a lacustrine gdgt temperature calibration from the scandinavian arctic to antarctic renewed potential for the application of gdgt paleothermometry in lakes quantitative climate reconstructions are fundamental to understand long term trends in natural climate variability and to test climate models used to predict future climate change recent advances

alkenones alkenoates and organic matter in coastal environments of nw scotland assessment of potential application for sea level reconstruction reconstruction of late quaternary sea level history in areas of glacioisostatic uplift often relies on sediment archives from coastal isolation basins natural coastal rock depressions previously isolated from or connected to the sea at different times proxy indicators for marine brackish or lacustrine conditions combined with precise dating can constrain the time when the sea crossed the sill threshold and isolated or connected the basin the utility of isolation basins in investigations of sea level change is well known but investigations have been mostly limited to microfossil proxies the application of which can be limited by preservation and nonanalog problems here we investigate the potential of long chain alkenones alkenoates and bulk organic parameters toc corg n for reconstructing past sea level changes in isolation basins in nw scotland we analyze organic biomarkers and bulk parameters from both modern basins at different stages of isolation from the sea and fossil basins with sea level histories reconstructed from established proxies logit regression analysis was employed to find which of the biomarker metrics or bulk organic measurements could reliably characterize the sediment samples in terms of a marine brackish or isolated lacustrine origin the results suggested a good efficiency for the alkenone index c37 4 at predicting the depositional origin of the sediments this study suggests that alkenones could be used as a novel proxy for sea level change in fossil isolation basins especially when microfossil preservation is poor

marine deposition and sea surface temperature changes during the last and present interglacials in the west coast of taiwan strait abstract in order to reconstruct the environmental and climatic conditions of the last and present interglacials this study has examined a 52 m long core obtained from a coastal embayment chang le on the west coast of taiwan strait the analyses of particle size distributions total carbon content organic carbon isotope ratios n alkane indices and alkenones from the core reveal two periods of marine transgression together with the radiocarbon and optically simulated luminescence dating analyses the environmental proxies indicate that the older marine sequence m1 was deposited during the period of rising sea level in the early to middle part of mis5e the younger marine sequence m2 was confirmed as a deposit formed during the stable sea level of the latter part of the present interglacial the shallow marine facies and the abundant alkenones from m2 suggest a deeper water environment under full marine conditions during the last interglacial the sub tidal to intertidal facies and weak appearance of alkenones in m1 imply a shallow water environment under weak marine influence because the site was close to upland landscape high input of terrigenous material for both periods is evident the alkenone based sea surface temperature sst reconstructions indicate that the sst during mis5e fluctuated slightly around 28 1 c which is about one degree higher than that of mis1 consistent with records from the northern coast of the south china sea the depositional conditions and the burial depths of the two marine sequences also provide hints for the local tectonic movements

holocene crustal movements and sea level changes in great britain crustal downwarping has occurred throughout southern and south eastern england and most of wales for at least the last 4000 years but the type of movement in some areas of southern and eastern england is more complicated than simple linear subsidence highest estimated rates of subsidence since 4000 bp are for the thames estuary and norfolk up to 2 mm yr glacio isostatic processes have resulted in uplift in northern england and mainland scotland the rates of uplift have decreased throughout the holocene estimates for the present range from zero in south lancashire and the tees estuary to over 1 mm yr though less than 2 mm yr in central scotland over 400 sea level index points from the databank of 904 cases collected for igcp project 200 are grouped into 15 main areas and used to investigate the nature of crustal movements in great britain since 8800 bp but there are significant deficiencies in available data which constrain the analysis

a novel proxy for terrestrial organic matter in sediments based on branched and isoprenoid tetraether lipids we propose a novel tracer for terrestrial organic carbon in sediments based on the analysis of tetraether lipids using high performance liquid chromatography mass spectrometry hplc ms analysis of terrestrial soil and peats shows that branched tetraether lipids are predominant in terrestrial environments in contrast to crenarchaeol the characteristic membrane lipid of non thermophilic crenarchaeota which is especially abundant in the marine and lacustrine environment based on these findings an index was developed the so called branched and isoprenoid tetraether bit index based on the relative abundance of terrestrially derived tetraether lipids versus crenarchaeol this bit index was applied to surface sediments from the angola basin where it was shown to trace the outflow of the congo river furthermore analyses of particulate organic matter from the north sea showed relatively higher bit indices in water column particulate organic matter near large river inputs a survey of globally distributed marine and lacustrine surface sediments shows that the bit index in these environments correlates with the relative fluvial input of terrestrial organic material making this index generally applicable the new proxy allows the rapid assessment of the fluvial input of terrestrial organic material in immature sediments up to 100 ma old

environmental controls on branched tetraether lipid distributions in tropical east african lake sediments abstract quantifying past continental temperature changes is an important aspect of paleoclimate research as it allows us to constrain the amplitude of natural variability test predictive climate models and provide a proper context for changes that may arise in response to anthropogenically induced climate change the recently developed biomarker based methylation index of branched tetraethers cyclization ratio of branched tetraethers mbt cbt proxy shows potential as a new method for continental temperature reconstruction but thus far it has only been applied successfully in ocean margin sediments to assess whether this proxy is also applicable to the sedimentary record in tropical lacustrine systems we investigated the distribution of branched glycerol dialkyl glycerol tetraethers gdgts in recently deposited sediments from 46 lakes in tropical east africa these lakes span a substantial range in surface elevation 770 4500 m above sea level and thus also a wide gradient of mean annual temperature we find that saline lakes excepted branched gdgts are universally abundant in the lakes investigated and can be used to predict mean annual air temperature maat with a high degree of accuracy however the existing global mbt cbt calibration for maat based on soils predicts inaccurate temperatures when applied to our african lake dataset this observation together with the fact that surface water ph and to lesser extent lake depth appear to influence the distribution of branched gdgts among sites leads us to conclude that in situ production of branched gdgts in lakes is likely the robust relationship between branched gdgt distribution and the temperature and ph of african freshwater lakes makes these compounds suitable for paleoenvironmental reconstruction however we urge caution in using branched gdgts in lake sediments to infer past temperatures unless their exact origin can be determined

