reflectances of ophiolite rocks in the landsat mss bands relevance to lithological mapping by remote sensing radiometry performed in situ on natural rock surfaces in the oman ophiolite demonstrates the muting of spectral distinctions between rock types due to metamorphism alteration and weathering within class variation and between class overlaps can be minimized by intensity normalization the use of intensity normalized spectral bands enables maximum likelihood classification to discriminate some lithologies more effectively than by using ordinary mss bands however there is a trade off between reduction of overlapping reflectances between different rock types and loss of albedo information which is diagnostically useful in some cases

cosmogenic 3he production rates from 39 n to 46 n latitude western usa and france the in situ production rate of cosmogenic 3he was determined in seven different olivine or pyroxene bearing rocks between the latitudes 39 n and 46 n the integrated production rate over the last 17 500 years is about 115 4 atoms gram yr for high latitude at sea level the variation in the integrated production rate between 2000 and 18 000 years is less than 30 and is probably on the order of 20 or less

influence of late quaternary climatic changes on geomorphic and pedogenic processes on a desert piedmont eastern mojave desert california radiocarbon dating of late quaternary deposits and shorelines of lake mojave and cation ratio numerical age dating of stone pavements dorn 1984 on the adjacent soda mountains piedmont provide age constraints for alluvial and eolian deposits these deposits are associated with climatically controlled stands of lake mojave during the past 15 000 yr six alluvial fan units and three eolian stratigraphic units were assigned ages based on field relations with dated shorelines and piedmont surfaces as well as on soil geomorphic data all but one of these stratigraphic units were deposited in response to time transgressive climatic changes beginning approximately 10 000 yr ago increased eolian flux rates occurred in response to the lowering of lake mojave and a consequent increase in fine sediment availability increased rates of deposition of eolian fines and associated salts influenced pedogenesis stone pavement development and runoff infiltration relations by 1 enhancing mechanical weathering of fan surfaces and hillslopes and 2 forming clay and silt rich surface horizons which decrease infiltration changes in alluvial fan source areas from hillslopes to piedmonts during the holocene reflect runoff reduction on hillslopes caused by colluvial mantle development and runoff enhancement on piedmonts caused by the development of less permeable soils inferred increased in early to middle holocene monsoonal activity resulted in high magnitude paleo sheetflood events on older fan pavements this runoff triggered piedmont dissection which in turn caused increased sediment availability along channel walls thus runoff infiltration changes during the late quaternary have occurred in response to eolian deposition of fines pedogenesis increased sheetflood activity in the holocene and vegetational changes which are related to many complicated linkages among climatic change lake fluctuations and eolian hillslope and alluvial fan processes

models of rock varnish formation constrained by high resolution transmission electron microscopy nanometre scale transmission electron microscope imagery of manganiferous rock varnishes from death valley california peru antarctica and hawaii confirms prior infrared mineralogy studies the building blocks of rock varnish are clay minerals that are cemented to the rock by oxyhydroxides of manganese and iron rock varnish is layered on the scale of nanometres with the basic structure defined by the subparallel alignment of detrital clay minerals although only a few examples of bacteria were found possible cell wall encrustations are ubiquitous and aligned with the clay minerals mn fe oxides appear to be mobilized from bacterial casts and then reprecipitate on clay minerals that weather into monolayers these observations have implications for varnish dating and palaeoenvironmental techniques k ar and uranium series dating of rock varnish oxides can only yield minimum ages however this small spatial scale of mobilization would not alter the signal from micron scale microchemical laminations

hydrothermal altered serpentinized zone and a study of ni magnesioferrite magnetite awaruite occurrences in wadi hibi northern oman mountain discrimination through aster mapping abstract economic important minerals and ore deposits are common in hydrothermal altered serpentinized zone advanced spaceborne thermal emission and reflection radiometer aster satellite sensor is capable of discrimination of such hydrothermal mineralized zone and detection of hydrothermal altered minerals in the present study the hydrothermal altered serpentinized harzburgites of wadi hibi area of northern oman mountains have been discriminated by using aster vnir swir spectral bands by image processing methods and the occurrences of ni magnesioferrite magnetite awaruite in the rocks are studied the color composite rgb image developed using aster spectral bands 8 4 and 1 mapped well the occurrence of weathered peridotites by pale green to dark blue in colors and discriminated the hydrothermally altered serpentinized rocks by pale brown to dark blue colors due to the strong absorption of oh and mg oh molecules that occurred in the serpentine minerals of the rocks in the study area the aster band ratios 4 7 4 1 and 2 3 4 3 rgb images studied are capable of discrimination of hydrothermal mineralized areas more clear by pale blue to purple colors due to the strong absorption of such hydroxyl bearing serpentine minerals the studied image processing methods are evaluated by applying to the region of wadi sarami situated in the semail ophiolite oman in addition to that the occurrence of serpentine minerals namely lizardite and antigorite in the hydrothermally altered serpentinized region are detected qualitatively and quantitatively using spectral angle mapper sam supervised classification image processing method and studied the interpreted images are verified in the field and checked for the occurrences of minerals including ni magnesioferrite magnetite pentlandite and awaruite and are confirmed through laboratory studies petrographic study of serpentinized harzburgites shows that the rocks consist predominantly of antigorite and lizardite serpentines olivine and have the opaque minerals assemblage of ni magnesioferrite magnetite awaruite pentlandite developed during serpentinization of the rock the occurrences of such minerals are confirmed by xrd electron microprobe analyses and spectral measurements in the laboratory aster sensor proved its capability in discriminating the hydrothermal altered serpentinized zone and detecting the mineral occurrences and thus the study recommends the technique to the exploration geologists scientists and mining geologists for mapping of such rocks and minerals in the similar arid region

