diviner lunar radiometer observations of cold traps in the moon s south polar region diviner lunar radiometer experiment surface temperature maps reveal the existence of widespread surface and near surface cryogenic regions that extend beyond the boundaries of persistent shadow the lunar crater observation and sensing satellite lcross struck one of the coldest of these regions where subsurface temperatures are estimated to be 38 kelvin large areas of the lunar polar regions are currently cold enough to cold trap water ice as well as a range of both more volatile and less volatile species the diverse mixture of water and high volatility compounds detected in the lcross ejecta plume is strong evidence for the impact delivery and cold trapping of volatiles derived from primitive outer solar system bodies

carnian norian biomagnetostratigraphy at silicka brezova slovakia correlation to other tethyan sections and to the newark basin correlations of upper triassic magnetic stratigraphies from tethyan sections have been hampered by difficulties with conodont biostratigraphy and taxonomy and discontinuous sedimentation particularly in the hallstatt limestones of turkey and austria the magnetic stratigraphy and conodont biostratigraphy from the upper carnian to upper norian limestones exposed at silickabrezova slovakia can be correlated to other tethyan sections and to the continental succession in the newark basin the resulting correlations help to resolve some of the apparent discrepancies in existing conodont zonations and result in a revised correlation to north american terrestrial vertebrate and palynological zones the correlations imply that the norian rhaetian boundary lies within newark polarity zone e17r at v207 ma the carnian norian boundary lies close to the base of newark polarity zone e7r at v226 ma this implies durations for the norian and rhaetian stages of 19 myr and 7 myr respectively 2002 elsevier science b v all rights reserved

evidence for shock metamorphism in sandstones from the libyan desert glass strewn field microscopic analysis of sandstones from the southern libyan desert glass strewn field reveals a sequence of progressive deformation features which range from unaffected rock to extreme brecciation the quartz grains show a wide range of deformation features crushing and fracturing undulatory extinction mosaicism oriented cleavage partial isotropization and multiple sets of planar deformation features this preliminary report provides the first description of these shock indicators which are typical for hypervelocity impact in bedrock material that is assumed to be related to the libyan desert glass

progradation geometries of carbonate platforms examples from the triassic of the dolomites northern italy various types of progradation of triassic carbonate platforms are described from the dolomites of the southern alps the internal and external geometric relationships are exposed in spectacular natural sections and moreover their scale 500 1000 m of thickness is such that they can be compared with features found in seismic profiles the different types of progradation are controlled by a number of factors which normally interact with each other these factors include rate of basinal sedimentation rate of subsidence width of the platform depth of the surrounding basin and eustatic variations of sea level progradation is not a continuous process but episodic moments of massive debris input during which the platform advances alternate with long periods of negligible progradation during which basinal sediments accrete and onlap the toe of slope upper boundary relationships of the prograding platforms include offlap toplap and erosional truncation lower boundary relationships are horizontal climbing and descending progradations a variety of phenomena and circumstances have caused the cessation of progradation of the triassic platforms they include volcanism collapse of margins drowning rapid relative rise of sea level subaerial exposure relative fall of sea level and probably a natural decay of the system in the triassic of the dolomites two main progradation models can be put forward in the ladinian model progradation took place simultaneously with aggradation relative rise of sea level whereas the characteristic feature of the carnian model is toplap relative stillstand of sea level

triassic latemar cycle tops subaerial exposure of platform carbonates under tropical arid climate the triassic latemar platform in the dolomites italy is the site of several ongoing controversies perhaps the most interesting debate focuses on apparent cyclic deposition within the latemar platform whose nature and duration are still open to debate further disagreement concerns the lack of meteoric diagenesis related isotope shifts at cycle tops that bear circumstantial petrographic evidence for subaerial emergence here an evaluation of the nature of latemar cycle tops is presented combining evidence from previous work and new field petrographic and geochemical data cycle tops are ranked according to increasing exposure duration and spatial extent type i surfaces lacking unequivocal evidence of prolonged supratidal conditions type ii dolomite caps formed in warm evaporitic intertidal lagoonal waters followed by exposure of perhaps intermediate duration type iii clastic rich red calcareous horizons with some showing platform wide extent representing prolonged supratidal conditions and type iv discontinuities in tepee belts genetically related to type ii and iii surfaces but likely representing shorter lived exposure stages petrographic and geochemical criteria indicate that most diagenesis occurred in the shallow marine and burial domain whilst an extensive meteoric overprint of cycle tops is lacking this is underlined by the scarcity of meteoric diagenetic fabrics such as gravitational cements that where present are here interpreted as marine vadose in origin the scarcity of carbon and oxygen isotope signatures commonly assigned to subaerial exposure stages is best explained in the context of mid triassic climate the low latitude tropical but arid setting of the latemar situated in the western extension of the tethys ocean its isolation from nearby continental areas and overall short term emergence episodes are in agreement with a limited degree of meteoric alteration of most cycle tops high amounts of aeolian clastic material beneath some cycle tops along with high fe and mn elemental abundances argue for intermittent subaerial conditions this study proposes an enhancement of the classical allan and matthews 1982 isotope model for subaerial exposure under strongly arid climates as the subaerial exposure nature of latemar cycle tops and therefore eustasy as the cause for cyclicity have been previously challenged due to the lack of meteoric induced isotopic signatures the outcome of this study is of significance for the ongoing latemar stratigraphic controversy

lunar surface rock abundance and regolith fines temperatures derived from lro diviner radiometer data 1 surface temperatures derived from thermal infrared measurements provide a means of understanding the physical properties of the lunar surface the contrasting thermophysical properties between rocks and regolith fines cause multiple temperatures to be present within the field of view of nighttime multispectral data returned from the lunar reconnaissance orbiter lro diviner radiometer between 60 n s latitudes regolith temperatures are influenced by the presence of rocks in addition to factors such as the thermophysical properties of the regolith fines latitude and local slopes and radiative heating from adjacent crater walls preliminary comparisons of derived rock concentrations with lro camera images show both qualitative and quantitative agreement although comparisons of derived rock concentrations with circular polarization ratio radar data sets display general similarities there are clear differences between the two data sets in the relative magnitude and areal extent of rocky signatures several surface units can be distinguished based on their regolith temperature and rock concentration values and distributions including maria and highlands surfaces rocky impact craters rilles and wrinkle ridges dark mantled deposits and isolated cold surfaces rock concentrations are correlated with crater age and rocks are only preserved on the youngest surfaces or where steep slopes occur and mass wasting prevents mantling with fines the presence of rocky surfaces excavated by young impacts allows for the estimation of minimum regolith thickness from the size of the impact the derived rock concentrations confirm the presence of thicker regolith cover in the highlands and in locations of radar dark haloes

lithium in tektites and impact glasses implications for sources histories and large impacts abstract lithium li abundances and isotope compositions were determined in a representative suite of tektites moldavites muong nong type tektites and an australite ivory coast tektites and bediasites impact related glasses libyan desert glass zhamanshinites and irghizites a glass fragment embedded in the suevite from the ries impact crater and sedimentary materials in order to test a possible susceptibility of li to fractionation during hypervelocity impact events and to de convolve links to their potential parental sources the overall data show a large spread in li abundance 4 7 58 ppm li and 7 li values 3 2 to 26 0 but individual groups of tektites and impact glasses have distinctive li compositions most importantly any significant high temperature li isotope fractionation can be excluded by comparing sedimentary lithologies from central europe with moldavites instead we suggest that li isotope compositions in tektites and impact related glasses are probably diagnostic of the precursor materials and their pre impact geological histories the muong nong type tektites and australite specimen are identical in terms of li concentrations and 7 li and we tentatively endorse their common origin in a single impact event evidence for low temperature rayleigh fractionation which must have operated prior to impact induced melting and solidification is provided for a subset of muong nong type tektites although li isotope variations in most tektites are broadly similar to those of the upper continental crust libyan desert glass carries high 7 li 24 7 which appears to mirror the previous fluvial history of parental material that was perhaps deposited in lacustrine environment or coastal seawater lithium isotopes in impact related glasses from the zhamanshin crater define a group distinct from all other samples and point to melting of chemically less evolved mafic lithologies which is also consistent with their major and trace element patterns extreme shock pressures and the related extreme post shock temperatures alone appear not to have any effect on the li isotope systematics therefore useful information on parental lithologies and magmatic processes may be retrieved from analyses of martian and lunar meteorites moreover lack of significant li depletion in tektites provides further constraints on the loss of moderately volatile elements during the moon forming impact

re os geochronology of arctic black shales to evaluate the anisian ladinian boundary and global faunal correlations abstract boreal and tethyan faunas differ throughout the triassic limiting the use of biostratigraphy for global correlation rhenium osmium re os dating of organic rich black shales calibrated with existing biostratigraphy provides a new means to establish correlations of global fauna using absolute time here we present re os radiometric ages for middle triassic organic rich shales from two biostratigraphically defined sections at svalbard and the svalis dome in the barents sea mature black shales from svalbard inferred to be middle to late anisian define a 241 2 2 2 ma isochron with an initial 187 os 188 os ratio of 0 831 0 025 the highest seawater os isotope ratio yet recorded between the cambrian and lower jurassic svalis dome shales in the uppermost anisian yield a 239 3 2 7 ma age and initial 187 os 188 os ratio of 0 679 0 020 the higher initial 187 os 188 os ratio for svalbard shales most likely reflects global seawater at the time of deposition whereas the lower initial 187 os 188 os ratio for the svalis dome may represent seawater with limited communication to the open ocean as suggested by the ratio of trace metal abundances and total organic carbon contents these age data indicate a maximum age of 239 3 2 7 ma for the anisian ladinian boundary in the arctic boreal realm this age agrees with the proposed boundary in the tethyan realm 240 to 243 ma and thus confirms the correlations between boreal and tethys based on biostratigraphy and magnetostratigraphy our study affirms that re os geochronology of black shale is a reliable method for obtaining depositional ages and establishing biostratigraphic correlations between paleogeographically separated regions

