soil mineralogy trends in california landscapes california s diverse environmental gradients serve as natural experiments for examining controls on soil mineral distribution in landscapes in this paper we use example soilscapes from throughout california to examine how lithology climate topography and duration of pedogenesis interact to produce distinctive weathering environments and characteristic suites of soil minerals seven soil geomorphic sequences were assembled from the literature to illustrate major soil mineralogical trends 1 granitic terrain of the peninsular ranges 2 granitic terrain of the central sierra nevada 3 andesitic terrain of the northern sierra nevada 4 fluvial terraces on the east side of the great valley 5 marine terraces of the central coast 6 ultramafic terrain of the klamath mountains and 7 an alluvial fan in the mojave desert results of this analysis show that kaolin is present in virtually all pedons irrespective of climate parent material age or topographic position kaolin does not form in ultramafic soils due to insufficient aluminum many secondary clay minerals reflect the state s strong climatic influence with palygorskite smectite and vermiculite in the dry hot environments hydroxy interlayered minerals gibbsite and short range ordered minerals in the cool moist environments in arid and semi arid regions the distribution of calcite gypsum and soluble salts is strongly related to patterns of eolian dust deposition and water infiltration and leaching

the role of perched aquifers in hydrological connectivity and biogeochemical processes in vernal pool landscapes central valley california relatively little is known about the role of perched aquifers in hydrological biogeochemical and biological processes of vernal pool landscapes the objectives of this study are to introduce a perched aquifer concept for vernal pool formation and maintenance and to examine the resulting hydrological and biogeochemical phenomena in a representative catchment with three vernal pools connected to one another and to a seasonal stream by swales a combined hydrometric and geochemical approach was used annual rainfall infiltrated but perched on a claypan duripan and this perched groundwater flowed downgradient toward the seasonal stream the upper layer of soil above the claypan duripan is 0 6 m in thickness in the uplands and 0 1 m in thickness in the vernal pools some groundwater flowed through the vernal pools when heads in the perched aquifer exceeded 0 1 m above the claypan duripan perched groundwater discharge accounted for 30 60 of the inflow to the vernal pools during and immediately following storm events however most perched groundwater flowed under or around the vernal pools or was recharged by annual rainfall downgradient of the vernal pools most of the perched groundwater was discharged to the outlet swale immediately upgradient of the seasonal stream and most water discharging from the outlet swale to the seasonal stream was perched groundwater that had not flowed through the vernal pools therefore nitrate nitrogen concentrations were lower e g 0 17 to 0 39 mg l 1 and dissolved organic carbon concentrations were higher e g 5 97 to 3 24 mg l 1 in vernal pool water than in outlet swale water discharging to the seasonal stream though the uplands vernal pools and seasonal stream are part of a single surface water and perched groundwater system the vernal pools apparently play a limited role in controlling landscape scale water quality copyright 2005 john wiley sons ltd

environmental conditions for the presence of magnetofossils in the last glacial maximum inferred from magnetic parameters of sediments from the ulleung basin east sea abstract magnetic characterization of sediments from the ulleung basin in the east sea japan sea was carried out to decipher changes in environmental conditions over the last 39 000 years magnetic susceptibility intensities of natural remanent magnetization nrm anhysteretic remanent magnetization arm partial arm parm and saturation isothermal remanent magnetization sirm were measured for selected samples irm acquisition hysteresis and first order reversal curve forc measurements were made the ratios of rock magnetic parameters such as arm sirm arm and s ratio were determined to identify magnetic grain size and mineralogical variations along with electron microscope observations of magnetic mineral extracts down core variations in rock magnetic parameters for the 5 21 m long sediment core reveal distinct intervals with different grain size concentration and composition of magnetic minerals the uppermost portion and the high magnetic intensity zone hiz in marine isotope stage mis 2 are characterized by higher concentrations of fine grained magnetite whereas the mis 1 and 3 intervals contain lower concentrations of coarser grained magnetic minerals with increasing influence of hematite and or iron sulphide minerals the hiz interval is inferred to contain high occurrences of fine grained bacterial magnetosomes based on geochemical proxies east sea conditions for the hiz interval coincident with the last glacial maximum lgm can be summarized as having low total organic carbon toc enhanced eolian contributions from terrestrial organic particles and iron bearing minerals under the influence of an intensified east asian winter monsoon along with iron reducing but not sulphidic conditions that favoured growth and preservation of magnetotactic bacteria the delicate balance between reductive dissolution of magnetofossils under sulphidic conditions and production and preservation of magnetotactic bacteria in overlying iron reducing sediments for the hiz interval is responsible for the resultant abundance variations of magnetosomes in the studied sediments

unravelling the development of a spheroidally weathered diorite gabbro santa margarita ecological reserve peninsular ranges southern california usa abstract within santa margarita ecological reserve smer southern california an 108 ma diorite gabbro pluton has weathered spheroidally resulting in the formation of concentric rindlets i e a rindlet zone around an unaltered ellipsoidal core of the parent rock to our knowledge little is known about how spheroidal weathering is produced in mediterranean climates like that characteristic of portions of the peninsular ranges hence we undertook a detailed study aimed at determining the textural and chemical changes associated with the spheroidal weathering of the diorite gabbro pluton the parental spheroidally weathered corestone is characterized by a hypidomorphic granular texture and consists primarily of plagioclase amphibole and biotite along with minor amounts of pyroxene and quartz within the corestone sericite and uncommonly calcite and chlorite replace plagioclase the latter mineral also infrequently replaces portions of amphibole and biotite such alteration products are derived from sub solidus deuteric alteration of the pluton xrd clay mineral analysis of the 13 rindlets indicates the presence of mostly kaolinite and vermiculite and a far lesser volume of green smectite thin section study of rindlet samples suggests that vermiculite is derived from the weathering of biotite the most extensively altered mineral in the rindlet zone such alteration is paralleled by statistically significant losses of k mass across the rindlet zone in addition statistically significant losses of ca and na mass across the rindlet zone likely reflect conversion of sericite to kaolinite in contrast the absence of statistically significant losses of mg fe and mn over most of the rindlet zone implies that fluids were mostly oxidizing and that any mg leached from amphibole was likely fixed within smectite while leached fe and mn precipitated out as oxides or oxyhydroxides though calcite was present in the corestone its absence in the rindlets indicates that fluids were sufficiently acidic to dissolve and remove it previous studies have shown that spheroidal weathering occurs when volume expansion produced by a positive v of reaction builds up internal elastic strain energy in the rock for example this type of reaction occurs when iron oxidizes within biotite resulting in an expansion of d 001 from 10 a to 10 5 a or when biotite is transformed into vermiculite leading to an expansion of d 001 from 10 a to 14 a data presented here suggest that the conversion of biotite to vermiculite and the resulting positive v produced the spheroidal fracturing of the corestone at smer hence these and other data discussed in this paper suggest that the weathering of biotite is the primary driving force in the formation of spheroidally weathered corestone in the mediterranean climate of the peninsular ranges

a comparison of synthetic p tau sections for proposed models of two ophiolites analyses of slant stacks of synthetic record sections generated from velocity models for ophiolites by the reflectivity method show that even 90 km long refraction lines having a 10 hz source and a 1 km intertrace spacing barely distinguish between fine scale crustal structures which are of current interest such data are sufficient however to distinguish between young and old oceanic crust tripling the spatial sampling period degrades the quality of the synthetic slant stacks for this temporal frequency content a major implication of the study is that most currently available field data being sparser and poorer in quality due to both noise and instrument responses offer little hope of resolving thin low velocity layers or small changes in velocity gradients by using newly proposed inversion techniques based on slant stacking last a simple first order correction to a downward continuation algorithm namely the inclusion of the phase shift caused by postcritical reflection at each ray parameter is proposed

pedogenetic investigation of soil degradation on a deforested loess hillslope of golestan province northern iran abstract genesis mineralogy and micromorphology of soils formed on a forest and adjacent cultivated loess hillslope were investigated to assess the effects of deforestation and hillslope position on soil properties and the intensity of soil degradation the study revealed that deforestation caused a loss of soil organic carbon a reduction of cation exchange capacity and an increase in carbonates in the surface soil the soils of the different slope positions of the forest land were alfisols and mollisols with well developed argillic horizons speckled b fabric of the argillic horizons and the crystallitic b fabric of the underlying calcic horizon are evidence for a more stable landscape under forest ecosystem downward leaching caused decalcification of the upper horizons and clay movement in the profile formation of the mollic epipedon in the forest land confirms the accumulation of organic carbon and lower erosion in the surface soil soils of the adjacent cultivated area however are less developed and classified as inceptisols and mollisols absence of the mollic epipedon in the shoulder backslope and footslope positions presence of the near surface calcic horizon and absence of argillic horizon in all slope positions are due to severe erosion absence of speckled b fabric in all the slope positions of the deforested land is evidence that downward and surface movements of water have resulted in soil erosion and flooding higher smectite concentrations and occurrence of vermiculite in the forest area indicate favorable moisture availability pedology is an effective way of documenting the adverse effects of land use change especially in the hilly regions

orbital scale stratigraphy and high resolution analysis of biogenic components and deep water oxygenation conditions in the japan sea during the last 640 kyr abstract paleoceanographic conditions in the japan sea changed drastically during the late quaternary in association with orbital and suborbital cycles and glacio eustatic sea level changes however few studies have examined long term sediment records older than 160 ka because of the lack of long and continuous cores and the difficulty in constructing high resolution age models in this study we first constructed an orbital scale stratigraphy of the sediments covering the last 640 kyr by comparing the specmap 18o curve and the 18o curve of planktonic foraminifera 18opf in the japan sea together with the combination zones of dominant planktonic foraminifera species then we reconstructed temporal variations in biogenic silica biosil and biogenic carbonate biocarb contents calculated from high resolution major element analysis data determined by an xrf microscanner in order to evaluate the deep water oxygenation conditions we also defined excess s as the difference between the content of s in the sediments and that for normal marine sediments calculated from the organic carbon content corg estimated from lightness l by assuming a total sulfur content stotal corg ratio of 0 36 and examined its variability biosil shows orbital scale variation and is generally low except during interglacial maxima when global sea level was high enough to allow a strong influx of the tsushima warm current biocarb shows orbital and suborbital scale variations and tends to be higher in dark layers deposited during glacial stages whereas the relationship is reversed during interglacial stages the low biocarb in dark layers deposited during interglacial stages is probably due to dissolution of biogenic carbonate caused by the increase in surface productivity as a result of the strong influx of nutrient rich east china sea coastal water and consequent increase in surface productivity and decomposition rate of organic matter in the intermediate water excess s tends to be higher in thicker dark layers deposited during glacial maxima when the sea level dropped below 90 m compared to adjacent light layers suggesting development of euxinic deep water conditions during these periods the results demonstrated the presence of orbital and suborbital scale variations in biosil and biocarb and their association with dark and light layers in the japan sea that reflect variations in the nature and strength of inflow through the tsushima strait controlled by both climatic and sea level changes whereas higher excess s reflects the development of euxinic deep water condition during glacial maxima in association with glacio eustatic sea level drops below 90 m during the last 640 kyr

