calcareous nannofossil zonation of the jurassic cretaceous boundary interval and correlation with the geomagnetic polarity timescale abstract calcareous nannofossil stratigraphy has been investigated in six european land sections and at two deep sea drilling project sites 391c and 534a ranging from the upper kimmeridgian to the lower valanginian most of the sections contain a continuous record of the jurassic cretaceous boundary interval a time of rapid increase in nannofossil abundance and diversity and allow development of a revised nannofossil zonation scheme for this period numerous nannofossil lineages have been studied in detail and the results help to increase potential stratigraphic resolution in this interval the proposed scheme consists of six zones which are units recognizable in all sections regardless of nannofossil preservation and eleven subzones determinable in all but the most poorly preserved material thirty eight additional biohorizons are proposed based on the stratigraphy of the two dsdp sites these can be accurately established only in moderately well preserved material but spotty occurrences of these taxa in other sections may be stratigraphically useful most of the sections studied have been investigated magnetostratigraphically and the results of this study allow correlation between nannofossil zonation and the geomagnetic polarity time scale magnetostratigraphy indicates that many nannofossil events can be quite precisely determined and are not significantly time transgressive finally the magnetostratigraphic definitions of two stage boundaries are refined the kimmeridgian tithonian and berriasian valanginian boundaries are placed within chrons cm22n and cm15n respectively two new genera faviconus and umbria and seven new species are described umbria granulosa rhagodiscus nebulosus cretarhabdus octofenestratus faviconus multicolumnatus nannoconus infans nannoconus compressus and nannoconus wintereri eight subspecies and three taxonomic emendations are also described

a different perspective on glauconite as a chronometer for geologic time scale studies there are advocates of the use of glauconite as a chronometer for geologic time scale studies who insist that if the geohistory of the sample in question is known in detail one can ascertain before hand that the sample will yield a radiometric result that is accurate in the geological sense examples are presented indicating that while some glauconite samples may yield the correct age within their assigned analytical uncertainties when compared to high temperature minerals others clearly do not and are too young by varying degrees the outright acceptance of published results on glauconite can result in erroneous age estimates of various biostratigraphic levels and stage or epoch boundaries

investigation of ionospheric electron content variations before earthquakes in southern california 2003 2004 1 it has been proposed that earthquakes are preceded by electromagnetic signals detectable from ground and space based measurements ionospheric anomalies such as variations in the electron density a few days before earthquakes are one of the precursory signals proposed since global positioning system gps data can be used to measure the ionospheric total electron content tec the technique has received attention as a potential tool to detect ionospheric perturbations related to earthquakes here we analyze 2 years 2003 2004 of data from the southern california integrated gps network scign a dense network of 265 continuous gps stations centered on the los angeles basin for possible precursors this time period encompasses the december 2003 m6 6 san simeon and september 2004 m6 0 parkfield earthquakes we produce tec time series at all scign sites and apply three different statistical tests to detect anomalous tec signals preceding earthquakes we find anomalous tec signals but no statistically significant correlation in time or in space between these tec anomalies and the occurrence of earthquakes in southern california for the 2003 2004 period this result does not disprove the possibility of precursory phenomena but show the signal to noise ratio of a hypothetical tec precursor signature is too low to be detected by the analysis techniques employed here precursors may still be revealed for future large earthquakes in well instrumented areas such as california and japan if the tests can be developed into techniques that can better separate external influences from the actual tec signal

worldwide initiation of holocene marine deltas by deceleration of sea level rise radiocarbon dated deltaic sequences of holocene age from different parts of the world began to accumulate within a restricted time range from about 8500 to 6500 years ago evaluation of major delta processes indicates that deceleration in sea level rise was the key factor in holocene delta formation within many deltas there is as much as a 2000 year age range between basal deposits in seaward and landward cores this age difference records the progressive landward migration of near mean sea level depositional environments during the lower to mid holocene establishment of a chronostratigraphic framework for holocene delta development provides a fundamental global baseline for distinguishing sea level change from vertical land motion by tectonism and isostasy and for evaluating rates of future marine incursion into low lying deltas

comment on formation and thrusting in some great valley rocks near the franciscan complex california and implications for the tectonic wedging hypothesis by r a glen

a statistical investigation of preearthquake ionospheric anomaly 1 empirical evidence of the preearthquake ionospheric anomalies peias is reported by statistically investigating the relationship between variations of the plasma frequency at the ionospheric f2 peak fof2 and 184 earthquakes with magnitude m 5 0 during 1994 1999 in the taiwan area the peia defined as the abnormal decrease more than about 25 in the ionospheric fof2 during the afternoon period 1200 1800 lt significantly occurs within 5 days before the earthquakes moreover the odds of earthquakes with peia increase with the earthquake magnitude but decrease with the distance from the epicenter to the ionosonde station these results indicate that the peia is energy related

high resolution 40ar 39ar dating of the oldest oceanic basement basalts in the western pacific basin 1 we report new 40ar 39ar ages for the oldest pacific oceanic floor at ocean drilling program site 801c in the pigafetta basin and site 1149d close to the izu bonin subduction zone in the nadezhda basin these ages were determined by applying high resolution incremental heating experiments including 15 30 heating steps to better resolve the primary argon signal from interfering alteration signatures in these low potassium ocean crust basalts combined with previous results from pringle 1992 for site 801b and 801c we arrive at a multistage history for the formation of the pigafetta ocean crust the oldest part of the pacific plate was formed at the spreading ridges at 167 4 1 4 3 4 ma n 2 2 internal absolute error offering an important calibration point on the geological reversal timescale grts since it represents the old end of the mesozoic magnetic anomalies this mid ocean ridge basalt sequence however is overlain by more tholeiites and alkali basalts that were formed 7 3 1 5 myr later around 160 1 0 6 ma n 7 2 internal error the older age group is confirmed independently by radiolarian ages ranging from late bajocian to middle bathonian 167 173 ma bartolini and larson 2001 and by profound differences in the structural characteristics of this basement section pockalny and larson 2003 thin layers comprising hydrothermal deposits separate these sequences which in addition to the difference in isotopic age show distinct major and trace element compositions this indicates that key volcanic and hydrothermal activity took place 400 600 km away from the spreading ridges on the basis of a jurassic 66 km myr half spreading rate in the pacific it remains unclear if these processes were active continuously after the initial formation of the pacific oceanic crust but all our observations seem to point to an episodic history site 1149d gives another important calibration point on the grts of 127 0 1 5 3 6 ma n 1 2 internal absolute error for anomaly m12 that is slightly younger when compared to current timescale compilations 134 2 2 1 ma gradstein et al 1995 this might suggest that the dated basalt from site 1149d does not represent the age of the ocean crust formed at its ridge axis it may also be part of the early cretaceous intraplate events that have produced dolerite sills in the pacific crust at sites 800 and 802 around 114 126 ma

magnetostratigraphy across the berriasian valanginian stage boundary early cretaceous at cehegin murcia province southern spain abstract the berriasian valanginian stage boundary near the town of cehegin in the eastern subbetic cordillera of spain is documented by a detailed ammonite zonation in pelagic limestones two magnetostratigraphic sections spanning the uppermost ammonite subzone of the berriasian and the lower two zones of the valanginian yielded identical magnetic polarity patterns remanent magnetization is predominantly carried by magnetite and characteristic directions were obtained by thermal demagnetization the mean characteristic directions from both sites have an inclination of 48 however the site declinations are divergent 030 and 074 due to the tectonic disturbance of the region the cehegin polarity pattern can be correlated by means of ammonite and calpionellid zonation to the magnetostratigraphies of the berriasian stratotype and several italian sections thereby enabling a unique correlation to the m sequence magnetic polarity time scale the berriasian valanginian stage boundary is in the middle of normal polarity chron m15n

jurassic cretaceous boundary age and mid ocean ridge type mantle source for shatsky rise basalt sills cored in lowermost berriasian sediments on shatsky rise in the northwest pacific yield a mean 4 0 ar 3 9 ar incremental heating age of 144 6 0 8 ma providing a minimum estimate on the age of the jurassic cretaceous boundary the largest part of the rise was emplaced at rates similar to those of several continental flood basalts the rise formed at an oceanic triple junction and the sills as well as lavas from two dredge sites exhibit an ocean ridge type nd pb sr isotope signature this signature is provisionally consistent with either a perisphere or meteorite impact model but is not predicted by the plume head model of plateau formation however no model can yet be rejected given the very sparse sampling of shatsky rise

mesozoic transpression transtension subduction and metallogenesis in northern and central california middle paleozoic to middle jurassic terrane assemblies in the klamaths and sierran foothills consist of mafic ultramafic complexes fine grained terrigenous strata derived from previously accreted continental margin belts sutured oceanic terranes reflect c 230 myr of margin parallel slip involving chiefly transtension and transpression quartzofeldspathic clastic rocks and blueschists eclogites are very rare little devolatilization occurred at magmagenic depths hence coeval hydrothermal ore deposits and granitoids are uncommon in contrast nearly head on cretaceous subduction of the farallon plate generated the massive klamath sierra nevada volcanic plutonic arc reflecting dewatering of the eastward descending oceanic lithosphere in the magmagenic zone immature great valley forearc and franciscan trench deposits shed from the arc record c 70 myr of rapid crustal growth au bearing solutions rising from magmagenic depths exsolved from plutons and expelled from heated wall rocks were mobilized attending arc construction precipitation of gold bearing quartz veins occurred where h2o co2 bearing fluids encountered major geochemical discontinuities in the wall rocks

