subsurface imaging of the garlock fault cantil valley california imaging of the garlock fault from seismic reflection data tests tectonic models for the mojave desert region of southern california models developed from geologic and geodetic evidence of fault movement rates disagree on whether the garlock fault should dip north or south such models are further at odds with focal mechanism and dislocation analyses consistent with a vertical strike slip fault our analysis demonstrates a nonvertical southward dip for the garlock fault consortium for continental reflection profiling mojave line 5 collected seismic reflection data across the garlock in cantil valley where the 3 km deep cantil pull apart basin has developed between the southwest and east branches of the fault we analyze the reflection data for evidence of the fault s structure to 5 km depths garlock fault plane reflections on unprocessed shot gathers merge with the first arrival as the source progresses to the surface trace of the east branch explicitly tracing the garlock fault as a seismic reflector from depth to the mapped contemporary fault trace the apparent velocity of these reflections gives a 37 10 south dip for the east branch of the fault a prestack kirchhoff sum migration images the east branch reflector with a 45 south dip our migration process fully accounts for the bending of seismic rays through the strong lateral velocity variations in cantil basin the south dip of the garlock s east branch together with basement steps that decrease to the south suggest that cantil basin developed from a 0 4 1 mm yr component of extension normal to the fault development of the basin by detachment provides a mechanism to widen it as left lateral motion lengthens it allowing the pull apart to maintain the globally constant length to width ratio of 3 detachment by the garlock at cantil valley similarly requires 0 4 1 mm yr of dextral strike slip on a northwest striking fault such as the helendale that cuts the mojave between the garlock and pinto mountain faults such motion is consistent with regional tectonic models

common depth point method for determining and displaying the shear velocity reflectivities of a geologic formation a novel method for determining and displaying the shear velocity reflectivities of geologic formations is disclosed wherein a compression wave common depth point seismic data gathering technique is utilized to produce both normal incidence compressional velocity reflectivity sections and shear velocity reflectivity sections for reflection points in given geologic formations the subject method includes the gathering of common depth point information for a plurality of incidence angles theta and estimating the linear coefficients r pp 0 and r pp 1 of a linear function fitted to the amplitudes vs sin 2 theta measured for each point of reflection the common depth point gather is conducted at angles of offset of less than 20 30 degrees such that assumptions concerning various elastic parameters density compressional wave velocity and shear wave velocity can be made which allow the application of linear fitting techniques to the gathered data the sum of these coefficients corresponds to the shear velocity reflectivity of the reflection point and may be presented with similar data for other points in appropriate shear reflectivity sections

high concentrations of manganese and sulfur in deposits on murray ridge endeavour crater mars mars reconnaissance orbiter hirise images and opportunity rover observations of the 22 km wide noachian age endeavour crater on mars show that the rim and surrounding terrains were densely fractured during the impact crater forming event fractures have also propagated upward into the overlying burns formation sandstones opportunity s observations show that the western crater rim segment called murray ridge is composed of impact breccias with basaltic compositions as well as occasional fracture filling calcium sulfate veins cook haven a gentle depression on murray ridge and the site where opportunity spent its sixth winter exposes highly fractured recessive outcrops that have relatively high concentrations of s and cl consistent with modest aqueous alteration opportunity s rover wheels serendipitously excavated and overturned several small rocks from a cook haven fracture zone extensive measurement campaigns were conducted on two of them pinnacle island and stuart island these rocks have the highest concentrations of mn and s measured to date by opportunity and occur as a relatively bright sulfate rich coating on basaltic rock capped by a thin deposit of one or more dark mn oxide phases intermixed with sulfate minerals we infer from these unique pinnacle island and stuart island rock measurements that subsurface precipitation of sulfate dominated coatings was followed by an interval of partial dissolution and reaction with one or more strong oxidants e g o 2 to produce the mn oxide mineral s intermixed with sulfate rich salt coatings in contrast to arid regions on earth where mn oxides are widely incorporated into coatings on surface rocks our results demonstrate that on mars the most likely place to deposit and preserve mn oxides was in fracture zones where migrating fluids intersected surface oxidants forming precipitates shielded from subsequent physical erosion

a 130 ka reconstruction of precipitation on the chinese loess plateau from organic carbon isotopes abstract we study the relationship between organic carbon isotopes 13ctoc in soil and mean annual precipitation map in the east asian monsoon area by combining the results of carbon isotope studies of plants c4 c3 ratios and precipitation in the modern ecosystem of the chinese loess plateau based on this relationship we estimate the amount of paleoprecipitation that has occurred in the southeastern part of the loess plateau since the last interglacial stage using the carbon isotopic compositions of the soil organic matter som the results show that the annual precipitation in that region was high during the interglacial stages with a maximum value of 850 mm and that it decreased during the last glacial stage to a minimum value of 350 mm we suggest that the use of organic carbon isotopic composition in paleosol sediments is a reliable method for reconstructing paleoprecipitation due to the clear relationships between soil 13ctoc c4 c3 abundance and precipitation in modern ecosystems

surface wave profiling of the lithosphere beneath the mojave desert using terrascope data we have applied surface wave analysis to the mojave desert in southern california to extract the regional lithosphere velocity structure seismograms from teleseismic sources recorded by the terrascope stations a recently established network of broadband instruments were used to determine the phase velocity dispersion data of rayleigh waves for wave paths crossing the mojave desert an inversion analysis on the dispersion data for each path gave the shear wave velocity structure beneath the path inversion results show that there is a low velocity layer at the middle and lower crust which is particularly pronounced for paths traversing the western part of the mojave desert this low velocity layer at the midcrust may reflect the existence of a transition zone from the brittle to the ductile regimes where there is an absence of earthquake occurrence

chemistry and mineralogy of outcrops at meridiani planum analyses of outcrops created by the impact craters endurance fram and eagle reveal the broad lateral continuity of chemical sediments at the meridiani planum exploration site on mars approximately ten mineralogical components are implied in these salt rich silicic sediments from measurements by instruments on the opportunity rover compositional trends in an apparently intact vertical stratigraphic sequence at the karatepe west ingress point at endurance crater are consistent with non uniform deposition or with subsequent migration of mobile salt components dominated by sulfates of magnesium striking variations in cl and enrichments of br combined with diversity in sulfate species provide further evidence of episodes during which temperatures ph and water to rock ratios underwent significant change to first order the sedimentary sequence examined to date is consistent with a uniform reference composition modified by movement of major sulfates upward and of minor chlorides downward this reference composition has similarities to martian soils supplemented by sulfate anion and the alteration products of mafic igneous minerals lesser cementation in lower stratigraphic units is reflected in decreased energies for grinding with the rock abrasion tool survival of soluble salts in exposed outcrop is most easily explained by absence of episodes of liquid h2o in this region since the time of crater formation

the deep crustal structure of the mojave desert california from cocorp seismic reflection data cocorp seismic reflection profiling in the western and northern mojave desert of southern california has revealed the presence of numerous major low angle reflecting horizons within the crust these complex though laterally continuous horizons are interpreted to represent major southwesterly dipping crustal fault zones and as such they place important constraints on the tectonic evolution of the region the upper most horizon is interpreted to be the rand thrust which where exposed places precambrian and late cretaceous crystalline rocks over possibly younger pelona rand orocopia schist this reflecting horizon extends for 25 km southwest of the rand mountains where it appears to be truncated at a depth of about 7 4 km by another horizon which may be a later low angle normal fault the other reflecting horizons are not traceable to the surface and so greater ambiguity remains in their interpretation the most prominent of these horizons occurs at midcrustal depths 15 6 km exhibits a ramp and flat geometry and extends over the northern area of the mojave survey into the basin and range province a lower horizon at depths of 20 30 km in the northern part of the survey area is antiformal and appears to terminate above a flat and relatively continuous moho depth horizon the crustmantle transition appears to be represented by a continuous series of reflections which occur at about 10 s 33 km in the north of the survey and at about 8 9 s 26 29 km in the south these reflections are offset in the vicinity of the town of mojave the deep intracrustal fault zones inferred from the cocorp survey may represent 1 the deep crustal continuation of the system of mesozoic thrusts which crops out in southern nevada and southeastern california 2 late cretaceous to early cenozoic northeast vergent thrusts related to the uplift of the pelona orocopia rand schist or 3 low angle normal faults related to early miocene northeast southwest directed crustal extension the cocorp survey also traversed the major strike slip faults that bound the mojave block the san andreas fault zone appears to truncate reflectors at depths of 6 8 and 20 km within the mojave basement suggesting that it is a major vertical feature which extends to at least 20 km depth conversely the garlock fault does not offset an underlying reflecting horizon which occurs at 9 km depth and therefore appears to be a relatively shallow crustal feature

reconstructing in situ vegetation dynamics using carbon isotopic composition of biopolymeric residues in the central chinese loess plateau abstract carbon isotopic compositions of total organic carbon toc or leaf waxes in soils have been used to reconstruct past changes in the relative abundance of c 3 and c 4 plants however toc contains organic matter of different source organisms plants animals fungi bacteria etc and its isotopic ratios could be modified during diagenesis since different organic fractions e g carbohydrates proteins lipids etc have different isotopic ratios and degradation rates leaf waxes on the other hand are transported by wind and hence represent vegetation input from a large geographic area we report in this paper a new approach to extract in situ paleovegetation information from late quaternary paleosols by determining carbon isotopic compositions of biomarkers derived from aliphatic bio and geopolymers of plant origin we show that c 9 to c 17 n alkenes derived from aliphatic bio and geopolymers are the dominant compounds released by flash pyrolysis of insoluble organic matter isolated from the late quaternary paleosols in the chinese loess plateau because the aliphatic polymeric substances are mainly derived from plant leaves bark and roots the isotopic signatures of these alkenes determined using pyrolysis gas chromatography isotopic ratio mass spectrometry reflect in situ vegetation changes our down core 13 c data from the xifeng loess paleosol profile show significant coherence among biopolymer derived n alkenes leaf wax n alkanes and toc for the past 40 kyr however the different amplitudes of the temporal isotopic changes among these data sets are indicative of variability in in situ and regional vegetation dynamics organic sources and effect of diagenesis our data also imply that below ground biomass is a major source of soil organic matter in the central china loess sediment

