anomalous accumulation of acid volatile sulphides avs in a coastal marine sediment saguenay fjord canada sulpha te reduction usually leads to the formation and accumulation of authigenic pyrite fes2 in organic rich coastal marine sediments iron monosulphides fesx are most often found as a minor constituent of the reduced sulphur pool in these sediments and are believed to be precursor phases which convert to pyrite during early diagenesis abnormally high ratios of acid volatile sulphides avs to pyrite however are found in the sediments of the saguenay fjord canada the avs s fes2 s ratio observed throughout the anoxic zone in three sediment cores collected along the main axis of the fjord generally exceeds 1 and reaches values as high as 7 at the head of the fjord to document and explain this anomaly solid phase components avs fes2 s reactive iron feno coro and total n as well as porewater constituents so4 fe and mn were analyzed degree of pyritization dop values were low 0 1 11 and generally decreased toward the mouth of the fjord in contrast degree of sulphidization dos esti mates were high and reached values of up to 43 at the head of the fjord these latter values indicate that pyrite formation is not limited by iron availability but a large excess of reactive iron may in fact inhibit the build up of reduced sulphur zh2s in the porewaters as a result of avs s precipitation in the absence of a strong eh2s gradient slow diffusion to the redox boundary and limited formation of soluble inter mediate reduced sulphur species may hinder the conversion of avs to pyrite

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

microstructural and fabric studies from the rocks of the moine nappe eriboll nw scotland abstract microstructures and quartz c axis fabric diagrams from mylonites and psammitic moine schists collected in traverses across the lower levels of the moine nappe in the eriboll area are presented on approaching the moine thrust from the kyle of tongue the following microstructural sequence is encountered interlayered coarse grained biotite psammitic and schistose tectonites being in part mylonitic with two platy slide zones one containing biotite and the other only muscovite and chlorite and both showing quartz microstructures indicative of post tectonic relaxation these pass into more mylonitic rocks nearer the thrust zone which in turn passes into the main chlorite grade mylonite belt and finally adjacent to the moine thrust into reworked lower chlorite grade mylonites although there is some local variation the overall quartz c axis fabric is an incomplete asymmetric type i girdle the main variation is the development of type ii girdles in the reworked ultrafine grained mylonites the extent of the mylonitization is more extensive than previously reported studies of folds within the mylonite belt have revealed eye structures and small scale folds many are sheath folds they cannot be unequivocally correlated with large scale recumbent folds within the moine nappe the results presented indicate that mylonitization is not limited to a single phase and raises the possibility that there may be earlier caledonian or possibly precambrian structural elements present in the eriboll region moines prior to much of the mylonitization

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

shear zone structures in the oygarden area west norway abstract investigation of shear related sheath like folds from blastomylonitic gneisses in the oygarden complex norway shows that the folds have not initiated with fold axes systematically normal to or with another fixed angle to the lineation their short limbs do however pass from a period of thickening to final thinning as the folds close and the short limbs become inverted the formation of the folds appears to be controlled by local geometries within the shear zone and we suggest three fold generating mechanisms in one the mylonitic foliation curves ahead of a tectonic lens and starts to fold and in another mesoscopic shear bands with normal fault geometries cut subplanar mylonites and folds are generated by the accretion of material in the evolving gap between the hangingwall and the footwall the third mechanism involves perturbation of the main foliation by slip along an inclined s foliation so that shear folds may develop all the mechanisms involve a rotation of the mylonitic foliation into the compressional field of the instantaneous strain ellipse

a proterozoic granulite facies terrane on roan mountain western blue ridge belt north carolina tennessee polymetamorphosed gneisses of proterozoic age crop out on roan mountain north carolina tennessee near the western edge of the blue ridge belt these gneisses display grenville age granulite facies assemblages including two pyroxene metabasites and gar net sillimanite orthoclase metapelites all gneisses were intruded by diabase dikes of the late precambrian bakersville gabbro paleozoic amphibolite facies metamorphism locally formed garnet and amphibole in mafic rocks and kyanite in metapelitic rocks two pyroxene geothermometry and mineral stability curves define temperature pressure ranges of 750 847 c and 6 5 8 0 kbar for the granulite facies metamorphism this metamorphism probably occurred within the lower crust at depths of 23 28 km pressure temperature conditions for the major paleozoic metamorphism are not well constrained but are estimated to be 700 740 c and 7 5 9 0 kbar

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

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

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

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

new timing and geochemical constraints on the capitanian middle permian extinction and environmental changes in deep water settings evidence from the lower yangtze region of south china the capitanian guadalupian witnessed one of the major crises of the phanerozoic and like many other extinctions it coincided with the eruption of a large igneous province in this case the emeishan traps of sw china however the timing and causal relationships of this event are in dispute this study concentrates on the deep water chert mudstone strata of the gufeng formation and its transition to the yinping formation at chaohu zircons from tuffs in the uppermost gufeng formation yield a u pb age of 261 6 1 6 ma and comparison with sections around emeishan suggests that the tuffs appeared in the jinogondolella altudaensis conodont zone and persisted to the jinogondolella xuanhanensis zone this coincides with the emeishan eruptions and suggests that the tuffs probably derived from this province mineralogical and geochemical characteristics also show the tuffs are of acid volcanogenic origin and have a geochemical fingerprint of the emeishan large igneous province our dating shows that a crisis amongst radiolarian and a subsequent productivity decline occurred during the middle capitanian prior to the guadalupian lopingian boundary the emeishan eruptions began immediately before this indicating a likely causal relationship between these events major regression and marine anoxia euxinia are two other important extinction relevant environmental changes that occurred during this critical interval

significance of folds and mylonites at the grenville front in ontario the grenville front is defined as the northwestern limit of the grenville structural province of the canadian shield stockwell 1964 wynne edwards 1972 it strikes northeast southwest and is approximately 1 600 km long extending from lake huron to the labrador sea the front separates the grenville structural province from either the nain churchill superior or southern structural province and is commonly associated with mylonitic fabrics see higgins 1971 for terms usage which strike approximately parallel to the front and dip steeply to the southeast

progressive development of structures in a ductile shear zone in the singhbhum shear zone of eastern india successive generations of folds grew in response to a progressive ductile shearing during this deformation a mylonitic foliation was initiated and was repeatedly transposed the majority of fold hinges were formed in an arcuate manner at low angles to the y axis in an e w trending subhorizontal position and major segments of the fold hinges were then rotated towards the down dip northerly plunging x axis the striping and intersection lineations were rotated in the same manner the down dip mylonitic lineation is a composite structure represented by rotated early lineations and newly superimposed stretching lineations the consistent asymmetry of the folds the angular relations between c and s surfaces and the evidence of two dimensional boudinage indicate that the deformation was non coaxial but with a flattening type of strain with 1 2 the degree of non coaxiality varied both in space and time from the progressive development of mesoscopic structures it is concluded that the 2 3 km wide belt of ductile shear gave rise to successive anastomosing shear zones of mesoscopic scale when a new set of shear lenses was superimposed on already sheared rocks the preexisting foliation generally lay at a low angle to the lenses no new folds developed where the acute angle was sympathetic to the sense of shear displacements where the acute angle was counter to the sense of shear the pre existing foliation lying in the instantaneous shortening field was deformed into a set of asymmetric folds

