lunar global shape and polar topography derived from kaguya lalt laser altimetry a global lunar topographic map with a spatial resolution of finer than 0 5 degree has been derived using data from the laser altimeter lalt on board the japanese lunar explorer selenological and engineering explorer selene or kaguya in comparison with the previous unified lunar control network ulcn 2005 model the new map reveals unbiased lunar topography for scales finer than a few hundred kilometers spherical harmonic analysis of global topographic data for the moon earth mars and venus suggests that isostatic compensation is the prevailing lithospheric support mechanism at large scales however simple rigid support is suggested to dominate for the moon venus and mars for smaller scales which may indicate a drier lithosphere than on earth especially for the moon and venus

limits on the age of the deccan traps of india from paleomagnetic and plate reconstruction data and their uncertainties revised limits on the age of the deccan traps of india are provided by recent improvements to reconstructions of india relative to surrounding plates since late cretaceous time realistic estimates of the uncertainties in the plate reconstructions and recent paleomagnetic data from the deccans traps and from north america we estimate the age of the deccan traps by rotating its paleomagnetic pole into the north american reference frame different assumed ages for the deccan traps result in very different positions for its paleomagnetic pole relative to north america comparing these positions with the north american apparent polar wander path and accounting for uncertainties in both the paleomagnetic poles and in the reconstructions we place limits on the age of the deccan traps of 62 72 ma significantly younger than found in several prior studies the 62 72 ma limits are consistent with ages obtained independently from radiometric dating and paleontology and are consistent with the hypothesis that the deccan traps were extruded rapidly during reversed polarity chron 29r which contains the cretaceous tertiary boundary

island wakes and headland eddies a comparison between remotely sensed data and laboratory experiments island wakes and headland eddies in coastal waters are identified from spaceborne and airborne remotely sensed imagery in the visible wavelengths the imagery were obtained for the bristol and english channels united kingdom which are characterized by high tidal currents and levels of turbidity suspended matter in the surface waters is used as a passive tracer for the flow features scaling parameters e g the reynolds ekman and rossby numbers obtained from the depth averaged equation of motion are presented based upon information on oceanographic conditions at the times of the overpasses the parameters are compared then with data obtained from laboratory model investigations presented by other experimenters in the published literature the remotely sensed data demonstrate that in coastal waters with nonuniform obstacles and bathymetry for a given ekman number the flow regimes occur at a lower rossby number than might be expected from laboratory experiments in the absence of a method for the accurate determination of the horizontal eddy viscosity hence the reynolds number it is concluded that an island wake parameter wolanski et al 1984a should be adopted to describe such features in coastal waters

upper cretaceous paleocene biostratigraphy and magnetostratigraphy hell creek and tullock formations northeastern montana fossils from the hell creek and tullock formations in northeastern montana provide detailed documentation of terrestrial faunal and floral evolution during latest cretaceous lancian and early paleocene puercan time here the replacement of lancian faunas by those of puercan age most obviously signaled by the extinction of dinosaurs and the changes in pollen floras sometimes used to mark the cretaceous tertiary boundary occurred during a period of reversed magnetic polarity paleontological correlations suggest that dinosaur extinction and the change in pollen floras took place in the red deer valley area alberta during the same period of reversed polarity furthermore also on the basis of paleontological correlations the extinction of dinosaurs in the san juan basin new mexico appears to have occurred either during the same period of reversed polarity or possibly during the preceding period of normal polarity

high resolution magnetostratigraphy of the upper nacimiento formation san juan basin new mexico usa implications for basin evolution and mammalian turnover lower paleocene deposits in the san juan basin document one of the best records of mammalian change and turnover following the cretaceous paleogene mass extinction and is the type area for the puercan pu and torrejonian to north america land mammal age nalma one of the largest mammalian turnover events in the early paleocene occurs between the torrejonian 2 to2 and torrejonian 3 to3 nalma interval zones the nacimiento formation contains the only deposits in north america where the to2 to3 mammalian turnover can be constrained however the precise age and duration of the turnover is poorly understood due to the lack of a precise chronostratigraphic framework we analyzed paleomagnetic samples produced a 40ar 39ar detrital sanidine age and developed a detailed lithostratigraphy for four sections of the upper nacimiento formation in the san juan basin new mexico kutz canyon escavada wash torreon west and east to constrain the age and duration of the deposits and the to2 to3 turnover the polarity stratigraphy for the four sections can be correlated to chrons c27r c26r of the geomagnetic polarity time scale gpts using the local polarity stratigraphy for each section we calculated a mean sediment accumulation rate and developed a precise age model which allows us to determine the age of important late torrejonian mammalian localities using the assigned ages we estimate the to2 to3 turnover was relatively rapid and occurred over 120 kyr 60 50 kyr between 62 59 and 62 47 ma this rapid duration of mammalian turnover suggests that it was driven by external forcing factors such as environmental change driven by the progradation of the distributive fluvial system across the basin and or changes in regional or global climate additionally comparisons of the mean sediment accumulation rates among the sections that span from the basin margin to the basin center indicate that sediment accumulation rates equalized across the basin from the end of c27r through the start of c26r suggesting an accommodation minimum in the basin associated with the progradation of a distributive fluvial system into the basin this accommodation minimum also likely led to the long hiatus of deposition between the paleocene nacimiento formation and the overlying eocene san jose formation

