orbital scale glacio eustasy in the middle devonian detected using oxygen isotopes of conodont apatite implications for long term greenhouse icehouse climatic transitions abstract results from previous paleoclimate studies indicate gondwanan glaciation marking the onset of middle paleozoic icehouse climate conditions began by the latest devonian famennian more recently 18o trends from conodont apatite suggest cooling middle devonian subtropical seasurface temperatures 20 my prior to famennian glaciation and high latitude temperatures cool enough to permit the growth of continental glaciers which controlled longer term my scale glacio eustasy this study evaluates the details and patterns of middle devonian high frequency thirteen complete middle devonian givetian subtidal cycles 0 5 3 m thick in the little cedar formation of southeastern iowa are characterized by oxygenated offshore facies transgression poorly oxygenated offshore facies maximum flooding a return to oxygenated facies and are capped by bioturbated lower shoreface facies regression lowstand which lack evidence of subaerial exposure across shelf cyclostratigraphic facies relationships suggest relatively subdued water depth changes were responsible for cycle development measured 18o values from conodont apatite range from 15 9 to 18 4 and repeated systematic intracycle trends are dominated by lower isotopic values in offshore facies and higher isotopic values in cycle capping lower shoreface facies which is consistent with glacio eustasy driving the water depth changes the average 0 6 magnitude of intracycle isotopic shift 0 2 to 1 0 total range suggests 15 23 m glacio eustatic oscillations were responsible for observed water depth changes the higher range of intracycle isotopic magnitudes may be the result of increased subtropical evaporation rates during glacial stages which locally enriched surface seawater 18o values orbital scale

venus cloud level circulation during 1982 as determined from pioneer cloud photopolarimeter images ii solar longitude dependent circulation abstract a strong solar locked dependence of cloud level circulation is observed in the averaged cloud motions as well as in the ultraviolet reflectivity of the venus cloud layer as determined from pioneer venus orbiter images acquired during 1982 s s limaye c grassotti and m j kuetemeyer 1988 icarus 73 193 211 the cloud motions were determined by manually tracking cloud features while the ultraviolet reflectivity was determined by removing the scattering geometry dependence of the observed intensities in ultraviolet images of venus via a minnaert scattering model in low latitudes the average zonal component is slowest at about 10 40 am local solar time while the maximum poleward flow occurs at noon at most latitudes the cloud motions are divergent with the maximum horizontal divergence 5 10 6 sec 1 occurring in equatorial latitudes just past noon and become convergent at about 30 morning to 40 afternoon lat on both sides of the equator the lowest ultraviolet reflectivity is found near the equator at local noon peak reflectivity is found in broad tilted with respect to latitude circles bands near 45 lat in the north and south hemispheres an apparent relationship between the horizontal divergence and ultraviolet is indicated such that the highest reflectivities are found in regions of convergence in high latitudes and lower values where the motions are divergent in equatorial latitudes in solar locked coordinates the root mean square deviation of the normalized ultraviolet brightness is not uniformly distributed about the subsolar point but tends to be higher around 45 lat than in equatorial regions and over periods of about 2 weeks shows substantial small scale structure as well

palaeobathymetric reconstruction of peritidal carbonates late barremian urgonian sequences of provence se france abstract peritidal platform carbonates of late barremian age early cretaceous cropping out in the marseille region provence se france tend to be arranged stratigraphically in deepening up or shallowing up sequences seven facies types lithofacies were defined in the studied stratigraphic interval ranging from supratidal to shallow subtidal settings there is a good correspondence between the inferred relative water depth of facies and their average bed thickness cumulative thickness of facies types expresses quantitatively their palaeobathymetric range and provides an estimate of their average water depth calculations show that the palaeobathymetry of supratidal intertidal facies types is from 0 to 40 cm i e a pertaining to a palaeotidal microtidal range the average palaeobathymetry of rudist facies ascribed to subtidal settings fluctuates between 40 cm and nearly 160 cm measuring a large number of beds belonging to both shallowing up and deepening up sequences and averaging the results appear relevant to minimise the effect of compaction pressure solution and synsedimentary progressive or abrupt changes in accommodation which are expected to modify bed thickness and its original palaeobathymetric significance the method proposed here has a good potential for palaeobathymetric reconstruction of ancient peritidal carbonates

