flow transmission along an arid zone anastomosing river cooper creek australia cooper creek is characterized by an exceptionally wide floodplain and a complex system of anastomosing channels which together can accommodate a large range of highly variable flows in consequence flood frequency curves are unusually steep with minimal tributary contribution over the two study lengths currareva nappa merrie 400 km and nappa merrie innamincka 32 km downstream output is largely controlled by upstream input so that similar flow regimes and hydrograph forms can be maintained despite transmission losses and the variable activation of channels input output relationships defined in terms of total flow volume and peak discharge suggest that above a threshold flow of about 25 duration transmission losses exceed 75 on average over the currareva nappa merrie length the large difference in absorption between primary channels on the one hand and subsidiary channels and the floodplain surface on the other means that transmission losses vary non linearly with stage they are relatively low when flow is confined to the primary channels but increase at higher stages as lesser channels and the floodplain are activated early levels do not recur until flows of 0 5 duration are attained when output input ratios increase rapidly with discharge the influences of seasonality and background flow on output discharge are small relative to that of input discharge despite the long river distance peak flows at currareva and nappa merrie are well correlated however over the shorter nappa merrie innamincka length with its more confined system of channels correlations are better and transmission losses less they vary from 60 just above the threshold discharge to lo at flows below 20 duration over this length outflow hydrographs can be effectively estimated by the three parameter muskingum procedure at least on an event by event basis but further application must await additional records to understand fully how the parameters vary in an environment where streamflow is transmitted through a highly variable system of channels

multispectral bathymetry using a simple physically based algorithm a simple method for estimating water depths from multispectral imagery is described and is applied to several ikonos data sets for which independent measurements of the water depth are available the methodology is based on a physical model for the shallow water reflectance and is capable of correcting for at least some range of water quality and bottom reflectance variations corrections for sun glint effects are applied prior to the application of the bathymetry algorithm the accuracy of the depth algorithm is determined by comparison with ground truth measurements and comparisons between the observed and calculated radiances are presented for one case to illustrate how the algorithm corrects for water attenuation and or bottom reflectance variations

mapping submarine sand waves with multiband imaging radar 2 experimental results and model comparison on august 16 1989 and on july 12 1991 experiments were performed to study the mapping of submarine sand waves with the airborne imaging radar a polarimetric and in 1991 interferometric airborne p l and c band synthetic aperture radar system the experiments took place in an area 30 km off the coast of the netherlands where the bottom topography is dominated by sand waves with a height between 2 and 6 m and a crest to crest distance of about 400 m at an average depth of 22 m ground measurements were recorded on a nearby platform and on a ship in the test area which also acted as a position fix on august 16 1989 the wind was 5 m s directed toward the northeast while the surface current velocity was around 0 5 m s directed toward the southwest one overflight was made with the flight direction parallel to the sand wave crests and the radar looking upwind at p band the sand waves are clearly visible as dark bands as predicted by theory while at l band the sand waves show up as sawtooth shaped modulations on july 12 1991 wind and surface current had the same opposite directions as in 1989 though the wind was much higher 10 m s three flights were made with the radar pointing upwind cross wind and downwind the upwind and downwind images are very similar despite the high wind speed the sand waves are clearly visible as sawtooth shaped modulations at p band and vaguely visible at l band at c band only wind streaks can be seen all cross wind images show the sand waves as dark bands now with the highest modulations at c band the wind streaks that dominated the upwind and downwind images at c band are much less pronounced in the cross wind images the images are compared with predictions from a new model of the imaging mechanism which includes contribution to the radar cross section of waves moving both from and to the radar wave blocking or wave reflection is treated in an approximate manner for the radar looking upwind or downwind the predicted modulations at p and l band agree well with the observations while those at c band are too high for the radar looking cross wind the model severely underestimates the modulations it is questioned whether a local relaxation source term can describe such a situation the interferogram shows some structure caused by bottom induced surface current variations

very high spatial resolution imagery for channel bathymetry and topography from an unmanned mapping controlled platform the increasing availability of aerial photography and satellite imagery offers new possibilities for characterizing river morphology the precision of new very high resolution vhr images allows smaller scale objects within river corridors to be studied high survey frequencies provide increased opportunities for the monitoring of river restoration following this evolution in platform technology a small radio controlled motorized vehicle flying at low altitude was used to study both channel water depth and gravel bar geometry the vhr imagery provided by this equipment allowed both channel bathymetry and a high accuracy photogrammetric digital elevation model dem to be realized using case studies from the ain and the drome rivers in france the accuracy of the results is presented and the various challenges associated with the new platform are discussed one significant issue is that due to the low elevation of the survey the coverage of a target area is usually based on several photographs which leads to variations in illumination conditions that stem from atmospheric changes the images were processed to minimize this source of error but a number of issues have yet to be resolved bathymetric models with r2 values between 0 59 and 0 90 were created in spite of the lack of channel bed homogeneity at the various sites the gravel bar was also effectively mapped and the photogrammetrically predicted dem provided a 5 10 cm pixel resolution with a vertical precision between 2 and 40 cm according to the position within the image this paper shows that despite unstable image acquisition unmanned radio controlled platforms provide significant advantages for the study of river processes offering a flexible very high resolution data source for both channel bathymetry and gravel bar topography copyright 2007 john wiley sons ltd

geothermal type alteration in a burial metamorphosed volcanic pile central chile the upper cretaceous and tertiary volcanic sequences in the chilean andes are affected by burial metamorphism for example in central chile between 32 30 and 35 s the abanico formation a folded upper cretaceous to palaeogene unit composed of basic lavas tuffs and ash flows of intermediate composition and volcaniclastic sandstones is characterized by heulandite to laumontite bearing zeolite facies assemblages in its upper part passing with depth to prehnite pumpellyite facies assemblages however at c 33 30 s in the abanico hill area located just east of a graben at santiago the longitudinal central valley the alteration pattern is unrelated to stratigraphic depth it is characterized by a lateral increase in grade defined by assemblages with yugawaralite reported for the first time in the andes laumontite then wairakite epidote and finally with abundant epidote successively closer to the graben boundary this pattern was formed in a palaeogeothermal system with a high t and a very low p gradient geothermal alteration has also been inferred from the border zone of a neogene caldera in the abanico hill area and from the western fault boundary of the graben these expressions of geothermal alteration together with the occurrence of caldera structures the huge volume of ignimbrites and numerous epithermal precious metal deposits of late cretaceous and tertiary age in central and northern chile suggest that fossil geothermal systems of this age are probably common features in the chilean andes

systematic variations of h o c isotopes in different alteration zones of sandstone hosted uranium deposits in the southern margin of the yili basin xinjiang china a review and implications for the ore forming mechanisms abstract the meso cenozoic yili basin in northwestern china hosts important uranium and coal resources the uranium deposits are mainly hosted by sandstones and are characterized by clay and carbonate alterations within and surrounding the orebodies h o c isotopes of clay minerals and carbonate cement in the different alteration zones of the uranium deposits in the southern margin of the yili basin are summarized to examine the mechanisms of uranium mineralization the alteration zones associated with the uranium mineralization include an intensely oxidized zone a weakly oxidized zone a transitional mineralization zone and a reduced zone the d and 18o values of the parent fluids calculated from clay minerals from the different alteration zones show a linear trend that intersects the global meteoric line at a point with a 18ov smow of ca 5 and a dv smow of ca 30 which coincide with the upper end of the d 18o trend along the meteoric line of formation waters in the basin suggesting that the uranium mineralizing fluid was of meteoric origin the general trends of decreasing d and 13c and increasing 18o from the intensely oxidized zone to the reduced zone together with the fact that calculated dv smow values of the mineralizing fluids are lower than the original meteoric fluid and that the 13c values of the calcite cement overlap with those of organic matter in sedimentary rocks suggest that hydrocarbons were involved in uranium mineralization the hydrocarbons may have been important reducing agents causing precipitation of uranium minerals the hydrogen ion released from oxidation of the hydrocarbons may have been buffered by the formation of clay minerals which favors co development of clay alteration and calcite cement deviation of h o c isotopes from the general variation trends as expected from the above redox mechanism likely resulted from the dynamic nature of the redox front which changed its position in response to hydrodynamic balance between a downward flow of uranium bearing oxidizing fluid and an upward flow of reductants bearing reducing fluid from the lower part of the basin

characterization of complex fluvial systems using remote sensing of spatial and temporal water level variations in the amazon congo and brahmaputra rivers the surface water and ocean topography swot satellite mission will provide global space based estimates of water elevation its temporal change and its spatial slope in fluvial environments as well as across lakes reservoirs wetlands and floodplains this paper illustrates the utility of existing remote sensing measurements of water temporal changes and spatial slope to characterize two complex fluvial environments first repeat pass interferometric sar measurements from the japanese earth resources satellite are used to compare and contrast floodplain processes in the amazon and congo river basins measurements of temporal water level changes over the two areas reveal clearly different hydraulic processes at work the amazon is highly interconnected by floodplain channels resulting in complex flow patterns in contrast the congo does not show similar floodplain channels and the flow patterns are not well defined and have diffuse boundaries during inundation the amazon floodplain often shows sharp hydraulic changes across floodplain channels the congo however does not show similar sharp changes during either infilling or evacuation second shuttle radar topography mission measurements of water elevation are used to derive water slope over the braided brahmaputra river system in combination with in situ bathymetry measurements water elevation and slope allow one to calculate discharge estimates within 2 3 accuracy these two studies illustrate the utility of satellite based measurements of water elevation for characterizing complex fluvial environments and highlight the potential of swot measurements for fluvial hydrology copyright 2010 john wiley sons ltd

geological characteristics and metallogenic mechanism of no 511 sandstone type uranium ore deposit in yili basin xinjiang the ore bodies of the no 511 uranium deposit on the southern edge of yili basin are mainly hosted in cycle sandstone of lower to middle jurassic shuixigou group the deposit is one of the recently discovered large size isl amenable sandstone type uranium deposits in china a detailed study of ore body geological characteristics and a tentative discussion on mineralization were conducted in this paper based on field work as well as such indoor analytical methods as chemical analysis scanning electron microanalyzer sem analysis and electron microprobe analysis it is shown that the cycle interlayer oxidation zone can be divided into oxidized zone redox zone and unoxidized zone ore bodies are hosted in sandstone of the redox zone and their spatial distribution is strictly controlled by the interlayer oxidation zone uranium mainly occurs in pitchblende and coffinite which are mainly dispersed in the fossil wood cells and pelitic cement of sandstone detrital grains and partly adsorbed by clay minerals or carbonaceous debris the interlayer oxidation zone was formed in the process of water rock reaction between oxygen bearing interlayer water and sandstone uranium was activated transferred deposited and concentrated in the redox zone by the ore forming fluids which contained oxidization components such as organic acids so 2 4 and fe 3 the development of the interlayer oxidation zone and the ore forming process started in early himalayan period 66 ma in a surficial environment the ore forming process was characterized by rolling and protracted development mineralization seems to have been closely related to the reducing function of microbial bacteria

late cretaceous to miocene volcanism sedimentation and upper crustal faulting and folding in the principal cordillera central chile field and geochronological evidence for protracted arc volcanism and transpressive deformation

determination of water depth with high resolution satellite imagery over variable bottom types a standard algorithm for determining depth in clear water from passive sensors exists but it requires tuning of five parameters and does not retrieve depths where the bottom has an extremely low albedo to address these issues we developed an empirical solution using a ratio of reflectances that has only two tunable parameters and can be applied to low albedo features the two algorithms the standard linear transform and the new ratio transform were compared through analysis of ikonos satellite imagery against lidar bathymetry the coefficients for the ratio algorithm were tuned manually to a few depths from a nautical chart yet performed as well as the linear algorithm tuned using multiple linear regression against the lidar both algorithms compensate for variable bottom type and albedo sand pavement algae coral and retrieve bathymetry in water depths of less than 10 15 m however the linear transform does not distinguish depths 15 m and is more subject to variability across the studied atolls the ratio transform can in clear water retrieve depths in 25 m of water and shows greater stability between different areas it also performs slightly better in scattering turbidity than the linear transform the ratio algorithm is somewhat noisier and cannot always adequately resolve fine morphology structures smaller than 4 5 pixels in water depths 15 20 m in general the ratio transform is more robust than the linear transform