structural geology of impact craters abstract the formation of impact craters is a highly dynamic and complex process that subjects the impacted target rocks to numerous types of deformation mechanisms understanding and interpreting these styles of micro meso and macroscale deformation has proved itself challenging for the field of structural geology in this paper we give an overview of the structural inventory found in craters of all size ranges on earth and look into the structures of craters on other planetary bodies structural features are discussed here that are caused by i extremely high pressures and temperatures that occur during the initial passage of the shock wave through the target rock and projectile ii the resulting flow field in the target that excavates and ejects rock materials and iii the gravitationally induced modification of the crater cavity into the final crater form a special focus is put on the effects that low angle impacting bodies have on crater formation we hope that this review will help both planetary scientists and structural geologists understand the deformation processes and resulting structures generated by meteorite impact

negative δ18o δ13c relationship of pedogenic carbonate from northern china indicates a strong response of c3 c4 biomass to the seasonality of asian monsoon precipitation abstract evaluating how future climate changes may impact c3 c4 biomass in east asia depends largely on the understanding of the relationship between past c3 c4 variations and asian monsoon circulation the glacial interglacial variations in c3 c4 biomass have been readily ascribed to the summer monsoon however the internal processes governing the link of c3 c4 vegetation to the asian monsoon have not been clearly described here we present isotopic results of pedogenic carbonate from northern china for the holocene the last and penultimate interglacial periods comparison of the observed and predicted 18o values of modern soil carbonate from gravelly soils suggests that pedogenic carbonate forms mainly in warm rainy season carbonate nodules from the chinese loess demonstrate a distinct negative 18o 13c relationship and a wider scatter of isotopic values in the southern loess plateau than in the northern part by combining rainfall 18o of precipitation and the peak of c3 and c4 plant metabolism we develop a conceptual model to explain the isotopic signatures of the carbonate nodules our model shows that a narrowly focused season of monsoon precipitation at a specific site produces low 18o values of soil water and simultaneously favors c4 over c3 plants our model further suggests that the scattered isotopic values of soil carbonate reflect a strong summer monsoon while the focused values indicate a weak summer monsoon 13c values of soil carbonate indicate a striking pattern of northward increasing c4 vegetation for the last interglacial while a flat spatial pattern is seen for the penultimate interglacial and the holocene it is inferred that the summer monsoon was stronger during the last interglacial than during the penultimate interglacial and the holocene leading to a northward displacement of c3 forest ecosystems into the southern loess plateau in addition an in phase relationship between intra nodule 13c and 18o values suggests a strong and possibly rapid response of c3 c4 biomass to the seasonality of asian monsoon precipitation in this context if the last interglacial period mis 5 is taken as an analog for the projected near future then c3 plants may be favored in the south while c4 plants may be efficient in the north

seasonal and geographic climate variabilities during the last glacial maximum in north america applying isotopic analysis and macrophysical climate models abstract climate models provide estimates of climatic change over periods of time in the ancient past macrophysical climate models mcm differ from the more widely used general circulation models gcm in that mcms provide temporally high resolution 100 years and site specific estimations of monthly values of climate variables such as temperature and precipitation in this paper seasonal changes in climate variables are modeled for six 14c dated fossil localities in north america five of these localities represent the time of maximum extent of ice during the most recent glacial episode the full glacial 25 15 ka including one at the peak of the last glacial maximum 17 15 ka the other locality represents the time as the ice began to recede the late glacial 15 11 ka seasonal variations in temperature and precipitation modeled by mcm are herein compared with interpretations of seasonal variation based upon oxygen isotopes from serially sampled hypsodont teeth mostly equus and bison collected from each of these localities additionally the mcm modeled seasonal variations are used to predict the expected abundances of different plant functional groups pfg during those times especially c3 and c4 functional groups using modern relationships these predictions are compared with carbon isotopic values from the same teeth the importance of atmospheric pco2 for the relative abundance of plants utilizing the c4 metabolic pathway is discussed given that glacial episodes are known to have been times of lower atmospheric pco2 interpretations of seasonal variability and the relative abundance of c3 versus c4 vegetation based upon isotopes from tooth enamel are in broad agreement with predictions using the mcm and the modern distribution of pfgs with climate variables the influence of pco2 on the distribution of c4 vegetation during glacial times appears to be negligible

regional climate driven c3 and c4 plant variation in the cheollipo area korea during the late pleistocene abstract marine isotope stage 3 mis3 spanning from 25 to 60 ka bp was a time of substantial environmental change that included changes in the global ice volume and atmospheric composition with resultant regional climate changes to understand past vegetation responses to such environmental changes in korea we estimated the abundance of c3 and c4 plants using the c n and carbon isotope ratios of sedimentary organic matter the mis3 sedimentary unit at the cheollipo site located in a western coastal area of korea is characterized by a dark to light gray colored sedimentary unit 3 05 to 5 05 m in elevation mis3 which is between an underlain oxidized yellowish sedimentary unit 5 05 m in elevation the estimated abundance of c4 plants varied between 60 and 10 during the mis3 the suborbital scale variation in the estimated percentage of c4 plants was similar to those reported in continental ice volume and the east asian monsoon intensity suggesting that c4 plants prevailed under colder and drier conditions intensified winter monsoon whereas c3 plants have favored a warmer and wetter climate intensified summer monsoon compared with high latitude regions e g chinese loess plateau and lake baikal where low summer temperature suppressed aridity and pco2 influences during the last glacial period vegetation change in cheollipo area may have more sensitively responded to aridity change which had been affected by the summer winter monsoon intensity the climate change in the western coastal area yellow sea side of korea during the late pleistocene may have been controlled by regional climate change coupled with continental ice volume change

overview of the microscopic imager investigation during spirit s first 450 sols in gusev crater the microscopic imager mi on the mars exploration rover spirit has returned images of mars with higher resolution than any previous camera system allowing detailed petrographic and sedimentological studies of the rocks and soils at the gusev landing site designed to simulate a geologist s hand lens the mi is mounted on spirit s instrument arm and can resolve objects 0 1 mm in size or larger this paper provides an overview of mi operations data calibration processing and analysis of mi data returned during the first 450 sols mars days of the spirit landed mission the primary goal of this paper is to facilitate further analyses of mi data by summarizing the methods used to acquire and process the data the radiometric and geometric accuracy of mi data products and the availability of archival products in addition scientific results of the mi investigation are summarized mi observations show that poorly sorted soils are common in gusev crater although aeolian bedforms have well sorted coarse sand grains on their surfaces abraded surfaces of plains rocks show igneous textures light toned veins or fracture filling minerals and discrete coatings the rocks in the columbia hills have a wide variety of granular textures consistent with volcaniclastic or impact origins case hardening and submillimeter veins observed in the rocks as well as soil crusts and cemented clods imply episodic subsurface aqueous fluid movement which has altered multiple geologic units in the columbia hills the mi also monitored spirit s solar panels and the magnets on the rover s deck

changes in vegetation type on the chinese loess plateau since 75 ka related to east asian summer monsoon variation abstract floral communities in terrestrial habitats such as steppes are highly sensitive to regional climate changes here we generated carbon and nitrogen isotope profiles for soil organic matter som in the weinan loess paleosol section in order to investigate changes in floral communities on the chinese loess plateau clp and their relationship to climate variation since 75 ka 13csom at weinan ranges from 23 6 to 18 0 and 15nsom ranges from 3 4 to 5 5 modeling based on the 13csom record suggests that the proportion of c4 plants c4 has varied from lower during cold intervals with minima of 24 32 at 73 1 ka 20 9 ka lgm and 0 6 ka to higher during warm intervals with maxima of 62 64 at 53 0 ka and 8 2 ka the 13csom and 15nsom profiles are strongly correlated r 0 82 p

spirit mars rover mission overview and selected results from the northern home plate winter haven to the side of scamander crater spirit mars rover mission overview and selected results from the northern home plate winter haven to the side of scamander crater

middle holocene environmental change in central korea and its linkage to summer and winter monsoon changes to trace the surficial responses of lowlands to past climate change we investigated 13c in total organic carbon toc c n ratios magnetic susceptibility ms and silicon si intensity directly proportional to concentration in wetland sediments collected from the gimpo area of central korea covering 6600 4600 cal yr bp two organic layers with high toc negatively depleted 13ctoc values 27 to 29 low ms values and low si intensities were found at 6200 5900 and 5200 4800 cal yr bp respectively these middle holocene wet periods corresponded to relatively intensified summer monsoon and solar activity periods the intervening dry period 5900 5200 cal yr bp with high ms high si and low toc corresponded to an intensified dust activity interval and stronger winter monsoon this multi centennial climatic fluctuation of wet periods 6200 5900 cal yr bp and 5200 4800 cal yr bp and an intervening dry period 5900 5200 cal yr bp in central korea was more synchronous with climate change in the arid inner part of china than with that in south china suggesting possible strong high latitude driven climatic influences e g north atlantic cooling events during the middle holocene

athena microscopic imager investigation 1 the athena science payload on the mars exploration rovers mer includes the microscopic imager mi the mi is a fixed focus camera mounted on the end of an extendable instrument arm the instrument deployment device idd the mi was designed to acquire images at a spatial resolution of 30 microns pixel over a broad spectral range 400 700 nm the mi uses the same electronics design as the other mer cameras but has optics that yield a field of view of 31 31 mm across a 1024 1024 pixel ccd image the mi acquires images using only solar or skylight illumination of the target surface a contact sensor is used to place the mi slightly closer to the target surface than its best focus distance about 66 mm allowing concave surfaces to be imaged in good focus coarse focusing 2 mm precision is achieved by moving the idd away from a rock target after the contact sensor has been activated the mi optics are protected from the martian environment by a retractable dust cover the dust cover includes a kapton window that is tinted orange to restrict the spectral bandpass to 500 700 nm allowing color information to be obtained by taking images with the dust cover open and closed mi data will be used to place other mer instrument data in context and to aid in petrologic and geologic interpretations of rocks and soils on mars