measurements of the mean solar fixed temperature and cloud structure of the middle atmosphere of venus data from the orbiter infrared radiometer oir of the pioneer venus mission have allowed the global structure of the middle atmosphere of venus to be studied in detail for the first time between 4 december 1978 and 14 february 1979 this instrument made over 300 000 soundings in ten spectral channels covering most of the northern and some of the southern hemisphere in the altitude range 65 100 km 100 0 01 mb preliminary analyses indicate that mean atmospheric structure in this region is strongly dependent on latitude and local time of day although day to day variations are seen this paper presents the mean temperature field and cloud top structure retrieved from the data of five oir channels averaged in a solar fixed coordinate system the retrieval scheme and the derivation of the weighting functions that characterize the vertical response of each channel are also described the middle atmosphere can be divided into two distinct regions separated by a low latitude temperature minimum of less than 170k at 95km in the retrieved zonal mean temperature field below 95km day night temperature contrasts are small but above 70km pole equator contrasts are positive reaching a maximum of 20 25 k at 85km fourier analysis shows that within 45 of the equator the longitudinal variation of temperature is dominated by wavenumber 2 tidal structure with a phase that moves eastwards with increasing altitude above 95km the pole equator temperature gradient is reversed day night contrasts become appreciable and wavenumber 1 longitudinal structure dominates at equatorial latitudes mean cloud optical depth at 11 5 n is unity at 100mb 66 5 km and the cloud top has a scale height of 0 85 times the atmospheric value the cloud top falls slowly with increasing latitude and has a wavenumber 1 longitudinal dependence of 20mb 1 km with the highest cloud found just before the evening terminator retrievals are insensitive to cloud structure in the polar regions but it is clear that the cool collar that surrounds the warm polar region is not a high cloud feature it is in fact a deep temperature inversion in which temperatures can be more than 30 k less than equatorial values at the same level

solar migrating atmospheric tides in the winds of the polar region of venus we study the effects of migrating solar tides on the winds at the cloud tops of the polar region of venus the winds were measured using cloud tracking on images obtained at wavelengths of 3 9 and 5 0 l mb y the instrument virtis m onboard venus express these wavelengths probe about the same altitude close to the cloud tops allowing for the first time to retrieve winds simultaneously in the day and nightside of the planet we use a dataset with observations from 16 orbits covering a time span of 289 days and a latitude range between 70s and 85s the region where the so called cold collar resides diurnal and quarter diurnal tides wavenumbers 1 and 4 were detected in the wind field with a decoupled influence on the zonal and meridional directions the diurnal tide is the dominant harmonic with amplitudes of about 4 7 m s exclusively affecting the meridional component of the wind and forcing a solar to antisolar circulation at the polar region the quarter diurnal mode is only apparent in the zonal wind in a restricted latitude range with amplitudes 2 2 m s the spatial structure of the diurnal tide has also been investigated obtaining a vertical wavelength of about 8 km in accordance with predictions by models finally a theoretical relation between the amplitudes of tidal temperature and tidal wind has been derived and its validity tested with models and results from previous missions

solar related waves in the venusian atmosphere from the cloud tops to 100 km abstract a diagnostic quasi linear model has been developed which uses observed solar related temperatures and a specified zonal mean circulation and thermal structure to find the solar related circulation above the clouds of venus because there are no observations of the mean circulation above the clouds it has been calculated using an independent model although the model derived solar related circulation depends on the mean flow to a much greater degree than is the case for terrestrial tides and although there is uncertainty in this mean flow several important conclusions have been drawn concerning the solar related circulation and thermal structure given that the solar forcing is likely to have a maximum in equatorial regions there is an anomalously large response in the polar regions it is primarily because of this unusual polar thermal structure that the model requires some process such as dissipation to act as an important sink for momentum in the model dissipation is specified as a ra

testing periodicity of depositional cyclicity cisco group virgilian and wolfcampian texas abstract periodicities of 15 cyclic sections of the cisco group are tested through gamma and spectral analyses the sections are composed of marine and nonmarine carbonate and siliciclastic rocks deposited on the eastern shelf north central texas in late pennsylvanian and early permian time gamma analysis generates facies dependent thickness time conversion factors s to construct corrected time series which are more realistic than the uncorrected series obtained by proportional conversion positive and stable s and improved resolution of the corrected spectra indicate successful tuning on the cisco spectra a short eccentricity peak 95 131 ky is the most prominent and persistent long eccentricity 413 ky and obliquity 34 and 43 ky peaks are persistent and precessional index peaks 17 and 21 ky are less persistent a persistent peak of period 50 80 ky may be a combination tone between obliquity and precessional index cycles non milankovitch peaks are sporadic the validity of gamma and spectral results is indicated by consistent estimated ages among the cisco sections and reasonable effective sedimentation rates calculated on the basis of milankovitch spectral calibrations the results combined with geologic evidence suggest that the cisco cyclicity was controlled dominantly by milankovitch climatic forcing

