mangrove forest evolution in a sediment rich estuarine system opportunists or agents of geomorphic change the majority of the world s mangrove forests occur on mostly mineral sediments of fluvial origin two perspectives exist on the biogeomorphic development of these forests i e that mangroves are opportunistic with forest development primarily driven by physical processes or alternatively that biophysical feedbacks strongly influence sedimentation and resulting geomorphology on the firth of thames coast new zealand we evaluate these two possible scenarios for sediment accumulation and forest development using high resolution sedimentary records and a detailed chronology of mangrove forest avicennia marina development since the 1950s cores were collected along a shore normal transect of known elevation relative to mean sea level msl activities for lead 210 pb 210 caesium 137 cs 137 and beryllium 7 be 7 and sediment properties were analysed with pb 210 sediment accumulation rates sars compensated for deep subsidence similar to 8 mm yr 1 used as a proxy for elevation gain at least four phases of forest development since the 1950s are recognized an old growth forest developed by the late 1970s with more recent seaward forest expansion thereafter excess 210pb profiles from the old growth forest exhibit relatively low sars near the top 7 12 mm yr 1 and bottom 10 22 mm yr 1 of cores separated by an interval of higher sars 33 100 mm yr 1 a general trend of increasing sar over time characterizes the recent forest biogeomorphic evolution of the system is more complex than simple mudflat accretion progradation and mangrove forest expansion surface elevation gain in the old growth forest displays an asymptotic trajectory with a secondary depocentre developing on the seaward mudflat from the mid 1970s two to ten fold increases in 210pb sars are unambiguously large and occurred years to decades before seedling recruitment demonstrating that mangroves do not measurably enhance sedimentation over annual to decadal timescales this suggests that mangrove forest development is largely dependent on physical processes with forests occupying mudflats once they reach a suitable elevation in the intertidal copyright c 2015 john wiley sons ltd

the structure biological activity and biogeochemistry of cryoconite aggregates upon an arctic valley glacier longyearbreen svalbard glacier surfaces support unique microbial food webs dominated by organic and inorganic debris called cryoconite observations from longyearbreen spitsbergen show how these aggregate particles can develop an internal structure following the cementation of mineral grains mostly quartz and dolomite by filamentous microorganisms measurements of carbon and dissolved o2 show that these microorganisms mostly cyanobacteria promote significant rates of photosynthesis average 17 gc g 1 d 1 which assist aggregate growth by increasing the biomass and producing glue like extracellular polymeric substances the primary production takes place not only upon the surface of the aggregates but also just beneath due to the translucence of the quartz particles however since total photosynthesis is matched by respiration average 19 gc g 1 d 1 primary production does not contribute directly to cryoconite accumulation upon the glacier surface the microorganisms therefore influence the surface albedo most by cementing dark particles and organic debris together rather than simply growing over it time lapse photographs show that cryoconite is likely to reside upon the glacier for years as a result of this aggregation these observations therefore show that a better understanding of the relationship between supraglacial debris and ablation upon glaciers requires an appreciation of the biological processes that take place during summer

bayhead deltas and shorelines insights from modern and ancient examples abstract bayhead deltas are important components of the rock record as well as modern estuaries hosting important hydrocarbon reservoirs and many coastal cities ports and large expanses of wetlands despite their significance few studies have summarized their occurrence and sedimentary characteristics in this paper we review the stratigraphic sedimentary and geomorphic characteristics of 68 modern and ancient bayhead deltas bayhead deltas are found in incised valleys structural basins fjords interdistributary bays of larger open ocean deltas and other backbarrier environments except for within fjords they generally prograde into shallower and more brackish waters than their open ocean equivalents as a result 80 of modern 68 of quaternary and 67 of ancient bayhead deltas have clinoform thicknesses of 10 m or less with 73 of modern bayhead deltas having clinoform thicknesses of 5 m or less additionally 89 of modern 81 of quaternary and 77 of ancient bayhead deltas examined are fluvial dominated we distinguish true bayhead deltas from their genetically similar bayhead shorelines which are not constructional features but sites of enhanced marsh or estuarine sedimentation near river mouths with inadequate rates of sediment delivery to form distributary channels and prograde into the estuary or lagoon we also distinguish confined bayhead deltas found in incised valleys structural basins and fjords from unconfined bayhead deltas found as incipient lobes of larger delta complexes and other back barrier lagoons the architecture of confined bayhead deltas is largely influenced by the limited accommodation brought about by the walls of the flooded valleys in which they are located as such confined bayhead delta ontogeny is controlled by many autogenic interactions within these valley walls both confined and unconfined bayhead deltas are sensitive to sea level rise climate controlled changes in sediment flux and tectonics their relatively small size connection with the terrestrial system and protected nature make them the ideal depositional system to record earth history including sea level and climate changes

geologic studies of the columbia plateau part ii upper miocene basalt distribution reflecting source locations tectonism and drainage history in the clearwater embayment idaho the clearwater embayment of western idaho represents the easternmost encroachment of columbia river basalt against the western side of the rocky mountains several new units of the columbia river basalt group have been identified in the embayment and the distribution of these and other previously recognized flows reflects 1 the location of vents feeder dikes and source areas from which the flows were erupted 2 tectonic events during the eruptive episode and 3 the development of erosional channels that were filled subsequently by successive flows the lewiston and stites basins were filled by wanapum and saddle mountains flows erupted in the north fork of the clearwater river area flows poured into the stites basin from surrounding plateau surfaces but they spread into the lewiston basin after advancing down ancestral clearwater river canyons as an ancestral clearwater river would lose its canyon to an invading flow water would spill onto the low lying areas of the lewiston basin and deposit sediment this event was repeated several times and resulted in a sequence of alternating flows and intercalated sediment in the lewiston basin

cryoconite hole connectivity on the wright lower glacier mcmurdo dry valleys antarctica cryoconite holes can be important sources and stores of water and nutrients on cold and polythermal glaciers and they provide a habitat for various forms of biota understanding the hydrological connectivity of cryoconite holes may be the key to understanding the transport of nutrients and biological material to the proglacial areas of such glaciers this paper aims to characterize and explain spatial variability in the connectivity of ice lidded cryoconite holes on a small piedmont glacier in the mcmurdo dry valleys through geochemical analysis of cryoconite hole waters solute concentrations in both surface and near surface ice and cryoconite holes vary greatly along the glacier centerline and all sample types displayed similar spatial patterns of variability using chloride as a tracer we estimated variations in cryoconite hole connectivity along the glacier centerline we found that a previously used mass transfer method did not provide reliable estimates of the time period for which cryoconite hole waters had been isolated from the atmosphere we attribute this to spatial variability in both the chloride content of the surface ice and surface ablation rates the approach may however be used to qualitatively characterize spatial variations in the hydrological connectivity of the cryoconite holes these results also suggest that ice lidded cryoconite holes are never truly isolated from the near surface drainage system

