the sanandaj sirjan zone in the neo tethyan suture western iran zircon u pb evidence of late palaeozoic rifting of northern gondwana and mid jurassic orogenesis abstract the zagros orogen marking the closure of the neo tethyan ocean formed by continental collision beginning in the late eocene to early miocene collision was preceded by a complicated tectonic history involving pan african orogenesis late palaeozoic rifting forming neo tethys followed by mesozoic convergence on the ocean s northern margin and ophiolite obduction on its southern margin the sanandaj sirjan zone is a metamorphic belt in the zagros orogen of gondwanan provenance zircon ages have established pan african basement igneous and metamorphic complexes in addition to uncommon late palaeozoic plutons and abundant jurassic plutonic rocks we have determined zircon ages from units in the northwestern sanandaj sirjan zone golpaygan region a sample of quartzite from the june complex has detrital zircons with u pb ages mainly in 800 1050 ma with a maximum depositional age of 547 32 ma latest neoproterozoic earliest cambrian a shrimp u pb zircon age of 336 9 ma from gabbro in the june complex indicates a carboniferous plutonic event that is also recorded in the far northwestern sanandaj sirjan zone together with the permian hasanrobat granite near golpaygan they all are considered related to rifting marking formation of neo tethys scarce detrital zircons from an extensive package of metasedimentary rocks hamadan phyllite have ages consistent with the triassic to early jurassic age previously determined from fossils these ages confirm that an orogenic episode affected the sanandaj sirjan zone in the early to middle jurassic cimmerian orogeny although the cimmerian orogeny in northern iran reflects late triassic to jurassic collision of the turan platform southern eurasia and the cimmerian microcontinent we consider that in the sanandaj sirjan zone a tectonothermal event coeval with the cimmerian orogeny resulted from initiation of subduction and closure of rift basins along the northern margin of neo tethys

characteristics distribution origin and significance of opaline silica observed by the spirit rover in gusev crater mars 1 the presence of outcrops and soil regolith rich in opaline silica 65 92 wt sio2 in association with volcanic materials adjacent to the home plate feature in gusev crater is evidence for hydrothermal conditions the spirit rover has supplied a diverse set of observations that are used here to better understand the formation of silica and the activity abundance and fate of water in the first hydrothermal system to be explored in situ on mars we apply spectral chemical morphological textural and stratigraphic observations to assess whether the silica was produced by acid sulfate leaching of precursor rocks by precipitation from silica rich solutions or by some combination the apparent lack of s enrichment and the relatively low oxidation state of the home plate silica rich materials appear inconsistent with the originally proposed hawaiian analog for fumarolic acid sulfate leaching the stratiform distribution of the silica rich outcrops and their porous and brecciated microtextures are consistent with sinter produced by silica precipitation there is no evidence for crystalline quartz phases among the silica occurrences an indication of the lack of diagenetic maturation following the production of the amorphous opaline phase

early cambrian ocean anoxia in south china the cause of the most marked changes in the evolution of life which define the first order stratigraphic boundary between the precambrian and the phanerozoic eon remains enigmatic and a highly topical subject of debate a global ocean anoxic event triggered by large scale hydrogen sulphide h 2 s release to surface waters has been suggested by wille et al on the basis of two data sets from south china and oman to explain the fundamental biological changes across the precambrian cambrian pc c boundary here we report a new precise shrimp u pb zircon age of 532 3 0 7 million years myr ago fig 1 for a volcanic ash bed in the critical unit that reflects the ocean anoxic event the lowermost black shale sequence of the niutitang formation in the guizhou province south china this age is significantly younger than the precise pc c boundary age of 542 0 0 3 myr ago approximately 10 myr younger than the extinction of the ediacaran fauna and thus challenging the view of a major ocean anoxic event having been responsible for the major changes in the direction of evolution at the pc c boundary

