Pre-existing Fabrics

Abstract

Continental rifts are not random and generally tend to follow the mobile belts. A well accepted classification of factors that give inheritance is: (i) discrete, and (ii) pervasive. Pervasive fabrics- slaty cleavages, close-spaced joints or beddings, laminations, flow layers of pre-rift sedimentary or volcanic rocks, and foliations such as schistosity and gneissosity- may persist throughout the rock volume. We show examples of inheritance due to pervasive fabric from East African Rift System, Thailand Tertiary Rift System, South Atlantic Passive Margins, East and West Indian Passive Margins. Discrete/isolated fabrics are planar to curvi-planar elements that lead to anisotropy in terms of strength and material properties with respect to the surrounding rocks. We show examples of inheritance due to discrete fabric from East African Rift System, Brazilian Rifts, Tertiary Rifts of Thailand, North Atlantic Passive Margin, Eastern North American Rift System, Rhine Graben, East and West Indian Passive Margins.