a cenozoic record of the equatorial pacific carbonate compensation depth atmospheric carbon dioxide concentrations and climate are regulated on geological timescales by the balance between carbon input from volcanic and metamorphic outgassing and its removal by weathering feedbacks these feedbacks involve the erosion of silicate rocks and organic carbon bearing rocks the integrated effect of these processes is reflected in the calcium carbonate compensation depth which is the oceanic depth at which calcium carbonate is dissolved here we present a carbonate accumulation record that covers the past 53 million years from a depth transect in the equatorial pacific ocean the carbonate compensation depth tracks long term ocean cooling deepening from 3 0 3 5 kilometres during the early cenozoic approximately 55 million years ago to 4 6 kilometres at present consistent with an overall cenozoic increase in weathering we find large superimposed fluctuations in carbonate compensation depth during the middle and late eocene using earth system models we identify changes in weathering and the mode of organic carbon delivery as two key processes to explain these large scale eocene fluctuations of the carbonate compensation depth

rapid stepwise onset of antarctic glaciation and deeper calcite compensation in the pacific ocean the ocean depth at which the rate of calcium carbonate input from surface waters equals the rate of dissolution is termed the calcite compensation depth at present this depth is 4 500 m with some variation between and within ocean basins the calcite compensation depth is linked to ocean acidity which is in turn linked to atmospheric carbon dioxide concentrations and hence global climate1 geological records of changes in the calcite compensation depth show a prominent deepening of more than 1 km near the eocene oligocene boundary 34 million years ago 2 when significant permanent ice sheets first appeared on antarctica3 4 5 6 but the relationship between these two events is poorly understood here we present ocean sediment records of calcium carbonate content as well as carbon and oxygen isotopic compositions from the tropical pacific ocean that cover the eocene oligocene boundary we find that the deepening of the calcite compensation depth was more rapid than previously documented and occurred in two jumps of about 40 000 years each synchronous with the stepwise onset of antarctic ice sheet growth the glaciation was initiated after climatic preconditioning7 by an interval when the earth s orbit of the sun favoured cool summers the changes in oxygen isotope composition across the eocene oligocene boundary are too large to be explained by antarctic ice sheet growth alone and must therefore also indicate contemporaneous global cooling and or northern hemisphere glaciation

pedogenic carbonates forms and formation processes abstract soils comprise the largest terrestrial carbon c pool containing both organic and inorganic c soil inorganic carbon sic was frequently disregarded because 1 it is partly heritage from soil parent material 2 it undergoes slow formation processes and 3 has very slow exchange with atmospheric co2 the global importance of sic however is reflected by the fact that sic links the long term geological c cycle with the fast biotic c cycle and this linkage is ongoing in soils furthermore the importance of sic is at least as high as that of soil organic carbon soc especially in semiarid and arid climates where sic comprises the largest c pool considering the origin formation processes and morphology carbonates in soils are categorized into three groups geogenic carbonates gc biogenic carbonates bc and pedogenic carbonates pc in this review we summarize the available data and theories on forms and formation processes of pc and relate them to environmental factors after describing the general formation principles of pc we present the specific forms and formation processes for pc features and the possibilities to use them to reconstruct soil forming factors and processes the following pc are described in detail earthworm biospheroliths rhizoliths and calcified roots hypocoatings nodules clast coatings calcretes and laminar caps the second part of the review focuses on the isotopic composition of pc 13c 14c and 18o as well as clumped 13c and 18o isotopes known as 47 the isotopic signature of pc enables reconstructing the formation environment the dominating vegetation 13c temperature 18o and 47 and the age of pc formation 14c the uncertainties in reconstructional and dating studies due to pc recrystallization after formation are discussed and simple approaches to consider recrystallization are summarized finally we suggest the most important future research directions on pc including the anthropogenic effects of fertilization and soil management in conclusion pc are an important part of sic that reflect the time periods and formation processes in soils a mechanistic understanding of pc formation is a prerequisite to predict terrestrial c stocks and changes in the global c cycle and to link the long term geological with short term biological c cycles

environmental changes since 8 4 ka reflected in the lacustrine core sediments from nam co central tibetan plateau china the tibetan plateau induces and enhances the asian monsoon that influences the plateau itself east china and even the whole of asia pursuing the changing monsoon history and its impact in this environment sensitive area is a key for understanding the climatic changes here we present the initial results from core sed iments in nam co central tibet to elucidate the holocene environment changes in this area the studied lake nam co is the second largest lake with an elevation of 4718 m water area of 2015 km 2 and catchment area of 10 610 km 2 by using echo seismic profiling and hydro echosounding we investigated the bathymetric dis tribution of the whole lake one 332 cm long piston core was successfully taken in the east part of the lake at 60 m water depth twelve ams 14 c dates from top to bottom of this core established a good time sequence toc tn n alkanes grain size clay minerals fe mn sr ba and caco3 content were analysed with sampling intervals from 1 cm to 10 cm results showed that since 8400 yr bp the environment changes in this region indicate three stages the early stage 8400 6900 yr bp was characterized by slight shifting from warm to cold with a cold dry interval at 8100 7800 yr bp the middle stage was from 6900 to 2900 yr bp during which cli mate changed from warm humid to cold dry however around 2900 yr bp the climate once was slightly cold but strongly dry the late stage from 2900 yr bp to present was characterized by a general tendency toward cold dry the first temperature decline was around 1700 1500 yr bp following which temperature increased once before decreasing again around 600 300 yr bp which might be the result of the little ice age

