open co2 underground water system in the west carpathians south poland chemical and isotopic evidence in the open co2 water system 13c of the total dissolved carbonate i e 13c tdc is pco2 and 13c co2 g dependent as tdc is pco2 dependent the variation of 13c tdc in such a system is described by the following equilibrium equation 13c tdc 13c co2 g 1000 0 h2co03 0k1 hco 3 h 0k1k2 co2 3 h 21 h2co03 k1 hco 3 h k1k2 co2 3 h 2 1000 chemical and isotopic data of waters in the west carpathians south poland when subjected to the necessary computation reflect properties of a system open to co2 pco2 of the waters of interest at the earth s surface is close to 1 2 atm their initial chemical speciation has been assigned to this value using program phreeqe then 13c values of dissolved carbonate species in the waters were calculated according to the wigley plummer pearson procedure to obtain the value for 13cf tdc which corresponds to pco2 1 2 atm resulting 13cf tdc values when plotted as a function of tdcf and phf fall well between two curves independently derived for 13c co2 g 1 and 3 and pco2 1 2 atm t 10 c and i 0 1 this implies that waters from the west carpathians are under almost constant co2 pressure and constant 13c co2 g moreover it suggests that a single origin of co2 is quite possible

travertine precipitation in the paleoproterozoic kuetsjarvi sedimentary formation pechenga greenstone belt ne fennoscandian shield abstract precambrian travertines tufas and speleothems either formed rarely or they have not been identified in previous studies in the absence of high pco2 soils in paleoproterozoic karst solution and speleothem formation occurred by processes distinct from those commonly found in present day low temperature karst environments however the high pco2 atmosphere could itself have encouraged karst formation the paleoproterozoic kuetsjarvi sedimentary formation of the pechenga greenstone belt nw russia includes abundant terrestrial carbonate precipitates these precipitates were sampled from a drillcore representing a complete section of the ca 120 m thick formation and were investigated for c and o isotopes acid soluble elemental contents and petrography the newly obtained results were used to constrain the origins of the precipitates and to illuminate different terrestrial carbonate types the investigated drillcore includes abundant small scale cavities and veins which are commonly filled with dolomite and quartz dolomite crusts are found both in the cavities and on bedding erosional surfaces dolomite cements coat uneven surfaces and surficial rock fragments the surficial dolomite crusts form distinct and discrete layers whereas the cements do not the cavity and vein fills are likely post depositional in origin whereas the surficial dolomite crusts and dolomite cements are likely syn depositional precipitates the investigated precipitates often show 13c values lower than those reported from their host rocks suggesting the influence of an external carbon source petrographic features and geochemical data suggest dissolution and precipitation of carbonate material originating from deep sourced co2 bearing fluids likely at high earth surface temperatures

the north sea silverpit crater impact structure or pull apart basin the silverpit crater consists of a set of concentric faults up to 20 km in diameter in the southern north sea although formerly described as the first impact structure to be recognized in the uk its spatial association with local tectonic and stratigraphic features suggests that it is unlikely to have been caused by a random extra terrestrial event this paper proposes a terrestrial origin for the silverpit crater as a palaeogene pull apart basin linked to strike slip faulting in the carboniferous basement faulting and thinning of permian evaporites underlying the crater acted as a buffer to basement extension and caused both a flexural collapse of the overlying triassic strata and circumferential listric faulting in the cretaceous succession reactive diapirism in lower jurassic shales may have contributed to the formation of a central uplift at base cretaceous level the paper compares the tectonic setting of two contemporaneous strike slip related structures in southern england bovey basin in devon and the compton valence structure in dorset with that of the silverpit crater and concludes by briefly considering whether a pull apart model can help to explain the formation of upheaval dome a similar putative impact structure in the canyonlands national park of utah

an analysis of the quiet time day to day variability in the formation of postsunset equatorial plasma bubbles in the southeast asian region presented is an analysis of the occurrence of postsunset equatorial plasma bubbles epbs detected using a global positioning system gps receiver at vanimo the three year data set shows that the epb occurrence maximizes minimizes during the equinoxes solstices in good agreement with previous findings the vanimo ionosonde station is used with the gps receiver in an analysis of the day to day epb occurrence variability during the 2000 equinox period a superposed epoch analysis sea reveals that the altitude and the change in altitude of the f layer height is 1 standard deviation 1 larger on the days for which epbs were detected compared to non epb days these results are then compared to results from the thermosphere ionosphere electrodynamics general circulation model tiegcm which show strong similarities with the observations the tiegcm is used to calculate the flux tube integrated rayleigh taylor r t instability linear growth rate a sea reveals that the modeled r t growth rate is 1 higher on average for epb days compared to non epb days and that the upward plasma drift is the most dominant contributor it is further demonstrated that the tiegcm s success in describing the observed daily epb variability during the scintillation season resides in the variations caused by geomagnetic activity as parameterized by kp rather than solar euv flux as parameterized by f10 7 geomagnetic activity varies the modeled high latitude plasma convection and the associated joule heating that affects the low latitude f region dynamo and consequently the equatorial upward plasma drift key points day to day epb occurrence in southeast asia investigated using ground based gps tiegcm exhibits similiar daily variability to the epb observations small changes in kp strongly influence daily epb occurrence variability

