Pollen records and age determinations from 2 profiles at Lake Nikolay, Lena Delta

Radiocarbon-dated pollen, rhizopod, chironomid and total organic carbon (TOC) records from Nikolay Lake (73°20'N, 124°12'E) and a pollen record from a nearby peat sequence are used for a detailed environmental reconstruction of the Holocene in the Lena Delta area. Shrubby Alnus fruticosa and Betula exilis tundra existed during 10,300-4800 cal. yr BP and gradually disappeared after that time. Climate reconstructions based on the pollen and chironomid records suggest that the climate during ca. 10,300-9200 cal. yr BP was up to 2-3 °C warmer than the present day. Pollen-based reconstructions show that the climate was relatively warm during 9200-6000 cal. yr BP and rather unstable between ca. 5800-3700 cal. yr BP. Both the qualitative interpretation of pollen data and the results of quantitative reconstruction indicate that climate and vegetation became similar to modern-day conditions after ca. 3600 cal. yr BP. The chironomid-based temperature reconstruction suggests a relatively warm period between ca. 2300 and 1400 cal. yr BP, which corresponds to the slightly warmer climate conditions reconstructed from the pollen. Modern chironomid and rhizopod assemblages were established after ca. 1400 cal. yr BP.

本数据集采用采自尼古拉湖（73°20'N，124°12'E）的放射性碳定年花粉、根足类（rhizopod）、摇蚊（chironomid）及总有机碳（total organic carbon, TOC）记录，辅以附近泥炭剖面的花粉记录，对勒拿河三角洲地区的全新世环境开展精细化重建。10300~4800校准年BP（cal. yr BP）期间，区域分布有由灌木状桤木（Alnus fruticosa）与细叶桦（Betula exilis）构成的苔原植被，该植被组合在该时段后逐渐消退。基于花粉与摇蚊记录的气候重建结果显示，约10300~9200 cal. yr BP时期的气温较现代偏高2~3℃。花粉重建结果表明，9200~6000 cal. yr BP时期气候相对温暖，而约5800~3700 cal. yr BP时期气候波动相对剧烈。无论是花粉数据的定性解译还是定量重建结果均显示，约3600 cal. yr BP之后，区域气候与植被状况逐渐趋近现代水平。基于摇蚊的温度重建结果显示，约2300~1400 cal. yr BP为相对温暖期，这与花粉记录重建的偏暖气候条件相吻合。现代摇蚊与根足类生物组合于约1400 cal. yr BP之后最终形成。