A Multidisciplinary Approach for Dating Human Colonization of Pacific Atolls

The timing of reef platform emergence and the detailed chronology of reef island development provides a powerful backdrop for constraining the earliest period possible for prehistoric human colonization of low-lying atolls. Since Pacific atolls consist of biogenetic sediments, we dated foraminifera sands composed of well-preserved shallow-water species that are reliable indicators of facies formation. From transect excavations across the largest islet of Utrok Atoll (11 degrees 13'N, 169 degrees 50'E) and Maloelap Atoll (8 degrees 47'N, 171 degrees 05'E), Marshall Islands, we selected nine foraminifera dating samples and five charcoal samples from prehistoric ovens in well-defined cultural layers and charcoal from buried A horizons. We document that: 1) the largest islets of Utrok and Maloelap atolls expanded towards the lagoon shore at a rate of similar to 70 m/kyr and similar to 200m/kyr, respectively; 2) foraminifera sands immediately below buried A horizons in the islet's core areas represents the timing of islet development at similar to 2750 and similar to 2400 cal BP, respectively; and 3) the oldest cultural dates (1850 and 1790 cal BP, similar to 900-600 years younger than islet development) indicates that occupation much older than 2000 cal BP is unlikely, which is supported by sea level falling from its high stands to the present levels around 2000 cal BP for the northwestern Pacific.