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

geomorphology internal structure and successive development of a glacier foreland in the semiarid chilean andes cerro tapado upper elqui valley 30 08 s 69 55 w we use geomorphological analysis sedimentological survey remote sensing and ground penetrating radar gpr in order to understand the complex landform assemblage found in front of the cerro tapado glacier in the upper elqui river catchment semiarid andes of chile the geomorphological analysis highlights prominent boundaries dividing the landform assemblage into from the upper part to the lower part an upper latero frontal moraine complex an upper debris covered glacier a lower debris covered glacier two rock glaciers and a lower morainic complex the sedimentological survey highlights the rather small size of the surface debris in general 400 m receding of the glacier occurred along with downslope displacements dm m y 1 of most of the landform units and a significant evolution of the thermokarst features on the debris covered glaciers considerable surface lowering occurred in the upper part of the assemblage while localized bulging is seen along the morphological boundaries in the lower units the gpr profiles highlight spectacular internal structure in the upper debris covered glacier with up to 80 m of buried ice in the other landform units the internal structure is less visible and more heterogeneous the analysis of the radar wave velocity along the gpr profiles reveals the occurrence of air filled and moist zones in the internal structure the geomorphological assemblage is fundamentally characterized by its morphological structural and dynamical boundaries and defined as a young probably 2000 years polygenetic construction with landform units having added to overlapped one another the rock glaciers do not derive from the present debris covered glacier but preexist to it

lateglacial and holocene relative sea level changes and first evidence for the storegga tsunami in sutherland scotland we reconstruct one of the longest relative sea level rsl records in northwest europe from the north coast of mainland scotland using data collected from three sites in loch eriboll sutherland that we combine with other studies from the region following deglaciation rsl fell from a late glacial highstand of 6 8 m od ordnance datum c mean sea level at c 15 k cal a bp to below present then rose to an early holocene highstand and remained at c 1 m od between c 7 and 3 k cal a bp before falling to present we find no evidence for significant differential holocene glacio isostatic adjustment between sites on the northwest lochinver loch laxford north loch eriboll and northeast wick coast of mainland scotland this suggests that the region was rapidly deglaciated and there was little difference in ice loads across the region from one site at the head of loch eriboll we report the most westerly sedimentary evidence for the early holocene storegga tsunami on the scottish mainland the presence of the storegga tsunami in loch eriboll is predicted by a tsunami wave model which suggests that the tsunami impacted the entire north coast of scotland and likely also the atlantic coastline of northwest scotland

a geological constraint on relative sea level in marine isotope stage 3 in the larsemann hills lambert glacier region east antarctica 31 366 33 228 cal yr bp abstract in this paper we present geological evidence from the larsemann hills lambert glacier amery ice shelf region east antarctica of marine sediments at an altitude of c 8 m a s l as revealed by diatom pigment and geochemical proxies in a lake sediment core the sediments yielded radiocarbon dates between c 26 650 and 28 750 14c yr bp 31 366 33 228 cal yr bp this information can be used to constrain relative sea level adjacent to the lambert glacier at the end of marine isotope stage 3 these data are compared with the age and altitude of marine isotope stage 3 marine deposits elsewhere in east antarctica and discussed with reference to late quaternary ice sheet history and eustatic sea level change

overwash processes along a gravel beach in south east ireland recent overwashing and to a more limited extent overtopping has occurred on a gravel dominated beach just west of carnsore point in south east ireland at relatively low points swash excursions have breached the duneline and extensive gravel fans have formed on landward facing slopes also at interbreach positions swash ramps have been built up in front of previously eroding dune cliffs allowing overtopping at heights of up to 5 m above mhwost spreading a veneer of sediment over the adjacent dune ridge in both cases events appear to be preceded by erosion and backbeach sand and gravel deposition stratigraphic textural and fabric analyses assist in identifying environmental conditions that prevailed during overwash throat and fan and overtopping ramp sedimentation

sedimentary pigments as markers for environmental change in an antarctic lake abstract fossil pigments were identified in a sediment core from kirisjes pond a small lake in the larsemann hills east antarctica using reversed phase hplc and lc ms ms chlorophyll a and b derived components indicate the presence of oxygenic primary producers steryl chlorin esters provide evidence of grazing while shifts in their esterifying sterol composition record changes in the primary producer community bacteriochlorophyll c and d derived components indicative of photic zone anoxia were identified with structural variations including extensive alkylation in the macrocycle up to c 6 the pigment distribution reveals a change from oxygenated freshwater to a stratified water body with development of photic zone anoxia this coincides with a marine incursion identified from diatom records and is followed by re isolation and reversion to oxygenated freshwater conditions

