Climates and sea-level controls on chemical weathering in the northern shelf of the Okhotsk Sea in the past 23 ka

Abstract

The Okhotsk Sea, a subarctic marginal sea with a wide shelf and abundant weathering products, provides ample information about the chemical weathering in the geological past. However, insufficient investigation in the Okhotsk Sea, especially in its shelf, limits our knowledge of the intensity of chemical weathering in high-latitudes. In this study, high-resolution geochemical elements compositions of the core LV87-54-1 were measured to reveal the provenance change in the Northern Okhotsk Sea Shelf since the Last Glacial Maximum (LGM) and to discuss the influential factors of the deep-sea weathering records. The elemental ratios suggested that the sediment provenance remained stable during 23–11.4 ka, mainly transported from the Okhotsk-Chukotka volcanic belt; whereas the sediment input from the Kamchatka Peninsula to the study area has been enhanced since 11.4 ka. During 23–14 ka, the chemical index of alteration (CIA) was observed to align with climatic changes in the Northern Hemisphere. Synchronized climatic deterioration (i.e., cooling and drying) in the Northern Hemisphere mainly contributed to the reduced alteration of the sediments eroded from the Okhotsk-Chukotka volcanic belt. During 14–11.4 ka, the reworking of older weathered sediments caused by sea-level rise overwhelmed climates in controlling silicate weathering, resulting in an increased alteration of sediments. During the Holocene, the core sediment witnessed a lower weathering degree, compared to the LGM–Deglaciation. We attribute this to an increased sediment input from the Kamchatka Peninsula that supplied more weaker weathered sediments to the study area.