the shape and internal structure of the moon from the clementine mission global topographic and gravitational field models derived from data collected by the clementine spacecraft reveal a new picture of the shape and internal structure of the moon the moon exhibits a 16 kilometer range of elevation with the greatest topographic excursions occurring on the far side lunar highlands are in a state of near isostatic compensation whereas impact basins display a wide range of compensation states that do not correlate simply with basin size or age a global crustal thickness map reveals crustal thinning under all resolvable lunar basins the results indicate that the structure and thermal history of the moon are more complex than was previously believed

multispectral studies of western limb and farside maria from galileo earth moon encounter 1 new visible and near infrared multispectral images of the moon obtained by the galileo solid state imaging system along with lunar orbiter images for crater counts and spectral mixing analyses were used to characterize western limb and eastern farside maria and determine compositional and age relationships in selected regions results indicate that 1 western limb mare deposits have less variability in titanium content 6 wt tio2 mare basalts were observed on the western limb and farside which may reflect the inability of such denser magmas to penetrate the thicker farside crust

mineralogy of the mafic anomaly in the south pole aitken basin implications for excavation of the lunar mantle the mineralogy of south pole aitken basin spa the largest confirmed impact basin on the moon is evaluated using five color images from clementine although olivine rich material as well as basalts rich in clinopyroxene are readily identified elsewhere on the farside the dominant rock type observed across the interior of spa is of a very noritic composition this mineralogy suggests that lower crust rather than the mantle is the dominant source of the mafic component at spa the lack of variation in observed noritic composition is probably due to basin formation processes during which extensive melting and mixing of target materials are likely to occur

lunar dark haloed impact craters origin and implications for early mare volcanism remote sensing and photogeologic data were used to determine the composition and origin of lunar dark haloed craters near infrared reflectance spectra were obtained for numerous dark haloed impact craters located on either the ejecta blankets of large impact craters or imbrian and nectarian age light plains deposits spectral thermal radar and photogeologic data conclusively demonstrate that copernicus h and other dark haloed craters on the ejecta blanket of copernicus excavated mare basalts from beneath lighter surface deposits rich in highlands material analyses of reflectance spectra of dark haloed craters on light plains indicate that in every instance these craters exposed mare basalt which had previously been covered by varying thicknesses of highlands debris in the schiller schickard region a relatively thick highlands unit was emplaced as a result of the orientale impact event on the interior of balmer basin marelike basalt has been excavated from beneath much thinner highlands deposits emplaced by nearby craters mafic orbital geochemical anomalies are commonly associated with regions with abundant light plains deposits which exhibit dark haloed impact craters apparently some mare material has been incorporated into the regolith either by local mixing during the emplacement of the highlands debris or by subsequent vertical mixing the results of recent remote sensing photogeologic and lunar sample studies strongly indicate that mare volcanism was a significant process during much of the pre imbrian and may have been initiated as early as 4 2 4 3 ga these very early volcanic episodes contributed materials to the lunar surface which were incorporated into the upper portion of the highlands crust by subsequent impact mixing models concerning the extent and duration of mare volcanism as well as those involving the composition and thermal evolution of the lunar interior will have to be revised

petrography and geochemistry of sandstones interbedded with the rooiberg felsite group transvaal sequence south africa implications for provenance and tectonic setting abstract the 2150 ma rooiberg felsite group transvaal sequence contains thin sandstone interbeds within its 3500 5000 m thick volcanic succession whereas uppermost feldspathic arenites and wackes are thought to represent reworked felsitic material quartz arenites and subordinate lithic sandstones present throughout most of the rooiberg sequence comprise mainly reworked sedimentary detritus probably belonging to the underlying pretoria group sandy braided river systems probably transported clastic material into the basin from relatively stable source areas subject to intense chemical weathering geochemistry and sandstone petrography indicate that mixing of pretoria group detritus with sediment derived from erosion of felsitic material occurred within the basin during late rooiberg ti es the inferred hiatuses in volcanism represented by the predominant siliceous sedimentary interbeds appear to have been of relatively short duration and occur throughout much of the rooiberg stratigraphy upper arkosic sandstones indicate longer breaks in volcanism as rooiberg eruptions came to an end the sandstones provide evidence compatible with an impact origin for the rooiberg felsite group and for its successor the bushveld complex

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

mariner 10 multispectral images of the eastern limb and farside of the moon we present the first analysis of mariner 10 multispectral image data for the eastern limb and farside of the moon a new rigorous calibration of these data is used that provides results that are consistent with independently derived data sets from these newly calibrated data a color ratio image 0 48 0 58 m is produced to show relative tio2 abundances in mare units on the eastern limb and farside of the moon our results indicate that the farside lunar mare deposits examined have tio2 contents that are intermediate to low 2 5 tio2 relative to mare deposits on the nearside we find no evidence for areally extensive deposits of either very low titanium vlt or high to very high titanium vht basalts in these portions of the moon our findings support previous interpretations that the source regions for lunar mare basalts are laterally heterogeneous additionally examination of highland units reveals a relatively blue region that corresponds with a previously proposed cryptomare suggesting enhanced tio2 for this unit finally based on these mariner 10 data telescopic spectral data galileo multispectral image data and lunar meteorite analyses we speculate that volcanism in farside mare deposits did not include high titanium basalts 8 wt

