Agro-industrial alluvium in the Swale catchment, northern England, as an event marker for the Anthropocene

Abstract

Physically and chemically distinctive late-Prehistoric and historical age alluvial deposits are characteristic of many upland and lowland river systems in the UK. Despite their widespread distribution, there have been few attempts to construct robust chronologies or to identify environmental factors that governed their formation. The Swale catchment in northern England is typical in this respect, with large areas of its valley floor covered by sedimentologically distinctive laminated sands and silts, enriched in organic material and Pb, and underlain by uncontaminated and structureless silts. Using 14C dating, chemostratigraphy, lichenometry and historical maps, a catchment-wide change in sedimentation style has been dated to between the mid 18th and early 19th centuries ad. Several causative factors were responsible for this change in sedimentation style and include the initiation of large-scale, intensive lead mining from the latter half of the 18th century onwards, embankment construction in the lowlands and historical peat erosion in the uplands. Transformation of the Swale floodplain also reflects longer-term land-use and climate change. In particular, deforestation of headwater tributaries by monastic grazing practices in the High Middle Ages (ad 1000–1300) led to a period of fine-grained sedimentation in upland catchments, as well as priming hillslopes for erosion and widespread channel network incision and increased fine sediment flux during the climatic downturn of the ‘Little Ice Age’. Sediment facies of a similar nature have been widely recorded in other northern English river catchments and represent a regional land use–climate signal characteristic of the Anthropocene. We introduce the term ‘agro-industrial alluvium’ to describe these types of deposit. They have similarities to post-settlement alluvium in North America and Australia, where historical land-use change had a similar impact on valley floor sedimentology.

Human‐induced sedimentation patterns of a channelized lowland river

“…The near‐bank zones of these rivers became a specific environment for deposits in the late‐nineteenth and twentieth centuries; these deposits differ in color, organic matter content, metal concentration, and stratification from older and floodplain deposits. These features are also diagnostic of other deposits of the industrial era affected by mining and extensive agriculture and have been recently named ‘agro‐industrial alluvium’ (Foulds et al ., ). It is believed that recently agriculture has been a less important source of polluted organic matter than sewage effluents in the Odra and Vistula Rivers.…”

Creep and Floodplain Defluxion Study in the East of the Russian Plain

“…These movements are of hydrothermal nature and are due to variations in moisture and temperature of soil, slope inclination of slopes and bottom channel, including freezing and thawing. Fluctuations in humidity and temperature lead to periodic changes in the volume of soil (Foulds, 2013;Panin, 1997). Thanks to them the soil develops tension which is directed in all directions.…”

Marking time in Geomorphology: should we try to formalise an Anthropocene definition?

“…This is termed by Foulds et al . () as ‘agro‐industrial alluvium’ and provides a regional event marker for the Anthropocene. Prehistoric and historical farming, as well as mining, have all accelerated or modified sedimentation, but this and the global record are diachronous and strongly differentiated according to societal development stage (Hoffmann et al ., ; Brown et al ., ).…”

“…Earlier periods have been systematically evidenced by analysis of a large database (Macklin et al, 2012) of all published carbon-14 ( 14 C) dated Holocene fluvial deposits in the UK (Figure 1). Importantly this is based on objective discrimination between dated alluvial units using sedimentological, palynological and geochemical indicators for deforestation, cultivation and metal mining impact (Foulds et al, 2013;Macklin et al, submitted for publication) to identify what we term anthropogenic alluvium. Impact onsets unsurprisingly occurred at different times from the Bronze Age (c. 4400 cal.…”