strontium hydrothermal systems and steady state chemical weathering in active mountain belts abstract hydrothermal systems are a common feature of active collisional orogens these systems can have a profound effect on the sr fluxes and sr isotopic composition of riverine waters through the direct input of sr from hot springs and groundwaters and the chemical weathering of hydrothermal calcite in an effort to quantify the role of calcite weathering we present an analytical model that examines the relationship between rock uplift and steady state chemical weathering of granites and greywackes that contain trace amounts we compare model results with sr fluxes and isotopic composition of riverine waters from the southern alps of new zealand an area that is frequently used as an example of a steady state collisional orogen as our model predicts roughly 50 of sr flux is from the weathering of calcite in the areas of highest uplift along the west flank of the southern alps this proportion decreases substantially

alternative biological sources for 1 2 3 4 tetramethylbenzene in flash pyrolysates of kerogen pyrolysates of kerogens isolated from indian ocean surface sediments and from black sea unit ii contain abundant 1 2 3 4 tetramethylbenzene 1 2 3 4 tmb suggesting the presence of macromolecularly bound isorenieratane skeletons derived from isorenieratene biosynthesized by green sulphur bacteria cf hartgers et al 1994c however the 13c content of 1 2 3 4 tmb is identical to that of algal lipids excluding an origin from green sulphur bacteria the presence of 1 2 3 4 tmb in pyrolysates of stable residues of several marine algae indicates that it can also have an algal origin therefore the assessment of photic zone anoxia on the basis of the abundant presence of 1 2 3 4 tmb in the pyrolysate is not possible without determination of its stable carbon isotopic composition and comparison with those of algal lipids

kelvin helmholtz waves in precipitating midlatitude cyclones abstractthis study examines kelvin helmholtz kh waves observed by dual polarization radar in several precipitating midlatitude cyclones during the olympic mountains experiment olympex field cam

estimating millennial scale rates of dust incorporation into eroding hillslope regolith using cosmogenic nuclides and immobile weathering tracers 1 dust fluxes are of wide interest because of the effects of dust on climate oceanic primary productivity terrestrial biogeochemical cycles and regolith composition estimating long term dust deposition rates however can be difficult especially in steep eroding terrain here we present a geochemical mass balance method for estimating long term average rates of dust incorporation into regolith on steadily eroding hillslopes this method requires measurements of the local regolith production rate and the concentrations of two immobile elements in the regolith its parent rock and dust dust incorporation rates inferred with this method are averaged over the long timescale of regolith residence on the hillslope typically 103 105 years and thus may serve as long term averages against which modern day dust fluxes may be compared we apply this model to 17 field sites in the south fork of the salmon river in the idaho batholith where rock and regolith compositions imply that mafic rich material has been added to the otherwise granitic regolith we suggest that the most likely source of this mafic material is dust sourced from the same glacial outburst flood sediments that generated the palouse loess on the columbia plateau and we use the published composition of these sediments to infer dust incorporation rates of 3 13 t km 2 yr 1 at these sites comparable to modern day dust fluxes elsewhere in the western united states

storm induced concentration of sulfurized marine origin organic matter as a possible mechanism in the formation of petroleum source rock abstract black shales though laminated are not systematically synonymous with quiet conditions of deposition a number of papers report about black shales yielding sedimentary structures echoing relatively high hydrodynamic conditions here we examine two sedimentary sequences pertaining to the late jurassic argiles de ch tillon formation of the boulonnais area northernmost france each of them including a meter thick black shale horizon the two laminated black shales contain sulfurized i e organic s rich organic matter reaching a maximum of 9 however some differences set the two black shales apart the lower one was deposited under calm suboxic to anoxic bottom water conditions the classic way the upper black shale was deposited under oxic agitated bottom water conditions not compatible with stable sulfidic conditions required for organic matter sulfurization the upper black shale experienced hydrodynamically induced concentration of sulfurized recalcitrant organic matter of marine origin the sulfurized organic matter could be preserved and quantitatively accumulated owing to its non putrescible nature leading to the formation of a potential hydrocarbon source rock the association of pyrite inclusions with sulfurized organic matter probably modified the hydrodynamic behavior of organic particles the storm induced remobilization and concentration of sulfurized organic matter implies that the sulfurization factory operated in proximal shallow environments such as estuaries mud flats or mangrove environments such a model is in agreement with findings from modern coastal shelf environments notably mangroves and fully transposable to many other sedimentary situations of any geological time period

organic sulfur compounds formed during early diagenesis in black sea sediments abstract sediments from units i and ii of the black sea were analyzed to assess the early diagenetic formation of organic sulfur compounds osc a series of isomeric c28 2 4 dialkylthiophenes was found at low concentrations in surface sediments osc with c25 highly branched isoprenoid rbi skeletons were not found in surface sediments even though there was a rapid decrease in the concentrations of c25 hbi alkenes in the same sediments nor were osc found which contained carbon skeletons derived from c37 c39 alkenes which are also abundant in the sediment as depth increased in unit i concentrations of the c28 2 4 dialkylthiophenes decreased while c25 and c30 hbi thiolanes appeared at the bottom of unit i and increased in concentration into unit ii treatment of macromolecular material from sediment extracts with raney nickel yielded phytane as the dominant hydrocarbon as well as series of c25 and c30 hbi hydrocarbons carotane and isorenieratane these latter two components were generally absent from the free hydrocarbon fractions these results indicate that sulfur incorporation into functionalized lipids can occur during the very early stages of sedimentary diagenesis even at the sediment water interface on the other hand the rapid loss of c25 hbi alkenes in surface sediments could not be accounted for by sulfur quenching and other potential osc precursors such as c37 c39 alkenes also apparently did not incorporate sulfur into readily analyzable material

timing of early diagenetic sulfurization of organic matter a precursor product relationship in holocene sediments of the anoxic cariaco basin venezuela abstract the incorporation of reduced inorganic sulfur into organic matter is a significant mechanism for the preservation of functionalized organic compounds in the sedimentary environment but the timing of this process is not currently known analysis of organic matter in the holocene and latest pleistocene sediments of the cariaco basin indicates conversion of a triunsaturated tricyclic triterpenoid 17e 13 h malabarica 14 27 17 21 triene identified by isolation and subsequent one and two dimensional 1 h and 13 c nmr spectroscopy to a monounsaturated triterpenoid thiane through incorporation of reduced inorganic sulfur species into the isoprenoid side chain within the upper 6 m of sediments time control provided by ams 14 c dates was used in conjunction with measured relative abundances of the two compounds to calculate the reaction rate for the sulfurization of this triterpenoid and empirically determine the first order rate constant 2 10 4 yr 1 for the reaction this is the first time that such a precursor product relationship has been positively identified for a sulfurization reaction in sediments

early diagenesis of organic matter and related sulphur incorporation in surface sediments of meromictic lake cadagno in the swiss alps samples of recent anoxic sediment 100 yr bp from the meromictic lake cadagno switzerland were examined to study sulphur incorporation into organic matter at a very early stage of diagenesis trace amounts of two organosulphur compounds were identified in the extractable organic matter desulphurization of the heterocompound and asphaltene fractions with nickel boride yielded hydrocarbons with a strong dominance of phytane and minor amounts of n alkanes steranes and squalane but may also have converted ester bound moieties into hydrocarbons as shown by a control experiment with a chloropyll a standard the amount of sulphur bound compounds is always higher than the amount of the free precursors even in the shallowest sediments this indicates that the formation of organosulphur compounds starts already in the water column or is very effective in the uppermost millimeters of the sediment layer stable carbon isotope data of the sedimentary compounds and of biological material from the water column and from land biota growing around the lake show that the sulphur bound phytane in the youngest samples is dominated by phytane of bacterial origin with increasing depth the amount of phytane of terrestrial origin slightly increases

sulfurized carbohydrates an important sedimentary sink for organic carbon abstract in contrast to the general belief that carbohydrate carbon ccho is preferentially degraded and is not extensively preserved in the sedimentary record it is shown here that ccho forms a large fraction of the organic matter om of the total organic carbon toc rich upper jurassic kimmeridge clay formation as a result of early diagenetic sulfurization a previously unrecognized pathway of om preservation this is evident from both changes in the molecular composition of the insoluble om and from 13ctoc shifts of 6 with varying ccho contents furthermore experiments simulating the natural sulfurization of the ccho rich alga phaeocystis spp demonstrated that sulfurization can indeed lead to a substantial preservation of ccho with a molecular fingerprint identical to that of the kimmeridge clay and many other recent and ancient marine om rich sediments these results imply that preservation of ccho can exert a fundamental control on 13ctoc in om rich sediments complicating the interpretation of 13ctoc records with regard to estimating terrestrial versus aquatic om fractions reconstruction of past atmospheric co2 levels and global carbon budget models

