terrigenous sediment supply in the scotia sea southern ocean response to late quaternary ice dynamics in patagonia and on the antarctic peninsula geochemical and mineralogical compositions of modern and late quaternary marine sediments from the scotia sea trace sources and transport paths of terrigenous sediment we discuss downcore variations of compositional data of two sediment cores from the northern and southern scotia sea that correlate with fluctuations in magnetic susceptibility sediments were derived from very different sources at both localities as revealed by contrasting clay mineral assemblages however a common feature is the input of more basic and undifferentiated crustal material with the potential of high magnetic susceptibility during glacial periods indicated by variable quartz feldspar ratios and major trace and rare earth elements terrigenous sediments mainly originate from nearby terrestrial sources or are introduced through interbasinal sediment transfer from adjacent seas the observed temporal compositional variations have to be attributed to changes in the relative detrital contributions from the diverse source areas ice mass extensions in southern patagonia on the antarctic peninsula and adjacent islands likely control the supply of glaciogenic detritus to the open ocean during times of glacial expansion diluting the sediment input of interbasinal origin current transport is mainly responsible for sediment dispersal to the pelagic scotia sea and may amplify the glaciological source signals during glacial climate periods because of a stronger wind forcing of the antarctic circumpolar current

evaluating zr rb ratio from xrf scanning as an indicator of grain size variations of glaciomarine sediments in the southern ocean the ln zr rb count ratio derived from x ray fluorescence xrf core scanning holds potential as a high resolution tracer for grain size variations of glaciomarine sediments to evaluate this appro

clay minerals in cenozoic sediments off cape roberts mcmurdo sound antarctica reveal palaeoclimatic history abstractthe clay mineral assemblages of the ca 1600 m thick cenozoic sedimentary succession recovered at the crp 1 crp 2 2aand crp 3 drill sites off cape roberts on the mcmurdo sound shelf antarctica were analysed in order to reconstruct thepalaeoclimate and the glacial history of this part of antarctica the sequence can be subdivided into seven clay mineral unitsthat reflect the transition from humid to subpolar and polar conditions unit i 35 33 6 ma is characterised by an almostmonomineralic assemblage consisting of well crystalline authigenic smectite and therefore does not allow a palaeoclimaticreconstruction unit ii 33 6 33 1 ma has also a monomineralic clay mineral composition however the assemblage consistsof variably crystallized smectite that at least in part is of detrital origin and indicates chemical weathering under a humidclimate the main source area for the clays was in the transantarctic mountains minor amounts of illite and chlorite appear forthe first time in unit iii 33 1 31 ma and suggest subordinate physical weathering the sediments of unit iv 31 30 5 ma have strongly variable smectite and illite concentrations indicating an alternation of chemical weathering periods and physicalweathering periods unit v 30 5 24 2 ma shows a further shift towards physical weathering unit vi 24 2 18 5 ma indicates strong physical weathering under a cold climate with persistent and intense illite formation unit vii 18 5 ma topresent documents an additional input of smectite derived from the mcmurdo volcanic group in the south d 2005 elsevier b v all rights reserved

distribution of clay minerals in surface sediments from the eastern barents and south western kara seas surface samples from the eastern barents and south western kara seas have been analysed for clay mineralogy transport paths the role of regional sources and local bedrock outcrops and the influence of hydrodynamic and glacigenous processes for clay distribution on the shelves are discussed in relation to central arctic ocean deep sea and sea ice sediments franz josef land and novaya zemlya show significantly different clay mineral associations although smectite concentrations are fairly high franz josef land can be excluded as a source for central arctic sea ice sediments which are relatively rich in smectite in the kara sea smectite concentrations in coastal sediments surpass even the franz josef land concentrations the large cyclonic gyre in the eastern barents sea between novaya zemlya and franz josef land which serves as a mixing zone between arctic and north atlantic water is apparently reflected within the smectite distribution pattern with the exception of franz josef land the area of investigation is typically low in kaolinite in particular coastal areas and areas north of novaya zemlya influenced by the inflow of arctic waters show the lowest kaolinite concentrations a high kaolinite occurrence within the nansen basin is most probably related to franz josef land and emphasizes the importance of long range downslope transport of sediments across the continental slope the surface water circulation pattern in close interaction with local outcrops onshore novaya zemlya and locally restricted occurrences within the eastern barents sea significantly alter the illite dispersal pattern illite concentrations are lowest around franz josef land chlorite is generally low in the area of investigation submarine outcrops and important chlorite occurrences onshore novaya zemlya bias its distribution pattern

significance of clay mineral assemblages in the antarctic ocean abstract typical examples from different morphological and geological settings in the antarctic ocean are reviewed in order to discuss the value of clay mineral assemblages for reconstructing the glacial history of antarctica the paleoceanographic history of the antarctic ocean and the sedimentary processes at the antarctic continental margin the significance of clay minerals for paleoenvironmental reconstructions strongly varies with both the position of the sites under investigation and the age of the sediments in late mesozoic to paleogene sediments clay mineral assemblages are sensitive tools for reconstructing climatic conditions for example the shift from smectite dominated assemblages to illite and chlorite dominated assemblages in the earliest oligocene clearly documents the transition from chemical weathering conditions under a warm and humid climate to physical weathering under cooler conditions submarine elevations such as maud rise and kerguelen plateau give the best record for direct paleoclimatic and paleoceanographic studies at the proximal sites of the continental slope and shelf as well as in the deep sea the paleoclimatic information normally is masked by a variety of processes resulting in sediment redistribution at those sites in contrast the clay mineral assemblages bear a wealth of information on different sedimentary processes after the establishment of a continental east antarctic ice sheet physical weathering prevailed variations in the clay mineral records predominantly reflect the influence of different sediment sources resulting from different glacial hydrographic or gravitational transport processes because these sedimentation processes are generally linked to climatic variations the clay mineral assemblages in most of the neogene and quaternary sediments provide indirect paleoclimatic information the processes are best documented in the clay mineral composition in those areas where changes in source regions with distinct petrographic differences are expected and where distances from the source region are low

stepwise palaeoclimate change across the eocene oligocene transition recorded in continental nw europe by mineralogical assemblages and d 15 n org rennes basin france the eocene oligocene transition eot 34 ma is the largest global cooling of the cenozoic era and led the earth s climatic system to change from a greenhouse to an icehouse mode although it is well documented in marine settings the few studies focusing on continental environments have demonstrated regional heterogeneities the study core cdb1 located in the rennes basin western france is a unique terrestrial lacustrine palustrine record comprising well preserved and terrestrial derived organic rich sediments encompassing the eot clay minerals and the first organic nitrogen isotope record d 15 n org of terrestrial origin for this period are used to reconstruct palaeoclimate changes across this key interval as suggested in worldwide marine and a few continental records a stepwise transition from warm humid conditions in the late eocene to cooler drier conditions in the early oligocene is confirmed in the area in addition an episode of drier conditions in the late eocene and humid dry cycles in the early oligocene are suggested terra nova 00 1 9 2016

detrital sediment supply in the southern okinawa trough and its relation to sea level and kuroshio dynamics during the late quaternary abstract during leg 195 of the ocean drilling program site 1202 was drilled in the subtropical northwestern pacific ocean beneath the kuroshio black current between northern taiwan and the ryukyu island arc on the northern flank of the i lan ridge at 1274 m water depth the upper 110 m of the site 1202 section composed of dark grey calcareous silty clay provide an expanded record of environmental changes during the last 28 kyr the sediments were deposited at high sedimentation rates between 3 0 and 5 0 m kyr and peak values of 9 0 m kyr between 15 1 and 11 2 ka bp variations in the modes and sources of detrital sediment input as inferred from sediment granulometry mineralogy and elemental xrf scanner data reflect changes in environmental boundary conditions related to sea level changes kuroshio variability and the climate driven modes of fluvial runoff the provenance data point to increased sediment supply from northwestern taiwan between 28 and 19 5 ka bp and from east china sources between 19 5 and 11 2 ka bp the change in provenance at 19 5 ka bp reflects increased fluvial runoff from the yangtze river and strong sediment reworking from the east china sea shelf in the course of increased humidity and postglacial sea level rise particularly after 15 1 ka bp the holocene was dominated by sediments that originated from rivers in northeastern taiwan for the pre holocene period prior to 11 2 ka bp low portions of sortable silt 63 10 m show that the kuroshio did not enter the okinawa trough because of low sea level in turn high proportions of sortable silt and sediment provenance from northeastern taiwan point to strong ocean circulation under the direct and persistent influence of the kuroshio during the holocene the reentrance of the kuroshio to the okinawa trough was heralded by two pulses in relative current strengthening at 11 2 and 9 5 ka bp as documented by stepwise increases in sortable silt in the lower holocene section from a global perspective environmental changes in the southern okinawa trough show affinities to climate change in the western pacific warm pool with little influence of climate teleconnections from the north atlantic realm otherwise seen in many other marine and terrestrial palaeoclimate records from southeastern asia

a comparison of early paleogene export productivity and organic carbon burial flux for maud rise weddell sea and kerguelen plateau south indian ocean 1 marine biological productivity has been invoked as a possible climate driver during the early paleogene through its potential influence on atmospheric carbon dioxide concentrations however the relationship of export productivity the flux of organic carbon c from the surface ocean to the deep ocean to organic c burial flux the flux of organic c from the deep ocean that is buried in marine sediments is not well understood we examine the various components involved with atmosphere to ocean c transfer by reconstructing early paleogene carbonate and silica production using carbonate and silica mass accumulation rates mars export productivity using biogenic barium bio ba mars organic c burial flux using reactive phosphorus p mars redox conditions using uranium and manganese contents and the fraction of organic c buried relative to export productivity using reactive p to bio ba ratios our investigations concentrate on paleocene eocene sections of sites 689 690 from maud rise and site 738 from kerguelen plateau in both regions export productivity organic c burial flux and the fraction of organic c buried relative to export productivity decreased from the paleocene early eocene to the middle eocene a shift is indicated from an early paleogene two gyre circulation in which nutrients were not efficiently recycled to the surface via upwelling in these regions to a circulation more like the present day with efficient recycling of nutrients to the surface ocean export productivity was enhanced for kerguelen plateau relative to maud rise throughout the early paleogene possibly due to internal waves generated by the plateau regardless of gyre circulation

