decadal scale change of infiltration characteristics of a tephra mantled hillslope at mount st helens washington the cataclysmic 1980 eruption of mount st helens radically reduced the infiltration characteristics of 60 000 ha of rugged terrain and dramatically altered landscape hydrology two decades of erosional biogenic cryogenic and anthropogenic activity have modified the infiltration characteristics of much of that devastated landscape and modulated the hydrological impact of the eruption we assessed infiltration and runoff characteristics of a segment of hillslope thickly mantled with tephra but now revegetated primarily with grasses and other plants to evaluate hydrological modifications due to erosion and natural turbation eruptive disturbance reduced infiltration capacity of the hillslope by as much as 50 fold between 1980 and 2000 apparent infiltration capacities of plots on the hillslope increased as much as ten fold but remain approximately three to five times less than the probable pre eruption capacities common regional rainfall intensities and snowmelt rates presently produce little surface runoff however high magnitude low frequency storms and unusually rapid snowmelt can still induce broad infiltration excess overland flow after 20 years erosion and natural mechanical turbation have modulated but not effaced the hydrological perturbation caused by the cataclysmic eruption copyright 2005 john wiley sons ltd

the impact of hydrothermal mineral replacement reactions on the formation and alteration of carbonate hosted polymetallic sulfide deposits a case study of the artemis prospect queensland australia abstract hydrothermal sulfidation of carbonate rocks and the reverse replacement of sulfides by carbonates are important processes responsible for the formation and subsequent alteration of ore deposits these processes have been recognized in the case study of the artemis zn cu au prospect which is located in the cloncurry district within the eastern succession of the mount isa inlier nw queensland australia the high grade polymetallic mineralization displays a complex association of massive sulfides and carbonates hosted in a vertical marble lens adjacent to garnet bearing schist staurolite muscovite schist and quartzo feldspathic psammite petrographic analyses of drill core specimen by optical and electron microscopy micro x ray florescence elemental maps electron probe microanalyses cathodoluminescence and bulk geochemistry suggested three major stages of mineralization i pre ore stage marble calcite 0 ii ore stage involving sulfidation of the marble and precipitation of calcite 1 and spherical sulfide inclusions in the first episode and the formation of calcite 2 and massive sulfide in the second episode and iii post ore stage involving replacement of sulfides by calcite 3 and garnet mineral replacement reactions are dominant processes in rocks of ore stage and post ore stage the ore stage involved the dissolution of coarse and pristine calcite 0 ca0 95mn0 3fe0 2co3 and the precipitation of sulfides and calcite 1 ca0 96mn0 3fe0 1co3 and calcite 2 ca0 96mn0 3fe0 1co3 the sulfide assemblage consists of pyrrhotite sphalerite chalcopyrite galena arsenopyrite cobaltite costibite bi cubanite ag sulfides and au in decreasing order of abundance in episode 1 calcite 1 contains spherical sulfide inclusions while in episode 2 calcite 2 envelopes calcite 1 the replacement of co rich arsenopyrite fe0 75co0 26as1 13s0 83 by relatively co poor arsenopyrite fe0 86co0 15as0 99s0 99 via a coupled dissolution precipitation reaction occurred in episode 2 based on arsenopyrite geothermometry the temperatures for the first and second episode are 650 50 and 450 70 c respectively micro xrf elemental maps of the garnet bearing schist adjacent to the sulfidized marble revealed the sulfidation front where pre ore garnet and amphibole were replaced by pyrrhotite chalcopyrite au biotite and muscovite in the post ore stage calcite 2 was partially replaced by siderite and calcite 3 ca0 94mn0 4fe0 2mg0 1co3 which shows sectoral and oscillatory zoning galena was replaced by calcite 3 as documented by embayed lobate grain boundaries between these minerals and pyrrhotite fe 1 x s x 0 091 0 119 was pervasively replaced by garnet mn1 2fe1 2ca0 6 al2si3o12 the microscale investigations of the mineralization processes in the artemis orebody document the impact of hydrothermal mineral replacement reactions on metal sequestration mineral replacement reactions facilitate the formation of ore deposits and subsequent alteration processes which may lead to the loss of economic value of the deposit

source discrimination of fine grained deposits occurring on marine beaches the calvados beaches eastern bay of the seine france in tide dominated systems fine grained deposits occur in intertidal areas of inner estuaries as loci of convergence of fluvial and marine material even in the vicinity of estuaries mud deposits are rare on open sandy beaches this study focuses on temporary occurrences of muddy sediments on marine beaches along the calvados coastline in normandy adjacent to the macrotidal seine estuary france clay mineralogy major minor trace elements and radionuclides were used as particulate markers to determine the provenance of the mud deposits the fine fraction defined here as particles 50 m was analysed in surficial muddy sediments on seven beaches between the seine estuary and the orne river mouth sampled between february 2002 and june 2003 the deposits were compared to earlier holocene relict deposits which crop out on some beaches and on the shoreface and to mesozoic marls and limestones which have detached from the coastal cliffs the use of the three types of particulate markers revealed no significant seasonal or geographical variations between the beaches the muddy deposits were made up of the same sedimentary pool of particles the clay mineralogical and geochemical characteristics of these mud deposits enabled modern i e present day and earlier holocene fine silts and clays to be distinguished from ancient i e mesozoic sediments the use of radionuclides 60co and 137cs confirmed the marine influence in the modern deposits with a decreasing gradient along the calvados beaches towards the east the presence of several specific major minor trace elements e g ti p revealed that some of the fine material originated in the seine estuary despite the occurrence of easily erodable rocks i e clays marls and limestones in the coastal cliffs this source represented a limited supply which is only of local significance small rivers such as the orne dives and touques which discharge in the study area act as secondary suppliers of fine grained material to this system in spite of the exposed coastal setting where strong tidal currents and waves occur the beaches have become a distal part of the seine estuarine system and form a temporary sink for strongly mixed fine material mainly of riverine seine river and open marine bay of the seine and the central english channel origins this is consistent with the infilling of the estuary the reduction in accommodation space in its inner part and the offshore shifting of the depocentre of the mud

erosion of tephra from the 1980 eruption of mount st helens erosion of tephra on hillslopes north of mount st helens was measured at intervals of several months between 1980 and 1983 using large arrays of stakes rill erosion was initially greater than sheetwash but its importance decreased comparatively quickly both rill erosion and sheetwash decreased by one to two orders of magnitude over the three year period because a stable rill network developed and more permeable and less erodible substrates were created or exposed the decrease occurred prior to recovery of plants the causes for the rapid decline in erosion at mount st helens explain patterns of erosion following several other recent tephra eruptions basin wide annual rates of erosion were computed by mapping the surface cover the hillslope gradient and the texture and thickness of tephra and by using statistical relations developed between them and erosion rates annual erosion decreased from 26 mm between may 1980 and may 1981 to 1 8 mm between may 1982 and may 1983 projecting this rate of decline into the future indicated that only about one sixth of the tephra on hillslopes will be removed by water erosion before soil creep and other forms of mass wasting again dominate hillslope evolution