origins of aircraft damaging clear air turbulence during the 9 december 1992 colorado downslope windstorm numerical simulations and comparison with observations results from numerical simulations of the colorado front range downslope windstorm of 9 december 1992 are presented although this case was not characterized by severe surface winds the event caused extreme clearair turbulence cat aloft as indicated by the severe structural damage experienced by a dc 8 cargo jet at 9 7 km above mean sea level over the mountains detailed measurements from the national oceanic and atmospheric administration environmental research laboratories environmental technology laboratory doppler lidar and wind profilers operating on that day and from the defense meteorological satellite program satellite allow for a uniquely rich comparison between the simulations and observations four levels of grid refinement were used in the model the outer domain used national centers for environmental prediction data for initial and boundary conditions the finest grid used 200 m in all three dimensions over a 48 km by 48 km section the range of resolution and domain coverage were sufficient to resolve the abundant variety of dynamics associated with a time evolving windstorm forced during a frontal passage this full range of resolution and model complexity was essential in this case many aspects of this windstorm are inherently three dimensional and are not represented in idealized models using either 2d or so called 2d 3d dynamics both the timing and location of wave breaking compared well with observations the model also reproduced cross stream wavelike perturbations in the jet stream that compared well with the orientation and spacing of cloud bands observed by satellite and lidar model results also show that the observed cat derives from interactions between these wavelike jet stream disturbances and mountain forced internal gravity waves due to the nearly east west orientation of the jet stream these two interacting wave modes were orthogonal to each other thermal gradients associated with the intense jet stream undulations generated horizontal vortex tubes hvts aligned with the mean flow these hvts remained aloft while they propagated downstream at about the elevation of the aircraft incident and evidence for such a vortex was seen by the lidar the model and observations suggest that one of these intense vortices may have caused the aircraft incident reports of strong surface gusts were intermittent along the front range during the period of this study the model showed that interactions between the gravity waves and flow aligned jet stream undulations result in isolated occurrences of strong surface gusts in line with observations the simulations show that strong shears on the upper and bottom surfaces of the jet stream combine to provide an episodic downburst of turbulence in the present case the perturbations of the jet stream provide a funnel shaped shear zone aligned with the mean flow that acts as a guide for the downward transport of turbulence resulting from breaking gravity waves the physical picture for the upper levels is similar to the surface gusts described by clark and farley resulting from vortex tilting the cat feeding into this funnel came from all surfaces of the jet stream with more than half originating from the vertically inclined shear zones on the bottom side of the jet stream visually the downburst of turbulence looks similar to a rain shaft plummeting to the surface and propagating out over the plains leaving relatively quiescent conditions behind

impact of dia and catagenesis on sulphur and oxygen sequestration of biomarkers as revealed by artificial maturation of an immature sedimentary rock hydrous pyrolysis of an immature ro 0 25 sulphur rich marl from the gessoso solfifera formation messinian in the vena del gesso basin was carried out at 160 c t 330 c for 72 h to study the effect of progressive diagenesis and early catagenesis on the abundance and distribution of sulphur containing and sulphur and oxygen linked carbon skeletons in low molecular weight and high molecular weight fractions e g kerogen to this end compounds in the saturated hydrocarbon fraction monoaromatic hydrocarbon fraction polyaromatic hydrocarbon fraction alkylsulphide fraction and ketone fraction were quantified as well as compounds released after desulphurisation of the polar fraction and hilialh4 treatment of the desulphurised polar fraction sulphur bound phytane and 20r 5 14 17 h and 20r 5 14 17 h c27 c29 steranes in the polar fraction become less abundant with increasing maturation temperature whereas the amount of their corresponding hydrocarbons increases in the saturated hydrocarbon fraction carbon skeletons that are bound in the kerogen by multiple bonds e g c38n alkane and isorenieratane are first released into the polar fraction and then as free hydrocarbons these changes occur at relatively low levels of thermal maturity ro 0 6 as evidenced by the immature values of biomarker maturity parameters such as the c35 hopane ratio and the 22s 22s 22r 17 21 h c35 hopane ratio sulphur and oxygen bound moieties present in the polar fraction are not stable with increasing thermal maturation however alkylthiophenes ketones 1 2 di n alkylbenzenes and free n alkanes seem to be stable thermal degradation products of these sulphur and oxygen bound moieties thus apart from free n alkanes which are abundantly present in more mature sedimentary rocks and crude oils alkylthiophenes 1 2 di n alkylbenzenes and ketones can also be expected to occur the positions of the thiophene moiety and the carbonyl group coincide with the original positions of the functional groups of their precursors thus important information about palaeobiochemicals is retained throughout the sequestration degradation process

spectrocolorimetric interpretation of sedimentary dynamics the new q7 4 diagram colour is a fundamental property of sediment and is often used for lithographic description to determine sedimentological structures facies etc however the sedimentary information contained in this parameter is difficult to extract because it is difficult to quantify colour can be quantified by spectrocolorimetry which provides very high resolution data quickly and non destructively when adapted to sedimentology spectrocolorimeters prove to be powerful tools due to their low purchase and maintenance costs and some are portable and easily used in the field several methods have been used to extract sedimentological data from colorimetric spectra first derivatives factorial analysis etc in the present study we first provide a review of the sedimentological application of spectrophotometers and after having described these methods their advantages and disadvantages we then describe a new tool called the q7 4 diagram abscissa l ordinates 700 400 ratio this new technique permits sedimentological units to be defined allows the identification of different sediment components and provides 5 distinct poles clayey deposits organic rich deposits chlorophyll a and by products altered organic matter deposits iron rich deposits carbonated deposits coupled with the analysis of first derivative spectra it is possible to distinguish different pigments linked to the degradation and or nature of the organic material chlorophyll a melanoidin etc the state of iron oxidation for example hematite and goethite like signatures and the nature of clays the q7 4 diagram permits rapid acquisition of high resolution data on changes of sediment dynamics in geosystems that have been subjected to highly varied climatic environmental conditions the instrument is non destructive easy to use and maintain portable for use in the field fast to implement is capable of high resolution and has a vast range of possible applications spectrocolorimetry appears to provide many advantages and could become an essential and robust tool for preliminary sedimentological studies

algal and bacterial hydrocarbons in particulate matter and interfacial sediment of the cariaco trench particulate matter samples 53 m size fractions and sediment from the sediment water interface were collected in the cariaco trench an anoxic marine basin on the continental shelf of venezuela and analyzed for hydrocarbons concentrations of hydrocarbons were highest 10 20 ng 1 in oxic surface waters 0 150 m and at the top of the anoxic zone 350 600 m and were low 3 4 ng l in the low oxygen zone above the oxic anoxic interface 150 250 m and anoxic bottom waters 600 1150 m branched c25 trienes and tetraenes dominated the hydrocarbon distributions in 53 m particles particle size and depth distributions of the hydrocarbons demonstrate the importance of algal hydrocarbons in surface waters coupled with increased abundances of bacterial hydrocarbons especially in the 53 m particles in the anoxic zone these observations illustrate the importance of oxic anoxic interfaces even in the oceanic water column as zones of intense microbial alteration of organic matter and as sources of some of the organic compounds found in sediments

early diagenetic pyrite morphology in a mudstone dominated succession the lower jurassic cleveland ironstone formation eastern england abstract diagenetic pyrite in the mudstones and ironstones of the lower jurassic cleveland ironstone formation of eastern england exhibits two distinct morphologies framboidal pyrite commonly associated with organic matter and euhedral pyrite associated with detrital clay pellets these two morphologies are mutually exclusive in occurrence framboidal pyrite is present in clay rich mudstones ooidal ironstones apatite rich units and some silt rich mudstones euhedral pyrite is present in silt rich and sand rich mudstones 34s isotopic analysis of six samples of pyrite suggests that both types of pyrite morphology precipitated during early diagenesis from porewaters with open access to overlying sea water although both probably acted as sites for continued pyrite precipitation during burial it is proposed that framboidal pyrite precipitated from iron dominated porewaters at sites of sulfide supply i e in the region of organic matter as a result of bacterial sulfate reduction where locally sulfide production rates were high enough for porewaters to reach supersaturation with respect to fes euhedral pyrite also precipitated from iron dominated porewaters but sulfide production rates from organic matter was such that fes saturation was not reached at the sites of sulfide production instead euhedral pyrite was precipitated directly from porewater when fes2 saturation was reached the control over pyrite morphology was probably the amount and reactivity of the organic matter within the deposited sediments the sand rich mudstones contained less reactive organic matter due to clastic dilution and deposition in shallower environments with o2 rich bottom waters the ironstones and apatite rich units were deposited under very low sedimentation rates and as a result organic matter contents were very low and iron reduction dominated early diagenesis which inhibited sulfate reduction the presence of minor framboidal pyrite within these units however suggests that sulfide reduction took place in micro environments during early diagenesis

molybdenum accumulation in cariaco basin sediment over the past 24 k y a record of water column anoxia and climate molybdenum mo concentrations in a sediment core from the cariaco basin on the venezuelan continental shelf can be partitioned between a marine fraction and a terrigenous fraction the accumulation rate of the marine fraction of mo increased abruptly 15 000 calendar years ago 15 ka from 2 yr 1 to 4 g cm 2 yr 1 and then decreased abruptly at 9 ka the accumulation rate remained high throughout this 6 k y period but exhibited maxima at 15 14 and 12 5 ka corresponding in time to meltwater pulse ia into the gulf of mexico and the onset of the younger dryas cold event respectively the marine fraction of mo is interpreted in terms of redox conditions of bottom water as dictated by both the flux of settling organic matter and bottom water residence time correspondence between geochemical extremes in this core with changes in sea level and global climate demonstrates the high degree to which this ocean margin basin has responded to the paleoceanographic regime throughout the past 24 k y

origin of cariaco basin southern caribbean sea abstract the cariaco basin an anoxic basin in the central eastern venezuelan continental borderland is located in the area of overlap of two en echelon right lateral strike slip fault zones the moron and el pilar fault zones on the basis of 28 acoustic reflection profiles across it the basin is interpreted as a pull apart basin due to east west tension in the area of the right step between the two fault zones 125 km of overlap and 35 km separation the offset along the fault zones is less than 100 km and at least 25 km its age is most probably quaternary as suggested by the thickness of the sedimentary fill and the estimated rate of deposition and because strike slip displacement along the master faults probably began no earlier than the late tertiary the cariaco basin is the largest pull apart basin along the bocono moron el pilar fault system which is a part of the caribbean south america plate boundary

