paleoclimatic implications of middle wisconsinan pollen and a paleosol from the purcell trench south central british columbia a paleosol and organic rich horizons occur in bessette sediments near meadow creek south central british columbia the paleosol is at least 42 000 years old and formed on a paleoslope adjacent to some precursor to meadow creek on higher parts of the paleoslope the soil developed under locally dry conditions and influxes of eolian material a regosol formed near the base of the paleoslope marginal to a floodplain pollen assemblages from the organic rich horizons are grouped into two assemblage zones mc 1 approximately 42 000 years old is dominated by arboreal pollen mainly picea mc 2 approximately 34 000 years old is dominated by picea in conjunction with significant amounts of tsuga heterophylla paleoclimatic implications of the assemblages are that temperatures 42 000 years ago were approximately 3 c cooler than present but by 34 000 years ago had ameliorated and were similar to or slightly cooler than present

a new data reduction approach for the clementine nir data set application to aristillus aristarchus and kepler the clementine spacecraft launched in january 1994 has performed a nearly global surface mapping of the moon in eleven broad spectral bands at a resolution of 200 m the uv visible uv vis camera performed observations in five bands ranging from 0 415 to 1 0 m while the near infrared camera nir acquired data in six spectral bands ranging from 1 1 to 2 78 m uv vis images are calibrated to 4 the calibrated nir data set is yet to be finalized due to instrumental problems independently of the calibration effort for the full data set which is under the responsibility of the pi team we present here the first results of a heuristic approach to extract mineralogical information from raw images in regions of particular interest we processed images of craters aristillus aristarchus and kepler we computed band ratios using 0 75 0 9 0 95 1 0 1 1 1 25 1 5 and 2 0 m images to map the compositional heterogeneity and to discriminate between pyroxene olivine or feldspar rich areas absolute reflectance spectra have been derived using telescopic spectra as ground truth high orthopyroxene and clinopyroxene contents have been detected and spatially mapped on aristillus our results are in good agreement with previous studies in the case of aristarchus and show additional details due to the improved registration two regions exhibit spectra consistent with a high proportion of olivine with 25 pyroxene the rim of kepler exhibits a strong feature at 2 m correlated with the 1 m feature suggesting either a high orthopyroxene content or a very immature soil our method could be of interest for further investigations of the lunar surface using clementine nir data

the nature of crater rays the copernicus example crater rays are formed during a cratering event as target material is ballistically ejected to distances of many crater radii forming narrow generally high albedo approximately linear features extending outward from the crater the nature of crater rays was examined for the lunar crater copernicus using new information on the composition of surface material from near ir reflectance measurements surface roughness from radar backscatter measurements and photogeologic data from available images part of the data analysis included use of mixing models to quantify the mixing systematics observed between primary ejecta and local substrate of the ray on the basis of compositional parameters from reflectance spectra primary material from copernicus can be detected in the surface material of rays in decreasing amounts with increasing radial distance e g 20 25 primary ejecta at six crater radii for distances greater than three crater radii the proportion of local material to primary ejecta observed from these compositional reflectance data is approximately equal to that predicted by previous laboratory and ballistic studies of craters within three crater radii the compositional data indicate a higher proportion of primary ejecta than predicted for extended areas along the ray that do not contain large secondary craters the primary ejecta is intimately mixed on the granular scale with local material throughout the regolith the relatively high albedo of the rays of copernicus is due to the feldspathic composition highland of the primary ejecta in rays emplaced on a mare substrate immature local substrate is only observed in copernicus s ray at large unmantied secondary craters or other areas with sufficient topographic slope to prevent the accumulation of mature soils crater rays are filamentous generally high albedo features that emanate nearly radially from young impact structures rays are narrow in relation to the crater radius extend distally for many crater radii and constitute a distinctive albedo feature around some of the largest and freshest lunar craters visible from earth synoptic views of ray systems figure la give the strong impression that the rays comprise bright material that has been excavated from the crater cavity and been emplaced beyond the continuous ejecta deposit if this visual impression is correct then the process that forms crater rays represents a significant mechanism for the lateral transport of primary material to great distances from its point of origin and particularly for craters larger than a let tens of kilometers in diameter constitutes a fundamental process for the regional mixing of crustal materials earth based telescopic images of the moon allowed the first studies and descriptions of rays and ray systems shoemaker 1962 described the arcuate and loop shaped streaks of the copernicus ray systems and showed that these patterns could be locally resolved into individual en echelon feather shaped elements 15 20 km in length with their long axes oriented approximately radially to the crater he noted the presence of elongate depressions or gouges in the ray system ranking in diameter from 8 km down to the limits of resolution and generally located at the proximal ends of the individual ray elements shoemaker observed that some of the gouges were

the manicouagan impact structure an analysis of its original dimensions and form manicouagan quebec 51 23 n 68 42 w is the most intensively studied large complex terrestrial impact structure in a predominantly crystalline target the ground truth data available from manicouagan have considerable potential for interpreting the subsurface characteristics of lunar impact structures of comparable morphology and size two contrasting hypotheses however exist for the preerosional form of manicouagan 1 a multi ring basin with a final diameter of 75 km and a transient cavity diameter of 30 45 km floran and dence 1976 and 2 an endogenically modified peak ring basin with a final diameter of 100 km and a transient cavity diameter of 80 km orphal and schultz 1978 both hypotheses are based largely on topographic data and interpret the prominent 65 km diameter annular moat as a graben like feature formed either 1 by collapse of the outer slope of the transient cavity rim or 2 by uplift of the final crater floor through post impact intrusive activity the present analysis suggests that this annular moat is primarily an erosional feature and that the original form of the impact structure cannot be determined unequivocally on the basis of present topography if all the available topographic geologic and geophysical data are considered however then an internally consistent interpretation of original dimensions is possible the distribution of shock deformation effects in the basement rocks of the present crater floor suggests an original transient cavity diameter of 60 km the 55 km diameter impact melt covered inner plateau provides a minimum estimate for the diameter of the final floor of the crater and the annular moat with its outliers of downdropped ordovician limestone is interpreted as marking the contact between the floor and the innermost slump blocks of the final rim there is no compelling evidence to regard the annular moat as a graben by analogy with fresh lunar and mercurian structures a floor width of 55 km suggests a final rim diameter of 86 95 km this is consistent with the topographic data from outside the annular moat and with the residual peripheral gravity low which suggests a final rim diameter of 85 95 km due to erosion it is difficult to assign manicouagan to a particular morphological class of impact structure but on the basis of the available data it is most likely that the preerosional form was that of a central peak crater or possibly a peak ring basin at the time of its formation manicouagan may have been dimensionally and possibly morphologically similar to the 96 km diameter lunar crater copernicus

shallow erosion beneath turbidity currents and its impact on the architectural development of turbidite sheet systems erosion by turbidity currents changes the morphology of the sea floor the relief of the scoured surface may affect the dynamics of the flow and thereby the pattern of deposition this could in turn affect flow and deposition patterns in subsequent events this study investigates shallow centimetre to decimetre scale erosion beneath turbidite sheet sandstones of the oligocene macigno formation of north west italy where erosion and deposition are variably coupled at the bed scale in a net aggradational setting the research focus was on i the recognition of scour edges and erosive surfaces ii quantification of spatial differences in the amount of erosion and iii an investigation of how this differential erosion can be compensated by the deposits directly overlying the erosional surfaces where they can be observed scour edges commonly have sills of the overlying sandstone intruding beneath blocks and wings of the substrate that is being eroded a consequence of this de laminating scouring style is that erosional surfaces are bedding parallel when followed away from the scour edges giving the appearance of normal conformable bed bases despite their cryptic nature such bedding parallel scour surfaces can be recognized by comparing serial detailed sedimentary logs here 16 bed parallel scour surfaces were identified in a succession comprising 95 beds different styles of compensation by the overlying turbidite beds are defined based on differential sedimentation inside and outside of the scour relief it is found that differential erosion is on average under compensated by differential sedimentation in some cases the overlying deposits anti compensate being thinner at the location where more erosion has occurred unequal spatial distribution of differential erosion in the study area combines with sedimentary under compensation to result in a trend of accumulating section thickness differences over multiple beds in one ca 25 m thick package the maximum cumulative change in lateral gradient during some 20 events reached 0 17 before being reset by a single event this process can be interpreted either as a lobe compensation effect or as a scour enhancement effect depending on the orientation of the palaeohorizontal datum if allowed to proceed the latter process could force the system past a channellization threshold prompting a change from sheet to channelled architecture this type of shallow substrate scouring and differential deposition is likely to be an important process in the build up of sheet turbidite sandstone units and could play a major role in autocyclic adjustment of local sea floor gradients

