the 7be 210pbxs ratio as an indicator of suspended sediment age or fraction new sediment in suspension reported here is a technique to use the 7be 210pbxs ratio as a measure of suspended sediment age or as an indicator of the fraction of the suspended sediment that is recently eroded from the landscape although both 7be and 210pbxs are delivered seasonally and stochastically to the landscape by precipitation the ratio of the two radionuclides varies substantially less the 7be 210pbxs ratios measured in three different catchments decrease in the following manner precipitation c 16 suspended sediments in rivers 6 7 suspended sediments in estuaries 4 6 sediment collected in sediment traps in the estuary c 1 surface sediment of the estuary c 0 5 decreases in the 7be 210pbxs ratio in suspended sediments can be interpreted to be the result of increased age of the sediment since 7be decays faster than 210pb alternatively a decrease in the 7be 210pbxs ratio in suspended sediments can be interpreted to be the result of dilution of newly tagged 7be rich sediment by 7be dead sediment for example by erosion of soil below the 7be enriched surface layer or by resuspension of 7be dead bottom sediment presented here is a model which uses the 7be 210pbxs ratio in suspended sediments to determine the time since the particles were tagged by precipitation derived radionuclides i e the age of the suspended sediment in addition an alternative model is presented to determine the fraction of the sediment that is newly tagged these two models are applied to three catchments old woman creek ohio weeks bay alabama and south slough oregon and yield similar findings at all three sites sediment ages increase from 0 in newly tagged material to 50 80 days in rivers to about 80 100 days in the estuaries to about 200 days in the sediment traps to about 300 days on surface bottom sediments alternatively the percentage new sediment decreases from 100 per cent in newly tagged material to about 35 50 per cent in rivers to 25 35 per cent in the estuary to less than 10 per cent in the sediment traps to 1 4 per cent on the surface of the bottom sediments

evidence for perchlorates and the origin of chlorinated hydrocarbons detected by sam at the rocknest aeolian deposit in gale crater 1 a single scoop of the rocknest aeolian deposit was sieved 150 m and four separate sample portions each with a mass of 50mg were delivered to individual cups inside the sample analysis at mars sam instrument by the mars science laboratory rover ss ample acquisition system the samples were analyzed separately by the sam pyrolysis evolved gas and gas chromatograph mass spectrometer analysis modes several chlorinated hydrocarbons including chloromethane dichloromethane trichloromethane a chloromethylpropene and chlorobenzene were identified by sam above background levels with abundances of 0 01 to 2 3nmol the evolution of the chloromethanes observed during pyrolysis is coincident with the increase in o2 released from the rocknest sample and the decomposition of a product of n methyl n tert butyldimethylsilyl trifluoroacetamide mtbstfa a chemical whose vapors were released from a derivatization cup inside sam the best candidate for the oxychlorine compounds in rocknest is a hydrated calcium perchlorate ca clo4 2 nh2o based on the temperature release of o2 that correlates with the release of the chlorinated hydrocarbons measured by sam although other chlorine bearing phases are being considered laboratory analog experiments suggest that the reaction of martian chlorine from perchlorate decomposition with terrestrial organic carbon from mtbstfa during pyrolysis can explain the presence of three chloromethanes and a chloromethylpropene detected by sam chlorobenzene may be attributed to reactionsofmartian chlorine released during pyrolysiswith terrestrial benzene or toluene derived from 2 6 diphenylphenylene oxide tenax on the sam hydrocarbon trap at this time we do not have definitive evidence to support a nonterrestrial carbon source for these chlorinated hydrocarbons nor do we exclude the possibility that future sam analyses will reveal the presence of organic compounds native to the martian regolith

phytoliths indicators of grassland dynamics during the late holocene in intertropical africa abstract the reconstruction of african tropical grassland history during the late holocene can be carried out using phytolith analysis fossil phytolith assemblages from lake guiers in the sahelian region of senegal and from lake sinnda in the guineo congolian region of congo were investigated the results are interpreted on the basis of modern phytolith assemblages from the same regions and compared to pollen data previously obtained tall or short grass associations are discriminated by their phytolith index iph saddle cross dumbel saddle while the density of shrubs and trees is indicated by relative proportions of the dicotyledon phytoliths the phytolith data emphasize that in the guineo congolian region around lake sinnda the driest phase of the late holocene occurred between 4000 and 1200 yr b p commencing with the opening of the dense forest and its replacement by a short grass savanna from ca 1000 yr b p wetter climatic conditions developed as represented by the setting up of a tall grass savanna woodland the modern shrub and tall grass savanna was developed ca 700 yr b p in the sahelian region around lake guiers the driest phase occurred after about 2000 yr b p and has not been followed by moister conditions a tall grass savanna woodland was gradually replaced by a shrub and short grass savanna which still occurs a short period of development of swampy vegetation which can be related to a lake level change interrupted the semi arid adaptation of the vegetation between about 2000 yr b p and the present

palaeoecological implications of the lower pleistocene phytolith record from the dmanisi site georgia archaeological investigations of the lower pleistocene deposits at dmanisi lesser caucasus georgia have yielded an assemblage of hominin and faunal remains within a well dated context although abundant vertebrate fossils have been recovered paleobotanical studies have been limited to address this phytolith analysis has been conducted on two sections in order to reconstruct the distribution and evolution of vegetation throughout the entire sedimentary sequence large concentrations of phytoliths were recovered and analysed permitting the reconstruction of climatic indices the environmental data obtained from these phytolith assemblages are consistent with other palaeoecological data i e geological faunal and other archaeobotanical records when considered together they indicate an environment in which grasses were well represented in addition the climatically important water stress indices derived from dmanisi s phytolith assemblages suggest a period of increased aridity in the middle part of the stratigraphic sequence which is contemporaneous with human occupations of the site

cat scan analysis of sedimentary sequences an ultrahigh resolution paleoclimatic tool paleoclimate research is essential to determine the natural variability of climate and to place the current climate change into its natural context the current need is to generate the highest temporal resolution paleoclimatic reconstructions possible in order to assess the natural variability of the climate system but also to test the ability of numerical models to simulate conditions different from the ones observed with the relatively short instrumental records in this paper we show that cat scan analysis of sedimentary sequences with its 1 mm downcore resolution can be used to identify millennial to seasonal cycles in sedimentary sequences in examples from the st lawrence estuary eastern canada spectral analysis of the cat scan data from holocene postglacial sediments revealed millennial to centennial scale oscillations possibly associated with either solar variability changes in relative sea level or tidal amplitude similarly spectral analysis of holocene and sangamonian glaciomarine sequences revealed decadal to annual scale oscillations with periods close to the one previously associated with the north atlantic oscillation nao whereas spectral analysis of the cat scan data from the sangamonian rhythmites possibly revealed seasonal cycles

astronomical theory of the pleistocene ice ages a brief historical review abstract this paper traces the evolution of the astronomical theory of the pleistocene ice ages from its origin in the work of adhemar and croll through its quantitative transformation in the hands of milankovitch to its current renaissance emphasis is given to the interplay between climatic theory and geologic observation from 1941 when milankovitch published his final version of the theory until the early 1970s most attempts to test the theory empirically were carried out in the time domain by comparing the geologic record of climate with predicted climate curves these attempts ran into serious difficulties particularly the inaccuracy of the geologic time scale and the ambiguity of climate predictions early attempts to evaluate the theory with simple radiation balance models appeared to indicate that the climatic response to secular changes in the orbit would be too small to be observed geologically but by the mid 1970s the advent of an improved time scale for pleistocene marine deposits and the availability of long closely sampled records made it possible to arrange generalized but unambiguous tests of the theory in the frequency domain by comparing orbital and climatic spectra these results decisively confirmed the idea that orbital variations significantly influenced the earth s climate during the pleistocene but they did not tell us how this influence was exercised the emphasis of current work has therefore shifted to the identification and quantitative modeling of physical mechanisms by which the climate system responds so dramatically to the predicted rather subtle changes in radiative boundary conditions

environment and landscape management during the middle neolithic in southern france evidence for agro sylvo pastoral systems in the middle rhone valley abstract rescue excavations in the middle rhone valley have provided opportunities to develop innovative strategies for the study of palaeoenvironments these strategies involve sampling and analysis of botanical remains recovered not only from archaeological sites but also in off site pedosedimentary sequences thought to be poor in botanical remains thus these remains phytoliths pedo charcoal give access to unexplored depositional contexts such as alluvial plains moreover off site data are useful because they minimise the hazard of cultural bias e g selection of species during wood gathering comparison of data collected in the alluvial plain with data obtained via anthracological analyses of karstic caves and rock shelters in the hinterland suggests a complex agro sylvo pastoral management of the landscape during the middle neolithic we propose a pattern that supposes considerable specialization in use of plains vs slopes in the landscape and a strong and continuous human pressure on the vegetation and soils between 4500 and 3500 cal bc nevertheless these constraints are not sufficient to explain the persistence of such a system for more than a millennium favourable climatic conditions are thought to have been a determining factor in the persistence of an ecologically meta stable relationship between human societies and their natural environment

the evolution of pleistocene climate a time series approach abstract in the later part of the pleistocene variations in global ice volume have been dominated by an approximate 100 000 year cycle analysis of 2 myr long oxygen isotope record from an equatorial pacific core indicates that this is true only for the last 900 000 years prior to this time the amplitude of the 100 000 year cycle is much reduced as is the variance of all oscillations with periods greater than 60 000 years based on results of time series analysis of this 2 myr long record the pleistocene glacial cycles can be divided into three sections 1 the late pleistocene 0 900 kyr b p where the variations in the isotope record are dominated by the 100 000 year cycle 2 the middle pleistocene 900 1450 kyr b p in which low frequency components are not as important as in the later period of the pleistocene and 3 the early pleistocene late pliocene 1450 2000 kyr b p where general reductions of importance at all frequencies is seen as compared to the later intervals recent modeling efforts which describe variations in global ice volume show that the dominant low frequency component observed in the late pleistocene can result from different time constants for the rate of glacial growth and decay in response to variations in the earth s orbital parameters it is hypothesized that during the early pleistocene the rate of growth and decay of glaciers were more similar and that continental erosion by successive glacial advances lowered the land surface in areas of ice cap formation to below sea level when the ice caps became marine based more rapid decay of the ice became possible

