multiple charcoal profiles in a scottish lake taphonomy fire ecology human impact and inference abstract sedimentary microscopic charcoal in lacustrine environments has received much attention although this has been concerned largely with the deposition of modern charcoal or with distributions through time based on single profiles lake sediments are dynamic entities however and the phenomenon of sediment focusing for example will lead to the redistribution of pollen spores and charcoal the process may not always result in greatly altered fossil assemblage in percentage terms but values for individual indicators or their absolute values may be affected strongly this is investigated using multiple microscopic charcoal profiles covering many thousands of years from black loch fife eastern scotland relative and absolute measures of charcoal depiction are considered as a prelude to discussion of microscopic charcoal taphonomy in the context of a small lake fire ecology and human impacts the charcoal measures concentrations influx and charcoal to pollen ratios all follow similar patterns though with very different numerical values two cores have charcoal influx values of similar orders of magnitude for much of the holocene whereas quantities in two other cores vary by a factor of 16 after 1000 cal bp the differences between influx measures for total pollen and charcoal indicate that focusing effects between the two indicators are dissimilar correlations with pollen and spore taxa are explored and demonstrate the problems of discrepant data between profiles charcoal pollen patterns for specific cultural periods are examined for one profile and they provide data suggesting that a direct fire vegetation relationship for the site is unproven the need to adopt a multi causal approach to inference is emphasised

ventifacts at the pathfinder landing site about half of the rocks at the mars pathfinder ares vallis landing site appear to be ventifacts rocks abraded by windborne particles comparable resolution images taken by the imager for mars pathfinder imp camera and the viking landers show that ventifacts are more abundant at the pathfinder site the ventifacts occur in several forms including rocks with faceted edges finger like projections elongated pits flutes grooves and possible rills the trends of elongated pits flutes grooves and rills cluster at 280 330 clockwise from north and generally dip 10 30 away from their trend direction these orientations are indicative of southeast to northwest winds and differ from the trend of wind tails at the landing site the direction of local wind streaks and predictions of the global circulation model all of which indicate northeast to southwest winds the disparity between these data sets strongly suggests that local circulation patterns have changed since the abrasion of the ventifacted rocks the greater number of ventifacts at the pathfinder site compared to either of the viking sites is most easily explained as being due to a larger supply of abrading particles composed of either sand sized grains or indurated dust aggregates and higher surface roughness which should increase the momentum of saltating grains the pathfinder ventifacts may have formed shortly after the deposition of outflow channel sediments nearly 2 gry ago when a large local supply of abrading particles should have been abundant and atmospheric conditions may have been more conducive to rock abrasion from saltating grains based on how ventifacts form on earth the several ventifact forms seen at the pathfinder site and their presence on some rocks but not on others are probably due to local airflow conditions original rock shape exposure duration rock movement and to a lesser extent rock lithology the abundance of ventifacts at the pathfinder site together with other evidence of weathering indicates that unaltered rock surfaces are rare on mars

cosmogenic 10be and 26al exposure ages of tors and erratics cairngorm mountains scotland timescales for the development of a classic landscape of selective linear glacial erosion abstract the occurrence of tors within glaciated regions has been widely cited as evidence for the preservation of relic pre quaternary landscapes beneath protective covers of non erosive dry based ice here we test for the preservation of pre quaternary landscapes with cosmogenic surface exposure dating of tors numerous granite tors are present on summit plateaus in the cairngorm mountains of scotland where they were covered by local ice caps many times during the pleistocene cosmogenic 10be and 26al data together with geomorphic relationships reveal that these landforms are more dynamic and younger than previously suspected many cairngorm tors have been bulldozed and toppled along horizontal joints by ice motion leaving event surfaces on tor remnants and erratics that can be dated with cosmogenic nuclides as the surfaces have been subject to episodic burial by ice an exposure model based upon ice and marine sediment core proxies for local glacial cover is necessary to interpret the cosmogenic nuclide data exposure ages and weathering characteristics of tors are closely correlated glacially modified tors and boulder erratics with slightly weathered surfaces have 10be exposure ages of about 15 to 43 ka nuclide inheritance is present in many of these surfaces correction for inheritance indicates that the eastern cairngorms were deglaciated at 15 6 0 9 ka glacially modified tors with moderate to advanced weathering features have 10be exposure ages of 19 to 92 ka these surfaces were only slightly modified during the last glacial cycle and gained much of their exposure during the interstadial of marine oxygen isotope stage 5 or earlier tors lacking evidence of glacial modification and exhibiting advanced weathering have 10be exposure ages between 52 and 297 ka nuclide concentrations in these surfaces are probably controlled by bedrock erosion rates instead of discrete glacial events maximum erosion rates estimated from 10be range from 2 8 to 12 0 mm ka with an error weighted mean of 4 1 0 2 mm ka three of these surfaces yield model exposure plus burial ages of 295 71 84 520 141 178 and 626 85 102 ka a vertical cosmogenic nuclide profile across the oldest sampled tor indicates a long term emergence rate of 31 2 mm ka these findings show that dry based ice caps are capable of substantially eroding tors by entraining blocks previously detached by weathering processes bedrock surfaces and erratic boulders in such settings are likely to have nuclide inheritance and may yield erroneous too old exposure ages while many cairngorm tors have survived multiple glacial cycles rates of regolith stripping and bedrock erosion are too high to permit the widespread preservation of pre quaternary rock surfaces

outgassed water on mars constraints from melt inclusions in snc meteorites the snc shergottite nakhlite chassignite meteorites thought to be igneous rocks from mars contain melt inclusions trapped at depth in early formed crystals determination of the pre eruptive water contents of snc parental magmas from calculations of the solidification histories of these amphibole bearing inclusions indicates that martian magmas commonly contained 1 4 percent water by weight when combined with an estimate of the volume of igneous materials on mars this information suggests that the total amount of water outgassed since 3 9 billion years ago corresponds to global depths on the order of 200 meters this value is significantly higher than previous geochemical estimates but lower than estimates based on erosion by floods these results imply a wetter mars interior than has been previously thought and support suggestions of significant outgassing before formation of a stable crust or heterogeneous accretion of a veneer of cometary matter

stable oxygen isotope and pollen records from eastern scotland and a consideration of late glacial and early holocene climate change for europe the presence of marl deposits belonging to the lateglacial period in a former lake basin at lundin tower in fife scotland has allowed palaeoenvironmental investigations by means of carbonate 13c and 18o and organic matter 13c in addition to palynology the variations that emerge reveal strong similarities between the pollen and isotope records and these are interpreted as reflecting climatic shifts the classic late glacial pattern of oldest dryas bolling older dryas allerod younger dryas may be evident and other climatic oscillations are shown to have occurred not only during the allerod but also in the preboreal the problem of the time discordance between isotopic change and pollen representation is addressed through explanations involving lags in plant colonization a comparison of the 18o records from 43 sites across europe reveals two different regional patterns which raises fundamental questions over the nature of late glacial palaeoclimates

chemically striking regions on mars and stealth revisited 1 the mars odyssey gamma ray spectrometer suite has yielded global chemical information for mars in this work we establish regions of unusual chemical composition relative to average mars primarily on the basis of ca cl fe h k si and th using data from mars odyssey the mars exploration rovers the mars reconnaissance orbiter imaging and 3 5 cm and 1 35 cm radar observations from earth we examine a chemically striking 2 e6 km2 region and find it to overlap significantly with a radar stealth region on mars it is remarkably enriched in cl and depleted in fe and si along with minor variations in h k and th relative to average mars surface dust observed at the two rover sites mixed with and indurated by ca mg bearing sulfate salts would be a reasonable chemical and physical analog to meter scale depths we describe potential scenarios that may have contributed to the unique properties of this region the bulk dust component may be an air fall deposit of compositionally uniform dust as observed in situ hydrothermal acid fog reactions on the flanks of nearby volcanoes may have generated sulfates with subsequent deflation and transport alternatively sulfates may have been produced by low temperature regional scale activity of ground ice driven brine and or regional scale deposition of acidified h2o snowfall

the direction of fluid flow during contact metamorphism of siliceous carbonate rocks new data for the monzoni and predazzo aureoles northern italy and a global review periclase formed in siliceous dolomitic marbles during contact metamorphism in the monzoni and predazzo aureoles the dolomites northern italy by infiltration of the carbonate rocks by chemically reactive h2o rich fluids at 500 bar and 565 710 c the spatial distribution of periclase and oxygen isotope compositions is consistent with reactive fluid flow that was primarily vertical and upward in both aureoles with time integrated flux 5 000 and 300 mol fluid cm2 rock in the monzoni and predazzo aureoles respectively the new results for monzoni and predazzo are considered along with published studies of 13 other aureoles to draw general conclusions about the direction amount and controls on the geometry of reactive fluid flow during contact metamorphism of siliceous carbonate rocks flow in 12 aureoles was primarily vertically upward with and without a horizontal component directed away from the pluton fluid flow in two of the other three was primarily horizontal directed from the pluton into the aureole the direction of flow in the remaining aureole is uncertain earlier suggestions that fluid flow is often horizontal directed toward the pluton are likely explained by an erroneous assumption that widespread coexisting mineral reactants and products represent arrested prograde decarbonation reactions with the exception of three samples from one aureole time integrated fluid flux was in the range 102 104 mol cm2 both the amount and direction of fluid flow are consistent with hydrodynamic models of contact metamorphism the orientation of bedding and lithologic contacts appears to be the principal control over whether fluid flow was either primarily vertical or horizontal other pre metamorphic structures including dikes faults fold hinges and fracture zones served to channel fluid flow as well

effects of h2o ph and oxidation state on the stability of fe minerals on mars 1 on mars there is evidence that solutions may have been present on the surface episodically in the past these solutions were derived by weathering minerals such as olivine and sulfides found in mafic ultramafic rocks and possibly sulfates and meteorite fragments upon removal of water and or supersaturation of solutions secondary minerals formed we present a theoretical model for the formation of the solutions and the subsequent precipitation of fe bearing phases the first fe bearing phases to weather via oxidation are sulfides troilite or pyrrhotite which produce secondary fe hydr oxides or fes 2 pyrite or marcasite and fe 2 sulfates such as melanterite melanterite may be replaced by fe sulfates that have decreasing h 2 o 3fe 3 2fe 2 increasing oxidation and increasing bulk oh oh 2so 4 at meridiani planum the presence of jarosite indicates that the solutions were oxidized with ph 4 5 the solutions were likely fe mg ca s04 cl rich and precipitated fe hydr oxides fe phosphates fe sulfates with low oh oh so 4 ca mg sulfates and possible halides along with si rich phases the minerals indicating an acid environment were preserved by either removing components such as salts or water from the system e g in dust storms or episodic aqueous events isolating the mineral surfaces from fluids using disequilibrium processes or a combination at other localities jarosite is below detection limits and schwertmannite may be present if schwertmannite is present the solution had near neutral ph 4 ph 10 and fe hydr oxides would have crystallized rapidly leaving mg na ca s04 cl rich solutions that likely precipitated ca phosphates ca mg na sulfates fe sulfates with moderate high oh oh so 4 halides si rich phases and possibly fe mg ca carbonates

a global view of martian surface compositions from mgs tes thermal emission spectrometer tes data from the mars global surveyor mgs are used to determine compositions and distributions of martian low albedo regions two surface spectral signatures are identified from low albedo regions comparisons with spectra of terrestrial rock samples and deconvolution results indicate that the two compositions are a basaltic composition dominated by plagioclase feldspar and clinopyroxene and an andesitic composition dominated by plagioclase feldspar and volcanic glass the distribution of the two compositions is split roughly along the planetary dichotomy the basaltic composition is confined to older surfaces and the more silicic composition is concentrated in the younger northern plains