aster mapping of limestone formations and study of caves springs and depressions in parts of sultanate of oman caves springs and large depressions of limestone karst formations are becoming more attractive tourist places and have potential importance on socio economic development the present study is a multi scale point of view on limestone karst from the space images to microscopic fabric here the karst features consist of limestone formations of cretaceous albian cenomanian age of tanuf valley and tertiary late paleocene middle eocene age of sur region of parts of sultanate of oman which are mapped in the visible near infrared and shortwave infrared spectral bands of advanced spaceborne thermal emission and reflection radiometer aster using decorrelated stretch image processing technique and the occurrences of caves springs and depressions of the formations in the field were studied the decorrelated rgb images of aster spectral bands 8 3 and 1 discriminated well the limestone formations and associated lithology the limestone formations of tanuf valley natih formations of hajar unit are thick bedded massive shallow marine limestone and clayey limestone which have caves and springs large depressions are studied as collapsed structures at the boundary between abat formations they consist of gray to white marly or micritic limestone with chert nodules and seeb formation of bioclastic limestone calcarenite marl and sandstone of sur region interpretations of limestone formations their occurrences and distributions of caves springs and depressions of these regions are verified and confirmed in the field and studied in the laboratory occurrences of more springs and depressions in the limestone formations of the study sites are interpreted and located on the google earth image the study proved the capability of aster sensor in mapping of limestone formations and recommends the technique to other geographical regions where similar geological questions need to be resolved

nanometer scale complexity growth and diagenesis in desert varnish nanometer scale element mapping and spectroscopy of desert varnish from the northern sonoran desert in southwestern arizona reveal a dynamic disequilibrium system characterized by postdepositional mineralogical chemical and structural changes activated by liquid water lack of equilibrium is suggested by the large variety of coexisting mn phases sparse secondary ba and sr sulfates also occur as do carbonaceous particles individual mn oxide particles contain variable concentrations of ba and ce reflecting their role as repositories of trace elements presumably derived from atmospheric aerosols desert varnish is analogous to more familiar sediments in displaying authigenic and diagenetic structures but with total sediment thicknesses 1 mm and structures at the nanometer scale as such it is neither a weathering rind nor patina but a unique subaerial sediment that is in dynamic disequilibrium our results suggest continuing adjustment of varnish to changing environmental conditions

how fast does rock varnish grow rates of rock varnish accumulation have never been systematically documented owing to the difficulty in accurately determining both varnish thickness and age in this study we quantitatively assess varnish accumulation rates through thin sectioning and microscopic examination of rock varnish from radiometrically dated geomorphic features of late quaternary age in the western united states drylands our data indicate that rock varnish grows at rates ranging from 1 to 40 m k y on subaerially exposed rock surfaces and rarely reaches a thickness exceeding 200 m regardless of age our data also indicate that varnish accumulation rates vary greatly from sample to sample at a given site suggesting that varnish thickness does not correlate with the age of the associated geomorphic feature invalidating the potential use of varnish thickness as a relative age indicator in geomorphology and archaeology nevertheless being the slowest known accumulating terrestrial sedimentary deposit rock varnish constitutes a unique long term microscale sedimentary archive of past environmental changes in deserts

processes in magma chambers beneath spreading axes evidence from magmatic associations in the oman ophiolite ophiolite complexes where complete consist of tectonized ultramafic rocks overlain by layered gabbros and peridotites isotropic gabbros and plagiogranites a sheeted dyke swarm and pillowed volcanics this pseudo stratigraphy has been interpreted as oceanic crust and upper mantle dewey bird 1971 moores vine 1971 the base of the crust being drawn at the base of the layered series malpas 1978 in oman this succession is particularly well exposed in a 500 km long 14 km thick ophiolite nappe of upper cretaceous age glennie et al 1973 magmatic associations in its lower crustal and upper mantle portions oceanic layers 3 and 4 are currently being studied to determine the processes of magma supply and fractionation in oceanic magma chambers in the first section of this report we list the evidence for the greater part of the plutonic sequence of the ophiolite forming in a dynamic long lived open system magma chamber beneath a spreading axis in the second section the remainder of the plutonic sequence is described as a series of later short lived possibly closed system off axis plutons a fuller treatment of magma chamber processes during the spreading event is presented elsewhere smewing in press the earliest and volumetrically most significant magmatic event is represented by up to 3 5 km of layered gabbros and peridotites and an overlying unit of up to 200 m of isotropic gabbros and plagiogranites intruding the base of the sheeted dyke swarm the layered series rests with a sharp contact

cenozoic alluvial fan systems of interior oman palaeoenvironmental reconstruction based on discrimination of palaeochannels using remotely sensed data

improved discrimination of rock units using landsat thematic mapper imagery of the oman ophiolite the short wavelength infrared channels recorded by the landsat thematic mapper make this instrument more suitable than the landsat multispectral scanner for lithological mapping using enhanced imagery the weathering mineralogy of igneous rocks causes absorption features in their reflectance spectra which are particularly characteristic in the near infrared a landsat thematic mapper band 7 5 4 red green blue false colour composite of part of the oman ophiolite confirms much of the previous mapping and indicates certain hitherto unrecorded features these include a new mafic ultramafic late intrusive complex and differences between deeper and near crustal levels in the mantle sequence which may be related to the environment in which serpentinization took place decorrelation stretching is an excellent means of accentuating colour variations within an image as an aid to visual interpretation

baking black opal in the desert sun the importance of silica in desert varnish comment and reply reply we welcome the opportunity to reply to dorn 2007 who outlines the classical issues of desert varnish formation we agree that most previous research has suggested a biological mechanism bacterial enhancement of manganese in manganese rich coatings is intriguing however as we have published