late holocene sea level rise in tampa bay integrated reconstruction using biomarkers pollen organic walled dinoflagellate cysts and diatoms a suite of organic geochemical micropaleontological and palynological proxies was applied to sediments from southwest florida to study the holocene environmental changes associated with sea level rise sediments were recovered from hillsborough bay part of tampa bay and studied using biomarkers pollen organic walled dinoflagellate cysts and diatoms analyses show that the site flooded around 7 5 ka as a consequence of holocene transgression progressively turning a fresh brackish marl marsh into a shallow restricted marine environment immediately after the marine transgression started limited water circulation and high amounts of runoff caused stratification of the water column a shift in dinocysts and diatom assemblages to more marine species increasing concentrations of marine biomarkers and a shift in the diol index indicate increasing salinity between 7 5 ka and the present which is likely a consequence of progressing sea level rise reconstructed sea surface temperatures for the past 4 kyrs are between 25 and 26 c and indicate stable temperatures during the late holocene a sharp increase in sedimentation rate in the top 50 cm of the core is attributed to human impact the results are in agreement with parallel studies from the area but this study further refines the environmental reconstructions having the advantage of simultaneously investigating changes in the terrestrial and marine environment 2009 elsevier ltd

incorrect when uncorrected reconstructing vegetation history using n alkane biomarkers in loess paleosol sequences a case study from the saxonian loess region germany abstract this study aims at contributing to the reconstruction of the paleoenvironment of the saxonian loess region by investigating sedimentary n alkanes as plant leaf wax derived biomarkers in two loess paleosol sequences lpss namely the gleina and the rottewitz lpss the weichselian paleosols are characterised by n alkane concentration maxima when compared to the loess layers when this coincides with high odd over even predominances oeps this points not only to increased n alkane input and or production but also to increased n alkane preservation in the soils namely in gleysols with water logged edaphic conditions by contrast the buried cambisols reveal low oeps indicating accelerated degradation under aerobic edaphic conditions the n alkane concentrations in the truncated eemian interglacial paleosol are very low this reflects the removal of the formerly n alkane enriched eemian topsoil low n alkane input into the b t s d horizon subsoil horizon of the eemian luvisol and or strong soil organic matter mineralization four investigated n alkane ratios show distinct variations during the weichselian tempting inferences of vegetation changes in terms of varying contributions of tree shrub derived dominated by n c 27 or n c 29 versus grass derived dominated by n c 31 or n c 33 n alkanes however using the oep as a proxy for degradation and considering that n alkane ratios are prone to degradation effects the above interpretation is very likely incorrect degradation can account for most variability of the n alkane ratios applying an endmember model based on a modern n alkane reference dataset allows estimating the contribution of tree shrub versus grass derived n alkanes semi quantitatively these modelling results suggest that both the gleina and the rottewitz lpss were formed under prevailing grassland minor contributions of trees shrubs are only likely for the gleinaer soil complex in rottewitz lps for the top of a brown gleysol in gleina lps and the holocene soil the weichselian vegetation changes as inferred from the uncorrected n alkane ratios are not confirmed overall the n alkane results support the idea that the gleinaer soil complex in gleina and rottewitz lps respectively are not identical but rather are chronostratigraphic equivalents more favourable regional climatic conditions presumably occurred in the southwesterly exposed rottewitz locality and allowed tree shrub vegetation to grow during favourable periods of the weichselian a major shortcoming of the n alkane biomarker method is that only vegetation changes of deciduous woodland to grassland and vice versa can be reconstructed because coniferous trees exhibit by two to three orders of magnitude lower n alkane concentrations

the palaeoenvironmental and palaeohydrological evolution of padul peat bog granada spain over one million years from elemental isotopic and molecular organic geochemical proxies abstract the elemental concentration of organic carbon atomic h c and c n ratios isotopic 13 c values of organic matter and molecular predominant n alkane chain length and carbon preference index cpi organic components were measured for 600 samples taken from a 107 m long core from the padul basin andalusia spain the record runs from the lower pleistocene ca 1 ma b p to the mid holocene ca 4 5 ka b p with in general little diagenesis removal of components two markedly different hydrogeological scenarios were interpreted 1 from ca 1 ma to ca 400 ka b p run off recharge was significant and water depths were greater lacustrine scenario from ca 400 to 4 5 ka b p the padul basin became a peat bog s s with the major water input coming from groundwater inflow from ca 400 to ca 180 ka b p alternating episodes with either predominant grasses trees or aquatic macrophytes which were linked to wet dry phases took place an important deglaciation episode has been interpreted to occur between ca 180 and 170 ka b p the global climatic changes occurring from ca 170 to 25 ka b p were not recorded in the proxies though they do show important variations linked to the last glacial maximum and the beginning of the holocene ca 25 10 ka b p 2 cold phases coexisting with dry periods produced the recession of forests and the development of grasses after these periods as both temperature and precipitation increased forests expanded and the water level linked to thaw rose especially at ca 20 ka b p few changes occurred during the holocene although there were short alternations between wet and dry episodes overall the techniques applied proved to be excellent palaeoenvironmental proxies for studying the basin s palaeoclimatological and palaeohydrological evolution

terminal antarctic melting inferred from a far field coastal site abstract the contribution of the antarctic ice sheet ais to deglacial sea level rise is poorly constrained this shortfall gives rise to concerns because incorrect ais estimates impact significantly on our ability to predict sea level change in the course of global warming given the scarcity of geological data and the complexity of the antarctic response to glacio isostatic adjustment processes there is a need for accurate data to constrain the timing of the ice sheet retreat here we provide such data on the holocene antarctic melting through an isolated geographic site on the northern hemisphere which we show is sensitive to the antarctic signal using both our site and other mid latitudinal relative sea level sites our model provides a consensus estimate that the ais released water corresponding to 5 m equivalent sea level at 8 ka and ceased melting at 6 ka this is different to most ais models which release an equal amount of water at 11 ka or after 6 ka our findings change model assumptions about the terminal ais melting and show that future holocene sea level research should focus on broad shelves and large coast embayments in the mid latitudes