magnetic susceptibility of loess in china abstract the low field susceptibility of the loess deposits in the chinese loess plateau is due to both paramagnetic and ferromagnetic minerals paramagnetism can be seen in the less to unweathered loess horizons where superparamagnetic contributions which arise from ultrafine magnetite particles are not as strongly developed as in the heavily weathered palaeosols frequency dependent susceptibility and minimum unblocking temperatures of low temperature thermoremanent magnetization generally indicate finer grain sizes in the palaeosols as compared to the loess beds this grain size difference and the fact that susceptibilities of the same stratigraphic palaeosol layer vary by an order of magnitude between the western and central regions of the plateau are considered as strong evidence that the ultrafine magnetite is not of detrital aeolian origin but was formedin situ the pedogenetic processes are clearly related to palaeoclimatic changes therefore the various susceptibility properties may serve for a detailed reconstruction of the continental palaeoclimatic conditions for the last 2 5 ma since the palaeomagnetically dated beginning of loess sedimentation in china

alpha particle x ray spectrometer apxs results from gusev crater and calibration report 1 the chemical composition of rocks and soils on mars analyzed during the mars exploration rover spirit mission was determined by x ray analyses with the alpha particle x ray spectrometer apxs details of the data analysis method and the instrument calibration are presented measurements performed on mars to address geometry effects and background contributions are shown cross calibration measurements among several instrument sensors and sources are discussed an unintentional swap of the two flight instruments is evaluated new concentration data acquired during the first 470 sols of rover spirit in gusev crater are presented there are two geological regions the gusev plains and the columbia hills the plains contain soils that are very similar to previous landing sites on mars a meteoritic component in the soil is identified rocks in the plains revealed thin weathering rinds the underlying abraded rock was classified as primitive basalt one of these rocks contained significant br that is probably associated with vein filling material of different composition one of the trenches showed large subsurface enrichments of mg s and br disturbed soils and rocks in the columbia hills revealed different elemental compositions these rocks are significantly weathered and enriched in mobile elements such as p s cl or br even abraded rock surfaces have high br concentrations thus in contrast to the rocks and soils in the gusev plains the columbia hills material shows more significant evidence of ancient aqueous alteration

ries crater and suevite revisited observations and modeling part i observations we report results of an interdisciplinary project devoted to the 26 km diameter ries crater and to the genesis of suevite recent laboratory analyses of crater suevite occurring within the central crater basin and of outer suevite on top of the continuous ejecta blanket as well as data accumulated during the past 50 years are interpreted within the boundary conditions imposed by a comprehensive new effort to model the crater formation and its ejecta deposits by computer code calculations artemieva et al 2013 the properties of suevite are considered on all scales from megascopic to submicroscopic in the context of its geological setting in a new approach we reconstruct the minimum maximum volumes of all allochthonous impact formations 108 116 km3 of suevite 14 22 km3 and the total volume of impact melt 4 9 8 0 km3 produced by the ries impact event prior to erosion these volumes are reasonably compatible with corresponding values obtained by numerical modeling taking all data on modal composition texture chemistry and shock metamorphism of suevite and the results of modeling into account we arrive at a new empirical model implying five main consecutive phases of crater formation and ejecta emplacement numerical modeling indicates that only a very small fraction of suevite can be derived from the primary ejecta plume which is possibly represented by the fine grained basal layer of outer suevite the main mass of suevite was deposited from a secondary plume induced by an explosive reaction fuel coolant interaction of impact melt with water and volatile rich sedimentary rocks within a clast laden temporary melt pool both melt pool and plume appear to be heterogeneous in space and time outer suevite appears to be derived from an early formed melt rich and clast poor plume region rich in strongly shocked components melt clasts and originating from an upper more marginal zone of the melt pool crater suevite is obviously deposited from later formed clast rich and melt poor plumes dominated by unshocked and weakly shocked clasts and derived from a deeper central zone of the melt pool genetically we distinguish between primary suevite which includes dike suevite the lower sublayer of crater suevite and possibly a basal layer of outer suevite and secondary suevite represented by the massive upper sublayer of crater suevite and the main mass of outer suevite

multimode migration of scattered and converted waves for the structure of the hikurangi slab interface new zealand reflectivity imaging of local earthquake seismograms has revealed the structure of the hikurangi subduction interface at the location of two strong earthquakes that occurred in 1990 the earthquakes originated within the continental plate of the north island of new zealand and below in the subducting pacific slab we used seismograms from 500 well located events in two earthquake sequences recorded by a small temporary seismograph deployment to directly image the structure and multiphase reflectivity of the plate interface synthetic tests of the imaging method show the effects of the poor 3 d geometric coverage afforded by the seismometer array kirchhoff summation image sections computed from synthetics show accurate depth imaging of backscattering interfaces phase converting interfaces imaged with forward scattered waves are smeared by poor ray coverage to 5 km depth inaccuracy and are only imaged over a small range of their horizontal extent from the data we computed image sections for p p p s s p and s s scattering we mitigated imaging artifacts due to poor ray coverage with an obliquity factor an antialiasing criterion and enhancement by resampling statistics imaging used a sharply layered velocity model we tested for the effects of imaging with first arriving headwaves by imaging through smoothly varying velocity models for our ray geometry early arrival headwaves contribute little to the images the plate interface appears as a 3 5 km thick p p and possibly s s backscatterer with 5j nw dip offset 5 km down to the nw above a normal fault in the slab when illuminated from below a wedge of the interface on the downdip side of the slab fault forms a very prominent p p forward scatterer the edges of the wedge forward scatter some s p and s s energy but an order of magnitude less than the p p forward scattering the imbalances between forward scattering of p and s energy suggest a wedge of subducted sediment retaining significant porosity but with rigidity close to that of surrounding rocks d 2002 elsevier science b v all rights reserved

tectonics of complex crater formation as revealed by the haughton impact structure devon island canadian high arctic the results of a systematic field mapping campaign at the haughton impact structure have revealed new information about the tectonic evolution of mid size complex impact structures these studies reveal that several structures are generated during the initial compressive outward directed growth of the transient cavity during the excavation stage of crater formation 1 sub vertical radial faults and fractures 2 sub horizontal bedding parallel detachment faults and 3 minor concentric faults and fractures uplift of the transient cavity floor toward the end of the excavation stage produces a central uplift compressional inward directed deformation results in the duplication of strata along thrust faults and folds it is notable that haughton lacks a central topographic peak or peak ring the gravitational collapse of transient cavity walls involves the complex interaction of a series of interconnected radial and concentric faults while the outermost concentric faults dip in toward the crater center the majority of the innermost faults at haughton dip away from the center complex interactions between an outward directed collapsing central uplift and inward collapsing crater walls during the final stages of crater modification resulted in a structural ring of uplifted intensely faulted sub vertical and or overturned strata at a radial distance from the crater center of 5 0 6 5 km converging flow during the collapse of transient cavity walls was accommodated by the formation of several structures 1 sub vertical radial faults and folds 2 positive flower structures and chaotically brecciated ridges 3 rollover anticlines in the hanging walls of major listric faults and 4 antithetic faults and crestal collapse grabens oblique strike slip i e centripetal movement along concentric faults also accommodated strain during the final stages of readjustment during the crater modification stage it is clear that deformation during collapse of the transient cavity walls at haughton was brittle and localized along discrete fault planes separating kilometer size blocks

middle pleistocene dynamics of southern africa s winter rainfall zone from δ13c and δ18o values of hoedjiespunt faunal enamel abstract stable carbon and oxygen isotopes of fossil fauna have become important tools in linking palaeoecology and palaeoclimate in the case of grazing ungulates enamel 13c reflects c3 c4 grass abundance which in turn is primarily a reflection of minimum growing season temperature the south western cape is today a winter rainfall area where grasses are almost entirely c3 other parts of the country in contrast have summer rainfall and c4 grass flora in palaeoenvironmental studies the presence of c3 grasses serve as an important proxy for the presence of a winter rainfall regime and as a test of regional models of glacial interglacial climate change however evidence for the extent and intensity of the winter rainfall regime beyond the last glacial period is currently thin and a coherent picture of the long term evolution of this system has not yet emerged here we present a set of 13c and 18o values of fauna from paleontological layers at hoedjiespunt 1 hdp1 a fossilised brown hyaena parahyaena brunnea lair dating to between 200 and 350 ka on the west coast of south africa the assemblage is dominated by large grazing species which were resident during a glacial period when sea levels were lower and grasslands were widespread and productive grazers had predominantly c3 diets an indication of the dominance of c3 grass taxa comparison with other sites shows an extended picture of c3 grass dominance and hence winter rainfall regime on the west coast of south africa throughout the pleistocene however a positive shift in 13c values relative to those expected for pure c3 consumers is noted across all species in part this may reflect fluctuations in the global carbon isotopic content of the atmosphere but most likely indicates a small but significant intrusion of c4 grasses into the vegetation mosaic this phenomenon is most consistent with models which predict that c4 grasses should be favoured over c3 species at very low pco2 and reveals a hitherto unknown subtlety in our understanding of the evolution of this important biome

diverse lithologies and alteration events on the rim of noachian aged endeavour crater meridiani planum mars in situ compositional evidence we report the results of geological studies by the opportunity mars rover on the endeavour crater rim four major units occur in the region oldest to youngest the matijevic shoemaker grasberg and burns formations the matijevic formation consisting of fine grained clastic sediments is the only pre endeavour impact unit and might be part of the noachian etched units of meridiani planum the shoemaker formation is a heterogeneous polymict impact breccia its lowermost member incorporates material eroded from the underlying matijevic formation the shoemaker formation is a close analog to the bunte breccia of the ries crater although the average clast sizes are substantially larger in the latter the grasberg formation is a thin fine grained homogeneous sediment unconformably overlying the shoemaker formation and likely formed as an airfall deposit of unknown areal extent the burns formation sandstone overlies the grasberg but compositions of the two units are distinct there is no evidence that the grasberg formation is a fine grained subfacies of the burns formation the rocks along the endeavour crater rim were affected by at least four episodes of alteration in the noachian and early hesperian i vein formation and alteration of preimpact matijevic formation rocks ii low water rock alteration along the disconformity between the matijevic and shoemaker formations iii alteration of the shoemaker formation along fracture zones and iv differential mobilization of fe and mn and caso 4 vein formation in the grasberg and shoemaker formations episodes ii and iii possibly occurred together but i and iv are distinct from either of these