chemical weathering of a marine terrace chronosequence santa cruz california i interpreting rates and controls based on soil concentration depth profiles abstract the spatial and temporal changes in element and mineral concentrations in regolith profiles in a chronosequence developed on marine terraces along coastal california are interpreted in terms of chemical weathering rates and processes in regoliths up to 15 m deep and 226 kyrs old quartz normalized mass transfer coefficients indicate non stoichiometric preferential release of sr ca na from plagioclase along with lesser amounts of k rb and ba derived from k feldspar smectite weathering results in the loss of mg and concurrent incorporation of al and fe into secondary kaolinite and fe oxides in shallow argillic horizons elemental losses from weathering of the santa cruz terraces fall within the range of those for other marine terraces along the pacific coast of north america residual amounts of plagioclase and k feldspar decrease with terrace depth and increasing age the gradient of the weathering profile bs is defined by the ratio of the weathering rate r to the velocity at which the profile penetrates into the protolith a spreadsheet calculator further refines profile geometries demonstrating that the non linear regions at low residual feldspar concentrations at shallow depth are dominated by exponential changes in mineral surface to volume ratios and at high residual feldspar concentrations at greater depth by the approach to thermodynamic saturation these parameters are of secondary importance to the fluid flux qh which in thermodynamically saturated pore water controls the weathering velocity and mineral losses from the profiles long term fluid fluxes required to reproduce the feldspar weathering profiles are in agreement with contemporary values based on solute cl balances qh 0 025 0 17 m yr 1 during saturation controlled and solute limited weathering the greater loss of plagioclase relative to k feldspar is dependent on the large difference in their respective solubilities instead of the small difference between their respective reaction kinetics the steady state weathering rate under such conditions is defined as r q h m sol m total 1 s v b s the product of qh and the ratio of solubilized to solid state feldspar msat mtotal define the weathering velocity the weathering gradient bs reflects the kinetic rate of reaction where sv is the volumetric surface area of the residual feldspar both this rate expression and the spreadsheet calculations produce similar plagioclase weathering rates r 5 14 10 16 mol m 2 s 1 which agree with those reported for other environments of comparable climate and age weathering dependent concentration profiles are commonly described in literature the present paper provides methods by which these data can yield a more fundamental understanding of the weathering processes involved

reconstruction of environmental changes using a multi proxy approach in the ulleung basin sea of japan over the last 48 ka based on elemental geochemical data we reconstructed the sediment provenance surface productivity and bottom water redox conditions for the last 48 ka in the ulleung basin sea of japan and inferred the factors controlling them al2o3 tio2 ratio and chemical index of alteration cia suggest that sediment provenance changed during the glacial period 48 18 ka compared to the deglacial ca 18 11 ka and holocene mass accumulation rates of total organic carbon toc caco3 phosphorus cadmium and excess barium reveal low paleoproductivity during low sea stand during 18 11 ka productivity increased due to increasing inflow of nutrient rich water masses the oyashio and the east china sea coastal water in tandem with the rising sea level maximum productivity occurred during younger dryas and pre boreal periods when sea level was at 60 m and then gradually decreased as the tsushima warm current inflow kicked off at ca 9 3 ka consistent with other paleoredox proxies which reveal the presence of anoxic bottom water during ca 12 9 ka with the changes in paleoredox proxies and their ratios toc mo u mn c s ratio and uauthigenic and mo contents we hypothesized that the redox changes were mainly ventilation driven and were superimposed on the influence of circulation induced productivity changes the global climate and sea level changes on a millennial timescale play a major role in enhancing paleoproductivity and restrict bottom water advection subsequently driving the oxygenation of bottom water in the ulleung basin copyright 2012 john wiley sons ltd

contributions of water supply from the weathered bedrock zone to forest soil quality one measure of forest soil quality is the ability of the soil to support tree growth in mediterranean type ecosystems such as most of california s forests there is virtually no rainfall during the summer growing season so trees must rely on water stored within the substrate water is the primary limitation to productivity in these forests many forest soils in california are relatively thin but are underlain by thick zones of weathered bedrock weathered granitic bedrock the most prevalent lithology has available water capacities 0 12 cm water cm rock that approach those of soils 0 2 cm water cm soil and because the weathered rock zone is usually so much thicker several meters than the soil 1 m it almost always constitutes the larger storage reservoir for plant available water the weathered bedrock retains the original rock fabric and is friable and easily excavated but the primary minerals are not thoroughly altered to clay minerals so it is not considered saprolite roots of ponderosa pine pinus ponderosa seedlings penetrate through the soil and encounter weathered bedrock within the first 2 years on many sites thus the influence of the weathered bedrock zone on plant growth begins early root access to the weathered bedrock is restricted to fractures which are often spaced about 50 cm apart water is extracted from the intervening rock matrix through unsaturated flow toward the root mat in the fractures and by mycorrhizal fungal hyphae that penetrate the rock matrix at one site in the sierra nevada 30 year old jeffrey pine p jeffreyi depleted the soil held water by mid june and relied on water stored in the weathered bedrock until the rainy season began in october in this case the weathered bedrock supplied at least 70 of the water used by the trees during the growing season in the same area we found that thin soils are not a detriment to pine productivity when they are underlain by a thick zone of weathered bedrock in mediterranean type ecosystems the weathered bedrock zone is an essential component of the plant water supply system and is thus an important contributor to forest soil quality

paleotemperature response to monsoon activity in the japan sea during the last 160 kyr abstract paleo sea surface temperatures in the northeastern and southeastern parts of the japan sea were reconstructed for the last 160 kyr using alkenone temperatures u k 37 temperatures u k 37 temperatures at two sites show distinct glacial interglacial changes during the last 160 kyr except for the interval corresponding to middle mis 3 to mis 2 on orbital timescales u k 37 temperature tends to be high during mis 5e mis 5c and mis 5a which coincides with the intervals of stronger east asian summer monsoon activity the amplitude of temperature fluctuations in the japan sea is significantly higher than those in the neighboring seas we suggest that the sst variation was amplified by the increasing source water kuroshio water temperature and the changes in the volume transport of the tsushima warm current twc and or the north south oscillation of the sub polar front position within the japan sea millennial scale temperature fluctuations in the japan sea show that the temperature at the northern site was higher than that at the southern site during warmer periods of mis 5 which is called temperature reversal by analogy with modern oceanography the temperature reversal could reflect the enhanced volume transport of the twc and the spatial relationship between the studied site and the branches of the twc which is an essential factor in north south temperature reversal around the eastern japan sea temperature drops were found at 114 ka 111 ka 93 ka 87 ka and 77 ka in mis 5 those events were associated with an increase in organic carbon and alkenone contents and can be correlated with the abundance peaks of ice rafted debris ird at site gh05 1208 in the northern japan sea suggesting that the surface water was cooled by enhanced mixing and consequent upwelling in a stronger winter monsoon regime

surface control of desert pavement pedologic process and landscape function cima volcanic field mojave desert california desert pavement is a distinctive feature widespread across arid lands of the world it plays a dynamic role in geomorphic hydrologic and ecologic processes where desert pavement predominates infiltration is limited and rainfall is delivered as runoff to nearby bare ground areas where shrubs cluster desert pavement surfaces may appear monotonously flat and barren but we have found instead that they are a complex association of landscape and hydrologic elements governed by their surface characteristics previously we identified six unique surface mosaic types that accurately capture the subtle but distinct variations in surface clast arrangements for a desert pavement landscape formed on a single aged basalt flow in the mojave desert we now report that these surface mosaics predict the spatial distribution of fundamental desert vegetation and soil characteristics characteristics of soil morphology and texture the leaching depth of soluble salts percent plant cover and shrub species diversity are remarkably consistent for each mosaic type across a 580 000 year old basalt flow even when measured 1 km apart hydrologic character is distinctly different between desert pavement and bare ground regions and vegetation distributions reflect the spatially heterogeneous soil moisture where desert shrubs cluster on the three bare ground surface mosaics leaching is deep removing most soluble salts to below the 50 cm depth where shrubs are absent or few on the three desert pavement mosaics leaching depths are shallow with soluble salt depth

rates of soil development from four soil chronosequences in the southern great basin abstract four soil chronosequences in the southern great basin were examined in order to study and quantify soil development during the quaternary soils of all four areas are developed in gravelly alluvial fans in semiarid climates with 8 to 40 cm mean annual precipitation lithologies of alluvium are granite gneiss at silver lake granite and basalt at cima volcanic field limestone at kyle canyon and siliceous volcanic rocks at fortymile wash ages of the soils are approximated from several radiometric and experimental techniques and rates are assessed using a conservative mathematical approach average rates for holocene soils at silver lake are about 10 times higher than for pleistocene soils at kyle canyon and fortymile wash based on limited age control holocene soils in all four areas appear to develop at similar rates and pleistocene soils at kyle canyon and fortymile wash may differ by only a factor of 2 to 4 over time spans of several millennia a preferred model for the age curves is not linear but may be exponential or parabolic in which rates decrease with increasing age these preliminary results imply that the geographical variation in rates within the southern great basin mojave region may be much less significant than temporal variation in rates of soil development the reasons for temporal variation in rates and processes of soil development are complexly linked to climatic change and related changes in water and dust erosional history and internally driven chemical and physical processes

foraminiferal records of bottom water oxygenation and surface water productivity in the southern japan sea during 160 15ka associations with insolation changes abstract analyses of the benthic and planktonic foraminiferal record were conducted to understand temporal variations in sea floor oxygenation and surface productivity during periods of dark layer deposition between 160 and 15 ka based on data from sediment core images md01 2407 water depth 932 m from the southern japan sea the dark layers in the core were classified into six types on the basis of benthic foraminiferal assemblages which reflect the nature and amount of organic material on the sea floor as well as the degree of oxygenation of bottom waters three of the dark layer types were deposited in conditions strongly associated with increased surface productivity which correlates with positive or negative peaks of summer insolation in the northern hemisphere during periods of insolation maxima summertime surface productivity was enhanced because of the inflow of nutrient rich surface waters associated with high precipitation in eastern asia caused by intensification of the east asian summer monsoon in contrast relatively sustained organic matter fluxes to the sea floor occurred during insolation minima possibly affected by active vertical mixing when the east asian summer and winter monsoons were both intensified in a given period well oxygenated bottom water environments combined with high surface productivity may have resulted in dark layer deposition because of a combination of strong wintertime water convection and increased summertime surface productivity it is likely that the organic carbon content of sediments underestimates surface productivity during depositional conditions favoring the sedimentary decomposition of organic matter

paleoenvironmental changes in the japan sea during the last 85 000 years five distinct changes in the paleoenvironment of the japan sea within the last 85 000 years are revealed from the sedimentary record of a piston core recovered from the oki ridge changes in both surface and deepwater conditions are registered by changes in lithology calcium carbonate content organic carbon content oxygen and carbon isotope ratios and microfossil assemblages including calcareous nannoplankton diatoms radiolaria and foraminifera between 85 and 27 ka the warm tsushima current did not flow into the japan sea and cold surface water conditions prevailed environments at the seafloor fluctuated between dysaerobic to weakly oxic conditions between 27 and 20 ka freshwater input to the japan sea probably from the huang ho river in china stratified the water column and the severe anoxic conditions eliminated most benthic fauna between 20 and 10 ka the cold oyashio current flowed into the japan sea through the tsugaru strait reestablishing deepwater ventilation shallow water benthic assemblages of the north pacific ocean subsequently colonized the japan sea and occupied the vacant niches of the deep basins between 10 and 8 ka the foraminifer compensation level fcl gradually rose to a depth shallower than 1000 m and bottom conditions changed from dysaerobic to oxic at 10 ka the warm tsushima current started to flow into the japan sea through the tsushima strait to establish the modern oceanographic regime which has existed since 8 ka the eustatic sea level during the last glacial maximum was above the sill depths 130 m of the tsushima and tsugaru straits assuming that tectonic movements at these straits were negligible for the last 20 ka