miocene sedimentary environment and climate change in the northwestern qaidam basin northeastern tibetan plateau facies biomarker and stable isotopic evidences abstract facies biomarker and stable isotopic records from the miocene lacustrine sediments in the northwestern qaidam basin were investigated to reconstruct the miocene sedimentary environment and climatic history three distinct facies can be recognized these include the following 1 gray black laminated mudstone and marlstone which represent a semi deep fresh to semi brackish lake environment 2 gray yellowish massive mudstone marlstone and siltstone and 3 yellowish massive sandstone which imply a shallow brackish lake environment the decreasing c 27 c 31 and c 27 c 29 c 31 c 33 values the increasing acl mean chain length values of n alkanes and the vertical evolution of sedimentary environments indicate the overall intensified aridity which is considered to be an integrated result of high elevation of the himalaya tibetan system retreat of the paratethys and global cooling high fluctuations of the 18 o values and primary dolomite contents reveal the hydrologically closed paleolake with intermittently open conditions in the study area during middle late miocene the qaidam basin is suggested to be hydrologically segmented based on the stable isotopic data comparison between the study area and the northeastern area the most negative end of the oscillations of the 18 o values indicating the minimal evaporation which likely represents the isotopic ratio of the meteoric water surprisingly conveys stability in the shang youshashan and shizigou formations and displays a positive 2 5 shift this significant shift was probably due to the climatic aridification and air mass changes around 10 8 ma rather than the global cooling

the bathymetry of a titan sea construct the depth profile the bathymetry of titan s large sea ligeia mare from cassini radar data collected during the 23 may 2013 t91 nadir looking altimetry flyby we find the greatest depth to be about 160 m and a seabed slope that is gentler toward the northern shore consistent with previously imaged shoreline morphologies low radio signal attenuation through the sea demonstrates that the liquid for which we determine a loss tangent of 3 1 10 5 is remarkably transparent requiring a nearly pure methane ethane composition and further that microwave absorbing hydrocarbons nitriles and suspended particles be limited to less than the order of 0 1 of the liquid volume presence of nitrogen in the ethane methane sea expected based on its solubility and dominance in the atmosphere is consistent with the low attenuation but that of substantial dissolved polar species or suspended scatterers is not

miocene crustal extension and uplift in southeastern nevada constraints from fission track analysis the gold butte block of southeastern nevada appears to be a cross section through the upper approximately 17 km of colorado plateau crust tilted eastward and tectonically denuded via top to the west normal faulting in tertiary time the east side of the block exposes a steeply dipping cratonic paleozoic section 2 to 3 km thick proterozoic basement to the west is continuously exposed for an apparent thickness of approximately 15 km structurally below the basal cambrian unconformity apatite fission track dating and confirmed track length distributions have been used to determine the time of unroofing of the gold butte block and hence the timing of one episode of extension in this part of the basin and range province samples collected in as east west transect along the block indicate an abrupt transition from a period of relative thermal and tectonic stability to the onset of rapid cooling the fission track data indicate that the unroofing of the gold butte block was rapid and that the crustal section was brought to within a few kilometers of the surface at ca 15 ma

probing pluto s underworld ice temperatures from microwave radiometry decoupled from surface conditions present models admit a wide range of 2015 surface conditions at pluto and charon where the atmospheric pressure may undergo dramatic seasonal variation and for which measurements are imminent from the new horizons mission one anticipated observation is the microwave brightness temperature heretofore anticipated as indicating surface conditions relevant to surface atmosphere equilibrium however drawing on recent experience with cassini observations at iapetus and titan we call attention to the large electrical skin depth of outer solar system materials such as methane nitrogen or water ice such that this observation may indicate temperatures averaged over depths of several or tens of meters beneath the surface using a seasonally forced thermal model to determine microwave emission we predict that the southern hemisphere observations in polar night of new horizons in july 2015 will suggest effective temperatures of 40 k reflecting deep heat buried over the last century of summer even if the atmospheric pressure suggests that the surface nitrogen frost point may be much lower

geotechnical tests of sands following bioinduced calcite precipitation catalyzed by indigenous bacteria recentexperimentshaveshownthatexogenousbacteriacanbeintroducedintosoilforthepurposeofinducingcalciteprecipitation a series of tests are documented in this paper that demonstrate that natural indigenous bacteria can also be stimulated to induce calcite precip itation with measurable changes in geotechnical properties tests reported in this paper include a microcosm experiment with cone penetration testing and cyclic triaxial shear tests these experiments demonstrate that indigenous bacteria can induce significant quantities of calcite pre cipitation that calcite precipitation can result in measurable changes to geotechnical soil properties and that the cyclic resistance ratio can be increased substantially with moderate levels of calcite precipitation using indigenous bacteria to modify soil properties is a significant step in making biomodification of soils economically viable doi 10 1061 asce gt 1943 5606 0000781 2013 american society of civil engineers ce database subject headings biological processes soil liquefaction cement bacteria soil stabilization earthquake author keywords biological processes liquefaction cementation bacteria calcite stabilization earthquake soil improvement

late cretaceous to early eocene deformation in the northern tibetan plateau detrital apatite fission track evidence from northern qaidam basin abstract unraveling the growth of northern tibet is crucial to understanding the geodynamic processes of the india eurasia collision evaluating plateau uplift models and reconstructing associated paleoclimate history however pre middle miocene deformation history of northern tibet remains poorly understood we use detrital apatite fission track detrital aft thermochronology of mesozoic and cenozoic sedimentary rocks from northern qaidam basin to constrain the early growth of northern tibet detrital aft ages of the mesozoic samples are younger than their depositional ages indicating that the mesozoic succession underwent two stages of exhumation after deep burial during 80 61 ma and 54 47 ma detrital aft ages of the cenozoic samples are older than their depositional ages and reveal that their source region experienced two periods of exhumation peak ages in 86 59 ma and 54 36 ma these results suggest that the northern tibet successively experienced late cretaceous early paleocene and early middle eocene deformation the late cretaceous early paleocene deformation implies that the extent of pre collisional india eurasia deformation region in the plateau were much larger than previously known the static detrital aft peak ages 54 51 ma based on lag time analysis for the paleogene samples demonstrate the early eocene deformation was a rapid and short lived event which was a far field response to the india eurasia collision hence we advocate synchronous deformation throughout the northern plateau at the collision time lag time analysis results also demonstrate absence of oligocene to early miocene cooling ages and post eocene decreasing exhumation rates in the cenozoic source regions this suggests relatively quiescent tectonic settings in the qilian mountains during the oligocene early miocene and agrees that the lateral strike slip movement of the altyn tagh fault was accommodated out of the plateau by the end of the early miocene