ancient impact and aqueous processes at endeavour crater mars the rover opportunity has investigated the rim of endeavour crater a large ancient impact crater on mars basaltic breccias produced by the impact form the rim deposits with stratigraphy similar to that observed at similar sized craters on earth highly localized zinc enrichments in some breccia materials suggest hydrothermal alteration of rim deposits gypsum rich veins cut sedimentary rocks adjacent to the crater rim the gypsum was precipitated from low temperature aqueous fluids flowing upward from the ancient materials of the rim leading temporarily to potentially habitable conditions and providing some of the waters involved in formation of the ubiquitous sulfate rich sandstones of the meridiani region

understanding the signature of rock coatings in laser induced breakdown spectroscopy data surface compositional features on rocks such as coatings and weathering rinds provide important information about past aqueous environments and water rock interactions the search for these features represents an important aspect of the curiosity rover mission with its unique ability to do fine scale chemical depth profiling the chemcam laser induced breakdown spectroscopy instrument libs onboard curiosity can be used to both identify and analyze rock surface alteration features in this study we analyze a terrestrial manganese rich rock varnish coating on a basalt rock in the laboratory with the chemcam engineering model to determine the libs signature of a natural rock coating results show that there is a systematic decrease in peak heights for elements such as mn that are abundant in the coating but not the rock there is significant spatial variation in the relative abundance of coating elements detected by libs depending on where on the rock surface sampled this is due to the variability in thickness and spatial discontinuities in the coating similar trends have been identified in some martian rock targets in chemcam data suggesting that these rocks may have coatings or weathering rinds on their surfaces

lower temperature as the main cause of c4 plant declines during the glacial periods on the chinese loess plateau abstract the distribution of c3 and c4 plants changed in regionally contrasting ways during the last glacial period c4 plant expansion in low latitude africa and america coincided with c4 plant decreases in mesoamerica and the us great plains this c4 plant expansion has been attributed to lower pco2 and increased aridity and the decline in c4 plants is believed to have been caused by increased winter precipitation and lower temperatures however it is still difficult to generalize whether pco2 temperature or aridity was mainly responsible for c3 vs c4 vegetation changes during glacial periods paleoclimate conditions on the chinese loess plateau clp offer opportunities to further evaluate the role of temperature in the c3 vs c4 competition detailed climate records have shown that the clp region was drier and colder during glacial periods with aridity favoring c4 expansion and lower temperatures favoring c3 expansion here we present two high resolution compound specific carbon isotope records of n alkanes from the clp as vegetation biomarkers to estimate the relative abundance of c4 plants during the last two glacial interglacial transitions more negative 13c values during the glacial periods from two clp sites clearly show that in contrast with low latitude sites c4 plants declined this decrease in c4 abundance was caused by lower temperature despite the lower pco2 and increased aridity on the clp during glacial time

physical properties of deep crustal reflectors in southern california from multioffset amplitude analysis analysis of reflection waveforms before stack can constrain the physical properties of reflectors in the deep crust to simplify this analysis recorded amplitudes are assumed to be reflections from weak elastic heterogeneities with these assumptions trends in reflection amplitudes with offset may indicate whether the signs of a reflector s density and rigidity contrast agree with or oppose the sign of its lame s parameter contrast the slope of the trend indicates the degree of poisson s ratio contrast no attempt is made to invert for the individual modulus or density contrasts by examining only gross amplitude versus offset avo trends deep reflections constrain some crustal properties two seismic reflection surveys in the mojave desert recorded deep reflections that show amplitude changes with offset both the 1985 calcrust ward valley survey in the eastern mojave and the 87 km cocorp mojave line 3 in the western mojave incorporate long offsets of 10 km or more prestack traces are equalized usi

in flight calibration and performance of the mars exploration rover panoramic camera pancam instruments 1 the mars exploration rover panoramic camera mer pancam instruments have acquired more than 60 000 high resolution multispectral stereoscopic images of soil rocks and sky at the gusev crater and meridiani planum landing sites since january 2004 these images combined with other mer data sets have enabled new discoveries about the composition mineralogy and geologic geochemical evolution of both sites one key to the success of pancam in contributing to the overall success of mer has been the development of a calibration pipeline that can quickly remove instrumental artifacts and generate both absolute radiance and relative reflectance images with high accuracy and precision in order to influence tactical rover driving and in situ sampling decisions this paper describes in detail the methods assumptions and models algorithms in the calibration pipeline developed for pancam images based on new measurements and refinements performed primarily from flight data acquired on mars major calibration steps include modeling and removal of detector bias signal active and readout region dark current electronic shutter smear and pixel to pixel responsivity flatfield variations pancam images are calibrated to radiance w m2 nm sr using refined preflight derived calibration coefficients or radiance factor i f using near in time measurements of the pancam calibration target and a model of aeolian dust deposition on the target as a function of time we are able to verify that the absolute radiance calibration of most pancam images is accurate to within about 10 or less and that the filter to filter and pixel to pixel precision of the calibrated relative reflectance data both based on measurements of the pancam calibration target are typically about 3 and 1 or less respectively examples are also presented of scientific applications made possible by the high fidelity of the calibrated pancam data these include 11 color visible to near ir spectral analysis calculation of true color and chromaticity values and generation of super resolution image data products this work represents a follow on and enhancement to the pancam preflight calibration process described by bell et al 2003

cenozoic climate change in eastern asia part i abstract this special issue provides new studies in the field of cenozoic climate change in eastern asia the papers in this volume are multidisciplinary in nature and examine a range of topics including paleovegetation sedimentology clay mineralogy geochemistry magnetostratigraphy and climate modelling the findings of these studies demonstrate that analysis of terrestrial paleoclimate changes in eastern asia may offer insights into the effects of tibetan plateau uplift and ultimately the dynamic processes of global change that took hold throughout the cenozoic the second part of this special issue to be published later will add a paleoecology component examining how cenozoic climate change has impacted floras and faunas in eastern asia

separation of pedogenic and lithogenic components of magnetic susceptibility in the chinese loess palaeosol sequence as determined by the cbd procedure and a mixing analysis summary magnetic susceptibility variations in the chinese loess palaeosol sequences have been used extensively for palaeoclimatic interpretations the magnetic signal of these sequences must be divided into lithogenic and pedogenic components because the palaeoclimatic record is primarily reflected in the pedogenic component in this paper we compare two methods for separating the pedogenic and lithogenic components of the magnetic susceptibility signal the citrate bicarbonate dithionite cbd extraction procedure and a mixing analysis both methods yield good estimates of the pedogenic component especially for the palaeosols the cbd procedure underestimates the lithogenic component and overestimates the pedogenic component the magnitude of this eect is moderately high in loess layers but almost negligible in palaeosols the mixing model overestimates the lithogenic component and underestimates the pedogenic component both methods can be adjusted to yield better estimates of both components the lithogenic susceptibility as determined by either method suggests that palaeoclimatic interpretations based only on total susceptibility will be in error and that a single estimate of the average lithogenic susceptibility is not an accurate basis for adjusting the total susceptibility a long term decline in lithogenic susceptibility with depth in the section suggests more intense or prolonged periods of weathering associated with the formation of the older palaeosols the cbd procedure provides the most comprehensive information on the magnitude of the components and magnetic mineralogy of loess and palaeosols however the mixing analysis provides a sensitive rapid and easily applied alternative to the cbd procedure a combination of the two approaches provides the most powerful and perhaps the most accurate way of separating the magnetic susceptibility components

variation and paleoclimatic significance of organic carbon isotopes of ili loess in arid central asia as an indicator for terrestrial paleovegetation the stable isotopic composition of total organic matter delta c 13 org in loess sediments has been widely used for paleoclimatic reconstruction in western europe the great plains of north america and the chinese loess plateau clp however little is known about the variation and paleoclimatic significance of the loess delta c 13 org in arid central asia aca we report delta c 13 org data from an axike axk loess paleosol profile from the eastern ili basin eastern central asia along the profile the delta c 13 org values were more negative in the paleosol layers observed in the field and were confirmed by environmental magnetic proxies and a higher concentration of total organic carbon toc consistent with results for western europe and the northwestern clp our results demonstrate that the loess delta c 13 org in this region documents mainly the response of delta c 13 of locally predominant c 3 plants to paleoclimatic variation especially paleoprecipitation our results also suggest that the loess delta c 13 org values in the area have the potential for quantitative paleoprecipitation reconstruction on the basis of detailed delta c 13 org results from modern plants and surface soils in the future c 2013 elsevier ltd all rights reserved

retrieval of compositional end members from mars exploration rover opportunity observations in a soil filled fracture in marathon valley endeavour crater rim the opportunity rover investigated a gentle swale on the rim of endeavour crater called marathon valley where a series of bright planar outcrops are cut into polygons by fractures a wheel scuff performed on one of the soil filled fracture zones revealed the presence of three end members identified on the basis of pancam multispectral imaging observations covering 0 4 to 1 m red and dark pebbles and a bright soil clod multiple overlapping alpha particle x ray spectrometer apxs measurements were collected on three targets within the scuff zone the field of view of each apxs measurement contained various proportions of the pancam based end members application of a log maximum likelihood method for retrieving the composition of the end members using the 10 apxs measurements shows that the dark pebble end member is compositionally similar to average mars soil with slightly elevated s and fe in contrast the red pebble end member exhibits enrichments in al and si and is depleted in fe and mg relative to average mars soil the soil clod end member is enriched in mg s and ni thermodynamic modeling of the soil clod end member composition indicates a dominance of sulfate minerals we hypothesize that acidic fluids in fractures leached and oxidized the basaltic host rock forming the red pebbles and then evaporated to leave behind sulfate cemented soil