silt and fine sand fractions dominate k fixation in soils derived from granitic alluvium of the san joaquin valley california abstract much of the previous work on potassium k fixation by soils and pure minerals has focused on k fixation and release by the clay size fraction however in soils containing considerable amounts of silt and sand size k fixing minerals such as vermiculite and hydrobiotite k fixation capacity may be substantial in the coarser size fractions we measured the contribution of clay silt very fine sand vfs and fine sand fs fractions to k fixation in five sierra nevada granitic alluvium soils mineralogy of size fractions was determined by x ray diffraction potassium fixation of the whole soil and size fractions was measured by shaking samples for 1 h with 2 mmol kcl followed by a 30 min extraction with nh4cl smectite and mica were dominant clay fraction minerals vermiculite and hydrobiotite dominated the silt fractions while quartz feldspars amphiboles mica and some vermiculite were present in the vfs and fs fractions soil materials from most soil horizons fixed from about 8 to 95 of added k depth weighted average k fixation by clay fractions ranged from 2 3 to 6 5 mmol kg 1 clay meaning that k was released not fixed on a whole soil basis calculated k fixation was highest in the silt fractions in all ap horizons 0 5 to 3 1 mmol kg 1 soil in subsurface horizons fs fixed 0 04 to 4 6 mmol k kg 1 soil and vfs fixed 0 1 to 3 4 mmol k kg 1 soil whereas silt fractions fixed 0 9 to 5 5 mmol k kg 1 soil overall the highest percentage of added k was fixed by the silt fractions dominated by vermiculite and hydrobiotite in pedons where vfs and fs are dominant these fractions constituted the main locus of k fixation

pedogenic evidence of urmia lake s maximum expansion in the late quaternary abstract the urmia lake recession and the resulting increase in vast barren area around it has been rapid in recent decades and thus has attracted attention of environmentalists and geoscientists alike however evidence for its different strandlines and the largest extension of the lake during the late quaternary has not been reported yet the principal goals of the current research were to figure out pedological evidence of its maximum expansion during the late quaternary and mapping out the different strandlines along the western shores of urmia lake over time thirty two soil pedons at different landscape positions geomorphic surfaces and distances from urmia lake were studied during autumn in 2013 and 2014 micromorphological and mineralogical studies were performed for some diagnostic horizons results showed along the transect under study three different entities diagnostic of the lake s history 1 lithological discontinuities 2 saline lacustrine sediments 3 buried soils however almost 2 km from the closest pedon to the lake no evidence of saline playa sediments were detected based on previous chronology results from urmia lake which indicated high lake levels with very low salinity since about 180 ky bp the sediments of this part of the study area were considered to have been deposited at the same period of time indicating a maximum expansion of urmia lake during the late quaternary the current results demonstrate that soil pedons which were situated at various distances from urmia lake denote different stages of the lacustrine evolution along with the distance from the lake the development of soils increases due to a longer and more intensive impact of pedogenic processes on the topstratum the overall soil system becomes more mature the study of buried soils and their comparison to upper non buried soils revealed that in some cases the buried soils were more evolved than their upper soils or vice versa through these observations the periods of exposure to soil forming processes after each sedimentation period was detected and schematic diagrams illustrating periods of highstands and lowstands recessions of urmia lake were reconstructed this study demonstrates that even though multiple episodes of lake recession were apparent the level of urmia lake increased during hydroclimatic events conducive to lake expansion which affected the soil evolution due to several fluctuations during the late quaternary

paleoenvironmental changes in the east japan sea during the last 48 ka indications from high resolution x ray fluorescence core scanning paleoceanographic changes in the east japan sea during the late quaternary based on high resolution elemental variations particularly correlations between dark light laminations and millennial scale climatic changes have remained poorly understood because of the lack of the high resolution proxies the recent application of micro x ray fluorescence xrf core scanning provides the potential for high resolution study on the laminations deposited in the east japan sea in this study we present a geochemical study by using micro xrf core scanning on a 730 cm core recovered from the east japan sea elemental variations and factor analysis indicate that the sedimentary environment changed from anoxic to suboxic conditions from marine isotope stage mis 2 3 to mis 1 which is induced by increased contribution of high salinity sea water from the open ocean due to the rising sea level the dark and light laminations during mis 2 3 were correlated with dansgaard oeschger cycles and summer monsoon proxy with dark colored sediments related to higher terrigenous concentration corresponding to warm moist and enhanced summer monsoon period during the interstadial period more terrigenous sediments were transported to the east japan sea via the strengthened fluvial discharge from the surrounding continents caused by enhanced monsoon rainfall thus the development of the east asian summer monsoon and consequent variations in fluvial discharge would have significantly affected the paleoceanographic conditions in the east japan sea during the mis 2 3 sea level lowstand copyright 2012 john wiley sons ltd

carbon sulfur plots to show diagenetic and epigenetic sulfidation in sediments abstract organic carbon vs sulfide sulfur plots are now being used regularly by many geochemists to help understand recent and ancient depositional environments and diagenetic processes usually these plots are useful to recognize nonmarine vs marine environments or oxic vs anoxic vs euxinic depositional environments however c vs s plots can also indicate diagenetic and epigenetic events that produce excess sulfide four new examples are presented and discussed

genetic interpretations of elemental and chemical differences in a soil chronosequence california abstract soils developed on fluvial terraces in central california have similar parent materials climatic settings vegetation cover and slopes but range in age from 40 000 to 3 000 000 years the soils have chemical compositions that change systematically with increasing age such chemical differentiation is most likely the result of long term weathering and mineralogical transformations that occurred since deposition of terrace fills and stabilization of the geomorphic surfaces the changes in composition with time closely mimic other studies on mineral weathering in which alkali and alkali earth elements are lost more rapidly than transitional elements the relative rates of element loss were determined by changes in element ratios over time net losses and gains of elements in different size fractions were monitored by their concentrations relative to zr the most stable constituent both sand and finer size fractions have lost considerable amounts of ca mg na and k aluminum appears to have been lost from the sand fraction and gained in the fine fraction over a 3 million year time span although there is no evidence for losses of fe and ti from sands there is a net influx of fe and ti into finer fractions probably gained from undetectable yet significant weathering of sand grains etching of sand grains clay mineralogy and microprobe analyses also indicate that the soils have undergone these chemical transformations during their formation mineralogical analyses also mimic other studies on mineral weathering in which the pyroxenes weather more rapidly than hornblende which weathers more rapidly than sphene or zircon

paleozoic continent ocean transition in the ouachita mountains imaged from passcal wide angle seismic reflection refraction data a wide angle reflection reflection experiment sponsored by the program for array seismic studies of the continental lithosphere passcal was conducted in the ouachita mountains area of southwestern arkansas and northwestern louisiana this experimental employed 400 state of the art seismic recorders and overlapped the southern one third of the cocorp consortium for continental reflection profiling deep seismic reflection profile in the area a wide variety of data processing and interpretation techniques was employed to derive an earth model from these data the model depicts a preserved early paleozoic continental margin buried beneath allochthonous paleozoic strata and younger sedimentary rocks the southern part of the model indicates the presence of oceanic or highly extended continental crust overlain by about 15 km of mostly paleozoic sedimentary rock these results are consistent with little if any shortening of crystalline continental crust during the ouachita orogeny

soil parent material relationship in a mountainous arid area of kopet dagh basin north east iran abstract the effects of parent rock types on soil evolution in arid areas were studied in a sequence of soils derived from different lithologies in the kopet dagh basin northeastern iran using micromorphology clay mineralogy magnetic susceptibility and physico chemical properties the selected parent rocks and associated soils were shale haplocalcids claystone haplotorrerts gypsiferous marl haplogypsids limestones haplocalcids and torriorthents siltstone and sandstones torriorthents the results showed that the properties and development of soils were mainly affected by grain size and mineralogy of parent materials soil magnetic susceptibility lf variations were attributed to the types of parent material and pedogenic processes redistribution of calcite and gypsum in soil profiles and natural and pedogenic formation of ferrimagnetic minerals were responsible for lf variations the soils clay mineral origins were found to be mainly of inheritance from parent materials smectite was the dominant clay mineral of the most soils based on the micromorphological index of soil evolution miseca the soils studied were categorized into weakly developed orthents weakly to moderately developed aridisols gypsids and calcids and moderately developed soils including calcids and torrerts the degree of microstructure development alteration of weatherable minerals and calcitic features were the most important criteria influencing assessment of soil development degree by miseca index the vertic features were only observed in soils of claystone in which there were considerable amounts of clay and smectite high amounts of gypsum and low smectite content were mainly responsible for the lack of vertic behavior in other fine grained soils derived from shale and marl

soils on igneous and metavolcanic rocks in the sonoran desert of baja california mexico soils were examined on the widespread volcanic plutonic and metavolcanic rocks within the sonoran desert of baja california in order to focus on in situ weathering and pedogenesis most of the soils studied were on stable nearly level summits the combination of summit landscape positions and the aridic moisture regime tended to yield shallow soils yet these soils display features of strong morphologic development including eluvial horizons subsoil clay increases strong blocky and prismatic structure reddish hues and illuviation and stress argillans soils derived from volcanic materials are paleargids with clayey natric horizons saline subsoils and petrocalcic horizons soils on granodiorite and metavolcanic rocks are loamy haplargids that are neither saline nor sodic and are entirely noncalcareous the granodiorite derived soils had ph values as low as 4 0 apparently the result of metal sulfide weathering in the hydrothermally altered ore bearing rock torripsamments have formed in the reworked mantle of grus on an extensive tonalite pediment despite the variety of parent materials smectite and kaolin are ubiquitous in the clay fraction of the soils the smectites are dioctahedral and are neoformed and or transformed from biotite or chlorite depending on the parent material the kaolin is l largely the result of feldspar weathering a paleargid on rhyolite contained abundant palygorskite in the clay and silt fractions particularly in association with the petrocalcic horizon in all of the soils oxalate extractable si plus al was 1 of the fine earth fraction most of the soils contained 2 3 dithionite extractable fe but fed values were as high as 11 in the soil on metavolcanic rock goethite and hematite are the dominant fe oxides judging from low feo fed ratios and 1oyr 2 5yr soil hues only the soils on basalt and rhyolite were calcareous but the amount of caco3 in the soils was unrelated to the ca content of the rock since these two rocks contained the most and the least amounts of ca respectively of the five rock types represented in the study apparently cac03 accumulation in the soils is more dependent on dust contributions possibly from nearby calcareous plays and fluvial sediments than on in situ mineral weathering

cocorp seismic reflection profiling in the ouachita mountains of western arkansas geometry and geologic interpretation cocorp seismic reflection profiling in the ouachita mountains of western arkansas indicates that 1 carboniferous foreland basin deposits within the arkoma basin thicken dramatically toward the south reaching an aggregate thickness in excess of 12 km 4 5 s two way travel time beneath the southern edge of the frontal thrust zone 2 evidence for northward directed low angle thrusting within this clastic sequence is prominent with a probable decollement surface lying at or near the contact with underlying early paleozoic shelf carbonates 3 beneath the benton uplift a sequence of discontinuous events defines a broad antiform cresting at approximately 7 km 2 8 s this structure appears to mimic the anticlinorial shape of the benton uplift indicated by the surface outcrop pattern 4 beneath the southern ouachitas south dipping stratified events are observed to depths in excess of 14 km 5 0 s 5 deeper in the section a prominent gently north dipping reflection occurs at approximately 22 km depth 7 6 s beneath the northern coastal plain southern ouachitas extrapolation of data along strike in the ouachita belt and consideration of large scale structure observed in other collisional orogenic belts suggest that the reflection events observed beneath the benton uplift represent early paleozoic shelf carbonates correlative with those that floor the arkoma basin to the north this interpretation requires that the early paleozoic deep water sediments exposed in the core of the ouachitas be allochthonous and also implies significant basement uplift beneath the core zone to the south the prominent package of layered reflections occurring beneath the southern ouachitas and northern coastal plain indicates that a significant portion of the crust in that region is composed of imbricate sedimentary and or metasedimentary strata at relatively shallow levels these strata are correlative with the carboniferous flysch cropping out in the southern ouachitas and at somewhat deeper levels they are correlative with the early to middle paleozoic deep water sediments exposed on the benton uplift