climatic change and caco3 preservation an 800 000 year bathymetric reconstruction from the central equatorial pacific ocean sixteen deep sea cores from the central equatorial pacific are used to reconstruct a continuous 800 000 year 800 kyr record of bathymetric variations in carbonate preservation as measured by calcium carbonate caco3 content the depth of the sedimentary lysocline has fluctuated markedly in conjunction with late pleistocene climate cycles while the carbonate critical depth ccrd which is the water depth where the sediments contain 10 caco3 has remained relatively constant as a result the depth of the lysocline controls the bathymetric position and thickness of the caco3 transition zone defined as the depth from the lysocline to the ccrd modern and interglacial aged sediments show poor caco3 preservation and thick caco3 transition zones glacial aged sediments show good preservation and deep thin zones due to the deepening of the lysocline detailed comparison of the caco3 preservation and oxygen isotope records from the central equatorial pacific confirms the observation that preservation maxima and minima tend to occur during the latter half of glacial and interglacial stages and on climate transitions rather than during the middle of climatic stages during the nine major glacial stages of the last 800 kyr the lysocline deepened by at least 400 to 800 m this deepening indicates an increase in the abyssal carbonate ion concentration co3 and a depression of the calcite saturation horizon best explained by the deeper presence of a more carbonate saturated water mass the bottom of the transition zone has remained at a relatively constant depth during the brunhes chron indicating a balance between caco3 sedimentation and dissolution in the deepest waters of the central equatorial pacific

response of western pacific marginal seas to glacial cycles paleoceanographic and sedimentological features abstract this paper reviews the recent progress in late quaternary studies in five northwestern pacific marginal seas especially the south china sea as an example a series of marginal seas separate asia from the pacific ocean and significantly modify the material and energy flux linkage between land and sea during glacial cycles the sea level induced environmental signal was amplified in the marginal seas giving rise to drastic changes in areas and configurations of these seas and to reorganization of sea water circulation in basins since most of the western pacific marginal seas are influenced by monsoon circulation and some of these are located within the western pacific warm pool the glacial geographic changes have produced a profound impact on regional and global climate for example the decrease of sea area and sea surface temperature sst in the marginal seas was one of the factors responsible for the enhanced aridity of inland china during the glaciation glacial intensification of the winter monsoon and increased seasonality of sst in marginal seas might explain at least partly the apparent discrepancy between the tropical paleotemperature estimations based on terrestrial and open ocean records in this region as the western pacific marginal seas trap terrigenous material supplied by east asia the deep water sedimentation rates there can be one to two orders of magnitude higher than in the open ocean down slope sediment transport is more active when the sea level changes particularly during the deglaciation at least four types of carbonate cycles have been recognized in the western pacific marginal seas and each of those contains environmental signals from the surface and deep sea water as well as from the drainage basin

the ch4 cycles on pluto over seasonal and astronomical timescales abstract pluto s surface is covered in numerous ch4 ice deposits that vary in texture and brightness as revealed by the new horizons spacecraft as it flew by pluto in july 2015 these observations suggest that ch4 on pluto has a complex history involving reservoirs of different composition thickness and stability controlled by volatile processes occurring on different timescales in order to interpret these observations we use a pluto volatile transport model able to simulate the cycles of n2 and ch4 ices over millions of years by assuming fixed solid mixing ratios we explore how changes in surface albedos emissivities and thermal inertias impact volatile transport this work is therefore a direct and natural continuation of the work by bertrand et al 2018 which only explored the n2 cycles results show that bright ch4 deposits can create cold traps for n2 ice outside sputnik planitia leading to a strong coupling between the n2 and ch4 cycles depending on the assumed albedo for ch4 ice the model predicts ch4 ice accumulation 1 at the same equatorial latitudes where the bladed terrain deposits are observed supporting the idea that these ch4 rich deposits are massive and perennial or 2 at mid latitudes 25 70 forming a thick mantle which is consistent with new horizons observations in our simulations both ch4 ice reservoirs are not in an equilibrium state and either one can dominate the other over long timescales depending on the assumptions made for the ch4 albedo this suggests that long term volatile transport exists between the observed reservoirs the model also reproduces the formation of n2 deposits at mid latitudes and in the equatorial depressions surrounding the bladed terrain deposits as observed by new horizons at the poles only seasonal ch4 and n2 deposits are obtained in pluto s current orbital configuration finally we show that pluto s atmosphere always contained over the last astronomical cycles enough gaseous ch4 to absorb most of the incoming lyman flux

mineralogical and geochemical investigations of sediment source region changes in the okinawa trough during the past 100 ka images core md012404 abstract we present a mineralogical and geochemical study of core md012404 retrieved from the central okinawa trough ot of the east china sea our studies reveal that the sediment sources of the core have been changed through time during the past 100 ka our mineralogical proxies indicate that the sediments source from the yangtze river correlates well sea level changes before 24 ka our ti al ratios otherwise indicate an increase of sediment supply from eastern taiwan after 26 ka the cooler climate of the last glacial maximum lgm 23 19 ka led to a reduction in fluvial sediments from the yangtze river however subsequent climate warming after 19 ka resulted in an abrupt increase in fluvial sediments after the lgm the kuroshio intrusion flow into the ot may have increased we also infer anomalous changes in eolian sources transported by winter monsoons during the lgm and at 80 ka based on an eolian mineralogical indicator feldspar we conclude that the sediment source of core md012404 is primarily of terrestrial origins but influenced by sea level changes and variations in the east asian monsoon

