trace element chemistry of non marine ostracods as a means of palaeolimnological reconstruction an example from the quaternary of kashmir northern india abstract recent work has demonstrated the use of sr ca and mg ca ratios in the calcite of ostracod shells for reconstructing the palaeosalinity and palaeotemperature of lakes in this study the technique was applied to a lacustrine sequence of late quaternary age the upper karewa formation in kashmir northwest himalaya ostracods are the only fossils found in abundance in the upper karewa sediments and are thus important for the reconstruction of upper karewa palaeoenvironments trace element analyses of multiple shell samples of the ostracod ilyocypris bradyi sars 1890 were performed using inductively coupled plasma atomic emission spectrometry the results show that the palaeo lake was even more dilute than the modern residual lakes in kashmir reconstructed molar sr ca ratios for the palaeo lake waters vary between 30 10 4 and 42 10 4 compared with observed values of 46 110 10 4 for the modern residual lakes changes in the molar mg ca ratios with unchanging sr ca are attributed to variations in water temperature the palaeo lake probably receded from the study site at between 116 and 80 ka and lacustrine sedimentation gave way to subaerial loess deposition the lack of any increasing trend in the reconstructed sr ca values together with structural and sedimentological evidence suggests that the lake was drained by tectonic tilting or warping of the basin floor rather than by climatically induced desiccation

biological remains geochemistry and stable isotopes for the reconstruction of environmental and hydrological changes in the holocene lakes from north sahara abstract a detailed reconstruction of the holocene palaeoenvironments and palaeohydrology is presented for wwamp and lacustrine calcareous sediments which lie in closed depressions along the northern margin of the great western erg algeria it is based on a multidisciplinary approach using numerous techniques the chronological framework is established on the basis of 23 14 c dates on inorganic calcite and mollusc shells ranging from ca 9300 to 3000 yr b p and on an isolated 14 c age of ca 10 900 yr b p the significance of various environmental markers is discussed biological remains are abundant and diversified about 150 taxa including diatoms chrysophytes charophytes ostracods molluscs and foraminifera they provide information on the water chemistry total salinity ionic ratio ph and partial pressure of carbon dioxide and on the habitats water depth development of aquatic plants ephemerality etc emphasis is given to the total salinity individual organisms and palaeobiological assemblages are ordered as a function of their salt requirements and tolerances calibration based on modern diatom samples allows a tentative estimate of the palaeosalinities which range from fresh to marine like and even hypersaline waters attention is drawn to the possible colonization of marine organisms in continental basins without any connection with the sea stable isotope analyses have been carried out on both inorganic and biogenic mollusc and ostracod shells charophyte gyronites carbonates the 18 o contents demonstrate wide changes in the hydrological balance fluctuations in 13 c contents inform on water mixing residence time and on the importance of biological effects on total dissolved inorganic carbon geochemical analyses were performed on inorganic calcite and on ostracod shells high contents in fe and mn indicate reducing environments during stages of high salinity sr ca and mg ca are used as salinity indicators zn mg ratios suggest that the major water supply was the aquifer of the great western erg today down to about 50 m rather than surface waters from the atlas mountains salinities resulted from the balance between inputs from the water table evaporation rate leaching of pre existing salt crusts and seepage through the lake bottom a reconstruction of the evolution of the palaeosystems through time and space has been attempted with special attention to the instability of the water and ionic balances for different time scales short term fluctuations occurring during a single hydrological cycle annual or seasonal are deduced from the apparent discrepancies between the various indicators found in a given sample long term 10 2 10 3 years changes confirm the existence of a climatic phase being wetter than today from at least ca 9300 and may be from ca 10 900 yr b p to 3000 yr b p for the first time the salinity deduced from diatoms and the 18 o content of the water deduced from that of the carbonate at 25 c are used simultaneously to model the hydrological history of the basins and to estimate the relative humidity of the atmosphere during the holocene major environmental trends recorded from ca 9300 to 3000 yr b p do not show a clear synchronims between the different profiles studied therefore they cannot be interpreted in terms of palaeoclimate but instead demonstrate the importance of local hydrology in the evolution of closed basins associated with groundwater a common situation in arid and semi arid zones

middle pleistocene climate and hydrological environment at the boxgrove hominin site west sussex uk from ostracod records the sediments of the slindon formation at the junction of the chalk south downs and the west sussex coastal plain as revealed and studied at boxgrove contain evidence for early middle pleistocene environments in southern england around half a million years ago the archaeological importance of the deposits is attested to by the recovery of stone and organic tools butchered fauna and fossil hominin remains we combine palaeoecological and geochemical analyses of ostracods from the coastal plain deposits to reconstruct the climate and environment at one period of the hominin occupation the stratigraphy of our study area is indicative of a terrestrial environment surrounding a small lake or pond ostracod assemblages from the sediments indicate that the ponds were shallow but permanent and fed by groundwater and springwater however the species alone cannot confirm that these ponds were completely fresh application of mutual climatic range mcr techniques shows that summer temperatures were similar to present day values and winter temperatures were probably colder whereas mean annual air temperature was similar to present or perhaps slightly cooler trace element and strontium isotope analyses of ostracods from the sediments support the conclusion that the ponds were fed largely by fresh groundwater derived from the chalk although there may have been a minor seawater input the carbon isotope ratios of the ostracod shells are consistent with a groundwater source although they also indicate that the dissolved inorganic carbon most likely did not reach equilibrium with atmospheric carbon dioxide suggesting that the ponds had short residence time the combination of palaeotemperature estimates with oxygen isotope values from ostracod shells allowed us to reconstruct the oxygen isotope ratio of the pond water which was close to the value of early middle pleistocene precipitation at this site values were similar to present day suggesting that there may have been a change in seasonality or precipitation source since the mean air temperatures might have been lower