molecular marker records of land use change abstract evidence of a changing environment in the catchment area of a small lake gormire yorkshire uk over the past 3000 years is provided by the mean carbon number of n alkanes and the ratio of lignin thermochemolysis products together with pollen analysis and bulk organic geochemistry periods of deforestation which commenced at 600 bc and ad 1200 display a significant decrease in organic carbon contents of the lake sediments which probably reflects dilution by enhanced influx of clastic material the mean carbon number of waxy c27 c31 n alkanes closely corresponds with the percentage of pollen derived from grass in the sediments a higher plant derived triterpenoid tentatively identified from its mass spectrum as 28 carboxyursen 12 enol appears exclusively in samples where tree and shrub derived pollen is dominant thermochemolysis of lignin confirms that there was a significant change in the nature of material deposited in the lake sediments from woody to grass dominated changes in both the sedimentary c n ratios and yields of lignin derived phenols suggest that deforestation events led to enhanced aquatic productivity initially through the development of reed swamp vegetation

erratum holocene coastal environmental changes on the periphery of an area of glacio isostatic uplift an example from scapa bay orkney uk the first detailed investigation of a deep coastal sedimentary basin in orkney reveals a complex holocene history of back barrier morphodynamics at scapa bay the sea flooded a freshwater marsh after ca 9400 yr bp at ca 5 4 m od before ca 7800 bp abundant sediment from nearby cliffs was mobilised inland into a series of gravel barriers across the valley mouth by ca 7500 bp direct marine influence was restricted in the back barrier area although saltmarsh persisted until ca 5900 bp by then at least four gravel ridges had enclosed the backing lagoon where freshwater inputs became dominant as terrestrial sediments filled the basin another freshwater marsh developed the multiple barrier complex demonstrates progradation resulting from continuous sediment supply in a sheltered embayment the progressively rising height of the barrier crests seawards probably resulted from a combination of factors such as barrier morphodynamics increased storminess and long term rising relative sea levels the dominant vegetation surrounding scapa bay changed from open grassland to scrub ca 9400 bp then to deciduous woodland ca 7800 bp and to dwarf shrub heath ca 2600 bp the latter probably a response to a combination of climate change and human activity copyright 2007 john wiley sons ltd

mechanisms to account for the longshore spacing of overwash throats on a coarse clastic barrier in southeast ireland abstract the longshore spacing of overwash throats on two contrasting sections of a coarse clastic reflective barrier beach in southeast ireland is examined for evidence of spatial periodicity a fixed barrier section carnsore with an irregular barrier top dune field exhibits random longshore throat positions related to pre existing irregularities in the seaward dune boundary a free barrier section tacumshin without a barrier top dune field shows regular longshore throat positions with a peak throat to throat periodicity of between 30 40 m similar longshore periodicity is found in persistent high level beach cusps above mhws though not always spatially in phase there is no consistent near shore rhythmic morphology that can account for this spacing the storm event which generated the tacumshin overwash appears to have dominant longer incident wave periods than normal in celtic sea storms on weight of circumstantial evidence it is reasoned that this dominant wave period range 9 11 s can be related to a zero mode sub harmonic edge wave whose longshore wavelength matches the peak periodicity of overwash spacing overwash sites on this reflective barrier may be determined by an edge wave controlled extension of run up which generates high level cusps and thereby creates washover routeways the presence or absence of a barrier top dune field is a secondary control on whether washover is successful in reaching the back barrier usually only where surge penetration and pre existing dune irregularities coincide does washover occur

a review of molecular organic proxies for examining modern and ancient lacustrine environments molecular organic geochemical proxies are increasingly being utilized to reconstruct past environmental conditions as new tools continue to be discovered and developed to date organic geochemical proxies have been developed mainly for use in marine systems and are widely used in paleoceanography in contrast organic proxies have been less commonly used on lacustrine sedimentary records one reason for this is that the wide range in the physical and chemical properties of lakes complicates application of some organic geochemical proxies in lacustrine settings furthermore in comparison to marine studies presently only a small number of studies have conducted or are currently conducting fundamental research aimed at developing organic geochemical proxies for use in lacustrine settings despite this an increasing number of paleo limnological studies are currently applying organic geochemical techniques to examine present and past environmental conditions in this manuscript we review the use of a number of commonly utilized organic geochemical and isotopic proxies and discuss their potential for environmental reconstruction in quaternary lacustrine deposits

late devensian and holocene relative sea level changes on the isle of skye scotland uk detailed litho and biostratigraphical analyses from three coastal sites in contrasting coastal settings on the isle of skye scotland uk reveal evidence for several changes in relative sea level during the late devensian and holocene at the start of the record relative sea level in the area was high at ca 12 500 14c ca 14 800 cal yr bp but then fell reaching a low point during the younger dryas at ca 11 000 10 000 14c ca 13 000 11 600 cal yr bp when a rock platform correlated with the main rock platform was formed in the early middle holocene relative sea level was rising by ca 8000 14c ca 8800 cal yr bp and in northeast skye a lagoonal surface correlated with the main postglacial shoreline was formed at ca 6600 14c ca 7500 cal yr bp by the late holocene relative sea level was again falling but a rise registered at at least two sites began probably before ca 4000 14c ca 4500 cal yr bp and a second lagoonal surface in northeast skye correlated with the blairdrummond shoreline was formed although by ca 3000 14c ca 3200 cal yr bp relative sea level in the area had resumed its downward trend the pattern of relative sea level changes disclosed is compared with evidence elsewhere in scotland