manganese rich rock varnish does occur in antarctica abstract despite accounts to the contrary we have found that mn rich rock varnish is present in antarctica as others have before it is chemically and texturally similar to many varnishes found in lower latitudes antarctic varnishes show considerable potential as a dating and paleoenvironmental research tool

cause and implications of rock varnish microchemical laminations rock varnish is a dark coating composed mostly of clays and manganese and iron oxides1 that accretes on rock surfaces in all terrestrial environments2 perry and adams3 first observed micron scale manganese rich and manganese poor relatively iron rich layers in varnish and proposed that these may be related to unspecified environmental changes electron microprobe analyses reported here suggest that mn fe ratios vary systematically with depth in varnishes on k ar dated volcanic rocks from the coso and cima volcanic fields eastern california and on talus flatirons in the negev desert israel these microchemical laminations probably reflect past fluctuations in the level of aeolian alkalinity and possibly climatic change this new indicator of terrestrial environmental change may be of importance to research on geomorphology archaeology palaeoclimatology and quaternary studies in arid environments

correspondence on erosion rates and weathering history of rock surfaces associated with aboriginal rock art engravings petroglyphs on burrup peninsula western australia from cosmogenic nuclide measurements by brad pillans and keith fifield quaternary science reviews 69 98 106

3he surface exposure dating and its implications for magma evolution in the potrillo volcanic field rio grande rift new mexico usa dating of very young igneous activity has been hampered by lack of suitable chronometers we report here the results of 3he surface exposure dating kurz 1986a b craig and poreda 1986 for lavas from the potrillo volcanic field this field is particularly suited to the technique because it has well preserved young 700 ka surfaces the study applies 3he dating in a systematic manner to a well characterized volcanic field and shows the power of the technique in deciphering both relative and absolute chronologies dates are reproducible to within 14 for different samples from the same surface and are similar to within 8 for samples which based on field relations represent synchronous events cosmogenic 3he21ne confirms that 3he is retained by the samples comparison of the relative chronology with compositional trends of the lavas suggests that eruptive centers within the volcanic field are fed by individual magma chambers ages range from 80 ka to 17 ka consistent with estimates from geomorphology soil profile development and some k ar determinations

surface properties of ancient cratered terrain in the northern hemisphere of mars the hilly and cratered material of scott and carr 1978 interpreted to be the oldest extensively exposed surface of mars has been examined where it is covered by high resolution 16 62 km2 infrared data from the viking irtm this allows spatial variations in observed properties to be associated directly with geologic features and an assessment to be made of the contribution to the remotely determined properties from the ancient rock unit the measured nighttime temperatures at 20 and 11 m indicate that from 0 to 20 of the surface consists of high thermal inertia blocks assumed to be i 30 10 3 cal cm 2 s k 1 surrounded by lower thermal inertia soil i 1 5 to 7 5 block abundances are typically 9 within the arabia low thermal inertia region i 1 5 to 3 0 identified from global mapping and increase away from arabia particularly to the south geologic features crossed by the irtm data generally show no distinguishable difference from the regional properties with the exceptions of dark patch material and craters near 27 n 338 w the dark patch material typically within craters has block abundances 5 20 and soil thermal inertias 5 0 7 0 for an albedo of 0 15 distinctly different from the arabia material nonunit emissivity for this material would make the block abundances upper limits and the soil thermal inertias lower limits the effective grain diameter of the dark patch material 160 to 360 m is indicative of sand sized particles capable of saltation two craters near 27 n 338 w have slightly higher soil thermal inertias 3 5 corresponding to 70 m and lower block abundances 0 5 than the surrounding arabia material but no prominent dark patches are associated with them imaging data from within and around the arabia region indicate that subdued surface morphology is not always associated with low thermal inertias the extensive mantling of northern hemisphere locations of ancient cratered terrain by fine grained material does not allow thermal measurements to be directly related to rock unit properties but less mantling may be present in southern hemisphere locations of this material

spectral mapping of alaskan ophiolites using landsat thematic mapper data abstract ophiolites are sections of oceanic lithosphere that have been exposed by thrusting in mountain belts thematic mapper three band color composites have been used to differentiate the main rock types of the ophiolites of the western brooks range alaska and to map mineralogic variations produced by processes that affect oceanic lithosphere such as mantle partial melting hydration of ultramafic rock formation of cumulate layers and hydrothermal alteration and metamorphism of basalt scaled composites of tm bands 7 3 1 and 5 4 2 and 3 2 1 displayed in red green and blue are most useful for visually differentiating rocks of the ophiolites ternary diagrams of digital number valves are used to evaluate color variations observed in the three band composites geologic maps interpreted from tm images and reconnaissance field studies are presented for the asik mountain maiyumerak mountains avan hills and misheguk mountain ophiolites the mapping results are being used to guide additional studies of the tectonics of the brooks range ophiolites

spatial temporal and geographic considerations of the problem of rock varnish diagenesis article i nfo the rock varnish literature hosts an abundance of prima facie contradictory empirical data past and perhaps future empirical contradictions however can be resolved by theoretical considerations of different spatial and temporal scales of varnish diagenesis as well as the geomorphic position of different types of varnishes for example twentieth century contamination by lead and other heavy metals has led to claims of accumulation rates in the last century far more rapid than prior published empirical studies a consideration of spatial scales resolves this contradiction nanoscale processes allow migration of lead into varnish deposited well before the twentieth century time of heavy metal pollution evidence of nanometer scale disequilibrium in three samples led to claims that varnish cannot be used in paleoclimatic research these data rest in contrast to replicable patterns in varnish deposition observed by dr tanzhuo liu and others in over ten thousand micro sedimentary basins this contraction can be resolved by understanding that the types of varnishes studied differ and that processes differ substantially between the nanoscale and the micron scale a lack of evidence of mn oxidizers in genetic analyses contrasts with culturing studies and in situ evidence of mn enhancement by bacteria this contradiction has a likely resolution in vastly different temporal scales dna material analyzed may be no older than 200 years but in situ fossilized remains of bacteria may be preserved for thousands of years recording palaeoecological conditions favoring growth of mn enhancing bacteria

