A stratigraphic investigation of the marshland adjacent to the five main estuaries in Suffolk and offshore of the Alde estuary has been made. The results are used to establish a Holocene evolution for the Suffolk coast and are compared with coastal sequences elsewhere in East Anglia. The stratigraphy of the Blyth estuary in north Suffolk comprises four lithostratigraphic units; a basal freshwater peat overlain by estuarine Lower Clay, Middle Peat and Upper Clay representing two phases of transgressive overlap sandwiching a phase of regressive overlap. Peat formation began about 6750 yrs BP and continued until 6500 yrs BP when the sequence was inundated and eroded by marine waters during the initial phases of transgressive overlap. Estuarine silt/clay deposition (both low and high intertidal flat) persisted until about 4500 yrs, BP when a transition to further peat growth occurred. The second phase of estuarine sedimentation (predominantly high intertidal flat) began at about 4300 yrs BP. These dates correlate well with dates for similar tendencies of sea-level movement in the Fens, north Norfolk and Broadland. The Blyth sequence contrasts with the Holocene sequence in the Deben, Orwell and Stour estuaries in south Suffolk which comprises a continuous estuarine clastic sequence without an intermediate peat. Estuarine conditions are believed to have begun about 8000 yrs BP and a high subsidence rate combined with low'sediment accumulation rates caused the estuaries to remain flooded throughout the Holocene. The onshore data, plus data offshore from the Alde estuary has been used to evaluate the position of the coast after 8700 yrs BP. The coastal evolution is interpreted to have been controlled by the movement of coastal barrier or spit systems. A significant barrier breaching episode is believed to have occurred post-7000 yrs BP causing erosional contacts and development of higher energy-estuarine environments. After, this time, the, Blyth estuary was significantly affected by further spit or barrier growth. The Alde, Deben, Orwell and Stour estuaries, however, were essentially barrier (spit) free during the Holocene and protected from southerly longshore drift by a land barrier north of the Alde estuary. The land barrier was eventually breached and subsequent formation of Orford Ness and Landguard Spit began. The present-day inland saline penetration up the river Blyth is the maximum achieved at any time during the Holocene. This contrasts with Broadland and Fenland where the maximum penetration occurred about 2000 years earlier. The main reason for the differences appears to be a higher coastal erosion rate in Suffolk compared to Norfolk (Fenland is actively prograding).
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:235628 |
| Date | January 1990 |
| Creators | Brew, David Scott |
| Publisher | University of East Anglia |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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