discussion on c3 and c4 plant contribution calculation abstract the research reported by jaesoo lim et al 2010 jaesoo lim wook hyun nahm jin kwan kim dong yoon yang 2010 regional climate driven c3 and c4 plant variation in the cheollipo area korea during the late pleistocene palaeogeography palaeoclimatology palaeoecology 298 370 377 provides an interesting northeast asian case for palaeoecological response to palaeoclimatic change however the method used in the paper to determine the contribution of c3 and c4 plant in bulk organic carbon isotope values deserves discussion when the proportion of c3 and c4 plant is used as an important indicator for palaeoecological analysis

organic geochemical proxies of paleoceanographic paleolimnologic and paleoclimatic processes abstract organic matter constitutes a minor fraction of marine and freshwater sediments yet its important contribution to the sedimentary record can be used to reconstruct marine and continental paleoenvironments the organic matter content of sediments is the residue of past biota the amounts and types of organic matter present in sediments consequently reflect environmental conditions that impacted ecosystems at different past times general sources of the organic matter are inferred from bulk properties such as elemental compositions carbon and nitrogen stable isotope ratios rock eval pyrolysis data and organic petrography details of organic matter origins are refined by analyses of biomarker molecular compositions source changes are proxies for fluctuations in sea level oceanic surface currents and continental climates algal paleoproductivity rates are indicated by organic carbon mass accumulation rates and carbon and nitrogen stable isotopic compositions these parameters record past availability of nutrients and therefore are proxies of surface mixing in the oceans and amount of land runoff to lakes sea surface paleotemperatures are recorded by the number of carbon carbon double bonds in lipid biomarkers produced by marine algae larger proportions of the double bonds are proxies for the cooler surface waters that accompanied periods of global glaciation and intervals of enhanced upwelling the 13c and d values of plant organic matter record past concentrations of carbon dioxide in the atmosphere and changes in delivery of atmospheric moisture respectively diagenesis which causes the concentration and composition of organic matter in sedimentary settings to differ from those of the original biologically synthesized materials can bias organic geochemical paleoenvironmental records the magnitude of this potential source of misinformation must always be considered and evaluated comparison of multiple organic geochemical proxies of past conditions helps to compensate for the effects of diagenetic alterations and thereby to improve interpretations of paleoenvironmental change

assessing δ13c and c n ratios from organic material in archived cores as holocene sea level and palaeoenvironmental indicators in the humber estuary uk organic 13c and c n analyses of estuarine deposits provide proxies for changes in the source of organic matter which can be driven by fluctuations in relative sea level river discharge and catchment disturbance here we present the results of a comprehensive vegetation and sediment 13c and c n survey of welwich marsh outer humber estuary uk together with high resolution 13c and c n analyses of holocene cores collected nine years previously from the humber estuary and the lincolnshire marshes eastern england uk the contemporary intertidal 13c and c n dataset shows a gradual increase in surface sediment 13c with decreasing marsh height and suggests that 13c is controlled by the degree of tidal inundation and thus reflects organic matter source however sediment c n ratios are less sensitive to tidal changes and the recent introduction of c4 salt marsh species complicates the contemporary analogue the holocene 13c and c n records are in general agreement with existing microfossil data and provide additional palaeoenvironmental information this includes support for an estuary wide expansion of marine conditions from c 3 3 ka cal yr bp followed by a contraction of marine conditions after c 2 7 ka cal yr bp and evidence for an increase in delivery of terrigenous organic matter to the inner estuary in the late holocene bulk organic 13c and c n analysis is shown to be a reliable and independent indicator of coastal environmental change and is therefore a complementary technique to the more commonly used microfossil approach however this study also shows that in some circumstances the technique may be compromised when applied to sediments from cores that have been stored for a period of time

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

organic matter composition and sulfate reduction intensity in oman margin sediments abstract petrographical and geochemical studies of neogene marine sediments from the oman sea leg 117 sites 720 724 726 and 730 show a close relationship between the nature and amount of the organic matter and the degree of degradation of organic matter by sulfate reduction i e pyritization petrographically three major pyritization types were observed 1 finely dispersed pyrite framboids in sediments from oman margin and indus fan enriched in autochthonous marine organic matter 2 infilling of pores by massive pyrite crystals in oman margin sediments with a low toc and a high microfossil content 3 pyrite mineralization of lignaceous fragments in organic depleted sediments from the indus fan leading to more massive pyrite geochemically we can define a sulfate reduction index sri as the percentage of initial organic carbon versus that of residual organic carbon finely laminated pliocene pleistocene sediments from the oman margin exclusively contain organic matter deriving from organic phytoplankton for which the quantity toc positively correlates with the geochemical quality hydrogen index we think that the occurrence of this residual organic matter is linked mainly to a high primary paleo productivity the intensity of sulfate reduction is constant for sediments with toc up to 2 and becomes more important when organic input decreases this degradation process can destroy up to 50 of the initial organic matter but is not sufficient to explain some of the encountered very low toc values it can be seen that sharp increases of certain plankton species with mineral skeletons are responsible for a pronounced degradation of organic matter due to increased sulfate reduction in that case the organic matter may be strongly degraded high sri although deposited in an oxygen depleted environment conversely miocene pliocene sediments contain an autochthonous organic matter that is typical of both low productivity and oxic processes their very low sulfate reduction index indicates that very little metabolizable organic matter was initially present

seismic evidence for shallow gas escape features associated with a retreating gas hydrate zone offshore west svalbard active gas venting occurs on the uppermost continental slope off west svalbard close to and upslope from the present day intersection of the base of methane hydrate stability bmhs with the seabed in about 400 m water depth in the inter fan region between the kongsfjorden and isfjorden cross shelf troughs from an integrated analysis of high resolution two dimensional pre stack migrated seismic reflection profiles and multibeam bathymetric data we map out a bottom simulating reflector bsr in the inter fan region and analyze the subsurface gas migration and accumulation gas seeps mostly occur in the zone from which the bmhs at the seabed has retreated over the recent past 1975 2008 as a consequence of a bottom water temperature rise of 1 c the overall margin parallel alignment of the gas seeps is not related to fault controlled gas migration as seismic evidence of faults is absent there is no evidence for a bsr close to the gas flare region in the upper slope but numerous gas pockets exist directly below the predicted bmhs while the contour following trend of the gas seeps could be a consequence of retreat of the landward limit of the bmhs and gas hydrate dissociation the scattered distribution of seeps within the probable hydrate dissociation corridor and the occurrence of a cluster of seeps outside the predicted bmhs limit and near the shelf break indicate the role of lithological heterogeneity in focusing gas migration

long chain alkenones and alkyl alkenoates as palaeotemperature indicators their production flux and early sedimentary diagenesis in the eastern north atlantic the production and fate of long chain alkenones and alkenoates was examined with regard to their use as palaeotemperature indicators alkenoate abundances were higher than previously reported for other regions and more strongly correlated with temperature than was alkenone unsaturation u37k suggesting biogeographical variability in alkenone and alkenoate production in surface waters we define the aa36 ratio to parameterize alkenoate abundance and present an empirical temperature calibration derived from our euphotic zone samples for use in the north atlantic t 17 35 25 12 u37k 26 73 aa36 93 90 u37k aa36 significant diagenetic losses of alkenones and alkenoates were found within the water column and near surface sediments in spite of diagenetic losses the temperature signal recorded by these compounds in the sediments remains largely unaltered and corresponds to the euphotic zone water temperature during the springtime period of maximum coccolithophorid production and flux rather than the average annual sea surface temperature

lignin geochemistry of a late quaternary sediment core from lake washington long term lignin stability and paleovegetation patterns were investigated using cuo oxidation products of sediments from an 11 m core of late quaternary sediment collected from the mid basin of lake washington washington state relatively constant yields of lignin derived phenols normalized to organic carbon from the entire core indicate minimal in situ lignin degradation over the last 13 000 years compositional patterns within the phenolic suite and increased corresponding yields from baseextracted sediments indicate that sedimentary lignins are present predominantly as well preserved plant tissue fragments abundance patterns of vanillyl syringyl and cinnamyl phenols record four distinct sequences within the core characterized by 1 a high concentrations of gymnosperm wood in a basal horizon of glacial flour 11 10 m 2 b an essentially pure mixture of nonwoody angiosperm tissues in late pleistocene sediments 10 8 m 3 c relatively high concentrations of angiosperm woods in the bottom half of a limnic peat sequence deposited approximately 10 000 7 000 years b p 8 4 m and 4 d a progressive enrichment in gymnosperm woods at the expense of angiosperm woods over the last 7 000 years in the upper limnic peat 4 0 m vascular plant tissues account for less than half the total sedimentary organic carbon throughout the core

gas origin and migration in the ulleung basin east sea results from the second ulleung basin gas hydrate drilling expedition ubgh2 abstract we have investigated the gas chemistry of marine sediments up to 250 m below seafloor m bsf recovered during the second ulleung basin gas hydrate drilling expedition ubgh2 to identify and compare the gas origin and its migration at seismically non chimney truncated chimney and chimney sites in this basin the molecular and isotopic data c1 c2 ratios 300 13 c ch 4 d ch 4 kim et al 2012 and thought to reflect two phase methane transport processes in chimney sites deep sourced methane migrates independently of the carbon dioxide which remains dissolved in the aqueous phase leading to the extremely low c values observed in the upper 30 m bsf upward methane diffusion at non chimney sites may also add a transport induced fractionation as evidenced in mixing diagrams but this process does not significantly affect the c values 13 c co 2 shows usually minimum values at the sulfate methane transition zone smtz at all sites however in chimney sites these values have a much more depleted signature indicating faster rates of methane consumption by anaerobic oxidation of methane aom supported by the higher methane flux moreover here the massive hydrate that forms in shallow sediments incorporates gases with a lower c1 c2 ratio higher c2 c1 than the surrounding sediment as documented in hydrate bound gas bg and void gas vg samples gas hydrate dissociation during the core recovery is released enriched ethane c2h6 trapped in gas cage which leads to have high c2h6 in vg samples

