mars near infrared spectral reflectance of surface regions and compositional implications reflectance spectra 0 65 2 50 m are presented for 11 martian areas the spectral resolution is 1 and the spatial resolution is 1000 2000 km these are the first high quality spectrophotometric data at these wavelengths for regions on the surface spectral features previously observed are confirmed and better defined and a number of important spectral properties are characterized for the first time the spectra show water ice absorptions in the 1 5 and 2 0 m regions which if due to surface frost would imply the presence of 1 to 2 mg cm2 h2o however other studies have shown that the presence of an unprotected surface frost in late morning is unlikely water ice is stable at night even at the equator and might persist until late morning when the air is well undersaturated if it is intimately dispersed in weathering products especially if clays are present the dark region spectra indicate about 4 times less water ice than seen in bright regions since some bright material is present in dark regions there may be no water ice associated with the dark materials themselves this tends to confirm that weathering products thought to be more abundant in bright regions are involved in the mechanism that allows temporary persistance of unstable water ice the presence of weak 2 3 m features in many of the spectra are consistent with the presence of hydroxylated magnesium rich minerals such as sheet silicates serpentine talc and magnesian smectites or amphiboles anthophyllite the apparent absence of a 2 2 m absorption implies that montmorillonite may not be a major component of the martian regolith many of the spectra also show an apparent absorption at 1 9 m in the wing of the 2 0 m martian atmospheric co2 absorption which would indicate bound molecular water observed dark regions have distinctive near infrared spectral shapes previously not well determined which are characteristic of thin semi transparent alteration coatings overlying dark unaltered rock previously observed ferrous and ferric iron absorptions in the 1 m region are better defined by these new data clinopyroxene augite is definitely present but olivine is not spectrally apparent

holocene fire and vegetation changes in southeastern brazil as deduced from fossil charcoal and soil carbon isotopes abstract carbon isotopes of soil organic matter som and radiocarbon dating on charcoal from nine soil profiles collected under native forest vegetation in londrina state of parana anhembi botucatu and jaguariuna sao paulo and salitre minas gerais southeastern brazil were used to evaluate the vegetation changes and to establish the chronology 13 c and 14 c data in som and charcoal respectively indicate that c 4 plants were the dominant vegetation in londrina and jaguariuna during the late pleistocene until middle holocene probably associated with the presence of a drier climate in anhembi and botucatu c 3 plants dominate the landscape during the period a probable mixture of c 3 and c 4 plants occurred in salitre during the holocene this study is part of a main research program related to palaeoenvironmental reconstruction of vegetation and climate in distinct regions of brazil during the last 20 000 years

mars definition and characterization of global surface units with emphasis on composition units of similar optical properties have been defined for a large part of the surface of mars using primarily viking 2 approach maps of red 0 59 m and violet 0 45 m normal albedo of available global data sets spectral albedo most closely relates to surface mineralogy the resultant unit map represents mars at the time the viking images were acquired ls 103 105 morning northern hemisphere summer in 1976 computer processing of these data reveals clusters of albedo values which relate to specific contiguous regions on the planet final unit definitions were determined by an interactive iterative process which included scientific judgment on the part of the researchers the results therefore are not the product of an unsupervised statistical classification some unit boundaries are of a gradational nature while others are more discrete certain of the units are temporal and relate to the presence of condensates at the time of observation other units by virtue of their redness and low albedo are almost certainly not affected by condensates a study of the albedo properties of analog materials measured in the laboratory and of telescopic spectrophotometry of mars indicates that both hydroxylated low temperature or secondary and hematitic high temperature or primary oxidized materials exist on the surface the most likely surface expression of global dust and or high albedo soils is in the classical bright region arabia this material is probably a low temperature hydrated oxidation product of mafic volcanic glass such as a palagonite or amorphous iron silica gel most low albedo features in the region studied have red and violet albedos consistent with a dark substrate such as basalt coated by or mixed with the fine grained alteration product mentioned above there may be no genetic relationship between these two components in this majority of low albedo surface materials certain of the other low albedo regions are also the most red highest r v areas observed on the planet these areas are consistent with a nonhydroxylated more hematitic material such as that produced by high temperature hydrothermal alteration of basalt some of these dark very red regions correlate with exposures of very ancient terrain at this spatial resolution 10 20 km pixel there is no evidence of surface exposures of uncoated or unweathered basaltic rock or glass comparisons of the unit map with other data sets available to us revealed no striking detailed correlations larger scale correlations certainly do exist however among the various albedo data sets and with thermal inertia data

mars express high resolution stereo camera spectrophotometric data characteristics and science analysis 1 the high resolution stereo camera hrsc on the mars express mex spacecraft in orbit about mars is delivering images of the mars surface and atmosphere from its high inclination elliptical orbit that are intended to cover most of the mars surface by the end of the mission these are acquired in four specific spectral passbands that sample the scene at different parts of the extended visual spectrum from near 0 4 m to about 1 m and in five additional channels four used for stereo and one nadir that use the same fifth spectral passband these channels view from different angles and can be used for photometric and spectral analysis the data allow a variety of studies of the surface and atmosphere of mars but these require detailed understanding of the data characteristics as there are several effects including of the observation geometry and the atmosphere that need to be treated this article is a report to the science community on the current understanding of the hrsc color data after an initial analysis and also a demonstration of their capabilities for study of mars which from this study appear to be considerable we first discuss the characteristics and calibration of the hrsc spectral data the atmospheric influence on the photometric appearance of the surface materials is explored and methods of compensating are considered reflectances are calculated for surface units by assuming the dark material is basalt and scaling the entire hrsc scene using a laboratory basalt spectrum for the selected dark material area the results and the correction factors for different orbits are compared we present several examples of what could become a large volume of future science results utilizing the hrsc spectrophotometric data in conjunction with photo interpretation for example we find relatively few but very important distinct spectral components at the hrsc resolution including what we interpret as iron oxide rich material unoxidized basalt and polar ice consistent with past works the major spectral components are distributed in ways that suggest compositional mixing and the need to revise the current geologic understanding of major regions

climate records covering the last deglaciation the oxygen 18 oxygen 16 ratio of molecular oxygen trapped in ice cores provides a time stratigraphic marker for transferring the absolute chronology for the greenland ice sheet project gisp ii ice core to the vostok and byrd ice cores in antarctica comparison of the climate records from these cores suggests that near the beginning of the last deglaciation warming in antarctica began approximately 3000 years before the onset of the warm bolling period in greenland atmospheric carbon dioxide and methane concentrations began to rise 2000 to 3000 years before the warming began in greenland and must have contributed to deglaciation and warming of temperate and boreal regions in the northern hemisphere

mapping of spectral variations on the surface of mars from high spectral resolution telescopic images abstract we analyze a high spectral resolution r 200 visible and near infrared 0 44 1 02 m telescopic spectral image of mars to explore surface material variations across the observed face of the planet which is centered on sinus meridiani two independent analysis methods are employed linear mixture modeling and supervised spectral pattern classification with an artificial neural network four endmember type regions are identified with linear mixing further refinement is achieved with the nonlinear neural network classification algorithm separating eight units of geological significance differences in spectral features among the mapped units are characterized among the medium to high albedo units northern lowlands typified by chryse planitia show far less evidence of bulk crystalline hematite than western arabia or any other highland regions the relationship of these bright units to the globally distributed aeolian dust is not yet clear within our image low albedo regions with the most pronounced crystalline hematite signature primarily correlate with the classic dark regions with the exception of acidalia planitia spectral evidence for pyroxenes also correlates well with most of the classic low albedo regions but again acidalia planitia is the major exception significant spectral anomaly is also found in an equatorial region deucalionis regio a companion paper in this issue discusses the soil properties of deucalionis our data and analysis support a compositional trend that is consistent with the global geologic crustal dichotomy of mars namely that the younger northern lowlands contain less bulk crystalline hematite than southern highlands

