changes in phytoplankton productivity and community structure in the northern south china sea during the past 260 ka abstract a high resolution molecular organic geochemical study of core md05 2904 reveals changes in the productivity and community structure of paleo phytoplankton during the last 260 ka in the northern south china sea scs multiple biomarkers including c37 alkenones dinosterol brassicasterol and c30 diols are used as representatives of haptophytes dinoflagellates diatoms and eustigmatophytes respectively the abundances and mass accumulation rates of biomarkers indicate that phytoplankton productivity was relatively higher during glacial periods than during interglacial periods however the phytoplankton community structure inferred from the relative abundance of biomarkers does not display any evident glacial interglacial cycles in agreement with previous studies our results also suggest a linkage between the increased paleo productivity and the enhanced east asian winter monsoon in the glacial northern scs the relatively stable pcs may reflect a lack of sensitivity of the phytoplanktonic groups to variations of nutrient composition on glacial interglacial and shorter time scales a long term decrease in the c37 alkenone abundance since mis 5 might have been related to the increasing influence of the northward intrusion of antarctic intermediate water and or sub antarctic mode water on the scs thermocline waters moreover the evolution of alkenone producers and changes in the coccolithophore genera on c37 alkenones might also have contributed to the long term decrease in the c37 alkenone abundance

large scale pseudotachylytes and fluidized cataclasites from an ancient subduction thrust fault in the kodiak accretionary complex kodiak island alaska pseudotachylyte occurs in black locally vitreous ultrafine grained fault rock microscopic observations show that the pseudotachylytes are composed of glass with vesicles amygdules microlites and flow structures indicating a frictional melt the pseudotachylyte is gradational to cataclasite and shows outcrop scale injection and ductile deformation structures the cataclasite was ductily mobile i e fluidized simultaneous with the formation and emplacement of pseudotachylyte melt the pseudotachylytic rocks postdate the stratal disruption fabric of associated shear zone melanges and show similar direction of thrust transport and have undergone limited subsequent deformation we interpret the stratal disruption as resulting from underthrusting of the subducting plate and pseudotachylyte development as the final activity of this thrust surface the gradational contacts between pseudotachylyte and cataclasite demonstrate that the cataclasite also formed as a seismic product and may represent paleoseismic rupture zones possibly of very great earthquakes with or without accompanying pseudotachylytes the pseudotachylytes are voluminous and many are spatially disconnected from generation surfaces this style is distinct from pseudotachylytes described in other environments and this may explain the rarity of documented examples of subduction thrust pseudotachylyte

frictional melting processes in planetary materials from hypervelocity impact to earthquakes frictional melting is the result of the conversion of mechanical deformation to heat under adiabatic conditions of slip within planetary materials which are mainly natural ceramics frictional melting occurs at high strain rates typically 10 2 s 1 and at slip velocities greater than 0 1 m s 1 t he pathway to friction melting is controlled by the mechanical properties of a rock s constituent minerals especially fracture toughness minerals with the lowest fracture toughnesses and breakdown temperatures are preferentially comminuted and fused to form the melt the product is a polyphase suspension comprising mineral and rock fragments enclosed in a liquid matrix this cools to form the rock type known as pseudotachylyte and at even higher strain rates it forms shock veins in meteorites and in impact craters which may contain high pressure mineral polymorphs the generation of melt on sliding surfaces can lubricate earthquake faults facilitate the post shock modification of impact craters and make landslides more hazardous

spring carbonate chemistry dynamics of surface waters in the northern east china sea water mixing biological uptake of co2 and chemical buffering capacity we investigated sea surface total alkalinity talk dissolved inorganic carbon dic dissolved oxygen do and satellite derived chlorophyll a in the connection between the yellow sea and the east china sea ecs during april to early may 2007 in spring changjiang dilution water cdw ecs offshore water and together with yellow sea water ysw occupied the northern ecs using 16 day composite satellite derived chlorophyll a images several algal blooms were identified in the cdw and ecs offshore water correspondingly biological dic drawdown of 73 20 mol kg 1 oversaturated do of 10 110 mol o2 kg 1 and low fugacity of co2 of 181 304 atm were revealed in these two waters ysw also showed co2 uptake in spring due to the very low temperature however its intrusion virtually counteracted co2 uptake in the northern ecs in the cdw and the ecs offshore water revelle factor was 9 3 11 7 and 8 9 10 6 respectively while relatively high revelle factor values of 11 4 13 0 were revealed in ysw in the ecs offshore water the observed relationship between dic drawdown and oversaturated do departed from the redfield ratio indicating an effect of chemical buffering capacity on the carbonate system during air sea reequilibration given the fact that the chemical buffering capacity slows down the air sea reequilibration of co2 the early spring dic drawdown may have durative effects on the sea surface carbonate system until early summer although our study is subject to limited temporal and spatial coverage of sampling these insights are fundamental to understanding sea surface carbonate chemistry dynamics in this important ocean margin