on the origin of gypsum in the mars north polar region 1 we describe the distribution and concentration of the largest martian gypsum deposit discovered to date by the mars express omega observatoire pour le mineralogie l eau les glaces et l activite imaging spectrometer its relationship to the late amazonian aged north polar dunes in which it is found and its likely origin gypsum has not been discovered anywhere within the north polar region outside of the olympia undae dune sea in the areas of highest gypsum a concentration 35 pure gypsum grains of a few tens of micrometers in size mixed with 65 millimeter sized gypsum grains containing dark spectrally featureless inclusions best fit the omega observations the gypsum rich dunes contain no significant average albedo temperature or morphological anomalies we propose that water emanating from nearby channels carved during melting of the polar layered deposits infiltrated the eastern end of the polar dune sea percolating through the dunes deposits of gypsum resulted from a combination of direct in situ alteration of sulfide and high calcium pyroxene bearing dunes and from formation of evaporitic gypsum crystals in the pore spaces of these dunes this gypsum deposit formed in a unique local environment and is disconnected from sulfate forming events elsewhere on mars which are thought to have occurred much earlier during the late noachian and hesperian by various means sulfates have not been discovered in any other collection of dunes on mars

cyanobacterial precipitation of gypsum calcite and magnesite from natural alkaline lake water results from transmission electron microscopy provide direct evidence for cyanobacterial biomineralization of gypsum and calcite in aquatic environments laboratory simulations using filter sterilized natural lake water inoculated with synechococcus sp isolated from fayette ville green lake new york revealed epicellular biomineralization of gypsum calcite and magnesite experimental electron microscopical and sedimentological evidence indicates that synechococcus is responsible for a major proportion of the marl sediment and carbonate bioherms in green lake the elucidated role of synechococcus in biomineralization and its ubiquitous distribution in nature have widespread implications for cyanobacterial mineralization in marine and freshwater environments since late archean time

use of a limited area model nested in a general circulation model for regional climate simulation over europe a limited area model lam nested in a general circulation model gcm is applied to the simulation of wintertime january climate over europe the output of a coarse scale gcm is used to drive a high resolution lam over an area including central and western europe the british isles with adjacent oceans and the western mediterranean the models used are the community climate model ccm1 of the national center for atmospheric research ncar and the pennsylvania state university ncar mesoscale model mm4 the january climatology of a 10 year simulation with the standard ccm1 at a 7 5 4 5 r15 longitude latitude resolution is first analyzed the model simulates realistic average large scale circulations major storm tracks and large scale precipitation patterns over the region although cyclogenesis over the mediterranean is not captured due to the coarseness of the model topography using the output of the r15 simulation to provide driving lateral boundary conditions 10 januaries are simulated with the nested mm4 at 70 km grid point spacing a spacing sufficient to resolve the main topographical features and coastlines of western europe two storm cases simulated with the nested mm4 are discussed in detail which show how the model captures cyclogenetic processes over the mediterranean and in the lee of the alps and simulates realistic development of synoptic systems owing to its better representation of topography and coastlines the nested mm4 produces a regional distribution of climatic variables such as precipitation surface air temperature cloudiness and snow cover which is much more realistic than that of the driving ccm1 alone and compares well with high resolution observations

the simulation of stationary and transient geopotential height eddies in january and july with a spectral general circulation model abstract we examine the characteristics of stationary and transient eddies in the geopotential height field as simulated by a spectral general circulation model the model possesses a realistic distribution of continents and oceans and realistic but smoothed topography two simulations with perpetual january and july forcing by climatological sea surface temperatures sea ice and insulation were extended to 1200 days of which the final 600 days were used for the results in this study we find that the stationary waves are well simulated in both seasons in the northern hemisphere where strong forcing by orography and land sea thermal contrasts exists however in the southern hemisphere where no continents are present in midlatitudes the stationary waves have smaller amplitude than that observed in both seasons in both hemispheres the transient eddies are well simulated in the winter season but are too weak in the summer season the model fails to generate a sufficiently intense summertime midlati

exploring for a record of ancient martian life the immediate task facing exopaleontology is to define a strategy to explore mars for a fossil record during the decade long exploration program that lies ahead consideration of the quality of paleontological information preserved under different geological conditions is important if we are to develop a strategy with broad applicability the preservation of microbial fossils is strongly influenced by the physical chemical and biological factors of the environment which acting together determine the types of information that will be captured and retained in the rock record in detrital sedimentary systems preservation is favored by rapid burial in fine grained clay rich sediments in chemical sedimentary systems preservation is enhanced by rapid entombment in fine grained chemical precipitates for long term preservation host rocks must be composed of stable minerals that are resistant to chemical weathering and that form an impermeable matrix and closed chemical system to protect biosignatures from alteration during subsequent diagenesis or metamorphism in this context host rocks composed of highly ordered chemically stable mineral phases like silica e g cherts or phosphate e g phosphorites are especially favored such lithologies tend to have very long crustal residence times and along with carbonates and shales are the most common host rocks for the precambrian microfossil record on earth although we make the defensible assumption that mars was more like the earth early in its history clearly the geological and historical differences between the two planets are many such differences must be carefully considered when adapting an earth based strategy to mars

