discharges on the order of 103 cumecs and braiding parameter up to about 3 individual channel segments had bankfull widths maximum depths and slopes on the order of 102 m 101 m and 10 4 respectively and sinuosities around 1 1 these rivers are comparable to many of those flowing over the megafans of the modern indo gangetic basin and a similar depositional setting is likely thin sandstone bodies within mudstone sequences extend laterally for on the order of 102 m and have lobe wedge sheet and channel form geometries they represent crevasse splays levees and floodplain channels mudstones are relatively bioturbated disrupted and represent mainly floodbasin and lacustrine deposition mudstones and sandstones are extremely disrupted in places showing evidence of prolonged pedogenesis these mature palaeosols are m thick and extend laterally for km lateral and vertical variations in the nature of their horizons apparently depend mainly on deposition rate the 500 m thick nagri formation has a greater proportion and thicker sandstone bodies than the overlying 700 m thick dhok pathan formation the thick sandstone bodies and their large scale stratasets thicken and coarsen through the nagri formation then thin and fine at the base of the dhok pathan formation compacted deposition rates increase with sandstone proportion 0 53 mm year for nagri 0 24 mm year for dhok pathan and palaeosols are not as well developed where deposition rates are high within both formations there are 100 m scale variations representing on the order of 105 years in the proportion and thickness of thick sandstone bodies and tens of m scale alternations of thick sandstone bodies and mudstone sandstone strata that represent on the order of 104 years formation scale stratal variations extend across the potwar plateau for at least 100 km although they may be diachronous however 100 m and smaller scale variations can only be traced laterally for up to tens of km alluvial architecture models indicate that increases in the proportion and thickness of thick sandstone bodies can be explained by increasing channel belt sizes mainly average deposition rate and avulsion frequency on a megafan comparable in size to modern examples 100 m scale variations in thick sandstone body proportion and thickness could result from regional shifts in the position of major channels possibly associated with fan lobes on a single megafan or with separate megafans however such variations could also be related to local changes in subsidence rate or changes in sediment supply to the megafan system formation scale and 100 m scale stratal variations are probably associated with interelated changes in tectonic uplift sediment supply and basin subsidence increased rates of hinterland uplift sediment supply and basin subsidence recorded by the nagri formation may have resulted in diversion of a relatively large river to the area alternatively changing river sizes and sediment supply rates may be related to climate changes affecting the hinterland possibly linked to tectonic uplift climate during deposition of the siwalik group was monsoonal although the deposits contain no direct evidence for climate change independent evidence indicates global cooling throughout the miocene and the possibility of glacial periods e g around 10 8 ma corresponding to base of nagri formation if the higher himalayas were periodically glaciated a mechanism would exist for varying sediment supply to megafans on time scales of 104 105 years although eustatic sea level changes are related to global climatic change they are not directly related to siwalik stratigraphic changes because the shoreline was many 100 km away during the miocene

two mode long distance propagation of coseismic ionosphere disturbances 1 using gps total electron content tec measurements we analyzed ionosphere response to the great kurile earthquake of 4 october 1994 high spatial resolution of the japanese dense array of gps receivers geonet provided us the unique opportunity to observe the evolution of coseismic ionospheric disturbances cid which propagated for more than 1800 km away from the epicenter plotting a traveltime diagram for the cid and using an array processing technique within the approximation of a spherical cid wavefront we observed a phenomenon of cid separation into two modes and we found that characteristics of the cid depend on the distance from the epicenter the maximum of the cid amplitude was observed at 500 km from the epicenter within the first 600 700 km the cid propagation velocity was about 1 km s which is equal to the sound speed at the height of the ionospheric f layer starting from 600 to 700 km out from the epicenter the disturbance seems to divide into two separate perturbations with each propagating at a different velocity about 3 km s for the one and about 600 m s for the other apparently the tec response in the far field of the cid source is a mixture of signals that further splits into two modes because of the difference in their velocities our observations are in good agreement with the results of space time data processing in the approximation of a spherical wavefront of cid propagation

high latitude gps tec changes associated with a sudden magnetospheric compression 1 using ionospheric total electron content tec measured by global positioning system gps receivers of the canadian high arctic ionospheric network chain we provide clear evidence for a systematic and propagating temporary tec enhancement produced by compression of the magnetosphere due to a sudden increase in solar wind dynamic pressure the magnetospheric compression is evident in themis goes satellite data application of a gps triangulation technique revealed that the tec changes propagated with a speed of 3 6 km s in the antisunward direction near noon and 8 km s in the sunward direction in the pre noon lower latitude sector characteristics of these tec changes along with riometer absorption measurements seems to indicate that the tec change is due to electron density enhancement in the f region and is possibly due to particle precipitation associated with sudden magnetospheric compression

tepee shaped agglutinated microbialites an example from a famennian carbonate platform on the lennard shelf northern canning basin western australia distinctive metre scale antiformal structures are well developed in a famennian carbonate platform in the chedda cliffs area of the lennard shelf reef complexes the structures are distinguished by chevron shaped crests and thickened cores and contain abundant non skeletal allochems ooids pisoids peloids and intraclasts of silt to pebble size and variably developed laminations and fenestrae the internal morphology and pervasive occurrence of fenestral clotted and wavy laminated fabrics suggest that these structures are microbial mounds composed of agglutinated stromatolites and thrombolites microbial fabrics most probably originated through sediment trapping and binding by microbial mats with early lithification involving microbial calcification and cementation of trapped sediment the facies and stratigraphic context of the mounds support a shallow subtidal transitional backreef to reef flat setting however alone these mounds do not provide unequivocal environmental information other large antiformal structures in famennian platforms on the lennard shelf previously described as tepee structures show morphological similarities to the chedda cliffs mounds which suggests that these other structures may also be microbial mounds the presence of microbial mounds in platform successions further highlights the importance of microbial communities in the lennard shelf reef complexes