mid miocene propagation of the yellowstone mantle plume head beneath the columbia river basalt source region columbia river flood basalt volcanism is the product of mid miocene distortion of the yellowstone mantle plume head against the precambrian margin of north america the overall migration pattern of columbia river basalt vents reflects northward propagation of the plume head beneath the west southwest migrating north american plate thermal uplift mimics the vent migration over the 1 5 m y of grande ronde basalt extrusion the projected crest of the plume head migrated 105 km 7 cm yr from the chief joseph dike swarm east oortheast into the clearwater embayment where uplift occurred over the same period at a rate of 0 67 mm yr chemical variations reflect progressive melting of the plume and mantle lithosphere followed by the mixing of these components with an enriched source from the overriding craton rapid thickening of the plume head against the cratonic margin led to decompressional melting and magma rise beneath a thin oceanic lithosphere of accreted terranes

evolution of cryoconite holes and their contribution to meltwater runoff from glaciers in the mcmurdo dry valleys antarctica cryoconite holes are water filled holes in the surface of a glacier caused by enhanced ice melt around trapped sediment measurements on the ablation zones of four glaciers intaylorvalley antarctica show that cryoconite holes cover about 4 6 of the ice surface they typically vary in diameter from 5 to 145 cm with depths ranging from 4 to 56 cm in some cases huge holes form with 5 m depths and 30 m diameters un like cryoconite holes elsewhere these have ice lids up to 36 cm thick and melt from within each spring about one half of the holes are connected to the near surface hydrologic system and the remainder are isolated the duration of isolation estimated from the chlor ide accumulation in hole waters commonly shows ages of several years with one hole of 10 years the cryoconite holes in the mcmurdo dryvalleys create a near surface hydro logic system tens of cm below the ice surface the glacier surface itself is generally frozen and dry comparison of water levels between holes a few meters apart shows independent cycles of water storage and release most likely local freeze thaw effects control water passage and therefore temporary storage rough calculations indicate that the holes gen erate at least 13 of the observed runoff on the one glacier measured this hydrologic system represents the transition between a melting ice cover with supraglacial streams and one entirely frozen and absent of water abstract cryoconite holes are water filled holes in the surface of a glacier caused by enhanced ice melt around trapped sediment measurements on the ablation zones of four glaciers intaylorvalley antarctica show that cryoconite holes cover about 4 6 of the ice surface they typically vary in diameter from 5 to 145 cm with depths ranging from 4 to 56 cm in some cases huge holes form with 5 m depths and 30 m diameters un like cryoconite holes elsewhere these have ice lids up to 36 cm thick and melt from within each spring about one half of the holes are connected to the near surface hydrologic system and the remainder are isolated the duration of isolation estimated from the chlor ide accumulation in hole waters commonly shows ages of several years with one hole of 10 years the cryoconite holes in the mcmurdo dryvalleys create a near surface hydro logic system tens of cm below the ice surface the glacier surface itself is generally frozen and dry comparison of water levels between holes a few meters apart shows independent cycles of water storage and release most likely local freeze thaw effects control water passage and therefore temporary storage rough calculations indicate that the holes gen erate at least 13 of the observed runoff on the one glacier measured this hydrologic system represents the transition between a melting ice cover with supraglacial streams and one entirely frozen and absent of water

a case of simple magma mixing in the columbia river basalt group the wilbur creek lapwai and asotin flows saddle mountains formation three small sequential saddle mountains flows occupying similar areas on the columbia plateau were erupted over a short interval of time in the lewiston basin area the middle flow of the trio lapwai has intermediate mineralogy and lies on a straight mixing line between the other two flows for virtually all twenty five elements analyzed systematic changes in the ratios of incompatible elements demonstrate that these relationships are a result of magma mixing rather than either crystal fractionation or variable degrees of partial melting the lapwai flow has a composition approximately midway between the two homogeneous end members and is itself relatively homogeneous this implies efficient mixing between equal amounts of asotin and wilbur creek magmas and suggests that mixing was completed in a magma reservoir prior to eruption the wilbur creek and asotin end members have isotopic features which are believed to result from different degrees of assimilation of crustal material by magma derived from an enriched mantle source carlson 1984 the mixing processes described here cannot be related to that earlier mantle crust mixing process

the chemical composition of runoff from canada glacier antarctica implications for glacier hydrology duringa cool summer variations in the chemical composition of subsurface runoff within canada glacier antarctica are used to identify the main source waters which are vertical surfaces and melt from solar heated debris within channels cryoconite holes and pools the main flow paths are subsurface connections between cryoconite holes pools and riffles the latter may become partially disconnected during hard freeze the chemical composition of runoff at the outlet of canada glacier during january 2000 was dominated by ca 2 hco 3 and sea salt na and cl and became depleted in sea salt and non sea salt so 4 2 as the subsurface drainage system in a frozen pool and riffle system was flushed and the melting ice surface became depleted of overwinter dry deposited salts only during 2 days of hard freeze did sea salt and so 4 2 increase in concentration together otherwise sea salt and so 4 2 declined while ca 2 and hco 3 increased the latter ions are derived from the chemical weathering of sediment in frozen topped pools channels and cryoconite holes it is inferred that the hydrochemical processes which occur in the vestigial subsurface drainage system are the elution of ions from ice melt dilution of these ions downstream by ice melt from vertical surfaces and the dissolution of dust in subsurface pools channels and or cryoconite holes

geochemical evidence of the 8 2 ka event and other holocene environmental changes recorded in paleolagoon sediments southeastern brazil abstract the paleoclimatic record of jureia paleolagoon coastal southeastern brazil includes cyclic and gradual changes with different intensities and frequencies through geological time and it is controlled by astronomical geophysical and geological phenomena these variations are not due to one single cause but they result from the interaction of several factors which act at different temporal and spatial scales here we describe paleoenvironmental evidence regarding climatic and sea level changes from the last 9400 cal yr bp at the jureia paleolagoon one of the main groups of protected south atlantic ecosystems geochemical evidences were used to identify anomalies from multi proxy analyses of a paleolagoon sediment core the anomalies of centennial scale were correlated to climate and transgression regression cycles from the holocene period decadal scale anomalous oscillations in the quaternary paleolagoon sediments occur between 9400 and 7500 cal yr bp correlated with long and short term natural events which generated high sedimentation rates mainly between 8385 and 8375 cal yr bp 10 cm yr our results suggest that a modern day short duration north atlantic climatic event such as the 8 2 ka event could affect the environmental equilibrium in south america and intensify the south american summer monsoon

