sedimentology and isotope geochemistry of carnian deep water marl limestone deposits from the sicani mountains sicily environmental implications and evidence for a planktonic source of lime mud abstract the upper triassic halobia bearing marl limestone deposits from the sicani mountains sicily record the sedimentary evolution of the sicanian basin through the middle and late carnian time dark marls and interbedded grey calcilutites of julian age are characterized by abundant pyrite sparse bioturbation and negative carbonate carbon 13c values they accumulated in a basin with dominantly anoxic to dysaerobic bottom waters lower tuvalian dark grey pyritic marls and calcilutites which contain carbonate minerals with relatively high mn contents and widely fluctuating 13c signatures were deposited under dysaerobic conditions middle and upper tuvalian cherty limestones show intense bioturbation and nearly invariable positive 13c values around 2 for calcite they form a thick and monotonous succession accumulated in a deeper and more oxygenated basin the halobia bearing deposits preserve some calcareous nannoplanktonic forms the nannofossils varying in size from 7 to 32 m are significantly abundant in the cherty limestones pointing to a notable role of the calcareous nannoplankton as a source of carbonate mud in the deep water basins of the southern tethys during the late triassic time

early diagenetic silica deposition in algal cysts and spores a source of sand in black shales abstract devonian black shales deposited on the north american craton contain abundant tasmanites cysts although these are typically flattened because of compaction a small proportion are filled with diagenetic silica the latter are spherical to ellipsoidal 0 1 0 5 mm and filled with chalcedony microquartz and megaquartz and single quartz crystals chalcedonic cyst fillings are preserved best in cheat and phosphate nodules whereas megaquartz and single quartz crystals are most common in shale matrix together with colloform textures this suggests that the various silica types originated from recrystallization of early diagenetic silica deposits thin sandstone beds in the chattanooga shale e g bransford sandstone contain abundant quartz sand that is much coarser than the detrital quartz component of the underlying black shales because of this their quartz component is thought to have been transported over considerable distances from the basin margin however because certain shale horizons contain as much as 10 silicified cysts that upon reworking could have yielded quartz grains of fine to coarse sand size the quartz component of these sandstone beds may actually have formed in situ indeed petrographic examination of the sandstone beds shows them to contain quartz grains with morphological and textural features of cyst quartz e g rounding sphericity chalcedony pyrite inclusions lobate grain margins thus silica deposition in algal cysts may provide a significant component of intrabasinal quartz sand in shale sequences distinction of this type of quartz from extrabasinal detrital quartz is important to the reconstruction of the depositional history of shale sequences

carnian norian biomagnetostratigraphy at silicka brezova slovakia correlation to other tethyan sections and to the newark basin correlations of upper triassic magnetic stratigraphies from tethyan sections have been hampered by difficulties with conodont biostratigraphy and taxonomy and discontinuous sedimentation particularly in the hallstatt limestones of turkey and austria the magnetic stratigraphy and conodont biostratigraphy from the upper carnian to upper norian limestones exposed at silickabrezova slovakia can be correlated to other tethyan sections and to the continental succession in the newark basin the resulting correlations help to resolve some of the apparent discrepancies in existing conodont zonations and result in a revised correlation to north american terrestrial vertebrate and palynological zones the correlations imply that the norian rhaetian boundary lies within newark polarity zone e17r at v207 ma the carnian norian boundary lies close to the base of newark polarity zone e7r at v226 ma this implies durations for the norian and rhaetian stages of 19 myr and 7 myr respectively 2002 elsevier science b v all rights reserved

integrated upper carnian to lower norian biochronology and implications for the upper triassic magnetic polarity time scale abstract we summarize the ammonoid conodont and halobiid biochronology of the upper carnian to lower norian based on a discussion of data in the alps sicily balkans turkey himalayas and timor with this integrated biostratigraphic scale the pizzo mondello section sicily can be recalibrated and the carnian norian boundary more precisely located there as a result the magnetostratigraphy of this section is now in good agreement with previous results from turkey although the latter series are more condensed cross correlation of available magnetostratigraphic data from marine tethyan sections allow us to construct a composite upper carnian to upper norian geomagnetic polarity time scale gpts this gpts leads us to question previously proposed magnetobiostratigraphic and chronostratigraphic correlations within the upper triassic newark non marine sedimentary sequence

emplacement of pyroclastic density currents pdcs in a deep sea environment the val d aveto formation case northern apennines italy abstract the occurrence of pdc deposits in a foredeep basin sequence named val d aveto formation 32 29 ma northern apennines italy provides new information on the behavior of pyroclastic density currents entering the water in this work stratigraphic petrographic and mineralogical features that characterize three pyroclastic deposits have been described and analyzed in the field facies and lithological analysis on the blocky size fraction and in the laboratory image analyses on the blocky size detritus optical analyses of the microtextures mineralogical analyses through x ray powder diffraction xrpd and scanning electron microscope with energy dispersive x ray spectometry sem eds the deposits are lapilli to blocky size with a blocky size fraction constituted of accidental detritus in thin sections their groundmass texture varies from porphyritic to eutaxitic where coarser particles become close each others growth rims have been also detected around plagioclase crystals pyrite habits and oxidation and plagioclase albitization are consistent with hydrothermal temperature conditions of 200 c all these results have been compared with the information provided by modern examples of pdc deposits and laboratory experiments on the behavior of water hot particles mixing grain to grain collision has been considered as the main flow mechanism that sustained and avoided the disaggregation of the pdcs entering the water

subaqueous explosive eruption and welding of pyroclastic deposits silicic tuffs infilling an ancient submarine caldera at mineral king in california show microscopic fabrics indicative of welding of glass shards and pumice at temperatures 500 degrees c the occurrence indicates that subaqueous explosive eruption and emplacement of pyroclastic materials can occur without substantial admixture of the ambient water which would cause chilling intracaldera progressive aggradation of pumice and ash from a thick fast moving pyroclastic flow occurred during a short lived explosive eruption of approximately 26 cubic kilometers of magma in water 150 meters deep the thickness high velocity and abundant fine material of the erupted gas solids mixture prevented substantial incorporation of ambient water into the flow stripping of pyroclasts from upper surfaces of subaqueous pyroclastic flows in general both above the vent and along any flow path may be the main process giving rise to buoyant convective subaqueous eruption columns and attendant fallout deposits

water magma interaction some theory and experiments on peperite formation experiments using molten thermite as a magma analog produce peperite when the melt interacts with wet sand these experiments also show explosive behavior developing strombolian and surtseyan like bursts the results demonstrate that the application of fuel coolant interaction fci theory is appropriate for interpretation of peperites the theory described includes discussion of the importance of mass interaction ratios of wet sediment and magma rs which determine thermal equilibrium temperature limits and contact interface dynamics the dynamics of the interface between magma and wet sediments involves heat transfer over a wide range of rates from passive quenching to explosive fragmentation a vapor film layer develops at the interface and acts both as an insulating barrier promoting passive quenching as well as a potential energy reservoir that can cause magma fragmentation mingling of the magma with wet sediments and explosive quenching when the vapor film becomes unstable an important parameter in determining the behavior of the vapor film is the value of rs which controls whether heat can be convectively removed from the layer as more is being added from its contact with magma if rs 1 for fully saturated sediments there is enough water in the sediments to make convective heat flow effective in quenching the magma but below that value there is the potential that the vapor film will be unstable producing highly dynamic phenomena including explosive fragmentation at values of rs 0 1 there is insufficient water to allow the escalation of explosive fragmentation

evolution of pangea paleomagnetic constraints from the southern alps italy abstract a new early late triassic paleopole for adria has been obtained from the val sabbia sandstone in the southern alps as early permian and jurassic cretaceous paleomagnetic data from para autochthonous regions of adria such as the southern alps are consistent with african apwps 1 2 paleomagnetic data from this region can be used to bolster the west gondwana apwp in the poorly known late permian triassic time interval the southern alpine paleopoles are integrated with the west gondwana and laurussia apwps of van der voo 1 and used to generate a tectonic model for the evolution of pangea the early permian overall mean paleopole for west gondwana and adria in conjunction with the coeval laurussia paleopole support pangea b of morel and irving 3 the late permian early triassic and the middle late triassic paleopoles from adria and laurussia support pangea a 2 of van der voo and french 4 the phase of transcurrent motion between laurasia and gondwana 5 that caused the pangea b to a 2 transition occurred essentially in the permian at the end of variscan orogeny with an average relative velocity of approximately 10 cm yr finally the late triassic early jurassic paleopoles from west gondwana and laurussia agree with pangea a 1 of bullard et al 6 the widely accepted pangea configuration at the time of the jurassic breakup

chemical weathering of mafic rocks in boreal subarctic environment northwest russia under influence of glacial moraine deposits abstract chemical weathering of mafic rocks represents substantial sink of atmospheric co2 yet the mechanismes of this process in high latitude regions are poorly understood this work addresses geochemical migration and partitioning of major and trace elements between rock soil and surface waters during chemical weathering of mafic rocks and soil formation under the influence of a glacial moraine in the northwestern russian subarctic we used multidisciplinary approach which included major and trace element chemical analysis sr isotopic measurements and mineralogical structural and microscopic investigations quaternary pleistocene deposits were observed even in the deepest horizons of soil profiles and confirm a strong moraine influence as most soils showed podzolic features chemical and sr isotopic analyses revealed a strong impact of the moraine on soil chemistry and mineralogy mineralogical studies showed the presence of non aeolian quartz and zircon in soils which were not linked to the nature of the parental rocks i e mafic and felsic at the same time we observed the presence of etch pit corrosion on the surface of zircons and feldspars and a newly formed matter adjacent to the surface of primary phases the chemical index of alteration cia showed weak or no weathering of rocks within the soil profile and the weathering intensity scale confirmed the felsic chemical composition of soils developed over mafic and ultramafic rocks analysis of sr radiogenic isotopes demonstrated preferential removal of easily weatherable and less radiogenic minerals over the full depth of soil profile and a more radiogenic signature of the granitic moraine compared to mafic and felsic bedrocks the composition of most surface waters reflected the weathering of silicate rocks but did not allow for distinguishing purely mafic source the chemical weathering rates of ultramafic rocks were calculated to be higher than those for the granitic till but the moraine depositions which dominate this region hide evidence of the real weathering process this could be due to retention of mg and ca in soil due to precipitation of secondary phases such as mg vermiculite or divalent cation adsorption on mineral organic or organo mineral phases as a result weathering rates estimated for the olivinite rock appear to be lower than the weathering rates of mafic rocks reported in other boreal and subarctic regions overall the felsic moraine deposits are capable to sizably decrease the weathering intensity of mafic rocks which should be taken into account for chemical weathering modelling of high latitude regions subjected to glaciation in the past

