the philippine sea new survey results reveal the structure and the history of the marginal basins the hydrographic department of japan initiated a long term geological and geophysical survey of the philippine sea in 1983 we here summarize the bathymetry and magnetic anomalies of this area focusing on the structure and the evolutionary process of the marginal basins the shikoku and parece vela basins developed as one backarc system in the later phase of their formation the significant difference between the two basins however is clearest near the extinct spreading centers the steep oki daito escarpment located in the northern west philippine basin was mapped for the first time during this survey the n s trending spreading fabric north of the escarpment is in striking contrast to the nw se to e w lineament in the south our data reveal a more complicated history of the western philippine sea than has been proposed in previous studies

thermal conductivities under high pressure in core samples from iodp nantroseize drilling site c0001 we examined the effects of high pressure on thermal conductivity in core samples from the slope apron facies and the upper part of the accretionary prism at site c0001 of the nantroseize drilling program and in other samples of five terrestrial rock types thermal conductivity clearly increased with increasing pressure for both wet water saturated and dry samples we determined the rate of thermal conductivity change of the nantroseize sediments to be 0 014 wm 1k 1 mpa when pressure was increased and 0 01 wm 1k 1 mpa when pressure was decreased using the rate determined for decreasing pressure we estimated that thermal conductivities measured at atmospheric pressure rather than at in situ pressure may be underestimated by 7 for a core sample from around 1 km depth and by 20 for a core sample from around 3 km depth in general the rate of thermal conductivity change with pressure showed a positive correlation with porosity however the relationship of the rate of thermal conductivity change to porosity is also dependent on the fabric mineral composition and pore structure of the sediments and rocks furthermore for two sandstones we tested the effect of pressure on thermal conductivity for dry samples was greater than that for wet samples

early diagenesis of bone and tooth apatite in fluvial and marine settings constraints from combined oxygen isotope nitrogen and ree analysis abstract fossil bones and teeth of late pleistocene terrestrial mammals from rhine river gravels rs and the north sea ns that have been exposed to chemically and isotopically distinct diagenetic fluids fresh water versus seawater were investigated to study the effects of early diagenesis on biogenic apatite changes in phosphate oxygen isotopic composition 18opo4 nitrogen content wt n and rare earth element ree concentrations were measured along profiles within bones that have not been completely fossilized and in skeletal tissues bone dentine enamel with different susceptibilities to diagenetic alteration early diagenetic changes of elemental and isotopic compositions of apatite in fossil bone are related to the loss of the stabilizing collagen matrix the ree concentration is negatively correlated with the nitrogen content and therefore the amount of collagen provides a sensitive proxy for early diagenetic alteration ree patterns of rs and ns bones indicate initial fossilization in a fresh water fluid with similar ree compositions bones from both settings have nearly collagen free ree u f and sr enriched altered outer rims while the collagen bearing bone compacta in the central part often display early diagenetic pyrite void fillings however ns bones exposed to holocene seawater have outer rim 18opo4 values that are 1 1 to 2 6 higher compared to the central part of the same bones 18opo4 18 2 0 9 n 19 surprisingly even the collagen rich bone compacta with low ree contents and apatite crystallinity seems altered as ns tooth enamel 18opo4 15 0 0 3 n 4 has about 3 lower 18opo4 values values that are also similar to those of enamel from rs teeth therefore ree concentration n content and apatite crystallinity are in this case only poor proxies for the alteration of 18opo4 values seawater exposure of a few years up to 8 kyr can change the 18opo4 values of the bone apatite by 3 therefore bones fossilized in marine settings must be treated with caution for palaeoclimatic reconstructions however enamel seems to preserve pristine 18opo4 values on this time scale using species specific calibrations for modern mammals a mean 18oh2o value can be reconstructed for late pleistocene mammalian drinking water of around 9 2 0 5 which is similar to that of late pleistocene groundwater from central europe

thermal regime of the costa rican convergent margin 2 thermal models of the shallow middle america subduction zone offshore costa rica at the costa rica margin along the middle america trench along strike variations in heat flow are well mapped these variations can be understood in terms of either ventilated fluid flow where exposed basement allows fluids to freely advect heat between the crustal aquifer and ocean or insulated fluid flow where continuous sediment cover restricts heat advection to within the crustal aquifer we model fluid flow within the subducting aquifer using nusselt number approximations coupled with finite element models of subduction and explore its effect on temperatures along the subduction thrust the sensitivity of these models to the initial thermal state of the plate and styles of fluid flow either ventilated or insulated is explored heat flow measurements on cool crust accreted at the east pacific rise are consistent with ventilated hydrothermal cooling that continues with subduction these models yield much cooler temperatures than predicted from simulations initialized with conductive predictions and without hydrothermal circulation heat flow transects on warm crust accreted at the cocos nazca spreading center are consistent with models of insulated hydrothermal circulation that advects heat updip within the subducting crustal aquifer near the trench these models are warmer than conductive predictions and cooler than conductive predictions downdip of the trench comparisons between microseismicity and modeled isotherms suggest that the updip limit of microseismicity occurs at temperatures warmer than 100 c and that the downdip extent of microseismicity is bounded by the intersection of the subduction thrust with the base of the overriding crust

episodic slow slip events accompanied by non volcanic tremors in southwest japan subduction zone 1 episodic slow slip events have been recognized by means of tilt changes in the western shikoku area southwest japan the crustal tilt deformation was observed repeatedly with a recurrence interval of approximately six months coincident with the occurrences of major non volcanic deep tremor activities in this area observed tilt changes can be explained by slow slip events occurring around the source area of tremors in each episode the source of the slow slip event and tremor migrate simultaneously the spatial and temporal coincidence of tremors and slow slip events indicates that they both may be coupling phenomena reflecting the stress accumulation process at the subducting plate

heat flow variations correlated with buried basement topography on the juan de fuca ridge flank systematic heat flow variations are commonly observed on sedimented flanks of mid ocean ridges these variations have been attributed to the convective circulation of pore fluids within the oceanic crust and have been used to estimate the scale and pattern of this circulation here we report similar systematic variations observed in a detailed heat flow and seismic reflection survey over sediment covered 3 myr old sea floor on the eastern flank of the juan de fuca ridge we find that heat flow peaks are located above buried basement ridges and adjacent to two minor basement outcrops heat flow lows are found where thick sediments fill basement valleys the simple inverse relationship between heat flow and sediment thickness defined by the data indicates that hydrothermal circulation sealed within the permeable portion of the oceanic crust is vigorous enough to maintain approximately isothermal 10 k conditions at the sediment crust interface as no systematic variations in estimated basement temperatures are observed it seems that at this location the heat flow variations result only from sediment thickness variations and do not reflect a particular convective pattern

heat flow distribution and thermal structure of the nankai subduction zone off the kii peninsula detailed heat flow surveys were carried out in the central part of the nankai trough southeast of the kii peninsula off kumano for investigation of the thermal structure of the subducting plate interface at stations in the kumano trough forearc basin and its vicinity long term monitoring of temperature profiles in surface sediments was conducted because bottom water temperature variations btv significantly disturb subbottom sediment temperatures heat flow values were successfully determined at seven stations by removing the influence of btv from temperature records for 300 to 400 days the surface heat flow data were combined with estimates from depths of methane hydrate bottom simulating reflectors to construct a heat flow profile across the subduction zone heat flow decreases from 90 110 mw m2 on the floor of the nankai trough to 50 60 mw m2 at around 30 km from the deformation front while it is rather uniform 40 60 mw m2 in the kumano trough the values measured on the nankai trough floor are concordant with the value estimated from the age of the subducting philippine sea plate about 20 m y taking into account the effect of sedimentation the obtained heat flow profile was used to constrain thermal models of the subduction zone the subsurface thermal structure was calculated using a two dimensional steady state model in which the frictional heating along the plate interface and the radioactive heat production are treated as unknown parameters comparison of the calculated surface heat flow in the kumano trough with the observed data indicates that the effective coefficient of friction is small about 0 1 or less and thus the shear stress on the plate interface is very low in this subduction zone

on the high heat flow in the nankai trough area a simulation study on a heat rebound process abstract a concentration of high heat flow as high as 120 160 mw m2 has been observed in the nankai trough off southwest japan where the philippine sea plate shikoku basin is subducting beneath the japanese landmass we interpret this high heat flow in the subduction zone as being caused by the recovery of conductive heat flow to the theoretically expected value for the young shikoku basin lithosphere after cessation of hydrothermal heat exchange through sediment the thickening sedimentary cover suppresses the rapid heat exchange between basement and sea water whereas the topmost part of the basement allows a hydrothermal circulation within it to pump up heat from the hot plate to the sediment cover we propose to call this process heat rebound numerical simulation shows that significant heat flow recovery can occur and is largely influenced by the sedimentation rate we believe that the high heat flow in the nankai trough is one of the heat rebound cases however rapid sedimentation in the trough also indicates that heat flow recovery expected by the simulation is not large enough to explain the trough high heat flow by the heat rebound process only

the measurement of thermal conductivity of solids with a transient linear heat source on the plane surface of a poorly conducting body abstract during the last ten years the transient hot wire method for measuring thermal conductivity of ocean bottom muds and other soft materials has been adapted for measuring the conductivity of solid rocks because it is cheaper and quicker than the steady state methods such as the divided bar this is done by embedding the hot wire in the form of a hypodermic needle or a ribbon flush into the surface of a block of a poorly conducting material when a flat surface of a specimen is placed on the surface of such a sensor the line source can be said to diffuse heat into an infinite half space if one neglects the heat absorbed by the poorly conducting block into which the needle is embedded the rate of the temperature rise of the line source with respect to the logarithm of time elapsed since turning on the heater is inversely proportional to the conductivity in practice the rates of temperature rise are compared for the unknown and for a standard specimen a fused silica plate in our case the percentage of the total heat flowing into the sensor block is in general different for the standard and for the unknown thus possibly creating an error when the conductivity of the sensor block is neglected it was determined experimentally that the temperature rise for a silica plate is decreased only by 1 3 by the heat absorbed by the material of the sensor block an empirical equation is proposed to correct errors arising from this source this correction needs to be used only for materials of conductivity less than 2 mcal cm c s the equation gives somewhat larger but still acceptable conductivity values for substances in the range of 0 208 3 25 mcal cm c s as shown in table 1 and fig 2 for measurements on common rocks corrections for the heat diffused into the material of the sensor block can be neglected