discussion on an eocene age for the proposed silverpit impact crater journal vol 165 781 794 a recent paper in the jgs wall et al 2008 presented a reassessment of seismic data predicated on the assumption that the structure known as the silverpit crater was formed by a meteorite impact stewart allen 2002 this speculative hypothesis is merely based on a perceived similarity between the morphology of the silverpit crater and impact craters and has no scientific support stewart allen 2002 dated the geological event that formed the circular faults mapped at the top chalk level by taking the lowest seismic reflector not affected by the faulting apart from minor accommodation to represent the latest date before which the faulting must have occurred the unjustified assertion made now is that all coherent seismic events below the reflector cf wall et al 2008 fig 5 and top chalk are sea bed multiples in particular the package mu wall et al 2008 however the time interval between the possible sea bed multiple a strong peak just above the base of the sequence and the primary from which it may have been derived the trough picked as ha decreases up dip there is no indication from other published profiles of the area that the sea depth changes rapidly enough to cause such convergence nor could it be due to a migration effect because the actual dips about 4 5 are too shallow furthermore coherent reflectors on other profiles wall et al 2008 fig 8 to the ese of the crater fig 4 to the nw of the crater fig 5b to the right

early diagenetic processes during mn carbonate formation evidence from the isotopic composition of authigenic ca rhodochrosites of the baltic sea the formation of authigenic ca rich rhodochrosite acr in sapropelic sediments of the gotland basin baltic sea is governed by deepwater renewal processes whereby saline water from the north atlantic flushes the brackish anoxic baltic deeps the carbon and oxygen isotopic compositions of these mn carbonates suggest that acr formation takes place just below the sediment surface and that dissolved compounds from the deepwater column such as water and bicarbonate molecules were incorporated in acr during authigenesis porewaters near the sediment surface display 18 o values of 5 4 vsmow and are generally depleted in 18 o compared to the oxygen isotopic composition of water in equilibrium with mn carbonate solid solutions acr 18 o values are 4 6 this suggests that early burial diagenetic processes significantly modify the initial isotopic composition of water during mn carbonate formation the reduction of sulfate having 18 o values of 8 4 accounts for a permanent enrichment of porewater 18 o and observed 18 o values at depth equal to 4 6 however this process does not explain the observed disequilibrium in the oxygen isotopic composition between water and acr close to the sediment surface where mn carbonate formation takes place based on isotopic mass balance calculations we suggest that mno2 with 18 o values of 8 9 released oxygen enriched in 18 o into the anoxic porewaters close below the sediment surface this process should occur after oxygenation events during deepwater renewal when mno2 accumulates at the surface of anoxic sediments manganese carbonates formed in these waters display 18 o values of 1 0 heavier than values expected solely from the initial deepwater composition this quantitatively explains the discrepancy between paleosalinities calculated from acr 18 o based on mn carbonate water isotopic equilibrium fractionation and direct observations for the same period our results emphasize the important role of microbial mno2 reduction during rhodochrosite authigenesis and suggest that mn ii activity rather than alkalinity is the limiting component for sedimentary mn carbonate formation copyright 2002 elsevier science ltd

effects of tidal forcing conductivity gradient and active seeding on the climatology of equatorial spread f over kwajalein plasma structure in nighttime equatorial f layer referred to as equatorial spread f esf displays climatology whose seasonal variation depends on longitude at longitudes where esf favors equinoxes times when maxima occur can be predicted in terms of the day of year when e region sunset is simultaneous in conjugate hemispheres i e sunset nodes aside from occurrences around equinoxes there are only three longitudes where esf also occurs during a solstice one is the central pacific region here esf activity is strong during the june solstice when solar activity is high to understand this puzzling behavior esf climatology over the kwajalein atoll was compared with properties of the postsunset rise pssr of the f layer and seeding activity in the troposphere the key findings are as follows 1 maxima in pssr velocity vpssr are better aligned with equinoxes than with sunset nodes hence seasonal pattern of vpssr not only sunset nodes should be included in interpretation of esf climatology 2 the source of vpssr during solstice appears to differ from that during equinoxes 3 equinoctial maxima in vpssr could be related to a semiannual variation in equatorial electrojet strength and its contribution to polarization of the f region dynamo current 4 enhanced vpssr during the june solstice is interpreted in terms of tidal forcing with a wave number of 2 5 displacements of maxima in esf climatology from maxima in vpssr are shown to be consistent with deep convective activity

satellite traces an ionogram signature for large scale wave structure and a precursor for equatorial spread f 1 although the source that controls day to day variability in the occurrence of equatorial plasma structure i e equatorial spread f or esf remains to be identified progress is being made there is evidence that the appearance of large scale wave structure lsws in the bottomside f layer around the time of its post sunset rise pssr is a more direct precursor of esf than the pssr itself the bulk of the evidence however is in the form of satellite f traces in ionograms which may be viewed as less than convincing because these signatures have not been shown to be causally related to lsws in this paper incoherent scatter radar and ionosonde data both collected on 24 july 1979 from the kwajalein atoll marshall islands are used to show that this is indeed the case

searching for travertines calcretes and speleothems in deep time processes appearances predictions and the impact of plants common models for modern calcite precipitation in and around caves soils springs and streams involve co 2 supplied by thick high p co 2 biogenic soils which were probably thin or non existent before vascular plants indeed plant influenced chemical weathering might have caused accelerated terrestrial carbonate production from the devonian onwards however terrestrial carbonates have also been documented from the archaean proterozoic cambrian ordovician and silurian mechanisms which could have caused non marine carbonates to precipitate without organic rich soils are described and some geological events likely to have influenced non marine carbonate precipitation up to the origin of vascular plants are highlighted as organisms have evolved so have the petrographic characteristics of non marine carbonates some examples of this are also given here

