Holocene sulphur-rich palaeochannel sediments: diagenetic conditions, magnetic properties and archaeological implications


Brown, A.G., Ellis, C. and Roseff, R. (2009) Holocene sulphur-rich palaeochannel sediments: diagenetic conditions, magnetic properties and archaeological implications. Journal of Archaeological Science, 9pp. (doi:10.1016/j.jas.2009.08.009).

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Description/Abstract

Extensive aggregate extraction in the middle Trent valley, England, has revealed a sequence of Holocene palaeochannels associated with nationally important, and predominantly organic, archaeological remains. This paper reports observations of hyper-acidity (below pH 2), high natural magnetism and metallic sphaerules (framboids) in Holocene palaeochannel sediments at two sites in the middle Trent valley. These properties are associated with high natural remanent magnetism which has allowed the successful palaeomagnetic dating of palaeochannel fills at one of these sites (Hemington). These sediment properties are the result of the formation of ferromagnetic iron sulphides, including griegite, under conditions of high sulphur availability (from groundwater) in the presence of metallic ions and organic matter under low redox conditions, with later oxidation producing the extreme natural acidity through oxidation of disulphide (pyrite). These findings explain why, under certain groundwater conditions, alluvial palaeochannel sediments can carry post-depositional remanent magnetisation and be suitable for palaeomagnetic dating. The low pH may also be beneficial in the initial stage of wood preservation and if the sediments remain waterlogged, but probably not retard decomposition after drainage and acidification, a process that is increasingly being recognised as a threat to archaeological sites in wetland environments

Item Type: Article
ISSNs: 0305-4403 (print)
Related URLs:
Keywords: palaeochannels, iron sulphides, diagenesis, framboids, palaeomagnetic dating
Subjects: C Auxiliary Sciences of History > CC Archaeology
Q Science > QE Geology
G Geography. Anthropology. Recreation > GB Physical geography
Divisions: University Structure - Pre August 2011 > School of Geography > Environmental Processes and Change
ePrint ID: 69009
Date Deposited: 20 Oct 2009
Last Modified: 27 Mar 2014 18:48
URI: http://eprints.soton.ac.uk/id/eprint/69009

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