a middle late triassic ladinian rhaetian carbon and oxygen isotope record from the tethyan ocean abstract we obtained bulk sediment 18o and 13c data from biostratigraphically constrained tethyan marine sections at aghia marina greece guri zi albania and brumano and italcementi quarry italy and revised the published chemostratigraphy of the pizzo mondello section italy we migrated these records from the depth to the time domain using available chronostratigraphic tie points generating ladinian rhaetian 13c and 18o records spanning from 242 to 201 ma the 18o record seems to be affected by diagenesis whereas the 13c record appears to preserve a primary signal and shows values increasing by 1 in the ladinian followed by an 0 6 decrease across the ladinian carnian boundary followed by relatively constant but oscillatory carnian values punctuated by a negative excursion at 233 ma in the early carnian a second negative excursion at 229 5 ma across the early late carnian boundary and a positive excursion at 227 ma across the carnian norian boundary the norian record is characterized by a long term decreasing trend and a negative excursion at 216 ma rapid increases and decreases in 13c have been observed in the rhaetian but these may be at least in part due to mixing of different sources of carbonate carbon with different 13c values our triassic 13c record has been compared to data from the literature and a composite 13c record spanning the last 242 myr of earth s history has been generated this composite record shows a sequence of dated 13c trends and events that can be used for stratigraphic correlation as well as for a better understanding of the global carbon cycle in the mesozoic cenozoic

microseismic hydraulic fracture imaging the path toward optimizing shale gas production economic shale gas production involves hydraulic fracture stimulation in order to create permeable flow paths within these low permeability reservoirs microseismic monitoring has shown that often these fracs consist of complex fracture networks with large surface contact areas with the reservoir optimized production is therefore dependent on the ability of the stimulation to activate an extensive fracture network much of the current attention around hydraulic fractures focuses on microseismic imaging of the activated network however the path toward optimized shale gas production also requires methods to both predict and model the fracture networks along the path engineers will be able to close the loop for an optimally designed stimulation being able to predict monitor and assess the stimulated fracture network as an industry we are just starting down this path and this paper describes a few case studies that highlight recent advancements before we can ultimately predict the fracture netw

hydrothermal dolomites in sw sardinia italy evidence for a widespread late variscan fluid flow event abstract epigenetic replacive and saddle dolomite frequently forming zebra structures geodic dolomite affected cambrian limestones and early diagenetic dolomites across large areas of the iglesiente sulcis mining district sw sardinia italy the dolomite crops out in an area of more than 500 km 2 and reaches a thickness of up to 600 m or even more this rock represents one of the most extensive dolomites of epigenetic origin yet documented prior to dolomitization the cambrian carbonates underwent ductile deformation and greenschist facies metamorphism the same is true for the overlying tectonic nappes fluid inclusion analysis combined with o and sr isotope data indicate that the dolomitizing fluid can be categorized as a basinal brine the spread in homogenization temperatures shows a gradient with values decreasing from east to west the higher temperatures mean of around 100 c have been measured in eastern parts of the iglesiente area whereas the lowermost temperatures mean of about 85 c have been found along the western coast of iglesiente this fluid certainly can neither have come directly from the low grade metamorphic lithotypes undergoing dolomitization nor from the low temperature metamorphic rocks within the overlying nappes it is assumed that a late variscan hydrothermal event which coincided with extensional tectonics set brine circulation into motion dolomitization may have occurred within circulation cells which were driven by high heat flow fluids originated in the underlying rocks and circulated upward to affect the overlying cambrian carbonates an alternative model is that the dolomitization was caused by hydrothermal brines that originated within basinal areas of the variscan orogenic pile circulating deep within the crust and ascended in the external zone iglesiente sulcis whatever the origin these reducing saline fluids which carried radiogenic sr dolomitized a large volume of early paleozoic rocks the many subhorizontal open cavities within the geodic dolomite only partly filled with cement might indicate fluid overpressure at the time of dolomitization

east pacific rise near 13 n geology of new hydrothermal fields abundant massive sulfide deposits are present at the crest of the east pacific rise near 13 north where the opening rate is about 12 centimeters per year large manganese and helium 3 anomalies in seawater samples evidence of intense present day activity of hydrothermal springs indicate that sulfides are still being produced along this segment of the rise massive sulfides also occur on adjacent off axis seamounts

long term cycles of triassic climate change a new δ18o record from conodont apatite jat and isw gratefully acknowledge financial support from the australian research council dp1096252 mr is grateful for financial support from progetto d ateneo 2009 cpda090175 09 and 2012 cpda 121100 and prin 2008 2008bef5z7 005

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

liquid and plastic limits of mountain soils as a function of the soil and horizon type soil degradation by processes such as soil erosion shallow landslides debris flows etc is a significant problem in mountain areas and is a crucial issue for natural hazard assessment in mountain areas several soil properties among which are the liquid and plastic limits i e moisture contents for which a soil passes from the plastic to liquid state liquid limit ll and from the semisolid to plastic state pl plastic limit have been proposed as indicators for soil vulnerability to degradation processes both of natural and anthropogenic origin in this research we investigated the liquid and plastic limits of the main soil groups of world reference base for soil resources wrb classification present in aosta valley n w italian alps from a pedogenic perspective in particular we compared 1 soils at different stages of development and 2 different genetic horizons our main aim was to provide and interpret data on soils consistency and mechanical behavior that may be used as indexes for the assessment of soil vulnerability despite its relatively small area the aosta valley is characterized by a wide range of soil types sixty two soils with different profile evolution stages representative of 7 wrb soil groups were investigated and ll and pl in genetic horizons were studied at the soil type and genetic horizons level in general soil consistency was largely determined by the organic matter content both in topsoils and organic matter enriched subsurface horizons but in spodic horizons and some c horizons a role of poorly crystalline and pedogenic iron oxides was observed too considering the vulnerability to consistency loss that can result in erosion processes and overall soil degradation surface horizons were generally less vulnerable as could be expected on the basis of previous research i e showed higher ll and pl values than the deeper ones generally characterized by a reduction of soil consistency therefore topsoil could receive higher water inputs while still preserving their consistency and strength this was not confirmed in podzols where the organic matter enrichment of spodic horizons determined a discontinuity in physical properties between the e horizons more vulnerable and the underlying spodic ones the same trend was observed for calcisols with a deep cemented bkm horizon the research provided a novel overview on ll and pl in the common soil types present in the alpine region integrating the already existing research on topsoil vulnerability to degradation processes erosion consistency losses losses of strength and the regional soil database the use of ll and pl as indicators of soil physical quality was approached with a pedogenic perspective which might be helpful for a better definition of hazard assessment at the regional scale

subaqueous eruption fed density currents and their deposits density currents fed directly from subaqueous eruptions can be divided conceptually into three groups based on modes of fragmentation and transport i explosive fragmentation with deposition from a gas supported current ii explosive fragmentation with deposition from a water supported current iii fragmentation of flowing lava with deposition from a water supported current fig 1 group i products include subaqueously emplaced welded ignimbrite and other high temperature emplaced subaqueous pyroclastic flow deposits group ii products are the most varied and include representatives of both high and low concentration turbidity currents grainflows and debris flows and are termed eruption fed aqueous density currents some clasts in such currents are transported and even deposited at high temperature but the transporting currents ranging from grain flows to dilute turbidity currents are water dominated even though steam may be developed along large clasts margins group iii products formed from lava flow fed density currents tend to be weakly dispersed down gradient along the seafloor and generally consist largely of fragments formed by dynamo thermal quenching and spalling bursting of bubbles formed by vapor expansion probably contributes to some group iii beds distinctive column margin fall deposits may form in water excluded zones that developed very locally around vents in association with group i and ii deposits and are distinguished by heat retention structures indicators of gas phase transport and absence of current formed depositional features 2000 elsevier science b v all rights reserved

organic geochemistry of mississippian shales bowland shale formation in central britain implications for depositional environment source rock and gas shale potential abstract marine carboniferous shales are proven hydrocarbon source rocks in central britain in this contribution the depositional environment and shale gas liquid potential of the lower namurian part of the bowland shale formation is studied using 77 thermally immature samples from the duffield borehole the bowland shale formation comprises mudstone and turibidite lithofacies reflecting a pronounced sea level controlled cyclicity the total organic carbon toc content of the mudstones lithofacies including marine bands and of fine grained rocks within the turibidite lithofacies varies between 1 3 and 9 1 hydrogen index hi values imply the presence of kerogen type iii ii according to biomarker ratios and bulk geochemical parameters marine bands maximum flooding surfaces mfs were deposited in deep water with slightly enhanced normal or slightly reduced salinity mudstones of the highstand systems tract hst were deposited in environments with normal to reduced salinity whereas photic zone anoxia favoured the preservation of marine organic matter during deposition of the mfs and the hst the supply of landplant debris increased during the hst turbidites and their non calcareous mudstone equivalents represent lowstand systems tracts deposited in low salinity environments terrestrial organic matter dominates in turbiditic sediments marine organisms prevail in time equivalent mudstones mudstone beneath marine bands represents transgressive systems tracts when normal marine conditions and photic zone anoxia were re established the mudstone lithofacies exhibits a very good to excellent potential to generate conventional mixed oil and gas toc content of fine grained rocks in the turbidite lithofacies depends on the amount of detrital minerals supplied from the south moreover their organic matter is gas prone high toc contents and large thicknesses of the mudstone lithofacies show that the bowland shale formation holds a significant shale gas liquid potential in areas with appropriate maturity a relatively low average hi and high clay contents may have negative effects on the shale gas potential

vegetation influence on soil formation rate in a proglacial chronosequence lys glacier nw italian alps abstract climate change has huge impacts on alpine ecosystems one of the most visible effects in the alps is glacier retreat since the end of the little ice age lia which caused the exposure of previously glaciated surfaces these surfaces are open air laboratories verifying theories regarding ecosystem and soil development in order to increase our knowledge on the effects of time and vegetation primary succession on soil development in proglacial areas we sampled soils and surveyed plant communities on stable points in the proglacial area of the lys glacier in the italian north western alps valle d aosta region the sampling points were located on dated sites based on literature and or historical photographs glacial till is attacked by weathering processes immediately after deposition and stabilization with a consequent loss of soluble compounds decrease of ph and primary mineral weathering the speed of these processes was largely increased after the establishment of a continuous vegetation cover thanks to the organic matter accumulation caused by litter input and root decomposition below the soil surface on sialic glacial tills below timberline and under a quasi climax larch rhododendron forest fast and steady decrease in ph values increase in organic matter content and horizon differentiation were observed in particular genetic eluvial horizons formed in approximately 60 years while diagnostic albic horizons were developed after ca 90 years pointing to an early start of the podzolization processes cheluviations of fe and secondarily al were analytically verified however illuviations of fe al and organic matter in incipient b horizons were not sufficient to obtain diagnostic spodic horizons on lia materials under grazed grassland below timberline and alpine prairie above timberline acidification and weathering were slightly slower and no redistribution with the depths of fe and al oxi hydroxides was observed a cambic bw horizon developed on the oldest lia moraines therefore it seemed that this fast onset of the podzolization process in comparison to other proglacial chronosequences in the alps was mainly driven by vegetation properties rather than by specific climatic conditions

