An Investigation into the Structural Indicators of the Nesje Headland, Western Norway

Angela Halfpenny, David J Prior

Department of Earth Sciences, University of Liverpool, 4 Brownlow Street, Liverpool, L69 3GP, U.K.

halfpenny_a@hotmail.co.uk

An integrated outcrop scale and microstructural investigation into the structural indicators of the Nesje Headland has revealed a correlation between the deformation mechanisms of outcrop scale and microstructural scale. The outcrop scale deformation history shows that the shape lineation overprints the folding and was formed by stretching along 077°- 257°. Quartz crystallographic fabrics were collected to characterize the deformation around a fold. The techniques used to measure CPOs in the thin sections were computer integrated polarisation (Duyster 1999) and electron backscatter diffraction (EBSD) using the scanning electron microscope (SEM). There was a distinct pattern to the c-axis fabrics, which showed singular c-axis concentrations and not girdles. The c-axis fabrics did not vary around the fold. Therefore the crystallographic preferred orientation, although it may have originally recorded the deformation due to the folding, is now showing overprinting by the later phase of deformation, which formed the lineation.


Fig. 1 Shows the location of the EBSD and corresponding AVA data. The AVA data varies around the fold, but the c-axis orientation does not show much variability. The EBSD data also shows little variation in the c-axis and only shows singular concentrations, no cross girdles.

Duyster, J. 1999. Microstructural classification of quartzites using automated AVA. Institut fur Geologie, Mineralogie und Geophysik, Ruhr-Universitat, D-44780 Bochum, Germany, 1-28.