quaternary reactivation of a basement structure in the barreirinhas basin brazilian equatorial margin the pirapemas lineament is a remarkable 200 km long ne sw trending structure in the barreirinhas basin one of the several brazilian coastal basins this lineament splits the study area in two sectors of distinctive morphology drainage patterns and sedimentary covers terrain northward of the lineament presents a smooth topography with sub parallel to sub dendritic drainage patterns whereas a dissected plateau characterized by incised valleys and rectangular drainage pattern occurs southward suggesting a structural control by joints and faults geological field data crossed with thermal luminescence tl and optically stimulated luminescence osl dating revealed that the surface southward of the lineament consists mostly of miocene and late pleistocene sedimentary deposits represented by the barreiras formation and the post barreiras sediments respectively in contrast relatively younger sands mantle most of the northward terrain as indicated by well preserved paleodune deposits that grade into active aeolian dunes of the lencois maranhenses national park geomorphological and geological data analysis suggests that the northern sector is under the effect of subsidence proving that the pirapemas lineament is an active agent modeling the landscape in the region geophysical data gravity and seismic confirm that such a structural feature is the surface expression of an active deep seated basement fault

late pleistocene holocene climatic and vegetational history of the brazilian caatinga the fossil dunes of the middle sao francisco river palynological studies of a peat bog sequence with a basal date of 10 990 80 yr b p provide a history of vegetational and climatic changes in the icatu river valley located inside a large system of stabilized sand dunes at the middle sao francisco river at 10o24 0 s 43o13 0 w in northeastern brazil the present day vegetation of the valley is vereda a mauritia vinifera palm swamp forest bordered by a narrow strip of semi deciduous tropical forest the adjacent dunes are stabilized by arboreal caatinga and cerrado vegetation in some areas the palynological profile of the saquinho locality within this valley was divided into five pollen zones zone sa1 10 990 10 540 yr b p contains pollen of taxa found in present amazonian and atlantic forests as well as from montane taxa thus suggesting very humid climatic conditions synchronous with more reduced temperatures zone sa2 10 540 6790 yr b p has pollen spectra from a vegetation type dominated by mauritia suggesting progressive warming and high humidity levels the period between 8920 and 8910 yr b p has rapid sedimentation rate few thermoluminescence tl dates pronounced increase of mauritia and ilex pollen suggesting a very moist climate from 8910 to 6790 yr b p there is a progressive decline in forest taxa and a gradual increase of caatinga and cerrado taxa on the landscape zone sa3 6790 ca 6230 yr b p does not contain palynomorphs possibly indicating semi arid conditions zone sa4 ca 6230 ca 4535 yr b p marks the return of mosaic vegetation composed of gallery forest cerrado and caatinga taxa indicating moister climatic conditions a marked decline in moisture levels characterizes the period between 4240 yr b p and present as suggested by an increase in caatinga and cerrado species and a decline in gallery forest taxa zone sa5 ca 4535 yr b p present establishes the present vegetational and climatic pattern of the icatu river valley 1999 elsevier science b v all rights reserved

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

amazonia during the last glacial abstract new data on the vegetational history and quaternary geology of amazonia permit an improved reconstruction of past environments in amazonia during the last glacial period although limited data from rondonia carajas and guyana show that in certain areas savanna type vegetation and savanna forest had replaced the rain forest during the late pleniglacial ca 22 000 13 000 yr b p the amazonian forest may have been split up into one major west amazonian and several other medium size forest areas this suggests a decline in rainfall of 500 to 1000 mm a reduction of 25 to 40 temperatures may also have been 2 to 6 c 4 2 c lower than today possibly substancially influencing amazonian vegetation during the humid middle pleniglacial 55 000 26 000 yr b p rivers carried a lot of water and sediment resulting in the deposition of lower terrace sediments with one dry interruption around 40 000 yr b p carajas and katira in carajas there is evidence of dry periods ocurring at about 40 000 yr b p and during the early pleniglacial ca 60 000 yr b p rivers carried little water and incised into the low terrace sediments during the dry late pleniglacial water levels rose during the late glacial 13 000 10 000 yr b p or at the beginning of the holocene 10 000 yr b p sedimentation in and of the present inundation valleys commenced after that

late glacial cooling in amazonia inferred from pollen at lagoa do caco northern brazil new pollen data from a core at lagoa do caco maranhao state brazil 2 58 s 43 25 w 120 m elevation show higher frequencies of podocarpus at the end of the pleistocene than today the increase in podocarpus which follows the successive increase of various pioneer species such as didymopanax melastomataceae combretaceae and cecropia implies a progressive late glacial increase of moist and cool climatic conditions a comparable increase in podocarpus is found in other lowland records in amazonia a review of published pollen data from amazonia suggests that the moisture source was from the southeast by contrast present day moisture comes from the tropical atlantic and from the amazon basin with its convective precipitation the likely cause for the southeastern moisture source between ca 15 000 and 14 500 cal yr b p was enhanced polar antarctic advection that reached low latitudes and maintained year round the meteorological equator in its austral winter position at northern latitudes or reduced drastically its southward summer displacement this hypothesis is consistent with marine and ice core records

late pleistocene holocene evolution of the doce river delta southeastern brazil implications for the understanding of wave influenced deltas abstract brazil s coast displays many wave influenced deltas that are still incompletely understood despite their significance for reconstructing the history of late pleistocene holocene sea level changes in this region and the potential to advance in the knowledge of wave influenced deltas among them the doce river delta is the most expressive given its larger geographic extension the present work shows that this is a wave influenced delta that evolved within the context of late pleistocene holocene sea level fluctuations rather than a mid holocene lagoonal delta as proposed elsewhere the delta had an initial progradation at an osl age of 132 7 9 1 ka after the marine isotope stage mis 5e which was followed by major progradation between 45 775 49 391 and 29 678 29 226 cal yr bp beach ridges spits formed during these phases were in part destroyed during an ensuing transgression between 8161 7933 and 4974 4850 cal yr bp the central delta remained dominated by fluvial processes which kept pace with the rising sea level due to relatively high rainfall in the doce river drainage basin the doce river delta started to grow again after the late holocene transgression a process still on going at the present time during this evolution the doce river was deflected northward and then southward a process that did not result in any significant facies change when the updrift and downdrift sides of the river s mouth are compared such a pattern is in disagreement with previously proposed asymmetry index models for wave influenced deltas which predict an uneven distribution of sandy or muddy rich deposits in the updrift and downdrift sides of the river s mouth respectively several other deltas along the brazilian coast also display facies configuration similar to the doce river delta or have patterns opposed to those proposed by the asymmetry index models based on these analogs it can be stated that the geometries and facies patterns of wave dominated deltas are not determined simply by the interplay of fluvial and marine processes instead they can be strongly influenced by the fluvial influx sea level changes and or tectonic reactivations as it appears to be the case of brazilian wave influenced deltas including the doce river delta such a conclusion calls for a word of caution when applying processes based facies models to reconstruct wave influenced deltas in the sedimentary record

tropical climates in the game of two hemispheres revealed by abrupt climatic change the climatically sensitive equatorial regions provide important information for evaluation of the phasing between high and low latitude climate variability a high resolution pollen record from northern brazil demonstrates a significant abrupt and rapid environmental change associated with the northern hemisphere younger dryas temperature reversal this finding is consistent with the model in which the younger dryas had a stronger influence on temperature in the northern hemisphere than south of the equator because of the larger temperature gradient between pole and equator in the northern hemisphere than in the southern hemisphere one consequence of the younger dryas changes would be the location of the intertropical convergence zone in a southern position so that even tropical regions would have been under arctic influence

