Geomorphology of the Anthropocene: time-transgressive discontinuities of human-induced alluviation

Alluvial sediments are an integral and environmentally sensitive component of the geological record and may be preserved both in subsiding basins and by uplift. This paper examines the Holocene alluvial record of a high-order fluvial discontinuity within the mid to late Holocene that is evident on all continents except Antarctica. The time-transgressive nature of this discontinuity, even over short distances, is revealed by two similar small-catchments in the UK which have a similar response to arable cultivation but separated in time by approximately 3000 years. It is argued that this anthropogenic discontinuity is likely to be an enduring signal as it exists well outside potentially future-glaciated areas and will be preserved in Holocene river terraces due to recent and future channel incision. This will make a marked lithological and sedimentological difference between this Middle-Late Holocene terrace and Pleistocene terraces which will also include a biological turnover with the appearance of new taxa, largely domesticates and synanthropes. Discussions of the Anthropocene as a geological period will have to accommodate this data and this may have important implications for the status and demarcation of the Anthropocene as a period in Earth System history.