probabilistic models for cyclic straining of saturated clean sands a maximum likelihood framework for the probabilistic assessment of postcyclic straining of saturated clean sands is described databases consisting of cyclic laboratory test results including maximum shear and postcyclic volumetric strains in conjunction with relative density number of stress strain cycles and index test results were used for the development of probabilistically based postcyclic strain correlations for this purpose in addition to the compilation of existing data from literature a series of stress controlled cyclic triaxial and simple shear tests were performed on laboratory constituted saturated clean sand specimens the variabilities in testing conditions i e type of test consolidation procedure confining pressure rate of loading etc were corrected through a series of correction schemes the effectiveness of which were later confirmed by the discriminant analyses results volumetric and shear strain boundary curves were developed in the cyclic stress ratio versus n1 60

venus cloud level circulation during 1982 as determined from pioneer cloud photopolarimeter images i time and zonally averaged circulation abstract new measurements of cloud motions on venus during 1982 reveal significant changes in the mean cloud level circulation compared to that seen during 1974 s s limaye and v e suomi 1981 j atmos sci 38 1220 1235 as well as 1979 s s rossow a d del genio s s limaye l d travis and p h stone 1980 j geophys res 85 8107 8128 s s limaye c j grund and s p burre 1982 icarus 51 416 439 in order to establish the validity of these changes two individuals measured cloud motions independently in nearly identical sets of images the results of these independent estimates for 1982 are in remarkable agreement for not only the average zonal and meridional components but also for the measured meridional transport of momentum by the eddy circulation unlike the results for 1979 the latitudinal profile of the time and longitudinally averaged zonal component of the cloud motions for 1982 shows pronounced jets near 45 north and south lat while the average zonal component near the equator is weaker than by more than 10 msec 1 the time and longitudinally averaged meridional component is found to be slightly greater than that during 1979 at all measured latitudes the estimated poleward transports of angular momentum by the mean and eddy circulation are qualitatively similar to those estimated from 1979 measurements with the eddy transport being of the same sign as that of the mean circulation an accompanying paper presents the structure seen in the observed motions seen in a solar locked longitude latitude system interpreted to be the signature of the solar thermal tides s s limaye 1988 icarus 73 212 226

thermal tides in the atmosphere of venus comparison of model results with observations a linearized primitive equation lpe model is developed to study thermal tides in the atmosphere of venus the lpe model describes diurnal and semidiurnal oscillations of a cyclostrophically balanced atmosphere in which zonal velocity varies with altitude and latitude the numerical algorithm follows staniforth and daley the solar thermal forcing is increased algebraically in time to separate the forced tidal response from free atmospheric oscillations parameters of the basic state and forcing agree with pioneer venus observations results of the model are compared with the solar fixed component of brightness temperature variations measured by taylor et al and elson using data from the pioneer venus orbiter infrared radiometer oir the comparison is made by convolving the computed model radiances with the weighting functions of the oir channels agreement between lpe model results and oir observations is excellent two interesting features of the oir data are accounted for namely the slow variation of phase with altitude and the dominance of the semidiurnal oscillation over the diurnal oscillation success of the lpe model opens the way for calculating tidal transports of heat and momentum and assessing the role of tides in maintaining the venus super rotation

distinguishing the roles of autogenic versus allogenic processes in cyclic sedimentation cisco group virgilian and wolfcampian north central texas meter scale transgressive regressive cycles of the subsurface cisco group are composed of marine and nonmarine carbonate and siliciclastic rocks deposited on the eastern shelf of the midland basin during late pennsylvanian and early permian time five cycle types are characterized by thickness magnitude order and principal lithofacies cycle magnitude is defined as the maximum facies shift in a cycle indicating extent of shoreline migration cisco cycles belong to three orders minor intermediate and major and they are superimposed and form a stratigraphic hierarchy each order of cycles has a distinct range of thickness and possibly duration a cycle is also divided into a lower sand poor interval during which coarse siliciclastic supply at the depositional site was diminishing and an upper sand rich interval during which coarse siliciclastic supply was high regional thickness and lithofacies variations of sand rich intervals indicate that progradational infilling at a depositional site lagged marine regression suggesting a delay in sediment supply from the upland source relative to the time of base level fall regional systematic variations in cycle abundance continuity and characteristics along depositional dip and strike record the interplay among regional topography pattern of siliciclastic supply and shelf subsidence which controlled distribution of depocenters and bypass zones and thus stratigraphic completeness and resolution regional persistence of cycles suggests a eustatic control on regional ordered transgressive regressive events in contrast local variations of cycle characters suggest controls by local topography and depositional dynamics which determined depositional loci differential compaction and erosion a predominantly autocyclic cisco record in the upper platform does not imply the absence of allogenic processes an allocyclic cisco record in the lower platform contains abundant autocyclic imprints because allogenic controls on cyclic sedimentation were accomplished through local autogenic processes distinguishing the roles of autogenic versus allogenic processes in cyclic sedimentation is an important step in establishing a high resolution meter scale chronostratigraphy of any sedimentary record 1

