source rock palaeoenvironments and controls on the distribution of dibenzothiophenes in lacustrine crude oils bohai bay basin eastern china abstract the applicability of sulphur aromatic parameters based on ratios of dibenzothiophene dbt and its alkylated homologues as indicators of oil maturity has been investigated in 27 oils from the damintun and zhuanhua depressions bohai bay basin the oils were characterised by bulk composition and environmentally sensitive aliphatic biomarkers and were derived from a wide range of lacustrine source depositional environments ranging from highly reducing hypersaline sulphur rich oils to terrestrial input dominated freshwater very high wax oils with maturities ranging from immature to probable mid mature dibenzothiophene based maturity parameters are not well correlated with sterane isomerization ratios and immature oils in particular could not be discriminated by these aromatic maturity indicators in contrast dbt based parameters are strongly correlated with pristane to phytane and ts tm ratios high methyldibenzothiophene ratios mdr are associated with fresh water source deposition whilst low mdrs are found in oils of hypersaline source affinity unusually high relative concentrations of 2 3 mdbt were observed in some of the immature oils inferred to be sourced by lacustrine organic laminites the data provide further evidence that thermal stress is not the sole factor controlling the distribution patterns of dibenzothiophenes in oils and that source depositional environments can exert a dominant influence when their range of variation is large absence of dbt in some biodegraded oils is tentatively attributed to its aqueous solubility during associated water washing

carboniferous submarine volcanism at herbornseelbach lahn dill area germany a 100 m thick sequence of carboniferous submarine dominantly basaltic volcanic rocks at herbornseelbach lahn dill area is subdivided into six units two pillow volcanoes show a characteristic change from basal megapillows up to 5 m across through normal pillows 0 5 to 0 8 m across to a top facies of small pillows 0 5 m across and or breccias of scoriaceous clasts and discontinuous lava stringers sheet flows 0 5 to 4 m thick can be distinguished from sills by asymmetric cooling structures and textures vesicle concentrations near the top basal flow wrinkles and ponding of sediments on irregular flow tops

peculiarities of salt lake sediments as potential source rocks in china abstract hypersaline lake sediments are widely distributed in china and can be good sources for petroleum the palaeogene sediments of the jianghan basin in eastern china are a typical example composed of salt lake evaporite clastic facies in fault subsided basins their organic matter is variable but is dominated by type ii kerogen the biological marker characteristics of core extracts and oils from the jianghan basin include i low oep values for n alkanes and occasionally an even odd predominance ii a high concentration of phytane iii a relatively high gammacerane 17 h 21 h hopane ratio and iv abundant mainly nickel porphyrins sample guang 33 k 33 is typical of the immature oils found in the jianghan basin geological and geochemical data both indicate that it was generated from source rocks in the maturity range r 0 0 45 0 55 its characteristics are similar to those of immature source rocks with high concentrations of phytane steranes triterpanes and nickel porphyrins and for an oil extremely low values for molecular parameters of maturity such as c 29 20s 20s 20r 14 h 17 h steranes c 32 22s 22s 22r 17 h 21 h hopanes and dpep dpep etio porphyrins

using formation micro imaging wireline logs and onshore analogues to distinguish volcanic lithofacies in boreholes examples from palaeogene successions in the faroe shetland basin ne atlantic

the oligocene maikop series of lahich eastern azerbaijan paleoenvironment and oil source rock correlation abstract the maikop formation deposited in eastern azerbaijan during oligocene and early miocene represents a prolific source unit for the oils found within the southern gobustan area and the kura depression based on biomarker characteristics the oils are believed to have originated from a clastic source rock deposited in an anoxic to suboxic transitional marine environment with low to moderate input of terrigenous organic matter however due to the thermal immaturity of accessible maikop rocks oil source rock correlation based on biomarker fingerprints is hampered the results from a sedimentary succession sampled in the shemakha gobustan area near the village of lahich revealed the presence of marginally mature rr 0 6 0 7 maikop rocks based on lithology geochemical data and paleontological analyses the sampled section contains upper eocene and lower oligocene sediments palynological analyses of dinoflagellate cysts indicate an early rupelian to early chattian oligocene age for the upper part of the investigated maikop succession however the stratigraphic position of the middle and lower part of the succession remains unclear maceral composition as well as biomarker and stable isotope c n data indicate a major contribution of aquatic organisms and variable inputs from macrophytes and land plants to organic matter deposition during the oligocene microbial communities most probably included heterotrophic bacteria and cyanobacteria as well as green sulfur bacteria higher inputs of terrigenous organic matter occurred during deposition of the lower part of the succession increased remineralisation of organic matter in the water column is suggested to result in low toc and hydrocarbon contents as well as 15n enriched total nitrogen of the eocene to earliest oligocene sediments organic carbon accumulation during the oligocene occurred in a stratified episodically euxinic environment this is indicated by low toc s ratios and higher contents of aryl isoprenoids in several samples from the upper units a moderate to good oil source rock correlation with oils from the kura depression is indicated by sterane and triterpane fingerprints as well as carbon isotopic composition of hydrocarbon fractions

lithofacies of deep marine basalts emplaced on a jurassic backarc apron baja california mexico basalts of the mid jurassic gran canon formation cedros island mexico were emplaced on a volcani clastic apron in a deep marine backarc basin elongate pillows and lava tubes as well as paleocurrent data from the volcaniclastic apron indicate a southward regional paleoslope away from the island arc source basalts emplaced on relatively proximal parts of the apron are nearly entirely pillowed and have thick flow units with mega pillows basalts on distal parts of the apron about 15 to 20 km down paleo current are dominated by pillow fragment breccias flow foot rubble and individual lava flows are generally thin with small pillows suggesting that the distal ends of lava flows erupted upslope are represented these distal flow fronts however are interstratified with features that typically form close to a vent including thick massive to mega pillowed lavas and lava tubes up to 8 m in diameter it is inferred that a fissure or system of fissures extended from the arc into the backarc basin

oil source correlation in the slope of the qikou depression in the bohai bay basin with discriminant analysis abstract the commonly used tools for oil source correlation such as mass chromatograms of biomarkers and bivariate cross plots of geochemical parameters cannot deal with multiple geochemical parameters and plenty of samples simultaneously leading to uncertainties in the results and even failures sometimes in this paper the discriminant analysis da is selected from supervised machine learning algorithms as it is superior to the commonly used tools as well as other multivariate statistical methods with the accumulation of geochemical data of source rocks and oils in the slope of the qikou depression the main source rocks in the third es3 and first members es1 of the paleogene shahejie formation were deposited in similar depositional environments the source rocks cannot be distinguished with the commonly used tools we firstly extended geochemical parameters and then used stepwise da to select informative parameters and to develop a discriminant model for oil source correlation the 22 selected parameters are supported by geochemical characteristics of the source rocks in the study area the da of these parameters for oil source correlation achieved a high correct rate of original validation 96 8 and leave one out cross validation 89 4 indicating a sufficient discriminatory power the oil source correlation results with high posterior probabilities showing strong similarity between the sources and oils coincide with geological conditions and illustrate that there is still much exploration potential in the study area especially for the es3 petroleum system all these illustrate that da is one of the most useful tools for oil source correlation with the accumulation of geochemical data of source rocks and oils

interpretation of the relations between massive pillowed and brecciated facies in an archean submarine andesite volcano amulet andesite rouyn noranda canada abstract the amulet andesite formation in the archean terrain of rouyn noranda p q consists of 19 flows distinguished by variations in phenocryst content and vesicularity and by the presence of concentric contraction fractures detailed mapping of flows revealed the presence of three main facies 1 massive facies 2 pillowed facies and 3 foreset bedded brecciated facies the massive facies consists of 50 massive lava overlain by pillow lava and or pillow breccia the pillowed facies consists of 50 pillows in some flows the pillowed facies contains a thin sheet of massive lava at the base of the flow facies 2a generally massive lava fills braided channels 10 50 m wide facies 2b facies 2c consists of pillows and large irregular megapillows determination of the flow direction shows that facies 1 is proximal facies 2 distal the foreset bedded facies 3 consists of alternating thin 1 2 m lobes of massive lava pillow lava and broken pillow breccia it makes up flows 16 19 at the top of the sequence flow m a unit entirely composed of massive lava is ponded against flows 9 and 10 we interpret the growth of the amulet andesite volcano in the light of new work on ocean floor basalt and on the 1969 1973 mauna ulu eruption the feeding fissure was located in the area of massive facies at the beginning of eruptions lava spread laterally as a sheet flood flow massive base of facies 2a but rapidly became channelized the pillow lava and in particular the facies 2b 2c and 3 are considered as the subaqueous equivalents of tube fed pahoehoe flow m probably represents a lava lake shallowing upward of the sequence during the built up of the volcano is indicated by increasing vesicularity of the flows and by an upward increase of the proportion of broken pillow breccia this increase is gradual from flow 1 to flow 15 but abrupt from flow 15 to 16 19

pipe vesicles in hawaiian basaltic lavas their origin and potential as paleoslope indicators study of several hawaiian tholeiitic volcanoes shows that pipe vesicles form only in thin pahoehoe flow units standing on a ground slope of less than about 4 the vesicles thus have potential as paleoslope indicators two examples are given of their use to deduce that the steep dip of certain intracaldera lavas is due to tilting pipe vesicles are attributed to gas bubbles rising through lava at a stage in its cooling history when it had acquired a yield strength of a few tens of n m 2 sufficient to prevent closure of lava behind the bubbles

hawaiian xenolith populations magma supply rates and development of magma chambers hawaiian volcanoes pass through a sequence of four eruptive stages characterized by distinct lava types magma supply rates and xenolith populations magma supply rates are low in the earliest and two latest alkalic stages and high in the tholeiitic second stage magma storage reservoirs develop at shallow and intermediate depths as the magma supply rate increases during the earliest stage magma in these reservoirs solidifies as the supply rate declines during the alkalic third stage these magma storage reservoirs function as hydraulic filters and remove dense xenoliths that the ascending magma has entrained during the earliest and latest stages no magma storage zone exists and mantle xenoliths of lherzolite are carried to the surface in primitive alkalic lava during the tholeiitic second stage magma storage reservoirs develop and persist both at the base of the ocean crust and 3 7 km below the caldera only xenoliths of shallow origin are carried to the surface by differentiated lava during the alkalic third stage magma in the shallow subcaldera reservoir solidifies and crustal xenoliths including oceanic crustal rocks are carried to the surface in lava that fractionates in an intermediate depth reservoir worldwide xenolith populations in tholeiitic and alkalic lava may reflect the presence or absence of subvolcanic magma storage reservoirs

source facies of the paleozoic petroleum systems in the tabei uplift tarim basin nw china implications from aryl isoprenoids in crude oils abstract aryl isoprenoids have been detected for the first time in crude oils from paleozoic petroleum systems in the tabei uplift tarim basin northwestern china the principal compounds possess the 1 alkyl 2 3 6 trimethyl substitution pattern characteristic of diaromatic carotenoids found in the chlorobiaceae family of photosynthetic sulfur bacteria with a predominance of c13 c23 homologues in these samples flash pyrolysates of the asphaltene fractions isolated from crude oils show an unusual abundance of 1 2 3 4 tetramethylbenzene an indicator for a significant contribution of diaromatic carotenoids to the source kerogen of these oils the wide distribution of these compounds in crude oils reveals that penetration of the photic zone by sulfidic waters during deposition enabled prolific growth of photosynthetic green sulphur bacteria chlorobiaceae this suggests that the source rocks for the paleozoic petroleum systems in the tabei uplift were likely deposited under euxinic conditions with sulfate and sulfide rich water bodies which doesn t support previously published conclusions of a middle upper ordovician source that marks the slope facies at the margins of structural uplifts

molecular and isotopic stratigraphy in an ombrotrophic mire for paleoclimate reconstruction a 40 cm deep sphagnum dominated peat monolith from bolton fell moss in northern england was systematically investigated by lipid molecular stratigraphy and compound specific 13c and d analysis using gas chromatography gc gc mass spectrometry gc ms gc combustion isotope ratio ms gc c irms and gc thermal conversion irms gc tc irms techniques 210pb dating showed the monolith accumulated during the last ca 220 yr a period encompassing the second part of little ice age while the distributions of lipids including n alkan 1 ols n alkan 2 ones wax esters sterols n alkanoic acids alkandioic acids and hydroxy acids display relatively minor changes with depth the cooler climate event was recorded in the concentrations of n alkanes and organic carbon cpi values of n alkanes and n alkanoic acids and the ratio of 5 n alkylresorcinols sterols superimposed on the fossil fuel effect the relatively cooler climate event was also recorded by 13c values of individual hydrocarbons especially the c23n alkane a major compound in certain sphagnum spp the d values of the c29 and c33n alkanes correlated mainly with plant composition and were relatively insensitive to climatic change in contrast the c23n alkane displayed variation that correlated strongly with recorded temperature for the period represented by the monolith agreeing with previously reported deuterium records in tree ring cellulose spanning the same period in scotland germany and the usa with more negative values occurring during the second part of little ice age these biomarker characteristics including the compound specific 13c and d records provide a new set of proxies of climatic change potentially independent of preserved macrofossils which will be of value in deeper sections of the bog where the documentary records of climate are unavailable and humification is well advanced