dating geomorphologic surfaces using cosmogenic 3he cosmogenically produced 3he in rocks can be used to date geomorphologic surfaces using the late pleistocene bonneville flood event the subsequent development of the provo shoreline and associated volcanic rocks a production rate of 432 atoms g yr in olivine is determined for 38 56 n latitude present geomagnetic latitude 46 5 at 1445 m altitude integrated over the last 14 400 years measurements of cosmogenic helium in flood deposits on river scoured surfaces and lava flows show that it is possible to date directly large scale events such as volcanic eruptions and catastrophic floods olivine and pyroxene are both satisfactory minerals for cosmogenic dating by the 3he method however in most cases plagioclase and quartz are unsuitable because they do not quantitatively retain helium isotopes in their lattices

cosmogenic ages for earthquake recurrence intervals and debris flow fan deposition owens valley california model exposure ages beryllium 10 aluminum 26 of boulders on an offset debris flow fan yield an earthquake recurrence interval between 5800 and 8000 10be 26al years for a strand of the owens valley fault in california which last ruptured in an earthquake of moment magnitude 7 5 in 1872 cosmogenic age estimates for this and several nearby fan surfaces flanking the eastern sierra nevada are consistent with stratigraphic relations and suggest that these surfaces were abandoned after 1000 8000 and 21 000 10be 26al years ago the wide scatter and nonconcordance of 10be 26al ages on an older fan surface suggest that boulder erosion and lowering of the fan surface there have influenced apparent exposure ages

mapping in the oman ophiolite using enhanced landsat thematic mapper images abstract the large areal extent and complex nature of the terrain has meant that previous largely field based mapping programmes in the oman ophiolite have produced maps of internally inconsistent quality recognition of subtle changes and minor outcrops across the area of a 1 1 map sheet is possible in the field only by unrealistically exhaustive mapping by using parts of the short wavelength infrared spectrum landsat thematic mapper data have the capacity to capitalize on distinctions in the spectral reflectances of different rock types and their weathering products and to allow consistent mapping across the whole ophiolite decorrelation stretching of these data produces images in which it is possible to recognize variations in gabbro composition to identify small acidic gabbroic and ultramafic intrusions to discriminate the uppermost mantle from the deeper mantle to locate the moho precisely and to delineate gossans and areas subject to chloritic epidotic alteration off axis plutonism is more widespread and dispersed than previously appreciated the significance of certain faults is reassessed in the light of new insights provided by the imagery such data could be a valuable mapping tool in similarly exposed terrains in arid and semi arid regions even where already mapped at the 1 100 000 scale

mapping of moho and moho transition zone mtz in samail ophiolites of sultanate of oman using remote sensing technique abstract moho and moho transition zone mtz of the samail ophiolite of sultanate of oman are characteristic to potential occurrences of chromite deposit hydrothermal mineralization and serpentinization mapping of moho and mtz and discriminating them in between the mafic and ultramafic rocks in ophiolite sequence are more significant and important the present study describes the remote sensing spectral characters of minerals and rocks of the moho and mtz and discriminates the moho of wadi al abyad of nakhl massif and wadi nidab and wadi abda regions of sumail massif in the visible and near infrared vnir and short wavelength infrared swir spectral regions using low cost multispectral satellite data of the advanced spaceborne thermal emission and reflection radiometer aster results of this study show that the red green blue rgb color composite images of aster spectral bands 8 3 and 1 and 8 7 and 4 are able to delineate the moho and mtz of the regions the rgb images of aster band ratios 4 8 4 1 3 2 4 3 and 1 3 2 4 6 5 7 9 8 are capable to discriminate the mantle material ultramafic harzburgites and crustal rocks mafic gabbros the occurrence of such rock types is demonstrated by detection of their minerals using spectral angle mapper sam image processing method the presence of moho and mtz and associated lithologies are verified in field at wadi al abyad wadi nidab wadi abda wadi tayin wadi fizh and several locations of nakhl regions of samail ophiolites the laboratory study shows the occurrence of typical minerals namely olivine orthopyroxene and clinopyroxene in the harzburgite and the minerals such as plagioclase clinopyroxene hornblende orthopyroxene and olivine in the layered gabbro the spectral properties of the rocks are studied using portable infrared mineral analyzer pima spectrometer and the occurrences of minerals are confirmed by x ray diffraction xrd analyses this study demonstrates the sensor capability of aster to map moho and mtz and thus it is recommended to the geoscientists and geophysicists working on moho and mtz the satellite image interpretations of moho and mtz and the associated rocks and minerals are consistent with the field research studies carried out in these regions our images have potential to map the chromites mineralized zone and dunites refractory materials bearing mtz