bone and enamel diagenesis from the crystal to the environment a tribute to jean francois saliege a universite de lyon france cnrs france ecole normale superieure de lyon site monod 15 parvis rene descartes bp7000 lyon f 69342 france universite claude bernard lyon 1 43 bd du 11 novembre 1918 f 69622 villeurbanne cedex france b museum national d histoire naturelle cnrs departement ecologie et gestion de la biodiversite usm 303 umr 7209 du cnrs archeozoologie archeobotanique societes pratiques et environnements case postale 56 55 rue buffon f 75231 paris cedex 05 france

configuration of subducting philippine sea plate beneath southwest japan revealed from receiver function analysis based on the multivariate autoregressive model 1 we construct a detailed image of velocity discontinuity beneath southwest japan by using receiver functions we first propose an improved receiver function estimation method based on the statistical multivariate autoregressive model then we apply the new method to the teleseismic waveform data recorded by the high density seismograph network in southwest japan the results show a clear velocity discontinuity at 30 km depth beneath the southern shikoku region this discontinuity corresponding to the boundary between the oceanic crust and the high velocity layer the oceanic moho of the philippine sea plate phs continues down to the north indicating that the aseismic phs extends to the central chugoku region the continental moho is also clearly imaged beneath the chugoku region the depth contour of the phs shows a rather complicated feature with ridges and valleys the most significant ridge is located around longitude 133 e west of which the contours are basically directed north south changing to west east to the east beneath the western part of this ridge hypocenters of microearthquakes are located above this velocity discontinuity while earthquakes mainly occur below the discontinuity within the oceanic mantle beneath the eastern part of the ridge

effects of diagenesis on strontium carbon nitrogen and oxygen concentration and isotopic composition of bone abstract paleodietary analysis based on variations in the trace element and stable isotopic composition of inorganic and organic phases in fossil bone depends on the assumption that measured values reflect in vivo values to test for postmortem alteration we measured 87 sr 86 sr 13 c 12 c 18 o 16 o and 15 n 14 n ratios and sr concentrations in modern and prehistoric 610 to 5470 yr old bones of animals with marine or terrestrial diets from greenland bones from modern terrestrial feeders have substantially lower sr concentrations and more radiogenic 87 sr 86 sr ratios than those from modern marine feeders this contrast was not preserved in the prehistoric samples which showed almost complete overlap for both sr concentration and isotopic composition in bones from the two types of animals leaching experiments x ray diffraction analysis and infrared spectroscopy indicate that alteration of the sr concentration and isotopic composition in prehistoric bone probably results from nearly complete exchange with groundwater oxygen isotope ratios in fossil apatite carbonate also failed to preserve the original discrimination between modern terrestrial and marine feeders the c isotope ratio of apatite carbonate did not discriminate between animals with marine or terrestrial diets in the modern samples even so the ranges of apatite 13 c values in prehistoric bone are more scattered than in modern samples for both groups suggesting alteration had occurred 13 c and 15 n values of collagen in modern bone are distinctly different for the two feeding types and this distinction is preserved in most of the prehistoric samples our results suggest that postmortem alteration of dietary tracers in the inorganic phases of bone may be a problem at all archaeological sites and must be evaluated in each case while collagen analyzed in this study was resistant to alteration evaluation of the possibility of diagenetic alteration of its isotopic composition in bones from other contexts is also warranted

thermal effects of hydrothermal circulation and seamount subduction temperatures in the nankai trough seismogenic zone experiment transect japan 1 we examine the thermal effects of seamount subduction seamount subduction may cause transient changes in oceanic crust hydrogeology and plate boundary fault position prior to subduction seamounts provide high permeability pathways between the basaltic crustal aquifer and overlying ocean that can focus fluid flow and efficiently cool the oceanic crust as the seamount is subducted the high permeability pathway is closed shutting down the advective transfer of heat if significant fluid flow occurs it would be restricted after seamount subduction and would result in a redistribution of heat warming the trench and cooling landward parts of the system additionally subducting seamounts can influence the position of the plate boundary fault that has thermal consequences by locally controlling the proportions of incoming sediment that subduct and accrete shifting the decollement to the seafloor at the trench in the wake of seamount subduction causes limited cooling focused at the toe of the margin wedge we apply these features of seamount subduction to a thermal model for the nankai trough seismogenic zone experiment transect on the margin of japan models with hydrothermal circulation provide an explanation for anomalously high surface heat flux observations near the trench they yield temperatures of 100 c 295 c for the rupture area of the 1944 tonankai earthquake temperatures in the region of episodic tremor and slip are estimated at 290 c 325 c 70 c cooler than a model with no fluid circulation

contrast comparison of differential diagenetic pathways of lower tithonian carbonate materials from the betic cordillera s spain evidence for physico chemical paleo seawater properties abstract the reconstruction of paleoenvironmental conditions is based on the study of ancient rock materials for this purpose skeletal materials are often assumed to have higher preservation potential sometimes favored over the use of matrix micrite however factors such as ecology depositional setting mineralogy and diagenetic processes may obscure original geochemical signals and care must be taken when reading such an intricate record this work provides a thorough comparison between geochemical signatures of different carbonate materials interpreted in the light of their paleoenvironmental significance burial and diagenetic processes are taken into account contextualized by ammonite and belemnite ecology two sections deposited in epioceanic tethyan areas and corresponding to the same lower tithonian ammonite biozone are under scope a condensed pelagic and cephalopod rich limestone the alamedilla sector intercalated in thick mafic rocks piles and a typical ammonitico rosso facies the cardador section in contrast to depositional and taphonomic histories typical for a tethyan top swell site i e rather calcareous ammonitico rosso events of carbonate mud deposition rapid burial and early lithification synsedimentary sliding and over imposition of firmground horizons characterize pelagic cephalopod rich limestones differential taphonomy of carbonate skeletals agrees with differential preservation favoring inner cast preservation in ammonitico rosso and shell preservation neomorphic calcite in pelagic cephalopod rich limestones stable carbon and oxygen isotope data together with trace element data sr mg fe mn are presented for a wide range of carbonate materials matrix micrite neomorphic ammonite shells belemnite rostra and carbonate cements optical inspection including cathodoluminescence imaging and geochemical data suggest a fair preservation of the above mentioned materials except for diagenetic marine burial carbonate cements carbon isotope values fall within the typical tethyan late jurassic range ca 2 except data from belemnite rostra which are depleted around 1 which is interpreted as resulting from metabolic fractionation oxygen isotope values are more variable but the clustering of different carbonate materials within a narrow range of values between 1 and 1 is consistent with conservative diagenesis warmer burial fluids explain lower values in later diagenetic carbonate cements no evidence of pervasive diagenetic imprint is revealed by elemental composition the increased abundance of mg fe and especially mn up to 1500 ppm is recognized as hydrothermal contamination proximity to hydrothermal sources the mid subbetic volcanic ridge accords with higher mn concentration at the alamedilla site interestingly the timing of the mineralogical stabilization of each carbonate material reveals a potential record of a post sedimentary geochemical event the obtained information demonstrates the complexity of ancient carbonate records and encourages future research focused on the preservation potential of geochemical proxies throughout time the studied case hopes to be a representative example to approach the interpretation of potential past and present rare analogs

solubilities of bone mineral from archaeological sites the recrystallization window abstract bone mineral solubility is an important parameter for understanding the preservation of bones in the archaeological and palaeontological records in this study we have measured the solubility of the carbonated hydroxyl apatite of sub recent and fossil bones as well as synthetic hydroxyl apatite in deionized water and in ph buffered solutions the solutions were open to the atmosphere and the ph values were around neutral measurement conditions that are relevant to bone mineral preservation in nature but that were absent from most previous studies we obtained internally consistent results from both the water and the buffered experiments supporting the notion that we are measuring an inherent property of the mineral phase we found that bone mineral is much more soluble than synthetic hydroxyl apatite we measured the ionic activity products at steady state conditions and we identify a recrystallization window between ph 7 6 and 8 1 which defines the conditions under which bone crystals dissolve and reprecipitate as a more insoluble form of carbonated hydroxyl apatite as these conditions are common in nature most fossil bones will not maintain their original crystals with time we also found that bones that contained small amounts of calcite did not dissolve at all during our experiments these results provide a basis for better understanding the conditions in sediments under which bones are preserved and the relative states of preservation of bone they also have important implications for the selection of the most appropriate bone samples for paleoenvironmental and paleodiet analyses and dating

thermal models of the middle america trench at the nicoya peninsula costa rica 1 we present thermal models of the 24 ma cocos plate subducting under the caribbean plate at the nicoya peninsula costa rica our modeling incorporates the effect of hydrothermal cooling of the seafloor and the absence of an accretionary prism initial geotherms of the incoming plate representing different effective cooling depths of hydrothermal circulation affect the thermal structure and temperatures along the main subduction thrust excluding the deforming prism results in a higher heat flow immediately landward of the trench than previous models and therefore significant frictional heating is not required conductive plate cooling over predicts heat flow across the frontal forearc with no or very low frictional heating models with hydrothermal cooling to depths of 2 km under predicts the heat flow comparisons with recently determined hypocenter locations indicate that the updip limit of seismicity is consistent with temperatures between 100 150 c but there are large along strike variations in both the seismicity and thermal regime