post 12 m y rotation of southwest washington paleomagnetic field directions from the basalt of pack sack lookout are compared to those from the pomona member of the saddle mountains basalt of the columbia river basalt group the pomona crops out over a wide region on the columbia plateau east of the cascade range and the basalt of pack sack lookout crops out well to the west of the cascades about 30 to 60 km east of the washington coast our paleomagnetic results support existing geologic and geochemical evidence that both these units are part of a single 12 m y old flow that erupted in western idaho and flowed to the washington coast the magnetic data further indicate that southwest washington has undergone clockwise rotation with respect to the columbia plateau and stable north america the data suggest that both a large scale regional rotation of 16 and locally complex small scale rotations exist the two being present to different degrees in the eastern and western regions of southwest washington the cascade range appears to coincide with the tectonic boundary separating rotated and unrotated regions of washington state rotation of southwest washington appears to have been associated with the rotation of large pieces of western oregon and southern washington possibly as a result of either a ridge push force from the basin and range province or shear along the pacific north america plate boundary

les variations du niveau de la mer durant les derniers 17 500 ans bp l exemple de la plate forme continentale du rio grande do sul bresil abstract the horizontal coastline translation on the rio grande do sul continental shelf during the post glacial wisconsinian period differed markedly between the northern region where it was about 8 6 m year and the southern region where the translation was 16 7 m year the northern region with a narrow continental shelf and a relatively strong pendant suffered a slow transgression characterized by a stronger hydrodynamic regime in the southern region the transgression was quite faster and combined with a lower energy regime caused by the presence of a wider continental shelf and a soft pendant the vertical coastline translation on the rio grande do sul continental shelf between 17 500 and 6500 yrs b p initiated from 130 m to the current sea level three intermediary stabilizations the first one at 11 000 yrs b p between 60 and 70 m the second one at 9000 yrs b p between 32 and 45 m and the third at 8000 yrs b p between 20 and 25 m on rio grande do sul continental shelf morphosedimentary marks confirm the sea level stabilizations they are characterized by an increasing of the shelf pendant associated to a biodetritical and coarse sand sedimentation at the profile trench as well as the presence of heavy mineral concentrations

seasonal evolution of supra glacial lakes on the greenland ice sheet abstract a survey of supra glacial lakes on the western margin of the greenland ice sheet reveals a seasonally driven hydrological system culminating in widespread lake drainage in late summer we used satellite imagery to study the evolution of 292 lakes across two sites totalling 22 000 km 2 in area during 2001 the lakes combined area increased to 75 5 km 2 by the beginning of july over the following 25 days an area totalling 36 3 5 km 2 drained from 216 lakes at one study site we used meteorological data and a positive degree day model to calculate the volume of water generated by melting in the lake catchments based on this estimate the mean depth of filling lakes surveyed rose from 1 5 0 7 m on 7th july to 3 9 1 1 m on 1st august in agreement with a value for one lake of 4 4 0 9 m we have derived from airborne altimetry during this 25 day period we estimate that 38 18 10 7 m 3 of water drained from the surface at this site and that there was an average water flux of 1 3 0 3 m 3 s 1 passing through each lake that drained completely

post 12 million year clockwise rotation in the central columbia plateau washington the pomona flow 12 m y b p of the columbia river basalt group was sampled for paleomagnetic analysis at 32 sites in the yakima fold belt of the central columbia plateau to assess the pattern of deformation field directions from anticlinal ridges are found to be rotated clockwise relative to sites from synclinal areas two geographic patterns of rotation are present the primary pattern is one in which the greatest amount of rotation occurs in the crest hinge area of the anticlines and decreases into synclines a secondary pattern in which the amount of rotation is consistent within a geometric segment but varies among them is superimposed on the primary pattern the pattern of clockwise rotation is interpreted to be the result of local tectonic rotation occurring along a closely spaced north northwest trending primary shear system and northeast trending secondary shear system the shear system and concurrent rotation are interpreted to have developed during the growth of the yakima folds the relationship between the paleomagnetic data and the geologic structures can be used to constrain tectonic models for the columbia plateau the data reported in this study indicate that clockwise rotation can not be attributed to rigid block or microplate rotation but support models that predict localized dextral shear furthermore it is postulated that this mechanism may contribute to clockwise rotation observed in other parts of the western united states

sea level sediment supply and coastal changes examples from the coast of ireland abstract sediment supply and pre existing shoreline morphology are crucial factors in controlling coastal changes due to sea level rise using examples from both southeast and northeast ireland it can be shown that sea level change may trigger a sequence of events which leads to both static and dynamic shoreline equilibrium cliff erosion and longshore sediment movement in east co wexford has led to injection of sediment onto the shelf and the growth under both wave and tide regimes of linear offshore shoals these shoals now control the pattern of shoreline erosion and provide a template for possible stepwise evolution of the coast under any future sea level rise in contrast the nearby coast of south co wexford comprises a series of coarse clastic barriers moving monotonously onshore via overwash processes here the behavior of the barrier is conditioned by the antecedent morphology of both the beach face and stream outlet bedforms finally the rock platform coast of co antrim presents a far more resistant shoreline to incident marine processes yet even here there is strong evidence of present process control over so called raised platforms and embayments it is concluded that coastal sediment supply and dynamics together with coastal morphology and its interaction with waves present a far more complex variety of sea level indicators than is normally acknowledged

distributed modeling of ablation 1996 2011 and climate sensitivity on the glaciers of taylor valley antarctica here the mcmurdo dry valleys of antarctica host the coldest and driest ecosystem on earth which is acutely sensitive to the availability of water coming from glacial runoff we modeled the spatial variability in ablation and assessed climate sensitivity of the glacier ablation zones using 16 years of meteorological and surface mass balance observations collected in taylor valley sublimation was the primary form of mass loss over much of the ablation zones except for near the termini where melt primarily below the surface dominated microclimates in 10 m scale topographic basins generated melt rates up to ten times higher than over smooth glacier surfaces in contrast the vertical terminal cliffs on the glaciers can have higher or lower melt rates than the horizontal surfaces due to differences in incoming solar radiation the model systematically underpredicted ablation for the final 5 years studied possibly due to an increase of windblown sediment surface mass balance sensitivity to temperature was 0 02 m w e k 1 which is among the smallest magnitudes observed globally we also identified a high sensitivity to ice albedo with a decrease of 0 02 having similar effects as a 1 k increase in temperature and a complex sensitivity to wind speed

environmental and sea level variations on the southeastern brazilian coast during the late holocene with comments on prehistoric human occupation abstract analysis of organic sediments including their diatom and pollen contents was carried out in a swamp forest on the coastal plain of sao paulo state southeastern brazil a palaeoenvironmental reconstruction was made regarding this region where communities of fisher gatherers lived in prehistory producing numerous shell mounds from at least 4900 until 3470 cal yr bp the site was a lagoon surrounded by a relatively open forest the occurrence of shell mounds 50 km from the coast and the peak of human occupation between 5700 and 3300 cal yr bp can be linked to the presence of this great lagoon which formed an important food source the lagoon desiccated ca 3470 cal yr bp i e during the late holocene sea level fall and was replaced by a swamp forest that still exists today this forest was altered during a short period between 1300 and 675 cal yr bp when a freshwater lake or marsh was formed as a result of a rise in groundwater level the climate in the area throughout the middle late holocene ca 5000 cal yr bp to the present has not changed significantly except for three slightly more humid episodes at 3470 2750 ca 1940 and 1300 675 cal yr bp no indications of human impact on the vegetation during this period could be identified our results show that from 4900 to 3470 cal yr bp sea level was higher than at present contradicting a widely accepted relative sea level trend that suggests that at least two negative sea level oscillations occurred during the holocene i e at 4560 4150 and 3200 2800 cal yr bp our data confirm recent studies instead proposing a continuously declining relative sea level during the late holocene