the last 50 000 years in the neotropics southern brazil evolution of vegetation and climate abstract in the lagoa campestre lake of salitre 19 s 46 46 w 970 m elev there are plant taxa belonging to many ecological groups that are encountered nowhere else at this latitude frequent incursions of polar advections causing cooling and humidity a cool and foggy climate in the middle of the depression and warmer temperatures on the surrounding slopes help to maintain all these groups within a fairly restricted area late pleistocene holocene climatic change has had a considerable impact on the flora and vegetation of salitre the pollen record of the 6 m deep core lc3 shows how cold forest trees such as araucaria angustifolia and drimys brasiliensis semi deciduous forest halophytic plants and peat bog started to develop on this site the initial period between c 50 000 and 40 000 yr b p was an arid phase not recorded in any other neotropical lowland site it was followed by a period of high moisture levels 40 000 to 27 000 yr b p with a maximum estimated at c 35 000 yr b p the late glacial maximum is missing because of a gap in sedimentation humidity gradually increased during the late pleistocene between 16 000 and 11 000 yr b p the early holocene 9500 to 5000 yr b p is characterized by a more marked seasonal pattern and higher temperatures reaching a maximum c 5000 yr b p the spread of semi deciduous forest between 4000 and 3000 yr b p attests to a return of humidity comparison with the serra negra section 19 s 46 45 46 w 1170 m elev not far from salitre confirms the high moisture rates recorded at c 35 40 000 yr b p although temperatures were cooler at the altitude of serra negra as is attested by the presence of araucaria forest and also confirms the strong impact of polar advections on the climate of southeastern brazil

non tectonic liquefaction induced large surface displacements in the aso valley japan caused by the 2016 kumamoto earthquake revealed by alos 2 sar abstract we constructed and analyzed full 3 d ground surface displacement field associated with the 2016 kumamoto japan earthquake using satellite radar images from alos 2 displacements reflect not only tectonic crustal deformation caused by main earthquake faults but also non tectonic surface deformations the largest deformations in the earthquake sequence were found in the aso valley along the nw outer rim of the mt aso caldera large independent surface deformations occurred in three areas with diameters of 500 m 2 km in the aso valley and each area was horizontally displaced by more than 2 m to the nnw these areas are underlain by thick lake bottom deposits of saturated silt with low penetration resistance as the direction of the displacements was parallel to the ground slope in each area the strong seismic motion of the earthquake most probably induced liquefaction in the lake bottom deposits and the ground surface slid horizontally along the slope on the liquefied silt because the areas of the large displacements are closely related to the thickness and shape of the lake bottom deposits amplification of the seismic wave in these deposits likely contributed to the liquefaction a seismograph installed at the aso valley recorded co seismic movement within several seconds of the main shock indicating a possibility of the strong seismic motion amplifying the horizontal displacement of this area on the sse side of the deformed areas numerous graben like ruptures developed as these ruptures are caused by surface tension during the large horizontal displacement they are not earthquake fault traces and the process of this deformation is non tectonic

surface deformation and coherence measurements of kilauea volcano hawaii from sir c radar interferometry the shuttle imaging radar c x synthetic aperture radar sir c x sar radar on board the space shuttle endeavor imaged kilauea volcano hawaii in april and october 1994 for the purpose of measuring active surface deformation by the methods of repeat pass differential radar interferometry observations at 24 cm l band and 5 6 cm c band wavelengths were reduced to interferograms showing apparent surface deformation over the 6 month interval and over a succession of 1 day intervals in october a statistically significant local phase signature in the 6 month interferogram is coincident with the pu u o o lava vent interpreted as deformation the signal implies centimeter scale deflation in an area several kilometers wide surrounding the vent peak deflation is roughly 14 cm if the deformation is purely vertical centered southward of the pu u o o caldera delays in the radar signal phase induced by atmospheric refractivity anomalies introduce spurious apparent deformation signatures at the level of 12 cm peak to peak in the radar line of sight direction though the phase observations are suggestive of the wide area deformation measured by global positioning system gps methods the atmospheric effects are large enough to limit the interpretation of the result it is difficult to characterize centimeter scale deformations spatially distributed over tens of kilometers using differential interferometry without supporting simultaneous spatially distributed measurements of refractivity along the radar line of sight studies of the interferometric correlation of images acquired at different times show that l band is far superior to c band in the vegetated areas even when the observations are separated by only 1 day these results imply longer wavelength instruments are more appropriate for studying surfaces by repeat pass observations

holocene palaeoenvironmental reconstruction in norteastern brazi inferred from polen charcoal and carboon isotope records soils in the barreirinhas region maranhao state were sampled for 613 c analysis and buried charcoal fragments in the soils were radiocarbon dated three soil profiles collected in forested areas around the lagoa do caqo and one in a woody savanna mixture of non arboreal and arboreal species located approximately 10 km southeast of the lagoa were studied a high resolution pollen record was obtained from lake sediments showing that forest vegetation was predominant in the area in the early holocene from approximately 10 000 14c yr bp the pollen spectrum gradually changed suggesting the dominance of open savanna communities these were transformed to a more forested landscape woody savanna from approximately 7500 yr bp the lake sediments also record evidence of fire indicated by buried charcoal particles at several soil depths during the holocene the 613 c analysis of soil organic matter som indicates that from between approximately io0000 yr bp and 9000 yr bp to 4000 yr bp a woody savanna

3 d surface deformation of the 2000 usu eruption measured by matching of sar images a subpixel level offset estimation technique was applied to sar synthetic aperture radar images of usu volcano japan using radarsat sar amplitude images acquired from ascending and descending orbits we generated a map of three dimensional displacement vectors showing ground deformation associated with criptdome formation in april 2000 moreover displacement velocities and volume changes were estimated from april 3 29 inflation was observed with vertical and horizontal displacements each exceeding 20m during the period of major activity from april 3 5 uplift and n s spreading velocities reached 3 3m day and 2 7m day respectively while volume change was 3 4 106 m day although this technique is less precise than other methods and is not very sensitive to local deformations it provides several key advantages including 1 personnel are not required to enter hazardous areas 2 it provides wide spatial coverage and 3 it does not depend on coherence making it more widely applicable than insar

stratigraphic control and chronology of peat bog deposition in the serra do espinhaco meridional brazil abstract peat bogs consist of a heterogeneous substrate whose physical characteristics vary in accordance with botanical composition inorganic sediment content and the degree of organic matter om decomposition although rare in the tropical zone of south america they can form in places where temperature and drainage favor the accumulation of om due to the anoxic character of the environment om remains preserved providing a valuable record of the climate during its genesis in the serra do espinhaco bogs can be found buried under sand deposits and given the difficulty of mapping such deposits by conventional methods ground penetrating radar gpr was used in their location and the study of the relationship between peat bog genesis and bedrock setting gpr data revealed blocks of quartzite located perpendicular to the drainage pattern which are assumed to partially restrict the water flow and maintain wet conditions upstream favoring the development of hygrophilous vegetation and the accumulation of om radiocarbon dating showed that buried bogs are contemporary to the deeper parts of non buried peats and that there is a strong correlation between their stratigraphy and climatic conditions between 30 250 and 12 400 years before present bp the conditions were favorable for the accumulation of om between 12 400 and 7900 years bp erosive processes caused sand deposition in the depression favorable conditions for deposition of om resumed around 7900 years bp and lasted until about 3300 years bp over the past 2600 years the climate has been similar to the present with three brief periods favorable to om deposition

landscape evolution during the late quaternary at the doce river mouth espirito santo state southeastern brazil article the sedimentary deposits of the deltaicplain of the doce and barra seca rivers southeastern brazil were studied by faciesanalysis pollenrecords 13 c c n analysis and ams 14 c dating today thisdeltaicplain isdominated by beach ridges and sandy terraces occupied by arboreal and herbaceous vegetation between 47 500 and 29 400 cal yr b p a deltaic system was developed in response mainly to eustatic sea level fall although the studied stratigraphic succession is compatible with the trend of global sea level fall the earlier sea level sug gested by the topographic position of these deltaic deposits was above the one expected during the mis3 stage a tectonic uplift likely occurred during the late quaternary and raised these deposits the post glacial sea level rise caused a marine incursion with invasion of embayments and broad valleys and it favored the evolution of an estuary with wide tidal mud flats occupied by mangroves between 7400 and 5100 cal yr b p the high river sand supply and or the relative sea level fall in the late holocene led to seaward and downward translation of the shoreline during normal forced regression producing progradational deposits with shrinkage of mangrove stands and expansion of marshes colonized by herbaceous vegetation therefore the stratigraphic architecture and evolution of the doce river deltaic plain suggest that fluvial sediment supply and relative sea level fluctuations related to quaternary global climatic changes and local tectonism exerted major controls on sedimentation through the variation of accommodation space and base level changes