titanium mobilization by hydrocarbon fluids related to sill intrusion in a sedimentary sequence scotland abstract an occurrence of vein hosted bitumen in carboniferous rocks central scotland exhibits unusual enrichments in titanium zirconium and chromium detected by electron microprobe these elements occur as mineral inclusions of titanium and titanium iron oxides a close association between titanium rich tuffs and a quartz dolerite sill suggests that metals were leached from igneous rocks by a hydrocarbon rich fluid generated by the heat of the intrusion into organic rich shales this occurrence supports other evidence for widespread titanium mobility under low temperature conditions inclusions of nickel arsenide may reflect regionally important mineralization including former ore deposits related to sills and dykes as sills are extensively intruded into petroleum prospective basins offshore they may have a significant influence upon sediment geochemistry

the holocene salinity history of bosten lake xinjiang china inferred from ostracod species assemblages and shell chemistry possible palaeoclimatic implications abstract a sediment core from bosten lake the largest freshwater lake in the tianshan mountains and in the northwesternmost province of china provided a high resolution record of environmental change covering the last 8500 cal a bp higher salinity levels of bosten lake were reconstructed from assemblages the stable isotope composition and sr ca and mg ca ratios of ostracod shells between 7800 and 5600 cal a bp a period of low and moderate salinities between 5600 and 4900 cal a bp was followed by the re establishment of higher salinities between 4900 and 4300 cal a bp since then bosten lake has recorded fluctuating conditions with a number of multi centennial phases of low and moderate salinities although the salinity lake level relationship of bosten lake is not fully understood a higher salinity at the core site seems to correspond to periods of higher lake levels this contradictory interpretation is explained tentatively by the changing distance of the core site to the freshwater providing river mouth with changing lake levels and potentially resulting lateral shifts of the salinity distribution pattern within the lake assuming this explanation is correct the record from bosten lake reflects higher moisture availability and a strong climatic influence of the indian monsoon in the early mid holocene until about 4000 cal a bp and more unstable drier conditions susceptible to minor changes in the regional circulation patterns and temperature variations afterwards

palaeoenvironmental reconstruction of a pleistocene lacustrine sequence from faunal assemblages and ostracode shell geochemistry baza basin se spain abstract we have reconstructed the early pleistocene palaeoenvironmental record for a shallow lacustrine sequence from the baza basin southern spain using faunal assemblages and the shell chemistry of two ostracode species candona sp and cyprideis torosa in the ne basin sector orce area a lower pleistocene lacustrine sequence up to 10 m thick contains alternating phases of two fossil assemblages which differ in their salinity requirements the faunal assemblages record phases of 1 slightly saline ca bicarbonate rich water when freshwater organisms predominated and 2 saline nacl dominant water in which marine like organisms lived the ostracode shells from intervals with a saline fauna have higher 18o values than those from intervals with a freshwater fauna this feature corresponds to a parallel alternation of positive and negative hydrologic balances 18o and 13c values from ostracode calcite display a covariant trend which indicates that the ostracodes lived in a closed lacustrine system the isotopic data show a better agreement with the inferences from faunal assemblages than with trace element trends the trace element data although locally fitting well with the isotope and faunal interpretations suggest overall that trace element contents in ostracodes are not consistent indicators of salinity and or temperature variations but depend on a set of complex factors which may not be easily deciphered the alternation of concentration dilution phases recorded in the studied section can be correlated with climatic cycles described from synchronous ocean basin records from the late matuyama chron

the plio pleistocene geologic and climatic record of the kashmir valley india a review and new data abstract the kashmir valley located in the northwestern himalayas provides an intermontane valley fill comprising unconsolidated fluvio lacustrine sediments of more than a km thickness datable at 4 myr these sediments have been investigated for the last 7 years under an interdisciplinary multi agency project using a variety of proxy climatic data techniques and other analyses to decipher climatic change as a result of this study a variety of proxy climatic data from a long continental record is available now from northernmost south asia in this paper we briefly review the lithostratigraphic and chronologic framework of the sediment profile and proxy climatic data based on flora fauna stable isotopes pedology mineral magnetics and sedimentology lastly the climatic events are put in an absolute time frame for comparison with the global climatic trends the chronology is based on 14c thermoluminescence tl palaeomagnetic and fission track techniques

