Chrono-environmental dynamics of Yercaud Lake sediments (Eastern Ghats, South India) over the last 2500 years: Insights from AMS radiocarbon dating, particle size distribution, and stable isotope composition

IF 1.3 4区地球科学 Q3 GEOSCIENCES, MULTIDISCIPLINARY

Journal of Earth System Science Pub Date : 2024-09-14 DOI:10.1007/s12040-024-02371-7

Gopal Veeramalai, Hema Achyuthan, Christopher Eastoe

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Abstract

A 40-cm core of lake-bottom silt from Yercaud Lake (Eastern Ghats, south India) dates from 2500 years ago to the present, as confirmed by AMS radiocarbon dating. The average deposition rate varied from 0.024 to 0.008 cm/yr. Sediment particle size distribution, stable isotopes (δ¹³C and δ¹⁵N), C/N, and total organic carbon (TOC) were investigated as indicators of environmental change. In the top 10 cm are the coarsest sediments, which range from silt to silty sand and have a TOC of up to 5%. Algal lacustrine organic matter is combined with terrestrial or wetland organic matter from vascular plants to form organic matter (OM) with a C/N ratio of 12–18. High C/N levels are associated with low ¹³C and high TOC contents, indicating periods of drier climate between 0–500 and 800–2000 years BP. Grain-size characteristics, which fluctuate independently of OM qualities, are likely to have changed because of intensive human use of the lake basin in the past 600 years. Climate changes observed in OM do not correspond to changes observed in other south Indian lakes where precipitation is primarily from the southwest monsoon.

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耶尔考德湖沉积物（印度南部东高止山脉）过去 2500 年的年代环境动态：从 AMS 放射性碳年代测定、粒度分布和稳定同位素组成中获得的启示

经 AMS 放射性碳测年确认，耶尔考德湖（印度南部东高止山脉）40 厘米湖底淤泥岩芯的年代为 2500 年前至今。平均沉积速率从 0.024 厘米/年到 0.008 厘米/年不等。沉积物粒度分布、稳定同位素（δ13C 和 δ15N）、C/N 和总有机碳（TOC）是环境变化的指标。顶部 10 厘米处是最粗糙的沉积物，从淤泥到淤泥质沙不等，总有机碳含量高达 5%。藻类湖沼有机物与维管束植物产生的陆地或湿地有机物相结合，形成 C/N 比值为 12-18 的有机物（OM）。高 C/N 含量与低 13C 和高 TOC 含量有关，表明在公元前 0-500 年和 800-2000 年之间气候较为干燥。粒度特征的波动与 OM 质量无关，可能是由于过去 600 年人类对湖盆的大量使用而发生了变化。在 OM 中观察到的气候变化与在印度南部其他湖泊中观察到的变化不一致，这些湖泊的降水主要来自西南季风。

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来源期刊

Journal of Earth System Science Earth and Planetary Sciences-General Earth and Planetary Sciences

CiteScore

3.20

自引率

5.30%

发文量

226

期刊介绍： The Journal of Earth System Science, an International Journal, was earlier a part of the Proceedings of the Indian Academy of Sciences – Section A begun in 1934, and later split in 1978 into theme journals. This journal was published as Proceedings – Earth and Planetary Sciences since 1978, and in 2005 was renamed ‘Journal of Earth System Science’. The journal is highly inter-disciplinary and publishes scholarly research – new data, ideas, and conceptual advances – in Earth System Science. The focus is on the evolution of the Earth as a system: manuscripts describing changes of anthropogenic origin in a limited region are not considered unless they go beyond describing the changes to include an analysis of earth-system processes. The journal''s scope includes the solid earth (geosphere), the atmosphere, the hydrosphere (including cryosphere), and the biosphere; it also addresses related aspects of planetary and space sciences. Contributions pertaining to the Indian sub- continent and the surrounding Indian-Ocean region are particularly welcome. Given that a large number of manuscripts report either observations or model results for a limited domain, manuscripts intended for publication in JESS are expected to fulfill at least one of the following three criteria. The data should be of relevance and should be of statistically significant size and from a region from where such data are sparse. If the data are from a well-sampled region, the data size should be considerable and advance our knowledge of the region. A model study is carried out to explain observations reported either in the same manuscript or in the literature. The analysis, whether of data or with models, is novel and the inferences advance the current knowledge.