three dimensional sequence stratigraphy and subtle stratigraphic traps associated with systems tracts west cameron region offshore lousiana gulf of mexico abstract three dimensional sequence stratigraphy is a potent exploration and development tool for the discovery of subtle stratigraphic traps reservoir morphology heterogeneity and subtle stratigraphic trapping mechanisms can be better understood through systematic horizontal identification of sedimentary facies of systems tracts provided by three dimensional attribute maps used as an important complement to the sequential analysis on the two dimensional seismic lines and the well log data on new prospects as well as on already producing fields the additional input of sequential analysis on three dimensional data enables the identification location and precise delimitation of new potentially productive zones the first part of this paper presents four typical horizontal seismic facies assigned to the successive systems tracts of a third or fourth order sequence deposited in inner to outer neritic conditions on a clastic shelf the constructiion of this synthetic representative sequence is based on the observed reproducibility of the horizontal seismic facies response to cyclic eustatic events on more than 35 sequences registered in the gulf coast plio pleistocene and late miocene offshore louisiana in the west cameron region of the gulf of mexico the second part shows how three dimensional sequence stratigraphy can contribute in localizing and understanding sedimentary facies associated with productive zones a case study in the early middle miocene cibicides opima sands shows multiple stacked gas accumulations in the top slope fan prograding wedge and basal transgressive systems tract of the third order sequence between sb 15 5 and sb 13 8 ma

volumes of lunar lava ponds in south pole aitken and orientale basins implications for eruption conditions transport mechanisms and magma source regions in an effort to characterize individual eruptive phases and events 86 isolated mare deposits ponds in the lunar south pole aitken and orientale regions were analyzed to obtain information on areas volumes and other characteristics deposits likely to represent single eruptive episodes have area mean values of 2000 km2 in the south pole aitken basin and 1100 km2 in the orientale basin pond volumes range from 35 to 8745 km3 with a mean value of 860 km3 for south pole aitken and 10 to 1280 km3 with a mean value of 240 km3 for the orientale region no evidence was found for shallow crustal magma reservoirs the relatively common occurrence of sinuous rilles in orientale is consistent with very high effusion rates and the large volumes of individual eruptive episodes tens to many hundreds of km3 are comparable to flood basalt eruption volumes on earth pond morphologies are consistent with extrusion from deep probably subcrustal reservoirs distribution of deposits suggests that many ponds may be derived from single reservoirs comparison of ponds in both basins shows a higher areal density and average volume of lava ponds in the south pole aitken basin relative to the orientale area this is plausibly attributed to the extreme depths of the south pole aitken basin and the correspondingly thinner crust there relative to the orientale region these observations are consistent with magma ascent and eruption mechanisms that are strongly dependent on the overpressurization of deep seated source regions the subsequent propagation of dikes and the thickness of the intervening lunar crust through which these dikes must rise

sedimentology and fractal based analysis of permeability data john henry member straight cliffs formation upper cretaceous utah u s a interpretation of depositional environments combined with field measurement of permeability for a portion of the upper cretaceous straight cliffs formation near escalante utah provides new results for understanding and modeling facies dependent perme ability variations offshore transition lower shoreface upper shore face and foreshore environments are interpreted for part of the john henry member on the basis of outcrop investigation using a newly designed drillhole minipermeameter probe permeability was measured for two of the facies within this unit lower shoreface bioturbated sand stone and upper shoreface cross bedded sandstone approximately 500 permeability measurements at a sample spacing of 15 cm were made along four vertical profiles and three horizontal transects o na6m 3 21 m outcrop permeability ranges from 41 to 1 675 millidarcies md in the bio turbated sandstone facies which is massive bedded moderately to well sorted and very fine to fine grained in contrast permeability ranges from 336 to 5 531 md in the moderately to moderately well sorted fine to medium grained cross bedded sandstone facies a high degree of variability in permeability of the cross bedded facies is caused by small scale variations in grain size and structure related to depositional processes the geometric mean permeability in the bio turbated sandstone is 253 md compared with 1 395 md in the cross bedded facies while the facies dependent differences in permeability k are ap parent and related to depositional and biological processes fractal based statistical analysis of the horizontal ln k increments yields near ly identical results for the bioturbated facies and the cross bedded fa cies possibly suggesting an underlying statistical commonality in the formation of both facies increment distributions from both facies ap pear similar with peaking around the mean ln k increments from the smaller vertical data set appear similar also but with a variance approximately 3 7 times larger than the horizontal value variance scaling analyses of horizontal and vertical data both yield a hurst co efficient near 0 26 which is characteristic of negative spatial correla tion of the increments the methodology developed herein offers a po tential high resolution alternative to existing methods for understand ing and characterizing subsurface properties

reconstructing a mid cretaceous landscape from paleosols in western canada abstract the albian stage of the mid cretaceous was a time of equable climate conditions with high sea levels and broad shallow epeiric seas that may have had a moderating affect on continental climates a late albian landscape surface that developed during a regression and subsequent sea level rise in the western canada foreland basin is reconstructed on the basis of correlation of paleosols penetrated by cores through the paddy member of the peace river formation reconstruction of this landscape refines chronostratigraphic relationships and will benefit future paleoclimatological studies utilizing continental sphaerosiderite proxy records the paleosols developed in estuarine sandstones and mudstones and they exhibit evidence of a polygenetic history upon initial exposure and pedogenesis the paddy member developed deeply weathered well drained cumulative soil profiles later stages of pedogenesis were characterized by hydromorphic soil conditions the stages of soil development interpreted for the paddy member correlate with inferred stages of pedogenic development in time equivalent formations located both basinward and downslope upper viking formation and landward and upslope boulder creek formation on the basis of the genetic similarity among paleosols in these three correlative formations the paleosols are interpreted as having formed along a single continuous landscape surface results of this study indicate that the catena concept of pedogenesis along sloping landscapes is applicable to ancient successions sphaerosiderites in the paddy member paleosols are used to provide proxy values for meteoric 18o values at 52 n paleolatitude in the cretaceous western interior basin the meteoric 18o values are used to refine existing interpretations about the mid cretaceous paleolatitudinal gradient in meteoric 18o values and the mid cretaceous hydrologic cycle

