One objective of the Ocean Drilling Program (ODP) Leg 178 expedition was to search for sediment deposits related to the late Pliocene impact of the Eltanin asteroid. This is a unique deposit in the known sedimentary record. It is the only known deposit recording the events surrounding the impact of a kilometer-sized asteroid into a deep (5 km) ocean basin. The exact point of impact is unknown, but it is believed to have occurred in the Bellingshausen Sea in a region ~1000 km west of Cape Horn (58°S, 90°W). Details of the study of this impact are found in a series of five papers (Kyte et al., 1981, 1988; Kyte and Brownlee, 1985; Margolis et al., 1991; Gersonde et al., 1997). The impact ejecta deposits near ground zero contain millimeter- to centimeter-sized debris composed of Ir-rich impact melt and unmelted meteorites. About 500 km east of the impact region, at USNS Eltanin site E10-2, debris as large as ~1 mm was recovered (Kyte et al., 1988). These deposits provide a natural laboratory for studying processes related to the formation and preservation of Ir-rich meteoritic ejecta. The current estimate of the size of the projectile (Gersonde et al., 1997), from 1 to 4 km in diameter, is well within the range of asteroid sizes proposed to have global consequences (Chapman and Morrison, 1994). This impact must have generated large tsunamis throughout much of the Pacific basin and around much of the Southern Ocean.
Finding and characterizing the ejecta deposits at new sites would be an important next step in understanding the magnitude of this impact event. Nearly all of the data on this impact are restricted to five piston cores, all within a radius of ~70 km (Gersonde et al., 1997) and quite near the suspected impact site. New data at sites with greater distances from the impact would provide better constraints on the size, and thus the energy, of the impact event. ODP Leg 178 researchers drilled shelf and rise sediments along the western side of the Antarctic Peninsula in an area ~1300 km southeast of the Eltanin impact area and thus had the potential to recover deposits from this impact. In this paper, results of the attempt to find evidence of this deposit are described.