Holocene flood records from palaeochannel sediments : the River Rede, North Tyne Basin, UK
Research on a 2.5 km long reach of the River Rede, northern England, has sought to evaluate the utility of palaeochannel fill sediments as a means of extending the record of large floods beyond the documentary period. This study has taken advantage of an unusually long Holocene alluvial record preserved in a series of discrete, meandering palaeochannels, with well-preserved planform morphology on terrace surfaces. There are ca. 30 palaeochannels within the extended study reach of which seven have been studied in this work.
The palaeochannel alluvial records have been analysed via a detailed programme of sediment coring along the long-profile and multiple transects of each surveyed palaeochannel. The channel fills typically comprise peaty and organic-rich fine sands and silts that are interbedded with sandy minerogenic sediments, interpreted as overbank flood deposits post-dating channel abandonment. However one of the studied palaeochannels does not display the peaty material in the infill sediments, this is attributed to local morphological conditions.
A total of 46 radiocarbon assays (15 from existing work and 31 new assays) on peaty and organic-rich sediments indicate that channel fill sequences were deposited over thousands of years and when combined offer a near-continuous alluvial record spanning ca. 500-10,000 cal. BP. Analysis of chronology in relation to stratigraphy resulted in nearly 25% of the radiocarbon assays being rejected as a result of them being erroneous. Within the palaeochannel fills studied, 31 flood-deposited minerogenic horizons have been identified within the fill sediments. All of these flood deposits can be linked to published records of climatic shifts of wetter/colder conditions locally and within central Europe and North America. A number of these flood events can be linked to periods of Holocene valley floor development.