thermal regime of the southwest japan subduction zone effects of age history of the subducting plate abstract during a mid miocene at about 15 ma tectonic reorganization an ocean spreading ridge perpendicular to the strike of the nankai trough subduction zone stopped spreading since that time there has been subduction of the cooling fossil spreading ridge in the present study we have developed a time dependent thermal subduction model for this region using the finite element method there are good seismological and geological constraints for the plate geometry and for the subduction history of the past 15 ma boundary conditions are specified so that the oceanic plate subducting at the nankai trough becomes cooler as it gets older the model results agree with the present heat flow trend that decreases landward and explain the paleothermal regime of high mid miocene temperatures inferred from land geological studies the tectonics of the region prior to 15 ma has some uncertainties assuming subduction of an active spreading ridge or an 80 ma old lithosphere prior to 15 ma give the same results for the present thermal regime of the seaward portion of the forearc but different results for the most landward region 250 km the thermal history of the forearc since 15 ma can be summarized as a rapid warming period as a consequence of ridge subduction followed by a cooling trend to the present as a result of the aging of the subducting plate the results illustrate the thermal consequences of one type of ridge subduction they also demonstrate that the thermal regime of a subduction zone depends critically on the age history of the subducting oceanic lithosphere especially if it is young as well as such parameters as the subducting plate dip angle and thickness of insulating sediments on the incoming oceanic crust this dependence is especially important when the thermal regime is used to constrain the seismogenic behaviour of the subduction thrust fault

f content variation in mammoth ivory from aurignacian contexts preservation alteration and implications for ivory procurement strategies abstract this article presents the results of two series of micro pixe pige analysis on mammoth ivory samples from four aurignacian sites in france abri castanet grotte d isturitz and germany hohle fels vogelherd specifically we report variation in ivory preservation as indicated by fluorine f content and ratios of mgo cao from aurignacian horizons known to contain ivory industries though all samples derive from respectively homogenous sedimentary contexts results show very different pattern of f content variation among sites f uptake in ivory is a more complex process than that observed for bone and the structural morphological reasons for this are explained high resolution data on the archaeological context of the samples from abri castanet also allows for examination of the effects of horizontal and vertical distribution on f content and the sorting of f content data by sedimentary unit a definitive model for fluorine uptake during ivory diagenesis will require further investigation but a close examination of the current data provides novel insight into processes of taphonomy and diagenesis in this exceptional and highly valued raw material as well as further evidence to support regionally distinct strategies of ivory procurement in the early aurignacian in combination with additional lines of faunal and archaeological evidence it is demonstrated that ivory procurement in the swabian jura focused on fresh local sources of ivory while procurement strategies in northern aquitaine focused on ivory collection from natural deposits of varying age

thermal constraints on the seismogenic portion of the southwestern japan subduction thrust for coastal cities an important factor in earthquake hazard from subduction zone earthquakes is the landward extent of the seismogenic portion of the subduction thrust fault in this study we test the hypothesis that the maximum downdip extent is defined by a critical temperature we have developed a transient thermal model for the nankai subduction zone of southwest japan to allow comparison of the thermally estimated downdip extent of the seismogenic zone with that from 1 seismicity and tsunami data for two great subduction earthquakes 2 the coseismic faulting extent of these events estimated from geodetic deformation data and 3 the interseismic locked zone determined from interseismic geodetic data the nankai margin has extensive heat flow and heat production data to control thermal models and thus crustal temperatures it has earthquake tsunami and geodetic data that constrain the coseismic rupture portion of the subduction thrust fault for past great earthquakes and the portion of the thrust fault that is locked and storing interseismic elastic strain on the nankaido margin off shikoku island the thermal model indicates that a temperature of 350 c taken to be the limit for seismic initiation from laboratory and field data is reached on the subduction thrust fault 150 km from the trench a transition zone into which rupture may extend with decreasing offset taken to be 450 c extends an additional 45 km downdip the thermal model results are in excellent agreement with the maximum downdip extent of coseismic displacement for the 1946 nankaido ms 8 2 earthquake off shikoku island and with the downdip extent of the present locked zone in the region of the 1944 tonankai ms 8 2 earthquake to the northeast the subduction angle is much steeper and the thermal models indicate a narrower downdip seismogenic extent the seismogenic locked zone from earthquake and geodetic data is also narrower thus our analysis of the southwest japan margin indicates that all three constraints on the downdip extent of the seismogenic zone thermal coseismic and interseismic geodetic data are in general agreement the study also supports the hypothesis that the seismogenic portion of subduction thrust faults is limited primarily by temperature the thermal control implies that subduction thrust faults with shallow dip have wider seismogenic zones compared to those with steep dip the subducting plate age and thus heat flow and the thickness of the insulating sediments on the incoming plate are also very important to the thermal regime and thus to the seismogenic width the relation of the maximum seismic rupture area to the interseismic locked zone is particularly important for earthquake hazard estimation on subduction margins such as cascadia where there have been no great historical events

petrography trace elements and oxygen and carbon isotopes of gordon group carbonates ordovician florentine valley tasmania australia gordon group carbonates are a thick 2 km stratigraphically continuous ordovician sequence that ranges in age from the arenig to the ashgill they were deposited in subtidal intertidal supratidal and channel depositional environments at a paleolatitude of about 10 n the biota is similar to modern tropical chlorozoan assemblages with abundant corals oncolites calcareous algae and stromatolites non skeletal grains are abundant and are predominantly intraclasts and pellets with some oolites and aggregates micrite is abundant with some sparry calcite cement dolomite which commonly replaces micrite extensive burrows and mud cracks formed mostly during early diagenesis by marine to mixed marine waters the gordon group limestones are characterized by high sr na ratios 2 6 4 6 similar to modern aragonitic carbonates the stratigraphic variations of sr na and mn are related to depositional environments diagenesis and dolomitization the low mn concentrations indicate oxidizing peritidal depositional environments with high rates of carbonate deposition na varies with salinity and the sr varies with facies the largest sr concentrations are in corals and micrites the sr na and mn concentrations have been affected by two stage meteoric diagenetic stabilization the first stage involves marked depletion of sr and na with no appreciable gain of mn due to inversion of aragonite to low mg calcite the second stage involves no significant change in sr and na with appreciable gain of mn which is due to recrystallization of low mg calcites and addition of spar cement in a semi closed diagenetic system sr concentrations decrease whereas mn and fe concentrations increase with increasing mg concentrations due to dolomitization in predominantly marine waters with some influx of meteoric waters the 18o and 13c isotopic fields of calcites and dolomites partly overlap and the dolomites are enriched relative to co existing calcites by 2 to 3 in 18o and by about 1 in 13c similar to modem marine and mixed marine dolomites low mn and fe concentrations indicative of least meteoric diagenetic change correspond to 5 0 0 5 18o and 1 0 05 13c suggesting that these values were the original late ordovician marine calcite values in tasmania these isotopic values are similar to the least altered late ordovician brachiopods and marine calcite cements from other areas the middle ordovician 18o and 13c values of marine cements are 7 and 0 respectively and these values match the marine cement values of the same age from other areas this shift towards heavier isotopic values from middle to late ordovician is probably due to both glaciation in the higher latitudes of gondwana and a slight drop in temperature 4 c depletion in 13c 18o sr and na and enrichment in mn in the lower and upper most part of the late ordovician tasmanian limestones indicative of pronounced meteoric diagenesis coincide with a major australia wide marine regressions

micro pixe pige analysis of palaeolithic mammoth ivory potential chemical markers of provenance and relative dating abstract micro proton induced x ray and gamma ray emission micro pixe pige provide non destructive methods for the evaluation of the major minor and trace element compositions of archaeological material the current study applies micro pixe pige analysis to mammoth ivory artefacts from four palaeolithic sites abri castanet vogelherd cave grottes de la verpilliere i and ii in france and germany in order to assess the effectiveness of this approach to material older than 30 000 y bp it has thus far not been established whether such methods of analysis can yield results of scientific and archaeological interest on ivory material that has undergone such extended periods of diagenesis this approach evaluated preservation state in terms of mean elemental concentrations mg vs ca and a comparative assessment of f content as an indication of relative burial time the results also indicate that analysis of trace elements sr zn br can provide chemical markers of archaeological provenance the results of this study are compared to data in the existing database established by the same methods of analysis on ivory objects from several different time periods and archaeological sources the implications of these results for the study of archaeological ivories from palaeolithic contexts are discussed

crustal structure across the coseismic rupture zone of the 1944 tonankai earthquake the central nankai trough seismogenic zone 1 differences in the coseismic rupture process between the 1944 tonankai and the 1946 nankaido earthquakes have been studied by many fault models to understand what factors control coseismic rupture zones it is important to investigate differences in deep crustal structures of the rupture zones between the 1944 and 1946 earthquakes the previously published crustal structure of the rupture zone of the 1946 earthquake shows that the coseismic rupture extends to the neogene quaternary accretionary prism however little is known about the structure of the rupture zone of the 1944 earthquake to obtain a complete image of the seismogenic zone of the 1944 earthquake a wide angle seismic survey was performed across the presumed coseismic rupture zone of the 1944 earthquake from ocean to land our model for the crustal structure is based on ocean bottom seismographic data the crustal structure appears characteristic for subducting oceanic crust and a neogene quaternary accretionary prism bounded by an island arc crust the neogene quaternary accretionary prism reaches a maximum thickness of 7 km at 50 km distance landward from the deformation front the subducting oceanic crust can be traced down to 35 km the subduction angle becomes steeper landward reaching up to 11 beneath the island arc crust the depth of the top of subducting oceanic crust at the downdip limit of the rupture zone is 23 km while the updip limit is located beneath the island arc upper crust similar structures of the updip and downdip limits are also published for several other subduction zones

manganese distribution in the carbonate fraction of shallow and deep marine lithofacies middle ordovician eastern tennessee abstract a marked increase in manganese content from shallow to deep marine lithofacies can be observed within the carbonate fraction of the middle ordovician sequence in eastern tennessee the distribution of manganese is controlled by 1 the original aragonite and calcite mineralogy of shallow and deep marine environments respectively 2 preferential substitution of manganese for calcium in the rhombohedral structure of calcite 3 anoxic depositional and diagenetic environments and 4 possibly volcanism