from the imbrium basin to crater tycho the first regional spectral distribution map derived from sir 2 near infrared data abstract near infrared nir data obtained at the moon by the sir 2 instrument aboard chandrayan 1 have been analyzed and classified according to their spectral absorption characteristics this approach yielded a new nir map based on 10 spectral categories that we have identified which cover a substantial portion of the lunar nearside the inferred distribution of materials that share similar reflectance patterns resembles existing geologic maps where were drawn using a range of complementary methods but differs from these in respect of detailed structures in particular new features were found in the distributions of mare flows within the imbrium basin as well as across boundary regions and in circumbasin formations which lead to new geological interpretations a new map of crater tycho and its surroundings was in addition constructed based on eight spectral types differentiated between ejected materials and crater infill

understanding the lunar surface and space moon interactions the surface of the moon is a critical boundary that shapes our understanding of the moon as a whole all geologic mapping and remote sensing techniques utilize only the outermost portion of the moon before leaving the moon for study in our laboratories all lunar samples that have been studied existed at or very near the surface with the exception of the deeply probing geophysical techniques our understanding of the interior of the moon is derived from surficial but not superficial information coupled with boundary of the lunar crust it is the lower boundary layer of the tenuous lunar atmosphere and constitutes both a source and a sink for atmospheric gases the surface is also where the moon interacts with the space environment causing changes in the physical nature of lunar materials and provides a laboratory for the study of processes that occur on all airless bodies the data obtained remotely by the galileo clementine and lunar prospector missions as well as data derived from lunar meteorites have resulted in major changes to our understanding of global distributions of chemistry and rocks this chapter summarizes the current understanding of this critical interface the surface of the moon in its role as the lower boundary of the lunar atmosphere the upper boundary of the crust and the window through which we view through remote sensing the composition of the crust and the history of the moon in this post lunar prospector time the view of the moon has changed lending new perspectives to lunar samples and lunar processes but the new view will likely remain in flux as we continue to digest the results from these recent space missions and move forward to a new era of lunar exploration despite the freshness of our perspective this is an important moment to capture

sand rich turbidite system of the late oligocene northern apennines foredeep physical stratigraphy and architecture of the macigno costiero coastal tuscany italy

lock exchange gravity currents with a low volume of release propagating over an array of obstacles the study discusses based on high resolution 3 d large eddy simulation results the evolution of lock exchange boussinesq gravity currents with a low volume of release lvr propagating over an array of identical two dimensional 2 d obstacles large roughness features in the form of dunes and ribs corresponding to eroded substrates in a rectangular horizontal channel the study analyzes the effect of the shape and height of the roughness elements and scale effects between reynolds numbers at which most laboratory experiments of lock exchange currents are conducted and reynolds numbers closer to field scale currents in geophysical applications on the temporal variation of the front velocity mixing and flow structure within the gravity current the temporal evolution of the flow instabilities e g kelvin helmholtz billows forward and backward propagating interfacial waves forming as a result of the interaction of the front of the current with the obstacles and bed friction velocity distributions are analyzed during the different stages of the evolution of the current the focus is on the later stages of the propagation of lvr currents after the transition to the self similar drag dominated regime has started the differences between the evolution and structure of gravity currents with a low and a high volume of release are highlighted

geology and paleoecology of early holocene lacustrine deposits in the columbia river valley near fauquier southern british columbia early holocene lake sediments are exposed near fauquier on the east side of the arrow lakes in the columbia river valley of british columbia a glacial lake occupied the valley at the time of deglaciation but by 10 ka bp this had been replaced by a nonglacial lake that was at least 250 km long and as much as 5 km wide comparison of pollen and macroscopic plant remains in these nearshore and littoral deposits with modern vegetation indicates that many of the plants present between 9 and 10 ka bp are found in the area today either along the valley floor or at higher elevations in the subalpine zone nearby some of the organic material may be allochthonous this complicates paleoecological and paleoclimatological interpretations it appears that the climate in the columbia river valley between 9 and 10 ka bp was as wet or wetter than at present the presence of many of these species in the southern columbia river valley of british columbia during early holocene time suggests that elements of the modern ve

multiple scale characterization of sand rich distal lobe deposit variability examples from the annot sandstones formation eocene oligocene se france abstract the present paper investigates the outcrop scale architecture of submarine gravity flow deposits in both moderately to highly confined settings a significant dataset was gathered on the sand rich confined siliciclastic turbidite system of the annot sandstone formation se france we focused on thick sedimentary bodies formed by depletive gravity flows in relatively distal settings sand rich lobes the purpose was to investigate the architectural variability of their small scale components beds and bedsets and consequently to evaluate the associated heterogeneities facies changes grain size sedimentary features sediment thickness etc therefore we provide a set of detailed descriptions on well exposed outcrops through very high resolution correlation panels built thanks to multiple vertical logs these turbidite system end members have rarely been described in such details and have often been considered as laterally continuous and homogeneous on the basis of the hierarchical subdivisions of turbidite lobes results show a high complexity in internal architecture from lobe bed to lobe scale whereas large scale scenery seismic scale is characterized by apparently homogeneous tabular and very extensive sandbodies thus corresponding to the classical definition of sheet sands this complexity implies heterogeneities not only in terms of sediment thickness changes abrupt pinch outs and variable scale compensation features but also in terms of facies and associated sedimentary features distributions tractive structures internal scours with associated by pass freezed mudclast rich layers etc this facies variability is controlled by the interplay between internal erosive bedforms i e large scours and constructive bedforms such as dome shaped or laterally stacked bedsets that are related to local topographic controls and compensation processes variability then appears both laterally and vertically besides results also showed small scale evidences of interactions between turbidite flows and basin floor only expressed at lobe bed to lobe element scale especially on the basin sides where paleoslope is subject to erosion and remobilisation and where flows can undergo significant changes concerning both seismic and reservoir implications although those deposits are characterized by a sheet like geometry this high internal variability necessarily implies heterogeneities in terms of petrophysical characteristics porosity permeability that may have a significant impact on fluid circulation these elements lead us to reconsider both sedimentary processes involved in their building and also reservoir models that can be established on field analogues

remote sensing studies of the lomonosov fleming region of the moon 1 lomonosov fleming is a 620 km pre nectarian impact basin centered at 19 n 105 e clementine multispectral images and a variety of spacecraft photographs were used to investigate the composition and origin of geologic units in the region mare basalt deposits in the lomonosov fleming region are small and exhibit varying degrees of highlands contamination four previously unrecognized dark mantle deposits of probable pyroclastic origin were identified and mapped a major expanse of cryptomare was mapped in and around the lomonosov fleming basin spectral and chemical data obtained for dark haloed craters dhc established that these impact craters excavated mare basalt from beneath higher albedo highlands rich surface units the buried basalts exposed by dhcs in the region exhibit a variety of compositions which range from very low titanium basalt to intermediate tio2 mare basalt nectarian aged units with subjacent cryptomare are much more extensive than imbrian aged deposits with underlying basalt at least some of the buried mare basalts in the region may have been emplaced during pre nectarian time while both impact basins and craters played a role in cryptomare formation by transporting highlands material to mare surfaces the evidence indicates that most of the cryptomare inside the basin are of the distal basin ejecta type the enhanced feo and tio2 abundances exhibited by these cryptomare surfaces usually light plains units demonstrate that ballistic erosion and sedimentation played an important role in their formation

