Multidisciplinary study of a key section on the Laptev Sea Coast (Bykovsky Peninsula, east Lena Delta) in 1998-2001 provides the most complete record of Middle and Late Weichselian environments in the East Siberian Arctic. The 40-m high Mamontovy Khayata cliff is a typical Ice Complex section built of icy silts with a network of large syngenetic polygonal ice wedges, and is richly fossiliferous. In combination with pollen, plant macrofossil and mammal fossils, a sequence of ca 70 insect samples provides a new interpretation of the environment and climate of the area between ca 50 and 12 ka. The large number of radiocarbon dates from the section, together with an extensive 14 C database on mammal bones, allows chronological correlation of the various proxies. The Bykovsky record shows how climate change, and the Last Glacial Maximum in particular, affected terrestrial organisms such as insects and large grazing mammals. Both during the presumed ''Karginsky Interstadial'' (MIS 3) and the Sartanian Glacial (MIS 2), the vegetation remained a mosaic arctic grassland with relatively high diversity of grasses and herbs and dominance of xeric habitats: the tundra-steppe type. This biome was supported by a constantly very continental climate, caused by low sea level and enormous extension of shelf land. Variations within the broad pattern were caused mainly by fluctuations in summer temperature, related to global trends but overprinted by the effect of continentality. No major changes in humidity were observed nor were advances of modern-type forest or forest-tundra recorded, suggesting a major revision of the ''Karginsky Interstadial'' paradigm. The changing subtypes of the tundra-steppe environment were persistently favourable for mammalian grazers, which inhabited the shelf lowlands throughout the studied period. Mammal population numbers were lowered during the LGM, especially toward its end, and then flourished in a short, but impressive peak in the latest Weichselian, just before the collapse of the tundra-steppe biome. Throughout MIS 3 and MIS 2, the climate remained very favourable for the aggradation of permafrost. No events of regional permafrost degradation were observed in the continuous Bykovsky sequence until the very end of the Pleistocene. r

correlation of certain stratigraphic levels in various deposiDetailed tephrochronological studies in Kamchatka Peninsula, tional successions. Their ages being determined, they beRussia, permitted documentation of 24 Holocene key-marker come excellent time markers and can be used in geochronotephra layers related to the largest explosive eruptions from 11 logical investigations. Tephra (volcanic ash) horizons are volcanic centers. Each layer was traced for tens to hundreds of among the best marker beds of this kind. C yr B.P.) SH 2 (É1000 yr B.P.) and SH 3 (É1400 yr B.P.) from is a few tens of centimeters thick in areas distant from the Shiveluch volcano; KZ (É7500 yr B.P.) from Kizimen volcano; active volcanoes and increases up to several meters at their KRM (É7900 yr B.P.) from Karymsky caldera; KHG (É7000 yr foot. This cover provides a continuous record of the explo-B.P.) from Khangar volcano; AV 1 (É3500 yr B.P.), AV 2 (É4000 sive eruptions during the Holocene, while earlier ash layers yr B.P.), AV 4 (É5500 yr B.P.), and AV 5 (É5600 yr B.P.) from in Kamchatka were almost everywhere destroyed during Avachinsky volcano; OP (É1500 yr B.P.) from the Baraniy Amfi-Late Pleistocene glaciation and occur as isolated beds. stratigraphic value and 9 important local marker ash layers.from Shtyubel cone in Ksudach volcanic massif; and KO (É7700 yr B.P.) from the Kuril Lake-Iliinsky caldera. Tephra layers SH 5 Identification of tephra sources was possible due to prelimi-(É2600 yr B.P.) from Shiveluch volcano, AV 3 (É4500 yr B.P.) nary studies that included detailed mapping of the Holocene from Avachinsky volcano, OP tr (É4600 yr B.P.) from Opala vol-eruptive centers (Melekestsev et al., 1974) and investigations cano, KS 3 (É6100 yr B.P.) and KS 4 (É8800 yr B.P.) from Ksudach of geochemical types and petrology of Late Cenozoic volcacalderas, KSht 1 (É1100 yr B.P.) from Shtyubel cone, and ZLT nic rocks (Volynets, 1994). These data allowed us to identify

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The ages of most of calderas,

Natural middle-and late-Holocene environmental development of Kunashiri Island reflects global climatic changes and the migration of warm and cold currents. Dry and cool climate changed to warm and moist about 7000–6500 BP, later than on Hokkaido Island. At this time Kuroshio Current system became more active. On Kunashir Island birch assemblages were replaced by cool-temperate broadleaf forests in the south and mixed coniferous/broadleaf forests in the north. The highest sea-level position reached 2.5–3 m above PSL about 6500–6300 BP. Cooling about 4700–4500 BP island vegetation weakly changed that connected with warm current influence. Major regression at this period led to formation of extensive coastal dunefields. The warming at the beginning of the late Holocene was almost similar to the Holocene Optimum. Two minor transgressions are recorded about 4010–3400 and 2950–2620 BP. Active entrance of detrital material to the coastal zone resulted in growth of accumulative landforms. Vegetation changes and climatic deterioration took place in the second half of the late Holocene. Coniferous and mixed coniferous/broadleaf forests shifted southward and occupied a large part of the island. During cooling at 1700–1300 BP the isthmus area increased, coastal wetlands with lakes and coastal dunes were formed, and grassland and swamp landscapes developed. Late-Holocene warming was not intensive. Active aeolian accumulation took place during the ‘Little Ice Age’ cooling and regression.

We present and discuss a full list of radiocarbon dates for woolly mammoth and other species of the Mammoth fauna available from Wrangel Island, northeast Siberia, Russia. Most of the radiocarbon dates are published here for the first time. Of the124 radiocarbon dates on mammoth bone, 106 fall between 3700 and 9000 yr ago. We believe these dates bracket the period of mammoth isolation on Wrangel Island and their ultimate extinction, which we attribute to natural causes. The absence of dates between 9–12 ka probably indicates a period when mammoths were absent from Wrangel Island. Long bone dimensions of Holocene mammoths from Wrangel Island indicate that these animals were comparable in size to those on the mainland; although they were not large animals, neither can they be classified as dwarfs. Occurrence of mammoth Holocene refugia on the mainland is suggested. Based on other species of the Mammoth fauna that have also been radiocarbon on Wrangel Island, including horse, bison, musk ox and woolly rhinoceros, it appears that the mammoth was the only species of that fauna that inhabited Wrangel Island in the mid-Holocene.

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