occurrence and seismic characteristics of gas hydrate in the ulleung basin east sea abstract multi channel seismic reflection and well log data from the ulleung basin east sea reveal several seismic signatures indicative of gas hydrate occurrence in the ulleung basin that are associated with vertically and or laterally stacked mass transport complexes the seismic indicators include a a bottom simulating reflector bsr b a seismic chimney c high amplitude reflections within the gas hydrate stability zone ghsz d acoustic blanking e enhanced reflections below the bsr and f seafloor gas escape features the bsr associated with enhanced reflections below is most commonly found over much of the basin indicating a physiochemical boundary of gas hydrates overlying free gas seismic chimneys are characterized by velocity pull up and reduced reflectivity on the seismic sections which appear to be caused by active migration of fluid gas vertically into the ghsz the logging data retrieved from the seismic chimneys showed elevated electrical resistivity 80 ohm m and p wave velocity 2000 m s indicating the presence of gas hydrate another seismic characteristic observed in gas hydrate bearing sediments is the strong amplitude reflections defined by the relatively high reflectivity within the ghsz acoustic blanking is likely to be the result of hydrate accumulation in the sediments causing a significant reduction of acoustic impedance contrast between sedimentary layers where the upward migrating gas seeps into the deep water column seafloor pockmarks and mud mounds may be formed gas hydrate was recovered from the ulleung basin east sea in 2010 during the second ulleung basin gas hydrate drilling expedition ubgh2 under the korean national gas hydrate program based on the results gas fluids migrate into the ghsz through two distinct pathways 1 structural conduits which include fault and fracture systems associated with seismic chimneys and 2 stratigraphic conduits associated with inclined turbidite hemipelagic layers two types of gas hydrate occurrence were identified in the basin 1 a stratally bound type pore filling within turbidite sand layers and 2 a locally concentrated type massive nodule or fracture filling within upward growing chimneys associated with near vertical faults relatively high concentrations of gas hydrate however tend to occur in localized seismic chimneys rather than in the strata related features the successful recovery indicates that the ulleung basin provides favorable conditions for gas hydrate formation

distribution and height of methane bubble plumes on the cascadia margin characterized by acoustic imaging submersible investigations of the cascadia accretionary complex have identified localized venting of methane gas bubbles in association with gas hydrate occurrence acoustic profiles of these bubble plumes in the water column in the vicinity of hydrate ridge offshore oregon provide new constraints on the spatial distribution of these gas vents and the fate of the gas in the water column the gas vent sites remained active over the span of two years but varied dramatically on time scales of a few hours all plumes emanated from local topographic highs near the summit of ridge structures the acoustic images of the bubble plumes in the water column disappear at water depths between 500 to 460 m independent of the seafloor depth this coincides with the predicted depth of the gas hydrate stability boundary of 510 to 490 m suggesting that the presence of a hydrate skin on the bubble surface prevents them from rapid dissolution the upper limit of the acoustic bubble plumes at 460 m suggests that dissolution of the residual bubbles is relatively rapid above the hydrate stability zone

migration and venting of deep gases into the ocean through hydrate choked chimneys offshore korea it has recently been recognized that in addition to low concentrations of widespread natural gas hydrate associated with bottomsimulating seismic refl ectors highly concentrated hydrate can occur in local seafl oor fl uid venting structures such structures extend upward into the regional gas hydrate stability fi eld and sometimes allow gases to escape into the overlying ocean these hydrate choked chimneys are especially prospective as an energy resource because they contain high hydrate concentrations furthermore they may be one of the most important conduits into the ocean atmosphere system for deep methane we present an analysis of two dimensional seismic refl ection data from offshore korea that give a complete picture of gas migrating from a deep source zone to feed hydrate choked vent structures at the seafl oor the gases migrate upward through networks of fractures imaged as steep amplitude striations in both diffuse and concentrated distributions we present an example of a high fl ux gas vent fed through fracture swarms emanating from a 10 15 km wide catchment zone of source gases residing 3 4 km below the seabed the geological context and the inferred distribution of hydrate within this feature are consistent with recent models in which seabed gas venting is a consequence of elevated pore fl uid salinities that are produced by a high fl ux of gases migrating independently of the pore water in contrast a nearby vent that is not plumbed into the same high fl ux system appears to be dominated more by gas rich liquids we present these two vent structures as type cases for high and lowfl ux fl uid escape systems in the seabed furthermore we suggest that since the amount of gas trapped as hydrate within the vents is small compared with the amount in the underlying reservoir the greatest risk for increased methane input to the atmosphere associated with climate driven oceanic warming is not the melting of hydrate but an increase in the number of deep reservoirs able to vent gases through the seabed that occurs as the regional gas hydrate stability zone thins

a review of holocene solar linked climatic variation on centennial to millennial timescales physical processes interpretative frameworks and a new multiple cross wavelet transform algorithm article i nfo wereportontheexistenceandnature of holocene solar andclimaticvariationson centennialto millennial time scales we introduce a new solar activity proxy based on nitrate no3 concentration from the talos dome ice core east antarctica we also use a new algorithm for computing multiple cross wavelet spectra in time fre quency space that is generalized for multiple time series beyond two our results provide a new interpretive framework for relating holocene solaractivity variations on centennial to millennial timescales to co varying cli mate proxies drawn from a widespread area around the globe climatic proxies used represent variation in the north atlantic ocean western pacific warm pool southern ocean and the east asian monsoon regions our wavelet analysis identifies fundamental solar modes at 2300 yr hallstattzeit 1000 yr eddy and 500 yr unnamed periodicities leaves open the possibility that the 1500 1800 yr cycle may either be fundamental or derived and identifies intermediary derived cycles at 700 yr and 300 yr that may mark rectified responses of the atlantic thermohaline circulation to external solar modulation and pacing dating uncertainties suggest that the 1500 yr and 1800 yr cycles described in the literature may represent either the same or two separate cycles but in either case and irrespective too of whether it is a fundamental or derived mode in the sense of dima and lohmann 2009 the 1500 1800 yr periodicity is widely represented in a large number of paleoclimate proxy records it is obviously premature to reject possible links between changing solar activity at these multiple scales and the variations that are commonly observed in paleoclimatic records

holocene millennial scale vegetation changes in the yugu floodplain kongju area central south korea abstract to understand vegetation responses to past climate change on millennial timescales the holocene record of floodplain vegetation change in central south korea was reconstructed using the stable isotopic composition 13 c and pollen in buried soils low volume overbank deposition of fine grained alluvium by yugu stream over the past 10 000 years has produced a sequence that is well suited for 13 c analysis of soil organic matter the 13 c values varied between 25 and 20 during the holocene showing significant millennial scale fluctuations in five stages 11 000 8900 cal bp 8900 6100 cal bp 6100 3300 cal bp 3300 1200 cal bp and 1200 cal bp to present the abundance of c 4 plants estimated from a binary mixing model changed from approximately 17 57 during the stages from 3300 to 1200 cal bp and from 8900 to 6100 cal bp c 4 plant abundance and the percentage of arboreal pollen were high but the percentage of spores mainly moss and the freshwater algal sum were low indicating more arid environments temporal comparison of c 4 plant abundance change during the holocene with other reconstructed climate data from east asia suggests that millennial scale vegetation change or aridity change in central south korea was generally more synchronous with regional climate change during the late holocene than during the early to mid holocene this study suggests that the past vegetation in the yugu area has evolved in response to summer monsoon intensity in a non linear manner

the free gas zone beneath gas hydrate bearing sediments and its link to fluid flow 3 d seismic imaging offshore mid norway abstract hydrate recycling and vertical migration of fluids from deep sources are processes evoked as controllers of the formation and stability of the free gas zone fgz beneath the base of the gas hydrate stability zone bghsz these processes have been often investigated through analytical and numerical modeling at some locations in continental margins however the seismic response of sediments deformed by such mechanisms has been poorly investigated due to the lack of reliable seismic resolution to clearly image anomalies confined to the fgz the present study is dedicated to the seismic characterization of the fgz beneath the bghsz at a hydrate site offshore mid norway using high resolution p cable 3d seismic data dim amplitude anomalies showing mainly lineations in a polygonal pattern of distribution 50 80 m vertical extension 150 300 m lateral extension and up to a few kilometers long are interpreted as evidence of sediment remobilization possibly aided by hydrate dissociation at focused fluid flow zones below former bases of the ghsz the exclusive occurrence of the anomalies within a depth range comprising estimated paleo bghszs during the last 200 kyr suggests that the anomalies are associated to paleo hydrate bearing sediment seals emplaced at depths controlled by overburden it also supports recently reported indications of main periods of fluid expulsion towards the seafloor occurring between 200 and 130 ka bp

structural stratigraphic control on the umitaka spur gas hydrates of joetsu basin in the eastern margin of japan sea abstract integrated geological geochemical and geophysical exploration since 2004 has identified massive accumulation of gas hydrate associated with active methane seeps on the umitaka spur located in the joetsu basin on the eastern margin of japan sea umitaka spur is an asymmetric anticline formed along an incipient subduction zone that extends throughout the western side of the japanese island arc system seismic surveys recognized chimney structures that seem strongly controlled by a complex anticlinal axial fault system and exhibit high seismic amplitudes with apparent pull up structures probably due to massive and dense accumulation of gas hydrate bottom simulating reflectors are widely developed in particular within gas chimneys and in the gently dipping eastern flank of the anticline where debris can store gas hydrates that may represent a potential natural gas resource the axial fault system the shape of the anticline and the carrier beds induce thermogenic gas migration to the top of the structure and supply gas to the gas hydrate stability zone gas reaching the seafloor produces strong seepages and giant plumes in the sea water column

methane rich plumes on the carolina continental rise associations with gas hydrates seafloor venting of microbial gases occurs at 2167 m water depth over the blake ridge diapir gas rich plumes were identified acoustically in the water column up to 320 m above a pockmarked sea floor associated with active chemosynthetic biological communities plumes and venting fluids emanate from near a small fault that extends downward toward a dome in the bottom simulating reflector indicating that fluid and or gas migration is associated with gas hydrate bearing sediment below these plumes might be caused by gas bubbles or buoyant dumps of gas hydrate that float upward from the seafloor 18 refs 3 figs

multiple expansions of c4 plant biomass in east asia since 7 ma coupled with strengthened monsoon circulation the expansion of plants using the c4 photosynthetic pathway is one of the most prominent changes in the global ecosystem during the cenozoic era a significant late miocene expansion is well documented however the existence and cause of subsequent expansions are still not clear owing in part to the lack of long continuous climate vegetation records here we present two high resolution carbon isotope time series covering the past 7 m y derived from eolian deposits on the chinese loess plateau the data indicate three intervals of significant c4 plant expansions within the semiarid monsoonal region of east asia ca 2 9 2 7 ma 1 3 0 9 ma and 0 6 ma present these expansions covary with strengthened east asian summer monsoon circulation we conclude that in east asia large scale late miocene c4 c3 vegetation changes in semiarid areas have been primarily driven by warm seasonal precipitation and temperature variations associated with changes in monsoon circulation

