sedimentology of the archean dore metasediments arliss lake area southern michipicoten greenstone belt superior province dore metasediments in the arliss lake area of the michipicoten greenstone belt predominantly represent submarine fan sedimentation in mid to outer fan settings subaerial deposition was rare occurring in a sandy braided stream environment and as mud poor debris flows in a probable fan delta setting the arliss lake subbasin was likely small and of an irregular configuration which restricted down fan sediment distribution promoting aggradational lobe development it existed on a convergent plate margin felsic pyroclastic volcanism was periodically synchronous with epiclastic sedimentation but only rarely dominated paleogeographic development addressed by comparing juxtaposed thrust fault bounded lithological packages of similar facing suggests that the subbasin experienced several episodes of instability which caused dramatic changes in relative sea level

sustained increase in ice discharge from the amundsen sea embayment west antarctica from 1973 to 2013 we combine measurements of ice velocity from landsat feature tracking and satellite radar interferometry and ice thickness from existing compilations to document 41 years of mass flux from the amundsen sea embayment ase of west antarctica the total ice discharge has increased by 77 since 1973 half of the increase occurred between 2003 and 2009 grounding line ice speeds of pine island glacier stabilized between 2009 and 2013 following a decade of rapid acceleration but that acceleration reached far inland and occurred at a rate faster than predicted by advective processes flow speeds across thwaites glacier increased rapidly after 2006 following a decade of near stability leading to a 33 increase in flux between 2006 and 2013 haynes smith pope and kohler glaciers all accelerated during the entire study period the sustained increase in ice discharge is a possible indicator of the development of a marine ice sheet instability in this part of antarctica key points sustained ase mass flux increase 77 since 1973 thwaites accelerated by 33 during the last 6 years speed changes are pervasive and rapid major implications for ice flow modeling 2014 american geophysical union all rights reserved

orbital forcing of the east antarctic ice sheet during the pliocene and early pleistocene the pliocene and early pleistocene between 5 3 and 0 8 million years ago span a transition from a global climate state that was 2 3 c warmer than present with limited ice sheets in the northern hemisphere to one that was characterized by continental scale glaciations at both poles growth and decay of these ice sheets was paced by variations in the earth s orbit around the sun however the nature of the influence of orbital forcing on the ice sheets is unclear particularly in light of the absence of a strong 20 000 year precession signal in geologic records of global ice volume and sea level here we present a record of the rate of accumulation of iceberg rafted debris oshore from the east antarctic ice sheet adjacent to the wilkes subglacial basin between 4 3 and 2 2 million years ago we infer that maximum iceberg debris accumulation is associated with the enhanced calving of icebergs during ice sheet margin retreat in the warmer part of the record between 4 3 and 3 5 million years ago spectral analyses show a dominant periodicity of about 40 000 years subsequently the powers of the 100 000 year and 20 000 year signals strengthen we suggest that as the southern ocean cooled between 3 5 and 2 5 million years ago the development of a perennial sea ice field limited the oceanic forcing of the ice sheet after this threshold was crossed substantial retreat of the east antarctic ice sheet occurred only during austral summer insolation maxima as controlled by the precession cycle

facies provenance and paleoclimate interpretation using spectral gamma logs application to the lower cretaceous of the scotian basin abstract spectral gamma logging has been useful in some settings for correlation of wells for identification of sediment facies and for interpretation of hinterland paleoclimate we have taken advantage of the hundreds of geochemical analyses of sandstones and shales from conventional core that are available from the scotian basin to test the relationship of the elements k u and th measured by spectral gamma to sedimentary facies these elements are also known to be useful in characterising provenance of sediment to different parts of the basin the geochemical and spectral gamma data both show that there are subtle differences in k u and th in different lithofacies such as higher th u in low sedimentation rate facies but they are not sufficiently distinctive to identify the lithofacies of any unknown interval the main control on abundance of these elements is the effect of grain size that is the proportion of sand to mud in sediment volcanic sources have a high k th ratio and early albian sediments with relatively high volcanic component have unusually high k th in distal shale prone successions the grain size effect is sufficiently small that climate controlled variations in th k ratio are recognised in the early cretaceous with the ratio being higher at times of humid weathering on land the variations in th k ratio through time are broadly similar to those known from western european sections notably with topmost hauterivian and topmost aptian humid events overall this study provides an assessment of the use and pitfalls of spectral gamma logs in a deltaic succession