turbulence generation by kelvin helmholtz instability in the tropical tropopause layer observed with a 47 mhz range imaging radar 1 detailed structure of kelvin helmholtz kh instability in the tropical tropopause layer is presented using a 47 mhz clear air doppler radar referred to as the equatorial atmosphere radar ear installed at west sumatra indonesia 0 20 s 100 32 e during 12 20 december 2008 radiosondes revealed that the altitude of temperature minimum was 16 1 16 4 km from 12 14 december and then descended with time and reached 13 4 km on 20 december the altitude of easterly wind maximum corresponded well with that of the temperature minimum and enhanced eastward vertical wind shear was produced above it because of a sharp decrease of easterly wind with altitude during this period to attain high range resolution of a few tens of meters the ear was operated in range imaging mode using frequency diversity ear observations revealed that enhanced radar echo above the temperature minimum had a thin layered structure less than or about 200 m in depth during 12 14 december and then frequently showed upward wisp like structures resulting from kh instability in the intensive kh instability cases on 16 and 18 december kh billows had a depth of up to 1 km and upward and downward velocities reaching greater than 2 m s 1 were observed within the billows considerations using the linear wave theory suggest that a breaking of equatorial kelvin wave might have been responsible for the onset of well developed kh instability

chemical weathering mass loss and dust inputs across a climate by time matrix in the hawaiian islands we determined the total mass loss and rate of chemical weathering from three minimally eroded hawaiian lava flows that are 10 170 and 350 ka old using a backhoe we sampled the entire weathering zone at 28 sites and measured the depletion or enrichment of each major element in each soil horizon relative to parent material we were able to assess the influence of both climate and substrate age on chemical weathering because each flow crosses a precipitation gradient from 600 to 2500 mm yr 1 mass loss rates were highest for the 0 10 ka interval under the wettest climatic conditions 54 t km 2 yr 1 and decreased to near zero in the wet sites during the 10 170 and 170 350 ka intervals not surprisingly weathering rates were lower in drier sites 24 t km 2 yr 1 from 0 10 ka to b 2tk m 2 yr 1 thereafter however the effects of precipitation were non linear there was a precipitation threshold below which mass loss was relatively small and above which mass loss was substantial but insensitive to increased rainfall chemical weathering rates depend on tectonic uplift erosion climate rock type or some combination thereof by working on stable uneroded surfaces of a single rock type across a well constrained precipitation gradient we were able to identify another potential driver the rate of dust deposition although hawai i is one of the least dusty places in the northern hemisphere dust inputs reached 82 of the total mass loss from the weathering zone at some sites and averaged 30 on the 170 ka flow this highlights the potential importance of dust as a component of observed weathering fluxes from catchments worldwide

a theoretical model coupling chemical weathering rates with denudation rates uplift of the himalayas has been proposed to have locally accelerated chemical weathering thus leading to enhanced co2 sequestration and global cooling this hypothesis assumes that rapid erosion exposes fresh highly reactive minerals at earth s surface empirical studies quantifying the relationship between erosion and weathering have produced apparently conflicting results where the nature of the relationship is dependent on the weathering regime of the sampled landscapes we derive a quantitative model that defines this relationship across the range of weathering regimes from supply limited to kinetically limited conditions the model matches trends in field data collected by others and reconciles apparently conflicting results the model also demonstrates that as erosion rates increase potential increases in weathering rate from the exposure of fresher materials are offset by the decrease in the total volume of minerals exposed due to thinner regolith we conclude that the relationship between weathering and erosion is one of diminishing returns in which increases in erosion rate lead to progressively smaller increases in weathering rate indeed at the highest erosion rates weathering rates may decline the ability therefore of accelerated uplift and erosion to stimulate greater co2 sequestration may be significant in landscapes eroding at rates of 10 102 t km 2 yr 1 however where erosion rates are greater than 102 t km 2 yr 1 increases in denudation may not be matched by increases in chemical weathering finally our results suggest that watersheds with regolith thicknesses of 0 5 m will yield the greatest solute fluxes

geochemical study of macromolecular organic matter from sulfur rich sediments of evaporitic origin messinian of sicily by chemical degradations abstract selective chemical degradations have been performed on sulfur rich macromolecular organic matter from sediments of the messinian of sicily upper miocene italy the biomarkers released upon different desulfurization experiments are much more abundant than the free lipids and display completely different distributions which reflect the selective trapping of poly functionalized molecules by inorganic sulfur species at an early stage of diagenesis the bound biomarker distributions reveal a dominant phytoplanktonic input originating from an upper oxic water layer and a moderate bacterial reworking of the organic matter a contribution from cyanobacteria to the organic matter cannot be excluded the presence of carotenoids typical from photosynthetic sulfur bacteria attests to a stratified water body where an anoxic photic zone occurred lialh4 hydrogenolysis of sulfur rich macromolecules revealed that polysulfide bridges contribute to a large extent in the cross linking the results of deuterium labelling experiments are discussed in terms of sulfur incorporation on functionalized lipids

layered structure associated with low potential vorticity near the tropopause seen in high resolution radiosondes over japan horizontal wind and temperature data obtained from operational radiosondes over japan have recently been available with high vertical resolution analyzing these data over 4 yr has indicated horizontal velocity layers with vertical scales of about 5 km lasting for a week or more the layers appear frequently in winter at several stations simultaneously and are dominant in the height range of 8 16 km an empirical orthogonal function eof analysis for the time series of layered disturbance amplitude in winter indicates that there are two dominant principal components the first component eof1 describes layered disturbances in the middle of japan 308 378n and the second one eof2 describes disturbances in the south of japan 238 308n using global analysis data the background field of the layered disturbances was examined an interesting result is that the background potential vorticity pv is approximately zero or negative for eof2 disturbances even though located in a relatively high latitude region this fact suggests that the eof2 disturbances are due to inertial instability it is also shown that negative pv occurs more than 30 of the time in winter in a zonally elongated region of 238 298n in the western pacific on an isentropic surface of 345 k 10 km altitude such a high frequency of negative pv is not observed at other longitudes in this latitude band to determine the origin of the anomalous pv backward trajectories were analyzed for eof2 disturbances air parcels having mostly negative pv are traced back to the equatorial region in the longitude band 208w 1408e within a few days this is due to a strong northward branch of the hadley circulation associated with deep convection over the maritime continent and a strong northeastward subtropical jet stream on the other hand the background pv is low but scarcely negative for eof1 disturbances air parcels at eof1 stations are traced back to the far west because they are advected mostly by a strong eastward jet stream thus it is inferred that the eof1 disturbances may be due to inertia gravity waves trapped in a duct of the westerly jet core

the cycling and redox state of nitrogen in the archaean ocean organisms that produce oxygen through photosynthesis existed during the late archaean eon about 2 500 million years ago but controversial evidence suggests that they may have evolved several hundred million years earlier oxygen is expected to react with oceanic nitrogen altering its redox state the reaction leaves a signature in the isotopic composition of the nitrogen bound in organic matter here we present a record of the nitrogen isotopic composition of kerogen extracted from minimally altered shales from the campbellrand malmani platform in south africa between the palaeo archaean and about 2 670 million years ago the 15n values of the kerogen rose by about 2 we interpret this increase as an indication of the onset of coupled nitrification and denitrification or anammox reactions in the surface oceans which require the presence of free oxygen a second increase in nitrogen isotopic composition around 2 520 million years ago implies instability of the n cycle with loss of fixed n this evidence for available oxygen in the oceans occurs at least 200 million years before geochemical indications of the presence of significant levels of atmospheric oxygen we suggest that coupled nitrification and denitrification drove the loss of fixed inorganic nitrogen leading to nitrogen limitation and conclude that the low levels of biologically available nitrogen limited the growth of oxygen producing plankton delaying the accumulation of oxygen in the atmosphere the initial production of oxygen in early earth s oceans altered the redox chemistry and cycling of nitrogen a record of nitrogen isotopes from preserved organic matter indicates nitrogen cycling in the presence of free oxygen 2 67 billion years ago about 200 million years before the first geochemical evidence for atmospheric free oxygen

tectonics fracturing of rock and erosion 1 we argue that by fracturing rock not by raising it relative to base level tectonics plays its most important role in causing rapid incision of valleys and rapid erosion of hillslopes tectonic deformation riddles the upper crust with fractures which not only provide avenues for water flow and thus promote weathering and further disintegration of rock but also fragment bedrock into debris that is readily extracted and transported by surface processes bends in active faults require straining of adjacent rock masses aftershocks that occur subsequent to slip on primary faults reflect penetrative brittle deformation of the upper crust at least some aftershocks must nucleate or lengthen cracks which contribute to the comminution of these rock masses scaling rules suggest that dimensions of ruptures for very small m 2 earthquakes can be meters or less the gutenberg richter recurrence relationship implies that such earthquakes are common as high magnification seismographs in low noise environments confirm moreover large differences among fault plane solutions for aftershocks show that the small faults on which they occur are not parallel to one another some faults must intersect thus the upper crust in tectonically active regions should be fragmented into blocks down to the scale of boulders or smaller dismembered rock arrives at the earth s surface already prepared to be transported away as a corollary both deeply exhumed lower crust and posttectonic igneous rock never deformed under brittle conditions and not deformed recently should be less susceptible to detachment and subsequent transport than fractured rock

computation of clear air radar backscatter from numerical simulations of turbulence 2 backscatter moments throughout the lifecycle of a kelvin helmholtz instability 1 franke et al 2011 describe a numerical simulation of the instability and turbulent breakdown of kelvin helmholtz kh billows at a high reynolds number numerical assessment of radar backscatter and accuracies of inferred doppler spectral moments for one test volume those results suggest a potential for significant measurement biases for radars that obtain backscatter from refractive index fluctuations we present in this paper the morphology of computed radar moments throughout the kh instability lifecycle for two radar configurations in order to reveal the evolving character of radar backscatter and compare the radar velocity estimates with true velocities throughout the evolution and to provide guidance and cautions for the interpretation of these dynamics in observational data results reveal strong variations in backscatter moments and character and dependence on radar measurement parameters that should be beneficial in the interpretation of such measurements in the atmosphere backscatter power predictions agree reasonably with observations of such events and their temporal evolutions our results also reveal a potential for significant measurement or sensitivity biases some of which were predicted previously examples include a lack of significant backscatter power in well mixed billow cores suggesting possibly weak turbulence where in fact it may be strongest maximum backscatter power in the billow exteriors where refractive index fluctuations are large but turbulence is weak underestimated vertical velocities within the kh billows at early times and inferred significant vertical velocities where true vertical velocities are near zero at late stages of restratification especially in the edge regions of the turbulence layer