ice melt collapse pits and associated features in the 1991 lahar deposits of volcan hudson chile criteria to distinguish eruption induced glacier melt in subaerial volcaniclastic sequences structures formed by ice blocks can provide information about a volcano s history of lahar generation by glacier melt at volcan hudson in chile catastrophic lahars were initiated by eruption induced melting of glacier ice in august and october 1991 they transported large ice blocks 50 km down the rio de los huemules valley to the sea large current crescents with lee side lenses were formed where ice blocks were deposited during waning stages of the flood when stranded blocks of ice melted they left cone shaped and ring shaped heaps of ice rafted debris on the sediment surface several hundred ice blocks were completely buried within the aggrading lahar sediment and when these melted circular collapse pits formed in the sediment collapse types included subsided coherent blocks of sediment bounded by an outward dipping ring fracture trapdoor structures with horseshoe shaped fractures downsag pits with centroclinal dips locally up to 60 pits with peripheral graben and crevasses piecemeal highly fragmented collapse structures and funnel shaped pits containing disaggregated sediment a sequence of progressive collapse is inferred in which initial downsag and subsidence on an outward dipping ring fracture produces a small diameter pit this is followed by widening of the pit by progressive development of concentric ring fractures and downsag outside the early formed pit and by collapse of overhanging pit walls to produce vertical to inward dipping walls and aprons of collapse debris on the pit floor the various structures have potential for preservation even in regions prone to high rainfall and flooding and they can be used to indicate that former lahars contained abundant blocks of ice

low latitude ionospheric density irregularities and associated scintillations investigated by combining cosmic ro and ground based global positioning system observations over a solar active period

first observations of large scale wave structure and equatorial spread f using certo radio beacon on the c nofs satellite 1 first observations of large scale wave structure lsws and the subsequent development of equatorial spread f esf using total electron content tec derived from the ground based reception of beacon signals from the certo coherent electromagnetic radio tomography radio beacon on board c nofs communications navigation outage forecasting system satellite are presented selected examples of tec variations using measurements made during january 2009 from bac lieu vietnam 9 2 n 105 6 e geographic 1 7 n magnetic dip latitude are presented to illustrate two key findings 1 lsws appears to play a more important role in the development of esf than the post sunset rise pssr of the f layer and 2 lsws can appear well before e region sunset other findings that lsws does not have significant zonal drift in the initial stages of growth and can have zonal wavelengths of several hundred kilometers corroborate earlier reports

some characteristics of spread f at the magnetic equatorial station fortaleza spread f in ionograms of both the range and frequency spread types is studied for the magnetic equatorial station fortaleza geographic coordinates 38 w 4 s dip latitude 1 7 for a 1 year period during 1978 1979 satellite traces suggesting ionization structures with scale sizes of 100 200 km are found to be necessary precursors to the formation of the irregularities that give rise to range type spread f whereas frequency type spread f was observed under different circumstances striking differences are noted in the spread f characteristics and related parameters over fortaleza as compared with huancayo geographic coordinates 75 3 w 12 05 s dip latitude 0 6 and jicamarca geographic coordinates 76 8 w 11 95 s dip latitude 0 9 situated within only 38 in longitude west of fortaleza the postsunset maximum in h f in winter is delayed by about 1 hr with respect to other seasons over fortaleza as compared with huancayo where it occurs earlier in winter than in other seasons similar differences also exist in the prereversal peak near sunset in the vertical drift velocity vz between fortaleza and jicamarca the differences are attributed possibly to the large difference in the magnetic field declination and to other factors such as the difference in the magnetic field intensity and the relative separation between geographic and magnetic equators that exist between fortaleza and the other stations

on seeding large scale wave structure equatorial spread f and scintillations over vietnam 1 understanding the day to day variability in occurrence of equatorial spread f esf remains as a high priority objective in space weather research a major difficulty has been an inability to resolve the roles being played by large scale wave structure lsws and the post sunset rise pssr of the equatorial f layer in the production of esf in this paper we show conclusively that total electron content tec measured as a function of latitude and longitude provides clear routine descriptions of lsws then together with ionosonde data we show for the first time that while a seed for lsws can occur in the late afternoon its amplification takes place mostly during the pssr implications of these findings are discussed in light of existing theories

carbon isotope fractionation between dissolved carbonate co32 and co2 g at 25 and 40 c abstract carbon isotope fractionations e hco 3 co 2 g and e co 3 co 2 g have been obtained in open system experiments at medium ph measured isotopic fractionations e between total dissolved carbonate tdc and co 2 g were 7 32 0 07 and 6 15 0 08 at 25 and 40 c respectively assuming e co 2 aq co 2 g 1 06 from vogel et al 19 5 and ion speciation in the solution calculated fractionations e hco 3 co 2 g are 8 21 at 25 c and 6 71 at 40 c at high ph measured isotopic fractionations between tdc and co 2 g were 8 30 0 09 and 6 69 0 15 at 25 and 40 c respectively considering ion speciations and the above fractionation e hco 3 co 2 g we derived e co 3 co 2 g as equal to 8 38 at 25 c and 6 67 at 40 c

discovery of ring faults associated with salt withdrawal basins early cretaceous age in the east texas basin abstract the jurassic louann salt in the east texas basin has played a dominant role in influencing the structural and depositional history of the basin particularly during the jurassic and cretaceous periods salt tectonics is closely associated with sandstone distribution depositional facies and reef growth and consequently with petroleum traps in the basin salt withdrawal basins developed during the early cretaceous in response to salt movement and dissolution processes are characterized by the presence of an expanded section of lower cretaceous marine and deltaic sedimentary rocks recognition of fault sets associated with the evolution of these salt withdrawal basins has gone undetected until the recent coherence cubetm processing of a non proprietary 3 d seismic survey conducted by schlumberger in the la rue dome fairway field area henderson county texas images from coherence cube processing aptly exhibit extraordinary sets of concentric ring faults that comprise the periphery of two salt withdrawal basins the fairway oil field is located at the junction of these two sets of ring faults the structural style of these high angle ring faults creates a multitude of possible fault traps in a previously unattractive structural setting early cretaceous age of the ring faults establishes that these faults are a significant element in evaluating petroleum migration patterns and traps in the basin the discovery of early cretaceous ring faults in the east texas basin by coherence cube processing brings new perspectives to development and exploration drilling in this mature petroleum province

