SEDIMENT CHARACTERISTICS AND CHRONOLOGY OF AEOLIAN SEDIMENTS ON A TROPICAL PACIFIC CORAL ATOLL

Aeolian deposits on Kiritimati, Republic of Kiribati, a low-lying coral atoll in the central tropical Pacific (CTP), are a potential paleoenvironmental archive for terrestrial changes associated with Pacific climate variability and landscape disturbance. Sedimentological data and stratigraphic observations associated with paired organic–inorganic radiocarbon dates from aeolian deposits and a buried paleosol indicate at least three periods of dune development since the late-Holocene on Kiritimati. Radiocarbon dates on foraminifera from aeolian sand, representing maximum ages, indicate that aeolian sediment was deposited 3,216 ± 90 cal years B.P., to 305 ± 64 cal years B.P. A paleosol, evidence for a period of dune stability and a less arid environment, dates to approximately 756 ± 30 cal years B.P (1194 ± 30 C.E.). Although the duration of paleosol formation is uncertain, the timing of the paleosol coincides with a switch from drier to wetter conditions indicated by a Kiritimati lake sediment record. Calibrated, post-bomb radiocarbon ages from the late 1950’s C.E. in the uppermost sediments to the paleosol surface boundary point to recent erosion followed by rapid deposition of the upper aeolian unit in the last several decades. We infer the surface of the paleosol was exposed in the 1950’s and 1960’s C.E., coincident with the occupation of Kiritimati by thousands of servicemen conducting hydrogen bomb tests, suggesting that military occupation caused destabilization and remobilization of the dune surface. Based on this nascent chronology, dune systems on Kiritimati appear sensitive to landscape disturbance, yet prior to the mid 20^th century military operations, may reflect predominantly large-scale shifts in central tropical Pacific atmospheric moisture, and therefore represent a useful terrestrial archive of regional climate.