melting and mingling of phonolitic pumice deposits with intruding dykes an example from the otago peninsula new zealand abstract a mound of bedded phonolitic pumice lapilli ash was deposited on the marine shelf modern otago peninsula new zealand during a shallow subaqueous eruption in the miocene basaltic dykes subsequently intruded the unconsolidated pumice deposit and formed an unusual peperite dyke sediment interaction began with weak steam driven mixing accompanied by fluidisation at the contact zone that produced a metres broad zone in which bulbous tongues up to 3 m of the dykes extended into and locally engulfed host sediment irregular sinuous contacts of dykes with the pumice are marked by black glass that formed by partial melting shearing and remoulding of the glassy pumice such melting and remoulding of host sediment is not a typical peperite feature temperature evolution volume of water vapour load pressure and time as well as initial contact temperature control the welding and remoulding of pumice and glass shards a slow cooling rate of the dykes at the dyke contacts is inferred from remoulding textures and is attributed to continuous feeding of the dyke seawater may have promoted softening and remoulding of the pumice because na and k if partially taken into the glass structure can decrease the melting point of glass dramatically and reduce the viscosity of the shards remoulding may have occurred by continuous conversion of seawater in the peperite to steam which is inferred to have enhanced transfer of na and k from seawater to pumice glass

diagenesis of a mixed siliciclastic evaporitic sequence of the middle muschelkalk middle triassic the catalan coastal range ne spain the middle muschelkalk middle triassic of the catalan coastal range north east spain comprises sandstone mudstone anhydrite and minor carbonate layers interbedded sandstones and mudstones which are dominant in the north eastern parts of the basin are terminal alluvial fan deposits south westward in the basin the rocks become dominated by interbedded evaporites and mudstones deposited in sabkha mudflat environments the diagenetic and pore water evolution patterns of the middle muschelkalk suggest a strong facies control during eodiagenesis formation of microdolomite anhydrite baryte magnesite k feldspar and mixed layer chlorite smectite was favoured within and adjacent to the sabkha mudflat facies whereas calcite haematite mixed layer illite smectite and quartz formed mainly in the alluvial facies low 18osmow values for microdolomite 23 7 to 28 4 and k feldspar overgrowths 17 3 to 17 7 suggest either low temperature isotopic disequilibrium or precipitation from low 18o porewaters low 18o waters might have developed at least in part during low temperature alteration of volcanic rock fragments during mesodiagenesis precipitation of quartz overgrowths and coarse dolomite occurred in the alluvial sandstones whereas recrystallization of microdolomite was dominant in the sabkha mudflat facies the isotopic compositions of these mesogenetic phases reflect increasing temperature during burial upon uplift and erosion telogenetic calcite and trace haematite precipitated in fractures and replaced dolomite the isotopic composition of the calcite 18osmow 21 5 to 25 6 o 13c 7 7 to 5 6 o and presence of haematite indicate infiltration of meteoric waters

criteria for interpreting kimberlite as coherent insights from the muskox and jericho kimberlites nunavut canada the jurassic muskox and jericho kimberlites northern slave province nunavut canada contain a variety of facies exhibiting different geometries contact relationships internal organisation country rock abundance and olivine shapes although many have similar matrix groundmass mineralogies and textures five facies are examined that either have characteristics consistent with coherent rocks in general i e intrusive and extrusive non fragmental rocks or are mineralogically and texturally similar to kimberlite described as coherent or apparent coherent three facies are interpreted as coherent on the basis of 1 geological setting 2 apparent porphyritic texture 3 sharp contacts with fragmental kimberlite 4 relative abundance of elongate and unbroken olivine crystals and 5 paucity of country rock xenoliths while the remaining two facies are interpreted as fragmental on the basis of 1 the gradational contacts with demonstrably fragmental kimberlite 2 relative abundance and range of sizes of country rock lithic clasts and 3 numerous broken olivine crystals comparisons are made with coherent and apparent coherent kimberlite from the literature our three coherent facies are similar to literature reported coherent kimberlite dykes hosted in country rock ckd in terms of internal organisation low abundance of country rock xenoliths and apparent porphyritic texture conversely our two fragmental facies share attributes with previously described pipe filling coherent and apparent coherent kimberlite ckpf in terms of geometry internal organisation and abundance of country rock xenoliths we conclude that ckd and most ckpf although similar in matrix groundmass mineralogy and texture can be distinguished on the basis of internal organisation country rock lithic clast abundance texture e g apparent porphyritic texture and possibly olivine crystal shapes and suggest that fragmental kimberlite is more common than reported

high quality insar data linked to seasonal change in hydraulic head for an agricultural area in the san luis valley colorado in the san luis valley slv colorado legislation passed in 2004 requires that hydraulic head levels in the confined aquifer system stay within the range experienced in the years 1978 2000 while some measurements of hydraulic head exist greater spatial and temporal sampling would be very valuable in understanding the behavior of the system interferometric synthetic aperture radar insar data provide fine spatial resolution measurements of earth surface deformation which can be related to hydraulic head change in the confined aquifer system however change in cm scale crop structure with time leads to signal decorrelation resulting in low quality data here we apply small baseline subset sbas analysis to insar data collected from 1992 to 2001 we are able to show high levels of correlation denoting high quality data in areas between the center pivot irrigation circles where the lack of water results in little surface vegetation at three well locations we see a seasonal variation in the insar data that mimics the hydraulic head data we use measured values of the elastic skeletal storage coefficient to estimate hydraulic head from the insar data in general the magnitude of estimated and measured head agree to within the calculated error however the errors are unacceptably large due to both errors in the insar data and uncertainty in the measured value of the elastic skeletal storage coefficient we conclude that insar is capturing the seasonal head variation but that further research is required to obtain accurate hydraulic head estimates from the insar deformation measurements

miocene phreatomagmatic volcanism at tihany pannonian basin hungary abstract a late miocene 7 56 ma maar volcanic complex tihany maar volcanic complex tmvc is preserved in the pannonian basin and is part of the bakony balaton highland volcanic field base surge and fallout deposits were formed around maars by phreatomagmatic explosions caused by interactions between water saturated sediments and alkali basalt magma carrying peridotite lherzolite xenoliths as well as pyroxene and olivine megacrysts subsequently nested maars functioned as a sediment trap where deposition built up gilbert type delta sequences at the onset of eruption magma began to interact with a moderate amount of groundwater in the water saturated sand as eruption continued phreatomagmatic blasts excavated downward into limestones providing access to abundant karst water and deeper to sandstones and schist both providing large amount of fracture filling water at the surface this wet eruption led to the emplacement of massive tuff breccias by fall surge mudflow and gravity flow deposition the nature of the tmvc maar eruptions and their deposits appears to depend on the hydrological condition of the karst and or fracture filling aquifer which varies seasonally with rainfall and spring runoff the west and east maar volcanoes of tmvc are interpreted to represent low water input from the karst and or fracture filling aquifer summer vent whereas the east maar is interpreted to have formed when abundant karst and or fracture filling water was available spring vent

facies architecture of a silicic intrusion dominated volcanic centre at highway reward queensland australia abstract the highway reward massive sulphide deposit is hosted by a silicic volcanic succession in the cambro ordovician seventy mile range group northeastern australia three principal lithofacies associations have been identified in the host succession the volcanogenic sedimentary facies association the primary volcanic facies association and the resedimented syn eruptive facies association the volcanogenic sedimentary facies association comprises volcanic and non volcanic siltstone and sandstone turbidites that indicate submarine settings below storm wave base lithofacies of the primary volcanic facies association include coherent rhyolite rhyodacite and dacite and associated non stratified breccia facies autoclastic breccia and peperite the resedimented volcaniclastic facies association contains clasts that were initially formed and deposited by volcanic processes but then redeposited by mass flow processes resedimentation was more or less syn eruptive so that the deposits are essentially monomictic and clast shapes are unmodified this facies association includes monomictic rhyolitic to dacitic breccia resedimented autoclastic facies siltstone matrix rhyolitic to dacitic breccia resedimented intrusive hyaloclastite or resedimented peperite and graded lithic crystal pumice breccia and sandstone pumiceous and crystal rich turbidites the graded lithic crystal pumice breccia and sandstone facies is the submarine record of a volcanic centre s that is not preserved or is located outside the study area pumice shards and crystals are pyroclasts that reflect the importance of explosive magmatic and or phreatomagmatic eruptions and suggest that the source vents were in shallow water or subaerial settings the lithofacies associations at highway reward collectively define a submarine shallow intrusion dominated volcanic centre contact relationships and phenocryst populations indicate the presence of more than 13 distinct porphyritic units with a collective volume of 0 5 km 3 single porphyritic units vary from the size and shape of the lavas and intrusions reflect a restricted supply of magma during eruption intrusion the style of emplacement and the subaqueous emplacement environment due to rapid quenching and mixing with unconsolidated clastic facies the sills and cryptodomes did not spread far from their conduits the shape and distribution of the lavas and intrusions were further influenced by the positions of previously or concurrently emplaced units magma preferentially invaded the sediment avoiding the older units or conforming to their margins large intrusions and their dewatered envelope may have formed a barrier to the lateral progression and ascent of subsequent batches of magma

volcano sedimentary characteristics in the abu treifiya basin cairo suez district egypt example of dynamics and fluidization over sedimentary and volcaniclastic beds by emplacement of syn volcanic basaltic rocks abstract this paper describes the neogene lava sediment mingling from the abu treifiya basin cairo suez district egypt the lava sediment interactions as peperites have been identified for the first time at the study area and can be used as paleoenvironmental indicators the identification of peperite reflects contemporaneous time relationship between volcanism and sedimentation and this finding is of primary importance to address the evolutional reconstruction of the abu treifiya basin characterization of the facies architecture and textural framework of peperites was carried out through detailed description and interpretation of their outcrops the peperites and sedimentary rocks are up to 350 m thick and form a distinct stratigraphic framework of diverse lithology that is widespread over several kilometers at the study area lateral and vertical facies of the peperites vary from sediment intercalated with the extrusive intrusive basaltic rocks forming peperitic breccias to lava sediment contacts at a large to small scales respectively peperites encompass five main facies types ascribed to i carbonate sediments hosted fluidal and blocky peperites ii lava flow hosted blocky peperites iii volcaniclastics hosted fluidal and blocky peperites iv sandstone siltstone rocks hosted blocky peperites and iv debris flows hosted blocky peperites soft sediment deformation structures vesiculated sediments sediments filled vesicles and fractures in lava flows indicate that lava flows mingled with unconsolidated wet sediments all the peperites in this study could be described as blocky or fluidal but mixtures of different clast shapes occur regardless of the host sediment the presence of fluidal and blocky juvenile clasts elucidates different eruptive styles reflecting a ductile and brittle fragmentation the gradual variation from fluidal to blocky peperite texture producing the vertical grading is affected by influencing factors e g the viscosity magma temperature confining pressure sediment fluidization and vapor film at the magma sediment interactions peperites in the study area record deposition within a shallow marine and fluvio lacustrine environment accumulated in a rift related basin developed during pre to syn rift phase respectively the facies transitions peperites in this area resulted from the explosive and sediment depositional processes which were mingled separately by volcanism under contrast geological conditions the development of such contrast in the depositional sequences reflects variation in the accommodation to sediment supply in the same accumulation space inside the depocenters during the rifting of the abu treifiya basin hydrothermal mineralizations comprising quartz and carbonate are restricted to peperites and lava flows

eruptive and depositional history of a pliocene tuff ring that developed in a fluvio lacustrine basin kissomlyo volcano western hungary abstract kissomlyo volcano is a pliocene erosion remnant of an alkaline basaltic tuff ring belonging to the little hungarian plain volcanic field late miocene shallow subaqueous fluvio lacustrine sand and mud units underlie sub horizontally bedded lapilli tuff and tuff beds with an erosional contact the pyroclastic units a sequence up to 20 m thick constitute a semi circular mound with gentle

