Cryospheric and Oceanographic Evolution in the Arctic Makarov Basin Since the Early Pleistocene Revealed by Bulk Mineral Assemblages.

NORTH America; ARCTIC regions

We present the glacial history of the Makarov Basin (western Arctic Ocean) during the last ∼1.1 Myr, with sediment provenances using the newly refined chronostratigraphy of core ARA03B‐41GC02. According to the principal component analysis of the bulk mineral assemblages, felsic minerals were dominant, and their ratios (K‐feldspar/plagioclase and quartz/feldspars) indicated that sediment supply to the Makarov Basin was mainly from the Siberian margin and partly from northern North America, including the Canadian Arctic. However, their occurrence did not vary significantly between interglacials and glacials due to the mixed sources. In contrast, clinopyroxene and dolomite indicated specific sediment origins from the eastern Siberian margin and northern North America, respectively. The clinopyroxene content followed an eccentricity cycle (∼100‐Kyr) during the early to middle Pleistocene, suggesting that the eustatic sea level changes may have influenced its input from the eastern Siberian margin. The dolomite, transported primarily by icebergs from the Arctic sector of the Laurentide Ice Sheet (LIS) in northern North America, has also followed the same cycle since the early Pleistocene. Thus, the mineralogical signals highlight that sediment origins and transport processes in the Makarov Basin were related to ice sheet evolution at the eccentricity cycle. In addition, dolomite deposition in the Makarov Basin began by the early Pleistocene (∼790 ka), ∼150 ka earlier than in previous North Atlantic records (∼640 ka), indicating the earlier LIS calving in the Arctic sector than in the Atlantic sector. Plain Language Summary: We investigated past mineralogic changes in the Makarov Basin (western Arctic Ocean) over the last 1.1 million years using marine sediment core ARA03B‐41GC02. Bulk mineral analysis revealed that sediments in the Makarov Basin mainly originated from the Siberian margin, with a partial contribution from northern North America. However, sediments deposited during interglacial and glacial periods were mixed from different sources. Nevertheless, specific minerals such as clinopyroxene and dolomite allow us to distinguish different sediment sources between the eastern Siberian margin and northern North America. The clinopyroxene content fluctuated on a cycle of ∼100‐Kyr during the early to middle Pleistocene, suggesting an association with global sea level changes. The variation in dolomite content followed the same cycle, indicating that sediments containing dolomite were mainly transported by icebergs from the Laurentide Ice Sheet (LIS) in northern North America. These results linked sediment sources and transport processes to glacier evolution over cycles of ∼100‐Kyr. Interestingly, our study shows that dolomite deposition in the Makarov Basin began about 790,000 years ago, which is about 150,000 years earlier than previously reported (∼640 ka) in the North Atlantic, suggesting an earlier LIS calving into in the Arctic sector than in the North Atlantic sector. Key Points: Sediment provenances of clinopyroxene and dolomite are different (eastern Siberian margin and North America) in the Makarov BasinVariations in dolomite and clinopyroxene during the Pleistocene follow a ∼100 Kyr cycle of eccentricityDolomite in Makarov Basin ∼150 Kyr earlier than N. Atlantic implies Laurentide Ice Sheet calved into Arctic before extending to N. Atlantic [ABSTRACT FROM AUTHOR]

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