influences of riverine and upwelling waters on the coastal carbonate system off central chile and their ocean acidification implications a combined data set combining data from field campaigns and oceanographic cruises was used to ascertain the influence of both river discharges and upwelling processes covering spatial and temporal variation in dissolved inorganic carbon dic and aragonite saturation state this work was conducted in one of the most productive river influenced upwelling areas in the south pacific coasts 36 s additionally further work was also conducted to ascertain the contribution of different dic sources influencing the dynamics of dic along the land ocean range six sampling campaigns were conducted across seven stations at the biobio river basin covering approximately 200 km three research cruises were undertaken simultaneously covering the adjacent continental shelf including 12 sampling stations for hydrographic measurements additionally six stations were also sampled for chemical analyses covering summer winter and spring conditions over 2010 and 2011 our results evidenced that seaward extent of the river plume was more evident during the winter field campaign when highest riverine dic fluxes were observed the carbonate system along the river ocean continuum was very heterogeneous varying over spatial and temporal scales high dic and pco2 were observed in river areas with larger anthropogenic effects co2 supersaturation at the river plume was observed during all campaigns due to the influence of low ph river waters in winter spring and high pco2 upwelling waters in summer 13cdic evidenced that main dic sources along the river and river plume corresponded to the respiration of terrestrial organic matter we have linked this natural process to the carbonate saturation on the adjacent river influenced coastal area suggesting that aragonite undersaturation in surface subsurface waters is largely modulated by the influence of both river discharge and coastal upwelling events in this productive coastal area conditions of low aragonite might impact negatively physiological traits for marine organisms such as bivalves gastropods and crustaceans therefore local populations from river influenced sites could be inherently more tolerant to ocean acidification than organisms living in regions with lower aragonite variability

the combined effects of ocean acidification mixing and respiration on ph and carbonate saturation in an urbanized estuary puget sound is a large estuary complex in the u s pacific northwest that is home to a diverse and economically important ecosystem threatened by anthropogenic impacts associated with climate change urbanization and ocean acidification while ocean acidification has been studied in oceanic waters little is known regarding its status in estuaries anthropogenically acidified coastal waters upwelling along the western north american continental margin can enter puget sound through the strait of juan de fuca in order to study the combined effects of ocean acidification and other natural and anthropogenic processes on puget sound waters we made the first inorganic carbon measurements in this estuary on two survey cruises in february and august of 2008 observed ph and aragonite saturation state values in surface and subsurface waters were substantially lower in parts of puget sound than would be expected from anthropogenic carbon dioxide co2 uptake alone we estimate that ocean acidification can account for 24e49 of the ph decrease in the deep waters of the hood canal sub basin of puget sound relative to estimated pre industrial values the remaining change in ph between when seawater enters the sound and when it reaches this deep basin results from remineralization of organic matter due to natural or anthropogenically stimulated respiration processes within puget sound over time however the relative impact of ocean acidification could increase significantly accounting for 49e82 of the ph decrease in subsurface waters for a doubling of atmospheric co2 these changes may have profound impacts on the puget sound ecosystem over the next several decades these estimates suggest that the role ocean acidification will play in estuaries may be different from the open ocean published by elsevier ltd

