seismic evidence for reactivation of a buried hydrated fault in the pacific slab by the 2011 m9 0 tohoku earthquake 1 we employ seismic tomography to estimate detailed 3d seismic velocity structures in the focal area of an intraslab earthquake m7 1 which occurred on april 7 1 month after the 2011 tohoku earthquake m9 0 near its source area the results show a low velocity zone around the focal area of the m7 1 event and that the aftershock activity is limited to the upper 15 km of the oceanic mantle the lateral extent of the low velocity zone is comparable to the distribution of aftershocks suggesting a concentration of fluids in the aftershock area the angle between the aftershock alignment and the dip of the slab surface is estimated to be 60 which is consistent with the dip of an oceanward dipping normal fault observed at the outer trench slope these observations suggest that the m7 1 intraslab event occurred as a result of reactivation of a buried hydrated fault that formed prior to subduction the upper 15 km of the oceanic mantle may be locally hydrated by bending related tensional faulting at the outer trench slope

the 2006 2007 kuril islands great earthquake sequence the southwestern half of a 500 km long seismic gap in the central kuril island arc subduction zone experienced two great earthquakes with extensive preshock and aftershock sequences in late 2006 to early 2007 the nature of seismic coupling in the gap had been uncertain due to the limited historical record of prior large events and the presence of distinctive upper plate trench and outer rise structures relative to adjacent regions along the arc that have experienced repeated great interplate earthquakes in the last few centuries the intraplate region seaward of the seismic gap had several shallow compressional events during the preceding decades notably an m s 7 2 event on 16 march 1963 leading to speculation that the interplate fault was seismically coupled this issue was partly resolved by failure of the shallow portion of the interplate megathrust in an m w 8 3 thrust event on 15 november 2006 this event ruptured 250 km along the seismic gap just northeast of the great 1963 kuril island m w 8 5 earthquake rupture zone within minutes of the thrust event intense earthquake activity commenced beneath the outer wall of the trench seaward of the interplate rupture with the larger events having normal faulting mechanisms an unusual double band of interplate and intraplate aftershocks developed on 13 january 2007 an m w 8 1 extensional earthquake ruptured within the pacific plate beneath the seaward edge of the kuril trench this event is the third largest normal faulting earthquake seaward of a subduction zone on record and its rupture zone extended to at least 33 km depth and paralleled most of the length of the 2006 rupture the 13 january 2007 event produced stronger shaking in japan than the larger thrust event as a consequence of higher short period energy radiation from the source the great event aftershock sequences were dominated by the expected faulting geometries thrust faulting for the 2006 rupture zone and normal faulting for the 2007 rupture zone a large intraplate compressional event occurred on 15 january 2009 m w 7 4 near 45 km depth below the rupture zone of the 2007 event and in the vicinity of the 16 march 1963 compressional event the fault geometry rupture process and slip distributions of the two great events are estimated using very broadband teleseismic body and surface wave observations the occurrence of the thrust event in the shallowest portion of the interplate fault in a region with a paucity of large thrust events at greater depths suggests that the event removed most of the slip deficit on this portion of the interplate fault this great earthquake doublet demonstrates the heightened seismic hazard posed by induced intraplate faulting following large interplate thrust events future seismic failure of the remainder of the seismic gap appears viable with the northeastern region that has also experienced compressional activity seaward of the megathrust warranting particular attention

chemical weathering indices applied to weathering profiles developed on heterogeneous felsic metamorphic parent rocks abstract chemical weathering indices are commonly used for characterizing weathering profiles by incorporating bulk major element oxide chemistry into a single metric for each sample generally on homogeneous parent rocks weathering indices change systematically with depth however the weathering of heterogeneous metamorphic rocks confounds the relationship between weathering index and depth in this paper we evaluate previously defined chemical weathering indices for their suitability in characterizing weathering profiles developed on felsic heterogeneous metasedimentary bedrock from coweeta hydrologic laboratory north carolina usa among the weathering indices evaluated here the weathering index of parker wip is the most appropriate for application to weathering profiles on heterogeneous and homogeneous parent rock because the wip includes only the highly mobile alkali and alkaline earth elements in its formulation it yields values that differ greatly from those of the parent rock in addition the wip allows for aluminum mobility unlike other weathering indices these characteristics combine to make the weathering index of parker the most applicable index for studying the weathering of heterogeneous metasedimentary rocks however the wip should be applied judiciously as alkali and alkaline earth metals may be readily depleted during weathering in addition to reflecting weathering the chemical index of alteration cia chemical index of weathering ciw plagioclase index of alteration pia and vogt s residual index v may be sensitive to subtle geochemical changes such as hydrothermal alteration along a fault and or alteration at the water table weathering indices that include iron in their calculations were not included in this study because they do not distinguish between ferric and ferrous iron the oxidation state and distribution of iron in a weathering profile is influenced by the proportion of oxidation states in the pre weathered metamorphic rock and interaction with groundwater during weathering

changes in planktonic assemblages during sapropel s5 deposition evidence from urania basin area eastern mediterranean 1 a micropaleontological study of planktonic assemblages on the partially laminated sapropel s5 late pleistocene marine isotope stage mis 5e was performed in two piston cores from urania basin area eastern mediterranean west of crete um94pc16 and um94pc31 recovered during a paleoflux project cruise the abundance of florisphaera profunda indicates the development of a deep chlorophyll maximum dcm before the anoxic condition at bottom were established whereas patterns of upper photic zone coccoliths suggest extreme oligotrophy in surface water the short appearance of globorotalia scitula and the presence of globigerinoides ruber in the lower part of sapropel testify to a thermal stratification also recorded by changes in primary producers during g scitula occurrence diatoms mainly represented by pseudosolenia calcar avis appear and bloom because of their capability in using nutrients from dcm scanning electron microscope analyses performed on selected intervals from um94pc16 show that the sapropel is organized in microlaminae mostly composed by siliceous microfossils in particular sapropel s5 could be related to an enhanced nutrient availability in the lower middle part of the photic zone stratified conditions and a higher continental input

normal faulting earthquakes beneath the outer slope of the japan trench after the 2011 tohoku earthquake implications for the stress regime in the incoming pacific plate 1 after the 2011 mw 9 1 tohoku earthquake numerous intraplate earthquakes occurred beneath the outer slope of the japan trench based on ocean bottom seismograph observations these earthquakes occurred in the oceanic crust and uppermost mantle of the pacific plate at depths shallower than about 40 km and had normal faulting focal mechanisms at all depths before the 2011 earthquake normal faulting earthquakes beneath the outer trench slope occurred only at depths shallower than 20 km whereas those at depths of around 40 km had reverse faulting mechanisms these observations suggest that the stress regime in the pacific plate was changed by the 2011 earthquake the tensional stresses that now extend to depths of about 40 km may play an important role not only in the occurrence of large normal faulting earthquakes but also in hydration of the uppermost mantle of the incoming pacific plate prior to the subduction

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

precursors of the paleocene eocene thermal maximum petm in the subathu group nw sub himalaya india abstract the paleocene eocene thermal maximum petm is one of the most pronounced and widely documented global warming events in the geological history that occurred at the beginning of the eocene 56 ma causing substantial changes in biota and geochemistry it is marked worldwide by a negative isotopic excursion of 13c the biotic changes associated with the petm in marine realm include bloom of the dinoflagellate apectodinium turnover of larger foraminiferids diversification of planktic foraminiferids and carbonate dissolution of calcareous test shells etc while the geochemical changes include decrease in carbonates and increase in abundance of silicates and phyllosilicates etc conspicuously there has been no attempt to identify the petm in the himalaya even though some himalayan sections are known to have paleocene eocene transition beds to fill this lacuna we investigated the basal part of the late paleocene middle eocene subathu group exposed at the village kurla near subathu in himachal pradesh nw sub himalaya for biotic mineralogical and geochemical signatures of this abrupt warming event the significant results of this study include carbon isotope excursion cie of 3 4 occurrence of index dinoflagellate genus apectodinium and carbonate dissolution of the larger benthic foraminiferids the mineralogical changes noted across the paleocene eocene transition include increase in quartz and phyllosilicates and decrease in carbonates the geochemical changes include i increase in sio2 al2o3 k2o and fe2o3 ii decrease in caco3 iii decreasing trend of si al fe al and mg al ratios iv increasing trend of k al ti al and zr al ratios v changes in trace element abundance vi maximum chemical index of alteration cia of 85 89 and vii increase in abundance of rare earth elements the aforementioned dataset is clearly very close to the petm and even reflects its probable onset and peak phases however it is insufficient to definitively identify the petm in the studied section nevertheless since this study is the first from a himalayan section and brings out considerable new information all results and interpretations are presented and discussed here

early paleogene wildfires in peat forming environments at schoningen germany wildfire activity in early paleogene greenhouse conditions can be used as an analogue to gauge the effect of future warming trends on wildfire in the current climate system inertinite fossil charcoal in coal from 11 autochthonous early paleogene lignite seams from the schoningen mine germany was quantified using macerations in situ pillars and industry standard crushed samples a new three transect method was developed to quantify in situ charcoal the combination of in situ pillars and crushed samples accounts for temporal and spatial variation in charcoal through a stratigraphically oriented pillar whilst maintaining comparability with industry standards and previous work charcoal occurs as a range of randomly distributed particle sizes indicating that fires were burning locally in the schoningen peat forming environment and in the surrounding areas but according to petrological data not in an episodic or periodic pattern although charcoal abundance is low relative to previous high fire worlds such as the cretaceous three quantitative and semi quantitative methods show increased wildfire activity relative to the modern world in the warmest parts of the early paleogene as atmospheric oxygen levels stabilised to modern values and precipitation and humidity became the main control on wildfire increased rainfall followed by drier intervals would have created an environment rich in dry fuel in which wildfires could easily propagate if humidity was low enough in the later part of the early eocene ypresian charcoal abundance fell to levels similar to those found in modern peats this indicates that the transition to the modern low fire world occurred within the early eocene earlier than previous records suggest

black shale deposition and faunal overturn in the devonian appalachian basin clastic starvation seasonal water column mixing and efficient biolimiting nutrient recycling integrated geochemical data suggest that black shale deposition in the devonian geneseo formation of western new york was initiated by the coincidence of siliciclastic starvation and the intensification of seasonal water column stratification and mixing once established however black shale deposition was maintained through efficient recycling of biolimiting nutrients which enhanced primary productivity recycling efficiency was achieved through a positive feedback loop of oscillating benthic redox conditions that enhanced n and p regeneration from sediments sustained high primary productivity by returning nutrients to the photic zone during mixing and ensured a downward flux of organic matter that drove or enhanced the episodic development of benthic anoxia during stratification this feedback was ultimately disrupted by rising siliciclastic influx which diluted organic matter and restored benthic redox stability the abrupt overturn of diverse long standing appalachian basin marine communities may have been the result of trophic resource destabilization during geneseo deposition