three dimensional seismic characterization of a venting site reveals compelling indications of natural hydraulic fracturing based on a three dimensional high resolution seismic survey off vancouver island canada we show that natural hydraulic fracturing is an efficient process to create permeable pathways for focused fluid upflow at submarine venting sites the pockmark structure examined in this study is located on top of an accreted ridge where the low permeability base of the gas hydrate stability field is also elevated and fluid overpressure will be induced tectonically elongated hydraulic fractures reveal decreased reflection amplitudes and are oriented along the maximum principal stress direction perpendicular to nearby fault planes a surface expression is created by fluid and material expulsion forming an irregular noncircular rim along the axis of the upflow zone our findings confirm a relationship between lateral variations in seismic reflectivity and sediment distribution regional tectonics episodic fluid flow and the formation and dissociation of gas hydrate they explain the presence of gas hydrate at the top of the upflow zone which requires transport of large volumes of gas through the gas hydrate stability field since hydraulic fracturing is not restricted to compressional regimes it is a likely explanation for the nature shape and orientation of upflow zones as well as for seismic blanking widely observed at both active and passive continental margins

distribution of lipid class compounds in bottom sediments of freshwater lakes with different trophic status in japan abstract unbound and bound lipid class compounds mono and di carboxylic acids and hydroxy acids n alkanes n alcohols and perylene were studied in bottom sediments collected from four freshwater lakes in japan with different trophic status lakes motosu biwa haruna and suwa concentrations of some lipid components relative to total organic carbon toc showed positive or negative correlations with the primary productivity of the lakes n saturated c12 c19 fatty acids fa s branched chain fa s unsaturated fa s and c14 c19 fatty alcohols which are probably of autochthonous origin appear to increase with an increase in primary productivity whereas n saturated c20 c32 fa s c20 c30 fatty alcohols dicarboxylic acids n alkanes and perylene which are probably of terrestrial origin appear to decrease with an increase in primary productivity these results indicate that primary productivity of lakes is an important factor controlling the distributions of organic molecules in the bottom sediments on the other hand concentrations of hydroxy acids relative to toc did not show a correlation with primary productivity because these acids are derived from bacterial activity their distributions may be controlled by sedimentary environments such as oxic or anoxic rather than primary productivity

regional climate driven c3 and c4 plant variation in the cheollipo area korea during the late pleistocene abstract marine isotope stage 3 mis3 spanning from 25 to 60 ka bp was a time of substantial environmental change that included changes in the global ice volume and atmospheric composition with resultant regional climate changes to understand past vegetation responses to such environmental changes in korea we estimated the abundance of c3 and c4 plants using the c n and carbon isotope ratios of sedimentary organic matter the mis3 sedimentary unit at the cheollipo site located in a western coastal area of korea is characterized by a dark to light gray colored sedimentary unit 3 05 to 5 05 m in elevation mis3 which is between an underlain oxidized yellowish sedimentary unit 5 05 m in elevation the estimated abundance of c4 plants varied between 60 and 10 during the mis3 the suborbital scale variation in the estimated percentage of c4 plants was similar to those reported in continental ice volume and the east asian monsoon intensity suggesting that c4 plants prevailed under colder and drier conditions intensified winter monsoon whereas c3 plants have favored a warmer and wetter climate intensified summer monsoon compared with high latitude regions e g chinese loess plateau and lake baikal where low summer temperature suppressed aridity and pco2 influences during the last glacial period vegetation change in cheollipo area may have more sensitively responded to aridity change which had been affected by the summer winter monsoon intensity the climate change in the western coastal area yellow sea side of korea during the late pleistocene may have been controlled by regional climate change coupled with continental ice volume change

first measurement of the displacement rate of the pacific plate near the japan trench after the 2011 tohoku oki earthquake using gps acoustic technique the subduction rate of an oceanic plate may accelerate after large earthquakes rupture the interplate coupling between the oceanic and overriding continental plates to better understand postseismic deformation processes in an incoming oceanic plate we directly measured the displacement rate of the pacific plate near the japan trench after the 2011 tohoku oki earthquake using a gps acoustic technique over a period of 2 years september 2012 to september 2014 the displacement rate was measured to be 18 0 4 5 cm yr 1 n302 0 e relative to the north american plate which is almost twice as fast as the predicted interseismic plate motion because the sum of steady plate motion and viscoelastic response to the tohoku oki earthquake roughly accounts for the observed displacement rate we conclude that viscoelastic relaxation is the primary mechanism responsible for postseismic deformation of the pacific plate and that significant subduction acceleration did not occur at least not during the observation period

a review of coastal palaeoclimate and relative sea level reconstructions using δ13c and c n ratios in organic material holocene reconstructions of relative sea level rsl and environmental change in the coastal zone have become progressively more numerous since the importance of assessing possible future sea level rises has become apparent traditionally this has been achieved using a combination of biological and physical indicators e g pollen diatoms foraminifera grain size etc in some circumstances microfossils can be rare or absent from holocene sediments and in these cases carbon isotope ratios 13c and organic carbon to total nitrogen ratios c n can be used because they have the potential to provide information as to the origin of organic material preserved in coastal environments the distinction in 13c and c n of the various sources of carbon to estuarine sediments has led to its wide use as a tracer of carbon pathways and storage in estuaries more recently these techniques have been applied to holocene sediments to decipher changes in palaeocoastal environments and thus position relative to sea level and or palaeoriver discharge which have direct relevance to palaeoclimate this paper reviews the studies that have utilised this technique and explores examples from a wide range of coastal environments saltmarshes estuaries lagoons isolation basins and fjords it also discusses the potential alteration of geochemical signatures as a result of decompositional processes organic matter decomposition has been shown to change sediment 13c and c n values and thus an understanding of the processes involved is necessary in order to have confidence in the palaeoenvironmental interpretation of holocene 13c and c n decompositional shifts in c n and particularly 13c can occur over a relatively short time period however it is the direction of change in 13c and c n rather than absolute values that is key for interpreting changes in relative sea level and thus such changes are commonly preserved

coherent changes in relative c4 plant productivity and climate during the late quaternary in the north american great plains evolution of the mixed and shortgrass prairie of the north american great plains is poorly understood because of limited proxies available for environmental interpretations buried soils in the great plains provide a solution to the problem because they are widespread both spatially and temporally with their organic reservoirs serving as a link to the plants than once grew on them through stable carbon isotopic analysis of soil organic carbon d

controls on the formation and stability of gas hydrate related bottom simulating reflectors bsrs a case study from the west svalbard continental slope 1 the growth and stability of the free gas zone fgz beneath gas hydrate related bottom simulating seismic reflectors bsrs is investigated using analytical and numerical analyses to understand the factors controlling the formation and depletion of free gas for a model based on the continental slope west of svalbard a continental margin of north atlantic type we find that the fgz is inherently unstable under a wide range of conditions because upward flow of under saturated liquid depletes free gas faster than it is produced by hydrate recycling in these scenarios the 150 m thick fgz that presently exists there would deplete within 105 106 years we suggest the fgz is in a stable state however that is formed by a diffusion dominated mechanism that produces low concentrations of gas in a fgz of steady state thickness gas forms across a thick zone because the upward fluid flux is relatively low and because the gas water solubility decreases to a minimum several hundred meters below the seabed this newly understood solubility curvature effect is complementary to hydrate recycling but becomes the most important factor controlling the presence and properties of the bsr in environments where the rate of upward fluid flow and the rate of hydrate recycling are both relatively low i e rifted continental margins if the present day fgz is in steady state we estimate that the upward fluid flux in the west svalbard site must be less than 0 15 mm a 1

joint inversion of strong motion teleseismic geodetic and tsunami datasets for the rupture process of the 2011 tohoku earthquake 1 the 2011 tohoku earthquake was observed by dense strong motion teleseismic geodetic and tsunami networks we first inverted each of the datasets obtained by the networks separately for the rupture process of the earthquake we then performed checkerboard resolution tests for assessing the resolving power of these datasets in order to overcome the limited resolutions of the separate inversions and differences in their results we performed a quadruple joint inversion of all these data to determine a source model most suitable for explaining all the datasets in the obtained source model the maximum coseismic slip was approximately 35 m and the total seismic moment was calculated to be 4 2 1022 nm which yielded mw 9 0 the main rupture propagated not only in the strike direction but also in the dip direction and included both the deep area called the miyagi oki region and the compact shallow area near the japan trench

two subevents across the japan trench during the 7 december 2012 off tohoku earthquake mw 7 3 inferred from offshore tsunami records a tsunamigenic earthquake with a moment magnitude of 7 3 occurred near the japan trench off tohoku northeast japan on 7 december 2012 operational seismic monitoring inferred that the earthquake was composed of doublet sources of comparable magnitudes the first event was reverse faulting and the second event which occurred 10 20 s later was normal faulting an associated tsunami was observed at offshore stations having an amplitude of 10 1 to 101 cm inverse modeling using the observed tsunami records reveals possible vertical seafloor deformations we can then constrain in terms of the source location that the tsunamigenic earthquake involves two subfaults across the japan trench one is the outer trench reverse faulting as the first event and the second is the inner trench normal faulting the present study shows that tsunami analysis with seismograph analyses effectively constrains the epicenter locations even in the case of complex earthquakes like doublets

climatic and environmental controls on the variation of c3 and c4 plant abundances in central florida for the past 62 000 years lake tulane provides one of the few continental sediment records beyond the late glacial period 15 000 cal years b p for eastern north america its continuous organic rich sediment has yielded pollen assemblages that date back 62 000 years here we report the first organic geochemical characterization of the sediment core from lake tulane based on compound specific carbon isotopic analyses of higher plant leaf waxes our millennium resolution carbon isotope data allow us to quantitatively assess the variations in the relative abundances of c3 and c4 plants in central florida under contrasting climate conditions and different atmospheric pco2 levels during the last glacial interglacial cycle specifically our results indicate large changes in the relative abundance of c3 and c4 plants with 40 higher input from c4 plants during the last glacial maximum lgm than during the holocene during the last glacial period c4 plant abundance decreased dramatically during the pine phases when precipitation increased indicating that increasing precipitation overrode the impact of low atmospheric pco2 leading to expansions of c3 plants our results provide new insights on the forcing mechanisms and first quantitative estimates on the c3 and c4 plant variation in central florida for the last 62 000 cal years d 2005 elsevier b v all rights reserved

distribution and origin of seismic chimneys associated with gas hydrate using 2d multi channel seismic reflection and well log data in the ulleung basin east sea abstract analysis of multi channel seismic reflection and well log data from the ulleung basin east sea reveals that two distinct types of seismic chimneys have been identified in the basin based on their geometries seismic reflection patterns well log response and lithology type i is a mound like feature with a transparent or chaotic reflection pattern well log interpretation and lithology of this type indicate that type i consists of mobilized homogeneous mud including fracture filling gas hydrate this type is mainly located on the structural highs and is mostly restricted to the pliocene sedimentary succession in contrast type ii is a pipe like feature with vertically stacked distorted reflectors based on well log data and lithology type ii filled with fracture filling gas hydrate without breaking up primary sedimentary structure this type appears along the deep seated fault and mainly developed within the quaternary deposit our primary conclusion is that type i resulted from the subsurface sedimentary remobilization in response to regional uplift in the pliocene whereas type ii resulted from the focused vertical fluid flow through fractures triggered by reactivation of deep seated fault during the quaternary