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

authigenic sulfide and carbonate mineral formation in holocene sediments of the baltic sea formation of authigenic sulfides and carbonates in holocene 14c dated sediments is interpreted based on analyses of cations fes s fes2 s corg and sulfur isotopes mineral distribution was studied in thin sections and mineral morphology with sem eds the sediments were deposited in the gotland deep baltic sea during freshwater and brackish stages calcium rich rhodochrosite mnco3 occurs in concentrations up to 17 dw in brackish water sediments and are mainly confined to 0 02 0 5 mm thick laminae the frequency with which these laminae occur suggests that they formed with a periodicity of one to a few years and their purity suggests that formation took place in a few weeks we propose that these carbonate laminae resulted from oxic water inflow to the euxinic basin mn ii dissolved in the water column was rapidly oxidized and large amounts of mn oxides reached the sediment reduction of these mn oxides in a high alkalinity environment facilitated rhodochrosite precipitation at the sediment surface pyrite in the brackish water sediments formed at or above the sediment water interface in an iron limited environment due to alternating oxic and euxinic conditions fes was oxidized resulting in a high fes2 sfes s ratio median 170 formation of iron sulfides in the freshwater sediments occurred below the sediment water interface in a sulfate limited environment as a result of the rapid exhaustion of reactive iron in the brackish water sediments excess h2s diffused downwards to pyritize the uppermost part of the underlying freshwater sediments

coupled primary production benthic foraminiferal assemblage and sulfur diagenesis in organic rich sediments of the benguela upwelling system abstract episodically deposited dark organic rich pleistocene and late pliocene sediments from the lower continental slope off southwest africa reveal complex interactions between changes in primary production benthic foraminiferal assemblage and anaerobic microbial processes the organic rich layers contain diatom assemblages characteristic of intense seasonal coastal upwelling whereas stratigraphically adjacent sediments reflect pelagic primary production coastal upwelling dominated depositional intervals coincide with periods of enhanced carbon flux to the seafloor enhanced organic carbon export during dark layer deposition was accompanied by decreases in the diversity of benthic foraminifera to few opportunistic species adapted to high phytodetritus accumulation rates and low o 2 conditions in all sediments the sulfur isotopic composition of pyrite indicates redox cycling of sulfide close to the sediment water interface the sulfur isotopic evidence and the permanent presence of abundant low o 2 adapted benthic foraminifera throughout the organic rich layers suggest an oxygenated benthic environment efficient oxidation of sulfide and removal of sulfide by sulfidization of organic matter inhibited buildup of toxic hydrogen sulfide from bacterial sulfate reduction at the sediment water interface these data imply that in continental slope sediments underneath productive surface waters benthic dysoxic conditions are maintained by the lateral advection of dissolved oxygen to support a small but well adapted benthic community

the geometry and kinematics of flow perturbation folds abstract minor folds formed synchronous with ductile deformation in high strain zones can preserve a record of the scale and kinematics of heterogeneous flow using structures associated with wnw directed caledonian thrusting in n scotland we show that localised perturbations in flow resulted in the generation of predominantly cylindrical minor folds with hinges lying at low angles to the transport direction these define a series of larger scale fold culminations reflecting surging flow or depressions reflecting slackening flow that are bisected by transport parallel culmination and depression surfaces the fold patterns suggest a dominance of layer normal differential shearing due to gradients in shear strain normal to transport culmination surfaces are marked by along strike reversals in the polarity of structural facing and vergence of minor folds which contrary to classic fold patterns define reverse asymmetric relationships culmination surfaces separate folding in to clockwise z folds and anticlockwise s folds domains relative to the transport lineation the dip of fold axial planes systematically increases as their strike becomes sub parallel to transport resulting in a 3d statistical fanning arrangement centred about the transport direction thus mean s and z fold axial planes intersect precisely parallel to the transport lineation and potentially provide a means of determining transport directions in cases where lineations are poorly preserved culminations display convergent fold patterns with fold hinges becoming sub parallel to transport towards the culmination surface and underlying detachment whilst axial planes define overall concave up listric geometries which are bisected by the culmination surface thus around culminations and depressions there are ordered scale independent relationships between transport direction shear sense fold facing vergence and hinge axial plane orientations the techniques described here can be applied and used predictively within any kinematically coherent system of ductile flow

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

organic facies variations source rock potential and sea level changes in cretaceous black shales of the quebrada ocal upper magdalena valley colombia a 290 m thick middle cretaceous black shale sequence in the upper magdalena valley a present day intramontane basin located between the central and eastern cordilleras of colombia was investigated with organic geochemical and microscopic analyses as a result of the investigation we were able to 1 differentiate four organic facies types 2 estimate their source rock potential and 3 integrate these facies into a sequence stratigraphic framework the four organic facies types were type c bc b and d type c contains a distinct terrigenous organic matter component in lowstand or highstand deposits organic facies type bc is characterized by an increase and a better preservation of marine organic matter bc belongs to the lower part of the transgressive systems tract sediments of organic facies type b have the highest amount of marine organic matter due to excellent preservation under anoxic conditions the absence of bioturbation and the enrichment of trace metals are further implications for deposition under anoxic conditions facies type b is found in the upper part of the transgressive systems tract and contains the best petroleum source rock potential facies b occurrence coincides with sea level highstand and correlates especially with a maximum flooding in northern south america during the turonian organic facies type d is also related to highstand deposits but shows a high rate of reworking and degradation of organic matter

porphyroclast systems as kinematic indicators porphyroclasts of relatively strong minerals in mylonites commonly have an internal monoclinic shape symmetry defined by tails of dynamically recrystallized material the geometry of a porphyroclast and its tails called a porhyroclast system can serve as a valuable indicator of the sense of vorticity porphyroclast systems have been divided into and types on the basis of the geometry of the tails types have wedge shaped recrystallized tails whose median lines lie on opposite sides of a reference plane parallel to the tails and containing the symmetry axis for the system types are further subdivided into a a types in which the porphyroclast is isolated in a relatively homogeneous matrix and b types in which the porphyroclast system is associated with a shear band foliation in the matrix types typically have narrow recrystallized tails whose median lines cross the reference plane adjacent to the porphyroclast consequently embayments of matrix material occur adjacent to the porphyroclasts and the tails display characteristic bends a porphyroclast system in a mylonite develops when the relatively weak dynamically recrystallized grain aggregate in the porphyroclast mantle changes its shape due to non coaxial flow in the adjacent matrix this behaviour has been modelled in shear box experiments passive marker lines around rigid cylinders embedded in silicone putty were subjected to simple shear the experiments were modified to simulate a change in recrystallization rate r with respect to rate of deformation by decreasing the diameter of the rigid cylinder during deformation at variable rates the ratio r appears to be one of the most important factors in determining which porphyroclast system will develop at high r values flow of recrystallized material away from the porphyroclast is continuously appended by the production of new grains and wedge shaped a type tails develop at low r values relatively few new grains are added to the tails which become thinned and deflected by drag due to the spinning motion of the porphyroclast in addition most porphyroclast systems at low shear strains are of a type or lack monoclinic symmetry whereas types are only developed at high shear strain values complex porphyroclast systems characterized by two generations of tails are observed in many of the natural and model shear zones studied and may form due to fluctuating r conditions that allow isolated a and type porphyroclast systems to be used as sense of vorticity indicators are the systems should have a monoclinic shape symmetry matrix grain size should be small with respect to porphyroclast size matrix fabric should be homogeneous deformation history should be simple and observations should be made on sections normal to the inferred bulk vorticity vector for the mylonite

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

planar dispersion of folds in ductile shear zones and kinematic interpretation of fold hinge girdles abstract as indicated by theory and multiple case studies hinge lines of minor folds in ductile shear zones are dispersed in a plane that is incompletely rotated toward mylonitic foliation this yields a geometric relationship between the fold hinge girdle and mylonitic foliation that can be used to determine sense of shear statistical study of published data from various shear zones and of new data from the blue ridge thrust complex reveals a small to moderate angle between the best fit plane to hinge lines and mean mylonitic foliation this angle is 4 9 in eight of 12 test cases moderate angles 22 34 are associated with nappes kinematic analyses of 12 fold hinge girdles indicate the sense of shear otherwise determined for host shear zones a theoretical model of contemporary fold rotation in simple shear closely simulates the geometric relationships described above for natural folds using this model large shear strains 10 are implied by the 4 9 angle between the fold hinge girdle and mylonitic foliation