applicability and calibration of the tex86 paleothermometer in lakes abstract we have conducted a global survey of archaeal glycerol dialkyl glycerol tetraether gdgt lipids in lake sediments in order to develop the tex86 paleotemperature proxy for application in continental systems surface sediments of 46 globally distributed lakes were analyzed for gdgt but isoprenoid gdgt derived from aquatic crenarchaeota were only unambiguously detected in 20 of the 46 lakes analyzed aquatic crenarchaeotal gdgt were detected mainly in sediments from large lakes 4000 km2 and hydrothermal or volcanic lakes suggesting that in some mostly smaller lakes either aquatic crenarchaeota are present at low abundance resulting in sedimentary lipids below levels of detection or they are absent branched gdgt thought to be derived primarily from soil bacteria were identified in all lake sediments analyzed correlation of the tex86 in those lakes with sufficient amounts of putative crenarchaeotal gdgt with annual mean lake temperature is reasonably good r2 0 68 n 20 in order to reduce the influence of soil derived isoprenoid gdgt on the tex86 lake temperatures we have applied a filter based on relative soil derived inputs as determined by the bit branched and isoprenoid tetraether index which results in a calibration relationship with r2 0 86 n 12 and an estimated temperature error of 3 6 c our results suggest that the tex86 should be applied only in lakes with sufficient production of gdgt by aquatic crenarchaeota relative to isoprenoid gdgt derived from soil in the watershed or other aquatic sources

origin and significance of 13 2 hydroxychlorophyll derivatives in sediments abstract the authenticity of hydroxychlorophyll derivatives in sediments has been verified by subjecting pure chlorophyll preparations to the extraction method used for sediments model studies of chlorophyll autoxidation reveal hydroxychlorophyll as the major product formed in the presence of hydrogen peroxide its stability to further oxidation implies that hydroxychlorophyll derivatives are not precursors of aetioporphyrins and are more likely to produce cycloalkanoporphyrins via the processes of diagenesis the occurrence of 13 2 hydroxyphaeophytin a throughout a sediment core from loch ness confirms it to be a widespread chlorophyll oxidation product formed during early diagenesis profiles of hydroxychlorophyll derivatives in a sediment core from an antarctic lake demonstrate their potential for use as markers of oxidation processes in palaeoenvironmental assessment

late quaternary environmental change of yellow river basin an organic geochemical record in bohai sea north china abstract bulk geochemical characterization total organic carbon grain size distribution carbon isotope composition and molecular biomarkers lignin phenols straight chain aliphatic hydrocarbons glycerol dialkyl glycerol tetraethers were analyzed for a 21 m core from the bohai sea north china spanning ca 21 ka bp these paleo proxies presented remarkable differences between the late glacial period and the holocene reflecting continental and coastal environments respectively two peat layers were deposited during the period of ca 9000 8460 yr bp thereafter the core site has been consistently covered by seawater until recent reclamation of land from the sea the occurrence of a total organic carbon maximum from ca 6000 3800 yr bp was attributed to delivery of organic carbon enriched sediments via the yellow river consistent with increased vegetation density and higher development of soil under warm and humid mid holocene climate conditions the distributions of lignin phenol compositions and c 31 c 29 n alkane ratio suggested the largest expansion of woody plants between ca 5300 and 4000 yr bp corresponding to the extremely favorable climatic conditions since ca 3800 yr bp an abrupt increase in the c 31 c 29 n alkane ratio suggested higher abundance of grasses consistent with a drying climate trend after the mid holocene since our coastal sediments close to the yellow river outflow contain catchment integrated environmental signals of the river basin molecular proxies demonstrate that the variability of vegetation distributions in the holocene is a widespread phenomenon in those areas adjacent to yellow river basin

distributions of branched gdgts in a tropical lake system implications for lacustrine application of the mbt cbt paleoproxy branched glycerol dialkyl glycerol tetraether gdgt lipids are abundant and ubiquitous in lake sediments potentially allowing for a paleolimnological application of the so called mbt cbt proxy methylation index of branched tetraethers cyclization ratio of branched tetraethers to investigate the origin and characteristics of these compounds in lacustrine environments we examined the distributions of gdgts in soils river sediments and lake sediments from lake towuti on the island of sulawesi indonesia we found significant differences in the degree of methylation and cyclization expressed by way of the mbt and cbt indices between the soil samples and the aquatic samples suggesting that there may be in situ production of gdgts in the aquatic environment based on these findings we urge caution in the application of the mbt cbt paleoproxy to lake sediments and encourage more rigorous study of these compounds in freshwater environments