provenance signatures recorded in transgressive sandstones of the upper cretaceous iberian seaway abstract maximum mesozoic transgressions flooded many continental areas worldwide forming a wide and shallow seaway on the iberian microplate during the late cretaceous several siliciclastic and mixed siliciclastic carbonate units developed along the iberian massif cratonic area while at the same time epeiric carbonate platforms spanned iberia these siliciclastic deposits unconformably cover the variscan basement as well as the permian and triassic deposits this study focuses on sandstone provenance in central spain in a transgressive relatively quiet tectonic setting with a wide rock variety in the potential source areas results shown in this paper can be applied in analogue systems transgressive sandstones often form important hydrocarbon reservoirs due to their high primary porosity the cretaceous siliciclastic deposits are included in four formations ranging in age from the cenomanian to the early coniacian the deposits were initially of fluvial origin followed by a coastal tidal setting quantitative petrographic analysis of sandstones from these formations reveals compositional variations related to provenance and weathering degree the oldest formation utrillas fm was deposited on a paleorelief surface sandstone composition changes from arkosic sandstones in the depressed area petrofacies p1a to younger quartzarenites when sediments were deposited on top of the paleotopographic high petrofacies p1b quartz grains in both sub petrofacies are angular to subangular and the framework is poorly sorted intense weathering conditions are deduced for petrofacies p1b manifested by grain infiltration clay coatings and the absence of plagioclase grains and alteration features on k feldspars all these observations have been related to wetter conditions during p1b deposition main source areas of the utrillas fm were ordovician metasediments and orthogneisses permian volcanic rocks and triassic buntsandstein facies petrofacies 2 encompasses the three coastal tidal formations constituted mainly by subarkoses generally showing a subangular and poorly sorted framework the deduced source areas are mainly associated with variscan granitoids pre ordovician schists and paragneisses and ordovician metasediments glauconite and carbonate grains support intrabasinal inputs the low degree of sorting of this petrofacies related to a low energy sedimentary environment produced lower values of original porosity compared to transgressive sandstone hydrocarbon reservoirs also intrabasinal inputs promoted carbonate cementation and contribute to almost occlude the porosity

new insights into the structure of the south caspian basin from seismic reflection data gorgan plain iran this research presents an integrated study of 2d seismic reflections and calibrated well data to outline the structural development of the gorgan plain on the border of the south caspian hydrocarbon basin in the alborz and kopeh dagh ranges of northeast iran eight seismic horizons including two unconformities have been identified ranging in age from early jurassic to quaternary analysis and interpretation of geophysical data provide an understanding of the structural geology of the gorgan plain crucial for investigation of structural traps seismic interpretation indicates structural features such as deep reverse listric faults inverted normal faults for older formations strike slip and normal faults in younger sequences dome and basin interference patterns of folding for all the top formations well data demonstrate the occurrence of a disconformity at the base of upper cretaceous beds and an angular unconformity at the base of paleogene evidence identified in well and seismic reflection data proves a complex pattern of tectonic phases since the early jurassic it seems reasonable to suppose that these structural patterns are related to a change in direction of tectonic compression which in turn has produced structural hydrocarbon traps in crests of domes in the gorgan area

depositional mechanics and sequences of base surges songaksan tuff ring cheju island korea the songaksan mount in the southwestern part of cheju island korea is a taalian tuff ring produced by phreatomagmatic explosions at an aquifer a detailed analysis of proximal to distal facies changes reveals that the tuff ring sequence can be represented by 21 sedimentary facies one lateral facies sequence lfs and three vertical facies sequences vfs the vfs 1 and 2 are representative of facies relationships in horizontal near vent deposits the vfs 1 comprises scour fill bedded tuff inversely graded tuff massive tuff and laminated tuff from base to top the vfs 2 is a variant of the vfs 1 replaced by an inversely graded lapilli tuff unit at the base the sequences suggest traction carpet suspension and minor traction sedimentation from a high concentration near vent base surge the lfs 1 and the vfs 3 are distilled from outward dipping flank deposits both sequences begin with disorganized lapilli tuff followed successively by stratified lapilli tuff dune bedded lapilli tuff very thinbedded tuff and accretionary lapilli they are suggestive of waning base surge which decreases in particle concentration suspended load fall out rate and flow regimes with an increase in traction and sorting these facies sequences suggest that a base surge experiences flow transformation with its flow characters changing with time and space a near vent base surge is turbulent uniformly mixed and highly concentrated and produces scour fill bedded tuff as capacity decreases the surge transforms into a dense and laminar underflow and a dilute and turbulent upper part gravity transformation depositing inversely graded massive and normally graded lapilli tuff ensuing loss of sediment load and mixing of ambient air result in flow dilution surface transformation stratified and dune bedded units are produced by tractional processes of turbulent and low concentration surge further dilution causes deceleration and cooling and results in precipitation of moistened ash and accretionary lapilli from suspension

composite tuff ring cone complexes in jeju island korea possible consequences of substrate collapse and vent migration hydromagmatic volcanoes tuff rings and tuff cones in jeju island korea are divided into holocene volcanoes that were constructed upon rigid plateau forming lavas and early to middle pleistocene volcanoes that underlie the lavas and were constructed upon fragile unconsolidated sediments the older volcanoes are distinguished from the holocene volcanoes in that the former have irregular morphologies the irregular morphologies resulted from superposition or juxtaposition of multiple rim deposits of partial tuff rings and or tuff cones that have contrasting lithofacies characteristics bed attitudes and paleoflow directions the rim deposits are bounded by laterally persistent truncation surfaces which suggest large scale collapse of the substrate together with the overlying tephra piles and or erosion during a break in eruptive activity collapse was probably caused by the instability of the friable sedimentary substrate removal of lateral support because of downward quarrying of volcanic conduits and liquefaction of the water saturated substrate by volcanic seismicity the path of magma supply was diverted in some cases after collapse giving rise to migration of the active vent in other cases the eruption style changed abruptly from cone forming fallout dominated to ring forming surge dominated eruptions after collapse the resultant volcanic edifices thus consist of multiple rim beds of partial tuff rings and or tuff cones commonly with non circular morphologies substrate collapse and lateral vent migration as observed in jeju island appears to be an important phenomenon in hydromagmatic volcanoes because they are commonly constructed upon unstable sedimentary substrates substrate collapse and vent migration needs to be taken into account as an important control on volcano morphology and structures and as a means of lateral enlargement of terrestrial submarine or extraterrestrial volcanoes

closed system burial diagenesis in reservoir sandstones examples from the garn formation at haltenbanken area offshore mid norway abstract the middle jurassic garn formation of the haltenbanken area has been studied using mineralogical and geochemical data from 21 wells ranging in burial depths from 2 0 to 4 1 km relative to seafloor rsf k feldspar and plagioclase contents show variations on a regional scale both laterally and as a function of burial depth the content of pore filling authigenic illite increases sharply and the content of k feldspar and kaolinite decreases in garn sandstones presently at depths greater than 3 6 3 7 km rsf 120 130 c the depletion in k feldspar below 3 7 km rsf is not accompanied by lower potassium values in the bulk chemical composition wt k2o this suggests that the potassium released during k feldspar dissolution is retained in the sandstones and is precipitated as illite the variations in bulk contents of potassium and sodium are therefore considered to be related principally to primary variations in sandstone mineralogy the shallower sandstones 1 3 have a k feldspar kaolinite ratio greater than one the deeply buried 3 7 km rsf sandstones with similar potassium contents contain excess k feldspar and most of the kaolinite is illitized however deeply buried sandstones containing an average of 0 38 wt k2o k al molar ratio 1 4 contain a significant amount of kaolinite but negligible k feldspar this suggests that the k feldspar kaolinite ratio before the onset of illitization was less than one and hence that the kaolinite illite reaction has been restricted by an insufficient supply of potassium absence of k feldspar this illustrates how illitization of kaolinite depends upon k feldspar as a local source of potassium prediction of illitization in sandstones therefore must be based on integration of models for provenance facies and early diagenesis in addition to burial and thermal history the formation of pore filling authigenic illite in these sandstones is an important influence on the total reservoir quality

peperite as a record of early stage phreatomagmatic fragmentation processes an example from the hopi buttes volcanic field navajo nation arizona usa abstract peperite is the product of near surface magma wet sediment mingling some peperites are inferred to record frozen coarse mixing stage fuel coolant interactions fcis and hence can be used in attempts to determine specific parameters related to phreatomagmatic fragmentation such as water magma mass ratios confining pressures and vent region hydrology two lamprophyric dikes in the miocene pliocene hopi buttes volcanic field arizona contain ellipsoidal regions of dilation buds associated with peperite these peperite rimmed zones occur within identifiable stratigraphic horizons and at known depths beneath the elevation of the local pre eruptive surface the presence of both fluidal and blocky juvenile clasts combined with physical aspects of the sediment lamprophyre contacts suggest that coarse mixing stage fci was a potential fragmentation mechanism within these systems confining pressures calculated for sites of single buds range from 0 6 to 1 0 mpa average inferred water magma ratios within peperite bodies at the time they formed vary from 0 09 to 0 16 consistent with experimental values for water melt mixing ratios necessary for explosive heat transfer a number of factors may have inhibited further explosive activity in these peperite forming mixing events including anisotropic saturation of the host sediment low confining pressures and water melt ratios and damped explosive interactions resulting from increased density viscosity and surface tension of sediment water coolants nevertheless these deposits record localized thermohydraulic interactions between magma and wet sediment and provide valuable information about the geometry and mixing ratios present during peperite formation

confined aquifer head measurements and storage properties in the san luis valley colorado from spaceborne insar observations interferometric synthetic aperture radar insar a remote sensing technique for measuring centimeter level surface deformation is used to estimate hydraulic head in the confined aquifer of the san luis valley slv colorado reconstructing head measurements from insar in agricultural regions can be difficult as insar phase data are often decorrelated due to vegetation growth analysis of 17 l band alos palsar scenes acquired between january 2007 and march 2011 demonstrates that comprehensive insar deformation measurements can be recovered over the vegetated groundwater basin with an improved processing strategy local skeletal storage coefficients and time delays between the head change and deformation are estimated through a joint insar well data analysis insar subsidence estimates are transformed to head changes with finer temporal and spatial resolution than is possible using existing well records alone both insar and well data suggest that little long term water storage loss occurred in the slv over the study period and that inelastic compaction was negligible the seasonal head variations derived from insar are consistent with the existing well data at most locations where confined aquifer pumping activity dominates our results demonstrate the advantages of insar measurements for basin wide characterization of aquifer storage properties and groundwater levels over agricultural regions

detection of aquifer system compaction and land subsidence using interferometric synthetic aperture radar antelope valley mojave desert california interferometric synthetic aperture radar insar has great potential to detect and quantify land subsidence caused by aquifer system compaction insar maps with high spatial detail and resolution of range displacement 10 mm in change of land surface elevation were developed for a groundwater basin 103 km2 in antelope valley california using radar data collected from the ers 1 satellite these data allow comprehensive comparison between recent 1993 1995 subsidence patterns and those detected historically 1926 1992 by more traditional methods the changed subsidence patterns are generally compatible with recent shifts in land and water use the insar detected patterns are generally consistent with predictions based on a coupled model of groundwater flow and aquifer system compaction the minor inconsistencies may reflect our imperfect knowledge of the distribution and properties of compressible sediments when used in conjunction with coincident measurements of groundwater levels and other geologic information insar data may be useful for constraining parameter estimates in simulations of aquifer system compaction

deciphering vertical deformation and poroelastic parameters in a tectonically active fault bound aquifer using insar and well level data san bernardino basin california summary using insar and hydrogeologic time series spanning 1995 to 2000 we characterize the elastic storage and surface deformation in the vicinity of the san bernardino basin california the region encompasses a complex major aquifer located at the junction of the san andreas and san jacinto faults that supplies groundwater to over 600 000 people we remove the elastic vertical surface displacement associated with changes in groundwater levels from the insar time series by a least squares inversion our method estimates a poroelastic ratio at 60 well sites which we normalize by basin depth allowing for comparison of the elastic response of the aquifer skeleton from site to site our method also estimates residual vertical displacement rates at each well site surface displacement not explained by observed trends in groundwater levels residual vertical displacement rates reveal patterns of subsidence and uplift across the basin over the 5 yr period from 1995 to 2000 in a narrow zone of observed residual subsidence near the san jacinto fault where many normalized poroelastic ratios trend higher than expected we find permanent compaction of clay rich strata to be the most likely explanation for 0 5 2 0 mm yr 1 of residual subsidence this permanent compaction is likely a result of delayed compaction due to previous overdraft conditions and or a result of the installation of deep production wells during the span of the insar time series observations of localized subsidence within stepovers of the san jacinto fault zone and relative uplift at the range fronts are consistent with current basin development models however interseismic strain modelling of the regional faults does not reproduce the surface displacement pattern or magnitude of these observations

estimating temporal changes in hydraulic head using insar data in the san luis valley colorado the sustainability of the confined aquifer system in the san luis valley colorado is of utmost importance to the valley s agricultural economy there is a dearth of hydraulic head measurements in the confined aquifer to which the current groundwater flow model can be calibrated here we investigate the extent to which spatially and temporally dense measurements of deformation from interferometric synthetic aperture radar insar data can be used to fill in spatial and temporal gaps in the head data set by calibrating the insar data with head at the monitoring well locations we conduct this calibration at 11 wells where we expect sufficient deformation for reliable insar measurement given the accepted level of uncertainty 1 cm in the san luis valley crop growth degrades the quality of the insar signal which means that the high quality deformation data may not be collocated with the wells we use kriging to estimate the deformation directly at the well locations we find that the calibration is valid at three well locations where the seasonal magnitude of the deformation is much larger than the uncertainty of the insar measurement at these well locations we predict head prior to and within the temporal sampling window of the head measurements we find that 59 of the insar predicted hydraulic head values agree with the measured values within the uncertainty of the data given our success in extending the hydraulic head data temporally the next step in our research is to use insar data to interpolate spatially between head measurements