the global albedo of the moon at 1064 nm from lola the lunar orbiter laser altimeter lola measures the backscattered energy of the returning altimetric laser pulse at its wavelength of 1064 nm and these data are used to map the reflectivity of the moon at zero phase angle with a photometrically uniform data set global maps have been produced at 4 pixels per degree about 8 km at the equator and 2 km resolution within 20 latitude of each pole the zero phase geometry is insensitive to lunar topography so these data enable characterization of subtle variations in lunar albedo even at high latitudes where such measurements are not possible with the sun as the illumination source the geometric albedo of the moon at 1064 nm was estimated from these data with absolute calibration derived from the kaguya multiband imager and extrapolated to visual wavelengths the lola estimates are within 2 of historical measurements of geometric albedo no consistent latitude dependent variations in reflectance are observed suggesting that solar wind does not dominate space weathering processes that modify lunar reflectance the average normal albedo of the moon is found to be much higher than that of mercury consistent with prior measurements but the normal albedo of the lunar maria is similar to that of mercury suggesting a similar abundance of space weathering products regions within permanent shadow in the polar regions are found to be more reflective than polar surfaces that are sometimes illuminated limiting analysis to data with slopes less than 10 eliminates variations in reflectance due to mass wasting and shows a similar increased reflectivity within permanent polar shadow steep slopes within permanent shadow are also more reflective than similar slopes that experience at least some illumination water frost and a reduction in effectiveness of space weathering are offered as possible explanations for the increased reflectivity of permanent shadow porosity is largely ruled out as the sole explanation the south polar crater shackleton is found to be among the most reflective craters in its size range globally but is not the most reflective so mass wasting cannot be ruled out as a cause for the crater s anomalous reflectance models of the abundance of ice needed to account for the reflectance anomaly range from 3 to 14 by weight or area depending on assumptions regarding the effects of porosity on reflectance and whether ice is present as patches or is well mixed in the regolith if differences in nanophase iron abundances are responsible for the anomaly the permanently shadowed regions have between 50 and 80 the abundance of nanophase iron in mature lunar soil

growth mode of middle triassic carbonate platforms in the western dolomites southern alps italy abstract the correlation of carbonate platform and slope sediments with biostratigraphically and radiometrically dated basinal successions in the western dolomites allows the reconstruction of the growth of a middle triassic carbonate platform schlern rosengarten over a time interval of approximately five ammonoid zones reitzi secedensis curionii gredleri archelaus zones the whole platform evolution had a total duration of

brownish inclusions and dark streaks in libyan desert glass evidence for high temperature melting of the target rock dark streaks and different types of inclusions in libyan desert glass ldg collected from the ldg strewn field in egypt were investigated rare transparent spherules enclosed in the glassy matrix are characterized by concentric cracks irregular internal cracks intense twinning and considerable amounts of ti and al raman spectra show that the spherules are a cristobalite their occurrence together with lechatelierite indicates quick heating of the source rock to at least 1550 c followed by rapid quenching leading to crystallization of b cristobalite which upon cooling inverted into a cristobalite brownish inclusions are irregularly shaped elongated objects with smooth contacts to the surrounding glass they contain small roundish to elliptical droplets and a few larger angular grains which compositionally and according to their raman spectra most closely resemble low ca al rich orthopyroxene composition and texture of the orthopyroxene suggest that the brownish inclusions formed by incomplete melting of an al rich orthopyroxene bearing precursor e g mafic phases present in desert surface sands or also of orthopyroxene bearing granulite dykes in the ldg target experimental data on ca poor enstatite also support that the inclusions were heated to about 1550 c analyses of dark streaks in ldg reveal high abundances of al ti mn cr fe and ni and a pronounced correlation between the abundances of cr mn fe and ni as the fe ni mn ni and cr ni ratios are all clearly nonchondritic the source of this material is most likely terrestrial and the dark streaks studied here represent a different type of schlieren compared to those which contain a meteoritic component these findings suggest ldg formation during a short high temperature event melting of al rich orthopyroxene bearing target material seems to suggest an asteroid impact rather than a near surface airburst

regolith thickness over the lunar nearside results from earth based 70 cm arecibo radar observations the inversion of regolith thickness over the nearside hemisphere of the moon from newly acquired earth based 70 cm arecibo radar data is investigated using a quantitative radar scattering model the radar scattering model takes into account scattering from both the lunar surface and buried rocks in the lunar regolith and three parameters are critically important in predicting the radar backscattering coefficient the dielectric constant of the lunar regolith the surface roughness and the size and abundance of subsurface rocks the measured dielectric properties of the apollo regolith samples at 450 mhz are re analyzed and an improved relation among the complex dielectric constant bulk density and regolith composition is obtained the complex dielectric constant of the lunar regolith is estimated globally from this relation using the regolith composition derived from lunar prospector gamma ray spectrometer data to constrain the lunar surface roughness and abundance of subsurface rocks from radar data nine regions are selected as calibration sites where the regolith thickness has been estimated using independent analysis techniques for these sites scattering from the lunar surface and buried rocks cannot be perfectly distinguished and a tradeoff relationship exists between the size and abundance of buried rocks and surface roughness using these tradeoff relations as guidelines for globally representative parameters the regolith thickness of four regions over the lunar nearside is inverted and the inversion uncertainties caused by calibration errors of the radar data and model input parameters are analyzed the regolith thickness of the maria is generally smaller than that of highlands and older surfaces have thicker regolith thicknesses our approach cannot be applied to regions where the surface roughness is very high such as with young rocky craters and regions in the highly rugged highlands

mid triassic integrated u pb geochronology and ammonoid biochronology from the balaton highland hungary ladinian middle triassic strata of the balaton highland west central hungary comprise interbedded marine carbonate and volcaniclastic rocks the sediments are noted for their rich ammonoid faunas which allow detailed biostratigraphic subdivision and correlation for the first time isotopic dating of the tuff layers was carried out to calibrate the age of ammonoid zones and subzones four successive horizons were dated from the felsouu ors section a candidate stratotype for the base of the ladinian stage within the reitzi zone which is interpreted here as the basal ladinian unit the following biostratigraphically tightly constrained u pb zircon ages were obtained felsoeoersensis subzone 241 1 0 5 ma liepoldti subzone 241 2 0 4 ma reitzi subzone 240 5 0 5 and 240 4 0 4 ma a redeposited tuff from the gredleri zone at liter yielded an additional u pb age of 238 7 0 6 ma the new isotopic ages are in agreement with published u pb dates from the southern alps together they allow estimation of the start of the ladinian at 241 5 ma and of the end of the stage at 237 ma a duration of

lunar surface geochemistry global concentrations of th k and feo as derived from lunar prospector and clementine data abstract accurate estimates of global concentrations of th k and feo have an important bearing on understanding the bulk chemistry and geologic evolution of the moon we present empirical ground truth calibrations transformations for lunar prospector gamma ray spectrometer data k and th and a modified algorithm for deriving feo concentrations from clementine spectral reflectance data that incorporates an adjustment for tio 2 content the average composition of soil samples for individual landing sites is used as ground truth for remotely sensed data among the apollo and luna sites apollo 12 and 14 provide controls for the incompatible element rich compositions apollo 16 and luna 20 provide controls for the feldspathic and incompatible element poor compositions and apollo 11 15 and 17 and luna 16 and 24 provide controls for fe rich compositions in addition to these apollo and luna sample data we include the composition of the feldspathic lunar meteorites as a proxy for the northern farside highlands to extend the range of the calibration points thus providing an additional anorthositic end member composition these empirical ground truth calibrations for lunar prospector th and k provide self consistency between the existing derived data and lunar sample data clementine spectral reflectance data are used to construct a tio 2 sensitive feo calibration that yields higher feo concentrations in areas of high fe low ti mare basalt rich surfaces than previous feo algorithms the data set so derived is consistent with known sample compositions and regolith mixing relationships

first microwave map of the moon with chang e 1 data the role of local time in global imaging abstract among recent lunar orbiters only the chinese chang e 1 ce 1 was equipped with a passive microwave radiometer mrm to measure the natural microwave emission from the lunar surface the microwave emission characterized by a frequency dependent brightness temperature tb is related to the physical temperature and dielectric properties of the lunar surface by measuring the brightness temperature at different frequencies detailed thermal behavior and properties of the lunar surface can be retrieved using ce 1 s microwave data we present here a set of microwave maps of the moon constructed through a rescaling of tb to noontime or midnight the adopted processing technique helps to reduce the effect of mixing up the temporal and spatial variations introduced by the satellite s localized measurements which cover different locations of the globe at different lunar local times the resulting maps show fine structures unseen in previous microwave maps that disregarded the local time effect we discussed the new features revealed and their possible connections with the lunar geology