organic matter preservation and sulfur uptake in sediments from the continental margin off pakistan abstract the bulk and molecular geochemical characteristics of a suite of kerogens isolated from organic matter rich sediments from the pakistan margin has been characterised by elemental analysis rock eval pyrolysis and pyrolysis gas chromatography py gc special attention was given to the geochemistry of alkylthiophenes which are thought to reflect the incorporation of sulfur into organic matter om in the context of early diagenetic sulfate reduction organically bound sulfur comprises up to 60 of total sedimentary sulfur the weight ratios for organic sulfur s org over organic carbon c org varies from 0 01 in some of the recently deposited sediments to 0 11 in older samples the results show that sulfur incorporation into organic matter occurs primarily within the upper few meters of the sediments the amount of sulfur which can be incorporated into the organic matter clearly depends on the quality of om the hydrogen index values hi which characterise the total amount of generated hydrocarbon equivalents of the pyrolysate in mg hc equiv g c org are related to the extent of reworking of organic matter either in the water column or at the sediment water interface or to remineralization processes by sulfate reduction itself which is strongly controlled by the availability of reactive iron high quality organic matter characterised by elevated hi values is capable of sequestering higher amounts of sulfur as expressed by the thiophene content which represent the organically bound sulfur of the pyrolysate in mg g c org as indicated by the ratio of thiophenes versus hi which characterises the proportion of thiophenes in the total pyrolysate sulfurisation of organic matter seems to be terminated at a ratio of 0 01

organic matter sulfurization on protracted diagenetic timescales the possible role of anaerobic oxidation of methane abstract kerogens from the anoxic sediments of the cariaco basin spanning the last 130 ky were analyzed in order to determine the organic matter om preservation pathways and the evolution of these pathways with time the kerogens were isolated using a protocol avoiding the formation of artificial melanoidins bulk elemental content spectroscopic and pyrolytic features of the kerogens show that sulfurization is an important process in the insolubilisation of the om even in the most recent sample studied 400 a the degree of om sulfurization on the studied interval depends on the redox conditions of the sediment during deposition and is largely correlated to the total organic carbon content of the sediment a trend of downward increasing sulfurization of the organic matter is observed in the sediments of the studied two interglacials from the available porewater analyses of cariaco sediments and comparison with black sea sediments the data suggest that downward progressive sulfurization of the om is mainly due to the production of h 2 s by sulfate dependent anaerobic oxidation of methane occurring at the sulfate methane transition zone located a few meters below sea floor

responses of soil mantled hillslopes to transient channel incision rates 1 channel incision drives hillslope morphology in humid soil mantled landscapes when channel incision rates change numerous hillslope soil properties e g erosion rates soil thickness and soil production adjust in response to this change here we investigate the timescales of adjustment of hillslope soil properties when channel incision rates change in time an idealized soil mantled hillslope linear sediment flux law and soil density equal to bedrock density is investigated and the transient evolution of this hillslope is determined analytically this analysis reveals two dominant adjustment timescales the longer of these two timescales determines the rate at which the entire hillslope adjusts to a change in channel incision rates and is proportional to 4 2 2d where is the length of the hillslope and d is the sediment diffusivity numerical simulations are then used to examine responses of hillslopes that involve nonlinear behavior e g hillslopes that experience nonlinear sediment transport or have soil thicknesses that respond to the soil production function using these numerical models we show that the ratio between the soil density s and the density of the soil parent material can alter the long term response of the hillslope such that the characteristic timescale becomes 4 2 2d s in addition we show that the adjustments of the soil erosion rate the soil production rate and the soil thickness have different characteristic response timescales hillslopes that experience sediment flux that is proportional to the depth slope product respond on longer timescales than hillslopes that experience a linear sediment flux law when channel incision rates increase we illustrate how the spatial pattern of hillslope response to changes in channel incision rates can be used to constrain either channel incision histories or hillslope response timescales if the hillslope response timescale is known the pattern of hillslope disturbance can be used to constrain the celerity of a incision wave as it moves upstream through a channel if the channel incision history is known the hillslope response timescale may be evaluated on the basis of the spatial pattern of hillslope disturbance

preservation of elemental and isotopic source identification of sedimentary organic matter the amount and type of organic matter in the sediments of lakes and oceans contribute to their paleoenvironmental and paleoclimatological records only a small fraction of the initial aquatic organic matter survives destruction and alteration during sinking and sedimentation selective degradation modifies the character of the surviving small fraction of organic matter which becomes incorporated in bottom sediments organic matter alterations can continue to sub bottom depths of hundreds of meters corresponding to millions of years source and paleoenvironmental information nonetheless remains preserved in the molecular elemental and isotopic compositions of organic matter c n and 13c values of total organic matter in particular appear to retain paleoenvironmental information for multi myr time periods

chemical evidence of kerogen formation in source rocks and oil shales via selective preservation of thin resistant outer walls of microalgae origin of ultralaminae abstract new structures termed ultralaminae were recently observed by transmission electron microscopy usually in high amounts in a number of kerogens from oil shales and source rocks morphological similarities were noted between ultralaminae and the thin ca 15 nm resistant outer walls composed of non hydrolyzable macromolecules algaenans commonly occurring in extant chlorophyceae especially in the cosmopolitan genus scenedesmus identification of the pyrolysis products of s quadricauda algaenan showed i a highly aliphatic structure based on a macromolecular network of long up to c32 polymethylenic chains probably cross linked by ether bridges and ii a close correlation based on the formation of n alkylnitriles between this algaenan and two ultralaminar kerogens the rundle oil shale mainly composed of ultralamina accumulations and the green river shale ultralaminae dispersed within an amorphous matrix these fossil ultralaminae therefore likely originated from the selective preservation of the thin algaenan containing outer walls of scenedesmus and or of other chlorophyceae containing outer walls of a similar morphology and composition relative distributions of n alkylnitriles and of n alkanoic acids in the pyrolysates of s quadricauda algaenan and of the rundle oil shale indicated that nitriles are not derived from secondary reactions of carboxylic acids but originate from preexisting nitrogen functions likely amides previous evidence of kerogen formation via selective preservation of algaenans was restricted to rather uncommon kerogens the present results added to ultralamina common occurrence and abundance point to a wide involvement and to a large contribution of the selective preservation of algaenan containing thin outer walls of chlorophyceae in the formation of kerogens in a number of lacustrine source rocks and oil shales all the available information suggest that the three way correlation selective preservation of algaenans from thin resistant chlorophycean outer walls formation of fossil ultralaminae presence of n alkylnitriles with a typical distribution in the pyrolysates of ultralaminar kerogens observed in this study might be of a general character

origin of low molecular weight alkylthiophenes in pyrolysates of sulphur rich kerogens as revealed by micro scale sealed vessel pyrolysis abstract micro scale sealed vessel mssv pyrolysis experiments have been conducted at temperatures of 150 200 250 300 330 and 350 c for various times on a thermally immature type ii s kerogen from the maastrichtian jurf ed darawish oil shale jordan in order to study the origin of low molecular weight lmw alkylthiophenes these experiments indicated that the lmw alkylthiophenes usually encountered in the flash pyrolysates of sulphur rich kerogens are also produced at much lower pyrolysis temperatures i e as low as 150 c as the major apart from hydrogen sulfide sulphur containing pyrolysis products mssv pyrolysis of a long chain alkylthiophene and an alkylbenzene indicated that at 300 c for 72 h no cleavage leading to generation of lmw alkylated thiophenes and benzene occurs in combination with the substantial production of lmw alkylthiophenes with a linear carbon skeleton at these conditions this indicated that these thiophenes are predominantly formed by thermal degradation of multiple poly sulfide bound linear c 5 c 7 skeletons which probably mainly originate from sulphurisation of carbohydrates during early diagenesis lmw alkylthiophenes with linear carbon skeletons seem to be unstable at mssv pyrolysis temperatures of 330 c either due to thermal degradation or to methyl transfer reactions lmw alkylthiophenes with a branched carbon skeleton most likely derive from both multiple poly sulfide bound branched c 5 c 7 skeletons and alkylthiophene units present in the kerogen

cosmogenic nuclides topography and the spatial variation of soil depth abstract if the rate of bedrock conversion to a mobile layer of soil depends on the local thickness of soil then hillslopes on uniform bedrock in a landscape approaching dynamic equilibrium should be mantled by a uniform thickness of soil conversely if the depth of soil varies across an actively eroding landscape then rates of soil production will also vary and consequently the landscape will not be in morphologic equilibrium the slow evolution of hillslopes relative to the tempo of climatic variations and tectonic adjustments would suggest that local morphologic disequilibrium may be expected in many landscapes here we explore this issue of equilibrium landscapes through a previously developed model that predicts the spatial variation in thickness of soil as a consequence of the local balance between soil production and erosion first we confirm the assumption in the model that soil production varies inversely with the thickness of soil using two independent methods one method uses the theoretical prediction that at local steady state soil production equals removal the depth of soil should vary inversely with hillslope curvature the second method relies on direct measurements of in situ produced concentrations of cosmogenic 10 be and 26 al in bedrock at the base of the soil column for our study site in northern california the two methods agree and yield the expression that the rate of soil production declines exponentially with the thickness of soil from 0 077 mm year with no soil mantle to 0 0077 mm year under 1 m of soil we then use this function of soil production in a coupled production and diffusive model of sediment transport to explore the controls on the spatial variation of the depth of soil on four separate spur ridges noses where we measured the data for the function of soil production model predictions are sensitive to boundary conditions grid scale and run time nonetheless we found good agreement between predicted and observed depths of soil as long as we used the observed function of soil production the four noses each have spatially varying curvature and consequently have varying depths of soil implying morphologic disequilibrium we suggest that our study site has been subjected to a wave of incision and varying intensities of erosion because of tectonic and climatic oscillations that have a frequency shorter than the morphologic response time of the landscape