inverse modeling of interbed storage parameters using land subsidence observations antelope valley california 1 we use land subsidence observations from repeatedly surveyed benchmarks and interferometric synthetic aperture radar insar in antelope valley california to estimate spatially varying compaction time constants and inelastic specific skeletal storage coefficients s kv in a previously calibrated regional groundwater flow and subsidence model the observed subsidence patterns reflect both the spatial distribution of head declines and the spatially variable inelastic skeletal storage coefficient using the nonlinear parameter estimation program ucode we estimate compaction time constants between 3 8 and 285 years the s kv values are estimated by linear estimation and range from 0 to almost 0 09 we find that subsidence observations over long time periods are necessary to constrain estimates of the large compaction time constants in antelope valley the insar data used in this study cover only a three year period limiting their usefulness in constraining these time constants this problem will be alleviated as more sar data become available in the future or where time constants are small by incorporating the resulting parameter estimates in the previously calibrated regional model of groundwater flow and land subsidence we can significantly improve the agreement between simulated and observed land subsidence both in terms of magnitude and spatial extent the sum of weighted squared subsidence residuals a common measure of model fit was reduced by 73 with respect to the original model however the ability of the model to adequately reproduce the subsidence observed over only a few years is impaired by the fact that the simulated hydraulic heads over small time periods are often not representative of the actual aquifer hydraulic heads errors in the simulated hydraulic aquifer heads constitute the primary limitation of the approach presented here

interactions between andesitic magma and poorly consolidated sediments examples in the neogene shirahama group south izu japan abstract the upper miocene lower pliocene shirahama group of south izu japan is a sequence of volcanielastic shallow sea sediments and subaqueous lava flows it is gently warped with indistinct preferred orientation and is cross cut by many andesitic intrusive bodies which range in size from less than a meter to several hundred meters the intrusive bodies exhibit various shapes and weak preferred orientation and often have hyaloclastic and peperitic textures along their peripheries hydrothermally altered and chaotically disturbed zones of host rocks also occur along the contacts the areas where the intrusive bodies are abundant are almost coincident with the areas where the more inclined beds and synsedimentary faults are developed the intrusive bodies dragged the surrounding beds with or without synsedimentary faults some intrusions occurred along the faults conjugate sets of the faults indicate that they were produced under unstable stress conditions these relationships between the beds and the intrusive bodies are assumed to have originated mostly by interaction between hot magma and poorly consolidated wet sediments at a shallow depth beneath the sea floor when the intrusions took place the stress conditions in the beds were irregular and unstable judging from the shapes and orientation of the intrusive bodies and also from the deformation characteristics of the enclosing beds some of the intrusive bodies are probably feeder dikes which supplied lave to the shirahama group

variation in peperite textures associated with differing host sediment properties peperites formed by mixing of magma and wet sediment are well exposed along punta china baja california mexico where two sills intrude a section of lava flows limestones and volcaniclastic rocks irregular lobes and dikes extend from the sills several meters into host sediments including highly comminuted flow top breccias lithic lapilli tuff breccias and shelly micrites whereas intrusive contacts with lava flows are sharp and planar where one sill intruded both coarse grained volcaniclastic rock and fine grained limestone textural differences between the hosts produced strikingly different styles of peperite blocky masses of the basaltic intrusions up to 1 m in size were dispersed for distances up to 3 m into host lithic lapilli tuff breccias the blocks consequently underwent in situ fragmentation as they were rapidly quenched the high degree of dispersion resulted from steam explosions as the magma enveloped pockets of water in the coarse grained permeable host elutriation of fine grained material from vertical pipes in tuff breccia above the lower sill provides evidence for meter scale fluidization of the host the contact zone between the basaltic magma and the shelly micrite host resembles a mixture of two viscous immiscible fluids fluidal peperite intrusion occurred behind a stable vapor film which entrained lime mud particles and carried them off grain by grain as magma advanced into the host thin section scale elutriation pipes formed microglobular peperite represents a frozen example of a fuel coolant interaction fci between basaltic magma and fluidized micrite host the intimate intermixing of magma and host at the submillimeter level is attributed to fluid instabilities developed along the magma vapor host interface such intimate intermixing of magma and water bearing fragmental debris is commonly a precursory step toward explosive hydrovolcanism

blocky versus fluidal peperite textures developed in volcanic conduits vents and crater lakes of phreatomagmatic volcanoes in mio pliocene volcanic fields of western hungary abstract volcanic fields in the pannonian basin western hungary comprise several mio pliocene volcaniclastic successions that are penetrated by numerous mafic intrusions peperite formed where intrusive and extrusive basaltic magma mingled with tuff lapilli tuff and non volcanic siliciclastic sediments within vent zones peperite is more common in the pannonian basin than generally realised and may be also important in other settings where sediment sequences accumulate during active volcanism hajagos hegy an erosional remnant of a maar volcano was subsequently occupied by a lava lake that interacted with unconsolidated sediments in the maar basin and formed both blocky and globular peperite similar peperite developed in kissomlyo a small tuff ring remnant where dykes invaded lake sediments that formed within a tuff ring lava foot peperite from both hajagos hegy and kissomlyo were formed when small lava flows travelled over wet sediments in craters of phreatomagmatic volcanoes at sag hegy a large phreatomagmatic volcanic complex peperite formed along the margin of a coherent intrusion all peperite in this study could be described as globular or blocky peperite globular and blocky types in the studied fields occur together regardless of the host sediment

diagenetic paths in the margin of a triassic basin nw zone of the iberian chain spain buntsandstein deposits generated in a slowly subsiding basin on the western margin of the iberian chain are represented by a stratigraphic succession of fluvial deposits less than 100 m thick conglomerates sandstones and shales diagenetic processes in sandstones can be grouped as eodiagenetic mesodiagenetic and telodiagenetic eodiagenesis can be associated with muschelkalk keuper and probably early jurassic times mesodiagenesis is probably related to jurassic times diagenetic chemical reactions suggest a maximum burial less than 1 5 km and low temperatures 120oc patterns of porosity reduction by compaction and cementation suggest four diagenetic stages 1 loss of primary porosity by early mechanical compaction 2 early cementation kfeldspar and dolomite 3 dissolution of cements and 4 framework collapse by re compaction these stages are manifested by the presence of two types of sandstone type i sandstones present high intergranular volume mean 30 type ii sandstones are characterized by high compactional porosity loss and exhibit low values of intergranular volume mean 16 9 type ii sandstones are associated with the dissolution of cement and later re compaction of type i sandstones an intermediate telodiagenetic phase is deduced and related to the sharp unconformity between lower cretaceous sediments and the underlying sediments this suggests that a mechanically unstable framework collapsed during the cretaceous generating type ii sandstones the analyzed diagenetic paths have a wide applicability on similar marginal areas of rift basins

structures and grain size distribution in surge deposits as a tool for modelling the dynamics of dilute pyroclastic density currents at la fossa di vulcano aeolian islands italy abstract turbulent dilute pyroclastic density currents surges represent the most common and hazardous type of eruptive event at la fossa di vulcano during the volcanic history these currents have frequently passed over the topographic barrier of la fossa caldera maintaining a high velocity we interpret lateral facies variation in terms of fluid dynamic behaviour by analyses of structures thickness and grain size of correlated surge layers from the palizzi succession using these data we validate a sedimentation model of traction fed by a low concentration turbulent and stratified current by the use of a sedimentological model we have then reconstructed the fluid dynamic parameters of the current and calculated the maximum horizontal distance that solid particles travelled before deposition results have been checked against actual deposit features consistency of data indicates that the method used in this study even if it is approximate and needs further refinement by specific experimental approaches and numerical simulations gives a reasonable indication of surge characters such as velocity and density which are relevant for hazard calculation and risk assessment

rothenberg scoria cone east eifel a complex strombolian and phreatomagmatic volcano rothenberg scoria cone eifel formed by an alternation of three strombolian and three phreatomagmatic eruptive phases eruptions took place from up to six vents on a 600 m long fissure building an early tuff ring and then two coalescing scoria cones strombolian volcanism dominated volumetrically as the supply of external water was severely limited magma water interaction only occurred during the opening stages of eruption at any vent when discharge rates were low and the fragmentation surface was below the water table the phreatomagmatic deposits consist of relatively well sorted fall beds and only minor surge deposits they contain juvenile clasts with a wide range of vesicularity and grain size implying considerable heterogeneity in the assemblage of material ejected by the phreatomagmatic explosions the transition from phreatomagmatic to strombolian eruption at any vent was rapid and irreversible and strombolian volcanism persisted even when eruption rates are inferred to have waned at the close of each eruptive phase as by then the fragmentation surfaces were high in the growing cones and water was denied access to the magma the strombolian deposits are relatively homogenous consisting of alternating coarser and finer grained well sorted fall beds erupted during periods of open vent eruption and partial blockage of the vent respectively the intervals of strombolian eruption were always a delicate balance between discharge of freely degassing magma and processes such as ponding of degassed magma in the vent collapse of the growing cones and repeated recycling of clasts through the vent clear evidence of the instability of the rothenberg cones is preserved in numerous unconformities within deposits of the inner walls of the cones the close of strombolian phases was probably marked by a decreasing supply of magma to the vents accompanied by ponding and stagnation of lava in the craters

diagenetic processes influencing porosity in sandstones from the triassic buntsandstein of the iberian range spain abstract sandstones of the triassic buntsandstein of spain were studied in an attempt to quantify effects of diagenetic processes such as compaction cementation and leaching on reservoir properties samples were taken from shell well siguenza 44 3 some 110 km northeast of madrid drilled on the siguenza high in the iberian range the sandstones are arkoses to sublitharenites of a typical triassic redbed facies characteristic of the whole region the present day depth of the base buntsandstein is 538 m whilst a maximum burial depth of ca 2600 m was estimated from vitrinite reflectance 0 94 to 1 14 kaolinite temperature 76 c and illite crystallinity kuebler index 4 9 from an estimated average initial porosity of 38 porosity was reduced to the present value of 13 the strongest process to reduce porosity was found to be mechanical compaction causing a loss of 15 followed by chemical compaction pressure solution with a loss of about 6 the cement 11 4 r v apparently reduced the initial porosity by about only 5 early carbonate and sulphate cements are interpreted to have stabili sed the rock framework working against mechanical compaction and pressure solution this is supported by an increase in sutured grain contacts where early cements are absent or rare the later quartz cement interpreted to be largely the product from pressure solution has reduced porosity in a ratio of 0 5 1 this suggests that compaction continued after the formation of the late quartz cement although leaching was observed especially in feldspar grains clay and k feldspar neomorphosis is interpreted to have counteracted the formation of substantial secondary porosity permeability in the buntsandstein is generally low average 17 4 md and has been strongly affected by the alteration of feldspars to clay causing a wide range of permeability from 0 11 to 73 0 md

fragmentation versus transportation mechanisms in the pyroclastic sequence of monte pilato rocche rosse lipari italy abstract monte pilato is a rhyolitic pumice cone formed about 1400 years ago during the last volcanic activity which occurred at lipari its activity consisted of numerous explosive episodes ending with the extrusion of the rocche rosse obsidian lava flow we have identified nine different pyroclastic lithofacies of which four main lithofacies represent 90 of the erupted products they include 1 deposits consisting of decimeters to meters thick well sorted graded beds of pumice lapilli which are of fall origin 2 massive deposits consisting of decimeters thick beds of pumice lapilli in an ash matrix interpreted as being of pyroclastic flow origin 3 deposits of centimeters thick ash beds of surge origin 4 decimeter thick fine ash layers with scattered subcentimetric accretionary lapilli of turbulent flow origin the complex grain size distributions of the main lithofacies were distinguished using a multivariate statistic analysis r mode factor analysis variations of the grain size characteristics in relation to the distance from the vent area have been investigated in order to discriminate the roles played by fragmentation and transportation processes in the lithofacies 1 fall deposits the grain size distribution is always unimodal and varies from a rosin type distribution near the vent to a gaussian one in the distal outcrops this is caused by the transport process and the different particle trajectories in lithofacies 2 3 and 4 the grain size distributions are always polymodal the polymodality is not caused by preferential processes occurring during transportation but seems rather to be connected with the original fragmentation of the pyroclastic material the pumice lapilli present both in lithofacies 1 and 2 have mean vesicularity index values always in excess of 65 and the value is homogeneous throughout the sample these data suggest that for these two lithofacies the pumice lapilli originated from exsolution of magmatic gases in contrast the fine ash particles in lithofacies 2 and also the main mode of lithofacies 3 and 4 deposits show typical features of hydromagmatic fragmentation processes the grain size population is always centered at 4 5 0 032 0 064 mm and interestingly the same grain size has been obtained recently zimanowski et al 1991 for fragments produced by experimental magma water interaction field and laboratory data suggest that during monte pilato rocche rosse eruptions magmatic and hydromagmatic mechanisms were frequently operative at the same time