phytolith assemblages as indicators of coastal environmental changes and hurricane overwash deposition we demonstrate that phytolith assemblages are a useful proxy for reconstructing coastal environmental changes and for validating the overwash origin of sand layers in palaeotempestology studies phytolith analysis was conducted on 50 topsoil or surface sediment samples collected from a variety of coastal plant communities or depositional environments in the southeastern usa the data suggest that different coastal subenvironments can be distinguished by their modern phytolith assemblages for example coastal marsh samples contain a diverse phytolith assemblage dominated by smooth elongate and square morpho types and maritime forest samples are dominated by phytoliths from palms and broadleaf dicotyledonous plants remarkably the phytolith assemblages from sand dunes are characterized by high percentages of two horned tower flat tower spool horned tower and short saddle types phytolith analysis of three prehistoric sand layers in a sediment core from western lake northwestern florida shows that they contain a phytolith assemblage similar to those characteristic of sand dunes and interdune meadows these observations are confirmed by the results of principal components analysis and discriminant analysis on the modern and fossil phytolith data sets our study results support the interpretation that the sand layers in western lake were indeed formed by the erosion of sand dunes during overwash processes caused by landfalling catastrophic hurricanes

phytolith transport in soil a field study using fluorescent labelling abstract soil phytoliths have been widely applied to reconstruct vegetational history to date however the transport behaviour of phytoliths in soil is poorly understood causing uncertainties in the interpretation of phytolith data the present study was therefore designed 1 to determine transport rates of phytoliths in loamy and sandy soils under field conditions and 2 to elucidate the effect of phytolith size and shape on their transport behaviour in sandy and loamy soils for this purpose we adopted a fluorescent labelling technique from veterinary science the phytoliths were extracted from common reed phragmites australis labelled with the fluorescent dye fluorescein isothiocyanate and applied to a loamy sand soil haplic cambisol and a silty loam soil stagnic luvisol in southern germany one year after application the soils were sampled to analyse phytolith distribution with soil depth the weighted mean transport distance of phytoliths after one year was 3 99 1 21 cm for the cambisol and 3 86 0 56 cm for the luvisol phytolith size significantly affected transport behaviour indicating a preferential translocation of small sized phytoliths our study provides direct evidence for a significant downward mobility of phytoliths in sandy and loamy soils under natural conditions this should be taken into account when using phytoliths as palaeoenvironmental tracers quantifying phytoliths in soil with fluorescent labelling makes it possible to identify artificially applied phytoliths without using the conventional extraction method

phase relationships of north atlantic ice rafted debris and surface deep climate proxies during the last glacial period we report stable isotope core scanning xrf and ice rafted detritus ird data in glacial aged sediments from piston core kn166 14 jpc 13 hereafter referred to as jpc 13 retrieved at 53 1 n 33 5 w on the southern gardar drift north atlantic a chronology was established by correlating millennial scale features in the benthic delta 18o record to portuguese margin core md95 2042 once the alignment of benthic delta 18o of jpc 13 to md95 2042 is fixed the relative timing of proxy variables is used to determine the phasing of changes in ird and surface deep hydrography each peak in north atlantic ird coincided with a decrease in benthic delta 18o that in turn has been linked to warming in antarctica events a1 a7 the ird pulses are followed shortly thereafter by abrupt decreases in planktonic delta 18o indicating warming and increased heat transport to the subpolar north atlantic associated with greenland interstadials gis 8 12 14 and 16 17 grain size and elemental k ti variations indicate that iceland scotland overflow water isow was stronger during these long warm interstadial periods of marine isotope stage mis 3 the results are consistent with interhemispheric phase relationships inferred from iberian margin sediment cores and with methane synchronization of greenland and antarctic ice cores

recent clastic sedimentation processes in lake puyehue chilean lake district 40 5 s clastic sedimentation processes in lake puyehue 40 5 s 72 5 w chile are described based on correlation of high resolution seismic profiles and multidisciplinary analysis of short sediment cores from two contrasting coring sites pu i and pu ii two main sedimentary environments are recognized in this oligotrophic lake i a proximal one which includes the delta of the main tributary the golgol river and is a deep flat basin with a ponded geometry and limited acoustic penetration and ii a distal one that is composed of several sub basins highlighting a drape geometry and better acoustic penetration based on the correlation of seismic data and sediment cores dated by radionuclides and the identification of tephra layers rininahue1907 cordon caulle 1921 22 and 1960 we argue that clastic sedimentation results essentially from the development of homopycnal flows at the end of the winter season in this monomictic lake whereas distal clastic environments pu ii coring site are dominated by biogenic production and appear to have been little affected by the 1960 chilean earthquake mw 9 5 and nearby volcanic eruptions this may not be the case for more proximal clastic environments pu i coring site which also experience sporadic hyperpycnal flows during major flood events in may june 1960 for example as several earthquake triggered landslides dammed the course of the golgol river and ca 7 106 m3 of volcaniclastic sediments fell over the drainage basin of the lake during the earthquake induced puyehue cordon caulle eruption successive outbursts in the golgol valley induced a mega flood in lake puyehue this hyperpycnal flow reworked a mixture of volcaniclastic and regolith derived sediments from the catchment as well as lacustrine sediments surrounding the golgol delta during the rising limb of the flood these recently reworked sediments are strikingly enriched in excess 210pb activity suggesting that positive anomalies in the activity of this isotope can be used to determine the source area of clastic sediments

40ar 39ar dating and phytolith analysis of the early pleistocene sequence of kvemo orozmani republic of georgia chronological and palaeoecological implications for the hominin site of dmanisi abstract the kvemo orozmani locality contains a 15 m thick early pleistocene fluvio lacustrine sequence bracketed by two lava flows located 13 km up the masavera river valley west from the dmanisi site kvemo orozmani is therefore of prime interest to improve the paleoecological framework as well as dating dmanisi 40 ar 39 ar ages obtained on the two lava flows indicate that kvemo orozmani sequence brackets the dmanisi sediments between 1 825 0 021 ma and 1 765 0 021 ma phytolith assemblages found at the bottom of the sequence indicate a warm and humid climate while the assemblages found at the top suggest dryer colder climatic conditions the shift in phytolith assemblages observed at kvemo orozmani is similar to the one already described in dmanisi and occurs near the end of the oluduvai subchron the new palaeoecological and chronological data confirm the hypothesis made in dmanisi about the palaeoenvironmental context during the hominin occupation that suggests a temperate climate becoming drier the age we obtained on the overlying lava flow establishes a minimum age for the climatic transition at both kvemo orozmani and the dmanisi site of 1 765 0 021 ma

understanding holocene variations in the vegetation of sao joao river basin southeastern coast of brazil using phytolith and carbon isotopic analyses abstract to understand variations in the vegetation of the southeastern coast of brazil during the holocene and to identify roughly when they took place we make use of phytolith morphology and carbon stable isotope analyses coupled with 14c dating of soil profiles the soil profile studied is located in the sao joao river basin close to cabo frio rio de janeiro state we evaluated the soil characteristics which showed great variations in granulometry with larger texture in upper horizons that enabled the movement of particles to lower layers the accumulation soil horizons revealed several palaeoclimatic aspects higher phytolith stocks a higher density of trees and a lower water stress at the bottom of the profile and a predominance of c3 grasses throughout the holocene carbon stable isotopic ratios of the soil profile confirm the predominance of c3 plants except for e bt horizon which was enriched in 13c the soil organic matter mean residence time ranges from post bomb topsoil to 10 245 years cal bp at the base of the profile the results of this study are compatible with other evidence of a more humid environment in the first half of the holocene

magnetic and geochemical signatures of flood layers in a lake system river floods holds the capasity to erode and transport sediments that are deposited whenever the discharge is redused in catchments that are subjected to repeated flooding downstream lakes can therefore contain a record of past events across multiple timescales high resolution core scanning analyses such as x ray fluorescence xrf scanning and magnetic susceptibility ms provide data that are frequently used to detect flood layers in soft sediment archives such as lakes fjords and ocean basins deposits of past floods also can potentially reveal information about the evolution of flood events as well as source area here we explore ways in which subtle variability in high resolution data can be utilized and subsequently vetted by high precision measurements in order to delineate the copious information that can be extracted from soft sediment records by combining magnetic hysteresis measurements and first order reversal curves forcs with inductively coupled plasma optical emission spectrometer icp oes measurements of chemical elements on 36 samples questions about flood dynamics and variability are raised and also sources of noise in high resolution scanning techniques are discussed specifically we show that a lake flood record from southern norway containing 92 floods distributed over 10 000 years can be sub divided into two groups of floods that were generated either by spring snow melting intense summer rainstorms or a combination of both the temporal evolution of this pattern shows a marked shift towards spring floods around 2000 years ago compared to the earlier part of the record this article is protected by copyright all rights reserved

