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

measurements of intrinsic and scattering seismic attenuation in the crust intrinsic and scattering attenuation parameters qi and qs have been measured in three different tectonic areas for local and shallow earthquakes located close to the receiver the approach developed by wennerberg 1993 which takes into account the numerical correction of the coda q parameter for the multiple scattering formulation of zeng was used to infer from the estimates of coda q and direct s wave q the intrinsic qi and scattering qs q values results for 1 to 12 hz range show that qi is comparable to qs for the etna volcano and for the campi flegrei area while qi for the tectonically active area of granada is lower than qs coda q is close to intrinsic q suggesting that at least in the crust coda q is a good estimate of the intrinsic q volcanic areas show a reasonable higher degree of heterogeneity if compared with the nonvolcanic area of granada

evidence for a transgressive barrier within a regressive strandplain system implications for complex coastal response to environmental change clastic depositional strandplain systems have the potential to record changes in the primary drivers of coastal evolution climate sea level and the frequency of major meteorological and oceanographic events this study seeks to use one such record from a southern brazilian strandplain to highlight the potentially complex nature of coastal sedimentological response to small changes in these drivers following a 2 to 4 m highstand at ca 5 8 ka in southern brazil falling sea level reworked shelf sediment onshore forcing coastal progradation smoothing the irregular coastline and forming the 5 km wide pinheira strandplain composed of ca 500 successive beach and dune ridges sediment cores grab samples and 11 km of ground penetrating radar profiles reveal that the strandplain sequence is composed of well sorted fine to very fine quartz sand since the mid holocene highstand the shoreline prograded at a rate of ca 1 to 2 m yr 1 through the deposition of a 4 to 6 m thick shoreface unit a 1 to 3 m thick foreshore unit containing ubiquitous ridge and runnel facies and an uppermost beach and foredune unit however the discovery of a linear 100 m wide barrier ridge with associated washover units a 3 to 4 m deep lagoon and 250 m wide tidal inlet within the strandplain sequence reveals a period of shoreline transgression at 3 3 to 2 8 ka during the otherwise regressive developmental history of the plain the protected nature of pinheira largely buffered it from changes in precipitation patterns wave energy and fluvial sediment supply during the time of its formation however multiple lines of evidence indicate that a change in the rate of relative sea level fall probably due to either steric or ice volume effects may have affected this coastline thus whereas these other potential drivers cannot be fully discounted this study provides insights into the complexity of decadal scale to millennial scale coastal response to likely variability in sea level change rates

study of tidal periodicities using a transatlantic telecommunications cable we report the results of determinations of tidal periods from spectral analysis of the voltage induced across an unpowered length of the tat 7 telecommunications cable in the north atlantic ocean over an approximately 19 day interval particularly prominent spectral components are observed at several frequencies including those identified as corresponding to the diurnal declination luni solar k1 semi diurnal principal solar s2 semidiurnal principal lunar m2 and monthly lunar mm components in addition a large amplitude spectral component of high statistical significance was observed at a frequency of 3 0051 cpd approximately one third the sidereal day this component does not appear to be related to the solar component s3 and possibly corresponds to a declination luni solar k3 frequency although the amplitude is very much larger than that which might be expected other common lunar tides appear to be a minor component of the data such cable data can be used for studies and refinement on a global scale of large scale tidal ocean and ionosphere models

large scale electric field measurements on the earth s surface a review there exist only a few reported measurements of quasi stationary near dc electric potentials over very large spatial scales hundreds of kilometers or more on the earth s surface such measurements have typically been made using unpowered submarine telecommunications cables the measurements pose unique experimental challenges and require careful procedures to avoid data contamination by electrode contact potentials and local ground currents in addition there are possible interpretational problems from pervasive poorly understood low frequency electric fields induced by ocean water motion through the earth s stationary magnetic field nevertheless estimates of the magnitude of the electric field computed from large scale potential difference measurements made principally to date in the pacific ocean can be used to place a limit on the size of the toroidal magnetic field at the core mantle boundary under certain conditions on the earth s electrical conductivity profile thus large scale electric potential measurements can serve as an adjunct probe of the earth s dynamo process in addition to measurements of the poloidal magnetic field and its secular changes made at and above the surface of the earth a review of all of these data suggests that the toroidal and poloidal magnetic fields at the top of the core are comparable in magnitude