structure of the lower crust beneath the carolina trough u s atlantic continental margin data from three large offset seismic profiles provide information on the crustal structure beneath the carolina trough the profiles obtained by the u s geological survey the naval oceanographic research development agency and the scripps institution of oceanography in 1985 were oriented parallel to the trough and were located 1 seaward of the east coast magnetic anomaly ecma which is generally thought to represent the boundary between oceanic and continental crust 2 along the axis of the trough between the ecma and the hinge zone which is thought to reflect the landward limit of highly stretched and altered transitional crust and 3 along the carolina platform landward of the basement hinge zone on crust thought to have been thinned only slightly during rifting these data constrain the velocity structure of the lower crust and provide evidence for a thick lens of high velocity 7 1 km s lower crustal material that extends beneath the carolina trough and the adjacent ocean basin this lens reaches a maximum thickness of about 13 km beneath the deepest part of the trough thins to about 5 km seaward of the ecma and is either very thin or absent landward of the hinge zone it is interpreted to represent material that was underplated beneath and or intruded into the crust during the late stage of continental rifting and that led to an anomalously thick plutonic layer during the early seafloor spreading phase these data thus support the recent conclusions of white et al 1987b and mutter et al 1988 that the initiation of seafloor spreading is attended in many if not most cases by the generation of an anomalously large volume of melt

velocity structure of reflective lower crust beneath the grand banks of newfoundland a seismic refraction experiment using air guns and ocean bottom seismometers was carried out on the southern grand banks in order to study the velocity structure of highly reflective lower crust observed on a previous deep multichannel reflection profile the data were analyzed by interactive forward modeling of travel times and amplitudes wide angle normal moveout analysis and downward continuation of slant stacks laterally varying structure was used in the final stage of modeling the results indicate an upper crust with a p velocity of 6 0 6 2 km s a zone of high velocity gradient from about 19 to 24 km depth and a lower crustal velocity of 6 6 6 8 km s moho is at 29 km the depth of the transition zone is uncertain by 2 or 3 km and its detailed velocity structure is not well resolved however the top of the zone corresponds approximately to the onset of reflectivity while the lower crustal layer is characterized by more coherent and continuous reflections a thin 1 km localized high velocity around 7 2 km s layer is tentatively correlated with one of the reflectors in the lower crust bulk anisotropy of the lower crust is less than 5 the presence of well defined high velocity layers and the lack of anisotropy tend to support mafic intrusion as the mechanism for reflectivity in the lowest part of the crust however there is no evidence of a thick high velocity underplated layer at the base of the crust

variations in osl components from quartz from japan sea sediments and the possibility of reconstructing provenance abstract osl components from quartz from two sediment cores md01 2407 and kt94 15 pc5 from the japan sea are analysed and the results are compared with the electron spin resonance esr intensity of e 1 center of quartz and the grain size of the detrital component of the sediments the osl components of quartz from japanese granites and rhyolites of different ages are also analysed to investigate the relationship between the host rock age and the relative composition of osl components in quartz all these data are then used to examine the potential of reconstructing the provenance of the sediments the results suggest that the ratio of the fast component to the sum of fast and medium f f m appears to increase with increasing host rock age it is suggested that the f f m ratio in sedimentary quartz can be used as an indicator of source rock age

reconstructing a high paleolatitude mesozoic paleoenvironment from a truncated and deeply buried regolith norwegian north sea abstract the paleoregolith in this study was unconformably overlain by lower cretaceous valanginian marine deposits of the asgard formation and buried below two kilometers of sediments on the utsira high norwegian north sea the upwards intensification of chemical alteration manifested in the replacement of feldspars by clays leaching of base cations and reduced mechanical rock strength in addition to the presence of terrestrial biotitic features suggested weathering during subaerial exposure of the utsira high during the mesozoic the paleoregolith can be divided into three weathering facies altered coherent rock saprock and saprolite whereas the absence of true soil horizons suggested erosional truncation of the regolith before burial possible remnants of the eroded soil were identified as pedogenic mud aggregates in the overlying asgard formation bearing similar compositional characteristics as the saprolite clay mineralogy bulk geochemical composition micromorphology and depth of biotic features were used to reconstruct the paleoenvironmental conditions that prevailed during the formation of the regolith in the mesozoic north sea our results point to a regolith formation under periodically water restricted conditions promoting the co existence of interstratified illite smectite beidellite and kaolinite deep presence of endomycorrhizae the fungal extension of the root structure and precipitation of iron oxide nodules application of recently developed geochemical climofunctions indicated that the regolith formed in a mesic 10 12 c and subhumid 1157 1406 mm yr environment and under strongly acidic soil conditions ph 5 2 5 6

a granulometry and secondary mineral fingerprint of chemical weathering in periglacial landscapes and its application to blockfield origins abstract a review of published literature was undertaken to determine if there was a fingerprint of chemical weathering in regoliths subjected to periglacial conditions during their formation if present this fingerprint would be applied to the question of when blockfields in periglacial landscapes were initiated these blocky diamicts are usually considered to represent remnants of regoliths that were chemically weathered under a warm neogene climate and therefore indicate surfaces that have undergone only a few metres to a few 10s of metres of erosion during the quaternary based on a comparison of clay and silt abundances and secondary mineral assemblages from blockfields other regoliths in periglacial settings and regoliths from non periglacial settings a fingerprint of chemical weathering in periglacial landscapes was identified a mobile regolith origin under at least seasonal periglacial conditions is indicated where clay 0 5 silt 8 across a sample batch this contrasts with a mobile regolith origin under non periglacial conditions which is indicated where clay 0 5 silt 6 across a sample batch with clay 0 5 silt 8 in at least one sample a range of secondary minerals which frequently includes interstratified minerals and indicates high local variability in leaching conditions is also commonly present in regoliths exposed to periglacial conditions during their formation clay silt ratios display a threshold response to temperature related to the freezing point of water but there is little response to precipitation or regolith residence time lithology controls clay and silt abundances which increase from felsic through intermediate to mafic compositions but does not control clay silt ratios use of a sedigraph or coulter counter to determine regolith granulometry systematically indicates lower clay abundances and intra site variability than use of a pipette or hydrometer in contrast to clay silt ratios secondary mineral assemblages vary according to regolith residence time temperature and or precipitation a microsystems model is invoked as a conceptual framework in which to interpret the concurrent formation of the observed secondary mineral ranges according to the fingerprint of chemical weathering in periglacial landscapes there is generally no evidence of blockfield origins under warm neogene climates nearly all blockfields appear to be a product of quaternary physical and chemical weathering a more dominant role for periglacial processes in further bevelling elevated low relief non glacial surface remnants in otherwise glacially eroded landscapes is therefore indicated

morphology and genesis of carbonate soils on the kyle canyon fan nevada u s a the physical and chemical properties of soils formed in an arid climate on calcareous alluvium of the kyle canyon alluvial fan southern nevada were studied in order to infer the rates and relative importance of various soil forming processes these studies included field and microscopic observations and analyses of thin sections major oxides extractable iron and clay minerals the results are interpreted to reflect five major pedogenic processes 1 the calcic horizons and calcretes of kyle canyon soils form by precipitation of caco3 derived from eolian dust and alluvium as clast coats matrix cement and massive layers 2 the a and uppermost b horizons are essentially dust derived for they contain large amounts of detrital material not present in the alluvial parent material and their major oxide content is similar to that of modern dust 3 clay particles are translocated from a into b horizons 4 iron bearing minerals in the near surface b horizons are slowly oxidized 5 carbonate and aluminosilicate grains are both displaced and replaced by pedogenic caco3 the silica released by replacement of aluminosilicates may be locally precipitated as amorphous or opaline silica and or incorporated into newly formed palygorskite and sepiolite rates of soil development at kyle canyon are approximate due to uncertainties in age estimates some soil field properties change at rates that are similar to rates for soils formed in rhyolitic parent material near mercury nevada the rate of accumulation of caco3 3 5 g m 2 yr 1 at kyle canyon is an order of magnitude faster than that near mercury but is comparable to rates calculated for soils in southern new mexico and utah

rates and processes of soil evolution on uplifted marine terraces northern california time dependent changes in soil development have been evaluated for two flights of uplifted marine terraces with similar site characteristics and a range in terrace ages 3 9 ka to 330 ka in northern california six pedogenic properties of soils developed in unconsolidated deposits overlying bedrock marine platforms have systematic time dependent trends but each property differs in rate of change and in the time period over which its changes are useful as relative age dating or correlation tools changes in accumulated mass of organic carbon and ph are useful properties only for the youngest soils and probably for soils less than 10 20 ka in this climatic region soils on terraces older than 29 ka have nearly similar amounts of mass of organic carbon with values of about 3 6 by weight for the upper meter of the soil profile soil reaction ph in the top 20 cm of the soil profile decreases at a rapidly declining rate reaching and maintaining a value of 5 by 39 40 ka total mass of accumulated clay is an excellent indicator of relative soil age during all stages of soil development the rate of accumulation of clay is about 0 4 g cm2 soil column per thousand years so that pedons on terraces with inferred ages of about 124 ka have accumulated at least 50 g cm2 soil column of clay systematic and linear increases in accumulated mass of several forms of pedogenic iron make them very useful for chronological purposed for at least 240 ky of soil development crystalline forms of iron enable greater distinction among young soils than amorphous forms which have negligible accumulations until at least 40 ka the rate of accumulation of crystalline forms of iron fed feo is about 0 02 g cm2 soil column per thousand years so that pedons on terraces with inferred ages of about 124 ka have accumulated about 3 g cm2 soil column of crystalline forms of pedogenic iron changes with time in accumulated mass of amorphous forms of pedogenic aluminum alo are negligible within the first 29 ka then reflect a rapid increase in rate of accumulation until at least 124 ka two pedons from the same terrace inferred age 124 ka contain strikingly different amounts of pedogenic alo however and suggest that alo may be an unreliable indicator of the degree of soil development in addition to mass values of different soil substances maximum percent values were calculated soils developed on marine terraces older than 29 ka have at least 10 maximum clay older than 100 ka at least 30 maximum clay and older than 240 ka at least 40 50 maximum clay soils on terraces younger than 29 ka have less than 1 maximum fed and soils older than 240 ka at have at least 4 maximum fed these easily obtained values provide textural and chemical boundaries for separating marine terraces younger or older than about 29 100 and 240 ka in this region but are useful only as very general tools for correlation maximum percent clay is a more reliable indicator of soil age than maximum percent fed as the latter is greatly influenced by local groundwater flux and percent values of fed have a high degree of scatter

transformations of 2 1 phyllosilicates in 41 year old soils under oak and pine abstract the large unconfined lysimeters at the san dimas experimental forest in southern california provide a unique setting in which to study decade scale vegetation effects on mineral weathering we investigated the 2 1 phyllosilicate mineralogy of lysimeter soils under 41 year old monocultures of scrub oak quercus dumosa nutt and coulter pine pinus coulteri b don and compared the results to archived original fill material x ray diffraction showed that mica increased relative to vermiculite in the clay and medium silt fractions of a horizons under both oak and pine compared to the archived original fill material the increase however was far greater under oak than under pine no mineralogical differences were observed in the subsurface horizons of either oak or pine compared to archived material nonexchangeable k increased by 23 in the clay fraction of the oak a horizon and increased by 5 in the clay fraction of the a horizons under pine relative to archived parent material strong evidence supports biocycling as the basis for observed decade scale mineral transformations we conclude that the return of k to the soil surface through litter decomposition and subsequent fixation by vermiculite resulted in increased mica contents in a horizons more k may have been fixed by vermiculite in the oak a horizon compared to pine due to greater k concentration in the oak litter pool earthworm mediated mineralization of k from organic matter under oak and presence of fewer roots at the surface under oak and consequently less plant removal of k from the a horizon