shoreface translation and the holocene stratigraphic record examples from nova scotia the mississippi delta and eastern australia abstract classic descriptive models of barrier sedimentation have been developed with data from the atlantic and gulf coasts of the united states these models are dominated by low to moderate rates of relative sea level rsl rise and wave energy barriers respond by landward recycling of sediment through the mechanism of shoreface retreat sedimentation processes on the central coast of new south wales n s w australia consist of rapid rsl rise in early holocene times followed by a stillstand since 6500 b p wave energy is relatively high year round and sand sources for barrier formation are only found on the inner shelf barrier sedimentation on the central coast of n s w exhibits a thick composite sequence composed of a basal marine transgressive sand overlain by regressive beach and dune facies the louisiana coast surrounding the mississippi delta is underlain by compacting deltaic muds which generate very rapid rates of rsl rise the louisiana coast experiences low wave energy punctuated by high energy tropical and extra tropical storm events barrier sediments accumulate from the erosion of deltaic headlands and undergo a transformation from subaerial barrier island systems to subaqueous shoals located on the inner shelf drumlins experience coastal erosion on the eastern shore of nova scotia and provide a sediment source for compartmented estuary mouth barriers an ongoing moderate rise of rsl results from the passage of a glacial forebulge wave energy is intermediate between louisiana and n s w and displays a seasonal pattern dominated by frequent winter storms coastal barrier sedimentation is episodic consisting of a period of beach ridge progradation followed by barrier destruction and re establishment further landward the three contrasting sedimentary sequences found in examples from louisiana n s w and nova scotia indicate that presently available sedimentation models from locations such as the middle atlantic or texas coasts of the united states may only represent well documented regional case studies a true generalised coastal sedimentation model is required which can identify the parameters controlling vertical and horizontal translation of the depositional surface and provide relationships between these parameters which quantitatively predict the genesis distribution and geometry of coastal sedimentary facies

the mcmurdo dry valleys a landscape on the threshold of change abstract field observations of coastal and lowland regions in the mcmurdo dry valleys suggest they are on the threshold of rapid topographic change in contrast to the high elevation upland landscape that represents some of the lowest rates of surface change on earth a number of landscapes have undergone dramatic and unprecedented landscape changes over the past decade including the wright lower glacier wright valley ablated several tens of meters the garwood river garwood valley has incised 3 m into massive ice permafrost smaller streams in taylor valley crescent lawson and lost seal streams have experienced extensive down cutting and or bank undercutting and canada glacier taylor valley has formed sheer 4 meter deep canyons the commonality between all these landscape changes appears to be sediment on ice acting as a catalyst for melting including ice cement permafrost thaw we attribute these changes to increasing solar radiation over the past decade despite no significant trend in summer air temperature to infer possible future landscape changes in the mcmurdo dry valleys due to anticipated climate warming we map at risk landscapes defined as those with buried massive ice in relative warm regions of the valleys results show that large regions of the valley bottoms are at risk changes in surface topography will trigger important responses in hydrology geochemistry and biological community structure and function

the ablation zone in northeast greenland ice types albedos and impurities ice types albedos and impurity content are characterized for the ablation zone of the greenland ice sheet in kronprinz christians land 80 n 24 w along this ice margin the width of the ablation zone is only about 8 km the emergence and melting of old ice in the ablation zone creates a surface layer of dust that was originally deposited with snowfall high on the ice sheet this debris cover is augmented by locally derived wind blown sediment subsequently the surface dust particles often aggregate together to form centimetre scale clumps that melt into the ice creating cryoconite holes the debris in the cryoconite holes becomes hidden from sunlight raising the area averaged albedo relative to surfaces with uniform debris cover spectral and broadband albedos were obtained for snow ice hummocks debris covered ice cryoconite studded ice and barren tundra surfaces broadband ice albedos varied from 0 2 for ice with heavy loading of uniform debris to 0 6 for ice hummocks with cryoconite holes the cryoconite material itself has albedo 0 1 when wet areal distribution of the major surface types was estimated visually from a transect video as a function of distance from the ice edge 330 m a s l ablation rates were measured along a transect from the ice margin to the slush zone 8 km from the margin 550 m a s l traversing both pleistocene and holocene ice ablation rates in early august averaged 2 cm d 1 impurity concentrations were typically 4 3 mg l 1 in the subsurface ice surface concentrations were about 16 g m 2 on surfaces with low impurity loading and heavily loaded surfaces had concentrations as high as 1 4 kg m 2 the mineralogical composition of the cryoconite material is comparable with that of the surrounding soils and with dust on a snowdrift in front of the ice margin implying that much of the material is derived from local sources a fine mode clay is present in the oldest ice but not in the nearby soil suggesting that its origin is from wind deposition during pleistocene glaciation

cryoconite hole thermodynamics energy sources governing the growth of cryoconite holes have been investigated by monitoring the meteorological balance at the surface of the manatee glacier british columbia the dimensions of 125 holes and the thermal conditions within them cryoconite holes are shown to be rough indicators of the energy balance at the glacier surface both atmospheric and biological energy sources operate thereby suggesting a genetic classification of holes with solar and biological end members

late holocene development of a mangrove ecosystem in southeastern brazil itanhaem state of sao paulo abstract most palynological studies of mangroves have been carried out in the indo pacific region but few have investigated these ecosystems along the southern atlantic coast this paper provides information on the palynology of a mangrove at itanhaem state of sao paulo on the southeastern brazilian coast this mangrove occurs on microtidal flats adjacent to a fluvial tidal channel mouth itanhaem river part of an estuarine lagoon system established in the mid holocene pollen samples were collected from the surface and from bromeliad water in order to define the composition of modern pollen rain in the study area the results show a strong presence of rain forest taxa in the mangrove pollen spectra which differ from those obtained from northern brazilian mangroves which are characterized by higher percentages of the mangrove taxa rhizophora and avicennia based on palynological and 14 c chronological analysis of a shallow core measuring 135 cm in depth the itanhaem mangrove already existed by 1300 years bp and began expanding about 1000 years bp reaching its present extent sometime after 300 years bp its evolution is related to the sedimentary filling of the estuarine lagoonal depositional system two factors may have controlled the development of this mangrove the relative increase of intertidal areas due to this sedimentary filling and the decrease in wave action and increase in pelitic deposition in the intertidal zone related to the partial closing of the estuarine lagoonal inlets these processes were favored by the advance of bayhead deltas and by the development of sand spits as a part of the regression of the holocene strandplain

