rhodoliths uniformitarianism and darwin pleistocene and recent carbonate deposits in the cape verde and canary archipelagos abstract visiting st jago santiago in the cape verde islands in 1832 and again in 1836 aboard hms beagle charles darwin was the first to trace and describe the tri part sequence of white limestone and sandstone beds stratigraphically located between two levels of basalt exposed almost uninterrupted for 10 km along coastal cliffs the pleistocene carbonate sediments dominated by rhodoliths and rhodolith debris accumulated on a basalt shelf and subsequently became buried by subaerial and submarine basalt on the southeast coastline of santiago the main goal of this contribution is to re examine darwin s stratigraphic sequence the secondary goal is to provide a general taphonomical model based on the observation of recent rhodolith deposits for evaluation of fossil rhodolith assemblages environmental uniformitarianism is employed to understand the depositional history of the southern santiago rhodolith bearing strata the mixed clastic carbonate sequence includes a basalt derived basal conglomerate with an intertidal to shallow subtidal fossil assemblage mainly denoted by limpets and oysters upper layers typically demonstrate swaley and hummocky cross stratification incorporating rhodolith debris further modified by bioturbation pillow basalts from 10 to 18 m in thickness succeeded by subaerial flows imply swift burial of the carbonate succession under equivalent water depths the calcareous nannofossil assemblage was investigated to more precisely date the deposits darwin s paleoshore is reinterpreted to represent two different transgressions occurring between approximately 1 1 and 0 7 ma taphonomic grades from whole rhodoliths to finely crushed rhodolith debris observed under present day conditions on maio cape verde islands and fuerteventura canary islands were used to model rhodolith preservation and to constrain the depositional settings to which rhodoliths may be transported from the offshore banks where they naturally thrive coastward transport of rhodoliths commonly ends with deposition in subtidal storm beds tidal pools and platform over wash deposits as well as beach berm hurricane tsunami and coastal dune deposits

recent macroids on the kikai jima shelf central ryukyu islands japan sandy and gravelly carbonate sediments found off kikai jima southern japan a coral reef related island shelf represent the northernmost sub tropical carbonate deposits in the central ryukyu islands ryukyus on the kikai jima shelf at water depths of 61 to 105 m these sediments are characterized by macroid pavements since the abundance of very small and of exceptionally large macroids may indicate specific hydrodynamic controls regarding constraints on growth and taphonomy the detailed analysis of recent and fossil macroid pavements is meaningful ecologically and environmentally macroids ranging in size from ca 25 to 130 mm in diameter are spheroidal and sub spheroidal in shape and consist mainly of the encrusting foraminifer acervulina inhaerens and subordinate thin encrusting and lumpy coralline algae accessory components include bryozoans serpulids and to a lesser extent encrusting arborescent foraminifera homotrema and miniacina low sedimentation rates and occasional movement due to current action are indicated by sizes shapes and growth forms of the studied macroids the entobia gastrochaenolites trypanites maeandropolydora ichnocoenosis and the bioerosion index for coated grains introduced herein the deep water tidally induced current energy was sufficient to maintain multi directional growth spheroidal shapes of the larger macroids and to initiate macroid growth using the diverse biogenic remnants as nuclei the asymmetrical inner arrangement suggests possible periods of stability for the macroids the residence time of the coated grain in its original environment determines the size and morphology of the macroid and the selection of coating organisms the composition of the coating community is mainly a consequence of component growth rates in relation to turnover time and residence time long term studies are needed to assess the spatial and temporal resolution of present day encrusting communities across biogeographic provinces and shelf to slope regions

erosion rates on mars and implications for climate change constraints from the pathfinder landing site the observation that the mars pathfinder landing site looks very similar to its appearance after it was deposited by catastrophic floods around 1 8 3 5 ga allows quantitative constraints to be placed on the rate of change of the site since that time the abundance of erosional features such as an exhumed former soil horizon sculpted wind tails ripplelike and other tag deposits and ventifacts fluted and grooved rocks all suggest the site has undergone net deflation or loss of 3 7 cm of material the presence of barchan dunes and ventifacts argues for erosion by saltating crystalline sand size particles entrained in the wind most ventifacts probably formed soon after the catastrophic flood which likely introduced a large fresh supply of sand size particles distributed across the rocky plain the strongest winds blew toward the northwest during this time resulting in the sculpting of ventifacts deflation of the surface collections of dunes within big crater and other lows and possibly preferentially eroding small crater rims the predominant wind direction changed to blow toward the southwest similar to today these winds further deflated the surface completed the deposition of sand size material in dunes and ultimately trapped these dunes in lows the erosional features observed by pathfinder indicate extremely low long term deflation rates of 0 01 0 04 nm yr since the end of the hesperian 1 8 3 5 ga similar to less precise rates of 1 nm yr based on the preservation of craters at the viking 1 and pathfinder landing sites short term redistribution rates deposition and removal of atmospheric dust at the pathfinder landing site and preexisting dust and sand at other locations on mars are up to 10 5 nm yr estimates of erosion rates on mars show a rapid decrease by 3 6 orders of magnitude from 10 2 10 4 nm yr in noachian terrains characterized by rimless flat floored craters and valley networks to the exceedingly slow rates 10 2 10 nm yr operating during the hesperian and amazonian noachian erosion rates comparable to low continental denudation rates on earth are consistent with erosion by running water and perhaps a more clement climate the rapid decrease in erosion rates is consistent with a major climatic change during the noachian at the tail end of heavy bombardment and a cold dry desiccating climate similar to today s since that time

discovery of jarosite within the mawrth vallis region of mars implications for the geologic history of the region abstract analysis of visible to near infrared reflectance data from the mro crism hyperspectral imager has revealed the presence of an ovoid shaped landform approximately 3 by 5 km in size within the layered terrains surrounding the mawrth vallis outflow channel this feature has spectral absorption features consistent with the presence of the ferric sulfate mineral jarosite specifically a k bearing jarosite kfe3 so4 2 oh 6 terrestrial jarosite is formed through the oxidation of iron sulfides in acidic environments or from basaltic precursor minerals with the addition of sulfur previously identified phyllosilicates in the mawrth vallis layered terrains include a basal sequence of layers containing fe mg smectites and an upper set of layers of hydrated silica and aluminous phyllosilicates in terms of its fine scale morphology revealed by mro hirise imagery the jarosite bearing unit has fracture patterns very similar to that observed in fe mg smectite bearing layers but unlike that observed in the al bearing phyllosilicate unit the ovoid shaped landform is situated in an east west bowl shaped depression superposed on a north sloping surface spectra of the ovoid shaped jarosite bearing landform also display an anomalously high 600 nm shoulder which may be consistent with the presence of goethite and a 1 92 m absorption which could indicate the presence of ferrihydrite goethite jarosite and ferrihydrite can be co precipitated and or form through transformation of schwertmannite both processes generally occurring under low ph conditions ph 2 4 to date this location appears to be unique in the mawrth vallis region and could represent precipitation of jarosite in acidic sulfur rich ponded water during the waning stages of drying

firmness profiles associated with tidal creek deposits the temporal significance of glossifungites assemblages indentation tests are used to detail firmness profiles from intertidal creek deposits and wave exhumed substrates at willapa bay both of these sedimentological settings are characterized by occur rences of modern glossifungites assemblages firm substrates associ ated with the intertidal creek deposits are derived from dewatered modern sediments whereas firmgrounds associated with wave erosion consist of dewatered and compacted pleistocene strata the pleistocene firmgrounds are notably firmer than those derived from modern de posits a strong correlation between sediment firmness and burrowing behavior is evident in these deposits in tidal creek systems the comparatively firm cutbank is character ized by unlined large diameter open burrows that form a glossifun gites assemblage intertidal point bar deposits contain a softground suite consisting of mucous lined small diameter dominantly vertical traces finally a softground suite of robust mucous or mud lined vertical and horizontal traces are observed in intertidal flat deposits in contrast pleistocene firmgrounds generally contain large and small diameter traces with dominantly vertical architectures thalas sinoides gastrochaenolites diplocraterion or arenicolites like bur rows depending upon the firmness of the substrate glossifungites occurrences on modern firmgrounds are temporally insignificant whereas similar occurrences in pleistocene substrates are temporally significant contrasting these two databases suggests that the stratigraphic significance of a glossifungites demarcated disconti nuity can be assessed in the rock record several criteria that are useful for identifying temporally significant surfaces are suggested including absence of compaction of the glossifungites assemblage presence of well preserved burrow sculptings and planar to gently undulatory ero sional surfaces as opposed to surfaces with notable topographic relief conceptual models demonstrate that muddy substrates potentially re quire several millennia to compact and dewater sandy deposits on the other hand have indeterminate significance

hydrated silicate minerals on mars observed by the mars reconnaissance orbiter crism instrument phyllosilicates a class of hydrous mineral first definitively identified on mars by the omega observatoire pour la mineralogie l eau les glaces et l activitie instrument preserve a record of the interaction of water with rocks on mars global mapping showed that phyllosilicates are widespread but are apparently restricted to ancient terrains and a relatively narrow range of mineralogy fe mg and al smectite clays this was interpreted to indicate that phyllosilicate formation occurred during the noachian the earliest geological era of mars and that the conditions necessary for phyllosilicate formation moderate to high ph and high water activity were specific to surface environments during the earliest era of mars s history here we report results from the compact reconnaissance imaging spectrometer for mars crism of phyllosilicate rich regions we expand the diversity of phyllosilicate mineralogy with the identification of kaolinite chlorite and illite or muscovite and a new class of hydrated silicate hydrated silica we observe diverse fe mg oh phyllosilicates and find that smectites such as nontronite and saponite are the most common but chlorites are also present in some locations stratigraphic relationships in the nili fossae region show olivine rich materials overlying phyllosilicate bearing units indicating the cessation of aqueous alteration before emplacement of the olivine bearing unit hundreds of detections of fe mg phyllosilicate in rims ejecta and central peaks of craters in the southern highland noachian cratered terrain indicate excavation of altered crust from depth we also find phyllosilicate in sedimentary deposits clearly laid by water these results point to a rich diversity of noachian environments conducive to habitability

the timing of martian valley network activity constraints from buffered crater counting abstract valley networks concentrations of dendritic channels that often suggest widespread pluvial and fluvial activity have been cited as indicators that the climate of mars differed significantly in the past from the present hyperarid cold desert conditions some researchers suggest that the change in climate was abrupt while others favor a much more gradual transition thus the precise timing of valley network formation is critical to understanding the climate history on mars we examine thirty valley network incised regions on mars including both cratered upland valley networks and those outside the uplands and apply a buffered crater counting technique to directly constrain when valley network formation occurred the crater populations that we derive using this approach allow assessment of the timing of the last activity in a valley network independent of the mapping of specific geological units from these measurements we find that valley networks cluster into two subdivisions in terms characteristics and age 1 valley network activity in the cratered highlands has an average cessation age at the noachian hesperian boundary and all valleys that we crater counted are early hesperian or older no evidence is found for valley networks in the cratered uplands of late hesperian or amazonian age the timing of the cessation of cratered upland valley network activity at the noachian hesperian boundary also corresponds to a decline in the intensity of large crater formation and degradation and to the apparent end of phyllosilicate type weathering 2 a few valley network incised regions formed outside of the cratered uplands on volcanic edifices in association with younger impact craters and on the rim of valles marineris we applied our buffered crater counting technique to four such valleys on the volcanoes ceraunius tholus hecates tholus and alba patera and on the rim of echus chasma and find that each has distinctive and different late hesperian or early amazonian ages indicating that valley networks formed from time to time in the post noachian period unlike the cratered upland valley networks these isolated occurrences are very local and have been interpreted to represent local conditions e g snowpack melted during periods of intrusive volcanic activity in contrast to a gradual cessation in the formation of valley networks proposed by some workers our new buffered crater counting results indicate a relatively abrupt cessation in the formation of the widespread cratered upland valley networks at approximately the end of the noachian followed only by episodic and very localized valley network formation in later mars history very likely due to specific conditions e g local magmatic heating these valley network ages and correlations are thus consistent with a major change in the near surface aqueous environment on mars at approximately the noachian hesperian boundary the noachian environment supported surface running water and fluvial erosion across mars in the cratered uplands enhanced crater degradation and a weathering environment favoring the formation of phyllosilicates the hesperian amazonian environment was more similar to the hyperarid cold desert of today with valley networks forming only extremely rarely and confined to localized special conditions sources of water for these latter occurrences are likely to be related to periodic mobilization and equatorward migration of polar volatiles due to variations in spin axis orbital parameters and to periodic catastrophic emergence of groundwater