high resolution upb dating of middle triassic volcaniclastics time scale calibration and verification of tuning parameters for carbonate sedimentation abstract we report high resolution single zircon u pb age data for middle triassic volcaniclastic intercalations in biostratigraphically calibrated pelagic successions of the southern alps the results require a redefinition of the chronometric scale for the middle triassic moreover they do not support current models relating cyclic sedimentation in platform carbonates of the dolomites to orbital tuning tight concordant age clusters were obtained for five volcaniclastic layers in three ammonoid biozones of late anisian to early ladinian age two layers in the nevadites secedensis zone yielded identical mean 206 pb 238 u ages of 241 2 0 8 0 8 ma and 241 2 0 8 0 6 ma errors given at the 95 confidence level a layer in the gredleri zone is dated at 238 8 0 5 0 2 ma and two horizons in the archelaus zone yield similar ages of 237 9 1 0 0 7 ma and 238 0 0 4 0 7 ma these results are significantly older than the age values of 233 235 ma assigned to the anisian ladinian boundary by several current time scales 1 4 moreover our estimate of 240 7 241 3 ma depending on biostratigraphic collocation for the anisian ladinian boundary casts doubts on the reliability of age values of 245 250 ma proposed by most time scales for the permian triassic boundary the occurrence of pelagic fossils in basinal sediments as well as in age equivalent shallow marine middle triassic platform carbonates in the dolomites allows the sedimentary sequences of both environments to be correlated the 800 m thick latemar platform western dolomites is characterized by cyclic stacking patterns which have been interpreted as results of milankovitch type high frequency low amplitude sea level fluctuations the 12 m y interval of platform growth postulated from the assignment of orbital periodicities to the platform carbonate cycles 5 6 is in conflict with a maximum time span of 4 7 m y allowed by the present zircon data

evidence for a 200 100 ka meteorite impact in the western desert of egypt abstract in this study we present evidence in the form of unusual silicate glasses for a meteorite impact event 200 100 ka in the dakhleh oasis western desert egypt these glasses known locally as dakhleh glass were derived from the shock melting of a series of unconsolidated sediments underlain by interbedded carbonates sandstones and phosphate rich lithologies hypervelocity impact in to a volatile rich target resulted in the production of impact glasses with cao and al 2 o 3 contents of up to 25 and 18 wt respectively other notable properties include the presence of globules of immiscible calcite and pyrrhotite melt phases shattered quartz grains and fragments of silicified plant matter dating of geoarchaeological artefacts associated with the dakhleh glass support preliminary 40 ar 39 ar data indicating a 200 100 ka age for the impact event geoarchaeological evidence indicates that archaic homo sapiens and early modern humans continually inhabited this region of the western desert during this period while it is unclear at present whether the dakhleh glass was formed during a cratering event or a large aerial burst the effect on the environment and inhabitants of dakhleh would have been catastrophic

high resolution stratigraphy and zircon u pb geochronology of the middle triassic buchenstein formation dolomites northern italy precession forcing of hemipelagic carbonate sedimentation and calibration of the anisian ladinian boundary interval orbitally forced cyclic variations in sedimentary sequences provide evidence for short term fluctuations of earth climate and a tool for high resolution timescale calibration we here present stratigraphic and geochronological evidence for precession forcing in middle triassic hemipelagic limestones of the buchenstein formation dolomites northern italy high resolution stratigraphy of several correlative sections of the buchenstein formation documents a coherent cycle pattern isotope dilution thermal ionization mass spectrometry zircon u pb geochronology of tuffs bracketing the cyclic interval reveals an average cycle duration of 18 5 2 1 kyr consistent with a shorter climatic precession cycle in the middle triassic compared with today this suggests a predominantly precession controlled climate in this low latitude setting of the western tethys and allows high precision calibration of the anisian ladinian boundary interval from integrating cyclostratigraphic and u pb geochronological constraints our best estimate for the age of the anisian ladinian boundary is 241 464 0 064 0 097 0 28 ma we also provide precise estimates for lithostratigraphic boundaries biostratigraphic markers and magnetic reversals within the boundary interval stratigraphic intervals with elevated sedimentation rate record a sub milankovitch signal that may be equivalent to patterns in adjacent carbonate platforms such as the latemar platform the origin of this sub milankovitch signal remains unknown but highlights the potential to investigate shorter term climatic variations in mesozoic sedimentary sequences supplementary material isotope dilution thermal ionization mass spectrometry u pb and laser ablation inductively coupled plasma mass spectrometry trace element data tables as well as the results of the bayesian age modelling are available at https doi org 10 6084 m9 figshare c 3861817

resolving milankovitchian controversies the triassic latemar limestone and the eocene green river formation although orbital forcing is commonly proposed as the driver of ancient sedimentary rhythms the lack of adequate independent time control radio isotopic data to calibrate these cycles has stood as a major challenge to evaluation of the hypothesis here i apply a new statistical approach to evaluate cyclicity in two historically important rhythmic units for which orbital forcing has been proposed the triassic latemar limestone dolomites italy and the eocene green river formation wyoming usa a major advance of the new method is its explicit evaluation of the null hypothesis of no orbital signal the null hypothesis can be rejected with a high degree of confi dence in the latemar limestone probability 0 30 and green river formation probability 0 07 the analyses also resolve controversies about the specifi c orbital calibrations at each site both data series reveal the expected precession obliquity and eccentricity orbital components and yield astrochronologies that are consistent with proposed radio isotopic based time scales

a mesozoic time scale we present an integrated geomagnetic polarity and stratigraphic time scale for the triassic jurassic and cretaceous periods of the mesozoic era with age estimates and uncertainty limits for stage boundaries the time scale uses a suite of 324 radiomenc dates including high resolution 40 ar 39 ar age estimates this framework involves the observed ties between 1 radiometric dates biozones and stage boundaries and 2 between biozones and magnetic reversals on the seafloor and in sediments interpolation techniques include maximum likelihood estimation smoothing cubic spline fitting and magnetochronology

strontium and neodymium isotopic study of libyan desert glass inherited pan african age signatures and new evidence for target material libyan desert glass ldg is an impact related natural glass of still unknown target material we have determined rb sr and sm nd isotopic ratios from seven ldg samples and five associated sandstones from the ldg strewn field in the great sand sea western egypt planar deformation features were recently detected in quartz from these sandstones 87sr 86sr ratios and e nd values for ldg range between 0 71219 and 0 71344 and between 16 6 and 17 8 respectively and hence are distinct from the less radiogenic 87sr 86sr ratios of 0 70910 0 71053 and e nd values from 6 9 to 9 6 for the local sandstones from the ldg strewn field previously published isotopic ratios from the libyan bp and oasis crater sandstones are generally incompatible with our ldg values ldg formation undoubtedly occurred at 29 ma but neither the rb sr nor the sm nd isotopic system were rehomogenised during the impact event as we can deduce from pan african ages of 540 ma determined from the regression lines from a total of 14 ldg samples from this work and the literature together with similar sr and nd isotopic values for ldg and granitoid rocks from northeast africa west of the nile these findings point to a sandy matrix target material for the ldg derived from a precambrian crystalline basement ruling out the cretaceous sandstones of the former nubian group as possible precursors for ldg

middle triassic magnetostratigraphy and biostratigraphy from the dolomites and greece abstract magnetostratigrapic and biostratigraphic data across the anisian ladinian middle triassic boundary were obtained from the frotschbach seceda section from the dolomites region of northern italy and the vlichos section from the greek island of hydra where the aghia triada published section was also resampled the frotschbach seceda section includes two radiometrically dated u pb tuff levels and covers two of the three chief candidates for the position of the base of the ladinian namely at the base of the secedensis zone or the subsequent curionii zone the aghia triada section yields biochronological evidence for the base of the secedensis zone whose significance is however critically discussed in the light of the magnetostratigraphic correlation with frotschbach seceda the vlichos section can be correlated with aghia triada and frotschbach seceda by means of magnetic polarity stratigraphy and sparse fossil occurrences the satisfactory correlation of the magnetozones allows us to construct a composite geomagnetic polarity sequence tied to tethyan ammonoid and conodont biostratigraphy for about a 2 4 myr interval across the anisian ladinian boundary

the age of the permian triassic boundary abstract the 5 cm boundary clay bed in the chinese stratotype section through the permian triassic boundary has been recognised as a bentonite shrimp ion microprobe dating of zircons in the bentonite indicates a magmatic age of 251 2 3 4 ma 2 this is the first direct constraint on the numerical age of the permian triassic boundary future refinements of ages at this important but poorly constrained level of the phanerozoic timescale may depend on re analysis of this uniquely placed volcanic horizon and other bentonites in the fossiliferous chinese upper permian and lower triassic the utility of defining the permian triassic boundary in the chinese stratotype section in the vicinity of known dateable horizons should be considered