mars north polar deposits stratigraphy age and geodynamical response the shallow radar sharad on the mars reconnaissance orbiter has imaged the internal stratigraphy of the north polar layered deposits of mars radar reflections within the deposits reveal a laterally continuous deposition of layers which typically consist of four packets of finely spaced reflectors separated by homogeneous interpacket regions of nearly pure ice the packet interpacket structure can be explained by approximately million year periodicities in mars obliquity or orbital eccentricity the observed 100 meter maximum deflection of the underlying substrate in response to the ice load implies that the present day thickness of an equilibrium elastic lithosphere is greater than 300 kilometers alternatively the response to the load may be in a transient state controlled by mantle viscosity both scenarios probably require that mars has a subchondritic abundance of heat producing elements

neoproterozoic to early cambrian small shelly fossil assemblages and a revised biostratigraphic correlation of the yangtze platform china abstract small shelly fossils ssfs occur widely on the yangtze platform and have great potential for biostratigraphic subdivision of pre trilobitic early cambrian strata based on the ssf record of the shallow water realm five biozones can be recognized for the meishucunian stage in ascending order the biozones are anabarites trisulcatus protohertzina anabarica assemblage zone paragloborilus subglobosus purella squamulosa assemblage zone watsonella crosbyi assemblage zone formerly heraultipegma yunnanensis zone poorly fossiliferous interzone sinosachites flabelliformis tannuolina zhangwentangi assemblage zone in addition one ssf biozone is recognized for the overlying qiongzhusian stage pelagiella subangulata taxon range zone the formerly used siphogonuchites triangularis paragloborilus subglobosus zone and heraultipegma yunnanensis zone are discussed and redefined approximately 80 species of ssfs were screened for their spatial and temporal distribution on the yangtze platform variations in lithofacies and biofacies can be recognized throughout the yangtze platform extending over an area of 2000 900 km in a deeper water shelf setting the first zone is represented by the protohertzina anabarica kaiyangites novilis assemblage zone while younger zones are not recognized in the southern region at the northern platform margin the qiongzhusian is represented by the ninella tarimensis cambroclavus fangxianensis assemblage zone and the rhombocorniculum cancellatum taxon range zone the southeastern shaanxi western hubei region followed a slightly different lithological and faunal development than the rest of yangtze platform indicating a stronger similarity with parts of east gondwana some taxa such as w crosbyi p subangulata r cancellatum microdictyon effusum a trisulcatus protohertzina unguliformis and p anabarica occur nearly worldwide and support an international correlation of early cambrian sequences between the yangtze platform and smaller west gondwanan blocks siberia newfoundland and australia the six investigated zones of the yangtze platform comprise an interval spanning the early nemakit daldynian to the late atdabanian early botoman stage on the siberian platform palaeobiogeographic analysis revealed a strong taxic similarity between the yangtze platform and the tarim platform a smaller number of species are shared with other west gondwanan platform fragments such as india and iran palaeobiogeographic results do not support the previously reported position of the south china block between australia and siberia during the early cambrian

extreme enrichment of polymetallic ni mo pge au in lower cambrian black shales of south china an os isotope and pge geochemical investigation extreme metal enrichments occur in the lower cambrian niutitang formation a thick black shale sequence deposited on the yangtze platform of south china and form a regionally distributed conformable polymetallic ni mo pge au sulfide horizon the origin for the extreme enrichment of metals in these black shales is discussed based on a comprehensive geochemical investigation of re os isotopes and platinum group elements the black shales of the lower cambrian niutitang formation in guizhou province yielded an re os isochron age of 535 11 ma with an initial 187 os 188 os ratio of 0 80 0 04 which is similar to the initial 187 os 188 os ratio 0 78 0 19 of the ni mo sulfide ores but slightly lower than the initial 187 os 188 os ratio 1 18 0 02 of lower cambrian black shales from the lesser himalaya india a comparison of os isotope data among the chinese ni mo sulfide ores the seafloor massive sulfide deposits and contemporaneous seawater suggests a possible similar hydrothermal forming mechanism for these deposits the pge concentrations pt anomaly pt pt pt pd ir pd au pd ratios of the chinese ni mo sulfide ores are similar to those metal rich black shales of submarine volcanogenic hydrothermal origin from czech republic namibia and canada but are different from those data of the ocean floor fe mn crusts that have scavenged their pge and other metals directly from seawater it is therefore suggested that the ni mo sulfide ores from the niutitang black shale sequence in south china had a submarine hydrothermal origin the anoxic environments and abundant organic matter in the ocean basin also played a key role for the extreme metal enrichments the discharge of hydrothermal fluids into the cambrian ocean may have had a great effect on life during the cambrian explosion 2007 elsevier b v all rights reserved

