deducing the age of the dense venus atmosphere abstract we show how crater size density counts may be used to help constrain the history of the venus atmosphere based on the predictions of simple but reasonable models for crater production surface erosion and the effects of atmospheric drag and breakup on incident meteors in the venus atmosphere if the atmosphere is old we may also be able to determine the importance of breakup as a mechanism for destroying incident meteors in a dense fluid in particular if the atmosphere is young the old uneroded surfaces will have crater densities upward of 10 4 km 2 and a ratio of small 4 km craters to large 128 km craters near 103 if the atmosphere is old and the breakup mechanism is dominant absolute crater densities on venus surfaces will be diminished by several orders of magnitude relative to the young atmosphere case if atmospheric drag is dominant and the atmosphere is old the absolute crater density will be lowered by perhaps an order of magnitude relative to the young atmosphere case and the ratio of small to large craters will be reduced to a value near 101 5 according to the models the comparison of crater populations on young as well as old surfaces on venus can help in distinguishing the young and old atmosphere scenarios especially since the situation may be complicated by currently undetermined erosional and tectonic processes once a large fraction of venus surface has been imaged at kilometer resolution as the voir project promises to do it could be possible to make an early determination of the age of the venus atmosphere

the geology of the terrestrial planets during the last four years our knowledge of the geology of the terrestrial planets has advanced rapidly the advances are particularly noticeable for venus and mars improved understanding of venus has come largely from the pioneer venus mission colin 1980 which has given us our first global view of the planet albeit at fairly low resolution the period was also one of almost continuous data gathering for mars as the viking orbiters and landers emplaced at the planet in 1976 continued to function

late cretaceous early palaeogene tectonic development of se asia abstract the late cretaceous early palaeogene history of the continental core of se asia sundaland marks the time prior to collision of india with asia when se asia from the tethys in the west to the palaeo pacific in the east lay in the upper plate of subduction zones in myanmar and sumatra subduction was interrupted in the aptian albian by a phase of arc accretion woyla and mawgyi arcs and in java eastern borneo and western sulawesi by collision of continental fragments rifted from northern australia subsequent resumption of subduction in the myanmar thailand sector explains 1 early creation of oceanic crust in the andaman sea in a supra subduction zone setting 95 ma 2 the belt of granite plutons of late cretaceous early palaeogene age starting 88 ma in western thailand and central myanmar and 3 amphibolite grade metamorphism between 70 and 80 ma seen in gneissic outcrops in western and central thailand and 4 accretionary prism development in the western belt of myanmar until glancing collision with the ne corner of greater india promoted ophiolite obduction deformation and exhumation of marine sediments in the early palaeogene the ranong strike slip fault and other less well documented faults were episodically active during the late cretaceous palaeogene time n to nw directed subduction of the palaeo pacific ocean below southern china vietnam and borneo created a major magmatic arc associated with rift basins metamorphic core complexes and strike slip deformation which continued into the late cretaceous the origin and timing of termination of subduction has recently been explained by collision of a large luconia continental fragment either during the late cretaceous or palaeogene evidence for such a collision is absent from the south china sea well and seismic reflection record and here collision is discounted instead relocation of the subducting margin further west possibly in response of back arc extension which created the proto south china sea is preferred lying between the two subduction related arcs the khorat basin is of predominantly late jurassic early cretaceous age but stratigraphic and apatite fission track data also indicates deposition of 1 2 km of late cretaceous sediments the synformal basin geometry probably arose due to the dynamic topography created by converging tethyan and palaeo pacific subduction zones the aptian albian slowing of basin subsidence and onset of evaporite deposition coincides with collision of the mawgyi and woyla island arcs extensive palaeogene deformation and exhumation 3 km in places affected all margins of the khorat plateau deformation includes folds of the phu phan uplift and strike slip faults thrusts and folds on the southern and eastern margins south of the khorat plateau outcrop and seismic reflection data from the ton le sap basin cambodia and the gulf of thailand indicate syn depositional fault controlled subsidence was important during cretaceous deposition the hot thickened crust developed during the late cretaceous palaeogene events follows the weak indosinian crustal scale inthanon and sukhothai zones which persistently guided the location of later structures including cenozoic extensional and post rift basins and influenced the widespread occurrence of low angle normal faults metamorphic core complexes and eastern gulf of thailand super deep post rift basins

models of diffusion limited uptake of trace elements in fossils and rates of fossilization abstract many fossils are assumed to take up trace elements by a process of combined diffusion plus adsorption da yet in principle composition profiles can be explained by several different diffusion limited processes including diffusion plus reaction or recrystallization dr and double medium diffusion dmd the da and dmd models are supported by ree and u composition profiles across fossil teeth measured by laser ablation icp ms that show error function like diffusion profiles into enamel from the dentine enamel interface and concentrations in the interior of enamel that are at original biogenic levels or higher published composition and age profiles in some pleistocene bones may be better explained by a dr model all three diffusion models imply linear behavior between age and distance squared vastly simplifying u series dating methods for pleistocene fossils modeled uptake rates for fossil teeth yield a strict minimum bound on durations of about one decade to one century the similarity of diffusion profiles in teeth irrespective of depositional ages ranging from 30 ka to 30 ma implies that uptake occurred quickly with a maximum duration of a few tens of kyr for typical fossil enamel faster uptake is implied for typical fossil bone and dentine disparities in these uptake estimates compared to some archeological bone may reflect sampling and preservation bias for paleontological vs archeological materials

early diagenesis and recrystallization of bone abstract one of the most challenging problems in paleobiology is determining how bone transforms from a living tissue into a fossil the geologic record is replete with vertebrate fossils preserved from a range of depositional environments including wetland systems however thermodynamic models suggest that bone modeled as hydroxylapatite is generally unstable in a range of varying geochemical conditions and should readily dissolve if it does not alter to a more thermodynamically stable phase such as a fluorine enriched apatite here we assess diagenesis of alligator bone from fleshed articulated skeletons buried in wetland soils and from de fleshed bones in experimental mesocosms with and without microbial colonization when microbial colonization of bone was inhibited bioapatite recrystallization to a more stable apatite phase occurred after one month of burial ca fe phosphate phases in bone developed after several months to years due to ion substitutions from the protonation of the hydroxyl ion these rapid changes demonstrate a continuum of structural and bonding transformations to bone that have not been observed previously when bones were directly in contact with sediment and microbial cells rapid bioerosion and compositional alteration occurred after one week but slowed after one month because biofilms reduced exposed surfaces and subsequent bioapatite lattice substitutions microbial contributions are likely essential in forming stable apatite phases during early diagenesis and for enabling bone preservation and fossilization

identifying the reworking and stratigraphic provenance of bones by exploring multivariate geochemical relationships with the perio spot technique abstract erosional processes often rework materials of different ages into the same sedimentary facies producing time averaged deposits such reworking is common at archaeological sites and researchers must consider the resulting time averaging effects when using natural stratigraphy to situate artifacts and remains in time at scladina cave a neandertal site in belgium we developed a method for identifying reworked facies and the stratigraphic provenance of mammal bones based on their post mortem trace element characteristics and crystallinity we collected sixty two faunal remains from throughout the site s sedimentary sequence and analyzed them for trace element concentrations and crystallinity with laser ablation inductively coupled plasma mass spectrometry and raman spectroscopy our novel approach the perio spot technique quantifies the trace element characteristics and crystallinity from the most diagenetically altered part of a bone with high spatial resolution trace element concentrations rare earth element patterns and crystallinity of perio spots correlate throughout the scladina sedimentary sequence based on stratigraphic trends in bone chemistry and crystallinity we subdivide the scladina sequence into two successive periods of early diagenesis a period of later diagenesis and a transitional period between the early and later diagenesis periods the period boundaries also correspond to major climatic fluctuations identified in the site s stratigraphy by other means e g palynology and heavy mineralogy the stratigraphic provenance of nine cave bear femora support the confinement of reworking to within each of the diagenetic periods the provenance of two indeterminate faunal remains that visually resemble the taphonomic alteration of the scladina neandertal taphonomic proxies suggest that the individual may be significantly older than previously hypothesized evaluating the temporal integrity of exhumed assemblages and the original sedimentary context of bones with our method is thus a valuable addition to archaeological analyses especially beyond the temporal range of radiocarbon dating or in contexts with very low preservation potential of organic materials

the structure of mars lower atmosphere from mars express radio science mars occultation measurements 1 the mars express radio science experiment mars investigates the lower and middle atmosphere of mars between the surface and about 40 km with a very high vertical resolution more than 600 profiles of temperature pressure and neutral number density were retrieved between 2004 and 2011 covering four martian years mys 27 30 radio occultation experiments provide the unique possibility to retrieve geopotential height information to supplement temperature values the temperature field in the northern winter hemisphere displays strong temperature inversions indicating a pronounced polar warming in the northern polar night my 27 the temperature and geopotential fields imply the presence of a strong zonal jet with peak wind speeds of more than 170 m s at an altitude of about 30 km 15 pa and a latitude of 60 65 n the longitudinal temperature and geopotential fields in the southern winter of martian year 30 at latitudes between 49 and 69 s are dominated by a stationary zonal wave s 1 structure in the lower atmosphere associated meridional wind fields retrieved by assuming geostrophic balance have amplitudes up to 12 m s at the 200 pa level an investigation of small scale atmospheric waves reveals enhanced gravity wave activity in the daytime atmosphere above elevated terrain and in the winter extratropics radio occultation experiments also provide unique insight into the structure of the planetary boundary layer the deepest convective boundary layers up to 10 km are found over elevated terrain

microstructural evolution and deformation mechanisms of khao kho fault thailand abstract lithologies and microstructures of fault rocks from the khao kho fault in thailand are investigated to understand fault behavior and underlying deformation mechanisms fault gouges in the shear zone are mainly composed of kaolinite illite mica and illite smectite and exhibit weak preferred orientation ranging from 1 2 to 2 3 m r d these fault cores are characterized by high localized strain and intense deformation due to cataclasis and frictional granular flow mechanisms which produce transgranular fractures rounded quartz grains and an ultrafine clay matrix in contrast wall rocks show stronger clay preferred orientation up to 3 9 m r d despite having less clay content than the fault gouges much larger fault related bent and sheared clay grains are present in the wall rocks suggesting less severe deformation the discrepancy between fault cores and wall rocks indicate that the development of fabrics is related to faulting and authigenic processes weak fabrics in the slip zone are attributed to the comminution of grains and neomineralization allowing clay platelets to grow and rotate in many directions in addition the abundance of metal oxides indicates extensive multiple fluid alteration processes which further influence microstructures and fault properties

reports venus identification of banded terrain in the mountains of ishtar terra high resolution images obtained with the arecibo radar system at a wavelength of 12 6 centimeters reveal numerous parallel 10 to 20 kilometer wide bands of high radar backscatter situated on and oriented parallel to the major mountain ranges of the ishtar terra region of venus geometric and morphological characteristics suggest that the bands represent earth like tectonic deformational features such as folds and faults