impact of gravity on hydrate saturation in gas rich environments we extend a one dimensional analytical solution by including buoyancy driven flow to explore the impact of gravity on hydrate formation from gas injection into brine saturated sediments within the hydrate stability zone this solution includes the fully coupled gas and liquid phase flow and the associated advective transport in a homogeneous system we obtain the saturations assuming darcy flow under combined pressure and gravity gradients capillary forces are neglected at a high gas supply rate the overpressure gradient gradient of water pressure deviation from the hydrostatic pressure dominates the gas flow and the hydrate saturation is independent of the flow rate and flow direction at a low gas supply rate the buoyancy the drive for gas flow induced by the density difference between gas and liquid dominates the gas flow and the hydrate saturation depends on the flow rate and flow direction hydrate saturation is highest for upward flow and lowest for downward flow hydrate saturation decreases with flow rate for upward flow and increases with flow rate for downward flow in all cases hydrate saturation is constant behind the hydrate solidification front gas saturation is homogeneous and close to the residual value for upward flow at a low rate gas flows at the rate it is supplied gas saturation is much greater than the residual value and decreases from the gas inlet to the hydrate solidification front for downward flow at a very low rate the effect of gravity is usually negligible in laboratory experiments yet is significant in natural hydrate systems

climatically forced organic carbon burial in equatorial atlantic and pacific oceans over the past ten years sedimentary geochemists have noted that climate changes associated with pleistocene glaciations have had a pronounced effect on the rate of organic carbon burial found in the tropical oceans1 4 in particular two to five times higher organic carbon accumulation rates have been observed for the 18 kyr bp glacial maximum than for the holocene in several short sediment cores from both oceans see fig 1 here i present 300 kyr time series for organic carbon mass accumulation rate from four sediment cores two each from the equatorial pacific and atlantic and show that orbital forcing of global climate has strongly affected the rate of organic carbon burial in the equatorial oceans

evidence from three dimensional seismic tomography for a substantial accumulation of gas hydrate in a fluid escape chimney in the nyegga pockmark field offshore norway in recent years it has become evident that features commonly called gas chimneys provide major routes for methane to pass through the methane hydrate stability zone in continental margins and escape to the ocean one of many such chimneys lying beneath pockmarks in the southeastern voring plateau off norway was investigated with a high resolution seismic experiment employing a 2 d array of sixteen 4 component ocean bottom seismic recorders at approximately 100 m separation and a dense network of shots to define the 3 d variation of the chimney s structure and seismic properties the tomographic model derived from p wave travel times shows that p wave velocity inside the chimney is up to 300 m s higher than in the surrounding strata within the methane hydrate stability zone the zone of anomalously high velocity about 500 m wide near its base narrowing to about 200 m near the seabed extends to a depth of 250 m below the seafloor the depth extent of this zone and absence of high velocity beneath the base of the methane hydrate stability field make it more likely that it contains hydrate rather than carbonate if a predominantly fracture filling model is appropriate for the formation of hydrate in low permeability sediment the maximum hydrate concentration in the chimney is estimated to be 14 27 by total volume depending on how host sediment properties are affected by hydrate formation doming of the strata penetrated by the chimney appears to be associated with the emplacement of hydrate accompanying the invasion of the gas hydrate stability zone by free gas

spatial distribution of the faulting types of small earthquakes around the 2011 tohoku oki earthquake a comprehensive search using template events we developed a new method to classify the faulting types of small earthquakes using interevent waveform similarity and applied it to earthquakes in the northeast japan subduction zone in the method we used separate time windows for p and s waves and established a relationship between waveform similarity and differences in focal mechanisms from event pairs whose focal mechanisms we know then we applied the relationship to many pairs of such focal mechanism known events 5607 from the moment tensor catalogue and 3623 events from the interplate repeating earthquakes catalogue and focal mechanism unknown events for the period from 1984 to 2013 as a result 8984 earthquakes were newly classified into interplate n 5401 noninterplate thrust n 631 normal n 1070 and strike slip faulting earthquakes n 165 from the new data set which doubles the number of mechanism types we confirmed that there have been almost no interplate earthquakes in the area of large coseismic slip of the tohoku oki earthquake since that event we also saw that this trend continued until at least the end of 2013 suggesting a nearly complete stress release and slow interplate stress recovery the abundant interplate aftershocks also indicate the precise spatial extent of postsesimic slip which is usually difficult to obtain from land based geodetic data the postseismic slip also suggests stress concentration at the asperities of the 1968 tokachi oki m7 9 and 1994 sanriku oki m7 6 earthquakes the present day faulting types offshore tohoku correlated well with the static stress change from the tohoku oki earthquake suggesting a stress state change during the earthquake cycle of megathrust earthquakes

probable patterns of gas flow and hydrate accretion at the base of the hydrate stability zone marine gas hydrate is the largest carbon reservoir in the global organic carbon cycle but there is limited knowledge of how hydrate is accreted in space and time three dimensional seismic imaging of the dipping base of the deep water marine gas hydrate from offshore mauritania reveals extraordinary patterns of vertical chimneys and connected teardrop shaped trails of both high and low seismic reflection amplitudes the high amplitude trails are interpreted as being caused by the downward transition from hydrate to free gas bearing sediments their teardrop form shows that gas emanating from the chimneys flowed updip along the base of the hydrate the geometrically similar lower amplitude trails are possibly earlier flows that may have already converted to hydrate for this area we propose a model of intermittent flow of gas to the base of the hydrate active flows were blocked updip by earlier probably hydrate clogged chimneys and may have been laterally confined by flows that had already converted to hydrate that were in their path the process of hydrate formation reduces sediment permeability and may suppress subsequent gas flows resulting in the emergence of patterns of gas flow and hydrate accretion

lower temperature as the main cause of c4 plant declines during the glacial periods on the chinese loess plateau abstract the distribution of c3 and c4 plants changed in regionally contrasting ways during the last glacial period c4 plant expansion in low latitude africa and america coincided with c4 plant decreases in mesoamerica and the us great plains this c4 plant expansion has been attributed to lower pco2 and increased aridity and the decline in c4 plants is believed to have been caused by increased winter precipitation and lower temperatures however it is still difficult to generalize whether pco2 temperature or aridity was mainly responsible for c3 vs c4 vegetation changes during glacial periods paleoclimate conditions on the chinese loess plateau clp offer opportunities to further evaluate the role of temperature in the c3 vs c4 competition detailed climate records have shown that the clp region was drier and colder during glacial periods with aridity favoring c4 expansion and lower temperatures favoring c3 expansion here we present two high resolution compound specific carbon isotope records of n alkanes from the clp as vegetation biomarkers to estimate the relative abundance of c4 plants during the last two glacial interglacial transitions more negative 13c values during the glacial periods from two clp sites clearly show that in contrast with low latitude sites c4 plants declined this decrease in c4 abundance was caused by lower temperature despite the lower pco2 and increased aridity on the clp during glacial time

palaeoprecipitation reconstruction by inverse modelling using the isotopic signal of loess organic matter application to the nusloch loess sequence rhine valley germany a modified version of the biome4 vegetation model for simulation of the mean 13c of plant communities is presented and used to reconstruct palaeoprecipitation we treat all fractionations by c3 and c4 plants in all coexistent plant functional types weighted by their respective net primary production we constrain the range of variation in the intracellular versus atmospheric co2 concentration by fixing a lower limit finally we replace some constant parameters by functions of external forcing to account for their responses to environmental variation the new version of biome4 was applied as an inverse model and tested on three modern data sets the fit between observations and simulations is very close to the 1 1 relationship with respective slopes of 0 90 0 02 r2 0 98 n 29 for 13c and 0 97 0 06 r2 0 90 n 29 for precipitation inverse modelling was applied using the metropolis hastings algorithm to the nusloch loess sequence over the last glaciation simulated palaeoprecipitation varies between 240 mm year 1 and 400 mm year 1 this study clearly demonstrates atmospheric teleconnections with the greenland ice sheet extension by matching dansgaard oeschger events with precipitation increase of ca 100 200 mm year 1

gas hydrate fluid flow and free gas formation of the bottom simulating reflector abstract gas hydrate in continental margins is commonly indicated by a prominent bottom simulating seismic reflector bsr that occurs a few hundred metres below the seabed the bsr marks the boundary between sediments containing gas hydrate above and free gas below most of the reflection amplitude is caused by the underlying free gas gas hydrate can occur without a bsr however and the controls on its formation are not well understood here we describe two complementary mechanisms for free gas accumulation beneath the gas hydrate stability zone ghsz the first is the well recognised hydrate recycling mechanism that generates gas from dissociating hydrate when the base of the ghsz moves upward relative to hydrate bearing sediment the second is a recently identified mechanism in which the relationship between the advection and diffusion of dissolved gas with the local solubility curve allows the liquid phase to become saturated in a thick layer beneath the ghsz when hydrate is present near its base this mechanism for gas production called the solubility curvature mechanism is possible in systems where the influence of diffusion becomes important relative to the influence of advection and where the gas water solubility decreases to a minimum several hundred metres below the ghsz we investigate a number of areas in which gas hydrate occurs to determine where gas formation is dominated by the solubility curvature mechanism and where it is dominated by hydrate recycling we show that the former is dominant in areas with low rates of upward fluid flow such as old rifted continental margins low rates of seafloor uplift and high geothermal gradient and or pressure conversely free gas formation is dominated by hydrate recycling where there are rapid rates of upward fluid flow and seabed uplift such as in subduction zone accretionary wedges using these two mechanisms to investigate the formation of free gas beneath gas hydrate in continental margins we are able to resolve a number of problems these include why sub bsr free gas zones are generally thin in convergent margins and thick in passive margins and why areas such as the gulf of mexico and mackenzie delta do not have regional bsrs finally we use our understanding of how bsrs are formed to show that regional gas hydrate is unlikely to exist in substantial quantities in passive continental margins outside areas with an observable bsr

