dinoflagellate cysts sea level changes and planktonic foraminifers across the cretaceous tertiary boundary at el haria northwest tunisia abstract dinoflagellate cysts and planktonic foraminifers have been studied from the cretaceous tertiary k t boundary interval at el haria northwest tunisia a high resolution integrated biostratigraphy is presented the k t boundary is drawn at the level of extinction of cretaceous planktonic foraminifers and is coincident with the first occurrence of the dinoflagellate cyst species danea californica the final extinction of planktonic foraminifers is foreshadowed by a reduction in their total abundance some 5 kyr earlier at the base of the boundary clay this reduction is coeval with reported anomalies in siderophyle elements and 13 c values in the same area dinoflagellate cysts do not show accelerated rates of extinction at k t time associations of dinoflagellate cysts however change drastically and parallel changes in relative numbers of sporomorphs spores and pollen and in the quantity of land derived organic matter jointly these changes reflect a rapidly falling sea level during the final 17 kyr of the mesozoic which culminates at the level of the k t boundary this steep sea level fall at k t time represents a peak regressive pulse at the end of the well documented latest cretaceous regressive trend this short term sea level fall might show to be a wide spread phenomenon which could have caused an excess shrinking of the already reduced areal extent of marginal seas since deep waters in cretaceous oceans were primarily produced in shallow marginal seas the rate of formation of deep water might have been minimized at k t time minimum rates of formation of deep water might have curtailed the slow upward mixing of relatively cool and nutrient rich deeper water through which the thermocline weakened and surficial waters became depleted in nutrients consequently phytoplankton productivity rapidly diminished which in combination with a weakened thermal gradient pushed the highly depth stratified cretaceous planktonic foraminiferal fauna to extinction over a period of time of some 5 kyr guembelitria cretacea was the sole planktonic foraminifer which could accommodate to the low productivity conditions the oscillating rise in sea level at the beginning of the cenozoic reinforced the upward mixing of relatively cool and nutrient rich deeper water steepened the thermocline and replenished the photic layer with nutrients concomitant niche differentiation in the photic layer progressively stimulated morphological innovation amongst early cenozoic planktonic foraminifers the final return of normally sized planktonic foraminifers and of stable and well balanced dinoflagellate cyst associations at about 125 kyr after the k t boundary seems to indicate that primary productivity and niche differentiation in the photic layer begin to revert to optimum levels the earliest cenozoic planktonic foraminiferal species globoconusa minutula and parvularugoglobigerina fringa are thought to have developed from a benthic foraminiferal species rather than having a planktonic ancestry

wildfires in the late palaeozoic of central europe an overview of the rotliegend upper carboniferous lower permian of the saar nahe basin sw germany abstract fossil charcoal from a number of different sedimentary settings e g lakes floodplains tuffs tuffites is reported from the rotliegend late carboniferous early permian of the saar nahe basin in sw germany it is one of the largest carboniferous permian basins which developed during the late variscan in europe the sedimentary deposits encompass the carboniferous permian boundary thus enabling us to examine the development of fire regimes parallel to the reconstructed drop in atmospheric o 2 across this boundary the majority of the identified macroscopical charcoal remains belongs to the conifers or other gymnosperms maybe pointing to a more fire prone vegetation in the drier hinterland preferentially inhabited by these plants most wildfires especially those which took place during the deposition of the lower rotliegend late carboniferous have probably been ignited by lightning whereas in the upper rotliegend early permian an intense volcanism may have also acted as an important additional source of ignition in the lower rotliegend charcoals occur in nearly all sedimentary facies types whereas in the upper rotliegend charcoal has so far only been found in some volcanically influenced deposits the absence of charcoal in most sediments from the upper rotliegend may be explained by i low atmospheric oxygen levels leading to reduced fire frequencies ii a generally sparse vegetation cover iii the mechanical breakdown of macroscopic charcoal under the prevailing semiarid conditions

wind related features in gusev crater mars 1 gusev crater has a complex history beginning with its formation by an impact in the noachian period and subsequent evolution including erosion and deposition associated with ma adim vallis which cut through gusev crater from the south various wind related features are found on the crater floor including albedo patterns bedforms such as barchan dunes and elongated hills possibly reflecting erosion by the wind comparisons of the orientations of these features with predictions from global and atmospheric models show wind patterns as functions of season and time of day strongest global winds occur out of the southeast in the late fall and early winter and appear to be responsible for the formation of a large dark streak that drapes 100 km across the crater floor on an intermediate scale bright wind streaks correlate with nighttime winds that flow into the crater from the rim and outlying high areas these streaks are interpreted to be deposits of dust settled from the atmosphere during times of positive atmospheric static stability smaller features include various dark streaks and duneforms the orientations of which are inferred to represent local zones of high wind shear surface stress these features also tend to correlate with strong afternoon upslope winds caused by the uneven heating of the atmosphere across the crater thus the large dark streak reflects global scale wind patterns the smaller dark features and duneforms represent flow of strong winds out of the crater in the afternoon and the small bright streaks represent deposition of dust associated with nighttime flow of wind into the crater the correlation between the wind regime predicted by the models and the orientations of the aeolian features gives confidence that the models are essentially correct because gusev is a prime candidate landing site for landers including the mars exploration rovers understanding the interplay of the atmosphere and the surface including the erosion and deposition of windblown particles is important in assessments of the science potential for these missions despite the abundance of wind related features on the floor of gusev only about 1 2 of the proposed landing ellipse area is covered with organized bedforms e g dunes although mantles of sand and dust are also likely to be present on the basis of an analysis of random landing points within the ellipse traverse distances to ridges ejecta from small craters and other potential sources of rocks are within 150 m traverse distance for 95 of the touchdown points