flood and earthquake disturbance of 210pb geochronology lake anterne nw alps dating recent lake sediment records yielding disturbed 210pb profiles has been a problem of wide interest in palaeoclimatic and palaeoseismic studies over the last few centuries when applied to an alpine lake sedimentary record a high resolution sedimentological study reveals that the 210pb profile is disturbed by the occurrence of single event deposits triggered by two different mechanisms flood events deposits and gravity reworking removing disturbed layers from the 210pb profile yields a logarithmic depth activity relationship using a simple 210pb decay model cfcs provides an assessment of mean accumulation rate of continuous sedimentation as opposed to event linked sedimentation the correlation of the thickest four gravity reworked deposits with historically known earthquakes permits both validation and refinement of the age depth relationship this refinement highlights variations in accumulation rate consistent with post little ice age climatic variations

the dominant erosion processes supplying fine sediment to three major rivers in tropical australia the daly nt mitchell qld and flinders qld rivers abstract the tropics of northern australia have received relatively little attention with regard to the impact of soil erosion on the many large river systems that are an important part of australia s water resource especially given the high potential for erosion when long dry seasons are followed by intense wet season rain here we use 137cs concentrations to determine the erosion processes supplying sediment to two major northern australian rivers the daly river northern territory and the mitchell river queensland we also present data from five sediment samples collected from a 100 km reach of the cloncurry river a major tributary of the flinders river queensland concentrations of 137cs in the surface soil and subsurface channel banks and gully samples were used to derive best fit probability density functions describing their distributions these modelled distributions are then used to estimate the relative contribution of these two components to the river sediments our results are consistent with channel and gully erosion being the dominant source of sediment with more than 90 of sediment transported along the main stem of these rivers originating from subsoil we summarize the findings of similar studies on tropical australian rivers and conclude that the primary source of sediment delivered to these systems is gully and channel bank erosion previously as a result of catchment scale modelling sheet wash and rill erosion was considered to be the major sediment source in these rivers identifying the relative importance of sediment sources as shown in this paper will provide valuable information for land management planning in the region this study also reinforces the importance of testing model predictions before they are used to target investment in remedial action

cat scan in marine stratigraphy a quantitative approach abstract computed axial tomography cat scan gives a pseudo 3d representation of sedimentary cores sediments may be described and numerically processed from digitized high resolution images a 150 m long borehole was drilled and sampled at ile aux coudres middle estuary of the st lawrence quebec and analysed by a tomodensitometer cat scanner this borehole represents mainly the illinoian sangamonian transition series isotopic stage 5e 130 80 kyr b p of a post glacial glacioisostatic marine invasion and the subsequent regressive prodelta four representative samples 900 mm long were chosen for analysis from a transition zone between glacial and prodeltaic sediments they have been described from tomographic longitudinal and transversal sections from ct number series and also from classical analysis such as grain size organic matter and carbonates ct numbers reflect sedimentary characteristics and are closely linked to grain size and to organic matter carbonates are only weakly correlated probably because of its low concentration bed thickness and numerical processing of ct number series are used to characterize lamina and allow for depicting sub annual annual and longer periodicities clay facies fine and thick rhythmites and isolated diamicton beds were identified from bottom to top the first sample contains homogeneous clay rhythmites typical of a distal environment the second is composed of diamictons and thin alternating light dark annual lamina sets in the third sample annual light dark rhythmites are slightly thicker and display subtle semi annual cyclicities in the fourth sample annual rhythmites are several centimetres in thickness and contain preserved sub annual events of possible seasonal cyclicity this succession of facies and associated stratal periodicities may be typical of transgressive sedimentation in a basin such as the st lawrence estuary during the transition from glacial to non glacial conditions

orbital signature of interglacials a specific orbital configuration high obliquity combined with the june perihelion marked the beginning of the past three interglacials this suggests that the primary cause of the glacial cycle may be astronomical an astronomical climate index aclin is introduced which combines the three orbital variables in the time lag bivariant model designed to predict the major climate changes in the late and middle pleistocene and in the near future aclin closely correlates with the major climatic events revealed by independently dated proxy climate indicators of the past 130 000 yr it successfully differentiates the interglacials and displays a 100 000 yr periodicity it predicts an early end of the present inter glacial and the start of a new one in 114 000 yr

reply to comment by biemann and bada on reanalysis of the viking results suggests perchlorate and organics at midlatitudes on mars

oceanic mechanisms for amplification of the 23 000 year ice volume cycle situated adjacent to the largest northern hemispher ice sheets of the ice ages the mid latitude north atlantic ocean has an important role in the earth s climate history it provides a significant local source of moisture for the atmosphere and adjacent continents forms a corridor that guides moisture bearing storms northward from low latitudes and at times makes direct contact along its shorelines with continental ice masses evidence of major ice ocean air interactions involving the north atlantic during the last 250 000 years is summarized outflow of icebergs and meltwater initially driven by summer insolation over the ice sheets affects midlatitude ocean temperatures summer heat storage winter sea ice extent and global sea level these oceanic responses in turn influence the winter moisture flux back to the ice sheets as well as ablation of land ice by calving spectral data indicate that the oceanic moisture and sea level feedbacks in part controlled by glacial melt products amplify milankovitch insolation forcing of the volumetrically dominant mid latitude ice sheets at the 23 000 year precessional cycle

calibrating grass phytolith assemblages in climatic terms application to late pleistocene assemblages from kansas and nebraska abstract the use of modern phytolith assemblages for the interpretation of fossil phytolith assemblages demonstrates the utility of phytolith analysis in reconstructing grassland vegetation and climate in the great plains of north america the modern data presented are the typical average assemblages for 34 modern localities taken throughout the great plains modern assemblage variability across the region is substantial this variability shows a coherent geographical pattern consistent with modern grassland composition these modern phytolith assemblages are calibrated in terms of modern climate data specifically july mean temperature seven fossil assemblages from three late pleistocene localities in the central great plains are presented two alternative phytolith temperature regression models are applied to these fossil assemblages to estimate paleo temperature resulting estimates are consistent with other efforts to calculate late pleistocene temperature departures in the region ca 8 0 to 7 0 c the fossil data also show rapid change in grassland composition and climate during the pleistocene holocene transition these results demonstrate how phytolith analysis can complement or substitute for pollen analysis in the great plains of north america

paleoenvironmental history of post toya ash tephric deposits and paleosols at iwate volcano japan using aeolian dust content and phytolith composition abstract physicochemical mineralogical and geochemical analyses of post toya ash 90 130 ka tephric and aeolian deposits at the foot of iwate volcano northeastern japan revealed the accumulation of deposits of long range aeolian dust transported from the asian continent and interstratified with the tephric deposits oxygen isotopic ratios of quartz in the 1 10 m fractions from two paleosols formed in the aeolian units shibutami cracked layers are 16 2 and 17 0 consistent with this fine grained quartz being of an aeolian origin the accumulation of asian aeolian dust onto tephric deposits in northeastern japan was dominant in the cold stages of the last glacial period 20 34 ka and 50 70 ka we determined the changes in vegetation and climate by using opal phytolith distribution in the tephra and aeolian deposits and associated paleosols similarly we interpreted the paleoenvironmental history of the tephric deposits by relating the vegetation history to the dust flux and fossil periglacial phenomena i e involution observed on tephra beds the paleoclimate sequence obtained coincides closely with the marine oxygen isotope curves indicating that opal phytolith analysis is useful in determining the interglacial glacial cycle recorded in aeolian and tephric deposits

soil phytoliths as indicators of initial human impact on san cristobal island galapagos abstract i analyzed phytoliths from soil profiles on san cristobal island in the galapagos islands to determine whether historical human impact and recent vegetation dynamics are visible in the phytolith record i extracted phytoliths from soil samples taken from four test pits located at the village an abandoned field a forest and an active agricultural field all located within the former el progreso plantation ad 1860 1920 changes in the ratio of tree to grass phytoliths with depth in all four samples suggest changes in vegetation composition from forest to open vegetation dominated by grasses which reflects the removal of forest with colonization and the first permanent human occupation of the archipelago in the middle 19th century this paper shows that the changes in vegetation brought about by colonization and land clearing for plantations are documented in the soil phytoliths record and suggests that phytoliths can be used as an indicator of past vegetation change in future work on the historical ecology of the galapagos archipelago

periodicities of palaeomagnetic intensity and palaeoclimatic variations a walsh spectral approach abstract the walsh power spectral technique has been applied to the non sinusoidal palaeoclimatic thegloborotalia menardii climatic curve and palaeomagnetic intensity variation records of the last 1 2 myr the analysis reveals in the case of palaeomagnetic variations statistically significant peaks at 90 confidence level centered around 150 60 and 24 kyr the palaeoclimatic spectrum however indicates only two significant peaks of 60 and 24 kyr the identical periodicities in both the phenomena may suggest a causal link between the geomagnetic intensity variations and climatic changes

temporal variability of suspended sediment sources in an alpine catchment combining river rainfall monitoring and sediment fingerprinting influence of the rainfall regime on erosion and transfer of suspended sediment in a 905 km 2 mountainous catchment of the southern french alps was investigated by combining sediment monitoring rainfall data and sediment fingerprinting based on geochemistry and radionuclide concentrations suspended sediment yields were monitored between october 2007 and december 2009 in four subcatchments 22 713 km 2 automatic sediment sampling was triggered during floods to trace the sediment origin in the catchment sediment exports at the river catchment outlet 330 pm 100 t km 2 yr 1 were mainly driven 80 by widespread rainfall events long duration low intensities in contrast heavy local and short duration storms generated high peak discharges and suspended sediment concentrations in small upstream torrents however these upstream floods had generally not the capacity to transfer the sediment down to the catchment outlet and the bulk of this fine sediment deposited along downstream sections of the river this study also confirmed the important contribution of black marls up to 70 to sediment transported in rivers although this substrate only occupies c 10 of the total catchment surface sediment exports generated by local convective storms varied significantly at both intra and inter flood scales because of spatial heterogeneity of rainfall however black marls marly limestones contribution remained systematically high in contrast widespread flood events that generate the bulk of annual sediment supply at the outlet were characterized by a more stable lithologic composition and by a larger contribution of limestones marls quaternary deposits and conglomerates which corroborates the results of a previous sediment fingerprinting study conducted on riverbed sediment