dynamics of hypersaline coastal waters in the great barrier reef the coastal waters of the great barrier reef gbr are hypersaline salinity 37 during the dry season as a result of evaporation greatly exceeding rainfall of shallow waters and of the presence of numerous bays along the coast preventing rapid flushing these hypersaline waters are not flushed out by salinity driven baroclinic currents because these waters are vertically well mixed instead these waters are transported by a longshore residual current and thus form a coastal boundary layer of hypersaline waters as a result the hypersalinity distribution is 2 d with both cross shelf and longshore gradients of salinity the cross shelf gradients are largely controlled by turbulent diffusion while the longshore gradients are controlled by the residual currents that transport hypersaline waters longshore south ward in the central and southern regions of the gbr because every bay supplies hypersaline waters the width of the coastal hypersaline layer increases southwards steady state is reached in about 100 days which is the typical duration of the dry season the dynamics of the gbr hypersaline coastal boundary layer thus differ from the classical inverse hypersaline systems e g in saloum river estuary laguna san ignacio mission bay tomales bay san diego bay hervey bay shark bay coorong coast lagoon spencer gulf gulf of california and many others where the salinity gradient is mainly 1 d with a dominant along channel salinity gradient

magnetostratigraphy of the ludlow member of the fort union formation lower paleocene in the williston basin north dakota to determine the geomagnetic polarity stratigraphy and the duration and age of the ludlow member of the fort union formation lower paleocene we constructed a 325 m composite lithostratigraphic section of the upper cretaceous hell creek formation and the lower paleocene ludlow and tongue river members of the fort union formation in the little missouri river valley of north dakota usa we analyzed paleomagnetic samples from nine of the logged sections the principal magnetic carrier in the ludlow member sediments is likely titanomaghemite as indicated by predominantly irreversible thermomagnetic curves measured from sandstone siltstone and carbonaceous shale samples the analyzed paleomagnetic samples document a series of polarity zones that can be correlated from c29n to c27r on the geomagnetic polarity time scale gpts we infer that the magnetization of the samples is primary because the characteristic directions are consistent with those of the paleocene of north america and the reversal stratigraphy from this section corresponds to the gpts with reasonable sediment accumulation rates by extrapolating the measured sediment accumulation rate from the cretaceous tertiary k t boundary to the top of c28n and then to the top of the ludlow member we estimate the duration of the member to range from 2 31 to 2 61 m y this is the fi rst estimate for the duration and age of the ludlow member and it can be used as an important tool for interpreting rates of biotic recovery after the k t extinction

lunar crater detection based on terrain analysis and mathematical morphology methods using digital elevation models lunar impact craters are the most typical geomorphic feature on the moon and are of great importance in studies of lunar terrain features this paper presents a crater detection algorithm cda that is based on terrain analysis and mathematical morphology methods the proposed cda is applied to digital elevation models dems to identify the boundaries of impact craters the topographic and morphological characteristics of impact craters are discussed and detailed steps are presented to detect different types of craters such as dispersal craters connective craters and con craters the dem from the lunar reconnaissance orbiter which has a resolution of 100 m is used to verify the proposed cda the results show that the boundaries of impact craters can be detected the results enable increased understanding of surface processes through the characterization of crater morphometry and the use of crater size frequency distributions to estimate the ages of planetary surfaces

magnetic polarity stratigraphy and biostratigraphy of paleocene and lower eocene continental deposits clark s fork basin wyoming paleomagnetic samples were collected at 273 sites within a 2012 m continental sedimentary sequence in the clark s fork basin near powell wyoming the lower 1158 m is in the polecat bench fm while the upper 854 m is within the willwood fm although significant secondary components of magnetization were present alternating field demagnetization to 300 oe peak field revealed the polarity of the primary component of the natural remanent magnetism a well defined polarity zonation is observed the polecat bench fm is dominantly of reversed polarity but does contain two normal polarity zones the willwood fm in this section is entirely of reversed polarity abundant tiffanian clarkforkian and wasatchian faunas indicate that the age range of the sediments is from late paleocene through early eocene these age constraints along with the characteristic polarity sequence allow the magnetic polarity sequence to be correlated with the magnetic polarity time scale the section correlates with the magnetic polari

a global adjustment method for photogrammetric processing of chang e 2 stereo images the chang e 2 ce2 lunar orbiter was the second robotic orbiter of the chinese lunar exploration program as well as the pioneer robotic orbiter in the soft landing project in the second phase of the program it used a two line stereo camera to acquire stereo images with global coverage at a resolution of 7 m the stereo images have a large potential for producing the best lunar topographic map however errors and uncertainties in the interior orientation io and exterior orientation eo parameters of the camera seriously affected the accuracy of the global topographic mapping in this paper a global adjustment method is proposed to eliminate the effects of these errors the error models are represented by a chebyshev polynomial the polynomial coefficients were estimated as unknowns using five lunar laser ranging retroreflector lrrr points as ground control points in the adjustment the experimental results show that the planimetric and height deviations between the neighboring strips were 5 and 2 m less than 1 pixel respectively which were decreased by 32 6 and 31 5 times respectively relative to those derived from the original eo parameters the large inconsistencies in the ce2 trajectory data were significantly reduced after the adjustment in comparison with the lrrr positions the planimetric and height errors ranged from 21 to 97 m and 19 to 10 m respectively a new seamless mosaic and high precision absolute position topographic map has been generated using this method