multi instrument observation on co seismic ionospheric effects after great tohoku earthquake in this paper evidence of quake excited infrasonic waves is provided first by a multi instrument observation of japan s tohoku earthquake the observations of co seismic infrasonic waves are as follows 1 effects of surface oscillations are observed by local infrasonic detector and it seems these effects are due to surface oscillation excited infrasonic waves instead of direct influence of seismic vibration on the detector 2 these local excited infrasonic waves propagate upwards and correspond to ionospheric disturbances observed by doppler shift measurements and gps tec 3 interactions between electron density variation and currents in the ionosphere caused by infrasonic waves manifest as disturbances in the geomagnetic field observed via surface magnetogram 4 within 4 hours after this strong earthquake disturbances in the ionosphere related to arrivals of rayleigh waves were observed by doppler shift sounding three times over two of the arrivals were from epicenter along the minor arc of the great circle with the second arrival due to a rayleigh wave propagating completely around the planet and the other one from the opposite direction all of these seismo ionospheric effects observed by hf doppler shift appear after local arrivals of surface rayleigh waves with a time delay of 8 10 min this is the time required for infrasonic wave to propagate upwards to the ionosphere

100 kyr sedimentary record of marginal gangetic plain implications for forebulge tectonics abstract the gangetic foreland is a consequence of continent continent collision and formation of the himalayan thrust and fold belt in the more distal part of the peripheral gangetic foreland basin the late quaternary sedimentary architecture analysis from 17 stratigraphic successions together with optically stimulated luminescence dating osl divulge interaction of peripheral bulge tectonics and climate over the past 100 kyr these sections exhibit three sedimentary packages formed under different environmental conditions detailed vertical and lateral sedimentary architecture delineates nine lithofacies that are grouped into three facies associations i flood plain facies association ii channel facies association and iii interfluve facies association the basal package i 114 ka old was deposited by sandy meandering channels and overlying to this with a hiatus of 30 ka is package ii 80 54 ka deposited by gravelly rivers the sediments of both the packages i ii are derived from rocks exposed in the peripheral bulge region overlain package iii deposited by small meandering channels consist of the sediments derived from the himalaya the results indicate that the duration of 80 54 ka was a period of forebulge uplift when gravelly fans prograded basinward below the fan sediments lies a peripheral bulge unconformity marked by regionally significant pedogenic horizon this pedogenic horizon qualifies as to be termed as peripheral bulge uncomformity after 54 ka the fine himalayan sediments onlap the cratonic sediments implying rather a stable forebulge tectonics coupled with fluctuating climatic conditions occasionally bringing micaceous gray coloured sand silt of himalayan origin

nostradamus the radar that wanted to be a seismometer 1 surface waves emitted after large earthquakes are known to induce by dynamic coupling atmospheric infrasonic waves propagating upward through the neutral and ionized atmosphere those waves have been detected in the past at ionospheric heights using a variety of techniques such as hf doppler sounding or gps receivers the hf doppler technique particularly sensitive to the ionospheric signature of rayleigh waves is used here to show ionospheric perturbations consistent with the propagation of rayleigh wave phases r1 and r2 following the sumatra earthquake on the 28 march 2005 m 8 6 this is in our knowledge the first time that the phase r2 is detected by ionospheric sounding in addition we prove here that the ionospheric signature of r2 is also observed by over the horizon oth radar the latter was never used before to detect seismic signature in the ionosphere adding the oth radar to the list of the ionospheric seismometers we discuss and compare the performances of the three different instruments mentioned above namely hf doppler sounding gps receivers and oth radar

giant ionospheric disturbances excited by the m9 3 sumatra earthquake of 26 december 2004 1 an mw 9 3 earthquake originated in the indian ocean off the western coast of northern sumatra at 00 58 53 universal time ut on 26 december 2004 two giant ionospheric disturbances at 01 19 and 04 10 ut are observed by a network of digital doppler sounders in taiwan the first disturbance excited mainly by rayleigh waves which consists of a packet of short period doppler shift variations results in vertical ionospheric fluctuations with a maximum velocity of about 70 m s and displacement of about 200 m the second disturbance in a w shaped pulse propagating at a horizontal speed of 360 70 m s is attributable to coupling of the atmospheric gravity waves agw excited by broad crustal uplift together with the following big tsunami waves around the earthquake source zone the accompanying ionosonde data suggest that the agw in the atmosphere may have caused the ionosphere to move up and down by about 40 km

ionospheric and geomagnetic disturbances caused by the 2008 wenchuan earthquake a revisit previous works have shown that coseismic ionospheric disturbances cids after the tsunamigenic 2011 tohoku earthquake tohoku eq mw9 1 covered a vast area and were observed thousands of kilometers away from the epicenter for the purpose of making a comprehensive comparison between powerful oceanic and inland eqs we conduct a retrospective investigation of cids and geomagnetic responses to the 2008 wenchuan eq mw7 9 using a combination of techniques total electron content hf doppler and ground magnetometer it is the very first study to present cids recorded by different techniques at co located sites and profiled with regard to changes of both ionospheric plasma and current geomagnetic field simultaneously the integrated observation also shows that 1 in the wenchuan case most of the ionospheric and geomagnetic disturbances were observed within 1000 km distance which is far less than the tohoku case 2 two groups of cids were found with maximum amplitudes in the direction of azimuth 150 and 135 respectively and 3 the geomagnetic changes were only registered by three magnetometers located to the east and southeast of the epicenter all the facts indicate that the main directional lobe of wenchuan eq energy propagation is to southeast and perpendicular to the direction of the fault rupture but this kind of directivity is not that distinct in the tohoku case we suggest that the different fault slip inland or submarine affecting the way of couplings of lithosphere with atmosphere may contribute to the discrepancies between the two events