spectral and geological study of the sulfate rich region of west candor chasma mars sulfates have been discovered by the omega spectrometer in different locations of the planet mars they are strongly correlated to light toned layered deposits in the equatorial regions west candor chasma is the canyon with the thickest stack of layers and one with the largest area covered by sulfates a detailed study coupling mineralogy derived from omega spectral data and geology derived from hrsc imager and other datasets leads to some straightforward issues the monohydrated sulfate kieserite is found mainly over heavily eroded scarps of light toned material it likely corresponds to a mineral present in the initial rock formed either during formation and diagenesis of sediments or during hydrothermal alteration at depth because it is typically found on outcrops that are eroded and steep polyhydrated sulfates that match any ca na fe or mg sulfates with more than one water molecule are preferentially present on less eroded and darker outcrops than outcrops of kieserite these variations can be the result of a diversity in the composition and or of the rehydration of kieserite on surfaces with longer exposure the latter possibility of rehydration in the current or recent atmosphere suggests the low surface temperatures preserve sulfates from desiccation and also can rehydrate part of them strong signatures of iron oxides are present on sulfate rich scarps and at the base of layered deposits scarps they are correlated with tes gray hematite signature and might correspond to iron oxides present in the rock as sand size grains or possibly larger concretions that are eroded and transported down by gravity at the base of the scarp pyroxenes are present mainly on sand dunes in the low lying terrains pyroxene is strongly depleted or absent in the layered deposits when mixed with kieserite local observations favor a spatial mixing with dunes over layered deposits sulfates such as those detected in the studied area require the presence of liquid water to form by precipitation either in an intermittent lacustrine environment or by hydrothermal fluid circulation both possibilities require the presence of sulfur rich groundwater to explain fluid circulation the elevation of the uppermost sulfate signatures suggests the presence of aquifers up to 2 5 km above datum only 1 km below the plateau surface

characterization of hydrated silicate bearing outcrops in tyrrhena terra mars implications to the alteration history of mars abstract the tyrrhena terra region of mars is studied with the imaging spectrometers omega observatoire pour la mineralogie l eau les glaces et l activite onboard mars express and crism compact reconnaissance infrared spectrometer for mars onboard mars reconnaissance orbiter through the observation of tens of craters that impacted into this part of the martian highlands the 175 detections of hydrated silicates are reported mainly associated with ejecta blankets crater walls and rims and central up lifts sizes of craters where hydrated silicates are detected are highly variable diameters range from less than 1 km to 42 km we report the presence of zeolites and phyllosilicates like prehnite mg chlorite mg rich smectites and mixed layer chlorites smectites and chlorite vermiculite from comparison of hyperspectral infrared observations with laboratory spectra these minerals are associated with fresh craters post dating any aqueous activity they likely represent ancient hydrated terrains excavated by the crater forming impacts and hence reveal the composition of the altered noachian crust although crater related hydrothermal activity may have played a minor role for the largest craters 20 km in diameter most detected minerals formed over relatively high temperatures 100 300 c likely due to aqueous alteration of the noachian crust by regional low grade metamorphism from the noachian thermal gradient and or by extended hydrothermal systems associated with noachian volcanism and ancient large impact craters this is in contrast with some other phyllosilicate bearing regions like mawrth vallis where smectites kaolinites and hydrated silica were mainly identified pointing to a predominance of surface shallow sub surface alteration and where excavation by impacts played only a minor role smooth plains containing hydrated silicates are observed at the boundary between the noachian altered crust dissected by fluvial valleys and the hesperian unaltered volcanic plains these plains may correspond to alluvial deposition of eroded material the highlands of tyrrhena terra are therefore particularly well suited for investigating the diversity of hydrated minerals in ancient martian terrains

calciturbidite dynamics and endobenthic colonisation example from a late barremian early cretaceous succession in southeastern france three lower cretaceous calciturbidite bundles well exposed in the southeastern france are studied with a combined sedimentological and ichnological approach they were deposited in a toe of slope setting in the western border of the vocontian trough during the late barremian the bundles appear to be the result of a cyclic sedimentation with recurrent ichnotaxa including common thalassinoides planolites zoophycos and less abundant taenidium chondrites and ophiomorpha these trace fossils constitute some ichnoassemblages that follow and superimpose each other analysis of the tiering produced may help to estimate the time interval between two turbiditic events indeed the presence of zoophycos indicates a low frequency of the turbiditic supplies which allowed the substrate to firm up a necessary condition for the construction and the persistence of this spreite trace fossil therefore a decreasing frequency of the turbiditic events is pointed out from the base to the top of each turbidite bundle the trace fossil distribution may also be influenced by the grain size in fact zoophycos producers seem to have thrived in a fine grained sediment 0 1 0 2 mm moreover the organic matter exported from the platform is better preserved in these fine grained substrates and may be more available to opportunistic burrowers in the studied succession two different morphologies of zoophycos have been observed one of them lobed form probably indicates an opportunistic behaviour of an organism quickly exploiting the organic matter between two turbiditic events by comparison the other unlobed form is produced later by a more specialised organism exploiting large amounts of organic matter during episodes of lower frequency of turbiditic supplies the ichnofauna studied is characterized by a low diversity and this may be related to an inner submarine fan setting

mixed carbonate siliciclastic record on the north african margin malta coupling of weathering processes and mid miocene climate we investigated rock outcrops spanning the middle miocene global climate cooling step on the maltese islands in order to reconstruct continental weathering rates and terrigenous fluxes as well as to explore the coupling between these later regional climate and carbonate accumulations sedimentation at this location was dominated during the oligocene and early miocene by a transitional platform to slope carbonates but progressively switched to a clay rich carbonate slope system in the middle miocene around 13 ma an abrupt change toward clay dominated marls occurred and marl deposition persisted until the tortonian ca 12 ma when a shallow water carbonate ramp was reestablished clay mineralogy and bulk rock oxygen isotope analyses suggest that the deposition of the blue clay formation was mainly caused by global climate change and related change in the rate of continental weathering a significant negative correlation r 2 0 65 exists between the carbonate content and the 1 8 o record this combined with the variation of mass accumulation rate of terrigenous material suggests that shorter term periods of globally cooler climate mi events were associated with higher rates of accumulation in continental derived material since during the miocene malta was attached to the north african margin we propose that the observed trends were due to a regional increase in rainfall during cooler periods which consequently increased continental weathering and runoff we further suggest that this pattern was linked to the perturbation of atmospheric fronts due to an increased thermal gradient during the miocene thus regional increase in rainfall might have been linked to the northward migration of the intertropical convergence zone itcz

evidence for weathering on early mars from a comparison with terrestrial weathering profiles abstract phyllosilicates on mars are widespread in the ancient crust suggesting the presence of liquid water at the martian surface and therefore warmer conditions during its early history however the role of the ancient climate in the alteration process which produced these phyllosilicates remains under debate because similar mineral assemblages can be produced by hydrothermal alteration at depth this paper focuses on the origin of coincident outcrops of fe mg bearing phyllosilicates and al bearing phyllosilicates which are observed in several regions of mars we performed a detailed mineralogical comparison between a section in nili fossae mars and a weathering profile located at murrin murrin western australia the murrin murrin profile is developed in archaean serpentinized peridotite massifs over a 40 m thick sequence it has three alteration zones the serpentine mineral saprolite is found at the bottom immediately overlain by fe mg bearing smectites and then al bearing phyllosilicates kaolinite mixed with iron hydroxides this example illustrates how al dominated minerals can derive from the alteration of initially al poor ultramafic rocks by the intense leaching of mg2 this mineralogical sequence is very similar to that detected locally in nili fossae by orbital spectroscopy by analogy we propose that the mineral assemblage detected on mars is the result of long term weathering and thus could be the best evidence of past weathering as a direct result of a climate significantly warmer than at present

reflectance spectroscopy and optical functions for hydrated fe sulfates visible and near infrared wavelength vnir 0 35 5 m laboratory diffuse reflectance spectra and corresponding optical functions real and imaginary refractive indices for several iron sulfates natural k and na jarosite szomolnokite rhomboclase are presented on mars jarosite has been identified in meridiani planum mawrth vallis melas chasma and eridania basin szomolnokite has been found as distinct layers at columbus crater and as outcrops at juventae chasma and rhomboclase has been identified at gusev crater constraining the mineralogy and chemistry fe vs mg rich of the sulfates on mars may contribute to our understanding of the environmental and aqueous conditions present on mars during their formation the data presented here will help to constrain the mineralogy abundance and distribution of sulfates on the martian surface which will lead to improvements in understanding the pressure temperature and humidity conditions and how active frost groundwater and atmospheric processes once were on mars

the emergence of volcanic oceanic islands on a slow moving plate the example of madeira island ne atlantic the transition from seamount to oceanic island typically involves surtseyan volcanism however the geological record at many islands in the ne atlantic all located within the slow moving nubian plate does not exhibit evidence for an emergent surtseyan phase but rather an erosive unconformity between the submarine basement and the overlying subaerial shield sequences this suggests that the transition between seamount and island may frequently occur by a relative fall of sea level through uplift eustatic changes or a combination of both and may not involve summit volcanism in this study we explore the consequences for island evolutionary models using madeira island portugal as a case study we have examined the geologic record at madeira using a combination of detailed fieldwork biostratigraphy and 40ar 39ar geochronology in order to document the mode timing and duration of edifice emergence above sea level our study confirms that madeira s subaerial shield volcano was built upon the eroded remains of an uplifted seamount with shallow marine sediments found between the two eruptive sequences and presently located at 320 430 m above sea level this study reveals that madeira emerged around 7 0 5 6 ma essentially through an uplift process and before volcanic activity resumed to form the subaerial shield volcano basal intrusions are a likely uplift mechanism and their emplacement is possibly enhanced by the slow motion of the nubian plate relative to the source of partial melting alternating uplift and subsidence episodes suggest that island edifice growth may be governed by competing dominantly volcanic and dominantly intrusive processes

does antarctic glaciation force migration of the tropical rain belt high resolution similar to 3 6 k y upper ocean temperature and salinity estimates derived from planktic foraminiferal delta 18 o and mg ca in ocean drilling program odp site 1146 reveal stepwise changes in the precipitation evaporation balance of the subtropical northwestern pacific during the middle miocene 15 7 to 12 7 ma we attribute the punctuated pattern of surface warming and freshening following antarctic ice growth episodes at 14 6 14 2 13 9 and 13 1 ma to successive northward movements of the intertropical convergence zone implying high sensitivity of tropical rain belts to the interhemispheric temperature gradient driven by high latitude climate this dynamic interaction has implications for future warmer climate regimes with differential warming of the northern hemisphere as it may lead to changes in the latitudinal penetration of tropical pacific moisture over southeast asia

