evidence for post metamorphic metasomatism of high grade orthogneisses from sri lanka abstract here we discuss the post metamorphic metasomatism of high grade orthogneisses by studying granite looking pink coloured microcline bearing rocks exposed around ambagaspitiya sri lanka these rocks are medium to coarse grained and are more or less homogeneous and isotropic textural and petrographic analyses clearly show that these special rocks are neither deformed nor metamorphosed and that they are not any kind of intrusive rocks the present study shows that these rocks have formed through k metasomatism of once intensely deformed and metamorphosed granodiorite tonalite monzodiorite and quartz monzodiorite the modal compositions of most of these metasomatic rocks of ambagaspitiya are very similar to those of syenite quartz syenite monzonite quartz monzonite and quartz monzodiorite all the original metamorphic rocks namely granitic gneiss metagranite metagranodiorite metatonalite metamonzodiorite metaquartz monzodiorite metadiorite basic dikes and metapelites had undergone at least five ductile deformations d 1 to d 5 and had been metamorphosed under upper amphibolite to granulite facies conditions prior to the metasomatism almost all the parent metamorphic rocks had acquired a well developed gneissic foliation s2 and had suffered at least two intense folding events f 3 and f 5 before the metasomatism occurred all the metamorphic and deformational fabrics of affected metamorphic rocks have been completely or partially obliterated by the metasomatism this indicates that the metasomatic process post dates all ductile deformations d 1 d 5 and the regional metamorphism of the parent metamorphic rocks metagranodiorite metatonalite metamonzodiorite and metaquartz monzodiorite have undergone intense metasomatism it is shown that the metasomatism has nucleated along late stage post d 5 shear zones which may form an interconnected network potassium bearing metasomatic fluids derived from a deep seated k rich source may have migrated along these shear zones the fluids which entered the shear zones have pervaded the orthogneisses through foliation planes and along grain boundaries and microcracks in minerals transforming the host gneisses to metasomatic rocks the main metasomatic transformation has taken place through the replacement of metamorphic plagioclase and plagioclase quartz by microcline and through formation of myrmekite further studies are necessary to unravel the nature composition and the source of these late stage k rich fluids in the lower crust

spore diversity trends in the middle devonian of the chaco salteno plain northwestern argentina abstract devonian deposits in northwestern argentina were historically studied with stratigraphical purposes since these layers conform the source rocks of the producing basins of the region a fairly well preserved palynomorph assemblage from the tonono formation provides an opportunity to perform the first quantitative analysis to study the evolution of diversity in the succession two associations are here defined by both stratigraphic distribution of species and cluster analysis ranging from the lower eifelian to the lower givetian rarefaction analysis reveals the existence of a relatively rich miospore population species richness increases while there is a drop in diversity and evenness towards the top of the column the increment of the marine components towards the latter section indicates shifts in the shoreline the influx of warmer water into higher latitudes as highlighted by the arrival of the brachiopod tropidoleptus could have favored the inception of new spore species in the settled community these results add to evidence that some groups build up the number of species in disturbed settings and evenness is reduced with each new species introduced

a depositional model for organic rich duvernay formation mudstones abstract the upper devonian duvernay formation of western canada is an organic rich shale formation now targeted as a hydrocarbon reservoir we present a detailed sedimentological analysis of the duvernay formation in order to better understand organic rich mudstone depositional processes and conditions and to characterize the vertical and lateral heterogeneity of mudstone lithofacies that affect petrophysical and geomechanical rock properties organic rich mudstone facies of the duvernay formation were deposited in a dynamic depositional environment by a variety of sediment transport mechanisms including suspension settling turbidity currents and bottom water currents in variably oxygenated bottom waters suspension settling dominated in distal relatively deep areas of the basin but evidence for weak turbidity currents and bottom water currents was observed in the form of graded beds and thin grain supported siltstone laminae organic enrichment primarily occurred in distal areas as a result of bottom water anoxia and low depositional rates of inorganic sediment in deep water locations near platform margins alternating silty sandy contourite beds and organic rich mudstone beds are present the former interpreted to have been deposited and reworked by bottom water currents flowing parallel to slope in shallower more oxygenated settings mudstone lithologies vary from calcareous to argillaceous these sediments were deposited from suspension settling turbidity currents and bottom water currents although primary sedimentary structures are often obscured by extensive bioturbation locally organic enrichment in dysoxic rather than anoxic bottom waters was driven by a slightly increased sedimentation rate and possibly also by aggregation of sedimentary particles in the water column due to interaction between organic matter and clay minerals large variations observed in sediment composition from siliceous to calcareous to argillaceous reflect multiple biogenic carbonate and clastic sediment sources sediment composition is influenced by basin morphology circulation patterns sea level variation and proximity to sediment sources