timing of the antarctic cold reversal and the atmospheric co2increase with respect to the younger dryas event the transition from the last glacial to the holocene is a key period for understanding the mechanisms of global climate change ice cores from the large polar ice sheets provide a wealth of information with good time resolution for this period however interactions between the two hemispheres can only be investigated if ice core records from greenland and antarctica can be synchronised accurately and reliably the atmospheric methane concentration shows large and very fast changes during this period these variations are well suited for a synchronisation of the age scales of ice cores from greenland and antarctica here we confirm the proposed lead of the antarctic cold reversal on the younger dryas cold event the antarctic cooling precedes the younger dryas by at least 1 8 kyr this suggests that northern and southern hemispheres were in anti phase during the younger dryas cold event a further result of the synchronisation is that the long term glacial interglacial increase of atmospheric co 2 was not interrupted during the younger dryas event and that atmospheric co 2 changes are not necessarily dominated by changes in the north atlantic circulation

mars near infrared comparative spectroscopy during the 1986 opposition abstract near infrared 0 7 2 5 m spectral observations of mars during the 1986 opposition were carried out at the mauna kea observatory utilizing the university of hawaii 2 2 m telescope spectra were obtained of several martian locations using a continuously variable filter cvf spectrometer with a resolution of 1 25 during two separate runs in june and august approximately 60 distinct spots between 354 w and 163 w and 32 n and 53 s were observed at an angular resolution of 0 5 to 1 5 arcsec corresponding to a spatial resolution on mars of 200 to 460 km varying with nightly seeing conditions these different spots fall roughly into a set of eight distinct geologic regions volcanic regions ridged plains ridged volcanic plains scoured plains impact basins channels and canyons densely cratered regions and layered terrain and ice the spectra exhibit typical noise related or weather induced errors of less than 4 of the full scale signal to analyze these spectral data spot to spot ratios or relative reflectance spectra were produced between spectra taken in different geologic regions spectral features observed in these ratios can act as indicators of mineralogic differences between areas under consideration perhaps the most striking result obtained from the many ratios taken close in time and under similar viewing geometries was the consistent lack of noticeable differences between spectra taken of areas which in geologic maps and viking orbiter images appear to have very different morphologies this observation leads to several possible conclusions a the spectral feature differences are below the detection limit of these measurements b the spatial resolution of spots observed on mars was not high enough to merit comparison with medium to high resolution viking orbiter images and geologic maps i e the local morphology varies significantly within the aperture region and a mixing or averaging effect operates to reduce the spectral feature differences c all of these regions are the same spectrally in the near infrared it is likely that all three of these effects operate to some degree to prevent spectral features from being observed among the areas measured possibility c may best explain these results as it is consistent with several previous studies indicating a grossly uniform mantle of global dust over much of the observed surface the message to mars orbiting spectroscopy experiments such as mars observer vims is that the spectral differences are small only a few percent of the continuum or nonexistent among many areas on mars on the scale of several hundred kilometers

optical scattering properties of terrestrial varnished basalts compared with rocks and soils at the viking lander sites basalt flows at the pisgah volcanic field california are mantled by aeolian silt sized deposits the bright mantle is overlain by a dense pavement of basalt cobbles smoothed by aeolian abrasion and coated with glossy dark gray and red desert varnishes in contrast the two viking landing sites on mars lack desert pavements and rocks have glossy surfaces that in some cases are brighter than soils to pursue further the scattering characteristics of varnished basalt cobbles for comparison to mars rocks laboratory measurements of bidirectional reflectance 0 69 m center wavelength were made as a function of incidence and emission angle along the principal plane for varnished and fresh basalt surfaces the reflectance data fit with a scattering model that includes specular reflections from rough surfaces and volume penetration and reflection show that the red varnished surfaces have higher single scattering albedoes and higher surface roughness values than the dark gray varnished surfaces 0 56 and 0 42 21 and 17 respectively fresh cut surfaces have lowest values 0 40 and 6 results are consistent with observations made from thin sections for these surfaces and with field observations that show dark gray varnished surfaces are smoothed by exposure to wind abrasion dark red varnished surfaces tend to be rougher because they are embedded in the aeolian mantle and develop in a protected environment application of the model to atmospherically corrected radiometrically calibrated viking lander images 0 60 to 0 74 m shows that many rocks are smoother and have single scattering albedoes higher than soils 9 versus 27 0 71 versus 0 63 respectively results are consistent with a model in which rocks at the surface of mars become smoothed by aeolian abrasion and coated with atmospheric dust lack of desert pavement on mars is probably associated with a scarcity of cobbles and a lack of soil forming processes similar bright smooth coatings are expected at other locations on mars including the pathfinder ares vallis site

interhemispheric synchrony of the last deglaciation inferred from alkenone palaeothermometry the relative timings of the last deglacial warming in the southern and northern hemispheres are not well constrained but are a crucial component in understanding the mechanisms of deglaciation1 a clearer picture of the degree of interhemispheric synchrony has been obscured by a dearth of high resolution temperature records that can be tied to the absolute calendar timescale moreover the quantification of tropical temperatures during the last glacial cycle is controversial2 8 here we apply the alkenone method of sea surface temperature reconstruction9 10 to several high resolution sediment cores recovered from the tropical indian ocean between 20 n and 20 s the inferred initial sea surface temperature warming 15 000 calendar years ago at 20 s is in phase with northern hemisphere sea this study and air11 temperature changes but lags antarctic warming12 14 by several millennia this finding along with the results of recent modelling studies15 16 provides strong support for the idea that changes in the ocean s global thermohaline circulation were not the only cause of interhemispheric climate teleconnection during the last deglaciation

global color and albedo variations on io abstract three multispectral mosaics of io have been produced from voyager imaging data a global mosaic from each of the voyager 1 and voyager 2 data sets and a high resolution mosaic of the region surrounding the volcano ra patera the mosaics are maps of normal albedo and color in accurate geometric map formats io s photometric behavior mapped with a two image technique is spatially variable especially in the bright white areas the disk integrated color and albedo of the satellite have been remarkably constant over recent decades despite the volcanic activity and the many differences between voyager 1 and 2 images acquired just 4 months apart this constancy is most likely due to the consistent occurrence of large pele type plumes with relatively dark red deposits in the region from long 240 to 360 a transient brightening southeast of pele during the voyager 1 encounter was probably due to real changes in surface and or atmospheric materials rather than to photometric behavior the intrinsic spectral variability of io as seen in a series of two dimensional histograms of the multispectral mosaics consists of continuous variation among three major spectral end members the data were mapped into five spectral units to compare them with laboratory measurements of candidate surface materials and to show the planimetric distributions unit 1 is best fit by the spectral reflectance of ordinary elemental sulfur and it is closely associated with the peletype plume deposits unit 2 is strongly confined to the polar caps above about latitude 50 but its composition is unknown unit 5 is probably so 2 with relatively minor contamination it is concentrated in the equatorial region and near the long lived prometheus type plumes units 3 and 4 are gradational between units 1 and 5 in addition to so 2 and elemental sulfur other plausible components of the surface are polysulfur oxides fecl 2 na 2 s and nahs

global imaging of mars by hubble space telescope during the 1995 opposition hubble space telescope hst imaging of mars near the 1995 opposition resulted in excellent synoptic scale images of the planet during the spring season in the northern hemisphere because this season coincides with the aphelion position of mars in its orbit it is therefore the most difficult for ground based observation because of the relatively small angular size of mars this is the first sequence of images fully utilizing the capability of the new planetary camera to produce global synoptic images of the planet the images reveal bright discrete clouds associated with topographic features superimposed on a zonal band of condensate clouds between latitudes 10 and 30 the maximum violet optical depth of the cloud band is about 0 3 in a few instances the appearance of clouds beyond the morning terminator can be used to infer cloud heights of roughly 8 km a large dark albedo feature in the cerberus region observed for many years by ground based observers has almost disappeared in the 1995 hst images other aspects of mars such as the north polar cap appear much as they did during previous oppositions although cloudy regions were observed by spacecraft during this season the hst images uniquely reveal the global extent of significant optical depth clouds

paleohydrology and paleoclimate of the past 33 000 years at the tamandua river central brazil abstract deposits of the tamandua river contain evidence for four major paleohydrologic stages in the last 33 000 years a wet period between 33 000 and 20 000 14 c yr b p produced a high water table that allowed organic rich deposition in the tamandua valley a dry interval 17 000 10 000 14 c yr b p produced sandy deposits of braided channels and alluvial fans river aggradation during this period probably resulted from a high sediment load promoted by intense slope erosion and from flash floods a wet period after 10 000 and before 6000 14 c yr b p was marked by reduced slope erosion and by high discharge that led to erosion of the valley fill during that time forests developed widely in brazil a drier climate after 6000 14 c yr b p caused a reduction of discharge but allowed a high water table to be maintained

