MIDDLE TO LATE HOLOCENE COASTAL EVOLUTION AT TANGINAK SPRING ARCHEOLOGICAL SITE, SITKALIDAK ISLAND, ALASKA

The Tanginak Spring archaeological site represents one of the oldest known occupations of the Kodiak Archipelago (c. 7500-6000 cal BP). Although excavations at this site have led to a better understanding of the prehistoric inhabitants in the region, little is known about the evolution of local coastal geomorphology during this time period. We undertook a reconstruction of the local sedimentological history during the summer of 2003. Excavations near the site and in the surrounding region provide the data necessary to perform this reconstruction. Using tephrastratigraphy, we have established that the sediments in the modern salt marsh were not present during the time of human occupation of the site. This finding suggests two possible scenarios for the middle to late Holocene evolution of Tanginak Anchorage. 1. The hill where the archaeological site is located was exposed to the open sea during occupation, and the lagoonal complex and modern shoreline have developed since site abandonment. 2. Significant erosional and progradational episodes have created the modern coastline, making it difficult to reconstruct coastal geomorphology at the time of occupation. We think that the latter is less likely due to absence of evidence of erosional truncations of former coastlines within the modern salt marsh. Additionally, preliminary results from ground-penetrating radar support the former scenario. Further analysis will yield a more complete understanding of Holocene evolution of this region.