a sea floor spreading event captured by seismometers two thirds of earth s surface is formed at mid ocean ridges yet sea floor spreading events are poorly understood because they occur far beneath the ocean surface at 9 50 n on the east pacific rise ocean bottom seismometers recently recorded the microearthquake character of a mid ocean ridge eruption including precursory activity a gradual ramp up in activity rates since seismic monitoring began at this site in october 2003 suggests that eruptions may be forecast in the fast spreading environment the pattern culminates in an intense but brief 6 hour inferred diking event on 22 january 2006 followed by rapid tapering to markedly decreased levels of seismicity

seismic velocity ratio in the crust and uppermost mantle in southeast wellington province new zealand the regional variation of the seismic velocity ratio over a 200 km long traverse has been studied by means of microearthquake surveys the wadati plot method is used with a minimum of four p and s arrivals for each of 49 earthquakes the area as a whole is found to be characterized by a value of 1 74 1 76 for earthquakes of depth 12 40 km except in a 50 km long section near wellington where is low at 1 60 this low has been attributed to the fault zones in the region a small change of is observed between the upper crust 5 km and lower crust 12 km but there is no change of between the lower crust and uppermost mantle

second order segmentation the relationship between volcanism and tectonism at the mar 38 n 35 40 n deep tow sidescan sonar data acquired along 240 km of the mid atlantic ridge mar between 35 40 n and 38 n have been combined with new bathymetric compilations and used to establish the recent tectonic and volcanic history of six second order segments and their bounding non transform offsets ntos the segments show a range of volcanic and tectonic types but in general the northernmost segments i e those with greater influence from the azorean hotspot are shallower and more volcanically robust than those to the south with hydrothermal activity in segment centres for example menez gwen and lucky strike nonetheless this generalisation requires some modification due to temporal variations in the balance between magmatic supply and tectonic dismemberment the ntos are broad right stepping discontinuities locally up to 25 km wide and accommodate offsets between 10 and 50 km the discontinuities are mostly sediment floored and link the spreading segment tips with a range of structures these include locally dense arrays of en echelon extensional normal faults short lengths of linear strike slip fault strands occasionally cutting basement blocks apparently stranded within the offsets basement blocks within the offsets are cross cut by complexes of intersecting faults suggesting that deformation is distributed across the zone the pervasive faulting taking place at the ntos favours fluid circulation and associated hydrothermal activity as at the rainbow site at 36 17 n

magnetic fingerprint of the late holocene inception of the rio de la plata plume onto the southeast brazilian shelf abstract measurement of changes in the assembly of magnetic particles in sediment records is useful both for paleoclimatic and paleoceanographic reconstructions and for assessing provenance and pathways of sediment transport in this study we provide detailed rock magnetic analysis along with scanning electron microscopy sem ti ca ratio and particle size distribution of the decarbonated fraction of sediments to trace terrigenous source changes during the last 6 cal kyr bp in core 7610 collected on the se brazilian continental shelf magnetic mineralogy data indicate a gradual shift between two distinct sources of sediments 1 dust from southern south america patagonia central western argentina and puna altiplano plateau and 2 sediments eroded from the weathered volcanics of parana basin these materials reached the continental margin off argentina and uruguay by different pathways and were transported northward by the brazilian coastal current bcc the chronology of events related to the environmental record of core 7610 indicates that between 6 and 4 7 cal kyr bp dry conditions over continental south america resulted in enhanced eastward eolian transport of the argentinean loess and a limited discharge of the rdlp river load into the atlantic ocean at this time the sedimentary magnetic fraction that reached the se brazilian shelf reflect predominantly loessic sources transported from the pampean terraces to the argentinean and uruguay shelves and then distributed northward by the shelf current system from 4 7 to 2 cal kyr bp the climate became gradually wetter over the continent and the contribution of oxidized phases from the weathered parana basin mainly from the basaltic and acidic volcanics started to become important this change in climate overlaps in time a with the late holocene sea level fall recorded along the se south american coast later from 2 up to 0 9 cal kyr bp even wetter conditions were prevalent in s and se south america and the rdlp sedimentary load became the main source of sediments transported to the se brazilian shelf by the bcc the magnetic record of core 7610 reported here together with other paleoenvironmental tracers palynology geochemistry and stable isotopes thus indicates that the inception of the rdlp plume onto the se brazilian shelf started as early as 4 7 cal kyr bp and has been strengthened since then mostly due to changes in precipitation over south america and to a smaller extent by sea level changes

the geochemical signature of suspended sediments in the parana river basin implications for provenance weathering and sedimentary recycling abstract the parana river basin is one of the largest hydrological systems in south america the present study focuses on the mineralogical and chemical composition of the suspended sediments exported by the parana river to the atlantic ocean with the aim of analyzing their provenance the chemical weathering signature and the likelihood of sedimentary recycling the particulate matter of the middle parana river and its main tributaries i e the paraguay and the upper parana rivers is mostly composed of quartz plagioclase k feldspar and clays such as illite and kaolinite different geochemical approaches indicate that the suspended sediments transported by the parana river preserve the chemical signature of its sources and its composition is not significantly modified during transport these sediments are mainly supplied by acidic arc sources located in the andean headwaters of the bermejo and pilcomayo rivers and transported by the paraguay river and by tholeiitic basalts outcropping in the headwaters of the upper parana river the incomplete mixing of both main tributaries produces a transverse geochemical asymmetry in the particulate material of the middle parana river which was detected 32 km downflow the confluence the suspended load transported by the paraguay river which includes the contributions from the bermejo and pilcomayo rivers indicates incipiently to moderately weathering whereas the particulate matter exported by the upper parana river reveals a higher degree of chemical alteration this is the result of the different lithology and climatic regimes that prevail in the headwaters of both tributaries the weathering signature of the middle parana river s suspended load resembles that of the paraguay river which in turns supplies most of the particulate matter through the bermejo river this work also shows that the suspended load exported by the parana river basin has a mixed origin where the chemical signatures from young materials derived from undifferentiated volcanic rocks and from recycled materials affected by intracrustal differentiation can be distinguished