spectral evidence for the mineralogy of high albedo soils and dust on mars because of the lack of direct mineralogic data available for mars spectral remote sensing techniques and in particular earth based reflectance spectroscopy remain the primary source of this information presented here are laboratory observations which further constrain the mineralogy and origin of the high albedo soils and dust earth based observations show the reflectance spectra of classical bright regions to be fairly uniform with a strong fe3 o2 charge transfer absorption edge extending from the near uv through the visible this absorption is relatively smooth unlike those observed for crystalline ferric oxides which have superimposed fe3 crystal field bands dilution of ferric oxide with a spectrally more neutral medium montmorillonite weakens the charge transfer and crystal field absorptions together and does not serve to make the ferric oxide spectrum more mars like smoother nontronite ferric iron bearing smectite clay was also investigated for spectral agreement with telescopic observations pure nontronite has fe3 absorptions analogous to but different from ferric oxides as in the previous case the absorptions are very distinct and inappropriate for mars admixture of neither montmorillonite nor ferric oxide serves to improve the nontronite spectrum the conclusion is that nontronite is not a major component of martian soils although the presence of other iron poor clays cannot be totally excluded based on currently available observational data the best spectral analogs known for high albedo soil and dust are a specific type of palagonite from hawaii x ray amorphous weathering products of mafic volcanic glass the indication is therefore that ferric iron on mars is likely to occur in poorly defined crystallo graphic sites such as found in these amorphous materials these materials form slowly under semiarid conditions at ambient temperature even low temperature hydrothermal alteration of glass might provide enough ion mobility to favor some formation of crystalline clays over amorphous gels and may therefore not be the primary mechanism responsible for soil formation on mars the amorphous hawaiian soils exist metastably for thousands of years on earth similar materials on mars would be expected to survive considerably longer under the present cold and dry climatic conditions

surface compositional properties of the malea planum region of the circum hellas volcanic province mars abstract we used thermal emission spectrometer tes thermal emission imaging system themis high resolution stereo camera hrsc and observatoire pour la mineralogie l eau les glaces et l activite omega data to assess the physical and compositional properties of the malea planum portion of the circum hellas volcanic province chvp our analysis of surface materials shows that the thermal inertia decreases from north to south and that there is greater dust cover on the flanks of the chvp volcanoes than in their putative calderas local variations in thermal inertia in malea planum are likely due to variations in surface material caused by aeolian and periglacial permafrost processes whereas regional variations are likely due to seasonal deposition and sublimation of ice at higher latitudes spectral analysis of omega data indicates the widespread presence of pyroxenes and or olivine particularly in the rims of craters that likely excavated volcanic materials dark materials occur throughout the chvp but are concentrated in topographic lows such as crater and caldera floors derivation of modal mineralogies from omega data show a variation in composition of dark materials across malea planum eastern dark deposits have higher olivine and low calcium pyroxene contents lower high calcium pyroxene contents and higher ratios of low calcium to total pyroxene relative to western dark deposits correlation with cratering model age estimates suggests that the western deposits are associated with older features 3 8 ga than the eastern deposits 3 6 ga but these age differences are within uncertainties nevertheless these results suggest a potential change in composition of volcanic materials in the malea planum portion of the chvp with space and possibly time

meltwater pulse 1a from antarctica as a trigger of the bolling allerod warm interval meltwater pulse 1a mwp 1a was a prominent feature of the last deglaciation which led to a sea level rise of 20 meters in less than 500 years concurrent with mwp 1a was the onset of the bolling allerod interstadial event 14 600 years before the present which marked the termination of the last glacial period previous studies have been unable to reconcile a warm northern hemisphere with mwp 1a originating from the laurentide or fennoscandian ice sheets with the use of a climate model of intermediate complexity we demonstrate that with mwp 1a originating from the antarctic ice sheet consistent with recent sea level fingerprinting inferences the strength of north atlantic deep water nadw formation increases thereby warming the north atlantic region and providing an explanation for the onset of the bolling allerod warm interval the established mode of active nadw formation is then able to respond to subsequent freshwater forcing from the laurentide and fennoscandian ice sheets setting the stage for the younger dryas cold period the melting of continental ice sheets during the last deglaciation provided a freshwater source to the ocean that affected global sea level and the strength of the thermohaline circulation an exceptionally large melting event inferred from far field relative sea level records occurred

impact melts and glasses on mars 1 dark mobile materials on mars are widely considered to be volcanically derived windblown particulates such a conclusion is consistent with the large volcanic edifices on mars and the assumption that a volatile rich crust would not favor significant impact melt generation several post viking discoveries however provide new perspectives for reconsidering alternative origins not only for some of the mobile dark veneers but also certain materials at the pathfinder and viking landing sites first certain dark materials on mars do not exhibit the expected mafic absorption features in their reflectance spectra second the pathfinder mission revealed unexpected feldspathic compositions of vesicular blocks that lead to a preliminary conclusion that they represent andesites or basaltic andesites rather than basalts third recent discoveries of holocene to miocene impacts in argentine loessoid deposits provide new insights for the nature of melts generated from eolian sediments fourth global dispersal of impact melt products are now recognized in the terrestrial record throughout the cenozoic consequently the generation and preservation of impact glass on mars should be reconsidered possible occurrences include possible tektite like strewnfields downrange from recent oblique impacts dark avalanches emerging from backwasting cliffs of easily eroded unconformable deposits global dispersal of glassy ejecta from hesperian and amazonian craters of chicxulub scale and dark mobile veneers emerging from noachian craters we propose that the mobile dark materials comprising many of the named features of mars as well as some blocks at the pathfinder viking landing sites may represent impact melt products

mars surface mineralogy from hubble space telescope imaging during 1994 1995 observations calibration and initial results visible to near infrared observations of mars were made with the hubble space telescope hst during 1994 1995 with the goals of monitoring seasonal variability of the surface and atmosphere and mapping specific spectral units to constrain the planet s surface mineralogy this paper presents the details of the collection and calibration of the data concentrating specifically on the near ir data that were obtained exclusively for the surface mineralogy aspect of our hst mars observing program we also present some initial results from the calibrated data set our calibration procedures included the standard pipeline processing steps supplemented by special procedures required for use with the linear ramp filters on the wide field planetary camera 2 instrument and an additional point spread function deconvolution procedure applied in order to realize the full potential spatial resolution of the images 23 to 64 km pixel between august 1994 and august 1995 the calibration results in a set of images projected onto a standard map grid and presented in radiance factor i f units having an estimated 5 photometric accuracy based on the performance of hst and comparisons with previous ground based and spacecraft mars spectra initial scientific analyses of these data reveal 1 distinct red blue color units within the classical bright regions similar to those seen in viking orbiter images and possibly related to variations in nanophase and or crystalline ferric mineral abundance 2 near ir spectral slope variations correlated with albedo on a large scale darker is bluer near ir slope but exhibiting wider variations among many of the small scale features visible in the data 3 an absorption at 860 nm that occurs in all regions but which is 3 to 5 stronger in many of the classical dark regions than in the bright regions possibly because of a greater abundance of a well crystalline ferric phase like hematite or a very low ca pyroxene or opx cpx mixture and 4 an absorption from pyroxene at 953 nm with a band depth that is inversely correlated with albedo bright regions 0 to 5 deep dark regions 7 to 15 deep and which shows the highest band depth values in individual craters calderas and other small geologic units that are resolved in the images

red violet contrast reversal on mars significance for eolian sediments abstract albedo markings on mars can exhibit reversed contrast with their surroudings when imaged in red and violet light a complete search of viking orbiter images shows this phenomenon on scales less than 300 km is restricted to specific eolian features intracrater deposits and wind streaks originating from the deposits contrast reversal is not found between features such as lava flows of different ages that might expose different materials without a largely eolian influence laboratory simulations suggest that iron oxides are the most likely materials involved in contrast reversal on the martian surface red violet contrast reversal is achieved easily but not exclusively between samples from which very fine particles m in diameter have been removed and corresponding samples in which larger grains are coated by such fine particles substantial particle size dependent albedo and color viriations exist for material which can be carried in suspension on mars m thus all fine grained eolian deposits on mars need not be the same as the brighter parts of arabia which have colors and albedos similar to the fine m component of martian dust storms the observed contrast reversal characteristics and colors of the intracrater dunes and related sediments can be explained readily if they are essentially free of adhering dust as would be the case if such eolian features were subject toactive saltation