integration of geochemical mass balance with sediment transport to calculate rates of soil chemical weathering and transport on hillslopes 1 we developed a process oriented hillslope soil mass balance model that integrates chemical and physical processes within hillslope soils the model explicitly factors that soil chemical weathering at any hillslope position is related to the flux of soil eroded from upslope as well as soil production from underlying bedrock the model was merged with measurements of soil elemental chemistry and cosmogenic radionuclide based saprolite to soil conversion rates along a 50 m transect of a semiarid granodiorite hillslope in the southeastern australian highlands inverse modeling results in the simultaneous quantification of the rates of soil chemical weathering and soil transport as a function of hillslope position soil chemical weathering rates per land surface area systematically varied along the transect from losses of 0 035 kg m 2 yr 1 on the ridge to gains of 0 035 kg m 2 yr 1 at the lowest slope position the mass loss via soil chemical weathering would have been overestimated by 40 if the impact of soil transport on soil chemistry was ignored the chemical mobility of elements combined with biological nutrient demand controlled the spatial redistribution of individual elements p and ca were preferentially retained relative to si al and fe within the hillslope base the calculated soil transport rate is linearly related to the product of soil thickness and slope gradient instead of slope alone soil residence time was determined by calculating the time length for a 3 dimensional box volume 1 m2 surface area soil thickness to be entirely removed by mass flux of soil transport 4 ka on the ridge to 0 9 ka at the hillslope base these soil residence times combined with soil chemical weathering rates indicate that a 1 m2 area of soil loses 1 800 kg via chemical weathering while passing through the upslope portion of the hillslope but that it regains 90 kg probably via clay precipitation and biological retention of cations during its passage through the lower segments of the transect this study provides a previously unrecognized linkage between physical soil transport and soil chemical weathering that have implications for hillslope evolution as well as biogeochemistry

high resolution observations with mu radar of a kh instability triggered by an inertia gravity wave in the upper part of a jet stream kelvin helmholtz kh instability is likely one of the most important sources of clear air turbulence in the lower atmosphere it produces billows which mix and transport heat and materials vertically in the stably stratified atmosphere billows can also dissipate energy therefore they can affect the larger scale dynamics while only a few direct observations have been reported in the tropopause region in this work the authors report very detailed observations of billow structures around 16 km altitude in the upper part of the jet stream observations were made with very high frequency vhf band mid and upperatmosphere mu radar shigaraki japan 34 85 n 136 10 e whose height resolution was improved with a range imaging technique kh billow structures were observed for at least 2 h and were found to have horizontal wavelengths of about 5 3 km and vertical extents between 0 5 and 1 0 km analysis of wind and temperature profiles measured by radiosondes launched from nearby meteorological stations indicated the presence of nearly monochromatic disturbances likely due to a dominant inertia gravity wave igw superimposed on the background wind field the presence of the igw was also confirmed by analysis of wind profiles measured by the mu radar just before the kh billows were detected by the observations in range imaging mode the igw with vertical and horizontal wavelengths of about 3 5 and 600 km respectively may have been a direct radiation from the jet stream as suggested by recent works and likely played a major role in the onset of the observed kh instability

range imaging of e region field aligned irregularities by using a multifrequency technique validation and initial results this paper reports the first use of a multifrequency range imaging rim technique for observing e region field aligned irregularities fais in the midlatitude ionosphere the middle and upper atmosphere radar mur 34 85 n 136 10 e was used to conduct experiments with five equally spaced frequencies between 46 25 and 46 75 mhz three types of rim data were examined data with 13 element binary barker codes with 16 element binary complementary codes and without phase codes moreover two calibration approaches were adopted to validate the applicability of the rim technique which functioned as intended excellent rim performance such as the ability to resolve several striations in an echo region of fais was demonstrated however sidelobe echoes caused by pulse coding mechanisms were occasionally observed at altitudes above and below the source regions in the coded data therefore a procedure was developed according to one of the calibration approaches to identify and remove such kind of sidelobe echoes which was shown to be applicable for the complementary coded data in addition to fais a thin plasma layer with a thickness of approximately 1 km was identified as being structured with some tilted finer structures which could not be observed in the original intensity images with a range resolution of 600 m preliminary estimates of the doppler velocities indicated that a wind shear effect could be the cause of such tilted finer structures

climate induced variations in productivity and planktonic ecosystem structure from the younger dryas to holocene in the cariaco basin venezuela a high resolution molecular organic geochemical study of sediments in the anoxic cariaco basin indicates significant changes in primary productivity and planktonic community structure associated with the transition from the younger dryas to the holocene variations in climate conditions over the past 12 14c kyr have induced large scale changes in upwelling intensity which directly affected levels of primary productivity as reflected in accumulation rates of bulk productivity proxies concentrations and accumulation rates of sterol and alkenone biomarkers have been used to identify how productivity changes affected the structure of the planktonic ecosystem a shift in the dominant primary producer from diatoms younger dryas to coccolithophores holocene is identified if productivity and ecosystem variations like those identified in the tropical upwelling zone of the cariaco basin region occur throughout the tropical oceans they have the potential to affect global climate through perturbations in the biogeochemical cycle of carbon

chemical weathering response to tectonic forcing a soils perspective from the san gabriel mountains california abstract what controls the chemical weathering of soils in tectonically active landscapes recent field and modeling studies suggest that tectonic forcing and associated increases in erosion rates may either promote or hinder soil chemical weathering these competing trajectories are dependent on two primary controls the availability of fresh minerals and their residence time on the landsurface here we explore rates and extents of soil weathering in the san gabriel mountains of california where previous work has measured clear tectonic fingerprints on rates of long term exhumation hillslope erosion and landscape morphology we quantify chemical weathering across this landscape by elemental analysis of soils saprolites and bedrock on six sites that bracket the low gradient hillslopes of the relict upland plateau and the high gradient hillslopes at the margins of the tectonically driven incising landscape average chemical depletion fractions which measure weathering losses from soil relative to unweathered parent material decrease with increasing elevation and decreasing temperature reflecting a combination of climate influence and potential dust inputs from the mojave desert weathering fluxes from non dust affected sites with similar elevations climates and lithology correlate with both erosion rates and hillslope gradient on low gradient hillslopes 25 weathering intensities and rates both decrease as erosion rates increase and soils thin at the highest denudation rates 300 t km 2 y 1 saprolite production is outpaced and soils are produced directly from fractured rock these patterns are consistent with those predicted by a previously published model for denudation weathering relationships based on mineral weathering kinetics variable weathering extents in soils indicate that weathering in the sgm is largely kinetically limited this study is the first to quantify decreases in both rates and extents of soil chemical weathering with increasing erosion rates and suggests tectonic uplift in rapidly eroding and incising landscapes may not stimulate increased silicate weathering

glacial interglacial variations in production and nitrogen fixation in the cariaco basin during the last 580 kyr the effect of sea level change on nutrient supply to the anoxic cariaco demonstrates the fundamental importance of nitrogen n2 fixation and phosphate to oceanic production as n2 fixation produces biomass of low 15n and has been reported to be an important component of the nitrogen cycle in the modern cariaco basin we propose that it contributes to the light interglacial 15n 2 3 values observed in the ocean drilling program odp site 1002 sediment record during the glacials the sediments are bioturbated oxic conditions with low total organic carbon toc contents and sedimentary 15n values of 5 suggesting that nitrogen n2 fixation contributed little to the n nutrition of cariaco surface waters the most plausible explanation for the inferred glacial interglacial changes in n2 fixation in the cariaco is that they have occurred in response to variations in the n p ratio of the nutrient supply driven by changes in denitrification

vertically pointing airborne doppler radar observations of kelvin helmholtz billows abstract a train of kelvin helmholtz billows in a deep stratiform cloud over a mountain range is documented using data from a high resolution vertically pointing airborne doppler radar the billows had a spacing of 2 2 5 km and a small aspect ratio the formation and decay of the billows appear to be related to flow acceleration over a mountain

photochemical sulfurization of sedimentary organic matter a widespread process occurring at early diagenesis in natural environments abstract the possibility of light induced formation of sedimentary organo sulfur compounds has been investigated with simulation experiments these experiments using mono and diunsaturated hydrocarbons and reduced sulfur species in particular h 2 s and elemental sulfur were conducted under mild conditions sunlight low temperature likely to occur in the photic zone of anoxic environments these experiments showed an efficient sulphurization of the organic matter under sunlight conditions leading to the formation of organo sulfur compounds such as thiophenes and sulfur cross linked macromolecules very similar to those occurring in sediments deposited in anoxic environments these results show the potential for photochemically induced sulfurization of organic matter in environments with photic zone anoxia such a process would be especially favored in evaporitic environments with a shallow anoxic boundary extending well into the photic zone