87 sr 86 sr applied to age discrimination of the palaeozoic carbonates of the ossa morena zone sw iberia variscides four distinct palaeozoic episodes of marine carbonate sedimentation are reported in the ossa morena zone sw iberian variscides among them the cambrian and the devonian episodes are those that are well represented in the portuguese domains of the ossa morena zone in this zone the strong variscan deformation and metamorphic recrystallization obliterate the biostratigraphic contents of some carbonate local successions and their ages have been based on lithostratigraphic correlations the 87sr 86sr values for the ossa morena zone carbonate rocks allow to make an isotopic lithostratigraphic correlation based on the comparison between strontium ratios of marine carbonate rocks without chronological data and carbonate rocks with a good age control moreover the established 87sr 86sr fingerprints of the marine carbonate episodes from ossa morena zone should be simultaneously correlated with the worldwide seawater 87sr 86sr curve despite the interaction of the marine carbonate sedimentation with late secondary dolomitization processes or with high temperature metamorphic metasomatic fluids which increases the primary 87sr 86sr ratios this methodology allows to define two main distinct clusters of 87sr 86sr for the ossa morena zone marine carbonates a devonian cluster with strontium ratios lower than 0 708000 and a cambrian cluster ranging from 0 708777 to 0 708299 0 708575 0 000161 that can reach 0 709227 0 708866 0 709087 0 000118 if incipient late secondary dolomitization or high temperature metamorphism metasomatism operated the obtained 87sr 86sr isotopic ratios corroborate the lithostratigraphic correlations between the carbonate rocks of abrantes assumar estremoz viana alvito ficalho and escoural successions with the ovetian marianian limestones of alter do chao elvas succession moreover this methodology allows to establish the isotopic discrimination between the upper silurian devonian limestones of ferrarias barrancos and bencatel successions and the marbles of estremoz succession

thermal inertia and bolometric bond albedo values for mimas enceladus tethys dione rhea and iapetus as derived from cassini cirs measurements abstract spectra taken by cassini s composite infrared spectrometer cirs between 10 and 600 cm 1 17 1000 m of surface thermal emission of mimas enceladus tethys dione rhea and iapetus have been used to derive the thermal inertia and bolometric bond albedo values only an upper limit for the bolometric bond albedo of iapetus dark leading side could be determined due to the insensitivity of the thermal model to albedo when albedos are very low the thermal inertia in this region however is better constrained the cirs coverage of enceladus is extensive enough that the latitudinal variation in these values from 60 s to 70 n has been determined in 10 wide bins the bolometric bond albedos determined here are consistent with literature values which show the surface of the saturnian icy moons to be covered in ice contaminated to varying degrees the thermal inertia of the moons is shown to be in the range 9 20 j m 2 k 1 s 1 2 approximately 2 6 times lower than that of the galilean satellites implying a less well consolidated and more porous surface the thermal inertias of iapetus and phoebe are somewhat higher suggesting that the very low thermal inertias of satellites from rhea inwards may be related to their probable coating of e ring material latitudinal variations on the surface of enceladus show that the bolometric bond albedo and thermal inertia increase towards the active plume source at the south pole

present and past glaciation on pluto abstract modern n2 ice glaciers flow from highlands to the east of the 750 1400 km2 lowland of sputnik planum sp and merge with the ices of similar composition on sp we explore the possibility that glaciation may be fed by n2 sublimation from sp followed by redeposition on the highlands the uplands to the northeast north and west of sp have been erosionally sculpted into a variety of dissected terrains that feature linear depressions valleys locally in dendritic networks we interpret these dissected terrains to have been carved by n2 glaciers formerly covering the uplands depositional glacial landforms moraines eskers outwash have not been identified however n2 glaciation would have a different erosional manifestation because the substrate porous water ice and ch4 rich mantles probably has lower density than n2 and also because of the lack of freeze thaw weathering if sufficiently thick 1 4 km n2 glaciers might have experienced basal melting past flow of n2 glaciers from the highlands into sp may have detached and transported the prominent mountainous water ice mountains along the western border of sp

carbonate budget of a cold water coral mound challenger mound iodp exp 307 abstract cold water coral ecosystems represent a worldwide distributed carbonate factory which is so far not considered in global carbonate budget estimations the herein presented study evaluates the carbonate budget of a complete cold water coral mound sequence from challenger mound belgica mound province porcupine seabight sw offshore ireland drilled during iodp expedition 307 reaching back to the late pliocene versus background sediment derived calcite dominated carbonate cores from adjacent drift deposits were examined for comparison studies challenger mound which developed in a fast growth phase unit m1 2 7 to 1 6 ma and a slower growth phase or mound decline unit m2 0 8 ma until today separated by a so called mound crisis displays increased carbonate accumulation rates for both phases 17 3 g cm 2 ka for unit m1 and 5 7 g cm 2 ka for unit m2 compared to adjacent drift deposits but only about 33 to 40 wt of the carbonate is derived from corals bulk sedimentation rates of on and off mound deposits suggest a decline of challenger mound since the onset of drift deposition in the area about 1 2 ma ago yet total carbonate accumulation rates as well as hemipelagic background sediment derived carbonate accumulation rates from challenger mound unit m2 still exceed the carbonate accumulation rates of the adjacent drift deposits the selective enrichment of background sediment derived carbonate by a factor of 2 0 in a cwc mound is herein observed for the first time this might be caused by the different hydrodynamic behaviour and slower settlement of marine fluff rich in calcareous detritus compared to siliciclastic sediments and its effective baffling by the coral framework and or the active catch of the calcareous plankton by the corals the carbonate accumulation rates of challenger mound are about 4 to 12 of the carbonate accumulation rates of tropical shallow water reefs but exceeds the carbonate accumulation rates of continental slopes by a factor of 3 9 to 11 8 the carbonate production for the entire belgica mound province is estimated with 3 2 10 3 t a for unit m1 and 1 0 10 3 t a for unit m2

reservoir characterization and hydrocarbon accumulation in late cenozoic lacustrine mixed carbonate siliciclastic fine grained deposits of the northwestern qaidam basin nw china abstract late cenozoic lacustrine mixed carbonate siliciclastic sequences in the northwestern qaidam basin nw china are mainly composed of high porosity and low permeability fine grained rocks but have big potentials of oil gas commercial production however how these fine grained rocks generate high quality reservoirs and accumulate hydrocarbons remains poorly known this study focuses on shallow buried shang youshashan formation middle late miocene n22 and shizigou formation late miocene pliocene n23 reservoirs and hydrocarbons in xiaoliangshan area of the northwestern qaidam basin we conduct mineralogy petrography and porosity and permeability analysis for reservoir rocks and biomarker analysis for hydrocarbons and potential source rocks the results indicate that the n22 high quality reservoirs are dominated by fractured marlstones and lime mudstones and constitute structural traps whereas the n23 hydrocarbon reservoirs are mainly composed of siliciclastic dominantly rocks and form stratigraphic lithologic traps similar biomarker ratios between crude oil samples and paleogene organic matter rich rocks reveal that hydrocarbons in the shallow system were likely derived from deep buried source rocks rather than late cenozoic lacustrine fine grained rocks themselves in this case large scale vertical fractures created by kink band structures in the northwestern qaidam basin are supposed to facilitate hydrocarbon migration and accumulation preliminary production data and exploration well oil gas test results demonstrate highest yields and thus large hydrocarbon potentials in the n22 marlstone and lime mudstone reservoirs collectively we suggest that relatively high permeability fractured and carbonate rich reservoirs on structural highs are favorable targets for future oil gas exploration in the northwestern qaidam basin this petroleum system provides a typical and significant example for hydrocarbon exploration and development in mixed carbonate siliciclastic fine grained rocks of nonmarine petroliferous basins