the relationship between near axis hydrothermal cooling and the spreading rate of mid ocean ridges recent seismic observations and new crustal thermal models suggest that near axis 1 km from the spreading axis hydrothermal cooling increases linearly with increasing spreading rate we present here the first corroborating evidence from near axis hydrothermal plume observations comprehensive surveys of plume distributions have now been conducted on multi segment portions of ridge crest with full spreading rates from 20 to 150 km myr these surveys find thatph the fraction of ridge crest length overlain by hydrothermal plumes and full spreading rate us are related byph us where 0 004 myr km we recast this large scale spatial variability into long term temporal variability by postulating that any vent field site is hydrothermally active for an us fraction of geologic time we then use this relationship and the mean of eight studies that have determined instantaneous heat flux ha at vent field scales 75 45 mw km to estimate the time averaged heat flux ha asha us applying these scaled values ofha to the distribution of mid ocean ridge spreading rates yields a global near axis heat flux ha of 8 8 1011 w this value is 10 of the total oceanic hydrothermal heat flux and agrees with a crustal cooling model derived value of ha of 9 1011 w our estimate of ha implies a mean global3he heat ratio of 2 4 8 3 10 13 cm3 j stp and high temperature hydrothermal fluid flow of 1 8 1013 kg yr

hydrothermal activity on the southern mid atlantic ridge tectonically and volcanically controlled venting at 4 5 s we report results from an investigation of the geologic processes controlling hydrothermal activity along the previously unstudied southern mid atlantic ridge 3 7 s our study employed the noc uk deep tow sidescan sonar instrument tobi in concert with the whoi usa autonomous underwater vehicle abe to collect information concerning hydrothermal plume distributions in the water column co registered with geologic investigations of the underlying seafloor two areas of high temperature hydrothermal venting were identified the first was situated in a non transform discontinuity ntd between two adjacent second order ridge segments near 4 02 s distant from any neovolcanic activity this geologic setting is very similar to that of the ultramafic hosted and tectonically controlled rainbow vent site on the northern mid atlantic ridge the second site was located at 4 48 s at the axial summit centre of a second order ridge segment there high temperature venting is hosted in an 18 km2 area of young lava flows which in some cases are observed to have flowed over and engulfed pre existing chemosynthetic vent fauna in both appearance and extent these lava flows are directly reminiscent of those emplaced in winter 2005 06 at the east pacific rise 9 50 n and reference to global seismic catalogues reveals that a swarm of large m 4 6 5 6 seismic events was centred on the 5 s segment over a 24 h period in late june 2002 perhaps indicating the precise timing of this volcanic eruptive episode temperature measurements at one of the vents found directly adjacent to the fresh lava flows at 5 s mar turtle pits have subsequently revealed vent fluids that are actively phase separating under conditions very close to the critical point for seawater at 3000 m depth and 407 c the hottest vent fluids yet reported from anywhere along the global ridge crest

rare earth elements in river waters we measured rare earth element ree concentrations in river waters to characterize the suspended and dissolved river flux of the ree to the oceans the ree pattern of river suspended materials is sensitive to drainage basin geology a positive correlation is observed between la yb ratios and nd model ages for the rivers studied major rivers have light ree enriched patterns relative to the north american shale composite nasc with la yb n 1 6 2 7 river water dissolved material 0 2 m is heavy ree enriched relative to suspended material and the most pronounced negative ce anomalies occur in rivers of high ph light ree concentrations vary by approximately 3 orders of magnitude and are inversely related to ph and major cation concentrations from these data we estimate that typical major river runoff has heavy ree depleted suspended material with la yb n 1 9 we conclude that the terrigenous input to the oceans from major rivers is heavy ree depleted relative to shales from the available data average river water dissolved material appears to be heavy ree enriched with la yb n 0 4 estuarine removal processes lower the dissolved ree river flux by approximately 60 and result in a flux that is more heavy ree enriched with la yb n 0 2 calculated oceanic residence times with respect to river input range from 2300 to 21 000 years are shortest for ce and greatest for the heavy ree and la such long residence times may suggest the presence of additional sources of ree in seawater

fluxes to sediments underlying the rainbow hydrothermal plume at 36 14 n on the mid atlantic ridge abstract a geochemical investigation has been conducted of a suite of four sediment cores collected from directly beneath the hydrothermal plume at distances of 2 to 25 km from the rainbow hydrothermal field as well as a large biogenic component 80 caco3 these sediments record clear enrichments of the elements fe cu mn v p and as from hydrothermal plume fallout but only minor detrital background material systematic variations in the abundances of hydrothermal elements are observed at increasing distance from the vent site consistent with chemical evolution of the dispersing plume further pronounced ni and cr enrichments at specific levels within each of the two cores collected from closest to the vent site are indicative of discrete episodes of additional input of ultrabasic material at these two near field locations radiocarbon dating reveals mean holocene accumulation rates for all four cores of 2 7 to 3 7 cm kyr 1 with surface mixed layers 7 to 10 cm thick from which a history of deposition from the rainbow hydrothermal plume can be deduced deposition from the plume supplies elements to the underlying sediments that are either directly hydrothermally sourced e g fe mn cu or scavenged from seawater via the hydrothermal plume e g v p as holocene fluxes into to the cores surface mixed layers are presented which typically are an order of magnitude greater than background authigenic fluxes from the open north atlantic one core collected closest to the vent site indicates that both the concentration and flux of hydrothermally derived material increased significantly at some point between 8 and 12 14c kyr ago the preferred explanation is that this variation reflects the initiation intensification of hydrothermal venting at the rainbow hydrothermal field at this time perhaps linked to some specific tectonic event in this fault controlled hydrothermal setting

seismic character of volcanic activity at the ultraslow spreading gakkel ridge never before has a volcanic eruption on a slow or ultraslow spreading mid ocean ridge been both observed seismically and confirmed on the seafloor during the first half of 1999 a long lived volcanic spreading event occurred on the ultraslow spreading gakkel ridge in the arctic ocean the seismicity associated with this event was unprecedented in duration and magnitude for a seafloor eruption sonar images from the u s s hawkbill which passed over the area within four months of the start of activity are consistent with the presence of a large recently erupted flow and a volcanic peak directly in the area of seismic activity seismic activity began in mid january and continued vigorously for three months a reduced rate of activity persisted for an additional four months or more in total 252 events were large enough to be recorded on global seismic networks although a limited number of volcanic spreading events have been observed globally the duration and magnitude of the gakkel ridge swarm when compared with volcanic seismicity at ridges spreading at intermediate and fast spreading rates suggest that a negative power law relationship may exist between these parameters and spreading rate fault activation in response to magmatic emplacement appears to have occurred over a broad region suggesting that magma may have been tapped from mantle depths the slow migration of the largest magnitude events along the axis of the rift valley suggests multiple magmatic pulses at depth in combination with bathymetric setting and sidescan sonar confirmation the seismic data for this event have provided a unique look at the scale and character of eruption processes at ultraslow spreading rates

