the last phase of conodont evolution during the late triassic integrating biostratigraphic and phylogenetic approaches abstract for the upper triassic conodonts are the primary tools utilized in biostratigraphic investigations for an effective biostratigraphic zonation the species should be constrained by clear phylogenetic relationships in which the stratigraphic ranges and taxonomy are reliable unfortunately a phylogenetic framework for the late triassic pectiniform conodonts is almost missing except for particular intervals such as the carnian norian boundary the purpose of this study is to examine the latest norian and rhaetian pectiniform conodonts in detail in an attempt to determine their phylogenetic relationships by applying novel phylogenetic methodologies that incorporate both morphological and stratigraphic data this work is based on the conodont assemblages from the upper triassic strata of the lagonegro basin southern apennines southern italy and the cs var area north central hungary complemented with data from the literature the calibrated phylogenetic analysis of the latest norian and rhaetian conodonts supports a two step evolutionary history a first radiation 211 210 ma of the parvigondolella species and the first representative of the genus misikella followed by a second phase 206 5 205 ma leading to the final radiation of the misikella species furthermore the systematic revision of uppermost triassic conodonts is provided along with the description of misikella kolarae n sp

carbon mass balance isotopic tracers of biogenic methane and the role of acetate in coal beds powder river basin usa abstract a multi isotope c h o investigation of biogenic gas 13c ch4 13c co2 d ch4 and coal bed waters d 18o 13c dic 13c acetate was conducted along a 25 km basinward sampling transect in the powder river basin prb in wyoming and montana usa to address inconsistencies among isotope fingerprinting techniques and to apply mass balance isotope modeling to biogenic coalbed methane cbm results include the first published compound specific 13c acetate values from a natural biogenic cbm system providing new constraints on acetate s role in biogenic ch4 generation coal bed water chemistry is anoxic and dominated by na and hco3 with high alkalinity concentrations 14 8 33 0 meq l the deep basin interior environment contains sulfate free na hco3 dominated waters exhibiting signs of methanogenesis ch4 and co2 generally become 13c enriched from the shallow basin edge to the deep basin interior 13c ch4 78 2 to 56 2 and 13c co2 24 7 to 4 7 also compound specific 13c acetate is more positive in the basin interior compared to the basin edge setting range 34 3 to 15 1 using a steady state mass balance isotope model the observed variations in 13c ch4 and 13c co2 can be explained in terms of the favorability of methanogenesis fch4 relative to heterotrophic bacterially mediated non methanogenic pathways such as bacterial sulfate reduction which compete with methanogenesis for substrates at the basin interior fch4 exceeds 0 4 approaching its inferred limiting value hypothesized from the oxidation state of low molecular weight compounds detected in prb formation waters therefore methanogenesis is likely a dominant biogeochemical pathway consuming substrates in the deeper coal beds the basinward shift toward 13c enriched acetate broadly indicates linkage between acetate ch4 and co2 and likely records acetate synthesis effects modified by methanogenic fractionation these results suggest that acetate plays a role in methanogenesis in prb coal beds not necessarily a dominant role while other c isotope and microbial evidence suggests that hydrogenotrophic methanogenesis is also a significant methane producing pathway the results of this study broadly suggest multiple viable methanogenic pathways and c cycling that affects acetate a more complex view of coal bed geochemistry than implied by traditional c and h isotope fingerprinting of accumulated products ch4 co2 and coexisting water

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

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

chemosynthetic origin of 14 c depleted dissolved organic matter in a ridge flank hydrothermal system hydrothermal fluids circulate through the upper portion of the oceanic crust isotopic analyses suggest that chemosynthetic microbial communities in the crust synthesize dissolved organic carbon in hydrothermal ridge flank fluids

a rise in the carbonate compensation depth of western tethys in the carnian late triassic deep water evidence for the carnian pluvial event the upper triassic of the lagonegro basin southern apennines southern italy is represented by hemipelagic cherty limestones of the calcari con selce formation deposited in an oceanic setting two stratigraphic sections petina chiana and pignola 2 representative of the evolution of the lagonegro basin during the carnian have been studied in detail with a multidisciplinary approach in the pignola 2 section within the calcari con selce formation a unique interval composed of green shales and radiolarites has been identified the absence of carbonate deposition within this interval is interpreted as evidence of a contemporaneous shallowing of the carbonate compensation depth conodont and palynomorph biostratigraphy constrain the age of this interval to the julian tuvalian lower carnian upper carnian boundary the age and characteristics of this interval suggest correlation with a putative climatic event known as the carnian pluvial event which has also been recognized in continental and shallow marine successions from different european localities this event is thus now documented also in a deep marine setting like the continental and shallow water settings it is characterized by a sudden input of siliciclastics petina chiana and pignola 2 integrate current knowledge of the carnian distribution of conodonts paragondolella praelindae kozur to date known only from the lower tuvalian has now been documented from the uppermost julian moreover a drastic turnover was recorded between julian and tuvalian conodont assemblages which is clearly associated with the carnian pluvial event thus a biotic crisis oceanographic changes associated with the rise of the carbonate compensation depth increased rainfall and an anomalous siliciclastic input occur contemporaneously at the time of the carnian pluvial event a similar pattern is associated with perturbations of the carbon cycle that occur during the jurassic and cretaceous e g in the early aptian thus it is hypothesized that the carnian pluvial event may have analogous causes

dissociation of oceanic methane hydrate as a cause of the carbon isotope excursion at the end of the paleocene isotopic records across the latest paleocene thermal maximum lptm indicate that bottom water temperature increased by more than 4 c during a brief time interval 104 years of the latest paleocene 55 6 ma there also was a coeval 2 to 3 excursion in the 13c of the ocean atmosphere inorganic carbon reservoir given the large mass of this reservoir a rapid 13c shift of this magnitude is difficult to explain within the context of conventional hypotheses for changing the mean carbon isotope composition of the ocean and atmosphere however a direct consequence of warming bottom water temperature from 11 to 15 c over 104 years would be a significant change in sediment thermal gradients and dissociation of oceanic ch4 hydrate at locations with intermediate water depths in terms of the present day oceanic ch4 hydrate reservoir thermal dissociation of oceanic ch4 hydrate during the lptm could have released greater than 1 1 to 2 1 1018 g of carbon with a 13c of approximately 60 the release and subsequent oxidation of this amount of carbon is sufficient to explain a 2 to 3 excursion in 13c across the lptm fate of ch4 in oceanic hydrates must be considered in developing models of the climatic and paleoceanographic regimes that operated during the lptm

marine silicate weathering in the anoxic sediment of the ulleung basin evidence and consequences marine silicate weathering msiw in anoxic sediments has been recently shown to be a significant sink for co2 generated by methanogenesis independently the roles of clay dehydration illitization in producing water and driving upward fluid advection have been well established in deep marine sediments but to date the k source required for the reaction has not been established here we present chemical and strontium isotope properties of pore fluids from seven cores in the ulleung basin which show radiogenic 87sr 86sr values up to 0 71045 very high alkalinity values maximum 130 mm and enrichment in h4sio4 na k and mg2 consistent with msiw this reaction consumes co2 generates alkalinity and acts as a k source for illitization water released from msiw supported illitization drives upward fluid flow our results highlight the importance of msiw along continental margins and its underappreciated role in carbon cycling silicate diagenesis and hydrogeology of marine systems

hydrocarbon sources of cold seeps off the vesteralen coast northern norway abstract we investigated active methane seeps in a water depth of 200 m in the hola area off the coast of vesteralen northern norway to assess 1 hydrocarbon sources 2 migration pathways and 3 the influence of hydrocarbon seepage on sediment pore water and water column chemistry the seepage area is characterised by the presence of gas flares in the water column as revealed by hydro acoustic surveys and elevated methane concentrations of up to 42 nm ca 5 m above the seafloor pore water analyses of three gravity cores from the seepage area show varying depths of the sulphate methane transition zone smtz between 80 cm and 250 cm indicating spatially heterogeneous methane ascent the isotopic composition of methane 13 c from 40 to 63 and 2 h from 191 to 225 and 13 c depth profiles of methane and dissolved inorganic carbon show that the hydrocarbons are predominantly of thermogenic origin consistent with 13 c values of c 2 to c 4 hydrocarbons isotope data also indicate considerable biodegradation of propane seismic profiles from the study area reveal major faults and steeply dipping unconformities between the basement and overlying mesozoic sedimentary rocks we propose that these act as migration pathways for the hydrocarbons from late jurassic to early cretaceous source rocks

correlation of early cretaceous carbon isotope stratigraphy and platform drowning events a possible link the early cretaceous carbonate carbon isotope record is marked by three positive high amplitude 1 5 excursions each covering time spans of more than 106 years they are of late valanginian hauterivian and early and late aptian age in a case study along a transect across the western tethys ocean we identified a coincidence between 13c excursions black shale formation and widespread carbonate platform drowning events we conclude that the 13c excursions reflect a change in partitioning of carbon between the organic and carbonate carbon sinks which was triggered by climate induced ecological changes in cretaceous pelagic and neritic environments episodes of intensified greenhouse climate conditions led to an increase in weathering erosion and runoff rates and to elevated nutrient transfer rates from continents into oceans the resulting increase in oceanic nutrient levels favoured marine phytoplankton production and black shale deposition while conditions for carbonate producing biotas became unfavourable partial choking of carbonate production along river influenced coasts resulted in widespread carbonate platform drowning during times of sea level rise in the valanginian and aptian widespread contemporaneous black shale deposits and drowned carbonate platforms therefore reflect the contrasting response of the marine organic and carbonate carbon pumps to nutrient enhanced phytoplankton productivity the change in marine carbon partitioning is mirrored in a shift of the 13c record towards more positive values the transition to the 13c peak values lasted up to several hundred thousand years the peaks of the excursions also covering a time span of up to several hundred thousand years reflect a new stabilisation of the carbon partitioning between carbonate and organic carbon sinks a renewed intensification of carbonate sedimentation under mesotrophic conditions was facilitated by stabilisation of the sea level rise at a high level decreasing 13c values record increasing carbonate carbon burial rates at constant or decreasing organic carbon accumulation rates these changes contributed to the stabilisation of the marine carbon budget and the global carbon cycle up to millions of years after its initial perturbation