new geochemical constraints on the paleocene eocene thermal maximum dababiya gssp egypt the paleocene eocene thermal maximum petm shows an extraordinary drop in the 13c of carbonate and organic matter across the globe suggesting massive release of 13c depleted carbon dioxide into the ocean and atmosphere over a very short time interval probably 20ky we report a geochemical and mineralogical study of 106 samples spanning the most expanded petm at the dababiya global stratotype standard section and point gssp near luxor egypt the field and laboratory observations reveal that the deposition occurred in a submarine channel extended laterally about 200 m with the deepest part 0 88 m at the designated gssp although all bio zones are present stable isotope records of both carbonate and organic carbon show decreases starting 0 6 m below the paleocene eocene boundary peb and culminating at the erosion surface a persistent shift in 15norg values to near zero reflects a gradual increase in bacterial activity high ti k and zr and low si contents at the peb coincide with increased kaolinite contents which suggests intense chemical weathering under more humid conditions at the petm onset two negative ce anomalies indicate intervals of anoxic conditions during the lower and middle petm base and top of zone e1 the first anoxic event is represented by a negative ce anomaly high v c rand v v ni ratios negative mn and an abundance of idiomorphic pyrite crystals that indicate anoxic to euxinic conditions the anoxic event middle petm is marked by high u mo v fe and abundant small sized 2 5 m pyrite framboids increased cu ni and cd at the same level suggesting anoxic conditions linked to high surface water productivity above this interval oxic conditions returned as indicated by the precipitation of phosphorus and barium these data reveal an expanded petm interval marked by intense weathering as a crucial parameter during the recovery phase

initiation of the great mw 9 0 tohoku oki earthquake abstract we determined the location size mechanism and the frequency content of the first 4 0 s of the 2011 tohoku oki earthquake since the beginning of this earthquake is very small we develop a comparative approach against a near by reference earthquake the master event we first determined the water depth near the master event using the differential timing between the water phase pwp reflected from the air water interface and the depth phase pp reflected from the water crust interface then we located the master event using the well known ocean bathymetry in the area after calibrating teleseismic arrays 30 to 90 at short periods for timing and amplitude with respect to the master event we were able to determine the initiation of the main event it began as a small m w 4 9 thrust event located at 38 19 n 142 68 e at a depth of 21 km and a few seconds later evolved into a slower extremely large slip event up dip

sediment effect on tsunami generation of the 1896 sanriku tsunami earthquake the 1896 sanriku earthquake was one of the most devastating tsunami earthquakes which generated an anomalously larger tsunami than expected from its seismic waves previous studies indicate that the earthquake occurred beneath the accretionary wedge near the trench axis it was pointed out recently that sediments near a toe of an inner trench slope with a large horizontal movement due to the earthquake might have caused an additional uplift in this paper the effect of the additional uplift to tsunami generation of the 1896 sanriku tsunami earthquake is quantified we estimate the slip of the earthquake by numerically computing tsunamis and comparing their waveforms with those recorded at three tide gauges the estimated slip for the model without the additional uplift is 10 4 m and those with the additional uplift are 5 9 6 7 m this indicates that the additional uplift of the sediments near the trench has a large effect on the tsunami generation

a modern vs permian black shale the hydrography primary productivity and water column chemistry of deposition the sediment currently accumulating in the cariaco basin on the continental shelf of venezuela has an elevated organic carbon content of approximately 5 is accumulating under o2 depleted bottom water conditions so42 reduction is composed dominantly of foraminiferal calcite diatomaceous silica clay and silt and is dark greenish gray in color upon lithification it will become a black shale recent studies have established the hydrography of the basin and the level of primary productivity and bottom water redox conditions these properties are used to model accumulation rates of cd cr cu mo ni v and zn on the seafloor the model rates agree closely with measured rates for the uppermost surface sediment the model is applied to the meade peak phosphatic shale member of the phosphoria formation a phosphate deposit of permian age in the northwest united states it too has all of the requisite properties of a black shale although the deposit is a world class phosphorite it is composed mostly of phosphatic mudstone and siltstone chert limestone and dolomite it has organic carbon concentrations of up to 15 is strongly enriched in several trace elements above a terrigenous contribution and is black the trace element accumulation defines a mean primary productivity in the photic zone of the phosphoria basin as moderate at 500 g m 2 year 1 organic carbon comparable to primary productivity in the cariaco basin the source of nutrient enriched water that was imported into the phosphoria basin upwelled into the photic zone and supported primary productivity was an o2 minimum zone of the open ocean the depth range over which the water was imported would have been between approximately 100 and 600 m the mean residence time of bottom water in the basin was approximately 4 years vs 100 years in the cariaco basin the bottom water was o2 depleted but it was denitrifying or no3 reducing rather than so42 reducing

palaeoenvironmental and climatic changes during the palaeocene eocene thermal maximum petm at the wadi nukhul section sinai egypt the palaeocene eocene thermal maximum petm interval at the wadi nukhul section sinai egypt is represented by a 10 cm thick condensed clay rich layer corresponding to the np9a np9b nannofossil subzone boundary the wadi nukhul palaeocene eocene boundary peb is characterized by 1 an abrupt negative excursion in carbonate and organic carbon isotope ratios 6 in 13 c carb and 2 13 c org 2 an abrupt persistent negative shift in organic nitrogen isotope values 15 n org 3 a significant increase in phosphorus concentrations just above the carbon isotope excursion 4 a decrease in carbonate content and significant increase in kaolinite and 5 high vanadium and low manganese contents coincident with the occurrence of framboidal pyrite the abrupt correlative isotopic excursions of 13 c carb 13 c org and 15 n suggest that the lowermost part of the petm is missing the decrease in carbonate content indicates dilution by high detrital input triggered by acid weathering and carbonate dissolution in response to increased atmospheric co 2 resulting from the oxidation of methane the sudden increase in kaolinite content reflects a short lived change to humid conditions the 15 n values close to 0 above the peb suggest a bloom of n 2 fixing cyanobacteria increased bacterial activity may be either the cause or the result of the anoxia locally associated with the petm

neural dynamic modelling on earthquake magnitude series summary earthquake magnitude prediction is of vital importance for human safety the earthquake is a very complicated and non linear dynamic process it cannot be described adequately by any deterministic models in this paper a neural dynamic modelling for earthquake magnitude prediction is reported historical records of earthquake magnitude series are used to construct the optimal non linear dynamic model and the consequent outcome of the earthquake behaviour is then predicted by this model in turn the latest recorded data set can be fed back to improve the accuracy of the neural dynamic model the modelling of experiments of three earthquake magnitude series in china and japan and their extrapolated predictions are included in this paper the values predicted by extrapolation are in good agreement with the historical data

extinction and recovery of benthic foraminifera across the paleocene eocene thermal maximum at the alamedilla section southern spain abstract a complete succession of lower bathyal upper abyssal sediments was deposited across the paleocene eocene thermal maximum petm at alamedilla betic cordillera southern spain where the benthic foraminiferal turnover and extinction event associated with the negative carbon isotope excursion cie across the petm have been investigated detailed quantitative analyses of benthic foraminifera allowed us to distinguish assemblages with paleoecological and paleoenvironmental significance pre extinction fauna extinction fauna survival fauna including disaster and opportunistic fauna and recovery fauna these assemblages have been associated with significant parts of the 13 c curve for which a relative chronology has been established the correlation between the benthic turnover the 13 c curve the calcite and silicate mineral content and sedimentation rates allowed us to establish the sequence of events across the petm at alamedilla the benthic extinction event bee affected 37 of the species and it has been recorded over a 30 cm thick interval that was deposited in c a 10 ky suggesting a gradual but rapid pattern of extinction the beginning of the bee coincides with the onset of the cie 0 ky and with an interval with abundant calcite and it has been recorded under oxic conditions at the seafloor as inferred from the benthic foraminiferal assemblages and the reddish colour of the sediments we conclude that dissolution and dysoxia were not the cause of the extinctions which were probably related to intense warming that occurred before the onset of the cie the bee is immediately overlain by a survival interval dominated by agglutinated species the glomospira acme the low calcite content recorded within the survival interval may result from the interaction between dilution of the carbonate compounds by silicicate minerals as inferred from the increased sedimentation rates and the effects of carbonate dissolution triggered by the shoaling of the ccd we suggest that glomospira species disaster fauna may have bloomed opportunistically in areas with methane dissociation in and around the north atlantic the disaster fauna was rapidly replaced by opportunistic taxa which point to oxic and possibly oligotrophic conditions at the seafloor the ccd gradually dropped during this interval and calcite preservation improved towards the recovery interval during which the 13 c values and the calcite content recovered c a 71 25 to 94 23 ky and stabilized 94 23 ky coeval with a sharp decrease in sedimentation rates

responses of calcareous nannofossil assemblages mineralogy and geochemistry to the environmental perturbations across the paleocene eocene boundary in the venetian pre alps responses of calcareous nannofossil assemblages mineralogy and geochemistry to the environmental pertubartions across the paleocene eocene boundary in the venetian pre alps

carbon isotope geochemistry of the frasnian famennian transition abstract carbon isotope records for inorganic and total organic carbon toc as well as for individual organic biomarkers show two positive excursions in the late frasnian with comparable shape and amplitude in 13c the positive shifts in 13c can be correlated with the deposition of the kellwasser horizons the inorganic carbon isotope excursions are explained by an enhanced organic carbon burial that is expected to lower the concentration of oceanic dissolved co2 toc 13c values do not exhibit a larger shift than that recorded by inorganic carbon 13c values this is unexpected since a decrease in the dissolved co2 concentration should result in lower carbon isotope fractionation during photosynthesis ep 13c values of presumed algal biomarkers low molecular weight n alkanes pristane phytane although offset by 2 5 exhibit essentially identical records as toc and confirm this unexpected result it is proposed that high atmospheric and oceanic co2 concentrations during the devonian resulted in maximum photosynthetic fractionation any change in the co2 concentration would thus not affect ep as such 13c of primary organic carbon and 13ccarb will exhibit parallel excursions the data imply that carbon isotopes and the relationship between ep and co2 will not be effective to study changes in pco2 levels during the devonian since co2 concentrations were too high

