Abstract

Conformable domes can result from diapirism as well as cross buckling and other types of cross folding. The total-strain pattern of natural structures offers a means of discriminating between diapiric domes and nondiapiric domes. Similarly, one may distinguish between diapiric ridges and other types of antiforms.Immature diapirs in metamorphic terrains and appropriate quantitative models are characterized by crestal zones of horizontal extension. Similar zones occur in the convex-hinge regions of very competent buckles and the adjacent incompetent matrix of fold models. But these model experiments are rarely applicable to natural buckle folds in metamorphic terrains, which typically involve low competency contrasts. Where upright buckle folds can be identified by means of independent evidence, their hinge zones are generally devoid of stratiform foliation and other features due to horizontal extension. An Archean gneiss dome of the northwestern Ontario is subjected to structural analysis, and interpreted as an immature diapir on the basis of widespread subhorizontal foliation about the dome's centre. The strain pattern of the gneiss dome corresponds to that of salt diapirs in New Brunswick.

You do not currently have access to this article.