refining the jurassic cretaceous boundary re os geochronology and depositional environment of upper jurassic shales from the norwegian sea abstract limited chronological information for upper jurassic rocks hampers precise age assignment of the jurassic cretaceous j k boundary this study presents re os geochronology rock eval pyrolysis and geochemical data for upper jurassic rocks in the nordland vii area offshore northern norway four intervals of organic rich shale were investigated two from the krill and one from the alge member of the hekkingen formation and one from the underlying masnykan formation drilled cores 6814 04 u 01 and 6814 04 u 02 rock eval pyrolysis data indicate immature organic matter with mixed type ii iii oil gas potential in these units among the four intervals re os isochroneity prevails only for the hekkingen formation samples data from the shale interval in the otherwise sand rich masnykan formation deposited in a shoreface to foreshore marine environment are not isochronous non isochroneity of the samples from relatively proximal setting is attributable to non conservative elemental desorption of os from sediments to dissolved phase and isotopic exchange of os at this depositional site the re os isochron age for the alge member 153 2 7 3 ma model 3 mswd 29 n 9 is consistent with its biostratigraphic kimmeridgian age 152 1 157 3 ma a re os isochron for the lower part of the krill member yields an age of 144 5 1 4 ma model 3 mswd 3 7 n 10 with an initial 187os 188os ratio of 0 552 0 007 given the interval s lower tithonian biostratigraphic age the re os age suggests that the j k boundary must be a few myr younger than its currently assigned age of 145 0 ma 2017 02 time scale www stratigraphy org a re os model age for shales from the upper part of the krill member places an upper age limit for the j k boundary at 142 2 ma hence the j k boundary is between 142 ma and 144 5 ma fe and s concentrations for the hekkingen formation show strong correlation and the s fe slope 1 19 mimics the stoichiometric s fe ratio for pyrite 1 15 a fe s toc ternary diagram for these samples points to an iron limiting sulphidic depositional environment anoxic to sulphidic depositional conditions for the hekkingen shales are also evident from relatively higher authigenic enrichment of mo compared to u unlike the hekkingen formation shales from the more sandy masnykan formation have lower s fe ratios and lower enrichment factors for redox sensitive elements indicating relatively oxygenated marine conditions during deposition

neotectonic implications and regional stress field constraints on mud volcanoes in offshore southwestern taiwan abstract recently discovered numerous mud volcanoes mvs and mud diapirs mds in sw taiwan both onshore and offshore show eruption lineaments suspected to be related to neotectonic processes spatial and temporal distribution of the mvs eruption events shows an obvious switch of the lineament orientation from nne ne n s nw and e w trending in n s direction the mud volcanoes have experienced multi stage eruptions and should have occurred

transport of terrestrial organic carbon to the oceans by rivers re estimating flux and burial rates this study re estimates one important component in the global carbon cycle the modern global fluviatile organic carbon discharge and burial rates according to these results approximately 430 1012 g of terrestrial organic carbon are transported to the ocean in modern times this amount is higher than the latest estimates but takes into account new data from oceania not previously considered in global flux studies however only the minor amount of 10 or approximately 43 1012 gc year 1 is most likely buried in marine sediments this amount is similar to the burial of marine organic carbon in the coastal ocean 55 1012 gc year 1 adding both estimates gives approximately 100 1012 gc year 1 which is the value calculated by berner 1982 for terrestrial deltaic shelf sediments however the results in this study suggest that on a global scale the organic carbon content in coastal ocean sediments is not solely of terrestrial origin but a mixture of nearly equal amounts of marine and terrestrial organic carbon the major part of the terrestrial organic carbon that enters the ocean by rivers approximately 400 1012 gc year 1 seems to be either a remineralised in the ocean whereas the mechanism by which the terrestrial organic carbon is oxidised in the ocean are unknown or b is dispersed throughout the oceans and accumulates in pelagic sediments

reply to comment by f masci and j n thomas on temporal and spatial precursors in ionospheric total electron content of the 16 october 1999 mw7 1 hector mine earthquake

carbon storage in a holocene deltaic sequence an example from the nobi plain central japan abstract we estimated the rate of accumulation and total amount of organic carbon oc stored in holocene sediments of the nobi plain of central japan by analyzing 2701 existing borehole sections and 218 14c ages reconstructing the three dimensional stratigraphic architecture of the delta system calculating the volume of sediments in the delta and using oc contents measured from sediments from eight boreholes on the plain we calculated that a total of 167 tg of oc was stored in deltaic deposits on the plain during the past 6000 years a dramatic increase in the amount of stored oc since 1000 cal bp is probably a combined result of increases in sediment supply to the delta in response to human activities in the drainage basin and expansion of the area of subaerial delta as a result of progradation oc accumulation rates for the nobi plain during the past 6000 years ranged from 15 3 to 37 5 g m 2 y 1 which are comparable to rates obtained from other holocene delta and to rates from floodplain and lake systems with higher oc contents in their sediments the higher sedimentation rates of the deltaic deposits compensates for their lower oc contents

seismoionospheric gps total electron content anomalies observed before the 12 may 2008 mw7 9 wenchuan earthquake 1 the global ionospheric map gim is used to observe variations in the total electron content tec of the global positioning system gps associated with 35 m 6 0 earthquakes that occurred in china during the 10 year period of 1 may 1998 to 30 april 2008 the statistical result indicates that the gps tec above the epicenter often pronouncedly decreases on day 3 5 before 17 m 6 3 earthquakes the gps tec of the gim and electron density profiles probed by six microsatellites of formosat3 cosmic f3 c are further employed to simultaneously observe seismoionospheric anomalies during an mw7 9 earthquake near wenchuan china on 12 may 2008 it is found that gps tec above the forthcoming epicenter anomalously decreases in the afternoon period of day 6 4 and in the late evening period of day 3 before the earthquake but enhances in the afternoon of day 3 before the earthquake the spatial distributions of the anomalous and extreme reductions and enhancements indicate that the earthquake preparation area is about 1650 km and 2850 km from the epicenter in the latitudinal and longitudinal directions respectively the f3 c results further show that the ionospheric f2 peak electron density nmf2 and height hmf2 significantly decreases approximately 40 and descends about 50 80 km respectively when the gps tec anomalously reduces

a mesozoic time scale we present an integrated geomagnetic polarity and stratigraphic time scale for the triassic jurassic and cretaceous periods of the mesozoic era with age estimates and uncertainty limits for stage boundaries the time scale uses a suite of 324 radiomenc dates including high resolution 40 ar 39 ar age estimates this framework involves the observed ties between 1 radiometric dates biozones and stage boundaries and 2 between biozones and magnetic reversals on the seafloor and in sediments interpolation techniques include maximum likelihood estimation smoothing cubic spline fitting and magnetochronology

new constraints on the jurassic cretaceous boundary in the high andes using high precision u pb data abstract the jurassic cretaceous j k boundary is poorly constrained and is the only phanerozoic system boundary that lacks an internationally accepted reference stratigraphic section gssp precise radio isotopic u pb data are unavailable for the earliest stage of the cretaceous the berriasian the age of the jurassic cretaceous boundary was based on several assumptions including the relative duration of ammonite zones the constant spreading rates of magnetic anomalies and the extrapolation of rb sr or k ar isotopic data this paper discusses a site in an andean basin of western gondwana showing the j k boundary interval with geographically widespread nannofossil markers which are here uniquely combined with precise radiometric dates the recent finding of a sequence of marine black shales in the high andes of argentina interbedded with ash fall tuffs provides important constraints on this boundary this succession bears calcareous nannofossils and ammonites which allow correlation with well established tethyan floras and faunas in the northern hemisphere the tithonian berriasian transition in the andes was recognized on the basis of ammonite zones and nannofossil bioevents for the first time in the southern hemisphere the new ages obtained are 137 9 0 9 ma by sensitive high resolution ion microprobe shrimp and 139 55 0 09 0 18 ma by chemical abrasion isotope dilution thermal ionization mass spectrometry tims near the base of the berriasian these new ages can be interpreted in two different ways the first alternative would indicate that the present geological time table is correct and the fossil levels should be late berriasian the second alternative is that the j k boundary is 5 ma younger than the recently published geological time scale the authors support the last alternative and propose that the j k boundary should be close to 140 ma

jurassic savannah plant taphonomy and climate of the morrison formation upper jurassic western usa abstract the morrison formation contains six plant taphofacies wood whole leaf leaf mat root common carbonaceous debris and rare carbonaceous debris none of these taphofacies is common in the morrison particularly striking is the paucity of wood even in more reducing environments the flora of the morrison formation is distinct in the kimmeridgian and tithonian parts of the section the plant taphofacies are consistent with a predominantly herbaceous vegetation evidence from the plant taphofacies floras and sedimentology of the morrison is consistent with a warm seasonal semi arid climate throughout changing from dry semi arid to humid semi arid from the kimmeridgian to the tithonian parts of the formation

geochemistry of tectonically expelled fluids from the northern coast ranges rumsey hills california usa tectonic compression has created abnormally high pressure on deep basinal fluids causing their expulsion from areally exposed upper cretaceous rock along the eastern margin of the california coast ranges the fluids emerge as near neutral perennial sodium chloride springs at high elevations with flow rates as high as 10 l per min higher spring discharges are more common around the exposure of a west vergent fault propagation fold axis spring waters range from 1000 to 27 000 mg l tds the least saline water 18o 7 5 closely represents local meteoric water that mixes with saline fluid 18o 5 3 and forms a slope of 3 5 on a d vs 18o plot a na 125 to 8000 mg l vs cl 150 to 17 000 mg l plot shows a linear dilution trend that extends close to but below the values for modern seawater calcium 75 3000 mg l is considerably enriched relative to seawater and forms a nonlinear trend with chloride in detail the na deficit defined by the difference between the measured na content and the na concentration on a hypothetical seawater dilution line is approximately balanced by the ca excess similarly defined by the seawater dilution line this relationship strongly suggests that the fluid is diluted seawater that is being modified by active albitization of plagioclase at different depths simultaneous b and 18o enrichment of the fluids accompanied by deuterium depletion further suggest that the seawater modification is influenced by clay diagenesis bicarbonate and sio2 concentrations show an inverse correlation with cl with most waters being saturated or slightly oversaturated with calcite and quartz at the discharge temperatures some freshwater springs with near meteoric stable isotope values may represent mixing of young groundwater from perched aquifers but in many cases the freshwater springs emerge along the same structures and have the same perennial nature as the saline fluids and expulsion of an older fresh groundwater component that is under abnormal fluid pressures cannot be ruled out basinal fluids elsewhere commonly show dilution trends with local meteoric water and in the case of the rumsey hills some of the dilute saline waters may indicate deep penetration of meteoric water 1 km in the pleistocene before the latest tectonic uplift geothermometry of the spring waters maximum 90 c suggest an origin from as deep as 4 0 km this depth is consistent with the depth of the core of a fault propagation anticline below the surface of the rumsey hills developed by active internal deformation of an east tapering wedge beneath the southwestern sacramento valley active tectonic compression causes near lithostatic fluid pressures in the shallow subsurface below the rumsey hills and volume strain within the core of the anticline that results in upward expulsion of the saline fluids from the indicated depths