the distribution of olivine in the crater copernicus we employed multispectral imaging in the visible and near ir at four wavelengths 0 73 0 96 1 45 and 1 99 m of copernicus crater in order to map the distribution of olivine rich pyroxene poor material known previously to occur in the central peak complex we identified three additional portions of the crater to exhibit spectral characteristics similar to those of the central peaks strongly suggesting the presence of material similar to that exposed in the central peaks these areas are a scarp forming a portion of the northern rim of copernicus and two slump blocks in the north wall which may have been derived from the same portion of the ejecta now exposed in the rim scarp these occurrences decrease the minimum allowable depth for this unusual material in the copernicus target site though still represent some of the deepest material exposed by copernicus

geology of 243 ida abstract the surface of 243 ida is dominated by the effects of impacts no complex crater morphologies are observed a complete range of crater degradation states is present which also reveals optical maturation of the surface darkening and reddening of materials with increasing exposure age regions of bright material associated with the freshest craters might be ballistically emplaced deposits or the result of seismic disturbance of loosely bound surface materials diameter depth ratios for fresh craters on ida are 1 6 5 similar to gaspra results but greater than the 1 5 ratios common on other rocky bodies contributing causes include rim degradation by whole body ringing relatively thin ejecta blankets around crater rims or an extended strength gradient in near surface materials due to low gravitational self packing grooves probably represent expressions in surface debris of reactivated fractures in the deeper interior isolated positive relief features as large as 150 m are probably ejecta blocks related to large impacts evidence for the presence of debris on the surface includes resolved ejecta blocks mass wasting scars contrasts in color and albedo of fresh crater materials and albedo streaks oriented down local slopes color data indicate relatively uniform calcium abundance in pyroxenes and constant pyroxene olivine ratio a large relatively blue unit across the northern polar area is probably related to regolith processes involving ejecta from azzurra rather than representing internal compositional heterogeneity a small number of bluer brighter craters are randomly distributed across the surface unlike on gaspra where these features are concentrated along ridges this implies that debris on ida is less mobile and or consistently thicker than on gaspra estimates of the average depth of mobile materials derived from chute depths 20 60 m grooves 30 m and shallowing of the largest degraded craters 20 50 m minimum 100 m maximum suggest a thickness of potentially mobile materials of 50 m and a typical thickness for the debris layer of 50 100 m

large mineralogically distinct impact melt feature at copernicus crater evidence for retention of compositional heterogeneity 1 despite several lines of evidence for efficient mixing of impact melt in complex craters we document mineralogical heterogeneity in impact melt deposit on a scale of tens of kilometers on the moon in the 96 km diameter copernicus crater this heterogeneity is in the form of a large sinuous impact melt feature on the floor and northern wall that is spectrally distinct from melt in its immediate vicinity this melt feature spanning 30 km in length and 0 5 5 km in width has relatively short wavelength narrow ferrous absorption bands near 900 nm and 2000 nm indicating a more mg rich pyroxene composition as compared to impact melt deposit in the vicinity which is relatively rich in fe ca pyroxenes this distinction provides evidence for the preservation of compositional heterogeneity in impact melt in complex craters on the moon and documents an example of inefficient mixing of melt during the cratering process

deflection versus reflection of sediment gravity flows in the late llandovery rhuddnant grits turbidite system welsh basin the rhuddnant grits turbidite system was deposited in an elongate fault bounded trough an apparently ideal locality for the reflection of sediment gravity flows as solitons however 280 palaeocurrent readings from turbidite sandstones do not show the expected high angle discrepancies between palaeocurrent directions from sole structures and those from cross lamination palaeocurrents orthogonal to the bounding lineament are not generally observed instead there is a gradual progressive anticlockwise deflection of the currents with distance from source this may be explained by banking of the currents against an intrabasinal slope by the coriolis effect or by a combination of the two processes

optical maturity of ejecta from large rayed lunar craters lucey et al 2000 have developed a methodology for extracting an optical maturity parameter omat from multispectral clementine images the omat parameter characterizes the overall maturity of lunar soils and crater ejecta by changes in reflectance spectra using these omat images we surveyed large craters 20 km diameter on the moon that had previously been mapped as possessing or possibly possessing rayed ejecta we generated average radial profiles of omat values for rays of these large craters from these profiles we classified the craters into three relative age groups 1 older than copernicus inferred age of 810 myr 2 intermediate and 3 as young or younger than tycho inferred age of 109 myr we suspect that there is a bias to our classification scheme such that the omat profiles of smaller craters look like that of larger but older craters nevertheless some large craters such as eudoxus 67 km and aristillus 55 km are now known from this study to have optically mature ejecta and therefore are suspected to be older than copernicus this is consistent with an age of 1 3 gyr suggested for aristillus by ryder et al 1991 such craters were included by mcewen et al 1997 when estimating the density of craters younger than or contemporaneous with copernicus therefore the case for a modest increase in the cratering rate in the past 800 myr versus the previous 2 4 gyr indicated from that work has been weakened grier and mcewen 2001 given current constraints on dating large and recent lunar craters we cannot support or disprove the hypothesis that there has been a significant increase in the rate of large terrestrial impact events in the past 100 400 myr

mapping the feo and tio2 content of the lunar surface with multispectral imagery the derivation of quantitative elemental concentrations from multispectral imaging of the moon has long been a goal of lunar remote sensing concentration maps at the spatial resolutions available from the recent clementine mission would provide a revolutionary new tool for understanding the origin and evolution of the lunar crust lucey et al 1995 presented a method for extracting the concentration of fe from multispectral imaging of the moon this paper examines and quantifies important aspects ofthat technique left unexamined by lucey et al which had the potential to severely limit its utility these aspects include the effects of maturity grain size mineralogy shading due to topography and the presence of glass we also present a new algorithm for derivation of tio2 from multispectral imaging of both mare and highland units we find that both techniques are only weakly sensitive to maturity and that they have about 1 wt accuracy based on examination of the spectral properties and compositions of resolved lunar sampling stations presented by blewett et al 1997 we also discuss these findings in the context of two contrasting views of the effect of composition on lunar spectral properties presented by pieters and coworkers and hapke and coworkers we find the view of hapke and coworkers to be more consistent with our observations using a global mosaic of clementine multispectral data and these element derivation algorithms we find that the global modal abundance of feo is 4 5 wt 1 wt and the global modal abundance of tio2 is 0 45 wt 1 wt

the phanerozoic impact cratering rate evidence from the farside of the moon the relatively recent 1 b y flux of asteroids and comets forming large craters on the earth and moon may be accurately recorded by craters with bright rays on the moon s farside many previously unknown farside rayed craters are clearly distinguished in the low phase angle images returned by the clementine spacecraft some large rayed craters on the lunar nearside are probably significantly older than 1 ga rays remain visible over the maria due to compositional contrasts long after soils have reached optical maturity most of the farside crust has a more homogeneous composition and only immature rays are visible the size frequency distribution of farside rayed craters is similar to that measured for eratosthenian craters up to 3 2 b y at diameters larger than 15 km the areal density of farside rayed craters matches that of a corrected tabulation of nearside copernican craters hence the presence of bright rays due to immature soils around large craters provides a consistent time stratigraphic basis for defining the base of the copernican system the density of large craters less than 3 2 b y old is 3 2 times higher than that of large farside rayed craters alone this observation can be interpreted in two ways 1 the average cratering rate has been constant over the past 3 2 b y and the base of the copernican is 1 ga or 2 the cratering rate has increased in recent geologic time and the base of the copernican is less than 1 ga we favor the latter interpretation because the rays of copernicus 800 850 m y old appear to be very close to optical maturity suggesting that the average copernican cratering rate was 35 higher than the average eratosthenian rate other lines of evidence for an increase in the phanerozoic 545 ga cratering rate are 1 the densities of small craters superimposed on copernicus and apollo landing sites 2 the rates estimated from well dated terrestrial craters 120 m y and from present day astronomical observations and 3 the proterozoic rate suggested by the crater record of australia the hypothesis most consistent with several key observations is that the cratering rate has increased by 2x during the past 300 m y

