early eocene leptictida pantolesta creodonta carnivora and mesonychidae mammalia from the eureka sound group ellesmere island nunavut we describe the leptictid prodiacodon the pantolestids palaeosinopa sp nov cf palaeosinopa and pantolestidae gen et sp indet the creodonts palaeonictis and prolimnocyon the carnivorans viverravus cf vulpavus and miacis and the mesonychid pachyaena from early eocene i e wasatchian strata of the eureka sound group on central ellesmere island nunavut palaeosinopa and palaeonictis may have originated in mid latitude north america and subsequently migrated to europe via a north atlantic land bridge while prolimnocyon and pachyaena probably originated in asia additionally the occurrence of pachyaena in the early eocene of europe probably is best explained by dispersal from high latitude north america to europe via a north atlantic land bridge we update the eureka sound group mammalian faunal list

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

assessing lithologic discontinuities and parent material uniformity within the texas sandy mantle and implications for archaeological burial and preservation potential in upland settings alfisols within the texas gulf coast plain commonly exhibit textural contrasts between sandy artifact bearing a e horizons i e sandy mantle and artifact sterile clay rich bt argillic horizons this has invoked debate about parent material uniformity and pedogenic versus geomorphic sandy mantle origins which has implications for the scientific value of buried archaeological sites to improve our understanding of archaeological burial in upland settings we evaluated parent material uniformity within five pedons to distinguish pedogenically derived textural changes from geomorphologically created lithologic discontinuities depth trends in clay free particle size classes and stable immobile ti and zr constituents failed to reveal lithologic discontinuities between the sandy mantle and bt horizons and the observed textural differences are interpreted to have resulted from pedogenic processes this interpretation is supported by clay skins fine clay increases in bt horizons and micromorphological observations consequently artifacts buried in upland summits have likely moved down the soil profile due to biomantle processes deep sandy mantle sites non parallel contacts between the sandy mantle and bt horizons and paleogullies incised into eocene bedrock are better explained by colluvial soil creep processes adjacent to summits where archaeological materials may exhibit preservation potential no single explanation can account for sandy mantle origins and we advocate a case by case approach

pleistocene paleosol development and paleoenvironmental dynamics in east africa a multiproxy record from the homo bearing aalat pedostratigraphic succession dandiero basin eritrea abstract the climatic changes during the early middle pleistocene transition are a key to understand the ecosystem dynamics that involved the homo erectus ergaster distribution the aalat pedostratigraphic succession represents a continental archive in the african rift valley eritrea where remains of homo around 1 ma were identified high resolution magnetostratigraphy dated this succession between the base of the jaramillo subchron and the lower brunhes chron despite the present arid desert climate the aalat section records a persistence of water driven fluvio lacustrine environments which suggests a major tectonic control on sedimentation although climate changes are clearly overprinted macro and micromorphological physico chemical mineralogical and geochemical features up to now poorly available for pleistocene paleosols in east africa depict a poor to moderate degree of development although calcic and petrocalcic petrogypsic horizons at different stratigraphic heights indicate phases of geomorphic stability the concurrent alternation of these horizons with iron stained layers suggests cyclical changes from dry to wet conditions which fit well with aeolian dust fluxes and marine isotope stages of glacials and interglacials at higher latitudes stable isotope data are consistent with these climatic cycles and suggest a succession of monsoonal and non monsoonal conditions the homo erectus settlement lasted apparently for a short time span because a long high discharge fluvial sedimentation and or an aridity phase at the base of the fluvial facies could have made the area less suitable for human settling and could have hindered preservation of fossils and artifacts

a regional scale study of chromium and nickel in soils of northern california usa abstract a soil geochemical survey was conducted in a 27 000 km 2 study area of northern california that includes the sierra nevada mountains the sacramento valley and the northern coast range the results show that soil geochemistry in the sacramento valley is controlled primarily by the transport and weathering of parent material from the coast range to the west and the sierra nevada to the east chemically and mineralogically distinctive ultramafic um rocks e g serpentinite outcrop extensively in the coast range and sierra nevada these rocks and the soils derived from them have elevated concentrations of cr and ni surface soil samples derived from um rocks of the sierra nevada and coast range contain 1700 10 000 mg kg cr and 1300 3900 mg kg ni valley soils west of the sacramento river contain 80 1420 mg kg cr and 65 224 mg kg ni reflecting significant contributions from um sources in the coast range valley soils on the east side contain 30 370 mg kg cr and 16 110 mg kg ni lower cr and ni concentrations on the east side of the valley are the result of greater dilution by granitic sources of the sierra nevada chromium occurs naturally in the cr iii and cr vi oxidation states trivalent cr is a non toxic micronutrient but cr vi is a highly soluble toxin and carcinogen x ray diffraction and scanning electron microscopy of soils with an um parent show cr primarily occurs within chromite and other mixed composition spinels al mg fe cr chromite contains cr iii and is highly refractory with respect to weathering comparison of a 4 acid digestion hno 3 hcl hf hclo 4 which only partially dissolves chromite and total digestion by lithium metaborate libo 3 fusion indicates a lower proportion of chromite bound cr in valley soils relative to um source soils groundwater on the west side of the sacramento valley has particularly high concentrations of dissolved cr ranging up to 50 g l 1 and averaging 16 4 g l 1 this suggests redistribution of cr during weathering and oxidation of cr iii bearing minerals it is concluded that regional scale transport and weathering of ultramafic derived constituents have resulted in enrichment of cr and ni in the sacramento valley and a partial change in the residence of cr

early holocene soil cryoturbation in northeastern usa implications for archaeological site formation abstract the study of buried soil archives in alluvial settings can be used to characterize floodplain and terrace habitats and complement other paleoenvironmental and archaeological archives this study examines the early holocene alluvial paleopedology along the delaware river valley in the northeastern usa chronological and alluvial stratigraphic data show that a widespread loam alluvial paleosol formed from 10 7 to 9 3 ka herein referred to as the jennings lane pedocomplex jlp the jlp at the jennings lane locality along the delaware river nj is a loam to silt loam soil that formed on mixed alluvium and windblown and or reworked dust likely sourced from nearby periglacial fines this finding supports previous interpretations of late quaternary dust deposition and reworking in the region fragic properties e g firm peds with brittle manner of failure and rapid slaking in water and cryogenic micromorphological features lenticular pores stone jacking and shattered grains present within the jlp suggest cryoturbation soil mass balance modeling suggests that the strain in immobile elements ti and zr show a dilation collapse profile these data indicate that organic matter and or dust addition and freeze thaw created soil dilation at the jlp paleosurface mass balance additions in fe k and mg are consistent with illuviated fe rich clay coatings present in thin section the x ray diffraction results show that these clays are illite vermiculite and kaolinite paleosol data presented here suggest that the jlp was overprinted by later pedogenic processes during the middle holocene ti na shows minimal loss throughout much of the profile although rapid thaws may have promoted downward translocation of fines the cold environment impeded base loss through either minimal release of cations from primary minerals or negligible water flux as suggested by ti na profiles and gains in ti k and ti mg this silt rich jlp pedofacies experienced minimal chemical depletion over the course of 1200 3500 years this cold climate weathering coincides with rapid temperature fluctuations 10 5 9 3 8 2 ka during the early holocene in northeastern usa this soil cryoturbation evidence has archaeological implications as well the cryoturbation in this early holocene pedocomplex suggests that vertical and lateral artifact redistribution is possible archaeologists should use caution when interpreting archaeological stratigraphy and intrasite artifact patterns at mid to high latitude archaeological sites

paleohydrologic evolution and geochemical dynamics of cumulative supergene metal enrichment at la escondida atacama desert northern chile quantitative limonite mapping within the leached capping of the porphyry copper deposit at la escondida chile permits reconstruction of the paleohydrologic and chemical evolution of a well developed supergene ore forming system the mineralogy textures and relative abundance of supergene limonite minerals hematite goethite and jarosite are used to reconstruct the former ratio of pyrite to chalcocite and the preoxidation copper grade based on empirical limonite sulfide correlations after locke 1926 blanchard 1968 and loghry 1972 estimates of preoxidation copper grades in surface exposures and tops of drill holes at la escondida are significantly lower than actual copper grades in the underlying enrichment blanket at depth this apparent inconsistency is explained by a progressive increase in the copper grade of the sulfide enrichment blanket as it descended to its present location in response to a descending water table this systematic trend of reconstructed grades of supergene enriched copper sulfide increasing with depth offers the first quantitative proof of cumulative downward enrichment in a supergene profile as proposed by locke 1926 the consistent trends of limonite mineralogy and abundance in vertical profiles indicate that water table descent at la escondida was relatively continuous in space although not necessarily in time evidence for cumulative downward enrichment in vertical profiles through leached capping allows quantitative analysis of chemical mass balance in dynamic supergene systems slopes of linear regressions for profiles of reconstructed enriched copper grades vs depth indicate lateral fluxes into or out of a given vertical profile this method provides independent verification of conclusions from a previous study of copper mass balance at la escondida brimhall et al 1985 which showed that lateral fluxes of copper were a significant factor during supergene leaching and enrichment

regolith mass balance inferred from combined mineralogical geochemical and geophysical studies mule hole gneissic watershed south india the aim of this study is to propose a method to assess the long term chemical weathering mass balance for a regolith developed on a heterogeneous silicate substratum at the small experimental watershed scale by adopting a combined approach of geophysics geochemistry and mineralogy we initiated in 2003 a study of the steep climatic gradient and associated geomorphologic features of the edge of the rifted continental passive margin of the karnataka plateau peninsular india in the transition sub humid zone of this climatic gradient we have studied the pristine forested small watershed of mule hole 4 3 km2 mainly developed on gneissic substratum mineralogical geochemical and geophysical investigations were carried out i in characteristic red soil profiles and ii in boreholes up to 60 m deep in order to take into account the effect of the weathering mantle roots in addition 12 electrical resistivity tomography profiles ert with an investigation depth of 30 m were generated at the watershed scale to spatially characterize the information gathered in boreholes and soil profiles the location of the ert profiles is based on a previous electromagnetic survey with an investigation depth of about 6 m the soil cover thickness was inferred from the electromagnetic survey combined with a geological pedological survey taking into account the parent rock heterogeneity the degree of weathering of each of the regolith samples has been defined using both the mineralogical composition and the geochemical indices loss on ignition weathering index of parker chemical index of alteration comparing these indices with electrical resistivity logs it has been found that a value of 400 ohm m delineates clearly the parent rocks and the weathered materials then the 12 inverted ert profiles were constrained with this value after verifying the uncertainty due to the inversion procedure synthetic models based on the field data were used for this purpose the estimated average regolith thickness at the watershed scale is 17 2 m including 15 2 m of saprolite and 2 m of soil cover finally using these estimations of the thicknesses the long term mass balance is calculated for the average gneiss derived saprolite and red soil in the saprolite the open system mass transport function indicates that all the major elements except ca are depleted the chlorite and biotite crystals the chief sources for mg 95 fe 84 mn 86 and k 57 biotite only are the first to undergo weathering and the oligoclase crystals are relatively intact within the saprolite with a loss of only 18 the ca accumulation can be attributed to the precipitation of caco3 from the percolating solution due to the current and or the paleoclimatic conditions overall the most important losses occur for si mg and na with 286 106 mol ha 62 of the total mass loss 67 106 mol ha 15 of the total mass loss and 39 106 mol ha 9 of the total mass loss respectively al fe and k account for 7 4 and 3 of the total mass loss respectively in the red soil profiles the open system mass transport functions point out that all major elements except mn are depleted most of the oligoclase crystals have broken down with a loss of 90 the most important losses occur for si na and mg with 55 106 mol ha 47 of the total mass loss 22 106 mol ha 19 of the total mass loss and 16 106 mol ha 14 of the total mass loss respectively ca al k and fe account for 8 6 4 and 2 of the total mass loss respectively overall these findings confirm the immaturity of the saprolite at the watershed scale the soil profiles are more evolved than saprolite but still contain primary minerals that can further undergo weathering and hence consume atmospheric co2