studies on holocene mangrove ecosystem dynamics of the braganca peninsula in north eastern para brazil abstract three sediment cores from the braganca peninsula located in the coastal region in the north eastern portion of para state have been studied by pollen analysis to reconstruct holocene environmental changes and dynamics of the mangrove ecosystem the cores were taken from an avicennia forest bosque de avicennia bda a salt marsh area campo salgado cs and a rhizophora dominated area furo do chato pollen traps were installed in five different areas of the peninsula to study modern pollen deposition nine accelerator mass spectrometry radiocarbon dates provide time control and show that sediment deposits accumulated relatively undisturbed mangrove vegetation started to develop at different times at the three sites at 5120 14c yr bp at the cs site at 2170 14c yr bp at the bda site and at 1440 14c yr bp at the fdc site since mid holocene times the mangroves covered even the most elevated area on the peninsula which is today a salt marsh suggesting somewhat higher relative sea levels the pollen concentration in relatively undisturbed deposits seems to be an indicator for the frequency of inundation the tidal inundation frequency decreased probably related to lower sea levels during the late holocene around 1770 14c yr bp at bda around 910 14c yr bp at fdc and around 750 14c yr bp at cs the change from a mangrove ecosystem to a salt marsh on the higher elevation around 420 14c yr bp is probably natural and not due to an anthropogenic impact modern pollen rain from different mangrove types show different ratios between rhizophora and avicennia pollen which can be used to reconstruct past composition of the mangrove in spite of bioturbation and especially tidal inundation which change the local pollen deposition within the mangrove zone past mangrove dynamics can be reconstructed the pollen record for bda indicates a mixed rhizophora avicennia mangrove vegetation between 2170 and 1770 14c yr bp later rhizophora trees became more frequent and since ca 200 14c yr bp avicennia dominated in the forest

emplacement of columbia river flood basalt evidence is examined for the emplacement of the umatilla wilbur creek and the asotin members of columbia river basalt group these flows erupted in the eastern part of the columbia plateau during the waning phases of volcanism the umatilla member consists of two flows in the lewiston basin area and southwestern columbia plateau these flows mixed to form one flow in the central columbia plateau the composition of the younger flow is preserved in the center and the composition of the older flow is at the top and bottom there is a complete gradation between the two flows of the wilbur creek and asotin members erupted individually in the eastern columbia plateau and also mixed together in the central columbia plateau comparison of the emplacement patterns to intraflow structures and textures of the flows suggests that very little time elapsed between eruptions in addition the amount of crust that formed on the earlier flows prior to mixing also suggests rapid emplacement calculations of volumetric flow rates through constrictions in channels suggest emplacement times of weeks to months under fast laminar flow for all three members a new model for the emplacement of columbia river basalt group flows is proposed that suggests rapid eruption and emplacement for the main part of the flow and slower emplacement along the margins as the of the flow margin expands

measurement and parameterization of aerodynamic roughness length variations at haut glacier d arolla switzerland spatial and temporal variations in aerodynamic roughness length z0 on haut glacier d arolla switzerland during the 1993 and 1994 ablation seasons are described based on measure ments of surface microtopography the validity of the microtopographic z0 measurements is established through comparison with independent vertical wind profile z0 measurements over melting snow slush and ice the z0 variations are explained through correlation and regression analyses using independent measurements of meteorological and surface variables and parameterizations are developed to calculate z0 variations for use in surface energy balance melt models several independent variables successfully explain snow z0 variation through their correlation with increasing surface roughness caused by ablation hollow formation during snow melt non linear parameterizations based on either accumulated melt or accumulated daily maximum temperatures since the most recent snowfall explain over 80 of snow z0 variation the z0 following a fresh snowfall on an ice surface is parameterized based on relationships with the underlying ice z0 snow depth and accumulated daily maximum temperatures none of the independent variables were able to successfully explain ice z0 variation although further comparative studies are needed the results lend strong support to the microtopo graphic technique of measuring z0 over melting glacier surfaces

seasonal sediment fluxes forcing supraglacial melting on the wright lower glacier mcmurdo dry valleys antarctica cold based glaciers exist in low temperature and low humidity environments in which shortwave radiation is the largest source of energy to the glacier surface and the energy budget is very sensitive to the surface albedo consequently the presence of relatively low volumes of debris on glacier surfaces has a significant impact on the timing magnitude and rate of ablation at the surface the aim of this study is to understand how the presence of sediment on the glacier surface at the start of the melt season can affect meltwater generation and delivery on a cold based glacier a combination of field measurements energy balance modelling and chemical mixing modelling were used on the wright lower glacier mcmurdo dry valleys antarctica between october 2005 and january 2006 to address this aim in this system sediment was transported onto the glacier surface during the winter months march october by foehn winds which reduced surface albedo at the start of the summer melt season the areas of the glacier on which sediment accumulated began to melt earlier than other parts of the glacier and experienced a longer melt season over the study period the total ablation on the dirty surfaces was nine times greater than for clean ice ablation on the dirty surfaces is dominated by melting whereas sublimation dominates the clean ice as the sediment was unevenly distributed over the glacier surface the variation in melt amount and timing drove the development of a cryoconite hole system copyright 2012 john wiley sons ltd

influence of paleorelief on the mid miocene climate variation in southeastern washington northeastern oregon and western idaho usa abstract terrestrial climate proxy records repeatedly show spatial heterogeneity because regional climate condition is largely influenced by the relationship between large scale atmospheric circulation patterns and regional topographic features the paleosols developed on the top of columbia river basalt flows emplaced between 15 3 and 15 8 ma in the northwestern united states show significant spatial variations in the mid miocene soil forming processes the paleosol in the northwestern part of the study area has the least degree of chemical weathering fine scale and very shallow penetrating depth of root traces with the estimated paleoprecipitation and paleotemperature of about 550 mm and 16 c respectively the paleosols in the southeastern part of the study area indicate more intense chemical weathering with the estimated paleoprecipitation and paleotemperature of approximately 1400 to 1500 mm and 17 c respectively the spatial variations in paleo pedogenesis were predominantly affected by spatial heterogeneity in the mid miocene regional climate and regional paleotopographic features taking the other ancient soil forming factors including time parent rock materials and biological activities into account we suggest that intrusions of hot columbia river basalt magma into the crust were responsible for the regional surface uplift and the paleoclimate heterogeneity because the major vent systems of the columbia river basalt eruptions were located in the area where development of the mid miocene high topography existed within the blue mountains paleotopography of the earth s surface can be reconstructed by the paleoprecipitation and paleotemperature estimations from several spatially distributed chrono stratigraphic paleosols although it is difficult to estimate the magnitude of the paleorelief precisely