a statistical study of ionospheric earthquake precursors monitored by using equatorial ionization anomaly of gps tec in taiwan during 2001 2007 abstract in this paper we examine pre earthquake ionospheric anomalies by the total electron content tec derived from a ground based receiver of the global positioning system gps a network of eight gps receivers is used to construct daily latitude time tec ltt plots to monitor the crest of equatorial ionization anomaly eia in the taiwan area three parameters of the strength location and formation time of the eia crest are extracted a 15 day running medians of the three parameters and the associated upper and lower quartiles are utilized as the references for identifying abnormal signals for all of the 150 m 5 0 earthquakes in the taiwan area during 2001 2007 results show that the eia crest significantly moves equatorward poleward and appears in an earlier later time of the afternoon period a few days before after the earthquakes along the taiwan longitude the two parameters of the eia crest location and occurrence time can be employed to detect ionospheric earthquake precursors the results further imply that atmospheric electric fields generated around the epicenter of a forthcoming earthquake during the preparation period are essential

a carbon storage perspective on alluvial sediment storage in the rhine catchment abstract floodplains are important sinks in terms of the sediment and carbon flux in fluvial systems despite the large amount of detailed geomorphological studies which include measurements on total organic carbon little is known of the coupling of long term carbon and sediment flux and on the amount of carbon storage in floodplains therefore the influence of the sedimentary facies in fluvial systems was investigated based on a statistical analysis of 1948 organic carbon measurements in different parts of the rhine catchment the analysis allows to develop a conceptual carbon budget model of fluvial systems which was coupled with a holocene alluvial sediment budget to estimate the holocene sequestration rates of carbon storage in floodplains averaged over the rhine catchment the sedimentary carbon sequestration ranges between 3 4 to 25 4 g m 2 yr 1 with more reasonable values between 5 3 to 17 7 g m 2 yr 1 compared to the recent particulate carbon export these values are in the same order of magnitude but somewhat smaller indicating that approximately the same amount of the exported carbon may be stored in floodplains however compared to sedimentary carbon sequestration rates obtained elsewhere the presented values are at the lower limit corresponding to the lower mean holocene soil erosion and floodplain accumulation rates

holocene floodplain sediment storage and hillslope erosion within the rhine catchment the response of fluvial systems to land use and climate change varies depending on catchment size while forcing response mechanisms of small catchments are reasonably well understood the response of larger drainage basins is less clear in particular the impact of land use and climate change on the rhine system is poorly understood because of the catchment size 185 000 km 2 and the long history of human cultivation which started approximately 7500 years ago a sediment budget is calculated to specify the amount of alluvial sediment that was deposited during the holocene and to estimate long term soil erosion rates the results suggest that 599 14 10 9 t of holocene alluvial sediment is stored in the non alpine part of the rhine catchment south and central germany eastern france the netherlands about 50 of holocene alluvial sediment is deposited along the trunk valley and the delta upper rhine lower rhine coastal plain while the rest is stored along the tributary valleys the floodplain sediment storage corresponds to a mean erosion rate of 0 559 0 16 t ha per yr 38 59 10 7 mm kyr across the rhine catchment outside the alps this holocene averaged estimate amounts for sediments that were delivered to the channel network and is at the lower limit of erosion rates from other studies of different methodology

recalibration of the geomagnetic polarity timescale the quest for improved time control to estimate rates of geologic and paleoenvironmental processes is central to the earth sciences until the middle of this century geochronology was based solely on macrofossil evolution providing the largely unmodified definition of geologic stages in the last few decades with impetus from the deep sea drilling project dsdp and the ocean drilling program odp microfossil biostratigraphy has become increasingly important although new radiometric techniques have resulted in improved absolute age precision the direct correlation of absolute ages to biozonations and hence to geologic stage boundaries remains poor this is due to the difficulty of finding materials suitable for radiometric dating which can be directly correlated to biozonations the bridge between biozonations and absolute ages and the interpolation between absolute ages are best accomplished particularly for cenozoic and late mesozoic time through the geomagnetic polarity timescale gpts the template for late jurassic to quaternary geomagnetic polarity is derived from oceanic magnetic anomalies as demonstrated by heirtzler et al 1968 the gpts can be constructed using oceanic magnetic anomaly record s assuming constant seafloor spreading rate s and interpolating between available radiometric ages in the last quadrennium there have been outstanding developments in radiometric dating and astrochronology which have greatly improved the absolute age control of the gpts

sediment and carbon storages in the yahagi river delta during the holocene central japan abstract we estimated stored sediment and carbon during the holocene for each layer of the yahagi river delta central japan and discussed the provenance of stored carbon to estimate the bulk density and the carbon content of each layer we collected two 30 m deep undisturbed cores the volume of each layer was calculated using arcview 3d analyst although the volume ratio of each layer to the total volume was calculated to be 9 5 for the top mud layer 34 9 for the upper sand layer 32 8 for the middle mud layer and 22 9 for the lower sand layer the mass ratio of each layer to the total mass was calculated to be 8 5 40 9 25 2 and 25 4 respectively and the stored carbon ratio in each layer to the total stored carbon was 20 4 4 7 55 9 and 18 9 respectively these results suggest that the top mud and middle mud layers have a significant role as a place for carbon sequestration during postglacial time total stored carbon in the study area of only 92 1 km 2 was estimated at 26 tg c which is equivalent to 0 003 of atmospheric carbon this suggests that deltas on the globe have accumulated a massive amount of carbon during the evolution the inorganic carbon ratio to total carbon reached more than 45 around the boundary between the middle mud and lower sand layers the increasing trend in the c org n total ratio accompanied with a decrease in 13 c from the bottom to the top horizon in the middle mud layer indicates a gradual increase in terrestrial organic matter contribution the relative proportion of terrestrially derived materials decreases with increasing distance seaward

a quantitative study of lower cretaceous cyclic sequences from the atlantic ocean and the vocontian basin se france milankovitch type periodicity was identified within lower cretaceous cyclic sequences from the western central atlantic ocean and the vocontian basin southeast france through application of the walsh spectral method to detailed stratigraphic sections the repetitious bedding in these sequences appears to be the product of cyclic climatic changes controlled by the orbital forcing obliquity seems to be the most important and persistent orbital element responsible for cyclic sedimentation whereas precession is less important upper berriasian and valanginian strata from the atlantic ocean contain indications of eccentricity induced periodicity and of a nonlinear response of the climatic system variations in orbitally tuned pelagic sedimentation rates in the atlantic ocean correlate with the changes in the character of cycles and with the occurrence of calcareous turbidites therefore this suite of sedimentary features are responding to evolving paleoceanographic conditions and possible relative sea level fluctuations the orbitally tuned durations of the valanginian and hauterivian stages in the vocontian basin are a minimum of 5 9 and 5 3 m y respectively

berriasian early cretaceous radiometric ages from the grindstone creek section sacramento valley california abstract the grindstone creek section glenn county northern california is a sequence of hemipelagic mudstone siltstone and sandstone interbedded with concretionary limestone and a few thin tuffs and bentonites two tuffs have been collected from a narrow interval of this sequence and subjected to mineralogical and isotopic analyses uzpb isotopic analyses of zircon fractions from these volcanic horizons indicate an age of 137 1 1 6 0 6 ma a detailed investigation has been conducted on the calcareous nannofossil stratigraphy of this section based on numerous samples with moderately preserved assemblages the nannoflora is largely of tethyan affinity and allows direct correlation with the berriasian stratotype section with sections with published magnetostratigraphies and with a dsdp site drilled between known magnetic anomalies the dated tuffs lie in the lower part of the upper berriasiancretarhabdus angustiforatus zone assipetra infracretacea subzone and within the narrow range ofrhagodiscus nebulosus at three different sections this subzone can be correlated with m sequence polarity zones m16 and m16n an independent magnetostratigraphic correlation is provided at dsdp site 387 drilled between anomalies m15 and m16 where basal sediments containr nebulosus buchia collected within a meter of the lower tuff lie within theb uncitoides zone which is berriasian in age the upper tuff level which occurs 65 m above the lower tuff is situated within the overlyingb pacifica zone this zone had previously been correlated with the early valanginian but is clearly also partly of berriasian age based on nannofossil stratigraphy our results allow an estimate of the age of the berriasian valanginian and jurassic cretaceous boundaries of 135 1 ma and 141 1 ma respectively and these fall within the range of but differ significantiy from several published time scales

