late pleistocene and holocene vegetation changes in northeastern brazil determined from carbon isotopes and charcoal records in soils abstract northeastern brazil represents a strategic area in terms of quaternary records of environmental changes in south america due to its distinct semi arid climate in near equatorial latitudes in this study carbon isotope and charcoal distribution records in soils are used to characterize vegetation dynamics forest fires and their relation to climate change since the late pleistocene in the states of ceara piaui and paraiba northeastern brazil at the ceara site the carbon isotope record showed an enrichment trend from 24 to 19 during the early mid holocene indicating an opening of vegetation and expansion of savanna vegetation c 4 plants during this period a trend toward more depleted 13 c values 32 in the late holocene indicates an expansion of forest vegetation c 3 plants a similar trend is observed at the piaui and paraiba sites where values of 24 are associated with open forest vegetation during the late pleistocene in the early mid holocene 13 c values of up to 18 0 suggest the expansion of c 4 plants based on the carbon isotope data it is postulated that from 18 000 cal yr b p to 11 800 cal yr b p 10 000 cal yr b p arboreal vegetation was dominant in northeastern brazil and is associated with humid climates the savanna expanded from 10 000 cal yr b p to 4500 3200 cal yr b p due to a less humid drier climatic phase also supported by the significant presence of fires charcoal fragments in the soil from approximately 3200 2000 cal yr b p to the present carbon isotope records suggest forest expansion and a more humid phase these results form part of a regional pattern since they are in agreement with paleovegetation records obtained in regions of maranhao northeastern brazil and in the amazon and rondonia states northern brazil

holocene fire and vegetation changes in southeastern brazil as deduced from fossil charcoal and soil carbon isotopes abstract carbon isotopes of soil organic matter som and radiocarbon dating on charcoal from nine soil profiles collected under native forest vegetation in londrina state of parana anhembi botucatu and jaguariuna sao paulo and salitre minas gerais southeastern brazil were used to evaluate the vegetation changes and to establish the chronology 13 c and 14 c data in som and charcoal respectively indicate that c 4 plants were the dominant vegetation in londrina and jaguariuna during the late pleistocene until middle holocene probably associated with the presence of a drier climate in anhembi and botucatu c 3 plants dominate the landscape during the period a probable mixture of c 3 and c 4 plants occurred in salitre during the holocene this study is part of a main research program related to palaeoenvironmental reconstruction of vegetation and climate in distinct regions of brazil during the last 20 000 years

high resolution record of the environmental response to climatic variations during the last interglacial glacial cycle in central europe the loess palaeosol sequence of dolni věstonice czech republic abstract high resolution multidisciplinary investigation of key european loess palaeosols profiles have demonstrated that loess sequences result from rapid and cyclic aeolian sedimentation which is reflected in variations of loess grain size indexes and correlated with greenland ice core dust records this correlation suggests a global connection between north atlantic and west european air masses herein we present a revised stratigraphy and a continuous high resolution record of grain size magnetic susceptibility and organic carbon 13c of the famous of dolni vestonice dv loess sequence in the moravian region of the czech republic a new set of quartz osl ages provides a reliable and accurate chronology of the sequence s main pedosedimentary events the grain size record shows strongly contrasting variations with numerous abrupt coarse grained events especially in the upper part of the sequence between ca 20 30 ka this time period is also characterised by a progressive coarsening of the loess deposits as already observed in other western european sequences the base of the dv sequence exhibits an exceptionally well preserved soil complex composed of three chernozem soil horizons and 5 aeolian silt layers marker silts this complex is at present the most complete record of environmental variations and dust deposition in the european loess belt for the weichselian early glacial period spanning about 110 to 70 ka allowing correlations with various global palaeoclimatic records osl ages combined with sedimentological and palaeopedological observations lead to the conclusion that this soil complex recorded all of the main climatic events expressed in the north grip record from greenland interstadials gis 25 to 19

application of osl single aliquot and single grain dating to quartz from anthropogenic soil profiles in the se united states abstract reduced luminescence intensity in soils is a widespread phenomenon but is not understood we examine the distributions of equivalent dose d e values of quartz from surface and buried soils from earthen mounds in louisiana where pedoturbation is the likely cause of luminescence resetting we first investigated the effectiveness of optical bleaching in surface samples similar in composition and environment to those at depth resulting d e distributions from the top 10 cm of the topsoils approach 0 gy the concentration of zero age grains decreases rapidly with depth paleosol ages based on low values of the d e distribution demonstrate good agreement with previously published ages we propose a three zone model for the explanation of surface bleaching in which the soil surface is continuously stressed and loaded by subsurface turbation mechanisms creating surface relief surface relief is reduced by subaerial impact and transport forces causing disaggregation and single grain dispersion this results in a surface bleaching zone where soil particles and topography are in constant transition suggesting that many soils may offer frequent and thorough presentation of mineral grains to surface insolation and thus high concentrations of zero dose grains