a seismicity gap beneath the inner wall of the japan trench as derived by ocean bottom seismograph measurement abstract an ocean bottom seismograph obs array covered the area of the japan trench about 40 n off the tohoku district of northeastern honshu japan the obs array was operated for two weeks in june 1981 arrival time data of 8 obss were used to study a spatial distribution of microearthquakes around the trench during the observation period 400 500 events with a signal to noise ratio greater than 2 were detected by each obs the arrival times of 223 of these events could be picked 38 earthquakes were located in the area of the japan trench within the latitude range of 38 5 41 0 n and the longitude range of 142 0 146 0 e and about a hundred events were located beneath or near honshu island s p time distribution recorded by each obs showed seismic activities to exist on both sides of the trench axis while the seismic level was low beneath the inner wall of the trench epicentral distribution showed a seismicity gap beneath the inner wall of the trench the area of the landward activity continued eastward up to the position where the water depth is about 4000 m seismic activity existed beneath the trench axis and the seaward wall of the trench the seismicity gap suggested from the 1980 obs observations in the vicinity of the present study area was clearly confirmed by the present observations the obs array enabled us to determine the focal depth of microearthquake activity with better resolution than was possible from land observations the obs data showed that the landward activity beneath the continental slope was concentrated in the very shallow part of the lithosphere at a depth less than 30 km foci started to deepen westward with a very low dip angle of less than 10 which was the most shallow part of the upper plane of the double seismic zone the focal depth distribution showed that events just beneath the trench axis occurred to depths slightly greater than 50 km while the foci of the seaward activity were concentrated in the uppermost lithosphere at depths less than 30 km seismic cross sections clearly show that the activity beneath the trench axis and seaward wall of the trench is separated from the landward activity which is a shallow extension of the double seismic zone by the seismicity gap

the late frasnian kellwasser horizons of the harz mountains germany two oxygen deficient periods resulting from different mechanisms in the harz mountains germany three late devonian sections aeketal huhnertal and kellwassertal were analyzed for major and trace element concentration the inorganic geochemical data were used to determine the environmental conditions associated with the deposition of the two late frasnian black kellwasser horizons in a submarine rise environment low ti al and zr al values and slight enrichment in nutrient and organic matter related trace elements e g ba cu and ni suggest that the kellwasser horizons were deposited during two periods of minimum detrital input but relatively elevated primary production enrichments in u v and mo in both black kellwasser horizons and values of redox indices including u th v cr and ni co indicate oxygen restricted conditions prevailed during the late frasnian times under oxygen depleted conditions reductive diagenesis caused precipitation of iron sulphides such as pyrite that are observed with sem however variations in major and trace element concentrations are not similar in the two kellwasser horizons particularly regarding redox markers the lower kellwasser horizon seems to be more o2 depleted than the upper kellwasser horizon in some german sections on the basis of these results we propose that the two kellwasser horizons are not caused by identical conditions the lower kellwasser horizon results from increased primary productivity enhanced by land derived nutrient loading and which triggered the anoxic conditions recorded in drowned platform setting in contrast the upper kellwasser horizon results from the onset of oxygen impoverished bottom water in the deepest part of the ocean due to episodic water stratification during maximum frasnian flooding oxygen depleted water may have impinged shallower environment during the linguiformis transgressive pulse nutrients would have been released from organic matter decay under reducing conditions and brought up to the photic zone during episodic water mixing

palaeoenvironmental changes at the frasnian famennian boundary in key european sections chemostratigraphic constraints abstract the study aims to put constraints on global environmental changes which took place during the frasnian famennian f f transition by using a geochemical multiproxy approach for this several key european f f boundary sections deposited in different palaeogeographic settings were selected including in addition to the stratotype and parastratotype sections of coumiac montagne noire france and steinbruch schmidt branau germany respectively also some other sections thoroughly characterized by other authors the drilling budesheimer bach prumer mulde germany kowala section holy cross mountains poland la serre france changes in the detrital flux along the sections were evaluated on the basis of both variations in mineral composition and in some diagnostic element ratios like ti al the biogenic flux was assessed as a function of the corg content the input of nutrients or the palaeoproductivity was determined by the p2o5 and ba in excess the degree of anoxia during deposition was constrained by determining the concentration of redox sensitive metals e g fe mn in the bulk sediment of specific element ratios e g v cr as well as the size of pyrite grains together with the degree of pyritization dop in the budesheimer bach core the hydrothermal and volcanic influence in the sedimentary record was detected using e g the al al fe mn and zr al2o3 ratios the kellwasser horizons are characterized by a general decrease in the detrital input together with the increase of al normalized concentration of some of the transition metals these changes are interpreted as reflecting a relative sea level rise and a higher hydrothermal influence in contrast to these the establishment of dysoxic anoxic conditions in the depositional environment as well as the increase of organic matter burial are not always restricted to the kellwasser horizons kwh moreover the hydrothermal influence can lead to misinterpretation with respect to redox conditions and productivity due to the additional input of some specific elements our results indicate the coincidence of sea level rise with hydrothermalism and volcanism during the deposition of the kwh in the area of south laurussia and north gondwana the resulting enrichment in metals and nutrients is coupled in several f f boundary sections with a higher microbial activity as already observed by some authors these effects coupled with a general lowering of the degree of oxygenation of the water bodies could have played a significant role in the demise of the biota

aftershocks near the updip end of the 2011 tohoku oki earthquake abstract the march 2011 m w 9 0 tohoku oki earthquake activated shallow aftershocks with normal faulting focal mechanisms near the trench axis to investigate stress state in the shallow subduction zone near the trench axis we used ocean bottom seismographs obss to record earthquakes from august to october 2011 we estimated hypocenter locations and focal mechanisms of the recorded earthquakes by using a grid search method in a 2 d velocity model based on an active seismic survey the results show that most of the earthquakes occurred within both the overriding and subducting plates with very few on the plate interface and none in the most seaward 45 km of the overriding plate aseismic wedge the low seismicity along the plate interface is consistent with the nearly complete stress drop on the megathrust fault in the m w 9 0 earthquake focal mechanisms indicate that trench normal tension is pre dominant in both plates and extends to a depth of about 30 km at least on the other hand several trench normal compressional earthquakes were located at the landward end of the aseismic wedge these earthquakes suggest horizontal compression of the overriding prism that may be caused by a strengthening of the shallowest part of the megathrust

warm arctic continents during the palaeocene eocene thermal maximum the palaeocene eocene thermal maximum petm 55 5 ma is a geologically relatively brief episode of extreme warmth both deep and surface ocean temperatures increased by up to 5 c in equatorial waters and up to 8 c in mid and high latitude waters from the continents the annual mean air temperature response during the petm is still largely unknown mainly due to a lack of quantitative temperature proxies and sufficient suitable continuous high resolution records recently a new proxy for continental temperature reconstructions has been proposed based on the distribution of membrane lipids of bacteria in present day soils j w h weijers s schouten j c van den donker e c hopmans j s sinninghe damste 2007 environmental controls on bacterial tetraether membrane lipid distribution in soils geochimica et cosmochimica acta 71 703 713 and shown to reconstruct annual mean air temperature in this study we applied this new proxy in an attempt to reconstruct the air temperature in high latitude continental areas during the petm by analysis of a marine sedimentary sequence obtained from the lomonosov ridge in the central arctic ocean integrated ocean drilling program expedition 302 site 004 hole a the results indicate a warming of 8 c above background values of 17 c this warming is coincident with a similar rise in sea surface temperatures documented earlier our results thus further confirm the warm conditions in the arctic and point to a strongly reduced latitudinal temperature gradient during the petm 2007 elsevier b v all rights reserved

prediction of some weathering trends of plutonic and volcanic rocks based on thermodynamic and kinetic considerations abstract the exposed crust consists mainly of plagioclase 35 quartz 20 k feldspar 11 volcanic glass 12 biotite 8 and muscovite 5 quartz is a resistate thus feldspars and glass represent approximately 75 percent of the labile minerals the weathering characteristics of these constituents are summarized in the context of thermodynamic mass balance and kinetic considerations experimentally determined release rate constants were used to predict the proportions of ca na and k released by feldspars of plutonic rocks granites to gabbros to weathering solutions the chemical weathering trends of the weathered residues calculated from the kinetic data conform closely to the initial trends observed in some recent weathering profiles demonstrating the accuracy of the predictions since the weathering of feldspars is controlled by processes that should not change through geological time the relative release rates of ca na and k from the feldspars of granitic rocks can be calculated for future and past episodes of continental weathering experimentally determined release rate constants are not available for a wide range of volcanic glass compositions but the limited data indicate that compositional trends are predictable in weathering profiles developed on volcanic rocks the kinetic data available for rhyolitic glasses accurately predict the initial weathering trends observed in a recent rhyolite weathering profile

environmental dynamics during the paleocene eocene thermal maximum petm in the northeastern peri tethys revealed by high resolution micropalaeontological and geochemical studies of a caucasian key section abstract the sedimentary record of the paleocene eocene thermal maximum petm in the wide epeiric sea of the ne peri tethys contains a sapropelitic bed sbd characterized by a specific microfossil assemblage and negative oxygen and carbon isotope excursions cie new results obtained from a high resolution sampling of this interval in the kheu section central caucasus allows us to explore the succession interrelationships and consequences of global and regional palaeoenvironmental events during the petm the cie apparently lasted twice as long as the sbd accumulation period thus the sbd represents a response to the early and most dramatic phase of the petm related to rapid transgression and greatly enhanced eutrophication of the basin the lithological architecture of the sbd represents four bands each of which consists of a dark low calcareous toc rich clay and relatively paler calcareous clays the highest toc concentrations are found in the lower and upper bands of the sbd however the lower band mostly consists of basinal organic matter while the upper band represents mixed basinal and terrestrial organic matter pre petm events include the initial evolution of the rhomboaster nannofossil lineage with the early first appearance of a short arm species relatively reduced calcareous plankton productivity changes in the ratios of dinocyst ecological groups and minor fluctuations in 13c and 18o the onset of the cie corresponds to the base of the sbd which exhibits a dramatic decrease in total nannofossil abundance and an increase in total dinoflagellate abundance the occurrence of excursion taxa of nannofossils rhomboasters asymmetric discoasters and dinocysts axiodinium augustum epelidinium pechoricum and significant variations in the species ratios of both nannoplankton and dinoflagellate communities with widespread dominance of warm water and eutrophic species above the sbd but during the late phase of cie the nannofossil abundance and species composition show a slight recovery but most paleocene taxa become extinct during the cie recovery apectodinium spp significantly decrease in abundance above the sbd but rare specimens of ax augustum persist higher in the section after the end of the cie thus the major extinction of the paleocene nannofossil taxa occurs after the termination of the most critical conditions during the cie recovery phase while the dinocyst excursion taxa survive even later