stream capture and piracy recorded by provenance in fluvial fan strata abstract stream capture and piracy in tectonically active regions have been described in geomorphic systems worldwide however few studies show the influence stream capture has on the rock record we present an analysis of fluvial fan stratigraphy that developed as a result of multiple stream capture events building a complex stratigraphic succession beneath the lawrence livermore national laboratory llnl california the llnl site is located in the southeast portion of the tectonically active livermore basin a transpressional basin in the california coast ranges geomorphic evidence for this stream capture include 1 the arroyo seco enters the basin from the south through an uplifted fault block 2 south of this fault block lies an abandoned arroyo seco fluvial fan 3 north of the fault block in the livermore basin arroyo seco built a 7 km2 fluvial fan apparently forcing the arroyo las positas a smaller stream that enters the basin from the east northward around the arroyo seco fan and 4 a knickpoint exists near the point of capture on arroyo seco stratigraphic evidence reflecting this shift in the arroyo seco position into the livermore basin was evaluated through a provenance study of 215 gravel units from 34 boreholes spaced evenly over the 2 6 km2 llnl site the arroyo seco derives its sediment from both the jurassic cretaceous franciscan assemblage and the altamont hills which are comprised of mesozoic great valley group and tertiary continental sediments the arroyo las positas drains only the altamont hills and thus lacks the franciscan assemblage derived clasts the origin of the individual gravel units was determined by the percentage of franciscan assemblage indicator pebbles red chert green chert and blueschist in the samples through this analysis we determined that high percentage franciscan assemblage derived clasts were present below a depth of approximately 35 m below the surface low percentage franciscan assemblage derived clasts were present at depths between 35 m and 18 m and high percentage franciscan assemblage derived clasts were present from depths of approximately 18 m to the surface of the fluvial fan these results indicate that the arroyo seco flowed north and deposited sediments at the llnl site then was later absent from the basin at which time it formed a fan south of the fault block during this absence of the arroyo seco the arroyo las positas a westerly flowing stream dominated the sediment supply at the llnl site the arroyo seco was then captured by a gully headward eroding through the uplifted fault block redirecting the arroyo seco into the basin once again this history of multiple stream captures created three stratigraphic units with alternating overall channel and paleoflow orientations

statistical evidences of seismo ionospheric precursors applying receiver operating characteristic roc curve on the gps total electron content in china abstract evidence of the seismo ionospheric precursor sip is reported by statistically investigating the relationship between the total electron content tec in global ionosphere map gim and 56 m 6 0 earthquakes during 1998 2013 in china a median based method together with the z test is employed to examine the tec variations 30 days before and after the earthquake it is found that the tec significantly decreases 0600 1000 lt 1 6 days before the earthquake and anomalously increases in 3 time periods of 1300 1700 lt 12 15 days 0000 0500 lt 15 17 days and 0500 0900 lt 22 28 days before the earthquake the receiver operating characteristic roc curve is then used to evaluate the efficiency of tec for predicting m 6 0 earthquakes in china during a specified time period statistical results suggest that the sip is the significant tec reduction in the morning period of 0600 1000 lt the sip is further confirmed since the area under the roc curve is positively associated with the earthquake magnitude

the ionospheric anomalies prior to the m9 0 tohoku oki earthquake the gps total electron content tec data were used to investigate the ionospheric abnormal behaviors prior to the 2011 tohoku oki earthquake the observations show a significant enhancement in tec on march 8 2011 and during the same period the solar activity also has a large increase both an empirical model and a theoretical model were used to check whether the tec anomalies were entirely contributed by the increase in solar radiation the comparison between the observations and the simulation results shows that only the solar radiation enhancement was not enough to produce the observed significant tec enhancement it means that some additional mechanisms such as the per earthquake ionospheric disturbance or the geomagnetic activities may play a significant role in the significant tec enhancement on march 8 the temporal spatial distribution of the extreme tec enhancement within 30 days before the earthquake was particularly pursued it is found that the extreme enhancement was persistently located in the region adjacent to the epicenter and the magnetic conjugate point for a long time of 16 h in addition a geomagnetic disturbance with kp 4 occurred on march 7 therefore the significant tec enhancement on march 8 might be related to the m9 0 tohoku oki earthquake and the geomagnetic disturbance

temporal and spatial precursors in ionospheric total electron content of the 16 october 1999 mw7 1 hector mine earthquake 1 in this paper temporal and spatial analyses are employed to detect seismo ionospheric precursors sips in the ionospheric total electron content tec during the 16 october 1999 mw7 1 hector mine earthquake to discriminate anomalies caused by global effects such as solar radiations magnetic storms etc and local effects such as earthquake we cross examine the gps tecs and their gradients in the eastward and northward directions at epicenter centers of the hector mine area and the other two reference areas at similar magnetic latitudes in europe and japan temporal variations of the northward tec gradient suggest sips most likely appearing on days 6 5 before the earthquake a global search by using the tec of the global ionosphere map shows that the tec increase and decrease anomalies continuously and specifically appear around the epicenter on day 5 before the earthquake

observations and simulations of seismoionospheric gps total electron content anomalies before the 12 january 2010 m7 haiti earthquake 1 in this paper the total electron content tec of the global ionosphere map gim is used to detect seismoionospheric anomalies associated with the 12 january 2010 m7 haiti earthquake and an ionospheric model is applied to simulate the detected anomalies the gim temporal variation shows that the tec over the epicenter significantly enhances on 11 january 2010 1 day before the earthquake the latitude time tec ltt plots reveal three anomalies 1 the northern crest of equatorial ionization anomaly eia moves poleward 2 the tecs at the epicenter and its conjugate increase and 3 the tecs at two dense bands in the midlatitude ionosphere of 35 n and 60 s further enhance the spatial analysis demonstrates that the tec enhancement anomaly appears specifically and persistently in a small region of the northern epicenter area the simulation well reproduces the three gim tec anomalies which indicate that the dynamoelectric field of the ionospheric plasma fountain might have been perturbed by seismoelectric signals generated around the epicenter during the earthquake preparation period

temporal and spatial precursors in the ionospheric global positioning system gps total electron content observed before the 26 december 2004 m9 3 sumatra andaman earthquake 1 we report seismo ionospheric precursors of anomalous decreases in the total electron content tec appearing day 5 prior to an m9 3 earthquake the largest one in the last five decades which occurred in sumatra andaman indonesia on 26 december 2004 sequences of global ionosphere maps of the tec derived from worldwide ground based receivers of the global positioning system gps are used to statistically study the temporal and spatial precursors of the earthquake it was found that the temporal precursor of the gps tec around the epicenter was significantly reduced during the afternoon period on d 5 before the earthquake the spatial precursors prominently persistently and simultaneously appear around the epicenter and its conjugate areas of the sumatra andaman earthquake

variations of ionospheric total electron content during the chi chi earthquake on 20 september1999 ut 21 septemberin local time lt a large earthquake mw 7 7 struck central taiwan nearthe small town of chi chi the greatest plasma frequency in the ionosphere fof2 observed by the chung li ionosonde 25 0 n 121 2 e reveals three clear precur sors at 1 3 and 4 days prior to the earthquake this paper examines the ionospheric total electron content tec ob served by a network of the global positioning system gps receivers in taiwan area it is found that variations in fof2 and overhead tec recorded at chung li have a similar ten dency combining the data of the network of 13 gps re ceivers time and spatial variations of tec prior to the chi chi earthquake are examined results show that the equa torial anomaly crest moves equatorward and its tec value significantly decreases 1 3 and 4 days before the earth quake a comparison between the disturbed and reference previous 15 day median days confirms that tec decreases significantly around the epicenter in the afternoons of these days finally possible mechanisms are proposed and dis cussed

preseismic ionospheric anomalies detected before the 2016 kumamoto earthquake on 15 april 2016 the kumamoto earthquake mw 7 3 occurred in japan with no warning signals global navigation satellite system gnss receivers provide useful information on disturbances in the ionosphere by calculating the changes in total electron content tec which is the number of electrons in the ionosphere here we show our recently proposed correlation analysis of tec data which can detect the preseismic ionospheric anomalies from the public gnss data our method detected the ionospheric anomaly several tens of minutes before the 2016 kumamoto earthquake near its epicenter furthermore we gave an indicator to distinguish between the preseismic tec anomalies and the medium scale traveling ionospheric disturbances mstids by calculating the anomalous area rates these results support the hypothesis for existence of the preceding phenomena before large earthquakes

m sequence geomagnetic polarity time scale mhtc12 that steadies global spreading rates and incorporates astrochronology constraints 1 geomagnetic polarity time scales gptss have been constructed by interpolating between dated marine magnetic anomalies assuming uniformly varying spreading rates a strategy to obtain an optimal gpts is to minimize spreading rate fluctuations in many ridge systems however this has been possible only for a few spreading centers we describe here a monte carlo sampling method that overcomes this limitation and improves gpts accuracy by incorporating information on polarity chron durations estimated from astrochronology the sampling generates a large ensemble of gptss that simultaneously agree with radiometric age constraints minimize the global variation in spreading rates and fit polarity chron durations estimated by astrochronology a key feature is the inclusion and propagation of data uncertainties which weigh how each piece of information affects the resulting time scale the average of the sampled ensemble gives a reference gpts and the variance of the ensemble measures the time scale uncertainty we apply the method to construct mhtc12 an improved version of the m sequence gpts late jurassic early cretaceous 160 120 ma this gpts minimizes the variation in spreading rates in a global data set of magnetic lineations from the western pacific north atlantic and indian ocean nw of australia and it also accounts for the duration of five polarity chrons established from astrochronology cm0r through cm3r this gpts can be updated by repeating the monte carlo sampling with additional data that may become available in the future

late cretaceous eocene nannofossil and magnetostratigraphic correlations near gubbio italy abstract using a modified sample preparation technique we have been able to establish a detailed lower campanian to upper eocene nannofossil stratigraphy in the bottaccione and contessa highway sections near gubbio appearance and extinction levels of virtually all the commonly used calcareous nannofossil zonal markers have been recognized and can now be closely correlated with the planktonic foraminifera zonation and the magnetic reversal stratigraphy previously established in these sections comparisons with the nannofossil calibrations of the oceanic magnetic anomaly sequence in deep sea drilling project dsdp sites suggest that magmetic subchrons c17n and c25n are missing in the bottaccione section the observed variability of the relative stratigraphic position of most plankton events is confirmed to less than one magnetic subchron absolute abundance paleobiogeographic restriction and differential preservation render some of the traditionally used biostratigraphic events less reliable than others