the martian surface the past four years have been particularly fruitful for martian research as the enormous volumes of data collected during the viking mission became readily available to the general science community and as reformatting of the remote sensing data into cartographic products made the data more useable the 1 5 000 000 scale map series is complete and 1 2 000 000 scale controlled mosaics of the entire planet are nearing completion in addition 1 500 000 scale mosaics have been prepared of about thirty local areas a uniform scale digital imaging data base is in preparation batson 1986 and the infrared data have been reformatted to make it more accessible to the general user martin and kieffer 1985

bone diagenesis and origin of calcium phosphate nodules from a hominid site in the lukeino formation tugen hills kenya the lukeino formation 6 09 5 68 ma kenya is a fossiliferous fluvio lacustrine sedimentary sequence 100 m thick which yielded the fossil remains of the oldest east african bipedal hominid called orrorin tugenensis at one of the hominid sites aragai centimetric to pluri centimetric indurated calcium phosphate nodules occur in a specific sedimentary layer mineralogical and geochemical analyses coupled with sem optical microscopy and cathodoluminescence observations were performed on four calcium phosphate nodules and one bone showing differential alteration with characteristics locally similar to that of the nodules in order to determine the nature and origin of these nodules a crystallinity index ci and histological index hi were also assigned to these samples to characterize their degree of transformation analyses reveal that all nodules and the studied bone have a similar mineralogical and chemical composition nodules show no internal structure and are composed of a carbonate fluorapatite matrix including feldspars clays and spheres of iron and manganese oxides their high ci indicates significant recrystallization compared to modern bone the altered bone shows infilling of the trabecular cavities characterized by a clay deposit along the walls oxide spheres with a silica center and carbonate fluorapatite baguettes in the highly altered area of the bone a phenomenon of dissolution and dismantlement of bone structures adjacent to an area characterized by the presence of a phosphate matrix is observed the genesis of these calcium phosphate nodules seems to result from an advanced stage of transformation of bones due to a combination of physical chemical and biological bacterial processes the different stages of diagenesis are characterized by the incorporation of components from the sedimentary layer including diatoms and by neoformations of clays and oxides in the bone pores the bone structure is affected by fracturing and dissolution of carbonate hydroxylapatite which reprecipitated in bone cavities under the form of carbonate fluorapatite automorphic crystals then the bone structures and mineral neoformations were affected by a dismantlement phenomenon which increased the dissolution of the bone apatite this resulted in a carbonate fluorapatite matrix in which no trace of the initial bone structure is visible this particular mechanism of genesis of calcium phosphate nodules most probably takes place by action of fluid circulation in a confined environment such as a lake edge or marsh

viking bistatic radar experiment summary of results in near equatorial regions viking bistatic radar data have been processed using hagfors scattering function to obtain estimates of rms surface roughness b from ground tracks primarily in mars equatorial region roughness varies from as little as 0 75 rms east of solis and sinai plana to at least 8 on the western slope of arsia mons these values are appropriate to effective horizontal scales of about 25 m estimated roughness in cratered terrain is generally b 5 implying the existence of smoothing processes possibly aeolian on scales less than 100 m which are not apparent in orbital images there is good agreement between bistatic roughness estimates and earth based results at ground track intersections near the equator in both cratered terrain and plains surface tilt probability density functions derived from these observations are usually more sharply peaked than the hagfors function for similar values of b both the observed forms and the hagfors model are considerably sharper near 0 and fall off more slowly at large tilts than gaussian forms earlier results obtained using the gaussian model simpson and tyler 1981 appear to have overestimated surface roughness by 30 40 we infer that the true surface has more flat segments and more edges than does a gently undulating surface described by gaussian statistics

heterogeneous rare earth element ree patterns and concentrations in a fossil bone implications for the use of ree in vertebrate taphonomy and fossilization history abstract a bone fragment cgdq 3 of falcarius utahensis a therizinosaur from the early cretaceous cedar mountain formation utah contained within a carbonate nodule was analyzed by laser ablation inductively coupled plasma mass spectrometry la icp ms in order to investigate ree variability within a thin walled phalanx previous studies have found depth related ree pattern variations however in cgdq 3 variation occurs along the circumference of the bone nasc normalized ree patterns and concentrations vary between two apparent end members a light ree enriched lree pattern similar to solution icp ms analysis of this bone characterizes approximately two thirds of the bone fragment total ree concentrations are high and do not vary significantly from the periosteal surface to the medullar surface conversely the remaining one third of the bone has ree patterns that are mree depleted and low in total ree concentrations ree concentrations in this part of the bone do not vary significantly from the periosteal to the medullar surface a positive ce anomaly is found throughout the entire bone and is greatest within the lree enriched portion of the bone this in combination with the lree enrichment suggests that the bone fossilized under reducing conditions the distance between the lree enriched and mree depleted regions is less than 1 mm isotopic and petrographic analyses of the bone and surrounding carbonate matrix suggest the ree patterns in the bone were the result of partial fossilization incomplete filling of micro pore spaces around bone crystallites in an environment with changing redox conditions the lower mree depleted part of the bone fossilized contemporaneously with a pendant cement that formed on the underside of the bone in the vadose zone formation of the pendant cement restricted water flow through the bone isolating the lower portion which incorporated a mree depleted pattern the upper part of the bone lree enriched side fossilized under more reducing conditions than the lower part this resulted in reductive dissolution of minerals such as hydrous ferric oxides and manganese oxides which were lree enriched with positive ce anomalies these ree were then incorporated into the upper part of the bone this likely occurred after the bone entered the saturated zone below the water table the thinness of the bone and presence of a pendant cement helped facilitate partial fossilization of the bone preserving the ree signature of an earlier fluid as demonstrated by this case study differences in ree patterns within a fossil may record changes in geochemical conditions during fossilization particularly when bones are encased in a material that reduces fluid permeability such as micritic vadose calcite analysis of such bones may offer the opportunity to decipher complex fluid histories that occur during fossilization la icp ms should be utilized to confirm solution icp ms analysis if it yields high ree variability prior to an interpretation of reworking or time averaging

atomic scale transformation of bone in controlled aqueous alteration experiments abstract the chemical and isotopic compositions of biogenic apatite are important geochemical markers which can suffer modifications during fossilisation compared with modern ones fossil apatites generally exhibit variations in carbonate content enrichment in fluorine incorporation of trace elements and an increase in crystallinity parameters detailed understanding of these transformations induced by fossilisation should help assess the preservation of geochemical records in apatites in this contribution we investigate the transformation of modern bone altered under controlled conditions modern bone samples were soaked in aqueous solutions of neutral to alkaline ph 9 10 for one and three weeks at various temperatures 20 and 70 c and experiments were duplicated in fluorine free and in 10 2 m naf solutions bone transformation was monitored through the modifications of chemical f ca p and isotopic 13c 18oc 18op composition as well as using vibrational atr ftir raman and solid state 1h 13c 19f nmr spectroscopies the observed modifications sustain a transformation mechanism through partial dissolution of biogenic apatite and precipitation of secondary apatite this transformation occurs irrespective of the presence or absence of fluorine and leads to the formation of carbonate bearing fluorapatite or carbonate bearing hydroxylapatite respectively the fraction of secondary apatite seems to be limited to 60 suggesting that its formation has a protecting role against further dissolution of the primary apatite the observation of clumped co32 f defects in the structural b site of some samples as well as perturbation of the isotopic compositions attest to carbonate incorporation in the secondary apatite although the incorporation of fluoride ions can serve as a probe revealing dissolution recrystallization of bone the present study also underlines the difficulty to systematically relate mineralogical transformations to an open system behaviour in bioapatite

volcanism on mars more than 15 years of planetary exploration of mars have given insight into the geologic processes that have shaped its surface the newly acquired viking data have shown that volcanism is one of the most important geologic processes operating on mars throughout its history in situ chemical analyses of martian soil by the viking lander spacecraft indicate mafic to ultramafic source rocks this is consistent both with available remote sensing data which indicate the presence of mafic minerals such as pyroxene and olivine and with petrologic modeling based on available geophysical data which suggest that martian lavas are probably iron rich and ultramafic these data strongly suggest that basaltic volcanism is widespread on mars and much of the photogeological data may be studied in this context photogeological analysis of the martian surface has shown two main types of volcanic morphologies the first type is central volcanoes which are volcanic landforms developed by continued and prolonged eruption from a point source vent this category includes 1 shields the classic low profile volcanic mountains of which olympus mons is the most spectacular example 2 domes steep sided constructs such as tharsis tholus that may represent lower rates of eruption than the shields or possibly more silicic lava compositions 3 highland patera radially textured low profile volcanoes that occur in the cratered terrain and are interpreted as ash shields 4 alba patera an apparently unique volcanic landform consisting of a vast volcanic center over 1500 km across with flank slopes of less than a tenth of a degree and 5 various small features such as cinder cones the second major category is volcanic plains which are units recognized by several criteria of which the presence of mare ridges and flow lobes are the most useful volcanic plains are subdivided into four main groups 1 simple flows broad smooth to rolling plains that contain numerous mare type ridges but no flow lobes interpreted as being composed of thick single cooling units 2 complex flows displaying multiple overlapping flow lobes interpreted to be indicative of thin multiple cooling units 3 undifierentiated flows plains that typically lack any morphologic identifying feature but are considered to be volcanic partly on the basis of their association with large volcanic centers and 4 questionable plains volcanic units heavily modified by other processes erosion tectonism etc so that their origins are uncertain when these categories of volcanic morphologies are combined with relative age data provided by crater statistics a volcanic history for mars can be derived as follows early heavy bombardment of mars was accompanied and followed by small scale fluvial channeling extensive flood volcanism the plateau plains and ash shield volcanism in the cratered terrain shortly after this time less extensive flood volcanism continued to resurface the planet during formation of the northern southern hemisphere dichotomy central volcanism became more prominent with the development of the alba patera center as well as the older shields and domes of the northern hemisphere early tharsis and elysium regions the development of the tharsis and elysium uplifts may have triggered the release of large scale catastrophic floods producing large channels continued uplift and lithospheric thinning concentrated volcanic activity in the tharsis region producing large shield volcanoes and extensive lava plains both central vent and plains volcanism have been active throughout martian history but the volumes of extrusion have gradually decreased with time this is consistent with a moonlike thermal history involving a lithosphere of increasing thickness with time gradually turning off the volcanism although many questions remain regarding martian volcanism the viking data have provided a remarkable detailed overview of the probable nature of the volcanic history of mars

mars south polar spring and summer behavior observed by tes seasonal cap evolution controlled by frost grain size thermal emission spectrometer tes observations of the recession phase of mars south polar cap are used to quantitatively map this recession in both thermal and visual appearance geographically nonuniform behavior interior to the cap is characterized by defining several small regions which exemplify the range of behavior for most of the cap while temperatures remain near the co2 frost point albedos slowly increase with the seasonal rise of the sun then drop rapidly as frost patches disappear over a period of 20 days a cryptic region remains dark and mottled throughout its cold period tes observations are compared with first order theoretical spectra of solid co2 frost with admixtures of dust and h2o the tes spectra indicate that the cryptic region has much larger grained solid co2 than the rest of the cap and that the solid co2 here may be in the form of a slab the mountains of mitchel remain cold and bright well after other areas at comparable latitude apparently as a result of unusually small size of the co2 frost grains we found little evidence for a significant presence of h2o although co2 grain size may be the major difference between these regions incorporated dust is also required to match the observations a self cleaning process carries away the smaller dust grains comparisons with viking observations indicate little difference in the seasonal cycle 12 martian years later the observed radiation balance indicates co2 sublimation budgets of up to 1250 kg m 2 regional atmospheric dust is common localized dust clouds are seen near the edge of the cap prior to the onset of a regional dust storm and interior to the cap during the storm