distribution of glycerol dialkyl glycerol tetraether gdgt lipids in a hypersaline lake system isoprenoid glycerol dialkyl glycerol tetraethers isogdgts of archaeal origin and branched br gdgts of bacterial origin occur in a diverse range of lacustrine sedimentary environments they have attracted attention as potential temperature proxies providing high resolution palaeo environmental reconstruction from continental interiors for this study the distribution of gdgts in and application of gdgt based proxies to surface samples from chaka salt lake china as well as soils and in flow river sediments were investigated to assess whether gdgt based proxies were applicable to this hypersaline lake system we show that iso and brgdgts were present in all sediments and soils from the chaka salt lake system gdgt 0 and crenarchaeol were generally the two most abundant isogdgts suggesting thaumarchaeota as a major biological source of isogdgts the low ratio of crenarchaeol crenarchaeol regioisomer suggests that thaumarchaeota of the lake sediments is likely thaumarchaeota group i 1b derived from the surrounding alkaline soils arguing against the use of the tex86 proxy in this system because alkaline soils generally have high isogdgt concentrations it is likely that a large allochthonous input of isogdgts would be a pervasive challenge to palaeoclimate applications in such settings on the other hand the brgdgt distributions in the lake and river sediments differed markedly from those in the surrounding soils suggesting that instead of deriving from the surrounding soils at least part of the brgdgts is synthesized in situ or delivered from more distal upland soils taken together our results indicate that the mixed sources of gdgts in chaka salt lake complicate the application of gdgt based proxies and it will be challenging to use such proxies in this system

discussion of geomorphology internal structure and successive development of a glacier foreland in the semiarid chilean andes cerro tapado upper elqui valley 30 08 s 69 55 w by s monnier c kinnard a surazakov and w bossy geomorphology 207 2014 126 140 abstract recently monnier et al 2014 geomorphology 207 126 140 suggested that diffraction events with air wave velocities along profile cd were caused by an air filled void at depth within one of the glaciers of the cerro tapado chile this is not physically possible the velocity at which radar travels to and from the scattering feature that causes a diffraction is at the velocity that surrounds and overlies the scatterer thus their air wave velocity features are on the surface of the glacier not at depth their three layer model for profile cd therefore is more appropriately a two layer model with a lower density layer with more air and debris overlying a denser layer likely corresponding to the firn ice transition in addition they carried out common mid point cmp velocity profiles while it is encouraging that they have made such an attempt the results will be affected significantly by the surface and subsurface topography truncated beds unconformities etc because cmp profiles inherently assume flat lying surface and subsurface boundaries the cmp results while useful must therefore be treated with caution and assumed to be highly inaccurate and only be used as general guides to vertical velocity variations

extent and deglacial chronology of the last british irish ice sheet implications of exposure dating using cosmogenic isotopes over 160 10be and 36cl exposure ages pertaining to the extent and chronology of the last british irish ice sheet biis are critically reviewed despite uncertainties inherent in the use of exposure ages this approach has demonstrated that at the last glacial maximum lgm ca 26 21 ka the biis extended over all low ground in scotland and all or almost all of ireland consistent with recent models depicting extension of the last biis to the atlantic shelf edge all exposure ages obtained for high level sites above trimlines on the mountains of northwestern scotland and ireland pre date the lgm this finding confirms that high plateaux in these areas escaped significant glacial erosion probably under a protective cover of cold based glacier ice that remained frozen to the underlying substrate in terms of deglaciation chronology the southern irish sea basin was probably deglaciated by 19 18 ka with extensive deglaciation of low ground in ireland and northeastern scotland prior to ca 14 5 ka ice cover on low ground in northwestern scotland apparently persisted after 14 0 ka suggesting survival of ice in favourable locations during the lateglacial interstade ca 14 5 12 9 ka attempts to date readvances have had mixed success the wester ross readvance in northwestern scotland was initially dated to ca 16 3 ka but more recent research implies a much younger age ca 14 0 13 5 ka exposure ages indicating a prolonged stillstand during ice sheet retreat in the cairngorms at ca 14 5 14 0 ka conflict with ages obtained on postglacial rockslides and basal radiocarbon dates which indicate deglaciation before ca 15 5 15 0 ka exposure dating has been successfully employed to confirm a loch lomond stadial ca 12 9 11 5 ka age for moraines in several mountain areas and to constrain the minimum altitude of the ice cap that extended over the western grampians at that time copyright 2009 john wiley sons ltd

mechanistic controls on diverse fates of terrestrial organic components in the east china sea terrestrial carbon transferred from the land to sea is a critical component of the global carbon cycle a range of geochemical proxies has been developed to fingerprint the fate of terrestrial organic matter tom in marine sediments however discrepancies among different proxies limit our ability to quantify and interpret the terrestrial signals in marine sediments with consequences for the investigation of both the modern carbon cycle and past environmental change to mechanistically understand these discrepancies we examined the distributions of a range of terrestrial proxies and their aquatic counterparts i e marine proxies in the yangtze river east china sea yr ecs shelf system where tom experiences extensive modification during transport and burial tom proxies in the yr ecs system collectively fit a power law model but with distinct attenuation rates the a values for individual molecular proxy groups among a range of tom proxies the modeled a values decrease in the order soil marker bhps triterpenols lignin hmw n alkanols branched gdgts hmw n alkanes for biomarkers and rsoil bit tomiso for proxies tracing tom rapid loss of tom components through dissociation in the narrow estuary followed by oxidation over the wide open shelf are best described by power curves inherent chemical reactivity i e the number of functional groups responses to hydraulic sorting and in situ production regulate the individual attenuation rates of them chemical reactivity plays the most important role on proxy behavior supported by a strong correlation between a values and standard molal gibbs energies both physical protection and chemical reactivity fundamentally control the overall behavior of tom components with the relative importance being setting dependant the former is relatively important in the estuary whereas the later is the primary control over the open shelf moreover regional variation of different marine counterparts is also significant over the river ecs shelf system seemingly regulated by regional nutrient distributions therefore for tom estimates using molecular ratio approaches the specific behavior of individual terrestrial components and marine counterparts and the physical biological and chemical characteristics of depositional settings all need to be considered