formation of the hydrothermal system in geysers valley kronotsky nature reserve kamchatka and triggers of the giant landslide abstract the geysers valley hydrothermal system is hosted within a system of two permeable faults revealed by mapping thermal features located above a suggested partially melted magmatic body and recharged by meteoric water along the outcrops of rhyolite dacite extrusions fast erosion is stimulating the significant discharge rate the geyser s cycling mode and landslide events natural state thermal hydrodynamic modeling shows that 20 30 ka of high temperature upflow of 250 kg s and an enthalpy of 900 kj kg could build up the hydrothermal system in the geysers valley basin with output discharge parameters comparable to those at the current level modeling also shows that steam accumulation below an inclined caprock may have hydrothermal eruption potential the giant landslide took place on june 3 2007 when 20 10 6 m 3 of rocks were shifted 2 km downstream more than 23 geysers were buried or submerged and podprudnoe lake was dammed injecting cold water into submerged geysers possible triggers of the giant landslide include the inclination of the sliding plane towards the geysernaya river basin a pressure increase in the fluid magma system hanging block saturation by water during spring flooding hydrothermal alteration weakening of the sliding plane and steam explosions recent geysers cycling activity monitoring data 2007 2010 hydrogeochemical sampling and thermal area infra red ir survey data are also discussed

evaluating the role of sulfide weathering in the formation of sulfates or carbonates on mars orbital and landed missions to mars have revealed complex sulfate and fe oxide bearing mineralogical assemblages which have been interpreted as the result of a late planet wide acidic period due to large so2 emissions however this global scenario does not explain the recent discovery of hesperian and noachian aged carbonates in several regions because they should have been dissolved by the acidic conditions nor the restriction of sulfate occurrences in preferential regions here we present the results of a 4 year long experimental study designed to test the impact of fe sulfides pyrrhotite fe0 9s on the weathering of basaltic silicates olivine clino and orthopyroxene under an early martian like co2 rich atmosphere our weathered silicate sulfide mixtures showed complex parageneses containing elemental sulfur hydrated sulfates gypsum hexahydrite jarosite and fe oxy hydroxides olivine only samples produced nesquehonite an mg carbonate precursor of hydromagnesite and magnesite these secondary phases are similar to those observed in the martian sulfate and carbonate bearing deposits therefore we propose a geochemical model in which on the one hand martian sulfates mainly formed from weathering of sulfide enriched basalts producing locally acidic environments and on the other hand carbonates were preserved and could even have formed in regions initially devoid of sulfides thereby resolving the apparent paradox arising from the possible coeval formation of the two types of minerals these results raise doubts on the need for a global acidic event to produce the sulfate bearing assemblages suggest that regional sequestration of sulfate deposits is due to regional differences in sulfide content of the bedrock and pave the way for reevaluating the likelihood that early sediments preserved biosignatures from the earliest times

re os dating of polymetallic ni mo pge au mineralization in lower cambrian black shales of south china and its geological significance a discussion sir thirty years ago fan et al 1973 reported an entirely new type of ore from cambrian black shales of south china containing percent values for ni mo as and in some cases zn together with substantial amounts of pt pd and au 100 1 000 ppb subsequently chen et al 1982 and fan 1983 described additional ni mo ore bed occurrences in a 1 600 km belt between kunming and hangzhou mao et al 2002 p 1057 describe the deposits as a thin layer having a wide lateral extent over hundreds of kilometers in southern china that contrasts with the lenticular shape of exhalative deposits which are usually located near hydrothermal vents and are continuous over only a few kilometers at most actually the known shale hosted ni mo deposits of china do consist of restricted lenticular occurrences that are clustered in eight relatively small areas lott et al 1999 near zunyi the principal but now exhausted deposit on tianeshan measures approximately 150 by 1 000 m in plan view and gaps occur between it and outliers at tuanshanbao and xintugou lott et al 1999 these deposits in turn are separated by 5 to 7 km from the newly described mineralized zone at huangjiawan mine mao et al 2002 the thicknesses of ni mo ore beds or lenses are extremely variable typically ranging from 1