solid bitumen reflectance and rock eval tmax as maturation indices an example from the nordegg member western canada sedimentary basin abstract marine organic rich rock units commonly contain little for vitrinite reflectance v r 0 measurement the most commoly used method of assessing thermal maturity this is true of the lower jurassic nordegg member a type i ii sulphur rich source rock from the western canada sedimentary basin this study examines the advantages and pitfalls associated with the use of rock eval t max and solid bitumen reflectance b r 0 to determined maturity in the nordegg vitrinite reflectance data from cretaceous coals and known coalification gradients in the study area are used to extrapolate v r 0 values for the nordegg t max increases non linearly with respect to both b r 0 and extrapolated v r 0 values a sharp increase in the reflectaance of both solid bitumen and vitrinite occurs between t max 440 450 c and is coincident with a pronounced decrease in hydrogen index values and the loss of solid bitumen and telalginite fluorescence over the same narrow t max interval this t max range is interpreted as the main zone of hydrocarbon generation in the nordegg and corresponds to extrapolated v r 0 values of 0 55 0 85 the moderate to high sulphur contents in the kerogen played a significant role in determining the boundaries of the nordegg oil window a linear relationship between b r 0 and extrapolated v r 0 as proposed elsewhere is not true for the nordegg b r 0 increases with respect to extrapolated v r 0 according to jacob s 1985 formula v r 0 0 618 b r 0 0 40 up to v r 0 0 72 b r 0 0 52 beyond this point b r 0 increases sharply relative to extrapolated v r 0 according to the relatioship v r 0 0 277 b r 0 0 57 r 2 0 91 the break in the b r 0 v r 0 curve at 0 72 v r 0 is thought to signifiy the peak of hydrocarbon generation and represents a previously unrecognized coalification jump in the solid bitumen analogous to the first coalification jump of liptinites

records and causes of holocene salinity shifts in laguna de bay philippines abstract a 7000 year record of salinity shifts from molluscan and diatom assemblages and verified geochemical salinity proxies c s s sr ca and sr ba is reconstructed from philippines largest freshwater lake laguna de bay the salinity shifts are interplays of millennial scale sea level change centennial scale tectonic activity from the west marikina valley fault wmvf and decadal scale climatic changes currently only 1 m above mean sea level the lake is connected to manila bay through the pasig napindan river which meanders across a densely populated paranaque strip partly occupied by metropolitan manila the controversial wmvf borders the lake on its western shore our 10 5 m sediment core from the western lobe reveal that the deposits are from a marine environment deposited 6600 cal bp to 4700 cal bp during a sea level still stand above present mean sea level apmsl in southeast asia and the philippines episodic decreases in salinity with 260 y cycles were traced to the activity of the wmvf that would have accounted for at least 6 m of uplift of the paranaque strip the vertical component of movement raised a sill and emergent landmass that started to isolate the paleo laguna de bay from manila bay subsequent episodic uplifts and sea level fall decreased depths to intertidal levels by 4700 cal bp salinity to brackish but highly influenced by marine waters by 4100 cal bp and to freshwater by 3100 cal bp the latest salinity increase since mid 1960 is attributed to renewed saltwater incursion due to abnormally dry years low lake levels and pasig river delta plain subsidence

structures and facies associated with the flow of subaerial basaltic lava into a deep freshwater lake the sulphur creek lava flow north cascades washington abstract the ca 8800 14c yrs bp sulphur creek lava flowed eastward 12 km from the schriebers meadow cinder cone into the baker river valley on the southeast flank of mount baker volcano the compositionally zoned basaltic to basaltic andesite lava entered crossed and partially filled the 2 km wide and 100 m deep early holocene remnant of glacial lake baker the valley is now submerged beneath a reservoir but seasonal drawdown permits study of the distal entrant lava as a lava volume that may have been as much as 180 106 m3 entered the lake the flow invaded the lacustrine sequence and extended to the opposite east side of the drowned baker river valley the volume and mobility of the lava can be attributed to a high flux rate a prolonged eruption or both basalt exposed below the former level of the remnant glacial lake is glassy or microcrystalline and sparsely vesicular with pervasive hackly or blocky fractures together with pseudopillow fractures these features reflect fracturing normal to penetrative thermal fronts and quenching by water a fine grained hyaloclastite facies was probably formed during quench fragmentation or isolated magma water explosions although the structures closely resemble those developed in lava ice contact environments establishing the depositional environment for lava exhibiting similar intense fracturing should be confirmed by geologic evidence rather than by internal structure alone the lava also invaded the lacustrine sequence forming varieties of peperite including sills that are conformable within the invaded strata and resemble volcaniclastic breccias the peperite is generally fragmental and clast or matrix supported fine grained and rounded fluidal margins occur locally the lava formed a thickened subaqueous plug that as the lake drained in the mid holocene was exposed to erosion the baker river then cut a 52 m deep gorge through the shattered highly erodible basalt

cenozoic structural deformation and dynamic processes of the bohai bay basin province china abstract cenozoic structures in the bohai bay basin province can be subdivided into eleven extensional systems and three strike slip systems the extensional systems consist of normal faults and transfer faults the normal faults predominantly trend nne and ne and their attitudes vary in different tectonic settings paleogene rifting sub basins were developed in the hanging walls of the normal faults that were most likely growth faults neogene quaternary sequences were deposited in both the rifting sub basins and horsts to form a unified basin province the extensional systems were overprinted by three nne trending right lateral strike slip systems fault zones although the principal displacement zones pdz of the strike slip fault zones are developed only in the basement and lower basin sequences in some cross sections the structural deformation characteristics of the upper basin sequences also indicate that they are basement involved right lateral strike slip fault zones according to the relationships between faults and sedimentary sequences the extensional systems were mainly developed from the middle paleocene to the late oligocene whereas the strike slip systems were mainly developed from the oligocene to the miocene strike slip deformation was intensified as extensional deformation was weakened extensional deformation was derived from horizontal tension induced by upwelling of hot mantle material whereas strike slip deformation was probably related to a regional stress field induced by plate movement

palaeoclimatic evolution during eocene and its influence on oil shale mineralisation fushun basin china the fushun basin is a small explored coal and oil shale bearing cenozoic fault basin in the liaoning province northeast china the basin mainly consists of eocene swamp to lacustrine deposits of the guchengzi to xilutian formation and contains the biggest opencast oil shale mine in asia this mine has provided an ideal opportunity to undertake palaeoclimate reconstruction in this basin based on a single geological profile and the analyses of 93 samples using various approaches namely field geological observation clay mineralogical and geochemical sr ba sr cu stable c and o isotope analyses all of which were compared with palaeobotanical data the eocene climate of fushun basin evolved from warm temperate to north subtropical and generally changed from warm humid to subhumid semiarid paleoclimatic and geochemical parameters shows that the very warm and humid climate during jijuntun formation increased the initial productivity of lake water and caused a steady stratification of the lake water then caused oxygen lack in the bottom of water productivity of the lake provides the mean origin of organic matters for oil shale formation and steady anoxic environment is beneficial for the conservation of organic matters

lava flows from a mid 1980s submarine eruption on the cleft segment juan de fuca ridge a series of lava flows with a total volume of 0 05 km3 were erupted in the mid 1980s along 17 km of the northern cleft segment of the juan de fuca ridge observations from camera tows and submersible dives show that the new flows are all similar in appearance and consist entirely of pillow lava with a mixture of smooth and striated surface textures suggesting a relatively uniform eruption rate approaching 1 m3 s at point source vents the flows vary in size from small patches to large steep sided ridges and were probably erupted from a dike intruded along the ridge axis because they are aligned along a linear fissure graben system observations at north cleft show that the physical appearance of new flows changes more rapidly than previously realized and that earlier qualitative dating of young lavas based on sediment cover and glassy surface texture were probably overestimates by an order of magnitude sediment accumulation on the lavas is quite variable and locally surprisingly substantial mainly due to hydrothermal deposits that formed while the lava flows were cooling biological vent communities photographed on the new flows in 1989 show that vent animals can colonize new vent sites rapidly but that warm water was still venting only in a few places nonvent animals are much slower to colonize the new flows and rates of colonization observed at north cleft may be useful for making improved age estimates of young 10 years lava flows elsewhere the north cleft eruption represents about 2 of the estimated average annual volcanic output along the global mid ocean ridge implying that many other submarine eruptions are occurring undetected

carbon isotopic composition of individual biomarkers in gilsonites utah abstract carbon isotopic compositions of saturated hydrocarbon aromatic hydrocarbon nso resin and asphaltene fractions of vein forming gilsonites cowboy bonanza independence wagonhound and harrison veins in the ne uinta basin utah are all similar and isotopically resemble mahogany zone shale extracts of the green river formation 13 c 29 to 31 individual molecular fossils in the gilsonites show a wider variability in compositions indicative of their paleoecological origins within the eocene uinta greater green river paleolake system carbon isotopic compositions of c28 and c29 steranes 13 c 25 to 32 pristance and phytane 33 to 34 and perhydro carotene carotane 13 c 33 2 suggest that organisms producing these compounds grew near the lake surface the c33 carotenoid lexane is isotopically identical to the c40 carotenoid carotane supporting a common c40 carotenoid precursor two groups of hopanes can be differentiated in the gilsonites based on carbon isotopic compositions c29 c31 and c32 hopanes and moretanes 40 9 to 44 3 consistent with a source from midwater bacteria and c30 hopanes and moretanes 51 0 and 60 5 for which the strong 13c depletion suggests at least partial derivation from methylotrophs the isotopic signatures of these molecular fossils suggest the source beds of the gilsonites were deposited in a stratified paleolake system with a depositional environment similar to that which formed the mahogany zone shales of the piceance creek basin algal biomarkers in the gilsonites are isotopically uniform throughout the area of the gilsonite vein occurrence 1500 km3 and resemble those in the mahogany zone shale in the piceance creek basin over 50 km to the east this remarkable lateral uniformity suggests that very similar photic zone water conditions existed across the entire uinta piceance creek paleolake system at the time of deposition of the gilsonite source bed mahogany zone shale sterane isotopic compositions are effective for the genetic correlation of the solid bitumens immature oils in contrast the carbon isotopic compositions of the bacterial biomarkers in the gilsonites vary significantly suggesting that conditions in deeper waters of the paleolake system were more variable carbon isotopic signatures of individual hopane biomarkers in the green river formation appear to be valuable for identifying different source facies characteristics within the same paleolake depositional system

palaeovolcanology and tectonic setting of a proterozoic metatholeiitic sequence near the baltic shield margin northern norway abstract the kvenvik greenstone formation 1500 m thick is a very well preserved 2 0 1 8 ga old sequence of morb type tholeiitic metabasaltic lavas and volcaniclastic rocks they were deposited as cyclically repeated couplets in a continental shallow water to terrestrial environment near the margin of the baltic shield the effusive facies comprise massive and amygdaloidal lava pillow lava pillow breccia and hyaloclastite volcaniclastic facies are ash and accretionary lapilli tuff lapilli tuff and tuffaceous sedimentary rocks lithofacies associations and primary structures in the tuffs indicate air fall base surge and pyroclastic flow deposits with little input of epiclastic material the prevalence of shallow water to subaerial emplacement throughout the kvenvik greenstone formation and correlative sequences to the south indicates deposition in a spasmodically subsiding basin almost certainly formed by taphrogenic tectonism the rifting may have been incidental to coeval plate convergence tectonism evidenced by calc alkalic magmatism in the repparfjord komagfjord area 50 100 km northeast of the kvenvik area

subglacial volcanics on the control of magma chemistry on pillow dimensions abstract axial dimensions glass thicknesses and plunges of 822 icelandic pillows of olivine tholeiitic to andesitic compositions are presented the pillows formed during subglacial volcanic eruptions at water depths of a few hundred meters their average diameters are olivine tholeiite 40 cm tholeiite and basaltic andesite 15 cm and andesite 30 cm the olivine tholeiite pillows have highly vesicular glass rims and vesicular interiors whereas the tholeiite and basaltic andesite pillows are characterized by very low vesicularity throughout the andesite pillows have nonvesicular glass margins but commonly highly vesicular interiors the glass rims thicken linearly with increasing diameter both for the olivine tholeiite and the andesite pillows although the increment is much faster for the latter the small average diameter pillows of tholeiite and basaltic andesite are characterized by highly abundant and evenly dispersed euhedral grains of magnetite during formation the olivine tholeiite pillows can apparently expand relatively freely prior to the crust attaining sufficient strength to prevent further growth the non vesicular and relatively thick crust of tholeiite basaltic andesite and andesite pillows apparently obtains strength quickly to prevent further growth

