Shape fabric variations in deformed conglomerates at the base of the Laksefjord Nappe, Norway

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Abstract
Detailed strain mapping of deformed conglomerates at the base of the Laksefjord Nappe, Finnmark, N Norway has been carried out in an attempt to identify strain gradients adjacent to the basal Laksefjord thrust. Statistical analysis of shape fabric orientation data was also undertaken. A rapid ‘harmonic mean’ analysis of deformed clasts has been evaluated in terms of possible error factors in the method, and it is felt that patterns of strain across the area are real, whereas absolute strain values may be subject to only slight errors. Generally, strain magnitude is seen to increase with proximity to the basal thrust and above internal thrusts within the conglomerate unit, reaching a maximum value of ϵ̄ s = 3.95. The geometry of shape fabric is dominantly flattening (0 < v ≤ 1) but small, isolated areas of constrictional strain occur (– 1 ≤ v < 0). A tectonic model involving a variable simple shear component accompanied by a constant component of pure shear is proposed for the origin of the conglomerate shape fabrics.