holocene environmental change in eastern spain reconstructed through the multiproxy study of a pedo sedimentary sequence from les alcusses valencia spain abstract we present a multiproxy characterization of a complex polycyclic soil sequence from les alcusses moixent valencia se spain the area has abundant settlements dating from early neolithic to roman times the sequence comprises six main units dating back to 8 7 8 5 ka cal bp we integrated mineralogy inorganic ph grain size elemental composition and organic chemistry pyrolysis gas chromatography mass spectrometry pyrolysis gc ms micro charcoal pollen and non pollen palynomorph npp data all data is contextualized within a framework of archaeological information and radiocarbon dating with the aim of deciphering the holocene environmental changes we infer a shift from wetter and warmer in the early mid holocene to drier and cooler climatic conditions with increased fire occurrence in the mid late holocene particularly after 5 3 ka cal bp although the pollen record indicates a rapid forest retreat and expansion of grasslands for the neolithic period local proxies molecular soil om indicators and npp point to the presence of pine forest in the studied location well after the regional decline started the same proxies suggest a sharp forest decline after about 7 0 ka cal bp strong soil erosion likely linked both to climatic instability and the intensification of human exploitation resulted in a hiatus from the late neolithic to the roman period a certain climate amelioration wetter conditions and land abandonment or at least lower human pressure are suggested for the late roman period early middle ages direct evidence of changes in soil properties due to agriculture was not detected in the sequence except for the upper soil unit studied which reflects intense agricultural management with the possible use of agrochemicals

weak influences of climate and mineral supply rates on chemical erosion rates measurements along two altitudinal transects in the idaho batholith 1 chemical weathering promotes regolith production physical erosion nutrient supply and drawdown of atmospheric co2 although mineral dissolution rates show dependences on temperature and moisture in theoretical models and laboratory experiments effects of climate on chemical erosion rates in nature remain uncertain in part because variations in physical erosion rates and lithology can obscure climatic signals in chemical erosion rate measurements here we present new estimates of millennial scale chemical and physical erosion rates along two altitudinal transects in the idaho batholith our measurements suggest that chemical erosion rates and the extent of regolith chemical alteration are insensitive to mean annual regolith temperature even though the study sites span a wide range in temperatures 4 8 c 10 9 c these data also suggest that rates of chemical erosion and the extent of regolith chemical alteration are weakly correlated with the annual duration of high regolith moisture conditions lastly our measurements show that the sampled regoliths tend to grow more chemically weathered with increasing regolith residence time implying that weathering at these sites is primarily limited by mineral dissolution kinetics rather than mineral supply rates to the regolith the lack of strong control by mineral supply means that chemical erosion rates at these sites could potentially vary in response to climatic factors such climatically driven variation in chemical erosion rates is not obvious in our data however instead our measurements suggest that chemical erosion rates at these sites are insensitive to mean annual regolith temperature and only weakly dependent on the length of the wet season

metamictization and chemical durability of detrital zircon we have investigated the effect that metamictization has on the weathering of zircon in detrital continental sediments and tropical soils of the amazon basin brazil the degree of radiation damage in the near surface region of the zircon grains was determined by raman microprobe in each of the four series investigated i e sediment podzol topsoil and subsoil horizons of lateritic soil the degree of radiation damage ranges from less than 1014 to 3 5 1015 decay mg the maximum degree of radiation damage coincides with the first percolation threshold of the metamictization process at 3 5 1015 decay mg below this threshold amorphous volumes in the structure of damaged zircon are not connected to each other the ranges of u th and pb contents in ppm measured by proton induced x ray emission pixe microanalysis are 100 u 7000 100 th 18000 and 100 pb 1300 chemical ages assessed from u th and total pb range between 0 15 ga and 2 8 ga this range is roughly consistent with the ages reported for the precambrian shields of the amazon basin 0 45 3 5 ga corresponding radiation doses range between 2 1015 and 3 1016 decay mg comparison of calculated doses with the degree of structural damage indicates that most of the zircon grains have experienced significant annealing however the degree of annealing differs from one grain to another thus the acute maximum limit observed for the degree of radiation damage of the whole zircon series is better explained by low temperature alteration or weathering processes than by thermal resetting following this interpretation our results provide evidence for a dramatic decrease in the chemical durability of zircon in natural weathering environments when the radiation dose exceeds 3 5 1015 decay mg below the first percolation threshold the zircon population survives the soil formation intact but more damaged zircons are dissolved during weathering alteration processes

life at the top of the greenhouse eocene world a review of the eocene flora and vertebrate fauna from canada s high arctic early middle eocene ca 53 38 ma sediments of the eureka sound group in canada s arctic archipelago preserve evidence of lush mixed conifer broadleaf rain forests inhabited at times by alligators turtles and diverse mammals including primates tapirs brontotheres and hippo like coryphodon this biota reflects a greenhouse world offering a climatic and ecologic deep time analog of a mild ice free arctic that may be our best means to predict what is in store for the future arctic if current climate change goes unchecked in our review of the early middle eocene arctic flora and vertebrate fauna we place the arctic fossil localities in historic geographic and stratigraphic context and we provide an integrated synthesis and discussion of the paleobiology and paleoecology of these eocene arctic forests and their vertebrate inhabitants the abundance and diversity of tapirs and plagiomenids both rare elements in midlatitude faunas and the absence of artiodactyls early horses and the hyopsodontid condylarth hyopsodus well represented at midlatitude localities are peculiar to the eocene arctic the eocene arctic macrofloras reveal a forested landscape analogous to the swamp cypress and broadleaf floodplain forests of the modern southeastern united states multiple climate proxies indicate a mild temperate early middle eocene arctic with winter temperatures at or just above freezing and summer temperatures of 20 c or higher and high precipitation at times this high precipitation resulted in freshwater discharge into a nearly enclosed arctic ocean basin sufficient to cause surface freshening of the arctic ocean supporting mats of the floating fern azolla fluctuating arctic ocean sea level due to freshwater inputs as well as tectonics produced temporary land bridges allowing land plants and animals to disperse between north america and both europe and asia

constraining the physical chemical conditions of pleistocene cavernous weathering in late paleozoic granites abstract cavernous weathering such as tafoni alveoles and honeycomb structures have been recorded from a great variety of bedrocks and landforms in the present study cavernous weathering from late variscan granites was discussed as to its physical chemical regime of formation u pb dating yielded a maximum age of 1 52 0 03 ma supergene u mineralization is accompanied by kaolinite nontronite and fe iii phosphates based upon eh ph diagrams calculated for u fe p mineralization the physical chemical conditions may be described as oxidizing with ph values fluctuating around neutral at near ambient temperatures of 25 c alteration occurs in two stages dissolution of rock forming minerals and neoformation of hydrosilicates under mildly acidic conditions followed by phosphate precipitation under near neutral conditions

geochemical modeling of steady state fluid flow and chemical reaction during supergene enrichment of porphyry copper deposits in this study motivated by detailed field work and laboratory analysis we numerically simulate the supergene enrichment of porphyry copper deposits we utilize a new program developed to model simultaneously advective solute transport in variably saturated porous media and chemical fluid rock interactions incorporating mineral dissolution kinetics field and laboratory analytic and mineralogic data from supergene enrichment systems at butte montana and ok tedi located in western papua new guinea are used to provide geochemical lithologic and hydrologic initial and boundary conditions required for geologically relevant modeling we have simulated the weathering and supergene enrichment of porphyry copper potassium silicate proto ore or protore containing disseminated pyrite and chalcopyrite in a one dimensional vertically oriented flow region under steady flow conditions for a total model time of about 12 000 yr during this time primary chalcopyrite dissolves completely from the leached and blanket zones pyrite is destroyed in the leached zone and magnetite dissolves from the entire flow region we therefore investigate both supergene enrichment processes and the response of the system to complete dissolution of a protore reactant computed mineral assemblages are generally in excellent agreement with those observed in natural systems although copper is remobilized in the simulation by leaching above the model ground water table and reprecipitation below it the resulting differentiated weathering profile is chemically closed with respect to copper this is because nearly all of the transported copper is fixed below the ground water table by secondary sulfide precipitation therefore an important conclusion to be drawn from the modeling is that in natural oxidative weathering vertical copper fluxes out of supergene systems are probably negligible even over extremely long periods of geologic time these theoretical results confirm earlier calculations of amounts of erosion and erosion rates and reconstructions of paleotopography assuming copper mass balance in regions of vertical fluid flow brimhall et al 1985 alpers and brimhall 1988 1989 sulfur in contrast is mobile during the simulation and significant quantities of sulfate leave the flow region with time modeling results indicate that the dominant source of sulfur for secondary copper sulfide mineral formation in the enrichment blanket is the preexisting protore sulfides not electrochemical reduction of the sulfate transported out of the leached zone the numerical simulation demonstrates that oxygen fugacity is the primary control governing the nature and extent of low temperature reequilibration of the fossil magmatic hydrothermal system in the near surface weathering environment

characterization of properties and main processes related to the genesis and evolution of tropical mountain mires from serra do espinhaco meridional minas gerais brazil abstract the properties and components of the peat allow peatlands to function as water reservoirs which participate in the hydrological cycle by modulating water discharge in particular mountain peatlands from serra do espinhaco meridional minas gerais state brazil provide water of good quality for the nearby cities and also serve as habitats for wildlife and flora with unique endemic species in this paper we present the characterization of four mountain mires pau de fruta sao joao da chapada pinheiros and sempre viva based on morphological physical chemical and elemental properties analyzed in five selected peat cores pdf i pdf ii sjc pi and sv radiocarbon dating indicates that they started to form during the late pleistocene principal components analysis was applied to synthesize their main peat properties and underlying processes the first principal component pc1 is related to the relative content in inorganic versus organic matter of the peat most probably related to the evolution of the soils of the mires catchments i e soil erosion pc2 seems to be related to the incorporation of inorganic material by deposition of dust from regional sources pc3 reflects the content and preservation of plant remains and pc4 indicates the degree of peat decomposition our results suggest that mountain tropical mires from serra do espinhaco meridional are complex peatland ecosytems with a large potential for the reconstruction of environmental changes i e climate change occurred since the late pleistocene and that they should be fully protected

soil genesis optical dating and geoarchaeological evaluation of two upland alfisol pedons within the tertiary gulf coastal plain abstract much of the gulf coastal plain is mantled by sandy a and e soil horizons overlying finer grained bt horizons researchers have applied optical stimulated luminescence osl dating to a variety of depositional settings such as hillslopes and terraces in an attempt to understand depositional versus pedogenic origins of the sandy horizons and archaeological burial processes these investigations have documented a range of integrity conditions from pristine to highly bioturbated however little work has been conducted in upland summits thus we integrated field morphological descriptions constituent mass balance reconstruction and optical dating to reconstruct the timing and pedogenic pathways of two summit alfisols on the tertiary gulf coastal plain in texas investigations reveal that the sandy a and e horizons and the bt horizons in each pedon are genetically related with textural contrasts resulting from pedogenic processes optical dating revealed highly complex age structures strongly influenced by bioturbation weathering and the presence of coarse clay plus total silt particle sizes pedogenic mixing is extensive in the a and e horizons which effect apparent osl ages

effect of north and south exposure on weathering rates and clay mineral formation in alpine soils abstract a comparison was made between two soil climosequences on north and south facing slopes in northern italy to determine the influence of slope aspect on soil processes the climosequences span an elevational gradient ranging from moderate 1200 m a s l to high alpine 2420 m a s l climate zones on surfaces having an age of about 15 000 years the soils were investigated with respect to organic c oxalate and dithionite extractable fe al and si elemental losses ca mg k na fe al si mn and clay minerals the stocks of soil org c as well as of oxalate extractable fe and al was greatest in the subalpine zone near the timberline there are no clear differences in organic c content between the soils on north and south facing sites fe oxalate and to a lesser extent alo stocks were however greater on north facing sites indicating that weathering is greater there eluviation and illuviation of al and fe within the soil profile typical for podzolisation was more distinctly expressed on the n slopes the probability of itm imogolite type material formation in the soil seemed to be greater on south facing sites on the north facing sites element leaching was most intense in the subalpine zone close to the timberline while on the south facing sites this was only the case for the base cations the n slopes exhibited higher leaching of elements which generally indicates a higher weathering intensity on south facing sites typical podzolisation processes were measurable only above 2000 m a s l the development of smectites is also a reflection of the weathering intensity smectite was discernible in the surface horizon at all sites on n slopes but the highest amount was detected in the sub alpine climate zone for the south facing sites only in the alpine climate zone could smectite be detected higher temperatures and an increased number of freeze thaw cycles on south facing slopes should theoretically enhance rates of chemical weathering this could however not be confirmed with our measurements the degree of chemical weathering increases from the south to the north facing sites that are characterised by lower temperatures lower evapotranspiration and consequently by a higher humidity although precipitation in alpine regions is abundant the availability and flux of water through the soil is the prime factor in weathering intensity

