关键词: 断层相关褶皱, 运动学模型, 河流阶地, 褶皱陡坎, 翼旋转, 膝折带迁移, 生长地层

Abstract: Fluvial terraces,like growth strata,provide geomorphic markers that can record progressive deformation and mechanisms on underlying fault-related folds. Because terraces are generally preserved within the pre-growth strata,they record the deformation mechanism in the core of the fold. To explore the fold evolution and subsequent geometry of deformed terraces,we present ideal kinematic models for successively emplaced horizontal unconformities (terraces) across pre-growth strata in three types of growing fault-related fold. Three common mechanisms for fold growth are considered: hinge migration (Limb-lengthening),limb rotation,and a combination of the two. Both angular-hinge and curved-hinge zone migration are considered. Each model predicts distinct terrace architecture,fold scarps,and different angular relationships between the terraces and the pre-growth strata.Limb-lengthening fault-bend fold results in self-similar growth,marked by parallel pre-growth and terrace strath orientations across much of the fold,and steeply dipping asymmetric fold scarps along the fold's flanks.Limb-lengthening fault-propagation fold models result in self-similar growth parallel terraces,and step fold scarps in the back limb. Deformation by limb rotation detachment fold is marked by progressively less tilted terraces across the limbs and symmetric fold scarps along the fold's flanks.Migration of an angular hinge of detachment fold results in parallel,uplifted terraces in the core and steeply dipping symmetric fold scarps along the fold's flanks. When limb rotation and hinge migration are combined,the terrace architecture is consistent with the kinematics of each kink panel.The result of limb lengthening by migration of a curved hinge is dependent on the width of the curved hinge.If the hinge is wide and terrace abandonment is frequent compared to the migration rate,fanning terraces and fold scarps result. In additional,changes in base level have significant effects on the final terrace geometry. Uniform incision along the river profile results in an apparent uplift of the older terraces,while aggradation will cause older terraces to truncate into the less tilted,younger terraces.

Key words: fault-related fold, kinematic model, fluvial terrace, fold scarp, limb rotation, hinge migration, growth strata