the lamongan volcanic field east java indonesia physical volcanology historic activity and hazards abstract the lamongan volcanic field lvf in east java indonesia consists of up to 61 basaltic cinder or spatter cones a minimum of 29 prehistoric maars and a central compound complex comprising three main vents including the historically active lamongan volcano the field lies on the sunda volcanic arc and abuts onto the currently active tengger caldera semeru complex to the west between 1799 and 1898 lamongan was persistently active and discharged up to 15 lava flows of basaltic to basaltic andesite composition which is probably more than what was erupted by any other indonesian volcano in that period several seismic crises have been recorded in the lvf since lamongan s last eruption there are no existing records of cinder cone or maar forming eruptions in the area despite the possible hazards posed by future activity in the lvf the history and structure of the field have been subject to little scrutiny this contribution presents the results of a detailed morphometric and volumetric investigation of prehistoric vents and historic lava flows in the lvf using field data historic records satellite imagery and modelling of erupted volumes a typical lvf maar is characterised as a crater with a diameter of 450 m generated by an eruption with a model ejecta volume of 0 016 km 3 dense rock equivalent dre and a model juvenile component volume of 0 0096 km 3 dre diameter depth ratios of some maars display a morphological freshness comparable to recently formed phreatomagmatic eruption craters elsewhere the median lvf cinder spatter cone has a basal diameter of 600 m a height of 75 m a volume of 0 009 km 3 and a model total erupted volume of 0 014 km 3 variation in cone basal diameter to height ratios indicates that the age of some prehistoric cones may not exceed a few centuries and morphological classification identifies the youngest prehistoric vents on the northern flanks of the central edifice historic activity from vents on the western flanks of lamongan produced at least 0 05 km 3 of basaltic to basaltic andesite lava resurfacing rates at lamongan in the 19th century imply an age of 900 2100 years for the surface of the volcano the steady state eruptive rate from 1843 1898 is evaluated as 0 025 m 3 s 1 which is low in comparison to estimates from many presently active systems using eruptive rate and volume data the age of the lvf is estimated as between 13 and 40 ka placing it among the youngest dated indonesian volcanoes complex regional tectonics in conjunction with magmatic pressure have probably been the major influences on the distribution of volcanism in the lvf the occurrence of maar forming eruptions may have been controlled by a porous substrate possibly a deposit from the holocene iyang argapura complex to the east volcanic hazards from future eruptions in the lvf include base surges ash flows ashfall and ejected blocks associated with phreatomagmatic activity and ashfall and ejecta from magmatic eruptions

age of lassen peak california and implications for the ages of late pleistocene glaciations in the southern cascade range lassen peak is a large volcanic dome of late pleistocene age at the southern end of the cascades arc this dacitic dome has a complex phenocryst assemblage of mixed magma origin and has been effectively dated for the first time using the 40 ar 39 ar technique emplacement of the dome occurred after an advance of late pleistocene glaciers from an older volcanic cone to the southwest and from a large volcanic plateau to the east emplacement of the lassen peak dome before the latest major pleistocene glaciation correlated by previous workers with the tioga glaciation of the sierra nevada formed a high peak that intercepted some of the precipitation that previously had fed the plateau ice cap forming a 10 km long glacier from a cirque on the northeast side of the peak the weighted mean 40 ar 39 ar age of the dacite of lassen peak is 28 3 2 7 ka comparison of its remanent magnetic direction to that of sedimentary deposits at mono lake california indicates a correlation to strata of 27 1 ka the dacite of kings creek which erupted from the site of lassen peak before a glacial advance that predated the lassen peak dome overlies peat that has a u th calibrated 14 c age of 37 6 0 2 ka the dacite of kings creek yielded a 40 ar 39 ar age of 32 17 ka the paleomagnetism of this dacite is similar to that of mono lake sediments of 35 1 ka age thus a late pleistocene glacial advance probably began in the lassen region between about 35 and 27 ka

element mobility during alteration of silicic ash to kaolinite a study of tonstein a laterally persistent kaolinitic mudstone parting tonstein occurring in a wyoming coal bed of eocene age was sampled to estimate the compositional contrast with a probable silicic ash precursor and to determine the compositional influence of leached ash on immediately adjacent coal with the exception of al and possibly ti the tonstein is highly to moderately leached of major elements relative to a range of compositions estimated for silicic ash of the region in agreement with the behaviour of geochemically similar major elements alkali trace elements rb cs are highly leached transition series metals moderately leached and ga is residual additional immobile trace elements are zr and hf but some other trace elements that are considered relatively immobile during low temperature alteration th ta nb ree y were apparently leached by the low eh low ph organic rich pore fluids of the coal forming swamp the migrational range of many of the leached elements is highly limited by the intimate association of tonstein with enclosing organic matter mixtures of coal minor tonstein that occur within 20 mm of contacts are consistently enriched in some elements relative to either tonstein or nearby coal u cu or relative to calculated mixtures of tonstein and coal in their measured proportions th y ree pb ba v ti direct observations by fission track radiography and electron microprobe indicate a preference of u and fe for the organic component of mixtures metal fixation is probably by adsorption on insoluble organic matter humic acids or by precipitation as minor sulphides in these low sulphur coals

birth growth and morphologic evolution of the laghetto cinder cone during the 2001 etna eruption we have undertaken detailed observations of the formation of the laghetto cinder cone a new cone that formed during a 2 week period of intense activity in piano del lago on the upper slopes of mount etna in summer 2001 we describe the events leading to the formation of a small graben the formation of pit craters on the base of the graben the onset of phreatomagmatic activity a transition to intense strombolian activity and a return to phreatomagmatic activity as the eruption came to an end we discuss the reasons for these transitions and describe the morphological development of the cone during these events arcuate cracks on the southern part of the cone were related to withdrawal of magma at the end of the eruption other slope instabilities that developed during the eruption include the formation of small radial grain flows on the outer flanks of the cone and the collapse into the crater of part of the crater rim some of the failure planes we observed were first identified using a flir tm 695 thermal infrared camera this is the first time that infrared thermography has been used to detect instability of volcanic structures results obtained during this test case demonstrate that thermal cameras are a very useful tool for studies of volcanic instability

rare earth patterns with positive cerium anomaly in alkaline waters from lake van turkey abstract the distribution of rare earth elements has been studied for aerobic alkaline ph 9 6 carbonate rich waters from lake van turkey shale normalized ree ree sn patterns display an almost linear increase from the light to the heavy rees and strong positive ce sn anomalies there exist neither positive nor negative gd sn anomalies the ree sn patterns are consistent with domination of ree speciation in solution by poly carbonato complexes generating enrichment of the heavy rees that is even more pronounced than that seen in seawater this is the first report of positive ce sn anomalies observed in ree sn patterns of aerobic natural waters these anomalies apparently result from stabilization of penta carbonato ce iv complexes in solution leading to enhanced abundances of ce in comparison with its trivalent ree neighbours thus in remarkable contrast to seawater positive ce sn anomalies may be general features of alkaline carbonate rich and aerobic lake waters

burial of organic carbon and pyrite sulfur in sediments over phanerozoic time a new theory in present day marine sediments almost all of which are deposited in normal oxygenated seawater rates of burial of organic carbon c and pyrite sulfur s correlate positively and bear a constant ratio to one another c s 3 on a weight basis by contrast calculations based on the isotopic model of garrels and lerman 1981 indicate that at various times during the phanerozoic the worldwide burial ratio must have been considerably different than the present day value this ratio change is caused by the requirement that increases in the worldwide mass of organic carbon must be accompanied by equivalent decreases in the mass of sedimentary pyrite sulfur in order to maintain a roughly constant level of o2 in the atmosphere such apparently contradictory behavior can be explained if the locus of major organic carbon burial has shifted over time from normal marine environments as at present to non marine freshwater or to euxinic environments in the geologic past a shift to predominantly freshwater burial can help explain predicted high c s ratios in permo carboniferous sediments and a shift to euxinic environments can help explain predicted low c s ratios during the early paleozoic it is demonstrated that the three environments today exhibit distinguishably different average c s ratios

paleoclimate and paleoceanography over the past 20 000 yr in the mediterranean sea basins as indicated by sediment elemental proxies abstract marine sediments record paleoenvironmental changes over time through variations in major and trace element concentrations the main objective of this paper is to review such changes in the mediterranean sea basins over the last 20 ka using the inorganic chemistry and mineralogy of marine sediment records elemental ratio proxies that are mostly used are discussed and the uncertainties involved in using them for paleoclimate and paleoceanographic reconstructions are evaluated the focus on the mediterranean region is based on the sensitivity of this region to global climate changes due to its semi enclosed nature the elemental ratios that have been particularly useful for reconstructing terrigenous inputs into the mediterranean have been ti al and zr al ratios as proxies for eolian dust input and mg al k al and rb al ratios as proxies for fluvial input redox sensitive elements e g u mo v co ni cr have provided reliable reconstructions of oxygen conditions at the time of deposition some of these elements are also particularly susceptible to post depositional remobilization and record diagenetic processes instead of the original environmental signatures regarding productivity fluctuations most of the paleoproductivity reconstructions are based on the abundance of barite and ba excess algorithms the biogeochemistry of ba is however not fully understood and mechanisms for barite precipitation in the water column are not yet known two case studies are presented the eastern mediterranean sapropel s1 deposited between 10 8 and 6 1 cal ka bp and the westernmost mediterranean paleoclimate record over the last 20 ka

provenance derived from the geochemistry of late paleozoic early mesozoic mudrocks of the pyeongan supergroup korea late carboniferous early triassic pyeongan supergroup korea was deposited in paralic to nonmarine environments developed disconformably on a lower paleozoic platformal sequence pyeongan supergroup mudrocks show progressive upsection changes in major trace and rare earth element compositions mudrocks in the lower and middle parts of the pyeongan supergroup are strongly depleted in cao and na2o while those in the upper part are enriched in these elements in parallel with cao and na2o the ratio of k2o al2o3 in the lower and middle sections is less than 0 3 while uppermost strata are enriched in k2o having k2o al2o3 ratios greater than 0 3 the index of compositional variability a measure of compositional maturity is less than 0 6 in the lower to middle section whereas in the uppermost strata it is greater than 0 7 similar trends are reflected in a cn k space compared to paas mudrocks of the pyeongan supergroup except for those in uppermost units they are depleted in mn ca and na and are slightly depleted in mg and p contrasting major oxide trends between the lower and middle parts of the pyeongan and the uppermost units are due to decreasing proportions of clay minerals and a concomitant increase in the proportion of nonclay silicate minerals due to increasing input of first cycle detritus excursions marked by increases in mgo na2o and cao reflect large scale input of nonclay first cycle minerals from crystalline source rocks due to large scale basement uplift incompatible elements are generally enriched in mudrocks of the pyeongan supergroup relative to paas while transition metals co ni cr and v are progressively depleted in younger parts of the section total rare earth element concentrations are higher than paas but chondrite normalized patterns display the typical lree enriched pattern of paas eu anomalies for most mudrocks are close to that of paas the youngest mudrocks in the pyeongan supergroup have the most negative values these trends can be explained by a sedimentary system dominated by detritus derived from recycled highly weathered granitic materials in the lower to middle pyeongan section with an increased proportion of less weathered detritus derived from fractionated granitic materials in uppermost strata such an interpretation is consistent with the results of studies on coarse grained sediments of the pyeongan supergroup