the loess and coversands of northern france and southern england loess and coversands are widespread on either side of the english channel in southern england loess is generally thin and discontinuous but locally reaches thickness of about 4 m in east kent coversands occur mainly in areas well north of the channel such as parts of east anglia and the southern side of the bristol channel most of the loess and coversand deposits in southern england date from the late devensian cold stage marine oxygen isotope stage mois 2 but there are also a few localised patches of older mainly mois 6 and 12 loess which are the dissected remnants of originally more extensive covers in france loess is widespread and locally very thick up to 12 m especially in northern and northeastern france in normandy and in the somme basin some long records indicate that accumulation began at the end of the lower pleistocene at about 900 ka nevertheless the main accumulations of typical calcareous loess are related to the upper weichselian and upper saalian stages mois 2 and end of mois 3 and mois 6 indeed before about 160 170 ka loess deposition was generally restricted to special sediment traps such as fluvial and marine terraces exposed to the east or northeast these older deposits are characterised by more sandy facies derived from local fluvial sources mainly by northwest to north northwest winds coversands occur locally along the coast of the mont saint michel bay and over the northern part of the seine estuary near le havre the main differences in thickness and extent of the loess deposits between southern england and northern france are linked to their location in relation to the source areas channel and north sea to ice sheets and to the main wind directions northwest to north northwest in france and western england but northeast in eastern england copyright 2003 john wiley sons ltd

rivers and loess the significance of long river transportation in the complex event sequence approach to loess deposit formation abstract rivers are essential for loess deposit formation river systems which relate directly to loess deposit formation include the danube and the rhine the mississippi and the missouri the thames and the medway the indus ganges and brahmaputra the dnepr don and volga the clutha mataura and rakaia new zealand rivers the yellow river rivers in south america siberian rivers flowing north the odra and the wisla between the mountains and the ice the syr darya and amu darya into the desert the contention is that rivers are not just important in major loess deposit formation they are mandatory necessary imperative obligatory essential indispensable requisite for a complete and satisfactory study of a loess deposit we need to know how the material is produced how it is transported and distributed across the landscape how intermediate deposits are formed how transportation provides the defining properties i e open structure collapsibility draping across the landscape and what may happen post deposition e g chernozemisation fragipan formation increased collapsibility etc if rivers are essential then it would appear that the british loess is probably alpine material delivered by the proto rhine and the polish loess is not derived from the ice sheet to the north but from the mountains to the south the lack of loess in canada is explained by the absence of suitable rivers the loess in russia and neighbouring countries can be classified as jefferson et al jefferson i f evstatiev d karastenev d mavlyanova n g smalley i j 2003b the engineering geology of loess and loess like deposits a commentary on the russian literature engineering geology 68 333 351 suggested on the basis of associated rivers a new deposit of glacial loess is recognised associated with the dnepr don and volga rivers the uswr loess the smalley leach smalley i j leach j a 1978 the origin and distribution of the loess in the danube basin and associated regions of east central europe a review sedimentary geology 21 1 26 available from www geo edu ro sgr mod downloads pdf smalley sedgeo 1978 pdf vision of the loess in the danube basin and east central europe is probably misconceived they assigned a great significance to glacial action and put loess in a northern band it appears that this proposed glacial influence is minimal and that the danube loess is essentially mountain loess derived from the alps the carpathians the sudeten mountains and other high regions the danube system is a classic example of a river controlling loess distribution

high resolution chronologies for loess comparing ams 14c and optical dating results the nuxloch loess section in south west germany is famous in central europe for its thick deposits from the last glacial maximum it has therefore been intensively studied during the past few years and offers an excellent opportunity to compare the performance of different dating techniques covering the period 15 45 ka here we present results fromoptical and ams 14 c dating the silt sized polymineral fraction of the clastic sediments and a multiple aliquot approach was used for ir osl dating 14 c dating was carried out on organic macro remnants and humin fractions extracted fromthe sedim ents with the exception of samples taken from the uppermost 1 5 m of the section ir osl and calibrated 14 c ams ages are consistent over the entire period the inconsistencies in the upper meters are thought to be due to disturbances during soil formation in the holocene the good agreement obtained on the remaining sequence demonstrates the high accuracy of both methods when studying loess sections for the ir osl ages no significant age underestimations are obvious the results clearly document that accurate chronologies can be developed for such continental sedimentary sequences this gives access to archives that can now be studied with a high temporal resolution and allows the establishment of new paleoclimatic proxies for the study of terrestrial responses to past climatic changes r 2003 elsevier science ltd all rights reserved

late quaternary vegetation dynamics in the southern amazon basin inferred from carbon isotopes in soil organic matter abstract carbon isotopes of soil organic matter som were used to evaluate and establish the chronology of the vegetation dynamics of an ecosystem presently composed of savannas surrounded by forests the study was carried out on a 200 km transect along highway br 319 on the border of amazonas and rondonia states in southern amazon brazil large ranges in 13 c values were observed in som collected from profiles in the savanna 27 to 14 and forest regions 26 to 19 reflecting changing distribution of 13 c depleted c 3 forest and 13 c enriched c 4 savanna vegetation in response to climate change these results indicate that from about 17 000 to 9000 14 c yr b p the study area was covered by forest vegetation between approximately 9000 and 3000 14 c yr b p savanna vegetation expanded at the expense of the forest although the expansion of savanna did not occur with the same intensity along the study transect this process was very clearly registered by 13 c enrichment in the som since 3000 14 c yr b p the carbon isotope data suggest that forested regions have expanded this study adds to the mounting evidence that extensive forested areas existed in the amazon during the last glaciation and that savanna vegetation expanded in response to warm and dry conditions during the early to middle holocene