athena mars rover science investigation 1 each mars exploration rover carries an integrated suite of scientific instruments and tools called the athena science payload the primary objective of the athena science investigation is to explore two sites on the martian surface where water may once have been present and to assess past environmental conditions at those sites and their suitability for life the remote sensing portion of the payload uses a mast called the pancam mast assembly pma that provides pointing for two instruments the panoramic camera pancam and the miniature thermal emission spectrometer mini tes pancam provides high resolution color stereo imaging while mini tes provides spectral cubes at mid infrared wavelengths for in situ study a five degree of freedom arm called the instrument deployment device idd carries four more tools a microscopic imager mi for close up imaging an alpha particle x ray spectrometer apxs for elemental chemistry a mossbauer spectrometer mb for the mineralogy of fe bearing materials and a rock abrasion tool rat for removing dusty and weathered surfaces and exposing fresh rock underneath the payload also includes magnets that allow the instruments to study the composition of magnetic martian materials all of the athena instruments have undergone extensive calibration both individually and using a set of geologic reference materials that are being measured with all the instruments using a mer like rover and payload in a number of field settings we have devised operations processes that will enable us to use the mer rovers to formulate and test scientific hypotheses concerning past environmental conditions and habitability at the landing sites

limitations of quantitative analysis of deep crustal seismic reflection data examples from glimpce amplitude preservation in seismic reflection data can be obtained by a relative true amplitude rta processing technique in which the relative strength of reflection amplitudes is preserved vertically as well as horizontally after compensating for amplitude distortion by near surface effects and propagation effects quantitative analysis of relative true amplitudes of the great lakes international multidisciplinary program on crustal evolution seismic data is hampered by large uncertainties in estimates of the water bottom reflection coefficient and the vertical amplitude correction and by inadequate noise suppression processing techniques such as deconvolution f k filtering and migration significantly change the overall shape of amplitude curves and hence calculation of reflection coefficients and average reflectance thus lithological interpretation of deep crustal seismic data based on the absolute value of estimated reflection strength alone is meaningless the relative strength of individual events however is preserved on curves generated at different stages in the processing we suggest that qualitative comparisons of relative strength if used carefully provide a meaningful measure of variations in reflectivity simple theoretical models indicate that peg leg multiples rather than water bottom multiples are the most severe source of noise contamination these multiples are extremely difficult to remove when the water bottom reflection coefficient is large 0 6 a condition that exists beneath parts of lake superior and most of lake huron

regularization of mars reconnaissance orbiter crism along track oversampled hyperspectral imaging observations of mars mars reconnaissance orbiter compact reconnaissance imaging spectrometer for mars crism hyperspectral image data have been acquired in an along track oversampled ato mode with the intent of processing the data to better than the nominal 18 m pixel ground resolution we have implemented an iterative maximum log likelihood method mlm that utilizes the instrument spectral and spatial transfer functions and includes a penalty function to regularize the data products are produced both in sensor space and as projected hyperspectral image cubes at 12 m pixel preprocessing steps include retrieval of surface single scattering albedos ssa using the hapke function and disort based radiative modeling of atmospheric gases and aerosols resultant ssa cubes are despiked to remove extrema and tested to ensure that the remaining data are poisson distributed an underlying assumption for the mlm algorithm implementation two examples of processed ato data sets are presented ato0002ec79 covers the route taken by the curiosity rover during its initial ascent of mount sharp in gale crater ssa data are used to model mineral abundances and grain sizes predicted to be present in the namib barchan sand dune sampled and analyzed by curiosity crism based results compare favorably to in situ results derived from curiosity s measurement campaign ato0002ddf9 covers marathon valley on the cape tribulation rim segment of endeavour crater ssa spectra indicate the presence of a minor component of fe 3 and mg 2 smectites on the valley floor and walls localization to 12 m pixel provided the detailed spatial information needed for the opportunity rover to traverse to and characterize those outcrops that have the deepest absorptions the combination of orbital and rover based data show that the smectite bearing outcrops in marathon valley are impact breccias that are basaltic in composition and that have been isochemically altered in a low water to rock environment

a habitable fluvio lacustrine environment at yellowknife bay gale crater mars the curiosity rover discovered fine grained sedimentary rocks which are inferred to represent an ancient lake and preserve evidence of an environment that would have been suited to support a martian biosphere founded on chemolithoautotrophy this aqueous environment was characterized by neutral ph low salinity and variable redox states of both iron and sulfur species carbon hydrogen oxygen sulfur nitrogen and phosphorus were measured directly as key biogenic elements by inference phosphorus is assumed to have been available the environment probably had a minimum duration of hundreds to tens of thousands of years these results highlight the biological viability of fluvial lacustrine environments in the post noachian history of mars

vegetation variation of loess deposits in the southeastern inner mongolia ne china over the past 1 08 million years abstract the stable carbon isotopic composition of organic matter of aeolian silt deposits is regarded as an appropriate proxy index of paleovegetation especially in the chinese loess plateau in central china in this study a loess paleosol sequence in the southeastern inner mongolia autonomous region in northeastern ne china which is located outside the chinese loess plateau is chosen to reconstruct the vegetation history since 1 08 ma temperature exhibits a threshold value which determines the growth of c4 plants in this study area the organic matter of the samples is derived from two different vegetation types namely the mixed c3 and c4 plants and the pure c3 plants the 13c of the organic matter shows negative values in loess units and higher values in paleosol units this finding reflects the influence of temperature and summer monsoon intensity on the vegetation dynamics over glacial interglacial cycles on a longer time scale the 13c values are higher between 1 1 and 0 9 ma and after 0 35 ma and lower between 0 9 and 0 35 ma which may be attributed to a long term temperature variation our analysis shows that regional temperature is the most important limiting factor that forces vegetation changes at the glacial interglacial time scale in ne china

did an extensive forest ever develop on the chinese loess plateau during the past 130 ka a test using soil carbon isotopic signatures abstract pleistocene vegetation history on the chinese loess plateau has been traditionally investigated using palynological methods and questions remain regarding whether an extensive broadleaf deciduous forest ever developed on the loess table under favorable climatic conditions the authors have employed a c isotope approach to address this question by comparing 13 c values in soil organic matter from different loess ecological domains with known source vegetation to the c isotope values obtained from a paleosol section that can be dated back to 130 ka the c isotopic compositions of modern soils from the loess table and the loess desert transition gave 13 c values of 24 5 to 18 2 and 25 7 to 20 7 respectively these c isotopic ratios are consistent with the standing modern vegetation that is dominated by a mixture of c 3 and c 4 plants and can be distinguished from that in the patchy forest areas where exclusive c 3 trees yield a narrow 13 c value range from 26 9 to 25 average 26 1 obtained 13 c compositions from paleosols and loess sediments in the lantian and the luochuan profiles vary from 24 to 16 9 indicating a grass dominated steppe with shifting c 3 and c 4 contributions controlled mainly by paleoclimatic changes during the late pleistocene the present results suggest no extensive forest coverage on the loess table during the past 130 ka even under the most suitable conditions for forest development this conclusion supports the explanation of natural causes for the development of only patchy forests on the modern loess table and provides critical historical information toward the vegetation restoration project that is currently underway on the chinese loess plateau

reinterpreting climate proxy records from late quaternary chinese loess a detailed osl investigation abstract numerous authors have utilised physical properties of chinese loess and red clay deposits to develop apparently detailed and continuous past climate records from the miocene into the holocene many of these studies have further suggested that the principal climatic agent responsible for the aeolian emplacement and diagenesis of chinese loess the east asian monsoon has fluctuated rapidly on millennial to sub millennial timescales in concert with dramatic changes in the north atlantic dansgaard oeschger cycles and heinrich events and the western pacific el nino southern oscillation much of this evidence is based on reconstructions and age models that are tied to assumptions concerning the nature of loess sedimentation and diagenesis for example the belief that loess sedimentation can be viewed as essentially continuous some authors have however cast doubt on these assumptions and suggest that the application of radiometric techniques may be required to determine their validity recent studies utilising optically stimulated luminescence osl methods have reinforced these doubts and here osl dates obtained at 10 cm intervals from three sites along a transect across the chinese loess plateau have been used in combination with climate proxy evidence to test the existing assumptions that underpin many palaeoclimatic reconstructions from loess in this way the first time continuous and independently dated late quaternary climate reconstruction is developed from loess the data indicate that sedimentation is episodic and that once emplaced loess is prone to pedogenic disturbance diagenetic modification and in some cases erosion the relationships between proxies and sedimentation rates are also assessed and climatic interpretations based on different age models compared the implications of these findings for reconstructions of climate from loess are explored and comparisons are made between the developed palaeoclimate records and evidence from ice and ocean cores this exercise also highlights important information concerning the relative influence of forcing mechanisms behind east asian monsoon change over the late quaternary

relative amplitude preserving processing for crustal seismic reflection data an example from western canada abstract most crustal scale seismic reflection profiles are processed using methods that preserve reflection geometries but not true relative amplitudes and therefore do not provide direct constraints on the magnitude of impedance contrasts at major crustal boundaries the effects of attenuation in the crust or the maximum time of signal penetration here we describe a new relative amplitude preserving rap processing scheme tailored for high fold land based acquisition systems that can be used to provide some of these constraints our processing philosophy employs a statistical treatment of amplitudes and is based on the following assumptions 1 temporal decay of recorded amplitudes is proportional to the product of zero offset geometrical spreading in a layered earth and attenuation based on a constant q model and 2 spatial variations in recorded amplitudes are surface consistent we apply this methodology to a profile from western canada where well logs from oil and gas exploration are available to calibrate observed seismic reflections using a spectral ratio method tailored for noisy data we obtain an estimate of 450 for apparent q in the sub phanerozoic crust signal penetration is frequency dependent and is estimated to decrease from 20 to 13 s over the frequency range of 10 to 40 hz application of our processing methodology leads to a stack section in which lower crustal reflectivity is much more prominent than reflectivity in the middle crust compared with conventional processing of the same data which yields a stack section characterized by conspicuous mid crustal reflections the p wave reflection coefficient for the moho is estimated to be about 0 1