carbon sources in the north sea evaluated by means of radium and stable carbon isotope tracers a multitracer approach is applied to assess the impact of boundary fluxes e g benthic input from sedimentsor lateral inputs from the coastline on the acid base buffering capacity and overall biogeochemistry of the north sea analyses of both basin wide observations in the north sea and transects through tidalbasins at the north frisian coastline reveal that surface distributions of the d13c signature of dissolved inorganiccarbon dic are predominantly controlled by a balance between biological production and respiration in particular variability in metabolic dic throughout stations in the well mixed southern north sea indicatesthe presence of an external carbon source which is traced to the european continental coastline usingnaturally occurring radium isotopes 224ra and 228ra 228ra is also shown to be a highly effective tracer ofnorth sea total alkalinity at compared to the more conventional use of salinity coastal inputs of metabolicdic and at are calculated on a basin wide scale and ratios of these inputs suggest denitrification as aprimary metabolic pathway for their formation the at input paralleling the metabolic dic release preventsa significant decline in ph as compared to aerobic i e unbuffered release of metabolic dic finally longtermph trends mimic those of riverine nitrate loading highlighting the importance of coastal at productionvia denitrification in regulating ph in the southern north sea

altered carbon cycling and coupled changes in early cretaceous weathering patterns evidence from integrated carbon isotope and sandstone records of the western tethys abstract in this study we investigate if a major perturbation of the early cretaceous carbon cycle was accompanied by altered weathering and erosion rates the large aptian carbon isotope anomaly records the response of the biosphere to widespread volcanic activity and probably resulting changes in atmospheric pco 2 levels elevated pco 2 levels should also result in an accelerated hydrological cycle and increased silicate weathering creating a negative feedback loop removing co 2 from the atmosphere we propose to interpret the widespread occurrence of quartz sandstones in the tethys atlantic seaway as a result of altered weathering and erosion rates in the wake of the aptian carbon cycle excursion we challenge the traditional notion that these are flysch deposits associated with early cretaceous orogenic movements in the western tethys we propose that these sandstones were most likely part of a large conveyor belt system acting along the iberian and european margin of the tethys seaway using chemostratigraphic correlations we show that the activity of this system was only short lived and coeval with changes in coastal ecology and the aptian carbon cycle perturbations we tentatively relate the existence of this system to a transient climate regime characterized by fluctuating pco 2 levels

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

middle upper triassic carbonate platforms in minorca balearic islands implications for western tethys correlations abstract in order to progress in the knowledge of the middle to upper triassic evolution of the western tethys realm an integrated approach which includes new sedimentological sequence stratigraphic and biostratigraphic data has been accomplished in the carbonate marine successions muschelkalk facies of that age in minorca balearic islands spain the new biostratigraphy which includes six successive ammonoid biozones allowed to assign these carbonate successions to the uppermost anisian lower carnian interval the integration of the new chronostratigraphic framework with the sedimentological analysis allowed to recognize five main successive stages of carbonate platform evolution 1 initial marine transgression and shallow ramp development uppermost anisian 2 carbonate ramp drowning anisian ladinian boundary 3 prevalence of open sea conditions ladinian early carnian 4 abrupt sea level drop intra lower carnian and 5 shallow carbonate ramp and transition to sabkha systems keuper facies furthermore the sequence stratigraphic analysis allowed to divide some of these stages into depositional sequences minorca was located in the westernmost tethys area during the triassic in a key paleogeographic location close to the present day iberia sardinia and the cottian and southern alps the new data have allowed an interregional comparative analysis among these areas with recognition of major suprarregional events and episodes in the framework of the western tethys evolution

uptake of elements from seawater by ferromanganese crusts solid phase associations and seawater speciation marine fe mn oxyhydroxide crusts form by precipitation of dissolved components from seawater three hydrogenetic crust samples one phosphatized and two hydrothermal mn oxide samples were subjected to a sequential leaching procedure in order to determine the host phases of 40 elements those host phase associations are discussed with respect to element speciation in seawater the partitioning of elements between the two major phases mn oxide and fe oxyhydroxide can in a first order approximation be explained by a simple sorption model related to the inorganic speciation of the elements in seawater as has been proposed in earlier models free and weakly complexed cations such as alkali and alkaline earth metals mn co ni zn tl i and partly y are sorbed preferentially on the negatively charged surface of the mno2 in hydrogenetic crusts the driving force is a strong coulombic interaction all neutral or negatively charged chloro cd hg tl carbonate cu y pb and u and hydroxide be sc ti fe zr nb in sn sb te hf ta bi th and tl iii complexes and oxyanions v cr as se mo and w bind to the slightly positively charged surface of the amorphous feooh phase while coulombic interaction can explain the sorption of the negatively charged species the binding of neutral species is based on specific chemical interaction organic complexation of elements in deep ocean water seems to be at most of minor importance surface oxidation can explain some strong metal associations e g of co and tl with the mno2 and te with the feooh sorption reactions initially driven by coulombic forces are often followed by the formation of specific bonds between the adsorbate and the atoms of the oxide surface differences in the associations of some metals between the non phosphatized and phosphatized hydrogenetic crusts and between the hydrogenetic and the hydrothermal samples reflect the different physico chemical environments of formation and speciations in oxic seawater vs less oxic fluids especially for the redox sensitive metals such as mo and v these environmental related differences indicate that the methodology of chemical speciation used here in combination with spectroscopic methods may allow for the detection of changes in paleoceanographic conditions recorded during the several tens of millions of years of crust growth

the late triassic extinction at the norian rhaetian boundary biotic evidence and geochemical signature abstract the latest triassic was an interval of prolonged biotic extinction culminating in the end triassic extinction ete the ete is now associated with a perturbation of the global carbon cycle just before the end of the triassic that has been attributed to the extensive volcanism of the circum atlantic magmatic province camp however we attribute the onset of declining latest triassic diversity to an older perturbation of the carbon cycle 13corg of global extent at or very close to the norian rhaetian boundary nrb the nrb appears to be the culmination of stepwise biotic turnovers that characterize the latest triassic and includes global extinctions of significant marine and terrestrial fossil groups these biotic events across the nrb have been largely under appreciated yet together with a coeval disturbance of the carbon cycle were pivotal in the history of the late triassic here we present new and published 13corg data from widespread sections italy greece odp australia new zealand usa canada these sections document a previously unknown perturbation in the carbon cycle of global extent that spanned the nrb the disturbance extended across the panthalassa ocean to both sides of the pangaean supercontinent and is recorded in both the northern and southern hemispheres the onset of stepwise late triassic extinctions coincides with carbon perturbation 13corg at the nrb indicating that a combination of climatic and environmental changes impacted the biota at a global scale the nrb event may have been triggered either by gas emissions from the eruption of a large igneous province pre dating the nrb by a bolide impact of significant size or by some alternative source of greenhouse gas emissions as yet it has not been possible to clearly determine which of these trigger scenarios was responsible the evidence is insufficient to decisively identify the causal mechanism and merits further study

triassic jurassic boundary events inferred from integrated stratigraphy of the csővar section hungary abstract processes and causes of biotic and environmental change at the triassic jurassic transition remain controversial partly because of a scarcity of triassic jurassic boundary sections studied in detail continuous marine strata spanning the boundary are exposed at cs var hungary where new integrated stratigraphic data were obtained from multidisciplinary investigations to help reconstruct the end triassic and early jurassic events boundary strata are predominantly slope to basinal carbonates deposited in a periplatform basin the position of the system boundary is constrained by radiolarian foraminiferan conodont and ammonoid biostratigraphy pronounced radiolarian turnover is observed between assemblages assigned to the late rhaetian globolaxtorum tozeri zone and the early hettangian canoptum merum zone benthic foraminifera suffered lesser extinction successive conodont faunas of the latest rhaetian misikella posthersteini and misikella ultima zones record a marked drop in diversity and abundance but sporadic survivors persist into the earliest hettangian the extinction is also recorded in a reduction of biogenic components in carbonates decline of benthic and planktic biota is followed by a negative 13ccarb excursion of up to 6 that is composed of short term fluctuations revealed by dense sampling carbon and oxygen isotope ratios are positively correlated in the lower part of the section and appear to reflect primary variations drivers of the stable isotope trends are interpreted as warming in excess of 10 c and concomitant episodic short term perturbations of the global carbon cycle possibly due to methane release from gas hydrate dissociation induced by rapid climatic events the main biotic and isotopic events occurred within a single sedimentary cycle but sea level does not appear to have exerted a critical influence on these changes the triassic jurassic boundary crisis appears a short but not instantaneous event

assessing the record and causes of late triassic extinctions accelerated biotic turnover during the late triassic has led to the perception of an end triassic mass extinction event now regarded as one of the big five extinctions close examination of the fossil record reveals that many groups thought to be affected severely by this event such as ammonoids bivalves and conodonts instead were in decline throughout the late triassic and that other groups were relatively unaffected or subject to only regional effects explanations for the biotic turnover have included both gradualistic and catastrophic mechanisms regression during the rhaetian with consequent habitat loss is compatible with the disappearance of some marine faunal groups but may be regional not global in scale and cannot explain apparent synchronous decline in the terrestrial realm gradual widespread aridification of the pangaean supercontinent could explain a decline in terrestrial diversity during the late triassic although evidence for an impact precisely at the boundary is lacking the presence of impact structures with late triassic ages suggests the possibility of bolide impact induced environmental degradation prior to the end triassic widespread eruptions of flood basalts of the central atlantic magmatic province camp were synchronous with or slightly postdate the system boundary emissions of co2 and so2 during these eruptions were substantial but the contradictory evidence for the environmental effects of outgassing of these lavas remains to be resolved a substantial excursion in the marine carbon isotope record of both carbonate and organic matter suggests a significant disturbance of the global carbon cycle at the system boundary release of methane hydrates from seafloor sediments is a possible cause for this isotope excursion although the triggering mechanism and climatic effects of such a release remain uncertain d 2003 elsevier b v all rights reserved

