BIOGEOGRAPHY OF NON-MARINE OSTRACODES FROM A LATE-GLACIAL BERINGIAN LACUSTRINE RECORD

New analysis of core 70-92 taken in the Chukchi Sea at ­­­69°57.2’, 165°21.6’ during a previous investigation by the USGS indicates an ostracode record of terrestrial freshwater environments dated from ca 13,000 – 11,000 ¹⁴C years BP. This record is composed of four ostracode zones beginning at 12,640 + 45 ¹⁴C years BP with fresh to slightly oligohaline fauna (Zone 1), including Holarctic species Pteroloxa cumuloidea and Candona rectangulata. This system gives way to a freshwater habitat (< 1000 mg/l) ranging from ephemeral (Zone 2) to permanent (Zone 3) systems, ca 12,470 + 45 ¹⁴C years BP. Zone 2 includes Fabaeformiscandona rawsoni and Limnocythere inopinata. Zone 3 is dominated by Cytherissa lacustris and Candona candida. This freshwater basin is subsequently infilled and replaced by wetland peats, containing species of Cyclocypris and Cypria. The final zone culminates in a marine transgression. Only Zone 1 contains species which are exclusively found in the high arctic today. Subsequent zones are characterized by freshwater species that occupy temperatures commonly present in modern mid-latitude North America and Eurasia. Biogeography of these species drawn from modern ostracode distributions highlights the absence of high arctic and polar fauna in Zones 2-4, suggesting that following Zone 1, temperatures were similar to modern sub-arctic mid-latitude ranges. This conclusion is consistent with results from other workers on pollen and plant macrofossil records for the region, and help to narrow the time window in which fauna and humans would have been most likely to cross the Bering land bridge in late glacial time.