diagenetic effects on the oxygen isotope composition of bones of dinosaurs and other vertebrates recovered from terrestrial and marine sediments assessing effects of diagenesis on oxygen isotope composition of bone is essential to its use in reconstructing habitats and lifestyles of ancient vertebrates these effects are a matter of controversy particularly in the case of extinct animals such as dinosaurs to investigate the effects of diagenesis on isotopic composition of fossil bone bone samples from both marine and terrestrial campanian sediments from alberta canada have been analysed the isotopic compositions of oxygen 18 o smow were determined in bones sampled from articulated skeletons of exclusively terrestrial animals recovered from the terrestrial dinosaur park formation and compared with bones from the marine bearpaw formation the articulated skeleton of an exclusively terrestrial dinosaur hadrosaur found in marine sediments yielded similar 18 o values for both structural carbonate and phosphate fractions mean 18 o smow values 22 6 and 16 9 respectively in bone to marine reptiles mosasaurs recovered from the same locality mean 18 o smow values 24 2 and 17 3 respectively the isotopic composition of both skeletons recovered from marine sediments was significantly more positive than that of articulated hadrosaur skeletons recovered from contemporaneous terrestrial sediments mean phosphate 18 o smow value 12 9 and outside the range of phosphate 18 o smow values previously reported for terrestrial dinosaur skeletons c 9 14 these data suggest that the isotopic composition of oxygen in the phosphate and structural carbonate ions in the bone apatite was altered during diagenesis and can be used for neither palaeoclimate nor physiological reconstruction

temperatures in zones of steady state underthrusting of young oceanic lithosphere abstract rapid conduction of heat through the top surface of young oceanic lithosphere can contribute at least some of the heat necessary for high temperature low pressure metamorphism of rock buried in subduction zones and perhaps for melting in such environments we show that the steady state temperature on a major underthrust fault underlain by a slab of downgoing lithosphere equals the quotient of the temperature that would exist due to the cooling of a slab below the wedge in the absence of advection of heat by the downgoing slab divided by a dimensionless divisor this divisor depends only on the speed and dip of subduction the depth of the fault the coefficient of thermal diffusivity and the ratio of coefficients of thermal conductivity in the downgoing slab and in the overlying wedge this result extends an earlier analysis that did not take into account either the cooling of lithosphere as it is subducted or different coefficients of thermal conductivity in the slab and overlying wedge for a wide range of geologically common parameters numerically calculated steady state temperature fields for two dimensional heat transfer differ by less than a few percent and by at most 10 from those given by this simple analytical approximation this approximation also concurs with numerical calculations of james et al 1 that show that temperatures as high as 400 c at a depth of only 10 km in a subduction zone would require the subducted lithosphere to be younger than roughly 1 ma if no other source of heat were available in addition the formalism presented here permits a simple assessment of the relative importance of the youth of the subducted lithosphere and dissipative heating in the enhancement of temperatures near the fault surface for example modest shear stresses of about 50 mpa on faults with high slip rates of 100 mm yr or more at depths as small as 10 km can contribute as much as 200 c to temperatures on the fault making temperatures of 400 c at 10 km possible even when lithosphere as old as 20 30 ma is subducted

western nankai trough seismogenic zone results from a wide angle ocean bottom seismic survey the nankai trough southwestern japan is recognized as a vigorous seismogenic zone with well studied historic earthquakes this paper presents results of a wide angle ocean bottom seismographs obs study at the western nankai trough seismogenic zone the obs data used were acquired on a profile 250 km long across the presumed coseismic slip zone of the 1946 nankaido earthquake ms 8 2 the main purpose of the seismic study is to obtain an entire crustal cross section of the seismogenic zone for the 1946 earthquake the crustal model is characterized by a gentle sloping of subducting oceanic crust and thick overlying sedimentary wedge p wave seismic velocities of the subducting oceanic crust show normal oceanic crustal velocities vp 5 0 5 6 km s and 6 6 6 8 km s in oceanic layers 2 and 3 respectively the maximum thickness of the sedimentary wedge is 9 km at 70 km from the trough axis with vp 3 4 4 6 km s in the deeper part the subducting oceanic crust traced down to 25 km depth shows that the subduction angle becomes steeper landward 3 2 and 7 2 at 0 50 km and 50 100 km from the trough axis respectively the oceanic crust is smooth to the hypocenter zone down to 40 km depth beneath shikoku island our crustal model shows that the downdip limit of the coseismic slip area does not extend to the deep end of the oceanic crust island arc crust contact zone even though there is large uncertainty about the seaward limit of the coseismic slip zone the crustal model clearly indicates that the updip limit of the coseismic slip zone extends beneath the young accretionary prism

stresses in the subducting slab beneath southwest japan and relation with plate geometry tectonic forces slab dehydration and damaging earthquakes 1 we infer stresses in the subducting slab beneath southwest japan from focal mechanisms and discuss their geodynamical implications the majority of the 824 fault plane solutions used in this study were obtained by the japan meteorological agency for earthquakes that occurred during 1970 2002 and were previously unpublished the focal mechanisms are believed to reflect stresses in both the untransformed slab crust and the slab mantle the stresses are controlled by tectonic forces and the earthquakes are facilitated by local dehydration the slab experiences a regional e w stretch that is downdip and margin parallel tension at the kyushu and nankai margins respectively we propose that the margin parallel component of mantle resistance to the obliquely subducting young slab at nankai provides an easterly stretch acting against the westerly slab pull of the older and colder part of the slab at northern kyushu despite the complex slab geometry along the nankai margin the direction of tension is largely parallel with the local strike of the slab indicating that the slab is a stress guide the complex slab geometry is not related to the present stress regime but likely reflects severe deformation in the past when an extremely young and incompetent plate was forced to subduct against its own buoyancy the maximum margin parallel stretch and a sharp bending of the slab both occur in the area of the 2001 m 6 7 geiyo earthquake using a simple strength envelope model we demonstrate that normal faulting failure of the slab mantle can occur under such conditions

early diagenesis of elephant tusk in marine environment three elephant tusks recovered from a 18th century dutch shipwreck in brittany seawaters were analyzed to study early diagenetic changes of ivory in a marine environment micro small angle x ray scattering saxs analysis revealed sub microscopic structural modifications of ivory hydroxyapatite particle thickness mineralized collagen fibers organization and orientation chemical compositional changes of the organic fraction nitrogen and carbon loss and of the mineral part magnesium loss carbonate calcium chlorine and strontium uptake were investigated by non invasive micro particle induced x ray emission gamma ray emission rutherford and elastic backscattering spectrometry analysis pixe pige rbs ebs these chemical and structural markers can serve as proxies for the early diagenesis of elephant tusk in marine settings the results show that the macroscopic preservation state of the tusk surface does not reflect its microscopic preservation state a diagenetic sequence is proposed depending on the local environment of each tusk first collagen hydrolysis and ion adsorptions from the marine environment are proposed to occur second a tusk buried in the sand was protected from ca enrichment of the surface and the formation of a flaky white concretion whereas tusks out of the sand were subjected to these latter phenomena as well as sea urchin attacks third ion leaching and uptake increased crystallinity of the hydroxyapatite crystals and the modifications of the mineralized collagen fiber network are assumed to happen for all three tusks with different level of completion

petrographic and geochemical evidence for original aragonite mineralogy of upper jurassic carbonates mozduran formation sarakhs area iran abstract diverse skeletal and non skeletal grains with abundant red and blue green calcareous algae evaporites and early diagenetic dolomites in the mozduran carbonates are similar to those of modern warm water shallow marine carbonates isopachous and fibrous intragranular sparry calcite cements resemble modern aragonite morphologies concentric and radial ooids are like modern aragonitic forms which are formed in turbulent and in low energy environments respectively deformed ooids shattered micritic envelopes and spalled ooids indicate aragonite dissolution during meteoric diagenesis meteoric cements are equant mosaic to drusy calcites burial cements only occur as vein fillings sr and na covariance with mn supports evidence of inversion of aragonite to calcite with subsequent open phreatic diagenesis fe concentrations are a magnitude higher than mn due to a reducing phreatic environment high sr na ratios suggest original aragonite mineralogy the 18 o and 13 c field of mozduran limestone lies at the edge of the modern shallow marine field indicating a range from marine to meteoric cements differences in 18 o values between marine calcites and meteoric derived calcites is similar to that in the modern tropics the surface marine diagenetic trend line that passes through shallow marine modern whole carbonates cuts the mozduran limestone isotope field due to their formation in warm shallow marine waters given that atmospheric co 2 levels were similar to those at present increasing mn and fe values decreasing na and uniform sr values with increasingly lighter values of both 18 o and 13 c are exlained by extensive meteoric diagenesis the least altered marine calcite 18 o value of 2 6 pdb corresponds to 29 or 24 c depending on whether 0 of present seawater and 1 2 of ancient seawater with no ice caps are taken as a base an original calcite mineralogy postulated for some jurassic limestones is related to a non tropical origin

mud coated intraclasts a criterion for recognizing sandy mass transport deposits deep lacustrine massive sandstone of the upper triassic yanchang formation ordos basin central china abstract numerous examples of sandy mass transport deposits smtds in deep marine and deep lacustrine environments have been documented by researchers worldwide in recent years however it is an enormous challenge that how to distinguish the subaqueous mass transport processes from the depositional records after the rigorous examination of several outcrops in the ordos lacustrine basin in central china we propose that the mud coated intraclasts in the deep water thick massive sandstone of the yanchang formation are a viable criterion to recognize deposition from sandy debris flows in delta front environments these so called mud coated intraclasts are a newly discovered special depositional phenomenon in the massive clean sandstones in china s lacustrine basins a mud coated intraclast generally consists of two components an inner core and a mud coating the inner core is generally composed of muddy blobs or sandy lumps the mud coatings are generally composed of thin shales or mud rich fine grained sediments the inner core which is generally coated by nearly concentric ring shaped mud coatings is embedded in massive deep water sandstones because these features have never been documented in the geological literature the present authors called them mud coated intraclasts in the present study the depositional features suggest that the sediments that contain these mud coated intraclasts were characterized by en masse emplacement i e a bingham plastic behavior and were supported by the strength of the plastic medium at all times i e no flow transformations occurred during their transport and deposition accordingly mud coated intraclasts are one of the most significant criteria that indicate sandy debrites as the origin of the deep water thick massive sandstones in the yanchang formation this diagnostic feature may be useful to identify analogous smtds in other locations