formation pathways of proto kerogens in holocene sediments of the upwelling influenced cariaco trench venezuela abstract proto kerogens were isolated by extraction and hf hc1 treatment from core samples of holocene sediments of the cariaco trench with interpolated ages of 900 2850 and 6000 years and examined via a combination of microscopic spectroscopic and pyrolytic methods it appears that these proto kerogens were chiefly formed from phytoplanktonic components via the degradation recondensation pathway the natural sulfurisation pathway only afforded a minor contribution in spite of the conditions prevailing in the water column and sediments that correspond to those generally considered as especially favourable for the formation of sulfurised organic matter proto kerogen formation via sulfurisation i e the endpoint of the continuum leading to insoluble high molecular weight structures cross linked by sulfur and resistant to acid hydrolysis is therefore a rather slow process under these conditions however the contribution of sulfurised moieties to the total proto kerogen substantially increased with depth due to continuous sulfurisation in the time depth interval whereas formation through degradation recondensation is almost complete for the 900 years old sample onwards proto kerogen formation via carbohydrate sulfurisation is faster than lipid sulfurisation and only sulfurised carbohydrates were detected in the shallowest sample in contrast sulfurised lipids occur in the other two proto kerogens moreover their contribution relative to sulfurised carbohydrates increases with depth probably due to the higher resistance of lipids to mineralisation compared to carbohydrates

accretion of asian dust to hawaiian soils isotopic elemental and mineral mass balances hawaiian soils contain a mixture of material derived from in situ weathering of parent material plus atmospheric inputs including sea salt aerosols and asian dust we use soil mineralogy and radiogenic isotope geochemistry sr and nd to evaluate the impact of asian dust on a chronosequence of hawaiian soils dust becomes an important constituent of soils 20 ky and older near surface 50 cm depth horizons contain as much as 30 quartz a mineral absent from local parent material basaltic sr and nd isotope signatures in these horizons have been completely overprinted by asian dust signatures with 87sr 86sr ratios as high as 0 723 and end values as low as 7 ree patterns in these soils are indistinguishable from that of average upper continental crust quartz abundance and nd isotopes provide two independent tracers of long term dust additions to the chronosequence soils the two tracers indicate a minimum long term average dust accretion rate of 125 mg cm 2 ky 1 at the 150 ka chronosequence site roughly a factor of three higher than holocene dust accumulation rates estimated from north pacific sediment cores we find that the mass of dust preserved in these soil profiles does not increase with age in soils 150 ka and older requiring a loss mechanism for accreted dust on the basis of the geomorphic stability of these sites observed preferential loss of dust derived mica relative to quartz and estimates of soil si leaching rates we argue that chemical weathering is the dominant loss mechanism for dust from these soils dust has a profound effect on the budgets of elements that are susceptible to leaching losses dust becomes the dominant source of soil nutrients si and p in the oldest most intensely weathered soils we calculate a dust derived p input flux of 0 8 mg cm 2 ky 1 and a dust derived si input flux of 35 mg cm 2 ky 1 si leaching fluxes are high 1400 mg cm 2 ky 1 in the youngest 2 ka soils and drop systematically with soil age to a value that closely balances the dust derived si input flux by 4100 ka extremely refractory elements such as nb which are concentrated in soils by residual enrichment processes are much less readily impacted by dust addition although dust has had a pronounced impact on sr and nd isotopic budgets and on soil mineral composition at the 150 ka site dust cannot have contributed 4 of the total nb contained in this soil profile

kerogen asphaltene sulfur relationships in sulfur rich monterey oils abstract monterey oils in the santa maria basin onshore and offshore are generally low maturity oils because of low thermal exposure relatively shallow burial for short times they are generated as heavy high sulfur oils because of the composition of the unusual type ii source kerogens which are exceptionally rich in organic sulfur 8 14 these high sulfur kerogens which we designate type ii s appear to generate oil at significantly lower thermal exposures than ordinary type ii kerogens with less than 6 s in contrast to common type ii kerogens which generate oil largely by cleavage at oxygen bridge groups and carbon carbon bonds eliminating co2 h2o and hydrocarbon fragments type ii s kerogens have an additional complement of weak bonds associated with bound sulfur the preferential cleavage at weak sulfur linkages tends to produce larger fragments leading to high initial amounts of asphaltenes resins and sulfur rich aromatics together with smaller amounts of saturated hydrocarbons elemental analyses of monterey kerogens and asphaltenes clearly support the concept that the asphaltenes are essentially fragments of kerogen cleaved sufficiently to be soluble or peptized in this heavy oil system solubilization of asphaltenes is attributed to their interactions with the abundant resins and aromatics this sysstem is sufficiently stable under source and reservoir conditions to allow expulsion and migration for reasonable distance without significant fractionation or changes in gross properties initial asphaltenes have essentially the same atomic h c ratios as the source kerogen but have significantlyy lower o c ratios and slightly lower s c ratios the n c ratios are nearly the same for kerogens and their derived asphaltenes with increasing maturity the h c ratios in asphaltenes decrease much like maturation changes in kerogen the s c ratio also decreases significantly however the o c ratios initially low in asphaltenes and n c ratios increase slightly due to material balance caused by other losses these element composition and atomic ratio relationships allow some important inferences concerning source kerogen composition from analysis of asphaltenes alone this can be useful when potential source rock samples are not available for analysis and or when a choice between alternate source rock possibilities must be made

kerogen origin evolution and structure kerogen commonly defined as the insoluble macromolecular organic matter om dispersed in sedimentary rocks is by far the most abundant form of om on earth this fossil material is of prime importance as the source of oil and natural gas moreover kerogen can provide essential information on major topics such as past environments climates and biota this review reports the main advances in kerogen studies since the comprehensive synthesis edited by durand durand b ed kerogen insoluble organic matter from sedimentary rocks editions technip paris 1980 it is organized into eight sections the first two are concerned with the successive definitions of kerogen and the definition used here the different techniques used for kerogen isolation without loss or degradation and basic kerogen analysis the third and fourth focus on sedimentary om sources and preservation processes in relation to depositional environment including sedimentation conditions favourable for kerogen accumulation and extrapolation to past geological time great strides have been made in the latter topics over the last 25 years owing to a combination of classical studies in organic geochemistry and studies in other domains such as biogeochemistry oceanography hydrology and soil science along with the development of powerful analytical tools the next two sections deal with the different kerogen classifications by type and kerogen evolution and maturation upon burial in sediments structural modelling of coal and kerogen based on physical and or chemical structural analysis is described in the following section although only statistical the models thus derived provide a synthetic view of the main structural resemblances and differences among various samples in relation to source maturity or physicochemical properties finally the last section explores some of the advances in kerogen understanding expected for the near future the review includes a list containing about 500 references

mu radar and lidar observations of clear air turbulence underneath cirrus abstract turbulence generation mechanisms prevalent in the atmosphere are mainly shear instabilities breaking of internal buoyancy waves and convective instabilities such as thermal convection due to heating of the ground in the present work clear air turbulence underneath a cirrus cloud base is described owing to coincident observations from the vhf 46 5 mhz middle and upper atmosphere mu radar a rayleigh mie raman rmr lidar and a balloon radiosonde on 7 8 june 2006 at shigaraki japan 34 85 n 136 10 e time height cross section of lidar backscatter ratio obtained at 2206 lt 7 june 2006 showed the presence of a cirrus layer between 8 0 and 12 5 km msl downward penetrating structures of ice crystals with horizontal and vertical extents of 1 0 4 0 km and 200 800 m respectively have been detected at the cirrus cloud base for about 35 min at the same time the mu radar data revealed clear air turbulence layers developing downward from the cloud base in the environment of the protuberances

cenomanian turonian organic sedimentation in north west africa a comparison between the tarfaya morocco and senegal basins abstract the cenomanian turonian oceanic anoxic event was recognised in north western africa in various depositional settings from abyssal areas to continental shelves to derive information on environmental conditions in these different settings and define a depositional model a petrographical and geochemical study of the organic matter was performed on sediments from the tarfaya morocco and senegal basins the results obtained for these two locations were compared to those of previous studies namely from dsdp wells petrographic and geochemical data allow the differentiation of two main organofacies a shallow depositional facies continental shelf is characterised by low total organic carbon toc contents the second organofacies deposited in the deep marine environment slope and abyssal shows a high toc content 7 the predominance of fluorescing amorphous om combined with high hi values suggests good preservation conditions the s c ratio 0 36 and abundance of organic sulphur compounds support this interpretation and indicate a development of anoxic conditions to explain the organic contrast between both environments a depositional model has been developed which is based on limited water exchange between both depositional settings the main factor which has determined black shale sedimentation is the restricted water circulation related to the presence of isolated depositional environment during atlantic ocean opening compared to present upwelling zones the palaeoproductivity in the studied area was relatively moderate during cenomanian turonian and seems not to be the only determining factor of organic matter accumulation

quantification of the transient response to base level fall in a small mountain catchment sierra nevada southern spain 1 we integrated optically stimulated luminescence dating and 10be cosmogenic nuclide measurements to quantify short to medium term 102 104 years catchment dynamics and response to active tectonics in the 27 km2 rio torrente catchment sierra nevada southern spain rapid base level fall has triggered knickpoint migration up both trunk and tributary channels resulting in two distinct geomorphic zones 1 a steep lower catchment with concordant rates of hillslope erosion and channel incision over both short 100 years 5 8 mm yr 1 and medium 12 ka 5 1 mm yr 1 timescales and 2 a low relief soil mantled upland topography with uniformly low bedrock and hillslope erosion rates 0 05 0 02 mm yr 1 the uniformity of erosion in this upland surface indicates that catchment topography was previously in steady state rapid river incision below the channel knickpoints has resulted in the development of steep landslide dominated hillslopes that are essentially tracking the incising channel the magnitude of base level fall required to generate these steep hillslopes is 100 m at least 50 m of this base level fall occurred during the past 21 ka these steep hillslopes are eroding back into the low angled upland surface at a much slower rate than the channel knickpoint consequently the trunk channel knickpoint has already reached the catchment headwaters while hillslopes continue to adjust to the new base level indicating that the channel profile will regain equilibrium form long before hillslopes thus hillslopes are the limiting factor for the duration of landscape transience in this small mountain catchment