inversion for crustal structure using reflections from the passcal ouachita experiment an interface inversion has been tested and applied to wide angle reflection data from the 1986 passcal ouachita experiment an interface corrugation with a relief of 10 km and a width of 30 km was successfully imaged in a test of the interface inversion velocity depth curves derived for shot points 14 19 using the tail sum method are similar to an average one dimensional velocity model from forward modeling using travel time correlations from southern profiles 14 19 the similarity of these velocity depth curves positioned over the southern half of the passcal experiment suggests that crustal structure in this region is approximately laterally homogeneous lower crustal velocities are not well resolved due to the recording on most profiles of only small segments of the travel time triplications a two dimensional velocity structure was derived by using the average one dimensional velocities for the deeper crustal layers and formally inverting for depth to interfaces the final inversion model is found to be consistent with previous refraction interpretations south of the ouachita orogenic trend and concurrent interpretations of the passcal data set inversion results for the central and southern portion of the passcal profile indicate a depth of 10 12 km for a midcrustal layer which thins southward from approximately 10 km to about 4 km a lower crustal layer with an average thickness of 12 km and a moho depth of approximately 29 5 km are also determined interface depths are in agreement with a normal moveout stack of the passcal data set in particular the shallowing of the moho to a depth of 30 km over the northern 50 km of the profile matches previous interpretations of the data set and has been interpreted here and in previous studies as the location of the paleozoic continental margin geophysical studies of the modern atlantic continental passive margin provide the simplest comparison to the crustal structure derived here the lower crustal layer found south of the shallowing of the moho to 30 km beneath the passcal profile is analogous in thickness and position to rift stage lower crust however other tectonic interpretations are possible given the uncertainties in velocity and lithology relationships

a case study of a precariously balanced rock its partially exhumed corestone platform and encasing saprock and soil abstract lying between the elsinore and san jacinto faults 0 5 km se of roundtop is a tonalitic corestone perched precariously on an exhumed corestone base such features are referred to as precariously balanced rocks pbrs cosmogenic 10be data listed in an online abstract suggest a tentative exhumation age of the pbr near roundtop at 35 000 years ago the absence of pbrs adjacent to the elsinore and san jacinto faults implies that they were shaken free from their perches during ground shaking alternatively their absence may reflect a more highly fractured and intensely weathered terrane because the weathering histories of pbrs have not been studied previously we analyzed the texture clay mineralogy and geochemistry of the roundtop pbr to answer several basic questions can the characteristics of the regolith that once encased the precariously balanced rock be reconstructed what chemical processes operated in the regolith prior to exhumation and are these processes still occurring following exhumation did new fracture development modify the original regolith to answer these questions we extracted three 1 m long cores from the pbr near roundtop and collected 23 saprock and 9 pebbly sandy loam samples from a trench excavated near the base of the corestone platform plagioclase and biotite alteration along with the concomitant loss of ca na sr ba k mg mn nb and p mass are the primary evidence of weathering intensity within the saprock additionally the presence of mostly kaolinite and lesser quantities of mixed layer biotite smectite in the saprock along with the above observations and data point to significant fluid rock interations during saprock development subsequent formation of pebbly sandy loam appears to have been accomplished primarily through pedoturbation within the uppermost portions of the underlying already weathered saprock and produced little additional chemical weathering hence our data support the general idea that roundtop is an area of weak ground shaking and that since current exhumation little weathering has affected this pbr locality

large near surface nitrate pools in soils capped by desert pavement in the mojave desert california we found exceptionally high nitrate levels up to 12 750 kg ha 1 at shallow depths 1 m in soils mantled by desert pavement a common land surface feature in arid regions nearby soils without desert pavement had nitrate contents that were one to two orders of magnitude lower the soil conditions coincident with desert pavement i e stability antiquity and virtually no leaching favor the retention and accumulation of nitrate delivered by atmospheric deposition or in situ fixation the nitrate stored in soils under desert pavement is a previously unrecognized pool of nitrogen that has the potential to increase the global nitrogen inventory for near surface desert soils to five times previous estimates its near surface occurrence makes this labile nitrogen pool particularly susceptible to mobilization by climate change or human disturbance risking contamination of surface and groundwaters

sediment fabrics oxygenation history and circulation modes of japan sea during the late quaternary abstract the quaternary hemipelagic sediments of the japan sea are characterized by centimeter to decimeter scale alternations of heavily bioturbated organic poor light layers and finely laminated organic rich dark layers these dark and light layers which can be correlated throughout the deeper part of the basin are considered to reflect changes in bottom water oxygenation however depositional mechanisms responsible for individual dark layers and causes of oxygen depletion are not fully understood two possible settings for deposition of organic rich dark layers are recognized one is a stratified ocean like the black sea where limited vertical advection results in euxinic conditions in the deeper parts of the basin the other is an upwelling region like the arabian sea where the oxygen minimum zone is intensified by enhanced nutrient upwelling and surface productivity in this study fabrics of hemipelagic sediments deposited in the japan sea during the last 160 ka were studied in three cores collected from different latitudes and water depths fabrics were classified into 4 classes based on corresponding bottom water oxygenation level five dark layer types were defined based on the distribution patterns of sediment fabric classes within each dark layer comparison of dark layer types at shallower and deeper sites in a chronologic framework provided evidence for five different modes of deep water circulation these circulation modes which reflect relative intensities of upwelling and density stratification appear to be related to global sea level changes as well as climate impact on the nature of water influx through the tsushima strait

evaluating u series tools for weathering rate and duration on a soil sequence of known ages four soil profiles of known age 40 250 600 and 3000 ka from the merced soil chronosequence in california were analysed for u and th isotopes and for major and trace element compositions to test the assumption that leaching of u series isotopes is a first order process with an invariant rate constant as frequently assumed when applying this isotopic tool to determine weathering duration and sediment residence time average 230 th 238 u values for each profile decrease from a high of 1 28 in the youngest soil 40 ka to 1 09 0 99 and 0 98 in the 250 ka 600 ka and 3000 ka soils respectively 234 u 238 u values also show variation across the 4 soils the simultaneous variation in 230 th 238 u and 234 u 238 u cannot be explained by a first order kinetic model with invariant rate constants and instead requires that leaching coefficients for the u series isotopes change with time the observed data is consistent with a two stage model that reflects an initial period of fast leaching of u and th from a readily weathered soil pool such as grain boundaries or defects followed by slow leaching from a more resistant soil pool application of such a two stage model may lead to significantly shorter calculated timescales of weathering than those obtained by the widely applied single stage model of u series weathering which assumes no change in leaching coefficients over time the results of this study have wide implications for published and future use of u series tools in weathering studies

chemical weathering rates of a soil chronosequence on granitic alluvium iii hydrochemical evolution and contemporary solute fluxes and rates although long term changes in solid state compositions of soil chronosequences have been extensively investigated this study presents the first detailed description of the concurrent hydrochemical evolution and contemporary weathering rates in such sequences the most direct linkage between weathering and hydrology over 3 million years of soil development in the merced chronosequence in central california relates decreasing permeability and increasing hydrologic heterogeneity to the development of secondary argillic horizons and silica duripans in a highly permeable younger soil 40 kyr old pore water solutes reflect seasonal to decadal scale variations in rainfall and evapotranspiration et this climate signal is strongly damped in less permeable older soils 250 to 600 kyr old where solutes increasingly reflect weathering inputs modified by heterogeneous flow elemental balances in the soils are described in terms of solid state exchange and pore water reservoirs and input output fluxes from precipitation et biomass solute discharge and weathering solute mineral nutrients are strongly dependent on biomass variations as evidenced by an apparent negative k weathering flux reflecting aggradation by grassland plants the ratios of solute na to other base cations progressively increase with soil age discharge fluxes of na and si when integrated over geologic time are comparable to solid state mass losses in the soils implying similar past weathering conditions similarities in solute and sorbed ca mg ratios reflect short term equilibrium with the exchange reservoir long term consistency in solute ratios when contrasted against progressive decreases in solid state ca mg requires an additional ca source probably from dry deposition amorphous silica precipitates from thermodynamically saturated pore waters during periods of high evapotranspiration and result in the formation of duripans in the oldest soils the degree of feldspar and secondary gibbsite and kaolinite saturation varies both spatially and temporally due to the seasonality of plant respired co2 and a decrease in organically complexed al in deeper pore waters k feldspar is in equilibrium and plagioclase is about an order of magnitude undersaturated hydrologic heterogeneity produces a range of weathering gradients that are constrained by solute distributions and matrix and macropore flow regimes plagioclase weathering rates based on precipitation corrected na gradients vary between 3 and 7 10 16 mol m 2 s 1 these rates are similar to previously determined solid state rates but are several orders of magnitude slower than for experimental plagioclase dissolution indicating strong inhibitions to natural weathering partly due to near equilibrium weathering reactions

wave field processing of data from the 1986 program for array seismic studies of the continental lithosphere ouachita experiment in may 1986 a wide aperture seismic field experiment was conducted in southwestern arkansas and northwestern louisiana this experiment was sponsored by the incorporated research institutions for seismology as part of the program for array seismic studies of the continental lithosphere the survey line runs from the south edge of the ouachita mountains out into the gulf coastal plain the experiment involved 21 shot points and two major deployments each of 400 recorders with an effective aperture of 200 km the goal of the experiment was to attempt to provide constraints on the diverse development sequences that have been proposed to explain the structure of the area the data were processed using a previously developed prestack common source acoustic finite difference migration to produce images of reflectivity in a slice 200 km long and 40 km deep this migration algorithm has no dip restrictions and uses a two dimensional variable velocity distribution for wave extrapolation interpretation of the results of the prestack processing together with the results of complementary two dimensional ray trace modeling not shown here of the data provides an enhanced picture of the structure of the paleozoic continental margin that is consistent with the observations in most previous geophysical and geological studies the main physical and temporal features of the model are crustal thinning during precambrian rifting a continent ocean boundary sedimentary wedge and carbonate bank thrusting of deepwater sediments during the ouachita orogeny and triassic rifting

recognizing non steady state weathering conditions in ancient submarine fan systems correcting for k metasomatism reveals a late cretaceous non steady state weathering regime point loma formation southwestern california u s a abstract during steady state weathering the rate of removal of the exposed weathering zone is balanced by the rate of generation of mineralogically identical material through chemical weathering as steady state conditions prevail the mineralogical and chemical composition of sediments derived from the weathering profile should be invariant over time in a cn k space a steady state weathering condition is characterized by tightly grouped compositions with dispersion between sands and muds a consequence of sorting during fluvial transportation the purpose of this study was to assess whether such a condition was present during the development of the upper cretaceous point loma formation published paleotectonic reconstructions portray the upper campanian lower maastrichtian point loma formation as being deposited in a forearc basin developed westward of a continental margin magmatic arc in such accounts during the subduction of an oceanic plateau or aseismic ridge or during constant dip subduction rocks in the magmatic arc were uplifted and the volcanic cover nearly stripped clean exposing its plutonic roots published detrital zircon data derived from samples of the point loma formation indicate that exposed igneous rocks in the source area were mainly from 135 ma to 100 ma plutons located in the western zone of the peninsular ranges batholith new point count xrd and chemical data show that detritus in mudstones and some fine grained feldspathic sandstones of the point loma formation following deposition and shallow burial were subjected to a k metasomatic event after correcting for introduction of k and consideration of the effects of hydraulic sorting resulting mudstone and fine grained sandstone data plot in a cn k space in overlapping fields whereas samples of coarse grained sandstone lie between rays extending through the most and least weathered mudstones hence detritus in the point loma formation was derived mainly from regolith during non steady state weathering conditions