pressure solution lithification as a mechanism for the stick slip behavior of faults many major faults including a large fraction of the san andreas appear to be virtually quiescent between great earthquakes the locked sections of the san andreas near san francisco and los angeles have little or no seismic activity on the primary fault trace although secondary faults may be active stick slip behavior on a fault can be explained in terms of a static coefficient of friction which is larger than the dynamic or sliding coefficient in this paper we propose a modification of the friction hypothesis in which chemical lithification cementation occurs on the fault between earthquakes as the stress on the fault increases it becomes large enough to break the cemented bonds between particles causing slip on the fault we treat this problem quantitatively assuming that pressure solution is responsible for the cementation an advantage of this model is that the hydrostatic pressure approaches the lithostatic pressure during cementation so that low fault strengths are predicted

elevated temperature irsl dating of loess sections in the east eifel region of germany abstract it has been shown that the infrared stimulated luminescence signals measured at elevated temperature after an ir stimulation at 50 c post ir irsl are significantly more stable than the conventional irsl at 50 c ir 50 in this study a post ir irsl protocol using a second ir stimulation temperature of 290 c pirir 290 was applied to 17 polymineral fine grain 4 11 m samples from various loess sections in the eifel region wannenkopfe dachsbusch karlich and ariendorf with independent age control to test the reliability of ages using the pirir 290 signal the laboratory measured fading rates are below 1 decade on average for the pirir 290 both ir 50 and pirir 290 signals of 9 samples were found to be in field saturation the average ratio of the sensitivity corrected natural signal to the laboratory saturation level for the pirir 290 is 0 98 0 02 n 9 showing that field saturation is equal to laboratory saturation for the pirir 290 signal from polymineral fine grains from the eifel region minimum equivalent dose estimates were calculated from the characteristic saturation dose of the dose response curves giving minimum ages estimates of 230 420 ka and suggesting that the pirir 290 signal can be used to date loess to 300 ka the pirir 290 ages estimates of the samples from the wannenkopfe and dachsbusch sites are in good agreement with independent age control showing that the irsl dating using pirir 290 signal without fading correction is apparently reliable our data suggest that the loess units e f g and the lower part of h at the karlich site were accumulated 270 ka and that the palaeosol of the karlich interglacial i most likely developed during marine isotope stage mis 9 or earlier the pedocomplex on the top of loess bed ii at the ariendorf section can be correlated with mis 7

evidence of dry and cold climatic conditions at glacial times in tropical southeastern brazil last glacial paleoenvironments have been reconstructed from a pollen and charcoal record analyzed in organic sediments and dated between ca 18 000 and 48 00014c yr b p the site is located near the village catas altas in the lower highland region of southeastern brazil the last glacial landscape was covered by extensive areas of subtropical grasslands and small areas of gallery forests along the rivers where tropical semideciduous forests and cerrado ecosystems exist today the subtropical gallery forests were composed ofaraucariaforest trees such asaraucaria angustifolia podocarpus drimys ilex andsymplocos paleofires were frequent the record indicates that subtropical grassland vegetation which today is found in patches on the highlands in southern brazil especially in the state of santa catarina expanded from southern brazil to southeastern brazil over a distance of more than 750 km from latitudes of about 28 s to at least 20 s the completely different last glacial environment in comparison to the present day environment reflects a dry and cold climate with strong frosts during the winter months temperatures of 5 7 c below those of the present are inferred for the last glaciation

vegetation dynamics during the late pleistocene in the barreirinhas region maranhao state northeastern brazil based on carbon isotopes in soil organic matter abstract the study place is in the barreirinhas region maranhao state northeastern brazil a vegetation transect of 78 km was studied among four vegetation types restinga coastal vegetation cerrado woody savanna cerradao dense woody savanna and forest as well as three forested sites around lagoa do caco located approximately 10 km of the transect soil profiles in this transect were sampled for 13c analysis as well as buried charcoal fragments were used for 14c dating the data interpretation indicated that approximately between 15 000 and 9000 14c yr b p arboreal vegetation prevailed in the whole transect probably due to the presence of a humid climate approximately between 9000 and 4000 3000 14c yr b p there was the expansion of the savanna probably related to the presence of drier climate from 4000 3000 14c yr b p to the present the results indicated an increase in the arboreal density in the area due to the return to a more humid and probably similar climate to the present the presence of buried charcoal fragments in several soil depths suggested the occurrence of palaeofires during the holocene the vegetation dynamic inferred in this study for northeastern brazil is in agreement with the results obtained in areas of amazon region based on pollen analysis of lake sediments and carbon isotope analysis of soil organic matter som implying than similar climatic conditions have affected these areas during the late pleistocene until the present