the role of seamount volcanism in crustal construction at the mid atlantic ridge 24 30 n an analysis of approximately 6000 km2 of sea beam swaths indicates that the floor of the median valley of the mid atlantic ridge mar between 24 30 n is strewn with near circular volcanoes we have identified 481 seamounts in the height range 50 650 m because many of the features which appear to be seamounts do not meet our criteria fully they have not been counted and our numbers are likely a minimum estimate of the population the large abundance of seamounts on the median valley floor indicates that seamount volcanism plays an important role in the accretionary processes at this section of the mar the summit height distribution of the mar seamount population is consistent with the exponential frequency size distribution model for off axis eastern pacific seamounts jordan et al 1983 smith and jordan 1987 the model parameters for the mar population yield an average of about 195 seamounts per one thousand square kilometers and a characteristic height of about 60 m shape statistics compiled from the 481 seamounts give parameters that are exactly the same or cover the same range in values as those obtained from a study of pacific seamounts in the height range 140 3800 m smith 1988 implying a universal control on seamount construction based on the volcanic morphology we identify 18 spreading segments along the ridge all except two contain a prominent axial volcanic ridge many of the seamounts identified are associated with the axial ridges from the sea beam swaths we infer that the ridges are composed of piled up seamounts and hummocky flows and interpret them to be the primary sites of crustal construction this style of volcanism contrasts strongly with that observed at the east pacific rise where seamounts are virtually absent at the spreading axis the construction of seamounts and hummocky flows may be directly related to the fact that the mar is fed by magma chambers that are limited in size and frequency we suggest that small magma pockets with slow eruption rates produce seamounts either from pipes or initial fissure eruptions that collapse to construct a single edifice small magma bodies with somewhat higher eruption rates produce hummocky fissure fed flows using buoyancy arguments the heights of the mar seamounts are related to the depth of the magma bodies we hypothesize that small magma bodies rise buoyantly to the base of the hydrothermally cooled brittle lid where they are trapped and then erupt if this hypothesis is correct the thickness of the brittle lid controls seamount height and the exponential distribution of seamount summit heights implies that the thickness of the brittle hd follows an exponential distribution in time and space with characteristic thickness 1 4 1 9 km if seamounts and hummocky flows are fed each from their own discrete magma body trapped at the brittle ductile transition then the lower crust of the mar will be made up of the products of a multitude of small plutons

computer simulation models of scoria cone degradation abstract long term erosional modifications of the relatively simple morphology of scoria cinder cones are ideally suited for study by field and computer simulation methods a series of temporally distinct cones in the san francisco and springerville volcanic fields of arizona provides the foundation for documenting the degradational evolution of scoria cones in a semi arid climate progressive changes due to erosion are illustrated by the systematic decrease with increasing age of various morphometric parameters including scoria cone height cone height width ratio hco wco crater depth width ratio and slope angle for example holocene latest pleistocene cones in the san francisco field have a mean hco wco value of 0 178 0 041 a mean maximum slope angle of 29 7 4 2 and a mean average slope angle of 26 4 7 3 whereas the group of pliocene cones have values of 0 077 0 024 20 5 5 8 and 8 7 2 7 respectively comparative morphology of scoria cones is a potentially useful dating tool for mapping volcanic fields in order to better understand the degradational modifications of these volcanic landforms we have developed a numerical approach to simulate the surficial processes responsible for the erosion of a typical scoria cone the simulation algorithm can apply either a linear diffusion equation model or a model with a nonlinear transport law using a finite difference formulation the simulation operates upon a three dimensional scoria cone input as a matrix of elevation values utilizing both field and model results the correlation between changing hco wco value cone age and computer time step was expressed graphically to derive comprehensive values of the transport or diffusion coefficient df for both volcanic fields for the san francisco volcanic field df had a calculated value of 21 4 m2 kyr for the linear model and 5 3 m kyr for the nonlinear model while for the springerville volcanic field df had a calculated value of 24 4 m2 kyr for the linear model and 6 3 m kyr for the nonlinear model

extension and rotation of crustal blocks in northern central america and effect on the volcanic arc sinistral displacements across the north american caribbean plate boundary in northern central america are distributed among major arcuate faults that have been active in neogene time south of the jocotan and motagua faults in guatemala extensional tectonics has accompanied rotation of the trailing edge of the caribbean plate around these faults segmentation of the volcanic arc in northern central america hitherto attributed to transverse breaks in the subducting cocos plate may instead be a result of this block rotation accompanying changes along the arc are observed in seismicity gravity anomaly patterns volume and composition of volcanic products and topography therefore the complex volcano tectonic geology south of the main boundary faults may be explained by interaction and rotation of crustal blocks in the overriding caribbean plate above the magma production zone along the downgoing cocos slab

illite smectite formation and potassium mass transfer during burial diagenesis of mudrocks a study from the texas gulf coast paleocene eocene abstract mudrock samples from a well penetrating eocene and paleocene strata 1235 4455 m of the texas gulf coast have been studied to assess geochemical redistribution in mudrocks during burial diagenesis and the mechanism by which detrital smectitic illite smectite i s is transformed into diagenetic illitic i s idealized smectite and illite end member compositions for interstratified i s are estimated to be k0 00x 10 56mg0 39fe0 57al1 13si3 90o10 oh 2 and k0 53x 10 18mg0 17fe0 16al2 28 si3 40o10 oh 2 respectively there is no obvious difference in the amount of k addition to i s in random and ordered interstratified i s aluminum substitution into both tetrahedral and octahedral sites suggests that the smectite to illite reaction is a complete dissolution precipitation reaction rather than a solid state k 1 al 3 for si 4 substitution reaction depth relat d mineral trends and mass balance calculations suggest that illitic i s may form from kaolinite and possibly illite or mica as well as from smectitic i s although most whole rock element abundances are invariant over the sampled depth interval k2o content increases from ca 2 0 weight percent at 1500 m of burial to ca 3 8 weight percent at 4000 m some of this increase is probably caused by import of k into the shale via fluids derived from interbedded sandstones implying that gulf coast mudrocks behave as open chemical systems during burial diagenesis if this is the case a minimum of 103 pore volumes of fluid must have passed through the most k enriched shales to have introduced the added potassium provided that the k content of present day formation water is representative of that of ancient formation water

studying monogenetic volcanoes with a terrestrial laser scanner case study at croscat volcano garrotxa volcanic field spain erosional processes natural or anthropogenic may partly destroy the relatively small sized volcanic edifices characteristic of monogenetic volcanic zones leaving their internal structure well exposed nevertheless the study of these outcrops may be extremely challenging due to restricted accessibility or safety issues digital representations of the outcrop surface have been lately used to overcome such difficulties data acquired with terrestrial laser scanning instruments using light detection and ranging technology enables the construction of such digital outcrops the obtained high precision 3 d terrain models are of greater coverage and accuracy than conventional methods and when taken at different times allow description of geological processes in time and space despite its intrinsic advantages and the proven satisfactory results this technique has been little applied in volcanology related studies here we want to introduce it to the volcanological community together with a new and user friendly digital outcrop analysis methodology for inexperienced users this tool may be useful not only for volcano monitoring purposes but also to describe the internal structure of exposed volcanic edifices or to estimate outcrop erosion rates that may be helpful in terms of hazard assessment or preservation of volcanic landscapes we apply it to the croscat volcano a monogenetic cone in the la garrotxa volcanic field catalan volcanic zone ne spain quarrying of which leads to a perfect view of its interior but restricts access to its uppermost parts croscat is additionally one of the most emblematic symbols of the la garrotxa volcanic field natural park and its preservation is a main target of the park administration

morphometry of scoria cones located on a volcano flank a case study from mt etna italy based on high resolution lidar data abstract by using new high resolution 2 m digital elevation model derived from the 2005 lidar survey of mt etna volcano italy our study measured the classical morphometrical parameters for scoria cones i e w co cone width w cr crater diameter h cone height as well as volume inclination of cone slope and substrate and a number of other parameters for 135 scoria cones of mt etna volume and age distribution of cones shows that there is no direct structural control on their emplacement in terms of etna s rift zones the cones are progressively smaller in size toward summit which can be explained by the large volcano s feeding system and progressively frequent lava burial toward top a careful analysis of h w co ratio determined as 0 18 for other volcanic fields worldwide shows that this ratio strongly depends on 1 the calculation method of h and 2 lava burial of cone for etnean cones applying an improved method for calculating h relative to the dipping substrate results in a significantly lowered standard h w co ratio 0 137 which in turn questions the validity of the classical value of 0 18 in the case of large central volcanoes the reduction of the ratio is not only due to methodology but also to the common lava burial this can be expressed even better if h mean is used instead of h max h mean w co 0 098 using this measure at etna well formed cones have higher ratios than structurally deformed e g double or rifted cones furthermore although the sampled scoria cones at etna have formed in a relatively narrow time interval h w co corresponding to erosional changes detected globally h w co 0 143 0 135 and 0 115 for three age classes of etna s scoria cones corresponding to average slopes of 26 6 23 9 and 23 7 because the morphometrical effect of position on a dipping substrate as well as lava burial exceeds the effect of erosion we call attention to use caution in simply using the h w co ratio of scoria cones for detecting age especially on large active volcanoes

geochemistry and tectonic setting of lewisian clastic metasediments from the early proterozoic loch maree group of gairloch nw scotland abstract the early proterozoic 2 0 ga loch maree group lmg of the lewisian complex consists of a supracrustal sequence of metasedimentary schists and associated tholeiitic metavolcanic amphibolites within the archaean basement the metasediments comprise three main mapped units the flowerdale schists kerrysdale schists and charlestown schists together with numerous narrower bands the dominant clastic metasediments within the schist units semipelites and psammites are chemically distinguished as a series of greywackes and lithic sandstones with variable lil and transition element abundances fractionated ree patterns and overall compositions similar to paas three chemical groups are recognized whose range of composition largely reflects the mixing between two main source components lewisian gneissose basement with an intermediate acid continental crust composition and local rift related amphibolites with a primitive tholeiitic composition which also incorporates components not preserved within the lmg the geochemistry of the clastic metasediments confirms a previous tectonic model for the lmg as an intracontinental extensional rift receiving clastic detritus from the adjacent uplifted basement as well as from internal volcanogenic sources

