late miocene to pleistocene sequences at the new jersey outer continental shelf odp leg 174a sites 1071 and 1072 abstract 2 d seismic wireline log and core data at odp leg 174a sites 1071 and 1072 on the outer continental shelf of new jersey reveal two major depositional sequences of late miocene pliocene and pleistocene age the late miocene pliocene sequence is a thick 100 m deepening upward succession landward of the clinoform rollover and a shoaling upward succession seaward of the clinoform rollover the pleistocene sequence deepens abruptly near its base shoals upward and then deepens again before it is truncated by its overlying unconformity there is no onlap onto clinoforms no lowstand wedge in either sequence sequence stratigraphic analysis and a geometric depositional model are used to interpret that the unusually thick transgressive component of the late miocene pliocene sequence was formed by high frequency eustatic cycles 1 2 m y superimposed on a longer term eustatic rise 5 m y this conclusion is supported by independent evidence of eustasy the sequences of this study are correlated to sequences in the north atlantic coastal plain and in the great bahama bank these sequences have very different architectures than underlying middle miocene sequences which contain thick lowstand wedge deposits and are interpreted to have formed by high frequency eustatic cycles superimposed on longer term eustatic fall

undulating topography on the antarctic ice sheet revealed by noaa avhrr images undulating topography on the east antarctic ice sheet was clearly revealed by noaa avhrr the following three patterns of undulating topography were detected by using high pass filtered images from the visible to thermal infrared channels in coastal regions below 2000 m a s l undulation can be clearly detected by the fluctuation of reflectance in visible channel it has wavy structure with spacing less than 10 km and alignment at a right angle to the ice flow lines in the katabatic zone from 2000 m a s to 3000 m a s well defined fluctuations of albedo stpectrum can be seen with spacing from 10km to 20km aligned at right angles to the ice flow lines or prevailing katabatic wind direction ground survey data show that the undulating topography is associated with large variations of net accumulation rate on the inland plateau above 3000 m a s l undulation can be clearly seen in the fluctuation of thermal infrared channel in winter ground survey data show that the signal corresponds to the undulating topography the alignment of the undulation is at a right angle to the ice flow lines and the spacing is longer than 20 km the characteristics of these undulations represent the ice flow dynamics and

melting runoff and the formation of frozen lakes in a mixed snow and blue ice field in dronning maud land antarctica large scale melting phenomena such as meltwater drainage channels and meltwater accumulation basins of frozen lakes were surveyed on the land ice mass in jutulgryta dronning maud land antarctica during the norwegian antarctic research expedition in 1989 90 nare 1989 90 the largest frozen lake that was observed was close to 1 km in width these melting features were also detected in a landsat thematic mapper image recorded on 12 february 1990 then during nare 1993 94 a 5year glaciological programme was started in this area in spite of negative air temperatures and the presence of a frozen ice surface sub surface melting and runoff were found within the uppermost metre in blue ice fields the sub surface melting is a consequence of solar radiative penetration and absorption within the ice i e the solid state greenhouse effect temperatures in blue ice were about 6 c higher than for snow internal melt and meltwater transport were observed throughout the 1 month of measurements the conditions for active melting in jutulgryta are probably marginal a slight increase of air temperatures can result in more classical surface melting whereas a cooling may disable sub surface melting studies of how the extent and characteristics of the melting features change with time can be particularly valuable as indicators of climate change this ongoing programme clearly identifies the importance of analyzing how these melting features originate of mapping their present areal distribution of determining how sensitive they are to climate change and of studying changes in the past and possible changes in the future

variable methane fluxes in shallow marine systems over geologic time abstract carbon cycling is an important but poorly understood process on passive continental margins in this study we use the ionic and stable isotopic composition of interstitial waters and the petrology mineralogy and stable isotopic composition of authigenic carbonates collected from ocean drilling program odp leg 174a sites 1071 and 1072 to constrain the origin of the carbonates and the evolution of methane on the outer new jersey shelf the pore fluids of the new jersey continental shelf are characterized by 1 a fresh brackish water plume and 2 organic matter degradation reactions which proceed through sulfate reduction however only minor methanogenesis occurs the oxygen isotopic composition of the pore fluids supports a meteoric origin of the low salinity fluids authigenic carbonates are found in nodules thin 1 cm layers and carbonate cemented pavements siderite is the most common authigenic carbonate followed by dolomite and calcite the oxygen isotopic composition of the authigenic carbonates i e 1 3 6 5 peedee belemnite pdb indicates an origin in marine pore fluids the carbon isotopic composition of dolomite cements range from 16 4 to 8 8 pdb consistent with formation within the zone of sulfate reduction siderite 13c values show a greater range 17 67 16 4 but are largely positive mean 2 8 and are interpreted to have formed throughout the zone of methanogenesis in contrast calcite 13c values are highly negative as low as 41 7 and must have formed from waters with a large component of dissolved inorganic carbon derived from methane oxidation pore water data show that despite complete sulfate reduction methanogenesis appears not to be an important process presently occurring in the upper 400 m of the outer new jersey shelf in contrast the carbon isotopic composition of the siderites and calcites document an active methanogenic zone during their formation the methane may have been either oxidized or vented from shelf sediments perhaps during sea level fluctuations if this unaccounted and variable methane flux is an areally important process during neogene sea level fluctuations then it likely plays an important role in long term carbon cycling on passive continental margins