carbonate cycle stacking patterns and hierarchies of orbitally forced eustatic sealevel change ordered stacking of meter scale upward shallowing cycles manifested as repeated thickness hierarchies within cratonic carbonate sequences has been considered primary evidence for causal relations between orbitally forced climate change and eustatic sealevel variation explicit in this argument is the assumption that each individual cycle represents a single sealevel rise sensitivity testing of one dimensional forward models incorporating a depth threshold of carbonate accumulation indicates that multiple upward shallowing cycles may originate during any single rise in sealevel variation in resultant cycle stacking pattern is sensitive to changes in sealevel amplitude sedimentation rate and subsidence rate with highest stacking ratios ratio of number of cyclic units to number of eustatic periods produced by low sealevel amplitudes and high sedimentation and subsidence rates these relations indicate that direct correlation between multiple frequency eustatic sealevel variations and meter scale cycle stacking hierarchies is unwarranted thus prevalent interpretations regarding the stacking record of orbital forcing in ancient carbonate rock sequences should be reevaluated

global regolith thermophysical properties of the moon from the diviner lunar radiometer experiment we used infrared data from the lunar reconnaissance orbiter lro diviner lunar radiometer experiment to globally map thermophysical properties of the moon s regolith fines layer thermal conductivity varies from 7 4 10 4 w m 1 k 1 at the surface to 3 4 10 3 w m 1 k 1 at depths of 1 m given density values of 1100 kg m 3 at the surface to 1800 kg m 3 at 1 m depth on average the scale height of these profiles is 7 cm corresponding to a thermal inertia of 55 2 j m 2 k 1 s 1 2 at 273 k relevant to the diurnally active near surface layer 4 7 cm the temperature dependence of thermal conductivity and heat capacity leads to a 2x diurnal variation in thermal inertia at the equator on global scales the regolith fines are remarkably uniform implying rapid homogenization by impact gardening of this layer on timescales 100 j m 2 k 1 s 1 2 in the interiors and ejecta of copernican aged impact craters and lower thermal inertia 50 j m 2 k 1 s 1 2 within the lunar cold spots identified by bandfield et al 2014 observed trends in ejecta thermal inertia provide a potential tool for age dating craters of previously unknown age complementary to the approach suggested by ghent et al 2014 several anomalous regions are identified in the global 128 pixels per degree maps presented here including a high thermal inertia deposit near the antipode of tycho crater

the global surface temperatures of the moon as measured by the diviner lunar radiometer experiment abstract the diviner lunar radiometer experiment onboard the lunar reconnaissance orbiter lro has been acquiring solar reflectance and mid infrared radiance measurements nearly continuously since july of 2009 diviner is providing the most comprehensive view of how regoliths on airless bodies store and exchange thermal energy with the space environment approximately a quarter trillion calibrated radiance measurements of the moon acquired over 5 5 years by diviner have been compiled into a 0 5 resolution global dataset with a 0 25 h local time resolution maps generated with this dataset provide a global perspective of the surface energy balance of the moon and reveal the complex and extreme nature of the lunar surface thermal environment our achievable map resolution both spatially and temporally will continue to improve with further data acquisition daytime maximum temperatures are sensitive to the albedo of the surface and are 387 397 k at the equator dropping to 95 k just before sunrise though anomalously warm areas characterized by high rock abundances can be 50 k warmer than the zonal average nighttime temperatures an asymmetry is observed between the morning and afternoon temperatures due to the thermal inertia of the lunar regolith with the dusk terminator 30 k warmer than the dawn terminator at the equator an increase in albedo with incidence angle is required to explain the observed decrease in temperatures with latitude at incidence angles exceeding 40 topography and surface roughness influence temperatures resulting in increasing scatter in temperatures and anisothermality between diviner channels nighttime temperatures are sensitive to the thermophysical properties of the regolith high thermal inertia ti materials such as large rocks remain warmer during the long lunar night and result in anomalously warm nighttime temperatures and anisothermality in the diviner channels anomalous maximum and minimum temperatures are highlighted by subtracting the zonal mean temperatures from maps terrains can be characterized as low or high reflectance and low or high ti low maximum temperatures result from high reflectance surfaces while low minimum temperatures from low ti material conversely high maximum temperatures result from dark surface and high minimum temperatures from high ti materials impact craters are found to modify regolith properties over large distances the thermal signature of tycho is asymmetric consistent with an oblique impact coming from the west some prominent crater rays are visible in the thermal data and require material with a higher thermal inertial than nominal regolith the influence of the formation of the orientale basin on the regolith properties is observable over a substantial portion of the western hemisphere despite its age 3 8 gyr and may have contributed to mixing of highland and mare material on the southwest margin of oceanus procellarum where the gradient in radiative properties at the mare highland contact is broad 200 km

large perturbations of the carbon cycle during recovery from the end permian extinction high resolution carbon isotope measurements of multiple stratigraphic sections in south china demonstrate that the pronounced carbon isotopic excursion at the permian triassic boundary was not an isolated event but the first in a series of large fluctuations that continued throughout the early triassic before ending abruptly early in the middle triassic the unusual behavior of the carbon cycle coincides with the delayed recovery from end permian extinction recorded by fossils suggesting a direct relationship between earth system function and biological rediversification in the aftermath of earth s most devastating mass extinction

zircon petrochronology and 40ar 39ar thermochronology of the adamello intrusive suite n italy monitoring the growth and decay of an incrementally assembled magmatic system the adamello intrusive suite is a composite batholith in northern italy with an estimated 2000 km3 volume assembled incrementally over a time span of 10 to 12 million years the history of crysta

improving the upper triassic numerical time scale from cross correlation between tethyan marine sections and the continental newark basin sequence abstract magnetostratigraphic cross correlations between biochronologically well dated tethyan marine sections and the astronomically tuned sedimentary sequence from the continental newark basin eastern north america help to improve the upper triassic time scale we show here that the most recent radiometric results constraining the age of the base and top of the upper triassic 237 and 200 ma respectively strengthen the chronostratigraphic calibration of the newark sedimentary sequence proposed by krystyn et al earth planet sci lett 203 2002 343 351 these results allow one to reconcile the milankovitch based cyclostratigraphy from the newark sequence the magnetostratigraphic data from both marine and continental environments and upper triassic biostratigraphy including data on tethyan marine faunas and on terrestrial vertebrates according to this calibration the successive upper triassic stages would have very different durations 10 myr for the carnian 237 227 ma 25 myr for the norian 227 202 ma and 2 myr for the rhaetian 202 200 ma but only if the entire rhaetian is recorded in the newark sequence we further show that the biozone durations in the upper triassic would have been highly variable and as a whole would have lasted much longer than in the lower and middle triassic

mapping the feo and tio2 content of the lunar surface with multispectral imagery the derivation of quantitative elemental concentrations from multispectral imaging of the moon has long been a goal of lunar remote sensing concentration maps at the spatial resolutions available from the recent clementine mission would provide a revolutionary new tool for understanding the origin and evolution of the lunar crust lucey et al 1995 presented a method for extracting the concentration of fe from multispectral imaging of the moon this paper examines and quantifies important aspects ofthat technique left unexamined by lucey et al which had the potential to severely limit its utility these aspects include the effects of maturity grain size mineralogy shading due to topography and the presence of glass we also present a new algorithm for derivation of tio2 from multispectral imaging of both mare and highland units we find that both techniques are only weakly sensitive to maturity and that they have about 1 wt accuracy based on examination of the spectral properties and compositions of resolved lunar sampling stations presented by blewett et al 1997 we also discuss these findings in the context of two contrasting views of the effect of composition on lunar spectral properties presented by pieters and coworkers and hapke and coworkers we find the view of hapke and coworkers to be more consistent with our observations using a global mosaic of clementine multispectral data and these element derivation algorithms we find that the global modal abundance of feo is 4 5 wt 1 wt and the global modal abundance of tio2 is 0 45 wt 1 wt

stability of the astronomical frequencies over the earth s history for paleoclimate studies the expected changes over the past 500 million years in the principal astronomical frequencies influencing the earth s climate may be strong enough to be detectable in the geological records and such effects have been inferred in several cases calculations suggest that the shortening of the earth moon distance and of the length of the day back in time induced a shortening of the fundamental periods for the obliquity and climatic precession from 54 to 35 41 to 29 23 to 19 and 19 to 16 thousand years over the last half billion years at the same time the precessional constant increased from 50 to 61 arc seconds per year the changes in the frequencies of the planetary system due to its chaotic motion are much smaller their influence on the changes of the periods of climatic precession obliquity and eccentricity of the earth s orbit around the sun can be neglected eccentricity periods used for quaternary climate studies may therefore be considered to have been more or less constant for pre quaternary times

libyan desert glass new field and fourier transform infrared data results are presented of new geological observations and laboratory analyses on libyan desert glass ldg a unique kind of impact glass found in egypt probably 28 5 29 4 million years in age a new ldg occurrence has been discovered some 50 kilometers southward of the main ldg occurrences in the great sand sea from fourier transform infrared ftir analysis the molecular structure of ldg is refined and significant differences are shown between ldg specimens and other pure silica glasses fulgurite industrial fused quartz and amorphous biogenic silica that are related to differences in their structures the slight variations observed here for the mean si o si angle between the different glasses are attributed to their thermal histories with regard to the other glasses analyzed the ldg infrared spectral parameters point to a higher ratio of discontinuities and defects in the tetrahedral sio4 network the quantitative mineralogical constitutions of sandstones and quartzites from the ldg geological setting were analyzed by ftir cretaceous sandstones have a specific composition about 90 wt quartz 10 dickite clearly different from the palaeozoic ones about 90 wt quartz but 7 kaolinite it is shown that the reddish silts bearing the ldg are constituted mainly by microquartz enriched with dickite whose particle size distribution is characteristic of fluvio lacustrine deposits probably oligocene to miocene in age the target rocks most probably quartz sand resulted from the weathering loss of the cementing microquartz of the cretaceous sandstones from the gilf khebir plateau with deposition in a high energy environment