meteorology of proposed mars exploration rover landing sites 1 a descriptive study of the near surface meteorology at three of the potential mars exploration rover mer landing sites terra meridiani gusev crater and melas chasma is presented using global and mesoscale models the mesoscale model provides a detailed picture of meteorology on scales down to a few kilometers but is not well constrained by observations away from the viking and pathfinder landing sites as such care must be taken in the interpretation of the results with there being high confidence that the types of circulations predicted will indeed occur and somewhat less in the quantitative precision of the predictions and the local time phasing of predicted circulations all three landing sites are in the tropics and are affected by hadley circulation by diurnal variations due to the global thermal tide and by planetary scale topography in these particular cases from tharsis elysium and the global topographic dichotomy boundary terra meridiani is least affected by large variations in local topography mean winds at terra meridiani during mer landing would be less than 10 m s with little vertical shear however these low wind speeds result from strong mixing in the early afternoon convective boundary layer which creates its own hazard in the horizontal variation of vertical winds of up to 8 m s both upward and downward in gusev crater the topography of ma adim vallis and the crater rim generates strong diurnally reversing channeling of wind in ma adim vallis and diurnally reversing radial flow in the crater associated with thermal slope winds on the crater rim the overturning circulation in gusev crater slightly suppresses the daytime convective boundary layer melas chasma in valles marineris provides an example of strong topographic forcing of near surface circulation of particular interest is the channeling of regional scale wind toward the center of the tharsis plateau during the evening this results in a surface level jet along the canyon of over 25 m s drainage of air from the plateau and into the canyon produces vertical winds down the canyon walls in the evening of over 5 m s in contrast during the early afternoon mer landing time horizontal winds at the proposed mer landing site are relatively calm with little mean shear with height this results from the proposed site being in a region of local divergence and the action of daytime convection the nature of flow in melas chasma results in an interesting dual maximum in boundary convection and depth with the usual daytime afternoon free convective maximum being joined by a mechanically forced nighttime boundary layer of almost 2 km depth

postglacial rebound observed by lageos and the effective viscosity of the lower mantle sixty four observations of the orbital node made by the lageos satellite over a five year time interval reveal an acceleration of 8 1 or 1 8 x 10 to the 8 power arcseconds day 2 due to a source which is not presently modeled in the geodyn orbit determination computer program this acceleration cannot be explained by the ocean tide with 18 6 year period assuming it to be an equilibrium tide instead it seems to be due to postglacial rebound which changes the j 2 coefficient in the spherical harmonic expansion of the earth s gravitational field at the rate of 8 2 or 18 x 10 to the 19th power s this in turn accelerates the node this rate does not agree with the 32 x 10 to the 19th power s predicted by wu and peltier s 1982 l2 model which has upper and lower mantle effective viscosities of 10 to the 21st and 22nd powers pa s respectively it does agree well with their l1 model which gives about 10 x 10 to the 19th power s since the effective viscosity is 10 to the 21st power pa s throughout the entire mantle in the l1 model the results support the contentions that the efective viscosity is near 10 to the 21st power pa s everyhere in the mantle and this relatively low value for the effective viscosity may have permitted several degrees of polar wander due to glaciation during the quaternary ice age previously announced in star as n84 13705

time calibration of triassic jurassic microfloral turnover eastern north america abstract palynological data from the newark basin of the newark supergroup reveal a spike in the spore pollen ratio at the triassic jurassic boundary this spore spike is coincident with a 60 regional extinction of the palynoflora and approximately synchronous with terrestrial vertebrate extinctions orbitally controlled sedimentary cycles allow stratigraphic sections to be calibrated in time constraining the duration of the microfloral turnover to an interval of 21 ky the geologically brief palynofloral break is similar to cretaceous tertiary boundary fern spikes these data support a triassic jurassic boundary impact extinction scenario

a refined gravity model from lageos gem l2 a refined gravity field model goddard earth model gem l2 has been derived using the lageos orbital data yielding better baseline measurements for the analysis of tectonic plate motion this field also contributes to an improved understanding of long wavelength features such as the sea slope across broad ocean basins through its significant improvement of the long wavelength geoid through degree and order 4 the geoid for these terms has an accuracy estimated at 8 cm in gem l2 gem l2 as in all recent goddard earth models relies heavily on the precise near earth satellite laser ranging data in this case provided by nasa s crustal dynamics program two and a half years of lageos laser data acquired from over 20 well distributed stations were combined with the existing data from the best satellite derived model gem 9 to develop the new lageos model testing shows that the lageos gravity field error at long wavelengths is less than half that for gem 9 independent tests using well determined longitude accelerations of 24 hour satellites have verified the improved accuracy of the new model a comparison of global laser base stations from independent data sets of alternating 15 day data segments over the 2 1 2 years of lageos show total inter station positioning to 1 8 cm when using this new field the same comparison using the 1979 versus the 1980 lageos data yields 5 2 cm this difference in agreement reflects the change in data distribution and other systematic errors along with the tectonic motion which has occurred between these chronologically distinguishable data sets five day average polar motion values with a precision of 10 cm and change in length of day values accurate to better than 5 msec have been derived in the solution the adjustment of these parameters are necessary to achieve the accurate stations and geopotential results in gem l2

tectonic motion and deformation from satellite laser ranging to lageos satellite laser ranging slr to lageos acquired during the period 1978 1988 has been analyzed to yield estimates of tectonic motion for 22 laser tracking stations situated on seven major plates the analysis is based on the precise modeling of the orbit dynamics of lageos and includes the determination of other geodynamic and nonconservative force model parameters involved in the orbit determination problem at the centimeter level site velocities were recovered from station positions determined each calendar quarter using a network adjustment procedure which maintains the reference frame within the stable interior of tectonic plates the recovered motions indicate good agreement with existing estimates of stress fields particularly across northern europe the eastern pacific and in the basin and range province of north america a comparison of the intersite motions for stations centrally located on separate plates between slr and those implied by the nuvel 1 geologic motion model yield a strong positive correlation of 0 989 and a 3 7 scale difference which may be attributable to recent changes in relative velocities or geologic time scale uncertainties sites located at or within 250 km of convergent plate boundaries have additional components of motion indicating a need for further tectonic modeling beyond that provided by simple rigid plate motions for lines crossing the north atlantic the san andreas fault and within the basin and range province the geodesic rates determined by slr are in good agreement with those determined by very long baseline interferometry an alternative space geodetic technique

