active high resolution compressional wave attenuation tomography at newberry volcano central cascade range in this study we use the seismic data from a previous study at newberry to compute its three dimensional compressional wave attenuation structure the data consist of eight explosions recorded on an array of about 120 seismograph stations the shots are located on two concentric circles centered on the caldera with radii of 39 and 85 km attenuation is estimated using spectral ratios to compute t at each station for each shot the data are inverted using a least squares technique our results indicate that regions of inferred boiling water i e two phase pore fluid are correlated spatially with regions of high attenuation not corresponding to low velocities two regions are of particular interest one is underneath the newberry ii drill hole in the central part of the caldera where results from a flow test suggest that two phase fluid conditions existed in the bottom of the hole before the flow test the other region is beneath the west flank of the volcano which has been interpreted as an attractive geothermal prospect because of a shallow conductive anomaly our results are consistent with the suggestion made in an earlier paper by us that two phase geothermal reservoirs can be located within complex three dimensional structures by using jointly interpreted compressional wave velocity and attenuation images

electrical structure of newberry volcano oregon from the interpretation of magnetotelluric transient electromagnetic and schlumberger resistivity soundings the electrical structure of newberry volcano in central oregon is found to consist of four units from the surface downward the geoelectrical units are 1 very resistive young unaltered volcanic rock 2 a conductive layer of older volcanic material composed of altered tuffs 3 a thick resistive layer thought to be in part intrusive rocks and 4 a lower crustal conductor this model is similar to the regional geoelectrical structure found through the cascade range inside the caldera the conductive second layer corresponds to the steep temperature gradient and alteration minerals observed in the usgs newberry 2 test hole drill hole information on the south and north flanks of the volcano test holes ges n 1 and geo n 3 respectively indicates that outside the caldera the conductor is due to alteration minerals primarily smectite and not high temperature pore fluids on the flanks of newberry the conductor is generally deeper than inside the caldera and its deepens with distance from the summit

grain size and heavy minerals of the late quaternary eolian sediments from the imbituba jaguaruna coast southern brazil depositional controls linked to relative sea level changes abstract the stratigraphic subdivision and correlation of dune deposits is difficult especially when age datings are not available a better understanding of the controls on texture and composition of eolian sands is necessary to interpret ancient eolian sediments the imbituba jaguaruna coastal zone southern brazil 28 29 s stands out due to its four well preserved late pleistocene eolian generation 1 to holocene eolian units eolian generations 2 3 and 4 in this study we evaluate the grain size and heavy mineral characteristics of the imbituba jaguaruna eolian units through statistical analysis of hundreds of sediment samples grain size parameters and heavy mineral content allow us to distinguish the pleistocene from the holocene units the grain size displays a pattern of fining and better sorting from generation 1 older to 4 younger whereas the content of mechanically stable dense and hard heavy minerals decreases from eolian generation 1 to 4 the variation in grain size and heavy mineral content records shifts in the origin and balance input versus output of eolian sediment supply attributable mainly to relative sea level changes dunefields submitted to relative sea level lowstand conditions eolian generation 1 are characterized by lower accumulation rates and intense post depositional dissection by fluvial incision low accumulation rates favor deflation in the eolian system which promotes concentration of denser and stable heavy minerals increase of ztr index as well as coarsening of eolian sands dissection involves the selective removal of finer sediments and less dense heavy minerals to the coastal source area under a high rate of relative sea level rise and transgression eolian generation 2 coastal erosion prevents deflation through high input of sediments to the coastal eolian source this condition favors dunefield growth coastal erosion feeds sand from local sources to the eolian system including sands from previous dunefields eolian generation 1 and from drowned incised valleys therefore dunefields corresponding to transgressive phases inherit the grain size and heavy mineral characteristics of previous dunefields leading to selective enrichment of finer sands and lighter minerals eolian generations 3 and 4 developed during a regressive progradational phase holocene relative sea level highstand the high rate of sediment supply during the highstand phase prevents deflation the lack of coastal erosion favors sediment supply from distal sources fluvial sediments rich in unstable heavy minerals thus dunefields of transgressive and highstand systems tracts may be distinguished from dunefields of the lowstand systems tract through high rates of accumulation low deflation in the former the sediment source of the transgressive dunefields high input of previously deposited coastal sands differs from that of the highstand dunefields high input of fluvial distal sands based on this case study we propose a general framework for the relation between relative sea level sediment supply and the texture and mineralogy of eolian sediments deposited in siliciclastic wet coastal zones similar to the imbituba jaguaruna coast

evaluation of the applicability of acid leaching for the 238u 230th internal isochron method abstract the 238 u 230 th internal isochron method has great potential for determining eruption ages of young volcanic materials if the separated groundmass phases have a sufficiently wide range of u th ratios we examined the fractionation behavior of u and th in aged i e 0 5 ma basaltic samples by 6 m hydrochloric acid leaching to evaluate the applicability of acid leaching treatment for the 238 u 230 th internal isochron method acid leaching of aged basaltic rocks in 238 u 234 u 230 th secular equilibrium at the bulk rock scale results in 230 th 238 u and 234 u 238 u radioactive disequilibria for both leachates and residues these radioactive disequilibria can be explained by redistribution of 234 th parent of 234 u and 230 th between acid soluble and acid resistant phases due to recoil the number of 230 th atoms redistributed by recoil can be calculated by using a mass conservation equation for 234 u atoms and by the relative amount of recoiled 230 th and 234 th the latter proportional to the kinetic energy of the recoiled nuclide when the fraction of daughter nuclide 234 u remaining in either the residue or leachate after recoil redistribution of 238 u is large enough 95 the corrected 230 th 238 u values of leachate and residue show radioactive equilibria this result demonstrates that preferential fractionation between u and th does not occur during acid leaching for basaltic samples if there is no selective etching of the recoil track this study implies that acid leaching can be used in conjunction with the 238 u 230 th internal isochron method for dating young volcanic rocks by evaluating the degree of the recoil redistribution of 234 u

sedimentary evolution of the holocene subaqueous clinoform off the shandong peninsula in the yellow sea abstract a subaqueous clinoform wraps around the end of the shandong peninsula in the yellow sea the clinoform previously called the shandong mud wedge is up to 40 m thick nearshore and thins seaward its origin has been controversial since it was first noted in the 1980s for our recent investigation offshore of the northeastern shandong peninsula high resolution shallow seismic profiles covering about 1700 km were obtained and two drilling cores penetrating the clinoform were recovered we described the lithofacies characteristics identified benthic foraminifera and ostracoda measured grain size analyzed the mineral components of the cores and obtained ams 14 c dates on 28 samples to decipher the sedimentary evolution of the clinoform in response to postglacial sea level changes the shallow seismic profiles show that the clinoform comprises three units a lowermost seismic unit su 3 less than 2 3 m thick showing a retrogradational aggradational stacking pattern with subhorizontal internal reflectors a middle seismic unit su 2 up to 35 m thick showing a prograding reflection pattern with mostly seaward stepping reflectors separated by several erosive surfaces and an uppermost seismic unit su 1 maximum thickness 18 m exhibiting an aggradational reflection pattern with subparallel reflectors the three seismic units are bounded on the bottom by distinct erosion surfaces analyses of the two cores indicate that the clinoform comprises three depositional units du 1 du 2 and du 3 in descending order corresponding respectively to su 1 su 2 and su 3 the depositional units are distinguished by lithofacies characteristics and the downcore distributions of benthic foraminiferal and ostracod assemblages mineral components of the cores suggest that the clinoform s provenance is predominantly yellow river derived sediments ams 14 c dates suggest that du 3 was formed from about 11 6 to 9 6 cal kyr bp du 2 from 9 6 to 6 5 cal kyr bp and du 1 after ca 6 5 cal kyr bp some major meltwater pulse mwp events during the deglacial transgression were registered in the clinoform stratigraphy with the basal surfaces sediments of du 3 and du 2 corresponding respectively to mwp 1b ca 11 6 11 3 cal kyr bp and mwp 1c ca 9 6 9 2 cal kyr bp events and with du 2 being largely formed after the 8 4 8 2 cal kyr meltwater event rapid centennial to multidecadal scale flooding events were presumably responsible for the erosive surfaces separating the downlapping internal reflectors in su 2 the change of depositional pattern from progradational in su 2 to aggradational in su 1 is attributed to a change from strong dominantly to and fro tidal currents to the modern circulation in the bohai sea as well as to the weakening of the tidal current field during the highstand after about 6500 cal yr bp as a product of complex interactions among sediment supply sea level changes and hydrodynamic regimes the clinoform can be regarded as the distal part of the tidal depositional system in the eastern bohai sea which was largely derived from the yellow river

dating recent volcanic rocks through 230th 238u disequilibrium in accessory minerals example of the puy de dome french massif central precise dating of very young 10 000 yr silicic volcanic rocks can be achieved by measurements of 230 th 238 u disequilibria in accessory minerals such as apatite and zircon it is illustrated here by the isochron age of 12 000 1000 yr obtained on a trachyte from the puy de dome french massif central the crystallization age is virtually the same as the eruption age determined by thermoluminescence and 14 c dating this indicates a short time interval a few centuries at most between crystallization and eruption in such small volume silicic magmas

man s influence on the erosion and transport of sediment by asian rivers the yellow river huanghe example during the holocene sediment input from the yellow river to the yellow sea and adjacent areas has amounted to about 3000 km 3 detailed records from river gauging stations over the past 70 yrs together with estimates based on earlier historic records suggest that the river has contributed 2300 km 3 of sediment during the last 2300 yrs an average discharge of 1 km 3 yr 1 x 10 9 t yr prior to extensive agricultural use of the loess plateau in northern china beginning about 200 bc therefore the river s load must have been about 0 1 km 3 yr an order of magnitude lower than that at present a broad delta 20 m below sea level suggests that early holocene rates were higher than the pre agricultural average and therefore that middle holocene loads were low

