methane in underground air in gibraltar karst abstract little is known about the abundance and geochemical behaviour of gaseous methane in the unsaturated zone of karst terrains the concentrations and 13 c of methane in background atmosphere soil air and cave air collected at monthly intervals over a 4 yr period are reported for st michaels cave gibraltar where the regional climate surface and cave processes are well documented methane concentrations measured in gibraltar soil are lower than the local background atmosphere average of 1868 ppb and fall to 13 c relationships in soil air methane lack strong seasonality and suggest mixing between atmosphere and a 12 c depleted residue after methanotrophic oxidation methane abundances in cave air are also lower than the local background atmosphere average but show strong seasonality that is related to ventilation controlled annual cycles shown by co 2 cave air methane abundances are lowest in the co 2 rich air that outflows from cave entrances during the winter and show strong inverse relationship between ch 4 abundance and 13 c which is diagnostic of methanotrophy within the cave and unsaturated zone anomalies in the soil and cave air seasonal patterns characterised by transient elevated ch 4 mixing ratios with 13 c values lower than 47 suggests intermittent biogenic input dynamically ventilated gibraltar caves may act as a net sink for atmospheric methane

origin and morphology of limestone caves limestone caves form along ground water paths of greatest discharge and solutional aggressiveness flow routes that acquire increasing discharge accelerate in growth while others languish with negligible growth as discharge increases a maximum rate of wall retreat is approached typically about 0 01 0 1 cm yr determined by chemical kinetics but nearly unaffected by further increase in discharge the time required to reach the maximum rate is nearly independent of kinetics and varies directly with flow distance and temperature and inversely with initial fracture width discharge gradient and pco2 most caves require 104 105 yr to reach traversable size their patterns depend on the mode of ground water recharge sinkhole recharge forms branching caves with tributaries that join downstream as higher order passages maze caves form where 1 steep gradients and great undersaturation allow many alternate paths to enlarge at similar rates or 2 discharge or renewal of undersaturation is uniform along many alternate routes flood water can form angular networks in fractured rock anastomotic mazes along low angle partings or sponge work where intergranular pores are dominant diffuse recharge also forms networks and spongework often aided by mixing of chemically different waters ramiform caves with sequential outward branches are formed mainly by rising thermal or h2s rich water dissolution rates in cooling water increase with discharge co2 content temperature and thermal gradient but only at thermal gradients of more than 0 01 c m can normal ground water co2 form caves without the aid of hypogenic acids or mixing artesian flow has no inherent tendency to form maze caves geologic structure and stratigraphy influence cave orientation and extent but alone they do not determine branch work versus maze character

reconstruction of palaeoclimate in shalaii cave se of sangaw kurdistan province of iraq abstract shalaii cave is a closed system cave that contains old and active speleothems it is located on the northeast limb of the ashdagh anticline in sangaw district in northeastern iraq the study presents new data on cave monitoring and the geochemistry of stalagmite archives relevant for the palaeoclimate of iraq an extensive cave monitoring program was conducted from june 2014 to march 2015 which included analyses of cave air temperature relative humidity cave air dripwater and modern calcite precipitates on glass slides physical parameters were measured monthly and continuously using data loggers and meteorological data rainwater and dripwater samples were acquired for stable isotope analyses and hydrochemistry analysis stable isotopes of oxygen and carbon and absolute dating of u th series dating was used to determine palaeoclimate conditions the microclimate of shalaii cave during the studied period june 2014 to march 2015 the average temperature at the entrance point and inside the monitored cave was 17 05 c and 20 18 c respectively the relative humidity at the entrance point and inside the cave was 66 6 and 100 respectively eleven samples of dripwater and five samples of rainwater were acquired for isotope analyses and thirteen samples of dripwater for hydrochemical analysis from the environmental isotopes analysis 2h and 18o all water samples fall between the global meteoric water line gmwl and sangaw meteoric water line smwl the precipitation samples plot well above the gmwl the mechanism of recharge is direct recharge two stalagmites shc 01 and shc 02 were sampled from the cave the first sample shc 01 is dated from 1012 42 to 494 29 yr b p and the second sample shc 02 dates between 8025 38 to 6977 219 yr b p oxygen and carbon isotope results show that there are two climate conditions for palaeoclimate reconstruction in the sangaw district conditions were generally wetter and colder during 8025 38 to 6977 219 yr b p than current conditions from 1012 42 to 494 29 yr b p drier and warmer conditions prevail more similar to today