dolomite occurrence evolution and economically important associations abstract dolomite is not a simple mineral it can form as a primary precipitate a diagenetic replacement or as a hydrothermal metamorphic phase all that it requires is permeability a mechanism that facilitates fluid flow and a sufficient supply of magnesium dolomite can form in lakes on or beneath the shallow seafloor in zones of brine reflux and in early to late burial settings it may form from seawater from continental waters from the mixing of basinal brines the mixing of hypersaline brine with seawater or the mixing of seawater with meteoric water or via the cooling of basinal brines bacterial metabolism may aid the process of precipitation in settings where sulfate reducing species flourish and microbial action may control primary precipitation in some hypersaline anoxic lake settings dolomite is a metastable mineral early formed crystals can be replaced by later more stable phases with such replacements repeated a number of times during burial and metamorphism each new phase is formed by the partial or complete dissolution of an earlier dolomite this continual re equilibration during burial detracts from the ability of trace elements to indicate depositional conditions and resets the oxygen isotope signature of the dolomite at progressively higher temperatures because subsurface dolomite evolves via dissolution and reprecipitation a bed of dolomite can retain or create porosity and permeability to much greater burial depths and into higher temperature realms than a limestone counterpart dolomitization also creates new crystals with new rhomb growth following the dissolution of less stable precursors repetition of this process without complete pore cementation can generate intercrystalline porosity a number of times in the rock s burial history intercrystalline porosity is a highly interconnected style of porosity that gives dolomite reservoirs their good fluid storage capacity and efficient drainage the fact that many dolomite reservoirs formed via brine reflux means that they sit beneath an evaporite seal in both platform and basinwide evaporite settings the same association of evaporites sulfate source and entrained hydrocarbons means that burial conditions are also suitable for thermochemical sulfate reduction and the precipitation of base metals this tends to occur at higher temperatures 60 c 80 c and so the resulting dolomites tend to be ferroan and consist of saddle shaped crystals

highly seasonal and perennial fluvial facies implications for climatic control on the douglas creek and parachute creek members green river formation southeastern uinta basin utah u s a abstract the early to middle eocene green river formation consists of continental strata deposited in laramide ponded basins in utah colorado and wyoming this study 1 documents fluvial and lacustrine strata from the douglas creek and parachute creek members of the middle green river formation southeastern uinta basin utah and 2 uses new interpretations of the link between climate and fluvial sedimentary expression to interpret the terrestrial evolution of early eocene climate the stratigraphy was analyzed via outcrops along a 10 km transect in main canyon on the tavaputs plateau and is divided into three distinct stratigraphically separated depositional settings 1 the lowermost interval 1 is dominated by amalgamated sandstone channels that contain 70 100 upper flow regime sedimentary structures the channels are interpreted to represent fluvial deposits controlled by a highly seasonal climate where most deposition was limited to seasonal flooding events 2 interval 2 is dominated by alternating siliciclastic and carbonate lacustrine deposits interpreted as local pulsed fluvial siliciclastic input into shallow lake uinta and periods of fluvial quiescence represented by littoral carbonate deposition 3 the uppermost interval 3 is dominated by erosionally based trough cross bedded sandstone channels interbedded with littoral lacustrine and deltaic deposits the interval 3 sandstone channels are interpreted as perennial fluvial deposits with relatively little variation in annual discharge akin to modern humid temperate fluvial systems the stratigraphic transition from seasonally controlled interval 1 to perennial interval 3 fluvial deposits is interpreted to represent a fundamental shift in eocene climate from the peak hyperthermal regime of the early eocene climatic optimum eeco to a more stable post eeco climate

geostatistical cross association method used for the lithostratigraphic correlation of coal measure profiles abstract the case study from the early permian coal bearing barakar formation in the east bokaro sub basin of jharkhand india demonstrates that the non parametric geostatistical method of cross association can give a reliable lithostratigraphic correlation of borehole or outcrop profiles at a confidence level of at least 95 the inclusion of lithofacies details in the stratigraphic criteria does not necessarily enhance the correlation and may actually render it less reliable because the main lithological units vary internally on a local scale and their lateral variability is virtually irrelevant to basin scale correlation

interpreting complex fluvial channel and barform architecture carboniferous central pennine province northern england the bashkirian lower brimham grit of north yorkshire england is a fluvio deltaic sandstone succession that crops out as a complex series of pinnacles the three dimensional arrangement of which allows high resolution architectural analysis of genetically related lithofacies assemblages combined analysis of sedimentary graphic log profiles architectural panels and palaeocurrent data have enabled three dimensional geometrical relationships to be established for a suite of architectural elements so as to develop a comprehensive depositional model small scale observations of facies have been related to larger scale architectural elements to facilitate interpretation of the palaeoenvironment of deposition to a level of detail that has rarely been attempted previously thereby allowing interpretation of formative processes detailed architectural panels form the basis of a semi quantitative technique for recording the variety and complexity of the sedimentary lithofacies present their association within recognizable architectural elements and thus the inferred spatio temporal relationship of neighbouring elements fluvial channel fill elements bounded by erosional surfaces are characterized internally by a hierarchy of sets and cosets with subtly varying compositions textures and structures simple cross bedded sets represent in channel migration of isolated mesoforms dunes cosets of both trough and planar tabular cross bedded facies represent lateral accreting and downstream accreting macroforms bars characterized by highly variable yet predictable patterns of palaeocurrent indicators relationships between sandstone dominated strata bounded by third order and fifth order surfaces which represent in channel bar deposits and incised channel bases respectively chronicle the origin of the preserved succession in response to autocyclic barform development and abandonment major episodes of incision probably influenced by episodic tectonic subsidence differential tilting and fluvial incision associated with slip on the nearby north craven fault system overall the succession represents the preserved product of an upper delta plain system that was traversed by a migratory fluvial braid belt system comprising a poorly confined network of fluvial channels developed between major sandy barforms that evolved via combined lateral accretion and downstream accretion