moon near infrared spectral reflectance a first good look a positive identification of the minerals olivine plagioclase and several types of pyroxenes were made at several locations on the lunar surface by using remote measurements for example the crater aristarchus is found to have an average pyroxene composition of augite and plagioclase is obviously present a dark mantle deposit in the crater j herschel is at least partly composed of a mixture of 70o7o olivine and 30o7o pyroxene these determinations were possible because the reflectance spectra for 10 20 km diameter lunar areas have been measured for the first time in the ir spectral region 0 65 2 5 m with sufficient spectral resolution and photometric precision to define mineral electronic absorption bands the reflectance for all lunar regions observed over 100 to present continues to increase toward longer wavelengths to at least 2 5 m and several mineral absorption bands appear the telescopic spectra are of similar quality and contain features similar to laboratory spectra of lunar samples the absorption features in several spectra have been quantitatively analyzed using newly developed computer processing techniques including thermal flux removal and absorption band fitting to produce these mineral identifications detection and quantitative analysis of these absorptions provide a much improved basis for remotely determining and mapping surface mineralogy quantitatively from the ground or using airborne or spacecraft platforms

megafloods and clovis cache at wenatchee washington immense late wisconsin floods from glacial lake missoula drowned the wenatchee reach of washington s columbia valley by different routes the earliest debacles nearly 19 000 cal yr bp raged 335 m deep down the columbia and built high pangborn bar at wenatchee as advancing ice blocked the northwest of columbia valley several giant floods descended moses coulee and backflooded up the columbia past wenatchee ice then blocked moses coulee and grand coulee to quincy basin became the westmost floodway from quincy basin many missoula floods backflowed 50 km upvalley to wenatchee 18 000 to 15 500 years ago receding ice dammed glacial lake columbia centuries more till it burst about 15 000 years ago after glacier peak ashfall about 13 600 years ago smaller great flood s swept down the columbia from glacial lake kootenay in british columbia the east wenatchee cache of huge fluted clovis points had been laid atop pangborn bar after the glacier peak ashfall then buried by loess clovis people came five and a half millennia after the early gigantic missoula floods two and a half millennia after the last small missoula flood and two millennia after the glacial lake columbia flood people likely saw outburst flood s from glacial lake kootenay

did the orientale impact melt sheet undergo large scale igneous differentiation by crystal settling significant quantities of shock induced melt are predicted to form during basin scale impact events and may contribute substantially to compositional variation in the lunar crust through differentiation processes knowledge of the evolution of impact melt sheets and the cooling and crystallization processes involved is therefore important to understanding the geology and petrology of the moon here we perform a case study on the orientale basin and investigate the possibility of differentiation of the impact melt sheet by assessing the thermal and physical processes that drive cooling and crystallization focusing on crystal settling results predict that convective processes within the impact melt sheet enhance cooling and solidification and inhibit settling of crystals 1 5 mm in diameter and smaller preventing differentiation at or below this size impact melt sheet thickness is predicted to have minimal influence on crystallization history suggesting that crystal size is the primary factor controlling lunar impact melt sheet differentiation

turbidites in foreland and on thrust basins of the northern apennines abstract turbiditic sediments are associated with all stages of development of the apennines orogen not only the classical flysch of oligo miocene age macigno cervarola marnoso arenacea but also the coeval smaller bodies based on thrust sheets loiano of ranzano sequence and the younger molasse of the plio pleistocene foredeep except for more recent ones quaternary turbidite units are affected to some degree by thrusting and later block faulting the equivalent marginal deposits were also deformed uplifted and eroded to a great extent however identification and correlation of sequences and paleoenvironments across the orogenic belt can be helped by a deposits with rather strong eustatic imprint high stands and b preservation of marginal sediments by early remobilization cannibalism into deeper depocentres the following categories of basins can be recognized main foreland basin or foredeep in front of thrust sheets based on undeformed or previously rifted continental crust thrust top basins meso autochthonous auct in absence of a well defined major foredeep satellite basins thrust based but inwardly associated with a foredeep and of much smaller size linear dimensions in the order of kilometers and ten of kilometers volume of fill in the order of tens to hundreds cubic kilometers the foredeep persisted for the whole orogenic cycle but changed its character and was more or less segmented two main stages can be recognized conventionally labelled as the flysch stage up to the late miocene appenines mostly submerged and the molasse stage late miocene to recent present relief already in existence satellite basins floating on the ligurian sheet epi ligurian persisted up to the mid pliocene but received turbidites only in the oligocene and miocene others were created later on thrusts of different style involving the foreland sedimentary cover piggyback basins of ori and friend 1984 turbidite lithosomes of the flysch group are the largest ones volumes up to 30 000 km 3 with maximum size and lateral continuity of individual beds megaturbidites they are not seen as overlapping units filling coexisting and adjacent basins but as distinct superposed isochronous units within which only time transgressive sedimentation could occur macigno thus stands for all oligocene turbidites of the northern apennines foredeep cervarola for early miocene ones and marnoso arenacea for mid late miocene ones it is assumed that these units reflect sedimentary cycles of some order correlatable with global charts and splittable into depositional sequences sensu vail and collaborators

origin of olivine at copernicus the central peaks of copernicus are among the few lunar areas where near infrared telescopic reflectance spectra indicate extensive exposures of olivine other parts of copernicus crater and ejecta which were derived from highland units in the upper parts of the target site contain only low ca pyroxene as a mafic mineral the exposure of compositionally distinct layers including the presence of extensive olivine may result from penetration to an anomalously deep layer of the crust or to the lunar mantle we suggest that the procellarum basin and the younger superposed insularum basin have provided access to these normally deep seated crustal or mantle materials by thinning the upper crustal material early in lunar history the occurrences of olivine in portions of the compositionally heterogeneous aristarchus region in a related geologic setting may be due to the same sequence of early events

bunte breccia of the ries continuous deposits of large impact craters the ries crater an impact structure of 26 km diameter in south germany is the largest terrestrial crater where substantial amounts of ejecta are preserved on occasion 100 m deep further the target stratigraphy is well known and it is possible to relate specific clasts and breccia lithologies to initial target depth as a consequence the continuous deposits of the ries also known as bunte breccia may be studied with exceptional field control we report field observations and laboratory analyses obtained from 560 m core materials taken at nine different locations that range from 16 to 37 km in radial distance from the impact center the objective is to relate the ries observations to ejection and to emplacement processes of large scale planetary crater deposits the observations regarding the modal stratigraphic characteristics of the bunte breccia may be summarized as follows only 600 m some 0 7 is composed of triassic clasts originating from 300 to 600 m depths lower and middle jurassic horizons approximately 300 150 m constitute some 2 3 and upper jurassic 0 150 m makes up some 31 5 in addition the bunte breccia contains tertiary materials in the form of 1 cm clasts 29 1 and as highly comminuted fine grained matrix 10 gpa constitute 0 1 weight of the entire deposit which indicates that bunte breccia was emplaced at essentially ambient temperatures when possible the above observations are quantified via linear regressions throughout the text all of these observations are consistent with if not predicted by a ballistic emplacement scenario as postulated by oberbeck and co workers primary crater ejecta are expelled ballistically and will form secondary craters in the local substrate a mixture of primary and secondary ejecta results and combines into a highly turbulent ground hugging debris surge as the final phase of ejecta emplacement total emplacement time for the bunte breccia 200 km is estimated to be of the order of 5 min only these findings are compared with cratering theory relating to a number of ejecta thickness decay models and with the so called z model addressing material flow during various stages of crater formation qualitative to fair agreement of observations and predictions results an initial crater radius of 6 5 km an excavation depth of 1650 m an excavation volume of 136 km and an associated transient cavity volume of aproximately 230 km appear to be reasonable estimates approximately 170 km of material was involved in slumping and restoration of the transient cavity for the above radius and z 2 7 the modal composition of ries ejecta with regard to preimpact target stratigraphy indicates that materials contained in the continuous deposits of large complex planetary craters are predominantly derived from depths as small as one hundredth the apparent crater diameter a number of implications are addressed regarding remote sensing of planetary surfaces and investigation of lunar and meteoritic impact breccias