slow earthquakes coincident with episodic tremors and slow slip events we report on the very low frequency earthquakes occurring in the transition zone of the subducting plate interface along the nankai subduction zone in southwest japan seismic waves generated by very low frequency earthquakes with seismic moment magnitudes of 3 1 to 3 5 predominantly show a long period of about 20 seconds the seismicity of very low frequency earthquakes accompanies and migrates with the activity of deep low frequency tremors and slow slip events the coincidence of these three phenomena improves the detection and characterization of slow earthquakes which are thought to increase the stress on updip megathrust earthquake rupture zones

a synthesis of heat flow determinations and thermal modeling along the nankai trough japan 1 we review marine heat flow data along the nankai trough and show that observations 30 km seaward of the deformation front are 20 below conductive predictions 129 94 mw m 2 but consistent with the global heat flow average for oceanic crust of the same age 16 28 ma heat flow values 30 km seaward of the deformation front are generally 20 higher than conductive predictions this heat flow pattern is consistent with the advection of heat by fluid flow in the subducting oceanic crust and explains both the high heat flux in the vicinity of the trench 200 and 140 mw m 2 and steep landward declines to values of approximately 60 mw m 2 over distances of 65 and 50 km along the muroto and kumano transects respectively along the ashizuri transect the lack of heat flow data precludes a definitive interpretation we conclude that fluid flow in the subducting oceanic crust leads to temperatures that are generally 25 c higher near the toe of the margin wedge and 50 100 c lower near the downdip limit of the seismogenic zone than estimated by purely conductive models

distribution of methane hydrate bsrs and its implication for the prism growth in the nankai trough abstract detailed mapping of a bottom simulating reflector bsr which marks the phase transition from the methane hydrate layer above the reflector to free gas below was conducted in the nankai accretionary prism off shikoku and tokai bsrs are widely distributed in the prism slope from the toe region to the forearc basin bsr positions provide us with the regional heat flow variations using pressure temperature conditions for methane hydrate stability estimated heat flows generally show constant values about 50 mw m2 shallower than the middle slope of the prism and gradually increase seaward in the lower prism slope occurrences of bsrs are regarded as accumulation of free gas beneath the base of a gas hydrate stability field bghs and or concentration of methane hydrate above the bghs these conditions can be accomplished by updip migration of methane gas because it is unlikely that such methane concentration is completed by in situ biogenic methanogenesis within sediments including low total organic carbon moreover sedimentation uplifting and sediment stacking by thrust faulting cause upward migration of the bghs and migration of methane from the dissociated hydrate to new bghs such recycling of methane gas may have actively occurred in accretionary prisms in contrast there are five regions of no bsrs the nankai trough floor prism toe slope basin steep slope and deep sea canyon the trough floor the prism toe and the slope basin are characterized by young sediments with low production of methane gas and sub horizontal strata unsuitable for migration of gases and fluids erosion at the steep slope and the canyon causes removal of hydrated sediments and downward movement of the bghs bsr distribution and thermal structure estimated from bsr positions offer information about active processes occurring in accretionary prisms

splay fault branching along the nankai subduction zone seismic reflection profiles reveal steeply landward dipping splay faults in the rupture area of the magnitude m 8 1 tonankai earthquake in the nankai subduction zone these splay faults branch upward from the plate boundary interface that is the subduction zone at a depth of approximately 10 kilometers approximately 50 to 55 kilometers landward of the trough axis breaking through the upper crustal plate slip on the active splay fault may be an important mechanism that accommodates the elastic strain caused by relative plate motion

seismogenic zone temperatures and heat flow anomalies in the to nankai margin segment based on temperature data from iodp expedition 333 and thermal model the location of the seismogenic zone across the to nankai margin segment has been widely investigated using geodetic tsunami seismologic and heat flow data as well as thermal models seafloor heat flow measurements show large scatter raising questions about the thermal state of the incoming and overriding plates in this study new temperature and conductivity measurements recorded in the philippine sea plate psp and in the accretionary prism during iodp expedition 333 are integrated with recent data on the margin structure and seismicity to improve constraints on the thermal structure of the incoming plate and the subduction zone as well as the thermal conditions within the seismogenic zone iodp expedition 333 measurements provide heat flow values that are lower than the average of nearby seafloor measurements thermal modeling for the psp suggests that hydrothermal warming is insignificant in the trench thus an observed widespread positive thermal anomaly in the shikoku basin that peaks at the kashinozaki knoll more likely results from vigorous thermal convection in the upper mantle in back arc context the modeled thermal structure of the margin from the trench to the mantle shows a significantly colder interplate contact than in previous studies the seismogenic zone is likely to be 30 170 km from the deformation front corresponding to the 100 340 c temperature range the 1944 co seismic slip zone extends farther southward where temperatures are about 60 c slow slip earthquakes are located in the downdip transition zone between 340 and 440 c across the intersection of the moho and the megathrust fault this improved thermal structure from the trench to the mantle results mainly from a better estimate of oceanic plate age slab dip and sedimentation rate variations in the trench this last parameter cools the interplate contact until a depth of 35 km shifting the thermally defined seismogenic zone landward by 20 km and significantly diminishing its influence near the corner flow area

nature and origin of authigenic rhodochrosite and siderite from the paleozoic aquifer northeast mississippi u s a abstract botryoidal rhodochrosite siderite and pyrite are the principal authigenic phases in fractured chert comprising the paleozoic aquifer of northeast mississippi locally alternating bands of near end member composition rhodochrosite and siderite occur in veinlets up to 2 mm wide in the fractured chert carbon isotope data for the carbonates 13c values ranging from 9 6 to 11 3 pdb indicate that both inorganic and organic c were incorporated into the authigenic phases the paleozoic aquifer is hydraulically connected with the overlying upper cretaceous coastal plain strata groundwater in the coastal plain units is undersaturated with respect to calcite and has relatively high fe and mn contents the latter apparently caused by the dissolution of fe mn oxyhydroxides the natural downward recharge of these waters into the paleozoic aquifer causes calcite dissolution in limestone at the base of the chert which in turn leads to the precipitation of rhodochrosite and siderite additionally pyrite is precipitated as so4 reduction occurs in the same zone rhodochrosite has not been previously documented as an authigenic phase in a fresh water aquifer system suggesting that the geochemical environment necessary for its precipitation is not common the alternating bands of rhodochrosite and siderite observed in this study coupled with available thermodynamic data indicate that the groundwater a mn2 afe2 ratio must have fluctuated over time variations in the ratio are best explained by variable eh conditions at the site where fe mn oxyhydroxide dissolution occurs

biodegradation of temperate water skeletal carbonates by boring sponges on the scott shelf british columbia canada abstract boring sponges are a major agent of shell destruction and in the process an important contributor of fine grained carbonate detritus in temperate skeletal carbonate deposits on scott shelf northwestern vancouver island intensive boring is encouraged by the generally low rates of carbonate production and sedimentation skeletal grains become considerably weakened by sponge boring and break preferentially along the directions of sponge excavated tunnels and galleries within the shell boring also facilitates shell dissolution by significantly increasing the surface area weight ratio of shells and by breaking down the organic matrix of shells the large aragonitic bivalves glycymeris and humilaria appear especially susceptible to sponge biodegradation and have become thoroughly bored and corroded within about 1000 years in ambient shelf waters thus their preservation potential is low selective loss of aragonitic biota from ancient cool water shelf skeletal carbonate deposits is anticipated and is evident in many temperate latitude occurrences of new zealand cenozoic limestones

deformation cycles of subduction earthquakes in a viscoelastic earth subduction zones produce the largest earthquakes over the past two decades space geodesy has revolutionized our view of crustal deformation between consecutive earthquakes the short time span of modern measurements necessitates comparative studies of subduction zones that are at different stages of the deformation cycle piecing together geodetic snapshots from different subduction zones leads to a unifying picture in which the deformation is controlled by both the short term years and long term decades and centuries viscous behaviour of the mantle traditional views based on elastic models such as coseismic deformation being a mirror image of interseismic deformation are being thoroughly revised snapshots of subduction zones using space geodesy reveal that the viscous behaviour of the mantle controls crustal deformation requiring the revision of traditional elastic models for earthquake risk assessment space geodesy the use of satellites to monitor earth has revolutionized our view of crustal deformation between consecutive earthquakes however the brevity of such measurements means that studies must be done by comparing multiple subduction zones at different stages of the earthquake cycle by piecing together geodetic snapshots from the sumatra chile and cascadia subduction zones this review presents a unifying picture in which deformation is controlled by the viscous behaviour of the mantle in both the short term years and the long term decades to centuries

age depth correlation of the philippine sea back arc basins and other marginal basins in the world abstract statistical analysis of underway bathymetric profiles of the philippine sea back arc basins the mariana trough the shikoku basin the parece vela basin and the west philippine basin reveals an age depth correlation in the basins the basement depths of the philippine sea range from 3200 to 6000 m with their ages from 0 to 60 ma the age depth curve of the whole philippine sea can be represented by the following equation depth m 3222 366 age ma the equation shows that the basement depth of the philippine sea is about 800 m deeper than that of the major ocean floors of the same age the coefficient of 366 in this equation is close to that for major oceans 350 this suggests that the cooling processes of the lithospheres in the philippine sea and major oceans are similar to each other whereas the structure and composition of the deeper layers of the philippine sea seem to be different from those of major oceans our analysis of etop digital bathymetric data however indicates that this relationship does not hold for some other marginal basins marginal basins other than back arc basins generally follow the age depth curve of major oceans young back arc basins