the late pleistocene loess deposits and palaeosols of eastern belgium new tl age determinations fourteen samples from the pleistocene loess exposures at kesselt belgian limbourg have been dated with the thermoluminescence method using the regeneration technique and a double analysis with two types of blue transmittant filters reproducible age estimates were obtained up to about 130 140 ka for the basal part of the late weichselian brabant loess and the underlying cryorurbated nagelbeek horizon we arrived at ages of 20 22 ka which is consistent with the radiocarbon age of this horizon 22 3 ka our tl dates further constrain the formation of a lower luvisol profile the bt horizon of which has been correlated with the rocourt palaeosol to the period 50 60 ka these dates however may overstimate the true age of the sediment because they were obtained on reworked loess they indicate that this palaeosol was formed during a middle weichselian interstadial and not during the eemian as is generally accepted the boundary between the weichselian and the older loess is situated at a lower level in the kesselt profile the loess bracketing the deeper tundra gleysols yielded tl ages up to 130 140 ka and the ages further rapidly increased with depth indicating that the sediments may even be much older than saalian 1998 john wiley sons ltd

south and southeast brazilian grasslands during late quaternary times a synthesis fourteen pollen records from the south s and the southeast se brazilian regions have been synthesised late glacial records from s brazilian highlands document the predominance of grassland campos where today araucaria forests occur records from se brazil show that during pre and full glacial times modern tropical semideciduous forest and cerrado savanna to dry forest were mostly replaced by grassland and some subtropical gallery forest modern montane araucaria forests and cloud forests in se brazil were mostly replaced by grassland during pre and full glacial times there is evidence that the modern tropical atlantic rainforest in s brazil was significantly reduced and replaced by cold adapted forest taxa or grassland during glacial especially during full glacial times the synthesis indicates that grasslands dominated the s and se brazilian landscape during the late pleistocene where today different forest ecosystems exist grassland extended over 750 km from s to se brazil from latitudes of about 28 27 s to at least 20 s these results indicate that climates in the region were markedly drier and 5 7 c cooler during glacial times antarctic cold fronts must have been much stronger and more frequent than today studies from s brazil show that huge areas of late pleistocene campos vegetation were still found on the s brazilian highlands during early and mid holocene times reflecting dry climatic conditions with an annual dry period of probably 3 months modern wet climatic conditions with no or only short dry periods were not established until the late holocene period when araucaria forests replaced large areas of grassland vegetation after about 3000 14c yr b p and especially after 1500 1000 14c yr b p

osl chronologies of paleoenvironmental dynamics recorded by loess paleosol sequences from europe case studies from the rhine meuse area and the neckar basin abstract loess paleosol sequences lps represent an important terrestrial archive for the reconstruction of the paleoenvironmental evolution during the last glacial cycle in europe in the rhine meuse area and the southwestern germany there are only few numerical ages determined with state of the art luminescence methods which limits the robustness of established chronostratigraphies this study presents a comparative dating approach using quartz and feldspar post infrared pirir 290 optically stimulated luminescence osl from fine and medium grained samples of five loess paleosol sequences paleoenvironmental dynamics are reconstructed by high resolution grain size analysis the osl ages are evaluated as being robust and consistent with other records furthermore we show that ages for hillslope deposits are sometimes overestimated due to low frequency high magnitude erosive processes the integration of osl ages stratigraphy and high resolution grain size data contributes to a temporal more complete data record from western and central europe secondly we propose a combined stratigraphic model for lps of the last glacial cycle which is developed and discussed in the context of other key sites such as havrincourt schwalbenberg ii tonchesberg nussloch and dolni v stonice comparable chronologies and patterns in proxy data between sites with a large spatial distance suggest a possible semi synchronous response to climatic changes in europe by combining our data with the eifel laminated sediment archive elsa and the ngrip ice core a relationship of loess archives and large scale climatic signals is discussed and a proxydata based event stratigraphy is developed this model refines existing chronostratigraphic models and contributes to solve open discussion concerning the timing and demarcation of sedimentary units and sequences from for western and central europe

the chronological position of the lohne soil in the nussloch loess section re evaluation for a european loess marker horizon abstract the loess section of nussloch in southwestern germany is a key profile for the reconstruction of the terrestrial palaeo environment of central europe at the time of the last glacial and interglacial recently the significance of the site for palaeo environmental and geoarchaeological research increased additionally with the discovery of unique palaeolithic cultural remains from anatomically and culturally modern humans that invaded southwestern germany during the weichselian wurmian pleniglacial period at nussloch a chrono stratigraphical key position is taken by a middle pleniglacial cambisol remain which under the designation lohne soil serves as an important pedostratigraphic marker horizon for the greater area repeatedly greenland interstadial gis 8 was suggested as a likely period of soil formation for the lohne soil this interpretation is yet not justified on the basis of published chronometric data critical assessment of the data points to a later period of soil formation likely during gis7 to gis5 this conclusion is supported by a new set of radiocarbon ages for the nussloch site which are presented here for the first time consequences of a revised chronology for correlations of pleniglacial cryosols below and above the lohne soil with greenland interstadials are discussed the implications are important for european loess research as the nussloch section serves as a reference base for loess sections throughout europe