late holocene phytolith and carbon isotope record from a latosol at salitre south central brazil abstract the reliability of paleovegetation records inferred from soil phytolith assemblages and som soil organic matter carbon isotope analysis was examined in light of previous pollen and charcoal reconstructions the sampled latosol is located in south central brazil salitre at a boundary between forest and cerrado the derived mean age of phytoliths and som at each level is the result of a balance between continuous translocation and selective dissolution it increases with depth in a regular quantifiable fashion that allows paleoenvironmental interpretation phytoliths and som tracers first record a savanna phase associated with the last holocene long dry period occurring between ca 5500 and 4500 yr b p two periods of tree community development followed between ca 4000 and 3000 and after ca 970 yr b p leading to the present cerrado forest association the dry spell interrupted this trend about 970 60 yr b p the second development of woody elements was contemporaneous with an increase in anthropogenic fires therefore climate was more important than fires and human activities in constraining the growth of vegetation during the last nine centuries at salitre more generally despite pedogenic processes soil phytoliths and 13c values of the som may be accurate tracers of vegetation changes

phytoliths as paleoenvironmental indicators west side middle awash valley ethiopia phytolith assemblage analysis offers the potential to refine our knowledge of paleoecosystems where grasses and sedges predominate in this work holocene and pleistocene sediments from an arid tropical region in ethiopia have been analyzed for their phytolith content presented as detailed counts and diagrams according to the twiss classification the aim is to test the usefulness of phytolith assemblages to indicate paleoenvironments at middle awash where fossil pollen grains are poorly preserved in sediments that yielded abundant archaeological remains the vegetation in the middle awash subdesertic valley is currently a shrub steppe dominated by c4 grasses adapted to arid conditions with a narrow riparian forest limited to the awash river our results show that modern surface samples holocene and pleistocene sediments contain well preserved and different phytolith assemblages and therefore that no translocation processes from modern soil to geological strata seem to occur fossil records and modern assemblages are interpreted using phytolith ratios to estimate the density of the tree cover the aridity and the proportion of c3 versus c4 grasses as applied to phytolith assemblages from north america and west africa the phytolith assemblages from modern soil samples correctly reflect the proportion of trees and shrubs versus grasses different in the riparian vegetation and the shrub steppe modern phytolith assemblages appear to be a mixed signature of local and regional vegetation phytolith analysis of the holocene sample suggests a grassland where the grass community is constituted by the chloridoideae subfamily adapted to warm and dry conditions and where c3 pooideae cover the highlands phytolith analysis of the pleistocene sample evidences grassland formation with scattered woody elements where c4 panicoideae grasses adapted to warm and humid conditions dominate the grass cover however these conclusions need to be confirmed by more complete study on phytolith assemblages from modern vegetation from ethiopia

perchlorate induced low temperature carbonate decomposition in the mars phoenix thermal and evolved gas analyzer tega 1 simulated thermal evolved gas analyzer tega analyses have shown that a co2 release detected between 400 c and 680 c by the phoenix lander s tega instrument may have been caused by a reaction between calcium carbonate and hydrated magnesium perchlorate in our experiments a co2release beginning at 385 12 c was attributed to calcite reacting with water vapor and hcl gas from the dehydration and thermal decomposition of mg perchlorate the release of co2 is consistent with the tega detection of co2 released between 400 and 680 c with the amount of co2increasing linearly with added perchlorate x ray diffraction xrd experiments confirmed cacl2 formation from the reaction between calcite and hcl these results have important implications for the mars science laboratory msl curiosity rover heating soils may cause inorganic release of co2 therefore detection of organic fragments not co2 alone should be used as definitive evidence for organics in martian soils

a quick and low cost technique to identify layers associated with heavy rainfall in sediment archives during the anthropocene long term records are needed to investigate the impact of extreme events inthe current framework of global change sedimentary reconstruction with ahigh resolution remains difficult without conducting expensive destructiveand or time consuming analyses in this study high resolution ct scan profiles 0 6 mm resolution were used to investigate their potential for detecting flood deposits induced by heavy rainfall events this method was applied to a sediment core dated with fallout radionuclides covering 120 year period collected in a pond draining a small forested catchment french massif central central france between 1960 and 2017 28 layers were deposited seventy six percent of these deposits were correlated to the occurrence of heavy rainfall 50 mm recorded during one or two consecutive days the remainder of the deposits detected with the computer tomo graphy ct scanner n 5 were not correlated to weather events they mainly occurred in response to landscape management operations for example afforestation works as a result of the major 1999 storm this period was indeed characterized by an increase in the delivery of137cs enriched sediment demonstrating a greater topsoil contribution to sediment during majorforest management operations the intensity of detrital layers has significantly decreased throughout time after a major land use change that tookplace in 1948 and land abandonment the frequency of heavy rainfall anassociated detrital deposits has nevertheless increased by 60 and 75 respectively between the years 1960 and 2017 these results outline the potential of ct scan for reconstructing long term flood deposits associated with heavy precipitation

recent climatic and anthropogenic imprints on lacustrine systems in the pyrenean mountains inferred from minerogenic and organic clastic supply vicdessos valley pyrenees france high resolution seismic profiling has been combined with geochemical analyses of both watershed samples and five lacustrine cores retrieved from two natural lacustrine basins of glacial origin lake majeur and lake sigriou 1630 m a s l and 1995 m a s l respectively eastern french pyrenees identifying specific minerogenic and organic markers of autochthonous and allochthonous supply data allow documenting past climatic and anthropogenic pressures over the past century the lacustrine sediment of lake majeur has been essentially composed of algae drastically contrasting with the natural sedimentary infill of the basin mainly resulting from soil erosion from the mid late holocene since ad 1907 the lake majeur has been used for hydroelectricity production human induced lake level regulations affecting up to 37 of the lacustrine surface have increased by fourfold the accumulation rate of the lake and favoured water enrichment rubidium abundance within the lacustrine sediments of the two lakes reflects the mid late holocene palaeohydrology after dam construction in ad 1907 greater quantities of rubidium found in lake majeur sedimentary infills indicate drier climatic periods such as from ad 1975 to ad 1982 during which water reservoirs were particularly in demand inversely before the dam was built rubidium fluctuations were correlated with wetter conditions and hydrological events were recorded as sandy layers deposited by canyon reactivation synchronous with european climatic deterioration phases we notably document that the mediaeval climate anomaly was interrupted by some humid periods dated c ad 940 ad 1080 ad 1100 and ad 1250 we also date the onset of the little ice age c ad 1360 and identify that this period was wetter after c ad 1500

examining suspended sediment sources and dynamics during flood events in a drained catchment using radiogenic strontium isotope ratios 87sr 86sr soil erosion is recognized as one of the main processes of land degradation in agricultural areas high suspended sediment loads often generated from eroding agricultural landscapes are known to degrade downstream environments accordingly there is a need to identify suspended sediment sources and to investigate their dynamics here soil and sediment strontium isotopic ratios were used to examine suspended sediment sources and dynamics in a lowland drained catchment in france suspended sediment n 14 was collected in stream and at tile drain n 4 outlets during three flood events between december 2013 and february 2014 potential source soils n 28 representative of the carbonate and silicate substrates found in the catchment were sampled and analyzed strontium isotopic ratios 87sr 86sr were measured in different particle size fractions 2 m 63 m and 2 mm soil 87sr 86sr ratios significantly discriminated between source samples classified as carbonate 0 712625 to 0 717815 and silicate 0 719287 to 0 724631 soils 87sr 86sr ratios measured in suspended sediment 0 713660 to 0 720571 reflect variations in source contributions during different hydrological conditions the 87sr 86sr ratios varied in the different fractions of soil samples i e 2 m 63 m and 2 mm and in suspended sediment samples suspended sediment was interpreted as a mixture of two end members with the dominant contribution of the 2 m fraction of soil samples occurring during small scale flood events and the 2 mm fraction during more intense flood events modelling results indicate that carbonate source soil contributions are variable with their highest contributions occurring during the two first flood events compared to the last flood event the results also show that the tile drainage system enhances the connectivity between cultivated hillslopes and the river network providing a preferential pathway for fine 2 m particles this study demonstrates the potential of using strontium isotopic ratios to examine the variations of suspended sediment sources in drained catchments with contrasting carbonate and silicate sources more importantly the results highlight the need to improve the management of sediment exported from tile drains in similar agricultural environments as they were demonstrated to transfer very fine material to the riverine environment