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

ages of regional metamorphism and ductile deformation in the central and southern appalachians abstract a summary of available geochronology of deformational fabrics formed at greenschist and higher grades in the central and southern appalachians is presented as a map showing the ages of regional metamorphism and ductile deformation the ca 480 435 ma taconic event affected most of the piedmont and blue ridge provinces the ca 380 340 ma acadian event was milder and was centered in the west central piedmont and eastern blue ridge the 330 230 ma alleghanian event exhibits an abrupt ductile deformation front in the eastern piedmont and extends an unknown distance eastward below the atlantic coastal plain

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

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 model for stratigraphic and metamorphic inversions at sulitjelma central scandes the relationship between disposition of metamorphic isograds and early strain history is examined for the sulitjelma fold nappe of the central scandes evidence for stratigraphic inversion and the widespread inversion of the garnet isograd is reviewed and new evidence for the nature of early scandian deformation is presented a two stage model is presented which explains the inversions by i an initial phase of horizontal compression resulting in crustal thickening by vertical stretching during closure of a marginal basin followed by ii continued horizontal compression and crustal thickening by eastward directed nappe emplacement the emplacement of the sulitjelma fold nappe during the latter phase of progressive simple shear dominated deformation was accompanied by the development of sheath fold geometries and the overturning of isotherms to produce the widespread inversion of the garnet isograd

organic carbon sulfur relationships in sediment cores from the western and eastern continental margins of india abstract two sediment cores from the western continental margin wm1 wm2 and one core from the eastern continental margin em1 of india have been analysed to determine the relative importance of factors such as oxidizing reducing environment mass deposition and terrigenous influx on organic carbon sulfur relationship the results indicate that the cores consist of two stratigraphic units an upper unit of holocene age and a lower unit of late pleistocene age the upper unit of wm1 and wm2 has c s relationships similar to those of normal marine oxic sediments whereas in the lower unit the relationship is controlled by mass sedimentation processes and the amount of terrestrial organic matter in em1 organic carbon and sulfur do not show any significant correlation since their abundance is mainly controlled by the amount of detrital pyrite further a synthesis of data of all the three cores resulted in delineation of different clusters which reflect the importance of sedimentary processes and the types of organic matter

factors affecting the kinematic interpretation of asymmetric boudinage in shear zones abstract based on work along a major mylonite zone in the northern appalachians and scale model studies a new mechanism for the origin of asymmetric boudins in shear zones is proposed along the honey hill fault in southern connecticut granitic sills intruded into calc silicate gneisses and schists were oblique to the boundaries of the mylonite zone and experienced the following sequence in the production of sigmoidal boudins 1 as the calc silicate schists experienced mylonitization and flow the more competent coarse grained granitic sills deformed by extensional fracturing and quartz veining 2 continued extension of granitic sills was accommodated by normal shear on early formed quartz veins 3 continuing extension of sills and ductile modification of the corners of boudins resulted in granitic fish with tails which stream from the top of the boudin in the down dip direction and from the bottom in the up dip direction based on a variety of kinematic indicators the sense of asymmetry of the tails is identical to that expected for recrystallization tails on sheared augen structure models composed of silicone putty and plasticine were created to investigate the effect of pre shearing geometry on boudin evolution and were deformed in a simple shear device the models reproduce the kinematics deduced from field relations and suggest that one of the primary factors in controlling the amount of extension is the angle which early veins make with the shear zone boundary varying the angular relationships in the models suggests that other pre shearing geometric factors may affect the geometry of boudins formed in this way boudins formed through this mechanism appear very similar to hanmer s type ii asymmetric boudins because the pre shearing geometry can exert a control on boudin asymmetry caution should be used when attempting to deduce shear sense or shear strain values from asymmetric boudinage

the ashe metamorphic suite northwest north carolina metamorphism and observations on geologic history the ashe metamorphic suite ams consists of amphibolite schist and gneiss metabasalts pelitic schist and gneiss metasediments and ultramafic rocks evidence for four metamorphic events m1 m2 m3 m4 exists m1 affected only the ultramafic rocks in the suite the peak metamorphism m2 was an upper amphibolite facies event that affected all lithologies in the ams during the ordovician taconic orogeny three m2 zones of the amphibolite facies are recognizable in the pelitic rocks conditions during m2 are estimated to have been p 7 kb and t 700 degrees c the effects of m3 and m4 are minor in the pelitic and mafic rocks and identified with the growth of chlorite upon partial hydration of these rocks there are at least four possible plate tectonic sites for the origin of the ams 1 on a passive ensialic margin 2 on a passive ensimatic or transitional margin 3 on an active ensimatic margin and 4 in an ensialic or ensimatic back arc basin modified journal abstract

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

shear zone related folds folds in ductile shear zones are common structures that have a variety of origins these can be pre existing folds that become modified or folds developed during the shearing event among the syn shearing folds a second subdivision is based on the relative age of the folded surface which can be pre existing or newly formed during the shearing event in each of the three categories final fold geometry and orientation show complex relationships with the kinematic frame the final fold geometry depends on the vorticity within the shear zone the rheology and the initial orientation of the folded surface relative to the kinematic framework it follows that folds are complex structures difficult to use as kinematic indicators however in shear zones where undeformed wall rocks with pre shear structures are accessible and where kinematics can be well established folds can provide a valuable natural means to understand the initiation and evolution of structures under non coaxial regimes we point to the need of discriminating among different plausible categories based on the nature of the folded surface and on the inherent structural features of each category q 2004 elsevier ltd all rights reserved

sedimentary sulfur geochemistry of the paleogene green river formation western usa implications for interpreting depositional and diagenetic processes in saline alkaline lakes abstract the sulfur geochemistry of the lacustrine paleogene green river formation colorado utah and wyoming usa is unlike that of most marine and other lacustrine rocks distinctive chemical isotopic and mineralogical characteristics of the formation are pyrrhotite and marcasite high contents of iron mineral sulfides strikingly enriched in 34 s cyclical trends in sulfur abundance and 34 s values and long term evolutionary trends in 34 s values analyses that identified and quantified these characteristics include carbonate free abundance of organic carbon 0 13 47 wt total iron 0 31 13 wt reactive iron 70 of total iron total sulfur 0 02 16 wt acid volatile monosulfide s av disulfide s di 70 of total sulfur sulfate s so 4 and organosulfur s org isotopic composition of separated sulfur phases 34 s di av up to 49 and mineralogy morphology and paragenesis of sulfide minerals mineralogy morphology 34 s di av and 34 s org have a distinctive relation reflecting variable and unique depositional and early diagenetic conditions in the green river lakes when the lakes were brackish dissimilatory sulfate reducing bacteria in the sediment produced h 2 s which initially reacted with labile iron to form pyrite framboids and more gradually with organic matter to form organosulfur compounds during a long lived stage of saline lake water the amount of sulfate supplied by inflow decreased and alkalinity and ph of lake waters increased substantially extensive bacterial sulfate reduction in the water column kept lake waters undersaturated with sulfate minerals a very high h 2 s so 4 ratio developed in stagnant bottom water aided by the high ph that kinetically inhibited iron sulfidization progressive removal of h 2 s by coeval formation of iron sulfides and organosulfur compounds caused the isotopic composition of the entire dissolved sulfur reservoir to evolve to 34 s values much greater than that of inflow sulfate which is estimated to have been 20 a six million year interval within lake uinta cores records this evolution as well as smaller systematic changes in 34 s interpreted to reflect 100 000 year lake level cycles when porewater was exceptionally reducing unstable fes phases eventually recrystallized to pyrrhotite during diagenesis a much later reaction related to weathering altered pyrrhotite to marcasite