reply to discussion on an eocene age for the proposed silverpit impact crater journal vol 165 781 794 we welcome the opportunity to further clarify aspects of our paper and challenge key elements of owen s discussion and the inferences he makes regarding the rigour our interpretations and those of previous workers on the origin of the silverpit structure we deal with each of his comments in the order that he raises them owen refers to the interpretation of the silverpit structure as an impact crater as a speculative hypothesis this is consistent with an earlier statement he has made this feature termed the silverpit crater has earlier been interpreted as a meteor impact structure stewart allen 2002 without a shred of scientific justification thomson et al 2005 the inference that the hypothesis lacks any observational basis disregards a wealth of 3d seismic analysis by stewart allen 2002 2005 the statement is at best disingenuous as owen chooses to ignore the thorough work of earlier workers although all the observations for and against a impact origin are based upon 3d seismic data and there are as yet no other independent supportive lines of evidence we would highlight the vast body of work on impact cratering and the numerous impact craters on planetary bodies that have been identified purely from their surface morphology melosh 1989 in other words the absence of shocked quartz and other impact criteria does not invalidate the impact crater interpretation we have been very careful to term the silverpit structure a probable impact crater and will continue to do so until such unequivocal evidence is discovered in our paper we identify a key reflection that we term cf

overburden deformation related to the pre piercement development of salt structures in the north sea the nature of the stress regime imposed on a clastic overburden by a developing salt structure changes with time these changes are directly related to the evolving morphology of the salt structure in a sequence of events which is now quite well understood the stress pattern produced by initial almost purely vertical uplift changes rapidly into a more complex pattern as the flanks of the rising salt mass collapse progressively with flow of salt towards the crestal zone the two main stress elements involved derive from extension within the superincumbent overburden produced by the salt uplift and the effects of gravity that exercise an increasingly important influence as the structure develops vertically other factors also affecting the form taken by the overburden deformation are outlined the discussion is illustrated with examples of migrated seismic data

calcite from the quaternary spring waters at tylicz krynica polish carpathians at tylicz near krynica spa polish carpathians spelean deposits fill fissures and caverns in eocene flysch rocks they occur as 1 clastic cave sediments transformed into hard crusts due to cementation by finely crystalline low mg calcite 2 drusy calcite that covers crust surfaces and fills voids in the crust and 3 colloform calcite two varieties of drusy calcite are distinguished acicular and columnar the acicular calcite is built up of crystallites forming spherulitic fans or cones in places it is syntaxially covered with colloform calcite the drusy calcite is low mg ferroan calcite with non ferroan subzones whereas the colloform calcite is a low mg non ferroan variety the columnar calcite crystals form fan like bundles cross sections cut perpendicular to the c axes of columnar crystals are equilateral triangular in shape although some have slightly curved edges the columnar crystals have steep rhombic terminations and most have curved triangular faces i e gothic arch calcite saddle crystals have also been observed the columnar crystals are composed of radially orientated crystallites whose long dimension is parallel to the c axis the curved crystal faces of such polycrystals are interpreted as a result of differential growth rates of the crystallites the spelean calcites precipitated from co2 saturated water the high rate of caco3 precipitation is thought to be responsible for the formation of radial structures finely crystalline calcite formed within pore spaces of clastic sediments close to the water air interface drusy calcite crystallized beneath the water air interface and colloform calcite precipitated from thin films of water

a satellite derived climatology of the itcz abstract this paper presents fundamental climatological characteristics of the intertropical convergence zone itcz in a simple concise manner using the highly reflective cloud hrc dataset this satellite derived dataset uses both visible and infrared observations to measure the frequency of occurrence of large scale convective systems over the global tropics at a 1 spatial resolution these dataset characteristics make the hrc particularly well suited for climatological analysis of the itcz because the dataset is based on estimates of organized deep convective cloud systems rather than observations of clouds as a whole and it provides the spatial resolution needed to identify thew large wale convective structures furthermore the dataset covers a time period extending nearly two decades which provides for a fairly robust climatology and the opportunity to examine seasonal and interannual variability of both the convection and the latitude of the itcz

continuous generation and two dimensional structure of equatorial plasma bubbles observed by high density gps receivers in southeast asia high density gps receivers located in southeast asia sea were utilized to study the two dimensional structure of ionospheric plasma irregularities in the equatorial region the longitudinal and latitudinal variations of tens of kilometer scale irregularities associated with equatorial plasma bubbles epbs were investigated using two dimensional maps of the rate of total electron content change index roti from 127 gps receivers with an average spacing of about 50 100 km the longitudinal variations of the two dimensional maps of gps roti measurement on 5 april 2011 revealed that 16 striations of epbs were generated continuously around the passage of the solar terminator the separation distance between the subsequent onset locations varied from 100 to 550 km with 10 min intervals the lifetimes of the epbs observed by gps roti measurement were between 50 min and over 7 h the epbs propagated 440 3000 km toward the east with velocities of 83 162 m s 1 the longitudinal variations of epbs by gps roti keogram coincided with the depletions of 630 nm emission observed using the airglow imager six epbs were observed by gps roti along the meridian of equatorial atmosphere radar ear while only three epbs were detected by the ear the high density gps receivers in sea have an advantage of providing time continuous descriptions of latitudinal longitudinal variations of epbs with both high spatial resolution and broad geographical coverage the spatial periodicity of the epbs could be associated with a wavelength of the quasiperiodic structures on the bottomside of the f region which initiate the rayleigh taylor instability