formation pathways of light hydrocarbons in deep sediments of the danube deep sea fan western black sea abstract we report on the geochemistry of light hydrocarbons and pore water in sediments down to 147 m below seafloor mbsf at two sites within the gas hydrate stability field of the danube deep sea fan black sea sediments were drilled with marum mebo200 and comprise the transition from limnic to the recent marine stage stable c n ratios mean 5 1 and 5 6 and 13c corg values mean 25 8 v pdb suggest relatively uniform bulk organic matter compositions in contrast pore water 2h and 18o values varied considerably from approx 120 to 30 v smow and from 15 to 3 v smow respectively these data pairs plot close to the global meteoric water line and indicate paleo temperature variations depletions of pore water in 2h and 18o below 40 mbsf indicate low temperatures and likely reflect conditions during the last glacial period s methane was much more abundant than the only other hydrocarbons found in notable concentrations ethane and propane c1 c2 c3 20 000 relatively constant 13c ch4 70 v pdb and 13c c2h6 52 v pdb values with depth indicate that methane and ethane are predominantly of microbial origin and that their formation was not limited by carbon availability in contrast 2h ch4 values varied in a large range approx 310 to 240 v smow with depth and positively correlated with trends observed for 2h h2o isotope separations 13c ch4 co2 2h ch4 h2o substantiate that microbial carbonate reduction cr is the prevalent methanogenic pathway throughout the sediments irrespective of their geochemical history remarkably in 13c ch4 2h ch4 diagrams widely used samples characterized by 2h ch4 values more negative than approx 250 plot out of the field assigned for pure cr we conclude that assignments of microbial methanogenic pathways based on classical interpretations of 13c ch4 2h ch4 pairs can lead to misinterpretations as severe 2h depletions of methane formed through microbial cr can result from 2h depletions of the pore water generated during low temperature climatic periods

sources and turnover of organic carbon and methane in fjord and shelf sediments off northern norway to better understand the present and past carbon cycling and transformation processes in methane influenced fjord and shelf areas of northern norway we compared two sediment cores from the hola trough and from ullsfjorden we investigated 1 the organic matter composition and sedimentological characteristics to study the sources of organic carbon corg and the factors influencing corg burial 2 pore water geochemistry to determine the contribution of organoclastic sulfate reduction and methanogenesis to total organic carbon turnover and 3 the carbon isotopic signature of hydrocarbons to identify the carbon transformation processes and gas sources high sedimentation and corg accumulation rates in ullsfjorden support the notion that fjords are important corg sinks the depth of the sulfate methane transition smt in the fjord is controlled by the supply of predominantly marine organic matter to the sediment organoclastic sulfate reduction accounts for 60 of the total depth integrated sulfate reduction in the fjord in spite of the presence of ethane propane and butane we suggest a purely microbial origin of light hydrocarbons in the sediments based on their low 13c values in the hola trough sedimentation and corg accumulation rates changed during the deglacial to post glacial transition from approximately 80 cm ka 1 to erosion at present thus corg burial in this part of the shelf is presently absent low organic matter content in the sediment and low rates of organoclastic sulfate reduction only 3 of total depth integrated sulfate reduction entail that the shallow depth of the smt is controlled mostly by ascending thermogenic methane from deeper sources this article is protected by copyright all rights reserved

the stable carbon isotope biogeochemistry of acetate and other dissolved carbon species in deep subseafloor sediments at the northern cascadia margin abstract ocean drilling has revealed the existence of vast microbial populations in the deep subseafloor but to date little is known about their metabolic activities to better understand the biogeochemical processes in the deep biosphere we investigate the stable carbon isotope chemistry of acetate and other carbon bearing metabolites in sediment pore waters acetate is a key metabolite in the cycling of carbon in anoxic sediments its stable carbon isotopic composition provides information on the metabolic processes dominating acetate turnover in situ this study reports our findings for a methane rich site at the northern cascadia margin ne pacific where expedition 311 of the integrated ocean drilling program iodp sampled the upper 190 m of sediment at site u1329 13c values of acetate span a wide range from 46 0 to 11 0 vs vpdb and change systematically with sediment depth in contrast 13c values of both the bulk dissolved organic carbon doc 21 6 1 3 vs vpdb and the low molecular weight compound lactate 20 9 1 8 vs vpdb show little variability these species are interpreted to represent the carbon isotopic composition of fermentation products relative to doc acetate is up to 23 1 depleted and up to 9 1 enriched in 13c broadly 13c depletions of acetate relative to doc indicate flux of carbon from acetogenesis into the acetate pool while 13c enrichments of pore water acetate relative to doc suggest consumption of acetate by acetoclastic methanogenesis isotopic relationships between acetate and lactate or doc provide new information on the carbon flow and the presence and activity of specific functional microbial communities in distinct biogeochemical horizons of the sediment in particular they suggest that acetogenic co2 reduction can coexist with methanogenic co2 reduction a notion contrary to the hypothesis that hydrogen levels are controlled by the thermodynamically most favorable electron accepting process further the isotopic relationship suggests a relative increase in acetate flow to acetoclastic methanogenesis with depth although its contribution to total methanogenesis is probably small our study demonstrates how the stable carbon isotope biogeochemistry of acetate can be used to identify pathways of microbial carbon turnover in subsurface environments our observations also raise new questions regarding the factors controlling acetate turnover in marine sediments

acetate cycling in the water column and surface sediment of long island sound following a bloom a number of workers have suggested that rates of acetate cycling in sediments may approximate the rates of anaerobic decomposition of organic matter however few studies have examined whether this relationship holds over very short time scales such as those encountered during the deposition of the spring bloom into coastal sediments in this study we measured acetate concentrations and uptake rate constants in surface and bottom waters and in the top few centimeters of sediment in long island sound samples were collected every 2 3 weeks from early spring to early summer of 1993 acetate concentrations varied from 85 to 530 nm in the water column and from 2 to 29 8 fm in pore water acetate concentrations in pore water showed a strong depth variation with a concentration maximum in the surface few millimeters as well as a strong temporal variation the concentration of acetate averaged over the top 4 cm varied from about 5 pm in the early spring to 14 3 pm following the addition of spring bloom dcrivcd organic carbon acetate uptake rate constants in the water column varied from 0 0012 to 0 037 h l turnover time 33 4 to 1 13 d the avcragc uptake rate constants in the sediment over the top 4 cm varied from 0 07 to 0 59 h l turnover time 0 59 to 0 07 d and tended to increase over the course of the experiment in both the sediment and the water column in the water column acetate uptake rates calculated as rate constant times concentration varied from less than one nanomolc per liter per hour in the early spring to tens of nanomoles per liter per hour in the early summer in the sediment over the same period acetate uptake rates averaged over the top 4 cm varied from 0 13 to 5 25 pm i h i rates of acetate metabolism to co agreed within a factor of two to cstimatcs of the x0 flux from the sediments and both increased sharply following the deposition of the spring bloom however because temperatures were also increasing during this period we are unable to separate unambiguously the effects of supply of labile carbon and of temperature on the acetate uptake rate

new paleontological evidence of the carnian strata in the mežica area karavanke mts slovenia conodont data for the carnian pluvial event abstract the carnian carbonate succession in the me ica area called raibl beds karavanke mts slovenia on the north of the periadriatic line in the eastern alps includes three clastic horizons of marly shaly rocks the most interesting is the second clastic horizon that contains unique layers or lenses of micritic limestone although many samples were collected for conodonts only one single sample yielded well preserved carnian julian specimens the monospecific conodont fauna is marked by elements of nicoraella budaensis that enables us to reconstruct a multielemental apparatus the sporomorph associations of the first and the second clastic horizons are well correlated to the humid sub phases in the raibl beds the recovered conodont fauna verifies the julian age of the second clastic horizon in the me ica area and it provides new significant information for definition of the carnian pluvial event in the karavanke mts

mesozoic alpine facies deposition as a result of past latitudinal plate motion the fragmentation of pangaea as a consequence of the opening of the atlantic ocean is documented in the alpine mediterranean region by the onset of widespread pelagic sedimentation1 shallow water sediments were replaced by mainly pelagic limestones in the early jurassic period radiolarian cherts in the middle late jurassic period and again pelagic limestones in the late jurassic cretaceous period1 during initial extension basin subsidence below the carbonate compensation depth ccd is thought to have triggered the transition from early jurassic limestones to middle late jurassic radiolarites1 it has been proposed that the transition from radiolarites to limestones in the late jurassic period was due to an increase in calcareous nannoplankton abundance when the ccd was depressed below the ocean floor1 but in modern oceans sediments below the ccd are not necessarily radiolaritic here we present palaeomagnetic samples from the jurassic cretaceous pelagic succession exposed in the lombardian basin italy on the basis of an analysis of our palaeolatitudinal data in a broader palaeogeographic context we propose an alternative explanation for the above facies tripartition we suggest that the lombardian basin drifted initially towards and subsequently away from a near equatorial upwelling zone of high biosiliceous productivity our tectonic model for the genesis of radiolarites adds an essential horizontal plate motion component to explanations involving only vertical variations of ccd relative to the ocean floor it may explain the deposition of radiolarites throughout the mediterranean and middle eastern region during the jurassic period

geochemical origin of hydrothermal fluid methane in sediment associated fields and its relevance to the geographical distribution of whole hydrothermal circulation abstract we investigated the chemical composition of hydrothermal fluids and deduced the origin of hydrothermal fluid methane in a sediment associated minami ensei me hydrothermal field the okinawa trough the endmember hydrothermal fluid of the me field contained isotopically 13 c enriched methane 26 0 to 24 7 which suggested a thermogenic origin however the observed methane dominating hydrocarbon compositions c 1 c 2 10 3 suggested that biogenic methane not thermogenic hydrocarbons is predominant the conflict between these geochemical indications can be resolved by the hypothesis that the thermal reaction of sedimentary organic matter initially generates the primary source of hydrocarbons and the secondary thermal decomposition of hydrocarbons increases the c 1 c 2 ratio as high as that of biogenic methane the low molecular hydrogen concentration 0 04 mmol kg in the me fluid suggests that the thermal fluid sediment interaction occurred in the recharge stage not the discharge stage of hydrothermal circulation less biogenic methane in the me fluid implies a laterally shrunken hydrothermal fluid circulation that reduced biogenic methane incorporation at the recharge stage a comparison of hydrothermal fluid chemistry and geological geographical settings among the global sediment associated hydrothermal systems also suggests representative patterns in the geochemical origins of hydrothermal fluid methane and their relevance to hydrothermal fluid circulation as a whole

new constraints on the end triassic upper norian rhaetian magnetostratigraphy abstract the end triassic was marked by one of the five important phanerozoic global mass extinctions the construction of a detailed magnetic polarity time scale for this period that would integrate data from marine and terrestrial realms is thus of particular interest we report new magnetostratigraphic data from the oyuklu section located in southwestern turkey which allow one to propose a complete late upper norian sevatian 2 to rhaetian magnetic polarity sequence two correlations are discussed between the new tethyan marine sequence and the continental magnetic polarity record previously determined from the newark basin in eastern north america both options suggest that the rhaetian is at least partly missing in the newark basin which would reconcile most late triassic magnetostratigraphic results and biotic features obtained from marine and continental environments following our preferred correlation the rhaetian would have a duration as short as 2 myr and 4 5 myr if the sevatian 2 zone is included as part of the rhaetian