a review of the superior province of the canadian shield a product of archean accretion abstract the superior province consists of northern and southern high grade gneiss subprovinces and a central region of alternating granite greenstone and metasedimentary belts subprovinces are commonly fault bounded and display contrasting lithological assemblages metamorphic and structural styles geophysical characteristics and ages they are comparable to phanerozoic suspect terranes the middle and late archean rocks of the superior province are of mantle and juvenile crustal origin with little evidence of inheritance of components older than ca 3 1 ga high grade gneiss subprovinces are mainly deeper level equivalents of the supracrustal rich belts but one minnesota river valley is part of an older ca 3 6 ga terrane that was juxtaposed late in the tectonic history granite greenstone terranes are characterized by low grade volcano sedimentary sequences tholeiitic komatiitic submarine lava plain tholeiitic calc alkalic submarine to subaerial central complexes early platform type quartz arenite stromatolitic carbonate late timiskaming type shoshonitic alkalic volcanic fluvial sediment that range in age from ca 3 0 ga to 2 7 ga the volcanics represent oceanic island arc and continental arc volcanism the quartz arenite carbonate sequences deposition on relatively stable early formed ca 3 0 ga crust and the timiskaming type sequences deposition in pull apart basins developed along strike slip faults late archean ca 2 75 2 70 ga greenstone sequences occur throughout the superior province middle archean ca 3 0 2 8 ga sequences are common in northern and central superior province rare or absent in the south volcanism was accompanied by mafic to trondhjemitic plutonism the metasedimentary belts consist of variably metamorphosed volcanogenic turbidites with detrital zircons ranging in age from ca 3 0 ga to 2 7 ga the metasediments were deposited after major volcanism and probably represent accretionary prisms late archean orogenesis accompanied and followed by calc alkalic plutonism youngs southward from about 2 73 2 72 ga to 2 70 2 68 ga it involved large scale north south compression and dextral transpression and displays thin to thick skinned transitions the contemporaneity of events along the lengths of the belts and their southward younging coupled with the evidence of major compression are consistent with subduction driven oblique accretion of oceanic and continental volcanic arcs accretionary sedimentary wedges older microcontinental fragments etc in a convergent margin setting analogous to parts of the pacific rim differences eg abundance of komatiites and tonalitic plutonic suites are attributable to a hotter archean mantle

u pb age constraints for deposition of clastic metasedimentary rocks and late tectonic plutonism michipicoten belt superior province the study investigates the ages of clastic metasedimentary rocks and of late tectonic alkalic to calc alkalic intrusions and puts constraints on the timing of major deformation in the michipicoten greenstone belt of the wawa subprovince a trondhjemitic boulder in the dore conglomerate of the southern metasedimentary belt is dated at 2698 2 ma this is a maximum age of sedimentation that is also supported by ages of detrital zircons in the matrix and may directly reflect the time of synvolcanic deposition detrital zircons in metapsammites of the central and northern sedimentary belts yield younger ages of 2682 3 and 2680 3 ma respectively suggesting that sedimentation occurred significantly later in the northern than in the southern parts of the greenstone belt the 2682 ma sedimentary rocks were affected by multiphase deformation that is related to the development of a large scale recumbent fold and superimposed folds and faults this tectonism was followed by the emplacement of the granodiorit

hydrologic cycling over antarctica during the middle miocene warming global warmth 20 15 million years ago allowed vegetation to grow on formerly ice covered areas of antarctica leaf wax and pollen data show that this growth was supported by increased hydrologic activity over the antarctic coast derived from a local moisture source

unusual distributions of long chain n alkanes and n alkenes in antarctic soil abstract hydrocarbons in soil samples from the mcmurdo dry valleys of southern victoria land antarctica were studied to examine their features and to elucidate source materials normal alkanes and n alkenes were found at concentrations ranging from 13 to 2200 and from 1 1 to 5000 ng g of dry soil respectively unexpectedly the major hydrocarbons were all odd carbon numbered long chain n alkanes with maximum concentrations n c 23 n c 25 or n c 27 this may be due to the erosion of sedimentary materials containing vascular plant debris formed during the pre and inter glaciation periods of antarctica miocene pliocene and microbial debris such as fungi and microalgae normal alkenes maximize at n c 23 1 carbon chain length number of double bonds n c 25 1 n c 27 1 or n c 29 2 which could be derived from cyanobacteria and microalgae that lived in the past in the antarctic cold desert and or organic debris of wind transported cyanobacterial mats