the agricultural history of human nitrogen interactions as recorded in ice core δ15n no3 1 the advent and industrialization of the haber bosch process in the early twentieth century ushered in a new era of reactive nitrogen distributions on earth since the appearance of the first commercial scale haber bosch fertilizer plants fertilizer application rates have greatly increased in the u s while the contributions of fertilizer runoff to eutrophication and anoxic dead zones in coastal regions have been well documented the potential influences of increased fertilizer applications on air quality and precipitation chemistry are poorly constrained here we combine a 255 year record of precipitation nitrate isotopes preserved in a greenland ice core historical reconstructions of fertilizer application rates and field characterization of the isotopic composition of nitrogen oxides produced biogenically in soils to provide new constraints on the contributions of biogenic emissions to north american nox inventories our results indicate that increases in twentieth century commercial fertilizer use led to large increases in soil no a byproduct released during nitrification and denitrification reactions these large shifts in soil no production are evidenced by sharp declines in ice core 15n no3 values further these results suggest that biogenic nox emissions are underestimated by two to four fold in the u s nox emission inventories used to construct global reactive nitrogen budgets these results demonstrate that nitrate isotopes in ice cores coupled with newly constrained 15n nox values for nox emission sources provide a novel means for estimating contemporary and historic contributions from individual nox emission sources to deposition

nitrate in greenland and antarctic ice cores a detailed description of post depositional processes a compilation of nitrate no 3 data from greenland has shown that recent no 3 concentrations reveal a temperature dependence similar to that seen in antarctica except for sites with very low accumulation rates lower temperatures tend to lead to higher no 3 concentrations preserved in the ice accumulation rate which is closely linked to temperature might influence the concentrations preserved in snow as well but its effect cannot be separated from the temperature imprint processes involved in no 3 deposition are discussed and shown to be temperature and or accumulation rate dependent apart from scavenging of nitric acid hno 3 during formation of precipitation uptake of hno 3 onto the ice crystal s surface during and after precipitation seems to contribute further to the no 3 concentrations found in surface snow post depositional loss of no 3 from the top snow layers is caused by release of hno 3 and by photolysis of no 3 it is suggested that photolysis accounts for considerable losses at sites with very low accumulation rates depending on the site characteristic and given that the temperature and accumulation rate dependence is quantified it should be possible to infer changes in atmospheric hno 3 concentrations

the pliocene seamount series of la palma canary islands a pliocene submarine series of alkali basaltic pillow lavas hyaloclastites and breccias a a sheeted dike swarm b and a basal suite of gabbro and ultramafic rocks c from la palma canary islands is interpreted as a cross section through an uplifted seamount this series has been tilted to its present orientation of 50 230 plunge and azimuth probably by upwarping due to intrusions in the central portion of the island the basal plutonic complex c also includes intrusives coeval with up to 2000 m of younger subaerial alkali basaltic lavas unconformably overlying the submarine series the plutonic suite c is overlain abruptly by more than 1800 m of sills b 0 4 1 m thick on average with minor screens of lavas and breccias extrusives a form a 1750 m thick sequence of pillow lavas breccias and hyaloclastites the clastic rocks increase in abundance upward and are of four main types 1 breccias consisting of partly broken pillows formed nearly in situ 2 heterolithologic pillow fragment breccias 3 hyaloclastites composed dominantly of highly vesicular lapilli and ash sized shards the latter thought to have formed by near surface explosive eruptions and been subsequently transported downslope by mass flows 2 and 3 being interpreted to have been resedimented and 4 pillow scoria breccias from the upper 700 m of the extrusive section consisting of amoeboidal highly vesicular pillows and lava stringers and local bombs probably formed by cracking and bleeding of gas rich expanding pillow lava and some shallow submarine subaerial lava fountaining the extrusive series is chemically and mineralogically crudely zoned with the most differentiated rocks metatrachytes and mugearites at the base and most picritic lavas occurring near the top of the series subsequent to emplacement the entire extrusive and intrusive series has been hydrothermally altered the lower part to greenschist and the upper part to smectite zeolite facies mineral assemblages the la palma succession combined with evidence from surface studies of seamounts suggests that seamounts are formed by intrusive and extrusive processes in approximately equal portions the nature of eruptive clastic and depositional mechanisms changes drastically during growth of a seamount if the critical depth for major magmatic degassing is surpassed and especially if magmatic explosive processes can occur at very shallow water depth the critical depth depending on magma and thus volatile composition changes in slopes of a seamount influence depositional processes based on these factors at least three major depositional sites develop as a seamount grows summit flank and apron facies nonexplosive extrusive processes prevail in the deep water stage dominantly producing pillow lavas 75 these consist of individual pillow volcanoes up to 200 m high with large pillows near the base and decreasing pillow size toward the top of a volcano pillow breccias and pillow fragment breccias comprise approximately 20 of this facies the deep water flank and apron facies are characterized by debris flow deposits with possibjy rather dense matrix material the shallow water shoaling stage is reached when the seamount top reaches the critical depth for drastic increase in exsolution of magmatic volatiles about 800 m for the alkali basaltic seamount of la palma resulting in formation of mainly clastic rocks 70 in situ pillow rind breccias and scoriaceous amoeboidal breccias and pillows are formed in the summit regions of the seamount by repeated expansion and leaking of frothy pillow lava possibly by lava fountaining resedimented heterolithologic pillow fragment breccias lapilli breccias and hyaloclastites are deposited on the flanks and aprons of the seamount pillow lavas comprise 30 of these deposits

application of an eutrophic lake model to the origin of ancient organic carbon rich sediments in this paper we approach the problem of the origin of organic carbon rich sediments by using an integrated isotopic and organic geochemical study of the annual productivity eutrophication cycle in the water column of lake greifen switzerland and the historical expression of such cycles as found in the sediments the lake greifen water column and sediment studies reveal that 13c carbonate organic matter is correlated with the hydrogen indices hi of kerogens explicable in terms of changing productivity and preservation of the organic matter and the co2 budget of the water body the lake model implies that if high productivity in co2 limited surface waters high nutrient co2 ratio was controlling the preservation of organic matter a correlation between decreasing 13c carbonate organic matter and increasing hi values may be observed in contrast if low to moderate productivity in co2 unlimited surface waters low nutrient co2 ratio where bottom water anoxia promotes the preservation of organic matter a correlation between increasing 13c carbonate organic matter and increasing hi values may be observed application of this model to two well known jurassic sequences gave a correlation of increasing hi values with decreasing 13c carbonate organic matter for the kimmeridge clay formation united kingdom and increasing hi values with increasing 13c carbonate organic matter for the early toarcian shales france this suggests that the controlling factor of the former deposit was high primary bioproductivity and of the latter deposit anoxic bottom water conditions

subaqueous strombolian eruptions and eruption fed pyroclastic deposits in a paleoproterozoic rifted arc hidden formation flin flon canada abstract the hidden formation of the paleoproterozoic flin flon arc assemblage comprises the stratigraphic hanging wall to the volcanogenic massive sulfide vms deposits at flin flon manitoba canada it represents a basaltic volcanic edifice erupted within a large subsidence structure developed in a rifted arc environment it is predominately pillow lavas with subordinated amounts volcaniclastic rocks rocks that stratigraphically overly the schist and mandy vms deposits 5 km southeast of the main flin flon deposits have been correlated through litho and chemo stratigraphy with the hidden formation they display evidence of pyroclastic volcanism and concomitant subsidence pillow lavas and hyaloclastite are unequivocal evidence of subaqueous eruption the hidden formation in the schist mandy area comprises mafic tuff mafic megabreccia basalt lava fluidal clast breccia and plagioclase crystal rich volcaniclastic lithofacies intruded by synvolcanic dikes and sills the megabreccia lithofacies is characterized by angular basalt clasts 1 20 m in a matrix of finer basalt clasts and is interpreted to have been deposited by mass flows due to slumping of the caldera wall a within flow vertical transition in the lavas from massive to pillowed flows suggests a slowing of emplacement velocity decrease in temperature and an increase in the viscosity during eruption based on the monolithic nature of the fluidal clast breccias and the fluidal shapes of clasts with delicate tails and intact glassy margins they are interpreted to be the result of strombolian eruptions an increase in the ingestion of water in the vent s lead to a change from magmatic to phreatomagmatic fragmentation planar and cross laminations graded beds and the abundance of broken plagioclase crystals in combination with scoria and lithic clasts suggest the mafic tuff and plagioclase crystal rich volcaniclastic lithofacies were deposited by subaqueous eruption fed density currents derived from a phreatomagmatic eruption detailed mapping of the volcanic lithofacies in the schist mandy area has facilitated the identification of synvolcanic faults defining inner caldera margins and volcanic vents these structures when traced downwards through stratigraphy define structural corridors corresponding with the schist and mandy vms deposits indicating they represent long lived structures that also acted as magmas and fluid pathways

organic and isotope geochemistry of the early cretaceous rift sequence in the camamu basin brazil paleolimnological inferences and source rock models abstract the camamu basin located at the eastern brazilian continental margin is characterized by a thick early cretaceous organic rich rift sequence the integration of bulk geochemical isotopic and biomarker data with paleontological and geological information provided the basis for a better assessment of rift lake evolution hydrological regime redox potential salinity etc and its impact on source rock development pyrolysis and visual kerogen analyses reveal the dominance of lipid rich algal bacterial type i kerogen through the entire rift sequence paleolimnological reconstruction suggests that the lower rift sequence morro do barro formation neocomian was deposited in a fault bounded deep lake with fresh to brackish water stable water column stratification and water bottom anoxia high hydrogen indices 700 900 mg hc gtoc and 13c depleted carbon isotopic composition of the organic matter 13c values around 30 might reflect enhanced organic preservation the recycling of light ch4 generated by methanogenesis and the incorporation of isotopically light lipid rich bacterial biomass on the other hand the upper rift sequence rio de contas formation barremian was probably deposited within a broader shallower lake with a higher frequency of water column overturn and a deeper thermocline high organic carbon contents and strong 13c enrichment of the organic matter 13c excursions of up to 23 are interpreted to have resulted from enhanced primary productivity triggered by an increased input recycling of nutrients favored by lake morphology and humid climate

chlorobiaceae in palaeozoic seas revealed by biological markers isotopes and geology biomarker hydrocarbons in oils and sediments have considerable potential for assessing the nature of biological processes in the past but only a few can be uniquely related to particular organisms reef hosted oils in the silurian of the michigan basin canada and the devonian of western canada have high abundances of 1 alkyl 2 3 6 trimethylbenzenes their precise structures suggest that they are diagenetic products of aromatic carotenoids of the green sulphur bacteria individual components are enriched in 13c by 7 8 relative to the saturated hydrocarbons of the same oil an isotopic anomaly of this magnitude and direction correlates with a component of photosynthetic carbon assimilation by the reductive tricarboxylic acid cycle these results together with data on palaeoenvironments provide compelling evidence for the existence in ancient restricted seas of microbial communities containing chlorobiaceae organisms with distinctive biochemistry which leave morphologically identifiable remains

the role of algal blooms in the formation of lacustrine petroleum source rocks evidence from jiyang depression bohai gulf rift basin eastern china abstract algal blooms are responsible for the laminae in the lacustrine shahejie formation in the jiyang depression one of the sub basins of the bohai gulf rift basin in eastern china about 65 oil fields have been discovered in this depression during the past 40 years and the oil is mainly derived from three types of finely laminated lacustrine rocks of shahejie formation eocene oligocene these lacustrine petroleum source rocks are oil shales calcareous shales and calcareous laminated mudstones optical sem and bsei analyses of these source rocks reveal that there are algal coccoliths and dinoflagellates laminae in the rocks the individual algal lamina is generally composed almost wholly of one species such as reticulofenestra bohaiensis in coccolith laminae and fromea as well as bohaidina in dinoflagellate laminae this distribution suggests that the algal laminae formed from algal blooms in the ancient lake other components of source rocks included organic matter laminae carbonate laminae and clay rich laminae we also discuss the sedimentation of organic matter laminae and carbonate laminae which were related to algal blooms we conclude that the laminated lacustrine petroleum source sediment of jiyang depression formed during episodes of algal blooms alternating with chemical and detrital sedimentation and this represents the primary mechanism responsible for the formation of lacustrine petroleum source rocks

biogenic alteration of volcanic glass from the troodos ophiolite cyprus alteration of basaltic glass through the entire volcanic sequence of the troodos ophiolite is partly bio mediated the following observations support this conclusion alteration textures resembling microbes in form and size altered glass locally shows high carbon concentrations at the alteration front and organic remains the absence of dna suggests that the bio alteration is a fossil process temperatures calculated from 18 o of carbonate assumed to have been in equilibrium with seawater yield 27 65 c and 18 o silicate versus h 2 o relationships indicate seawater alteration these data are consistent with biogenic alteration during an early stage of ocean floor alteration of the troodos oceanic crust some 70 90 ma ago