on the role of isostasy in the evolution of normal fault systems the footwalls of west dipping normal faults that separate the west central colorado plateau from the basin and range province record at least 5 7 km and perhaps as much as 15 20 km of west side up neogene uplift with an axis just 10 20 km west of undeformed plateau strata the uplift is expressed as folding and steep faulting in pre tertiary cratonic and disconformably overlying neogene strata forming a basement cored anticline and coincident topographic high on the western margin of the plateau the authors interpret the uplift as a nonelastic response of the crust to buoyancy forces accompanying the tectonic denudation of the plateau margin profound isostatically driven deformation of the footwalls of major normal faults may be common in extensional terrains calling into question several assumptions fundamental to existing models of the evolution of normal fault systems

evaluating optical lightness as a proxy for carbonate content in marine sediment cores abstract optical lightness is increasingly being used as a proxy for the carbonate content of marine sediment we compared three measurements of optical lightness gray scale brightness and l to carbonate content to test the reliability of these measurements as carbonate content proxies in five piston cores from isotope stages 1 though 6 0 130 ka all measures of optical lightness are reasonable proxies of relative but not absolute changes in carbonate content in contrast in the upper sediments of odp hole 997a which are holocene to pliocene in age lightness values in only the top 10 m of the 180 m analyzed exhibit a strong correlation to carbonate content to better understand which factors control the optical lightness of sediments we analyzed samples in which carbonate content remained constant while the composition of three common clay minerals chlorite illite and kaolinite was varied kaolinite even at a concentration of 20 did not significantly change optical lightness however 20 illite reduced optical lightness by 30 and 20 chlorite reduced lightness by 20 we conclude that regional and temporal changes in the composition of the non carbonate sediment fraction may significantly alter the relationship between lightness and carbonate content we recommend that care must be taken when applying these measures to sediment sequences which span long time intervals or to sediment samples taken over a broad geographical areas

provenance of tertiary sandstone in the northern qaidam basin northeastern tibetan plateau integration of framework petrography heavy mineral analysis and mineral chemistry abstract an exceptionally thick cenozoic sedimentary succession has developed in the qaidam basin of the northeastern tibetan plateau the provenance remains enigmatic thus more precise investigations are needed an integrated study of sandstone framework petrography heavy mineral analysis and mineral chemistry was adopted to perform provenance analysis of the tertiary sandstones in the northern qaidam basin no individual method exists that can provide comprehensive provenance interpretations on spatial and temporal variations based on three types of data three depositional areas can be distinguished sandstones of area a exhibit relatively high abundances of quartz garnet and zircon as well as relatively high textural maturity implying long distance sources multi composition garnets and tourmalines reveal derivations of metasedimentary rocks and intermediate acidic igneous rocks sandstones of area b are rich in metamorphic lithic fragments epidote and garnet a dominance of fe rich garnets with low mg low mn and variable ca contents and dravites demonstrates predominant derivation of metasedimentary rocks therefore the north qaidam and south qilian terranes are potential source areas for these two depositional areas additionally high metamorphic heavy mineral abundances in the upper formations imply increasing contributions of these two metamorphic belts during the tertiary tectonic uplift however sandstones of area c are characterized by relatively high abundances of feldspar igneous heavy minerals and high fe mn garnet which suggest a main source of igneous rocks the altun and qilian mountains are potential source regions furthermore increasing amounts of feldspar and igneous heavy minerals in the upper formations indicate a significant presence of igneous parent rocks which are most likely a response to the multi stage uplift events in the altun mountains since the early eocene

laboratory measurements of cryogenic liquid alkane microwave absorptivity and implications for the composition of ligeia mare titan the complex dielectric constants of liquids methane and ethane were measured at 90 k and 14 1 ghz close to the frequency of the cassini radar the liquid ethane loss tangent is far greater than that of liquid methane facilitating discrimination by remote sensing the results suggest a methane dominated composition for the northern sea ligeia mare on the basis of a recent loss tangent determination using cassini radar altimetry this contrasts a previous far higher loss tangent for the southern lake ontario lacus which is inconsistent with simple mixtures of methane and ethane the apparent nonequilibrium methane to ethane ratio of ligeia mare can be explained by poor admixture of periodically cycled methane with a deeper ethane rich alkanofer system consistent with obliquity driven volatile cycling sequestration of ethane from the hydrocarbon cycle by incorporation into crustal clathrate hydrates or periodic flushing of ligeia mare into adjacent kraken mare by fresh rainfall

holocene environmental and climatic changes inferred from wulungu lake in northern xinjiang china abstract sedimentological geochemical and palynological data from wulungu lake in northern xinjiang china are used to reconstruct environmental and climate changes since 9550 cal yr bp high abundance of sparganium and poaceae low md median diameter and 13 c organic values indicate aridity between 9550 and 6730 cal yr bp high md and 13 c organic values and the prevalence of desert steppe and steppe vegetation between 4200 and 560 cal yr bp indicate that effective moisture increased after 6730 cal yr bp peaking at 4200 and 560 cal yr bp low md values a negative excursion of 13 c org and the transition from steppe to desert vegetation since 560 cal yr bp reflect a decrease in effective moisture during the latest holocene late holocene human activities were indicated by sharp increase in the abundance of pediastrum then variations in carbonate contents indicate that temperature was generally high between 9550 and 7740 cal yr bp low between 7740 and 6730 cal yr bp intermediate between 6730 and 560 cal yr bp and low during the last 560 yr regional comparison indicates that the asian monsoon did not extend to wulungu lake and westerlies were the main factor in determining the moisture availability during the holocene