the submarine eruption of the bombarda volcano milos island cyclades greece the milos volcanic field includes a well exposed volcaniclastic succession which records a long history of submarine explosive volcanism the bombarda volcano a rhyolitic monogenetic center erupted 1 7 ma at a depth 200 m below sea level the aphyric products are represented by a volcaniclastic apron up to 50 m thick and a lava dome the apron is composed of pale gray juvenile fragments and accessory lithic clasts ranging from ash to blocks the juvenile clasts are highly vesicular to non vesicular the vesicles are dominantly tube vesicles the volcaniclastic apron is made up of three fades massive to normally graded pumice lithic breccia stratified pumice lithic breccia and laminated ash with pumice blocks we interpret the apron beds to be the result of water supported volcaniclastic mass how emplacement derived directly from the collapse of a small volume subaqueous eruption column and from syn eruptive down slope resedimentation of volcaniclastic debris during this eruptive phase the activity could have involved a complex combination of phreatomagmatic explosions and minor submarine effusion the lava dome emplaced later in the source area is made up of flow banded lava and separated from the apron by an obsidian carapace a few meters thick the near vertical orientation of the carapace suggests that the dome was intruded within the apron remobilization of pyroclastic debris could have been triggered by seismic activity and the lava dome emplacement

the aftermath of the cpe and the carnian norian transition in northwestern sichuan basin south china the northwestern sichuan basin south china was a portion of eastern tethys where during the late triassic a sharp lithological transition from oolitic bioclastic limestones and sponge reef mounds to dark grey terrigenous clays siltstones and sandstones is visible in several localities the timing and significance of this major facies transition is still unclear here we report new biostratigraphic and carbon stable isotope data from hanwang and jushui northwestern sichuan basin sporomorphs ammonoids conodonts and halobiid bivalves show that the lithological change is late carnian to early norian in age this amended age determination facilitates recalibration of the magnetostratigraphy in the area allowing correlation between the late triassic of the sichuan basin and the astrochronostratigraphic polarity time scale a carbon stable isotopic perturbation across the carnian norian boundary cnb is missing in our sections or it is concealed because of the mixed organic matter sources our findings pinpoint the position of the cnb to a short stratigraphic interval of c 12 m thickness in the sichuan basin the studied sections greatly extend the palaeogeographical documentation of the cnb and provide novel information on biostratigraphy and chemostratigraphy that should be considered in defining the best position of the norian global stratotype section and point

organic matter hosted pore system marcellus formation devonian pennsylvania the marcellus formation of pennsylvania represents an outstanding example of an organic matter om hosted pore system most pores detectable by field emission scanning electron microscopy fe sem are associated with om instead of mineral matrix in the two wells studied here total organic carbon toc content is a stronger control on om hosted porosity than is thermal maturity the two study wells span a maturity from late wet gas vitrinite reflectance ro 1 0 to dry gas ro 2 1 samples with a toc less than 5 5 wt display a positive correlation between toc and porosity but samples with a toc greater than 5 5 wt display little or no increase in porosity with a further increasing toc in a subset of samples 14 across a range of toc 2 3 13 6 wt the pore volume detectable by fe sem is a small fraction of total porosity ranging from 2 to 32 of the helium porosity importantly the fe sem visible porosity in om decreases significantly with increasing toc diminishing from 30 of om volume to less than 1 of om volume across the range of toc the morphology and size of om hosted pores also vary systematically with toc the interpretation of this anticorrelation between om content and sem visible pores remains uncertain samples with the lowest om porosity higher toc may represent gas expulsion pore collapse that was more complete as a consequence of greater om connectivity and framework compaction whereas samples with higher om porosity lower toc correspond to rigid mineral frameworks that inhibited compactional expulsion of methane filled bubbles alternatively higher toc samples may contain om low initial hydrogen index relatively unreactive that is less prone to development of fe sem detectable pores in this interpretation om type controlled by sequence stratigraphic position is a factor in determining pore size distribution

the late triassic timescale age and correlation of the carnian norian boundary the late triassic timescale is poorly constrained due largely to the dearth of reliable radio isotopic ages that can be related precisely to biostratigraphy combined with evident contradictions between bio stratigraphic and magnetostratigraphic correlations these problems are most apparent with regard to the age and correlation of the carnian norian boundary base of the norian stage we review the available age data pertaining to the carnian norian boundary and conclude that the long norian in current use by many workers which places the carnian norian boundary at 228 ma is incorrect the evidence supports a norian stage that is much shorter than proposed by these workers so the carnian norian boundary is considerably younger than this close to 220 ma in age critical to this conclusion is the correlation of the carnian norian boundary in nonmarine strata of europe and north america and its integration with existing radioisotopic ages and magnet ostratigraphy three bio stratigraphic datasets palynomorphs conchostracans and tetra pods reliably identify the same position for the carnian norian boundary within normal limits of bio stratigraphic resolution in nonmarine strata of the chinle group american southwest newark supergroup eastern usa canada and the german keuper these biostratigraphic datasets place the carnian norian boundary at the base of the warford member of the lower passaic formation in the newark basin and as was widely accepted prior to 2002 this correlates the base of the norian to a horizon within newark magnet ozone e13n in recent years a correlation based solely on magnetostratigraphy has been proposed between the pizzo mondello section in sicily and the newark section this correlation which ignores robust biostrati graphic data places the norian base much too low in the newark basin section at the base of the lockatong formation correlative to a horizon near the base of newark magnet ozone e8 despite the fact that this correlation is falsifiable on the basis of the bio stratigraphic data it still became the primary justification for placing the carnian norian boundary at 228 ma based on newark cyclo stratigraphy the long norian created thereby is unsupported by either bio stratigraphic or reliable radioisotopic data and therefore must be abandoned while few data can be presented to support a carnian norian boundary as old as 228 ma existing radio isotopic age data are consistent with a norian base at 220 ma although this date is approximately correct more reliable and precise radio isotopic ages still are needed to firmly assign a precise age to the carnian norian boundary

fine grained volcanic hydrothermal sedimentary rocks in permian lucaogou formation santanghu basin nw china implications on hydrocarbon source rocks and accumulation in lacustrine rift basins abstract subaqueous volcanic hydrothermal field is a complex hybrid geological system where sediments originated from volcanic hydrothermal lacustrine terrestrial and biotic sources are mixed recent petrological studies on such sediments have indicated a potential relationship between volcanic hydrothermal activities and oil generation and accumulation here we explore the mechanisms of sedimentation and oil accumulation in well laminated organic rich fine grained sedimentary rocks in permian lucaogou formation deposited in the lacustrine santanghu rift basin nw china we conducted petrographic carbon and oxygen isotopic and organic geochemical analyses of fifty four core samples from three wells forty eight samples from well w1 two from w2 four from w3 designed for tight oil exploration four main observations and interpretations are 1 the fine grained sediments are a mixture of volcanic hydrothermal detrital feldspar grains authigenic quartz crystals and primary lacustrine dolomite forming interbedded tuffaceous shale and dolostone 2 authigenic quartz crystals were precipitated from acidic hydrothermal fluids whereas fine grained angular alkaline feldspars were derived from subaqueous volcanic eruption 3 the toc content and oil generation potential increase with increased mixing of feldspars and carbonate minerals hence the dolomite bearing tuffaceous shale and tuffaceous dolostone are the best source rocks and 4 the fine grained sedimentary rocks are interpreted as a subaqueous volcanic hydrothermal deposit that controls the source potential the sedimentary processes of an ancient sediment hosted geothermal system and its implications on hydrocarbon source rocks and accumulation were first identified algal bloom induced by subaqueous eruptions is the main cause for episodic deposition of organic matter and extreme heterogeneity in both lithofacies and source rock distribution the results suggest that cone shaped buildups on seismic sections which were formed by volcanic hydrothermal deposits and contain highly mixed feldspar and carbonate sediments are the best hydrocarbon reservoirs and demonstrate a strong relationship between volcanic hydrothermal activities and hydrocarbon accumulation in an extensional tectonic setting

norian magnetostratigraphy from the scheiblkogel section austria constraint on the origin of the antalya nappes turkey abstract late triassic magnetostratigraphic investigations in southwestern turkey have suggested that parts of the antalya nappes are constituted of a melange of blocks originally deposited either in the vicinity of the northern tip of arabia or more surprisingly directly north of india in the southern hemisphere in order to ascertain this result more clearly we have correlated the turkish series with austrian sections of corresponding age from the northern calcareous alps for which the hemisphere of deposition is beyond doubt the new magnetostratigraphic results obtained from the scheiblkogel section austria confirm the previously suggested middle to late norian magnetic polarity sequence and support the heterogeneous character of the antalya nappes

cathodolumenescence spectra of quartz as provenance indicators revisited abstract we present a discrimination scheme for cathodoluminescence cl spectra of quartz as a tool in provenance studies we analyzed 1000 quartz crystals from 58 samples of different plutonic volcanic metamorphic and pegmatitic rocks the technique is based on the measurement of the relative intensity of the two main emission centers in visible light at 470 490 nm and 600 640 nm the results confirm a red violet or bright to medium blue luminescence for volcanic phenocrysts mainly bright blue colors for felsic plutonic and high temperature metamorphic quartz as well as brown to dark blue cl for quartz of low temperature metamorphic origin these and additional results for mafic plutonic dark blue and pegmatitic quartz bright blue lead to a possible discrimination with the following rock grouping 1 volcanic quartz 2 low temperature metamorphic and mafic plutonic quartz and 3 felsic plutonic high temperature metamorphic and pegmatitic quartz in the proposed scheme 87 of the spectra are classified correctly the three quartz groups can be taken as an estimate for the amount of volcanic metamorphic and plutonic quartz in sediments unless major input from plutonic high temperature metamorphic or pegmatitic quartz has taken place hence despite criticism within the literature during the last decades the cl colors of detrital quartz still can be used as provenance indicators we finally conclude that the measurement of wavelength spectra is a fast and straightforward method to determine quartz bearing source rocks of siliciclastic sediments

magnetostratigraphy of the kavur tepe section southwestern turkey a magnetic polarity time scale for the norian we present the magnetostratigraphy of the late triassic pelagic kavur tepe section from the taurides southwestern turkey the section investigated is about 30 m thick and consists of fine grained whitish limestones the biostratigraphy based on the conodont zonation gives an age from the lacian 2 zone lower norian to the sevatian 2 zone upper norian the paleomagnetic analyses indicate very favourable behaviour with two magnetic components which can be isolated both by thermal and af demagnetization the magnetization is carried by magnetite and goethite which are clearly evident in irm experiments the first component of normal magnetic polarity has roughly the direction of the present day field the high unblocking temperature component shows directions of both polarities in total fifteen magnetic polarity intervals are observed within the kavur tepe section the characteristic calculated fisherian mean direction is particularly tightly grouped d 220 2 and i 32 1 with k 40 9 95 1 7 and nsamp 179 after bedding correction polarity correlations with two other sections in turkey and in austria northern calcareous alps show that the kavur tepe sediments were deposited in the southern hemisphere by combining the magnetostratigraphic results from the bolucektasi tepe 1 and the kavur tepe sections an almost complete norian magnetic polarity sequence is established showing 30 magnetic intervals that are well calibrated with the conodont and ammonoid zonations a magnetic reversal frequency close to about 2 7 reversals myr is derived for the norian this medium frequency is in agreement with the hypothesis of a long time constant 150 200 myr in the changes of the magnetic reversal frequency since the kiaman reversed superchron