shale oil occurring between salt intervals in the dongpu depression bohai bay basin china abstract the saline mudstone sequence of the paleogene shahejie formation in the dongpu depression of bohai bay basin is a major source rock for conventional hydrocarbons however shale oil having a density of 0 9 g cm 3 and a viscosity of 21 mpa s has also been discovered and is being produced from these mudstones to better understand the occurrence of such shale oil geochemical petrological and mineralogical investigations were carried out on a suite of saline mudstone samples by using rock eval x ray diffraction and sem the shahejie formation samples analyzed in the current study are characterized by type ii kerogen with lesser amounts of types i and iii such that petroleum generation ranges from fair to excellent in general terms with the exception of es1 uppermost member which is immature to marginally mature for oil generation the sequence studied ranges from mature for oil generation to mature for wet gas generation on the basis of vitrinite reflectance data the most prospective depths for shale oil condensate generation are between 2300 and 4000 m depth in area studied the saline mudstones comprise mainly clay minerals followed by carbonates quartz and feldspar based solely on the brittle mineral index the amounts of carbonate and quartz in many of the samples lead to a similar or greater suitability for hydraulic fracturing than for many haynesville woodford and upper bakken shales sem studies show that abundant micro fractures commonly occur in the mudstones and these include tectonic fractures bedding plane fractures shrinkage fractures and over pressured fractures for the es3 m middle third member unit shale oil prospectivity is likely to be enhanced around the towns of wl wenliu lt liutun and hbz hubuzhai due to the increased frequency of tectonic fractures which would contribute to oil storage and flow mineral interparticle mineral intraparticle and organic matter pores are well developed in the rocks studied mineral dissolution has created secondary pores in some areas such that reservoir capacity is increased the increased concentration of organic acids between 2800 and 3500 m is likely to lead to enhanced shale oil prospectivity the micro fractures and dissolution pores are probably the main reservoirs for shale oil accumulation the association of these features with saline facies potentially offers an exploration tool for further shale oil occurrences in the studied area as well as in other areas containing similar lithologies

growth of pillow lobes evidence from pillow lavas of hokkaido japan and north island new zealand pillow lavas of cretaceous and neogene age well exposed in hokkaido japan and those of neogene age in north island new zealand provide evidence of their mode of growth some pillow lobes diverge by formation of longitudinal surface spreading cracks the others grow by formation of transverse spreading cracks leaving one or more crusts ending toward the front of the lobes and constrictions therefore it is possible to determine the direction of growth of pillow lobes by tracing the crusts and or constrictions

recognizing distinct portions of seamounts using volcanic facies analysis examples from the archean slave province nwt canada abstract archean volcanic rocks in the mafic dominated ca 2 66 2 69 ga point lake and beaulieu river belts slave province northwest territories are significant in demonstrating the facies that characterize specific portions of pillow volcanoes or seamounts irrespective of tectonic setting three distinct localities mapped in detail display facies consistent with 1 proximal deep water 2 medial to distal deep water and 3 medial shallow water seamount settings the proximal facies in the point lake belt include a 55 m thick non vesicular pillowed sequence cut by numerous mafic dykes and sills dykes contain multiple chilled margins indicating successive magma pulses which contributed to edifice construction abundant feeder conduits in addition to the absence of fragmental facies and vesicles are typical of the central deep water portion of seamounts where growth is initiated the medial to distal deep water facies in the point lake belt are represented by a 30 80 m thick assemblage of disorganized pillow breccia and pillowed and massive flows with 5 27 vesicularity massive non vesicular hyaloclastite intermingled with sedimentary material fluidal peperite in addition to thin shale units interstratified with pillow breccia and hyaloclastite indicate that sedimentation and volcanism were contemporaneous an increase in fragmental units and vesicularity relative to the proximal deep water facies is suggestive of the medial to distal part of a seamount in shallower water bedded tuffs laterally along strike with massive flows are the results of turbidity current deposition immediately following localized subaqueous eruptions a medial shallow water seamount setting is represented in the beaulieu river belt by a 5 85 m thick sequence of vesicular lobate pillowed and massive flows stratified pillow breccia and hyaloclastite and mafic dykes vesicularity ranges from 21 49 in pillowed flows 5 40 in massive flows and 20 35 in pillow breccia and hyaloclastite stratified pillow breccia developed along steep flow fronts in shallow water whereas bedded hyaloclastite formed during reworking and redeposition of autoclastic hyaloclastite on seamount flanks in shallow water the volcanic facies associations in the study areas are analogous to those of modern seamounts associated with the mid atlantic ridge and east pacific rise as well as mesozoic cenozoic seamounts in the canary islands fiji southwest japan the sea of japan and cyprus volcanological studies in the point lake and beaulieu river volcanic belts and subsequent comparisons with phanerozoic analogues demonstrate the manner in which distinct portions of ancient seamounts can be recognized in similar archean terranes

ophiolites as faithful records of the oxygen isotope ratio of ancient seawater the solund stavfjord ophiolite complex as a late ordovician example

first ice core records of no3 stable isotopes from lomonosovfonna svalbard samples from two ice cores drilled at lomonosovfonna svalbard covering the period 1957 2009 and 1650 1995 respectively were analyzed for no 3 concentrations and no3 stable isotopes n 15

pillow lavas and fluvio lacustrine deposits in the northeast of parana continental magmatic province brazil abstract the northeast edge of the parana continental magmatic province was marked by a topographical barrier that gave rise to a predominantly peridesertic environment this high allowed the recurrent of above average rainfall in this area of the province in contrast with other areas where many evidences indicate that lava flows have settled in an arid climate in a desert environment as a result alluvial fan debris flows and fluvio lacustrine systems developed occasionally this paper presents one of these sequences which is remarkable for the presence of sedimentary rocks and two sets of pillow lavas both sets of pillow lavas show interaction with the fluvio lacustrine sediments with distinctive grain size from pebbly sand to clay that locally preserve the original sedimentary structures such as bedding and lamination this interaction gives rise to peperites which show a diversity of textures for different sedimentary granulometries hyaloclastites and fragments of lava also occur in the interpillow material and may be intricately mixed with sediment these features based mainly on detailed field observations in the northeastern region demonstrate that the palaeorelief sedimentary environment stratigraphy and morphology of sedimentary units and basaltic flows are contrasting from the central and southern regions of the parana continental magmatic province

nature of and controls on volcanism in the ca 2 32 2 06ga pretoria group transvaal supergroup kaapvaal craton south africa abstract the time of deposition of the pretoria group between 2 32 and 2 06 ga on south africa s kaapvaal craton was characterized by the first major increase in atmospheric oxygen it was accompanied by the extrusion of significant thicknesses of volcanic deposits namely the bushy bend lavas of the timeball hill formation the hekpoort formation and the machadodorp volcanic member of the silverton formation marking the three major volcanic events within the transvaal supergroup which are thought to be precursors to the succeeding bushveld complex magmatism the bushy bend lava member of the timeball hill formation is characterized by subaqueous basaltic andesitic fissure eruptions with fumarolic activity and probably minor subaerial explosive eruptions in the hinterland of the transvaal supergroup basin the subaerial volcanism of the hekpoort formation appears to have been dominated by fissure eruptions with a preponderance of lava flows and locally important pyroclastic material intermittent hiatuses in volcanism were marked by local lacustrine shale deposition finally the machadodorp lava member can be interpreted as the deposits of several seamounts aligned along a fissure probably within an extensional environment the geodynamic control inferred for the evolution of the pretoria group basin encompasses two cycles of prerift uplift subsequent mechanical rifting and long lived thermal subsidence the limited extent of the bushy bend lavas in the south of the pretoria group depository attests to the likelihood that volcanism accompanying the first rifting event was short lived in contrast the second rifting cycle postulated for the pretoria group basin has a strong association with widespread and large scale volcanism of the hekpoort ongeluk flood basalts which may have been plume related the scale of the second cycle volcanism and its importance in influencing the upper part of the pretoria group basin fill is underlined by the machadodorp volcanism probably related to hot spot volcanism as the ongeluk hekpoort plume waned

underwater observations of active lava flows from kilauea volcano hawaii underwater observation of active submarine lava flows from kilauea volcano hawaii in march june 1989 revealed both pillow lava and highly channelized lava streams flowing down a steep and unconsolidated lava delta the channelized streams were 0 7 1 5 m across and moved at rates of 1 3 m s the estimated flux of a stream was 0 7 m 3 s jets of hydrothermal water and gas bubbles were associated with the volcanic activity the rapidly moving channelized lava streams represent a previously undescribed aspect of submarine volcanism

hydrogen index and carbon isotopes of lacustrine organic matter as lake level indicators abstract optical and geochemical techniques were applied to organic matter of late quaternary sediments from lakes victoria and rukwa east africa variations in total organic carbon toc and hydrogen content expressed as hydrogen index hi can be related to known changes in lake level and used to identify periods of very low water or subaerial exposure in basinal sequences toc and hi both decline as an exposure surface is approached mainly due to the selective removal of unstable components by bacterial respiration and inorganic oxidation inert organic material of very low hi is typically concentrated at the overlying transgression surface the carbon isotopic composition of the particulate organic matter tends to be less negative in sediments associated with exposure surfaces although weathering may be partially responsible isotopic variations are mainly due to changes in the relative importance of material from plants using c4 photosynthesis such as grasses and sedges growing around the shore and on the exposed lake muds and of material from planktonic algae and terrestrial c3 plants

geochemistry characteristics and genetic types of natural gas in central part of the tarim basin nw china abstract according to the chemical carbon isotopic and hydrogen isotopic compositions and 3 he 4 he ratios of 127 natural gas samples the natural gas in the tarim basin is mainly composed of gaseous alkanes dominated by methane the contents of the gaseous alkanes decrease with the increase of their carbon numbers the 13 c values of ch 4 c 2 h 6 and c 3 h 8 in the platform area of the tarim basin vary in the range of 54 4 24 4 an average value of 39 2 43 1 26 7 an average value of 36 1 and 37 9 21 6 an average value of 31 8 respectively the overall carbon isotopic composition of the alkanes follows the trend of 13 c 1 13 c 2 13 c 3 13 c 4 and in some cases varies with 13 c 1 13 c 2 or 13 c 3 13 c 4 the lower carbon isotope values of methane 13 c 1 13 c 2 may be attributed to thermal sulfate reduction tsr and the higher propane value 13 c 3 13 c 4 was caused by the mixing of the natural gases of the same genetic type formed at different stages the methane hydrogen isotopes 2 h c 1 of the natural gases in the tarim basin are in the range of 195 122 with an average value of 156 the 3 he 4 he ratios of the natural gases are in the range of 2 3 10 8 66 8 10 8 suggesting that there is no deep mantle derived gas in the platform area of the tarim basin the carbon isotope fractionation of alkane gases 13 c 2 13 c 3 1 c 2 vs lnc 2 c 3 and c 2 c 3 vs 13 c 2 13 c 3 of the natural gases indicate that the oil type gas in the tarim basin has different predominant formation processes including kerogen cracking oil cracking oil and gas cracking secondary gas cracking and mixing of the kerogen cracking and oil cracking gases the gas evolved from gas cracking gas to oil and gas cracking gas and oil cracking gas along the direction from the west side of the manjar sag to the central tarim basin the natural gases in some areas of tazhong are the mixtures of the kerogen cracking and oil cracking gases

toothpaste lava characteristics and origin of a lava structural type transitional between pahoehoe and aa toothpaste lava an important basalt structural type which illustrates the transition from pahoehoe to aa is particularly well displayed on the 1960 kapoho lava of kilauea volcano its transitional features stem from a viscosity higher than that of pahoehoe and a rate of flow slower than that of aa viscosity can be quantified by the limited settling of olivine phenocrysts and rate of flow by field observations related to the low angle slope on which the lava flowed much can be learned about the viscosity rheologic condition and flow velocity of lavas long after solidification by analyses of their structural characteristics and it is possible to make at least a semiquantitative assessment of the numerical values of these parameters

miocene pillowed sills in the shimane peninsula sw japan abstract two miocene basaltic andesite pillowed sills in the shimane peninsula sw japan were intruded into wet marine sediments plastically deforming them the pillows are elongated constricted interconnected and relatively closely packed individual pillows have a poorly to moderately vesiculated somewhat crystalline rind thinner than a few centimeters and a moderately to well vesiculated more crystalline core contraction cracks and spreading cracks are poorly developed the pillows in the sills morphologically resemble pillow lava flows and during sill intrusion the magma bifurcated into pillow lobes in a manner similar to pillow lavas formation of pillows in sill probably occurs when the magma is intruded into wet sediments and protrudes fingers by the instability of the magma sediment interface with little turbulence of magma flow