coseismic slip resolution along a plate boundary megathrust the nankai trough southwest japan geodetic survey measurements are used to estimate the coseismic slip distribution in the 1944 tonankai mw 8 1 and 1946 nankaido mw 8 3 earthquakes and to assess quantitatively the degree to which this slip is resolved on the plate boundary megathrust data used include 798 angle changes from triangulation surveys 328 leveling section differences and 5 coseismic tidal gage offsets many of the nominally coseismic triangulation data span 50 years nearly half the earthquake cycle and correction for interseismic deformation using post 1950 observations is applied microseismicity is used to define the configuration of the plate boundary interface and approximate it with a continuous multisegment fault model because the onshore geodetic data have very limited resolving power for offshore fault segments offshore coseismic slip was constrained by satake s 1993 estimation based on tsunami data the majority of the coseismic slip occurs between 15 and 25 km depth although resolution declines toward the trench axis it is sufficiently good to define two distinct high slip regions one off southeastern shikoku island 11 m maximum and the other offshore of kii peninsula 3 m maximum the slip magnitude off southeastern shikoku coupled with the plate convergence rate would imply an recurrence interval of about 270 years much longer than the average repeat time of 120 years for historical great earthquakes on the nankai trough however the maximum coseismic slip is sensitive to the assumed fault geometry and slippage on trough parallel splay faults could significantly decrease the maximum slip to about 6 m

manganese minerals and associated fine particulates in the streambed of pinal creek arizona u s a a mining related acid drainage problem the pinal creek drainage basin in arizona is a good example of the principal non coal source of mining related acid drainage in the u s a namely copper mining infiltration of drainage waters from mining and ore refining has created an acid groundwater plume that has reacted with calcite during passage through the alluvium thereby becoming less acid where o2 is present and the water is partially neutralized iron oxides have precipitated and farther downstream where the ph of the stream water is near neutral high mn crusts have developed trace metal composition of several phases in the pinal creek drainage basin illustrates the changes caused by mining activities and the significant control mn crusts and iron oxide deposits exert on the distribution and concentration of trace metals the phases and locales considered are the dissolved phase of webster lake a former acid waste disposal pond selected sections of cores drilled in the alluvium within the intermittent reach of pinal creek and the dissolved phase suspended sediments and streambed deposits at specified locales along the perennial reach of pinal creek in the perennial reach of pinal creek manganese oxides precipitate from the streamflow as non cemented particulates and coatings of streambed material and as cemented black crusts chemical and x ray diffraction analyses indicate that the non cemented manganese oxides precipitate in the reaction sequence observed in previous laboratory experiments using simpler solution composition mn3o4 to mnooh to an oxide of higher oxidation number usually 4 0 i e na birnessite and that the black cemented crusts contain ca mn mg co3 and a 7 aphyllomanganate mixture of rancieite ca mn mn4o9 3h2o and takanelite mn ca mn4o9 3h2o in the laboratory aerating and increasing the ph of pinal creek water to 9 00 precipitated ca mn mg co3 from an anoxic groundwater that contained co2 hco3 and precipitated mn3o4 and subsequently mnooh from an oxic surface water from which most of the dissolved co2 had been removed it is suggested that the black cemented crusts form by precipitation of fe on the mn enriched carbonates creating a site for the mnfe oxidation cycle and thus encouraging the conversion of the carbonates to 7 aphysllomanganates the non magnetic 63 m size fractions of the black cemented crusts consisted mostly of the manganese calcium oxides but also contained about 20 ca mn mg co3 5 fe calculated as feooh 2 4 exchangeable cations and trace amounts of several silicates

structural factors controlling the rupture process of a megathrust earthquake at the nankai trough seismogenic zone summary the nankai trough is a vigorous subduction zone where large earthquakes have been recorded with a recurrence time of 100 200 yr the 1946 nankaido earthquake is well known as an unusual event among these earthquakes because the rupture zone estimated from long period geodetic data is more than twice as large as that derived from seismic wave data in the summer of 1999 an onshore offshore deep seismic survey was performed along a 355 km long profile in the western nankai trough seismogenic zone seismic signals both from an airgun array 207 l and land explosions maximum of 500 kg were recorded simultaneously by 98 oceanbottom seismographs and 93 land seismic stations conventional 2 d seismic reflection data were also acquired along part of the offshore profile from the wide angle seismic data we found a subducting seamount at the centre of the proposed rupture zone with dimensions of 13 km thick by 50 km wide at 10 km depth the seismic velocity image also shows that the seamount is now colliding with the japanese island arc crust from this significant structure this paper proposes that the subducted seamount functioned as a barrier at least during the 1946 earthquake i e the rupture of the 1946 earthquake extended over the entire locked zone to the east of the subducted seamount and then the rupture was deflected around the subducted seamount at the down dip end of the locked zone between cape muroto and cape ashizuri another significant structure a highly reflective layer is obtained beneath shikoku island a very slow p wave velocity 3 km s 1 is necessary in a thin layer at the base of the island arc crust in order to explain the observed high amplitude reflection phases an area of low resistivity obtained by a previous magnetotelluric study corresponds to the highly reflective layer this suggests a possible water layer at the base of the island arc crust the water may be generated by dehydration of the downgoing probably partially serpentinized mantle which is implied by a low p wave velocity 7 5 km s 1 beneath the subducted seamount a locally observed non slip region during the 1946 earthquake at the eastern part of shikoku island is interpreted as a result of weak coupling at the possible water layer

the effects of sedimentation and compaction on oceanic heat flow summary the estimation of environmental effects forms an important part of the interpretation of oceanic heat flow measurements in particular the perturbations associated with sedimentation and surface temperature changes must be taken into account analytical solutions can be obtained only for individual simplified versions of these problems whereas any real example is complicated by the process of sediment compaction which changes the bulk thermal properties with depth a physical model is developed which uses sediment porosity trends to predict the thermal parameters and material advection rates for an evolving sediment basement system these values are then used in a numerical solution to the heat flow equation to give estimates of the perturbed surface heat flux through time in addition to variations in sedimentation rate sediment type radioactive heat production and surface temperature changes are considered heat flow corrections may vary by up to a factor of 2 according to sediment type while radioactive heat production can offset the effects of sedimentation by as much as 40 per cent the results also indicate that alterations determined from simple analytical models tend to over estimate the true perturbation to the flux

subduction of the philippine sea plate beneath southwestern japan slab geometry and its relationship to arc magmatism 1 we carry out high resolution three dimensional seismic tomography of the crust and upper mantle beneath southwestern sw japan using arrival time data obtained from the nationwide seismograph network the tomographic images provide new insights into the configuration of the philippine sea slab and arc magmatism the results confirm the existence of an aseismic portion of the philippine sea slab at greater depths beyond the seismic portion the philippine sea slab is subducting aseismically down to at least a depth of 200 km in chubu 60 80 km in kinki and 60 km in chugoku and is subducting seismically to depths of 150 200 km in kyushu in the chubu district it is subducting seismically at a shallow dip and then bends downward beneath the volcanic area whereas in the kinki district it is subducting subhorizontally as far as the japan sea the differences in the slab geometry between adjacent regions correlate with the differences in volcanic activity suggesting the importance of the geometry of the philippine sea slab on arc magmatism our tomographic images further imply subduction of the philippine sea slab down to a depth of around 70 km northwest of the izu peninsula the philippine sea slab in that region might have split into western and eastern parts separated by a slab tear and collided with the pacific slab at depths of 150 200 km

crustal velocity field of southwest japan subduction and arc arc collision we investigate crustal deformation in southwest japan over a 3 year period revealed by a permanent dense global positioning system gps array southwest japan is a part of the amurian plate a microplate moving about 10 mm yr toward the east with respect to the eurasian plate it overrides the philippine sea plate at the nankai trough and collides with the northeast japan arc in the central part of japan in this paper we first derive gps site velocities relative to the stable part of the amurian plate in order to isolate signals of crustal deformation caused by the subduction and or the collision the velocity field has a conspicuous feature indicating the interseismic elastic loading by the philippine sea plate slab at the nankai trough characterized by the northwestward movements of points throughout the studied area their amplitudes are the largest at the pacific coast and decay toward the japan sea coast with a subtle systematic shift of azimuths a model assuming an elastic half space the convergence rate at the nankai trough based on a refined euler vector and the strength of the coupling inferred from a thermal model could explain the velocity field in the western part of the studied area to a large extent those in the eastern part systematically deviate from them and the residual components there show east west shortening and north south extension this may represent crustal thickening and trenchward extrusion of crustal blocks caused by the collision between southwest and northeast japan this suggests that the collision between southwest and northeast japan gives rise to not only crustal thickening but also trenchward extrusion of crustal block a velocity contrast was found across the median tectonic line the largest inland active fault in japan but the current permanent gps network is not dense enough for us to discuss its coupling depth

tectonic controls of phanerozoic sedimentary rock cycling the cyclic nature of the phanerozoic sedimentary rock distribution carbon sulphur coupling and material transfer among sedimentary reservoirs appears to be controlled by tectonic factors the distribution of preserved sedimentary mass in terms of rock mass remaining u geologic age shows a minimum c 300 350 ma ago which separates two subcycles of erosion and deposition of sedimentary rocks the older subcycle was interrupted because of the major continental collisions of the devonian and late carboniferous these collisions resulted in a reduction of outcrop areas of rocks of the older cycle relative to their masses leading to a decline in the probability of destruction and an increase in half life of these older sediments a strong correlation exists between the long term cyclicity in the phanerozoic global sea level curve and the distribution of carbon and sulphur among their major exogenic reservoirs this correlation is related to two principal tectonic modes of the phanerozoic oscillatory and submergent it is postulated that the submergent mode of active plate convergence obduction and subduction of sediments large ridge volume and high sea level gave rise to low erosion and sedimentation rates less restricted environments of carbonate deposition and relatively high atmospheric co 2 levels high temperatures resulting from an increased rate of production of co 2 from diagenetic and metamorphic reactions at subduction zones as sea level rose carbon was transferred from the sedimentary reservoir of reduced organic carbon to that of oxidized inorganic carbon in limestones whereas sulphur moved from the oxidized sulphate reservoir to the reduced sulphide reservoir as sea level fell reservoir transfers were opposite to those above culminating in the oscillatory mode of generally elevated continental interiors these reservoir transfers are consistent with secular changes observed in the distribution of 13 c and 34 s in sedimentary materials during the phanerozoic petrographic examination of phanerozoic oolite formations shows that ooids with preserved calcitic relict textures are characteristic of pre carboniferous carbonate rocks whereas ooids with relict textures indicative of initial aragonite mineralogy are dominant in rocks of younger age these changes in ooid mineralogy may be interpreted as reflecting changes in co 2 levels of the ocean atmosphere system consistent with the above tectonic considerations atmospheric co 2 levels were higher prior to carboniferous time favouring formation of calcitic ooids and skeletal parts after the carboniferous co 2 levels fell and aragonite and mg calcites of greater than 8 mol mg increased in abundance as precipitates