the age isotopic signature and significance of the youngest mesozoic granitoids in the jiaodong terrane shandong province north china craton abstract most cretaceous granitoids in the jiaodong terrane of shandong province north china craton were intruded between 130 and 122 ma however four granitoid batholiths are significantly younger with an average zircon u pb shrimp emplacement age of 116 2 ma these are the sanfoshan batholith 118 1 ma the aishan batholith 116 1 ma the yashan pluton 113 2 ma and the laoshan batholith 115 2 ma these granitoids post date proposed delamination that occurred prior to 125 ma in the eastern ncc and their geochemistry thus provides information about the nature of the continental crust at this time the rocks are mostly monzogranites and syenogranites of i type affinity with local alkali feldspar granite of a type affinity in addition a monzogranite sample from the aishan batholith records an age of 125 3 ma indicating a direct association with the slightly older granitoids in the area indeed they all contain inherited zircons with ages of 125 120 ma indicating interaction with these earlier granitoids most samples are metaluminous enriched in light rare earth elements and depleted in high field strength elements paleo to neoarchean t dm2 model ages ranging from 3900 ma to 2491 ma and negative e hf t values imply the involvement of archean basement and older recycled continental crustal material in the magma source region they were likely derived from partial melting of the lower or middle crust due to mafic magma underplating followed by various degrees of interaction between mantle derived mafic magma and felsic crustal magma accompanied by fractional crystallization we propose that lithospheric thinning and extension in the early cretaceous due to roll back of the pacific plate beneath the eastern north china craton led to asthenospheric upwelling and basaltic magmatism this underplating in turn led to crustal melting and evolution of the granitic intrusions described here

paleotidal regime in the changjiang yangtze estuary the east china sea and the yellow sea at 6 ka and 10 ka estimated from a numerical model abstract two dimensional paleotidal simulations were carried out to investigate the paleotides and paleotidal currents in the changjiang yangtze estuary the east china sea and the yellow sea calculations were made for 10 ka 6 ka and the present an age of 10 ka corresponds to a period during the last deglaciation when the sea level was about 45 m below its present level at that time the changjiang estuary extended southeastward to the east china sea for about 400 km the second period 6 ka coincides with the maximum holocene transgression in eastern china the paleotopography around the changjiang estuary was reconstructed for 10 ka and 6 ka using available borehole datasets to remove the holocene strata at 10 ka the spatial distribution of m2 tides was different from today no amphidrome was present in the yellow sea and the current velocity was generally larger on the continental shelf strength and ellipticity of the simulated tidal currents indicated that the northern part of the moribund tidal sand ridge system in the east china sea might have been formed at around this period on the other hand the tidal field at 6 ka was similar to that at present except for the region within and adjacent to the paleo changjiang estuary a radial tidal flow pattern was originated from the estuary mouth which seemed to have enhanced tides and tidal currents in the estuary

holocene development of the yellow river s subaqueous delta north yellow sea high resolution seismic profiles from the north yellow sea reveal a 20 40 m thick subaqueous clinoform delta that wraps around the eastern end of the shandong peninsula extending into the south yellow sea this complex sigmoidal oblique clinoform containing an estimated 400 km 3 of sediment overlies prominent relict transgressive surfaces the nearshore topset of the clinoform 50 m contain less than 1 m of holocene sediment with low sedimentation rates 1 mm year in contrast to other clinoforms the shandong clinoform appears to be a compound subaqueous deltaic system with what we interpret to be proximal and distal phases of clinoform development the underlying proximal sequence formed proximally between f11 and 9 2 ka in response to a temporary pause in the rapid postglacial sea level rise after the meltwater pulse 1b mwp 1b and increased discharge from the yellow river to the north yellow sea due to intensification of the summer monsoon a flooding surface appears to separate the proximal and distal phases corresponding to the next rapid sea level rise 9 5 9 2 ka bp mwp 1c since 9 2 ka bp an overlying distal sedimentary sequence has accumulated reflecting the backstepping and shifting river mouth westward to the gulf of bohai some inputs from coastal erosion and nearby small streams may be locally important along shore transport cross shelf advection and upwelling in the north yellow sea have reworked post lgm sediment and have helped maintain the morphology of the clinoform in the shandong mud wedge d 2004 elsevier b v all rights reserved

gravity and magnetic studies of the subglacial grimsvotn volcano iceland implications for crustal and thermal structure the highly active subglacial grimsvotn volcano is associated with a 20 mgal bouguer gravity high and a broad magnetic low the magnetic low roughly coincides with the gravity high but short wavelength magnetic highs are superimposed on the low especially along caldera rims forward models of the gravity and magnetic fields show variable magnetization 0 12 a m 1 in the uppermost 1 2 km of the crust probably reflecting differences in the proportions of crystalline rocks and hyaloclastites and variations in hydrothermal alteration the models are consistent with but do not require a 10 km3 molten magma chamber in the shallow crust beneath the main caldera between 1 5 and 4 km depth a dense body 2 95 3 0 mg m 3 with a volume of 400 km3 is located probably composed of gabbro modeling suggests that this intrusive body is nonmagnetic which may imply that its temperature is at or above the curie point the distribution of geothermal activity at the glacier bed is consistent with heat extraction from this dense hot intrusive body it may be an important source for the presently observed geothermal heat output of 2000 4000 mw at grimsvotn this high heat transfer rate is difficult to reconcile with estimates of long term heat production in an icelandic rift zone volcano the heat flux may be a transient phenomenon caused by enhanced vertical permeability due to a recent caldera collapse and subsequent heat mining of the intrusive body

the chemical and hydrologic structure of poa s volcano costa rica comparison of the chemical characteristics of spring and river water draining the flanks of poa s volcano costa rica indicates that acid chloride sulfate springs of the northwestern flank of the volcano are derived by leakage and mixing of acid brines formed in the summit hydrothermal system with dilute flank groundwater acid chloride sulfate waters of the rio agrio drainage basin on the northwestern flank are the only waters on poa s that are affected by leakage of acid brines from the summit hydrothermal system acid sulfate waters found on the northwestern flank are produced by the interaction of surface and shallow groundwater with dry and wet acid deposition of so2 and h2so4 aerosols respectively the acid deposition is caused by a plume of acid gases that is released by a shallow magma body located beneath the active crater of poa s no evidence for a deep reservoir of neutral ph sodium chloride brine is found at poa s the lack of discharge of sodium chloride waters at poa s is attributed to two factors 1 the presence of a relatively volatile rich magma body degassing at shallow depths 1 km into a high level summit groundwater system and 2 the hydrologic structure of the volcano in which high rates of recharge combine with rapid lateral flow of shallow groundwater to prevent deep seated sodium chloride fluids from ascending to the surface the shallow depth of the volatile rich magma results in the degassing of large quantities of so2 and hcl these gases are readily hydrolyzed and quickly mix with meteoric water to form a reservoir of acid chloride sulfate brine in the summit hydrothermal system high recharge rates and steep hydraulic gradients associated with elevated topographic features of the summit region promote lateral flow of acid brines generated in the summit hydrothermal system however the same high recharge rates and steep hydraulic gradients prevent lateral flow of deep seated fluids thereby masking the presence of any sodium chloride brines that may exist in deeper parts of the volcanic edifice structural stratigraphic and topographic features of poa s volcano are critical in restricting flow of acid brines to the northwestern flank of the volcano a permeable lava lahar sequence that outcrops in the rio agrio drainage basin forms a hydraulic conduit between the crater lake and acid chloride sulfate springs spring water residence times are estimated from tritium data and indicate that flow of acid brines from the active crater to the rio agrio source springs is relatively rapid 3 to 17 years hydraulic conductivity values of the lava lahar sequence calculated from residence time estimates range from 10 5 to 10 7 m s these values are consistent with hydraulic conductivity values determined by aquifer tests of fractured and porous lava pyroclastic sequences at the base of the northwestern flank of the volcano fluxes of dissolved rock forming elements in rio agrio indicate that approximately 4300 and 1650 m3 of rock are removed annually from the northwest flank aquifer and the active crater hydrothermal system respectively over the lifetime of the hydrothermal system 100 s to 1000 s of years significant increases in aquifer porosity and permeability should occur in marked contrast to the reduction in permeability that often accompanies hydrothermal alteration in less acidic systems average fluxes of fluoride chloride and sulfur calculated from discharge and compositional data collected in the rio agrio drainage basin over the period 1988 1990 are approximately 2 38 and 30 metric tons day these fluxes should be representative of minimum volatile release rates at poa s in the last 10 to 20 years

three dimensional p velocity structure of the crust below newberry volcano oregon utilizing teleseismic p residuals we have detected a column of high p velocity material extending from within 10 km of the surface below the summit of newberry volcano oregon to midcrustal depths near 25 km we interpret this column to be the expression of a swarm of predominantly subsolidus gabbroic sills and dikes which were intruded as the volcano was built the high p velocities observed below the volcano severely limit the size of magma chambers which could presently exist in the crust below newberry volcano those possible include a few percent of partial melt distributed through large volumes of a mafic intrusion zone in the midcrust a few smaller higher melt fraction zones in the midcrust with dimensions less than 6 km and whose aggregate volume is only a few percent of enclosing volumes of 200 km sup 3 small magma bodies with dimensions of a few kilometers located within the upper 10 km of the crust or a mafic crystal rich magma of arbitrary dimensions located in the upper few km the low p velocities detected in the upper 4 km beneath the center of the summit caldera may be partially caused by a magma chamber in the second ofmore these catagories less