chemistry microstructure petrology and diagenetic model of jurassic dinosaur bones dinosaur national monument utah abstract the fossil bone mineral in dinosaurs from the morrison formation is well crystallized stoichiometric francolite the closely packed subparallel francolite crystals have equidimensional cross sections mostly 10 40 nm wide in contrast crystallites in unaltered mammal bone tissue are poorly crystallized nonstoichiometric carbonate hydroxyapatite a few nanometers thick and plate rod or needle shaped the diagenetic francolite crystals are elongated in the c axis direction as are bone tissue crystallites along permeable cracks francolite crystals grew to 250 nm wide compared to unaltered crystallites in mammal bones the francolite has higher concentrations of ba ce cr f la mn ni pb rb sr th u v and y and perhaps zr na and mg are lower in concentration diagene ic francolite grew from groundwater enriched in ions from silicic ashes in the brushy basin member and from dissolution of bone tissue crystallites after burial francolite grew on crystallite seeds filling the space formerly occupied by collagen perhaps half the tissue volume and dissolved crystallites the micron scale structures such as haversian canals and laminae are preserved because the diagenetic francolite retains the orientations of the seeds the laminae 1 10 m thick commonly preserve an orthogonal plywood structure the diagenetic growth of francolite during this type of bone fossilization implies that oxygen isotopic ratios measured in dinosaur bones even those that appear fresh and unaltered may dominantly reflect groundwater temperature rather than dinosaur body temperature trace element concentrations in the francolite may reflect groundwater composition rather than dinosaur diet pore filling cements precipitated in the sands and bones at shallow burial depths as evidenced by the 35 52 minus cement porosities of the sandstones and numerous uncompacted oversize pores filled by cements gypsum and calcite were precipitated from shallow alkaline groundwater as the groundwater became increasingly dominated by ions from silicic ash argentite chalcopyrite native gold native silver tiemannite and uraninite replaced areas of bone a few microns to tens of microns in size along cracks a thin chlorite crust commonly mantled francolite crystals along bone cracks and lined openings in bones and sandstones pervasive precipitation of a chalcedony crust followed with pseudomorphs of chalcedony after gypsum in larger cancellous openings the remaining space was fi led by the various forms of silica the bones are brown due to goethite filled cracks that cut pore filling minerals

tectonics and evolution of venus the global tectonics of venus differs significantly from that of earth most markedly in that the surface is covered predominately by gently rolling terrain there apparently are no features like ocean rises the gravity is positively correlated with topography at all wavelengths and the few highlands are estimated to be supported or compensated at a depth of approximately 100 kilometers the surface of venus appears to be covered mainly by an ancient crust the high surface temperature making subduction difficult it seems likely that well over 1 billion years ago water was destabilized at the surface and soon after plate tectonics ceased the highlands appear to be actively supported presumably as manifestations of long enduring hot spots

large southward motion and clockwise rotation of indochina throughout the mesozoic paleomagnetic and detrital zircon u pb geochronological constraints abstract we report a combined paleomagnetic and u pb geochronologic study of sedimentary rocks from the huai hin lat and nam phong formations of mesozoic age in ne thailand in order to provide independent constraints on the tectonic movement of the indochina block during convergence of the major blocks now comprising east asia the maximum allowable depositional age of the two formations is estimated to be 227 ma and 215 ma respectively from detrital zircon u pb geochronologic analysis which also indicates a sediment source transition in the khorat plateau basin during the middle late jurassic a formation mean paleomagnetic direction of d g i g 21 4 38 1 k g 19 5 95 9 6 before and d s i s 43 0 48 0 k s 47 4 95 6 1 n 13 after tilt correction is derived from samples with different lithologies bedding attitudes magnetic carriers and polarities and yields a positive fold test hence the magnetization is likely primary the revised mesozoic apwp of the indochina block yields paleolatitudes for a reference site of 22 n 102 e of 33 4 7 2 n during the norian late triassic 25 9 5 9 n during the late triassic to early jurassic 23 9 8 n during the late jurassic to early cretaceous 27 5 3 2 n during the early cretaceous and 24 5 4 9 n by the late cretaceous corresponding declinations are 45 2 8 6 38 0 6 6 36 3 8 8 29 6 3 6 and 24 9 5 4 respectively these data indicate a significantly southward displacement accompanied by clockwise rotation during the mesozoic a reconstruction of the indochina block within the now well studied merging process of south china and north china indicates that the indochina block was located at a higher latitude than the south china block during the norian stage of late triassic times whilst no significant relative poleward displacement apparently occurred during the early jurassic to early cretaceous interval our study supports a post cretaceous tectonic extrusion model with a southeastward displacement of indochina with respect to the south china block estimated to be 1000 850 km since the late cretaceous

calcium isotope fractionation upon experimental apatite formation abstract carbonated hydroxy apatite ca10 b nh4 k na 2b po4 6 y co3 2x 3 2 y oh 2 2x chap was synthesized in batch type experiments by mixing of calcium ca and phosphate bearing aqueous solutions and the transformation of calcite powder in aqueous solution between 11 and 65 c compositional changes of the mother solution and solid phase products were followed by powder xrd scanning electron microscopy sem edx raman spectroscopy and elemental analysis it was found that the transformation at ph values between 7 5 and 7 9 occurs via the dissolution of calcite followed by the precipitation of chap in the mixing approach crystallization of chap took place via precipitation of metastable brushite cah po4 2h2o as precursor phase that was further transformed into apatite calcium isotope fractionation led to an enrichment of the light isotope by about 0 5 to 1 1 in the solid chap compared to the aqueous solution consistently in all experimental approaches essentially independent of temperature in some experiments metastable brushite formed prior to transformation to chap and showed a reduced fractionation compared to the chap the observed ca isotope fractionation into the chap lattice resembles that of natural phosphorites and lies within the range of recently published experiments

mars dual polarization radar observations with extended coverage abstract thirteen centimeter wavelength radar observations of mars made in 1982 at arecibo observatory yield accurate measurements of the full backscatter spectrum in two orthogonal polarizations the data which were obtained for several widely separated subradar longitudes at 24 n latitude provide the first global view of the distribution of small scale surface roughness on mars the diffuse component of the echo exhibits strong spatial variations areas of maximum depolarization correlate well with volcanic regions tharsis and elysium while the heavily cratered upland terrain yields relatively low depolarization parts of tharsis give near complete depolarization polaziation ratio c 1 when viewed at oblique angles of incidence northern martian plains regions tharsis elysium and amazonis may comprise the most extensive area of severe decimeter scale surface roughness in the inner solar system on the average the northern martian tropics yield higher diffuse radar cross sections d 0 05 0 12 and a higher of degree disk integrated depolarization c 0 1 0 4 than is found for the moon mercury and venus comparisons between the moon and mars using radar data ground truth and simple scattering models suggest that mars possesses a relatively high average coverage by decimeter scale rocks also discussed are several of the more interesting quasispecular scattering results the most unsual of which were obtained over the olympus mons aureole region

alteration of enamel carbonate environments during fossilization an understanding of enamel diagenesis is necessary to ensure sound isotopic palaeodietary and palaeoenvironmental reconstructions although carbon isotope signals of browsing and grazing herbivores remain distinct in enamel even after millions of years subtle alteration of isotopic signatures does occur to better understand this change we analysed modern and fossil enamel from a number of south african sites using fourier transform infra red spectroscopy our results indicate that while there is little evidence of increased crystallinity in fossil enamel there is a small but significant change in the proportion of carbonate ions occupying hydroxyl and phosphate sites this seems to occur early in the process of fossilization after which there is no noticeable change it is also important to note that the degree of alteration varies significantly within and between sites we suggest that this change results from one or some combination of three mechanisms exogenous carbonate incorporation endogenous carbonate loss and endogenous carbonate reorganization determining which mechanism s contribute to this alteration is important because all three are likely to affect biogenic carbon isotope ratios differently ftir spectroscopy promises to increase our knowledge of diagenesis and in so doing should improve our palaeodietary and palaeoenvironmental reconstructions

on the possibility of plate tectonics on venus abstract several arguments have been put forward suggesting that venus has no place tectonics we examine some of these arguments and suggest that because conditions on the surface of venus are very different from those on earth the arguments should be reconsidered we show that in the absence of an ocean the differential hypsographic curve of earth would probably have only one mode like that for venus we show that the atmosphere of venus is quite capable of erosion provided that near surface velocities are about 1 m sec 1 or more and that therefore the oceanic areas on venus should they exist are probably covered with some thickness of sediment if sedimentation on venus is at all rapid it is likely that subduction zones could be filled up and made unrecognizable topographically because venus does not have an ocean and because its surface temperature is much greater than that on earth ridge crests on venus have a much smaller topographic expression than those on earth if significant sedimentation occurs they would be completely unrecognizable topographically

the first palynological records from the lower cretaceous of the northern sichuan basin china palynostratigraphical and paleoenvironmental significance abstract majority of the aeolian deposits that are widely distributed throughout the low latitudes during the cretaceous have been considered to be the result of downdraft influence controlled by the subtropical high pressure belt however a lack of relevant fossil material has hindered both the chronostratigraphic framework of these deposits and the reconstruction of their corresponding palaeoenvironments this study presents detailed palynological records from two drillcores through the lower cretaceous canxi and bailong formations in the sichuan basin southwest china classopollis pollen followed by the bisaccate conifer pollen together with other rare types of palynomorph dominate the palynological assemblages that are recorded within some age diagnostic palynomorphs especially dicheiropollis indicate an age of valanginian to hauterivian for the cangxi and bailong formations classopollis dominated palynoflora indicate an extremely dry climate for this part of the history of the sichuan basin region in addition the occurrence of dicheiropollis indicates that the sichuan basin should belong to the dicheiropollis province that surrounds the tethys ocean which implies that the tethys ocean may have exhibited a stronger climatic impact on the sichuan basin regions as compared to that exhibited by the pacific ocean

variability of mars north polar water ice cap i analysis of mariner 9 and viking orbiter imaging data abstract previous studies interpreted differences in ice coverage between mariner 9 and viking orbiter observations of mars north residual polar cap as evidence of interannual variability of ice deposition on the cap however these investigators did not consider the possibility that there could be significant changes in the ice coverage within the northern residual cap over the course of the summer season our more comprehensive analysis of mariner 9 and viking orbiter imaging data shows that the appearance of the residual cap does not show large scale variance on an interannual basis rather we find evidence that regions that were dark at the beginning of summer look bright by the end of summer and that this seasonal variation of the cap repeats from year to year our results suggest that this brightening was due to the deposition of newly formed water ice on the surface we find that newly formed ice deposits in the summer season have the same red to violet band image ratios as permanently bright deposits within the residual cap we believe the newly formed ice accumulates in a continuous layer to constrain the minimum amount of deposited ice we used observed albedo data in conjunction with calculations using mie theory for single scattering and a delta eddington approximation of radiative transfer for multiple scattering the brightening could have been produced by a minimum of 1 a 35 m thick layer of 50 m sized ice particles with 10 dust or 2 a 14 m thick layer of 10 m sized ice particles with 50 dust