minero petrographical features of weathering profiles in calabria southern italy abstract the paper reports interdisciplinary research of weathering profile stages on gneiss with regard to tectonic and landscape evolutions of the western sila grande massif southern italy the outcropping rocks consist of medium to coarse grained biotite garnet and sillimanite gneiss bgs g and medium to coarse grained biotite muscovite migmatitic gneiss m g the bgs g rocks are fractured and weathered with either massive or foliated texture whereas the m g rocks are intensely weathered and fractured with a massive texture and frequent pegmatite veins petrographical and mineralogical variations show that both gneissic rocks bgs g and m g samples underwent weathering processes characterized by a progressive chemical attack on the labile minerals with generation of neoformed minerals and substitution of the original rock fabric the weathering processes produced phyllosilicates and fe oxides neoformed clay minerals and ferruginous products replaced feldspars and biotite during the most advanced weathering stage microfractures and morphological variations occur on the original rock and thereby affect the surrounding landscape processes the weathering profile mineralogy and rock textures viewed in the context of landscape evolution provide useful insights into the widespread slope movement phenomena in the sila grande massif gneiss

stratigraphic record of the yellowstone hotspot track neogene sixmile creek formation grabens southwest montana abstract the sixmile creek formation fills deep grabens in southwest montana and preserves a stratigraphic record of the evolution of the yellowstone hotspot track from 17 ma to 2 ma the ruby beaverhead big hole deer lodge medicine lodge grasshopper three forks canyon ferry jefferson melrose wise river and paradise grabens were active during outbreak of the hotspot they appear to be parts of a radial system of extensional structures that may have formed on a broad dome that was centered on the hotspot outbreak area in southwest idaho and southeast oregon early in the evolution of the grabens massive debris flows surged down paleogene paleovalleys from uplifted and tilted horst blocks and accumulated in the grabens the grabens captured runoff from the hotspot dome with thick deposits of river gravel that appear to have been derived in part from east central idaho as the hotspot track propagated along the eastern snake river plain silicic ash fell into the graben drainage basins and was reworked into thick fluvial beds along graben axes the grabens were cross cut by northwest trending late neogene grabens that propagated on the flanks of silicic volcanic centers along the hotspot track the late neogene grabens diverted the middle miocene drainage patterns in southwest montana

land based evidence for tertiary climatic variations northern rockies paleoclimatic interpretations of sedimentation patterns paleosol mineralogy and vertebrate faunal assemblages of extensive tertiary continental clastic sediments of montana and idaho indicate four major changes in precipitation in this area during tertiary time wet to dry in late eocene dry to wet in late early miocene wet to dry in early middle miocene and dry to wet in late miocene pliocene time this climate pattern is synchronous with similar climatic changes inferred from deep ocean sedimentation rates for the indian pacific and atlantic oceans and to oxygen isotope paleo temperature data for the north pacific ocean and new zealand other paleoclimatic evidence supports the pattern the evidence suggests widespread synchronous tertiary climate changes that may provide useful time stratigraphic markers

subterranean karst environments as a global sink for atmospheric methane abstract the air in subterranean karst cavities is often depleted in methane ch4 relative to the atmosphere karst is considered a potential sink for the atmospheric greenhouse gas ch4 because its subsurface drainage networks and solution enlarged fractures facilitate atmospheric exchange karst landscapes cover about 14 of earth s continental surface but observations of ch4 concentrations in cave air are limited to localized studies in gibraltar spain indiana usa vietnam australia and by incomplete isotopic data to test if karst is acting as a global ch4 sink we measured the ch4 concentrations 13 cch4 and 2 hch4 values of cave air from 33 caves in the usa and three caves in new zealand we also measured co2 concentrations 13 cco2 and radon rn concentrations to support ch4 data interpretation by assessing cave air residence times and mixing processes among these caves 35 exhibited subatmospheric ch4 concentrations in at least one location compared to their local atmospheric backgrounds ch4 concentrations 13 cch4 and 2 hch4 values suggest that microbial methanotrophy within caves is the primary ch4 consumption mechanism only 5 locations from 3 caves showed elevated ch4 concentrations compared to the atmospheric background and could be ascribed to local ch4 sources from sewage and outgassing swamp water several associated 13 cch4 and 2 hch4 values point to carbonate reduction and acetate fermentation as biochemical pathways of limited methanogenesis in karst environments and suggest that these pathways occur in the environment over large spatial scales our data show that karst environments function as a global ch4 sink