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

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

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

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

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

from phytoplankton to oil shale reservoirs a 19 million year record of the late cretaceous tethyan upwelling regime in the levant basin abstract the complexity of sedimentary organic matter formation its source to burial and influence on bottom water communities are addressed in this study of the 19 million years long upper cretaceous tethyan upwelling regime in the levant a multi proxy approach is amalgamated into a model through which the paleoceanographic complexity of an intense and long lasting upwelling system is better understood a shift in primary producer assemblages and reorganization of the bottom water bacterial consortium followed the campanian maastrichtian boundary enforcing conspicuous sedimentological and faunal changes the siliceous and phosphatic bearing sediments of the campanian gave way to maastrichtian uniform and regionally distributed organic rich carbonates accompanied by an increase in sedimentation rates from 1 to 6 cm kyr this has facilitated both the increase in organic matter production and its excellent preservation and through diagenetic pathways affected its elemental composition these paleoceanographic modifications have also affected foraminiferal assemblages from massive blooms of triserial buliminid benthic foraminifera during the campanian which have sequestered diatom chloroplasts to diverse trochospiral forms during the maastrichtian using nitrate instead of oxygen for their respiratory pathways we propose that shifts in the type of primary producers promote a change in the amount and type of preserved organic matter in bottom water communities on the lithological composition of the rock mass and ultimately on the hydrocarbon generation potential of the studied source rock the continued rise of southern tethyan sea level and global highstands during the upper maastrichtian culminating into arabian plate wide maximum flooding surfaces cause the migration of upwelling activity away from the study area terminating the high productivity sequence in the levant

s c mylonites two types of foliations are commonly developed in mylonites and mylonitic rocks a s surfaces related to the accumulation of finite strain and b c surfaces related to displacement discontinuities or zones of relatively high shear strain there are two types of s c mylonites type i s c mylonites described by berthe et al typically occur in deformed granitoids they involve narrow zones of intense shear strain which cut across mylonitic foliation type ii s c mylonites described here have widespread occurrence in quartz mica rocks involved in zones of intense non coaxial laminar flow the c surfaces are defined by trails of mica fish formed as the result of microscopic displacement discontinuities or zones of very high shear strain the s surfaces are defined by oblique foliations in the adjacent quartz aggregates formed as the result of dynamic recrystallization which periodically resets the finite strain clock these oblique foliations are characterized by grain elongations alignments of segments of the grain boundary enveloping surfaces and by trails of grains with similar c axis orientations examples of this aspect of foliation development in mylonitic rocks are so widespread that we suggest the creation of a broad class of s c tectonites and a deviation from the general tradition of purely geometric analysis of foliation and time relationships kinematic indicators such as those discussed here allow the recognition of kilometre scale zones of intense non coaxial laminar flow in crustal rocks and unambiguous determination of the sense of shear

rotation of fold hinge lines associated with simple shear during southerly directed thrusting ouachita mountains southeastern oklahoma abstract the broken bow uplift in southeastern oklahoma contains the oldest rocks exposed in ouachita orogenic belts and has experienced tour phases of deformation first generation folds are tight overturned sverging and have a well developed slaty cleavage second generation folds are coaxial with first generation structures are open to tight are inclined and reveal s vergence northerly dipping faults truncate second generation fold limbs third phase structures including recumbent folds and pencil structures are interpreted to be contemporaneous with s directed thrusting the hinges of earlier folds documented in the area least affected by thrusting are horizontal and trend e w the hinges of folds of the same generation within fault zones plunge 30 50 toward the north or northwest thus it is concluded that the earlier folds have been passively rotated during s direeted thrusting as have the contemporaneous folds and pencil structures a simple shear model associated with s directed thrusting is proposed to explain these geometrical relations the rotated fold hinges provide quantifiable shear strain gauges which can be used to quantify shear strain in the broken bow uplift as well as in other orogenic belts a model for shear strain calculation is developed using the general geometric relationship between fold hinge lines the shear direction and the shear plane

development of a high productivity and anoxic euxinic condition during the late guadalupian in the lower yangtze region implications for the mid capitanian extinction event abstract widespread marine anoxia is considered one of the most important causes for the mid capitanian mass extinction however the mechanisms and subsequent sulfidic process for the mid capitanian mass extinction are still debated here we focus on a comprehensive study including marine productivity and redox conditions of the lower yangtze area across the mid capitanian mass extinction based on multiple geochemical indicators our results show that the redox conditions and marine productivity have gone through three stages the pre extinction early middle capitanian is characterized by anoxic conditions with intermittent euxinic episodes and moderate high productivity whereas the middle capitanian is dominated by stronger euxinic conditions and higher productivity subsequently an oxic shallow water environment and low productivity are recognized by significant decreases in all of these geochemical indicators across the mid capitanian the appearance and development of the anoxic euxinic conditions was probably caused by high productivity related to enhanced upwelling which led to the intensified heterotrophic respiration and subsequent oxygen depletion of the water column more sluggish oceanic circulation that resulted from the global warming associated with the eruption of the emeishan large igneous province and upward movement of the chemocline due to great regression also further exacerbated the euxinic conditions during the middle capitanian the development of these euxinic conditions may have played a major role in triggering the super anoxic ocean and is also coincident with the mid capitanian biotic crisis which suggests the possible causal link between them with comprehensive analysis of profiles across the globe sulfidic models showing that the sulfidic water first occurred in the deep water during the early middle capitanian and shoaled to shallow water in the middle late capitanian could be established despite the fact that the temporally and spatially heterogeneous sulfidic processes in the late guadalupian are still debated

a marine biogeochemical perspective on black shale deposition abstract deposition of marine black shales has commonly been interpreted as having involved a high level of marine phytoplankton production that promoted high settling rates of organic matter through the water column and high burial fluxes on the seafloor or anoxic sulfidic water column conditions that led to high levels of preservation of deposited organic matter or a combination of the two processes here we review the hydrography and the budgets of trace metals and phytoplankton nutrients in two modern marine basins that have permanently anoxic bottom waters this information is then used to hindcast the hydrography and biogeochemical conditions of deposition of a black shale of late jurassic age the kimmeridge clay formation yorkshire england from its trace metal and organic carbon content comparison of the modern and jurassic sediment compositions reveals that the rate of photic zone primary productivity in the kimmeridge sea based on the accumulation rate of the marine fraction of ni was as high as 840 g organic carbon m 2 yr 1 this high level was possibly tied to the maximum rise of sea level during the late jurassic that flooded this and other continents sufficiently to allow major open ocean boundary currents to penetrate into epeiric seas sites of intense upwelling of nutrient enriched seawater would have been transferred from the continental margins their present location onto the continents this global flooding event was likely responsible for deposition of organic matter enriched sediments in other marine basins of this age several of which today host major petroleum source rocks bottom water redox conditions in the kimmeridge sea deduced from the v mo ratio in the marine fraction of the kimmeridge clay formation varied from oxic to anoxic but were predominantly suboxic or denitrifying a high settling flux of organic matter a result of the high primary productivity supported a high rate of bacterial respiration that led to the depletion of o2 in the bottom water a high rate of burial of labile organic matter albeit a low percentage of primary productivity in turn promoted anoxic conditions in the sediment pore waters that enhanced retention of trace metals deposited from the water column

