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  • 2010-2014  (3)
  • 1970-1974  (2)
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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    International journal of earth sciences 59 (1970), S. 805-826 
    ISSN: 1437-3262
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Description / Table of Contents: Abstract 172 carbonate samples from the Alps (mainly the Northern Calcareous Alps) ranging from Norian to Middle Liassic age, have been investigated for their18O/16O-content. Paleotemperatures have been determined. The analysed samples — fossils, mainly with primary calcitic shells, ooids and carbonatic sediments —were carefully selected by optical and x-ray methods. The results are given in fig. 2. Paleotemperatures are plotted in groups of the same age and equal or similar facies. The maximum of each group is assumed to represent the average water-temperature of that time. The interpretation of the paleotemperatures refers also to paleogeographic factors, e. g. bathymetry and salinity. The Noric shelf-sea paleotemperatures are in the range of about 25° C and show a systematic decrease to the Upper Rhaetian; a minimum temperature during the Lower Liassic (18° C) was followed by a warmer climatic period in the Middle Liassic. It is assumed that the Upper Triassic coral-reefs of the Northern Calcareous Alps died out because of the low temperature.
    Abstract: Résumé Pour 172 échantillons carbonates allant du Norien jusqu'au Lias moyen des Alpes on a déterminé les paleotemperatures d'après le rapport18O/16O. Étudiant surtout des fossiles, nous avons préféré ceux qui, dès l'origine, consistaient en grande partie ou totalement en calcite; en outre nous avons utilisé des ooides et des roches. Pour éviter l'altération diagénétique du rapport18O/16O, on a examiné le degré de la diagnèse sous le microscope et à l'aide des rayons X; le matériel visiblement récristallisé a été exclu de l'étude. Les températures déterminées — groupées selon l'âge et le faciès (fig. 2) —s'accumulent pour la plupart clairement autour de valeurs qui, vraisemblablement, représentent les températures originales de l'eau de mer — vu le nombre élevé des échantillons et les conditions variées de diagenèse qu'ils ont subi. Cette supposition a été vérifiée par des températures determinées sur de l'aragonite pour le Rhétien (Kaltenegger 1967). En interprétant les paléotempératures on a tenu compte des facteurs de paléogéographie (bathymétrie, salinité etc.). Les échantillons noriens provenant d'une mer peu profonde ont donné des températures d'environ 25° C, les échantillons rhétiens des valeurs un peu plus basses. Un minimum pendant le Lias inférieur a été suivi, pendant le Lias moyen, par un réchauffement de plusieurs degrés. On peut donc penser que les récifs coralliens du Trias supérieur dans les Alpes calcaires septentrionales se sont retirés pour des raisons climatiques au cours du Lias inférieur.
    Notes: Zusammenfassung Für 172 karbonatische Proben aus Nor bis Mittellias der Alpen wurden Paläotemperaturen nach dem18O/16O-Mischungsverhältnis bestimmt. Untersucht wurden vor allem Fossilien, und zwar bevorzugt solche, die primär vorwiegend oder gänzlich aus Calcit bestanden haben; daneben auch Ooide und Gesteine. Um diagenetischen Verschiebungen des18O/16O-Verhältnisses aus dem Wege zu gehen, wurde der Diagenese-Grad jeweils optisch und mit der röntgenographischen Phasen-Analyse geprüft; sichtbar rekristallisiertes Material wurde nicht verwertet. Die ermittelten Paläotemperaturen zeigen — nach Alter und Fazies-Gruppen getrennt dargestellt (Abb. 2) — meist deutliche Häufungen, die angesichts der relativ großen Probenzahlen und der unterschiedlichen diagenetischen Bedingungen für die einzelnen Proben den ursprünglichen Wasser-Temperaturen annähernd entsprechen dürften; diese Annahme wird durch Paläotemperaturen aus aragonitischem Material für das Rät bestätigt. Bei der Interpretation der Paläotemperaturen wurden paläogeographische Faktoren (Bathymetrie, Salzgehalt u. a.), soweit bekannt, berücksichtigt. Für die norischen Flachmeer-Proben ergeben sich Temperaturen um 25°C, für die rätischen etwas niedrigere Werte. Einem Temperatur-Minimum im Unterlias folgte im Mittellias eine Erwärmung um mehrere Grade. Demnach dürften die obertriassischen Korallen-Riffe in den Nördlichen Kalkalpen während während des Unterlias aus klimatischen Gründen abgestorben sein.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Contributions to mineralogy and petrology 40 (1973), S. 159-168 
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Oxygen isotope analyses on minerals of a metamorphic profile from Hohe Tauern, Austria indicate that the oxygen isotopes of the coexisting minerals quartz, garnet, and biotite have been reequilibrated during alpidic metamorphism. The K/Ar-ages of these biotites are in the range of 20–30 my. Metamorphic temperatures can be calculated from the quartz-biotite and quartz-garnet isotopic fractionations. The metamorphic temperature in the northern part of the region under investigation is 440° C and increases in direction to Tauernhauptkamm to about 600° C. Indicated by petrographic investigations, two samples from this area show no remarkable metamorphic influence. K/Ar-determinations on hornblendes and biotites yielded variscan ages. The isotopic temperatures of these samples, calculated by the oxygen isotope fractionations of quartz-biotite, quartz-magnetite, and feldspar-magnetite are equal within the limits of instrumental error and represent the crystallisation temperature of a granodioritic magma of 660–670° C.
