The Quaternary history of Beringia and of the Arctic–Pacific marine connection via the Bering Strait is poorly
understood because of the fragmentary stratigraphic record from this region. We report new borehole
and seismic-reflection data collected in 2006 in the southwestern Chukchi Sea. Sediment samples were
analyzed for magnetic properties, grain size, heavy minerals, and biostratigraphic proxies (spores and pollen,
foraminifers, ostracodes, diatoms, and aquatic palynomorphs). Two shallow boreholes drilled between the
Chukotka Peninsula and the Wrangel Island recovered sediments of two principal stratigraphic units with a
distinct unconformity between them. Based on predominantly reverse paleomagnetic polarity of the lower
unit and pollen spectra indicative of forested coasts and climate warmer than present, the age of this unit
is estimated as Pliocene to early Pleistocene (broadly between ca. 5 and 2 Ma). Attendant sedimentary
environments were likely alluvial to nearshore marine. These deposits can be c