Generation and modification of finite strain patterns by progressive thrust faulting in the Laksefjord Nappe, Finnmark

Abstract

Using deformed conglomerates as finite strain markers, a strain map of the base of the Laksefjord Nappe has been produced and is presented. Finite strains are predominantly of flattening type and are explained in terms of a variable simple shear superimposed on a constant pure shear. Strain patterns are examined in terms of their three dimensional geometry and are shown to be clearly related to the presence of the basal Laksefjord thrust. Late, brittle thrust faulting has modified early finite strain patterns and a progressive thrusting model is presented to explain present-day strain patterns. Finite strains developed in a mid-crustal, sub-horizontal shear zone at lower greenschist facies account for only a small proportion of total nappe translation.