the origin of channels on lower taylor glacier mcmurdo dry valleys antarctica and their implication for water runoff well developed surface channels on taylor glacier mcmurdo dry valleys antarctica begin as medial moraines incised as shallow narrow surface depressions and retain this geometry for tens of km over a distance of 1100m the channel geometry dramatically changes reaching depths 20m and widths 100m after rapidly enlarging the channels appear to evolve toward a new equilibrium geometry compared to the glacier surface the air temperature in the channels is warmer by 1 78c wind speed is reduced by 2 4m s and net shortwave radiation is greater by 14wm the microclimate in the channel shifts the energy balance towards enhanced melt field evidence and energy balance modeling indicate ablation in the deep channels is 4 5 times greater than the local horizontal glacier surface and that melt accounts for 99 of the summer ablation compared to 75 on the adjacent horizontal glacier surface melt in these channels supplies 65 of the unaccounted water discharge into the neighboring lake in large part the channels generate the water they carry rather than merely route water generated elsewhere

mangrove vegetation changes on holocene terraces of the doce river southeastern brazil article i nfo high resolution sedimentological geochemical and pollen analysis on sediment core from the coastal plain of the doce river southeastern brazil revealed changes in the depositional system and vegetation caused by combined action of oscillations in relative sea level rsl and sedimentary supply during the holocene two main phases were discerned using sedimentary features 13 c 15 n total organic carbon toc total ni trogen n c n and cluster analysis of pollen data temporally synchronized with radiocarbon age dating the data indicates the presence of a lagoon system surrounded by a tidal plain colonized by mangroves and its sedimentary organic matter sourced from c4 plants between 8050 and 7115 cal yr bp however during the mid and late holocene the mangroves shrank and freshwater vegetation expanded c3 plants proba bly due to a marine regression during this phase the development of a lacustrine environment was followed by the colonization of herbs trees and shrubs the continuous sediment infilling into the lake allowed the ex pansion of a herbaceous plain as seen today this geomorphologic and vegetation evolution is in agreement with the mid holocene rsl maximum above present rsl and subsequent fall to the present time

lava sediment interaction and drainage system development in a large igneous province columbia river flood basalt province washington state u s a abstract large igneous provinces lips have been implicated in some of the largest environmental perturbations to have affected the earth through geological time yet the impact of lip development on drainage and ecosystem development in the immediate vicinity of these provinces are still poorly constrained to date based on a detailed integrative facies scheme we characterize the interaction between volcanism and fluvial lacustrine and wetland environments in the miocene columbia river flood basalt province crbp lip exposed in central washington state usa the facies scheme proposed here comprises a detailed description and interpretation of siliciclastic bioclastic diatomite volcaniclastic and paleosol facies and subfacies intercalated with lavas of the columbia river basalt group crbg facies and facies associations of individual interbeds are further correlated to reconstruct changes in sedimentary settings and topography of lava fields during deposition field observations and facies analysis help to explain the effects of flood basalt volcanism on drainage system development we propose a generic model of lava drainage interplay and distribution of sedimentary settings in flood basalt provinces which will contribute to our understanding of sedimentological environmental and volcanic processes in the crbp hydrocarbon exploration in volcanic terrains requires detailed information on the distribution and development of sedimentary settings this model will help to better predict the character and distribution of sedimentary bodies and potential hydrocarbon reservoirs in volcanic terrains

foehn winds in the mcmurdo dry valleys antarctica the origin of extreme warming events abstract foehn winds resulting from topographic modification of airflow in the lee of mountain barriers are frequently experienced in the mcmurdo dry valleys mdvs of antarctica strong foehn winds in the mdvs cause dramatic warming at onset and have significant effects on landscape forming processes however no detailed scientific investigation of foehn in the mdvs has been conducted as a result they are often misinterpreted as adiabatically warmed katabatic winds draining from the polar plateau herein observations from surface weather stations and numerical model output from the antarctic mesoscale prediction system amps during foehn events in the mdvs are presented results show that foehn winds in the mdvs are caused by topographic modification of south southwesterly airflow which is channeled into the valleys from higher levels modeling of a winter foehn event identifies mountain wave activity similar to that associated with midlatitude foehn winds these events are found to be caused by str

optical characteristics of cryoconite surface dust on glaciers the relationship between light absorbency and the property of organic matter contained in the cryoconite

contrasting responses of two caribbean mangroves to sea level rise in the guajira peninsula colombian caribbean abstract local geomorphology plays an important role in the response of mangrove communities to both sea level rise and precipitation changes mostly because it exerts an important control of the erosion progradation balance here we present contrasting changes in the palynological records of two sediment cores retrieved from locations occupied by mangroves in the northeastern caribbean coast of colombia calancala and navio quebrado sediments were treated with standard procedures used in palynologycal analysis and dated with ams 14 c and 210 pb age depth models of both cores were constructed by linear interpolation between dated samples the main modern differences between the studied sites are fresh water availability and sediment supply throughout the year while calancala located at the rancheria river delta has direct fresh water influence throughout the year coastal lagoon navio quebrado is only sporadically influenced by fresh water sources according to our findings two main factors contributed to mangrove establishment in the colombian caribbean i high and accelerated sea level rise around 6000 cal yr bp originating coastal lagoons that favored mangrove establishment and ii marine still stand and high precipitation around 3000 cal yr bp leading to a second wave of mangrove expansion a drought between about 2850 and 2450 cal yr bp and the strengthening of easterly trade winds caused a change from rhizophora dominated to avicennia dominated stands increased precipitation after 2500 cal yr bp and subsequent increase of fluvial sediment input promoted recovery of rhizophora dominated mangroves sea level rise during the last 150 yr has caused landward mangrove expansions in deltas and progradation of coastal environments however the general pattern shows a net loss of mangrove vegetation as the result of coastal erosion

comments on the use of chemically based mixing models in glacier hydrology the assumptions involved in the use of chemically based mixing models for analysis of flow routing of meltwaters in glacierized basins are critically evaluated the assumption that glacial drainage systems consist of only two primary flow components is arbitrary and must be supported by independent evidence recent studies of the processes by which meltwaters acquire solute indicate that the assumption that flow components have unique and constant chemical compositions is unlikely to lie correct source water composition and weathering potential will vary over the course of a melt season and the extent of subglacial weathering is strongly dependent upon such factors as meltwater residence time and the availability of reactive sediment both of which are known to vary on diurnal to seasonal time scales mixing of flow components does not appear to be confined to the terminal regions of glaciers and is therefore unlikely to be conservative as assumed a multi parameter mixing model is applied to the analysis of data on the chemistry of waters sampled from bureholes drilled through haut glacier d arolla switzerland to demonstrate the range of dissolved species for which the assumption of conservative mixing is violated the consequences of this violation for quantitative hydrograph separation are shown to be highly significant the utility of mixing models as a tool for the investigation of glacier hydrological systems is questionable and the results of previous studies are unreliable