volcanic sources and diagenetic alteration of permian triassic boundary k bentonites in guizhou province south china abstract terrestrial permian triassic boundary ptb sequences in south china usually contain one to three ash beds k bentonites which provide evidence of a possible trigger for the terrestrial mass extinction and are useful as a distinct marker for correlation of the ptb boundary interval from terrestrial to marine areas here we investigate the clay mineralogy and geochemistry of ash beds in the zhejue and jiucaichong sections representing paludal and lacustrine environments respectively in order to better understand the source s and preservation of these ash beds the two zhejue k bentonites exhibit similar compositions that are distinctly different from that of the jiucaichong k bentonite the former contain mainly clay minerals with minor quartz anatase and lepidocrocite and the clay minerals in these layers are mainly r1 and r3 mixed layer illite smectite i s and well crystallized to poorly crystallized kaolinite whereas the latter consists mainly of r3 i s with minor quartz feldspars and anatase the former have higher cia values 92 2 and 93 8 than the latter 79 4 indicating more intense chemical weathering that may have been related to deposition in a paludal setting with high organic acid concentrations in pore fluids these k bentonites also exhibit differences in major element chemistry mgo and k2o contents are higher at jiucaichong due to lesser weathering intensity and possibly early diagenetic uptake from pore fluids ree chemistry jiucaichong exhibits a larger eu anomaly and nd isotopic compositions zhejue k bentonites have 143nd 144nd ratios of 0 512436 and 0 512400 higher than the 0 512190 ratio for jiucaichong although some of these compositional differences may be related to the dissimilar chemical environments in which diagenesis occurred i e paludal vs lacustrine the differences in eu anomalies and nd isotopic compositions imply heterogeneous volcanic ash sources the source of these k bentonites was probably a continental volcanic arc located on the paleo southern margin of the south china craton within which multiple volcanic vents may have been active concurrently

the july august 2001 eruption of mt etna sicily the july august 2001 eruption of mt etna stimulated widespread public and media interest caused significant damage to tourist facilities and for several days threatened the town of nicolosi on the s flank of the volcano seven eruptive fissures were active five on the s flank between 3 050 and 2 100 m altitude and two on the ne flank between 3 080 and 2 600 m elevation all produced lava flows over various periods during the eruption the most voluminous of which reached a length of 6 9 km mineralogically the 2001 lavas fall into two distinct groups indicating that magma was supplied through two different and largely independent pathways one extending laterally from the central conduit system through radial fissures the other being a vertically ascending eccentric dike furthermore one of the eccentric vents at 2 570 m elevation was the site of vigorous phreatomagmatic activity as the dike cut through a shallow aquifer during both the initial and closing stages of the eruption for 6 days the magma column feeding this vent was more or less effectively sealed from the aquifer permitting powerful explosive and effusive magmatic activity while the eruption was characterized by a highly dynamic evolution complex interactions between some of the eruptive fissures and changing eruptive styles its total volume 25 106 m3 of lava and 5 10 106 m3 of pyroclastics was relatively small in comparison with other recent eruptions of etna effusion rates were calculated on a daily basis and reached peaks of 14 16 m3 s 1 while the average effusion rate at all fissures was about 11 m3 s 1 which is not exceptionally high the eruption showed a number of peculiar features but none of these except the contemporaneous lateral and eccentric activity represented a significant deviation from etna s eruptive behavior in the long term however the 2001 eruption could be but the first in a series of flank eruptions some of which might be more voluminous and hazardous placed in a long term context the eruption confirms a distinct trend initiated during the past 50 years toward higher production rates and more frequent eruptions which might bring etna back to similar levels of activity as during the early to mid seventeenth century

scoria cones on mars detailed investigation of morphometry based on high resolution digital elevation models we analyze the shapes of 28 hypothesized scoria cones in three regions on mars i e ulysses and hydraotes colles and coprates chasma using available high resolution imaging science experiment and context camera ctx digital elevation models we determine the basic morphometric characteristics of the cones and estimate from ballistic modeling the physical parameters of volcanic eruptions that could have formed them when compared to terrestrial scoria cones most of the studied cones show larger volumes up to 4 2 109m3 larger heights up to 573m and smaller average slopes the average slopes of the ulysses hydraotes and coprates cones range between 7 and 25 and the maximum slopes only rarely exceed 30 which suggests only a minor role of scoria redistribution by avalanching ballistic analysis indicates that all cones were formed in a similar way and their shapes are consistent with an ejection velocity about 2 times larger and a particle size about 20 times smaller than on earth our results support the hypothesis that the investigated edifices were formed by low energy strombolian volcanic eruptions and hence are equivalent to terrestrial scoria cones the cones in hydraotes colles and coprates chasma are on average smaller and steeper than the cones in ulysses colles which is likely due to the difference in topographic elevation and the associated difference in atmospheric pressure this study provides the expected morphometric characteristics of martian scoria cones which can be used to identify landforms consistent with this type of activity elsewhere on mars and distinguish them from other conical edifices

provenance tectonic setting and age of the sediments of the upper disang formation in the phek district nagaland abstract integrated petrographic and geochemical studies of sandstones and geochemical studies of shales of turbidites from the upper disang formation phek district nagaland have been carried out to determine their provenance weathering conditions and tectonic setting paleomagnetic studies were carried out for magnetostratigraphic purposes studies indicate that most of these sediments were derived from felsic and mafic sources with minor contribution from low to medium grade metamorphic rocks most of the felsic components have been transported from distant sources as evidenced from extensive reworking of grains the most likely source rocks are the granite granite gneiss of the karbi anglong crystalline complex to the west of the study area however the bulk of the sediments have been contributed from nearby basic and ultrabasic sources this would correspond to the fast rising naga ophiolite which probably emerged above sea level during the mid eocene prevailing high temperatures and humid climate caused intense chemical weathering of the source rocks the sediments from the west were transported great distances by turbidity currents into an easterly deepening basin sediments from the nearby east were rapidly dumped on the seafloor causing rapid mixing leading to textural and chemical immaturity paleomagnetic studies endorse published paleontological evidence to indicate that most of the sediments of the upper disang formation were deposited during the late eocene deposition took place in a westward migrating accretionary prism complex in an active margin setting at the convergence of the indian and burma plates this was a rapidly closing basin where anoxic conditions prevailed towards the end of the eocene this basin closed completely with the destruction of the tethyan ocean

morphometry of scoria cones and their relation to geodynamic setting a dem based analysis abstract the morphometry of a great number of scoria cones belonging to volcanic fields of various geodynamic settings has been measured and analyzed addressing the question whether there is a relation between the prevalent cone shape in a given field and the geodynamic setting of the field itself morphometric analysis was carried out on freely downloadable digital elevation models dems the accuracy of the used dems and the associated error in scoria cone morphometry were determined by cross comparing high resolution lidar derived dems usgs ned tinitaly dem and aster gdem the 10 m tinitaly 01 and usgs ned dems are proven to be suitable for scoria cone morphometry whereas aster gdem can be used reliably for cones with volume greater than 30 10 6 m 3 according to a detailed morphometry of all scoria cones we propose that the cones related to subductional setting show relatively higher values of h c o w co and lower values of w cr w co than the cones related to extensional setting the detected differences can be imputable to peculiar eruption dynamics resulting in slight but systematic changes in shape and differences in lithological and sedimentological characteristics that govern post eruptive erosion to constrain the pathway of scoria cone erosion the detected morphometric changes were also interpreted using a simple linear degradation model utilizing the obtained simulation results the inferred initial cone base and the age of scoria cones we calculated a diffusion coefficient k for several dated cones which are related to the prevalent climate our results despite the high error associated allow to assess the median k for all volcanic fields due to the complexity of the factors behind it is not easy to understand if the prevalent shape characterizing a certain volcanic field is due mainly to sin eruptive or post eruptive mechanisms however our distinction between the two main geodynamic settings may be the first step to decipher these factors

mineralogy geochemistry and genesis of clays interlayered coal seams succession in the neogene lacustrine seyitomer coal deposit kutahya western turkey abstract the seyitomer coal deposit is an important source of energy in turkey this study aims to determine mineralogical geochemical characteristics and genesis of clays associated with coal seams in order to identify their precipitation environment the late miocene pliocene units comprise organic rich shale organic rich marl marl coal seam siltstone and sandstone deposited in a fluvial and lacustrine environment with associated tuff and tuffite in the seyitomer coal deposit serpentinite sandstone organic rich shale and tuffaceous host rocks of the coal deposit are partly to completely argillized and partially carbonate cemented having also stockwork type silica in fill fissures smectite illite and kaolinite are associated with quartz feldspar olivine gypsum and pyrite oriented flaky illite with irregular outlined kaolinite and smectite flakes edging and coating relict feldspar and volcanic glass grains developed by a dissolution precipitation mechanism in an alkaline micro environment during deposition and diagenetic process the occurrence of subrounded microorganisms on resorbed feldspar and the coexistence of smectite illite flakes with organic matter pyrite and siderite indicates that degradation of feldspar and devitrification of volcanic glass is biologically mediated the slight enrichment of heavy rare earth elements hree compared to light rare earth elements lree with a positive eu and ce anomalies reflects fractional crystallization of feldspar and amphibole alteration of feldspar biotite serpentine and volcanic glass resulted in the concentration of al fe mg and k in a stagnant environment and precipitation of beidellitic smectite and illite in an alkaline environment kaolinite precipitated in an acidic open hydrological system an increase in ni co and v v ni ratios in altered units also suggest anoxic and anoxic to dysoxic conditions occurrence of pityosporites microalatus pinus laevigatosporites haardti pityosporites spp polyvestibulopollenites verus alnus compositae and graminae in the seyitomer coal deposit suggest subtropical to warm temperature humid climate during late oligocene middle miocene period association of argillization and silicification with coal microorganisms pyrite and gypsum indicates a swampy environment and partial hydrothermal processes this interpretation is corroborated by the calculated formation temperatures from stable isotope analysis of 30 463 c for smectite and 140 156 c for illite the high 34s isotope values 16 8 33 3 indicate a mixed diagenetic and hydrothermal origin for the sulphide and sulfate minerals

geomorphology morphometry spatial distribution and ages of mafic monogenetic volcanoes of the peinado and incahuasi fields southernmost central volcanic zone of the andes abstract the back arc southern puna region south of 24 s in the central volcanic zone of the andes contains hundreds of miocene to quaternary mafic monogenetic volcanoes roughly distributed in several volcanic fields analysis of the geomorphology morphometry spatial distribution and age of 36 mafic monogenetic centers in the peinado and incahuasi fields at the southwestern margin of the puna plateau gives insights on the links that mafic monogenetic volcanism can have with main and secondary structures and the effects of degradation on scoria cone shape degree of preservation morphometry and six new unspiked k ar ages indicate two distinct age groups old centers 2 ma and young centers 1 ma the older mafic centers consist of degraded scoria cones and lava flows with an estimated cumulative bulk volume of 2 2 km3 the younger mafic centers display a variety of well preserved landforms scoria cones lava flows maars tuff rings domes and have an estimated cumulative volume of 6 2 km3 their distribution in a main nne ssw and secondary ene wsw trends suggests a control by the regional nne ssw striking peinado and san francisco fault systems in a dextral strike slip configuration scoria cone and lava flow morphometries are similar in both fields but a marked difference indicating hydrovolcanic activity is the presence of tuff rings maars and tephra fallout deposits only in the peinado field morphometric analysis of dated pristine and degraded scoria cones of the southern puna region shows that parameters related to crater depth and inner crater steepness decrease consistently with age suggesting that crater infilling is the degradation related process that is most sensitive to age at scoria cones in the southern puna high values of crater depth crater width crater depth cone height and mean inner crater slope are indicative of a young 1 ma age as young cones can have initially low values