lunar microwave brightness temperature model interpretation and inversion of spaceborne multifrequency observations by a neural network approach understanding the lunar physical properties has been attracting the interest of scientists for many years this paper is devoted to a numerical study on the capability of retrieving the thickness of the first layer of regolith as well as the temperature profile behavior from satellite based multifrequency radiometers at frequencies ranging from 1 to 24 ghz to this purpose a forward thermal electromagnetic numerical model able to simulate the response of the lunar material in terms of upward brightness temperature tb has been used the input parameters of the forward model have been set after a detailed investigation of the scientific literature and available measurements different choices of input parameters are possible and their selection is carefully discussed by exploiting a monte carlo approach to generate a synthetic data set of forward model simulations a physically based inversion methodology has been developed using a neural network technique the latter has been designed to perform from multifrequency tb s the temperature estimation at the lunar surface the discrimination of the subsurface material type and the estimate of the near surface regolith thickness results indicate that within the simplified scenarios obtained by interposing strata of rock ice and regolith the probability of detection of the presence of discontinuities beneath the lunar crust is on the order of 84 the estimation uncertainty of the near surface regolith thickness estimation ranges from 11 to 81 cm whereas for the surface temperature its estimation uncertainty ranges from about 1 5 k to 3 k conditioned to the choice of radiometric frequencies and noise levels

cause of upper triassic climate crisis revealed by re os geochemistry of boreal black shales abstract the triassic period is bracketed by two of the big five phanerozoic mass extinctions though long viewed as a period of climatic stability emerging data suggest multiple climatic swings and at least one severe ecological crisis linking these climatic instabilities with probable causes is hampered by poor age control within the triassic time scale here we present new re os ages for shale sections straddling middle upper triassic stage boundaries nominal re os isochron ages of 236 6 and 239 3 ma for the top and base of the ladinian upper middle triassic bring absolute time into the contentious triassic time scale and place the beginning of the late triassic about 12 m y earlier than previously assigned a marked decrease in initial 187os 188os in upper ladinian shale records input from wrangellian flood basalts an instigator in the carnian late triassic pluvial event and accompanying radiation of key fossil groups e g dinosaurs and calcareous nanoplankton an absolute time scale is proposed for the anisian ladinian carnian boundaries based on re os geochronology

shock metamorphism of quartz in nature and experiment ii significance in geoscience the occurrence of shock metamorphosed quartz is the most common petrographic criterion for the identification of terrestrial impact structures and lithologies its utility is due to its almost ubiquitous occurrence in terrestrial rocks its overall stability and the fact that a variety of shock metamorphic effects occurring over a range of shock pressures have been well documented these shock effects have been generally duplicated in shock recovery experiments and thus serve as shock pressure barometers after reviewing the general character of shock effects in quartz the differences between experimental and natural shock events and their potential effects on the shock metamorphism of quartz are explored the short pulse lengths in experiments may account for the difficulty in synthesizing the high pressure polymorphs coesite and stishovite compared to natural occurrences in addition post shock thermal effects are possible in natural events which can affect shock altered physical properties such as refractive index and cause annealing of shock damage and recrystallization the orientations of planar microstructures however are unaffected by post impact thermal events except if quartz is recrystallized and provide the best natural shock barometer in terms of utility and occurrence the nature of planar microstructures particularly planar deformation features pdfs is discussed in some detail and a scheme of variations in orientations with shock pressure is provided the effect of post impact events on pdfs is generally limited to annealing of the original glass lamellae to produce decorated pdfs resulting from the exsolution of dissolved water during recrystallization basal 0001 pdfs differ from other pdf orientations in that they are multiple mechanical brazil twins which are difficult to detect if not partially annealed and decorated the occurrence and significance of shock metamorphosed quartz and its other phases namely coesite stishovite diaplectic glass and lechatelierite are discussed for terrestrial impact structures in both crystalline non porous and sedimentary porous targets the bulk of past studies have dealt with crystalline targets where variations in recorded shock pressure in quartz have been used to constrain aspects of the cratering process and to estimate crater dimensions at eroded structures in sedimentary targets the effect of pore space results in an inhomogeneous distribution in recorded shock pressure and temperature which requires a different classification scheme for the variation of recorded shock compared to that in crystalline targets this is discussed along with examples of variations in the relative abundances of planar microstructures and their orientations which are attributed to textural variations in sedimentary target rocks examples of the shock metamorphism of quartz in distal ejecta such as at the k t boundary and from nuclear explosions are illustrated and are equivalent to that of known impact structures except with respect to characteristics that are due to long term post shock thermal effects finally the differences between the deformation and phase transformation of quartz by shock and by endogenic tectonic and volcanic processes are discussed we confirm previous conclusions that they are completely dissimilar in character due to the vastly different physical conditions and time scales typical for shock events compared to tectonic and volcanic events well characterized and documented shock effects in quartz are unequivocal indicators of impact in the natural environment

a primary analysis of microwave brightness temperature of lunar surface from chang e 1 multi channel radiometer observation and inversion of regolith layer thickness abstract in china s first lunar exploration project chang e 1 ce 1 a multi channel microwave radiometer was aboard the satellite with the purpose of measuring microwave brightness temperature tb from lunar surface and surveying the global distribution of lunar regolith layer thickness in this paper the primary 621 tracks of swath data measured by ce 1 microwave radiometer from november 2007 to february 2008 are collected and analyzed using the nearest neighbor interpolation to collect the tb data under the same sun illumination global distributions of microwave brightness temperature from lunar surface at lunar daytime and nighttime are constructed based on the three layer media modeling the top dust soil regolith and underlying rock media for microwave thermal emission of lunar surface the ce 1 measured tb and its dependence upon latitude frequency and feo tio2 content etc are discussed the ce 1 tb data at apollo landing sites are especially chosen for validation and calibration on the basis of available ground measurements using the empirical dependence of physical temperature upon the latitude verified by the ce 1 multi channel tb data at apollo landing sites the global distribution of regolith layer thickness is further inverted from the ce 1 brightness temperature data at 3 ghz channel those inversions at apollo landing sites and the characteristics of regolith layer thickness for lunar maria are well compared with the apollo in situ measurements and the regolith thickness derived from the earth based radar data finally the statistical distribution of regolith thickness is analyzed and discussed

biostratigraphic and radiometric age data question the milankovitch characteristics of the latemar cycles southern alps italy the combination of age diagnostic fossils in platform carbonates geometrical relationships with coeval basinal successions and single zircon u pb ages from volcaniclastic layers in basinal deposits constrain the age of a cyclic succession in the interior of the latemar platform to a narrow time span in the middle triassic with a duration shorter than 5 m y precession induced milankovitch band sea level oscillations are therefore excluded as controls for most of the 600 platform cycles reported from latemar statistical evaluation and graphic space time analyses of cycle stacking patterns alone may therefore not allow an unambiguous recognition of milankovitch frequencies in ancient platform carbonates

the dakhleh glass product of an impact airburst or cratering event in the western desert of egypt impact cratering is a ubiquitous geological process on the terrestrial planets meteorite impact craters are the most visible product of impact events but there is a growing recognition that large aerial bursts or airbursts should occur relatively frequently throughout geological time in this contribution we report on an unusual impact glass the dakhleh glass dg which is distributed over an area of 400 km 2 of the dakhleh oasis egypt this region preserves a rich history of habitation stretching back to over 400 000 years before the emergence of homo sapiens we report on observations made during recent fieldwork and subsequent analytical analyses that strengthen previous suggestions that the dg formed during an impact event the wide distribution and large size of dg specimens up to 50 cm across the chemistry e g cao and al2o3 contents up to 25 and 18 wt respectively the presence of lechatelierite and burnt sediments and the inclusion of clasts and spherules in the dg is inconsistent with known terrestrial processes of glass formation the age and other textural characteristics rule out a human origin instead we draw upon recent numerical modeling of airbursts to suggest that the properties of dg coupled with the absence of a confirmed crater can best be explained by melting of surficial sediments as a result of a large airburst event we suggest that glass produced by such events should therefore be more common in the rock record than impact craters assuming that the glass formed in a suitable preserving environment

compositional analyses of lunar pyroclastic deposits abstract the 5 band clementine uvvis data at 100 m pixel were used to examine the compositions of 75 large and small lunar pyroclastic deposits lpds and these were compared to representative lunar maria and highlands deposits results show that the albedo spectral color and inferred composition of most lpds are similar to those of low titanium mature lunar maria these lpds may have consisted largely of fragmented basalt with substantial components of iron bearing mafic minerals pyroxenes olivine and smaller amounts if any of volcanic glass several smaller lpds also show substantial highland components three classes of very large deposits can be distinguished from most lpds and from each other on the basis of crystallinity and possible titanium content of their pyroclastic components one class has spectral properties that are dominated by high titanium crystallized black beads e g taurus littrow a second consists of a mixture of high titanium glasses and beads with a higher glass bead ratio sulpicius gallus than that of taurus littrow and a third has a significant component of quenched iron bearing volcanic glasses aristarchus with possible moderate titanium contents although areally extensive these three classes of very large pyroclastic deposits compose only 20 of the 75 deposits studied 27 and eruption of such materials was thus likely to have been less frequent on the moon

