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Deglaciation history and age estimate of the Younger Dryas end moraines in the Kalevala region, NW Russia

2011; Elsevier BV; Volume: 30; Issue: 27-28 Linguagem: Inglês

10.1016/j.quascirev.2011.09.023

1873-457X

Niko Putkinen, Juha Pekka Lunkka, Antti Ojala, Emilia Kosonen,

Geomagnetism and Paleomagnetism Studies

Abstract Three lake basins were cored in the Kalevala area, northwestern Russia in order to determine the Weichselian deglaciation history of the eastern flank of the Scandinavian Ice Sheet and to date the Kalevala and Paajarvi end moraines adjacent to these basins. Two of the lake basins, Ala-Kuittijarvi and Keski-Kuittijarvi, are situated on the proximal side of the Kalevala end moraine while the third lake basin, Tuoppajarvi, is located on the distal side of the Paajarvi end moraine. One site from each lake basin was chosen for sedimentological and chronological study. The chronology presented in this paper is based on palaeomagnetic measurements and counting of varved clays and the results are compared to the Finnish palaeomagnetic master curve. The results indicate that the deglaciation sediments in the Ala-Kuittijarvi and Keski-Kuittijarvi lakes were deposited mainly by extra-marginal rivers, while those in Tuoppajarvi were deposited in an ice-contact setting. After the glacial meltwater input ceased, typical large lake gyttja clay/clay gyttja sediment accumulated in all three basins. The palaeomagnetic record obtained from the Ala-Kuittijarvi sediment sequence extends back to 10,900 cal. BP, while that of Keski-Kuittijarvi and Tuoppajarvi dates back to 9800 cal. BP. The palaeomagnetic record, together with 450 counted varves in Ala-Kuittijarvi, indicates that the basin was deglaciated at around 11,350 ± 300 cal. BP. Based on palaeomagnetic results, geomorphological considerations and ice retreat rates, it is estimated that the Kalevala end moraine was formed prior to 11,450 ± 350 cal. BP, while the Paajarvi end moraine, west of Tuoppajarvi, was formed at prior to 11,000 ± 250 cal. BP.