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

a critical review of mid to late holocene sea level fluctuations on the eastern brazilian coastline abstract the eastern coast of brazil is 7000 km long and has been the subject of systematic paleo sea level investigations for more than 35 years more than 1000 samples have been radiocarbon dated and paleo sea level trends have been determined for 14 coastal sectors these trends have in common a mid holocene sea level maximum pmt above present sea level and a subsequent fall to the present time the time and elevation of the pmt the time when relative sea level rose above present mean sea level and the nature of late holocene sea level fall can however differ significantly discrepancies are observed not only between neighboring coastal sectors but also between different studies in a same coastal sector this paper discusses all the key radiocarbon dated samples used to establish regional trends in relative sea level on the eastern coast of brazil it is concluded that although many of the key sea level indicators are imprecise in time and space there is widespread evidence 30 of the data set for a progressive decline possibly with uneven rates of relative sea level since the end of the pmt

quaternary fault control on the coastal sedimentation and morphology of the sao francisco coastal plain brazil abstract the role of neotectonic faulting in shaping topography and controlling sediment deposition has been increasingly documented along the stable continental margin of south america but the level of the present day tectonic stability of this margin is still a matter of debate this paper presents an investigation of the effects of quaternary fault reactivation on the sao francisco coastal plain sfcp this feature is a 56 km long progradational coastal plain located in the sergipe alagoas basin along the continental margin of brazil the sfcp is bounded on the west by a system of normal faults striking n s to ne sw the horst that bounds this plain is capped by the miocene barreiras formation and quaternary debris flow and fluvial deposits whereas the graben is filled with braided stream deposits and sandy beach ridge sediments the faulting contributed to the generation of accommodation space for the deposition of coastal sediments on the plain these processes started with the reactivation of cretaceous faults during the miocene during the quaternary fault reactivation and associated soft sediment deformation occurred between 82 and 8 3 ka with minor pulses between 1700 and 60 cal yr bp several faults along this margin are tectonically active and may represent the onshore continuation of gravitational collapses that have been documented offshore along the continental shelf and slope

impact of oceanic warming on electromagnetic oceanic tidal signals a cmip5 climate model based sensitivity study in contrast to ocean circulation signals ocean tides are already well detectable by electromagnetic measurements oceanic electric conductivities from the coupled model intercomparison project phase 5 cmip5 climate simulations are combined with tidal currents of m2 and o1 to estimate electromagnetic tidal signals and their sensitivity to global warming ninety four years of global warming leads to differences of 0 3 nt in tidal magnetic amplitudes and 0 1 mv km in the tidal electric amplitudes at sea level locally the climate induced changes can be much higher e g 1 nt in the north atlantic in general all studied electromagnetic tidal amplitudes show large scale climate induced anomalies that are strongest in the northern hemisphere and amount to 30 of their actual values consequently changes in oceanic electromagnetic tidal amplitudes should be detectable in electromagnetic records electric and magnetic signals as well as tides of different frequencies contain complementary regional information

δ 18 o of carbonate quartz and phosphate from belemnite guards implications for the isotopic record of old fossils and the isotopic composition of ancient seawater belemnite guards of cretaceous and jurassic age were found to contain varying amounts of quartz deposited both on the external surface and inside the rostrum the oxygen isotopic composition of coexisting carbonate quartz and phosphate from the same rostrum was measured according to well established techniques none of these compounds showed isotopic values in equilibrium with one another assuming 18o values of the diagenetic water within the range of meteoric waters the 18o sio2 yield temperatures in agreement with the apparent secondary origin of this phase the 18o co32 range with a certain continuity between 10 8 and 0 97 pdb 1 with most of the intermediate values being within the range of the carbonate isotopic values of mesozoic fossils the most positive isotopic results obtained from phosphate are close to 23 24 v smow they can hardly be related to a secondary origin of the phosphate or to the presence of diagenetic effects since these results are among the most positive ever measured on phosphate as far as we know there is no widespread diagenetic process determining an 18o enrichment of phosphate the very low concentration of phosphate did not allow the determination of its mineralogical composition all the available 18o po43 values from belemnite and non belemnite fossils of marine origin of tertiary and mesozoic age are reported along with the newly measured belemnites the following conclusions may be drawn from the data reported 1 the pristine oxygen isotope composition of fossil marine organisms either carbonate or phosphate may easily undergo fairly large changes because of oxygen isotope exchange processes with diagenetic water this process is apparent even in the case of geologically recent fossils 2 the 18o po43 of belemnite rostra seems to be at least in the case of the most positive results in isotopic equilibrium with environmental water because of the similarity between the results from cretaceous belemnites and the results from cretaceous and lower tertiary pelecypods and fish teeth 3 if so the only feasible interpretation that can be suggested for the 18o enriched data is the possibility of a relatively large variation of the oxygen isotopic composition of ocean paleowater from jurassic to recent time