shock metamorphism of quartz at the submarine mjolnir impact crater barents sea shock metamorphosed quartz grains have been discovered in a drill core from the central peak of the late jurassic marine mjolnir structure this finding further corroborates the impact origin of mjolnir the intersected strata represent the upper jurassic hekkingen formation and underlying jurassic and upper triassic formations the appearance orientation and origin of shock features in quartz grains and their stratigraphic distribution within the core units have been studied by optical and transmission electron microscopy the quartz grains contain planar fractures pfs planar deformation features pdfs and mechanical brazil twins the formation of pfs is the predominant shock effect and is attributed to the large impedance differences between the water rich pores and constituent minerals in target sediments this situation may have strengthened tensional extensional and shear movements during shock compression and decompression the combination of various shock effects indicates possible shock pressures between 5 and at least 20 gpa for three core units with a total thickness of 86 m from 74 00 m to 171 09 m core depth crater fill material from the lower part of the core typically shows the least pressures whereas the uppermost part of the allochthonous crater deposits displays the highest pressures the orientations of pfs in studied quartz grains seem to become more diverse as the pressure rises from predominantly 0001 pfs to a combination of 0001 and orientations however the lack of experimental data on porous sedimentary rocks does not allow us to further constrain the shock conditions on the basis of pf orientations

analysis of chang e 2 brightness temperature data and production of high spatial resolution microwave maps of the moon abstract the microwave radiation passively emitted from the moon is valuable for investigating the physical properties of the lunar regolith microwave maps which can reveal subsurface characteristics at depths of centimeters to meters give clues to understanding the evolution of the lunar surface china s chang e 2 ce 2 spacecraft carried a microwave radiometer mrm and conducted passive microwave remote sensing of the moon at 3 7 8 19 35 and 37 ghz 10 3 84 1 55 and 0 81 cm wavelengths during 2010 2011 brightness temperature tb data derived from the mrm orbital observations cover the entire moon and the time coverage is over a complete lunation in this paper we use spherical harmonic fits to model the tb variation as functions of local time and latitude using these fits we normalized the day and nighttime tb data measured at various local times into noon time and midnight conditions the spatial sampling of the normalized tb maps is 6 km pixel much higher than ground based observations and higher resolution than the mrm maps derived from chang e 1 by removing the variation in tb related to local time and latitude we produced a series of microwave maps that reveal differences in the properties of the regolith across the lunar surface the microwave behavior of various lunar surface features can be explained primarily by differences in the microwave loss tangent of the materials for example we find that the high ti maria have high daytime tb and exhibit lower nighttime tb than the other maria as a result of the high dielectric loss tangent of ilmenite the ilmenite rich materials are less transparent to microwaves and hence emissions emerge from closer to the surface which is heated strongly in the day and cools quickly at night most fresh craters correspond to low tb spots in the nighttime microwave maps in contrast to their behavior as hot spots in nighttime infrared data suggesting that the higher loss tangent of rocks compared to soils suppresses microwave emission at night the aristarchus plateau has a lower loss tangent relative to its surroundings because it is blanketed by fine grained rock poor pyroclastic material the pyroclastic blanket is more transparent to microwaves than the nearby maria causing the plateau to have relatively cool daytime tb and warm nighttime tb as a consequence of microwave emissions that originate at greater depths the orientale basin is another prominent anomaly in the microwave maps indicating that orientale materials differ in thermophysical and or dielectric properties from typical highland lithologies brightness temperature differences among prominent rayed craters indicate that the very youngest crater rays e g giordano bruno have lower thermal inertia than older but still optically immature rays e g tycho

middle triassic orbital signature recorded in the shallow marine latemar carbonate buildup dolomites italy a new time frequency analysis of sea level controlled carbonate platform cycles in the middle triassic latemar massif dolomites italy reveals a strong depositional signature with characteristics of dominant forcing by climatic precession modes corresponding to long and short precession components at 1 21 7 k y and 1 17 6 k y underwent amplitude modulations matching earth9s orbital eccentricity with major frequency components at 1 400 k y 1 125 k y and 1 98 k y obliquity appears as a minor component at 1 35 4 k y the latemar signature thus constitutes the oldest pristine milankovitch signature yet observed in the geologic record its fidelity rivals that of the pliocene pleistocene record originally used to confirm the theory of orbitally forced climates this evidence deepens a widely noted disagreement between radiometric and cyclostratigraphic time scales for the latemar buildup the latemar cycles indicate that orbitally forced sea level oscillations were operative in the ice free middle triassic hothouse world

a rock model for the cold and hot spots in the chang e microwave brightness temperature map thermal anomaly spots both hot and cold have been found in the global 37 ghz brightness temperature tb map of the moon based on the chang e ce microwave radiometer measurements to explain their origin a rock model is proposed to simulate the tb variation against latitude along the profile of a fresh crater in a single track way which is selected to highlight the topographic effect and avoid any modification to the data a mixed upper layer made up of rock and soil regolith and dust was employed into our previous multilayer model the thermal properties thermal conductivity and heat capacity of the mixture layer are presumed to be linear with the fraction of rocks given that high frequency 37 ghz measurements are chosen only the meter size and larger rocks of the upper mixed layer are considered to avoid scattering effects several fresh craters poor rich in ilmenite are selected as testing sites despite uncertainties in parameters such as rock abundance ra and iron and titanium abundances three conclusions can be reached from these cases 1 ra has a significant effect on both the tb value and tb variation trend against latitude its contribution over some craters may be as high as 15 k 2 the simulations based on our rock model fit the ce observations better than those when rocks are not included and 3 the rock and ilmenite contributions could be the main cause for the cold and hot spots found in the ce microwave map

density and porosity of the lunar crust from gravity and topography 1 newly obtained gravity and topography data of the moon combined with a lithospheric flexure model that considers both surface and subsurface loading are used to place constraints on the density of the upper crust from a localized spectral admittance analysis subsurface loads are found to be relatively unimportant in the highlands and when subsurface loads are neglected the best fitting bulk densities for a number of highland regions are found to vary from 2590 to 2870 kg m 3 with a mean value of 2691 kg m 3 crustal rock densities estimated from geochemical considerations and global iron and titanium abundances imply somewhat greater densities which we interpret as porosity affecting the gravity derived bulk density estimates the average porosity in the upper few kilometers of crust is calculated to be about 7 7 which is consistent with porosity estimates of impact fractured meteorites and terrestrial impact craters

earth based observations of radar dark crater haloes on the moon implications for regolith properties 1 earth based radar can be used in conjunction with other data sets collected remotely or in situ to characterize the physical and chemical properties of the lunar regolith we use previously existing and newly acquired earth based radar measurements at 70 cm wavelength to investigate the properties of distinctive low return haloes surrounding 39 nearside impact craters these haloes are distinct from the well known optically dark haloes associated with volcanic craters or with impacts into cryptomare deposits we examine two possible mechanisms for formation of radar dark haloes 1 excavation of high tio2 high loss tangent basalt and 2 deposition of a mantling layer produced in the impact process that is depleted in meter sized blocks comparison of the radar data with apollo and lunar orbiter images indicates a general spatial correspondence between radar dark crater haloes and radial ridged ejecta facies distal to the radar bright crater rims comparison with clementine uv vis multispectral data indicates no apparent spatial correlation between regions of enhanced tio2 content and radar dark haloes though variations in tio2 content may play a role for some mare craters they are insufficient to account for the observed offsets in radar echo power we conclude that the radar dark haloes result from a block poor ejecta deposit that disappears over time with meteoroid bombardment a more detailed and comprehensive analysis of ejecta degradation processes and rates following acquisition of additional high resolution radar data could lead to a refinement of the lunar geologic timescale

high resolution estimate for the depositional duration of the triassic latemar platform a new magnetostratigraphy and magnetic susceptibility cyclostratigraphy from basinal sediments at rio sacuz italy 1 a new magnetostratigraphy and magnetic susceptibility cyclostratigraphy from middle triassic basinal sediments at rio sacuz northern italy suggests a depositional duration of 1 myr for most of the 670 m carbonate latemar platform giving a high resolution estimate for the duration for the latemar s deposition the new magnetostratigraphy from rio sacuz clarifies the ambiguities in a previous magnetostratigraphic study of the latemar caused by lightning strike remagnetizations our rio sacuz study was unaffected by lightning using thermal demagnetization we show a normal reversed normal reversed sequence at the latemar correlated locality of rio sacuz with a polarity interval duration of 0 25 0 5 myr for the middle triassic this gives a depositional duration of 1 2 myr rock magnetic experiments show that the magnetic carrier is magnetite suggesting a primary depositional age remanence measurement of magnetic susceptibility at 1 m intervals from rio sacuz reveals eight short eccentricity cycles 95 125 kyr bundled into slightly more than two 405 kyr long eccentricity cycles indicating a more precise duration for the rio sacuz section of 0 8 to 1 myr the shorter depositional duration required by this study forces a sub milankovitch time scale of 1 2 kyr for the latemar platform s meter scale rhythmic bedding and provides strong evidence for nonorbitally driven climate change in the middle triassic