pattern style and timing of british irish ice sheet retreat shetland and northern north sea sector the offshore sector around shetland remains one of the least well studied parts of the former british irish ice sheet with several long standing scientific issues unresolved these key issues include i the dominance of a locally sourced shetland ice cap vs an invasive fennoscandian ice sheet ii the flow configuration and style of glaciation at the last glacial maximum i e terrestrial vs marine glaciation iii the nature of confluence between the british irish and fennoscandian ice sheets iv the cause style and rate of ice sheet separation and v the wider implications of ice sheet uncoupling on the tempo of subsequent deglaciation as part of the britice chrono project we present new geological seabed cores geomorphological marine geophysical and geochronological data from the northernmost sector of the last british irish ice sheet north of 59 5 n to address these questions the study area covers ca 95 000 km2 an area approximately the size of ireland and includes the islands of shetland and the surrounding continental shelf some of the continental slope and the western margin of the norwegian channel we collect and analyse data from onshore in shetland and along key transects offshore to establish the most coherent picture so far of former ice sheet deglaciation in this important sector alongside new seabed mapping and quaternary sediment analysis we use a multi proxy suite of new isotopic age assessments including 32 cosmogenic nuclide exposure ages from glacially transported boulders and 35 radiocarbon dates from deglacial marine sediments to develop a synoptic sector wide reconstruction combining strong onshore and offshore geological evidence with bayesian chronosequence modelling the results show widespread and significant spatial fluctuations in size shape and flow configuration of an ice sheet ice cap centred on or to the east of the orkney shetland platform between 30 and 15 ka bp at its maximum extent ca 26 25 ka bp this ice sheet was coalescent with the fennoscandian ice sheet to the east between 25 and 23 ka bp the ice sheet in this sector underwent a significant size reduction from ca 85 000 to 50 000 km2 accompanied by several ice margin oscillations soon after connection was lost with the fennoscandian ice sheet and a marine corridor opened to the east of shetland this triggered initial and unstable re growth of a glaciologically independent shetland ice cap ca 21 20 ka bp with a strong east west asymmetry with respect to topography ice mass growth was followed by rapid collapse from an area of ca 45 000 km2 to ca 15 000 km2 between 19 and 18 ka bp stabilizing at ca 2000 km2 by 17 ka bp final deglaciation of shetland occurred ca 17 15 ka bp and may have involved one or more subsidiary ice centres on now submerged parts of the continental shelf we suggest that the unusually dynamic behaviour of the northernmost sector of the british irish ice sheet between 21 and 18 ka bp characterized by numerous extensive ice sheet ice mass readvances rapid loss and flow redistributions was driven by significant changes in ice mass geometry ice divide location and calving flux as the glaciologically independent ice cap adjusted to new boundary conditions we propose that this dynamism was forced to a large degree by internal glaciological factors specific to the strongly marine influenced shetland ice cap

quantitative compositional analysis of martian mafic regions using the mex omega reflectance data 2 petrological implications abstract the primary objectives of this paper are to determine the modal mineralogy of selected low albedo terrains of different ages ranging from noachian to amazonian exposed on the surface of mars this analysis is conducted using the spectral modeling of the observatoire pour la mineralogie l eau les glaces et l activite omega reflectance data results from this work are consistent with the major results of previous spectroscopic studies plagioclase 40 60 in volume and high calcium pyroxene 20 40 hcp are the dominant minerals of the most regions low calcium pyroxene 10 15 lcp and minor amounts of olivine are also present the oldest terrains are characterized by the largest amount of lcp and the lowest concentration of plagioclase these overall compositions are consistent with two pyroxene basalts the particle sizes are in the range of a few hundreds of micrometers which is in good agreement with the thermal inertia of the martian low albedo regions in the region around the nili fossae localized concentrations of olivine up to 40 with millimeter particle size similar to picritic basalts observed in situ by the spirit rover in the gusev crater are inferred chemical compositions are calculated for the first time from omega spectra they are quite consistent with gusev rocks and shergottite compositions but they appear to be significantly sio2 poorer than thermal emission spectrometer data a decreasing low calcium pyroxene abundance with the decreasing age of the low albedo regions is reported this may be indicative of decreasing degree of partial melting as thermal flux decreases with time we propose that the ancient noachian aged lcp rich terrains could have been formed from h2o bearing melts then dry basaltic volcanism occurred leading to decreasing lcp abundance with time due to decreasing degree of partial melting the olivine bearing material modeled in nili fossae resembles the composition of alh77005 and chassigny meteorites consistent with prior studies implications on the formation of the basaltic shergottites are discussed

palaeolimnological approaches to climate change with special regard to the biological record abstract lakes systems respond physically chemically and biologically to changes in climate and these responses are registered in many various ways in lake sediment records this paper focuses principally on the biological record and describes recent research that aims to reconstruct i past variability in effective moisture and ii past variability in temperature changes in effective moisture are manifested especially by changes in lake water level in closed lake basins water level change can cause significant changes in water salinity that is registered in sediments by changes in the composition of fossil assemblages especially diatoms in open freshwater lake basins changes in water level are best reconstructed from the aquatic macrofossil record and potentially from the ratio of open water to littoral species of cladocera ostracods and diatoms the most promising biological method for reconstructing past temperature is chironomid analysis and a range of new chironomid temperature transfer functions are being developed however biological responses to changing temperature are usually indirect as a result of temperature effects on water column stratification nutrient cycling and alkalinity generation and in most cases a correct interpretation of the climatic significance of changes in the fossil record requires an understanding of the processes that are operating in the water column a multi proxy whole lake approach is advocated as the best way forward not only as a means of reconstructing past climate but also as a means of assessing the impact of climate change on lake systems

growth and deformation mechanisms of talc along a natural fault a micro nanostructural investigation this paper documents the occurrence of large amounts of talc within a continental normal fault the talc in reaction is deformation enhanced and occurs by the interaction between dolostones and silica rich hydrothermal fluids in the high strain foliated fault core talc forms an interconnected network of oriented 001 lamellae 200 300 nm thick locally associated with minor tremolite fibres up to 300 nm in diameter the talc structure is affected by several strain induced defects among which 001 interlayer delamination that produces talc sublamellae down to 10 30 nm thick micro nanostructural observations definitely point to a predominant deformation mechanism of 001 frictional sliding further enhanced by pervasive delamination that gives rise to an almost infinite number of possible sliding surfaces these effects have fundamental implications in fault mechanics resulting in significant fault weakening

persistence of pre metamorphic c and o isotopic signatures in marbles subject to pan african granulite facies metamorphism and u th mineralization tranomaro southeast madagascar abstract the status of fluid regimes during the pan african granulite facies metamorphism in southern madagascar was examined by means of a mineralogical and stable isotope study of marble lithologies in the granulitic tranomaro area which is made up of metasedimentary rocks metapelitic leptynitic felsic and calc silicate metasediments and intruded by syn granulitic granitic bodies syn granulitic mineralization th u and metasomatic transformations marbles pyroxenites demonstrate that fluid circulation has occurred the tranomaro marbles can be subdivided into two compositional groups either mg poor or mg rich this division reflects pre metamorphic compositional differences rather than different p t x co 2 histories on a regional scale the marbles display a large variation in 18 o from 19 to 6 5 relative to smow but have a more restricted 13 c range from 1 4 to 2 5 relative to pdb the lowest 18 o values are observed in magnesian marbles whereas calcic ones do not have 18 o values lower than 13 5 both initially low and high 18 o marbles may have locally been infiltrated by the syn metamorphic fluid flow which gave rise to pyroxenites and th u ores thorianite 18 o values of carbonate in mg rich marbles evolve from 7 up to 8 5 towards the contact with a metasomatic pyroxenite in a meter scale profile across an infiltration zone the mineralogy as well as the large and small scale isotopic results argue for i a pre metamorphic origin for the isotopic variations probably related to pre granulitic dolomitization ii a lack of pervasive fluid infiltration capable of erasing pre metamorphic isotopic compositional differences iii an absence of mantle derived c bearing fluids in the infiltrated zones for the area as a whole the present data are consistent with the decarbonation of impure siliceous limestones and dolostones coupled with fluid release from syn metamorphic granitic intrusions

chassigny petrogenesis melt compositions intensive parameters and water contents of martian magmas abstract the snc meteorites are a class of eight basaltic achondrites that have extremely young crystallization ages 1 3 ga chassigny a unique snc meteorite is a dunite containing fo68 olivines and rare poikilitic ca pyroxenes it is one of the most primitive snc meteorites and thus is most likely to reveal information about the snc basalt source region this study presents a detailed examination of partially crystallized melt inclusions in cumulus olivine grains in chassigny these trapped melts are argued to be representative samples of the melt that existed when chassigny crystallized this melt has been modified however by interaction with the host olivine and by closed system crystallization the phases inside the melt inclusions include hydrous ti rich amphibole kaersutite biotite two pyroxenes and rhyolitic and alkali feldspar glasses all phases have been extensively analyzed with an electron microprobe the new mineralogical information is combined with a complementary experimental study of kaersutite melt equilibria this combined data set can be used to formulate a system of linear equations which can then be solved to determine the composition of the originally trapped melt this calculation reveals that the trapped melt was an feo rich and al2o3 poor basalt the melt composition is shown to be consistent with the crystallization sequence both inside the melt inclusions and in the rock matrix the major element chemistry of this liquid closely resembles terrestrial boninite lavas the new data also allow the intensive conditions temperature total pressure and water fugacity of chassigny crystallization to be estimated two pyroxene geothermometry indicates that equilibration temperatures were 1000 50 c although amphibole does not coexist with melt until t 960 c the trapped liquid initially contained 1 5 wt dissolved water crystallization of anhydrous phases caused water to buildup in the trapped melt prior to kaersutite crystallization the melt must have contained at least 4 wt dissolved water suggesting that a minimum of 1 5 kbar total pressure is required a maximum total pressure cannot be inferred but all available data are consistent with low pressure 5 kbar crystallization finally x h2o in the fluid in the melt inclusion is estimated to have been at least 0 8 in order to stabilize amphibole without plagioclase implying that the water fugacity was 1480 bars the existence of hydrous melts and conditions appropriate for amphibole crystallization suggest that evolved sio2 rich lavas exist on the chassigny parent body mars

the chemical composition of martian soil and rocks returned by the mobile alpha proton x ray spectrometer preliminary results from the x ray mode the alpha proton x ray spectrometer apxs on board the rover of the mars pathfinder mission measured the chemical composition of six soils and five rocks at the ares vallis landing site the soil analyses show similarity to those determined by the viking missions the analyzed rocks were partially covered by dust but otherwise compositionally similar to each other they are unexpectedly high in silica and potassium but low in magnesium compared to martian soils and martian meteorites the analyzed rocks are similar in composition to terrestrial andesites and close to the mean composition of earth s crust addition of a mafic component and reaction products of volcanic gases to the local rock material is necessary to explain the soil composition

the impact of the north atlantic ocean on the younger dryas climate in northwestern and central europe the main results of multiproxy climate reconstructions for the younger dryas and experiments carried out with an atmospheric general circulation model are discussed quantitative temperature inferences for northwestern and central europe show that winter conditions were remarkably extreme with values of 20 30 c below that of today annual temperature ranges with a continental signature 30 34 c were reconstructed for the entire study area compared with today the greatest cooling was experienced in the seaboard area the comparison of the climate reconstructions and simulation experiments indicates that sea ice in the north atlantic ocean played a decisive role in the climate of the study area by cooling the surface air temperatures and by controlling the position of the storm track surface air circulation was westerly even during younger dryas winters a slight northward shift of the mean atlantic sea ice margin during winter may explain the proposed subdivision of the younger drays into a phase of maximum cold and humidity succeeded by a less cold and relatively dry phase 1998 john wiley sons ltd

hematite pyroxene and phyllosilicates on mars implications from oxidized impact melt rocks from manicouagan crater quebec canada visible and near ir reflectivity mossbauer and x ray diffraction data were obtained on powders of impact melt rock from the manicouagan impact crater located in quebec canada the iron mineralogy is dominated by pyroxene for the least oxidized samples and by hematite for the most oxidized samples phyllosilicate smectite contents up to 15 wt were found in some heavily oxidized samples nanophase hematite and or paramagnetic ferric iron is observed in all samples no hydrous ferric oxides e g goethite lepidocrocite and ferrihydrite were detected which implies the alteration occurred above 250 c oxidative alteration is thought to have occurred predominantly during late stage crystallization and subsolidus cooling of the impact melt by invasion of oxidizing vapors and or solutions while the impact melt rocks were still hot the near ir band minimum correlated with the extent of aleration fe3 fetot and ranged from 1000 nm high ca pyroxene to 850 nm bulk well crystalline hematite for least and most oxidized samples respectively intermediate band positions 900 920 nm are attributed to low ca pyroxene and or a composite band from hematite pyroxene assemblages manicouagan data are consistent with previous assignments of hematite and pyroxene to the 850 and 1000 nm bands observed in martian reflectivity spectra manicouagan data also show that possible assignments for intermediate band positions 900 920 nm in martian spectra are pyroxene and or hematite pyroxene assemblages by analogy with impact melt sheets and in agreement with observables for mars oxidative alteration of martian impact melt sheets above 250 c and subsequent erosion could produce rocks and soils with variable proportions of hematite both bulk and nanophase pyroxene and phyllosilicates as iron bearing mineralogies if this process is dominant these phases on mars were formed rapidly at relatively high temperatures on a sporadic basis throughout the history of the planet the manicouagan samples also show that this mineralogical diversity can be accomplished at constant chemical composition which is also indicated for mars from analyses of soil at the two viking landing sites