millennial to secular time scale impacts of climate and sea level changes on mangroves from the doce river delta southeastern brazil this work integrates geomorphological sedimentological and palynological data with radiocarbon dating as well as 13c 15n and c n from sedimentary organic matter to provide a model of mangrove dynamics during the evolution of a wave dominated delta in southeastern brazil mangrove dynamics are analyzed within the context of millennial and secular climatic and sea level changes tidal flats positioned at highest limit of the intertidal zone along the edge of a lagoon sheltered by beach ridges were occupied by wetlands represented by mangrove and herbaceous vegetation during the mid holocene high sea level after considering the relative sea level fall and relatively higher fluvial sediment discharge during the last 6350 years progradation took place along this shoreline resulting in extensive beach ridge deposits that overlie transgressive muds this process led to loss of mangrove area similar dynamics were repeated at 3043 cal yr bp although in a relatively more distal i e seaward posi

variation of coastal dynamics during the last 7000 years recorded in beach ridge plains associated with river mouths example from the central brazilian coast abstract the reconstruction of relative sea level changes during the last 7000 years has shown that the central brazilian coast was been subjected to submergence until approximately 5100 yr b p however the emergence after 5100 yr b p was interrupted by two important fluctuations with an amplitude of approximately 2 3 m and a duration of 200 300 yr this evolutionary history which is quite different from that of several other regions in the world played an essential role in the development of the central brazilian coastal plains whether or not they are associated with important river mouths the periods of submergence characterized by erosional phases introduced noticeable changes in the geometry of the coastal deposits the periods of emergence gave rise to sandy terraces covered by beach ridges whose orientation is determined by the longshore drift elsewhere on a low sandy coast the direction of longshore sand transport depends on the orientation of the swell in a coast subjected to various swell patterns the efficient swells are defined as those which determine the resulting longshore transport direction such swells are not necessarily the most prevalent for instance along the central brazilian coast the southern sector waves in spite of their infrequent occurrences are much more powerful than the northern sector waves and therefore generate a longshore sand transport from south to north when fossil beach ridges are present as is the case on the central brazilian coast their geometry reflects the past directions of longshore sand transport this makes it possible to determine the provenance of past efficient swells and to establish the past wind patterns a detailed study of the beach ridge geometry of some sections of the central brazilian coast showed a sequence of reversals of the longshore drift during the last 5100 yr with a duration ranging from 10 to 100 yr these reversals represent changes in the direction of effective waves which determine the longshore transportation of sediments and consequently indicate changes in the wind pattern

electromagnetic study of the atlantic continental margin using a section of a transatlantic cable the induction of currents in an approximately 1200 km length of the tat 7 transatlantic telecommunications cable by geomagnetic field fluctuations is studied analyses of the induced voltage drop across the essentially geomagnetically east west oriented cable and of magnetic field data obtained at field sites at the cable head tuckerton new jersey and in new hampshire show a very high correlation over a wide frequency range between the induced currents in the cable and the east west magnetic field fluctuations the observations do not correspond to the classical ocean coast effects discussed in the literature the results of the analyses suggest that there are telluric currents flowing in an approximately north south direction off the east coast of the united states the electrical current flow could be primarily confined in the ocean water or channeled in a conductivity structure within the earth s crust and upper mantle if the latter situation exists as may be likely because of the wide range of frequencies over which the effect is seen then the region of the induced current flow could be related to the east coast magnetic anomaly ecma in this case these results would indicate that in addition to being a static magnetic anomaly the ecma is a structure with significant electrical characteristics such as higher conductivity