is an unusual large enhancement of ionospheric electron density linked with the 2008 great wenchuan earthquake 1 on 12 may 2008 at 0628 ut a major earthquake ms 8 0 struck wenchuan county 31 0 n 103 4 e in southwest china the maximum ionospheric electron density at f2 peak nmf2 recorded an unusual large enhancement during the afternoon sunset sector by the chinese ionosondes over wuhan 30 5 n 114 4 e and xiamen 24 4 n 123 9 e which are close to the earthquake epicenter an averaged increase at these two stations is about 2 times on a geomagnetic quiet day 9 may kp 2 3 days prior to the earthquake relative to the median value of 1 12 may whereas the increase was much less significant over yamagawa 31 2 n 130 6 e and okinawa 26 7 n 128 2 e in japan combining the data from the network of 58 global positioning system receivers around china and the global ionospheric map the variations of the total electron content reveal the region where enhancement persisted for a long period to be within longitudes 90 130 e our results suggest that this abnormal enhancement is most possibly a seismo ionospheric signature

facies and architectural analysis of channel sandy macroforms in the upper parana river abstract the upper parana river in the area under analysis has a multichanneled pattern with many islands and channel bars channel bars are sandy macroforms classified as central and lateral bars this paper presents a sedimentological analysis of these bars according to their textures facies and facies architecture central bars are unstable deposits situated in the highest flow energy sites of the main channel with intensive processes of deposition and erosion they are composed of cross stratified medium to coarse sand sp and st facies lateral bars are very stable macroforms situated in the lower flow energy areas with no or very few erosional processes where flaser and climbing rippled fine sand to mud sr so fl and fm facies are the most common sediments

the influence of valley aggradation and listric normal faulting on styles of river avulsion a case study of the brazos river texas usa abstract the holocene avulsion history of the lower brazos alluvial valley of east texas usa was studied using 10 drill cores 26 radiocarbon dates aerial photos and a digital elevation model this study shows that two long term processes aggradation and localized valley tilting along a normal listric fault are responsible for generating two styles of avulsion the first process precedes avulsion by progradation while the second process precedes avulsion by annexation as valley aggradation migrated updip over the last 7 5 ka three regional backstepping avulsions occurred along the lower 140 km of the valley and each generated sizable deposits a pattern emerges of landward stepping progradational avulsions tracking the locus of valley aggradation and of valley aggradation migrating inland even after the rate of sea level rise diminishes at the same time several local nodal avulsions occurred between 50 and 55 km updip of the current highstand shoreline but generated no observable deposits geomorphic evidence indicates that since the late pleistocene active movement along a previously undocumented normal listric fault has occurred at the location of the nodal avulsion these two long term processes do not operate mutually exclusive of each other to promote avulsions rather they operate concurrently only aggradation promotes avulsions that affect floodplain alluviation although the total volume of these deposits comprises a small portion of the valley fill

detection of ruptures of andaman fault segments in the 2004 great sumatra earthquake with coseismic ionospheric disturbances 1 near field coseismic perturbations of ionospheric total electron content tec caused by direct acoustic waves from focal regions can be observed with global positioning system gps they appear 10 15 min after the earthquake with typical periods of 4 5 min and propagate as fast as 1 km s toward directions allowed by ambient geomagnetic fields ionospheric disturbance associated with the 2004 december 26 great sumatra andaman earthquake was recorded with nine continuous gps receiving stations in indonesia and thailand here we explore the possibility to constrain the rupture process of the earthquake with the observed ionospheric disturbances we assumed linearly distributed point sources along the zone of coseismic uplift extending 1300 km from sumatra to the andaman islands that excited acoustic waves sequentially as the rupture propagate northward by 2 5 km s tec variations for several satellite receiver pairs were synthesized by simulating the propagation of acoustic waves from the ground to the ionosphere and by integrating the tec perturbations at intersections of line of sights and the ray paths the tec perturbations from individual point sources were combined using realistic ratios and the total disturbances were compared with the observed signals prescribed ratios based on geodetically inferred coseismic uplifts reproduced the observed signals fairly well similar calculation using a rupture propagation speed of 1 7 km s degraded the fit suppression of acoustic waves from the segments north of the nicobar islands also resulted in a poor fit which suggests that ruptures in the northern half of the fault were slow enough to be overlooked in short period seismograms but fast enough to excite atmospheric acoustic waves coseismic ionospheric disturbance could serve as a new indicator of faulting sensitive to ruptures with timescale up to 4 5 min

halogens and noble gases in sedimentary formation waters and zn pb deposits a case study from the lennard shelf australia abstract halogen ratios br cl and i cl and concentrations provide important information about how sedimentary formation waters acquire their salinity but the possible influence of organic br derived from sedimentary wall rocks is rarely quantified here it is demonstrated that br cl versus i cl mixing diagrams can be used to deconvolve organic br contributions that organic matter has a limited range of br i ratios and that organic br is a more significant component in zn pb deposit ore fluids than previously recognised the significance of these findings is illustrated for the lennard shelf zn pb deposits of western australia fluid inclusions related to lennard shelf zn pb mineralisation have variable salinity and hydrocarbon contents the halogen data from these fluid inclusions require mixing of three fluid end members 1 an evaporated seawater bittern brine 30 wt nacl equiv with greater than seawater br cl ratio 2 a lower salinity pore fluid 5 wt nacl equiv with moderately elevated br cl and i cl and 3 fluids with br cl ratios of 5 times seawater and extremely elevated i cl ratios of 11 500 times seawater the first two fluids have 40 ar 36 ar of 300 400 and greater than air saturated water 36 ar concentrations that are typical of fluid inclusions related to zn pb mineralisation the third organic rich fluid has the highest 40 ar 36 ar ratio of up to 1500 and a depleted 36 ar concentration mineralisation is interpreted to have resulted from mixing of zn rich evaporitic brines and h 2 s present in hydrocarbons it is suggested that aqueous fluids acquired organic br and i from hydrocarbons and that hydrocarbons exsolving from the aqueous fluid removed noble gases from solution interaction of variably saline brines and hydrocarbons could account for the variable br cl and i cl composition and 36 ar concentrations recorded by lennard shelf fluid inclusions the distinct 40 ar 36 ar signature of the fluid with the highest i cl ratio suggests the hydrocarbons and brines were sourced independently from different parts of the sedimentary basin these data indicate the complementary nature of halogen and noble gas analysis and provide new constraints on important mixing processes during sediment hosted zn pb mineralisation

