HR: 10:20h
AN: GP52A-01 INVITED     [Abstracts]
TI: Magneto-biostratigraphy of the Vikinghøgda Fm, Central Svalbard and the Geomagnetic Polarity Timescale for the Lower Triassic
AU: * Hounslow, M W
EM: m.hounslow@lancs.ac.uk
AF: CEMP, geography, Lancaster University, Bailrigg, Lancaster, LA1 4YB, United Kingdom
AU: Peters, C
EM: cp34@st-andrews.ac.uk
AF: Geography and Earth Science, St Andrews Univ., Scotland, St Andrews, United Kingdom
AU: Mørk, A
EM: Atle.Mork@iku.sintef.no
AF: SINTEF Petroleum Research, N-7465, Trondheim, Norway
AU: Weitschat, W
EM: fg6a106@geowiss.uni-hamburg.de
AF: Geological-Palaeontological Institute and Museum, University of Hamburg, Bundesstr. 55, Hamburg, D-20146, Germany
AU: Vigran, J
EM: vigran@online.no
AF: SINTEF Petroleum Research, N-7465, Trondheim, Norway
AU: Hu, M
EM: m.hu@lancs.ac.uk
AF: CEMP, geography, Lancaster University, Bailrigg, Lancaster, LA1 4YB, United Kingdom
AU: Karloukovski, V
EM: v.karloukovski@lancs.ac.uk
AF: CEMP, geography, Lancaster University, Bailrigg, Lancaster, LA1 4YB, United Kingdom
AB: A composite magneto-biostratigraphy for the Lower Triassic is constructed, using as a framework the high resolution ammonoid biostratigraphy available for arctic Boreal successions, using new data from Spitsbergen and published data from the Sverdrup basin. The magneto-biostratigraphy through the Vikinghødga Fm has been determined in central Spitsbergen, using the type section in Deltadalen, with additional sampling from an additional section at Milne Edwardsfjellet some 15 km distant. The successions here are horizontally bedded and essentially undeformed, and can be closely related to several nearby sections on the southern flanks of Sassendalen. Combined thermal and alternating field demagnetisation is effective in isolating characteristic Triassic directions, whose mean directions fall close to the European apparent polar wander path for the Lower Triassic. However, the Triassic reversed and normal directions are partially overprinted with a frequently strong, probably recent magnetisation. The remanence appears to be predominantly carried by magnetite, although an unidentified magnetic sulphide is important in some intervals (particularly the Vendomdalen Mbr). The polarity stratigraphy from the Vikinghødga Fm, when integrated with the ammonoid and meager conodont data is similar to that previously determined from the Canadian arctic successions. Together, these allow the construction of a composite boreal magneto-biostratigraphy for the Lower Triassic tied to the boreal ammonoid zonations. In the Vikinghødga Fm the Permian Triassic boundary cannot be accurately located, occurring between 1.7- ~10 m above the base of the Deltadalen Mbr either below or at about the level with an Otoceras boreale fauna. The Late Griesbachian to the early part of the E. romunderi Zone is mostly reverse polarity, with 3 substantive normal polarity intervals. The mid and upper Smithian (lower Olenekian) part of the Vikinghøgda Fm, which has the best ammonoid age control, is dominantly normal polarity, and can be closely correlated to that in the Sverdrup Basin. Integrating data through the Spathian (upper Olenekian) is complicated by poor biostratigraphic age control in the Sverdrup basin, and large changes in sedimentation rate in the Spitsbergen succession. The Spathian appears to be dominantly normal polarity, with evidence of at least 3 major reverse polarity intervals.
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