geoelectric power spectra over oceanic distances we present initial results of simultaneous measurements of the geoelectric potential as measured across two long cable routes in the pacific guam to philippines and california to hawaii separated by 6h in local time and 30 o in latitude over the fre quency range 10 5 to 1 67 x 10 3 hz the power levels tend to be enhanced near local noon along the two routes especially during geomagnetic quiet intervals during the seven days analyzed geoelectric power levels up to 104 mv km 2 km were measured on a geomagnetically disturbed day the power levels at the longest periods 17m to 150m are gen erally found to be largest along the route at lower geomagnetic latitudes guam to philippines when comparisons are made at equivalent local times in con trast the power levels for periods in the hydromagnetic wave region periods 5m tend to be larger at all local times for the higher geomagnetic latitude route the nightside geoelectric power levels along the higher lati tude route tend to increase with increasing geomagnetic activity

a reply to relative sea level during the holocene in uruguay abstract martinez and rojas 2013 published a paper about the relative sea level during the holocene in uruguay the paper of martinez and rojas could be handled as an attempt to construct a sea level curve from data collected from different sources open ocean coast the rio de la plata coastline and the outlet of uruguay river in this sense several processes were involved storm effects at open ocean beaches the holocene enclosing of coastal lagoons storms within the funnel shaped estuary and the floods of the uruguay river however they included a series of omissions inaccuracies errors and critics to our work that need to be amended rectified and argued in response we present a historical background about the research on this issue in uruguay we refute the comments about the empirical framework used to construct the first sea level curve for uruguay bracco et al 2008 2011b we point out that the assumptions on which the curve proposed by martinez and rojas 2013 is based are mistaken in addition there are limitations of the performed statistical techniques and errors mainly systematic within their formulation we present evidence that the decrease in sea level from middle holocene would not have been constant instead a rapid sea level decrease would have taken place by 4300 yr bp finally we not only compare our sea level curve with that proposed by martinez and rojas but also we corrected the altimetry errors incurred in their formulation we conclude that the similarity supports the validity of our curve

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

coastal response to late stage transgression and sea level highstand coastal morphologic features associated with past shoreline transgressions and sealevel highstands can provide insight into the rates and processes associated with coastal response to the modern global rise in sea level along the eastern and southern brazilian coasts of south america 6000 years of sea level fall have preserved late stage transgressive and sea level highstand features 1 4 m above present mean sea level and several kilome ters landward of modern shorelines gps with real time kinematics data ground penetrating radar stratigraphy and radiocarbon dating within a 2 3 km wide river associated strandplain in central santa catarina southern brazil uncovered a diverse set of late stage transgressive and highstand deposits here the highstand took the forms of 1 an exposed bedrock coast in areas of high wave energy and low sediment supply 2 a 3 8 m high transgressive barrier ridge where landward barrier migration was prohibited by the presence of shallow bedrock and 3 a complete barrier island complex containing a 5 2 m high barrier ridge washover deposits a paleo inlet and a backbarrier lowland formed in a protected cove with ample sediment supply from small local streams and the erosion of upland sediments similar signatures of the mid holocene highstand can be traced across all coastal brazilian states this study presents the fi rst complete compilation of the diversity of these sedimentary sequences they are broadly classifi ed here as exposed bedrock coasts type a back barrier deposits type b transgressive barrier ridges type c and barrier island complexes type d according to localized conditions of upland migration potential wave exposure and sediment supply these brazilian systems present a paradigm for understanding future coastal response to climate change and accelerated sea level rise the recognition of a minimum threshold sea level rise rate of 2 mm yr 1 above which transgression proceeded too rapidly for the formation of these stable accretionary shoreline features demonstrates the nonlinearity of coastal response to sea level change and the site specifi city of conditions associated with the formation of each highstand deposit type even within a single small embayment demonstrates the non uniformity of that response

