Peat palynomorphs from Eugenio de Melo, middle valley of Paraiba do Sul River, Sao Paulo, Brazil.

Peat palynomorphs from Eugenio de Melo, middle valley of Paraiba do Sul River, Sao Paulo, Brazil. This paper presents palynomorphs identified in the peats of the Eugenio de Melo region, the middle valley of the Paraiba do Sul River, Sao Paulo State. The samples were collected at intervals of 10 cm from a core with 3.90 m deep, aged between 11400-11220 and 490-290 cal. years B.P. Three types of algae were identified and presented, and ten spores, two gymnosperm pollen grains and thirty-nine angiosperms were described, with their own ecological information.

Chronology of Lake El'gygytgyn sediments – a combined magnetostratigraphic, palaeoclimatic and orbital tuning study based on multi-parameter analyses

A 318-metre-long sedimentary profile drilled by the International Continental Scientific Drilling Program (ICDP) at Site 5011-1 in Lake El’gygytgyn, Far East Russian Arctic, has been analysed for its sedimentologic response to global climate modes by chronostratigraphic methods. The 12 km wide lake is sited off-centre in an 18 km large crater that was created by the impact of a meteorite 3.58 Ma ago. Since then sediments have been continuously deposited. For establishing their chronology, major reversals of the earth’s magnetic field provided initial tie points for the age model, confirming that the impact occurred in the earliest geomagnetic Gauss chron. Various stratigraphic parameters, reflecting redox conditions at the lake floor and climatic conditions in the catchment were tuned synchronously to Northern Hemisphere insolation variations and the marine oxygen isotope stack, respectively. Thus, a robust age model comprising more than 600 tie points could be defined. It could be shown that deposition of sediments in Lake El’gygytgyn occurred in concert with global climatic cycles. The upper �160m of sediments represent the past 3.3 Ma, equivalent to sedimentation rates of 4 to 5 cm ka−1, whereas the lower 160m represent just the first 0.3 Ma after the impact, equivalent to sedimentation rates in the order of 45 cm ka−1. This study also provides orbitally tuned ages for a total of 8 tephras deposited in Lake El’gygytgyn.

Determinação de marcadores orgânicos no perfil sedimentar do complexo estuarino de Paranaguá (PR) por CG-EM

A avaliação do aporte de matéria orgânica no ambiente aquático por atividades antrópicas pode ser realizada através da identificação e quantificação de marcadores moleculares. Diversos estudos apontam à aplicação dos marcadores moleculares com esta finalidade, no entanto, poucos avaliam a variação das concentrações desses compostos ao longo do tempo, registrada nas camadas sedimentares. O presente trabalho realiza um estudo a partir de três classes de marcadores moleculares presentes em perfis sedimentares da região do Complexo Estuarino de Paranaguá (CEP) no Paraná (PR), que nos últimos anos vêm sofrendo com o crescente desenvolvimento de atividades antrópicas. Como objetivo, tem-se identificar as principais fontes de matéria orgânica e estudar o histórico destes aportes em colunas sedimentares do CEP, relacionando as taxas de sedimentação com a deposição de origem natural e antrópica. A legislação vigente para o monitoramento ambiental, no que diz respeito à contaminação por esgoto fecal, sugere a avaliação por indicadores microbiológicos, porém, indicadores químicos como os esteróides fecais são uma alternativa bastante promissora, pois estes são persistentes, sendo menos sensíveis a variações ambientais. Outros dois marcadores moleculares de aportes antrópicos ao ambiente que foram determinados neste estudo são os alquilbenzenos lineares (LABs), presente em detergentes, que indicam aportes antrópicos oriundos de esgoto doméstico e a determinação de cafeína, tendo em vista que os esteróides fecais podem ser originários de fezes de animais de sangue quente, podendo indicar outras fontes. Para o presente trabalho foram coletados 12 testemunhos de até 1 m de profundidade em maio de 2006, totalizando 12 pontos de coleta e um montante de 121 amostras. As análises foram realizadas por cromatografia em fase gasosa com detecção por espectrometria de massas (CG-EM). Os esteróides encontrados em maior concentração foram o β- sitosterol (71,4 µg g-1), estigmasterol (8,7 µg g-1), colestanol (3,6 µg g-1) e o estigmastanol (2,8 µg g-1), todos oriundos de fonte natural, indicando que a maior contribuição para o CEP é por aporte biogênico. O coprostanol, que é um esterol fecal, foi encontrado entre as concentrações de 0,001 e 4,10 µg g-1, outros dois esteróides de origem fecal também foram detectados, coprostanona e epicoprostanol, onde as maiores concentrações foram 3,6 e 0,2 µg g-1, respectivamente, sendo encontrados em regiões próximas a centros urbanos, indicando origem antrópica. As maiores concentrações para o ∑LABs também foram encontradas em regiões próximas às cidades de Antonina e Paranaguá, sendo a maior encontrada no testemunho #3 Gererês (208 ng g-1). Para o último marcador molecular analisado, a cafeína, foi encontrada a maior concentração de 18,41 ng g-1, sendo este ponto localizado longe dos centros urbanos, porém este contaminante é bastante solúvel em água podendo ser transportado na coluna d’água e percorrer grandes distâncias. Através dos compostos analisados, pode-se perceber que a intervenção antropogênica foi mais marcante nos testemunhos coletados no eixo leste-oeste do CEP, ficando registrado nas camadas sedimentares.