bathymetric distribution of ichnocoenoses from recent subtropical algal nodules off fraser island eastern australia abstract coralline algal nodules living on the subtropical shelf off fraser island eastern australia from the inner to the uppermost outer shelf from 28 to 117 m water depth are pervasively bioeroded five ichnogenera have been identifed as nodule borers comprising one ichnotaxon attributed to bivalves gastrochaenolites one to sponges entobia and three to polychaetes and barnacles trypanites maeandropolydora rogerella microtraces comparable to those produced by fungi algae bacteria and or sponges are also present two ichnocoenoses have been recognised the shallow water ichnocoenosis egtm occurs at 60 m and shallower depths and includes all identified ichnogenera the deep water ichnocoenosis from 68 to 117 m is characterised by trypanites and the trypanites maeandropolydora network tm ichnocoenosis with a generally higher boring density than in shallower nodules decreasing size of algal nodules and reduced thickness of the coralline thalli probably explain the decrease in diversity of ichnogenera with depth as the larger bioeroders are excluded from the ichnoassemblages lower growth rates favour higher density of bioerosion in deeper algal nodules

mineralogy and stratigraphy of phyllosilicate bearing and dark mantling units in the greater mawrth vallis west arabia terra area constraints on geological origin 1 analyses of mro crism images of the greater mawrth vallis region of mars affirm the presence of two primary phyllosilicate assemblages throughout a region 1000 1000 km these two units consist of an fe mg phyllosilicate assemblage overlain by an al phyllosilicate and hydrated silica assemblage the lower unit contains fe mg smectites sometimes combined with one or more of these other fe mg phyllosilicates serpentine chlorite biotite and or vermiculite it is more than 100 m thick and finely layered at meter scales the upper unit includes al smectite kaolin group minerals and hydrated silica it is tens of meters thick and finely layered as well a common phyllosilicate stratigraphy and morphology is observed throughout the greater region wherever erosional windows are present this suggests that the geologic processes forming these units must have occurred on at least a regional scale sinuous ridges interpreted to be inverted channels and narrow channels cut into the upper clay bearing unit suggesting that aqueous processes were prevalent after and possibly during the deposition of the layered units we propose that layered units may have been deposited at mawrth vallis and then subsequently altered to form the hydrated units the fe mg phyllosilicate assemblage is consistent with hydrothermal alteration or pedogenesis of mafic to ultramafic rocks the al phyllosilicate hydrated silica unit may have formed through alteration of felsic material or via leaching of basaltic material through pedogenic alteration or a mildly acidic environment these phyllosilicate bearing units are overlain by a darker relatively unaltered and indurated material that has probably experienced a complex geological history

global mineral distributions on mars 1 determining the mineralogy of mars is an essential part of revealing the conditions of the surface and subsurface a deconvolution method was used to remove atmospheric components and determine surface mineralogy from thermal emission spectrometer data at 1 pixel per degree ppd minerals are grouped into categories on the basis of compositional and spectral similarity and global concentration maps are produced all binned pixels are fit well with rms errors of 0 005 in emissivity higher rms errors are attributed to short wavelength particle size effects on dust covered surfaces significant concentrations 0 10 of plagioclase high ca pyroxene sheet silicates high si glass and hematite are detected and display distributions consistent with previous studies elevated concentrations of plagioclase and high ca pyroxene are consistent with basaltic surfaces and are located in low albedo highlands regions north of 45 s significant concentrations of plagioclase and sheet silicates high si glass and low concentrations of high ca pyroxenes are consistent with andesitic surfaces and are concentrated in both southern and northern high latitude low albedo regions andesitic surfaces in the southern hemisphere have a lower spectral contrast than northern surfaces an isolated surface located in solis planum is spectrally distinct but compositionally similar to other surfaces interpreted to be andesitic in composition concentrations of olivine below the detection limit correctly identify its presence in two of three locations potassium feldspar low ca pyroxene basaltic glass olivine sulfate carbonate quartz and amphibole are not detected with confidence at 1 ppd the results presented here indicate a predominance of volcanic compositions within martian dust free surfaces

miocene to pleistocene transatlantic dispersal of ceratoconcha coral dwelling barnacles and north atlantic island biogeography coral dwelling pyrgomatid barnacles subfamily ceratoconchinae were widely dispersed throughout the paratethys and mediterranean seas as well as the atlantic ocean during the neogene but today are limited to the western atlantic herein the paleobiogeographic origin and dispersal of the genus ceratoconcha is studied based on a combination of field taxonomic and literature studies the first confirmed appearances of ceratoconcha occur in lower miocene strata burdigalian with two closely related species on both sides of the atlantic in western france and florida fossils from the miocene of lanzarote in the canary islands and pleistocene of maio in the cape verde islands extend the known geographical and temporal range of the ceratoconcha barnacles in the eastern atlantic during the neogene dispersal of marine taxa was a two way process due to tectonic changes both influencing oceanic circulation and appearance and disappearance of oceanic islands during the early miocene gyre formation was weak and the atlantic ocean mid latitudes were warmer than today this resulted in increased hurricane activity and the expansion of hermatypic coral hosts farther north in the north atlantic normal ocean circulation transported barnacle larvae from east to west but currents generated by hurricanes may have transported them in the opposite direction towards the margins of the northeastern atlantic islands in between abetted barnacle contact and dispersal the temporal range for ceratoconcha is extended considerably in the eastern atlantic from the early pliocene to the pleistocene the hermatypic host corals of ceratoconcha suffered a severe decline in the eastern atlantic and the mediterranean after the miocene corals were present during the pliocene and pleistocene in the cape verde islands this suggests that the southernmost oceanic islands acted as a tropical refuge for host corals and their likely barnacle symbionts

what darwin did not see pleistocene fossil assemblages on a high energy coast at ponta das bicudas santiago cape verde islands funding for fieldwork on santiago island in june 2011 was provided under grant cgl2010 15372 bte from the spanish ministry of science and innovation to project leader eduardo mayoral university of huelva financial support to a santos came from the spanish ministry of science and technology juan de la cierva subprogram ref jci 2008 2431 additional support by the junta de andalucia spanish government to the research group rnm276 is also acknowledged partial funding to j ledesma vazquez on this project came from the programma integral de fortalecimiento institucional 2010 we thank christopher k pham department of oceanography and fisheries university of the azores portugal for help with identification of the fossil barnacles and ricardo ramalho institut fur geophysik westphalishe wilhelms universitat germany for discussions about bioerosion by sea urchins on basalt surfaces

mineralogy of the nili fossae region with omega mars express data 2 aqueous alteration of the crust 1 nili fossae is a region with fresh exposures of old material omega spectral data have revealed a strong diversity of minerals in the nili fossae region including mafic minerals and phyllosilicates phyllosilicates are found to be primarily fe rich smectites a type of clay minerals these phyllosilicates are observed only on the noachian crust in four types of locations three are without any signatures other than phyllosilicates on 1 smooth layered deposits 2 massive exhumed material and 3 crater ejecta and one type of location is associated with olivine 4 over an altered mafic unit this diversity suggests a widespread liquid water activity and a variety of alteration processes the formation of phyllosilicates underwent considerable reduction if not cessation by the time of formation of syrtis major lava flows in the hesperian period phyllosilicates are spatially and chronologically disconnected from the fluvial and depositional landforms observed in the nili fossae region observations suggest that these landforms formed after the extensive formation of phyllosilicates during short periods of time and or temperatures close to freezing

hydrothermal activity recorded in post noachian aged impact craters on mars hydrothermal systems have previously been reported in ancient noachian and hesperian aged craters on mars using crism but not in amazonian aged impact craters however the nakhlite meteorites do provide evidence of amazonian hydrothermal activity this study uses crism data of 144 impact craters of 7 km diameter and 14 smaller craters 3 7 km diameter within terrain mapped as amazonian to search for minerals that may have formed as a result of impact induced hydrothermal alteration or show excavation of ancient altered crust no evidence indicating the presence of hydrated minerals was found in the 3 7 km impact craters hydrated minerals were identified in three complex impact craters located at 52 42 n 39 86 e in the ismenius lacus quadrangle at 8 93 n 141 28 e in elysium and within the previously studied stokes crater these three craters have diameters 20 km 62 km and 51 km the locations of the hydrated mineral outcrops and their associated morphology indicate that two of these three impact craters the unnamed ismenius lacus crater and stokes crater possibly hosted impact induced hydrothermal systems as they contain alteration assemblages on their central uplifts that are not apparent in their ejecta chlorite and fe serpentine are identified within alluvial fans in the central uplift and rim of the ismenius lacus crater whereas stokes crater contains a host of fe mg al phyllosilicates however excavation origin cannot be precluded our work suggests that impact induced hydrothermalism was rare in the amazonian and or that impact induced hydrothermal alteration was not sufficiently pervasive or spatially widespread for detection by crism

martian polar and circum polar sulfate bearing deposits sublimation tills derived from the north polar cap previous spectroscopic studies have shown the presence of hydrated minerals in various kinds of sedimentary accumulations covering and encircling the martian north polar cap more specifically gypsum a hydrated calcium sulfate has been detected on olympia planum a restricted part of the circum polar dune field to further constrain the geographical distribution and the process of formation and accumulation of these hydrated minerals we performed an integrated morphological structural and compositional analysis of a key area where hydrated minerals were detected and where the main polar landforms are present by the development of a spectral processing method based on spectral derivation and by the acquisition of laboratory spectra of gypsum ice mixtures we find that gypsum bearing sediment is not restricted to the olympia planum dunes but is also present in all kinds of superficial sediment covering the surface of the north polar cap and the circum polar dune field spectral signatures consistent with perchlorates are also detected on these deposits the interpretation of landforms reveals that this gypsum bearing sediment was released from the ice cap by sublimation we thus infer that gypsum crystals that are now present in the circum polar dune field derive from the interior of the north polar cap gypsum crystals that were initially trapped in the ice cap have been released by sublimation of the ice and have accumulated in the form of ablation tills at the surface of the ice cap these gypsum bearing sublimation tills are reworked by winds and are transported towards the circum polar dune field comparison with sulfates found in terrestrial glaciers suggests that gypsum crystals in the martian north polar cap have formed by weathering of dust particles either in the atmosphere prior to their deposition during the formation of the ice cap and or in the ice cap after their deposition

rhodolith transport and immobilization on a volcanically active rocky shore middle miocene at cabeco das laranjas on ilheu de cima madeira archipelago portugal abstract extraordinary deposits of fossil rhodoliths occur at the cabeco das laranjas portuguese hill of the oranges in a small fault block at the northwest end of ilheu de cima off porto santo in the madeira archipelago stratigraphic repetitions of densely packed rhodolith beds up to 2 6 m thick are associated with a receding rocky shoreline and are interpreted as the result of hurricanes the initial storm deposit sits unconformably on basalt and eroded basalt boulders associated with tuff and volcaniclastic breccia approximately 90 000 rhodoliths of middle miocene age 14 15 ma are exposed on the upper surface of the initial deposit over a 450 m2 shelf exhumed from the hill s southeast side ranging in diameter from 3 cm to 20 cm many of the rhodoliths generated by crustose coralline red algae are now iron stained and resemble a mass of oranges in gross appearance sea stacks and large boulders rise through the thick basal rhodolith bed to form small catchment areas that held the deposit in place after the storm s passage the succeeding rhodolith deposits are variably separated by layers with mixed carbonate and volcanic sand pure volcanic lapilli and volcaniclastic tephra mixed with tuff showing swaley cross stratification three out of four rhodolith beds are truncated against the flank of the adjoining rocky shore only the youngest fourth rhodolith layer is fully exposed around the perimeter of the hill and can be shown to cross a basalt barrier that is traceable for 70 m in cross section as an erosional ramp dipping from 6 to 8 southeast the entire fossil rich sequence is capped by a basalt flow showing columnar disjunction based on thin section analysis three genera of coralline red algae are recognized in the basal rhodolith deposit sporolithon lithothamnion and neogoniolithon associated biodiversity is low represented by 16 kinds of marine invertebrates dominated by encrustations and borings on the rhodoliths and very few free body fossils the madeira region of the north atlantic may have been susceptible to major cyclonic storms immediately after the middle miocene climate optimum when a northward shift of the inter tropical convergence zone was stimulated by a steeper temperature gradient in the southern hemisphere related to expansion of continental glaciers on antarctica