zonal winds in the middle atmosphere of venus from pioneer venus radio occultation data abstract pioneer venus radio occultation data for four seasons between december 1978 and october 1981 are used to construct meridional cross sections of temperature and zonal wind velocity for the middle atmosphere of venus in the altitude range of 40 80 km and in the latitude range of 1 5 85 wind speeds are derived assuming cyclostrophic balance the wind field contains as many as three jets first a prominent one above the clouds situated between 50 and 55 latitude with a maximum speed of 140 m s 1 a second with a speed of 95 m s 1 centered at 70 and at 60 km altitude and a possible third jet at 15 and 65 km altitude with a speed of 100 m s 1 the notable midlatitude jet is associated with the cold polar collar wind speeds above 70 km generally decrease with height because of the warm pole at these levels however within the jet the speed is 100 m s 1 at 83 km the jets may be barotropically unstable and inertial instability may occur above the clouds on the equatorial side of the main

improved automatic estimation of winds at the cloud top of venus using superposition of cross correlation surfaces abstract accurate wind observation is a key to study atmospheric dynamics a new automated cloud tracking method for the dayside of venus is proposed and evaluated by using the ultraviolet images obtained by the venus monitoring camera onboard the venus express orbiter it uses multiple images obtained successively over a few hours cross correlations are computed from the pair combinations of the images and are superposed to identify cloud advection it is shown that the superposition improves the accuracy of velocity estimation and significantly reduces false pattern matches that cause large errors two methods to evaluate the accuracy of each of the obtained cloud motion vectors are proposed one relies on the confidence bounds of cross correlation with consideration of anisotropic cloud morphology the other relies on the comparison of two independent estimations obtained by separating the successive images into two groups the two evaluations can be combined to screen the results it is shown that the accuracy of the screened vectors are very high to the equatorward of 30 degree while it is relatively low at higher latitudes analysis of them supports the previously reported existence of day to day large scale variability at the cloud deck of venus and it further suggests smaller scale features the product of this study is expected to advance the dynamics of venusian atmosphere

orbital cyclostratigraphy of the devonian frasnian famennian transition in south china abstract superbundlesets bundlesets bundles and laminae were formed in the carbonate successions of the devonian frasnian famennian transition in guangxi south china their hierarchical structures ratio relationships and arrangement order within conodont zones are lasting and stable in the stratigraphical sequences and can be traced across the different facies belts and sedimentary basins the hierarchically organized superbundlesets bundlesets bundles and laminae correspond to a long eccentricity eccentricity obliquity and precession and sub milankovitch cyclothem respectively the ratio of long eccentricity to eccentricity is 1 4 below the boundary between frasnian famennian and 1 3 above the boundary between frasnian famennian eccentricity to obliquity is 1 3 and eccentricity to precession is 1 6 in the devonian since the eccentricity periodicity of 100 000 years remains essentially steady through geological time the periodicity of the long eccentricity obliquity precession and sub milankovitch cycle was 400 000 33 333 16 667 and 8000 or 17 000 years these ratios are different from those of the permian cretaceous and quaternary and coincide well with those calculated theoretically by berger et al science 255 1992 560 this reinforces the hypothesis of the slowing of the earth s rotation and the lengthening of precession and obliquity periods since at least the devonian time on the basis of the hierarchical milankovitch cyclothems the chronostratigraphical subdivision and correlation of the frasnian famennian transition can be made at the resolution of 100 000s and 10 000s of years the duration of the upper rhenana zone linguiformis zone and lower middle and upper triangularis zone is 0 6 0 8 0 3 0 3 and 0 3 ma respectively