water levels in the amazon basin derived from the ers 2 and envisat radar altimetry missions article i nfo this study sets out to analyze the stages of water bodies in the amazon basin derived from the processing of ers 2 and envisat satellite altimetry data for envisat gdr measurements for both ice 1 and ice 2 tracking algorithms were tested for ers 2 the ice 2 data produced by the oscar project was used water level time series over river segments of very different width from several kilometers to less than a hundred of meters were studied the water level time series that can be derived from narrow riverbeds are enhanced by off nadir detections conversely the off nadir effect may degrade the series over large bodies if not properly accounted for comparison at crossovers and with in situ gauges shows that the quality of the series can be highly variable from 12 cm in the best cases and 40 cm in most cases to several meters in the worse cases cautious data selection is clearly a key point to achieve high quality series indeed low quality series mostly result from inclusion of outliers in the data set finally retained for the computation of the series ice 2 and ice 1 tracking algorithms in the envisat data perform almost equally well envisat altimetry is clearly an improvement on ers 2 altimetry

combustion metamorphism of bituminous sediments and the formation of melts of granitic and sedimentary composition during combustion metamorphism i e the heating of sediments rich in organic matter by spontaneous subsurface combustion temperatures obtained are frequently high enough to cause partial or total melting of the original rocks these melts are of particular geochemical interest because at lower temperatures their composition closely simulates that of granitic and at higher temperatures that of common sedimentary rocks at the california localities studied here the parent rocks are mainly bituminous mudstones with smaller amounts of diatomites and phosphorites and lesser dolomites limestones shales and cherts it is estimated that rock melting started below 1000 c the first partial melts correspond to a melt fraction of about 5 have a constant composition which is controlled by the eutectic of the dominant mudstones and are undistinguishable in major and trace element composition from common s type granites compared with the original rocks these melts are enriched in sio2 al2o3 k2o na2o as well as in ta hf zr th and ree and are depleted in all other elements studied the only difference between these low temperature melts and granitic ones is their oxygen isotope composition which is that of the sedimentary parent rocks these melts intruded the country rocks as sills and dikes and cooled to glassy rocks simulating obsidians as temperatures rose the melts changed composition and left the magmatic field at the highest temperatures in excess of 1650 c their composition equals that of the original sediments from which they are derived except for volatile components such as h2o and co2 these melts formed intrusive bodies mainly stocks up to several kilometers across on cooling these melts formed fine grained but holocrystalline rocks the dominant minerals of which are cristobalite and tridymite calcic plagioclase cordierite wollastonite gehlenite andradite and apatite where the parent rocks included phosphorites two immiscible melts formed an emulsion in which droplets of apatitic composition are surrounded by a silicate melt almost devoid of p2o5

application of integrated gnss hydroacoustic measurements and gis geodatabase models for bottom analysis of lake hancza the deepest inland reservoir in poland since almost 40 of the world s largest lakes have not yet been studied their volumes are therefore approximated shiklomanov and rodda 2003 the most challenging situation is with smaller reservoirs and inland lakes due to high costs and time required for acquiring bathymetric data some inland reservoirs have not been investigated there are some probes to estimate certain morphometric parameters using existing publicly available datasets hollister and milstead 2010 h ollister et al 2011

evidence of uranium biomineralization in sandstone hosted roll front uranium deposits northwestern china we show evidence that the primary uranium minerals uraninite and coffinite from high grade ore samples u3o8 0 3 in the wuyiyi wuyier and wuyisan sandstone hosted roll front uranium deposits xinjiang northwestern china were biogenically precipitated and psuedomorphically replace fungi and bacteria uranium vi which was the sole electron acceptor was likely to have been enzymically reduced post mortem accumulation of uranium may have also occurred through physio chemical interaction between uranium and negatively charged cellular sites and inorganic adsorption or precipitation reactions these results suggest that microorganisms may have played a key role in formation of the sandstone or roll type uranium deposits which are among the most economically significant uranium deposits in the world

palaeoclimate and human occupation in southeastern arid australia abstract this review focuses on the relationships between palaeoenvironmental change and prehistoric occupation in the driest part of the australian arid zone palaeoclimatic evidence from the last 60 ka identified fluctuating periods of wet and dry conditions during the late pleistocene and holocene for most of this period conditions were arid including during the holocene and maximum aridity occurred at the lgm which peaked at 21 ka maximum wetness occurred before 45 ka at 33 31 ka and episodically during the deglaciation between 18 and 11 ka the pre lgm archaeological record is extremely sparse but records from the lgm through to the mid holocene show people occupied the dunefields and stony plains during prolonged wet periods in the deglaciation and largely abandoned them during drier phases retreating to better watered refuges human occupation in dunefields from the lgm through to the mid holocene can be used as a proxy for past climates from the late holocene changes in settlement patterns were made possible by the social economic and technological adaptations which allowed people to occupy what became an increasingly harsh environment these reconstructions were facilitated by discoveries in the roxby dunefield of buried stratified layers of stone artefacts in dune sands dated by single grain luminescence analyses these discoveries indicate the possibility that hitherto unreported cultural sequences potentially dating back to 50 ka may be present in many australian dunefields

lake eyre palaeohydrology from 60 ka to the present beach ridges and glacial maximum aridity lake eyre is presently an ephemeral playa lake in an extremely large 1 3 million km2 internal drainage basin with most of its inflow derived from monsoon watered northern australia the hydrologic state of the lake has varied in the past in response to climate change from a perennial lake up to 25 metres deep to a groundwater controlled playa marked by substantial sediment deflation this paper is concerned with the stratigraphic record of the last 60 ka of that hydrologic history particularly the character and age of a playa marginal unit formed by deflation from the playa and of stranded high beach ridges a major deflation episode between 60 and 50 ka excavated the present lake eyre basin and deposited a gypsum and clay rich aeolian phase the williams point aeolian unit at a number of sites around the lake after deflation ceased a thick secondary gypsum profile developed on the dune early in oxygen isotope stage 3 evidence for the state of lake eyre at this time is equivocal preliminary results from a substantial suite of amino acid racemization aar analyses of mollusc shell and bird eggshell samples from beach ridges at 5 and 10 m australian height datum ahd suggest that they are oxygen isotope stage 5 in age sedimentologic evidence suggests that it is unlikely that the shells are reworked from older deposits these aar results apparently conflict with early oxygen isotope stage 3 thermoluminescence tl dates from the 5 m ahd beach ridge nanson et al this volume however the age difference is not substantial the calibration of the aar is still at a preliminary stage and only one site was sampled for both techniques further stratigraphic and chronologic work is required to fully assess the apparent discrepancy between about 30 000 and 12 000 yr b p lake eyre was at least as dry as it is today at many sites around madigan gulf a lunette like playa marginal aeolian unit the shelly island unit was deposited during this period formed by material deflated from the playa floor forty ams radiocarbon dates span the period 35 000 to 10 000 yr b p from the shelly island unit 11 and from aeolian sediment close to playa level 29 indicating that the lake was dry during this period this evidence conflicts strongly with 2 tl dates from latest oxygen isotope stage 3 and oxygen isotope stage 2 from the 5 and 10 m ahd beach ridges nanson et al this volume additionally the aar results from the high beach ridges cannot be reconciled with these tl dates after 10 000 yr b p a minor lacustral phase occurred until the modern ephemeral playa regime became established at 3000 4000 yr b p

calderas of the sierra madre occidental volcanic field western mexico approximately 296 000 km2 of western mexico is covered by a volcanic sequence that has an average thickness of 1 km and is mostly ash flow tuff although some 350 calderas are suggested by this tremendous volume only a few have been located or described in the state of durango the only well documented examples are in the 30 ma old chupaderos caldera complex near durango city although the complex is mostly covered by quaternary basalt and sediment the exposed portion reveals nested calderas that produced two major rhyolitic ash flow tuffs a third major tuff appears to have been erupted from the complex but no caldera has yet been found the caldera formed by the first eruption contains a resurgent dome and a thick sequence of moat sedimentary rocks and lava flows that are hosts for significant iron and tin deposits other possible durango calderas exist at el salto west of durango city at temoaya south of durango city and in the sierra de la silla to the north calderas in chihuahua have beep described from mountain ranges in the central part of the state and from the sierra madre occidental to the west a composite resurgent caldefa 35 ma old and approximately 22 km in diameter has been de scribed from the sierra pastorias immediately south of chihuahua city the main erupted unit is well exposed in the caldera s resurgent dome and a second tuff found outside the caldera was emplaced from a trap door structure nested in the caldera s northwest corner the area also contains a younger smaller resurgentiy domed caldera other possible calderas include a relatively large 35 km in diameter structure in the sierra del nido 75 km north of chihuahua city and a poorly defined structure related to a sequence f older 45 ma silicic volcanic rocks at cerro jesus maria 25 km northwest of chihuahua city calderas in the sierra madre plateau have been described from the tomochic and ocampo areas of western chihuahua the tomochic area records volcanic activity from 34 5 to 28 9 ma and contains at least three calderas these include the tomochic caldera a strikingly well preserved resurgent caldera approximately 20 by 25 km in diameter the north structural margin of the tomochic caldera cuts the intracaldera facies of an ash flow tuff related to the older las varas caldera epithermal precious metal fissure veins are located where the tomochic structural margin cuts this older unit a third structure the corallitos caldera is located only a few kilometers to the northeast reconnaissance studies in far western chihuahua indicate the existence of a large 40 km resurgent caldera centered on the village of ocampo landsat imagery shows a well developed arcuate drainage pattern and maps of the area show a distribution of lithologies that is consistent with the caldera interpretation gold and silver deposits hosted almost exclusively in precaldera rocks are best developed where the older rocks are cut by faults of the caldera s ring fracture zone and resurgent dome in general the calderas thus far mapped in western mexico follow the valles type resurgent caldera model variations however of the ideal caldera cycle are common as are repetitions of the cycle to form caldera complexes all of the better known calderas have associated mineral deposits although they may be best developed in precaldera rocks

late quaternary mega lakes fed by the northern and southern river systems of central australia varying moisture sources and increased continental aridity optically stimulated and thermoluminescence ages from relict shorelines along with accelerator mass spectrometer 14c ages from freshwater molluscs reveal a record of variable moisture sources supplied by northern and southern river systems to lake mega frome in southern central australia during the late quaternary additional lacustrine palynological and terrestrial proxies are used to reconstruct a record that extends back to 105 ka confirming that lakes mega frome and mega eyre were joined to create the largest system of palaeolakes on the australian continent as recently as 50 47 ka the palaeohydrological record indicates a progressive shift to more arid conditions with marked drying after 45 ka subsequently lake mega frome has filled independently at 33 31 ka and at the termination of the last glacial maximum to volumes some 40 times those of today further sequentially declining filling episodes to volumes 25 10 those of today occurred immediately prior to the younger dryas stadial in the mid holocene and during the medieval climatic anomaly southern hemisphere summer insolation maxima are a poor predictor of palaeolake filling episodes an examination of multiple active moisture sources suggests that palaeolake phases were driven independently of insolation and at times by some combination of enhanced southern ocean circulation and strengthened tropical moisture sources