climate and landscape reconstruction of the arroyo chijuillita member of the nacimiento formation san juan basin new mexico providing environmental context to early paleocene mammal evolution abstract the sedimentologic stratigraphic and paleopedologic attributes of a laterally continuous outcrop exposure of the basal portion of the lower paleocene arroyo chijuillita member of the nacimiento formation located in the bisti de na zin wilderness area was examined to provide paleoenvironmental context for the puercan north american land mammal age nalma terrestrial ecosystems of the san juan basin new mexico the studied outcrop spans the middle and late puercan pu2 pu3 nalma and thus is an ideal location to assess the potential causes of faunal turnover between pu2 and pu3 the stratal succession consists of fluvial channel and laterally continuous sandstone and associated fine grained floodplain deposits including paleosols that document variability in drainage and maturity quantitative and qualitative reconstructions of paleoclimate from paleosols supplemented by analyses of fossil floras indicate no change in climate through the studied interval further there is no evidence that regional tectonics relate to changes in depositional environments given the lack of evidence for climate change or regional tectonics and the characteristics of the fluvial facies and the paleosols across the study locality we interpret the spatial and temporal variability in paleopedologic and sedimentologic characteristics to be the result of autocyclic channel avulsion and migration additionally the stable climatic conditions and lack of tectonic influence between the pu2 and pu3 biozones suggest that mammalian turnover is unlikely to have been caused by extrinsic environmental changes i e climate or tectonics and is instead probably the result of rapid evolution following the k pg boundary and or competition from the migration of new mammalian species into the basin

gld100 the near global lunar 100 m raster dtm from lroc wac stereo image data 1 we derived near global lunar topography from stereo image data acquired by the wide angle camera wac of the lunar reconnaissance orbiter camera lroc system from polar orbit tracks the lroc wac provides image data with a mean ground resolution at nadir of 75 m pixel with substantial cross track stereo overlap wac stereo images from the one year nominal mission and the first months of the science mission phase are combined to produce a near global digital terrain model dtm with a pixel spacing of 100 m the global lunar dtm 100 m or gld100 it covers 79 s to 79 n latitudes 98 2 of the entire lunar surface we compare the gld100 with results from previous stereo and altimetry based products particularly with the lunar orbiter laser altimeter lola altimetry which is the current topographic reference for the moon we describe typical characteristics of the gld100 and based upon the comparison to the lola data set assess its vertical and lateral resolution and accuracy we conclude that the introduced first version of the stereo based gld100 is a valuable topographic representation of the lunar surface complementary to the lola altimetry data set further improvements can be expected from continuative investigations

relative dispersion of surface drifters in a barrier reef region 1 the spreading of two clusters of satellite tracked surface drifters was quantified by relative dispersion and relative diffusivity the time derivative of relative dispersion in two regions of the southern great barrier reef gbr a low density reef matrix of complex topography and a shelf lagoon over flat bathymetry although based on a small data set averaged values of these parameters over a 12 day period with concurrent measurements for the two regions indicated that relative dispersion and diffusivity of drifter pairs were 182 and 52 times greater respectively along the reef matrix than found in the lagoon relative diffusivities in the southern gbr were anisotropic and varied largely in space and time within the spatial scales of 1 100 km and temporal scales of hours to 16 20 days they were considerably enhanced by high frequency tidal processes submesoscale processes 20 km were important in the southern gbr particularly in areas with complex topography where secondary circulations around the reefs and regions of steep bathymetry caused abrupt increase in dispersion although the dispersion was much higher along the reef matrix the presence of ring circulations around the islands and wake eddies in the lee of islands can act as trapping mechanisms to keep particles within the reef matrix retarding the loss to open water areas this provides an efficient physical mechanism for both enhancing larval connectivity between reefs and at the same time trapping larvae when in the vicinity of reefs

the constitution and structure of the lunar interior the current state of understanding of the lunar interior is the sum of nearly four decades of work and a range of exploration programs spanning that same time period missions of the 1960s including the rangers surveyors and lunar orbiters as well as earth based telescopic studies laid the groundwork for the apollo program and provided a basic understanding of the surface its stratigraphy and chronology through a combination of remote sensing surface exploration and sample return the apollo missions provided a general picture of the lunar interior and spawned the concept of the lunar magma ocean in particular the discovery of anorthite clasts in the returned samples led to the view that a large portion of the moon was initially molten and that crystallization of this magma ocean gave rise to mafic cumulates that make up the mantle and plagioclase flotation cumulates that make up the crust smith et al 1970 wood et al 1970 this model is now generally accepted and is the framework that unifies our knowledge of the structure and composition of the moon the intention of this chapter is to review the major advances that have been made over the past decade regarding the constitution of the moon s interior much of this new knowledge is a direct result of data acquired from the successful clementine and lunar prospector missions as well as the analysis of new lunar meteorites as will be seen results from these studies have led to many fundamental amendments to the magma ocean model much of what we know from sample analyses has been previously summarized elsewhere and only their most important aspects will be discussed in this chapter the reader is referred to the relevant chapters in the books basaltic volcanism on the terrestrial planets basaltic volcanism study project 1981 the

did the european dinosaurs disappear before the k t event magnetostratigraphic evidence abstract debate on the non catastrophic or catastrophic extinction of the dinosaurs by an asteroid impact k t event remains a controversy and is mainly based on the interpretation of the sedimentary continental sequences in the north american western interior the global aspect of this event needs to be tested in sedimentary record from all continents where continuous terrestrial deposits through the cretaceous paleogene are well preserved in the western mediterranean realm recognition of the cretaceous paleogene boundary is limited by the lack of biostratigraphic data in the upper cretaceous lower tertiary continental sedimentary sequences new magnetostratigraphic results were obtained from the analysis of two sections in southern france and compared to previous results in northern spain the last occurrence of in situ dinosaurs eggshells the only dinosaur remains found is located in chron 30n southeast france or 31n southwest france and northern spain this last occurrence could demonstrate that the extinction of the european dinosaurs occurred prior to the cretaceous paleogene boundary and would therefore support the idea of a gradual or stepwise extinction unlinked to the k t event