measuring ground displacements from sar amplitude images application to the landers earthquake ers sar amplitude images are utilized to map ground displacements from a sub pixel correlation method it yields a ground two dimensional displacement field with independent measurements about every 128m in azimuth and 250m in range the accuracy depends on the characteristics of the images for the landers test case the 1 uncertainty is 0 8m in range and 0 4m in azimuth we show that this measurement provides a map of major surface fault ruptures accurate to better than 1km and information on coseismic deformation comparable to the 92 gps measurements available although less accurate this technique is more robust than sar interferometry and provides complementary information since interferograms are only sensitive to the displacement in range

pleistocene climatic instability drove the historical distribution of forest islands in the northeastern brazilian atlantic forest abstract to investigate the past spatial dynamics of atlantic forest af island like enclaves in northeastern brazil we employed ecological niche modeling enm using a set of georeferenced records of 13 woody plant species enms were constructed using the ensemble forecasting approach and were projected into past climatic conditions for the last interglacial period lig 120 kyr last glacial maximum lgm 21 kyr and the middle holocene mh 6 kyr our results suggest an expansion of wetter forests during the lgm into areas currently covered by the caatinga seasonally dry woodlands with recent retraction to the current distribution central af islands located south of the sao francisco river underwent a different history compared to northern af islands north of this river the former were mostly connected to coastal af since the lig with a very recent separation whereas the latter presented a more dynamic historical distribution results reveal contrasting spatiotemporal histories of forest instability and isolation across the various enclaves supporting three main biogeographic hypotheses i moderate connectivity with coastal af and a recent population bottleneck in the araripe and pernambuco paraiba enclaves ii low connectivity to and long term isolation from other enclaves as well as recent population bottleneck in the northernmost north ceara enclaves and iii high connectivity with coastal af and recent population expansion in the southernmost chapada diamantina enclaves future comparative phylogeography studies will largely aid in assessing the herein proposed biogeographic scenarios during the highly dynamic recent history of the af enclaves

lower cambrian halkieriids from oxfordshire uk lower cambrian sediments from the withycombe farm borehole oxfordshire yield isolated halkieriid sclerites all bear prominent ridges and most appear to be either cultrates or palmates although distinction between the two in the available material is generally difficult two other sclerites are more elongate one may represent a spinose sclerite while the other is possibly derived from the siculate zone of the original scleritome adjacent horizons of the withycombe formation yield disc like fossils superficially similar to hyolith opercula or monoplacophorans these are tentatively identified as deriving from the same halkieriid scleritome two main types are identified and these may correspond to the anterior and posterior shells of halkieria evangelista from the lower cambrian sirius passet fauna of north greenland the age of the withycombe formation within the cambrian is not entirely resolved but faunal evidence suggests an equivalence to the cuslett formation of southeast newfoundland which corresponds to either the upper tommotian or lower atdabanian of the standard siberian section

late pleistocene glacial forest of humaita western amazonia abstract glacial aged vegetation dynamics of the humaita western brazilian amazonia were studied by pollen sedimentary facies 14 c dating 13 c org and c n molar two sediment cores were taken to a depth of 10 and 8 m from areas covered by grassland and dense open forest respectively the deposits represent a succession of sediment accumulation in active channel 42 600 cal yr b p abandoned channel floodplain 42 600 to 39 000 cal yr b p and oxbow lake sedimentary environments 39 000 cal yr b p to modern the predominance of mud sediments depletion of 13 c org and decrease in c n molar values identify the lake establishment in these settings low energy subaqueous conditions were developed locally favoring preservation of a pollen assemblage representing herbaceous vegetation some modern taxa from amazonia and cold adapted plants from the andes represented by alnus 2 11 hedyosmum 2 17 weinmannia 0 18 podocarpus 0 4 ilex 0 4 and drymis 0 1 at least between 42 600 and alnus with other cold adapted plants from the andes during the late pleistocene indicates that alnus probably penetrated the western amazonia lowland or was growing closer to the study site due to cooler temperatures during glacial times the present study presents the first report of a glacial age forest containing alnus in areas of the brazilian amazonian lowlands in addition to its palaeogeographical importance this work demonstrates the effectiveness of using a combination of proxies for reconstructing sedimentary environments associated with vegetation

late quaternary vegetational and climatic changes in cerrado and palm swamp from central brazil abstract geochemical and palynological analyses of core cr1 from crominia goias provided information on the paleoenvironmental history of central brazil the records show that prior to 32 400 yr b p the vegetation of the crominia region was similar to the present one characterized locally by a complex of cerrado gallery forest and palm swamp indicating a semi humid tropical climate a palm swamp occupied the coring site from 32 400 to about 20 000 yr b p a treeless grassland replaced the arboreal cerrado and the gallery forest suggesting that humidity increased but temperature probably decreased the site was a shallow lake between ca 27 000 and 20 000 yr b p humidity started to decrease at ca 18 500 yr b p and the period from ca 18 500 to ca 11 500 yr b p was very dry a sparse vegetation was growing in the region during that time the dry climate continued until 6500 yr b p and the core site probably dried out several times at ca 5000 yr b p humidity increased again the palm swamp vegetation returned to the site and cerrado vegetation and gallery forest started to grow in the region the abundant charcoal particles prior to 20 000 yr b p and from 10 500 to ca 3500 yr b p document a long history of fires in the region results are compared with those from other sites in central brazil and with the climate sequence of the last glacial maximum and postglacial time in the tropical andes

vertical deformation of the japanese islands 1996 1999 1 the interseismic vertical deformation field of the japanese islands is derived from the global positioning system gps data between 1996 and 1999 although vertical components of the gps velocities have rarely been used as important information because of their higher noise level information on the vertical deformation field will enable us to separate rigid plate motions from deformation due to interplate coupling because horizontal displacements contain both effects whereas vertical displacements contain only the interplate coupling effect the results show that 1 the precision of the vertical velocity is generally better than 2 mm yr 2 the existence of clear uplift peaks of about 8 mm yr in the shikoku and tokai regions is consistent with strong coupling with a gradual brittleplastic transition zone at the nankai and the suruga trough respectively 3 clear uplift peaks do not seem to exist in the tohoku region because the japan trench plate boundary is too far oceanward from the gps sites 4 significant uplift is obtained in the western part of hokkaido which may be associated with the long term postseismic deformation due to the 1983 japan sea and the 1993 hokkaido nansei oki m 7 6 earthquakes and 5 uplift in northeastern japan along the japan sea coast is apparently associated with distributed compression due to incipient subduction

relation between carbon isotopes of plants and soils on marajo island a large tropical island implications for interpretation of modern and past vegetation dynamics in the amazon region abstract we assess the relation between the contrasting vegetation types of rainforest open savanna and wooded savanna coexisting in close contact on marajo island at the mouth of the amazon river floristic and carbon isotopic characterizations of modern plants were combined with organic matter carbon isotope and grain size records of soil to characterize vegetation evolution at six locations on southeastern and northeastern marajo island and its relations to climate changes since the late pleistocene c3 plants contribute 100 of the biomass in the rainforest on post barreiras sediments site 1 no significant vegetation changes are evident in these places since at least 7860 cal yr b p rainforests on paleochannels sites 4 and 6 are protected from flooding by slightly elevated sandy levee and have flora very similar to site 1 these forests were formed since the early mid holocene after channel abandonment c3 grasses are predominant in open savanna areas sites 4 5 and 6 with less representation in wooded savannas sites 2 and 3 however c4 grasses despite having fewer species constitute significant biomass in the wooded 60 and open savanna vegetation areas especially during the dry season the reconstructions of past vegetation together with the distributions of modern vegetation allow prediction that climate changes to drier conditions can significantly influence the future marajo island landscape likely enabling expansion of c4 plants in the flooding zone and of trees in the rainforests