oxygen isotopes sea level changes and the temperature history of a coral reef environment in new guinea over the last 105 years abstract coral reef terraces consisting of an upward succession of fringing and barrier reef types are preserved on land along the raising coast of huon peninsula new guinea seven coral reef units i vii from the coast landwards spaced at about 20 kyr interval provide a rather complete record of sea levels oxygen isotopes and temperature of teh surface tropical ocean over the duration of the high sea level events of the last glacial cycle the systematic sampling of the coral reefs was restricted to the massive tridacna gigas species the giant clam which are about 0 7 0 enriched in 18o relative to calcite equilibrium value and the presence of symbionts seems to have no effect on the 18o of their aragonitic skeleton sea levels rose rapidly to 5 6 5 m above present during the last interglacial which on stratigraphic grounds and 18o compositions can be separated into an early phase whose 18o is similar to modern reef viia dated at 138 kyr and a late phase that is 0 6 0 heavier reef viib dated at 118 kyr fringing reefs vi v iv iii and ii record short lived high sea levels stands at 107 85 60 45 to 40 and 31 kyr respectively that stopped short of the present sea level 12 19 28 32 to 42 m the general decline of the high sea level stands corresponds to an average 18o enrichment of 1 7 0 measured between the early interstadials of isotope stage 5 vi and v and the late interstadials of isotope stage 3 iv iiia iiib and ii the maximum 18o enrichment of 1 7 0 relative to present was registered during a regressive phase of reef iiia stratigraphic evidence indicates that sea level lows in the range of 37 to 55 m below present have occurred in between the high sea level stands but those are unlikely to represent the lowest sea levels of the last glacial cycle sea levels and 18o ddta pair offer important clues regarding the partitioning of ice volume and temperature in 18o records the results suggest that the ice volume effect accounts for the observed 18o changes during the early interstadial culminations but only for 29 46 during the late interstadial culminations sea water cooling beyond the threshold limit of coral reef growth 18 c did not occur during the last glacial cycle the temperature of the surface tropical ocean was similar to present during the early interstadials of isotope stage 5 and cooler by 3 c below present during the later interstadials of isotope stage 3

determining the modal mineralogy of martian soils 1 a method for identifying the major and minor minerals and quantifying their proportions by weight in soils at the mars exploration rovers landing sites is presented the procedure utilizes modeled mossbauer data for iron bearing minerals chemical calculations of alpha particle x ray spectrometer data for iron absent minerals and modeling of minites thermal infrared spectra for silica and clays two models are formulated using different assumptions about the mineralogy of sulfur and chlorine sulfate chloride or incorporated in or adsorbed onto schwertmannite akaganeite the actual soil mineralogy may be bracketed by these results using either model average dark soils on the gusev crater plains and on meridiani planum are shown to be composed of a mixture of igneous olivine pyroxene plagioclase fe ti cr spinels phosphate and alteration amorphous silica hematite nanophase oxides clays plus sulfate chloride or oxysulfate oxychloride minerals this assemblage suggests that soil alteration did not occur in situ and that the igneous and alteration components were likely derived from different sources the model dependent mixing ratio of igneous and alteration components is identical at the two sites on opposite sides of the planet implying that martian soils may provide a representative mineralogical sampling of the exposed crust

observational evidence of crystalline iron oxides on mars visible to near ir 0 4 1 0 mu m spectral reflectance observations of mars during the 1988 opposition were performed at mauna kea observatory using a circular variable filter spectrometer at a spectral resolution r lambda delta lambda approx 80 on august 13 and 14 1988 ut 41 regions 500 600 km in diameter were observed on mars the data have been reduced both to reflectance relative to solar analog mars 16 cyg b and to relative reflectance spot spot the spectra show the strong near uv reflectance dropoff characteristic of mars as well as absorptions at 0 62 0 72 mu m and 0 81 0 94 mu m both seen here clearly for the first time these absorption features are interpreted as fe sup 3 electronic transition bands that indicate the presence of crystalline ferric oxide or hydroxide minerals on the martian surface comparison of these data with laboratory spectra obtained by other workers supports the conclusion that a single iron oxide phase most likely hematite could account for all of the observed spectral behavior of the martian surface soils and airborne dust in the 0 4 1 0 mu m region this possibility must be reconciled with data from other possible spectral analogs and other wavelength regions as well as geochemical and mineral stability considerations to arrive at amore more complete understanding of the role of ferric minerals in martian surface mineralogy and weathering less

environmental change geomorphic processes and land degradation in tropical highlands abstract the international symposium highland2006 held in mekelle ethiopia from 21 to 25 september 2006 was the second time that ethiopia could host a major international scientific event on geomorphological processes highland2006 created a forum for those conducting research on the impacts of environmental change on geomorphic processes and land degradation in east african highlands as well as in similar regions around the globe discussions of results and exchange of experiences during indoor sessions as well as excursions have resulted in this distinctive set of scientific papers the two main questions addressed in this special issue through case studies in tropical mountain areas on all continents are 1 how have environmental changes impacted the type and intensity of geomorphic processes in tropical mountains since late pleistocene times the answer to this question is strongly linked to our knowledge on changes in climate vegetation cover human activities hydrology hillslope and fluvial processes for such environments 2 which factors control the intensity of land degradation its on site and off site impacts in tropical mountains this question addresses the role of natural and anthropogenic factors in the degradation of the vegetation cover and in controlling the intensity of hydrological processes soil erosion landsliding reservoir sedimentation and flooding in parallel with this special catena issue a number of selected papers on land degradation and its mitigation in tropical highlands are presented in a special issue of soil tillage research

near synchronous interhemispheric termination of the last glacial maximum in mid latitudes isotopic records from polar ice cores imply globally asynchronous warming at the end of the last glaciation however 10be exposure dates show that large scale retreat of mid latitude last glacial maximum glaciers commenced at about the same time in both hemispheres the timing of retreat is consistent with the onset of temperature and atmospheric co2 increases in antarctic ice cores we suggest that a global trend of rising summer temperatures at the end of the last glacial maximum was obscured in north atlantic regions by hypercold winters associated with unusually extensive winter sea ice

chronology of weathered materials and soil age determination in pedostratigraphic sequences abstract subdivision of weathered soil continuums on the basis of age relationships often proves to be a difficult and contentious issue geochronological separation of weathered materials is normally achieved by application of absolute and relative dating methods radiocarbon residence times uranium series dating zircon fission track ages and thermoluminescence techniques have for example been used to estimate the timing of weathering events because many weathered materials are not amenable to isotopic age determination relative dating methodologies which employ sedimentologic and stratigraphic principles have been applied to advantage in the chronological ordering of weathering mantles particle size grading downslope and provenance of litho and pedo relicts help identify soil sedimentary sequences interpretation of soil geomorphic relationships lithologic discontinuities and pedogenetic overprinting as well as concepts of relative and effective soil age micromorphological analysis of soil fabric sequences and investigation of skeleton grain morphologies are useful in the reconstruction of weathered sedimentary environments surface textures and mineral grain shapes in particular seem to offer clues to mineral provenance and geochronology of weathered deposits

the circum hellas volcanic province mars assessment of wrinkle ridged plains abstract wrinkle ridged plains common on the terrestrial planets are inferred to form by tectonic deformation of volcanic or sedimentary surfaces if wrinkle ridged plains adjacent to volcanic features originated from volcanic activity associated with the features then the plains should have similar ages to the volcanic features as well as other morphological or compositional indicators of volcanism we test this hypothesis on several regions of wrinkle ridged plains bounding the circum hellas volcanic province chvp we constructed themis daytime ir mosaics spatial resolution 100 m pixel and performed crater counts to determined cratering model formation ages of these regions we found ages of 3 4 3 7 ga for se malea planum 3 6 3 7 ga for w promethei terra 3 5 3 7 ga for hesperia planum and 3 6 3 8 ga for the eastern hellas basin floor all of which are contemporaneous with the formation of the major volcanic edifices 3 6 3 8 ga in the chvp although examination of available moc ctx hirise themis and hrsc data shows few examples of features definitive of a volcanic origin of these wrinkle ridged plains hrsc true color images 50 100 m pixel show that large areas of these plains have a dark blue black color consistent with previous viking and mars express hrsc and omega color spectral studies indicative of basaltic compositions however in some areas this color may be due to aeolian mantles rather than underlying bedrock thus we cannot demonstrate unequivocally that these wrinkle ridged plains are volcanic beyond the synchronicity of their formation ages with those of the chvp volcanoes nevertheless if these wrinkle ridged plains were originally formed by volcanic activity or other processes induced by volcanic activity then the inclusion of these regions brings the size of the chvp to 4 86 106 km 2 comparable in size to the elysium volcanic province thus the chvp may have been a dominant source of volcanism early in martian history