distribution of rare earth elements in surface sediments of the western gulf of thailand constraints from sedimentology and mineralogy abstract to understand the modern sedimentation and land sea interaction processes in the asian margin seas we analyze rare earth element contents ree i e la ce pr nd sm eu gd tb dy ho er tm yb lu and grain sizes detrital minerals from 158 surface sediment samples collected from the western gulf of thailand got the results reveal that the ree contents ranged from 25 42 g g to 201 21 g g with an average value of 137 21 g g and that the got is characterized by higher accumulations of lree relative to hree together with negative eu anomalies based on the spatial distribution characteristics of ree contents ce and eu the western got can be classified into three geochemical provinces the province i covers the northern and northwestern coastal zones of the got including the entire upper got its coarse size fraction and distribution pattern of hornblende and quartz dominated minerals caused ree contents to be the lowest and these sediments were mainly derived from the rivers around the upper got including the chao praya river and the kea klong river the province ii is located in the central got and has the highest ree concentrations due to finer sediment composition and higher contents of zircon authigenic pyrite and biogenetic limestone the province ii has two accumulation centers around samui island and koh chang island with ree spatial distribution influenced by the seasonal setting and mixed derived from multiple provenances around the got the province is located in the lower got close to malaysia the sediment type in this region is similar to that of province i except for different detrital mineral compositions especially the presence of siderite that is responsible for higher ree contents the sediments in this region exhibits similar distribution patterns to those of terrestrial materials from the malaysian peninsula such as that from the kelantan river the transportation processes of sediments in this region are mainly controlled by the coastal current

thickness distribution texture and stratigraphy and a simple probabilistic model for dynamical thickening of sea ice in the southern sea of okhotsk 1 sea ice thickness data and sea ice samples were analyzed to examine the characteristics of the ice thickness distribution and ice texture and to understand ice growth processes in the southern sea of okhotsk ice thickness data and samples were obtained aboard the icebreaker soya in early february the ice growth season ice thickness data which were obtained with a video monitoring system installed on the side deck of the ship each winter from 1991 to 2000 except 1995 show that the average thickness ranges from 19 7 to 55 23 cm and that it matches the characteristics of a poisson distribution ice structure analysis reveals that granular texture occupies about three quarters of the total ice thickness and that the ice exhibits a layered structure with unit thickness averaging 5 to 10 cm stratigraphy and stable isotopic composition of the ice indicate that snow ice accounts for 10 and frazil ice accounts for 64 of the total ice thickness this suggests that dynamic ice thickening processes such as frazil ice growth and piling up are more significant than congelation growth on the basis of these characteristics which resemble more those of antarctic than arctic sea ice we propose a conceptual model for the ice thickening process in this region it is shown that this model can explain the shape of the ice thickness distribution well and is analogous with the concept of the pancake cycle and multiple rafting of antarctic sea ice growth and thickening

estimation of sea ice thickness and volume in the sea of okhotsk based on icesat data sea ice thickness in the sea of okhotsk is estimated for 2004 2008 from icesat derived freeboard under the assumption of hydrostatic balance total ice thickness including snow depth h t o t averaged over 2004 2008 is 95 cm the interannual variability of h t o t is large from 77 5 cm 2008 to 110 4 cm 2005 the mode of h t o t varies from 50 60 cm 2007 and 2008 to 70 80 cm 2005 ice thickness derived from icesat data is validated from a comparison with that observed by electromagnetic induction instrument em aboard the icebreaker soya near hokkaido japan annual maps of h t o t reveal that the spatial distribution of h t o t is similar every year ice volume of 6 3 10 11 m 3 is estimated from the icesat derived h t o t and amsr e derived ice concentration a comparison with ice area demonstrates that the ice volume cannot always be represented by the area solely despite the fact that the area has been used as a proxy of the volume in the sea of okhotsk the ice volume roughly corresponds to that of annual ice production in the major coastal polynyas estimated based on heat budget calculations this also supports the validity of the estimation of sea ice thickness and volume using icesat data

an intrusion related origin for cu au mineralization in iron oxide copper gold iocg provinces major cu au deposits of iron oxide copper gold iocg style are temporally associated with oxidized potassic granitoids similar to those linked to major porphyry cu au deposits stable and radiogenic isotope evidence indicates fluids and ore components were likely sourced from the intrusions iocg deposits form over a range of crustal levels because co2 rich fluids separate from the magmas at higher pressures than in co2 poor systems thereby promoting partitioning of h2o cl and metals to the fluid phase at deep levels the magma fluid system cannot generate sufficient mechanical energy to fracture the host rocks as in porphyry systems and the iocg deposits therefore form in a variety of fault related structural traps where the magmatic fluids may mix with other fluids to promote ore formation at shallow levels the iocg deposits form breccia and fracture hosted mineralization styles similar to the hydrothermal intrusive breccias and sulphide vein systems that characterize many porphyry cu au deposits the fluids associated with iocg deposits are typically h2o co2 salt fluids that evolve by unmixing of the carbonic phase and by mixing with fluids from other sources in contrast fluids in porphyry systems typically evolve by boiling of moderate salinity fluid to produce high salinity brine and a vapor phase commonly with input of externally derived fluids these different fluid compositions and mechanisms of evolution lead to different alteration types and parageneses in porphyry and iocg deposits porphyry cu au deposits typically evolve through potassic sericitic and intermediate and or advanced argillic stages while iocg deposits typically evolve through sodic calcic potassic and carbonate rich stages and at deeper levels generally lack sericitic and argillic alteration the common association of porphyry and iocg cu au deposits with potassic oxidized intermediate to felsic granitoids together with their contrasting fluid compositions alteration styles and parageneses suggest that they should be considered as part of the broad family of intrusion related systems but that they are typically not directly related to each other

distribution of rare earth elements thorium and uranium in gulf of thailand s sediments distribution of rare earth elements rees thorium and uranium in 54 marine sediments collected from five selected areas along the gulf of thailand is discussed in this paper these areas have been selected as potential sites to set up thermal and nuclear power plants concentration of elements was determined using inductively coupled plasma mass spectrometry icp ms absolute concentrations of rees th and u show a sample to sample variation and may be due to different geological characteristic of area as well as grain size effect total ree concentrations not including y range between 9 4 and 206 g g the chondrite normalized ree patterns of all samples are similar to post archean australian shale paas and average upper continental crust with lrees enrichment relative to hrees lan ybn 6 5 29 fairly flat hrees patterns gdn ybn 1 0 3 8 and ubiquitous negative eu anomaly eu eu 0 3 0 7 th concentrations 0 9 28 g g are relatively higher than those of uranium 0 4 4 0 g g th u ratios 1 5 9 9 are higher than the average upper crust these results are consistent with terrigenous sediments that formed from the weathering and erosion of felsic rocks

rare earth elements geochemistry in surface floodplain sediments from the xiangjiang river middle reach of changjiang river china abstract the xiangjiang river is one of the most important tributaries of the changjiang river in southern china in this study floodplain sediments from the xiangjiang river have been analyzed for sediment grain size and trace and rare earth elements rees the results have been used to characterize the sediments ree composition and distribution and to identify the sediment sources and the effects of industrial pollution the total ree ree concentrations of the river sediments show wide variations ranging from 37 5 to 237 4 g g 1 with an average of 145 6 g g 1 the chondrite normalized ree patterns can be differentiated into two groups whereas the average upper continental crust ucc normalized ree pattern can be classified four groups ree shows strong positive correlations with clay r 0 91 and r 0 89 and strong negative correlations with sand r 0 91 implying that the grain size is an important factor in controlling the ree abundance because rees are preferentially enriched in clay minerals in fine sediments and diluted by quartz and carbonate minerals in coarse sediments ree yields strong positive correlations with mn r 0 78 and fe r 0 97 suggesting that the ree composition of xiangjiang river sediments is controlled by clay mineral compositions the reason is that fe and mn oxyhydroxides accumulate in fine grained sediments and control the ree abundance two stations xj08 and xj14 show different ucc and chondrite normalized ree distribution patterns with relative light rare earth element lree depletion and heavy rare earth element hree enrichment compared with other stations suggesting they have been polluted by industrial effluents therefore rees can be effectively used to trace sediment provenance and pollution sources