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

a 21 000 cal years paleoclimatic record from caco lake northern brazil evidence from sedimentary and pollen analyses abstract sedimentological studies including seismic profiles mineralogy and organic geochemistry on two cores from the center and margin of caco lake maranhao state northern brazil revealed variable climatic and environmental conditions during the last 21 cal kyr bp between 21 and 17 cal kyr bp during the late glacial maximum regional climate was predominantly dry interrupted by short humid phases as reflected by a succession of very thin layers of sand and organic matter the late pleistocene climate was relatively wet as is suggested by rapid lake level rise and forest expansion the late pleistocene humid climate differed significantly from present conditions we suggest that late glacial humid conditions were the consequence of intensification of the inter tropical convergence zone or shifts of its position resulting in antarctic cold front occurrences the abrupt climatic changes during this period were marked by siderite deposition into caco lake which appears to be related to regional hydrologic changes linked to global northern hemisphere events the holocene was characterized by lower moisture availability and a distinct dry period until 7 cal kyr bp in response to south american insolation conditions

use of multi proxy approaches to determine the origin and depositional processes in modern lacustrine sediments carajas plateau southeastern amazon brazil abstract geochemical and isotopic compositions of surficial sediments from a plateau lake in carajas southeastern amazon region were investigated to understand the spatial distribution of major and trace elements 13 c 15 n and c n ratio depositional processes and the origin of inorganic and organic fractions the 13 c 15 n and c n ratio indicate mainly an autochthonous source with siliceous sponge spicules and algae being the major source of organic matter in the center of the lake sector 3 while an allochthonous source mainly derived from c3 vascular forest plants dominates in the shallowest portion of the lake sector 1 consequently there was an apparent dilution of c4 plants montane savanna in the sediment water interface among major elements fe 2 o 3 is highly enriched in sector 3 which is controlled by the erosion of catchment laterites and underwater topography while al 2 o 3 and p 2 o 5 enrichment near the northern border of the lake is controlled by the weathering of mafic rocks similar spatial distribution of sio 2 with total organic carbon toc and isotopic evidence indicate that si distribution is partially controlled by organic components such as siliceous sponge spicules and algae the occurrence of most of the trace and rare earth elements ree is independent of fe 2 o 3 and toc but controlled by detrital aluminum silicates and heavy minerals indicating a lack of post depositional diagenetic control on their distribution the distribution of as and mo are possibly controlled by organic matter mineralization during early diagenesis and subsequently precipitation of fe phases the values of the chemical index of alteration cia in the sediments are very high 94 99 and similar to those of the source rocks suggesting that sediment composition is mainly controlled by mechanical weathering rather than chemical weathering geochemical indices al k ti k al ti la th ti zr zr hf hf nb la al co th ba sr and th sc together with the a cn k plot suggest that the provenance of the inorganic sediments remained relatively uniform or constant during the depositional period and that they were mainly derived from laterite crusts and subordinately from mafic soils this inference was further substantiated by the chondrite normalized ree patterns and discrimination plots geochemical indices such as u th authigenic u mo al and v cr indicate that the sediments were deposited under an oxic environment

locations and types of ruptures involved in the 2008 sichuan earthquake inferred from sar image matching 1 we have detected detailed ground displacements in the proximity of the longmen shan fault zone lmsfz by applying a sar offset tracking method in the analysis of the 2008 sichuan earthquake an elevation dependent correction is indispensable for achieving sub meter accuracy a sharp displacement discontinuity with a relative motion of 1 2 m appears over a length of 200 km along the lmsfz which demonstrates that the main rupture has proceeded on the beichuan fault bf among several active faults composing the lmsfz and a new active fault is detected on the northeastward extension of the bf the rupture on the bf is characterized by a right lateral motion in the northeast while in the southwest an oblique right lateral thrust slip is suggested in contrast to the northeast where a major rupture proceeded on the bf only in the southwest multiple thrust ruptures have occurred in the southeastern foot of the pengguan massif

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

deflation of mount etna monitored by spaceborne radar interferometry ground based measurements of volcano deformation can be used to assess eruptive hazard but require the costly and often hazardous installation and maintenance of an instrument network here we show that spaceborne radar interferometry which has already shown its utility in mapping earthquake related deformation1 can be used to monitor long term volcano deformation two families of synthetic aperture radar images acquired from ascending and descending orbits by the satellite ers 1 and looking at mount etna from opposite sides cover the time period from 17 may 1992 to 24 october 1993 and include the second half of etna s most recent eruption despite artefacts of the interferometric technique we can observe a volcano wide deflation which is an expected consequence of the eruption but which had not previously been appreciated we quantify it using a simple model based on the change of pressure in a sphere located in an elastic half space the modelled deformation increases linearly with time until the end of the eruption our results show that it will be possible to use this technique to detect the inflation of volcanic edifices that usually precedes eruptions

holocene palaeoenvironmental history of the amazonian mangrove belt abstract wetland dynamic in the northern brazilian amazon region during the holocene was reviewed using palynological carbon and nitrogen isotopes records and c n ratio previously published the integration of 72 radiocarbon dates recorded in 34 sediment cores sampled along the marine and fluvial littoral and mainly influenced by the amazon river reveals that marine influence and mangrove vegetation were wider than today on the mouth of amazon river between 8990 8690 and 2300 2230 cal yr bp forming a continuous mangrove belt along the northern brazilian amazon littoral the establishment of this mangrove strip is a direct consequence of the marine incursion caused by post glacial sea level rise possibly associated with tectonic subsidence during the early and middle holocene in the late holocene in areas influenced by the amazon river discharge the mangroves were replaced by freshwater vegetation and the coast morphology evolved from an estuarine dominated into a rectilinear coast due to coastal progradation nevertheless the marine influenced littoral which is currently dominated by mangroves and salt marsh vegetation has persistently had brackish water vegetation over tidal mud flats throughout the entire holocene likely the fragmentation of this continuous mangrove line during the late holocene was caused by the increase of river freshwater discharge associated to the change from dry into wet climates in the late holocene this caused a significant decrease of tidal water salinity in areas near the mouth of amazon river these changes in the amazon discharge are probably associated with dry and wet periods in the northern amazon region during the holocene

holocene environmental changes from the rio curua record in the caxiuana region eastern amazon basin abstract holocene environments have been reconstructed by multiproxy studies of an 850 cm long core from rio curua dating to 8000 14 c yr b p the low energy river lies in the eastern amazon rain forest in the caxiuana national forest reserve 350 km west of belem in northern brazil sedimentological mineralogical and geochemical dates demonstrate that the deposits correspond to two different environments sediments of an active river before 8000 14 c yr b p and later a passive river system the pollen analytical results indicate four different local and regional holocene paleoenvironmental periods 1 a transition to a passive fluvial system and a well drained terra firme unflooded upland amazon rain forest with very limited development of inundated forests varzea and igapo 7990 7030 14 c yr b p 2 a sluggish river with a local mauritia palm swamp and similar regional vegetation as before 7030 5970 14 c yr b p 3 a passive river forming shallow lake conditions and with still abundant terra firme forest in the study region 5970 2470 14 c yr b p and 4 a blocked river with high water levels and marked increase of inundated forests during the last 2470 14 c yr b p increased charcoal during this last period suggests the first strong presence of humans in this region the atlantic sea level rise was probably the major factor in paleoenvironmental changes but high water stands might also be due to greater annual rainfall during the late holocene

absence of last glacial maximum records in lowland tropical forests abstract environmental conditions of the lowland tropical forests during the last glacial maximum lgm between ca 20 000 and 18 00014c yr b p are reevaluated in terms of dating control and lithology analyzed in seven pollen records from south america the reevaluation shows that probably in none of the published records are lgm sediments present or abundant this conclusion is based on the occurrence of abrupt lithologic changes coupled with changes in sedimentation rate interpolated from radiocarbon dates these findings suggest that the lgm was represented probably by a hiatus of several thousand years indicative of drier climates than before or after