sedimentary patterns in the late quaternary southern ocean the spatial and temporal distribution of biogenic and lithogenic sediments in the late quaternary southern ocean reflects the zonal character of the antarctic circumpolar current and is basically controlled by glacial dynamics in antarctica sea ice distribution temperature gradients wind patterns and thermohaline ocean circulation carbonate patterns in most places reveal a decline in biogenic carbonate preservation during glacial periods mainly attributed to a reduced influx of north atlantic deep water and increased ocean stratification which modified deep water chemistry towards more corrosivity an important lithological feature of the southern ocean is the circumpolar opal belt which today is situated between the polar front and the seasonal sea ice limit to the south during the glacial periods the opal belt shifted to the north in response to a wider sea ice extension that reduced light availability and diatom productivity to the south biosiliceous productivity to the north likely was fueled by detrital iron supplied by aeolian dust input and or hemipelagic processes lithogenic fluxes generally increased during the glacial periods provenance studies on the origin and dispersal of detrital materials suggest combined effects of low sea level stands increased glaciogenic input and enhanced current transport to have caused elevated detrital fluxes the relative and absolute contribution of aeolian dust is difficult to decipher and awaits further clarification by integrated provenance studies of both marine sediments and more reference materials from the potential terrestrial source areas ice rafted debris ird represents a minor fraction of lithogenic sediments but can be used to infer both antarctic ice sheet dynamics and the fate of both sea ice and iceberg survival in the distal southern ocean future work should be concentrated on a better identification of ird origin in terms of volcaniclastic influences the distinction of east and west antarctic sediment sources and sea ice versus iceberg transportation

early pliocene marine sediments coastline and climate of east antarctica we record the first onshore late tertiary fossiliferous marine deposit from the 8000 km long coastline of east antarctica glaciomarine sediments containing abundant diatoms and molluscs were deposited in shallow waters off an open coast during the early pliocene 4 5 3 5 ma and are now exposed less than 15 m above sea level on marine plain in the vestfold hills lat 68 359s long 78 009e marine diatoms suggest early pliocene as the most probable age of the sediments fossil sand wedges show that the deposit was above sea level at least briefly before it was covered with water and subsequently capped with glaciomarine till the coastline at the time of deposition of the marine sediments is inferred to have been close to but farther inland than that of today the ice margin may have been 50 km farther inland considerably reducing the ice volume of antarctica climate at the time of deposition was interglacial and perhaps warmer than the present

distribution of chlorite and kaolinite in eastern atlantic sediments off north africa chlorite in the atlantic sediments is predominantly derived from the atlas mountains kaolinite originates in the southern sahara and sahel zone these minerals may be used to reconstruct the tracks of two superimposed wind systems trade winds and harmattan wind a modified method for determining relative abundances of chlorite and kaolinite is presented

weddell sea abyssal sediments a record of antarctic bottom water flow abstract deep circulation in the weddell sea is a clockwise gyre with bottom water formed by mixing along the southern and western margins most antarctic bottom water originates here leaving the weddell sea to the east depths 4500 m or to the north depths 16 m ma sediments from the deep weddell basin are hemipelagic muds with ash laminae and mainly in the centre of the gyre distal turbidites derived from the southwest thin debris flows occur near seamounts the hemipelagic muds become coarser from the centre to the edge of the gyre winnowing by strong bottom currents is localised along the northern margin of the basin the absence of diatoms from the weddell basin sediments may result from dissolution as well as low productivity sediments from jane basin consist of alternating diatomaceous and barren hemipelagic muds considered to represent interglacial and glacial conditions respectively the diatomaceous sediments contain more silt suggesting that bottom water flow increases during interglacial periods

late pliocene sedimentation in lake baikal implications for climatic and tectonic change in se siberia abstract within the framework of the baikal drilling project bdp a 192 m long sediment core bdp 96 1 was recovered from the academician ridge a submerged topographic high between the north and central basins of lake baikal sedimentological clay mineralogical and geochemical investigations were carried out on the core interval between 90 and 124 m depth corresponding to ca 2 4 3 4 ma the aim was to reconstruct the climatic and tectonic history of the continental region during the intensification of northern hemisphere glaciation in late pliocene time a major climate change occurred in the lake baikal area at about 2 65 ma enhanced physical weathering in the catchment mirrored in the illite to smectite ratio and temporarily reduced bioproduction in the lake reflected by the diatom abundance evidence a change towards a colder and more arid climate probably associated with an intensification of the siberian high in addition the coincident onset of distinct fluctuations in these parameters and in the zr al ratio suggests the beginning of the late cenozoic high amplitude climate cycles at about 2 65 ma fluctuations in the zr al ratio are traced back to changes in the aeolian input with high values in warmer more humid phases due to a weaker siberian high assuming that the sand content in the sediment reflects tectonic pulses the lake baikal area was tectonically active during the entire investigated period but in particular around 2 65 ma tectonic movements have likely led to a gradual catchment change since about 3 15 ma from the western towards the eastern lake surroundings as indicated in the geochemistry and clay mineralogy of the sediments the strong coincidence between tectonic and climatic changes in the baikal area hints at the himalayan uplift being one of the triggers for the northern hemisphere glaciation

aerial infrared imaging reveals large nutrient rich groundwater inputs to the ocean 1 regional high resolution 0 1 c 0 5 m low altitude thermal infrared imagery tir reveals the exact input locations and fine scale mixing structure of massive cool groundwaters that discharge into the coastal zone as both diffuse flows and as 30 large point sourced nutrient rich plumes along the dry western half of the large volcanic island of hawaii these inputs are the sole source of new nutrient delivery to coastal waters in this oligotrophic setting water column profiling and nutrient sampling show that the plumes are cold buoyant nutrient rich brackish mixtures of groundwater and seawater by way of example we illustrate in detail one of the larger plumes which discharges ca 12 000 m3 d 1 ca 8 600 m3 d 1 freshwater rates comparable in volume to high flux groundwater outputs in better known tropical karst terrains we further show how nutrient mixing trends may be integrated into tir sea surface temperatures to produce surface water nutrient maps of regional extent

biogeochemical weathering under ice size matters 1 the basal regions of continental ice sheets are gaps in our current understanding of the earth s biosphere and biogeochemical cycles we draw on existing and new chemical data sets for subglacial meltwaters to provide the first comprehensive assessment of sub ice sheet biogeochemical weathering we show that size of the ice mass is a critical control on the balance of chemical weathering processes and that microbial activity is ubiquitous in driving dissolution carbonate dissolution fueled by sulfide oxidation and microbial co2 dominate beneath small valley glaciers prolonged meltwater residence times and greater isolation characteristic of ice sheets lead to the development of anoxia and enhanced silicate dissolution due to calcite saturation we show that sub ice sheet environments are highly geochemically reactive and should be considered in regional and global solute budgets for example calculated solute fluxes from antarctica 72 130 t yr 1 are the same order of magnitude as those from some of the world s largest rivers and rates of chemical weathering 10 17 t km 2 yr 1 are high for the annual specific discharge 2 3 4 1 10 3 m our model of chemical weathering dynamics provides important information on subglacial biodiversity and global biogeochemical cycles and may be used to design strategies for the first sampling of antarctic subglacial lakes and other sub ice sheet environments for the next decade

clay mineral fluctuations and surface textural analysis of quartz grains in pliocene quaternary marine sediments from wilkes land continental rise east antarctica paleoenvironmental significance abstract pliocene quaternary marine sediments from wilkes land continental rise were investigated using clay mineral analysis and quartz grain surface texture observations the studied piston cores were collected during a geophysical and geological survey in the framework of the italian and australian wega project the cores were collected along two transects crossing the channel mound system that characterizes the wilkes land continental rise massive and laminated facies were recognized in these sedimentary sequences the clay mineral assemblages are dominated by illite smectite and chlorite occur in intermediate amounts whereas kaolinite is scarce illite derives from the hinterland of the mertz and ninnis glaciers smectite and kaolinite derive from the ross sea area and they are transported by westward marine bottom currents chlorite is derived both from the adjacent continent and from the victoria land different concentrations of individual clay minerals in the massive and laminated facies are controlled by the interplay between different source areas and the main sedimentary processes glacial and eolian quartz grains prevail in the massive units indicating short transportation and rapid deposition from melting ices with no further significant transport action by marine currents in the laminated facies the high amount of quartz grains affected by high energy subaqueous transport features are related both to turbiditic processes and to bottom current transport

the origin of clay minerals in soils of king george island south shetland islands west antarctica and its implications for the clay mineral compositions of marine sediments abstract clay minerals in the soils of king george island south shetland islands west antarctica were investigated to evaluate their influence upon the composition of marine sediments derived from them paleohydrothermal activity has developed phyllic argillic alteration zones in restricted areas of the volcanic bedrock illite and kaolinite show a highly localized distribution in the soils of the phyllic argillic zones whereas chlorite dominates in the soils of unaltered bedrock the localized distribution indicates that illite and kaolinite are residues from altered bedrock whereas chlorite originates from unaltered bedrock smectite in the soils is rather uniformly distributed with no relationship to the phyllic argillic zones it is mostly the alteration product of eolian pumice shards which are found scattered throughout the soils on a microscopic scale the eolian provenance of smectite associated with pumice shards is supported by a uniform distribution of smectite coexistence of fresh and altered pumice shards and rather short exposure after deglaciation smectites likely have been formed in a remote source around volcanic craters and reworked by repeated eruptions formation of clay minerals by chemical weathering as suggested in previous studies appears to be insignificant on king george island even though the climate is warmer and more humid than in other antarctic regions smectite and kaolinite in seafloor sediments around the south shetland islands do not indicate chemical weathering in the source area instead their occurrence suggests that volcanism igneous intrusion and related hydrothermal alterations were active in the south shetland islands during the cenozoic