vegetation response during the lead up to the middle miocene warming event in the northern rocky mountains usa abstract the mid miocene climatic optimum mmco initial warming beginning ca 18 ma and with peak warming ca 17 14 75 ma constitutes the earth s most recent greenhouse episode characterized by a transient shift to higher global atmospheric co 2 levels and warmer possibly wetter climatic conditions combined with the spread of grass dominated habitats it has been suggested that the mmco lead to significant turnover and modernization of fauna and flora however records documenting local vegetation change during the mmco are rare hence this hypothesis remains largely untested herein we combine phytolith assemblages and 13 c records from paleosol organic matter from the railroad canyon section rcs eastern idaho to provide the first direct detailed and continuous long term record of vegetation composition and structure in a single basin during the lead up to the mmco 22 9 15 2 ma late arikareean early barstovian phytolith assemblage analysis indicates that grasses primarily c 3 pooids dominated early middle miocene vegetation potential c 4 pacmad grasses were present by ca 21 6 20 7 ma late arikareean and vary in abundance 0 4 17 2 of diagnostic phytoliths through the section although relatively rare overall pacmad grasses decrease significantly through time in parallel with declining diatom abundances and an increase in pooid grasses in contrast paleosol 13 c org indicates 0 29 1 c 4 vegetation but no consistent temporal change where both phytolith and isotope based estimates are made from the same paleosol they are within error most 82 of the time thus the apparent discrepancy in temporal trends could either be due to differences in the resolution of the two records or could be explained if many pacmads were not c 4 grasses but instead water loving c 3 species overall these data suggest that open habitat mosaic vegetation with grass dominated grasslands and open woodlands occurred in the north rocky mountains usa by at least the early miocene more comparable to the timing for the spread of grass dominated habitats in the great plains than previously thought additionally phytolith data suggest that overall vegetation structure remained relatively stable throughout the rcs inconsistent with published paleosol morphology data this points to regionally unique floral patterns decoupled from global climate change leading into the mmco

rocky mountain tertiary coal basin models and their applicability to some world basins abstract tertiary intermontane basins in the rocky mountain region of the united states contain large amounts of coal resources the first major type of tertiary coal basin is closed and lake dominated either mud rich e g north park basin colorado or mud plus carbonate e g medicine lodge basin montana which are both infilled by deltas the second major type of tertiary coal basin is open and characterized by a preponderance of sediments that were deposited by flow through fluvial systems e g raton basin colorado and new mexico and powder river basin wyoming and montana the setting for the formation of these coals varies with the type of basin sedimentation paleotectonism and paleoclimate the mud rich lake dominated closed basin transpressional paleotectonism and warm humid paleoclimate where infilled by sandy gilbert type deltas contains thick coals low ash and low sulfur formed in swamps of the prograding fluvial systems the mud and carbonate rich lake dominated closed basin is infilled by carbonate precipitates plus coarse grained fan deltas and fine grained deltas here thin coals high ash and high sulfur formed in swamps of the fine grained deltas the coarse clastic open basins compressional paleotectonism and warm paratropical paleoclimate associated with flow through fluvial systems contain moderately to anomalously thick coals high to low ash and low sulfur formed in swamps developed in intermittently abandoned portions of the fluvial systems these coal development patterns from the tertiary rocky mountain basins although occurring in completely different paleotectonic settings are similar to that found in the tertiary cretaceous and permian intermontane coal basins in china new zealand and india

late miocene vegetational and climatic variations inferred from a pollen record in northwest wyoming a pollen stratigraphy from late miocene lacustrine strata teewinot formation in jackson hole wyoming permits analysis of vegetation and climate history over a time interval of less than 300 000 years with better temporal resolution of data than has been reported from terrestrial tertiary deposits the flora was essentially modern and six successive pollen assemblages indicate alternating dry and wet conditions the frequency of climatic change in this record is similar to that inferred from marine isotope records for both late tertiary and quaternary time

terrestrial methane seeps and mud volcanoes a global perspective of gas origin abstract a global database of gas composition and methane stable isotopes of 143 terrestrial mud volcanoes from 12 countries and 60 seeps independent from mud volcanism from eight countries was compiled and examined in order to provide the first worldwide statistics on the origin of methane seeping at the earth s surface sixteen seep data were coupled with their associated subsurface reservoirs the surface seepage data indicate that at least 76 of the mud volcanoes release thermogenic gas with only 4 biogenic and 20 with mixed character the average 201 data of methane concentration and methane carbon isotope ratios 13 c 1 of mud volcanoes are 90 v v and 46 4 respectively the other types of seeps which are independent from mud volcanism have an average 13 c 1 value that is slightly higher 42 9 gases from mud volcanoes are generally lighter more methane less ethane and propane than their associated reservoir gases suggesting a molecular fractionation during advective fluid migration other types of seeps especially dry seeps maintain the reservoir c 1 c 2 c 3 bernard ratio mud volcanoes behave like a natural refinery and the origin of gas more isotopically enriched than 50 and with c 1 c 2 c 3 500 should be attributed to a thermogenic source rather than partial oxidation of biogenic gas some data that appear biogenic in the bernard diagram can be explained by molecular fractionation of mixed gas consequently the bernard parameter may be misleading when applied to mud volcanoes since it does not always reflect the original gas composition the mechanisms of the molecular advective segregation should be studied quantitatively by specific models and experiments