geochemical correlation in deltaic successions a reality check whole rock geochemical analysis can aid the stratigraphic correlation of faunally barren successions compared to petrographic techniques or heavy mineral separations such analysis is quick and objective yet rarely has the reliability of the method been tested against unequivocal correlations we have applied it to the kenilworth member of the upper cretaceous blackhawk formation a well exposed and easily correlated 100 m thick unit in the deltaic successions of the book cliffs utah united states this is the first evaluation of geochemical analysis as an aid to sequence stratigraphic interpretation at the parasequence scale from the geochemistry alone it is not possible with statistical confidence to separate individual parasequences or systems tracts nor the fluvial incised valley from the marine shoreface units the magnitude of geochemical variation in a single sandstone bed over a 30 m lateral traverse is as great as vertically through an entire parasequence y nb rb and ti abundances are inversely correlated with grain size thus geochemical signatures follow sedimentological trends and distal parts of a parasequence appear distinct from proximal parts y ratios compensate for this grain size effect but introduce confusing distortions for elements such as zr that are not correlated with grain size contrary to some predictions zr is as common in the finest grained units as the coarsest and sr is not correlated with ca in some sections sr is also inversely correlated to grain size and cannot be used as an indicator for cement abundance

evaluation of sediment provenance using magnetic mineral inclusions in clastic silicates comparison with heavy mineral analysis magnetic fe oxide inclusions within framework clastic grains in sediments provide an indication of the provenance of the enclosing host silicate particles magnetic mineral inclusion characterisation is performed using a variety of magnetic properties that are related to magnetic mineral abundance magnetic grain size domain state oxidation state and magnetic grain interaction the magnetic methodology extends that based on a conventional set of environmental magnetic measurements using a variety of recent sediments transported from known rock sources within the uk and eire it is demonstrated using discriminant function analysis that the magnetic properties of the fe oxide inclusions provide a clear distinction of primary provenance this is both at the large scale in terms of various gneiss schist and granite sources and also at a smaller scale when considering subdivisions of these sources using case studies from the marine upper jurassic piper formation and non marine triassic sediments otter bank sandstone and foula sandstone formations it is shown that provenance differences clearly expressed by the results of heavy mineral analysis are also sensitively displayed by the magnetic mineral inclusion data the provenance classification is based around use of hierarchical cluster analysis and multidimensional scaling simple statistical tools are developed to determine a least noisy subset of magnetic parameters which are most suitable for stratigraphic provenance discrimination the triassic case study has indicated the magnetic mineral inclusion technique is most sensitive when using the sediment fractions larger than 150 m

strontium content of ostracods indicates lacustrine palaeosalinity individual non marine ostracod valves contain sr in proportion to the sr content of their host lake water two commonly coexisting large planktonic species mytilocypris praenuncia and australocypris robusta have a sr distribution coefficient kd sr ca of 0 082 which is independent of temperature in the range 10 18 c if the relationship between salinity and the sr content of a hydrologically simple lake is known palaeosalinities can be calculated from fossil ostracods we present here palaeosalinities for the past 10 000 yr for lake keilambete victoria calculated from ostracod sr ca of fossil material which are in striking agreement with independent interpretations of palaeosalinity the range of salinity spans 14 95 we also show that a reliable quantitative continuous indicator of lacustrine palaeosalinity is important for the elucidation of continental palaeoenvironments for palaeoclimatology and archaeology and ocean continent climatic correlations and interactions

magnesium content of non marine ostracod shells a new palaeosalinometer and palaeothermometer abstract ostracods are microcrustaceans with calcitic carapaces each consisting of two valves or shells that grow by moulting and regeneration of sequentially larger valves up to nine times before reaching maturity the mg content of these valves is species dependent and is a function of their growth stage and the temperature salinity mg content and mg ca ratio of their host water newly formed partly calcified valves of the non marine nektic ostracod mytilocypris henricae have high mg contents 100 000 ppm mg in caco3 at individual shell weights of 2 g this relative mg content decreases as calcification proceeds until shell weights exceed 120 g whereupon the mg content is constant and useful as an indicator of the ostracod s environment mg ca ratios in individual ostracod valves from several species of the genera mytilocypris and australocypris from culture experiments and a series of australian lakes indicate that the valve s mg content increases as a function of increasing temperature and salinity within the range 11 25 c and for waters containing 24 2325 ppm mg the molar mg ca ratio in these ostracods fully calcified valves increases by 0 0015 or 370 ppm mg in caco3 per 1 c and per change of 125 ppm mg in solution for most mainland australian lakes a change in water composition of 125 ppm mg corresponds to a change of 3 5 in salinity for a given mg content of a lake the mg ca ratio of the water may vary within the range of common lacustrine values without significantly affecting mg uptake in the ostracod valves these relationships can provide palaeosalinities and or palaeotemperatures for ostracods recovered from continental sediments for mg partitioning an increase in temperature and salinity produce increased mg content in ostracods whereas for 18o fractionation in biogenic calcite an increase in temperature produces a decrease in 18o of the ostracod and an increase in salinity leads to an increase in 18o of the ostracod thus a combination of 18o and mg measurements on non marine ostracods should enable unique resolution of palaeotemperature and palaeosalinity variations