application of image cross correlation to the measurement of glacier velocity using satellite image data abstract image to image cross correlation software is applied to pairs of digital satellite images to map the velocity field of moving ice this technique uses small scale glacial surface features such as crevasse scars and snow dunes as markers on the surface of the moving ice displacements of the surface features are mapped by selecting small image areas centered on distinct features or by dividing a large area of densely featured glacial surface into a grid of areas and searching a subsequent image for matching areas using a cross correlation algorithm interpolation of the peak correlation values allows the displacements to be measured to subpixel accuracy resulting in very precise velocity measurements cross correlation is also applied to provide image coregistration in areas devoid of bedrock exposures in such areas subtle large scale topographic undulations in the ice surface related to underlying bedrock structure may be correlated by using large image areas and low pass filtered images both types of applications are demonstrated using ice stream d and ice stream e in west antarctica as test areas a high resolution map of the velocity field of the central portion of ice stream e generated by the displacement measuring technique is presented the use of cross correlation software is a significant improvement over previous manually based photogrammetric methods for velocity measurement and is far more cost effective than in situ methods in remote polar areas

the frontier mountain meteorite trap antarctica the frontier mountain blue ice field is an important antarctic meteorite trap which has yielded 472 meteorite specimens since its discovery in 1984 remote sensing analyses and field campaigns from 1993 to 1999 have furnished new glaciological data on ice flow ice thickness bedrock topography ice ablation and surface mass transport by wind along with detailed descriptions of the field situation at the trap this solid set of data combined with an updated meteorite distribution map and terrestrial ages available from literature allows us to better describe the nature of the concentration mechanism in particular we observe that the meteorite trap forms in a blue ice field 1 located upstream of an absolute and a shallow sub ice barriers 2 characterized by compressive ice flow with horizontal velocities decreasing from 100 to 10 cm year on approaching the obstacle 3 undergoing mean ablation rates of 6 5 cm year 4 nourished by a limited snow accumulation zone extending 20 km upstream of the blue ice area we also draw the following conclusions 1 the origin of the meteorite trap can be explained according to the present day glaciological situation 2 the meteorite concentration develops according to the general principles of the ice flow model 3 the accumulation model can be described as stagnant ice or slow moving ice against an absolute and submerged barriers according to the descriptive schemes present in literature 4 the frontier mountain ice field is an effective trap for meteorites weighing more than 200 g for smaller masses the combination of wind and glacial drift may remove meteorites in less than a few tens of thousands of years 5 although the activation age of the frontier mountain trap is not yet constrained we infer that one of the most important findsites may be as old as 50 ka predating the last glacial maximum

studies of snow surface characteristics by landsat tm in dronning maud land antarctica large scale melting phenomena like meltwater drainage channels and meltwater accumulation basins or frozen lakes have been surveyed on the land ice mass in dronning maud land antarctica these melting features were also detected in a landsat thematic mapper tm image recorded on 12 february 1990 image processing techniques such as principal component pc analysis band ratioing and histogram equalizing are carried out to emphasize the melting phenomena interestingly a histogram equalized single tm band 5 image appears to be a good discriminator leaving the melting phenomena as bright areas in the tm scene the largest frozen lake is close to 1km wide while some of the drainage channels stretch more than 5 km there is also a comparison of satellite derived and in situ reflectance and temperature the atmospheric corrected satellite data underestimate surface snow albedo by about 16 while tm measurements of surface temperature are 2 to 6 c lower than that measured on the ground