quantitative mineralogical analysis of carbonate sediments by x ray diffraction a new automatic method for sediments with low carbonate content a new x ray diffraction method has been developed whereby the weight percentages of aragonite and low and high magnesium calcite are determined from the integrated peak areas of samples peak areas are measured by a step scanning method the weight percentages of mgco3 in calcite are determined from the angular position of the calcite peak this technique uses a direct calculation method which simplifies the preparation of the samples and the calibration processes and increases the quality of the results the fully automatic method uses a desk top computer to guide the diffractometer and to carry out the necessary calculations tests on precision and accuracy of the method indicate that results with less than 4 error mineral and 0 6 error mgco3 are obtainable for all samples even those with a low 10 carbonate content

kinematic evolution of a large offset continental normal fault system south virgin mountains nevada the south virgin mountains and grand wash trough comprise a mid miocene normal fault system that defines the boundary between the unextended colorado plateau to the east and highly extended crust of the central basin and range province to the west in the upper 3 km of the crust the system developed in subhorizontal cratonic strata in the foreland of the cordilleran fold and thrust system the rugged topography and lack of vegetation of the area afford exceptional three dimensional exposures compact stratigraphy and well defined prefaulting configuration of the rocks permitted a detailed reconstruction of the system reconstruction of cross sections based on more than 300 km2 of detailed mapping at a scale of 1 12 000 shows that the fault system accommodated more than 15 km of roughly east west directed miocene extension extension was initially accommodated on moderately to steeply dipping listric normal faults as the early faults and fault blocks tilted steeply to moderately dipping faults initiated within the fault blocks soling into the early faults some of the early faults were active at dips of 20 isostatically driven tilting is superimposed on tilting due to active slip and domino style rotation of the fault blocks collectively these processes rotated originally steeply dipping faults to horizontal orientations the kinematics are inconsistent with the widely accepted view that many near horizontal normal faults were rotated to their present orientations by later crosscutting normal faults however reexamination of other areas suggests that the evolutionary sequence seen in the south virgin mountains may in fact be widely applicable

the geochemistry of carbonate diagenesis the past present and future stable carbon and oxygen isotopes 18o and 13c values and trace elements have been applied to the study of diagenesis of carbonate rocks for over 50 years as valuable as these insights have been many problems regarding the interpretation of geochemical signals within mature rocks remain for example while the 18o values of carbonate rocks are dependent both upon the temperature and the 18o value of the fluid and additional information including trace element composition aids in interpreting such signals direct evidence of either the temperature or the composition of the fluids is required such information can be obtained by analysing the 18o value of any fluid inclusions or by measuring the temperature using a method such as the clumped isotope technique such data speak directly to a large number of problems in interpreting the oxygen isotope record including the well known tendency for 18o values of carbonate rocks to decrease with increasing age unlike the 18o 13c values of carbonates are considered to be less influenced by diagenesis and more a reflection of primary changes in the global carbon cycle through time however many studies have not sufficiently emphasized the effects of diagenesis and other post depositional influences on the eventual carbon isotopic composition of the rock with the classic paradigm that the present is the key to the past being frequently ignored finally many additional proxies are poised to contribute to the interpretation of carbonate diagenesis although the study of carbonate diagenesis is at an exciting point with an explosion of new proxies and methods care should be taken to understand both old and new proxies before applying them to the ancient record

characterization of gas shale pore systems by porosimetry pycnometry surface area and field emission scanning electron microscopy transmission electron microscopy image analyses examples from the barnett woodford haynesville marcellus and doig units the nanometer scaled pore systems of gas shale reservoirs were investigated from the barnett marcellus woodford and haynesville gas shales in the united states and the doig formation of northeastern british columbia canada the purpose of this article is to provide awareness of the nature and variability in pore structures within gas shales and not to provide a representative evaluation on the previously mentioned north american reservoirs to understand the pore system of these rocks the total porosity pore size distribution surface area organic geochemistry mineralogy and image analyses by electron microscopy were performed total porosity from helium pycnometry ranges between 2 5 and 6 6 total organic carbon content ranges between 0 7 and 6 8 wt and vitrinite reflectance measured between 1 45 and 2 37 the gas shales in the united states are clay and quartz rich with the doig formation samples being quartz and carbonate rich and clay poor higher porosity samples have higher values because of a greater abundance of mesopores compared with lower porosity samples with decreasing total porosity micropore volumes relatively increase whereas the sum of mesopores and macropore volumes decrease focused ion beam milling field emission scanning electron microscopy and transmission electron microscopy provide high resolution 5 nm images of pore distribution and geometries image analysis provides a visual appreciation of pore systems in gas shale reservoirs but is not a statistically valid method to evaluate gas shale reservoirs macropores and mesopores are observed as either intergranular porosity or are confined to kerogen rich aggregates and show no preferred orientation or align parallel with the laminae of the shale networks of mesopores are observed to connect with the larger macropores within the kerogen rich aggregates

late pleistocene loess palaeosol sequences in the vojvodina region north serbia late pleistocene loess palaeosol sequences are widespread in the vojvodina region with thicknesses reaching a maximum of about 20 m our investigations include more than 40 of these loess sections geochronology of the last glacial loess palaeosol sequences based on lumines cence dating and amino acid racemisation provides correlations between upper pleistocene loess palaeosol sediments in vojvodina and comparable deposits at other european localities sedimentary logs of magnetic susceptibility grain size measurements and carbonate content combined with malacological evidence indicate two main relatively cold and arid phases during the last glacial period related to intensive accumulation of loess units l1l1 and l1l2 as well as many brief episodes of dry and windy climatic conditions suggesting a possible relationship with cold events recorded in the north atlantic region generally late pleistocene climate in the region was dry and relatively warm compared with glacial period sites in central europe and was characterised by sharp differences between glacial and interglacial modes new data and interpretations presented in this study emphasise the significance of loess palaeosol sequences in vojvodina for the reconstruction of the temporal and spatial evolution of late pleistocene palaeoclimate in this part of europe copyright 2007 john wiley sons ltd

