characteristic straight chain lipid ratios as a quick method to assess past forest paramo transitions in the ecuadorian andes to assist sustainable reforestation efforts in the andes in northern ecuador the position of the natural upper forest line ufl has to be assessed to this end new vegetation reconstruction techniques to complement traditional reconstruction methods such as pollen analysis are being developed one such technique is the biomarker ratio approach that uses changes in characteristic ratios of extractable lipids such as n alkanes and n alcohols for a quick assessment at high spatial resolution of abrupt past vegetation changes in the present study we assessed the applicability of this approach as indicator of past vegetation shifts from forest to paramo or vice versa in northern ecuador we looked at the n alkane and n alcohol signals of two soil monoliths one taken in a forest patch located 100 m above the current ufl and the other at the same altitude in the surrounding paramo the monoliths were sampled to a depth corresponding to at least 1500 cal yr bc links were sought between biomarker ratio signals in soil organic matter som and those found in plants from the vicinity during previous research based on the outcome an attempt was made at determining whether the forest patch had been part of the continuous forest further down slope during the last 3500 cal years results show that specific ratios of extractable straight chain lipids can be used to get a quick indication of whether an area was forested or not in the past in som the n alkane relationship c29 c31 1 combined with the n alcohol relationship c22 c24 1 was found to be characteristic for dominant forest vegetation while the opposite relationships were indicative for past paramo vegetation the n alkane relationship could be explained very well by the lipid ratios of the current forest and paramo vegetation in the area while agreeing well with the n alkane signal the n alcohol signal was less robust probably partially due to degradation of wax esters in the soil contrary to expectations we conclude that the investigated forest patch was never part of the continuous forest in the vicinity in the past 3500 cal years instead our biomarker ratio approach suggests that the forest patch soil was once covered by paramo vegetation overall this study shows that the biomarker ratio approach in volcanic ash soils can serve as a quick method for an assessment of abrupt vegetation changes such as associated with past ufl shifts at a high spatial resolution and at the location where the shift occurred as such it is highly complementary to traditional proxies such as pollen analysis

sedimentology of quaternary perched springline and paludal tufas criteria for recognition with examples from guadalajara province spain outcrop scale geometries and bed relationships of ambient temperature freshwater carbonates are poorly understood because many described tufas have been dismantled by erosion and present only part of a particular depositional model at the field scale four end member models encompass the tufa continuum 1 perched springline 2 paludal 3 fluvial and 4 lacustrine tufas individual bed types can occur with variable dominance within several of these models but one or more beds are characteristically dominant only within a single tufa model so it can be differentiated from relatively isolated outcrop fragments two models perched springline tufas and paludal tufas are known in outline only in the literature despite being present within the quaternary deposits of most karstic regions perched springline tufas generally form lobate fan shaped mound morphologies on hillslopes and develop from single or multiple spring resurgences mature deposits show a subhorizontal top and a steep face on the downflow side the steep outer zones of tufa mounds may be developed into cascades with moss curtains or can be dominated by shallow rimstone pools according to face angle tufa deposits lying downslope of the mounds are usually detrital in nature especially if some dismantling of the mound has occurred the relatively thin subhorizontal lobe top deposits commonly contain organic rich deposits paludal tufas develop predominantly in waterlogged valley bottom situations where line sourced waters emerge from valley side and bottom aquifers lime mud precipitation predominates in these sites mud is deposited as subhorizontal laminites that thin towards the valley axis and downstream of resurgences tufa spring mounds may form where lesser volumes of water are involved individual tussocks phytoherm cushions of grasses and rushes are the most diagnostic feature of the model but sapropels and peats may be intercalated diagenesis in both models is rapid lithification of individual beds is virtually instantaneous and always occurs before the decay of the associated living vegetation the resulting highly porous and permeable fabrics remain fresh in holocene tufas but aggrading neomorphism and partial spar infill of vegetation moulds is common in older deposits dissolution in many perched springline tufas is small scale many large cavities are primary but with later coatings of speleothems early removal of organics from paludal tufas is responsible for autobrecciation and differential compaction

applications of organic geochemistry to paleolimnological reconstructions a summary of examples from the laurentian great lakes the organic matter content of lake sediments contains information that helps to reconstruct past environmental conditions evaluate histories of climate change and assess impacts of humans on local ecosystems the elemental isotopic and molecular compositions of organic matter buried in sediment provide evidence of the biota that have lived in a lake and its catchment area and they serve as proxies of organic matter delivery and accumulation sedimentary records from the north american great lakes provide examples of applications of organic geochemistry to paleolimnological reconstructions the records of these lakes date from retreat of the laurentide ice sheet around 12 ka include the mid holocene hypsithermal and show consequences of recent human changes low corg ntotal ratios indicate that most of the sediment organic matter in the great lakes is from algal production yet changes in biomarker molecule compositions also show that varying amounts of land plant organic matter have been delivered to the lakes elevated algal productivity that accompanies nutrient enrichments of lake waters is recorded as excursions to less negative 13c values in the organic matter of sediments that were deposited in the 1960s and 1970s increased organic carbon mass accumulation rates mirror the isotopic excursions in most parts of the great lakes accumulations of petroleum residues and pyrogenic polycyclic aromatic hydrocarbons in sediments identify fluvial and eolian delivery of organic matter components to different parts of the great lakes emerging applications of multiple and novel organic geochemical proxies to paleolimnological reconstructions are promising yet some potentially important measurements remain underutilized

calcrete profile development in quaternary alluvial sequences southeast spain implications for using calcretes as a basis for landform chronologies a detailed study of the morphology and micro morphology of quaternary alluvial calcrete profiles from the sorbas basin shows that calcretes may be morphologically simple or complex the simple profiles reflect pedogenesis occurring after alluvial terrace formation and consist of a single pedogenic horizon near the land surface the complex profiles reflect the occurrence of multiple calcrete events during terrace sediment aggradation and further periods of pedogenesis after terrace formation these complex calcrete profiles are consequently described as composite profiles the exact morphology of the composite profiles depends upon 1 the number of calcrete forming events occurring during terrace sediment aggradation 2 the amount of sediment accretion that occurs between each period of calcrete formation and 3 the degree of pedogenesis after terrace formation simple calcrete profiles are most useful in establishing landform chronologies because they represent a single phase of pedogenesis after terrace formation composite profiles are more problematic pedogenic calcretes that form within them may inherit carbonate from calcrete horizons occurring lower down in the terrace sediments in addition erosion may lead to the exhumation of older calcretes within the terrace sediment calcrete inheritance may make pedogenic horizons appear more mature than they actually are and produce horizons containing carbonate embracing a range of ages calcrete exhumation exposes calcrete horizons whose morphology and radiometric ages are wholly unrelated to terrace surface age composite profiles are therefore only suitable for chronological studies if the pedogenic horizon capping the terrace sequence can be clearly distinguished from earlier calcrete forming events thus a detailed morphological micro morphological study is required before any chronological study is undertaken this is the only way to establish whether particular calcrete profiles are suitable for dating purposes copyright 2003 john wiley sons ltd