spectral evidence for weathered basalt as an alternative to andesite in the northern lowlands of mars mineral abundances derived from the analysis of remotely sensed thermal emission data from mars have been interpreted to indicate that the surface is composed of basalt surface type 1 and andesite surface type 2 1 the global distribution of these rock types is divided roughly along the planetary dichotomy which separates ancient heavily cratered crust in the southern hemisphere basalt from younger lowland plains in the north andesite 1 but the existence of such a large volume of andesite is difficult to reconcile with our present understanding of the geological evolution of mars here we reinterpret martian surface rock lithologies using mineral abundances from previous work1 and new mineralogies derived from a spectral end member set representing minerals common in unaltered and low temperature aqueously altered basalts our results continue to indicate the dominance of unaltered basalt in the southern highlands but reveal that the northern lowlands can be interpreted as weathered basalt as an alternative to andesite the coincidence between locations of such altered basalt and a suggested northern ocean basin implies that lowland plains material may be composed of basalts weathered under submarine conditions or weathered basaltic sediments transported into this depocentre

determination of the chemical composition of martian soil and rocks the alpha proton x ray spectrometer the alpha proton x ray spectrometer apxs for the mars pathfinder mission is designed to provide a complete and detailed analysis of chemical elements in martian soil and rocks near the landing site the apxs instrument is carried on the pathfinder microrover which will provide transportation to places of interest on the martian surface it consists of a complex sensor head mounted on a simple but sophisticated apxs deployment mechanism adm outside the warm electronics box web of the microrover and the instrument electronics mounted inside the web the adm permits the instrument sensor head to be placed against soil and rock samples in arbitrary positions ranging from horizontal to vertical in order to perform in situ analysis the possibility to transport the apxs to an arbitrary location preselected on earth and to perform in situ analysis there constitutes one of the most exciting aspects of the pathfinder mission the principle of the apxs technique is based on three interactions of alpha particles from a radioisotope source with matter simple rutherford backscattering production of protons from p reactions on light elements and generation of characteristic x rays upon recombination of atomic shell vacancies created by a bombardment measurement of the intensities and energy distributions of these three components yields information on the abundance of chemical elements in the sample in terms of sensitivity and selectivity data are partly redundant and partly complementary alpha backscattering is superior for light elements c o while proton emission is mainly sensitive to na mg al si s and x ray emission is more sensitive to heavier elements na to fe and beyond a combination of all three measurements enables determination of all elements with the exception of h and he present at concentration levels above typically a fraction of 1

abrupt increase in greenland snow accumulation at the end of the younger dryas event the warming at the end of the last glaciation was characterized by a series of abrupt returns to glacial climate the best known of which is the younger dryas event1 despite much study of the causes of this event and the mechanisms by which it ended many questions remain unresolved1 oxygen isotope data from greenland ice cores2 4 suggest that the younger dryas ended abruptly over a period of about 50 years dust concentrations2 4 in these cores show an even more rapid transition 20 years this extremely short timescale places severe constraints on the mechanisms underlying the transition but dust concentrations can reflect subtle changes in atmospheric circulation which need not be associated with a large change in climate here we present results from a new greenland ice core gisp2 showing that snow accumulation doubled rapidly from the younger dryas event to the subsequent preboreal interval possibly in one to three years we also find that the accumulation rate change from the oldest dryas to the bo11ing allerod warm period was large and abrupt the extreme rapidity of these changes in a variable that directly represents regional climate implies that the events at the end of the last glaciation may have been responses to some kind of threshold or trigger in the north atlantic climate system

dynamic early holocene vegetation development on the faroe islands inferred from high resolution plant macrofossil and pollen data vegetation dynamics during the earliest part of the holocene 11 250 10 250 cal yr bp have been reconstructed from a lacustrine sequence on sandoy the faroe islands using detailed plant macrofossil and pollen evidence the plant macrofossils suggest the initial vegetation was sparse herb and shrub tundra with salix herbacea and open ground species followed by the development of a denser and more species rich arctic heathland after 11 150 cal yr bp despite high pollen values for betula nana macrofossils are rare the bulk of the macrofossils recorded are s herbacea and empetrum leaves with numerous herb taxa and an abundance of racomitrium moss conditions start to change around 10 800 cal yr bp with increased catchment erosion and sediment delivery to the lake from ca 10 600 cal yr bp and a transition to alternating cyperaceae and poaceae communities between ca 10 450 and 10 250 cal yr bp this vegetation change which has been recorded throughout the faroes has previously been interpreted as a retrogressive shift from woody shrubs to a herbaceous community the detailed plant macrofossil data show the shift is the replacement of an empetrum arctic heathland by grassland and moist sedge communities these taxa dominate the modern landscape c 2009 university of washington published by elsevier inc all rights reserved less

fluid inclusion and stable isotope constraints c o h on the dagbasi fe cu zn skarn mineralization trabzon ne turkey abstract the dagbasi fe cu zn skarn mineralization developed along the contact between the block and lens shaped limestones of the lower cretaceous berdiga formation and the upper cretaceous dagbasi granitoid the exoskarn type mineralization is characterized by prograde stage garnet and pyroxene while the retrograde stage is characterized by epidote tremolite actinolite and chlorite quartz and calcites were observed in both stages of the skarn development the ore minerals mainly consist of magnetite and hematite with a lesser amount of pyrrhotite pyrite chalcopyrite sphalerite and minor galena the homogenization temperatures th and salinity values of the prograde stage halite bearing fluid inclusions are in the range of 412 514 c and 48 8 61 8 wt nacl equ respectively the second stage liquid and vapor rich fluid inclusion assemblage reveals that boiling at temperatures of 353 458 c took place after the formation of halite bearing fluid inclusions final stage liquid rich fluid inclusions were characterized by low th 160 and 327 c and salinity values 0 5 and 6 2 wt nacl equ the decreasing salinity trend of the fluid inclusions versus th indicated that meteoric water was involved in the hydrothermal solutions eutectic temperatures te of the prograde stage fluid inclusions were found to be cacl2 dominated while retrograde stage inclusions contained different salt combinations rather than a specific salt type the minimum trapping pressures of the early stage brine fluid inclusions were calculated to be between 710 and 884 bar while later stage inclusions had much lower trapping pressures between 195 and 445 bar the 18o isotopes of prograde stage quartz garnet and pyroxenes are close to the composition of the hydrothermal solutions of magmatic sources moreover retrograde stage quartz epidote tremolite actinolite and calcite minerals and their equilibrated solutions were found to be highly depleted by 18o isotopes therefore the fluid inclusion and stable isotope constraints suggest that the hydrothermal solutions of magmatic origin were responsible for the prograde skarn stage while a mixture of magmatic and meteoric solutions were responsible for the ore formation in a shallow skarn environment

development of interconnected talc networks and weakening of continental low angle normal faults fault zones that slip when oriented at large angles to the maximum compressive stress i e weak faults represent a significant mechanical problem here we document fault weakening induced by dissolution of dolomite and subsequent precipitation of calcite abundant talc along a low angle normal fault within the fault core talc forms an interconnected foliated network that deforms by frictional sliding along 50 200 nm thick talc lamellae the low frictional strength of talc combined with dissolution precipitation creep can explain slip on low angle normal faults in addition the stable sliding behavior of talc is consistent with the absence of strong earthquakes along such structures the development of phyllosilicates such as talc by fluid assisted processes within fault zones cutting mg rich carbonate sequences may be widespread leading to profound and long term fault weakness

lateglacial and early holocene climates of the atlantic margins of europe stable isotope mollusc and pollen records from orkney scotland the margins of mainland europe and especially those areas coming under the influence of north atlantic weather systems are ideally placed to record changing palaeoclimates cores from an infilled lake basin at crudale meadow in mainland orkney revealed basal deposits of calcareous mud marl beneath sedge peat stable isotope palynological and molluscan analyses allowed the establishment of palaeoenvironmental changes through the devensian lateglacial and the early holocene the 18omarl record exhibited the existence of possibly four climatic oscillations in the lateglacial one of which within event cf gi 1c is not often commented upon as well as the preboreal oscillation and other holocene perturbations the cold episodes succeeding the preboreal oscillation were demarcated conservatively and one of these event c5 11 0 ka may have previously been unremarked while the putative 9 3 and 8 2 ka events seem not to produce corresponding palynologically visible floristic changes the events at crudale meadow are consistent with those recorded at other sites from britain ireland and elsewhere and can be correlated with isotopic changes shown by the greenland ice cores the multi proxy approach enriches the environmental reconstructions from the site although the synchronicity of the response of the various proxies is sometimes equivocal depending upon the time period concerned taphonomy and the nature of the deposits the site may contain the most northerly lateglacial isotope record from northwest europe and it has yielded one of the best archives for the demonstration of abrupt early holocene events within britain

carbon and oxygen isotope records from the southern eurasian seaway following the triassic jurassic boundary parallel long term enhanced carbon burial and seawater warming abstract fossil shells of benthos and nektobenthos have been shown to be faithful recorders of seawater carbon and oxygen isotope geochemistry and thus also useful to track the relationship between carbon cycle and palaeotemperature in this study we present an extensive dataset from lower jurassic hettangian and lower sinemurian mollusc and brachiopod hard parts collected from biostratigraphically well calibrated uk coastal outcrops bristol channel and hebrides basins these basins lay palaeogeographically in the southern part of the laurasian seaway that connected the tethys and boreal oceans all samples have been subject to screening for diagenesis on the basis of elemental composition light microscopy and sem observations in the case of some localities within the hebrides basin alteration by hydrothermal systems around paleogene intrusions has led to re setting of carbonate oxygen isotopes but the original carbon isotope values from the shells are largely preserved above the prominent and apparently short lived 3 per mil 13ccarb amplitude positive carbon isotope excursion cie that occurs immediately above the triassic jurasic t j boundary in the tilmanni ammonite biozone a pronounced negative cie the so called main negative cie spans the entire hettangian stage at the hettangian sinemurian boundary and through the lower sinemurian the carbon isotope values of the skeletal carbonate again trend towards progressively more positive values but representing a time of several million years the heaviest 13ccarb values of about 4 3 per mil are evident towards the top of the lower sinemurian and are comparable with values observed from the tilmanni zone and from the lower toarcian higher in the jurassic this long term positive hump which confirms trends derived from bulk organic matter carbon isotope records is supporting evidence of prolonged enhanced organic carbon burial that is inferred to have occurred in the extensive system of lacustrine and marine rifts that traversed a fragmenting pangaea after emplacement of the central atlantic magmatic province in parallel oxygen isotope values of the skeletal carbonate show a continuous downward trend from the lower part of the hettangian 1 per mil 18ocarb in the planorbis zone to the top of the lower sinemurian 2 5 per mil 18ocarb in the higher turneri zone oxygen isotope values may be interpreted as due to gradually increasing palaeotemperature and or addition of a meteoric or cryospheric water component in the case of the laurasian seaway palaeoceanographic and palaeoecological considerations point towards a dominant palaeotemperature signal consequently any atmospheric carbon dioxide drawdown effect on global palaeotemperatures as suggested by progressively increasing 13ccarb values and assuming a constant silicate weathering sink was more than counterbalanced in the seaway by regional processes that led to significantly warmer bottom water temperatures