influences of eolian and pedogenic processes on the origin and evolution of desert pavements well developed desert pavements are present above eolian deposits that mantle flows of the cima volcanic field located in the mojave desert california soil stratigraphic data and geochemical data demonstrate that eolian and pedogenic processes play major roles in the evolution of these pavements eolian dust 1 accelerates mechanical fragmentation of flow rock providing the source material for pavements and 2 accumulates slowly below basaltic colluvium in flow depressions eventually promoting development of cumulate soils below the evolving stone pavement an increase in dust flux during the holocene has raised ancient pleistocene pavements as much as 20 cm above the former land surface the results of our studies demonstrate for the first time that most desert pavements do not form by deflation by overland flow or by upward migration of stones through a slowly formed clayey argillic horizon desert pavements are born and maintained at the surface

soil development along an elevational transect in the western sierra nevada california soil development along an elevational transect on the western slopes of the the central sierra nevada was investigated to assess the effects of climate on soil properties and processes the transect of seven soils formed in granitic residuum spans elevations from 198 to 2865 m with mean annual temperature and precipitation differences of 13 c 3 9 16 7 and 94 cm 33 127 respectively soil ph decreased by about two units and base saturation decreased from 90 to 10 with increasing elevation concentrations of organic c in the solum increased with elevation with the largest single increase occurring between the oak woodland 5 6 kg c m2 and mixed conifer sites 10 15 kg c m2 clay mineralogy showed a general trend of desilication and hydroxy al interlayering of 2 1 layer silicates with increasing elevation the degree of chemical weathering based on clay and secondary fe oxide concentration in the solum showed a maximum clay 536 kg m2 and fe oxides 24 kg m2 at mid elevations having intermediate levels of precipitation and temperature while some soil properties show a continuous progression e g organic carbon base saturation clay mineralogy with elevation other properties e g ph soil color clay and secondary fe oxide concentrations show a pronounced change threshold type step over a short distance at about 1600 m the explanation for the abrupt nature of this shift is not known however it coincides with the approximate elevation of the present day average effective winter snow line

paleoceanographic changes of surface and deep water based on oxygen and carbon isotope records during the last 130 kyr identified in md179 cores off joetsu japan sea abstract we reconstructed the paleoenvironmental history of surface and deep water over the last 130 kyr from oxygen and carbon isotope ratios of planktonic and benthic foraminifera in two cores md179 3312 and md179 3304 from the joetsu basin eastern margin of the japan sea our data showed that paleoceanographic changes such as influx of surface currents and vertical circulation were associated with global glacial interglacial sea level change surface water conditions were influenced by the influx of tsushima current east china sea coastal or off shore waters through the tsushima strait during interglacial or interstadial stages and strongly affected by freshwater input during the glacial maximum during interglacial maximums such as marine isotope stages 1 and 5e development of well oxygenated bottom water was indicated a density stratified ocean with weak ventilation was inferred from the isotopic records of benthic foraminifera during the last glacial maximum local negative excursions in carbon isotopes during deglacial or interglacial periods may suggest the dissolution of gas hydrates or methane seep activities

anoxia vs productivity what controls the formation of organic carbon rich sediments and sedimentary rocks discussion the prevailing explanation for the origin of organic rich sediments and rocks invokes deposition under conditions of anoxia however recent research suggests that high primary production and not water column anoxia provides the first order control on the accumulation of organic rich facies in the modern oceans oxygen minima do not appear to have any direct effect on carbon accumulation in continental margin or marginal sea environments sediments accumulating in the modern black sea the type euxinic basin are not particularly enriched in organic matter despite the presence of an anoxic water column although a sapropel containing extremely high carbon concentrations was deposited during the holocene at a time when the basin was oxic results of a recently published co pled ocean atmosphere model indicate that during the cretaceous thermohaline and surface circulation in the oceans was similar to or more intense than modern conditions despite the overall equable climate such conditions confound the idea that circulation in the cretaceous atlantic for example was punctuated by oceanic anoxic events brought about by more sluggish circulation sporadic temporal and spatial increases in primary production reflecting changes in the behavior and or state of the ocean atmosphere system constitute a more tenable explanation for the occurrence of modern and quaternary carbon rich sediments and cretaceous black shales consequently the fundamental control on the accumulation of carbon rich facies in the oceans and marginal seas is not the presence or absence of anoxia

a soil chronosequence on quaternary marine terraces san clemente island california a soil chronosequence on marine terraces was examined on san clemente island california in an arid mediterranean climate in order to see which soil properties differ most systematically with time ages of the geomorphic surfaces were determined by radiocarbon uranium series and amino acid racemization techniques and range from 1 000 000 yrs soils on surfaces 200 000 yrs old are vertisols or alfisols with vertic properties such as slickensides and cracks and they exhibit both prismatic and angular blocky sphenoidal or only angular blocky structure solum thickness increases linearly with age of geomorphic surface clay soluble salts ald smectite mica ratios in the clay fraction and quartz plagioclase ratios in the silt fraction when expressed as profile summations show increases with age of geomorphic surface the best fit regression equations are linear with the exception of ald which is best expressed as a power function important soilforming processes appear to be alteration of mica to smectite accumulation at depth of soluble salts derived from marine aerosols possibly additions of eolian materials clay illuviation in the younger soils and pedoturbation in the older soils the observations reported here allow the following conclusions to be drawn about soils in this environment 1 certain soil properties which show distinct trends with time can be used for relative age dating in geomorphic and stratigraphic studies 2 soils have not reached a steady state condition with respect to many of their properties and 3 alfisols and mollisols with natric b horizons may be precursors to vertisols

airborne dust transport to the eastern pacific ocean off southern california evidence from san clemente island 1 islands are natural dust traps and san clemente island california is a good example soils on marine terraces cut into miocene andesite on this island are clay rich vertisols or alfisols with vertic properties these soils are overlain by silt rich mantles 5 20 cm thick that contrast sharply with the underlying clay rich subsoils the silt mantles have a mineralogy that is distinct from the island bedrock silt mantles are rich in quartz which is rare in the island andesite the clay fraction of the silt mantles is dominated by mica also absent from local andesite and contrasts with the subsoils dominated by smectite ternary plots of immobile trace elements sc th la and ta nd cr show that the island andesite has a composition intermediate between average upper continental crust and average oceanic crust in contrast the silt and to a lesser extent clay fractions of the silt mantles have compositions closer to average upper continental crust the silt mantles have particle size distributions similar to loess and mojave desert dust but are coarser than long range transported asian dust we infer from these observations that the silt mantles are derived from airborne dust from the north american mainland probably river valleys in the coastal mountains of southern california and or the mojave desert although average winds are from the northwest in coastal california easterly winds occur numerous times of the year when santa ana conditions prevail caused by a high pressure cell centered over the great basin examination of satellite imagery shows that easterly santa ana winds carry abundant dust to the eastern pacific ocean and the california channel islands airborne dust from mainland north america may be an important component of the offshore sediment budget in the easternmost pacific ocean a finding of potential biogeochemical and climatic significance

application of wave field continuation to the inversion of refraction data three examples of the inversion of refraction data by downward continuation illustrate the applicability of the method to field data the first example is a refraction profile from the mojave desert california these data are spatially aliased and contain clear evidence of lateral inhomogeneity the inversion in this case produces a broken image in the slowness depth domain due to the lateral inhomogeneity but a useful average velocity model is still obtained the second example is a shallow marine reflection profile here the truncation effects due to the finite horizontal aperture of the recording cable produce artifacts in the slowness depth domain the velocity model is however distinct from these artifacts and the presence of strong precritical reflections aids in the inversion the third example is another shallow marine reflection profile the inversion of these data illustrate the utilization of constraints provided by multiples as well as primary arrivals

high resolution climate and environmental changes of the northern japan east sea for the last 40kyr inferred from sedimentary geochemical and pollen data abstract high resolution lithological and isotope geochemical analyses were made on a well age constrained sediment from the northeastern japan east sea which recorded 10 dark layers dl over the last 40 ka bp pollen analysis of the core allows us to reconstruct the history of surrounding landmass vegetation and to determine pronounced vegetation climate changes we found that dl 10 which correlated with a do chinese interstadial 8 was forced by increased east asian humidity and influx of the nutrient rich water into the sea dl 5 formed during the cold heinrich event 3 he at 30 31 ka bp was most likely to be initiated by the global sea level descent and reduction of seawater exchange with the north pacific high resolution of 18 o pf records reflects a unique sensitivity of the japan east sea to input of the north pacific water through the shallow tsushima and tsugaru straits this led us to the important evidence of the eustatic sea level changes during the last 40 ka bp since 29 ka bp 18 o pf curve shows a continuous descending sea level interrupted by sharp drops of he 2 with a following rise of do interstadial 2 a sharp 18 o pf increase since 18 6 ka bp is consistent with coral results which indicate abrupt termination of lgm low stand by a rapid sea level rise initiated at 19 0 ka bp

fine structure of dark layers in the central japan sea and their relationship with the abrupt climate and sea level changes over the last 75 ka inferred from lithophysical geochemical and pollen results abstract high resolution of the color lightness productivity proxies toc chlorin caco 3 ba bio mo and u and lithological description defined alternation of dark layers dls and light layers in sediment core lv53 23 recovered from the central japan sea west yamato rise over the last 75 ka age model was constructed by ams 14c data tephrochronology 18 o of planktonic foraminifera record and the correlation of dls with lightness of japan sea core md01 2407 and with millennial interstadials recorded in the greenland ice cores and east asia stalagmites regional interstadials were also independently established and dated by vegetation amelioration of the surrounded land inferred from the pollen results correlation of the dls with millennial scale climate and sea level changes indicate that both interstadial warming and sea level fluctuations influence on its formation providing their individual features during mis 3 with sea level above 90 m dl was formed mostly consistent with the tada et al 1999 s hypotheses during mis 2 and 4 when sea level was nearly and below 90 m sea level descending led to water column stratification oxygen depletion in bottom water and facilitates the dls formation high resolution lightness and productivity proxies defined the subtle structure of pronounced interstadials 14 and 12

tephra layers of large explosive eruptions of baitoushan changbaishan volcano in the japan sea sediments this paper is based on the results of a comprehensive investigations of sediments from seven cores sampled during the international russian chinese cruise 53 of the r v akademik lavrentyev 2010 in the frames of the russian chinese collaboration between the pacific oceanological institute of the far eastern branch of the russian academy of sciences poi feb ras vladivostok russia and the first institute of oceanography fio qingdao china baitoushan chanbaishan volcano had several powerful explosive eruptions during the middle pleistocene holocene which produced widespread tephra layers the paper reports chemical composition of volcanic glasses and minerals from six tephra layers labeled as b og b sado b j b un1 b v and b tm which belong to baitoushan volcano and were identified in sediments of the northwestern part of the sea of japan the tephras were dated using geochronological data for the host sediments the estimated ages for the middle pleistocene tephra is 488 ka the late pleistocene tephras are 71 1 71 9 cal k b sado 50 8 cal ka b j 38 3 cal ka b un1 and 29 0 29 4 cal ka b v the ash layers consist of alkali rich glass of trachydacitic to alkaline rhyolitic composition and specific assemblage of minerals including fe rich augite hedenbergite aegirine augite aegirine arfvedsonite and fayalite the mineral assemblage is typical for alkalic volcanic rocks from continental rift setting aenigmatite a rare mineral from the group of inosilicates was firstly identified in distal tephra of baitoushan volcano supplied into marine sediments the composition of glasses and minerals from all layers are similar it testifies about steady state conditions of the magma accumulation under baitoushan volcano and about the bimodal character of magmatic chambers during the late pleistocene and holocene since 100 ka