regional implications of geochemistry and style of emplacement of miocene i type diorite and granite delos cyclades greece abstract the miocene plutons of the cyclades were emplaced in a subduction setting during regional back arc extension of continental crust that led to flat lying mid crustal detachment faulting mapping of the island of delos shows that quartz diorite and tonalite were emplaced as dykes in country rock of schist and marble within shear zones parallel to the extension direction mafic magmas were followed by numerous small batches of felsic magma with magmatic and ductile deformation synchronous with magma emplacement late granite dykes occupy brittle fractures in the more deformed rocks mafic and intermediate rocks show a bimodal distribution of incompatible trace elements with one group of broadly tholeiitic character and the other with substantial enrichment in sr nb and hfse but low th and ba these differences appear to be inherited from two distinct mafic sources that are different from the mafic source for the plutons of the eastern cyclades voluminous granodiorite results from these mafic magmas fractionating and or mixing with felsic crustal material some of which was derived by anatexis of a sedimentary protolith indicated by high b and mn some late granites appear derived from partial melting of hercynian paragneiss regionally the shear zones appear to be feeders to more extensive granitic plutons located at space produced at ramps in detachment fault zones the shear zones parallel the mid cycladic lineament a broad zone of displacement between two crustal blocks rotating in opposing directions as rollback took place at the hellenic subduction zone distinctive geochemical features in miocene igneous rocks suggests that these two blocks had quite different geological histories the localisation of plutonism and core complexes near the mid cycladic lineament suggests that this crustal scale shear played a role in bringing subduction derived magmas to mid crustal levels the heat supplied by the mafic magmas promoted ductile deformation high in the crust where extension was concentrated leading to the formation of core complexes the regional extension resulted in progressive shallowing of the position of the granite solidus within the crust leading to welding of the mid cycladic lineament which is no longer seismically active

multiple origins of methane in the earth methane occurrences in the earth s crust are predominantly of biogenic origin i e their ultimate source is biologically formed organic matter methane can also form through inorganic reactions and is consequently termed abiogenic biogenic methanes can either form through bacterial or thermogenic processes bacterial processes follow a co2 reduction and or fermentation pathway the fermentation processes are quantitatively more important in recent fresh sediments and swamps methane formed by co2 reduction however is most common in older sediments and commercial gasfields temperature organic substrate and age may be the major factors controlling the relative importance of the two pathways stable isotope concentrations in thermogenic methanes seem to be controlled by the extent of conversion of organic matter the timing of gas expulsion and trapping the different character of methane in individual sedimentary basins may be a result of the geologic history geothermal methanes are most likely derived from pyrolysis of organic matter abiogenic methane occurs in hydrothermal vents and ophiolite complexes inorganic reactions either surficial or deep seated are the likely source of such methanes a uniform mantle origin of methane is not supported by the observed isotope variations in naturally occurring methanes

nodular silcretes of the cypress hills formation upper eocene to middle miocene of southern saskatchewan canada siliceous nodules in the upper eocene to middle miocene cypress hills formation in southern saskatchewan formed on the distal portions of an extensive braidplain the nodules are similar to silcretes described elsewhere in the literature but their morphology and occurrence suggests that they are of a rare variety the silcretes are discrete equant to disc shaped nodules 1 3 cm thick and up to 15 cm long the silicretes form horizontal discontinous layers parallel to bedding within an unweathered profile void spaces and fractures within the nodules are lined or filled with drusy quartz the silcretes contain less than 0 07 tio2 the tio2 sio2 al2o3 and tio2 sio2 fe2o3 ratios are similar to values obtained from nodules formed in an arid to semi arid environment based on comparison with modern silcretes this interpretation is confirmed by independent sedimentological and palaeontological climatic evidence for an arid to semi arid climate throughout oligocene time in the western canadian plains

paleogene postcompressional intermontane basin evolution along the frontal cordilleran fold and thrust belt of southwestern montana the paleogene renova formation is the earliest record of postcompressional sedimentation within and adjacent to the helena salient of the cordilleran fold and thrust belt in southwestern montana paleocurrent and compositional data from basin margin facies document radiating paleodispersal away from high relief 2 km highlands coincident with modern mountainous areas source rocks within the paleohighlands included the same archean metamorphic proterozoic paleozoic and mesozoic sedimentary and mesozoic plutonic and vo l canic rocks as exposed in modern uplifts paleocurrent and compositional data from trunk fluvial conglomerates and sandstones document the existence of an interbasinal drainage system that connected the three forks western gallatin and townsend basins with headwaters farther to the west and southwest near the present day montana idaho border overall the distribution of paleogene mountainous areas and basins closely resembled modern geography and the paleogene drainage network was strikingly similar to the modern missouri river headwater system the renova formation records the early stages of decay of the cordilleran orogenic belt including the evolution of a complex intermontane basin network in southwestern montana high energy late cretaceous to early eocene fluvial systems carved deep large scale paleovalleys into the orogenic wedge along zones of structural and stratigraphic weakness at least a 5 km thickness of overburden was removed during this time incision was temporally correlative with early cenozoic regional uplift and subtropical climatic conditions subsequent deposition of the renova formation was temporally correlative with the cessation of uplift the initiation of crustal extension and climatic cooling however extension is not interpreted to have played a major role in earliest basin development

