Tidal-inlets and gravel deposition during the late Norwich Crag (Lower Pleistocene) of north-eastern Suffolk, U.K.

The Norwich Crag of north-eastern Suffolk is mainly composed of near-shore sands representing several sequences (cycles of transgression and regression). It is difficult to separate out the different sequences but the final sequence here is well known for the localised development of beds of flint gravel that have been interpreted as the in-situ remnants of prograding beaches. While a review of the evidence supports the involvement of this sedimentary environment in the overall processes, the evidence shows that virtually only gravels associated with rip-channels represent in-situ beach gravels and that thicker gravel beds are the infill of much larger channels. From consideration of the characteristics of the large channels it is concluded that these large channels were tidal-inlets between prograding barrier islands and that the gravels were derived from the adjacent up-drift beach faces of the barrier-islands.