locating the spreading axis along 80 km of the mid atlantic ridge south of the atlantis transform the zone of active eruptive fissuring the spreading axis is investigated at an accretionary segment of the mid atlantic ridge high resolution side scan images are used to produce a detailed geologic map of the median valley floor of segment 18 located immediately south of the atlantis transform 30 n the spreading axis is defined by distinguishing between primary eruptive vents seamounts and hummocky ridges fed by underlying dikes and secondary vents seamounts and terraces fed from lava tubes or channels and is found to be about 2 km wide or less along the entire segment it is impossible to narrow the width further with the data we have in hand for comparison at faster spreading ridges such as the east pacific rise the spreading axis is generally equated to the width of the axial summit trough typically 50 100 m wide within the brunhes anomaly the high resolution structure of the central anomaly magnetic high camh obtained from several cross axis deep tow tracks is used to define regions of recent major volcanism the locations of the camh peaks generally conform to our pick of the spreading axis in some places the peaks are located several kilometers away from the spreading axis possibly indicating that large volumes of lava have been deposited there our interpretation of many volcanic structures as secondary vents at segment 18 leads to the conclusion that lava channels and tubes commonly develop to transport lava to these off axis deposition sites

young volcanism and related hydrothermal activity at 5 s on the slow spreading southern mid atlantic ridge the effect of volcanic activity on submarine hydrothermal systems has been well documented along fast and intermediate spreading centers but not from slow spreading ridges indeed volcanic eruptions are expected to be rare on slow spreading axes here we report the presence of hydrothermal venting associated with extremely fresh lava flows at an elevated apparently magmatically robust segment center on the slow spreading southern mid atlantic ridge near 5 s three high temperature vent fields have been recognized so far over a strike length of less than 2 km with two fields venting phase separated vapor type fluids exit temperatures at one of the fields reach up to 407 c at conditions of the critical point of seawater the highest temperatures ever recorded from the seafloor fluid and vent field characteristics show a large variability between the vent fields a variation that is not expected within such a limited area we conclude from mineralogical investigations of hydrothermal precipitates that vent fluid compositions have evolved recently from relatively oxidizing to more reducing conditions a shift that could also be related to renewed magmatic activity in the area current high exit temperatures reducing conditions low silica contents and high hydrogen contents in the fluids of two vent sites are consistent with a shallow magmatic source probably related to a young volcanic eruption event nearby in which basaltic magma is actively crystallizing this is the first reported evidence for direct magmatic hydrothermal interaction on a slow spreading mid ocean ridge

is chemical index of alteration cia a reliable proxy for chemical weathering in global drainage basins the chemical weathering of silicate rocks in continents as an important sink of atmospheric co2 is of great significance for global environmental change rivers play a key role in earth surface processes and are regarded as the most important carrier of terrigenous materials into the sea the chemical index of alteration cia has been widely used as a proxy for chemical weathering in sediment source area in this paper the cia values of suspended particulate matters from 44 rivers worldwide are recalculated the cia values vary significantly with the highest average value occurring in african rivers and the lowest in north american rivers the correlation analyses suggest that on a global scale the cia is sensitive to land surface temperature latitude at river mouth and soil depth in the drainage basins but poorly correlated with drainage area precipitation average elevation and runoff however the cia of the rivers draining east china are closely related to temperature precipita tion latitude and runoff primarily reflecting the dominant control of monsoon climate on chemical weathering in the catchments it is therefore unrealistic to find a simple law of regulating chemical weathering in continents the cia actually reflects the integrated weathering history in the drainage basins and therefore caution should be taken while using it as a direct and quantitative proxy for evaluating the intensity of instantaneous chemical weathering in continents

geochemistry of large river suspended sediments silicate weathering or recycling tracer this study focuses on the major and trace element composition of suspended sediments transported by the world s largest rivers its main purpose is to answer the following question is the degree of weathering of modern river borne particles consistent with the estimated river dissolved loads derived from silicate weathering in agreement with the well known mobility of elements during weathering of continental rocks we confirm that river sediments are systematically depleted in na k ba with respect to the upper continental crust for each of these mobile elements a systematics of weathering indexes of river borne solids is attempted a global consistency is found between all these indexes important variations in weathering intensities exist a clear dependence of weathering intensities with climate is observed for the rivers draining mostly lowlands however no global correlation exists between weathering intensities and climatic or relief parameters because the trend observed for lowlands is obscured by rivers draining orogenic zones an inverse correlation between weathering intensities and suspended sediment concentrations is observed showing that the regions having the highest rates of physical denudation produce the least weathered sediments finally chemical and physical weathering are compared through the use of a simple steady state model we show that the weathering intensities of large river suspended sediments can only be reconciled with the silicate derived dissolved load of rivers by admitting that most of the continental rocks submitted to weathering in large river basins have already suffered previous weathering cycles a simple graphical method is proposed for calculating the proportion of sedimentary recycling in large river basins finally even if orogenic zones produce weakly weathered sediments we emphasize the fact that silicate chemical weathering rates and hence co2 consumption rates by silicate weathering are greatly enhanced in mountains simply because the sediment yields in orogenic drainage basins are higher hence the parameters that control chemical weathering rates would be those that control physical denudation rates

discovery of ancient and active hydrothermal systems along the ultra slow spreading southwest indian ridge 10 16 e 1 we report the discovery of active and fossil hydrothermal systems during r v knorr cruise 162 legs vii and ix along a 400 km long segment of the ultra slow southwest indian ridge swir between 10 and 16 e where the effective spreading rate for mantle upwelling is the slowest of any ocean ridge explored to date 8 4 mm yr 1 full rate eight of forty one optical temperature profiles contain hydrothermal plume characteristics that indicate firm evidence for two active vent sites and tentative evidence for as many as three others fossil hydrothermal material was recovered in 6 of the 38 dredge hauls and includes an occurrence of partially oxidized sulfide breccias four deposits ofsepiolite and silica as well as mn oxide and nontronite cemented breccias the massive sulfide deposit likely developed during mixing of upwelling hot fluids with cold seawater within a shallow permeable fault breccia along a deep seated normal fault bounding the southern rift valley wall silica and sepiolite deposits were found mostly on the rift valley walls and likely formed during low to moderate temperature ultramafic hosted hydrothermal activity the abundance of hydrothermal material and the frequency of localized hydrothermal activity is remarkable because the mantle upwelling and magma supply rates and hence the magmatic heat input along this section of the swir are lower than on any other explored segment of the global mid ocean ridge system this observation suggests that high mantle upwelling and magma supply rates are not required to drive mid ocean ridge hydrothermal systems and that a close relationship between magmatic heat input and hydrothermal activity may not be established at the ultra slow end of the ridge spreading spectrum the frequency and distribution of hydrothermal activity in the study area may reflect a largely tectonic control on fluid circulation with hydrothermal vent sites being preferentially associated with long lived faults that provide fluid pathways our results suggest the contribution of magma starved ridge segments to the global ocean lithosphere geochemical budget is potentially much larger than previously thought