early proterozoic deformation along the southern margin of the kisseynew gneiss belt trans hudson orogen a 30 ma progressive deformation cycle fold axes and lineations across the southern margin of the kisseynew gneiss belt were progressively reoriented from northwesterly to northeasterly during an early proterozoic southwest directed compressive deformation cycle partitioning of deformation resulted in a concentration of non coaxial strain along the boundary between the kisseynew gneiss belt and flin flon snow lake belt the structural evolution was complicated by streamlining of the movement vector around the comparatively rigid flin flon snow lake belt the relationship of metamorphic assemblages to kinematic fabrics indicates that deformation was coeval with a prograde retrograde metamorphic cycle progressive deformation occurred during a period of 30 ma which is consistent with phanerozoic orogenic time scales

obduction related planar and linear fabrics in oman under the oman ophiolites three different types of alpine synmetamorphic fabrics are seen each of them is taken as the signature of a particular stage of the obduction process the complex high grade fabric in the basal metamorphic sheet is linked to the intraoceanic detachment stage pre obduction sensu stricto the l s fabric of the muscat nappes and hatat internal border associated with low temperature high pressure metamorphism is regarded as the effect of an early obduction that is the epicontinental thrusting of the matrah peridotites the much simpler fabric of the anchizonal hawasina and autochthonous cover resulted from the gravity sliding of the semail ophiolites during the final obduction phase

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

geochemistry of reduced inorganic sulfur reactive iron and organic carbon in fluvial and marine surface sediment in the laizhou bay region china understanding the geochemical cycling of sulfur in sediments is important because it can have implications for both modern environments e g deterioration of water quality and interpretation of the ancient past e g sediment c s ratios can be used as indicators of palaeodepositional environment this study investigates the geochemical characteristics of sulfur iron and organic carbon in fluvial and coastal surface sediments of the laizhou bay region china a total of 63 sediment samples were taken across the whole laizhou bay marine region and the 14 major tidal rivers draining into it acid volatile sulfur chromium ii reducible sulfur and elemental sulfur total organic carbon and total nitrogen were present in higher concentrations in the fluvial sediment than in the marine sediment of laizhou bay the composition of reduced inorganic sulfur in surface sediments was dominated by acid volatile sulfur and chromium ii reducible sulfur in fluvial sediments sulfate reduction and formation of reduced inorganic sulfur were controlled by toc and reactive iron synchronously high c s ratios in the marine sediments indicate that the diagenetic processes in laizhou bay have been affected by rapid deposition of sediment from the yellow river in recent decades

early diagenesis of organic matter rich sediments in a ria environment organic matter sources pyrites morphology and limitation of pyritization at depth abstract the subtidal sediments of the inner ria de vigo nw spain are fine grained rich in organic matter and accumulate at rates of around 3 mm yr redoxomorphic pyrites formation was studied in four sediment cores four operationally defined iron fractions were determined hcl extracted silicate bound organic and pyritic and the dimensions and morphology of pyrites which mainly occurred as isolated framboids 3 5 m in diameter were studied by sem sediment appearance and degree of pyritization dop identified an oxic zone limited to the top few millimetres a suboxic zone that in most cores was just a few decimetres thick the exception was a core obtained in an area of strong turbulent currents and an underlying anoxic zone with dop values of around 60 pyritic iron increased at the expense of the hcl extracted fraction in approximately the top metre but no further pyrite formation occurred at greater depths pyrite formation in these lower levels was not limited by lack of either hcl extracted iron or metabolizable organic matter but apparently by lack of sulphate ion the diffusion of which to these depths was probably prevented by the fine texture of the sediments our findings highlight the interest of studying transitional sedimentary environments in order to explore in detail the geochemical parameters controlling pyrite formation

vergence and facing patterns in large scale sheath folds the careful geometric analysis of minor structural detail elucidates the relationships and evolution of associated large scale curvilinear hinge geometries developed during wnw directed caledonian thrusting exposed in neoproterozoic moine psammites of the moine nappe reversals in the polarity of structural facing associated with minor folding mark the position of major sheath folds which parallel transport upwardly convex sheaths closing in the direction of thrust transport cored by older gneissose basement inliers are termed culminations whilst those opening in the transport direction and cored by moine psammites are termed depressions sheath folds are bisected by transport parallel and foliation normal culmination depression surfaces which separate not only the reversals in facing but also delineate zones of minor fold hinge obliquity into clockwise and anticlockwise domains relative to the transport direction the sense of obliquity of minor z and s folds is thus dependent on position with respect to the surfaces of culmination and depression and not the fold axial surfaces surfaces of culmination and depression may be superimposed on original overturned antiformal and synformal folds to produce a variety of dome culmination on antiform saddle depression on antiform inverted saddle culmination on synform and basin depression on synform configurations the curvilinear hinges of minor folds may also be asymmetrical about the transport direction and within the plane of the regional foliation to define patterns of fold hinge line vergence classical concepts of fold limb vergence may thus relate to larger antiformal and synformal hinges whilst the fold hinge line vergence defines major curvilinear hinges associated with culminations and depressions major sheath folds may therefore be interpreted in terms of both minor fold hinge line and limb vergence coupled with fold axis obliquity and reversals in the polarity of structural facing the ability to recognise consistent and reliable structural relationships between facing and hinge obliquity at small scales indicates that the regional deformation process forms a linked and coherent system through several orders of magnitude 1999 elsevier science ltd all rights reserved

progressive refolding in ductile shear zones abstract the foliation formed in a ductile shear zone can become folded by continuing shear in the zone without the foliation having to enter the shortening sector of the flow field if the foliation lies parallel to the shear plane infinitesimal variations in the rate of shear strain cause compensating rotations that may amplify into folds small increases in the rate cause backward rotations counter to the sense of shear these do not amplify small decreases cause forward rotations that do amplify

strain and deformation mechanisms in the variscan nappes of vendee south brittany france abstract the variscan nappes of vendee south brittany france were displaced westward through a mechanism of regional subhorizontal ductile shear involving the entire body of the nappes ductile shear also affected the upper part of the silurian footwall including the rhyolite of chapelle hermier which was mylonitized and sheared with upward increasing intensity as well as the calcalkaline vendee porphyroids of volcanic and volcanoclastic origin which form a mylonite sheet outlining the major basal thrust zone of the nappes nappe displacement was accompanied by a severe extensional strain estimated at up to 300 400 in both the porphyroids and the rhyolite and indicating that the deformational history may have involved a gravitational spreading component within the mylonitic rhyolite accommodation of the bulk strain was mainly by solution assisted mass transfer as shown by 1 growth of quartz fibres in low pressure zones 2 development of polycrystalline ribbons through continuous growth of quartz grains in pressure shadows and 3 crystallization of muscovite at the expense of the felsitic groundmass a similar deformation process was probably active in the mylonitic porphyroids at the sole of the nappe suggesting that pressure solution flow was an important mechanism in nappe displacement

regulation of bacterial sulfate reduction and hydrogen sulfide fluxes in the central namibian coastal upwelling zone abstract the coastal upwelling system off central namibia is one of the most productive regions of the oceans and is characterized by frequently occurring shelf anoxia with severe effects for the benthic life and fisheries we present data on water column dissolved oxygen sulfide nitrate and nitrite pore water profiles for dissolved sulfide and sulfate 35 s sulfate reduction rates as well as bacterial counts of large sulfur bacteria from 20 stations across the continental shelf and slope the stations covered two transects and included the inner shelf with its anoxic and extremely oxygen depleted bottom waters the oxygen minimum zone on the continental slope and the lower continental slope below the oxygen minimum zone high concentrations of dissolved sulfide up to 22 mm in the near surface sediments of the inner shelf result from extremely high rates of bacterial sulfate reduction and the low capacity to oxidize and trap sulfide the inner shelf break marks the seaward border of sulfidic bottom waters and separates two different regimes of bacterial sulfate reduction in the sulfidic bottom waters on the shelf up to 55 of sulfide oxidation is mediated by the large nitrate storing sulfur bacteria thiomargarita spp the filamentous relatives beggiatoa spp occupy low o 2 bottom waters on the outer shelf sulfide oxidation on the slope is apparently not mediated by the large sulfur bacteria the data demonstrate the importance of large sulfur bacteria which live close to the sediment water interface and reduce the hydrogen sulfide flux to the water column modeling of pore water sulfide concentration profiles indicates that sulfide produced by bacterial sulfate reduction in the uppermost 16 cm of sediment is sufficient to account for the total flux of hydrogen sulfide to the water column however the total pool of hydrogen sulfide in the water column is too large to be explained by steady state diffusion across the sediment water interface episodic advection of hydrogen sulfide possibly triggered by methane eruptions may contribute to hydrogen sulfide in the water column