pore structure characteristics of lower silurian shales in the southern sichuan basin china insights to pore development and gas storage mechanism abstract silurian shale in sichuan basin is currently the most important target zone for shale gas exploration and development in china pore structure characteristics of lower silurian longmaxi shales from southern sichuan basin were investigated the combination of field emission scanning electron microscope fe sem and argon ion beam milling was utilized to describe the nanometer to micrometer scale 1 2 nm pore systems the shales were characterized by organic geochemical and mineralogical analyses total porosity pore size distribution psd specific surface area and gas content were determined controls of organic matter richness thermal maturity and mineralogy on porosity were examined the contribution of individual mineral components to total porosity was analyzed quantitatively total gas contents of the shales determined from canister desorption data were compared with theoretical sorptive and volumetric gas storage capacities the total organic carbon toc content of the shale samples ranges between 0 1 and 8 0 wt and helium porosity varies between 0 7 and 5 7 maturity in terms of equivalent vitrinite reflectance of bitumen reqv ranges from 1 8 to 3 2 toc content is a strong control for the pore system of these shales and shows a positive correlation with porosity porosity increases with increasing thermal maturity when reqv is less than 2 5 but decreases for higher thermal maturity samples fe sem reveals four pore types related to the rock matrix that are classified as follows organic matter om hosted pores pores in clay minerals pores of framework minerals and intragranular pores in microfossils pores in clay minerals are always associated with the framework of clay flakes and develop around rigid mineral grains because the pressure shadows of mineral grains prevent pores from collapsing pores of framework minerals are probably related to dissolution by acidic fluids and the dissolution related pores promote porosity of shales a unimodal psd exists in the micropore range of toc rich samples while the psd of carbonate rich samples are bimodal a psd maximum in the micropore range is attributed by om and another maximum in the range of mesopore macropores is probably caused by the dissolution of carbonate minerals quantitative evaluation of the contribution of individual mineral components to porosity shows that the organic matter contributes approximately 62 to the total porosity framework minerals quartz feldspar and carbonates et al and clay minerals contribute 25 and 13 respectively the total gas content of these shales ranges from 0 4 to 6 2 m3 t and the total gas contents of selected samples determined from canister desorption tests agree with the theoretically estimated original gas in place ogip om hosted pores are the main space for gas storage and accounted for about 78 55 adsorbed gas plus 23 free gas of the ogip while pores in the inorganic matter accommodate 22 free gas of the ogip

pluto s climate modeled with new observational constraints abstract pluto has a nitrogen atmosphere in vapor pressure equilibrium with surface ice n 2 is mobile and is transported seasonally even at pluto s cold temperatures in the outer solar system a thermal model developed by hansen and paige in 1996 to model pluto s climate has been re deployed in response to new data and in anticipation of the new horizons flyby of pluto in 2015 a number of stellar occultations have been observed in the last 11 years as pluto has crossed the galactic plane new hubble space telescope images show a variegated surface these recent observations allow us to model pluto s climate with much tighter constraints our findings suggest that pluto s atmosphere will not collapse prior to the arrival of new horizons although pressure will be dropping as n 2 condenses on the south polar cap this finding is in contrast to the olkin et al olkin et al 2013 arxiv1309 0841o prediction that permanent volatiles in the northern hemisphere maintain pluto s atmospheric pressure throughout its orbit the range of surface pressures predicted for 2015 for nine cases with very good matches to observables is 0 3 3 2 pa the best match predicts that new horizons will detect an atmospheric pressure of 2 4 pa

a comparative study of methods for determining carbonate content in marine and terrestrial sediments abstract carbonate can be produced in a variety of environments on the earth s surface such as shallow seas and deep oceans continental lakes soils and subsurface aquifers the carbonate content of sediments is an important proxy in paleoceanography and paleoclimatology and is often used to reconstruct paleoenvironmental evolution of the earth many methods have been reported to measure the content of carbonate in sediments but how those methods perform e g degree of accuracy and precision error induced factors operability cost and time remains understudied here we employ three widely used non instrumental methods including acid base titration gasometric method and loss on ignition loi based on muffle combustion together with x ray diffraction for mineral phase analysis to compare the carbonate content data of sediments from deep ocean water depths from 1218 m to 6147 m of the western pacific and cenozoic sedimentary rocks from the qaidam basin northern tibetan plateau the results show that data accuracies of most methods are closely related to mineral compositions in sediments e g carbonate species and clay mineral contents and analytical operations non instrumental methods generally demonstrate low precisions avg rsd of 3 36 in determining sediments with low carbonate contents

isotopic constraints on intensified aridity in central asia around 12 ma abstract the relationship between central asian aridification and the evolution of the himalayan tibetan orogen remains elusive new isotopic data from pedogenic and lacustrine carbonates sampled from well dated neogene strata 15 7 1 8 ma in the northeastern qaidam basin of the northern tibetan plateau identify a positive shift of 2 5 in 18 o values from 12 ma to 10 7 ma high values were maintained until 3 3 ma when 18 o values drop by 1 the timing of the positive shift in 18 o values is remarkably consistent with isotopic records from a vast region along and within the northern tibetan plateau isotopic mineralogical petrologic and facies analyses suggest that diagenetic effects and detrital contamination are minimal the positive shift in 18 o values as well as high 13 c values from pedogenic carbonates which are suggestive of low soil respiration rates is interpreted to indicate intensified aridity in central asia ca 12 ma the recognition of intensified aridity is critical to understanding the climatic effects of the development of the himalayan tibetan orogen we attribute this climatic change in the central asia to 1 retreat of paratethys from central asia strengthening the seasonal contrast and resulting in the loss of a nearby moisture source 2 attainment of high elevations in the himalayas and south central tibet blocking moisture bearing air masses from the indian and pacific oceans and 3 enhanced isolation and outward growth of the northern tibetan plateau the negative shift around 3 3 ma might be related to the onset of northern hemisphere glaciation intensification of the east asia monsoon and or effects of orographic rain out