a record of glacial aridity and milankovitch scale fluctuations in atmospheric dust from the pennsylvanian tropics abstract atmospheric dust is an important climatic agent as well as a valuable climatic archive this study documents systematic variations in a single upper pennsylvanian shallow water carbonate buildup of the midland basin west texas that was isolated from fluvio deltaic input and consists almost entirely of carbonate bounded by sequence boundaries thin 0 02 to 1 m intervals of dark pyritic siliciclastic mudrock with subtle pedogenic features occur commonly at the sequence boundaries and are interpreted as loessite deposited during lowstands primarily on the basis of paleogeographic isolation of the buildup the silicate mineral fraction smf extracted from the underlying carbonate which includes quartz clay and trace feldspars and heavy minerals varies in concentration weight from 0 015 to 6 69 in the carbonate this smf contains both fine grained detrital and authigenic silica interpreted to be eolian on the basis of geochemical petrographic and grain size characteristics as well as paleogeography hence the smf is considered a proxy for atmospheric dust whole rock geochemistry suggests that the dust was at least partly derived from uplifts of the ancestral rocky mountains with a possible minor contribution from active volcanic centers located to the present day south and southwest the estimated mean accumulation rate mar of dust in highstand carbonate facies full interglacial relative to carbonate facies that formed during relative fall in sea level suggest that dust flux increased 4 to 10 times accompanying the transition to glacial conditions mars in the siliciclastic mudrock which accumulated at lowstand full glacial to incipient transgression suggest glacial phase increases in dust flux of nearly 400 to 4000 times relative to full interglacial conditions spectral analyses of dust abundance through the study section show variations consistent with milankovitch forcing

maintenance of strong rotational winds in venus middle atmosphere by thermal tides the cloud level atmosphere of venus takes little more than 4 days to complete one rotation whereas the solid planet below has a 243 day period computer simulations of the circulation of the venus middle atmosphere between 40 and 85 kilometers as driven by solar radiation absorbed in the clouds reproduce i the observed cloud level rotation rate ii strong vertical shears above and below the cloud tops and iii midlatitude jets and strong poleward flow on the day side simulated circulations converge to yield nearly the same zonal winds when initialized with both stronger or weaker rotation rates these results support the hypothesis that the observed cloud top rotation rate is maintained by statistical balance between fluxes of momentum by thermal tides and momentum advection by mean meridional circulation

dynamical effect of thermal tides in the lower venus atmosphere 1 the thermal tides in the lower atmosphere of venus are examined it is shown that both the diurnal and semidiurnal tides excited in the cloud layer propagate to the ground and the existence of thermal tides below the cloud bottom can be attributed almost to the solar heating in the cloud layer at altitudes of 0 10 km the atmospheric superrotation is accelerated and decelerated by the momentum transport associated with the diurnal and semidiurnal tides respectively the effect of diurnal tide is much smaller than that of the semidiurnal tide so that the mean zonal flow is accelerated in the direction opposite to the venus rotation there it is argued that this momentum transport by the semidiurnal tide is balanced with the surface friction in the atmospheric layer adjacent to the ground and the net momentum is supplied from the solid venus to maintain the atmospheric superrotation

sediments facies tracts and variations in sedimentation rates of holocene platform carbonate sediments and associated deposits northern belize implications for representative sedimentation rates full text is not available on soar publisher s website http jsedres geoscienceworld org cgi content abstract 74 4 498 doi 10 1306 012004740498

carbonate deposition and sequence stratigraphy of the terminal cambrian grand cycle in the southern appalachians u s a abstract the cessation of shale and carbonate deposition of the conasauga group grand cycles middle to upper cambrian and the establishment of the widespread peritidal carbonate deposition of the knox group upper cambrian to lower ordovician represent a prominent change in sedimentation along the early paleozoic passive continental margin in the southern appalachians to evaluate the causes for this change this study focuses on the maynardville formation which is the uppermost carbonate unit of the conasauga group the maynardville consists of 1 a lower subtidal facies succession which is underlain by the nolichucky shale and resembles the rest of the conasauga group carbonate deposits and 2 an upper peritidal facies succession which is conformably overlain by similar peritidal deposits of the copper ridge dolomite knox group deposition of shale and subtidal carbonate took place in deep ramp nolichucky to shallow ramp subtidal shoal and lagoonal settings lower maynardville the carbonate ramp was westward sloping toward the conasauga intrashelf shale basin to the east the ramp was linked to a broad semiarid carbonate tidal flat encompassing a variety of peritidal environments upper maynardville and copper ridge the maynardville is a shallowing upward succession that formed by carbonate platform aggradation and basinward progradation the transition between the maynardville and the copper ridge dolomite is within a conformable peritidal carbonate succession that contains common siliciclastic sand size detritus this interval is interpreted as a sequence boundary correlative with the craton wide late steptoean dresbachian franconian or sauk ii sauk iii unconformity the change from a conasauga to a knox depositional style may be related to distinct stages in passive margin evolution the end of grand cycle deposition in the early late cambrian is coincident with the cessation of tectonic activity along extensional features an intracratonic graben and other fault systems and marks the transition into a mature passive margin setting the mature margin was characterized by decreased rates of thermal subsidence which coupled with the infilling of the conasauga intrashelf basin favored shallow water carbonate deposition the final stabilization of the margin is reflected in the deposition of the thick peritidal carbonate strata of the knox group