electro magnetic earthquake bursts and critical rupture of peroxy bond networks in rocks abstract we propose a mechanism for the low frequency electromagnetic emissions and other electromagnetic and electric phenomena which have been associated with earthquakes the mechanism combines the critical earthquake concept and the concept of crust acting as a charging electric battery under increasing stress the electric charges are released by activation of dormant charge carriers in the oxygen anion sublattice called peroxy bonds or positive hole pairs php where a php represents an o 3 x oo yo 3 with x y si 4 al 3 i e o in a matrix of o 2 of silicates we propose that php are activated by plastic deformations during the slow cooperative build up of stress and the increasingly correlated damage culminating in a large critical earthquake recent laboratory experiments indeed show that stressed rocks form electric batteries which can release their charge when a conducting path closes the equivalent electric circuit we conjecture that the intermittent and erratic occurrences of em signals are a consequence of the progressive build up of the battery charges in the earth crust and of their release when crack networks percolate through the stressed rock volumes providing a conductive pathway for the battery currents to discharge em signals are thus expected close to the rupture either slightly before or after that is when percolation is most favored the proposed mechanism should be relevant for the broader understanding of fractoemissions

atmospheric anomalies observed during earthquake occurrences 1 appearance of anomalies in the atmosphere before earthquakes eqs has been verified through observation of anomalous transmission of vhf electromagnetic em waves beyond line of sight anomalous increase of the received intensity for a few minutes several hours on a day was identified by the previous 15 day running median and its inter quartile range the cross correlation between the eq occurrences and the anomalies shows that the appearance of anomalies was significantly enhanced within 5 days before m 4 8 eqs the one day average number of the anomaly appearance within 5 days was found 2 4 times larger than that of other days through the polarization measurement of the received em waves the anomalies were found to occur in the atmosphere index terms 6904 radio science atmospheric propagation 6964 radio science radio wave propagation 7223 seismology seismic hazard assessment and prediction citation fujiwara h m kamogawa m ikeda j y liu h sakata y i chen h ofuruton s muramatsu y j chuo and y h ohtsuki 2004 atmospheric anomalies observed during earthquake occurrences geophys res lett 31 l17110

biostratigraphic correlation of mesozoic polarity chrons cm1 to cm23 at capriolo and xausa southern alps italy abstract two pelagic limestone sections in the southern alps spanning the kimmeridgian late jurassic to barremian early cretaceous interval yield magnetostratigraphies which can be correlated to oceanic magnetic anomalies m1 m3 and m8 m23 this includes the interval m11 m13 which has not previously been correlated to a sedimentary section detailed investigations of nanofossils and calpionellids in these sequences allow precise correlation of polarity chrons to biostratigraphic events and these results compare favorably to those of previous studies the close correspondence in polarity pattern between that interpreted from the m8 to m15 interval in the hawaiian lineations and that recorded at the capriolo section suggests that sedimentation rates in this sequence and spreading rates in the hawaiian lineations were rather constant during this interval in contrast the sedimentation rate at the xausa section appears to increase up section with the facies transition from the rosso ammonitico to the maiolica formation

ionosphere plasma bubbles and density variations induced by pre earthquake rock currents and associated surface charges 1 recent ionospheric observations indicate that the total electron content tec may anomalously decrease or increase up to 5 20 before the occurrence of big earthquakes the ionospheric density variations can be caused by earth surface charges currents produced from electric currents associated with the stressed rock we formulate a coupling model for the stressed rock earth surface charges atmosphere ionosphere system the stressed rock acts as the dynamo to provide the currents for the coupling system the electric fields and currents in the atmosphere and the lower boundary of ionosphere are obtained by solving the current continuity equation j 0 where j is the current density a three dimensional ionosphere simulation code is then used to study the ionospheric dynamics based on the obtained electric fields and currents the simulation results show that a current density jrock 0 2 10 a m2 in an earthquake fault zone is required to cause daytime tec variations of 2 25 the simulation results also show that a current density jrock 0 01 1 a m2 can lead to nighttime tec variations of 1 30 as well as the formation of a nighttime plasma bubble equatorial spread f extending over the whole magnetic flux tube containing the earthquake epicenter we suggest that observations of daytime and nighttime tec variations and a nighttime plasma bubble within the affected region can be used as precursors for earthquake prediction

magnetostratigraphy of the berriasian stratotype section berrias france the berriasian early cretaceous stratotype section berrias ardeche france 30 m thick consists of well bedded blue gray pelagic limestone the biostratigraphic subdivision of this section is based on ammonite and calpionellid zonations magnetostratigraphic study has yielded a reliable magnetic polarity sequence magnetite is the principal ferrimagnetic mineral and the characteristic remanent magnetization chrm directions are clearly defined after thermal or alternating field demagnetization ammonite and calpionellid zones allow biostratigraphic calibration of the magnetic polarity sequence with precision on the order of an ammonite sub zone this magnetic polarity sequence can be correlated with marine magnetic anomalies m15 to m17n m15 occurs within the upper part of theboissieri ammonite zone while m17n occurs within theoccitanica ammonite zone

valanginian to aptian calcareous nannofossil stratigraphy and correlation with the upper m sequence magnetic anomalies abstract calcareous nannofossil stratigraphy has been investigated in lower cretaceous italian sections at gorgo a cerbara presale and frontale all in the umbrian apennines and at cismon southern alps a modified sample preparation technique has allowed a thorough stratigraphic study of the well lithified maiolica limestone and although nannofossil preservation is generally quite poor the major valanginian to aptian marker species can be detected nine nannofossil events can be determined and correlated to magnetic stratigraphies previously established in these sections nannofossil stratigraphy confirms most magnetostratigraphic correlations made between sections and allows a more precise correlation of magnetic chrons m 0 to m 11 with the valanginian hauterivian barremian and aptian stages the results obtained differ considerably from previous timescales nannofossil events recorded in the various sections may be time transgressive by as much as one magnetic chron probably due to differential preservation

spatial and temporal characteristics of the microseismicity preceding the 2016 m l 6 6 meinong earthquake in southern taiwan before the ml 6 6 meinong earthquake in 2016 intermediate term quiescence qi foreshocks and short term quiescence qs were extracted from a comprehensive earthquake catalog in practice these behaviors are thought to be the seismic indicators of an earthquake precursor and their spatiotemporal characteristics may be associated with location magnitude and occurrence time of the following main shock hence detailed examinations were carried out to derive the spatiotemporal characteristics of these meaningful seismic behaviors first the spatial range of the qi that occurred for 96 days was revealed in and around the meinong earthquake second a series of foreshocks was present for 1 day clustered at the southeastern end of the meinong earthquake third qs was present for 3 days and was pronounced after the foreshocks although these behaviors were recorded difficultly because the qi was characterized by microseismicity at the lower cut off magnitude between ml 1 2 and 1 6 and most of the foreshocks were comprised of earthquakes with a magnitude lower than 1 8 they carried meaningful precursory indicators preceding the meinong earthquake these indicators provide the information of 1 the hypocenter which was indicated by the area including the qi foreshocks and qs 2 the magnitude which could be associated to the spatial range of the qi 3 the asperity locations which might be related to the areas of extraordinary low seismicity and 4 a short term warning leading of 3 days which could have been announced based on the occurrence of the qs particularly qi also appeared before strong inland earthquakes so that qi might be an anticipative phenomenon before a strong earthquake in taiwan

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

hydrothermal alteration of volcanic rocks at the mclaughlin gold deposit northern california the plio pleistocene mclaughlin mine is a large hot spring gold silver mercury deposit located in the northern coast ranges of california two distinctly different suites of volcanic rocks host mineralization an upper jurassic basalt part of the coast range ophiolite and an upper cenozoic basaltic andesite part of the clear lake volcanic field the two suites of volcanic rocks range from least altered rocks showing primary igneous mineralogy to intensely altered rocks composed of an assemblage of quartz montmorillonite sericite and adularia mass balance calculations indicate almost total loss of na ca mg and sr and large gains in and ba as a result of the hydrothermal alteration the mass flux corresponds to the replacement of plagioclase feldspar with sericite and adularia and mafic minerals with montmorillonite trace elements show no evidence for mobility rocks adjacent to the hydrothermal system have the greatest 18o values and the highest calculated mass flux suggesting the greates

subionospheric vlf signal perturbations possibly related to earthquakes a likely vlf subionospheric signal effect related to seismic activity was first reported by hayakawa et al 1996a b in association with the great kobe earthquake we have analyzed similar data during periods around 10 other great earthquakes magnitude m 6 in order to understand the main features of such an effect the following characteristics emerged from our analysis the effect appears as a transient oscillation with a 5 to 10 day period which is initiated a few days before a large earthquake and decays over a few days to weeks after it it is mainly related to crustal earthquakes it appears when resonant atmospheric oscillations with periods in a range of 5 11 days exist before the earthquake the seismic influence on the vlf signal is probably explained by the generation of long period gravity waves during the earthquake process and their intensification at heights of 70 90 km

a systematic compilation of earthquake precursors article a survey of published scientific literature was undertaken to identify and catalog observed earthquake pre cursors the earthquake precursors selected for analysis included electric and magnetic fields gas emissions groundwater level changes temperature changes surface deformations and seismicity for each of these precursors the published scientific literature was searched to document the statistics of each reported earth quake precursor spatial extent time duration amplitude signal noise ratio to analyze dependence of the observable for each precursor on earthquake magnitude and to explore proposed physical models to explain eachearthquakeprecursor somegeneralcharacteristics wereobservedfortheseprecursoryphenomena first the largest amplitude precursory anomalies tend to occur before the largest magnitude earthquakes also the number of precursory anomalies tends to increase the closer in time to the occurrence of the earthquake finally theprecursoryanomaliestendtooccurclosetotheeventualepicenterof theearthquake ingeneral the physical models indicate that all of the precursory phenomena are related to deformation that occurs near the fault prior to the main earthquake while the models provide plausible physical explanations for the pre cursors there are many free parameters in the models that are poorly resolved