low albedo surfaces and eolian sediment mars orbiter camera views of western arabia terra craters and wind streaks 1 high spatial resolution 1 5 to 6 m pixel mars global surveyor mars orbiter camera images obtained september 1997 to june 2001 show that each of the large dark wind streaks of western arabia terra originate at a barchan dune field on a crater floor the streaks consist of a relatively thin 1 m coating of sediment deflated from the dune fields and their vicinity in most cases this sediment drapes over a previous mantle that more thickly covers nearly all of western arabia terra no concurrent eolian bedforms are found within the dark streaks nor do any dunes climb up crater walls to deliver sand via saltation to the streaks the relations between dunes wind streak and subjacent terrain imply that dark toned grains finer than those that comprise the dunes are lifted into suspension and carried out of the craters to be deposited on the adjacent terrain previous eolian physics and thermal inertia studies suggest that under modern martian conditions such grains likely include silt 3 9 62 5 m very fine sand 62 5 125 m and possibly fine sand to 210 m the streaks change in terms of extent relative albedo and surface pattern over periods measured in years however through june 2001 very little evidence for recent eolian activity dust plumes storms dune movement was observed

dry and humid phases in the highlands of southern brazil during the last 34 000 years and their influence on the paleoenvironments of the region abstract the palynology of the last 34 000 years was determined for a sedimentary profile from a bog in sao francisco de paula rio grande do sul eastern plateau using radiocarbon dates profile 29 19 05 s 50 08 18 w this is a rare older palynological sequence studied in the quaternary of southern brazil between 34 300 and 28 000 bp the records suggest a cold and semi arid climate with rarefied vegetation that was dominated by sparse grassland the araucaria forest probably in refuges between 28 000 and 23 500 bp a cold and humid climate was clearly detected at the last glacial stage the vegetation generally developed with a grassland dominion and a water reservoir was in the study site between 23 500 and 12 000 bp cold and semi arid climate promoted the reduction of grassland and the local water reservoir began to be filled by sediment between 12 000 and 10 000 bp the rise in temperature and humidity resulted in the development of regional vegetation and the araucaria forest probably expanded a little from the refuges herbaceous marsh dominated the study site between 10 000 and 7500 bp an elevated temperature and dry conditions promoted a general decrease in vegetation cover between 7500 and 3000 bp a progressive increase in humidity permitted the development of local and regional vegetation and the arborous pioneers migrated from the refuges with the expansion of forest taxa such as araucaria angustifolia bertol kuntze there was the beginning and expansion of the bogs from 6000 bp onward the grassland decreased after 4000 bp probably due to the forest cover the records indicate a high regional humidity after 3000 bp which is favorable to araucaria forest however the temperature elevation during this phase probably reduced the reproductive capacity of the araucaria forest taxa resulting in a lower rate of expansion on the grassland the same factor probably reduced the regional bogs from 2000 bp onward

facies and microfacies of slope deposits abstract this paper reviews the facies and microfacies of the main types of slope deposits lamination and sorting when preserved are good evidence for overland flow features due to deformation folds boudins coatings and tails due to the rotation of clasts are associated with the early stages of deformation in earth slides other mass movements such as debris flows rock avalanches earth flows and to a certain extent dry grain flows may be characterised by similar microscopic facies typically a poorly sorted porphyric material porosity gives evidence for both liquefaction debris flows and frost induced mass movement solifluction however this criterion is thought to be irrelevant for fossil deposits owing to the rapidity and scale of post depositional changes wetting and drying freezing and thawing bioturbation at present only a detailed analysis of both the macro and micromorphological characteristics of the deposits allows an accurate identification of past slope dynamics

dust streaks on mars global mapping and photometry of selected areas on mars are used to investigate the nature of bright and dark wind streaks that extend from topographic obstacles occurrence of both bright and dark streaks is strongly latitude dependent and is only weakly correlated with surface properties such as albedo and thermal inertia data on the colors albedos and phase behavior of streaks are consistent with models of bright streaks as mosaics of plains material and brighter redder dust less than 20 of the ground need be covered by the optically thick dust in the brightest parts of the streaks the amount of dust in optically thick layers could be as little as 10 3 g cm2 dark streaks can be interpreted as erosional windows in a patchy dust cover our model of dust deposition in optically thick patches is sedimentologically different from scenarios involving the deposition of ubiquitous optically thin layers it has the advantage that large amounts of dust can be deposited without affecting regional albedos

the spatial distribution of rocks on mars abstract the spatial distribution of rocks exposed at the surface of mars has been mapped using viking infrared thermal mapper irtm observations overall there are no regions on the surface of mars at a scale of 1 1 in latitude and longitude that are rock free the modal value of rock abundance is 6 areal coverage with no areas having more than 30 35 rock cover the model developed to determine rock abundance relates the thermal emission in each of the four surface sensing irtm bands to temperature contrasts within the field of view non unit thermal emissivity due to absorption bands in the surface materials and the absorption and scattering of the outgoing energy by atmospheric dust and water ice each of these effects produce characteristic spectral and diurnal signatures allowing them to be separated the temperature contrasts provide a means to determine both the abundance of exposed rocks and the fine component thermal intertia rock abundance alone does not produce the observed variation in bulk thermal inertia of the surface low inertia fine bright surfaces have fewer rocks exposed than do high inertia coarse dark surfaces rock abundance does not correlate well with the rms slope nor reflectivity determined from delay doppler radar measurements there is however a possible correlation between rms slope determined from continuous wave radar observations dual polarization radar measurements which provide the best radar measure of small scale roughness indicate that the tharsis volcanic region is very rough whereas thermal measurements indicate very few rocks and a covering of dust together these observations suggest an approximately 1 m thick mantle of fines covering a very rough subsurface this fine material may be an aeolian deposit of dust storm fallout valles marineris together with several major channels and chaotic terrains have high rock abundances as does the acidalia planitia basin this observed distribution may reflect the initial deposition of coarse material associated with channel formation syrtis major is unique in having a high inertia but a very low rock abundance together with low radar roughness these observations are consistent with mantling of rocks by sand the observed distribution of rocks and fines indicates that aeolian processes both erosional and depositional play a dominant role in shaping the present martian surface

spectral identification of geological units on the surface of mars related to the presence of silicates from earth based near infrared telescopic charge coupled device imaging during the september 1988 mars opposition the authors obtained new high spatial 100 150 km and spectral delta lambda lambda 1 resolution near ir telescopic charge coupled device images of mars from pic du midi observatory these images allow the association of spectral units with morphologic surface units on mars especially within the dark regions which exhibit much greater variability than the bright regions mineralogical interpretation of the data leads to a global description of the surface state of alteration consistent with the spatial distribution of bright and dark regions with the bright regions being more altered than the dark within the less altered regions fe sup 2 crystal field absorption bands are detected indicative of the presence of mafic minerals opx cpx o1 in agreement with a likely crustal basaltic composition the most conspicuous fe sup 2 absorption features are clearly related to the volcanic regions of the syrtis major shield and hesperia planum unit the strongest observed absorptions due to olivine and clinopyroxene are spatially associated with the restricted central caldera complex of nili meroe paterae within syrtis major and the tyrrhena patera unit within hesperia planum and indicate an ultramafic composition

martian intracrater splotches occurrence morphology and colors abstract martian intracrater splotches and related streaks are studied with global data on their occurrence and regional data on color and morphology the fraction of craters with splotches is greatest at high latitudes splotch occurrence is not strongly correlated with surface properties such as albedo and thermal inertia except where these correlate with substantial sediment cover large numbers of splotches are or include dunes especially at high southern latitudes color data show that the dune and nondune materials in splotches are part of one related group of materials that may be of similar composition but varying particle sizes the color data also show that some streaks are simply material deflated from splotches and mixed with local plains material while other streaks are more complex and may involve erosion of thin surface layers by material blown from the splotches splotches appear to be trapped eolian sand but probably have been formed by a great variety of mechanisms a large percentage of craters with splotches show evidence of complex histories of sediment deposition and erosion many splotches may be lag deposits from erosion of regional sediment cover present sediment budgets in splotches are not known but there is some evidence for loss of material and no evidence for resupply from outside the craters