different isotopic evolutionary trends of δ34s and δ18o compositions of dissolved sulfate in an anaerobic deltaic aquifer system abstract concentration and isotope ratios 34sso4 and 18oso4 of dissolved sulfate of groundwater were analyzed in a very large anaerobic aquifer system under the lower central plain lcp 25 000 km2 in thailand groundwater samples were collected in two different kinds of aquifers type 1 with a saline water contribution and type 2 lateritic aquifers with no saline water contribution two different isotopic compositional trends were observed in type 1 aquifers sulfate isotope ratios range from low values 2 2 for 34sso4 and 8 0 for 18oso4 to high values 49 9 for 34sso4 and 17 9 for 18oso4 in type 2 aquifers sulfate isotope ratios range from low values 0 1 for 34sso4 and 12 2 for 18oso4 to high 18oso4 ratios 18 4 but with low 34sso4 ratios

model for prediction of organic carbon content in possible source rocks abstract a quantitative model has been developed to improve the prediction of the occurrence of marine siliciclastic source rocks and their likely organic carbon content the input parameters of this quantitative model are organic matter supply in the surface layer of the ocean photic zone water depth calculation of the carbon flux sedimentation rate and preservation conditions presence or absence of oxygen at the sediment water interface to handle the difficulties in the quantification of input parameters a probabilistic approach is applied depending on the available data or the interpretation of the kind of environment different risk distribution functions are used to describe the possible range of each input parameter the calculation is then carried out using the monte carlo simulation technique resulting in a probability distribution of the total organic carbon content which forms the basis of the analysis different scenarios currently under debate e g high primary productivity or the possible effects of enhanced preservation under anoxic bottom water conditions and the influence of varying water depth and sedimentation rate can be tested very quickly using examples of recent peru continental margin and ancient lower toarcian shale germany organic rich marine shales the potential of this tool is demonstrated firstly to quantify souce rock quality in this case total organic carbon content only secondly to assess quantitatively the uncertainties in source rock prediction e g evaluation of organic matter supply water depth and sedimentation rates and thirdly to determine source quality risk values to be used in the appraisal of sedimentary basins and prospects

sulfur and oxygen isotope studies of melt country rock interaction babbitt cu ni deposit duluth complex minnesota the babbitt cu ni deposit formerly known as minnamax occurs within troctolitic and gabbroic rocks of the precambrian duluth complex both massive and disseminated mineralizations are found in the deposit pyrrhotite cubanite chalcopyrite and minor pentlandite mineralization occurs near the basal contact with pelitic metasedimentary rocks of the virginia formation or higher in the igneous sequence associated with abundant country rock xenoliths cloud zones sulfur and oxygen isotope studies have been carried out to evaluate the importance of melt country rock interaction in localizing sulfide mineralization the delta 34 s values of pyrrhotite plus pyrite from the virginia formation located outside the contact aureole range from 5 6 to 13 7 per mil pyrrhotite from footwall virginia formation hornfels or inclusions in the basal zone exhibits delta 34 s values ranging from 1 5 to 6 2 per mil whereas delta 34 s values of pyrrhotite from xenoliths in cloud zones range from 2 6 to 21 4 per mil isotopic values of basal zone cu ni sulfides range from 6 0 to 13 0 per mil with a mode at 8 to 9 per mil two features highlight basal zone delta 34 s values first delta 34 s values of sulfide mineralization are higher than those of pyrrhotite in immediately adjacent virginia formation hornfels second higher grade ore areas 1 cu show 34 s enrichment with delta 34 s values in the range of 9 to 13 per mil sulfides in cloud zones show a wide range in delta 34 s values from 0 7 to 19 7 per mil sulfur isotope data suggest that most of the sulfur found in the deposit has been derived from sedimentary country rocks however an in situ process of sulfur derivation is not indicated sulfur in basal mineralized zones must have been derived at depth within an auxiliary magma chamber or during magma ascent and emplacement isotopic homogenization was not achieved during the sulfide forming process as evidenced by the spatial variability of delta 34 s values oxygen isotope values of both mildly metamorphosed virginia formation and footwall hornfels range from 8 2 to 14 0 per mil inclusions of virginia formation show pronounced isotopic effects due to interaction with melt xenolith margins may have values as low as 7 to 8 per mil and are depleted in 18 o with respect to xenolith interiors the delta 18 o values of igneous rocks from the babbitt deposit range from 3 9 to 12 2 per mil zones of 18 o depletion are rare and suggest that exchange with a low 18 o fluid phase was spatially restricted anomalous delta 18 o values in excess of 7 to 7 5 per mil are common throughout the deposit but are limited to within 3 m of virginia formation xenoliths a model of diffusion controlled 18 exchange between igneous material and xenoliths best describes the delta 18 o distribution devolatilization and desilicification of the xenoliths occurred early in their history when physical mixing in the host magma was possible addition of high 18 o material from these processes into a large volume of melt affected delta 18 o distributions only slightly continued exchange of oxygen after major cation transfer produced the observed delta 18 o profiles in the case of basal zone cu ni mineralization at babbitt isotopic evidence indicates that sulfide saturation was not caused by in situ addition of sulfur silica or oxygen sulfide saturation is thought to have been achieved at depth triggered by assimilation of large quantities of sulfide liberated through devolatilization reactions occurring in country rocks

alluvial sandstone composition and paleoclimate i framework mineralogy abstract systematic variations in compositional maturity of first cycle fluvial sandstones are found in the cutler formation permian and fountain formation permian pennsylvanian in colorado and in the gondwana supergroup permian triassic of peninsular india these variations reflect changing climate during deposition climate is considered to be the critical factor affecting maturity because source rocks granite granite gneiss and tectono environmental setting alluvial systems associated with basement cored block uplifts were similar and remained relatively unchanged throughout deposition of all three of the units the roughly 3 200 m thick gondwana succession consisting of five sandstone petrofacies is characterized by the following sequence of change oldest to youngest in compositional maturity expressed in q f r percentages 54 42 4 88 10 2 62 34 4 82 16 2 99 1 0 this sequence is a function of the changing paleoclimate glacial arid temperate humid warm semiarid warm semihumid warm humid associated with the overall global limatic change and the changing latitudinal location of india as it moved from a location close to the south pole northward during the interval of time represented by gondwana deposition lithologic and fossil evidence indicates that during deposition of the fountain formation climate gradually changed from relatively wet and warm to at least semiarid and warm this climatic change is the main factor responsible for the difference in compositional maturity of the older fountain sandstone q f r 65 26 9 relative to the younger q f r 54 36 10 cutler sandstone was deposited in an arid climate and has maximum compositional immaturity q f r 49 44 7 a log log plot of the ratio of total quartz to total feldspar plus rock fragments against the ratio of total polycrystalline quartz to to al feldspar plus rock fragments is a sensitive discriminator of first cycle sandstones with differing climatic heritage bulk chemical composition data support interpretation of climate from framework mineralogy but by themselves are not sensitive enough to be unequivocal indicators the same is true for the ztr index and observations of degree and abundance of solution pits embayments on detrital quartz results of this study support the conclusion of earlier empirical and theoretical analyses which suggest that the optimum conditions for the production and preservation of a distinctive climatic signature on sand composition are met in extensional plate tectonic settings such settings are characterized by coarse grained crystalline parent rocks short transport distances in low order streams deposition in nonroutine environments and shallow burial diagenesis however even in such optimum settings only rarely will climate be a more important determinant of sandstone composition than the tectonic setting itself

characterisation of oil and potential source rocks in the northeastern song hong basin vietnam indications of a lacustrine coal sourced petroleum system oil discovered in the b10 stb 1x well in the northeastern song hong basin vietnam has typical lacustrine coaly geochemical features indicating the existence of a principally lacustrine sourced petroleum system with minor contributions from a coal source the presence of lacustrine source rocks in the basin is indicated by distinct high amplitude seismic reflectors in undrilled half grabens and outcrops of oligocene immature mudstones and humic coals at dong ho and on bach long vi island the mudstones from dong ho generally have a toc content of 8 17 wt and hi values 500 mg hc g toc the organic matter is principally composed of fluorescing amorphous organic matter and liptodetrinite alginite with botryococcus morphology is present the organic matter corresponds to type i kerogen the bach long vi island mudstones contain 2 7 wt toc and have hi values from 200 700 mg hc g toc the organic matter is largely similar to that in the dong ho mudstones but in addition may contain some marine organic material the b10 stb 1x oil shows features common to both the dong ho and bach long vi island mudstones but was probably principally generated from a source similar to the dong ho mudstones with contributions from higher land plant organic matter a prominent activation energy peak dominates the activation energy distributions of the mudstones and upon artificial maturation hydrous pyrolysis the mudstones show extensive hydrocarbon generation over a narrow temperature range hydrocarbon expulsion has been estimated to occur at a vitrinite reflectance of 0 75 ro the source of the b10 stb 1x oil may be located in the thuy nguyen graben and maturity modelling shows that the lacustrine mudstones will be thermally mature in this graben

precipitation gradients during the miocene in western and central turkey as quantified from pollen data abstract in the present paper we have analyzed thirty five palynofloras covering the time span from the early miocene aquitanian to the late miocene middle tortonian in turkey the results obtained are presented in tables and maps showing temporal palaeoprecipitation values the mean annual precipitation map exceeds 1200 mm during the aquitanian and early middle serravallian it is suggested to have been between 1000 and 1300 mm in the latest serravallian earliest tortonian in western and central turkey in the early middle tortonian the lower boundary of map decreases to below 1000 mm in central and eastern turkey today maps are represented by lower values around 600 1000 mm in western and 400 600 mm in central turkey for the driest month lmp the rainfall was not distributed homogeneously in the aquitanian the calculations are between 36 and 48 mm with humid conditions in western and eastern turkey during the burdigalian and middle miocene the driest month precipitation varied with respect to locations however it is clear that there was a reduction in precipitation during the early middle tortonian with values around 26 27 mm in central and eastern turkey the same pattern is observed for the wettest month precipitation hmp with estimates higher than 200 mm during the aquitanian and earliest tortonian although some areas received low rainfall hmp was reduced between 130 and 140 mm in the early middle tortonian the warmest month precipitation wmp varied from 96 to 140 mm except for konya ilgin kirsehir hacibektas and manisa soma that received 88 mm during the early middle miocene in the early middle tortonian the amount of summer rainfall lay between 58 and 88 mm the reason of the decrease in all rainfall parameters during the early middle tortonian could be related to several factors such as climatic cooling altitude aridification palaeotopograhy or continentality however it is necessary to indicate that the tortonian cooling had previously been proposed by akgun et al 2007 as the explanation using a large number of palynological assemblages in turkey we also observe a decrease in precipitation parameters during the middle miocene this could be related to fact that either low species diversity can result in wide coexistence intervals or the monterey cooling event was related to a cooling during the langhian and serravallian