abiotic methane on earth 1 over the last 30 years geochemical research has demonstrated that abiotic methane ch4 formed by chemical reactions which do not directly involve organic matter occurs on earth in several specific geologic environments it can be produced by either high temperature magmatic processes in volcanic and geothermal areas or via low temperature 100 c gas water rock reactions in continental settings even at shallow depths the isotopic composition of c and h is a first step in distinguishing abiotic from biotic including either microbial or thermogenic ch4 herein we demonstrate that integrated geochemical diagnostic techniques based on molecular composition of associated gases noble gas isotopes mixing models and a detailed knowledge of the geologic and hydrogeologic context are necessary to confirm the occurrence of abiotic ch4 in natural gases which are frequently mixtures of multiple sources although it has been traditionally assumed that abiotic ch4 is mainly related to mantle derived or magmatic processes a new generation of data is showing that low temperature synthesis related to gas water rock reactions is more common than previously thought this paper reviews the major sources of abiotic ch4 and the primary approaches for differentiating abiotic from biotic ch4 including novel potential tools such as clumped isotope geochemistry a diagnostic approach for differentiation is proposed

role of melt during deformation in the deep crust deformation in the deep crust is strongly influenced by the presence of melt injected melt or magma weakens the crust because strain will tend to localize where melt is present the amount of strain a pluton may accommodate is dependent on the length of time it takes for a pluton to crystallize and the strain rate for plutons that intrude into rocks which are near the solidus temperature of the melt crystallization times can be quite long 1myr partial melting of deep crustal rocks can lead to melt enhanced embrittlement this occurs because the volume change for most melting reactions is positive therefore when the rate of melt production outpaces the rate at which melt can leave the system the melt pressure increases eventually the melt pressure may become sufficiently high that the melting rocks behave in a brittle fashion and fracture conjugate sets of dilatant shear fractures filled with melt occur in migmatite from the central gneiss belt canada this suggests that melt enhanced embrittlement occurred in these rocks an expression which relates the magnitude of differential stress to the angle between conjugate dilatant shear fractures is derived assuming that migmatite has a small tensile strength differential stresses are 20 mpa in migmatitic rocks at the time melt enhanced embrittlement occurs the occurrence of melt enhanced embrittlement shows that a switch in deformation mechanism from plastic flow to cataclasis is possible in the deep crust during melting furthermore repeated episodes of melt enhanced embrittlement in migmatitic rocks may be an efficient mechanism for extracting melt from partially melted terrains

cave air ventilation and co2 outgassing by radon 222 modeling how fast do caves breathe abstract in general the rate and timing of calcite precipitation is in part affected by variations in cave air co2 concentrations knowledge of cave ventilation processes is required to quantify the effect variations in co2 concentrations have on speleothem deposition rates and thus paleoclimate records in this study we use radon 222 222rn as a proxy of ventilation to estimate co2 outgassing from the cave to the atmosphere which can be used to infer relative speleothem deposition rates hollow ridge cave a wild cave preserve in marianna florida is instrumented inside and out with multiple micro meteorological sensor stations that record continuous physical and air chemistry time series data our time series datasets indicate diurnal and seasonal variations in cave air 222rn and co2 concentrations punctuated by events that provide clues to ventilation and drip water degassing mechanisms average cave air 222rn and co2 concentrations vary seasonally between winter 222rn 50 dpm l 1 where 1 dpm l 1 60 bq m 3 co2 360 ppmv and summer 222rn 1400 dpm l 1 co2 3900 ppmv large amplitude diurnal variations are observed during late summer and autumn 222rn 6 to 581 dpm l 1 co2 360 to 2500 ppmv we employ a simple first order 222rn mass balance model to estimate cave air exchange rates with the outside atmosphere ventilation occurs via density driven flow and by winds across the entrances which create a venturi effect the most rapid ventilation occurs 25 m inside the cave near the entrance 45 h 1 1 33 min turnover time farther inside 175 m exchange is slower and maximum ventilation rates are 3 h 1 22 min turnover time we estimate net co2 flux from the epikarst to the cave atmosphere using a co2 mass balance model tuned with the 222rn model net co2 flux from the epikarst is highest in summer 72 mmol m 2 day 1 and lowest in late autumn and winter 12 mmol m 2 day 1 modeled ventilation and net co2 fluxes are used to estimate net co2 outgassing from the cave to the atmosphere average net co2 outgassing is positive net loss from the cave and is highest in late summer and early autumn about 4 mol h 1 and lowest in winter about 0 5 mol h 1 modeling of ventilation net co2 flux from the epikarst and co2 outgassing to the atmosphere from cave monitoring time series can help better constrain paleoclimatic interpretations of speleothem geochemical records