hydroclimatic interpretation of quaternary shorelines on south australian playas abstract the catchment of lake eyre is one of the world s largest internally drained basins the playas near its depocentre the driest region of australia contain a partial record of quaternary climatic and hydrologic events for the last full glacial cycle and probably beyond ancient beach ridges marginal to lakes eyre frome callabonna and blanche have been dated using thermoluminescence tl to provide evidence for major changes in the hydrological regime of the basin beach ridges around lake eyre provide evidence of high lake stands up to 27 m above the present lake floor during what probably corresponds to the middle to latter part of marine oxygen isotope stage 5 there is evidence also for even higher lake stands associated with earlier isotope stages three tl dates identify a period of aeolian activity during stage 4 and a further 5 tl dates from lakes eyre and frome indicate that high lake stands occurred between about 55 and 40 ka corresponding with stage 3 the stage 5 and stage 3 high stands both relate to periods of enhanced fluvial activity previously identified in the lake eyre basin and elsewhere in australia in contradiction with other work a few tl dates from some playas suggest a possible major episode of high lake levels immediately preceding or at the start of the last glacial maximum lgm 26 22 ka this may relate to a sharp temperature suppression and an increase in runoff by rivers fed from monsoons in the north while a set of relatively low elevation late holocene beaches have been dated on two of the playas a period of enhanced precipitation and stream flow in the early to mid holocene appears not to have formed higher beaches possibly due to high temperatures and evaporation rates at that time the filling of lake eyre during and since stage 5 appears to have been to no more than to a level of 12 m australian height datum ahd possibly due a spillway at about this elevation in the form of the warrawoocara channel connecting lake eyre with playas to the southeast lakes gregory blanche callabonna and frome such overflows from one large basin to another would have had a major impact on the hydrology of the region in addition to enhanced runoff essential for the maintenance of high lake levels must have been local temperatures and evaporation rates significantly reduced from present day levels

topography of the salar de uyuni bolivia from kinematic gps the salar de uyuni in the bolivian andes is the largest salt flat on earth exhibiting less than 1 m of vertical relief over an area of 9000 km 2 we report on a kinematic global positioning system gps survey of a 45 by 54 km area in the eastern salar conducted in september 2002 to provide ground truth for the ice cloud and land elevation satellite icesat mission gps post processing included corrections for long period gps noise that significantly improved survey accuracy we fit corrected gps trajectories with 2 d fourier basis functions from which we created a digital elevation model dem of the surface whose absolute accuracy we estimate to be at least 2 2 cm rmse with over two magnitudes better vertical resolution than the shuttle radar topography mission data this dem reveals decimetre level topography that is completely absent in other topographic data sets longer wavelengths in the dem correlate well with mapped gravity suggesting a connection between broad scale salar topography and the geoid similar to that seen over the oceans

misr based passive optical bathymetry from orbit with few cm level of accuracy on the salar de uyuni bolivia abstract we demonstrate that under ideal circumstances passive optical measurements can yield surface water depth estimates with an accuracy of a few centimeters our target area is the salar de uyuni in bolivia it is a large active salt flat or playa which is maintained as an almost perfectly level and highly reflective surface by annual flooding to a mean depth of 30 50 cm we use misr data to estimate spatial and temporal variations in water depth during the waning portion of the 2001 flooding cycle we use a single icesat laser altimetry profile to calibrate our water depth model though the salt surface is probably the smoothest surface of its size on earth with less that 30 cm rms height variations over an area of nearly 104 km2 it is not completely featureless topography there includes a peripheral depression or moat around the edge of the salt and several sets of prominent parallel ridges with 5 km wavelength and 30 cm amplitude the process by which these features form is still not well characterized

continental aridification and the vanishing of australia s megalakes the nature of the australian climate at about the time of rapid megafaunal extinctions and humans arriving in australia is poorly understood and is an important element in the contentious debate as to whether humans or climate caused the extinctions here we present a new paleoshoreline chronology that extends over the past 100 k y for lake mega frome the coalescence of lakes frome blanche callabonna and gregory in the southern latitudes of central australia we show that lake mega frome was connected for the last time to adjacent lake eyre at 50 47 ka forming the largest remaining interconnected system of paleolakes on the australian continent the final disconnection and a progressive drop in the level of lake mega frome represents a major climate shift to aridification that coincided with the arrival of humans and the demise of the megafauna the supply of moisture to the australian continent at various times in the quaternary has commonly been ascribed to an enhanced monsoon this study in combination with other paleoclimate data provides reliable evidence for periods of enhanced tropical and enhanced southern ocean sources of water filling these lakes at different times during the last full glacial cycle

determining bathymetry of shallow and ephemeral desert lakes using satellite imagery and altimetry water volume estimates of shallow desert lakes are the basis for water balance calculations important both for water resource management and paleohydrology climatology water volumes are typically

tertiary volcanism during extension in the andean foothills of central chile 33 15 33 45 s this lithologic and geochemical study treats two tertiary volcanic formations in the andean foothills of central chile deposited during and after an inferred culmination of crustal attenuation the abanico and farellones formations which are described in their type localities just east of santiago formed from volcanic arcs in continental basins during the oligocene and early miocene respectively aphyric basic lavas of tholeiitic affinity acid pyroclastic rocks and lacustrine deposits constitute the 3100 m thick abanico formation the overlying 2100 m thick farellones formation consists of calc alkaline lavas basalts absent with thick pyroclastic deposits at the base both formations have nd sr isotope signatures within the mantle array the abanico rocks end 5 7 plot closer to n morb normal mid oceanic ridge basalt than the farellones rocks end 3 9 to 5 1 the ree rare earth element patterns indicate greater depth to the mantle source and a smaller degree of partial melting with time the abanico lavas segregated within the stability field of spinel whereas the lavas of the upper farellones member show residual garnet in their source geochemical changes with time are systematic the greatest contrast is between the middle and upper farellones members in 1 2 m y e g for basaltic andesites la yb increases from 4 3 abanico to 5 6 6 0 and 11 6 lower middle and upper farellones members the bimodal composition of the abanico formation and the lower farellones member indicates that volcanism took place during episodes of extensional conditions extension with subsidence is independently shown by the burial metamorphic pattern voluminous pyroclastic flows structural relationships and other evidence suggest recurrent caldera collapse the first extensional episode ended with contraction and folding of the abanico rocks and the second episode resulted in uplift of the lower and middle farellones members followed by a more passive tectonic regime sequences showing many similarities with the abanico and farellones formations occur along the andean foothills of chile they decrease in age from late cretaceous paleocene at 23 s to early miocene late miocene at 35 s and might be explained by oblique subduction of oceanic ridge

hydrology of lake eyre australia el nino link abstract all major ephemeral rivers of australia lie in the lake eyre basin dry for years on occasions they carry enormous floods with annual volumes of 40 km 3 and instantaneous discharges of the order of 30 000 m 3 s 1 mean annual runoff of the basin is 4 km 3 or 3 5 mm significantly less than the 57 mm for the whole of australia this paper examines lake eyre and its drainage basin describing the historical hydrology of the catchment both in terms of instrument records and inflows hindcast using a model based on the technique of coral fluorescence palaeohydrological reconstruction coral fluorescence is a function of nearby river discharge and can be used to reconstruct annual river outputs reconstruction coral fluorescence is a function of nearby river discharge and can be used to reconstruct annual river outputs beyond the instrument period the burdekin river catchment runoff history is strongly paralleled by the volumes of lake eyre inflows during the period of common reliable instrument gaugings the burdekin runoff data have been extended back to 1735 a d using the correlation between river discharge and annual growth band fluorescence in an old coral from pandora reef off the north queensland coast for the instrument period 1952 to 1980 73 of the variance between coral fluorescence and burdekin discharge is common during the period 1949 1980 41 of the variance between coral fluorescence and lake eyre inflow data is common modelled inflows to lake eyre for the period 1885 1948 are based on the latter data set

a linkage between uranium mineralization and high diagenetic temperature caused by coal self ignition in the southern yili basin northwestern china abstract jurassic sediments in the southern yili basin of the xinjiang province northwestern china host several sandstone hosted uranium deposits the jurassic uranium enriched white sandstones are in the transitional zone between the oxidized and reduced zones in addition burnt rocks are common in nearby outcrops and occur occasionally in drill cores mineralogical and geochemical compositions of sediments from the oxidized the uranium enriched transitional and the reduced zones were measured using optical microscopy field emission scanning electron microscopy in conjunction with energy dispersive x ray spectrometry x ray powder diffraction and inductively coupled plasma mass spectrometry icp ms chromite limonite and ilmenite are the typical accessory minerals in the brown sandstones of oxidized zone whereas calcite and saddle dolomite are typical accessory minerals in the sandstones of transitional zone the suite of vitrinite reflectance ro illitic crystallinity and homogenization temperature for fluid inclusions in calcites indicates a relatively high diagenetic temperature 100 c in the jurassic sandstones from both the oxidized and transitional zones in the southern yili basin an interesting relationship was discovered between the diagenetic high temperature conditions and coal self ignition the anomalous uranium concentrations in the burnt claystone from a drill hole and in the altered coals 0 10 cm below the burnt rocks in an outcrop section imply a relationship between the coal self ignition and uranium mineralization in the southern yili basin one option to interpret the uranium mineralization is a supergene descending from surface hydrothermal fluid model in which the downwelling fluids were heated as they penetrated through the warm burnt rocks and then underwent a chemical reaction as they progressively cooled when they traversed down through the underlying permeable sandstone beds accordingly we establish the linkage between uranium mineralization and high diagenetic temperature caused by coal self ignition

sensitivity of the australian summer monsoon to tilt and precession forcing abstract the response of the australian summer monsoon to orbital forcing is studied using a coupled general circulation model gcm with the focus on the relative roles of tilt and precession on the forcing of the northern australian summer monsoon it was found that unlike the northern hemisphere monsoons which are dominated by precession forcing the australian monsoon can be enhanced significantly not only by precession forcing but also by tilt forcing coupled to oceanic feedback the new insights obtained from a series of experiments with differing tilt precession configurations allow an interpretation of the australian late quaternary monsoon record in which insolation forcing plays a significant role

late oligocene early miocene compressional tectosedimentary episode and associated land mammal faunas in the andes of central chile and adjacent argentina 32 37 s abstract a reassessment of the geologic and land mammal fossil evidence used in attribution of a tectosedimentary episode in the andes between 32 and 37 s to the middle eocene incaic tectonic phase of peru indicates that the episode occurred during late oligocene early miocene times 27 20 ma from west to east three structural domains are recognized for this time span in the study area a volcanic arc chile a thin skinned e verging fold thrust belt cordillera principal chile argentina border strip and a foreland basin argentina initiation of thrusting in the cordillera principal fold thrust belt produced the coeval initiation of sedimentation in the foreland basin of adjacent argentina this onset of foreland deposition postdates strata bearing a divisaderan land mammal age fauna i e 35 30 ma and is marked at 36 30 s by the base of the rodados lustrosos conglomerates which are conformably overlain by sedimentary rocks containing a deseadan land mammal age fauna i e 29 21 ma geologic relationships between the thick volcanic abanico coya machali and farellones formations also demonstrate that this tectosedimentary episode practically ended at 20 ma at least in the volcanic arc and was therefore roughly coeval with the major tectonic crisis 27 19 ma known in northwestern andean bolivia some 1500 km to the north this strongly suggests that a long outstanding tectonic upheaval affected at least an extended 12 37 s segment of the andean margin of south america during late oligocene and early miocene times

monitoring playa lake inundation in the western united states modern analogues to late holocene lake level change abstract closed basin playas are among the most sensitive hydrologic systems globally and are excellent indicators of current and past climatic variability this variability can significantly impact hydrologic regimes and biotic communities and is often expressed in lake bed deposits and shoreline features we analyzed two playa basins in western north america that lie to either side of the current divide between monsoon and westerly precipitation regimes using a 23 year sequence of landsat images at a 16 day time step we determined the playa inundation response to varying precipitation inputs our results show that a strongly contrasting lake inundation response occurs in lake basins separated by only 200 km the animas lordsburg basin shows a marked lake area increase in response to winter precipitation events while the more southerly palomas basin shows a stronger response to monsoonal and el nino type events this sensitivity to different input sources over short distances may explain some of the apparent asynchronous behavior of playa response found in lake records comprehensive regional scale inundation records could be used to understand the dynamics of playa inundation events and how these events are linked to atmospheric circulation and possibly to understand the observed asynchronous behavior of lake basins during the late pleistocene and holocene