deposition and interpretation of long narrow sandbodies underlain by a basinwide erosion surface cardium formation cretaceous western interior seaway alberta canada abstract sand bodies of the cardium alloformation burnstick allomember occur in three parallel linear trends in the garrington caroline crossfield and lochend oilfields they are extremely long up to 100 km straight and narrow up to 4 km and are encased in marine mudstones suggesting their former interpretation as offshore bars our study of 189 cores and over 800 resistivity well logs shows that below the burnstick the hornbeck allomember consists entirely of dark mudstones deposited in quiet water the hornbeck burnstick contact where seen in cores is extremely sharp in cross sections resistivity well log markers are truncated by the lower surface of the burnstick and the sand bodies rest in asymmetrical one sided elongate scours with erosional relief of up to 7 m above he scoured surface there is a basal lag of mudstone intraclasts and chert pebbles overlain by a sandier upward succession of mudstones sandstones and conglomerates the sandstones are extensively burrowed but show some cross stratification the burnstick sandier upward succession is overlain by black mudstones of the raven river allomember the morphology of the scoured surface as defined in isopach maps does not indicate its formation in an open marine setting the long straight asymmetrical scours are parallel to regional strike and do not suggest subaerial erosion instead we suggest that a major relative lowering of sea level first exposed the hornbeck mudstones to subaerial erosion subsequently marine transgression of this surface removed evidence of its subaerial exposure pauses in transgression stillstands resulted in incised shoreface profiles the asymmetrical scours and at this time rivers supplied coarse sediment to the shoreface this sediment was reworked alongshore to form what are now the very long straight narrow sand bodies continued transgression resulted in the burial of the shoreface sand bodies by black mudstone basal part of the raven river allomember incised shoreface environments provide an alternative to the offshore bar settings suggested for other long linear sand bodies

lunar floor fractured craters evidence for viscous relaxation of crater topography in this paper we evaluate quantitatively the hypothesis that topographic modification of floor fractured craters on the moon was accomplished predominantly by viscous relaxation adopting the simple assumption that the moon may be modeled as having a uniform newtonian viscosity we compare the observed topographic profiles for a number of floor fractured craters with the profiles predicted from the viscous relaxation of topography of fresh craters of similar diameter despite the simplicity of the rheological model the comparison is quite good the floor uplift the rim subsidence and the apparent subsidence outside the rim for the several floor fractured craters considered are well matched by the viscous relaxation hypothesis floor fractures while indicating that a purely viscous model is not strictly valid can be explained by the effects of isostatic adjustment on a thin brittle lithosphere the association of many floor fractured craters with impact basins and with the time of mare volcanism can be understood in terms of a pronounced acceleration of crater relaxation in local regions of anomalously high near surface temperatures and therefore of low effective viscosity and thin lithosphere the quantitative extent of relaxation of floor fractured craters can be interpreted in terms of a limited time interval of substantial relaxation for each crater that time interval ended for each crater after local cooling had been sufficient for the viscosity to rise for the lithosphere to thicken and for the present topographic relief to be frozen in thus viscous relaxation is a viable hypothesis to explain the topographic profiles of a number of lunar floor fractured craters and the extent of viscous relaxation of crater topography may serve as a tool to map lateral and temporal variations in the shallow thermal structure of the moon and of other planets and satellites

recognition of facies bounding surfaces and stratigraphic patterns in foreland ramp successions an example from the upper devonian appalachian basin u s a abstract a detailed stratigraphic study of the upper devonian lock haven formation in the appalachian basin provides new interpretations applicable to understanding sedimentation and stratigraphic architecture in the foreland ramp setting the common occurrence of graded beds hummocky cross stratification and shell lags indicates that storm processes played an important role in deposition gradational based coarsening upward shoreface sequences of interbedded sandstone and mudstone formed during gradual fall in relative sea level in contrast sharp based regressive sequences consist of laminated sandstone facies overlying a submarine erosion surface that developed in response to more rapid fall in relative sea level transgressive sequences become finer grained upward from conglomerate lag which was deposited on a basal transgressive surface to heterolithic facies and mudstone facies a combination of eustasy and tectonic subsidence of the foreland ramp produced changes of relative sea level these fluctuations provided a means for transporting sand onto the ramp and for producing repetition of stratigraphic patterns in the lock haven formation the upper devonian clastic succession which includes both the lock haven formation and the catskill formation represents northwestward progradation of shoreline to nonmarine environments as sediment supply to the foreland ramp exceeded the rate of formation of accommodation compared to passive margin shelves thick fine grained successions such as the lock haven formation are more likely to form in foreland basins where tectonic subsidence provides a mechanism for creating accommodation sediment influx from uplifted areas and absence of a slope break on the foreland ramp results in a higher rate of fine grained clastic sedimentation than occurs on shelves of passive margins