ionospheric gravity waves detected offshore hawaii after tsunamis 1 on board satellites techniques provide global coverage and could play an important role in the continuous oceanic survey to prevent the damage produced by powerful tsunamis we report here new ionospheric observations related to three significant transpacific tsunami events triggered by the 2006 kuril earthquake the 2009 samoa earthquake and the 2010 chile earthquake total electron content tec variations extracted from data recorded by a dense global positioning system gps network based in hawaii show ionospheric disturbances within the hours following the tsunami wave passage at sea level for each event we observe ionospheric gravity waves propagating with velocity direction and arrival time coherent with the tsunami the tsunamigenic signature in the ionosphere is also compared to in situ sea level measurements these observations provide new examples of the sensitivity of the ionosphere to tsunamigenic gravity waves and confirm that ionospheric monitoring by gps can provide complementary information on tsunami propagation

three dimensional waveform modeling of ionospheric signature induced by the 2004 sumatra tsunami 1 the sumatra december 26th 2004 tsunami produced internal gravity waves in the neutral atmosphere and large disturbances in the overlying ionospheric plasma to corroborate the tsunamigenic hypothesis of these perturbations we reproduce with a 3d numerical modeling of the ocean atmosphere ionosphere coupling the tsunami signature in the total electron content tec data measured by the jason 1 and topex poseidon satellite altimeters the agreement between the observed and synthetic tec shows that ionospheric remote sensing can provide new tools for offshore tsunami detection and monitoring

stratigraphy and static connectivity of braided fluvial deposits of the lower escanilla formation south central pyrenees spain this study addressed the architecture and dimension distributions of fluvial deposits of the olson member of the escanilla formation through analysis of outcrops in the southern buil syncline ainsa basin south central pyrenees spain the olson member consists of wide multistory channels alternating with mud rich intervals composed of flood plain deposits and isolated individual channels field descriptions and a combination of terrestrial light detection and ranging data and digital orthophotographs were used to map and document the abundance distribution and dimensions of sandstone bodies these data show that channels are distributed according to the local stratigraphic framework and differential subsiding areas morphology width depth and sinuosity of the channels throughout the sequence evolve according to their stratigraphic position during low accommodation periods channels stacked laterally forming wide multistory channel belts under these conditions single channels have a mean width to thickness w t ratio of 49 during high accommodation periods single channels have a mean w t ratio of 29 moreover the tendency of narrower and thicker channels having developed during high accommodation periods is also clearly observable vertically from the base to the top of high accommodation intervals throughout the sequence this pattern of deposition results in increasing vertical connectivity even in mud rich high accommodation periods a geocellular three dimensional model has been performed using object based simulations a succession of stochastic simulations was performed from the simplest one random simulations to more elaborated simulations integrating successively outcrop observations these simulations serve to image sandstone bodies connectivity evolution according to outcrop observations and sedimentologic knowledge subsurface application of such vertical channel morphology evolutions and distribution could lead to more predictive flow unit definitions and extensions

fluvial architecture of the upper permian raniganj coal measure in the damodar basin eastern india abstract the upper permian raniganj formation of the damodar basin consists of an interbedded assemblage of sandstone shale carbonaceous shale and coal facies the trough cross bedded sandstone bodies st facies formed by migration of dunes in sand bar point bars are widely developed in the lower part of raniganj formation the planar cross bedded facies sp of transverse and diagonal bars and massive sandstone of longitudinal bars abound in the upper part of the eastern raniganj and jharia coalfields the succeeding ripple cross laminated sr facies with or without reactivation surface alternating with thick beds of fine clastics suggestive of flood deposits is widespread in the western bokaro and north karanpura coalfields markov chain statistics reveals a fining upward cyclical order of superposition throughout the raniganj sequence the integrated results of paleocurrent channel morphology texture and petrography suggest that the raniganj sedimentation was brought about in an extensive unified alluvial plain drained by a system of west northwest flowing streams whose channel sinuosity increased and depth decreased progressively in a downcurrent direction from east to west post gondwana faulting and subsequent erosion account for the disconnected disposition of the coalfields

evolution of miocene fluvial systems in the himalayan foredeep through a two kilometer thick succession in northern pakistan abstract sedimentological variations through a kilometer thick coarsening upward succession in the miocene himalayan foredeep basin fluvial chinji and nagri formations of the siwalik group are documented in the chinji village area on the potwar plateau of northern pakistan from the chinji formation upwards into the nagri formation 1 the proportion of major sandstone bodies increase relative to mudstone dominated beds 2 average thickness and mean grainsize of channel deposits increase 3 sediment aggradation rates increase 4 there is a reported change in sediment providence 5 paleocurrents are generally to the southeast and vary little upsection and 6 paleosols are more distinct lower in the section where there is also more evidence of ponding of water on the floodplain smaller scale 100 m thick cyclic variations in the proportion of major channel sandstone bodies also occur in both formations in the modern himalayan basin sediment dispersal away from the mountain belt is associated with 1 major rivers that flow along the basin axis 2 large rivers that drain substantial areas of the mountain belt and deposit low relief sediment fans extending hundreds of kilometers into the basin and 3 smaller rivers in fan and interfan areas that drain local areas and carry finer sediment loads sediment variations through the chinji nagri formation boundary can be related to a shifting of depositional environments within such fan and interfan areas major basin axial rivers are not exposed in this area it appears that kilometer thick upsection variations in these deposits record the progradation of the sediment fan formed by a large river system river discharge on the order of 104 m3 s over the floodplain of a smaller river system river discharge on the order of 103 m3 s large scale vertical sediment variations over hundreds of meters to kilometers appear to reflect changes in the basin subsidence and the rate of sediment input to the basin over time scales on the order of 105 106 years upsection variations can not easily be related to climatic change or eustatic variations in sea level the most likely explanation for upsection changes is tectonism deposition rates and shifting positions of river systems within the basin responded more quickly to changes in basin subsidence rate whereas increases in the proportion of sandstone bodies and increases in floodplain slopes lagged behind deposit variations in the siwalik group clearly record variations between different scale river systems delivering sediment to the basin as well as the overall basin evolution