rock abrasion tool mars exploration rover mission 1 the rock abrasion tool rat is an integral part of the athena science payload serving primarily as the geologist s rock hammer the rat will expose fresh surfaces of martian rocks to other instruments on the payload the rat also brushes dust and debris from an excavated hole or unaltered rocks to accomplish these tasks autonomously the rat a sophisticated 3 axis precision controlled device was designed data products derived from rat telemetry enable the rat to also act as an important rock physical properties science instrument the returned rat grinding and penetration rate data will be inverted and compared to a rock library on the earth the design is also very compact and lightweight the rat is contained within a cylinder 128 mm long and 85 mm in diameter and has a mass of 687 g

crustal resistivity structure from magnetotelluric soundings in the colorado plateau basin and range provinces central and western arizona resistivity structure to about 25 km depth is defined from two dimensional modeling of 29 magnetotelluric mt soundings 0 002 5 hz that traverse 280 km of the southwestern colorado plateau transition zone and basin and range provinces in arizona from the surface to 5 km depth the mt model suggests structural relationships between low resistivity sedimentary and volcanic rocks 50 300 ohm m and high resistivity granitic and gneissic basement 500 9000 ohm m in the basin and range province the mt model and a seismic reflection section show a generally consistent distribution of supracrustal rocks that have relatively low to moderate resistivity mt and relatively strong locally coherent reflectivity the supracrustal zone defined by these physical properties is inferred to be composed of upper plate rocks above a middle tertiary detachment fault system which has been mapped in surrounding ranges some low angle fault zones inferred from seismic reflections to extend into high resistivity basement below the supracrustal rocks are not resolved by the mt model a low resistivity zone with a conductance of 500 s or more is modeled in the crust at an average depth of about 15 km in the basin and range province and transition zone and may deepen below the southwestern part of the colorado plateau in the basin and range province the top of the low resistivity may correspond to a reflective layer with a 6 s two way travel time this deep low resistivity zone might be caused by a small fraction of connected hydrous solutions or silicic melts

context of ancient aqueous environments on mars from in situ geologic mapping at endeavour crater using the mars exploration rover opportunity we have compiled one of the first field geologic maps on mars while traversing the noachian terrain along the rim of the 22 km diameter endeavour crater latitude 2 16 33 longitude 5 10 51 in situ mapping of the petrographic elemental structural and stratigraphic characteristics of outcrops and rocks distinguishes four mappable bedrock lithologic units three of these rock units predate the surrounding burns formation sulfate rich sandstones and one the matijevic formation represents conditions on early mars predating the formation of endeavour crater the stratigraphy assembled from these observations includes several geologic unconformities the differences in lithologic units across these unconformities record changes in the character and intensity of the martian aqueous environment over geologic time water circulated through fractures in the oldest rocks over periods long enough that texturally and elementally significant alteration occurred in fracture walls these oldest pre endeavour rocks and their network of mineralized and altered fractures were preserved by burial beneath impact ejecta and were subsequently exhumed and exposed the alteration along joints in the oldest rocks and the mineralized veins and concentrations of trace metals in overlying lithologic units is direct evidence that copious volumes of mineralized and or hydrothermal fluids circulated through the early martian crust the wide range in intensity of structural and chemical modification from outcrop to outcrop along the crater rim shows that the ejecta of large 8 km in diameter impact craters is complex these results imply that geologic complexity is to be anticipated in other areas of mars where cratering has been a fundamental process in the local and regional geology and mineralogy

ancient aqueous environments at endeavour crater mars opportunity has investigated in detail rocks on the rim of the noachian age endeavour crater where orbital spectral reflectance signatures indicate the presence of fe 3 rich smectites the signatures are associated with fine grained layered rocks containing spherules of diagenetic or impact origin the layered rocks are overlain by breccias and both units are cut by calcium sulfate veins precipitated from fluids that circulated after the endeavour impact compositional data for fractures in the layered rocks suggest formation of al rich smectites by aqueous leaching evidence is thus preserved for water rock interactions before and after the impact with aqueous environments of slightly acidic to circum neutral ph that would have been more favorable for prebiotic chemistry and microorganisms than those recorded by younger sulfate rich rocks at meridiani planum

multiple origins and interpretations of the magnetic susceptibility signal in chinese wind blown sediments abstract in most chinese loess paleosol sequences high magnetic susceptibility values are found in the soil horizons with low values in the loess layers the susceptibility signal has been widely used as a proxy climatic indicator however both the causes and mechanisms which control susceptibility still remain controversial our recent studies challenge some earlier interpretations of the magnetic susceptibility signal in chinese wind blown sediments first the prevailing hypothesis of pedogenic origin cannot totally account for the susceptibility variations in many sections second in some cases the principal carrier of the magnetization seems not to be the ultrafine pedogenic minerals rather coarse lithogenic magnetic minerals derived from local sources can also contribute significantly to the susceptibility signal finally not all the chinese soils have higher susceptibility values than that of loess or sand layers opposite relationships do exist it is concluded that the source and causes of susceptibility may be different from site to site or even at different times at a given site any single hypothesis cannot completely account for the susceptibility variations in the chinese loess plateau and its surrounding regions besides the previous explanations of carbonate leaching pedogenic processes and organic decomposition the contribution of source materials to magnetic susceptibility must also be taken into account

mossbauer mineralogy of rock soil and dust at meridiani planum mars opportunity s journey across sulfate rich outcrop basaltic sand and dust and hematite lag deposits additonal co authors p gutlich e kankeleit t mccoy dw mittlefehldt f renz me schmidt b zubkov sw squyres re arvidson

esperance multiple episodes of aqueous alteration involving fracture fills and coatings at matijevic hill mars in the search for evidence of past aqueous activity by the mars exploration rover opportunity fracture filling veins and rock coatings are prime candidates for exploration at one location within a segment of remaining rim material surrounding endeavour crater a set of boxwork fractures in an outcrop called esperance are filled by a bright hydrated and highly siliceous sio2 66 wt material which has overall a montmorillonite like chemical composition this material is partially covered by patches of a thin dark coating that is sulfate rich so3 21 wt but also contains significant levels of si fe ca and mg the simultaneous presence of abundant s si and fe indicates significant mineralogical complexity within the coating this combination of vein and coating compositions is unlike previous analyses on mars both materials are heterogeneously eroded presumably by eolian abrasion the evidence indicates at least two separate episodes of solute precipitation from aqueous fluids at this location possibly widely separated in time in addition to the implications for multiple episodes of alteration at the surface of the planet aqueous chemical environments such as these would have been habitable at the time of their formation and are also favorable for preservation of organic material

middle pleistocene climate and habitat change at zhoukoudian china from the carbon and oxygen isotopic record from herbivore tooth enamel the pleistocene deposits at zhoukoudian often referred to as the bpeking manq site contain dental remains from a diverse group of herbivores including equus sanmeniensis cervus elaphus cervus nippon megaloceros pachyosteus sus lydekkeri and dicerorhinus choukoutienensis the carbon and oxygen isotopic compositions of structural carbonate within the enamel of these teeth are used to reconstruct the paleodiet and paleoenvironment of the mammals the d 13 c values of enamel from zhoukoudian range from 2 3x to 13 0x indicating that these mammals consumed between 25 and 100 c3 plants the presence of significant amounts of c4 plants in the diets of some herbivore species indicates that at the onset of the middle pleistocene local habitats included mixed c3 c4 vegetation by approximately 470 000 yr ago c3 plants dominated the diets of herbivores studied suggesting that the abundance of c4 flora had decreased in the area for all deer analyzed in this study the values of d 13 c and d 18 o decrease substantially from about 720 000 to 470 000 yr ago this trend may be due to a strengthening of the winter monsoon during the middle pleistocene

paleosol nodules as pleistocene paleoclimatic indicators luochuan p r china abstract loess deposits with their interbedded paleosols in central china record the world wide climatic changes of the past 2 5 ma the carbon and oxygen isotopic compositions of carbonate nodules in a loess profile at luochuan record paleoclimatic and paleoecologic conditions of paleosol formation interglacial periods during the past several 100 000 years it appears that the climatic and ecologic conditions during different periods of paleosol s 1 s 8 formation interglacial periods were very similar at luochuan and are marked by a presence of a mixed c 3 and c 4 type flora or mixed grass and wood and or shrublands

link between climate and catchment erosion in the himalaya during the late quaternary abstract few studies using geochemistry of sediments from plains and delta of the himalayan river system have reported contrasting results on the shift in erosion of different lithotectonic units across the strike of himalayan orogen in response to changes in the intensity of indian summer monsoon ism and glacial cover during the late quaternary here we present records of the 143nd 144nd end and 87sr 86sr ratios and 13c of sediment organic matter 13csom in bulk sediment samples from two 45 m long alluvial cores collected from a paleo sutlej channel in sirhind punjab at an upstream connection of a large river ghaggar hakra with present day sutlej river in nw india the isotopic variations are compared with the available proxy records that document changes in the ism and himalayan glacial extent significant covariation in down core profiles of end 14 1 to 22 2 and 87sr 86sr 0 72251 0 79456 reveals changing contributions of sediment derived from the higher and lesser himalaya end member sources in the catchment higher end and lower 87sr 86sr during early marine isotope stage mis 1 and late mis3 reflects increased contribution from the higher himalaya as a result of receding glacial cover as well as intense ism that penetrates into the interior of the higher himalaya during warm periods the 13csom varies from 28 5 to 21 3 and shows a 5 7 increase from colder mis2 to warmer early mis1 implying an increase in c4 plant abundance during the same period in response to intensification of the ism in the post last glacial maximum period these variations in sediment provenance and vegetation pattern thus highlight the pronounced influence of climate on distribution of erosion and vegetation types in the nw himalaya