lunar mare volcanism stratigraphy eruption conditions and the evolution of secondary crusts abstract lunar mare basalt deposits cover 17 of the lunar surface occur preferentially in topographic lows on the nearside and have a total volume estimated at 1 107 km3 analysis of returned samples and photogeologic and remote sensing studies shows that mare volcanism began prior to the end of heavy bombardment the period of cryptomare formation in pre nectarian times and continued until the copernican period a total duration approaching 3 5 4 ga stratigraphic analyses show that the flux was not constant but peaked in early lunar history during the imbrian period which spans the period 3 85 3 2 ga average volcanic output rate during this peak period was about 10 2 km 3 a very low relative to the present global terrestrial volcanic output rate and comparable to the present local output rates for individual volcanoes such as vesuvius and kilauea hawaii volcanic landforms indicate that many eruptions were of high volume and long duration some eruptions associated with sinuous rules may have lasted of the order of a year and emplaced 103 km3 of lava representing the equivalent in one year of about 70 000 years at the average flux shallow magma chambers were uncommon the nearsidefarside mare deposit asymmetry can be readily explained by differences in crustal thickness magma ascending from the mantle or from a buoyancy trap at the base of the crust should preferentially extrude to the surface on the nearside but should generally stall and cool in dikes in the farside crust extruding only in the deepest basins the occurrence of farside maria within craters whose diameter is generally near to or less than the thickness of the crust may be accounted for by the difference between local and regional compensation dikes that establish pathways to the surface on the nearside should have very high volumes comparable to the volumes associated with many observed flows and sinuous rilles an abundance of dikes should exist in the lower crust of the moon many more than those feeding surface eruptions the upper limit is 37 50 of the crust by volume the presence and abundance of such dike swarms have important implications for the interpretation of the average composition of the lunar crust and the composition of basin and crater ejecta the interplay between thermal contraction and differentiation leads to net cooling and ultimate contraction of the outer portions of the moon resulting in a regional horizontal compressive stress acting on the lunar crust in addition overall cooling and deepening of sources require the production of ever larger volumes of magma in order to reach the surface with time stresses became high enough so that few dikes could open to the surface causing eruptive activity to be severely diminished in the eratosthenian and perhaps to cease in the copernican period lower stress levels are required to terminate eruptive activity on the lunar farside consistent with the imbrian age of the farside maria and the nearside location of the youngest maria lunar mare deposits provide an example of the transition from primary crusts to secondary crusts and illustrate the significance of several factors in the evolution of secondary crusts such as crustal density variations in crustal thickness presence of impact basins state and magnitude of stress in the lithosphere and general thermal evolution these factors are also responsible for the extremely low volcanic flux even during periods of peak extrusion

beginning and end of lunar mare volcanism mare volcanism on the moon is commonly attributed to an important but relatively short lived epoch of internal heating after 3 900 myr bp but before about 2 500 myr bp refs 1 2 although some studies suggested that mare volcanism had started earlier3 5 than times indicated by dated lunar samples only recently have photogeological spectral and geochemical data6 8 documented the importance of a pre 4 000 myr bp epoch similarly early earth based geological mapping revealed a bright rayed crater lichtenberg superposed by mare units9 thereby indicating that mare volcanism must have extended to times significantly more recent than 3 100 myr bp lunar orbital photography confirmed this inferred strati graphical relationship10 but crater statistics indicated that the youngest units were at least twice the age of copernicus or between 1 700 and 2 000 myr bp refs 11 13 we present here the inferred distribution and style of the early phases of mare volcanism based on current evidence and conclude that certain regions of the moon underwent two distinct pulses of igneous activity we then examine crater statistics for the post lichtenberg mare unit and other selected units and conclude that mare volcanism extended to a time comparable with that of the copernicus impact or 1 myr bp these reassessments of the oldest and youngest maria provide new constraints on geophysical models of the internal thermal history of the moon

fault type predictions from stress distributions on planetary surfaces importance of fault initiation depth faults on planetary surfaces initiate at depth where stresses due to the weight of overburden are important consequently the prediction of fault type from calculated stresses at depth can yield different faults than those predicted using the surface criteria commonly employed in geophysical models for elastic plate flexure models of mascon loading on the moon stresses calculated at the surface predict that the most likely faulting is strike slip for which there is no direct evidence at a distance from the basin center where grabens are found modifying these plate flexure calculations to account for the weak surface layer of ejecta megaregolith 1 3 km thick that overlies the relatively strong lunar lithosphere results in model stresses in the outer layers of the moon tens of bars that are an order of magnitude lower than in the lithosphere hundreds of bars because faults bounding lunar grabens initiate at the mechanical discontinuity between the megaregolith and lithosphere and because the reverse faults likely responsible for wrinkle ridges probably initiate at the basalt basin floor contact 0 5 2 km deep model stresses must be calculated at these depths superposing nonisotropic stresses due to the weight of the overburden at the depths of these mechanical discontinuities with plate flexure model stresses correctly predicts maximum stress differences in an interior zone of expected wrinkle ridges surrounded by a zone of concentric normal faults or grabens and effectively eliminates the strike slip zone in agreement with observations the absence of strike slip faults from almost all planetary and satellite surfaces may be explainable if lithospheric deformation model stresses are calculated at important shallow crustal mechanical discontinuities where the maximum compressive stress is vertical thereby favoring the formation of normal faults if true mechanical discontinuities in the shallow crusts of planets and satellites play an extremely important and hitherto unrecognized role in the formation of structures observed on their surfaces