importance of titanohematite in detrital remanent magnetizations of strata spanning the cretaceous paleogene boundary hell creek region montana intermediate composition titanohematite fe2 ytiyo3 with 0 5 y 0 7 is seldom the focus of paleomagnetic study and is commonly believed to be rare in nature while largely overlooked in magnetostratigraphic studies intermediate titanohematite has been identified as the dominant ferrimagnetic mineral in an array of late mesozoic and early cenozoic laramide clastic deposits throughout the central united states intermediate titanohematite is ferrimagnetic and has similar magnetic properties to titanomagnetite except its unique self reversing property due to these similarities and with detrital remanent magnetizations masking its self reversing nature intermediate titanohematite is often misidentified in sedimentary deposits past studies relied upon nonmagnetic techniques including x ray diffraction and electron microprobe analysis while these techniques can identify the presence of intermediate titanohematite they fail to test whether the mineral is the primary recorder to facilitate the identification of intermediate titanohematite in sedimentary deposits we characterize this mineral using low temperature magnetometry and high temperature susceptibility experiments and present a new identification technique based on titanohematite s self reversing property for sediments that span the cretaceous paleogene boundary hell creek region montana results from the self reversal test indicate that the majority of remanence is held by minerals that become magnetized parallel to an applied field but that intermediate self reversing titanohematite y 0 53 0 63 is an important ancillary carrier of remanence while earlier literature suggests that intermediate titanohematite is rare in nature reanalysis using specialized rock magnetic techniques may reveal that it is more abundant in the rock record particularly within depositional basins adjacent to calc alkaline volcanics than previously thought

magnetostratigraphy in pursuit of missing links since the last quadrennial report magneto stratigraphy has continued to flourish the primary issues have been 1 refinements to the geomagnetic reversal time scale grts including recalibrations correlation of biostratigraphic data to the crts and revision of the terminology 2 use of magnetostratigraphic data for estimating rates of such processes as sediment accumulation evolution and faunal migration and 3 magnetic mineralogy and the origin of remanence for convenience we have divided the publications into studies of continental and marine sediments and highlight the most exciting issues within each of these sub headings in the first section of this review we will concentrate on the development of the geomagnetic reversal time scale grts with particular emphasis on refinements from the last few years we then turn our attention to applications of magnetostratigraphy in marine and continental sequences

an investigation of dispersion characteristics in shallow coastal waters abstract hydrodynamic dispersion has a significant impact on the mass transport of sediments and contaminants within coastal waters in this study apparent horizontal dispersion in a tidally dominated shallow estuary was investigated using field observations and a numerical model a cluster of four lagrangian drifters was released in two shallow regions inside moreton bay australia between two small islands and in an open water area during a 16 h tracking period the drifters generally showed similar behaviour initially moving with the dominant current and remaining together before spreading apart at the change of tide two dispersion regimes were identified a slow dispersion during the earlier stage and a rapid dispersion during the latter stage of deployment such change in regime typically occurred during the succeeding ebb or flow tides which may be attributable to residual eddies breaking down during reversal of tidal direction in addition a power function of the squared separation distance over the apparent dispersion coefficient produced an r2 exceeding 0 7 indicating a significant relationship between them by applying a three dimensional hydrodynamic model the trajectories of artificial particles spreading in the bay were simulated which allowed the calculation of dispersion coefficients throughout the entire bay the study results demonstrate that the tidal effects on dispersion were dependent on the effect of tidal excursion and residual current the tide was found to be the most dominant driver of dispersion in the bay when unobstructed by land however bathymetric and shoreline characteristics were also significant localised drivers of dispersion between the two islands as a result of island wake

integration of chang e 1 imagery and laser altimeter data for precision lunar topographic modeling lunar orbital imagery and laser altimeter data are two major data sources for lunar topographic modeling most of the previous work has processed imagery and laser altimeter data separately usually though there are inconsistencies between the topographic models derived from them this paper presents an endeavor to integrate the chang e 1 imagery and laser altimeter data for consistent and precision lunar topographic modeling a combined adjustment model for the chang e 1 imagery and laser altimeter data is developed in which the participants are the laser altimeter points image exterior orientation eo parameters and tie points collected from the stereo images a weighting scheme is designed for the participants in the adjustment and a local surface constraint is imposed to improve the adjustment performance the output of the combined adjustment is the refined image eo parameters and laser ground points experimental results using the chang e 1 data in the apollo 15 and 16 landing site areas show that the proposed combined adjustment approach can reduce the misregistrations between the imagery and the laser altimeter data by a maximum of 1 18 pixels in image space the japanese selenological and engineering explorer selene laser altimeter data at the apollo 15 and 16 landing site areas are employed for comparison analysis small shifts between the selene and chang e 1 laser altimeter data were found the topography derived from chang e 1 data after the combined adjustment shows a relatively consistent trend with the topography determined by the selene laser altimeter data