dual isotope measurements reveal zoning of nitrate processing in the summer changjiang yangtze river plume riverine nitrogen input into the coastal zone has increased remarkably in recent decades yet its transformation and recycling within hydrodynamically active regions remains unclear using observations of nitrate concentration and dual isotopic composition across the changjiang river plume within a three end member mixing model we found deviations between the observed and expected values for mixing alone revealing the nonconservative behavior of nitrate using cross correlations between concentrations and dual isotope deviations we identified three nitrogen transformation zones which correspond to separate portions of the plume nitrification and sedimentary denitrification occurred near the river mouth nitrification prevailed further offshore under the plume and finally phytoplankton assimilation occurred in the outer surface plume 100 km offshore where it was fueled by nitrate that had already been strongly modified by microbial processes information was assembled into a conceptual model offering an overview of nitrogen transformations in a large river plume

coseismic fluid rock interactions at high temperatures in the chelungpu fault chemical and isotopic variations in crushed material along the chelungpu fault in taiwan are suggestive of interactions at high temperatures with coseismically generated aqueous fluids high fluid pressures along the fault zone during the magnitude 7 6 chi chi earthquake in 1999 could have reduced friction and fault strength aqueous fluids are thought to have an essential role in faulting and the dynamic propagation of earthquake rupture fluid overpressure can affect earthquake nucleation1 2 and in a process termed thermal pressurization pore fluid pressure produced by frictional heating can reduce the effective normal stress acting on the fault surface3 4 5 this may lead to a marked reduction in fault strength during slip however the coseismic presence of fluids within slip zones and the role of fluids in dynamic fault weakening is still a matter of debate here we present compositions of major and trace elements as well as isotope ratios of core samples representing relatively undamaged as well as very fine grained deformed material from three active zones of the chelungpu fault taiwan depth profiles across the most intensely sheared bands that range in thickness from 2 15 cm exhibit sharp compositional peaks of fluid mobile elements and of strontium isotopes we suggest that high temperature fluids 350 c derived from heating of sediment pore fluids during the earthquake interacted with material within the fault zone and mobilized the elements the coseismic presence of high temperature fluids under conditions of low hydraulic diffusivity6 within the fault zone is favourable for thermal pressurization this effect may have caused a dynamic decrease of friction along the chelungpu fault during the 1999 magnitude 7 6 chi chi earthquake

shallow depth caco3 dissolution evidence from excess calcium in the south china sea and its export to the pacific ocean national basic research program of china 973 program 2009cb421201 2009cb421206 national science foundation of china nsfc 40821063 90711005 south china sea institute of oceanology the chinese academy of sciences

dynamics of the carbonate system in a large continental shelf system under the influence of both a river plume and coastal upwelling national basic research program of china 973 program 2009cb421201 national science foundation of china nsfc 90711005 40821063 nsfc rgc 40731160624 n hkust623 07 scope project

spring of no kuroshio intrusion in the southern taiwan strait 1 the taiwan strait connects the east china sea ecs to the south china sea scs typically in spring the water in the scs and a branch of the kuroshio occupy the eastern part of the strait while the china coastal waters including a large contribution from the changjiang yangtze river occupy the western part during spring 2008 when the taiwan strait was under the influence of la nina and according to field observations the kuroshio branch did not contribute much to the waters in the southern taiwan strait a numerical model verifies this observation the china coastal waters also seem to have had less effect than in typical years since the scs waters contain more nutrients than the kuroshio branch more nutrients may be transported from the scs to the ecs in a la nina spring than at other times

disappearing ink how pseudotachylytes are lost from the rock record abstract melt origin pseudotachylytes are the most widely accepted feature recording earthquake slip in the fault rock record however reports of pseudotachylytes are rare compared to the frequency and distribution of earthquakes in active faults suggesting melting occurs only under exceptional circumstances and therefore that pseudotachylytes are rarely formed in this paper we document the processes whereby pseudotachylytes are overprinted destroyed and otherwise removed from the rock record we present examples of recrystallized altered and cataclastically and crystal plastically deformed pseudotachylytes from a variety of ancient faults based on these observations we identify characteristics of pseudotachylytes that are resistant to change over geologic time and develop criteria to allow recognition of relict pseudotachylytes our results imply that pseudotachylytes are vastly under reported due to their vulnerability to destruction and the resulting difficulty in identification as a consequence the significance of frictional melting is underestimated the criteria we propose to distinguish relict pseudotachylytes can help to reconcile the observed frequency of earthquakes with the difficulty of demonstrating ancient seismic slip in the rock record