meteorological controls on sand transport and dune morphology in a polar desert victoria valley antarctica the hyperarid polar desert of the mcmurdo dry valleys contains an abundance of aeolian sedimentary deposits the largest in antarctica providing a unique setting for studying cold climate aeolian processes and dune morphology meteorological controls on sand transport and changes in dune morphology were monitored for 11 days in november december 2004 on a barchan dune in the victoria valley mcmurdo dry valleys sand transport in this environment was found to be influenced by 1 interparticle cohesion ice bonding 2 diurnal variations in the speed of thermally driven easterly valley winds due to reduced solar heating by night and 3 topographically modified foehn southwesterly winds the threshold entrainment velocity during easterly valleys winds was 5 3 m s at 0 4 m 0 21 m s warm dry and gusty foehn southwesterly winds were found to promote aeolian processes by dislodging surface sediments with dune morphology responding rapidly importantly no diurnal signal in sand transport was observed under these conditions when wind speed and sand transport occurred independently of solar heating measured changes in dune morphology indicate that the dune field of the victoria valley under current environmental conditions is in dynamic equilibrium with frequent up valley sand transport by thermally generated valley winds balanced by less frequent but greater magnitude down valley sand transport by moderate to strong foehn southwesterlies this results in little net movement of dunes and subsequent change in the position of the dune field accordingly we believe that regional scale shifts in climate that cause change in the synoptic circulation patterns of the ross sea region that affect the frequency of either the up valley easterlies or down valley foehn winds will result in a net change in the morphology of the victoria valley s dune field such change in circulation may become apparent early as change in the morphology of the victoria valley sand dunes we therefore suggest this site should be monitored as an indicator site for identifying change in regional weather and climate

extreme hydrochemical conditions in natural microcosms entombed within antarctic ice cryoconite holes are near vertical tubes that form in the surface of glaciers when solar heated debris melts into the ice those that form in the mcmurdo dry valleys of antarctica are distinctive in that they have ice lids and are closed to the atmosphere for periods of years to decades photoautotrophs and heterotrophs grow within this closed environment perturbing the poorly buffered water chemistry yet maintaining the potential for photosynthesis microbial excretion and decomposition of organic matter produces dissolved organic carbon doc dissolved inorganic carbon ratios of 1 2 much of the dissolved nitrogen pool 80 100 exists as dissolved organic nitrogen don the don doc ratio is 1 11 mol mol typical of organic particulate material at the earth s surface the combination of photoautotrophy heterotrophy and weak chemical buffering within these microcosms promotes values of ph pco2 o2 saturation and percentage total dissolved nitrogen as don that reach 10 99 10 7 6 atm 160 and 100 respectively which are a unique combination among the surface waters on earth these ice sealed cryoconite holes could be important analogues of refugia on snowball earth and other icy planets

kinetic energy transfer through impact and its role in entrainment by wind of particles from frozen surfaces while extensive aeolian deposits are associated with glaciation little is known of the mechanisms which produced them observation of glaciofluvial sediments in pangnirtung pass n w t indicates that peak deflation occurs in the fall and winter months so that the nature of sediment transport involving frozen surfaces greatly differs from warm environments laboratory experiments indicate that such surfaces are mobilized through abrasion and are most susceptible at low volumetric water content less than 20 and low temperature 20 c stable surfaces have volumetric water contents in excess of 30 and temperatures of 15 c surface stability also increases with decreasing particle size density and possibly transport load collisions with frozen surfaces are relatively elastic with significantly greater kinetic energy transfer to ejected surface grains than observed for loose dry surfaces saltation transport in cold environments could therefore be sustained at lower windspeeds than for dry surfaces provided that some loose particles are available initially but do not accumulate at the surface

glacial lake victoria a high level antarctic lake inferred from lacustrine deposits in victoria valley we present evidence of a large lake glacial lake victoria that existed in victoria valley in the dry valleys region of antarctica between at least 20 000 and 8600 14c yr bp at its highstands glacial lake victoria covered 100 km2 and was ca 200 m deep the chronology for lake level changes comes from 87 ams radiocarbon dates of lacustrine algae preserved in deltas and glaciolacustrine deposits that extend up to 185 m above present day lakes on the valley floor the existence of glacial lake victoria as well as other large lakes in the dry valleys indicates a climate regime significantly different from that of today at the last glacial maximum and in the early holocene copyright 2002 john wiley sons ltd

the brazilian sea level curves a critical review with emphasis on the curves from the paranaguaand cananeia regions abstract relative sea level curves for the mid to late holocene have been proposed for eight different sectors along the brazilian coast this paper aims to review the data used to construct the curves proposed for two sectors the paranaguaand cananeia regions in southeast brazil more specifically we analyze the palaeo sea level indicators vermetid tubes shells wood fragments and shell midden deposits related to 1 the sea level maximum of the mid holocene and 2 the two secondary oscillations that would have occurred between 4100 3800 years b p and 3000 2700 years b p the sedimentary deposits of the coastal plain as well as vermetid datings suggest a mid holocene sea level maximum between 3 5 and 4 m the great majority of the indicators used to infer the secondary oscillations in previous studies were derived from shell middens besides being unreliable palaeo sea level indicators these data also showed inconsistencies that undermine the existence of such oscillations the plot of all the data derived from vermetid samples found along the brazilian coast also indicate a rather smoother sea level fall in the last 5100 years

barrier island evolution middle atlantic shelf u s a part ii evidence from the shelf floor where the atlantic coastal gradient is low and the substrate is unconsolidated shoreface processes lead to an equilibrium shoreface surface characterized by a straightened plan view and a concave up profile maintenance of this surface during the post glacial sea level rise may lead to barrier formation by mainland beach detachment where the outer oceanic shoreface is maintained by wave and current processes downwelling storm currents sweep sand from the shoreface of the middle atlantic bight transport it downcoast and seaward and deposit it on the adjacent inner shelf some of this sand is returned by the action of asymmetrical wave orbital currents during fair weather however there is a net loss in most areas the loss is not made good by river sand input since on the atlantic coast all river sand is trapped by estuaries as a result the shoreface in these areas is undergoing erosional retreat mean horizontal retreat rates are on the order of 1 3 m yr 1 but most movement occurs in brief episodes with recurrence rates on the order of several events per century erosional shoreface retreat coupled with aeolian overshoot storm washover and the movement of sand through inlets into the lagoons has lead to landward migration of the atlantic barriers through the holocene period of sea level rise the landward retreat of the barrier as a whole is as dependent on inlet formation as it is on erosional shoreface retreat repeated inlet breaching and the downdrift migration of inlets yields coalescing flood tidal deltas within the lagoon the resulting surface forms a platform on which the subaerial barrier deposits can advance under the impetus of storm washover and aeolian action the backbarrier deposits eventually re emerge at the shoreface where their upper beds are eroded and recycled the barrier thus migrates over a pavement of its own flood tidal deltas and washover fans sand is added to the system partly through the erosion of updrift headlands but mainly by means of scour in inlets which reaches down to the underlying pleistocene the modern shelf sand sheet is the debris blanket resulting from the retreat process the leading edge occurs as a thin veneer of rip current fallout on the shoreface this is periodically stripped off by winter storms to expose the underlying backbarrier strata further seaward shelf sands eroded from the shoreface rest disconformably on backbarrier deposits shoreface beach and dune strata are always missing every grain of sand in this shelf sand sheet has occupied a position on the beach or upper shoreface within the recent past however the sheet as a whole has been reconstituted its primary structures are those of the inner shelf floor backbarrier sand and mud deposits characterized by channeling and landward dipping reflectors can be traced for over 100 km seaward across the middle atlantic shelf beneath the modern sand sheet the backbarrier stratum together with the overlying shelf sand layer constitutes the record of barrier retreat across the atlantic shelf surface during holocene time the sheet like nature of this record indicates that viewed at the appropriate time scale barrier migration is a continuous process