opaline silica in young deposits on mars high spatial and spectral resolution reflectance data acquired by the mars reconnaissance orbiter compact reconnaissance imaging spectrometer for mars crism instrument reveal the presence of h 2o and sioh bearing phases on the martian surface the spectra are most consistent with opaline silica and glass altered to various degrees confirming predictions based on geochernicall experiments and models that amorphous silica should be a common weathering product of the basaltic martian crust these materials are associated with hydrated fe sulfates including h 3o bearing jarosite and are found in finely stratified deposits exposed on the floor of and on the plains surrounding the valles marineris canyon system stratigraphic relationships place the formation age of these deposits in the late hesperian or possibly the amazonian implying that aqueous alteration continued to be an important and regionally extensive process on mars during that time

pitted cones and domes on mars observations in acidalia planitia and cydonia mensae using moc themis and tes data 1 domes and cones with summit pits located in acidalia planitia and cydonia mensae were studied using moc and themis images and a tes derived thermal inertia map north of 40 5 n latitude the features have a dome like morphology and south of that latitude the morphology is more cone like layering is apparent in the summit craters of fresher looking southern cones and asymmetric aprons were observed in some instances some of the northern domes also display layering in their summit craters but asymmetric aprons were not observed the northern domes can also display multiple summit pits or no summit pits at all and can occur in association with higher albedo pancake features the northern domes are higher in albedo but have apparent thermal inertias that are lower than the surrounding plains the apparent thermal inertia values of the southern cones range from values comparable to the surrounding plains to slightly lower from the tes thermal inertia map we infer that the thermal inertia values of the pitted cones are between those of basaltic fine dust and sand while those of the surrounding plains are closer to that of basaltic sand while a unique interpretation of the origin of the pitted cones is not possible with the available data we do not find compelling evidence to suggest an origin related to either basaltic volcanism or ground ice instead an origin for these features through some combination of mud volcanism and evaporite deposition around geysers and or springs is most consistent with the observations

a search for early to mid noachian chloride rich deposits on mars abstract chloride bearing deposits on mars that are recognizable in orbital infrared data are thought to date to the late noachian period 3 6 gyr ago during the last stages of surface water that persisted long enough over large regions to have emplaced aqueously formed minerals detectable from orbit we conducted an intensive regional search for older buried and exhumed chloride rich deposits and found none resolvable from orbit placing constraints on the upper age limit for this type of deposit

spectral reflectance and morphologic correlations in eastern terra meridiani mars the mars express observatoire pour la mineralogie l9eau les glaces et l9activite omega hyperspectral image data covering eastern terra meridiani indicate the ubiquitous presence of molecular water in etched terrain materials that disconformably overlie heavily cratered terrains and underlie the hematite bearing plains explored by the opportunity rover identification of crystalline water in kieserite mgso4 h2o is linked to materials exposed in a valley and plateau to the north of hematite bearing plains the mineralogical similarities between the etched terrain deposits examined with omega data and the layered rocks examined by opportunity imply that the ancient aqueous environments inferred from analyses of the rover data extend over regional scales

orbital evidence for clay and acidic sulfate assemblages on mars based on mineralogical analogs from rio tinto spain outcrops of hydrated minerals are widespread across the surface of mars with clay minerals and sulfates being commonly identified phases orbitally based reflectance spectra are often used to classify these hydrated components in terms of a single mineralogy although most surfaces likely contain multiple minerals that have the potential to record local geochemical conditions and processes reflectance spectra for previously identified deposits in ius and melas chasma within the valles marineris mars exhibit an enigmatic feature with two distinct absorptions between 2 2 and 2 3 m this spectral doublet feature is proposed to result from a mixture of hydrated minerals although the identity of the minerals has remained ambiguous here we demonstrate that similar spectral doublet features are observed in airborne field and laboratory reflectance spectra of rock and sediment samples from rio tinto spain combined visible near infrared reflectance spectra and x ray diffraction measurements of these samples reveal that the doublet feature arises from a mixture of al phyllosilicate illite or muscovite and jarosite analyses of orbital data from the compact reconnaissance imaging spectrometer for mars crism shows that the martian spectral equivalents are also consistent with mixtures of al phyllosilicates and jarosite where the al phyllosilicate may also include kaolinite and or halloysite a case study for a region within ius chasma demonstrates that the relative proportions of the al phyllosilicate s and jarosite vary within one stratigraphic unit as well as between stratigraphic units the former observation suggests that the jarosite may be a diagenetic authigenic product and thus indicative of local ph and redox conditions whereas the latter observation may be consistent with variations in sediment flux and or fluid chemistry during sediment deposition

geological and geochemical legacy of a cold early mars 1 we consider the hypothesis that mars never experienced an early warm wet period and the implications of a continuously cold martian climate for the hydrology and geochemistry of the planet geomorphic evidence previously interpreted to indicate a more temperate early climate can be explained by cold climate processes and the transient flow of liquid water at the surface rather than a terrestrial like hydrological cycle in this scenario freezing and confinement of crustal aquifers lead to the eruption of water or brines to the surface hesperian events formed massive ice sheets and triggered floods that carved the outflow channels while smaller present day aqueous eruptions are responsible for the seepage and gully like landforms identified in high resolution imaging this process may have fluxed a significant volume of groundwater to the surface and the polar caps a primordial source of groundwater reconciles the present d h isotopic ratio of the atmosphere with fractionating atmospheric escape and a primordial martian d h inferred from hydrous phases of snc meteorites a cold early climate and a thin co2 atmosphere are consistent with the ubiquity of primary igneous minerals and the apparent absence of secondary minerals and copious carbonates on the surface aqueous eruptions introduced soluble chloride and sulfate salts into martian soils leaving clays and carbonates within the crust if the martian crust hosts a deep biosphere aqueous eruptions can bring organisms or their chemical signature to the surface the biotic component of any recent eruptions may be preserved in transient ice in cold traps on the surface

a late amazonian alteration layer related to local volcanism on mars hydrated minerals on mars are most commonly found in ancient terrains dating to the first billion years of the planet s evolution here we discuss the identification of a hydrated light toned rock unit present in one chasma of the noctis labyrinthus region stratigraphy and topography show that this alteration layer is part of a thin unit that drapes pre existing bedrock crism spectral data show that the unit contains hydrated minerals indicative of aqueous alteration potential minerals include sulfates such as bassanite caso4 1 2h2o or possibly hydrated chloride salts the proximity of a smooth volcanic plain and the similar crater model age late amazonian 100 myr of this plain and the draping deposits suggest that the alteration layer may be formed by the interaction of water with ash layers deposited during this geologically recent volcanic activity the alteration phases may have formed due to the presence of snow in contact with hot ash or eventually solid gas interactions due to the volcanic activity the relatively young age of the volcanic plain implies that recent alteration processes have occurred on mars in relation with volcanic activity but such local processes do not require conditions different than the current climate

clay minerals in delta deposits and organic preservation potential on mars clay rich sedimentary deposits are often sites of organic matter preservation and have therefore been sought in mars exploration however regional deposits of hydrous minerals including phyllosilicates and sulphates are not typically associated with valley networks and layered sediments that provide geomorphic evidence of surface water transport on early mars the compact reconnaissance imaging spectrometer for mars crism has recently identified phyllosilicates within three lake basins with fans or deltas that indicate sustained sediment deposition eberswalde crater holden crater and jezero crater here we use high resolution data from the mars reconnaissance orbiter mro to identify clay rich fluvial lacustrine sediments within jezero crater which has a diameter of 45 km the crater is an open lake basin on mars with sedimentary deposits of hydrous minerals sourced from a smectite rich catchment in the nili fossae region we find that the two deltas and the lowest observed stratigraphic layer within the crater host iron magnesium smectite clay jezero crater holds sediments that record multiple episodes of aqueous activity on early mars we suggest that this depositional setting and the smectite mineralogy make these deltaic deposits well suited for the sequestration and preservation of organic material

components facies and ramps redefining upper oligocene shallow water carbonates using coralline red algae and larger foraminifera venetian area northeast italy abstract chattian mixed carbonate siliciclastic deposits from two palaeogeographic units of southern alps the lessini shelf and venetian foreland basin of northeast italy are studied with respect to facies distributions and controlling ecological factors on dominant biogenic components these ramp depositional systems are located in the western southern alps on the lessini shelf and in the eastern southern alps in the venetian foreland basin the successions show an extensive geographic distribution of at least 150 km 40 km at the southern margin of the southern alps palaeoenvironments are inferred following microfacies characteristics and floral and faunal indicators especially those of coralline red algae and larger foraminifera an inner to middle homoclinal ramp morphology is reconstructed based on facies distributions and taxonomic and coralline algal growth form proxy data the distribution along depositional strike shows variation from thinner carbonate dominated sequence in the west monti berici and monti lessini to a more variable mixed carbonate siliciclastic dominated environment to the east vittorio veneto alpago facies character and occurrence are controlled by local hydrodynamic conditions and varying water turbidity of the studied ramp depositional system the general facies succession shows a transgressive sequence from the proximal inner to proximal middle ramp a shoal belt of trough cross bedded sandstones occurs in a proximal inner ramp position in all of the studied areas in a gentle dipping homoclinal ramp most benthic organisms inhabited the relatively quite environments off these shoals in a distal inner ramp setting basinward environments proximal middle ramp constitute areas of maximal carbonate production and consist primarily of larger foraminiferal facies and rhodolith pavements larger foraminifera represented by two larger foraminiferal assemblages are most diversified in the shallower settings near the fair weather wave base distal inner proximal middle ramp whereas coralline algae predominate in deeper areas proximal middle ramp constructing extensive rhodolith pavements rhodolith pavements are distinguished with respect to rhodolith shape size growth forms and coralline algal taxonomic composition larger foraminifera are interpreted with respect to shell structures shell architectures and comparable recent counterparts the analysed benthic communities thrived in a mesotrophic regime within trophic gradients constrained by fluvial influence coralline algal dominance and a moderately diverse larger foraminiferal assemblage suggest a tropical warm temperate transition the considerable stability imposed on sediments by the rhodolith pavement must also have significantly contributed to the maintenance of a middle ramp profile bulge this study will contribute to a better understanding of oligocene carbonates which have received less attention than their eocene or miocene counterparts

an analysis of open basin lake deposits on mars evidence for the nature of associated lacustrine deposits and post lacustrine modification processes abstract a large number of candidate open basin lakes low lying regions with both inlet valleys and an outlet valley have been identified and mapped on mars and are fed by valley network systems that were active near the noachian hesperian boundary the nature of processes that modified the open basin lake interiors subsequent to lacustrine activity and how frequently sedimentary deposits related to lacustrine activity remain exposed has not been extensively examined an analysis of 226 open basin lakes was undertaken to identify evidence for 1 exposed deposits of possible lacustrine origin and 2 post lacustrine activity processes that may have modified or resurfaced open basin lakes spectroscopic data from the compact reconnaissance imaging spectrometer for mars crism instrument were analyzed over identified exposed open basin lake deposits to assess the mineralogy of these deposits particular attention was paid to the possible detection of any component of aqueous alteration minerals e g phyllosilicates hydrated silica zeolites or evaporites e g carbonates sulfates chlorides associated with these exposed deposits the aim of this paper is to act as a broad survey and cataloguing of the types of lacustrine and post lacustrine deposits that are present within these 226 paleolake basins results of the morphologic classification indicate that 79 open basin lakes 35 of the population contain exposed deposits of possible lacustrine origin identified on the basis of fan delta deposits layered deposits and or exposed floor material of apparent lacustrine origin additionally all 226 open basin lakes examined appear to have been at least partially resurfaced subsequent to their formation by several processes including volcanism glacial and periglacial activity impact cratering and aeolian activity results from the analysis of crism data show that only 10 29 of the 34 deposits with crism coverage of the exposed open basin lake deposits contain positively identified aqueous alteration minerals with one deposit also containing evaporites the identified hydrated and evaporite minerals include fe mg smectite kaolinite hydrated silica and carbonate with fe mg smectite the most commonly identified mineral these results indicate that hydrated and evaporite minerals are not as commonly associated with lacustrine deposits on mars as they are on earth this suggests in situ alteration and mineral precipitation a common source of such minerals in terrestrial lakes was not a major process occurring in these paleo lacustrine systems and that the observed minerals are likely to be present as transported material within the lacustrine deposits the lack of widespread in situ alteration also suggests that either the water chemistry in these paleolake systems was not conducive to aqueous alteration and mineral precipitation or that the open basin lake systems were relatively short lived