weathering and global denudation a negative correlation between sediment yield and weathering history as measured by the chemical alteration cia of the suspended sediment is observed for many of the world s major rivers and other regions of denudation the weathering history is a first order control on the sediment yield of such areas termed equilibrium denudation regions for other areas data scatter with either apparent increases or decreases of sediment yield for given cia values these areas are termed nonequilibrium denudation regions low sediment yields can be attributed to moderated erosion either natural or human induced and or the incorporation of unweathered glacial debris accelerated erosion resulting in high sediment yield is primarily human induced and results from cultivation and other land use each of these effects has a profound influence on global sediment discharge from the continents pre human suspended sediment discharge from the continents is estimated to be 12 6 times 10 15 g yr or about 0 6 the

evidence of recent volcanic activity on the ultraslow spreading gakkel ridge seafloor spreading is accommodated by volcanic and tectonic processes along the global mid ocean ridge system as spreading rate decreases the influence of volcanism also decreases and it is unknown whether significant volcanism occurs at all at ultraslow spreading rates 1 5 cm yr 1 here we present three dimensional sonar maps of the gakkel ridge earth s slowest spreading mid ocean ridge located in the arctic basin under the arctic ocean ice canopy we acquired this data using hull mounted sonars attached to a nuclear powered submarine the uss hawkbill sidescan data for the ultraslow spreading approximately 1 0 cm yr 1 eastern gakkel ridge depict two young volcanoes covering approximately 720 km2 of an otherwise heavily sedimented axial valley the western volcano coincides with the average location of epicentres for more than 250 teleseismic events detected in 1999 suggesting that an axial eruption was imaged shortly after its occurrence these findings demonstrate that eruptions along the ultraslow spreading gakkel ridge are focused at discrete locations and appear to be more voluminous and occur more frequently than was previously thought

hydrothermal activity along the southwest indian ridge twenty years after the discovery of sea floor hot springs vast stretches of the global mid ocean ridge system remain unexplored for hydrothermal venting the southwest indian ridge is a particularly intriguing region as it is both the slowest spreading of the main ridges1 and the sole modern migration pathway between the diverse vent fauna of the atlantic and pacific oceans2 a recent model postulates that a linear relation exists between vent frequency and spreading rate3 and predicts vent fields to be scarcest along the slowest spreading ridge sections thus impeding migration and enhancing faunal diversity2 here however we report evidence of hydrothermal plumes at six locations within two 200 km long sections of the southwest indian ridge indicating a higher frequency of venting than expected these results suggest that fluxes of heat and chemicals from slow spreading ridges may be greater than previously thought and that faunal migration along the southwest indian ridge may serve as an important corridor for gene flow between pacific and atlantic hydrothermal fields

new insights into mid ocean ridge volcanic processes from the 2005 2006 eruption of the east pacific rise 9 46 n 9 56 n digital seafloor imagery collected on 37 camera tows and alvin dives in which we identify 186 contacts between new and old lava are used to create the most detailed map of a mid ocean ridge mor eruption to date lava flows erupted in 2005 2006 at the east pacific rise epr covered an area of 14 6 km2 along 18 km of the epr crest between 9 46 and 9 56 n the 2005 2006 lava is characterized by inflated lobate and sheet morphologies in the flow interiors and pillow forms at terminal flow fronts numerous lava channels 10 50 m wide and 1 5 m deep trending approximately east west served as distributory pathways eruptions were sourced from fissures within the epr axial summit trough as well as fissures located on an off axis fissure mound 600 m east of the epr axis between 9 52 and 9 56 n portions of the lava flow reached as far as 2 km east of the axis near 9 51 2 n using a conservative estimate of 1 5 m for the average flow thickness implies that the 2005 2006 eruptions produced 22 106 m3 of lava 4 5 times larger than estimated volumes of 1991 1992 epr lava flows estimated lava volume for the 2005 2006 eruptions represents 15 of the magma available in the axial magma chamber

hydrothermal scavenging at the mid atlantic ridge modification of trace element dissolved fluxes abstract we have carried out an icp ms study of the distributions of trace elements fe ca mg al mn cu zn v as cr co pb y mo ag sn cd and be in particulate material collected from the tag hydrothermal plume 26 n mid atlantic ridge to examine the extent to which fluxes of dissolved trace elements emitted from hydrothermal vent fluids are balanced by the precipitation of associated particulate phases comparison of particulate trace element distributions with particulate fe concentrations within the neutrally buoyant plume reveals that the distribution of trace elements within the plume is controlled by the following processes i co precipitation from vent fluids ii scavenging from seawater and iii preferential settling from the plume and oxidative dissolution within the water column for y and be continuous scavenging from seawater appears to be important whereas for v as and cr it appears that conditions suitable for uptake into particles may be restricted to the buoyant portion of the hydrothermal plume from a comparison of trace element fe ratios in the particles and associated mid atlantic ridge vent fluids it appears that for many elements e g cu co ag pb al cd be and zn the flux of dissolved material from vent fluids is matched closely by the precipitation of hydrothermal particulate phases of the various elements studied here hydrothermal activity only appears to act as a significant source for dissolved ca and dissolved mn