a high resolution record of rare earth element compositional changes from the mud deposit on the inner shelf of the east china sea implications for paleoenvironmental changes abstract a paleoenvironmental reconstruction of the east china sea ecs is presented using rare earth element ree analysis of sediments from core mz02 which was retrieved from the inner continental shelf s mud area the analytic results show that the total rees in the fine sediment vary between 137 76 g g and 231 53 g g with an average value of 187 69 g g obvious changes were found during the process of sedimentation by comparing with the ree compositions from the potential provenances the ratios of la sm ucc and gd yb ucc revealed that the sediments were mainly derived from river detrital outputs of the changjiang yangtze river minjiang and mountainous rivers from western taiwan island the contributions of terrestrial materials from these three main provenances were controlled by sea level change and the taiwan warm current twc chinese coastal current ccc system which is mainly driven by the east asian monsoon the high sedimentation rate during the transgression period between the late pleistocene and early holocene 13000 9800 a b p was caused by a well proportioned mixed provenance from changjiang western taiwanese rivers and minjiang sediments due to the lower sea level and the location of the foreshore nearshore face because of the stronger sediment reworking and erosion at the shelf edge during the early holocene 9800 7300 a b p the strengthening summer east asian monsoon transported the minjiang and western taiwanese river material northeastward and it became the main sediment source for fine sediments in the shallow sea region of the ecs while the changjiang provided a relatively minor amount of detrital sediment to the shelf the increasing strength of the twc might have played an important role in sediment dispersal and deposition on the ecs inner shelf during the period 7300 3500 a b p thus mountainous river material became the dominant sediment on the shelf of the ecs furthermore the results indicate that the east asian monsoon and the weakening of the twc were linked to an abrupt increase in changjiang derived terrigenous detritus material since 3500 a b p the source and sink pattern during this period is consistent with the modern sedimentation environment

rare earth element geochemistry of laminated diatom mats from tropical west pacific evidence for more reducing bottomwaters and higher primary productivity during the last glacial maximum rare earth elements ree along with selected major and trace elements were measured in laminated ethmodiscus rex diatom mats and associated sediments diatomaceous clay and pelagic clay in two sediment cores collected from the parece vela basin of the eastern philippine sea ree distributions are characterized by strong enrichment of middle ree mree and heavy ree hree over light ree lree and slight enrichment of mree over hree this distribution pattern suggests that ree compositions of the laminated e rex diatom mats were not the product of e rex blooms an inference also supported by the fact that ti normalized ree concentrations are not clearly different from those in the diatomaceous clay and pelagic clay comparison of ree patterns with the vertical distribution of authigenic phases in the sediment indicates that lree were dominantly associated with detrital materials whereas mree and hree were selectively enriched by mn oxyhydroxides and authigenic phosphates in the pelagic clay a weak negative ce anomaly cannot be linked to oxic depositional conditions but instead is attributed to the retention of a negative ce anomaly associated with authigenic phosphates in the laminated e rex diatom mats a weak positive ce anomaly is consistent with depositional sulfidic anoxic conditions and is interpreted to represent enhanced scavenging of reduced aqueous ce3 by barite in a strongly reducing environment moreover variably negative to positive ce anomalies in the diatomaceous clay may reflect the concurrent operation of the two processes controlling ce accumulation in the laminated e rex diatom mats and pelagic clay the study cores show a ubiquitous positive eu anomaly owing to the presence of volcanic materials the smaller eu anomaly in the laminated e rex diatom mats and diatomaceous clay relative to that in the pelagic clay may be attributed to the release of reduced eu2 from mineral phases to the sediment pore water under strongly reducing conditions previous studies have shown that the advection of lower circumpolar water lcpw strengthened during the last glacial maximum lgm which should have resulted in better ventilation of the deep eastern philippine sea evidence presented here for more reducing bottomwater conditions during the laminated e rex diatom mats formation implicates elevated primary productivity and enhanced organic sinking fluxes as primary controls on redox changes in the eastern philippine sea during the lgm enhanced primary productivity and more reducing bottomwaters during the laminated e rex diatom mats deposition resulted in a larger respired carbon pool in the deep eastern philippine sea which may have been part of a larger scale modulation of atmospheric co2 variation during pleistocene glacial interglacial cycles by deep ocean carbon storage c 2011 elsevier b v all rights reserved

rare earth element fractionation by selective sediment dispersal in surface sediments the skagerrak abstract neutron activation analysis was carried out to study the abundance distribution and fractionation of ree rare earth elements in surface sediment samples of 28 box cores collected along transects across the skagerrak results show that the clays have 3 5 times higher contents of k sc cr fe co rb k cs ta and th lree la and ce and mree sm eu and tb compared to sands and silts the hree yb and lu are only up to two times enriched in the clays and silts compared with the values measured in sands shale normalized ree patterns vary from flat for the sands towards enrichment 1 3 1 5 times of lree relative to hree in the clays this is consistent with published ree data for oceanic and riverine sediments and evidences fractionation hf and zr are up to thee times enriched in sands and silts compared to clays samples with highest contents of hf show hree enrichment in shale normalized ree patterns simple model calculations show that on the average zircon grains in skagerrak silts and sands contain 800 1200 ppm yb assuming that this value is also valid for the zircon grains in the shales this indicates that lower hree contents observed in atlantic ocean shelf and oceanic sediments compared to shales cannot be related to a greater abundance of zircon in shales

low latitude meteoric fluid flow along the cloncurry fault cloncurry district nw queensland australia geodynamic and metallogenic implications hydrothermal alteration within the mount isa block mib is typically largely to have ceased at the end of the isan orogeny ca 1 50 ga however late large brittle quartz rich vein systems including those of the cloncurry fault cut mesoproterozoic tectonic fabrics intrusions and products of regional na ca hydrothermal alteration associated features display affinities to iron oxide cu au ore deposits including specular hematite bearing veins and cu au u lree ba mineralization stable isotope data suggest late veins in the vicinity of the cloncurry fault eastern fold belt efb formed from fluids with 18oh2o and dh2o 250 c of 4 to 3 and 22 to 4 respectively the high dh2o moderate 18oh2o and cacl2 nacl rich character of the saline fluids indicates they were mixtures of low latitude meteoric fluids and evaporite derived basinal brines which with time became progressively dominated by meteoric water deposited barite and cooled the low latitude meteoric signature demonstrates that the fault fracture systems were active when in equatorial regions paleomagnetic data for the mib and the australian protocontinent together with structural and thermal considerations and geochronological arguments suggest the veins probably formed sometime after 1 10 ga and potentially as late as during the alice springs orogeny ca 0 34 ga the late quartz veining was unrelated to two phases of regional na ca alteration and economically significant fe oxide cu au mineralization at 1 60 1 58 and 1 53 1 50 ga