an estimate of equatorial gravity from terrestrial and satellite data equatorial gravity has been estimated from terrestrial gravity data and from satellite implied data the terrestrial estimate was based on the analysis of 43271 1 1 mean free air gravity anomalies the value estimated was 978032 35 0 5 mgals this value may be slightly 0 to 1 5 mgals too low because of the neglect of the downward continuation of surface free air anomalies to the geoid an alternate estimate based on the comparison of terrestrial anomalies and altimeter derived anomalies yields 978032 6 mgals equatorial gravity from space data depends on gm from lageos and lunar laser data and on a new estimate 6378136 2 0 5 m of the equatorial radius based on doppler tracking station positions and a new spherical harmonic expansion of the earth s gravity field to degree 360 the resultant equatorial gravity is 978032 78 0 2 mgals the difference between the two terrestrial estimates is 0 4 and 0 2 mgals or 0 4 ppm or 0 2 ppm the agreement is within the accuracy of the two separate estimates these comparisons can put constraints on parameters of non newtonian force models

variation of seismic slip in the gulf of california and the possible effect on geodetic measurements of pacific north american plate motion the gulf of california is a unique tectonic transition zone which progresses from an oceanic ridge transform system at the mouth of the gulf to a predominantly continental transform system in southern california slip rates estimated from seismic moment data amount to about 17 to 30 of the accumulated tectonic slip in the gulf predicted by the nuvel 1 plate motion model even after accounting for the transition in crustal structure the seismic to tectonic slip ratios also appear to increase slightly from south to north this trend in the seismic moment release may reflect changes in the accommodation of pacific north american plate motion along the gulf which can be examined geodetically on the other hand geodetic measurements of the relative plate motion can be disturbed by short term effects associated with episodic seismicity to assess these effects the surface displacements due to typical transform events in the gulf are estimated using a simple dislocation model the results of this numerical calculation suggest that if a large transform event m0 1 5 1026 dyne cm were to occur within 100 to 200 km of a geodetic baseline for example one comprised in the geomex global positioning system network across the southern gulf the relative distance measurements could be affected by up to 15 mm this is marginally at the error level of a few millimeters plus 2 parts in 108 of baseline length for geomex measurements which thus are sensitive only to the far field displacement along the plate boundary over baselines of a few hundred kilometers in length

wildfires in the late palaeozoic of central europe the zechstein upper permian of nw hesse germany abstract fossil charcoal as the direct evidence of wildfires is present in most of the plant bearing deposits from the central european zechstein upper permian the charcoal content of upper permian sediments collected at the locality frankenberg geismar nw hesse germany is allochthonous and the shape of the fragments and the rounded edges indicate transport over relatively long distances charcoalified conifer needles are very rare and usually highly fragmented the anatomical diversity of charred wood is higher than that of the permineralised woods from the zechstein that have been described previously it is not yet clear whether this represents a higher diversity of natural taxa or anatomicaly different parts belonging to only a few taxa until now virtually nothing is known about the fire ecology of late palaeozoic conifer dominated upland vegetation the presence of charcoal indicates that these vegetation which grew under mesic to xeric conditions may have experienced more or less regular wildfires wildfires may have been relatively frequent during the late permian as compared to climatically comparable modern ecosystems

extinction and survival of plant life following the cretaceous tertiary boundary event western interior north america the palynological cretaceous tertiary boundary is recognized in the northern part of the western interior by the abrupt disappearance of a few characteristic cretaceous pollen genera principally proteacidites and aquilapollenites in the southern part the boundary is recognized by the disappearance of a somewhat different group of pollen proteacidites tilia wodehousei and trisectoris the abrupt change in both regions takes place precisely at the stratigraphic horizon at which boundary clay layers containing anomalously high concentrations of iridium interpreted to be the result of an asteroid impact are found although some characteristic cretaceous taxa apparently became extinct others were minimally affected by this boundary event and reappear in strata above however all the principal cretaceous pollen genera though not species that disappear regionally have been reported from tertiary rocks in other parts of north america differential apparent extinction and or survival reflects a pronounced temporary disruption of plant life immediately after the event some cretaceous plants must have persisted in refugia to have provided the propagules for the rapid recovery of the flora no massive total extinction of plant genera at the end of the cretaceous can be seen from the palynologic record

meteorological predictions for 2003 mars exploration rover high priority landing sites 1 the mars regional atmospheric modeling system is used to predict meteorological conditions that are likely to be encountered by the mars exploration rovers at several proposed landing sites during entry descent and landing seven areas five of which contain specific high priority landing ellipses are investigated hematite two sites isidis planitia elysium planitia two sites valles marineris and gusev crater the last two locations are in regions of extreme topography and the local and regional thermal circulations that result are equally extreme horizontal wind speeds near the floor of valles marineris exceed 50 ms 1 vertical velocities near the walls exceed 40 ms 1 and penetrate 10 km in altitude above the rim of the canyon thermal convection is suppressed within valles marineris by subsidence that forms in response to the upslope flows along the canyon walls wind magnitudes at gusev crater are approximately one third of those at the canyon but horizontal wind shear is greater deep convective thermals are noted at the relatively flat hematite site where 10 ms 1 updrafts rising to heights of 5 km are not uncommon during the midafternoon linearly organized convective updrafts superimposed on upslope circulations dominate over most of isidis planitia hexagonal and linearly organized convection predominates at elysium planitia afternoon circulations at all sites pose some risk significant risk in some cases to entry descent and landing most of the atmospheric hazards are not evident in current observational data and general circulation model simulations and can only be ascertained through mesoscale modeling of the region

an introduction to the global positioning system and some geological applications receivers equipped to measure dual frequency carrier phase signals from satellites of the global positioning system gps have been capable under special conditions of determining relative horizontal positions among stations separated by one to a few hundred kilometers with a precision of one to several millimeters since the early 1980s the major obstacles to making this capability routine extending it to all parts of the globe and extending it to longer station separations have been equipment cost limitations in the gps satellite constellation arduous data analysis uncertainties in satellite orbits uncertainties in propagation delays associated with variable tropospheric water vapor and difficulties in resolving carrier phase cycle ambiguities recent improvements have occurred in all these areas the increasing ease and reduced cost of gps data acquisition and analysis are having a significant impact on studies of near fault crustal deformation and earthquake processes until recently the province of conventional terrestrial geodetic techniques the enhanced satellite constellation improved models and establishment of global tracking networks have extended several millimeters horizontal positioning capability to station separations of 1000 km or more in virtually all parts of the world this enables study of new classes of tectonic problems that previously were difficult to attack with any geodetic technique examples include a complete kinematic description of ongoing crustal deformation in broad complex continental plate boundary zones and measurement of relative plate motion at convergent boundaries where global models may be poorly constrained