a shift in heavy and clay mineral provenance indicates a middle miocene onset of a perennial sea ice cover in the arctic ocean during the arctic coring expedition acex a 428 m thick sequence of upper cretaceous to quaternary sediments was penetrated the mineralogical composition of the upper 300 m of this sequence is presented here for the first time heavy and clay mineral associations indicate a major and consistent shift in provenance from the barents kara western laptev sea region characterized by presence of common clinopyroxene to the eastern laptev east siberian seas in the upper part of the section characterized by common hornblende amphibole sea ice originating from the latter source region must have survived at least one summer melt cycle in order to reach the acex drill site if considering modern sea ice trajectories and velocities this shift in mineral assemblages probably represents the onset of a perennial sea ice cover in the arctic ocean which occurred at about 13 ma thus suggesting a coeval freeze in the arctic and antarctic regions

high resolution in situ thermal imaging of microbial mats at el tatio geyser chile shows coupling between community color and temperature 1 microbial mats have spatially heterogeneous structured communities that manifest visually through vibrant color zonation often associated with environmental gradients we report the first use of high resolution thermal infrared imaging to map temperature at four hot springs within the el tatio geyser field chile thermal images with millimeter resolution show drastic variability and pronounced patterning in temperature with changes on the order of 30 c within a square decimeter paired temperature and visual images show that zones with specific coloration occur within distinct temperature ranges unlike previous studies where maximum minimum and optimal temperatures for microorganisms are based on isothermally controlled laboratory cultures thermal imaging allows for mapping thousands of temperature values in a natural setting this allows for efficiently constraining natural temperature bounds for visually distinct mat zones this approach expands current understanding of thermophilic microbial communities and opens doors for detailed analysis of biophysical controls on microbial ecology

persistent environmental change after the paleocene eocene thermal maximum in the eastern north atlantic the paleocene eocene thermal maximum petm 56 ma is associated with abrupt climate change carbon cycle perturbation ocean acidification as well as biogeographic shifts in marine and terrestrial biota that were largely reversed as the climatic transient waned we report a clear exception to the behavior of the petm as a reversing climatic transient in the eastern north atlantic deep sea drilling project site 401 bay of biscay where the petm initiates a greatly prolonged environmental change compared to other places on earth where records exist the observed environmental perturbation extended well past the 13 c recovery phase and up to 650 kyr after the petm onset according to our extraterrestrial 3he based age model we observe a strong decoupling of planktic foraminiferal 18 o and mg ca values during the petm 13 c recovery phase which in combination with results from helium isotopes and clay mineralogy suggests that the petm triggered a hydrologic change in western europe that increased freshwater flux and the delivery of weathering products to the eastern north atlantic this state change persisted long after the carbon cycle perturbation had stopped we hypothesize that either long lived continental drainage patterns were altered by enhanced hydrological cycling induced by the petm or alternatively that the climate system in the hinterland area of site 401 was forced into a new climate state that was not easily reversed in the aftermath of the petm

sedimentary record of the mid pleistocene climate transition in the southeastern south atlantic odp site 1090 abstract one important goal of leg 177 of the ocean drilling program odp was to explore the nature of the mid pleistocene climate transition mpt on the southern hemisphere a suitable mpt record was encountered at site 1090 in the southeastern south atlantic where a 44 m thick sequence of quaternary diatom bearing foraminiferal muds and oozes was recovered on the agulhas ridge environmental responses to the mpt comprised changes in terrestrial climate biological productivity and regional ocean circulation as inferred from compositional sediment data and clay mineralogy a shift towards more arid conditions occurred between 900 and 800 ka in southern africa changes in palaeoceanography already started earlier since 1150 ka northward displacements of the polar front appeared during glacial periods and shifted the area of dominant diatom deposition towards site 1090 likewise glacial interglacial contrasts in regional conveyor circulation strengthened after 1200 ka and became most severe after 650 ka however while changes in regional conveyor circulation likely responded in tune with global ice volume changes and show the onset of 100 kyr cycles after 1200 ka an unusual 130 kyr pattern characterises the pattern of frontal movements between 1200 ka and 650 ka probably in response to imperfect adaptation of regional climate to the global 100 kyr climate cycles

clay minerals in the sediments of lake baikal a useful climate proxy lake baikal in south central siberia has been the focus of an international effort the baikal drilling project bdp to obtain continuous long cores upwards of 100 m from this unique rift valley lake and to interpret the paleoclimatic history from various proxy data as part of this effort the clay minerals were examined by two research teams a consistent clay mineral assemblage containing illite inter stratified illite smectite chlorite and kaolinite as the major minerals characterizes much of the modern sediments the relative abundance of these minerals changes with depth in both short piston cores from various parts of the lake and in 100 m long cores taken from the distal toe of the selenga delta bdp 93 independent analyses of the abun dance changes and correlation with other data from the cores show that the clays are responding to two influences 1 climatic fluctua tions particularly in the upper 40 m of the sedimentary record which show the relative amount of illite smectite and sometimes kaolinite increasing during warmer climate episodes and 2 source area chang es which are most evident below 40 m in the bdp 93 cores and mark a shift from an eastern buguldeika river to a western selenga river source the clay mineral based climate fluctuations are correlative with the marine oxygen isotope record through stage 7 and provide a relatively simple and cost effective tool for gaining insight into the pa leoclimate of this interior continental site

distribution and provenance of wind blown se pacific surface sediments article i nfo the reconstruction of low latitude ocean atmosphere interactions is one of the major issues of paleo environmental studies the trade winds extending over 20 to 30 of latitude in both hemispheres between the subtropical highs and the intertropical convergence zone are major components of the atmospheric circulation and little is known about their long term variability on geological time scales in particular in the pacific sector we present the modern spatial pattern of eolian derived marine sediments in the eastern equatorial and subtropical pacific 10 n to 25 s as a reference data set for the interpretation of se pacific paleo dust records the terrigenous silt and clay fractions of 75 surface sediment samples have been investigated for their grain size distribution and clay mineral compositions respectively to identify their provenances and transport agents dust delivered to the southeast pacific from the semi to hyper arid areas of peru and chile is rather fine grained 4 8 m due to low level transport within the southeast trade winds nevertheless wind is the dominant transport agent and eolian material is the dominant terrigenous component west of the peru chile trench south of 5 s grain size distributions alone are insufficient to identify the eolian signal in marine sediments due to authigenic particle formation on the sub oceanic ridges and abundant volcanic glass around the galapagos islands together with the clay mineral compositions of the clay fraction we have identified the dust lobe extending from the coasts of peru and chile onto galapagos rise as well as across the equator into the doldrums illite is a very useful parameter to identify source areas of dust in this smectite dominated study area

the geochemical and mineralogical fingerprint of west antarctica s weak underbelly pine island and thwaites glaciers abstract the marine based west antarctic ice sheet wais is considered the most unstable part of the antarctic ice sheet with particular vulnerability in the amundsen sea sector where glaciers are melting at an alarming rate far field sea level data and ice sheet models have pointed towards at least one major wais disintegration during the late quaternary but direct evidence for past collapse s from ice proximal geological archives remains elusive in order to facilitate geochemical and mineralogical tracing of the two most important glaciers draining into the amundsen sea i e pine island glacier pig and thwaites glacier tg we here provide the first multi proxy provenance analysis of 26 seafloor surface sediment samples from pine island bay our data show that the fingerprints of detritus delivered by pig and tg are clearly distinct near the ice shelf fronts of both ice stream systems for all grain sizes and proxies investigated glacial detritus delivered by pig is characterised by low end values 9 high 87sr 86sr ratios 0 728 low smectite content the geochemical and mineralogical fingerprints for pig and tg reported here provide novel insights into sub ice geology and allow us to trace both drainage systems in the geological past under environmental conditions more similar to those envisioned in the next 50 to 100 years

origin of detrital fluxes in the southeast indian ocean during the last climatic cycles because of a close relationship between detrital flux variations and magnetic susceptibility ms flux ms cm 3 of bulk sediment multiplied by the linear sedimentation rate variations in the southeast indian basin of the southern ocean ms flux profiles have been used to examine the spatial and temporal detrital flux changes in this basin during the last climatic cycle results indicate a general increase in detrital material input during the coldest periods suggesting a widespread phenomenon at least on the basin scale mineralogical data geochemical data and 87sr 86sr isotopic ratios have been used to determine the origin and transport mechanisms responsible for increased detrital flux during glacial periods mineralogical and geochemical data show that these glacial highs are due to increases in both kerguelen crozet volcanic and antarctic detrital inputs the 87sr 86sr isotopic composition of the 45 m fraction indicates that the kerguelen crozet province contributes to at least 50 of the coarse particule input to the west this contribution decreases eastward to reach less than 10 these tracers clearly indicate that the crozet kerguelen province was a major source region of detrital in the western part of the basin during glacial times in contrast material of antarctic origin is well represented in the whole basin fine and coarse fractions because of the minor amount of coarse particles in the sediments volcanic particles from kerguelen and crustal particles from antarctica have most probably been transported by the antarctic bottom water current and or the circumpolar deepwater current during glacial periods as is the case today nevertheless the presence of coarse particles even in low amount suggests also a transport by ice rafting sea ice and icebergs originated from both kerguelen and antarctic sources however the relative importance of both hydrographic and ice rafting modes of transport cannot be identified accurately with our data during low sea level stands glacial maximum periods increasing instability and erosion of the continental platform and shallow plateaus could have resulted in a more efficient transfer of crustal and volcano detrital material to the southeast indian basin at the same time extension of the grounded ice shelves over the continental margins and increase in the erosion rate of the antarctic ice sheet could have induced a greater input of ice rafted detritus ird to southern ocean basins enhancement of the circumpolar deepwater current strength might have also carried a more important flux of detrital material from kerguelen however an increase in the bottom water flow is not necessarily required