downsag and extension at calderas new perspectives on collapse geometries from ice melt mining and volcanic subsidence structures at calderas may form as a result of precursory tumescence subsidence due withdrawal of magmatic support resurgence and regional tectonism structural reactivation and overprinting are common to explore which types of structures may derive directly from subsidence without other factors evidence is reviewed from pits caused by the melting of buried ice blocks mining subsidence scaled subsidence models and from over 50 calderas this review suggests that complex patterns of peripheral deformation with multiple ring and arcuate fractures both inside and outside caldera rims topographic embayments arcuate graben and concentric zones of extension and compression may form as a direct result of subsidence and do not require a complex subsidence and inflation history downsag is a feature of many calderas and it does not indicate subsidence on an inward dipping ring fault as has been inferred previously where magmatic inflation is absent or slight initial arcuate faults formed during collapse are likely to be multiple and dip outwards to vertical associated downsag causes the peripheries of calderas undergo radial centripetal extension and this accounts for some of the complex peripheral fractures arcuate crevasses graben and some topographic moats the structural boundary of a caldera defined here as the outermost limits of subsidence and related deformation including downsag commonly lies outside ring faults and outside the embayed topographic wall it is likely to be funnel shaped i e inward dipping even though ring and arcuate fractures within it may dip outward inward dipping arcuate normal faults at shallow levels and steep inward dipping contacts between a caldera s fill and walls may both occur at a caldera that has initially subsided on outward dipping ring faults they arise due to peripheral surficial extension gravitational spreading and scarp collapse topographic enlargement at some calderas and the formation of embayments may reflect general progressive downsag and localized downsag respectively these processes may occur in addition to surficial degradation of oversteep ring fault scarps

an eocene age for the proposed silverpit impact crater three dimensional seismic analysis is used to describe the detailed morphology of the silverpit crater a proposed marine impact crater located in the southern north sea uk we examine and constrain for the first time the geometry extent and age of the post crater sediment units that define the crater fill a circular bowl shaped depression has been mapped and interpreted to represent the upper limit of impact deformation and the geometry of the crater at the end of cratering processes reflections exhibit a parallel onlap fill onto the bowl shaped crater floor indicating that accommodation space was created instantaneously without any contemporaneous sedimentation using regional lithostratigraphic markers constrained by microfossil and calcareous nannofossil analysis we have dated the first onlapping sediments onto the crater the age of the onlapping sediments allows us to constrain the crater formation to be middle eocene in age this date is c 10 15 ma younger than the previous ascribed age for the crater formation and rules out the silverpit crater as a k t boundary impact the age of crater formation considerably predates regional folding and accompanying salt flowage effectively ruling out a salt withdrawal origin for the silverpit crater

on equatorial spread f establishing a seeding hypothesis 1 a comprehensive explanation for the complex climatology of the so called equatorial spread f esf has eluded researchers for more than 70 years recently however a seeding hypothesis has been proposed which appears to provide the final major piece of this puzzle the hypothesis is based on the discovery that a direct link exists between regions of deep convective activity in the troposphere where atmospheric gravity waves gws are spawned and the occurrence frequency of esf during solstices the objective here is to answer two questions that may impede the general acceptance of this hypothesis we first show why seed plasma perturbations should develop from gw driven neutral wind perturbations but only when the gw source region is located very close to the magnetic dip equator we then reexamine this relationship using a data set on gw source regions that is better matched in time and longitudinal coverage than that used previously to the data set on esf activity used by tsunoda 2010a we conclude that seeding is indeed playing an important role in the development of esf

on the generation and growth of equatorial backscatter plumes 1 wave structure in the bottomside f layer we examine the initial conditions that lead to backscatter plume development in the equatorial f region ionosphere by analyzing altair radar data we obtained the following principal results 1 prior to plume development an altitude modulation of electron density contours exists in the bottomside f layer these quasi periodic variations were mapped spatially over a 1200 km east west distance by using incoherent scatter measurements and found to consist of three cycles with an average spatial wavelength of 400 km 2 the wave structure observed in the bottomside electron density contours grew in amplitude at a rate consistent with that predicted by the generalized gradient drift instability 3 bottomside backscatter developed on the west walls of all three altitude modulated regions followed by plume development from near the crests of these regions

diagenetic mineralization in pennsylvanian coals from indiana usa 13c 12c and 18o 16o implications for cleat origin and coalbed methane generation cleats and fractures in southwestern indiana coal seams are often filled with authigenic kaolinite and or calcite carbon and oxygen stable isotope ratios of kaolinite calcite and coalbed co2 were evaluated in combination with measured values and published estimates of 18o of coalbed paleowaters that had been present at the time of mineralization 18omineral and 18owater values jointly constrain the paleotemperature of mineralization the isotopic evidence and the thermal and tectonic history of this part of the illinois basin led to the conclusion that maximum burial and heat sterilization of coal seams approximately 272 ma ago was followed by advective heat redistribution and concurrent precipitation of kaolinite in cleats at a burial depth of 1600 m at 78 5 c post paleozoic uplift the development of a second generation of cleats and subsequent precipitation of calcite occurred at shallower burial depth between 500 to 1300 m at a lower temperature of 43 6 c the available paleowater in coalbeds was likely ocean water and or tropical meteoric water with a 18owater 1 25 versus vsmow inoculation of coalbeds with methanogenic co2 reducing microbes occurred at an even later time because modern microbially influenced 13c enriched coalbed co2 i e the isotopically fractionated residue of microbial co2 reduction is out of isotopic equilibrium with 13c depleted calcite in cleats