lipid geochemistry of a post glacial lacustrine sediment abstract the post glacial environmental history of voua de la motte a small pond was studied by the lipid geochemistry of a 6 m long core palynological studies show that the deepest part of the core goes back to 10 000 yr bp corresponding to the time of formation of the lake following the retreat of the rhodanian glacier hydrocarbons aldehydes linear alcohols sterols monocarboxylic and monohydroxy fatty acids were determined throughout the core both in the free and bound lipid fractions as well as in the tightly bound fraction for the carboxylic acids there is no clear evidence of a transformation from the unbound to the bound form except perhaps for the hydroxy acids qualitative as well as quantitative fluctuations in the distributions of these lipid classes were observed upward in the core an attempt is made to correlate these fluctuations with the bioenvironmental and climatological evolution of the basin on the basis of information obtained from palynology

late quaternary large scale rotational slides induced by river incision the arroyo de gor area guadix basin se spain the arroyo de gor is a highly incised stream up to 200 m that has eroded into the pliocene pleistocene infill of the guadix basin in the betic cordillera se spain this paper concentrates on a particular reach of this stream namely the cenascuras gorafe reach where abundant inactive rotational slides can be recognized on both hillslopes of the canyon shaped valley the rotational slides have surface areas of 5 15 ha and volumes of mobilized material of 5 15 hm3 these rotational slides can be recognized by their main scarps which are still well featured at both margins of the valley as well as by the counter hillslope rotation of the strata in their bodies the surfaces of rupture are concave their width being greater than their length i e the landslides are elongated in a direction perpendicular to the landsliding displacement and parallel to the stream at depth the surfaces of rupture developed on fine grained sediments mostly clays underlying the conglomerates and sands affected by the rotational slides the clays at the surface of rupture are smectite rich and show several features produced by the landsliding such as striations and sigmoidal shaped structures the cenascuras gorafe canyon has been developed by a combination of entrenchment fracturing and landsliding initial deep entrenchment of the stream is attributed to a base level lowering related to the capture of the former endorheic basin by the gualdalquivir river in the late pleistocene this river incision created a canyon with subvertical unstable walls which due to gravitational instability would give way to vertical open tension cracks some distance from the canyon edge the tension cracks would end at depths equal to the base of the canyon which also coincides with the contact between the conglomerates and the underlying clays the rotational slides are thought to have occurred during heavy rains by a combination of piping which would have lengthened the tension cracks and infiltration which would reduce the shear strength along the gently dipping contact between conglomerates and the underlying clays thus the blocks bounded by the tension cracks and the subhorizontal lithological contact would slide under their own weight on the subhorizontal surfaces of reduced shear strength several age constraints lead us to tentatively assign the landslides to the isotope stage 5 around 32 ka an interglacial period agreed to be wetter and slightly warmer than the present day semi arid climate

distribution of terrigenous lipids in marine sediments off northeastern taiwan surface sediments on the continental margin off northeastern taiwan have been analyzed for terrigenous lipids including n alkanes n fatty alcohols and sterols marine input to the sediments is particularly low based on the average n c17 n c29 alkane and n c16 n c28 fatty alcohol ratios 0 15 0 13 and 0 13 0 06 respectively this may be due to the fact that marine lipids are more prone to degradation than terrestrial ones the study area has the highest plant wax n alkane contribution average carbon preference index 3 9 1 2 among the coastal marine areas surrounding taiwan lateral particle transport from the southern east china sea shelf and river runoff from the east taiwan coast are considered to be the major contributors the distributions of plant wax n alkane and n alkanol concentrations normalized to total organic carbon toc in the study area generally show maximum values on the upper slope of the southernmost okinawa trough but not for phytosterols linear regression of toc versus plant wax n alkane concentrations show a weak relationship r 0 64 p 0 001 and an even weaker relationship r 0 42 p 0 05 between toc and plant wax n fatty alcohol concentrations is found this could be attributed to several factors 1 a complex input not a point source of terrigenous organic matter to the study area 2 toc also including marine organic matter 3 temporal variations in river flow due to flooding and 4 different rates of degradation for toc and individual biomarkers however in spite of those factors toc and phytosterol concentrations are positively linearly correlated r 0 85 p 0 001 implying that the dilution of phytosterols in terrigenous organic carbon with marine organic carbon with or without the phytosterols follows a nearly constant ratio which is remarkable in addition the predominant source of diploptene in the sediments does not appear to be of higher plant origin

glacial interglacial variations in carbon cycling revealed by molecular and isotope stratigraphy of lake nkunga mt kenya east africa abstract the lipid content n alkanes n alkanols n alkanoic acids and the 13c values of these lipids were measured in nineteen sediment samples taken from a 21 18 m long core from lake nkunga a high altitude 1820 m a s l freshwater lake situated in the montane rain forest on mt kenya the record spans the early last glacial marine isotope stages 5a to 4 and the late holocene 1030 45 14c yr bp to the present day the intervening hiatus spans the last glacial maximum and the early to mid holocene the molecular biogeochemical results are interpreted in terms of past changes in climate vegetation and atmospheric co2 concentration three different sources of organic matter input were identified from the n alkyl lipids namely terrestrial plants aquatic plants and algae unusual distribution patterns of dominant mid chain length n alkanes c23 25 n alkanols c22 24 and n alkanoic acids c22 24 are attributed to aquatic macrophytes an 11 decrease in bulk carbon isotope values between the sediments of early glacial 17 and late holocene age 28 is also apparent in the individual homologues of the n alkyl lipids the observed isotopic shift in terrestrial higher plant biomarkers is similar to that observed in nearby sacred lake and is consistent with an expansion of c4 grasses or sedges during the early glacial the corresponding vegetation was a dry montane juniper olive forest with a grassy understorey representing cold dry conditions with lower co2

evidence of terrestrial organic matter deposition across the early toarcian recorded in the northern lusitanian basin portugal abstract the pliensbachian toarcian lower jurassic in the lusitanian basin portugal is particularly well exposed through marl limestone alternations very rich in nektonic and benthonic macrofauna in the general context of toarcian oceanic anoxic event t oae the lower toarcian polymorphum and levisoni ammonite zones marks important sedimentological changes in the marine paleoenvironment to better understand the paleoenvironmental changes that occurred during the latest pliensbachian early toarcian a high resolution study of organic matter was undertaken in the alcabideque section in the northern sector of the basin based on the analysis of 14 samples from a section 20 m thick this study involved organic geochemistry total organic carbon toc sulfur and biomarkers and palynofacies the results confirm that sediments are particularly poor in organic matter with the highest toc values reaching 0 41 wt around the top of polymorphum zone the palynofacies analysis provides evidence that the organic matter largely consists of particles belonging to phytoclasts and palynomorphs groups the phytoclasts present were generally degraded and oxidized with significant representation in the emaciatum and polymorphum zones the palynomorphs were mainly composed by sporomorphs with a sporadic increase in marine palynomorphs mainly dinocysts at the top of the emaciatum and polymorphum zones continental organic matter was predominant at the base of levisoni zone t oae through the deposition of brownish marls chocolate marls which was confirmed by the occurrence of tetrads and polyads pollen grain agglomerates and by biomarkers with the major presence of long chain n alkanes n alkane c17 c20 tricyclic terpane c24 tetracyclic terpane and c29 regular sterane the gammacerane index shows a peak at the top of polymorphum zone clearly associated with the increase of marine palynomorphs and the maximum marine influence in the series