6700 yr sedimentary record of climatic and anthropogenic signals in lake aydat french massif central a 19 meters long sedimentary record that was retrieved in lake aydat french massif central covers the last 6700 yrs at a high resolution a multi proxy approach density magnetic susceptibility xrf rock eval analyses pollen and non pollen palynomorphs analyses and historical archives study was used to characterise and tentatively propose a model of the sedimentation the important deposition rate results from the narrow and incised fluvial valley dammed by a lava flow ca 8550 years ago two contrasted periods of sedimentation 6700 200 3180 90 cal bp and 1770 60 cal bp now are characterized the lower unit mid holocene displays a fine and regular lamination and holds a single major flood deposit this unit is capped by an erosive mass wasting deposit triggered ca 1770 60 cal bp the upper unit late holocene is made of organic rich and fine grained faintly laminated sediment with numerous interbedded flood deposits 56 events and layers resulting from blooms of diatoms the sedimentation was principally controlled by climatic forcings solar activity until ca 1100 cal bp accompanied by detritic events linked to human activities around the lake then a more detrital input attested by numerous and recurrent flood deposits can be linked to the intensification of a persistent anthropogenic impact on the catchment two phases of lake eutrophication are highlighted a first phase between 1200 1130 cal bp as a result of increased anthropogenic pressure and the current phase that could have started ca 150 cal bp

phytolith transport in sandy sediment experiments and modeling abstract phytoliths are minerals of amorphous silicon dioxide forming in cell lumina and intercellular spaces of living plants because of their morphological specificity and their stability in soils phytoliths have been widely used in paleoenvironmental reconstructions however the mechanisms of phytolith displacement in soil are not well understood which causes uncertainties in the interpretation of phytolith data the objectives of the present study were 1 to determine phytolith transport in sandy sediment under different rainfall and 2 to assess the long term phytolith displacement with moving water by modeling phytoliths extracted from phragmites australis were added to the upper 1 cm layer of columns packed with medium sand two rainfall regimes 1 low frequency irrigation 40 mm 2 times per month and 2 high frequency irrigation 40 mm 8 times per month were simulated over a period of 5 months at the end of this period the distribution of phytoliths was examined in the columns the weighted mean travel distance of phytoliths was 2 7 1 6 mm and 3 7 0 2 mm at the low frequency and high frequency treatments respectively under the high frequency irrigation 22 of the applied phytoliths were leached from the application layer two modeling approaches were tested against the experimental data of the high frequency irrigation treatment the first model was a convection dispersion model with attachment detachment and straining terms in the second model reversibility of straining was additionally taken into account both models resulted in an equally good agreement with observations however the long term predictions calculated with the two approaches were contradictory the first model showed no significant translocation after a period of thousand years whereas the second model predicted that phytoliths would on average be displaced by 19 cm we hence conjecture that our set of observations was not sufficient to distinguish between two models long term experiments on phytolith transport in undisturbed soil are required to ascertain proper modeling of phytolith transport in a sandy soil

palaeoflood activity and climate change over the last 1400 years recorded by lake sediments in the north west european alps a high resolution sedimentological and geochemical study of a high altitude proglacial lake lake blanc aiguilles rouges 2352m a s l revealed 195 turbidites 190 of which are related to flood events over the last 1400 years we used the coarsest sediment fraction of each turbidite as a proxy for the intensity of each flood event because most flood events at this locality are triggered by localized summer convective precipitation events the reconstructed sedimentary record reveals changes in the frequency and intensity of such events over the last millennium comparisons with other temperature palaeohydrological and glacier reconstructions in the region suggest that the most intense events occurred during the warmest periods i e during the medieval climate anomaly ad 800 1300 and the current period of global warming on a multi decadal time scale almost all the flood frequency peaks seem to correspond to warmer periods whereas multi centennial variations in flood frequency appear to follow the regional precipitation pattern consequently this new alpine flood record provides further evidence of a link between climate warming and an increase in the frequency and intensity of flooding on a multidecadal time scale whereas the centennial variability in flood frequencies is related to regional precipitation patterns

changes in holocene tree cover density in cabo frio rio de janeiro brazil evidence from soil phytolith assemblages the coastal region of cabo frio in the brazilian state of rio de janeiro is characterized by xeric vegetation surrounded by humid forest it is considered as a phytogeographical enclave the vegetation is adapted to the dry conditions which are present locally mainly due to the cabo frio coastal upwelling although quaternary changes in the intensity of the upwelling were reconstructed from coastal lagoons and oceanic sediment records the lack of continental deposits has precluded vegetation reconstructions the objective of this study was to investigate the pedogenic features of two soil profiles developed under patches of dry forest in the cabo frio area and to assess their potential for inferring past changes in tree cover density from their phytolith assemblages for this purpose field and petrographical observations c content c n ratio phytolith content and phytolith assemblages were investigated soil phytolith assemblages were compared to modern phytolith assemblages the deepest soil organic carbon soc samples were analyzed in c 14 ams related c 14 mean age values were interpreted as the youngest ages of the oldest soc these data suggest a first soil development phase occurring after 13 ka cal bp followed by erosive and depositional episodes and by a second soil development phase given the complexity of the studied soil sequences an attempt to quantify the sources of soc and phytoliths would require investigation of many more soil samples than the ones collected this prevents interpretation of the phytolith sequences as continuous chronological sequences however for both profiles phytolith indices d p from a ab and bottom horizons can be compared assuming a bicompartmental distribution of phytoliths in relation with each of the soil development phases d p values range from 0 8 to 4 in agreement with what would be expected for dry forest d p values and do not substantially change in both profiles this comparison suggests that the tree cover density of the successive vegetation sources did not suffer considerable change over the period under analysis last 13 ka for profile a and never reached the tree density of the humid forest currently widespread in the rio de janeiro state c 2012 elsevier ltd and inqua all rights reserved

a model study of the role of high latitude topography in the climatic response to orbital insolation anomalies abstract the response of a combined global zonal averaged energy balance model and a continental ice sheet model to insulation anomalies produced by orbital perturbations is examined although the role of ice sheet dynamics is included in the model this paper focuses mostly on the response of the atmosphere hydrosphere to the perturbations the model developed from that of suarez and held 1979 explicitly incorporates surface topography surface energy balances snow and sea ice budgets and variable static stability the ice sheet model is based on a power law rheology it is found that the presence of a high latitude plateau significantly increases the sensitivity of the climate to the insolation perturbation the sensitivity is maximized when the elevation of the summer snowline is near the elevation of the plateau as appears to be the case with baffin island today there appears to be a rapid response of the seasonal cycle to an insolation anomaly through albedo temperature feedback and with the

phytolith and carbon isotope evidence for late quaternary vegetation and climate change in the southern black hills south dakota abstract analyses of phytoliths and carbon isotopes document change in late quaternary grasslands in the red valley of the southern black hills late pleistocene grassland composition was equivalent to the c3grass parklands of modern central alberta the rise of mixed grassland occurred rapidly between 11 000 and 9000 yr b p early holocene mixed grasslands included both short and tall c4grasses a mid holocene erosional unconformity ca 8000 to 4500 yr b p precludes phytolith or isotope analysis but suggests lack of vegetation and landscape denudation caused by a drier climatic basin wide stability and soil development followed the erosional episode ca 4500 to 3600 yr b p mesic adapted c4panicoid grasses increased during this period of soil development low magnitude fluctuation in the c4 dominated mixed grassland occurred throughout the late holocene 3600 yr b p to present rise in 13c values during the last 1000 yr without corresponding change in phytoliths may indicate a decrease in woodlands caused by increased fire frequency

a paleoclimate model of northern hemisphere ice sheets abstract a model for predicting the growth and decay of ice sheets based on the astronomical theory of climate change is presented the purpose of the study in part is to isolate the role of the ice sheet physics and earth response under varying ice load by simplifying to the extreme the role of the hydrosphere atmosphere ice sheet physics and the response of the lithosphere asthenosphere under the ice load are modeled explicitly insolation anomalies taken at a fixed latitude directly force latitudinal displacement of the snow line accumulation rate a and ablation rate a evaluated at mean sea level are specificed as external constants a a decrease linearly with ice sheet elevation rough tuning of the model to the general shape of the ice volume record of the last two major glacials determines the external constants model predictions of the ages of several events in the last major glaciation compare well with the radiological ages the six glacial terminatios i vi over the last 600 000 yr are identified and the predicted ages compare reasonably well with the 18 o record for two deep sea cores a direct comparison of model power spectra of ice volume as a function of period with spectra of the 18 o record shows apparent underprediction of power near 100 000 yr when a quantitative but heuristic method for taking into account the red noise spectrum evident in the geological records is used a much more favorable comparison is possible the model prediction lends support to the hypothesis that the nonlinearity of the ice sheet physics is responsible for the 100 000 yr periodicity in the geological record of the late pleistocene

characterization and palaeoecological significance of archaeological charcoal assemblages during late and post glacial phases in southern france abstract archaeological sites at abeurador and font juvenal have produced extensive charcoal rich horizons the results of the charcoal analysis based on the identification of woody species from anatomical features contribute to the elaboration of plain phases within the development of vegetation in southern france they are presented here in a new diagram and are interpreted as four major vegetation phases from 11 000 14 c yr b p to the recent past in order to interpret the palaeoecological significance of the charcoal assemblages we have used multivariate analysis the data base consists of 42 taxa and 48 archaeological levels the division into four vegetation phases based on analytical interpretation is complemented by the more synthetic interpretation based on correspondence factor analysis cfa the results reveal the patterns of the vegetation history over the last 11 millennia each being characterized by a key plant species

a simple ice sheet model yields realistic 100 kyr glacial cycles records of global ice volume for the past 700 kyr based on oxygen isotopic data from deep sea cores and reflecting mainly the changing northern hemispheric ice sheets show a dominant cycle of roughly 100 kyr period the records also show smaller amplitude oscillations with spectral peaks at roughly 40 and 20 kyr periods which are well correlated with the milankovich insolation variations due to perturbations in the earth s orbital parameters however no model has accurately simulated the 100 kyr glacial cycle recently birchfield et al 1 and oerlemans2 have obtained encouraging agreement with some features of the glacial cycle by using a simple ice sheet model with a realistic time lag in the response of the bedrock to the ice load this study extends their basic model first by including topography to represent high ground in the north improved results can then be obtained but only with unrealistic parameter values and for some aspects of the record further improvements areobtained by crudely parameterizing possible calving at the equatorward ice sheet tip during deglaciation by proglacial lakes and or marine incursions from the atlantic as emphasized by andrews3 the resulting ice volume curves agree fairly well with the observed records and their power spectra over the past 700 kyr