timing and development of the heise volcanic field snake river plain idaho western usa the snake river plain srp developed over the last 16 ma as a bimodal volcanic province in response to the southwest movement of the north american plate over a fixed melting anomaly volcanism along the srp is dominatedby eruptions of explosive high silica rhyolites and represents some of the largest eruptions known basaltic eruptions represent the final stages of volcanism forming a thin cap above voluminous rhyolitic deposits volcanism progressed generally from west to east along the plain episodically in successive volcanic fields comprised of nested caldera complexes with major caldera forming eruptions within a particular field separated by ca 0 5 1 ma similar to and in continuation with the present day yellowstone plateau volcanic field passage of the north american plate over the melting anomaly at a particular point in time and space was accompanied by uplift regional tectonism massive explosive eruptions and caldera subsidence and followed by basaltic volcanism and general subsidence the heise volcanic field in the eastern srp idaho represents an adjacent and slightly older field immediately to the southwest of the yellowstone plateau volcanic field five large volume 0 5 km 3 rhyolitic ignimbrites constitute a time stratigraphic framework of late miocene to early pliocene volcanism for the study region field relations and high precision 4 0 ar 3 9 ar age determinations establish that four of these regional ignimbrites were erupted from the heise volcanic field and form the framework of the heise group these are the blacktail creek tuff 6 62 0 03 ma walcott tuff 6 27 0 04 ma conant creek tuff 5 51 0 13 ma and kilgore tuff 4 45 0 05 ma all errors reported at 2a the fifth widespread ignimbrite in the region is the arbon valley tuff member of the star light formation 10 21 0 03 ma which erupted from a caldera source outside of the heise volcanic field these results establish the conant creek tuff as a distinct and widespread ignimbrite in the heise volcanic field eliminating former confusion resulting from previous discordant k ar and fission track dates new 4 0 ar 3 9 ar determinations when combined with geochemical lithologic geophysical and field data define the volcanic and tectonic history of the heise volcanic field and surrounding areas volcanic units erupted from the heise volcanic field also provide temporal control for tectonic events associated with late cenozoic extension in the snake range and with uplift of the teton range wyoming in the snake range movement of large 0 10 km 3 slide blocks of mississippian limestone exposed 50 km to the east of the heise field occurred between 6 3 and 5 5 ma and may have been catastrophically triggered by the caldera eruption of the 5 51 0 13 ma conant creek tuff this slide block movement of 300 vertical meters indicates that the snake range had significant relief by at least 5 5 ma in jackson hole the distribution of outflow facies of the 4 45 0 05 ma kilgore tuff related to eruption from the kilgore caldera in the heise volcanic field on the eastern srp indicates that the northern teton range was not a significant topographic feature at this time

crustal scale geometry and kinematics of late orogenic extension in the central aegean cyclades and ewia island abstract the aegean continental domain is known to be the site of widespread back arc extension since at least the middle miocene overprinting structures related to the mesozoic cenozoic hellenic orogeny features attributed to early thrusting include the overall ductile deformation within two broad belts that have suffered hp lt metamorphism across the aegean this study summarizes the results of a structural study in the central aegean area cyclades and evvia island examining in particular the relationship between ductile and brittle deformation on a regional scale extension appears to be responsible for most of the ductile deformation within hp rock units that have experienced penetrative greenschist facies and higher grade metamorphic overprinting on each island studied progressive extensional deformation has occurred through the development of a major normal sense detachment zone down to depths of about 18 25 km the geometry of the extensional system on the scale of the central aegean is described taking into account the characteristic features of the regional scale ductile strain field at least two probably three subparallel major north dipping detachment zones are identified trending nw se in the northwestern cyclades and e w in the southeastern cyclades both with initial dips estimated at around 30 45 the present geometry of the extensional system implies that these detachment zones and related metamorphic core complexes interfere with each other two main evolutionary models are considered which can account for such a kinematic link between parallel detachment zones structural data favour the sequential development of synthetic major detachments zones in a direction opposite to the sense of dip of the detachments early oligocene lower miocene detachment type extension in the area studied is related to a late orogenic post thickening back arc setting