fault source modeling of the 2008 wenchuan earthquake based on alos palsar data abstract we use crustal deformation data sets derived from satellite based synthetic aperture radar sar to develop a fault source model of the 2008 m w 7 9 wenchuan earthquake china that occurred at the longmen shan fault zone the data sets include interferometric sar insar range offset and azimuth offset data acquired at seven ascending paths the range and azimuth offset data are particularly important exhibiting a single major rupture to the northeast ne and multiple ruptures to the southwest sw our preferred model consists of six segments four follow the previously mapped traces of the beichuan fault bf and its ne extension one corresponds to the pengguan fault pf to the sw and the other is included to represent a conjugate fault to the sw fixing the location and geometry of those segments we solve the variable slip distribution whose patch size increases toward the greater depth we use a nonnegative least squares method with a smoothing constraint on the distributed slip the geodetically estimated moment is 1 05 10 21 n m m w 7 9 which is close to the seismological estimate and suggests that there are insignificant postseismic signals in the data maximum slip of 10 m consisting of both thrust and right lateral slip components is identified at the shallowest patches to the ne along the bf the multiple fault segments to the sw show that the thrust slip component initially dominates and the strike slip becomes significant toward the ne examining the sensitivity of the predicted azimuth offset data to the assumed dip angle we found that the dip angle changed significantly from 35 45 at the sw fault segment for the pf to 80 90 at the ne extension of the bf

variations of the amazonian rainforest environment a sedimentological record covering 30 000 years abstract two cores css 2 and css 10 were collected from two lakes situated in the carajas area 6 35 s 49 30 w that show different stages of silting up the results of geochemical and petrographic organic analyses backed up by 14 c radiometric dating lead to a reconstruction of the variations in the hydrological regime of these lakes over the last 30 000 years evidence is revealed for a period of drying up characterized by a sedimentary hiatus between 22 000 and 13 000 14 c years bp followed by a period of refilling between 13 000 and 11 000 14 c years bp 15 400 12 900 cal years bp the latter interval is primarily characterized by a mainly clastic sedimentary input rich in quartz kaolinite and iron hydroxides leading on to the authigenic formation of siderite this type of sedimentation implies the erosion of the small catchment basin during periods of transition between arid and humid climatic regimes from 8000 to 4000 14 c years bp 8900 4500 cal years bp as well as from 2700 to 1500 14 c years bp 2780 1360 cal years bp special hydrological conditions prevailed they are characterized in the sedimentary record by the presence of micro laminae containing wood charcoal interlayered with sponge spicule material this interlamination reflects the rapid alternation of dry and humid periods a comparison with the results obtained by pollen analysis shows that sedimentological indicators once filtered for strictly local effects can provide a full record of the regional scale variations in the environment

paleoenvironmental reconstruction of the lower mogi guacu river basin sao paulo state brazil morphopedosedimentary records and fluvial processes abstract the mogi guacu river rises in bom repouso minas gerais state brazil in the mantiqueira ridge and flows into the rio pardo river at an elevation of 483 m in pontal sao paulo state brazil after running a 530 km long course especially along the lower mogi guacu basin the river morphology is extremely sinuous characterized by intense processes of channel migration avulsion abandonment and reactivation of the channel producing an extensive alluvial plain composed of a series of associated relief forms and sedimentary facies among these forms point bar deposits by lateral accretion abandoned meanders paleo channels and fluvial terraces are notable features in this sense the objective of this work was to investigate whether these features could be linked to environmental changes to reach this goal soil properties of a catena of the jatai ecological station luiz antonio sao paulo state were analyzed in four sectors slope terrace i terrace ii and alluvial plain the results from grain size determination geochemical and isotopic studies dating paleopalynology coal fragments and micromorphology are presented in this paper from these analyses a paleo environmental evolution divided in three stages is proposed for the area 130 000 ybp upper pleistocene when the mogi guacu river base level was approximately 6 m above the present one a drier second phase 10 250 years bp lower holocene when an organic horizon was formed inside of an abandoned meander oxbow lake and a third phase 2096 ybp upper holocene of reactivation of a warm and humid climate that promoted the development of a two meters thick typic udifluvent in a sector where the mogi guacu river no more floods due to the incision of its thalweg reaching more than six meters depth in the last 130 000 years bp thus this paper used a fluvial geomorphologic approach and its interplay with climate to understand how the landscape was shaped from upper pleistocene to holocene however neotectonics might have played a relevant role as well not only in the mogi guacu river basin but also in the parana sedimentary basin

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

relative sea level and climatic changes in the amazon littoral during the last 500 years abstract an integrated approach focused on sedimentology geochemistry palynology c and n isotopes and radiocarbon dating of a sediment core from an herbaceous plain not flooded by tides of the amapa littoral near the amazon river mouth allowed identification of two phases with marine and terrestrial influences mangroves occurred over tidal mud flats with marine influence between 5610 5470 and 470 310 cal yr bp the absence of mangrove vegetation since 470 310 cal yr was followed by the transition of brackish water organic matter to terrestrial c3 plants also the geochemical data indicate a decrease in sea water influence during this last time interval likely the displacement of mangrove forest to lower surfaces was caused by a relative sea level fall that may be associated with drier conditions with less rainfall during the second part of the last millennium as suggested by this work slight relative sea level fluctuations caused by regional or global climatic change may affect significantly the current mangrove area

direct measurement of ocean waves velocity field from a single spot 5 dataset we present a method based on space borne optical imagery from the spot5 satellite to directly measure the phase velocity fields of ocean waves the panchromatic and multispectral scenes acquired by spot5 the same day on the same area are not strictly superimposable due to the different locations of the ccds charged coupled device in the focal plane of the instrument in this manuscript we propose a method that exploits the temporal lag that exists between the panchromatic and multispectral scenes to measure the ocean wave velocity fields we firstly discuss the principle and the methodology then we apply it offshore la reunion island finally we compare and discuss the results against a swell propagation model our method is proven reliable and can be immediately extended to other push broom sensors

rift parallel block like motion of the graben floor during the 2005 2010 afar rifting episode abstract crustal deformations associated with rifting episodes are often explained by both normal faulting and tensile opening in an elastic body suggesting no significant rift parallel displacements in this study using alos palsar pixel offset and multiple aperture interferometry mai data we detected 1 m of northwestward block like cumulative horizontal motion in the graben floor during the latter half of the 2005 2010 afar rifting episode ethiopia this horizontal block like motion can be explained by additional shallower strike slip on normal fault surfaces which was presumably aseismic due to the very small number of strike slip earthquakes and a significant gap between seismic and geodetic moment releases we conclude that the rift parallel movement can be interpreted by the strain accommodation of plate oblique spreading associated with dike intrusions as has been demonstrated for the 2014 bar arbunga dike intrusion episode although we do not propose direct evidence for the plate oblique spreading the complicated tectonic setting caused by the rotation of the danakil block and the upwelling plume beneath the afar triple junction may be drivers of the rift parallel motion associated with the afar dike intrusion

late quaternary vegetational and climate dynamics in northeastern brazil inferences from marine core geob 3104 1 abstract late quaternary paleoenvironments from northeastern ne brazil have been studied by pollen analysis of marine sediment the studied core geob 3104 1 3 40 s 37 43 w 767 m b s l from the upper continental slope off ne brazil is 517 cm long and 42 000 14 c yr bp old chronological control was obtained by 12 radiocarbon ams dates from individuals of the foraminiferal species globigerinoides sacculifer modern pollen analogs were received from 15 river lake and forest soil surface samples from ne brazil marine pollen dates indicate the predominance of semi arid caatinga vegetation in ne brazil during the recorded period between 42 000 and 8500 14 c yr bp the increased fluvial input of terrigenous material with high concentrations of pollen and specially fern spores into the marine deposits about 40 000 33 000 and 24 000 14 c yr bp and between 15 500 and 11 800 14 c yr bp indicate short term periods of strong rainfall on the ne brazilian continent the expansion of mountain floodplain and gallery forests characterize the interval between 15 500 and 11 800 14 c yr bp as the wettest recorded period in ne brazil which allowed floristic exchanges between atlantic rain forest and amazonian rain forest and vice versa the paleodata from core geob 3104 1 confirm the in general dry pre last glacial maximum lgm and lgm conditions and the change to wet lateglacial environments in tropical south america the annual movement of the intertropical convergence zone over ne brazil the strong influence of the antarctic cold fronts and changes of the high pressure cell over the southern atlantic may explain the very wet lateglacial period in ne brazil the documented ne brazilian short term signals correlate with the documented dansgaard oeschger cycles and heinrich events from the northern hemisphere and suggest strong teleconnections