double difference tomography the method and its application to the hayward fault california we have developed a double difference dd seismic tomography method that makes use of both absolute and relative arrival times by reducing systematic errors using the more accurate relative arrival times the method produces an improved velocity model simultaneously it yields event locations of a quality equivalent to those of the dd location method while avoiding simplifying assumptions of that method we test this method on a synthetic dataset and find that it produces a more accurate velocity model and event locations than standard tomography we also test this method on a hayward fault california earthquake dataset spanning 1984 1998 the earthquakes relocated by this method collapse to a thin line along the fault trace consistent with previous results the dd velocity model has sharper velocity contrasts near the source region than the standard tomography model

geochemical and climatic effects of increased marine organic carbon burial at the cenomanian turonian boundary perhaps the most significant event in the cretaceous record of the carbon isotope composition of carbonate1 2 other than the 1 2 5 negative shift in the carbon isotope composition of calcareous plankton at the cretaceous tertiary boundary3 is the rapid global positive excursion of 2 13c enrichment which took place between 91 5 myr and 90 3 myr late cenomanian to earliest turonian c t boundary event 1 4 5 this excursion has been attributed to a change in the isotope composition of the marine total dissolved carbon tdc reservoir resulting from an increase in rate of burial of 13c depleted organic carbon which coincided with a major global rise in sea level5 during the so called c t oceanic anoxic event oae 6 here we present new data from nine localities which demonstrate that a positive excursion in the carbon isotope composition of organic carbon at or near the c t boundary7 8 is nearly synchronous with that for carbonate and is widespread throughout the tethys and atlantic basins fig 1 as well as in more high latitude epicontinental seas the postulated increase in the rate of burial of organic carbon may have had a significant effect on co2 and o2 concentrations in the oceans and atmosphere and consequent effects on global climate and sedimentary facies

north american continental margin records of the paleocene eocene thermal maximum implications for global carbon and hydrological cycling the impacts of the paleocene eocene thermal maximum petm 55 ma one of the most rapid and extreme warming events in earth history are well characterized in open marine and terrestrial environments but are less so on continental margins a major carbon sink here we present stable isotope carbonate content organic matter content and c n ratio records through the petm from new outcrop sections in california and from cores previously drilled on the new jersey margin foraminifer 18o data suggest that midlatitude shelves warmed by a similar magnitude as the open ocean 5 c 8 c while the carbon isotope excursion cie recorded both in carbonate and organic matter 13c records is slightly larger 3 3 4 5 than documented in open ocean records sediment accumulation rates increase dramatically during the cie in marked contrast to the open ocean sites in parallel mass accumulation rates of both organic and inorganic carbon also increased by an order of magnitude the estimated total mass of accumulated carbon in excess of pre cie rates suggests that continental margins at least along north america became carbon sinks during the cie mainly because of weathering feedbacks and rising sea level this result is significant because it implies that the negative feedback role of carbon burial on continental margins was greater than previously recognized

late cretaceous to early paleocene climate and sea level fluctuations the tunisian record abstract climate and sea level fluctuations across the cretaceous tertiary k t transition in tunisia were examined based on bulk rock and clay mineralogies biostratigraphy and lithology in five sections el melah el kef elles ain settara and seldja spanning from open marine to shallow inner neritic environments late campanian to early danian trends examined at el kef and elles indicate an increasingly more humid climate associated with sea level fluctuations and increased detrital influx that culminates at the k t transition this long term trend in increasing humidity and runoff in the tethys region is associated with middle and high latitude cooling results of short term changes across the k t transition indicate a sea level lowstand in the latest maastrichtian about 25 100 ka below the k t boundary with the regression marked by increased detrital influx at el kef and elles and a short hiatus at ain settara a rising sea level at the end of the maastrichtian is expressed at elles and el kef by deposition of a foraminiferal packstone a flooding surface and condensed sedimentation mark the k t boundary clay which is rich in terrestrial organic matter the p0 p1a transition is marked by a sea level lowstand corresponding to a short hiatus at ain settara where most of p0 is missing and a period of non deposition and erosion in the lower part of p1a 64 95 ma at seldja p0 and possibly the topmost part of cf1 are missing these sea level fluctuations are associated with maximum humidity these data suggest that in tunisia long term environmental stresses during the last 500 ka before the k t boundary and continuing into the early danian are primarily related to climate and sea level fluctuations within this long term climatic trend the pronounced warm and humid event within the latest maastrichtian zone cf1 may be linked to greenhouse conditions induced by deccan volcanism the absence of any significant clay mineral variations at or near the k t boundary and ir anomaly suggests that the bolide impact had a relatively incidental short term effect on climate in the tethys region

perturbation at the sea floor during the paleocene eocene thermal maximum evidence from benthic foraminifera at contessa road italy abstract detailed analyses of the benthic foraminiferal assemblages extracted with the cold acetolyse method together with high resolution geochemical and mineralogical investigations across the paleocene eocene p e boundary of the classical succession at contessa road western tethys allowed to recognize and document the paleocene eocene thermal maximum petm interval the position of the benthic extinction event bee and the early recovery of benthic faunas in the aftermath of benthic foraminiferal extinction the stratigraphical interval spanning the p e boundary consists of dominantly pelagic limestones and two prominent marly beds benthic foraminifera indicate that these sediments were deposited at lower bathyal depth not deeper than 1000 1500 m the carbon isotope excursion cie interval is characterized by high barite abundance with a peak at the base of the same stratigraphic interval indicating a complete although condensed record of the early cie a succession of events and changes in the taxonomic structure of benthic foraminifera has been recognized that may be of use for supra regional stratigraphic correlation across the p e boundary interval the composition of the benthic foraminiferal assemblages dominated by infaunal taxa indicates mesotrophic and changing conditions on the sea floor during the last 45 kyr of the paleocene the bee occurs at the base of the cie within the lower marly bed and it is recorded by the extinction of several deep water cosmopolitan taxa then the lysocline ccd rose and severe carbonate dissolution occurred preservation deteriorated the faunal density and simple diversity dropped to minimum values and a peak of glomospira spp has been observed stress tolerant and opportunistic groups represented mainly by bi and triserial taxa dominate the low diversity post extinction assemblages indicating a benthic foraminiferal recovery under environmental unstable conditions probably within a context of sustained food transfer to the bottom a three phase pattern of faunal recovery is recognizable at first the lysocline ccd started to descend and then recovered small sized bulimina oridorsalis umbonatus and tappanina selmensis rapidly repopulated the severely stressed environment later on siphogenerinoides brevispinosa massively returns dominating the assemblage together with other buliminids nuttallides truempyi and anomalinoides sp 1 finally a marked drop in abundance of s brevispinosa is followed by a bloom of the opportunistic and recolonizer agglutinated pseudobolivina that for the first time is recorded within the main cie a second interval of dissolution but less severe than the previous one has been recognized within the upper marly bed uppermost part of the main cie interval and it is interpreted as a renewed less pronounced shoaling of the lysocline ccd that interrupted the recovery of benthic faunas this further rise likely represents a response to persistent instability of ocean geochemistry in this sector of the tethys before the end of the cie in the cie recovery and post cie intervals the composition of the benthic foraminiferal assemblages suggests mesotrophic and unstable conditions at the sea floor according to the geochemical proxy for redox conditions the deposition of the petm sediments at contessa road occurred in well oxygenated waters leading out a widespread oxygen depletion as major cause of the bee changing oceanic productivity carbonate corrosivity and global warming appear to have played a much more important role in the major benthic foraminiferal extinction at the p e boundary

sedimentary geochemistry of manganese implications for the environment of formation of manganiferous black shales the sedimentary geochemistry of manganese is dominated by the redox control of its speciation higher oxidation states mn super 3 and super 4 occurring as insoluble oxyhydroxides in well oxygenated environments and the lower oxidation state mn super 2 being much more soluble in oxygen deficient settings its geochemical behavior is therefore quite different in oxic and anoxic environments and where oxic and anoxic conditions are juxtaposed mn is recycled between the two environments in modern marine sediments mn is present above its crustal abundance as an oxyhydroxide in all slowly accumulating pelagic sediments of the deep ocean and in surficial deposits of continental margin environments diagenetic recycling of mn in the latter causes surficial deposits to have larger mn enrichments than in many pelagic sediments bottom sediments of permanently anoxic basins show no enrichments and have mn concentrations that are controlled solely by the aluminosilicate fraction manganese carbonates kutnohorite and calcic rhodochrosite are found only in anoxic sediments accumulating beneath surface oxic horizons and therefore under oxygenated bottom waters in many nearshore environments such enrichments are due to delivery of mn by burial of surface oxyhydroxides into the subsurface anoxic environment where they are dissolved pore water mn levels can reach saturation with respect to a mixed mn ca carbonate phase in such sediments the diagenetic origin for these phases is shown by their carbon isotope compositions which typically indicate a carbon source from decomposing organic matter the presence of mn carbonates therefore signifies that the host sediment must have accumulated under oxygenated bottom waters on the basis of this information it is proposed that in contrast to several current explanations for the formation of mn carbonates kutnohorite and rhodochrosite in ancient organic rich shales limestone and marl sequences and in many mn ore deposits the occurrence of these mineral phases indicates that the sediments originally accumulated beneath oxygenated bottom waters by analogy with the present mn carbonates could not have formed in the bottom waters of anoxic basins these diagenetic phases however did form where mn was supplied at a high rate namely by the burial of oxyhydroxide enriched surface sediments to a subsurface anoxic environment this situation could only have occurred under oxygenated bottom waters the presence of mn carbonates in ancient black shales and in some carbonate rich rocks lends strong support to the notion that these rocks did not necessarily form in anoxic basins but owe their carbon richness to a high supply of organic matter to sediments deposited under oxygenated bottom waters probably in continental margin settings

benthic foraminiferal extinction and repopulation in response to latest paleocene tethyan anoxia the latest paleocene benthic foraminiferal extinction event has been studied in two marlstone successions in the tethys at wadi nukhl egypt and torangly turkmenistan both sections yield a sapropelic layer at the level of the extinction event at nukhl this layer underlies a thin calcareous bed that has also been found in other middle east upper paleocene sections with the onset of anoxia at the tethyan sea floor the aerobic and oligotrophic gavelinella beccariiformis deep sea community collapsed eutrophic to mesotrophic and low oxygen conditions most likely resulting from enhanced organic carbon fluxes to the sea floor triggered an 100 200 k y repopulation sequence marked by downslope migration of several neritic communities that were dominated by opportunistic and tolerant taxa the initial ecosystem restoration was completed when an aerobic and oligotrophic nuttallides truempyi deep sea community became established we suggest that this repopulation mode could be typical for the central tethys

