Drainage evolution in a rifted basin, Corinth graben, Greece

Abstract

Intrabasinal basement highs and transfer faults, distance from source, and the underlying geology influence the drainage pattern and the evolution of the 41 river basins in the northern Peloponnesus. These rivers were classified as antecedent (10), multistory (17), re-established (5) and juvenile (9) drainage types. Antecedent drainage is when a river has maintained its original direction of flow across later tectonic topography. Multistory drainage consists of a re-established drainage and of a reverse drainage. Reverse drainage, when flow direction along part of a river is reversed, consists of two opposing drainage components: a misfit and a reverse element; the area between these two elements, termed “wind gap”, is a dry valley. Re-established drainage is when a reverse element returns to its original flow direction. Juvenile drainage consists of small incising and headward-eroding streams. The sediments that the rivers flow across (soft uncohesive marls or coarse-grained deposits and Pre-Neogene basement with limestones), river power (strong close to the source or weak far from the source), presence or absence of transfer faults and tilted blocks due to the activity of synthetic and antithetic faults, all influence whether an antecedent drainage will remain unchanged or will be changed to a reverse drainage. When transfer faults cross-cut the area of a wind gap and the underlying sediments were soft uncohesive marls, reverse drainage changed to a re-established drainage. In other cases, where transfer faults were absent and underlying deposits were coarse-grained sediments or limestones, in the area of the wind gap, then reverse drainage remained unchanged.