Between the deposition of the uppermost Cretaceous rocks and the Eocene it is probable that a considerable interval elapsed, during which the Cretaceous was elevated into land, with much folding and fracturing of the rocks and subsequent denudation.[62] It was probably during this upheaval that the Cretaceous of Baharia assumed its anticlinal structure. Subsequently, subsidence taking place, the Eocene sea submerged the area, and deposits were laid down on the uneven Cretaceous land in an unconformable and overlapping manner. In Baharia the lowest member of the Eocene of Egypt, the Esna Shales, is not present, although further to the south towards Farafra it has been observed. On the east side, some sandstones and clays met with below the white chalk beds of the outer plateau may belong to this division. The first undoubted Eocene deposits in the Baharia area are the limestones with _Operculina_ and _Nummulites_ which unconformably overlie different members of the Cretaceous in the north and west sides, and eastward of the south end. The whole of the Eocene deposits are here, however, only a few metres thick, which contrasts strangely with the enormous thickness of the deposits of the same age in the Nile Valley. This is intelligible, however, on the supposition that near the subsiding Cretaceous land the conditions for continued accumulation of deposits were not so favourable as further to the east, where deeper water conditions obtained. Subsequently, in Post-Eocene times, the whole underwent upheaval, and it is probable that during this elevation the main synclinal fold[63] was produced, together with the minor anticline. The evidence for placing the date of the formation of the syncline anterior to the deposition of the ferruginous grits, limonite, etc. (Series No. 3) stands on the following basis: the absence of proof of the folding in question having affected the beds of Series 3, and the presence of a horizontal deposit of limonite on the upturned edges of the strata, at the point where the fold meets the eastern scarp (page 66). About the same time, probably, basalt and dolerite was intruded into the Cenomanian rocks below. [Sidenote: Formation of depression.]