hydrogeochemistry of alpine springs from north slovenia insights from stable isotopes abstract spring water chemistry and carbon cycling in our study mainly depend on geological composition of the aquifer the investigated alpine springs in slovenia represent waters strongly influenced by chemical weathering of mesozoic limestone and dolomite only one spring was located in permo carboniferous shales the carbon isotopic composition of dissolved inorganic carbon dic and suspended organic carbon poc as well as major solute concentrations yielded insights into the origin of carbon in alpine spring waters the major solute composition was dominated by carbonic acid dissolution of calcite waters were generally close to saturation with respect to calcite and dissolved co 2 was up to fortyfold supersaturated relative to the atmosphere 13 c of dic indicates the portion of soil co 2 contributed in water and is related with soil thickness of infiltrating water in aquifer and could be therefore used as a tool for vulnerability assessment the 13 c of dic ranged from 15 8 to 1 5 and indicated less and more vulnerable aquifers mass balances of carbon for spring waters draining carbonate rocks suggest that carbonate dissolution contributes from approximately 49 to 86 and degradation of organic matter from 13 7 to 51 4 depending on spring and its relation with rock type soil environment and geomorphic position stable oxygen isotope composition of water 18 o h2o and tritium values range from 12 2 to 9 3 and from 6 4 to 9 8 tu respectively and indicate recharge from modern precipitation according to active decay of tritium and tritium in modern precipitation the age of spring waters are estimated to be about 2 6 years for springs located in julian alps about 5 years for springs located in karavanke and about 5 years for springs located in kamnisko savinjske alps

characteristics of large scale wave structure observed from african and southeast asian longitudinal sectors the spatial large scale wave structure lsws at the base of f layer is the earliest manifestation of seed perturbation for rayleigh taylor instability hence found to play a deterministic role in the development of equatorial plasma bubbles epbs except for a few case studies a comprehensive investigation has not been conducted on the characteristics of lsws because of the complexity involved in detecting the lsws particularly in spatial domain in this scenario a comprehensive study is carried out for the first time on the spatial and temporal characteristics of lsws observed in spatial domain over african and southeast asian longitudinal sectors during the year 2011 the observations indicate that these wave structures can be detected a few degrees west of e region sunset terminator and found to grow significantly at longitudes past the sunset terminator the phase fronts of these spatial structures are found to align with the geomagnetic field b lines over a latitudinal belt for at least 5 6 500 600 km centered on dip equator the zonal wavelengths of these structures are found to vary from 100 to 700 km which is consistent with the earlier reports and the epbs were consistently observed when the amplitudes of lsws were grown to sufficient strengths these results would provide better insights on the underlying physical processes involved in excitation of lsws in terms of important roles being played by e region electrical loading and polarization electric fields induced via spatially varying dynamo current due to neutral wind perturbations associated with atmospheric gravity waves

discussion on the north sea silverpit crater impact structure or pull apart basin ken thomson writes the suggestion that the silverpit crater is a pull apart basin smith 2004 and not an impact structure stewart allen 2002 demonstrates that its origin requires further investigation as noted by underhill 2004 the coincidence of the structure with a salt withdrawal basin suggests that halokinesis may provide an alternative mechanism although the model provided by smith involves salt movement it is overly complex as strike slip detachment tectonics are not required instead gravitational collapse of the post salt cover provides a simpler mechanism the southern north sea is dominated by the development of large linear salt swells jenyon 1988 stewart coward 1995 elevation and tilting of the swell flanks results in gravitational instability and a range of deformation styles can develop jenyon 1988 stewart coward 1995 thomson 2004 the instability commonly leads to listric faulting of the post salt cover down slope towards the adjacent salt low jenyon 1988 stewart coward 1995 thomson 2004 detachment levels for the listric faults occur at a number of stratigraphic levels the top of the upper permian zechstein group salt which forms the swells provides a detachment at the base of the post salt cover whilst detachment within the post salt cover in both the triassic rot halite and within the upper cretaceous chalk have also been recognized jenyon 1988 stewart coward 1995 thomson 2004 the majority of the flank collapse faults dip in the same direction as the cover rocks they displace i e towards the salt withdrawal basin and away from the swell but occasionally listric faults can be found which dip away from the salt withdrawal basin towards the swell jenyon 1988 associated with the listric faulting rollover anticlines can develop in the hanging walls stewart coward 1995 whilst slump folds

longitudinal variability of annual changes in activity of equatorial spread f and plasma bubbles global distribution maps of equatorial spread f esf activity for various annual periods were derived from the topside soundings by the ionosphere sounding satellite b iss b in 1978 1980 the esf activity during the northern winter period reveals maximum enhancement at the atlantic longitudes of large westward geomagnetic declination and during the northern summer at the pacific longitudes of large eastward declination on several orbits passing over the region of the esf activity enhancement abrupt depletions of the electron density or equatorial plasma bubbles were observed at the satellite altitude of about 1100 km it has also been found that the background electron density distributions tend to be symmetric with respect to the magnetic equator in the region of the enhanced esf activity and asymmetric in the region of the suppressed esf activity these observations are taken account of by the influence of a transequatorial thermospheric wind upon the suppression of the rayleigh taylor type plasma instability

a 20 km diameter multi ringed impact structure in the north sea most craters found on earth are highly eroded poorly preserved and only exposed on land here we describe a multi ringed impact structure discovered in the north sea from the analysis of three dimensional seismic reflection data the structure is 20 km in diameter and has at least ten distinctive concentric rings located between 2 and 10 km from the crater centre the structure affects cretaceous chalk and jurassic shales and is well preserved below several hundred metres of post impact tertiary strata which constrains its age to be 60 65 myr old the formation of concentric ringed impact structures at this relatively small scale had not previously been thought possible especially on the terrestrial planets we have mapped the ring structures at a resolution of tens of metres both laterally and in depth and show that the rings are fault bounded graben structures similar to fault arrays formed in low strain rate detachment tectonic settings strata deeper than 500 m palaeodepth appear unfaulted and we infer that the concentric ring structures may have accommodated post impact extension towards the excavated crater through detachment on weak layers within the chalk