sulfur isotopic studies of continental flood basalts in the noril sk region implications for the association between lavas and ore bearing intrusions previous studies of both ore and non ore bearing intrusives in the permo triassic flood basalts of the siberian platform in the noril sk area have shown that high grade ni cu platinum group elements pge mineralization is associated with anomalously high 34s values of 8 to 12 in addition several researchers have proposed that observed depletions in the cu ni and pge content of basaltic lavas of the nadezhdinsky nd formation are related to diffusional exchange with and upgrading in metal tenor of sulfides in the volcanic conduit system sulfur isotopic studies of the lavas at noril sk were initiated to determine if interaction with crustally derived sulfur in the conduit system was evident and if the nd lavas in particular were characterized by an anomalous isotopic signature 34s values of the lavas range from 4 5 to 8 7 vienna canon diablo troilite vcdt with s concentrations from 40 to 1373 ppm the majority of 34s values range from 0 to 4 and are similar to those from s poor intrusions in the noril sk area although textural data are not supportive of early sulfide saturation and the presence of immiscible sulfide droplets in the lavas recrystallization may have erased expected mineralogical and textural evidence mineralogical data indicate that hydrothermal alteration of the lavas has occurred but s redistribution has been restricted to localized areas and 34s values have not been affected the relatively low s concentrations of the lavas are thought to be due in large part to degassing of the lavas in the shallow conduit system and during eruption our calculations are consistent with the premise that degassing of basaltic magmas at temperatures in excess of 900 c at qfm leads to only minor 34s depletion of sulfur remaining in the melt and decreases in 34s values of less than 2 at 90 degassing for this reason all lavas with 34s values in excess of 2 require a contribution of 34s enriched country rock sulfur because of the high s content and 34s value 16 20 of evaporites in the country rocks at noril sk contamination of less than 0 5 is required to explain the most 34s enriched lavas the nd lavas have an average 34s of 2 9 but show no difference in s isotopic composition relative to the other lavas suggesting that metal depletion involved only limited s transfer or that exchange between mantle derived s and s of crustal origin buffered 34s values to less than 5 anomalously positive 34s values similar to those of the ore bearing intrusives in the noril sk region are not consistently found in low s rocks either lavas or intrusives although the mechanism for the derivation of sulfide in the ore bearing intrusions remain speculative it is clear that the formation of sulfide ores characterized by high metal tenors proceeded only in the presence of sulfur of crustal origin

geochemistry of rare elements in waters and sediments of alkaline lakes in the sasykkul depression east pamirs abstract the saline lakes tuzkul chukurkul sasykkul lakes of the sasykkul depression located in the semidesert part of the pamirs provide a prominent example of the evaporative concentration of alkaline waters in a closed basin under arid climate conditions chemical evolution of the lake waters has resulted in the development of residual na cl co3 so4 and na cl co3 brines the contents of a number of rare elements were determined in waters and sediments of the sasykkul depression lakes speciation modelling suggests that the main aqueous species of ag are chloride complexes cu pb zn mn are carbonate complexes be bi nb are hydroxocomplexes mo w as v are oxyanions it was established that the salt lake sediments are significantly enriched in b ba mo w u th high contents of trace elements are considered to be due to chemical weathering of rocks within the catchment basin significant contribution from thermal springs derived from the residual fluids associated with acid igneous and volcanic rocks and following evapoconcentration in a closed basin the processes of evaporative concentration solution complexation chemical precipitation and water sediment interaction lead to the partitioning of trace metals in the salt sediments

occurrence and genesis of tonsteins in the miocene lignite tuncbilek basin kutahya western turkey abstract abundant beige and white kaolinite claystone layers 2 50 cm thick from the tuncbilek basin have the characteristics of tonsteins the aim of this study was to determine the mode of formation of the tonsteins together with their mineralogical and geochemical characteristics in order to identify their environment of deposition the miocene lacustrine units in the tuncbilek lignite deposit associated with tuff and tuffite are comprised of organic rich shale organic rich marl marl claystone silty claystone siltstone sandstone coal seam and conglomerate deposited in a fluvial and lacustrine environment sanidine plagioclase biotite and chlorite are partly to completely argillized and enclosed in an authigenic clay matrix in the rhyolitic to rhyodacitic tuff tuffite sandstone organic rich shale and serpentinite host rocks of the clay deposit abundant kaolinite and quartz are associated with smectite illite feldspar calcite dolomite siderite pyrite barite and gypsum development of oriented 7 a halloysite tubes on in altered volcanogenic materials associated with kaolinite and the occurrence of vermiform kaolinite edging disordered kaolinite locally siderite and pyrite crystals may suggest formation of halloysite following kaolinite the reaction pathway is volcanic glass feldspar muscovite biotite 7 a halloysite kaolinite the slight enrichment of light rare earth elements lree compared to heavy rare earth elements hree with positive eu anomalies based on upper continental crust ucc normalized values reflects fractional crystallization of feldspar and amphibole in the parent volcanic rocks and organic rich shale alteration of feldspar biotite and volcanic glass resulted in the concentration of al si fe mg and k and precipitation of kaolinite in an acidic open hydrological system while in a stagnant and alkaline environment smectite and illite are the alteration products the al2o3 tio2 and low cr ni ratios suggest felsic parent rocks the trace elements ratios such as ni co v cr cu zn and u th among the basement complex source rocks units also suggest oxic suboxic and anoxic conditions the occurrence of pinus alnus quercus alnus carya taxodiaceae and myrica palymorphs reflect a subtropical to warm temperature humid climate low elevations and swamp vegetation condition during the early middle miocene period in the study area association of argillization and silicification with coal pyrite and gypsum indicates a swampy environment and hydrothermal processes this interpretation is corroborated by the calculated formation temperatures from stable isotope analysis of 148 8 168 c for kaolinite and 145 169 2 c for smectite the low s isotope values of pyrite 19 to 2 9 and high positive values of gypsum 11 5 21 7 indicate a mixed diagenetic and hydrothermal origin for the sulfide and sulfate mineral

syn eruptive morphometric variability of monogenetic scoria cones according to wood s model morphometric parameters such as slope angle can provide valuable information about the age of conical volcanic edifices such as scoria cones assuming that their initial slopes range from 30 to 33 measured manually on topographic maps and assuming that their inner architectures are homogenous this study examines the morphometric variability of nine young a few thousand years old small volume scoria cones from tenerife canary islands using high resolution digital elevation models in order to assess their slope angle variability because of the young age and minimal development of gullies on the flanks their morphometric variability can be interpreted as the result of syn eruptive processes including 1 pre eruptive surface inclination 2 vent migration and lava outflow with associated crater breaching and 3 diversity of pyroclastic rocks accumulated in the flanks of these volcanic edifices results show that slope angles for flank sectors differ by up to 12 among the studied volcanoes which formed over the same period of time this range greatly exceeds the 2 3 indicated by wood the greater than expected original slope range suggests that use of morphometric data in terms of morphometry based relative dating and detection of erosional processes and settings must be done with great care or detailed knowledge about absolute ages and eruption history especially in field scale morphometric investigation

ophiolitic source rocks for taconic age flysch trace element evidence flysch generated along the appalachian orogen during the ordovician taconic orogeny ranges in age from late arenig to early caradoc allochthonous flysch and from late llanvirn to ashgill autochthonous flysch sandstones in these units are dominantly lithic arenites with a heavy mineral suite containing common to abundant mg rich chromite north of the canada united states border the only reasonable sources for the chromite were the lower ultramafic units of obducted ophiolites trace element analyses cr ni v cu ti zr y of flysch sandstones indicate a striking increase in cr and ni concentrations from the united states appalachians to the canadian appalachians in the united states units cr is in the range of 10 to 50 ppm canadian flysch units average an order of magnitude more cr these results suggest that ophiolite obduction either did not occur or was of minor importance during the taconic orogeny in the united states appalachians the difference in ophiolite abundance between the canadian and united states appalachians suggests a fundamental difference in tectonic style along the orogen a feature that must be accommodated by plate tectonic models new models will probably need to consider both obliquity of subduction and geological complexity of the ordovician collision zone in order to explain the spatial distribution of obducted ophiolite sheets

detecting short term evolution of etnean scoria cones a lidar based approach the 2001 and 2002 2003 flank eruptions on mount etna italy were characterized by intense explosive activity which led to the formation of two large monogenetic scoria cones one from each eruption on the upper southern flank of the volcano continuous monitoring of etna especially during flank eruptions has provided detailed information on the growth of these cones they differ in genesis shape and size a set of high resolution 1 m digital elevation models dems derived from light detection and ranging lidar data collected during four different surveys 2004 2005 2006 and 2007 has been used to map morphology and to extract the morphometric parameters of the scoria cones by comparing lidar derived dems with a pre eruption 1998 10 m dem the volume of the two scoria cones was calculated for the first time comparison of the lidar derived dems revealed in unprecedented detail morphological changes during scoria cone degradation in particular the morphologically more exposed and structurally weaker 2002 2003 cone was eroded rapidly during the first few years after its emplacement mainly due to gravitational instability of slopes and wind erosion

evaluation of morphometry based dating of monogenetic volcanoes a case study from bandas del sur tenerife canary islands morphometry based dating provides a first order estimate of the temporal evolution of monogenetic volcanic edifices located within an intraplate monogenetic volcanic field or on the flanks of a polygenetic volcano two widely used morphometric parameters namely cone height width ratio hmax wco and slope angle were applied to extract chronological information and evaluate their accuracy for morphometry based ordering based on these quantitative parameters extracted from contour based digital elevation models dems two event orders for the bandas del sur in tenerife canary islands were constructed and compared with the existing k ar paleomagnetic and stratigraphic data the results obtained suggest that the commonly used hmax wco ratio is not reliable leading to inappropriate temporal order estimates while the slope angle gives slightly better results the overall performance of such descriptive parameters was however generally poor i e there is no strong correlation between morphometry and age the geomorphic morphometric mismatches could be the result of 1 the diversity of syn eruptive processes i e diverse initial morphologies causing geomorphic morphometric variability 2 contrasting edifice specific degradation that depends partly upon the inner facies architecture of the volcanic edifices 3 various external environmental controls e g tephra mantling from pyroclastic density currents unrelated to the edifice evaluated and 4 differences in the scale resolution of input data the observed degradation trend and changes in morphometric parameters over time do not support a simple degradation model for monogenetic scoria cones volcanoes