geochemistry of post 1540 ma granites in the cloncurry district northwest queensland proterozoic fe oxide cu au co mineralization in the cloncuriy district is spatially and temporally related to intrusion of voluminous postpeak metamorphic granites that form most of the williams and naraku batholiths detailed mapping and geochemical study of these granites in the southern part of the district have identified two groups of intrusions that are referred to here as the cloncurry supersuite and eureka supersuite the cloncurry supersuite is composed mainly of monzogranite and syenogranite which consist of quartz plagioclase alkali feldspar hornblende biotite with accessory magnetite titanite apatite and zircon the timing of intrusion of the wiley igneous complex is interpreted to be pre or syn d 3 based on overprinting relationships while hornblende geobarometry suggests an emplacement depth of approximately 14 km the granites are subalkaline high k metaluminous rocks and range from 59 to 74 wt percent sio 2 increasing sio 2 is accompanied by increasing k 2 o rb and th and decreasing mgo fe 2 o 3 feo tio 2 cao p 2 o 5 sr eu zr cu zn ni v and sc this is consistent with fractionation of observed phases including plagioclase amphibole biotite magnetite titanite and apatite the eureka supersuite ranges from diorite to syenogranite in composition more mafic varieties contain pyroxene and hornblende while more felsic varieties contain biotite as the only ferromagnesian silicate sodiccalcic alteration events are closely linked in space and time to intrusion of eureka supersuite magmas the timing of intrusion is interpreted to be pre and post d 3 based on overprinting relationships between different plutons and mylonitic fabrics hornblende geobarometry suggests an emplacement depth of approximately 10 km for the mount angelay igneous complex eureka supersuite granites in the mount angelay igneous complex range from 51 to 76 wt percent sio 2 the granites are alkaline and k 2 o rich leading to their classification as a shoshonite series with increasing sio 2 content tio 2 al 2 o 3 fe 2 o 3 t mno mgo cao p 2 o 5 sr eu cu zn ni v and sc decrease indicating fractionation of observed minerals including apatite magnetite pyroxene hornblende plagioclase and biotite some samples are characterized by very high abundances of k 2 o p 2 o 5 sr ba and light rare earth elements lree compared to other eureka supersuite samples this may reflect their derivation from a source that was variably enriched in incompatible elements compared with many other shoshonitic rocks high k eureka supersuite samples are strongly depleted in sr and to a lesser extent eu and enriched in y and heavy rare earth elements hree this suggests that garnet was not a stable phase in the source region that the source contained plagioclase as a stable phase and or the granites evolved by extensive plagioclase fractionation partial melting in the lower crust to generate post 1540 ma granites was most likely caused by intrusion of basic magma into the crust eureka supersuite magmas were probably derived from partial melting of variably incompatible element enriched gabbroic rocks while cloncurry supersuite magmas were most likely derived from partial melting of more felsic material of dioritic to tonalitic composition

effects of forest land management on erosion and revegetation after the eruption of mount st helens the 1980 eruption of mount st helens covered soils with a tephra blanket and killed the forest tree cover in a 550 km2 area after the eruption rates of sheetwash and rill erosion and plant cover were measured on tephra covered hillslopes which had been subject to three land management practices grass seeding scarification and salvage logging on rapidly eroding hillslopes subject to grass seeding limited plant covers were established only after erosion had declined sharply logging of trees downed by the eruption and scarification of previously logged surfaces slowed erosion although the effect was small because erosion rates had already slowed substantially by the time these two practices were implemented the factors controlling erosion revegetation and their relative timing at mount st helens are similar to those following explosive volcanic eruptions elsewhere suggesting that grass seeding is not likely to be effective at slowing erosion following most tephra eruptions and that early mechanical disturbance could be an effective erosion control measure the results also indicate that even without deliberate conservation measures processes which mechanically disturb a surface layer of low hydraulic conductivity such as frost action or trampling can radically reduce runoff and erosion before revegetation has an important effect

stable lead isotope ratios and metals in freshwater mussels from a uranium mining environment in australia s wet dry tropics abstract concentrations of fe mn cu zn u and pb and stable pb isotopes 206pb 207pb and 208pb were measured via inductively coupled plasma mass spectrometry in sediments water and freshwater mussels velesunio angasi from two catchments in the alligator rivers region australia sediment u and pb concentrations were higher in magela creek downstream than upstream of the ranger u mine due to the mineralised nature of the catchment and potential local input of sediment from the mine site water metal concentrations were highest in georgetown creek which is a tributary of magela creek and part drains the ranger mine site but there was little difference in concentrations between the magela creek upstream and downstream sites metal concentrations in mussels collected immediately upstream and downstream of the mine site also showed little difference whereas pb isotope ratios displayed a very distinct pattern the 206pb 207pb and 208pb 207pb isotope ratios were more uranogenic downstream than upstream of the site and also more uranogenic than ratios measured in sandy billabong a reference billabong in a catchment not influenced by u mineralisation isotope ratios were also more uranogenic in younger mussels potentially due to the increasing footprint of the mine site over the past decade the most uranogenic ratios were found in mussels from georgetown creek and at a site approximately 2 km downstream at mudginberri billabong approximately 12 km downstream of the ranger mine the relative contribution of uranogenic pb to the total pb concentration in mussels was small and overwhelmed by the input of industrial pb with a broken hill type pb signature whereas metal uptake by and thus concentrations in mussel flesh are influenced by water chemistry mussel condition and metabolic rates pb isotope ratios are independent of these factors and provide a powerful means of source apportionment of contaminants in mussels and waterways in particular in an u mining environment

using nd sr isotopes and rare earth elements to study sediment provenance of the modern radial sand ridges in the southwestern yellow sea abstract the radial sand ridges rsrs in the southwestern yellow sea off the jiangsu coast east china have been intensively studied at least since 1975 despite decades of studies the provenance of the rsr sediments remains uncertain in this study the nd sr isotopic and ree geochemical compositions of residual sediments i e the acid insoluble fractions were investigated to determine the provenance of the rsr sediments the nd isotopic composition paas normalized ree patterns and characteristic parameters e g sm nd la sm n gd yb n were merely associated with source rocks but not with particle sorting while the sr isotopic composition and ree contents of residual sediments were affected by particle sorting in addition to source rocks the onshore rsr sediments originated mainly from mixing of the fine grained sediments from various parts of the offshore rsr in terms of ree geochemical and isotopic analyses isotopic and ree geochemical comparison further reveals that the rsrs off the jiangsu coast were fed chiefly by the dispersal of surface sediments from the yangtze river mouth surface sediments from the yangtze river mouth were directly dispersed to the rsrs along the jiangsu coast and significantly affected the seaward part of the offshore rsr and the old yellow river delta area by a northward branch of the changjiang diluted freshwater plume only minor quantities of surface sediments from the modern yellow river mouth were introduced into the rsrs by the jiangsu coastal current and mainly contaminated the landward part of the offshore rsr area our findings highlighted the potential of the nd isotopes with ree geochemistry to trace the provenance of coastal sediments

