Geological Society of London
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The anatomy of a Fenland roddon: sedimentation and environmental change in a lowland Holocene tidal creek environment

posted on 2016-06-21, 11:14 authored by Dinah M. Smith, Jan A. Zalasiewicz, Mark Williams, Ian P. Wilkinson, James J. Scarborough, Mark Knight, Carl Sayer, Martin Redding, Steven G. Moreton

A Holocene sand/silt-filled tidal creek, locally called a roddon, excavated at Must Farm near Whittlesey, Cambridgeshire, within the English Fenland, preserves an unprecedented record of Fenland tidal creek evolution. The tidal creek was formed sometime between c. 4735 BP and c. 3645 BP. Its infill comprised centimetre-scale, laminated, tidal sand-mud couplets, numbering some 600 in total, with microfossils that show marine and coastal derivation of the sediment. The nature of the infill suggests rapid sedimentation that choked the creek system, perhaps in as little as a few years. At least three successive generations of roddons are present in the Fenland, suggesting at least three distinct episodes of tidal creek formation. The Must Farm roddon belongs to the first generation. A later, mud-filled channel was subsequently incised into the roddon, perhaps initiated by a marine surge. It quickly transformed into a slowly flowing river, as suggested by molluscs, ostracods and diatoms. Infill of this late-stage channel was slow, perhaps over about 1200 years between c. 3250 and 2050 BP (c. 1300–100 cal BC), as shown by archaeological finds. The mud-filled channel superficially resembles late-stage, organic-rich channel infills visible on aerial photographs, but is wider and deeper and might have been part of a more substantial long-lived ‘river’, perhaps a tributary of the proto-Nene.