a gis based reconstruction of late quaternary paleohydrology lake eyre arid central australia lake eyre is the terminal playa in a large closed basin which receives the majority of its moisture from the summer monsoon modern lake eyre receives intermittent floodings at times of increased monsoon intensity generally associated with the la nin a phase of the enso cycle lake eyre was a perennial lake during several phases of increased monsoon activity during the late quaternary specifically about 125 ka 80 ka 65 ka and 40 ka magee 1997 late quaternary environments and palaeohydrology of lake eyre arid central australia unpubl ph d thesis australian national university canberra these lake highstands are reflected by elevated shorelines mapped around lake eyre and to a lesser degree around the frome gregory system to the southeast of lake eyre comprehensive research in the lake eyre catchment over the last several decades has constrained the ages and elevations of these shoreline deposits which now enable us to use digital elevation models to map these paleo lakes by incrementally filling each lake meter by meter the areas and volumes of the paleo lakes are calculated and the paleohydrologic processes including the flow direction across spillovers are reconstructed at the peak 125 ka highstand lake eyre stood at 10 m australian height datum ahd and covered nearly 35 000 km 2 more than three times the area of the current playa together with the frome gregory system it held 430 km 3 of water by contrast the deepest historic filling held 30 km 3 these lake levels represent climatic conditions very different from the modern situation due to discontinuous preservation of the shoreline deposits around the lakes and due to the scale of the lake systems mapping the former levels of lake eyre and the frome gregory system has been impossible prior to the availability of a digital elevation model paramatizing the area volume relationships of water required to fill the lake to varying levels will provide data for quantification of climate and precipitation changes over time h 2003 elsevier b v all rights reserved

disentangling the impacts of climate and human colonization on the flora and fauna of the australian arid zone over the past 100 ka using stable isotopes in avian eggshell abstract throughout the quaternary the flora and fauna of australia evolved and adapted to the high amplitude low and high frequency climate changes that characterized the ice age cycles however during the last glacial cycle between 120 and 15 ka unprecedented irreversible changes in flora and fauna occurred and in that same interval modern humans established their first firm presence in the landscape disentangling the impacts of the first order trend toward a colder drier planet through the late quaternary from the impacts of human colonization has been challenging from both the chronological and paleoenvironmental perspectives we utilize the stable isotopes of carbon and oxygen preserved in near continuous time series of dromaius emu eggshell from five regions across australia to provide independent reconstructions of ecosystem status and climate over the past 100 ka carbon isotopes are determined by the diet consumed by the female bird whereas oxygen isotopes record the status of local moisture balance in the months prior to breeding together 13 c and 18 o provide ecosystem status and climate from the same dated sample reducing correlation uncertainties between proxies combined with recent improvements in the chronologies of late quaternary shorelines fringing inland lake basins and deflation during arid times these data collectively reaffirm that australia generally became increasingly albeit irregularly drier from the last interglaciation through to the last glacial maximum dromaius eggshell 18 o documents peak aridity between 30 and 15 ka but shows no evidence of exceptional climate change between 60 and 40 ka in contrast dromaius 13 c diet documents an irreversible loss of the majority of palatable summer rainfall related c4 grasses across the australian arid zone between 50 and 45 ka about the same time that the giant megafaunal bird genyornis became extinct and coincident with human dispersal across the continent our data indicate that changes unique to australia occurred between 50 and 45 ka that led to a new climate vegetation relationship and an overall reduction in effective moisture across much of the continent the large summer rainfall dominated lakes of interior australia failed to re fill subsequently despite a wide range of global climate states a full explanation for the mechanisms behind these changes remains elusive but they are almost certainly related to human agency plausible explanations include a change in fire regime resulting from human lit fires a change in fire regime following extinction of megafaunal browsers and or a threshold response to increasing aridity of these the climate change explanation is least likely given the lack of evidence for unprecedented aridity between 60 and 40 ka and the successful adaptation of australian ecosystems to 2 5 ma of similar changes

dry lake beds as sources of dust in australia during the late quaternary a volumetric approach based on lake bed and deflated dune volumes abstract dust affects earth s climate ecology and economies across a broad range of scales both temporally and spatially and is an integral part of the earth s climate system previous studies have highlighted the importance of inland lake beds to dust emissions both locally and globally this study aims to explore the relative volumetric importance of ephemeral lakes that emit dust to the australian southeastern dust path over the last glacial cycle srtm dems and gis analyses of long term up to 80 ka lake bed deflation volumes and deposition of sand sized sediment onto downwind source bordering dunes were used to derive estimates of transported dust mass a strong power relationship was found between lake area and the mass of deflated lake bed sediments total dust masses for the largest 53 lakes in southeastern australia were derived using the relationship between lake area and dust mass and used to determine an upper value for total dust mass deflated from lake beds in southeastern australia ephemeral lake derived dust was found to represent at most 13 of the dust derived from southeastern australia deposited in the southern pacific over the last 80 ka or 22 over the last 40 ka lake eyre the largest lake has contributed at most 3 of the australian southeast dust plume these results imply that there are significant additional sources of dust in australia over these timescales such as floodplains or dunefields and that modelling must allow for diverse climatic and geomorphic controls on dust production

morphodynamics of nearshore rhythmic sandbars in a mixed energy environment sw france i mapping beach changes using visible satellite imagery abstract this paper presents a new method to analyze the morphology and migration of shallow water sandbanks based on the retrieval of maps from high resolution spot satellite imagery this approach was applied to the study of intertidal ridge and runnel systems and subtidal crescents that border the southwest coast of france maps were obtained from 16 spot images recorded between 1986 and 2000 ridge and runnel shapes with regard to a reference level were delineated using a watercolor reflectance code parameterized and validated with field data crescent plan shapes which appear on the images due to water transparency or breaking induced foam were directly extracted the spatial maps show that in conformity with field surveys the mean alongshore spacing of intertidal systems and crescents range from 370 146 m variability is indicated by standard deviation to 462 188 m and from 579 200 to 818 214 m respectively several couples of images also show that ridge and runnel systems and crescents move in the longshore drift direction southward by about 2 4 3 1 and 1 m day 1 respectively alongshore migration rates of intertidal systems are confirmed by field surveys whilst crescent dynamics cannot be validated because there is no in situ data available to complete these measurements an analysis of the influence of wave climate on both the shape and movements of these rhythmic sedimentary patterns is proposed in a companion paper

trace element geochemistry of no 511 uranium ore deposit in xinjiang systematical studies of main and trace element geochemistry indicate that the no 511 uranium ore deposit in northwestern china is a sandstone type composite ore deposit characterized by multi element enrichment se re ga ge v and mo are concentrated to different extents in this deposit of which se re and ga are of economic significance se re ge mo v and other zones of these trace elements are recognized successively in the development direction of interlayer oxidation integration of these trace element data further shows that there exists a positive correlation between u and re suggesting that re and se may be important indicators of uranium ore deposits

integrating historical topographic maps and srtm data to derive the bathymetry of a tropical reservoir this paper proposes a cheap and fast method for est imating the bathymetry of hydroelectric reservoirs brazil has more than 30 l arge hydroelectric reservoirs with volume exceeding one billion cubic meters the hydroelectric sector is responsible for 97 of energy generation being the largest hydroele ctric park in the world these dams however cause a series of environmental social an d economic impacts which need to be monitored among the variables affecting the env ironmental impact posed by reservoirs depth has a key role because it acts on the aquatic system hydrodynamics reservoir depth distribution the bathymetry is al so a fundamental factor controlling physical chemical and biological properties of the system in brazil the acquisition of bathymetric information for the large reservoirs h owever is not a simple task because 1 most of the topographic maps available in the ar ea covered by the lake have very small scale 1 100 000 and smaller 2 larger char ts are property of the hydropower companies and are classified 3 the size of the re servoirs prevent the use of bathymetric surveys due the challenge therefore is how to comb ine the use of low precision topographic charts from the period previous to rese rvoir filling srtm data to obtain a bathymetric map which could be used for planning echo bathymetric missions so as reducing both cost and time of data acquisition and processing

evolution of melt pond volume on the surface of the greenland ice sheet 1 the presence of surface meltwater on ice caps and ice sheets is an important glaciological and climatological characteristic we describe an algorithm for estimating the depth and hence volume of surface melt ponds using multispectral aster satellite imagery the method relies on reasonable assumptions about the albedo of the bottom surface of the ponds and the optical attenuation characteristics of the ponded meltwater we apply the technique to sequences of satellite imagery acquired over the western margin of the greenland ice sheet to derive changes in melt pond extent and volume during the period 2001 2004 results show large intra and interannual changes in ponded water volumes and large volumes of liquid water stored in extensive slush zones

relationship between the hydrogeochemical environment and sandstone type uranium mineralization in the ili basin china this paper describes the occurrence and distribution of u within groundwater of the ili basin in xinjiang china dissolved major ions dissolved gases ph eh and salinity in groundwater were employed to distinguish different hydrogeochemical environments and associated processes affecting u transport within the aquifer the results show that dissolution and deposition of u by groundwater are closely related to reactions with organic c and minerals such as sulfides carbonates and silicates along groundwater flow paths different chemical reactions predominate and account for changes in the occurrence of u in the rock and water of the oxidized zone the redox transition zone and the reduced zone knowledge of these associations between u and hydrogeochemical environments could enhance the understanding of relationships of groundwater circulation and u mineralization and could have implications for prospecting for sandstone type u deposits

inversion of an oligocene volcano tectonic basin and uplifting of its superimposed miocene magmatic arc in the chilean central andes first seismic and gravity evidences abstract a new structural model is presented for the cenozoic part of the main range east of santiago a chain made up of thick miocene ignimbrites and andesitic lavas overlying primitive oligocene volcanoclastics deposited on a thin continental crust because the latter coya machali formation locally show tight folding close to the margins of the miocene volcanics they had previously been described as deformed prior to construction of the arc our field observations analysed along two profiles at 33 and 34 15 s however support the conclusion hinted at by ongoing geochronological and geochemical studies deformation of both formations is synchronous and related to late miocene inversion of the coya machali intra arc basin uplift of the rigid arc rocks and part of its volcanoclastic basement took place mainly along two northward shallowing boundary structures that seem to share a lower decollement the eastern fierro out of sequence thrust and a series of western back thrusts that resemble triangle zones seismic data obtained from el teniente porphyry copper mine 34 s rockbursts and two gravimetric profiles at the western end of the southern profile are compatible with a decollement located at that locality 2 3 km under the surface

calderas and ash flow tuffs of the mogollon mountains southwestern new mexico the mogollon mountains are a major volcanic source area in the southwestern mogollon datil volcanic field where about 2000 m of middle tertiary rocks are exposed the volcanic sequence includes eight major 100 km3 ash flow units believed to represent four caldera related compositionally zoned ash flow sequences each caldera related sequence shows normal compositional zonation from high silica rhyolite to rhyolite and dacite the mogollon caldera 34 ma is preserved only as a fragment in the wall of the bursum caldera the emory caldera 34 ma is about 50 km east of the mogollon mountains and only the high silica facies of its presumed outflow sheet fall canyon tuff reaches the mogollons the gila cliff dwellings caldera 30 ma earlier interpreted as the source of the bloodgood canyon tuff probably is a large remnant of a caldera or pair of calderas that were the source of the davis canyon and shelley peak tuffs the bloodgood canyon tuff was most likely erupted from the bursum caldera 29 28 ma but ponded in the gila cliff dwellings caldera the resurgent dome of the approximately 40 km diameter bursum caldera is the predominant topographic and structural feature of the mogollon mountains the caldera probably collapsed initially in response to eruption of the bloodgood canyon tuff then was largely filled with apache spring tuff prior to resurgent doming the cyclical eruption beginning about 34 ma of similar compositionally zoned ash flows from separate shallow magma chambers suggests derivation from a common parent magma of batholithic proportions a regional bouguer gravity low of about 40 mgals has been interpreted to reflect the presence of such a batholith major ash flow eruptions in the mogollon datil field were followed 26 25 ma by fundamentally basaltic volcanism characterized mainly by andesite about 22 21 ma high silica rhyolite tholeiitic basalt and alkali basalt were erupted as a bimodal suite roughly coincident with the beginning of basin range extensional faulting alkali olivine basalt as young as 5 5 ma is interlayered with basin fill gila conglomerate adjacent to the mogollon mountains