sea ice thickness variability in the chukchi sea spring and summer 2002 2004 abstract measurements of sea ice thickness were obtained from drill holes an ice based electromagnetic induction instrument iem and a ship borne electromagnetic induction instrument sem during the early melt season in the southern chukchi sea in 2002 and 2004 and in late summer 2003 at the time of minimum ice extent in the northern chukchi sea an ice roughness criterion was applied to distinguish between level and rough or ridged ice ice thickness modes in the probability density functions pdfs derived from drill hole and iem measurements agreed well with modes at 1 5 1 6 and 1 8 1 9 m for all data from level ice the pdfs derived from sem measurements show that the primary modes are at 0 1 and 1 1 m in 2003 and 0 7 m in 2004 in 2002 and 2004 significant fractions between one third and one half of level ice were found to consist of rafted ice segments snow depth varied significantly between years with 2004 data showing more than half the snow cover on level ice to be at or below 0 05 m depth in late spring ice growth simulations and examination of ice drift and deformation history indicate that impacts of atmospheric and oceanic warming on level ice thickness in the region over the past few decades are masked to a large extent by variability in snow depth and the contribution of deformation processes in comparison with submarine sonar ice thickness data from previous decades a reduction in ice thickness by about 0 5 1 m is in part explained by the replacement of multi year with first year ice over the chukchi and beaufort shelves

what drives the southward drift of sea ice in the sea of okhotsk abstract the sea of okhotsk is the southernmost sea ice zone with sizable ice it is widely believed that the prevailing northwesterly wind and the southward east sakhalin current esc are the two main factors that drive the southward drift of sea ice however the relative contributions of these factors have not been understood in this paper by using the current and ice drift data measured with the moored acoustic doppler current profiler a 3 d ocean model simulation objective analysis data of the wind and satellite sea ice data we examine to what degree and how the ice drift is determined by the wind and ocean current from a linear regression of the observed ice drift ocean current and wind the wind forced component of the ice drift was best fitted when sea ice is assumed to move with a speed of 1 6 of the geostrophic wind with a turning angle of 17 6 to the left of the wind such a relationship was adopted as the wind drift component for all sea ice pixels detected from special sensor microwave imager data for the ocean forced component of the ice drift we adopted the current at 20 m depth from a numerical model simulation that reproduces well the esc and its variability we then evaluated the sea ice drift over 46 54 n during 1998 2005 for the southward drift of sea ice the contribution of the wind component is found to be larger than the oceanic component although the ocean contribution becomes larger typically comparable to the wind contribution near the coast and in the northern region where the esc is stronger we estimated the average annual cumulative southward ice transport to be 3 0 0 9 10 11 m 3 at 53 n this ice transport is comparable to the annual discharge of the amur river the ratio of wind to oceanic components in the transport is estimated to be 1 2 1 8 we also conducted ice drift simulations based on the modeled current velocity and the assumed wind drift of 1 5 geostrophic wind with a turning angle of 15 to the left the simulations reproduce well the ice drift north of 47 n but not south of 47 n likely due to the poor representation of the current system at the latter underevaluation of the wind factor near the ice edges and the neglect of ice formation and melt

variability of sea ice draft off hokkaido in the sea of okhotsk revealed by a moored ice profiling sonar in winter of 1999 1 using a moored ice profiling sonar along with an adcp a spatial section of draft across 855 km of sea ice was obtained for the first time in the southwestern part of the okhotsk sea near hokkaido in winter of 1999 the draft evolved from 0 20 m in mid february to 1 45 m in late march with the overall value of 0 72 m the draft characteristics were quite different between february and march before and after the period of strong winds the increase of the mean draft from february to march was associated with the increase of deformed ice the maximum draft observed was 17 m ice volume was dominated by the contribution from portions of deformed ice especially in march these results suggest that deformed ice dominated in the region of observation and dynamical processes were mainly responsible for the evolution of draft

rare earth elements as provenance indicators in north australian estuarine and coastal marine sediments rare earth elements ree in three grain size fractions of clay dominated estuarine and coastal sediments from the north australian coastline have been investigated for use as potential provenance indicators comparisons of data based on instrumental neutron activation analysis and inductively coupled plasma mass spectrometry revealed that hf digestions of zircon bearing samples resulted in unsatisfactory recovery of ree instead a relatively simple fast and safe partial digestion using hclo4 hno3 was used to extract ree mainly from clay minerals while excluding extraction of ree from zircons a comparison with published data for primary rock units within river catchments showed that the main ree systematics has been preserved in downstream clay rich sediments analysis of variance of la gd paas la yb paas and eu eu paas ratios in five areas showed that the 63 m fraction possessed the greatest discriminating power all five areas could be distinguished from each other at highly significant levels based on one or more of these ratios

anthropogenic units fingerprinted by ree in archaeological stratigraphy mas d is spain case abstract on occasions archaeologists have to deal with serious difficulties to differentiate between processes that ultimately are responsible for the formation of stratigraphic units sometimes we face problems related with depositional units in multilayered deposits and other times we ask for the character of some dark surface soils very similar to natural paleosols and usually associated with archaeological findings in both cases the problems we must address concern the relative impact of human activities the imbalance between anthropic and natural processes in the formation of archaeological deposits is crucial for a correct interpretation of the processes involved in the formation of archaeological sites but also of their occupation abandonment dynamics and the understanding of their spatial behaviors and relationship with the environment in this paper we propose a new methodological approach for the identification of anthropogenic fingerprints in stratigraphic units through rare earth elements ree soil analysis the role of ree for the effective identification of sediment provenance due to their coherent behavior during weathering erosion and fluvial transportation and their high resistance to chemical mobilization is well known in other areas of knowledge we try to explore its potentiality in a challenging archaeological context our purpose was to identify human traces in stratigraphic units where archaeological materials are scarce or absent intertwined with others richer in archaeological remains by the determination of multiple elements and statistical studies we believe that rare earth elements ree soil analysis provides unique insights for a better characterization of natural and archaeological sediments but more importantly to recognize different stages of the gradient we expect to discern between natural versus anthropic units and between primary versus secondary deposits redeposition using the case of the neolithic site of mas d is alicante spain as an example the application of the principal component analysis pca remarks differences in ree values those analysis show differences between units of undoubtedly anthropogenic origin and control samples taken from natural sediments including marls bedrock in their vicinity but also we could notice finer nuances like the degree of human contributions to paleosols formation

structure of the isan orogeny under cover to the east of the mount isa inlier revealed by multiscale edge analysis and forward and inverse modelling of aeromagnetic data aeromagnetic data reveals the presence of three north south orientated tens of kilometre scale elliptical structures under cover to the east of the mount isa inlier in queensland australia the holy joe creek boot creek and nora creek structures are typically defined by three narrow continuous magnetic ridges highly magnetically susceptible amphibolite bodies similar to those exposed in the inlier are probably the source of most of these magnetic anomalies multiscale edge analysis 2d forward modelling and 3d inverse modelling methods have been used to resolve the geometry and near surface dip of the structures these techniques indicate that the structures dip moderately to steeply around their edges the holy joe creek structure exhibits sub vertical to steeply west dipping sides and a moderate plunge around the northern closure the boot creek and nora creek structures are more complex magnetically but their eastern edges also have sub vertical to steep westerly dips diapirism and domes in an egg box style type 1 fold interference pattern are considered as possible origins for the elliptical structures however disparity between the shape of the structures and possible diapiric bodies and the lack of complementary basin structures to the domes makes these two explanations unlikely a more plausible alternative is that the structures are the result of deformation in a single phase producing folds with a variable hinge line plunge these results indicate that east west shortening during the d2 event of the isan orogeny was the major deformation in the buried rocks of the study area suggesting a shared structural history with the mount isa inlier to the west