updated global map of martian valley networks and implications for climate and hydrologic processes 1 martian valley networks have long been viewed as some of the best evidence of prolonged surface water on mars analysis from viking data showed that valleys were primarily contained on the ancient crust drainage networks were immature and large undissected regions occurred in between individual systems these observations led many to propose that they formed primarily by groundwater processes and limited or no climate change from the present state was required using more recent and higher resolution data sets including visible infrared and topographic data we have manually remapped valleys on a global scale more than eight times as many valleys have been identified on the surface and calculated drainage densities are on average higher by a factor of 2 further regions previously thought to be undissected have significant incision by fluvial processes most of these systems seem to have formed around the noachian hesperian boundary 3 8 3 6 ga minor valley formation continued through the hesperian and into the early amazonian epoch approximately 2 8 ga ago the new data reveal characteristics of sustained precipitation and surface runoff including inner braided channels terraces multiple periods of formation complex network morphology and correlation with other fluviosedimentary features and chloride salts on mars groundwater processes or a transient steam atmosphere generated by impacts played at most a minor role these new results imply that mars had a long lived period or periods of clement conditions toward the end of the noachian epoch that supported a hydrologic cycle and potentially a biosphere

high silica deposits of an aqueous origin in western hellas basin mars 1 data from the thermal emission spectrometer and the thermal emission imaging system have been used to identify isolated high silica surfaces in western hellas basin deconvolution results indicate that the surfaces are composed of nearly 80 high silica phases amorphous silica phyllosilicates or zeolites the deposits may be derived from alcoves in the terrain immediately to the north the high silica deposits are an additional indicator of a variety of past aqueous processes on mars

retrieving the hydrous minerals on mars by sparse unmixing and the hapke model using mro crism data the hydrous minerals on mars preserve records of potential past aqueous activity quantitative information regarding mineralogical composition would enable a better understanding of the formation processes of these hydrous minerals and provide unique insights into ancient habitable environments and the geological evolution of mars the compact reconnaissance imaging spectrometer for mars crism has the advantage of both a high spatial and spectral resolution which makes it suitable for the quantitative analysis of minerals on mars however few studies have attempted to quantitatively retrieve the mineralogical composition of hydrous minerals on mars using visible infrared visir hyperspectral data due to their distribution characteristics relatively low concentrations located primarily in noachian terrain and unclear or unknown background minerals and limitations of the spectral unmixing algorithms in this study we developed a modified sparse unmixing msu method combining the hapke model with sparse unmixing the msu method considers the nonlinear mixed effects of minerals and avoids the difficulty of determining the spectra and number of endmembers from the image the proposed method was tested successfully using laboratory mixture spectra and an airborne visible infrared imaging spectrometer aviris image of the cuprite site nevada usa then it was applied to crism hyperspectral images over gale crater areas of hydrous mineral distribution were first identified by spectral features of water and hydroxyl absorption the msu method was performed on these areas and the abundances were retrieved the results indicated that the hydrous minerals consisted mostly of hydrous silicates with abundances of up to 35 as well as hydrous sulfates with abundances 10 several main subclasses of hydrous minerals e g fe mg phyllosilicate prehnite and kieserite were retrieved among these fe mg phyllosilicate was the most abundant with abundances ranging up to almost 30 followed by prehnite and kieserite with abundances lower than 15 our results are consistent with related research and in situ analyses of data from the rover curiosity thus our method has the potential to be widely used for quantitative mineralogical mapping at the global scale of the surface of mars

stratigraphy in the mawrth vallis region through omega hrsc color imagery and dtm abstract the mawrth vallis region contains an extensive at least 300 km 400 km and thick 300 m finely layered at meter scale clay rich unit detected by omega we use omega hrsc dtms derived from stereoscopic imagery hrsc color imagery and high resolution imagery such as moc ctx and hirise to characterize the geometry and the composition of the clay rich unit at the regional scale our results show that the clay bearing unit can be divided into sub units on the basis of differences in color and composition in false color visible imagery alternating white bluish and orange red colored units correspond to a compositional succession of respectively al and fe or mg phyllosilicate rich material geological cross sections are presented along the principal outcrops of the region in order to define the stratigraphy of these sub units this method shows that the dips of the sub units are frequently close to the slopes of the present topography except for scarps visible at the dichotomy boundary inside impact craters walls and outcrops inside mawrth vallis in addition to the al and fe or mg phyllosilicate rich sub units an altered surface is identified as the lower basement unit we propose two possible end member scenarios to explain the derived stratigraphy 1 alteration of volcaniclastic aeolian or aqueous layered deposits of various compositions by groundwater resulting in distinct altered rocks or 2 alteration coeval with the deposition of sediments under varying chemical conditions in wet pedodiagenetic environment

geology and landscape evolution of the hellas region of mars hellas basin on mars has been the site of volcanism tectonism and modification by fluvial mass wasting and eolian processes over its more than 4 b y existence our detailed geologic mapping and related studies have resulted in the following new interpretations the asymmetric distribution of highland massifs and other structures that define the uplifted basin rim suggest a formation of the basin by the impact of a low angle bolide having a trajectory heading s60 e during the late noachian the basin was infilled perhaps by lava flows that were sufficiently thick 1 km to produce wrinkle ridges on the fill material and extensional faulting along the west rim of the basin at about the same time deposits buried northern malea planum which are interpreted to be pyroclastic flows from amphitrites and peneus paterae on the basis of their degraded morphology topography and the application of a previous model for pyroclastic volcanism on mars peneus forms a distinctive caldera structure that indicates eruption of massive volumes of magma whereas amphitrites is a less distinct circular feature surrounded by a broad low dissected shield that suggests generally smaller volume eruptions during the early hesperian a 1 to 2 km thick sequence of primarily fined grained eolian material was deposited on the floor of hellas basin subsequently the deposit was deeply eroded except where armored by crater ejecta and it retreated as much as 200 300 km along its western margin leaving behind pedestal craters and knobby outliers of the deposit local debris flows within the deposit attest to concentrations of groundwater perhaps in part brought in by outflow floods along the east rim of the basin these floods may have deposited 100 200 m of sediment subduing wrinkle ridges in the eastern part of the basin floor during the late hesperian and amazonian eolian mantles were emplaced on the basin rim and floor and surrounding highlands their subsequent erosion resulted in pitted and etched plains and crater fill irregular mesas and pedestal craters local evidence occurs for the possible former presence of ground ice or ice sheets 100 km across however we disagree with a hypothesis that suggests that the entire south rim and much of the floor of hellas have been glaciated orientations of dune fields and yardangs in lower parts of hellas basin follow directions of the strongest winds predicted by a recently published general circulation model gcm transient frost and dust splotches in the region are by contrast related to the gcm prediction for the season in which the images they appear in were taken

present day and fossil rhodolith pavements compared their potential for analysing shallow water carbonate deposits abstract coralline red algae represent the main biogenic components in most shallow water carbonate successions from the eocene to the recent they contribute significantly to sediment production on open platforms carbonate sediments formed by unattached coralline algae include rhodolith pavements rps which represent dense accumulations of rhodoliths as well as maerl which is composed of rhodoliths coralline algal branches and their detritus recent rps sampled off sesoko jima okinawa jima southern japan occur at depths of 50 70 m on a submarine terrace the taxonomic coralline composition is dominated by melobesioids associated with minor amounts of mastophoroids and sporolithaceans the rhodoliths are characterised by various nuclei an encrusting inner arrangement encrusting to warty outer growth forms and sub spheroidal shapes bioerosion encrustation and abrasion are the most prevalent taphonomic features possible fossil counterparts were identified in chattian and priabonian rps from middle ramp depositional systems from the venetian area north east italy a direct comparison between recent and fossil rps is possible by contrasting the constituent rhodolith characteristics including taxonomic composition nature of the nucleus inner arrangement outer growth forms size and shape as well as taphonomic signatures this allows factors controlling rhodolith formation and growth in rps to be compared especially with respect to hydrodynamic regimes and substrate type

characterization of phyllosilicates observed in the central mawrth vallis region mars their potential formational processes and implications for past climate mawrth vallis contains one of the largest exposures of phyllosilicates on mars nontronite montmorillonite kaolinite and hydrated silica have been identified throughout the region using data from the compact reconnaissance imaging spectrometer for mars crism in addition saponite has been identified in one observation within a crater these individual minerals are identified and distinguished by features at 1 38 1 42 1 91 and 2 17 2 41 m there are two main phyllosilicate units in the mawrth vallis region the lowermost unit is nontronite bearing unconformably overlain by an al phyllosilicate unit containing montmorillonite plus hydrated silica with a thin layer of kaolinite plus hydrated silica at the top of the unit these two units are draped by a spectrally unremarkable capping unit smectites generally form in neutral to alkaline environments while kaolinite and hydrated silica typically form in slightly acidic conditions thus the observed phyllosilicates may reflect a change in aqueous chemistry spectra retrieved near the boundary between the nontronite and al phyllosilicate units exhibit a strong positive slope from 1 to 2 m likely from a ferrous component within the rock this ferrous component indicates either rapid deposition in an oxidizing environment or reducing conditions formation of each of the phyllosilicate minerals identified requires liquid water thus indicating a regional wet period in the noachian when these units formed the two main phyllosilicate units may be extensive layers of altered volcanic ash other potential formational processes include sediment deposition into a marine or lacustrine basin or pedogenesis

weathering of olivine under co2 atmosphere a martian perspective abstract recent analyses from the curiosity rover at yellowknife bay gale crater mars show sedimentary rocks deposited in a lacustrine environment and containing smectite clays thought to derive from the alteration of olivine however little is known about the weathering processes of olivine under early martian conditions and about the stability of smectite clays in particular here we present a 3 month experiment investigating the weathering of forsteritic olivine powders fo 90 under a dense co 2 atmosphere and under present day terrestrial conditions for comparison the experiment also evaluates the potential effects of hydrogen peroxide h 2 o 2 as a representation of the highly oxidizing compounds produced by photochemical reactions throughout martian history the weathered samples were characterized by means of near infrared spectroscopy nir x ray diffraction xrd transmission electron microscopy with energy dispersive x ray spectrometry tem edx mossbauer spectroscopy and thermogravimetry the results show that a mg rich smectite phase formed from the weathering of olivine under co 2 conditions although in lower abundance than under terrestrial conditions the main secondary phase formed under co 2 turns out to be a silica rich phase possibly acting as a passivating layer with a non diagnostic near infrared spectral signature the use of h 2 o 2 highlights the critical importance of both the redox conditions and fe content of the initial olivine on the nature of the secondary phases