barium sio2 excess and p2o5 as proxies of biological productivity in the middle east during the palaeocene and the latest palaeocene benthic extinction event the distribution of barium and other elements related to biological productivity has been studied in two palaeocene sections from the middle east in the bathyal ben gurion section israel ba ba al2o3 15 concentrations are low in the range 0 04 to 0 3 in the lower palaeocene and very high 1 to 2 throughout most of the upper palaeocene in the neritic gebel aweina section in egypt ba values are low 0 1 throughout the entire palaeocene the ba enrichments at ben gurion and their correlations with increases in p2o5 and opaline silica and local and global 13c maxima indicate that upwelling and high productivity were important in this region during the late palaeocene the absence of ba enrichments in the shallower gebel aweina section probably reflects the strong depth dependence of biobarium deposition in the uppermost palaeocene at the level where the global benthic extinction event is registered ba concentrations in the ben gurion section increase to anomalous 6 which suggests that upwelling and possibly wind strengths intensified during this event the results speak against deep water formation in this region since downwelling and not upwelling is required

interelement relationships in ferromanganese crusts from the central pacific ocean their implications for crust genesis the fine scale chemical variations in ferromanganese fe mn crusts from the central pacific ocean were investigated using a variety of techniques in order to elucidate their genesis thirty seven major minor and trace elements were determined by icp oes and icp ms in sub samples collected at approximately 2 mm intervals throughout the crust sequences an inverse relationship is observed between the logarithm of the elemental distribution coefficients log cmncsw and the mean residence time tr of elements in seawater these associations provide evidence supporting the strong link between seawater and fe mn crust chemistry results of factor analysis reveal that elements in crusts can generally be partitioned into four major groups with selected elements displaying associations with several groups these statistical associations are interpreted to represent hydrogenetic mn ni co cu ce zn biogenic ba zn cu pt fe detrital al si fe and carbonate fluorapatite ca p ree groups a comparison between elemental associations in fine scale data from individual crust sequences and bulk compositional data from samples collected in separate locations reveals very similar elemental associations the similar elemental associations in bulk samples and in fine scale subsamples from individual crusts are consistent with the notions that hydrogenetic crusts exhibit no significant post depositional remobilization of elements and that elemental distributions within crusts reflect the chemistry of oceanic water during the period in which they accreted chemical paleotracks are proposed based on factor scores derived from chemical variations as a function of depth in individual crusts our results show that there is internal consistency between the chemical evolution previously proposed seamount paleotracks and nanofossil biostratigraphy dating results

on the mesozoic ionian basin summary new seismic reflection profiles of the italian deep crust project crop provide new insights on the structure of the ionian sea in spite of the apennines and hellenides neogene subduction zones two conjugate passive continental margins are preserved at the margins of the ionian sea along the malta escarpment to the southwest and the apulian escarpment to the northeast the ionian sea is likely to be a remnant of the mesozoic tethys ocean confined by these two conjugate passive continental margins the transition from continental to oceanic crust appears sharper to the northeast than to the southwest the basin between southeast sicily and southwest puglia was about 330 km wide and suggests a low spreading rate the inferred oceanic ridge should have been flattened by thermal cooling and buried by later sediments based on stratigraphic and structural constraints to the north in the apennines belt the ocean continued to the northwest this palaeogeography is supported by the seismicity of the apennines slab underneath the southern tyrrhenian sea which implies downgoing oceanic lithosphere the adjacent absence or paucity of deep seismicity does not imply absence of subduction but rather it can be interpreted as due to the more ductile behaviour of the subducted continental lithosphere surprisingly we note that where the oceanic inherited basin is subducting underneath the apennines in the hangingwall of the subduction hinge there are outcropping slices of continental crystalline basement previously deformed by the alpine orogen

phosphogenesis carbon isotope stratigraphy and carbonate platform evolution along the lower cretaceous northern tethyan margin we distinguish three different stages in the evolution of the tithonian late jurassic to aptian early cretaceous northern tethyan carbonate platform 1 carbonate production in the coral oolite mode late tithonian to early valanginian early barremian to early aptian 2 carbonate production in the crinoid bryozoan mode early valanginian haute rivian late aptian and 3 platform retrogradation and destruction condensation and phosphogenesis that is platform drowning early valanginian to early hauterivian middle hauterivian late hauterivian to early barremian early to early late aptian and latest aptian to earliest albian transitions from the coral oolite mode to the crinoid bryozoan mode and consequently to platform drowning may have been driven by increases in nutrient levels on the shelf phases of relative sea level rise in times of carbonate production in the coral oolite mode are named constructive because of the observed platform regeneration following phases of widespread emersion during late sea level highstands in contrast phases of relative sea level rise in times of platform drowning are termed destructive the 13 c stratigraphies obtained from valanginian hauterivian and aptian albian hemipelagic successions beyond the platform correlate well with the early cretaceous pelagic 13 c record positive excursions in the pelagic 13 c record correspond in time to episodes of platform drowning this suggests the existence of a coupling mechanism between changes in the global carbon cycle and platform drowning in our view the early cretaceous crises in carbonate platform growth were the consequence of reinforced greenhouse conditions which may have been triggered by episodes of extensive flood basalt volcanism strong greenhouse conditions may have induced the following chain of feedback mechanisms enabling the biosphere to return to normal conditions climate warming sea level rise accelerated water cycle intensified weathering nutrient mobilization platform destruction increased productivity increased phosphogenesis and carbon burial weakened greenhouse conditions

multi year pressure ridges in the canadian beaufort sea abstract pressure ridges and hummocks are the largest of the sea ice relief features seen in the ice cover which characterizes the canadian beaufort sea due to their massiveness and structural integrity multi year pressure ridges are generally considered to be the most formidable formations in this area and represent not only a significant impediment to shipping but also a major problem in the design of offshore structures here the findings of a field study designed to generate fundamental data on multi year pressure ridges in the near shore zone of the canadian beaufort sea are presented the study investigated the geometry of eleven floating multi year ridges or ridge fragments and the sail height and keel depth of four additional multi year ridge fragments the cross sections of multi year ridges with total thicknesses varying between 9 6 and 41 8 m were examined and the results suggest that they can be adequately represented by one ridge model with a constant sail to keel ratio and geometry it is also shown that the ice comprising multi year ridges is solid with the interblock voids existing at the time of their formation being completely filled with ice the data obtained from this study is being used in the engineering design of exploration and production systems for the beaufort sea in the shallow waters of this area exploratory drilling from artificial islands has been carried out since 1973 and since 1976 the exploration effort has extended into the deeper waters of the beaufort sea using drillships

a global analysis of mid ocean ridge axial topography summary current views of mid ocean ridges are strongly influenced by extensive mapping of the mid atlantic ridge and east pacific rise the global picture of the mid ocean ridge system particularly in the sparsely surveyed southern oceans is still based primarily on underway bathymetry profiles collected over the past 40 years this study presents a quantitative analysis of global mid ocean ridge morphology based on 156 of these underway bathymetric profiles thereby allowing commonly recognized features such as axial valleys and axial ridges to be compared on a global basis an empirical orthogonal function eof analysis is used to separate deterministic and stochastic components of axial morphology and to quantify the dependence of each on parameters such as spreading rate and axial depth it is found that approximately 50 per cent of the variance in axial morphology may be described as a linear combination of five independent symmetric and anti symmetric modes the remainder is considered stochastic maximum axial valley relief decreases with spreading rate for rates less than 80 mm yr 1 while axial ridge relief remains relatively constant for all rates greater than 50 mm yr 1 the stochastic component of the axial morphology referred to as bathymetric roughness also decreases with spreading rate for rates less than 80 mm yr 1 and remains relatively constant at higher rates although both axial valley relief and bathymetric roughness near the ridge axis show a similar spreading rate dependence they are weakly correlated at slow spreading centres the distinct differences in morphologic variability of fast and slow spreading ridges may result from the episodicity of magmatic heat input which controls the lithospheric rheology at slow spreading ridges these observations support the notion of a critical threshold separating two dynamically distinct modes of lithospheric accretion on mid ocean ridges

modeling sulfate reduction in methane hydrate bearing continental margin sediments does a sulfate methane transition require anaerobic oxidation of methane the sulfate methane transition smt a biogeochemical zone where sulfate and methane are metabolized is commonly observed at shallow depths 1 30 mbsf in methane bearing marine sediments two processes consume sulfate at and above the smt anaerobic oxidation of methane aom and organoclastic sulfate reduction osr differentiating the relative contribution of each process is critical to estimate methane flux into the smt which in turn is necessary to predict deeper occurrences of gas hydrates in continental margin sediments to evaluate the relative importance of these two sulfate reduction pathways we developed a diagenetic model to compute the pore water concentrations of sulfate methane and dissolved inorganic carbon dic by separately tracking dic containing 12c and 13c the model also computes 13c dic values the model reproduces common observations from methane rich sediments a well defined smt with no methane above and no sulfate below and a 13c dic minimum at the smt the model also highlights the role of upward diffusing 13c enriched dic in contributing to the carbon isotope mass balance of dic a combination of osr and aom each consuming similar amounts of sulfate matches observations from site u1325 integrated ocean drilling program expedition 311 northern cascadia margin without aom methane diffuses above the smt which contradicts existing field data the modeling results are generalized with a dimensional analysis to the range of smt depths and sedimentation rates typical of continental margins the modeling shows that aom must be active to establish an smt wherein methane is quantitatively consumed and the 13c dic minimum occurs the presence of an smt generally requires active aom

sr isotope variations in the upper triassic succession at pizzo mondello sicily constraints on the timing of the cimmerian orogeny abstract the late triassic cimmerian orogeny was a result of the final closure of the palaeotethys ocean and the accretion of gondwana derived cimmerian continents to southern eurasia determining the timing of the cimmerian orogeny is crucial to our understanding of the large scale climate changes driven by the uplift of the cimmerian mountains here we present stratigraphic variations in 87sr 86sr values of upper triassic pelagic limestone from the pizzo mondello section sicily italy that constrain the timing of uplift of the cimmerian mountains the 87sr 86sr values remain relatively constant in the lower part of the section decreasing slightly in the tuvalian upper carnian and lacian lower norian however 87sr 86sr ratios rise sharply at the lacian alaunian lower middle norian boundary and continue to rise through to the sevatian upper norian this observation indicates an increased input of radiogenic strontium derived from continental weathering which resulted from the rapid uplift and erosion of the cimmerian mountains at this time the climatic and environmental changes following the uplift of the cimmerian mountains provide an explanation for 1 an intense sea surface temperature warming event in the western tethys ocean and 2 a rapid increase in precipitation on the northern coast of the tethys during the alaunian sevatian