bathymetry retrieval from hyperspectral remote sensing data in optical shallow water in this paper an algorithm for estimating shallow water depth from hyperspectral data is proposed this methodology is based on the different responses of shallow water reflectance on depth and substrate type two parameters similarity coefficient and pearson correlation coefficient are introduced to describe the different types of responses and a linear logarithm ratio model is established using hyperion data over the coastal regions of o ahu island and saint thomas island the retrieved bathymetry is compared with the airborne lidar data the validation results show that the proposed method has good performance and the root mean square error is less than 1 5 m over shallow water shallower than 20 m

morphodynamics of nearshore rhythmic sandbars in a mixed energy environment sw france 2 physical forcing analysis abstract the morphology and migration of rhythmic intertidal ridge and runnel systems and subtidal crescentic bars that border the southwest coast of france were characterized using in situ surveys and maps obtained by remote sensing methods the period from 1986 to 2000 was investigated a total of 35 km of coast was mapped this data set shows several specificities the origin of which are examined in the present report using hydrodynamic data a complete analysis of the influence of wave climate on both the shape and the movements of these rhythmic sedimentary patterns was performed in addition swan and morphodyn coupled numerical models were used to provide quantification of both wave breaking and longshore currents for wave parameters that were representative of the mean values and of the energetic conditions this study demonstrated the short time response of intertidal systems to the wave forcing when the offshore significant wave height h s was lower than 2 5 m regular coastal ridge and runnel systems developed in the intertidal zone and migrated in the longshore drift direction at a rate of 1 7 3 1 m day 1 by contrast the ridge and runnel system morphology abruptly changed when the h s exceeded 2 5 m and after the storm the typical ridge and runnel rhythmic topography was recovered within 5 9 days the crescentic bars which had a convex seaward shape were affected by waves with h s values greater than 3 m slightly less for short waves depending on the wave orientation the crescentic bars moved in the longshore drift direction at a rate that reached 1 m day 1 the data suggested a slight negative correlation between the mean alongshore length of the crescentic bar and the mean h s finally it seemed that increasing the wave obliquity with respect to the coast resulted in the flattening of the crescentic bars thus coupling spot and in situ mapping to hydrodynamic records allow the characterization of coastal morphology and dynamics with time and space samplings that are particularly well adapted to the little studied alongshore morphodynamics this approach should improve the difficult parameterization of morphodynamic models in high energy environments

how does modifying a dem to reflect known hydrology affect subsequent terrain analysis summary many digital elevation models dems have difficulty replicating hydrological patterns in flat landscapes efforts to improve dem performance in replicating known hydrology have included a variety of soft i e algorithm based approaches and hard techniques such as stream burning or surface reconditioning e g agree or anudem using a representation of the known stream network these methods trench or mathematically warp the original dem to improve how accurately stream position stream length and catchment boundaries replicate known hydrological conditions however these techniques permanently alter the dem and may affect further analyses e g slope this paper explores the impact that commonly used hydrological correction methods stream burning agree aml and anudem v4 6 3 and anudem v5 1 have on the overall nature of a dem finding that different methods produce non convergent outcomes for catchment parameters such as catchment boundaries stream position and length and differentially compromise secondary terrain analysis all hydrological correction methods successfully improved calculation of catchment area stream position and length as compared to using the dem without any modification but they all increased catchment slope no single method performing best across all categories different hydrological correction methods changed elevation and slope in different spatial patterns and magnitudes compromising the ability to derive catchment parameters and conduct secondary terrain analysis from a single dem modification of a dem to better reflect known hydrology can be useful however knowledge of the magnitude and spatial pattern of the changes are required before using a dem for subsequent analyses

satellite derived digital elevation model dem selection preparation and correction for hydrodynamic modelling in large low gradient and data sparse catchments digital elevation models dems that accurately replicate both landscape form and processes are critical to support modelling of environmental processes topographic accuracy methods of preparation and grid size are all important for hydrodynamic models to efficiently replicate flow processes in remote and data scarce regions high resolution dems are often not available and therefore it is necessary to evaluate lower resolution data such as the shuttle radar topography mission srtm and advanced spaceborne thermal emission and reflection radiometer aster for use within hydrodynamic models this paper does this in three ways i assessing point accuracy and geometric co registration error of the original dems ii quantifying the effects of dem preparation methods vegetation smoothed and hydrologically corrected on hydrodynamic modelling relative accuracy and iii quantifying the effect of the hydrodynamic model grid size 30 2000 m and the associated relative computational costs run time on relative accuracy in model outputs we initially evaluated the accuracy of the original srtm 30 m seamless c band dem srtm dem and second generation products from the aster aster gdem against registered survey marks and altimetry data points from the ice cloud and land elevation satellite icesat srtm dem rmse 3 25 m had higher accuracy than aster gdem rmse 7 43 m based on these results the original version of srtm dem the aster gdem along with vegetation smoothed and hydrologically corrected versions were prepared and used to simulate three flood events along a 200 km stretch of the low gradient thompson river in arid australia using five metrics peak discharge peak height travel time terminal water storage and flood extent the hydrologically corrected dems performed best across these metrics in simulating floods compared with vegetation smoothed dems and original dems the response of model performance to grid size was non linear and while the smaller grid sizes 120 m improved the hydrodynamic model results these offered only slight improvements at very significant computational costs compared to grid size of 120 m with grid sizes 250 m and greater decreasing in model accuracy this study highlights the important impact that the quality of the underlying dem has and in particular how sensitive hydrodynamic models are to preparation methods and how important vegetation smoothing and hydrological correction of the base topographic data for modelling floods in low gradient and multi channel environments

low grade regional metamorphism in the mesozoic cenozoic volcanic sequences of the central andes all the mesozoic and cenozoic volcanic rocks of the central andes from southern ecuador to central chile except recent ones have been affected by episodes of regional metamorphism without change in texture and structure the metamorphism which ranges from low zeolite to greenschist facies can be classified as burial metamorphism because there is an overall increase in metamorphic grade with stratigraphic depth in the individual volcanic sequences separated by regional unconformities some sequences display metamorphic patterns transitional to ocean floor and to geothermal field types reflecting variations along and across the andes in tectonic setting and thermal gradients volcanism was closely followed by metamorphism during each cycle characterizing the geological history of the central andes the episodic nature of the metamorphism has led to breaks in metamorphic grade at regional unconformities and repetition of facies series where strata of higher grade may even overlie those of lower grade the existence of permeability controlled distribution patterns of secondary minerals within individual flows shows that gradients of chemical activity rate of reaction and pfluid were acting in addition to temperature and p tot overall gradients during the regional metamorphism the alteration is accompanied by chemical changes and disturbances of the k ar and rb sr isotope systems similarities between mesozoic facies series in the western and eastern flanks of the andes are consistent with a mechanism of ensialic spreading subsidence

seasonal evolution of supraglacial lake volume from aster imagery water stored in and released from supraglacial lakes is an important factor when considering the seasonal and long term evolution of the greenland ice sheet here we use a radiative transfer model to estimate changes in the depth and volume of a supraglacial lake on the surface of jakobshavn isbrae west greenland between 2002 and 2005 when compared to estimates of the lake depth determined from airborne lidar observations we estimate that the root mean square departure of the modelled lake depths was 0 3 m during cloud free conditions the maximum lake area depth and volume were 3 4 km 2 9 6 1 0 m and 18 6 3 7 106 m3 respectively when sequenced according to the number of positive degree days pdds accumulated prior to each image we observe that the lake volume evolves in three distinct phases at the start of the melting season the rate of filling is slow after approximately 80 pdds the rate of filling increases by a factor 3 and after approximately 125 pdds the lake drains rapidly we estimate that the lake drains at a minimum rate of 2 66 0 53 106 m3 d 1 over a 6 day period

hydrological transformation coincided with megafaunal extinction in central australia central to the debate over the extinction of many of australia s last surviving megafauna is the question was climate changing significantly when humans arrived and megafauna went extinct here we present a new perspective on variations in climate and water resources over the last glacial cycle in arid australia based on the study of the continent s largest lake basin and its tributaries by dating paleoshorelines and river deposits in the lake eyre basin we show that major hydrological change caused previously overflowing megalakes to enter a final and catastrophic drying phase at 48 2 ka just as the giant bird genyornis newtoni went extinct 50 45 ka the disappearance of genyornis and other megafauna has been previously attributed to ecosystem collapse coincident with the spread of fire wielding humans our findings suggest a climate driven hydrological transformation in the critical window of human arrival and megafaunal extinction and the results call for a re evaluation of a humanmediated cause for such extinctions in arid australia

a reappraisal of episodic burial metamorphism in the andes of central chile the jurassic to miocene sequences of the central andes east of santiago reputedly show repeated cycles of episodic sub greenschist facies burial metamorphism that are identified by sharp breaks in metamorphic grade at major stratigraphic boundaries this paper presents the first detailed petrochemical analysis of these low grade metamorphic sequences by examining the progressive development of secondary minerals reaction progress in mafic phyllosilicates and topological variations in the low grade assemblages as a means of testing this model the results indicate a progressive increase from zeolite facies through to close to the onset of greenschist facies from miocene to jurassic rocks combined analysis of reaction progress in mafic phyllosilicates and petrochemical relationships of chlorite pumpellyite actinolite in metabasites provides no evidence for sharp metamorphic breaks at major stratigraphic boundaries integrating the results presented here with the most recent models of stratigraphic tectonic development of the central andes shows that the metamorphism took place in two episodes and was not episodic on a 40 million year cycle an absence of sharp breaks in metamorphic grade in any part of the succession as demonstrated here shows that the original petrographic establishment of low grade facies provided insufficient resolution of changes in metamorphic conditions to establish definitive evidence of such breaks accordingly this study suggests that re assessment of metamorphic breaks reputedly developed in other areas of the andean cordillera is imperative in order to resolve the questions raised here about the origin of the low grade metamorphism

a growing sandstone type uranium district in south yili basin nw china as a result of extension of tien shan orogen evidences from geochronology and hydrology abstract the mesozoic yili basin of nw china represents the largest known concentration of u deposits in china and contains five major deposits namely from west to east the 512 kujie ertai 513 511 510 mengqiguer and 509 deposits pre mining resources within the explored sandstone type uranium deposits in this area are reportedly as much as 20 000 t contained u the mineralization is hosted by the middle lower jurassic shuixigou group which from base to top is divided into the badaowan sangonghe and xishanyao formations the u pb isotopic analysis of ores from the kujie ertai and mengqiguer deposits indicate that they contain high and variable amounts of initial common pb meaning that the only possible way to date these deposits is by using u pb isochrons two major stages of uranium mineralization have been identified by the u pb isotope dating of uranium ores in this region the kujie ertai deposit apparently formed between 23 4 3 3 and 20 18 0 49 ma corresponding to a period of crustal thickening and uplift within the tien shan orogen this event 35 21 ma accommodated the majority of the strain generated by the northward collision of the indian plate with the asian plate however the dating of samples from the mengqiguer deposit yielded much younger ages between 0 61 0 24 and 0 347 0 0048 ma the western tien shan mountains expanded until the pliocene as a result of the far field influence of continuous penetration of the indian plate into the asian plate this activated reverse faults and folds in the piedmont of the tien shan mountains and caused the continuous uplift of the southern flank of the yili basin the uplift caused the erosion of anticline hinge zones introducing significant amounts of oxidizing water into the shuixigou group generating a second stage of uranium mineralization hydrological sampling also suggests that the mengqiguer deposit continues to grow indicating a possible third stage of uranium mineralization 0 ma this also indicates that the u within these deposits is derived not only from u bearing sediments but from the tien shan mountains as a result of groundwater cycling the evolution of the u contents of groundwater that was initially derived from cold springs that flow into the mineralized units indicates that these cold springs have an essential role in mobilizing u from the tien shan mountains with rivers flowing through areas of outcropping mineralized units acting as a source of mineralizing fluids during the formation of the mengqiguer deposit