the geology mineralogy petrography and geochemistry of the miocene dursunbey coal within fluvio lacustrine deposits balikesir western turkey abstract the dursunbey coalfield a typical example of coalfields in the western anatolia hosts a mineable coal seam about 9 0 m coal thickness with altered tuff layers within early miocene fluvio lacustrine sequences the aim of this study is to identify peat accumulation conditions and factors controlling the mineralogy and geochemistry of this seam the standard coal features and petrographical mineralogical and elemental compositions display changes throughout the seam ash yields display decreasing trends towards to the upper parts of seam while total c contents and gross calorific values are increasing furthermore the coal facies patterns evidence changes of depositional conditions and vegetation in the palaeomires during initial stages of peat accumulation the contribution of herbaceous peat forming plants were more common and palaeomires were open to detrital inputs whereas woody peat forming were becoming predominant and the water table was stable and high which caused development of anoxic conditions during late stages therefore the content of detrital minerals such as quartz and clay minerals illite smectite and chlorite increases in the lower parts of seam while that of pyrite increases in the upper parts in addition the sem edx data show that matrices of clay mineral aggregates are illitic in composition in the lower parts of seam while those of smectite prevalence are more common below and above altered tuff layers interestingly authigenic rhomboid k feldspar grains are observed within smectite clay aggregates in the samples from the upper parts of seam framboidal pyrite grains and clusters were also commonly identified from these samples as well this data shows that synchronous volcanic inputs were altered within a hydrologically closed system under slight acidic to neutral conditions during late syngenetic stages the enriched elements such as cr ni cs and v display moderate to strong positive correlations with ash yields while al2o3 and k2o indicate an aluminosilicate affinity clay mineral and feldspar considering the presence of metamorphic and ophiolitic rocks in the basement and the adjacent areas clastic inputs into the palaeomire seems to be controlling aluminosilicate affiliated elements additionally the sem edx analyses denoted that ni and as are associated with pyrite the ni and as bearing epigenetic pyrite infillings are mostly identified in coal samples below altered tuff layers hence as and ni enrichments are controlled by precipitation of leached pore waters from altered tuff layers nevertheless as and ni bearing syngenetic pyrite grains and clusters are related with the development of anoxic conditions within palaeomires this could also favour a mo and u enrichment which is another testimony for synchronous volcanic inputs altered under anoxic conditions overall high detrital input ratios from adjacent areas during initial stages of peat accumulation in the study area controlled by enrichments of aluminosilicate affiliated elements whereas during late stages of peat accumulation the development of a hydrologically closed system and redox conditions within the palaeomire caused as ni mo and u enrichments and the formation of smectite and authigenic k feldspars

upper permian lacustrine organic facies evolution southern junggar basin nw china abstract the jingjingzigou lucaogou and hongyanchi formations of the southern junggar basin together comprise over 1000 m of organic rich lacustrine facies they record an overall evolution from relatively shallow evaporative lakes to freshwater lakes associated with fluvial systems the jingjingzigou formation is characterized by low toc and hi and biomarker features such as abundant carotane consistent with a specialized saline or hypersaline biota biomarker distributions in jingjingzigou formation extracts most closely resemble oils from the giant karamay oilfield the lucaogou formation represents one of the richest and thickest lacustrine source rock intervals in the world yet it contradicts conventional lacustrine source rock models in at least two important aspects first deposition occurred at middle paleolatitudes 39 43 n rather than in the tropics second limited nutrient supply in a drainage basin dominated by intermediate volcanic rocks appears to have caused low to moderate primary productivities stable salinity stratification and low inorganic sedimentation rates in a deep lake nonetheless resulted in deposits with up to 20 toc and hi near 800 the overlying hongyanchi formation has 1 5 toc but low hi and was deposited in freshwater oxic to sub oxic lakes

petrographic properties of major coal seams in turkey and their formation abstract most types of coal in turkey are generally low in rank lignite and subbituminous most of the coal was formed during the miocene eocene and pliocene ages there are only a few thin jurassic age coal occurrences in turkey pennsylvanian age bituminous coal is found on the black sea coast general implications of the petrographic properties of turkey s coal seams and coal deposits have not yet been taken into consideration comparatively or as a whole for this study about 190 channel samples were collected from different locales the composite profile samples of the seams were taken into considerations the content and depositional properties as well as some chemical and physical properties of the main coal seams are compared all coal samples tend to have similar coal petrographic properties and were deposited in intermontane lacustrine basins later they were affected by faulting and post depositional volcanic activity as a result there are variations in the properties and rank of the coal samples the most abundant coal maceral group is huminite and the most abundant maceral is gelinite the liptinite and inertinite contents of the coal are low and the maceral contents of the coals show great similarity the depositional environments of the all coals are lacustrine dominated

the growth and erosion of cinder cones in guatemala and el salvador models and statistics abstract morphologic data for 147 cinder cones in southern guatemala and western el salvador are compared with data from the san francisco volcanic field arizona usa cima volcanic field california usa michoacan guanajuato volcanic field mexico and the lamongan volcanic field east java the guatemala cones have an average height of 110 50 m an average basal diameter of 660 230 m and an average top diameter of 180 150 m the general morphology of these cones can be described by their average cone angle of slope 24 7 average height to radius ratio 0 33 0 09 and their flatness 0 24 0 18 although the mean values for the guatemalan cones are similar to those for other volcanic fields e g san francisco volcanic field arizona cima volcanic field california michoacan guanajuato volcanic field mexico and lamongan volcanic field east java the range of morphologies encompasses almost all of those observed worldwide for cinder cones three new 40ar 39ar age dates are combined with 19 previously published dates for cones in guatemala and el salvador there is no indication that the morphologies of these cones have changed over the last 500 1000 ka furthermore a re analysis of published data for other volcanic fields suggests that only in the cima volcanic field of those studied is there clear evidence of degradation with age preliminary results of a numerical model of cinder cone growth are used to show that the range of morphologies observed in the guatemalan cinder cones could all be primary that is due to processes occurring at the time of eruption

factors controlling the trace element distribution in fine grained rocks the albian kaolinite rich deposits of the oliete basin ne spain abstract this paper combines mineralogical data x ray diffraction petrographic and scanning electron microscopy techniques and geochemical analyses in order to investigate the composition of a set of samples claystones siltstones and sandstones which belong to the albian deposits of the oliete basin in spain the aims of the study are to characterize the distribution of major and trace elements in kaolinite rich rocks to infer the role played by accessory phases and clay minerals on the trace element distribution and to assess the source area composition of these materials mineralogical analyses show that these rocks are mainly composed of different proportions of quartz and clay minerals kaolinite and illite with minor feldspar micron accessory minerals such as monazite zircon pyrite marcasite fe oxides and ti oxides have also been detected the sandstone framework implies that the source area of these sediments was probably a granitoid source which underwent low rank metamorphism the major element distribution reflects the mineralogy of the rocks plots in the a cn k diagram as well as their cia values indicate that these sediments were generated from an intensely weathered source area this produced the development of relatively cation poor clays such as kaolinite and claystones with large rare earth elements ree contents the fact that transition element contents in claystones are greater than in siltstones and sandstones suggests that they are preferentially linked to clay minerals probably by surficial sorption in comparison with other lithologies the high abundances of high field strength elements in siltstones imply that accessory minerals such as zircon and nb bearing phases are mainly concentrated in siltstones it should be noted that siltstones are also the lithology which displays the highest ree abundances the statistical analysis of the geochemical data suggests that ree are mainly controlled by ti and nb bearing phases such as titanite and nb and ti oxides although clay minerals are not the main phases in the ree control they probably also have some influence as the analyses show in addition other accessory phases such as monazite secondary phosphates and zircon also contribute to the ree contents although much less than amorphous fe oxides in some samples according to the ree patterns and elemental ratios such as la sc th sc th co etc the source area of the studied outcrops was probably felsic and with intermediate composition between granite and granodiorite

volcanic geomorphological classification of the cinder cones of tenerife canary islands spain this paper proposes a method to establish a morphological classification of tenerife s cinder cones on the basis of a dual analysis of qualitative existence geometry and disposition of craters and quantitative morphometric parameters major and minor diameters and cone elongation major and minor diameters and crater elongation the result obtained is a morphological classification of the cinder cones of tenerife which can be sub divided into four types ring shaped cones horseshoe shaped volcanoes multiple volcanoes and volcanoes without crater in tenerife there is a clear dominance of horseshoe shaped volcanoes 69 0 over ring shaped cones 13 1 volcanoes without craters 11 4 and multiple volcanoes 6 4 the classification presented in this paper is characterized by its simplicity which makes it possible to include all morphological types of volcanoes found in tenerife this fact also renders our classification a useful tool to apply in other both insular and continental volcanic areas to eventually analyze and systematize the study of eruptive edifices with similar traits

properties of a lacustrine subbituminous k1 seam with special reference to the contact metamorphism soma turkey abstract the subbituminous k1 seam in the middle miocene soma formation of western turkey reaches a thickness of 24 m typical samples on an air dried basis have 9 5 14 2 moisture 4 3 13 8 ash and 0 57 2 54 total sulphur the coal rank parameters and non agglomerating behaviour show that the coals are of subbituminous a rank the k1 seam is huminite rich coal with a mean random ulminite reflectance rr between 0 46 and 0 49 fluorescence emission measurements show that the sporinite cutinite resinite and alginite present have typical fluorescence spectra between 460 and 700 nm the soma formation was intruded by an olivine basalt during the pliocene pleistocene which caused local contact metamorphism at the top of the k1 seam on the basis of proximate ultimate and petrographic analyses the intruded seam can be divided into normal coal transition zone and natural coke intervals each differing in their degree of metamorphism moisture volatile matter hydrogen and oxygen contents very rapidly decrease close to the contact point with the intrusion whilst calorific value carbon content and mean random reflectance value increase a diagram ofo c versus h c also shows a distinct increase in rank caused by the intrusion minor illite siderite and plagioclase feldspar are present in the natural coke samples butpyrrhotite is not observed mineralogical geochemical and reflectance studies indicate that the general temperature during formation of natural coke was probably relatively low