the last forests on antarctica reconstructing flora and temperature from the neogene sirius group transantarctic mountains abstract fossil bearing deposits in the transantarctic mountains antarctica indicate that despite the cold nature of the continent s climate a tundra ecosystem grew during periods of ice sheet retreat in the mid to late neogene 17 2 5 ma 480 km from the south pole to date palaeotemperature reconstruction has been based only on biological ranges thereby calling for a geochemical approach to understanding continental climate and environment there is contradictory evidence in the fossil record as to whether this flora was mixed angiosperm conifer vegetation or whether by this point conifers had disappeared from the continent in order to address these questions we have analysed for the first time in sediments of this age plant and bacterial biomarkers in terrestrial sediments from the transantarctic mountains to reconstruct past temperature and vegetation during a period of east antarctic ice sheet retreat from tetraether lipids mbt cbt palaeothermometer we conclude that the mean continental summer temperature was ca 5 c in agreement with previous reconstructions this was warm enough to have allowed woody vegetation to survive and reproduce even during the austral winter biomarkers from vascular plants indicate a low diversity and spatially variable flora consisting of higher plants moss and algal mats growing in microenvironments in a glacial outwash system abietane type compounds were abundant in some samples indicating that conifers most likely podocarpaceae grew on the antarctic continent well into the neogene this is supported by the palynological record but not the macrofossil record for the continent and has implications for the evolution of vegetation on antarctica

rb sr and u pb ages of volcanism and granite emplacement in the michipicoten belt wawa ontario the michipicoten greenstone belt at wawa ontario is typical of archean volcanic belts in the superior province the supracrustal rocks are divisible into lower middle and upper metavolcanic sequences which are separated by iron formation and clastic metasedimentary rocks these are intruded by granitic stocks and embayed by granitic batholiths this study reports whole rock rb sr and zircon u pb ages for the lower and upper metavolcanics for the granitic rocks that are physically within the greenstone belt internal granites and for the granitic rocks that embay the greenstone belt external granites the apparent rb sr ages for the lower metavolcanics are 2530 90 2285 70 and 2680 490 ma the u pb ages are 2749 2 and 2744 10 ma the internal granites give an rb sr age of 2560 270 ma and a u pb age of 2737 6 ma the external granite at hawk lake indicates an rb sr age of 2550 175 ma and a u pb age of 2747 7 ma it is possible that this unit contains elements older than 2812 ma as

dynamic behaviour of the east antarctic ice sheet during pliocene warmth warm intervals within the pliocene epoch 5 33 2 58 million years ago were characterized by global temperatures comparable to those predicted for the end of this century1 and atmospheric co2 concentrations similar to today2 3 4 estimates for global sea level highstands during these times5 imply possible retreat of the east antarctic ice sheet but ice proximal evidence from the antarctic margin is scarce here we present new data from pliocene marine sediments recovered offshore of adelie land east antarctica that reveal dynamic behaviour of the east antarctic ice sheet in the vicinity of the low lying wilkes subglacial basin during times of past climatic warmth sedimentary sequences deposited between 5 3 and 3 3 million years ago indicate increases in southern ocean surface water productivity associated with elevated circum antarctic temperatures the geochemical provenance of detrital material deposited during these warm intervals suggests active erosion of continental bedrock from within the wilkes subglacial basin an area today buried beneath the east antarctic ice sheet we interpret this erosion to be associated with retreat of the ice sheet margin several hundreds of kilometres inland and conclude that the east antarctic ice sheet was sensitive to climatic warmth during the pliocene