variations in the composition of the clay fraction of the cenozoic pagodroma group east antarctica implications for determining provenance abstract the cenozoic pagodroma group in the northern prince charles mountains east antarctica is a glaciomarine succession of fjordal character comprising four uplifted formations of different ages the composition of the the assemblage of the upper oligocene to lower miocene mount johnston formation is characterised by the dominance of illite and intermediate concentrations of chlorite similar to that assemblage is the clay mineral suite of the middle miocene fisher bench formation where illite and chlorite together account for 95 of the clay minerals the middle to upper miocene battye glacier formation is the only formation with significant and persistent smectite concentrations although illite is still dominant the kaolinite concentration is also high and is even higher than that of chlorite the clay fraction of the upper pliocene to lower pleistocene bardin bluffs formation is characterised by maximum kaolinite concentrations and relatively low illite and chlorite concentrations the bulk of the clay fraction in each formation can be explained by the physical weathering and erosion of a nearby source under glacial conditions in the case of mount johnston formation and fisher bench formation this source may be situated in the metavolcanic and gneissic rocks of fisher massif the sediments of the bardin bluffs formation indicate a local source within the amery oasis where proterozoic granitoid rocks and gneisses and permo triassic fluvial rocks of the amery group are exposed these results suggest a strong local imprint on the glacial sediments as northwards flowing ice eroded the bedrock in these areas the origin of the clay fraction of the battye glacier formation is a matter of debate the smectite and kaolinite content most easily can be explained by erosion of sources largely hidden beneath the ice upstream less likely these clay minerals reflect climatic conditions that were much warmer and wetter than today facilitating chemical weathering

an antarctic stratigraphic record of stepwise ice growth through the eocene oligocene transition earth s current icehouse phase began 34 m y ago with the onset of major antarctic glaciation at the eocene oligocene transition changes in ocean circulation and a decline in atmospheric greenhouse gas levels were associated with stepwise cooling and ice growth at southern high latitudes the antarctic cryosphere plays a critical role in the ocean atmosphere system but its early evolution is still poorly known with a near field record from prydz bay antarctica we demonstrate that antarctic ice growth was stepwise and had an earlier onset than previously suggested prydz bay lies downstream of a major east antarctic ice sheet drainage system and its sedimentary records uniquely constrain the timing of ice sheet advance onto the continental shelf we investigated a detrital record extracted from three ocean drilling program drill holes within a new depositional and chronological framework spanning the late eocene to early oligocene ca 36 33 ma the chemical index of alteration cia and the s index calculated from the major element geochemistry of bulk samples yielded estimates of chemical weathering intensities and mean annual temperature on the east antarctic continent we document evidence for late eocene mountain glaciation along with transient warm events at 35 8 34 8 ma from 34 4 ma associated with the eocene oligocene transition precursor 18o excursion glaciers advanced into prydz bay coincident with a decline in chemical weathering and temperature we conclude that antarctic continental ice growth commenced with the eocene oligocene transition precursor glaciation during a time of subantarctic surface ocean cooling and a decline in atmospheric pco2 these results call for dynamic high latitude feedbacks that are currently poorly represented in earth system models and emphasize the need for additional near field glacio sedimentological high latitude sea surface temperature and pco2 records across the eocene oligocene transition

deciphering color reflectance data of a 520 kyr sediment core from the southern ocean method application and paleoenvironmental implications sediment color reflectance contains important information on paleoenvironmental changes such data are routinely measured on sediment cores from the southern ocean their usefulness however is undervalued here for the first time color reflectance of an 520 kyr sediment core retrieved off prydz bay east antarctica was intensively investigated to correlate sediment color changes to changes in sediment compositions total carbon total organic carbon x ray fluorescence derived fe ti and br ti ratios water content and mineral composition of sediment from this core and color reflectance of another two sediment cores retrieved nearby were analyzed in this study the raw reflectance data were transformed into their first order derivatives and subjected to factor analysis algorithms a four factor model was selected to unmix the data set explaining 80 of the total data variance its robustness is supported by similar factor analysis results from the other two cores the four factors represent from factors 1 4 pulses of sedimentary mn enrichment and fe3 fe2 changes in clay minerals relative content changes of colorless components hematite and goethite and water respectively scores of factor 1 show high spikes at glacial terminations recording enhanced deglacial ventilation in the abyssal southern ocean scores of factor 2 mainly reflect biogenic components and chlorite but are further complicated by refractory terrigenous organic carbon and mn oxides hydroxides higher scores of factor 3 occur mainly at peak interglacial intervals associated with enhanced transport of sediment of antarctic origin by oceanic currents water content factor 4 in the core sediment was significantly influenced by opal content and sediment grain size compositions

sedimentological evidence for the formation of an east antarctic ice sheet in eocene oligocene time middle eocene to late oligocene sediments recovered at ocean drilling program sites 689 and 690 on maud rise in the southernmost atlantic ocean and at sites 738 and 744 on kerguellen plateau in the southernmost indian ocean were analysed in order to study the depositional environment and the palaeoclimate special emphasis was placed on the reconstruction of the formation of a cryosphere on the antarctic continent the investigations include quantifications of carbonate and opal contents grain size analyses and studies of clay mineral assemblages the sedimentary sequence at all sites under investigation is highly pelagic with nannofossil oozes and chalks dominant the first indication of probable glacierization at sea level is in the form of isolated gravel and terrigenous sand grains which indicate ice rafting from middle eocene time at c 45 5 ma this is supported by enhanced concentrations of detrital chlorite and reworked kaolinite probably some glaciers reached the sea while most of the continent remained under the influence of a humid and warm to temperate climate the growth of the inland ice resulted in enhanced physical weathering and in increased contents of detrital chlorite and kaolinite from about 40 ma a strengthening of the glacial conditions and the onset of continental east antarctic glaciation is recorded in early oligocene sediments with an age of 36 ma all major sediment parameters document this event the clay mineralogy changed between c 36 3 ma and c 35 5 ma from smectite dominated assemblages to illite and chlorite dominated assemblages the latter being indicative of physical weathering under cooler climates large quantities of ice rafted gravel and sand accumulated on the kerguelen plateau between 36 0 ma and 35 8 ma at the same time an increase in opal content occurred as well as a decrease in carbonate the sediment parameters imply that the east antarctic continent was more or less totally buried beneath the ice during oligocene time the ice sheet however probably did not have a polar but a temperate character as indicated by the occurrence of nothofagus and relatively warm surface water temperatures prohibiting the long distance transport of debris by icebergs

late quaternary sedimentation and glacial history of the western svalbard continental margin abstract glacigenic sediments recovered in shallow cores from the western svalbard continental slope are subdivided into five facies associations based on grain size sedimentary structure mineralogy petrography and geochemistry two diamicton facies are recognised one of which is interpreted as hemipelagic mud with variable amounts of ice rafted debris ird and the other as a product of mass movement the diamictons are associated with melting of icebergs during glacial melt events and debris flow deposition on the submarine fans during peak glaciation respectively laminated to layered mud and turbidites seem to be closely related to eustatic fall in sea level and erosion of banks located on the continental shelf resulting in accumulation of fine grained organic rich deposits and thin silt and sand layers on the continental slope middle weichselian was characterised by several phases of extensive iceberg production and input of ird the first phase 60 55 ka is correlated with a glacier advance on svalbard but the following phases 54 44 ka can not be correlated with glacier advances on land this demonstrates that there may have been more glaciations than recorded on svalbard and that ice sheets at high northern latitudes fluctuated more frequently than previously assumed the composition of the ird deposited after 54 ka suggests that the ice sheets during these advances were located in the eastern svalbard barents sea area the late weichselian growth of the svalbard barents sea ice sheet occurred probably in two steps nucleation of a continental based ice sheet between 27 and 22 5 ka followed by a rapid advance to the shelf edge when the ice margin reached the soft clay rich sediments on the continental shelf eustatic lowering of the sea level during the initial phase led to bank exposure and erosion bringing large quantities of fine grained organic rich sediments to the deep sea during peak glaciation glaciers provided a localised supply of sediments to the shelf troughs and the upper slope which were redistributed by debris flows the marine based svalbard barents sea ice sheet started to retreat around 14 5 ka through massive iceberg discharge the retreat was interrupted by a short lived advance accompanied by erosion of the shelf banks and redistribution of organic rich sediments to the continental slope the final ice recession started around 12 ka and ended close to 9 ka when the fjords of svalbard were essentially ice free large amounts of meltwater released during the removal of the svalbard barents sea ice sheet cooled down the surface waters of the norwegian greenland sea and formed a widespread sea ice cover between 12 and 8 ka input of terrigenous material was greatly reduced during the early part of holocene the present interglacial is characterised by erosion of the shelf and upper slope by bottom currents leaving a prominent lag deposit

plio quaternary sedimentation on the wilkes land continental rise preliminary results abstract the wilkes land continental rise is characterised by mounds and channels with approximately a north south elongation perpendicular to the margin proximal mound relief is up to 1000 m decreasing to about 300 m in the central part during the geophysical and geological survey conducted on in february march 2000 by the joint italian and australian wega project onboard r v tangaroa 11 piston cores were collected along two transects crossing the channel mound system all cores were logged for physical magnetic susceptibility and density and acoustic properties p wave velocity split cores were x rayed and samples were analysed for clay mineral assemblages chemical and micropaleontological diatoms foraminifera and nannofossils content glacial and interglacial intervals have been recognised in the sediment cores the interglacial facies consists of massive mud distinguished by a bioturbated massive mud occasionally with fine grained ice rafted debris ird and b structureless massive mud with abundant fine to coarse grained ird containing well preserved open ocean diatoms the glacial facies is represented by laminated mud with planar and or cross laminations with occasional isolated dropstones and rare poorly preserved sea ice diatoms the sharp boundary characterizing the limit between massive to laminated facies is interpreted to indicate a fast glacial onset in contrast the smooth passage presents from laminated to massive sediments indicates a gradual glacial waning recent down slope gravity flows have been identified in a turbidite a normally graded coarse grained sand recovered in the thalweg of jussie canyon and probably also in the massive debris facies from the steep side of mound a the massive debris is characterised by structureless and unsorted gravel and pebbles within a muddy matrix clay mineral assemblages and grain lithologies indicate a hinterland wilkes basin and continental shelf provenance for the terrigenous fraction