aeromagnetic mapping of the structure of pine canyon caldera and chisos mountains intrusion big bend national park texas analysis of aeromagnetic and gravity data reveals new details of the structure igneous geology and temporal evolution of the prominent enigmatic ca 32 ma pine canyon caldera and the chisos mountains big bend national park texas the main caldera fi lling pine canyon rhyolite the oldest member of the south rim formation is reversely magnetized allowing it to be used as a key marker bed for determining caldera fi ll thickness modeling of gravity and magnetic anomalies indicates that the pine canyon rhyolite is probably thicker in the northeastern part of the caldera lineaments in the magnetic data suggest the presence of buried faults beneath the caldera that may have led to increased downdrop in the northeast versus the southwest allowing a thicker section of caldera fi ll to accumulate there the pine canyon caldera has been interpreted as a downsag caldera because it lacks surfi cial faulting so these inferred faults are the fi rst mapped features there that could be responsible for caldera collapse the caldera boundary correlates well with the margins of a gravity low general features of the caldera match well with basic models of downsag calderas meaning that the pine canyon caldera may be a classic example of downsagging of which few well described examples exist in terms of a geophysical signature the source of a long wavelength magnetic high over the chisos mountains is interpreted as a previously unknown broad intrusion the long axis of which trends parallel to a major crustal boundary related to the ouachita orogeny or an even earlier precambrian margin this feature represents the largest intrusion 28 34 km diameter 1 4 km thick 700 3000 km 3 in volume in an area where relatively small laccoliths are ubiquitous the intrusion most likely represents a long lived 1 m y reservoir replenished by small batches of magma of varying composition as refl ected in the variation of eruptive products from the pine canyon and sierra quemada calderas the intrusion may represent the easternmost occurrence of voluminous tertiary magmatism in the southwestern united states

210po 210pb dating of recent volcanic eruptions on the sea floor the globe encircling mid ocean ridge system accounts for most of the earth s volcanism and influences its heat budget morphology and the composition of the oceans it is therefore important to constrain the size frequency and compositional variability of ridge eruptions but this is made difficult by the remoteness of much of the sea floor and the paucity of applicable radioactive chronometers remote monitoring has provided indirect evidence for active ridge volcanism1 3 which in some cases has been strengthened by submersible observations4 5 but it has not been possible to date these eruptions directly here we present a new chronometer based on 210po 210pb radioactive disequilibrium which allows us to date glassy eruption products within a few years of their eruption our first results on lavas from 9 50 n on the east pacific rise confirm that the ridge erupted only months before sample collection and indicate that the eruptions extended over at least one year the chronometer begins with po volatilization during eruption all glasses analysed were 75 100 degassed a crystalline pillow interior was 20 degassed however implying that the flow surface may control po degassing during deep submarine eruptions although the 210po 210pb chronometer is useful for only a short time frame it should prove valuable for dating recent but unobserved submarine eruptions and determining details of eruptive sequences

an alternative isochron method for measuring cosmogenic 3he in lava flows this study evaluates an alternative isochron method designed to improve the precision and the accuracy of the measurement of cosmogenic 3he 3hec and the calibration of 3hec production rates in lava flows while the accuracy of the standard two steps routine i crushing ii melting may be affected by possible crushing induced release of matrix sited 3hec this new isochron technique does not involve the preliminary crushing step such advance is thus potentially able to improve the accuracy of 3hec determination moreover this method has the advantage to yield cosmogenic 3he concentrations using only one type of extraction technique cosmogenic 3he isochrons can be built successfully measuring the 3he and 4he concentrations of several phenocrysts replicates fused in vacuo provided that these aliquots have identical magmatic 3he 4he ratios identical 3hec concentrations and variable magmatic helium contents when plotted in the 3he 4he vs 1 4he space such a suite of data define a straight line whose intercept yield the magmatic 3he 4he mag ratio and whose slope is the cosmogenic 3he concentration the frequent addition of radiogenic 4he 4helow asterisk may be easily accounted taking advantage of a property that is characteristic of non eroded lava flows the 3hec 4helow asterisk ratio is not time dependent this radiogenic correction of the isochron slope involves the r factor whose calculation requires that the u and th abundances in the phenocrysts and the host lava be known as well as the diameter and the shape of the analyzed minerals this correction also requires that all the analyzed aliquots have identical radiogenic 4he concentration the isochron method was tested on surface samples of three quaternary basalt flows from mount etna and mauna loa aged of 6 1 8 2 0 1 and 41 3 ka the obtained data set yielded statistically robust isochrons and cosmogenic 3he concentrations that are not significantly different from those obtained with the standard method importantly for samples with high magmatic cosmogenic 3he ratio the isochron technique offers both better accuracy and precision than the standard two steps method this alternative technique should thus open new perspectives for the particularly important task of 3hec production rate calibrations from lava flow surfaces

effects of ambient currents and waves on gravity driven sediment transport on continental shelves abstract observations from several shelf environments show that down slope gravity driven transport may constitute an important mode of suspended sediment dispersal across shelves and highlight the influence of ambient waves and currents on gravity induced sediment flux the phenomena discussed here involve high concentrations of suspended sediment mixed with seawater and thus differ in genesis from hyperpycnal plumes released directly from sediment laden rivers the field sites examined are the gulf of bohai off the mouth of the yellow river huanghe the northern california shelf off the mouth of the eel river and the louisiana shelf west of the mouths of the mississippi river off the yellow river rapid down slope transport over distances of a few km occurred when frictional resistance induced by strong along shelf currents was temporarily relaxed more prolonged down slope motion over longer distances occurred following floods of the eel river when wave and current agitation provided turbulence to sustain gravity driven transport of fluid mud on the louisiana inner shelf the down slope gravity force was much weaker but observations suggest that thin gravity flows may still have occurred in the presence of waves a simple analytical theory is developed that incorporates the influence of ambient shelf currents on gravity driven transport of suspended sediment this theory is quantitatively consistent with the observations from the three sites if the supply of easily suspended sediment is less than the capacity of ambient currents including waves to carry sediment then intense turbulence limits gravity induced sediment transport by increasing the drag at the base of the flow when ambient currents abruptly cease rapid down slope transport can then occur over short distances until the sediment settles such flows do not remain intensely turbulent because the slope of the continental shelf is too gentle to induce shear instability within the gravity flow the maximum sustained rate of gravity induced sediment transport occurs when ambient currents are strong but the supply of easily suspended sediment exceeds the resuspension capacity of the ambient currents feedback then leads to values of the gradient richardson number ri within the flow that are near the critical value of 1 4 this partially damps bottom drag but still allows the generation of sufficient turbulence to maintain sediment in suspension observations also indicate systematic relationships among ri the supply of easily suspended sediment and the bottom drag coefficient acting on the gravity flow

source of the basinal sediments in the marmara sea investigated using heavy minerals in the modern beach sands abstract the source of recent turbidites in the deep basins of the marmara sea was investigated by comparing their heavy mineral composition with those from the beach sands of the marmara sea the marmara sea is an inland sea between the mediterranean and black seas it consists essentially of three strike slip basins over 1000 m deep which are forming along the north anatolian fault the thickness of the pliocene to recent syn transform sediments in the marmara basins exceeds several kilometers sand samples were studied at 49 locations along the marmara sea beaches and in 15 samples from seven cores from the basins based on the amount and type of heavy minerals four heavy mineral provinces are distinguished in the beach sands beach sands from the northwestern marmara sea are characterized by a scarcity of the heavy minerals which are represented mainly by mica and chlorite they are derived from erosion of the soft and friable miocene sandstones exposed in the region in the north central marmara sea the beach sands have a relatively high proportion of heavy minerals which are dominated by opaques epidote and garnet the heavy mineral composition of these beach sands reflects those of the oligocene sandstones in the hinterland beach sands in the eastern marmara sea are varied in their heavy mineral composition reflecting a heterogeneous hinterland beach sands in the southern marmara sea are characterized by a high proportion of heavy minerals dominated by amphibole pyroxene epidote and opaque heavy minerals in the sandy layers in the gravity cores differ from those of the beach sands by a decrease in the concentration of high density heavy minerals and increase in mica and chlorite related to transport processes nevertheless comparison of the heavy mineral assemblages and heavy mineral ratios between the beach sands and sands from the deep basins suggests a sediment transport from the west from the miocene sandstones for the western tekirdag basin for the central basin sandy layers from a single gravity core show variable heavy mineral assemblages suggesting derivation from both north and south of the marmara sea the eastern cinarcik basin receives at least some of its sandy sediment from the east through the bay of izmit

combined u th he and 40ar 39ar geochronology of post shield lavas from the mauna kea and kohala volcanoes hawaii late quaternary post shield lavas from the mauna kea and kohala volcanoes on the big island of hawaii have been dated using the sup 40 ar sup 39 ar and u th he methods the objective of the study is to compare the recently demonstrated u th he age method which uses basaltic olivine phenocrysts with sup 40 ar sup 39 ar ages measured on groundmass from the same samples as a corollary the age data also increase the precision of the chronology of volcanism on the big island for the u th he ages u th and he concentrations and isotopes were measured to account for u series disequilibrium and initial he single analyses u th he ages for hamakua lavas from mauna kea are 87 40 ka to 119 23 ka 2 sigma uncertainties which are in general equal to or younger than sup 40 ar sup 39 ar ages basalt from the polulu sequence on kohala gives a u th he age of 354 54 ka and a sup 40 ar sup 39 ar age of 450 40 ka all of the u th he ages and all but one spurious sup 40 ar sup 39 ar ages conform to the previously proposed stratigraphy and published sup 14 c and k ar ages the ages also compare favorably to u th whole rock olivine ages calculated from sup 238 u sup 230 th disequilibria the u th he and sup 40 ar sup 39 ar results agree best where there is a relatively large amount of radiogenic sup 40 ar 10 and where the sup 40 ar sup 36 ar intercept calculated from the ar isochron diagram is close to the atmospheric value in two cases it is not clear why u th he and sup 40 ar sup 39 ar ages do not agree within uncertainty u th he and sup 40 ar sup 39 ar results diverge the most on a low k transitional tholeiitic basalt with abundant olivine for the most alkalic basalts with negligible olivine phenocrysts u th he ages were unattainable while sup 40 ar sup 39 ar results provide good precision even on ages as low as 19 4 ka hence the strengths and weaknesses of the u th he and sup 40 ar sup 39 ar methods are complimentary for basalts with ages of order 100 500 ka