topography of the moon from the clementine lidar range measurements from the lidar instrument carried aboard the clementine spacecraft have been used to produce an accurate global topographic model of the moon this paper discusses the function of the lidar the acquisition processing and filtering of observations to produce a global topographic model and the determination of parameters that define the fundamental shape of the moon our topographic model a 72nd degree and order spherical harmonic expansion of lunar radii is designated goddard lunar topography model 2 gltm 2 this topographic field has an absolute vertical accuracy of approximately 100 m and a spatial resolution of 2 5 the field shows that the moon can be described as a sphere with maximum positive and negative deviations of 8 km both occurring on the farside in the areas of the korolev and south pole aitken s p aitken basins the amplitude spectrum of the topography shows more power at longer wavelengths as compared to previous models owing to more complete sampling of the surface particularly the farside a comparison of elevations derived from the clementine lidar to control point elevations from the apollo laser altimeters indicates that measured relative topographic heights generally agree to within 200 m over the maria while the major axis of the lunar gravity field is aligned in the earth moon direction the major axis of topography is displaced from this line by approximately 10 to the east and intersects the farside 24 north of the equator the magnitude of impact basin topography is greater than the lunar flattening 2 km and equatorial ellipticity 800 m which imposes a significant challenge to interpreting the lunar figure the floors of mare basins are shown to lie close to an equipotential surface while the floors of unflooded large basins except for s p aitken lie above this equipotential the radii of basin floors are thus consistent with a hydrostatic mechanism for the absence of significant farside maria except for s p aitken whose depth and lack of mare require significant internal compositional and or thermal heterogeneity a macroscale surface roughness map shows that roughness at length scales of 10 1 10 2 km correlates with elevation and surface age

surf zone diffusivity on a rip channeled beach absolute and relative diffusivity are measured on a rip channeled beach using 30 position tracking drifters released in clusters 4 12 drifters deployed on 7 days with different wave forcing and tidal elevations at sand city monterey bay california diffusivity and dispersion were found to be larger on days with rip current flow patterns and larger waves rip currents cause material to diffuse quickly for t 0 9 two independent methods are used to measure the small scale turbulent diffusion contribution kxy which are found significantly correlated r2 0 95 with each other and calculated surf zone wave breaking induced turbulent eddy viscosity here kxy is small relative to the total dispersion ke kxy 3 30 indicating that the shear flow is the primary mechanism responsible for dispersion in a rip current system

lagrangian and eulerian characterization of two counter rotating submesoscale eddies in a western boundary current in recent decades high spatial resolution ocean radar and satellite imagery measurements have revealed a complex tangle of submesoscale filaments and eddies in the surface velocity temperature and chlorophyll a fields we use a suite of high resolution data to characterize two counter rotating short lived eddies formed at the front between the warm east australian current eac and temperate coastal waters 308s eastern australia in this region submesoscale filaments and short lived eddies are dynamically generated and decay at time scales of hours to days dominant cyclonic filaments of o 1 rossby number formed along frontal jets and eddy boundaries generating localized ageostrophic circulations at the submesoscale measurements of over ocean wind direction and surface currents from high frequency radars reveal the influence of the short term small scale wind forcing on the surface circulation enhancement of the horizontal shear frontal jet destabilization and the generation and decay of the cyclonic eddy by contrast the anticyclonic eddy formation was most likely associated with eac mesoscale instability and anticyclonic vorticity lagrangian tracks show that surface particles can be temporarily trapped in the eddies and frontal convergent zones limiting their transport mixing between eac derived and coastal waters was increased along the frontal regions and particles starting at the divergent regions around the eddies experienced significant dispersion at submesoscales the cyclonic cold core eddy entrained high chlorophyll a shelf waters on its convergent side suggesting spiral eddy cyclogenesis

a successful rock magnetic technique for correctng paleomagnetic inclination shallowing case study of the nacimiento formation new mexico the accuracy of an inclination shallowing correction technique was tested on the remanence of the paleocene nacimiento formation the correction assumes that changes in paleomagnetic inclination during deformation will be directly related to changes in remanence anisotropy the remanence anisotropy is also a function of the magnetic anisotropy of the individual magnetic grains the nacimiento formation was selected for this test because its inclination is shallow by 7 to 8 and previous paleomagnetic studies indicate that it has a primary remanence with a well constrained age and that magnetic overprints are minimal tectonics are an unlikely explanation for its shallow inclination these conditions allow the inclination corrected remanence to be compared to a well defined paleomagnetic pole to determine the accuracy of the technique the characteristic remanence from 20 nacimiento sites was isolated by alternating field and thermal demagnetization and was corrected using the anisotropy of anhysteretic remanence measured for three to five samples per site individual particle anisotropy was determined by drying a magnetic separate epoxy mixture in a 35 50 mt magnetic field laboratory compaction of disaggregated nacimiento material was also used to yield an effective individual magnetic particle anisotropy the two techniques resulted in similar values for individual particle anisotropy and similar inclination shallowing corrections both corrections were successful and the inclination corrected formation mean direction was indistinguishable from the direction predicted by north america s paleocene paleopole the inclination shallowing correction technique reported here should be applied routinely in paleomagnetic studies provided that the remanence is a primary depositional remanence that has been affected only by syndepositional or early postdepositional processes e g compaction

the end of the cretaceous sharp boundary or gradual transition evidence indicates that the cretaceous tertiary boundary is very sharp and within the limits of resolution it is apparently synchronous at the various boundary localities arguments to the contrary particularly those of officer and darke are shown to invalid

sea surface temperature as a tracer to estimate cross shelf turbulent diffusivity and flushing time in the great barrier reef lagoon accurate parameterization of spatially variable diffusivity in complex shelf regions such as the great barrier reef gbr lagoon is an unresolved issue for hydrodynamic models this leads to large uncertainties to the flushing time derived from them and to the evaluation of ecosystem resilience to terrestrially derived pollution in fact numerical hydrodynamic models and analytical cross shore diffusion models have predicted very different flushing times for the gbr lagoon nevertheless scarcity of in situ measurements used previously in the latter method prevents derivation of detailed diffusivity profiles here detailed cross shore profiles of diffusivity were calculated explicitly in a closed form for the first time from the steady state transects of sea surface temperature for different sections of the gbr lagoon we find that diffusivity remains relatively constant within the inner lagoon 20 km where tidal current is weak and increases linearly with sufficiently large tidal amplitude in reef devoid regions but increases dramatically where the reef matrixes start and fluctuates with reef size and density the cross shelf profile of steady state salinity calculated using the derived diffusivity values agrees well with field measurements the calculated diffusivity values are also consistent with values derived from satellite tracked drifters flushing time by offshore diffusion is of the order of 1 month suggesting the important role of turbulent diffusion in flushing the lagoon especially in reef distributed regions the results imply that previous very large residence times predicted by numerical hydrodynamic models may result from underestimation of diffusivity our findings can guide parameterization of diffusivity in hydrodynamic modeling