gravitational signatures of atmospheric thermal tides on venus abstract thermal tides in the atmosphere of venus transport a considerable amount of mass on a wide range of spatial and temporal scales we use simulated values of the surface atmospheric pressure distribution to estimate the time varying gravitational potential exterior to venus the expected amplitudes of gravitational signatures of thermal tides are below the errors from existing magellan mission doppler data and have not yet been detected however they are large enough that we expect them to be well resolved by any of several measurement configurations for future venus gravity missions

whither cyclostratigraphy testing the gamma method on upper pleistocene deep sea sediments north atlantic deep sea drilling project site 609 1 abstract gamma analysis a procedure for tuning cyclic sediments in which gamma is defined as 1 sedimentation rate was applied to the upper pleistocene gray scale record of deep sea drilling project site 609 from the north atlantic the spectrum of the gamma tuned time series produces eccentricity obliquity and precession index signals when the primary periodicity is tuned to the precessional beat frequency however the timescales are significantly too long suggesting that some of the primary cycles used in the gamma tuning procedure have higher frequency than the precessional beat by filtering the specmap calibrated time series at i 0 12 kyr the spurious cy cles are removed from the tuning procedure in this case the resulting gamma corrected spectra look much more like that of the specmap tuned time series however the time series remains slightly too long forward modeling is consistent with the results from modeling the core that is the gamma method is quite robust at revealing orbital periodicity in an orbitally controlled re cord for which sedimentation rates are facies dependent however the method does not produce an accurate time series criteria for complete rejection of gamma results are clarified as either 1 least squares results include negative gamma values or 2 the resulting spectrum does not show an or bital signature variation on sedimentation rates greater than 5 result in incorrect time series however variations on sedimentation rates as high as 15 generally reproduce strong orbital spectra and occasionally the method can also generate an orbital spectrum with up to 25 noise the method is not as robust in predicting gamma values or sedimentation rates although it generally distinguishes facies with relatively high sedimentation rates from facies with relatively low sedimentation rates the values predicted may be incorrect by a factor of2 thus while gamma tuning of the time series is an improvement over observed thicknesses the resulting timescale is not correct the implications of these results for cyclostratigraphy are significant the generation of an orbital spectrum from a time series that is demonstrably incorrect casts doubt on cyclicity as a dating tool

probabilistic and spatial assessment of liquefaction induced settlements through multiscale random field models abstract evaluation of liquefaction induced settlements over an extended area requires the integration of different solution models that can account for the liquefaction resistance of a given soil profile and its spatial dependence across scales in this paper a cpt based liquefaction model is adopted to estimate the liquefaction induced settlement at individual sounding locations the model is then integrated with multiscale random field models to account for spatial variability of soil properties one important advantage of the proposed framework is its ability to consistently refine and provide settlement estimations across different scales from regional and geologic unit scales down to a local site specific scale the proposed methodology is then applied to the alameda county california an earthquake prone region to illustrate the procedure for probabilistic and spatial assessment of liquefaction induced settlements at different scales

topographical and local time dependence of large stationary gravity waves observed at the cloud top of venus the existence of large stationary gravity waves was discovered during akatsuki s first observation sequence in 2015 in this study the further detection of large stationary gravity waves in brightness temperature images over a 1 5 year period is reported the waves periodically appeared mostly above four specific highland regions in the low latitudes when these regions were in the local afternoon the wave amplitudes attenuated after the wave locations passed beyond the evening terminator and the locations of the waves tended to slowly drift eastward over their lifetimes the appearances of stationary waves depend not only on surface topography but also on latitude and local time suggesting that solar heating during the daytime and atmospheric structure affected by solar heating may control the excitation and propagation of stationary waves