southern ocean temperature records and ice sheet models demonstrate rapid antarctic ice sheet retreat under low atmospheric co2 during marine isotope stage 31 abstract over the last 5 million years the earth s climate has oscillated between warm interglacial and cold glacial states some particularly warm interglacial periods i e super interglacials occurred under low atmospheric co2 and may have featured extensive antarctic ice sheet collapse here we focus on an extreme super interglacial known as marine isotope stage 31 mis31 between 1 085 and 1 055 million years ago and is the subject of intense discussion we reconstructed the first southern ocean and antarctic margin sea surface temperatures ssts from organic biomarkers and used them to constrain numerical ice sheet shelf simulations our ssts indicate that the ocean was on average 5 c 1 2 c warmer in summer than today between 50 s and the antarctic ice margin our most conservative ice sheet simulation indicates a complete collapse of the west antarctic ice sheet wais with additional deflation of the east antarctic ice sheet we suggest the wais retreated because of anomalously high southern hemisphere insolation coupled with the intrusion of circumpolar deep water onto the continental shelf under poleward intensified winds leading to a shorter sea ice season and ocean warming at the continental margin in this scenario the extreme warming we observed likely reflects the extensively modified oceanic and hydrologic system following ice sheet collapse our work highlights the sensitivity of the antarctic ice sheets to minor oceanic perturbations that could also be at play for future changes

climatic changes in the upwelling region off cap blanc nw africa over the last 70 kyear a multi biomarker approach abstract molecular statigraphic records of core su94 11k 21 n 18 w 1200 m water depth were reconstructed for organic carbon oc carbonates alkenones n alkanols and sterols over the last 70 ky to study past changes of production and paleoceanographic conditions in the coastal upwelling of northwest africa u k 37 derived sea surface temperatures sst show a 2 5 c warming during the last deglaciation surprisingly they also indicate that during the last glacial period between 24 and 15 kyear sst rose by 1 c it can be seen from the values of marine and terrigenous biomarker mass accumulation rates mar that this time interval was also the period of lowest marine production and dust supply suggesting a major change in the north east trade winds system this situation would have lasted until the onset of the deglaciation from which upwelling progressively intensified to produce highest marine biomarker mar at the holocene our data also show a reduced terrigenous supply in late holocene sediments that may reflect lower emission rates from the vegetation and or changes in the wind conditions

environmental magnetic record of antarctic palaeoclimate from eocene oligocene glaciomarine sediments victoria land basin summary the onset of continent wide glaciation in antarctica is still poorly understood despite being one of the most important palaeoclimatic events in the cenozoic the eocene oligocene boundary interval has recently been recognized as a critical time for antarctic climatic evolution and it may mark the preglacial glacial transition magnetic susceptibility intensity of natural and artificial remanences hysteresis parameters and magnetic anisotropy of the lower half late eocene early oligocene of the ciros 1 core from mcmurdo sound antarctica reveal alternating intervals of high and low magnetic mineral concentrations that do not correspond to lithostratigraphic units in the core pseudo single domain magnetite is the main magnetic mineral throughout the sequence and sharp changes in magnetite concentration match changes in clay mineralogy beneath and at the eocene oligocene boundary the detrital magnetite originated from weathering of the ferrar group which comprises basic extrusive and intrusive igneous rocks weathering processes and input of magnetite to the victoria land basin were intense during periods when the antarctic climate was warmer than today but during intervals when the climate was relatively cool chemical weathering of the ferrar group was suppressed and input of detrital magnetite to the victoria land basin decreased our results also indicate that a cold and dry climate was not established in antarctica until the eocene oligocene boundary with major ice sheet growth occurring at the early late oligocene boundary some earlier cold intervals are identified which indicate that climate had begun to deteriorate by the middle late eocene boundary

antarctic and southern ocean influences on late pliocene global cooling the influence of antarctica and the southern ocean on late pliocene global climate reconstructions has remained ambiguous due to a lack of well dated antarctic proximal paleoenvironmental records here we present ice sheet sea surface temperature and sea ice reconstructions from the andrill and 1b sediment core recovered from beneath the ross ice shelf we provide evidence for a major expansion of an ice sheet in the ross sea that began at 3 3 ma followed by a coastal sea surface temperature cooling of 2 5 c a stepwise expansion of sea ice and polynya style deep mixing in the ross sea between 3 3 and 2 5 ma the intensification of antarctic cooling resulted in strengthened westerly winds and invigorated ocean circulation the associated northward migration of southern ocean fronts has been linked with reduced atlantic meridional overturning circulation by restricting surface water connectivity between the ocean basins with implications for heat transport to the high latitudes of the north atlantic while our results do not exclude low latitude mechanisms as drivers for pliocene cooling they indicate an additional role played by southern high latitude cooling during development of the bipolar world