a 1 year record of global radiation and albedo in the ablation zone of morteratschgletscher switzerland we analyse data on solar radiation measured with an automatic weather station on morteratschgletscher switzerland for the period 1 october 1995 30 september 1996 the station is in the lower ablation zone due to shading by surrounding mountains and atmospheric attenuation only 49 of the annual extraterrestrial irradiance mean 292 w m 2 reaches the glacier surface about 48 of this is absorbed at the surface mean 79 w m 2 annual albedo of 0 53 we present a simple albedo scheme for use in glacier mass balance models we fit the model to the 1 year dataset by optimizing five control parameters optimal values in brackets albedo of snow 0 75 albedo of firn 0 53 albedo of ice 0 34 e folding constant for effect of ageing on snow albedo 21 9 days and e folding constant for effect of snow depth on albedo 3 2 cm the input consists of daily albedo snow depth and dates of snowfall events the correlation coefficient between observed and simulated albedo is 0 931 the corresponding rms difference being 0 067

genesis of flood basalts and basin and range volcanic rocks from steens mountain to the malheur river gorge oregon the middle and south forks of the malheur river provide a unique mapping corridor connecting two flood basalt successions steens basalt to the south and the basalt of malheur gorge to the north each contains chemically defined subtypes which merge stratigraphically across the north south length of the map area the lowermost flows of steens basalt are stratigraphically equivalent to the lowermost flows of the basalt of malheur gorge the uppermost flows of steens basalt pinch out in the map area but are partly interbedded with the middle and uppermost flows of the basalt of malheur gorge which continue to thicken northward the upper part of the tholeiitic succession is interbedded with a group of previously unrecognized lavas the venator ranch basalt flows tholeiitic volcanism ceased at ca 15 3 ma the last tholeiitic unit erupted is the hunter creek basalt which also thickens northward subsequent younger than 15 3 ma more localized eruptions were dominated by calc alkaline to mildly alkaline lavas associated with basin and range extension local uplift generated deep canyons which were filled by andesitic lavas of the keeney sequence ca 13 10 ma the final eruptive products include the devine canyon tuff ca 9 7 ma the drinkwater basalt ca 6 9 ma and the voltage flow older than 32 000 yr b p major and trace element analyses demonstrate that 1 crystal fractionation was a universal process in the derivation of the

late quaternary vegetation and coastal environmental changes at ilha do cardoso mangrove southeastern brazil abstract a 190 cm mangrove sediment core from the ilha do cardoso state park state of sao paulo southeastern brazil was analyzed for pollen diatoms as well as carbon and nitrogen isotopes the goal was to determine the dynamics of the coastal terrestrial aquatic ecosystems vegetation history and climate change in this region of the brazilian atlantic rainforest during the late pleistocene and holocene the values for total organic carbon toc from 3 up to 40 c n ratios from 10 up to 130 and 15n 0 to 8 are associated with well preserved aquatic and terrestrial organic matter and possibly influenced by nitrogen cycling e g denitrification that caused 15n enrichment between 40 000 cal yr b p and 23 000 cal yr b p depleted 13c values 28 0 are also observed and indicate the predominance of c3 plants during this time interval the pollen analysis reveals the presence of the genera ilex alchornea weinmannia myrsine symplocos drimys and podocarpus on a site currently occupied by mangrove vegetation these data suggest that in the past prevailed a colder and more humid climate than today with a low relative sea level from 23 000 cal yr b p to 2200 cal yr b p a sedimentary hiatus likely occurred related to an erosive event associated to the post glacial sea level rise since at least 2200 cal yr b p sediments are marked by relatively low c n ratios from 2 to 27 exhibit more enriched 13c from 26 0 to 24 0 and 15n up to 7 values and are characterized by the presence of marine diatoms this indicates the return of the marine coastal line to its current position and consequently the development of mangrove

celadonite in continental flood basalts of the columbia river basalt group celadonite is a common alteration product of basalts in marine environments it has been argued that marine fluids are necessary for celadonite formation possibly by providing a source of k and other dissolved cations laterally extensive deposits of celadonite occur in basalts of the grande ronde basalt of the columbia river basalt group the celadonite is found in scoriaceous flow tops of layered basalt flows where it fills vesicles and replaces the surrounding groundmass evolved interstitial glasses are present in the basalts and dissolution of these glasses may provide sufficient k for celadonite formation whereas dissolution of groundmass augite provides a source of mg and fe these observations show that alteration by seawater or any other external source of dissolved ions is not necessarily required for celadonite formation

assessing the transferability and robustness of an enhanced temperature index glacier melt model we investigate the transferability of an enhanced temperature index melt model that was developed and tested on haut glacier d arolla switzerland in the 2001 season the model s empirical parameters temperature factor tf and shortwave radiation factor srf are recalibrated for 1 other locations on haut glacier d arolla 2 subperiods of distinct meteorological conditions 3 different years on haut glacier d arolla and 4 other glaciers in different years the model parameters are optimized against simulations of an energy balance model validated against ablation observations results are compared with those obtained with the original parameters the model works very well when applied to other sites seasons and glaciers with the exception of overcast conditions differences are due to underestimation of high melt rates the parameter values are associated with the prevailing energy balance conditions showing that high srf are obtained on clear sky days whereas higher tf are typical of locations where glacier winds prevail and turbulent fluxes are high we also provide a range of parameters clearly associated with the site s location and its meteorological characteristics that could help to assign parameter values to sites where few data are available

calculating ice melt beneath a debris layer using meteorological data generalized numerical models of sub debris ice ablation are preferable to empirical approaches for predicting runoff and glacier response to climate change as empirical methods are site specific and strongly dependent upon the conditions prevailing during the measurement period we present a modified surface energy balance model to calculate melt beneath a surface debris layer from daily mean meteorological variables despite numerous simplifications the model performs well and modelled melt rates give a good match to observed melt rates suggesting that this model can produce reliable estimates of ablation rate beneath debris layers several decimetres thick this is a useful improvement on previous models which are inappropriate for thick debris cover