climate variability in southern south america associated with el nino and la nina events a comprehensive view is given of the precipitation and circulation anomalies associated with the various stages of el nino en and la nina ln events all over southern south america ssa this view comprises the delineation of coherent regions with respect to precipitation anomalies the identification of the seasons of maximum anomalies the indication of their magnitude and the assessment of their consistency during those events in addition the spatial and temporal variability of these anomalies is detailed by calculating the expected precipitation percentiles and the consistency of wet and dry anomalies for each station and each three month running season during en and ln events composites of circulation anomalies and an assessment of their consistency are also presented and their connection with the precipitation anomalies is discussed southern brazil presents the strongest average signal in en events the general behavior toward opposite signals in the precipitation and circulation anomalies over ssa during almost the same periods of the en and ln events indicates a large degree of linearity in the response to these events the timing of the anomalies changes throughout ssa leading to the identification of eight different coherent regions in the en case and six in the ln case this regionalization is mostly caused by different processes leading to precipitation anomalies in ssa during those events all these regions show a significant response in some part of each event the magnitude and consistency of this response show a large spatial variability and some areas present very strong and consistent anomalies sometimes not disclosed when large coherent regions are analyzed in spite of the differences in timing some features of the precipitation anomalies are rather uniform throughout the region during en and ln events in en episode there is a tendency to lower than median precipitation in the year before the event which continues until march of the year of the event in a vast region east of the andes the strongest positive precipitation anomalies occur in spring of this year when the circulation anomalies concur to enhance rainfall over several regions during the summer of the mature stage the positive precipitation anomalies almost disappear and then reappear in some regions in late summer early autumn and in winter of the year following the starting year of the event this description holds partially for the ln event but with opposite signs although there is a larger spatial variability in the ln related anomalies in the following year and some shifts in timing as for precipitation the symmetry of the geopotential height anomaly fields with opposite signs between ln and en cases is also remarkable especially during the year 0

stratigraphy of near valley head quaternary deposits and evidence of climate driven slope channel processes in southern brazilian highlands abstract during the past 40 years colluvial and alluvial deposits have been used in brazil as good indicators of regional landscape sensitivity to quaternary environmental changes in spite of the low resolution of most of the continental sedimentary record geomorphology and sedimentology may favor palaeoenvironmental interpretation when supported by independent proxy data this paper presents results obtained from pedostratigraphic sequences in near valley head sites of southern brazilian highlands based on geomorphologic sedimentologic micromorphologic isotopic and palynologic data results point to environmental changes with ages that coincide with marine isotopic stages mis 5b 3 2 and 1 during the late pleistocene although under temperatures and precipitation lower than today the local record points to relatively wet local environments where shallow soil water saturated zones contributed to erosion and sedimentation during periods of climatic change as during the transition between mis 2 and mis 1 late pleistocene events with ages that coincide with the northern hemisphere younger dryas are also depicted during the mid holocene slope wash deposits suggest a climate drier than today probably under the influence of seasonally contrasted precipitation regimes the predominance of overland flow related sedimentary deposits suggests an excess of precipitation over evaporation that influenced local palaeohydrology this environmental condition seems to be recurrent and explains how slope morphology had influenced pedogenesis and sedimentation in the study area due to relative sensitiveness resilience and short source to sink sedimentary pathways near valley head sites deserve further attention in quaternary studies in the humid tropics

quaternary colluvial eluvial covers of the eastern parana basin southeastern brazil abstract colluvial eluvial sandy clayey deposits are widespread quaternary covers in the interior of the state of sao paulo southeastern brazil and neighboring areas in the parana basin these sediments were formerly designated as the santa rita do passa quatro formation qsr the formation is thin 5 20 m thick and contains about 20 detrital kaolinitic clay enveloping rounded quartz grains producing a porous and fragile framework that causes hazardous geomorphic processes such as surface erosion piping and collapse phenomena charcoal of holocene age is common in the colluvial eluvial covers its distribution suggests colluvial and eluvial illuvial processes together with biological turnover of the regolith the presence of sandstones of the parana basin as source rocks and the geomorphological setting control the occurrence of the colluvial eluvial covers these are common over sandy substrata and are absent only upon the youngest among five planation surfaces recognized in the area suggesting that there was not enough time for accumulating the covers the colluvial eluvial covers are regarded as the product of long term surface accumulation of weathering materials that began at the end of tertiary however the formative processes are still active nowadays they comprise weathering of unstable minerals eluviation illuviation and leaching authigenesis of clay minerals concentration of quartz water erosion colluviation of regolith and biological turnover of weathered friable materials

late quaternary vegetation climate and fire history from the tropical mountain region of morro de itapeva se brazil late quaternary paleoenvironments have been interpreted from a 35 000 yr b p pollen and charcoal record from morro de itapeva 22 47 s 45 32 w 1850 m a s l in the se brazilian highlands changes in taxa composition and elevational shifts in high elevation grassland campos de altitude araucaria forest cloud forest and atlantic rain forest all of which can be found in the study area today indicate climatic changes in the past expanded high elevation grasslands absence of araucaria forest cloud forest and atlantic rain forest during the recorded last glacial period ca 35 000 17 000 yr b p suggest a climate markedly cooler and drier than today development of a sphagnum peat bog rare presence of araucaria forest taxa and existence of a narrow cloud forest and rain forest belt at lower elevations during the late glacial period 17 000 ca 10 000 yr b p indicate a change to a cool and somewhat moister climates during the early holocene cloud forest developed close to the study site reflecting a warm and moist climate on the east facing slopes but a drier climate on the highland plateau evidenced by the rare presence of araucaria and podocarpus only during the late holocene moisture increases in the highlands suggested by the higher frequency of araucaria and podocarpus fires were more frequent during the last glacial than during the holocene

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

dark materials in valles marineris indications of the style of volcanism and magmatism on mars rifting on the equatorial canyon system of valles marineris provides a unique view of the interior of the martian crust to depths reaching 7 km exposing several in situ bedrock units which testify to past volcanic and magmatic processes on mars a thick regionally extensive deposit observed in coprates and juventae chasmata is interpreted on the basis of spectral reflectance erosional morphology and tendency for eolian mobilization to be composed of mafic glass possibly an ancient martian analogue of the lunar terra mantling deposits spectral mapping suggests that the dark floor covering materials in the lower canyons are derived from this unit a series of cliffs in the ophir chasma wall rock is interpreted to be exposures of resistant bedrock the spectral signature of this massive and uniform unit most closely resembles that of terrestrial mafic rocks altered to or coated by crystalline hematite application of computer mapping techniques to probable young volcanic materials in the central troughs yields an inferred distribution of volcanic activity consistent with the interpretation of extrusion along faults near the margins of the canyon floors this result supports the hypothesis that the valles originated through tectonic extension

radiolarian based paleotemperatures during the last 160 kyr at odp site 1089 southern ocean atlantic sector two cores site 1089 odp leg 177 and ps2821 1 recovered from the same location 40 56 ps 9 54pe at the subtropical front stf in the atlantic sector of the southern ocean provide a high resolution climatic record with an average temporal resolution of less than 600 yr a multi proxy approach was used to produce an age model for core ps2821 1 and to correlate the two cores both cores document the last climatic cycle from marine isotopic stage 6 mis 6 ca 160 kyr bp ka to present summer sea surface temperatures sssts have been estimated with a standard error of ca 8 1 16 c for the down core record by using q mode factor analysis imbrie and kipp method the paleotemperatures show a 7 c warming at termination ii last interglacial transition from mis 6 to mis 5 this transition from glacial to interglacial paleotemperatures with maximum temperatures ca 3 c warmer than present at the core location occurs earlier than the corresponding shift in n 18 o values for benthic foraminifera from the same core this suggests a lead of southern ocean paleotemperature changes compared to the global ice volume changes as indicated by the benthic isotopic record the climatic evolution of the record continues with a progressive temperature deterioration towards mis 2 high frequency millennial scale climatic instability has been documented for mis 3 and part of mis 4 with sudden temperature variations of almost the same magnitude as those observed at the transitions between glacial and interglacial times these changes occur during the same time interval as the dansgaard oeschger cycles recognized in the n 18 oice record of the grip and gisp ice cores from greenland and seem to be connected to rapid changes in the stf position in relation to the core location sudden cooling episodes younger dryas yd type and antarctic cold reversal acr type of events have been recognized for both termination i acr i and yd i events and ii acr ii and yd ii events and imply that our core is located in an optimal position in order to record events triggered by phenomena occurring in both hemispheres spectral analysis of our ssst record displays strong analogies particularly for high sub orbital frequencies to equivalent records from vostok antarctica and from the subtropical north atlantic ocean this implies that the climatic variability of widely separated areas the antarctic continent the subtropical north atlantic and the subantarctic south atlantic can be strongly coupled and co varying at millennial time scales a few to 10 ka periods and eventually induced by the same triggering mechanisms climatic variability has also been documented for supposedly warm and stable interglacial intervals mis 1 and 5 with several cold events which can be correlated to other southern ocean and north atlantic sediment records d 2002 elsevier science b v all rights reserved