the 2009 samoa tonga great earthquake triggered doublet great earthquakes having seismic magnitudes of at least 8 usually involve abrupt sliding of rock masses at a boundary between tectonic plates such interplate ruptures produce dynamic and static stress changes that can activate nearby intraplate aftershocks as is commonly observed in the trench slope region seaward of a great subduction zone thrust event1 the earthquake sequence addressed here involves a rare instance in which a great trench slope intraplate earthquake triggered extensive interplate faulting reversing the typical pattern and broadly expanding the seismic and tsunami hazard on 29 september 2009 within two minutes of the initiation of a normal faulting event with moment magnitude 8 1 in the outer trench slope at the northern end of the tonga subduction zone two major interplate underthrusting subevents both with moment magnitude 7 8 with total moment equal to a second great earthquake of moment magnitude 8 0 ruptured the nearby subduction zone megathrust the collective faulting produced tsunami waves with localized regions of about 12 metres run up that claimed 192 lives in samoa american samoa and tonga overlap of the seismic signals obscured the fact that distinct faults separated by more than 50 km had ruptured with different geometries with the triggered thrust faulting only being revealed by detailed seismic wave analyses extensive interplate and intraplate aftershock activity was activated over a large region of the northern tonga subduction zone

gas hydrate versus geological features the south shetland case study abstract a gas hydrate reservoir is hosted in marine sediments of an accretionary prism located offshore the south shetland islands antarctic peninsula and affected by widespread deformations to analyse gas hydrate distribution and fluid circulation inside sediments available velocity models were used seismic velocities are translated in terms of hydrate porosity which is the difference between the reference porosity i e the porosity without gas hydrate and the effective porosity i e the porosity reduced by the gas hydrate presence the pre stack depth migration sections underlined the presence of several geological features such as gentle and open folds fractures and faults in this paper we observed a relationship between syncline anticline structures and hydrate presence in particular a relationship is underlined between the hydrate porosity values and the distance from the hinge of the anticline the hydrate porosity increases toward the limbs of anticline the micro fracturing model supports the idea that the syncline favours the hydrate formation while the anticline favours the free gas accumulation below the bottom simulating reflector

chemical evidence of differential particle dispersal in the southern washington coastal environment aliphatic hydrocarbons cupric oxide oxidation products of lignin and polycyclic aromatic hydrocarbons pah were analyzed by capillary gas chromatography in sediments from the southern washington continental shelf and slope the concentration of diploptene relative to plantwax n alkanes increased systematically in surface sediments with distance offshore along east west transects of the study area and remained constant in surface sediments along the midshelf silt deposit analogous trends were also observed for the concentration of cinnamyl phenols relative to vanillyl phenols and total methylphenanthrenes relative to phenanthrene these changes in sedimentary composition are evidence that diploptene from some terrestrial source lignin characteristic of non woody vascular plant tissue and a fossil organic material contained within weathered rock debris disperse across the washington continental shelf and slope in geographic patterns distinct from that for other river derived chemically related materials the compositional variations are explained by the particulate associations of the land derived chemicals and differential hydraulic dispersion of their respective carrier particles after discharge at the mouth of the columbia river

submarine pingoes indicators of shallow gas hydrates in a pockmark at nyegga norwegian sea complex pockmarks up to 300 m wide and 12 m deep are located in the nyegga area in the norwegian sea bathymetric data and direct visual documentation and sampling with rovs remotely operated vehicles have shown that these pockmarks contain abundant methane derived authigenic carbonate rocks furthermore geochemical results and the finding of seep associated organisms including tubeworms and bacteria shows that the pockmarks are still active fluid flow locations hovland m svensen h forsberg c f johansen h fichler c fossa j h jonsson r rueslatten h 2005 complex pockmarks with carbonateridges off mid norway products of sediment degassing marine geology 218 191 206 here we report the discovery of localized pingo like sediment mounds up to 1 m high and 4 m wide they occur inside one of the nyegga complex pockmarks g11 all of the seven structures we investigated have four characteristics in common 1 they have a positive topography rounded mounds and cones 2 they are partly covered in bacterial mats indicating ongoing fluid flow 3 they are partly covered in a carpet of small living tubeworms polychaetes which utilize methane 4 they have distinct corrosion pits on their surfaces indicating fluidization and point source corrosion of the covering sediments probably caused by localized sub surface hydrate dissociation we interpret the features as true submarine pingoes formed by the local accumulation of hydrate ice below the sediment surface it is inferred that the pingoes are formed as documented hydrocarbon gases methane ethane propane and butane migrate upwards through distinctive sub surface channels or conduits inside the pockmark we suggest that these submarine hydrate pingoes manifest the exact locations where fluid flow through the seafloor is currently active and that they can therefore be used as small scale indicators of active seepage

pore fluid chemistry from the second gas hydrate drilling expedition in the ulleung basin ubgh2 source mechanisms and consequences of fluid freshening in the central part of the ulleung basin east sea during the second gas hydrate drilling expedition in the ulleung basin ubgh2 pore fluids were collected from sites that sampled sediments from the continental slope to the basin center and included locations within and outside seismic identified chimney like features at five non chimney sites established during the ubgh2 discrete excursions to low cl concentrations within the gas hydrate occurrence zone ghoz are associated with water enriched in d and 18o as expected from gas hydrate dissociation during core recovery estimates of gas hydrate saturation values sh based on cl and d values are in good agreement and show that when gas hydrate occurs in discrete horizons or within strata bound fractures throughout the ghoz it occupies 5 65 of the pore space fluids recovered from three sites characterized by seismic inferred chimneys show massive hydrate accumulation near the seafloor accompanied by the formation of shallow cl rich brines with d and 18o values lower than seawater chemical and isotopic data from fluids sampled at all drilled sites reveal significant fluid freshening below the gas hydrate stability zone ghsz the distribution of cl k and d indicate that the observed freshening is predominantly caused by clay mineral dehydration illitization previously reported heat flow values in the center of the basin indicate that the sediments deeper than 800 mbsf meter below seafloor are warm enough to expect clay diagenesis with the onset of smectite to illite transformation source fluid temperatures 70 c are confirmed through the use of na li and mg2 li geothermometry based on these observations we propose the following scenario for the evolution of formation fluids in the ulleung basin where high formation temperatures and rapid sedimentation at the basin center led to sediment compaction and clay dehydration reactions that result in fluid overpressures and associated fracturing of the formation sediment fractures and fluid possible gas migration in the chimney features imaged in seismic records are consistent with our postulated upward transport of fluids from 800 m depth though the ghsz and to the seafloor

preservation of elemental and isotopic source identification of sedimentary organic matter the amount and type of organic matter in the sediments of lakes and oceans contribute to their paleoenvironmental and paleoclimatological records only a small fraction of the initial aquatic organic matter survives destruction and alteration during sinking and sedimentation selective degradation modifies the character of the surviving small fraction of organic matter which becomes incorporated in bottom sediments organic matter alterations can continue to sub bottom depths of hundreds of meters corresponding to millions of years source and paleoenvironmental information nonetheless remains preserved in the molecular elemental and isotopic compositions of organic matter c n and 13c values of total organic matter in particular appear to retain paleoenvironmental information for multi myr time periods

reply to comment on regional climate driven c3 and c4 plant variation in the cheollipo area korea during the late pleistocene by j lim w h nahm j k kim d y yang palaeogeography palaeoclimatology palaeoecology 298 2010 370 377 abstract ouyang et al 2013 in this issue raise two concerns regarding carbon isotope analysis and its use for reconstructing past vegetation changes recently published by lim et al 2010 one issue questions the formation of sedimentary organic matter by competitive contribution of c 3 and c 4 plants and calculation of the relative contributions of c 3 and c 4 plants with a binary mixing model using their mean 13 c values the second issue questions the use of the 13 c value of flora from other regions or of the current flora as a universal reference to determine the composition of plants in the remote past pointing out the importance of understanding the exact assemblage of local plants in the past by complete sporo pollen assemblage analysis and molecular biomarker analysis in response to these concerns we provide a detailed description of the tracing process for determining the source of sedimentary organic matter using 13 c values and c n ratios and assess the suitability of calculating the relative contributions of c 3 and c 4 plants using a binary mixing model finally based on its advantages compared to other biological proxies we explain the utility of using 13 c toc values for reconstructing past vegetation changes

δ13c of loess organic matter as a potential proxy for paleoprecipitation paleoprecipitation reconstructions on the basis of pollen are well known but they do not provide high temporal resolution for glacial periods high resolution paleoprecipitation reconstructions for the last glaciation based on the isotopic record organic matter in loess from nussloch rhine valley germany are consistent with paleoprecipitation inferred from peat in the same area using an independant method thus 13c of loess organic matter can be used as a proxy for paleoprecipitation

c4 plant productivity and climate co2 variations in south central texas during the late quaternary abstract a continuous record of organic carbon 13c from a buried soil sequence in south central texas demonstrates 1 strong coupling between marine and adjacent continental ecosystems in the late pleistocene as a result of glacial meltwater entering the gulf of mexico and 2 ecosystem decoupling in the holocene associated with a reduction of meltwater and a shift in global circulation patterns in the late pleistocene reduction in c4 plant productivity correlates with two well documented glacial meltwater pulses 15 000 and 12 000 14c yr b p indicating a cooler than present adjacent continental environment increased c4 production between 11 000 and 10 000 14c yr b p suggests that the younger dryas was a warm interval responding to the diversion of glacial meltwater away from the mississippi river with waning meltwater flow c4 productivity generally increased throughout the holocene culminating in peak warm intervals at 5000 and 2000 14c yr b p shifts in the abundances of c3 c4 plants through the late quaternary show no correlation to ecophysiological responses to atmospheric co2 concentration

seismic evidence of free gas migration through the gas hydrate stability zone ghsz and active methane seep in krishna godavari offshore basin abstract seismic amplitude versus offset avo analysis was performed on the multichannel seismic data in the vicinity of site nghp 01 10 where thick fracture filled gas hydrate is reported to understand the fluid migration in fracture dominated gas hydrate system amplitude preserved common image gathers cig are used in extracting the seismic amplitude with offset for seafloor bottom simulating reflectors bsr and different horizons within the gas hydrate stability zone ghsz the extracted amplitudes are fitted with three term shuey s avo approximation to estimate the intercept and gradient values based on the intercept and gradient values two distinct classes of seismic avo responses are observed class iv avo decreasing negative amplitudes with increasing offsets and class iii avo increasing negative amplitudes with increasing offsets for the bsr and other horizons above the bsr the large negative intercept and gradient values which indicate class iii avo ranges from 0 2 to 1 8 for the inline seismic profile and from 0 01 to 0 3 for the crossline profile the presence of class iii avo anomaly within the gas hydrate stability zone ghsz provides evidence of existence of free gas which may be migrating along the fault system some of the active faults are exposed on the surface and show gas venting signatures such as gas flares and pockmarks in the multibeam data