high resolution records of location and stratigraphic provenance from the rare earth element composition of fossil bones abstract bone apatite acts as a natural timed sampling device scavenging trace elements from local pore waters over timescales of ca 1 50 ka the rare earth element ree and u th composition of fossil bones reflects associated pore water compositions during the period of recrystallisation the ree composition of fossil bones is controlled by partitioning of ree between pore waters and particle surfaces and the ree composition of fossil bones reflects the ree composition of pore waters which vary spatially and temporally light ree are preferentially sorped onto particle surfaces thus the high la yb values seen in many bones from coastal marine and aeolian environments are best explained by release of ree from light ree enriched particles to local pore waters and subsequent immobilisation in recrystallising bones the ree compositions of bones recovered from pedogenically altered diatomite sediments of the olorgesailie formation of southern kenya vary over spatial scales of less than 10 m location accounts for 48 of the observed variation in bone chemistry and bones recovered from eight discrete excavations within the same time equivalent stratigraphic layer can be assigned to their excavation location with 70 accuracy based on a discriminant analysis of ree u and th composition despite this within layer variation bones recovered from different stratigraphic horizons within the olorgesailie formation can also be distinguished on the basis of their trace element composition bones recovered from four stratigraphic horizons spanning ca 0 5 million years were assigned to their correct stratigraphic layer with 90 accuracy where sedimentological conditions are favourable the trace element composition of fossil bone may be used to test stratigraphic provenance and burial location in excavated bone with a temporal resolution of

solubilities of bone mineral from archaeological sites the recrystallization window abstract bone mineral solubility is an important parameter for understanding the preservation of bones in the archaeological and palaeontological records in this study we have measured the solubility of the carbonated hydroxyl apatite of sub recent and fossil bones as well as synthetic hydroxyl apatite in deionized water and in ph buffered solutions the solutions were open to the atmosphere and the ph values were around neutral measurement conditions that are relevant to bone mineral preservation in nature but that were absent from most previous studies we obtained internally consistent results from both the water and the buffered experiments supporting the notion that we are measuring an inherent property of the mineral phase we found that bone mineral is much more soluble than synthetic hydroxyl apatite we measured the ionic activity products at steady state conditions and we identify a recrystallization window between ph 7 6 and 8 1 which defines the conditions under which bone crystals dissolve and reprecipitate as a more insoluble form of carbonated hydroxyl apatite as these conditions are common in nature most fossil bones will not maintain their original crystals with time we also found that bones that contained small amounts of calcite did not dissolve at all during our experiments these results provide a basis for better understanding the conditions in sediments under which bones are preserved and the relative states of preservation of bone they also have important implications for the selection of the most appropriate bone samples for paleoenvironmental and paleodiet analyses and dating

ancient and modern slopes in the tharsis region of mars the directions of lava flows in the tharsis region of mars are used to identify regional palaeo slopes vent areas and local topography a comparison is made between these flow directions and the present day radar measured topography good agreement between these data sets indicates that little infra regional tectonic deformation has occurred following the emplacement of the preserved lavas

evaluating the consequences of diagenesis and fossilization on bioapatite lattice structure and composition abstract changes to hydroxylapatite mineral structure composition and lattice configuration must occur during the transformation of fresh bone to fossil bioapatite mineral phases a paucity of analytical methods to characterize atomic level lattice composition and bonding arrangements in modern and fossil bone has resulted in limited knowledge of how depositional environments and thus diagenetic conditions may influence fossilization processes synchrotron based analyses can provide insight into bone fossilization specifically x ray absorption near edge structure xanes spectroscopy at the p and ca k edges to aid in the interpretation of xanes spectral data from modern bones and from late neogene and late cretaceous fossil bones we applied other established techniques used to characterize bone mineralogy and composition including x ray diffraction fourier transform infrared spectroscopy electron microprobe analysis and thermal analysis specific bone depositional origins and ages likely influenced the varying elemental chemistry preservation of organic matter and mineral content fossilized bones ranging from an almost pure fluorapatite to carbonated fluorapatite mineral phases had less preserved organic material than modern bone the atomic level p and ca lattice structures of fossilized bones differed from modern bones specifically having shifted and shortened ca o bonds due to ca 2 substitution by ionic phases such as iron or rare earth elements and carbonate substitution for phosphate the modified lattice structure regardless of bulk mineral chemistry provides thermodynamic stability in geochemically dynamic depositional environments that may dictate bioapatite preservation over geologic time

petrography mineralogy and geochemistry of cretaceous sediment samples from western khorat plateau thailand and considerations on their provenance abstract at mo hin khao on the western flank of khorat plateau thailand the phra wihan formation reveals litharenite and sublitharenite with some subarkose and arkose a cuesta in the eroded sedimentary sequence exhibits spectacular rock pillars of considerable geotourist potential the rock sequence is high in silica sio2 67 98 wt and contains quartz mica magnetite chert fragments and accessory minerals such as zircon and tourmaline and amphibole species these accessory minerals suggest felsic rocks such as granite granodiorite and pegmatite were sources for the sandstones geochemical analyses of the sedimentary sequence suggest that source rocks may lie in the passive continental margin before sediment transport and deposition in the khorat basin by rivers flowing across a large flood plain many depositional sequences episodes formed thick beds of cross bedded clastic rocks a high average maturity index 5 indicates sedimentary reworking recycling chemical index of alteration cia values range from 47 to 98 suggesting variable chemical weathering within the source area rocks largely representing moderate to high degrees of weathering the average cia value of these sediments 78 suggests that relatively extreme alteration factors were involved

radar images of mars full disk images of mars have been obtained with the use of the very large array vla to map the radar reflected flux density the transmitter system was the 70 m antenna of the deep space network at goldstone california the surface of mars was illuminated with continuous wave radiation at a wavelength of 3 5 cm the reflected energy was mapped in individual 12 minute snapshots with the vla in its largest configuration fringe spacings as small as 67 km were obtained the images reveal near surface features including a region in the tharsis volcano area over 2000 km in east west extent that displayed no echo to the very low level of the radar system noise the feature called stealth is interpreted as a deposit of dust or ash with a density less than about 0 5 gram per cubic centimeter and free of rocks larger than 1 cm across the deposit must be several meters thick and may be much deeper the strongest reflecting geological feature was the south polar ice cap which was reduced in size to the residual south polar ice cap at the season of observation the cap image is interpreted as arising from nearly pure co 2 or h 2o ice with a small amount of martian dust less than 2 percent by volume and a depth greater than 2 to 5 m only one anomalous reflecting feature was identified outside of the tharsis region although the elysium region was poorly sampled in this experiment and the north pole was not visible from earth

xenoxylon a boreal fossil wood in the mesozoic redbeds of southeast asia potential for the stratigraphy of the khorat group and the palinspatic reconstruction of southeast asia abstract the fossil wood genus xenoxylon is reported in situ for the first time in thailand it originates from the indosinian terrane from the mesozoic continental redbeds of the phu kradung formation khorat group palinspatic reconstruction palaeobiogeography and correlation with other occurrences of the genus in southern china as well as in vietnam suggest a middle to late jurassic age for the phu kradung formation level yielding the fossil wood the dating of this formation is still controversial and thus our data is an important step towards a better understanding of its geological history and palaeoecology as well as of the southeast asia mesozoic continental redbeds significance for the evolution of the vertebrates

identification of an anastomosing river system in the early cretaceous khorat basin northeastern thailand using stratigraphy and paleosols abstract the phu kradung and phra wihan formations of the early cretaceous khorat group were investigated to characterize the depositional system and paleoclimate based on stratigraphy paleosol features paleosol profiles and reworked deposits the sediments of both formations are classified into 12 facies on the basis of their primary depositional attributes such as bedding grain size texture and sedimentary structures furthermore these facies are grouped into eight architectural elements based on stratigraphic relationships and outcrop scale macroforms the proportions of each architectural element indicate that the depositional system was that of an anastomosing river the anastomosing river system in the studied section is characterized by a high rate of vertical floodplain aggradation and the development of a relatively stable crevasse channel paleosols are developed mainly in floodplain deposits and are characterized by the development of calcretes a semi arid to sub humid paleoclimate is deduced from the occurrence of the calcretes in addition their microstructures suggest that these calcretes were formed under several different conditions with micritic carbonate precipitating under relatively arid climates and alveolar septal structures under semi arid to sub humid conditions using the thicknesses of the calcrete horizons we conclude that the difference in the amount of precipitation between the wet and dry periods was highly variable without any order during deposition of the studied section the thicknesses of intervals between successive calcrete horizons indicate that the inflow of fine materials occurred randomly across the floodplain partly superimposed multiple calcrete horizons were developed during periods of low sediment supply a random deposition of floodplain sediments appears to characterize the anastomosing river system of the khorat basin

dinosaur bones fossils or pseudomorphs the pitfalls of physiology reconstruction from apatitic fossils abstract a prerequisite to any attempt to reconstruct thermophysiology of ancient animals through analysis of stable isotopes of oxygen is the assumption that apatitic fossils are isotopically unaltered parts of their original skeletons we suggest that sufficient evidence is available to seriously question this assumption because living bones contain about 1 3 by weight of organic matrix mass balance considerations show that at least half of an apatitic fossil must be new material added post mortem furthermore living apatitic skeletons contain almost no rare earth elements and uranium whereas apatitic fossils bear high concentrations of these elements additionally we found that while in living fish correlation between 18o of oxygen in the phosphate and that in the carbonate of apatite is poor these two values are linearly correlated in fossil fish this suggests diagenetic recrystallization has taken place perfect preservation of micro textures such as haversian canals does not prove the pristine condition of a fossil some of the most beautifully preserved fossils are highly silicified most apatitic fossils probably are pseudomorphs replacing original skeletal elements whereas distribution of stable isotopes of oxygen in fossils might provide information about their burial environment it could be misleading in attempts to interpret the organisms physiology this cautionary note is supported by the similarity of 18op in bones of coexisting fossil fish dinosaurs and various other reptiles at different latitudes the overlap of predicted 18op values in fish and mammals living in contact with the same environmental water also weakens the hope that ectotherms can be distinguished from endotherms by the isotopic composition of oxygen in their bones and teeth