estimation of source to sink mass balance by a fulcrum approach using channel paleohydrologic parameters of the cretaceous dunvegan formation canada abstract trunk rivers transport the bulk of the sediment in a source to sink s2s system and total mass passing through any cross section i e fulcrum of a trunk river over geologic time should allow matching of source area sediment delivery budgets to downstream sediment volumes deposited in the basin we analyze the paleohydrology of ancient trunk channels and link downstream deltaic strata of allomember e of the cretaceous dunvegan alloformation in the western canadian sedimentary basin to test the total mass balance fulcrum approach bankfull channel depth and width grain size paleoslope velocity and discharge are derived from outcrop core and well logs some parameter estimates use multiple methods providing a range of values and serve as a cross check of independent methods estimates of annual flood frequency and paleodischarge associated with long term geologic time estimates are derived from chronostratigraphic analysis and allow calculation of cumulative sediment discharge isopach maps are used to measure sink area sediment volumes the results indicate that the trunk river of allomember e was 10 15 m deep and 150 250 m wide carried fine to medium grained 200 microns sand and flowed over a low gradient paleoslope of 4 1 6 1 10 5 annual total sediment discharge is estimated to have ranged from 5 4 to 12 106 m3 within 25 000 years the river is estimated to have transported 135 307 km3 of sediment into the basin this is consistent with the 130 km3 of sediment mapped in the study area however the upper range estimate of sediment delivered into the sink is 2 5 times the measured sediment volume in the map area which if accurate suggests significant sediment escape this supports the hypothesis that in dunvegan time mud was widely dispersed southward along the alberta foreland basin by geostrophic currents associated with storm processes and counterclockwise oceanic gyres in the cretaceous seaway

volcanism and the dynamics of open magma chambers the repeated eruption of many volcanoes is now accounted for by events taking place in a subterranean magma chamber which is open in the sense that the inflow of material to the chamber from below leads to a magma pressure p which exceeds the lithostatic pressure pl by an amount greater than the tensile strength of the chamber walls before the contents of the magma chamber have reached thermodynamic and geochemical equilibrium this is the condition which must be satisfied when an eruption occurs we have now derived a relationship giving the critical volume of added material v required to cause an eruption as a function of magma compressibility and the volume by which the chamber expands

isolated highstand shelf sandstone body of turbiditic origin lower kenilworth member cretaceous western interior book cliffs utah usa abstract an isolated highstand shelf sandstone body of turbiditic origin has been identified in the lower kenilworth member hatch mesa area book cliffs utah relative to most other marine mudstone encased isolated sandstone bodies the hatch mesa succession has an abundance of bouma like turbidite beds a greater proportion of mudstone and siltstone is thinner 6 20 m and is weakly coarsening upward these attributes in combination with locally abundant hummocky cross stratified sandstones a paucity of wave ripples in the background fair weather deposits carbonaceous matter in all facies a lack of clinoforms and a low diversity abundance trace fossil suite suggest deposition in a prodelta environment between fair weather and storm wave base a three component shoreface to shelf model consisting of delta front subaqueous channel and prodelta turbidite deposits is proposed to explain the depositional environment and setting of the hatch mesa succession regional correlation has demonstrated that the hatch mesa succession is time equivalent with the second parasequence in the kenilworth kps2 which is characterized by inner shelf turbidite bodies at a number of other localities paleogeographic reconstructions reveal that the hatch mesa succession was deposited at least 16 km basinward of the kps2 lower shoreface in approximately 20 m of water the kps2 hatch mesa sandstone body package is part of the early highstand systems tract indicating that isolated or stray sandstone bodies are not solely restricted to the falling stage or lowstand systems tracts

paralic parasequences associated with eocene sea level oscillations in an active margin setting trihueco formation of the arauco basin chile abstract the eocene trihueco formation is one of the best exposed successions of the arauco basin in chile it represents a period of marine regression and transgression of second order duration during which barrier island complexes developed on a muddy shelf the strata are arranged in classical shoaling upward parasequences of shoreface and beach facies capped by coal bearing back barrier lagoon deposits these fourth order cycles are superimposed upon third order cycles which caused landward and seaward shifts of the coastal facies belts the final punctuated rise in sea level is represented by shelf mudrocks with transgressive incised shoreface sandstones relative sea level oscillations as revealed in the stratigraphy of the trihueco formation show a reasonable correlation with published eocene eustatic curves

the lunar crust global structure and signature of major basins new lunar gravity and topography data from the clementine mission provide a global bouguer anomaly map corrected for the gravitational attraction of mare fill in mascon basins most of the gravity signal remaining after corrections for the attraction of topography and mare fill can be attributed to variations in depth to the lunar moho and therefore crustal thickness the large range of global crustal thickness 20 120 km is indicative of major spatial variations in melting of the lunar exterior and or significant impact related redistribution the 61 km average crustal thickness constrained by a depth to moho measured during the apollo 12 and 14 missions is preferentially distributed toward the farside accounting for much of the offset in center of figure from the center of mass while the average farside thickness is 12 km greater than the nearside the distribution is nonuniform with dramatic thinning beneath the farside south pole aitken basin with the global crustal thickness map as a constraint regional inversions of gravity and topography resolve the crustal structure of major mascon basins to half wavelengths of 150 km in order to yield crustal thickness maps with the maximum horizontal resolution permitted by the data the downward continuation of the bouguer gravity is stabilized by a three dimensional minimum slope and curvature algorithm both mare and non mare basins are characterized by a central upwarped moho that is surrounded by rings of thickened crust lying mainly within the basin rims the inferred relief at this density interface suggests a deep structural component to the surficial features of multiring lunar impact basins for large 300 km diameter basins moho relief appears uncorrelated with diameter but is negatively correlated with basin age in several cases it appears that the multiring structures were out of isostatic equilibrium prior to mare emplacement suggesting that the lithosphere was strong enough to maintain their state of stress to the present

