Palaeomagnetic Study of the Middle Carboniferous Hyrnefjellet Formation From the Hornsund Region, Southern Spitsbergen
Abstract
The Middle Carboniferous Hyrnefjellet Formation of the southern part of the West Spitsbergen Alpine Trust and Fold Belt (SW Torell Land at Hyrnefjellet, Kruseryggen and Lorchebreen and the northern Sorkapp at Meranpynten and Austjokulen) were palaeomagnetically analyzed (six localities, 120 cores drilled from 36 independently oriented samples). Hematite proved to be the main magnetic carrier in the Hyrnefjellet Formation. Almost all specimens from investigated sites, yielded soft and moderate components (labeled A and B, respectively), and reversely magnetized, high temperature NRM component (C), with unblocking temperature spectra ranging from 500C to 680C. Components C from all six locations show the best grouping after unfolding to paleohorizontal, pointing to prefolding origin of this component. Restored to paleohorizontal, C components are directed SW and W with shallow inclinations. The upper age limit for the C components is constrained by (Paleogene) time of folding, bracketing a time error for the component acquisition to ca. 260 Ma. Site mean directions for four sites show overlapping circles of confidence. Overall mean direction is D = 217, I = -30; alfa95 = 4,4, k = 41,58. A corresponding paleopole (PLAT=25.7N, PLONG=155,7E) falls into the Late Devonian - Early Carboniferous sector of APWP for Baltica, suggesting primary age of the remanence. This interpretation would suggest that Svalbard remained in the present day orientation with respect to Baltica since the mid-Carboniferous time. We note, however, that declinations determined for other two sites, situated in the eastern limb of the Hyrnefjellet Anticline and the western limb of the Meranpynten Syncline, display declinations rotated dextrally by 20 to 60 degrees from C components, inclinations being virtually identical. Assuming the same origin for the components in these two sites, the rotation could be due to activation of strike-slip faults. Activation of dextral faults had to take place before Alpine tectonic events, since the NNW-SSE dominating tectonic trend of the West Spitsbergen Alpine Thrust and Fold Belt in the sampled locations is not disturbed.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2005
- Bibcode:
- 2005AGUFMGP11A0013L
- Keywords:
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- 1525 Paleomagnetism applied to tectonics: regional;
- global