garnet compositions in scottish and norwegian basement terrains a framework for interpretation of north sea sandstone provenance detrital garnets have proved to be useful discriminators of north sea sandstone provenance because they show a wide range of potential compositions and are relatively stable during burial diagenesis it has been less easy to use garnet data to provide a direct link between sediment and source because of the lack of a comprehensive database of garnet compositions in basement terrains forming the north sea hinterland this paper presents garnet compositional data from river sediments sourced from northern scotland and norway and demonstrates the presence of marked variations in garnet compositions from different regions related to fundamental differences in basement lithology the value of the river sediment database is demonstrated by comparing it with garnet compositions in paleocene sandstones from the north sea and more basins enabling the establishment of direct links between source and sediment paleocene sandstones in the gannet field area on the southwestern margin of the central north sea were derived from the dalradian of the grampian highlands those in the northern north sea were derived from the moine dalradian rocks of shetland and those along the more basin margin were derived from western norway by contrast paleocene sandstones in the nelson field central north sea and in the beryl embayment northern north sea have a garnet component that cannot be readily traced back to any basement terrain in either scotland or norway this component which was ultimately derived from granulite facies metasediments or charnockites is interpreted as being recycled from triassic sandstones which were themselves derived from an exotic source probably to the west of the british isles q 2004 elsevier ltd all rights reserved

variability in ostracod partition coefficients d sr and d mg implications for lacustrine palaeoenvironmental reconstructions living and sub recent ostracods were collected from four lakes and foul springs located in belgium france and spain characterized by low water mg ca ratios from 0 08 to 0 65 valves of ostracods belonging to cyprideis torosa candona neglecta c marchica and c candida have been extensively analysed for their magnesium and strontium contents with respect to calcium comparisons of these results are made using the same elements from the waters in which the ostracod valves calcified our results offer new and somewhat different interpretations with respect to the uptake of mg and sr in the calcitic ostracod valves these findings include the following 1 the partition coefficient l sr for ostracods belonging to the same genus candona is not a constant the observed variability in d sr values could be due to the rare of biological calcification although more investigations are necessary to assess the influence of this factor it is possible that some taxa grouped under the genus candona belong to a different genus 2 even at the species level cyprideis torosa the ostracod d sr cannot be considered to be constant at low water mg ca ratio 0 65 our d sr value for c torosa is higher than those determined by others for c torosa calcified in evolved marine water 3 the mg ca ratio of the water appears as a major factor influencing d mg for ostracods for low water mg ca values similar to 2 d mg drastically increases this phenomenon is also effective for inorganic calcite implying a non biologic effect that could be linked to mg2 adsorption consequently large variations in me content of fossil ostracod valves from selected lacustrine sequences with expected low water mg ca similar to 2 can be due to small variations in water mg ca c 1998 elsevier science b v all rights reserved

a late quaternary palaeolimnological record from jamaica based on trace element chemistry of ostracod shells abstract the trace element chemistry of ostracod shells provides one of the most promising methods for palaeolinmological reconstruction in this paper molar sr ca and mg ca ratios in shells of the ostracod cypretta brevisaepta furtos 1934 were used to reconstruct the late quaternary palaeolimnology of wallywash great pond a small freshwater coastal lake in jamaica analyses of modern jamaican ostracods were undertaken to establish molar distribution coefficients kd d m s for this species k d sr 0 306 0 069 k d mg 0 0142 0 0088 these values were used to reconstruct past levels of sr ca water and mg ca water for a 9 23 m lake sediment core from wallywash great pond the results were coupled with previously published stable isotope 18 o and 13 c determinations on fine grained calcite to reconstruct the salinity palaeohydrology and palaeoproductivity of the lake over the last 125 ka b p 10 3 calendar years before present three major highstands with slightly elevated salinity occurred during marine isotope stage 5 under elevated sea level and a humid climate the lake dried out 93 5 ka b p as sea level felll and the climate became drier it refilled around 10 7 ka b p three separate highstands during the holocene were sustained by humid conditions and high relative sea level although there were small increases in salinity during the holocene when sea level was close to the deepest part of the lake significant saltwater intrusion appears to have been prevented by freshwater discharge from inland throughout the late quaternary the salinity of the great pond showed low absolute variations from 0 3 to 0 6 o the long term trends in lake level reflect both orbitally induced changes in insolation and eustatic sea level water level fluctuations during the holocene however reflect climatic changes on the millennial timescale rather than orbital forcing or sea level change