near simultaneous great earthquakes at tongan megathrust and outer rise in september 2009 the tsunami that struck the samoan and northern tongan islands in september 2009 was preceded by a magnitude 8 earthquake on the outer slope of the oceanic trench where the pacific plate bends as it enters the subduction zone this was initially thought to be the sole source of the tsunami but a more complex picture is emerging two groups report the occurrence of two earthquakes a triggered doublet at nearly the same time and place what is not clear is which triggered the other beavan et al use an analysis of global positioning system station displacements and tsunami models to show that the outer rise earthquake was accompanied possibly triggered by a near simultaneous mega thrust earthquake in the adjacent tonga subduction zone lay et al analyse the available seismic data and their model suggests that the outer rise event triggered megathrust faulting either way this dual strike suggests a mechanism for the occasional large tsunamis generated at the tonga subduction zone on 29 september 2009 a tsunami devastated the samoan and northern tongan islands it is shown here that an unusual earthquake sequence preceded this tsunami a magnitude 8 earthquake in the outer rise intraplate region occurred almost simultaneously with rupture of the shallow subduction interplate interface equivalent to a magnitude 8 earthquake the findings provide information on strain release mechanisms at subduction zones and a possible mechanism for the occasional large tsunamis generated at the tonga subduction zone the earth s largest earthquakes and tsunamis are usually caused by thrust faulting earthquakes on the shallow part of the subduction interface between two tectonic plates where stored elastic energy due to convergence between the plates is rapidly released1 2 the tsunami that devastated the samoan and northern tongan islands on 29 september 2009 was preceded by a globally recorded magnitude 8 normal faulting earthquake in the outer rise region where the pacific plate bends before entering the subduction zone preliminary interpretation suggested that this earthquake was the source of the tsunami3 here we show that the outer rise earthquake was accompanied by a nearly simultaneous rupture of the shallow subduction interface equivalent to a magnitude 8 earthquake that also contributed significantly to the tsunami the subduction interface event was probably a slow earthquake with a rise time of several minutes that triggered the outer rise event several minutes later however we cannot rule out the possibility that the normal fault ruptured first and dynamically triggered the subduction interface event our evidence comes from displacements of global positioning system stations and modelling of tsunami waves recorded by ocean bottom pressure sensors with support from seismic data and tsunami field observations evidence of the subduction earthquake in global seismic data is largely hidden because of the earthquake s slow rise time or because its ground motion is disguised by that of the normal faulting event earthquake doublets where subduction interface events trigger large outer rise earthquakes have been recorded previously4 but this is the first well documented example where the two events occur so closely in time and the triggering event might be a slow earthquake as well as providing information on strain release mechanisms at subduction zones earthquakes such as this provide a possible mechanism for the occasional large tsunamis generated at the tonga subduction zone5 where slip between the plates is predominantly aseismic6

the biogeochemistry of ellesmere lake u k i source correlation of leaf wax inputs to the sedimentary lipid record abstract analyses of the free lipid distributions from ellesmere lake sediments taken from two depths and comparison with leaf wax lipid distributions from six deciduous tree species around the lake were made in order to assess lipid sources close correlations of aliphatic lipid distributions in the carbon number range c 20 c 50 were seen c 28 and c 29 sterols were observed in both sediment and leaf waxes but c 27 sterols were only present in the sediments and were thus assigned a nonleaf wax source unsaturated steroidal ketones were observed both in the sediment and in certain leaf waxes and were assigned specific sources alkan 2 ones were not present in the leaf waxes but were present in the sediment samples with an almost identical distribution to the sediment n alkanes indicating a microbially mediated source c 20 c 30 n aldehydes which have not previously been widely reported in free lipid distributions of freshwater lacustrine sediments were prominent in the surface sediment and in the leaf waxes examined

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

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

gas hydrate destabilization enhanced dewatering benthic material turnover and large methane plumes at the cascadia convergent margin mixed methane sulfide hydrates and carbonates are exposed as a pavement at the seafloor along the crest of one of the accretionary ridges of the cascadia convergent margin vent fields from which methane charged low salinity fluids containing sulfide ammonia 4he and isotopically light co2 escape are associated with these exposures they characterize a newly recognized mechanism of dewatering at convergent margins where freshening of pore waters from hydrate destabilization at depth and free gas drives fluids upward this process augments the convergence generated overpressure and leads to local dewatering rates that are much higher than at other margins in the absence of hydrate discharge of fluids stimulates benthic oxygen consumption which is orders of magnitude higher than is normally found at comparable ocean depths the enhanced turnover results from the oxidation of methane hydrogen sulfide and ammonia by vent biota the injection of hydrate methane from the ridge generates a plume hundreds of meters high and several kilometers wide a large fraction of the methane is oxidized within the water column and generates 13c anomalies of the dissolved inorganic carbon pool

explanation of temporal clustering of tsunami sources using the epidemic type aftershock sequence model temporal clustering of tsunami sources is examined in terms of a branching process model it previously was observed that there are more short interevent times between consecutive tsunami sources than expected from a stationary poisson process the epidemic type aftershock sequence etas branching process model is fitted to tsunami catalog events using the earthquake magnitude of the causative event from the centennial and global centroid moment tensor cmt catalogs and tsunami sizes above a completeness level as a mark to indicate that a tsunami was generated the etas parameters are estimated using the maximum likelihood method the interevent distribution associated with the etas model provides a better fit to the data than the poisson model or other temporal clustering models when tsunamigenic conditions magnitude threshold submarine location dip slip mechanism are applied to the global cmt catalog etas parameters are obtained that are consistent with those estimated from the tsunami catalog in particular the dip slip condition appears to result in a near zero magnitude effect for triggered tsunami sources the overall consistency between results from the tsunami catalog and that from the earthquake catalog under tsunamigenic conditions indicates that etas models based on seismicity can provide the structure for understanding patterns of tsunami source occurrence the fractional rate of triggered tsunami sources on a global basis is approximately 14 online material figures of residual analysis for tsunami and earthquake catalogs

the relationship between sedimentary organic carbon isotopic composition and organic biomarker compound concentration abstract a study of organic biomarker compounds which could serve as tracers of terrigenous and marine sedimentary organic matter sources was performed on samples from a 208 7 m hydraulic piston core hole dsdp hole 619 from the hemipelagic pigmy basin in the northern gulf of mexico organic carbon normalized concentrations of total long chain c37 c39 alkenones and some individual c27 c29 desmethyl sterols were determined to be useful proportional indicators tracers of preserved marine and terrigenous organic carbon respectively the alkenones whose only known source is marine phytoplankton of the class prymnesiophyceae generally occurred in higher concentrations in interglacial isotope stages 1 and 5a b than in the intervening glacial stages sterols c27 c29 apparently of a dominantly terrigenous origin occurred in lower concentrations during interglacial stages than in glacial stages tracers of both terrigenous and marine organic matter appear to be affected by the differential diagenetic alteration of the biomarker corg ratios as indicated by a simple first order kinetic model the lack of any desmethylor 4a methylsterol which is linearly related to the proportion of marine sedimentary organic matter as scaled by 13corg indicates that either 1 1 sedimentary diagenesis has obscured the biomarker corg vs 13corg record 2 2 phytoplanktonic assemblage changes caused variations in the biomarker corg ratio of the primary input preferential preservation of terrigenous sterols may result in a biased sedimentary record of sterol input which could be misinterpreted as indicating solely terrigenous sterol sources a simple model which characterizes the effects of sedimentary diagenesis on the relationship between corg normalized biomarker ratios and 13corg demonstrates the potential problems of long term differential diagenetic skewing on those tracer records

seismic characterization of hydrates in faulted fine grained sediments of krishna godavari basin unified imaging 1 a combination of diffusion and advection in fine grained sediments can create a patchy bottom simulating reflector bsr which has little to no apparent correlation with the overlying hydrate distribution using 2d seismic data from faulted clay rich sediments in the krishna godavari kg basin we show both the hydrate distribution and the bsr structure are fault controlled our demonstration hinges upon a kinematically accurate p wave velocity vp model which is estimated using a composite traveltime inversion depth migration method in an iterative manner the flexibility of the method allows simultaneous usage of traveltimes from multiple discontinuous reflectors the application begins with a simple vp model from time processing which is reflective of a diffusive continuous hydrate and free gas bearing system the application converges in three iterations yielding a final vpmodel which is suggestive of a patchy distribution of hydrates and free gas possibly developing through a combined diffusive advective system the depth image corresponding to the final vp model can be interpreted for faults that suggest ongoing tectonism the bsr appears to be truncated at active faults zones both the final vp model and the corresponding depth image can be reconciled with the hydrate distribution and bsr depth at logging coring sites located 250 m away from the line by projecting the sites along the strike direction of the regional faults

a deep outer rise reverse fault earthquake immediately triggered a shallow normal fault earthquake the 7 december 2012 off sanriku earthquake mw 7 3 1 teleseismic body wave analysis revealed that the 7 december 2012 off sanriku earthquake mw 7 3 at the outer rise of japan trench consisted of two successive subevents the first subevent with reverse fault mechanism event 1 mw 7 1 at 56 km depth was followed by approximately 20 s later the second subevent with normal fault mechanism event 2 mw 7 2 at 6 km depth finite fault slip models show that the slip of event 1 was concentrated around the initial rupture point with the maximum of 2 7 m and that event 2 had two asperities with the maximum of 4 5 m at both sides of the initial rupture point the static coulomb failure function analyses suggested that event 1 triggered event 2 and that both subevents were promoted by the 2011 tohoku earthquake mw 9 1

terrestrial organic carbon contributions to sediments on the washington margin elemental and stable carbon isotopic compositions and biomarker concentrations were determined in sediments from the columbia river basin and the washington margin in order to evaluate geochemical approaches for quantifying terrestrial organic matter in marine sediments the biomarkers include an homologous series of long chain n alkanes derived from the surface waxes of higher plants phenolic and hydroxyalkanoic compounds produced by cuo oxidation of two major vascular plant biopolymers lignin and cutin all marine sediments including samples collected from the most remote sites in cascadia basin showed organic geochemical evidence for the presence of terrestrial organic carbon using endmember values for the various biomarkers determined empirically by two independent means we estimate that the terrestrial contribution to the washington margin is 60 for shelf sediments 30 for slope sediments and decreases further to 15 in basin sediments results from the same geochemical measurements made with depth in gravity core 6705 7 from cascadia seachannel suggest that our approach to assess terrestrial organic carbon contributions to contemporary deposits on the washington margin can be applied to the study of sediments depositing in this region since the last glacial period