gypsum in modern kamchatka volcanic hot springs and the lower cambrian black shale applied to the microbial mediated precipitation of sulfates on mars gypsum is a mineral that commonly precipitates in hydrothermal environments this study reports the electron microscopic analyses of gypsum morphologies and crystal sizes found in hot springs on the kamchatka peninsula russia and compares these analyses with gypsum morphologies of hydrothermal genesis found in lower cambrian black shale in sediments of the kamchatka hot springs we observed prismatic prismatic pseudo hexagonal fibrous tubular lenticular and twinned gypsum crystals with crystal sizes ranging from 200 m the coexistence of diverse crystal habits of gypsum implies a constant interaction between hot spring geochemistry and the metabolisms of the microbial community the crystallization of ca and ba sulfates in the black shale of the lower cambrian which shows similar but less varied morphology was influenced by post depositional hydrothermal fluids the partial replacement of pyrite by sulfates in a situation coexisting with rich biomass deposits and animal fossils indicates limited modification of the sedimentary records by biological materials if the gypsum precipitated on mars underwent similar interactions between microbial communities and their geochemical environments the resulting crystal habits could be preserved even better than those on earth due to the weak geodynamics prevailing on mars throughout its evolutionary history

a review of meteorite evidence for the timing of magmatism and of surface or near surface liquid water on mars 1 there is widespread photogeological evidence for ubiquitous water flowing on the surface of mars however the age of surface and near surface water cannot be deduced with high precision from photogeology while there is clear evidence for old and young fluvial features in the photogeologic record the uncertainty in the absolute calibration of the martian crater flux results in uncertainties of 1 5 gyr in the middle period of martian geologic history aqueous alteration of primary igneous minerals produces secondary minerals in martian meteorites here we use the ages of secondary alteration minerals in martian meteorites to obtain absolute ages when liquid water was at or near the surface of mars aqueous alteration events in martian meteorites occurred at 3929 37 ma carbonates in alh84001 633 23 ma iddingsite in nakhlites and 0 170 ma salts in shergottites furthermore these events appear to be of short duration suggesting episodic rather than continuous aqueous alteration of the meteorites the martian meteorites appear to be contaminated by martian surface pb characterized by a 207pb 206pb ratio near 1 lead of this composition could be produced by water based alteration on the martian surface the high 129xe 132xe ratio in the martian atmosphere compared to martian meteorites indicates fractionation of i from xe within 100 myr after nucleosynthesis of 129i such fractionation is difficult to achieve through magmatic processes however water very efficiently fractionates i from xe raising the intriguing possibility that mars had a liquid water ocean within its first 100 myr 1

pedogenesis and clay mineralogical investigation of soils formed on gypsiferous and calcareous materials on a transect southwestern iran abstract this study examined pedogenesis as well as the clay mineralogy of soil and rock samples obtained from a transect of gypsiferous and calcareous materials the main objectives of this research were to study the relationship between clay minerals and physiographic units as well as the relative importance of key pedogenic processes in controlling clay mineralogy palygorskite chlorite illite smectite quartz and interstratified minerals were observed in both soil and rock samples using xrd tem and edx analyses illite chlorite and interstratified minerals are inherited largely from parent rocks most of the smectite is inherited from highly smectite marl formations although some may be the product of palygorskite weathering and transformation of illite particularly at the surface horizons neoformation of palygorskite as a result of calcite and gypsum precipitation seems to be a major pathway for the occurrence of this mineral especially on plateau physiographic units although inheritance has less importance gypsiferous soils showed more pedogenic palygorskite as compared to calcareous soils three morphological forms of palygorskite related to degree of weathering were identified in the studied pedons new great groups and subgroups of ustepts aridic gypsiustepts and aridic calcic gypsiustepts are suggested to be included in soil taxonomy based on the properties of some of the studied pedons dissolution and transport of anhydrite from outcrops is considered the main source of pedogenic gypsum in these soils micromorphological studies including thin section observations and sem analyses indicated variable habits of gypsum crystals suggested a dynamic soil environment