emplacement of lobate sheet flows with hyaloclastites onto soft sediment the erquy neoproterozoic lava pile armorican massif france abstract the neoproterozoic volcano sedimentary succession of the heussaye headland erquy belongs to the cadomian block located in the north east of the armorican massif france the volcanism dated at approximately 608 7 ma zircon u pb data occurred in a back arc basin this site exhibits a noteworthy verticalized pile of moderately metamorphosed greenschist facies basaltic andesite flows of arc back arc tholeiite affinity alternating with metasedimentary layers sandstones and siltstones a large range of volcanic facies characteristic of an underwater soft substrate environment can be continuously studied for over than 200 m parallel to the flow edges they include pillow lavas lava lobes fluidal peperites and sediment matrix hyaloclastites the presence of parallel lava lobes in a sector where one lava flow is capped by a variably thick hyaloclastite carapace together with the occurrence of asymmetric turbiditic folds in interbedded metasedimentary layers suggests the existence of an easterly facing gentle paleoslope the sudden thinning of this hyaloclastite carapace in two spots located approximately 60 m from each other is attributed to the synvolcanic activity of two conjugate normal paleofaults this hypothesis is supported by the observation of a hyaloclastite accumulation in one of the two spots close to a strike slip fault which may have been extensional at the time of the volcanism water entered the lava flow along the faults resulting in an interstitial network of hyaloclastites by quench fragmentation in the upper part of the hanging wall block all these observations are consistent with a model of lava emplacement along a subaqueous slope resulting from synmagmatic extensional faulting in a marginal basin context

multiple rind structure in pillow lava as an indicator of shallow water multiple rind structure is common among shallow water pillows with diameters larger than about 1 m in oamaru new zealand on the columbia plateau usa and elsewhere a rind consists of sideromelane tachylyte and tachylytic basalt a multiple rind is a concentric set of repeated rinds in various forms e g a portion of a broken rind thrust under another part a series of short and detached subparallel rinds or a pouch shaped depression transitions and combinations of these three forms are common multiple rind structure develops at any part of the pillow perimeter but does not cover the pillow completely it is always accompanied by a rupture in the outermost rind up to 13 rinds have been observed but two to four rinds are most common the multiple rind structure is formed by implosion resulting from condensation of exsolved h2o when h2o condenses a pressure difference between the interior and exterior of a pillow is created above a certain threshold pressure difference the outer skin of a pillow is torn at weak points such as radial joints and thrusts under the neighboring skin buckles to form a pouch shaped depression or produces some variation of these one set of multiple rinds is thus formed further exsolution and condensation of h2o in solidifying pillows may cause development of additional rinds h2o exsolution and condensation and subsequent implosion are limited to low pressure environments so that multiple rind structure is characteristic of shallow water pillow lava

cyclic volcanic stratigraphy in a late ordovician marginal basin west norwegian caledonides the well preserved extrusive sequence of the solund stavfjord ophiolite complex ssoc in the west norwegian caledonides enables reconstruction of the uppermost oceanic crust that developed in a marginal basin basaltic sheet flows pillow lavas and volcanic breccias are the main components of the extrusive sequence and show stratigraphic and structural evidence for a cyclic development the first stage in a volcanic cycle is characterized by high extrusion rates yielding sheet flows commonly with the thickest flow units at the base sequences of sheet flows can be correlated laterally for at least 6 5 km pillow lavas succeed the sheet flows later in a volcanic cycle with progressively smaller pillows forming at decreasing extrusion rates volcanic breccias occur towards the end of a volcanic cycle but may also occur at lower stratigraphie levels they are made generally of pillow breccias and hyaloclastites the extrusive sequence of the ssoc oceanic crust was constructed through seven volcanic cycles that resulted in stratigraphic units with thicknesses ranging from 40 to 225 m this architecture is comparable to sequences in in situ oceanic crust developed along slow to intermediate spreading ridges

an organic geochemical record of sierra nevada climate since the lgm from swamp lake yosemite abstract sediment records from swamp lake sl in the central sierra nevada california provide evidence of climatic change on millennial and centennial timescales over the last 20 000 years total organic carbon toc abundance varied in concert with elemental and isotopic tracers of organic matter c n 13 c org 15 n biogenic silica content total magnetic susceptibility and sediment lithology we interpret the down core proxy records as representing the response of the lake environment in terms of temperature seasonal ice cover mixing regimes runoff and in situ om and nutrient cycling to shifting climate states these environmental factors in turn drove changes in algal productivity om sources microbial om regeneration and secondary production and detrital input the late pleistocene 19 7 10 8 cal kyr bp was dominated by fluctuations between relatively warm dry intervals with high toc 17 4 16 5 15 8 15 0 13 9 13 2 11 4 11 0 cal kyr bp and cold wet intervals 16 5 15 8 14 8 13 9 13 1 11 6 11 0 10 7 cal kyr bp characterized by low toc and high detrital input the holocene 10 7 cal kyr bp present was characterized by three abrupt increases in toc after 10 8 8 0 and 3 0 cal kyr bp and numerous century scale fluctuations toc increases reflected enhanced lake productivity and om recycling and reduced detrital input in response to changing winter temperature and hydrologic regimes inferred environmental changes at sl correlate with other sierra nevada paleorecords and with reconstructed sea surface temperatures along the california margin parallel changes in the sl and sst records over the past 20 000 years provide new evidence that continental climate in the sierra nevada and the california current system have responded on multiple timescales to common drivers in north pacific ocean atmospheric circulation

the character and origin of lacustrine source rocks in the lower cretaceous synrift section congo basin west africa lower cretaceous synrift lacustrine shales from the congo basin west africa have been analyzed with sedimentological and geochemical techniques to characterize source rock quality and identify triggers for deposition of intervals richest in organic carbon the sequence includes a lower active rift section deposited during active faulting and subsidence overlain by an upper late rift section deposited during reduced faulting and subsidence total organic carbon toc averages 2 3 wt throughout the active rift siliciclastic shale section 6 in marls in the lower part of the late rift section and 1 2 in deltaic shales in the upper part of the late rift section organic matter consists of mixed types i and iii kerogen in the active rift shales pure type i kerogen in the late rift marls and a type i and iii mixture in the late rift deltaic shales redox proxies indicate that the deep lake was relatively reducing throughout deposition of the active rift and lower late rift sections therefore enhanced anoxia did not trigger deposition of the richest source rocks decreased sedimentation rates in the late rift do not account for the full increase in toc nor the shift on organic matter type the richest source rocks are associated with high rates of organic productivity and chemical sedimentation indicating that flux of dissolved components to the rift lake including nutrients for algae growth was critical we propose that reduced topography associated with the late rift was necessary for efficient cycling of plant derived carbon into soil carbonate and ultimately the rift lake and for enhancing chemical weathering and nutrient flux

subaqueous calderas in the archean abitibi greenstone belt an overview and new ideas abstract the 300 700 km abitibi greenstone belt in canada contains numerous world class archean volcanogenic massive sulfide vms deposits yet documentation of archean subaqueous calderas hosting such deposits is lacking the modern sunrise deposit in the myojin knoll caldera of the izu bonin arc shows that submarine calderas are first order sites for vms the hunter mine and normetal calderas as well as the blake river megacaldera complex are reviewed with respect to geometry regional geology physical volcanology dyke emplacement and hydrothermal carbonate alteration these subaqueous calderas are placed into the geodynamic context of the abitibi greenstone belt the abitibi belt displays a complex history of oceanic arc formation evolution collision and fragmentation with numerous types of volcanic edifices and sedimentary basins controlled by oblique subduction and mantle plumes analogue models yielding new insights into the sequence of caldera forming events and their synvolcanic fault patterns are applied to explain archean examples underpressure experiments develop a consistent sequence of fault patterns that compare favourably with natural caldera events during subsidence two sets of faults propagate from the magma chamber margin 1 early reverse outward dipping faults and 2 normal inward dipping faults the largest massive sulfide deposits form preferentially at the caldera margin based on experimental studies and detailed facies mapping the hunter mine caldera is of the segmented piecemeal variety and the normetal caldera is akin to a piston structure the blake river megacaldera contains 1 the e w trending misema 2 the nw trending new senator and 3 the ne trending noranda calderas with the latter two being nested graben type calderas consistent with oblique archean subduction the poorly documented hydrothermal carbonate alteration is discussed and a new exploration model for calderas is presented the alteration study was evaluated at three levels microprobe analysis geochemical staining of drill core and whole rock analyses there were two principal stages of alteration related to vms formation an early silicification phase developed either at depth and or at the seawater interface whereby silicification was bedding parallel in fine grained volcaniclastic deposits near the water surface a pervasive and extensive semi conformable carbonate alteration zone with a discordant focused root zone along faults evolved subsequently three distinct carbonate pairings were observed 1 proximal siderite sideroplesite fe ankerite next to the vms deposit 2 an intermediate ankerite fe dolomite zone and 3 a distal calcite dolomite zone the carbonate phase is associated with the mineralizing event transitions between carbonate species are subtle and changes are indicated by mineral assemblage overlap the silica carbonate hydrothermal alteration pattern is a replacement product and is far more widespread than has been documented this alteration can be easily confused with primary carbonates and chemical precipitation deposits e g banded iron formation if detailed volcano sedimentary facies mapping with alteration has not been conducted and if outcrop is insufficient

geochemical and isotopic approach to maturity source mixing estimations for natural gas and associated condensates in the thrace basin nw turkey abstract the tertiary thrace basin located in nw turkey comprises 9 km of clastic sedimentary column ranging in age from early eocene to recent in age fifteen natural gas and 10 associated condensate samples collected from the 11 different gas fields along the nw se extending zone of the northern portion of the basin were evaluated on the basis of their chemical and individual c isotopic compositions for the purpose of the study the genesis of ch4 thermogenic c2 gases and associated condensates were evaluated separately methane appears to have 3 origins group 1 ch4 is bacteriogenic calculated 13cc1 c 61 48 silivri field and found in oligocene reservoirs and mixed with the thermogenic group 2 ch4 they probably formed in the upper oligocene coal and shales deposited in a marshy swamp environment of fluvio deltaic settings group 2 13cc1 c 35 80 hamitabat field and group 3 13c1 c 49 10 degirmenkoy field methanes are thermogenic and share the same origin with the group 2 and group 3 c2 gases the group 2 c2 gases include 63 of the gas fields they are produced from both eocene overwhelmingly and oligocene reservoirs these gases were almost certainly generated from isotopically heavy terrestrial kerogen 13c 21 present in the eocene deltaic hamitabat shales the group 3 c2 gases produced from one field were generated from isotopically light marine kerogen 13c 29 lower oligoce ne mezardere shales deposited in pro deltaic settings are believed to be the source of these gases the bulk and individual n alkane isotopic relationships between the rock extracts gases condensates and oils from the basin differentiated two groups of condensates which can be genetically linked to the group 2 and 3 thermogenic c2 gases however it is crucial to note that condensates do not necessarily correlate to their associated gases maturity assessments on the group 1 and 2 thermogenic gases based on their estimated initial kerogen isotope values 13c 21 29 and on the biomarkers present in the associated condensates reveal that all the hydrocarbons including gases condensates and oils are the products of primary cracking at the early mature st age req 0 55 0 81 it is demonstrated that the open system source conditions required for such an early mature hydrocarbon expulsion exist and are supported by fault systems of the basin

abundances distribution and sizes of volcanoes in the pacific ocean and implications for the origin of non hotspot volcanoes abstract in this paper i present data on the abundances sizes and crustal age for all volcanoes volcanic islands and seamounts which appear on published bathymetric charts of the pacific ocean these new data shed light on the origin of non hotspot volcanoes and are important in combination with data on the chemical compositions of seamounts and volcanic islands for estimates of the bulk composition of ocean crust these data also provide firm constraints on off ridge oceanic volcanism models results of this study show that the size frequency distribution of pacific volcanoes is poisson like and that the smallest volcanoes are much more abundant than large ones this study shows clearly that the most abundant volcanoes on the earth are the submerged oceanic volcanoes which comprise 5 25 of the oceanic volcanic layer on pacific crust of eocene age and younger the abundance of volcanoes number of volcanoes per unit area increases monotonically with increasing age assuming steady state the production rate of new off ridge volcanoes number of volcanoes per unit area per unit time is inversely proportional to the square root of the lithosphere age 1 on crust older than eocene the number of volcanoes per unit area of crust decreases monotonically with increasing age however the total volume of lava represented by these edifices increases with increasing age size frequency distributions of volcanoes on swaths of successively older crust indicate that these abundance patterns are partly due to the effect of sediment burial of small edifices on old pacific crust as well as the effect of increased lithosphere thickness on seamount size these general patterns are not appreciably changed by omitting from consideration known hotspot volcanoes 2 and volcanoes built at fossil constructional plate margins 3