magnetostratigraphy of the dahonggou section northern qaidam basin and its bearing on cenozoic tectonic evolution of the qilian shan and altyn tagh fault article i nfo the timing of uplift of the tibet plateau has a central role in the development of tectonic models for the tibet plateau and cenozoic global climate change a detailed magnetostratigraphic study of the dahonggou section northern qaidam basin reveal that the section spans from 34 to 8 5 ma and the ages of the shang ganchaigou xia youshashan and shang youshashan formations are from 34 to 22 20 ma 22 20 to 13 ma and 13 to 8 5 ma respectively variations in lithofacies sedimentation rate and magnetic susceptibility k suggest that the southern qilian shan was tectonically inactive and didn t respond to the rapid slip on the altyn tagh fault at 30 ma in contrast the similar sedimentary records in the dahonggou section the xishuigou section along the altyn tagh fault and even more localities along much of the qilian range front imply that the qilian shan and the altyn tagh fault were synchronously tectonically active at about 12 ma the lower k between 12 ma and 8 5 ma in the sediments of the dahonggou section is interpreted to be due to long distanced oxidation and sorting which cause not only that magnetite was oxidated to hematite but also that magnetic minerals are enriched in fine grained sediments and coarse grained sediments bear few magnetic mineral

relationships between porosity organic matter and mineral matter in mature organic rich marine mudstones of the belle fourche and second white specks formations in alberta canada abstract this study presents approaches for evaluating hybrid source rock reservoirs within tight rock petroleum systems the emerging hybrid source rock reservoir shale play in the upper cretaceous second white specks and belle fourche formations in central alberta canada is used as an example to evaluate organic and inorganic compositions and their relationships to pore characteristics nineteen samples from a 77 5 m long core were analyzed using organic petrography organic geochemistry several methods of pore characterization and x ray powder diffraction xrd the lower part of the studied section includes quartz and clay rich mudrocks of the belle fourche formation with low carbonate content whereas the upper portion contains calcareous mudrocks of the second white specks formation strata are mineralogically composed of quartz plus albite 18 56 wt carbonates calcite dolomite ankerite 1 65 wt clays illite kaolinite chlorite 15 46 wt and pyrite 2 12 wt petrographic examinations document that organic matter represents marine type ii kerogen partly biodegraded with limited terrestrial input vitrinite reflectance r o 0 74 0 87 t max values 438 446 c and biomarkers indicate mid maturity within the oil window the relatively poor remaining hydrocarbon potential expressed as an s2 value between 2 1 and 6 5 mg hc g rock may result from an estimated 60 83 of the original kerogen having been converted to hydrocarbons with the bulk having migrated to adjacent sandstone reservoirs however the present day remaining total organic carbon toc pd content remains relatively high 1 7 3 6 wt compared with the estimated original toc o of 2 4 5 0 wt the calculated transformation ratio of 60 83 suggests that the remaining 17 40 wt of kerogen is able to generate more hydrocarbons the studied section is a tight reservoir with an average swanson permeability of 3 37 10 5 md measured on two samples and total porosity between 1 7 and 5 0 vol 3 vol on average the upper part of the sandy belle fourche formation with slightly elevated porosity values 3 5 5 vol likely represents the interval with the best reservoir properties in the studied core interval total pore volume ranges between 0 0065 and 0 0200 cm 3 g measured by a combination of helium pycnometry and mercury immersion mesopores 2 50 nm are the most abundant pores and occupy 34 67 of total porosity or a volume of 0 0030 0 0081 cm 3 g in comparison micropores 3 g and macropores 50 nm reach up to 57 with the exception of some samples failing to indicate the presence of this pore fraction volume 0 0000 0 0107 cm 3 g macroporosity is mostly responsible for variations in total porosity as suggested by macroporosity s strongest correlation with total porosity within the section the relatively narrow ranges of toc and minerals contents among measured samples limit our ability to further deconvolute factors that influence changes in total porosity and pore size distribution

iapetus near surface thermal emission modeled and constrained using cassini radar radiometer microwave observations abstract since its arrival at saturn the cassini spacecraft has had only a few opportunities to observe iapetus saturn s most distant regular satellite these observations were all made from long ranges 100 000 km except on september 10 2007 during cassini orbit 49 when the spacecraft encountered the two toned moon during its closest flyby so far in this pass it collected spatially resolved data on the object s leading side mainly over the equatorial dark terrains of cassini regio cr in this paper we examine the radiometry data acquired by the cassini radar during both this close targeted flyby referred to as ia49 3 and the distant iapetus observations in the radar s passive mode the receiver functions as a radiometer to record the thermal emission from planetary surfaces at a wavelength of 2 2 cm on the cold icy surfaces of saturn s moons the measured brightness temperatures depend both on the microwave emissivity and the physical temperature profile below the surface down to a depth that is likely to be tens of centimeters or even a few meters combined with the concurrent active data passive measurements can shed light on the composition structure and thermal properties of planetary regoliths and thus on the processes from which they have formed and evolved the model we propose for iapetus microwave thermal emission is fitted to the ia49 3 observations and reveals that the thermal inertias sensed by the cassini radiometer over both cr and the bright mid to high latitude terrains namely ronceveaux terra rt in the north and saragossa terra st in the south significantly exceed those measured by cassini s cirs composite infrared spectrometer which is sensitive to much smaller depths generally the first few millimeters of the surface this implies that the subsurface of iapetus sensed at 2 2 cm wavelength is more consolidated than the uppermost layers of the surface in the case of cr a thermal inertia of at least 50 j m 2 k 1 s 1 2 and most probably 200 j m 2 k 1 s 1 2 is inferred this suggests a gradient in density with depth or more likely that the radiometer has probed the icy substrate underlying the dark layer furthermore the measured thermal emission is found to arise from the upper few meters of the subsurface which points to tholins rather than iron oxide compounds as the primary contaminants of the dark material we also find that although there is a latitudinal decrease probably related to the thinning of the dark layer away from the equator the cr region exhibits a high 2 2 cm emissivity 0 87 in average which is close to the emissivity of phoebe a putative source of the dark matter in the case of rt st model fitting points to a mean thermal inertia of 160 j m 2 k 1 s 1 2 along with the possible presence of an absorbing compound in the regolith of the bright terrains nevertheless this layer is transparent enough for the radiometer to capture the seasonal contrast between the northern and southern hemispheres lastly a global decline of the microwave emissivity with latitude is revealed it is probably indicative of a progressive increase of the water ice content in the near surface