lipids of aquatic organisms as potential contributors to lacustrine sediments ii abstract the relationship between the lipid composition of organisms in the water column of an eutrophic lake and the lipid composition of underlying sediments previously examined for n alkanols and steroids is now reported for hydrocarbons ketones and carboxylic acids the n c7 alkane and alkenoic acids from two primary sources are rapidly metabolized in the water column and surficial sediment bacterial biomarkers including hopenes and i ai branched fatty acids were detected in the photosynthetic bacterial layer occurring just above the sediment water interface within the sediment the apparent conversion of free n alkanes alkan 2 ones and hydroxy acids to the corresponding bound form is noted microbiological oxidation of n alkanes to alkan 2 ones is supported by the detection of the intermediate alkan 2 ols with a distribution similar to that of the ketones the geochemistry of sediment deposited c 1900 prior to biological study of the site was interpreted from stable biomarkers and the diagenetic changes recognised in the study of contemporary deposition a qualitative difference in algal input to the older sediment is inferred from the low 7 sterol content and presence of 2 6 10 trimethyl 7 3 methylbutyl dodecane however there was still significant dinoflagellate input as indicated by the presence of 4 methylsterols a difference in higher plant input to the older sediment indicated from the n alkane alkene and triterpenoid ketone distributions is consistent with the recent development of tree cover

low productivity and slow deep water circulation in mid cretaceous oceans paleofertility estimates are derived from organic carbon accumulation rates determined in nonbioturbated mid cretaceous deep sea deposits using organic carbon preservation factors observed in laminated sediments from anoxic holocene environments the estimated mid cretaceous primary production rates are as much as an order of magnitude lower than those measured in today s oceans an evaluation of dissolved oxygen budgets using a simple oceanic circulation model indicates very low deep water renewal rates in mid cretaceous oceans 28 references 2 tables 4 figures

diagenetic changes of lignin compounds in a more than 0 6 million year old lacustrine sediment lake biwa japan a vertical profile of lignin in the upper 700 m layer of a 1400 m sediment core of lake biwa an oligotrophic freshwater lake in japan was determined using a cuo oxidative degradation method the results indicated that lignin is found throughout the core demonstrating lignin to be very stable for over 0 6 million years moreover the upper 250 m approximately 0 6 million years old segment of the sediment core was investigated to determine the apparent long term degradation rate of lignin a downward lignin concentration decrease is observed over the upper 250 m of the core which corresponds to a calculated half life of at least approximately 40 104 years assuming that lignin decrease is due to its in situ degradation diagenesis

late pleistocene vegetation change in korea and its possible link to east asian monsoon and dansgaard oeschger d o cycles abstract late pleistocene carbon isotope 13c records from a paleolithic sedimentary sequence collected from baeki hongcheon central korea show long term changes with superimposed short term isotopic excursions the 13c value of the sedimentary organic matter a proxy for past vegetation change varied from 26 to 23 for the period between 30 and 90 ka with a long term variation similar to insolation changes high amplitude 1 to approximately 1 5 fluctuations superimposed on the long term changes in the 13c values decreased during stronger summer monsoon intervals but increased during the weakened summer monsoon this millennial scale pattern is generally similar to greenland dansgaard oeschger d o cycles the possible connection between the hongcheon area korea and high latitudes may be explained by atmospheric circulation changing in response to the d o oscillations in the northern hemisphere

rupture process of the 1946 nankai earthquake estimated using seismic waveforms and geodetic data the rupture process of the 1946 nankai earthquake mjma 8 0 was estimated using seismic waveforms from teleseismic and strong motion stations together with geodetic data from leveling surveys and tide gauges the results of joint inversion analysis showed that two areas with large slip are more confined than in previous studies in our inversion we assumed spatially varying strike and dip angles and depth of each subfault by fitting those to the actual complex shape of the upper surface of the philippine sea plate in the nankai trough region as a result we calculated the total seismic moment m0 5 5 1021 nm the moment magnitude mw 8 4 and a maximum slip of 5 1 m occurring at a point south of cape muroto the estimated slip distribution on the west side of the fault plane appears somewhat complicated but it explains well the vertical deformations at tosashimizu and in the vicinity of inomisaki arguments have been made that the westernmost part slipped slowly after the earthquake over a period of days or months as an afterslip because the seismic waveforms can be largely explained without the slip in this part however in order to explain the displacement recorded by the tide gauge at tosashimizu we conclude that the westernmost part slipped simultaneously with the earthquake splay faulting which was suggested in previous studies is not required in our model to explain the seismic waveforms and geodetic data

terrestrial vegetation change inferred from n alkane σ13c analysis in the marine environment abstract we report gas chromatography isotope ratio monitoring mass spectrometry gc irm ms measurements of the 13c values of individual biomarker compounds n alkanes extracted from a 3 m marine sediment core taken near the mouth of the johnstone river north queensland australia the technique allows a purely terrestrial isotope signal to be discerned despite mixing of terrestrial and marine derived carbon the results indicate that there has been a 2 increase in the 13c values of terrestrially derived n alkanes c29 c33 since clearing of the forested johnstone river drainage basin for sugarcane and pasture began in the late 19th century a much slower 1 increase in 13c values after 6 000 years bp and prior to european settlement may be related to a decrease in rainfall in the basin or to an increase in the abundance of c4 plants as a result of increased aboriginal burning the results from the sediment core are consistent with data obtained for modern river sediments from forested and cleared subcatchments within the basin and demonstrate that the 13c values of terrestrially derived n alkanes in the marine environment can be used to assess basin wide vegetation changes in adjacent river catchments on geological timescales

elastic wave velocity in marine sediments with gas hydrates effective medium modeling we offer a first principle based effective medium model for elastic wave velocity in unconsolidated high porosity ocean bottom sediments containing gas hydrate the dry sediment frame elastic constants depend on porosity elastic moduli of the solid phase and effective pressure elastic moduli of saturated sediment are calculated from those of the dry frame using gassmann s equation to model the effect of gas hydrate on sediment elastic moduli we use two separate assumptions a hydrate modifies the pore fluid elastic properties without affecting the frame b hydrate becomes a component of the solid phase modifying the elasticity of the frame the goal of the modeling is to predict the amount of hydrate in sediments from sonic or seismic velocity data we apply the model to sonic and vsp data from odp hole 995 and obtain hydrate concentration estimates from assumption b consistent with estimates obtained from resistivity chlorinity and evolved gas data

a mechanism for the formation of methane hydrate and seafloor bottom simulating reflectors by vertical fluid expulsion bottom simulating reflectors bsr are observed commonly at a depth of several hundred meters below the seafloor in continental margin sedimentary sections that have undergone recent tectonic consolidation or rapid accumulation they are believed to correspond to the deepest level at which methane hydrate clathrate is stable we present a model in which bsr hydrate layers are formed through the removal of methane from upward moving pore fluids as they pass into the hydrate stability field in this model most of the methane is generated below the level of hydrate stability but not at depths sufficient for significant thermogenic production the methane is primarily biogenic in origin the model requires either a mechanism to remove dissolved methane from the pore fluids or disseminated free gas carried upward with the pore fluid the model accounts for the evidence that the hydrate is concentrated in a layer at the base of the stability field for the source of the large amount of methane contained in the hydrate and for bsrs being common only in special environments strong upward fluid expulsion into the hydrate stability field does not occur in normal sediment depositional regimes so bsrs are uncommon upward fluid expulsion does occur as a result of tectonic thickening and loading in subduction zone accretionary wedges and in areas where rapid deposition results in initial undercconsolidation in these areas hydrate bsrs are common the most poorly quantified aspect of the model is the efficiency with which methane is removed and hydrate is formed as pore fluids pass into the hydrate stability field the critical boundary in the phase diagram between the fluid plus hydrate and fluid only fields is not well constrained however the amount of methane required to form the hydrate and limited data on methane concentrations in pore fluids from deep sea boreholes suggest very efficient removal of methane from rising fluid that may contain less than the amount required for free gas production in most fluid expulsion regimes the quantity of fluid moved upward to the seafloor is great enough to continually remove the excess chloride and the residue of isotope fractionation resulting from hydrate formation thus as observed in borehole data there are no large chloride or isotope anomalies remaining in the local pore fluids the differences in the concentration of methane and probably of co2 in the pore fluid above and below the base of the stability field may have a significant influence on early sediment diagenetic reactions

depressurization experiment of pressure cores from the central ulleung basin east sea insights into gas chemistry abstract we performed depressurization experiments on pressure cores pcs recovered from holes ubgh1 10b and ubgh2 11b which were drilled during two separate expeditions in the ulleung basin ubgh1 and ubgh2 various lines of evidence such as convex curvature in the p v curves obtained by depressurization as well as x ray images and resistivity at bit rab data point to the presence of gas hydrates at these holes we estimated gas hydrate saturation sh at these holes to range from 5 23 based on the amount of gas released from pcs these sh values are in agreement with those reported at other high gas flux settings molecular c1 c2 and isotopic 13cch4 dch4 13cc2h6 indicators delineate a microbial source for the ch4 and c2h6 in core ubgh1 10b 5r the carbon isotopic fractionation factor between co2 and ch4 ec 13cco2 13cch4 was observed to increase from 50 to 68 as pressure was reduced during our experiments these changes illustrate the isotope fractionation that results from the preferential release of 13c depleted co2 during the early stages of depressurization the constant carbon isotope separation 10 20 between co2 in void gases and in the dissolved inorganic carbon dic pool shown in cores from the ulleung basin has also been observed in gas hydrate bearing sediments elsewhere it is important to consider this effect when using carbon isotopic data in carbon cycling models specifically when unraveling metabolic pathways of methane generation in situations where partial co2 degassing of a core is suspected we recommend the use of the carbon isotope ratio of dic instead of the gas measurements to best delineate the methane cycling pathways in marine systems

effects of turbidity flows on organic matter accumulation sulfate reduction and methane generation in deep sea sediments on the iberia abyssal plain non steady state sedimentation has affected preservation of organic matter in a pliocene pleistocene turbidite sequence sampled by the ocean drilling program at four closely spaced drill sites on the iberia abyssal plain organic carbon concentrations average ca 0 7 in sediments from sites 897 and 898 and ca 0 4 at sites 899 and 900 headspace concentrations of interstitial methane exceed 100 000 ppm in sediments from sites 897 and 898 but are essentially zero in those from sites 899 and 900 methane concentrations do not rise until interstitial sulfate concentrations are virtually depleted suggesting the presence of deep in situ methanogenic bacterial activity at sites 897 and 898 and its absence at sites 899 and 900 two factors associated with the turbidity flows that created the sedimentary sequence evidently influenced post depositional diagenesis at these sites the principal factor is that the rapidly deposited turbidite sequences at sites 897 and 898 protected organic matter from early oxic degradation and thereby permitted subsequent anoxic degradation to proceed in contrast organic matter in the more slowly deposited turbidites at sites 899 and 900 was oxidized soon after deposition and was therefore not available for later microbial utilization a lesser factor is that the turbidity flows may have obtained their entrained organic matter from different environments and consequently delivered organic matter with different characteristics both factors contributed to heterogeneity of the types and amounts of organic matter that accumulated in these deep sea sediments and this variability has influenced subsequent sulfate reduction and methanogenesis