provenance characteristics of detrital opaque fe ti oxide minerals abstract we have investigated petrogenetic characteristics of detrital opaque fe ti oxide minerals dopq in sand samples collected from holocene streams draining exclusively igneous and metamorphic source rocks in the rocky mountain region under a semi arid climate and from the appalachian mountains under a humid climate our sampling strategy allows us to compare and contrast the properties of detrital mineral grains not only from igneous and metamorphic source rocks but also those from dissected arc and recycled orogen provenances reflected light petrography including extensive modal analysis and electron probe microanalysis of polished grain mounts were the two principal methods of data gathering between 25 and 50 of all dopq show oxidation exsolution and or other lamellar intergrowth textures i e they are polymineralic grains lamellar intergrowth texture is present in about twice as many grains derived from igneous source rocks as from metamorphic source rocks lamellae thinner than 2 m are predominant in grains derived from dissected arc provenance whereas lamellae thicker than 10 m are predominant in grains derived from recycled orogen provenance exsolution lamellae along 111 planes of magnetite three directions and presumably along 0001 planes of ilmenite one direction characterize dissected are and recycled orogen provenance respectively detrital ilmenites derived from the igneous source rocks studied show a wide range of tio2 co tent with a mode around 47 whereas those from the metamorphic source rocks show a tight cluster around 52 tio2 content dopq derived from metamorphic source rocks contain 0 5 mgo whereas those from igneous rocks may contain up to 1 2 mgo both mgo and mno are low 0 3 and 2 5 respectively in dopq derived from dissected arc provenance but may be relatively high up to 1 2 and 8 0 respectively in grains derived from recycled orogen provenance whereas no single character of dopq may be diagnostic of provenance discriminant function analysis of the complete set of data show that collectively they are diagnostic in 95 to 100 of cases we recommend the use of 1 presence of exsolution texture 2 minimum lamellae widths and the number of crystallographic orientation of the lamellae and 3 chemical composition including minor elements of dopq as important properties for provenance identification this should supplement and refine existing criteria for provenance determination

a new approach to provenance studies electron microprobe analysis of detrital garnets from middle jurassic sandstones of the northern north sea reading provenance from heavy mineral suites is hampered by the depletion of diagnostic but unstable heavy minerals through intrastratal solution a common phenomenon in deep sedimentary basins such as the north sea this paper demonstrates the potential of electron microprobe analysis in overcoming this problem by concentrating on the compositional variations shown by detrital garnets which are relatively resistant to intrastratal solution studies of the garnets from the brent group middle jurassic of the murchison and tern oilfields in the northern north sea reveal that three distinct areas supplied detritus association 1 which characterizes the broom formation in both areas and recurs higher in the sequence in the tern field is ascribed to an orkney shetland source the location of the areas supplying the garnets of association 2 best represented in murchison and association 3 common to both fields is less clear their ultimate sources clearly include high grade metamorphics and therefore probably lie on the norwegian landmass the orkney shetland platform or conceivably the scottish landmass but the possibility of recycling makes it difficult to judge their immediate provenances nevertheless the presence of three garnet associations indicates that the most widely accepted model of brent sedimentation with sands derived from a domal uplift in the outer moray firth and channelled northward along the viking graben is untenable

stratigraphic correlation of late palaeocene sand deposits in the sogne basin area of the danish and norwegian central north sea a stratigraphic analysis of late palaeocene sands of the sogne basin and the western part of the norwegian danish basin shows that the sand bodies are of differenct ages the geographic distribution of the sand deposits shows that they are related to underlying mesozoic structures suggesting a controlling effect of tertiary tectonics on the deposition of sand during the late palaeocene however the structural setting of various sand bodies varies from reactivation of older faults and reactivation of salt structures the local character of the structures active during the late palaeocene introduces minor depressions with no lateral connection the sand bodies which are interpreted as having been deposited in these depressions are thus in general separate bodies with no lateral connection the fennoscandian shield and eroded mesozoic sediments along the fennoscandian border zone are suggested as source area for the late palaeocene sand deposits

elemental mobility in sandstones during burial whole rock chemical and isotopic data frio formation south texas abstract the deepest 3 5 km and most altered oligocene frio sandstones from south texas typically contain authigenic minerals that exceed 30 volume percent of the rock elemental and isotopic analyses of whole rocks confirm conclusions based on petrography that authigenesis is accompanied by substantial material transfer involving both import to and export from the sandstone from petrographic observations zr is apparently less mobile than other immobile elements such as al ti and ree but nonuniform initial distribution of zr due to sorting limits its usefulness for normalizing elemental variations if zr is assumed to be strictly immobile and zr was once uniformly distributed then volume loss of approximately 38 from the silicate fraction of the deepest sandstones is suggested over the range of burial depths for samples used in this study 0 9 4 3 km elemental trends controlled by feldspar reactions are the most readily documented dissolution and replacement of detrital k feldspar is accompanied by loss of 2 3 weight percent of k2o from the whole rock loss of more than half of the initial rb sr and pb also correlate with alteration of detrital feldspars 87sr 86sr ratios for whole rock and silicate fractions increase with depth as loss of nonradiogenic strontium characteristic of the volcanic rich detrital fraction is overwhelmed by more radiogenic strontium derived from deeper in the basin relatively constant na is compatible with feldspar alteration in which dissolution exceeds albitization changes in nd concentrat ons and nd also closely track the progress of alteration of detrital feldspar magnesium gain accompanies precipitation of authigenic chlorite and very minor ferroan dolomite whole rock calcium values are dominated by calcite that includes both detrital and authigenic components significant dissolution of detrital carbonate grains does not occur and calcium in authigenic carbonate cement exceeds by about 5 times the calcium released by dissolution of detrital silicates thus requiring considerable import of calcium and co2 material transfer on the scale observed demonstrates that burial diagenesis is an open system process for several major elements and introduces a major obstacle to use of elemental data for provenance interpretation defining the sources of materials transported into sandstones and the fate of materials exported is key to documenting the scale of system closure in sedimentary basins and requires a better understanding of diagenetic processes in mudrocks