orbital and millennial scale changes of radiolarian assemblages during the last 220 kyrs in the japan sea abstract significant abundance changes of seven radiolarian species during the last 220 kyrs in the japan sea are reported herein based on three sediment cores during the interglacial periods warm water species the tetrapyle octacantha group and warmer high nutrient water species lithomelissa setosa occurred commonly which may indicate inflows of the tsushima warm current on the other hand cold water species such as ceratospyris borealis and stylochlamydium venustum dominated the assemblage during the glacial periods when the japan sea was mostly isolated from the adjacent seas due to lower eustatic sea level however at glacial maxima the habitat of s venustum was strongly limited due to low salinity surface waters the abundance of the deep water species cycladophora davisiana seems to have changed significantly possibly related to the intrusion of oxygen and organic materials into deeper waters higher abundances of this species in mis marine isotope stage 1 mis 3 and mis 5c resulted from well ventilated deep water and high organic flux while its low abundance during the glacial maxima and mis 5e was probably caused by oxygen poor deep water millennial scale variations of c davisiana abundance show high abundance at the transition intervals from interstadial to stadial periods of the dansgaard oeschger cycles the disappearance events of lychnocanoma nipponica sakaii and amphimelissa setosa were recognized at 54 ka and 85 ka respectively both of these events in the japan sea can be correlated with those in the north pacific bering sea and sea of okhotsk

seismic imaging of upper crustal structure using travel times from the passcal ouachita experiment a first arrival travel time inversion applied to the 1986 passcal ouachita experiment has been used to image upper crustal structure twenty one shot points every 10 km were recorded along two 100 km long segments with 400 seismographs on each segment a splined velocity model parameterization allowed for the inversion of laterally inhomogeneous models but not velocity discontinuities over 800 travel times were used in the inversion with a variable data covariance weighting the multiple source nature of the experiment design allowed the use of reciprocity relationships among 21 shot points to enhance data correlation a succession of models with velocities specified at 30 90 171 and 221 nodes were inverted for whose horizontal node spacing decreased from 100 to 12 5 km in the final 221 node model vertical node spacings of 3 0 and 1 5 km were used the results of the inversions indicate changes in depth of isovelocity lines which are interpreted as triassic fault structure based on nearby well data the final rms travel time residual is 0 045 s resolution using first arrivals deteriorates rapidly below 9 km depth three distinct velocity gradients can be correlated with geologic units surface exposed cretaceous and jurassic sediments with velocities from 3 0 tomore 3 5 km s extend to 1 5 km depth triassic rift fill sediments which do not outcrop have inverted velocities ranging from 3 5 to 4 75 km s between depths of 1 5 3 0 km paleozoic sediments are imaged by a decreased velocity gradient below a depth of 3 0 km lack of resolution at depths greater than 9 km necessitates detailed modeling of wide angle reflected phases to further constrain deeper crustal structure less

assessing volumetric strains and mass balance relationships resulting from biotite controlled weathering implications for the isovolumetric weathering of the boulder creek granodiorite boulder county colorado usa abstract an important process often cited in the development of saprock and saprolite is the isovolumetric weathering of granitic bedrock evidence for isovolumetric weathering includes the observation that the texture of the granitic protolith often remains recognizable in its weathered products in contrast to the above often cited view we present results from a study of two sites located on the 1 65 ga boulder creek granodiorite near boulder colorado usa in which weakly chemically altered saprock derived from tonalitic and granodioritic tonalitic bedrock records volumetric strains on the order of 7 6 8 5 and 7 9 8 2 respectively we show that dilation is likely due to the alteration of biotite to vermiculite during the early stages of weathering and is associated with an expansion normal to the 001 cleavage of 40 theoretical calculations of volumetric strains based on the modal biotite present in the protolith support such an interpretation

millennial scale oscillations of the westerly jet path during the last glacial period abstract it has been established that east asian summer monsoon intensity varies with dansgaard oeschger cycles suggesting a connection between the climates of east asia and the north atlantic on a millennial timescale however the dynamics of such a connection are still unsolved here we demonstrate that temporal changes in the provenance of aeolian dust in japan sea sediments which we interpret to reflect changes in the westerly jet path over east asia exhibit variations in harmony with dansgaard oeschger cycles the dominance of dust with a mongolian gobi provenance during stadials suggests a westerly jet axis located to the south of the himalaya tibetan plateau throughout most of the year whereas the co dominance of dust from both the taklimakan desert and the mongolian gobi during interstadials suggests that the westerly jet axis jumped to the north of the tibetan plateau at latest in summer as the shift of the westerly jet axis to the north of the tibetan plateau is closely related to the onset of the east asian summer monsoon changes of the westerly jet path apparently critically affect the teleconnection between the climates of asia and north atlantic on a millennial timescale

varves in marine sediments a review the global compilation of reported marine varved sedimentary records throughout the quaternary contains 52 sites marine varve deposition and preservation typically depend on environmental and sedimentological conditions such as a sufficiently high sedimentation rate severe depletion of dissolved oxygen in bottom water to exclude bioturbation by macrobenthos and a seasonally varying sedimentary input to yield a recognizable rhythmic varve pattern additional oceanographic factors include the strength and depth range of the oxygen minimum zone omz and regional anthropogenic eutrophication from point sources such as large polluted rivers quaternary marine varves are not only found in those parts of the open ocean that comply with these conditions but also in fjords embayments and estuaries with thermohaline density stratification and nearshore marine lakes with strong hydrologic connections to ocean water this review critically describes settings and sedimentological characteristics of marine sites where varves have been reported broader applications of marine varve records are discussed for example in terms of radiocarbon calibration on high resolution time scales constraining paleoceanographic variability and global change teleconnections diagnosing factors affecting modern fish population dynamics based on past performance detailing biogeochemical cycles and deciphering complex factors influencing marine productivity varves in saline water bodies without hydrologic connection to the global ocean are not included in this review and instead pertain to the companion review on lacustrine varves where also general and fundamental principles of varve deposition classification and dating are covered zolitschka et al 2015 the postulated occurrence of varves in pre quaternary rocks is critically discussed in this review with representative examples in the case of non evaporitic laminations in fine grained ancient marine rocks such as banded iron formations and black shales laminations may not be varves but instead may have multiple alternative origins such as event beds or formation via bottom currents that transport and sort silt sized particles clay floccules and organic mineral aggregates in the form of migrating bedload ripples

formation of pockmarks and submarine canyons associated with dissociation of gas hydrates on the joetsu knoll eastern margin of the sea of japan abstract this study based on 3 5 khz sbp 3d seismic data and long piston cores obtained during md179 cruise elucidated the timing and causes of pockmark and submarine canyon formation on the joetsu knoll in the eastern margin of the sea of japan gas hydrate mounds and pockmarks aligned parallel to the axis on the top of the joetsu knoll are associated with gas chimneys pull up structures faults and multiple bottom simulating reflectors bsrs suggesting that thermogenic gas migrated upward through gas chimneys and faults from deep hydrocarbon sources and reservoirs seismic and core data suggest that submarine canyons on the western slope of the joetsu knoll were formed by turbidity currents generated by sand and mud ejection from pockmarks on the knoll the pockmark and canyon formation probably commenced during the sea level fall lasting until transgression stages subsequently hydropressure release during the sea level lowering might have instigated dissociation of the gas hydrate around the base of the gas hydrate leading to generation and migration of large volumes of methane gas to the seafloor accumulation of hydrate caps below mounds eventually caused the collapse of the mounds and the formation of large depressions pockmarks along with ejection of sand and mud out of the pockmarks thereby generating turbidity currents prolonged pockmark and submarine canyon activities might have persisted until the transgression stage because of time lags from gas hydrate dissociation around the base of the gas hydrate until upward migration to the seafloor this study revealed the possibility that submarine canyons were formed by pockmark activities if that process occurred it would present important implications for reconstructing the long term history of shallow gas hydrate activity based on submarine canyon development

pedogenesis in a wetland meadow and surrounding serpentinitic landslide terrain northern california usa landslide deposits in serpentinitic terrain of northern california are common and often support wet meadows which are strikingly different from the surrounding xeric landscape these landslide deposits provide an opportunity to observe pedogenic processes across differing moisture conditions and depositional environments in ultramafic terrain the objective of this study was to assess predominant pedogenic processes by landscape position for a stabilized landslide bench and the surrounding area in serpentinitic terrain distributions of dithionite extractable metals and exchangeable cations were compared to interpret processes involved in element redistribution landscape positions were defined as the scarp flanks foot and bulge the foot which supports a wet meadow is inundated during a significant part of the year due to water ponding behind the bulge the forested scarp and flank positions are subject to episodes of erosion probably following wildfires thereby delivering sediments to the lower landscape positions the major pedogenic processes on the slopes of the scarp and flanks include mineral weathering oxidation and illuviation of clay as evidenced by argillic horizons in which cr and al bearing fe oxyhydroxides are concentrated serpentine weathering products are transported from the scarp and flanks to the poorly drained foot where fine sediments and neoformed smectite yield clayey soils on the foot cycles of vegetation growth and deposition of sediments coupled with reducing conditions result in deep organic rich soils

mining soil databases for landscape scale patterns in the abundance and size distribution of hillslope rock fragments landscape scale variation in rock fragments on soil mantled hillslopes is poorly understood despite the potential importance of rock fragments in soil weathering and coarse sediment supply to river networks we explored the utility of soil survey databases for data mining with the goals of identifying landscape scale patterns in the abundance and size distribution of rock fragments diameter d 2 mm and potential controls on grain size production we focus on data from three regions the hawaiian islands and the sierra nevada and cascade mountains where elevation transects span a range of environmental conditions we selected pedons from pits dug on hillslopes with active soil production and transport for the 27 pedons selected we constructed depth averaged grain size distributions and calculated the mass fraction of rock fragments frf and the median rock fragment grain size d50rf we also categorized as bimodal size distributions with a clear breakpoint between fine and coarse modes several strong patterns emerge from the data we find rock fragments in 85 of the pedons primarily in distinct coarse modes within bimodal size distributions values of frf and d50rf are strongly correlated although the best fit power law scaling between frf and d50rf differs between the warmer hawaiian and colder sierra nevada and cascade mountain sites we also find a regional contrast in the variation in frf with elevation frf declines with elevation in hawaii but increases in the mainland sites although this contrast could be an artifact of variable lithology precipitation may influence many patterns in the data lower mean annual precipitation correlates with higher frf dominantly bimodal distributions and surface enrichment in the vertical distribution of rock fragments these observations may be useful in refining models of coarse sediment supply to rivers and suggest opportunities for future work to test mechanistic hypotheses for rock fragment production on soil mantled hillslopes copyright 2011 john wiley sons ltd

geomorphic and pedogenic evolution in coastal sediments central california abstract studies of soil chronosequences on marine terraces facilitate the use of terraces for tectonic and paleoclimatic interpretation however many areas on the california coast have received substantial eolian deposits after pedogenesis began so do not qualify as chronosequences these areas are worthy of study because they are widespread coastal landscape features and they enable us to interpret pedogenic and geomorphic processes in sandy regolith the objective of this study was to use soil and deep regolith morphology and chemistry to interpret pedogenic and geomorphic evolution on a sequence of four marine terraces san luis obispo county california the terraces are numbered 1 2 3 and 4 from oldest to youngest the eroded terrace platforms have been tentatively dated at 560 420 or 480 320 and 120 ka respectively the sand deposits on each platform may be considerably younger the amount of land surface dissection and the depth of stream incision increase with increasing terrace age and elevation morphological features suggest that the soils xeropsamments on terrace 4 haploxerolls on terrace 3 on the two youngest terraces are well drained and their morphological development is typical of soils in eolian sand deposits morphological and chemical features of the basal regolith contrast with those of the soils clay fe oxides and opaline silica were deposited by groundwater flow above the bedrock platform above the shoreline angle where the deep regolith receives additional groundwater from higher terraces redoximorphic features have developed gray mottles are larger more common and more distinct in the basal regolith of progressively older terraces erosion has removed much of the overburden on terraces 2 and 1 and soils epiaqualfs on terrace 2 epiaqualfs on terrace 1 have developed in what was once deep regolith the landscape soils and deep regolith show an evolution of processes whereby the path and direction of water movement through the regolith is controlled first by terrace morphology and stratigraphy then by the development of pedogenic features in the soil and deep regolith and by terrace dissection

