Abstract

The Schoonrewoerd fluvial system in the central Rhine–Meuse delta was active as a Rhine distributary between 3900 and 3800 ¹⁴C years BP. Based on planform patterns, cross-sectional facies architecture, reconstructed paleodischarge, and its short period of activity, the Schoonrewoerd fluvial system is interpreted to represent a failed avulsion.

The Schoonrewoerd system consists of a complex of (ribbon) channel sand bodies encased in a lens of clayey deposits, and it can be traced for more than 35 km in a downstream direction. Prominent features of the system are longitudinal facies-architecture change, with channel sand-body width/thickness ratio decreasing downstream from ~ 40 to 5, and high lateral facies variability. Multiple anastomosing sand bodies occur in its upper and middle reaches. Paleodischarge reconstruction indicates that the Schoonrewoerd system was only a minor distributary within the Rhine–Meuse deltaic system. Specific stream power in the lower reach is estimated to have been low (0.5 to 1.8 W/m²). The short period of activity of the Schoonrewoerd system suggests that very high floodplain sedimentation rates were associated with the avulsion process, with the formation of meters-thick fine-grained sedimentary successions in ~ 100 years.

The facies architecture of the short-lived Schoonrewoerd system is interpreted to reflect the first stages of avulsion (broadly analogous to the modern Saskatchewan River avulsion in Canada; Smith et al. 1989, Sedimentology, v. 36, p. 1–23), having escaped from later erosion by a more mature channel belt. Many other systems (often partly eroded) with similar facies architecture exist in the west-central Rhine–Meuse delta, suggesting that "avulsion-belt deposits" are a major component of the Holocene delta deposits. The facies-architecture model of the Schoonrewoerd avulsion-belt deposits presented in this paper may provide clues for the interpretation of fine-grained sedimentary successions in ancient fluviodeltaic deposits.