impact cratering in and around the orientale basin results from recent high resolution remote sensing datasets abstract impact craters are the predominant geological features on the lunar surface data about the craters are crucial for inferring information about surface age the generation processes of the geological units and the sequences of geological events the higher resolution remote sensing datasets collected by recent lunar missions enable the investigation of impact craters of smaller size and provide more accurate information this paper presents an investigation of the distribution and population characteristics of impact craters in and around the orientale basin based on high resolution datasets first an update to the crater catalogue for the orientale basin and its surrounding area is provided including craters as small as 1 km in diameter based on the updated crater catalogue the crater densities and depth to diameter ratios in and around the orientale basin are investigated the inclusion of small craters enables a crater density map with higher resolution revealing a significantly higher crater density of the study area also the surface age of orientale basin is estimated from the size frequency distribution sfd using the new crater catalogue showing an age of 3 75 ga using the production function of neukum et al 2001 which is in good agreement with previous studies finally distribution patterns of secondary craters around the orientale basin are investigated indicating the orientale basin may be caused by an oblique impact with a downrange direction of about 235 260 and an offset strength towards the direction of about 305 350

surface drifter pair spreading in the north atlantic 1 this study examines spreading of surface drifter pairs deployed as part of the clivar mode water dynamic experiment climode project in the gulf stream region the spreading is resolved at hourly resolution and quantified by relative dispersion and finite scale lyapunov exponents at scales from 1 3 km to 300 500 km the dispersion follows richardson s law indicating stirring by eddies comparable in scale to the pair separation distance at larger scales the spreading becomes a random walk described by a constant diffusivity the behavior from 1 3 km to the local deformation radius is inconsistent with the enstrophy cascade of 2 d quasigeostrophic turbulence to test various hypotheses for this result drifter pair spreading is examined for pairs that were not launched together pairs deployed in the eastern subtropical north atlantic and climode pairs subsampled to daily temporal resolution our results indicate the presence of significant energy at the submesoscale in the gulf stream region which flattens the wave number spectrum and dominates surface stirring at this scale range results in the less energetic subtropical eastern atlantic are more equivocal

flow separation and vertical motions in a tidal flow interacting with a shallow water island this paper reports on the case study of rattray island great barrier reef northeast australia lying perpendicular to tidal flow in shallow waters at ebb and flood attached stable eddies develop in the wake where swirls of turbidity suggest that sediment laden waters are brought to the surface as a result of vertical transport both eddy and tip upwellings are encountered in the tidal flow around rattray island but there is currently no clear cut answer as to which secondary flow generates upwelling with the largest intensity this paper addresses this specific issue through idealized and realistic high resolution numerical experiments the analysis is supported by physical arguments based on the theory of flow separation given rattray s geometry and surrounding bathymetry the mechanism of flow separation in shallow waters helps explain the asymmetry in size of the eddies and their intensity the results of idealized numerical experiments also suggest that eddy and tip upwellings may be of similar intensity at rattray island

integration of chang e 2 imagery and lro laser altimeter data with a combined block adjustment for precision lunar topographic modeling abstract lunar topographic information is essential for lunar scientific investigations and exploration missions lunar orbiter imagery and laser altimeter data are two major data sources for lunar topographic modeling most previous studies have processed the imagery and laser altimeter data separately for lunar topographic modeling and there are usually inconsistencies between the derived lunar topographic models this paper presents a novel combined block adjustment approach to integrate multiple strips of the chinese chang e 2 imagery and nasa s lunar reconnaissance orbiter lro laser altimeter lola data for precision lunar topographic modeling the participants of the combined block adjustment include the orientation parameters of the chang e 2 images the intra strip tie points derived from the chang e 2 stereo images of the same orbit the inter strip tie points derived from the overlapping area of two neighbor chang e 2 image strips and the lola points two constraints are incorporated into the combined block adjustment including a local surface constraint and an orbit height constraint which are specifically designed to remedy the large inconsistencies between the chang e 2 and lola data sets the output of the combined block adjustment is the improved orientation parameters of the chang e 2 images and ground coordinates of the lola points from which precision lunar topographic models can be generated the performance of the developed approach was evaluated using the chang e 2 imagery and lola data in the sinus iridum area and the apollo 15 landing area the experimental results revealed that the mean absolute image residuals between the chang e 2 image strips were drastically reduced from tens of pixels before the adjustment to sub pixel level after adjustment digital elevation models dems with 20 m resolution were generated using the chang e 2 imagery after the combined block adjustment comparison of the chang e 2 dem with the lola dem showed a good level of consistency the developed combined block adjustment approach is of significance for the full comparative and synergistic use of lunar topographic data sets from different sensors and different missions

