Archaeologically-dated horizons in Olway Valley floodplain alluvium at Usk (Gwent, UK)

Two sites are described from the Olway Valley at Usk, Gwent, where discrete horizons containing archaeological material occur within floodplain alluvium. Modern horizons, one dating to AD 1920 and another more loosely dated as late-nineteenth-/early-twentieth-century, occur within the upper part of the alluvial sequence at both sites. Also, a deeper horizon, characterized by a stone layer containing rounded and angular stone clasts, and medieval and abraded Roman pottery occurs at one of the sites only. It is suggested that this lower stone layer may represent a stone platform constructed to broaden the historic resource use of the pre-drained floodplain. These horizons provide dates that may be used to construct sedimentation rates for floodplain alluvium.