a long pollen sequence of neogene age alaska range abstract a thick sediment sequence 590 m of neogene age exposed in the nenana coal field alaska at a latitude of 63 5 n provides an extensive pollen and spore record spanning most of the miocene and probably part of the early pliocene the sediments of the upper usibelli group miocene and overlying nenana gravel pliocene are the basis of this study the flora from both leaves and pollen of the usibelli group connotes a vegetation similar to the mixed northern hardwood forest of northeastern united states and the northern part of east china northern korea and southern hokkaido the warmest pollen and leaf assemblages of the miocene occur in the suntrana formation in the lower third of the unit and these correlate very well with flora of the upper seldovian stage as the reference section on cook inlet which is of late early to early middle miocene age shifts in forest composition from suntrana formation sediments upper seldovian stage into the overlying sediments of the lignite creek and grubstake formations connote a cooling with minor changes of vegetation and climate these cooler phases are correlative with the homerian and clamgulchian stages of cook inlet mean annual temperature mat estimate based on fossil pollen and leaves from the lower suntrana formation is ca 9 c and summers were consistently warm and wet in the cooler phases of the late miocene the mat probably dropped to about 5 c

zircon an immobile index in soils interpretation of any element s mobility in soils needs rigorous means of calculating losses or gains in relation to parent rock the first mass balance calculations were based on isoelement changes major elements during conversion of fresh rocks to weathered materials harrisson 1933 leneuf 1959 isovolumetric mass balance calculations were applied for the first t ime in 1955 to determine mass transfers in saprolite millot and bonifas 1955 since that time numerous works have been carried out on mass balance calculations in determining transfers during weathering brimhall and dietrich 1986 recently equations used to calculate volumetric changes and net mass gain or loss of mobile elements have been based on zirconium mostly from the mineral zircon the aim of the paper is to question the axiomatic immobility of zircon in soils and then to assess the limit of mass balance calculations in surficial weathering systems

pseudomorphic transformation of plagioclases during the weathering of granitic rocks in galicia nw spain abstract microscopic study of twelve weathering profiles developed on granitic rocks in galicia nw spain showed that in most cases the transformation of the parent rock into saprolite occurs with pseudomorphic alteration of the plagioclases it was seen that the transformation and the retention of plagioclases in the alteration profile are directly related to the conservation of the general structure of the rock and this in its turn depends on the mineralogical composition and texture the most unstable constituents in the galician environment are biotites and plagioclases there being a clear difference in the rate of alteration between the plagioclases and the k feldspars this implies that a large part of the fabric of the rock remains unaltered when the plagioclases are completely weathered so that the pores caused by the weathering of the plagioclases are filled by their own alteration products with regard to the influence of the texture it was observed that fine grained rocks are altered more easily than coarse grained ones especially if they are rich in biotites in this study we show various examples in which even with high levels of alteration the morphological features of the original plagioclase crystals are preserved twins original zoning myrmekitic textures and perthites the pseudomorphic transformation of plagioclase is independent of the products to which it gives rise and here we show examples where gibbsite 1 1 dioctahedral phyllosilicate or a mixture of both appear as secondary minerals the mineralogical nature of a newly formed product depends mainly on the intensity of the leaching to which the profile is subjected which is influenced by the rainfall in the area where they are found as well as the size of existing voids in the material

redistribution and mobilization of titanium zirconium and thorium in an intensely weathered lateritic profile in western australia abstract the mobility of titanium zirconium and thorium elements commonly considered insoluble during supergene weathering is still not well understood especially in intensely weathered regolith thus an intensely weathered lateritic profile jg developed on meta granitoids in jarrahdale western australia was investigated the mobility of ti zr and th has been assessed at both mineral assemblage and profile scales and the mode of occurrence has been investigated through the combined use of geochemical data from bulk regolith particle size fractions and sequential extractions with in situ data determined by electron probe micro analyzer and synchrotron x ray powder diffraction neoformed poorly crystalline phases containing trace to minor amounts of zr ce and th unassociated with silicates or phosphates were identified on the walls of al fe rich pores in the ferruginous duricrust this implies that some mobilization and redistribution of zr and th occurs within a sample scale breakdown of primary thorite and rare earth element rich fluorocarbonates is thought to be the source for zr and th in the neoformed phases rather than zircon thus the mineral hosts of zr ti and th in the parent rock and their relative susceptibility to weathering are the fundamental controls on subsequent mobility during initial weathering trace amounts of th in secondary phases such as rhabdophane and florencite show translocation of th at the mineral scale while strong partitioning of th into gravel rather than matrix reflects redistribution of th at the profile scale the absence of primary sphene from the regolith and the presence of partially dissolved ilmenite and rutile grains in the ferruginous mottled zone suggest mobilization and translocation of ti at a mineral assemblage scale furthermore the fluctuation of ti zr in the ferruginous zone is in contrast to the consistency of zr hf throughout the profile in general within the range of parent meta granitoid this suggests that ti and zr fractionate from each other and partition between gravel and matrix during extreme weathering and advanced lateritization this study demonstrates that ti zr and th are mobile at a variety of scales an important consideration that is often overlooked when calculating element mass flux in intensely weathered regolith

14 kyr of atmospheric mineral dust deposition in north eastern china a record of palaeoclimatic and palaeoenvironmental changes in the chinese dust source regions a multi proxy record of holocene and late pleistocene aeolian mineral dust is reconstructed using a combination of geochemical trace elements mineralogical and grain size analyses on cores from

geochemistry of laterites stability of al goethite al hematite and fe super 3 kaolinite in bauxites and ferricretes an approach to the mechanism of concretion formation

toward process based modeling of geochemical soil formation across diverse landforms a new mathematical framework we present a mathematical model that integrates geochemical and geomorphic processes responsible for soils elemental and mineralogical evolution on diverse landforms eroding to depositional to level grounds this new model combines a hillslope sediment mass balance and a soil geochemical mass balance we model soils as the sum of a physically disturbed zone pdz and the underlying physically undisturbed but chemically altered zone caz the model considers processes including the production of pdz weathering front propagation mineral specific dissolution colloidal translocation and colluvial transport thus this study serves to 1 review preexisting models of pedogenic processes and to 2 offer a framework to integrate the geochemical and geomorphic processes active in soils we further discuss the implications of our model in 1 scaling chemical weathering reactions from mineral grains to pedons to soil catenas 2 understanding the emergence of geochemical soil catenas and 3 coupling physical and chemical weathering processes

compressibility and collapse characteristics of arid saline sabkha soils abstract arid saline soils are well distributed over the globe with a variety of nomenclature along the seaboard of the arabian gulf these soils exist widely and are known as sabkhas despite the cemented and saline characteristics of the sabkha matrix a recent investigation indicated that flooding the saline sabkha with distilled water in the conventional oedometer apparatus was incapable of producing a sudden reduction in volume and or a significant collapse this study proposes a modification to the conventional oedometer on undisturbed sabkha specimens to consolidating specimens under a constant head tests were therefore conducted on undisturbed sabkha specimens to assess their compressibility and collapse potential whereby percolation of water was commenced under two pressures to evaluate the role of sustained pressure on the collapse mechanisms despite the low compressibility of sabkhas results of these tests indicated that these arid saline soils possess a high collapse potential attributable primarily to dissolution of sodium chlorides leaching of calcium ions and soil grain adjustment the collapse potential increases with an increase in the acting pressure at which percolation of water takes place in contrast to other typical soils the collapse of arid saline soils is not instantaneous but requires sufficient volume of water to percolate in order to enhance the dissolution of the cementing agents

shoreline displacement and human resource utilization in the southern baltic basin coastal zone during the early holocene new insights from a submerged mesolithic landscape in south eastern sweden along parts of the hano bay coast in south eastern sweden remains of a submerged landscape can be found down to depths of almost 25 m b s l the coastal landscape was formed during two periods of

the last termination in the central south atlantic lake sediments and peat deposits from two basins on nightingale island 37 degrees s in the tristan da cunha archipelago south atlantic have been analyzed the studies were focused on the time period 16 2 10 0 cal ka bp determined by 36 c 14 dates from the two sequences a wide variety of proxies were used including pollen and diatom analyzes biogenic silica content c and n analyzes stable isotopes c 13 and n 15 elemental concentrations and magnetic susceptibility measurements to detect environmental changes that can be related to shifts of the circulation belts of the southern ocean in addition climate model simulations were carried out we find that the sediments are underlain by a 2 cal ka bp long hiatus possibly representing a dried out lake bed the climate simulations corroborate that the area might have been exposed to arid conditions as a consequence of the heinrich i event in the north and a southward displacement of the itcz the development on the island after 16 2 cal ka bp is determined by the position of the subtropical front stf and the southern hemisphere westerlies shw the period 16 2 14 75 cal ka bp was characterized by varying influence from shw and with stf situated south of tristan da cunha ending with a humidity peak and cooler conditions the stable conditions 14 7 14 1 cal ka bp with cool and fairly arid conditions imply that stf and shw were both north of the islands during the first part of the antarctic cold reversal the most unstable period 14 1 12 7 cal ka bp indicates incessant latitudinal shifts of the zonal circulation perhaps related to climate variability in the northern hemisphere and bipolar seesaw mechanisms as the strength of the atlantic meridional overturning circulation amoc varied at 12 7 cal ka bp the holocene warming began with a gradually drier and warmer climate as a result of a dampened amoc during the younger dryas cooling in the north with itcz stf and shw being displaced southwards peak warming seems to have occurred in the earliest part of the holocene but this period was also characterized by humidity shifts possibly an effect of retraction and expansion phases of shw during amoc variations in the north c 2015 elsevier ltd all rights reserved less

geotechnical behaviour of saline sabkha soils the behaviour of salt cemented sabkha soil was investigated by considering the effect of brine and distilled water on its properties laboratory and field testing programmes were conducted to examine the effect of soaking and leaching on the structure compressibility collapse permeability load carrying capacity and settlement of sabkha soil results indicate that the percolation of distilled water through the sabkha causes destruction of the natural cementation leading to collapse increase in permeability reduction in strength and increase in settlement dissolution and leaching of halite gypsiferous and calcarenite cements occur leaving the quartz particles covered by a thin loose mat of illitic clay with large voids the collapse deformation of sabkha is inclusively linked to the ambient salt complex which determines the structural properties of the soil and promotes the development of collapse on wetting the soaking of sabkha produces practically negligible collapse leaching causes a signif

effect of the addition of granitic powder to an acidic soil from galicia nw spain in comparison with lime high amounts of granitic powders are produced in the granite industry in galicia nw spain whose accumulation could pose environmental threats at least locally due to its natural alkalinity the powder could be used to correct the acidity of soils or mining residues where it would act at the same time as a source of plant nutrients a greenhouse experiment was conducted to test the growth of italian ryegrass on an acid soil amended with different rates of granitic powder 2 5 5 and 10 soil amended with lime or with lime in combination with p k fertilizer and the granitic powder alone was used for comparison with the unamended soil as control after a growth period of 14 weeks the plants were completely removed and washed dry weight yield was recorded for roots and shoots and their contents in nutrients and heavy metals were determined cation exchange capacity cec ph total c and n nutrient elements and heavy metals were also determined in soil samples the addition of granitic powder ameliorated the soil conditions for plant growth with increments in soil ph cec and available nutrients as well as a reduction of aluminium saturation as a consequence a significant increment in plant yield at increasing granitic powder rates was observed in comparison to the other amendments up to 75 higher than in the soil without amendment the results of this study allow considering granitic powder as a suitable alternative to the traditional lime based amendments for acid soils