study of ionospheric response to the 4b flare on 28 october 2003 using international gps service network data 1 using the gps data from as many as 114 gps stations of the international gps service for geodynamics igs the morphological features of the ionospheric total electron content tec variations on the sunlit hemisphere during the 4b solar flare on 28 october 2003 is studied it is found that the strongest sudden increase of tec sitec happened during the flare and the magnitudes of sitec vary at regions with different local solar zenith angle sza in the northern hemisphere the tec enhancement is approximately symmetrical to the local noon and its value is usually greater than 14 tecu 1 tecu 1016 m2 if the sza is less than 60 on the whole as the sza increases the value of tec enhancement in the northern hemisphere decreases it is worth mentioning that even in the regions of sza between 90 and 100 the sitec was still seen from the temporal tec curves using a photochemical model the electron production rate over the sunlit boundary region is calculated and some obvious features of sitec over this region are analyzed in the polar region the effect of this flare on the ionosphere exceeds the effect of the ionospheric scintillations and it seems that the ionosphere in the northern polar region responses more sensitively to this flare in the end superimposed on the curves of the rate of tec change there are some small disturbances spikes synchronously appearing on all curves and thus indicating an existence of similar structures in the euv band of the flare

first ionospheric images of the seismic fault slip on the example of the tohoku oki earthquake 1 1hz gps measurements from the japanese gps network geonet allowed to retrieve information on the seismic fault of the great m9 0 tohoku oki earthquake from the ionosphere total electron content tec measurements the first arrival of the tec perturbation was registered 464 seconds after the earthquake 140 km on the east from the epicenter within next 45 seconds the distribution of ionospheric points imaged a rectangular area 37 39 39 28 n 142 8 143 73 e which coincides with the area of the coseismic crustal uplift from this source region the coseismic ionospheric perturbation further propagated at 1 3 1 5 km s such velocity values are 30 40 higher than previously reported for acoustic waves it is likely that we observed shock acoustic waves propagating at supersonic speed and having blown all the electrons available between the ground and the height of detection this fact is coherent with registration of the first arrival of perturbation 464 sec after the earthquake that is generally speaking too short time for a regular acoustic wave to reach the ionosphere our findings show that the real time gps monitoring of seismo active areas could inform about the parameters of coseismic crustal displacements and can be subsequently used for short term tsunami warnings in the case of the 03 11 2011 earthquake the first ionosphere perturbations were registered 17 minutes before the tsunami arrived on the east coast of honshu

a review of recent research in fluvial sedimentology this volume has been compiled to represent the current status of research into fluvial sedimentology as part of the proceedings for the 5th international conference on fluvial sedimentology 5icfs brisbane july 1993 the volume contains papers on a wide variety of topics representing the diversity of interests covered by the icfs this review serves to introduce these papers within the context of recent research post1988 in fluvial sedimentology icfs papers may be somewhat arbitrarily divided into those which report fundamental studies of sediment transport studies of modern alluvial and coastal systems studies of environmental management of fluvial systems facies analyses of ancient fluvial sequences studies of controls on alluvial stratigraphy and basin fill and applied sedimentological studies of fluvialhosted mineral resources it is interesting to compare the balance of papers in this volume with that of previous icfs volumes miall 1978 collinson and lewin 1983 ethridge et al 1987 marzo and puigdefabregas 1993 as a guide to changing emphasis in fluvial sedimentology figure 1 illustrates the distribution of papers over the five icfs meetings categorised as above among various trends two are worthy of comment the first being the marked peak in interest in controls on fluvial sequence and basin fill at the 4icfs and the second the influx of papers on environmental management in this volume although there has been a steady level of activity in fundamental aspects of sediment transport and bedform generation the rela

fluvial channel and overbank deposits from the westphalian of the durham coalfield ne england the westphalian upper carboniferous coal measures of the durham coalfield in ne england were deposited in lower and upper delta plain environments distributary channels crossed the plain and were separated by shallow interdistributary lakes and bays detailed observation of three dimensional 3 d opencast surface mine exposures in collaboration with subsurface borehole analysis has revealed the existence of five varieties of channel deposits and two associated overbank facies within the durham coal measures major distributary channels were the major avenues of sediment transport across the coal measures plain were variably sinuous mostly 1 2 km wide and deposited elongate belts of sand mostly up to 5 km wide proximal major crevasse splay channels formed by the breaching of major channel banks during flood events were straight sand filled and up to 400 m wide minor distributary channels formed by the sustained operation of such crevasses varied from straight to highly sinuous and deposited shoestring sand mud belts up to a few hundred metres wide minor crevasse channels generally straight and up to 50 m wide were formed through bank breaching of minor and in a few cases major distributaries distal feeder channels formed down palaeocurrent extensions of minor distributaries which supplied interdistributary minor delta subsystems were generally straight and up to 200 m wide of the two types of channel overbank levee deposits recognized one comprising thinly interbedded fine grained sandstone and siltstone claystone is mostly though not exclusively associated with major distributary channels the other consisting of massive siltstones with regularly spaced thin claystone bands is uniquely developed at the margins of minor distributary channels the lower part of the westphalian a succession in the northern pennines records a change in the depositional environment upwards from a lower to upper delta plain through this transition major channel deposits show evidence of having evolved from being of dominantly low sinuosity to being more variable in morphology channel sedimentation was profoundly influenced by regular possibly seasonal variations in flow stage and sediment load