morphology and propagation styles of miocene submarine basanite lavas at stanley northwestern tasmania australia miocene submarine basanite pillows lava lobes megapillows and sheet lavas in the stanley peninsula northwestern tasmania australia are well preserved in three dimensions the pillows have ropy wrinkles transverse wrinkles symmetrical wrinkles contraction cracks and three types of spreading cracks on their surfaces and concentric and radial joints in the interior the lava lobes have ropy wrinkles and contraction cracks on their surfaces the megapillows are cylindrical with a smoothly curved upper surface and steep sides and are characterized by distinct radial columnar joints in the interior they are connected to pillows that propagate radially from its basal margin the sheet lavas are tabular and have vertical columnar joints in the interior the largest sheet lava shows a remarkable gradation from a lower 5 m thick pillow facies to an upper massive facies the pillows lava lobes megapillows and sheet lavas are inferred to have been emplaced completely below sea level but in a shallow marine environment their morphological features suggest that the pillows grew by episodic rupture of a near solid crust and emergence of hot lava whereas the lava lobes propagated by continuous stretching of the outer skin at the flow front the megapillows and sheet lavas were master feeder channels by which molten lava was conveyed to the advancing pillows the sheet lavas propagated by repeated processes of pillow formation and overriding by an upper massive part alternating pillow and massive facies commonly found in ocean floor drill cores and exposed in cross section in many subaqueous volcanic successions may have formed by propagation of pillows from the basal margins of advancing sheet lavas

morphology and growth style of a miocene submarine dacite lava dome at atsumi northeast japan abstract a miocene submarine lava dome at tate iwa atsumi yamagata japan displays well preserved primary morphological features the dome currently rises above a wave cut coastal platform and is 55 m high and 90 180 m across it comprises a massive core and a lava lobe hyaloclastite rim both of which are composed of compositionally uniform feldspar phyric dacite sio2 64 wt the boundary between these two zones is distinct but gradational the massive core consists of homogeneous coherent dacite and is characterized by flow banding along the margin and by columnar joints radiating from the centre to the margin the lava lobe hyaloclastite rim encircles the massive core and consists of a complex of 80 90 dacitic lava lobes and 10 20 hyaloclastite the lava lobes are 1 6 m thick 3 12 m wide and more than 5 m long each lobe consists of a radially columnar jointed core and a glassy rim 10 30 cm thick the hyaloclastite comprises polyhedral dacite clasts 5 100 cm across in a matrix of dacite fragments up to 5 mm across the lava lobes and hyaloclastite have gradational contacts in places paleobathymetric studies based on foraminifera in sediment beneath the dome and the k ar age of the dome suggest that it was extruded in a middle bathyal environment 1500 2000 m below sea level at 12 9 0 6 ma the internal structures of the dome suggest that it formed by a combination of exogenous growth involving extrusions of small dacite lobes and endogenous growth involving a continuous magma supply and simple expansion from the interior the presence of small lava lobes along the rim suggests that the magma had relatively low viscosity at the time of extrusion in spite of its high silica content magma temperatures calculated by two pyroxene and fe ti oxide geothermometers were 999 1042 and 957 1005 c respectively the inferred low viscosity may be attributed to the high temperature of the magma and or a high confining pressure resulting from the deep sea environment

air mass trajectories to summit greenland a 44 year climatology and some episodic events the seasonal variation in atmospheric transport patterns to summit greenland is examined using a 44 year record of daily 10 day isobaric back trajectories at the 500 hpa level over 24 000 modeled trajectories are aggregated into distinct patterns using cluster analysis ten day trajectories reaching summit are longest during winter with 67 extending upwind westward as far back as asia or europe trajectories are shortest during summer with 46 having 10 day origins over north america during all seasons a small percentage 3 7 of trajectories originate in west asia europe and follow a meridional path over the arctic ocean before approaching summit from the northwest trajectories at the 700 hpa level tend to be shorter than at 500 hpa with many of the 700 hpa trajectories from north america tracking over the north atlantic and approaching summit from the south the long range transport climatology for summit is similar to a year round climatology prepared for dye 3 located 900 km to the south davidson et al 1993b an analysis of several aerosol species measured at summit during summer 1994 reveals examples of the usefulness and also the limitations of using long range air trajectories to interpret chemical data

basaltic to andesitic volcaniclastic rocks in the blake river group abitibi greenstone belt 2 origin geochemistry and geochronology the archean blake river group brg of ontario and quebec is dominated by submarine mafic to intermediate lavas with more restricted felsic volcanic rocks given the good quality of outcrop and high level of preservation of some brg rocks the mafic to intermediate lavas were used in the 1970s and 1980s to better understand the evolution of massive and pillowed submarine flows and their associated fragmental facies pillow breccias hyaloclastite potentially the brg could also represent a useful volcanic succession for the study of explosive submarine eruption products in the ancient record before this is possible however a regional inventory of the mafic to intermediate volcaniclastic units is needed in order to clarify their characteristics and origins in this paper we compare and contrast volcaniclastic rocks from three areas within the same formation of the northern brg in quebec the monsabrais area the lac duparquet area and the d alembert tuff area close examination reveals pronounced differences in terms of lateral continuity thickness grading bedding clast shapes textures etc in the volcaniclastic rocks these differences are interpreted to reflect vastly different emplacement processes ranging from hyaloclastite generation as a result of self fragmentation and lava contact with water dominant in the monsabrais and lac duparquet areas to aqueous density currents likely fed directly by explosive submarine eruptions dominant in the d alembert tuff

structure and organization of submarine basaltic flows sheet flow transformation into pillow lavas in shallow submarine environments distal pillows occur associated with a sheet flow and megapillows in the menakoz outcrops of the basque cantabrian basin n spain basaltic volcanic rocks are interbedded with turonian sediments and depict typical features of shallow submarine emissions an exceptional basaltic flow displays four types of morphology 1 sheet lava with columnar jointing 2 welded columnar breccia 3 megapillows and 4 pillow lavas with sparse megapillows the field data from menakoz combined with experimental and field data from the literature for similar volcanic facies can be integrated into a new propagation model for the transition from sheet flows to pillow lavas in underwater environments at near vent high emission rates lava flows develop a thin crust immediately after its emplacement and break at the front under the magma pressure allowing for the massive propagation of lava as a sheet flow increased cooling promotes thickening of the lava outer crust far from the vent while continuous supply of fresh magma increases the pressure onto the thick crust until its rupture the lava emitted in small volumes from the flow front promotes the formation of megapillows and pillow lavas that are later on covered by the advancing sheet flow the lava flow freezes progressively toward more distal parts gradually increasing its viscosity until it stops the crust temporarily holds the residual melt pressure increasing the volume of the flow distal section by inflation finally the internal magma pressure breaks the crust and liberates lava at moderate to low flow rates producing pillows while lava drainage inside the inflated sheet flow produces lava tunnels and gravitational collapse of the roofs by hydrostatic pressure to form breccias nurtured by columnar lava fragments

in situ hydroclastic fragmentation of subaqueous ponded lavas new senator caldera abitibi greenstone belt quebec canada abstract subaqueous ponded lavas have been recognized within the structure of the new senator caldera in the blake river group of the abitibi greenstone belt quebec canada sub vertical to near vertical dips of extrusive volcanic facies within the southern sector of the caldera permit the identification of the internal architecture of an archean subaqueous volcanic complex detailed facies analyses of the dominantly mafic sequences have shown two localities with atypical primary volcanic structures and facies inconsistent with those observed at modern subaqueous mafic seamounts combined with the use of facies specific geochemical analyses a coherent model for the two localities accounting for all observed volcanic structures and features has been developed mapping completed at a scale of 1 100 at localities 1 and 2 reveals a series of sub parallel to parallel hyaloclastite rich horizons separating aphanitic to medium grained ponded units several primary volcanic structures are observed within the hyaloclastite horizons and are identified as pillowed forms cigar forms and v shaped structures ponded units range in thickness from 2 5 to 5 m with the exception of one unit which is approximately 30 m thick in central portions this thick unit is medium grained and has a sub ophitic texture units at locality 1 strike approximately nw while those at locality 2 strike ene several families of mafic dykes cross cut locality 1 and trend e w and nne both volcaniclastic and effusive facies have similar compositions affinities and trace and rare earth element signatures all facies have a tholeiitic affinity range in composition from basalt to andesite and have morb type trace and rare earth element signatures locality 1 appears slightly more evolved than locality 2 with later dykes and a late sill being the most evolved facies volcanic facies at localities 1 and 2 are consistent with subaqueous ponded lavas bounding synvolcanic structures and volcanic facies validate this interpretation and indicate these ponded lavas are hosted within a large synvolcanic depression at the summit of a mafic shield complex primary volcanic structures within hyaloclastite horizons formed via in situ fragmentation when water entered the system as ponded lavas began to cool water entered the system through synvolcanic fractures and encountered semi molten pockets of lava leading to hydroclastic fragmentation of the lavas v shaped and cigar structures formed during more energetic events and changed laterally into pillowed forms as energy dissipated from the system

a high resolution palaeoclimatic record for the last 27 500 years in tropical west africa from the carbon and nitrogen isotopic composition of lacustrine organic matter variations in the carbon and nitrogen isotopic composition of bulk organic matter in the sediments of lake bosumtwi ghana reflect climatically induced changes to the lake and the catchment flora cores spanning the last 27 5 kyr of sedimentation in the lake show large oscillations in 13corg pdb and 15norg air the late pleistocene record is particularly detailed showing changes of ca 20 in carbon and ca 10 in nitrogen isotopic compositions these variations are of complex origin although different in magnitude major isotopic excursions in the two records are generally in phase and reveal the occurrence of two major dry intervals at and immediately following the last glacial maximum the allerod younger dryas period also seems to have been marked by generally dry conditions in this part of tropical west africa nitrogen isotopic evidence suggests that during the period 9 2 3 2 kyr the lake had an extremely stable water column probably due to the absence of a windy or cool dry season or both regular circulation of the water column recommenced during the late holocene and has persisted until the present day

structural anatomy and dynamics of evolution of the qikou sag bohai bay basin implications for the destruction of north china craton abstract the qikou sag is a complex cenozoic faulted basin at the center of the bohai bay basin the paleogene sediments in the basin show a maximum thickness of 11 000 m in paleogene representing intense crustal extension the sag has a typical dish like structure in the upper part with the central domain represented by a deep half graben and surrounded by different types of gentle slopes and sub sags linked with the basin margin uplifts the inner structure of the sag is jointly controlled by the basin margin extensional faults intrabasinal extensional tectonics and transfer tectonics the sag is divided into four different extensional tectonic domains by the basement fault along the coastline the haihe xingang fault and the qidong fault these sub sags are in turn controlled by different detachment systems the listric cangdong and hangu faults mark the major boundary faults controlling the extensional structure of the basin the structure and tectonics of the qikou sag provide a direct record of the late stages of rifting and destruction of the north china craton the mesozoic basement structures of the sag determine the tectonic styles in different sub sags the complete inversion of the structures in mesozoic profoundly influenced the development and evolution of the basin during paleogene we identify three main stages in the tectonic evolution of the qikou the oligocene faulting stage the miocene pliocene thermal subsidence stage and the pleistocene quaternary depression stage in the oligocene fault activities and the basin architecture were mainly controlled by the listric boundary fault system of the basin and the secondary fault system in the hanging wall under the detachment and extension in the upper crust since miocene the boundary fault of the basin underwent weak extension the upwelling of the upper mantle and the formation of corresponding shallow depressions contributed to the evolution and tectonic architecture of the qikou sag

source rock potential of evaporitic environment examination of modern saline lakes solar evaporation ponds and lagoons shows that the evaporitic environment can be very productive of organic matter few species survive in the brines but those that do commonly exist in great profusion in a marine evaporitic embayment the flow of surface currents is persistently toward regions of highest salinity so that there is a continual supply and concentration of nutrients prolific growth of phytoplankton may be similar to that in areas of upwelling in modern oceans only carbonates precipitate in the mesosaline part 4 to 12 salinity of such an evaporitic environment and no great dilution of organic matter by clastic or biogenic sediments occurs because stratification of brine may occur and reducing conditions may be a sociated with the bottom waters much of the organic matter produced can be preserved upon maturation the result may be a rich carbonate source rock frequently unrecognized in the geologic column in the middle east mesosaline conditions are known to have occurred many times from the triassic to cretaceous and may be responsible for the vast reserves of petroleum in the area evaporitic conditions may also have played a part in the petroleum productivity of many other areas including the michigan and paradox basins