selection of the mars exploration rover landing sites 1 the selection of meridiani planum and gusev crater as the mars exploration rover landing sites took over 2 years involved broad participation of the science community via four open workshops and narrowed an initial 155 potential sites 80 300 30 km to four finalists based on science and safety engineering constraints important to the selection included 1 latitude 10 n 15 s for maximum solar power 2 elevation less than 1 3 km for sufficient atmosphere to slow the lander 3 low horizontal winds shear and turbulence in the last few kilometers to minimize horizontal velocity 4 low 10 m scale slopes to reduce airbag spin up and bounce 5 moderate rock abundance to reduce abrasion or strokeout of the airbags and 6 a radar reflective load bearing and trafficable surface safe for landing and roving that is not dominated by fine grained dust the evaluation of sites utilized existing as well as targeted orbital information acquired from the mars global surveyor and mars odyssey three of the final four landing sites show strong evidence for surface processes involving water and appear capable of addressing the science objectives of the missions which are to determine the aqueous climatic and geologic history of sites on mars where conditions may have been favorable to the preservation of evidence of possible prebiotic or biotic processes the evaluation of science criteria placed meridiani and gusev as the highest priority sites the evaluation of the three most critical safety criteria 10 m scale slopes rocks and winds and landing simulation results indicated that meridiani and elysium planitia are the safest sites followed by gusev and isidis planitia

a comparison between lageos laser ranging and very long baseline interferometry determined baseline lengths the nasa crustal dynamics project uses satellite laser ranging slr and very long baseline interferometry vlbi data collected and analyzed by the goddard space flight center and the jet propulsion laboratory for the measurement of geodynamic and geodetic parameters an important parameter is the determination of the baseline length or intersite distance since october 1979 baselines determined from slr data and vlbi data have been compared to help assess the accuracy of the baseline measurements from these independent techniques eight locations in the continental united states participated in the comparison westford massachusetts fort davis texas platteville colorado and quincy owens valley goldstone pasadena and monument peak california twenty two baseline lengths between these locations as determined by slr were differenced from the corresponding vlbi determinations the rms scatter about zero for the length differences is 5 2 cm with a mean of 1 0 1 1 cm and there is no apparent scale factor between these two distance determinations for this result the monument peak quincy baseline has been adjusted for tectonic plate motion by using the slr determined baseline rate for the eight other baselines crossing a plate boundary tectonic motion was not modeled if a model for this motion based upon baseline changes derived from strain rates is applied the rms scatter about zero for the 22 differences becomes 7 2 cm with a mean of 1 0 1 1 cm the above results are within the combined error budgets of the slr and vlbi baseline length determinations

assessment of mars exploration rover landing site predictions comprehensive analyses of remote sensing data during the three year effort to select the mars exploration rover landing sites at gusev crater and at meridiani planum correctly predicted the atmospheric density profile during entry and descent and the safe and trafficable surfaces explored by the two rovers the gusev crater site was correctly predicted to be a low relief surface that was less rocky than the viking landing sites but comparably dusty a dark low albedo flat plain composed of basaltic sand and haematite with very few rocks was expected and found at meridiani planum these results argue that future efforts to select safe landing sites based on existing and acquired remote sensing data will be successful in contrast geological interpretations of the sites based on remote sensing data were less certain and less successful which emphasizes the inherent ambiguities in understanding surface geology from remotely sensed data and the uncertainty in predicting exactly what materials will be available for study at a landing site

rapid 10 yr recovery of terrestrial productivity in a simulation study of the terminal cretaceous impact event abstract investigations of short term up to 103 yr environmental change across the cretaceous tertiary boundary provide evidence for reduced temperatures consistent with the injection of debris and sulphate aerosols into the upper atmosphere by a large impact event concomitant with this was a postulated massive addition of co2 to the atmospheric carbon reservoir by impact vaporisation of the chicxulub carbonate platform taken together a high co2 but low irradiance environment would have created unusual conditions for the operation of the terrestrial biosphere here we have evaluated this environmental influence on terrestrial ecosystems using a process based dynamic global vegetation model forced with post impact global climates derived by modification of the genesis atmospheric climate model simulation for the latest cretaceous our results suggest that terrestrial primary productivity initially collapsed and then recovered to pre impact levels within a decade global terrestrial carbon storage in vegetation biomass exhibited a similar collapse but complete recovery took place on a 60 80 yr timescale the recovery of both terrestrial net primary productivity and vegetation biomass was largely mediated by the high co2 concentration stimulating ecosystem photosynthetic productivity in the warm low latitudes an apparently rapid recovery of terrestrial ecosystem function stands in marked contrast to the situation for the marine realm where the organic carbon flux to the deep ocean was suppressed for up to 3 million years

the mars limited area model and simulations of atmospheric circulations for the phoenix landing area and season of operation 1 the mars limited area model mlam has been used to simulate martian northern polar atmospheric circulation phenomena during the planned season of the phoenix lander touching down on the surface ls 76 initial and boundary conditions are from thermal emission spectrometer observations assimilated via the united kingdom mars general circulation model the higher resolution north pole centric nestings grid lengths about 17 30 km and 8 5 15 km respectively resolve phenomena such as shallow mesoscale katabatic drainage flows spiraling out of the cold polar dome strong valley winds out of chasma borealis and diurnal slope winds embedded on the easterly basic flow e g at phoenix landing area d there conditions appear to be mild for mars and baroclinic activity is low low level jets with wind speeds exceeding 20 m s are however possible but they are most likely nocturnal and would hence not endanger the early afternoon landing of phoenix dust lifting is predicted for strong wind areas near the landing area b where baroclinic activity appears to be high and in the general area of the landing area d primarily east of it