abundance and distribution of iron on the moon the abundance and distribution of iron on the moon is derived from a near global data set from clementine the determined iron content of the lunar highlands crust 3 percent iron by weight supports the hypothesis that much of the lunar crust was derived from a magma ocean the iron content of lower crustal material exposed by the south pole aitken impact basin on the lunar farside is higher 7 to 8 percent by weight and consistent with a basaltic composition this composition supports earlier evidence that the lunar crust becomes more mafic with depth the data also suggest that the bulk composition of the moon differs from that of the earth9s mantle this difference excludes models for lunar origin that require the earth and moon to have the same compositions such as fission and coaccretion and favors giant impact and capture

magnetostratigraphic confirmation of a much faster tempo for sea level change for the middle triassic latemar platform carbonates new magnetostratigraphic data for the 470 m thick latemar carbonate platform which includes 600 shallowing upward bedding cycles are consistent with litho and biostratigraphic correlations of the section to a 10 m thick interval in the basinal buchenstein beds that most likely represents only 1 m y of deposition according to published u pb single crystal zircon dates a reappraisal of reported cycle stratigraphic analyses of the latemar suggests that the visibly obvious meter scale bedding is not due to milankovitch precessional forcing but rather reflects tempos an order of magnitude faster that may involve millennial scale tidal amplitude variations d 2004 elsevier b v all rights reserved

the middle triassic magnetostratigraphy from the peri tethys basin in poland abstract the paper presents the first complete magnetic polarity scale obtained for the middle triassic of the northern peri tethys area the roetian and muschelkalk deposits of southern poland upper silesia the holy cross mountains were studied paleomagnetically the obtained paleopole a 52 n 143 e fits well to the middle triassic ca 240 ma segment of the stable european apwp a set of various quality characteristic directions isolated in 106 samples was used for construction of the composite polarity scale this peritethyan scale has been tied with conodont zonation and referred to the scale erected earlier in the tethyan realm comparison of both scales indicates that the whole roetian succession in the southern polish basin should be correlated with the latest olenekian the normal marine sedimentation ceased in the polish basin as early as in the late fassanian time the obtained magnetostratigraphic scale combined with the sequence stratigraphic framework enables a reliable chronological correlation of the late olenekian ladinian succession over the entire peri tethys basin

reply to discussion of magnetostratigraphic confirmation of a much faster tempo for sea level change for the middle triassic latemar platform carbonates by d v kent g muttoni and p brack earth planet sci lett 228 2004 369 377 by l hinnov

lunar equatorial surface temperatures and regolith properties from the diviner lunar radiometer experiment 1 the diviner lunar radiometer experiment onboard the lunar reconnaissance orbiter has measured solar reflectance and mid infrared radiance globally over four diurnal cycles at unprecedented spatial and temporal resolution these data are used to infer the radiative and bulk thermophysical properties of the near surface regolith layer at all longitudes around the equator normal albedos are estimated from solar reflectance measurements normal spectral emissivities relative to the 8 m christiansen feature are computed from brightness temperatures and used along with albedos as inputs to a numerical thermal model model fits to daytime temperatures require that the albedo increase with solar incidence angle measured nighttime cooling is remarkably similar across longitude and major geologic units consistent with the scarcity of rock exposures and with the widespread presence of a near surface layer whose physical structure and thermal response are determined by pulverization through micrometeoroid impacts nighttime temperatures are best fit using a graded regolith model with a 40 increase in bulk density and an eightfold increase in thermal conductivity adjusted for temperature occurring within several centimeters of the surface

spectral analysis of the middle triassic latemar limestone abstract the middle triassic latemar limestone in the dolomites region northern italy consists of hundreds of vertically stacked meter scale platform carbonate cycles each cycle is composed of a shallow marine subtidal carbonate unit with a thin centimeter scale vadose diagenetic dolomite cap these latemar couplets are the products of repeated episodes of submergence emergence with durations estimated at 20 000 yr the couplets are arranged in upward thinning bundles of five indicating the presence of a 100 000 year modulating component we examined this high frequency cycling in the platform buildup using a variety of classical and advanced spectral analysis techniques we found si nificant evidence for the presence of a milankovitch forcing signal in this cycling we also present evidence that the adjacent coeval basinal facies the livinallongo formation exhibits a similar bundling pattern in its cm scale hemipelagic carbonate shale alternations we conclude that milankovitch forced small amplitude sea level oscillations were the most likely cause of these middle triassic carbonate rhythms

lateral variations in sediment composition and bedding in middle triassic interplatform basins buchenstein formation southern alps italy hemipelagic deposits are widespread in triassic sequences of the alpine belt and provide important data for stratigraphy and the study of bedding rhythms the area of the western and central dolomites of northern italy escaped strong alpidic deformation and preserves such deposits in their original palaeogeographic setting the buchenstein formation the object of this study was deposited in up to 1000 m deep middle triassic interplatform basins which extend over an area of 500 km 2 within the dolomites excellent outcrops and volcaniclastic markers allow a detailed correlation of the formation in both laminated anoxic and bioturbated facies down to a bed scale and show its relationship to coeval carbonate platforms correlation of lithostratigraphically well constrained intervals in the bioturbated facies reveal that lateral thickening and thinning of the deposits depends on the amount of shallow water debris in the succession and is a function of the distance to coeval carbonate platform sources in the laminated background deposit thickness variations in limestones and marls parallel the thickness variations in ash layers and were caused by local redeposition of sediment on the basin floor lateral persistence of laminae indicates that bottom currents were weak in the buchenstein basin but were able to redeposit mud in a significant way in the area around seceda and geisler western dolomites a lateral transition from dark grey laminated to grey bioturbated to red bioturbated facies is observed which is probably linked to local relief with different oxygenation conditions on the sea floor a comparison shows that decimetre scale bedding is preserved in all facies types and that the bedding rhythm is partly the result of different cementation of the sediment during early diagenesis correlation of individual layers in the bioturbated facies reveals that beds are thicker and enriched in lime mud in the western part of the basin and decrease in thickness and contain less micrite towards the east further away from the main shallow water areas nearslope calciturbidites change gradually from distinct layers into lateral arrays of micrite nodules and bands further out in the basin these observations point to a platform source of lime mud in the buchenstein basin

lunar iron and titanium abundance algorithms based on final processing of clementine ultraviolet visible images the clementine mission to the moon returned global imaging data collected by the ultraviolet visible uvvis camera this data set is now in a final state of calibration and a five band multispectral digital image model dim of the lunar surface will soon be available to the science community we have used observations of the lunar sample return sites and stations extracted from the final dim in conjunction with compositional information for returned lunar soils to revise our previously published algorithms for the spectral determination of the feo and tio2 content of the lunar surface the algorithms successfully normalize the effects of space weathering so that composition may be determined without regard to a surface s state of maturity these algorithms permit anyone with access to the standard archived dim to construct high spatial resolution maps of feo and tio2 abundance such maps will be of great utility in a variety of lunar geologic studies

formation mechanisms of planar deformation features in naturally shocked quartz abstract shock waves induce peculiar defects in quartz shock mosaics high pressure polymorphs coesite and stishovite diaplectic glass and planar deformation features pdfs together these features are the indices of shock metamorphism pdfs appear under the optical microscope as straight and narrow defects parallel to the 10 1n rhombohedral planes with n 3 and 2 as most frequent values although n 1 4 and i e basal plane are also found we report in the first part of this paper a detailed investigation by transmission electron microscopy of the fine structure of pdfs in shocked quartz grains from a variety of sites slate islands la malbaie and manson in north america the vredefort complex in south africa the ries crater in germany and the cretaceous tertiary boundary layer at raton basin colorado we distinguish four pdf fine structures 1 bands of dislocations 2 lamellae of mixtures in various proportions of amorphous silica and small crystallites 3 thin brazil twin lamellae 4 short parallel lamellae forming serrated ladder structures the possible formation mechanisms of these pdfs are discussed in the second part of the paper it is suggested that the dislocation bands are probably not original pdf structures but stem from a later recrystallization stage the brazil twins have been produced by relatively large deviatoric stresses which accompanied the shock wave the other pdf structures which consist of partial amorphization in the 10 1 n planes must result from elastic instabilities of the shear modulus of the quartz structure at high pressure in these planes theoretical estimates of the elastic stiffness coefficients indicate that amorphization should start at approximately 10 gpa the growth of the straight and narrow amorphous lamellae would be driven by the front of the shock wave

