878 resultados para Localities extracéntricas


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To better acquaint seniors in Geology and mining with actual field practice, the Montana School of Mines offer a course in Geologic Field Mapping, during the three weeks preceding the opening of the fall semester. The first two weeks are spent in actual field mapping of the geologic formations near Whitehall, Montana, while the third week is spent back on the campus compiling data and finishing maps started in the field.

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Fossil leaves of the Voltziales, an ancestral group of conifers, rank among the most common plant fossils in the Triassic of Gondwana. Even though the foliage taxon Heidiphyllum has been known for more than 150 years, our knowledge of the reproductive organs of these conifers still remains very incomplete. Seed cones assigned to Telemachus have become increasingly well understood in recent decades, but the pollen cones belonging to these Mesozoic conifers are rare. In this contribution we describe the first compression material of a voltzialean pollen cone from Upper Triassic strata of the Transantarctic Mountains. The cone can be assigned to Switzianthus Anderson & Anderson, a genus that was previously assumed to belong to an enigmatic group of pteridosperms from the Triassic Molteno Formation of South Africa. The similarities of cuticle and pollen morphology, together with co-occurrence at all known localities, indicate that Switzianthus most probably represents the pollen organ of the ubiquitous Heidiphyllum/Telemachus plant.

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Thirty-seven varieties of a Mediterranean durum wheat collection grown in Tunisia and Spain were analysed for their allelic composition in prolamins, as well as their protein concentration, sodium dodecyl sulphate sedimentation (SDSS) test and mixograph parameters. Genotype was a greater source of variation in all measurements than locality. Uncommon high and low molecular glutenin subunits (HMW-GS and LMW-GS) were found (V and 2? subunits at Glu-A1, 13 þ 16 at Glu-B1, 5* subunit and ax allele at Glu-A3). The rare combinations 2 þ 4þ14 þ 18 and 8 þ 9þ13 þ 16þ18 subunits at the Glu-B3 locus were found. Glu-A3ax had a positive influence on SDSS and mixograph parameters. Of all the prolamins, those that have the B-LMW-GS composition aaa (for Glu-A3, Glu-B3 and Glu-B2 loci, respectively), when associated with the Glu-A1c and Glu-B1d gave the best semolina quality. By contrast, semolina quality is poor when this same composition is associated with the Glu-A1c and Glu-B1e and even poorer when associated with the Glu-A1c and Glu-B1f. In addition, the cultivars with B-LMW-GS allelic composition aab (for Glu-A3, Glu-B3 and Glu-B2 loci, respectively), when associated with the Glu- A1c and Glu-B1d, gave high quality, whereas when associated with the Glu-A1c and Glu-B1e or with Glu- A1o and Glu-B1f, the quality was very poor.

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In ganz Norddeutschland werden bei jeder tieferen Bohrung bis zu mehrere 100 m maechtige Schichten des Diluviums durchbohrt, die aus scheinbar voellig unregelmäßigen Folgen von Sand, Kies und Geschiebemergel bestehen. Diese Absätze lassen sich in den meisten Fällen mit den bisherigen Methoden nicht weiter untergliedern. Aus besonders günstigen Aufschlüssen und Profilen ist bekannt, daß mindestens drei Vereisungen während des Diluviums über das norddeutsche Flachland hinweggegangen sind. Wenn in den Bohrungen nicht zufällig sichere Interglazialschichten auftreten, was äußerst selten der Fall ist, so ist es also im allgemeinen nicht möglich, das erbohrte Diluvium auf die drei bekannten Vereisungen aufzuteilen. Es besteht für Tagesaufschlüsse im Diluvium durch die Geschiebezählmethode nach Milthers, Heesemann u. a. wenigstens eine Möglichkeit, stratigraphische Einordnungen vorzunehmen. Arbeitsmethoden und Ergebnisse der Geschiebezählmethode sollen hier jedoch nicht näher besprochen werden. Dreimanis 1936 gibt eine Methode an, um aus Bohrproben durch Zählungen der Mineralkörner der Grobsand- und Feinkiesfraktionen Anhaltspunkte für vergleichende stratigraphische Untersuchungen zu gewinnen.

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Fossil manganese nodules and encrustations from seamount' and basin' localities in the Transdanubian Central Mountains of Hungary are lithologically, mineralogically and chemically similar to some modern marine ferromanganese oxide deposits, and show no evidence of postdepositional changes other than cementation. Five groups of deposits were encountered: Fe/Mn nodules, encrusted shells, pavements, stains, and Fe oxide encrusted intraclasts, the first three of which are specific to the 'seamount' environment and the last to the basins'. Optical and electron microprobe investigation of the samples shows them to exhibit many similarities with modern ferromanganese oxide deposits, and that many of the nodules are surrounded by a halo of dispersed ferromanganese oxides, strongly suggesting that they continued to accrete metals through the pore waters of unlithified sediments for a period after burial. By contrast, pavements which appear to have grown on hardgrounds at the sea floor show little or no evidence of derivation of metals from underlying sediments. Geochemical investigations on the deposits show the seamount' varieties to be closer in composition to most modern nodules and crusts than the basin' varieties, and that the latter are essentially manganese and trace-element-poor ferruginous deposits. Nevertheless, all can be more or less compositionally equated with modern ferromanganese oxide deposits forming in marginal Atlantic environments, which would be in accord with the proposed depositional environment of the Transdanubian Central Mountains based on other evidence.

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National Highway Safety Bureau, Washington, D.C.

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Loose-leaf.

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National Highway Safety Bureau, Washington, D.C.

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Mode of access: Internet.

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Mode of access: Internet.