paleoenvironmental implications of molecular and carbon isotopic distributions of n alkanes in the hominoid bearing upper miocene sediments from the zhaotong basin southwestern china abstract it is crucial to understand the relationship between hominoid primates and their living environment located at the southeastern margin of the tibetan plateau the shuitangba stb outcrop from the zhaotong basin is famous for bearing the remains of the youngest known ape fossil in the terminal miocene 6 2 ma in this study the molecular and carbon isotope compositions of n alkanes together with the loss on ignition and the bulk carbon isotope composition of total organic matter were investigated in the stb outcrop to infer the paleoenvironmental conditions in this uppermost miocene sedimentary sequence with the emphasis on the habitat of the stb hominoid in the hominoid bearing peaty clay layer and the surrounding lignite layers the n alkane molecular and carbon isotope compositions support a primary contribution from terrestrial higher plants in contrast n alkanes in the upper shallow lake sediments are derived from multiple origins mainly from aquatic plants and bacteria both carbon preference index cpi and average chain length acl vary closely with the lithology but the cpi record shows the larger amplitude of change than the acl and varies sharply during the lithological boundary it is notable that the changes of the molecular and carbon isotope compositions of long chain n alkanes do not parallel with the abrupt increase of poaceae pollen percentage during the stb hominoid appearing stage such an inconsistency between herb pollen percentage and n alkane ratios may result from the different sources our results clearly support that these organic matter based ratios have the potential to record the paleoenvironmental changes in ancient lacustrine sediments

comparison of extraction techniques for bound carboxylic acids in recent sediments 2 β hydroxyacids abstract various multi step extraction procedures were used in order to determine the hydroxyacid content of a recent lacustrine sediment similar distribution but important quantitative differences were noted all the hydroxyacids are derived from the same origin but the commonly used methanolic saponification is inappropriate for the release of bound hydroxyacids all the extraction techniques produce either 3 methoxy or 3 chloro and 2 unsaturated carboxylic acids as artifacts from the 3 substituted fatty acids a two step procedure is recommended for the extraction of the maximum amount of hydroxyacids with the minimum formation of artifacts

lipid geochemistry of sediments from upton broad a small productive lake major lipid classes isolated from 3 sections of the sediment profile of upton broad a shallow lake formed about 500 yr ago were correlated with input and with changes attributable to early diagenesis surficial sediment contains lipids characteristics of the known recent algal and microbial input preservation of chlorophyll pigments and absence of appropriate markers suggest that diagenesis is minimal older deposits from the eutrophic phase of the lake s history contain higher levels of bacterial lipids and diagenetic products the earliest sediment contains lipids characteristic of terrigenous input subjected to more extensive diagenesis than the younger sediment recognition of early diagenesis in anoxic sediment suggests that distributions of the shorter chain homologous free n alkanes alkanols and alkanoic acids result from microbial synthesis using material initially deposited at the sediment surface rather than partial preservation of the lipids of primary source organisms

reconstruction of late glacial and holocene climate evolution in southern china from geolipids and pollen in the dingnan peat sequence we have carried out a multi proxy analysis of a radiocarbon dated peat core that records the history of paleoclimate change dating from 18 ka in the dingnan region of southern china fatty acid and hydrocarbon distributions total organic carbon toc concentrations pollen assemblages and sediment lithology reveal a succession of three major paleoclimate intervals plant waxes are the predominant origin of the n alkanoic acid and n alkane compositions of this sedimentary sequence contributions of these geolipid components vary relative to toc and with changes in lithology and help to refine a pollen based reconstruction of local paleoclimate evolution a period of cool and fairly wet climate 15 630 10 450 cal abp follows accumulation of coarse fluvial sediments under relatively dry deglacial conditions the second period 10 450 6040 cal abp experienced the warmest climate and the highest precipitation indicated by a minimum c18 1 c18 0 ratio together with the low cpi values of n alkanes and high acl values the third time interval 6040 3800 cal abp was a moderately dry and cool period the climate record of the most recent period 3800 cal abp is obscured by agricultural disturbance the younger dryas 12 900 11 600 cal abp appears in this record as a period of variable and very wet climate during the interval 10 450 6040 cal abp both temperature and the precipitation evaporation ratio maximized therefore we consider this period to represent the holocene optimum which coincides with that of the northern hemisphere moreover our results do not fit the spatially asynchronous pattern of the east asian monsoon holocene optimum in china suggested by previous studies they instead parallel the pattern of global paleoclimate change and consequently show that the evolution of holocene paleoclimate in southern china is consistent with changes in northern hemisphere solar radiation

the timing of quaternary calcrete development in semi arid southeast spain investigating the role of climate on calcrete genesis quaternary aged calcrete horizons are common weathering products in arid and semi arid regions it is however unclear how calcrete forming processes respond to the major oscillations in climate that occur over the quaternary period this paper presents a u series based calcrete age database from the sorbas basin southeast spain the study constructs an age frequency distribution of these ages which is consequently compared to a range of palaeoenvironmental records from the mediterranean the age distribution presented here suggests that the formation of pedogenic calcrete horizons in the sorbas basin primarily occurs during warm isotope stages mis 1 and 5 with very few calcrete ages occurring during cold glacial stadial stages mis 2 3 and 4 it is suggested that this is a function of the environments that existed during warm isotope stages being more conducive to calcrete development than those that existed during cold climate episodes in a semi arid region such as the sorbas basin it is likely that increased aridity during glacial stages coupled with reduced vegetation and accelerated landscape instability was crucial in reducing rates of calcrete formation in a semi arid region such as southeast spain calcrete formation during the quaternary therefore oscillates with climate change but is primarily a warm episode phenomenon it is suggested that further studies are required to see how calcrete genesis responds to environmental change in more humid parts of the mediterranean

a calcrete based u th chronology for landform evolution in the sorbas basin southeast spain nodular and massive calcretes from alluvial terraces in the sorbas area of southeast spain have been dated by the u th isochron method to between 8 350 ka alternative approaches have been used to generate the multiple samples for the isochron method for several of the calcretes dates agreed closely when obtained by total dissolution of a number of nodules or by the sequential dissolution in different acids of a single nodule however fractional dissolution of a single nodule in the same acid revealed two stages of precipitation of different age it is considered that the calcretes may not be strictly pedogenic in origin and that groundwater processes linked to the alluvial environment may have been involved also nevertheless their dates provide minimum ages for a chronostratigraphic framework for terrace evolution

paleoenvironment of the eocene coal seam in the fushun basin ne china implications from petrography and organic geochemistry abstract the fushun basin in northeast china is a strike slip basin filled with coal bearing eocene sediments the basin fill includes from base to top volcaniclastic rocks a 20 to 145 m thick coal seam lower eocene guchengzi formation and lacustrine oil shale up to 300 m thick jijuntun formation the sub bituminous coal of the guchengzi formation famous for the amber inclusions is exploited in the largest opencast coal and oil shale mine in asia in the present contribution the depositional environment and the thermal history of the guchengzi formation are investigated based on macro and micropetrographic data bulk geochemical parameters biomarker analysis stable isotope geochemistry and vitrinite reflectance measurements according to our interpretation accumulation of the low sulfur coal commenced in a low lying mire near a shallow lake subsequently low ash coal was deposited either in a low lying mire protected from clastic influx or in a raised mire finally high subsidence rates typical for strike slip basins caused the flooding of the mire and terminated peat accumulation pristane phytane ratios suggest a gradual change from oxic to less oxic conditions during the drowning phase of the seam organic rich shales accumulated in the newly formed freshwater lake and resulted in the deposition of the overlying oil shale bearing jijuntun formation the coal is rich in liptinite macerals especially sporinite gymnosperms dominated the paleovegetation of the mire something that is also reflected by the frequent occurrence of resinite and amber and their biomarker composition the coal reached the sub bituminous or even the high volatile bituminous stage despite the limited burial depth simple 1d models suggest that this is a result of high heat flow rather than of deep burial and erosion the hydrogen rich coal is oil prone