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

controls on c s ratios in hemipelagic upwelling sediments the relationship between organic carbon and reduced sulfur concentrations was investigated in hemipelagic sediments underlying highly productive regions of the ocean and oxic to suboxic waters the benguela upwelling area peru and oman margins at all three sites the degree of pyritization averaged close to 0 4 indicating that reactive iron was probably not limiting for pyrite formation complete sulfate reduction occurred in the upper sections of the sediments from the oman and peru margins however dissolved sulfate never decreased below 5 mm in the benguela upwelling sediments the authors attribute this to more advanced organic matter degradation at the benguela upwelling site c s ratios increased with increasing organic carbon concentrations at all sites for sediments with greater than 3 wt toc the c s ratio averaged about 1 3 and 1 8 times the normal marine ratio of 2 8 at the benguela upwelling and peru margin sites respectively but 2 9 times this value in the oman margin sediments they hypothesize that the quality of the organic matter undergoing burial and rates of near interfacial transport processes are the dominant controls on sulfur burial in these sediments

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

geochemical characteristics palaeoenvironment and formation model of eocene organic rich shales in the beibuwan basin south china sea abstract lacustrine organic rich shales in the eocene are the most important source rock in the beibuwan basin palynological petrographical and geochemical data were applied to define their palaeoenvironment formation and petroleum potential toc values range from 2 84 to 14 77 and the kerogens of these dark gray or brown shales with numerous lamalginites can be classified as oil prone type i and type ii1 biomarkers are characterized by a high abundance of c30 4 methylsteranes a low content of oleanane and diterpanes relatively abundant pentacyclic terpanes which indicate that the organic matter in the shales is typically algal and microbial origin abundance of amorphous organic matter the presence of low level gammacerane small amounts of pyrite pr ph ratios of 1 38 2 42 and v v ni ratios of 0 74 0 84 suggest that the organic rich shales were formed in a less oxic to anoxic stratified fresh brackish lake environment with a relatively low sedimentation rate for this starved lake basin the bloom and death of algae in nutrient rich surface water supplied a large amount of organic matter to the lacustrine sediments the oxygen depleted bottom waters of the palaeo lakes favored the accumulation and preservation of sedimentary organic matter resulting in the formation of the organic rich shale a high quality source rock future exploration or assessment of the petroleum potential of the basin could be assisted by considering the proposed formation model of the organic rich shales and their distribution relative to potential traps

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

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

sulfur isotope and porewater geochemistry of florida escarpment seep sediments abstract distributions of porewater constituents so 4 nh 4 cl co 2 and h 2 s solid phase iron and sulfur concentrations and the sulfur isotopic composition of dissolved and solid phases were investigated in sediments from abyssal seeps at the base of the florida escarpment despite the apparent similarity of seep sediment porewater chemistry to that of typical marine sediments undergoing early diagenesis relationships between chemical distributions and isotopic measurements revealed that the distribution of pore fluid constituents was dominated by processes occurring within the platform rather than by in situ microbial processes ammonium and sulfate concentrations were linearly correlated with chloride concentrations indicating that variations in porewater chemistry were controlled by the admixture of seawater and a sulfate depleted brine with a chlorinity of 27 5 1 9 and 2 2 1 3 mm ammonium concentration at sites dominated by seepage dissolved sulfate isotopic composition remained near seawater values despite depletion in porewater concentrations porewater co 2 concentrations were found to be elevated relative to seawater but not to the extent predicted from the observed sulfate depletion sediment solid phase sulfur was predominantly pyrite at concentrations as high as 20 s by weight in contrast to typical marine deposits pyrite concentrations were not related to the quantity of sedimentary organic matter pyrite 34 s values ranged from 29 to 21 cdt however only positive 34 s values were observed at sites associated with high pyrite concentrations isotopically heavy pyrite was observed at sites with porewater sulfate of seawater like isotopic composition isotopically light pyrite was associated with sites where porewater sulfate exhibited 34 s values greater than those in seawater indicating the activity of in situ microbial sulfate reduction thus dual sulfide sources are suggested to explain the range in sediment pyrite isotopic composition a 34 s enriched 10 to 20 source adverted from within the florida platform and a lighter 34 s depleted component generated in situ from microbial reduction of seawater sulfate the degree of pyritization of seep sediments was as high as 0 9 and was controlled by pyrite concentrations which varied over a wider range than did the non pyrite solid phase iron concentrations the highest non sulfide solid phase iron concentrations were observed in sediments that are believed to be at the front of the advancing seep fluids i e hemipelagic sediments newly exposed to the seep fluids indicating that dissolution of hemipelagic background sediment may be the source of at least half of the iron to the highly pyritized seep sediments porewater sulfide concentrations were variable reaching a maximum of 5 7 mm and were not correlated with the degree of pyritization of the sediments suggesting that iron was not particularly limiting to pyrite formation

successive development of plane noncylindrical folds in progressive deformation in the history of superposed deformations of the iron formations at the western border of the kolar gold field in s india an important event was the successive growth of broadly coaxial plane noncylindrical folds in course of a progressive deformation concomitant with development of ductile mesoscopic shear zones the noncylindrical folds were initiated as active folds by the creation of a buckling instability at successive stages on newly developed foliation surfaces the nucleation of noncylindrical folds and the subsequent axial plane folding of the tightened mature folds are explained by the mechanical inhomogeneity of the rocks and the heterogeneous character of strain the correlation between increasing tightness and increasing noncylindricity of the folds indicates that the initial curvatures of hinge lines were accentuated by an extension parallel to the subhorizontal stretching lineation from the patterns of deformed lineations over folds of varying tightnesses it is concluded that the passive accentuation of hinge line curvatures was mostly achieved when the folds had already become isoclinal or very tight