measuring snow and glacier ice properties from satellite satellite remote sensing is a convenient tool for studying snow and glacier ice allowing us to conduct research over large and otherwise inaccessible areas this paper reviews various methods for measuring snow and glacier ice properties with satellite remote sensing these methods have been improving with the use of new satellite sensors like the synthetic aperture radar sar during the last decade leading to the development of new and powerful methods such as sar interferometry for glacier velocity digital elevation model generation of ice sheets or snow cover mapping some methods still try to overcome the limitations of present sensors but future satellites will have much increased capability for example the ability to measure the whole optical spectrum or sar sensors with multiple polarization or frequencies among the methods presented are the satellite derived determination of surface albedo snow extent snow volume snow grain size surface temperature glacier facies glacier velocities glacier extent and ice sheet topography in this review emphasis is put on the principles and theory of each satellite remote sensing method an extensive list of references with an emphasis on studies from the 1990s allows the reader to delve into specific topics

snow megadunes in antarctica sedimentary structure and genesis 1 megadune fields occupy large areas in the interior of the east antarctic ice sheet and are the result of unusual snow accumulation and redistribution processes they therefore are important to surface mass balance and ice core interpretation field observations gps gpr and surface measurements have provided a detailed description of megadune sedimentation and morphology over a 70 km2 area located 200 km east of dome c a combination of remote sensing analysis using landsat and satellite radar altimetry and field measurements indicate that slope in the prevailing wind direction spwd and climatic conditions play a crucial role in megadune genesis the megadune areas tend to be characterized by slightly steeper regional slope and the presence of highly persistent katabatic winds the megadunes represent 2 to 4 m amplitude waves of 2 to 5 km wavelength formed by variable net accumulation ranging between 25 leeward faces to 120 windward faces of the accumulation in adjacent nonmegadune areas leeward faces are characterized by glazed sastrugi free surfaces and extensive depth hoar formation windward faces are covered by large rough sastrugi up to 1 5 m in height

dissolved rare earth elements in the southern ocean cerium oxidation and the influence of hydrography abstract analysis of dissolved ree distributions in the southeastern atlantic ocean has revealed that progressive oxidative removal of dissolved ce from deepwater 1 km occurs over the mixing time of the oceans ce anomaly ce ce values measured in deep waters from the southeastern atlantic are similar to but slightly higher than those from deep ocean stations throughout the indian and pacific oceans typically falling in the range 0 08ce ce 0 12 only deepwater samples from the north atlantic exhibit values greater than ce ce 0 12 with the exception of southeastern atlantic bottomwaters which are influenced by antarctic bottomwater covariation of dissolved ree concentrations with salinity and or dissolved si concentrations at this site has allowed dissolved ree compositions for various southern ocean water masses to be predicted end member concentrations for antarctic bottom water aabw derived in this way indicate high dissolved ree concentrations similar to average pacific deep water but with significantly enhanced dissolved ce concentrations and less pronounced hree enrichment this result is consistent with the proximity of our study site to active aabw deepwater formation and evolution of that water mass during transport to the pacific ocean

impact of spatial spectral and radiometric properties of multispectral imagers on glacier surface classification abstract using multispectral remote sensing glacier surfaces can be classified into a range of zones the properties of these classes are used for a range of glaciological applications including mass balance measurements glacial hydrology and melt modelling however it is not immediately evident that multispectral data should be optimal for imaging glaciers and ice caps thus this investigation takes an inverse perspective taking into account spectral and radiometric properties in situ spectral reflectance data were used to simulate glacier surface response for a suite of multispectral sensors sensor simulated data were classified and compared in addition airborne multispectral imagery was classified for a range of spatial resolutions and intercompared in three different ways in these analyses the most important property which determined the suitability of a multispectral imager for glacier surface classification was its radiometric range i e gain settings low resolution imagery 250 m pixels is too coarse to represent the true complexity present on a glacier while medium resolution imagery 60 m 30 m or 20 m accurately represented the results derived from high resolution airborne imagery of those studied here the satellite imagers currently in use that are most suitable for glacier surface classification are landsat tm etm and aster each with particular gain settings both sentinel 2 and the oli on landsat 8 are also expected to be similarly qualified landsat mss is also found to be radiometrically well suited for glacier surface classification but its lower spatial resolution makes it a secondary selection

tide transformation in the guadalquivir estuary sw spain and process based zonation an edited version of this paper was published by agu copyright 2012 american geophysical union