short term bank gully retreat rates in mediterranean environments abstract in this study short term headcut retreat was monitored from 46 active bank gullies selected in the guadalentin and the guadix basin in southeast spain the measurements were carried out manually using an orthogonal reference system fixed by erosion pins around the gully heads between april 1997 and april 1999 with a 1 year interval the average volumetric retreat rate for all gullies was 4 0 m 3 year 1 corresponding with an average linear retreat rate of 0 1 m year 1 but more erosion took place during the first monitored year 1997 1998 compared to the second 1998 1999 an interplay of spatial variations in rainfall distribution and tension crack activity is assumed to be responsible for the important difference in annual headcut retreat compared to the small difference in annual rainfall amounts statistical analysis showed that the present drainage basin area a p was the most important topographical factor explaining average gully headcut retreat rate both in terms of annual eroded volume v e and annual linear retreat r l and expressed by the power relationships v e 0 04 a p 0 38 r 2 0 39 and r l 0 01 a p 0 23 r 2 0 39 the v e a p relationship was compared with the relationship between original drainage basin area a o and total eroded bank gully volume vol i e vol 1 71 a o 0 60 r 2 0 65 the importance of runoff generation from a drainage basin is shown by the positive correlation of linear headcut retreat and the runoff curve number cn representative for the conditions in the drainage basin high cn values tend to coincide with higher annual eroded volumes in the relationship between present drainage basin area a p and annual eroded volume v e but this effect was not observed in the relationship between original drainage basin area a o and total eroded bank gully volume vol stepwise multiple regression selected the relevant environmental parameters explaining annual eroded volume and linear retreat in both equations the present drainage basin area explained the largest part of the variation the cn was selected as another common parameter height of the headcut was the second most important variable explaining annual eroded volume indicating the role of energy transfers and undercutting at the headcut linear retreat was further explained by the average slope of the present drainage basin area representing the effect of decreasing transmission losses and increasing flow velocity with steeper catchment slopes and by the sand content decreasing the cohesion of the soil material promoting soil fall and headcut retreat spatial extrapolation of the measured volumetric retreat rate of 4 0 m 3 year 1 revealed that active bank gully heads contribute up to 6 of the sediment yearly filling up the puentes reservoir estimated gully ages i based on the ergodic principle and ii by linear extrapolation of actual gully retreat rates in the past range between 63 years and 1539 and between 64 and 1720 years respectively the high correlation between the gully ages estimated by the two methods is attributed to the fact that most gullies have not reached the evolutionary stage of significantly declining retreat rates since medium term gully retreat rates are more dependent on drainage basin area compared to the short term retreat rates obtained in this study the estimated gully ages represent maximum values assuming that present land use and climate conditions prevailed over the last two millennia

sedimentary patterns in perched spring travertines near granada spain as indicators of the paleohydrological and paleoclimatological evolution of a karst massif perched spring travertines of the granada basin south spain constitute a perched system with four well defined steps which are formed by several facies associations deposited in different sub environments travertine pools dams and cascades these perched travertines are considered as a freshwater reef system with a facies zonation and stratigraphic architecture closely resembling that of marine reef terraces and prograding carbonate platforms the travertine deposits have been dated by 230 th 234 u and 14 c methods as in other mediterranean areas the travertine deposition occurred episodically during warm and wet interglacial periods coinciding with isotopic stages 9 7 and 5 and with the transition between isotopic stages 2 1 during these periods underground dissolution large outflow in the springs and subsequent calcium carbonate precipitation occurred in the same way that evolution of reef systems indicates sea level changes the geomorphology age and architecture of perched spring travertine systems may be used to interpret former climatically controlled changes in outflow in base level marked by the altitude of springs and in the chemistry of spring waters thus aggradation or climbing progradation may indicate an increase of outflow at the spring progradation with toplap is due to a stable base level and conversely dowlapping progradation may signify that the base level was gradually dropping therefore the travertines can be considered semiquantitative indicators of the paleohydrological evolution of karstic massifs and used as an important terrestrial proxy climate record d 2003 elsevier science b v all rights reserved

quantifying time scales of pedogenic calcrete formation using u series disequilibria abstract time scales of pedogenic calcrete development are quantified by subsampling carbonate from within a mature stage v pedogenic calcrete profile from southeast spain and dating the material by u series disequilibria the location of the earliest and latest cements can be estimated by comparing previous studies of calcrete morphological development with micromorphological analysis of the study profile carbonate was sampled and dated from three locations within the profile 1 below the lower surface of clasts within the hardpan representing the earliest cement present 207 11 ka 2 from the centre of cement filled pores within the hardpan reflecting the final plugging of the calcrete hardpan 155 9 ka and 3 from the laminar calcrete overlying the hardpan representing the latest cement 112 15 ka these results show that the hardpan took between 73 and 31 ka to form whilst the mature stage v profile took between 121 and 69 ka to form this is the first time that rates of mature calcrete development have been established by direct radiometric dating of the authigenic carbonate the technique is appropriate for dating mature calcretes in dryland regions worldwide and offers the opportunity of increasing our understanding of the spatial and temporal variability in rates of pedogenic calcrete development

molecular and isotopic records of c4 grassland expansion in the late miocene abstract siwalik paleosol and bengal fan sediment samples were analyzed for the abundance and isotopic composition ofn alkanes in order to test for molecular evidence of the expansion of c4 grasslands on the indian subcontinent the carbon isotopic compositions of high molecular weight alkanes in both the ancient soils and sediments record a shift from low 13c values ca 30 to higher values ca 22 prior to 6 ma this shift is similar in magnitude to that recorded by paleosol carbonate and fossil teeth and is consistent with a relatively rapid transition from dominantly c3 vegetation to an ecosystem dominated by c4 plants typical of semi arid grasslands the n alkane values from our paleosol samples indicate that the isotopic change began as early as 9 ma reflecting either a growing contribution of c4 plants to a dominantly c3 biomass or a decrease in water availability to c3 plants molecular and isotopic analyses of other compounds including n alcohols and low molecular weightn alkanes indicate paleosol organic matter contains contributions from a mixture of sources including vascular plants algae and or cyanobacteria and microorganisms a range of inputs is likewise reflected in the isotopic composition of the total organic carbon from these samples in addition then alkanes from two samples show little evidence for pedegenic inputs and we suggest the compounds were derived instead from the paleosol s parent materials we suggest the record of vegetation in ancient terrestrial ecosystems is better reconstructed using isotopic signatures of molecular markers rather than bulk organic carbon this approach provides a means of expanding the spatial and temporal records of c4 plant biomass which will help to resolve possible tectonic climatic or biological controls on the rise of this important component of the terrestrial biosphere