the signature of river and wind borne materials exported from patagonia to the southern latitudes a view from rees and implications for paleoclimatic interpretations abstract riverine and wind borne materials transferred from patagonia to the sw atlantic exhibit a homogeneous rare earth element ree signature they match well with the ree composition of recent tephra from the hudson volcano and hence this implies a dominance of material supplied by this source and other similar andean volcanoes due to the trapping effect of proglacial and reservoir lakes the larger patagonian rivers deliver to the ocean a suspended load with a slightly modified andean signature that shows a ree composition depleted in heavy rees in this paper we redefine patagonia as a source of sediments which is in contrast with other sources located in southern south america quaternary sediments deposited in the northern and to a lesser extent in the southern scotia sea and most of the dust in ice cores of east antarctica have ree compositions very similar to the loess from buenos aires province and to patagonian eolian dust however we rule out buenos aires province as a holocene major source of sediments similarly to buenos aires loess a proximal facies it is likely that the ree compositions of most sediment cores of the scotia sea and antarctica reflect a distal transport of dust with an admixed composition from two main sources a major contribution from patagonia and a minor proportion from source areas containing sediments with a clear upper crustal signature e g western argentina or from bolivia s altiplano evidence indicates that only during the last glacial maximum patagonian materials were the predominant sediment source to the southern latitudes

hydrothermal activity on the ultra slow spreading southern knipovich ridge we report first evidence for hydrothermal activity from the southern knipovich ridge an ultra slow spreading ridge segment in the norwegian greenland sea evidence comes from optical backscatter anomalies collected during a systematic side scan sonar survey of the ridge axis augmented by the identification of biogeochemical tracers in the overlying water column that are diagnostic of hydrothermal plume discharge mn ch4 atp analysis of coregistered geologic and oceanographic data reveals that the signals we have identified are consistent with a single high temperature hydrothermal source located distant from any of the axial volcanic centers that define second order segmentation along this oblique ridge system rather our data indicate a hydrothermal source associated with highly tectonized seafloor that may be indicative of serpentinizing ultramafic outcrops consistent with this hypothesis the hydrothermal plume signals we have detected exhibit a high methane to manganese ratio of 2 3 1 this is higher than that typical of volcanically hosted vent sites and provides further evidence that the source of the plume signals reported here is most probably a high temperature hydrothermal field that experiences some ultramafic influence compare to rainbow and logachev sites mid atlantic ridge while such sites have previously been invoked to be common on the sw indian ridge this may be the first such site to be located along the arctic ultra slow spreading ridge system

particle geochemistry in the rainbow hydrothermal plume mid atlantic ridge we report the analysis of 18 large volume 500 1500 l in situ filtered samples of particulate material from the largest hydrothermal plume on the mid atlantic ridge overlying the ultramafic hosted rainbow hydrothermal field at 36 deg 14 n measured particulate iron concentrations reach 614 nm high concentrations of particulate fe oxyhydroxides result from the extremely high fe concentration 24 mm and fe h2s ratio 24 of the vent fluids and persist to at least 10 km away from the vent site due to the advection of plume material with the ambient along axis flow two of the nine pairs of pump deployments appear to have intercepted the buoyant or otherwise very young portion of the hydrothermal plume these samples are characterized by anomalously compared to neutrally buoyant plume samples high concentrations of mg u and chalcophile elements and low concentrations of mn ca v y and the rare earth elements ree within the neutrally buoyant plume elemental distributions are largely consistent with previously observed behaviors preferential removal of chalcophile elements conservative behavior of oxyanions p v and u and continuous scavenging of y and the ree this consistency is particularly significant in light of the underlying differences in fluid chemistry between rainbow and other studied sites chalcophile elements are preferentially removed from the plume in the order cd zn co cu phosphorus iron and vanadium iron ratios for the neutrally buoyant plume are consistent with global trends with respect to the concentration of dissolved phosphate in ambient seawater comparison of buoyant and neutrally buoyant plume ratios with data from hydrothermal sediments underlying the rainbow plume cave et al 2002 indicates however that while p fe ratios are indeed constant v fe ratios increase progressively from early stage plume particles to sediments ree distributions in the buoyant and neutrally buoyant plume appear most consistent with a continuous scavenging process during dispersion through the water column

hydrothermal plumes above the east scotia ridge an isolated high latitude back arc spreading centre we have identified first evidence for the presence of submarine hydrothermal activity along the east scotia ridge an isolated back arc spreading centre located at 55 60 s in the atlantic sector of the southern ocean using a combination of in situ optical light scattering sensor data and total dissolvable mn concentrations we demonstrate the existence of hydrothermal plumes overlying two segments of this 500 km ridge crest both segments exhibit anomalous topography and at least one segment is also underlain by an axial magma chamber seismic reflector future investigation of the fauna that inhabit these remote hydrothermal environments may provide an important missing link between the distinct biogeographical provinces delimited from previous investigation of northern atlantic versus eastern pacific vent sites

organic synthesis during fluid mixing in hydrothermal systems hydrothermal circulation can lead to fluid mixing on any planet with liquid water and a source of heat aqueous fluids with differing compositions especially different oxidation states are likely to be far from thermodynamic equilibrium when they mix and provide a source of free energy that can drive organic synthesis from co 2 and h 2 and or supply a source of geochemical energy to chemolithoautotrophic organisms results are presented that quantify the potential for organic synthesis during unbuffered fluid mixing in present submarine hydrothermal svstems as well as hypothetical systems that may have existed on the early earth and mars dissolved hydrogen present in submarine hydrothermal fluids owing to the high temperature reduction of h 2 o as seawater reacts with oceanic crustal rocks provides the reduction potential and the thermodynamic drive for organic synthesis from co 2 or bicarbonate as hydrothermal fluids mix with seawater the potential for organic synthesis is a strong function of the h 2 content of the hydrothermal fluid which is in turn a function of the prevailing oxidation state controlled by the composition of the rock that hosts the hydrothermal system hydrothermal fluids with initial oxidation states at or below those set by the fayalite magnetite quartz mineral assemblage show the greatest potential for driving organic synthesis these calculations show that it is thermodynamically possible for 100 of the carbon in the mixed fluid to be reduced to a mixture of carboxylic acids alcohols and ketones in the range 250 50 c as cold seawater mixes with the hydrothermal fluid as the temperature drops larger organic molecules are favored which implies that fluid mixing could drive the geochemical equivalent of a metaholic system this enormous reduction potential probably drives a large portion of the primary productivity around present seafloor hydrothermal vents and would have been present in hydrothermal systems on the early earth or mars the single largest control on the potential for organic synthesis is the composition of the rock that hosts the hydrothermal system