apxs derived chemistry of the bagnold dune sands comparisons with gale crater soils and the global martian average we present apxs data for the active bagnold dune field within the gale impact crater msl mission we derive an apxs based average basaltic soil abs composition for mars based on past and recent data from the msl and mer missions this represents an update to the taylor and mclennan 2009 average martian soil and facilitates comparison across martian datasets the active bagnold dune field is compositionally distinct from the abs with elevated mg ni and fe suggesting mafic mineral enrichment and uniformly low levels of s cl and zn indicating only a minimal dust component a relationship between decreasing grain size and increasing felsic content is revealed the bagnold sands possess the lowest s cl of all martian unconsolidated materials gale soils exhibit relatively uniform major element compositions similar to meridiani planum and gusev crater basaltic soils mer missions however they show minor enrichments in k cr mn and fe which may signify a local contribution the lithified eolian stimson formation within the gale impact crater is compositionally similar to the abs and bagnold sands which provide a modern analogue for these ancient eolian deposits compilation of apxs derived soil data reveals a generally homogenous global composition for martian soils but one that can be locally modified due to past or extant geologic processes that are limited in both space and time

chemical composition of martian soil and rocks complex mixing and sedimentary transport chemical compositions of martian soil and rocks indicate complex mixing relationships mixing of rock and soil clearly takes place and explains some of the chemical variation because sulfur chlorine magnesium and perhaps iron are positively correlated due to their control from a secondary sedimentary mineralogy e g mg and possibly fesulfate fe oxides that is present within the soils certain deviations from simple soil rock mixing are consistent with mineralogical fractionation of detrital iron and titanium oxides during sedimentary transport

bounce rock a shergottite like basalt encountered at meridiani planum mars additional co authors thanasis economou steven p gorevan brian c hahn gostar klingelhofer timothy j mccoy harry y mcsween jr douglas w ming richard v morris daniel s rodionov steven w squyres heinrich wanke shawn p wright michael b wyatt albert s yen

spectroscopic evidence for hydrous iron sulfate in the martian soil 1 despite in situ analyses by several landers the composition of the martian soil remains unclear recently constituent minerals in the soil have been proposed from thermal emissivity and mossbauer spectroscopic data from mars these data were interpreted to show spectral evidence for carbonate and an unspecified mineral containing bound water as well as olivine here we present an alternative interpretation suggesting that these spectral features can be satisfied by a single type of mineral namely hydrous iron sulfates acidic waters necessary for production of hydrous iron sulfates would preclude carbonate formation and indicate a dramatically different chemical environment on mars in which olivine would be highly unstable and unlikely to survive soil formation regardless of its presence in the rocks hydrous iron sulfates are efflorescent salts and may be crusting agents in the martian soils

the behavior of li and b in lunar mare basalts during crystallization shock and thermal metamorphism implications for volatile element contents of martian basalts late stage rims of magmatic pyroxenes from some martian basalts show decreases in li and b contents relative to earlier formed pyroxene cores this behavior is different than expected from their documented incompatible element behavior previous workers interpreted such depletions to reflect the loss of several wt magmatic water during basalt crystallization this interpretation has profound implications for the nature of the martian mantle and recent exchange of volatiles between the martian mantle and atmosphere to assess alternative mechanisms that may influence the behavior of li and b in the absence of aqueous fluid activity the effects of changing pyroxene composition during crystallization shock pressure and shock associated thermal metamorphism were studied lithium and b depletions are documented in late stage rims of pyroxenes from anhydrous lunar basalts indicating that mechanisms other than aqueous fluid activity must have influenced li and b partitioning in these pyroxenes depletions of li and b are most likely associated with changing pyroxene composition during crystallization and occur in lunar and martian pyroxenes with late stage fe enrichment it is interesting that pyroxenes without late stage fe enrichment show no concomitant li and b increases lithium loss may occur during breakdown of metastable pyroxferroite additionally changes in cr content may influence the substitution mechanism involved for incorporating li shock does not redistribute li or b but may facilitate subsequent thermally driven diffusion by the introduction of mechanical defects in grains thermally metamorphosed pyroxenes exhibit higher li and lower b contents relative to unheated pyroxenes it is likely therefore that li and b are redistributed through interactions between pyroxenes and surrounding zones of mesostasis during thermal metamorphism

the devensian weichselian lateglacial palaeoenvironmental record from gransmoor east yorkshire england a contribution to the north atlantic seaboard programme of igcp 253 termination of the pleistocene abstract palynological and coleopteran data are described from a section through late devensian weichselian deposits at gransmoor east yorkshire england the pollen evidence shows that following an initial open habitat episode first juniperus scrub and later betula woodland became established in the area during the lateglacial interstadial this woodland was replaced during the loch lomond younger dryas stadial by a predominatly herbaceous flora with arctic alpine steppe and halophytic elements the coleopteran evidence indicates a similar local environment and that the thermal maximum of the interstadial when mean july temperatures may well have exceeded 18 c occurred prior to the deposition of the earliest polleniferous sediments by the time of the juniperus expansion summer temperatures had fallen by 2 4 c to levels comparable with those of the present day a further temperature decline followed the expansion of betula during the later interstadial and another fall occurred at the lateglacial interstadial loch lomond stadial boundary during the loch lomond stadial mean july temperatures of 9 11 c are implied with winter temperatures as low as 15 to 20 c collectively the evidence reemphasises the point that for the first 1000 years or so of the lateglacial interstadial there was a disequilibrium between the palynological and coleopteran records in terms of climatic signal during the later interstadial however a closer relationship is apparent between both proxy data sources of particular significance in this respect is the fluctuation in reconstructed summer and winter temperatures and a rise and subsequent fall in betula pollen frequencies this may be the correlative of one of the pre younger dryas climatic oscillations recorded in other proxy data sources including palynological records from britain and eastern canada oxygen isotope traces from swiss lake sediments isotopic and electrical conductivity profiles from the greenland ice sheet and diatom and foraminiferal records in cores from the norwegian sea and the north atlantic ocean

frictional properties of a low angle normal fault under in situ conditions thermally activated velocity weakening the zuccale fault is a regional low angle normal fault exposed on the isle of elba in central italy that accommodated a total shear displacement of 6 8 km the fault zone structure and fault rocks formed at 8 km crustal depth the present day fault structure is the final product of several deformation processes superposed during the fault history in this study we report results from a series of rotary shear experiments performed on 1 mm thick powdered gouges made from several fault rock types obtained from the zuccale fault the tests were done under conditions ranging from room temperature to in situ conditions i e at temperatures up to 300 c applied normal stresses up to 150 mpa and fluid saturated the ratio of fluid pressure to normal stress was held constant at either 0 4 or 0 8 to simulate an overpressurized fault the samples were sheared at a constant sliding velocity of 10 m s for at least 5 mm after which a velocity stepping sequence from 1 to 300 m s was started to determine the velocity dependence of friction this can be represented by the rate and state parameter a b which was determined by an inversion of the data to the rate and state equations friction of the various fault rocks varies between 0 3 and 0 8 similar to values obtained in previous studies and decreases with increasing phyllosilicate content friction decreases mildly with temperature whereas normal stress and fluid pressure do not affect friction values systematically all samples exhibited velocity strengthening conditionally stable behavior under room temperature conditions and a b increased with increasing sliding velocity in contrast velocity weakening accompanied by stick slips was observed for the strongest samples at 300 c and sliding velocities below 10 m s an increase in fluid pressure under these conditions led to a further reduction in a b for all samples so that they exhibited unstable stick slip behavior at low sliding velocity the results suggest that phyllosilicate bearing fault rocks can deform by stable aseismic creep at low resolved shear stress and low shear rate conditions an increase in fluid pressure or loading of stronger portions could lead to a runaway instability the runaway instability might be limited in size because of 1 the fault heterogeneity 2 the observed strengthening at higher sliding velocities and 3 a co seismic drop in pore fluid pressure

elemental dispersion and stable isotope fractionation during reactive fluid flow and fluid immiscibility in the bufa del diente aureole ne mexico evidence from radiographies and li b sr nd and pb isotope systematics the 31 6 0 3 ma old bufa del diente alkali syenite ne mexico intruded a sequence of cretaceous limestones with intercalated sub horizontal chert layers the cherts acted as aquifers that facilitated transport of brines and pegmatitic melts within the shallow level 1 kbar contact metamorphic aureole fluid driven reactions between chert and marble wallrock and the influx of late melts and various fluids gave rise to distinct chemical and isotopic signatures within the aquifer and across the zones of infiltration and fluid driven reaction aqueous brines of magmatic origin produced thick wollastonite mantles around the chert layers wollastonite formation occurred at the expense of limestone and chert and generated co2 this co2 induced fluid unmixing into an aqueous brine and a low density co2 rich fluid which was lost to the overlying marble where it oxidized organic matter and caused 13c and 18o shifts in a zone some 5 10 cm wide after wollastonite formation the chert aquifers were locally intruded by pegmatite veins carrying alkali feldspar quartz aegirine augite eudialyte zircon and apatite aqueous fluids that exsolved during crystallization of the pegmatite veins escaped along late cross fractures and migrated along the inner and outer borders of the wollastonite margins chemical dispersion patterns of u al na k p s fe and ree across the chert to marble boundary and its metasomatic rims are shown by autoradiography and neutron induced radiography scavenging of cations at mineralogical contacts and cation transport into the marbles occurred only on the mm to cm scale isotopic data for pb and sr across a simple metachert marble boundary and for pb sr nd b and li across a metachert pegmatite marble sequence demonstrate the following 1 the pb and sr isotopic signature of early fluids was buffered by the carbonate wallrock only late fluids shielded from wallrock interaction by a wollastonite mantle variably preserved a memory of their initial magmatic signature 2 since the nd isotope signature of marble and chert is bound to calcite and clay minerals systematic shifts to unradiogenic nd in marble reflect loss of carbonate bound nd as the wollastonite margin is approached nd in the wollastonite margin is dominated by nd originally bound to clay minerals the later emplacement of the pegmatite which carried the nd isotope signature of its alkali syenite source had little effect on the nd isotopic composition of the wollastonite rim 3 although the li and b isotopic compositions reflect the alkali syenite source they are also affected by isotopic fractionation and partitioning between melt fluid and solids

multiproxy devensian late glacial and holocene environmental records at an atlantic coastal site in shetland marine erosion at clettnadal west burra island off the west coast of shetland caused the drainage of a small water body at clettnadal exposing deposits of late devensian and holocene age pollen diatom and invertebrate analyses have provided variable records of environmental change during stratigraphical event gi 1 event gs 1 is revealed by the non pollen evidence especially by coleoptera by sediment stratigraphy and by radiocarbon dating in contrast the pollen evidence indicates that an arctic tundra flora in which dwarf shrubs were prominent persisted throughout the late glacial the holocene brought colonisation by tree birch but by ca 9000 14 c yr bp the taxon had almost disappeared this contrasts strongly with other holocene pollen records for shetland where both betula and corylus avellana type survived longer at some sites for example until ca 2900 yr bp the extreme westerly and exposed coastal situation of clettnadal appears to be responsible both for a muted late glacial response in the pollen record of terrestrial vegetation and for the early replacement of woodland by a maritime grassland the results provoke questions concerning biological stability at times of marked climatic change copyright 2003 john wiley sons ltd journal of quaternary science

fluid infiltration effects on stable isotope systematics of the susurluk skarn deposit nw turkey abstract a calcic skarn deposit occurs along the contact zone between oligo miocene cataldag granitoid and mesozoic limestones in susurluk northwestern turkey the skarn zone with little or no retrograde stage is represented by fluid inclusions with high homogenization temperatures up to 600 c and a wide range of salinity 12 to 70 wt nacl pluton derived fluids facilitated occurrence of continuous prograde reactions in the country rocks particularly in the proximal zone and oxygen isotopic depletion in calc silicate and calcite minerals 18o of anhydrous minerals within proximal and distal zones indicate that skarn forming fluids had a magmatic origin the 18o values are 5 93 9 08 mean 6 8 for garnet 4 08 9 94 mean 6 4 for pyroxene 4 89 7 92 mean 6 4 for wollastonite and 6 65 8 28 mean 7 5 for vesuvianite temperatures estimated by isotopic compositions of mineral pairs are significantly lower than those measured from the fluid inclusions indicating that isotopic equilibrium is not preserved between the skarn minerals 18o and 13c values are systematically depleted from marbles to skarn carbonates calc silicate forming reactions and permeability increase triggered by volatilization and consequent strong infiltration of h2o rich siliceous fluids into the system promoted fluid rock interaction causing isotopic resetting and isotopic depletion of silicates e g pyroxene and wollastonite and skarn calcites