equivalent number of uniform stress cycles for soil liquefaction analysis the seismic demand on potentially liquefiable soils can be approximated by a series of uniform shear stress cycles procedures are reviewed for converting an arbitrary acceleration time history to a series of uniform cycles with amplitude 0 65 of the peak the number of cycles n at this amplitude is evaluated so as to represent a seismic demand for liquefaction triggering equivalent to that of the accelerogram an assumed relationship between n and magnitude m underlies so called magnitude scaling factors used to adjust the liquefaction resistance of soil for the effects of duration magnitude scaling factors can alternatively be related directly to n which enables the effects of factors other than m for example site source distance r to be quantified we develop empirical models for n that are applicable to active tectonic regions and find a strong dependence on m and r and a weaker dependence on site condition and near fault rupture directivity effects the model for n is used to develop new s

zonal winds near venus cloud top level an analytic model of the equatorial wind speed abstract it is proposed that the equatorial wind speed near venus cloud top level is maintained by a balance between the pumping effect of the semidiurnal tide and vertical advection by the hadley circulation both integrated across the thermal driving region a consequence of this hypothesis is that the maximum equatorial zonal wind speed is proportional to nh where n is buoyancy frequency and h is a measure of the thickness of the driving region the proportionality constant is a weakly increasing function of the heating rate and a decreasing function of h where is an inverse length characterizing the mean zonal wind shear the equilibrium solution considered is shown to be stable for the class of solutions investigated there is a threshold value of heating rate below which there is no equilibrium satisfying the hypothesized balance but this result depends on the assumption that the shape of the zonal wind profile is invariant with thermal forcing amplitude

sensitivity of thermal tides in the venus atmosphere to basic zonal flow and newtonian cooling 1 a numerical model is constructed to investigate sensitivity of thermal tides in the venus atmosphere to distributions of basic mean zonal wind and newtonian cooling rate it is found that the amplitude and spatial structure of the diurnal tide are strongly influenced by the midlatitudinal jets and the newtonian cooling rates in all cases examined in this study the diurnal tide propagates downward in the lower atmosphere below the cloud levels and reaches the ground the semidiurnal tide is generally less dependent on these parameters but its zonal winds are increased in the upper jet regions

milankovitch climatic signals in lower triassic olenekian peritidal carbonate successions nanpanjiang basin south china abstract meter scale peritidal carbonate strata from an isolated platform in the nanpanjiang basin of south china were tested for the presence of periodic or quasi periodic climatic signals these signals provide information on factors controlling cyclic sedimentation in the equatorial eastern tethys during the early triassic greenhouse period parasequences are composed of shallowing upward successions of subtidal facies including skeletal packstone and grainstone calcimicrobial boundstone and oolitic packstone and grainstone intertidal laminated lutite and ribbon rock and rare supratidal microbial laminite parasequence stacking patterns display three orders of cyclicity suggesting hierarchical stratigraphic relationships gamma analysis of kominz and bond earth planet sci lett 48 1990 233 244 was used to estimate facies dependent thickness time conversion factors i e s and to construct tuned and untuned time series for two stratigraphic sections spectra of these time series indicate the presence of quasi periodic signals with prominent short eccentricity 94 9 131 2 kyr short obliquity 35 8 kyr and long precessional index 21 2 kyr peaks and minor long eccentricity 412 9 kyr long obliquity 45 3 kyr short precessional index 17 7 kyr and constructional tone 9 7 kyr peaks when calibrated on the tuned spectra thus milankovitch climatic forcing probably greatly influenced sedimentation the calibration indicates that the subtidal facies has a sedimentation rate of 24 6 30 7 cm kyr and the intertidal supratidal facies has a rate of 2 7 6 0 cm kyr the estimated duration of deposition of the two sections is 1139 1423 kyr and corresponds to a stratigraphic completeness of 32 92 the completeness is much greater than that of icehouse stratigraphic records we speculate that variations in carbonate productivity and environmental conditions driven by milankovitch climatic forcing combined with low amplitude sea level fluctuations were likely major controls on cyclic sedimentation furthermore evolutional spectra of the two sections show that dominant milankovitch climatic forcings varied from short eccentricity obliquity to long precessional index during the course of sedimentation some spectral differences between the two sections suggest variations in depositional recording mechanisms of milankovitch climatic signals between platform interior and windward platform margin