depositional history source rock quality and thermal maturity of upper ordovician lower silurian organic rich sedimentary rocks in the central part of the baltic basin lithuania abstract this study provides a comprehensive geochemical and mineralogical characterisation of the fine grained organic matter rich sedimentary rocks of the lower palaeozoic in the central part of the baltic basin western lithuania the primary objective was to deduce environmental conditions for the lower palaeozoic succession which is very well preserved in the baltic basin while the secondary goal was to obtain information on maturation and thermal history of the rocks the sample set covers different stratigraphic units of the ordovician lower silurian succession and was analysed with a wide range of different methods including elemental analysis organic petrography rock eval pyrolysis molecular geochemical analysis of saturated and aromatic hydrocarbon fractions inorganic geochemistry mineralogy xrf xrd analysis and magnetic susceptibility ms of rock samples their integration allowed a determination of the redox conditions paleoproductivity and clastic input during sediment deposition the fine grained sediments are dominated by clay minerals and quartz and to a lesser extent carbonate pyrite and feldspar microscopic analysis revealed abundant solid bitumen and zooclasts biomarker data indicate a marine origin for the precursor organic matter maturity parameters revealed the presence of a thermal maturity anomaly in the southwestern part of lithuania where the late phase of oil generation and possibly beginning of condensate wet gas generation with corresponding maximum paleotemperatures of 140 180 c has been reached bottom water conditions varied from oxic to anoxic euxinic during deposition driven by interaction of climate states water mass circulation and stratification water geochemistry and sea bottom bathymetry four shaly horizons at the upper ordovician fjacka and mossen fms silurian dobele fm and near llandovery wenlock boundary levels were recognized as being formed in oxygen depleted benthic settings as indicated by high toc and ts contents sedimentation features high metal enrichment or degree of piritization the deposition of highly organic matter rich silurian dobele fm might have coincided with oceanic anoxia and late aeronian bioevent accompanied by an upwelling regime with increased paleoproductivity the interpreted coarsening upward trend at the early silurian adavere regional stage terminates with fall in relative sea level at the llandovery wenlock boundary the geochemical proxies near llandovery wenlock boundary may reflect the perturbations in oceanic water geochemistry which in turn may have eventually led to ireviken mass extinction event

sulfidization processes in seasonally hypoxic shelf sediments a study off the west coast of india abstract continental shelves are the major sites for organic carbon burial and sulfate reduction organic carbon degradation and sulfidization along continental shelves are expected to play a significant role in global carbon sulfur iron c s fe cycles here we report sediment pore water chemistry and iron sulfur speciation in two short cores ssk 42 9 and 10 collected off malvan from the seasonally hypoxic shelf region off the west coast of india wci at water depths of 30 and 13 m respectively concentration profiles of pore water so42 nh4 dic hs and depth integrated sulfate reduction rates jso4 suggest a variable influence of sedimentation rates the composition of organic matter marine and terrestrial and anaerobic oxidation of methane aom on the pore fluid chemistry chromium reducible sulfur crs and organic bound sulfur obs are the detectable solid phase sulfur species in the studied sediment cores sulfur content and isotope ratios of chromium reducible sulfur crs and organic bound sulfur obs phases produced via hs sx2 pathways sulfidization and sulfurization show contrasting profiles in ssk42 9 and 10 apparently influenced by the availability of reactive iron the relative significance of early and late diagenetic processes source of obs detritus of marine origin and sulfurized organic molecules and diffusion of hs produced via aom across the smtz the marked influence of aom driven sulfate reduction and the diffusion of isotopically enriched hydrogen sulfide across the sulfate methane transition zone smtz is apparent from the 34scrs profiles in ssk 42 10 sediment toc ts ratios recorded in this study are significantly less than that of average modern marine surface sediments 2 8 1 underlying oxygenated water and this is attributed to the enhanced sulfidization and burial of iron sulfur minerals in the seasonally hypoxic regions since the inner shelf of wci experiences seasonal alternation from normoxia to hypoxia which may have a profound influence on the benthic community structure nature and depth of bioturbation bioirrigation we propose that the impact of these processes need to be studied at a significantly higher resolution for better understanding c s fe biogeochemical cycle

analysis of transpressional deformation from geometrical evolution of mesoscopic structures from phulad shear zone rajasthan india abstract transpressional deformation in ductile shear zones may be analyzed by simultaneous wall parallel simple shear with strain rate xy along with three dimensional coaxial deformation with strain rates x y and z several types of transpression may be distinguished on the basis of relative values of strain rate ratios x a y b and z c it is possible to identify the nature of transpressional deformation from a detailed analysis of shear zone structures in the phulad shear zone of rajasthan india evidence of general flattening a thrusting sense of shear occurrence of transport parallel stretching lineation frequent occurrence of sheath folds with apical direction parallel to the stretching lineation and occurrence of u shaped lineation patterns indicate that the deformation was transpressional with b a ratio ranging between 1 and 2 the bulk deformation was not dominated by simple shear but involved both simple and pure shear with extrusion along the transport direction much greater than along the vorticity vector rotation of long tectonic clasts caused reorientation of monoclinic rolling structures so that strongly monoclinic structures with opposite senses of asymmetry in different domains appear on subhorizontal outcrops parallel to the vorticity vector although the component of simple shear is zero on these surfaces

inorganic geochemistry of albian sediments from the lower saxony basin nw germany palaeoenvironmental constraints and orbital cycles abstract within the international albicore project upper albian sediments from a 245 m core kirchrode i drilled in hannover were studied by inorganic geochemical methods more than 650 samples minimum sample spacing 0 5 m were analysed for major and minor element concentrations this chemical database was used to reconstruct the depositional environment and to investigate the influence of high frequency milankovitch cycles on the chemical composition of the sediments the chemical composition of the sedimentary sequence is primarily controlled by variations in carbonate content corresponding to ca al ratios variations in both ti al and si al ratios are interpreted as fluctuations in detrital composition resulting from increases in smectite and quartz content in the upper section of the core high amounts of reactive iron but low pyrite concentrations the lack of enrichment of redox sensitive trace elements v cr and high mn concentrations indicate oxic bottom water conditions and the absence of an oxygen minimum zone for the upper albian at the kirchrode site the nutrient related trace elements ba p zn suggest a generally oligotrophic setting with slightly elevated productivity only in the uppermost upper albian only one layer was identified as containing volcanogenic material at 87 20 m this layer is characterised by elevated montmorillonite zr and nb mass balance calculations for the entire core suggest that the high mn values cannot be explained by riverine input alone therefore a coastal oxygen minimum zone south of the kirchrode site is postulated as an additional mn source cyclic variations in both carbonate content and al normalised concentrations of predominantly detrital elements like si and ti are seen in a 60 m interval 40 100 m where sedimentological palaeontological and geochemical data suggest stable depositional conditions although carbonate cyclicity cyclicity in detrital input and nutrient related element abundances do not correlate with each other three strong peaks in the results of spectral analysis of these chemical data for this interval appear to correspond to milankovitch frequencies in the eccentricity obliquity and precession bands

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

rotation of long tectonic clasts in transpressional shear zones abstract the two dimensional analysis of rotation of rigid ellipsoidal inclusions is not applicable to situations in which either the bulk deformation deviates from plane strain or one of the principal axes of the inclusion is at an angle to the vorticity vector both these situations may occur in certain types of transpressional ductile shear zones the model presented here shows how long cylindrical or ellipsoidal tectonic clasts with the longest axis parallel to the walls of the shear zone but at an angle to the vorticity vector rotate in transpressional shear zones long clasts initially at a low angle to the vorticity vector and at a large angle to the stretching lineation will rotate and tend to become subparallel to the stretching lineation the rotation of the principal axes of the elliptical cross section around the cylinder axis cannot be unlimited for any inclusion including the inclusion with circular cross section r 1 if the deformation is sufficiently large there is always a stable position of orientation the model explains simultaneous occurrence of monoclinic rolling structures in sections parallel and perpendicular to the vorticity vector depending upon the initial orientation the long axes of different clasts in the foliation plane may rotate clockwise and counterclockwise consequently opposite senses of asymmetry of rolling structures may appear in sections parallel to the vorticity vector