what do yellowish brown soils and stone layers tell us about late quaternary landscape evolution and soil development in the humid tropics a field study in the serra dos orgaos southeast brazil abstract the occurrence spatial distribution and properties of yellowish brown soils and stone layers allow deriving conclusions about landscape evolution and soil development in the humid tropics in this study standard soil profiles and saprolite and subsoil samples along an altitudinal gradient from the high mountain ranges 1500 m a s l to the lowlands 8 m a s l in the serra dos orgaos mountain range in the brazilian state of rio de janeiro are analyzed field mapping techniques and laboratory methods are used to analyze the samples and reconstruct late quaternary landscape and soil development processes it is suggested that the formation of stone layers is polygenetic with dissolution processes geogenic bioturbation pedogenic and slope processes including coverage of terrace gravels geomorphic as possible mechanisms yellowing of the upper soil horizons is assumed to be the result of bio chemical processes xanthization chelation which took and take place in periods of wet climate conditions and closed forest cover in the late quaternary it can be distinguished between pre colonial and modern yellowish brown colluvial deposits with or without stone layer s it is suggested that the deposition of pre colonial colluvial soils primarily took place in dryer periods and forest retreat during the late pleistocene and holocene however it is proposed that the model of cyclic changes between geomorphic activity with colluviation on the one hand and stability and pedogenesis on the other hand need to be further differentiated due to small scale temporal and spatial climatic changes and sensitive vegetation responses to these fluctuations moreover it is suggested that due to the very steep relief and intense rainfall in the central mountain ranges of the serra dos orgaos accelerated displacement of soil material by landslides and mudslides took also place under closed forest cover in the late holocene modern colluvial deposits have originated from deforestation and land use intensification processes within the last 300 years they cover wide parts of the lower slopes foothills and depressions and indicate massive erosion and deposition processes since the european colonization

clay mineral provenance of sediments in the southern bellingshausen sea reveals drainage changes of the west antarctic ice sheet during the late quaternary the belgica trough and the adjacent belgica trough mouth fan in the southern bellingshausen sea pacific sector of the southern ocean mark the location of a major outlet for the west antarctic ice sheet during the late quaternary the drainage basin of an ice stream that advanced through belgica trough across the shelf during the last glacial period comprised an area exceeding 200 000 km 2 in the west antarctic hinterland previous studies mainly based on marine geophysical data from the continental shelf and slope focused on the bathymetry and seafloor bedforms and the reconstruction of associated depositional processes and ice drainage patterns in contrast there was only sparse information from seabed sediments recovered by coring in this paper we present lithological and clay mineralogical data of 21 sediment cores collected from the shelf and slope of the southern bellingshausen sea most cores recovered three lithological units which can be attributed to facies types deposited under glacial transitional and seasonally open marine conditions the clay mineral assemblages document coinciding changes in provenance the relationship between the clay mineral assemblages in the subglacial and proglacial sediments on the shelf and the glacial diamictons on the slope confirms that a grounded ice stream advanced through belgica trough to the shelf break during the past thereby depositing detritus eroded in the west antarctic hinterland as soft till on the shelf and as glaciogenic debris flows on the slope the thinness of the overlying transitional and seasonally open marine sediments in the cores suggests that this ice advance occurred during the last glacial period clay mineralogical acoustic sub bottom and seismic data furthermore demonstrate that the palaeo ice stream probably reworked old sedimentary strata including older tills on the shelf and incorporated this debris into its till bed the geographical heterogeneity of the clay mineral assemblages in the sub and proglacial diamictons and gravelly deposits indicates that they were eroded from underlying sedimentary strata of different ages these strata may have been deposited during either different phases of the last glacial period or different glacial and interglacial periods additionally the clay mineralogical heterogeneity of the soft tills recovered on the shelf suggests that the drainage area of the palaeo ice stream flowing through belgica trough changed through time c 2009 elsevier b v all rights reserved

evaluating the paleoclimatic significance of clay mineral records from a late pleistocene loess paleosol section of the ili basin central asia in this study we present clay mineral records from a late pleistocene loess paleosol sequence in the ili basin central asia and assess their significance for paleoclimatic reconstruction the results show that the clay minerals are mainly illite average 60 and chlorite 28 with minor kaolinite 9 and smectite 3 illite was of detrital origin with no obvious modification to its crystal structure increases in illite content in the loess are ascribed to wind intensity rather than pedogenesis high proportions of illite in the clay fraction and of muscovite in the bulk samples of the paleosol units may lead to an overestimation of the weathering intensity kaolinite was likely inherited from the sedimentary rocks while chlorite might have been inherited from both sedimentary and metamorphic rocks the paleoclimatic signals of kaolinite and chlorite were unclear due to reworking by both fluvial and eolian systems smectite was more likely formed by the transformation of biotite and illite and its variation in the loess sequence was also controlled by wind intensity this was largely due to aggregation and is unlikely to reflect moisture changes although the interpretation of paleoclimate evolution may contain some uncertainties clay mineralogy does provide the possibility of tracing dust provenance

ocean circulation patterns and dust supply into the south atlantic during the last glacial cycle revealed by statistical analysis of kaolinite chlorite ratios abstract multivariate statistical analysis on the kaolinite chlorite ratios from 20 south atlantic sediment cores allowed for the extraction of two processes controlling the fluctuations of the kaolinite chlorite ratio during the last 130 000 yrs 1 the relative strength of north atlantic deep water nadw inflow into the south atlantic ocean and 2 the influx of aeolian sediments from the south african continent the nadw fluctuation can be traced in the entire deep south atlantic while the dust signal is restricted to the vicinity of south africa our data indicate that nadw formation underwent significant changes in response to glacial interglacial climate changes with enhanced export to the southern hemisphere during interglacials the most pronounced phases with enhanced south african dust export esade occurred during cold marine isotope stage mis 5d and across the late glacial holocene transition from 16 ka to 4 ka mis 2 to 1 this particular pattern is attributed to the interaction of antarctic sea ice extent the position of the westerlies and the south african monsoon system

formation of silica oncoids around geysers and hot springs at el tatio northern chile siliceous oncoids up to 4 cm in diameter are common on the laterally extensive sinter aprons that surround the spectacular geysers and hot springs at el tatio in northern chile many of these complex oncoids developed close to geyser and spring vents that discharge boiling water internally the oncoids which are composed of precipitated amorphous silica are formed of complex arrays of spicules and concentric laminae as well as detrital volcanic grains spicular growth is dominant in most examples the formation and growth of the spicules and concentric laminae were mediated by a microbial community which included filamentous microbes mucus and possibly bacteria the microbes and mucus were silicified by replacement and encrustation in some laminae the filamentous microbes lay parallel to the growth surface in other laminae most filaments forming the thin mats were suberect amorphous silica precipitated between the filaments occluded porosity and commonly disguised the microbial fabric the oncoids grew on the proximal sinter aprons around the geyser vents and hot spring pools most growth took place subaerially with the silica delivered to the precipitation sites by splashing water from the geysers and or periodic shallow flooding of the discharge aprons unlike silica oncoids at other geothermal sites vertical growth of oncoids that formed in some rimstone pools was not limited by water depth

late quaternary glacial marine to marine sedimentation in the pennell trough ross sea antarctica abstract late pleistocene and holocene palaeoenvironmental changes were studied in four gravity cores up to 7 8 m long from the pennell trough a nw se trending basin 160 km long and 60 km wide in the central ross sea antarctica with depths occasionally greater than 600 m differences in environments and depositional processes during the last glacial and postglacial epochs were investigated using x rays and volume magnetic susceptibility vms further analyses included bulk and clay mineral composition micropalaeontological studies both benthic and planktic foraminifera and radiometric dating we compare our sedimentological geochemical organic carbon and nitrogen content and geotechnical shear strength and water content results to those on cores previously taken from the region these analyses suggest that prior to the last glacial maximum lgm a glacial marine diamicton

the hot spring and geyser sinters of el tatio northern chile abstract the siliceous sinter deposits of el tatio geothermal field in northern chile have been examined petrographically and mineralogically these sinters consist of amorphous silica opal a deposited around hot springs and geysers from nearly neutral silica saturated sodium chloride waters water cooling and evaporation to dryness are the main processes that control the opal a deposition in both subaqueous and subaerial settings in close spatial relation to microbial communities all fingerprints of organisms observed in the studied sinter samples represent microbes and suggest that the microbial community is moderately diverse cyanobacteria green bacteria and diatoms the most important ecological parameter is the temperature gradient which is closely related to the observed depositional settings 1 geyser setting water temperature 70 86 c boiling point at el tatio 4200 m a s l coarse laminated sinter macrostructure with rapid local variations biota comprises non photosynthetic hyperthermophilic bacteria 2 splash areas around geysers water temperature 60 75 c laminated spicule and column macrostructure locally forming cupolas

reconstruction of changes in the weddell sea sector of the antarctic ice sheet since the last glacial maximum the weddell sea sector is one of the main formation sites for antarctic bottom water and an outlet for about one fifth of antarctica s continental ice volume over the last few decades studies on glacial geological records in this sector have provided conflicting reconstructions of changes in ice sheet extent and ice sheet thickness since the last glacial maximum lgm at ca 23 19 calibrated kiloyears before present cal ka bp terrestrial geomorphological records and exposure ages obtained from rocks in the hinterland of the weddell sea ice sheet thickness constraints from ice cores and some radiocarbon dates on offshore sediments were interpreted to indicate no significant ice thickening and locally restricted grounding line advance at the lgm other marine geological and geophysical studies concluded that subglacial bedforms mapped on the weddell sea continental shelf subglacial deposits and sediments over compacted by overriding ice recovered in cores and the few available radiocarbon ages from marine sediments are consistent with major ice sheet advance at the lgm reflecting the geological interpretations different ice sheet models have reconstructed conflicting lgm ice sheet configurations for the weddell sea sector consequently the estimated contributions of ice sheet build up in the weddell sea sector to the lgm sea level low stand of 130 m vary considerably in this paper we summarise and review the geological records of past ice sheet margins and past ice sheet elevations in the weddell sea sector we compile marine and terrestrial chronological data constraining former ice sheet size thereby highlighting different levels of certainty and present two alternative scenarios of the lgm ice sheet configuration including time slice reconstructions for post lgm grounding line retreat moreover we discuss consistencies and possible reasons for inconsistencies between the various reconstructions and propose objectives for future research the aim of our study is to provide two alternative interpretations of glacial geological datasets on antarctic ice sheet history for the weddell sea sector which can be utilised to test and improve numerical ice sheet models