lidar observations of a breaking mountain wave associated with extreme turbulence observations from a doppler lidar which are enhanced by stratospheric aerosols from mount pinatubo s eruption provide unique measurements of mountain waves over the rocky mountains including nearly instantaneous observations of wave breaking in the lower stratosphere the wave breaking is revealed by a flow reversal aloft that marks a localized critical layer created when the wave amplitude was great enough to cause overturning the altitude spatial scale and duration of this wave induced critical layer are documented the mountain waves led to turbulence affecting commercial aircraft including one accident in which a cargo jet lost an engine and part of a wing in extreme turbulence at the same time the lidar was making observations nearby although earlier observations of mountain wave drag assumed wave stationarity over 3 5 h significant changes over less than 2 h are documented here such nonstationarity could contribute to discrepancies remaining between observations and simulations of mountain wave drag

indirect climatic control of the clay mineral composition of quaternary sediments from the cariaco basin northern venezuela odp site 1002 abstract variations in the clay mineral composition of mid late quaternary sediments recovered from the cariaco basin are interpreted in terms of changes in paleoclimate the results indicate the changing contribution of regional and local sediment sources during interglacial high stands vs glacial low stands the relative contribution of illite increases during interglacial stages and decreases during glacial stages illite smectite shows a much weaker negative relationship to glacial eustacy the abundances of kaolinite and chlorite show no correlation with paleoclimate sediments sourced from rivers adjacent to the cariaco basin contain low illite and provide a significant influx of illite smectite during low sea level stands but during interglacial periods they are probably deposited on the shallow continental shelf bordering the local coastline clays sourced from the amazon and orinoco rivers are richer in illite and their contribution is reduced in times of low sea level stands as the continental shelf becomes much narrower and sediment is discharged directly onto the continental rise during the last glacial period changes in clay mineral composition were magnified relative to previous glaciations possibly due to tectonic evolution of the region the sill depth between the cariaco basin and the open caribbean sea was reduced to a minimum decreasing further the relative importance of the amazon orinoco contribution

from a black to a gray box a mass balance interpretation of pedogenesis we utilize chemical elements as tracers in a mass balance analysis that provides functional relationships among soil chemical composition bulk density and volume change in relation to parent material these analytical functions are based on the principle of conservation of mass and include a term quantifying mass flux into out of the soil and between horizons we apply the technique to the oldest member of a chronosequence developed on marine terraces in northern california it is an alfisol that evolved from beach sand to its present state nearly one third of its weight is composed of secondary clay minerals in about 240 ky aside from large increases in organic carbon desilication is the dominant factor in soil evolution 29 50 83 g cm 2 si was leached from the beach sand during pedogenesis the rate of desilication is roughly 2 1 t km 2 yr 1 0 21 g cm 2 ky 1 an order of magnitude slower than that implied by the si denudation rate calculated for the mattole river watershed weathering of primary minerals and synthesis of secondary minerals is relatively well advanced suggesting that the rate of desilication may be declining the local beach is composed of quartz and sodic plagioclase with smaller amounts of chlorite mica and kaolinite the soil has substantially different mineralogy sand is dominated by quartz and clay is dominated by kaolinite halloysite chloritic intergrades and gibbsite bases are also leached though the total mass was much less 57 2 55 g cm 2 of na in the beach sand was lost as plagioclase weathered by focusing on elemental and mineralogical gains and losses we emphasize the essential connection between the pedologic environment and the external hydrochemical environment

denudation processes and rates in the transverse ranges southern california erosional response of a transitional landscape to external and anthropogenic forcing 1 quantification of denudation in the transverse ranges of california permits reconstruction of spatial and temporal variations in erosion that represent both the response and evolution of interacting hillslopes and channels on the southern front of the san gabriel mountains observational records of the infilling of debris basins and dams define twentieth century landscape erosion rates averaging 1 6 and 0 9 mm yr 1 respectively although all major sediment transport occurs during intense winter storms debris production on hillslopes is greatly enhanced by recurrent fires consequently in this populated region anthropogenic fires have augmented the natural erosion rates we perform a global inversion to estimate the role of precipitation intensity burned areas and local slope on catchment denudation rates after subtracting the effects of anthropogenic fires we estimate landscape denudation rates given natural fire ignition rates increased fire during the past century has augmented sediment production in debris basins by an average of 60 and individual basins show increases up to 400 to identify the dominant hillslope erosion processes the volumetric contribution of landslides was estimated using repeat aerial photographs for the same time interval over which the debris basins have been operative between 1928 and 1973 landsliding produced only 10 of the sediment in debris basins even in the long term when infrequent but volumetrically important landslides occur bedrock landslides appear to contribute a maximum of 50 to the long term landscape denudation previous mapping of soil slippage in the san dimas experimental forest within the san gabriel mountains rice et al 1969 rice and foggin 1971 indicates that shallow landsliding is likely to be the dominant modern hillslope erosion process when compared to incision rates derived from a fluvial shear stress model and to exhumation rates based on low temperature thermochronological data blythe et al 2000 modern natural erosion rates are comparable to denudation rates since the pliocene comparisons of modern erosion rates suggest that debris production on hillslopes and first order channels is directly dependent on vegetation cover and precipitation intensity for higher order channels drainage areas 2 km2 only major storms convey the sediments down valley during the past century some temporal decorrelation occurs between small scale and large scale catchments because hillslope produced sediment is stored in second order and higher channels until major storms mobilize it thus the larger fluvial network damps the episodic fire induced hillslope sediment pulses that occur within small watersheds at a longer temporal scale however uplift and denudation may have been sustained sufficiently long in much of the san gabriel mountains for the topography to reach a macroscale steady state in contrast to rapidly eroding 2 mm yr 1 ranges for which quantification of bedrock landsliding will approximate the sediment flux the san gabriel mountains occupy a niche of intermediate rates 0 1 1 0 mm yr 1 in which a broad suite of hillslope processes including shallow seated and deep seated landslides debris flows and wet and dry ravel contribute to the sediment flux

enhanced trapping of molybdenum by sulfurized marine organic matter of marine origin in mesozoic limestones and shales there have been many studies devoted to trace metals and their value in assessing the paleoredox conditions of ancient marine deposition among them molybdenum mo is frequently cited as an effective proxy for sediments and sedimentary rocks recently helz et al helz g r miller c v charnock j m mosselmans j l w pattrick r a d garner c d vaughan d j 1996 mechanisms of molybdenum removal from the sea and its concentration in black shales exafs evidences geochim cosmochim acta 60 3631 3642 and adelson et al adelson j m helz g r miller c v 2001 reconstructing the rise of recent coastal anoxia molybdenum in chesapeake bay sediments geochim cosmochim acta 65 237 252 suggested that mo does not behave conservatively in the water column when h2s reaches a threshold concentration above this concentration a switch operates and mo is scavenged by forming bonds with metal rich notably iron particles sulfur rich organic molecules and pyrite in this paper mo trapping by sulfur rich organic matter om in ancient marine deposits is emphasized the following mesozoic geological formations were selected for study because of their relatively high concentration of sulfurized om the akkuyu formation turkey the calcaires d orbagnoux france and kimmeridge clay uk and its timeequivalent in boulonnais france the kashpir oil shales russia and the la luna formation venezuela the sulfur rich om is identified by either measured organic s abundance or kerogen microscope observation our results show that mo is systematically more enriched relative to the other redox sensitive sulfide forming elements studied u v ni cu zn cr and mo enrichment is positively correlated with the amount of sulfurized om but not with pyrite abundance these results illuminate the role played by sulfurized om in geologic scale mo capture and retention but they also underline the role played by reactive iron significant om sulfurization is only possible when reactive iron is limited nevertheless pyrite formation though limited could act as an initial mo trap prior to mo uptake by om that is sulfurized after the pyritization step in future paleoenvironmental reconstructions attention must be paid to this enhanced mo enrichment in the presence of sulfurized organic matter in such cases the use of mo could lead to overestimation of the reducing conditions of the depositional environment

polarimetric doppler radar observations of kelvin helmholtz waves in a winter storm abstractkelvin helmholtz waves were observed by the twin lakes oklahoma ktlx weather surveillance radar 1988 doppler wsr 88d the norman oklahoma koun polarimetric wsr 88d and the polarimetric collaborative adaptive sensing of the atmosphere casa radars on 30 november 2006 during a winter storm in central oklahoma the life cycle and structure of the waves are analyzed from the radar data and the nearby atmospheric conditions are examined the initial perturbations associated with the waves are first evident only in the radars radial velocity fields as the waves mature perturbations become discernable in the reflectivity factor z and spectrum width sw fields of both radars and in the differential reflectivity zdr and to a lesser extent the cross correlation coefficient hv fields of koun as the waves break and begin to dissipate the perturbations subside a dual doppler analysis is synthesized to examine the kinematic structure of the waves and to relate the polarimetric observation

observations of kelvin helmholtz instability at a cloud base with the middle and upper atmosphere mu and weather radars 1 using the very high frequency 46 5 mhz middle and upper atmosphere radar mur ka band 35 ghz and x band 9 8 ghz weather radars a kelvin helmholtz kh instability occurring at a cloud base and its impact on modulating cloud bottom altitudes are described by a case study on 8 october 2008 at the shigaraki mu observatory japan 34 85 n 136 10 e kh braids were monitored by the mur along the slope of a cloud base gradually rising with time around an altitude of 5 0 km the kh braids had a horizontal wavelength of about 3 6 km and maximum crest to trough amplitude of about 1 6 km nearly monochromatic and out of phase vertical air motion oscillations exceeding 3 m s 1 with a period of 3 min 20 s were measured by the mur above and below the cloud base the axes of the billows were at right angles of the wind and wind shear both oriented east north east at their altitude the isotropy of the radar echoes and the large variance of doppler velocity in the kh billows including the braids indicate the presence of strong turbulence at the bragg 3 2 m scale after the passage of the cloud system the kh waves rapidly damped and the vertical scale of the kh braids progressively decreased down to about 100 m before their disappearance the radar observations suggest that the interface between clear air and cloud was conducive to the presence of the dynamical shear instability by reducing static stability and then the richardson number near the cloud base downward cloudy protuberances detected by the ka band radar had vertical and horizontal scales of about 0 6 1 1 and 3 2 km respectively and were clearly associated with the downward air motions observed oscillations of the reflectivity weighted doppler velocity measured by the x band radar indicate that falling ice particles underwent the vertical wind motions generated by the kh instability to form the protuberances the protuberances at the cloud base might be either kh billow clouds or perhaps some sort of mamma reflectivity weighted particle fall velocity computed from doppler velocities measured by the x band radar and the mur showed an average value of 1 3 ms 1 within the cloud and in the protuberance environment