towards constraining h2 concentration in subseafloor sediment a proposal for combined analysis by two distinct approaches molecular hydrogen h 2 is a central metabolite that couples organic matter degradation and terminal electron accepting processes h 2 levels in natural environments are often regulated by microbial syntrophy therefore pore water h 2 concentration is a useful parameter for studying biogeochemical processes in sediments however little is known about h 2 concentrations in marine subsurface sediments previous studies applying either a headspace equilibration technique or an extraction method for the analysis of pore water h 2 in deeply buried sediments have generated results that sometimes contradict the principles established based on studies of microbial culture and surface sediments in this study we first evaluated and optimized an extraction method which was then applied in combination with a headspace equilibration method to determine concentrations of pore water h 2 in subseafloor sediments along a transect of five sites of different water depths and geochemical regimes at the continental margin off namibia se atlantic the two methods generated depth profiles with some similarities in curve shape but the extraction method yielded higher h 2 values than the headspace equilibration technique by comparing the two data sets with thermodynamic calculations of potential terminal electron accepting processes we were able to provide a first evaluation of syntrophic conditions in subseafloor sediment from the perspective of h 2 biogeochemistry we observed that in the sulfate reduction zone the h 2 concentrations are higher than the h 2 threshold allowed for the next most favorable terminal metabolism methanogenesis suggesting relaxation of coupling between h 2 producing and h 2 consuming activities at these depths in contrast the h 2 concentrations in the upper methanogenic zone are low enough for methanogens to outcompete co 2 reducing acetogens our findings suggest the existence of varied extents of syntrophic h 2 coupling in subseafloor sediment

scavenged excess aluminum and its relationship to bulk titanium in biogenic sediment from the central equatorial pacific ocean we present results from chemical analyses of al and ti in surface sediment sampled along two cross equator latitudinal transects at 135w and 140w in the central equatorial pacific ocean although traditionally both al and ti are considered to reside exclusively within terrigenous phases in marine sediment these sediments present extremely high al ti ratios that are several times that of average shale and other potential crustal sources a sharp maximum in al ti is observed slightly south of the equator where sedimentary bulk accumulation rate bar is also highest reflecting elevated productivity in the overlying water caused by surface water divergence bulk al ti decreases sharply away 2 latitude to near crustal values at 4 north and south the latitudinal profiles of al ti are entirely unrelated to the concentration of the biogenic components as well as to the absolute accumulation of al and ti these results indicate the presence of a significant scavenged component of al sourced directly from seawater during particle settling the data from the two transects analytically and oceanographically confirms our earlier work that was based on the single 135w transect calculations of alexcess indicate that the highest al ti ratios correspond to 50 of the total al being unsupported by the small amount of terrigenous phases present these results are consistent with previous and ongoing studies of biogenic sediment suspended particulate matter and sediment trap material quantitative use of al as an index of terrigenous material may therefore lead to an overestimation by a factor of two of the true terrigenous load in marine sediment sedimentary rock and settling particles because bulk al ti appears to respond to sedimentary bar which in biogenic regimes is linked to surface water productivity downcore records of al ti in biogenic sediment may track productivity changes through time such al ti proxy records may be applicable in sediment of all ages unlike radionuclide tracers which are limited by radioactive decay to use over the past hundreds of kyr

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

top bottom multisensor remote sensing of arctic sea ice the arctic sea ice cover has been studied using near simultaneous observations by passive and active synthetic aperture radar sar microwave sensors upward looking and sidescan sonars a lidar profilometer and an infrared sensor data from two aircraft and a submarine over an approximately 100 km track of central arctic sea ice were registered and analyzed to evaluate the characteristics of the ice cover and the utility of each sensor in ice studies the results of comparative and correlation analyses are as follows the probability density functions of ice draft from sonar and elevation from lidar were found to be almost identical when isostasy is taken into account this result suggests that the basic ice thickness distribution can be derived from the surface topography measurements alone reasonable correlation was found between sar backscatter and ice draft or elevation especially when scales were adjusted such that 15 20 sar pixels were averaged however surface roughness derived directly from standard deviations in the lidar elevation data was found to be poorly correlated to the sar backscatter these results indicate that the sar values are affected more by scattering from the ice than from the snow covered surface the active and passive microwave sensors are shown to generally complement each other as the two sensors are especially sensitive to different physical properties of the sea ice undeformed first year ice showed low backscatter values but high brightness temperatures while some multiyear ice showed high backscatter values and low brightness temperature however surfaces identified as multiyear ice by the passive system have a large spread in the unaveraged sar backscatter indicating limitations when using a one channel sar for ice type identification at the highest resolution also ridged ice identified by sonar and sar data covers a large range of passive microwave emissivity suggesting considerable variability in the age and salinity of this type of ice significant variations about 0 11 in the minimum emissivity of consolidated multiyear ice are observed in different regions of the arctic using the high resolution 30 m passive microwave data this suggests that regional variations in texture and scattering characteristics of multiyear ice in the arctic are present likely influenced by different histories of formation of the ice in different regions

reef expansion during the triassic spread of photosymbiosis balancing climatic cooling the paleoreefs database indicates that reef abundance increased profoundly during the triassic period from a pronounced low in the early triassic to a major peak in the norian this expansion is also evident when standardizing for sampling corresponding to the reef expansion is a relative increase of scleractinian corals as reef builders whereas the contribution of hypercalcifying sponges and microbes decreased during the triassic the numerical expansion of corals is paralleled by a proportional increase of morphological features that are suggestive of photosymbiosis such that the norian reef boom might be explained by the spread of photosymbiosis in corals the geographical expansion of reefs was far less pronounced especially concerning palaeolatitude late triassic reef growth was limited to more or less the same latitudinal range as modern reefs as oxygen isotope data and new modeling results indicate declining temperatures and co2 concentrations during the late triassic the lack of latitudinal expansion might be attributed to global cooling reef development during the triassic can thus be explained by the evolutionary spread of photosymbiosis balancing the effects of climatic cooling

the partition of air ice ocean momentum exchange as a function of ice concentration floe size and draft a coupled sea ice ocean model is used to examine the relative magnitudes of terms in the sea ice momentum equation for ice concentrations less than 100 this numerical model for steady state horizontally homogeneous flow includes two terms that have previously been neglected in such quantitative models these are oceanic form drag and wave radiation pressure both of which are lateral forces that act on the sides of floes the former is generally decelerative while the latter is accelerative the model accepts as input variables average ice draft areal concentration and floe diameter it is found that form drag can be greater than or of the same order as skin friction drag for small thick floes at low concentrations an exception to this rule occurs when the effect of wakes between floes reduces the local form drag the higher net drag that generally exists at low concentrations implies lower ice floe speeds wave radiation pressure is negligible in all cases although this is sensitive to our choice of fetch parameterization ocean drag is often parameterized in numerical models of sea ice as a skin friction term alone with a constant drag coefficient between ice and prescribed geostrophic current velocities results from the present model are plotted in terms of such a drag coefficient which is a function of concentration floe size and draft this could be useful in future work where floe size data become regularly available for instance from radar satellite imagery

the effect of diagenesis and fluid migration on rare earth element distribution in pore fluids of the northern cascadia accretionary margin analytical challenges in obtaining high quality measurements of rare earth elements rees from small pore fluid volumes have limited the application of rees as deep fluid geochemical tracers using a recently developed analytical technique we analyzed rees from pore fluids collected from sites u1325 and u1329 drilled on the northern cascadia margin during the integrated ocean drilling program iodp expedition 311 to investigate the ree behavior during diagenesis and their utility as tracers of deep fluid migration these sites were selected because they represent contrasting settings on an accretionary margin a ponded basin at the toe of the margin and the landward tofino basin near the shelf s edge ree concentrations of pore fluid in the methanogenic zone at sites u1325 and u1329 correlate positively with concentrations of dissolved organic carbon doc and alkalinity fractionations across the ree series are driven by preferential complexation of the heavy rees simultaneous enrichment of diagenetic indicators doc and alkalinity and of rees in particular the heavy elements ho to lu suggests that the heavy rees are released during particulate organic carbon poc degradation and are subsequently chelated by doc ree concentrations are greater at site u1325 a site where shorter residence times of poc in sulfate bearing redox zones may enhance ree burial efficiency within sulfidic and methanogenic sediment zones where ree release ensues cross plots of la concentrations versus cl li and sr delineate a distinct field for the deep fluids z 75 mbsf at site u1329 and indicate the presence of a fluid not observed at the other sites drilled on the cascadia margin changes in ree patterns the presence of a positive eu anomaly and other available geochemical data for this site suggest a complex hydrology and possible interaction with the igneous crescent terrane located east of the drilled transect

temperature limits to deep subseafloor life in the nankai trough subduction zone microorganisms in marine subsurface sediments substantially contribute to global biomass sediments warmer than 40 c account for roughly half the marine sediment volume but the processes mediated by microbial populations in these hard to access environments are poorly understood we investigated microbial life in up to 1 2 kilometer deep and up to 120 c hot sediments in the nankai trough subduction zone above 45 c concentrations of vegetative cells drop two orders of magnitude and endospores become more than 6000 times more abundant than vegetative cells methane is biologically produced and oxidized until sediments reach 80 to 85 c in 100 to 120 c sediments isotopic evidence and increased cell concentrations demonstrate the activity of acetate degrading hyperthermophiles above 45 c populated zones alternate with zones up to 192 meters thick where microbes were undetectable

structural evolution of the lucanian apennines southern italy abstract in this paper we present a study of an entire segment of the southern apennines of italy extending from the pollino mountain range to the south to the agri valley to the north in which all the units of the chain are represented combining regional information with detailed structural data obtained from the different tectonic units forming the orogenic belt the structure as well as the tectonic evolution of this portion of the orogenic belt are proposed the overall architecture of this segment of the southern apennines mountain chain represents the result of a complete orogenic cycle in which oceanic subduction syn collisional and post collisional events are well recorded structurally this segment of the orogenic belt exhibits two distinct structural levels separated by a major detachment surface the sole thrust of the accretionary wedge that occur at the surface in the allochthonous nappes and at depth in the adria continental margin the upper level is characterized by an imbricated fan system affecting the allochthonous terranes emplaced during oceanic subduction and the first stages of continent continent collision the lower level is represented by a duplex geometry that has developed in the post collisional stage during evolution of the foreland migrating thrust system involving the carbonate platform basin system of the adria block during the last stages of the mountain building process when the foreland thrust migration was locked by the thickening of the colliding continental crusts the southern apennines were thus affected by a severe strike slip tectonics that dissects the entire mountain belt deeply modifying the previous thrust geometry