effects of geomorphology and groundwater level on the spatio temporal variability of riverine cold water patches assessed using thermal infrared tir remote sensing temperature is a key factor for river ecosystems in summer patches of cold water are formed in the river by groundwater seepage these patches have strong ecological significance and extend to the surface water in a well mixed riverine system these patches can serve as thermal refuges for some fish species during summer in this study the temporal variability and spatial distribution of cold water patches were explored along a 50 km river reach the lower ain river france using thermal infrared airborne remote sensing this study examines a new range of processes acting on cold water patches at different scales that have not previously been touched upon in the literature three airborne campaigns were conducted during the summers of 2010 2011 and 2014 based on these images a large number of cold water patches were identified using an automated method four types of patches were observed tributary plumes cold side channels former channels or point bar backwater channels side seeps located directly in the river channel and gravel bar seeps occurring at the downstream end of gravel bars logistic regression was used to analyze the longitudinal distribution of cold water patches according to geomorphologic indicators reflecting current or past fluvial process side seeps were found to be related to the local geology cold side channels were correlated to contemporary and past lateral river mobility gravel bar seeps were related to the current development of bars and are more prevalent in wandering reaches than in single bed incised and paved reaches the logistic model was subsequently used to evaluate gravel bar seep variability in the past the model suggests larger numbers of seeps in the mid 20th century when bar surface area was higher interannual variability in the occurrence and spatial extent of side seeps and gravel bar seeps appear to be related to groundwater level fluctuations cold side channels exhibited greater interannual stability nonetheless among all patch types some are quite stable over time while others are transient these results can be used to target areas with high densities of stable and spatially extensive cold water patches that are considered ecological refuges in the context of pronounced low flow and a rise in water temperature

magnetobiostratigraphic chronology of the eocene oligocene transition in the ciros 1 core victoria land margin antarctica implications for antarctic glacial history in 1986 cores were obtained to a depth of 702 m with 98 recovery from the ciros 1 drill hole beneath the ross sea on the victoria land margin glaciogene sediments identified near the base of the hole mark the earliest known record of antarctic glaciation initial biostratigraphic analysis indicated that the lower 336 m of the core is early oligocene in age and that the upper 366 m is of late oligocene early miocene age recently the chronology of the ciros 1 core has been questioned we developed a magnetostratigraphy for the lower 400 m of the ciros 1 core to clarify the chronology our magnetobiostratigraphic results indicate that the base of the ciros 1 core is early late eocene in age corresponding to chron c16r ca 36 5 ma we identify the eocene oligocene boundary at about 410 420 m within a 20 m thick poorly stratified bioturbated sandy mudstone this makes the ciros 1 core the highest latitude site 77 1 s from which this datum event has been recognized at 366 m a 4 m y hiatus which lies immediately beneath fluvial sediments accounts for most of chrons c11 and c12 we recognize three major climatic episodes in the ciros 1 core 1 the late eocene 34 5 36 5 ma 430 702 m when relatively warm conditions dominated and there were high sedimentation rates and some glacial activity 2 the late eocene early oligocene boundary interval 28 5 34 5 ma 340 430 m which was a transition from relatively warm to cooler conditions that coincided with glacial intensification sea level fall and subaerial erosion of the shelf and 3 the late oligocene early miocene 22 28 5 ma 50 340 m when large scale glaciation dominated the region and glaciers grounded across the continental shelf from correlation with global oxygen isotope and sea level records we infer that the antarctic climate and surrounding oceans cooled after separation of australia and antarctica and development of deep water circulation between them this marked the onset of the eocene oligocene transition at ca 34 5 ma a major east antarctic ice sheet did not develop until the early late oligocene boundary toward the end of the eocene oligocene transition ca 28 5 ma outlet glaciers did not breach the transantarctic mountains and ground across the ross sea shelf until 0 5 m y later ca 28 ma

implications of late eocene to early miocene clay mineral assemblages in mcmurdo sound ross sea antarctica on paleoclimate and ice dynamics abstract the clay mineral assemblages of upper eocene to lower miocene sediments recovered at the ciros 1 and mssts 1 drill sites on the mcmurdo sound shelf antarctica were analyzed in order to reconstruct the cenozoic antarctic paleoclimate and ice dynamics the assemblages are dominated by smectite and illite with minor amounts of chlorite and kaolinite the highest smectite amounts and best smectite crystallinities occur in the upper eocene part of ciros 1 below 425 445 mbsf they indicate that during their deposition chemical weathering conditions prevailed on the nearby continent large parts of east antarctica were probably ice free at that time but some glaciers reached the sea and contributed to the glaciomarine sedimentation in contrast only minor total amounts of smectite are present in oligocene and younger sediments due to the shift to mainly physical weathering on an ice covered antarctic continent however relative smectite percentages rise to more than 60 during two late oligocene intervals ca 27 5 26 2 and 25 0 24 5 ma and during one early miocene interval starting at ca 23 3 ma these intervals are characterized by ice masses coming probably from the south where volcanic rocks acted as a source as also indicated by the composition of the sand and gravel fractions during the other intervals the ice came from the west where the physical erosion of basement rocks and sedimentary rocks of the beacon supergroup in the transantarctic mountains provided high illite concentrations because the two drill sites are only 4 km apart their clay mineral records can be correlated this led to a new interpretation of the oligocene paleomagnetic data of the mssts 1 site and to a more detailed lithostratigraphic correlation of the miocene parts of the cores

environmental history of the south eastern south atlantic since the middle miocene evidence from the sedimentological records of odp sites 1088 and 1092 during leg 177 of the ocean drilling program odp well preserved middle miocene to pleistocene carbonate rich sediment records were recovered on a north south transect through the south eastern atlantic sector of the southern ocean at site 1088 on the agulhas ridge and site 1092 on meteor rise both sites were dominated by the deposition of calcareous nannofossil oozes through the miocene indicating low biological productivity in warm to temperate surface waters a continuous increase in the proportions of foraminifera since the latest miocene 6 5 ma points to enhanced nutrient supply possibly related to the global biogenic bloom event across the miocene pliocene boundary since the late pliocene different styles of biological productivity developed between the sites enhanced deposition of biosiliceous constituents at the southern site 1092 particularly in the early pleistocene is consistent with the formation of the circum antarctic opal belt since 2 5 ma in a setting near the polar front whereas carbonate deposition still prevailed at the northern site 1088 situated near the subtropical front clay mineral tracers of water mass advection together with the pattern of sedimentation rates and hiatuses reflect distinct pulses in the development of regional ocean circulation between 14 and 12 ma around 8 ma and since 2 8 ma these pulses can be related to antarctic ice sheet extension that mediates the production and flow of southern source water and stepwise increases in north atlantic deep water production that drives global conveyor circulation at site 1088 illite chemistry and silt clay ratios of the terrigenous sediment fraction reflect the history of terrestrial climate in southern africa with humid conditions prior to the early late miocene 9 7 ma followed by a dry episode until 7 7 ma the latest miocene and early pliocene were characterized by a humid episode until modern aridity was established in the late pliocene between 4 0 and 2 8 ma these climate changes were related to the latitudinal migration of climate belts in response to tectonically caused reorganizations in atmospheric and ocean circulation

late miocene early pliocene stratigraphy and paleoceanography of the south atlantic and southwest pacific oceans a synthesis the stratigraphy and paleoceanography of the late miocene and early pliocene have been examined at six sites in the south atlantic and southwest pacific oceans deep sea drilling project dsdp sites 284 516a 519 588 and 590 and two piston cores from chain cruise 115 a consistent stratigraphy was developed among sites using graphic correlation which resulted in age models for all sites that are tied to the revised paleomagnetic time scale of berggren et al 1985 applying these chronologies we assessed latitudinal and interocean contrasts in the stratigraphic ranges of late miocene early pliocene planktonic foraminiferal and nanno fossil datums salient stratigraphic results include 1 the last appearance datum lad of globoquadrina dehiscens is a late miocene 6 4 ma event in the subtropics and is not useful for the placement of the miocene pliocene m p boundary in this biogeographic province 2 the first appearance datum fad of globorotalia crassaformis occurred at 5 1 ma in the south atlantic near the m p boundary suggesting that gr crassaformis may have first evolved in the south atlantic and later migrated to other regions 3 in the southwest pacific the fads of gr margaritae 5 97 ma gr puncticulata 5 09 ma and gr crassaformis 4 87 ma are significantly time transgressive between temperate and warm subtropical regions time lags of 1 0 m y were required for these species to adapt to physical and or biotic conditions peripheral to their endemic biogeographic provinces 4 between the subtropics of the south atlantic and southwest pacific many planktonic foraminiferal datums fad of dentogloboquadrina altispira gr cibaoensis gr conomiozea gr margaritae and gq dehiscens and lad of gr cibaoensis markedly depart from the correlation suggested by magnetostratigraphy indicating that these datum levels are unreliable for correlation between these ocean basins 5 in contrast available calcareous nannofossil datum levels fall on or near the paleomagnetic correlation line indicating synchroneity of events within the subtropics 6 biostratigraphic magnetic and 87sr 86sr correlation between sites 588 and 519 and the m p neostratotype at capo rossello sicily suggests that the base of the zanclean stratotype occurs at 5 1 5 0 ma in the lower reversed subchron of the gilbert about 2 3 105 years above the gilbert chron 5 boundary oxygen isotopic results from dsdp sites 284 519 and ch115 piston cores confirm a prolonged benthic 18o increase in the latest miocene between 5 6 and 5 0 ma as originally proposed by shackleton and kennett 1975 at dsdp site 588 the benthic 18o record in the latest miocene is marked by high frequency fluctuations with amplitude variations of 0 5 and a long period wavelength component of 400 000 years maximum 18o values however occurred during the late miocene kapitean stage between 5 5 and 5 1 ma the late miocene 18o changes resulted from mid and high latitude cooling and pulses of ice sheet expansion and contraction glacial events were most intense during the latest miocene kapitean stage and occurred at 5 50 5 35 ma and at 5 10 ma glacial events are estimated to have lowered sea level by 40 to 60 m and contributed to the isolation and desiccation of the mediterranean basin during the late messinian interglacial conditions prevailed at 5 2 ma and between 5 0 and 4 1 ma ihe early pliocene the beginning of the pliocene was marked by changes in many proxy climatic indicators at all sites suggesting a prolonged interval of warm interglacial conditions between 5 0 and 4 1 ma during the earliest pliocene supplementary tables are available with entire article onmicrofiche order from american geophysical union 2000florida avenue n w washington dc 20009 documentp86 001 2 50 payment must accompany order