the process of glauconitization chemical and isotopic evidence sequential leaching experiments were made on recent glauconies and clay fractions of the associated mud from off shore africa near the estuary of the congo river analyses of major rare earth elements ree and nd isotopic compositions on the resulting leachate and residue pairs allow identification of at least three important and isotopically distinct components which contributed to the glauconitization process 1 a detrital component with relatively high 87sr 86sr and relatively low 143nd 144nd isotopic ratios 2 a phosphate phase rich in ree and sr with sea water sr and nd isotopic characteristics 3 a component rich in organic matter and ca with a sea water sr isotopic signature a relatively low nd isotopic composition and elevated sm nd ratios this latter component probably represents the suspended organic and carbonate rich river load the detrital and the river components were mixed up in the muddy off shore sediment ingested by worms and integrated into faecal pellets the resulting material has sr and nd isotopic signatures intermediate between those of the detrital and river components and represents the precursor of the glaucony minerals during the subsequent dissolution crystallization process the glauconitic pellets remain isotopically closed to any external supply but expulsion of sr and nd with increasing degree of maturation is observed without any effect on the sr and nd isotopic compositions at a higher maturation stage k2o 4 5 the sr and nd isotopic compositions tend to decrease and increase respectively approximating the isotopic composition values of the phosphate rich phase because the sr and nd concentrations decrease the evolution of the glauconies toward lower sr and higher nd isotopic compositions can only be explained by expulsion of sr and nd of the detrital component with high sr and low nd isotopic signatures dissolution of the chemically unstable wormdigested clay material from mud may be responsible for the liberation of these elements consequently the phosphate rich phase with sea water sr and nd isotopic signatures becomes increasingly important for the isotopic characteristics of the maturing glauconite grains and sea water isotopic signatures can be reached during the stage of mature glauconite k2o 6 5 without chemical exchange with the depositional environment

snow dunes and glazed surfaces in antarctica new field and remote sensing data as part of the international trans antarctic scientific expedition project the italian antarctic programme undertook two traverses from the terra nova station to talos dome and to dome c along the traverses the party carried out several tasks drilling glaciological and geophysical exploration the difference in spectral response between glazed surfaces and snow makes it simple to identify these areas on visible near infrared satellite images integration of field observation and remotely sensed data allows the description of different mega morphologic features wide glazed surfaces sastrugi glazed surface fields transverse dunes and megadunes topography global positioning system ground penetrating radar and detailed snow surface surveys have been carried out providing new information about the formation and evolution of mega morphologic features the extensive presence up to 30 of glazed surface caused by a long hiatus in accumulation with an accumulation rate of nil or slightly negative has a significant impact on the surface mass balance of a wide area of the interior part of east antarctica the aeolian processes creating these features have important implications for the selection of optimum sites for ice coring because orographic variations of even a few metres per kilometre have a significant impact on the snow accumulation process remote sensing surveys of aeolian macro morphology provide a proven high quality method for detailed mapping of the interior of the ice sheet s prevalent wind direction and could provide a relative indication of wind intensity

mapping tide water glacier dynamics in east greenland using landsat data landsat multispectral scanner and thematic mapper images were co registered for the kangerdlugssuaq fjord region in east greenland and were used to map glacier drainage basin areas changes in the positions of tide water glacier termini and to estimate surface velocities of the larger tide water glaciers statistics were compiled to document distance and area changes to glacier termini the methodologies developed in this study are broadly applicable to the investigation of tide water glaciers in other areas the number of images available for consecutive years and the accuracy with which images are co registered are key factors that influence the degree to which regional glacier dynamics can be characterized using remotely sensed data three domains of glacier state were interpreted net increase in terminus area in the southern part of the study area net loss of terminus area for glaciers in upper kangerdlugssuaq fjord and a slight loss of glacier terminus area northward from ryberg fjord local increases in the concentrations of drifting icebergs in the fjords coincide with the observed extension of glacier termini positions ice surface velocity estimates were derived for several glaciers using automated image cross correlation techniques the velocity determined for kangerdlugssuaq gletscher is approximately 5 0 km a 1 and that for kong christian iv gletscher is 0 9 km a 1 the continuous presence of icebergs and brash ice in front of these glaciers indicates sustained rates of ice front calving