intensified upwelling over a widened shelf in the northeastern south china sea 1 observational and three dimensional modeling studies reveal that the intensified upwelling in the northeastern south china sea nscs is formed as a result of intensified upslope advection of dense deep waters that cross the middle shelf toward the inner shelf over a distinctly eastward widened shelf the strongest advection occurs over the converging isobaths near the head of the widened shelf as these dense deep waters advance shoreward they are advected downstream by the quickly developed upwelling current over the inner shelf and eventually outcropped at the lee of a coastal cape dynamically the shoreward cross isobath transport over the widened shelf is geostrophically enhanced by a quasi barotropic negative westward along isobath pressure gradient force as a result of the net rate of the momentum influx and by an intensified bottom frictional transport owing to the flow confluence near the head of the widened shelf a negative pressure gradient also exists at the lee of the coastal cape over the inner shelf and locally amplifies shoreward motion induced by the respective widened shelf and the coastal promontory the along isobath variations of cross isobath transport in the water column over the middle and inner shelves interactively characterize intensified upwelling in the nscs

high resolution topography for understanding earth surface processes opportunities and challenges abstract in the last decade a range of new remote sensing techniques has led to a dramatic increase in terrain information providing new opportunities for a better understanding of earth surface processes based on geomorphic signatures technologies such as airborne and terrestrial lidar light detection and ranging to obtain high resolution topography have opened avenues for the analysis of landslides hillslope and channellization processes river morphology active tectonics volcanic landforms and anthropogenic signatures on topography this review provides an overview of the recent flourishing literature on high resolution topographic analyses underlining their opportunities and critical issues such as their limitations the goal is to provide answers to questions such as what kind of processes can be analyzed through high resolution topographic data and how to do it the review focuses on two different environments natural and engineered landscapes in both contexts high resolution topography offers opportunities to better understand geomorphic processes from topographic signatures particular attention is given to engineered landscapes in which the direct anthropic alteration of processes is significant the last part of the review discusses future challenges

aragonite saturation state dynamics in a coastal upwelling zone 1 coastal upwelling zones may be at enhanced risk from ocean acidification as upwelling brings low aragonite saturation state ar waters to the surface that are further suppressed by anthropogenic co2 ar was calculated with ph pco2 and salinity derived alkalinity time series data from autonomous ph and pco2 instruments moored on the oregon shelf and shelf break during different seasons from 2007 to 2011 surface ar values ranged between 0 66 0 04 and 3 9 0 04 compared to an estimated pre industrial range of 1 0 0 1 to 4 7 0 1 upwelling of high co2 water and subsequent removal of co2 by phytoplankton imparts a dynamic range to ar from 1 0 to 4 0 between spring and autumn freshwater input also suppresses saturation states during the spring winter ar is less variable than during other seasons and is controlled primarily by mixing of the water column

variability of alkalinity and the alkalinity salinity relationship in the tropical and subtropical surface ocean the variability of total alkalinity ta and its relationship with salinity in the tropical and subtropical surface ocean were examined using data collected in various marine environments from a ship of opportunity in the open ocean regions of the atlantic pacific and indian oceans sea surface ta variability was observed to be mainly controlled by the simple dilution or concentration sdc effect of precipitation and evaporation and the measured concentrations of ta agreed well with those predicted from salinity and temperature non sdc changes in alkalinity in ocean margins and inland seas were examined by comparing the salinity normalized alkalinity with that of the open ocean end member non sdc alkalinity additions to the western north atlantic margin eastern north pacific margin and mediterranean sea were identified which mainly resulted from river inputs and shelf currents in contrast removal of ta through formation and sedimentation of calcium carbonate was observed to be an important control in the red sea the concentration of the river end member can only be reliably derived from the y intercept of ta s regression tas0 in river dominated systems such as estuaries and river plumes in coastal regions where other processes evaporation shelf currents upwelling calcification etc are more influential tas0 can significantly deviate from the river water concentration and hence be an unreliable indicator of it negative values of tas0 can result from non sdc ta removal at the low salinity end relative to the salinity of the oceanic end member and or non sdc ta addition at high salinities as occurs in the mediterranean sea