antarctic climate southern ocean circulation patterns and deep water formation during the eocene we assess early to middle eocene seawater neodymium nd isotope records from seven southern ocean deep sea drill sites to evaluate the role of southern ocean circulation in long term cenozoic climate change our study sites are strategically located on either side of the tasman gateway and are positioned at a range of shallow 500 m to intermediate deep 1000 2500 m paleowater depths unradiogenic seawater nd isotopic compositions reconstructed from fish teeth at intermediate deep indian ocean pelagic sites ocean drilling program odp sites 738 and 757 and deep sea drilling project dsdp site 264 indicate a dominant southern ocean sourced contribution to regional deep waters end t 9 3 1 5 iodp site u1356 off the coast of adelie land a locus of modern day antarctic bottom water production is identified as a site of persistent deep water formation from the early eocene to the oligocene east of the tasman gateway an additional local source of intermediate deep water formation is inferred at odp site 277 in the sw pacific ocean end t 8 7 1 5 antarctic proximal shelf sites odp site 1171 and site u1356 reveal a pronounced erosional event between 49 and 48 ma manifested by 2 end unit negative excursions in seawater chemistry toward the composition of bulk sediments at these sites this erosional event coincides with the termination of peak global warmth following the early eocene climatic optimum and is associated with documented cooling across the study region and increased export of antarctic deep waters highlighting the complexity and importance of southern ocean circulation in the greenhouse climate of the eocene

clay mineral distribution in surface sediments of the south atlantic sources transport and relation to oceanography abstract surface samples mostly from abyssal sediments of the south atlantic from parts of the equatorial atlantic and of the antarctic ocean were investigated for clay content and clay mineral composition maps of relative clay mineral content were compiled which improve previous maps by showing more details especially at high latitudes large scale relations regarding the origin and transport paths of detrital clay are revealed high smectite concentrations are observed in abyssal regions primarily derived from southernmost south america and from minor sources in southwest africa near submarine volcanoes of the antarctic ocean south sandwich bouvet island smectite contents exhibit distinct maxima which is ascribed to the weathering of altered basalts and volcanic glasses the illite distribution can be subdivided into five major zones including two maxima revealing both south african and antarctic sources a particularly high amount of mg and fe rich illites are observed close to east antarctica they are derived from biotite bearing crystalline rocks and transported to the west by the east antarctic coastal current chiorite and well crystallized dioctaedral illite are typical minerals enriched within the subantarctic and polarfrontal zone but of minor importance off east antarctica kaolinite dominates the clay mineral assemblage at low latitudes where the continental source rocks west africa brazil are mainly affected by intensive chemical weathering surprisingly a slight increase of kaolinite is observed in the enderby basin and near the filchner ronne ice shelf the investigated area can be subdivided into ten large scale clay facies zones with characteristic possible source regions and transport paths clay mineral assemblages of the largest part of the south atlantic especially of the western basins are dominated by chlorite and illite derived from the antarctic peninsula and southernmost south america and supported by advection within the circumantarctic deep water flow in contrast the east antarctic provinces are relatively small assemblages of the eastern basins north of 30 s are strongly influenced by african sources controlled by weathering regimes on land and by a complex interaction of wind river and deep ocean transport the strong gradient in clay mineral composition at the brazilian slope indicate a relatively low contribution of tropically derived assemblages to the western basins

spatio temporal pattern of detrital clay mineral supply to a lake system on the north eastern tibetan plateau and its relationship to late quaternary paleoenvironmental changes abstract clay mineral fingerprints from modern and fossil lake sediments from lake donggi cona situated on the north eastern tibetan plateau were studied to determine changes in sediment provenance and environmental development since the late glacial to infer the source areas of the lake sediments characteristic facies units cover sediments and soils from the catchment of the lake were studied concerning their clay mineral compositions and through statistical analyses using the fuzzy c means algorithm sediment contributions from the various geological provinces in the catchment of the lake are reflected in a systematic spatial pattern of variable clay mineral assemblages which is most pronounced in modern fluvial and lake sediments downcore changes in the clay mineral fingerprints of lake sediments provide information on the spatio temporal variability of detrital sediment supplies related to climate influenced changes in environmental boundary conditions since the late glacial water level fluctuations driven by glacier melt appear to have exerted the greatest control over the transport paths of detrital sediments probably glacial melt waters carried mainly illitic rich pre cenozoic debris into the lake from the northern and north western catchment areas during the holocene the detrital clay mineral supply was mainly controlled from pre cenozoic and neogene sources however because of the increased summer monsoon precipitation the lake level rose dramatically to at least modern levels resulting in a relative increase in the supply from pedogenic karstic weathering sources mainly from the east which during the holocene was possibly flooded more widely than today during the late holocene a decreasing input of smectite suggests a relative reduction in the supply of far traveled aquatic suspensions into the lake in contrast during the same interval kaolinite concentrations increased which suggests a relatively strong sediment supply from the east possibly triggered by a current flowing from east to west

distribution of clay minerals and proxies for productivity in surface sediments of the bellingshausen and amundsen seas west antarctica relation to modern environmental conditions surface sediments from the antarctic continental margin in the bellingshausen and amundsen seas pacific sector of the southern ocean were investigated in order to decipher their capability to record modern environmental conditions spatial distribution of terrigenous sand and mud reflect regional differences in current induced redeposition of glaciogenic debris clay mineral assemblages in the shelf sediments are controlled by the supply of terrigenous detritus from source rocks in the adjacent hinterland suggesting the occurrence of yet unknown sedimentary rocks in the hinterland of the amundsen sea clay mineral distribution on the continental rise in the bellingshausen sea points to the continuation of a bottom current from the antarctic peninsula rise to at least 94 w foraminifer bearing and opal poor deposits prevail on the continental margin in the western bellingshausen sea and the amundsen sea whereas diatom bearing and carbonate free sediments characterize the eastern bellingshausen sea different modes of biological production which were deduced from accumulation rates of biogenic barium during marine isotope stage 1 and recent productivity measurements obviously control the spatial pattern of opal and carbonate bearing sediments in the study area

deglacial changes in the strength of deep southern component water and sediment supply at the argentine continental margin the deep southern component water scw comprising lower circumpolar deep water lcdw and antarctic bottom water aabw is a major component of the global oceanic circulation it has been suggested that the deep atlantic water mass structure changed significantly during the last glacial interglacial cycle however deep scw source proximal records remain sparse here we present three coherent deep scw paleocurrent records from the deep argentine continental margin shedding light on deep water circulation and deep scw flow strength in the southwest atlantic since the last glacial maximum lgm based on increased sortable silt values we propose enhanced deep scw flow strength from 14 to 10 cal ka b p relative to the early deglacial lgm and the holocene we propose a direct influence of deep northern component water ncw on deep scw flow strength due to vertical narrowing of deep scw spreading concurrent with a migration of the high energetic lcdw aabw interface occupying our core sites we suggest a shoaled ncw until 13 cal ka b p thereby providing space for deep scw spreading that resulted in reduced carbonate preservation at our core sites increased carbonate content from 13 cal ka b p indicates that the ncw expanded changing deep water properties at our core sites in the deep southwest atlantic however southern sourced terrigenous sediments continued to be deposited at our core sites suggesting that deep scw flow was uninterrupted along the argentine continental margin since the lgm

provenance and dispersal of glacial marine surface sediments in the weddell sea and adjoining areas antarctica ice rafting versus current transport abstract mineralogical and granulometric properties of glacial marine surface sediments of the weddell sea and adjoining areas were studied in order to decipher spatial variations of provenance and transport paths of terrigenous detritus from antarctic sources the silt fraction shows marked spatial differences in quartz contents in the sand fractions heavy mineral assemblages display low mineralogical maturity and are dominated by garnet green hornblende and various types of clinopyroxene cluster analysis yields distinct heavy mineral assemblages which can be attributed to specific source rocks of the antarctic hinterland the configuration of modern mineralogical provinces in the near shore regions reflects the geological variety of the adjacent hinterland in the distal parts of the study area sand sized heavy minerals are good tracers of ice rafting granulometric characteristics and the distribution of heavy mineral provinces reflect maxima of relative and absolute accumulation of ice rafted detritus in accordance with major iceberg drift tracks in the course of the weddell gyre fine grained and coarse grained sediment fractions may have different origins in the central weddell sea coarse ice rafted detritus basically derives from east antarctic sources while the fine fraction is discharged from weak permanent bottom currents and or episodic turbidity currents and shows affinities to southern weddell sea sources winnowing of quartz rich sediments through intense bottom water formation in the southern weddell sea provides muddy suspensions enriched in quartz the influence of quartz rich suspensions moving within the weddell gyre contour current can be traced as far as the continental slope in the northwestern weddell sea in general the focusing of mud by currents significantly exceeds the relative and absolute contribution of ice rafted detritus beyond the shelves of the study area