thermodynamic and mass balance constraints on iron bearing phyllosilicate formation and alteration pathways on early mars 1 widespread occurrences of phyllosilicates predominantly nontronite and mg saponite in the noachian aged crust of mars place constraints on water availability and surface conditions however the noachian atmosphere likely lacked oxidants capable of forming nontronite from the basaltic crust and its origins are thus uncertain in this study scenarios for the formation of iron bearing phyllosilicates from the weathering and hydrothermal alteration of martian basalt were investigated using geochemical modeling to establish plausible pathways of nontronite generation and the effect of redox conditions on associated secondary phases hydrothermal alteration produced feii and mg saponite serpentine and zeolites at 100 c and chlorite prehnite and talc at 250 c consistent with phases observed in crater deposits on mars anoxic weathering produced primarily feii and mg saponite high water rock ratios produced al clays and amorphous silica and high pco2 conditions inhibited smectite formation because of carbonate precipitation oxic weathering produced primarily nontronite and mg saponite later oxidation of anoxic weathering products also formed nontronite mg saponite assemblages oxidation products of hydrothermal assemblages included nontronite mg saponite and either al smectites or residual zeolites or prehnite these calculations demonstrate that there are multiple plausible routes to form fe mg smectites on early mars and that an oxidizing atmosphere need not have existed in the noachian decoupling iron oxidation from initial clay formation raises the possibilities that mars transitioned to conditions favoring widespread iron oxidation after phyllosilicate formation ceased and that residual unoxidized ferrous iron phyllosilicates still exist today in the martian subsurface

climatic implications of the s5 paleosol complex on the southernmost chinese loess plateau the s5 is the most prominent paleosol unit in the chinese loess plateau and is distinguished by its great thickness dark color and well developed clay coatings previous studies led to the proposal that the s5 developed under much warmer and wetter conditions than at present implying a climatic optimum however the s5 is a paleosol complex corresponding in time to a period of weak glacial interglacial oscillations as recorded by marine oxygen isotope stages 15 through 13 to understand the character of this climatic interval two profiles of the paleosol s5 in the guanzhong basin were studied with most of the emphasis being placed on the uppermost and best developed pedon s5 i grain size mineralogical and chemical data indicate that the major pedogenic processes experienced by the s5 i included complete decalcification and mechanical translocation of fine particles chemical alteration of silicate minerals has been weak stable carbon isotope analyses of organic matter showed that c4 plant remains are abundant throughout the profiles these results suggest that grasslands dominated the paleovegetation during s5 i development the prominent development of the s5 paleosol complex may reflect a prolonged period of pedogenesis in contrast to previous reports paleoclimatic conditions perhaps even drier than at present are implied by the data for the s5 profiles the relative strength of the glacial interglacial oscillation in this region related to the east asian monsoon was similar to that indicated for global climate during s5 time

oxidation of manganese in an ancient aquifer kimberley formation gale crater mars the curiosity rover observed high mn abundances 25 wt mno in fracture filling materials that crosscut sandstones in the kimberley region of gale crater mars the correlation between mn and trace metal abundances plus the lack of correlation between mn and elements such as s cl and c reveals that these deposits are mn oxides rather than evaporites or other salts on earth environments that concentrate mn and deposit mn minerals require water and highly oxidizing conditions hence these findings suggest that similar processes occurred on mars based on the strong association between mn oxide deposition and evolving atmospheric dioxygen levels on earth the presence of these mn phases on mars suggests that there was more abundant molecular oxygen within the atmosphere and some groundwaters of ancient mars than in the present day

vnir multispectral observations of aqueous alteration materials by the pancams on the spirit and opportunity mars exploration rovers multispectral visible and near infrared vnir observations from the mars exploration rover pancam multispectral stereo camera systems are consistent with materials having been subjected to various aqueous processes ferric oxides in the form of hematite in the burns and grasberg formations of meridiani planum have been well characterized by opportunity on the basis of strong 535 and 864 nm absorptions and positive 754 1009 nm and 934 1009 nm slopes on the rim of noachian aged endeavour crater opportunity has observed light toned veins with high ca and s as determined by the rover s alpha particle x ray spectrometer apxs and a negative 934 1009 nm slope in vnir spectra extracted from pancam data indicative of a 1000 nm h2o overtone absorption together these observations indicate that the veins are composed of gypsum rocks overturned by opportunity on the murray ridge portion of the endeavour crater rim display dark and light toned coatings the dark toned coatings have a red featureless slope that is consistent with the slope observed in laboratory spectra of high valence manganese oxide minerals potential mn oxide coatings may also be associated with some exposures of the grasberg formation apxs results for high mg and s in the light toned coatings of the murray ridge overturned rocks and a negative 934 1009 nm slope are consistent with hydrated mg sulfates opportunity has also observed spectral features in rocks that are consistent with orbital observations of fe smectites as well as al smectites and possible hydrated silica in light toned fracture fill materials the spirit rover observed sulfate rich light toned soils exposed by the rover s wheels several of these soil observations contained spectral features such as a broad absorption centered near 800 nm consistent with ferric sulfate minerals a finding confirmed by the rover s mossbauer spectrometer spirit also excavated light toned si rich soils these soils have a flat near infrared spectrum with a drop in reflectance from 934 1009 nm that is consistent with free water contained in voids or adsorbed onto the surface of the silica

modeling aluminum silicon chemistries and application to australian acidic playa lakes as analogues for mars abstract recent mars missions have stimulated considerable thinking about the surficial geochemical evolution of mars among the major relevant findings are the presence in meridiani planum sediments of the mineral jarosite a ferric sulfate salt and related minerals that require formation from an acid salt brine and oxidizing environment similar mineralogies have been observed in acidic saline lake sediments in western australia wa and these lakes have been proposed as analogues for acidic sedimentary environments on mars the prior version of the equilibrium chemical thermodynamic frezchem model lacked al and si chemistries that are needed to appropriately model acidic aqueous geochemistries on earth and mars the objectives of this work were to 1 add al and si chemistries to the frezchem model 2 extend these chemistries to low temperatures frezchem is an equilibrium chemical thermodynamic model parameterized for concentrated electrolyte solutions using the pitzer approach for the temperature range from 4 no 3 oh hco 3 co 3 co 2 o 2 ch 4 si h 2 o system that now contain 95 solid phases there were similarities differences and uncertainties between australian acidic saline playa lakes and waters that likely led to the burns formation salt accumulations on mars both systems are similar in that they are dominated by 1 acidic saline ground waters and sediments 2 ca and or mg sulfates and 3 iron precipitates such as jarosite and hematite differences include 1 the dominance of nacl in many wa lakes versus the dominance of fe mg ca so 4 in meridiani planum 2 excessively low k concentrations in meridiani planum due to jarosite precipitation 3 higher acid production in the presence of high iron concentrations in meridiani planum and probably lower rates of acid neutralization and hence higher acidities on mars owing to colder temperatures and 4 lateral salt patterns in wa lakes the wa playa lakes display significant lateral variations in mineralogy and water chemistry over short distances reflecting the interaction of acid ground waters with neutral to alkaline lake waters derived from ponded surface runoff meridiani planum observations indicate that such lateral variations are much less pronounced pointing to the dominant influence of ground water chemistry vertical ground water movements and aeolian processes on the martian surface mineralogy

silica rich deposits and hydrated minerals at gusev crater mars vis nir spectral characterization and regional mapping abstract the mars exploration rover mer spirit has discovered surprisingly high concentrations of amorphous silica in soil and nodular outcrops in the inner basin of the columbia hills in pancam multispectral observations we find that an absorption feature at the longest pancam wavelength 1009 nm appears to be characteristic of these silica rich materials however spectral analyses of amorphous silica suggest that the 1009 nm spectral feature is not a direct reflection of their silica rich nature based on comparisons with spectral databases we hypothesize that the presence of h 2 o or oh either free as water ice adsorbed or bound in a mineral structure is responsible for the spectral feature observed by pancam the gertrude weise soil which is nearly pure opaline silica may have adsorbed water cold trapped on mineral grains the origin of the 1009 nm pancam feature observed in the silica rich nodular outcrops may result from the presence of additional hydrated minerals specific sulfates halides chlorides sodium silicates carbonates or borates using the 1009 nm feature with other spectral parameters as a hydration signature we have mapped the occurrence of hydrated materials along the extent of spirit s traverse across the columbia hills from west spur to home plate sols 155 1696 we have also mapped this hydration signature across large panoramic images to understand the regional distribution of materials that are spectrally similar to the silica rich soil and nodular outcrops our results suggest that hydrated materials are common in the columbia hills

mars exploration rover athena panoramic camera pancam investigation 1 the panoramic camera pancam investigation is part of the athena science payload launched to mars in 2003 on nasa s twin mars exploration rover mer missions the scientific goals of the pancam investigation are to assess the high resolution morphology topography and geologic context of each mer landing site to obtain color images to constrain the mineralogic photometric and physical properties of surface materials and to determine dust and aerosol opacity and physical properties from direct imaging of the sun and sky pancam also provides mission support measurements for the rovers including sun finding for rover navigation hazard identification and digital terrain modeling to help guide long term rover traverse decisions high resolution imaging to help guide the selection of in situ sampling targets and acquisition of education and public outreach products the pancam optical mechanical and electronics design were optimized to achieve these science and mission support goals pancam is a multispectral stereoscopic panoramic imaging system consisting of two digital cameras mounted on a mast 1 5 m above the martian surface the mast allows pancam to image the full 360 in azimuth and 90 in elevation each pancam camera utilizes a 1024 1024 active imaging area frame transfer ccd detector array the pancam optics have an effective focal length of 43 mm and a focal ratio of f 20 yielding an instantaneous field of view of 0 27 mrad pixel and a field of view of 16 16 each rover s two pancam eyes are separated by 30 cm and have a 1 toe in to provide adequate stereo parallax each eye also includes a small eight position filter wheel to allow surface mineralogic studies multispectral sky imaging and direct sun imaging in the 400 1100 nm wavelength region pancam was designed and calibrated to operate within specifications on mars at temperatures from 55 to 5 c an onboard calibration target and fiducial marks provide the capability to validate the radiometric and geometric calibration on mars