rapid formation of rock varnish and other rock coatings on slag deposits near fontana california manganiferous rock varnish silica glaze and iron skins have formed on 20 to 40 year old slag piles near fontana southern california rapid rock varnish formation is associated with an unidentified cocci bacterium that grows rapidly in culturing experiments combined with the likelihood that mn rich solutions flow over slag surfaces a new model is proposed for the formation of silica glaze involving soluble al si complexes and the nature of wetting films iron skins occur where runoff is concentrated and where iron bacteria grow observations indicate i substrate can be important in supplying mn as well as maintaining a stable surface and channelling runoff to microspots where varnish grows ii ignorance of boundary layer ph eh conditions makes chemical physical models of varnish formation speculative iii the balance between cementation of recently nucleated varnishes and erosional shear stresses is poorly understood but is probably an important limiting factor on varnish growth rates and iv there must be at least two steps in biotic varnishing accretion of mn fe in casts followed by cementation of clays by either in situ cast residue or mn fe remobilized from casts varnish accretion may be limited by the rate at which both steps occur rapid development of readily distinguishable manganiferous rock varnishes at this post 1952 site highlights the danger of speculation on the ages of landforms based solely on the appearance of rock varnish coatings

lithological mapping of the troodos ophiolite cyprus using airborne lidar topographic data traditional field based lithological mapping can be a time consuming costly and challenging endeavour when large areas need to be investigated where terrain is remote and difficult to access and where the geology is highly variable over short distances consequently rock units are often mapped at coarse scales resulting in lithological maps that have generalised contacts which in many cases are inaccurately located remote sensing data such as aerial photographs and satellite imagery are commonly incorporated into geological mapping programmes to obtain geological information that is best revealed by overhead perspectives however spatial and spectral limitations of the imagery and dense vegetation cover can limit the utility of traditional remote sensing products the advent of airborne light detection and ranging lidar as a remote sensing tool offers the potential to provide a novel solution to these problems because accurate and high resolution topographic data can be acquired in either forested or non forested terrain allowing discrimination of individual rock types that typically have distinct topographic characteristics this study assesses the efficacy of airborne lidar as a tool for detailed lithological mapping in the upper section of the troodos ophiolite cyprus morphometric variables including slope curvature and surface roughness were derived from a 4 m digital terrain model in order to quantify the topographic characteristics of four principal lithologies found in the area an artificial neural network the kohonen self organizing map was then employed to classify the lithological units based upon these variables the algorithm presented here was used to generate a detailed lithological map which defines lithological contacts much more accurately than the best existing geological map in addition a separate map of classification uncertainty highlights potential follow up targets for ground based verification the results of this study demonstrate the significant potential of airborne lidar for lithological discrimination and rapid generation of detailed lithological maps as a contribution to conventional geological mapping programmes

the application of remote sensing techniques to the study of ophiolites abstract satellite remote sensing methods are a powerful tool for detailed geologic analysis especially in inaccessible regions of the earth s surface short wave infrared swir bands are shown to provide spectral information bearing on the lithologic structural and geochemical character of rock bodies such as ophiolites allowing for a more comprehensive assessment of the lithologies present their stratigraphic relationships and geochemical character most remote sensing data are widely available for little or no cost along with user friendly software for non specialists in this paper we review common remote sensing systems and methods that allow for the discrimination of solid rock lithologic components of ophiolite complexes and their structural relationships ophiolites are enigmatic rock bodies which associated with most if not all plate collision sutures ophiolites are ideal for remote sensing given their widely recognized diversity of lithologic types and structural relationships accordingly as a basis for demonstrating the utility of remote sensing techniques we briefly review typical ophiolites in the tethyan tectonic belt as a case study we apply integrated remote sensing studies of a well studied example the muslim bagh ophiolite located in balochistan western pakistan on this basis we attempt to demonstrate how remote sensing data can validate and reconcile existing information obtained from field studies the lithologic and geochemical diversity of muslim bagh are representative of tethyan ophiolites despite it s remote location it has been extensively mapped and characterized by structural and geochemical studies and is virtually free of vegetative cover moreover integrating the remote sensing data with ground truth information thus offers the potential of an improved template for interpreting remote sensing data sets of other ophiolites for which little or no field information is available

cosmogenic 36cl dating of a young basaltic eruption complex lathrop wells nevada it has been proposed that the lathrop wells volcanic center a late quaternary basaltic complex in southern nevada has erupted more than once in common with most quaternary basalts this volcanic center has proved difficult to date by k ar and other commonly employed methods we have measured the accumulation of 36 cl in 11 samples from lava flows and volcanic bombs and obtained a combined average age of 81 7 9 ka with no systematic differences between sample subsets collected from different volcanic features the 36 cl dates do not support a history of multiple eruptions but neither do they completely preclude the possibility

quaternary glaciations in the rio mendoza valley argentine andes in the rio mendoza valley five pleistocene drifts and one holocene drift are distinguished by multiple relative age criteria including surface rock weathering development of rock varnish moraine morphology soil profile development and stratigraphic relationships several absolute ages suggest a preliminary chronology during the oldest uspallata glaciation a system of valley glaciers flowed 110 km from the andean drainage divide and 80 km from cerro aconcagua to terminate at 1850 m drift of this ice advance is older than a widespread tephra dated by fission track at 360 000 36 000 yr during the punta de vacas advance ice terminated at 2350 m while during the subsequent penitentes advance the glacier system ended at 2500 m a travertine layer overlying penitentes drift has u series age of 24 200 2000 yr b p the distribution of horcones drift which is inferred to represent the last glacial maximum delimits an independent ice stream that flowed 22 km down horcones valley to 2750 m a later readvance almacenes reached 3250 m confluencia drift is considered to be neoglacial in age and extends downvalley to 3300 m the moraine sequence is compared with those studied by caviedes 1972 along rio aconcagua on the chilean flank of the andes