estimation of duration of subaerial exposure in shallow marine limestones an isotopic approach abstract subaerial exposure surfaces in shallow marine limestones may represent a significant period of nondeposition and or erosion the minimum duration of subaerial exposure is estimated through modeling the maximum whole rock 13c depletion toward exposure surfaces in vadose meteorically altered limestones the model simulates the water rock interaction that caused the depletion and calculates the volume of meteoric water needed to achieve the observed 13c value then the duration of vadose meteoric diagenesis which approximates exposure duration is the volume of water divided by the infiltration rate of vadose water sensitivity tests indicate that estimated duration is moderately sensitive to many input parameters particularly the isotope composition and concentration of total dissolved carbon in vadose water sediment porosity and infiltration rate of vadose water the method is mostly effective in estimating exposure durations of less than 400 ky the estimated durations of nine subaerial exposures in pleistocene reef tracts of barbados west indies agree well with available radiometric dates application of the method to subaerial exposures in mississippian pennsylvanian and cretaceous shallow marine limestones confines their durations to 21 54 ky and distinguishes exposures of different durations the proposed method offers a potential tool and direction in estimating minimum duration of stratal hiatuses in meter scale stratigraphic studies

cyclic large strain and induced pore pressure models for saturated clean sands semiempirical probabilistic models are described to assess cyclic large strain and induced excess pore water pressure responses of fully saturated clean sands for this purpose available cyclic simple shear and triaxial tests were compiled and studied the resulting ru versus and versus n databases are composed of 101 and 84 cyclic test data respectively key parameters of the proposed ru and models are defined as critical shear strain relative density effective confining stress and equivalent number of loading cycles consistent with the maximum likelihood methodology model coefficients were estimated by maximizing the likelihood function for comparison purposes the compiled database was again used to evaluate the performance of existing ru models both for comparison and calibration purposes for each framework two separate sets of limit state models were used model implemented with 1 the original and 2 the updated model coefficients the model performances are assessed by simple st

quantitative analysis of a cyclic peritidal carbonate sequence the middle and upper devonian lost burro formation death valley california a possible record of milankovitch climatic cycles abstract the middle and upper part of the type section of the lost burro formation is composed of 186 m of peritidal limestone dolomite and quartz arenite meter scale analysis of lithology sedimentary structures fossil assemblages and microfacies delineated 54 primary depositional cycles of subtidal intertidal and supratidal facies and a larger scale trend of apparent sea level change gamma analysis of kominz and bond 1990 tests the assumptions that cycles have equal durations and that each facies has a unique time thickness relation in the primary gamma and spectral analysis signals of milankovitch climatic cycles are indicated on the spectrum of the spatial facies curve but gamma tuning failed to improve the spectrum in subsequent analysis the 54 cycles are subdivided into fi e subgroups of different mean durations based on cycle period distributions gammas of three subgroups are strikingly constant indicating that they least violate the gamma assumptions the grouping of cycles suggests that the primary cycles do not have the same duration gammas are used to convert the measured section into two time series one is gamma uncorrected uniformly stretched another gamma corrected nonuniformly stretched after calibrating the gamma time unit as 18 4 ky eight statistically significant spectral peaks on the gamma corrected spectrum match the predicted 377 ma milankovitch eccentricity 2035 413 131 and 95 ky obliquity 32 ky and precession index 20 17 and 9 ky the constructive tone peaks the match suggests that milankovitch climatic forcing wa an important control on the lost burro carbonate deposition the effective accumulation rates of the subtidal 280 mm ky intertidal 160 190 mm ky and supratidal 60 70 mm ky facies are used to establish the cyclostratigraphy of the measured section

cloud tracked winds from pioneer venus ocpp images abstract analysis of ultraviolet image sequences obtained from the pioneer venus orbiter cloud photopolarimeter and covering five 80 day periods from 1979 1985 provides the first climatological description of the cloud top circulation on venus the average zonal winds can be characterized as a 5 day retrograde rotation of the whole cloud level atmosphere with weak jets at middle to high latitudes both the midlatitude and equatorial zonal winds vary by about 5 8 m s 1 over time spans of 1 6 years the average meridional circulation is poleward in both hemispheres up to at least 60 latitude consistent with the presence of a thermally direct hadley circulation associated with the clouds the strength of the hadley circulation also varies with time four wave modes are clearly identified a diurnal solar tide a semi diurnal solar tide a 4 day equatorial wave and a 5 day midlatitude wave the semidiurnal tide appears to have an amplitude of about 5 m s 1 and to be approximately constant with time

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