Dating late Quaternary alluvial stratigraphic sequences

One of the most important aspects of constructing a late Quaternary alluvial stratigraphy is proper dating. Of primary importance is the context of the datable samples. Samples must be collected from contexts that will date periods of deposition, episodes of erosion, and the timing of landscape stability and soil formation. Further, the samples collected to constrain these events in the alluvial record must be dated by a reliable dating technique and the samples must be of the quality needed to yield accurate ages. A useful alluvial chronology hinges on accurate and precise dating. This chapter outlines the procedures for collecting samples to establish the age of deposition, erosion, and stability in the alluvial record. This is followed by a discussion of the radiocarbon method, which is an important dating technique that is used to establish the absolute chronology of these events. These techniques are illustrated with reference to dated late Quaternary alluvial stratigraphies in North American contexts.