parameters of seismic source as deduced from 1 hz ionospheric gps data case study of the 2011 tohoku oki event following the first time ionospheric imaging of a seismic fault here we perform a case study on retrieval of parameters of the extended seismic source ruptured during the great m9 0 tohoku oki earthquake using 1 hz ionospheric gps data from the japanese network of gps receivers geonet and several gps satellites we analyze spatiotemporal characteristics of coseismic ionospheric perturbations and we obtain information on the dimensions and location of the sea surface uplift seismic source we further assess the criterion for the successful determination of seismic parameters from the ionosphere the detection is possible when the line of sights from satellites to receivers cross the ionosphere above the seismic fault region besides we demonstrate that the multisegment structure of the seismic fault of the tohoku oki earthquake can be seen in high rate ionospheric gps data overall our results show that under certain conditions ionospheric gps derived tec measurements could complement the currently working systems or independent ionospherically based system might be developed in the future

sediment characteristics and transportation dynamics of the ganga river abstract understanding of river systems that have experienced various forcing mechanisms such as climate tectonics sea level fluctuations and their linkages is a major concern for fluvial scientists the 2525 km long ganga river derives its fluvial flux from northern part of the indian subcontinent and drops in the ganga brahmaputra delta and the bengal fan regions this paper presents a study of the ganga river sediments for their textural properties grainsize characteristics and transportation dynamics a suite of recently deposited sediments 189 bedload samples and 27 suspended load samples of the river and its tributaries was collected from 63 locations dry and wet sieve methods of grainsize analysis were performed and folk and ward s parameters were calculated transportation dynamics of the sediment load was assessed by means of channel hydrology flow sediment rating curves bedform mechanics grainsize images and cumulative curves textural properties of the bedload sediments of the ganga river tributaries originating from the himalaya orogenic belt the northern indian craton and the ganga alluvial plain regions are characterised by the predominance of fine to very fine sand medium to fine sand and very fine sand to clay respectively downstream textural variations in the bedload and suspended load sediments of the ganga river are therefore complex and are strongly influenced by lateral sediment inputs by the tributaries and channel slope at the base of the himalaya a very sharp gravel sand transition is present in which median grainsize of bedload sediments decreases from over 0 16 to 2 46 within a distance of 35 km downstream decline in mean grainsize of bedload sediments in the upper ganga river within the alluvial plain can be expressed by an exponential formula as mean grainsize in 0 0024 distance in kilometres from the himalayan front 1 29 it is a result of selective transport phenomena rather than of abrasion the condition attributed to channel competence with low gradient of 70 to 25 cm km coarsening of the bedload sediments in the middle segment of the river develops due to the coarse bedload sediments mean grainsize 1 8 2 2 supply from the tributaries of the northern indian craton region and increased unit stream power the ganga river sediments show a wide range of grainsize parameters bedload sediments mean grainsize 1 5 3 8 standard deviation 0 3 0 7 skewness 0 2 0 5 and kurtosis 0 8 2 4 suspended load sediments mean grainsize 2 9 5 0 standard deviation 0 6 1 6 skewness 0 6 0 4 and kurtosis 0 7 4 6 mean grainsize of the bedload sediments is 2 6 which is 1 3 units coarser than the suspended load sediments the cumulative grainsize curves of the bedload sediments show a distinct break in slope representing nearly 80 of the bedload sediment transported as graded suspension during the peak monsoon discharge most of the bedload sediments are transported as the discontinuous fine sandy graded suspension by the unidirectional unsteady shooting flow at a high transport rate about 8 106 tons d a model of sedimentation transportation at river channel is proposed the ganga river mobilises a total of 729 106 tons of sediments annually through a narrow zone within its river valley under the present hydrogeological conditions the river sedimentation is climatically controlled and is predicted to produce a 2000 km long 2 to 40 km wide and 25 to 50 m thick ribbon shaped well sorted symmetrically skewed fine sand body

teleseismic magnetic effects tmds of 2011 tohoku earthquake 1 anomalous magnetic variations were observed by ground magnetometers in east asia area after the 2011 tohoku earthquake some earlier reports showed that the seismo magnetic variations have obvious amplitude around the epicenter we emphasis here that the variations can still be notable at stations 2000 4000 km away from epicenter and we define it as teleseismic magnetic disturbances tmds tmds appear about 8 min later after the arrival of seismic rayleigh waves at teleseismic distances and propagate at a horizontal velocity of 3 9 0 1 km s the wave like tmds last for no longer than 10 min and have a main period of 2 1 3 3 min tmds are not generated by direct effects of processes in focal area crust or tsunami waves instead their properties consist with the rayleigh wave model of seismo ionospheric disturbances hence we conclude that the tmds are the magnetic manifestation of seismotraveling ionospheric disturbances stids generated by the interaction between the ionosphere and atmosphere through acoustic waves launched by traveling rayleigh waves our findings contribute to the knowledge of seismo electromagnetic effects in the atmosphere ionosphere system and further our understanding of couplings between various spheres of the earth

ionospheric disturbances infrasound waves over the czech republic excited by the 2011 tohoku earthquake 1 a train of large amplitude infrasound wave packets was observed by multipoint continuous doppler sounding system in the ionosphere over the czech republic on 11 march 2011 it is shown that these infrasound wave packets originated from vertical motion of the ground surface that was caused by arrival of seismic waves generated by the strong tohoku earthquake the infrasound wave packets were observed in the ionosphere at heights of 210 220 km about 9 min after the detection of corresponding wave packets on the ground which is consistent with the calculated time for vertically propagating infrasound waves absolute values of cross correlation coefficients between ionospheric and ground measurements are typically higher than 0 9 for two wave packets 0 98 the individual wave packets recorded on the ground have different observed horizontal velocities and correspond to different types of seismic waves a comparison of vertical velocities of ground motion with oscillation velocities of air particles in the ionosphere indicates that almost 1 10 of the infrasound energy flux excited at the ground reached the altitudes of 210 220 km for wave periods longer than 30 s estimates of sound attenuation are performed it is also shown that it is necessary to consider the value of electron density gradient at the reflection height of the sounding radio wave and air plasma compression owing to the infrasound wave to get reasonable estimates of oscillation velocities of air particles from doppler shift frequencies