late pleistocene landscape dynamics in saxony germany paleoenvironmental reconstruction using loess paleosol sequences abstract loess archives are of paramount importance for reconstructing regional paleoenvironmental conditions of past glacial periods the saxonian loess region is an area of transition between the western and the eastern european loess belt with this contribution a documented loess paleosol composite profile for the saxonian loess region is extended and a new chronostratigraphy established by high resolution osl dating of two profiles is described in addition for the first time osl age estimates for the loess paleosol sequence at seilitz are presented for the quartz and polymineral fine grain fraction based on the presented composite profile climatic and environmental conditions e g wind speed temperature are deduced based on high resolution osl dating it is possible to identify a hiatus spanning ca 30 ka this gap is located in the gleina complex where an underlying layer shows an age of ca 60 ka and the upper layer an age of ca 30 ka additionally two periods of strong loess accumulation with ages of ca 70 60 ka and 30 18 ka could be identified there is a general trend of grain size coarsening up towards the late glacial which shows a maximum at ca 21 ka correlations with french western german and polish loess sections are discussed

our oldest children age constraints for the krems wachtberg site obtained from various thermoluminescence dating approaches abstract we present several approaches to directly date the prehistoric human activity of lighting a fire at the early gravettian infant burial site of krems wachtberg austria by thermoluminescence tl methods blue thermoluminescence b tl from polymineral fine grain and orange red thermoluminescence r tl from fine grained quartz separates both extracted from the baked loess immediately underlying the hearth were employed the b tl dating followed the classic multiple aliquot additive dose maad protocol for r tl dating the multiple aliquot regenerative mar and a shortened single aliquot regeneration sar protocol were tested all thermoluminescence ages obtained agree within 1 uncertainties and assign a weighted mean age of 33 9 2 3 ka to the last use of the hearth and by inference to the infant burial anomalous fading is precluded due to the agreement of results from all luminescence protocols as well as with independent dating methods the tl ages are consistent with calibrated radiocarbon ages on associated charcoal osl dating of the sediment deposition and with age estimates obtained by two magnetic dating approaches

from the semiarid landscapes of southwestern usa to the wet tropical zone of southeastern brazil reflections on the development of cuestas pediments and talus abstract classical geomorphological models consider that escarpment retreat of cuesta landforms is fastest in arid and semiarid regions which would be expected to lead to increased talus production however this is in disagreement with the piedmont zone of the colorado plateau cliffs arid semiarid region of southwestern usa where talus is as inconspicuous as the deposits of the cuesta escarpment footslopes of the parana basin wet tropical region of southeastern brazil thus this paper discusses the evolutionary processes of cuesta escarpments pediments and piedmont deposits in both wet tropical regions and arid zones considering the key areas of the serra geral ridge in the parana basin and the eastern central colorado plateau as examples this manuscript constitutes a comprehensive and critical review of the principal literature on the landform development of such regions research has revealed that despite the production of sediment fine coarse from the escarpments in the arid southwestern usa geochemical weathering and freeze thaw cycles quickly destroy talus deposits furthermore chemical weathering dissolves minerals and forms caverns within the rock walls of mesas and in amphitheaters and canyons influencing escarpment retreat directly despite mechanical processes being the most important factors controlling landform development on the other hand in regions characterized by the wet tropical climate of brazil geochemical processes are more intense and they destroy the talus very quickly enhancing deep weathering however mechanical morphogenesis is also frequent in such regions forming in deforested areas features very similar to those found in the badlands of dry zones chemical and physical mechanical processes have very different intensities in dry arid and wet tropical areas but these processes are very relevant to landform development in both environments the rates of escarpment retreat are higher in the dry areas of the colorado plateau than estimated for the brazilian tropical zones which is in accordance with classical models these variations are probably related not only to climate but also to lithological differences the tops of the mesas on the colorado plateau are supported by thin strongly cemented conglomeratic fluvial sandstones whereas the caprocks of the brazilian cuesta landforms comprise thick basalt flows capped by ferruginous cuirasses in some cases lithological characteristics are more important than climate regarding escarpment retreat

optical dating studies of quartz and feldspar sediment extracts abstract continuing developmental work into optical dating has led to some clarification of the optical behaviour of quartz and feldspar sediment extracts we have verified the key assumption intrinsic to the method that the optical signal is zeroed completely upon exposure to daylight we also show that the rate of zeroing in optical dating is much more rapid than it is in tl dating studies concerned with the extraction of the thermally stable signal from laboratory irradiated samples showed that problems may arise from medium to high temperature preheating of young samples optical alternatives to thermal stabilization were tested using dye and krypton lasers using a krypton laser we have succeeded in obtaining an equivalent dose of 0 0 0 7 gy for the quartz from a modern intertidal sand and an average dose of 120 22 gy for the feldspar extract of a 70 ka sand unit both were obtained using six wavelengths from the infrared to the violet and no dependence on wavelength was found we found that the photon energies of infrared and deep red light can stimulate luminescence in unirradiated quartz and feldspar extracts of sediments this was not expected and suggests that the process of trap emptying is more complex than we had envisioned but implies a far greater than expected degree of technical flexibility for the optical dating method