a comparison of the impact of an envelope orography and of a parametrization of orographic gravity wave drag on model simulations results are presented from extended annual cycle integrations of the meteorological office 11 layer atmospheric general circulation model an 8 year control integration produces a good simulation in the southern hemisphere in both summer and winter and also in the northern hemisphere in summer in northern winter however there is excessive westerly near surface flow polewards of about 40 n it is argued that this indicates a lack of orographic forcing of the flow by the major mountain ranges two solutions which have been proposed for this problem are investigated the first is envelope orography and the second is a parametrization of the effects of orographic gravity wave drag each was included separately in 3 1 2 year integrations in parallel with the control both produce substantial changes in the model s climatology but envelope orography does not improve the westerly problem over the european area and it also degrades the summer circulation the gravity wave drag scheme however gives results which in general are in very good agreement with the observations in both hemispheres and seasons comparison of the zonally averaged torques from the three experiments demonstrates that with envelope orography the northern hemisphere near surface westerlies are reduced because of a dramatic increase in the mountain pressure torque in the experiment with the gravity wave scheme however the reduction is due to the gravity wave drag and the mountain torque is similar in magnitude to that in the control a study of the variability of the 500mb height fields on synoptic timescales demonstrates the improvement in the positions of the northern hemisphere storm tracks in this integration some remaining errors in the simulations are identified particularly in the stratosphere finally it is argued that despite these results it may be too early to come to a final conclusion as to the role of gravity wave drag in the general circulation and also as to the relative importance of dynamical and radiative processes in the polar winter stratosphere

model experiments on the impact of pacific sea surface temperature anomalies on blocking frequency abstract sensitivity experiments with a perpetual january version of a low resolution general circulation model are conducted to investigate the influence of pacific sea surface temperature sst anomalies on blocking in the northern hemisphere six 1200 day integrations each of which contains a different specified sst anomaly superimposed upon a fixed climatological sst distribution are compared with a 1200 day control simulation to examine the impact of both equatorial pacific and midlatitude north pacific anomalous forcing an ensemble of eight independent 90 day realizations is extracted from each simulation distributions of the ensemble mean differences in the total number of blocking days from the control simulation are presented along with estimates of the statistic significance of these differences pacific sst anomalies do not strongly affect the total number of days in which a block is present anywhere over the north pacific basin but they apparently can affect the preferred regions over th

gypsum nucleation and crystal morphology in analog saline terrestrial environments abstract gypsum crystals were grown in experimental conditions analogous to saline terrestrial environments within bentonite clay gels by diffusion control at three different temperatures four brine salinities and four tannic acid a model terrestrial humic substance concentrations the resulting crystals correspond to natural gypsum formed in terrestrial environments prismatic gypsum typically grew at both high and low temperatures in the absence of the organic additive with increasing organic acid concentrations the prismatic crystals progressively became flattened perpendicular to 001 and two temperature dependent trends developed at low temperatures a hemi bipyramidal habit dominated by 1111 faces developed whereas the lenticular e103 dominated habit forme at higher temperatures with progressively greater concentrations of organic material a 100 penetration twinning developed secondary complex nucleation occurred near the twin interfaces and finally rosette and rosette like aggregates formed higher temperatures generally favored better formed and larger rosettes the presence of 5 and 15 nacl greatly decreased nucleation density and resulted in larger single crystals and crystal aggregates the a 100 penetation twins appear to be diagnostic of gypsum growth in natural terrestrial sediments at a ph greater than 7 5

endolithic cyanobacteria in soil gypsum occurrences in atacama chile mojave united states and al jafr basin jordan deserts 1 soil sulfates are present in arid and hyperarid environments on earth and have been found to be abundant in soils on mars examination of soil gypsum from the atacama desert chile the mojave desert united states and al jafr basin jordan revealed endolithic cyanobacteria communities just below the surface of soil gypsum samples optical and scanning electron microscope observations of the colonized layers indicated that the unicellular chroococcidiopsis is the dominant cyanobacterium in all studied communities 16s rrna gene analysis revealed that in addition to chroococcidiopsis a few other cyanobacteria are present heterotrophic bacteria are also abundant in the colonized zones of the fine grained gypsum from the atacama and mojave desert but insignificant in the fibrous gypsum from the jordan desert endolithic life forms similar to these described here may exist or have existed on mars and should be targeted by the mars science laboratory and future in situ missions