evidence for a fold nappe in the high grade basement of central sri lanka terrane assembly in the pan african lower crust abstract structural analysis in the kadugannawa complex kc in central sri lanka reveals the presence of an early steep gneissic layering s 1 which has been overprinted by a younger event d 2 in the structurally deepest levels d 2 folds become progressively tighter towards the contact with the underlying highland complex hc the distribution of lithologies in the kc the distribution of steep s 1 and subhorizontal s 2 and the strain gradient towards the kc hc contact suggest that the kc is a d 2 fold nappe overlying the hc vergence of asymmetric sheath folds in sections parallel to a strong nnw sse lineation is towards nnw indicating a top to the nnw displacement granulite facies assemblages were formed during and after the final stages of d 2 in the kc d 2 was the main fabric forming event in the hc where meta igneous and metasedimentary gneisses show l s fabrics defined by the peak granulite facies assemblages the sense of shear deduced from asymmetric foliation boudinage is consistent with the top to the nnw displacement in the kc both units have been refolded around large scale upright d 3 folds the nappe model and nd model ages suggest that the kc and the eastern part of the hc may represent distinct lower crustal terranes juxtaposed during pan african high grade high strain events d 2 the contact between them is interpreted as a terrane boundary in a lower crustal environment the top to the nnw movement sense suggests that the kc may have been originally located south of the eastern highland complex this and the similarity in isotope signatures indicate a pre assembly link of the kc the western highland complex and the vijayan complex of eastern sri lanka

the clementine mission to the moon scientific overview in the course of 71 days in lunar orbit from 19 february to 3 may 1994 the clementine spacecraft acquired just under two million digital images of the moon at visible and infrared wavelengths these data are enabling the global mapping of the rock types of the lunar crust and the first detailed investigation of the geology of the lunar polar regions and the lunar far side in addition laser ranging measurements provided the first view of the global topographic figure of the moon the topography of many ancient impact basins has been measured and a global map of the thickness of the lunar crust has been derived from the topography and gravity

devonian sea level change in bolivia a high palaeolatitude biostratigraphical calibration of the global sea level curve article i nfo available online xxxx during the devonian period the cool water malvinokaffric realm was located at high palaeolatitudes in the southern hemisphere the realm is defined by its highly endemic marine benthic fauna which makes extra malvinokaffric correlations problematic investigation of the devonian palynomorphs from an extensive regional sub surface dataset 24 wells in the chaco basin bolivia reveals the presence of a number of stratigraphically restricted and regionally correlative epiboles peak abundances of the distinctive palynomorphs bimerga bensonii crucidia camirense evittia sommeri petrovina connata and ramochitina magnifica these palynomorph epiboles were then located at outcrop by a high resolution palynological investigation 225 samples of two bolivian outcrop localities in the chaco basin bermejo santa cruz department and campo redondo chiquisaca department the important evittia sommeri epibole in the basal los monos formation is related to a marine transgression that is present in both these outcrop sections additional chronostratigraphic control on this marine transgression comes from the occurrence of rare goniatites in the base of the huamampampa formation at campo redondo which are at least early eifelian in age post chot c event based on the goniatite together with spore data the marine transgression with evittia sommeri in the basal los monos formation can be tentatively assigned to the mid devonian mid late eifelian kacak event the presence of a datable malvinokaffric goniatite has shown that key spore taxa which are used zonally in both laurussia and gondwana do not all have coincident first occurrences in both areas furthermore despite the appearance of some cosmopolitan elements in the microflora mid and late devonian spore assemblages in bolivia are distinct from other regions in being relatively impoverished in both progymnosperm and lycopod spores this floral difference is attributable to the malvinokaffric realm continuing to retain a distinctive cool climatic signature throughout this interval however the sporadic occurrences of extra malvinokaffric macrofauna in restricted stratigraphic intervals of the middle devonian in south america and south africa are significant the oldest known occurrence of the extra malvinokaffric brachiopod tropidoleptus in bolivia is coincident with the late eifelian basal los monos formation transgression hence there was a relationship between influxes of this fauna and marine transgressions i e temporary periods of reduced climatic gradient the migration of devonian spores and particularly heterosporous spores between gondwana and laurussia clearly occurs during the mid and late devonian this is at variance with models claiming a wide rheic ocean during much of the devonian