dynamics and production of dissolved organic carbon in a large continental shelf system under the influence of both river plume and coastal upwelling we examined the dynamics and production of dissolved organic carbon doc on a large continental shelf in the northern south china sea which is largely shaped by a river plume and coastal upwelling based on a cruise in summer 2008 the plume water extended from the mouth of the pearl river estuary to the middle shelf and was characterized by high doc concentrations while the upwelled water occupying the nearshore area featured low doc concentrations biological production of doc was observed in both the river plume and the coastal upwelling zones with different behavior between regions the system appeared to be autotrophic in terms of doc throughout the plume while in the upwelling circulation the metabolism of doc was mixed trophic nevertheless the integrated net doc production rate of 11 5 6 9 mmol c m 2 d 1 in the upwelling zone was comparable to that in the plume 7 1 7 0 mmol c m 2 d 1 the net doc production correlated strongly with net consumption of dissolved inorganic carbon dic and inorganic nutrients suggesting that the net doc production was highly coupled to net community production ncp in both the plume and upwelling zones both regimes had similar doc ncp partitioning with 19 27 of ncp in the plume and 24 26 of ncp in the upwelling zones converted to doc a positive correlation was also found between particulate organic carbon poc and net dic consumption with higher poc production in the upwelling zones where large phytoplankton prevailed most ncp removal occurred through poc sinking and or the diffusion and horizontal transport of doc

acidification mediated by a river plume and coastal upwelling on a fringing reef at the east coast of hainan island northern south china sea we investigated the dynamics of carbonate system which was greatly modulated by a river plume and coastal upwelling in july 2014 and july 2015 at the east coast of hainan island where a fringing reef distributes inshore by using a three end member mixing model we semi quantitatively estimated the removal of dissolved inorganic carbon dic mediated by biological production in the river plume and upwelled water to be 13 17 mol kg 1 and 15 16 mol kg 1 respectively the enhanced organic production was mainly responsible for these dic consumptions in both two regimes however nearly a half of dic removal was attributed to biocalcification in the plume system while it was negligible in the upwelling system furthermore the modeled results over reefs revealed that river plume and coastal upwelling were two major threats of acidification to coral communities at the east coast of hainan island during cruises in comparison the biological contribution to acidification was limited for balancing between organic production and biocalcification during july 2014 cruise whereas the acidification was greatly intensified by organic degradation during july 2015 cruise it was verified that naturally local acidification physical and biological processes played a major role in great ph decreases on a short term scale leading to coastal waters more vulnerable to anthropogenic ocean acidification uptake of atmospheric co2 by reducing buffering capacity of waters finally effects of acidification associated with other local threats on a fringing reef was further depicted with a conceptual model

pseudotachylyte from an ancient accretionary complex evidence for melt generation during seismic slip along a master decollement pseudotachylyte is present in the shimanto accretionary complex in shikoku japan the pseudotachylyte occurs as a vein in a fault zone and displays flow structure tio 2 microlites and other melting related textures the mineral assemblage of the pseudotachylyte suggests that the temperature was raised at least 450 c above the background levels in the host rocks this is the first direct evidence of seismogenic fault rock from an accretionary complex the pseudotachylyte bearing fault is a roof thrust above underthrusted melange which is overlain by an offscraped package of coherent units the geologic setting of the pseudotachylyte is consistent with melt generation during seismic slip along the master decollement in the subduction zone

flood discharges of a small river into open coastal waters plume traits and material fate abstract the dynamics of plumes from large rivers are relatively well known many estuaries are small however and discharge directly onto exposed open shorelines and presumably produce smaller plumes that may have different properties therefore this study measured traits of a small estuary on the australian east coast as a model system focusing on a plume size b distinctness of plume edges and c imprints on the seafloor although plumes were found to be limited in spatial extent ca 1 km offshore 2 4 km longshore and were constrained near the shore by onshore winds they exported high nutrient loads from an urbanised watershed the small plumes were shallow