one year along beach variation in the maximum depth of erosion resulting from irregular shoreline morphology abstract beach erosion and accretion occur across multiple time scales over long time scales decades to millennia the shoreface ravinement surface which is recognized as a coarse lag deposit forms at the shoreface toe as a result of wave and current induced erosion during shoreline transgression over short time scales hours to days the depth of sediment disturbance which is recognized as coarse lamina and measured at the foreshore by devices and monitoring tracer beds forms as a result of wave and current induced reworking during a tidal cycle the maximum depth of erosion mdoe quantified here over 1 year is modulated by processes that operate over a time scale that is between the drivers of short term e g tides and waves and long term e g sea level rise beach erosion the mdoe integrates the erosion that occurs over a discrete time interval and records the maximum depth of erosion that is likely principally induced by storms which is difficult to quantify by other methods that rely on discrete observations e g changes in elevation or movement of the mean high water line a novel technique for quantifying the mdoe based on comparing the bedding and stratigraphy between cores collected at the same locations over a discrete time interval is presented here and applied at onslow beach nc usa this 12 km long barrier island has irregular shoreline morphology characterized by two embayments separated by a central headland this shape is largely the result of variations in the depth of underlying rock strata and produces a steeper beachface at the headland than at the embayments at each of the six sites examined along the barrier the mdoe is found to increase from the backshore to the middle intertidal zone and is higher at the sites closer to the headland these variations in the mdoe are likely due to the increase in average wave energy impacting the beachface from an offshore direction and steeper beaches intermediate beach state at the headland where the mdoe is within the beach facies it is not associated with a coarsening which is due to the heterolithic nature of the onslow beach strata where the mdoe is the contact between back barrier and beach facies it is always associated with a coarsening and a gravel rich lag deposit because in this case the mdoe is an amalgamation of multiple erosional events which is similar to the shoreface ravinement surface along beach variation in the mdoe does not correspond with discrete observations of beach change over the same period and is likely a better indicator of erosion potential than long term discrete observations such as changes in surface elevation or the position of the mean high water line

regressive depositional architecture on a mesoproterozoic siliciclastic ramp sequence stratigraphic and nd isotopic evidences from bhalukona formation singhora group chhattisgarh supergroup central india abstract a paleo environmental and sequence stratigraphic study of the mesoproterozoic bhalukona formation singhora group central india provides new interpretations applicable to understanding sedimentation and stratigraphic architecture in the proterozoic siliciclastic ramp settings under falling and lowstand sea level conditions beside delineation of two diachronous surfaces process based facies analysis identified fourteen facies types that are grouped under five different facies associations paleo environments range among continental fluvial beach foreshore upper shoreface lower shoreface and wave dominated delta front from the paleocurrent measurement within the fluvial channel sandstones and measurement of crest line orientations of wave generated swash bedforms it is inferred that the bhalukona sea had nne ssw shoreline trajectory and the south easterly flowing river system carried sediment on the shoreline from a source in the west northwest such inference though in clear discordance with the earlier proposed south southeastern sediment source for the singhora basin finds support in the shift in e nd t t 1 42 ga values from 3 5 3 3 to 9 3 2 2 indicating change in sediment provenance at the early bhalukona sedimentation history sediments in the bhalukona formation derived from more evolved or older continental crustal sources in comparison to those of the underlying saraipalli formation a tectonic forcing behind the shift in sediment provenance and fall in relative sea level is inferred that established the forced regressive and lowstand shoreline in the singhora basin during the bhalukona time abrupt basin ward shift of facies tract and incision on shelf is exhibited by the occurrence of poorly sorted coarse granular bhalukona fluvial system carrying rip up mud clasts directly above the argillaceous highstand saraipalli shelf with 10 m incision and is inferred as the signal for forced regression and development of type i sequence boundary in low gradient proterozoic ramp settings without shelf slope break we interpret that the bhalukona fluvial system incised the coastal prism developed on the saraipalli highstand coastline the low gradient of the ramp however prompted long distance 15 km regression represented by the offlapped and detached delta front lobe away from the shoreline the slow steady rise in sea level onset of lowstand and establishment of a wave dominated coastline caused reworking of fluvial sediments in the basinal part within the wave base and resulted development of ravinement deposit basin ward the surface grades into correlative conformity with aggradational and weak retrogradational stacking the beach foreshore upper and lower shoreface in order of superposition record the lowstand depositional history the basin scale transgression is witnessed with formation of transgressive surface of erosion tse and establishment of the chuipalli shelf system dominantly beyond storm wave base taking into consideration 23 m preserved shoreface succession 1 m per year eustatic rise consistent with present day rate and average rate of shoreface retreat 0 5 m per year 11 5 km retreat for the bhalukona shoreline is estimated in its lowstand history

characteristics of lunar mare deposits in smythii and marginis basins implications for magma transport mechanisms an analysis of 34 lunar lava flows and ponds in the eastern limb smythii and marginis basins was undertaken to examine and model the first stages of secondary crustal formation and assess processes involved in magma transport and eruption in order to isolate the characteristics of single eruptive episodes we focused on discrete mare ponds adjacent to the major mafia mean values for areas and volumes of deposits estimated to be good candidates for single eruptive phases are large approximately 950 1000 km 2 and 200 km 3 respectively these eruptive volumes are commensurate with the largest known terrestrial eruptions flood basalts the lack of geomorphological structures indicative of shallow magma reservoirs indicates that deep probably subcrustal source regions are prevalent with respect to crustal thickness relationships the magnitude and frequency of eruptive events are observed to be greatest in areas of thinnest crust specifically regions of major maria mare smythii mare marginis occur in areas of thinnest crust while isolated ponds occur where the crust is relatively thicker this is consistent with the correlation observed globally between crustal thickness and the magnitude and frequency of eruptive events ages of volcanic flows and pyroclastic events range from early imbrian to imbfian eratosthenian but are concentrated most heavily between 3 80 3 60 ga suggesting a period of peak volcanism beginning around 3 85 ga and lasting approximately 200 ma however the existence of dark halo crater clusters in non mare units within the region suggests the presence of cryptomaha which would indicate an earlier onset of volcanism and a volume of mare matehal potentially greater than that currently exposed on the surface typical nearest neighbor distances suggest deposits derive from reservoirs 100 km in diameter the observations made here are consistent with a magma transport model in which plumes rising diapirically stall at a density boundary under the lunar crust and propagate dikes to the surface through overpressufization