in situ measurements of tropospheric volcanic plumes in ecuador and colombia during tc4 a nasa dc 8 research aircraft penetrated tropospheric gas and aerosol plumes sourced from active volcanoes in ecuador and colombia during the tropical composition cloud and climate coupling tc 4 mission in july august 2007 the likely source volcanoes were tungurahua ecuador and nevado del huila colombia the tc 4 data provide rare insight into the chemistry of volcanic plumes in the tropical troposphere and permit a comparison of so 2 column amounts measured by the ozone monitoring instrument omi on the aura satellite with in situ so 2 measurements elevated concentrations of so 2 sulfate aerosol and particles were measured by dc 8 instrumentation in volcanic outflow at altitudes of 3 6 km estimated plume ages range from 2 h at huila to 22 48 h downwind of ecuador the plumes contained sulfate rich accumulation mode particles that were variably neutralized and often highly acidic a significant fraction of supermicron volcanic ash was evident in one plume in plume o 3 concentrations were 70 80 of ambient levels downwind of ecuador but data are insufficient to ascribe this to o 3 depletion via reactive halogen chemistry the tc 4 data record rapid cloud processing of the huila volcanic plume involving aqueous phase oxidation of so 2 by h 2o 2 but overall the data suggest average in plume so 2 to sulfate conversion rates of 1 2 h 1 so 2 column amounts measured in the tungurahua plume 0 1 0 2 dobson units are commensurate with average so 2 columns retrieved from omi measurements in the volcanic outflow region in july 2007 the tc 4 data set provides further evidence of the impact of volcanic emissions on tropospheric acidity and oxidizing capacity

trace element mobility during sub seafloor alteration of basaltic glass from ocean drilling program site 953 off gran canaria trace element concentrations of altered basaltic glass shards layer silicates and zeolites in volcaniclastic sediments drilled in the volcanic apron northeast of gran canaria during ocean drilling program odp leg 157 document variable element mobilities during low temperature alteration processes in a marine environment clay minerals saponite montmorillonite smectite replacing volcanic glass particles are enriched in transition metals and rare earth elements ree the degree of retention of ree within the alteration products of the basaltic glass is correlated with the field strength of the cations the high field strength elements are preferentially retained or enriched in the alteration products by sorption through clay minerals most trace elements are enriched in a boundary layer close to the interface mineral altered glass this boundary layer has a key function for the physico chemical conditions of the subsequent alteration process by providing a large reactive surface and by lowering the fluid permeability the release of most elements is buffered by incorporation into secondary precipitates sodium rich zeolites phillipsite fe and mn oxides as shown by calculated distribution coefficients between altered glasses and authigenic minerals chemical fluxes change from an open to a closed system behavior during prograde low temperature alteration of volcaniclastic sediments with no significant trace metal flux from the sediment to the water column

diagenesis of titaniferous minerals in jurassic sandstones from the norwegian sea abstract ti oxides anatase and in some cases rutile that attain various textures and modes of occurrence are minor yet very common authigenic minerals in the jurassic sandstones of the haltenbanken oil field offshore central norway these ti oxides pyrite commonly occur as pseudomorphs after detrital fe ti oxides usually ilmenite titanomagnetite and titanohematite pseudomorphs comprised of ti oxides as well as quartz and or calcite are believed to result upon alteration of detrital sphene ti oxides have also resulted upon kaolinization of detrital biotite and less significantly muscovite authigenic sphene occurs in very small amounts in some of the jurassic sandstones at burial depths 2000 m it displays three major crystallization habits 1 as almond shaped crystals that have most commonly crystallized on authigenic calcite 2 as discrete rhombic crystals that have crystallized adjacent to altered fe ti oxides and biotite and 3 as aggregates of euhedral and subhedral crystals these crystallization habits suggest that sphene has been formed by reaction of si and ti ions with calcite crystallization from pore fluids and replacement of fe ti oxides respectively microprobe analyses of authigenic sphene revealed that al and fe 3 substitute ti in appreciable amounts average 0 08 and 0 04 moles per 5 oxygen atoms respectively whereas substitutions of ca by mn k and na and of ti by mg are negligible