mid holocene evolution and paleoenvironments of the shoreface offshore transition north eastern argentina new evidence based on benthic microfauna abstract a sedimentary record spanning 5792 5511 cal yr bp and 3188 2854 cal yr bp was recovered at 36 45 43 s 56 37 13 w south west south atlantic the sedimentological features and micropaleontological benthic foraminifera and ostracoda content were analyzed in order to reconstruct paleoenvironmental conditions considerable environmental fluctuations are indicated by all these proxies five different stages were distinguished stage 1 ca 5800 5000 cal yr bp consists of muddy sand with abundant microfossils in this interval species typical for inner marine shelf environments maintained a high abundance stage 2 consists of plastic light greenish grey clays barren of microfossils and probably represents fluvial input from the de la plata river to the shelf contemporaneous of a lowering of sea level stage 3 is composed of brownish yellow sandy silts and represents increasing marine conditions in the area as reflected by higher faunal diversity and typical foraminifera of inner shelf environments stage 4 is made of homogeneous mud barren of microfossil which represents a new pulse of fluvial input to the shelf in consequence of a new fall in sea level the final part of the core stage 5 is a coarsening upward sequence grading from greeny brown clayey sandy silts to coarse shelly sands and represents the modern sedimentation in the area this interpretation strengthens the stepped model of late holocene sea level fall between 5511 5792 cal yr bp and 2854 3188 cal yr bp in buenos aires coast and agrees with the relative sea level history previously proposed by some authors from western south atlantic coasts

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

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

high resolution stratigraphy of holocene lagoon terraces of southern brazil abstract the northern portion of the coastal plain of the rio grande do sul state southernmost brazil comprises an outer sandy barrier that protects a complex lagoon system formed during the holocene the terraces of three different lagoons gentil malvas and pinguela formed along their margins record the depositional processes and the relative base level changes over the past 5000 yr therefore our main objective was to characterize and quantify base level fluctuations from the study of these terraces to correlate them to sea level changes and to describe the depositional architecture related to the distinct sea level stages high resolution sequence stratigraphy satellite images topographic and gpr profiles auger holes and radiometric dating were used the main results indicate a close relationship between relative base level and relative sea level changes a stillstand period just after the last transgressive maximum 4840 4650 cal yr bp and a subsequent overall relative sea level fall of about 3 m both a normal highstand systems tract and a forced regression falling stage systems tract controlled the geological record preserved in the terraces the highstand older terrace is characterized by agradational bedding whereas the falling stage comprises three progradational sets terraces bounded by erosive surfaces related to smaller scale sea level drops

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

assessing links between late holocene climate change and paleolimnological development of pena lagoon using opal phytoliths physical and geochemical proxies abstract opal phytolith geochemical and sedimentological data from two cores taken in pena lagoon a small water body on the atlantic shore of uruguay are presented in this paper the choice of this specific sampling location aimed to obtain high resolution records to infer late holocene environmental and climatic changes in southeastern uruguay in order to improve previous models for early and middle holocene the combined record of two cores extends to 2500 14c bp with a sedimentation rate ranging between 0 6 and 2 mm y 1 a multiproxy approach allowed the identification of changes in dynamics particularly organic matter and sediment input variability from the watershed with this information differences in the amount and extent of environmental signals were evaluated and a comprehensive climate change model was generated especially for the last 1500 years three main climatic events were distinguished the oldest which lasted until 700 ad was characterized by temperate and humid conditions the second extended until 1200 ad and warmer and wetter conditions were inferred but also a colder and drier pulse was observed in between this second event was assigned to the warm medieval period wmp during the third event assigned to the little ice age lia which extended until the present a high variability in climate was observed but also three dry cold phases reaching their maxima by 1300 1600 and 1900 ad were inferred

a taphonomic study of δ13c and δ15n values in rhizophora mangle leaves for a multi proxy approach to mangrove palaeoecology abstract the response of mangrove ecosystems to environmental change can be examined with stable isotopic tracers of c and n the 13c and 15n of a taphonomic series of rhizophora mangle l red mangrove leaves were analyzed from twin cays belize to facilitate reconstruction of past mangrove ecosystems on twin cays fresh leaves of dwarf r mangle trees 0 5 m high were found to have more negative 15n values mean 10 and more positive 13c values mean 25 3 compared to tall r mangle trees mean 15n 0 13c 28 3 these isotopic differences can be related to nitrogen and phosphorus availability ecology 83 2002 1065 we investigated three taphonomic stages in the fossilization of r mangle leaves into peat with the following 1 senescent leaves 2 fallen leaves on the surface of the peat and 3 sub fossil leaves found within mangrove peat in addition by examining natural leaf assemblages we established that 13c and 15n of r mangle leaves were not altered during senescence despite a significant 50 decrease in the n modern dwarf and tall trees could still be identified from 13c and 15n analyses of the leaf assemblages found directly below a tree dwarf and tall trees could also be identified from 13c analyses of leaves that had decomposed for four months although dwarf and tall trees could not be statistically separated after four months according to 15n analyses leaves with very negative 15n 7 were only collected below dwarf trees leaf fragments were present in 50 cm long cores of peat from four sites on the island and their isotopic compositions were determined the ranges of 13c 29 to 22 and 15n 11 to 2 values from sub fossil leaves were similar to the ranges from modern leaves 13c 29 to 23 15n 11 to 1 the sub fossil leaf isotopic compositions were independent values in comparison to the uniform values of the surrounding peat because of the stability and persistence of the stable isotopic signals they could contribute significantly to a multi proxy approach to mangrove palaeoenvironmental reconstruction