paleoclimatic conditions and paleoweathering processes on mesozoic continental redbeds from western central mediterranean alpine chains abstract chemical and mineralogical analyses of the triassic to lowermost jurassic mudstones from continental redbeds outcropping in the internal domains of the betic rifian and calabria peloritani chains have been used to infer the relationships between paleoclimatic conditions and paleoweathering processes during rifting of a continental crust block that finally detached from adjoining western tethyan realms to form an independent microplate mesomediterranean microplate from jurassic to lower miocene time the studied mudstone samples come from middle triassic and upper triassic beds of the saladilla formation both in the betic cordillera and in the rif whereas the calabria peloritani arc studied mudstones come from upper triassic to lowermost jurassic beds both in the sila and longi taormina units major and trace element concentrations based on the mass balance calculation relative to the upper continental crust show negative values both in gibraltar and calabria peloritani arcs implying that mudstone formation in the early mesozoic involved moderate to intense continental paleoweathering of the crust in particular cao na 2 o mgo sr ba fe 2 o 3 mno and transition metal elements v cr co and ni are more depleted in the triassic to upper jurassic samples of the calabria peloritani samples than in the middle to upper triassic betic rifian samples and suggest an increase of continental paleoweathering in the mediterranean region from the triassic to the jurassic in addition enrichment in sio 2 tio 2 al 2 o 3 k 2 o and incompatible elements in the calabria peloritani arc mudstones indicates sediment recycling effects that gradually increase from the triassic to jurassic time the hinterland paleoweathering and sediment recycling effects have been mathematically distinguished using principal component analysis pc1 is a measure of paleoweathering rate mainly due to humidity positive values against aridity negative values whereas pc2 corresponds to the extent of sediment recycling the results strongly indicate that humidity had increased from the triassic to the jurassic and that the depositional environments in calabria peloritani arc were probably more suitable for sediment recycling these seasonal climate alternations corresponding to an increase in paleoclimatic humidity that favored paleoweathering conditions and recycling processes these results are also confirmed by the mineralogical data which show a higher abundance of kaolinite typical of warm humid conditions in the calabria peloritani mudstones than in those of the betic cordillera and the rif furthermore the comparison among geochemical weathering index values of the studied samples and of recent soils from different climatic zones likely suggests a tropical rainforest climate in the studied area during the triassic to the lowermost jurassic

estimation of epikarst air pco2 using measurements of water δ13ctdic cave air pco2 and δ13cco2 abstract when present an epikarst represents the starting point the first karst compartment of water flow through a karst system the air characteristics in a karst and especially in an epikarst determine the initial water characteristics e g water aggressiveness which depends on the partial pressure of co2 p co 2 in equilibrium with water this paper proposes a method to estimate p co 2 in epikarst air using spring water measures as hco 3 temperature ph and 13c of total dissolved inorganic carbon tdic and cave air measures as p co 2 and 13c of co2 this method accounts for the tdic variations of 13c that are caused by co2 degassing and calcite precipitation from water the calculations are based on the influence of ph variations and carbon loss on 13c of tdic measurements are taken at two sites lascaux cave and the cussac cave sites located in perigord southwest of france four water springs are presented in this case study two springs from an epikarst compartment one spring from an unsaturated zone and one spring from a saturated zone the p co 2 in epikarst air is estimated to be from 4 4 44 000 ppm in winter to 10 in summer these values are higher than the values of air p co 2 measured in the soil 0 27 1 60 or in the caves 0 30 3 1 up to 7 50 in some parts of lascaux we show that in epikarst air p co 2 and 13 c co 2 are not constant values but vary annually with high p co 2 and depleted values 22 31 vpdb in the winter and higher p co 2 and more depleted values in the summer 24 20 vpdb

clay mineral formation and transformation in rocks and soils three mechanisms for clay mineral formation inheritance neoformation and transformation operating in three geological environments weathering sedimentary and diagenetic hydrothermal yield nine possibilities for the origin of clay minerals in nature several of these possibilities are discussed in terms of the rock cycle the mineralogy of clays neoformed in the weathering environment is a function of solution chemistry with the most dilute solutions favouring formation of the least soluble clays after erosion and transportation these clays may be deposited on the ocean floor in a lateral sequence that depends on floccule size clays undergo little reaction in the ocean except for ion exchange and the neoformation of smectite therefore most clays found on the ocean floor are inherited from adjacent continents upon burial and heating however dioctahedral smectite reacts in the diagenetic environment to yield mixed layer illite smectite and finally illite with uplift and weathering the cycle begins again

consumption of atmospheric methane in a limestone cave in indiana usa abstract recent observations suggest that karst landscapes may be an unaccounted sink for atmospheric ch4 but questions remain about the processes contributing to sub atmospheric ch4 mole fractions in caves the ch4 dynamics associated with karst environments were studied over 18 months at 6 locations in buckner cave southern indiana by measuring the mole fractions and stable isotopic composition of ch4 and carbon dioxide co2 co2 mole fractions were used to infer seasonal changes in airflow samples were obtained on a monthly basis ch4 mole fractions ranged from 1 9 0 1 ppm near the cave entrance to 0 1 0 1 ppm in the more remote parts of the cave the carbon and hydrogen stable isotopic compositions of ch4 in the cave ranged from 58 7 to 7 vpdb and 170 to 10 vsmow respectively the isotopic data suggest that the ch4 dynamics of buckner cave can be described by a seasonally variable mixing system in which atmospheric ch4 enters primarily through the main entrance and is subsequently consumed by methanotrophs additionally at least two smaller ch4 sources are evident when air has been stagnant the results suggest that subterranean karst cavities are an important sink for atmospheric ch4