genesis of subtropical soils with stony horizons in ne argentina autochthony and polygenesis abstract deep red soils combining characteristics of highly weathered materials together with a significant degree of clay illuviation and with stony horizons close to the saprolite are found in the province of misiones northeastern argentina two basic types of stony horizons have been found which with the fine grained material above are together considered autochthonous the first one is a ferruginous nodular horizon composed mainly of in situ goethitic nodules of gravel size resulting from weathering and glaebulization processes of basalt the second are siliceous horizons which are also in situ derived from pre existing quartz veins within the basalt in contrast different analytical evidences particularly the vertical and geographical variations in the som stable carbon isotope ratios and the mineralogical composition of fine and coarse fractions suggest that these red subtropical soils are polygenetic being the result of a two fold process linked to paleoecological fluctuations in the framework of these results different interpretations about the origin of these soils and their parent materials and particularly the tropical loess theory are discussed

the geochemical characteristics of the parana river suspended sediment load an initial assessment most water in the parana river drainage basin is supplied by the tropical upper parana over 60 of the total annual water discharge 550 km3 the total suspended solids tss load c 80 106 t year 1 however is essentially furnished 50 70 by the mountainous arid and mostly sediment mantled upper bermejo river drainage basin this characteristic suggests that the parana river solid load tss 600 km upstream from the mouth is largely recycled sedimentary material whose discharge weighted mean chemical index of alteration is c 71 the extended ucc normalized multi elemental diagrams are similar to those of other world rivers nevertheless the detailed inspection of ucc normalized rare earth element ree spidergrams reveals a lithological source for the parana river tss that might be compatible with either tholeiitic flood basalts widespread in the upper drainage or with young andean intermediate volcanic rocks in view of the bermejo river s dominant role as a sediment contributor we feel that the signature preserved in the parana s tss is the latter conversely the uruguay river tss ree signature is certainly determined by the extensive weathering products of jurassic cretaceous tholeiitic basalts copyright 2003 john wiley sons ltd

distribution of major elements in atlantic surface sediments 36 n 49 s imprint of terrigenous input and continental weathering 1 numerous studies use major element concentrations measured on continental margin sediments to reconstruct terrestrial climate variations the choice and interpretation of climate proxies however differ from site to site here we map the concentrations of major elements ca fe al si ti k in atlantic surface sediments 36 n 49 s to assess the factors influencing the geochemistry of atlantic hemipelagic sediments and the potential of elemental ratios to reconstruct different terrestrial climate regimes high concentrations of terrigenous elements and low ca concentrations along the african and south american margins reflect the dominance of terrigenous input in these regions single element concentrations and elemental ratios including ca e g fe ca are too sensitive to dilution effects enhanced biological productivity carbonate dissolution to allow reliable reconstructions of terrestrial climate other elemental ratios reflect the composition of terrigenous material and mirror the climatic conditions within the continental catchment areas the atlantic distribution of ti al supports its use as a proxy for eolian versus fluvial input in regions of dust deposition that are not affected by the input of mafic rock material the spatial distributions of al si and fe k reflect the relative input of intensively weathered material from humid regions versus slightly weathered particles from drier areas high biogenic opal input however influences the al si ratio fe k is sensitive to the input of mafic material and the topography of andean river drainage basins both ratios are suitable to reconstruct african and south american climatic zones characterized by different intensities of chemical weathering in well understood environmental settings

modelling of atmospheric co2 consumption by chemical weathering of rocks application to the garonne congo and amazon basins modelling of atmospheric co consumption by chemical weathering of rocks application to the garonne congo and amazon basins

geochemistry of high h2 and ch4 vent fluids issuing from ultramafic rocks at the rainbow hydrothermal field 36 14 n mar the flores diving cruise was part of the mast iii amores 1995 1998 program funded by the european union one of the major achievements of the flores cruise was the discovery of the rainbow hydrothermal field hosted in ultramafic rocks south of the amar segment on the mid atlantic ridge mar the rainbow hydrothermal fluids exhibit temperatures of 365 c ph of 2 8 high chlorinity 750 mmol kg and low silica 6 9 mmol kg the uniformity in endmember major minor trace element concentrations and gas contents suggests that all rainbow fluids originate from the same deep source although h2s content is relatively low 1 20 mmol kg all vent fluids show extraordinary high h2 16 mmol kg ch4 2 5 mmol kg and co 5 mol kg endmember concentrations compared to fluids collected from other vent sites along the mar hydrogen represents more than 40 of the total gas volume extracted from the fluids at rainbow h2 production is likely associated with alteration of olivine and orthopyroxene minerals during serpentinization given that exposures of ultramafic rock may be common particularly along slow spreading ridges the production of h2 may have important implications for microbial activity at and beneath the seafloor

discovery of abundant hydrothermal venting on the ultraslow spreading gakkel ridge in the arctic ocean submarine hydrothermal venting along mid ocean ridges is an important contributor to ridge thermal structure and the global distribution of such vents has implications for heat and mass fluxes from the earth s crust and mantle and for the biogeography of vent endemic organisms previous studies have predicted that the incidence of hydrothermal venting would be extremely low on ultraslow spreading ridges ridges with full spreading rates 2 cm yr 1 which make up 25 per cent of the global ridge length and that such vent systems would be hosted in ultramafic in addition to volcanic rocks here we present evidence for active hydrothermal venting on the gakkel ridge which is the slowest spreading 0 6 1 3 cm yr 1 and least explored mid ocean ridge on the basis of water column profiles of light scattering temperature and manganese concentration along 1 100 km of the rift valley we identify hydrothermal plumes dispersing from at least nine to twelve discrete vent sites our discovery of such abundant venting and its apparent localization near volcanic centres requires a reassessment of the geologic conditions that control hydrothermal circulation on ultraslow spreading ridges

hydrothermal plumes along segments of contrasting magmatic influence 15 20 18 30 n east pacific rise influence of axial faulting 1 vertical profiles of light backscattering and temperature recorded on 133 rock cores and dredge hauls between the orozco and rivera transform faults on the east pacific rise epr 15 20 18 30 n provide an opportunity to compare the hydrothermal environment of three adjacent but distinctly different segments that span the maximum range of axial cross section at a relatively constant spreading rate contrary to predictions based on data from other pacific ridges hydrothermal plumes over the inflated 16 n segment were less extensive and weaker than along the narrower rifted 17 n segment remarkably the 17 n segment has a plume incidence equal to the mean of superfast spreading segments from the southern epr the data suggest that the local permeability environment in this region controls the expression of hydrothermal activity in the water column the 16 n segment which has little or no indication of faulting may have its hydrothermal activity presently suppressed by widespread volcanic flows that act as an impermeable cap over much of the segment activity on the 17 n segment may be tectonically enhanced with hydrothermal fluids circulating through deep faults to a cracking front within each segment intense hydrothermal plumes characteristic of focused discharge seem associated with clearly rifted areas while weaker water column signals characteristic of diffuse discharge are associated with unrifted portions of the ridge axis that appear dominated by magmatism previous studies at intermediate to superfast spreading ridges have emphasized a positive correlation between local magmatic budget and hydrothermal activity our data suggest however that even at fast rates local tectonics can control the extent and nature of hydrothermal activity as documented for several sites on the slow spreading mid atlantic ridge despite the segment scale incongruity between hydrothermal activity and magmatic budget the fraction of total ridge length between 15 20 and 18 30 n overlain by plumes 0 39 follows the existing global correlation between plume incidence and spreading rate