quaternary sedimentary record in the northern okinawa trough indicates the tectonic control on depositional environment change abstract during the quaternary global sea level was characterized by large fluctuations in amplitude and increased frequency however the eastern marginal seas of china especially the northern east china sea and yellow sea did not experience large scale transgression until the middle pleistocene the zhe min zhejiang fujian uplift was an important barrier in the east china sea preventing transgression of sea water into the northern marginal seas of china but its quaternary evolution is still poorly constrained here we present a thick sand layer record the top age is 416 ka of the integrated ocean drilling program iodp site u1428 from the northern okinawa trough to reconstruct the history of the zhe min uplift since the middle pleistocene provenance analysis indicates that sediments from both sand and imbedded fine grained calcareous rich clay layers at the study site were mainly derived from the yellow river which for the first time indicates that the yellow river sediments could influence the northern okinawa trough since at least the middle pleistocene significant change of lithology at iodp site u1428 at 416 ka was attributed to the large scale subsidence of the zhe min uplift which is probably due to the rapid uplifting of tibet during 0 52 0 38 ma before 416 ka obstacle of the emersed zhe min uplift induced extremely severe reworking and promoted sand ridge formation in the shelf edge of southeastern yellow sea and supplied sand sediments to the northern okinawa trough during transgression and high sea level stages after the subsidence of the zhe min uplift at 416 ka westward of tidal sand ridge and yellow river mouth with the process of shelf transgressions favored fine grained sediments input to the northern okinawa trough even during low sea level stages the flat terrain of the east asian marginal sea shelf and low rainfall amount resulted in low discharge of yellow river and supplied fine grained particles to the northern okinawa trough

determining eruption ages and erosion rates of quaternary basaltic volcanism from combined u series disequilibria and cosmogenic exposure ages we present 238 u 230 th 226 ra disequilibria and cosmogenic 3 he and 36 cl data for the bluewater flow of the zuni bandera volcanic field in western new mexico the 238 u 230 th disequilibria measured on separated groundmass phases yield an internal isochron age of 68 ka 24 20 ka 2 this value cannot be directly compared with surface exposure ages unless erosion rates are known the apparent zero erosion ages determined from both the 3 he concentration 47 5 5 ka 2 and the 36 cl concentration 41 2 8 8 ka 2 are significantly younger than the u th isochron age when minimum estimates of surface erosion based on flow morphology are considered the 3 he concentrations indicate a minimum exposure age of 60 ka in good agreement with the u th isochron age with a minimum erosion rate of 1 7 mm k y and an erosion rate as high as 5 mm k y in other locations correcting for erosion has little effect on the model 36 cl age and as a result the 36 cl age is significantly younger than the u th isochron age and erosion corrected 3 he ages this discordance is attributed to a lack of closed system behavior in the 36 cl system these new ages have local significance for the geochronology of the zuni bandera volcanic field however their larger significance is in their applicability to dating quaternary basalts and quantifying erosion rates

geomorphic tectonic control of sediment discharge to the ocean the importance of small mountainous rivers analysis of data from 280 rivers discharging to the ocean indicates that sediment loads yields are a log linear function of basin area and maximum elevation of the river basin other factors controlling sediment discharge e g climate runoff appear to have secondary importance a notable exception is the influence of human activity climate and geology on the rivers draining southern asia and oceania sediment fluxes from small mountainous rivers many of which discharge directly onto active margins e g western south and north america and most high standing oceanic islands have been greatly underestimated in previous global sediment budgets perhaps by as much as a factor of three in contrast sediment fluxes to the ocean from large rivers nearly all of which discharge onto passive margins or marginal seas have been overestimated as some of the sediment load is subaerially sequestered in subsiding deltas before the proliferation of dam construction in the latter half of this century rivers

long term cosmogenic 3 he production rates from 40 ar 39 ar and k ar dated patagonian lava flows at 47 s exceptionally well preserved basaltic lava flows on the cool arid eastern side of the southern andes near lago buenos aires lba at lat 47 s provide ideal sites for calibration of in situ produced cosmogenic 3he we report new 3he measurements and independent age determinations using unspiked k ar and 40ar 39ar incremental heating measurements from two basalt flows both age techniques give concordant ages with analytical uncertainties of 5 demonstrating their utility for dating surfaces older than 35 ka the limit of 14c dating the weighted mean age of the cerro volcan flow is 109 3 ka and of the rio pinturas flow is 68 3 ka scaled to sea level and high latitude d lal earth planet sci lett 104 1991 424 439 and standard atmospheric pressure j o stone j geophys res 105 2000 23 753 23 759 3he production rates on the cerro volcan flow are 130 4 atoms g 1 a 1 in clinopyroxene and 139 4 atoms g 1 a 1 in olivine 2 consistent with a small compositional dependence of the production rate the 3he production rate in olivine from the younger rio pinturas flow is 129 6 atoms g 1 a 1 which is indistinguishable from that obtained on cerro volcan the 3he production rate is at least 11 higher than previous determinations from low mid latitudes in the northern hemisphere corrections for magnetic field strength variability lower the scaled lba production rates by only 1 and do not account for the discrepancy we infer that the enhanced production rates are caused by lower atmospheric pressure in patagonia during glacial periods the southern westerlies which are associated with the steep circumpolar atmospheric pressure gradient are presently centered on lat 50 s but based on independent marine and terrestrial evidence are thought to have migrated north at least 5 during glacial periods the inferred paleobarometry provides independent evidence for northward shifts in the patterns of southern hemisphere atmospheric circulation

the influence of radiogenic 4he on cosmogenic 3he determinations in volcanic olivine and pyroxene accurate determination of cosmogenic 3he concentrations in olivine and pyroxene phenocrysts requires knowledge of the amount of magmatic 3he also in the sample the magmatic 3he component is commonly estimated by measuring the magmatic 3he 4he ratio and assuming that all 4he is magmatic however this approach yields incorrect results if 4he produced by u and th decay is also present here we propose several strategies to account for the presence of radiogenic 4he the optimal approach depends on whether the helium closure age tc is similar to the exposure age te of the analyzed phenocrysts i when tc te which applies to uneroded lava flows the ratio of cosmogenic 3he to radiogenic 4he is constant and the correction for radiogenic helium is independent of time we provide a simple expression for a correction factor r that can be applied in this case ii in the more common case that tc te it is necessary to obtain an independent constraint on the closure age to estimate the radiogenic correction in either case a quantitative estimate of the radiogenic 4he production rate is required because of the long stopping distance of particles this production rate depends on the u and th concentrations of both phenocryst and host and also on phenocryst grain size to illustrate the magnitude and uncertainty of the necessary corrections we compiled u and th measurements on phenocrysts and whole rock samples of basalts and andesites supplemented by new measurements on hawaiian basalts and altiplano andesites our data and models suggest that some published cosmogenic 3he production rate determinations may have underestimated the true production rate by up to 5 because the presence of radiogenic 4he was not recognized similarly a recent study presenting cosmogenic 3he derived erosion rates in 4 ma hawaiian olivines probably overestimates true erosion rates by an order of magnitude or more

high precision 40 ar 39 ar dating of quaternary basalts from auckland volcanic field new zealand with implications for eruption rates and paleomagnetic correlations abstract the auckland volcanic field avf which last erupted ca 550 years ago is a late quaternary monogenetic basaltic volcanic field ca 500 km 2 in the northern north island of new zealand prior to this study only 12 out of the 53 identified eruptive centres of the avf had been reliably dated careful sample preparation and 40 ar 39 ar analysis has increased the number of well dated centres in the avf to 35 the high precision of the results is attributed to selection of fresh non vesicular non glassy samples from lava flow interiors sample selection was coupled with separation techniques that targeted only the groundmass of samples with 10 m wide coupled with ten increment furnace step heating of large quantities up to 200 mg of material the overall avf age data indicate an onset at 193 2 2 8 ka an apparent six eruption flare up from 30 to 34 ka and a 10 kyr hiatus between the latest and second to latest eruptions such non uniformity shows that averaging the number of eruptions over the life span of the avf to yield a mean eruption rate is overly simplistic together with large variations in eruption volumes and the large sizes and unusual chemistry within the latest eruptions rangitoto 1 and rangitoto 2 our results illuminate a complex episodic eruption history in particular the rate of volcanism in avf has increased since 60 ka suggesting that the field is still in its infancy multiple centres with unusual paleomagnetic inclination and declination orientations are confirmed to fit into a number of geomagnetic excursions with five identified in the mono lake two within the laschamp one within the post blake or blake and two possibly within the hilina pali