environmental magnetic record of paleoclimate unroofing of the transantarctic mountains and volcanism in late eocene to early miocene glaci marine sediments from the victoria land basin ross sea antarctica 1 we synthesize environmental magnetic results for sediments from the victoria land basin vlb which span a total stratigraphic thickness of 2 6 km and a 17 myr age range we assess how magnetic properties record paleoclimatic tectonic and provenance variations or mixtures of signals resulting from these processes the magnetic properties are dominated by large scale magnetite concentration variations in the late eocene and early oligocene magnetite concentration variations coincide with detrital smectite concentration and crystallinity variations which reflect paleoclimatic control on magnetic properties through influence on weathering regime high magnetite and smectite concentrations indicate warmer and wetter climates and vice versa during the early oligocene accelerated uplift of the transantarctic mountains gave rise to magnetic signatures that reflect progressive erosion of the precambrian mesozoic metamorphic intrusive and sedimentary stratigraphic cover succession associated with unroofing of the adjacent transantarctic mountains from the early oligocene to the early miocene a consistent fining upward of magnetite particles through the recovered composite record likely reflects increased physical weathering with glacial grinding contributing to progressively finer grained ferrar dolerite sourced magnetite after 24 ma the magnetic properties of vlb sediments are primarily controlled by the weathering and erosion of mcmurdo volcanic group rocks increased volcanic glass contents contribute to the fining upward of magnetite grain size overall long term magnetic property variations record the first order geological processes that controlled sedimentation in the vlb including paleoclimatic tectonic provenance and volcanic influences

u pb zircon ages and the evolution of the michipicoten plutonic volcanic terrane of the superior province ontario the archean michipicoten greenstone belt of the superior province in ontario is made up of supracrustal rocks divided into lower middle and upper metavolcanic rocks with associated metasedimentary rocks the belt has been intruded by granitic rocks and is also surrounded by granitic terranes based on u pb zircon geochronology it appears that volcanism in the area extended from at least 2749 to 2696 ma and plutonism and tectonic activity extended from at least 2888 to 2615 ma the various granitic and also one gabbroic plutons both internal and external to the greenstone belt were emplaced concomitantly with the three volcanic cycles as well as before and after the formation of the volcanic rocks zircon ages reported here together with previously published ages show that the area evolved in six major volcanic and plutonic events i 2888 ma plutonism ii 2743 ma volcanism and plutonism iii 2717 ma volcanism and plutonism iv 2696 ma volcanism and plutonism v 2668 ma plutonism and vi

the amplitude and origin of sea level variability during the pliocene epoch earth is heading towards a climate that last existed more than three million years ago ma during the mid pliocene warm period 1 when atmospheric carbon dioxide concentrations were about 400 parts per million global sea level oscillated in response to orbital forcing2 3 and peak global mean sea level gmsl may have reached about 20 metres above the present day value4 5 for sea level rise of this magnitude extensive retreat or collapse of the greenland west antarctic and marine based sectors of the east antarctic ice sheets is required yet the relative amplitude of sea level variations within glacial interglacial cycles remains poorly constrained to address this we calibrate a theoretical relationship between modern sediment transport by waves and water depth and then apply the technique to grain size in a continuous 800 metre thick pliocene sequence of shallow marine sediments from whanganui basin new zealand water depth variations obtained in this way after corrections for tectonic subsidence yield cyclic relative sea level rsl variations here we show that sea level varied on average by 13 5 metres over glacial interglacial cycles during the middle to late pliocene about 3 3 2 5 ma the resulting record is independent of the global ice volume proxy3 as derived from the deep ocean oxygen isotope record and sea level cycles are in phase with 20 thousand year kyr periodic changes in insolation over antarctica paced by eccentricity modulated orbital precession6 between 3 3 and 2 7 ma thereafter sea level fluctuations are paced by the 41 kyr period of cycles in earth s axial tilt as ice sheets stabilize on antarctica and intensify in the northern hemisphere3 6 strictly we provide the amplitude of rsl change rather than absolute gmsl change however simulations of rsl change based on glacio isostatic adjustment show that our record approximates eustatic sea level defined here as gmsl unregistered to the centre of the earth nonetheless under conservative assumptions our estimates limit maximum pliocene sea level rise to less than 25 metres and provide new constraints on polar ice volume variability under the climate conditions predicted for this century sea level varied by 13 5 metres on average but up to 25 metres over glacial interglacial cycles during the pliocene epoch due to partial collapses of antarctic ice sheets