cenozoic uplift and erosion of structural landforms in ne brazil abstract we investigate the evolution of uplifted areas in ne brazil which have been considered as residual landforms the study focuses on the 130 km long 41 km wide pereiro massif pm the structural control and the age of this uplift are the problems addressed in this study we carried out topographic analysis geomorphological and geological mapping detailed structural analysis and optically stimulated luminescence osl dating to address these problems the pm is bounded and cut by a system of steeply dipping normal and strike slip faults which control the morphology of the massif and associated sedimentary basins the maximum uplift rate of the pm is 34 m my 1 as constrained by the age of flat topography capped by miocene laterite which represents the previous peneplain subsequently uplifted by ca 600 m the minimum uplift rate is 13 m my 1 as constrained by fission track dating of differential crustal block movements across a nearby fault in the quaternary erosion occurred mainly by fault controlled scarp retreat under semi arid conditions with the formation of colluvial deposits along fault scarps and alluvial deposits in the low plains these deposits are now dated between 46 and 0 4 ka with a peak in sediment deposition in the pleistocene holocene transition it is concluded that the pm is a system of horsts and grabens that have been active in the cenozoic

microbial biofacies and the influence of metazoans in holocene deposits of the lagoa salgada rio de janeiro state brazil

late quaternary vegetation climate and fire history from the tropical mountain region of morro de itapeva se brazil late quaternary paleoenvironments have been interpreted from a 35 000 yr b p pollen and charcoal record from morro de itapeva 22 47 s 45 32 w 1850 m a s l in the se brazilian highlands changes in taxa composition and elevational shifts in high elevation grassland campos de altitude araucaria forest cloud forest and atlantic rain forest all of which can be found in the study area today indicate climatic changes in the past expanded high elevation grasslands absence of araucaria forest cloud forest and atlantic rain forest during the recorded last glacial period ca 35 000 17 000 yr b p suggest a climate markedly cooler and drier than today development of a sphagnum peat bog rare presence of araucaria forest taxa and existence of a narrow cloud forest and rain forest belt at lower elevations during the late glacial period 17 000 ca 10 000 yr b p indicate a change to a cool and somewhat moister climates during the early holocene cloud forest developed close to the study site reflecting a warm and moist climate on the east facing slopes but a drier climate on the highland plateau evidenced by the rare presence of araucaria and podocarpus only during the late holocene moisture increases in the highlands suggested by the higher frequency of araucaria and podocarpus fires were more frequent during the last glacial than during the holocene

the synchronization of palaeoclimatic events in the north atlantic region during greenland stadial 3 ca 27 5 to 23 3 kyr b2k two high resolution marine sediment cores located 83 km apart in the ne atlantic have been studied md95 2006 barra fan 57 01 82 n 10 03 48 w 2120 m water depth and md04 2822 rockall trough 56 50 54 n 11 22 96 w 2344 m water depth the records are anchored to the ngrip ice core stratigraphy and gicc05 chronology by the presence of geochemically characterized fugloyarbanki tephra and further tested by radiocarbon age control replicated sea surface temperature sst records show evidence for an abrupt and short lived warming within greenland stadial gs 3 to which we tentatively assign an age of ca 25 6 24 8 kyr gicc05 b2k based on these and another marine palaeoclimate record link17 from the faroe shetland channel we propose a new three fold event stratigraphy for gs 3 within the north east atlantic region the recognition of this warming event within gs 3 in ne atlantic sst records demonstrates that such events may not readily be identified within the coldest stadials of the greenland ice cores highlights the need for carefully constructed event stratigraphies independently tested by the use of tephra isochrones and radiocarbon and illustrates pervasive millennial scale climate variability of the north atlantic region dansgaard oeschger d o events is deeply embedded in the dynamics of atlantic meridional overturning circulation amoc

luminescence chronology of the loess record from the tonchesberg section a comparison of using quartz and feldspar as dosimeter to extend the age range beyond the eemian abstract the loess palaeosol sequences of the tonchesberg section located in the east eifel volcanic field germany provide an excellent climate archive of the late middle and the upper pleistocene in the middle rhine area loess deposits from the last glacial weichselian and the penultimate glacial saalian are up to 12 m and 15 m thick respectively and intercalated by palaeosols optically stimulated luminescence osl thermally transferred optically stimulated luminescence tt osl and infrared stimulated luminescence irsl measurements were carried out on 14 samples from the tonchesberg section to determine the deposition age and to set up a more reliable chronological framework for the penultimate and last interglacial glacial cycle the fine grained quartz osl and polymineral irsl ages are in good agreement with each other and also with the geologically estimated age but the quartz tt osl ages are overestimated the osl and irsl ages range from 16 8 1 2 to 189 16 ka indicating that the youngest loess and the weakly developed soils were deposited during marine isotope stage mis 2 and 3 and that the two marker loess were most likely accumulated in the transition mis 4 5 loess and reworked loess postdating the eemian soil yield ages of 110 115 ka indicating that these deposits very likely correlate to mis 5d loess deposits taken below the eemian soil are attributed to the transition mis 6 7 a weakly developed soil above the tonchesberg scoria yield an age of 189 16 ka indicating an interstadial soil formation during mis 7 this is in good agreement with preliminary 40ar 39ar ages for the tonchesberg scoria and the intercalated tephra layers reliable age estimates up to 70 ka could be obtained using quartz osl and up to 190 ka using the pulsed post ir ir signal from feldspar hence the infrared stimulated luminescence irsl is considered as the best approach to date the loess from the middle rhine area 70 ka