petrography of thoriferous hydrocarbon nodules in sandstones and their significance for petroleum exploration nodules of thorium rich hydrocarbon are recorded in sandstone sequences from several basins the hydrocarbon nodules contain mineral inclusions particularly of thorite or monazite there is evidence both for accretion of hydrocarbons around detrital heavy mineral grains and for epigenetic growth by interaction of hydrocarbons with thorium bearing fluids both mechanisms depend upon the precipitation of solid hydrocarbons induced by irradiation from thorium the nodules exhibit aggressive replacement of other grains a characteristic of radioanomalous hydrocarbons the occurrence of the nodules is dependent upon an appropriate plutonic source for the thorium but given this constraint they are important evidence for hydrocarbon migration pathways

tufa as a record of perennial fresh water in a semi arid rift basin kapthurin formation kenya lithological and biological features of a fossiliferous tufa in the kapthurin formation baringo kenya reveal the presence of a lush wetland in a semiarid environment during the middle pleistocene ca 500 ka in this portion of the east african rift valley four geological sections each between 3 m and 8 m in thickness exposed over a distance of 0ae5 km reveal a 1 to 2 m thick paludal tufa which is composed of three carbonate beds two dark grey silty claystones and a reddish brown silty palaeosol high resolution stratigraphic analysis carbonate petrography stable isotope and elemental geochemistry clay mineralogy and fossil remains molluscs ostracods diatoms and charophytes reveal a ground water fed system that fluctuated in depth and periodically disappeared altogether oxygen isotope ratios d 18 o of tufa matrix range from 4ae5 to 8ae0 vienna pee dee belemnite and become more positive up section indicating the decreasing influence of fault related fluids and increasing residence time or freshness of wetland water rather than evaporative enrichment this spring was situated on a lake margin during low lake levels thrived during periods of increased ground water input and was ultimately replaced by an alkaline lake the wetland would appear to have existed during a cool interval within the generally warm marine isotope stage 13 or perhaps during the warm second half of marine isotope stage 13 the ground water source of this wetland arose through a fault system thus the position of the tufa deposit is controlled structurally but the timing and duration of the wetland system may have been influenced by both climatic and tectonic factors

mid pliocene deep sea bottom water temperatures based on ostracode mg ca ratios abstract we studied magnesium calcium mg ca ratios in shells of the deep sea ostracode genus krithe from a short interval in the middle pliocene between 3 29 and 2 97 ma using deep sea drilling sites in the north and south atlantic in order to estimate bottom water temperatures bwt during a period of climatic warmth results from dsdp and odp sites 552a 610a 607 658a 659a 661a and 704 for the period ma reveal both depth and latitudinal gradients of mean mg ca values shallower sites 552a 610a and 607 have higher mean mg ca ratios 10 3 9 7 10 1 mmol mol than deeper sites 661a 6 3 mmol mol and high latitude north atlantic sites 552a 610a 607 have higher mg ca ratios than low latitude 658a 9 8 mmol mol 659a 7 7 mmol mol 661a 6 3 mmol mol and southern ocean 704 8 0 mmol mol sites converting mg ca ratios into estimated temperatures using the calibration of dwyer et al 1995 dwyer g s cronin t m baker p a raymo m e buzas j s correge t 1995 north atlantic deepwater temperature change during late pliocene and late quaternary climatic cycles science 270 1347 1351 suggests that mean middle pliocene bottom water temperatures at the study sites in the deep atlantic were about the same as modern temperatures however brief pulses of elevated bwt occurred several times between 3 29 and 2 97 ma in both the north and south atlantic ocean suggesting short term changes in deep ocean circulation

ostracod shell chemistry as proxy for paleoenvironmental change abstract the application of ostracod shell chemistry as a paleoenvironmental tool has grown within the past decades most studies have investigated mg and sr in ostracod shells as proxies for temperature and salinity and the use of a wide range of trace elements as prospective paleoenvironmental indicators has yet to be developed for lacustrine systems only a few preliminary studies have used trace metals in paleolimnological studies such as cd ba and zn as paleonutrient indicators or mn fe and u as redox and oxygenation indicators this paper reviews the state of the art of geochemical analyses in microfossils such as ostracods foraminifera and corals and provides insights in new trace element proxies with the goal to promote the use of trace elements in ostracod shells as paleoenvironmental proxies in paleoceanography foraminifera and corals are most prominently used to reconstruct past climate conditions well established proxies such as 18o mg ca and sr ca provide information about changes in sea surface temperatures in addition a great number of new proxies have been developed recently such as radiogenic isotopes and redox sensitive trace elements in paleolimnology ostracod shell chemistry is widely used to assess paleohydrological changes reconstruction of temperature and salinity changes in lake environments is often achieved by oxygen isotopes as well as mg ca and sr ca ratios but depending on the hydrological and geological settings of the lake system local calibrations are needed to assess which proxy is suited to reflect which processes new proxies need to be tested by novel techniques that recently have become available compared to conventional instrumentation used in ostracod shell chemistry methods such as laser ablation icp ms and nanosims allow single shell analysis and provide high resolution data the potential of ostracods in paleolimnology is not yet fully assessed but can be developed by learning from paleoceanographic studies