the miocene palaeoenvironmental and palaeoceanographic evolution of the gippsland basin southeast australia a record of southern ocean change abstract the gippsland basin in southeastern australia preserves up to 2 5 km thick tertiary to recent marine carbonate sediments included in the seaspray group during the neogene the seaspray group carbonates of the mackerel and flounder petroleum fields lay at the shelfal to bathyal palaeoenvironmental transition an ideal palaeoceanographic setting to study the neogene history of events in the evolving southern ocean seismic foraminiferal and facies analyses of the miocene seaspray group sediments at the mackerel 1 and flounder 1 wells have revealed the following palaeoenvironmental history of the area relatively cool to temperate upwelling conditions prevailed in the area during the earliest miocene during this time low energy upper slope globigerina ooze calcareous mudstone was deposited in the oxygen minimum zone during the early to lower middle miocene upper slope marl was deposited in oligotrophic conditions the presence of neritic subtropical foraminifera and abundant shallow and deep dwelling warm to cool temperate plankton in the upper slope suggests that warm poorly stratified oceanic conditions prevailed in the region this upper early miocene warm phase and mid miocene climatic optimum in gippsland corresponds to a time when global ocean conditions were much warmer and less vertically and latitudinally stratified than at present these oceanic conditions were associated with a reduced east antarctic ice sheet a higher sea level a relatively weak antarctic circumpolar current and weak atmospheric and wind driven circulation during the upper middle miocene to late miocene cool phase after c 14 5 ma strong upwelling and cooler oceanic conditions prevailed in the outer shelf to upper slope canyon facies in gippsland the occurrence of common deep dwelling plankton taxa in this interval suggests that regional oceanic conditions became more vertically stratified during this time from 14 5 and 5 million years ago the middle to late miocene palaeoenvironmental change recorded in seaspray group sediments corresponds to global cooling and major antarctic ice sheet expansion when the world s oceans became more vertically and latitudinally stratified from around 14 5 million years the transition from a warm miocene optimum to cooler oceanic conditions was associated with a strengthened antarctic circumpolar current and more intense wind driven atmospheric circulation in the southern ocean

reflectances of glaciers as calculated using landsat 5 thematic mapper data landsat 5 thematic mapper tm data have been used in previous work in order to locate zones of similar spectral reflectance on glaciers in austria and alaska and to relate these zones to the glacier facies which are indicative of glacier mass balance in this paper landsat 5 digital numbers dns have been used to compute the at satellite planetary reflectances p on spectrally similar zones on the meares and schwanda glaciers in alaska and the grossglockner glacier group in austria the patterns of tm derived reflectances in the ablation areas of the grossglockner glacier group and the meares glacier compare favorably with published reflectance curves measured on the surface of glacier ice though the surface reflectance of snow covered ice is higher than the landsat derived reflectance for the glaciers studied the accuracy of the at satellite planetary reflectances is shown to be affected by topographic and atmospheric effects and by the anisotropic nature of snow reflectance use of reflectance values for analysis of snow and ice facilitates scene to scene comparisons of glaciers

oligocene to holocene glauconite phosphorite grains from the head of the cape canyon on the western margin of south africa abstract glauconite and carbonate fluorapatite cfa are significant components of the condensed upper oligocene to holocene sediment succession recovered from the western margin of southern africa the detailed texture and geochemistry of these glauconite phosphorite grains are reported here within the stratigraphic framework established on the outer continental shelf in the head of the cape canyon area three texturally and stratigraphically distinct glauconite grain types are recognised oligo miocene infilled foraminiferal tests mio pliocene green and quaternary dark green to black grains most of these glauconitic grains include a minor to significant amount of cfa the upper oligocene to lower miocene sediment succession is dominated by fine sand sized benthic and planktic foraminifera glauconite grains constitute 20 50 of the sediment and represent tests infilled by variable proportions of glauconite and cfa cement with the test wall replaced by cfa only glauconite cfa formation during the late oligocene to early miocene was associated with warm water upwelling coupled with third order marine transgressions rare earth element ree chemistry indicates that sub oxic conditions prevailed during diagenesis mio pliocene green and quaternary dark green to black medium sand sized glauconite grains constitute between 20 and 95 of these predominantly siliciclastic sediments the green to black glauconite grains are texturally different but have similar major and ree chemistry since the mid miocene formation of glauconite cfa grains is associated with cold water upwelling and detrital fe rich terrigenous mud deposition in oxic to suboxic bottom waters analogous to the holocene coast parallel organic rich mudbelt on the shelf the texture of these grains indicates repeated cycles of glauconite and cfa authigenesis during marine transgressions and winnowing and reworking during marine regressions

antarctica measuring glacier velocity from satellite images many landsat images of antarctica show distinctive flow and crevasse features in the floating part of ice streams and outlet glaciers immediately below their grounding zones some of the features which move with the glacier or ice stream remain visible over many years and thus allow time lapse measurements of ice velocities measurements taken from landsat images of features on byrd glacier agree well with detailed ground and aerial observations the satellite image technique thus offers a rapid and cost effective method of obtaining average velocities to a first order of accuracy of many ice streams and outlet glaciers near their termini