small scale spatial variability in turbidity current flow controlled by roughness resulting from substrate erosion field evidence for a feedback mechanism abstract analysis of turbidity flow processes from turbidite outcrops remains difficult in this paper the distribution of orientations of paleoflow indicators around scours a few centimeters to a few decimeters deep is analyzed two examples are presented one from the gres de champsaur formation in southeastern france and one from the macigno formation in northern italy the orientations of paleoflow data sets on either side of the scours are analyzed and differ 10 15 over horizontal distances of only a few meters this mismatch is argued to represent a rotation of the flow whilst it flowed over the scour the reconstructed rotation is a new example of a feedback mechanism involving interaction between the current and its substrate paleoflow indicators only record flow direction at the base of the flow however the flow substrate interaction can be expected to affect the complete turbulent velocity structure of the flow so that erosion by frontal parts of the current influences the suspended sediment transport processes of hindward regions of the current

near infrared spectral reflectance of mineral mixtures systematic combinations of pyroxenes olivine and iron oxides near infrared spectral reflectance data are presented for systematic variations in weight percent of two component mixtures of ferromagnesian and iron oxide minerals mixtures were chosen for application to the study of the dark materials on mars but the results are equally applicable to mafic and ultramafic assemblages elsewhere in the solar system olivine spectral features are greatly reduced in contrast by admixture of other phases but remain distinctive even for low olivine contents clinopyroxene and orthopyroxene mixtures show resolved pyroxene absorptions near 2 m the addition of limonite greatly modifies pyroxene and olivine reflectance but does not fully eliminate distinctive spectral characteristics using only spectral data in the 1 m region it is difficult to differentiate orthopyroxene and limonite goethite in a mixture additional spectral coverage or other evidence may be required for a unique interpretation all composite mineral absorptions observed in this study are either weaker than or intermediate in strength to the end member absorptions and have bandwidths greater than or equal to those for the end members in general spectral properties in an intimate mixture combine in a complex nonadditive manner with features demonstrating a regular but usually nonlinear variation as a function of end member phase proportions

copernicus a regional probe of the lunar interior earth based telescopic spectral imaging techniques were used to document the spatial distribution of crater materials within the large lunar crater copernicus at the subkilometer scale on the basis of spectral ultraviolet visible near infrared characteristics the proposed spectral mixing analysis leads to a first order mapping of the impact melt material within the crater olivine was detected not only within the three central peaks but also along a significant portion of the crater rim consideration of an olivine bearing end member in the mixing model emphasizes the overall morphological pattern of the rim and wall terraces in the associated fraction image the identification of widely exposed olivine units supports the idea that the lower crust and possibly the lunar mantle itself are regionally at shallow depth

the formation of infilled craters on mars evidence for widespread impact induced decompression of the early martian mantle flat floored craters have long been recognized on mars with early work hypothesizing a sedimentary origin more recently high resolution thermal inertia measurements show that these craters contain some of the rockiest materials on the planet inconsistent with poorly consolidated sedimentary materials in this study the distribution physical properties morphology and thermal inertia and composition of these craters are thoroughly investigated over the entire planet the majority of the 2800 rocky crater floors identified are concentrated in the low albedo 0 1 0 17 cratered southern highlands these craters were infilled at 3 5 ga and are associated with the highest thermal inertia values and some of the most mafic materials identified on the planet although several processes may have led to the formation of the crater floors the most likely scenario is volcanic infilling through fractures created by the impact event the primitive magma source directly results from decompression melting of the martian mantle by the removal of the crustal material excavated by the impactor volcanic infilling of craters by decompression melting appears to only have occurred in early martian history when the lithosphere was still relatively thin and the thermal gradient was high this process was widespread and responsible for the eruption of significant volumes of primitive material inside and likely outside of craters impact induced decompression melting of the martian mantle accounts for the unusual infilling of martian craters and is a widespread planetary process that has gone previously undocumented

minimum age of deglaciation of upper elk valley british columbia discussion ferguson and osborn have reported a radionants but does not alter the basic isotopic composition carbon date of 13430 450years bp gx 5599 of the shells established while the gastropods were on gastropod shells from clay at the base of weary living and thus will not correct for old carbon effects bog in upper elk valley british columbia the date some indication of the magnitude of potential error in site is 29 km south of the mount joffre ice fields at the freshwater and terrestrial shell dates from western crest of the rocky mountains and therefore ferguson canada is provided by multiple radiocarbon determinaand osborn suggest that much or all of elk valley was tions on sundry organic materials from 1 early deglaciated before 13 500 years bp 2 postglacial lacustrine sediments in columbia valley because the interior plateau of british columbia near fauquier british columbia approximately 230 km remained covered by glacier ice until about 10500west southwest of weary bog lowdon and blake 11 000 years ago fulton 1971 clague 1980 1981 the 1976 p 10 and 2 postglacial fluvial or eolian weary bog date if valid has important implications for sediments adjacent to castle river near pincher creek the style and pattern of late wisconsin deglaciation in alberta approximately 120 km southeast of weary bog the southern canadian cordillera however for reasons lowdon and blake 1968 pp 220 22 1 outlined below i feel that deglaciation of upper elk five dates on wood and plant detritus at a single site valley before 13 500 years bp has not been conclusively near fauquier range from 8910 150 to 10 100 150 demonstrated by ferguson and osborn and i appeal years bp gsc 1212 and gsc 1012 shells anodonta for caution in the acceptance of their conclusions on the cf nuttalliana lea collected 1 m stratigraphically other hand in view of independent evidence that lower above wood dated 9590 150 years bp gsc 1613 elk valley perhaps was ice free by about 12 200 years yielded a date of 12 000 200 years bp gsc 1596 bp harrison 1976 i do not deny the possibility of early other shells from the same stratigraphic position as deglaciation gsc 1613 were dated at 12 800 250 years bp gscfreshwater and terrestrial shells commonly yield 1718 the dates on wood and plant detritus at this site errant radiocarbon dates due to incorporation of old are thought to be reliable because plant material is less carbon by mollusks prior to their death therefore the susceptible than shell to old carbon effects e g possibility that the true age of the weary bog gastropods hillaire marcel 1977 also the dates on wood and is younger than 13 430 450 years old must be plant detritus are compatible with independent radiocarconsidered ferguson and osborn briefly mention the bon geomorphic and stratigraphic data obtained elseincorporation of old carbon as a potential source of error where in columbia valley thus the shell dates at the in their shell date but elsewhere accept the date on face fauquier site probably are 2000 3000 years too old value without reservation as for example on p 1636 at castle river terrestrial gastropod shells and the date reported here suggests there was no major charcoal from the same stratum the charcoal is perhaps advance down the kananaskis valley after 13 500 years slightly lower in the sequence yielded radiocarbon bp and the canmore advance was probably dates of 3380 170 and 2680 140 years bp gscin retreat by 13 500 years bp the authors state that 741 and gsc 743 respectively the 700 year differsome potential error may have been prevented because ence between the two dates may be a result of old carbon the shells were leached in dilute hc1 to remove surface having been incorporated by the gastropods prior to their carbonate this procedure removes surface contamideath in view of the foregoing it seems likely that the weary bog shells are anomalously old although this note by a ferguson and g osborn 1981 canadian jourcannot be proved with the limited data on hand nal of earth sciences 18 pp 1635 1636 limestone and dolomite possible sources of dead 11 dates and time periods in this note are in radiocarbon carbon are common in the elk river basin upstream of years the date site and waters rich in bicarbonate probably