shelf and open ocean calcareous phytoplankton assemblages across the paleocene eocene thermal maximum implications for global productivity gradients abrupt global warming and profound perturbation of the carbon cycle during the paleocene eocene thermal maximum petm ca 55 ma have been linked to a massive release of carbon into the ocean atmosphere system increased phytoplankton productivity has been invoked to cause subsequent co2 drawdown cooling and environmental recovery however interpretations of geochemical and biotic data differ on when and where this increased productivity occurred here we present high resolution nannofossil assemblage data from a shelf section the u s geological survey usgs drill hole at wilson lake new jersey and an open ocean location ocean drilling program odp site 1209 paleoequatorial pacific these data combined with published biotic records indicate a transient steepening of shelf offshelf trophic gradients across the petm onset and peak with a decrease in open ocean productivity coeval with increased nutrient availability in shelf areas productivity levels recovered in the open ocean during the later stages of the event which coupled with intensified continental weathering rates may have played an important role in carbon sequestration and co2 drawdown

the 2011 tohoku oki earthquake displacement reaching the trench axis we detected and measured coseismic displacement caused by the 11 march 2011 tohoku oki earthquake moment magnitude mw 9 0 by using multibeam bathymetric surveys the difference between bathymetric data acquired before and after the earthquake revealed that the displacement extended out to the axis of the japan trench suggesting that the fault rupture reached the trench axis the sea floor on the outermost landward area moved about 50 meters horizontally east southeast and 10 meters upward the large horizontal displacement lifted the sea floor by up to 16 meters on the landward slope in addition to the vertical displacement

fault parameters of the 1896 sanriku tsunami earthquake estimated from tsunami numerical modeling the june 15 1896 sanriku earthquake generated devastating tsunamis with the maximum run up of 25 m and caused the worst tsunami disaster in the history of japan despite its moderate surface wave magnitude ms 7 2 and weak seismic intensity this is a typical tsunami earthquake which generates anomalously larger tsunamis than expected from its seismic waves previously proposed mechanisms of tsunami earthquakes include submarine slumping and slow rupture in the accretionary wedge or in the subducted sediments in this paper we estimate the fault parameters of the 1896 tsunami earthquake by numerically computing the tsunami and comparing the waveforms with those recorded at three tide gauge stations in japan the result indicates that the tsunami source is very close to the japan trench and the fault strike is parallel to the trench axis the fault width is about 50 km suggesting that the tsunami earthquake is a slow rupture in the subducted sediments beneath the accretionary wedge

evidence of surface water oligotrophy during the paleocene eocene thermal maximum nannofossil assemblage data from ocean drilling program site 690 maud rise weddell sea 1 nannoplankton assemblages at ocean drilling program site 690 maud rise weddell sea experienced an abrupt and dramatic transformation at the onset of the paleocene eocene thermal maximum petm at 55 m y the major assemblage shift suggests a change from colder more productive surface waters to warmer more oligotrophic conditions significant restructuring of assemblages during the later part of the petm indicates that nannoplankton communities were not stable and that surface water conditions changed although they remained warm and oligotrophic combined with benthic foraminiferal assemblage data nannoplankton assemblage results suggest increased sequestration of nutrients in shelf environments and starvation of the open ocean although the petm was a short lived event it appears to have had long term effects on nannoplankton leading to the extinction of fasciculithus a dominant paleocene genus

uncorking the bottle what triggered the paleocene eocene thermal maximum methane release the paleocene eocene thermal maximum petm was a time of rapid global warming in both marine and continental realms that has been attributed to a massive methane ch 4 release from marine gas hydrate reservoirs previously proposed mechanisms for this methane release rely on a change in deepwater source region s to increase water temperatures rapidly enough to trigger the massive thermal dissociation of gas hydrate reservoirs beneath the seafloor to establish constraints on thermal dissociation we model heat flow through the sediment column and show the effect of the temperature change on the gas hydrate stability zone through time in addition we provide seismic evidence tied to borehole data for methane release along portions of the u s continental slope the release sites are proximal to a buried mesozoic reef front our model results release site locations published isotopic records and ocean circulation models neither confirm nor refute thermal dissociation as the trigger for the petm methane release in the absence of definitive evidence to confirm thermal dissociation we investigate an alternative hypothesis in which continental slope failure resulted in a catastrophic methane release seismic and isotopic evidence indicates that antarctic source deepwater circulation and seafloor erosion caused slope retreat along the western margins of the north atlantic in the late paleocene continued erosion or seismic activity along the oversteepened continental margin may have allowed methane to escape from gas reservoirs trapped between the frozen hydrate bearing sediments and the underlying buried mesozoic reef front precipitating the paleocene eocene boundary methane release an important implication of this scenario is that the methane release caused rather than resulted from the transient temperature increase of the petm neither thermal dissociation nor mechanical disruption of sediments can be identified unequivocally as the triggering mechanism for methane release with existing data further documentation with high resolution benthic foraminiferal isotopic records and with seismic profiles tied to borehole data is needed to clarify whether erosion thermal dissociation or a combination of these two was the triggering mechanism for the petm methane release

phosphorus and the roles of productivity and nutrient recycling during oceanic anoxic event 2 four sections documenting the impact of the late cenomanian oceanic anoxic event oae 2 were studied in basins with different paleoenvironmental regimes accumulation rates of phosphorus p bound to iron organic matter and authigenic phosphate are shown to rise and arrive at a distinct maximum at the onset of oae 2 with an associated increase in 13 c values accumulation rates of p return to preexcursion values in the interval where the 13 c record reaches its fi rst maximum an offset in time between the maximum in p accumulation and peaks in organic carbon burial hydrogen indices and corg preact molar ratios is explained by the evolution of oae 2 in the following steps 1 an increase in productivity increased the fl ux of organic matter and p into the sediments the preservation of organic matter was low and its oxidation released p which was predominantly mineralized 2 enhanced productivity and oxidation of organic matter created dysoxic bottom waters the preservation potential for organic matter increased whereas the sediment retention potential for p decreased 3 the latter effect sustained high primary productivity which led to an increase in the abundance of free oxygen in the ocean and atmosphere system after the sequestration of co 2 in the form of black shales this oxygen helped push the ocean back into equilibrium terminating black shale deposition and removing bioavailable p from the water column

the spread of marine anoxia on the northern tethys margin during the paleocene eocene thermal maximum records of the paleoenvironmental changes that occurred during the paleocene eocene thermal maximum petm are preserved in sedimentary rocks along the margins of the former tethys ocean and peri tethys this paper presents new geochemical data that constrain paleoproductivity sediment delivery and seawater redox conditions from three sites that were located in the peri tethys region trace and major element iron speciation and biomarker data indicate that water column anoxia was established during episodes when inputs of land derived higher plant organic carbon and highly weathered detrital clays and silts became relatively higher anoxic conditions are likely to have been initially caused by two primary processes i oxygen consumption by high rates of marine productivity initially stimulated by the rapid delivery of terrestrially derived organic matter and nutrients and ii phosphorus regeneration from seafloor sediments the role of the latter process requires further investigation before its influence on the spread of deoxygenated seawater during the petm can be properly discerned other oxygen forcing processes such as temperature salinity driven water column stratification and or methane oxidation are considered to have been relatively less important in the study region organic carbon enrichments occur only during the initial stages of the petm as defined by the negative carbon isotope excursions at each site the lack of observed terminal stage organic carbon enrichment does not support a link between petm climate recovery and the sequestration of excess atmospheric co2 as organic carbon in this region such a feedback may however have been important in the early stages of the petm

interplate seismic activity near the northern japan trench deduced from ocean bottom and land based seismic observations the off sanriku area the landward slope area of the northern japan trench is characterized by its active seismicity which is directly related to the subduction process of the pacific plate in july august 1992 a seismic swarm activity was observed near the trench five earthquakes of m 6 occurred successively within 2 weeks at the beginning of the activity we deployed an ocean bottom seismograph obs array in the epicentral region to make an in situ observation of the spatial distribution of these events and to study the characteristics of the swarm activity in detail we relocated 357 events from 23 july to 26 august with focal depth errors less than 5 km by using both the obs and the land network data the swarm events are not distributed homogeneously over the plate boundary but form several clusters a remarkable concentration of the earthquakes was found in the vicinity of the hypocenter of the largest event during the obs observation m 6 2 29 july this formed the most active cluster almost all the earthquakes including the m 6 2 event occurred at depths of about 15 km and were concentrated along a thin plane dipping to the west at 5 the location of the plane coincides well with that of the plate boundary derived from previous seismic explorations we also relocated epicenters of the off sanriku events by introducing station corrections to the land network data during the period when the obs array was absent the corrections were estimated from the travel time residuals of the hypocenter relocation using the obs and the land network data the result of the epicenter relocation strongly indicates the existence of a zone of extremely low seismic activity beneath the inner trench wall where low seismic velocity mechanically weak unconsolidated sediments overly the subducting pacific plate

a reassessment of outer rise seismicity and its implications for the mechanics of oceanic lithosphere we use body waveform modelling to constrain the source parameters of earthquakes occurring globally in oceanic lithosphere beneath the subduction zone outer rise and outer trench slope these data are then used to map the stress state in the lithosphere of the downgoing plate as it bends into the subduction zone our results provide new constraints on the faulting of oceanic lithosphere at the outer rise which is important for understanding the transmission of plate driving forces through the subduction system in all cases shallow normal faulting earthquakes are observed at the top of the plate and are separated in depth from any deeper thrust faulting earthquakes no temporal variation associated with large thrust faulting earthquakes on the subduction interface is seen in the depth extent of each type of faulting at the outer rise the transition depth from trench normal extension to compression is found to vary in agreement with models in which deformation is driven by the combination of in plane stresses and bending stresses resulting principally from slab pull combining the seismologically derived constraints on the thickness of the elastic core of the plate with estimates of the plate curvature we place upper bounds on the strength of the lithosphere at the outer rise which is required to be 300 mpa for a constant yield stress model or governed by an effective coefficient of friction of 0 3

the ciw index a new chemical index of weathering abstract a new chemical index of weathering that can be applied to modern soils and precambrian paleosis is proposed ciw al2o3 the value of this index increases as the degree of weathering increases and the difference between ciw index values of the silicate parent rock and soil or sediment reflects the amount of weathering experienced by the weathered material

