Heavy mineral assemblages of the De Long Trough and southern Lomonosov Ridge glacigenic deposits:implications for the East Siberian Ice Sheet extent

• Main Authors: Alatarvas, R. (Raisa), O'Regan, M. (Matt), Strand, K. (Kari)
• Format: Article in Journal/Newspaper
• Language: English
• Published: Copernicus Publications 2022
• Subjects: De Long Islands; East Siberian Sea; East Siberian Shelf; Indigirka; Kolyma; Long Islands; Okhotsk; Verkhoyansk; Chukotka; Ice Sheet; kolyma river; Lomonosov Ridge; SWERUS-C3
• Online Access: http://urn.fi/urn:nbn:fi-fe202301031295

Abstract The Arctic’s glacial history has classically been interpreted from marine records in terms of the fluctuations of the Eurasian and North American ice sheets. However, the extent and timing of the East Siberian Ice Sheet (ESIS) have remained uncertain. A recently discovered glacially scoured cross-shelf trough extending to the edge of the continental shelf north of the De Long Islands has provided additional evidence that glacial ice existed on parts of the East Siberian Sea (ESS) during previous glacial periods MIS 6 and 4. This study concentrates on defining the heavy mineral signature of glacigenic deposits from the East Siberian continental margin which were collected during the 2014 SWERUS-C3 expedition. The cores studied are 20-GC1 from the East Siberian shelf, 23-GC1 and 24-GC1 from the De Long Trough (DLT), and 29-GC1 from the southern Lomonosov Ridge (LR). Heavy mineral assemblages were used to identify prominent parent rocks in hinterland and other sediment source areas. The parent rock areas include major eastern Siberian geological provinces such as the Omolon massif, the Chukotka fold belt, the Verkhoyansk fold belt, and possibly the Okhotsk–Chukotka volcanic belt. The primary riverine sources for the ESS sediments are the Indigirka and Kolyma rivers, the material of which was glacially eroded and re-deposited in the DLT. The higher abundances of amphiboles in the heavy mineral assemblages may indicate ESS paleovalley of the Indigirka River as a major pathway of sediments, while the Kolyma River paleovalley pathway relates to a higher share of pyroxenes and epidote. The mineralogical signature in the DLT diamicts, consisting predominantly of amphiboles and pyroxenes with a minor content of garnet and epidote, shows clear delivery from the eastern part of the ESIS. Although the physical properties of the DLT glacial diamict closely resemble a pervasive diamict unit recovered from the southern LR, their source material is slightly different. The assemblages with elevated amphibole and garnet ...