pseudotachylytes in an ancient accretionary complex and implications for melt lubrication during subduction zone earthquakes abstract pseudotachylyte bearing fault zones found in the shimanto accretionary complex southwest japan developed during subduction or underplating at seismogenic depths the pseudotachylytes occur in narrow dark veins less than a few millimeters thick that are sharply bounded by foliated cataclasites that originated from a melange the microstructures of pseudotachylytes are represented by a fragment laden glass supported texture resulting from the rapid cooling of the frictional melt transmission electron microscopy reveals the presence of glass in which euhedral microcrystals of mullite are locally developed the compositions of the pseudotachylyte matrix and the characteristics of the unmelted grains and microlites in the matrix suggest that frictional melting occurred in an illite rich slip zone with a minimum melting temperature of 1100 c the viscosities of the frictional melt were calculated from the pseudotachylyte matrix composition as well as from the volume fraction and aspect ratio of the unmelted grains the viscosities at 1100 c range from 85 to 290 pa s and the corresponding shear resistance along a 1 mm thick melt layer at a slip rate of 1 m s was 0 1 0 3 mpa the formation of a melt layer in an illite rich slip zone can possibly induce large stress drops increase the slip rate and enhance rupture propagation which together could affect the earthquake magnitude in a subduction zone

silicon isotope constraints on sources and utilization of silicic acid in the northern south china sea the stable silicon isotopic composition 30si of waters and diatoms has increasingly been used to investigate the biogeochemical cycling of si in the major ocean basins here we present the first si isotope data set from the northern south china sea nscs a large marginal sea system in the western north pacific to examine sources and utilization of silicic acid si oh 4 during two cruises in july august 2009 summer and january 2010 winter samples for isotope measurements of dissolved si oh 4 30sisi oh 4 and of biogenic silica 30sibsi in suspended particles were collected along a transect perpendicular to the coast from the inner shelf to the deep water slope as well as at the south east asian time series study seats station located in the nscs basin surface 30sisi oh 4 generally increased from values 2 3 on the inner shelf to 2 8 above the deep basin suggesting an increasing utilization of dissolved si oh 4 reflecting the transition from eutrophic to oligotrophic conditions the 30sibsi values were systematically lower than the corresponding 30sisi oh 4 in the euphotic zone above 100 m on the shelf and slope in contrast at station seats in the nscs basin 30sibsi signatures in both seasons were within error equal to 30sisi oh 4 in the surface mixed layer above 50 m and 30sibsi in waters below were significantly higher than the corresponding 30sisi oh 4 by comparing the field data with the si isotope fractionation revealed by the rayleigh or the steady state models we demonstrate the existence of variable si oh 4 origins in different areas of the nscs surface waters on the inner shelf were largely fed by nutrients from the pearl river input while the primary source of si oh 4 for the euphotic zone on the outer shelf and slope was upwelling or vertical mixing from underlying waters the si oh 4 in the surface mixed layer of the nscs basin might have originated from horizontal mixing with other highly fractionated surface waters as a consequence the si isotope dynamics in the nscs are largely controlled by variable biological fractionation of si in waters from different sources with different initial si isotopic compositions rather than any single source water

biological and physical forcing of carbonate chemistry in an upwelling filament off northwest africa results from a lagrangian study the mauritanian upwelling system is one of the most biologically productive regions of the world s oceans coastal upwelling transfers nutrients to the sun lit surface ocean thereby stimulating phytoplankton growth upwelling of deep waters also supplies dissolved inorganic carbon dic high levels of which lead to low calcium carbonate saturation states in surface waters with potentially adverse effects on marine calcifiers in this study an upwelled filament off the coast of northwest africa was followed using drifting buoys and sulphur hexafluoride to determine how the carbonate chemistry changed over time as a result of biological physical and chemical processes the initial phtot in the mixed layer of the upwelled plume was 7 94 and the saturation states of calcite and aragonite were 3 4 and 2 2 respectively as the plume moved offshore over a period of 9 days biological uptake of dic 37 mol kg 1 reduced pco2 concentrations from 540 to 410 atm thereby increasing phtot to 8 05 and calcite and aragonite saturation states to 4 0 and 2 7 respectively the increase 25 mol kg 1 in total alkalinity over the 9 day study period can be accounted for solely by the combined effects of nitrate uptake and processes that alter salinity i e evaporation and mixing with other water masses we found no evidence of significant alkalinity accumulation as a result of exudation of organic bases by primary producers the ongoing expansion of oxygen minimum zones through global warming will likely further reduce the caco3 saturation of upwelled waters amplifying any adverse consequences of ocean acidification on the ecosystem of the mauritanian upwelling system