diagenesis of shallowly buried miocene lacustrine carbonates from the hoh xil basin northern tibetan plateau implications for stable isotope based elevation estimates the oxygen isotopic composition of lacustrine carbonate deposits has been frequently used to reconstruct paleoaltimetry of orogenic belts however the primary oxygen isotopic composition of lacustrine carbonate can be partially or wholly altered by post depositional diagenetic processes such as deep burial recrystallization and the interaction with geologically younger meteoric waters to better understand how ancient lacustrine carbonates are diagenetically modified by meteoric waters we present detailed mineralogy petrography stable carbon and oxygen isotopic compositions and major and minor element geochemistry of lacustrine carbonates from the miocene wudaoliang group which underwent only shallow burial 300 m in the hoh xil basin northern tibetan plateau our observations indicate that the primary mineralogy in the wudaoliang carbonate muds consists of a mixture of both low mg and high mg calcite during or shortly after deposition the carbonate muds experienced stabilization and associated carbonate cementation in a closed phreatic meteoric diagenetic system interaction with 18 o depleted meteoric waters during diagenesis slightly reduced 18 o c values but overall the wudaoliang carbonates largely retained primary oxygen isotope compositions our data support previous interpretations that 18 o c values of the wudaoliang group lacustrine carbonates are indicative of the primary 18 o composition of miocene meteoric water and can be used for paleoelevation estimate of the miocene hoh xil basin northern tibetan plateau by demonstrating the oxygen isotopic fidelity of the wudaoliang carbonates we are able to rule out open system meteoric diagenesis from younger meteoric waters and subsequent isotopic alteration this study highlights that integration of scanning electron microscope and cathodoluminescence petrography with stable isotopic and mineralogical data enables the determination of the extent of meteoric diagenetic alteration in lacustrine carbonates particularly whether the diagenetic systems were open or closed with respect to the oxygen isotope

the updip and downdip limits to great subduction earthquakes thermal and structural models of cascadia south alaska sw japan and chile this study examines thermal and structural controls of the updip and downdip rupture limits of great subduction thrust earthquakes data on past great earthquake seismic limits have been compiled for four continental subduction zones cascadia sw japan south alaska and chile these limits have then been compared to the predictions of several models for what constrains great earthquake rupture temperatures on the subduction thrusts have been estimated by finite element numerical models the landward limits of the observed updip aseismic zones correspond to the position where the thrust temperature reaches about 100 c that is depths of about 2 to 10 km for the subduction zones studied this temperature agrees with the dehydration of stable sliding smectite clays to illite chlorite the temperatures in this region are controlled mainly by the thickness of sediment on the incoming crust and by the crustal age and thus heat flow the downdip limits correspond to the depth on the thrust where either 1 the temperature reaches about 350 c which corresponds to thermally activated stable sliding behavior for crustal rocks with a transition to 450 c or 2 about 40 km depth if 350 c is reached at greater depth depths of about 40 km approximately correspond to the intersection of the thrust with the continental forearc moho and this downdip limit may be a consequence of stable sliding serpentinite or talc and other hydrated forearc mantle rocks the primary temperature controls on the downdip region are the age of the subducting oceanic plate and the thrust dip profile secondary control comes from the thickness of incoming sediment the convergence rate and the radioactive heat generation in the overlying forearc the 100 c updip limit occurs near the trench for young subducting plates with a thick sediment section such as cascadia 6 8 ma and up to 80 km landward for older oceanic crust such as south alaska 50 ma the 350 c downdip thermal limit is applicable for young oceanic plates e g cascadia and nankai whereas the forearc mantle limit applies for older plates e g south alaska and chile except near the chile rise for the margins studied that have experienced great earthquakes there is generally good agreement between the postulated thermal and moho limits and the rupture or seismogenic zone as defined by the distribution of aftershocks and by waveform tsunami and dislocation modeling the downdip limit of the interseismic locked zone from dislocation modeling is also in agreement with these limits

geological setting and genesis of coticules spessartine metapelites in the lower ordovician of the stavelot massif belgium the lower ordovician in the caledonian stavelot massif belgium contains a coticule member probably arenig in age composed of red hematite rich shales alternating with thin yellowish coticule beds these coticules are fine grained highly manganiferous metamorphic rocks mainly composed of spessartine garnet mica and quartz similar rocks of about the same age occur in several localities along the appalachian and caledonian fold belts the belgian coticules are thought to have originated from marly sediments which had been deposited rapidly probably by density currents and in which caco 3 had been diagenetically replaced by mnco 3 during metamorphism spessartine garnets were formed from this mnco 3 and mica manganese and iron are thought to have originated from volcanic exhalative processes

high precision slip distribution of the 1944 tonankai earthquake inferred from tsunami waveforms possible slip on a splay fault abstract inversion of tsunami waveforms is a well established technique for estimating the slip distributions of subduction zone earthquakes with some of the most detailed results having been obtained for earthquakes in the nankai trough sw japan the present study although it uses a method and tsunami waveform data set almost identical to previous study aims to improve on previous work by using a more precise specification of initial conditions for the calculation of tsunami green s functions specifically we incorporated four improvements in the present study 1 we used a realistic plate model based only on seismic survey results and assumed it to be the fault plane of the 1944 tonankai earthquake 2 the smallest subfaults consistent with the long wavelength approximation were used in the tsunami inversion analysis 3 we included the effect of horizontal displacement of the ocean bottom on tsunami generation and 4 we performed a checkerboard resolution test as obtained in previous studies a zone of high slip 2 0 m was resolved off the shima peninsula however the more precise calculation of tsunami green s functions has revealed additional detail that was not evident in previous studies which we demonstrate is resolvable and correlates with the position of known faults in the accretionary prism while there was little or no slip near the trench axis in the eastern part of the rupture zone there was up to 1 5 m of slip resolved within 30 km of the trough axis in the western part along the coast of the kii peninsula this troughward slip zone coincides with the position of a large splay fault mapped in multichannel reflection surveys furthermore it is also clear that the upper edge of the enshu fault off shima and atsumi peninsulas is consistent with the up dip limit of slip in the eastern part of our model we tested the possibility that slip occurred on the former splay fault instead of on the plate interface during the 1944 tonankai earthquake and find that slip on this splay fault is also consistent with the data although we cannot distinguish whether slip was dominant on the splay fault or on the plate interface we further suggest that the position of the enshu fault may be determined by the subduction of topographic highs and that such faults may have an important influence on the up dip rupture limit of the 1944 tonankai and potentially other subduction zone earthquakes

reply to comment by w p schellart on the thermal structure of subduction zone back arcs 1 currie and hyndman 2006 documented the evidence that the majority of continental back arcs are uniformly hot with thin lithospheres over regional extents of hundreds of kilometers even if where is no thermally significant extension using a number of independent observations we showed that eight such current subduction zones have similar thermal regimes with moho temperatures greater than 800 c 35 40 km depth and lithosphere thicknesses of 60 km the one exception the peru flat slab region of south america supports our model explanation we then presented the hypothesis that the elevated back arc temperatures have a common mechanism efficient transport of heat by vigorous thermal convection in hydrated low viscosity back arc upper mantle 2 the paper was structured such that the observations indicating regionally high back arc temperatures were separate and independent from our proposed model the evidence for high uniform temperatures seems secure the discussion is on the explanation schellart 2007 appears to agree that the back arcs included in our study are characterized by hot thin lithospheres but does not agree with our interpretation of the underlying cause his main criticisms are that 1 local tectonics in particular extension may account for the high temperatures in some areas and 2 three dimensional mantle flow and complex slab dynamics may produce elevated temperatures 3 we acknowledge as stated in the original paper that a number of site specific processes may affect the thermal regime at each back arc we also recognize that nearly all back arc regions have undergone at least some past extension as described by schellart 2007 notable exceptions are central alaska and the northern canadian cordillera the key question is whether or not this extension is the primary cause of the observed uniformly hot thermal regimes 4 schellart 2007 argues that high surface heat flow at some back arcs is due to recent extension including parts of the sunda borneo and ryukyu korea back arcs we note that our compilation used a number of independent observational constraints on lithosphere temperatures not just surface heat flow mantle temperatures determined using only surface heat flow data are highly uncertain due to the point sampling and measurement uncertainties and uncertainties in the thermal parameters used to calculate the geotherm other temperature constraints on upper mantle thermal structure include seismic velocities from refraction pn and tomography mantle xenolith thermobarometry effective elastic thickness te etc for each back arc the upper mantle temperatures from all constraints are in good agreement and show no significant lateral variation on a regional scale this is especially illustrated by the uniform low upper mantle seismic velocities for different back arcs currie and hyndman 2006 and references therein 5 extension affects the thermal regime by locally decreasing lithosphere thickness and by inducing upwelling of hot underlying mantle modeling studies have shown that such extension should only affect lithosphere temperatures and surface heat flow within 100 km of the extended region morgan 1983 alvarez et al 1984 and for continental crust extension may actually decrease surface heat flow due to thinning of the crustal radioactive heat generation waples 2001 in addition limited local extension should not significantly perturb the deep thermal region for the back arcs in our compilation there is no evident upper mantle temperature increase in more strongly extended regions suggesting that a more regional phenomenon is required to produce regionally elevated temperatures we also note that extension can only occur if the lithosphere is sufficiently hot that it is weak enough to fail under available extensional stresses a normal cool lithosphere is too strong to be deformed by plate tectonic forces e g hyndman et al 2005 we suggest that back arc extension is a consequence of high temperatures and associated weak lithosphere and not the primary cause 6 schellart 2007 also suggests a thermal role for a number of upper mantle dynamical processes including along margin mantle flow associated with a slab edge slab retreat advance and slab break off we agree that each of these factors may affect the back arc thermal regime in some locations however these are local phenomena if they are thermally important they should be evident in lateral variations in mantle seismic velocity and other deep temperature indicators lateral variations are not apparent in the current observational data 7 as stated in the original paper currie and hyndman 2006 paragraph 71 we do not rule out local factors in journal of geophysical research vol 112 b11408 doi 10 1029 2007jb005415 2007 click here for full article