seismic coupling and outer rise earthquakes variation of interplate seismic coupling at subduction zones is a major factor controlling the size of the largest underthrusting events this variation also has a profound effect on the regional intraplate stresses in the vicinity of the subduction zone outer rise seismicity is strongly correlated with variations in interplate coupling reflecting the stress state of the interplate coupled zone over 200 outer rise earthquakes with known focal mechanisms are used to investigate the relationship between stresses in the outer rise and interplate seismic coupling these events occur within the downgoing i e oceanic plate near the bathymetric trench axes and generally fall into the categories of tensional normal or compressional thrust with their tensional or compressional stress axes oriented approximately horizontal and perpendicular to the trench in uncoupled subduction zones only tensional outer rise earthquakes occur which indicates that the outer rise is dominated by tensional stresses associated with plate bending and or slab pull forces in strongly coupled subduction zones both tensional and compressional outer rise events are found these events are related both spatially and temporally to the distribution of large underthrusting earthquakes and are thus an integral part of the earthquake cycle in the strongly coupled regions tensional outer rise events follow large underthrusting events as the outer rise is temporarily in tension due to the underthrusting motion compressional outer rise events take place as compressional stress slowly accumulates oceanward of locked sections of the interplate zone in four instances compressional outer rise earthquakes have been followed by large underthrusting events which have occurred 2 4 7 and 19 years after the associated outer rise event the remaining compressional outer rise events are located in regions that are either known seismic gaps or in regions where the seismic potential is unknown the occurrence of compressional outer rise earthquakes suggests that compressional stress is accumulating in the adjacent interplate region and that there is the potential for a future large underthrusting event in the region thirty compressional outer rise events have been located in trench segments of middle and south america the kurile islands the tonga and kermadec islands the new hebrides arc and the solomon islands regions in both the southern kamchatka and northern new hebrides regions the outer rise seismicity indicates that the stress regimes in the outer rise have changed with time from tensional following a previous large underthrusting event to compressional at present thus three stages of the cycle from underthrusting to tensional outer rise regime to compressional outer rise regime are present requiring only the occurrence of the next underthrusting event to complete the cycle the occurrence of compressional outer rise events is useful for assessing the seismic potential of a region on an intermediate time scale

time and space distribution of coseismic slip of the 2011 tohoku earthquake as inferred from tsunami waveform data a multiple time window inversion of 53 high sampling tsunami waveforms on ocean bottom pressure global positioning system coastal wave and tide gauges shows a temporal and spatial slip distribution during the 2011 tohoku earthquake the fault rupture started near the hypocenter and propagated into both deep and shallow parts of the plate interface a very large slip approximately 25 m in the deep part off miyagi at a location similar to the previous 869 jogan earthquake model was responsible for the initial rise of tsunami waveforms and the recorded tsunami inundation in the sendai and ishinomaki plains a huge slip up to 69 m occurred in the shallow part near the trench axis 3 min after the rupture initiation this delayed shallow rupture extended for 400 km with more than a 10 m slip at a location similar to the 1896 sanriku tsunami earthquake and was responsible for the peak amplitudes of the tsunami waveforms and the maximum tsunami heights measured on the northern sanriku coast 100 km north of the largest slip the average slip on the entire fault was 9 5 m and the total seismic moment was 4 2 1022 n m m w 9 0 the large horizontal displacement of seafloor slope was responsible for 20 40 of tsunami amplitudes the 2011 deep slip alone could reproduce the distribution of the 869 tsunami deposits indicating that the 869 jogan earthquake source could be similar to the 2011 earthquake at least in the deep plate interface the large tsunami at the fukushima nuclear power station is due to either the combination of a deep and shallow slip or a triggering of a shallow slip by a deep slip which was not accounted for in the previous tsunami hazard assessments online material table of estimated slip for all subfaults at 0 5 min invervals

climatic and human controls on holocene floodplain vegetation changes in eastern pennsylvania based on the isotopic composition of soil organic matter abstract a paleoenvironmental time series spanning the holocene was constructed using 29 radiocarbon ages and 149 standardized 13 c som values from alluvial terrace profiles along the middle delaware river valley there is good agreement between increasing 13 c som and panicoideae phytolith concentrations suggesting that variations in c 4 biomass are a major contributor to changes in the soil 13 c a measurement error deconvolution curve over time reveals two isotope stages ii i with nine sub stages exhibiting variations in average 13 c som average c 4 stage ii 10 7 4 3 ka shows above average 13 c som increase c 4 values with evidence of an early holocene warming and dry interval sub stage iib 9 8 8 3 ka that coincides with rapid warming and cool dry abrupt climate change events sub stage iid 7 0 4 3 ka is an above average 13 c som increase c 4 interval associated with the mid holocene warm dry hypsithermal the stage ii i shift at 4 3 ka documents a transition toward below average 13 c som decrease c 4 values and coincides with decreasing insolation and hydroclimatic change sub stages ib and id above average c 4 coincide with the first documented occurrence of maize in the northeastern usa and a substantial increase in human population during the late woodland these associations suggest that people influenced 13 c som during the late holocene

paleoclimatic implications of holocene lake level fluctuations owasco lake new york radiocarbon controlled stratigraphic data from owasco lake valley new york document two cycles of relative lake level change during the holocene in response to regional variations in effective precipitation lake highstands occurred at 10 5 and 6 9 ka with an intervening lowstand at 9 ka the 10 5 ka highstand occurred during the well known killarney younger dryas cold interval 11 2 10 0 ka in response to decreased evaporation and increased precipitation the driest interval of the early middle holocene occurred 9 ka at the time of maximum summer solar insolation a second highstand occurred during the hypsithermal 8 5 5 5 ka in response to increased precipitation at a time when the interior of north america underwent maximum aridity this out of phase relationship between northeastern north america and the midcontinent during the hypsithermal may have been a consequence of a northward shift of the jet stream and a change of precipitation patterns in response to increased global warmth if the hypsithermal can be used as an analog for potential global warming the northeastern united states may experience future increases in regional precipitation

climatically driven glacial interglacial variations in c3 and c4 plant proportions on the chinese loess plateau high resolution 13c records of bulk organic matter om from three loess paleosol successions from the central chinese loess plateau document systematic fluctuations in c3 and c4 plant abundance for certain intervals during the past 620 k y measured 13c values of om in paleosols are less negative by 0 5 4 and total organic carbon toc contents are higher by up to 0 5 wt relative to corresponding values in loess deposits the 13com and toc decrease from peak values in paleosols progressively into overlying and underlying loess deposits integrated 13com toc and magnetic susceptibility rec ords indicate an increase in c4 vegetation to 50 during peak paleosol formation and a decrease in c4 vegetation to 30 during loess deposition for three of the past glacial interglacial cycles these results indicate that c4 plant abundance declined during glacials in this mid latitude region driven primarily by a shift to enhanced winter precipitation and lower temperatures and further contribute to the rapidly growing body of evidence that low p co2 during pleistocene glacials was insufficient to trigger c4 plant expansion without coincident favorable climatic conditions

seismicity in the western great basin apparently triggered by the landers california earthquake 28 june 1992 within 24 hr after the landers earthquake there were three magnitude 3 4 events in western nevada and an unexpected widespread increase in the rate of small events based on combined catalogs for northern nevada southern nevada and southern california and a model that assumes statistical independence of events in these regions the probability of this happening in a 24 hr period by random chance is less than 10 12 per day therefore there is high statistical confidence that the increased seismicity was triggered by the landers event based on the statistical model we develop a list of 227 earthquakes in the first 83 days following the landers earthquake each of which has no more than 10 probability of occurring by random chance the suspect events are broadly distributed in regions that correlate with historical activity in the great basin the events are not uniquely associated with known volcanic activity or with zones that were previously active with microearthquakes or aftershock sequences the magnitudes of the largest triggered events appear to decrease with distance with time the number of suspect events decreases at a rate comparable to the rate of decrease of aftershocks of the landers and big bear earthquakes three of the most significant triggered events that that occurred were as follows mina 500 km from landers m 4 36 min after landers smith valley 590 km from landers m 3 4 56 min after landers and little skull mountain 280 km from landers m 5 6 22 3 hr after landers the evidence for triggering is particularly strong in the case of the little skull mountain event where an increased rate of microseismicity was evident as soon as small events could be identified in the coda of the landers earthquake we evaluate the seismic history for the past 3 yr to understand what was unique about the landers earthquake this includes identifying the previous earthquakes most likely to have caused the strongest shaking in various frequency bands based on a simple screening model the strains from the landers earthquake were uniquely large at low frequencies but at high frequencies they were exceeded frequently by small more local events thus we hypothesize that the cause of triggering is low frequency dynamic strains at periods of about 10 sec or greater and that there is a regional threshold that must be exceeded since previous events with calculated strains that were almost as strong were not causes of widespread triggering this mechanism for triggering satisfies the criterion of being a relatively rare phenomenon since it is likely to occur only when a large long period wave is radiated into an area where strain has been building slowly toward the point where faults are unstable

the 2011 northern kermadec earthquake doublet and subduction zone faulting interactions 1 a large intraslab earthquake doublet 6 july 2011 mw 7 6 21 october 2011 mw 7 4 occurred in the pacific plate beneath the outer trench slope of the northern kermadec subduction zone seaward of an interseismically coupled region of the megathrust the first large event a shallow 24 km centroid depth normal faulting rupture was followed by intraslab aftershocks within minutes and by aftershocks near the megathrust within hours the second large event a deeper 45 km centroid depth thrust faulting rupture below the northern portion of the first rupture plane was also followed by interplate and intraslab aftershocks the last large interplate activity in northern kermadec involved an underthrusting doublet on 14 january 1976 mw 7 8 7 9 previous studies interpret westward movement of the northern kermadec arc relative to the australian plate from gps measurements to be a result of interseismic coupling on the northern kermadec megathrust a locked plate interface in this region should tend to reduce trench slope extensional stresses coulomb stress change calculations using a finite fault model determined from teleseismic body wave inversions for the normal faulting event in the 2011 doublet favor activation of megathrust faulting coulomb stress changes for the october compressional event appear to reduce interplate thrust activity and for a short time reversed the westward motion of the upper plate the net effect of the doublet is a few bar increase of interplate thrust fault driving stress which may have advanced a future large megathrust event intraslab normal faulting may serve as a harbinger not only a response to large megathrust ruptures