The range of anthropogenic impacts is perhaps even more various than the sedimentation systems with which they are involved. In this paper we set out to analyze the extent

of enhanced deposition of material in floodplain environments following human activity, largely through the meta-analysis of a UK data set of Holocene 14C-dated alluvial units. We caution that sedimentation quantities relate both to supply factors (enhanced delivery from deforested or agricultural land, accelerated channel erosion, or as fine waste from other activity), to transportation-event magnitudes and frequency, to sedimentation opportunity (available sub-aqueous accommodation space), and to preservation from reworking (Lewin and Macklin, 2003). None of these has been constant R428 chemical structure spatially, or over Veliparib manufacturer later Holocene times when human impact on river catchments has

been more significant and widespread. The word ‘enhanced’ also begs a number of questions, in particular concerning what the quantity of fine alluvial deposition ‘ought’ to be in the absence of human activity in the evolving history of later Holocene sediment delivery. In the UK, there is not always a pronounced AA non-conformity, definable perhaps in colour or textural terms, as in some other more recently anthropogenically transformed alluvial environments, most notably in North America and Australasia. The non-anthropogenic trajectories of previous late-interglacial or early Holocene sedimentation, which might provide useful comparisons, are only known in very general terms (Gibbard and Lewin, 2002). Supplied alluvial material may be ‘fingerprinted’ mineralogically in terms of geological source, pedogenic components or pollutant content (e.g. Walling et al., 1993, Walling and Woodward, 1992, Walling and Woodward, 1995 and Macklin et al., 2006). These records may be dated, for BCKDHB example, by the inclusion of ‘anthropogenic’ elements from mining waste that can be related to ore production data (Foulds et al., 2013). We suggest that consideration of sediment

routing and depositional opportunity is of considerable importance in interpreting the context of AA deposition. For example, early Holocene re-working of Pleistocene sediment is likely to have been catchment-wide, though with differential effect: limited surface erosion on slopes, gullying and fan formation on steep valley sides, active channel incision and reworking in mid-catchment locations, and the deposition of winnowed fines down-catchment. However, by the end of the later mediaeval period circumstances were very different, with soil erosion from agricultural land fed through terraced valley systems to produce very large depositional thicknesses in lower catchment areas where overbank opportunities were still available. Field boundaries, tracks and ditches greatly affected sediment transfers (Houben, 2008). Channel entrenchment within the last millennium (Macklin et al.