new aspects on the formation of hydrocarbon source rocks episodic volcanism favors as shown by examples from europe the usa and brazil the formation of organic rich sediments hydrocarbon source rocks the examples examined from europe comprise the lower carboniferous oil shale group scotland upper carboniferous coal measures western germany upper jurassic kimmeridge shale north sea area lower cretaceous blattertonstein northwest germany and eocene messel oil shale rheingraben examples from the usa are devonian mississippian gas shales permian phosphoria shale middle cretaceous mowry shale eocene green river shale and miocene monterey shale examples from brazil are permian irati oil shale and oligocene paraiba valley oil shale volcanism is reflected during sedimentation 1 by exhalation of so2 and or co2 2 volcanic ashfalls 3 by generation of anoxia and preservation of organic matter and 4 by halmyrolytic alteration of volcanic ashes into highly surface active clay minerals montmorillonite

guidelines for evaluating petroleum source rock using programmed pyrolysis rock eval pyrolysis is used to rapidly evaluate the petroleum generative potential and thermal maturity of rocks accurate conclusions require programs every 30 60 ft 9 18 m understanding of interpretive pitfalls and supporting data such as visual kerogen vitrinite reflectance and elemental analyses the generative potential of coals is commonly overestimated by pyrolysis and is best determined by elemental analysis and organic petrography most coals show high s2 s3 5 and low hi values 300 mg hc g toc migrated oil and mud additives which alter rock eval data can sometimes be removed by special processing for immature rocks bimodal s2 peaks and pi values over 0 2 indicate contamination pyrolysis downgrades organic poor clay rich rocks which show lower hi and higher tmax values than isolated kerogen because of adsorption of pyrolyzate on the clays tmax values for small s2 peaks 0 2 mg hc g toc are unreliable tmax is affected by maturation organic matter type contamination and the mineral matrix s3 is sensitive to inorganic and adsorbed carbon dioxide and to instrumentation problems acidification of carbonate rich samples and proper maintenance improves s3 measurement constant sample weights 100 mg are recommended below a threshold weight tmax increases by up to 10 c and other parameters decrease organic rich samples which overload the detector can be diluted with carbonate detector linearity is determined by pyrolyzing various weights of an organic rich rock

titaniq a titanium in quartz geothermometer titanium is one of many trace elements to substitute for silicon in the mineral quartz here we describe the temperature dependence of that substitution in the form of a new geothermometer to calibrate the titaniq thermometer we synthesized quartz in the presence of rutile and either aqueous fluid or hydrous silicate melt at temperatures ranging from 600 to 1 000 c at 1 0 gpa the ti contents of quartz in ppm by weight from 13 experiments increase exponentially with reciprocal t as described by text log left x text qtz text ti right 5 69 pm 0 02 frac 3765 pm 24 t k application of this thermometer is straightforward typically requiring analysis of only one phase quartz this can be accomplished either by epma for crystallization temperatures above 600 c or by sims for temperatures down to at least 400 resulting temperature estimates are very precise usually better than 5 c potentially allowing detailed characterization of thermal histories within individual quartz grains although calibrated for quartz crystallized in the presence of rutile the thermometer can also be applied to rutile absent systems if tio2 activity is constrained

contemporaneous thrusting and large scale rotations in the western sicilian fold and thrust belt in the western sicilian fold and thrust belt large clockwise rotations of allochthons occurred during late cenozoic contraction of part of the southern tethyan margin the magnitude of rotation decreases stepwise from over 120 in the upper sheets lying on the north coast of sicily to no appreciable rotation in the frontal portion of the belt flanking the southern coast of the island the allochthons are composed of imbricate thrust sheets derived primarily from individual basin and platform assemblages of the old tethyan margin paleomagnetic and structural data indicate that the rotation of the allochthons was accommodated by coherent torsional displacements on relatively low angle detachment surfaces timing relations for the imbrication history of the sicilian fold and thrust belt are derived from stratigraphic overlap and local involvement of sediments deposited in a series of foreland and piggyback basins the locus of deposition within successive foreland basins first migrated easterly then southerly during progressive deformation in the orogen imbrication began in the early miocene burdigalian langhian and continued at least through the early pleistocene and appears to be continuing today rotation is related to thrusting and accompanies a 70 change in the tectonic transport direction from easterly to southerly easterly striking right oblique transpressional faults and associated northeasterly trending folds postdate thrust sheet rotation in the interior of the thrust belt and were active contemporaneously with south directed thrusting in the foreland region pleistocene and possibly older late pliocene extension strongly modified the older thrust morphology along the tyrrhenian coast of northwestern sicily with the development of down to the north listric normal faults the extensional structures apparently are related to the opening and subsequent deformation of the tyrrhenian sea to the north

magnetostratigraphic dating of the proposed rhaetian gssp at steinbergkogel upper triassic austria implications for the late triassic time scale the global stratotype section and point gssp for the rhaetian stage has recently been proposed at steinbergkogel in austria we re sampled the steinbergkogel sections stk a and stk b c in high resolution to establish a robust magnetostratigraphy that allows global correlation the palaeomagnetic signal at steinbergkogel is composed of three components which can be separated by thermal demagnetization the highest temperature component revealed between 280 300 and maximum 600 c is of dual polarity and is interpreted as primary rock magnetic experiments showed that the signal is carried by magnetite our results allow correlation between the two individual steinbergkogel outcrops subsequently we correlate the two key biostratigraphic horizons for the base of the rhaetian the fo of m hernsteini and the fad of m post hernsteini to other sections of the tethys domain the correlation to the astronomically dated continental successions of the newark basin indicates that these positions for the base of the rhaetian are most likely determined in chrons e16n and e16r respectively this correlation is confirmed by cyclostratigraphic control on the marine pizzo mondello italy section where a combination of long period milankovitch cycles 175 myr and short eccentricity cycles 100 kyr provide additional correlation constraints respectively supporting a long duration of the rhaetian our study implies that the norian and rhaetian stages have durations of 17 and 9 myr

discovery of sublacustrine hydrothermal activity and associated massive sulfides and hydrocarbons in the north tanganyika trough east african rift massive sulfides and carbonate mineral deposits associated with sublacustrine thermal springs were recently discovered along the zaire side of the north tanganyika trough western branch of the east african rift this hydrothermal activity investigated by scuba diving at a maximum depth of 20 m is located at the intersection of major north south normal faults and northwest southeast faults belonging to the tanganyika rukwa malawi trm strike slip fault zone the preliminary results presented here come from analyses of sulfide deposits hydrothermal fluids and associated hydrocarbons that result from geothermal activity in this part of the east african rift filled by a thick pile of sediment the north tanganyika trough

generic turnovers of carnian norian conodonts climatic control or competition abstract pizzo mondello section western sicily italy yields a very rich conodont record ranging from late carnian to rhaetian in age shedding new light into the evolution of conodonts across the carnian norian boundary conodont biostratigraphy around the carnian norian boundary is still problematic due to an inferred provincialism that affects most of the conodont species and to the occurrence of a great number of transitional forms linked to the fast recovery of conodonts after the middle carnian crisis the lower 144 m of the succession tuvalian to lacian in age were sampled in detail for a biostratigraphic and ecological study of five upper triassic conodont genera paragondolella carnepigondolella metapolygnathus epigondolella and norigondolella after a taxonomic revision of the genera studied meant to define the most significant morphological features for their classification a statistical approach was applied to the study of conodont populations quantitative curves of the absolute abundances for each genus show potential ecological competition between paragondolella carnepigondolella and later between metapolygnathus epigondolella and partially between epigondolella norigondolella recognition of morphoclines among species integrated by a similar ecological behaviour supports the phylogenetic derivation of norigondolella and metapolygnathus from paragondolella and that of epigondolella from carnepigondolella furthermore cross checks of the quantitative curves evidenced the presence of three major assemblage changes at metre 64 76 named event t1 carnepigondolella is replaced by its descendant epigondolella in an evolutionary step at metre 80 event t2 epigondolella is substituted by the mass occurrence of metapolygnathus and at metre 95 event t3 metapolygnathus is succeeded by advanced epigondolellae species and by norigondolella in looking for environmental explanations to these biological events the conodont assemblages are compared to coeval 18 o and 13 c isotopic curves based on new data from pizzo mondello from the comparison a correspondence appears between higher 13 c 12 c ratios and the interval between events t2 t3 but not with event t1 this is in accordance with the interpretation of event t1 as an evolutionary turnover in more detail we observe the possible influence of environmental conditions on the absolute abundances of all the studied genera while epigondolella proliferate when seawater 13 c ranges between 2 1 and 2 5 carnepigondolella proliferate in the range between 1 6 and 2 1 metapolygnathus instead appears to be limited to environmental conditions related to higher 13 c values in the seawater we explain this behaviour by interpreting the genus metapolygnathus as an opportunist taxon exactly as its forerunner the genus paragondolella

improving the upper triassic numerical time scale from cross correlation between tethyan marine sections and the continental newark basin sequence abstract magnetostratigraphic cross correlations between biochronologically well dated tethyan marine sections and the astronomically tuned sedimentary sequence from the continental newark basin eastern north america help to improve the upper triassic time scale we show here that the most recent radiometric results constraining the age of the base and top of the upper triassic 237 and 200 ma respectively strengthen the chronostratigraphic calibration of the newark sedimentary sequence proposed by krystyn et al earth planet sci lett 203 2002 343 351 these results allow one to reconcile the milankovitch based cyclostratigraphy from the newark sequence the magnetostratigraphic data from both marine and continental environments and upper triassic biostratigraphy including data on tethyan marine faunas and on terrestrial vertebrates according to this calibration the successive upper triassic stages would have very different durations 10 myr for the carnian 237 227 ma 25 myr for the norian 227 202 ma and 2 myr for the rhaetian 202 200 ma but only if the entire rhaetian is recorded in the newark sequence we further show that the biozone durations in the upper triassic would have been highly variable and as a whole would have lasted much longer than in the lower and middle triassic

conodont apatite δ88 86sr and δ44 40ca compositions and implications for the evolution of palaeozoic to early mesozoic seawater abstract we present high precision tims double spike stable isotope measurements of both 44 40 ca and 88 86 sr together with radiogenic 87 sr 86 sr ratios determined from conodont apatite these data represent five intervals ranging from the early ordovician to late triassic the conodont 44 40 ca values relative to nist 915a range from 0 47 to 0 15 with an apparent shift to more positive values between the early silurian and late devonian early carboniferous similar to the brachiopod based marine 44 40 ca record farkas et al 2007a we calculated a 44 40 ca seawater bio apatite fractionation factor of about 1 9 which allowed us to reconstruct a palaeo seawater 44 40 ca record from bio apatites despite a slightly positive offset of about 0 2 to 0 5 the 44 40 ca record obtained from bio apatites is consistent with the previously reported 44 40 ca seawater record inferred from carbonates we find that unlike the carbonate 44 40 ca records the 88 86 sr measurements from conodont apatite show unexpectedly large variations up to 1 with ratios ranging from 0 6 to 0 3 these reconnaissance data reveal a reasonable correlation between 88 86 sr and radiogenic 87 sr 86 sr r 2 0 60 n 13 p 0 002 suggesting that the controls from differential weathering regimes and or continental crustal compositions buffered ancient seawater compositions