recognising the taghanic crisis in the devonian terrestrial environment and its implications for understanding land sea interactions the late mid devonian eday marl formation from the orcadian basin scotland is a terrestrial equivalent of the marine devonian taghanic crisis the eday marl from orkney contains a high resolution archive of climatic change controlled by the relative strength of the seasonal insolation this includes several distinct and discrete episodes of basin flooding as demonstrated by the deposition of lacustrine laminites bedded evaporites marginal sheet flood sands and marine influenced bioturbated sheet sands these flooding events are intercalated with intense and sustained episodes of aridity indicating that insolation was relatively weak and the monsoon climate was ineffective at drawing in seasonal rainfall recognition of these basin flooding events has enabled the definition of three new units the wha taing roeberry and berstane members the eday marl formation can be correlated offshore and also recognised within marginal facies as an aeolian intercalation an environmental hydrological and climatic interpretation is given for the different events recognised in the eday marl this sequence of events when combined with the palynological age dates enables a detailed correlation to be made with the marine tully formation of new york state this suggests that regressions forced by climatic aridity are significant for understanding the deposition of the shallow water carbonates of the tully formation in what is otherwise a clastic depositional system comparison with the pelagic marine record shows that the latter as yet gives only limited resolution of the taghanic crisis recognising the taghanic as a rapid alternation of cool arid and relatively hotter pluvial events provides a unifying explanation for the associated collapse in the terrestrial vegetation and the parallel faunal changes in the marine realm

co existing cordierite almandine a key to the metamorphic history of sri lanka abstract a co existing cordierite almandine assemblage is described from the pelitic metasedimentary rocks of the precambrian granulite facies terrain of sri lanka the chemical control on this assemblage is demonstrated as has been observed in granulite facies terrains elsewhere the previous view of a low pressure origin of cordierite in pelitic rocks and the subdivision of the central granulite facies belt of sri lanka based thereon is hence doubtful

apollo 17 landing site topography photometric corrections and heterogeneity of the surrounding highland massifs 1 a high resolution digital elevation model for the apollo 17 landing site 20 n 31 e and surrounding region is used to correct the photometry of clementine ultraviolet visible multispectral data to standard viewing and illumination geometry on a pixel by pixel basis feo and tio2 concentrations were derived from these topographic photometrically corrected data and steep sloped highland massifs are used to assess the magnitude of the effects of the correction the effects are significant yielding errors as high as 5 wt feo and 4 wt tio2 absolute on 30 slopes the magnitude of the correction varies for sun facing versus anti sun slopes with greater changes on anti sun slopes because most of the apollo 17 sample stations were on surfaces with low slope values 5 the topography has only a small effect on the use of the apollo 17 site for calibration of feo and tio2 parameters topographically corrected data and derived compositional information are used to show accurately the variation in composition of the highland units such as the massifs and the sculptured hills on a fine scale massif compositions are consistent with mixtures of noritic impact melt and feldspathic granulitic material plus variable amounts of high ti basalt on flanks at low elevations and pyroclastic deposits at high elevations as surmised from previous studies an unexpected enrichment in feo at intermediate elevations in some places where massif surfaces have not been covered by mass wasting of impact melt rich material signals an older volcanic component not previously recognized this component may be correlative with an old high plains volcanic unit exposed northeast of the landing site and north of the sculptured hills downslope movement of regolith on steep slopes appears to have resulted in compositional or grain size sorting leading to an apparent enrichment in feo and tio2 from volcanic glass in valleys and draws the sculptured hills have highly variable compositions ranging from feldspathic patches to exposures of mafic rocks a strong but localized mafic anomaly within the sculptured hills may be a small postbasin volcanic feature consisting of very low ti basalt