diagenesis of carbonate cements in permo triassic sandstones from the iberian range spain evidence from chemical composition and stable isotopes petrographic chemical and stable isotope investigations have been made on calcite dolomite and fe dolomite ankerite from permian triassic clastic sequences from the iberian range spain calcite and dolomite cements have precipitated before the fe dolomite ankerite calcite however has also formed by calcitization of dolomite due to uplift the negative 13cpdb values 9 51 to 2 13 in these carbonates suggest derivation of carbon from oxidation of organic matter in the early carbonates and from decarboxylation of organic matter in the late fe dolomite ankerite early diagenetic dolomitic cements have heavier 13c 3 54 higher mn mn fe and mn mn mg and lower fe fe mg ratios than later diagenetic dolomitic cements the latters are also characterized by lighter 18opdb 10 64 than the early cements due to increase in temperature and to pore water mineral reactions

the fekete hegy balaton highland hungary soft substrate and hard substrate maar volcanoes in an aligned volcanic complex implications for vent geometry subsurface stratigraphy and the palaeoenvironmental setting the fekete hegy volcanic complex is located in the centre of the bakony balaton highland volcanic field in the pannonian basin which formed from the late miocene to pliocene period the eruption of at least four very closely clustered maar volcanoes into two clearly distinct types of prevolcanic rocks allows the observation and comparison of hard substrate and soft substrate maars in one volcanic complex the analyses of bedding features determination of the proportion of accidental lithic clasts granulometry and age determination helped to identify and distinguish the two types of maar volcanoes ascending magma interacted with meteoric water in karst aquifers in mesozoic carbonates as well as in porous media aquifers in neogene unconsolidated wet siliciclastic sediments the divided basement setting is reflected by distinct bedding characteristics and morphological features of the individual volcanic edifices as well as a distinct composition of pyroclastic rocks country rocks in hard substrate maars have a steep angle of repose leading to the formation of steep sided cone shaped diatremes enlargement and filling of these diatreme is mainly a result of shattering material by fci related shock waves and wall rock collapse during downward penetration of the explosion locus country rocks in soft substrate maars have much shallower angles of repose leading to the formation of broad bowl shaped structures or irregular depressions enlargement and filling of these diatremes is mainly the result of substrate collapse for example due to liquefaction of unconsolidated material by fci related shock waves and its emplacement by gravity flows the fekete hegy is an important example illustrating that the substrate of a volcanic edifice has to be taken into account as an important interface which can have major control on phreatomagmatic eruptions and the resulting characteristics of the volcanic complex

bayesian data fusion for water table interpolation incorporating a hydrogeological conceptual model in kriging 1 the creation of a contour map of the water table in an unconfined aquifer based on head measurements is often the first step in any hydrogeological study geostatistical interpolation methods e g kriging may provide exact interpolated groundwater levels at the measurement locations but often fail to represent the hydrogeological flow system a physically based numerical groundwater model with spatially variable parameters and inputs is more adequate in representing a flow system because of the difficulty in parameterization and solving the inverse problem however a considerable difference between calculated and observed heads will often remain in this study the water table interpolation methodology presented by fasbender et al 2008 in which the results of a kriging interpolation are combined with information from a drainage network and a digital elevation model dem using the bayesian data fusion framework is extended to incorporate information from a tuned analytic element groundwater model the resulting interpolation is exact at the measurement locations whereas the shape of the head contours is in accordance with the conceptual information incorporated in the groundwater flow model the bayesian data fusion methodology is applied to a regional unconfined aquifer in central belgium a cross validation procedure shows that the predictive capability of the interpolation at unmeasured locations benefits from the bayesian data fusion of the three data sources kriging dem and groundwater model compared to the individual data sources or any combination of two data sources

permanent scatterer insar reveals seasonal and long term aquifer system response to groundwater pumping and artificial recharge received 4 may 2007 revised 30 july 2007 accepted 10 october 2007 published 5 february 2008 1 permanent scatterer insar psinsark p rovides an ew high resolution methodology for detecting and precisely measuring long term and seasonal aquifer system response to pumping and recharge in contrast to conventional insar the permanent scatterer methodology utilizes coherent radar phase data from thousands of individual radar reflectors on the ground to develop displacement time series and to produce velocity field maps that depict aquifer system response with a high degree of spatial detail in this study we present the first results of a prototype study in las vegas valley nevada that demonstrate how this methodology can be utilized in heavily pumped groundwater basins to analyze aquifer system response to long term and seasonal pumping we have developed a series of velocity field maps of the valley for the 1992 1996 1996 2000 and 2003 2005 time periods that show that despite rising water levels associated with an artificial recharge program long term residual inelastic aquifer system compaction subsidence is continuing in several parts of the valley in other areas however long term subsidence has been arrested and locally reversed the seasonal elastic responses to alternating pumping and recharge cycles were segregated from the long term trends and analyzed for spatial and temporal patterns the results show oscillations in which the maximum seasonal responses are associated with the late stages of the annual artificial recharge cycles and that similar seasonal subsidence signals are related to summer pumping cycles the differentiation of the seasonal response through the use of time series data further allows the estimation of elastic and inelastic skeletal storage coefficients providing a basis for future work that could characterize the storage properties of an aquifer system with a high degree of spatial resolution

intra vent peperites related to the phreatomagmatic 71 gulch volcano western snake river plain volcanic field idaho usa abstract the western snake river plain volcanic field in sw idaho contains up to 400 basaltic vents and centers that produced lava shields pahoehoe lava fields scoria cones and a great variety of phreatomagmatic volcanoes between late miocene and middle pleistocene time tephra deposits produced by phreatomagmatic eruptions are particularly well exposed in the walls of the snake river canyon where thick accumulations of pyroclastic rocks indicate widespread phreatomagmatic eruptive events throughout most of the volcanic history of the region previously many of the phreatomagmatic deposits were considered to be the products of subaqueous eruptions that took place on the floor of one or more large freshwater intra continental lakes recent field based observations confirm the presence of widespread phreatomagmatic pyroclastic rocks however some that had been interpreted as being subaqueous exhibit textural features that are more consistent with subaerial depositional environments intrusive and extrusive magmatic bodies with features associated with peperite formation have also been identified most of these peperites can be attributed to magma sediment mixing in intra crater conduit or vent settings and therefore they can only be used as widespread paleoenvironmental indicators with limitations to demonstrate magma and surface water e g lake non explosive interaction one of the studied sites 71 gulch volcano was previously used to indicate the presence of a shallow lake at this site there is clear field evidence that peperitic feeder dykes contacted muddy sandy siliciclastic sediments forming globular peperite the peperitic feeder dykes transition to pillowed ponded lava up section the ponded lavas are partially surrounded by a 5 m thick unit composed of gently dipping dune bedded volcanic glass shard rich unsorted tuff and lapilli tuff containing abundant impact sags caused by volcanic lithics we suggest that the 3d architecture of the erosional remnant of 71 gulch volcano does not require the presence of a lake at the time of its formation it is equally possible that that it represents a subaerial phreatomagmatic upper conduit crater filling succession this interpretation opens up many questions about the mio pliocene evolution of sw idaho the timing of the volcanism and its association with the evolution of the lacustrine systems in the region in addition re evaluations of the volcanic features in sw idaho have some general implications for the usage of phreatomagmatic pyroclastic rocks for paleoenvironmental reconstruction

premixing of magma and water in mfci experiments experimental studies have been performed to evaluate pre explosive water melt mixes with respect to explosive volcanic molten fuel coolant interaction mfci i e phreatomagmatic explosion remolten ultrabasic volcanic rock was used as a magma simulant measurement of the explosion intensity was used to determine optimal premixing conditions a well defined optimal range was found for the hydrodynamic mixing energy differential flow speed of 4 2 m s as well as for the water melt mass ratio 0 03 to 0 04 under experimental conditions the mass flux of water had a minor influence on the explosion intensity additionally transparent mixing experiments with silicon oil and inked water were carried out they indicate a direct dependence of the pre explosive water melt interface area on the explosion intensity the experimental results show that the contact conditions of water and melt required for explosive mfci may easily be established in natural volcanic systems thus explosive mfci is a probable mechanism of explosive volcanism

three dimensional p and s wave velocity structure below unzen volcano abstract unzen volcano located in southwestern japan erupted on november 17 1990 after 198 years of dormancy and has been ejecting lava since may 20 1991 in this paper we present three dimensional p and s wave velocity variations below unzen volcano using 22 473 p and 14 349 s wave arrival times from 3457 local earthquakes recorded on a local network of twelve seismic stations the model was parameterized by 24 000 approximately 2 0 km cubic blocks targeting a volume of 120 100 20 km a prominent low velocity anomaly greater than 4 slowness perturbation starting from 2 5 to 5 0 km depth beneath the volcano is observed on both the p and s wave inversions below unzen volcano slightly lower amplitude low velocity anomalies are further observed to a depth of 12 5 km for p and 7 5 km for s waves shallow low velocity anomalies are observed below the chijiwa bay area northwest of unzen and deeper anomalies are seen below shimabara bay southwest of shimabara peninsula this nw se trending feature represents an elongated system of dykes which supply the shallow magma reservoirs

types of phreatomagmatic volcanoes in the western snake river plain idaho usa abstract the western snake river plain graben in southwestern idaho includes a large hydrovolcanic field which was produced in late miocene to pleistocene time by the interaction of rising basaltic magmas with the waters and water saturated deposits of an enormous freshwater lake lake idaho the phreatomagmatic volcanoes in this field may be grouped into three types emergent subaqueous and subaerial emergent volcanoes which began erupting under water and built up above the lake level are relatively large and symmetrical are dominated by bedded tuffs and late magmatic deposits and are excellent indicators of water depth at the time of the eruption subaqueous volcanoes which never built up above the lake level are relatively small and asymmetrical are dominated by basal massive deposits and are potentially useful in discriminating between deep and very deep water settings subaerial volcanoes which were formed when magmas intercepted buried aquifers and interacted explosively with water are small tuff rings and maars with variable shapes are composed of subequal although variable proportions of basal massive deposits bedded tuffs and late magmatic deposits and are useful in determining the stratigraphic successions underlying them

maar diatreme phreatomagmatism at hopi buttes navajo nation arizona usa remnants of an extensive maar diatreme volcanic field are magnificently exposed at various depths of erosion in the hopi buttes volcanic field of northeastern arizona field and petrographic studies of both the maar and diatreme elements of a selection of volcanoes within the field show that 1 lower sections of the maar rim sequences are typically rich in sandy mudrock derived from the pre eruptive mio pliocene bidahochi formation and the muddy bidahochi sediment was soft and wet at the time of maar eruptions 2 beds higher within the rims contain generally increased proportions of sandstone clasts from the triassic wingate formation in the diatremes late emplaced breccia has deeper seated lithics than more marginal breccia emplaced earlier and 3 many vents are topped by megacryst enriched scoria and spatter and deep seated xenoliths are known only from upper diatreme and craterfilling tephra these observations show that 1 eruptions at hopi buttes involved interaction of magma with unconsolidated mudrock at shallow levels and the phreatomagmatic processes that provided the bulk of the energy involved in the violent eruptions were driven by the interaction of magma and wet sediment 2 the locus of explosive activity migrated downward as eruptions progressed and 3 the closing stage of many eruptions was characterized by rapid magma rise and relative depletion of water

peperite a review of magma sediment mingling the study of peperite is important for understanding magma water interaction and explosive hydrovolcanic hazards this paper reviews the processes and products of peperite genesis peperite is common in arc related and other volcano sedimentary sequences where it can be voluminous and dispersed widely from the parent intrusions it also occurs in phreatomagmatic vent filling deposits and along contacts between sediment and intrusions lavas and hot volcaniclastic deposits in many environments peperite can often be described on the basis of juvenile clast morphology as blocky or fluidal but other shapes occur and mixtures of different clast shapes are also found magma is dominantly fragmented by quenching hydromagmatic explosions magma sediment density contrasts and mechanical stress as a consequence of inflation or movement of magma or lava magma fragmentation by fluid fluid shearing and surface tension effects is probably also important in fluidal peperite fluidisation of host sediment hydromagmatic explosions forceful intrusion of magma and sediment liquefaction and shear liquification are probably the most important mechanisms by which juvenile clasts and host sediment are mingled and dispersed factors which could influence fragmentation and mingling processes include magma host sediment and peperite rheologies magma injection velocity volatile content of magma total volumes of magma and sediment involved total volume of pore water heated presence or absence of shock waves confining pressure and the nature of local and regional stress fields sediment rheology may be affected by dewatering compaction cementation vesiculation fracturing fragmentation fluidisation liquefaction shear liquification and melting during magma intrusion and peperite formation the presence of peperite intraclasts within peperite and single juvenile clasts with both sub planar and fluidal margins imply that peperite formation can be a multi stage process that varies both spatially and temporally mingling of juvenile clast populations formed under different thermal and mechanical conditions complicates the interpretation of magma fragmentation and mingling mechanisms