stratigraphy sedimentology and palaeoecology of the dinosaur bearing kundur section zeya bureya basin amur region far eastern russia since 1990 the kundur locality amur region far eastern russia has yielded a rich dinosaur fauna the main fossil site occurs along a road section with a nearly continuous exposure of continental sediments of the kundur formation and the tsagayan group udurchukan and bureya formations the sedimentary environment of the kundur formation evolves from lacustrine to wetland settings the succession of megafloras discovered in this formation confirms the sedimentological data the tsagayan group beds were deposited in an alluvial environment of the gravel meandering type the dinosaur fossils are restricted to the udurchukan formation scarce and eroded bones can be found within channel deposits whereas abundant and well preserved specimens including sub complete skeletons have been discovered in diamicts these massive unsorted strata represent the deposits of ancient sediment gravity flows that originated from the uplifted areas at the borders of the zeya bureya basin these gravity flows assured the concentration of dinosaur bones and carcasses as well as their quick burial such taphonomic conditions allowed the preservation of sub complete hadrosaurid skeletons unearthed at the kundur site palaeobotanical data indicate a subtropical climate during the deposition of the kundur and udurchukan formations several elements in the composition of the kundur vertebrate fauna suggest a strong influence of the north american late cretaceous vertebrate communities the abundance of corythosaur like lambeosaurines the probable presence of a nodosaurid dinosaur and of a eucosmodontid or microcosmodontid multituberculate a late maastrichtian age is tentatively proposed for the dinosaur bearing sediments in amur region by comparison with the information collected in the western interior basin of north america as it is also observed in the latter area important floristic changes diminution of angiosperm pollens and predominance of modern families and the disappearance of dinosaurs mark the end of the maastrichtian age in the amur region late maastrichtian dinosaur localities from amur region are dominated by lambeosaurines whereas these dinosaurs apparently disappeared from western north america long before the iridium horizon that defines the k p boundary this local disappearance is therefore probably due to ecological factors rather than indicating a gradual extinction of the dinosaurs long before the k p boundary

mars exploration rover candidate landing sites as viewed by themis the analysis of six landing sites that were candidates for the two nasa mars exploration rovers mer benefited from recently available image data from the thermal emission imaging spectrometer themis onboard the 2001 mars odyssey spacecraft the combination of daytime and nighttime thermal infrared images from themis supplemented by additional data sets has lead to new or expanded insights into the nature of each landing site in meridiani planum a layer of lighter toned higher thermal inertia material is observable just below the hematite bearing layer gusev crater displays a more complex stratigraphy than previously observed including an upper layer with lobate margins the highest inertia unit of southern isidis planitia is confined to topographic lows in the rim basin margin and does not appear to be due to highland material transported onto the basin floor the enigmatic ovoid blocky terrain on the floor of melas chasma displays higher thermal inertia than its surroundings an indication that it contains coarser or more indurated material than the adjacent aeolian bedforms the myriad channels of athabasca valles display distinctive thermal signatures despite the presence of a bright layer of dust covering the region the presence of alluvial fans produced from spur and gulley erosion of the walls of eos chasma demonstrates that mass movements have occurred following the canyon scouring floods

high resolution topomapping of candidate mer landing sites with mars orbiter camera narrow angle images 1 we analyzed narrow angle mars orbiter camera moc na images to produce high resolution digital elevation models dems in order to provide topographic and slope information needed to assess the safety of candidate landing sites for the mars exploration rovers mer and to assess the accuracy of our results by a variety of tests the mapping techniques developed also support geoscientific studies and can be used with all present and planned mars orbiting scanner cameras photogrammetric analysis of moc stereopairs yields dems with 3 pixel typically 10 m horizontal resolution vertical precision consistent with 0 22 pixel matching errors typically a few meters and slope errors of 1 3 these dems are controlled to the mars orbiter laser altimeter mola global data set and consistent with it at the limits of resolution photoclinometry yields dems with single pixel typically 3 m horizontal resolution and submeter vertical precision where the surface albedo is uniform the dominant error is 10 20 relative uncertainty in the amplitude of topography and slopes after calibrating photoclinometry against a stereo dem to account for the influence of atmospheric haze we mapped portions of seven candidate mer sites and the mars pathfinder site safety of the final four sites elysium gusev isidis and meridiani was assessed by mission engineers by simulating landings on our dems of hazard units mapped in the sites with results weighted by the probability of landing on those units summary slope statistics show that most hazard units are smooth with only small areas of etched terrain in gusev crater posing a slope hazard

the mars regional atmospheric modeling system model description and selected simulations the mars regional atmospheric modeling system mrams is introduced and selected model results are presented and compared with landed meteorological data when possible mrams is descended from a nonhydrostatic earth mesoscale and cloud scale model that is widely used for forecasting weather and simulating atmospheric systems over complex terrain mesoscale models such as mrams are ideal tools for making use of the high resolution data sets arriving from mars global surveyor experiments simulation of the mars pathfinder mpf landing site at lsd 142 using 1 2 degree mars orbiter laser altimeter mola derived topography and thermal emission spectrometer thermal inertia is shown to be in good agreement with observed near surface temperature pressure and wind direction simulations of topographically induced thermal circulations and mountain induced gravity waves are shown to be consistent with theory and earlier studies that tie large amplitude mountain waves to strong winds capable of producing dust streaks and local dust lifting events a large eddy simulation of the convective boundary layer provides estimates of vertical profiles of heat flux momentum flux turbulent kinetic energy and vertical velocity variance the model results suggest that the martian atmosphere is roughly two to three times more turbulent than the terrestrial atmosphere during the afternoon but fluxes are roughly an order of magnitude smaller due to the lower density dust devillike circulations are also predicted in the large eddy simulation finally a simulation that examines atmosphere surface interactions near big crater is discussed predicted surface wind stress patterns are consistent with aeolian processes inferred through mars orbiter camera imagery of big crater located near the mpf landing site c 2001 academic press

vertebrate extinctions and survival across the cretaceous tertiary boundary abstract a critical analysis of the fossil vertebrate record across the cretaceous tertiary boundary shows that the available evidence is far less accurate than that concerning invertebrates and microfossils far reaching conclusions have been drawn from generalisations about vertebrate extinctions in the continental realm based on the local record from western north america but little is known about patterns of terminal cretaceous vertebrate extinctions in other parts of the world and even the western north american record is ambiguous despite this unsatisfactory record it clearly appears that terminal cretaceous vertebrate extinctions were highly selective with some groups e g dinosaurs becoming completely extinct whereas others seem to be virtually unaffected this argues against devastating catastrophes of the kind postulated by some recent impact scenarios however the survival of groups known to be sensitive to climatic deterioration such as crocodilians and other non dinosaurian reptiles indicates that alternative hypotheses involving gradual but fairly important climatic changes on a world wide scale are not convincing either the pattern of extinction and survival among vertebrates across the cretaceous tertiary boundary may be explained as a consequence of the disruption of some food chains following a crisis in the plant kingdom which itself may have been the result of the atmospheric consequences of unusual extraterrestrial or internal events