holocene climate change in central eastern brazil reconstructed using pollen and geochemical records of pau de fruta mire serra do espinhaco meridional minas gerais abstract studies dealing with the reconstruction of holocene climate change of tropical areas are scarce of these multi proxy investigations using peatlands are still absent in this paper we present the holocene record of environmental changes in central eastern brazil reconstructed from a core sampled in pau de fruta mire serra do espinhaco meridional brazil we combined palynological and geochemical analyses supported by core stratigraphy 14 c dating and multivariate statistics the location of the mire is ideal because it is in an area which is directly associated with the south atlantic convergence zone sacz six main phases of change suggested by vegetation and local and regional landscape dynamics were described in phase i 10 000 7360 cal yr bp the climate was very wet and cold and was accompanied by soil instability in the mire catchment severe local erosion and the 8 2 ka event was easily recognizable by a large increase in the deposition of regional dust phase ii 7360 4200 cal yr bp was characterized by wet and warm conditions catchment soil stability and enhanced deposition of regional dust in phase iii 4200 2200 cal yr bp climate was dry and warm and soil erosion in the catchment increased again in phase iv 2200 1160 cal yr bp dry and punctuated cooling was reconstructed together with enhanced deposition of regional dust phase v 1160 400 cal yr bp reflects sub humid climatic conditions like the current climate the lowest inputs of local and regional dust and the largest accumulation of peat in the mire while in phase vi

evidence for an unconformity at the scollard battle contact upper cretaceous strata alberta the scollard formation is the uppermost division of the edmonton group in the red deer river valley of central alberta it dates from the close of cretaceous and the beginning of tertiary time it rests on a very distinctive clay sequence consisting in descending order of the battle and whitemud formations which overlie in turn the horseshoe canyon formation the lowest division of the edmonton group near the top of the battle formation is a distinctive and widespread bed of volcanic origin kneehills tuff the contact of the battle clay above this bed with the scollard formation varies in level within single exposures a widespread coal seam ardley or no 14 divides the scollard formation into lower and upper members the thickness of the lower member decreases markedly from south to north as does the level of the highest recognized dinosaur remains there is a marked contrast between the dinosaur fauna of the lower scollard member and that of the horseshoe canyon formation a similar break has bee

geochemistry and grain size distribution of surface sediments of a large semi enclosed lagoon connected to the western bay of bengal abstract batticaloa is a large 135 5 km2 semi enclosed micro tidal lagoon that formed by barrier deposits in eastern sri lanka and has a unique geographic position due to its tropical monsoonal climate and absence of tectonics the recent soft bottom sediments of batticaloa lagoon were studied on the basis of geochemistry and grain size distribution in order to interpret their characteristics and provenance poor to moderately sorted medium sands are the dominant sedimentary deposits for the lagoon therefore a medium energy condition is suggested for sediment deposition the average silt and clay fraction of the lagoon sediments is less than 3 indicating medium or high energy flows coarser deposits are restricted to channel and lagoon mouths the scatter plots of nb zr cr and sc vs th and cr v vs y ni show a felsic provenance for the sediments the normalized diagrams of major element oxides and trace elements for the regional rocks vijayan complex of sri lanka indicate high country rock influence for the sedimentation for the semi enclosed setting the enrichment and distribution of zr th nb cr and tio2 suggest the possibility of mineral sands that are fractionated with hydrodynamic setting of the lagoon

constitutive mass balance relations between chemical composition volume density porosity and strain in metasomatic hydrochemical systems results on weathering and pedogenesis relations characterizing the chemical physical and mechanical changes resulting from metasomatic hydrochemical processes are developed using mass balance models which formally link chemical composition to bulk density mineral density volumetric properties porosity and amount of deformation strain rigorous analysis of aqueous solute transport effects is then made possible in a variety of porous media flow environments including chemical weathering pedogenesis soil formation diagenesis ore deposition and enrichment and metamorphism application of these linear constitutive relations to chemical weathering profiles shows that immobile and locally mobile chemical elements with masses conserved on the scale of soil profiles can be accurately identified from analysis of appropriate data arrays and then used as natural geochemical tracers to infer the nature and extent of hydrochemical weathering processes and volume changes during pedogenesis assumptions commonly made in the past about the supposed immobility of certain elements e g ti and zr become unnecessary quantitative differentiation between the effects of residual and supergene fractionation is then easily made these methods are applied to ni rich laterites developed by weathering of ultramafic rocks showing that during ordinary residual enrichment ni is concentrated by as much as 4 protolith peridotite concentrations this occurs simply by silicate mineral dissolution and removal of chemical elements other than ni e g mg with a corresponding reduction in saprolite density and increase in bulk porosity without significant deformation in contrast laterites with mineable concentrations of ni which are similarly undeformed such as the nickel mountain mine in riddle oregon have experienced in addition to residual enrichment strong supergene enrichment by fractionation of ore elements between a leached zone from which ni is extracted and a complementary enriched zone positioned farther along the direction of ground water flow soil forming processes in podzol chronosequences developed on sandy beach terraces of the mendocino coast of california involved soil column collapse of 60 percent by dissolution of silicate minerals in the albic horizon of al and fe leaching and 70 percent dilation expansion in the overlying organic rich layer by root growth the amount of erosion based upon paleosurface reconstructions using the excess mass of fe al pb ga and cu in the zone of supergene enrichment spodic horizon below the ground water table indicates that subsurface erosion by dissolutional collapse is three times that of surficial erosion finally using published chemical data for ti zr and cr on major bauxite deposits in australia where erosion rates are thought to be low we infer that there may have been major amounts of dissolutional collapse to explain the upwards increase of detrital zircon and rutile in weathering profiles

hydrological thresholds and basin control over paleoflood records in lakes the scarcity of long term hydrological data is a barrier to reliably determining the likelihood of floods becoming more frequent and or intense in a warmer world lake sediments preserve characteristic event layers offering the potential to develop widely distributed and unique chronologies of historical floods inferring flood magnitude remains a greater challenge previously overcome in part by analyzing sharply laminated polar or alpine sequences here we demonstrate an approach to obtain flood frequency and magnitude data from an unexploited resource the largely visually homogeneous organic sediments that typify most temperate lakes the geochemical composition and end member modeling of sediment trap and adjacent short core particle size data for brotherswater northwest england discriminates the signature of infrequent coarse grained flood deposits from seasonal and longer term allogenic enhanced discharge and sediment supply during winter and autogenic summer productivity thermal mixing depositional processes comparing the paleoflood reconstruction to local river discharges shows that hydrological thresholds censor event signature preservation with 4 yr recurrence intervals detectable in delta proximal sediments declining to 9 yr in the lake center event threshold discharge and process characterization are essential precursors to discerning flood magnitude from sediment archives implementation of our approach in globally prevalent temperate lakes offers a vast unique repository of long term hydrological data for hydrologists climate modelers engineers and policy makers addressing future flood risks

smectite formation produced by weathering in a coarse granite saprolite in galicia nw spain abstract weathering of a calcalkaline granite was studied in the south of galicia nw spain where the average annual precipitation is 1400 mm and the average annual temperature is 12 c the original rock contains perthitic k feldspars plagioclases with inclusions of muscovite and opaque minerals quartz and chloritized biotite with apatite zircon sphene and opaques as accessories in the saprolite the structure of the rock is preserved the plagioclases show up to grade 4 weathering and the biotites between 2 and 3 weathering in quartz and potassium feldspar crystals is manifested only by fracturing biotite changes following the parallel linear model and its weathering products are interstratified biotite vermiculite and iron oxyhydroxides the plagioclases change to a microgranular material by pseudomorphic transformation this material which substitutes the plagioclase includes small clearly delimited units which retain zones with the optic characteristics of muscovite x ray diffraction analyses of microsamples show that they are formed by 1 1 diocthaedral phyllosilicate smectite and a small quantity of mica from these facts we concluded that smectite is formed inside the plagioclase crystals and probably originates from the inclusions of muscovite contained in these crystals as it is suggested by the microscopic study which shows the increase in volume which occurs when the crystals of muscovite are transformed

particle fluxes in groundwater change subsurface shale rock chemistry over geologic time abstract most models of landscape evolution posit that particles leave the land surface by physical weathering i e erosion and solutes leave the subsurface by chemical weathering they assume that erosion does not affect the rock and soil chemistry however in this study of a shale catchment we discovered that particles are mobilized out of soil and weathering rock and are transported through the subsurface resulting in changes in the rock and soil chemistry we studied the solute and particle fluxes during six storms in the susquehanna shale hills critical zone observatory in pennsylvania usa and compared those to the record in regolith chemistry the stream s suspended particles primarily consisted of platy shaped m sized illite commonly coated with patchy amorphous submicron sized al fe and si rich oxides the chemistry of the stream particles always differed from that of surface soils except during intense dry season rainstorms stream particles were chemically similar to the laboratory extracted soil colloids at high discharge but to groundwater particles at low discharge implying a central role of flow path variations in controlling subsurface particle transport zr was effectively immobile in shale hills regolith chemistry revealed that the cumulative effects of particle loss to depths of 5 8 m in the fractured bedrock zone were estimated to account for 58 of k and 24 of mg losses in shale landscapes we propose that subsurface particle transport must be considered in landscape evolution models as an important contributor to changes in rock and soil chemistry over geologic time periods

preliminary fractionaltion patterns of ore metals through earth history abstract a systematic method of comparing fractionation patterns of ore metals to those of common rock forming elements is developed using the coherent electronic framework provided by the periodic table through its progressive filling of transition metal d and f orbitals four generalized fractionation processes in earth history are addressed 1 nebular condensation and accretion 2 core mantle interaction 3 continental crustal growth and 4 ore formation in supracrustal environments through each of these simplified processes preliminary fractionation patterns of ore metals within periods appear to vary smoothly with atomic number fractionation trends for each of these four processes can be ascribed respectively to 1 differential condensation volatility 2 multiple stages of core formation with partial separation of highly siderophile metals into the core 3 enrichment of the continental crust in ore metals and incompatible elements by ascent of mantle derived magmas and 4 efficient multistage magmatic and hydrochemical ore forming processes within the crust fractionation trends of ore metals are contiguous and collinear with those of rock forming metals in the same period implying common geochemical controls the systematic variation of enrichment and depletion factors across groups of elements within the same period are termed chemical fractionation spectra

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

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

refractory element mobility in volcanic soils refractory trace element concentrations in strongly weathered hawaiian soils ranging in age from 20 to 4100 ka are highly elevated over parent rock values due to extensive mass loss of more soluble major elements during pedogenesis nb and ta exhibit virtually no mobility soil nb ta ratios are within the range of fresh bedrock even when soil nb concentrations are residually enriched by a factor of 10 in contrast al zr and hf are depleted relative to nb in surface soil horizons but are enriched at depth clearly indicating mobility of these elements variations in th nb ratios in soil profiles indicate significant th mobility within the soil column however mass balance calculations require that accretion of th enriched asian dust has resulted in a net increase in th in some soils soils developed on a 150 ka rainfall gradient show that the mobility and loss of zr increase with mean annual precipitation

quantitative geochemical approach to pedogenesis importance of parent material reduction volumetric expansion and eolian influx in lateritization abstract using mass balance techniques we test the prevalent view that laterite genesis is dominated by in situ residual enrichment during chemical weathering of bedrock through calculation of net mass fluxes through the laterite soils in mali west africa we show that residual enrichment by removal of mobile elements with a corresponding increase in bulk porosity and decrease in bulk density contributes only a very minor fraction of the enrichment of al fe si and au instead we demonstrate that the abundance of these elements is due to the influx and accumulation by selective retention of chemically mature detritus of local and foreign origin clearly evident in micromorphological infilling features at the same sample depths that accumulation reaches extreme values we show that volumetric expansion in excess of 200 has occurred locally we infer that these spatially coincidental zones of mass influx of rock forming metals fe al si and also au with dilational hyperstrains result from a mutually reinforcing mechanical interaction between material influx and the effects of subsurface deformational processes such as shrink swell cycles and root growth and decay we propose that with progressive infilling of available connected voids by illuvial microsedimentary deposits of insoluble resistate and neoformed minerals the capacity for the combined skeleton and plasma to remain isovulumetric is exceeded we speculate that the resultant space problem is relieved by upwards expansion towards the overlying free surface continued translocation and void infilling occur and are limited to the depth where the size of translocational particles is smaller than that of the connected voids consequently progressive hyperstrains accumulate above this critical depth by the long term influence of a proposed translocational wedge of chemically resistant minerals against which numerous generations of plant roots have exerted stresses eclectic surficial contaminants involved are continuously derived from above leaving no indication of a relict source region within the present soil profile from which they might have been extracted instead the source region is largely the existing regolith column itself which releases local material and in addition is supplemented by deposition of colluvial detritus shed nearby by escarpment retreat

