The outer continental shelf in the South Western Approaches is underlain by an oceanward-dipping wedge of Neogene strata up to 400 m thick that is divisible into three units: (a) the early to mid-Miocene, parallel-bedded calcilutites of the Jones Formation, which rest with a marked eastward overstep on Palaeogene and Cretaceous strata; (b) the mid- to late Miocene Cockburn Formation, which consists of calcarenites fashioned into a series of linear tidal ridges that are separated locally by an unconformity from the underlying unit; (c) the Plio-Pleistocene Little Sole Formation, which sits with a planar unconformity on the Miocene strata and is divisible into a lower, wedge-like member, restricted to near the shelf edge, and an upper, more widespread, sheet-like member. Palaeo-bathymetric and seismo-stratigraphic evidence indicates that the shelf and adjacent land areas have suffered epeirogenic movement since the early Miocene.

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