rare earth elements in marine sediments and geochemical standards abstract a comparison was made of sediment dissolution methods used for analysis of rare earth elements ree and major elements fe al ti zr p dissolution by hf and lithium metaborate fusion were compared in seven geochemical standards and twenty marine sediments using hf dissolution of shelf and slope sediments this author previously observed that these marine sediments were significantly depleted in heavy ree hree relative to the crustal abundance i e shale this observation plus published ree compositions of river particles lead to the conclusion that the riverine input of particles to the oceans cannot be assumed to have the crustal abundance for ree comparisons of fusion total to hf dissolutions for marine sediments show that the latter method misses between 20 and 100 of the hree i e dy er yb lu and large percentages of zr in contrast fusion and hf dissolution yield similar concentrations for the light la ce nd and middle eu gd ree and other major elements the fusion data show that the marine sediments are more similar in ree composition to shales than previously reported by this author who underestimated the contribution of hf insoluble residues to the concentration of hree the heavy mineral zircon is the most likely cause of this observation zircons known to be enriched in hree were identified by x ray diffraction as a major component of the hf insoluble residues geochemical standards also have a significant but usually smaller fraction of their hree associated with hf insoluble phases these compositional differences have significance with respect to interpreting river inputs oceanic abundances and diagenesis of ree

mid crustal fluid mixing in a proterozoic fe oxide cu au deposit ernest henry australia evidence from ar kr xe cl br and i fluid inclusions in six quartz veins associated with cu au mineralisation at the giant ernest henry iron oxide copper gold deposit 167 mt 1 1 cu 0 54 ppm au in northwest queensland have been analysed for naturally occurring and neutron produced noble gas isotopes of ar kr and xe a combination of thermal and mechanical decrepitation methods enables distinction between four types of fluid inclusion ultra high salinity 30 to 70 wt nacl eq fluid inclusions have compositions that define two end members that are variably mixed in different samples the first end member has a 40 ar 36 ar value of 29 000 a 40 are cl value of 3 10 3 and mantle like br cl and i cl values of 1 2 10 3 and 11 10 6 respectively the second end member has a much lower 40 ar 36 ar value of less than 2500 a 40 are cl value of 10 6 low br cl values of 0 4 10 3 and i cl values of 1 2 10 6 all ratios are molar carbon dioxide and later lower salinity liquid vapour fluid inclusions have similar 40 ar 36 ar values of less than 2500 in all samples these data are compatible with genetic models in which cu au mineralisation formed at a depth of 6 10 km from circulation of magmatic fluids derived from regionally abundant a type granites and a high salinity halite dissolution brine generated from sedimentary formation waters in the upper crust the largest source of co2 was probably carbonate rich lithologies in the midcrust later lower salinity fluids with a surficial origin diluted the mineralising brines and are preserved in the latest secondary fluid inclusions these data provide insight on the composition of crustal fluids during the proterozoic furthermore the magmatic fluid endmember derived from melts generated by re melting lower crustal paleoproterozoic igneous rocks with a mantle source preserves mantle like br cl and i cl these geochemical characteristics are interpreted to provide insight on i recycling at subduction zones and the composition of seawater in the paleoproterozoic 2007 elsevier b v all rights reserved

evaluating estuarine sediment provenance from geochemical patterns in upper chesapeake bay abstract geochemical patterns in upper chesapeake bay sediments can reflect a variety of important processes spatial and down core geochemical patterns are useful for understanding the underlying conservative sediment provenance and non conservative salinity redox anthropogenic influences processes driving these patterns distinguishing conservative and non conservative processes to quantify sediment sources will help develop management strategies to limit excess sedimentation in estuaries in this study elemental concentrations were measured via inductively coupled plasma mass spectroscopy icp ms and analyzed using principal component analysis the sediment geochemistry data were then analyzed to evaluate contributions of susquehanna river and shoreline erosion to bottom sediments in the upper bay using a sediment provenance analysis elements associated with aluminosilicate minerals which were sensitive to grain size changes and rare earth elements which were sensitive to salinity changes explained the most variability in the dataset variability in heavy metal concentrations demonstrated decadal changes in anthropogenic inputs the results from the sediment provenance analysis indicated that the susquehanna river is the dominant source of fine sediment in the upper bay

the footprint altitude ratio for helicopter electromagnetic sounding of sea ice thickness comparison of theoretical and field estimates helicopter towed electromagnetic hem induction sounding systems are typically used for geologic surveys more recently hem systems have been used for the remote measurement of sea ice thickness and shallow sea bathymetry an important aspect of this remote sensing technology is the area or footprint in which the secondary field is predominantly generated by induced currents a knowledge of the size of the footprint is important to understanding the accuracy of hem sounding results over lateral variations in relief or conductivity conventional wisdom among workers in the field held that the footprint diameter is a few times the hem antenna altitude we confirm this view using airborne measurements over sea ice to calculate the footprint size antenna altitude ratio these findings are compared to various theoretical estimates and are found to be in reasonable agreement for a vertical coaxial coil antenna arrangement the apparent footprint diameter was found to be about 1 3 times the antenna height a

mineralogical and chemical evolution of the ernest henry fe oxide cu au ore system cloncurry district northwest queensland australia the ernest henry cu au deposit was formed within a zoned post peak metamorphic hydrothermal system that overprinted metamorphosed dacite andesite and diorite ca 1740 1660 ma the ernest henry hydrothermal system was formed by two cycles of sodic and potassic alteration where biotite magnetite alteration produced in the first cycle formed ca 1514 24 ma whereas paragenetically later na ca veining formed ca 1529 11 8 ma these new u pbtitanite age dates support textural evidence for incursion of hydrothermal fluids after the metamorphic peak and overlap with earlier estimates for the timing of cu au mineralization ca 1540 1500 ma a distal to proximal potassic alteration zone correlates with a large up to 1 5 km k fe mn ba enriched alteration zone that overprints earlier sodic alteration mass balance analysis indicates that k fe mn ba alteration largely produced during pre ore biotite and magnetite rich alteration is associated with k rb cl ba fe mn and as enrichment and na ca and sr depletion the aforementioned chemical exchange almost precisely counterbalances the mass changes associated with regional na ca alteration this initial transition from sodic to potassic alteration may have been formed during the evolution of a single fluid that evolved via alkali exchange during progressive fluid rock interaction cu au ore dominated by co precipitated magnetite minor specular hematite and chalcopyrite as breccia matrix forms a pipe like body at the core of a proximal alteration zone dominated by k feldspar alteration both the core and k feldspar alteration overprint na ca alteration and biotite magnetite k fe alteration ore was associated with the concentration of a diverse range of elements e g cu au fe mo u sb w sn bi ag f ree k s as co ba and ca mineralization also involved the deposition of significant barite k ba feldspar calcite fluorite and complexly zoned pyrite the complexly zoned pyrite and variable k ba feldspar versus barite associations are interpreted to indicate fluctuating sulphur and or barium supply together with the alteration zonation geochemistry and overprinting criteria these data are interpreted to indicate that cu au mineralization occurred as a result of fluid mixing during dilation and brecciation in the location of the most intense initial potassic alteration a link between early alteration na ca and k fe and the later k feldspathization and the cu au ore is possible however the ore related enrichments in particular elements especially ba mn as mo ag u sb and bi are so extreme compared with earlier alteration that another fluid possibly magmatic in origin contributed the diverse element suite geochemically independently of the earlier stages structural focussing of successive stages produced the distinctive alteration zoning providing a basis both for exploration for similar deposits and for an understanding of ore genesis

