DISJUNCTIVE CLEAVAGE FORMED AT SHALLOW DEPTHS IN SEDIMENTARY-ROCKS

Work of the past decade concerning tectonic cleavage has focused on nine topics: (1) appropriate terminology for cleavage classification, (2) processes involved in cleavage formation, (3) controls on cleavage distribution and morphology, (4) depth dependence of cleavage formation, (5) controls and causes of cleavage initiation, (6) nature of lithologic changes during cleavage development, (7) relation of cleavage to strain, (8) relation of cleavage to stress and (9) chronology of cleavage development. This paper reviews these issues as they apply to the formation of disjunctive cleavage in sedimentary rocks. Discussion is limited to cleavage that formed at shallow crustal conditions in which rock-water interaction, rather than plastic flow, recrystallization, or grain growth, is the dominant deformation process.