astronomical forcing of contrasting rainfall changes in tropical south america between 12 400 and 8800 cal yr b p abstract today precipitation over tropical south america is largely controlled by the seasonal movements of the inter tropical convergence zone itcz during the summer the itcz is shifted southward due to the warming of the continent paleoclimate data from southeastern amazonia and the central andes indicate that these two areas evolved similarly during the last 30 000 yr however between 12 400 and 8800 cal yr b p eastern amazonia received substantial moisture whereas the bolivian altiplano was arid this suggests that the itcz during summer was then farther north than it is today

icecap and subglacial crustal deformation inferred from sar pixel tracking the 2014 dike intrusion episode in the barðarbunga volcanic system iceland

a multi proxy evidence for the transition from estuarine mangroves to deltaic freshwater marshes southeastern brazil due to climatic and sea level changes during the late holocene abstract the present study investigates a paleo estuary at the doce river delta southeastern brazil through a multi proxy approach that links palynology diatoms sedimentology and geochemistry analyses i e total c total n 13 c and 15 n these analyses temporally synchronized with five radiocarbon ages revealed environmental changes from marine to continental over the last 7550 years the studied sedimentary succession recorded the upward transition from estuarine channel until 7550 cal yr bp to estuarine central basin 7550 to 5250 cal yr bp deposits the latter containing increased mangrove vegetation marine and marine brackish water diatoms the range of geochemical values 13 c 30 10 15 n 2 8 and c n 4 40 also indicate marine estuarine organic matter and c 3 terrestrial plants to that time interval a following period recorded two phases lake ria 5250 to 400 cal yr bp and fluvial channel 400 cal yr bp until modern age during this stage mangroves were replaced by trees shrubs and herbs grasses due to the disconnection with the marine realm as a result the corresponding sediments contain only organic matter sourced from freshwater and c 3 terrestrial plants 13 c 29 26 15 n 0 8 and c n 10 45 the equilibrium between fluvial sediment supply and relative sea level changes during the holocene controlled the morphologic and vegetation changes in the studied littoral the estuary became established during the early holocene as a resulted of a eustatic sea level rise when the fluvial sediment supply to the coast was relatively lower due to a dry period however during the late holocene the climatic force was more significant to the development of coastal morphology due to a wet period that caused an increase in sandy sediment supply to coastal system then the increase of fluvial discharge associated to a relative sea level fall caused a marine regression and shrinkage of mangroves during the late holocene the evaluation of mangrove dynamics according to climatic and sea level changes mainly during the late holocene is essential for the understanding of their survival ability under future scenarios with a probable accelerated sea level rise and intensification of extreme climatic events in southeastern brazil for the next century

pre columbian fire regimes in lowland tropical rainforests of southeastern peru abstract we document the fire history of the forests of a well studied ecological research station los amigos in western amazonia through soil charcoal analysis and compare results with data from a nearby lake district known to have supported pre columbian human populations we present novel methods of soil charcoal analysis that improve on its current limitations by accounting for variability in post fire charcoal deposition problematic age depth relationships and the presence of weathered or regionally deposited charcoal particles that allow statistical comparisons of fire history characteristics between regions the fire histories indicate that the research station experienced less intensive historical fire and pre columbian disturbance than the lake district dated charcoal particles indicated that while soil depth could not be used to predict fire age fragments below 20 cm depth were generally older than 500 years frequent fires have not occurred in either region during the last 1000 years but fire events in both regions were significantly synchronous from 1000 to 4000 cal yr bp the sampling design and methods that provide an ecologically and statistically valid avenue for comparing fire history characteristics between regions can be modified to suit other ecosystems the results presented here establish confidence that the patterns and processes of the lowland tropical rainforests studied at los amigos are not affected by intense or recurrent historical fires these data also suggest that forests of madre de dios peru are not post successional remnants of a cultural parkland as suggested by some amazonian archeologists

mangrove vegetation changes on holocene terraces of the doce river southeastern brazil article i nfo high resolution sedimentological geochemical and pollen analysis on sediment core from the coastal plain of the doce river southeastern brazil revealed changes in the depositional system and vegetation caused by combined action of oscillations in relative sea level rsl and sedimentary supply during the holocene two main phases were discerned using sedimentary features 13 c 15 n total organic carbon toc total ni trogen n c n and cluster analysis of pollen data temporally synchronized with radiocarbon age dating the data indicates the presence of a lagoon system surrounded by a tidal plain colonized by mangroves and its sedimentary organic matter sourced from c4 plants between 8050 and 7115 cal yr bp however during the mid and late holocene the mangroves shrank and freshwater vegetation expanded c3 plants proba bly due to a marine regression during this phase the development of a lacustrine environment was followed by the colonization of herbs trees and shrubs the continuous sediment infilling into the lake allowed the ex pansion of a herbaceous plain as seen today this geomorphologic and vegetation evolution is in agreement with the mid holocene rsl maximum above present rsl and subsequent fall to the present time

effects of syn pandemic fire reduction and reforestation in the tropical americas on atmospheric co2 during european conquest abstract a new reconstruction of late holocene biomass burning in the tropical americas is consistent with the expansion of fire use by mesoamerican and amazonian agriculturalists and a subsequent period of fire reduction beginning 500 years bp the marked reduction of biomass burning after 500 years bp a unique feature of the fire history of the tropical americas relative to other regions of the globe is synchronous with the collapse of the american indigenous population during pandemics accompanying european conquest we predict that fire reduction contemporaneous with pandemics in the tropical americas was associated with massive forest regeneration on 5 105 km2 of land and sequestration of 5 10 gt c into the terrestrial biosphere which contributed to the 2 global reduction in atmospheric co2 levels and the 0 1 increase in 13c of atmospheric co2 from 1500 to 1750 a d this study 1 builds upon prior fire history reconstructions by synthesizing a substantially greater number of stratigraphic charcoal accumulation records and soil charcoal 14c dates to resolve features of the late holocene biomass burning record in the tropical americas and 2 corroborates the hypothesis advanced by ruddiman ruddiman w f 2003 the anthropogenic era began thousands of years ago climatic change 61 261 293 ruddiman w f 2005 plows plagues and petroleum princeton university press princeton new jersey that biospheric carbon sequestration via reforestation of cropland abandoned during pandemics contributed to changes in atmospheric co2 concentration during the past millennium

onocerane attests to dry climatic events during the quaternary in the tropics an unusual molecular fossil onocerane i has been detected in quaternary lacustrine sediments lagoa do caco ne brazil for the first time this component was initially thought to attest to the former presence of ferns or club mosses from consideration of possible plant precursors of onocerane related molecules recorded in the literature and comparison with palynological results and palaeoclimatic data we here provide evidence that club mosses and ferns cannot account as sources of onocerane i in this setting onocerane i is abundant in the lipid extracts of sediments deposited during the two driest periods recorded in northern brazil last glacial maximum and younger dryas this component is therefore suspected to be diagnostic of the development of plants adapted to dry or semi arid conditions in this region

holocenic proxies of sedimentary organic matter and the evolution of lake arari amazon region abstract four sediment cores were sampled from lake arari located on marajo island at the mouth of the amazon river the island s vegetation cover is composed mainly of amazon coastal forest herbaceous and varzea vegetation the integration of data on sedimentary structures pollen carbon and nitrogen isotope records c n ratios and radiocarbon ages allowed the identification of changes in vegetation and the sources of organic matter accumulated in the lake during the holocene the data indicate a relatively high flow energy marine water influence and the presence of mangroves during the lagoon phase between 8990 and 8690 cal yr b p and 2310 2230 cal yr b p between 2310 and 2230 cal yr b p and 1000 cal yr b p the flow energy decreased and the mangroves were replaced by herbaceous vegetation following the decline in marine influence likely due to the increase in freshwater river discharge during the last 1000 years lake arari was established in association with the expansion of herbaceous vegetation and the dominance of freshwater algae

two histories of environmental change and human disturbance in eastern lowland amazonia two long palaeoecological records pollen diatoms 14c chemistry and charcoal provide a detailed record of holocene environmental conditions in the lowlands of the lower amazon changes in the composition of the terra firme forest are evident but a forest cover is maintained throughout fluctuations in lake level and changes in seasonality are tracked in both sedimentary sequences rising early holocene sea levels and the consequent rise of local water tables probably caused the flooding of one of the sites a stepped increase in precipitation is suggested with increases evident at 8800 yr bp 7400 bp and between 6100 and 5800 yr bp increased storminess is suggested between 7400 yr bp and 6100 yr bp human disturbance is manifested in the palaeoecological records at one study site as early as 5500 yr bp c 6500 years ago and an intensifi cation or onset of agriculture is evident at c 3350 yr bp the terminating phase of the long record of disturbance is a period of forest regrowth that may correlate to the depopulation of amazonia following euro pean contact