morphometric study of pillow size spectrum among pillow lavas measurements of h and v dimensions in the horizontal and vertical directions of pillows exposed in vertical cross section were made on 19 pillow lavas from the azores cyprus iceland new zealand tasmania the western usa and wales the median values of h and v plot on a straight line that defines a spectrum of pillow sizes having linear dimensions five times greater at one end than at the other basaltic toward the small size end and andesitic toward the large size end the pillow median size is interpreted to reflect a control exercised by lava viscosity pillows erupted on a steep flow foot slope in lava deltas can however have a significantly smaller size than pillows in tabular pillowed flows inferred to have been erupted on a small depositonal slope indicating that the slope angle also exercised a control pipe vesicles generally abundant in the tabular pillowed flows and absent from the flow foot pillows have potential as a paleoslope indicator pillows toward the small size end of the spectrum are smooth surfaced and grew mainly by stretching of their skin whereas disruption of the skin and spreading were important toward the large size end disruption involved increasing skin thicknesses with increasing pillow size and pillows toward the large size end are more analogous with toothpaste lava than with pahoehoe and are inferred from their thick multiple selvages to have taken hours to grow pseudo pillow structure is also locally developed an example of endogenous pillow lava growth that formed intrusive pillows between normal pillows is described from sicily isolated pillow like bodies in certain andesitic breccias described from iceland were previously interpreted to be pillows but have anomalously small sizes for their compositions it is now proposed that they may lack an essential attribute of pillows namely the development of bulbous forms by the inflation of a chilled skin and are hence not true pillows para pillow lava is a common lava type in the flow foot breccias it forms irregular flow sheets that are locally less than 5 cm thick and failed to be inflated to pillows perhaps because of an inadequate lava supply rate or too high a flow velocity

relationship between inferred redox potential of the depositional environment and geochemistry of the upper pennsylvanian missourian stark shale member of the dennis limestone wabaunsee county kansas u s a analyses of 21 samples collected from a core of the 52 8 cm thick stark shale member of the dennis limestone in wabaunsee county kansas demonstrate four cycles with two orders of magnitude variations in contents of cd mo p v and zn and order of magnitude variations in contents of organic carbon cr ni se and u the observed variability in amounts and or ratios of many metals and amounts and compositions of the organic matter appear related to the cause and degree of water column stratification and the resulting absence presence of dissolved o2 or h2s high cd mo u v zn and s contents a high degree of pyritization dop 0 75 0 88 and high high v v ni 0 84 0 89 indicate the presence of h2s in a strongly stratified water column intermediate contents of metals and s intermediate dop 0 67 0 75 and intermediate v v ni 054 0 82 indicate a less strongly stratified anoxic water column whereas low metal contents and low v v ni 0 46 0 60 indicate a weakly stratified dysoxic water column high p contents at the top of the organic matter rich intervals within the stark shale member indicate that phosphate precipitation was enhanced near the boundary between anoxic and dysoxic water compositions relatively abundant terrestrial organic matter in intervals deposited from the more strongly stratified h2s bearing water column indicates a combined halocline thermocline with the fresher near surface water the transport mode for the terrestrial organic matter the predominance of algal organic matter in intervals deposited from a less strongly stratified water column indicates the absence of the halocline and the presence of the more generally established thermocline relatively low amounts of degraded hydrogen poor organic matter characterize intervals deposited in a weakly stratified dysoxic water column the inferred variability in chemistry of the depositional environments may be related to climate variations and or minor changes in sea level during the general phase of deeper water deposition responsible for this widespread shale member

effects of an oceanic anoxic event on the stable carbon isotopic composition of early toarcian carbon the early toarcian transgression is marked by the occurrence of organic carbon rich shales in large parts of western europe and in other parts of the world as well based on the positive carbon isotope excursion of pelagic limestones in the middle to upper part of the falciferum zone in several of the tethyan sections the widespread occurrence of the early toarcian shales was explained by an oceanic anoxic event oae jenkyns 1988 jenkyns and clayton 1997 the rapid burial of large amounts of organic carbon which is rich in 12 c would have led to a relative enrichment in 13 c of the global carbon reservoir and hence to an increase in delta 13 c of the limestones in southwest germany and a number of other locations both organic and inorganic carbon display a negative isotope excursion in the upper part of the tenuicostatum zone and the lower part of the falciferum zone synchronous to black shale deposition and predating the positive isotopic excursion kuspert 1982 1983 it is presently unclear what the exact cause for this widespread negative isotopic excursion is jenkyns and clayton 1997 the objective of our study was to examine if the negative carbon isotope excursion of organic matter om in the southwest german toarcian shales can be attributed to compositional changes of the om or if the excursion is related to variations in delta 13 c sub co2 aq in the photic zone to this end we analyzed the molecular and stable carbon isotope composition of om in ten samples spanning the early toarcian toc 2 5 10 5 percent hi 350 700 biomarker distributions and kerogen pyrolysates differ only slightly among the samples and delta 13 c values of primary production markers follow closely those of associated carbonate and kerogen delta 13 c sub carb toc this strongly suggests that differences in delta 13 c toc are related to differences in delta 13 c of co 2 aq in the photic zone supporting kuspert9s model of advection of isotopically light organic matter derived co 2 from anoxic bottom waters evidence for euxinic conditions extending into the photic zone was found by the presence of derivatives of carotenoids such as isorenieratane from anoxygenic phototrophic sulfur bacteria their concentrations are extremely low in black shales from the tenuicostatum zone but are significant in the falciferum and bifrons zone with a maximum in the exaratum subzone suggesting that photic zone euxinia pze was a common feature of the early toarcian sea in southwest germany our data therefore support the kuspert model of advection of isotopically light organic matter derived co 2 from anoxic bottom waters to the upper part of the photic zone resulting in a negative isotope spike the enrichment in 13 c in the middle of the falciferum zone which followed the negative spike may be attributed to the burial of isotopically light organic matter through worldwide black shale deposition

pipe vesicles an alternate model for their origin most pipe vesicles occur near the base of basaltic flows where they are interpreted to be traces left by ascending gas bubbles some basaltic pillows also contain pipe vesicles but in these pillows pipe vesicles have a radial distribution indicating that buoyancy cannot be a factor in their formation pipe vesicles do not extend through chilled glassy margins at the base of flows or rims of pillows but rather they form only where there has been significant crystallization indicating that the gas forming these vesicles is exsolved from the lava and is not derived from an external source pipe vesicles in flows and pillows are proposed to form by the exsolution of gas onto bubbles that are attached to the zone of solidification as this zone advances into the cooling lava continued exsolution of gas causes the bubbles to grow normal to the solidification front as pipes gas tubes formed in a similar manner can be seen in most ice cubes lava near the advancing tip of a pipe vesicle cools more rapidly than elsewhere because heat is able to transfer along the pipe by radiation pipe vesicles therefore grow into the lava as cold fingers they cease growing when separate gas bubbles nucleate ahead of them in the ever broadening zone of solidification lava need contain no more than 0 01 wt h 2 o for pipe vesicles to form in this way

breccias and ores part 1 history organization and petrography of breccias abstract although the term breccia is one of the oldest rock names still in use and proliferating in its application a satisfactory definition remains problematic and an overall classification of breccias is non existent the names of breccia varieties several hundred please the heart rather than the computer and there is little interdisciplinary correlation among the more than fifty specialized schools of breccia study this contribution reviews briefly the history of breccia research and provides a list of the present study trends complete with references with emphasis on ore associated breccias wherever possible conventional breccia definitions and their shortcomings are discussed and a case is made for the introduction of the petrographic category of coarse fragmentites of which the typical sedimentary breccias and conglomerates as well as volcanic tectonic hydrothermal impact and other fragmental materials are members whether designated or not as breccia in the conventional literature this is followed by a proposed rational organization classification of coarse fragmentites and breccias based on the regime of formation and architecture fabric gefuge two fundamental end member sequences a b and a transitional suite c can be recognized a disaggregation fragmentites d breccias produced from a solid progenitor by increasing rate of fracturing expansion rotation mixing and attrition the transitional sequence is crackle mosaic rubble melange milled breccia b aggregation fragmentites a breccias generated by gathering aggregation and accumulation of originally dispersed fragments at the site of deposition these materials form a sequence ranging from tightly packed fragment supported matrix free fragmentites through matrix infilled matrix supported fragmentites to lonestone rocks c in transport fragmentites t breccias formed by redeposition of an aggregate gathered in an earlier phase of development as an a fragmentite or by transportation and redeposition of an advanced member i e rubble melange or milled fragmental aggregate of a d fragmentite examples of metallic mineralizations coeval with or superimposed on the fragmentite sequences are reviewed

stable carbon isotope compositions and source rock geochemistry of the giant gas accumulations in the ordos basin china ordos basin the second largest sedimentary basin in china contains enormous natural gas resources each of the four giant gas fields discovered so far in this basin i e sulige yulin wushenqi and jingbian has over 100 billion cubic meters bcm or 3 53 trillion cubic feet tcf of proven gas reserves this study examines the stable carbon isotope data of 125 gas samples collected from the four giant gas fields in the ordos basin source rocks in the upper paleozoic coal measures are suggested by the generally high 13c values of c1 c4 gaseous hydrocarbons in the gases from the sulige yulin and wushenqi gas fields while the 13cic4 value is higher than that of the 13cnc4 the dominant ranges for the 13c1 13c2 and 13c3 values in these upper paleozoic reservoired gases are 34 to 32 27 to 23 and 25 to 24 respectively the 13c values of methane benzene and toluene in gases from the lower paleozoic reservoirs of the jingbian field indicate a significant contribution from humic source rocks as they are similar to those in the upper paleozoic reservoirs of the sulige yulin and wushenqi gas fields however the wide variation and reversal in the 13c1 13c2 and 13c3 values in the jinbian gases cannot be explained using a single source scenario thus the gases were likely derived dominantly from the carboniferous permian coal measures with some contribution from the carbonates in the lower permian taiyuan formation the gas isotope data and extremely low total organic carbon contents 0 2 toc suggest that the ordovician majiagou formation carbonates are unlikely to be a significant gas source rock thus almost all of the economic gas accumulations in the ordos basin were derived from upper paleozoic source rocks

geochemical characterisation of a polyphase deformed altered and high grade metamorphosed volcanic terrane implications for the tectonic setting of the svecofennides south central finland abstract the virtasalmi metavolcanic belt forms part of the early proterozoic svecofennide terrane in central finland the preserved supracrustal lithologies 40 of the assemblage have undergone extensive synvolcanic hydrothermal alteration polyphase regional ductile deformation low pressure regional polyphase metamorphism to granulite facies with subsequent amphibolitisation and extensive emplacement of a synkinematic i type plutonic suite despite these overprinting events three chemically distinct suites of metatholeiites and one suite of coeval coarser grained intrusive lithologies are recognized and their petrogenesis resolved primary igneous geochemistry is preserved mainly by the hfses and cr and ni variable major and lil element mobility is demonstrated significant differences in geochemistry are reflected in different metamorphic assemblages between suites preservation of vesicular pillow lavas indicate subaqueous extrusion of the three metatholeiitic suites trace element geochemistry indicates that suite i compositions are controlled by low pressure fractional crystallization in contrast suite iii amphibolite compositions are controlled by batch partial melting with limited modification by open system fractional crystallization these differences in fractionation history point to the evolution of these two main suites within distinct upper crustal magmatic plumbing systems also differences in more hyg less hyg element and other incompatible element ratios point to derivation of suites i and iii by different degrees of partial melting from different heterogeneous mantle source regions coeval eruption of these suites indicates that variations in source geochemistry and melting processes reflect spatial rather than temporal differences the volumetrically smaller suite ii comprises lava flows and pillowed units that are interlayered with but have a more depleted chemistry than the other suites marked variation in cr and ni contents within a narrow range of zr contents in individual flows in subgroups iia 1 and iia 2 and marked tio 2 enrichment in subgroup iib suggests that the more depleted character of this suite is due to fractional crystallisation and crystal settling in high level magma chambers suite iv amphibolites comprise a number of small intrusive bodies that are emplaced within the volcanic pile they are coarser grained than the enveloping amphibolites and are interpreted as tectonised relics of high level magma chambers and or sills emplaced into the coeval metavolcanic assemblage they have a depleted geochemistry and there is textural and geochemical evidence to suggest a partial cumulate origin similarities in fractionation histories suggest that suite iv intrusions are cogenetic with suites i and ii enrichment in incompatible elements particularly nb demonstrates that the virtasalmi metatholeiites are not related to supra subduction zone magmatism all the amphibolites are within plate basalts or e type morbs with similar compositions known today from a range of tectonic settings however the interlayering of e morb metavolcanic rocks with marbles and voluminous fine grained clastic metasediments is more likely to indicate an intracratonic rift passive margin geotectonic setting subsequent deformation and metamorphism of the volcanics and syn kinematic calc alkaline intrusives are interpreted as accretion at a destructive margin the latter was most probably a continental calc alkaline arc various crustal levels of which are now exposed in the study area