devonian climate sea level and evolutionary events an introduction the face of planet earth has changed significantly through geological time dynamic processes active today such as plate tectonics and climate change have shaped the earth s surface and impacted biodiversity patterns from the beginning organisms on the other hand have the capacity to significantly alter earth s hydrological and geochemical cycles its atmosphere and climate sediments and even hard rocks deep down under the surface abiotic biotic interactions characterize earth s system history and together with biotic competition and food webs were the main trigger of evolutionary change innovations and biodiversity fluctuations within the palaeozoic the devonian was an especially interesting time interval as it was characterized by the mid paleozoic predator revolution signor brett 1984 brett 2003 and the related nekton revolution klug et al 2010 characterized by the blooms of free swimming cephalopods including the oldest ammonoids and fish groups e g toothed sharks and giant placoderms the rise of more advanced vertebrates including the oldest tetrapods e g blieck et al 2007 2010 niedzwiedzki et al 2010 the most extensive reef complexes of the phanerozoic e g kiessling 2008 and the greening of land by the diversification and spread of land plants including the oldest forests e g stein et al 2012 giesen berry 2013 which resulted in new soil types and changing weathering these major evolutionary trends did not unfold in a long interval of environmental stability but in times of numerous and repeated geologically brief global events that punctuated prolonged periods up to several million years in duration of relative stability termed ecological evolutionary subunits ee subunits boucot 1990 brett baird 1995 brett et al 2009 the bounding events even those of lesser intensity produced major re structuring in local to global ecosystems and are seen as critical drivers of long term evolutionary patterns brett 2012 these linked abiotic and biotic events and extinctions of different magnitude have been summarized by house 1983 1985 2002 walliser 1984 1996 and more recently by becker et al 2012 the devonian event succession is summarized in figure 1 two first order mass extinctions at the frasnian famennian boundary kellwasser crisis and at the end of the devonian hangenberg crisis characterized by the loss of major fossil groups classes and orders and complete ecosystems e g metazoan reefs early forests have to be viewed in the context of a complex global event sequence there are important similarities between discrete pulses phases of the major biotic crises and individual smaller scale events in our understanding second order global events are characterized by sudden extinctions in many groups and ecosystems including the complete disappearance of several widespread and diverse organism groups orders and families examples are the basal emsian atopus event where the planktonic graptolites finally died out the taghanic crisis frasnes events and lower kellwasser event third order global events show globally elevated extinction rates often at lower taxonomic level genera and species but within many clades and in several ecosystems examples are the silurian devonian boundary klonk event and the daleje chot c kacak condroz and annulata events fourth order global extinctions refer to the sudden disappearance of relatively fewer but widespread groups which implies a global not regional trigger this category may include the lochkovian pragian boundary

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

laser altimeter observations from messenger s first mercury flyby a 3200 kilometers long profile of mercury by the mercury laser altimeter on the messenger spacecraft spans approximately 20 of the near equatorial region of the planet topography along the profile is characterized by a 5 2 kilometer dynamic range and 930 meter root mean square roughness at long wavelengths topography slopes eastward by 0 02 degrees implying a variation of equatorial shape that is at least partially compensated sampled craters on mercury are shallower than their counterparts on the moon at least in part the result of mercury s higher gravity crater floors vary in roughness and slope implying complex modification over a range of length scales

palynological calibration of devonian events at near polar palaeolatitudes in the falkland islands south atlantic in the devonian the falkland islands were part of the high latitude cape basin west falkland palynological assemblages are at a low thermal maturity level but also very low in diversity and dominated by simple spores with rare chitinozoans and acritarchs the south harbour member contains rare verrucate and sculptured trilete spores and is early lochkovian the fish creek member palynofloras are late lochkovian the best correlative datum is the transgressive fox bay formation where the palynological assemblage includes ramochitina magnifica and is equivalent to the sequence b transgression in brazil dated as late pragian earliest emsian the early eifelian upper fox bay formation spore assemblage is comparable to the sequence c transgression in brazil and the chote event the facies and position of the base port philomel formation prasinophyte rich black shale suggests the late eifelian transgression ka ak event above this level is the inception of geminospora lemurata base givetian the upper port stanley formation contains a late but not latest famennian assemblage comparisons with both south africa and south america indicate a number of correlative transgressive and regressive events that match to euramerica these correlations are at a continental scale and confirm eustatic control of these devonian events