imaging of lunar surface maturity the physical evolution of the lunar surface with exposure to the space environment is termed maturation and maturity is the degree to which a particular lunar soil possesses quantitative characteristics consistent with that exposure several quantitative measures or indices of maturity have been proposed and employed including the abundance of solar wind gas abundance of various types of agglutinates various measures of grain size and is feo among the changes attendant with space exposure are striking changes in the optical characteristics of soils mature lunar soils are dark red and exhibit reduced spectral contrast relative to immature soils this paper presents an optical maturity index that quantifies the spectral effects of maturation we show that this optical maturity index correlates with other maturity indices about as well as the accepted maturity indices correlate among themselves and is only weakly coupled to composition the modest correlations among maturity indices suggest important controls on individual maturity indices other than age uncorrelated variations in the rates of accumulation of individual indicators or variations in depths over which indicators are emplaced in addition to mixing these effects conspire to reduce the equivalence of maturity and duration of surface exposure optical maturity illustrates some of these effects showing that ejecta of large and small craters mature at different rates and that the interiors and ejecta of large craters exhibit systematically different optical maturities the same or analogous effects are likely to influence other maturity indices

global distribution of bedrock exposures on mars using themis high resolution thermal inertia 1 we investigate high thermal inertia surfaces using the mars odyssey thermal emission imaging system themis nighttime temperature images 100 m pixel spatial sampling for this study we interpret any pixel in a themis image with a thermal inertia over 1200 j m 2 k 1 s 1 2 as bedrock which represents either in situ rock exposures or rock dominated surfaces three distinct morphologies ranked from most to least common are associated with these high thermal inertia surfaces 1 valley and crater walls associated with mass wasting and high surface slope angles 2 floors of craters with diameters 25 km and containing melt or volcanics associated with larger high energy impacts and 3 intercrater surfaces with compositions significantly more mafic than the surrounding regolith in general bedrock instances on mars occur as small exposures less than several square kilometers situated in lower albedo 350 j m 2 k 1 s 1 2 and relatively dust free dust cover index 0 95 regions however there are instances that do not follow these generalizations most instances are concentrated in the southern highlands with very few located at high latitudes poleward of 45 n and 58 s suggesting enhanced mechanical breakdown probably associated with permafrost overall mars has very little exposed bedrock with only 960 instances identified from 75 s to 75 n with likely 3500 km 2 exposed representing 1 ofthe total surface area these data indicate that mars has likely undergone large scale surface processing and reworking both chemically and mechanically either destroying or masking a majority of the bedrock exposures on the planet

a sharper view of impact craters from clementine data the ultraviolet visible camera on the clementine spacecraft obtained high spatial resolution images of the moon in five spectral channels impact craters mapped with these multispectral images show a scale of lithologic diversity that varies with crater size and target stratigraphy prominent lithologic variations feldspathic versus basaltic occur within the south wall of copernicus 93 kilometers in diameter on the scale of 1 to 2 kilometers lithologic diversity at tycho 85 kilometers in diameter is less apparent at this scale although the impact melt of these two large craters is remarkably similar in this spectral range the lunar surface within and around the smaller crater giordano bruno 22 kilometers in diameter is largely dominated by the mixing of freshly excavated material with surrounding older soils derived from a generally similar feldspathic lithology

igneous activity in the southern highlands of the moon 1 detailed investigations of both endogenic and exogenic dark haloed craters can provide critical information concerning the geology composition and evolution of portions of the lunar surface several dark haloed and dark rayed craters have been identified in the maurolycus region in the southeastern nearside highlands clementine and galileo multispectral imagery as well as earth based remote sensing data were used to investigate the composition and origin of dark haloed craters in the region a striking albedo anomaly is associated with buch b crater which exhibits both a dark halo and dark rays the result of a morphologic analysis clearly indicated that buch b is an impact structure not a volcanic vent the optical maturity image shows that the buch b ejecta deposits are immature and the radar and thermal data indicate a high abundance of fresh rocks and fragments in the 1 50 cm size range feo and tio2 data as well as five point spectra extracted from clementine uv vis images indicate that the dark ejecta is composed of immature mare like material and may contain minor amounts of highland debris buch b excavated either an isolated cryptomare or more likely a mafic intrusion one or more dikes of basaltic composition are possible candidates minor low albedo anomalies have been identified around three other impact craters maurolycus a and b and barocius m in the region while small feo enhancements are seen in portions of the ejecta deposits associated with these craters they do not approach the feo values 12 14 wt exhibited by the dark deposits of buch b and they do fall within the range of feo abundances 5 9 wt exhibited by highland terrain in the maurolycus region hence the presence of a basaltic component is not required and it cannot be concluded that either cryptomare or mafic intrusions were present in the target sites of these craters

the corsica sardinia massif as source area for the early northern apennines foredeep system evidence from debris flows in the macigno costiero late oligocene italy large isolated gravity flows debrites are widely present in the stratigraphic record of the northern apennines foreland basin system these strata may be useful for provenance signals and dispersal pathways during foreland evolution this paper examines a cohesive debris flow bed interbedded with turbidite strata of the macigno formation late oligocene tuscany italy in order to obtain new data on the provenance of the clastic material clasts in the debris flow are predominantly plutonic granodiorite tonalite and s granite and subordinately metamorphic gneiss and schist and sedimentary calcareous clasts the composition of the clasts within the debris flow is similar to the clastic composition of the interbedded turbidite sandstones of the macigno costiero the depositional features of the debris flow suggest that it traveled for a short distance within the basin before it was deposited not far from the slope the absence of a high pressure low temperature hp lt paragenesis in the plutonic and metamorphic clasts of the debris flow indicates a provenance from a crystalline basement not involved in the high pressure phases of the alpine orogenesis previous studies have indicated the central western alps as potential source areas for the macigno formation sediments the lack of hp lt metamorphic signatures in our studied samples excludes the pennidic and austroalpine nappes of the western alps as possible sources for the debris flows of the macigno costiero these new data sedimentological petrographical and microstructural suggest that the corsica sardinia hercynian basement lacking a hp lt paragenesis is the more accredited source area of the debris flow and of the related turbidite sandstones of the macigno costiero succession these foredeep feeding sediments were probably before deposited within an episutural basin developed close to the northern apennines orogenic wedge

spectral characteristics of lunar impact melts and inferred mineralogy abstract two suites of lunar impact melt samples have been measured in nasa s reflectance experiment laboratory relab at brown university suite 1 comprises seven apollo 17 crystalline impact melt breccias and seven quenched glass equivalents suite 2 is made up of 15 additional impact melt samples from apollo 12 15 16 and 17 which exhibit a range of textures and compositions related to cooling conditions and glass abundance a few of these samples have cooled slowly and fully crystallized and thus have the same spectral properties as igneous rocks of similar texture and composition they cannot be uniquely distinguished without geologic context however most of the impact melts and melt breccias contain either quantities of quenched glass and or have developed microcrystalline nonequilibrium textures with well defined diagnostic spectral properties the microcrystalline textures are associated with a distinctive 600 nm absorption feature apparently due to submicroscopic ilmenite inclusions in a transparent host typically fine grained plagioclase the reflectance properties of these lunar sample suites contribute to and constrain the identification and characterization of impact melts in remote sensing data

galileo observations of post imbrium lunar craters during the first earth moon flyby copernican age craters are among the most conspicuous features seen on the far side and western limb of the moon in the galileo multispectral images acquired in december 1990 among the new morphologic observations of far side craters are bright rays continuous ejecta deposits and dark rings associated with probable impact melt veneers these observations suggest that the mapped age assignments of several large far side craters ohm robertson and possibly lowell and lenz need revision new crater size frequency measurements on lunar orbiter images suggest the following age reassignments hausen 170 km diameter pythagoras 120 km and bullialdus 61 km from eratosthenian to upper imbrian and carpenter 60 km and harpalus 39 km from copernican to eratosthenian colors and albedos of craters away from impact melt veneers are correlated with their geologic emplacement ages as determined from counts of superposed craters these age color relations are used to estimate the emplacement age time since impact event for other copernican age craters these age color relations indicate a probable copernican age for 27 far side or western limb craters larger than 10 km diameter that were not previously mapped as copernican the apparent deficiency of copernican craters on the far side compared with the near side in published geologic maps is not present in our data age color trends differ between mare and highland regions and between the interiors and continuous ejecta of the craters similar trends are established for color and albedo versus soil maturity indices for the returned lunar samples with distinct trends for mare and highland soils however the mare versus highland offsets are reversed in the two comparisons these relations can be explained by variations in regolith thicknesses and rates of mixing with relatively fresh crystalline ejecta therefore the soil maturity trends represent longer geologic time periods in regions with thinner regoliths such as the maria