geology of the melas chasma landing site for the mars exploration rover mission 1 the melas chasma landing site was considered a high priority site for the mars exploration rover mer mission because of the opportunity to land on and study potential layered sedimentary deposits though no longer considered a candidate site because of safety concerns the site remains a scientifically interesting area that provides insight into the geologic history of valles marineris within the landing ellipse are dunes landslide material and unusual blocky deposits the blocky deposits are composed of rounded blocks some of which have meter scale layering and they show evidence of ductile deformation including bending and distortion of coherent blocks around each other the morphologic characteristics of the blocks are unique and they appear to have no terrestrial analogue however the gross morphology of these blocky deposits and their superposition on adjacent wallrock is consistent with the blocks having been transported downslope given the existence of other large mass failures in the area we propose the blocky deposits may also have originated from mass movement events the size of the blocks coupled with the distances they traveled indicates high mobility the distances the blocks were transported and their rounded irregular shapes suggest either water in the source material or deposition in a subaqueous environment the source for the main blocky deposit inside the landing ellipse is considered to be the wallrock to the south while the other two blocky deposits have source regions along the northern canyon walls the southern wallrock of melas chasma contains numerous valleys not seen elsewhere in valles marineris the identification of valley networks along the southern wallrock suggests that a source of water existed below the surface of the plateau and produced the valleys after intersecting the edge of the exposed canyon walls

analysis of atmospheric mesoscale models for entry descent and landing 1 each mars exploration rover mer is sensitive to the martian winds encountered near the surface during the entry descent and landing edl process these winds are strongly influenced by local mesoscale conditions in the absence of suitable wind observations wind fields predicted by martian mesoscale atmospheric models have been analyzed to guide landing site selection in order to encompass the available models and render them useful to the edl engineering team a series of statistical techniques was applied to the model results these analyses cover the high priority landing sites during the expected landing times 1200 1500 lt the number of sites studied is limited by the computational and analysis cost of the mesoscale models the statistical measures concentrate on the effective mean wind the wind as seen by the landing system and on the vertical structure of the horizontal winds both aspects are potentially hazardous to the mer landing system in addition a number of individual wind profiles from the mesoscale model were processed into a form that can be used directly by the edl monte carlo simulations the statistical analysis indicates that the meridiani planum and elysium landing sites are probably safe the gusev crater and isidis basin sites may be safe but further analysis by the edl engineers will be necessary to quantify the actual risk finally the winds at the melas chasma landing site and presumably other valles marineris landing sites are dangerous while the statistical parameters selected for these studies were primarily of engineering and safety interest the techniques are potentially useful for more general scientific analyses one interesting result of the current analysis is that the depth of the convective boundary layer and thus the resulting energy density appears to be primarily driven by the existence of a well organized mesoscale or regional circulation primarily driven by large scale topographic features at mars

late maastrichtian paleoenvironments and dinosaur biogeography in the western interior of north america during late maastrichtian time three major sedimentary depositional provinces existed in continental environments of the western interior region of north america the sediments accumulated within these provinces are herein termed the piedmont alluvial plain and coastal lowland lithosomes these sedimentary lithosomes correspond to broad paleoenvironmental and paleophysiographic provinces that resulted from the westward shift of the pacific coast the bisection and retreat of the interior epeiric sea and the development of an intermontane basin system during maastrichtian time these dramatic physiographic changes created environments markedly different from those that had prevailed during most of the late cretaceous when western north america consisted of a narrow peninsula flanked on the east by a remarkably stable and monotonous coastal plain in conjunction with these physiographic and environmental changes three diverse dinosaur dominated continental vertebrate faunas arose herein termed the leptoceratops triceratops and alamosaurus faunas each was peculiar to a sedimentary environmental province and among them there was little interchange the separation of these faunas indicates that the dinosaur dominated communities had adapted to changing or deteriorating environmental conditions at the close of cretaceous time the alamosaurus fauna characterized markedly seasonal semi arid environments of the intermontane basins south of about 35 n latitude the triceratops fauna inhabited humid coastal floodplains and swamps bordering the retreating northern embayment of the epeiric sea north of latitude 35 n the leptoceratops fauna inhabited cool piedmont environments flanking the mountainous cordilleran overthrust belt north of 35 n latitude recognition of this biogeographic zonation indicates that the triceratops biozone is only of local utility and that the biostratigraphy of upper cretaceous continental deposits in north america must reflect the provincialism now recognized moreover the evident adaptability of dinosaur faunas to varied and changing environmental conditions suggests that climatic change alone may not have been responsible for their demise

mass extinctions the view of a sceptic the concept of periodic mass extinctions by extraterrestrial impacts has contributed very strongly to the current revival of interest in the problem of mass extinctions in this context several radical claims have been made asserting that the newly emerging picture of mass extinctions as a separate class of biological phenomena caused by a separate class of processes demands a far reaching revision of the the neodarwinian paradigm of evolution and implies a vindication of the cuvierian perspective on earth9s history the validity of these claims however is questionable at all levels from the interpretation of particular events to the concept of mass extinctions as a special class of phenomena to their proposed causation by impacts and to their alleged historical pedigree and implications for current evolutionary theory mass extinctions may actually be clusters of more or less accidentally aggregated in time but causally distinct extinction episodes

end cretaceous mass extinction event argument for terrestrial causation the end cretaceous mass extinctions were not a geologically instantaneous event and were selective in character these features are incompatible with the original alvarez hypothesis of their being caused by a single asteroid impact that produced a world embracing dust cloud with devastating environmental consequences by analysis of physical and chemical evidence from the stratigraphic record it is shown that a modified extraterrestrial model in which stepwise extinctions resulted from encounter with a comet shower is less plausible than one intrinsic to the earth involving significant disturbance in the mantle