arctic terrestrial biota paleomagnetic evidence of age disparity with mid northern latitudes during the late cretaceous and early tertiary magnetostratigraphic correlation of the eureka sound formation in the canadian high arctic reveals profound difference between the time of appearance of fossil land plants and vertebrates in the arctic and in mid northern latitudes latest cretaceous plant fossils in the arctic predate mid latitude occurrences by as much as 18 million years while typical eocene vertebrate fossils appear some 2 to 4 million years early

influence of climate change and human activities on the organic and inorganic composition of peat during the little ice age el payo mire w spain the study of environmental change during the little ice age lia offers a great potential to improve our current understanding of the climate system and human environment interactions here a

circulation patterns in the late pennsylvanian north american midcontinent sea inferred from spatial gradients in sediment chemistry and mineralogy abstract the north american midcontinent sea nams reached its maximum extent during glacio eustatic highstands of the late paleozoic ice age during which organic rich core shales accumulated under a stratified water column with anoxic deep waters the core shales of cyclothems are composed of a lower organic rich laminated black shale and an upper bioturbated gray shale the present study investigates circulation patterns within the nams by examining secular variations and spatial gradients in the concentrations and ratios of major elements trace elements and organic carbon as well as carbon and nitrogen isotopes within one cyclothemic core shale the heebner shale the heebner shale represents the core shale member of the upper pennsylvanian lowermost gzhelian virgilian oread limestone formation in kansas and iowa and it is correlative with the teutopolis shale of the mattoon formation in illinois the heebner was sampled at high stratigraphic resolution at five sites on the northern midcontinent shelf and two sites in the illinois basin clay and silt fraction proxies show influences from multiple distinct terrestrial sources the paleosalinity proxy sr ba in combination with spatial patterns of clay and silt proxies implies large scale counterclockwise cyclonic rotation of the nams watermass which was possibly driven by the hydrodynamics of upwelling on the southern midcontinent shelf margin and or riverine discharge into the eastern nams spatial patterns of 13c and 15n are consistent with regionally variable productivity and redox conditions differences in the magnitude of a positive 15n excursion among the study sites record spatially variable water column denitrification rates enrichment of trace metals on the northern midcontinent shelf was a product of intensified water column recycling within an estuarine saltwater wedge trace metal enrichments and fe al ratios are consistent with moderate watermass restriction throughout the nams the results of the present study permit major refinement of the existing superestuarine circulation model for the nams algeo t j et al 2008 modern and ancient epeiric seas and the super estuarine circulation model of marine anoxia in b pratt and c holmden eds dynamics of epeiric seas geol assoc canada spec publ 48 pp 7 38

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

mineralization and element redistribution in the chah gheib ni laterite ore zone bavanat zagros belt iran abstract nickel laterites are supergene deposits derived from the weathering of serpentinized ultramafic rocks and they commonly accounts for over 70 of world land based ni resources serpentinized ultramafic rocks outcrop extensively in iran as result of collision between afro arabian and iranian micro plate during the late cretaceous two ni bearing laterite belts developed on the ultramafic rocks of the neyriz ophiolite have been recently discovered in the bavanat region south iran the chah gheib deposit as the biggest ni bearing laterite in the bavanat area hosts a total estimated reserve mineralization of about 102 000 tons of ore at 0 92 ni and 180 000 tons at 1 63 cr this study focuses on elemental fractionation and mineralogical control of major trace and rare earth elements in a selected profile from the chah gheib ni laterite in order to assess the conditions of ore formation and its paleo environmental significance four distinct horizons including saprolite lower limonite upper limonite and lateritic duricrust have been recognized from the bottom to the top of the studied profile iron oxy hydroxides are the dominant phases found in the laterite profile overall fe and other first raw transition metals i e cr ni v co cu and zn show abundances higher than those of the bedrock the main fe and cr carriers in the laterite deposit are fe oxy hydroxides and chromite respectively although authigenic ni and cr bearing palygorskite is also common throughout the profile elemental mobility estimated using th as immobile element showed that the major oxides are largely depleted with the exception of fe2o3 and cao among trace elements cr is the element resulting strongly enriched in those levels where large chromite crystals occurs while v co ni and zn are enriched only in some levels of the upper limonite horizon and in the lateritic duricrust likely as adsorbed cations onto iron oxy hydroxides and as a consequence of an alkaline ph environment alkaline ph conditions can also explain the cu depletion observed throughout the profile such a condition during lateritization appears further supported by both the occurrence of carbonates and palygorskite and by the distribution of the ba sr ratio carbonates and palygorskite as well as secondary quartz require dry climate to form and alternating wet dry climate may allow lateritization this study suggests that the chah gheib laterite formed in a subtropical climate possibly during the late cretaceous late paleocene period in a roughly 25 35 latitude range promoting si and mg mobilization during the wet season and carbonates quartz and mg rich silicate precipitation during the drier periods

palaeoecology of late cretaceous polar vegetation preserved in the hansen point volcanics nw ellesmere island canada abstract mesozoic polar forests represent an extinct biome subject to a polar light regime and elevated atmospheric co2 levels in this paper new cretaceous fossil plant assemblages are reported from nw ellesmere island canada at a paleolatitude of 75 n these occur in a campanian maastrichtian aged interval of the hansen point volcanics a unit interpreted as a coastal plain peat mire complex within an active volcanic setting studies of palynomorphs sterile and fertile foliage and wood indicate that mire environments were dominated by amber producing taxodiaceous conifers with other conifers ginkgos cycads angiosperms ferns lycopsids and bryophytes occurring in subordinate numbers leaf physiognomic studies imply that most vegetation was deciduous occurrence of traumatic rings in the woods together with a high year to year variability in ring width indicates disturbed growing conditions possibly linked to a combination of frosts volcanic eruptions and flooding abundant charcoal remains indicate that an additional important disturbance process was wildfire results of this study compare closely with those from coeval circum arctic fossil sites and augment our knowledge of the community scale ecology of the cretaceous polar biome

regolith production and chemical weathering of granitic rocks in central chile abstract we have evaluated the long term chemical and physical weathering mass balance of an anomalously thick saprolite profile 30 m thickness developed in granitic rocks near curacavi coastal range of central chile the results of geochemical mass balance calculations for the regolith profile point to a moderate depletion for na and sr due to the plagioclase dissolution and precipitation of kaolinite furthermore silicon shows a predominantly constant behaviour along the profile that is indicative of incongruent weathering of plagioclase strongly suggesting that quartz dissolution conditions are not reached in addition low depletion of k mg ca rb and ba in the saprolite indicates a low degree of k feldspar biotite and hornblende weathering denudation rates calculated using cosmogenic 10be data range from 20 to 70 m ma if the saprolite thickness has reached a steady state condition the reported denudation rates lead to mineral residence times in the upper part of the saprolite profile of about 0 5 to 1 8 ma with such duration a higher weathering degree than observed at curacavi would be expected this apparent contradiction might be explained if all of the weatherable plagioclase has been dissolved under the present day precipitation and temperature conditions of the curacavi region therefore we propose that the curacavi profile could be in local equilibrium with respect to the weatherable fraction of plagioclase a local equilibrium regime may be reached when the overall degree of depletion is small in a weathering profile uniform elemental distribution and low weathering degree in the thick weathering profile at curacavi defy the traditional notion of weathering regimes and reveal the importance of exploratory studies in order to better understand weathering process in mediterranean and semi arid climate regions

geotechnical aspects and associated problems of al shuaiba lagoon soil red sea coast saudi arabia al shuaiba lagoon area locates along the eastern red sea coast south of jeddah city saudi arabia its soil profile consists mainly of coarse grained saline sabkha soil based on the vertical variations of grain size the studied al shuaiba lagoon soil profile was subdivide into three zones a saline sandy gravels b calcareous sandy silts and c well graded sands according to the spt n60 values these soil zones were classified into stiff medium stiff and very stiff soil type the soil zone b has cc values vary from 0 234 to 0 279 thus it classifies into loose and very high compressible soil consequently based on the exchangeable sodium percentages vs cation exchange capacity cec classification chart the soil zone b was classified into medium dispersive potential soil type the studied soil samples contain a relatively higher tds values and high concentration of calcium carbonates sulfates and chlorides thus these salts can play an essential harmful effectiveness on the durability of concrete when reacted with cement alkalis

using short lived nuclides of the u and th series to probe the kinetics of colloid migration in forested soils abstract the recent chemical dynamics of a podzolic forest soil section from the strengbach watershed france was investigated using u and th series nuclides analyses of 238 u 230 th 226 ra 232 th 228 ra and 228 th activities in the soil particles the seepage waters and the mature leaves of the beech trees growing on this soil were performed by tims or gamma spectrometry the simultaneous analysis of the different soil sl compartments allows to demonstrate that a preferential th leaching over ra must be assumed to explain the 226 ra 230 th 228 ra 232 th and 228 th 228 ra disequilibria recorded in the soil particles the overall ra and th transfer schemes are entirely consistent with the prevailing acido complexolysis weathering mechanism in podzols using a continuous open system leaching model the 226 ra 230 th and 228 ra 232 th disequilibria measured in the different soil layers enable dating of the contemporary processes occurring in this soil in this way we have determined that a preferential th leaching from the shallow ah horizon due to a strong complexation with organic colloids began fairly recently 18 years ago at most the continual increase in ph recorded in precipitations over the last 20 years is assumed to be the cause of this enhanced organic complexation a lower soil horizon 50 60 cm is also affected by preferential th leaching though lasting over several centuries at least with a much smaller leaching rate the migration of th isotopes through this soil section might hence be used as a tracer for the organic colloids migration and the induced radioactive disequilibria demonstrate to be useful for assessing the colloidal migration kinetics in a forested soil ra and th isotopic ratios also appear to be valuable tracers of some mineral water plant interactions occurring in soil the 228 ra 226 ra ratio enables discrimination of the ra flux originating from leaf degradation from that originating from mineral weathering in shallow 10 cm seepage soil waters it appears that at least in some cases the ra isotopic ratio measured in forest soil seepage waters may not be representative of the ra isotopic ratio released from mineral weathering indicating that the different origins of the dissolved 226 ra and 228 ra must be taken into account

weathering of the new albany shale kentucky usa i weathering zones defined by mineralogy and major element composition abstract comprehensive understanding of chemical and mineralogical changes induced by weathering is valuable information when considering the supply of nutrients and toxic elements from rocks here minerals that release and fix major elements during progressive weathering of a bed of devonian new albany shale in eastern kentucky are documented samples were collected from unweathered core parent shale and across an outcrop excavated into a hillside 40 year prior to sampling quantitative x ray diffraction mineralogical data record progressive shale alteration across the outcrop mineral compositional changes reflect subtle alteration processes such as incongruent dissolution and cation exchange altered primary minerals include k feldspars plagioclase calcite pyrite and chlorite secondary minerals include jarosite gypsum goethite amorphous fe iii oxides and fe ii al sulfate salt efflorescence the mineralogy in weathered shale defines four weathered intervals on the outcrop zones a c and soil alteration of the weakly weathered shale zone a is attributed to the 40 a exposure of the shale in this zone pyrite oxidization produces acid that dissolves calcite and attacks chlorite forming gypsum jarosite and minor efflorescent salt the pre excavation active weathering front zone b is where complete pyrite oxidation and alteration of feldspar and organic matter result in increased permeability acidic weathering solutions seep through the permeable shale and evaporate on the surface forming abundant efflorescent salt jarosite and minor goethite intensely weathered shale zone c is depleted in feldspars chlorite gypsum jarosite and efflorescent salts but has retained much of its primary quartz illite and illite smectite goethite and amorphous fe iii oxides increase due to hydrolysis of jarosite enhanced permeability in this zone is due to a 14 loss of the original mass in parent shale denudation rates suggest that characteristics of zone c were acquired over 1 ma compositional differences between soil and zone c are largely attributed to illuvial processes formation of additional fe iii oxides and incorporation of modern organic matter

