HR: 0800h
AN: GP41F-04    [Abstracts]
TI: Intercalibration of Boreal and Tethyan Middle Triassic biostratigraphies: magnetostratigraphy from central Spitsbergen, Arctic Norway
AU: * Hounslow, M W
EM: M.Hounslow@lancs.ac.uk
AF: CEMP, Geography Dept., Bailrigg, Lancaster, LA! 4YB, United Kingdom
AU: Hu, M
AF: CEMP, Geography Dept., Bailrigg, Lancaster, LA! 4YB, United Kingdom
AU: Mork, A
AF: SINTEF Petroleum Research, N-7465, Trondheim, Norway
AU: Weitschat, W
AF: Geologisch-Paläontologisches Institut und Museum, Universität Hamburg, Bundesstrasse 55, 20146, Hamburg, Germany
AU: Vigran, J
AF: SINTEF Petroleum Research, N-7465, Trondheim, Norway
AB: Providing a high resolution intercalibration of high latitude and low latitude biostratigraphies potentially provides an important key in understanding Triassic climatic events at a global scale along with their relative timing. Here we present information which allows us to achieve this using an integrated magneto-biostratigraphic study of the Middle Triassic Botneheia Fm at Milne Edwardsfjellet, central Spitsbergen. The Botneheia Fm is a succession of mostly dark grey to black shales, more intensely laminated in its upper parts. Palaeomagnetic information was determined by combined thermal and alternating field demagnetization. The palaeomagnetic information from the Botneheia Fm are quite strongly contaminated by an overlapping present-day like magnetization, giving rise to mostly great-circle like trends to apparent Triassic-like magnetizations. The ammonoid biostratigraphic data suggests the Botneheia Fm at Milne Edwardsfjellet probably continues without significant break from the underlying Lower Triassic (Vikinghogda Fm). This is confirmed by the magnetostratigraphy, which indicates how to best equate Boreal- Tethyan successions at the Lower to Middle Triassic boundary. In spite of limited biostratigraphic constraints in the upper part of the Botneheia Fm, and insufficient magnetostratigraphic sampling density, over the condensed late Anisian-early Ladinian parts of the succession, the data does allow a clear magnetostratigraphic match to more intensely sampled magneto-biostratigraphies in Tethyan sections. This demonstrates the relationship between the disparate boreal and Tethyan biostratigraphies. A substantial hiatus characterizes the Ladinian- Carnian boundary (junction of Botneheia and Tschermakfjellet formations) in central Spitsbergen, so latest Ladinian magnetozones are absent.
DE: 0459 Macro- and micropaleontology (3030, 4944)
DE: 1520 Magnetostratigraphy
DE: 1527 Paleomagnetism applied to geologic processes
DE: 1535 Reversals: process, timescale, magnetostratigraphy
DE: 4952 Palynology
SC: Geomagnetism and Paleomagnetism [GP]
MN: 2007 Joint Assembly