What is Rifting? Introduction and Basic Definitions

Rifts can be summarized as geographical regions consisting of extensional sedimentary basins of various sizes, with various tectonic and sedimentary geometries that are linked in various structural contexts. This chapter provides a list of the main types of rifts and case examples. It provides the definition of the active and passive rifting categories, as these are regularly mentioned in the literature and are the primary designations of extensional rift settings. The chapter lists the major tectonic structures and basin types encountered in rifts and rifted margins. Subsidence is the stage that leads to the progressive deepening of the basin floor and hence allows the accumulation of sediments in rift basins. It is the process by which the lithosphere regains isostatic equilibrium. Sedimentation, although always present in rift basins, is extremely variable from one system to the other. Traditionally, sedimentary sequences of rift basins are subdivided into three categories: pre-, syn- and post-rifts.