vegetation dynamics during the last 7500 years on the extreme southern brazilian coastal plain abstract for the first time in the extreme southern brazilian coastal plain we analyzed palynomorphs in a continuous sequence using an outcrop profile of relict muds in hermenegildo beach 33 42 12 s 53 18 57 w santa vitoria do palmar rio grande do sul state five radiocarbon dates were obtained the results revealed the plant succession in an ancient water reservoir near the coastal line 7500 4000 bp marine organisms and freshwater taxa with herbaceous marsh at the margins marine taxa were markedly present from 6000 to 5000 bp the time of the maximum transgression regionally the vegetation was dominated by grasslands and forest groupings 4000 2000 bp regressive marine phase with an increased record of freshwater organisms due to increased rainfall a large increase in herbaceous marsh components resulted in a gradual filling in of the water reservoir and the development of regional vegetation 2000 1760 bp with the end of the marine regression progressive desalinization promoted the local herbaceous marsh development regionally grassland and forest also developed indicative of climate amelioration local plant succession ceased during this phase of herbaceous marsh ca 1760 bp when beach sands covered the sedimentary sequence this study reveals the phases of a hydrosere in a coastal water reservoir influenced by marine oscillations with gradual desalinization and filling in that culminated in an herbaceous marsh deposit these results provide a basis for understanding many other similar relict muds spread throughout the coastal plain in the extreme south of brazil

late pleistocene recent marine malacological assemblages of the colorado river delta south of buenos aires province paleoecology and paleoclimatology abstract the most recent quaternary marine transgressions are well represented along the south atlantic coast in the colorado river delta 39 15 s 39 55 s south of buenos aires province these deposits are mostly littoral ridges and tidal plains with abundant fossil marine fauna seventeen localities were analyzed five pleistocene seven holocene and five modern ones representing the interglacials mis 9 mis 5e and mis 1 a total of 51 species were recorded 29 bivalves and 22 gastropods together with nine micromolluscs mis 1 and the modern coast 37 and 42 species respectively are the richest ones in species unlike mis 5e and mis 9 18 and 2 species respectively in mis 9 the most abundant species is pitar rostratus mis 5e and mis 1 have in common the presence and abundance of the gastropod heleobia australis and the bivalve tagelus plebeius as typical fauna of low energy environments being the bivalve glycymeris longior and the gastropods bostrycapulus odites and buccinanops globulosus common species in both kinds of marine deposits approximately 90 of bivalves and 75 71 of gastropods of the marine fauna are recorded from mis 5e to the present according to the different descriptive analyses bray curtis index and ac the molluscan fauna was grouped in two and five assemblages respectively defined by age type of deposit and presence and or abundance of species marine species represented in the area of the colorado river delta vary in abundance among the interglacials but not in faunal composition one of the possible causes would be the global climatic changes e g rise of sea surface temperature sst and the heterogeneity of habitats that would have conditioned the development of the different faunal assemblages during the quaternary

hauts niveaux marins pleistocenes du littoral bresilien abstract the high sea level corresponding to the last pleistocene interglacial stade left the most important records represented by extensive beach ridge plains along the central and southern coasts of brazil during the maximum level which was dated at 123 000 yr b p by coral samples the relative sea level was situated 8 2 m above present level four generations of quaternary marine sandy deposits have been described in southern brazil state of rio grande do sul where they are known as barrier i ii iii and iv the barrier iv about 4 m high corresponds to the last great transgressive regressive phase whose maximum occurred about 5100 yr b p the barrier iii with a height of about 8 10 m corresponds to the penultimate transgressive regressive period whose maximum was produced about 123 000 yr b p the barrier ii about 13 15 m high and the barrier i about 20 25 m high situated at inner positions in relation to the previous ones have been formed during high sea levels older than 123 000 years along the coastal plains of the states of sergipe and bahia the high sea level older than 123 000 years is represented only by one phase through cliffs carved within the barreiras formation on the other side along the coastalp plains of sao paulo parana and santa catarina there are marine terraces with a minimum height of 13 m above present sea level which are certainly older than the barrier iii and are probably recording the transgressive regressive period of the barrier ii middle pleistocene