influence of survey strategy and interpolation model on dem quality accurate characterisation of morphology is critical to many studies in the field of geomorphology particularly those dealing with changes over time digital elevation models dems are commonly used to represent morphology in three dimensions the quality of the dem is largely a function of the accuracy of individual survey points field survey strategy and the method of interpolation recommendations concerning field survey strategy and appropriate methods of interpolation are currently lacking furthermore the majority of studies to date consider error to be uniform across a surface this study quantifies survey strategy and interpolation error for a gravel bar on the river nent blagill cumbria uk five sampling strategies were compared i cross section ii bar outline only iii bar and chute outline iv bar and chute outline with spot heights and v aerial lidar equivalent derived from degraded terrestrial laser scan tls data digital elevation models were then produced using five different common interpolation algorithms each resultant dem was differentiated from a terrestrial laser scan of the gravel bar surface in order to define the spatial distribution of vertical and volumetric error overall triangulation with linear interpolation tin or point kriging appeared to provide the best interpolators for the bar surface lowest error on average was found for the simulated aerial lidar survey strategy regardless of interpolation technique however comparably low errors were also found for the bar chute spot sampling strategy when tins or point kriging was used as the interpolator the magnitude of the errors between survey strategy exceeded those found between interpolation technique for a specific survey strategy strong relationships between local surface topographic variation as defined by the standard deviation of vertical elevations in a 0 2 m diameter moving window and dem errors were also found with much greater errors found at slope breaks such as bank edges a series of curves are presented that demonstrate these relationships for each interpolation and survey strategy the simulated aerial lidar data set displayed the lowest errors across the flatter surfaces however sharp slope breaks are better modelled by the morphologically based survey strategy the curves presented have general application to spatially distributed data of river beds and may be applied to standard deviation grids to predict spatial error within a surface depending upon sampling strategy and interpolation algorithm

subduction zones an introduction to comparative subductology abstract the subduction model for trench arc back arc systems was deduced more or less as a logical consequence of sea floor spreading many features in these systems such as thrust type inter plate earthquakes and deep earthquakes along wadati benioff zones are readily explained by the subduction model but other features such as extensional spreading and high heat flow in back arc regions and arc volcanism are difficult to explain an approach to solve these problems may be to recognize the existence of the two basically different modes of subduction one chilean type causing a compressional stress regime in the arc and back arc regions the other mariana type causing a tensional stress regime implications of the two types of the mode of subduction for some tectonic problems such as vertical movement and sediment accretion at trenches are discussed with special reference to the results of recent dsdp active margin drilling in discussing the possible causes of the two modes it is suggested that the large scale thermal and stress regimes in the back arc areas may not be the direct products of simple subduction but of some additional factors involving much greater energy such as mantle flow associated with the motion of major plates finally the possible great importance of various types of collision accretion and erosion at subduction zones is emphasized

mineral paragenesis and textures associated with sandstone hosted roll front uranium deposits nw china abstract we present a first paragenetic study of the wuyier wuyisan wuyiyi and shihongtan sandstone hosted roll front uranium deposits northwest china the mineralization is hosted by lower middle jurassic coarse to medium grained sandstones which are dark gray to black due to a mixture of ore minerals and carbonaceous debris the sandstone is alluvial fan braided river facies minerals associated with these deposits can be broadly categorized as detrital authigenic and ore stage mineralization ore minerals consist of uraninite and coffinite this is the first noted occurrence of coffinite in this type of deposit in china sulfide minerals associated with the uranium minerals are pyrite marcasite and less commonly sphalerite and galena the sulfide minerals are largely in textural equilibrium with the uranium minerals however these sulfide minerals occasionally appear to predate as well as postdate the uranium minerals this implies that there are multiple generations of sulfides associated with these deposits the ore minerals occur interstitially between fossilized wood cells in the sandstones as well as replace fossilized wood and biotite the deposits are generally low grade primary uranium minerals associated with the low grade deposits are generally too small ranging from 0 2 to 0 3 m in diameter to be observed by optical microscopy and are only observed by electron microscopy mineral paragenesis and textures indicate that these deposits formed under low temperature 30 50 c conditions

remote sensing of volumetric storage changes in lakes three dimensional remote sensing promises a giant leap forward for surface water hydrology in much the same way that radar altimetry transformed physical oceanography however the complex geometries of small terrestrial water bodies introduce difficulties particularly with respect to trade offs between changing water depth and inundation area we use in situ measurements of water surface stage h dt and remotely sensed area a to compute time varying storage changes s in nine lakes of the peace athabasca delta canada despite their identical geomorphic setting regression slopes between h and a vary significantly between lakes primarily from a predictable area effect but also small bathymetric variations between basins on average lateral contraction expansion versus stage adjustment contributes as little as 7 versus 93 to as much as 76 versus 24 of overall storage change s we conclude that both surface area and h dt rather than just either alone must be measured to confidently estimate s from space copyright 2009 john wiley sons ltd

spot shallow water bathymetry of a moderately turbid tidal inlet based on field measurements the determination of shallow water depth in high energy tidal inlets is essential to model and to forecast the navigation channel position or the short term topographic evolution of beaches colour satellite imagery provides at low cost complete maps of areas that are difficult to map by traditional hydrographic means due to their size and their rough underwater morphology in order to calibrate spot images to derive bathymetric maps a simple method applied to shallow waters of a moderately turbid tidal inlet has been carried out its development is based on a set of field measurements including the reflectance of the water and of the bottom sediment the vertically averaged diffuse attenuation coefficient and the concentrations of inorganic particles in suspension of chlorophyll a and pheopigments and of dissolved organic carbon doc from these data it appears first that the water reflectance is directly linked to the depth and second that the water reflectance varies slowly with the turbidity in this area for total suspended matter sm concentrations lower than 9 mg l 1 the extinction of light with depth has been characterized in the inlet the relationship obtained is slightly different from that observed in clear waters the bathymetric models established for the clearest waters do not calculate the depth accurately in the contrary reflectance code adapted to case ii water type calibrated with in situ measurements allows us to retrieve depth down to 6 m and for total sm concentrations ranging from 0 2 to 9 mg l 1 this relationship has been applied to five spot images of the mouth of arcachon lagoon the accuracy of the derived map has been assessed by in situ depth measurements the mean difference between measured depths and computed depths is about 20 this accuracy is adequate to assess the inlet morphodynamics quantitatively which is necessary for middle term to short term mathematical modeling of the 3d inlet evolution

continuous 150 k y monsoon record from lake eyre australia insolation forcing implications and unexpected holocene failure our reconstructed history of lake eyre provides the first continuous continental proxy record of australian monsoon intensity over the past 150 k y this continental record s broad correspondence to the marine isotope record demonstrates that this very large catchment with its hydrology dependent on a planetary scale climate element responds to milankovitch scale climate forcing abrupt transitions from dry phases to wet phases ca 125 and 12 ka coincide with northern hemisphere winter insolation minima rather than southern hemisphere summer insolation maxima indicating that northern hemi sphere insolation exerts a dominant control over the intensity of the australian monsoon stratigraphic and dating uncertainties of other wet phases preclude conclusive correlation to specific insolation signals but within the uncertainties are consistent with northern hemisphere forcing regardless of the hemispheric forcing the low intensity of the early holocene australian monsoon by comparison with the last interglacial and particularly the last high level lacustrine event at 65 60 ka when all forcing elements were modest is an enigma that can be explained by a change in boundary conditions within australia

remote sensing of stream depths with hydraulically assisted bathymetry hab models this article introduces a technique for using a combination of remote sensing imagery and open channel flow principles to estimate depths for each pixel in an imaged river this technique which we term hydraulically assisted bathymetry hab uses a combination of local stream gage information on discharge image brightness data and manning based estimates of stream resistance to calculate water depth the hab technique does not require ground truth depth information at the time of flight hab can be accomplished with multispectral or hyperspectral data and therefore can be applied over entire watersheds using standard high spatial resolution satellite or aerial images hab also has the potential to be applied retroactively to historic imagery allowing researchers to map temporal changes in depth we present two versions of the technique hab 1 and hab 2 hab 1 is based primarily on the geometry discharge and velocity relationships of river channels manning s equation assuming average depth approximates the hydraulic radius the discharge equation and the assumption that the frequency distribution of depths within a cross section approximates that of a triangle are combined with discharge data from a local station width measurements from imagery and slope measurements from maps to estimate minimum average and maximum depths at a multiple cross sections these depths are assigned to pixels of maximum average and minimum brightness within the cross sections to develop a brightness depth relation to estimate depths throughout the remainder of the river hab 2 is similar to hab 1 in operation but the assumption that the distribution of depths approximates that of a triangle is replaced by an optical beer lambert law of light absorbance in this case the flow equations and the optical equations are used to iteratively scale the river pixel values until their depths produce a discharge that matches that of a nearby gage r 2 values for measured depths versus depths estimated by hab 1 and hab 2 are 0 51 and 0 77 respectively in the relatively simple brazos river texas r 2 values for hab 1 and hab 2 are 0 46 and 0 26 respectively in the lamar river a complex mountain river system in yellowstone national park although the r 2 values are moderate depth maps and crosssections derived from the hab techniques are consistent with typical stream geomorphology patterns and provide far greater

icesat waveform measurements of within footprint topographic relief and vegetation vertical structure 1 the ice cloud and land elevation satellite icesat mission determines land surface vertical structure within laser footprints due to topographic relief and vegetation using received waveforms recorded by the geoscience laser altimeter system glas in low relief areas with tree cover the waveforms and derived elevation products provide useful biophysical parameters including maximum canopy height crown depth the outer canopy ruggedness and a measure of canopy cover for areas where within footprint topographic relief is large compared to vegetation height interpretation of the waveforms is complex the contribution of canopy and ground to received waveforms is illustrated by comparing them with co located waveforms computed using an instrument model applied to high resolution digital elevation models dems the model includes representations of the transmit pulse s spatial and temporal distributions and the receiver field of view sensitivity and temporal smoothing this provides a means to validate glas waveforms elevation products and footprint geolocation

a high resolution bathymetry dataset for global reservoirs using multi source satellite imagery and altimetry abstract although accurate 3 d reservoir bathymetry is a key input for multiple applications such as global hydrological models local water resources related studies and others such information is only available for very few locations to fill this knowledge gap we generated a 30 m resolution bathymetry dataset for 347 global reservoirs representing a total volume of 3123 km3 50 of the global reservoir capacity first area elevation a e relationships for the identified reservoirs were derived by combining altimetry data from multiple satellites with landsat imagery data next the resulting a e relationships were applied to the surface water occurrence swo data from the jrc global surface water gsw dataset to obtain bathymetry values for the dynamic areas of the reservoirs lastly an extrapolation method was adopted to help achieve the full bathymetry dataset the remotely sensed bathymetry results were primarily validated against the following 1 they were validated against area elevation a e and elevation volume e v relationships derived from the in situ elevations and volumes for 16 reservoirs with root mean square error rmse values of elevation from 0 06 m to 1 99 m and normalized rmse values of storage from 0 56 to 4 40 2 they were also validated against survey bathymetric maps for four reservoirs with r2 values from 0 82 to 0 99 and rmse values from 0 13 m to 2 31 m the projected portions have relatively large errors and uncertainties compared to the remotely sensed portions because the extrapolated elevations cannot fully capture the underwater topography overall this approach performs better for reservoirs with a large dynamic area fractions it can also be applied to small reservoirs e g reservoirs with surface areas of a few square kilometers or less where icesat observations are available and to large natural lakes with the contribution of icesat 2 this dataset has the potential to be expanded to thousands of reservoirs and lakes in the future