the rare earth element geochemistry of surface sediments in four transects in the south china sea and its geological significance seventy five samples of surface sediment were collected from four transects in the south china sea scs for analyses of rare earth element ree geochemistry total ree abundance ree in the scs varies from 45 to 195 ppm average 128 ppm lower than that of the upper continental crust the spatial distribution of ree is strongly dependent upon the geographical location and depositional environment low ree concentrations are observed on the continental slope e g xisha and nansha islands while high ree concentrations are present in the deep basin sediments on the slope are also characterized by lower lree hree la yb n eu eu and ce ce ratios relative to deep basin sediments there is a positive correlation between al2o3 and ree and a negative correlation between cao and ree conversely the relatively insignificant fe mn oxide accumulation in the scs suggests that manganese nodules do not make a significant contribution to the bulk ree composition of sediments therefore the sediment ree geochemistry is mainly controlled by terrigenous and biogenic sources biogenic carbonate has a diluting effect on ree concentrations but a significant influence on lree hree ce ce and la yb n values is found only in sediments with especially high biogenic carbonate levels the ree geochemistry of scs surface sediments indicates that their source is mainly post archean felsic rocks in the eastern sub basin the relatively low lree hree ratios and high eu eu values of the sediments indicate that significant terrigenous materials are derived from young volcanic rocks e g rocks in the luzon arc

sea ice thickness variability in storfjorden svalbard results from electromagnetic induction surveys of sea ice thickness in storfjorden svalbard reveal large interannual ice thickness variations in a region which is typically characterized by a reoccurring polynya the surveys were performed in march 2003 may 2006 and march 2007 with helicopter and ship based sensors the thickness distributions are influenced by sea ice and atmospheric boundary conditions 2 months prior to the surveys which are assessed with synthetic aperture radar sar images regional quikscat backscatter maps and wind information from the european centre for medium range weather forecasts ecmwf reanalysis dataset locally formed thin ice from the storfjorden polynya was frequently observed in 2003 and 2007 mean thickness 0 55 and 0 37 m respectively because these years were characterized by prevailing northeasterly winds in contrast the entire fjord was covered with thick external sea ice in 2006 mean thickness 2 21 m when ice from the barents sea was driven into the fjord by predominantly southerly winds the modal thickness of this external ice in 2006 increased from 1 2 m in the northern fjord to 2 4 m in the southern fjord indicating stronger deformation in the southern part this dynamically thickened ice was even thicker than multi year ice advected from the central arctic ocean in 2003 mean thickness 1 83 m the thermodynamic ice thickness of fast ice as boundary condition is investigated with a one dimensional sea ice growth model 1dice forced with meteorological data from the weather station at the island of hopen southeast of storfjorden the model results are in good agreement with the modal thicknesses of fast ice measurements in all years

episodic euxinia in the changhsingian late permian of south china evidence from framboidal pyrite and geochemical data abstract a multiproxy study of a new upper permian lower triassic section xiaojiaba in sichuan province china documents large changes in marine productivity redox conditions and detrital input prior to the latest permian mass extinction marine productivity as proxied by total organic carbon content toc biogenic sio 2 and excess barium displays a long term decline through most of the changhsingian stage late late permian culminating in very low values around the permian triassic boundary concurrently redox proxies including pyrite framboid 34 s py mo auth and u auth and c org p document a shift from suboxic to dysoxic oxic conditions that was interrupted by several episodes of benthic euxinia and detrital siliciclastic proxies al hf nb and rees suggest an increased flux of weathered material from land areas the long term changes in productivity redox conditions and terrigenous detrital fluxes were probably caused by a regional sea level fall across the south china craton on the other hand the brief euxinic episodes occurring during the late permian had oceanographic causes probably related to the transient upward expansion of the chemocline at the top of the oceanic oxygen minimum zone these euxinic episodes may have been harbingers of the more widespread anoxia that developed concurrently with the latest permian mass extinction and that may have played a major role in triggering the largest biotic crisis of the phanerozoic

a model to estimate the impact of climatic change on hillslope and regolith form abstract by placing a model for the evaluation of hillslope and regolith form in explicitely climatic terms the effect of climatic change can be forecast directly this provides a tool for investigating the impact of expected changes for instance those due to the accumulation of greenhouse gasses in the atmosphere the model is based on budgets for vegetation biomass total sediment representing elevation and regolith expressed as a deficit relative to bedrock composition the numerical model presented contains components representing vegetation growth leaf fall organic soil accumulation solution soil creep splash wash and shallow landslides expressions are rationally based on empirical and theoretical work with strong interactions between the various components the results are illustrated relative to the present climate of luxembourg showing the forecast effect of temperature changes of 10 c in either direction on vegetation cover soil thickness and erosion rates the method is designed to have a wide range of applicability and may be used either to make local forecasts or to point to environments which are sensitive to the temperature changes now forecast for the next century

sediment sources and channel dynamics daly river northern australia the daly river occupies a mainly undisturbed large catchment in the australian wet dry tropics concerns about possible increased sediment input to the river from clearing and cropping have motivated this study of fine sediment sources using geochemical tracers for both modern sediments and alluvial bench deposits it is shown that for the last 30 years 89 97 of the fine sediment originates from erosion by gullying and channel change there is no discernible input of top soil from the cleared land adjacent to the daly river in the study area the analysis and osl dating of the alluvial benches have also provided data on the age of and inferences about the causes of bench formation flood frequency change sedimentation rate change and episodes of sand transport the benches are being destroyed as the channel widens contributing sediment to the river and the bed of the daly appears to be shallowing both responses to increased overbank flows the sediment source created by channel widening is almost all the result of hydrologic change with no discernible role for land use

ship borne electromagnetic induction sounding of sea ice thickness in the southern sea of okhotsk recent observations have revealed that dynamical thickening is dominant in the growth process of sea ice in the southern sea of okhotsk that indicates the importance of understanding the nature of thick deformed ice in this area the objective of the present paper is to establish a ship based method for observing the thickness of deformed ice with reasonable accuracy since february 2003 one of the authors has engaged in the core sampling using a small basket from the icebreaker soya based on these results we developed a new model which expressed the internal structure of pack ice in the southern sea of okhotsk as a one dimensional multilayered structure since 2004 the electromagnetic em inductive sounding of sea ice thickness has been conducted on board soya by combining the model and theoretical calculations a new algorithm was developed for transforming the output of the em inductive instrument to ice snow thickness total thickness comparison with total thickness by drillhole observations showed fair agreement the probability density functions of total thickness in 2004 and 2005 showed some difference which reflected the difference of fractions of thick deformed ice

integration of bed characteristics geochemical tracers current measurements and numerical modeling for assessing the provenance of beach sand in the san francisco bay coastal system abstract over 150 million m3 of sand sized sediment has disappeared from the central region of the san francisco bay coastal system during the last half century this enormous loss may reflect numerous anthropogenic influences such as watershed damming bay fill development aggregate mining and dredging the reduction in bay sediment also appears to be linked to a reduction in sediment supply and recent widespread erosion of adjacent beaches wetlands and submarine environments a unique multi faceted provenance study was performed to definitively establish the primary sources sinks and transport pathways of beach sized sand in the region thereby identifying the activities and processes that directly limit supply to the outer coast this integrative program is based on comprehensive surficial sediment sampling of the san francisco bay coastal system including the seabed bay floor area beaches adjacent rock units and major drainages analyses of sample morphometrics and biological composition e g foraminifera were then integrated with a suite of tracers including 87sr 86sr and 143nd 144nd isotopes rare earth elements semi quantitative x ray diffraction mineralogy and heavy minerals and with process based numerical modeling in situ current measurements and bedform asymmetry to robustly determine the provenance of beach sized sand in the region