on the internal geometry of mylonite zones mylonite zones are generally characterized by abrupt and very large strain transitions which commonly result in excessively anastomosing schistosities on a wide range of scales when compared with nonmylonitic foliations this geometry is very susceptible to remodification during progressive mylonitization resulting in unusual and complex fold lineation and foliation geometries and interrelationships open folds of the mylonitic foliation with axes parallel to the stretching lineation in the surrounding mylonite cannot have formed by the rotation of fold axes through a large angle within their axial planes as has been usually proposed for isoclinal and sheath folds in mylonitic zones open folds initiate with axes parallel or close to the stretching lineation due to the geometric effects of folding a mylonitic foliation which anastomoses around an ellipsoidal pod of less deformed material this initial geometry also allows the generation of fold axes curved within their axial plane through 1800 about the stretching lineation at the time of nucleation successive mylonitic foliations develop during this folding and refolding process with boundaries that truncate and isolate earlier fold hinges and portions of fold limbs as a consequence stretching and intersection lineations can vary from plane to plane through the mylonite zone although careful examination often reveals a weak overprinting stretching lineation parallel to the bulk movement direction for the whole zone fold asymmetry in mylonite zones is a potential indicator of shear sense across a zone if the fold axes lie at an angle to the bulk stretching lineation direction in such circumstances however a single asymmetry projected onto a plane perpendicular to the mylonitic foliation and containing the bulk stretching lineation can indicate either sense of shear depending on a variety of factors these include whether the foliation folded is primary or mylonitic and in the latter case whether the mylonite zone formed with a steep dip and horizontal stretching lineation or in some other orientation the most satisfactory sense of shear indicator is the asymmetry of s and c planes

the burnsville fault evidence for the timing and kinematics of southern appalachian acadian dextral transform tectonics there has been a conspicuous absence of documented acadian structures in the blue ridge province of the southern appalachians even though a growing body of evidence suggests that the middle paleozoic acadian orogeny affected the rocks of this region new mapping along with structural petrologic and geochronologic data from western north carolina show that the contact between the metasedimentary and metavolcanic rocks of the ashe metamorphic suite and the grenville basement rocks of the western blue ridge corresponds to a devonian high grade dextral strike slip fault zone the burnsville fault timing of motion on the burnsville fault is constrained by field relationships metamorphic fabrics and assemblages and radiometric ages a u pb zircon crystallization age for a pegmatite sheared by the burnsville fault shows that the last movement on the fault must he younger than 377 ma previously published 4 0 ar 3 9 ar cooling ages show that the burnsville fault must be older than ca 360 ma we have mapped the burnsville fault for 100 km in northwest ern north carolina the gossan lead fault of northwesternmost north carolina and southwestern virginia is the likely continuation of the burnsville fault to the north east southwest of asheville north carolina the burnsville fault may connect to the devonian dahlonega shear zone or may be cut by post devonian thrust faults associated with the alleghanian orogeny diachroneity of acadian elastic wedge the presence of silurian devonian pull apart basins the presence of devonian high grade dextral shearing in the inner piedmont and recent plate reconstructions for the middle paleozoic support the interpretation that the late phase of the acadian orogeny in the southern appalachians was primarily a dextral transpressional event the burnsville fault and the inner piedmont formed the boundaries of a dextral transform margin that may have extended the length of the appalachian orogen this interpretation requires that models for the paleozoic tectonics of the appalachians incorporate major pre alleghanian dextral displacement

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

microtectonic evidence for eastward ductile shear in the jurassic orogen of sw japan abstract two jurassic deformation phases are responsible for the thrust and nappe structures in the infrastructure of the outer belt of the mesozoic chain of sw japan the first phase was synmetamorphic and took place under hp lt conditions microtectonic analysis shows that the penetrative deformation corresponded to a ductile shear directed from w to e parallel to the stretching and mineral lineation at the regional scale the first phase corresponded to the obduction of the greenschist nappes upon the kurosegawa continent during the second phase the greenschist nappes were sliced leading to an apparent reverse metamorphic zoning the first phase structures were then locally reworked by folds giving rise to an apparent westwards sense of shear

a structural analysis of the moine thrust zone between loch eriboll and foinaven nw scotland abstract the northern part of the moine thrust zone as exposed around the valley of srath beag sutherland was developed by thrusts propagating in the tectonic transport direction deformation on any particular thrust surface evolved from dominantly ductile to dominantly brittle with time the foreland has been progressively accreted onto the overriding moine thrust sheet by duplex formation a process which has continuously folded the roof thrust and the rocks above its hanging wall fold culminations and depression can be related to lateral ramps which may give the rocks above the hanging wall a complex history of extensional and compressional strains normal to the transport direction folds within the thrust zone are laterally independent because they are controlled by short lived variations in deformation style on an evolving thrust footwall topography therefore there may be no correlation between structures across or along the thrust zone this variation limits the construction of balanced cross sections as structure cannot be projected onto particular section lines

the geometry and topology of natural sheath folds a new tool for structural analysis abstract curvilinear sheath folds are classically depicted as displaying symmetrical geometries about two orthogonal mirror planes centred along the x y axial surface and the x z medial culmination depression surface which bisects the fold nose however 10 000 geometric analyses of minor folds and fabrics formed during ductile thrusting in the caledonides of northern scotland reveals that major dome and basin sheath folds can display distinct and predictable asymmetries across both axial and medial surfaces the strain is typically heterogeneous so that structural fabrics and younging evidence are preserved within sheath folds at varying stages of development this allows an analysis of the evolution of such structures from tongue folds to more extreme tubular forms geometric relationships between measured orientations of fold hinges axial planes extension lineations and foliations are compared on fabric topology plots ftps which provide an effective tool for monitoring planar and linear fabric rotations with increasing progressive non coaxial deformation they consistently display systematic variation from regions of lower to higher strain on passing from upper to lower fold limbs across major axial surfaces and on crossing medial surfaces from short to long hinge line segments axial and medial surfaces effectively therefore divide major sheath folds into quadrants with different amounts senses and combinations of planar and linear fabric rotation within each domain such heterogeneous deformation implies that models of intense non coaxial deformation uniformly affecting pre existing folds may overestimate bulk displacement and shear strain variable fold hinge line rotation about medial surfaces also provides an effective mechanism for the closure of major sheaths which may otherwise project for unfeasible distances in the x direction bedding cleavage intersections are developed at greater angles to the transport direction than fold hinges which they transect in a consistent and predictable sense thereby confirming the direction of fold rotation even in areas which lack information on fold facing in cross section asymmetric tear drop eyes indicate the sense of fold hinge line vergence whilst fold limb and hinge line asymmetry may be combined on 3 d vergence ranking and rotation grids which allow location and relative strain states of minor structures to be accurately predicted within the overall sheath framework systematic fabric analysis on ftps may be applied to the investigation of ductile deformation across a broad range of scenarios

organic carbon burial rates and carbon and sulfur relationships in coastal sediments of the southern baltic sea abstract organic c burial rates and c s relationships were investigated in the holocene sediment sequences of 3 shallow polymictic coastal lagoons in the southern baltic sea to better understand the biogeochemical cycling of c and s in these environmental systems the results show that these lagoons may have a considerable influence on the environmental status of the southern baltic sea area in having the potential to act as a temporary sink or source for heavy metals high organic c accumulation rates corg ar can be observed in the sediments due to a high organic matter supply from land and a high productivity of the water bodies as a result of eutrophication however organic c burial does not increase as a result of increasing sediment accumulation rates sar even when high sedimentation rates do occur there appears to be a thorough recycling and resuspension of the sediment enhancing the biological decay of organic matter before burial or the removal of organic matter from the system by transport that is why high sar in the coastal lagoons do not enhance pyrite formation and thereby permanent fixing of heavy metals in the sediments to the extent that could be expected from their magnitude initially there is a high potential for a temporary binding of heavy metals but the latter are likely to be subject to mobilization and redistribution within the sediments and the water column the patterns of burial of organic and mineral matter are different from those observed in the present day baltic proper implying possible important links in deposition between the central and coastal areas of the baltic sea and implications for c cycling in the ecosystem of the baltic sea