global dominance of coralline red algal facies a response to miocene oceanographic events rhodoliths free living coralline red algae can thrive under a wide range of temperatures reduced light and increased nutrient levels and often form a distinct so called rhodalgal lithofacies that is an important component of cenozoic shallow water carbonates global distributions illustrate that from the late early to early late miocene burdigalian early tortonian rhodalgal facies reached peak abundances and commonly replaced coral reef environments accompanied by a decline in other carbonate producing phototrophs we argue that the dominance of red algae over coral reefs was triggered in the burdigalian by enhanced trophic resources associated with a global increase in productivity as evidenced by a long term shift toward higher carbon isotope values rhodalgal lithofacies expanded further in the middle miocene when strengthened thermal gradients associated with the establishment of the east antarctic ice sheet led to enhanced upwelling while climate change generated increased weathering rates introducing land derived nutrients into the oceans globally cooler temperatures following a climatic optimum in the early middle miocene contributed to sustain the dominance of red algae and prevented the recovery of coral reefs the global shift in nearshore shallow water carbonate producers to groups tolerant of higher levels of trophic resources provides further evidence for increased nutrient levels during that time interval and shows the sensitivity of shallow water carbonate facies as indicators of past oceanographic conditions

mineralogical composition structure morphology and geological history of aram chaos crater fill on mars derived from omega mars express data 1 aram chaos is a crater 280 km in diameter centered at 2 5 n 338 5 e it is filled by chaotic terrains overlain by a dome shaped layered 900 m thick formation displaying spectral signatures of ferric oxides on thermal emission spectrometer tes and observatoire pour la mineralogie l eau les glaces et l activite omega medium spatial resolution data we describe in detail the mineralogical composition structure and morphology of this crater fill using high resolution data omega mars orbiter laser altimeter mars orbiter camera tes thermal emission imaging system and high resolution imaging science experiment we infer the following formation scenario the crater was first filled by a geological formation the composition of which remains unclear because it is covered by dust widespread fracturing of this formation led to the development of chaotic terrains later a second layered formation presently dome shaped was emplaced unconformably on the chaotic terrains this younger unit is composed of a bright poorly consolidated material that contains both monohydrated sulfates and ferric oxides according to omega data the surface of this formation is partially covered by dust and displays landforms indicating that the bright material has been mobilized by wind during or after its deposition after its emplacement this formation has been grooved down to various depths by large eolian erosion corridors in these corridors eolian removal of the bright material with a sulfate rich matrix has left debris fans sand sheets and dunes which display some of the strongest spectral signatures of ferric oxides on mars similar residual deposits enriched in ferric oxides overlying a layered formation containing both ferric oxides and sulfates have been observed by the opportunity rover in meridiani planum suggesting a common formation process

extensive surface pedogenic alteration of the martian noachian crust suggested by plateau phyllosilicates around valles marineris 1 thousands of phyllosilicate rich outcrops mainly iron or magnesium rich are exposed on noachian terrains in the martian southern highlands we analyzed 90 crism observations and more than a hundred hirise images located on the plateaus surrounding valles marineris we mapped an extensive al and fe mg phyllosilicate rich formation covering at least 197 000 km2 for which we introduce the name plateau phyllosilicates tens of meters in thickness this light toned formation crops out at various elevations on top of the noachian units npl1 and npl2 as flat exposures on plateaus and along scarps such as valley walls chasma walls pit walls and impact crater rims the fe mg phyllosilicate rich lower member of the formation is composed of fe mg smectites nontronite saponite and vermiculite the al phyllosilicate rich upper member of the formation contains al smectites montmorillonite beidellite and locally kaolinite and or halloysite we suggest that the plateau phyllosilicates were mainly formed by pedogenesis related to the weathering of the noachian bedrock by percolation of meteoric water or melted snow under a temperate and subarid climate during the noachian epoch in an alkaline to neutral environment kaolinite and or halloysite may have formed in areas of more intense drainage at the surface under slightly acidic environments during the noachian and hesperian epochs fluvial activity and deuteric alteration may have locally contributed to the genesis of phyllosilicates this study suggests that the alteration of the noachian basement of the plateaus surrounding valles marineris was widespread during the noachian epoch and was still active during the hesperian epoch even though the water availability was limited

martian surface mineralogy from observatoire pour la mineralogie l eau les glaces et l activite on board the mars express spacecraft omega mex global mineral maps 1 after 2 years of operation the observatoire pour la mineralogie l eau les glaces et l activite omega imaging spectrometer on board mars express has acquired data coverage of the martian surface with spatial resolution varying between 300 m and 4 8 km depending on the pericenter altitude of the spacecraft s elliptical orbit we report the global surface distributions of some minerals using the omega observations in the visible and near infrared vnir wavelength domains 0 35 2 5 m global maps of ferric phases mafic minerals pyroxenes and olivines and hydrated minerals have been derived from spectral parameters the limits of detection in terms of abundance for some minerals of different grain size distributions are given the distribution of pyroxenes is in general agreement with the mineral maps of previous telescopic and space observations the fe3 absorption feature in the visible wavelength region is present everywhere on the surface the spectra of the bright regions compare with anhydrous nanophase ferric oxides terrains with water bearing minerals cover a very small fraction of the martian surface olivine mg rich compositions is detected in more extensive regions of the pyroxene rich zones than previously reported olivine with higher iron content and or larger grain size 100 m is only detected in isolated areas the mineralogy of the northern low albedo regions is discussed in the light of these mineral maps chemical alteration or oxidation during extrusion producing a coating or varnish of anhydrous ferric phases over a dark basaltic surface best accounts for the vnir spectral properties of these regions although a glassy composition resulting from impact is also considered

modelling consolidation accelerated by vertical drains in soils subject to creep the settlement of embankments and reclamations over soft soils is frequently accelerated by the use of vertical drains the magnitude of long term settlement is sometimes reduced by the use of surcharge although there is often uncertainty about how long the surcharge should be maintained to minimise creep movement the design of vertical drains is generally based on closed form solutions of terzaghi s consolidation equation and rarely takes into account non linear stiffness and creep of the soil in this paper a one dimensional finite difference consolidation analysis is outlined showing how vertical and radial drainage of a multi layer soil profile in the zone of influence of a vertical drain may be modelled the analysis allows inclusion of a zone of peripheral smear around the drain and drain resistance permeabilities may be varied with void ratio and creep is modelled both during and after primary consolidation the application of the model is illustrated with back analysis of field data from cons

rhodolith bearing limestones as transgressive marker beds fossil and modern examples from north island new zealand rhodoliths are nodular structures composed mainly of the superimposed thalli of calcareous red algae because their development is controlled by an array of ecological parameters rhodoliths are a valuable source of palaeoenvironmental information however despite their common use in palaeoecological reconstructions the stratigraphic significance of rhodolith accumulations seldom has been addressed in detail in a study of cenozoic rhodolith bearing deposits from the north island of new zealand rhodolithic units usually of limited lateral extent typically occur above major unconformities at the base of deepening upwards successions two types of transgressive rhodolith bearing deposits may be distinguished on the basis of texture and rhodolith internal structure i type a deposits are clast supported rhodolithic rudstones containing abundant pebbles and cobbles reworked from the substrate and are characterized by rhodoliths with a compact concentric to columnar internal structure and a high nucleus to algal cover ratio ii type b deposits are rhodolithic floatstones with a matrix usually consisting of bryozoan fragments benthic foraminifera and echinoid fragments or terrigenous silty fine sand the rhodoliths of type b units usually have a loose internal framework with irregular to branched crusts the two contrasting rhodolith bearing units are interpreted as characteristic facies of transgressive systems tract deposits analogous to shell concentrations formed under conditions of low net sedimentation type a deposits are correlated with relatively high energy settings and or narrow submerged palaeotopographic lows whereas type b deposits are interpreted as forming in lower energy settings the association between transgression and development of rhodolithic facies is confirmed by observations of a modern rhodolith production site at whangaparaoa peninsula in north island where algal nodules grow above a ravinement surface cut during the holocene sea level rise and also by a review of published fossil examples many of which show stratigraphic and compositional attributes analogous to those of the new zealand occurrences the review indicates that transgressive rhodolith accumulations develop more commonly in but are not restricted to non tropical settings it is suggested that a combination of factors such as low net sedimentary input nature of the substrate sea level rise and inherited physiography contribute to determine the relationship between rhodolith bearing deposits and transgressive settings

palaeoecology taphonomy and preservation of a lower pliocene shell bed coquina from a volcanic oceanic island santa maria island azores abstract massive fossil shell accumulations require particular conditions to be formed and may provide valuable insights into the sedimentary environments favouring such concentrations shallow water shell beds appear to be particularly rare on reefless volcanic oceanic islands on account of narrow steep and highly energetic insular shelves where the potential for preservation is limited the occurrence of an exceptional coquina pedra que pica within the miocene pliocene deposits of santa maria island azores therefore provides a rare opportunity to understand the conditions that led to the formation and preservation of a massive shell bed at mid ocean insular setting this study provides a detailed analysis regarding a 10 11 m thick bivalve dominated fossil assemblage exposed at pedra que pica on santa maria island in the azores integration of taphonomical palaeoecological and sedimentological observations are used to reconstruct the genesis of the coquina bed and related events and to discuss why such exceptional sedimentary bodies are so rare on shelves around reefless volcanic oceanic islands the sequence at pedra que pica demonstrates a complex succession of sedimentary environments in response to the drowning of an existing coastline during a period of rapid sea level rise the pedra que pica shell bed incorporates storm related materials and possible debris falls that originated nearby in a shallow and highly productive carbonate factory deposition took place below fair weather wave base at around 50 m depth as inferred from the overlying volcanic succession the preservation of this coquina was favoured by deposition on a platform laterally protected by a rocky spur combined with rapid burial by water settled volcanic tuffs and subsequent volcanic effusive sequences the recent exhumation of the deposit is the result of island uplift and subsequent erosion

neogene marine sediments and biota encapsulated between lava flows on santa maria island azores north east atlantic an interplay between sedimentary erosional and volcanic processes

severe storms during earth history although severe storms are recognized as important agents in sediment transport many questions remain to demonstrate genetic links between specific sedimentary structures and textures and proposed generative agents a detailed physically based consideration of climatic and geographic controls on the generation and distribution of severe storms is presented on the basis of modern observations physical processes deduced from these observations and climate model experiments using past geographies the results suggest that simple latitudinal distinctions for storm type severe winter storm or hurricane or inference from estimates of global warmth are not adequate to consider genetic links for storm related deposits climate and geography produce substantial variability in storm generation rates and in storm distributions for example geography may inhibit poleward penetration of hurricanes or enhance a broad latitudinal distribution the record of tropical sea surface temperatures indicates that values may have been below hurricane generation thresholds during the eocene and glacial stages land sea distribution and associated thermal contrasts strongly influence the distribution and intensity of winter storms the results from models can be compared favorably with observations of probable storm sedimentation

smectite formation in the presence of sulfuric acid implications for acidic smectite formation on early mars the excess of orbital detection of smectite deposits compared to carbonate deposits on the martian surface presents an enigma because smectite and carbonate formations are both favored alteration products of basalt under neutral to alkaline conditions we propose that mars experienced acidic events caused by sulfuric acid h2so4 that permitted phyllosilicate but inhibited carbonate formation to experimentally verify this hypothesis we report the first synthesis of smectite from mars analogue glass rich basalt simulant 66 wt glass 32 wt olivine 2 wt chromite in the presence of h2so4 under hydrothermal conditions 200 c smectites were analyzed by x ray diffraction mossbauer spectroscopy visible and near infrared reflectance spectroscopy and electron microprobe to characterize mineralogy and chemical composition solution chemistry was determined by inductively coupled plasma mass spectrometry basalt simulant suspensions in 11 42 mm h2so4 were acidic with ph 2 at the beginning of incubation and varied from acidic ph 1 8 to mildly alkaline ph 8 4 at the end of incubation alteration of glass phase during reaction of the basalt simulant with h2so4 led to formation of the dioctahedral smectite at final ph 3 and trioctahedral smectite saponite at final ph 4 and higher anhydrite and hematite formed in the final ph range from 1 8 to 8 4 while natroalunite was detected at ph 1 8 hematite was precipitated as a result of oxidative dissolution of olivine present in adirondack basalt simulant formation of secondary phases including smectite resulted in release of variable amounts of si mg na and ca while solubilization of al and fe was low comparison of mineralogical and solution chemistry data indicated that the type of smectite i e dioctahedral vs trioctahedral was likely controlled by mg leaching from altering basalt and substantial mg loss created favorable conditions for formation of dioctahedral smectite we present a model for global scale smectite formation on mars via acid sulfate conditions created by the volcanic outgassing of so2 in the noachian and early hesperian