the provenance of triassic continental sandstones from the beryl field northern north sea mineralogical geochemical and sedimentological constraints a geochemical study of the heavy mineral suite in triassic strata from two wells in the beryl embayment was undertaken in order to identify changes in provenance through the lewis formation detailed provenance studies also allow the reconstruction of paleodrainage patterns and aid in predicting facies distributions the heavy mineral assemblage in the lewis formation is dominated by almandine pyrope garnets which are typically derived from pelitic metasediments together with zircon apatite tourmaline and rutile some of which are rich in niobium nb these latter phases could have been sourced either from metasediments or granitic protoliths although nb rich rutiles have a more restricted paragenesis being associated with alkaline plutonic rocks and granite pegmatites in the uppermost members of the lewis formation influxes of more exotic provenance specific heavy minerals such as cr spinel staurolite and chloritoid become more common the chemistry of the detrital cr spinel implies that it was derived from an ophiolitic source gross grain size and facies changes in the embayment suggest a nw to se dispersal of detritus although hydraulic sorting of the heavy mineral suite between relatively distal and proximal locations has resulted in subtle variations in whole rock trace element geochemical signatures the complete overlap in the geochemical data from distal and proximal wells requires that the sediments were essentially derived from a single source area the combination of mineralogical sedimentological and geochemical data implies that the dominant source for these sediments was the devonian old red sandstone ors the shetland ophiolite and the underlying dalradian metasedimentary rocks of the shetland isles and the east shetland platform provenance studies such as this are central to the reconstruction of paleo drainage patterns which in turn lead to improved prediction of potential reservoir quality distribution and connectivity

provenance evolution and chemostratigraphy of a palaeozoic submarine fan complex tanqua karoo basin south africa geochemical studies of mudstones from boreholes in the deep water permian skoorsteenberg formation in the karoo basin of south africa were undertaken to assess stratigraphic and provenance evolution and the feasibility of chemostratigraphic correlation in this sedimentary setting data for 38 major and trace elements including rare earth elements were obtained from four boreholes from 304 samples covering proximal to distal parts of the turbidite complex there are geochemical signals displaying systematic stratigraphic trends across the basin that imply a continuous evolution of one pre eminent source terrain that supplied the sediment changes in ratios of tio2 al2o3 la la lu and th th y suggest an increasingly mafic contribution to the depositional system with time perversely however increasing zr and hf abundance up the stratigraphic succession suggest that there was also an increase in the felsic content with time these apparently conflicting interpretations may be explained by a single source terrain that became increasingly igneous e g less sedimentary rocks being weathered and supplying new sediment with time although the progressively denuded rocks must have been predominantly mafic the chemical index of alteration decreased with time possibly suggesting that a less intense weathering regime in the hinterland developed with time the geochemical data set from the skoorsteenberg formation in the karoo basin have demonstrated that chemostratigraphy is not an ideal approach to correlation since the geochemical signals have substantial statistical noise that is not easily related to lithology q 2004 elsevier ltd all rights reserved

discrimination of density flow deposits using elemental geochemistry implications for subtle provenance differentiation in a narrow submarine canyon palaeogene danish north sea abstract elemental geochemistry of 1131 sandstone samples has been used to characterise five palaeogene sandstone members in a system of density flow deposits within an incised submarine canyon danish north sea diagenetic overprinting has complicated the use of most main and trace elements but a group of heavy mineral bound elements with low mobility ti y zr nb and th has proved highly potential for correlation the individual sandstone members exhibit very consistent relations between the heavy mineral elements along the canyon and based on zr ti plots two families of sandstone members can be distinguished the families are recognised on variations in inclination and intersection of linear regression lines which are related to subtle variations in provenance source area the inclination is believed to be controlled by the detrital heavy mineral hm suite and composition whereas the intersections are controlled by the background contribution such as hm inclusions in detrital rock forming minerals e g quartz and or feldspar as well as substituted and or adhered elements in glauconite the correlation pattern has been used to suggest a re interpretation of the stratigraphic relation of some of the sands

high resolution chemostratigraphy of quaternary distal turbidites a case study of new methods for the analysis and correlation of barren sequences

topography of the top chalk surface on and offshore denmark abstract a time structure map of the top of the upper cretaceous danian chalk group the top chalk surface in the entire danish sector is presented the present topography of the top chalk surface is a result of various erosional and tectonic events taking place during the cenozoic the analysis shows that the cenozoic is characterised by significant reactivation of the mesozoic structural elements of which the central graben the ringkobing fyn high and the sorgenfrei tornquist zone are the most important a tectonically controlled relief caused the generation of widespread sheet like erosion on the ringkobing fyn high and incisions along the margins of ringkobing fyn high during the mid paleocene incisions in the northern part of the danish sector formed valleys which probably transported sediment towards the west the present topography of top chalk in the eastern part of the danish sector is highly influenced by the late cenozoic erosion of the uplifted eastern margin of the north sea basin the topography of top chalk also reflects the distribution of mobile zechstein salt as collapse structures follow the pitch out line of mobile salt onto the ringkobing fyn high and numerous salt structures deformed the top chalk surface