mineral speciation and fate of some hazardous contaminants in coal waste pile from anthracite mining in portugal the coal anthracite a in douro coalfield nw of portugal has been exploited for many years and has been mainly used as fuel supply by a thermal power plant the mining activities inevitably impacted the environment which includes a large number of coal waste piles emplaced over the old mine sites and adjacent areas of the douro coalfield the disposal of coal mining residues represents significant environmental concerns due to their potential influence on soils and sediments as well as on the surface and groundwater of the surrounding areas in the present study the development of sequential extraction combined with various advanced analytical techniques was performed to provide an improved understanding of the complex processes related with sulfide rich coal waste oxidation sequences of mineral formation and the transport mechanisms of hazardous elements by specific neoformed soluble minerals the results showed the presence of amorphous iron oxy hydroxides and goethite with various degrees of crystallinity containing hazardous elements such as as cr hg mo se pb u and others some of the neoformed minerals found in the coal waste material are the same as those commonly associated with coal acid drainage in which oxidation of sulfides plays an important role the precipitated neoformed minerals include pickeringite blodite and a mixture of epsomite pickeringite and hexahydrite as these sulfates may dissolve after the first rain they may release above mentioned elements into surrounding water bodies

cosmic ray exposure dating with in situ produced cosmogenic 3he results from young hawaiian lava flows in an effort to determine the in situ production rate of spallation produced cosmogenic 3 he and evaluate its use as a surface exposure chronometer we have measured cosmogenic helium contents in a suite of hawaiian radiocarbon dated lava flows the lava flows ranging in age from 600 to 13 000 years were collected from hualalai and mauna loa volcanoes on the island of hawaii because cosmic ray surface exposure dating requires the complete absence of erosion or soil cover these lava flows were selected specifically for this purpose the 3 he production rate measured within olivine phenocrysts was found to vary significantly ranging from 47 to 150 atoms g 1 yr 1 normalized to sea level although there is considerable scatter in the data the samples younger than 10 000 years are well preserved and exposed and the production rate variations are therefore not related to erosion or soil cover data averaged over the past 2000 years indicate a sea level 3 he production rate of 125 30atoms g 1 yr 1 which agrees well with previous estimates the longer record suggests a minimum in sea level normalized 3 he production rate between 2000 and 7000 years 55 15atoms g 1 yr 1 as compared to samples younger than 2000 years 125 30 atoms g 1 yr 1 and those between 7000 and 10 000 years 127 19atoms g 1 yr 1 the minimum in production rate is similar in age to that which would be produced by variations in geomagnetic field strength as indicated by archeomagnetic data however the production rate variations a factor of 2 3 0 8 are poorly determined due to the large uncertainties in the youngest samples and questions of surface preservation for the older samples calculations using the atmospheric production model of o brien 1979 35 and the method of lal and peters 1967 11 predict smaller production rate variations for similar variation in dipole moment a factor of 1 15 1 65 because the production rate variations archeomagnetic data and theoretical estimates are not well determined at present the relationship between dipole moment and production rate will require further study precise determination of the production rate is an important uncertainty in the surface exposure technique but the data demonstrate that it is feasible to date samples as young as 600 years of age providing that there has been no erosion or soil cover therefore the technique will have important applications for volcanology glacial geology geomorphology and archaeology

an asymmetric upwind flow yellow sea warm current 1 new observations in the western yellow sea 1 the winter water mass along the yellow sea trough yst especially on the western side of the trough is considerably warmer and saltier than the ambient shelf water mass this observed tongue shape hydrographic feature implies the existence of a winter along trough and onshore current often referred to as the yellow sea warm current yswc however the yswc has not been confirmed by direct current measurements and therefore skepticism remains regarding its existence some studies suggest that the presence of the warm water could be due to frontal instability eddies or synoptic scale wind bursts it is noted that in situ observations used in most previous studies were from the central and eastern sides of the yst even though it is known that the warm water core is more pronounced along the western side data from the western side have been scarce here we present a set of newly available chinese observations including some from a coordinated effort involving three chinese vessels in the western yst during the 2006 2007 winter the data show unambiguously the existence of the warm current on the western side of yst both the current and hydrography observations indicate a dominant barotropic structure of yswc the westward deviation of yswc axis is particularly obvious to the south of 35 n and is clearly associated with an onshore movement of warm water to the north of 35 n the yswc flows along the bathymetry with slightly downslope movement we conclude that the barotropic current is mainly responsible for the warm water intrusion while the ekman and baroclinic currents play an important but secondary role these observations help fill an observational gap and establish a more complete view of the yswc

the sand ridge field of the south yellow sea origin by river sea interaction abstract the origin of a large field of sand ridges offshore from the north jiangsu coast in the south yellow sea has been investigated on the basis of bathymetry seabed samples high resolution seismic profiles and 31 to 71 m deep boreholes sediment composition including heavy minerals and clay minerals sampled from surface sediments shows that most of the sand was derived from the changjiang yangtze river but in the northern part of the field particularly the clay came from the huanghe yellow river seismic profiles show late pleistocene distributary channels of the ancient changjiang river underlying much of the southern part of the sand ridge field the holocene transgression cut a widespread ravinement surface reworking abundant late pleistocene sandy sediment the available sand was reworked by tidal currents into large ridges the location of the ridges is strongly influenced by relict channels in the southern part of the field and by tidal currents in the northern and especially the northeastern part of the field resulting in a radiating ridge pattern these ridges provide an example of the evolution of a large scale geomorphic feature resulting from river sea interaction in which climatic and sea level changes played an important role

comparison of wind and tidal contributions to seasonal circulation of the yellow sea 1 seasonal circulation of the yellow sea ys in response to wind and tidal forces is examined using a three dimensional numerical model wind forcing affects the wintertime circulation of the ys on the other hand the summer southerly monsoon is weak and therefore has little impact on the circulation on the basis of comparative experiments with and without wind conditions results indicate that the yellow sea warm current yswc along the ys trough exists regardless of wind forcing however strong winter northerly winds intensify the southward coastal flows along both coasts of the ys and therefore the northward intrusion of the yswc becomes stronger these flows in the ys are substantially weakened when wind forcing is not applied to the model in addition to wind driven circulation tide induced circulation is also dominant in the ys particularly in summer in winter the tidal effect weakens the upwind and downwind flows in response to the strong northerly winds while in summer tidal forcing induces a strong southward residual flow along the western slope and a cyclonic gyre with a bottom cold water dome at the central region of the ys the southward residual current possibly explains the southward movement of the yellow sea bottom cold water as observed in summer comparison to the effects of parameterized tidal mixing suggests that residual flow driven by explicit tidal forcing plays an important role in the summertime circulation of the ys

geologic evidence for a magma chamber beneath newberry volcano oregon at newberry volcano central oregon more than 0 5 m y of magmatic activity including caldera collapse and renewed caldera filling volcanism has created a structural and thermal chimney that channels magma ascent holocene rhyolitic eruptions 1 have been confined mainly within the caldera in an area 5 km in diameter 2 have been very similar in chemical composition phenocryst mineralogy and eruptive style and 3 have occurred as recently as 1300 years ago with repose periods of 2000 3000 years between eruptions holocene basaltic andesite eruptions are widespread on the flanks but are excluded from the area of rhyolitic volcanism basaltic andesite in fissures at the edge of the rhyolite area has silicic inclusions and shows mixed basalt rhyolite magma relations these geologic relations and the high geothermal gradient that characterizes the lower part of a drill hole in the caldera u s geological survey newberry 2 indicate that a rhyolitic magma chamber has existed beneath the caldera throughout the holocene its longevity probably is a result of intermittent underplating by basaltic magma

high resolution seismic tomography of compressional wave velocity structure at newberry volcano oregon cascade range compressional wave velocity structure is determined for the upper crust beneath newberry volcano central oregon using a high resolution active source seismic tomography method newberry volcano is a bimodal shield volcano east of the axis of the cascade range it is associated both with the cascade range and with northwest migrating silicic volcanism in southeast oregon high frequency 7 hz crustal phases nominally pg and a midcrustal reflected phase travel upward through a target volume beneath newberry volcano to a dense array of 120 seismographs this arrangement is limited by station spacing to 1 to 2 km resolution in the upper 5 to 6 km of the crust beneath the volcano s summit caldera the experiment tests the hypothesis that cascade range volcanoes are underlain only by small magma chambers a small low velocity anomaly delineated about 3 km below the summit caldera supports this hypothesis for newberry volcano and is interpreted as a possible magma chamber of a few to a few tens of km3 in volume a ring shaped high velocity anomaly nearer the surface coincides with the inner mapped ring fractures of the caldera it also coincides with a circular gravity high and we interpret it as largely subsolidus silicic cone sheets the presence of this anomaly and of silicic vents along the ring fractures suggests that the fractures are a likely eruption path between the small magma chamber and the surface

an interpretation of trends in grain size measures abstract the mean grain size sorting and skewness of a sedimentary deposit are dependent on the sediment grain size distribution of its source and the sedimentary processes of i winnowing erosion ii selective deposition of the grain size distribution in transport and iii total deposition of the sediment in transport if a source sediment undergoes erosion and the resultant sediment in transport is deposited completely the deposit must be finer better sorted and more negatively skewed than the source this trend is referred to as case i the lag remaining after erosion on the other hand must be coarser better sorted and more positively skewed case ii if sediment in transport undergoes selective deposition the resultant deposit can either be finer case iiia or coarser cas iiib than the source but the sorting will be better and the skew more positive although exceptions to these trends may occur they suggest that comparison of one sediment must be made with another for the proper identification of the sedimentary process and therefore it is not possible for a single grain size distribution to identify the depositional environment the trends also suggest that the skewness of a grain size distribution has been widely misinterpreted and implies neither the truncation of one of the tails nor the mixing of more than one mode rather a skewed sediment is the natural result of the sedimentary process in a system of related environments these trends can be used to identify both the probable source and the probable deposit and by inference the net sediment transport paths among sedimentary deposits such an analysis provides a rapid understanding of the sedimentary processes identifies patterns of erosion and accretion and may suggest transport processes