early diagenetic evolution of bone phosphate an x ray diffractometry analysis abstract a new crystallinity index ci based on the x ray powder diffractometric pattern of fossil bone carbonate hydroxylapatite is defined this ci value provides a semi quantitative way to estimate the diagenetic changes in archaeological and palaeontological bone phosphate the studied samples are 71 human bones from the french merovingian cemetery of saint linaire 1200 1700 bp 37 human bones from two necropoleis in niger 1000 5000 bp two cave bear bones from aldene cave southern france around 70 000 bp five bones of miocene mammals and 14 bones of mesozoic reptiles the main results are that 1 there is no correlation between the increase in the ci and the age of the sample even in one given locality 2 the ci seems to be related to the taphonomical conditions in archaeological and fossil bones 3 an increase in the ci is correlated with a loss in organic matter in one archaeological site but the quality of preservation of organic matter in fossil bones does not depend on the changes in the ci 4 the correlation between the increase in the ci and the decrease of co3amount in bones from the niger necropolies suggests a possible mechanism for the increase in crystallinity the changes of crystallinity reflect early diagenetic changes and depend on the burial environments

lunar craters with radar bright ejecta abstract a small fraction of the lunar impact craters with diameters of 1 km and greater have extensive enhanced 3 8 cm radar echoes associated with their ejecta deposits the physical properties of these ejecta deposits and the ages of the central craters have been characterized via various infrared radar and optical signatures most of these ejecta deposits are radar bright at the 3 8 cm wavelength but are not radar bright at the 70 cm wavelength some ejecta have large infrared signatures others do not although most of these ejecta have bright albedos in full moon photographs a significant fraction of the bright albedo markings do not extend beyond the crater this mix of remote sensing signatures indicates that craters with 3 8 cm radar bright halos are young and have ejecta deposits containing an excess of surface or near surface rocks relative to the surrounding terrain abundant centimeter sized rocks are inferred from the high 3 8 cm radar and infrared signatures the low 70 cm radar signatures indicate that larger blocks are much less numerous the population of craters with 3 8 cm radar bright craters on the moon is much smaller than the population of craters in a similar size range on a young mare oceanus procellarum and has a different slope this population is interpreted as a steady state population reflecting a balance between the production of fresh craters and the destruction of the high infrared and radar signatures by small scale cratering the slope of difference between visual and radar craters is attributed to more rapid destruction of the radar signatures in smaller craters relative densities of 3 8 cm radar bright craters and mare craters are estimated to be 0 04 in 0 042 0 016 at a 4 km diameter and 0 100 0 07 0 007 at a 32 km diameter assigning ages on the basis of these relative densities raises the question of whether the 4 to 32 km diameter visual crater population is truly representative of a 3 3 by age if it is and if crater rates between 3 3 by and the present have been uniform than the 3 8 cm radar crater lifetimes are estimated to be 0 13 0 04 0 25 by and 0 03 0 13 0 23 by at diameters of 4 and 32 km respectively similarly lifetimes of the infrared signatures of 4 km diameter craters may be as short as 10 7 years however some data suggest that these estimates may be in error by a factor of 5 too small comminution of blocky ejecta material and the smoothing of slopes by lunar surface processes could account for the elimination of radar signatures on these time scales and the development of a steady state crater population an altenative interpretation which we do not fsvor is that the 3 8 cm radar bright crater population is formed by a subpopulation of primary bodies or by secondary cratering

selection of the mars pathfinder landing site the mars pathfinder spacecraft will land on a depositional fan near the mouth of the catastrophic outflow channel ares vallis 19 5 n 32 8 w this site offers the prospect of analyzing a variety of rock types from the ancient cratered highlands intermediate age ridged plains and reworked channel deposits analyses of these rocks by pathfinder instruments will enable first order scientific questions to be addressed such as differentiation of the crust the development of weathering products and the nature of the early environment as well as their subsequent evolution on mars constraints imposed by 1 spacecraft and rover designs which are robust 2 entry descent and landing 3 scientific potential at various sites and 4 safety were important considerations in site selection engineering constraints require a 70 km by 200 km smooth flat low slopes area located between 10 and 20 n that is below 0 km elevation with average radar reflectivity little dust and moderate rock abundance three regions on mars are between 10 and 20 n and below 0 km elevation chryse amazonis and isidis elysium science considerations favor sites at the mouths of outflow channels grab bag sites offer an assay of rock types on mars highland sites early crustal differentiation and climate and sites covered with dark unoxidized material sites are considered safe if they are clearly below 0 km elevation appear acceptably free of hazards in high resolution 50 m pixel viking orbiter images and have acceptable reflectivity and roughness at radar wavelengths thermal inertia rock abundance red to violet ratio and albedo recent 3 5 cm wavelength radar observations were used to verify elevation reflectivity and roughness within the landing ellipses three sites meet all of these criteria ares vallis tritonis lacus and isidis although isidis appears to be safer than tritonis and ares the greater scientific potential at ares vallis resulted in its selection comparisons of the grand coulee channel and the depositional ephrata fan of the channeled scabland in eastern washington with ares vallis and its depositional fan also suggest the ares vallis landing site is safe and scientifically interesting

planetary radar astronomy planetary radar research reported during 1979 1982 was highlighted by radar observations of venus by the pioneer venus spacecraft earth based high resolution imaging of venus and the moon construction of accurate topographic profiles for martian tropical regions observational and theoretical advances in relating the radar signatures of mars and the moon to surface characteristics and the initial radar detections of echoes from a comet and a mainbelt asteroid this review begins with a brief synopsis of radar definitions and technical terminology and then summarizes recent results for individual targets readers interested in radar astronomy prior to the current quadrennium are directed to excellent reviews by jurgens 1982a pettengill 1978 evans 1969 muhleman 1966 and pettengill and shapiro 1965 detailed descriptions of planetary radar techniques include pettengill 1970 and evans and hagfors 1968

viking bistatic radar experiment summary of first order results emphasizing north polar data abstract bistatic radar observations of mars north polar region during 1977 1978 showed surface rms slope ranging from 1 to 6 these values apply to horizontal scales of 1 100 m values of roughness tend to decrease with increasing latitude especially over 65 80 n but there are many exceptions the smoothest surfaces 1 appear to be inclusions within generally rougher 3 terrain rather than broad expanses of very smooth material the permanent north polar cap is relatively uniform with 2 5 3 0 considerable structure has been found in echo spectra indicating a heterogeneous and perhaps anisotropic scattering surface echo spectra obtained from the same region but several months apart 1 l s

radar measurement of small scale surface texture syrtis major recent radar observations of syrtis major have shown it to be smooth and relatively homogeneous when sensed at centimeter wavelengths there is a gradual decrease in surface roughness east to west across the basin which correlates with an apparent decrease in small 1 km diameter crater density root mean square surface slopes range from more than 1 5 2 0 in the east to less than 0 5 along the western margin at 12 6 cm the surface appears somewhat rougher at 3 6 cm a 0 3 dependence is inferred radar reflectivity increases from about 5 to about 12 across syrtis major being greatest near the western margin high resolution 8 to 20 m pixel viking images suggest that an increasing amount of resurfacing has occurred in western syrtis major compared with the eastern parts the radar infrared and optical imaing evidence are consistent with resurfacing by geologically recent low viscosity lavas which were subsequently mantled by thin layers of aeolian material each data set may be taken as a unique source of scale dependent information on surface materials and properties from comparison of radar derived surface roughness with image derived crater density curves we conclude that processes other than cratering control the surface texture on 0 03 to 100 m surface scales

patterns of diagenesis in bone i the effects of site environments abstract we have measured a suite of diagenetic parameters for several populations of archaeological bones buried in a number of northwest european sites since the last ice age these are the structural damage due to microbes changes in bone micro and macro porosity protein content a measure of the crystallinity of hydroxyapatite as reflected in the phosphate infra red spectrum peak splitting and a measure of the carbonate content as given by the ratio of carbonate to phosphate infra red absorption peaks the results provide a database that clearly characterises the patterns which are often site dependent of diagenetic change in buried bone our main conclusions are that individual site hydrology appears to have a strong influence on the outcome of bone preservation and that porosity is the most effective single diagenetic parameter which both determines and reflects the preservation of bone in the burial environment

paleobiology and skeletochronology of jurassic dinosaurs implications from the histology and oxygen isotope compositions of bones fossil biogenic phosphate of fast growing primary bone tissue of dinosaurs can preserve a histologic and isotopic time series of annual seasonality in temperature variations similar to tooth enamel and other accretionary skeletal phases such as corals or wood on two bone fragments from sympatric dinosaurs with different histologic patterns of bone growth high resolution oxygen isotope profiles were analyzed along the radial direction of bone growth the investigated specimens are from the jurassic shishugou formation in the junggar basin nw china and have distinct patterns of compositional variation a fibrolamellar dinosaur bone with multiple lines of arrested growth lags and periodic growth cycles of decreasing bone laminae thickness displays a cyclic intra bone variation in 18o values of about 2 corresponding with the lags these growth cycles in fast growing fibrolamellar bone provide evidence for seasonal growth of dinosaurs in lower latitudes 45 n possibly influenced by a monsoon type paleoclimate seasonal changes in temperature and water supply are consistent with the oxygen isotope composition measured in dinosaur bone phosphate as well as with growth rings in contemporaneous fossil conifer wood from the same locality in contrast a plexiform sympatric sauropod bone displays continuous growth free of lags and has a lower intra bone variation of 0 8 differences in bone histology are also reflected in the oxygen isotopic composition and its intra bone variability indicating different physiological responses to external climatic stress between sympatric dinosaur species seasonal intra bone oxygen isotope variations combined with bone histology may thus yield new insights into species specific response to climatic stress and its influence on dinosaur growth formation of growth marks growth rates as well as dinosaur thermophysiology

dark material in the polar layered deposits and dunes on mars viking infrared thermal mapping and bistatic radar data suggest that the bulk density of the north polar erg material is much lower than that of the average martian surface or of dark dunes at lower latitudes we have derived a thermal inertia of 245 280 j m 2 s 1 2 k 1 5 9 6 7 10 3 cal cm 2 s 1 2 k 1 for the proctor dune field and 25 150 j m 2 s 1 2 k 1 0 6 3 6 10 3 cal cm 2 s 1 2 k 1 for the north polar erg the uniqueness of the thermophysical properties of the north polar erg material may be due to a unique polar process that has created them the visible and near infrared spectral reflectance of the erg suggests that the dark material may be composed of basalt or ferrous clays these data are consistent with the dark material being composed of basaltic ash or filamentary sublimate residue fsr particles derived from erosion of the layered deposits dark dust may be preferentially concentrated at the surface of the layered deposits by the formation of fsr particles upon sublimation of water ice further weathering and erosion of these areas of exposed layered deposits may form the dark saltating material that is found in both polar regions dark fsr particles may saltate for great distances before eventually breaking down into dust grains re mixing with the global dust reservoir and being recycled into the polar layered deposits via atmospheric suspension

a comparison of the thermal and radar characteristics of mars abstract there is a correlation between martian thermal inertia and radar cross section data centered on 22 latitude the correlation is strongest with 70 cm radar except between longitudes 10 and 90 where there is a slight anticorrelation and gets progressively weaker at 12 5 and 3 8 cm wavelengths respectively a correlation is expected because of the dependence of both properties on density but an increase in the average particle size of the surface with increasing dielectric constant is also required in order to explain the data this may take the form of an increased number of small rocks the anticorrelation may result from either the effects of atmospheric dust on the surface temperature or from the effects on radar of local variations in large scale roughness or scattering by rocks the relative behavior between the wavelengths can be understood in terms of appropriately sized rocks which act as radar scatterers the trend of the correlation agrees with the dichotomy of the planet into two types of terrain as noted in other remote sensing data and is consistent with an erosional versus depositional surface nature variations in the surface dielectric constant inferred from the 3 8 cm radar data can explain discrepancies between 2 8 cm radio emission observations and a simple model based on the global distribution of thermal inertia and albedo

