Site preservation along an active meandering and avulsing river: The Red River, Arkansas

Abstract

The low-gradient Red River is a rapidly migrating, sinuous stream with easily erodible banks. Avulsion is common at many scales, from individual meander bends that are cut off to major sections of the river that form multiple, complex meander belts. The present meander belt can be subdivided into mappable landforms—termed phases—that are associated with river courses of different ages and thus associated with archeological sites of different ages. Within the study area two phases are present. The younger Modern meander belt phase has formed within the past 0.2–0.3 ky, precluding preservation of prehistoric archaeological sites. Any protohistoric artifacts that may have been preserved in this meander belt phase would be deeply buried because as much as 2 m of the vertical accretion sediment has accumulated between artificial levees in <0.1 ky and 1–2 m of sediment has accumulated beyond the artificial levees in <0.2 ky. Archeological site preservation in this highly mobile fluvial end member can be used as a predictor for other, similar streams. A large prehistoric site is preserved on an older (0.5–1 kya) Late Prehistoric meander belt phase associated with an abandoned river course. In the study area a Fourche Maline 7 period (A.D. 800–900) through Caddo IV period (ca. A.D. 1500–1700) archeological site (3MI3/30) is preserved on this slightly higher altitude portion of the flood plain. At locations proximal to the river, the site may be buried by overbank sediment 0.4 m thick, but at more distant locations the site is at the surface or only buried by thin overbank sediment because of low sedimentation rates (0.04 cm yr−1) over the span of a millennium. Sites, such as 3MI3/30, that are occupied contemporaneous with overbank sedimentation may be stratified; however, localized erosion and removal of some archeological material may occur where channelized flow crosses the natural levee. © 1998 John Wiley & Sons, Inc.