sedimentological setting of sandstone type uranium deposits in coal measures on the southwest margin of the turpan hami basin china abstract sandstone type uranium deposits usually exist in coal measures this stratigraphy study found that the jurassic coal measures shuixigou group at the southwest margin of the turpan hami basin consist of the badaowan sangonghe and xishanyao formations which correspond to sequences a b and c respectively sequence c can be divided into the lowstand systems tract lst expanding lacustrine systems tract est and highstand systems tract hst uranium mineralization mainly develops in sequence c in which lst and hst are the main mineralization strata while est is the secondary mineralization stratum high resolution study of depositional systems tracts indicates that the fine sediments around the boundaries of parasequences can form the confining beds of uranium metallogenetic fluid systems within parasequences the braided channel sandstones and part large scale braided distributary channel sandstones have a close relationship with strong interlayer oxidation and uranium mineralization periodical development of parasequences conduces to the frequent growth of large skeletal sandstones and confining beds that is the essential reason for the complexity of uranium mineralization in depositional systems tracts the study also found that different depositional systems lead to obvious differences in the spatial distribution structures of skeletal sandstones and confining beds lst and hst mainly comprise braided stream depositional systems where uranium skeletal sandstones develop and are always located in the middle and lower parts of the parasequences while confining beds are always located in the upper part of parasequences while est mainly comprises braided delta depositional systems where uranium skeletal sandstones have a relatively small scale and are always located in the middle part of parasequences confining beds are always located in the lower and upper parts of parasequences thus the study of depositional systems tracts in sequence is only suitable for the primary exploration stage of sandstone type uranium deposits and parasequences are the best evaluation units in the advanced exploration stage

geochemical and mineralogical evidence for a coal hosted uranium deposit in the yili basin xinjiang northwestern china abstract the petrological geochemical and mineralogical compositions of the coal hosted jurassic uranium ore deposit in the yili basin of xinjiang province northwestern china were investigated using optical microscopy and field emission scanning electron microscopy in conjunction with an energy dispersive x ray spectrometer as well as x ray powder diffraction x ray fluorescence and inductively coupled plasma mass spectrometry the yili coal is of high volatile c b bituminous rank 0 51 0 59 vitrinite reflectance and has a medium sulfur content 1 32 on average fusinite and semifusinite generally dominate the maceral assemblage which exhibits forms suggesting fire driven formation of those macerals together with forms suggesting degradation of wood followed by burning the yili coals are characterized by high concentrations of u up to 7207 g g se up to 253 g g mo 1248 g g and re up to 34 g g as well as as up to 234 g g and hg up to 3858 ng g relative to the upper continental crust the rare earth elements rees in the coals are characterized by heavy or and medium ree enrichment the minerals in the yili coals are mainly quartz kaolinite illite and illite smectite as well as to a lesser extent k feldspar chlorite pyrite and trace amounts of calcite dolomite amphibole millerite chalcopyrite cattierite siegenite ferroselite krutaite eskebornite pitchblende coffinite silicorhabdophane and zircon the enrichment and modes of occurrence of the trace elements and also of the minerals in the coal are attributed to derivation from a sediment source region of felsic and intermediate petrological composition and to two different later stage solutions a u se mo re rich infiltrational and a hg as rich exfiltrational volcanogenic solution the main elements with high enrichment factors u se as and hg overall exhibit a mixed organic inorganic affinity the uranium minerals pitchblende and coffinite occur as cavity fillings in structured inertinite macerals selenium as and hg in high pyrite samples mainly show a sulfide affinity

la nina de australia contemporary and palaeo hydrology of lake eyre abstract the available records of inflows to lake eyre cover only forty five years their quality is questionable as longer time series of precipitation records are available the observed series of inflows to lake eyre can be extended with the help of a rainfall runoff model further reconstruction of the inflow series can be achieved by examining local evidence or with the help of proxy data however the limitations of these extensions and reconstructions of inflows are severe the inflows to lake eyre could be considered one of the most convincing manifestations of hydrological uncertainty however it is apparent that major flooding episodes in the lake eyre basin are most often associated with la nina phases of the el nino southern oscillation enso phenomenon the paper presents a hydrological description of the lake eyre basin and large scale contemporary and palaeo climatic patterns which affect the water balance of the catchment a simple water balance model has been constructed to determine storages of the lake when annual evaporation reaches equilibrium with annual runoff

wave period and coastal bathymetry using wave propagation on optical images we propose a method based on combining wave tracing and linear wave theory for the estimation of wave period and bathymetry in coastal areas from satellite images the method depends on several parameters for which we provide ranges of variations adapted to the instrument experimental results are conducted on several sites located around the hawaiian island of oahu using 13 landsat 8 images results show that wave period estimations are compatible with the wave buoy measurements in all cases in addition bathymetry estimation results show a standard deviation of less than 15 of the observed depth out of the surf zone until 20 m for sites with a direct exposure to the swell and with an absence of clouds the proposed method which does not rely on ancillary data represents a promising tool for bathymetry estimation using satellite images in which waves are present

tertiary andean volcanism in a caldera graben setting the miocene farellones formation in central chile 32 35 s is one of several up to 3000 mthick tertiary volcanic sequences in the central andes with ash flows and intercalations of lacustrine sediments in their lower part and intermediate to basic lavas and rhyolitic domes in their upper part the farellones rocks were probably deposited in a volcano tectonic graben formed through a series of caldera collapses this is suggested by a the fact that the formation frequently is delimited by normal faults towards which the subhorizontal strata pinch out and become upraised indicating deposition during subsidence b the huge volume of erupted acid magma and c a high paleothermal gradient of geothermal field type similar tertiary volcanic sequences in northern chile and central peru probably also formed by eruptions in a caldera graben setting this setting and the geothermal field type of alteration make these sequences good prospecting targets for epithermal preciousmetal deposits

application of grain size trend analysis for the determination of sediment transport pathways in intertidal areas abstract in this paper we apply the gao and collins procedure of grain size trend analysis for the first time in an intertidal sedimentary system our purpose is to evaluate a reliable method to determine residual transport directions in intertidal environments where sediment movement is not well understood residual transport patterns can be determined by grain size trend analysis if the following criteria are applied 1 a single sediment transport unit must be precisely defined and investigated 2 the thickness of sampling has to be chosen in order to investigate the most recent sedimentary event and 3 a regular mesh grid is sampled to avoid bias in the calculation of grain size trends the gao and collins method was undertaken simultaneously with a topographic survey and a tracer experiment during consecutive meteorological conditions of fair weather and a storm event the topographic changes observed between these two situations and the directions of sediment movement deduced from tracer tracking are coherent with the residual transport pattern calculated from the grain size trend analysis the method was tested on a ridge and runnel system which corresponds to the intertidal part of a macrotidal beach called la salie beach located along the southwest french coast in a high wave energy environment this study permits us to recognize two different residual transport patterns for this intertidal ridge and runnel system one for fair weather and a second for storm conditions during fair weather specific sites are subject to sand accretion while during storm conditions these sand stocks are subsequently spread out over the whole area and remain partly on the beach

the dynamism of salt crust patterns on playas playas are common in arid environments and can be major sources of mineral dust that can influence global climate these landforms typically form crusts that limit evaporation and dust emission modify surface erosivity and erodibility and can lead to over prediction or underprediction of 1 dust emission potential and 2 water and heat fluxes in energybalance modeling through terrestrial laser scanning measurements of part of the makgadikgadi pans of botswana a southern hemisphere playa that emits significant amounts of dust we show that over weeks months and a year the shapes of these surfaces change considerably ridge thrusting of 30 mm week and can switch among continuous ridged and degraded patterns ridged pattern development changes the measured aerodynamic roughness of the surface as much as 3 mm week the dynamic nature of these crusted surfaces must be accounted for in dust entrainment and moisture balance formulae to improve regional and global climate models

an excellent fossil wood cell texture with primary uranium minerals at a sandstone hosted roll type uranium deposit nw china abstract a fossil wood cell texture with pitchblende and coffinite found at a sandstone hosted roll type uranium deposit xinjiang nw china is first reported here for the country in the mineralized sandstone detrital grains consisting of quartz feldspar rock fragments carbonaceous trashes mica and accessory minerals were deposited in early turassic time and were cemented by clays and minor authigenic calcite and quartz pitchblende and minor coffinite are principal ore minerals at the deposit and selectively replaced carbonized fossil wood remnants or filled fossil wood cells an excellent fossil wood cell texture with primary uranium minerals formed replacement of organic debris by primary uranium minerals may be due to a local reducing environment resulting from the production of ch 4 h 2 s or h 2 so 3 in its decomposition and a biochemical reaction indicated by the common presence of framboidal pyrite

shoreline changes and morphology of spits along southern karnataka west coast of india a remote sensing and statistics based approach abstract the changes in shoreline positions and morphology of spits along the karnataka coast western india are investigated for the period from 1910 to 2005 using multi dated satellite images and topomaps the study area has been divided into four littoral cells and each cell into a number of transects at uniform intervals the rate of change in shoreline position has been estimated using the statistical linear regression method and cross validated with regression coefficient r 2 and root mean square error rmse methods past and future shoreline positions have been demarcated and future positions of shoreline are estimated for time periods of 10 and 24 years the study reveals that i about 57 of transects exhibit 10 m rmse values indicating better agreement between the estimated and satellite based shoreline positions and ii transects closer to the cell boundaries exhibit about 50 uncertainties in shoreline change rate estimations based on rmse values the influence of natural processes and anthropogenic factors on shoreline changes has been evaluated the cells transects dominated by natural processes reveal low rmse values whereas the cells transects influenced by anthropogenic activities such as sand mining construction of coastal structures exhibit higher rmse values however the variation in rmse values is not significant if the total number of transects is considered significant changes in morphology of spits have been recorded spits demonstrate variations in areal extent i e length and area if 1910 and 1967 are considered separately as base years the present study demonstrates that combined use of satellite imagery and statistical techniques such as linear regression and rmses can be very useful in quantifying shoreline changes and spit morphology

identifying extreme pluvials in the last millennia using optical dating of single grains of quartz from shorelines on australia s largest lake the filling of kati thanda lake eyre kt le australia s inland sea has captured scientific and cultural interest for over a century and a half however despite the presence of multiple shoreli

miocene fossil hydrothermal system associated with a volcanic complex in the andes of central chile abstract cenozoic deposits in the andes of central chile have been affected by very low grade burial metamorphism at about 33 s in the cuesta de chacabuco area approximately 53 km north of santiago two oligocene and miocene volcanic units form a ca 1300 m thick rock pile the miocene unit corresponds to a volcanic complex composed of two eroded stratovolcanoes secondary mineral assemblages in both units were studied petrographically and using x ray diffraction and electron microprobe analyses most of the igneous minerals are wholly or partially preserved and the ubiquitous secondary minerals are zeolites and mafic phyllosilicates the alteration pattern observed is characterized by a lateral zonation in secondary mineralogy related to a lateral increase in temperature but not to stratigraphic depth the following three zones were established mainly based on the distribution of zeolites zone i comprises heulandite thomsonite mesolite stilbite and tri smectite zone ii contains laumontite yugawaralite prehnite epidote and chlorite and zone iii comprises wairakite epidote chlorite diopside biotite and titanite for each zone the following temperature ranges were estimated zone i 100 180 c zone ii 180 270 c and zone iii 245 310 c the alteration episode was characterized by a high p fluid p total ratio ca 1 0 although slightly variable a high geothermal gradient of ca 160 c km 1 and fluid pressures below 500 bars although temperature was the main control on the mineral zonation several interrelated parameters mainly fluid composition porosity and permeability were also important hot near neutral to slightly alkaline ph alkali chloride hydrothermal fluids with very low dissolved co 2 contents deposited the secondary minerals the alteration pattern is the result of depositing fluids in outflow regions from a hydrothermal system developed inside a volcanic complex during the miocene the hydrothermal system has been eroded to a maximum depth of 1 7 km