reconstructing diagenetic conditions of bone at the gray fossil site tennessee usa abstract the preservation of vertebrate fossils requires transformation of the original bioapatite mineral matrix predominantly hydroxylapatite during diagenesis into a thermodynamically more stable phase fossil bone geochemistry and structure provides a wealth of information on the conditions present during diagenesis including site redox and ph and about sedimentation rates during burial the gray fossil site preserves late neogene lacustrine deposits that serve as one of a few records of north american paleoclimate during a critical period of the cenozoic despite having 40 vertebrate species and diverse plant assemblages none of the prior studies used bone composition to understand what paleoenvironmental and diagenetic conditions must have been like to facilitate bone preservation and fossilization alligator sp phalanges were examined using multiple geochemical tools including fourier transform infrared spectroscopy x ray diffraction and electron microprobe analyses evidence of bioerosion within thin cortical and isolated trabecular regions of bone suggests biotic utilization of organics collagen and or the mineral s following deposition chemically zoned and laminated cortical alligator bone is interpreted as preserved lines of arrested growth that developed during life and supports previous interpretations of a regional seasonal climate lastly the alligator bones are mineralogically heterogeneous as fluorinated and iron containing apatite phases compared to modern bone iron concentrations were high at up to 3 wt the uptake of fe by the alligator bones examined in this study suggests that fluids present during diagenesis that led to bone preservation within the lacustrine sediment at the gray fossil site were likely acidic anoxic and reducing

venus global surface radar reflectivity observations of the surface of venus carried out by the pioneer venus radar mapper at a wavelength of 17 centimeters reveal a global mean reflectivity at normal incidence of 0 13 0 03 over the surface variations from a low of 0 03 0 01 to a high of 0 4 0 1 are found with theia mons previously identified as possibly volcanic showing a value of 0 28 0 07 regions of high reflectivity may consist of rocks with substantial inclusions of highly conductive sulfides

a geochemical method to trace the taphonomic history of reworked bones in sedimentary settings rare earth element ree signatures can be used to identify the original mode of deposition of fossil bones and teeth that have been reworked this new technique may resolve the notoriously difficult problem of assessing the amount of transport or reworking undergone by fossil bones and teeth on the basis of physical parameters such as degree of abrasion different ree signals characterize different pore water environments bones and teeth composed of apatite incorporate rees rapidly during early diagenesis and the ree signature in the bone is controlled by that of the surrounding pore waters reworked bones and teeth may show ree traces suggesting early diagenetic pore water conditions different from those indicated by in situ sedimentary or geochemical evidence this situation is demonstrated in a case study from the rhaetian latest triassic of southwest england where different bone beds are compared in one case the original environmental setting of reworked bone is traced by matching ree traces with contemporaneous unreworked bone assemblages in neighboring areas

gecko global events impacting conodont evolution abstract with a record that spans approximately 300 million years late cambrian through the triassic jurassic transition i e the conodontozoic conodonts witnessed all principal events in the evolution of life on earth from the invasion of the land to the exploration of the air from the explosion of biomineralization in the oceans to the rise of dinosaurs and mammals including three of the major extinction events that occurred in the phanerozoic mainly used for biostratigraphic or geochemical studies the potential of conodonts to help unravel changes perceived to be of global extent rarely has been explored while specialists have identified rapid changes in conodont element morphology throughout their history the conodont animal has often been perceived to have been a static entity in a constantly evolving world when biological equilibrium in the oceans was undergoing profound alteration and faunal recoveries took place in phases that seem to have had recurrent patterns it is now essential that we begin to further investigate how conodonts as biologic entities responded to or were impacted by palaeogeographic changes eustatic and climatic fluctuations shifting redox conditions and major faunal turnovers and reorganizations that took place during the conodontozoic

burning and boiling of modern deer bone effects on crystallinity and oxygen isotope composition of bioapatite phosphate abstract the extent of preservation of stable isotope compositions in biomaterials exposed to burial and weathering continues to be a topic of some debate changes in the isotopic composition of archaeological bones and teeth during recrystallization are often suspected but difficult to prove here we examined the effects of heating burning boiling on the isotopic composition of phosphate oxygen 18 o p in bone bioapatite from two modern white tailed deer odocoileus virginianus our experiments simulated cooking and refuse disposal practices which have affected many archaeological samples original values for 18 o p were preserved at 18 o p above 300 c original values for 18 o p were preserved only at ftir ci 2 5 2 7 xrd ci values were not sensitive to changes in 18 o p below 625 c

from bone to fossil a review of the diagenesis of bioapatite the preservation of bone or bioapatite over geologic time has presented paleobiologists with longstanding and formidable questions namely to elucidate the mechanisms processes rates and depositional conditions responsible for the formation of a fossil from a once living tissue approaches integrating geochemistry mineralogy physics hydrology sedimentology and taphonomy have all furthered insights into fossilization but several fundamental gaps still remain notably our limited understanding of 1 the timing of processes during diagenesis e g early and or late 2 the rate of bioapatite transformation into thermodynamically more stable phases 3 the controls imparted by depositional environment and 4 the role of micro biology in determining the fate of bone bioapatite dissolution or preservation the versatility of fossil bioapatite to provide information on the biology of extinct vertebrates rests on our ability to identify and characterize the changes that occurred to bioapatite during diagenesis this review will evaluate our current understanding of bioapatite diagenesis and fossilization focusing on the biogeochemical transformations that occur during diagenesis to the mineral and organic components of bone excluding teeth and enamel the analytical approaches applied to evaluate fossilization processes and outline some suggestions for future promising directions

the spatial distribution of rocks on mars abstract the spatial distribution of rocks exposed at the surface of mars has been mapped using viking infrared thermal mapper irtm observations overall there are no regions on the surface of mars at a scale of 1 1 in latitude and longitude that are rock free the modal value of rock abundance is 6 areal coverage with no areas having more than 30 35 rock cover the model developed to determine rock abundance relates the thermal emission in each of the four surface sensing irtm bands to temperature contrasts within the field of view non unit thermal emissivity due to absorption bands in the surface materials and the absorption and scattering of the outgoing energy by atmospheric dust and water ice each of these effects produce characteristic spectral and diurnal signatures allowing them to be separated the temperature contrasts provide a means to determine both the abundance of exposed rocks and the fine component thermal intertia rock abundance alone does not produce the observed variation in bulk thermal inertia of the surface low inertia fine bright surfaces have fewer rocks exposed than do high inertia coarse dark surfaces rock abundance does not correlate well with the rms slope nor reflectivity determined from delay doppler radar measurements there is however a possible correlation between rms slope determined from continuous wave radar observations dual polarization radar measurements which provide the best radar measure of small scale roughness indicate that the tharsis volcanic region is very rough whereas thermal measurements indicate very few rocks and a covering of dust together these observations suggest an approximately 1 m thick mantle of fines covering a very rough subsurface this fine material may be an aeolian deposit of dust storm fallout valles marineris together with several major channels and chaotic terrains have high rock abundances as does the acidalia planitia basin this observed distribution may reflect the initial deposition of coarse material associated with channel formation syrtis major is unique in having a high inertia but a very low rock abundance together with low radar roughness these observations are consistent with mantling of rocks by sand the observed distribution of rocks and fines indicates that aeolian processes both erosional and depositional play a dominant role in shaping the present martian surface

thermal and albedo mapping of the polar regions of mars using viking thermal mapper observations 1 north polar region we present the first maps of the apparent thermal inertia and albedo of the south polar region of mars the observations used to create these maps were acquired by the infrared thermal mapper irtm instruments on the two viking orbiters over a 30 day period in 1977 during the martian late southern summer season the maps cover the region from 60 s to the south pole at a spatial resolution of 1 of latitude thus completing the initial thermal mapping of the entire planet the analysis and interpretation of these maps is aided by the results of a one dimensional radiative convective model which is used to calculate diurnal variations in surface and atmospheric temperatures and brightness temperatures at the top of the atmosphere for a range of assumptions concerning dust optical properties and dust optical depths the maps show that apparent thermal inertias of bare ground regions decrease systematically from 60 s to the south pole in unfrosted regions close to the south pole apparent thermal inertias are among the lowest observed anywhere on the planet on the south residual cap apparent thermal inertias are very high due to the presence of co2 frost in most other regions of mars best fit apparent albedos based on thermal emission measurements are generally in good agreement with actual surface albedos based on broadband solar reflectance measurements however in the frost free region poleward of 75 s best fit apparent albedos are significantly higher than measured lambert albedos implying that measured brightness temperatures in this area are up to 15 k colder than would be expected for surfaces with the same measured albedos during this season the one dimensional atmospheric model calculations also predict anomalously cold brightness temperatures close to the pole during late summer and after considering a number of alternatives it is concluded that the net surface cooling due to atmospheric dust is the best explanation for this phenomenon the observed systematic decrease in apparent thermal inertia from 60 s to the south pole during this season is also consistent with the predictions of atmospheric model calculations the region of lowest apparent thermal inertia close to the pole which includes the south polar layered deposits is interpreted to be mantled by a continuous layer of aeolian material that must be at least a few millimeters thick the low thermal inertias mapped in the south polar region imply an absence of surface water ice deposits which is consistent with viking mars atmospheric water detector mawd measurements which show low atmospheric water vapor abundances throughout the summer season however these observations do not necessarily imply a complete absence of water thermal model calculations that can reproduce observed diurnal temperature variations in the south polar region show that annual maximum subsurface temperatures at depths ranging from 4 to 20 cm are cold enough to permit the stability of ground ice deposits even if they are in excellent diffusive contact with the atmosphere therefore the presence of near surface ground ice in the south polar region is not inconsistent with the viking irtm and mawd observations

kalasinemys a new xinjiangchelyid turtle from the late jurassic of ne thailandh tong et al new xinjiangchelyid turtle from ne thailand a new xinjiangchelyid turtle kalasinemys prasarttongosothi n gen n sp is described on the basis of skull and shell material from the upper jurassic phu kradung formation at phu noi locality kalasin province in ne thailand this second xinjiangchelyid turtle from phu noi is distinct from phunoichelys thirakhupti by the smooth shell surface the presence of a cervical notch and vertebral 1 narrower than nuchal the skull presents an arterial system characteristic of the xinjiangchelyidae basal eucryptodira and its outline is similar to that of annemys spp known from the middle late jurassic of china and mongolia but distinct from the latter mainly by the wider triturating surface smaller foramen palatinum posterius and the shape of the prefrontal and frontal as well as that of the basisphenoid and basioccipital based on the turtle assemblages the correlation with mainland asia further supports a late jurassic age for the lower part of the phu kradung formation where phu noi site is located stratigraphically our study provides new insight on the evolution of the basal eucryptodiran turtles in asia