digital scanning of thin sections and peels abstract digital film scanners allow direct capture of high resolution digital images of entire petrographic thin sections or acetate peels a capability not available using standard petrographic microscopes using a small format 35 mm film scanner as an example this article describes a means of directly scanning at high resolution standard petrographic thin sections larger 2 3 in 5 08 7 62 cm thin sections and portions of acetate peels and saving them as digital images such images fall into the range of macrophotography and bridge the gap between standard photography and photomicrography because no film is used and the light passes through no distorting lenses the images obtained are of exceptional quality and can be processed and printed immediately by sandwiching the thin section between sheet polarizing filters scanned images through cross polarized light can be obtained simulating crossed nicols the images of acetate peels far exceed the quality of equivalent photographs other film scanners and scanning film backs are available in large format and can be mounted directly on microscopes for digital imaging at higher magnification and can eliminate the need for conventional film in petrographic studies

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

sea level fingerprinting as a direct test for the source of global meltwater pulse ia the ice reservoir that served as the source for the meltwater pulse ia remains enigmatic and controversial we show that each of the melting scenarios that have been proposed for the event produces a distinct variation or fingerprint in the global distribution of meltwater we compare sea level fingerprints associated with various melting scenarios to existing sea level records from barbados and the sunda shelf and conclude that the southern laurentide ice sheet could not have been the sole source of the meltwater pulse whereas a substantial contribution from the antarctic ice sheet is consistent with these records

landscape sensitivity to rapid environmental change a quaternary perspective with examples from tropical areas abstract a millennial scale of rapid change during the quaternary is recorded in grip and gisp2 ice core records and is also found in tropical oceans rapid warming episodes followed by gradual cooling associated with sub milankovich cycles implies an asymmetry in the behaviour of climate that is likely to be reflected in landscape responses slope failures floods colluvial alluvial sedimentation may reflect short term changes in the record but reorganisation of slope and fluvial systems involves significant time lags or delays often on a millennial scale and requiring changes to the vegetation cover while some records of sedimentation indicate major landscape instability during last 20 ky or in the early holocene others indicate pulses of activity throughout the last glacial cycle lgc these differences may reflect regional patterns of climate change but also illustrate the importance of landscape sensitivity to our understanding of the impacts of rapid environmental change methodological problems arise in attempting correlations between site specific records of sedimentation and integrated signals of hydrologic change found in deltaic and off shore fans

paleoclimate of the late pleistocene and holocene at lagoa dourada parana state southern brazil abstract a 12 m deep core from the sediments of lagoa dourada parana state southern brazil was analyzed about its diatoms extractable inorganic cations ca mg k available phosphorus organic matter water contents and sedimentology studies of the lake sequence with a basal date of 11 110 110 yr bp provide a history of climatic changes divided into nine zones zone a1 prior to 11 000 yr bp contains diatom taxa suggesting dry environments zone b1 around 11 000 yr bp indicates very humid climatic conditions synchronous with reduced temperatures around 8 710 150 yr bp the core does not contain diatoms and the convergence of some paleoclimatic indicators suggests that a drier paleoclimate is represented zone a2 and b2 have planktonic diatom spectra that suggest progressive high humidity a marked decline in moisture levels is expressed in zone c as suggested by an increase in only one dominant periphytic taxon the following periods zones d1 d2 and d3 were characterized by several water level oscillations with short and intensive dry events and longer intervening humid periods zone e establishes the present diatom and climatic pattern of lagoa dourada cultural disturbances could be indicated by the high k levels detected on the core top which are probably due to the agricultural boom in the catchment area

coastal wetlands sea level and the dimensions of geomorphic resilience abstract geomorphic system resilience is often perceived as an intrinsic property of system structure and interactions but is also related to idiosyncratic place and history factors the importance of geographical and historical circumstances makes it difficult to generate categorical statements about geomorphic resilience however network based analyses of system structure can be used to determine the dynamical stability resilience based on generally applicable relationships and to determine scenarios of stability or instability these provide guidelines for assessing place and history factors to assess resilience a model of coastal wetlands is analyzed based on interactions among relative sea level wetland surface elevation hydroperiod vegetation and sedimentation the system is generally but not always dynamically unstable and non resilient because of gradients of environmental factors and patchy distributions of microtopography and vegetation a coastal wetland landscape may have extensive local variations in stability resilience and in the key relationships that trigger instabilities this is illustrated by a case study where dynamically unstable fragmentation is found in two nearby coastal wetlands in north carolina s neuse river estuary otter creek mouth and anderson creek neither is keeping pace with relative sea level rise and both show unstable state transitions within the wetland system but locally stable relationships exist within the wetland systems

new radar derived topography for the northern hemisphere of mars earth based radar altimetry data for the northern equatorial belt of mars 6 s 23 n have recently been reduced to a common basis corresponding to the 6 1 mbar reference surface a first look at these data indicates that the elevations of tharsis elysium and lunae planum are lower by 2 5 km than has been suggested by previous estimates these differences show that the required amount of tectonic uplift or constructional volcanism for each area is less than has been previously envisioned atmospheric or surficial conditions are suggested which may explain the discrepancies between the radar topography and elevations measured by other techniques the topographies of chryse planitia syrtis major and valles marineris are also described

surficial geologic surveys of gale crater and melas chasma mars integration of remote sensing data abstract remote sensing observations of gale crater and melas chasma are synthesized to better understand the present surface layer in these two scientifically interesting regions data sets analyzed include geologic maps mars orbiter laser altimeter mola elevation thermal emission spectrometer tes albedo tes thermal inertia mola residual pulse width tes rock abundance and viking and mars orbiter camera images using these data sets we constrain the properties of and processes acting on the present surface and create self consistent models for the surface layer surface properties within gale crater are variable and complex and interpreting the surface layer is not straightforward observations indicate that aeolian processes have shaped some of the intracrater surface but other areas do not comply with this model and have counterintuitive surface characteristics in contrast aeolian activity appears to have played a large role in shaping the present day physical structure of all surfaces in melas chasma and is reflected in the remote sensing data sets here we summarize our analysis and discuss the surface attributes as determined from these data sets

the response of geomorphic systems to climatic and hydrological change during the late glacial and early holocene in the humid and sub humid tropics

the evolution of a tropical rainforest grassland mosaic in southeastern brazil since 28 000 14c yr bp based on carbon isotopes and pollen records the lack of paleoecological records from the montane atlantic rainforest of coastal brazil a hotspot of biological diversity has been a major obstacle to our understanding of the vegetational changes since the last glacial cycle we present carbon isotope and pollen records to assess the impact of the glaciation on the native vegetation of the serra do mar rainforest in sao paulo brazil from ca 28 000 to 22 000 14c yr bp a subtropical forest with conifer trees is indicative of cool and humid conditions in agreement carbon isotopic data on soil organic matter suggest the presence of c3 plants and perhaps c4 plants from 28 000 to 19 000 14c yr bp the significant increase in the sedimentation rate and algal spores from 19 450 to 19 000 14c yr bp indicates increasing humidity associated to an erosion process between 19 000 and 15 600 14c yr bp from 15 600 14c yr bp to present there is a substantial increase in arboreal elements and herbs indicating more humid and warmer climate from 19 000 to 1000 14c yr bp 13c values indicated the predominance of c3 plants these results are in agreement with studies in speleothems of caves which suggest humid conditions during the last glacial maximum