exceptional preservation of mn oxidizing microbes in cave stromatolites el soplao spain abstract many ferromanganese stromatolites of el soplao cave n spain are characterized for the exceptional preservation and high diversity of microbial fossils probably representing the best example of microbial preservation described in ferromanganese deposits so far the el soplao stromatolites are mainly formed by polymetallic mn rich oxides with subordinate and variable amounts of detrital material and consist of both dendritic and laminar microfacies in both microfacies microbial forms are abundant in the relatively pure mn oxide rich material whereas they are scarce in areas with significant detrital material microbial forms are observed either in cross section completely embedded in the mn oxide rich matrix or in three dimensions lining the walls of pores based on their morphology we have separated the most abundant microbial forms into six main morphotypes and six additional submorphotypes most of which can be assigned to bacteria most morphotypes consist of coccoid coccobacilus or filamentous forms therefore they are not diagnostic of any particular bacterial group however the ovoid cells of morphotype b show cylindrical polar protuberances typical of prosthecate alpha proteobacteria on the basis of characteristic morphological features three submorphotypes of morphotype b can be assigned to three alpha proteobacteria genera hyphomicrobium pedomicrobium and caulobacter this ascription is supported by the well known mn oxidizing behavior of both pedomicrobium and caulobacter and by the common presence of hyphomicrobium in ferromanganese deposits elsewhere the excellent microbial preservation is partly related to the origin of the ferromanganese oxides i e extracellular precipitation induced by microbial metabolism other factors contributing to the good microbial preservation are the relatively low degree of diagenetic alteration and the relatively high accretion rates of stromatolites compared to other ferromanganese deposits the generally low degree of diagenesis is likely because the stromatolites have remained relatively stable and at a rather low temperature since they were formed at least 1 ma ago still some stromatolites have suffered diagenetic alteration partial dissolution and replacement by calcium carbonates and fe rich oxides obscuring or even obliterating their bioforms the el soplao case represents an example of how easily biogenic mn oxides can be altered and their bioforms blurred in a relatively short geological time span in spite of being in a relatively stable alkaline and low temperature setting a geological implication is that the absence of bioforms in other ferromanganese deposits including rock varnish and precambrian iron formations does not disprove their possible biogenic origin since the high chemical reactivity of biogenic manganese oxides makes them highly vulnerable to diagenesis

chronology of expansion and contraction of four great basin lake systems during the past 35 000 years abstract during the past 35 000 years lake bonneville lake russell and lake searles underwent a major period of lake level change the lakes were at moderate levels or dry at the beginning of the period and seem to have achieved highstands between about 15 000 and 13 500 yr b p the rise of lake lahontan was gradual but not continuous in part because of topographic constraints intrabasin spill lake lahontan also had an oscillation in lake level at 15 500 yr b p radiocarbon age estimations for materials that were deposited in the lake basins indicate that lake bonneville rose more or less gradually from 32 000 yr b p and had major oscillations in level between 23 000 and 21 000 yr b p and between 15 250 and 14 500 yr b p lake russell and lake searles had several major oscillations in lake level between 35 000 and 14 000 yr b p the timing and exact magnitude of the oscillations are difficult to decipher but both lakes may have achieved multiple highstand states all four lakes may have had nearly synchronous recessions between about 14 000 and 13 500 yr b p after the recessions the lakes seem to have temporarily stabilized or experienced a minor increase in size between about 11 500 and 10 000 yr b p these data provide circumstantial evidence that the younger dryas event affected climate on at least a hemispheric scale during the holocene the four lakes remained at low levels and small oscillations in lake level occurred an important aspect of the lake level data is the accompanying expansion of lake surface area at the time of the last highstand lake bonneville and lake lahontan had surface areas about 10 times larger than their mean historical reconstructed areas whereas lake russell and lake searles had surface areas about 5 times larger than their mean historical reconstructed areas differences in the records of effective wetness may have been due to the locations of the basins relative to the position of the jetstream or they may have resulted from lake atmosphere feedback processes

interactive processing of satellite images for structural and lithological mapping in northeast africa interactive digital processing of multispectral satellite images landsat mss using principal components transformations and spatial filtering has clarified the position of continuous sutures linking apparently isolated pan african late proterozoic ophiolites these have been field checked and an arrangement of pan african suture zones is proposed spatial filtering has also highlighted faults with various trends which can be related to the late precambrian tectonics of the horn of africa region

rock varnish microlamination dating of late quaternary geomorphic features in the drylands of western usa abstract varnish microlamination vml dating is a correlative age determination technique that can be used to date and correlate various geomorphic features in deserts in this study we establish a generalized late quaternary i e 0 300 ka varnish layering sequence for the drylands of western usa and tentatively correlate it with the specmap oxygen isotope record we then use this climatically correlated varnish layering sequence as a correlative dating tool to determine surface exposure ages for late quaternary geomorphic features in the study region vml dating of alluvial fan deposits in death valley of eastern california indicates that during the mid to late pleistocene 5 15 ky long aggradation events occurred during either wet or dry climatic periods and that major climate shifts between glacial and interglacial conditions may be the pacemaker for alteration of major episodes of fan aggradation during the holocene interglacial time however 0 5 1 ky long brief episodes of fan deposition may be linked to short periods of relatively wet climate vml dating of alluvial desert pavements in death valley and the mojave desert reveals that pavements can be developed rapidly