early cretaceous vertebrates from the xinlong formation of guangxi southern china a review the vertebrate assemblage from the early cretaceous non marine xinlong formation of the napai basin in the south western part of guangxi zhuang autonomous region southern china is reviewed the assemblage includes chondrichthyans at least six species of hybodont sharks including hybodus thaiodus heteroptychodus and acrorhizodus actinopterygians halecomorphi and ginglymodi turtles the adocid shachemys and the carettochelyid kizylkumemys crocodilians cf theriosuchus and dinosaurs the sauropods fusuisaurus and liubangosaurus carcharodontosaurid and spinosaurid theropods iguanodontians and a possible psittacosaurid this assemblage shows many similarities to those from non marine formations of the khorat group of north eastern thailand it seems to be particularly close to that from the khok kruat formation considered as aptian in age as shown especially by sharks and turtles and by the presence of iguanodontians an aptian age is therefore proposed for the xinlong formation a study of the stable oxygen and carbon isotope compositions of reptile apatite suggests that this part of south china experienced subtropical arid conditions during the deposition of the xinlong formation in its composition the vertebrate fauna from the xinlong formation seems to be more similar to coeval faunas from se asia than to assemblages from northern china including the jehol biota although this may partly reflect different depositional and taphonomic environments fluvial for the xinlong formation versus lacustrine for the jehol biota it seems likely that during early cretaceous time southern china and se asia were part of a distinct zoogeographical province different from that corresponding to northern china this may be the result of both climatic differences with relatively cool climates in northern china versus a subtropical climate in the south and geographical barriers such as mountain chains

visualizing fossilization using laser ablation inductively coupled plasma mass spectrometry maps of trace elements in late cretaceous bones elemental maps generated by laser ablation inductively coupled plasma mass spectrometry la icp ms provide a previously unavailable high resolution visualization of the complex physicochemical conditions operating within individual bones during the early stages of diagenesis and fossilization a selection of la icp ms maps of bones collected from the late cretaceous of montana united states and madagascar graphically illustrate diverse paths to recrystallization and reveal unique insights into geochemical aspects of taphonomic history some bones show distinct gradients in concentrations of rare earth elements and uranium with highest concentrations at external bone margins others exhibit more intricate patterns of trace element uptake related to bone histology and its control on the flow paths of pore waters patterns of element uptake as revealed by la icp ms maps can be used to guide sampling strategies and call into question previous studies that hinge upon localized bulk samples of fossilized bone tissue la icp ms maps also allow for comparison of recrystallization rates among fossil bones and afford a novel approach to identifying bones or regions of bones potentially suitable for extracting intact biogeochemical signals

origin of archaeological black bones within a waterlogged context a multidisciplinary approach abstract this paper presents the interdisciplinary study on the origin of black bones at the neolithic lakeside settlement of dispilio greece 5500 3500 bce where animal bones have been recovered from a waterlogged and organic soil matrix containing charcoal ash and burnt cultural remains in the past this has been interpreted as the result of the destruction of the village by fire and abandonment this study aims to examine this theory through the distinction of burnt vs oxide stained bones a selection of 44 fish and 19 mammal bone samples are examined through optical microscopy scanning electron microscopy sem x ray microanalysis eds x ray diffraction xrd rietveld analysis infrared spectroscopy atr nir and chemical analyses icp ms alterations of histology mineralogy chemistry crystallinity and structural parameters prove that the black bones from dispilio owe their colour to mn and fe oxide staining light coloured bones found at the site have not been affected by this diagenetic procedure which suggests that they were buried in a totally different geochemical environment the analytical techniques employed did not offer any proof that the studied material is burnt however due to the fact that most techniques used to this day allow for the identification of thermal alteration of bone at temperatures usually higher than 300 450 c the possibility of thermal alterations due to an indirect fire thus at lower temperatures or a fire of small duration cannot be identified and thus be ruled out

surface characteristics of venus derived from pioneer venus altimetry roughness and reflectivity measurements the three primary data sets for the pioneer venus orbiter radar experiment topography roughness and reflectivity contain important information about the geological and textural characteristics of the surface of venus we have subdivided the range of roughness and reflectivity values into three categories as follows roughness in degrees rms slope relatively smooth 1 2 5 transitional from smooth to rough 2 5 5 and relatively rough 5 and fresnel reflectivity surfaces dominated by soil or porous material 0 2 we have analyzed each of these data sets and their relationships to each other in order to define areas of the surface that are characterized by distinctive properties e g rough rocky surfaces smooth soil surfaces we then describe the abundance and areal distribution of such areas and locally calibrate the geological significance of some of the surface types by examining high resolution images from spacecraft and earth based observatories we find that the majority of venus is covered by regionally contiguous rock and bedrock surfaces many of the smooth surfaces we interpret to be of volcanic origin most likely lava flows while rougher surfaces are locally characterized by tectonic deformation of several types soil surfaces cover less than about 27 of the planet and are generally patchy in their distribution on the basis of the distribution of these surfaces we see no evidence for the extensive preservation of an ancient global regolith or for widespread topographically controlled erosion lateral transport and sedimentation the small percentage of the surface of venus characterized by high dielectric material appears to originate from several processes including primary lava flows probably containing enrichments of high dielectric materials such as metal or metal oxides e g theia mons in beta regio and exposure of high dielectric materials by tectonic deformation e g maxwell montes in ishtar terra these global data set correlations provide a fundamental frame work for understanding the nature of the surface of venus and will permit extrapolation of local and regional findings from future geochemical and imaging experiments to a global context

diagenesis of archaeological bone and tooth an understanding of the structural complexity of mineralised tissues is fundamental for exploration into the field of diagenesis here we review aspects of current and past research on bone and tooth diagenesis using the most comprehensive collection of literature on diagenesis to date environmental factors such as soil ph soil hydrology and ambient temperature which influence the preservation of skeletal tissues are assessed while the different diagenetic pathways such as microbial degradation loss of organics mineral changes and dna degradation are surveyed fluctuating water levels in and around the bone is the most harmful for preservation and lead to rapid skeletal destruction diagenetic mechanisms are found to work in conjunction with each other altering the biogenic composition of skeletal material this illustrates that researchers must examine multiple diagenetic pathways to fully understand the post mortem interactions of archaeological skeletal material and the burial environment

why do crystallinity values fail to predict the extent of diagenetic alteration of bone mineral spectroscopic indicators of bone crystallinity such as the infrared splitting factor irsf are commonly used to determine the general state of preservation of ancient bone in principle such indices might be expected to act as a proxy for alteration of bone mineral and thus could be used to screen bones or portions of bones for likely preservation of in vivo biogenic trace element and stable isotope signals we tested the relationship between irsf and bone mineral composition in two suites of well characterised recent and pleistocene bones initially crystallinity change and trace element uptake are correlated apparently both controlled by decomposition of the organic phase and exposure of bone crystal surfaces this relationship breaks down in older bones where authigenic phosphate growth and mineral pore water interactions are no longer rate limited by the breakdown of collagen and exposure of crystal surfaces in these conditions the extent of chemical alteration of bone will be controlled by site specific conditions and thus while ftir spectra of bone provide a broad indication of organic content and apatite recrystallisation they are not reliable proxies for the degree of diagenetic alteration in terms of biogenic geochemical signals

surface properties of mars polar layered deposits and polar landing sites on december 3 1999 the mars polar lander and mars microprobes will land on the planet s south polar layered deposits near 76 s 195 w and conduct the first in situ studies of the planet s polar regions the scientific goals of these missions address several poorly understood and globally significant issues such as polar meteorology the composition and volatile content of the layered deposits the erosional state and mass balance of their surface their possible relationship to climate cycles and the nature of bright and dark aeolian material derived thermal inertias of the southern layered deposits are very low 50 100 j m 2 s 1 2 k 1 suggesting that the surface down to a depth of a few centimeters is generally fine grained or porous and free of an appreciable amount of rock or ice the landing site region is smoother than typical cratered terrain on 1 km pixel 1 viking orbiter images but contains low relief texture on 5 to 100 m pixel 1 mariner 9 and mars global surveyor images the surface of the southern deposits is older than that of the northern deposits and appears to be modified by aeolian erosion or ablation of ground ice

environment and ecology of east asian dinosaurs during the early cretaceous inferred from stable oxygen and carbon isotopes in apatite abstract during the cold late barremian early albian interval terrestrial environments in east asia were populated by rich and diverse vertebrate faunas characterized by a strong provincialism the latitudinal gradient of temperature and the existence of geographic barriers likely accounted for some aspects of this heterogeneous distribution of faunas other factors however such as local environmental conditions and interactions within vertebrate communities which could have influenced their distribution have not yet been fully identified and understood therefore new and published oxygen and carbon isotope compositions of apatite from chinese and thai reptiles dinosaurs crocodilians and turtles have been analyzed and interpreted in terms of ecology local air temperature and precipitation amounts differences in carbon and oxygen isotope compositions between various groups of sympatric plant eating dinosaurs sauropods ornithopods and ceratopsians indicate food resources partitioning among them most likely to avoid competition mid latitude environments where the jehol biota flourished were submitted to cool temperate climatic conditions with mean air temperature mat of 10 4 c and mean annual precipitations map of about 600 mm yr compatible with the existence of forest environments by contrast sub tropical regions characterized by mat of about 20 25 c were either submitted to high amounts of seasonal precipitations of about 1200 mm yr in thailand or to significant aridity map of about 400 mm yr in south china this difference in precipitation regime between thailand and south china may be attributed to the occurrence of the coastal cordillera extending along the east margin of the south china block these mountain ranges likely prevented humid air masses from the pacific to penetrate some parts of south china thus generating a rain shadow effect mosaic environments characterizing east asia during the late early cretaceous may have acted as a cradle for the origination of advanced dinosaur taxa that subsequently radiated over eurasia and north america during the late cretaceous

mars global surveyor bistatic radar probing of the mpl ds2 target area abstract mars global surveyor bistatic radar was used to probe the mars polar lander and deep space 2 target areas 76 s 195 w in may 2000 the behavior of quasi specular echoes at wavelength 3 6 cm indicates that the top few centimeters of regolith are similar in their reflecting properties everywhere along a track of approximately 1000 km which crosses the mpl ds2 area our provisional estimate of surface dielectric constant e 2 25 is consistent with loose soil moderately packed h 2 o snow solid co 2 or a mixture of at least two but other data rule out both h 2 o and co 2 near the surface in late southern summer l s 351 leaving dry soil with density 1 4 g cm 3 as the most likely material

palaeocurrent direction estimated in mesozoic redbeds of the khorat plateau lao pdr indochina block using anisotropy of magnetic susceptibility mesozoic redbeds in the western part of central and southern laos are the most abundant rocks of the khorat plateau in earlier studies palaeocurrent directions of the mesozoic redbeds in the khor