distribution of clay minerals in surface sediments of the aegean sea a compilation extensive published data sets and some new data on the clay mineral composition of surface sediments in the aegean sea northeastern mediterranean sea have been compiled in order to map the distribution patterns of clay mineral assemblages and to decipher source areas and transport paths we distinguished six provinces a northwest aegean province a marmara dardanelles province a west turkey province a southeast aegean province a kithira province and a central aegean province the clay mineral assemblages in the coastal and shelf areas carry the signature of the riverine sediment discharge from southeast europe and turkey respectively the southern aegean sea is probably influenced by the river nile discharge and transport of clay minerals by surface currents the clay minerals in the central aegean sea form a mixed assemblage comprising components of the other assemblages a dispersion and dilution of clay minerals by surface currents is obvious

early to middle eocene magneto biochronology of the southwest pacific ocean and climate influence on sedimentation insights from the mead stream section new zealand the mead stream section south island new zealand consists of a 650 m thick series of continuous well exposed strata deposited on a south pacific continental slope from the late cretaceous to the middle eocene we examined the uppermost paleocene middle eocene part of the section which consists of 360 m of limestone and marl for detailed magnetic polarity stratigraphy and calcareous nannofossil and foraminifera biostratigraphy magneto biostratigraphic data indicate that the section straddles magnetic polarity chrons from c24r to c18n calcareous nannofossil zones from np9a to np17 cnp11 cne15 following a recently revised paleogene zonation and from the waipawan to the bortonian new zealand stages i e from the base of the ypresian to the bartonian international stages the mead stream section thus encompasses 17 m y 56 39 ma of southwest pacific ocean history the ages of calcareous nannofossil biohorizons are consistent with low to midlatitude data from the literature indicating that during the early middle eocene the low to midlatitude calcareous nannofossil domain extended at least to 50 s 55 s in the south pacific correlation of the magnetic polarity stratigraphy from the mead stream section with the geomagnetic polarity time scale allows us to derive sediment accumulation rates sar which range between 8 and 44 m m y comparing the sar with paleotemperature proxy records we found that two intervals of increased sar occurred during the early eocene climatic optimum 52 50 ma and during the transient warming event peaking with the middle eocene climatic optimum 40 5 ma this correlation indicates that at mead stream the climate evolution of the early middle eocene is recorded in a sedimentation pattern whereby on a million year time scale warmer climate promoted continental weathering transportation and accumulation of terrigenous sediments

record of a mid pleistocene depositional anomaly in west antarctic continental margin sediments an indicator for ice sheet collapse abstract modern global warming is likely to cause future melting of earth s polar ice sheets that may result in dramatic sea level rise a possible collapse of the west antarctic ice sheet wais alone which is considered highly vulnerable as it is mainly based below sea level may raise global sea level by up to 5 6 m despite the importance of the wais for changes in global sea level its response to the glacial interglacial cycles of the quaternary is poorly constrained moreover the geological evidence for the disintegration of the wais at some time within the last ca 750 kyr possibly during marine isotope stage mis 11 424 374 ka is ambiguous here we present physical properties palaeomagnetic geochemical and clay mineralogical data from a glaciomarine sedimentary sequence that was recovered from the west antarctic continental margin in the amundsen sea and spans more than the last 1 myr within the sedimentary sequence proxies for biological productivity such as biogenic opal and the barium aluminum ratio and the supply of lithogenic detritus from the west antarctic hinterland such as ice rafted debris and clay minerals exhibit cyclic fluctuations in accordance with the glacial interglacial cycles of the quaternary a prominent depositional anomaly spans mis 15 mis 13 621 478 ka the proxies for biological productivity and lithogenic sediment supply indicate that this interval has the characteristics of a single prolonged interglacial period even though no proxy suggests environmental conditions much different from today we conclude that if the wais collapsed during the last 800 kyr then mis 15 mis 13 was the most likely time period apparently the duration rather than the strength of interglacial conditions was the crucial factor for the wais drawdown a comparison with various marine and terrestrial climate archives from around the world corroborates that unusual environmental conditions prevailed throughout mis 15 mis 13 some of these anomalies are observed in the pelagic southern ocean and the south atlantic and might originate in major ice sheet drawdown in antarctica but further research is required to test this hypothesis

clay mineralogy of the ocean sediments from the wilkes land margin east antarctica implications on the paleoclimate provenance and sediment dispersal pattern core u1359 collected from the continental rise off wilkes land east antarctica is analyzed for the clay mineralogy and carbon content the temporal variation of the clay mineralogical data shows a dominance of illite with chlorite smectite and kaolinite in decreasing concentration clay mineral illite is negatively correlated with smectite which shows enrichment during 6 2 6 8 5 5 5 8 4 5 and 2 5 ma the mineralogical analyses on the silt size fraction 2 53 m of some selected samples were also carried out the combined result of both the size fractions shows the presence of chlorite and illite in both size fractions smectite and kaolinite only in clay size fraction 2 m and similarity in the crystallinity and chemistry of illite in both fractions similar nature of illite in both fractions suggests negligible role of sorting probably due to the deposition from the waxing ice sheet during times of ice growth nearby cratonic east antarctica shield provided biotite rich sediments to the depositional site on the other hand the presence of smectite only in the clay size fraction suggests the effective role of sorting probably due to the deposition from distal source in ice retreat condition during times of ice retreat smectite rich sediment derived from ross orogen is transported to the core site through surface or bottom water currents poor crystallinity of illite due to degradation further corroborates the ice retreat condition the ice sheet proximal sediments of u1359 show that in the eastern part of wilkes land the warming was initiated during late miocene

underwater and drone based photogrammetry reveals structural control at geysir geothermal field in iceland abstract geysers are local hydrothermal vents with periodic gas bubble driven explosions at the surface little is known however on the control on distribution the dynamics and the geometry of the conduits of geysers to better understand the link between the deep and surface expression at the geysir geothermal field iceland a detailed analysis of the spatial distribution of the thermal expressions and their relationship to the tectonic framework was carried out by use of high resolution unmanned aerial vehicle uav based optical and radiometric infrared cameras we are able to identify 364 distinct thermal spots distributed over the area close analysis of their arrangement yields a clustered appearance following a preferred direction that is found to be consistent with the assumed tectonic trend in the area furthermore by using underwater cameras we are able to obtain for the first time detailed images from the two largest geysers at depths exceeding 20 m near to the surface the conduit of the geysers are near circular but at a depth of 9 12 m the shape changes into a crack like elongated fissure the elongation direction of these deep cracks is consistent with the identified thermal expression at the surface highlighting a structural or even tectonic control at the geysir geothermal field which may also explain the susceptibility for seismically triggered activity changes

palaeoglaciology of the alexander island ice cap western antarctic peninsula reconstructed from marine geophysical and core data abstract the glacial history of the continental shelf northwest of alexander island is not well known due mainly to a lack of targeted marine data on antarctica s palaeo ice sheets in their inter ice stream areas recently it has been argued that the region was ice free at the last glacial maximum lgm and thus a potential site for glacial refugia in this paper multibeam swath bathymetry sub bottom profiles and sediment cores are used to map the alexander island sector of the antarctic peninsula margin in order to reconstruct the shelf s palaeoglaciology sea floor bedforms provide evidence that an independent ice cap persisted on alexander island through the lgm and deglaciation we show that this ice cap drained via two major previously undescribed tidewater outlets rothschild and charcot glaciers sourced from an ice dome centred over the west of the island and near shore areas the glaciers grounded along deep fjord like cross shelf troughs to within at least 10 20 km of the shelf edge and probably reached the shelf break only one small outer shelf zone appears to have remained free of ice throughout an otherwise extensive lgm during retreat grounding line geomorphology indicates periodic stabilisation of charcot glacier on the mid shelf after 13 500 cal yrs bp while rothschild glacier retreated across its mid shelf by 14 450 cal yrs bp the timing of these events is in phase with retreat in nearby marguerite trough and we take this as evidence of a common history and forcing with the antarctic peninsula ice sheet the fine details of ice flow documented by our new reconstruction highlight the importance of capturing complex ice flow patterns in models e g in inter stream areas for understanding how region specific parts of antarctica may change in the future moreover the reconstruction shows that glacial refugia if present cannot have been extensive on the alexander island shelf at the lgm as indicated by previous biological studies instead we argue that any ice free refugia were probably restricted to isolated outer shelf pockets that opened closed or were maintained through diachronous ice sheet advance and retreat

chemical weathering signatures from mt achernar moraine central transantarctic mountains i subglacial sediments compared with underlying rock abstract in order to determine chemical weathering rates on the subglacial land surface of antarctica we compare the composition and mineralogy of freshly emerging fine sediments to that of the underlying bedrock as represented by glacially derived cobble sized clasts samples were collected from mt achernar moraine a large blue ice moraine where subglacial material naturally emerges through sublimation of the surrounding ice both rocks and sediments were analyzed for total elemental composition mineral abundance by x ray diffraction and by sequential extractions targeting chemical weathering products the fine sediment fraction is significantly enriched in chemical weathering products and depleted in primary minerals compared with the cobble clasts the alteration pathways consist primarily of the development of smectite kaolinite carbonate minerals and amorphous material extensive fe oxidation is evidenced by a decline in magnetic susceptibility and by increases in extractable fe if we assume the only input into the subglacial system is the water and ice trapped gas supplied by basal melt the net chemical alteration is explained through oxidation of organic matter equal to 0 7 of the bedrock mass and subsequent carbonation weathering the underlying sedimentary rock is sufficiently rich in organic matter for this pathway to be plausible for the o2 that is oxidizing organic matter to be supplied by basal meltwater water fluxes would need to be three orders of magnitude larger than sediment fluxes independent models of basal melt and sediment transport at our field site confirm that such a difference between water and sediment flux is likely at the study site the rate of subglacial carbonation weathering inferred from the mt achernar moraine site may be comparable to that found in high latitude subaerial environments if mt achernar moraine is typical of other antarctic sites the subglacial land surface of antarctica does play a role in global geochemical cycling