tectonic evolution of the south tianshan orogen and adjacent regions nw china geochemical and age constraints of granitoid rocks geochemical and geochronological evidence was obtained from granitoids of the south tianshan orogen and adjacent regions which consist of three individual tectonic domains the kazakhstan yili plate the central tianshan terrane and the tarim plate from north to south the central tianshan terrane is structurally bounded by the early paleozoic nikolaev line north nalati fault and late paleozoic atbashy inyl chek south nalati qawabulak fault zones against the kazakhstan yili and tarim plates respectively the meta aluminous to weakly peraluminous granitic rocks which are exposed along the kekesu river and the bikai river across the central tianshan terrane have a tholeiitic calc alkaline or high potassium calc alkaline composition i type geochemical trace element characteristics and the y versus rb nb or y versus nb discrimination diagrams favor a continental arc setting for these granitoid rocks shrimp u pb and la icp ms u pb zircon age data indicate that the magmatism started at about 480 ma continued from 460 to 330 ma and ended at about 275 ma the earlier magmatism 470 ma is considered to be the result of a simultaneous southward and northward subduction of the terskey ocean beneath the northern margin of the tarim plate and the kazakhstan yili plate respectively the later magmatism 460 330 ma is related to the northward subduction of the south tianshan ocean beneath the southern margin of the kazakhstan yili central tianshan plate the dataset presented here in conjunction with previously published data support a late paleozoic tectonic evolution of the south tianshan orogen not a triassic one as recently suggested by shrimp u pb zircon dating for eclogites

spatial and temporal variations in the andean subduction zone a comprehensive global study of the process of subduction of oceanic lithosphere has made it evident that a major role is played by the age of the subducted lithosphere the age dependence of subduction is of special interest in an understanding of the late cenozoic history of the andean subduction zone many of the complexities of this zone result from the peculiar circumstance that the zone is in transition from an early stage of consumption of old lithosphere 70 ma producing deep earthquakes towards the latest stage of consumption of young lithosphere without deep earthquakes this transition has induced an evolutionary pattern with significant temporal variations notably changes in dip and length of the subducted slab moreover the various segments of the south american subduction zone are in different stages of this evolution in comparison with the other segments the northern chile segment is in the earliest stage and therefore shows a much closer resemblance to the classic deep subduction zones in the western pacific than do other parts of the south american zone a roughly n s symmetry in development is found around northern chile with the ecuadorian and southern chilean near 40 45 s segments representing the latest stage to a large extent the temporal and spatial variations in lithospheric age at the trench originate from the reorganization in plate configuration which started with the break up of the farallon plate into the cocos plate and the nazca plate at about 25 ma

porphyry copper and tourmaline breccias at los bronces rio blanco chile the los bronces rio blanco deposit is located on the west side of the andes in central chile about 69 km from santiago los bronces is a breccia complex superimposed on the west side of an earlier major porphyry copper system the rio blanco mine currently exploits the north central part of this porphyry deposit and has started operating a large copper bearing tourmaline breccia sur sur about 2 km south of the present mine the los bronces rio blanco deposit was formed on the east side of the san francisco batholith this intrusion is strongly peraluminous and has a calc alkaline composition with an alkali calcic affinity the batholith took a minimum of 11 5 m y to form from the early miocene 20 1 m y to the late miocene 8 6 m y the porphyry copper mineralization alteration and copper tourmaline breccias were formed over a period of at least 2 5 m y between 7 4and 4 9 m y ago a postmineral volcanic neck or diatreme at la copa erupted within and removed a large segment of the northern part of the porphyry copper system thus marking the last evidence of magmatic activity in the area k ar age determinations of biotites indicate the diatreme erupted in the early pliocene between 4 9 and 3 9 m y ago the prebreccia porphyry system exhibits propylitic sericitic silicic and potassic alteration a unique alteration feature of this system is the replacement of mafic minerals by specularitc and or tourmaline within the propylitic zone the porphyry system contains disseminated and stockwork copper iron molybdenum sulfide mineralization within an area of about 12 km 2 los bronces is composed of at least seven different copper bearing tourmaline breccias that form one large contiguous kidney shaped body about 2 km long and 0 7 km wide at the present erosion surface the breccia body crops out at elevations between 4 150 and 3 450 m the various breccias are characterized by their locations matrices clasts shapes types and degrees of mineralization and alteration the breccias are usually monolithic but in some cases are bilithic or heterolithic with most clasts consisting of quartz monzonite or andesitc with locally minor amounts of quartz latite porphyry monzodiorite and vein quartz the breccia matrices consist of variable amounts of quartz tourmaline specularitc anhydrite pyrite chalcopyrite bornitc molybdenite sericite chlorite and rock flour the seven different breccias types are identified from oldest to youngest as ghost central western infiernillo anhydrite fine gray and donoso the breccia complex has sharp contacts with the surrounding intrusive rocks and andesites internally the breccia contacts are locally well defined but elsewhere they coalesce interfinger or display gradational contacts breccias at los bronces are interpreted as being emplaced explosively followed by collapse after pressure release of hydrothermal fluids the primary mineral distribution is best known in the donoso breccia which has been the center of mining activity since its discovery in 1864 in spite of the coarse and irregular nature of the sulfides in the matrix chalcopyrite pyrite and specularitc at the 3 670 m open pit operating level show a tendency to be distributed in irregular shells in which one of the three minerals predominates in any one shell the transitions between shells are rapid several semiellipsoidal shells of alternating high and low copper grades are also apparent from the copper distribution of underground level 3640 and from various cross sections the shells are approximately vertical subparallel to the donoso breccia contacts which dip inward secondary enrichment enhanced the primary grade in the southern two thirds of the los bronces breccia complex and in much of the surrounding porphyry copper system the degree and depth of enrichment are a function of breccia and fracture permeability and extend to a depth of more than 500 m in certain favorable sectors the shape and depth of the enrichment blanket and overlying leached capping suggest that the enrichment process is related to the present ground water regime and is still active

geology mineralization alteration and structural evolution of the el teniente porphyry cu mo deposit sir the el teniente cu mo deposit in central chile is an extraordinary accumulation of cu mo ore fig 1 and we welcome the opportunity provided by skewes and stern 2007 to discuss and clarify several important issues regarding its classification and interpretation and to address several incorrect assertions that they make regarding our manuscript cannell et al 2005 we have interpreted el teniente to be a typical porphyry deposit in terms of its alteration assemblages vein and breccia styles and spatial and temporal relationships between cu mo mineralization and felsic porphyries skewes and stern 2007 dispute our claims that mineralization occurred primarily in veins and was related to felsic intrusive activity they also take issue with our interpretations of the various geochronological datasets from el teniente and our classification of el teniente as a porphyry cu mo deposit we address each of these in turn below in order to facilitate the following discussion table 1 correlates the geologic nomenclature of skewes and stern 2007 with that of cannell et al 2005 figures 1 and 2 illustrate the location of the main geologic units on underground mine level 6 at el teniente also shown on figure 1 are the approximate locations of the hypogene sulfide mineral zones figure 2 shows the block model of mo grades in the mine for more details of geologic relationships at el teniente refer to figure 4 of cannell et al 2005 and figures 4 and 5 of skewes et al 2002 although the dacite porphyry dike is shown as a single unit on figure 1 note that rojas 2002 2003 mapped multiple phases within this composite intrusive body skewes and stern 2007 criticized our use of what they assert to be an outdated map of hypogene mineralization

a soil chronosequence on lake mega frome beach ridges and its implications for late quaternary pedogenesis and paleoenvironmental conditions in the drylands of southern australia abstract the terminal lake systems of central australia are key sites for the reconstruction of late quaternary paleoenvironments paleoshoreline deposits around these lakes reflect repeated lake filling episodes and such landforms have enabled the establishment of a luminescence based chronology for filling events in previous studies here we present a detailed documentation of the morphology and chemistry of soils developed in four well preserved beach ridges of late pleistocene and mid to late holocene age at lake callabonna to assess changes in dominant pedogenic processes all soil profiles contain evidence for the incorporation of eolian derived material likely via the formation of desert pavements and vesicular horizons and limited illuviation due to generally shallow wetting fronts even though soil properties in the four studied profiles also provide examples of parent material influence or site specific processes related to the geomorphic setting there is an overall trend of increasing enrichment of eolian derived material since at least 33 ka compared to the holocene profiles the derived average accumulation rates for the late pleistocene profiles are significantly lower and may suggest that soils record important regional changes in paleoenvironments and dust dynamics related to shifts in the southern hemisphere westerlies

an improved bathymetric model for the modern and palaeo lake eyre abstract here we demonstrate the applicability of using altimetry data and landsat imagery to provide the most accurate digital elevation model dem of australia s largest playa lake lake eyre we demonstrate through the use of geospatial techniques a robust assessment of lake area and volume of recent lake filling episodes whilst also providing the most accurate estimates of area and volume for larger lake filling episodes that occurred throughout the last glacial cycle we highlight that at a depth of 25 m lake mega eyre would merge with the adjacent lake mega frome to form an immense waterbody with a combined area of almost 35 000 km2 and a combined volume of 520 km3 this would represent a vast water body in what is now the arid interior of the australian continent the improved dem is more reliable from a geomorphological and hydrological perspective and allows a more accurate assessment of water balance under the modern hydrological regime the results presented using glas icesat data suggest that earlier historical soundings were correct and the actual lowest topographic point in australia is 15 6 m below sea level the results also contrast nicely the different basin characteristics of two adjacent lake systems lake eyre and lake frome

a pluvial episode identified in arid australia during the medieval climatic anomaly optically stimulated luminescence osl ages from a relict shoreline on lake callabonna record a major pluvial episode in southern central australia between 1050 70 and 1100 60 common era ce w

environmental character and history of the lake eyre basin one seventh of the australian continent abstract one of the world s largest internally drained endorheic basins the 1 14 million km 2 lake eyre hydrological basin leb covers nearly 15 of the australian continent palaeoclimatic and associated flow regime variations are recorded in an archive of fluvial aeolian and lacustrine sediments that are particularly accessible for deposits from the past 300 ka and are especially relevant for the past 50 ka during which humans have inhabited australia due to its great size economic resources and diverse latitudinal extent it has for over six decades been the focus of environmental scientific and resource based studies across numerous disciplines with an emphasis on assessing the scientific and environmental research over this period this paper is divided into four parts part a provides an introduction and background part b provides the geological history including evidence of substantial tertiary and quaternary climate change part c covers the contemporary environmental conditions and part d presents a conclusion and summary this not only represents the first comprehensive review of current knowledge of any of the world s truly large dryland drainage basins but also highlights how more multi disciplinary research is required key remaining questions revolve around the impact of global weather systems on the leb the lake level story in relation to a more precise picture of late quaternary climate change the role of humans and climate in the demise of the megafauna modern hydrological changes the role of vegetation in altering channel morphology and flow efficiencies and nature of flood transmissions

calibration of the anchizone a critical comparison of illite crystallinity scales used for definition instrumental settings for determination of illite muscovite crystallinity half height width of the 10 a x ray diffraction peak and the limits of the anchimetamorphic zone adopted by various authors fall into several groups the variation in the limiting peak widths between the authors that have adopted kubler s neuch tel boundary values of 0 42 and 0 25 2 can be interpreted in terms of variation in the instrumental settings the choice of time constants higher than those given by the formula causes peak broadening this effect is particularly marked at high scan rates the peak broadening is by constant increments that are virtually independent of the absolute peak width the differences between the kubler neuch tel derived limiting values and some other scales are appreciably greater than can be accounted for by these differences in instrumental settings many of these scales are not equivalent in particular the limits adopted by dunoyer de segonzac 1969 and subsequent workers at strasbourg are too broad their anchizone represents a range of grades of metamorphism lower than that of kubler widely overlapping the latter s diagenetic zone those adopted by some other mainly french authors are too narrow the limits of the anchizone should be calibrated by inter laboratory standards and the instrumental settings should be specified in full