Holocene evolution of the Blakeney Spit area of the North Norfolk coastline

Abstract

Blakeney Spit extends more than 12 km along the North Norfolk coast, from its origin near Weyboume in the east, to a location opposite a point halfway between Morston and Stiffkey in the west. Borehole investigations landward of the spit have revealed remarkably uniform sequences of intertidal sediments, sometimes passing from lower intertidal muds into upper intertidal saltmarsh, sometimes being rather uniform upper saltmarsh throughout. Similar intertidal sediments are found landward of an inter-tidal barrier extending from off Stiffkey to off Wells. The thickness of these deposits, resting either on glacial deposits or directly on Chalk, reaches over 15 m in places, along the line of an original E-W trough or channel. Adequate radiocarbon and other reliable dating of these deposits has proved somewhat difficult to determine, but the earliest are Post-Glacial non-marine deposits as old as 10 000 years bp , with the initiation of marine deposition at c . 7500-6500 years bp at the eastern end of the sector. Apart from the Stiffkey and Morston mainly gravel and sandy ‘Meals’ barriers, which are resting on top of saltmarsh deposits and probably date back to no more than 670-900 years bp , there are no other sand or shingle deposits, except in drainage channels, anywhere landward of Blakeney Spit. The spit itself is being produced by the erosion of the cliffs east of Weybourne, and the entire Holocene and glacial sequences on its seaward side, rolling the sand and shingle body over landward (at about 1 m per annum), and prograding westward, (at c . 3.5 m per annum) - as indicated by accurate maps constructed over the last 400 years.