is an unusual large enhancement of ionospheric electron density linked with the 2008 great wenchuan earthquake 1 on 12 may 2008 at 0628 ut a major earthquake ms 8 0 struck wenchuan county 31 0 n 103 4 e in southwest china the maximum ionospheric electron density at f2 peak nmf2 recorded an unusual large enhancement during the afternoon sunset sector by the chinese ionosondes over wuhan 30 5 n 114 4 e and xiamen 24 4 n 123 9 e which are close to the earthquake epicenter an averaged increase at these two stations is about 2 times on a geomagnetic quiet day 9 may kp 2 3 days prior to the earthquake relative to the median value of 1 12 may whereas the increase was much less significant over yamagawa 31 2 n 130 6 e and okinawa 26 7 n 128 2 e in japan combining the data from the network of 58 global positioning system receivers around china and the global ionospheric map the variations of the total electron content reveal the region where enhancement persisted for a long period to be within longitudes 90 130 e our results suggest that this abnormal enhancement is most possibly a seismo ionospheric signature

contrasting early and late mesozoic petrotectonic evolution of northern california devonian middle jurassic terrane assemblies in the klamath mountains and sierra nevada foothills consist chiefly of ophiolite chert argillite sequences mafic ultramafic complexes are oceanic whereas associated fine grained deep water terrigenous sediments were derived mainly from adjacent previously docked klamath sierran terranes coeval calc alkaline arc rocks are volumetrically rare geologic and petrochemical relations suggest a rifted arc origin for klamath mafic metavolcanic units inter layered with distal turbidites in the 170 200 ma north fork terrane detrital zircon u pb ages indicate that the clastic debris had a regional eastern klamath source the eastern hayfork cherty melange contains ophiolitic scraps and distinctive olistostromal sandstone blocks evidently derived from the nearby eastern klamath antelope mountain quartzite the seaward 200 ma rattlesnake creek terrane is an ophiolitic melange with north fork petrotectonic affinities the north fork eastern hayfork rattlesnake creek amalgam correlates with the calaveras complex and the outboard jura triassic arc belt in the sierran foothills geochemical bulk rock and zircon u pb age data support interpretation of the 200 ma jura triassic arc as an adjacent offshore mafic belt overlying a 300 ma ophiolitic basement these oceanic complexes were sutured against the central metamorphic belt eastern klamath feather river northern sierra terrane backstop before deposition and deformation of the outboard upper jurassic galice and mariposa formations klamath sierran terrane assemblies reflect 230 m y of transpression transtension involving only minor episodes of subduction producing ubiquitous ophiolite chert argillite lithologies and rare felsic arc rocks in contrast the late jurassic to largely cretaceous klamath sierra nevada quartzo feldspathic volcanic plutonic arc attests to massive calc alkaline magmatism attending a strong eastward component of underflow by the farallon plate the coeval galice mariposa formations followed by the cretaceous great valley forearc and franciscan trench deposits are first cycle felsic debris shed mainly from the klamath sierran arc these units record 70 m y of rapid sialic crustal growth attending major periods of approximately margin normal convergence this profound transition in northern california included devonian middle jurassic rifting drifting and stranding of ophiolite chert argillite terranes along an adjacent curvilinear continental margin then nearly head on cretaceous subduction that resulted in massive calc alkaline igneous activity the erosion of which generated the felsic great valley group forearc basin and franciscan complex trench clastic sedimentary units

facies history of the upper jurassic lower cretaceous great valley sequence response to structural development of an outer arc basin abstract the facies history of the great valley sequence is closely linked to structural events in an arc trench system upper jurassic lower cretaceous marine rocks as much as 8 500 m thick along the western margin of the sacramento valley northern california were deposited on slopes and submarine fans that extended over an unstable basement floored by ophiolitic rocks paleocurrent and paleoslope analyses indicate that eastward subduction initiated as early as kimmeridgian created an outer arc ridge which bounded the west side of the basin debris was shed dominantly from the north and east but significant contributions were ridge derived sediment fabrics structures and bedding styles indicate that earliest deposition on basin plains and on eastward facing slopes was followed at le st until the valanginian by a stable sedimentological framework of prograding and avulsing submarine fans characterized by broad shallow midfan channels depositional lobes and abundant thick deposits of interchannel mud the great valley rocks are transected by northwest trending faults that produced strike separation of the east dipping strata smooth facies transitions but with abrupt thickness variations across faults suggest that faulting with some normal component of motion was contemporaneous with deposition during latest jurassic and earliest cretaceous later movement either strike slip or reverse brought coarse inner fan facies that were deposited on klamath basement into fault contact with basin plain facies that were deposited on ophiolitic basement

a cretaceous and jurassic geochronology an integrated geomagnetic polarity and geologic time scale for the jurassic and cretaceous periods is presented based on various methods according to the availability of definitive isotopic ages an age calibrated sea floor spreading model is used to interpolate the ages of the kimmeridgian to barremian and the campanian to maestrichtian stages numerical age estimates for the aptian to santonian stage boundaries follow published isotopic age determinations the hypothesis of equal duration of ammonite zones is employed as a vernier to apportion time for the hettangian to oxfordian stages the new scale results in ages of 208 ma for the base of the jurassic 144 ma for the jurassic cretaceous boundary and 66 5 ma for the top of the cretaceous the integrated biostratigraphic magnetostratigraphic and geochronometric record serves as a working hypothesis for geologic correlation of jurassic and cretaceous strata

gradual reduction in ionospheric f 2 region before the 2013 lushan earthquake contributed to the forthcoming earthquake or solar activity ionospheric anomalies before earthquakes during geomagnetic quiet conditions have been extensively discussed due to the importance of earthquake prediction however because of the high variability of ionosphere a real caution should be adopted before attributing the observations to seismo ionospheric precursors sips in an investigation of contradictory results in ionospheric variation before 2013 lushan earthquake we examine the ionospheric variation versus solar activity in order to assess the influence of solar activity of 27 day periodicity on ionospheric variation a quadratic regression model is developed by using the data of f2 layer critical frequency fof2 in april of 2008 2014 using the model ionospheric variation before the 2013 lushan earthquake is analyzed the results show that fof2 was strongly correlated with solar activity index f10 7 and had a low correlation with the remaining by eliminating the contribution of solar radiation which indicates that the gradual reduction in fof2 before the earthquake was contributed to the variation of solar radiation rather than the forthcoming earthquake

a magnetic polarity time scale for the early cretaceous and late jurassic abstract the ages of polarity chrons in previous m sequence magnetic polarity time scales were interpolated using basal sediment ages in suitably drilled dsdp holes this method is subject to several sources of error including often large paleontological age ranges magnetostratigraphic results have now tied the early cretaceous and late jurassic paleontological stage boundaries to the m sequence of magnetic polarity the numeric ages of most of these boundaries are inadequately known and some have been determined largely by intuition an examination of relevant data suggests that 114 ma 136 ma and 146 ma are optimum estimates for the ages of the aptian barremian cretaceous jurassic and kimmeridgian oxfordian stage boundaries respectively each of these boundaries has a good correlation to the m sequence of magnetic reversals the magnetostratigraphic tie level ages are linearly related to the spreading distance and have been used to calculate a new magnetic polarity time scale for the early cretaceous and late jurassic all stage boundaries in this time interval were correlated by magnetic stratigraphy to the proposed new time scale which was then used to estimate their numeric ages these are with the approximate relative errors of placement within the m sequence aptian barremian 114 ma 0 5ma barremian hauterivian 121 ma 2 0 1 5ma hauterivian valanginian 126 ma 0 5 3 0ma valanginian berriasian 131 ma 0 5 2 5ma berriasian tithonian 136 ma 1 0ma tithonian kimmeridgian 143 ma 0 5ma kimmeridgian oxfordian 146 ma 0 2ma the absolute errors of these interpolated stage boundary ages depend on the accuracy of the tie level ages

seismo ionospheric signatures prior to m 6 0 taiwan earthquakes this paper examines variations of the greatest plasma frequency in the ionosphere fof2 recorded by the chung li ionosonde 25 0 n 121 1 e before m 6 0 earthquakes during 1994 1999 the 15 day running median and the associated inter quartile range are utilized as the reference and the upper or lower bounds to monitor the ionospheric fof2 variations for finding seismo ionospheric signatures precursors of the earthquakes it is found that precursors in the form of the recorded fof2 falling below its associated lower bound around 1200 1700 lt appear 1 6 days prior to these earthquakes on september 20 1999 ut september 21 taiwan local time a large mw 7 7 earthquake struck central taiwan near the small town of chi chi we analyzed the fof2 and found three clear precursors 1 3 and 4 days prior to the chi chi earthquake

spatiotemporal characteristics of the geomagnetic diurnal variation anomalies prior to the 2011 tohoku earthquake mw 9 0 and the possible coupling of multiple pre earthquake phenomena abstract xu et al 2013 and han et al 2015 have reported unusual behaviors of geomagnetic diurnal variation gdv in the vertical component prior to the 2011 off the pacific coast of tohoku earthquake mw 9 0 to make a better understanding of this phenomenon temporal spatial analyses of gdv have been applied in this study geomagnetic data of long term observations at 17 stations in japan have been analyzed using the same method in han et al 2015 ratios of diurnal variation range between the reference station kak and the target stations have been computed after removing seasonal variations the 15 day backward running mean values of the ratios in the vertical component shows a clear anomaly exceeding the statistical threshold about 2 months before the mega event at both esa and miz stations in the tohoku region locations of anomalies in spatial distribution show a good correlation with the epicenter of the mw 9 0 earthquake these spatiotemporal results are consistent with those obtained from other independent observations such as groundwater level and gps displacements the coupling of multiple pre earthquake phenomena may help to understand the preparation process of a mega earthquake in the subduction zone

