DEVELOPMENT OF A PALEOSHORELINE MODEL TO PREDICT THE LOCATION OF EARLY HOLOCENE HABITATION SITES on PRINCE OF WALES ISLAND AND THE ADJACENT OUTER ISLANDS, SOUTHEAST ALASKA

Understanding the position of paleoshorelines is key to locating early Holocene habitation sites. A recently compiled dataset of over 400 shell-bearing raised deposits throughout Southeast Alaska gives insight on the timing and complexity of isostatic crustal adjustments that resulted from glaciation and deglaciation, eustatic sea level change, forebulge development, and subsequent tectonic uplift.

In 2009, 20 shell-bearing raised deposits were sampled, dated, and elevation measured. To create a paleo-high tide elevation estimate, only sediments containing in-situ butter clam (Saxidomus giganteus) were considered. It was assumed that as today, paleo-butter clam existed in the littoral zone from between – 1 m to +2 m elevation relative to Mean Lower Low Water (MLLW) and that the average high tide of +5.88 m above MLLW had been constant through time. If butter clam can be found to an elevation of +2 m above MLLW then the paleo-high tide elevation should be approximately +3.88 m above the occurrence of in-situ butter clam. The resultant paleoshoreline model suggested that the paleo-high tide should have been 15.5 m +/- 1 m above MLLW between 7600 and 9200 RCYBP. Assuming that early inhabitants would have camped 1-3 m above the paleoshoreline, early Holocene sites should be located between 16 and 19 m above MLLW today.

GIS spatial modeling utilizing LiDAR generated Digital Elevation Models (DEM) and available 20m DEM's were used to predict the 9200 RCYBP paleoshoreline based on the sea level curve. Several test localities were selected based on terrace elevation, protected former shorelines and embayments, and the abundance of marine resources, i.e. salmon streams, intertidal and estuary habitat.

Surveys in 2009 confirmed four early to mid-Holocene habitation sites on terraces developed at 16 to 19 m above MLLW yielding basal dates of 9090±50 (Beta 264554), 8730±50 (Beta 254082), 8220±50 (Beta 268998), and 6890±40 (Beta 269000) RCYBP. Surveys in 2010 located 12 sites.