Late-Holocene advances of the Greater Azau Glacier (Elbrus area, Northern Caucasus) revealed by 14C dating of paleosols

Abstract

Three paleosols buried in the left lateral moraines of the Greater Azau Glacier (Northern Caucasus) were identified in an excavated outcrop (43.2658 N, 42.4766 E, 2370 m a.s.l.). When the glacier was overlying the surface of the lateral moraines at this site, the thickness of the ice was 50 m and more above the valley floor. Fragments of charcoal from the uppermost soil (S1) buried 0.6 m below the surface yielded the radiocarbon date 130 ± 20 yr BP (IGANAMS-6826) (AD 1680–1939). The middle soil (S2), buried at the depth of 13 m yielded two 14C dates 320 ± 20 yr BP (IGANAMS-8127) (bark of birch) (AD 1496–1641) and 1190 ± 20 yr BP (IGANAMS-8126) (AD 774–889) (charcoal). We suggest that the soil S2 has been formed between these dates during the Medieval Warm Period and in the early Little Ice Age. The lowermost (S3) unit lying 15 m below the surface is the thickest (0.4–0.6 m), well-developed paleosol. Charcoal collected at the top of S3, yielded the date 1300 ± 20 yr BP (IGANAMS-6826) (AD 663–773), indicating a prominent glacier advance occurred shortly before this date. Two dates from the charcoal buried at the bottom of S3 (2855 ± 20 yr BP (IGANAMS-8125) and 2880 ± 20 yr BP (IGANAMS-6827) mark the beginning of a long episode of restricted glacier extent that lasted for about 1600 years. The dates at the bottom of the S3 paleosol constrain the end of glacier advance that occurred before 2800–2900 14C yr BP. The timing of most prominent advances of the Greater Azau Glacier in the past 3500 years is in general agreement with the Late-Holocene glacial chronologies in the European Alps, Scandinavia and other regions of the Northern Hemisphere.