magnetostratigraphy of the jurassic cretaceous boundary there is no internationally recognized standard for the jurassic cretaceous boundary a precise biostratigraphical correlation between different paleobiogeographic provinces is impossible due to barriers blocking faunal exchange this problem may be overcome by using magnetic polarity events which are globally isochronous the magnetic polarity time scale of the latest jurassic and earliest cretaceous enables determination of the relative timing and age span of several possible definitions of this system boundary among different biostratigraphies within the tethys atlantic faunal realm therefore the polarity scale can be used as a regional standard for this interval of time the base of reversed polarity chron m18 falls in the middle of the interval covered by various recent definitions of the tethyan jurassic cretaceous boundary if polarity chron m18 also proves to be recognizable in the boreal realm then its basal magnetic reversal could serve as a precise globally correlatable event for defining the jurassic cretaceous boundary

short term earthquake prediction current status of seismo electromagnetics abstract loss of human lives as a result of earthquakes is caused overwhelmingly by the collapse of buildings within less than a few minutes of main shocks the most urgent countermeasure consists of two key elements one is strengthening of weak structures and the other is short term earthquake prediction short term prediction needs precursors although some promising precursors are reported the prevailing views in japan and elsewhere are overly pessimistic the pessimism largely roots in the fact that short term precursors are generally non seismic and tools developed for seismology are not designed to detect them nonetheless nationally funded large scale earthquake prediction programs always emphasize the need to reinforce seismometer networks they do not take into account the views of those in the science community who point to the importance of non seismic precursors while there are well founded causes to be skeptical the situation needs to be improved one reason for skepticism is that the observations of precursors have not yet been perfect enough and another is that some important fundamental aspects of non seismic precursors are still unresolved we review some of these problems

seismic reversal pattern for the 1999 chi chi taiwan mw 7 6 earthquake we in this study have calculated the standard normal deviate z value to investigate the variations in seismicity patterns in the taiwan region before and after the chi chi earthquake we have found that the areas with relatively high seismicity in the eastern taiwan became abnormally quiet before the chi chi earthquake while the area in the central taiwan with relatively low seismicity showed unusually active such a spatially changing pattern in seismicity strikingly demonstrates the phenomenon of seismic reversal and we here thus present a complete representative cycle of seismic reversal embedding in the changes of seismicity patterns before and after the chi chi earthquake

high accuracy synchronism for seismic reflectors and 14c ages holocene prodelta succession of the kiso river central japan abstract horizons at 500 yr intervals for the past 6000 years can be inferred in two cores drilled along a high resolution seismic line in the prodelta of the kiso river ise bay central japan these horizon ages clearly indicate that a given seismic reflection line in the profile is isochronous synchronism between ages and reflectors in the succession is especially distinct for the interval from 5000 to 2500 yr bp despite the reflectors having inclined planes and having the same ages at different depths these data indicate that the kiso river delta prograded to form a downlap surface before the maximum flooding stage of the post glacial relative sea level rise at about 6000 yr bp delta progradation beginning late in the transgressive stage was caused by the flow of large amounts of sediment into this steep river that is part of the active japanese volcanic arc

syncollisional basin development in the appalachian orogen the saint daniel melange southern quebec canada the saint daniel melange is an orogen scale sedimentary basin of the quebec appalachians that is commonly interpreted as the remnant of a subduction complex formed during the taconian orogeny however geochronological structural and stratigraphical data from laurentian continental margin rocks and adjacent ophiolitic rocks in southern quebec indicate that the saint daniel melange is an olistostromal syncollisional piggyback basin that represents the base of the magog group forearc basin the regional stratigraphic framework of the saint daniel melange and its relationships with underlying and overlying rock units have been established on the basis of six stratigraphic sections from the thetford mines asbestos and mont orford ophiolitic complexes our results imply that 1 the saint daniel melange is a sedimentary sequence that unconformably overlies different structural and pseudostratigraphic levels of the southern quebec ophiolites 2 it is made up of four distinct and laterally discontinuous units that record the obduction of ophiolites onto laurentia and exhumation of basement rocks followed by subsidence and deposition of the overlying saint victor formation of the magog group 3 the sedimentary rocks of the saint daniel record a transition from ophiolite dominated to continental sources indicating progressive exhumation of both the ophiolite and the continental margin upon which it was obducted 4 0 ar 3 9 ar analysis of muscovite from metamorphic rock fragments in debris flows of the melange yield an age of 467 2 ma which is within the range of ar ages measured in metamorphic rocks that underlie the ophiolites and indicates the uplift of metamorphosed continental deposits during or shortly after obduction 4 the saint daniel melange is stratigraphically overlain by the magog group and represents the base of a syncollisional basin developed in a forearc setting during the taconian orogeny

timing and structural expression of the nevadan orogeny sierra nevada california the nevadan orogeny was a very short lived event in the late jurassic that involved the deformation of a great variety of rock types and paleozoic and mesozoic terranes throughout the extent of the sierra nevada the nevadan structures show great variation in style but relatively constant orientations these relations can be explained by considering the prior histories of the various terranes slaty cleavages and tight folds are the characteristic main phase structures in the western belt of jurassic island arc volcanic rocks and flysch type sedimentary rocks a strip of phyllites and greenschists along the eastern edge of the belt apparently represents similar jurassic rocks that were deformed and metamorphosed at greater depths probably during underthrusting of the western belt beneath the central belt the central belt of paleozoic metasedimentary and metavolcanic rocks shows the most extreme variation in style of main phase structures from weak spaced to crenulation cleavages in the south where polyphase deformed rocks formed a structural basement to slaty and phyllitic cleavages and asymmetric to isoclinal folds in the north where most of the paleozoic basement rocks lack penetrative pre nevadan fabrics eastward directed thrust faulting apparently was important only in the northern part of the range where main phase deformation was most intense the eastern belt of jurassic and triassic magmatic arc volcanic and sedimentary rocks defines the core of a major synclinorium and the rocks contain penetrative slaty cleavages and asymmetric tight to isoclinal folds a late phase of nevadan structures consisting of northeast trending cleavages and minor folds also shows a marked variation in style from relatively intensely developed in the north to very weakly developed in the south the regional extent and geometry of the nevadan structures indicate that the nevadan orogeny involved underthrusting of island arc rocks on the west and significant crustal shortening in the central and eastern belts these features suggest that the nevadan orogeny resulted from the collision of the island arc western belt with an andean type arc eastern belt situated at the western edge of north america

early cretaceous transition from nonaccretionary behavior to strongly accretionary behavior within the franciscan subduction complex 1 during subduction at the franciscan trench beginning at 170 160 ma and continuing to the present marine sedimentary and lesser volcanic rocks have been underthrust accreted and metamorphosed to form the franciscan accretionary wedge the south fork mountain schist sfms forms the eastern margin and structural top of the wedge and so was apparently the first unit of substantial size to accrete into the franciscan new u pb ages of detrital zircons and 40ar 39ar ages of metamorphic white micas indicate that the sfms accreted surprisingly late in the time span of franciscan subduction probably at ca 123 ma at least parts of the valentine spring formation and yolla bolly terrane accreted soon thereafter therefore accretion of the sfms apparently marks a fundamental transition from virtually nonaccretionary behavior to strongly accretionary behavior in the franciscan forearc about 75 of modern forearcs are nonaccretionary so recognition of an early nonaccretionary period is consistent with modern examples the franciscan mafic high grade exotic blocks and related very small slabs which yield ca 132 to 169 ma metamorphic ages are the only well documented rock record of the early 40 m y long nonaccretionary period and represent very sparse accretion during that interval the transition into an accretionary regime at ca 123 ma was essentially synchronous with the end of the late jurassic early cretaceous magmatic lull in the sierra nevada magmatic arc with the waning of early cretaceous faulting and warping within the great valley forearc basin and possibly with changes in motion vectors of the pacific and farallon plates

reconstruction of holocene environmental changes in the kiso ibi nagara compound river delta nobi plain central japan by diatom analyses of drilling cores abstract holocene environmental changes were reconstructed by analyzing diatom assemblages from sediment cores ym kzn nk and mc from the nobi plain central japan five diatom assemblage zones were identified 1 at the beginning of the holocene freshwater species were dominant 2 then marine and brackish marine species increased indicating transgression 3 in the middle holocene proportions of marine and brackish marine species became almost constant with marine species dominant 4 marine species began to be replaced by freshwater species indicating marine regression as a result of delta progradation and 5 freshwater species again became dominant these diatom assemblages correlate with previously defined lithological units zones 1 and 2 with unit b fluvial to coastal plain zone 3 with unit c inner bay or prodelta zone 4 mainly with unit d1 delta front slope and zone 5 with units d2 delta front platform and e delta plain and flood plain although the shoreline migrated landward transgression faster than it migrated seaward regression transgressive diatom assemblage changes decrease in marine brackish water species took up to 1000 years whereas regressive changes required only a few hundred years diatom analysis is useful for reconstructing not only holocene sea level changes and sedimentary environments but also local geographic effects

paleomagnetic calibration of milankovitch cyclicity in lower cretaceous sediments abstract bedded pelagic limestones of early to mid cretaceous age may record cyclic climate variability driven by changes in the earth s orbit milankovitch cycles if properly calibrated the lithologic cycles could provide sedimentary chronometry at far shorter time scales than biostratigraphy and magnetic stratigraphy the lower cretaceous maiolica formation of northern and central italy displays rythmic bedding in sections whose magnetic reversal sequence is clearly correlated to the upper m series marine anomalies the magnetic reversals divide measured sections into 0 5 2 myr increments in which sedimentation rate assuming continous deposition can be measured to 15 25 accuracy paleomagnetically estimated sedimentation rates over a number of polarity zones establish with one exception a narrow range in periods of the carbonate cycles carbonate couplets have an estimated mean period of 23 5 kyr and prominent modulations in bedding thickness bundling have a mean period of 117 kyr kent and gradstein 1985 time scale the close match of sedimentary periodicities to orbital repeat times implies that the carbonate cycles reflect a combination of professional and eccentricity climatic forcing comparison of measured sections from different locations shows that bed to bed correlations are possible regionally cosistent with the milankovitch hypothesis episodes of barremian black shale deposition occur in the troughs of the short eccentricity cycle as roughly one half of the carbonate marl couplet or about 10 kyr duration it is possible to estimate both the timing relative to the top of reversed chron m 0 and duration of a period of unusual organic carbon rich deposition selli horizon in the early part of the cretaceous long normal magnetic polarity interval by tracing the sedimentary cycles up from the barremian strata

