| Autor: |
Richard J.O. Hamblin, James Rose, B.S.P. Moorlock |
| Rok vydání: |
2001 |
| Předmět: |
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| Zdroj: |
Quaternary International. 79:5-22 |
| ISSN: |
1040-6182 |
| DOI: |
10.1016/s1040-6182(00)00119-1 |
| Popis: |
Clast lithology and derived microflora are used to provide a basis for correlating pre-Anglian fluvial and coastal deposits in eastern England and to provide a lithostratigraphic framework for these Early and early Middle Pleistocene sediments. Three fluvial systems are recognised. (i) The Thames, which drained an area from Wales through midland England to the Thames basin and southern East Anglia. The catchment was truncated over the period concerned and the western headwaters diverted to other river systems. (ii) The Bytham river which drained midland England and the southern Pennines and reached the southern North Sea delta in the region of north central East Anglia. This river extended its catchment over the period concerned. (iii) The Ancaster river which drained the southern Pennines and received sediment from northeast England. Each of these catchments contributed sediment to the southern North Sea delta/estuary and contributed to the lithologies of the Red, Norwich, and Wroxham Crag formations. The lithostratigraphic subdivisions are based on the fact that: (i) the Pliocene and Early Pleistocene rivers and the equivalent Red and Norwich Crags are characterised by far-travelled microflora which was transported in suspension and a locally derived clast assemblage transported as bedload, and (ii) the later Early and early Middle Pleistocene rivers and the equivalent Wroxham Crag are characterised by a far-travelled microflora and a far-travelled clast assemblage. Variations in the amount and composition of far-travelled materials is determined by the relative importance of the three river systems. This provides a basis for identifying different formations of the Thames river sediments (older Sudbury Formation and younger Colchester Formation) and different members of the Wroxham Formation (Dobb's Plantation Member: local material with minor components of Thames and Ancaster river sediments; How Hill Member: local material with major components of Thames and Ancaster river sediments; Mundesley Member with major components of Bytham river sediments). These lithostratigraphic units are related to established North European biostratigraphy and Oxygen Isotope stratigraphy. The factors forcing the changes in river energetics are explained in terms of the relative importance of geomorphic processes operating within the river catchments determined by the patterns of Milankovitch orbital forcing. |
| Databáze: |
OpenAIRE |
| Externí odkaz: |
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