the post mortem history of a bone revealed by its trace element signature the case of a fossil whale rostrum abstract studies dedicated to palaeoenvironments and taphonomy have made wide use of rare earth elements ree contents of fossil bones as proxies however the complex diagenetic history of individual specimens combined with intra bone ree fractionation and the uncertain timing of ree uptake generally prevents the robust interpretation of ree patterns in this case study we show that combining ree analysis with on the one hand histology and microstructural observations and on the other hand additional analyses of other trace elements allows deciphering at least three distinct trace element uptake stages as well as one leaching event more than 35 trace elements including the ree are analysed using laser ablation inductively coupled plasma mass spectrometry la icpms within compact rostrum bones of the miocene pliocene beaked whale globicetus hiberus from deep sea deposits and a comparable extant specimen blainville s beaked whale mesoplodon densirostris comparison of the extinct and the extant bones allows a better quantification of the diagenetic trace element content this study highlights the crucial role played by diagenetic minerals such as the fe mn oxyhydroxides in the uptake and release of trace elements co ni ti v zr hf and nb and ree by bones in response to changes of the diagenetic fluid redox conditions over time such changes of the geochemical environment help constraining the post mortem history of the bone and its interaction with diagenetic fluids we conclude that the unique interpretation of geochemical proxies within individual fossil bones requires a thorough investigation of each individual specimen

earth based radar studies of planetary surfaces and atmospheres radar has been used as a remote sensing tool since 1946 when the first echoes from the moon were detected by ground based radar systems since then the sensitivity of our most powerful radar systems has increased by a factor of about 1012 and radar studies of mercury venus earth s moon mars the galilean moons of jupiter the rings of saturn and a dozen asteroids have been made specific studies range from simple measurements of distance or reflectivity to detailed maps or images of reflectivity altimetry and various other model parameters this paper presents a short review of the more recent observations and summarizes current research activities associated with each body an attempt is made to anticipate the observational data set that should be available during the next decade such data will be useful for remote sensing applications either directly or combined with data from other programs the usefulness of the radar data is also dependent upon theoretical models that explain the observed scattering such models often are dependent upon parameters that are not measurable by radar likewise models that predict other physical measurements may be influenced by parameters that are easily measured by radar thus many more exciting applications of radar data should become apparent as further observations are made by other techniques and as models are developed to explain the observed quantities

magnetostratigraphic study of the potash bearing strata from drilling core zk2893 in the sakhon nakhon basin eastern khorat plateau abstract the khorat plateau holds one of the world s largest potash deposits although many attempts have been made the age of the potash bearing strata remains poorly determined here we report a high resolution magnetostratigraphic study of a 595 4 m deep potash bearing borehole zk2893 in the southeast sakhon nakhon basin in central laos this borehole penetrated the whole potash bearing nong boua formation and reached the underlying sandstone beds of the nam noy formation a total of 500 383 level cubic paleomagnetic samples were collected k t curves and hysteresis loops revealed that hematite and magnetite were the main magnetic carriers and were likely of detrital origin as indicated by microscopic and electron microprobe analysis empa examinations progressive thermal and alternating field af demagnetization isolated 229 valid characteristic remnant magnetizations chrms which showed a normal and antipodal distribution of the inclination data both the microscopic and empa examinations and inclination only analysis suggest primary magnetizations of the chrms yielding nine normal and seven reversed polarity zones combined with regional palynological isotopic and sedimentologic evidence the obtained polarity zones were best correlated to the geomagnetic polarity time scale of gradstein et al 2012 gpts2012 yielding magnetostratigraphic ages of 63 5 ma to 92 ma for the potash bearing nong boua formation and 85 ma for the potash bed in its lower salt unit

new radar derived topography for the northern hemisphere of mars earth based radar altimetry data for the northern equatorial belt of mars 6 s 23 n have recently been reduced to a common basis corresponding to the 6 1 mbar reference surface a first look at these data indicates that the elevations of tharsis elysium and lunae planum are lower by 2 5 km than has been suggested by previous estimates these differences show that the required amount of tectonic uplift or constructional volcanism for each area is less than has been previously envisioned atmospheric or surficial conditions are suggested which may explain the discrepancies between the radar topography and elevations measured by other techniques the topographies of chryse planitia syrtis major and valles marineris are also described

states of preservation of bones from prehistoric sites in the near east a survey abstract a survey of the states of preservation of organic material in 30 fossil bones from 16 different prehistoric sites in the near east shows that whereas almost all the bones have little or no collagen preserved they do with few exceptions contain non collagenous proteins these macromolecules therefore represent an important reservoir of indigenous fossil bone constituents

global radar units on venus derived from statistical analysis of pioneer venus orbiter radar data unsupervised linear discriminant cluster analysis of pioneer venus reflectivity and rms slope data has produced a classification of 15 radar units examination of four hypsometric provinces previously established for venus has been used to show that although the highland 6053 to 6055 5 km and mountainous greater than 6055 5 km provinces are distinctly different in their radar unit compositions from each other and from the lowlands less than 6051 km and rolling plains 6051 to 6053 km provinces the lowlands and rolling plains provinces are very nearly the same in their radar properties this observation indicates that hypsometry alone is not a reliable criterion for quantitative examination of the surface geology on venus a classification unit encompassment scheme has been developed that shows the presence of three distinct trends two toward elevations higher than the planetary mean elevation and the other toward elevations lower than the mean venera lander data and earth based radar images have been used to infer that seven units within the two higher elevation unit encompassment trends represent materials of mostly basaltic composition that differ only in their surface morphologies the physical characteristics of these materials indicate that they form terrains ranging from banded through rift valley to relatively flat and that the materials are composed of bedrock and soil in variable ratios three other radar classification units appear to be morphologically transitional forms between units of these two higher elevation unit encompassment trends the five remaining units are associated with the lower elevation unit encompassment trend their geologic significance cannot be determined with any certainty with the existing pioneer venus radar data the radar units that correspond to those of an existing radar unit map produced by supervised analysis display similar areal distributions on venus however our radar unit map shows more detail and is relatively unbiased in terms of unit definition this global radar classification image of the venusian surface provides a working data base from which more exacting geologic interpretations can be made when higherresolution imagery becomes available

mineralogical and compositional changes in bones exposed on soil surfaces in amboseli national park kenya diagenetic mechanisms and the role of sediment pore fluids abstract bones exposed on tropical savannah grasslands of amboseli national park kenya undergo extensive post mortem alteration within 40 years a combined analytical approach involving tem microscopy trace metal analysis ftir spectroscopy and petrographic analysis has revealed a complex dynamic diagenetic environment operating within exposed bones driven by evaporative transport of soil water from the bone soil interface to the upper exposed surface of the bone this process results in extensive bone soil water interaction and is responsible for increases in the concentrations of trace elements such as ba and la of 100 1000 within 15 years the maximum and mean size of bone crystallites increases with continued exposure this change in mean crystallite length is correlated positively with increases in bone crystallinity which in turn is associated with degradation of the bone protein microbial decomposition is rarely observed in the amboseli bones but where present resulted in severe dissolution reprecipitation of bone mineral many bones showed extensive permineralization of the larger vascular spaces with calcite and barite and to a lesser extent crandallite permineralization of unburied bones may account for 95 reduction in macro micron millimeter scale porosity in the bone within 2 years of death we produce a model for pre burial diagenesis of bone in arid tropical environments that highlights extensive alteration of bone chemistry within 1 40 years post mortem

evaluating the impact of acetic acid chemical pre treatment on old and cremated bone with the perio spot technique and perios endos profiles abstract the impacts of diagenesis on archaeological and palaeontological bone complicate investigations of in vivo chemical and isotopic characteristics such bone is often pre treated in an attempt to remove diagenetic alteration prior to trace element or isotopic analyses although very few standardized approaches exist for evaluating pre treatment effectiveness in this pilot study we characterize the diagenetic alteration and assess the impact of acetic acid chemical pre treatment on the trace element and structural characteristics of four bones from belgium including an early medieval cremated bone from broechem and three representative old bones of different ages ca 40 130 ka from the late pleistocene sedimentary sequence of scladina cave each bone was analyzed before and after acetic acid pre treatment using the perio spot technique and perios endos profiles we measured trace element concentrations with laser ablation inductively coupled plasma mass spectrometry la icp ms and micro x ray fluorescence spectroscopy xrf structural characteristics were investigated with raman spectroscopy and fourier transform infrared spectroscopy ftir our results indicate that chemical pre treatment had little to no significant impact on the trace element content of the early medieval cremated bone had the most impact on the youngest bone from scladina cave and had less impact on the trace element content of two older bones from scladina cave this suggests that the effectiveness of acetic acid chemical pre treatment is greater for bones undergoing early diagenetic processes has minimal impact on highly crystalline cremated bone and may preferentially leach in vivo signatures from bones undergoing later diagenesis the weights of leachates removed from each bone also correspond well with their hypothetical diagenetic states indicating that researchers could potentially assess the diagenetic state of bones by weighing the leachates produced during acetic acid pre treatment therefore our new approach may provide a valuable step toward effectively and consistently differentiating among in and ex vivo trace element signatures and by proxy those of their isotopes in archaeological and palaeontological bone

dual polarization radar observations of mars tharsis and environs abstract observations of the tharsis region of mars with the 12 6 cm radar at arecibo observatory have yielded radar echoes which are highly depolarizes and which are in terms of total echo power dominated by diffuse rather than quasi specular backscattering the observations were made on february 7 8 and 9 1980 and the subradar track extended from 77 to 126 w longitude at 22 n latitude dual polarized reception was employed i e the echo was received in the same sense of circular polarization as transmitted depolarized sense as well as in the opposite polarized sense the disk integrated ratio of depolarized power to polarized power averages 0 37 and the ratio of diffuse power to quasi specular power averages 3 2 the depolarized spectra are dominated by a broad enhancement identified primarily with echoes from the tharsis ridge implying that extensive areas of tharsis are rough on decimeter scales the major tharsis shield volcanoes are candidates for sources of strong depolarization although they alone cannot account for the entire depolarization enhancement

radio science investigations with mars observer mars observer radio science investigations focus on two major areas of study the gravity field and the atmosphere of mars measurement accuracies expressed as an equivalent spacecraft velocity are expected to be of the order of 100 m s for both types of investigations from use of an improved radio transponder for two way spacecraft tracking and a highly stable on board oscillator for atmospheric occultation measurements planned gravity investigations include a combination of classical and modern elements a spherical harmonic or equivalent field model of degree and order in the range 30 50 will be obtained while interpretation will be in terms of internal stress and density models for the planet using the topography to be obtained from the mars observer laser altimeter atmospheric investigations will emphasize precision measurement of the thermal structure and dynamics in the polar regions which are regularly accessible as a result of the highly inclined orbit studies based on the measurements will include polar processes cycling of the atmosphere between the poles traveling baroclinic disturbances small scale waves and turbulence the planetary boundary layer and possibly the variability and altitude of the ionosphere as the radio occultation is insensitive to dust in the atmosphere per se and measures only the resulting change in thermal structure it is expected that the radio technique can contribute to understanding of dust storm phenomena mutual observations of the atmosphere by means of radio occultation and by the pressure modulator infrared radiometer and the thermal emission spectrometer are expected to strengthen the reliability and accuracy of all three investigations