geological context of water altered minerals in valles marineris mars 1 greater than 15 000 km2 of the layered deposits within valles marineris are associated with water altered minerals yet their origin and history of alteration remain a mystery there are numerous competing hypotheses for the formation of the interior layered deposits including aeolian lacustrine and volcanic recent orbiter spectroscopic data have indicated that water has played a role in their geological history thermal emission spectrometer tes measurements have revealed significant crystalline hematite bearing deposits within valles marineris typically related to interior layered deposits these hematite deposits found with a wide range of albedo values are associated with relatively steep bedrock exposures but can also be seen downslope on flat surfaces where they may be a lag deposit more recently observatoire la mineralogie l eau les glaces et l activite omega data have shown hydrated sulfates covering more than 13 000 km2 area of valles marineris sulfates are found in numerous topographic settings and geological units but are typically located along the flanks of interior layered deposits and nearby low lying floor units here we study the detailed morphologies of hematite and sulfate bearing units such as mantled wall units mass wasting blocky deposits massive floor deposits and tectonically altered floor units all of these terrains have diverse erosional styles and varied crater populations in both hematite and sulfate bearing units occasionally found in conjunction with one another formation processes require contributions from water the results indicate a wide range of diversity within an individual mineral class between mineral classes and also among morphological types the diversity of geological settings and properties suggest that any single unified formation mechanism is improbable

tidal variations of earth rotation we have rederived the periodic variations of the earth s rotation due to the tidal deformation of the earth by the sun and moon and included all terms with amplitudes 0 002 milliseconds 1 mm this series applies to the mantle plus crust and oceans which rotate together for characteristic tidal periods the parameter which scales the rotational series is k c where k is that fraction of the love number which causes the tidal variation in the moment of inertia of the coupled mantle and oceans while c is the dimensionless polar moment of inertia of the coupled units if the whole earth minus oceans were coupled rotationally then k 0 30 and c 0 33 ocean tides increase k by 0 04 decoupling of the fluid core from the mantle decreases k by 0 06 while c cmantle 0 29 since neither pressure viscous nor hydromagnetic coupling locks the fluid to the mantle for periods less than 5 to 25 years from the analysis of lunar laser ranging data we find that k c at monthly and fortnightly frequencies equals 0 99 0 15 and 0 99 0 20 as compared with a theoretical value of 0 94 0 04 in addition we have estimated theoretically the effects of ocean tides on earth rotation nutation and polar motion using models based on the laplace tidal equations

the geoscience laser altimetry ranging system the geoscience laser altimetry ranging system glars is a planned highly precise laser distance measuring system to be used for geoscience measurements requiring extremely accurate geodetic observations from a space platform the system combines the attributes of a pointable laser ranging system making observations to retroreflectors placed on the ground with those of a nadir looking laser altimeter making height observations to ground ice sheet and oceanic surfaces in the ranging mode centimeter level precise baseline and station coordinate determinations will be made on grids consisting of 100 to 200 targets separated by distances from a few tens of kilometers to about 1000 km these measurements will be used for studies of seismic zone crustal deformations and tectonic plate motions ranging measurements will also be made to a coarser but globally distributed array of retroreflectors for both precise geodetic and orbit determination applications in the altimetric mode relative height determinations will be obtained with approximately decimeter vertical precision and 70 100 m horizontal resolution altimetric profiles consisting of nearly contiguous spots will be available when the system is operated at 40 pulses per second the height data will be used to study surface topography and roughness ice sheet and lava flow thickness and ocean dynamics waveform digitization will provide a measure of the vertical extent of topography within each footprint

a new model to simulate the martian mesoscale and microscale atmospheric circulation validation and first results 1 the laboratoire de meteorologie dynamique lmd mesoscale model is a new versatile simulator of the martian atmosphere and environment at horizontal scales ranging from hundreds of kilometers to tens of meters the model combines the national centers for environmental prediction ncep national center for atmospheric research ncar fully compressible nonhydrostatic advanced research weather research and forecasting arw wrf dynamical core adapted to mars with the lmd general circulation model gcm comprehensive set of physical parameterizations for the martian dust co2 water and photochemistry cycles since lmd gcm large scale simulations are also used to drive the mesoscale model at the boundaries of the chosen domain of interest a high level of downscaling consistency is reached to define the initial state and the atmosphere at the domain boundaries a specific hybrid vertical interpolation from the coarse resolution gcm fields to the high resolution mesoscale domain is used to ensure the stability and the physical relevancy of the simulations used in synoptic scale mode with a cyclic domain wrapped around the planet the mesoscale model correctly replicates the main large scale thermal structure and the zonally propagating waves the model diagnostics of the near surface pressure wind and temperature daily cycles in chryse planitia are in accordance with the viking and pathfinder measurements afternoon gustiness at the respective landing sites is adequately accounted for on the condition that convective adjustment is turned off in the mesoscale simulations on the rims of valles marineris intense daytime anabatic 30 m s 1 and nighttime katabatic 40 m s 1 winds are predicted within the canyon corridors topographical channeling can amplify the wind a few kilometers above the ground especially during the night through large eddy simulations in gusev crater the model describes the mixing layer growth during the afternoon and the associated dynamics convective motions overlying gravity waves and dust devil like vortices modeled temperature profiles are in satisfactory agreement with the miniature thermal emission spectrometer mini tes measurements the ability of the model to transport tracers at regional scales is exemplified by the model s prediction for the altitude of the tharsis topographical water ice clouds in the afternoon finally a nighttime warm ring at the base of olympus mons is identified in the simulations resulting from adiabatic warming by the intense downslope winds along the flanks of the volcano the surface temperature enhancement reaches 20 k throughout the night such a phenomenon may have adversely affected the thermal inertia derivations in the region

a global geodetic reference frame from lageos ranging sl5 1ap a summary of the results obtained for a new comprehensive geodetic parameter solution from the analysis of lageos laser ranging data for the period may 1976 to the end of 1982 is presented estimates of each component of the polar motion and earth rotation the station coordinates the value of the earth s gravitational constant gm and the elements of the lageos orbit comprise this sl5 1ap solution the results differ from previously published values primarily through incorporation of more rigorous dynamic models for the ocean and solid earth tides the precision of the geodetic parameters are on average 5 marc sec polar motion 0 2 ms length of day better than 5 cm center of mass geodetic positioning 3 cm global baselines and 2 cm regional baselines an assessment of the contribution of systematic errors in the interstation distance determination is presented