quality of ptrm acquisition in pyrrhotite bearing contact metamorphic limestones possibility of a continuous record of earth magnetic field variations abstract the rockmagnetic and palaeomagnetic signal in pyrrhotite bearing limestones of different contact metamorphic settings were investigated related to intrusions ranging from small sills to large magmatic complexes magnetic susceptibility the pyrrhotite magnetite ratio and thermal modelling serve as an investigative tool to define three metamorphic zonations a contact zone of a mixed magnetic assemblage and low susceptibilities a pyrrhotite bearing transitional zone where full thermoremanent magnetisations trms are acquired due to temperatures above the curie temperature of pyrrhotite t c po and a marginal zone containing pyrrhotite and magnetite generated at temperatures below t c po the fact that trms can consist of independent ptrms is successfully tested by modified thellier experiments it is shown that a metamorphic environment with low fluid circulation provides a scenario for the recording of independent ptrms multicomponent behaviour of the nrm residing in samples from the transitional zone can therefore be interpreted as a continuous record of earth magnetic field variations

water in snc meteorites evidence for a martian hydrosphere the shergotty nakhla chassigny snc meteorites purportedly of martian origin contain 0 04 to 0 4 percent water by weight oxygen isotopic analysis can be used to determine whether this water is extraterrestrial or terrestrial such analysis reveals that a portion of the water is extraterrestrial and furthermore was not in oxygen isotopic equilibrium with the host rock lack of equilibrium between water and host rock implies that the lithosphere and hydrosphere of the snc parent body formed two distinct oxygen isotopic reservoirs if mars was the parent body the maintenance of two distinct reservoirs may result from the absence of plate tectonics on the planet

characteristics of the pathfinder apxs sites implications for the composition of martian rocks and soils an integrated study of spectral elemental abundance and image data from the pathfinder alpha proton x ray spectrometer apxs measurement sites has led to a better understanding of the nature of martian surface materials this rigorous analysis provides a new level of detail that forms the basis for the results reported here and that can be used by future scientists trying to understand rocks and soils on mars each apxs site has been precisely located by analyzing stereo imager for mars pathfinder imp and rover camera images to determine the position of the apxs during deployment rover and imp images are used to assess local geology namely the presence of pebbles clods and aeolian features in soils and surface textures and dust concentrations on rocks imp spectra using the latest calibrations for radiance and reflectance are analyzed at a number of different illumination geometries for each apxs site the three dimensional orientation of the sites has been determined and then used to compute the true sunlight incidence and viewing emission angles where suitable photometric coverage is available reflectances are fit to the hapke irvine function this is then used to adjust spectral reflectances to a normalized illumination geometry common to all rocks and soils comparing all the data sets shows a positive correlation among red blue reflectance ratio so3 content and dust abundance on rocks indicating that rocks are coated with varying amounts of sulfur rich red dust other elements such as silicon and iron are poor tracers for dust because their abundances within soil are similar to those within rock rock apxs targets that are bluer poorer in sulfur and have minimal dust coverage face toward the northeast the direction in which winds may be capable of efficiently removing loose material under current martian conditions the imp spectral properties of the soils show poor correlations with apxs elemental abundances on the basis of currently released apxs data bulk soils at the pathfinder landing site are richer in silica and sulfur than the viking landing sites suggesting a different composition the apxs soils with the most apparent pebbles are the poorest in sio2 indicating that either the pebbles are more mafic than the apxs rocks or the pebble free soil component is inherently enriched in sio2 compared to viking soils the mixture of materials at the apxs sites is a reflection of the overall complexity of martian surface materials a detailed understanding of which should drive the choice of future instruments and missions

acid sulfate weathering of synthetic martian basalt the acid fog model revisited the acid fog model has received considerable attention as a model of soil formation on mars previous evaluations of this model have focused on experimental weathering of terrestrial basalt samples however these samples differ significantly from what now is thought to be typical of martian basalt the acid fog model is tested here using synthetic basaltic analogs derived from mars pathfinder soil and rock compositions reaction of synthetic basalt with various acidic solutions and subsequent evaporation has led to the formation of several putative secondary mineral phases many of these phases were not produced in prior experimental studies aimed at aqueous interactions on mars of these alteration phases mg fe ca and al sulfates were identified in addition secondary ferric oxide phases formed via rapid fe oxidation under relatively high ph levels buffered by basalt dissolution amorphous silica is a ubiquitous product in these experiments and has formed by precipitation from solution and by the dissolution of minerals and glasses leaving behind leached surface layers composed of residual silica the secondary products formed in these experiments demonstrate the importance of primary mineralogy when testing models of aqueous interactions on mars new constraints are placed on both the reactivity of primary basalt and the secondary mineralogy present at the martian surface copyright 2004 by the american geophysical union

the preboreal oscillation around the nordic seas terrestrial and lacustrine responses the occurrence of an early preboreal climatic cooling oscillation pbo in lacustrine and glacial records from northwest europe iceland and greenland is reviewed and documented the often subtle response of the proxy records to this oscillation in combination with its short duration make it difficult to detect owing to its chronostratigraphic position between the 10 000 9900 and 9600 9500 14 c plateaux c 11 300 11 150 calendar yr bp it is also difficult to 14 c date with precision we find that the vegetation response to the pbo varies between sites and regions in contrast to the pioneer vegetation in iceland and southern sweden the expanding birch pine forest in germany denmark was more susceptible to deteriorating growing conditions the combined lacustrine tree ring and glacial records imply that the pbo was characterised by cool and humid conditions throughout northwestern and central europe this is documented by vegetation changes decreased aquatic production increased soil erosion increased 2 h and 13 c content in tree rings readvances or stillstands of the ice sheet in norway and finland and ingression of brackish water into the baltic icelandic proxy records from lake sediments and glacial moraines imply cooler conditions than during the previous preboreal period but not as extreme as during the younger dryas greenland records suggest that the early preboreal was characterised by ice readvances as an effect of cool climate and increased precipitation in relation to the younger dryas it was not until the end of the pbo that climate was warm enough to melt the land based ice sheet this preboreal oscillation found on both sides of the nordic seas is interpreted as an effect of increased freshwater forcing on the thermohaline circulation in the nordic seas which is implied by a simultaneous and distinct rise in the atmospheric 14 c 12 c ratio a slow down of the thermohaline circulation may tempor arily have pushed the polar front further south 1997 by john wiley sons ltd preboreal oscillation thermohaline circulation lacustrine records glacial records chronology

magnetic study of an antarctic weathering profile on basalt implications for recent weathering on mars abstract in order to better interpret the martian surface weathering related mineralogy we focused on a relevant analogue of the martian subsurface in terms of lithology and paleoclimate the jurassic aged ferrar dolerite priestley glacier transantarctic mountains weathered in cold and dry climate together with chemical and mineralogical studies rock magnetic properties were investigated and completed with mossbauer measurements weathering of the decimetric block is evidenced by chemical profiles showing an increase in fe content from 10 5 in the core to 13 wt in the surface and a decrease in si from 57 to 53 wt respectively according to mineralogical thermomagnetic and hysteresis properties the main opaque mineral is inherited titanomaghemite with a concentration about 1 enhancement in low field magnetic susceptibility from 4 10 6 to 10 10 6 m 3 kg respectively and saturation magnetization from 0 44 to 0 96 am 2 kg respectively indicates the neoformation of metastable maghemite neoformed red ferric oxy hydroxides are abundant in the surface high field susceptibility normalized to iron concentration and mossbauer spectra indicate a replacement of fe 2 from primary silicates pyroxene by poorly crystalline antiferromagnetic fe 3 oxy hydroxides thus highly magnetic titanomaghemite and maghemite coexist with nanosized ferric oxy hydroxides and primary silicates in accordance with martian in situ observations therefore this study supports the formation of the martian regolith as resulting from a slow weathering process in near present day conditions

chemical composition of martian fines of the 21 samples acquired for the viking x ray fluorescence spectrometer 17 were analyzed to high precision compared to typical terrestrial continental soils and lunar mare fines the martian fines are lower in al higher in fe and much higher in s and cl concentrations protected fines at the two lander sites are almost indistinguishable but concentration of the element s is somewhat higher at utopia duricrust fragments successfully acquired only at the chryse site invariably contained about 50 higher s than fines no elements correlate positively with s except cl and possibly mg a sympathetic variation is found among the triad si al ca positive correlation occurs between ti and fe sample variabilities are as great within a few meters as between lander locations 4500 km apart implying the existence of a universal martian regolith component of constant average composition the nature of the source materials for the regolith fines must be mafic to ultramafic

chemical compositions at mars landing sites subject to mars odyssey gamma ray spectrometer constraints 1 the mars odyssey gamma ray spectrometer grs is the first instrument suite to return elemental abundances throughout the midlatitudes of mars concentrations of cl fe h k si and th have been determined to tens of centimeter depths as mass fractions with reasonable confidence comparing such data with or normalizing them to in situ compositional data is difficult due to issues such as dramatic differences in spatial resolution difficulties in convolving densities abundances and compositions of different regolith components and a limited number of elements observed in common we address these concerns in the context of the grs using si at pathfinder to normalize remote data in addition we determine representative in situ compositions for spirit both with and without columbia hills rocks opportunity and viking 1 landing sites using grs derived h content to hydrate the soil component our estimate of the si mass fraction at pathfinder with 13 areal fraction of rocks is 21 the composition of major elements such as si and fe is similar across the four landing sites while minor elements show significant variability areal dominance of soil at all four landing sites causes representative compositions to be driven by the soil component while proportionally large uncertainties of bulk densities dominate the net uncertainties grs compositional determinations compare favorably with the in situ estimates for cl and k and for si by virtue of the normalization however the grs determined fe content at each landing site is consistently higher than the in situ value

mineral fluid equilibria in the system cao mgo sio2 h2o co2 nacl and the record of reactive fluid flow in contact metamorphic aureoles phase equilibria in the system cao mgo sio2 co2 h2o nacl are calculated to illustrate phase relations in metacarbonates over a wide range of p t x h2o co2 nacl conditions calculations are performed using the equation of state of duan et al geochim cosmochim acta 59 2869 2882 1995 for h2o co2 nacl fluids and the internally consistent data set of gottschalk eur j mineral 9 175 223 1997 for thermodynamic properties of solids results are presented in isothermal isobarical plots showing stable mineral assemblages as a function of fluid composition it is shown that in contact metamorphic p t regimes the presence of very small concentrations of nacl in the fluid causes almost all decarbonation reactions to proceed within the two fluid solvus of the h2o co2 nacl system

long term observations of southern winters on mars estimations of column thickness mass and volume density of the seasonal co2 deposit from hend odyssey data 1 in this paper we have analyzed neutron spectroscopy data gathered by the high energy neutron detector hend instrument on board mars odyssey for two martian years of orbital mapping we focused on the observations of the martian southern seasonal cap for this period of time nuclear methods based on numerical modeling allow us to derive an estimation of the distribution of co2 frost column density and mass from the temporal variations of neutron flux between summer and winter seasons we have estimated the seasonal behavior of both the column density and mass of co2 frost comparison between two martian years revealed minor 10 interannual variations of co2 thickness at the south pole during the middle of southern winter it was found that maximal mass of the southern seasonal cap is achieved at ls 160 and is equal to 6 6 0 6 1015 kg we found that this result corresponds well with previous hend results nasa ames gcm predictions gamma ray spectrometer estimates and estimations from gravity models based on mgs and mars odyssey tracking data in our analysis we also compared to processed mola data linear thicknesses of snow depths to measure the value of the volume density of the southern seasonal cap and we found that it may vary in the range 400 1250 kg m3

high resolution analyses of an early holocene climate event may imply decreased solar forcing as an important climate trigger early holocene lacustrine tree ring ice core and marine records reveal that the northern hemisphere underwent a short cooling event at 10 300 calendar yr b p 9100 14 c yr b p the records were compared on a common high resolution time scale and show that the event lasted less than 200 yr with a cooling peak of 50 yr and the event coincides with a distinct holocene thermohaline disturbance recognized in the north atlantic ocean in spite of wellknown freshwater forcings at the time of the event the negligible difference between the modeled d 14 c record based on the gisp2 greenland ice sheet project 2 10 be data and the measured values does not allow for detectable d 14 c changes related to global ocean ventilation we can however show that the onset of the cooling coincides with the onset of one of the largest holocene 10 be flux peaks this finding may imply that the climate system is more