geochemical and geochronological data on triassic volcanism of the southern alps of lombardy italy genetic implications a widespread volcanism mainly consisting of pyroclastic products and lava flows is found in the southern alps of lombardy the volcanics are interbedded with anisian ladinian carbonatic sequences and continental terrigenous or transitional deposits of ladinian carnian age the petrographic and geochemical data for this volcanism indicate a calc alkaline affinity with characters similar to those of convergent continental margins in this sector of the alps the geological evidences show that in the middle triassic general extensional movements were the dominant deformation event and do not support the existence of a subduction zone during this period the apparent contrast between the tectonic environment and the type of magmas erupted in the anisian carnian is tentatively explained by partial melting during the early stage of rifting of an upper mantle deeply modified during the previous hercynian orogenesis and contaminated by crustal material this hypothesis is in agreement with the preliminary sr isotopic ratios 0 705 and 0 709 k ar and rb sr ages on biotites date the beginning of the volcanism at around 225 m y

remote sensing of lunar pyroclastic mantling deposits abstract mantling deposits on the moon are considered to be pyroclastic units emplaced on the lunar surface as a result of explosive fire fountaining these pyroclastic units are characterized as having low albedos having smooth fine textured surfaces and consisting in part of homogeneous febearing volcanic glass and partially crystallized spheres mantling units exhibit low returns on depolarized 3 8 cm radar maps indicating an absence of surface scatterers in the 1 to 50 cm size range a number of reflectance spectra from several regional pyroclastic deposits are presented for the first time these data support a previous interpretation that mantling units have a unique spectral signature which is indicative of the presence of a significant fe bearing volcanic glass component the rima bode region is discussed as an example of an area in which several types of remote sensing data including 3 8 cm radar spectral reflectance and multispectral vidicon data were used to reconstruct the geologic events surrounding the emplacement of a regional pyroclastic mantling deposit the recognition of numerous varieties of volcanic glass samples especially relatively high albedo e g green yellow glasses suggests the existence of additional unrecognized mantling deposits with albedos higher than those studied to date on the basis of the remote sensing data summarized and presented five new areas have been identified which may represent higher albedo regional pyroclastic deposits

integrated anisian ladinian boundary chronology we report magnetostratigraphic and biostratigraphic data from the seceda core and the correlative outcrop section from the dolomites of northern italy the seceda rock succession consists of tethyan marine limestones and radiometrically dated volcaniclastic layers of the buchenstein beds of middle triassic age f238 242 ma the seceda outcrop section was correlated to coeval sections from the literature using magnetic polarity reversals and a selection of laterally traceable and isochronous lithostratigraphic marker beds this allowed us to import the distribution of age diagnostic conodonts ammonoids and daonellas from these sections into a seceda reference stratigraphy for the construction of an integrated biochronology extending across a consistent portion of the anisian ladinian boundary interval among the three options selected by the subcommission for triassic stratigraphy to establish the ladinian global stratigraphic section and point we propose to adopt the level containing the base of the curionii ammonoid zone at bagolino southern alps italy because this level is closely associated with a global means of correlation represented by the base of polarity submagnetozone sc2r 2r the first occurrence of neogondolella praehungarica in the dolomites predates slightly the base of the curionii zone and can be used to approximate the anisian ladinian boundary in the absence of ammonoids d 2004 elsevier b v all rights reserved

tracking an upper limit of the carnian crisis and or carnian stage in the western carpathians slovakia the late triassic timescale especially the carnian norian boundary is poorly constrained mainly due to a paucity of high precision radio isotopic ages that can be related accurately to contradictions between the biostratigraphic and magnetostratigraphic correlations la icp ms dating of detrital zircons from five samples of the lunz formation the upper triassic siliciclastic sediments from the western carpathians slovakia provided a wide spectrum of ages that vary from late archaean ca 2582 ma to triassic ca 216 ma these marine delta sediments represent a typical product of the carnian crisis a major climate change and biotic turnover that occurred during the carnian stage in the tethys ocean within the carbonate shelf and intrashelf basins in the northern calcareous alps and the western carpathians the supply of clastic material in the studied lunz formation was derived from several sources especially i from the recycled variscan orogen ii from the remote east european platform and iii from the contemporaneous triassic volcanic sources syn sedimentary volcanic zircons with a concordia age of 221 2 1 6 ma calculated from 12 single analyses represent the maximum age of deposition of the lunz formation and demonstrate that the upper limit of the carnian crisis and or the carnian stage in the alpine carpathians realm is younger than the current age of the carnian norian boundary at ca 227 ma listed on the international chronostratigraphic chart international commission on stratigraphy 2016 12 edition

the triassic timescale new constraints and a review of geochronological data a review of geochronological data underlying the geological time scale for the triassic yields a significantly different time scale calibration than that published in the most recent compi lation geologic time scale 2004 this is partly due to the availability of new radio isotopic data but mostly because strict selection criteria are applied and complications arising from biases both systematic and random are accounted for in this contribution the ages for the base and the top of the triassic are constrained by u pb ages to 252 3 and 201 5 ma respectively these dates also constrain the ages of major extinction events at the permian triassic and triassic jurassic bound aries and are statistically indistinguishable from ages obtained for the siberian traps and volcanic products from the central atlantic magmatic province respectively suggesting a causal link ages for these continental volcanics however are mostly from the k ar 40 ar 39 ar system which requires accounting and correcting for a systematic bias of c 1 between u pb and 40 ar 39 ar isotopic ages the 40 ar 39 ar ages being younger robust age constraints also exist for the induan olenekian boundary 251 2 ma and the early middle triassic olenekian anisian boundary 247 2 ma resulting in a surprisingly short dur ation of the early triassic which has implications for the timing of biotic recovery and major changes in ocean chemistry during this time furthermore the anisian ladinian boundary is con strained to 242 0 ma by new u pb and 40 ar 39 ar ages radio isotopic ages for the late triassic are scarce and the only reliable and biostratigraphically controlled age is from an upper carnian tuff dated to 230 9 ma yielding a duration of more than 35 ma for the late triassic all of these ages are from u pb analyses applied to zircons with uncertainties at the permil level or better the resulting compilation can only serve as a guideline and must be considered a snapshot resolving some of the issues mainly associated with inaccurate and misinterpreted data in previous publi cations however further advances will require revision of some of the data presented here

new perspectives on orbitally forced stratigraphy this survey of the current status of research into earth s orbitally forced paleoclimatic record summarizes recent developments in the theory of earth s orbital parameters and reviews how various techniques of data collection and analysis have fared in the search and recovery of orbital signals in ancient stratigraphy the emerging significance of the quasi periodicity of earth s orbital variations as a prin cipal tool in the analysis of orbitally forced stratigraphy is discussed in detail five case studies are presented that illustrate new directions in research a time series analysis of discontinuous strata b measurement of ultra high resolution stratigraphic signals c new perspectives on the 100 kyr pleistocene glaciation problem d strati graphic evidence for solar system resonance modes and e evaluating phanerozoic length of day from orbitally forced stratigraphy the study of how earth s orbital parameters came to be recorded in ancient stra tigraphy has recently moved into a new phase of scientific inquiry and discovery notable advances in celestial mechanics and in the analysis of stratigraphic data have given rise to new ways of solving old problems and have uncovered new problems for the first time new tools have facilitated the recovery of extended high resolution orbital signals from stratigraphy advanced analytical techniques have now been fully incorporated into the field an updated theory of earth s orbital parameters provides an accurate ephemeris for the past 16 million years for precision correlation between earth s orbital parameters and orbitally forced stratigraphy some orbital eccentricity modes can be used for orbital stratal cal ibrations to several hundred million years ago these breakthroughs have transformed the study of orbitally forced stratigra phy into an applied field that addresses long standing problems in disciplines as far ranging as geochronology geodynamics and astrodynamics orbital signals provide the framework for a high resolution orbital chronostratigraphy as far back

milankovitch and sub milankovitch cycles of the early triassic daye formation south china and their geochronological and paleoclimatic implications article the mass extinction at the end of permian was followed by a prolonged recovery process with multiple phases of devastation restoration of marine ecosystems in early triassic the time framework for the early triassic geological biological and geochemical events is traditionally established by conodont biostratigra phy but the absolute duration of conodont biozones are not well constrained in this study a rock magnetic cyclostratigraphy based on high resolution analysis 2440 samples of magnetic susceptibility ms and anhysteretic remanent magnetization arm intensity variations was developed for the 55 1 m thick early triassic lower daye formation at the daxiakou section hubei province in south china the lower daye formation shows exceptionally well preserved lithological cycles with alternating thinly bedded mud stone marls and limestone which are closely tracked by the ms and arm variations power spectral wavelet and amplitude modulation am analyses of the arm and ms series reveal strong evidence for the presence of milankovitch to sub milankovitch frequencies dominated by precession index signal and 4 5 ka cycles cy cles expressed by variations in ms and arm were likely controlled by changes in the input of fine grained detrital magnetite which in turn may have been driven by astronomically induced changes in monsoon in tensity in the equatorial eastern paleotethys during the early triassic greenhouse period on the basis of the 100 ka tuning results the astronomically constrained duration of the induan stage is 1 16 ma with the griesbachian and dienerian substages of 490 ka and 670 ka respectively the new astro nomical time scale also provides time constraints for the conodont and bivalve biozones and the carbonate carbon isotope 13 c records of the lower triassic daye formation time constraints for the conodont bio zones include 34 ka for hindeodus parvus 2 4 ka forisarcicella staschei i isarcica 366 ka for neogondolella planata ng carinata 66 ka for neogondolella discreta 255 ka for neospathodus kummeli and 415 ka for neospathodus dieneri the duration for the negative 13 c shift from high 13