provenance of late quaternary sediments on the southwestern slope of the ulleung basin east japan sea the provenance of fine grained sediments deposited since the late quaternary was recovered from drill site ubgh2 1 1 on the southwestern slope of the ulleung basin east japan sea based on geochemical analyses including rare earth elements rees the fine grained sediments could be interpreted as mixtures of sediments from china via various pathways and sediments discharged from the nakdong river nrs a comparison of variations in ree fractionation factor with marine isotope stages miss indicated that the provenance of the fine grained sediments on the southwestern slope of the ulleung basin was controlled by global eustatic sea level change during glacial periods most of the fine grained sediments were supplied via the atmospheric pathway by an intensified east asian winter monsoon and sediments from chinese rivers crs transported into the ulleung basin through the korea strait were limited due to the morphological characteristics of the korea strait and low sea level during interglacial periods the crs transported into the ulleung basin through the korea strait increased with sea level rise and eolian dust inputs decreased due to attenuated east asian winter monsoon simultaneously nrs also should have been deposited when sea level was higher than 40 m relative to present sea level during mis 1 and mis 5 in particular during mis 1 signals of nrs were revealed since 11 ka thus it can be suggested that the present coastal current system around the southeastern coast of korea became established by around 11 ka

peak flow responses to landscape disturbances caused by the cataclysmic 1980 eruption of mount st helens washington years of discharge measurements that precede and follow the cataclysmic 1980 eruption of mount st helens washington provide an exceptional opportunity to examine the responses of peak fl ows to abrupt widespread devastating landscape disturbance multiple basins surrounding mount st helens 300 1300 km 2 drainage areas were variously disturbed by 1 a debris avalanche that buried 60 km 2 of valley 2 a lateral volcanic blast and associated pyroclastic fl ow that destroyed 550 km 2 of mature forest and blanketed the landscape with silt capped lithic tephra 3 debris fl ows that reamed riparian corridors and deposited tens to hundreds of centimeters of gravelly sand on valley fl oors and 4 a plinian tephra fall that blanketed areas proximal to the volcano with up to tens of centimeters of pumiceous silt sand and gravel the spatially complex disturbances produced a variety of potentially compensating effects that interacted with and infl uenced hydrological responses changes to water transfer on hillslopes and to fl storage and routing along channels both enhanced and retarded runoff rapid posteruption modifi cations of hillslope surface textures adjustments of channel networks and vegetation recovery in conjunction with the complex nature of the eruptive impacts and strong seasonal variability in regional climate hindered a consistent or persistent shift in peak discharges overall we detected a short lived 5 10 yr increase in the magnitudes of autumn and winter peak fl ows in general peak fl ows were larger and moderate to large fl ows q 2 yr were more substantively affected than predicted by early modeling efforts proportional increases in the magnitudes of both small and large fl ows in basins subject to severe channel disturbances but not in basins subject solely to hillslope disturbances suggest that eruptioninduced modifi cations to fleffi ciency along alluvial channels that have very mobile beds differentially affected fl ows of various magnitudes and likely played a prominent and additional role affecting the nature of the hydrological response

petrographic rare earth elements and isotope constraints on the dolomite origin of ordovician majiagou formation jizhong depression north china abstract dolomites from the ordovician majiagou formation are considered as major hydrocarbon reservoir rocks in the yangshuiwu area jizhong depression however the origin of the dolomites remains unclear this study utilizes a composite analysis of seawater normalized rare earth elements rees petrography and isotopes c o and sr to trace dolomitizing fluids and processes three types of dolomite are identified planar s to nonplanar microcrystalline type d1 dolomite

rare earth elements in weathering profiles and sediments of minnesota implications for provenance studies abstract the relative abundance of rare earth elements in sediments has been suggested as a tool for determining their source rocks this correlation requires that weathering erosion and sedimentation do not alter the ree abundances or do so in a predictable manner we find that the rare earth elements are mobilized and fractionated by weathering and that sediments derived from the weathered materials can display modifications of the original pattern of rare earth elements of some due to grain size sorting of the weathered material however the ree distribution pattern of the provenance terrane can be recognized in the sediments

composition and trace element geochemistry of detrital clay and heavy mineral suites of the lowermost amazon river a provenance study abstract compositions of clays and heavy minerals as well as trace element geochemistry of the lowermost amazon sediments reflect source regions and the intense chemical weathering conditions illite and montmorillonite indicate mountainous sources under physical weathering conditions whereas kaolinite is related to the soil composition under humid tropical conditions where chemical weathering predominates the suite of unstable heavy minerals on the other hand reflects some sediment transport from the andes more supply from tributaries draining the basic and metamorphic rocks from the southeastern guiana shield and strongest influence of the upstream amazon and solimoes areas these source signals are damped by transitional storage and intense lateral sediment exchange between channel and floodplain the brazilian shield contribution via the xingu river seems to be of minor importance although the alter do chao and the barreiras formations which are products of erosion of the shields supply suites of stable heavy minerals that reflect recycling rare earth and trace element data from the clay and heavy mineral fractions provide additional clues to the source areas in the downstream direction superimposed upon provenance of sediments from an undifferentiated arc the andes is provenance from strongly weathered continental crust the precambrian shields as well as sedimentary recycling small scale provenance can be delineated by the most immobile elements heavy rare earth elements in the heavy mineral fraction increase downstream toward estreitos to the para river

discrimination of sediment provenance using rare earth elements in the ulleung basin east japan sea abstract in order to discriminate the origins of ulleung basin east japan sea sediments using rare earth elements rees sediments from 15 box cores and one piston core collected in the shelf slope and basin were analyzed for major elements al fe ca and mn and rees the major sedimentary components in this basin were presumed to be detrital materials from land even in the basin sediments based on al and organic contents carbon and opal post depositional recycling processes involving fe and mn were identified in the basin sediments thus the ce anomaly and the fractionation factors of light rees lrees and middle rees mrees relative to heavy rees hrees could not be used as provenance indicators in the deep basin sediments 2000 m of water depth based on a feasibility check using their covariation with fe and mn for the shelf slope and basin b sites near islands water depths of 1200 1800 m regions the eu anomaly lreen hreen and mreen hreen could be successfully used to discriminate possible provenances including nakdong river sediments nrs chinese river sediments crs ulleungdo volcanic rocks uvr and dokdo volcanic rocks dvr from the provenance indicators slope as well as the shelf sediments called the korea strait shelf mud kssm in the ulleung basin can be regarded as mixtures of nrs and crs with decreasing portions of nrs in the kssm with distance from the nakdong river basin b sediments were mixtures of uvr or dvr and crs these findings can be explained if sediments discharged from the nakdong river were transported and deposited kssm northward within the strong coastal front in normal periods and if sediment flumes from summer floods flowed out across the coastal front were carried with the tsushima warm current and then deposited in the slope area this study indicated that crs were very important detrital sediments and that ree compositions can be successfully used as a provenance indicator in even hemipelagic sediments close to land