co registration of lunar topographic models derived from chang e 1 selene and lro laser altimeter data based on a novel surface matchingmethod abstract various lunar digital topographic models dtms have been generated from the data collected from earlier and recent lunar missions there are usually inconsistencies among them due to differences in sensor configurations data acquisition periods and production techniques to obtain maximum value for science and exploration the multi source lunar topographic datasets must be co registered in a common reference frame only such an effort will ensure the proper calibration registration and analysis of the datasets which in turn will permit the full comparative and synergistic use of them this study presents a multi feature based surface matching method for the co registration of multiple lunar dtms that incorporates feature points lines and surface patches in surface matching to guarantee robust surface correspondence a combined adjustment model is developed for the determination of seven transformation parameters one scale factor three rotations and three translations from which the multiple dtms could be co registered the lunar dtms derived from the chang e 1 selene and lro laser altimeter data in the apollo 15 landing area and the sinus iridum area are examined in this study small offsets were found among the chang e 1 selene and lro dtms through experimental analysis the developed multi feature based method was proven able to effectively co register multiple lunar dtms the performances of the multi feature based surface matching method were compared with the point based method and the former was proven to be superior to the latter

magnetic mineralogy of continental deposits san juan basin new mexico and clark s fork basin wyoming magnetic concentrates were obtained from nine bulk samples from the late cretaceous through middle paleocene continental sedimentary section in the san juan basin new mexico and from two bulk samples from the late paleocene and early eocene section in the clark s fork basin wyoming strong field thermomagnetic js t curves of almost all the san juan basin concentrates show only a single curie temperature in the 175 195 c range indicating that the dominant ferrimagnetic mineral is detrital titanomagnetite fe3 xtixo4 of composition 0 51 x 0 54 the clark s fork basin concentrates exhibited curie temperatures of 200 c and 580 c indicating a mixture of x 0 5 titanomagnetite and magnetite respectively no evidence of hematite or other ferric oxides or oxyhydroxides was observed in the js t data isothermal remanent magnetization irm acquisition curves were determined for 56 samples from the clark s fork basin and 114 samples from the san juan basin although dominated by irm acquired in magnetizing fields of 300 mt additional irm was acquired in magnetizing fields from 300 to 700 mt the irm acquired above 300 mt is attributed to hematite or other ferric oxides or oxyhydroxides and is thought to be the result of minor oxidation probably during recent weathering these results indicate that irm acquisition behavior may be used to monitor the hematite content in continental sedimentary rocks and may indicate stratigraphic intervals within which the natural remanent magnetization nrm could contain significant chemical remanence overprints although minor hematite content is indicated the detailed sampling of irm acquisition behavior for the san juan basin and clark s fork basin sedimentary sequences did not reveal any significant correlation of irm behavior with polarity of the characteristic nrm these data thus support the previous conclusion based on paleomagnetic data that the characteristic nrm is a depositional remanence which provides a valid recording of the geomagnetic polarity sequence during deposition of these continental sedimentary sequences

near surface horizontal convergence and dispersion near the tidal mixing front on northeastern georges bank abstract horizontal dispersion and convergence are evaluated from near surface drifter data collected during the summer and autumn of 1988 and summer of 1989 in the vicinity of the tidal mixing front on northeastern georges bank the effective horizontal diffusivity coefficient k e estimated from the relative motion of the drifters over the duration of the cluster tracking increases as the cluster length scale with a range from approximately 100 to 450 m 2 s 1 for length scales of approximately 5 to 58 km at length scales k e is near zero with many negative estimates indicative of convergence at length scales 20 km k e increases in magnitude and scatter above 30 km length scales k e is typically between 200 400 m 2 s 1 the dispersion as a function of length scale is compared to published estimates using apparent diffusivities which are adjusted for the finite size of the drifter cluster at release georges bank shows lower apparent diffusivities at length scales 20 km the latter are believed to be principally due to the large horizontal gradients in the seasonal flow field although other processes perhaps associated with the large tidal currents may also contribute at the shorter length scales the low dispersion is due to convergent processes examples of convergence at different locations and under different wind and stratification conditions are presented convergence near the tidal mixing front tends to occur under light wind conditions and was observed in both seasons and in both years during two intense southwestward windstorms drifters also converged in the bank s vertically well mixed zone apparently due to a combination of spatially varying ekman depth and topographic effects

mineralogy of magnetic minerals and revised magnetic polarity stratigraphy of continental sediments san juan basin new mexico detailed paleomagnetic and rock magnetic analyses have been performed on samples from multiple sections through the cretaceous tertiary k t boundary and throughout a 750 m thick sequence of late cretaceous through middle paleocene continental deposits in the san juan basin new mexico curie temperatures have been determined for magnetic separates from 52 levels and with only two exceptions they range from 180 to 300 c along with microprobe and x ray analyses these data indicate that the detrital ferrimagnetic mineral is titanohematite with composition 0 45 x 0 60 this magnetic mineralogy indicates derivation of the continental san juan basin sediments from a volcanic probably dacitic or andesitic source these mineralogical data along with other geological data and the pattern of magnetic polarity zonation in multiple sections across the basin argue strongly for deposition of the late cretaceous and paleocene continental deposits in the san juan basin as a clastic wedge derived from a sourc

topographic modeling and analysis of the landing site of chang e 3 on the moon abstract the chinese lunar probe chang e 3 carrying the jade rabbit lunar rover successfully landed in the sinus iridum area on the moon on december 14 2013 this paper presents the characterization activities that were done for the selection of the landing area including topographic modeling and analysis based on multisource lunar remote sensing data seven meter resolution chang e 2 imagery and lunar orbiter laser altimeter data were integrated to generate a digital elevation model dem with a resolution of 20 m for the entire sinus iridum landing area long baseline slopes were assessed according to this dem for all of this area lunar reconnaissance orbiter narrow angle camera images and 1 5 m resolution chang e 2 imagery were used to derive dems with higher resolution 4 m at several local regions within the sinus iridum landing area slope analyses at lander footprint scale 8 m were performed in these local regions craters were detected from the dems and the derived orthophotos and size frequency distributions were generated crater morphological statistics including the depth diameter ratios rim height diameter ratios and wall slopes were analyzed the results showed that the sinus iridum landing area is relatively flat most of the area has slopes of less than 15 the steeper slopes are mainly alongside craters and ridges the crater size frequency distribution is close to the equilibrium distribution the crater ages as indicated by their morphological statistics vary from mature to relatively fresh in different regions these topographic modeling and analysis results were used for strategic planning to identify the landing site for the chang e 3 and made a useful contribution to the success of the chang e 3 mission