the asynchronous disappearance of conodonts new constraints from triassic jurassic boundary sections in the tethys and panthalassa abstract the end triassic extinction event ete has been recognized in numerous sections worldwide and it is usually marked by three negative carbon isotope excursions ncies named precursor p ncie initial i ncie and main m ncie negative carbon isotope excursions these three ncies are significant characteristics of this time interval and they are likely related to the emplacement of the central atlantic magmatic province camp that is considered the main trigger of the ete stable carbon isotope excursions commonly related to biotic turnovers and extinctions play an important role in stratigraphic correlations particularly around the triassic jurassic boundary tjb this time interval records the disappearance of conodonts elements of a feeding apparatus belonging to marine organisms that populated the paleozoic early mesozoic seas and which became extinct across the tjb so far the interpretation of conodont extinction has remained ambiguous as the timing of its last occurrence was debated which in turn hindered our understanding of the main cause s that could have led to their disappearance here we present and compare integrated data of nine tjb sections from different areas tethys and panthalassa and different depositional environments i e shallow vs deep water or proximal vs distal shelf each of these sections record both the last occurrences of latest triassic conodont taxa and pronounced changes in the carbon isotopic composition of organic matter across the tjb interval our analysis of chemo and integrated biostratigraphic correlation suggests that the final extinction of the taxon conodonta was asynchronous

clumped isotope signatures of methane derived authigenic carbonate presenting equilibrium values of their formation temperatures abstract the chemical and stable isotopic composition of methane derived authigenic carbonate mdac can be used to document paleoclimate and biogeochemical information in methane cold seeps such as temperature records determined through clumped isotope 47 analyses previous investigations of mdacs however have noted isotopic disequilibrium values limiting the application of 47 signatures as a proxy for the formation temperature of carbonates at present and former gas seep sites here we measured 49 mdac samples collected from 5 areas along the eastern margin of the japan sea and the northwest pacific region of japan all samples present equilibrium 47 signatures with respect to seafloor temperatures at the time of precipitation and the results do not appear to be influenced by the mg content mineralogy or mixing effect the pore water 18 o values estimated by the 47 thermometer reveal that most of these mdacs formed during glacial and or hydrate destabilization periods while our new data shows equilibrium 47 values the results do not discount the possibility that disequilibrium observed in previous studies could possibly be associated with extremely rapid rates of anaerobic oxidation of methane relevant potential mechanisms are discussed further investigations are crucial to clarify the utility of 47 in mdacs as a novel proxy for constraining the modern ancient methane seep environment this proxy also offers insights into formation and dissociation processes of gas hydrate a potential energy resource in the future

termination of carbonate slope progradation an example from the carnian of the dolomites northern italy abstract the demise of carbonate platforms during carnian time is a widespread phenomenon of the western tethys but the controlling factors are not well understood the dolomites of the southern alps northern italy are well known for their large scale ladinian and carnian prograding carbonate platforms platform growth stopped during the early carnian and both platforms and basinal areas were subsequently covered by mixed carbonate siliciclastic sediments raibl group we present a carbonate platform whose slope progradation came to a halt prior to draping by the siliciclastic sediments judging from the height of the clinoforms a platform to basin relief of at least 100 m existed during the final stage of progradation this paleo slope was colonized by coral patches draped by skeletal packstones to microbial bindstones forming typically lens shaped mounds on the steep slope the formation of mounds on the platform flank was only possible because the downslope transport of detritus from the platform and or upper slope was stopped the sedimentary evolution in the adjacent basin indicates a poorly oxygenated environment with abundant brackish water ostracods of low diversity based on the inherited platform to basin relief and the lithofacies of the basin fill a local sea level drop in the order of 60 80 m is postulated with rising sea level the accommodation space between former basin and platform became filled by shallow marine mixed carbonate siliciclastic sediments the abundance of epibenthic suspension feeders of the basin fill such as megalodonts suggests increased nutrient supply the termination of slope progradation was a multiphased process triggered by a stagnation of the regional subsidence a reduction of water circulation followed by a sea level drop the influx of freshwater and the input of siliciclastics fluctuating salinity caused intermittently a biotically stressed environment

gecko global events impacting conodont evolution abstract with a record that spans approximately 300 million years late cambrian through the triassic jurassic transition i e the conodontozoic conodonts witnessed all principal events in the evolution of life on earth from the invasion of the land to the exploration of the air from the explosion of biomineralization in the oceans to the rise of dinosaurs and mammals including three of the major extinction events that occurred in the phanerozoic mainly used for biostratigraphic or geochemical studies the potential of conodonts to help unravel changes perceived to be of global extent rarely has been explored while specialists have identified rapid changes in conodont element morphology throughout their history the conodont animal has often been perceived to have been a static entity in a constantly evolving world when biological equilibrium in the oceans was undergoing profound alteration and faunal recoveries took place in phases that seem to have had recurrent patterns it is now essential that we begin to further investigate how conodonts as biologic entities responded to or were impacted by palaeogeographic changes eustatic and climatic fluctuations shifting redox conditions and major faunal turnovers and reorganizations that took place during the conodontozoic

synchroneity of climatic change and extinctions in the late triassic although the late triassic was a time of widespread aridity evidence exists for a significant increase in rainfall during the middle to late carnian upper triassic playa lake sediments were interrupted by late carnian fluviatile sandstones with erosive bases and high kao linite illite ratios there was also an increase in the clastic component of marine sequences during this interval middle and upper carnian marine carbonates show an extreme depletion in 13 c values consistent with increased fresh water influx large scale karstic phenomena in limestone areas subaerially exposed during the late triassic are a further indication of increased rainfall important faunal and floral changes occurred during the carnian norian interval marine invertebrate turnover was greatest at the lower middle carnian boundary and terrestrial extinctions were concentrated at the carnian norian boundary the cause of this carnian pluvial episode may have been related to the rifting of pangea through disruption of atmospheric and oceanic circulation patterns eustatic changes or the effects of volcanism associated with rifting a change in surface ocean temperature salinity or ph or habitat loss may have caused the decline of many shallow marine invertebrates at the start of the middle carnian a return to arid conditions at the carnian norian boundary would account for the turnover among terrestrial vertebrates and plants

towards quantifying the reaction network around the sulfate methane transition zone in the ulleung basin east sea with a kinetic modeling approach abstract we present a kinetic model based upon pore water data collected from eight sites drilled during the second ulleung basin gas hydrate drilling expedition ubgh2 in 2010 three sites were drilled at locations where acoustic chimneys were identified in seismic data and the rest were drilled on non chimney i e background environments our model coupled a comprehensive compositional and isotopic data set is used to illustrate the different biogeochemical processes at play in those two environments in terms of reactions around the sulfate methane transition zone smtz organic matter decomposition is an important process for production of methane dissolved inorganic carbon dic and consumption of sulfate in the non chimney sites whereas anaerobic oxidation of methane aom dominates both carbon and sulfur cycles in the chimney environment different sources of methane mediate aom in the two settings internally produced methane through co 2 reduction cr and methanogenesis fuels aom in the non chimney sites whereas aom is sustained by methane from external sources in the chimney sites we also simulate the system evolution from non chimney to chimney conditions by increasing the bottom methane supply to a non chimney setting we show that the higher ch 4 flux leads to a higher microbial activity of aom and more organic matter decomposition through methanogenesis a higher methanogenesis rate and a smaller cr contribution relative to aom in the chimney sites is responsible for the isotopically light dic and heavy methane in this environment relative to the non chimney sites

brucite chimney formation and carbonate alteration at the shinkai seep field a serpentinite hosted vent system in the southern mariana forearc brucite carbonate chimneys were discovered from the deepest known 5700 m depth serpentinite hosted ecosystem the shinkai seep field ssf in the southern mariana forearc textural observations and geochemical analysis reveal three types i iii of chimneys formed by the precipitation and dissolution of constitutive minerals type i chimneys are bright white to light yellow have a spiky crystalline and wrinkled surface with microbial mat and contain more brucite these formed as a result of rapid precipitation under high fluid discharge conditions type ii chimneys exhibit white to dull brown coloration tuberous textures like vascular bundles and are covered with grayish microbial mats and dense colonies of phyllochaetopterus this type of chimney is characterized by inner brucite rich and outer carbonate rich zones and is thought to have precipitated from lower fluid discharge conditions than type i chimneys type iii chimneys are ivory colored have surface depressions and lack living microbial mats or animals this type of chimney mainly consists of carbonate and is in a dissolution stage stable carbon isotope compositions of carbonates in the two types i and ii of active chimneys are extremely 13c enriched up to 24 1 which may reflect biological 12c consumption under extremely low dissolved inorganic carbon concentration in alkaline fluid type iii chimneys have 13c compositions indicating re equilibration with seawater our findings demonstrate for the first time that carbonate chimneys can be form below carbonate compensation depth and provide new insights about linked geologic hydrologic and biological processes of the global deep sea serpentinite hosted vent systems this article is protected by copyright all rights reserved