practical aspects of wavefield separation of two component surface seismic data based on polarization and slowness estimates the processing of multicomponent seismic data carried out individually on the different wavetypes p s and converted waves should result in an improved image of the subsurface we examine the wavefield separation method proposed by cho and spencer we discuss practical aspects related to the separation of interfering waves on two component surface seismic data and illustrate these using synthetic data a sliding spatial window is used for analysis the choice of its width represents a trade off between stabilizing the method in the presence of random noise and ensuring a good spatial resolution no a priori knowledge of the subsurface is required but locally the characteristic parameters of the waves i e horizontal slowness and polarization are assumed to be constant inside the analysis window these parameters are estimated at each frequency but a statistical analysis provides a more robust estimate especially in the presence of random noise this approach also solves the problem of eigenvalue sharing and switching additional smoothing of the estimates according to a model may further improve the results the width of the analysis window may be decreased if the waves inside the data window differ significantly in amplitude the dominant wave in each case is separated from the lower amplitude waves and subtracted from the data this novel iterative approach thereby allows for the isolation of low amplitude events

a stratigraphic framework for the pliocene pleistocene continental sediments of the guadix basin betic cordillera s spain the central sector of the guadix basin betic cordillera s spain hosts some of the most significant pleistocene large mammal sites in europe the basin infill is divided into six genetic units the three lower with marine sediments and the remainder mainly continental as the environmental characterization of the sediments is crucial to understand the ecologic and geologic processes leading to the formation of these sites a stratigraphic sedimentologic and petrologic study is presented combining a lithologic correlation with previous biostratigraphic data and new magnetostratigraphic data a detailed litho bio and magnetostratigraphic scheme has been developed for the study area it shows the stratigraphic architecture of the central sector of the guadix basin together with the age and the relative spatial position of the most important mammal sites as well it has been also helpful to identify several isochronous surfaces to establish the exact position and the age of the boundary between the two last units of the continental infill in the guadix basin and to calculate sedimentation rates

reply to comment by j l diaz hernandez and r julia on quaternary landscape evolution and erosion rates for an intramontane neogene basin guadix baza basin se spain abstract we demonstrate that the age of 43 ka obtained for the topmost calcrete layer in the guadix baza remains the only reliable numerical dating of the flat geomorphic surface that marks the end of the sedimentation in the basin consequently the late pleistocene to holocene erosion rates derived from the incision of the present day drainage network into the flat geomorphic surface remain valid the calcrete radiometric ages reported by diaz hernandez and julia 2012 in their comment are untenable due to the contamination with detrital 230 th not corrected with the applied u th technique and the possible mix of textural elements with different ages older inherited grains and newly formed grains diaz hernandez and julia also quote u th ages for travertine terraces formed later than the calcrete layer these ages lack internal consistency probably due to systematic contamination and or weathering of the samples the archaeological ages reported by diaz hernandez and julia are subjected to great uncertainties but independently of the age assumed as most realistic they are completely compatible with the age of 43 ka that we obtained for the topmost calcrete layer in the guadix baza basin

changes in the trophic state of lake erie discordance between molecular δ13c and bulk δ13c sedimentary records abstract prior to 1980 anthropogenic phosporus p loadings resulted in increased algal productivity and the deterioration of water quality within lake erie we measured c and n elemental compositions geolipid concentrations and 13 c values for bulk organic material and individual alkanes in samples taken from a 40 cm sediment core from the eastern basin of lake erie to infer recent trends in primary productivity and diagenesis the predominance of autochthonous algal derived c throughout the core is evidenced by low c n values 9 10 and the persistent abundance of n c 15 to n c 17 alkanes throughout the core the 13 c values of bulk organic c from lake erie vary between 25 9 and 24 9 with a maximum corresponding to the period of elevated historical p loading within lake erie 13 c values of short chained algal derived alkanes n c 18 are lower approximately 1 0 than their terrestrial derived homologs n c 25 down core variations in the 13 c composition of algal derived short chained alkanes do not exhibit the same trend as that observed for bulk organic c down core variation in 13 c values of individual alkanes likely reflect multiple diagenetic effects including kinetic fractionation effects variations in the relative contributions of isotopically unique n alkanes to the sediments and or temporal changes in 13 c enrichments of n alkanes associated with a single source high sedimentation rates characteristic of this core emphasize temporal variations in molecular 13 c values that might not otherwise be observed whereas 13 c data for bulk sedimentary organic c appear to reflect variation in trophic state the isotopic record for algal derived n alkanes e g n c 17 and pristane from lake erie must be considered from the perspective of molecular transformations

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

comparison of pliocene organic rich lacustrine sediments in twin craters the organic matter of pliocene oil shales from maar type twin craters egyhazaskeszoand varkeszo in hungary was studied by diaerent analytical techniques rock eval pyrolysis bitumen analysis ftir elemental analysis and pyrolysis of the insoluble material the organic rich alginitic layers were deposited at the same time under the same palaeoclimatic conditions and have basically similar lithologies despite this the oil shale deposits from each crater show distinct diaerences furthermore within each crater the older oil shale deposits are diaerent from the younger this phenomenon can be explained both by variations in organic matter input and changes in the depositional envir onment the principal source of the organic matter is the microalgae botryococcus braunii but the terrestrial con tribution is also significant the prevalence of the algal material is supported by the elemental composition and kerogen pyrolysis data the pyrograms show that there is considerably more algal material in the varkeszosamples kerogens in the egyhazaskeszocrater contain much more organic sulphur and pyrite is more abundant the nominally type ii kerogens in the twin craters are the products of diverse processes varkeszokerogens are in fact mixtures of type i and type iii organic matter and are preserved relatively well egyhazaskeszokerogens must have suaered biological degradation and chemical alteration during pyrite formation resulting in medium sulphur rich type ii kerogen formation 2000 elsevier science ltd all rights reserved during the pliocene several oil shales were deposited in small maar type volcanic craters in hungary solti 1990 four to five million years ago in the pannonian lake system very intense and repeated volcanic erup tions disturbed the sedimentation the basic magma gave rise to stratavolcanoes and the formation of tua rings the craters formed by basalt volcanism filled with water of the pannonian lake after volcanic activity had ceased the small separate lakes were current free and oligohaline the depositional environment warm water caused by postvolcanic geysers and an abundant nutrient supply due to the intense weathering of the

geochronological position of badlands and geomorphological patterns in the guadix baza basin se spain abstract the guadix baza basin is one of a number of intramontane depressions located within the betic cordillera se spain where the geological and geomorphological evolution is controlled by tectonic activity the basin ceased to be closed after capture by the atlantic network when five main land systems developed late pleistocene geological evolution basically consisted of erosional modelling when badlands were deeply incised in highly erodible materials marls and silts three travertine platforms and several palaeolithic sites were used to determine that this main incision period fell within a 115 000 48 000 yr range there are few signs of geomorphological evolution of this basin in the last 48 000 yr based on these geomorphological data and soil development tectonic uplift of the basin probably played a secondary role in its evolution and climatic conditions in southern iberia in the 144 000 48 000 yr period were more humid and variable than later