a multi scale model of the hydrodynamics of the whole great barrier reef an unstructured mesh parallel hydrodynamic model of the whole great barrier reef is presented this model simultaneously simulates most scales of motion it allows interactions between small and large scale processes the depth averaged equations of motion are discretized in space by means of a mixed finite element formulation while the time marching procedure is based on a third order explicit adams bashforth scheme the mesh is made up of triangles their size and shape can be modified easily so as to resolve a wide range of scales of motion from those of the regional flows to those of the eddies or tidal jets that develop in the vicinity of reefs and islands the forcings are the surface wind stress the tides and the inflow from the coral sea east australian current coral sea coastal current the latter two forcings being applied along the open boundaries of the computational domain the numerical results compare favourably with observations of both longshore currents and the local perturbations due to narrow reef passages comparisons are also performed with the simulations of a three dimensional model applied to a small domain centered on rattray island showing that both models produce similar horizontal flow fields for a structured mesh model to yield results of the same accuracy there is no doubt that the computational cost would be much higher

magnetic carriers and remanence mechanisms in magnetite poor sediments of pleistocene age southern north sea margin pleistocene sedimentary sequences in the east anglian region of britain record both major and minor climatic oscillations and the impact of isostatic and eustatic variations intensively studied in terms of their lithology and biostratigraphy the sequences have been difficult to place in an absolute timeframe dating and correlation by magnetostratigraphy has been attempted over a num ber of years however these sediments are difficult to date by palaeomagnetic means because they are poor in detrital magnetite are subject to post depositional deformation and diagenesis and have unknown rates of sedimentation determining whether their natural remanence magnetisation nrm directions are reliable thus requires information on the mode and timing of remanence acquisition here we apply palaeomagnetic rock magnetic and mineralogical analyses to identify the nrm carriers in these sediments and hence their palaeomagnetic reliability within oxidised fluvial sediments the kesgrave formation the magnetic carriers appear to be relict magnetic minerals fer rian ilmenites chromites haematite and goethite which sometimes carry a reliable primary deposi tional remanence drm but often an overprinting viscous time varying remanence vrm within some reduced marine and intertidal sediments within the crag basin the iron sulphide greigite has been found to carry a reliable syn depositional chemical remanence crm in all the sediments magnetic inclusions within silicates are abundant are significant for the mineral magnetic signal but contribute little to any recoverable palaeomagnetic information copyright 2005 john wiley sons ltd

island wakes in shallow coastal waters rattray island northeast australia is 1 5 km long 300 m wide and lies in well mixed water approximately 25 m deep its long axis is inclined at about 60 into the direction of the dominant semidiurnal tidal current the length of the wake in the lee of the island as documented by aerial photographs and satellite imagery appears to equal that of the wake behind a flat plate in a two dimensional flow at a reynolds number of about 10 however current metering drogues measurements and temperature mapping indicate internal wake velocities much greater than would be consistent with such a simple low reynolds number model further estimates of the turbulent eddy coefficient suggest an effective reynolds number more in the vicinity of 103 to reconcile these observational differences and to explain the observed upwelling in the core of the wake an ekman pumping model is proposed it is postulated that the ekman benthic boundary layer driven by rotation in the wake allows the vertical vorticity introduced into the water at the tip of the island at the point of separation to be negated by the vorticity of opposite sign introduced at the bottom further it is shown that a large fraction of the kinetic energy of the upstream flow facing the island is used to drive the wake eddies leading to the conclusions that the trapping of water in the lee of islands greatly increases head losses on continental shelves with numerous islands coral reefs and rock outcrops

horizontal mixing of great barrier reef waters offshore diffusivity determined from radium isotope distribution the great barrier reef gbr northern australia is the largest coral reef system in the world and provides habitat for highly diverse tropical marine ecosystems mixing in the coastal waters of the gbr is an important parameter influencing the health of these ecosystems we have used the distribution of the four naturally occurring radium isotopes to determine the rate of mixing of nearshore waters of the central part of the gbr lagoon with water from the coral sea the observed radium distribution is modeled using a one dimensional diffusion model the model improves on previous radium offshore mixing models by incorporating the benthic flux of radium diffusing across the sediment water interface and offshore changes in water column depth we find that the inner lagoon diffusivity 20 km offshore is best estimated using the short lived isotopes 224ra and 223ra the concordance of k x estimated using the two different isotopes and the apparent consistency between measured riverine inflows to the lagoon and inflows inferred from the modeled salinity distribution provide confidence in the results the mean value of k x for the inner lagoon region of the southern central zone between latitudes 15 8 s and 19 0 s 265 36 m2 s 1 is more than twice that in the northern central zone 14 3 s to 15 8 s this difference likely reflects the different reef matrix density in the two zones the distribution of the longer lived isotope 228ra indicates more rapid mixing in the middle and outer lagoon these results indicate that central gbr water within 20 km of coast is flushed with outer lagoon water on a timescale of 18 45 days with the flushing time increasing northward