last glacial maximum lgm vegetation changes in the atlantic forest southeastern brazil abstract this study was carried out in a continental atlantic forest located in the southern region of sao paulo state southeastern brazil the aim of the study was to evaluate the vegetation dynamics in 70 km forest ecosystem transect that occurred during the late pleistocene and holocene in this region using the stable carbon isotopes 13 c analysis on soil organic matter som and the 14 c dating of buried charcoal fragments and the humin fraction of som the isotope data 13 c of som in the deeper horizons indicating the presence of more open vegetation than the present with a probable mixture of c 3 and c 4 plants suggesting the presence of a drier climate in the period of 20 ka to 16 14 ka bp from 16 to 14 ka bp to the present a significant predominance of c 3 plants was observed indicating an expansion of the forest probably associated with the presence of a more humid climate than the previous period the results indicated the presence of open vegetation during the late glacial probably associated with a drier period also observed in other regions of brazil the atlantic forest ecosystem seems to have developed at least since the early holocene in southeastern brazil

a continuous high resolution dust record for the reconstruction of wind systems in central europe eifel western germany over the past 133 ka 1 the last glacial cycle in central europe is dominated by processes of aeolian dust transport and accumulation these dust deposits are preserved in soils and lake sediments and provide detailed information about the climate variability during cold and dry periods especially the transitions from warm into cold periods are characterized by turbulent climate conditions the main problems of terrestrial paleoclimate reconstructions are the completeness of the core material and a sampling resolution to detect single dust storms we use a particle detection method which allows high resolution sub annual analyses of sediment structures in undisturbed samples the elsa eifel laminated sediment archive stack is a compilation of four different lake sediment cores of the eifel region western germany and comprise the period of the last 133 ka the results of our analyses show high frequencies of dust storm events during the first cold events c24 and c23 after the last warm stage in opposition the coldest periods of the last glacial cycle ois 4 70 60 ka bp and ois 2 35 14 ka bp are characterized by stable climate conditions that provide the accumulation of homogenous dust sediments

a stratigraphic framework for abrupt climatic changes during the last glacial period based on three synchronized greenland ice core records refining and extending the intimate event stratigraphy due to their outstanding resolution and well constrained chronologies greenland ice core records provide a master record of past climatic changes throughout the last interglacial glacial cycle in the north atlantic region as part of the intimate integration of ice core marine and terrestrial records project protocols have been proposed to ensure consistent and robust correlation between different records of past climate a key element of these protocols has been the formal definition and ordinal numbering of the sequence of greenland stadials gs and greenland interstadials gi within the most recent glacial period the gs and gi periods are the greenland expressions of the characteristic dansgaard oeschger events that represent cold and warm phases of the north atlantic region respectively we present here a more detailed and extended gs gi template for the whole of the last glacial period it is based on a synchronization of the ngrip grip and gisp2 ice core records that allows the parallel analysis of all three records on a common time scale the boundaries of the gs and gi periods are defined based on a combination of stable oxygen isotope ratios of the ice 18o reflecting mainly local temperature and calcium ion concentrations reflecting mainly atmospheric dust loading measured in the ice the data not only resolve the well known sequence of dansgaard oeschger events that were first defined and numbered in the ice core records more than two decades ago but also better resolve a number of short lived climatic oscillations some defined here for the first time using this revised scheme we propose a consistent approach for discriminating and naming all the significant abrupt climatic events of the last glacial period that are represented in the greenland ice records the final product constitutes an extended and better resolved greenland stratotype sequence against which other proxy records can be compared and correlated it also provides a more secure basis for investigating the dynamics and fundamental causes of these climatic perturbations

impact of mid to late holocene precipitation changes on vegetation across lowland tropical south america a paleo data synthesis a multi proxy paleo data synthesis of 110 sites is presented exploring the impact of mid to late holocene precipitation changes upon vegetation across southern hemisphere tropical south america we show that the most significant vegetation changes occurred in southwest amazonia and southeast brazil regions reliant on precipitation derived from the south american summer monsoon sasm a drier mid holocene in these regions linked to a weaker sasm favored more open vegetation savannah grasslands than present while increased late holocene precipitation drove expansion of humid forests e g evergreen tropical forest in southwest amazonia araucaria forests in southeast brazil the tropical forests of central western and eastern amazonia remained largely intact throughout this 6000 year period northeastern brazil s climate is antiphased with the rest of tropical south america but a lack of paleo data limits our understanding of how vegetation responded to a wetter drier mid late holocene from this paleo data perspective we conclude that ecotonal forests already close to their climatic thresholds are most vulnerable to predicted future drought but the forest biome in the core of amazonia is likely to be more resilient of greater concern are widespread deforestation and uncontrolled anthropogenic burning which will decrease ecosystem resilience making them more vulnerable than they might be without current anthropogenic pressures