using phytolith assemblages to reconstruct the origin and spread of grass dominated habitats in the great plains of north america during the late eocene to early miocene abstract this paper outlines a general approach for analyzing siliceous microfossils from plants phytoliths in geologic sediments and uses this method to reconstruct the evolution of grasslands in the central great plains during the late tertiary phytolith assemblage analysis is widely employed for reconstructing vegetation types in pleistocene holocene paleoecology and archaeology but no standardized methodology is currently available published phytolith studies are often system specific and tailored after specific modern analogues as a result they vary in extraction technique classification scheme and method of inference for ancient phytolith assemblages whose modern analogues are not well understood a more general analytic approach is necessary this analytic approach includes studying all size fractions 2 250 mm using a classification scheme based on the available literature and a comprehensive modern phytolith reference collection and comparing relative frequencies through time of all diagnostic phytoliths to interpret changes in habitat structure this general method was applied to late eocene to early miocene sediment samples from northwestern nebraska to deduce vegetation history and the results were compared to those obtained using a more specific technique stromberg paleogeogr paleoclimatol paleoecol 177 2002 59 in both studies phytoliths were extracted by means of heavy liquid separation from the following lithostratigraphic units 1 the late eocene chadron formation and the early oligocene brule formation white river group 2 the late oligocene early miocene monroe creek formation the early miocene harrison formation and anderson ranch formation arikaree group and 3 the early miocene runningwater formation and box butte formation ogallala group the two techniques general vs specific produced results that differ markedly data from the general approach indicate the presence of relatively closed habitats in late eocene to early oligocene typified by the presence of phytoliths from bambusoid grasses woody and herbaceous dicotyledons and palms the introduction and spread of modern open habitat grasses such as pooids arundinoids and panicoids occurred between the late oligocene and early miocene this resulted in a savanna or woodland type habitat by the early miocene in contrast analysis using the specific method suggested the presence of open habitats in northwestern nebraska from the late eocene onward the difference in interpretation based on the two approaches is principally due to inclusion of phytoliths 50 mm and the use of an expanded reference collection in the current study general analytic approach these results point to the importance of methodological choices in phytolith analysis and emphasize the usefulness of phytoliths as paleoecological indicators in the fossil record

loess stratigraphy in central china abstract the loess deposits in central china record world wide climate changes of the last 2 5 ma numerous climatic oscillations are marked by alternating loess and soil units with continuous coverage of the matuyama and brunhes epochs magnetic susceptibility of the deposits correlates closely with the oxygen isotope record of the deep sea sediments and provides an independent measure of climate and time the key marker bed of the chinese loess sequence is the paleosol s5 the time equivalent of the mid brunhes oxygen isotope stages 13 14 and 15 it marks a prolonged interval of warm humid climate lasting from approximately 615 to 470 thousand years ago several episodes of river downcutting coincide with deposition of the exceptionally thick loess units l1 oceanic oxygen isotope stages 2 to 4 l2 stage 6 l5 stage 12 l6 stage 16 l9 stage 22 l15 stage 38 about 1 15 ma and ws4 about 2 3 ma these erosional events are interpreted as a result of episodic uplift of the loess plateau the deposition of the earliest loess layers between 2 5 and 2 3 ma ago marks a first order shift from warm and humid environments toward harsh continental steppes comparable to those of the middle and late pleistocene little if any lithologic or paleontologic changes were noted within or above the olduvai magnetozone so that the proposed plio pleistocene boundary at approximately 1 65 ma has no lithostratigraphic and biostratigraphic representation in the chinese loess series comparison with the deep sea drilling program core 552a in the north atlantic and with the santerno river section near bologna shows that the occurrence of the earliest loess in china coincides with the timing of the first significant ice rafting in the north atlantic and with the appearance of cold water foraminifers in the marine deposits of northern italy an extension of the stage system of the oxygen isotope signal extended back to the gauss matuyama boundary is proposed

dynamics of production and accumulation of phytolith assemblages in the restinga of marica rio de janeiro brazil abstract the marica restinga located on the eastern part of rio de janeiro state brazil corresponds to one of the few remaining preserved areas of the state s coastal plain this coastline presents two sand barriers separated by a depression where there is a freshwater swamp and different plant communities distributed in areas of high ecological diversity accompanying the local topography and the range of marine spray this paper is a study of the soil phytolith assemblages in the marica restinga with the intent of establishing reference collections for paleoenvironmental studies of this coastal area during the quaternary phytoliths were chosen as proxies but their use for reconstruction of this type of vegetation is pioneer research so it was essential to characterize the phytolith assemblages for each plant community through the identification of the main morphotypes and whether or not they are preserved in coastal depositional environments under the effect of geomorphology and salinity eight plant communities distributed almost parallel to the coastline over sandy barriers lagoonal plain lagoon margin and weathered basement were identified halophile psamophile near the beach two scrub communities one over the holocene barrier and the other over the pleistocene barrier two herbaceous swamps one between the two sand barriers the other behind the pleistocene barrier slack in front of the pleistocene barrier shrubby vegetation on the shore of marica lagoon and dry forest over the weathered pre cambrian basement in general it was found that this type of environment is not very favorable for the formation and accumulation of phytoliths restinga plants did not prove to be large producers of phytoliths except those known as such as in the case of poaceae and cyperaceae it was also observed that the permanence of phytoliths in sediments is strongly influenced by its particle size and organic matter content the largest stocks of phytoliths were found in swamp communities due to the presence of organic matter and low energy dynamics and in dry forests where a process of pedogenesis already occurs despite the low phytolith stocks present in modern assemblages they show a high degree of conservation which enabled significant results for the study of this type of vegetation the calculated phytolith indices tree density and water stress consistently expressed in detail the environment of each community analyzed from the point of view of the type of vegetation cover and the conditions of water availability to plants

settlement and environmental history of a multilayered settlement mound in niederroblingen central germany a multi proxy approach a multi disciplinary palaeoecological approach on a sequence of dated archaeosediments was accomplished the sediments derive from a multilayered prehistoric settlement mound in central germany representing the remnants of a prehistoric village based on the analysis of biological remains and geochemical physical analysis of the settlement layers its environment was reconstructed there is a trend to increasing anthropogenic activities and impact on the environment represented through a rise of indicators for productive surplus from the early neolithic 5300 4900 bc until the roman times 400 ad during the early neolithic shifting flat settlements were situated in a locally opened landscape the immediate surrounding of the floodplain was used by the settlers for their economic requirements e g wood from the riparian forest after a hiatus of ca 1900 years a multilayered settlement mount rose from late neolithic times 3000 bc to roman times since the middle bronze age approximately 1500 bc the riparian forest was obviously replaced by agricultural fields and meadows and henceforward the hinterland used by the settlers probably grew in size the continuing demand of wood was maintained by the acquisition of more distant sources the onset of house constructions substituting wood by loam wattle and daub might be a possible societal response to this shortfall this is reflected in the growing thickness and composition of the settlement layers as well as in the archaeological record e g tumbled wattle and daub house walls the rising of the groundwater table and the start of severe floods of the adjacent river helme during pre roman iron age approx 800 100 bc might reflect a geomorphological response to the increased land use intensity at a regional scale

vostok ice core provides 160 000 year record of atmospheric co2 direct evidence of past atmospheric co2 changes has been extended to the past 160 000 years from the vostok ice core these changes are most notably an inherent phenomenon of change between glacial and interglacial periods besides this major 100 000 year cycle the co2 record seems to exhibit a cyclic change with a period of some 21 000 years

vostok ice core climatic response to co2 and orbital forcing changes over the last climatic cycle vostok climate and co2 records suggest that co2 changes have had an important climatic role during the late pleistocene in amplifying the relatively weak orbital forcing the existence of the 100 kyr cycle and the synchronism between northern and southern hemisphere climates may have their origin in the large glacial interglacial co2 changes

testing soil phytolith analysis as a tool to understand vegetation change in the sagebrush steppe and pinyon juniper woodlands of the great basin desert usa better biological proxy methods are needed to understand changes in arid ecosystems over the recent past our objective in this study was to examine the utility of soil phytolith analysis to reflect vegetation changes over the past 200 years from the end of the little ice age to present the sensitivity of phytoliths to record vegetation changes for this time period was tested by sampling in locations where vegetation changes were known to have occurred based on human records we used extraction weights to test for the trend in reduction of grasses and increase in woody vegetation over time we used the relative abundance of soil phytolith morphotypes from native versus introduced grasses to look for the increase in non native grasses then we examined the phytolith assemblages from soils in a continuous core sampling method with 1 cm increments extraction weights decreased by half from the surface to little ice age layers and may reflect increasing pinyon juniper woodland cover the relative abund

the application of fallout radionuclides to determine the dominant erosion process in water supply catchments of subtropical south east queensland australia previous studies using fallout radionuclides 137cs and 210pbex to determine the relative contributions of surface soil and channel erosion including gullies and channel banks to stream sediments have used a relatively small number of composite samples 25 to characterize the source end members and concentrations in each of the source end members have through the use of means and standard errors been assumed to be normally distributed here we examine 137cs activity concentrations to determine the erosion processes supplying sediment in seven water supply catchments in south east queensland first we test some of the underlying assumptions in the method using concentrations of 137cs and 210pbex in composite samples collected from 109 surface soil sites and 39 channel bank sites paired composite samples each consisting of 20 subsamples from five sites are used to demonstrate that this sampling approach was sufficient to average out any local variations in surface soil 210pbex and 137cs concentrations across the 300 m2 sampled we derive probability distributions for 137cs and 210pbex concentrations in the group of samples from each of the end members and show that only the distribution of 210pbex in samples from surface soils is normally distributed we use the probability distributions for 137cs which provides the greatest discrimination between sources to show that the 137cs concentrations on the river sediment samples are consistent with channel erosion being the dominant source conservation works aimed at reducing the supply of sediments in these catchments should therefore focus on rehabilitation of the channel network and decreasing the runoff to the channel network these findings are consistent with other similar studies on tropical australian rivers copyright 2012 john wiley sons ltd