mineralogical and compositional changes in bones exposed on soil surfaces in amboseli national park kenya diagenetic mechanisms and the role of sediment pore fluids abstract bones exposed on tropical savannah grasslands of amboseli national park kenya undergo extensive post mortem alteration within 40 years a combined analytical approach involving tem microscopy trace metal analysis ftir spectroscopy and petrographic analysis has revealed a complex dynamic diagenetic environment operating within exposed bones driven by evaporative transport of soil water from the bone soil interface to the upper exposed surface of the bone this process results in extensive bone soil water interaction and is responsible for increases in the concentrations of trace elements such as ba and la of 100 1000 within 15 years the maximum and mean size of bone crystallites increases with continued exposure this change in mean crystallite length is correlated positively with increases in bone crystallinity which in turn is associated with degradation of the bone protein microbial decomposition is rarely observed in the amboseli bones but where present resulted in severe dissolution reprecipitation of bone mineral many bones showed extensive permineralization of the larger vascular spaces with calcite and barite and to a lesser extent crandallite permineralization of unburied bones may account for 95 reduction in macro micron millimeter scale porosity in the bone within 2 years of death we produce a model for pre burial diagenesis of bone in arid tropical environments that highlights extensive alteration of bone chemistry within 1 40 years post mortem

the slip distribution of the 1946 nankai earthquake estimated from tsunami inversion using a new plate model abstract a new model for the shape of the philippine sea plate psp subducting beneath southwest japan was constructed by combining marine seismic survey results and seismicity data this resulted in a plate model that is generally 3 5 km shallower than previous estimates and contains new details of plate boundary structure near the nankai trough axis we estimated the slip distribution of the 1946 nankai earthquake by inverting tsunami waveforms using the new plate boundary model and found that the large slip off cape muroto and seismic moment were reduced by about 10 from the previous estimate of tanioka and satake 2001a however we also found reason to suspect the tide gauge closest to the epicenter at shimotsu and this resulted in a much more substantial reduction in the amount of slip in the eastern segment of the rupture area we also find that our new rupture model correlates well with features of the subducting plate boundary such as a large subducting seamount off cape muroto kodaira et al 2000a this suggests that such features have an important effect on either earthquake rupture propagation or the interseismic accumulation of elastic strain energy or both

revel a model for recent plate velocities from space geodesy 1 we present a new global model for recent plate velocities revel describing the relative velocities of 19 plates and continental blocks the model is derived from publicly available space geodetic primarily gps data for the period 1993 2000 we include an independent and rigorous estimate for gps velocity uncertainties to assess plate rigidity and propagate these uncertainties to the velocity estimates the velocity fields for north america eurasia and antarctica clearly show the effects of glacial isostatic adjustment and australia appears to depart from rigid plate behavior in a manner consistent with the mapped intraplate stress field two thirds of tested plate pairs agree with the nuvel 1a geologic 3 myr average velocities within uncertainties three plate pairs caribbean north america caribbean south america and north america pacific exhibit significant differences between the geodetic and geologic model that may reflect systematic errors in nuvel 1a due to the use of seafloor magnetic rate data that do not reflect the full plate rate because of tectonic complexities most other differences probably reflect real velocity changes over the last few million years several plate pairs arabia eurasia arabia nubia eurasia india move more slowly than the 3 myr nuvel 1a average perhaps reflecting long term deceleration associated with continental collision several other plate pairs including nazca pacific nazca south america and nubia south america are experiencing slowing that began 25 ma the beginning of the current phase of andean crustal shortening

geochemical evidence for sediment provenance in mudstones and fossil poor wackestones upper jurassic majorca island terra nova 24 437 445 2012 abstract the notion that diagenetic imprint on ancient carbonates significantly compromises palaeoenvironmental interpretations is revealed as an oversimplification the enigmatic case at the core of this research is an extended homogeneous macrofossil poor deposit showing distinctive dark brown colour and very fine grain size aumedra fm majorca island this markedly contrasts with standard ammonitico rosso ar facies known from jurassic epioceanic swells geochemical analysis of matrix micrite carbonate cements and belemnite rostra are used to interpret the aumedra carbonates stable carbon and oxygen isotopes and elemental abundance are compared with data from under and overlying deposits and coeval sections conspicuously higher than expected c and o isotope signature together with strontium enrichment and a typically low iron and manganese concentrations favour a distant shallower probably aragonitic sedimentary supply modern and ancient examples of carbonate deposition are integrated with possible hydrodynamic conditions justifying transport over the studied area a potential ne source is envisaged terra nova 00 1 9 2012

thermal conductivity determinations on solid rock a comparison between a steady state divided bar apparatus and a commercial transient line source device abstract two apparatuses were used to measure thermal conductivities on pairs of contiguous samples from 17 specimens of solid rock the usgs divided bar apparatus a steadystate comparative method and the shotherm quick thermal meter qtm which employs a transient strip heat source both devices were calibrated relative to fused silica both devices have a reproducibility of 5 or better depending to some extent on the physical nature of the specimen being tested for solid rocks specimen preparation for the divided bar is much more tedious and expensive than for the qtm which seems insensitive to minor surface roughness the qtm does however require quite large specimens 30 mm 60 mm 100 mm as a minimum for rocks with even larger specimens 50 mm 100 mm 100 mm required for higher conductivity material 3 5 w m 1 k 1 and greater experimental times are comparable however the qtm is a self contained unit that can be transported easily and set up quickly and requires no more space than a standard desk top from a formal statistical comparison it appears that over a large range of conductivities 1 4 to 5 w m 1 k 1 and rock types the two instruments will yield the same value of thermal conductivity for isotropic rocks

strontium increases and crystallinity changes in taphonomic and archaeological bone bone strontium levels and hydroxyapatite crystal sizes increased with time in two exposed wildebeest skeletons the strontium increases could not be removed by sequential washing according to the method of sillen a 1986 biogenic and diagenetic srca in plio pleistocene fossils of the omo shungura formation paleobiology12 311 323 human subfossil bone recovered archaeologically also showed evidence of extensive diagenetic reworking that resulted in crystal growth and elevated strontium levels the increase in bone strontium content was independent of nonapatitic contaminating crystal phases

distribution of radioactive heat production around an active fault and in accretionary prisms of southwest japan abstract contents of radioactive heat producing elements u th and k were measured on core samples from a borehole drilled into the shear zone of the active nojima fault southwest japan the heat production rate is rather uniform in a granite layer below 560 m with an average of 1 6 w m 3 in the lower part of the granite layer which is close to the fault zone the u th and u k ratios seem to be lower than those in the upper part a possible cause of this anomaly is redistribution of u by groundwater flows in highly fractured layers through monitoring of the temperature profile in the borehole a local anomaly which may be associated with groundwater flow along a fracture zone was detected in the uppermost part of the hole the conductive heat flow was found to increase with depth which is possibly due to downward fluid flow in the surrounding formations measurements of heat production were also made on rock samples from permian to cretaceous accretionary prisms in southwest japan the heat production of sandstone and mudstone major components of the accretionary prisms is about 1 5 w m 3 on average which is similar to the average value for granitic rocks in southwest japan these values are significantly higher than those reported in accreted terranes in the cascadia subduction zone

seismic consequences of warm versus cool subduction metamorphism examples from southwest and northeast japan warm and cool subduction zones exhibit differences in seismicity seismic structure and arc magmatism which reflect differences in metamorphic reactions occurring in subducting oceanic crust in southwest japan arc volcanism is sparse and intraslab earthquakes extend to 65 kilometers depth in northeast japan arc volcanism is more common and intraslab earthquakes reach 200 kilometers depth thermal petrologic models predict that oceanic crust subducting beneath southwest japan is 300 to 500 c warmer than beneath northeast japan resulting in shallower eclogite transformation and slab dehydration reactions and possible slab melting

thermal structure coupling and metamorphism in the mexican subduction zone beneath guerrero summary temperature is one of the most important factors that controls the extent and location of the seismogenic coupled and transition partially coupled segments of the subduction interplate fault the width of the coupled fault inferred from the continuous gps observations for the steady interseismic period and the transient width of the last slow aseismic slip event m w 7 5 that occurred in the guerrero subduction zone in 2001 2002 extends up to 180 220 km from the trench previous thermal models do not consider this extremely wide coupled interface in guerrero subduction zone that is characterized by shallow subhorizontal plate contact in this study a finite element model is applied to examine the temperature constraints on the width of the coupled area the numerical scheme solves a system of 2 d stokes equation and 2 d steady state heat transfer equations the updip limit of the coupling zone is taken between 100 and 150 c while the downdip limit is accepted at 450 c as the transition from partial coupling to stable sliding from the entire coupled zone the seismogenic zone extends only up to 82 km from the trench inferred from the rupture width of large subduction thrust earthquakes corresponding to the 250 c isotherm only a small amount of frictional heating is needed to fit the intersection of the 450 c isotherm and the subducting plate surface at 180 205 km from the trench the calculated geotherms in the subducting slab and the phase diagram for morb are used to estimate the metamorphic sequences within the oceanic subducting crust a certain correlation exists between the metamorphic sequences and the variation of the coupling along the interplate fault