facies architecture of the upper oligocene submarine smrekovec stratovolcano northern slovenia abstract the upper oligocene smrekovec volcanic complex svc represents the remains of a submarine stratovolcano which underwent early miocene tectonic dissection and large scale displacement along the periadriatic line according to the lithofacies architecture abundance and spatial distribution central medial and distal zones of the former volcano edifice have been recognized the zones extend at a distance of 0 2 km 2 5 km and 5 20 km south of the periadriatic line respectively lavas shallow intrusive bodies autobreccia peperite and hyaloclastite deposits occur mainly in the central zone which is extensively altered under hydrothermal conditions characterised by the development of zeolites mainly laumontite prehnite chlorite albite and epidote explosive volcanic activity intensified with the evolution of magma from basaltic andesitic to dacitic gas and water supported eruption fed density flows are assumed their deposits show lithofacies organisation in pyroclastic depositional units pdus similar to either volcaniclastic turbidites type 1 or thin subaqueous ignimbrites type 2 volcaniclastic debris flow deposits are developed as volcaniclastic breccia and sandy debris flow deposits the former occurs in the central and medial zones and the latter occurs in the medial zone only the most widespread lithofacies in the svc are volcaniclastic turbidite deposits three types of sedimentary unit tsu have been distinguished type 1 is 2 5 m thick and dominated by the massive division it mainly occurs in the central zone type 2 is 0 7 3 5 m thick and occurs in the central and medial zones it comprises the massive division bedded fining and thinning upward division and a horizontally wavy and cross laminated division topped by massive fine grained tuff type 3 is 0 1 1 5 m thick and mainly occurs in the distal zone the massive division is absent and thinly bedded and laminated divisions are topped by massive fine grained tuff volcaniclastic turbidites were settled from low density turbidity currents and related suspension clouds mixed volcaniclastic siliciclastic deposits are subordinate in occurrence and restricted to the distal zone they are commonly reworked by bottom currents

evolution of an englacial volcanic ridge pillow ridge tindar mount edziza volcanic complex ncvp british columbia canada abstract glaciovolcanic deposits are critical for documenting the presence and thickness of terrestrial ice sheets and for testing hypotheses about inferred terrestrial ice volumes based on the marine record deposits formed by the coincidence of volcanism and ice at the mount edziza volcanic complex mevc in northern british columbia canada preserve an important record for documenting local and possibly regional ice dynamics pillow ridge located at the northwestern end of the mevc formed by ice confined fissure fed eruptions it comprises predominantly pillow lavas and volcanic breccias of alkaline basalt composition with subordinate finer grained volcaniclastic deposits and dykes the ridge is presently 4 km long 1000 m in maximum width and 600 m high fifteen syn and post eruptive lithofacies are recognized in excellent exposures along the glacially dissected western side of the ridge we recognize five lithofacies associations 1 poorly sorted tuff breccia and dykes 2 proximal pillow lava dykes and tuff breccia 3 distal pillow lava poorly sorted conglomerate and well sorted volcanic sandstone 4 interbedded tuff lapilli tuff and tuff breccia units and 5 heterolithic volcanogenic conglomerate and sandstone given the abundance of pillow lavas and the lack of surrounding topographic barriers capable of impounding water we agree with souther souther j g 1992 the late cenozoic mount edziza volcanic complex geol soc can mem vol 420 320 pp that the bulk of the edifice formed while confined by ice but have found evidence for a more complex and variable eruption history than that which he proposed preliminary estimates of water ice depths derived from ftir analyses of h2o give ranges of 300 to 680 m assuming 0 ppm co2 and 857 to 1297 m assuming 25 ppm co2 variations in depth estimates among samples may indicate that water ice depths changed during the evolution of the ridge which is consistent with our interpretations for the origins of different lithofacies associations given that the age of the units are likely to be ca 0 9 ma souther j g 1992 the late cenozoic mount edziza volcanic complex geol soc can mem vol 420 320 pp pillow ridge may be the best documentation of a regional high stand of the cordilleran ice sheet cis in the middle pleistocene and an excellent example of the lithofacies and stratigraphic complexities produced by variations in water levels during a prolonged glaciovolcanic eruption

identification of aryl isoprenoids in source rocks and crude oils biological markers for the green sulphur bacteria abstract a series of c13 to c31 aryl isoprenoids 1 alkyl 2 3 6 trimethylbenzenes have been identified in reef hosted oils and their source rocks from the middle and upper silurian of the michigan basin and middle devonian of the alberta basin canada their structure has been confirmed by unambiguous synthesis of the c14 member of the series their structure and isotopic composition indicate that they are derived from isorenieratene from the chlorobiaceae family of sulphur bacteria these results are consistent with geological and geochemical studies that show that the source rocks were deposited under metahaline to hypersaline sulphate and sulphide rich water columns the distribution of other biomarkers in these oils and source rocks indicates that a diverse biota contributed organic matter to the source environment in conjunction with the aryl isoprenoids they show that there is a remarkable similarity in composition between the two sets of oils and source rocks despite their great temporal and geographic separation this reflects the similarity of their environments and emphasizes the importance of sedimentary facies in controlling the composition of organic matter in source rocks and their derived oils

the distribution of molecular fossils derived from dinoflagellates in paleogene lacustrine sediments bohai bay basin china steroids with unconventional side chains in ancient sediments and petroleum have been increasingly used as age diagnostic markers triaromatic dinosteroids and dinosteranes occur widely throughout the eocene oligocene shahejie formation in the southeastern bohai bay basin china consistent with its abundant fossil dinoflagellate assemblages in addition 24 norcholestane biomarkers which commonly appear in marine oils have been found in this lacustrine formation although a firm link has not been established between 24 norcholestane and specific modern taxa both diatoms and dinoflagellates are shown to be likely sources of 24 norcholestanes although the shahejie strata lack intact diatom frustules they do exhibit a good relationship between 24 norcholestane other molecular fossils of dinoflagellates and dinocysts dinoflagellates are important precursor taxa of 24 norcholestanes and the various species identified in eocene oligocene lacustrine shales and mudstones of the shahejie formation are all potential sources of the 24 norcholestanes

submarine volcaniclastic rocks in this chapter we are concerned with underwater volcaniclastic eruptions and products as well as pyroclastic flows and debris generated on land and transported by mass flowage into the sea submarine fallout deposits derived from land based eruptions are treated in chapter 7 clastic materials redistributed as mass flows or turbidity currents originating from the rapid build up of tephra and epiclastic volcanic debris along coastal parts of volcanoes are also discussed in various places throughout the text e g chap 13

the geneses of sedimentary organic matter with anomalous 13c enriched isotopic composition in saline and freshwater lakes a case study of lacustrine source rocks from dongpu and qikou sags bohai bay basin eastern china abstract the carbon isotopic composition of sedimentary organic matter 13com is notably important for the genetic identification of source rock and its products the sapropelic organic matter mostly plankton with high hydrogen index is generally depleted in 13c as compared to humic organic matter mainly higher plants with lower hydrogen index however some lacustrine sediments contain sapropelic source rocks with anomalous 13c enriched isotopic ratios especially reported in freshwater lakes the purpose of this study is to discuss the geneses of lacustrine sedimentary organic matter characterized by anomalous 13c enriched ratios in saline and freshwater sediments to this end we integrate the detailed organic geochemical data including rock eval analysis data total organic carbon contents total organic carbon isotopic compositions biomarkers and trace element concentrations of 64 saline lake sediments and 39 freshwater lake sediments obtained from the paleogene shahejie formation of dongpu sag and qikou sag separately in bohai bay basin of eastern china both sags exist samples with high hydrogen index values hi 400 mg g and high total organic carbon contents toc 2 but anomalous 13c enriched isotopic ratios up to 21 1 in qikou sag the 13com values of sapropelic kerogen correlate positively with toc contents the anomalous enrichment of 13c in organic matter is associated with extremely high productivity of algae such as algae bloom in dongpu sag the enrichment of 13c in organic matter is attributed to the significant increase of drought and salinity high salinity and aridity climate may lead to the abundance of c4 plants and chlorobium as well as the enrichment of 13c in plankton

ultrathin lava layers exposed near san luis obispo bay california sequences of extraordinarily thin 1 5 cm thick lava layers resembling individual lava flows are interbedded with jurassic and cretaceous pillowed lava flows near san luis obispo bay on the california coast such layers are formed inside submarine pillowed lava pipes or flow lobes as the lava surface in a pillow pipe falls to a lower level owing to diminished supply entering the pipe water enters the upper compartment through cracks in the outer crust and chills a new crust on top of the lava stream repeated lowerings of the lava level in the pipe create a series of discrete lava shelves each of which represents the upper crust of the lava stream flowing within the pipe these crusts are supported at different levels on their edges at the side of the pipe the weight of subsequent overlying lava flows collapses the partly hollow tube creating a stacked sequence of ultrathin lava layers progressively younger downward

morphological features of miocene submarine coherent lavas from the green tuff basins examples from basaltic and andesitic rocks from the shimokita peninsula northern japan basaltic and andesitic volcanic rocks of miocene age exposed in the shimokita peninsula northern japan illustrate morphological features of typical submarine coherent lavas of the green tuff basins in japan they are pillow lobes with surface structures such as ropey wrinkles corrugations spreading cracks and tensional cracks and lava lobes composed of a lithic core and glassy border zone or rim with an in situ breccia zone grading outward into surrounding hyaloclastite in addition they include massive lavas with columnar joints and jointed dykes the submarine coherent lavas and dykes are commonly associated with hyaloclastic breccias such as pillow fragment breccia and angular fragment breccia the descriptions of the miocene volcanic rocks in the shimokita peninsula provide good criteria for recognition of submarine coherent lavas of basalt and andesite

the environmental impact of a pre columbian city based on geochemical insights from lake sediment cores recovered near cahokia cahokia is the largest documented urban settlement in the pre columbian united states archaeological evidence suggests that the city located near what is now east st louis illinois began to rapidly expand starting around ad 1050 at its height cahokia extended across 1000 ha and included large plazas timber palisade walls and hundreds of monumental earthen mounds following several centuries of occupation the city experienced a period of gradual abandonment from about ad 1200 to 1400 here we present geochemical data from a 1500 year old sediment core from nearby horseshoe lake that records watershed impacts associated with the growth and decline of cahokia sedimentary analysis shows a distinctive 24 cm thick gray fine grained layer formed between ad 1150 and 1220 and characterized by low carbonate 13 c elevated sorbed metal concentrations and higher organic matter 15 n the deposition of this layer is contemporaneous with archaeological evidence of increased agricultural activity earthen mound construction and higher populations surrounding the lake we hypothesize that these human impacts increased soil erosion producing new sediment sources from deeper soil horizons and shifted dissolved transport to the lake producing lower carbonate 13 c values higher concentrations of lead copper potassium and aluminum and increased 15 n likely due to contributions of enriched nitrogen from sewage

subglacial intermediate volcanism at kerlingarfjoll iceland magma water interactions beneath thick ice the products of andesite and dacite glaciovolcanism at kerlingarfjoll are unlike others previously described in the literature three sequences of lithofacies are described and interpreted here the andesitic deposits at campsite gully are divided into massive vitriclastic lapilli tuff with intrusions fluidal clast bearing vitriclastic lapilli tuff and stratified pumice rich vitriclastic lapilli tuff at tindur andesitic eruptions produced contorted pillow fragment breccia and the clast supported lithic breccia finally pillow lava with intrusions and crudely bedded vitriclastic lapilli tuff of dacitic composition are described at haraldur abundant vitriclasts the presence of pillow lavas hackly fracturing of lava bodies and lack of oxidation of clasts demonstrate that each of these lithofacies formed in the presence of abundant water this contrasts with all other descriptions of subglacially erupted intermediate magmas which are characterised by jointed and glassy lava flows and domes with a marked scarcity of fragmental material the kerlingarfjoll sequences therefore demonstrate that it is possible for intermediate magmas to generate and interact with significant volumes of water at the base of a glacier preliminary estimates of volatile contents in glassy clasts correspond to quenching pressures equivalent to 500 m water or 550 m ice this is consistent with eruption beneath an ice sheet that was thick enough to overwhelm the underlying topography and where meltwater drainage was controlled by the morphology of the glacier surface it is argued that the drainage of water due to steep topography and or thin and fractured ice as opposed to thermodynamic considerations is the most likely explanation for the absence of evidence for significant magma water interaction in previously described instances of intermediate glaciovolcanism the apparent low viscosity of the kerlingarfjoll magmas may relate to relatively high eruption temperatures and or the inhibition of degassing of the magma due to high ambient pressures and the consequent limitation of groundmass crystallisation

pillow formation and layered flows in the circum superior belt of eastern hudson bay detailed sections mapped across well exposed aphebian tholeiitic and komatiitic flow assemblages on the islands of eastern hudson bay afford an insight into mechanisms of pillow development most of the flows with distinguishable boundaries are pillowed in their lower parts and massive in their upper parts pillow tubes are envisaged as developing therefore at the thin leading edge of a flow as the volume of flow is thus choked the lava behind overrides the impediment and repeats the process farther forward continued repetition of tube formation at flow fronts and the subsequent overriding or diversion of advancing lava result in formation of a carpet of pillow tubes over which the massive flowing lava meanders in the manner of a prograding river when lava production declines or ceases lava streams and trapped ponds distributed over the surface of the pillow mat freeze into the massive tops observed in section layered flows are a development of the same process illustrated in this paper by the hud