magnetostratigraphy in pursuit of missing links since the last quadrennial report magneto stratigraphy has continued to flourish the primary issues have been 1 refinements to the geomagnetic reversal time scale grts including recalibrations correlation of biostratigraphic data to the crts and revision of the terminology 2 use of magnetostratigraphic data for estimating rates of such processes as sediment accumulation evolution and faunal migration and 3 magnetic mineralogy and the origin of remanence for convenience we have divided the publications into studies of continental and marine sediments and highlight the most exciting issues within each of these sub headings in the first section of this review we will concentrate on the development of the geomagnetic reversal time scale grts with particular emphasis on refinements from the last few years we then turn our attention to applications of magnetostratigraphy in marine and continental sequences

pedogenesis of spatially associated red and black soils in purna valley from semi arid region of central india abstract eight representatives spatially associated red and black soils in purna valley from the semi arid region of central india were studied through mineralogical micromorphological and geochemical investigations to infer pedogenic transformations during changing climatic phase the morphology of soils showed that dissected alluvial plains over the basaltic landforms consists predominantly of dark reddish brown to dark yellowish brown soils with iron calcium carbonate nodules typic haplustepts and lithological discontinuities typic ustifluvents whereas pediplains and alluvial plains have clayey dark brown sodic slickensided bss horizons enriched with caco3 nodules typic haplusterts buried natrustalf on alluvial fans and floodplains has strong brown natric btn horizons with distinct ferriargillans and abundant caco3 nodules ferriargillans in alfisols indicates prevalence of humid climatic phase in the past during which alteration of plagioclase feldspars to smectites could have occurred thereafter termination of humid phase and an onset of semi arid climatic phase had favored drier non leaching environment which has resulted in the preservation of smectites in vertisols the randomness in soils are expressed as entropy index which showed that physical mixing in subgroups of vertisols and sodium enriched argrillic horizons in alfisols were the indicators of altered pedogenesis at steady state the formation of caco3 pedogenic carbonates and the concomitant development of sodicity during arid climatic phase were indicators of strong alkalinity and base accumulation in soils as a mark of aridity in red and black soils of the valley the chemical index of alteration weathering index and entropy index were served as good indicators for assessing intensity of chemical weathering rate with respect to hydrology and topography the study demonstrates that how the morphological physical chemical mineralogical and micromorphological data were useful in assessing pedogenetic processes in spatially associated red and black soils of purna valley

capturing digital data of rock magnetic gamma ray and ir spectrometry for in situ quality control and for the study of the physical chemical regime of residual kaolin deposits se germany abstract residual kaolin deposits are operated on a worldwide basis the majority of them is derived from chemical weathering of felsic rocks during the cenozoic this is true for the kaolin deposits on the western edge of the bohemian massif here this type of deposit provides industrial minerals for the ceramic industry in se germany this raw material formed under tropical climatic conditions during the miocene and pliocene across a vast peneplain only within the naab wondreb depression however were economic accumulations preserved from erosion here near tirschenreuth kaolin has been mined since its discovery in 1830 the semi consolidated regolith is composed of quartz and opaline material alkaline feldspar different types of kaolinite muscovite illite a variegated spectrum of 14 a phyllosilicates fe mn oxide hydroxides and minor heavy minerals mainly containing ti a precise determination of the mineralogical composition of the ceramic raw material has so far solely relied on laboratory techniques e g xrd xrf and spectroscopic methods to the contrary this study takes a different approach capturing digital data in the field to determine its mineralogical composition gamma spectrometry k u th measuring the susceptibility of and analyzing short wave infrared spectra allows for an in situ quality control of the run of mine raw material it further assists in mapping the monotonous lithology and enables the authors to constrain the physico chemical regime throughout formation of the kaolin deposit the benefit for technical mineralogy and applied economic geology and the strong points of capturing digital data in the field is the easy and cost efficient handling of the various methods methods that were applied in this way for the first time the in door calibration and test measurements as well as the data acquisition during the field survey are presented and the data are correlated with the enhancing or deteriorating impacts of the inferred minerals on the firing behavior of the ceramic product collecting digital data can also help constrain the physico chemical regime during formation of the argillaceous deposit and improve further exploration through fine tuning the genetic model of residual kaolin accumulation the late carboniferous granites around tirschenreuth underwent strong supergene alteration in the ph range of 2 5 7 at log a sio2 aq 2 5 to 3 5 which resulted in a thick kaolinitic regolith illite formed under slightly increased ph between 4 and 7 attests to a change from tropical to more temperate humid conditions in the area the chlorite group phyllosilicates and nontronitic members of the smectite group came into existence when the ph increased to a ph interval of 7 to 11 this considerable change in the ph of the meteoric solutions occurred at the end of the neogene between 4 55 ma and 3 99 ma the different field methods compensate for each others weak points neither method is successful on its own but the current configuration can easily be expanded to include additional methods as there are neutron and micro resistivity and air and space borne approaches to cover more swiftly a larger exploration or study area

fate of metals in coastal sediments of a mediterranean flood dominated system an approach based on total and labile fractions the dynamics of sediment bound metals cs cu ni pb ti and zn were studied off the tet river western gulf of lion a typical mediterranean coastal river punctuated by short and violent flash floods spatial and temporal sampling strategies were combined to elucidate the fate of these elements in response to both the riverine sediment input and the offshore transport of these sediments through hydrodynamics our results show the temporal entrapment of riverborne particles and associated metals consecutively to a major flood event in the nearshore sedimentary unit called prodelta here deposition and resuspension mechanisms define a sedimentological cycle that could be followed completely in this study in terms of speciation between reactive labile and residual fractions along the fluvio deltaic continuum our results show that cu pb and zn are the most labile potentially mobile metals in the river in accordance with their contributions from anthropogenic sources but in the marine surficial sediments two main behaviours can be discriminated when compared to the riverine suspended particulate matter while pb and zn depict rather a constant labile fraction cu is characterized by decreasing levels up to 50 difference in terms of environmental impact these contrasting trends have direct repercussions for the contaminant dispersal in the coastal area whereas pb and zn conserve their enhanced levels because of their stronger affinity with fine sediments cu is marked by the entire loss of its anthropogenic component that is progressively transferred to the dissolved phase likely mediated by organic ligands we ascribe these behaviours to different post depositional partition mechanisms with respect to oxidation of the particulate organic phase at the bottom sediment water interface also analysis of one sediment core from the prodelta indicates that these early diagenetic processes govern the chemical forms of land derived contaminants sequestrated in the nearshore sedimentary archives c 2011 elsevier ltd all rights reserved

potentials and problems of building detailed dust records using peat archives an example from store mosse the great bog sweden mineral dust deposition is a process often overlooked in northern mid latitudes despite its potential effects on ecosystems these areas are often peat rich providing ample material for the reconstruction of past changes in atmospheric deposition the highly organic up to 99 in some cases matrix of atmospherically fed mires however makes studying the actual dust particles grain size mineralogy challenging here we explore some of the potentials and problems of using geochemical data from conservative lithogenic elements al ga rb sc y zr th ti and ree to build detailed dust records by using an example from the 8900 yr peat sequence from store mosse the great bog which is the largest mire complex in the boreo nemoral region of southern sweden the four dust events recorded at this site were elementally distinct suggesting different dominant mineral hosts the oldest and longest event 6385 5300 cal yr bp sees a clear signal of clay input but with increasing contributions of mica feldspar and middle ree rich phosphate minerals over time these clays are likely transported from a long distance source 100 km while dust deposition was reduced during the second event 5300 4370 cal yr bp this is the most distinct in terms of its source character with eu eu ucc revealing the input of plagioclase feldspar from a local source possibly active during this stormier period the third 2380 2200 cal yr bp and fourth 1275 1080 cal yr bp events are much shorter in duration and the presence of clays and heavy minerals is inferred elemental mass accumulation rates reflect these changes in mineralogy where the relative importance of the four dust events varies by element the broad changes in major mineral hosts grain size source location and approximated net dust deposition rates observed in the earlier dust events of longer duration agree well with paleoclimatic changes observed in northern europe the two most recent dust events are much shorter in duration which in combination with evidence of their local and regional character may explain why they have not been seen elsewhere

lack of bedrock grain size influence on the soil production rate abstract our study deals with the part played by bedrock grain size on soil formation rates u and th series disequilibria were measured in two soil profiles developed from two different facies of the same bedrock i e fine and coarse grain size granites in the geomorphically flat landscape of the experimental breuil chenue forest site morvan france the u and th series disequilibria of soil layers and the inferred soil formation rate 1 2 mm ky 1 are nearly identical along the two profiles despite differences in bedrock grain size variable weathering states and a significant redistribution of u and th from the uppermost soil layers this indicates that the soil production rate is more affected by regional geomorphology than by the underlying bedrock texture such a production rate inferred from residual soil minerals integrated over the age of the soil is consistent with the flat and slowly eroding geomorphic landscape of the study site it also compares well to the rate inferred from dissolved solutes integrated over the shorter time scale of solute transport from granitic and basaltic watersheds under similar climates however it is significantly lower than the denudation or soil formation rates previously reported from either cosmogenic isotope or u series measurements from similar climates and lithologies our results highlight the particularly low soil production rates of flat terrains in temperate climates moreover they provide evidence that the reactions of mineral weathering actually take place in horizons deeper than 1 m while a chemical steady state of both concentrations and u series disequilibria is established in the upper most soil layers i e above 70 cm depth in such cases the use of soil surface horizons for determining weathering rates is precluded and illustrates the need to focus instead on the deepest soil horizons

a novel geochemical approach to paleorecords of dust deposition and effective humidity 8500 years of peat accumulation at store mosse the great bog sweden both bog surface wetness and atmospheric dust deposition are intricately linked to changes in the hydrological cycle and pairing these types of records at the same site provides complementary infor

seasonal variability in arctic temperatures during early eocene time abstract as a deep time analog for today s rapidly warming arctic region early eocene 52 53 ma rock on ellesmere island in canada s high arctic 79 n preserves evidence of lush swamp forests inhabited by turtles alligators primates tapirs and hippo like coryphodon although the rich flora and fauna of the early eocene arctic imply warmer wetter conditions than at present the quantification of eocene arctic climate has been more elusive by analyzing oxygen isotope ratios of biogenic phosphate from mammal fish and turtle fossils from a single locality on central ellesmere island we infer early eocene arctic temperatures including mean annual temperature mat of 8 c mean annual range in temperature of 16 5 19 c warm month mean temperature of 19 20 c and cold month mean temperature of 0 3 5 c our seasonal range in temperature is similar to the range in estimated mat obtained using different proxies in particular relatively high estimates of early eocene arctic mat and sst by others that are based upon the distribution of branched glycerol dialkyl glycerol tetraether gdgt membrane lipids in terrestrial soil bacteria and isoprenoid tetraether lipids in marine crenarchaeota fall close to our warm month temperature suggesting a bias towards summer values from a paleontologic perspective our temperature estimates verify that alligators and tortoises by way of nearest living relative based climatic inference are viable paleoclimate proxies for mild above freezing year round temperatures although for both of these reptilian groups past temperature tolerances probably were greater than in living descendants

paleodust deposition and peat accumulation rates bog size matters abstract we present a high resolution peat paleodust and accumulation rate record spanning the last 8300 years from draftinge mosse 400 ha southern sweden 57 06 27 6 n 13 42 54 1 e the record was analysed for peat accumulation rates par elemental concentrations mineralogy and plant macrofossil content five periods of increased mineral deposition were recorded the first event occurred between 6280 and 5570 cal bp during the fen to bog transition this is followed by four atmospheric mineral dust events de which were recorded in the ombrotrophic section of the sequence at cal bp 2200 1385 1150 830 590 and from 420 to the present statistical analysis and elemental ratios indicated that both the mineralogy and grain size shifted when the system transitioned from fen into bog showing that the governing transport process shifted with the peatland succession stages this highlights the importance of identifying peatland succession stages within peat paleodust studies following all four de increases in par were observed implying a coupling to dust deposition comparison of de and par with a paleodust record from store mosse a 20 times larger bog located ca 18 km away kylander et al 2016 showed that both par and dust deposition are largely represented by single core reconstructions indicating that they are driven by a common climate forcing mechanism however higher par and dust deposition rates were observed in the more moderately sized draftinge mosse suggesting that the size of the bog is important to consider in peat paleodust studies furthermore the smaller bog responded more rapidly to hydrological changes indicating that the size of the bog affects its buffering capacity authigenic carbonates observed here during episodes of rapid peat growth coincide with changes in ree ratios indicating that authigenic peat processes potentially cause ree fractionation

