Significance of structural trend in Precambrian terrain

Abstract

The development of the concept of structural trend and its use both in the study of Precambrian shields and intercontinental Precambrian correlations are examined. On the basis of examples from Scotland, Fennoscandia, East Africa, India and Western Australia it is shown that the concept has been useful where applied to regions in which a single feature, such as lithological layering, foliation, upright folds or major fault lineaments, dominates the structural regime. However, is unqualified use in regions of polyphase deformed rocks has often been misleading and resulted in erroneous correlations. This is particularly the case where the nature and origin of the particular trend is unspecified, where differences between cover tectonics and tectonic overprinting of basement are not demonstrated, or where the relationship of trend to a polyphase deformational sequence is not determined.Repeated reference in the literature to trends which are ill-defined or not representative of a structural regime often leads to their unquestioned acceptance. With the framework of Precambrian shields being important in atempts to reconstruct previous configurations of continental masses, assessment is necessary of any structural trend used as a basis of correlation.