Cuantificación de la deformación interna en rocas samíticas

Abstract

Strain analysis is made of the primary cleavage fabric in Precambrian and Palaeozoic psammites outcropping in a Northeastem area of the Iberian Range. The calculated total finite strain shows a decrease in the strain towards the highest part of the stratigraphic sequence. Rocks with a high proportion of matrix show oblate o uniaxial ellipsoids. Rocks with a very low proportion of matrix show slightly prolate ellipsoids or with an axial relation nearly l. These features have allowed to state an evolutive sequence in the cleavage development, defined by two main stages: Stage of embrionic cleavage, characterized by oblate ellipsoids whose x strain axis is nearly horizontal in rocks with a high proportion of matrix, coexisting with quarzitic rocks, with show prolate ellipsoids, whose x strain axis is nearly vertical. Stage of well developed cleavage, showing oblate ellipsoids whose x strain axis is nearly vertical.