petroleum composition in the cuu long basin mekong basin offshore southern vietnam abstract the cuu long basin mekong basin is a rift basin off southern vietnam and the most important petroleum producing basin in the country however information on petroleum type and characteristics has hitherto been largely unavailable to the public this paper presents petroleum geochemical data on nine oil samples from four different producing fields in the cuu long basin the dragon rong black lion sutu den sunrise rang ong and white tiger bach ho fields the oils are highly paraffinic with bimodal normal alkane distributions and show moderate pristane to phytane ratios and a conspicuous hyperbolic decrease in abundance with increasing carbon number of hopane homologues from c30 to c35 the tpp index of holba et al holba a g dzou l i wood g d ellis l adam p schaeffer p albrecht p greene t hughes w b 2003 application of tetracyclic polyprenoids as indicators of input from fresh brackish water environments organic geochemistry 34 441 469 is equal to 1 in all samples which in combination with tricyclic triperpane t26 t25 ratios 1 and the n alkane and hopane distributions mentioned above provide a strong indication of an origin from lacustrine source rocks this is supported by the absence of marine c30 desmethyl steranes i e 24 n propylcholestanes and marine diatom derived norcholestanes based on the overall biological marker distributions the lakes probably belonged to the overfilled or balanced fill types defined by bohacs et al bohacs k m carroll a r neal j e mankiewicz p j 2000 lake basin type source potential and hydrocarbon character an integrated sequence stratigraphic geochemical framework aapg studies in geology 46 3 34 the oils were generated from source rocks at early to mid oil window maturity presumably oligocene lacustrine shales that are present in the syn rift succession oils from individual fields may however be distinguished by a combination of biological marker parameters such as the oleanane index the gammacerane index the relative abundance of tricyclic terpanes the proportions of diasteranes and 28 norspergulane complemented by other parameters the oils of the cuu long basin show an overall similarity to the b 10 oil from the song hong basin off northern vietnam but are markedly different from the seepage oils known from dam thi nai on the coast of central vietnam

short paper ophiolitic detritus in the ordovician sediments of south mayo ireland sandstones from ordovician sediments of the south mayo trough western irish caledonides show marked stratigraphic variation in their major and trace element geochemistry high cr ni and mg concentrations of ultramafic derivation succeed high ti and fe concentrations of mafic provenance this sequence is interpreted as the result of the progressive unroofing of an ophiolite a possible sedimentary linkage with ophiolite lithologies in the clew bay domain to the north would indicate minimal post arenig transcurrent displacement the south mayo flysch with its ophiolitic detritus is typical of caledonian flysch sequences which pre date the mid ordovician taconic deformation but differs in character from those of late ordovician age

40ar 39ar ages from the rhyolite of alder creek california age of the cobb mountain normal polarity subchron revisited new 40 ar 39 ar age determinations on sanidine from the rhyolite of alder creek california indicate a 1 186 0 006 ma age for the cobb mountain normal polarity subchron the new age is statistically older 0 05 than the previously reported k ar age 1 12 0 02 ma and agrees with the age suggested by the astronomical polarity time scale incomplete extraction of radiogenic 40 ar 40 ar from the sanidine is the most likely reason for the disparity between the 40 ar 39 ar and k ar ages because the cobb mountain subchron is a worldwide short duration event and because no widely used interlaboratory 40 ar 39 ar standard younger than 27 ma exists we propose that sanidine from the rhyolite of alder creek be considered for use as a new quaternary 40 ar 39 ar mineral standard

eruptive history of the late quaternary ciomadul csomad volcano east carpathians part ii magma output rates this study which builds on high precision unspiked cassignol gillot k ar age determinations presents an advanced dem based volumetrical analysis to infer long term magma output rates for the late quaternary ciomadul csomad dacitic lava dome complex east carpathians romania the volcanic field of ciomadul developed on the erosional surface of lower cretaceous flysch and 2 ma old andesites and experienced an extended eruptive history from 850 to 30 ka predominantly effusive activity took place during the first stage 850 to 440 ka producing volumetrically minor isolated peripheral domes subsequently after a 250 ky repose interval a voluminous central dome cluster developed in the second stage 200 to 30 ka during the youngest phase of evolution 60 to 30 ka highly explosive eruptions also occurred resulting in the formation of two craters mohos and st ana the calculated 8 00 0 55 km3 total volume of the lava domes which includes the related volcaniclastic 1 57 km3 as well as erosionally removed 0 18 km3 material is in line with dimensions of other medium sized dacitic lava domes worldwide this volume was extruded at an average long term magma output rate of 9 76 km3 my 0 0098 km3 ky however most of the domes 7 53 0 51 km3 were formed in the 200 to 30 ka period implying a significantly increased magma output rate of 37 40 km3 my 0 0374 km3 ky more than 30 times higher than in the first stage within these long term trends individual lava domes of ciomadul e g those with volumes between 0 02 and 0 40 km3 would have been emplaced at much higher rates over a period of years to tens of years the active periods lasting up to hundreds of years would have been followed by repose periods 30 times longer the most recent eruption of ciomadul has been dated here at 27 7 1 4 ka this age which is in agreement with radiocarbon dates for the onset of lake sediment accumulation in st ana crater dates fragmented lava blocks which are possibly related to a disrupted dome this suggests that during the last typically explosive phase of ciomadul lava dome extrusion was still ongoing in a global context the analysis of the volumetric dynamism of ciomadul s activity gives insights into the temporal variations in magma output at lava domes short term day or week scale eruption rates smooth out in long term millenia scale output rates which are tens of times lower

geochemical paleoredox indicators in devonian mississippian black shales central appalachian basin usa the degree of anoxia that existed during accumulation of devonian mississippian black shales in central kentucky has been debated widely in this study geochemical data were used to elucidate paleodepositional environments for these units using analyses from ten cores collected from the outcrop belt in central kentucky sulfur carbon and selected trace element relationships were compared the sunbury shale tournasian lower mississippian and the cleveland and huron members of the ohio new albany shale fammenian upper devonian show different relationships between carbon sulfur and trace elements c s fe relationships for the sunbury suggest anoxic possibly even euxinic conditions prevailed during sediment accumulation analysis of c s fe data suggests that the cleveland may have accumulated under anoxic conditions with intermittent dysoxia whereas the huron member may have accumulated under a relatively wide range of conditions from anoxic to dysoxic to possibly oxic these three units exhibit different degrees of trace element enrichment with the approximate order of enrichment relative to an average shale being mo pb zn v ni cu cr co the sunbury shows the highest levels of enrichment followed by the cleveland with the huron showing only slight enrichment for most of these trace elements differing degrees of enrichment may reflect differences in depositional environment during accumulation high mo concentrations in the sunbury generally 200 550 ppm may infer euxinic conditions prevailed during sediment accumulation the cleveland and the huron both show considerably lower mo contents averaging around 100 ppm geochemical ratios including ni co v cr and v v ni also indicate variable paleoredox conditions for these shales based on previously established thresholds v cr and ni co ratios infer at least anoxic conditions during accumulation of the sunbury anoxic to dysoxic conditions during cleveland accumulation and dysoxic to oxic conditions for the huron v v ni ratios tend to indicate consistently lower oxygen regimes than do other paleoredox indicators and this discrepancy is greatest for the huron member it is suggested that thresholds established for paleoredox indicators in previous studies should not be applied strictly but that relative differences in these indicators collectively can infer variations in the degree of anoxia in addition relationships between corg and redox elements may help elucidate the role of anoxia in om accumulation it may be concluded from this study that the devonian mississippian black shales of central kentucky accumulated under variable bottom water conditions at least anoxic conditions prevailed during accumulation of much of the sunbury shale and the upper part of the cleveland member and possibly euxinic conditions for the sunbury bottom water conditions may have been intermittently anoxic and dysoxic during deposition of the lower cleveland during accumulation of the huron member it is likely that conditions ranged from anoxic to dysoxic to marginally oxic possibly being close to normal marine conditions at times during accumulation of the lowermost huron sediments

vegetation dynamics angiosperm radiation and climatic changes in the lusitanian basin portugal during albian times abstract the mid cretaceous is characterised by significant evolutionary changes in terrestrial ecosystems during this period the typical vegetation consisting of ferns conifers and other gymnosperms was replaced by an angiosperm dominated flora long ranging and continuous records from the continental realm are mostly lacking due to the prevalence of sedimentary gaps here a comprehensive palynological and clay mineralogical dataset covering early albian to early cenomanian strata from the shallow marine sao juliao section lusitanian basin portugal is analysed to reconstruct the vegetation composition as well as climate and weathering conditions in the continental realm the palynological assemblage is dominated by non saccate classopollis and inaperturopollenites gymnosperm pollen with low abundances of spores and angiosperm pollen the clay mineralogical data is mainly composed of kaolinite and mica and shows two conspicuous intervals of high kaolinite abundances in the late albian based on the ecological preferences of the associated parent plants of the spore pollen assemblage a gradual relative temperature increase is inferred in the hinterland of the lusitanian basin during the early albian to early cenomanian interval the clay mineralogy and palynological record show that the climate in the continental hinterland of the lusitanian basin was semi arid to sub humid and punctuated by two distinct humid phases during the late albian multivariate statistical analyses and a comparison with the nearby guincho section demonstrate the significance and reproducibility of the spore pollen record furthermore the palynological assemblage implies that angiosperms and ferns occupied similar palaeo ecological habitats namely as understorey in cheirolepidaceae araucariaceae and cupressaceae conifer dominated forests

monogenetic behind the front volcanism in southeastern guatemala and western el salvador 40ar 39ar ages and tectonic implications abstract eighteen lavas erupted from cinder cones behind the volcanic front in southeastern guatemala and western el salvador have been dated using the 40 ar 39 ar method on groundmass separates plateau ages range between 1069 5 22 1and 37 12 0 ka the majority of dated lavas are younger than 600 ka importantly cinder cone lavas become progressively younger toward the volcanic front trench in addition the lavas become systematically depleted in cs ba rare earth elements cs zr la zr and 18 o with time the baseline values of these same geochemical parameters increase with distance from the volcanic front the cinder cone lavas are closely associated with rifting south of the north american caribbean plate boundary the trenchward migration of behind the front volcanism may be linked to a westward migration of this rifting existing evidence suggests there was an important change in the face of volcanism behind the volcanic front in southeastern guatemala from a small number of large polygenetic volcanoes to abundant smaller monogenetic cones the temporal spatial changes in the geochemistry of cinder cone lavas is attributed to decreasing contamination by paleozoic basement rocks both with time and with diminishing distances to the volcanic front

geochemical characterisation of tithonian berriasian chia gara organic rich rocks in northern iraq with an emphasis on organic matter enrichment and the relationship to the bioproductivity and anoxia conditions abstract tithonian berriasian chia gara organic rich rocks located in kurdistan northern iraq were analysed based on inorganic and organic geochemistry to define the origin type of organic matter and the influencing factors of organic matter om enrichment including the om input and preservation and their relationship to the paleoenvironment conditions the 13 c org values of the chia gara rocks range from 29 99 to 26 93 with average values of approximately 28 8 indicating that the organic matter has a predominantly marine origin enhanced biological productivity within the photic zone of the water column during deposition of the chia gara fm is indicated by consistently high organic carbon content in most samples average 3 wt as well as by bulk geochemical and biomarker characteristics major contributions by aquatic algae and microorganisms with a minor terrigenous organic matter contribution are indicated by the n alkane distribution patterns and the composition of the hopanoids steroids and tricyclic terpenoids strongly reducing bottom water is indicated by low pristane phytane ratios homohopane distribution patterns and the redox sensitive trace elements geochemistry salinity stratification with alkaline bottom waters is indicated by high sr ba ratios and the presence of gammacerane in the analysed chia gara samples these data indicate that om enrichment in the tithonian berriasian chia gara rocks results from the combination of enhanced biological productivity and salinity stratification with anoxic bottom water conditions which favoured om preservation