    Type of Medium: Electronic Resource
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  • 3
    Publication Date: 2017-02-08
    Description: We present an SiF4 separation line, coupled to a laser fluorination system, which allows for an efficient combined silica d18O and d30Si analysis (50 min per sample). The required sample weight of 1.5–2.0mg allows for high-resolution isotope studies on biogenic opal. Besides analytical tests, the new instrumentation set-up was used to analyse two marine diatom fractions (〉63 mm, 10–20mm) with different diatom species compositions extracted from a Bølling/Allerød–Holocene core section [MD01-2416, North-West (NW) Pacific] to evaluate the palaeoceanographic significance of the diatom isotopic signals and to address isotopic effects related to contamination and species-related isotope effects (vital and environmental effects). While d30Si offsets between the two fractions were not discernible, supporting the absence of species-related silicon isotope effects, systematic offsets occur between the d18O records. Although small, these offsets point to species-related isotope effects, as bias by contamination can be discarded. The new records strengthen the palaeoceanographic history during the last deglaciation in the NW Pacific characterized by a sequence of events with varying surface water structure and biological productivity. With such palaeoceanographic evolution it becomes unlikely that the observed systematic d18O offsets signal seasonal temperature variability. This calls for reconsideration of vital effects, generally excluded to affect d18O measurements.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 4
    Publication Date: 2023-07-09
    Keywords: Actiniscus pentasterias; Actinocyclus curvatulus; Actinocyclus ochotensis; Actinocyclus oculatus; Actinoptychus senarius; AWI_Paleo; Biogenic silica, non-diatom; Contamination; Coscinodiscus marginatus; Coscinodiscus oculus-iridis; Coscinodiscus radiatus; Coscinodiscus spp.; Depth, bottom/max; DEPTH, sediment/rock; Depth, top/min; Diatoms; Emperor Seamounts; Giant piston corer; GPC; IMAGES VII - WEPAMA; Marion Dufresne (1995); MD012416; MD01-2416; MD122; Paleoenvironmental Reconstructions from Marine Sediments @ AWI; Porosira glacialis; Radiolarians; Rhizosolenia hebetata; Silica, non-biogenic; Sponge spiculae; Stellarima stellaris; Stephanopyxis turris; Sum; Thalassiosira antarctica var. borealis; Thalassiosira spp.; Thalassiosira trifulta
    Type: Dataset
    Format: text/tab-separated-values, 504 data points
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  • 5
    Publication Date: 2023-07-10
    Keywords: Actinocyclus actinochilus; Actinocyclus ochotensis; AWI_Paleo; Biogenic silica, non-diatom; Contamination; Coscinodiscus marginatus; Coscinodiscus oculus-iridis; Coscinodiscus spp.; Depth, bottom/max; DEPTH, sediment/rock; Depth, top/min; Diatoms; Diatoms, non-coscinodiscus; Emperor Seamounts; Eucampia antarctica; Giant piston corer; GPC; IMAGES VII - WEPAMA; Marion Dufresne (1995); MD012416; MD01-2416; MD122; Paleoenvironmental Reconstructions from Marine Sediments @ AWI; Radiolarians; Silica, non-biogenic; Stephanopyxis turris; Sum; Thalassiosira spp.
    Type: Dataset
    Format: text/tab-separated-values, 305 data points
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