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

3d seismic reflection mapping of the silverpit multi ringed crater north sea the first comprehensive mapping of the silverpit multi ringed crater is presented based on five adjoining 3d seismic surveys that together provide 78 216 km2 areal coverage of the structure with spatial and depth sampling of 10 m the top cretaceous surface shows an excavated crater 3 km in diameter surrounded by 10 15 concentric ring structures out to a radius of 9 4 km seismic sequence stratigraphy and drilled wells indicate the lower age bound is a disconformity spanning 74 54 ma the upper bound is eocene termination of concentric ring fault growth ca 45 ma the inner rings are extensional faults defining rotated fault blocks that would be considered part of the crater in an impact structure interpretation giving a final impact crater diameter of 8 km the outer rings show a surprising variation in style from graben in the west to compressional structures in the east this may be explained by postcratering gravity spreading on easterly dipping intra cretaceous detachments within the crater the top cretaceous seismic reflector is disrupted and blocky but defines a central uplift with a slight crestal depression below this uplift the prominent base cretaceous seismic reflector shows jurassic strata rising into a cone 300 m high and 1 km wide characterized by radial faults this central uplift within the crater may structurally balance the inner ring fault blocks via a slumping model but we also identify low seismic velocity in the uplifted jurassic so fracturing may have contributed to growth of the central peak at a radius of 2 5 km base cretaceous shows a dish shaped depression that we interpret as marking either the extent of slumping toward the crater at this structural level or the limit of shockwave induced porosity collapse seismic reflectors above the top cretaceous excavated crater show differential compaction during the eocene accommodated by drape structure plus two conical faults that define narrow ring graben and represent the final phase of crater related tectonics

reconstructing the terrestrial flora and marine plankton of the middle devonian of spain implications for biotic interchange and palaeogeography a rich and well preserved palynomorph assemblage from the middle devonian of northern spain is analysed with regard to palaeobiogeography and palaeocontinental reconstruction the communities of terrestrial plants dispersed spores marine zooplankton chitinozoans and marine phytoplankton acritarchs and prasinophytes all show significant endemism they are depauperate in some respects missing common species found elsewhere but also containing many endemic taxa measures of similarity and cluster analysis reveal little relatedness to other contemporary assemblages with both the spore and phytoplankton communities being sister groups to all other communities except one attempted correlation with local regional and global sea level and transgression regression schemes is complicated by the absence of key index palynomorphs in this unusual assemblage the distinctive sedimentary sequence of northern spain may reflect an increased clastic input to the marine shelf resulting from an increasingly monsoonal climate possibly connected to the kacak extinction event the assemblage9s unusual endemic character requires restrictions on dispersal the terrestrial spore assemblage suggests that large tracts of ocean existed without appreciable land bridges between the armorican terrane assemblage and laurussia to the north and gondwana to the south the phytoplankton communities support existing evidence for significant east to west ocean currents through the rheic ocean supplementary material supplementary tables 1 3 contain presence absence data for spores chitinozoans and phytoplankton respectively in various assemblages used to construct the dendrograms in figures 4 6 the tables are available at https doi org 10 6084 m9 figshare c 4726862

upb geochronology of the sri lankan basement abstract u pb ages of zircons and monazites from ortho and paragneisses representing the major crystalline basement units of sri lanka establish a new geochronological framework which is consistent with previously published work on sm nd model ages rb sr whole rock ages and u pb mineral ages in the highland complex three newly dated orthogneisses one previously dated by baur et al 1991 and one dated by kroner and williams 1992 all intruded 1 85 to 1 9 ga ago this widespread intrusion event occurred soon after the end of sediment deposition which is estimated at 1 9 to 2 0 ga using upper intercept ages of zircons from metapelites in the highland complex within the boundaries of this complex established by sm nd model age mapping milisenda et al 1994 only one orthogneiss has been found which is substantially younger than 1 8 ga this is the metatonalite from polonnaruwa which intruded 670 ma ago baur et al 1991 three orthogneisses from the vijayan complex which lies to the east of the highland complex yield similarly consistent crystallization ages of 1023 8 1016 28 and 1033 121 ma in the wanni complex which lies to the west of the highland complex a sillimanite bearing gneiss which is apparently of metasedimentary origin but contains zircons of igneous appearance yields a primary crystallization age of 793 4 ma consistent with a previously dated orthogneiss from kurunegala of 770 ma baur et al 1991 in addition single zircon data by kroner et al 1994 indicate primary crystallization ages of 1 0 to 1 1 ga for orthogneisses from the vavuniya charnockite province which is considered to be part of the wanni complex these results confirm the age contrast between the highland complex on the one hand and the vijayan complex and wanni complex on the other as previously inferred from sm nd model ages milisenda et al 1988 1994 post tectonic granitoids and pegmatites intruded throughout all three complexes 550 ma ago the age of regional high grade metamorphism mostly granulite facies in the highland complex mostly amphibolite facies in the vijayan complex and both granulite and amphibolite facies in the wanni complex is constrained to be less than 670 ma the primary crystallization age of the polonnaruwa metatonalite it is more closely defined by lower intercept zircon ages which include one concordant age of 608 4 ma and one discordant but well defined age of 611 23 ma and by a nearly concordant monazite age of 592 2 ma this indicates that peak metamorphic conditions occurred 610 ma ago numerous other lower intercept ages between 590 and 550 ma and post tectonic intrusion ages of 550 ma set a lower age limit for high grade conditions and deformation the temperature history between 610 and 550 ma is not yet well resolved and it is not clear whether there was a separate thermal event 550 ma ago previously published whole rock rb sr and sm nd isochrons for gneisses from the highland complex yielding ages of 2 ga and greater and previously interpreted to date the time of granulite grade metamorphism must be reinterpreted in the light of the new data presented here as well as other recently published results e g burton and o nions 1990b baur et al 1991 and in view of the accumulated evidence for very limited element mobility during high grade metamorphism these whole rock ages are in fact identical or close to the ages of primary granitoid emplacement rather than the age of granulite facies metamorphism