co seismic frictional melting along an out of sequence thrust in the shimanto accretionary complex implications on the tsunamigenic potential of splay faults in modern subduction zones abstract out of sequence thrusts ost play an important role in the thickening of accretionary prisms formation of forearc basins and tsunami generation in subduction zones by detailed investigations of geological and paleogeothermal structures an ancient seismogenic ost is identified in the shimanto accretionary complex southwest japan this ost consists of a mappable en echelon fault system developed at a late stage of the accretionary process the estimated accumulated displacement of 2 5 8 5 km and formation depth of 2 5 5 5 km based on a thermal analysis indicates much higher fault activities sense of slip with a sinistral slip and the large displacement was distributed among multiple small faults each with a small offset most of the faults in the en echelon fault system recorded repeated brittle failure and one fault preserves pseudotachylyte a fault rock indicative of seismic faulting this is the first report of pseudotachylyte along an ost in an accretionary prism repeated fracturing in the same narrow shear zones each only a few millimeters thick suggests the osts perform as major shear localized zone in the accretionary prism shallow estimated formation depth and consequent low normal stress also support the hypothesis by a weak coupling along this fault zone these findings are in accord with a thrust activity in the shallow portion of the accretionary prism being associated with rupture propagation from the deep seismogenic region this ost showed high activity and repeated faulting in the shallow portion of the accretionary prism comparable to that of the submarine tsunamigenic ost in the present nankai trough

a fault constitutive relation accounting for thermal pressurization of pore fluid 1 the heat generated in a slip zone during an earthquake can raise fluid pressure and thereby reduce frictional resistance to slip the amount of fluid pressure rise depends on the associated fluid flow the heat generated at a given time produces fluid pressure that decreases inversely with the square root of hydraulic diffusivity times the elapsed time if the slip velocity function is crack like there is a prompt fluid pressure rise at the onset of slip followed by a slower increase the stress drop associated with the prompt fluid pressure rise increases with rupture propagation distance the threshold propagation distance at which thermally induced stress drop starts to dominate over frictionally induced stress drop is proportional to hydraulic diffusivity if hydraulic diffusivity is 0 02 m2 s estimated from borehole samples of fault zone material the threshold propagation distance is 300 m the stress wave in an earthquake will induce an unknown amount of dilatancy and will increase hydraulic diffusivity both of which will lessen the fluid pressure effect nevertheless if hydraulic diffusivity is no more than two orders of magnitude larger than the laboratory value then stress drop is complete in large earthquakes

geochemical signals for determining the slip weakening mechanism of an ancient megasplay fault in the shimanto accretionary complex 1 to investigate the slip behavior of a megasplay fault branching from a subduction boundary megathrust we investigated the geochemistry of an out of sequence thrust that formed at 2 5 5 5 km depth rocks from the slip zone show major element and fluid immobile trace element compositions that are consistent with disequilibrium flash melting distinct depletions of li rb and cs in the slip zone rocks indicate fluid rock interactions at high temperatures 350 c these findings suggest a slip process in which high temperature pore fluids were generated by frictional slip but the thermally enhanced pressure might not have reached a sufficient level to cause thermal pressurization and the temperature continued to increase to attain melting of mica minerals comparison with slip zone that formed at a shallower depth 1 2 km where only thermal pressurization occurred suggests a transition from melt lubrication at depth to thermal pressurization at shallower depths along a megasplay faults

superheated friction induced melts in zoned pseudotachylytes within the adamello tonalites italian southern alps pseudotachylytes and cataclasites are present along a strike slip fault zone in the tonalites of the adamello intrusion italian southern alps ambient conditions during faulting were 0 25 0 3 gpa and 250 300 c pseudotachylyte veins thicker than 6 mm are zoned and consist of two symmetric microlitic domains towards the vein walls and a central spherulitic domain the thickness of the microlitic domains x increases linearly with the half total thickness a of the pseudotachylyte vein commonly 2 cm according to the relation x 0 29 0 12 a the spherulitic and microlitic domains have similar chemical composition but the microlitic domain has a lower amount of plagioclase clasts a numerical model explains zoning as the result of the different cooling rates and clast melt interactions at the center and periphery of thick veins zoning is compatible with the injection of a single pulse of superheated friction induced melt tmelt 1450 c melt temperatures estimated by the clast matrix ratio o hara 2001 are considerably lower 316 577 c it is suggested that the difference in the temperature estimates reflects a more complex slip history than a single seismic slip event along the fault during production of cataclasites pseudotachylytes