hydrous minerals on mars as seen by the crism and omega imaging spectrometers updated global view 1 the surface of mars has preserved the record of early environments in which its basaltic crust was altered by liquid water these aqueous environments have survived in the form of hydrological morphologies and alteration minerals including clays and hydrated salts because these minerals probe on earth aqueous environments compatible with biotic activity understanding their formation processes on mars is of great exobiological relevance and also offers insight into earth s now erased ancient water environments using remote sensing we conducted a large scale investigation of the distribution composition age and geomorphic settings of hydrous minerals on mars providing a sharpened global view of the early aqueous environments and their evolution with time aqueous alteration seems to have produced clays on a planetary scale but these are found to be restricted to the oldest observable terrains on mars 4 gyr however very diverse aqueous environments have also been found which suggest widespread complex aqueous settings from the surface to kilometric depths and spanning over 1 gyr by building a robust statistical sample of detections the global trends inferred here attempt to provide a broad view of our current understanding of hydrous minerals on mars and provide context for more localized in depth analyses collectively these trends suggest that at least transient conditions have existed on mars which may have been favorable for pre biotic to biotic activity

emission spectroscopy of clay minerals and evidence for poorly crystalline aluminosilicates on mars from thermal emission spectrometer data 1 to understand the aqueous history of mars it is critical to constrain the alteration mineralogy of the martian surface previously published analyses of thermal infrared 6 25 m remote sensing data of mars suggest that dark regions have 15 20 clay minerals however near infrared 1 3 m spectral results generally do not identify widespread clay minerals thermal infrared detections of clays on mars are difficult to interpret owing in part to the relative paucity of published spectral analyses of clay minerals and clay bearing materials using similar spectra thermal infrared emission spectra in this study we present an analysis of the thermal emission spectral features 6 25 m or 400 1650 cm 1 of a suite of clay mineral reference materials and clay bearing rocks linking their spectral features to the crystal chemical properties of the clays on the basis of this context provided by the emission spectral analysis of clay minerals and clay bearing rocks we reconsider the evidence for clay minerals on mars from thermal emission spectrometer tes results we propose that global scale clay abundances determined from tes probably represent a geologically significant surface component though they may actually correspond to poorly crystalline aluminosilicates with similar si o ratios to clay minerals 0 3 0 4 rather than well crystalline clays if clay minerals or clay like materials on mars are poorly crystalline and or dessicated they may be detectable in the thermal infrared but not easily detected with near infrared data sets

orbital identification of carbonate bearing rocks on mars geochemical models for mars predict carbonate formation during aqueous alteration carbonate bearing rocks had not previously been detected on mars surface but mars reconnaissance orbiter mapping reveals a regional rock layer with near infrared spectral characteristics that are consistent with the presence of magnesium carbonate in the nili fossae region the carbonate is closely associated with both phyllosilicate bearing and olivine rich rock units and probably formed during the noachian or early hesperian era from the alteration of olivine by either hydrothermal fluids or near surface water the presence of carbonate as well as accompanying clays suggests that waters were neutral to alkaline at the time of its formation and that acidic weathering proposed to be characteristic of hesperian mars did not destroy these carbonates and thus did not dominate all aqueous environments

martian cratering 8 isochron refinement and the chronology of mars abstract this paper reviews and refines the technique of dating martian surfaces by using impact crater isochrons defined as size distributions of impact craters on undisturbed martian surfaces of specified ages in the 1970s this system identified not only abundant ancient martian volcanic surfaces but also extensive lava plains with ages of a few 108 y old this dating was initially controversial but confirmed in the 1980s and 90s by martian meteorites the present update utilizes updated estimates of the mars moon cratering ratio the most important calibration factor improves treatment of gravity and impact velocity scaling effects combines aspects of the crater size distribution data from earlier work by both neukum and hartmann and for the first time applies a correction for loss of small meteoroids in the martian atmosphere from popova et al 2003 meteorit planet sci 38 905 925 the updated isochrons are not radically different from the previous 2002 iteration but fit observed data better and give somewhat older model ages for features dated from small craters diameter d 100 m crater counts from young lava flows in various areas give good fits to the new isochrons over as much as 3 orders of magnitude in d confirming the general isochron shape and giving crater retention ages in the range of some 106 to some 108 y interpreted as lava flow ages more complex older units are also discussed uncertainties are greatest if only small craters d 100 m are used suggestions by other workers of gross uncertainties due to local secondary craters and deposition exhumation are discussed they do not refute our conclusions of significant volcanic fluvial and other geologic activity in the last few percent of martian geologic time or the importance of cratering as a tool for studying processes such as exhumation indeed crater count data suggest certain very recent episodes of deposition exhumation and ice flow possibly associated with obliquity cycles of 10 7 y timescale evidence from ancient surfaces suggests higher rates of volcanism fluvial activity glaciation and other processes in noachian hesperian time than in amazonian time

global maps of anhydrous minerals at the surface of mars from omega mex 1 we here reassess the global distribution of several key mineral species using the entire omega mars express vis nir imaging spectrometer data set acquired from orbit insertion in january 2004 to august 2010 thirty two pixels per degree global maps of ferric oxides pyroxenes and olivines have been derived a significant filtering process was applied in order to exclude data acquired with unfavorable observation geometries or partial surface coverage with water and co2 frosts because of strong atmospheric variations over the 3 6 martian years of observations primarily due to the interannual variability of the aerosol opacity a new filter based on the atmospheric dust opacity calibrated by the mars exploration rovers measurements has also been implemented the fe3 absorption features are present everywhere on the surface with a variety of intensities indicating distinct formation processes the pyroxene bearing regions are localized in low albedo regions while the bright regions are spectrally comparable to anhydrous nanophase ferric oxides the expanded data set increases by a factor of about 2 the number of olivine detections reported in previous omega based studies olivine is mainly detected in three types of areas over the martian surface discontinuous patches on the terraces of the three main basins smooth inter crater plains and smooth crater floors throughout the southern highlands and crater sand dunes crater ejectas and extended bedrock exposures in the northern plains olivine is also detected in the low albedo pyroxene bearing dunes surrounding the northern polar cap

the 40ar 39ar age dating of the madeira archipelago and hotspot track eastern north atlantic the 40ar 39ar ages for 35 volcanic rocks and 14c ages for two charcoal samples from the madeira archipelago and ampere seamount eastern north atlantic are presented the volcanic evolution of madeira can be divided into a voluminous shield stage 4 6 0 7 ma and a subsequent low volume posterosional stage 70 myr old hotspot which formed porto santo island 11 1 14 3 ma seine ampere 31 ma corral patch and ormond 65 67 ma feraud et al 1982 1986 seamounts and the serra de monchique 70 72 ma mcintyre and berger 1982 complex in southern portugal age and spatial relationships result in a calculated absolute african plate motion above the hotspot of 1 2 cm yr around a rotation pole located at 43 36 n 24 33 w

role of impact excavation in distributing clays over noachian surfaces 1 spectrometers have detected clay bearing units in and on much of the ancient martian crust geothermally heated aquifers in basaltic rock provide conditions conducive to forming fe mg phyllosilicates at depth throughout the noachian period a high flux of km scale bolides excavated buried materials and distributed them over the surface we use the maxwell z model to quantify the volume and final location of excavated clay bearing material we focus on two potentially detectable properties the volume of clay bearing material ejected as a fraction of total ejected volume and the volume percentage of clay bearing material in the ejecta as a function of distance from the crater s rim generally the volume percentage of clays in the ejecta is greatest for craters less than 25 km in diameter larger crater sizes incorporate a higher fraction of clay poor material because they excavate to greater depths at which clays are likely absent specific trends in bulk clay volume fraction and the distribution of clay fraction across the ejecta deposit as a function of crater size depend on the depth to the clay rich layer and its thickness impact excavation likely explains clays associated with ejecta deposits and may reveal clues about the volatile content and stratigraphy of the upper noachian crust applying our model to the mawrth vallis region suggests that a clay layer a few hundred meters thick is buried at the 3000 m elevation contour given that clay layers are likely thin and buried in the upper 3 km of the crust we predict that small to mid sized craters 25 km will best exhibit detectable amounts of clays and that these clays will be most abundant in the crater wall and rim and less so in distal ejecta

silica deposits in the nili patera caldera on the syrtis major volcanic complex on mars the martian surface features abundant volcanoes and evidence for past liquid water extant or relict martian volcanic hydrothermal systems have therefore been sought in the pursuit of evidence for habitable environments the mars exploration rover spirit detected deposits highly enriched in silica with accessory minerals suggesting formation by hydrothermal leaching of basaltic rocks by low ph solutions however extensive erosion has obscured the context of the formation environment of these deposits silica deposits have also been identified remotely but also with limited contextual clues to their formation aqueous alteration products of basalt and volcanic ash are the most likely sources here we report the detection from orbit of hydrated silica deposits on the flanks of a volcanic cone in the martian syrtis major caldera complex near infrared observations show dozens of localized hydrated silica deposits as a result of the morphology of these deposits and their location in and around the cone summit we suggest that the deposits were produced by a volcanically driven hydrothermal system the cone and associated lava flows post date early hesperian volcano formation we conclude that if a relict hydrothermal system was associated with the silica deposits it may preserve one of the most recent habitable microenvironments on mars

eridania basin an ancient paleolake floor as the next landing site for the mars 2020 rover abstract the search for traces of past martian life is directly connected to ancient paleolakes where ponding water or low energy water fluxes were present for long time intervals the eridania paleolakes system located along the 180 meridian is one of the largest lacustrine environments that were once present on mars morphological features suggest that it was constituted by connected depressions filled by water to maximum depths of 2400 m and a volume of at least 562 000 km3 we focused our attention on the northern side of the eridania basin where high albedo uneven patches of material characterized by the absence of dust are present based on omega and crism orbital imaging spectroscopy data a large clay bearing unit has been identified there in particular a set of aqueous minerals in present in the stratigraphy being visible through erosional windows in the first several tens of meters of the sedimentary sequence below this capping unit a thin al rich clay stratum attributable to al smectite and or kaolins is present this overlies a fe rich clay stratum attributable to the nontronite smectite at the base of the mineralogic sequence a stratum that could be either a zeolite or more likely a hydrated sulfate is present in addition small deposits of alunite a rare phase on mars and jarosite are here found at several locations such stratigraphy is interpreted as originating from a surface weathering process similar to terrestrial abiotic pedogenesis nonetheless possible exobiologic processes can be also invoked to explain it nasa s spirit rover landed on gusev crater in 2004 near the mouth of the ma adim vallis which connects this crater with the considered paleolakes system the eridania site provides the unique opportunity to complete the measurements obtained in gusev crater while investigating the exposed mineralogical sequence in its depositionary setting in addition the extremely favorable landing parameters such as elevation slope roughness rock distribution thermal inertia and dust coverage support this location as a possible landing site for the nasa mars 2020 rover