geochemical components in martian soil abstract trends in element compositional variation among samples at the viking lander sites on mars provide evidence for multiple geochemical components in the soils a simple two component model can explain all pair wise trends of eight elements analyzed component a contains si and most or all the al ca ti and fe component b which is 16 3 by weight of the total contains s and most or all the cl and mg these results constrain several models of martian soil mineralogy but are consistent with a mixture of silicates and salts

geochemistry of martian basalts with constraints on magma genesis abstract over the past decade our knowledge of the geochemical and mineralogical diversity of martian rocks has greatly increased rocks on the surface of mars are older than most martian meteorites and have a wider range in bulk chemistry higher sio 2 higher total alkalis and lower mgo contents recent martian meteorite discoveries nwa 7034 nwa 7635 and nwa 8159 are also significantly older than the shergottites and nwa 7034 contains clasts which have a similar range in chemistry of the surface basalts in this invited review i summarize what is known about the bulk chemistry major elements of martian igneous rocks and use the chemistry to constrain the formation conditions in the interior and how these conditions have changed through time the basalts at gale crater are consistent with forming from a metasomatized mantle source which affected not only the chemistry of the basalts but also the formation conditions basalts at gusev crater bounce rock at meridiani planum and those basalts not affected by metasomatism like those at gale crater have a mantle potential temperature of 1450 c for the noachian conversely martian shergottites have a much higher mantle potential temperature 1745 c which has always been problematic to explain for such young rocks new formation conditions calculations are consistent with previous models of formation by a hot mantle plume but solve the pressure of formation paradox from the previous model combining the calculations for mantle potential temperature with previous estimates for grs measurements of surface volcanics from the hesperian and amazonian i calculate a baseline cooling curve and mantle melting conditions for the martian interior through time

distribution geomorphology and lithofacies of cliff top storm deposits examples from the high energy coasts of scotland and ireland abstract cliff top storm deposits ctsds occur on cliffs at elevations of up to 50 m above sea level at exposed sites on the deep water coasts of the british isles this study examines the distribution geomorphology and lithofacies of ctsds at sites from shetland orkney caithness and the outer hebrides in scotland and from the aran islands in galway bay in ireland ctsds are generated largely by the quarrying of blocks from the cliff top and transported by green water bores across cliff top platforms and ramps to be deposited in backing ridges or as debris spreads maximum boulder sizes reach 48 m 3 but it is likely that much larger blocks can be quarried prior to disintegration during transport eye witness accounts and field mapping demonstrate that formation and modification of ctsds has continued during major storms over recent decades recent ctsds bury a range of man made debris but older deposits lack this and instead show weathering effects that indicate a longer residence time in shetland osl dates on intercalated sands suggest that the oldest ctsds date from 800 ad radiocarbon dates on shell buried inside ctsd ridges relate to major storms between 1700 and 1900 ctsds represent an overlooked archive of storm sedimentation that has great potential for the elucidation of local storm chronologies ctsds also provide evidence of wave impacts on any part of the cliff face or top in fundamental contrast to the concentration of wave action at the cliff foot implicit in traditional models of the erosion of rock coasts

experimental epithermal alteration of synthetic los angeles meteorite implications for the origin of martian soils and identification of hydrothermal sites on mars 1 the dissolution behavior and secondary minerals generated by experimental alteration of a synthetic los angeles basaltic shergottite la were evaluated at epithermal 75 c conditions starting ph values of 1 1 and 3 6 and water rock ratios ranging from 100 to 2000 were studied using flow through and batch reactor experimental apparatus dissolution of plagioclase dominates effluent solution chemistry under all experimental conditions little mg is released to solution because nearly 100 of the mg in unaltered la is contained in pyroxene m1 sites which are relatively resistant to dissolution secondary minerals generated include siliceous residue amorphous sio2 lepidocrocite and ferrihydrite anhydrite alunogen rhomboclase ferrinatrite halite and unidentified ca and na sulfates the dominance of alteration products of plagioclase suggests that la type basalts have not contributed significantly to the martian soils the search for hydrothermal sites by remote sensing may be hampered by the general similarity of the alteration products found in the near surface epithermal environment to those thought to exist in martian soils sulfates iron oxyhydroxides amorphous silica however the unique chemical composition of secondary products formed by la alteration may make detection of recent hydrothermal alteration of evolved basaltic rocks more straightforward in addition alteration in terrestrial epithermal environments associated with mafic to intermediate volcanic rocks generally produces abundant sulfides and kaolinite two potentially unique mineral phases which might also indicate the presence of active or extinct hydrothermal systems

the incidence of microscopic charcoal in late glacial deposits abstract microscopic charcoal is not routinely counted by those investigating late glacial deposits it is largely the domain of those pursuing anthropogenic questions relating to the holocene interglacial 23 sites dating to the devensian late glacial ca 13 000 10 000 14c yr bp in scotland have charcoal records and seven of these can be shown to have a high charcoal content a phenomenon that has passed largely unremarked we discuss patterns of charcoal representation and explore possible explanations for high charcoal abundances especially in the loch lomond stadial including taphonomy e g secondary erosion of charcoal bearing deposits long distance transport aridity especially during the loch lomond stadial warmth and effective precipitation especially during the late glacial interstadial and humanly caused fires upper palaeolithic available data do not allow the establishment of clear relationships between vegetation types and charcoal abundance it is suggested that patterns of burning may need to be considered in the context of arid wet shifts in climate it is probable that combinations of factors are responsible for the late glacial charcoal records but the difficulty remains that too few data are routinely collected or available for study

palaeoenvironments the archaeological record and cereal pollen detection at clickimin shetland scotland abstract the loch of clickimin shetland is well known for its broch and associated monuments supposedly of the bronze and iron ages although the former date is disputed pollen diatom and sedimentological investigations permit fresh insights into the landscape and economic impacts of those who constructed the monuments reveal that the environs of the site experienced environmental change from neolithic times onward and provide the first holocene radiocarbon dates from the immediate locality the broch building period witnessed a continuation of pre existing pastoral husbandry for which heather burning may have exacerbated the natural spread of blanket peat initially no evidence was adduced for local arable activity in the present investigation and this was thought to be consistent possibly with the low numbers of excavated querns and the absence of cereal macrofossil finds when compared with other shetland broch sites the application of rapid scanning techniques however led to the discovery of a consistent cereal type pollen representation from bronze age times onwards the discrepancies between the palaeoenvironmental evidence and the environmental and palaeoeconomic inferences made by the excavator of the site are explored evidence is presented that both supports and contradicts previous assumptions surrounding an important archaeological site

fluid flow paths and mechanisms of fluid infiltration in carbonates during contact metamorphism the beinn an dubhaich aureole skye a textural study of marbles from the beinn an dubhaich granite contact aureole skye has shown that mass transport by diffusion was probably negligible during the metamorphic event and that the bulk of the carbonates reacted as a consequence of silica metasomatism permitting the use of calcsilicates as a tracer for fluid infiltration pathways fracture controlled infiltration was predominant in undeformed marbles whereas pervasive infiltration occurred during synmetamorphic ductile deformation some calcite marbles contain disseminated unoriented calcsilicate minerals that are associated with neither fractures nor a ductile deformation fabric consistent with an origin via infiltration of fluid along an interconnected grain edge porosity the inference of limited pervasive infiltration of undeformed carbonates is consistent with predictions based on experimentally determined fluid solid dihedral angles

analysis of terrestrial and martian volcanic compositions using thermal emission spectroscopy 2 application to martian surface spectra from the mars global surveyor thermal emission spectrometer atmospherically corrected thermal infrared spectra of large regions of the martian surface from the mars global surveyor thermal emission spectrometer mgs tes previously have been interpreted to represent two general spectral classes one class represents a basalt to basaltic andesite composition and the other class represents a basaltic andesite to andesite composition we have performed new linear deconvolutions of the two martian surface type spectra with an end member set tailored to represent volcanic rock types our preparatory study of laboratory spectra of terrestrial volcanic rocks acquired at 2 cm 21 sampling convolved to tes spectral sampling 10 cm 21 shows little degradation in deconvolution results when compared to results acquired using the higher spectral resolution data indicating that the deconvolution technique is valid for analyzing data at tes resolution our spectral fits to the martian data agree well with previous models and do not exhibit any notable deviations from the martian spectra that would indicate the absence of any significant end members in our model modal mineralogies obtained with these new spectral fits also compare favorably within the previously stated uncertainties to prior results the newly derived modal mineralogies are used with new and traditional classification schemes for volcanic igneous rocks introduced in a companion paper wyatt et al this issue to classify the martian compositions our results substantiate the previously proposed hypothesis that these two spectral classes on the martian surface represent volcanic compositions with distinguishable differences in silica content ranging from basalt to andesite

equilibrium and disequilibrium trace element partitioning in hydrous eclogites trescolmen central alps elements pb th and u whereas phengite hosts ba and is along despite the widespread presence of hydrous phases in subductionwith clinopyroxene and paragonite an important phase for b related systems experimental d trace element values for many however because of their low modal abundance in eclogite facies hydrous phases are lacking to fill this gap we present a set of rocks phengite and paragonite do not control the b whole rock budget d values where min indicates amphibole zoisite we infer that estimated d values from equilibrium phengite paragonite or apatite derived from equilibrium parageneses assemblages can be used as a good approximation for partition of eclogites from trescolmen central alps switzerland these coefficients under the given pt conditions 650 c and 2 0 data can be combined with experimental data for d gpa deformation induced dynamic recrystallization seems to be to estimate d values for the hydrous phases thus circumventing the driving process necessary for a close approach towards trace experimental problems with the direct determination of such values element equilibrium this process should work efficiently during we analysed li be b sr y zr nb ba ce nd sm pb th subduction close to the slab mantle interface affecting sediments and u in coexisting phases by laser ablation microprobe inductively and low t altered mid ocean ridge basalt but is of less importance coupled plasma mass spectrometry many of the values are extremely inside the slab knowledge of d values from equilibrium assemblages low for example nb ba ce th and u are in the lower ppb determined in this study is useful not only for large scale subductionrange in clinopyroxene attainment of equilibrium was evaluated zone modelling but also as an aid in the selection of equilibrium by textural and major and trace element characteristics nonsubassemblages in imperfectly equilibrated samples so that a equilibrated assemblages are common in most eclogite localities crystallization sequence can be derived including trescolmen and using such samples would lead to the derivation of erroneous values for equilibrium partitioning however four of the 10 studied eclogites from trescolmen having homogeneous

mixing relationships in the martian regolith and the composition of globally homogeneous dust abstract comparison of the chemical compositions of martian soils reveals distinct mixing trends resulting from admixture of variable amounts of sulfate chloride cement at viking landing sites and of the local andesitic rock fragments at the mars pathfinder site these trends most easily visualized in plots of oxides versus so 3 intersect approximately at a common composition thought to represent a global dust that has been homogenized by pervasive aeolian activity the source rocks that were weathered to produce the global dust are inferred to have been basalts rather than felsic rocks based on the observation that the dust lies along well established chemical weathering trends for terrestrial basalts the basaltic protolith was chemically similar e g high fe mg low al 2 o 3 to basaltic shergottite meteorites chemical changes during the weathering of martian basaltic rocks are apparently not as drastic as in terrestrial weathering perhaps because of evaporation of hydrous fluids that leave soluble components behind in the residue comparison with chemical trends for previously proposed martian soil formation mechanisms suggests that palagonitization of basalts more readily explains the dust composition than do hydrothermal alteration at higher temperatures or reactions of rocks with an acid fog produced by volcanic exhalations local or temporal processing of dust into soil involves not only cementation by salts and mixing with rock fragments but also chemical fractionations of fe 2 o 3 tio 2 presumably resulting from aeolian sorting by grain size and density if the global dust represents a broad average of the martian surficial or upper crustal composition the planet s surface geology is dominated by basaltic volcanic rocks and evaporitic salts

a new hypothesis for the origin and redistribution of sulfates in the equatorial region of western mars 1 the formation of sulfates on mars has been under debate since they were identified by several mars missions starting from the 1970s we propose that sulfates formed as evaporites in enclosed standing bodies of water in the valles marineris area following the early alteration of martian basaltic crust were then elevated by the tharsis uplift and transported together with rock materials to meridiani planum by periodic outbursts of water where they were deposited as sediments the proposed model comprehensively addresses all forms of sulfate occurrences near the equator in the western martian hemisphere and relates it to physiographic processes volcanic tectonic and sedimentary affecting the martian surface