subaqueous geothermal activity revealed by lacustrine sediments of the acidic nakadake crater lake aso volcano japan abstract lacustrine sediments were sampled from the inaccessible acidic ph 0 43 nakadake crater lake of aso volcano japan by a simple method the sediments contain an extremely high content 74 wt of sulfur which exits as elemental sulfur gypsum and anhydrite the abundant elemental sulfur is likely formed by the reaction of so 2 and h 2 s gases and by the so 2 disproportionation reaction in magmatic hydrothermal system below the crater lake based on the sulfur content of sediments and measurements of elevation change of the crater bottom the sulfur accumulation rate at the nakadake crater lake was calculated as 250 tonne day which is comparable with the so 2 emission rate 200 600 tonne day from the nakadake crater the sediments include a small amount 9 of clear glass shards that are apparently not altered in spite of the high reactivity of hyperacid lake water this finding suggests that the clear glass shards are fragments of recently emitted magmas from fumaroles on the bottom of the crater lake and the magma emissions continuously occur even in quiescent periods

characteristics of hydrothermal sedimentation process in the yanchang formation south ordos basin china evidence from element geochemistry abstract hydrothermal sedimentation occurred in the triassic yanchang formation ordos basin china however their macroscopic features at the scale of the stratum and hydrothermal sources still lack correlational research this paper performed element geochemical study on a large number of core samples collected from the yanchang formation of a new drilling well located in the south ordos basin the sio2 k2o na2o vs mno tio2 crossplot and fe vs mn vs cu co ni 10 ternary diagram demonstrate that the yanchang stratum in the study area has in general hydrothermal components the al al fe mn and fe mn ti ratios of the core samples range from 0 34 to 0 84 and 4 81 to 50 54 averaging 0 66 and 10 67 respectively indicating that the stratum is a set of atypical hydrothermal sedimentation with much terrigenous input data analysis shows that the hydrothermal source in the study area was from the deep north qinling orogen around the south margin of the basin where some active tectonic and volcanic activities took place rather than from the relatively stable internal basin early indosinian movement and volcanic activities activated basement faults around the southern margin of the basin providing vents for the deep hydrothermal fluid upwelling the hydrothermal indicators suggest that the study area experienced 4 episodes of relatively stronger hydrothermal activity namely during the chang 10 chang 9 1 chang 7 3 and chang 6 2 periods we also propose a new hydrothermal sedimentation model of hydrothermal fluids overflowing from basin margin faults for the yanchang formation which is reported here for the first time

mafic volcaniclastic deposits in flood basalt provinces a review flood volcanic provinces are assumed generally to consist exclusively of thick lavas and shallow intrusive rocks mostly sills with any pyroclastic rocks limited to silicic compositions however mafic volcaniclastic deposits mvds exist in many provinces and the eruptions that formed such deposits are potentially meaningful in terms of potential atmospheric impacts and links with mass extinctions the province where mvds are the most voluminous the siberian traps is also the one temporally associated with the greatest phanerozoic mass extinction a lot remains to be learned about these deposits and eruptions before a convincing genetic link can be established but as a first step this contribution reviews in some detail the current knowledge on mvds for the provinces in which they are better known i e the north atlantic igneous province including greenland the faeroe islands the british isles and tephra layers in the north sea basin and vicinity the ontong java plateau the ferrar and the karoo we also provide a brief overview of what is known about mvds in other provinces such as the columbia river basalts the afro arabian province the deccan traps the siberian traps the emeishan and an archean example from australia the thickest accumulations of mvds occur in flood basalt provinces where they underlie the lava pile faeroes n1 km ferrar province z400 m siberian traps 700 m in the faeroes case the great thickness of mvds can be attributed to accumulation in a local sedimentary basin but in the ferrar and siberian provinces the deposits are widespread n310 5 km 2 for the latter on the ontong java plateau over 300 m of mvds occur in one drill hole without any overlying lavas where the volcaniclastic deposits are sandwiched between lavas their thickness is much less in most of the cases reviewed primary mvds are predominantly of phreatomagmatic origin as indicated by the clast assemblage generally consisting of basaltic clasts of variable vesicularity dominantly non to poorly vesicular mixed with abundant country rock debris the accidental lithic components often include loose quartz particles derived from poorly consolidated sandstones in underlying sedimentary basins east greenland ferrar karoo these underlying sediments or sedimentary rocks were not only a source for debris but also aquifers that supplied water to fuel phreatomagmatic activity in the

insights into the dolomitization process and porosity modification in sucrosic dolostones avon park formation middle eocene east central florida u s a abstract the avon park formation middle eocene in central florida u s a contains shallow water carbonates that have been replaced by dolomite to varying degrees ranging from partially replaced limestones to highly porous sucrosic dolostones to less commonly low porosity dense dolostones the relationships between dolomitization and porosity and permeability were studied focusing on three 305 m long cores taken in the city of daytona beach stable isotope data from pure dolostones mean 18o 3 91 v pdb indicate dolomite precipitation in eocene penesaline pore waters which would be expected to have been at or above saturation with respect to calcite nuclear magnetic log derived porosity and permeability data indicate that dolomitization did not materially change total porosity values at the bed and formation scale but did result in a general increase in pore size and an associated substantial increase in permeability compared to limestone precursors dolomitization differentially affects the porosity and permeability of carbonate strata on the scale of individual crystals beds and formations at the crystal scale dolomitization occurs in a volume for volume manner in which the space occupied by the former porous calcium carbonate is replaced by a solid dolomite crystal with an associated reduction in porosity dolomite crystal precipitation was principally responsible for calcite dissolution both at the actual site of dolomite crystal growth and in the adjoining rock mass carbonate is passively scavenged from the formation which results in no significant porosity change at the formation scale moldic pores after allochems formed mainly in beds that experienced high degrees of dolomitization which demonstrates the intimate association of the dolomitization process with carbonate dissolution the model of force of crystallization controlled replacement provides a plausible explanation for key observations concerning the dolomitization process in the avon park formation and elsewhere 1 volume for volume replacement at a crystal scale 2 coupled growth of dolomite crystals and dissolution of host calcium carbonate matrix and 3 automorphic replacement by euhedral dolomite crystals the force of crystallization model also does not require an influx of externally derived water that is undersaturated with respect to calcite to dissolve calcite a fact that could simplify diagenetic models of porosity generation in dolostones the later addition of external carbonate can result in a substantial reduction in porosity by the precipitation of dolomite cement which could convert a high porosity sucrosic dolostone into a dense paleozoic type dolostone

high precision u pb zircon geochronology of the late triassic chinle formation petrified forest national park arizona usa temporal constraints on the early evolution of dinosaurs the triassic successions of the colorado plateau preserve an important record of vertebrate evolution and climate change but correlations to a global triassic framework are hampered by a lack of geochronological control tuffaceous sandstones and siltstones were collected from the upper triassic chinle formation exposed in the petrified forest national park arizona usa within a refined stratigraphic context of 31 detailed measured sections u pb analyses by the isotope dilution thermal ionization mass spectrometry id tims method constrain maximum depositional ages for nine tuffaceous beds and provide new insights into the depositional history of the chinle fluvial system the base of the blue mesa member of the chinle formation is placed at ca 225 ma and the top of the petrified forest member is placed at 208 ma or younger bracketing an 280 m thick section that spans nearly the entire norian stage of the late triassic estimated sediment accumulation rates throughout the section reflect extensive hiatuses and or sediment removal by channel erosion the new geochronology for the chinle formation underscores the potential pitfalls of correlation of fluvial units based solely on lithostratigraphic criteria a mid norian age ca 219 213 ma for the distinctive sonsela conglomeratic sandstone bed constrains the adamanian revueltian land vertebrate faunachron boundary our new data permit a significant time overlap between the lower chinle sequence and the dinosauromorph rich ischigualasto formation of northwestern argentina near contemporaneity of the trans american deposits and their faunal similarities imply that early dinosaur evolution occurred rapidly across the americas

soil development on moraines of mendenhall glacier southeast alaska 1 the moraines and soil morphology abstract soils on a sequence of well drained neoglacial moraines up to 240 years old plus an older soil were sampled to investigate soil development through the initial stages of podzolization pebbles and cobbles in the moraines are about 75 to 80 granitic rock computations based on minerals observed optically and on chemical analyses indicate that plagioclase and quartz are the predominant minerals in the fine earth the climate is perhumid leaching of the moraines may have begun before they were free of glacial ice but little organic matter accumulated under the initial vegetative cover of sparse dwarf fireweed 10 year site as alder thicket developed organic matter accumulated rapidly in oi oe and a horizons 38 year site as spruce trees began to replace alder organic matter was lost from the surface mineral soil to form an e horizon and an incipient bs horizon formed below it an oa horizon formed and the a horizon disappeared 70 and 90 year sites organic acid leaching continued to form a spodic bhs horizon in spruce forest 240 year site and a spodic bh horizon in spruce hemlock forest 240 year site hornblende has been etched slightly within 240 years apatite has been lost from e horizons and free fe presumeably in ferrihydrite has accumulated in b horizons the younger moraine soils both with and without incipient bs horizons are typic cryorthents and the 240 year old and older soils with spodic bhs and bh horizons are typic haplocryods they are expected to accumulate more organic matter and become andic humicryods which is the most common subgroup of soils in the area

magnetostratigraphy and biostratigraphy of the carnian norian boundary interval from the pizzo mondello section sicani mountains sicily the 146 5 m thick upper triassic limestone section at pizzo mondello in the sicani mountains of western sicily is characterized by high quality of exposure accessibility and stratigraphic continuity magnetostratigraphic results delineate 12 normal and reverse polarity magnetozones labelled successively from the base upwards as pm1n pm1r pm6n pm6r the carnian norian boundary based on conodont biostratigraphy falls somewhere in the pm3n to pm5n interval which corresponds to the e14n to e16n magnetozone interval in the newark reference sequence of polarity reversals comparison of magnetobiostratigraphic data from the newark basin pizzo mondello and other late triassic marine sections available from the literature suggests the existence of a reduction in sedimentation rate in the tethyan marine domain at around the carnian norian boundary although the newark and the expanded pizzo mondello sections correlate well with each other correlation with the condensed kavur tepe and scheiblkogel sections is unsatisfactory a re interpretation of the kavur tepe results suggests that the section is younger than its previous correlation with the newark section and that it was deposited in the northern instead of the southern hemisphere most of the condensed tethyan marine sections are seen to be highly discontinuous as evidenced by concantenated conodont total range zones q 2001 elsevier science b v all rights reserved