Bacterial communities and biogeochemical transformations of iron and sulfur in a high saltmarsh soil profile

Microbial community structure in saltmarsh soils is stratified by depth and availability of electron acceptors for respiration. However, the majority of the microbial species that are involved in the biogeochemical transformations of iron (Fe) and sulfur (S) in such environments are not known. Here we examined the structure of bacterial communities in a high saltmarsh soil profile and discuss their potential relationship with the geochemistry of Fe and S. Our data showed that the soil horizons Ag (oxic-suboxic), Bg (suboxic), Cri (anoxic with low concentration of pyrite Fe) and Cr-2 (anoxic with high concentrations of pyrite Fe) have distinct geochemical and microbiological characteristics. In general, total S concentration increased with depth and was correlated with the presence of pyrite Fe. Soluble + exchangable-Fe, pyrite Fe and acid volatile sulfide Fe concentrations also increased with depth, whereas ascorbate extractable-Fe concentrations decreased. The occurrence of reduced forms of Fe in the horizon Ag and oxidized Fe in horizon Cr-2 suggests that the typical redox zonation, common to several marine sediments, does not occur in the saltmarsh soil profile studied. Overall, the bacterial community structure in the horizon Ag and Cr-2 shared low levels of similarity, as compared to their adjacent horizons, Bg and Cr-1, respectively. The phylogenetic analyses of bacterial 16S rRNA gene sequences from clone libraries showed that the predominant phylotypes in horizon Ag were related to Alphaproteobacteria and Bacteroidetes. In contrast, the most abundant phylotypes in horizon Cr-2 were related to Deltaproteo-bacteria, Chloroflexi, Deferribacteres and Nitrospira. The high frequency of sequences with low levels of similarity to known bacterial species in horizons Ag and Cr-2 indicates that the bacterial communities in both horizons are dominated by novel bacterial species. (c) 2008 Elsevier Ltd. All rights reserved.

Fluid flow through the sedimentary cover in northern Switzerland recorded by calcite-celestite veins (Oftringen borehole, Olten)

Abundant veins filled by calcite, celestite and pyrite were found in the core of a 719 m deep borehole drilled in Oftringen near Olten, located in the north-western Molasse basin, close to the thrust of the Folded Jura. Host rocks are calcareous marl, argillaceous limestone and limestone of the Dogger and Malm. The delta O-18 values of vein calcite are lower than in host rock carbonate and, together with microthermometric data from fluid inclusions in vein calcite, indicate precipitation from a seawater-dominated fluid at average temperatures of 56-68A degrees C. Such temperatures were reached at the time of maximum burial of the sedimentary pile in the late Miocene. The depth profile of delta C-13 and Sr-87/Sr-86 values and Sr content of both whole-rock carbonate and vein calcite show marked trends towards negative delta C-13, high Sr-87/Sr-86, and low Sr content in the uppermost 50-150 m of the Jurassic profile (upper Oxfordian). The Sr-87/Sr-86 of vein minerals is generally higher than that of host rock carbonate, up to very high values corresponding to Burdigalian seawater (Upper Marine Molasse, Miocene), which represents the last marine incursion in the region. No evidence for internally derived radiogenic Sr (clay minerals) has been found and so an external source is required. S and O isotope composition of vein celestite and pyrite can be explained by bacterial reduction of Miocene seawater sulphate. The available data set suggests the vein mineralization precipitated from descending Burdigalian seawater and not from a fluid originating in the underlying Triassic evaporites.