lunar impact basins new data for the western limb and far side orientale and south pole aitken basins from the first galileo flyby compositional aspects of impact basin materials can be analyzed using multispectral image data acquired by the galileo solid state imaging ssi experiment during the december 1990 lunar encounter these data provide important information on the spectral properties of the western lunar limb and parts of the far side the ssi images cover the wavelength range 0 4 1 0 m allowing measurement of spectral slope and estimation of the strength of the 1 m absorption due to iron in the mafic minerals olivine and pyroxene among deposits of the 930 km diameter orientale basin exterior ejecta comprising the hevelius formation is relatively homogeneous and spectrally similar to mature apollo 16 soils suggesting an upper crustal source the centrally located maunder formation is distinct from the younger mare basalts but comparable to the hevelius formation in its spectral reflectance properties supporting an interpretation as basin impact melt the montes rook formation located in an annulus between the maunder and the hevelius shows a slightly stronger mafic absorption and may be the deepest crustal material excavated the distal orientale deposits show local mafic enhancements in the schiller schickard and mendel rydberg regions interpreted to represent pre orientale mare deposits or cryptomaria intermixed with overlying basin ejecta in this case maria of sizes comparable to those presently observed were widespread in this region before the orientale impact mixing model analyses are consistent with the ballistic erosion and sedimentation model for ejecta emplacement in the distal regions beyond the continuous ejecta deposit on the southern lunar farside a huge area with an enhanced mafic absorption corresponds to the interior and rim of the pre nectarian south pole aitken impact basin 2000 2500 km in diameter the anomaly is interpreted to be due to several factors including excavation into the more mafic lower crust and the presence of extensive early volcanic fill cryptomare similar to that seen in ancient basins such as smythii and australe these results show that although basin forming events are an important factor in producing lateral heterogeneities in crustal composition and in modifying preexisting deposits such as cryptomaria the majority of material in even the largest basins was excavated from crustal levels our results suggest a gradational vertical crustal stratigraphy consisting of an uppermost mixed crustal layer of anorthosite basin ejecta and cryptomaria deposits generally corresponding to the megaregolith an upper crustal layer of anorthosite and a lower more noritic layer many of the basic questions remaining from this study could be addressed by global high resolution geochemical and mineralogical data obtained by polar orbiting spacecraft

growth of planetary crusts the planets and satellites of the solar system show much diversity but most have formed crusts which differ substantially from their bulk compositions three principal types of crust may be broadly distinguished primary formed after accretional heating e g lunar highlands secondary formed following partial melting in planetary mantles e g lunar maria terrestrial oceanic crust and tertiary formed by processing of secondary crusts of which the continental crust of the earth is the only identifiable example crustal growth before 3800 m y was complicated by the heavy planetesimal bombardment active erosion on the earth is likely to have destroyed the brecciated rubble resulting from over 200 mare orientale scale events in this period the mercurian crust is probably primary perhaps analogous to the lunar highlands in contrast the observable martian and venusian crusts are secondary dominated by basaltic volcanism the icy crusts of the satellites of the outer planets are mixtures of both primary and secondary crusts with complex histories ganymede is of special interest in displaying a secondary grooved terrain water ice crust which has split an older more heavily cratered possibly primary crust slight expansion has resulted probably from polymorphic transitions from high density ice viii to low density ice i the primary lunar crust 12 of lunar volume grew in 108 years secondary crusts derived by partial melting of mantles grow at a much slower rate total production of terrestrial oceanic crust over 4000 m y is only 2 of planetary volume whereas terrestrial continental crustal growth is even slower producing over the same period a volume only about 0 33 that of the earth crustal growth on the other planets appears to be an irreversible process without evidence of recycling no evidence for massive planetary expansion as required by expanding earth hypotheses is apparent on the other planets or satellites of the solar system

surface deformation in volcanic rift zones abstract the principal conduits for magma transport within rift zones of basaltic volcanoes are steeply dipping dikes some of which feed fissure eruptions elastic displacements accompanying a single dike emplacement elevate the flanks of the rift relative to a central depression concomitant normal faulting may transform the depression into a graben thus accentuating the topographic features of the rift if eruption occurs the characteristic ridge trough ridge displacement profile changes to a single ridge centered at the fissure and the erupted lava alters the local topography a well developed rift zone owes its structure and topography to the integrated effects of many magmatic rifting events to investigate this process we compute the elastic displacements and stresses in a homogeneous two dimensional half space driven by a pressurized crack that may breach the surface a derivative graphical method permits one to estimate the three geometric parameters of the dike height inclination and depth to center and the mechanical parameter driving pressure rock stiffness from a smoothly varying displacement profile direct comparison of measured and theoretical profiles may be used to estimate these parameters even if inelastic deformation notably normal faulting creates discontinuities in the profile geological structures open cracks normal faults buckles and thrust faults form because of stresses induced by dike emplacement and fissure eruption theoretical stress states associated with dilation of a pressurized crack are used to interpret the distribution and orientation of these structures and their role in rift formation