diagenetic k feldspar pseudomorphs in the triassic buntsandstein sandstones of the iberian range spain early diagenetic k feldspar in the triassic buntsandstein of the iberian range spain occurs as pseudomorphs after detrital k feldspar or 99 untwinned commonly heavily clouded by vacuoles and tiny inclusions dark luminescing and are composed of numerous fine euhedral crystals of k feldspar the latter property suggests that the pseudomorphs form via dissolution of detrital k feldspar and plagioclase and precipitation of authigenic k feldspar x ray diffraction analysis shows that the authigenic k feldspar is intermediate microcline

ancient subaerial exposure and freshwater leaching in sandstones the authors present an example of leaching by meteoric water in the jurassic magnus sandstone member of the northern north sea the interpretation is based on information from several independent techniques including downhole natural gamma ray spectrometry detailed petrographic analysis and cross sectional time slice reconstructions from seismic data the initial lines of evidence that prompted further investigation into freshwater involvement in the magnus sandstone member were brackish formation water compositions and a potassium depletion shown by the gamma ray spectrometry log in sandstone beneath the unconformity at the base of the cretaceous section subsequent detailed petrographic study confirmed that the potassium depletion had been brought about by potassium feldspar dissolution resulting in precipitation of kaolinite and creation of secondary porosity the latter also revealed by conventional core analysis porosity and permeability measurements finally cross sectional time slice reconstructions from a regional seismic line across the magnus oilfield strongly suggested subaerial exposure of the magnus sandstone member in early cretaceous time and consequent freshwater leaching of the magnus sandstone member and generation of the unconformity at the base of the cretaceous the combination of several lines of evidence from the magnus field supports the process of subaerial exposure and freshwater leaching to create secondary porosity in sandstones

provenance of triassic feldspathic sandstones in the iberian range spain significance of quartz types abstract the base of the triassic in the iberian range is represented by detrital sediments buntsandstein facies deposited initially in a continental environment finally evolving into a marine environment that is represented at the top of the sequence the lithology of this facies is dominated by arkosic sandstones the aim of this study is to reconstruct the nature and position of the source areas of these sandstones provenance research was carried out by quartz grain typology eleven stratigraphic sections were sampled the amount of interstitital matrix has been considered in selecting samples because mechanical compaction suffered by sandstones with little matrix may give rise to a significant increase in the undulosity of monocrystalline quartz the ollo de sapo gneissic formation located in the hesperian massif has been mentioned as source rocks of feldspathic sandstones in previous works in order to verify the provenance of feldspathic sandstones in artificial sands derived by grinding gneisses and sand samples collected at stream heads that drain the gneiss outcrops we followed the methodology of basu et al 1975 analytical results indicate that two different areas within the triassic basin were notably influenced by different source areas a a western zone the nearest to the gneissic source rocks where monocrystalline nonundulatory quartz grains predominate qm 5 increase sediment evolution during transport processes is markedly reflected by the increase in qm 5 ratios in the westernmost zone away from the source area low values in the above mentioned ratios in the eastern zone are interpreted as results of local influence by low ranking metamorphic source areas finally this ethod also allows for the monitoring of the evolution of sediment maturity throughout the basin

water upwelling pipes and soft sediment deformation structures in lower pleistocene calcarenites salento southern italy a thin sedimentary blanket consisting mostly of subtidal unconformity bounded calcarenite units was deposited in the small novoli graben apulian foreland southern italy in pliocene2pleistocene time in a limited part of the study area the lower pleistocene calcarenite di gravina forming the thicker part of this blanket is crossed by continuous to discontinuous cylindrical pipes as much as 12 m high most commonly consisting of stacked concaveupward laminae locally grading upward into soft sediment deformation features and large dishes the evidence favors an origin linked to upwelling of overpressured groundwater from a large karstic reservoir hosted in the mesozoic carbonate rocks the reservoir periodically developed a relatively high hydrostatic head due to tertiary to pleistocene cover acting as an aquitard or aquiclude as a result submarine springs were generated the activity of which was primarily controlled by relative sea level fluctuations it is suggested that the pipes were located in those points where the hydrostatic pressure was sufficient to fluidize the overlying sediment and could be released without notably affecting the surrounding sediments some pipes cross calcarenitic infills of karstic sinkholes developed in the underlying units whereas others follow the course of vertical to high angle extensional synsedimentary tectonic fractures generated when the calcarenites were still in an unconsolidated to semiconsolidated state the former relationships suggest that vertical routes of water upwelling during highstand of base level commonly coincided with axes of vadose solution during base level lowstand the latter suggest that opening of fractures enhanced the connection of the deep aquifer with the surface hence intensifying water upwelling we think that fluidization along the fractures was not hindered by the partially coherent state and that pipes with a cylindrical geometry could form in spite of the planarity of the fractures the formation of the pipes and their internal structure of stacked concave upward laminae is thought to be consistent with a process of fluidization due to through flowing waters we believe that essential in this process is the role of upward migrating transient water filled cavities akin to the voidage waves hassett s 1961a 1961b parvoids experimentally reproduced by several authors in liquid fluidized beds and regarded as true instability phenomena of a fluidized suspension occurring above minimum fluidization velocity it is suggested that the process is akin to the production of the dish structure it consists of the filling of transient upward migrating water filled cavities through steady fallout of particles from the cavity roof their redeposition in a more consolidated state and subsidence of the roof due to water seepage upward from the cavity the process was accompanied by segregation of grains according to their size and density as well by elutriation of finest particles and led to a new pattern of sediment texture packing and fabric with respect to the surrounding calcarenites

facies variation of eruption units produced by the passage of single pyroclastic surge currents hopi buttes volcanic field usa abstract base surges are a significant volcanic hazard associated with phreatomagmatism but their transport and depositional dynamics are incompletely understood stratigraphic analysis and lateral tracing of surge eruption units produced by the passage of single base surges from haskie tuff ring hopi buttes volcanic field usa extend to 1 km from the vent and show similar downcurrent changes in lithofacies within 200 m of the vent eruption units are primarily disorganized lapilli tuff that is rich in juvenile pyroclasts at distances 200 m from the vent eruption units transform into a couplet of juvenile rich lapilli that grades upward into bedform bearing ash tuff at distances 900 m upper and lower beds of the eruption unit couplet transform into planar stratified beds at distances 1100 m couplets composing different eruption units are almost entirely composed of planar beds and amalgamate to form almost identical planar bedded ash tuff the collapse of dense eruption columns following explosive magma wet sediment interaction generated turbulent surge currents as the surges traveled away from the haskie vent they expanded and partitioned into a basal juvenile rich traction carpet and overlying accidental rich ash cloud surge near the limit of their runout the surges cooled and lost their pyroclastic load leaving planar beds of accidental rich ash the deposition of multiple surge eruption units with similar lateral and vertical facies transitions and a paucity of interbedded fallout suggests an eruption characterized by recurring phreatomagmatic explosions of similar size and the generation of surges with similar flow characteristics

physical volcanology of a large crater complex formed during the initial stages of karoo flood basalt volcanism sterkspruit eastern cape south africa abstract the sterkspruit complex exposed at the base of the karoo flood basalts in south africa is a complex of mostly massive volcaniclastic rocks dikes and lava that fills a crater 45 km 2 cut into country rock and is surrounded by a blanket of more distal bedded volcaniclastic rocks the moderately to steeply inward dipping margins of the crater are delineated by country rock breccia that grades into rocks within the complex intra complex rocks are dominated by massive polymict lapilli tuff and tuff breccia 150 m thick with intercalated lavas and minor bedded volcaniclastic rocks pillow lava 50 m thick and thinly bedded inferred lacustrine deposits cap the complex succession and are in turn covered by subaerial karoo flood basalts beyond the crater a succession of bedded finer grained volcaniclastic rocks 100 60 m thick rests on country rock and thins distally over at least 5 km magma emplaced over a broad area through a network of feeder dikes and sheets created many small vents that grew into their neighbours through lateral quarrying and vent migration and whose deposits overlap both within and outside the complex an abrupt end to eruptions that formed volcaniclastic deposits is recorded by flooding of the lowest part of the crater by first water then lava then subsequently by inundation of the complex and the surrounding landscape by voluminous effusion of flood basalt formation of the sterkspruit complex and many others like it in south africa confirms that the opening phases of karoo flood basalt volcanism were partly explosive the abundant volcaniclastic products at sterkspruit and in other flood basalt provinces result from eruptions that disperse ash and volcanic aerosols differently than effusive eruptions of lava and thus may have important implications for climate change and landscape development associated with the initial stages of flood basalt provinces

estimating the permanent loss of groundwater storage in the southern san joaquin valley california in the san joaquin valley california recent droughts starting in 2007 have increased the pumping of groundwater leading to widespread subsidence in the southern portion of the san joaquin valley vertical subsidence as high as 85 cm has been observed between june 2007 and december 2010 using interferometric synthetic aperture radar insar this study seeks to map regions where inelastic not recoverable deformation occurred during the study period resulting in permanent compaction and loss of groundwater storage we estimated the amount of permanent compaction by incorporating multiple datasets the total deformation derived from insar estimated skeletal specific storage and hydraulic parameters geologic information and measured water levels during our study period we used two approaches one that we consider to provide an estimate of the lowest possible amount of inelastic deformation and one that provides a more reasonable estimate these two approaches resulted in a spatial distribution of values for the percentage of the total deformation that was inelastic with the former estimating a spatially averaged value of 54 and the latter a spatially averaged value of 98 the former corresponds to the permanent loss of 4 14 108 m3 of groundwater storage or roughly 5 of the volume of groundwater used over the study time period the latter corresponds to the loss of 7 48 108 m3 of groundwater storage or roughly 9 of the volume of groundwater used this study demonstrates that a data driven approach can be used effectively to estimate the permanent loss of groundwater storage this article is protected by copyright all rights reserved

satellite interferometric observations of displacements associated with seasonal groundwater in the los angeles basin 1 the newport inglewood fault zone nifz displays interferometric synthetic aperture radar sar phase features along most of its length having amplitudes of up to 60 mm however interpretation in terms of right lateral shallow slip along the fault fails to match the range of geologic estimates of slip recently bawden et al 2001 proposed that these phase features as well as a broader deformation pattern in the los angeles basin are due to vertical motion related to annual variations in the elevation of the water table we confirm this hypothesis through the analysis of a longer span of data consisting of 26 sar images collected by the ers 1 and ers 2 spacecraft between june 1992 and june 2000 moreover we use continuous gps measurements from 1995 to the present to establish the amplitude and phase of the vertical deformation the los angeles basin becomes most inflated one quarter of the way through the year which is consistent with water table measurements as well as with the end of the rainy season when the aquifer should be at a maximum the spatial pattern of the amplitude of the annual signal derived from continuous gps measurements is consistent with the shape of the interferometric fringes gps sites both near the nifz and in a 20 by 40 km zone within the basin also show significant n s annual variations that may be related to the differential expansion across the fault since these horizontal signals have peak to trough amplitudes of 6 mm they mask the smaller tectonic signals and need to be taken into account when interpreting gps time series of site position moreover since the groundwater signal appears to have a long term vertical trend which varies in sign depending on location it will be difficult to distinguish interseismic tectonic slip along the nifz and within the affected areas in the basin

characterization of land deformation hydraulic head and aquifer properties of the gorgan confined aquifer iran from insar observations abstract in this study interferometric synthetic aperture radar insar is applied to analyze the land deformation across the gorgan plain iran where recent droughts and over exploitation of groundwater leading to widespread subsidence having significant long term and seasonal signals in head measurements analysis of tops s1 month scaled images from october 2014 to october 2016 exhibits significant inelastic 70 mm yr on average and seasonal elastic ranging from about 20 to 132 mm vertical land deformation over the gorgan confined aquifer system gcas according to the decomposed vertical displacement map the investigations indicate that these significant deformations are due to both severe head decline up to 2 m yr and the presence of thick aquitards intervening aquifers to obtain elastic land deformation totally recoverable and static head components the inelastic partially recoverable and long term head decline trends are removed by lines fitted to the land deformation and head time series respectively having a high cross correlation coefficient between the seasonal components of head and land deformation time series ranging from 0 60 to 0 93 0 78 on average we use a joint well insar data analysis to estimate bulk aquifer parameters of the elastic skeletal storativity 0 0035 to 0 0142 0 0085 on average specific storage 1 54 10 5 to 7 68 10 5 m 1 4 35 10 5 m 1 on average and compressibility 1 50 10 10 to 7 40 10 10 n m 2 4 20 10 10 n m 2 on average at 14 piezometer locations insar derived aquifer storage properties are reasonably correlated with the hydrogeological setting of gcas moreover the elastic land deformation data are acceptably transformed to head fluctuations at 14 piezometers and several arbitrary point locations it is observed that the heads reconstructed from insar and measured in piezometers are consistent over a broad portion of gcas seasonal elastic land deformations occurred between wet and dry seasons in 2015 are also used to map the confining degree across gcas the higher confining degree has been observed in those areas of higher subsidence signatures implying that the subsidence potential in confined aquifers is higher than that of unconfined aquifers in this study we have demonstrated more benefits of the insar observations in estimating aquifer storage properties and predicting head in confined aquifers of significant subsidence signatures with better temporal and spatial resolution than that can be retrieved from hydrogeological data alone

