AGGRADATION AND DEGRADATION AT THE NORTH CREEK SHELTER ARCHEOLOGICAL SITE: A SEDIMENTOLOGICAL HISTORY

Sedimentation and burial processes of the North Creek Shelter (NCS) archeological site were interpreted through examination of sedimentary features using photography and grain size analysis of pit wall samples. The outcrop setting suggests sediment was delivered to the shelter surface by alluvial processes associated with drainage of the overhanging Dakota Sandstone mesa. The sediment likely washed from the mesa surface into major fractures. As sediment exited the fractures, it was dispersed over the NCS surface. Interspersed large angular sandstone clasts are either: 1- colluvial dropstones, 2- transported by humans, or 3- deposited by alluvial processes during rare high energy storm events. There are two distinct phases of sedimentation at the NCS. The lower portion of the section represents an aggradational phase when sediment accumulation was relatively high, and the upper portion represents a degradational phase when non-deposition, erosion, or bioturbation (including human habitation) outpaced sediment build-up.