evaluating effects of chemical weathering and surface contamination on the in situ provenance analysis of building stones in the cuzco region of peru with portable xrf as the only type of instrument capable of determining artifact geochemistry in a wide variety of settings portable x ray fluorescence pxrf may be frequently utilized as probably the best option for collecting data when removal of objects in part or in whole is unfeasible however using pxrf in circumstances where sample selection and preparation diverge from standards developed for lab based instrumentation requires assessing the impact of new and potentially limiting factors to establish the validity of the method in these new contexts here we examine the effects of surface contamination and chemical weathering on the ability to assess provenance of igneous building stones used in the cuzco region of peru surface contamination was assessed through comparing low impact cleaning methods on diorite and andesite blocks and weathering was examined by comparing weathered vs fresh surfaces of samples from two andesite quarries in general the lightest elements were most impacted by contamination and weathering while measurements of many of the heavier elements commonly used in provenance studies were relatively unaffected concentrations of pb and zn were problematic in the urban context of cuzco because of pollution ability to determine provenance of building stones within those limitations i e the validity of this application of pxrf was demonstrated in a preliminary study by comparing measurements from uncleaned exposed building stones in the region to fresh quarry samples

aster detection of chromite bearing mineralized zones in semail ophiolite massifs of the northern oman mountains exploration strategy abstract economically viable chromite deposit occurrences are widespread in the ultramafic rocks of semail ophiolite massifs of the northern oman mountains particularly in the basal dunite and harzburgite unit of the mantle section geological mapping of this region is challenging primarily due to difficult access complexity of structures and lack of resolution and areal integrity of lithological differentiation using conventional mapping techniques the present research study evaluates the discrimination and occurrence of chromites bearing mineralized zones within ophiolites by analyzing the capabilities of landsat tm and advanced spaceborne thermal emission and reflection radiometer aster satellite data using a number of selected methods including decorrelated stretching different band rationing and principal component analysis image processing techniques exist in the scientific literature the study results show that the processed vnir and swir spectral wavelength regions are promising in detecting the areas of potential chromite bearing mineralized zones within the ophiolite region and proved to be successful for mapping of serpentinized harzburgite containing chromites exploration geologists industrialists and mine owners are advised to adopt this technique and avoid the limits in filed data alone for more exploration and exploitation of areas having chromite deposits in arid region elsewhere

the base of a sheeted dyke complex oman ophiolite implications for magma chambers at oceanic spreading axes the sheeted dyke complex in the maydan syncline area of the oman ophiolite was formed during a single sea floor spreading episode in some areas individual dykes from this sheeted dyke complex have been seen to root in the high level gabbro and others are truncated by high level gabbro diorite and trondhjemite however elsewhere dykes penetrate laterally into the layered part of the plutonic sequence this situation suggests that active magma chambers and zones of dyke injection were discontinuous along the spreading axis at any one time

remote sensing for porphyry copper deposits in southern arizona landsat multispectral scanners landsat 4 thematic mapper three porphyry copper deposits used as test sites landsat data useful for delineating areas of iron oxide on the surface limited spatial resolution of mss hampered mapping of some critical geologic relationships synoptic view well suited for examining regional tectonic patterns landsat 4 thematic mapper is an improved mapping tool compared to the previous landsat scanners modified journal abstract

segmentation of alluvial fans in death valley california new insights from surface exposure dating and laboratory modelling laboratory experiments recent paleoenvironmental analyses of rock varnish and surface exposure dating of geomorphic units have led to new insights into the process of entrenchment and segmentation of alluvial fans and into the history of quaternary sedimentation in death valley entrenchment begins at the fanhead as the trench deepens its down slope end migrates down fan taking several tens of thousands of years to reach lower parts of the fan laboratory experiments suggest however that a new segment begins to grow at the toe long before the trench reaches this part of the fan furthermore the initial slope of the segment is not the equilibrium slope field evidence supports this model the tectonic tilting that caused entrenchment and segmentation in death valley may have been triggered by loading of the valley with water sedimentation on the salt pan in southern death valley is not at present in equilibrium with that on the fans rather it seems to be adjusting to an increase in the amount of fine material reaching the playa due in part to breaching of the outlet of lake tecopa somewhat after 600 ka bp and in part to subsidence of different parts of the valley at different rates failure to recognize this disequilibrium resulted in errors in earlier estimates of the age of the segmentation events

manganese rich rock coatings from iceland manganese rich rock coatings are widespread in iceland especially in fractures in basalt lavas three common types of coating are described a thick subsurface coating is found on whaleback forms on high plateaux the most common type is thinner and occurs in hydrothermal clay filled fracture systems which are especially well developed in tholeiite lavas a third type occurs in younger rocks and is associated with tephra rich loessic sediment which fills open fractures and vesicles there are differences in the chemistry morphology and mineralogy of these coatings which are interpreted as being due to the different microenvironments in which they form the fracture microenvironment is regarded as being of much more importance to coating thickness and chemistry than simple age and in this respect the hydrothermal clays seem to favour rapid manganese concentration on the other hand there are variations in coating type both laterally and vertically through the lava succession which are related to regional distribution of hydrothermal alteration and rock type the regional patterns are the result of iceland s lateral drift and as a result there is an incidental connection between coating type and rock age there is some evidence to suggest that the manganese coatings may be both forming and being degraded rapidly in the present environment

dating of quaternary basalts using the cosmogenic 3he and 14c methods with implications for excess 40ar concordant radiocarbon and cosmogenic sup 3 he dates of 3 and 11 ka on basalt flows and associated scoria deposits from the zuni bandera volcanic field in new mexico further substantiate published production rates and latitudinal and altitudinal corrections for sup 3 he identical sup 3 he concentrations in coexisting olivine and clinopyroxene confirm that these two minerals have very similar production rates a cosmogenic sup 3 he date of 57 ka on another flow is concordant with a u series date and is younger than two k ar dates suggesting that this flow contains excess sup 40 ar this excess sup 40 ar is also evident in gases released by vacuum crushing of olivine clinopyroxene fractions from all three flows 27 refs 3 figs 3 tabs