exhalative mineralization in devonian reef complexes of the canning basin western australia lenticular stromatolite barite sulfide mounds interpreted as sedimentary exhalative deposits are exposed at several localities in devonian reef complexes of the canning basin western australia these mounds hundreds of meters long and tens of meters thick occur along contacts between basinal shales gogo formation and marginal slope limestones sadler limestone and adjacent to synsedimentary faults cutting the gogo formation the mounds are limestone buildups composed of stromatolites intergrown with barite and cut by iron sulfide veins the iron sulfides marcasite and pyrite are weathered to gossans at the surface they fill fissures that probably formed as a result of contemporary seismic activity and the early compaction of underlying and adjoining shales the stromatolite barite sulfide deposits also occur as allochthonous clasts in penecontemporaneous debris flow deposits postdepositional compaction of basinal shales in the gogo formation commonly amounted to about 75 percent this resulted in the expulsion of large volumes of fluids along permeable interbeds shale limestone contacts and synsedimentary faults reaching the sea floor as cool fluid seepages the expelled fluids carried dissolved carbonate barium iron and reduced sulfur they probably nourished chemosynthetic bacteria that mediated the deposition of stromatolites barite and iron sulfides resulting in growth of the stromatolite barite sulfide buildups there is no known economic mineralization in the exhalative buildups but some drill holes encountered minor uneconomic veins of epigenetic zn pb mineralization filling narrow fissures that postdate the exhalative deposits economic epigenetic zn pb deposits that have been mined elsewhere in the same general area of the canning basin were formed during the early carboniferous or latest devonian many millions of years after the exhalative deposits both exhalative and epigenetic phases of mineralization are thought to have been sourced through the compaction driven dewatering of shales the exhalative deposits are interpreted to have formed over seepages of cool fluids having salinities close to that of seawater whereas the epigenetic deposits formed from much hotter fluids probably brines expelled during subsequent shale compaction

strike slip earthquakes can also be detected in the ionosphere it is generally assumed that co seismic ionospheric disturbances are generated by large vertical static displacements of the ground during an earthquake consequently it is expected that co seismic ionospheric disturbances are only observable after earthquakes with a significant dip slip component therefore earthquakes dominated by strike slip motion i e with very little vertical co seismic component are not expected to generate ionospheric perturbations in this work we use total electron content tec measurements from ground based gnss receivers to study ionospheric response to six recent largest strike slip earthquakes the mw7 8 kunlun earthquake of 14 november 2001 the mw8 1 macquarie earthquake of 23 december 2004 the sumatra earthquake doublet mw8 6 and mw8 2 of 11 april 2012 the mw7 7 balochistan earthquake of 24 september 2013 and the mw 7 7 scotia sea earthquake of 17 november 2013 we show that large strike slip earthquakes generate large ionospheric perturbations of amplitude comparable with those induced by dip slip earthquakes of equivalent magnitude we consider that in the absence of significant vertical static co seismic displacements of the ground other seismological parameters primarily the magnitude of co seismic horizontal displacements seismic fault dimensions seismic slip may contribute in generation of large amplitude ionospheric perturbations

structurally controlled hydrothermal dolomite reservoir facies an overview structurally controlled hydrothermal dolomite htd reservoir facies and associated productive leached limestones are major hydrocarbon producers in north america and are receiving increased exploration attention globally they include multiple trends in the ordovician locally silurian and devonian of the michigan appalachian and other basins of eastern canada and the united states and in the devonian and mississippian of the western canada sedimentary basin they also occur in jurassic hosts along rifted atlantic margins in the jurassic cretaceous of the arabian gulf region and elsewhere hydrothermal dolomitization is defined as dolomitization occurring under burial conditions commonly at shallow depths by fluids typically very saline with temperature and pressure t and p higher than the ambient t and p of the host formation the latter commonly is limestone proof of a hydrothermal origin for htd reservoir facies requires integration of burial thermal history plots fluid inclusion temperature data and constraints on timing of emplacement hydrothermal dolomite reservoir facies are part of a spectrum of hydrothermal mineral deposits that include sedimentary exhalative lead zinc ore bodies and htd hosted mississippi valley type sulfide deposits all three hydrothermal deposits show a strong structural control by extensional and or strike slip wrench faults with fluid flow typically focused at transtensional and dilational structural sites and in the hanging wall transtensional sags above negative flower structures on wrench faults are favored drilling sites for htd reservoir facies saddle dolomite in both replacive and void filling modes is characteristic of htd facies for many reservoirs matrix replacive dolomite and saddle dolomite appear to have formed near contemporaneously and from the same fluid and temperature conditions the original host facies exerts a major influence on the lateral extent of dolomitization resultant textures pore type and pore volume breccias zebra fabrics shear microfractures and other rock characteristics record short term shear stress and pore fluid pressure transients particularly proximal to active faults high temperature hydrothermal pulses may alter kerogen in host limestones a process designated forced maturation basement highs underlying sandstone and or carbonate aquifers probably overpressured and overlying and internal shale seals and aquitards also may constrain or influence htd emplacement although many questions and uncertainties remain particularly in terms of mg and brine source and mass balance recognition and active exploration of the htd play continues to expand increasing use of three dimensional seismic imagery and seismic anomaly mapping combined with horizontal drilling oblique to linear trends defined by structural sags helps to reduce risk