sedimentary response to orogenic exhumation in the northern rocky mountain basin and range province flint creek basin west central montana middle eocene through upper miocene sedimentary and volcanic rocks of the flint creek basin in western montana accumulated during a period of significant paleoclimatic change and extension across the northern rocky mountain basin and range province gravity modelling borehole data and geologic mapping from the flint creek basin indicate that subsidence was focused along an extensionally reactivated sevier thrust fault which accommodated up to 800 m of basin fill while relaying stress between the dextral transtensional lewis and clark lineament to the north and the anaconda core complex to the south northwesterly paleocurrent indicators foliated metamorphic lithics 64 ma 40ar 39ar muscovite grains and 76 ma u pb zircons in a ca 27 ma arkosic sandstone are consistent with oligocene exhumation and erosion of the anaconda core complex the core complex and volcanic and magmatic rocks in its hangingwall created an important drainage divide during the paleogene shedding detritus to the nnw and ese

subterranean microbial oxidation of atmospheric methane in cavernous tropical karst abstract subterranean methanotrophy is a potentially important but overlooked sink for the atmospheric greenhouse gas methane ch 4 this study documents a microbial ch 4 sink in tropical subterranean karst cavities in vietnam s northern karst province where porosity steep topography and scarce soil and vegetation cover foster the exchange of subterranean air with the atmosphere our data are based on i surveys of ch 4 carbon dioxide and radon concentrations in the air of 11 caves ii in situ mesocosm experiments in caves as well as iii laboratory mesocosm measurements using sediment and rock from caves the extent of ch 4 depletion in cave air depends on the ventilation rate and the availability of moisture to provide a habitat for ch 4 oxidizing bacteria both of which are seasonally variable in northern vietnam and in part depend on monsoonal activity mesocosm experiments using fresh versus sterilized rock and sediment confirmed the role of microbial methanotrophy towards uptake of ch 4 from cave air our results also suggest that within cave heterogeneity of environmental variables like salinity may affect rates of ch 4 oxidation we conservatively estimate that 150 000 metric tons of atmospheric ch 4 are microbially oxidized annually in the 29 000 km 2 of vietnamese tropical karst which would compensate for 7 of vietnam s agricultural ch 4 emissions from rice farming and livestock future studies estimating the global fluxes of the atmospheric greenhouse gas ch 4 should consider subterranean karst as a potentially important ch 4 sink

spatial variability of cave air carbon dioxide and methane concentrations and isotopic compositions in a semi arid karst environment there is insufficient information on the movement of air in karst environments to constrain the uncertainty associated with quantifying sources and sinks of methane ch4 and carbon dioxide co2 within caves for global carbon accounting we analysed cave air samples for their co2 and ch4 concentrations co2 and ch4 and carbon isotopic compositions from sampling campaigns in winter august 2014 and summer february 2015 at numerous heights and locations throughout gaden and cathedral caves in a semi arid environment wellington caves nsw australia ventilation is the dominant control on cave air co2 and ch4 with the highest cave air co2 concentrations co2 cave occurring in summer in association with the lowest cave air ch4 concentrations ch4 cave analyses show that the cave air co2 has both atmospheric and soil sources soil air and cave air in both caves undergo methanogenesis and methanotrophy but we identify cave specific differences in cave air ch4 and co2 ch4 cave in cathedral cave shows an inverse relationship to co2 cave particularly in areas separated from the main cave passage in contrast gaden cave has near atmospheric ch4 cave and isotopic ratios present at all locations sampled in winter where no ventilation is occurring in summer ch4 cave in gaden cave decreases but remains reasonably high compared to cathedral cave our research shows adjacent caves vary in their ability to act as a net sink for ch4 and highlights the need for further studies before global generalisations can be made about the carbon budget of karst environments

cave air control on dripwater geochemistry obir caves austria implications for speleothem deposition in dynamically ventilated caves there are very few process studies that demonstrate the annual variation in cave environments depositing speleothems accordingly we initiated a monitoring program at the obir caves an austrian dripstone cave system characterized by a seasonally changing air flow that results in a predictable pattern of high pco2 during summer and low pco2 in winter although similar seasonal changes in soil pco2 occur they are not directly connected with the changes in the subsurface since the dripwaters are fed from a well mixed source showing little seasonal variation cold season flushing by relatively co2 poor air enhances degassing of co2 in the cave and leads to a high degree of supersaturation of dripwater with regard to calcite forced calcite deposition during the cold season also gives rise to a pronounced pattern of synchronous seasonal variations in electrical conductivity alkalinity ph ca and 13cdic which parallel variations recorded in 13ccave air chemical components unaffected by calcite precipitation e g d 18o sio2 so4 lack a seasonal signal attesting to a long residence in the karst aquifer modeling shows that degassing of co2 from seepage waters results in kinetically enhanced c isotopic fractionation which contrasts with the equilibrium degassing shown from the soreq cave in israel the obir caves may serve as a case example of a dripstone cave whose seepage waters and speleothems show intra annual geochemical variability that is primarily due to chemical modification of the groundwater by a dynamic bidirectional subsurface air circulation