u series isochron dating of immature and mature calcretes as a basis for constructing quaternary landform chronologies for the sorbas basin southeast spain immature and mature calcretes from an alluvial terrace sequence in the sorbas basin southeast spain were dated by the u series isochron technique the immature horizons consistently produced statistically reliable ages of high precision the mature horizons typically produced statistically unreliable ages but because of linear trends in the dataset and low errors associated with each data point it was still possible to place a best fit isochron through the dataset to produce an age with low associated uncertainties it is however only possible to prove that these statistically unreliable ages have geochronological significance if multiple isochron ages are produced for a single site and if these multiple ages are stratigraphically consistent the geochronological significance of such ages can be further proven if at least one of the multiple ages is statistically reliable by using this technique to date calcretes that have formed during terrace aggradation and at the terrace surface after terrace abandonment it is possible not only to date the timing of terrace aggradation but also to constrain the age at which the river switched from aggradation to incision this approach therefore constrains the timing of changes in fluvial processes more reliably than any currently used geochronological procedure and is appropriate for dating terrace sequences in dryland regions worldwide wherever calcrete horizons are present

lipid biomarkers in the zoige hongyuan peat deposit indicators of holocene climate changes in west china abstract lipid biomarkers extracted from a peat core obtained from the northeast edge of the tibetan plateau have provided a 13 kyr record of regional climate change a period of warmer climate corresponding to the holocene optimum between 9 ka and 5 ka is evident in greater alteration of n alkanoic acids and n alkanols and in the appearance of biomarkers indicative of greater microbial activity concomitant increases in local precipitation that raised the water level of the peat bog are recorded by increases in the proportions of c23 and c25 n alkanes that are mainly derived from submerged floating plants alternations in submergent and emergent plant n alkane proxies reveal multi decimeter scale rises and falls in the bog water level that relate to variation in precipitation on the tibetan plateau during the holocene major low water level events occurred around 12 6 11 3 10 7 9 4 8 3 6 0 4 5 3 1 2 1 and 1 0 ka these events correlate well with cold dry events recorded in same region from other climatic proxies that reflect millennial scale holocene instability in the asian monsoon system our biomarker results also indicate that peat accumulation and preservation on the tibetan plateau are more sensitive to variability in monsoonal precipitation than in annual temperature

diagenesis of free and bound lipids in terrestrial detritus deposited in a lacustrine sediment recent sediments from an oligotrophic lake loch clair having uniform organic input for 2000 yr show changes in lipid abundance and composition with increasing depth attributed to diagenesis stability of free lipids decreases in the order n alkanes alkan 2 ones sterols n alkanoic acids n alkanols n alkenoic acids diagenetic loss of shorter chain homologues is complete within 400 yr stabilisation of bound relative to free lipids increases the proportion of the former with sediment age and reduces loss of shorter chain bound homologues in an eutrophic lake cross mere shorter chain free and bound sedimentary lipids show increased abundance compared with loch clair the relative importance of higher input of shorter chain lipids derived from aquatic detritus and slower initial diagenesis due to the anoxic hypolimnion as causative factors for this difference between lake types cannot yet be assessed

u series dating of impure carbonates an isochron technique using total sample dissolution abstract u series dating is a well established technique for age determination of late quaternary carbonates materials of sufficient purity for nominal dating however are not as common as materials with mechanically inseparable aluminosilicate detritus detritus contaminates the sample with extraneous th we propose that correction for contamination is best accomplished with the isochron technique using total sample dissolution tsd experiments were conducted on artificial mixtures of natural detritus and carbonate and on an impure carbonate of known age results show that significant and unpredictable transfer of radionuclides occur from the detritus to the leachate in commonly used selective leaching procedures the effects of correcting via leachate residue pairs and isochron plots were assessed isochrons using tsd gave best results followed by isochron plots of leachates only

high frequency floral changes at the paleocene eocene boundary revealed by comparative biomarker and palynological studies abstract the cap d ailly area upper normandy france shows several terrestrial lagoonal sections recording the negative carbon isotope excursion cie associated with the paleocene eocene thermal maximum petm 55 8 ma a study of the biomarkers and spore pollen content of the vasterival section gave complementary information on paleofloral changes that occurred around the paleocene eocene p e boundary aliphatic hydrocarbon fractions revealed a high abundance of vascular plant biomarkers including tricyclic diterpanes derived from conifers fernenes derived from ferns and des a triterpenes derived from angiosperms whereas the vegetation of the depositional environment surroundings seemed alternately dominated by ferns and angiosperms revealed from biomarkers the regional flora seemed dominated strictly by angiosperms such as juglandaceae revealed by pollen spore pollen assemblages revealed no major turnover in the paleovegetation but slight variation in vegetation composition however both biomarkers and spores pollen exhibited two intervals of rapid floral change the first occurred around the p e boundary and the second at the top of the strictly terrestrial unit that coincides with a marine transgression comparison of the data with published paleoclimatic results obtained from the same samples indicated that the first interval of floral change correlates with strong paleohydrological perturbations whereas the second is linked to an increasing marine influence

biomarker records of palaeoenvironmental variations in subtropical southern africa since the late pleistocene evidences from a coastal peatland abstract southern africa s unique global position has given rise to a dynamic climate influenced by large sea surface temperature gradients and seasonal fluctuations in the inter tropical convergence zone due to the semi arid climate of the region terrestrial palaeorecords are rare and our understanding of the long term sensitivity of southern african terrestrial ecosystems to climatic drivers is ambiguous a 810 cm continuous peat core was extracted from the mfabeni peatland with a 14 c basal age of c 47 thousand years calibrated before present kcal yr bp positioning it as one of the oldest known sub tropical coastal peatlands in southern africa this peat core provides an opportunity to investigate palaeoenvironmental changes in subtropical southern africa since the late pleistocene biomarker n alkane n alkanoic acid and n alkanol analysis in conjunction with previously published bulk geochemical data was employed to reconstruct organic matter om sources rates of om remineralisation and peatland hydrology our results showed that the principal om source into the peatland was emergent and terrestrial plants with exception of shallow lake conditions when submerged macrophytes dominated c 44 5 42 6 29 7 26 1 23 1 16 7 7 1 and 2 2 kcal yr bp n alkane proxies suggest that local plant assemblages were predominantly influenced by peatland hydrology by incorporating temperature sensitive n alkanoic acid and n alkanol proxies it was possible to disentangle the local temperature and precipitation changes we report large variations in precipitation intensities but subdued temperature fluctuations during the late pleistocene the holocene period was characterised by overall elevated temperatures and precipitation compared to the preceding glacial period interspersed with a millennial scale cooling event a close link between the mfabeni archive and adjacent indian ocean marine core records was observed suggesting the regional ocean surface temperatures to be the dominant climate driver in this region since the late pleistocene

molecular composition of a leaf and root bearing oligocene oxbow lake clay in the weisselster basin germany abstract a plant fossil bearing clay profile from the upper oligocene thierbach strata weisselster basin germany has been sectioned into horizons and the plant macrofossils of each section surface have been identified by morphological and anatomical studies in the upper half of the profile leaves from populus germanica and carpinus grandis and branchlets from the conifer taxodium balticum vel t dubium dominate the horizons while the lower part contains only root remains of unknown higher plants in the soxhlet extracted samples from each section n alkanes n alkanols n carboxylic acids and several terpenoids amyrin 24 25 dinoreleana 1 3 5 10 12 tetraene olean 12 en 3 one simonellite and hop 17 21 ene were identified by combined gas chromatography mass spectrometry the comparison of the extracted chemical compounds and the macrofossil record of the profile shows that simonellite occurs preferentially in the taxodium bearing horizons n alkanes n alkanols n carboxylic acids and amyrin were found in all sections but are enriched in the root containing part of the profile the distribution of hop 17 21 ene is independent of the input of higher plant remains