vegetation change on papa stour shetland scotland a response to coastal evolution and human interference the first palynological and related sedimentological studies from papa stour shetland are presented and supplement the limited data available for the study of holocene vegetation change from the northern isles of scotland two pollen sites were located on an isthmus which has experienced the marked influences of waterlevel changes inundation by blown shell sand and probable grazing and arable activity in spite of the unpromising calcareous nature of the mineral materials at the sites very rich suites of pollen and spore taxa were recovered including those of taxa now absent from or rare in the islands the assemblages indicate a strong interplay between two major habitat types maritime heath and grassland in addition the sites demonstrate the effects of intermittent pool formation the study shows that the vegetational and geomorphological landscapes of the study area are both dynamic and closely linked

chemical multispectral and textural constraints on the composition and origin of rocks at the mars pathfinder landing site rocks at the mars pathfinder site are probably locally derived textures on rock surfaces may indicate volcanic sedimentary or impact generated rocks but aeolian abration and dust coatings prevent unambiguous interpretation multispectral imaging has resolved four spectral classes of rocks gray and red which occur on different surfaces of the same rocks pink which is probably soil crusts and maroon which occurs as large boulders mostly in the far field rocks are assigned to two spectral trends based on the position of peak reflectance the primary spectral trend contains gray red and pink rocks maroon rocks constitute the secondary spectral trend the spatial pattern of spectral variations observed is oriented along the prevailing wind direction the primary spectral trend arises from thin ferric coatings of aeolian dust on darker rocks the secondary spectral trend is apparently due to coating by a different mineral probably maghemite or ferrihydrite a chronology based on rock spectra suggests that rounded maroon boulders constitute the oldest petrologic unit a flood deposit succeeded by smaller cobbles possibly deposited by impact and followed by aeolian erosion and deposition nearly linear chemical trends in alpha proton x ray spectrometer rock compositions are interpreted as mixing lines between rock and adhering dust a conclusion supported by a correlation between sulfur abundance and red blue spectral ratio extrapolations of regression lines to zero sulfur give the composition of a presumed igneous rock the chemistry and normative mineralogy of the sulfur free rock resemble common terrestrial volcanic rocks and its classification corresponds to andesite igneous rocks of this composition may occur with clastic sedimentary rocks or impact melts and breccias however the spectral mottling expected on conglomerates or breccias is not observed in any apxs analyzed rocks interpretation of the rocks as andesites is complicated by absence of a 1 m pyroxene absorption band plausible explanations include impact glass band masking by magnetite or presence of calcium and iron rich pyroxenes and olivine which push the absorption band minimum past the imager s spectral range the inferred andesitic composition is most similar to terrestrial anorogenic icelandites formed by fractionation of tholeiitic basaltic magmas early melting of a relatively primitive martian mantle could produce an appropriate parent magma supporting the ancient age of pathfinder rocks inferred from their incorporation in hesperian flood deposits although rocks of andesitic composition at the pathfinder site may represent samples of ancient martian crust inferences drawn about a necessary role for water or plate tectonics in their petrogenesis are probably unwarranted

equatorial and midlatitude distribution of chlorine measured by mars odyssey grs 1 the 2001 mars odyssey gamma ray spectrometer grs has made the first measurement of the equatorial and midlatitude distribution of cl at the near surface of mars a mean concentration value of 0 49 wt cl has been determined from a grand sum of grs spectra collected over the planet excluding high latitude regions cl is significantly enriched within the upper few tens of centimeters of the surface relative to the martian meteorites and estimates for the bulk composition of the planet however cl is not homogeneously distributed and varies by a factor of 4 even after smoothing of data with a 10 arc radius filter several contiguous geographically large 20 regions of high and low cl concentrations are present in particular a region centered over the medusae fossae formation west of tharsis shows significantly elevated cl a large region north of syrtis major extending into utopia planitia in the northern hemisphere shows the lowest cl concentrations on the basis of hierarchical multivariate correlations cl is positively associated with h while negatively associated with si and thermal inertia we discuss four possible geologic mechanisms aeolian volcanic aqueous and hydrothermal that may have affected the cl distribution seen by grs while some of the distribution may be due to cl rich dust deposits transported by aeolian processes this mechanism does not appear to account for all of the observed variability we propose that reactions with volcanic exhalations may have been important for enriching cl in medusae fossae formation material

metasomatic vein formation by stationary fluids in carbonate xenoliths at the eastern margin of the bergell intrusion val sissone italy fluid flow is an important mechanism associated with heat and mass transport within the earth s crust the study of veins which represent channelling of fluids can thus be key in understanding these fluid movements unravelling fluid composition and origin paleo stress regimes and the history of the host rock new stable isotope data on carbonates and silicates have been combined with phase petrology mass balance and field observations to evaluate the formation mechanism of metasomatic reaction veins in dolomitic xenoliths in the bergell tonalites val sissone italy multiple generations of extensional veins can be followed from the contact zone between the dolomites and the intrusion to a few meters within either the tonalites with the epidote quartz veins or within the dolomites where they terminate each type of vein contains a central zone which is formed by open fracture crystallization this central fracture is framed by relatively symmetric replacement zones where the original dolomite reacted to form either forsterite diopside tremolite or talc all accompanied by calcite in either a succession of reaction zones or in simpler bi mineral silicate calcite veins the 18o and 13c values across the veins allow temperatures to be estimated from different mineral pairs silicate calcite and which confirm vein formation along a retrograde cooling path of the intrusion at least four different fluid infiltration events are required the first one around 555 c to form the forsterite calcite veins followed by the epidote quartz veins at temperatures around 430 c then the tremolite calcite veins at around 390 c and finally the talc calcite veins at around 140 c the shape of the 18o and 13c profiles which are flat across the central part and the replacement zones of the veins buffered by the intrusion change substantially over short distances both of these isotope profiles overlap with the equally sharp mineralogical front between the veins and the unreacted dolomites these profiles are interpreted to be the result of an isotopic exchange mechanism driven by dissolution and re precipitation reactions all veins are oriented perpendicular to the contact with the intrusive body except for the late talc veins elevated fluid pressures above the confining pressures caused by the regional and intrusion emplacement stress field are suggested to be responsible for the initial fracturing of the carbonates and intrusive rocks the contact zones between the tonalites and carbonates likely served as fluid conduits where fluids accumulated and the pressure built up until hydrofracturing occurred we propose that the veins formed through episodic pulses of highly reactive fluids that remained stationary during reaction rather than a system where fluids flushed through the veins based on the xco2 constrained mass balance the formation of the veins would only require a relatively small amount of fluid which could potentially originate from the intrusive rocks in vicinity of the xenoliths veining is not ubiquitous around the bergell intrusion suggesting that it only may have been a localized event and thus there is no need to involve a larger convective hydrothermal system for their formation

a unique piece of mars following the pioneering mars exploration rovers nasa s curiosity rover is actively exploring the crustal rocks of mars despite the exciting results returned by the rovers there is no substitute for a hand sample of crustal rock because such samples will not be returned to earth anytime soon geochemists who want a piece of mars in their labs must satisfy themselves with martian meteorites 1 these comprise a group of igneous rocks with telltale signs of martian alteration products 2 and have provided ground truth for the information returned by the rovers oddly however the hundred or so known martian meteorites are chemically unrepresentative of the martian crust determined by missions 3 on page 780 of this issue agee et al 4 put an end to this conundrum with the finding of a new martian meteorite northwest africa nwa 7034 a basaltic breccia unique among known martian meteorites with respect to age oxygen isotopes and petrology

structural and temporal evolution of a reactivated brittle ductile fault part i fault architecture strain localization mechanisms and deformation history abstract faults are by nature dynamic as their architecture and composition evolve progressively in space and through time steered by the interplay between strain weakening and hardening mechanisms this study combines structural analysis geochemistry and chlorite geothermometry to investigate deformation and strain localization mechanisms of the kvenklubben fault a paleozoic brittle ductile thrust in northern norway with the goal to constrain their temporal variations and the consequences thereof on fault architecture development and rheological behavior the fault evolved from an initially discrete brittle feature slipping mainly by seismogenic ruptures to a wide brittle ductile phyllonite deforming by aseismic creep the formation of mechanically weak phyllosilicates by decarbonation of footwall dolostones and carbonation of hanging wall metabasalts was the main weakening mechanism whereas partitioning of fluid flow and fracture sealing following transient high pore pressure driven embrittlement caused episodic and localized strain hardening the interplay between strain weakening and hardening mechanisms caused the fault core to widen we suggest that the ability for carbonate hosted faults to slip by seismogenic rupture is also a function of the faults structural evolutionary stage and that it decreases progressively with fault maturity this study demonstrates the importance of calibrating the present day fault anatomy against the dynamic character of faults which evolve geometrically compositionally and mechanically in space and through time

final chemical results from the mars pathfinder alpha proton x ray spectrometer 1 the calibrated pathfinder alpha proton x ray spectrometer apxs instrument is capable of measuring concentrations of all major and minor rock forming elements ranging from carbon through zirconium in atomic number therefore it is capable of constraining the petrology of the measured samples in particular the pathfinder data are the first in situ measurements of martian rocks and may be compared with previous remote sensing measurements as well as with the compositions of snc meteorites pathfinder soil and rock sample abundances from the alpha proton and x ray modes have been quantified the abundances suggest that 1 the rocks are covered with various amounts of soil 2 the soil free rocks on a volatile free basis have some element ratios similar to mars meteorites yet have different bulk chemistry indicative of more evolved rocks with higher silica abundances 3 the carbon and nitrogen contents are below detection limits and 4 the alpha mode oxygen reveals excess amounts of oxygen in some samples which is indicative of sample bound water contained within minerals or glasses in samples

an event stratigraphy for the last termination in the north atlantic region based on the greenland ice core record a proposal by the intimate group it is suggested that the grip greenland ice core should constitute the stratotype for the last termination based on the oxygen isotope signal in that core a new event stratigraphy spanning the time interval from ca 22 0 to 11 5 k grip yr bp ca 19 0 10 0 k 14 c yr bp is proposed for the north atlantic region this covers the period from the last glacial maximum through termination 1 of the deep ocean record to the pleistocene holocene boundary and encompasses the last glacial late glacial of the traditional northwest european stratigraphy the isotopic record for this period is divided into two stadial episodes greenland stadials 1 gs 1 and 2 gs 2 and two interstadial events greenland interstadials 1 gi 1 and 2 gi 2 in addition gi 1 and gs 2 are further subdivided into shorter episodes the event stratigraphy is equally applicable to ice core marine and terrestrial records and is considered to be a more appropriate classificatory scheme than the terrestrially based radiocarbon dated chronostratigraphy that has been used hitherto 1998 john wiley sons ltd

thermally altered palagonitic tephra a spectral and process analog to the soil and dust of mars we studied six palagonitic soil samples ph 1 through ph 6 which were collected at 30 cm intervals from a lava slab on mauna kea hawaii the samples represent an alteration sequence caused by heating during emplacement of molten lava over a preexisting tephra cone they are both spectral and weathering alteration process analogs to the martian surface techniques employed included visible and near ir spectroscopy mossbauer spectroscopy and magnetic analysis the two samples collected from beyond 90 cm from the slab ph 5 and ph 6 did not see the transient heating event and are composed of coarse grained glassy basaltic hawaiitic particles some of which have been moderately palagonitized since formation of the cone in the late pleistocene the four samples closest to the slab ph 1 through ph 4 have been strongly altered in response to heating during its emplacement their iron oxide mineralogy is dominated by nanophase ferric oxide the sample adjacent to the slab ph 1 which would have seen the highest temperatures has a factor of 3 less h2o and contains crystalline hematite and magnetite in addition to nanophase ferric oxide lesser amounts of magnetite but not hematite are present in samples 30 cm ph 2 and 60 cm ph 3 from the slab the reflectivity spectra of samples ph 2 through ph 4 are similar to spectra of palagonites reported by other workers to be good mars visible to near ir spectral analogs the reflectivity spectrum of ph 1 is an even better spectral analog to mars in that it exhibits absorption features indicative of both nanophase and crystalline ferric oxides similar to several new martian telescopic data sets our sampling site may also be a process analog for mars in that heating episodes by volcanism and or impact cratering could produce crystalline ferric oxides from poorly crystalline palagonitic material thus localized thermal alteration events may provide a volumetrically important mechanism for the palagonitization of basaltic glass and the production of crystalline ferric oxides on mars