stable carbon isotopic evidence for climate change across the late pleistocene to early holocene from lesotho southern africa although significant environmental and climatic changes are likely to have occurred across the pleistocene holocene transition in southern africa records are sparse with information regarding temperature change especially rare we thus know little about the conditions facing later stone age human populations at this time particularly those in the highland interior where temperature shifts would have had strong impacts on floral and faunal distributions in lesotho a well defined altitudinal distribution of c3 and c4 photosynthetic plant taxa and their remains in soil organic matter provides a means of estimating past temperature shifts we applied this principle to stratified sediments from two archaeological sequences in the lesotho lowlands c 1600 m a s l to produce a palaeotemperature record focusing on the period 14 000 9500 cal a bp the results show an overall trend from exclusively c3 vegetation at the last glacial maximum towards greater contributions of c4 taxa and thus warmer conditions during the holocene however large temperature fluctuations are evident within this trend with rapid changes of up to 4 c visible between 11 200 and 9500 cal a bp the continued presence of hunter gatherers during this time suggests that the region must have remained attractive to human populations despite significant climatic instability and cool episodes copyright 2013 john wiley sons ltd

complex crustal deformation of the 2016 kaikoura new zealand earthquake revealed by alos 2complex crustal deformation of the 2016 kaikoura new zealand earthquake revealed by alos 2

major environmental changes recorded by lacustrine sedimentary organic matter since the last glacial maximum near the equator lagoa do caco ne brazil sediment samples collected along a 6 m core drilled in the deepest part of the lagoa do caco ne brazil have been investigated in order to determine source s and degradation conditions of the organic matter om with special emphasis on paleoenvironmental implications bulk organic geochemistry rock eval pyrolysis c n determination 13c and 15n measurement and petrography combined with sedimentological evidence and radiocarbon dates allowed to identify four major intervals documenting major environmental changes that occurred during the last 20 000 years the first interval dating back to the end of the last glacial maximum lgm contains well preserved om derived from higher plants this material was most probably produced in an ephemeral palustrine system and rapidly buried by sands this level is thought to have been deposited under relatively arid climate conditions associated with strong but episodic rainfalls between 19 240 and 17 250 cal years bp the climate appears to have been more humid and seasonality more pronounced as suggested by the presence of a permanent lake after a drastic environmental change dating back to 17 250 cal years bp the sediment became truly lacustrine with restricted mineral input and highly degraded higher plant derived organic matter after that a stepwise improvement in the preservation of om occurred as revealed by several pronounced shifts in the rock eval tps2 signal these changes could document abrupt climatically driven changes during the late glacial finally around 5610 cal years bp environmental conditions approaching those prevailing today were established minor climatic changes during the holocene were probably buffered by a high water table which might explain the lack of paleoenvironmental fluctuations

influence of landscape evolution on the distribution of floristic patterns in northern amazonia revealed by δ13c data the amazonian lowlands include large patches of open vegetation which contrast sharply with the rainforest and the origin of these patches has been debated this study focuses on a large area of open vegetation in northern brazil where d 13 c and in some instances c n analyses of the organic matter preserved in late quaternary sediments were used to achieve floristic reconstructions over time the main goal was to determine when the modern open vegetation started to develop in this area the variability in d 13 c data derived from nine cores ranges from 32 2 to 19 6 but with nearly 60 of data above 26 5 the most enriched values were detected only in ecotone and open vegetated areas the development of open vegetation communities was asynchronous varying between estimated ages of 6400 and 3000 cal a bp this suggests that the origin of the studied patches of open vegetation might be linked to sedimentary dynamics of a late quaternary megafan system as sedimentation ended this vegetation type became established over the megafan surface in addition the data presented here show that the presence of c4 plants must be used carefully as a proxy to interpret dry paleoclimatic episodes in amazonian areas copyright 2012 john wiley sons ltd

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

late quaternary vegetation and climate change in the amazon basin based on a 50 000 year pollen record from the amazon fan odp site 932 hemipelagic sediments from the amazon deep sea fan odp site 932 5 12 7 n 47 1 8 w and continental shelf provide a 50 000 yr long pollen record of amazon basin vegetation the age model for hole 932a is constrained by eight magnetic remanence intensity features one paleomagnetic excursion and three ams14c dates alchornea melastomataceae myrtaceae and moraceae urticaceae are dominant taxa in the pollen record between 40 200 and 19 800 cal yr b p andean taxa such aspodocarpusandhedyosmum increase in abundance between 19 800 and 11 000 cal yr b p and prior to 40 200 cal yr b p the holocene pollen assemblage derived from amazon river and continental shelf sediments is dominated by secondary growth taxa such ascecropia climatic factors influencing the development of glacial and interglacial tropical vegetation are considered by comparing marine with terrestrial records of vegetation change this comparison shows that the amazon basin forests were not extensively replaced by savanna vegetation during the glacial period contradicting the refugia hypothesis

vegetation and environmental changes in tropical south america from the last glacial to the holocene documented by multiple cave sediment proxies abstract 18 o values in speleothems have been utilized to document past changes in south american monsoon intensity however changes in regional vegetation and ecosystems have not been part of this discussion and other cave proxies such as speleothem 13 c values a useful proxy for vegetation reconstruction have been neglected due to interpretive complexities here we report 13 c values and 87sr 86sr ratios in stalagmites together with xrf derived elemental chemistry 13 corg values and carbon content from a sedimentary profile from the same cave where the stalagmites were collected in combination with a previously published 18 o record this enables us to clarify climate and environmental shifts that occurred between the last glacial maximum and the holocene in central south america we show that vegetation was sparse during the last glacial period in spite of a previously inferred strong monsoon and that changes in atmospheric pco2 combined with local hydrological and temperature feedbacks may have determined vegetation development during this time

widespread uplift and trapdoor faulting on galapagos volcanoes observed with radar interferometry volcanic uplift caused by the accumulation of magma in subsurface reservoirs is a common precursor to eruptions1 2 but for some volcanoes uplift of metres or more has not yet led to an eruption3 here we present displacement maps of volcanoes in the galapagos islands constructed using satellite radar interferometry that might help explain this dichotomy we show that all but one of the seven volcanoes on the islands of isabela and fernandina deformed during 1992 99 cerro azul and fernandina erupted4 5 6 during the observation period and show evidence of inflation co eruptive deflation and shallow dyke intrusion in contrast the largest volcano sierra negra has not erupted yet exhibits spatially and temporally variable deformation with a maximum uplift of 2 7 m between 1992 and 1999 which can be modelled by a shallow inflating sill inflation during 1997 98 however was accompanied by trapdoor faulting on a steeply dipping fracture system within the caldera repeated trapdoor faulting over geological time has formed an arcuate intra caldera ridge within sierra negra and may have acted to relax stresses above the magma chamber inhibiting summit eruptions similar processes may help explain large uplift unaccompanied by eruptive activity at other volcanoes

radiocarbon and δ13c depth profiles of soil organic carbon in the u s great plains a possible spatial record of paleoenvironment and paleovegetation abstract soil profiles from undisturbed grassland sites around the great plains of the usa were sampled for analysis of soil organic carbon soc content radiocarbon age and stable carbon isotope composition 13 c with the exception of a few pronounced dating anomalies soc radiocarbon age generally increases steadily with depth back to 10 15 000 cal yr bp the deepest soil intervals in 9 of the 12 sites the radiocarbon ages were used to establish the chronology of changes in past plant distribution over time and space based on soc 13 c as an indicator of c 3 and c 4 plant abundance changes were referenced to an soc 13 c value of 20 which is the approximate mid point between c 3 and c 4 carbon isotope composition i e an equal mixture of c 3 and c 4 carbon prior to 10 000 cal yr bp the region was dominated by c 3 plants with the exception of the southernmost texas sites from 10 000 to 2000 cal yr bp c 4 plants expanded their range initially as a peninsula of c 4 predominant grasses extending northeastward and ultimately dominating all but the northernmost border of the region finally the c 3 predominant region re expanded after 1000 cal yr bp perhaps as a response to the little ice age cooling despite uncertainties associated with using radiocarbon dated soc depth profiles as a proxy the past c 3 and c 4 plant distribution inferred from soc 13 c conforms well to results from other paleoclimate proxies and differences may be helpful in targeting future research