remote sensing and geological studies of the hadley apennine region of the moon we have used data from the clementine and lunar prospector spacecraft in conjunction with reflectance spectra collected with earth based telescopes to study the geology of the hadley apennine portion of the lunar imbrium basin the apennine mountains and the imbrium backslope are composed of imbrium basin ejecta with a noritic or anorthositic norite composition we find that the two major facies of imbrium ejecta the apenninus material and the alpes formation differ in iron and titanium content pure anorthosite has tentatively been identified in the ejecta of the crater conon based on low iron content a difference in th and rare earth element ree abundance between the northeast apennine mountains lower and the southwest apennines higher is noted pyroclastic deposits are common in the region and are dominated by mare basalt material probably plug rock ejected in vulcanian eruptions the apennine bench formation which is likely to be a deposit of non mare volcanic material has an fe ti and th composition consistent with that of apollo 15 kreep basalt samples thought to be fragments of the bench aristillus crater is a th and ree hot spot and the stratigraphy of the impact target site has been reconstructed from knowledge of the composition of the crater interior and exterior deposits we infer that the target consisted of highland basement kreep plutonics and volcanics and both high and low ti mare basalt

geological mapping of impact melt deposits at lunar complex craters jackson and tycho morphologic and topographic diversity and relation to the cratering process abstract high resolution geological mapping aided by imagery and elevation data from the lunar reconnaissance orbiter lro and kaguya missions has revealed the scientifically rich character of impact melt deposits at two young complex craters jackson 71 km and tycho 85 km the morphology and distribution of mapped impact melt units provide several insights into the cratering process we report elevation differences 200 m among large coherent floor sections within a single crater and interpret them to be caused by crater wall collapse and or large scale structural failure of the floor region clast poor smooth melt deposits are correlated with floor sections at lower elevations and likely represent ponded deposits sourced from higher elevation regions viz crater walls in addition these deposits are also located in the inferred downrange direction of the impact melt coated large blocks spanning several kilometers are common on the crater floors and may represent collapsed wall sections or in some cases subdued sections of the central peaks spatial trends in the mapped impact melt units at the two craters provide clues to decipher the conditions during each impact event and subsequent evolution of the crater floor

near infrared spectroscopy of probable impact melt from three large lunar highland craters abstract the composition of small areas within three large lunar highland craters are compared using near infrared earth based telescopic data spectra from many areas in the walls and central peaks of the craters indicate the presence of crystalline components which include olivine two types of pyroxene and sometimes fe bearing feldspar spectra from other regions suspected of being impact melt deposits located on the floors and walls of the three craters have remarkably similar yet anomalous features these features are interpreted to indicate the presence of pyroxene fe bearing glass and fe bearing feldspar pyroxene and feldspar are believed to occur primarily in the form of lithic clasts and rapidly recrystallized impact melt the fe bearing glass is interpreted as impact melt glass

pulse propagation in turbidity currents submarine turbidity currents are a key mechanism in the transportation of clastic sediments to deep seas such currents may initiate with a complex longitudinal flow structure comprising flow pulses for example by being sourced from retrogressive sea floor slope failures or acquire such structure during run out for example following flow combination downstream of confluences a key question is how far along channel pathway complex flow structure is preserved within turbidity currents as they run out and thus if flow initiation mechanism and proximity to source may be inferred from the vertical structure of their deposits to address this question physical modelling of saline flows has been conducted to investigate the dynamics of single pulsed versus multi pulsed density driven currents the data suggest that under most circumstances individual pulses within a multi pulsed flow must merge therefore initiation signatures will only be preserved in deposits upstream of the merging point and may be distorted approaching it downstream of the merging point all initiation signals will be lost this new understanding of merging phenomenon within multi pulsed gravity currents broadens our ability to interpret multi pulsed turbidites

an in depth look at the lunar crater copernicus exposed mineralogy by high resolution near infrared spectroscopy abstract newly acquired sequentially spaced high resolution near infrared spectra across the central section of crater copernicus interior have been analyzed using a range of complementary techniques and indexes we have developed a new interpretative method based on a multiple stage normalization process that appears to both confirm and expand on previous mineralogical estimations and mapping in broad terms the interpreted distribution of the principle mafic species suggests an overall composition of surface materials dominated by calcium poor pyroxenes and minor olivine but with notable exceptions the southern rim displays strong ca rich pyroxene absorption features and five other locations the uppermost northern crater wall opposite rim sections facing the crater floor and the central peak pk1 and at the foot of pk3 show instead strong olivine signatures we also propose impact glass an alternative interpretation to the source of the weak but widespread olivine like spectral signature found in low reflectance samples since it probably represents a major regolith constituent and component in large craters such as copernicus the high quality and performance of the sir 2 data allows for the detection of diagnostic key mineral species even when investigating spectral samples with very subdued absorption features confirming the intrinsic high quality value of the returned data

remote sensing of lunar pyroclastic mantling deposits abstract mantling deposits on the moon are considered to be pyroclastic units emplaced on the lunar surface as a result of explosive fire fountaining these pyroclastic units are characterized as having low albedos having smooth fine textured surfaces and consisting in part of homogeneous febearing volcanic glass and partially crystallized spheres mantling units exhibit low returns on depolarized 3 8 cm radar maps indicating an absence of surface scatterers in the 1 to 50 cm size range a number of reflectance spectra from several regional pyroclastic deposits are presented for the first time these data support a previous interpretation that mantling units have a unique spectral signature which is indicative of the presence of a significant fe bearing volcanic glass component the rima bode region is discussed as an example of an area in which several types of remote sensing data including 3 8 cm radar spectral reflectance and multispectral vidicon data were used to reconstruct the geologic events surrounding the emplacement of a regional pyroclastic mantling deposit the recognition of numerous varieties of volcanic glass samples especially relatively high albedo e g green yellow glasses suggests the existence of additional unrecognized mantling deposits with albedos higher than those studied to date on the basis of the remote sensing data summarized and presented five new areas have been identified which may represent higher albedo regional pyroclastic deposits

volcanic glass signatures in spectroscopic survey of newly proposed lunar pyroclastic deposits moon mineralogy mapper spectroscopic observations are used to assess the mineralogy of five sites that have recently been proposed to include lunar dark mantle deposits dmds volcanic glasses have for the first time clearly been identified at the location of three of the proposed pyroclastic deposits this is the first time that volcanic glasses have been identified at such a small scale on the lunar surface from remote sensing observations deposits at birt e schluter and walther a appear to be glassy dmds deposits at birt e and schluter show 1 morphological evidence suggesting a likely vent and 2 mineralogical evidence indicative of the presence of volcanic glasses the walther a deposits although they show no morphological evidence of vents have the spectroscopic characteristics diagnostic of volcanic glasses the deposits of the freundlich sharonov basin are separated in two areas 1 the buys ballot deposits lack mineralogical and morphological evidence and thus are found to be associated with mare volcanism not with dmds and 2 the anderson crater deposits which do not exhibit glassy dmd signatures but they appear to be associated with possible vent structures and so may be classifiable as dmds finally dark deposits near the crater kopff are found to be associated with likely mare volcanism and not associated with dmds the spectral identification of volcanic glass seen in many of the potential dmds is a strong indicator of their pyroclastic origin

galileo multispectral imaging of the north polar and eastern limb regions of the moon multispectral images obtained during the galileo probe s second encounter with the moon reveal the compositional nature of the north polar regions and the northeastern limb mare deposits in these regions are found to be primarily low to medium titanium lavas and as on the western limb show only slight spectral heterogeneity the northern light plains are found to have the spectral characteristics of highlands materials show little evidence for the presence of cryptomaria and were most likely emplaced by impact processes regardless of their age