the rotation of the earth studies of the earth s rotation provide one of the best means of probing the interactions of the atmosphere oceans and solid earth as well as the structure of the core and mantle since the last report of the u s national report to the iugg tapley 1983 two developments have led to significant improvement in the measurement of the rotation the upgrading of the laser network of the national aeronautics and space administration nasa and the expansion of vlbi observations coordinated by the national geodetic survey ngs with the support of nasa and the u s naval observatory both of these developments have been complemented by strong contributions from other countries the availability of more accurate measurements together with healthy research support in this field by federal agencies has also created a ripe environment for progress in theoretical studies of the rotation

tectonic plate motion and deformation inferred from very long baseline interferometry we inverted 76 rates of change of baseline lengths measured with very long baseline interferometry vlbi during the period 1979 1989 to estimate the parameters of motions of the north american noam and eurasian eura plates relative to the pacific pcfc plate we considered two types of plate motion models namely rigid and non rigid models in the non rigid models we simultaneously determined the non rigid motions of several stations near plate boundaries due to intraplate deformation intraplate deformation in the regions far away from plate boundaries is assumed to be negligible among several models considered a non rigid model called m2 is found to fit most closely to the observed data in this model six stations are assumed to be capable of the non rigid motion those are goldvenu hatcreek mojave12 ovro 130 and vndnberg in the southwestern united states and kashima in japan m2 gives parameter sets of 0 827 0 035 m y about 50 5 1 2 n 78 5 5 3 w and 0 889 0 049 m y about 59 7 1 9 n 85 1 7 4 w representing the noam pcfc and eura pcfc relative motions the plate motion parameters of m2 are nearly identical to those of the newest global scale plate motion model nuvel 1 the noam pcfc and eura pcfc rotation rates of m2 respectively deviate only 0 044 m y and 0 010 m y from those of nuvel 1 these deviations are only about 6 and 1 respectively of the rotation rates themselves the noam pcfc and eura pcfc poles of m2 both lie only 2 from those of nuvel 1 within a 2 error ellipse of each pole nuvel 1 is determined from spreading rates at mid ocean ridges azimuths of transform faults and earthquake slip vectors since the spreading rates are estimated from marine magnetic anomalies integrated over a geological timescale nuvel 1 gives the plate motions averaged over this timescale thus we may conclude that there is no appreciable difference between the plate motions averaged over a geological timescale millions of years and those in a recent short period 10 yr m2 also gives the horizontal non rigid motions of vlbi stations in the southwestern united states at rates of 6 9 mm yr and roughly in opposite direction to the rigid motion of each station associated with plate motion hatcreek located near the northern part of the basin and range province b r also shows additional westward motion of about 9 mm yr suggesting crustal stretching in the northern b r the us vlbi stations show subsidence at rates of about 5 7 mm yr except for goldvenu and ovro 130 whose subsidence is negligible the japanese vlbi station kashima has a horizontal non rigid motion of about 20 mm yr in the west northwest direction roughly opposite to the direction of the rigid motion kashima also shows subsidence at a rate of about 12 mm yr which is larger than that deduced from geodetic data but consistent with the result from gps

observing tectonic plate motions and deformations from satellite laser ranging for the first time satellite laser ranging slr measurements from lageos are revealing changes in geodetic station positions suggestive of predicted global tectonic plate motions a detailed discussion of the latest slr results is given herein since the accuracy of tectonic plate velocities increases with the repetition rate and accuracy in the measurement of interplate distances activities are also described for increasing the temporal resolution and precision of baseline determinations the lageos laser data for the period january 1979 to the end of 1982 have been reanalyzed the results of this analysis are now approaching the useful accuracies required by geophysics for the better annually determined stations they include consistencies of 2 3 cm in station heights and 2 cm in annual baselines the slr results show overall agreement with the geologic tectonic rate model of minster and jordan with a linear cross correlation of 0 61 for 34 observed interstation rates improved temporal resolution was obtained in the measurement of specific baselines of moderate length through the large number of simultaneously observed passes

dispersed angiosperm cuticles their history preparation and application to the rise of angiosperms in cretaceous and paleocene coals southern western interior of north america abstract cuticle the decay resistant outer layer of leaves and young stems provides a reliable means of identifying fossil plant remains and reflects the vegetative adaptations of plants to climate and other environmental parameters the study of dispersed angiosperm cuticles originated prior to world war ii and has focused on the origin and paleoecology of coal activity in dispersed cuticles reached a high point during the 1950s and 1960s with the study of tertiary lignites in central europe then subsided in central europe as workers from other regions expanded the technique to other time periods and geographic regions data from dispersed cuticles augment data from palynomorphs because dispersed cuticles originate from a different generation of the vascular plant life cycle and have different taphonomic histories because the analysis of dispersed angiosperm cuticles is unfamiliar to many geologists methods for the analysis and preparation of dispersed angiosperm cuticles are detailed in an appendix dispersed cuticle assemblages from coals in the upper albian longford member of the kiowa formation and the maastrichtian paleocene raton formation of the southern western interior provide new constraints on the times that angiosperms entered coal swamps and rose to dominance the kiowa assemblages indicate that angiosperms first entered coal swamp environments by the late albian while the raton assemblages indicate that angiosperms dominated primary productivity in some subtropical coal swamps by the late maastrichtian angiosperms in kiowa coals probably comprised pioneer species in conifer dominated vegetation the most common family of angiosperms was chloranthaceae angiosperms in upper maastrichtian raton coals comprised the dominant seed plants to the exclusion of conifers magnoliid dicots and monocots were the dominant taxa and comprised diverse genera and families evidence from palynology and types of preserved cuticle indicates that ferns were subordinate to seed plants in biomass in raton coals in contrast to some described assemblages from the northern western interior paleocene coals from the raton basin show the loss of many cretaceous angiosperm taxa as well as the appearance of new taxa including conifers belonging to taxodiaceae however these taxodiaceae were evergreen and subordinate in abundance to angiosperms vegetational patterns shown by cretaceous paleocene coals of the southern western interior contrast with those of more northerly regions and indicate a poleward gradient in the timing of angiosperm dominance in coal swamps