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 late pleistocene early holocene archaeological record in brazil a geo referenced database abstract between 13 000 and 8000 14c bp eastern south america was settled by a stable and diversified population of hunter gatherers archaeological excavation in the past twenty years has yielded increasingly consistent evidence of occupation in different regions of brazil since the end of the pleistocene with dates at least contemporary to the clovis horizon in north america this is addressed by documenting and analysing the quantity quality and distribution of archaeological 14c dates from brazil during this period a total of 277 dates from 90 sites are tabulated mapped and included in the analysis during the late pleistocene there was a pioneer phase of human colonization with dispersal inland through the major river systems subsequently the early holocene saw the first phase of established settlement of brazil s interior there seems to be an archaeological threshold reached at ca 10 500 years 14c bp numbers of sites increase there is evidence of settlement of all major biomes and there is clear evidence of inter regional cultural diversity

2 5 d surface deformation of m6 1 earthquake near mt iwate detected by sar interferometry the two dimensional displacement vector field on the earth s surface associated with a large earthquake near iwate volcano in japan was mapped by combining satellite radar interferometry images from two different track directions the displacement reveals not only large main ruptures but details of many small faults movement of aftershocks and volcanic earthquakes the displacements of the aftershock faults coincide with a stress field reorganized by the main earthquake that accelerated the aftershock fault movements the displacements mimic the topography suggesting that repeated movements of the same faults in the quaternary have led to the presently existing topography

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

high resolution mapping of near field deformation with airborne earth observation data a comparison study we present an investigation into different approaches for high resolution mapping of near field surface displacement for strike slip earthquakes airborne laser scanning als and optical imagery are two common sources of earth observation data available to geoscientists for earthquake documentation and studies optical image correlation and point cloud differencing techniques are among the most widely used methods for retrieving displacement signals in the near field we compare the performances of these techniques for estimating near field deformation using pre and postevent high resolution als and airborne imagery of the august 24 2014 mw 6 0 napa california earthquake estimates of deformation agree with field observations within a decimeter at the expected accuracy level of the data we show that the correlation of intensity images from als data can unveil the near field deformation successfully and outperforms optical image correlation in vegetated areas as well as in the absence of geodetic markers man made structures furthermore we illustrate that the point clouds generated with structure from motion perform comparably to als point clouds for retrieving the displacement signal in unvegetated areas overall we conclude that als data are generally better than imagery for estimating near field deformation regardless of the estimation methodology and that the iterative closest point algorithm was more effective at recovering the displacement signal

craters of elevation revisited forced folds bulging and uplift of volcanoes the eighteenth nineteenth century craters of elevation theory required magma to uplift strata doming the surface and creating a central down fallen crater or graben exponents of craters of elevation attempted to apply it to explain the origin of all volcanoes and rapidly the contemporary competing craters of eruption theory replaced it as the paradigm for volcano construction several historic examples have shown that intrusions can cause uplift termed bulges and can create features like those proposed for craters of elevation e g at usu 1944 bezymianny 1955 and mt st helens 1980 work on sedimentary basins that have had igneous activity has shown that intrusions create forced folds that uplift and deform strata in a similar way to that originally proposed for craters of elevation in view of the above we investigate large scale intrusion related topographic changes at two sites where the craters of elevation theory was developed the monogenetic volcanoes of the chaine des puys france and the teide stratovolcano tenerife we combine observations of such features with examples of forced folding to integrate the two fields of research our observations in the chaine des puys show that 1 the petit puy de dome has a bulge of up to 150 m uplift the uplift has a central depressed area a graben a dense network of normal faults basal thrusts and an aborted landslide 2 the grosmanaux volcano is a forced fold created by uplift of a previously flat lying area and has dense faulting and a graben on the resultant topographic bulge it was the site also of a major vulcanian eruption from the associated kilian crater 3 the gouttes volcano was uplifted by an intrusion like the petit puy de dome but then collapsed to generate a landslide and lateral blast 4 excavation in the lemptegy volcano exposes intra eruption intrusions with associated uplift providing examples in cross section of the internal deformation likely to be found inside other chaine des puys uplifted bulges on teide a bulge near the summit shows similar structures and surface tilting as seen on the petit puy de dome and this bulging may have formed during the eruption of the lavas negras the most recent activity on the summit area fault scarps on teide also expose small cryptodomes like those seen at lemptegy these examples coupled with field studies on eroded intrusions data on forced folds in basins and analogue models show how large scale topographic remodelling and structural change can be created by intrusions these can rapidly and significantly change the volcanic edifice a crater of elevation bulge or forced fold that is stabilised by the cooling of the intrusion will remain an important structural element in a volcano this process starts even at the small scale of monogenetic volcanoes and could occur through the lifetime of any growing stratovolcano such activity may be commonplace but may be masked by concomitant eruption or removed by subsequent collapse monitoring and hazard strategies should be ready to deal with such large scale events that will seriously modify the eruptive activity and stability of a volcano within days or weeks

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

deep roots of upper plate faults and earthquake generation illuminated by volcanism 1 for many years the generation mechanism of disastrous intraplate earthquakes in the upper plate of a subduction zone have remained unclear largely because the roots of upper plate intraplate faults have particularly quiet inter seismic nature and limited visibility here we propose that the 2008 mw 6 9 iwate miyagi nairiku japan earthquake occurred on a dipping fault in a volcanic region contains previously unreported co seismic evidence of a ductile shear zone dsz present on the down dip fault extension beneath the seismogenic layer and dsz plays a dominant role in the seismogenesis we found the evidence in the spatial pattern of the co seismic ground displacement which was well captured by synthetic aperture radar reflecting geothermal anomalies there a dynamic forward model including the inter seismic deformation of dsz naturally reproduced this displacement pattern without kinematic inversions and consistently explained other independent observations this finding should make breakthroughs in observational and theoretical studies of earthquake generation

simulation of the holocene climate over south america and impacts on the vegetation we provide a comprehensive analysis of the holocene climate and vegetation changes over south america through numerical simulations holocene climate for several periods 8 ka 6 ka 4 ka 2 ka an

paleoecology of easter island evidence and uncertainties abstract the existence of palm dominated forests covering the island since the last glaciation and the recent deforestation by humans are paradigmatic in easter island s paleoecological reconstructions the timing and mode of the deforestation are controversial but there is general agreement that it actually occurred and it is often given as an example of a human induced environmental catastrophe with philosophical implications for the future of the whole planet to evaluate whether this is the only well supported hypothesis or if there might be other scenarios compatible with the paleoecological data this paper reviews all the available evidence on past vegetation changes on easter island the discussion is centered on three main points 1 the alleged nature and extension of the former forests 2 the taxonomic identity of the dominant palms and 3 the nature of the recent ecological changes leading to a treeless island the potential causes of the assumed deforestation are beyond the scope of this study concerning the first point palynological and anthracological results obtained so far are not only compatible with a forested island but also with other scenarios for example a mosaic vegetation pattern with forests restricted to sites with a high freshwater table gallery forests which are mostly around the permanent lakes and along the coasts with regard to palm identity some extant species have been proposed as potential candidates but the palms that dominated these forests seem to have become extinct and their identity remains unknown the existence of a sedimentary hiatus around the dates of forest decline complicates the picture and reinforces the possibility of climatic changes it is concluded that the hypothesis of a previously forested island has yet to be demonstrated therefore the recent ecological disaster human induced or not is still speculative several types of future studies are proposed for a better understanding of easter island s ecological history including modern analog studies from similar situations pollen dispersal modeling high resolution multi proxy studies along the cores obtained so far more coring campaigns in the search for older sediments and dna and isotopic analyses of plant remains for taxonomic identification purposes