comments on the blag model factors affecting atmospheric co 2 and temperature over the past 100 million years since publication of the blag model several new items have appeared that bear on the question of paleo atmospheric co 2 levels first there is a problem between recent estimates in the literature of cretaceous sea floor spreading rates being similar to today and many reports of much more abundant cretaceous volcanism second the temperature dependence of weathering assumed in the blag model is in agreement with present data on the relation between temperature and average riverine silica concentrations third increased worldwide organic carbon burial rates and increased land volcanism during the cretaceous can be used to infer increased co 2 uptake via rock weathering at that time finally new model calculations show that the simple extrapolations of the blag model give a paleotemperature versus co 2 relation that is in agreement with the new model results within the probable error of paleotemperature estimates modified journal abstract

fault structure and detailed evolution of a slow spreading ridge segment the mid atlantic ridge at 29 n we present preliminary results of a detailed near bottom study of the morphology and tectonics of the 29 n broken spur segment on the slow spreading mid atlantic ridge using principally the tobi deep towed instrument the survey covered two thirds of the segment length including all of its southern non transform boundary and extended off axis of 40 km 3 3 ma on either side we obtained nearly complete near bottom sidescan sonar coverage and deep towed three component magnetic observations along 2 km spaced e w tracks sidescan data reveal new details of fault structure and evolution faults grow by along axis linkage in the inside corner they also link in the axis normal direction by curving to meet the next outer older fault this leads to wider spaced faults compared to segment centre or outside corner outward facing faults exist but are rare the non transform offset is characterised by faults that are highly oblique not parallel to the spreading direction and show cross cutting relations with ridge parallel faults to the north suggesting along axis migration of the offset almost all volcanic activity occurs within 5 km of the axis most fault growth is complete within 15 km of the axis 1 2 ma though large scarps continue to be degraded by mass wasting beyond there crustal magnetisation is strongly three dimensional the current neovolcanic zone is slightly oblique to earlier reversal boundaries and its magnetisation rises to a maximum of 30 a m 1 near its southern tip the central magnetisation high tapers southwards and is asymmetric with a sharp western but gradual eastern boundary we infer a highly asymmetric accretion of layer 2 near the segment end older magnetic anomalies are kinked and sometimes missing we interpret these observations as evidence of a rapid 18 km southward migration of the segment boundary during the past 1 8 ma and present a series of reconstructions illustrating this tectonic history

material sources chemical weathering and physical denudation in the chubut river basin patagonia argentina implications for andean rivers abstract the chubut is a medium size 42 000 km2 river basin that drains the arid to semiarid patagonian seaboard and pours its waters into the southwestern atlantic ocean ca lat 43 20 documentclass aastex usepackage amsbsy usepackage amsfonts usepackage amssymb usepackage bm usepackage mathrsfs usepackage pifont usepackage stmaryrd usepackage textcomp usepackage portland xspace usepackage amsmath amsxtra usepackage ot2 ot1 fontenc newcommand cyr renewcommand rmdefault wncyr renewcommand sfdefault wncyss renewcommand encodingdefault ot2 normalfont selectfont declaretextfontcommand textcyr cyr pagestyle empty declaremathsizes 10 9 7 6 begin document landscape arcmin end document s long 65 04 documentclass aastex usepackage amsbsy usepackage amsfonts usepackage amssymb usepackage bm usepackage mathrsfs usepackage pifont usepackage stmaryrd usepackage textcomp usepackage portland xspace usepackage amsmath amsxtra usepackage ot2

the rainbow vent fluids 36 14 n mar the influence of ultramafic rocks and phase separation on trace metal content in mid atlantic ridge hydrothermal fluids fluids were collected from the rainbow vent field 36 14 n on the mid atlantic ridge mar during the 1997 diving flores cruise this vent field in ultramafic rocks at a depth of 2300 m is composed of 10 black smokers emitting acidic ph 2 8 fluids at 365 c the low ph of the hot temperature rainbow fluids likely results from seawater ultramafic rock interaction that releases h ions into reducing hydrothermal fluids fluid chemistry is strongly influenced by phase separation generating cl rich brines clem 750 mm strongly enriched with mn fe co ni cu zn ag cd cs pb y and rare earth elements ree ree and transition metal abundance particularly fe and mn in the rainbow fluids is dramatically higher than in other mar fluids the abundance of trace element and ree enrichment is due to the greater solubility of these elements that is strongly favored by cl complexation at low ph and high temperature conditions chondrite normalized ree patterns show strong lree enrichment with evidence of the typical eu anomaly this ree partitioning suggests that either 1 ultramafic rocks represent only a part of rocks leached during hydrothermal alteration and or 2 that the unique rainbow fluid temperature ph and redox state issued from the ultramafic character of leached substratum can produce unique ree partitioning

interaction of the south american monsoon system and the southern westerly wind belt during the last 14 kyr abstract surface currents and sediment distribution of the se south american upper continental margin are under the influence of the south american monsoon system sams and the southern westerly wind belt swwb both climatic systems determine the meridional position of the subtropical shelf front stsf and probably also of the brazil malvinas confluence bmc we reconstruct the changing impact of the sams and the swwb on sediment composition at the upper rio grande cone off southern brazil during the last 14 cal kyr bp combining sedimentological geochemical micropaleontological and rock magnetic proxies of marine sediment core geob 6211 2 sharp reciprocal changes in ferri and paramagnetic mineral content and prominent grain size shifts give strong clues to systematic source changes and transport modes of these mostly terrigenous sediments our interpretations support the assumption that the sams over se south america was weaker than today during most of the late glacial and entire early holocene while the swwb was contracted to more southern latitudes resembling modern austral summer like conditions in consequence the stsf and the bmc were driven to more southern positions than today s favoring the deposition of fe rich but weakly magnetic la plata river silts at the rio grande cone during the mid holocene the northern boundary of the swwb migrated northward while the stsf reached its northernmost position of the last 14 cal kyr bp and the bmc most likely arrived at its modern position this shift enabled the transport of antarctic diatoms and more strongly magnetic argentinean shelf sands to the rio grande cone while sediment contributions from the la plata river became less important during the late holocene the modern el nino southern oscillation set in and the sams and the austral tradewinds intensified causing a southward shift of the stsf to its modern position this reinforced a significant deposition of la plata river silts at the rio grande cone these higher magnetic silts with intermediate fe contents mirror the modern more humid terrestrial climatic conditions over se south america

