This article presents the results of the first comprehensive study of permafrost and frost mounds in the Sentsa River valley on the Oka Plateau (Eastern Sayan Ridge). The lacustrine-alluvial deposits are represented by clayey silts and silts with visible ice contents up to 90%. Ground ice mainly comprises bicarbonate calcium or bicarbonate magnesium, enriched in ammonium, aluminium, silicon, phosphorus, iron and zinc. Rare earth element content varies from 0.010 to 0.500 μg/L. The distribution of δ¹⁸O and δ²H in the ground ice to a depth of 20 m reflects repeated changes during the freezing of the deposit. The mean annual temperature of frozen rocks is −1.0°C. From 2016, mean annual ground temperatures have been observed to be gradually increasing at a depth of 1.0 m, which correlates with a stable, positive trend of the mean annual air temperatures on the Oka Plateau over the past 60 years. The species and quantitative composition of the palynospectra of the permafrost provides the evidence of repeated changes in the habitat area of forests, as well as changes in the sedimentation regime in the Holocene. According to ¹⁴C dating of the soil horizons in the upper parts of the frost mounds, after the emptying of the paleo-lake, organic material intensely accumulated in the drained areas (from 0.5 to 0.2 ka) and ice-mineral frost mounds began to form.

中文翻译：

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奥卡高原的永久冻土层（东萨彦岭）

本文介绍了对奥卡高原（东萨彦岭）仙沙河谷永久冻土和霜丘的首次综合研究结果。湖相冲积沉积物以粘土质淤泥和可见冰含量高达 90% 的淤泥为代表。碎冰主要包含碳酸氢钙或碳酸氢镁，富含铵、铝、硅、磷、铁和锌。稀土元素含量从 0.010 到 0.500 μg/L 不等。δ ¹⁸ O和δ ²的分布20 m 深的地面冰中的 H 反映了沉积物冻结过程中的重复变化。冻岩年平均温度为-1.0°C。从 2016 年开始，观测到 1.0 m 深度的年平均地温逐渐升高，这与过去 60 年奥卡高原年平均气温的稳定、正趋势相关。永久冻土的孢粉光谱的物种和数量组成提供了森林栖息地区域重复变化的证据，以及全新世沉积体系的变化。根据¹⁴霜丘上部土壤层的C测年，在古湖排空后，排水区（0.5～0.2ka）有机物质大量积累，冰矿物霜丘开始形成。