the baza fault a major active extensional fault in the central betic cordillera south spain in the guadix baza basin betic cordillera lies the baza fault a structure that will be described for the first time in this paper eight gravity profiles and a seismic reflection profile coupled with surface studies indicate the existence of a ne dipping normal fault with a variable strike with n s and nw se segments this 37 km long fault divides the basin into two sectors guadix to the west and baza to the east since the late miocene the activity of this fault has created a half graben in its hanging wall the seismic reflection profile shows that the fill of this 2 000 3 000 m thick asymmetric basin is syntectonic the fault has associated seismicity the most important of which is the 1531 baza earthquake since the late tortonian to the present i e over approximately the last 8 million years extension rates obtained vary between 0 12 and 0 33 mm year for the baza fault being one of the major active normal faults to accommodate the current ene wsw extension produced in the central betic cordillera the existence of this fault and other normal faults in the central betic cordillera enhanced the extension in the upper crust from the late miocene to the present in this regional compressive setting

glacis geometry as a geomorphic marker of recent tectonics the guadix baza basin south spain abstract the guadix baza basin occupies 4000 km 2 and constitutes the largest intramontane basin of the betic cordillera southern spain it has a well preserved geomorphic surface a glacis which started to be eroded when the basin conditions changed from endorheic to exorheic taking into account its large preserved surface area more than 1200 km 2 and its pre deformational geometry this geomorphic surface is a useful marker of recent deformation combining geological and geomorphological data and high resolution dem topographic profiles of the glacis have been produced to estimate vertical displacements caused by active compression and extension structures these structures have produced relative vertical displacements of up to 100 m from the late middle pleistocene to the present assuming an age for the glacis of between 205 and 600 ka it has been possible to estimate long term minimum and maximum vertical rates of the activity of normal faults and folds using this geomorphic surface as a marker vertical slip rates range from 0 07 to 0 49 mm year for the main active normal faults and vertical folding rates range from 0 05 to 0 17 mm year for several active folds these long term vertical slip and folding rates are in accordance with other values previously estimated in other sectors of the betic cordillera when present detailed geomorphic study of recent glacis is an excellent tool for evaluating active tectonics over large regions

synchronous change of temperature and moisture over the past 50 ka in subtropical southwest china as indicated by biomarker records in a crater lake abstract over the past few decades studies on the indian summer monsoon ism have been mainly based on paleo marine records whilst the sparsity of land records limits our understanding of the ism evolutionary process over continental landscapes here we provide paleoclimate reconstructions based on n alkanes and branched glycerol dialkyl glycerol tetraethers brgdgts from a 50 ka lacustrine sediment core collected from lake tengchong qinghai in southwestern subtropical china our results reveal that the botanical sources of sedimentary n alkanes in this lake are mainly from aquatic macrophytes and terrestrial plants the lake level evolution from the mis 3 to the holocene can be divided into four stages high in the mis 3 low in the lgm high in last deglacial and low in mid and late holocene our brgdgts based climate reconstructions indicate that the mean air temperature differences between the present day and the lgm were up to about 3 4 c from mis 3 to holocene there was a broadly and consistently synchronous trend between precipitation and air temperature in this ism region this is different from the asynchronous temperature and precipitation variations in the east asian summer monsoon easm regions in the period of last glacial termination our study shows that the climate in ism regions was primarily driven by changes in june summer solar insolation at 30 n and those glacial boundary conditions such as ice volume and sea surface temperature might also have affected the ism

quaternary landscape evolution and erosion rates for an intramontane neogene basin guadix baza basin se spain abstract the landscape evolution in neogene intramontane basins is a result of the interaction of climatic lithologic and tectonic factors when sedimentation ceases and a basin enters an erosional stage estimating erosion rates across the entire basin can offer a good view of landscape evolution in this work the erosion rates in the guadix baza basin have been calculated based on a volumetric estimate of sediment loss by river erosion since the late pleistocene to do so the distribution of a glacis surface at ca 43 kyr characterised by a calcrete layer that caps the basin infilling has been reconstructed to support this age new radiometric data of the glacis are presented the volume of sediment loss by water erosion has been calculated for the entire basin by comparing the reconstructed geomorphic surface and the present day topography the resulting erosion rates vary between 4 28 and 6 57 m3 ha 1 yr 1 and are the consequence of the interaction of climatic lithologic topographic and tectonic factors individual erosion rates for the guadix and baza sub basins 11 80 m3 ha 1 yr 1 and 1 77 m3 ha 1 yr 1 respectively suggest different stages of drainage pattern evolution in the two sub basins we attribute the lower values obtained in the baza sub basin to the down throw of this sub basin caused by very recent activity along the baza fault

initial stages of laminar calcrete formation by roots examples from the neogene of central spain thin carbonate laminae formed by root activity are common within miocene detrital deposits of the duero and madrid basins the laminae are about 3 cm thick extending several metres laterally and displace the original detrital sediment which ranges in grain size from fine gravel to sandy clay the thickness morphology microstructure and stable isotope compositions of the laminae indicate that they formed by the activities of roots and associated microorganisms within the soil the laminae are similar to those commonly recognised in thick laminar calcrete profiles three types of laminae are recognised differences in the micromorphology of the laminae are explained as reflecting the different organisms involved and whether calcification occurred when the root was alive or decaying the first type occurs in a profile at paracuellos the jarama where the laminae consist of a mosaic of 20 mm calcite crystals whose arrangement indicates that calcification took place in the medulla of the root and probably occurred while the plant was alive in a second type in the villacadima profile laminae comprise calcified root mats whose formation indicates the interplay of roots and fungi calcification of the cell walls and intracellular spaces took place in the cortices of the roots and not in the medullas as revealed by the presence of central pores in every calcified root a third type of lamina is recognised in profiles at vin egra de moran a and consists of mucilaginous sheets coated by needle fibre calcite crystals the occurrence of associated small root casts indicates that formation of the laminae occurred while the root was decaying and was also influenced by fungal activity these laminae occur within poorly developed soils and their formation was controlled by the relationship between sedimentation erosion and soil formation processes thus the occurrence of these laminae interbedded with detrital sediments reflects environments where sedimentation was relatively low and episodic so after the detrital sediment input surfaces were stable and root mats were able to develop renewed sedimentation accounted for the death of the root mats and the development of new ones on the new surfaces where the sedimentation rate is lower the laminae tend to amalgamate and thicker laminar calcrete profiles form with little or no interbedded detrital sediment

lipids of aquatic organisms as potential contributors to lacustrine sediments ii abstract the relationship between the lipid composition of organisms in the water column of an eutrophic lake and the lipid composition of underlying sediments previously examined for n alkanols and steroids is now reported for hydrocarbons ketones and carboxylic acids the n c7 alkane and alkenoic acids from two primary sources are rapidly metabolized in the water column and surficial sediment bacterial biomarkers including hopenes and i ai branched fatty acids were detected in the photosynthetic bacterial layer occurring just above the sediment water interface within the sediment the apparent conversion of free n alkanes alkan 2 ones and hydroxy acids to the corresponding bound form is noted microbiological oxidation of n alkanes to alkan 2 ones is supported by the detection of the intermediate alkan 2 ols with a distribution similar to that of the ketones the geochemistry of sediment deposited c 1900 prior to biological study of the site was interpreted from stable biomarkers and the diagenetic changes recognised in the study of contemporary deposition a qualitative difference in algal input to the older sediment is inferred from the low 7 sterol content and presence of 2 6 10 trimethyl 7 3 methylbutyl dodecane however there was still significant dinoflagellate input as indicated by the presence of 4 methylsterols a difference in higher plant input to the older sediment indicated from the n alkane alkene and triterpenoid ketone distributions is consistent with the recent development of tree cover