mineralogy composition and alteration of mars pathfinder rocks and soils evidence from multispectral elemental and magnetic data on terrestrial analogue snc meteorite and pathfinder samples major element multispectral and magnetic properties data were obtained at ares vallis during the mars pathfinder mission to understand the compositional mineralogical and process implications of these data we obtained major element mineralogical and magnetic data for well crystalline and nanophase ferric minerals terrestrial analogue samples with known geologic context and snc meteorites analogue samples include unaltered palagonitic and sulfatetic tephra from mauna kea volcano hydrolytic and acid sulfate alteration steam vent material from kilauea volcano hydrolytic alteration and impactites from meteor crater relithification salient results for mars pathfinder include 1 band depths bd530b and bd600 and the reflectivity ratio r800 r750 are consistent with the dominant ferric mineral being nanophase ferric oxide associated with an unknown amount of h2o and occurring in composite particles along with subordinate amounts of other ferric minerals hematite and hematite plus nanophase goethite are most consistent with the data but maghemite akaganeite schwertmannite and nanophase lepidocrocite are also possible interpretations ferric oxides that are consistently not favored by the data as sole alteration products are jarosites and well crystalline goethite and lepidocrocite 2 the strength of the ferric adsorption edge r750 r445 implies the fe3 fe2 values for pathfinder rock and soil are within the ranges 0 7 3 and 3 20 respectively 3 ferrous silicates are indicated for subsets of pathfinder rocks and soils one subset has a band minimum near 930 nm that can attributed to low ca pyroxene alternatively the band could be a second manifestation of certain ferric oxides including nanophase goethite maghemite akaganeite and schwertmannite another subset has a negative spectral slope from 800 to 1005 nm which could result from the high energy wing of a high ca pyroxene and or olivine band a mixture of bright and dark materials and for rocks thin coatings of bright dust on dark rocks 4 chemical data on pathfinder rocks and soils are consistent with two component mixtures between an andesitic rock with low mgo and so3 concentrations soil free rock and a global basaltic soil with high mgo and so3 concentrations rock free soil pathfinder rock free soil can be modeled as a chemical mixture of snc meteorites and the pathfinder soil free rock 5 pathfinder soil cannot be obtained by chemical alteration of pathfinder rocks by any of the hydrolytic and acid sulfate alteration processes we studied presumably global mixing has obscured and possibly erased the elemental signatures of chemical alteration 6 the strongly magnetic phase in palagonitic and sulfatetic tephra is titanomagnetite and possibly its oxidation product titanomaghemite fe ti spinels the saturation magnetization of the tephra samples 0 5 2 0 am2 kg is at or below the low end of the range inferred for martian dust 4 2 am2 kg implying that lithogenic fe ti spinels are a possible candidate for the martian strongly magnetic phase 7 the predominantly palagonitic spectral signature and magnetic nature of martian soil and dust are consistent with glassy precursors with imbedded fe ti spinel particles comparison with lunar glass production rates suggests that production of sufficient quantities of glassy materials on mars by volcanic and impact processes is sufficient to account for these observations

metasomatism and self organization of dolerite dyke marble contacts beinn an dubhaich skye dolerite dykes which intrude dolomitic marble in the aureole of the beinn an dubhaich granite on the isle of skye have developed metasomatized margins close to the contact with the younger granite in the southern part of torrin quarry these margins display well defined mineralogical zones which can be divided into two groups on the basis of composition chlorite bearing margins display the sequence dolerite diopside spinel chlorite calcite magnetite olivine calcite spinel dolomite whereas phlogopite bearing sequences have a phlogopite calcite fluorapatite layer in place of the chlorite bearing layer no spatial pattern is seen in the distribution of the two margin types but textural and compositional evidence points to an importance of metasomatism by localized infiltration of magmatic fluids in the development of the phlogopite bearing sequences extensive patterning of the phlogopite bearing margins by a process of self organization during grain growth has resulted in the formation of alternating silicate only calcite only layers parallel to the dyke margin on a millimetre to centimetre scale early development of chlorite bearing sequences at the dolerite dolomite contact during contact metamorphism was followed by metasomatism controlled growth of phlogopite and patterning at or after the peak of metamorphism associated with the expulsion of aqueous fluids from the crystallizing pluton

mineralogic and compositional properties of martian soil and dust results from mars pathfinder mars pathfinder obtained multispectral elemental magnetic and physical measurements of soil and dust at the sagan memorial station during the course of its 83 sol mission we describe initial results from these measurements concentrating on multispectral and elemental data and use these data along with previous viking snc meteorite and telescopic results to help constrain the origin and evolution of martian soil and dust we find that soils and dust can be divided into at least eight distinct spectral units based on parameterization of imager for mars pathfinder imp 400 to 1000 nm multispectral images the most distinctive spectral parameters for soils and dust are the reflectivity in the red the red blue reflectivity ratio the near ir spectral slope and the strength of the 800 to 1000 nm absorption feature most of the pathfinder spectra are consistent with the presence of poorly crystalline or nanophase ferric oxide s sometimes mixed with small but varying degrees of well crystalline ferric and ferrous phases darker soil units appear to be coarser grained compacted and or mixed with a larger amount of dark ferrous materials relative to bright soils nanophase goethite akaganeite schwertmannite and maghemite are leading candidates for the origin of the absorption centered near 900 nm in imp spectra the ferrous component in the soil cannot be well constrained based on imp data alpha proton x ray spectrometer apxs measurements of six soil units show little variability within the landing site and show remarkable overall similarity to the average viking derived soil elemental composition differences exist between viking and pathfinder soils however including significantly higher s and cl abundances and lower si abundances in viking soils and the lack of a correlation between ti and fe in pathfinder soils no significant linear correlations were observed between imp spectral properties and apxs elemental chemistry attempts at constraining the mineralogy of soils and dust using normative calculations involving mixtures of smectites and silicate and oxide minerals did not yield physically acceptable solutions we attempted to use the pathfinder results to constrain a number of putative soil and dust formation scenarios including palagonitization and acid fog weathering while the pathfinder soils cannot be chemically linked to the pathfinder rocks by palagonitization this study and mcsween et al 1999 suggest that palagonitic alteration of a martian basaltic rock plus mixture with a minor component of locally derived andesitic rock fragments could be consistent with the observed soil apxs and imp properties

incipient hydrothermal alteration of basalts and the origin of martian soil the martian soil is a fine grained regolith that is chemically basaltic in character with evidence for both gains and losses of volatile and mobile elements compared to martian basalt compositions these chemical fractionations provide clues to geochemical processes on the surface of mars geochemical processes contributing to the soil proposed in the past include the chemical and mechanical breakdown of rocks under surface conditions the addition of volcanic aerosols containing s and cl compounds and the alteration of basaltic glass to palagonite our studies of terrestrial analogs suggest that hydrothermal alteration processes involving impact craters and volcanism could also contribute to the major element trends observed in martian soil data from viking pathfinder and the current mer missions consistently show that relative to basaltic martian meteorite compositions the major element compositions of the soils are 1 depleted in the fluid mobile element calcium 2 generally similar or somewhat enriched in iron oxide and magnesium but mgo depleted compared to gusev rocks 3 locally variable in potassium 4 possibly poorer in aluminum and 6 very enriched in chlorine and sulfur the major element trends aside from the cl and s enrichment could be explained by the formation or addition of palagonite according to mcsween and keil 2000 but the missing cao remains a problem the chlorine and sulfur are probably derived from other processes such as volcanic aerosols and hydrothermal fluids mcsween and keil 2000 also argued that hydrothermal alteration of basalts produce alteration trends that are inconsistent with the mars soil but this study concludes otherwise we have used quantitative mass balance mixing models to investigate possible models involving mixtures of basaltic compositions with different types of alteration materials including palagonite we show that the mars soil composition can be matched with a combination of unweathered basaltic martian meteorites with basaltic feo rich cao poor alteration products palagonite is a possible but not a necessary component of successful model mixtures the hydrothermal alteration materials that form successful model mixtures are formed in low temperature low water rock ratio environments and they can reproduce the required geochemical trends because they are poorer in cao but not in feo compared to their respective protoliths these results argue that material altered by hydrothermal processes could be a plausible component of the soil and that removal of cao from the soil into some undiscovered reservoir after its formation is not required the current soil on mars therefore did not have to undergo an episode of in situ aqueous alteration but could represent a sink for materials that experienced aqueous processes in a different setting before erosion to form the soil the soil can also represent a sink for mobile elements e g s cl and br derived from other sources such as volcanic aerosols and hydrothermal fluids

devensian organic interstadial deposits and ice sheet extent in buchan scotland pre late devensian organic deposits in the buchan area of northeast scotland were investigated for their geomorphological and palaeoecological pollen plant macrofossils coleoptera properties close ecological agreement exists between fossil indicators and allows the inference that the environment in the vicinity of the deposits was a dwarf shrub tundra of the type met today in high latitude areas of scandinavia and arctic russia the latest in a series of radiocarbon dates from the site produced determinations beyond the limits of the method although the geomorphological and fossil evidence appears to point to an interstadial date within oxygen isotope stages 5a or 5c the site has special significance for arguments concerning the much debated concept of moraineless buchan indeed evidence is presented which supports the concept of extensive ice sheet glaciation during the late devensian for this crucial geographical area if buchan is to be seen as a further casualty amongst other disputed ice free enclaves then a return to earlier models of extensive ice sheet glaciation in the late devensian of scotland would seem to be necessary 1998 john wiley sons ltd

hydrothermal minerals and alteration rates at surtsey volcano iceland the volcanic island surtsey off the south coast of iceland was created by volcanic activity in 1963 1967 core from a 181 m deep hole extending 123 m below sea level shows the results of 12 yr of hydrothermal alteration of basaltic tephra the primary cause of heating of the tephra and of development of the hydrothermal system was the intrusion of dikes below sea level at present the hottest part of the hole at a maximum temperature of 150 c is cooling at 0 9 c per year palagonitization of sideromelane glass a dominant constituent of the tephra is an important alteration process that is strongly temperature dependent the rate doubling for every 12 c increase at 60 c 90 is palagonitized above 120 c olivine crystals are replaced on their edges by nontronite the thickness of clay doubles for each 8 c increase ten hydrothermal minerals have crystallized in the tephra at 25 to 150 c the dominant species are smectite nontronite analcite phillipsite and tobermorite the primary clay species of palagonite is probably nontronite other minerals are halite opal calcite chabazite xonotlite anhydrite and gypsum no major differences in mineral occurrence are noted above and below sea level but phillipsite and tobermorite tend to grow larger below sea level even at the same temperature analcite appears at lower temperature 55 c above sea level than below sea level 75 c anhydrite is most abundant deep in the hole where inflowing cool sea water precipitated sulfate due to reduced sulfate solubility at higher temperatures

paleoceanographic reconstructions of surface ocean conditions in the greenland iceland and norwegian seas through the last 14 ka based on diatoms prior reconstructions of the last glacial maximum and the holocene did not include detailed paleoclimate data from the greenland iceland and norwegian gin seas which cover sensitive areas for oceanographic boundaries sea ice distribution and deep water formation in order to fill this gap we studied nine well dated sediment cores from this area and reconstructed the paleoceanographic conditions of the surface gin seas at 2000 year intervals since 13 400 bp based on the diatom record results show that a n s extending sea ice free corridor had opened along norway already at 13 400 bp indicating a northward flow of a branch of the north atlantic drift possibly caused by a change in the jet stream flow due to the decreased height of the north american ice sheet a major change of climatic conditions occurred over the gin seas as the insolation anomaly reached its maximum around 9000 bp when the sea ice cover and the oceanic fronts retreated to a northwesterly position along greenland and the ocean temperatures rose the first half of the holocene is recorded as the warmest period during the last 13 400 bp in the gin seas the duration of this climatic optimum decreased both toward the north and toward the margins of the area the second half of the holocene is characterized by a cooling trend in step with the decreasing insolation these results support the proposal of imbrie et al 1992 that the gin seas region acts as an initial responder to insolation changes