high resolution seismic imaging in the japan trench axis area off miyagi northeastern japan 1 newly obtained high resolution seismic data reveal the detailed structure of the japan trench axis off miyagi japan in the region of large shallow slip during the 11 march 2011 m9 tohoku earthquake correlation of seismic images with previous drilling results identifies a possible basal chert rich layer and hemipelagic pelagic mudstones overlying igneous pacific crust mapping of acoustic basement depicts the subduction of horst and graben topography the basement and basal chert are subducted beneath a seismically chaotic frontal prism but the majority of overlying hemipelagic mudstones is offscraped and imbricated at the trench axis as a result of plate boundary compression a possible decollement is imaged as a seaward dipping reflection at landward part of the trench graben and was likely generated by loading and failure of underthrust sediments collectively these analyses provide a structural framework for understanding sedimentary inputs and the localization of shallow plate boundary slip at the japan trench

calcareous nannofossils from the paleocene eocene thermal maximum of the equatorial atlantic odp site 1260b evidence for tropical warming abstract independent geological and micropaleontological lines of evidence suggest a 200 kyr period of intense warming covering the paleocene eocene boundary interval petm it has been suggested that this warming was initiated by a massive release of methane from the continental slopes among other groups of organisms calcareous nannofossils are characterized by a remarkable increase of warm water taxa during this interval here we report the tropical response of calcareous nannofossils to the paleocene eocene interval in odp site 1260b 283 15 276 35 mbsf the petm is about 1 38 m thick 279 88 278 5 mbsf as defined by the onset and termination of the 13c excursion and is marked by a 12 cm thick laminated clay layer at the start of the excursion a 30 cm thick interval 279 75 279 45 mbsf directly above the clay layer is characterized by common discoaster spp and coccolithus subpertusus syn ericsonia subpertusus and the first occurrences of discoaster araneus rhomboaster cuspis and tribrachiatus bramlettei all five taxa are interpreted as proxies for warm surface waters the increase of discoaster spp during the petm is solely caused by the onset of the new species d araneus which is here seen as a malformed discoaster related to specific petm conditions these possibly include an acidification of the surface waters and or higher salinity the rhomboaster tribrachiatus group which first occurs in the petm is also thought to be a proxy for increased salinity the abundance of the genus toweius indicative for mesotrophic conditions declines simultaneously discoaster abundance decreases in the later stages of the petm being substituted by chiasmolithus and campylosphaera indicating a change to more eutrophic conditions the genus fasciculithus very common in the tropical paleocene suffered a dramatic decline in the clay layer basal petm without recovering later in the eocene this decline and the subsequent extinction of fasciculithus a solid robust nannolith are here thought to be related to a calcification crises perhaps caused by a high co2 concentration and an acidification of the oceans the observed changes in the composition of the calcareous nannofossils were relatively short lived following the course of the petm which was characterized by warm surface waters with possibly low ph conditions

latest on the absolute age of the paleocene eocene thermal maximum petm new insights from exact stratigraphic position of key ash layers 19 and 17 abstract we constructed a precise early eocene orbital cyclostratigraphy for dsdp site 550 leg 80 goban spur north atlantic utilizing precession related cycles as represented in a high resolution x ray fluorescence based barium core log based on counting of those cycles we constrain the exact timing of two volcanic ash layers in site 550 which correlate to ashes 19 and 17 of the fur formation in denmark the ashes relative to the onset of the paleocene eocene thermal maximum petm are offset by 862 kyr and 672 kyr respectively when combined with published absolute ages for ash 17 the absolute age for the onset of the petm is consistent with astronomically calibrated ages using the current absolute age of 28 02 ma for the fish canyon tuff fct standard for calibrating the absolute age of ash 17 is consistent with tuning option 2 in the astronomically calibrated paleocene time scale of westerhold et al 2008 westerhold t rohl u raffi i fornaciari e monechi s reale v bowles j and evans h f 2008 astronomical calibration of the paleocene time palaeogeography palaeoclimatology palaeoecology v 257 p 377 403 using the recently recalibrated absolute age of 28 201 ma for the fct standard is consistent with tuning option 3 in the astronomically calibrated paleocene time scale the new results do not support the existence of any additional 405 kyr cycle in the early paleocene astronomically tuned time scale

carbon addition and removal during the late palaeocene thermal maximum basic theory with a preliminary treatment of the isotope record at odp site 1051 blake nose the late palaeocene thermal maximum lptm was a brief interval at c 55 ma characterized by a 2 5 to 3 per thousand shift in the 13c of global carbon reservoirs the geochemical perturbation probably represents a massive input of 12c rich carbon to the exogenic carbon cycle largely unresolved issues concerning this carbon injection during the lptm are the rates of carbon input and removal simple expressions are developed here to describe a 13c excursion in the exogenic carbon cycle after carbon input a change in global 13c d ex dt can be explained to a first approximation by a set of parameters the initial mass and isotopic composition of the global carbon cycle mex o ex o and the fluxes and isotopic compositions of external carbon inputs outputs and injected carbon fin in fout out fadd add in general for a given exogenic carbon cycle a large fadd or low add results in a larger 13c excursion likewise for a given negative 13c excursion a large mex or low ex requires a greater input of 12c differences in fin in fout and out cause changes in the response of ex over time for a negative 13c excursion of given magnitude a greater fin requires a greater input of 12c and lessens the time for ex to return to initial conditions a decrease in out caused by an increase in the relative output of organic matter and carbonate has a similar effect variable dmadd dt produces transients in ex that are related to the source function but modified by carbon removal in theory a well dated and representative global 13c excursion could be used to derive the carbon inputs and ouputs ocean drilling program odp site 1051 has an expanded early palaeogene section and recent work at this location has provided a well dated 13c record across the lptm this 13c record contains transient variations of apparently global nature these observed transients are best explained by a pulsed injection of ch4 into an exogenic carbon cycle with a greater carbon throughput or enhanced burial of organic matter after carbon addition

planktic foraminiferal turnover across the paleocene eocene transition at dsdp site 401 bay of biscay north atlantic abstract planktic foraminifera across the paleocene eocene transition at dsdp site 401 indicate that the benthic foraminiferal mass extinction occurred within subzone p 6a of berggren and miller 1988 or p5 of berggren et al 1995 and coincident with a sudden 2 0 excursion in 13c values the benthic foraminiferal extinction event bfee and 13c excursion was accompanied by a planktic foraminiferal turnover marked by an influx of warm water species morozovella and acarinina a decrease in cooler water species subbotina a sudden short term increase in low oxygen tolerant taxa chiloguembelina and no significant species extinctions these faunal changes suggest climatic warming expansion of the oxygen minimum zone and a well stratified ocean water column oxygen isotope data of the surface dweller m subbotina suggest climate warming beginning with a gradual 0 5 decrease in 18o in the 175 cm preceding the benthic foraminiferal extinction event followed by a sudden decrease of 1 4 c at the bfee the 13c excursion occurred over 27 cm of sediment and assuming constant sediment accumulation rates represents a maximum of 23 ka recovery to pre excursion gd13c values occurs within 172 cm or about 144 ka climate cooling begins in subzone p 6c as indicated by an increase in cooler water subbotinids and acarininids with rounded chambers and a decrease in warm water morozovellids

rupture process of the 2011 tohoku oki earthquake and absolute elastic strain release 1 on 11 march 2011 the tohoku oki earthquake in eastern japan and the devastating tsunami that followed it caused severe damage and numerous deaths to clarify the rupture process of the earthquake we inverted teleseismic p wave data applying a novel formulation that takes into account the uncertainty of green s function which has been a major error source in waveform inversion the estimated seismic moment is 5 7 1022 nm mw 9 1 associated with a fault rupture 440 km long and 180 km wide along the plate interface the source process is characterized by asymmetric bilateral rupture propagation but we also found continuous slips up dip from the hypocenter which led to a large maximum slip 50 m long slip duration 90 s and a large stress drop 20 mpa the long slip duration large stress drop extensional normal faulting aftershocks in a previously compressional stress regime and low angle normal slips at approximately the depth of the plate interface suggest that the earthquake released roughly all of the accumulated elastic strain on the plate interface owing to exceptional weakening of the fault the stress accumulated on the plate interface was about 20 mpa near the trench and 0 10 mpa in the down dip source region

trace metal records of regional paleoenvironmental variability in pennsylvanian upper carboniferous black shales abstract regional geochemical differences within a laterally continuous cyclic pennsylvanian upper carboniferous shale in midcontinent north america are interpreted in light of models of glacioeustatic forcing and new views on water column paleoredox stability and trace metal behavior in black shale environments specifically we characterize differences in transition metal fe mn mo v ni zn pb and u concentrations in black shales of the hushpuckney shale member of the swope limestone in iowa and equivalent black shale beds of the coffeyville formation in oklahoma although c s fe systematics and uniform 34 s depleted isotope ratios of pyrite indicate pervasive euxinic deposition anoxic and sulfidic bottom waters for these shales regional variations can be inferred for the efficiency of mo scavenging and for the rates of siliciclastic sedimentation as expressed in spatially varying fe al ratios black shales in iowa show mo enrichment roughly five times greater than that observed in coeval euxinic shales in oklahoma by contrast fe al ratios in oklahoma shales are as much as five times greater than the continental ratio of 0 5 observed in the over and underlying oxic facies and in the coeval black shales in iowa recent work in modern marine settings has shown that enrichments in fe commonly result from scavenging in a euxinic water column during syngenetic pyrite formation in contrast to fe the concentrations of other transition metals mo v ni pb zn u are typically more enriched in the black shales in iowa relative to oklahoma the transition metal trends in these paleozoic shales are reasonably interpreted in terms of early fixation in organic rich sediments due to euxinic water column conditions however regional variations in 1 rates of siliciclastic input 2 organic reservoirs including relative inputs of terrestrial versus marine organic matter and 3 additional inputs of metals to bottom waters from contemporaneous hydrothermal vents are additional key controls that lead to geographic variation in the extent of metal enrichments preserved in ancient organic rich sediments