late quaternary stream sedimentation in the humid tropics a review with new data from ne queensland australia there is now a wide agreement that temperature depression in the humid tropics during the last glacial maximum lgm was at least 5 c most estimates of precipitation reduction at the lgm range from 25 30 to 50 65 based on proxy data but the recent ccm1 model envisages only around 12 dates obtained from river sediments indicate major changes to fluvial activity in the late quaternary isotope zone 3 sediments 58 28 ka bp are widespread and possibly indicate cooler conditions post 28 ka bp and certainly post 21 ka bp river regimes altered radically towards fan building braiding or major reduction in all activity this paper reports on fan formation in ne queensland between 26 and 14 ka bp and reviews evidence for comparable changes in humid tropical areas of s america w africa and se asia including records of holocene sedimentation within a global rhythm of major changes to river regimes in the humid tropics during the late quaternary it is now possible to detect regional variations in stream response to climatic change at the lgm reductions in stream power may have led to fan formation in ne queensland while vegetation changes may have contributed to increased sediment loads and braiding in some forest marginal areas but in w africa greater aridity may have been responsible for enfeebled streams leaving few records channel cutting then deposition of coarse sediment in braided rivers marked the transition to the early holocene in w africa and fans became entrenched in ne queensland this regime persisted until forest recovery was complete by 9 5 8 5 ka bp when widespread overbank deposition occurred and a change towards meandering channels took place widely across the humid tropical zone followed by several cut and fill episodes in the middle and late holocene

the nanophase iron mineral s in mars soil a series of surface modified clays containing nanophase np iron oxide oxyhydroxides of extremely small particle sizes with total iron contents as high as found in mars soil were prepared by iron deposition on the clay surface from ferrous chloride solution comprehensive studies of the iron mineralogy in these mars soil analogs were conducted using chemical extractions solubility analyses ph and redox x ray and electron diffractometry electron microscopic imaging specific surface area and particle size determinations differential thermal analyses magnetic properties characterization spectral reflectance and viking biology simulation experiments the clay matrix and the procedure used for synthesis produced nanophase iron oxides containing a certain proportion of divalent iron which slowly converts to more stable fully oxidized iron minerals the clay acted as an effective matrix both chemically and sterically preventing the major part of the synthesized iron oxides from ripening i e growing and developing larger crystals the precipitated iron oxides appear as isodiametric or slightly elongated particles in the size range 1 10 nm having large specific surface area the noncrystalline nature of the iron compounds precipitated on the surface of the clay was verified by their complete extractability in oxalate lepidocrocite gamma feooh was detected by selected area electron diffraction it is formed from a double iron fe ii fe iii hydroxy mineral such as green rust or ferrosic hydroxide magnetic measurements suggested that lepidocrocite converted to the more stable maghemite gamma fe2o3 by mild heat treatment and then to nanophase hematite alpha fe2o3 by extensive heat treatment after mild heating the iron enriched clay became slightly magnetic to the extent that it adheres to a hand held magnet as was observed with mars soil the chemical reactivity of the iron enriched clays strongly resembles and offers a plausible mechanism for the somewhat puzzling observations of the viking biology experiments their unique chemical reactivities are attributed to the combined catalytic effects of the iron oxide oxyhydroxides and silicate phase surfaces the reflectance spectrum of the clay iron preparations in the visible range is generally similar to the reflectance curves of bright regions on mars this strengthens the evidence for the predominance of nanophase iron oxides oxyhydroxides in mars soil the mode of formation of these nanophase iron oxides on mars is still unknown it is puzzling that despite the long period of time since aqueous weathering took place on mars they have not developed from their transitory stage to well crystallized end members the possibility is suggested that these phases represent a continuously on going extremely slow weathering process

timing of millennial scale climate change in antarctica and greenland during the last glacial period a precise relative chronology for greenland and west antarctic paleotemperature is extended to 90 000 years ago based on correlation of atmospheric methane records from the greenland ice sheet project 2 and byrd ice cores over this period the onset of seven major millennial scale warmings in antarctica preceded the onset of greenland warmings by 1500 to 3000 years in general antarctic temperatures increased gradually while greenland temperatures were decreasing or constant and the termination of antarctic warming was apparently coincident with the onset of rapid warming in greenland this pattern provides further evidence for the operation of a bipolar see saw in air temperatures and an oceanic teleconnection between the hemispheres on millennial time scales

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

young volcanic deposits in the valles marineris mars abstract a study of the interior deposits of the central valles marineris has led to the discovery of a sequence of deposits that cover the chasma floors and range in thickness from that of thin dust to several kilometers the emplacement of the deposits was the last major event in the history of the valles marineris following deposition of older layered interior beds warping faulting erosion and landslide emplacement the young deposits are of three major types 1 dark patches typically occurring along faults 2 light colored deposits locally associated with craters and 3 rugged mottled deposits with in places light colored lobate fronts these young materials may be of volcanic origin as suggested by the low albedo and spectrally gray colors of some their association with faults and possible volcanic craters and calderas and their embayment relations and lobate margins no other mechanism explains all the observed features and relations as well as volcanism if these deposits are volcanic implications are that 1 volcanism was associated with rifting in the valles marineris 2 the volcanism was explosive in places and 3 the volcanism may be as young as the late tharsis volcanism and locally may well be recent

nature and origin of materials exposed in the oxia palus western arabia sinus meridiani region mars abstract mars observer will map physical elemental and mineralogical properties of surface materials a key to understanding the regional variations in crustal composition will be the extent to which in situ debris produced from bedrock can be separated from laterally mixed eolian sediments viking orbiter image and thermal data covering equatorial cratered terrain in western arabia eastern oxia and sinuses sabaeus and meridiani were evaluated to test whether local materials related to bedrock could be identified characterized and mapped crater obliteration models imply that kilometers of debris have been produced locally although obliteration rates for the past few billion years have been less than 8 10 3 m year fluvial and eolian landforms clearly indicate lateral transport and mixing of tens of meters of debris six sets of calibrated violet green and red viking images covering the study area were mosaicked and examined in combination with block abundance and fine component inertias from irtm data three major color thermal units can be discerned bright red dust storm deposits brown materials that are probably indurated and dark less red materials that are probably composed of lithic fragments in the medium sand size range the unit boundaries are independent of bedrock geology and erosional landforms the brightest red material apparently mixes with each of the darker units the presence of dark splotches streaks and dunes associated with large craters in oxia indicates that the dark less red material is also mobile the surficial units exposed over the 6 10 6 km 2 study area are therefore likely to represent mixed eolian deposits predominantly decoupled from the underlying bedrock unraveling the mixtures and assignment of components to local bedrock origins will be a major challenge for mars observer

geochemical evidence of the anthropogenic alteration of element composition in lacustrine sediments from wuliangsu lake north china abstract wuliangsu lake is located in the upper reaches of the yellow river and its catchment is found in the hetao basin one of the three largest irrigation districts in china a 56 cm length sediment core was collected from the south side of the lake geochronology radiometric methods using 137 cs and 210 pb were subsequently used to date the short sediment core the concentrations of elements al fe ca mg na k ti co v cr be ba sr cu pb zn mn ni and p were studied in the solid phase at each 1 cm section based on correlation analysis and principal component analysis four groups of elements were identified the first group included total p cu and mn which indicate anthropogenic activities such as agriculture industry and sewage effluents the second group included co pb and zn that were influenced by both anthropogenic and natural factors the third group consisted of ca and sr the concentration profiles of ca and sr displayed a negative correlation with the remaining elements al k fe mg be etc which comprised the fourth group that were mainly terrigenous in addition the enrichment factors efs for all elements used as a means of identifying and quantifying human interference was evaluated the efs for cu mn pb zn co and p showed significant variation finally with constrained clustering analysis of efs for cu mn pb zn co and p the stages of regional environment were orderly and objectively divided before the 1960s efs for heavy metals displayed relatively constant values suggesting a little human influence the increasing severity of heavy metal accumulation evidenced by enhancement of efs for heavy metals began to appear in the 1960s which corresponded to local environmental development and therefore reflects strengthened human impacts the efs of total phosphorus and heavy metals then increased rapidly especially at the beginning of the 21st century