a review of anomalous rare earth elements and yttrium in coal abstract coal deposits have attracted much attention in recent years as promising alternative raw sources for rare earth elements and yttrium rey not only because the rey concentrations in many coals or coal ashes are equal to or higher than those found in conventional types of rey ores but also because of the world wide demand for rey in recent years has been greater than supply in addition to anomalies of enrichment or depletion of light medium and heavy rey in coal deposits normalized to upper continental crust post archean australian shale or north american shale composite anomalies of redox sensitive ce and eu and in some cases of non redox sensitive la gd and y could be used as geochemical indicators of the sediment source region sedimentary environment tectonic evolution and post depositional history of coal deposits factors controlling rey anomalies in coal deposits include the geochemistry of terrigenous source rocks ingress of hydrothermal fluids influence of marine environments percolating natural waters volcanic ashes and sedimentary environments of peat formation additionally the smoothness of a normalized rey distribution pattern provides a simple but reliable basis for testing the quality of rey chemical analyses for coal and other sedimentary rocks

barite accumulation ocean productivity and sr ba in barite across the paleocene eocene thermal maximum the paleocene eocene thermal maximum petm ca 55 ma was a period of extreme global warming caused by rapid emission of greenhouse gases it is unknown what ended this episode of greenhouse warming but high oceanic export productivity over thousands of years as indicated by high accumulation rates of barium ba may have been a factor in ending this warm period by carbon sequestration however ba has a short oceanic residence time 10 k y so a prolonged global increase in ba accumulation rates requires an increase in input of ba to the ocean increasing barite saturation we use a novel proxy for barite saturation sr ba in marine barite to demonstrate that the seawater saturation state with respect to barite did not change across the petm the observations of increased barite burial no change in saturation and the short residence time can be reconciled if ba burial decreased at continental margin and shelf sites due to widespread occurrence of suboxic conditions leading to ba release into the water column combined with increased biological export production at some pelagic sites resulting in ba sink reorganization

degradation of quaternary cinder cones in the cima volcanic field mojave desert california basaltic cinder cones in the cima volcanic field record a detailed history of progressive erosion in the arid environment of the eastern mojave desert these cones range in age from 0 015 m y to 1 09 0 08 m y as dated by radiocarbon or k ar analyses of the youngest lava flows from each cone cone heights range from 50 to 155 m and basal widths range from 400 to 915 m on younger cones height width ratios average 0 17 and crater width cone width ratios average 0 42 the degradational morphology of these cones displays several trends that are closely related to cone age 1 crater width cone width ratios decrease from 0 48 on the youngest cone to 0 21 on the oldest cone with a preserved crater 2 mean maximum side slopes tan sc decrease from 0 575 on the youngest cone to an average of 0 41 on the oldest cones studied 3 debris apron height cone height ratios increase from 0 10 on the youngest cone to an average of 0 34 on the oldest cones 4 cone drainage evolves from irregularly spaced rills and gullies on the youngest cone to regularly spaced gullies on 0 20 to 0 35 m y old cones to valleys as much as 110 m wide and 10 m deep on cones 0 59 m y old and older these trends form the basis of an empirical model of cinder cone degradation in arid environments this model documents 1 an erosional loss of 15 of cone volume during the first million years 2 progressive decline of cone slope at an average rate of 0 006 103 yr and cone height at an average rate of 2 25 cm 103 yr 3 initial rapid stripping of the loose cinder mantle from upper cone slopes accompanied by rapid debris apron formation and 4 a gradual transition between 0 25 and 0 6 m y from relatively uniform stripping of upper slopes to localized fluvial dissection of both cone slopes and debris apron this transition is apparently controlled by a concomitant change from diffuse subsurface drainage within the pervious cinder mantle to concentrated surface flow across the heterogeneous assemblage of agglutinate layers dikes and ponded flows of the cone interior

geomorphometric variability of monogenetic volcanic cones evidence from mauna kea lanzarote and experimental cones abstract volcanic cones are the most common volcanic constructs on earth their shape can be quantified using two morphometric ratios the crater cone base ratio wcr wco and the cone height width ratio hco wco the average values for these ratios obtained over entire cone fields have been explained by the repose angle of loose granular material i e scoria controlling cone slopes the observed variability in these ratios between individual cones has been attributed to the effect of erosional processes or contrasting eruptive conditions on cone morphometry using a gis based approach high spatial resolution digital elevation models and airphotos two new geomorphometry datasets for cone fields at mauna kea hawaii usa and lanzarote canary islands spain are extracted and analyzed here the key observation in these datasets is the great variability in morphometric ratios even for simple shape and well preserved cones simple analog experiments are presented to analyze factors influencing the morphometric ratios the formation of a crater is simulated within an analog cone i e a sand pile by opening a drainage conduit at the cone base results from experiments show that variability in the morphometric ratios can be attributed to variations in the width height and horizontal offset of the drainage point relative to the cone symmetry axis to the dip of the underlying slope or to the influence of a small proportion of fine cohesive material gis analysis and analog experiments together with specific examples of cones documented in the field suggest that the morphometric ratios for well preserved volcanic cones are controlled by a combination of 1 the intrinsic cone material properties 2 time dependent eruption conditions 3 the local setting and 4 the method used to estimate the cone height implications for interpreting cone morphometry solely as either an age or as an eruption condition indicator are highlighted

semi automatic delimitation of volcanic edifice boundaries validation and application to the cinder cones of the tancitaro nueva italia region michoacan guanajuato volcanic field mexico abstract the shape and size of monogenetic volcanoes are the result of complex evolutions involving the interaction of eruptive activity structural setting and degradational processes morphological studies of cinder cones aim to evaluate volcanic hazard on the earth and to decipher the origins of various structures on extraterrestrial planets efforts have been dedicated so far to the characterization of the cinder cone morphology in a systematic and comparable manner however manual delimitation is time consuming and influenced by the user subjectivity but on the other hand automatic boundary delimitation of volcanic terrains can be affected by irregular topography in this work the semi automatic delimitation of volcanic edifice boundaries proposed by grosse et al 2009 for stratovolcanoes was tested for the first time over monogenetic cinder cones the method based on the integration of the dem derived slope and curvature maps is applied here to the tancitaro nueva italia region of the michoacan guanajuato volcanic field mexico where 309 plio quaternary cinder cones are located the semiautomatic extraction allowed identification of 137 of the 309 cinder cones of the tancitaro nueva italia region recognized by means of the manual extraction this value corresponds to the 44 3 of the total number of cinder cones analysis on vent alignments allowed us to identify ne sw vent alignments and cone elongations consistent with a ne sw max and a nw se min constructing a vent intensity map based on computing the number of vents within a radius r centred on each vent of the data set and choosing r 5 km four vent intensity maxima were derived one is positioned in the nw with respect to the volcano tancitaro one in the ne one to the s and another vent cluster located at the se boundary of the studied area the spacing of centroid of each cluster 24 km can be related to the thickness of the crust 9 10 km overlying the magma reservoir

compositional variations of olivine and sulfur isotopes in the noril sk and talnakh intrusions siberia implications for ore forming processes in dynamic magma conduits olivine from the noril sk i main and northwestern talnakh ore bearing intrusions in the noril sk region occurs as inclusions discrete grains and poikilitic crystals the original compositions of olivine inclusions have been well preserved by their host oikocrysts from reaction with interstitial silicate and sulfide liquids in contrast the compositions of discrete and poikilitic olivine crystals have been variably modified by reequilibration with trapped silicate and sulfide liquids there are abrupt changes in the contents of nickel in olivine inclusions 500 1 500 ppm between different rock units in all three intrusions which indicates that the different rock units in these intrusions are not related to each other via in situ differentiation of a common parental magma but rather are consistent with separate pulses of magma with variable degrees of differentiation possibly involving olivine crystallization and assimilation of siliceous crustal material in a staging chamber the 34s values of the samples with high sulfur contents 800 ppm sulfur from all three ore bearing intrusions vary between 8 and 14 per mil two sulfur poor samples 600 ppm sulfur from the northwestern talnakh intrusion yield 34s values of 1 5 and 3 6 per mil these values are similar to the values of the sulfur poor rocks from the ore barren intrusions in the region and illustrate the fact that high sulfur contents couple with increasing 34s values such a relationship is consistent with the addition of crustally derived 34s enriched sulfur to the magma of the ore bearing intrusions in contrast to other models of sulfide segregation in closed systems we propose that sulfide segregation occurred in an open system and the magma involved was undersaturated in sulfur and undepleted in chalcophile elements we envision that the 34s enriched sulfur was introduced via circulating fluids that transported sulfur from evaporite in the underlying sedimentary sequence to the magma in a dynamic magma conduit the immiscible sulfide liquids that segregated during sulfur contamination settled down in the wider parts of the conduit as the magma continued to travel successive pulses of new magma entered the conduit reacted with the early sulfide and displaced much of the early magma in the conduit the ore bearing intrusions are thought to have crystallized within the wider parts of the conduits and their voluminous sulfide poor peripheral sills represent some if not all of the magma that flowed out of the conduits

sr ba in barite a proxy of barite preservation in marine sediments abstract the observation by bertram and cowen j mar res 55 1997 577 593 that the strontium content of marine barite decreased from the water column to the deep sea floor suggested that the sr ba ratio in barite was sensitive to barite dissolution following this observation we have investigated the potential of using the sr ba ratio in barite as a proxy of barite preservation by separating barite crystals from sediment cores collected at different water depths in the equatorial pacific and in the southern ocean our investigations do not reveal significant downcore variations in the sr ba ratios during the holocene period in the two basins and up to a few hundred thousand years in the equatorial pacific however a comparison of the mean sr ba ratios in individual cores suggests that the sr ba ratios in barite decrease with increasing water depth a feature that could be related to dissolution of barite crystals during settling to the deep sea floor and or at the sediment water interface if confirmed the sr ba ratios in barite could be used to infer the intensity of barite dissolution and the state of preservation of barite crystals in sediments such information could be employed usefully in paleoproductivity reconstructions for the purpose of distinguishing between productivity and dissolution signals affecting barite distributions in marine sediments

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

geochemical composition of oils in the dunga field western kazakhstan evidence for a lacustrine source and a complex filling history abstract the onshore mangyshlak basin located in western kazakhstan along the eastern coastline of the caspian sea is a prolific hydrocarbon province and home to numerous oil and gas fields the primary reservoirs are jurassic clastic sandstones but the dunga field contains hydrocarbons in lower cretaceous valanginian barremian aptian albian clastic and carbonate reservoirs the general perception is that these petroleum accumulations were charged from marine source rocks of likely middle triassic age a detailed organic geochemical investigation of oils from the cretaceous reservoirs of dunga field suggests that all were generated from the same lacustrine source rock facies organofacies c in mature kitchens in the offshore mangyshlak basin followed by a complex filling history the oils are characterised by relatively high wax content low sulfur content mainly