Cliff-top eolian deposits and associated molluscan assemblages as indicators of Late Pleistocene and Holocene environments in Beringia

Abstract

Northern Yukon cliff-top eolian deposits are indicators of past climates and environments. The deposits are located along the Ramparts of the Porcupine River, near the international boundary. These eolian deposits resulted from southwest wind regimes that operated at about 14,860BP, and more certainly at 11,640–8200BP and from 4600BP to present. Palynological analysis indicates that these three periods were marked by different vegetation covers: the earliest one being dominated with Cyperaceae, the intermediate one by Shepherdia canadiensis, and the most recent one by spruce (Picea). Molluscs are particularly numerous and diversified, which suggests that the cliff-top deposits were important refuges for these animals. Molluscan assemblages indicate that the climate was wetter at about 14,860BP than between 11,640BP and 8200BP. The xeric regime that marked the latter period is also indicated by gypsum concretions. It is suggested that the molluscs could have been introduced by migratory birds that, in turn, would also have been able to use the snail shells from the eolian deposits as an important dietary element. It is also suggested that the molluscs are relicts of endemic fauna.