Incised valleys are mountain-valley-like features that commonly result from river down cutting into coastal plains and continental shelves in response to marine regression.
Since sea-level fluctuations are most manifested in coastal areas, they are prominent in shallow water environments, where prior depositional surfaces are subject to subaerial erosion and fluvial systems continue carving downward.
As sea-level rises, the incised valleys are drowned and filled with non-marine though estuary to open marine sediments.
With the development of offshore petroleum exploration, incised valleys have been widely identified on multi-channel seismic data coverage on continental shelves.
[1] In northern Libya, a Late Miocene incised valley has been mapped with 150 kilometer length and at least 700 meter depth, far exceeding the Quaternary eustatic sea-level variations.