high resolution iridium δ13c δ18o foraminifera and nannofossil profiles across the latest paleocene benthic extinction event at zumaya spain in the expanded upper paleocene lower eocene section 30 m of zone p5 sediments at zumaya northern spain the highest occurrence of many late paleocene deep sea benthic foraminifera species 40 extinction coincides with a transition from marl to calcite free clay our high resolution studies chemical elements 613c 6180 calcareous nannofossils planktic and benthic foraminifera show that below the marl clay transition there is a 40 50 cm thick interval corresponding to 10 20 kyr containing a detailed record of a gradual succession of faunal and geochemical events culminating in the benthic extinctions planktic foraminiferal and nannofossil changes e g the onset of demise in fasciculithus genus occur a few meters below the marl clay transition in the limestone 50 cm below the base of the clay a prominent glauconite maximum indicates that sea floor oxygenation suddenly decreased glauconite continues to be common until the onset of clay deposition a whole rock negative 613c shift 1 6 0 most likely reflecting an original sea water trend is gradually developed over the 40 cm of greenish brown marls immediately below the clay at the base of these marls there is a small significant iridium anomaly of 133 ppt ir compared with an average background of 38 ppt in the marls the demise of the fasciculithus species accelerates gavelinella beccariiformis becomes extinct and the abundance of acarinina species begins to increase the superjacent 4 m of clay is devoid of original calcite in its lower part and has a low calcareous content higher up at calcareous levels in the clay an unusual planktic foraminifera fauna occurs dominated by acarinina species when marl deposition returns 613c gradually increases and then stabilizes at values about 0 5 o lower than before the isotopic excursion the 613c excursion spans in total 5 m probably corresponding to 200 400 kyr the fasciculiths disappear shortly after the stabilization of 613c here we also present a whole rock 6 3c profile through the entire paleocene section at zumaya the profile is very similar to previous profiles registered in well preserved deep sea material suggesting that whole rock 613c at zumaya can be used for correlation

stratigraphy of late palaeocene events in the middle east implications for low to middle latitude successions and correlations we have investigated the upper palaeocene stratigraphical record in four sections in egypt and one in israel the sections are arranged on a depth transect across the southern tethyan margin in all sections a 13 c excursion and benthic foraminiferal extinctions coincide at a level within planktic foraminiferal zone p5 in three sections a bed sapropelic in two of the deeper profiles contains extraordinarily transient benthic and planktic foraminifera assemblages these planktic assemblages are dominated by acarinina and contain rare to common morozovella allisonensis and globanomalina luxorensis but unusually few other morozovella the extremely restricted stratigraphical range of m allisonensis to the lower part of the 13 c excursion enables 1 a three fold subdivision of zone p5 2 accurate correlation to the best sections spanning the 13 c excursion in the atlantic and pacific and 3 assessment of stratigraphical completeness over the 13 c excursion in other sub tropical successions discontinuities and especially dissolution intervals in many low to middle latitude marine successions elsewhere as in two middle east sections preclude an accurate correlation within the lower part of the 13 c excursion m allisonensis zone p5b three studied sections can provide the best coverage of the sequence of events over the onset and early part of the 13 c excursion in the middle east but as in most known sections probably none constitutes a complete upper palaeocene lower eocene record

effects of weathering on nickel and vanadyl porphyrins of a lower toarcian shale of the paris basin the effects of weathering on the organic matter within a narrow sediment interval from surficial to 10 m depth belonging to the lower toarcian shales of the paris basin were studied at a molecular level among the compositional changes observed the most striking feature is a severe breakdown of the metalloporphyrins ni and vo at the surface as evidenced by quantitative data in addition this degradation of the geoporphyrins is accompanied by substantial modification of their composition with preferential degradation of porphyrins with exocyclic rings over polyalkylporphyrins these quantitative and qualitative changes are thought to result from exposure of the sediment to weathering conditions more specifically abiotic oxidation is likely to be the main weathering process responsible for this superficial alteration of the sedimentary porphyrins this is particularly suggested by oxidation experiments carried out on a mixture of sedimentary nickel and vanadyl porphyrins where oxidation of the former complexes occurs at a faster rate thus geoporphyrins may be used as molecular indicators to evaluate the degree of oxidation of weathered geological samples containing this kind of molecule

environmental perturbation in the southern tethys across the paleocene eocene boundary dababiya egypt foraminiferal and clay mineral records foraminiferal and clay mineral records were studied in the upper paleocene to lower eocene dababiya section egypt this section hosts the gssp for the paleocene eocene boundary and as such provides an expanded and relatively continuous record across the paleocene eocene thermal maximum petm deposition of illite smectite clay minerals is interpreted as a result of warm and arid conditions in the southern tethys during the latest paleocene benthic foraminiferal assemblages are indicative of seasonal variation of oxygen and food levels at the seafloor a sea level fall occurred in the latest paleocene followed by a rise in the earliest eocene foraminiferal diversity and densities decreased strongly at the p e boundary coinciding with the level of global extinction of benthic foraminifera bee and start of the carbon isotope excursion cie and petm in the lower cie the seafloor of the stratified basin remained nearly permanently anoxic and azoic a sudden increase in mixed clay minerals kaolinite and others suggests that warm and perennial humid conditions prevailed on the continent high levels of toc and phosphathic concretions in the middle cie are evidence for increased organic fluxes to the sea floor related to upwelling and to augmented continental runoff low densities of opportunistic taxa appeared indicating occasional ephemeral oxygenation and repopulation of the benthic environment the planktic community diversified although conditions remained poor for deep dwelling taxa an increase in illite smectite dominated clay association is considered to mark the return of a seasonal signature on climatic conditions during the late cie environmental conditions changed to seasonally fluctuating mesotrophic conditions and diverse and rich benthic and planktic foraminiferal communities developed post cie planktic faunas consisted of both deep and shallow dwelling taxa and buliminid dominated benthic assemblages reflect fluctuating mesotrophic conditions the frequent environmental perturbations during the cie petm at dababiya provided a rather specialized group of foraminiferal taxa i e anomalinoides aegyptiacus the opportunity to repopulate survive and subsequently dominate by a hypothesized capacity to switch to an alternative life strategy population dynamics habitat shift or different metabolic pathway the faunal record of dababiya provides insight into the cause and development of the bee various severe global changes during the petm e g ocean circulation caco3 dissolution productivity and temperature changes disturbed a wide range of environments on a geologically brief timescale explaining together the geographically and temporally variable character of the bee this allowed a number of specific but different foraminiferal assemblages composed of stress tolerant and opportunistic taxa to be successful during and after the periods of environmental perturbations associated with the petm

black carbon in paleocene eocene boundary sediments a test of biomass combustion as the petm trigger abstract several explanations have been proposed to account for the dramatic perturbation to earth s carbon cycle that led to extreme warming ocean acidification mass extinction and a major negative carbon isotope excursion cie at the paleocene eocene p e boundary one reason that the ultimate cause for this event remains ambiguous is the difficulty in directly testing these multiple hypotheses we conducted a test of one proposed mechanism the wildfire hypothesis that suggests that combustion of a significant fraction of abundant paleocene peat deposits within several thousand years could release enough co2 to earth s atmosphere to account for all of these observations soot and graphitic black carbon hereafter collectively referred to as gbc both combustion byproducts are widely distributed through smoke by subaerial combustion and are remarkably resistant to diagenetic degradation using samples provided by the ocean drilling program we measured gbc concentrations across the p e boundary in two important paleocene eocene thermal maximum petm sections to test a prediction of the wildfire hypothesis namely that the combustion of paleocene organic matter at the onset of the petm would produce a peak in sedimentary gbc in the bass river section new jersey margin gbc concentrations are uniformly high 121 358 ppm consistent with the core s continental margin setting but there is no evidence of increased gbc flux at the petm furthermore carbon isotopic ratios of gbc display the negative cie seen in petm organic matter indicating that this material was sourced from contemporaneous p e boundary biomass not geologically old carbon at site 1210 shatsky rise gbc concentrations were uniformly below our method s detection limit 0 5 ppm whereas the wildfire hypothesis would predict high gbc concentrations 3000 ppm accompanying the event together these data appear to refute but cannot conclusively rule out biomass burning as the cause for the petm event

trace element behavior and redox facies in core shales of upper pennsylvanian kansas type cyclothems the black shale submember of core shales of pennsylvanian kansas type cyclothems is highly enriched in redox sensitive trace elements tes relative to the overlying gray shale submember as well as to many other modern and ancient organic rich deposits controls on trace element behavior in the black shale can be inferred from trace element enrichment factors efs relative to gray shale and the relationship of tes to total organic carbon toc most tes conformed to one of two patterns 1 mo u v zn and pb exhibited moderate efs and strong covariation with toc in samples having 10 wt toc and 2 cu ni cr and co exhibited low efs and moderate to strong covariation with toc in all samples these patterns are inferred to represent different responses to benthic redox conditions the first pattern is characteristic of tes of strong euxinic affinity i e those taken up in solid solution by fe sulfide or involved in other reactions catalyzed by free h2s and resident mainly in authigenic phases whereas the second pattern is characteristic of tes of weak euxinic affinity i e those not strongly influenced by the presence of free h2s and resident mainly in the organic carbon or detrital fractions of the sediment these inferences allowed development of a multiproxy technique for assessing redox facies in black shale samples euxinic conditions were considered to have existed if at least two of four redox indicator trace elements mo u v zn showed euxinic levels of enrichment and nonsulfidic anoxic conditions were inferred otherwise the validity of the procedure is indicated by 1 agreement among all four redox indicators for a large majority of samples 69 of 185 2 among samples yielding a mixed redox signal a systematic sequence of te enrichment v zn mo u and 3 for tes of weak euxinic affinity reduced variance among samples representing each redox facies sequential enrichment may be a response to differential redox thresholds for accumulation e g v or postdepositional remobilization of trace elements e g u and may provide a basis for finer assessment of redox conditions in low oxygen paleoenvironments than permitted by simple classification schemes the multiproxy procedure for redox facies analysis developed in this study is likely to be more reliable than widely used single proxy indicators based on trace elements e g mo authigenic u or v v ni or c s fe systematics e g s toc or dop d 2004 elsevier b v all rights reserved

earthquake distribution in the subduction zone off eastern hokkaido japan deduced from ocean bottom seismographic and land observations summary in 1986 observations of microearthquakes were conducted with the use of five ocean bottom seismometers obss on the continental slope east of the kushiro submarine canyon ksc off hokkaido island japan the observation area is located about 50 100 km landward of the southern kuril trench beneath which the pacific plate is subducted toward hokkaido island the obs data were analysed together with land data on hokkaido island to determine the precise earthquake distribution and the geometry of the subducted plate the obs data revealed for the first time the seaward seismicity east of ksc high and shallow seismicity is concentrated in an area between the coast line of hokkaido island and the 2000 m isobath a region between the 2000 and 4000 m isobaths corresponds to the source area of an interplate earthquake occurring in 1973 the nemuro hanto oki earthquake m 7 4 the obs array detected more than 10 events in this region most of them however are classified as earthquakes occurring within the subducted plate and the remarkable aftershock activity of the 1973 event is not recognized the seismic activity is extremely low between the 4000 and 6000 m isobaths as is commonly seen in subduction zones the seismicity is also very low beneath the trench in contrast with the adjacent trench areas in a vertical section taken perpendicular to the trench axis most of the located events form a seismic plane dipping landward the dip angle of the plane is 20d 25d beneath the continental slope while 35d 40d under hokkaido island the change in dip angle occurs 150 km landward of the trench axis this seismic plane is located 30 40 km below the plate boundary defined from the aftershock distribution of the nemuro hanto oki event the seismicity on the plate boundary is correlated with the geometry of the subducted plate the high activity occurs in a restricted region where the subducted plate shows a remarkable bend the seismic activity obtained is different from those in the adjacent regions along the southern kuril trench in particular the regional difference in seismicity is remarkable between the western and eastern sides of ksc our result suggests that the subduction zone along the kuril trench is divided into several tectonic blocks and ksc is one of their boundaries