mobility of gold and silver in lateritic weathering profiles some observations from western australia experimental evidence suggests that very acid chloride solutions generated in lateritic profiles by ferrolysis oxidation and hydrolysis of iron are responsible for the dissolution of gold and silver au is subsequently reprecipitated by reduction of the aucl 4 super ion with fe super 2 reduction of the agcl complex does not similarly occur because of the relative redox potentials of fe super 2 fe super 3 and ag agcl thus chemical refinement of gold occurs during lateritization the development of low ph and the redistribution of gold and silver in lateritic weathering profiles appear to be more common over granitic and gneissic basement and may be inhibited by the presence of carbonate in the weathering zone of basic rock sequences modified journal abstract

formation and preservation of pedogenic carbonates in south india links with paleo monsoon and pedological conditions clues from sr isotopes u th series and rees the influence of the pedogenic and climatic contexts on the formation and preservation of pedogenic carbonates in a climosequence in the western ghats karnataka plateau south west india has been studied along the climosequence the current mean annual rainfall mar varies within a 80 km transect from 6000 mm at the edge of the plateau to 500 mm inland pedogenic carbonates occur in the mar range of 500 1200 mm in the semi arid zone mar 500 900 mm carbonates occur i as rhick hardpan calcretes on pediment slopes and ii as nodular horizons in polygenic black soils i e vertisols in the sub humid zone mar 900 1500 mm pedogenic carbonates are disseminated in the black soil matrices either as loose irregular and friable nodules of millimetric size or as indurated botryoidal nodules of centimetric to pluricentimetric size they also occur at the top layers of the saprolite either as disseminated pluricentimetric indurated nodules or carbonate cemented lumps of centimetric to decimetric size chemical and isotopic sr 87 sr 86 compositions of the carbonate fraction were determined after leaching with 0 25 n hcl the corresponding residual fractions containing both primary minerals and authigenic clays were digested separately and analyzed the trend defined by the sr 87 sr 86 signatures of both labile carbonate fractions and corresponding residual fractions indicates that a part of the labile carbonate fraction is genetically linked to the local soil composition considering the residual fraction of each sample as the most likely lithogenic source of ca in carbonates it is estimated that from 24 to 82 55 on average of ca is derived from local bedrock weathering leading to a consumption of an equivalent proportion of atmospheric co2 these values indicate that climatic conditions were humid enough to allow silicate weathering mar at the time of carbonate formation likely ranged from 400 to 700 mm which is 2 to 3 fold less than the current mar at these locations the sr u and mg contents and the u 234 u 238 activity ratio in the labile carbonate fraction help to understand the conditions of carbonate formation the relatively high concentrations of sr u and mg in black soil carbonates may indicate fast growth and accumulation compared to carbonates in saprolite possibly due to a better confinement of the pore waters which is supported by their high u 234 u 238 signatures and or to higher content of dissolved carbonates in the pore waters the occurrence of ce mn and fe oxides in the cracks of carbonate reflects the existence of relatively humid periods after carbonate formation the carbonate ages determined by the u th method range from 1 33 0 84 kyr to 7 5 2 7 kyr and to a cluster of five ages around 20 kyr i e the last glacial maximum period the young occurrences are only located in the black soils which therefore constitute sensitive environments for trapping and retaining atmospheric co2 even on short time scales the maximum age of carbonates depends on their location in the climatic gradient from about 20 kyr for centimetric nodules at mule hole mar 1100 mm yr to 200 kyr for the calcrete at gundlupet mar 700 mm yr durand et al 2007 the intensity of rainfall during wet periods would indeed control the lifetime of pedogenic carbonates and thus the duration of inorganic carbon storage in soils c 2010 elsevier ltd all rights reserved

chemical processes affecting the mobility of major minor and trace elements during weathering of granitic rocks abstract the behaviour of 38 major and trace elements as well as changes in the mineralogy have been examined in 10 weathering profiles developing on some portuguese granitic rocks element mobilities are calculated from geochemical data normalized with respect to ti in the fresh parent rock chemical elements are divided into two groups immobile and mobile on the basis of their geochemical distribution during weathering elements that are immobile during weathering are zr hf fe al th nb sc and the ree very mobile are ca na p k sr ba rb mg and si mobile elements are derived mainly from leachable minerals such as feldspars micas and apatites whereas immobile elements are either concentrated in resistate phases or strongly adsorbed by secondary minerals the geochemical behaviour of mn cr v fe and ce is very dependent on redox conditions redox transformations of these elements can be used to set limits on the oxidation state of a weathering suite the ree are mobilized or fractionated during late stages of weathering but not during moderate stages of weathering this fractionation is caused by selective leaching of rocks composed of both stable and unstable minerals containing ree

assessing parent material uniformity of a red and black soil complex in the landscapes abstract the distribution of red and black soil xeralfs xerolls associations in the monarto area south australia is complex and their genesis either being derived from a uniform parent material or a lithologic discontinuity is not known the objectives of this study were i to assess zr and ti bearing grains as minerals resistant to chemical weathering prior to employing zr and ti in determining parent material uniformity and ii to confirm whether pedological processes or a lithologic discontinuity may be responsible for the textural contrast within the red and black soil profiles scanning electron microscopy sem and energy dispersive x ray analysis edax were used to study chemical weathering and elemental composition of surfaces of zr and ti bearing grains x ray fluorescence xrf analysis was used to determine elemental concentrations in various soil fractions results showed that zr bearing grains consisted of only zircon having smooth clean surfaces which are characteristic of a mineral resistant to chemical weathering edax spectra confirmed that zr was a specific element to represent zircon suggesting its reliability to be used in assessing parent material uniformity on the other hand ti derived not only from minerals rutile anatase resistant but also from minerals ilmenite pseudorutile biotite susceptible to chemical weathering this limited the usefulness of ti as an index mineral for soil development studies except for zr ti ratio all other indicators of parent material uniformity i e depth distribution curves of zr and y in various fractions and y zr ratio showed no considerable inflection and variation with depth in a xeralf red soil this indicated the xeralf derived from a uniform parent material mica schists thereby texture contrast within a profile is due to pedological processes on the other hand depth distribution curves showed clear inflection and variation in xerolls black soils indicating soils developed from lithologic discontinuities so different trends in particle size fractions between 0 48 cm for ma5 and 0 59 cm for ma3 profiles compared to the underlying layers are due to parent material differences and not pedogenesis the presence of complex red and black soil association in the landscape is attributed to the difference in parent materials where the red soil developed from mica schist and the black soils from calcareous deposits

particle size fractionation of titanium and zirconium during weathering and pedogenesis of granitic rocks in nw spain abstract titanium and zr were analyzed in 10 weathering and pedogenetic soil profiles developed on granitic rocks from nw spain concentrations were obtained by xrf and the ti and zr bearing minerals were studied by petrographical sem and eds analysis both elements were measured in rock bulk soil and granulometric fractions sand 2000 50 m silt 50 2 m clay titanium concentrations in the rock varied between 0 5 and 4 2 g kg 1 and zr concentrations from 52 to 173 mg kg 1 concentrations in bulk soil for the different horizons remain almost unchanged and are strongly related to the element content of the parent rock in some epipedons ti content is relatively lower than that of the underlying horizons due to a dilution effect caused by the high organic matter content and the addition of fresh minerals from erosion upslope the mineralogical study revealed that zr is present exclusively in zircons while ti occurs in rutile ilmenite and titanite but mainly as a structural component of the biotite regarding the particle size fractions both elements behave differently zirconium is enriched in the silt fraction of all soil horizons with concentrations up to 5 times that of the parent rock while ti is enriched in the silt up to 5 times and clay fractions up to 12 times of the solum horizons and depleted in the sand fraction of the a horizons these results indicate that zr concentrations are mainly controlled by the abundance of zircons in the rock and their physical detachment from the host minerals upon weathering ti mainly depends on the release from the structure of biotites through chemical weathering and its reprecipitation as neoformed mineral phases this physicochemical fractionation of ti and zr in soils bears important implications for studies on soil genesis continuity of soil profiles and the calculation on enrichment factors which are based on the conservative behaviour of both elements

pedogenic processes and domain boundaries in a vertisol climosequence evidence from titanium and zirconium distribution and morphology abstract the occurrences of titanium ti and zirconium zr within eight vertisols formed in a climosequence on the upper beaumont formation of the texas gulf coastal plain were investigated in order to determine processes responsible for ti and zr redistribution during pedogenesis discontinuities defined by significant shifts in particle size distribution and the content in volume percent of zr are present at 160 to 260 cm depth in each pedon the discontinuities are interpreted to be functional boundaries i e physico chemical expressions of pedogenic domains between an upper soil domain dominated by open system pedogenesis and a lower more closed system domain dominated by chemical weathering the depth at which the functional boundary occurs is dependent on physical and hydrogeochemical influences which are largely a function of available water soil materials above the discontinuities are slightly coarser textured and enriched in zr whereas below the sediments are finer textured and have lower and more constant zr contents the zr is associated almost exclusively with zircon and zr contents correlate positively to the weight percent sand coarse silt with negligible zr present in the profile volume loss gain i e soil strain e a mass balance calculation that assumes zr or ti immobility during pedogenesis indicate ezr values nearly four times greater than eti large values of ezr within the upper soil domains are due primarily to sand and coarse silt additions to the vertisols and preclude use of zr as a basis of mass balance calculations in these soils despite its relative chemical stability by comparison ti is generally conserved within the clay rich soil profiles and is therefore better suited for mass balance calculations of volume change and mobile element translocation during pedogenesis

arcticanodon dawsonae a primitive new palaeanodont from the lower eocene of ellesmere island canadian high arctic a new genus and species of palaeanodont arcticanodon dawsonae is based on a single lower jaw fragment from lower eocene wasatchian strata of the margaret formation eureka sound group on central ellesmere island nunavut the new taxon is more derived than early paleocene escavadodontidae but lacks derived traits of metacheiromyidae it is therefore most similar to primitive epoicotheriids although the similarities are essentially in plesiomorphic features consequently arcticanodon dawsonae is classified as palaeanodonta incertae sedis pending discovery of more complete specimens resume un nouveau genre et une nouvelle espece de palaeanodonta arcticanodon dawsonae est base sur un seul fragment de mandibule inferieure provenant des strates de la formation de margaret eocene inferieur wasatchien du groupe d eureka sound au centre de l ile d ellesmere au nunavut le nouveau taxon est plus derive que escavadodontidae du paleocene precoce mais il ne presente pas les traits derives de metacheiromyidae il ressemble donc plus aux epoicotheriides primitifs bien que les similitudes se presentent surtout dans les caracteristiques plesiomorphiques par consequent arcticanodon dawsonae est classe en tant que palaeanodonta incertae sedis en attendant la decouverte de specimens plus complets traduit par la redaction rose et al 763

analysis of supergene ore forming processes and ground water solute transport using mass balance principles analysis of metal distribution in weathering profiles developed above ore deposits provides a simple and direct method to determine the geologic controls on surficial leaching and enrichment of metals by supergene descending fluids this approach offers an understanding of the interrelationships of metal concentration zone thicknesses and bulk rock density of the various zones within a weathered rock column analytical solutions to mass balance equations provide expressions describing the chemical evolution paths of enrichment blanket metal grade b in terms of original protore metal grade p leached zone metal grade 1 and the ratio of total leached zone column height to blanket thickness l o t b neglecting density terms for the sake of simplicity this function is expressed as b p l o t b p 1 linear data arrays in the coordinate system b versus p 1 for groups of drill holes in individual geologic domains e g wall rock types strongly suggest that enrichment blanket metal grades evolve from a protore metal grade p with a fairly constant slope of l o t b to a final value b determined by the extent of metal leaching in the zone of oxidation the constancy of the ratio l o t b within geologic domains indicates a simultaneous deepening of the zone of oxidation and thickening of the enrichment blanket under conditions of a descending ground water table analysis of metal mass balance in drilling profiles also provides a means of reconstructing paleosurficial topography at the time of active oxidation even in highly eroded terrains application of these methods using rock density and assay data from the butte district of montana shows the paleo oxidation surface to have been eroded by as much as 450 ft down to the present unconformity between weathered bedrock and overlying tertiary gravels geomorphic stability and slow erosion rates often thought necessary for effective chemical weathering are therefore questioned we propose instead a general balance of rates of erosion and descent of the ground water table for optimal enrichment preservation of the fossil weathering profiles occurs by submergence of the zone of oxidation below the paleoground water table resulting in cessation of supergene oxidation and preservation of the blanket the mass balance methods derived in this study also relate overall leaching efficiency to protore characteristics showing a strong hypogene alteration control at butte as described by mcclave 1973 lateral copper transport is evaluated by identifying local anomalies in the computed oxidation surface zones of copper introduction near faults and zones of high permeability appear as apparent topographic highs whereas zones of depletion appear as topographic depressions preliminary analysis of this type at the porphyry copper deposit at la escondida chile indicates deeper oxidation and leaching effects than at butte the assumption of vertically homogeneous protore copper grades leads to the conclusion that erosion of at least 200 m of leached capping has occurred throughout much of the la escondida district geologic domains defined by computed values of l o t b correlate well with hypogene alteration zoning computation of the magnitude and direction of overall subsurface lateral metal fluxes indicates transport distances of at least 1 km in directions consistent with present surface topography and fracture patterns there is a strong correlation of the thickest and highest grade enrichment zones with inferred positive lateral fluxes whereas the most thoroughly leached cap rocks make up zones of inferred negative lateral flux which are likely source regions alternative explanations to the lateral flux hypothesis are evaluated including assessment of variations in protore metal grade projections both in vertical and horizontal directions despite the approximations involved in the present calculations the lateral flux pattern appears to be the most likely interpretation of the present metal distribution in the supergene system at la escondida