use of multispectral scanner images for assessment of hydrothermal alteration in the marysvale utah mining area airborne multispectral scanner a color composite image was constructed using the following spectral band ratios 1 6 2 2 mu m 1 6 0 48 mu m and 0 67 1 0 mu m the color ratio composite successfully distinguished most types of altered rocks from unaltered rocks further division of altered rocks into ferric oxide rich and poor types modified journal abstract

remote sensing based approach for mapping of co2 sequestered regions in samail ophiolite massifs of the sultanate of oman abstract documentation of chemical weathering and co 2 sequestration in the samail ophiolite massifs of the sultanate of oman represents an important case study for geological carbon capture and storage system gccss the present research study demonstrates the capability of remote sensing technique for mapping of weathered zones and potential co 2 sequestration area abundances at different scales within peridotites in the northern mountain region of the samail ophiolite massifs the carbonate mineral index ci applied with other mineral indices to the tir wavelength region of advanced spaceborne thermal emission and reflection radiometer aster tir spectral bands 13 and 14 mapped co 2 sequestered minerals along the structural and wadi controlled co 2 flowing regions peridotites the source rocks of co 2 sequestration in the study area were mapped using an aster 8 3 and 1 band combinations the decorrelated landsat tm image discriminated the rock types associated with peridotites of ophiolite sequences and delineated the region of weathered and altered serpentinized peridotites in the zone of co 2 sequestration co 2 sequestration mapping was carried out using landsat tm satellite data that span 20 years 1986 1998 2000 2003 and 2006 to assess the present status of co 2 sequestration in this region the image interpretations are verified with existing geological maps and through field and laboratory studies the spectral measurements of carbonate minerals at 1300 to 2500 nm with the spectral resolution of 7 nm using a pima sp infrared spectrometer in the field and laboratory show the presence of hydroxyl bearing minerals and carbonates that have spectral absorption features around 1 4 m 1 9 m and 2 35 m the strong absorptions around 2 35 m are mainly due to c o bonds in carbonate minerals such as calcite caco 3 dolomite camg co 3 2 magnesite mgco 3 aragonite caco 3 and siderite feco 3 which form 15 to 57 12 to 53 9 to 38 11 to 21 and 3 to 8 respectively in the samples the absorptions around 1 4 m and 1 9 m are caused by hydration effects of hydroxyl minerals including antigorite and montmorillonite present at 10 to 21 and 37 to 81 respectively in the samples the alterations of serpentinite are evidenced by the presence of antigorite and lizardite minerals x ray powder diffraction analyses further confirms the occurrence of co 2 sequestered major carbonate minerals such as aragonite calcite and dolomite in the samples the study demonstrates that the aster and landsat tm satellite multispectral sensors are useful to detect the carbonate minerals to delineate the peridotites and to discriminate the areal abundance of potential co 2 sequestration this technique is a useful tool to map and monitor the region of co 2 sequestration in well exposed arid and semi arid regions and to analyze and understand this aspect of the world geological carbon capture and storage system

carbonate deposition pyramid lake subbasin nevada 2 lake levels and polar jet stream positions reconstructed from radiocarbon ages and elevations of carbonates tufas deposited in the lahontan basin most of the tufas in the pyramid lake subbasin were deposited within the last 35 000 yr including most of the mound tufas that border the existing lake many of the older tufas 21 000 yr b p contained in the mounds were formed in association with ground water discharge the radiocarbon 14c ages of the older tufas represent maximum estimates of the time of their formation lake lahontan experienced large and abrupt rises in level at 22 000 15 000 and 11 000 yr b p and three abrupt recessions in level at 16 000 13 600 and 10 000 yr b p the lake level rises that were initiated at 23 500 and 15 500 yr b p are believed to indicate the passage of the polar jet stream over the lahontan basin during expansion of the laurentide ice sheet the jet stream moved south across the basin and during the contraction of the ice sheet the jet stream moved north across the basin the bulk of the carbonate contained in the mound tufas was deposited during the last major lake cycle 23 500 12 000 yr b p indicating that ground and surface water discharges increased at 23 500 and decreased at 12 000 yr b p a lake level oscillation that occurred between 11 000 and 10 000 yr b p is represented by a 2 cm thick layer of dense laminated tufa that occurs at and below 1180 m in the low elevation tufa mounds and at 1205 m in the winnemucca lake subbasin

spectral characterization and aster based lithological mapping of an ophiolite complex a case study from neyriz ophiolite sw iran abstract the neyriz ophiolite occurs along the zagros suture zone in sw iran and is part of a 3000 km obduction belt thrusting over the edge of the arabian continent during the late cretaceous this complex typically consists of altered dunites and peridotites layered and massive gabbros sheeted dykes and pillow lavas and a thick sequence of radiolarites reflectance and emittance spectra of neyriz ophiolite rock samples were measured in the laboratory and their spectra were used as endmembers in a spectral feature fitting sff algorithm laboratory spectral reflectance measurements of field samples showed that in the visible through shortwave infrared vnir swir wavelength region the ultramafic and gabbroic rocks are characterized by ferrous iron and fe mg oh spectral features and the pillow lavas and radiolarites are characterized by spectral features of ferric iron and al oh the laboratory spectral emittance spectra also revealed a wide wavelength range of si o spectral features for the ophiolite rock units after continuum removal of the spectra the sff classification method was applied to the vnir swir 9 band stack and to the 11 band data set of swir and tir data sets of the advanced spaceborne thermal emission and reflection radiometer aster sensor using field spectra as training sets for evaluating the potential of these data sets in discriminating ophiolite rock units output results were compared with the geological map of the area and field observations and were assessed by the use of confusion matrices the assessment showed in terms of kappa coefficient that the sff classification method with continuum removal applied to the swir data achieved excellent results which were distinctively better than those obtained using vnir swir data and tir data alone