soil organic matter transport along an sub arctic river sea transect bacteriohopanepolyols bhps and glycerol dialkyl glycerol tetraethers gdgts have potential as soil tracing biomarkers for the extensive shelves of the arctic ocean in this work these biomarkers

ground penetrating radar for high resolution mapping of soil and rock stratigraphy ground penetrating radar is a technique which offers a new way of viewing shallow soil and rock conditions the need to better understanding overburden conditions for activities such as geochemical sampling geotechnical investigations and placer exploration as well as the factors controlling groundwater flow has generated an increasing demand for techniques which can image the subsurface with higher resolution than previously possible the areas of application for ground penetrating radar are diverse the method has been used successfully to map ice thickness water depth in lakes bedrock depth soil stratigraphy and water table depth it is also used to delineate rock fabric detect voids and identify karst features the effective application of the radar for the high resolution definition of soil stratigraphy and fractures in bedrock is highlighted the basic principles and practices involved in acquiring high quality radar data in the field are illustrated by selected case histories one example demonstrates how radar has been used to map the bedrock and delineate soil horizons to a depth of more than 20 m two case histories show how radar has been used to map fractures and changes of rock type to 40 m range from inside a mine another case history demonstrates how radar has also been used to detect and map the extent of groundwater contamination the corroboration of the radar results by borehole investigations demonstrates the power and utility of the high resolution radar method as an aid for interpolation and extrapolation of the information obtained with conventional coring programmes with the advent of new instrumentation and field procedures the routine application of the radar method is becoming economically viable and the method will see expanded use in the future

branched glycerol dialkyl glycerol tetraethers and crenarchaeol record post glacial sea level rise and shift in source of terrigenous brgdgts in the kara sea arctic ocean this study evaluates the glycerol dialkyl glycerol tetraether gdgt distribution and provenance in sediments spanning a minimum of 13 3 ka from the st anna trough northern kara sea the site has experienced extensive fluctuation in the delivery of river derived organic matter om caused by a eustatic change in sea level this is in line with the record of the concentration of the isoprenoid gdgt crenarchaeol produced by marine thaumarchaota which was low at the bottom of the core increasing gradually in the most shallow unit the concentration of branched br gdgts showed an opposite trend and a marked shift in distribution the deepest sediments 10 ka with a distribution currently encountered in surface sediments in front of the yenisei river are characterized by terrigenous brgdgts whereas the distribution in the shallowest unit 10 ka is strongly influenced by marine in situ brgdgts during the shift from terrigenous to marine sourced brgdgts there was one horizon where a pronounced shift in the brgdgt distribution was observed and the brgdgt concentration significantly decreased as the brgdgts delivered to the current kara sea system are derived from several sources we postulate that a temporary change in the relative importance of the brgdgt sources happened during this interval both in situ production and changing brgdgt provenance have implications for paleoclimate reconstruction using brgdgts in situ production of marine brgdgts results in a higher reconstructed ph however these in situ produced brgdgts did not influence the reconstructed mean annual air temperature mat when the matmrs calibration was used changes in the relative contribution of brgdgt sub pools were shown however to influence both soil ph reconstruction and mat reconstruction

mid to late holocene climate change an overview the last 6000 years are of particular interest to the understanding of the earth system because the boundary conditions of the climate system did not change dramatically in comparison to larger glacial interglacial changes and because abundant detailed regional palaeoclimatic proxy records cover this period we use selected proxy based reconstructions of different climate variables together with state of the art time series of natural forcings orbital variations solar activity variations large tropical volcanic eruptions land cover and greenhouse gases underpinned by results from general circulation models gcms and earth system models of intermediate complexity emics to establish a comprehensive explanatory framework for climate changes from the mid holocene mh to pre industrial time the redistribution of solar energy due to orbital forcing on a millennial timescale was the cause of a progressive southward shift of the northern hemisphere nh summer position of the intertropical convergence zone itcz this was accompanied by a pronounced weakening of the monsoon systems in africa and asia and increasing dryness and desertification on both continents the associated summertime cooling of the nh combined with changing temperature gradients in the world oceans likely led to an increasing amplitude of the el nin o southern oscillation enso and possibly increasingly negative north atlantic oscillation nao indices up to the beginning of the last millennium on decadal to multi century timescales a worldwide coincidence between solar irradiance minima tropical volcanic eruptions and decadal to multi century scale cooling events was not found however reconstructions show that widespread decadal to multi century scale cooling events accompanied by advances of mountain glaciers occurred in the nh e g in scandinavia and the european alps this occurred namely during the little ice age lia between ad w1350 and 1850 when the lower summer insolation in the nh due to orbital forcing coincided with solar activity minima and several strong tropical volcanic eruptions the role of orbital forcing in the nh cooling the southward itcz shift and the desertifi cation of the sahara are supported by numerous model simulations other simulations have suggested that the fingerprint of solar activity variations should be strongest in the tropics but there is also evidence that changes in the ocean heat transport took place during the lia at high northern latitudes with possible additional implications for climates of the southern hemisphere sh