Sedimentary environments and climate change: a case study (late Miocene, central Crete)

In this study, conditions of deposition and stratigraphical architecture of Neogene (Tortonian, 11-6,7Ma) sediments of southern central Crete were analysed. In order to improve resolution of paleoclimatic data, new methods were applied to quantify environmental parameters and to increase the chronostratigraphic resolution in shallow water sediments. A relationship between paleoenvironmental change observed on Crete and global processes was established and a depositional model was developed. Based on a detailed analysis of the distribution of non geniculate coralline red algae, index values for water temperature and water depth were established and tested with the distribution patterns of benthic foraminifera and symbiont-bearing corals. Calcite shelled bivalves were sampled from the Algarve coast (southern Portugal) and central Crete and then 87Sr/86Sr was measured. A high resolution chronostratigraphy was developed based on the correlation between fluctuations in Sr ratios in the measured sections and in a late Miocene global seawater Sr isotope reference curve. Applying this method, a time frame was established to compare paleoenvironmental data from southern central Crete with global information on climate change reflected in oxygen isotope data. The comparison between paleotemperature data based on red algae and global oxygen isotope data showed that the employed index values reflect global change in temperature. Data indicate a warm interval during earliest Tortonian, a second short warm interval between 10 and 9,5Ma, a longer climatic optimum between 9 and 8Ma and an interval of increasing temperatures in the latest Tortonian. The distribution of coral reefs and carpets shows that during the warm intervals, the depositional environment became tropical while temperate climates prevailed during the cold interval. Since relative tectonic movements after initial half-graben formation in the early Tortonian were low in southern central Crete, sedimentary successions strongly respond to global sea-level fluctuation. A characteristic sedimentary succession formed during a 3rd order sea-level cycle: It comprises mixed siliciclastic-limestone deposited during sea-level fall and lowstand, homogenous red algal deposits formed during sea-level rise and coral carpets formed during late rise and highstand. Individual beds in the succession reflect glacioeustatic fluctuations that are most prominent in the mixed siliciclastic-limestone interval. These results confirm the fact that sedimentary successions deposited at the critical threshold between temperate and tropical environments develop characteristic changes in depositional systems and biotic associations that can be used to assemble paleoclimatic datasets.

Rock-magnetic proxies from a sediment profile of Aike Lake

The sedimentary archive from Laguna Potrok Aike is the only continuous record reaching back to the last Glacial period in continental southeastern Patagonia. Located in the path of the Southern Hemisphere westerly winds and in the source region of dust deposited in Antarctica during Glacial periods, southern Patagonia is a vantage point to reconstruct past changes in aeolian activity. Here we use high-resolution rock-magnetic and physical grain size data from site 2 of the International Continental scientific Drilling Program (ICDP) Potrok Aike maar lake Sediment Archive Drilling prOject (PASADO) in order to develop magnetic proxies of dust and wind intensity at 52°S since 51,200 cal BP. Rock-magnetic analysis indicate the magnetic mineral assemblage is dominated by detrital magnetite. Based on the estimated flux of magnetite to the lake and comparison with distal dust records from the Southern Ocean and Antarctica, kLF is interpreted as a dust indicator in the dust source of southern Patagonia at the millennial time scale, when ferrimagnetic grain size and coercivity influence is minimal. Comparison to physical grain-size data indicates that the median destructive field of isothermal remanent magnetisation (MDFIRM) mostly reflects medium to coarse magnetite bearing silts typically transported by winds for short-term suspension. Comparison with wind-intensity proxies from the Southern Hemisphere during the last Glacial period and with regional records from Patagonia since the last deglaciation including marine, lacustrine and peat bog sediments as well as speleothems reveals similar variability with MDFIRM up to the centennial time scale. MDFIRM is interpreted as a wind-intensity proxy independent of moisture changes for southeastern Patagonia, with stronger winds capable of transporting coarser magnetite bearing silts to the lake.

Ether-derived alkanes from sedimentary organic matter

Glycerol ether lipids have been detected in the bitumen of DSDP sediments from Sites 467, 440B and 380 and from the Green River Shale. The alkyl side groups of these ethers were determined by conversion into deuteroalkanes. The presence of glycerol ethers produced by methanogenic bacteria was indicated in the DSDP bitumens by the formation of monodeuterated phytane and dideuterated biphytane. Other ethers were found with novel non-isoprenoidal side groups which may belong to sulfate-reducing or other, probably anaerobic, bacteria. Kerogen-bound alkoxy groups were determined using hydrogen iodide cleavage of the ether link followed by conversion of the iodoalkanes into corresponding deuteroalkanes. For this reaction, the kerogen was not isolated from the rock matrix. The structures so produced were found to include alkyl groups which have known bacterial precursors as well as others that are presently unknown in organisms. The Green River ether biomarker profile is interpreted as possibly indicative of bacterial diagenesis exclusive of biomethanogenesis.