The eastward intrusion of the Lena River into the East Siberian Sea since the early Holocene

Abstract

The sedimentary environments and material sources of the eastern and northeastern Lena Delta differ in coarse-grained components and garnet geochemistry, particularly in the Buor-Khaya Bay, where the material composition is primarily influenced by the Lena River, while the Yana Bay sediment is controlled by the Yana River. Analysis of detrital minerals in core LV83–32-3, located in northern Yana Bay, indicates dominant primarily fluvial input from the Yana River, with secondary contributions from the Lena River and minor inputs from coastal permafrost erosion since the early Holocene. During the sea-level rise period from 8.5 to 5 ka, four significant fluvial discharge events from the Yana River were identified, marked by high mica contents, associated with multiple climate warming events. From ∼5 to 1.6 ka, an increasing Lena River runoff transported coastal permafrost material via river flow or river ice, evident in a gradual rise in plagioclase content. After 1.6 ka, a sharp decrease in hypersthene and garnet contents suggests reduced Lena River discharge, coinciding with a similar decline in hypersthene content in the core of the East Siberian Sea since 1.8 ka. Two prominent Lena River fluvial events, dated to 7.1 and 3.7 ka, are identified by the event layers containing minerals typical of the Lena River, rich in hypersthene, garnet and zircon, along with substantial coarse-grained debris such as quartz, plagioclase, siderite and clayey tubes. These two events are also recorded in the East Siberian Sea. The 7.1 ka discharge event may coincide with the separation of the New Siberian Islands from the mainland, while the 3.7 ka event represents a widely distributed Lena River floodplain event.