362 resultados para Gustavia elliptica


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The continuously influence of human impacts on the seafloor and benthic habitats demands the knowledge of clearly defined habitats to assess recent conditions and to monitor future changes. In this study, a benthic habitat dominated by sorted bedforms was mapped in 2010 using biological, sedimentological and acoustic data. This approach reveals the first interdisciplinary analysis of macrofauna communities in sorted bedforms in the German Bight. The study area covered 4 km², and was located ca. 3.5 km west of island of Sylt. Sorted bedforms formed as sinuous depressions with an east west orientation. Inside these depressions coarse sand covers the seafloor, while outside predominantly fine to medium sand was found. Based on the hydroacoustic data, two seafloor classes were identified. Acoustic class 1 was linked to coarse sand (type A) found inside these sorted bedforms, whereas acoustic class 2 was related to mainly fine to medium sands (type B). The two acoustic classes and sediment types corresponded with the macrofauna communities 1 and 2. The Aoinides paucibranchiata-Goniadella bobretzkii community on coarse sand and the Spiophanes bombyx - Magelona johnstonii community on fine sand. A transitional community 3 (Scoloplos armiger - Ophelia community), with species found in communities 1 and 2, could not be detected by hydroacoustic methods. This study showed the limits of the used acoustic methods, which were unable to detect insignificant differences in the fauna composition of sandy areas.

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Neogene and Quaternary silicoflagellates, actiniscidians, and ebridians are described from Sites 679 through 688 in the eastern Pacific off Peru. Five silicoflagellate zones and one horizon can be distinguished in the Neogene and Quaternary sequences. The encountered Eocene and Oligocene sequences are barren in silicoflagellates. Several hiatuses were noted in the Neogene and early Pleistocene sequences. Displaced silicoflagellates and ebridians from older strata were found occasionally, with a distinct increase in the Quaternary at Site 688. Distribution lists for species found are presented for Sites 682, 683, 685 and 688. Systematic discussion centers on the Distephanus bioctonarius group, with special reference to Hole 681A. Two new forms (Distephanus bioctonarius f. decimarius and Distephanus speculum subsp. speculum f. pseudoseptenarius) are described from the eastern Pacific Quaternary sequence.

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Remains of diatoms, molluscs, ostracods, foraminifera and pollen exines preserved in the sediments of Lago d'Averno, a volcanic lake in the Phlegrean Fields west of Naples, allowed us to reconstruct the changes in the ecological conditions of the lake and of the vegetation around it for the period from 800 BC to 800 AD. Lago d'Averno was at first a freshwater lake, temporarily influenced by volcanic springs. Salinity increased slowly during Greek times as a result of subsidence of the surrounding land. Saline conditions developed only after the lake was connected with the sea by a canal, when Portus Julius was built in 37 BC. The first post-Roman period of uplift ended with a short freshwater phase during the 7th century after Christ. Deciduous oakwoods around the lake was transformed into a forest of evergreen oaks in Greek times and thrived there - apparently almost uninfluenced by man - until it was felled, when the Avernus was incorporated into the new Roman harbour in 37 BC, to construct a shipyard and other military buildings there. Land-use was never more intense than during Roman times and weakest in Greek and Early Roman times, when the Avernus was considered a holy place, the entrance to the underworld.

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The occurrence of Cenozoic silicoflagellates at three Ocean Drilling Program (ODP) Holes (660A, 662A, and 667A) was investigated to determine biostratigraphic and relative paleotemperature relations in the tropical Atlantic Ocean. This report presents the data obtained from a study of 37 samples and some preliminary comments on the data. The age of the single sparse assemblage at Hole 660A is late middle Eocene or late Eocene (Dictyocha hexacantha Zone); the sparse to common assemblages of Hole 667A are Oligocene and early Miocene and the common to abundant assemblages of Hole 662A are early Pliocene to Quaternary. Dissolution thinning of silicoflagellates is noted in most samples, even in Hole 662A, which is under the present productive Benguela Current.

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Vierlandian, Behrendorfian (Lower Hemmoorian), Oxlundian (Upper Hemmoorian), Lower and Upper Reinbekian, Langenfeldian and Gramian stages could be proved by evaluation of marine molluscan faunas. The diachrone base of 'Braunkohlensande' is demonstrated by underlying Vierlandian mica clay in the E, and by Hemmoorian substages more to the W, at last the fluviatile facies is replaced completely by euhaline to brachyhaline sandy to silty sediments. Brachyhaline effects in adjacent environments make possible an approximate dating on fluviatile sedimentation. The widest extension of 'Braunkohlensand' is during upper Oxlundian, whilst slightly brachyhaline Katzheide beds, defined in this paper to be of Lower Reinbekian age, indicate a limit of 'Braunkohlensande' more to the E. Winnert-fauna was found to be a mixture of Oxlundian and Langenfeldian; the overlying lignitic sands belong to the Kaolinsand group. Upper mica clay overlying Miocene Braunkohlensande can be divided into beds of Upper Reinbekian, Langenfeldian and Gramian ages.

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Silicoflagellates are described from Sites 588 (middle Eocene), 591 (middle Miocene to lower Pliocene), and 594 (middle Miocene to Quaternary) in the southwest Pacific. At Sites 591 and 594 a detailed silicoflagellate zonation is possible, although there are some obvious differences arising from the latitudinal position of the sites in the silicoflagellate assemblages. Comparison between the sequences recovered at Sites 591 and 206 (Leg 21) revealed two hiatuses in the latter, but helped to establish a zonation for this area from the lower Miocene to the Pleistocene and a correlation to standard nannoplankton zones. The stratigraphic implications of the taxonomy used by various authors and the species concept presented here are discussed in detail. Special reference is made to types described by Ehrenberg and to later synonyma, because the Ehrenberg collection is the base for all subsequent descriptions and evaluations of silicoflagellate taxa. Two new genera (Neonaviculopsis, Paramesocena), two new subspecies (Dictyocha fibula subsp. asymmetrica, Neonaviculopsis neonautica subsp. praenautica), and three new forms (Dictyocha perlaevis f. pentaradiata, Distephanus speculum subsp. speculum f. nonarius, and Mesocena ? hexalitha f. heptalitha) are described from the southwest Pacific Neogene and Pleistocene. Associated sponge spicules were noted and will be described in detail in a later paper, but some are documented on Plate 13.

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