seismic structure and seismogenesis off sanriku region northeastern japan summary in 1997 a seismic experiment using an airgun array and ocean bottom seismographs obss was performed in the forearc region of the northeastern japan nej arc the objectives of this experiment were to clarify seismic structures of the forearc region off sanriku japan using airgun obs data and to understand the nature of the japan trench seismogenic zone fundamental features of the structure are as follows i the subduction angle becomes steeper from east to west from 3 to 8 to 11 with the top of the plate located at depths of 11 km 40 km west from the trench 21 km 120 km west from the trench and 28 km 140 km west from the trench respectively ii the nej moho beneath the forearc is defined at a depth of approximately 20 km iii p wave velocity of the island arc upper mantle is approximately 8 km s 1 iv the p wave velocity of the cretaceous sedimentary layer exhibits significant lateral variability 4 0 5 5 km s 1 i nthe e w direction v the upper crust of nej forearc also has the significant lateral heterogeneity 5 0 6 3 km s 1 i nthe e w direction but not in the n s direction vi the middle crust defined on land extends in some locations 40 km east of the coastline vii lateral variability in the p wave velocity of the lower crust 6 7 7 0 km s 1 i ssmall compared with that of the upper crust according to these results it is suggested that the rupture areas of large earthquakes m7 in this region are limited within the contact zone between the nej arc crust and the subducting oceanic crust although a thin layer with low velocity is probably present within this contact zone the serpentinization of uppermost mantle wedge of the nej arc by reaction between the mantle materials and the water from the thin layer beneath forearc region is limited this might indicate that a significant volume of water and sediments subduct with the slab to depths of over 20 km

contrasting sulfur geochemistry and fe al and mo al ratios across the last oxic to anoxic transition in the cariaco basin venezuela an abrupt transition from oxic to anoxic sulfidic euxinic marine bottom waters occurred in the cariaco basin in response to increasing productivity resulting from the late pleistocene post glacial rise in sea level and corresponding increase in surface water nutrient availability the microlaminated sediments of the euxinic interval which span the last f14 5 ky suggest a predominance of water column syngenetic pyrite formation based on 1 high pyrite sulfur spy concentrations in the surficial sediment layers 2 values for degree of pyritization dop that generally do not increase appreciably with increasing burial 3 ratios of total iron fet to al that are elevated above the continental baseline recorded in the underlying oxic sediments and 4 spy isotope trends that largely mimic the d 34 shsof the modern water column intermediate dop values in the microlaminated deposits and fet al ratios that are slightly above continental levels indicate an iron reservoir controlled by scavenging during syngenetic pyrite formation in combination with intermediate rates of fe bearing siliciclastic accumulation as predicted from the relative rates of siliciclastic delivery fet al and dop data lie between end member values observed in the modern black sea as viewed broadly fet al and dop relationships in euxinic sediments reflect the balance between syngenetic fe scavenging and temporal and spatial gradients in siliciclastic input pyrite concentrations are generally low in the underlying oxic marine deposits because of limitations in the supply of organic carbon corg however the upper 80 cm of the fe rich corg poor bioturbated sediment show evidence for a strong diffusional hsoverprint from the overlying fe limited euxinic marine environment this post glacial transition manifests in pyrite overprints that are strongly 34 s depleted relative to those in restricted presently euxinic marine settings elsewhere in the world such as the black sea where the sedimentary sequence spanning the last glacial interglacial transition begins with a shift from freshwater to corg poor oxic marine deposition and thus dominantly sulfate diffusion trends for mo al ratios in the microlaminated sediments suggest that mo is enriched by roughly two orders of magnitude above the continental levels recorded in the oxic deposits organic matter plays a role by enhancing hsproduction and or by providing a substrate for mo scavenging significant mo enrichment via diffusion into the upper portion of the bioturbated zone was not observed despite hs rich pore waters as recorded in the heavy iron sulfide overprint we have

large terrestrial and marine carbon and hydrogen isotope excursions in a new paleocene eocene boundary section from tanzania recent onshore drilling expeditions in tanzania have yielded sediments spanning much of the late cretaceous and paleogene which show exceptionally good preservation of both calcareous microfossils and organic matter the interval of the paleocene eocene thermal maximum petm was recovered at tanzania drilling project tdp site 14 in 2004 the petm interval was identified using planktonic foraminifer and nannofossil biostratigraphy carbon isotopic measurements of planktonic foraminifera from the genus subbotina show a maximum measured negative shift in 13c values of approximately 4 5 which is significantly larger than has been observed for most deep sea foraminifer records higher plant derived n alkanes yield a ca 6 5 negative shift through the same interval as carbon isotope fractionation in higher plants varies amongst taxa and is influenced by humidity it is possible that this remarkably large shift in the n alkane 13c values records environmental and vegetation changes as well as changes in the 13c value of the ocean atmosphere reservoir however dramatic increases in humidity appear to be unlikely as higher plant biomarker d values shift to higher rather than lower values taken together the records suggest that the magnitude of the carbon isotope excursion cie in the ocean atmosphere reservoir may have been larger than has generally been accepted this has important implications for the source and quantity of 13c depleted carbon released at the petm

the great 1933 sanriku oki earthquake reappraisal of the main shock and its aftershocks and implications for its tsunami using regional tsunami and seismic data

implications of elemental concentrations for provenance redox conditions and metamorphic studies of shales and limestones near pueblo co usa abstract major element and some trace element compositions including the ree of shales carbonate rich shales and limestones of late cretaceous age have been analyzed at two outcrops near pueblo co elemental ratios that are characteristic of the provenance of terrigenous debris that are the least variable with changing percent acid insoluble residue vs percent calcite are th cr la co la lu cn and eu eu the ce ce la sc and la cr ratios however are only constant when greater than 30 of a sample is composed of acid insoluble residue at less than 30 acid insoluble residue these elemental ratios increase markedly the th co and th sc ratios are fairly constant from nearly 0 to about 60 acid insoluble residue above 60 residue these ratios increase due to the high concentration of th in the graneros to hartland shales at everhart ranch the average of the th co th sc th cr la co la sc and la cr ratios are similar to those of the mcs mid continent shales and paas post archean australian shales thus these carbonate rich to carbonate poor rocks analyzed in this study contain terrigenous debris that has been derived from granitoids similar to those that supplied debris to the mcs and paas the ce ce ratios are lower and the mn mn log mn sample mn shales fe sample fe shales values are more positive in the more calcite rich bridge creek and ft hays limestones than in the other units suggesting that they formed in an oxidizing environment the ce ce are the highest and the mn values are the most negative in the graneros to hartland shales suggesting that they formed under more reducing conditions the elemental concentration of one sample relative to that of another sample over a few meters distance usually vary in small amounts e g medians of the ratios of the same elements between adjacent samples ranges from 1 06 to 1 70 however the ratio of elemental concentrations between adjacent samples can sometimes be quite large the least variation of elemental ratios between adjacent samples often occurs within the more carbonate poor shales the greatest variation occurs within the limestones thus trying to decipher local movement of elements due to metamorphism in similar carbonate shale limestone sequences should be done cautiously since local elemental variation due to sedimentary processes can be large

extreme warming of mid latitude coastal ocean during the paleocene eocene thermal maximum inferences from tex86 and isotope data changes in sea surface temperature sst during the paleocene eocene thermal max imum petm have been estimated primarily from oxygen isotope and mg ca records generated from deep sea cores here we present a record of sea surface temperature change across the paleocene eocene boundary for a nearshore shallow marine section located on the eastern margin of north america the sst record as inferred from tex86 data indicates a minimum of 8 c of warming with peak temperatures in excess of 33 c similar ssts are estimated from planktonic foraminifer oxygen isotope records al though the excursion is slightly larger the slight offset in the oxygen isotope record may reflect on seasonally higher runoff and lower salinity

early cenozoic benthic foraminiferal isotopes species reliability and interspecies correction factors 1 oxygen and carbon isotope records are important tools used to reconstruct past ocean and climate conditions with those of benthic foraminifera providing information on the deep oceans reconstructions are complicatedby interspecies isotopic offsets that result from microhabitat preferences carbonate precipitation in isotopically distinct environments and vital effects species specific metabolic variation in isotopic fractionation we provide correction factors for early cenozoic benthic foraminifera commonly used for isotopic measurements cibicidoides spp nuttallides truempyi oridorsalis spp stensioina beccariiformis hanzawaia ammophila and bulimina spp showing that most yield reliable isotopic proxies of environmental change the statistical methods and larger data sets used in this study provide more robust correction factors than do previous studies interspecies isotopic offsets appear to have changed through the cenozoic either 1 as a result of evolutionary changes or 2 as an artifact of different statistical methods and data set sizes used to determine the offsets in different studies regardless of the reason the assumption that isotopic offsets have remained constant through the cenozoic has introduced an 1 2 c uncertainty into deep sea paleotemperature calculations in addition we compare multiple species isotopic data from a western north atlantic section that includes the paleocene eocene thermal maximum to determine the most reliable isotopic indicator for this event we propose that oridorsalis spp was the most reliable deepwater isotopic recorder at this location because it was best able to withstand the harsh water conditions that existed at this time it may be the best recorder at other locations and for other extreme events also

mantle wedge water contents estimated from seismic velocities in partially serpentinized peridotites 1 water carried into subduction zones with the down going plate and subsequently released by dehydration reactions at depth affects the composition of the mantle wedge triggers partial melting and affects subduction zone seismicity partially serpentinized peridotite may be a significant reservoir for water in the subducted plate the mantle wedge and the overriding plate here we develop a model that relates the degree of serpentinization and water content of partially serpentinized peridotites to their seismic p wave velocities in partially serpentinized ultramafic rocks a 1 decrease in p wave velocity corresponds to a 2 4 increase in serpentine content and a 0 3 0 18 moles m3 increase in h2o content up to a maximum of 13 where there is evidence of serpentinization mantle serpentine content is typically 15 corresponding to 4 5 wt h2o 6 10 moles m3