ocean cable measurements of the tsunami signal from the 1992 cape mendocino earthquake the movement of the seawater across the earth s magnetic field produces a large scale motional electric field using the point arena california to hanauma bay hawaii unpowered haw 1 cable we have studied the geopotential across this distance to look for possible tsunami induced fields that might have been produced following the april 1992 cape mendocino earthquake we have used a ten day interval prior to and including the earthquake as a reference for geopotential signals and for geomagnetic activity we have also used geomagnetic data from point arena honolulu and boulder as reference data the results of the analyses show that there are tsunami related effects in the cable geopotential data these are a larger voltage prediction errors residuals for the interval following the main shock b enhanced compared to the 10d reference interval geopotential spectral power following the main shock two enhancements are larger than geomagnetically induced spectral power enhancements in the same time interval and c strong evidence for an 30 min echo in the cable geopotential signal following the main shock

late pleistocene and holocene palaeoenvironments in golfo san jorge patagonia molluscan evidence palaeoenvironments suggested by molluscan assemblages preserved in late pleistocene and holocene raised marine terraces along the golfo san jorge central patagonia coastline argentina are reviewed in this work a better precision of the stratigraphical and geographical ranges of the molluscs through their systematic review shows that all taxa have living representatives mostly within the argentine and or magellanean zoogeographical provinces in general no significant taxonomic appearances or disappearances are evident along this coastal area since the last pleistocene highstand reinforcing that the modern palaeoceanographical pattern dominated by the cool malvinas falkland current has not been substantially modified and that the magellanean malacological province has lasted at least since the pleistocene although with varying boundaries the so called marine terrace v recently assigned to the last interglacial highstand oxygen isotope substage 5e showed in this area a molluscan assemblage characterised by very low diversity dominantly large shells of mulinia edulis and by cold water taxa in disagreement with higher sea surface temperatures within oxygen isotope substage 5e last interglacial maximum and suggesting softer substrates than in the modern adjacent littoral zone

taphonomic comparison between two bivalves mactra and brachidontes from late quaternary deposits in northern argentina which intrinsic and extrinsic factors prevail under different palaeoenvironmental conditions quaternary records of unique skeletal deposits studied at two coastal areas of the bonaerensean littoral bahia samborombon in the north at puente de pascua and canal 15 area and bahia blanca southwards are thick 4 5 m and exceptionally rich in molluscan assemblages ca 75 90 bivalve shells indicating different high sea level episodes through taphonomical aspects of target bivalves mactra brachidontes which differ in shell structure life habit and habitat abundantly present in the marine late quaternary from both areas the aims were 1 to establish quantitative grades of taphonomic alteration of mactra from four lithostratigraphical units at bahia samborombon and identify which signature s better discriminates palaeoenvironments 2 test whether mactra shows different alteration than does brachidontes in response to differences in intrinsic features and ecological requirements 3 compare isotaphonomic assemblages complementing independent geological and palaeoenvironmental interpretations attributes articulation fragmentation abrasion colour encrustation bioerosion were classified for about 5400 shells from 11 samples bar plots ternary taphograms and q mode cluster analysis discriminate beach beach ridges and tidal flat environments and two taphofacies late pleistocene and holocene high energy units and low energy holocene units only abrasion and colour allow discrimination between high and low energy conditions rules cannot be applied to the processes of deposition of shells at least for the late quaternary marine deposits along the buenos aires province coastal area despite the harder mactra or more fragile brachidontes shell architecture in softer mactra muddy substrates infaunal or harder brachidontes varied sandy rocky bottoms epibyssate and deeper mactra infralittoral or shallower waters brachidontes intertidal to supratidal the taphonomic grades of alteration are similar a product mainly of long after death exposure along the taphonomically active zone in high to moderate wave energy conditions