erosion and deposition from bottom currents during the givetian and frasnian response to intensified oceanic circulation between gondwana and laurussia abstract calcareous bottom current deposits in otherwise pelagic and hemipelagic successions of the harz mountains in germany herzyn limestone formation the eastern moroccan central massif ziar mrirt nappe and the carnic alps in austria italy valentin and pal limestone formation show strong evidence of bottom current reworking of carbonate ooze during givetian and early frasnian associated phosphates confirm that higher hydraulic energy temporarily prevailed the bottom current deposited facies builds up strongly condensed and reduced successions with stratigraphic gaps which also occur with similar features in other areas of central europe and northwest africa at the same stratigraphic interval the widespread current induced reworking of calcareous sediments and phosphate formation during the givetian and early frasnian as well as the associated erosional processes marked by pronounced hiatuses all signal a major circulation event the temporal and spatial positions of these fossil calcareous contourites in the devonian are discussed research concluded that thermohaline currents were intensified by the acceleration of flows constricted in the narrow oceanic passages between the approaching continental plates laurussia and gondwana areas affected were the southeastern rhenish sea shelf the disintegrated northern continental margin of gondwana and deep marginal plateaus of the noric terrane in the western part of the prototethys the disposition of the fossil calcareous contourites and faunal data corroborate palaeogeographic reconstructions that show an advanced convergence between gondwana and laurussia and the smaller continental plates such as the armorican and noric terranes during givetian and frasnian times

digital elevation models of the moon from earth based radar interferometry three dimensional 3d maps of the nearside and polar regions of the moon can be obtained with an earth based radar interferometer this paper describes the theoretical background experimental setup and processing techniques for a sequence of observations performed with the goldstone solar system radar in 1997 these data provide radar imagery and digital elevation models of the polar areas and other small regions at spl sim 100 m spatial and spl sim 50 m height resolutions a geocoding procedure relying on the elevation measurements yields cartographically accurate products that are free of geometric distortions such as foreshortening

topographic mapping from interferometric synthetic aperture radar observations interferometric synthetic aperture radar observations provide a means for obtaining high resolution topographic terrain maps from data acquired simultaneously at two slightly displaced antennas calculation of the three dimensional coordinates of all the points in a radar image can be made from the combination of along track slant range and interferometer fringe measurements thus the result compensates for the layover exhibited by conventional radar maps and removes the false targets generated by multiple signal paths to a given object in the scene we have derived a topographic map of a portion of the san francisco bay area utilizing data that were recorded by a radar system mounted on a nasa cv990 aircraft and processed by a general purpose digital computer this map displays the height above sea level of a region approximately 11 km by 10 km in size sampled on an 11 m pixel grid uncertainties in the estimated height result from imprecise knowledge of the observational geometry radar bandwidth limitations and finite signal to noise ratios for our system each factor contributed approximately 3 4 m to a relative rms error of about 6 m additional global errors of the order of 10 m can result from inaccurate monitoring of aircraft attitude the statistical variation of the height measurements from the ocean portion of the map which we can presume to be quite flat is 2 10 m rms which is consistent with the theoretical estimate comparison of our results with u s geological survey contour maps indicates a high degree of correlation between the two sets of altitude data