geochemical identification of cryptotephras using inaa from late quaternary hemipelagic sediments southwest japan abstract we present new compositional data on glass shards from cryptotephra layers in five marine sediment cores from the southern japan east sea the hand picked glass shards were extracted from cryptotephra horizons that were distinguished by sem eds for major elements and inaa for trace elements on individual shards most of the glass shards have alkaline and trachyte phonolite compositions and have major and trace element compositions similar to eruptive units on ulleung island stratigraphic inferences indicate the presence of at least four alkaline tephras u 3 post u oki u oki and pre u oki in the interval between the k ah rhyolitic tephra 7 3 cal ka bp and the tl1 regional dark sediment layer 11 8 cal ka bp the new trace elements on glass shards indicate minor compositional distinctions from one visible tephra and four cryptotephras that help to infer fine scale regional correlations the development of a more comprehensive alkaline tephrostratigraphical framework for this region will greatly aid in the reconstruction and chronology of regional stratigraphic variations the recognition of new alkaline cryptotephras in the marine sediments of the japan east sea also contributes towards a better understanding of the volcanic history of ulleung island and nearby seamounts

fire effects on cation exchange capacity of california forest and woodland soils abstract during natural and prescribed fires combustion of heavy surface fuel loads can expose underlying soil to high temperatures causing thermal alteration of soil minerals and other changes in soil properties we studied the effect of fire on soil cation exchange capacity cec by comparing severely burned soils to nearby unburned soils at five forest and woodland sites in california usa combusted logs and heavy fuel produced reddened zones of thermally altered soil underlain by blackened zones where heat exposure was lower the cation exchange capacities of the reddened soils were 57 to 82 lower than the unburned soil while the blackened soils had 31 to 53 less cec than unburned soil the reddened soil experienced the highest burning temperatures resulting in the loss of organic carbon oc the conversion of goethite to maghemite or hematite the destruction of kaolin and dehydroxylation and permanent collapse of vermiculite and chlorite overall most of the cec loss was due to thermal destruction of soil organic matter som but this cec will be restored in the post fire ecosystem succession as biomass re accumulates and rebuilds soil humus the loss of cec due to mineral alteration is longer lasting though limited in spatial extent

mineralogical and chemical variability of mountain red brown mediterranean soils the purpose of the current study was to quantitatively explore the dynamics of clay pedogenesis in red brown soils of the terra rossa type and associated soils mainly rhodoxeralfs of the mediterranean region with respect to bedrock and dust composition and the impact of the vegetation translocated elements silicon and potassium fifteen non cultivated shallow and leached mountain pedons were sampled in israel along three transects that represent various rainfall ranges and bedrock lithologies bulk and clay fraction chemical and mineralogical compositions as well as grain size were determined quantitative relative analysis of clay minerals displayed a large variability that was largely affected by leaching leaching was dependent on rainfall amount and bedrock soil permeability in general if the better soils were drained and leached the higher were the amounts of both kaolinite and illitic phases soil clay assemblages lay between two mineralogical end members one with dominance of smectite and the second with high values of kaolinite and illitization parameters potassium and silicon were mobile in soils relative to aluminum but under high rainfall or certain vegetation translocation by vegetation reached a degree that promoted illite or smectite formation local combinations of rainfall bedrock soil permeability and vegetation translocation of potassium and silicon dictated a large variability in clays including illite formation within a restricted group of red brown mediterranean soils

a 36 kyr geochemical record from the sea of japan of organic matter flux variations and changes in intermediate water oxygen concentrations intervals of organic c and carbonate rich laminated sediments occur in the sea of japan with roughly the same frequency as temperature changes observed in greenland ice cores providing clear evidence of rapid oceanographic change during the past 36 kyr planktonic foraminiferal 18o data suggest that only the laminated sediments deposited during the last glacial maximum lgm and perhaps one other interval formed during a period of increased water column stratification sedimentary re and mo data are consistent with bottom waters that were sulfidic during the lgm and suboxic during other laminated intervals results of a numerical model of corg and re burial are consistent with a mechanism whereby an increased corg flux to the seafloor drove oxygen concentrations toward depletion during times of deposition of the suboxic laminated intervals such a process could have resulted from increased upwelling driven either by increased deep water formation due to colder and or more saline surface waters or by stronger northeasterly monsoonal winds

land ocean linkages over orbital and millennial timescales recorded in late quaternary sediments of the japan sea late quaternary sediments of the japan sea are characterized by centimeter to meter scale alternations of dark and light layers which are synchronous basinwide high resolution analyses of the sediments from ocean drilling program site 797 reveal that deposition of the meter scale alternations reflect variations in paleoceanographic conditions which were closely associated with glacio eustatic sea level changes through the modulation of the volume and character of the influx to the sea through the tsushima strait the centimeter to decimeter scale alternations reflect millennial scale variations which are possibly associated with dansgaard oeschger d o cycles with each dark layer appearing to correspond to an interstadial this variability is attributed to the development of a humid climate in central to eastern asia and the consequent increase in discharge from the huanghe and changjiang rivers during interstadials this caused expansion of the east china sea coastal water ecscw which penetrated more strongly into the japan sea the increased influence of the lower salinity nutrient enriched ecscw reduced deep water ventilation and enhanced the surface productivity leading to the development of anoxic bottom waters and deposition of the dark layers thus the centimeter to decimeter scale alternations of the dark and light layers record wet and dry cycles in central to eastern asia possibly associated with d o cycles

slant stack velocity analysis of shot point 16 from the 1986 passcal ouachita experiment a x p slant stack algorithm is applied to shot point 16 of the 1986 passcal ouachita experiment to determine the optimal me dimensional velocity structure several enhancements to a standard slant stack algorithm are used to image a one dimensional velocity fimction from the shot point gathered data because only postcritical reflections and refractions are needed to image a velocity function significant muting of precritical energy is perfonned which reduces the effect of noise in calculating the stack for data sets with long offsets scaling the data by a factor equal to or greater than offset distance compensates for the effects of geometrical spreading and attenuation this enhances imaging of the deeper regions of the velocity model and balances amplitudes across the shot point gather finally ray parameter depth images can have difficulty imaging higher velocities since for higher velocities a small change in ray parameter results in a large increment in velocity this problem is overcome by slant stacking in equal increments of velocity instead of ray parameter the enhanced slant stack algorithm is applied to shot point 16 of the 1986 passcal ouachita data set which sufficienfiy satisfies the assumption of lateral homogeneity based on previous studies of the region other velocity models are found to be consistent with the envelope of velocity fimcfion imaged by the slant stack method maximum amplitudes on the x p image are used as a constraint to delineate a more detailed velocity model a seven layer velocity model is derived for shot point 16 which is found to be similar to those of others who have studied the area the top three layers are sedhnents associated with the gulf coastal plain followed by a thick layer derived from sedimentation associated with the closing of the proto gulf of mexico and the associated ouachita orogeny the determination of a more detailed velocity function from the envelope suggests somewhat higher velocities in the lower crustal layer than previous studies however given the one dimensional assumptions of the method as well as the signal to noise ratio of the data the velocity envelope is the most important constraint on the velocity models and tectonic interpretation provided by this analysis

isotopic studies of the upper and middle rio grande part 2 salt loads and human impacts in south new mexico and west texas abstract increasing groundwater and soil salinity is a threat to the land and water resources in arid regions global warming will likely increase salinity of dryland river systems in order to characterize salt loading into the semi arid portion of the rio grande in south new mexico and west texas we sampled seasonally 2009 2011 the river agricultural drains and saline groundwater in addition to major element chemistry these samples were analyzed for sulfur and oxygen isotope compositions 34s and 18o of dissolved so4 and in some cases for nitrogen and oxygen isotope compositions 15n and 18o of dissolved no3 uranium isotopes 234u 238u activity ratio were also measured for selected samples the natural inflow of basinal brines groundwater 34s of 8 to 11 in the semi arid rio grande study area was minor in the investigated seasons and could not be detected by the 34s mass balance however we did find localized increases of 34s 2 to 5 in the rio grande that were attributable to salt loads from the intersections of agricultural drains with the water table of a natural salt flat and associated evaporative brine 34s of 12 in the shallow subsurface in the areas with higher water use for land irrigation the 34s of the river and drain water was relatively consistent from 0 to 2 compared to the 18o from 2 to 6 most likely this resulted from application of s rich fertilizers e g ammonium sulfates elemental s sulfuric acid with low 34s 2 to 4 and high 18o 9 to 16 additionally we observed considerably lower 18o so4 in the rio grande and agricultural drains

diagenetic modification of magnetic properties observed in a piston core md01 2407 from the oki ridge japan sea abstract we investigated the magnetic properties of u channel samples from a giant piston core images md01 2407 in order to obtain high resolution records of past geomagnetic field and paleoenvironmental changes in the japan sea measurements of natural remanent magnetization nrm show occurrence of anomalous magnetic directions at several horizons which may represent geomagnetic polarity excursions in the brunhes chron however most of them occur close to the lithological boundary including tephra layers suggesting that these features might have been caused by deformation of core sediments intensity of nrm normalized by artificially induced remanence shows no significant correlation with a standard paleointensity record this is probably caused by a variation of lithology including volcanic ash layers and effect of the diagenetic changes of magnetic minerals down core variations of magnetic properties in the topmost part depict in detail the process of dissolution and alteration of magnetic minerals during reductive diagenesis which is to be expected for hemipelagic sediments characterized by a high sedimentation rate and a high organic matter content magnetic concentration parameters including low field susceptibility anhysteretic remanent magnetization and isothermal remanent magnetization irm indicate that a loss of fine grained magnetite occurs from 0 6 to 1 2 mbsf while remanence intensities below the level of the early diagenesis are one or two orders of magnitude lower than those in the topmost part most of the thinly laminated tl dark layers showed rather enhanced magnetic intensities typically tl2 shows a marked peak at the top with a gradual decrease towards the bottom variation of s ratio which gives the proportion of a low coercivity component in saturation irm suggests that low coercivity and fine grained ferromagnetic minerals are dominant these data suggest new magnetic minerals formed during deposition of the tl layers which may be analogous to the diagenetic magnetic enhancement known in sapropels of the mediterranean sea

reconciliation of late quaternary sea levels derived from coral terraces at huon peninsula with deep sea oxygen isotope records a major discrepancy between the late quaternary sea level changes derived from raised coral reef terraces at the huon peninsula in papua new guinea and from oxygen isotopes in deep sea cores is resolved the two methods agree closely from 120 ka to 80 ka and from 20 ka to 0 ka ka 1000 yr before present but between 70 and 30 ka the isotopic sea levels are 20 40 m lower than the huon peninsula sea levels derived in earlier studies new high precision u series age measurements and revised stratigraphic data for huon peninsula terraces aged between 30 and 70 ka now give similar sea levels to those based on deep sea oxygen isotope data planktonic and benthic 18o data using the sea level and deep sea isotopic data oxygen isotope ratios are calculated for the northern continental ice sheets through the last glacial cycle and are consistent with results from greenland ice cores the record of ice volume changes through the last glacial cycle now appears to be reasonably complete