distribution pattern and controlling factors of heavy mineral assemblages in surficial seafloor sediments offshore of the eastern shandong peninsula yellow sea the source and processes controlling the deposition of the sand fraction of muddy seafloor sediments remain poorly understood surficial seafloor sediments were collected offshore of the eastern shandong peninsula and were analyzed regarding their detrital heavy mineral constituents and grain size distributions to determine their spatial distribution patterns sand fraction provenance and transport pathways five sediment types were identified in the study area clayey silt silt sandy silt silty sand and sand each of these sediment types displayed distinct grain size parameters of their corresponding sand fractions moreover three statistical clusters of sand grains were identified suggesting variations in provenances and sedimentary processes from one cluster to the next twenty five species of detrital heavy minerals in the sand fraction were identified and then assigned to four categories based on their mineral stability i e ultrastable stable moderately stable and unstable the sandy sediments were enriched in ultrastable and stable heavy minerals indicating that these sand grains mostly originated from coastal erosion of granitic and or metamorphic rocks in contrast the muddy sediments were characterized by unstable heavy minerals dominated by hornblende and epidote the results of principal component analysis further suggested that these sand grains are similar in terms of their provenance coastal erosion but have undergone complex sedimentary processes relative sea level changes during the late quaternary caused shifts in the sediment sources and supplies which were the primary factors controlling the grain sizes of the sand fractions and heavy mineral assemblages in the surficial sediments of the study area

isotope geochemistry of minerals and fluids from newberry volcano oregon isotopic compositions were determined for hydrothermal quartz calcite and siderite from core samples of the newberry 2 drill hole oregon the 15o values for these minerals decrease with increasing temperatures the values indicate that these hydrothermal minerals precipitated in isotopic equilibrium with water currently present in the reservoirs the 18o values of quartz and calcite from the andesite and basalt flows 700 932 m have isotopic values which require that the equilibrated water 18o values increase slightly 11 3 to 9 2 with increasing measured temperatures 150 265 c the lithic tuffs and brecciated lava flows 300 700 m contain widespread siderite calculated oxygen isotopic compositions of waters in equilibrium with siderite generally increase with increasing temperatures 76 100 c the 18o values of siderite probably result from precipitation in water produced by mixing various amounts of the deep hydrothermal water 10 5 with meteoric water 15 5 recharged within the caldera the 13c values of calcite and siderite decrease with increasing temperatures and show that these minerals precipitated in isotopic equilibrium with co2 of about 8 the 18o values of weakly altered 5 alteration of plagioclase whole rock samples decrease with increasing temperatures above 100 c indicating that exchange between water and rock is kinetically controlled the water rock mass ratios decrease with decreasing temperatures the 18o values of rocks from the bottom of newberry 2 show about 40 isotopic exchange with the reservoir water the calculated 18o and d values of bottom hole water determined from the fluid produced during the 20 hour flow test are 10 2 and 109 respectively the d value of the hydrothermal water indicates recharge from outside the caldera

40ar 39ar evidence for early deglaciation of the central chilean andes spatial variability of deglaciation and warming since the last glacial maximum is critical for relating hemispheric or regional climate forcing mechanisms to global orbitally induced insolation changes radiocarbon ages of moraines ice cores and deep sea sediments from the southern hemisphere suggest that initial warming and glacial recession began before 23 000 years ago but that in latitudinal belts of concentrated precipitation glaciers readvanced 18 000 and 13 000 years ago 40 ar 39 ar dating of glaciated and unglaciated lava flows 2200 m in elevation at laguna del maule central chilean andes implies that at 36 s the southern andean ice cap retreated between 25 600 1 200 and 23 300 600 years ago and did not expand afterwards these ages are reconciled if increased insolation ablated sea ice cover and mountain glaciers in the southern hemisphere 5 000 years before the northern and if subsequently laguna del maule lay north of the westerly winds delivering moisture to more southerly 39 52 s portions of the ice cap

delta development and channel incision during marine isotope stages 3 and 2 in the western south yellow sea abstract approximately 4100 km of high resolution seismic profiles recently obtained from the western south yellow sea were subdivided into seven seismic units by six major seismic surfaces three sediment cores between 60 and 71 m in length obtained from localities on the seismic profile lines were analyzed for sedimentary characteristics clay mineral components and benthic foraminiferal and ostracod assemblages and were also dated by ams 14 c and optically stimulated luminescence to document the environmental history of the region stratigraphic units in the cores were confidently correlated with seismic units in the profiles stratigraphic correlation among these three cores and the previous well studied core qc 2 was facilitated by the cold water deposits in marine isotope stage mis 5 the three cores document the sedimentary sequence during the period from mis 6 up to mis 1 strata formation and sedimentary environment changes since mis 5 are strongly controlled by sea level fluctuations most of the successions were formed in mis 5 mis 3 and mis 1 with major erosions in mis 4 and mis 2 particularly our data revealed the presence of a large delta active during mis 3 likely from the early stage of mis 3 to about 40 cal kyr bp that was subsequently affected by channel incision the delta succession and incised channel fills have a high concentration of smectite in their clay mineral components suggesting that the paleo yellow river was the main contributor to the delta development and channel incision the delta sequence has a coarsening upward trend and consists of two seismic facies the upper facies shows lateral alternations of chaotic and oblique or very low angle reflectors which correspond to sandy proximal delta front and delta plain facies and the lower facies is characterized by seaward dipping clinoforms which correspond to muddy distal delta front and prodelta facies the top surface of the delta inclines very gently seaward consistent with a deltaic development associated with the sea level fall in mis 3 the incised channel system consists of two main channels with multiple tributaries in a dendritic pattern the incised channel fills begin with fluvial and then estuarine sediments which are truncated by a transgressive ravinement surface and capped by transgressive deposits the main incision channels have a terraced cross sectional morphology which is interpreted to reflect multiple episodes of sea level fall during incision presumably from the late mis 3 to the last glacial maximum

gravity model studies of newberry volcano oregon newberry volcano a large quaternary volcano located about 60 km east of the axis of the high cascades volcanoes in central oregon has a coincident positive residual gravity anomaly of about 12 mgals model calculations of the gravity anomaly field suggest that the volcano is underlain by an intrusive complex of mafic composition of about 20 km diameter and 2 km thickness at depths above 4 km below sea level however uplifted basement in a northwest trending ridge may form part of the underlying excess mass thus reducing the volume of the subvolcanic intrusive a ring dike of mafic composition is inferred to intrude to near surface levels along the caldera ring fractures and low density fill of the caldera floor probably has a thickness of 0 7 0 9 km the gravity anomaly attributable to the volcano is reduced to the east across a north northwest trending gravity anomaly gradient through newberry caldera and suggests that normal perhaps extensional faulting has occurred subsequent to caldera formation and may have controlled the location of some late stage basaltic and rhyolitic eruptions significant amounts of felsic intrusive material may exist above the mafic intrusive zone but cannot be resolved by the gravity data

sediment accumulation in a modern epicontinental shelf setting the yellow sea sediment accumulation in the yellow sea epicontinental shelf environment is investigated on 100 yr and 1000 yr time scales using 210pb and 14c geochronologies the distribution of modern 210pb accumulation rates in the yellow sea reveals that the loci of modern huanghe sediment accumulation are the topset 1 2 mm yr foreset 4 9 mm yr and proximal bottomset deposits 2 4 mm yr of the shandong subaqueous delta which extends south from the shandong peninsula 210pb rates in the distal bottomset deposits of the subaqueous delta in the central and southern yellow sea are generally low 0 3 0 9 mm yr a sediment budget demonstrates that between 9 15 of the annual huanghe discharge is accumulating in the yellow sea about two thirds of this sediment is accumulating in the topset foreset and proximal bottomset deposits of the shandong subaqueous delta with the remaining third accumulating as widespread distal bottomset deposits 14c age dates of subaqueous delta sediments indicate that the thick 40m clinoform structure formed predominantly between 6200 and 4060 yrs b p at rates approaching 20 mm yr observations in the yellow sea as well as on the amazon and ganges brahmaputra shelves demonstrate that subaqueous deltaic stratigraphy is the general rule where major rivers enter energetic shelves whether epicontinental or pericontinental the development of extensive bottomset deposits may be restricted to epicontinental shelf environments and may be diagnostic of sedimentation in this type of setting

the accumulation of cosmogenic chlorine 36 in rocks a method for surface exposure dating because of the reaction of cosmic rays with elements in minerals chlorine 36 accumulates in rocks exposed at the earth s surface this suggests that the ratio of chlorine 36 to stable chloride can be used as a geochronometer reasonable agreement has been obtained between measurements of chlorine 36 in volcanic rocks of known age and calculations of chlorine 36 production based on rock composition and cosmicray flux the buildup of chlorine 36 should be a useful means for measuring the surface exposure time of young volcanic rocks and geomorphic features in the age range of 10 3 to 10 6 years

development of depositional systems in the southeastern yellow sea during the postglacial transgression this study focuses on the development of depositional systems in the southeastern yellow sea during the postglacial transgression based on the analysis of closely spaced high resolution seismic profiles chirp and piston cores transgressive deposits comprise the paralic component of estuarine channel fills seaward prograding wedge and along shore prograding mound and the marine component of sand veneer mud blanket and offshore ridge these transgressive deposits were developed through three distinctive stages in terms of possible sea level position during the early stage tidal sand ridges and sand veneer formed south of jeju island resulting from shoreface erosion associated with a relatively slow transgression the following transgression in the middle stage inundated subaerially formed interfluves along the central part of the sea and affected development of estuarine environments with increasing tidal regime in the eastern part of the sea combined with the strong tidal reworking insufficient sand supply enhanced the formation of erosional ridges short period increase in fluvial discharge affected the deposition of coastal wedge in the western part fine grained sediments from either fluvial discharge or tidal reworking were dispersed seaward to form mud blanket the late stage was characterized by the deposition of veneered sands off the jiangsu coast which was due to relatively slow rise in sea level further offshore along shore prograding mound was constructed by huanghe derived sediment influx and subsequently eroded and redeposited by wave and tide activities thus detached from the proximal source the depositional processes and variability of the transgressive deposits in the southeastern yellow sea were largely controlled by changes in rate of sea level rise during the transgression most likely related to the global flooding events triggered by melt water pulses the changes in shoreline configuration and oceanographic regime have also influenced the distribution and morphology of the transgressive deposits a short period increase in riverine discharge caused the temporal sediment progradation off the jiangsu coast