the topography of tycho crater three dimensional mapping of the moon can be accomplished with an earth based radar interferometer elevation data and radar imagery obtained with this technique are presented for the tycho crater area with a spatial resolution of 200 m and a height resolution of 30 m the radar maps are displayed in standard cartographic projections with appropriate corrections for elevation induced geometric distortions the digital elevation model allows detailed morphometry of the 85 km diameter crater the floor of tycho lies 3970 m below a 1738 km radius sphere and the crater s central peak rises 2400 m above the floor the average rim crest elevation is 730 m above the 1738 km datum giving a mean rim to floor depth of 4700 m the floor has two distinct units with the western section being higher in elevation by 200 m this dichotomy is consistent with an asymmetry in the crater shape which reveals that maximum wall slumping occurred in the western and southwestern regions of the crater comparison of the radar derived topography with 87 altimetry points from the clementine lidar experiment shows rms deviations of 90 m after a 0 11 latitude correction to the location of all the clementine altimetry points

sequence stratigraphy and a revised sea level curve for the middle devonian of eastern north america abstract the well exposed middle devonian rocks of the appalachian foreland basin onondaga formation hamilton group tully formation and the genesee group of new york state preserve one of the most detailed records of high order sea level oscillation cycles for this time period in the world detailed examination of coeval units in distal areas of the appalachian basin as well as portions of the michigan and illinois basins has revealed that the pattern of high order sea level oscillations documented in the new york pennsylvania section can be positively identified in all areas of eastern north america where coeval units are preserved the persistence of the pattern of high order sea level cycles across such a wide geographic area suggests that these cycles are allocyclic in nature with primary control on deposition being eustatic sea level oscillation as opposed to autocylic controls such as sediment supply which would be more local in their manifestation there is strong evidence from studies of cyclicity and spectral analysis that these cycles are also related to milankovitch orbital variations with the short and long term eccentricity cycles 100 kyr and 405 kyr being the dominant oscillations in many settings relative sea level oscillations of tens of meters are likely and raise considerable issues about the driving mechanism given that the middle devonian appears to record a greenhouse phase of phanerozoic history these new correlations lend strong support to a revised high resolution sea level oscillation curve for the middle devonian for the eastern portion of north america recognized third order sequences are eif 1 lower onondaga formation eif 2 upper onondaga and union springs formations eif giv oatka creek formation giv 1 skaneateles giv 2 ludlowville giv 3 lower moscow giv 4 upper moscow lower tully and giv 5 middle tully geneseo formations thus in contrast with the widely cited eustatic curve of johnson et al 1985 which recognizes just one major transgressive regressive t r cycle in the early mid givetian if prior to the major late givetian taghanic unconformity iia upper tully geneseo shale we recognize four t r cycles if restricted ig ih and ii we surmise that third order sequences record eustatic sea level fluctuations of tens of meters with periodicities of 0 8 2 myr while their medial scale fourth order subdivisions record lesser variations primarily of 405 kyr duration long term eccentricity this high resolution record of sea level change provides strong evidence for high order eustatic cycles with probable milankovitch periodicities despite the fact that no direct evidence for middle devonian glacial sediments has been found to date

the origin of the pink granites of sri lanka another view abstract pink granites are common throughout the precambrian metasedimentary terrain of sri lanka and play a significant role in reconstructing the geologic evolution of this country essentially microcline bearing rocks they form conformable layers with the associated metasedimentary rocks and are always interlayered and associated with rocks possessing amphibolite facies mineral assemblages this association is seen throughout the terrain at all scales further they always tend to fold around the major structures of the terrain and contain conformable layers and enclaves of rare metasediments and have a gneissic appearance in places their field relations associations mineralogy petrography petrofabrics chemistry and also age suggest that they are metasediments probably arkoses which have undergone the same set of metamorphic and deformational events as other precambrian metamorphic rocks of sri lanka their present granite like character does not necessarily imply that they are the products of crystallization of magmatic or anatectic melts or that they have had a replacement origin rather chemical composition has determined their present granite like character due to granitization by simple isochemical recrystallization treptomorphism during highgrade metamorphism at a ph2o which was sufficient to retard their grade to amphibolite facies under granulite facies metamorphic conditions at which the other metasediments of sri lanka have metamorphosed