trace elements in hydrothermal quartz relationships to cathodoluminescent textures and insights into vein formation high resolution electron microprobe maps show the distribution of ti al ca k and fe among quartz growth zones revealed by scanning electron microscope cathodoluminescence sem cl from 12 hydrothermal ore deposits formed between 100 and 750 c the maps clearly show the relationships between trace elements and cl intensity in quartz among all samples no single trace element consistently correlates with variations in cl intensity however in vein quartz from five porphyry cu mo au deposits cl intensity always correlates positively with ti concentrations suggesting that ti is a cl activator in quartz formed at 400 c ti concentrations in most rutile bearing vein quartz from porphyry copper deposits indicate reasonable formation temperatures of 750 c using the titaniq geothermometer titanium concentrations of 10 ppm in all veins that formed at temperatures 350 c suggest a broad correlation between ti concentrations and temperature of quartz precipitation in quartz from most deposits formed at 2000 ppm but in high temperature quartz al concentrations are consistently in the range of several hundred ppm aluminum concentrations in quartz reflect the al solubility in hydrothermal fluids which is strongly dependent on ph aluminum concentrations in quartz therefore reflect fluctuations in ph that may drive metal sulfide precipitation in hydrothermal systems

a u pb and 40ar 39ar time scale for the jurassic published time scales provide discrepant age estimates for jurassic stage boundaries and carry large uncer tainties the u pb or 40 ar 39 ar dating of volcaniclastic rocks with precisely known stratigraphic age is the preferred method to improve the calibration a radiometric age database consisting of fifty u pb and 40 ar 39 ar ages was com piled to construct a revised jurassic time scale accepted ages have a precision of 5 ma 2 or better and are con fined to no more than two adjacent stages the majority of these calibration points result from integrated bio and geochronologic dating in the western north american cordillera and have not been previously used in time scales di rect dates are available only for the triassic jurassic boundary and the initial boundary of the crassicosta chron and the callovian stage the chronogram method was used to estimate all early and early middle jurassic zone boundaries attempted here for the first time late middle jurassic substage boundaries and late jurassic stage boundaries signif icant improvement is achieved for the pliensbachian and toarcian where six consecutive zone boundaries are deter mined the derived zonal durations are disparate varying between 0 4 and 1 6 ma the latest jurassic isotopic database remains too sparse therefore chronogram estimates are improved using interpolation based on magnetochronology the initial boundaries of jurassic stages are proposed as follows berriasian jurassic cretaceous 1418 18

conodont biostratigraphy of uppermost triassic deep water calcilutites from pizzo mondello sicani mountains evidence for rhaetian pelagites in sicily abstract rhaetian pelagites are described for the first time from western sicily in the pizzo mondello area sosio valley sicani mountains where a thick pile of upper triassic cherty calcilutites outcrops the upper triassic pelagic calcilutites of pizzo mondello are divided into three lithostratigraphic units the lower unit consists of a few meters of dark gray marls and clay marlstones equivalent to the mufara fm of carnian age followed by halobia bearing cherty limestones about 300 m thick of late carnian late norian age the upper unit consists of white calcilutites and grey greenish marls containing the conodonts misikella posthernsteini and zieglericonus rhaeticus of rhaetian age these rhaetian deposits are here informally named as portella gebbia limestone in the pizzo mondello succession the norian rhaetian boundary sensu kozur and mock 1991 can be approximated along the lowermost calcilutite bed of portella gebbia limestone containing the first occurrence of m posthernsteini

soil development on moraines of mendenhall glacier southeast alaska 2 chemical transformations and soil micromorphology abstract soils on holocene age moraines of the mendenhall glacier in southeast alaska range from morphologically undeveloped to soils having field identified spodic horizons that are more strongly expressed with increasing soil age a soil chronosequence was sampled to study development of spodic features and to compare the expression of these features with chemical and micromorphological properties organic c accumulates rapidly in these soils with o horizons forming within 38 yr organic c is highly correlated with cation exchange capacity r2 0 92 variable charge r2 0 94 extractable acidity r2 0 83 and 1500 kpa water retention r2 0 97 the ph of the 10 yr old pedon is acidic with a soil ph h20 ranging from 5 0 to 6 4 the ph decreases with soil age with the lowest ph in horizons at the organic mineral contact increases in dithionite citrate sodium pyrophosphate and acid oxalate extractable fe feo are most evident in the 240 yr old soil depth trends for these measured properties within pedons are most distinctive for fe which increases from surface mineral horizons a or e to underlying horizons in all pedons the feo fed ratio increases with soil age in b horizons and in pedons 70 yr this ratio ranges from 0 3 to 0 5 in the e horizons and from 0 4 to 0 83 in b horizons immediately below these data indicate a greater proportion of poorly crystalline fe in illuvial horizons with increasing soil age allophane content is low 240 yr old pedon this chronosequence study indicates that spodic development is achieved within a relatively short period of time in soils of this region

dissolution behaviour of fine grained magnetite and maghemite in the citrate bicarbonate dithionite extraction method mineral magnetic properties of soils and sediments are increasingly used as proxy parameters for environmental and palaeoclimate analysis to investigate which magnetic minerals contribute to the environmental signal in the samples chemical techniques such as the citrate bicarbonate dithionite cbd extraction method have been introduced in environmental magnetism studies this technique is assumed to distinguish lithogenic magnetite from pedogenic maghemite mineral content in soils and sediments unfortunately interpretation of the cbd extractions is not straightforward because the procedure is sometimes more suitable for distinction between grain size than for distinction between minerals the procedure of the cbd extraction technique was investigated to determine the influence of extraction temperature and iron oxide concentration on the dissolution behaviour of the samples synthetic samples were extracted at three different temperatures 60o 70o and 80oc at similar iron oxide concentration 5 wt and for three different concentrations 0 1 wt 1 wt and 5 wt at the same temperature 60oc our results show that a lower extraction temperature reduces the dissolution rate for all samples while decrease in iron oxide concentration increases the dissolution rate thus the parameters in the cbd procedure have a major influence on the dissolution behaviour of the samples in practice this means that when natural samples of differing iron oxide concentration are extracted with this technique the results of the extractions cannot be compared therefore the outcome of this type of extraction experiment can only be accurately interpreted when the effect of the procedure on the dissolution behaviour is taken into account 1999 elsevier science b v all rights reserved

analysis of the developmental characteristics and major regulating factors of fractures in marine continental transitional shale gas reservoirs a case study of the carboniferous permian strata in the southeastern ordos basin central china abstract fractures play an important role in the formation of shale gas reservoirs because they can enlarge the transport channels and aggregation spaces and increase the specific surface area of the gas shale for artificial hydraulic fracturing of these reservoirs the natural fracture system must be fully integrated with the artificial fracture system to form an intact fracture system in this study we first comprehensively examined the fractures in 42 shale gas wells using several approaches including a systematic examination and description of the cores and the casting of thin sections a compilation of the statistics of fracture feature parameters and observation of various analytical and test data such as the mineral composition the organic carbon contents and the rock mechanics properties for specimens from the corresponding fractured intervals the data enabled us to thoroughly explore the developmental features and major factors affecting organic rich shale fractures in the upper paleozoic carboniferous permian marine continental transitional coal bearing formation which is located in the southeastern ordos basin our results reveal that in comparison with the paleozoic marine shale in the united states and southern china as well as the paleozoic basin transitional shale in northern china the upper paleozoic black shale in the ordos basin is primarily characterized by a relatively low content of brittle minerals and a high content of clay ingredients the total content of brittle minerals e g quartz feldspar and siderite was approximately 33 which included 27 quartz and 0 3 k feldspar but did not include carbonate the total content of clay minerals reached 64 and was dominated by mixed layer illite smectite i s which accounted for more than 41 of the total clay ingredients the shale accommodated the widespread development of various types of macro and microfractures in the core specimens medium angle slip fractures and horizontal bedding cracks were the most common types of fractures whereas vertical and high angle fractures and horizontal bedding cracks were underdeveloped in the thin sections microfractures arising in organic matter laminations or at their edges as well as those of tectonic origin were the predominant type of fractures and they were mainly short narrow and open overall the surface fracture ratios of the thin sections were concentrated in a range of approximately 0 1 0 3 the developmental level of the fracture was influenced by various factors including tectonism lithology rock mechanics and organic matter and mineral content thus increased developmental level of fractures was correlated with higher paleostructural elevation and increased sand content whereas the developmental level of microfractures was correlated with high lamellation development high level of organic carbon leading to more pronounced laminations and high contents of quartz mixed layer i s and illite leading to low levels of kaolinite these findings were corroborated by other data generated in this study including the rock mechanics results for the upper paleozoic black shale and silty shale the observation results from the cores and from the thin sections sampled from more than 40 shale gas wells and the anomalies of gas logging

diagenetic origin of quartz silt in mudstones and implications for silica cycling mudstone the most abundant sedimentary rock type1 composed primarily of clay or silt sized particles contains most of the quartz found in sedimentary rocks2 these quartz grains which are chemically and mechanically resistant and therefore preserve their characteristics well have long been considered to be derived from the continental crust1 here we analyse quartz silt from black shales in the eastern usa dating back to the late devonian period about 370 million years ago using backscattered electron and cathodoluminescence imaging and measure oxygen isotopes with an ion probe our results indicate that up to 100 of the quartz silt in our samples does not originate from the continental crust instead it appears to have precipitated early in diagenesis in algal cysts and other pore spaces3 with silica derived from the dissolution of opaline skeletons of planktonic organisms such as radiolaria and diatoms transformation of early diatoms into in situ quartz silt might explain the time gap between the earliest fossil occurrences of diatoms about 120 myr ago4 and molecular evidence for a much earlier appearance between 266 or even 500 myr ago5 6 moreover if many other mudstone successions show similarly high proportions of in situ precipitated rather than detrital quartz silt the sedimentary record in mudstones may have been misinterpreted in the past with consequences for our estimates of palaeoproductivity as well as our perceptions of the dynamics and magnitude of global biogeochemical cycling of silica

oxygen isotopic evidence for late triassic monsoonal upwelling in the northwestern tethys the oxygen isotopic composition of conodonts from the pizzo mondello section in the sicani basin sicily italy on the northwestern tethys margin has been used to reconstruct regional paleoseawater conditions the 18 o phos values 21 21 9 measured by sensitive high resolution ion microprobe shrimp ii are consistent with previously published 18 o phos data from the contemporaneous marginal hallstatt meliata basin 20 3 22 5 located farther north but are distinctly higher than those previously reported from the open ocean setting of the nearby lagonegro basin 18 7 20 0 this 2 offset represents a temperature differential of 8 c suggesting that sea surface temperatures along the northwestern margin sicani and hallstatt meliata basins of the tethys ocean were lower than in the open ocean lagonegro basin during the late carnian tuvalian 2 to early norian lacian we interpret the cooler waters of the marginal basins to reflect coastal upwelling driven by strong monsoonal systems as predicted by existing paleoclimate models for this region

