Iceberg-rafted debris events from the glacial Kamchatka in the southwestern Okhotsk Sea over the past 110 kyrs

Abstract

High-resolution analyses of ice-rafted debris (IRD) and its light and heavy minerals in a sediment core sample from the SW Okhotsk Sea reveal the varying sources of terrigenous material and iceberg discharge events from the Kamchatka Peninsula into the SW Okhotsk Sea since the last interglacial period (Marine Isotope Stage (MIS) 5). Our results suggest the dominance of seasonal and mobile sea ice since 110 ka BP, with occasional perennial sea ice in the SW Okhotsk Sea, which is the most important agent for the basin-wide dispersal of land-sourced terrigenous material. Between 33 ka BP and 14 ka BP (MIS 2), prevalent sea ice formed on the northern shelves. Since 14 ka BP, instead, the IRD originated mainly from the Sakhalin Gulf, with a substantial increase in near-source material input. Thirteen events of IRDKamchatka were identified between 87 and 27 ka BP (mainly in MIS 4–3), with debris definitely originating from the Kamchatka Peninsula. Among these events, the four most prominent types of iceberg/ice sheet rafting occurred at ∼63 ka, ∼53 ka, ∼40 ka, and ∼33 ka BP. Simultaneously, they are consistent with the IRDiceberg events that occurred in the core of western Kamchatka and are also close to the age of H6, H5, H4 and H3 in the Heinrich Events. The initial source areas and transportation pathways of these iceberg armadas varied considerably over time. During ∼87–53 ka BP, icebergs originated from the western Kamchatka Peninsula and migrated southward. During ∼53–27 ka BP, IRDKamchatka inputs likely originated from the eastern Kamchatka Peninsula. This suggests that during MIS 4/3, the mountain glaciers of the Kamchatka Peninsula experienced a reduction in scale and retreated from the western to the eastern part of the peninsula. The event at 27 ka BP marks the last major IRDKamchatka contribution to the Okhotsk Sea from the Kamchatka Peninsula. Since 14 ka BP, the input of IRDKamchatka into the SW Okhotsk Sea has become very weak.