texture and mineralogy of the surface sediments of sharm obhur west red sea coast of saudi arabia abstract the present paper deals with the study of the grain size characteristics and the mineralogy of the bottom and beach sediments of sharm obhur most of the sediments are in digenous carbonates with little terrigenous material a major part of the sharm is covered with coarse to medium grained sediments heavy minerals make up 5 to 15 of the samples and are mainly composed of amphiboles pyroxenes biotite epidote and opaques the heavy mineral suite is apparently derived mainly from metamorphic source rocks with minor contribution from basalts the content of high mg calcite decreases landward in the sharm due to more inorganic precipitation of carbonate in the form of aragonite the high content of calcite in the beach sands from the shoreline of the sharm shows that the calcite rich old reef limestones that crop out along the sharm contribute considerable material of the beach sediments kaolinite mixed layer chlorite vermiculite and illite are the dominant clay minerals the alluvium derived from the low grade metamorphic rocks and basalts of the jeddah group forms the source of the clay minerals

geomorphic controls on mercury accumulation in soils from a historically mined watershed central california coast range usa abstract historic hg mining in the cache creek watershed in the central california coast range has contributed to the downstream transport of hg to the san francisco bay delta different aspects of hg mobilization in soils including pedogenesis fluvial redistribution of sediment volatilization and eolian transport were considered the greatest soil concentrations 30 mg hg kg 1 in cache creek are associated with mineralized serpentinite the host rock for hg deposits upland soils with non mineralized serpentine and sedimentary parent material also had elevated concentrations 0 9 3 7 mg hg kg 1 relative to the average concentration in the region and throughout the conterminous united states 0 06 mg kg 1 erosion of soil and destabilized rock and mobilization of tailings and calcines into surrounding streams have contributed to hg rich alluvial soil forming in wetlands and floodplains the concentration of hg in floodplain sediment shows sediment dispersion from low order catchments 5 6 9 6 mg hg kg 1 in sulphur creek 0 5 61 mg hg kg 1 in davis creek to cache creek 0 1 0 4 mg hg kg 1 these sediments deposited onto the floodplain during high flow storm events yield elevated hg concentrations 0 2 55 mg hg kg 1 in alluvial soils in upland watersheds alluvial soils within the cache creek watershed accumulate hg from upstream mining areas with concentrations between 0 06 and 0 22 mg hg kg 1 measured in soils 90 km downstream from hg mining areas alluvial soils have accumulated hg released through historic mining activities remobilizing this hg to streams as the soils erode

lower latitude mammals as year round residents in eocene arctic forests the arctic is undergoing rapid warming but the impact on the biosphere in particular on large terrestrial mammals is not clear among the best deep time laboratories to assess biotic impacts of arctic climate change early eocene ca 53 ma ago fossil assemblages on ellesmere island nunavut 79 n preserve evidence of forests inhabited by alligators tortoises and a diverse mammalian fauna most similar to coeval lower latitude faunas in western north america by analyzing carbon and oxygen isotope ratios of mammalian tooth enamel we show that large herbivores were year round inhabitants in the arctic a probable prerequisite to dispersal across northern high latitude land bridges if present day warming continues year round occupation of the arctic by lower latitude plants and animals is predicted

margin to craton expansion of late ordovician benthic marine invertebrates a biostratigraphic survey of 57 late ordovician marine shelly invertebrates from the climacograptus manitoulinensis zone of eastern canada supports suggestions that throughout the early phanerozoic benthic marine speciations occurred preferentially in marginal marine environments the species subsequently spread onto the craton there is no obvious positive correlation between the times of first appearance of new associations or novel communities along the continental margin and the first appearance on the craton of the species making up these communities taxonomic similarities between marine communities that occupied both marginal and cratonic regimes may reflect a more static local ecology than the evolutionary dynamics of a piecemeal species by species reassembly

five thousand years of atmospheric ni zn as and cd deposition recorded in bogs from nw iberia prehistoric and historic anthropogenic contributions abstract the analysis of environmental archives from across the world has demonstrated that human perturbation of the geochemical cycles of trace metals and the resultant atmospheric metal contamination date back at least several millennia however an understanding of the local processes and timing of changes in trace metal deposition is also essential for a proper global interpretation the iberian peninsula was a major mining area since prehistoric times and the analysis of environmental archives provides a good opportunity to improve our understanding of the history of mining and metallurgy in europe we present the results from three 14 c dated peat cores from the xistral mountains nw iberia these records are used to reconstruct past atmospheric deposition of ni zn as and cd the chronology of the changes in concentrations and metal accumulation rates was found to be concordant in the three bogs and showed great similarity to total pb hg and pb isotope ratios as determined in previous investigations they present a consistent view of changes in atmospheric pollution and the importance of metals in the development of human societies especially i the first evidence of atmospheric metal pollution 3400 years ago which is simultaneous with the expansion of the atlantic bronze koine ii a pollution event between 2350 and 2150 years ago associated to the development of so called celtic culture local late iron age iii a dramatic increase of metal fluxes in roman times iv a severe and rapid increase in the last 250 years corresponding to the beginning of the industrial revolution in europe reflecting the emergence of the new dominant sources of pollution and v the increase of long range atmospheric transport of pollutants our data suggest that all detected ancient until ca 1450 cal bp periods of enhanced ni zn as and cd accumulation may have had an anthropogenic origin related to the onset and development of mining and metallurgy

holocene history of landscape development in the catchment of lake skogstjern southeastern norway based on a high resolution multi proxy record a high resolution multi proxy record from sediments of a small sized lake situated in telemark southeastern norway was used to reconstruct the local landscape development of the past c 10 500 years our data demonstrate that changes in vegetation composition and structure in the first two thirds of the holocene are principally attributable to climatic changes and high erosion rates as deduced from geochemical and physical loss on ignition proxy analyses the highest signals of erosional inputs to the lake c 8030 5760 cal bp can be correlated with the first part of the holocene thermal maximum nevertheless evidence from pollen non pollen palynomorphs and microscopic charcoal analyses indicates the presence of nutrient rich and disturbed environments already during the middle mesolithic c 10 050 9400 cal bp it also shows traces of animal husbandry c 5580 cal bp and small scale cereal cultivation c 5520 cal bp in the early neolithic in subsequent periods human impact remains at a

middle miocene climatic change in the atacama desert northern chile evidence from supergene mineralization at la escondida geochronology and paleotopographic reconstruction of the porphyry copper deposit at la escondida chile are used to calculate long term erosion rates and to deduce the timing of tertiary climatic change for a portion of the atacama desert region hypogene hydrothermal alteration and protore mineralization at la escondida took place between 33 7 1 4 and 31 0 1 4 ma based on k ar dating of hydrothermal biotite and sericite supergene weathering and copper sulfide en richment processes were active from 18 0 0 7 to 14 7 0 6 ma based on k ar dating of supergene alunite distinguished from hypogene alunite by grain size color and sulfur isotopic composition reworked lenses of volcanic ash in the vicinity of la escondida provide useful time stratigraphic markers at 8 7 0 4 6 5 0 2 and 4 2 0 2 ma within present soil profiles long term average rates of erosion are determined by these age dates and quantitative calculation of eroded leached capping thickness at la escondida using mass balance analysis of geochemical profiles coupled with an estimate of unmineralized lithocap thickness based on alteration petrology and fluid inclusion geobarometry at similar deposits the observed trend of decreasing long term average erosion rates with time is consistent with arid to semiarid conditions in the early miocene changing to hyperarid conditions during the middle miocene this climatic desiccation caused termination of significant supergene copper suffide enrichment at la escondida and elsewhere in the atacama region and preservation of surficial features including the ash horizons and the leached capping middle miocene climatic desiccation in northern chile and southern peru was probably related to a pronounced decrease in temperature of coastal waters supplied by an ancestral humboldt current and an increase in upwelling intensity as the antarctic ice cap became established at approximately 15 to 13 ma the central andes cordillera which now provides a rain shadow protecting the atacama region from precipitation from the east must have attained at least half its present elevation prior to about 15 ma to have played a similar role in the middle miocene

growth ring analysis of early tertiary conifer woods from the canadian high arctic and its paleoclimatic interpretation abstract fossil forests where petrified stumps were preserved in growth position have been found within early tertiary sediments near strathcona fiord ellesmere island canadian arctic archipelago these fossil forests are obvious evidence for early tertiary climate much warmer than that of today we analyzed the growth rings of petrified woods from two fossil forest sites one in middle paleocene and the other in late early eocene to extract information on climate change the woods consist most abundantly of metasequoia and cf glyptostrobus suggesting that these forests grew in similar environments of warm to cool temperate climates mean ring width mean sensitivity and power spectrum were calculated for ring width sequences although significant difference in the mean ring width between the two forests was found a comparison with living trees suggests that the difference can be attributed to the specific difference between the forests so that a significant climate change may not necessarily be invoked we found little significant difference in the mean sensitivity and power spectrum between the forests neither did we find any strong indication of periodicities consideration of all features suggests that there was no significant difference in climate of middle paleocene and late early eocene time in the high arctic however the mean ring widths of these forests were significantly smaller than that reported for mid cretaceous high arctic fossil forest

magnetostratigraphy of the late cretaceous to eocene sverdrup basin implications for heterochroneity deformation and rotations in the canadian arctic archipelago the temporal and spatial patterns of sedimentation in the sverdrup basin provide clues to how deformation in the canadian arctic accommodated late cretaceous eocene relative motion between greenland and north america although the sediments contain a rich assemblage of mammal and megafloral fossils dating of the sequence has been controversial some work suggests a dramatic faunal and floral heterochroneity with species appearing in the arctic 2 18 m y prior to their appearance at lower latitudes to obtain a chronostratigraphic framework for these sediments a 2 6 km section of the eureka sound group and kanguk formation on western axel heiberg island was sampled for magnetostratigraphy after removal of a pervasive modern field overprint with thermal and alternating field demagnetization a characteristic remanent magnetization chrm is isolated despite high directional dispersion the chrms form 11 distinct polarity intervals which can be correlated to chrons 34 to 24r this correlation indicates that some of these sediments are 10 m y younger than thought previously reducing the need for large scale heterochroneity sedimentation rates derived from the magnetostratigraphy suggest that an increase in basin subsidence is recorded near the middle of the section sampled a similar pattern has been reported from the eureka sound group exposed on ellesmere island we interpret this increased sedimentation as a response to crustal flexure caused by lithospheric loading during the middle paleocene c26r the loading may be related to a blind thrust system to the west of axel heiberg island that marks compression between north america and greenland driven by rapid seafloor spreading in the labrador sea the new data together with prior results indicate that most of the cretaceous canadian arctic archipelago has undergone a counterclockwise vertical axis rotation the new data are more consistent with this rotation being related to events during chron 26r rather than marking block rotations associated with the terminal eocene phases of eurekan deformation