the critical role of climate and saprolite weathering in landscape evolution landscapes evolve in response to external forces such as tectonics and climate that influence surface processes of erosion and weathering internal feedbacks between erosion and weathering also play an integral role in regulating the landscapes response our understanding of these internal and external feedbacks is limited to a handful of field based studies only a few of which have explicitly examined saprolite weathering here we report rates of erosion and weathering in saprolite and soil to quantify how climate influences denudation by focusing on an elevation transect in the western sierra nevada mountains california we use an adapted mass balance approach and couple soil production rates from the cosmogenic radionuclide crn 10be with zirconium concentrations in rock saprolite and soil our approach includes deep saprolite weathering and suggests that previous studies may have underestimated denudation rates across similar landscapes along the studied climate gradient chemical weathering rates peak at middle elevations 1200 2000 m averaging 112 3 9 7 t km 2 y 1 compared to high and low elevation sites 46 8 5 2 t km 2 y 1 measured weathering rates follow similar patterns with climate as those of predicted silica fluxes modeled using an arrhenius temperature relationship and a linear relationship between flux and precipitation furthermore chemical weathering and erosion are tightly correlated across our sites and physical erosion rates increase with both saprolite weathering rates and intensity unexpectedly saprolite and soil weathering intensities are inversely related such that more weathered saprolites are overlain by weakly weathered soils these data quantify exciting links between climate weathering and erosion and together suggest that climate controls chemical weathering via temperature and moisture control on chemical reaction rates our results also suggest that saprolite weathering reduces bedrock coherence leading to faster rates of soil transport that in turn decrease material residence times in the soil column and limit soil weathering copyright 2009 john wiley sons ltd

strong tectonic and weak climatic control of long term chemical weathering rates the relationships among climate physical erosion and chemical weathering have remained uncertain because long term chemical weathering rates have been difficult to measure here we show that long term chemical weathering rates can be measured by combining physical erosion rates inferred from cosmogenic nuclides with dissolution losses inferred from the rock to soil enrichment of insoluble elements we used this method to measure chemical weathering rates across 22 mountainous granitic catchments that span a wide range of erosion rates and climates chemical weathering rates correlate strongly with physical erosion rates but only weakly with climate implying that by regulating erosion rates tectonic uplift may significantly accelerate chemical weathering rates in granitic landscapes

organic matter in a low productivity anoxic intraplatform basin in the triassic tethys this paper presents isotopic bulk geochemical and biomarker data measured on organic matter accumulated in a narrow extensional basin developed at the oceanward margin of the huge triassic carbonate platform in the alps appenines domain the integration of isotope signatures organic petrographical and biomarker evidence together with the composition of kerogen pyrolysates suggests immature organic matter predominantly of algal origin with a minor but not negligible higher plant derived and moderate bacterial contribution for the entire sequence the mineral sources are dominated by platform derived subtidal dachstein limestone with a minor palaeosol input and a moderate contribution of autochtonous quartz nevertheless parallel variations observed in the mineral content as well as in the amount and the quality of the organic matter reflect variations in the palaeoenvironment the increased humidity existing in the period of the accumulation of the upper section of the sequence led to the restriction of dolomitization a slightly greater higher plant derived contribution in this section is evidenced by the composition of bitumen and the results on gc and gcims analyses on the non aromatic hydrocarbon fraction of bitumen moreover the climate induced weathering enchanced the primary productivity and resulted in a pronounced increase in the toc content the average estimated value of the planktonic productivity is about three times higher for the calcite rich sequence than the dolomite rich one being 44 2 and 15 3 tc org m 2 ma respectively the low to moderate planktonic productivity shows that anoxic conditions observed for the entire succession are a consequence of the stagnant water stratification rather than high planktonic productivity depth trends in the data measured on kerogens hi oi 13 corg values composition of pyrolysate together with the 18 o excursions and 13 c values appear to be controlled by sea level fluctuations consistent with the high abundance of alkyltiophenes in kerogen pyrolysates the high s org c ratios ranging between 0 05 and 0 10 suggest the importance of natural sulfurization in the formation of the sulfur rich type ii s kerogen occurring in all of the samples

quantification of chemical weathering rates across an actively eroding hillslope abstract chemical weathering rates for landscapes are difficult to quantify because the timescales over which weathering occurs are often unknown in this study we use timescales defined by prior cosmogenic nuclide analyses and a suite of geochemical measurements to calculate weathering rates in saprolite and soil and to determine how these rates vary across an eroding hillslope we also estimate the relative contributions of solute and erosional mass loss to landscape lowering analyses were conducted on a soil mantled hillslope developed on a granodiorite pluton in southern nsw australia mass loss in solution accounts for 35 to 55 of the total mass loss from the hillslope saprolite close to the soil saprolite boundary is less weathered at the ridge than at distance from the ridge the calculated flux of silica from the saprolite is 5 tons km 2 yr 1 and does not vary with distance from the ridge or overlying soil thickness the assumption of steady state but spatially variable erosion rates with a temporally constant thickness of soil and saprolite allows us to calculate the downslope variation in the rate of solute losses soil silica weathering rates initially increase from 12 tons km 2 yr 1 at the ridge crest to 20 tons km 2 yr 1 on the convex region of the hillslope and then decrease to 13 tons km 2 yr 1 by the time soils have been transported 45 50 m soils closer to the surface are more weathered than deeper soils this geochemical stratification suggests that the soil column does not become thoroughly vertically mixed as soils move down slope dependence of solute loss on transport distance may explain the previously noted discrepancy between the observed soil thickness and that predicted based on curvature variation of solute loss with transport distance may also contribute to the linear dependence of soil thickness on distance from the ridge

a high resolution late quaternary upwelling record from the anoxic cariaco basin venezuela results are presented of a high resolution study of the planktonic foraminiferal faunas from two piston cores recovered from the cariaco basin in the southern caribbean sea the cariaco basin is a small anoxic marine basin on the northern continental margin of venezuela in an area today characterized by both seasonal trade wind induced upwelling and pronounced dry and wet seasons our data indicate that large changes in the intensity of upwelling and hence trade wind strength occurred in this region during the last glacial interglacial transition and throughout the holocene during the last glacial lowstand of sea level the cariaco basin was effectively isolated from the open caribbean along its northern margin by the then largely emergent tortuga bank oxic conditions existed in the deep cariaco basin at this time and surface productivity was low about 12 600 years ago the abrupt initiation of strong upwelling over the basin and the onset of permanent anoxia in the deep waters are coincident with the rapid rise of sea level that accompanied the peak interval of meltwater discharge from the laurentide ice sheet into the gulf of mexico strong upwelling between 12 600 and about 10 000 years ago may be related to intensified trade winds resulting in part from cooler sea surface temperatures in the caribbean and gulf of mexico after about 10 000 years ago upwelling intensity was reduced though highly variable a preliminary frequency domain analysis of the holocene portion of the cariaco basin time series suggests that solar forcing may explain a significant component of the century scale variability observed in the record of upwelling and trade wind strength

climatic and tectonic controls on chemical weathering in the new zealand southern alps abstract climatic and tectonic controls on the relative abundance of solutes in streams draining the new zealand southern alps were investigated by analyzing the elemental and sr isotope geochemistry of stream waters bedload sediment and hydrothermal calcite veins the average relative molar abundance of major cations and si in all stream waters follows the order ca2 50 si 22 na 17 mg2 6 k 5 for major anions the relative molar abundance is hco3 89 so42 7 cl 4 weathering reactions involving plagioclase and volumetrically small amounts of hydrothermal calcite define the ionic chemistry of stream waters but nearly all streams have a carbonate dominated ca2 and hco3 mass balance stream water ca sr and 87sr 86sr ratios vary from 0 173 to 0 439 mol nmol and from 0 7078 to 0 7114 respectively consistent with the ionic budget these ratios lie solely within the range of values measured for bedload carbonate ca sr 0 178 to 0 886 mol nmol 87sr 86sr 0 7081 to 0 7118 and hydrothermal calcite veins ca sr 0 491 to 3 33 mol nmol 87sr 86sr 0 7076 to 0 7097 streams draining regions in the southern alps with high rates of physical erosion induced by rapid tectonic uplift and an extremely wet climate contain 10 more ca2 and 30 more sr2 from carbonate weathering compared to streams draining regions in drier more stable landscapes similarly streams draining glaciated watersheds contain 25 more sr2 from carbonate weathering compared to streams draining non glaciated watersheds the highest abundance of carbonate derived solutes in the most physically active regions of the southern alps is attributed to the tectonic exhumation and mechanical denudation of metamorphic bedrock which contains trace amounts of calcite estimated to weather 350 times faster than plagioclase in this environment in contrast regions in the southern alps experiencing lower rates of uplift and erosion have a greater abundance of silicate versus carbonate derived cations these findings highlight a strong coupling between physical controls on landscape development and sources of solutes to stream waters using the southern alps as a model for assessing the role of active tectonics in geochemical cycles this study suggests that rapid mountain uplift results in an enhanced influence of carbonate weathering on the dissolved ion composition delivered to seawater