HR: 1340h
AN: GP43B-0862    [Abstracts]
TI: The Potential of Magnetostratigraphy for a Global Correlation of the Germanic Triassic - Case Study Buntsandstein
AU: * Szurlies, M
EM: szur@gfz-potsdam.de
AF: GeoForschungsZentrum Potsdam, Telegrafenberg Haus C, Potsdam, D-14473 Germany
AB: The Buntsandstein represents the lower group of the tripartite classic Germanic Triassic supergroup. In its type area of Central Germany, the thickness of the Buntsandstein is about 1000 m. The predominantly clastic sediments were deposited during latest Permian to earliest Middle Triassic times in mainly fluvio-lacustrine environments of a large intracratonic basin. Traditionally, the Buntsandstein is subdivided by lithological criteria, showing a distinct cyclicity, pragmatically subdivided in 5 to 25 m thick small-scale fining-upward cycles. Above all, these cycles are correlation cycles, that are obvious in wireline logs, cores and outcrops. With wireline logs (e.g., gamma-ray logs) they can be correlated over almost the entire epicontinental Central European Basin. The thickness of these fining-upward cycles corresponds to that of genetic cycles, which are considered to reflect climatic fluctuation of alternating drier and wetter periods due to solar-induced 100 ka eccentricity cycles. On the basis of this robust high-resolution lithostratigraphic framework a very precise positioning and verification of paleomagnetic results has been realized. In Central Germany eighteen sections (twelve outcrops, six wells) were collected at 1-2 m intervals, yielding a total of nearly 2100 oriented standard samples. From about 81 % of them a characteristic remanence was obtained, being carried by magnetite in the gray lithologies and by hematite in the red-brown lithologies, respectively. The inter-section correlation of all investigated profiles allows the creation of a well-defined composite magnetic polarity record for Central Germany, being in good agreement with polarity scales from the Boreal and Tethyan realms. The magnetozones of the Buntsandstein last 0.1-0.9 Ma, with an average duration of approx 0.3 Ma. According to magnetostratigraphic and biostratigraphic data, the position of the Hindeodus parvus calibrated Permian-Triassic boundary is located within the so-called "Graubankbereich" (= gray bed interval), about 20 m above the lithostratigraphic Zechstein-Buntsandstein boundary. In terms of magnetostratigraphy, it is situated within the lowermost part of a remarkable thick normal polarity zone, which is a distinctive feature occuring in virtually all magnetic records across the Permian-Triassic boundary. The boundary between the Calv”rde and Bernburg formations of the Lower Buntsandstein is close to the Griesbachian-Dienerian boundary.
DE: 1520 Magnetostratigraphy
DE: 1535 Reversals (process, timescale, magnetostratigraphy)
SC: Geomagnetism and Paleomagnetism [GP]
MN: 2004 AGU Fall Meeting