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

physical and chemical controls on habitats for life in the deep subsurface beneath continents and ice the distribution of life in the continental subsurface is likely controlled by a range of physical and chemical factors the fundamental requirements are for space to live carbon for biomass and energy for metabolic activity these are inter related such that adequate permeability is required to maintain a supply of nutrients and facies interfaces invite colonization by juxtaposing porous habitats with nutrient rich mudrocks viable communities extend to several kilometres depth diminishing downwards with decreasing porosity carbon is contributed by recycling of organic matter originally fixed by photosynthesis and chemoautotrophy using crustal carbon dioxide and methane in the shallow crust the recycled component predominates as processed kerogen or hydrocarbons but abiotic carbon sources may be significant in deeper metamorphosed crust hydrogen to fuel chemosynthesis is available from radiolysis mechanical deformation and mineral alteration activity in the subcontinental deep biosphere can be traced through the geological record back to the precambrian before the colonization of the earth s surface by land plants a geologically recent event subsurface life probably dominated the planet s biomass in regions of thick ice sheets the base of the ice sheet where liquid water is stable and a sediment layer is created by glacial erosion can be regarded as a deep biosphere habitat this environment may be rich in dissolved organic carbon and nutrients accumulated from dissolving ice and from weathering of the bedrock and the sediment layer

mineral formation during bacterial sulfate reduction in the presence of different electron donors and carbon sources national natural science foundation of china no 40976040 973 program 2009cb21950607 zhejiang pro vincial national natural science foundation of china no r5110215 and the us department of energy no de fg02 13er86571 funding for the establishment and operation of the environmental and bio lm mass spectrometry facility at montana state university msu was provided by the defense university research instrumentation program durip contract number w911nf0510255 and the msu thermal bi ology institute from the nasa exobiology program project nag5 8807

chronostratigraphic correlations their importance for the definition of geochronologic units abstract the present article resumes the philosophy underlying the re definition of chronostratigraphic geochronologic units through their boundaries by working groups of the international commission on stratigraphy ics following the ics guidelines with respect to the historical approach this philosophy implies a change in the way how stages are defined stages originally defined by their contents are now defined by their lower boundary only the concept of the global stratotype standard section and point gssp as before stages may be characterized by their contents but precise definitions of stages and their scope can only be attained via boundary definitions the following subjects are dealt with in detail 1 the choice of the level of a chronostratigraphic geochronologic boundary which is to be defined by a gssp this is determined by practical considerations concerning the correlation of the envisaged stratigraphic level 2 if traditional names are to be preserved some kind of compromise is always necessary because none of them is clearly and unequivocally defined this goal can be attained by a democratic vote 3 because of gaps and condensation even the more favorable historical stratotypes are unsuitable for the redefinition of classical stages by their lower boundaries

assessing sulfate reduction and methane cycling in a high salinity pore water system in the northern gulf of mexico pore waters extracted from 18 piston cores obtained on and near a salt cored bathymetric high in keathley canyon lease block 151 in the northern gulf of mexico contain elevated concentrations of chloride up to 838 mm and have pore water chemical concentration profiles that exhibit extensive departures concavity from steady state linear diffusive equilibrium with depth minimumd 13 c dissolved inorganic carbon dic values of 55 9 to 64 8 at the sulfate methane transition smt strongly suggest active anaerobic oxidation of methane aom throughout the study region however the nonlinear pore water chemistrydepth profiles make it impossible to determine the vertical extent of active aom or the potential role of alternate sulfate reduction pathways here we utilize the conservative non reactive nature of dissolved chloride to differentiate the effects of biogeochemical activity e g aom and or organoclastic sulfate reduction relative to physical mixing in high salinity keathley canyon sediments in most cases the dic and sulfate concentrations in pore waters are consistent with a conservative mixing model that uses chloride concentrations at the seafloor and the smt as endmembers conservative mixing of pore water constituents implies that an undetermined physical process is primarily responsible for the nonlinearity of the pore water depth profiles in limited cases where the sulfate and dic concentrations deviated from conservative mixing between the seafloor and smt the d 13 c dic mixing diagrams suggest that the excess dic is produced from a 13 c depleted source that could only be accounted for by microbial methane the dominant form of methane identified during this study we conclude that aom is the most prevalent sink for sulfate

a multidisciplinary biofacies characterisation of the late triassic late carnian rhaetian kapp toscana group on hopen arctic norway abstract a multidisciplinary study of the kapp toscana group de geerdalen flatsalen and svenskoya formations on hopen svalbard provides an enhanced palaeoenvironmental interpretation for the upper triassic succession on the island the biofacies of the formations were characterised using a combination of palynological palynofacies and micropalaeontological analyses micropalaeontological palynofacies and 13corg data are presented from hopen for the first time six distinct biofacies assemblages were recognised i lower undifferentiated de geerdalen formation characterised by a dominance of fern spores and low abundance assemblages of foraminifera and ostracods interpreted to reflect deposition in a deltaic environment during maximum marine regression ii upper de geerdalen formation hopen member rich in bisaccate gymnosperm pollen and the alga plaesiodictyon mosellaneum consistent with deposition in a brackish marginal marine setting iii lower flatsalen formation characterised by microforaminiferal linings marine phytoplankton and super abundant agglutinated foraminifera considered to reflect deposition in a shallow marine environment iv middle flatsalen formation dominated by dinoflagellate cysts radiolaria and ostracods indicating deposition in a relatively distal dysoxic anoxic marine environment a maximum flooding surface is inferred based on the acme of radiolarians and dominance of dinoflagellate cysts v upper flatsalen formation corresponding to a decrease in marine palynomorphs absence of radiolaria agglutinated foraminifera and ostracods and an increase in terrestrial organic matter and vi svenskoya formation characterised by a dominance of terrestrial palynomorphs and deposited in a fluvio deltaic environment the biofacies units are integrated with the established litho chrono and palynostratigraphic framework for the island and contribute to an enhanced palaeogeographic understanding of the barents sea region during the late triassic

anaerobic methane oxidation in low organic content methane seep sediments abstract sulfate dependent anaerobic oxidation of methane aom is the key sedimentary microbial process limiting methane emissions from marine sediments and methane seeps in this study we investigate how the presence of low organic content sediment influences the capacity and efficiency of aom at bullseye vent a gas hydrate bearing cold seep offshore of vancouver island canada the upper 8 m of sediment contains

methane sources and production in the northern cascadia margin gas hydrate system abstract the oceanographic and tectonic conditions of accretionary margins are well suited for several potential processes governing methane generation storage and release to identify the relevant methane evolution pathways in the northern cascadia accretionary margin a four site transect was drilled during integrated ocean drilling program expedition 311 the 13c values of methane range from a minimum value of 82 2 on an uplifted ridge of accreted sediment near the deformation front site u1326 1829 mbsl meters below sea level to a maximum value of 39 5 at the most landward location within an area of steep canyons near the shelf edge site u1329 946 mbsl an interpretation based solely on methane isotope values might conclude the 13c enrichment of methane indicates a transition from microbially to thermogenically sourced methane however the co existing co2 exhibits a similar trend of 13c enrichment along the transect with values ranging from 22 5 to 25 7 the magnitude of the carbon isotope separation between methane and co2 ec 63 8 5 8 is consistent with isotope fractionation during microbially mediated carbonate reduction these results in conjunction with a transect wide gaseous hydrocarbon content composed of 99 8 by volume methane and uniform dch4 values 172 8 that are distinct from thermogenic methane at a seep located 60 km from the expedition 311 transect suggest microbial co2 reduction is the predominant methane source at all investigated sites the magnitude of the intra site downhole 13c enrichment of co2 within the accreted ridge site u1326 and a slope basin nearest the deformation front site u1325 2195 mbsl is 5 at the mid slope site site u1327 1304 mbsl the downhole 13c enrichment of the co2 is 25 and increases to 40 at the near shelf edge site u1329 this isotope fractionation pattern is indicative of more extensive diagenetic alteration at sites with greater 13c enrichment the magnitude of the 13c enrichment of co2 correlates with decreasing sedimentation rates and a diminishing occurrence of stratigraphic gas hydrate we suggest the decreasing sedimentation rates increase the exposure time of sedimentary organic matter to aerobic and anaerobic degradation during burial thereby reducing the availability of metabolizable organic matter available for methane production this process is reflected in the occurrence and distribution of gas hydrate within the northern cascadia margin accretionary prism our observations are relevant for evaluating methane production and the occurrence of stratigraphic gas hydrate within other convergent margins

multielement species of misikella kozur and mock 1974 and axiothea n gen conodonta from the mamonia complex upper triassic cyprus the conodont genus misikella kozur and mock 1974 has previously been considered unimembrate and a possible junior synonym of neospathodus mosher 1968 in the present study misikella is considered a valid genus with a tetramembrate conodont apparatus only one species misikella longidentata is recognized as belonging in that genus other species previously brought to misikella are considered as having had a bimembrate apparatus and are referred to axiothea n gen

response of early cretaceous carbonate platforms to changes in atmospheric carbon dioxide levels during the late barremian and early aptian about 120 million years ago intense volcanic degassing and extremely rapid release of methane hydrates contained in marine sediments added high amounts of carbon to the ocean and atmosphere and resulted most probably in rising atmospheric carbon dioxide pressure in order to document the response of the shallow water carbonate producing communities to this pronounced disturbance of the carbon cycle we studied a late barremian to early aptian neritic carbonate succession deposited on the northern tethyan shelf swiss alps the sedimentological and stable carbon and oxygen isotope records of two sections located along a n s transect from proximal to more distal shelf environments were investigated the sediments correspond to outer mid and inner ramp deposits of a homoclinal carbonate ramp vertical facies variations within the two studied sections feature three progradation phases of the platform a highly resolved correlation of the shelf sediments with a pelagic succession from the southern alps northern italy is based on both 13c stratigraphy and biostratigraphy and indicates that the drowning of the helvetic carbonate platform coincided with a pronounced calcification crisis of calcareous nannofossils the biocalcification crisis started before but culminated during the aptian methane event recorded in a negative carbon isotope spike we propose that increased carbon dioxide concentrations in oceans and atmosphere related to volcanic activity and to sudden methane release reduced the marine calcium carbonate oversaturation and the calcification potential of benthic and planktonic organisms carbonate producing shallow water communities on platforms and ramps suffering from additional environmental stress such as extreme temperatures or high nutrient levels could not survive during times of rising sea level and as a consequence carbonate platforms drowned

archaeal lipids in neogene dolomites monterey and sisquoc formations california planktic versus benthic archaeal sources abstract the distribution of archaeal lipids including archaeol and glycerol dibiphytanyl glycerol tetraethers gdgts in dolomite concretions and surrounding sediment from the monterey formation miocene and the sisquoc formation miocene pliocene were examined to distinguish planktic from benthic contributions for this purpose dolomites with positive 13 c values 7 to 13 were chosen such highly positive values point to pronounced methanogenesis of benthic archaea in the sedimentary column at first glance distributions and relative abundances of gdgts in both dolomites and background sediment were similar resembling patterns of marine planktic crenarchaea a contribution of benthic euryarchaea to the gdgt pool became evident only from variations in the 13 c values of different biphytanes obtained after ether cleavage of gdgts whereas bi and tricyclic biphytanes had an isotopic signal typical of planktic archaea 13 c 23 6 to 20 5 and 23 4 to 21 2 respectively for both dolomite and background sediment acyclic and monocyclic biphytanes showed lower values for dolomite samples 25 1 to 22 6 and 27 6 to 24 7 respectively indicating a contribution of lipids from benthic archaea the isoprenoid diether archaeol 13 c 23 9 to 22 9 assigned to euryarchaea was only detected in dolomite samples also reflecting additional input from sedimentary archaea probably autotrophic methanogens the occurrence of lipids derived from methanogenic archaea agrees with the strong 13 c enrichment of dolomites and with mineral formation taking place in the zone of archaeal methanogenesis this implies that the lipid biomarker inventory of sedimentary strata needs to be interpreted carefully as it is often not straightforward to discriminate between input from the water column and sedimentary microbial activity

