Late Quaternary Deposits of the Northern Verkhoyansk Mountains: Geochronology and Questions of their Genesis

Using accelerator mass spectroscopy (AMS), it was possible to obtain 35 radiocarbon age dates from late Quaternary deposits of the Northern Verkhoyansk Mountains (Kharaulakh Ridge). The presented results showed that frozen sediments covering pre-Quaternary rocks in the studied areas are relatively young; their accumulation began only in the Karginsk Interstadial (MIS 3). Within the Kharaulakh structural-facial zone (the Kharaulakh Ridge), the age of the Quaternary deposits ranged from about 28 000 BP up to the present time. In the adjacent territory of the foothill plain that belongs to the Buor-Khaya structural-facial zone their ages ranged from about 48 000 BP to the Holocene. The sediments studied in two catchment areas of the Kharaulakh mountains were linked to relief forms (cirque-like areas, turning into terraced surfaces), which indicate their accumulation under the influence of nival processes associated with snowfields. This conclusion is confirmed by the rhythmic stratified structure of the investigated sediment sections that was caused by seasonal snowfield melting and the associated transport and sorting of detrital material. Measured ages suggest that these processes were especially common in the last phase of the Kargins interstadial (MIS 3) and at the beginning of the Sartan stadial (MIS 2), as well as during the late Holocene. The ages of alluvial deposits from the Khara-Ulakh River valley indicated that sedimentation began at the end of the Sartan stadial (MIS 2) − about 12 thousand years ago − and continues to the present day. These data confirm the young age of the Kharaulakh depression. At a similar time, the formation of the Khorogorsk depression in the northern part of the Kharaulakh Mountains occurred. Ice-rich sediments with polygonal ice wedges on the foothill plain at Cape Ogolokh-Tumsa located in the Buor-Khaya structural-facial zone are comparable with the very thoroughly studied section of the ice complex deposits on the Bykovsky Peninsula