consistent grain size distribution of pedogenic maghemite of surface soils and miocene loessic soils on the chinese loess plateau abstract there is agreement that ultra ne maghemite grains 100nm are responsible for themagnetic enhancement of chinese loess recent studies show that grain size distribution of ultra nepedogenic maghemite grains within the aeolian sequences on the central chinese loess plateaudeposited in the last 8 ma is consistent however whether the observed grain size distribution ofultra ne pedogenic maghemite grains can be observed in the western chinese loess plateau andmodernsoilsisnotentirelyclear herewe ndthatyoungsurfacesoilsamplesacrossthechineseloessplateau and early neogene loessic soils from the western chinese loess plateau also show consistentgrain size distribution with that of ultra ne pedogenic maghemite grains on the central chinese loessplateau the fact that young surface soil samples show apparent magnetic enhancement suggests thatthe ultra ne pedogenic maghemite grains derive from oxidation of ultra ne magnetite grains copy right 2009 john wiley sons ltd keywords loess plateau magnetic susceptibility arm miocene loess maghemite

warm fjords and vegetated landscapes in early pliocene east antarctica abstract the response of the antarctic ice sheets to future warming is uncertain the ipcc are predicting minimal melt from antarctica while others suggest increased meltwater contributions are possible the pliocene period 5 333 ma to 2 58 ma may provide insights into future ice sheet response because atmospheric co2 concentrations were similar to today 350 450 ppmv and the earth surface was between 2 c and 4 c warmer than the preindustrial conditions geological records indicate that antarctica s ice sheets were smaller and more dynamic at this time and many sea level estimates require meltwater input from the greenland west wais and east antarctic ice sheets eais however only a few records exist proximal to the antarctic ice sheet which allow for reconstruction of the pliocene climate state we present a multiproxy climate reconstruction from a sedimentary succession that was deposited in an ancient fjord within the transantarctic mountains covering discrete intervals between the early pliocene and the late pleistocene in contrast to modern frigid conditions our records indicate sea surface temperatures of about 5 6 c at c 4 1 ma the presence of a plant community at the fjord margins and evidence of soil formation simulations of potential vegetation cover in the pliocene indicate our reconstruction is most compatible with a complete collapse of the wais and a large scale retreat of the eais from the subglacial basins with atmospheric co2 levels of less than 450 ppmv our study indicates that under present day atmospheric co2 conditions in the early pliocene the antarctic ice sheets retreated significantly understanding the mechanisms driving this large scale ice sheet retreat would enable us to assess whether current atmospheric co2 concentrations will lead to the same ice sheet configuration once the earth system has come to a new equilibrium state

plio pleistocene climate sensitivity evaluated using high resolution co2 records theory and climate modelling suggest that the sensitivity of earth s climate to changes in radiative forcing could depend on the background climate however palaeoclimate data have thus far been insufficient to provide a conclusive test of this prediction here we present atmospheric carbon dioxide co2 reconstructions based on multi site boron isotope records from the late pliocene epoch 3 3 to 2 3 million years ago we find that earth s climate sensitivity to co2 based radiative forcing earth system sensitivity was half as strong during the warm pliocene as during the cold late pleistocene epoch 0 8 to 0 01 million years ago we attribute this difference to the radiative impacts of continental ice volume changes the ice albedo feedback during the late pleistocene because equilibrium climate sensitivity is identical for the two intervals when we account for such impacts using sea level reconstructions we conclude that on a global scale no unexpected climate feedbacks operated during the warm pliocene and that predictions of equilibrium climate sensitivity excluding long term ice albedo feedbacks for our pliocene like future with co2 levels up to maximum pliocene levels of 450 parts per million are well described by the currently accepted range of an increase of 1 5 k to 4 5 k per doubling of co2

