This chapter shows, from the theoretical point of view, that growth strata geometries above angular unconformities depend on the modification of initial unconformity angles due to different folding mechanisms operating in underlying layers. This theory is applied to the Sant Llorenc de Morunys growth structure, where the analysis of the unconformity angles shows that classic folding mechanisms, such as layer-parallel simple shear in both angular and curved folds, and tangential-longitudinal strain operated in the forelimb of a fault-propagation fold. These folding mechanisms, inferred from changes in unconformity angles, are consistent with the minor structures and lithological features of the involved stratigraphic units. Forward modeling, including limb rotation, hinge migration, and the above-mentioned folding mechanisms, explains the main structural features of the syntectonic sediments in the Sant Llorenc de Morunys fault-propagation fold.