large phreatomagmatic vent complex at coombs hills antarctica wet explosive initiation of flood basalt volcanism in the ferrar karoo lip the mawson formation and correlatives in the transantarctic mountains and south africa record an early eruption episode related to the onset of ferrar karoo flood basalt volcanism mawson formation rocks at coombs hills comprise mainly 80 vol structureless tuff breccia and coarse lapilli tuff cut by irregular dikes and sills within a large vent complex 30 km2 quenched juvenile fragments of generally low but variable vesicularity accretionary lapilli and country rock clasts within vent fill and pyroclastic density current deposits point to explosive interaction of basalt with groundwater in porous country rock and wet vent filling debris metre scale dikes and pods of coherent basalt in places merge imperceptibly into peperite and then into surrounding breccia steeply dipping to sub vertical depositional contacts juxtapose volcaniclastic rocks of contrasting componentry and grainsize these sub vertical tuff breccia zones are inferred to have formed when jets of debris steam water passed through unconsolidated vent filling deposits these jets of debris may have sometimes breached the surface to form subaerial tephra jets which fed subaerial pyroclastic density currents and fall deposits others however probably died out within vent fill before reaching the surface allowing mixing and recycling of clasts which never reached the atmosphere most of the ejecta that did escape the debris filled vents was rapidly recycled as vents broadened via lateral quarrying of country rock and bedded pyroclastic vent rim deposits which collapsed along the margins into individual vents the unstratified poorly sorted deposits comprising most of the complex are capped by tuff lapilli tuff and tuff breccia beds inferred to have been deposited on the floor of the vent complex by pyroclastic density currents development of the extensive coombs hills vent complex involved interaction of large volumes of magma and water we infer that recycling of water as well as recycling of pyroclasts was important in maintaining water supply for phreatomagmatic interactions even when aquifer rock in the vent walls lay far from eruption sites as a consequence of vent complex widening the proportion of recycled water increased with vent complex size in the same way that the proportion of recycled tephra did though water recycling leaves no direct rock record the volcaniclastic deposits within the vent complex show through their lithofacies structural architecture lithofacies characteristics and particle properties clear evidence for extensive and varied recycling of material as the complex evolved

satellite radar interferometry time series analysis of surface deformation for los angeles california 1 the los angeles california metropolitan area is a tectonically active region with surface deformation that is a combination of fault related tectonics plus a variety of natural and anthropogenic signals we apply the small baseline subset sbas algorithm to produce an interferometric synthetic aperture radar insar time series analysis for the los angeles area using data acquired by the ers satellites from late 1995 into 2002 the result is a space time deformation product that can be exploited to view not only the smoothly varying long term surface motion but also its time varying patterns large seasonal oscillations of the santa ana aquifer observed in southern california integrated gps network scign data are accurately matched in the insar time series moreover correlations of the insar time series with an annual sinusoid allows us to investigate the dynamics of the hydrologic system index terms 1243 geodesy and gravity space geodetic surveys 1294 geodesy and gravity instruments and techniques 1803 hydrology anthropogenic effects citation lanari r p lundgren m manzo and f casu 2004 satellite radar interferometry time series analysis of surface deformation for los angeles california geophys res lett 31 l23613 doi 10 1029 2004gl021294

characteristics of aquifer system deformation in the southern yangtse delta china excessive groundwater pumpage has caused regional cones of depression and severe land subsidence in the southern yangtse delta china the characteristics of aquifer system compaction are complex because of the difference in the types compositions and structures of the soils that the hydrostratigraphic units are composed of and in the histories of groundwater level change the hydrostratigraphic units have experienced based on the data measured from extensometer groups and observation wells the characteristics of deformation for individual hydrostratigraphic units are analyzed the results show that different hydrostratigraphic units have different kinds of deformation and that an identical unit may also present different deformation characteristics such as elasticity elasto plasticity and visco elasto plasticity at different sites of the cone of depression or in different periods if the groundwater level rises continuously and remains constant later the aquifers and the aquitard units that consist of hard clay primarily exhibit elastic behaviour but the aquitard units that consist of soft clay deform plastically and by creep and exhibit visco elasto plastic behaviour if the groundwater level falls but is much higher than the previous lowest value aquifers and aquitards consisting of hard clay exhibit elasto plastic behaviour if the groundwater level falls below the previous lowest value aquifers and aquitards consisting of hard clay deform plastically and by creep and exhibit visco elasto plastic behaviour

granulation of weak rock as a precursor to peperite formation coal peperite coombs hills antarctica abstract peperite formed by mingling of magma with coal and with fragmented coal plus other country rock is exposed at coombs hills antarctica in rocks of the mawson formation where ferrar supergroup basalt encountered the beacon supergroup continental sedimentary succession an internally laminated 0 5 m thick coal bed passes gradationally through a coal fragment dominated peperite into a glass rich basalt dominated coal fragment matrix peperite and then into coherent basalt initial interaction of magma with water saturated coal and host sediments locally brecciated the coal subsequent mingling of basalt with a slurry of coal fragments and water driven by viscosity and density contrasts between the basalt and the slurry and by flow inhomogeneities in intruding magma led to increasingly complex mingling of the two fluids via bifurcation of fingering viscous flows this mingling was complicated by the participation of phases with time and space dependent thermal properties and viscosity coal fragments coal water slurry and basaltic magma and the generation of multiple gas phases through devolatilisation of heated coal the initial elastic response of the coal fragments to stress resulted in a fluidal mingling of coal and basalt facilitated by softening of coal during heating associated with intrusion and b localised formation of blocky coal clasts during high stress events associated with passage of a liquid and or a gas phase s through the coal the presence of fluidal and blocky shaped coal fragments in the coal peperite with both curved and planar surfaces bounding single coal clasts suggests that clast morphology in the magma sediment dispersion was controlled at very small scales by the time temperature and stress dependent qualities of the coal fluidal and blocky clast shapes in the coal peperite coupled with vesicles in the coal clasts suggest that transient properties of either the host or intrusion during non explosive magma sediment interaction may exert a strong control on clast morphology and mingling characteristics

a quasi elastic aquifer deformational behavior madrid aquifer case study summary the purpose of this paper is to analyze the quasi elastic deformational behavior that has been induced by groundwater withdrawal of the tertiary detrital aquifer of madrid spain the spatial and temporal evolution of ground surface displacement was estimated by processing two datasets of radar satellite images sar using persistent scatterer interferometry psi the first sar dataset was acquired between april 1992 and november 2000 by ers 1 and ers 2 satellites and the second one by the envisat satellite between august 2002 and september 2010 the spatial distribution of psi measurements reveals that the magnitude of the displacement increases gradually towards the center of the well field area where approximately 80 mm of maximum cumulated displacement is registered the correlation analysis made between displacement and piezometric time series provides a correlation coefficient greater than 85 for all the wells the elastic and inelastic components of measured displacements were separated observing that the elastic component is on average more than 4 times the inelastic component for the studied period moreover the hysteresis loops on the stress strain plots indicate that the response is in the elastic range these results demonstrate the quasi elastic behavior of the aquifer during the aquifer recovery phase ground surface uplift almost recovers from the subsidence experienced during the preceding extraction phase taking into account this unique aquifer system a one dimensional elastic model was calibrated in the period 1997 2000 subsequently the model was used to predict the ground surface movements during the period 1992 2010 modeled displacements were validated with psi displacement measurements exhibiting an error of 13 on average related with the inelastic component of deformation occurring as a long term trend in low permeability fine grained units this result further demonstrates the quasi elastic deformational behavior of this unique aquifer system

fluidization of wet sediments during the emplacement and cooling of various igneous bodies during the emplacement and cooling of igneous bodies fluidization of wet sediment by water vapour may occur by heating or by pressure relief during the opening of fractures momentary fluidization causes sediment reconstitution and local transport continuous fluidization can result in substantial sediment displacement theoretical considerations show that fluidization due to heating is not likely to occur at depths where pressure is much greater than 312 bars studies of the emplacement of sills of andesite ayrshire fluid rhyolite ramsey island and viscous rhyolite moelwyn hills recognize a wide range of phenomena attributable to wet sediment fluidization and in places modify existing interpretations the transgressive bases of the subaqueously welded ash flow tuffs of the capel curig volcanic formation are consistent with emplacement attended by fluidization of the subjacent sediment evidently fluidization is a means by which large volumes of wet sediment can be replaced by igneous material with minimal disturbance of the remaining host also fluidization can result in exceptionally complex contact relationships between sedimentary host and intrusive rocks and can cause fractures formed during cooling to be thoroughly pervaded by sediment fluidization is commonly associated with the formation of peperites

unusually large clastic dykes formed by elutriation of a poorly sorted coarser grained source tuff dykes of unusual size invade coarser grained volcaniclastic rocks of the jurassic mawson formation at coombs hills and allan hills antarctica we infer that the material for the largest dykes was elutriated from their host9s matrix to our knowledge this mode of genesis has not been invoked before in this volcanic setting elutriation was driven by magmatic heat but the production of relatively finer grained clastic dykes by elutriation of material from coarser ill sorted sources may be significant in many settings

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

the miocene costa giardini diatreme iblean mountains southern italy model for maar diatreme formation on a submerged carbonate platform in this paper we present a model for the growth of a maar diatreme complex in a shallow marine environment the miocene age costa giardini diatreme near sortino in the region of the iblei mountains of southern sicily has an outer tuff ring formed by the accumulation of debris flows and surge deposits during hydromagmatic eruptions vesicular lava clasts accretionary lapilli and bombs in the older ejecta indicate that initial eruptions were of gas rich magma abundant xenoliths in the upper late deposited beds of the ring suggest rapid magma ascent and deepening of the eruptive vent is shown by the change in slope of the country rock the interior of the diatreme contains nonbedded breccia composed of both volcanic and country rock clasts of variable size and amount the occurrence of bedded hyaloclastite breccia in an isolated outcrop in the middle lower part of the diatreme suggests subaqueous effusion at a low rate following the end of explosive activity intrusions of nonvesicular magma forming plugs and dikes occur on the western side of the diatreme and at the margins close to the contact between breccia deposits and country rock they indicate involvement of volatile poor magma possibly during late stages of activity we propose that initial hydromagmatic explosive activity occurred in a shallow marine environment and the ejecta created a rampart that isolated for a short time the inner crater from the surrounding marine environment this allowed explosive activity to draw down the water table in the vicinity of the vent and caused deepening of the explosive center a subsequent decrease in the effusion rate and cessation of explosive eruptions allowed the crater to refill with water at which time the hyaloclastite was deposited emplacement of dikes and plugs occurred nonexplosively while the breccia sediment was mostly still soft and unconsolidated locally forming peperites the sheltered low energy lagoon filled with marine limestones mixed with volcaniclastic material eroded from the surrounding ramparts ultimately lagoonal sediments accumulated in the crater until subsidence or erosion of the tuff ring caused a return to normal shallow marine conditions

tectonic systems tract and depositional architecture of the western border of the triassic iberian trough central spain abstract during the permian and triassic a sedimentary wedge developed overlying a listric normal fault on the western border of the iberian trough central spain an area was selected for study that provides optimal conditions for a detailed analysis to be made of relationships between geometric strata arrangements tectonic control and sedimentary responses the excellent quality of the outcrops allows the observed patterns of strata to be related to fault growth and developmental of the basin the recognition and mapping of local discontinuities throughout the study area were possible packages of similar strata with different angularity can be discerned between the two main discontinuities geometrical relationships can be established for depositional unit boundaries the architectural style and sediment dispersal patterns interpreted as the results of interactions between sedimentation and tectonics are integrated into a three dimensional tectono sedimentary facies model to explain the basin s infilling is interpreted to be tectonic the rift related three dimensionally linked depositional systems recognized might be defined as tectonic systems tract prosser s 1993 rift related linked depositional systems and their seismic expression in williams g d dobb a eds tectonics and seismic sequence stratigraphy geol soc london spec publ 71 35 66 five such tracts are recognized and related to specific phases of tectonic development