magneto biostratigraphy of the middle to upper triassic transition central spitsbergen arctic norway palaeomagnetic and biostratigraphic data were obtained for the latest ladinian and most of the carnian botneheia formation to basal kapp toscana group from two sections in central spitsbergen svalbard archipelago thermal and alternating field af demagnetization reveals a magnetization of both normal and reversed polarities the mean directions pass reversal and fold tests and are similar to other european late triassic palaeopoles one of the sections displays 15 of vertical axis clockwise tectonic rotation on a decollement in the underlying botneheia formation the magnetostratigraphy is dominated by normal polarity in the uppermost botneheia formation and into the tschermakfjellet and basal de geerdalen formations a substantial hiatus characterizes the ladinian carnian boundary in central spitsbergen so reverse magnetozones identified in tethyan sections near this boundary are absent magnetostratigraphic correlation along with palynostratigraphic constraints indicates that most of the de geerdalen formation is lower carnian the magnetostratigraphy and palynology indicates that the isfjorden member upper unit of the de geerdalen formation is probably mid carnian in age change in the lithological architecture in the isfjorden member compared with the underlying parts of the de geerdalen fm suggests a hiatus near the base of the member which may represent a mid carnian unconformity not previously recognized on spitsbergen

podzolization over ophiolitic materials in the western alps natural park of mont avic aosta valley italy abstract soil surveys carried out on ophiolitic rocks and till under subalpine forest in the natural park of mont avic aosta valley west italian alps revealed the unexpected occurrence of soils showing a horizon set typical of the podzols podzolization is uncommon on mafic and ultramafic substrata the translocation of organo metallic compounds in soils developed from such parent materials slows down considerably due to the high fe and mg contents the high base saturation and the close to neutral ph in order to determine the real origin and evolution of such soils 6 pedons selected among 83 profiles with a similar podzol morphology were sampled and analyzed chemical mineralogical and petrographic analyses of the sampled soils and parent materials were performed and correlation analysis of the obtained data was carried out results show that in favourable environmental conditions mainly climate and vegetation even mafic and ultramafic parent materials can undergo different degrees of podzolization due to the adopted diagnostic criteria the most common classification systems particularly the wrb do not allow satisfactory taxonomic arrangement of such soils

authigenic k nh4 feldspar in sandstones a fingerprint of the diagenesis of organic matter abstract in arkosic sandstones of the san joaquin and los angeles basins presently at temperatures between 35 c and 174 c trace amounts of authigenic k nh4 feldspar are present as microfracture fillings and overgrowths on detrital k feldspar microchemical analyses of this authigenic phase reveal up to 80 mole buddingtonite the largest ammonium concentrations are observed in a sandy interval of the antelope shale 80 mole and in the stevens sands 50 mole of the san joaquin basin this latter unit was deposited as a turbidite in the organic rich fruitvale shale an equivalent of the antelope shale the lowest ammonium contents 0 16 mole are present in the shallow marine vedder sands and the marginal marin san joaquin formation in the same basin petrographic 18o 13c and 87sr 86sr analyses of a dolomite cement that postdates authigenic k nh4 feldspar indicate that the feldspar precipitated below 28 c in the zone of methanogenesis from pore waters with the same sr signature as sea water at the time of sedimentation authigenic k nh4 feldspar is thus an early diagenetic phase that crystallized prior to oil migration under anoxic conditions when organic matter releases ammonium the source of ammonium is bacterial decay of organic matter in the sandstones themselves and or in contemporaneous shales

podzolisation as a soil forming process in the alpine belt of rondane norway abstract in doralen the north eastern part of rondane mountains south norway strongly podzolised soils can be found from treeline up to the high alpine belt although organic matter production is low and the climatic conditions are rather unfavourable for associated chemical processes at treeline some soils have eluvial horizons more than 1 2 m thick in the high alpine belt even small amounts of organic matter under fragmentary mats of fruticose lichens have caused a considerable eluviation from the upper soil layer and translocation of organo metallic complexes into the subsoil leaching and translocation result from the low buffer capacity of the parent material sparagmite compared to typical lowland podzols the alpine podzols are less acid and c n ratios are narrow the soils are classified as haplic podzols according to the fao unesco system the investigation shows that podzolisation can be a major soil forming process in the boreo alpine belt

tethyan magnetostratigraphy from pizzo mondello sicily and correlation to the late triassic newark astrochronological polarity time scale we present the magnetostratigraphy and stable isotope stratigraphy from an expanded 430 m thick upper triassic marine limestone section at pizzo mondello sicily and review published biostratigraphic information that can be used to defi ne the location of the conodont carnian norian and norianrhaetian boundaries in this section pizzo mondello offers good potential for magnetostratigraphic correlation of marine biostratigraphic and chemostratigraphic data with the continental newark astrochronological polarity time scale apts for development of an integrated late triassic time scale the relatively stable average values of 18 o centered on 0 are a strong indication that the cherty limestone at pizzo mondello suffered very little diagenetic overprinting the conodont carnian norian boundary is located 12 5 m above a positive shift of 13 c a statistical approach was applied to evaluate various pizzo mondello to newark magnetostratigraphic correlations two correlation options have the highest correlation coeffi cients in option 1 the base of pizzo mondello correlates with the middle part of the newark apts whereas in option 2 the base of pizzo mondello starts toward the early part of the newark apts we prefer option 2 in which the carnian norian boundary based on conodonts as well as its closely associated positive 13 c shift correspond to newark magnetozone e7 at ca 228 227 ma adopting newark astrochronology implying a long norian with a duration of 20 m y and a rhaetian of 6 m y duration these ages are in fact not inconsistent with the few high quality radiometric dates that are available for late triassic time scale calibration based on its good exposure accessibility stratigraphic thickness and continuity and multiple chronostratigraphic correlation possibilities we propose pizzo mondello as global stratigraphic section and point for the base of the norian

geochemical and tight reservoir characteristics of sedimentary organic matter bearing tuff from the permian tiaohu formation in the santanghu basin northwest china abstract tuff reservoirs have been found in petroliferous basins but have not been sufficiently studied the discovery of the permian tiaohu formation reservoir in the santanghu basin in northwest china has offered an excellent opportunity to further enhance our knowledge of the tuff s geochemical and reservoir characteristics the tuff reservoir has the peculiar property of being a sedimentary organic matter bearing tuff in this study an integrated analysis of the organic geochemistry elemental and mineral compositions quartz crystallinity pore types and tight reservoir characteristics was conducted based on samples from the 20 30 m thick tuffs the extracted tuff samples have total organic carbon toc values of 0 5 1 0 wt total hydrocarbon yield values of 2 6 mg g and hydrogen index values of 20 336 mg hc g toc the organic matter consists predominantly of type iii and ii 2 kerogens and the temperature of the maximum yield of pyrolysate varies from 420 to 450 c which reflects the oil generating capacity of the rock the physical properties of the tuff are characterised by high porosity varying from 10 to 25 and low permeability the air permeability mainly ranges from 0 01 to 0 50 md the devitrification of vitreous textures within the tuff primarily dictates the reservoir s characteristics i e the greater the degree of devitrification the higher the porosity of the reservoir vitric tuffs have reservoirs with higher porosity than crystal vitric tuffs and the degree of devitrification is generally controlled by the burial depth temperature and organic matter organic acid content vitric tuffs with high porosity and permeability are usually located far from the crater and within the central lower part of the reservoir this research may influence geologists to pay more attention to the exploration value of this special type of reservoir in other regions

magnetostratigraphy of the mayerling section austria and erenkolu mezarlik turkey section improvement of the carnian late triassic magnetic polarity time scale abstract we present a magnetostratigraphic study of two carnian late triassic pelagic limestone sections from the northern calcareous alps mayerling section and southwestern turkey erenkolu mezarlik section biostratigraphic control is based on conodont zonation for the mayerling section and both on conodonts and ammonoids for the erenkolu mezarlik section in both sections the characteristic magnetization is essentially carried by a mineral of the magnetite family eight magnetic intervals are obtained from the mayerling section and fourteen from erenkolu mezarlik when these results are compared to the carnian magnetostratigraphic sequence obtained from the bolucektasi tepe section satisfactory correlations are observed and a composite carnian magnetic polarity time scale containing 24 intervals can be proposed by combining all these results the lower part of the upper carnian is however missing tuvalian 1 zone and lower part of the tuvalian 2 zone no clear correlation is observed between our composite sequence and the other published magnetostratigraphic data of carnian age the satisfactory correlation observed between the mayerling and the bolucektasi tepe sections indicates that both sections were deposited in the northern hemisphere thus providing constraints on the origin of the antalya nappes

triassic radiolarian biostratigraphy this paper summarizes 30 years of research on the biostratigraphy of triassic radio larians and presents a correlation of currently used radiolarian zonations established in north america europe japan and far east russia an up to date stratigraphic distribution of all hitherto described and still valid triassic genera is provided this new range chart consists of 282 genera and allows an accurate dating to substage level it also clearly manifests general trends in radiolar ian evolution through the triassic the end permian extinction the most severe extinction in the history of radiolarians was followed by a long recovery until the early anisian the middle and late anisian were then characterized by a rapid explosion of new morphologies maximum generic diversity was attained during the early carnian but the first severe extinctions also occurred in the carnian a progressive decline of diversity took place through the norian and rhaetian and ended in a mass extinction around the triassic jurassic boundary since the revolution that signified the use of the hydrofluoric acid method in extracting radiolarians from hard siliceous rocks radiolarians have proven to be of great importance in reconstructing the stratigraphy of the mesozoic particularly the triassic system this methodology discovered independently by dumitrica 1970 and pessagno newport 1972 together with the building of a new taxonomic system for mesozoic radiolarians

podzol formation in sandy soils of finland abstract podzolization occurs quickly in acidic parent materials with addition of acidic litter from coniferous trees this study was conducted to evaluate podzol formation and estimate lengths of time required to meet morphological and chemical criteria of podzolic b horizon and spodic horizon in finland soil color organic c odoe and extractable al and fe were measured in a seven pedon chronosequence 230 1800 years and four older pedons 8300 11 300 years the bulk mineralogical composition of the bc and c horizons was uniform with quartz plagioclase and k feldspar as main components and amphibole illite and chlorite as minor components the fine

