Lena River delta formation during the Holocene

[摘要] The Lena River delta, the largest delta of the Arctic Ocean, differs fromother deltas because it consists mainly of organomineral sediments, commonlycalled peat, that contain a huge organic carbon reservoir. The analysis ofdelta sediment radiocarbon ages showed that they could not have formed aspeat during floodplain bogging; rather, they accumulated when Laptev Sea water levelwas high and green mosses and sedges grew and were deposited on the surfaceof flooded marshes.

The Lena River delta formed as organomineral masses and layered sedimentsaccumulated during transgressive phases when sea level rose. In regressivephases, the islands composed of these sediments and other, more ancientislands were eroded. Each new sea transgression led to further accumulationof layered sediments. As a result of alternating transgressive andregressive phases, the first alluvial-marine terrace formed, consisting ofgeological bodies of different ages. Determining the formation age ofdifferent areas of the first terrace and other marine terraces on the coastallowed the periods of increasing (8000–6000 BP (years before present), 4500–4000, 2500–1500, and 400–200 BP) and decreasing(5000, 3000, and 500 BP) Laptev Sea levels to bedistinguished in the Lena Delta area.

[学科分类] 地球化学与岩石