the evolution of a tropical rainforest grassland mosaic in southeastern brazil since 28 000 14c yr bp based on carbon isotopes and pollen records the lack of paleoecological records from the montane atlantic rainforest of coastal brazil a hotspot of biological diversity has been a major obstacle to our understanding of the vegetational changes since the last glacial cycle we present carbon isotope and pollen records to assess the impact of the glaciation on the native vegetation of the serra do mar rainforest in sao paulo brazil from ca 28 000 to 22 000 14c yr bp a subtropical forest with conifer trees is indicative of cool and humid conditions in agreement carbon isotopic data on soil organic matter suggest the presence of c3 plants and perhaps c4 plants from 28 000 to 19 000 14c yr bp the significant increase in the sedimentation rate and algal spores from 19 450 to 19 000 14c yr bp indicates increasing humidity associated to an erosion process between 19 000 and 15 600 14c yr bp from 15 600 14c yr bp to present there is a substantial increase in arboreal elements and herbs indicating more humid and warmer climate from 19 000 to 1000 14c yr bp 13c values indicated the predominance of c3 plants these results are in agreement with studies in speleothems of caves which suggest humid conditions during the last glacial maximum

late quaternary vegetation and coastal environmental changes at ilha do cardoso mangrove southeastern brazil abstract a 190 cm mangrove sediment core from the ilha do cardoso state park state of sao paulo southeastern brazil was analyzed for pollen diatoms as well as carbon and nitrogen isotopes the goal was to determine the dynamics of the coastal terrestrial aquatic ecosystems vegetation history and climate change in this region of the brazilian atlantic rainforest during the late pleistocene and holocene the values for total organic carbon toc from 3 up to 40 c n ratios from 10 up to 130 and 15n 0 to 8 are associated with well preserved aquatic and terrestrial organic matter and possibly influenced by nitrogen cycling e g denitrification that caused 15n enrichment between 40 000 cal yr b p and 23 000 cal yr b p depleted 13c values 28 0 are also observed and indicate the predominance of c3 plants during this time interval the pollen analysis reveals the presence of the genera ilex alchornea weinmannia myrsine symplocos drimys and podocarpus on a site currently occupied by mangrove vegetation these data suggest that in the past prevailed a colder and more humid climate than today with a low relative sea level from 23 000 cal yr b p to 2200 cal yr b p a sedimentary hiatus likely occurred related to an erosive event associated to the post glacial sea level rise since at least 2200 cal yr b p sediments are marked by relatively low c n ratios from 2 to 27 exhibit more enriched 13c from 26 0 to 24 0 and 15n up to 7 values and are characterized by the presence of marine diatoms this indicates the return of the marine coastal line to its current position and consequently the development of mangrove

dust deposition and climate in the carpathian basin over an independently dated last glacial interglacial cycle dust deposition and climate in the carpathian basin over an independently dated last glacial interglacial cycle

link between european and north atlantic abrupt climate changes over the last glaciation 1 sub millennial timescale climate variations correlated with those in the north atlantic area are identified in the loess sequence from nussloch germany exceptionally developed over the interval between about 38 000 and 18 000 years ago the dansgaard oeschger do events 8 to 2 as well as some less pronounced warming episodes recorded in the greenland ice have their counterpart in the nussloch loess stratigraphy and in the variations of the loess grain size index gsi the north atlantic heinrich events 3 and 2 are expressed at nussloch as maxima of the gsi record the similarity of the fine variations in the nussloch loess and the greenland ice records points to an intimate link of climate changes in western europe with those in the north atlantic

particle size characteristics of suspended sediment in hillslope runoff and stream flow this study examines the particle size characteristics of hillslope soils and fluvial suspended sediments in an agricultural catchment samples of surface runoff and stream flow were collected periodically and analysed for the size distributions of the effective undispersed sediment this sediment was subsequently dispersed and the ultimate size distributions determined the median effective particle size of stream suspended sediment was considerably coarser than the median ultimate particle size indicating that most of the load included a substantial proportion of aggregates moreover the proportion of fine material i e silt and clay increased and the proportion of sand sized material decreased with increasing discharge this decrease in sediment size with increased flow which is contrary to the traditional assumption of a positive discharge particle size relationship is thought to reflect i the influx of silt and clay predominantly the former originating on the catchment slopes and brought to the stream by overland flow along vehicle wheelings roads and tracks and ii erosion of fine material from the channel bed and banks during large storms however the proportion of sand sized sediment increased during the rising limb of the hydrograph as a result of the entrainment of coarser source material from the valley floor during overbank flooding the stream suspended sediment was finer than the catchment soils and considerably finer than material eroding from the catchment slopes during storms the degree of clay and silt enrichment in the suspended sediments was largely the result of preferential deposition of the coarser fraction during the transport and delivery of sediment from its source to basin outlet the data from this study confirm that a significant mode of sediment transport in fluvial systems is in the form of aggregates and that the dispersed sediment size distribution is inappropriate for determining the transportability of sediment by flow 1997 by john wiley sons ltd