accumulation of organic carbon in five brazilian lakes during the holocene abstract a comparative study was made of organic carbon accumulation in five lacustrine environments in brazil large open water lake ponds with floating meadows and marshes the most representative cores were used to calculate the accumulation of total organic carbon toc in the sediment over the past 12 000 cal years bp carbon accumulation rates were determined using the toc concentration sediment in situ density 14 c calibrated ages and the interpolated sedimentation rate cm year 1 or sediment accumulation rate g m 2 year 1 the c n ratio and microscopic observations were used to characterise the sedimentary organic matter recent toc accumulation in the lakes was estimated at 7 41 g m 2 year 1 by averaging the last 500 years this variation roughly correlated with the present day ratio of watershed area vs lake area indicating that nutrient input is important for the modern accumulation of organic matter the accumulation rates were greatest in lakes with floating macrophytes the largest lake dom helvecio with a strong thermal stratification low primary production and low carbon accumulation had relatively well preserved organic matter when its low watershed area lake area ratio was considered the general increase in carbon accumulation during the holocene followed the expansion of lakes and the development of a wetter climate due to a growing penetration of the atlantic and amazonian wet air mass over brazil driven by insolation changes this change in carbon accumulation was not controlled by the higher water and nutrient inputs alone more organic matter was decomposed when lake levels were low at the beginning of the holocene some lakes were also influenced by higher inputs of allochthonous organic matter during the early and middle holocene these inputs included high concentrations of charcoal fragments lake morphology and its changes as the lake level rose as well as the nature of primary producers strongly influenced the carbon accumulation rates our understanding of how climate changes are linked to changes in the lacustrine environment should not be based on measuring organic matter alone but requires a good description of the organic matter and other limnological parameters

orbitally forced cyclical changes in the quantity of calcareous and siliceous microfossils in an upper jurassic to lower cretaceous pelagic basin succession bakony mountains hungary rhythmic changes were observed in the quantity of radiolarians and calpionellids preserved in an upper jurassic to lower cretaceous deep water succession in the bakony mountains of hungary statistical analysis revealed that for short periods order of 100 kyr the correlation of the two planktonic groups is negative over longer time intervals definite trends are recognized which can be explained by the combined effect of facies transition evolution of the calpionellids and rhythmic environmental climatic changes spectral analysis and time span calculations indicate that orbital forcing in the milankovitch frequency band influenced the observed changes

quantitative analysis of land transformation in a holocene delta an example from the tama river lowland central japan abstract human activities such as the expansion of agricultural and urban land use on subaerial deltas and landfilling of subaqueous deltas have large impacts on holocene deltas here we quantified the volume of the holocene deltaic deposits in the tama river lowland located in the tokyo metropolitan area by analyzing 3872 existing borehole sections using gis and evaluated artificial land transformation the total volume of deltaic deposits accumulated during the past 9000 years was estimated to be 3925 106 m3 of which artificially deformed near surface material ad 676 106 m3 occupies approximately 17 this ratio is much larger than that in the nobi plain 4 6 in the nagoya metropolitan area suggesting that the impact of anthropogenic disturbance on the delta has been greater in tokyo than in the nagoya metropolitan area approximately 71 of ad is distributed in the seaward area where landfills were created mainly after the taisho period 1912 1926 the source of the ad is considered to be dredged soil construction waste soil and mountain sand the remaining 29 of ad occurred in the landward area floodplain and delta plain and likely originates from the in situ disturbed sediments of the delta plain and floodplain in addition to earth fill the seaward ad deposits including redeposition by dredging within the delta accumulated at a rate of 4 79 106 m3 year which is much higher than that of the accumulation of natural deltaic deposits during the holocene 0 36 106 m3 year this clearly shows that anthropogenic forcing has become a strong influence on geomorphological and sedimentological processes within the delta

submarine crystal tuffs their origin using a lower devonian example from southeastern australia summary the submarine crystal rich volcaniclastics of the lower devonian merrions tuff contain concentrations of angular to euhedral volcanic quartz plagioclase and orthoclase lithic fragments largely altered vitriclasts are minor components and the average matrix content is 37 6 associated dacite andesite and rhyodacitic lavas have average groundmass contents of 64 2 rare shards in the graded pelitic tops of the thick volcaniclastic sedimentation units suggest that the mode of fragmentation originally was by explosive magmatic eruptions the sedimentology of the volcaniclastics suggests subsequent redeposition by cold state mass flow processes the volcaniclastics form an isotopically coherent suite and so redeposition must have occurred essentially contemporaneously with eruption the high crystal fragment concentration in these volcaniclastics is higher than lavas and ignimbrites and suggests some process whereby the groundmass fraction of the erupting magma is selectively removed so concentrating the crystal fraction the crystal rich character of the crystal tuffs is not simply due to explosive eruption several primary and secondary factors processes could have interacted to ultimately produce the crystal rich character these being i eruption of highly crystallized magmas 65 phenocrysts ii concentration of crystals in primary eruption columns iii concentration of crystals in any resulting pyroclastic flows fine vitric ashes being elutriated out and being carried away in accompanying trailing ash clouds iv concentration of crystals in secondary eruption columns generated by the flow of hot pyroclastic flows into the ocean and v concentration of crystals by the elutriation of fines into the trailing fine sediment cloud accompanying submarine mass flows resulting from the slumping of volcaniclastic aggregates from shallow marine subaerial settings

sediment facies and holocene deposition rate of near coastal fluvial systems an example from the nobi plain japan abstract floodplains are a major component of present near coastal fluvial systems that have evolved in response to postglacial changes in climate and sea level knowledge of sedimentary facies and deposition rates on a centennial to millennial time scale is required for considering floodplain evolution two cores ap1 and ap2 were acquired from an abandoned channel of the ibi river and its natural levee on the nobi plain central japan sediment facies analysis electrical conductivity and radiocarbon dating of borehole samples showed that in both cores organic rich dark gray floodbasin mud overlies deltaic deposits dating to after approximately 3200 years calibrated radiocarbon age cal bp in relation to delta progradation the accumulation of floodbasin mud continued at the both sites until about 400 cal bp around 400 cal bp the mud was eroded by the overlying channel sand and gravel at ap1 and was covered by fine grained natural levee deposits at ap2 with an abrupt contact this timing is concordant with the historical record of avulsion of the ibi river during the keicho era ad 1596 1615 averaged aggradation rates at the ap1 and ap2 sites were approximately 2 2 and 3 2 mm yr respectively faulting related subsidence along the western edge of the plain has influenced these rates by creating accommodation averaged deposition rates differed greatly between the floodbasin and the levee suggesting that rapid aggradation of the natural levee also occurred on a centennial to millennial scale these empirical data may be useful for testing models of the architecture and evolution of near coastal fluvial systems

ionospheric anomalies possibly associated with m 6 0 earthquakes in the japan area during 1998 2010 case studies and statistical study abstract in this paper we examine pre earthquake ionospheric anomalies in time series and perform a statistical test by using total electron content tec derived from global ionosphere maps gim around the japan area for the first time the normalized gim tec gim tec which is computed based on 15 days backward running mean of gim tec have been investigated for minimizing possible confounding effects of consecutive earthquakes and identify the abnormal signals meanwhile to reduce the effect of strong geomagnetic activities such as geomagnetic storms the criterion for removing the gim tec data have been adapted that is when dst index exceeds 60 nt temporal variations of gim tec for large and destructive earthquakes in japan have been studied which are the 2004 mid niigata prefecture earthquake m6 8 its aftershock m6 1 the 2007 offshore mid niigata earthquake m6 8 and the 2008 iwate miyagi nairiku earthquake m7 2 although there are some positive and negative tec anomalies before and after the four earthquakes there is a tendency that positive tec anomalies appear 1 5 days before all the above earthquakes even during the quiet geomagnetic condition superposed epoch analyses have been performed for the statistical analysis of tec anomalies associated with m 6 0 earthquakes during the 12 year period of may 1998 may 2010 the statistical result indicates the significance of the positive tec anomalies 1 5 days before earthquakes within 1000 km from the epicenter around japan

activity of the yoro fault system determined from coseismic subsidence events recorded in the holocene delta sequence of the nobi plain central japan the holocene delta sequence of the nobi plain central japan records coseismic subsidence in the western part of the plain caused during the past 6000 years by movement on the yoro fault we identified four episodes of upward fining deposition and increasing electrical conductivity in delta front deposits that occurred 600 200 1300 900 4200 3800 and 5600 4700 years ago suggesting that episodes of sea level rise interrupted progradation of the kiso river delta considering the general trend of relative sea level fall during the middle to late holocene under the influence of eustasy and hydroisostasy the temporal correspondence of rises of relative sea level with activity on the yoro fault suggests they reflect coseismic subsidence due to yoro fault activity the timing of the coseismic subsidence events identified in this study also corresponds with that of previously reported faulting events at the kuwana fault to the south of the yoro fault these results are consistent with the previous interpretation that the yoro and kuwana faults comprise a behavioral segment within the yoro fault system our off fault paleoseismic study shows that coseismic subsidence events detected in holocene delta sequences can provide further evidence of faulting events inferred from the on fault paleoseismic studies