large enigmatic crater structures offshore southern california summary digital mosaics of swath and conventional bathymetry data reveal large distinct near circular crater structures in the inner continental borderland offshore southern california two have maximum crater diameters that exceed 30 km and a third has a crater diameter of approximately 12 km all three features exhibit the morphology of large complex craters raised outer rim ring moat and central uplift yet their exact origin remains a mystery preliminary analyses of available seismic gravity and magnetic data over these structures reveal both similarities and distinct differences in geometry structure and geophysical signature to known impact sites all three crater structures however occur within the catalina terrane a highly extended volcanic and metamorphic province floored by catalina schist basement a likely alternative origin may thus involve explosive volcanism caldera collapse and resurgent magmatism and or possibly plutonism and schist remobilization associated with the catalina terrane no single model for crater formation whether impact caldera or pluton fully accounts for all of the present observations regarding the morphology internal structure and known geology of these near circular features timing of crater formation post dates the initial rifting and rotation of the western transverse ranges and appears to predate major right slip along the san clemente and san diego trough fault systems or approximately 18 to 16 ma regardless of their origin these complex craters represent some of the largest structures of their kind in western north america and provide a unique opportunity to better understand the development of unusual crater structures in a submarine environment

effects of the vertical plasma drift velocity on the generation and evolution of equatorial spread f we use radar observations from the jicamarca observatory from 1968 to 1992 to study the effects of the f region vertical plasma drift velocity on the generation and evolution of equatorial spread f the dependence of these irregularities on season solar cycle and magnetic activity can be explained as resulting from the corresponding effects on the evening and nighttime vertical drifts in the early night sector the bottomside of the f layer is almost always unstable the evolution of the unstable layer is controlled by the history of the vertical drift velocity when the drift velocities are large enough the necessary seeding mechanisms for the generation of strong spread f always appear to be present the threshold drift velocity for the generation of strong early night irregularities increases linearly with solar flux the geomagnetic control on the generation of spread f is season solar cycle and longitude dependent these effects can be explained by the response of the equatorial vertical drift velocities to magnetospheric and ionospheric disturbance dynamo electric fields the occurrence of early night spread f decreases significantly during equinox solar maximum magnetically disturbed conditions due to disturbance dynamo electric fields which decrease the upward drift velocities near sunset the generation of late night spread f requires the reversal of the vertical velocity from downward to upward for periods longer than about half an hour these irregularities occur most often at 0400 local time when the prompt penetration and disturbance dynamo vertical drifts have largest amplitudes the occurrence of late night spread f is highest near solar minimum and decreases with increasing solar activity probably due to the large increase of the nighttime downward drifts with increasing solar flux

atypical nighttime spread f structure observed near the southern crest of the ionospheric equatorial ionization anomaly 1 an atypical nighttime spread f structure is observed on ionograms at or above the f2 trace near the crest of the ionospheric equatorial ionization anomaly eia region this ionospheric atypical spread f phenomenon was observed using two closed spaced 115 km ionospheric soundings stations located in sao jose dos campos 23 21 s 45 97 w and cachoeira paulista 22 70 s 45 01 w brazil in a low latitude station near the southern crest of the eia region during nighttime low solar activity and quiet geomagnetic conditions this structure in the initial phase appears in the ionogram as a faint spread f trace above or at the f2 layer peak height after a few minutes it develops into a strong spread f trace and afterwards it moves to altitudes below the f2 layer peak heights finally the atypical nighttime f layer trace structure may remain for a while between the f layer bottom side and peak height or can move to an altitude above the f layer peak height and then it disappears in order to have a comprehensive view of the ionospheric environment characterizing the phenomenon under study complementary data from six gps station were used to investigate the ionosphere environment conditions during both events the six gps stations used in this study are distributed from near the equatorial region to low latitudes and provide evidence that the atypical nighttime spread f structures are not related with large scale equatorial irregularities plasma bubbles

on the occurrence of postmidnight equatorial f region irregularities during the june solstice 1 postmidnight equatorial f region irregularities efis are known to develop mainly during the solstitial months however it is not well understood whether they occur at all longitudes and what process causes their occurrence at different longitude sectors in this study we use the gps total electron content tec fluctuations obtained from a global gps network and spread f in ionograms from jicamarca 283 e 12 s dip 1 n in the american longitude sector and kwajalein 167 e 9 n dip 4 n bac lieu 106 e 9 n dip 2 n and chumphon 99 e 11 n dip 3 n in the pacific and asian longitude sectors during 2000 2009 to investigate the efi characteristics during june solstice results from global tec fluctuations show that at solar maximum the occurrence rate of postmidnight efis is high in african and pacific regions moderate in the southeast asian region and low in the peruvian region and that most postmidnight efis are the continuation of postsunset efis during solar minimum the postmidnight efis were rarely observed in tec but were very frequent in ionograms the latter had more frequent postmidnight onsets over peru whereas they were initiated during late postsunset hours in pacific and southeast asian longitudes in both longitudes the postsunset layer rise occurred with some delay the layer rise was more prominent on spread f nights over jicamarca and less so over pacific longitudes the results showing different degrees of association at the different longitudes between the postsunset postmidnight efis and f layer heights highlight the influence of other factors in the late night efi development perturbation seeds and plasma drifts neutral winds in particular are discussed as strong candidates for causing these irregularities in the june solstitial months of solar minimum years