δ13c analyses of individual lignin phenols in quaternary lake sediments a novel proxy for deciphering past terrestrial vegetation changes this study of the sediments from sacred lake mount kenya demonstrates that 13 c analyses of individual lignin phenols can be used to assess past changes in the proportion of c 3 and c 4 plants within different plant groups in the lake catchment vegetation changes resulting from climatic and atmospheric changes since the last glacial maximum can be deduced from specific lignin phenols lignin a major biopolymer in vascular plants differs from n alkyl lipids in 1 its higher specificity and more quantitative representation of vascular plant input and 2 its major transport mechanism into the sediments by fluvial runoff as opposed to the greater importance of eolian transport for leaf waxes and pollen lignin 13 c data support the hypothesis that atmospheric co 2 concentration is an important factor controlling the vegetation in tropical mountain ecosystems and provide additional insights into past changes in vegetation structure specifically the 13 c values of p coumaric acid indicate the persistence of c 4 grasses during the late glacial when the lake level was lower than today suggesting that aridity also played a role in controlling the abundance of c 4 plants

rock varnish evidence for latest pleistocene millennial scale wet events in the drylands of western united states rock varnish from late to latest pleistocene geomorphic features in the drylands of the western u s provides evidence of nine millennial scale wet events from 11 500 18 000 calendar yr b p represented by regionally replicable and approximately evenly spaced manganese and barium rich dark bands in varnish microstratigraphy preliminary radiometric age calibration indicates that these events appear to be broadly coeval with millennial scale cooling events identified in the greenland ice sheet project 2 gisp2 ice core record six of these wet events are associated with the cold intervals of the younger dryas and heinrich event h1 and the other three with the short lived cooling phases of the intra allerod cold period the older dryas and the oldest dryas these results combined with our previous documentation of millennial scale wet events in the holocene varnish record for the same region indicate that such wet oscillations in the western u s may be parts of regionally widespread manifestation of well documented pervasive millennial scale cycles of the north atlantic climate

geometry of the garlock fault zone based on seismic relection data detailed examination of shot gathers from line 3 of the consortium for continental reflection profiling mojave experiment indicates a low velocity high amplitude seismic event that may originate from a south dipping portion of the garlock fault zone part of this event was previously interpreted as a subhorizontal surface located in the midcrust our analysis indicates however that the distance to this event varies consistently with the distance of the shot and receivers from the fault zone and that the velocities are too low for seismic waves traveling through predominantly crystalline rocks these characteristics are more consistent with the presence of a subvertical reflector located near the garlock fault zone than with the previously inferred subhorizontal reflector beneath the seismic line

late quaternary loess in northeastern colorado part i age and paleoclimatic significance loess in eastern colorado covers an estimated 14 000 km 2 and is the westernmost part of the north american midcontinent loess province stratigraphic studies indicate there were two periods of loess deposition in eastern colorado during late quaternary time the first period spanned ca 20 000 to 12 000 14 c yr b p ca 20 14 ka and correlates reasonably well with the culmination and retreat of pinedale glaciers in the colorado front range during the last glacial maximum the second period of loess deposition occurred between ca 11000 and 9000 14 c yr b p this interval may be holocene or may correlate with a hypothesized younger dryas glacial advance in the colorado front range sedimentologic mineralogic and geochemical data indicate that as many as three sources could have supplied loess in eastern colorado these sources include glaciogenic silt derived from the colorado front range and two bedrock sources volcaniclastic silt from the white river group and clays from the pierre shale the sediment sources imply a generally westerly paleowind during the last glacial maximum new carbon isotope data combined with published faunal data indicate that the loess was probably deposited on a cool steppe implying a last glacial maximum july temperature depression relative to the present of at least 5 6 c overall loess deposition in eastern colorado occurred mostly toward the end of the last glacial maximum under cooler and drier conditions with generally westerly winds from more than one source

plio pleistocene vegetation changes in the north china plain magnetostratigraphy oxygen and carbon isotopic composition of pedogenic carbonates abstract the plio pleistocene history of c4 plant biomass in northwestern china has been documented from the loess soil sequences of the loess plateau region however how c4 plants evolved in the warmer and low elevation eastern china monsoon zone is still poorly known mainly because of the unavailability of well dated geological records in this study a 203 6 m core of floodplain deposits was recovered from the north china plain near tianjin and dated magnetostratigraphically the results define a chronosequence for the last 3 3 ma the late quaternary portion of the core consists of fluvio marine sediments while the rest of the section 3 3 0 6 ma contains abundant paleosols formed on the floodplain as confirmed by soil micromorphological evidence the stable carbon and oxygen isotopic composition of pedogenic carbonates was measured to document vegetation and climate changes the results reveal mixed c3 and c4 vegetation with an estimated c4 abundance of 40 60 from 3 1 to 2 2 ma and a subsequent gradual decline to 25 until 0 6 ma this trend is consistent with the data from the loess soil sequences further west on the loess plateau suggesting they are regionally significant changes the lowering of growing season temperature and or drier conditions induced by global cooling would explain this overall decline

climatically driven glacial interglacial variations in c3 and c4 plant proportions on the chinese loess plateau high resolution 13c records of bulk organic matter om from three loess paleosol successions from the central chinese loess plateau document systematic fluctuations in c3 and c4 plant abundance for certain intervals during the past 620 k y measured 13c values of om in paleosols are less negative by 0 5 4 and total organic carbon toc contents are higher by up to 0 5 wt relative to corresponding values in loess deposits the 13com and toc decrease from peak values in paleosols progressively into overlying and underlying loess deposits integrated 13com toc and magnetic susceptibility rec ords indicate an increase in c4 vegetation to 50 during peak paleosol formation and a decrease in c4 vegetation to 30 during loess deposition for three of the past glacial interglacial cycles these results indicate that c4 plant abundance declined during glacials in this mid latitude region driven primarily by a shift to enhanced winter precipitation and lower temperatures and further contribute to the rapidly growing body of evidence that low p co2 during pleistocene glacials was insufficient to trigger c4 plant expansion without coincident favorable climatic conditions

a carbon isotope record of the upper chinese loess sequence estimates of plant types during stadials and interstadials the upper three couplets of paleosol loess in the luochuan section of northern china were analyzed for carbon isotopes these units date back to about 205 ka and have been correlated with the marine oxygen isotope stages 1 6 calcite is present as nodules concretions and interstitial cement analyses were performed on bulk samples of slightly cemented soil and loess material an ashing study indicates the presence of organic matter in the samples and it is possible that analyzed gases included a contribution from this source the measured 13c values and the estimates of co2 content in the atmosphere over this time derived from studies of the vostok ice core and from the 13c values of planktic benthic foraminifera are used following the method of cerling 1984 1991 to calculate the proportions of c3 vs c4 plants which contributed co2 to the formation of calcite in the paleosols and the loess c3 plants were dominant at all times paleosols 70 80 loess 55 60 c3 and both loess and paleosols show a decrease toward the present these relationships suggest a progressive drying of the environments due either to climate change or to changes in the local drainage network

characteristics of desert varnish from nanometer to micrometer scale a photo oxidation model on its formation abstract rock varnish is a widespread mn rich rock coating commonly developed in arid environments but the mechanism for its formation is still under debate in this study rock varnish and adjacent soil dust collected from gobi desert were analyzed for exploring the possible abiotic oxidation mechanism of mn oxides the occurrence of rock varnish shows a direct and close relationship with strong irradiation of sunlight giving the first evidence of photochemical genesis abundant caves and tunnels with average diameter of 1 5 m are observed on varnish surface regions which facilitate the penetration of sunlight and water metal oxyhydr oxides including birnessite hematite goethite rutile and anatase account for the major components of rock varnish which are all solar light responsive semiconducting minerals the trace elements enrichment patterns revealed by la icp ms provide the indication of an aqueous origin the positive ce anomalies in varnish in contrast to the rock substrate as well as the positive correlation between ce and mn suggest a strong oxidizing environment in the genesis of rock varnish therefore the photo generated holes and reactive oxygen species ross on metal oxides in varnish can promote mn ii oxidation which are further demonstrated from thermodynamic and kinetic considerations ross including 1o2 and oh with strong oxidizing capability are detected by epr in varnish suspension providing the direct evidence for mn ii oxidation laboratory experimental simulations show the photocatalysis of metal oxides in rock varnish greatly promote mn ii oxidation by 2 10 7 97 times in comparison with homogenous solution oxidation all these lines of evidence suggest that light induced abiotic process may play important roles in the formation of rock varnish together with other abiotic and biotic pathways which can even provide implications for the evolution of mn oxides on surface of terrestrial planets

correlation between climate events in the north atlantic and china during the last glaciation episodes of massive iceberg release heinrich events 1 3 into the north atlantic ocean during the last glaciation were associated with recurring episodes of unusually cold north atlantic surface water bond cycles 4 and cold air temperatures over greenland dansgaard oeschger events 5 6 four of the youngest of these cold events have also been reported in climate records from sites outside the north atlantic region7 but until now the entire suite has been identified only in north atlantic marine sediments greenland ice core records and tentatively in french lake sediments8 here we examine grain size data from chinese loess and intercalated accretionary palaeosols of last glacial age for evidence of similar climate signals remote from the north atlantic region we see grain size maxima with ages that match those of the last six heinrich events which we interpret as an indication of the changing strength of the east asian winter monsoon which largely controls the transport and deposition of central asian aeolian dust thus it seems that these heinrich events have left their signature in the chinese loess record this is consistent with simulations of the glacial climate9 which imply that the climates of the north atlantic and china were linked by the effect of westerly winds

age dating and the orbital theory of the ice ages development of a high resolution 0 to 300 000 year chronostratigraphy using the concept of orbital tuning a continuous high resolution deep sea chronostratigraphy has been developed spanning the last 300 000 yr the chronology is developed using a stacked oxygen isotope stratigraphy and four different orbital tuning approaches each of which is based upon a different assumption concerning the response of the orbital signal recorded in the data each approach yields a separate chronology the error measured by the standard deviation about the average of these four results which represents the best chronology has an average magnitude of only 2500 yr this small value indicates that the chronology produced is insensitive to the specific orbital tuning technique used excellent convergence between chronologies developed using each of five different paleoclimatological indicators from a single core is also obtained the resultant chronology is also insensitive to the specific indicator used the error associated with each tuning approach is estimated independently and propagated through to the average result the resulting error estimate is independent of that associated with the degree of convergence and has an average magnitude of 3500 yr in excellent agreement with the 2500 yr estimate transfer of the final chronology to the stacked record leads to an estimated error of 1500 yr thus the final chronology has an average error of 5000 yr