late quaternary forcing of indian ocean summer monsoon winds a comparison of fourier model and general circulation model results past fluctuations in the strength of summer monsoon winds in the arabian sea can be inferred from the grain size of lithogenic material blown in from the peripheral deserts we partition a 400 kiloyear kyr time series of inferred wind strength into its dominant frequency components and develop a fourier model to evaluate the relative influence of potential monsoon forcing mechanisms operating over these dominant frequencies our results indicate that the primary external and internal forcing mechanisms determining the timing and strength of arabian sea monsoon winds over the late quaternary are 1 solar insolation and 2 latent heat collected from the southern subtropical indian ocean and released over the asian plateau our results further suggest that the extent of glacial conditions plays only a minor role in determining the timing and strength of the arabian sea paleomonsoon in contrast sensitivity experiments using the national center for atmospheric research community climate model ncar ccm indicate that glacial boundary conditions play a dominant role in forcing the strength of arabian sea paleomonsoon winds such inconsistencies are illustrated by comparing ccm wind strengths to those inferred from geological data ccm monsoon winds in the arabian sea are uniformly strong during interglacial oxygen isotope stages 1 and 5 and weak during glacial stage 2 the geological record in contrast indicates strong and weak monsoons during both glacial and interglacial stages examining ccm monsoon strength in the context of latent heat flux versus regional sea surface temperatures sst suggests that these discrepancies may be attributed to incorrect ocean atmosphere heat transfer in the southern hemisphere possibly associated with the effects of prescribed model sst fields

the 40 to 50 day oscillation in a perpetual january simulation with a general circulation model a 1200 day record from a perpetual january simulation with a general circulation model is analyzed for the presence of an oscillation resembling the 40 to 50 day oscillation observed in the atmosphere representation of the global velocity potential at 200 mbar by empirical orthogonal functions eofs reveals an eastward propagating disturbance having a principally zonal wave number 1 character it is determined from power spectra of the velocity potential at points around the equator that the period of the oscillation is in the range of 28 31 days time series of the coefficients of the first two eofs are used to define epochs for the compositing in equatorial latitudes of anomalies in zonal winds in 500 mbar convective heating and in precipitation time longitude diagrams of the zonal wind anomalies indicate the presence of an eastward propagating disturbance characterized by two longitudinal scales the principal anomalies in convective heating and precipitation appear as two stationary oscillations one situated in a zone extending from 120 e to the dateline and the other in a relatively narrow zone near 60 w

sensitivity of climate to late cenozoic uplift in southern asia and the american west numerical experiments experiments with general circulation models with no mountains half mountains and full modern mountains show the sensitivity of atmospheric circulation patterns to progressive amounts of uplift the experiments were motivated by geologic evidence for large kilometer scale uplift in the late cenozoic in southern asia and the american west particularly within the last 10 m y in january the amplitude of the mid latitude upper tropospheric planetary waves increased with uplift and the low level winds were progressively blocked or diverted around the topographic features in july the progressive uplift caused monsoonlike circulations to develop in the vicinity of the colorado and tibetan plateaus atmospheric heating rates midtroposphere vertical motion and upper tropospheric planetary wave amplitudes varied approximately linearly with progressive uplift these results suggest that geologically recent kilometer scale uplift may have had climatic consequences comparable in magnitude and pattern to those of earlier stages of uplift comparison of the simulated climatic effects of uplift with the geologic evidence for late cenozoic climatic change especially for the last 10 m y is given in accompanying papers

sulfate minerals and organic compounds on mars strong evidence for evaporitic sulfate minerals such as gypsum and jarosite has recently been found on mars although organic molecules are often codeposited with terrestrial evaporitic minerals there have been no systematic investigations of organic components in sulfate minerals we report here the detection of organic material including amino acids and their amine degradation products in ancient terrestrial sulfate minerals amino acids and amines appear to be preserved for geologically long periods in sulfate mineral matrices this suggests that sulfate minerals should be prime targets in the search for organic compounds including those of biological origin on mars

sulfates in the north polar region of mars detected by omega mars express the observatoire pour la mineralogie l eau les glaces et l activite omega imaging spectrometer observed the northern circumpolar regions of mars at a resolution of a few kilometers an extended region at 240 e 85 n with an area of 60 kilometers by 200 kilometers exhibits absorptions at wavelengths of 1 45 1 75 1 94 2 22 2 26 and 2 48 micrometers these signatures can be unambiguously attributed to calcium rich sulfates most likely gypsum this region corresponds to the dark longitudinal dunes of olympia planitia these observations reveal that water alteration played a major role in the formation of the constituting minerals of northern circumpolar terrains