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

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

unraveling the origin of carbonate platform cyclothems in the upper triassic durrenstein formation dolomites italy abstract facies analysis of the durrenstein formation central eastern dolomites northern italy indicates that this unit was deposited on a carbonate ramp as evidenced by the lack of a shelf break slope facies or a reef margin together with the occurrence of a molechfor biological association its deposition following the accumulation of rimmed carbonate platforms during the ladinian and early carnian marks a major shift in growth mode of the triassic shallow marine carbonates in the dolomites the durrenstein formation is characterized by a hierarchical cyclicity with elements strongly suggestive of an allocyclic origin including a subaerial exposure features directly above subtidal facies within meter scale cyclothems b purely subtidal carbonate cyclothems c symmetric peritidal carbonate cyclothems and d continuity of cyclothems of different orders through facies boundaries the durrenstein cyclothems are usually defined by transgressive and regressive successions and so most of them probably originated from sea level oscillations their allocyclic origin allows their use for high resolution correlations over distances up to 30 km a stratigraphic section in the tre cime di lavaredo area encompassing the upper part of the durrenstein formation and the lower part of the overlying raibl formation upper carnian was studied using time frequency analysis a strong milankovitch signal appeared when interference arising from a variable sedimentation rate was estimated and removed by tuning the short precession line in a spectrogram all of the principal periodicities related to the precession index and eccentricity calculated for 220 ma are present p1 21 9 ky p2 17 8 ky e1 400 ky e2 95 ky and e3 125 ky along with a peak at a frequency double that of the precession which is a predicted feature of orbitally forced insolation at the equator components possibly related to earth s obliquity at ca 35 ky and ca 46 ky are present as well the recovery of milankovitch periodicities allows reconstruction of a high resolution timescale that is in good agreement with published durations of the carnian based on radiometric ages the recognition of a milankovitch signal in the durrenstein and lower raibl formations as well as in other mesozoic carbonate platforms strongly supports a deterministic and predictable rather than stochastic control on the formation of carbonate platforms carbonate platforms might thus be used in the future for the construction of an astronomical time scale for the mesozoic

climatic and biotic change in the late triassic generally arid conditions that pervaded much of europe and north america during the late triassic were interrupted by a wet monsoonal climatic phase during middle and late carnian times extensive fluviatile sandstones deposited at this time throughout the region occur within a thick sequence of playa lake mudstones the sandstones occasionally contain kaolinite suggesting a humid climate an extreme 13 c depletion in a shallow marine sequence of this age in israel has been interpreted as evidence for an influx of freshwater a widespread change from carbonates to clastics in marine sequences at this time may also be climate related water course cave systems in limestone areas exposed during the late triassic indicate high levels of runoff during the middle and late carnian the marine invertebrate fauna shows a significant turnover at the end of the early carnian the terrestrial fauna and flora were relatively unaffected at this time but subsequently diversified prior to a major biotic turnover at the carnian norian boundary these periods of biotic change appear to be synchronous with the onset and cessation of a carnian humid phase the change to a monsoonal climate during this interval has been documented over more than 90 of longitude between 5 and 50 north of the triassic equator it may have been caused by rising atmospheric co 2 levels due to volcanism associated with the incipient dispersal of pangaea

global carbon cycle perturbations triggered by volatile volcanism and ecosystem responses during the carnian pluvial episode late triassic abstract the carnian pluvial episode cpe was a dramatic climatic event during the early late triassic the cpe has been recognized worldwide and is marked by the termination of carbonate platform successions and by pronounced negative 13c excursions denoted as the cpe excursion the onset of the cpe has been proposed to be linked with the volatile eruption of the wrangellia large igneous province w lip however this extreme climatic event remains disputed in terms of its precise global correlation timing of onset duration and global magnitude we compiled a database of 13 conodont biozone controlled stable isotope reference sections throughout the tethyan region after a reexamination of previously published conodont taxonomy from each section the statistics on the conodont assemblages zones yield a global set of 17 high resolution conodont unitary association zones uazs spanning the entire carnian successions a set of age tie points placed an age model on this global uaz scale we added paired 13ccarb and 13corg data from two sections in south china to other records in this global database and then normalized all carbon isotope datasets a pronounced negative 13ccarb excursion with a magnitude of 2 0 5 from an average of 3 to 1 is evident in these normalized trends and is recognized around the entire tethys realm the cpe excursion coincides with conodont uaz 4 234 ma through uaz 8 within the mazzaella carnica and paragondolella praelindae zones julian2 and has a duration of ca 1 5 myr we note that an apparent delayed onset of the cpe excursion in south china relative to elsewhere in the tethys as suggested by previous studies may have been an artifact caused by incomplete conodont stratigraphic records and or irregularities in taxonomic identification a carbon and phosphorus cycle model highlight the strong relationship between the eruption of the w lip and cpe excursion however the estimated amount of co2volatiles released by the w lip would directly account for only 25 of the total amount of light carbon required to explain the combined magnitude and duration of the global cpe excursion

evaluation of arctic sea ice thickness simulated by arctic ocean model intercomparison project models six aomip model simulations are compared with estimates of sea ice thickness derived from pan arctic satellite freeboard measurements 2004 2008 airborne electromagnetic measurements 2001 2009 ice draft data from moored instruments in fram strait the greenland sea and the beaufort sea 1992 2008 and from submarines 1975 2000 drill hole data from the arctic basin laptev and east siberian marginal seas 1982 1986 and coastal stations 1998 2009 despite an assessment of six models that differ in numerical methods resolution domain forcing and boundary conditions the models generally overestimate the thickness of measured ice thinner than 2 m and underestimate the thickness of ice measured thicker than about 2 m in the regions of flat immobile land fast ice shallow siberian seas with depths less than 25 30 m the models generally overestimate both the total observed sea ice thickness and rates of september and october ice growth from observations by more than four times and more than one standard deviation respectively the models do not reproduce conditions of fast ice formation and growth instead the modeled fast ice is replaced with pack ice which drifts generates ridges of increasing ice thickness in addition to thermodynamic ice growth considering all observational data sets the better correlations and smaller differences from observations are from the ecco2 and uw models

carbonate to biosilica transition at the norian rhaetian boundary controlled by rift related subsidence in the western tethyan lagonegro basin southern italy abstract the lagonegro basin located in the southern apennines italy records a transition from carbonate sediments of the calcari con selce fm cherty limestone to biosiliceous sediments of the scisti silicei fm siliceous shale around the norian rhaetian boundary nrb upper triassic sedimentologic and chemostratigraphic analysis of three sections pignola abriola monte volturino and madonna del sirino representing a proximal to distal transect across the basin document marine productivity redox and chemical weathering conditions the basin was characterized by low to moderate productivity and mainly oxic deep waters with no systematic secular variation throughout the 10 myr long study interval a weathering proxy the chemical index of alteration cia shifts toward higher values from 0 70 to 0 80 in all three study sections suggesting development of warmer and or more humid conditions just before the nrb the lack of evidence for changes in marine productivity or redox conditions and the time transgressive nature of the carbonate biosilica transition suggests that the latter was caused not by changes in planktonic communities but rather by a rise in the ccd the most likely cause of which was seafloor subsidence within the actively rifting ionian ocean i e the westernmost branch of the tethys ocean the tectonically active character of the lagonegro basin is also reflected in evidence of synsedimentary paleoseismic activity e g numerous debris flows around the basin margins the present study thus documents sedimentologic changes within a marginal basin in a geologically young ocean

tracking an upper limit of the carnian crisis and or carnian stage in the western carpathians slovakia the late triassic timescale especially the carnian norian boundary is poorly constrained mainly due to a paucity of high precision radio isotopic ages that can be related accurately to contradictions between the biostratigraphic and magnetostratigraphic correlations la icp ms dating of detrital zircons from five samples of the lunz formation the upper triassic siliciclastic sediments from the western carpathians slovakia provided a wide spectrum of ages that vary from late archaean ca 2582 ma to triassic ca 216 ma these marine delta sediments represent a typical product of the carnian crisis a major climate change and biotic turnover that occurred during the carnian stage in the tethys ocean within the carbonate shelf and intrashelf basins in the northern calcareous alps and the western carpathians the supply of clastic material in the studied lunz formation was derived from several sources especially i from the recycled variscan orogen ii from the remote east european platform and iii from the contemporaneous triassic volcanic sources syn sedimentary volcanic zircons with a concordia age of 221 2 1 6 ma calculated from 12 single analyses represent the maximum age of deposition of the lunz formation and demonstrate that the upper limit of the carnian crisis and or the carnian stage in the alpine carpathians realm is younger than the current age of the carnian norian boundary at ca 227 ma listed on the international chronostratigraphic chart international commission on stratigraphy 2016 12 edition

estimating the thickness of sea ice sea ice freeboard thickness and snow depth were measured from a series of closely spaced 5 to 10 m drill hole sites from five free floating multiyear ice floes in the beaufort sea during the spring of 1986 and 1987 a regression of ice thickness on ice draft was performed on the data from each floe and for the combined data set regressions were performed both on nonscreened data and data screened to eliminate pressure ridges a predictive equation was developed permitting the total ice thickness to be estimated from measured values of ice draft e g from submarine echo sounder traces t 1 115 d the keel sail height ratio for pressure ridges was found constant at 3 3 to 1 in agreement with past observations

contribution of dissolved organic species to the carbon and energy budgets of hydrate bearing deep sea sediments ocean drilling program site 997 blake ridge abstract pore water extracted from sediments penetrated on leg 164 of the ocean drilling program at the blake ridge west atlantic were analysed for acetate total dissolved organic carbon bromide and iodide to help explain the occurrence of subsurface maxima in bacteria biomass and activity reported previously from a nearby site the high concentrations of these organic matter decomposition by products in the pore waters from sediments with moderate concentrations of sedimentary organic matter can convincingly be modelled as resulting from upward migration of pore water the amount of acetate and unidentified doc transported by the pore water contribute significantly to the pool of metabolizable carbon and may be the most important substances in energetic terms