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

the aster spectral library version 2 0 abstract the advanced spaceborne thermal emission reflection radiometer aster on nasa s terra platform has been widely used in geological and other science studies in support of aster studies a library of natural and man made materials was compiled as the aster spectral library v1 2 and made available from http speclib jpl nasa gov the library is a collection of contributions in a standard format with ancillary data from the jet propulsion laboratory jpl johns hopkins university jhu and the united states geological survey usgs a new version of the library v2 0 is now available online or via cd which includes major additions to the mineral and rock spectra the aster library provides a comprehensive collection of over 2300 spectra of a wide variety of materials covering the wavelength range 0 4 15 4 m

detection of hydrated silicates in crustal outcrops in the northern plains of mars the composition of the ancient martian crust is a key ingredient in deciphering the environment and evolution of early mars we present an analysis of the composition of large craters in the martian northern plains based on data from spaceborne imaging spectrometers nine of the craters have excavated assemblages of phyllosilicates from ancient noachian crust buried beneath the plains cover the phyllosilicates are indistinguishable from those exposed in widespread locations in the southern highlands demonstrating that liquid water once altered both hemispheres of mars

miocene pliocene rocky shores on sao nicolau cape verde islands contrasting windward and leeward biofacies on a volcanically active oceanic island abstract north atlantic islands in the cape verde archipelago off the coast of west africa commonly feature an elongated n s shape in which reduced northern coasts and longer eastern shores absorb the brunt of wave activity and long shore currents generated by prevailing north east trade winds located in the middle windward islands sao nicolau is unusual in profile with an elongated e w configuration that offers a broad target against high energy wind driven waves conversely the south shore of sao nicolau provides relatively wide shelter in a leeward setting reconstruction of the proto island prior to the onset of the main eruptive stage during the late miocene at 5 1 ma reveals a moderately smaller island with essentially the same e w orientation this study combines previous data with results from a detailed stratigraphic log based on upper miocene limestone deposits on the island s south flank for comparison with stratigraphic profiles of upper miocene limestone from the island s northeast quarter logs from a pliocene sandy limestone outcropping on the south central coast of sao nicolau give added context to the diversity of marine invertebrates including branching coral colonies and delicate ramose bryozoans that found shelter in a leeward setting whole rhodoliths contribute the main fabric of carbonates deposited against rocky shores on the northern exposed side of the miocene island whereas only traces of worn rhodoliths and rhodolith sand occur as in finer miocene grainstone on the island s southern protected side miocene and pliocene carbonate deposits were terminated by submarine flows on an actively growing volcanic island the passage zone from submarine to subaerial flows on the island s flanks makes a useful meter stick to gauge absolute water depth at the moment of local extinction by volcanic activity

most mars minerals in a nutshell various alteration phases formed in a single environment in noctis labyrinthus 1 a closed depression in the noctis labyrinthus region of mars at 10 4 s 98 6 w believed to have formed in the late hesperian holds an inner pit partially filled with several hundred meters of stratified material compact reconnaissance imaging spectrometer for mars crism visible near infrared reflectance data reveal signatures of numerous hydrated minerals including halloysite kaolinite fe smectite si oh bearing phases and fe sulfates polyhydrated monohydrated and hydroxylated types including jarosite we use crism data high resolution imagery hirise and hrsc high resolution stereo camera derived elevation to analyze the morphology composition and stratigraphy of these materials we propose an alteration sequence including formation of acid sulfate solutions from groundwater and magmatic sulfur which then locally altered the basaltic bedrock and layered sediments mainly deposited from volcanic tephra forming fe smectite and fe sulfates the mineral variability can mostly be explained by local variations in the ph of the altering fluids with original acidity being buffered by dissolution of primary minerals and by variable fluid input and evaporation and or freezing rates resulting in various water rock ratios this site shows local formation of almost all classes of minerals identified thus far on mars without invoking global conditions processes related to local volcanic activity and associated hydrothermalism were able to produce during an era in which the climate is believed to have been cold a large variety of hydrated minerals this study highlights the importance of the geological setting of hydrated minerals in the understanding of mars geologic and climatic evolution

impact generated hydrothermal systems capable of forming phyllosilicates on noachian mars the early history of the terrestrial planets was punctuated by a period of heavy bombardment frequent large impacts condensed in a short 0 02 0 5 ga long time period resulted in heavily cratered planetary surfaces in volatile bearing planetary crusts each of these large impacts created a volume of hot rock and melt that drove vast subsurface hydrothermal systems in mars basaltic crust these systems produced a variety of alteration phases the nature of which we explored with thermochemical modeling using the computer code chiller we found a variety of oxides hydroxides and hydrous and water free silicates resulting from the hydrothermal alteration the main hydrous silicates are serpentine chlorite nontronite and other clay minerals some of the resulting assemblages contain up to 15 wt bound water our results constrain the temperature and water rock ratio at the time of alteration and compare well to the mineral assemblages found on mars by omega observatoire pour la mineralogie l eau les glaces et l activite and crism compact reconnaissance imaging spectrometer for mars and therefore provide an interpretative framework for analyzing martian mineralogy from orbital data our results also provide a geological template needed to select landing locations for future missions that search for water and energy sources associated with potential habitats on early mars

resurfacing history of the northern plains of mars based on geologic mapping of mars global surveyor data 1 geologic mapping of the northern plains of mars based on mars orbiter laser altimeter topography and viking and mars orbiter camera images reveals new insights into geologic processes and events in this region during the hesperian and amazonian periods we propose four successive stages of lowland resurfacing likely related to the activity of near surface volatiles commencing at the highland lowland boundary hlb and progressing to lower topographic levels as follows highest elevations indicated stage 1 upper boundary plains early hesperian 2 0 to 2 9 km stage 2 lower boundary plains and outflow channel dissection late hesperian 2 7 to 4 0 km stage 3 vastitas borealis formation vbf surface late hesperian to early amazonian 3 1 to 4 1 km and stage 4 local chaos zones early amazonian 3 8 to 5 0 km at acidalia mensa stage 2 and 3 levels may be lower 4 4 and 4 8 km respectively contractional ridges form the dominant structure in the plains and developed from near the end of the early hesperian to the early amazonian geomorphic evidence for a northern plains filling ocean during stage 2 is absent because one did not form or its evidence was destroyed by stage 3 resurfacing remnants of possible amazonian dust mantles occur on top of the vbf the north polar layered deposits appear to be made up of an up to kilometer thick lower sequence of sandy layers early to middle amazonian in age overlain by late amazonian ice rich dust layers both units appear to have outliers suggesting that they once were more extensive

analysis of phyllosilicate deposits in the nili fossae region of mars comparison of tes and omega data abstract diverse phyllosilicate deposits discovered previously in the nili fossae region with near infrared reflectance data are a window into the complex history of aqueous alteration on mars in this work we used thermal infrared data from the thermal emission spectrometer tes in combination with near infrared data from the observatoire pour la mineralogie l eau les glaces et l activite omega to better constrain the mineralogy and geologic origin of these deposits we developed a tes spectral index for identification of clay minerals which correctly identifies the phyllosilicates in the nili fossae area and points to several other interesting deposits in the syrtis major region however detailed inspection of the tes spectral features of nili fossae phyllosilicates shows a feature at low wavenumbers 350 550 cm 1 that is not an exact match to any specific fe 3 al or mg rich phyllosilicate phase instead the feature is more similar to basaltic glass and may indicate that the phyllosilicates in this region are 1 rich in fe 2 based on similarity to trends seen in laboratory data of clay minerals 2 poorly crystalline extremely disordered and or 3 present within a matrix of actual basalt glass this feature is similar to spectral features seen in altered rocks in the columbia hills region of gusev crater by previous authors by calibrating measured spectral index values against mathematical spectral mixtures of typical martian dark surfaces and known abundances of alteration minerals we are able to estimate an enrichment in abundance of alteration minerals in the altered surfaces many dark noachian deposits in the nili fossae area are enriched phyllosilicates by 20 30 10 15 relative to dark volcanic surfaces in the same region the distribution and abundance of these phases indicates that alteration in the region was pervasive but did not completely erase the original mineralogy of what was likely an fe rich basalt protolith as a group the nili fossae phyllosilicate deposits are fundamentally different from those found in the mawrth vallis region nili fossae deposits have strong thermal infrared features related to admixed pyroxene plagioclase and occasionally olivine whereas the mawrth vallis deposits contain no mafic minerals comparison of tes and omega data also illustrates some more general differences between the datasets including the impact of physical character of the martian surface on detectability of minerals in each spectral range

phyllosilicates in the mawrth vallis region of mars 1 omega mars express has discovered large outcrops rich in phyllosilicates in the region of mawrth vallis mars around 20 w 25 n the region is located in noachian highly cratered terrains close to the limit of the martian dichotomy where the outflow channel mawrth vallis cuts the highlands we have examined this region using omega spectra of the surface from 0 9 m to 2 6 m with spatial sampling from 500 m to 3 km offering a full coverage of the region omega spectra show two broad bands centered at 1 m and 2 2 m revealing the presence of clinopyroxene on dark surfaces phyllosilicates have been identified by absorption bands at 1 4 m 1 9 m and 2 2 or 2 3 m comparison with laboratory spectra reveals similarities with al oh smectites such as montmorillonites or fe or mg oh smectites such as nontronite a precise location of the phyllosilicate rich areas on visible hrsc images indicates that they are placed exclusively on bright outcrops mostly on the plateaus dated to the noachian period on hrsc and moc images the phyllosilicate rich outcrops reveal strong erosional features such as numerous residual buttes composed of layers a few meters thick the phyllosilicate rich unit corresponds to a geological unit more than 100 m thick over a horizontal extension approximately of 300 km 400 km this unit implies a large volume of altered rocks either in situ or after transport and deposition in noachian terrains revealing a different climatic and geologic environment from the present one

mineralogical structure of the subsurface of syrtis major from omega observations of lobate ejecta blankets 1 this paper focuses on the spectral characteristics of lobate ejecta across syrtis major volcano a dark region of mars presenting a mafic composition as revealed from the observatoire pour la mineralogie l eau les glaces et l activite omega instrument two spectrally distinct crater types are identified type i is enriched in high calcium pyroxene hcp relative to the volcanic rocks type ii is similar to the lava flow mineralogy driven by hcp compared to the noachian crust dominated by low calcium pyroxene lcp type i craters are systematically younger than type ii the type ii mineralogy has been likely affected by a long term weathering in a cold environment for the last 2 ga the axisymmetric spectral signatures of type i ejecta appear dominated by rock forming minerals rather than by soils and reflect the composition of excavated materials offering a window for exploring the subsurface a progressive change in the slope of the spectra around 1 5 2 m is observed across the ejecta layers pointing at a change in the hcp lcp ratio the deconvolution of the spectra by the modified gaussian model unravels a maximum of hcp lcp band strength ratio located between 1 2 and 3 crater radii for all type i craters using z modeling this observation translates into a maximum in the hcp lcp abundances at a few hundreds of meters depth and suggests a homogeneous subsurface structure of the volcanic edifice below this horizon the hcp lcp decrease may reveal a more ancient lava composition or the signature of the underlying noachian crust

metamorphism in the martian crust compositions of basaltic and ultramafic rocks analyzed by mars rovers and occurring as martian meteorites allow predictions of metamorphic mineral assemblages that would form under various thermophysical conditions key minerals identified by remote sensing roughly constrain temperatures and pressures in the martian crust we use a traditional metamorphic approach phase diagrams to assess low grade hydrothermal equilibrium assemblages basaltic rocks should produce chlorite actinolite albite silica accompanied by laumontite pumpellyite prehnite or serpentine talc only prehnite bearing assemblages have been spectrally identified on mars although laumontite and pumpellyite have spectra similar to other uncharacterized zeolites and phyllosilicates ultramafic rocks are predicted to produce serpentine talc and magnesite all of which have been detected spectrally on mars mineral assemblages in both basaltic and ultramafic rocks constrain fluid compositions to be h2o rich and co2 poor we confirm the hypothesis that low grade hydrothermal metamorphism affected the noachian crust on mars which has been excavated in large craters we estimate the geothermal gradient 20 c km 1 required to produce the observed assemblages this gradient is higher than that estimated from radiogenic heat producing elements in the crust suggesting extra heating by regional hydrothermal activity