midlatitude atmosphere ocean interaction during el nino part ii the northern hemisphere atmosphere abstract the influence of midlatitude air sea interaction on the atmospheric anomalies associated with el nino is investigated by coupling the community climate model to a mixed layer ocean model in the north pacific prescribed el nino conditions warm sea surface temperatures sst in the tropical pacific cause a southward displacement and strengthening of the aleutian low this results in enhanced reduced advection of cold asian air over the west central northwest pacific and northward advetion of warm air over the eastern pacific allowing air sea feedback in the north pacific slightly modified the el nino induced neu surface wind air temperature and precipitation anomalies the anomalous cyclonic circulation over the north pacific is more concentric and shifted slightly to the east in the coupled simulations air sea feedback also damped the air temperature anomalies over most of the north pacific and reduced the precipitation rate above the cold sst anomaly that develops in the central pacifi

southern hemisphere medium scale waves and total ozone disturbances in a spectral general circulation model the ozone distribution and its variability is simulated with a general circulation model gcm which includes self consistent representation of the physical processes and an accurate parameterization of the ozone photochemical sources and sinks emphasis is placed on analysis of the action of atmospheric waves on the o3 distribution in particular the model generates the medium scale waves which are often observed in the southern hemisphere these waves tend to form quasi regular o3 patterns with zonal wave numbers 4 5 and 6 in fairly good agreement with the observations baroclinic instability generates the waves in the lower troposphere but it is their equivalent barotropic structure in the upper troposphere lower stratosphere which produces the signal on the total ozone column since o3 disturbances are nearly in phase in this altitude range episodes of large amplitude of the medium scale waves occur when the transient waves interact with a stationary wave this standing wave has a zonal wave number close to 4 and appears to result from the large convective activity within the south pacific convergence zone and its southward extension at mid latitudes this study gives a good illustration of the important role played by gcms in understanding the interactions between dynamical and physical processes in the troposphere and wave activity and o3 distribution in the lower stratosphere

origin of terrestrial gypsum dunes implications for martian gypsum rich dunes of olympia undae abstract the estancia white sands guadalupe and cuatrocienegas dune fields are among the largest known aeolian gypsum sand dune accumulations on earth and occupy closed drainage basins within the rio grande rift high sedimentation rates of lacustrine gypsum occur in topographic depressions within the closed basins the gypsum accumulations result from long term complex interaction between tectonism climate and a hydrologic cycle that involves geochemical recycling of sulfur from older sedimentary rocks flanking and underlying the basins gypsum precipitation in lacustrine environments is strongly controlled by local groundwater bedrock interaction the ranges of 34s values per mil vs vcdt for gypsum sand in the white sands dune field 12 1 to 13 9 guadalupe dune field 10 2 to 12 5 and cuatrocienegas dune field 14 6 to 15 9 indicate that the main sources of dissolved sulfate are evaporite strata of lower permian middle permian and cretaceous ages respectively a spatial increase of 34s values across the white sands dune field in the direction of prevailing winds matches well with a stratigraphically upward increase of 34s values recorded in lake otero an ancient lake in the basin strata this finding supports previous suggestions that white sands dune field evolved as a result of the step wise deflation of previously stored sediments in lake otero the modern gypsum dune fields are primarily wet eolian systems in which dune accumulation is controlled by a near surface groundwater table which promotes early cementation of the dune accumulations early cementation in the interdune surfaces and to a lesser degree on the dune surfaces reduces the amount of sand available for transport and slows rates of dune migration based on an average migration rate of 2 m year the time needed for a dune at white sands to migrate the downwind distance of the dune field is approximately 6500 years which matches well with other estimates of the initiation of the dune field at approximately 7000 years ago and indicates that white sands likely evolved as a wet aeolian system as on earth gypsum rich dune fields apparently are rare on mars gypsum has been identified only within the olympia undae dune field which encircles a portion of the martian north polar residual ice cap analogous to terrestrial gypsum dunes the gypsum within the olympia undae gypsum rich dunes might have originated from transport and deposition via aeolian processes in this model gypsum rich source sediment could have been formed by confined groundwater or surface water activity and later transported by the wind any subsequent gypsum precipitation in the source area could have been initiated by episodic melting of the martian polar ice cap it is likely that the gypsum was deposited in the olympia undae dunes after the main deflation events that led to formation of the siliciclastic components of the dune field