vostok ice core a continuous isotope temperature record over the last climatic cycle 160 000 years a continuous deuterium profile along the 160 000 year vostok ice core antarctica is interpreted in terms of atmospheric temperature changes this climatic record is the awaited terrestrial complement of the deep sea records supporting the existence of a relation between the pleistocene climate and orbital forcing

pleistocene climatic variability at astronomical frequencies abstract spectral analysis of geological records show periodicities corresponding to those calculated for the eccentricity 400 and 100 ka the obliquity 41 ka and the climatic precession 23 and 19 ka it is precisely the geological observations of this bi partition of the precessional peak confirmed to be real in astronomical computations which was one of the most impressive of all tests for the milankovitch theory concerning the question of whether or not the observed cycles account for most of the climatic variability having periods in the range predicted by the astronomical theory substantial evidence from cross spectral analysis coherency analysis and modelling is provided that at least near frequencies of variation in obliquity and precession a considerable fraction of the climate variance is driven in some way by insolation changes accompanying changes in the earth s orbit the variance components centered near a 100 ka cycle dominate most ice volume records and seem in phase with the eccentricity cycle although the exceptional strength of this cycle needs a non linear amplification by the glacial ice sheets themselves and associated feedbacks as the insolation spectra change with latitudes and with the type of parameters considered the diversity of the spectra of different climatic proxy data recorded in different places of the world over different periods is used to better understand how the climate system responds to the insolation forcing this study of the physical mechanisms involved is also achieved through the analysis of the log log shape of the geological records and through the comparison in frequency domain between simulated climatic time series and proxy data the evidence both in the frequency and in the time domain that orbital influences are felt by the climate system implies that the astronomical theory may provide a clock with which to date quaternary sediments with a precision several times greater than is now possible

phytolith assemblages as a promising tool for reconstructing mediterranean holocene vegetation the reliability of phytolith assemblage analysis for characterizing mediterranean vegetation is investigated in this study phytolith assemblages are extracted from modern and buried holocene soils from the middle rhone valley france the relation between modern phytolith assemblages and the surrounding vegetation as well as between fossil assemblages and contemporaneous vegetation already reconstructed through other proxies is discussed we demonstrate that the main northwestern mediterranean biomes are well distinguished by soil phytolith assemblage analysis in particular the density of pine and nonconiferous trees densities expressed relatively to the grass cover and the overall degree of opening of the vegetation appear well recorded by three phytolith indexes north mediterranean vegetation changes during the holocene period mainly tree line shifts pine wood development and deforestation are poorly documented due to the scarcity of proxy preserving sites phytolith assemblage analysis of soils buried soils and sediments appears to be a promising technique to fill this gap

1500 years of lake sedimentation due to fire earthquakes floods and land clearance in the oregon coast range geomorphic sensitivity to floods during timber harvest period

north western alps holocene paleohydrology recorded by flooding activity in lake le bourget france abstract a 14 m long piston core was retrieved from lake le bourget nw alps france in order to provide a continuous record of flooding events of the rhone river during the holocene the selection of the coring site was based on high resolution seismic profiling in an area with limited mass wasting deposits and accumulated proximal rhone river inter and underflow deposits the age depth model of this core is based on i 14 ams radiocarbon dates ii radionuclide dating 137cs and iii the identification of historical data flood events eutrophication of the lake the sedimentary record dates back to 9400 cal bp and includes a thin mass wasting event deposited around 4500 cal bp a multi proxy approach was used to track the evolution and origin of clastic sedimentation during the holocene in order to identify periods of higher hydrological activity in the catchment area spectrophotometry was used to detect fluctuations in clastic supply and the study of clay minerals especially the illite crystallinity index allowed locating the main source area of fine grained clastic particles settling at the lake after flood events this dataset highlights up to 12 periods of more intense flooding events over the last 9400 years in lake le bourget and shows that the main source area of clastic particles during this period is the upper part of the arve river drainage basin this part of the catchment area drains several large glaciers from the mont blanc massif and fluctuations in rhone river flood supply in lake le bourget is interpreted as resulting essentially from mont blanc glacier activity during the holocene the comparison of clastic sedimentation in lake le bourget with periods of increasing land use and periods of alpine glacier and mid european lake level fluctuations suggest that the core ldb04 clastic record in lake le bourget is a continuous proxy of the holocene hydrological history of the nw alps

an opal phytolith and palynomorph study of extant and fossil soils in kansas u s a abstract soils from three plant communities in kansas shortgrass prairie tallgrass prairie and deciduous forest were analyzed for opal phytoliths pollen grains and fungal spores these data were used to correlate vegetation type with phytolith and palynomorph deposition the results were applied to the study of a paleosol to determine the vegetation and ecological conditions prior to burial statistical analyses of the data show that the phytolith composition differs significantly among the three extant soils pollen analysis failed to differentiate between tallgrass and shortgrass prairie because the pollen can not be accurately attributed to the different grass taxa that are characteristic of these vegetation types pollen analysis however distinguished woodland sites from the prairies because of the abundance of easily recognizable pollen of woody plants the comparison of the extant soils to the paleosol show that the plant community prior to burial may have been a cool season grassland the results demonstrate the importance of combined phytolith and pollen analysis in the characterization of grasslands

taphonomical aspects of silica phytoliths in the loess sediments of the argentinean pampas abstract although pampean loess and pedostratigraphy processes in the pampas have been widely studied phytoliths observed in these sediments have been only mentioned without further quantitative or qualitative studies the present work is a first step towards an understanding of the environmental significance of loess phytolith datasets and their validity for palaeoenvironmental reconstructions and to comprehend the environmental conditions of loess formation the research focused on the taphonomy of loess phytoliths investigating the loess morphological and sedimentological characteristics variability in the qualitative and quantitative assemblage composition the phytolith frequency and were also phytolith extraction techniques the results highlight that the phytolith pool of loess deposits still retains information about the past vegetation and phytolith analysis from these deposits can be a useful exercise to further comprehend past climatic and environmental conditions under which loess palaeosol sequences formed

reconstructing late holocene palaeoenvironments in bangladesh phytolith analysis of archaeological soils from somapura mahavihara site in the paharpur area badalgacchi upazila naogaon district bangladesh palaeoenvironmental reconstruction based on phytolith analysis of late holocene aged soils in and around the somapura mahavihara archaeological monastery site in the paharpur area badalgacchi upazila of naogaon district in northwestern bangladesh was undertaken results indicate five climate zones marked by alternatively cool and temperate events the phytolith assemblages of zones 1 3 and 5 are clearly characterized by a higher proportion of pooideae phytoliths the climate indices for these zones are all greater than 50 indicating cooler climatic conditions in contrast the phytolith assemblages of zones 2 and 4 are typified by a higher proportion of panicoideae phytoliths their climate indices are 42 and 44 respectively indicating the presence of a warmer more temperate climate in general the dominance of grasses over broad leaved trees throughout the sequences suggests that generally cool to temperate and dry conditions with some cyclical variability persisted around paharpur and the surrounding region throughout the pala dynasty from ad 730 to 1080 the question of whether these shifts in vegetation might be linked with el nino southern oscillation events and whether these might in turn have cultural responses is raised

phytolith analysis and reconstruction of palaeoenvironment at the nabokri valley plain buyeo korea abstract the soil profile between 12 0 and 14 0 m a s l was deposited at the nabokri valley plain buyeo korea from approximately 6000 bp to the present through phytolith analysis of 20 samples collected at 10 cm intervals five phytolith assemblage zones pazs are identified based on the number of various types of phytoliths and occurrence of specific families adapting to the particular climates this study yields the climatic indices reconstructs the paleoclimates and estimates the human activities during the reconstructed period the five pazs are well correlated to the chronology of sedimentary layers and construction periods of the artifacts at the archaeological excavation the buyeo area was temperate and wet during the neolithic age paz i and there is no phytolith evidence of vegetation change by humans the climate can be characterized as temperate and wet during the early bronze age paz ii but then cooling later during this period agricultural activities began with the panicoideae including oryza sativa in the early iron age the climate became warmer the climate during the proto three states age paz iii since 2000 bp was variable and species such as o sativa and panicoideae were actively cultivated the three states age can be characterized by variable climates similar to the proto three states age the ic climate index and iph humidity aridity index values indicate that the climates were first wet and then became drier agricultural activities are identified from the bronze age paz ii through three states age and joseon dynasty paz iv based on the presence of cultivation layers as well as specific phytolithic indicators of agriculture the uppermost layer paz v shows no evidence of agricultural activities due to the significant decrease in the number of phytoliths perhaps from recent abandonment

combining suspended sediment monitoring and fingerprinting to determine the spatial origin of fine sediment in a mountainous river catchment an excess of fine sediment grain size 2 mm supply to rivers leads to reservoir siltation water contamination and operational problems for hydroelectric power plants in many catchments of the world such as in the french alps these problems are exacerbated in mountainous environments characterized by large sediment exports during very short periods this study combined river flow records sediment geochemistry and associated radionuclide concentrations as input properties to a monte carlo mixing model to quantify the contribution of different geologic sources to river sediment overall between 2007 and 2009 erosion rates reached 249 75 t km 2 yr 1 at the outlet of the bleone catchment but this mean value masked important spatial variations of erosion intensity within the catchment 85 5000 t km 2 yr 1 quantifying the contribution of different potential sources to river sediment required the application of sediment fingerprinting using a monte carlo mixing model this model allowed the specific contributions of different geological sub types i e black marls marly limestones conglomerates and quaternary deposits to be determined even though they generate locally very high erosion rates black marls supplied only a minor fraction 5 20 of the fine sediment collected on the riverbed in the vicinity of the 907 km2 catchment outlet the bulk of sediment was provided by quaternary deposits 21 66 conglomerates 3 44 and limestones 9 27 even though bioengineering works conducted currently to stabilize gullies in black marl terrains are undoubtedly useful to limit sediment supply to the bleone river erosion generated by other substrate sources dominated between 2007 and 2009 in this catchment