rapidly changing styles of subsidence revealed by high resolution mudstone allostratigraphy coniacian of sweetgrass arch area southern alberta and northern montana marine mudstone of the coniacian muskiki member was deposited by storms on a shallow marine ramp across southern alberta and northern montana the rocks range from the c crassus crassus zone of the upper lower coniacian to the s depressus zone of the upper coniacian however upper coniacian strata are only a few metres thick at kevin montana and appear to be thin to absent beneath parts of the adjacent alberta plains probably because of minimal contemporaneous subsidence the muskiki member is partitioned into three packages by subtle bevelling unconformities cut during regional tectonic tilting the lower package indicates flexural subsidence in the nw whereas the middle package indicates subsidence in the sw the rotation of the axis of subsidence may indicate an along strike shift of the region of active thickening in the orogenic wedge the upper package is dominated by a nw trending region of stratal thickening forming a trough shaped rock body 100 km wide 250 km long and up to 50 m thick

galileo imaging observations of lunar maria and related deposits the galileo spacecraft imaged parts of the western limb and far side of the moon in december 1990 ratios of 0 41 0 56 gin filter images from the solid state hnaging ssi experiment provided information on the titanium content of mare deposits ratios of the 0 76 0 99 gm images indicated 1 gin absorptions associated with fe 2 in mafic minerals mare ages were derived froin crater statistics obtained from lunar orbiter images results on mare coinpositions in western oceanus procellarum and the humorurn basin are consistent with previous earth based observations thus providing confidence in the use of galileo data to extract compositional information mare units in the grimaldi and riccioli basins range in age froin 3 25 to 3 48 ga and consist of medium to medium high titanium 4 to 7 tio2 content lavas the schiller zucchius basin shows a higher 0 76 0 99 gm ratio than the surrounding highlands indicating a potentially higher mafic mineral content consistent with previous interpretations that the area includes mare deposits blanketed by highland ejecta and light plains materials the oldest mare materials in the orientale basin occur in south central mare orientale and are 3 7 ga old youngest mare materials are in lacus autumni and are 2 85 ga old these units are medium to medium high titanium 4 to 7 tio2 basalts thus volcanism was active in orientale for 0 85 ca but lavas were relatively constant in composition galileo data suggest that mendel rydberg mare is similar to mare orientale cryptomare are present as well thus the mare lavas on the western limb and far side to 178oe are remarkably uniform in coinposition being generally of medium to medium high titanium content and having relatively low 0 76 0 99 gin ratios this region of the moon is between two postulated large impact structures the procellarum and the south pole aitken basins and may have a relatively thick crust in areas underlain by an inferred thinner crust i e zones within large basins as at apollo titanium content is often higher however no mare deposits with titanium abundances approaching those of the high titanium 9 to 14 tio2 apollo 11 and 17 basalts nor of the high titanium regions of central oceanus procellarum are seen on the western limb or eastern far side light plains deposits are generally indistinct froin the surrounding highlands in the ssi data and are inferred to be derived primarily from the same material that forins the highlands some of the light plains are too young to be related to basin forming impacts suggesting possible volcanic origin dark mantle deposit compositions derived from ssi data are consistent with earth based observations of similar near side deposits and are interpreted to be pyroclastic materials however the modernitc albedo and 1 gin absorption of the dark mantle deposit on the southwest margin of the orientale basin suggest it is a local pyroclastic deposit contaminated with underlying highland materials from the orientale impact

morphology and origin of erosion surfaces in the cardium formation upper cretaceous western interior seaway alberta and their implications for rapid sea level fluctuations the morphology of three basin wide erosion surfaces has been defined using 7869 resistivity well logs over an area of about 50 000 km2 the lowest of these designated e6 is topographically smooth and has no incised steps or low areas it cuts into marine mudstones and indicates either an uninterrupted erosive transgression following a major lowering of relative sea level or wave scouring of the substrate following a very minor lowering of sea level erosion surface e6 5 also cuts into marine mudstones but its overall morphology is less well understood owing to subsequent dissection by surface e7 this surface e7 is characterized by three strike parallel linear low areas that die out northwestward these linear lows are up to 40 km wide 36 m deep and have irregular to symmetrical cross sectional profiles they cut into and are filled with marine mudstones and their origin is enigmatic the differences in the morphologies of the surfaces suggest the interplay of several controlling parameters

tectono sedimentary control on modern sand deposition on the forebulge of the western taiwan foreland basin abstract whether the formation of the isolated sand body deposition in the forebulge area of a foreland basin system is structure or deposition controlled has puzzled geologists for decades although sand body deposition is generally believed to be indicative of the position of the flexural forebulge in a foreland basin the formation of a modern sand body in the forebulge area is thus examined by multi scale geophysical observations based on combined reflection seismic profiles and compressed high intensity radar pulse chirp profiles across the sand deposition along the forebulge of the western taiwan foreland basin wtfb which is a late miocene present foreland basin in the overfilled stage these profiles suggest that the accumulation of the sand deposits along the forebulge of the wtfb is not directly associated with forebulge faultings the relief map of the forebulge deposit substratum shows a northwestward tilting slope and the isopach of the forebulge sand body indicates that a large part of the sand body accumulated along the axis of the taiwan strait and the subdued forebulge of the wtfb the difference between the prevailing directions of tidal currents between the taiwan strait and the east china sea reflects the probable sedimentary influence of the cratonward migrating fold thrust belt within a foreland shelf we suggest that the formation and distribution of the sand deposits along the forebulge of the wtfb are generally controlled not only by the transverse downslope sedimentation but also longitudinal hydrodynamic processes at distal parts of the foreland basin our explanation provides a plausible tectono sedimentary cause of the sand body deposition in the forebulge area in an overfilled foreland basin the sedimentary dynamics of the sand body in the taiwan strait may be applicable for understanding the formation of isolated sand bodies in the distal part of the cretaceous western interior foreland basin