a unique yellow river derived distal subaqueous delta in the yellow sea abstract newly acquired high resolution chirp sonar profiles reveal a unique yellow river derived alongshore distributed bidirectional landward and seaward across shelf transported omega shaped distal subaqueous deltaic lobe deposited around the eastern tip of the shandong peninsula in the yellow sea this clinoform deposit directly overlies the postglacial transgressive surface featured by convex up seafloor morphology up to 40 m thick locally radiocarbon 14 dates from the underlain pre holocene and transgressive sediments indicate this distal lobe has formed since the middle holocene highstand under a relatively stable sea level this along shelf distributed distal clinoform has been deposited mainly by the resuspended yellow river sediments carried down by the coastal current interacting with the local waves tides and upwelling collectively over the past 7000 years nearly 30 of the yellow river derived sediment has been re suspended and transported out of the bohai sea into the yellow sea overall the yellow river derived sediment could reach the 80 m water depth in the central south yellow sea about 700 km from the river mouth in contrast a very small fraction of the modern riverine sediment could escape the outer shelf or reach the okinawa trough

experimental evidence of resistivity frequency dispersion in magnetotellurics in the newberry oregon snake river plain idaho and campi flegrei italy volcano geothermal areas abstract we show that magnetotelluric measurements carried out in volcano geothermal areas can be significantly affected by the resistivity frequency dispersion phenomenon the polarization effects are recognized by comparing magnetotelluric and dc geoelectrical deep soundings performed in the same station indeed the conventional separate analysis of the two data sets sometimes gives unconformable results especially as it regards the resistivity and thickness of the conductive layers ascribable to the geothermal fluid filled rocks these apparent discrepancies can be overcome by admitting the occurrence of intense induced polarization effects inside the rocks having extensive alterations due to hydrothermal paragenesis the basic theory of the induced polarization effects over magnetotelluric measurements is at first briefly recalled then three impressive field examples taken from previous experiments performed in the newberry volcano snake river plain and campi flegrei geothermal areas are presented and discussed

sediment transport off the huanghe yellow river delta and in the adjacent bohai sea in winter and seasonal comparison abstract based on the data on the current velocity water temperature salinity turbidity and concentration of suspended sediment collected in november 2006 along three survey transects at three time series ship based stations off the huanghe yellow river delta and at twenty four grid survey stations in the adjacent bohai sea sediment transport off the huanghe delta and in the adjacent bohai sea under winter regime were studied and compared with those from the summer season the homogeneous distribution of salinity temperature and sediment in the water column indicated a well mixed body of water a zone of high suspended sediment concentrations ssc 100 mg l 1 with a width of 35 km was identified along the delta coast two highest ssc centers were found in the surface and middle water layers around the abandoned diaokou huanghe river mouth and the present huanghe river mouth and the third one in the bottom layer around the abandoned qingshuigou huanghe river mouth these three highest ssc centers become major sediment source areas in winter based on the location of the high bottom shear stress zone the prevailing wave directions and the protuberant topography of the river mouths we identified the resuspension origin of the three highest ssc centers caused mostly by the winter storm waves partially by tidal currents suspended sediment flux ssf along the three coastal transects indicated that the sediment in the northwest part of the delta was transported northeastward and southeastward along the coast of the recent delta lobe the ssc and ssf were higher in winter than summer by 1 7 27 1 and 2 122 5 times respectively except around the present river mouth this indicates that the intensity of sediment transport in winter is much stronger than in summer due to the powerful effect of winter storms although the river water and sediment discharges to the sea were much greater in summer the massive huanghe sediment to the sea was accumulated in a narrow coastal area due to weak hydrodynamics in summer and then strongly resuspended mostly by storm waves in winter and transported to the offshore area the coastal area off the huanghe delta acts as a sediment sink in summer and converted to be a sediment source in winter in response to the seasonal variation of the east asian monsoon in this region the erosion accumulation pattern of the huanghe subaqueous delta from 1976 to 2003 illustrates that river laden sediment is deposited mainly in the southern part off the coastal area and it is also the result of intensive southward sediment transport in winter

quantitative models of sediment generation and provenance state of the art and future developments abstract an overview of quantitative approaches to analysis and modelling of sediment generation and provenance is presented with an emphasis on major framework components as determined by means of petrographic techniques conceptual models of sediment provenance are shown to be consistent with two classes of numerical statistical models i e linear mixing models and compositional linear models these cannot be placed within a common mathematical framework because the former requires that sediment composition is expressed in terms of proportions whereas the latter requires that sediment composition is expressed in terms of log ratios of proportions additivity of proportions a fundamental assumption in linear mixing models cannot be readily expressed in log ratio terms linear mixing models may be used to describe compositional variability in terms of physical and conceptual un mixing models of physical un mixing are appropriate for describing compositional variation within transport invariant subpopulations of grains as a result of varying rates of supply of detritus from multiple sources conceptual un mixing governs the relations among chemical mineralogical and petrographic characteristics of sediments which represent different descriptive levels within a compositional hierarchy compositional linear process models may be used to describe compositional and or textural evolution resulting from selective modifications induced by sediment transport as well as chemical and mechanical weathering current approaches to modelling of surface processes treat the coupled evolution of source areas and sedimentary basins in terms of bulk mass transfer only and do not take into account compositional and textural sediment properties moving from the inverse modelling approach embodied in provenance research to process based forward models of sediment generation which provide detailed predictions of sediment properties meets with considerable albeit not insurmountable problems strategies for developing more advanced parameterizations of sediment properties and for simulating their evolution are proposed and expansion of current data acquisition protocols is discussed in the light of data requirements for such advanced sediment generation models inclusion of sediment generation modules in models of landscape evolution and basin filling will mark a significant step towards full fledged source to sink simulations of earth surface processes

mineralogy and leaching characteristics of beneficiated coal products from santa catarina brazil abstract petrographic mineralogical and geochemical studies have been carried out on beneficiated coal products from mines and preparation plants in the santa catarina basin southern brazil to investigate the range of characteristics exhibited by the materials and the potential impact of their stockpiling and storage on the environment the coals contain varying proportions of vitrinite and inertinite macerals and have vitrinite reflectance values ranging from 0 44 to 1 38 with the exception of one material blended with peat from an external source they have relatively high percentages of ash 30 58 and mineral matter 36 66 the mineral matter consists mainly of clay minerals kaolinite illite and illite smectite together with 15 25 quartz up to 10 feldspar up to 5 calcite and or dolomite and up to 5 pyrite and around 1 anatase and or rutile bassanite is also present in low temperature ash derived from the coals mainly derived from interaction of ca and s associated with the organic matter jarosite is formed by pyrite oxidation in coals that have been exposed in stockpiles for extended periods most of the trace elements in most of the coals have higher concentrations than average values for world coals generally probably due to the relatively high mineral matter content a lower ash product representing a blend of coal and peat has similar to lower concentrations of most elements but higher concentrations of b ba be cd ge and mn which may be associated with the peat component interaction of relatively fresh coals with water in laboratory tests produces leachates with near neutral to mildly acid ph values but leaching of oxidized jarosite bearing coal produces a strongly acid leachate with higher concentrations of cd co cu ni and zn leachates derived from coals in which the pyrite has been oxidized during storage would thus be expected to have a more adverse environmental impact than leachates derived from coals in which such oxidation has not had an opportunity to develop

upper crustal structure of newberry volcano from p wave tomography and finite difference waveform modeling 1 seismic tomography combined with waveform modeling constrains the dimensions and melt content of a magma body in the upper crust at newberry volcano we obtain a p wave tomographic image by combining travel time data collected in 2008 on a line of densely spaced seismometers with active source data collected in the 1980s the tomographic analysis resolves a high velocity intrusive ring complex surrounding a low velocity caldera fill zone at depths above 3 km and a broader high velocity intrusive complex surrounding a central low velocity anomaly at greater depths 3 6 km this second upper crustal low velocity anomaly is poorly resolved and resolution tests indicate that an unrealistically large low velocity body representing 60 km3of melt could be consistent with the available travel times the 2008 data exhibit low amplitude first arrivals and an anomalous secondary p wave phase originating beneath the caldera two dimensional finite difference waveform modeling through the tomographic velocity model does not reproduce these observations to reproduce these phases we predict waveforms for models that include synthetic low velocity bodies and test possible magma chamber geometries and properties three classes of models produce a transmittedp phase consistent with the travel time and amplitude of the observed secondary phase and also match the observed lower amplitude first arrivals these models represent a graded mush region a crystal suspension region and a melt sill above a thin mush region the three possible magma chamber models comprise a much narrower range of melt volumes 1 6 8 0 km3 than could be constrained by travel time tomography alone