a new windstorm proxy from lake sediments a comparison of geological and meteorological data from western germany for the period 1965 2001 1 the feasibility of detecting windstorm layers in lake sediments is explored by comparing quartz grain size data from a freeze core obtained from the schalkenmehrener maar eifel region western germany to recent meteorological wind data the schalkenmehrener maar is appropriate for such a calibration study because the morphological settings of the lake allow the conservation of windstorm layers in particular there is no fluvial sediment inflow and long term wind measurements are available from nearby stations the age model for the uppermost 30 cm of the sediment core is based on measurements of 137cs and 210pb concentrations an ultra high resolution grain size analysis is performed digitally on thin sections and reveals distinct 1 mm thick layers with increased quartz grain content and sharp gaussian grain size distributions which are shifted to larger grain sizes compared to the normal lake sediment in order to compare the occurrence of these layers with meteorological wind data a windstorm index is developed combining data from meteorological stations in the eifel region and reanalyses from the european centre for medium range weather forecast a statistical evaluation of matches between the windstorm index and the core s silt fraction data indicates that the sediment layers very likely coincide with the major windstorm events in the eifel region during the last decades six historical storm are identified this pilot study identifies the main requirements and proposes a novel methodological approach for using sediment data from lakes with similar settings as the schalkenmehrener maar as a new proxy to reconstruct the windstorm record of the geological past

a novel sedimentological method based on ct scanning use for tomographic characterization of the galicia interior basin abstract non destructive techniques of core analysis especially of marine cores are being broadly employed for sedimentary paleoceanographic and paleoclimate research in particular computed tomography scanning ct scanning allows acquisition of 3d and 2d images according to desired planes and thus the identification of sedimentary structures large grains and their distributions as well as direct measurements of material densities the most significant contribution of this technique is the possibility of getting results before opening the core in this work ct scan data obtained for five cores from the galicia interior basin gib nw peninsula iberia are presented and discussed focussing on 1 methodology of the ct scan use 2 tomographic description of sedimentary facies identified in the gib 3 treatment of the numeric data obtained with ct scanning using specific software anidoc and 4 comparison of tomographic data with data obtained by conventional methodologies of core analysis the most singular feature of gib cores is the presence of ice rafted debris ird deposited during late pleistocene heinrich events he which can be easily recognized using the ct scan by the presence of high radio density grains immersed in a low radio density matrix comparison of ct scan data with analytical sedimentary data and he proxies performed on the cores validates the ct scanning method as a powerful tool to improve correlations identify well constrained events and make more accurate basin reconstructions without opening all the cores in an oceanographic study

evidence for perchlorates and the origin of chlorinated hydrocarbons detected by sam at the rocknest aeolian deposit in gale crater evidence for perchlorates at rocknest

quantifying the dominant sources of sediment in a drained lowland agricultural catchment the application of a thorium based particle size correction in sediment fingerprinting soil erosion is one of the main factors influencing land degradation and water quality at the global scale identifying the main sediment sources is therefore essential for the implementation of appropriate soil erosion mitigation measures accordingly caesium 137 137cs concentrations were used to determine the relative contribution of surface and subsurface erosion sources in a lowland drained catchment in france as 137cs concentrations are often dependent on particle size specific surface area ssa and novel thorium th based particle size corrections were applied surface and subsurface samples were collected to characterize the radionuclide properties of potential sources sediment samples were collected during one hydrological year and a sediment core was sampled to represent sediment accumulated over a longer temporal period additionally sediment from tile drains was sampled to determine the radionuclide properties of sediment exported from the drainage network a distribution modelling approach was used to quantify the relative sediment contributions from surface and subsurface sources the results highlight a substantial enrichment in fine particles and associated 137cs concentrations between the sources and the sediment the application of both correction factors reduced this difference with the th correction providing a more accurate comparison of source and sediment samples than the ssa correction modelling results clearly indicate the dominance of surface sources during the flood events and in the sediment core sediment exported from the drainage network was modelled to originate predominantly from surface sources this study demonstrates the potential of th to correct for 137cs particle size enrichment more importantly this research indicates that drainage networks may significantly increase the connectivity of surface sources to stream networks managing sediment transferred through drainage networks may reduce the deleterious effects of suspended sediment loads on riverine systems in similar lowland drained agricultural catchments

seismically induced soft sediment deformation structures revealed by x ray computed tomography of boring cores abstract x ray computed tomography ct allows us to visualize three dimensional structures hidden in boring cores nondestructively we applied medical x ray ct to cores containing seismically induced soft sediment deformation structures ssdss obtained from the kanto region of japan where the 2011 off the pacific coast of tohoku earthquake occurred the ct images obtained clearly revealed various types of the seismically induced ssdss embedded in the cores a propagating sand dyke bent complexly by the preexisting geological structure deformed laminations of fluidized sandy layers and two types of downward mass movement ductile downward folding and brittle normal faulting as compensation for upward sand transport through sand dykes two advanced image analysis techniques were applied to the sand dyke ct images for the first time the growcut algorithm a specific digital image segmentation technique that uses cellular automata was used successfully to extract the three dimensional complex sand dyke structures embedded in the sandy sediments which would have been difficult to achieve using a conventional image processing technique local autocorrelation image analysis was performed to detect the flow pattern aligned along the sand dykes objectively the results demonstrate that x ray ct coupled with advanced digital image analysis techniques is a promising approach to studying the seismically induced ssdss in boring cores

long term variations of monthly insolation as related to climatic changes qualitative multivariate models which combine past insolations of selected months at selected latitudes explains 55 to 67 of the variance in the 135 millenia long oxygen isotope record of pleistocene climates

a fluvial record of the mid holocene rapid climatic changes in the middle rhone valley espeluche lalo france and of their impact on late mesolithic and early neolithic societies abstract this multi proxy study of a small floodplain in the rhone catchment area at the northern edge of the mediterranean morphoclimatic system provides valuable information concerning the impact of mid holocene climate variability 8 5 7 0 ka and the effects of two rapid climatic changes 8 2 and 7 7 7 1 ka on an alluvial plain its basin and the first farming societies of the rhone valley around 7 7 7 1 ka the combined effects of 1 a strong rate of change in insolation and 2 variations in solar activity amplified marine and atmospheric circulation in the north west atlantic bond event 5b which imply continental hydrological soil and vegetation changes in the small catchment area for this period strong fluctuations in the plant cover ratio have been identified related to a regime of sustained and regular fires as well as abundant erosion of the hill slopes and frequent fluvial metamorphoses which led to braiding of the watercourse in this floodplain there are few data available to evaluate the impact of natural events on prehistoric communities this continental archive offers clear multi proxy data for discussion of these aspects having 4 cultural layers interbedded in the fluvial sequence 1 late mesolithic 3 cardial epicardial earlier data indicate the difficulty in recognizing such cultural features in the low alluvial plains of southern france during the mesolithic early neolithic transition which should lead to caution when developing settlement models for this period

flood stratigraphies in lake sediments a review abstract records of the frequency and magnitude of floods are needed on centennial or millennial timescales to place increases in their occurrence and intensity into a longer term context than is available from gauged river flow and historical records recent research has highlighted the potential for lake sediment sequences to act as a relatively untapped archive of high magnitude floods over these longer timescales abyssal lake sediments can record past floods in the form of coarser grained laminations that reflect the capacity for river flows with greater hydrodynamic energy to transport larger particles into the lake this paper presents a framework for investigating flood stratigraphies in lakes by reviewing the conditioning mechanisms in the lake and catchment outlining the key analytical techniques used to recover flood records and highlighting the importance of appropriate field site and methodology selection the processes of sediment movement from watershed to lake bed are complex meaning relationships between measureable sedimentary characteristics and associated river discharge are not always clear stratigraphical palaeoflood records are all affected to some degree by catchment conditioning fluvial connectivity sequencing of high flows delta dynamics as well as within lake processes including river plume dispersal sediment focussing re suspension and trapping efficiency with regard to analytical techniques the potential for direct e g laser granulometry and indirect e g geochemical elemental ratios measurements of particle size to reflect variations in river discharge is confirmed we recommend care when interpreting fine resolution geochemical data acquired via micro scale x ray fluorescence xrf core scanning due to variable down core water and organic matter content altering x ray attenuation we also recommend accounting for changes in sediment supply through time as new or differing sources of sediment release may affect the hydrodynamic relationship between particle size and or geochemistry with stream power where these processes are considered and suitable dating control is obtained discrete historical floods can be identified and characterised using palaeolimnological evidence we outline a protocol for selecting suitable lakes and coring sites that integrates environmental setting sediment transfer processes and depositional mechanisms to act as a rapid reference for future research into lacustrine palaeoflood records we also present an interpretational protocol illustrating the analytical techniques available to palaeoflood researchers to demonstrate their utility we review five case studies of palaeoflood reconstructions from lakes in geographically varied regions these show how lakes of different sizes and geomorphological contexts can produce comprehensive palaeoflood records these were achieved by consistently applying site validated direct and proxy grain size measurements well established chronologies validation of the proxy process interpretation and calibration of the palaeoflood record against instrumental or historical records