water quality and hydrogeochemical characteristics of the river buyukmelen duzce turkey the river buyukmelen is located in the province of duzce in northwest turkey and its water basin is approximately 470 km2 the aksu kucukmelen and ugursuyu streams flow into the river buyukmelen it flows into the black sea with an output of 44 m3 s 1 the geological succession in the basin comprises limestone and dolomitic limestone of the yilanli formation sandstone clayey limestone and marls of the akveren formation clastics and volcano clastics of the caycuma formation and cover units comprised of river alluvium lacutrine sediments and beach sands the river buyukmelen is expected to be a water source that can supply the drinking water needs of istanbul until 2040 therefore it is imperative that its water quality be preserved the samples of rock soil stream water suspended bed and stream sediments and beach sand were collected from the buyukmelen river basin they were examined using mineralogical and geochemical methods the chemical constituents most commonly found in the stream waters are na mg2 so2 4 cl and hco3 in the guz stream water ca2 in the abaza stream water and k in the kuplu stream water the concentrations of na k ca2 mg2 so2 4 hco 3 cl as pb ni mn cr zn fe and u in the kuplu and guz stream waters were much higher than the world average values the dilaver gubi tepekoy maden celik and abaza streams interact with sedimentary rocks and the kuplu and guz streams interact with volcanic rocks the amount of suspended sediment in the river buyukmelen in december 2002 was 120 mg l 1 the suspended and bed sediments in the muddy stream waters are formed of quartz calcite plagioclase clay kaolinite illite and smectite muscovite and amphibole minerals as co cd cr pb ni zn and u have all accumulated in the buyukmelen river bed sediments the muddy feature of the waters is related to the petrographic features of the rocks in the basin and their mineralogical compositions as most of the sandstones and volcanic rocks basalt tuffite and agglomerate are decomposed to a clay rich composition at the surface thus the suspended sediment in stream waters increases by physical weathering of the rocks and water rock interaction owing to the growing population and industrialization water demand is increasing the plan is to bring water from the river buyukmelen to istanbul s drinking water reservoirs according to the water pollution regulations the river buyukmelen belongs to quality class 1 based on hg cd pb as cu cr zn mn se ba na cl and so2 4 and to quality class 3 based on fe concentration the concentration of fe in the river buyukmelen exceeds the limit values permitted by the world health organization and the turkish standard because water from the river buyukmelen will be used as drinking water it will have an adverse effect on water quality and humans if not treated in advance in addition the inclusion of mn and zn in the elmali drinking water reservoir of istanbul and fe in the river buyukmelen water indicates natural inorganic contamination mn zn and fe contents in the waters are related to geological origin moreover the river buyukmelen flow is very muddy in the rainy seasons and it is inevitable that this will pose problems during the purification process copyright 2005 john wiley sons ltd

manganese geochemistry near high temperature vents in the mid atlantic ridge rift valley in july 1985 the first high temperature hydrothermal vents ever discovered on the mar were found at 26 n tag a transponder navigated survey of a 4 8 km area was begun when on board measurements of manganese revealed concentrated hydrothermal plumes in the water column comparable in size and intensity to those found over geothermal fields on the epr these plumes also possess anomalously high light scattering properties and anomalously warm potential temperatures using relay transponder navigation with a rosette ctd system it was possible to sample bottom waters with temperature anomalies of several decidegrees samples collected near vent orifices possessed silica anomalies of up to 17 m and dissolved manganese anomalies as large as 360 nmol kg these manganese and silica anomalies are linearly related and predict amn si ratio of 20 mmol mol for these mar vent fluids a value essentially identical to that measured in 350 c fluid from the epr at 21 n the distribution of temperature anomalies in the water column over this area requires the presence of more than one active vent site a rough estimate of the convective heat loss from this section of the mar based on z profiles is 1 2 108 cal s which is similar to the heat loss estimated for the vent field on the epr at 21 n

the geochemistry of river particulates from the continental usa major elements river particulates have been collected from twenty three rivers from throughout the continental usa the rivers drain mostly large basins basin areas range from 2 1 x 10 3 to 2970 x 10 3 km2 composed of mixed lithologies and spanning a wide range of climatic conditions as evidenced by a large variation in air and ground water temperatures precipitation and runoff suspended particulates have been analyzed for organic and inorganic carbon as well as the major elements al fe mn k si ca mg and na also determined were suspended sediment loads at the time of sampling particle surface areas and grain size distributions five year average river water chemistry and suspended sediment concentrations obtained from usgs water supply reports are also included as supporting information particle chemistry systematically varies with rates of runoff with high runoff rivers transporting the most heavily altered particulates and low runoff rivers carrying the least altered degrees of alteration are indicated by the extent to which the refractory nonmobile elements al and fe are concentrated into the particulates and the extent to which the most easily weathered elements na ca and mg have been leached overall the susceptibility of elements towards leaching is consistent with numerous previous descriptions of element mobility on weathering a simple predictive model has been developed to explore and explain the observed trends between particle composition and river runoff thus the elemental composition of riverine particulates may be given by the expression pcoi propi tm dcoi ss where pcoi is the concentration of element i as the oxide in a riverine particulate propi is the proportion of i as the oxide in unweathered rock dcoi is the dissolved concentration of i as the equivalent oxide tm is the total rock derived mass dissolved in river water and ss is suspended sediment concentration to utilize this equation a model was first developed to predict the concentration of river solutes with the input of temperature precipitation and a limited number of weathering parameters combining this solute model with the above predictive equation for particle composition it was discovered that the observed trends between particle composition and runoff require the special circumstance of decreasing ss with increasing runoff hence the composition of river particulates depends both on the climate parameters of runoff and temperature as they control dissolved river chemistry and the nonclimate parameters including elevation relief tectonics and basin area that control the ss load of rivers