The sub-seabed sediments observed in Area 240 are an offshore extension to the Palaeo-Yare river system. The present-day remnants of the Palaeo-Yare valley system includes the Rivers Yare, Wensum and Waveney. The lower reaches of the River Yare and Waveney flow into Breydon Water, the remnants of an outer estuary, and flows east from Breydon Water and then south into the North Sea.

The reconstruction of Area 240 reveals a complex history of deposition and erosion. The Area is dominated by floodplain and channel-infill sediments deposited in a cold, estuarine environment dating to the Wolstonian some 250,000 years ago near the banks of a large river channel. During the subsequent Ipswichian interglacial, around 120,000 years ago, the Area was submerged as sea levels rose during climatic warming. During the early Devensian (approximately 110 thousand years ago) as the climate deteriorated the river channel was re-activated, recut and infilled with estuarine deposits. The most recent development in the area, prior to being inundated by rising sea level, relates to the development approximately ten thousand years ago of an early Holocene shallow, meandering partially infilled channel comprising intertidal mudflat/saltmarsh sediments. The Area was drowned most recently approximately 8000 years ago.