a multi proxy study of lake development in response to catchment changes during the holocene at lochnagar north east scotland abstract this paper describes a multi core lake sediment study using pollen diatoms and chironomids together with magnetics and sediment biogeochemistry as biotic and abiotic proxies to infer lake development in response to environmental change during the holocene at lochnagar in the eastern highlands of scotland diatoms are used to infer ph chironomids to infer temperature with pollen and plant megafossils acting as an independent proxy to validate these records and to provide insights into changes in catchment vegetation and soils lipid biomarkers are explored for their potential to provide additional information on lake productivity the results indicate highly distinctive fluctuations in the loss on ignition loi record which are in phase with changes in some biotic chironomid head capsule concentration and abiotic coarse silt particle size fraction and lipid and chlorine fractions variables catchment driven changes due to the development and degredation of soils and the natural succession and human intervention on terrestrial catchment vegetation have the strongest influence on the diatom and chironomid assemblages these catchment processes resulted in the natural acidification of the lake water post industrial acidification of the lake was also influential on the lake biota climate driven temperature change appears to have had only a weak influence on the biota with declines in cold stenothermic chironomid taxa in response to early holocene warming and declines in thermophilic chironomids in response to cooling at about 2600 cal yr bp

molecular stratigraphy a new tool for climatic assessment variations in sea surface temperatures over the past 500 000 years are inferred from the relative abundance behaviour of two organic compounds c37 alkenones over the upper 8 metres of a sediment core from the eastern equatorial atlantic this molecular record ascribed to contributions from prymnesiophyte algae correlates well with the variations in the 18 signal for the calcareous skeletons of certain planktonic foraminifera thus providing the first demonstration of a new stratigraphical technique which may be especially valuable where methods based on carbonate 18 fail

distributional variations in marine crenarchaeotal membrane lipids a new tool for reconstructing ancient sea water temperatures it has recently been shown that membrane lipids of marine crenarchaeota a ubiquitous and abundant component of plankton occur in relatively high concentrations in recent and ancient sediments in this study we investigated the environmental controls on the relative distribution of these lipids in surface sediments we especially focussed on temperature as it is known from the thermophilic genetic relatives of marine crenarchaetoa that the composition of their membrane strongly depends on growth temperature indeed a significant linear correlation r2 0 92 is found between the number of cyclopentane rings in sedimentary membrane lipids derived from marine crenarchaeota and the annual mean sea surface temperatures this suggests that the mechanism of physical adaptation of their membrane compositions to temperature is identical to that of their thermophilic relatives in turn archaeal lipid distributions in sediments may thus allow the reconstruction of sea water temperatures of ancient marine environments

the temperature of europe during the holocene reconstructed from pollen data we present the first area average time series reconstructions of warmest month coldest month and mean annual surface air temperatures across europe during the last 12 000 years these series are based on quantitative pollen climate reconstructions from over 500 pollen sites assimilated using an innovative four dimensional gridding procedure this approach combines three dimensional spatial gridding with a fourth dimension represented by time allowing data from irregular time series to be focussed onto a regular time step we provide six regional reconstructed temperature time series as well as summary time series for the whole of europe the results suggest major spatial and seasonal differences in holocene temperature trends within a remarkably balanced regional and annual energy budget the traditional mid holocene thermal maximum is observed only over northern europe and principally during the summer this warming was balanced by a mid holocene cooling over southern europe whilst central europe occupied an intermediary position changes in annual mean temperatures for europe as a whole suggest an almost linear increase in thermal budget up to 7800 bp followed by stable conditions for the remainder of the holocene this early holocene warming and later equilibrium has been mainly modulated by increasing winter temperatures in the west which have continued to rise at a progressively decreasing rate up to the present day

antarctic ice sheet palaeo thinning rates from vertical transects of cosmogenic exposure ages abstract constraining antarctic ice sheet evolution provides a way to validate numerical ice sheet models that aid predictions of sea level rise in this paper we collate cosmogenic exposure ages from exposed nunataks in antarctica that have been used or have the potential to be used to constrain rates of thinning of the antarctic ice sheets since the last glacial maximum we undertake quality control of the data and adopt a bayesian approach to outlier detection past thinning rates are modelled by monte carlo linear regression analysis we present thinning rates from 23 sites across antarctica the resulting data set is the first antarctic wide collation of past ice sheet thinning rates and provides an empirical starting point for future model data comparisons palaeo thinning rates are spatially variable with high rates appearing to correlate to areas of contemporary rapid changes on centennial timescales past thinning rates are comparable to modern day observations implying that modern day thinning has the potential to persist for centuries in numerous parts of antarctica the onset of abrupt thinning from all sites post dates meltwater pulse 1a suggesting that its source region s are distal to areas where exposure age constraints on ice surface geometry exist

holocene land and sea level changes in great britain analysis of more than 1200 radiocarbon dated samples that constrain relative sea levels in great britain over the past 16 000 yr provides estimates of current land level changes negative of relative sea level change maximum relative land uplift occurs in central and western scotland ca 1 6 mm yr 1 and maximum subsidence is in southwest england ca 1 2 mm yr 1 sediment consolidation arising from autocompaction as the sediment accumulates and from land drainage increases the subsidence in areas with thick sequences of holocene sediments with an average effect equivalent to at least an extra ca 0 2 mm yr 1 land subsidence but more in parts of southeast england 0 5 1 1 mm yr 1 modelled changes in tidal range during the mid to late holocene in eastern england suggest that the calculated rate of land subsidence is overestimated unless such changes are quantified the effect is most significant for large coastal lowlands the fenland and humber ca 0 5 and 0 6 mm yr 1 that were tidal embayments during the mid to late holocene