Abstract: | Archaeologists rely on the spatial and temporal distribution of artifacts and other site‐based materials to understand the stratigraphic integrity of the matrix in which remains are embedded. Although they are aware of taphonomic and site formation processes that can cause post‐depositional movement of objects, misinterpretation can occur. We used high‐precision 230Th dating of branch corals found throughout cultural layers of a coastal Hawaiian midden to identify the effects of post‐depositional disturbances to the archaeological record. Fifteen corals distributed in three cultural layers of a Mo'omomi bay site on west Moloka'i, Hawaiian Islands, were 230Th dated between A.D. 1513 and A.D. 1623. Even though the cultural layers appeared visually intact, the positions of the dated coral samples indicate stratigraphic mixing as there is no positive age–depth correlation. Consequently, all cultural layers should be considered one analytical unit for analysis of contents. This study is applicable to other Pacific archaeological sites, especially throughout Hawaii and East Polynesia generally, that have well‐preserved branch coral for 230Th dating. © 2010 Wiley Periodicals, Inc. |