gas blowout from shallow boreholes near fiumicino international airport rome gas origin and hazard assessment abstract in summer 2013 a toxic and polluting gas blowout 19 tonnes day 1 co2 95 kg day 1 ch4 occurred from two shallow boreholes drilled at only 50 m from the international airport of rome italy in the town of fiumicino another gas blowout occurred in the same period from a borehole located offshore 2 km away also generating sea water acidification it lasted only a couple of days onshore co2 was also diffusing from holes within the soil particularly toward the airport generating a soil flux up to 1 8 tonnes day 1 in 3 5 months 1500 tonnes of co2 and 5 4 tonnes of ch4 were emitted in the atmosphere temporal monitoring of gas geochemistry indicates that in this area a mixing occurs between shallow and pressurized gas pockets co2 dominated but with different chemical i e he ch4 ratio and isotopic 3he 4he 13c dch4 characteristics numerical simulation of co2 dispersion in the atmosphere showed that dangerous air co2 concentrations up to lethal values were only found near the vents at a height of 0 2 m fiumicino is a high blowout risk area as co2 rising through deep reaching faults pressurizes the shallow aquifer contained in gravels confined underneath shales of the tiber delta deposits the fiumicino blowout is a typical example of dangerous phenomenon that may occur in urban context lying nearby active or recent volcanoes and requires quick response on hazard assessment by scientists to be addressed to civil protection and administrators

aragonite dissolution sedimentation rates and carbon isotopes in deep water hemipelagites livinallongo formation middle triassic northern italy hemipelagic nodular limestones are a widespread facies in the triassic of the tethys often considered as being deposited at rather constant sedimentation rates the aim of this paper is to investigate the sedimentation rate variability in a case study from the middle triassic of the dolomites northern italy and to suggest possible causes the nodular cherty limestones of the livinallongo fm and correlated units were studied in four stratigraphic sections and compared to classical successions from the literature correlations between sections are based on ammonoid biostratigraphy and tephra stratigraphy correlation highlighted conspicuous changes in sedimentation rates through time and between sections associated with sedimentological evidence of deep water aragonite dissolution deep water dissolution is believed to have resulted in small hiatuses and in a bias of ammonoid assemblages towards taxa with more resistant shells carbonate petrography and geochemistry provide evidence of differential diagenesis of the livinallongo fm carbonate nodules were lithified at the water sediment interface and their c isotope composition is regarded as a proxy of the d 13 c of middle triassic bottom seawater the onset of nodular cherty limestones occurring contemporaneously at the basin scale and the coeval carbonate platform drowning events are tentatively explained by the inflow and local upwelling of cool deep water from panthalassa into the western tethys d 2005 elsevier b v all rights reserved

cyanobacterial blooms tied to volcanism during the 5 m y permo triassic biotic crisis widespread but episodic deposition of cyanobacterial mats occurred during the 5 m y permo triassic biotic crisis providing a critical record to decipher the long term stressful environmental conditions and thus a linkage with the killer here we document the timing and duration of these blooms indicated by lipid biomarkers and microbialites throughout south china and compare them to the timing of volcanic activity the initial cyanobacterial bloom has the longest duration and is associated with a prominent eu anomaly in southwestern china where the most intensive volcanism has been proposed to occur suggesting a causal relationship subsequent cyanobacterial blooms in the early triassic are associated with known volcanic events in south china and also with the most voluminous siberian flood basalts and with the largest negative carbon isotope excursions thus it appears that volcanic activity has had a significant impact on microbial development in south china south china volcanism around the permian triassic boundary ptb could have played a much larger role in biotic changes of both bacterial and calcified faunal ecosystems than previously thought the well known siberian volcanism is proposed herein on the basis of the current compilation of dating data to protract the early triassic faunal recovery rather than to cause the end permian extinction

paleomagnetically determined rotations in the western sicilian fold and thrust belt new paleomagnetic data from the west sicilian fold and thrust belt indicate large scale clockwise rotations during tectonic transport for the platform and seamount paleogeographic units of the fold and thrust belt panormide and trapanese units there is a general consistency in the magnitude of rotation along strike suggesting the existence of large coherent structural units for the panormide platform clockwise rotations in the range of 90 to 140 relative to the underlying iblean parautochthon are recorded along 125 km of outcrop strike in the case of the trapanese unit clockwise rotations in the range of 47 to 70 relative to iblei are recorded along about 90 km of outcrop strike intervening basinal paleogeographic units imerese and sicanian units show clockwise rotations of similar magnitude although few reliable data are available from these units palinspastic reconstruction of the thrust belt incorporating the rotations and arguments for the present orientation of the margins of the paleogeographic units implies that the panormide platform and trapanese seamounts were originally elongated more or less north south relative to the present orientation of iblei the two units apparently coalesced to the south and were discontinuous to the north they and their intervening basins were part of a passive continental margin which occupied a large part of the area that was subsequently rifted to form the tyrrhenian sea

sudden deep gas eruption nearby rome s airport of fiumicino 1 on 24 august 2013 a sudden gas eruption from the ground occurred in the tiber river delta nearby rome s international airport of fiumicino we assessed that this gas analogous to other minor vents in the area is dominantly composed of deep partially mantle derived co2 as in the geothermal gas of the surrounding roman comagmatic province increased amounts of thermogenic ch4 are likely sourced from meso cenozoic petroleum systems overlying the deep magmatic fluids we hypothesize that the intersection of ne sw and n s fault systems which at regional scale controls the location of the roman volcanic edifices favors gas uprising through the impermeable pliocene and deltaic holocene covers pressurized gas may temporarily be stored below these covers or within shallower sandy permeable layers the eruption regardless the triggering cause natural or man made reveals the potential hazard of gas charged sediments in the delta even at distances far from the volcanic edifices

hydrothermal activity in the lau back arc basin sulfides and water chemistry the submersible nautile completed 22 dives during the nautilau cruise r v nadir april 17 may 10 1989 for a detailed investigation of the southern lau basin near tonga the objective of the scientific team from france germany and tonga was to understand the process of sea floor ore formation associated with hydrothermal circulation along the valu fa back arc ridge behind the tonga kermadec trench the four diving areas between lat 21 25 s and 22 40 s in water 2000 m deep were selected on the basis of results from cruises of the r v jeancharcot and r v sonne the nadir cruise provided proof of hydrothermal activity in all four areas over more than 100 km as indicated by the widespread occurrence of hydrothermal deposits and by heat flow conductivity and temperature measurements near the sea bottom the most spectacular findings were high temperature white and black smokers and associated fauna and ore deposits hydrothermal water chemistry and sulfide composition data presented here indicate that this hydrothermal field is very different from the hydrothermal fields in oceanic ridges this difference is seen in the water chemistry of the hydrothermal fluid ph 2 and high metal content and the chemical composition of sulfides enrichment in ba as and pb

morphology genesis and distribution of nanometer scale pores in siliceous mudstones of the mississippian barnett shale research on mudrock attributes has increased dramatically since shale gas systems have become commercial hydrocarbon production targets one of the most significant research questions now being asked focuses on the nature of the pore system in these mudrocks our work on siliceous mudstones from the mississippian barnett shale of the fort worth basin texas shows that the pores in these rocks are dominantly nanometer in scale nanopores we used scanning electron microscopy to characterize barnett pores from a number of cores and have imaged pores as small as 5 nm key to our success in imaging these nanopores is the use of ar ion beam milling this methodology provides flat surfaces that lack topography related to differential hardness and are fundamental for high magnification imaging nanopores are observed in three main modes of occurrence most pores are found in grains of organic matter as intraparticle pores many of these grains contain hundreds of pores intraparticle organic nanopores most commonly have irregular bubblelike elliptical cross sections and range between 5 and 750 nm with the median nanopore size for all grains being approximately 100 nm internal porosities of up to 20 2 have been measured for whole grains of organic matter based on point count data from scanning electron microscopy analysis these nanopores in the organic matter are the predominant pore type in the barnett mudstones and they are related to thermal maturation nanopores are also found in bedding parallel wispy organic rich laminae as intraparticle pores in organic grains and as interparticle pores between organic matter but this mode is not common although less abundant nanopores are also locally present in fine grained matrix areas unassociated with organic matter and as nano to microintercrystalline pores in pyrite framboids intraparticle organic nanopores and pyrite framboid intercrystalline pores contribute to gas storage in barnett mudstones we postulate that permeability pathways within the barnett mudstones are along bedding parallel layers of organic matter or a mesh network of organic matter flakes because this material contains the most pores

a serpentinite hosted ecosystem the lost city hydrothermal field the serpentinite hosted lost city hydrothermal field is a remarkable submarine ecosystem in which geological chemical and biological processes are intimately interlinked reactions between seawater and upper mantle peridotite produce methane and hydrogen rich fluids with temperatures ranging from 40 to 90 c at ph 9 to 11 and carbonate chimneys 30 to 60 meters tall a low diversity of microorganisms related to methane cycling archaea thrive in the warm porous interiors of the edifices macrofaunal communities show a degree of species diversity at least as high as that of black smoker vent sites along the mid atlantic ridge but they lack the high biomasses of chemosynthetic organisms that are typical of volcanically driven systems

organic petrology and geochemistry of mudrocks from the lacustrine lucaogou formation santanghu basin northwest china application to lake basin evolution abstract exploration for tight oil in the frontier santanghu basin of northwest china has resulted in recent commercial discoveries sourced from the lacustrine upper permian lucaogou formation already considered a world class source rock in the junggar basin to the west here we apply an integrated analytical program to carbonate dominated mudrocks from the lucaogou formation in santanghu basin to document the nature of organic matter om in the context of an evolving lake system the organic rich samples toc 2 8 11 4 wt n 10 were widely spaced from an 200 m cored section interpreted from textural and mineralogical evidence to document transition from a lower under filled to an overlying balanced filled lake organic matter is dominated by moderate to strongly fluorescent amorphous material with type i geochemical signature hi values 510 755 n 10 occurring in a continuum from lamellar stringers 10 20 m thick some 1 mm in length possible microbial mat preserved only in lower under filled section to finely disseminated amorphous groundmass intimately intermixed with mineral matrix biomarkers for methanotrophs and photosynthetic cyanobacteria indicate a complex microbial consortium a unicellular prasinophyte green alga similar to tasmanites in marine rocks is present as discrete flattened discs 50 100 m in diameter type iii om including vitrinite some fluorescent and inertinite also is abundant solid bitumen indicating local kerogen conversion fills voids and occurs throughout the cored section vitrinite reflectance values are 0 47 0 58 consistent with strong om fluorescence but may be suppressed other proxies e g biomarker parameters indicate the lucaogou formation is in the early oil window at this location on average slightly more amorphous om and telalginite are present in the lower section consistent with a shallow stratified saline environment with low sediment dilution more inertinite is present in the upper section indicating greater terrestrial influx and consistent with higher quartz and plagioclase content dominantly authigenic chalcedony and albite laminated mudstones in the upper section indicate anoxia prevented bioturbation from benthic grazing also indicating stratified water column conditions a decrease upsection in authigenic dolomite with reciprocal increase of ankerite siderite is consistent with decreasing salinity as is an overall decrease in gammacerane index values these observations suggest evolution from a shallow stratified evaporative saline setting to a deeper stratified freshwater basin with higher water input during lucaogou deposition the evolution from an under filled to balance filled lake in santanghu basin is similar to lucaogou deposition in junggar basin suggesting similar tectonic and climatic controls paleoclimate interpretations from other researchers in this area suggested an evolution from semi arid to humid conditions during the roadian we interpret that the evolution from an under filled to balanced filled lake seen in our data is in response to climate change and may represent increased groundwater delivery to the santanghu basin