reservoir leakage along concentric faults in the southern north sea implications for the deployment of ccs and eor techniques high quality 3d seismic and borehole data in the broad fourteens basin southern north sea is used to investigate newly recognised concentric faults formed in salt withdrawal basins flanking reactivated salt structures throw depth and throw distance plots were used to understand the growth histories of individual faults as a result three families of concentric faults are identified a intra seal faults within a salt withdrawal basin b faults connecting the seal and the reservoir on the crest of an inverted anticline c raft bounding faults propagating into reservoir units they have moved obliquely and show normal throws even though they formed during a period of regional compression faults in the salt withdrawal basin and on the inverted anticline are highly segmented increasing the chances of compartmentalisation or localised fluid flow through fault linkages slip tendency analysis was carried out on the distinct fault families to compare the likelihood of slip along a fault at different pore fluid pressures and within different lithologies our results show that sections of the faults are optimally oriented with regards to maximum horizontal stresses hmax increasing the slip tendency the identified faults cut through a variety of lithologies allowing different values of pore fluid pressures to build up before faults reactivate within the vlieland sandstones pore fluid pressures of 30 mpa are not sufficient to reactivate pre existing faults whereas in the deeper posidonia shales faults might reactivate at pore fluid pressures of 25 mpa fluid flow features preferentially occur near fault segments close to failure heterogeneity in slip tendency along concentric faults and high degrees of fault segmentation present serious hazards when injecting co2 into the subsurface this study stresses the importance of high quality 3d seismic data and the need to evaluate individual fault systems when investigating potential reservoirs for carbon capture and storage and enhanced oil recovery

stable isotope composition of spelean calcites and gaseous co2 from tylicz polish carpathians abstract spelean calcites discovered in fissures and caverns within flysch deposits at tylicz polish carpathians have been examined isotopically together with co 2 rich water from several springs occurring in this area 13 c values of tdc and spelean calcites indicate that caco 3 has precipitated under conditions close to carbon isotope equilibrium with participation of co 2 of deep origin analyses of 18 o suggest the existence of oxygen isotope disequilibrium between water and gaseous co 2 which can be explained by the short time of contact between the co 2 flux and the shallow groundwaters of meteoric origin

a four component mixing model for water in a karst terrain in south central indiana usa using solute concentration and stable isotopes as tracers the study area lies in a highly karstified carbonate terrain in south central indiana sinkholes conduits and caves form large secondary pathways for the subsurface flow as a result the discharge from a main emergence point for the subsurface flow system the orangeville rise quickly responds to the storm events and shows wide variations in flow rate water chemistry and stable isotopic compositions these responses are attributed to the mixing of water in secondary pathways in the study area recharge occurs through the thick mantled karst plain and the sinkhole plains and the role of soil layer and epikarst in the recharge process is of great importance rain dic 2 hco3 mg l 13cdic 7 soil water dic 544 hco3 mg l 13cdic 14 7 epikarstic water dic 224 hco3 mg l 13cdic 13 6 and phreatic diffuse flow water dic 299 hco3 mg l 13cdic 11 8 generally showed unique and constant dissolved inorganic carbon dic and 13cdic values over time using dic and 13cdic as tracers a four component mixing model was established for the karstic flow system by constructing the discharge hydrograph separation curves the mixing ratio of each component rain 10 6 soil 3 1 epikarstic 52 3 and phreatic 34 0 water was determined for the orangeville rise discharge over the testing period of 104 h after the storm event of 10 4 90 vadose water occupied 55 4 of spring discharge and this demonstrates the importance of the unsaturated zone especially the epikarst in the karstic flow systems

multi reflected echoes another ionogram signature of large scale wave structure 1 one or more steeply sloped traces have been found in evening ionograms taken from the kwajalein atoll 4 3 n dip latitude during july 1979 their resemblance to the normal f trace suggests that they are echoes that have undergone a large number of reflections from the f layer these multi reflected echoes mres are interpreted in terms of focusing produced by curved isodensity contours in the bottomside f layer which appear to be associated with large scale wave structure lsws that develops in the bottomside f layer mres appear to be another signature for lsws together with satellite traces that appear later in time closer to the onset of plasma structure referred to as equatorial spread f mres are interesting because they display for the data set examined a strong preference to occur during the post sunset rise of the f layer which includes e region sunset how this finding affects our understanding of lsws is discussed

rietveld analysis of x ray powder diffraction patterns as a potential tool for the identification of impact deformed carbonate rocks previous x ray powder diffraction xrd studies revealed that shock deformed carbonates and quartz have broader xrd patterns than those of unshocked samples entire xrd patterns single peak profiles and rietveld refined parameters of carbonate samples from the sierra madera impact crater west texas unshocked equivalent samples from 95 miles north of the crater and the mission canyon formation of southwest montana and western wyoming were used to evaluate the use of x ray powder diffraction as a potential tool for distinguishing impact deformed rocks from unshocked and tectonically deformed rocks at sierra madera dolostone and limestone samples were collected from the crater rim lower shock intensity and the central uplift higher shock intensity unshocked equivalent dolostone samples were collected from well cores drilled outside of the impact crater carbonate rocks of the mission canyon formation were sampled along a transect across the tectonic front of the sevier and laramide orogenic belts whereas calcite subjected to significant shock intensities at the sierra madera impact crater can be differentiated from tectonically deformed calcite from the mission canyon formation using rietveld refined peak profiles weakly shocked calcite from the crater rim appears to be indistinguishable from the tectonically deformed calcite in contrast rietveld analysis readily distinguishes shocked sierra madera dolomite from unshocked equivalent dolostone samples from outside the crater and tectonically deformed mission canyon formation dolomite

on the enigma of day to day variability in equatorial spread f 1 we show that large scale wave structure lsws in plasma density in the bottomside f layer is a hitherto unheralded contributor to the long standing enigma of day to day variability in equatorial spread f esf little is known about lsws it seems to appear in altitude near a vertical shear in zonal plasma drift during the post sunset rise of the f layer and its growth via an interchange instability appears to predispose quasi periodically spaced regions to development of plasma bubbles first indications are that lsws development is necessary and sufficient for esf occurrence we suggest that variability in lsws development perhaps together with the shear in zonal drift may contribute to day to day esf variability a need revealed by this study is that a cluster of distributed sensors not isolated ones is necessary to pursue the problem of day to day variability