composition of the lunar highland crust from near infrared spectroscopy near infrared reflectance spectra of the lunar highlands are synthesized to obtain global information about the composition of the lunar near side crust immature exposed surfaces from small fresh craters mountains and massifs and large craters with central peaks are included in a survey of rock types across the lunar near side compositions recognized in these data include anorthosite noritic gabbric and troctolitic mineral assemblages three quarters of the areas studied that represent samples from the upper 1 2 km of lunar crust exhibit noritic compositions with different amounts of pyroxene and or brecciation alteration norites are ubiquitous across the near side and show no spatial clustering associated with any of the major basins in contrast to this noritic megaregolith of the upper crust material representing stratigraphically deeper zones 5 15 km of the lunar crust is dominated by gabbros anorthosites and troctolites with less than a quarter of the areas studied exhibiting a noritic composition the origin of the noritic megaregolith and its relation to deeper crustal material is thus somewhat of an enigma the current limited statistics for areas identified as anorthosites and troctolites are insufficient to derive global spatial distributions gabbroic areas however are notably concentrated in the western hemisphere although incomplete for a global assessment of crustal materials these data demonstrate that the lunar near side crust is clearly mineralogically heterogeneous both laterally and vertically and not well mixed below 1 2 km

integrated topographic photometric and spectral analysis of the lunar surface application to impact melt flows and ponds abstract this study provides an analysis of the impact melt deposits melt flows and ponds associated with eight lunar craters with diameters between 9 and 96 km in terms of their topographic photometric and spectral properties our analysis is based on an integrated method for construction of digital elevation models dem of high lateral resolution pixel wise photometric modelling construction of topographically corrected normalised reflectance maps extraction of spectral parameters and estimation of elemental abundances based on moon mineralogy mapper m 3 hyperspectral data and data of the lunar prospector gamma ray spectrometer instrument most of the examined geologically fresh impact melt flows are characterised by lower albedos than the surrounding surface and tend to originate from topographically low parts of the source crater rim as an exception we find that the impact melt deposits northeast of crater aristillus lack any optical signature and are not visible in monochrome images but can only be observed by their anomalously smooth surface inferred from the dem some impact melt flows and ponds exhibit photometric anomalies in terms of the asymmetries in the single particle scattering function and the slope of that parameter with respect to wavelength these photometric anomalies may be due to impact melt specific anomalies of the surface structure e g consolidated rock rather than regolith or anomalies in size or shape of the geometric surface elements e g individual grains or their aggregates on submillimetre spatial scales the strength of the hydroxyl absorption displays a negative anomaly with respect to the surrounding surface for the majority of the examined impact melt flows as an impact melt specific spectral behaviour we find a decrease in the absorption band depth around 2000 nm and in several cases a simultaneous increase of the absorption band depth near 1000 nm these observations are consistent with the laboratory analyses by tompkins et al tompkins s pieters c m 2010 meteorit planet sci 45 7 1152 1169 of chemically uniformly composed mixtures between crystalline and glass material for several impact melt flows their data allow to roughly estimate the fraction of glass material based on our spectral analysis

a comparative study of iron abundance estimation methods application to the western nearside of the moon abstract the feo weight percentage wt abundance of the moon s western nearside 55 s 55 n and 5 e 40 w is estimated using data from the infrared spectrometer 2 sir 2 and the moon mineralogy mapper m3 in this study we modified an feo abundance estimation algorithm bhatt m mall u bugiolacchi r mckenna lawlor s banaszkiewicz m nathues a ullaland k 2012 icarus 220 51 64 which relies exclusively on the 2 m absorption band parameters the modified feo abundance estimation algorithm and the regression based elemental abundance estimation algorithm wohler c grumpe a berezhnoy a bhatt m u mall u 2014 icarus 235 86 122 which is based on the 1 m and 2 m absorption band parameters is applied to the m3 data we have compared results obtained from these two modified algorithms with a previously published clementine s feo wt map lucey p g blewett d t jolliff b l 2000 j geophys res 105 20297 20306 the effects of topography and space weathering on feo wt estimates have been successfully minimized using the modified algorithm based on the 2 m absorption band parameters thus this algorithm can be successfully applied at middle to high latitudes furthermore a correction for tio2 is applied to the feo abundance estimation algorithm based on the 2 m absorption band parameters using the m3 data our comparative study shows a good correspondence between the three algorithms discussed there are two locations the crater tycho and the region around rima bode which show major discrepancies our modified algorithm based on the 2 m absorption parameters predicts 3 4 wt less feo for the ray system of tycho than for the surrounding region the average iron abundance for the lunar highlands is about 6 wt and for the mare regions is about 16 wt using the regression based elemental abundance estimation algorithm and the algorithm based on the 2 m absorption parameters this result is consistent with the previous analysis using lunar prospector gamma ray spectrometer data sets the feo wt is in the range 20 24 wt for the high ti basalts using both the modified iron abundance estimation and the regression based elemental abundance estimation algorithms

changes in flow direction at a point caused by obstacles during passage of a density current the flow pattern and sediment character of laboratory density currents partly blocked by bed topography is used to demonstrate how changes in paleocurrent direction through a turbidite at a single site can be explained these experiments confirm that a relatively small obstacle may affect bed thickness and paleocurrent patterns at considerable distances away from obstacles density currents generated by a lock exchange mechanism spread radially across the tank floor and were partially blocked by a wedge shaped obstacle with steep face scarp facing upstream when the body of the current impinged on the obstacle a thickened region of the flow developed upstream of the scarp with increased entrainment of ambient fluid above it the upflow edge of the thickened region was at a small angle to the obstacle front and propagated rapidly upflow and to the sides of the obstacle internal flow vectors observed with thread flags were radial from the lock before the head reached the obstacle after the head passed the obstacle flow vectors in the region of thickened flow upstream and to the sides of the obstacle were reoriented nearly parallel to the obstacle scarp thus flow vector at a point rotated by as much as 45 during passage of the current the deposits of sediment laden density currents thickened in the region of observed flow thickening because of an increased particle flux to the bed caused by velocity reduction the upflow limit of the influence of the obstacle on deposition is marked by an abrupt increase in the thickness of the deposits this area of thickening occurs in an area where the flow is accumulative

terrestrial analogues for lunar impact melt flows abstract lunar impact melt deposits have unique physical properties they have among the highest observed radar returns at s band 12 6 cm wavelength implying that they are rough at the decimeter scale however they are also observed in high resolution optical imagery to be quite smooth at the meter scale these characteristics distinguish them from well studied terrestrial analogues such as hawaiian p hoehoe and a lava flows the morphology of impact melt deposits can be related to their emplacement conditions so understanding the origin of these unique surface properties will help to inform us as to the circumstances under which they were formed in this work we seek to find a terrestrial analogue for well preserved lunar impact melt flows by examining fresh lava flows on earth we compare the radar return and high resolution topographic variations of impact melt flows to terrestrial lava flows with a range of surface textures the lava flows examined in this work range from smooth hawaiian p hoehoe to transitional basaltic flows at craters of the moon cotm national monument and preserve in idaho to rubbly and spiny p hoehoe like flows at the recent eruption at holuhraun in iceland the physical properties of lunar impact melt flows appear to differ from those of all the terrestrial lava flows studied in this work this may be due to a differences in post emplacement modification processes or b fundamental differences in the surface texture of the melt flows due to the melts unique emplacement and or cooling environment information about the surface properties of lunar impact melt deposits will be critical for future landed missions that wish to sample these materials

copernicus crater central peak lunar mountain of unique composition olivine is identified as the major mafic mineral in a central peak of copernicus crater information on the mineral assemblages of such unsampled lunar surface material is provided by near infrared reflectance spectra 0 7 to 2 5 micrometers obtained with earth based telescopes the composition of the deep seated material comprising the copernicus central peak is unique among measured areas other lunar terra areas and the wall of copernicus exhibit spectral characteristics of mineral assemblages comparable to the feldspathic breccias returned by the apollo missions with low calcium orthopyroxene being the major mafic mineral