origin and stratigraphy of phreatomagmatic deposits at the pleistocene sinker butte volcano western snake river plain idaho abstract sinker butte is the erosional remnant of a very large basaltic tuff cone of middle pleistocene age located at the southern edge of the western snake river plain phreatomagmatic tephras are exposed in complete sections up to 100 m thick in the walls of the snake river canyon creating an unusual opportunity to study the deposits produced by this volcano through its entire sequence of explosive eruptions the main objectives of the study were to determine the overall evolution of the sinker butte volcano while focusing particularly on the tephras produced by its phreatomagmatic eruptions toward this end twenty three detailed stratigraphic sections ranging from 20 to 100 m thick were examined and measured in canyon walls exposing tephras deposited around 180 of the circumference of the volcano three main rock units are recognized in canyon walls at sinker butte a lower sequence composed of numerous thin basaltic lava flows an intermediate sequence of phreatomagmatic tephras and a capping sequence of welded basaltic spatter and more lava flows we subdivide the phreatomagmatic deposits into two main parts a series of reworked mostly subaqueously deposited tephras and a more voluminous sequence of overlying subaerial surge and fall deposits most of the reworked deposits are gray in color and exhibit features such as channel scour and fill planar stratification high and low angle cross stratification trough cross stratification and bouma turbidite sequences consistent with their being deposited in shallow standing water or in braided streams the overlying subaerial deposits are commonly brown or orange in color due to palagonitization they display a wide variety of bedding types and sedimentary structures consistent with deposition by base surges wet to dry pyroclastic fall events and water saturated debris flows proximal sections through the subaerial tephras exhibit large regressive cross strata planar bedding and bomb sags suggesting deposition by wet base surges and tephra fallout medial and distal deposits consist of a thick sequence of well bedded tephras however the cross stratified base surge deposits are thinner and interbedded within the fallout deposits the average wavelength and amplitude of the cross strata continue to decrease with distance from the vent these bedded surge and fall deposits grade upward into dominantly fall deposits containing 75 95 juvenile vesiculated clasts and localized layers of welded spatter indicating a greatly reduced water melt ratio overlying these dryer deposits are massive tuff breccias that were probably deposited as water saturated debris flows lahars the first appearance of rounded river gravels in these massive tuff breccias indicates downward coring of the diatreme and entrainment of country rock from lower in the stratigraphic section the wetter nature of these deposits suggests a renewed source of external water the massive deposits grade upward into wet fallout tephras and the phreatomagmatic sequence ends with a dry scoria fall deposit overlain by welded spatter and lava flows field observations and two new 40 ar 39 ar incremental heating dates suggest the succession of lavas and tephra deposits exposed in this part of the snake river canyon may all have been erupted from a closely related complex of vents at sinker butte we propose that initial eruptions of lava flows built a small shield edifice that dammed or disrupted the flow of the ancestral snake river the shift from effusive to explosive eruptions occurred when the surface water or rising ground water gained access to the vent as the river cut a new channel around the lava dam water levels dropped and the volcano returned to an effusive style of eruption

turbulent boundary layer shear flows as an approximation of base surges at campi flegrei southern italy abstract small volume base surge deposits of astroni and agnano monte spina eruptions at campi flegrei consist of sets of beds formed by the passage of multiple pyroclastic density currents each set is made by a fining upward sequence consisting from base to top of 1 an inversely graded layer made of bombs and lapilli 2 a finely laminated layer with wavy bedforms made of coarse ash and fine lapilli 3 a structureless fine ash bed lack of discontinuities at layer contacts allows us to hypothesize that each set of beds represents the passage of one pyroclastic density current the sequence formed as a function of the decreasing particle transportation capability of the base surge during the waxing sustained waning phases of flowage we make the simplifying assumptions that the flow on passing from the deposition of the inversely graded layer to the deposition of the finely laminated layer had low particle concentration was quasi steady and incompressible by such assumptions some of the equations that regulate sediment mechanics are applicable to the base surges of campi flegrei to reconstruct flow density and shear velocity in between the deposition of the two layers structural and textural features of deposits stress the importance of shear and turbulence during transportation and suggest that the turbulent boundary layer shear flow is a good approximation to such pyroclastic density currents we used the coles formula to reconstruct velocity as a function of flow height during the formation of the finely laminated layer of astroni and agnano monte spina base surges the methodology we used allows the reconstruction of flow parameters just at a particular point in time and space of base surge evolution and does not provide the complete picture of the flow history of pyroclastic density currents nevertheless flow velocity and density data as obtained with the proposed approach point to dynamic pressure values that are compatible with those reported for similar currents on other volcanoes we conclude therefore that the results obtained give approximate but helpful information on the nature of such hazardous events at campi flegrei

geochemical constraints from formation water analyses from the north sea and the gulf coast basins on quartz feldspar and illite precipitation in reservoir rocks

seasonal subsidence and rebound in las vegas valley nevada observed by synthetic aperture radar interferometry analyses of areal variations in the subsidence and rebound occurring over stressed aquifer systems in conjunction with measurements of the hydraulic head fluctuations causing these displacements can yield valuable information about the compressibility and storage properties of the aquifer system historically stress strain relationships have been derived from paired extensometer piezometer installations which provide only point source data because of the general unavailability of spatially detailed deformation data areal stress strain relations and their variability are not commonly considered in constraining conceptual and numerical models of aquifer systems interferometric synthetic aperture radar insar techniques can map ground displacements at a spatial scale of tens of meters over 100 km wide swaths insar has been used previously to characterize larger magnitude generally permanent aquifer system compaction and land subsidence at yearly and longer timescales caused by sustained drawdown of groundwater levels that produces intergranular stresses consistently greater than the maximum historical stress we present insar measurements of the typically small magnitude generally recoverable deformations of the las vegas valley aquifer system occurring at seasonal timescales from these we derive estimates of the elastic storage coefficient for the aquifer system at several locations in las vegas valley these high resolution measurements offer great potential for future investigations into the mechanics of aquifer systems and the spatial heterogeneity of aquifer system structure and material properties as well as for monitoring ongoing aquifer system compaction and land subsidence

sandstone porosity loss a big picture view of the importance of compaction proper assessment of the relative importance of porosity loss by compaction and cementation is important to the prediction of porosity in sandstones studies of mass transport during diagenesis and the modeling of basin fluid flow quantitative estimation of the amounts of porosity loss by compaction and cementation can be made from standard point count data on cement and pore space abundance this method is discussed and its sources of error are evaluated error in the method arises mainly from uncertainty in initial sandstone porosities and the amount of local grain dissolution during burial data on the porosity of modern sands indicate that assumed initial porosities of 40 to 45 will produce small average errors in the calculation of compactional porosity loss for clean sandstones grain dissolution whether resulting in local porosity enhancement by export in solution of former grain mass or local precipitation of authigenic cement will cause an underestimation of the significance of compaction a large database of point count data from diverse sandstones is used to provide a broad perspective on the importance of compaction and cementation to sandstone porosity loss it is shown that the global importance of compactional porosity loss has generally been under appreciated in fact compaction mechanical and chemical is probably the dominant mechanism of porosity loss in most sandstones the extent of compactional porosity loss is related to sand grain composition and basin thermal structure

seismic expression and geological significance of a lacustrine delta in neogene deposits of the western snake river plain idaho high resolution seismic reflection profiles and well data from the western snake river plain basin are used to identify a buried lacustrine delta system within neogene idaho group sediments near caldwell idaho the delta system is detected 305 m 1000 ft deep near the center of the basin by progradational clinoform reflections having dips of 2 5 a slope typical of prodelta surfaces of modern lacustrine delta systems the prodelta slope relief corrected for compaction indicates the delta system prograded northwestward into a lake basin 255 m 837 ft deep resistivity logs in the prodelta mud and clay facies are characterized by gradual upward increase in resistivity and grain size over a thickness of about 100 m 300 ft lithology of the prodelta is mostly c lcareous claystone with several layers of fine sand some of which fine upward indicating a density flow mechanism of transport and deposition delta plain and front sediments are mostly very fine grained well sorted sand separated by thin mud layers these sediments produce several to five cycles of horizontal high amplitude reflections with a toplap relationship to prodelta clinoforms the sands have an abrupt lower contact with prodelta muds and have high resistivity on logs in this study permeable lacustrine sands within a predominantly mud and clay section are located by using high resolution seismic reflection data identification of a delta system in the idaho group provides insight into the history of pliocene lake idaho the present depth of the delta prodelta facies contact of 305 m 1000 ft is 445 to 575 m 1460 1900 ft below the lake deposits on the margins estimated subsidence from compaction is 220 m 656 ft and the remaining 225 to 325 m 740 1066 ft is attributed to tectonic downwarping and faulting the original lake area had been reduced to one third of the original 13 000 km2 5000 mi2 by the time the delta front prograded to the caldwell area the original lake area may have been sufficient to evaporate most of the inflow and the lake may have only occasionally spilled into other basins diminished area for evaporation later in the history of the lake combined with reduced evaporation accompanying onset of the ice ages may have caused the lake to rise and overtop a basin sill about 2 ma and subsequently deepen hells canyon

characterisation of hydraulic head changes and aquifer properties in the london basin using persistent scatterer interferometry ground motion data in this paper persistent scatterer interferometry was applied to ers 1 2 and envisat satellite data covering 1992 2000 and 2002 2010 respectively to analyse the relationship between ground motion and hydraulic head changes in the london basin united kingdom the integration of observed groundwater levels provided by the environment agency and satellite derived displacement time series allowed the estimation of the spatio temporal variations of the chalk aquifer storage coefficient and compressibility over an area of 1360 km2 the average storage coefficient of the aquifer reaches values of 1 10 3 and the estimated average aquifer compressibility is 7 7 10 10 pa 1 and 1 2 10 9 pa 1 for the periods 1992 2000 and 2002 2010 respectively derived storage coefficient values appear to be correlated with the hydrogeological setting where confined by the london clay the storage coefficient is typically an order of magnitude lower than where the chalk is overlain by the lambeth group psi derived storage coefficient estimates agree with the values obtained from pumping tests in the same area a simplified one dimensional model is applied to simulate the ground motion response to hydraulic heads changes at nine piezometers the comparison between simulated and satellite observed ground motion changes reveals good agreement with errors ranging between 1 4 and 6 9 mm and being 3 2 mm on average

entrainment of country rock during basaltic eruptions of the lucero volcanic field new mexico as magma rises through the lithosphere it may entrain wall rock debris the entrainment process depends on the local hydrodynamic regime of the magma e g velocity temperature bulk density the extent of interaction of magma with groundwater and the mechanical properties of the wall rocks wall rock entrainment results in local flaring of dikes and conduits which in turn affects the hydrodynamics of magma ascent and eruption we studied upper crustal xenoliths erupted from small volume basaltic volcanoes of the lucero volcanic field west central new mexico in order to assess the relative importance of various entrainment mechanisms during a range of eruptive styles including strongly hydrovolcanic strombolian and effusive processes total xenolith volume fractions ranged from 0 3 0 9 in hydrovolcanic facies to 10 4 10 2 in strombolian facies the volcanoes erupted through a thick well characterized sequence of paleozoic and lower mesozoic sedimentary rocks so that erupted xenolith

dynamic mingling of magma and liquefied sediments abstract hydrodynamic mingling of magma and liquefied sediments is generally accepted to represent the key process in the formation of some peperites experimental studies on simulant liquids and calculations based on recent empirical findings in the field of polymer research were undertaken to investigate the effectiveness of this process these studies show that for a wide range of shear rates a laminar flow behaviour of the system magma liquefied sediment can be expected i e turbulent mingling is not a realistic scenario formation of peperitic fabrics with grain sizes on a cm scale can hydrodynamically be explained under realistic intrusion velocities in addition to the hydrodynamics cooling processes must also be considered during peperite formation calculations of the cooling history of the juvenile magmatic component under realistic cooling conditions demonstrate a significant limitation of the hydrodynamic mingling time the consequence for peperite formation under normal intrusion conditions is that domains of magmatic melt and domains of liquefied sediment smaller than 10 cm are not probable however as smaller domain sizes peperitic grain sizes exist in nature we conclude that either those peperites represent the products of explosive events or that hydrodynamic mingling was accompanied by additional fragmentation processes

dating diagenesis in a petroleum basin a new fluid inclusion method the final porosity and permeability of sandstone petroleum reservoirs is greatly affected by the diagenetic growth of minerals after deposition for example a sand may be deposited with a porosity of 25 and a permeability of 5 000 mdarcy md 1 diagenetic growth of quartz around detrital sand grains may leave a rock with only 10 porosity and later growth of clays may partly fill these remaining pores and block inter pore connections reducing permeability to 100 md ref 2 if the depth and timing of such diagenetic alteration can be measured and the extent of diagenesis estimated then prediction of the diagenetic state of undrilled sandstones may become possible and diagenesis related more closely to the timing of hydrocarbon migration and the formation of hydrocarbon traps we present an example of a new method for estimating the date of quartz diagenesis using a combination of techniques from thin section petrography fluid inclusion thermometry organic geochemical thermometry and sedimentary basin stratigraphic analysis these results suggest that quartz in the beatrice oilfield was precipitated from moving and cooling pore fluids at a temperature between 68 c and 94 c in the late jurassic