viscosity determinations of some frictionally generated silicate melts implications for fault zone rheology at high strain rates analytical scanning electron microscopy has been used to determine the major element compositions of some natural and artificial silicate glasses and their microcrystalline equivalents derived by the frictional melting of intermediate to acid protoliths the data show that the matrices of the friction melts which cool to form pseudotachylytes are relatively basic and hydrous even when their protoliths are intermediate to acid this is because frictional fusion involves the selective comminution and nonequilibrium melting of minerals based on their individual mechanical properties and melting points not the formation of minimum melts through equilibrium mineral interaction this means that hydrous ferromagnesian minerals e g micas and amphiboles melt preferentially to form the liquid matrix while feldspars and especially quartz more readily survive as clasts pseudotachylytes generated by frictional melting are therefore not bulk melts and as clast melt suspensions they cannot be considered as simple newtonian fluids the calculated viscosities of the friction melts are low for example at 1200 c most friction melts possess zero shear suspension viscosities of 102 104 dpa s 1 dpa s 1 p this is equivalent to the viscosities of tholeiitic and alkaline basaltic magmas at the same temperature these viscosities are maximum determinations because as clast melt suspensions friction melts may undergo shear thinning and exhibit pseudoplasticity at high shear rates i e during slip on a fault surface contrary to earlier suggestions where the bulk melting of intermediate to acid protoliths was believed to result in the generation of viscous friction melts that could act to inhibit continued sliding this work shows that most pseudotachylytes are partial melts possessing low viscosities the formation of highly fluid suspensions during slip may have profound effects on the dissipation of stored strain energy in the rocks surrounding a fault interface lubrication could facilitate an increase in the slip rate and the rate of energy dissipation this would be manifest as an increase in high frequency seismic wave radiation and vibrational

channel network extent in the context of historical land use flow generation processes and landscape evolution in the north carolina piedmont intensive agricultural land use in the 18th to early 20th centuries on the southeastern piedmont resulted in substantial soil erosion and gully development today many historically farmed areas have been abandoned and afforested and such landscapes are an opportunity to study channel network recovery from disturbance by gullying channel initiation mapping watershed area slope relationships and field monitoring of flow generation processes are used to identify channel network extent and place it in hydrologic historical and landscape evolution context in six study areas in the north carolina piedmont 100 channel heads were mapped in fully forested watersheds revealing a channel initiation relationship of 380 as1 27 where a is contributing area m2 and s is local slope m m flow in these channels is generated by subsurface and overland flow the measured relative slope exponent is lower than expected based on literature values of 2 for forested watersheds with subsurface and overland flow suggesting that the channel network extent may reflect a former hydrological regime however geomorphic evidence of recovery in channel heads within fully forested watersheds is greater than those with present day pasture present day channel heads lie within hollows or downslope of unchanneled valleys which may be remnants of historical gullies and area slope relationships provide evidence of colluvial aggradation within the valleys channel network extent appears to be sensitive to land use change with recovery beginning within decades of afforestation channel initiation mapping and area slope relationships are shown to be useful tools for interpreting geomorphic effects of land use change copyright 2012 john wiley sons ltd

reconciling opposing views on carbon cycling in the coastal ocean continental shelves as sinks and near shore ecosystems as sources of atmospheric co2 despite their moderately sized surface area continental marginal seas play a significant role in the biogeochemical cycles of carbon as they receive huge amounts of upwelled and riverine inputs of carbon and nutrients sustaining a disproportionate large biological activity compared to their relative surface area a synthesis of worldwide measurements of the partial pressure of co2 pco2 indicates that most open shelves in the temperate and high latitude regions are under saturated with respect to atmospheric co2 during all seasons although the low latitude shelves seem to be over saturated most inner estuaries and near shore coastal areas on the other hand are over saturated with respect to atmospheric co2 the scaling of air sea co2 fluxes based on pco2 measurements and carbon massbalance calculations indicate that the continental shelves absorb atmospheric co2 ranging between 0 33 and 0 36 pg c yr 1 that corresponds to an additional sink of 27 to 30 of the co2 uptake by the open oceans based on the most recent pco2 climatology takahashi t sutherland s c wanninkhof r