paleocene eocene potential source rocks in the avengco basin tibet organic geochemical characteristics and their implication for the paleoenvironment abstract the avengco basin is located in the western part of the tibetan plateau and is similar to the nima basin in the central part of the plateau and the lunpola basin in the eastern part in terms of sedimentary characteristics and tectonic settings which are well known to provide a good source rock potential however the organic geochemical characteristics of the paleocene eocene potential source rocks in the avengco basin have been under debate thirty four marl and mudstone outcrop samples of the niubao formation in the avengco basin were collected and subjected to the following analyses total organic carbon toc rock eval pyrolysis stable carbon isotopes of kerogen gas chromatography gc and gas chromatography mass spectrometry gc ms here we present the results indicating the organic matter of the upper niubao formation is mainly composed of type ii kerogen with a mixed source which is dominated by algae however the lower niubao formation has the less oil prone type ii iii kerogen and the sources of the organic matter are mainly terrestrial plants with less plankton in addition the samples are thermally immature to marginally mature the niubao formation was deposited in an anoxic oxic environment which was brackish with an imperceptible stratified water column the upper niubao formation has a medium to good hydrocarbon generating potential however the lower niubao formation has a zero to poor hydrocarbon generating potential

the early to middle pleistocene boundary in the baza basin spain abstract the continental vertebrate fauna of cullar baza 1 granada spain occur immediately above the matuyama brunhes polarity boundary and therefore represent an initial record for the middle pleistocene all polarity zones for the late pliocene through middle pleistocene are found in an 80 m section which includes this fossil quarry the existing collection of abundant remains of micro mammals macro mammals and lithic artifacts indicating human activity can now be assigned an earliest middle pleistocene age of 0 75 ma another section 25 km across the neogene baza basin also has the matuyama brunhes polarity boundary however in this case the huescar 1 fossil quarry and the puerto lobo sites are both below the polarity boundary thus representing a record of the late early pleistocene at 0 9 ma differences in micro mammal species across these matuyama brunhes boundaries are significant and justify an approximately coincident biostratigraphic boundary between the biharian and toringian stages

dating fluvial terraces by 230th u on pedogenic carbonate wind river basin wyoming abstract reliable and precise ages of quaternary pedogenic carbonate can be obtained with 230th u dating by thermal ionization mass spectrometry applied to carefully selected milligram size samples datable carbonate can form within a few thousand years of surface stabilization allowing ages of quaternary deposits and surfaces to be closely estimated pedogenic carbonate clast rinds from gravels of glacio fluvial terraces in the wind river basin have median concentrations of 14 ppm u and 0 07 ppm 232th with median 230th 232th 270 making them well suited for 230th u dating horizons as thin as 0 5 mm were sampled from polished slabs to reduce averaging of long 105 yr and sometimes visibly discontinuous depositional histories dense translucent samples with finite 230th u ages preserve within rind stratigraphic order in all cases ages for terraces wr4 167 000 6 400 yr and wr2 55 000 8600 yr indicate a mean incision rate of 0 26 0 05 m per thousand years for the wind river over the past glacial cycle slower than inferred from cosmogenic nuclide dating terrace wr3 which formed penecontemporaneously with the final maximum glacial advance of the penultimate rocky mountain bull lake glaciation has an age of 150 000 8300 yr indicating that it is broadly synchronous with the penultimate global ice volume maximum

δ13corg and n alkane evidence for changing wetland conditions during a stable mid late holocene climate in the central tibetan plateau abstract this study has examined bulk and compound specific organic carbon isotopes 13corg and lipid n alkanes of modern plants and a wetland sediment sequence from the central tibetan plateau and explores the usefulness of these two methods for palaeoenvironmental reconstructions results show that a combination of 13corg values and n alkane indices can help differentiate organic matter from c3 terrestrial plant c4 terrestrial plant and submerged macrophytes the three main sources of organic matter in the study area the analyses of total organic carbon 13corg values and n alkane indices for the sediment sequence imply that a wetland habitat was established about 8000 years ago and the wetland conditions were largely stable with dominantly c3 wetland herbs covering the wetland however small fluctuations in the dominant organic matter supply between vascular and aquatic plants are revealed suggesting short duration changes in the extent of open water area within the wetland or variations in the productivity of submerged macrophytes and aquatic plants within the wetland ecosystem which reflects variations in the strength of precipitation and evaporation

hydrocarbon and fatty acid distributions in rostherne lake sediment england abstract hydrocarbon and carboxylic acid distributions in the top 30 cm section of a contemporary lacustrine sediment rostherne mere cheshire england of age 0 150 yr present variations which can be correlated with changes in input of organic material as well as the effects of early diagenesis thus the higher proportions of short chain and branched lipids in the top 0 7 cm sediment section are as expected on the basis of the relatively greater contribution of algal and other microbial matter to the surface sediment layer similarly the increase in the ratio of saturated to unsaturated straight chain acids with depth is in accord with the more facile diagenesis of the unsaturated components acid hydrolysis of solvent extracted sediment afforded lipid fractions featuring a more significant microbial contribution than pre hydrolysis extracts as denoted by the greater abundance of c15 and c17iso and anteiso branched acids also no trend with depth in the ratio of saturated to unsaturated acids was observed for post hydrolysis extracts indicating that bound compounds may be somewhat protected relative to soluble lipids a contribution from petroleum derived hydrocarbons to the sediment apparent from the complex branched cyclic b c alkane distributions decreases with depth and is virtually absent from the 18 30 cm sediment section

holocene monsoonal climate changes tracked by multiproxy approach from a lacustrine sediment core of the subalpine retreat lake in taiwan abstract the aim of this study is to improve the understanding of environmental changes and the linkages with the dynamics of the east asian monsoon eam during the holocene in the western north pacific we analyzed the pollen diatom and weak acid leachable fractions associated with extracted organic compounds of lacustrine sediments retrieved from the subalpine retreat lake in northwestern taiwan during the early holocene 10 100 8600 cal bp cool climate was inferred by the dominance of grass pollen with poor preservation of diatom valves in the record at that time derived biomarkers were also dominated by long chain alkanes originating from herbs the following holocene optimum 8600 6400 cal bp was characterized by a remarkable increase of tree pollen indicating the warmer and humid climate and a stronger summer eam the possible enhanced monsoon driven precipitation resulted in higher contents of total organic carbon buried in sediments however the climate and precipitation of the alpine area in taiwan might have been unstable the high variability of wetland pollen and diatom abundance reveals weak periods of eam during the late holocene optimum 6400 4500 cal bp the hiatus in the deposit during 4500 2100 cal bp suggests the continuously decline of the eam during the last 2100 years dominated wetland plant pollen accompanying stable diatom abundance indicated humid climatic conditions and a stable increase of the eam the climatic condition of study area was similar with modern situation during this late holocene