selective aerobic and anaerobic degradation of lipids and palynomorphs in the eastern mediterranean since the onset of sapropel s1 deposition abstract selective degradation of organic matter in sediments is important for reconstructing past environments and understanding the carbon cycle here we report on compositional changes between and within lipid classes and kerogen types represented by palynomorph groups in relation to the organic matter flux to the sea floor and oxidation state of the sediments since the early holocene for central eastern mediterranean site abc26 this includes the initially oxic but nowadays anoxic presapropelic interval the still unoxidised lower part of the organic rich s1 sapropel its postdepositionally oxidised and nowadays organic poor upper part as well as the overlying postsapropelic sediments which have always been oxic a general 2 3 times increase in terrestrial and marine input during sapropel formation is estimated on the basis of the total organic carbon toc pollen spore dinoflagellate cyst n alkane n alkanol and n alkanoic acid concentration changes in the unoxidised part of the sapropel the long chain alkenones 1 15 diols and keto ols loliolides and sterols indicate that some plankton groups notably dinoflagellates may have increased much more apart from the terrestrial and surface water contributions to the sedimentary organic matter anomalous distributions and preservation of some c 23 c 27 alkanes alkanols and alkanoic acids have been observed which are interpreted as a contribution by organisms living in situ comparison of the unoxidised s1 sapropel with the overlying oxidised sapropel and the organic matter concentration profiles in the oxidised postsapropelic sediments demonstrates strong and highly selective aerobic degradation of lipids and palynomorphs there seems to be a fundamental difference in degradation kinetics between lipids and pollen which may be possibly related with the absence of sorptive preservation as a protective mechanism for palynomorph degradation the n alkanes impagidinium and nematosphaeropsis are clearly more resistant than toc the n alkanols and n carboxylic acids are about equally resistant whereas the pollen all other dinoflagellate cysts and other lipids appear to degrade considerably faster which questions the practice of normalising to toc without taking diagenesis into account selective degradation also modifies the relative distributions within lipid classes whereby the longer chain alkanes alcohols and fatty acids disappear faster than their shorter chain equivalents accordingly interpretation of lipid and palynomorph assemblages in terms of pre or syndepositional environmental change should be done carefully when proper knowledge of the postdepositional preservation history is absent two lipid based preservation proxies are tested the diol keto ol oxidation index based on the 1 15c 30 diol and keto ols doxi and the alcohol preservation index api whereby the former seems to be the most promising

sensitivity of pliocene ice sheets to orbital forcing the stability of the earth s major ice sheets is a critical uncertainty in predictions of future climate and sea level change one method of investigating the behaviour of the greenland and the antarctic ice sheets in a warmer than modern climate is to look back at past warm periods of earth history for example the pliocene this paper presents climate and ice sheet modelling results for the mid pliocene warm period mpwp 3 3 to 3 0 million years ago which has been identified as a key interval for understanding warmer than modern climates jansen et al 2007 using boundary conditions supplied by the united states geological survey prism group pliocene research interpretation and synoptic mapping the hadley centre coupled ocean atmosphere climate model hadcm3 and the british antarctic survey ice sheet model basism we show large reductions in the greenland and east antarctic ice sheets gris and eais compared to modern in standard mpwp experiments we also present the first results illustrating the variability of the ice sheets due to realistic orbital forcing during the mid pliocene while gris volumes are lower than modern under even the most extreme cold mid pliocene orbit losing at least 35 of its ice mass the eais can both grow and shrink losing up to 20 or gaining up to 10 of its present day volume the changes in ice sheet volume incurred by altering orbital forcing alone means that global sea level can vary by more than 25 m during the mid pliocene however we have also shown that the response of the ice sheets to mpwp orbital hemispheric forcing can be in anti phase whereby the greatest reductions in eais volume are concurrent with the smallest reductions of the gris if this anti phase relationship is in operation throughout the mpwp then the total eustatic sea level response would be dampened compared to the ice sheet fluctuations that are theoretically possible this suggests that maximum eustatic sea level rise does not correspond to orbital maxima but occurs at times where the anti phasing of northern and southern hemisphere ice sheet retreat is minimised