chilling and brecciation of a devonian rhyolite sill intruded into wet sediments northern sierra nevada california localized pockets of peperite breccia occur near the base of a well exposed hypabyssal rhyolite sill within the upper devonian volcanic sequence of the northern sierra nevada the peperites resulted from chilling fragmentation and commingling of rhyolite with wet poorly consolidated sediment zones of hyaloclastite breccia extend into the sill above the peperites and represent areas where chilled rhyolite underwent fragmentation but was not intermixed with sediment a dense spherulitic intergrowth developed rapidly within the chilled rhyolite immediately prior to its fragmentation formation of this quench texture probably reflects a reduction in viscosity of the magma due to retention of volatiles in the melt under conditions of relatively high confining pressure

origin and metamorphism of peperite and associated rocks in the devonian elwell formation northern sierra nevada california the late devonian elwell formation is part of a late paleozoic island arc assemblage exposed in the northern sierra nevada california in the 10 km interval from mount elwell plumas county to packer lake sierra county it consists largely of numerous andesitic sills interleaved with phosphatic radiolarian chert and turbidity current and debris flow deposits peperite formed by interaction of intrusive andesitic magma and still moist incompletely lithified chert not far beneath the sea floor occurs sparingly the whole assemblage was thoroughly recrystallized greenschist facies regional metamorphism during the late jurassic nevadan orogeny the phosphatic chert is composed of white fluorapatite rich lenses and nodules enclosed in a black matrix consisting of microgranular quartz and carbonaceous material probably graphite radiolaria family entactiniidae are so abundant that the chert is thought to have originated as radiolarian ooze the phosphatic lenses and nodules probably formed by direct inorganic precipitation of fluorapatite from pore water within decaying radiolarians at the sediment water interface the andesitic sills are generally aphyric and aphanitic original textures varied from hyalopilitic in sill interiors to pilotaxitic at sill margins the andesite was charged with plagioclase now albite microlites and quench morphologies occur where sills intruded the wettest chert relatively thick sills commonly display columnar structure whereas a few originally more viscous sills are flow laminated the top of a sill emplaced essentially at the sediment water interface is pillowed many sills bear xenoliths of phosphatic chert and scarce quartz megacrysts evidently derived from the underlying dacitic sierra buttes formation appear nearly everywhere concentrations of major element oxides and immobile trace elements indicate that the andesite originated as part of the tholeiitic rock association of island arcs rare earth abundance patterns are particularly diagnostic of this paleotectonic setting most peperite has poorly sorted coarse ash to coarse block andesitic fragments uniformly distributed through a voluminous black chert matrix where invaded chert retained the most pore water quenched andesitic magma formed irregularly shaped lapilli and small pillows that initially exhibited ductile behavior rapid cooling below the softening point of glass resulted in brittle fracture of the lapilli during dispersal through the chert by steam explosions steam explosions also incorporated into the peperite rigid clasts of locally dewatered chert and shattered already formed phosphatic nodules where the invaded chert was better lithified freezing sill margins simply granulated quietly in situ by thermal contraction cracking of microlitic glass fluid chert injected widely spaced contraction joints deep within the sills in all cases there was sufficient heated connate water to cause palagonitization and chloritization of andesitic fragments greenschist facies metamorphism produced two mineral assemblages in the interiors of andesitic sills the second perhaps reflecting locally higher pco 2 ph 2 o during metamorphism 1 albite quartz epidote actinolite chlorite ti rich mineral calcite stilpnomelane white mica and 2 albite quartz chlorite ti rich mineral calcite stilpnomelane white mica epidote rich specks occurring sporadically in the sills represent metasomatism on a scale of millimetres to centimetres such specks are mineralogically zoned in andesitic fragments in intensely recrystallized peperite additional examples of local meta somatic activity include syntectonic crystallization of calcite rhombohedra across original vesicle walls in a sill cleavage developed locally during regional metamorphism is parallel to axial planes of closely appressed folds that deformed andesitic fragments in peperite and flow laminae in sills

eruptive styles and inferences about plumbing systems at hidden cone and little black peak scoria cone volcanoes nevada u s a we describe two small scoria cone volcanoes hidden cone and little black peak ages between 320 390 ka in the southwestern nevada volcanic field and discuss their eruption mechanisms and inferences about their plumbing systems cone forming pyroclastic deposits are consistent with eruptive styles ranging from strombolian to violent strombolian and lavas emanated from near the bases of the cones the volcanoes are monogenetic rather than polycyclic as allowed by previous geomorphic interpretations vents at each volcano appear to coincide with pre existing normal faults consistent with observations at older deeply eroded volcanoes in the region the existence of these two volcanoes on a topographically high area particularly hidden cone provides evidence for short feeder dike lengths 500 m at the surface we infer that this short length reflects the small length scale of the mantle source region that was tapped to feed each volcano

immense vent complex marks flood basalt eruption in a wet failed rift coombs hills antarctica large lava effusions can have impressive explosive antecedents although our picture of flood basalt is overwhelmingly effusive phreatomagmatic eruptions have preceded quiet effusion of some flood basalts and reflect the same influence of vent architecture and hydrology on eruptive style as seen for small volume eruptions the scale of phreatomagmatic deposits associated with flood basalts can be huge at coombs hills a vast but otherwise typical phreatomagmatic vent complex is exposed over more than 25 km 2 and its features are interpreted to reflect processes of tephra jet eruptions with diatreme development similar vent complexes are probably the source of laharic deposits reported elsewhere in the transantarctic mountains and in the karoo province of south africa

shallow plumbing systems for small volume basaltic volcanoes eruptive dynamics in basaltic volcanoes are controlled in part by the conduit geometry however uncertainties in conduit shape and dike to conduit transition geometry have limited our predictive capability for hazards assessments we characterize the subvolcanic geometry of small volume basaltic volcanoes magmatic volatile driven eruptions 0 1 to 0 5 km3 based on a synthesis of field studies of five basaltic volcanoes exposed to varying degrees by erosion and exhibiting feeder dikes conduits and vent areas 250 m depth study areas include east grants ridge new mexico usa basalt ridge east basalt ridge paiute ridge and southeast crater flat nevada usa basaltic feeder dikes 250 to 100 m deep have typical widths of 4 12 m with smooth host rock contacts rhyolite tuff at depths less than 100 m heterogeneities in the host rock form preferential pathways for small dike splays and sills resulting in a 30 m effective width at 50 m depth the development of a complex conduit at depths less than 70 m is reflected in bifurcating dikes and brecciation and incorporation of the country rock the overall zone of effect at depths less than 50 m is 110 m wide 220 m elongated along the feeder dike based on comparisons with theoretical conduit flow models the width of the feeder dike at depths from 250 to 500 m is expected to range from 1 to 10 m and is expected to decrease to about 1 2 m at depths greater than 500 m the flaring shape of the observed feeder systems is similar to results of theoretical modeling using lithostatic pressure balanced flow conditions sizes of observed conduits differ from modeled dimensions by up to a factor of 10 in the shallow subsurface 50 m depth but at depths greater than 100 m the difference is a factor of 2 to 4 this difference is primarily due to the fact that observed eroded conduits record the superimposed effects of multiple eruptive events while theoretical model results define dimensions necessary for a single steady eruption phase the complex details of magma host rock interactions observed at the study areas contact welding brecciation bifurcating dikes and sills and stoping represent the mechanisms by which the lithostatic pressure balanced geometry is attained the similarity in the normalized shapes of theoretical and observed conduits demonstrates the appropriateness of the pressure balanced modeling approach consistent with the conclusions of wilson and head j geophys res 86 2971 3001 1981 for this type of volcano

3d groundwater flow and deformation modelling of madrid aquifer abstract a novel methodological approach to calibrate and validate three dimensional 3d finite element fe groundwater flow and geomechanical models has been implemented using advanced differential interferometric sar a dinsar data in particular we show how a dinsar data can be effectively used to 1 constrain the model set up in evaluating the areal influence of the wellfield and 2 characterise the aquifer system specifically the storage coefficient values which represents a fundamental step in managing groundwater resources the procedure has been tested to reconstruct the surface vertical and horizontal movements caused by the manzanares jarama wellfield located northwest of madrid spain the wellfield was used to supply freshwater during major droughts over the period between 1994 and 2010 previous a dinsar outcomes obtained by ers 1 2 and envisat acquisitions clearly revealed the seasonality of the land displacements associated to the withdrawal and recovery cycles that characterized the wellfield development a time lag of about one month which is in the order of the time span between two sar acquisitions between the hydraulic head changes and the displacements has been detected in this site by a wavelet analysis of a dinsar and piezometer time series the negligible delay between the forcing factor and the system response and the complete subsidence recovery when piezometric head recovers supported the understanding of a minor role played by the pore pressure propagation within clay layers and the almost perfectly elastic behavior of the system viscosity is negligible respectively the developed geomechanical model satisfactorily reproduces the pumping induced deformations with a root mean square error rmse between observed and simulated land displacements in the order of 0 1 0 3 mm the results give insights about the approach benefits in deeply understanding the spatio temporal aquifer system response to the management of this strategic water resource for madrid

basaltic phreatomagmatic fissure at 71 gulch part 2 unusual pyroclasts from sediment magma mingling and melting the behavior of magma as it encounters unconsolidated sediment can be studied in fortuitous exposures of incised volcanic systems to help determine the conditions that control the transport arrest or mingling of that magma in the sediment the pliocene subaqueous basaltic fissure at 71 gulch idaho usa contains unusual light colored glassy mingled clasts that were produced through the incorporation of domains of siliciclastic sands and silts into basalt these clasts contain textures reflective of melting and mechanical mixing of these sediments with the rising basalt along intrusions at depths 30 m beneath the pre eruptive surface and transport into and through a shallow subsurface debris filled vent mingled clasts comprised colorless glass with locally high silica contents and visible swirls of sideromelane along with crystals derived from both the host sediment and the 71 gulch basalt the unique combination of textures minerals plus major and trace element geochemistry within the geologic context of 71 gulch points to a two phase mixing that did not contribute directly to nor impede the phreatomagmatic explosions that erupted the mingled clasts

shallow seated controls on styles of explosive basaltic volcanism a case study from new zealand abstract the pyroclastic deposits of many basaltic volcanic centres show abrupt transitions between contrasting eruptive styles e g hawaiian versus strombolian or dry magmatic versus wet phreatomagmatic these transitions are controlled dominantly by variations in degassing patterns magma ascent rates and degrees of interaction with external water we use crater hill a 29 ka explosive effusive monogenetic centre in the auckland volcanic field new zealand as a case study of the transitions between these end member eruptive styles the crater hill eruption took place from at least 4 vents spaced along a nne trending 600 m long fissure that is contained entirely within a tuff ring generated during the earliest eruption phases early explosive phases at crater hill were characterised by eruption from multiple unstable and short lived vents later dominantly extrusive volcanism took place from a more stable point source most of the crater hill pyroclastic deposits were formed in 3 phreatomagmatic p and 4 dry magmatic m episodes forming in turn the outer tuff ring and maar crater p1 m1 p2 and scoria cone 1 m2 m4 this activity was followed by formation of a lava shield and scoria cone 2 purely wet activity is represented by the bulk of p1 and p2 and purely dry activity by much of m2 m4 however m1 and parts of m2 and m4 show evidence for simultaneous eruptions of differing style from adjacent vents and rapid variations in the extent and timing of magma water interaction at each vent the nature of the wall rock lithics and these rapid variations in inferred water magma ratios imply interaction was occurring mostly at depths of 80 m and the vesicularity patterns in juvenile clasts from these and the p beds imply that rapid degassing occurred at these shallow levels we suggest that abrupt transitions between eruptive styles in time and space at crater hill were linked to changes in the local magma supply rate and patterns and vigour of degassing during the final metres of ascent

study of the land subsidence in orihuela city se spain using psi data distribution evolution and correlation with conditioning and triggering factors this paper presents a study about the subsidence affecting the city of orihuela placed on the western sector of the vega baja of the segura river basin se spain the study is based on deformation data obtained by differential sar interferometry dinsar and more precisely by the coherent pixels technique cpt an algorithm of the persistent scatterers interferometry psi family images acquired between june 1993 and april 2009 by ers and envisat satellite sensors have been processed by the cpt technique in order to retrieve the ground subsidence affecting this area accumulated deformation maps and displacement time series are analyzed moreover these data have been contrasted with subsidence triggering and conditioning factors by means of a geographical information system gis interface the performed analysis shows that there exists a relationship between subsidence and piezometric level evolution in time moreover the correlations among subsidence and location of pumping wells distance to the river geology and soil thickness have been derived from this analysis