late quaternary evolution of the yellow east china sea tidal regime and its impacts on sediments dispersal and seafloor morphology the evolution of a tidal current field in the yellow sea and east china sea yecs in response to the sea level rise since the last glacial maximum lgm was investigated using a two dimensional tidal model with special attention to changes in the sedimentary environment of the continental shelf region it was found that tidal currents on the yecs shelf have generally been semi diurnal throughout the post glacial stages with f ratio index of diurnal inequality and s2 m2 ratio index of spring neap cycle remaining similar to present on the other hand the spatial distribution of the tidal bottom stress associated with m2 and m4 tidal currents changed greatly during the transgression as the sea level rose two core regions showing high bottom stress values migrated shoreward from cheju island toward the west coast of korea and along the retreat path of the paleo changjiang estuary distribution of extremely intense tidal bottom stress suggested that intense tidal reworking may have occurred at sea levels from 90 to 45 m in the southeast yellow sea and at 75 to 60 m off the paleo changjiang estuary the latter of which agreed with the timing of a large terrigenous organic c flux observed on the shelf slope distribution of slightly weaker bottom stress indicated that the sand ridges off the changjiang estuary and in the southeast yellow sea also might have formed at during those periods on the other hand when the sea level was between 45 and 15 m the tidal bottom stress was generally not strong enough to invoke significant reworking even though the stress intensity may be stronger than present correlation with modern and relict sedimentary features suggested that the tidal process have played a significant role on the reworking and deposition of sediments on the yecs shelf

overview of the structure and geothermal potential of newberry volcano oregon evidence from a broad range of geological and geophysical investigations of newberry volcano in centeral oregon suggests the presence of a small magma body beneath the summit caldera drilling has encountered temperatures indicative of a hydrothermal system above the hypothesized magma body on the basis of hydrothermal mineralogy the temperature of the hydrothermal system is at or near its maximum value indicating that the hydrothermal system is young basaltic underplating is postulated to replenish the magma body the results of interdisciplinary studies at newberry volcano document that young silicic volcanism in the cascade range can have geothermal potential these results should be applied with caution to the rest of the cascade range because of the strong influence of basin and range extensional tectonics on newberry volcano s style of volcanism

off axis volcanism at the east pacific rise detected by uranium series dating of basalts recent detailed surveys of the east pacific rise have revealed the complexity of the volcanic and magmatic processes occurring along and across fast spreading ocean ridge crests1 7 in parallel with geological and geochemical investigations it is now possible to investigate the temporal and spatial pattern of volcanism at ocean ridges by dating young basalts using mass spectrometric uranium series disequilibria methods8 11 here we use 238u 230th and235u 231pa ages for basalts to quantify the spatial extent of young volcanism and crustal accretion at 9 31 n on the east pacific rise most of the ages are younger than would be expected based on off axis distance and spreading rate we infer from these anomalously young ages that most of the dated basalts on the crestal plateau were erupted 0 5 2 km outside the axial summit caldera with some volcanism occurring as far as 4 km off axis melts erupted outside the axial summit caldera can have crustal residence times and magmatic supply systems that differ from those of axial lavas

paleoenvironmental changes during the last 8400 years in the southern yellow sea benthic foraminiferal and stable isotopic evidence we used benthic foraminiferal stable isotopic and grain size data from an ams c 14 dated core from the southern yellow sea to decipher holocene paleoenvironmental changes large amplitude changes in 6180 613 c and benthic foraminiferal assemblage composition indicate that major environmental changes occurred during the last 8400 years in the southern yellow sea we recognize 3 stages of environmental development 1 a low salinity estuarine environment stage at 8 4 6 9 cal kyr bp 2 a low salinity shallow sea environment stage at 6 9 to about 6 5 cal kyr bp and 3 a modem marine shelf environment stage after about 6 5 cal kyr bp the delta o 18 and delta c 13 values of ammonia aomoriensis asano combined with benthic foraminiferal assemblage data indicate a low bottom water salinity 15 parts per thousand during stage 1 suggesting a large amount of river runoff abrupt increases in delta o 18 and delta c 13 around 6 9 cal kyr bp were accompanied by a decrease in mean grain size and in abundance of benthic foraminifera possibly caused by a north ward shift of the yellow river s outlet during subsequent stage 2 the southern yellow sea was still characterized by a low salinity 28 parts per thousand even though sea level was high possibly due to the continued strong influence of river input and or limited exchange between the southern yellow sea and the open ocean at about 6 5 cal kyr bp an a aomoriensis dominated benthic foraminiferal assemblage was replaced by an ammonia ketienziensis ishizaki dominated assemblage indicating an increase in bottom water salinity grain size and stable isotope data suggest that the modem circulation was probably established at that time we speculate that the combined impacts of reduced river runoff enhanced east asia winter monsoon and increased influence of southern warm ocean currents caused this transition c 2007 elsevier b v all rights reserved

origin and dispersal of recent clay minerals in the yellow sea abstract the clay minerals in the by considering the clay minerals supplied by rivers in china the old and present day huanghe river and korea the keum and yeongsan to the yellow sea continental shelf and the spatial variation in the distribution of clay minerals in the yellow sea this study indicates that the provenance of the cysm may be closely related to the old and present day huanghe river system whereas the clay minerals in the seysm seem to be largely associated with the keum and yeongsan rivers in addition smectite may be suggested as an important clay mineral in differentiating between cysm and seysm and understanding the sources of these two mud categories

dating of quaternary basalts using the cosmogenic 3he and 14c methods with implications for excess 40ar concordant radiocarbon and cosmogenic sup 3 he dates of 3 and 11 ka on basalt flows and associated scoria deposits from the zuni bandera volcanic field in new mexico further substantiate published production rates and latitudinal and altitudinal corrections for sup 3 he identical sup 3 he concentrations in coexisting olivine and clinopyroxene confirm that these two minerals have very similar production rates a cosmogenic sup 3 he date of 57 ka on another flow is concordant with a u series date and is younger than two k ar dates suggesting that this flow contains excess sup 40 ar this excess sup 40 ar is also evident in gases released by vacuum crushing of olivine clinopyroxene fractions from all three flows 27 refs 3 figs 3 tabs

magma cumulate mixing identified by u th disequilibrium dating magma mixing is believed to be important in magmagenesis1 particularly in volcanic arcs2 where its influence is revealed by heterogeneous phenocryst populations3 and quenched inclusions4 nevertheless isotope studies particularly of uranium series dis equilibria have concentrated on the analysis of bulk rock samples5 9 comprehensive u th mineral separate data from arc volcanics are scarce10 14 here we present the first u th isotopic evidence for mixing between a crystal mush and a magma in an andesite from the island of santorini in the aegean arc the lava contains crystal populations from two sources of distinct thorium isotope composition one from a basic cumulate the other phenocrysts from a dacite magma the crystal populations have statistically indistinguishable crystallization ages of 79 14 12kyr and 93 29 22kyr and are thought to have physically intermingled just before eruption the crystals did not re equilibrate and hence retain the isotopic compositions and ages of the parental materials

a strontium isotopic study of newberry volcano central oregon structural and thermal implications abstract ratios of 87 sr 86 sr were determined in twenty seven basaltic rocks from newberry these ratios range from 0 70330 to 0 70414 most fall between 0 7035 and 0 7038 covariance of al 2 o 3 feo ratio tio 2 content and th content with 87 sr 86 sr suggests that some isotopic ratios reflect shallow crustal contamination but the data also suggest that two mantle sources a prominent one at 0 7036 and a less prominent one at 0 7033 or less are represented the hypothesis of crustal contamination is supported by variations in 87 sr 86 sr ratios with locations of the vents from which these rocks erupted sr tends to be more radiogenic in rocks from vents either close to a silicic complex such as the caldera of the volcano or the amota butte sugar pine ridge complex or close to axes of the fault zones that underlie the edifice presumably local heating of the upper crust facilitates contamination of basaltic magma rising through it

controls on volcanism at intraplate basaltic volcanic fields a broad range of controlling mechanisms is described for intraplate basaltic volcanic fields ibvfs in the literature these correspond with those relating to shallow tectonic processes and to deep mantle plumes accurate measurement of the physical parameters of intraplate volcanism is fundamental to gain an understanding of the controlling factors that influence the scale and location of a specific ibvf detailed volume and geochronology data are required for this however these are not available for many ibvfs in this study the primary controls on magma genesis and transportation are established for the pliocene recent newer volcanics province nvp of south eastern australia as a case study for one of such ibvf the nvp is a large and spatio temporally complex ibvf that has been described as either being related to a deep mantle plume or upper mantle and crustal processes we use innovative high resolution aeromagnetic and 3d modelling analysis constrained by well log data to calculate its dimensions volume and long term eruptive flux our estimates suggest volcanic deposits cover an area of 23 100 530 km2 and have a preserved dense rock equivalent of erupted volcanics of least 680 km3 and may have been as large as 900 km3 the long term mean eruptive flux of the nvp is estimated between 0 15 and 0 20 km3 ka which is relatively high compared with other ibvfs our comparison with other ibvfs shows eruptive fluxes vary up to two orders of magnitude within individual fields most examples where a range of eruptive flux is available for an ibvf show a correlation between eruptive flux and the rate of local tectonic processes suggesting tectonic control limited age dating of the nvp has been used to suggest there were pulses in its eruptive flux which are not resolvable using current data these changes in eruptive flux are not directly relatable to the rate of any interpreted tectonic driver such as edge driven convection however the nvp and other ibvfs used for comparison have long term eruptive fluxes that are considerably less than definitive plume related volcanic systems along with their spatio temporal patterns and other analysis it is suggested that the nvp and the vast majority of low and high flux ibvfs appear to be the result of tectonic processes without requiring additional thermal input from a deep mantle source considering a control on volcanism by tectonic processes the range of eruptive flux of ibvfs is related to variations in the rate of the effecting tectonic process mantle composition and the size of the mantle source zone where melt generation and accumulation is taking place