Varve measurements from Eocene Lake Messel (core Messel 2001)

The El Niño-Southern Oscillation (ENSO) is a globally important factor in today's climate dynamics. Annually laminated oil shales from the maar lake of Messel (Germany) provide high-resolution sedimentological and paleoenvironmental data of a time interval of ~600 k.y. during the Eocene greenhouse phase. Individual laminae consist of a light spring and summer algal layer (Tetraedron minimum layer) and a dark winter layer composed of terrigenous background sediment. Four sections were selected from the core of the Messel 2001 well in order to count varves and to measure total varve thickness and the thickess of light and dark laminae. Spectral analyses were done in order to detect possible cyclic fluctuations in varve thickness. Fluctuations are significant in the quasi-biennial (2.1-2.5 yr) and low-frequency band (2.8-3.5 yr, 4.9-5.6 yr), thus showing that algal growth as well as the background sedimentation were controlled by ENSO effects at least over a time interval of 600 k.y. This confirms the existence of a previously postulated robust Eocene ENSO. Significant peaks within a quasi-decadal (10-11 yr), interdecadal (17-26 yr), and multidecadal band (~52 yr, ~82 yr) show either the enduring influence of more or less cyclic instabilities or the influence of solar cycles.

厄尔尼诺-南方涛动（El Niño-Southern Oscillation，ENSO）是当今气候动力学中具有全球重要性的核心因素。德国梅塞尔火山口湖的年层状油页岩，为始新世温室期约60万年时间区间内的沉积学与古环境演变提供了高分辨率数据支撑。单个纹层由浅色的春夏藻层（极小四面体藻层，Tetraedron minimum layer）及深色的冬季陆源背景沉积层构成。研究从2001年梅塞尔钻井岩心中选取四个剖面，开展纹泥计数、总厚度测量及深浅纹层厚度量化分析。通过光谱分析技术检测纹泥厚度的潜在周期性波动，结果显示准两年期（2.1-2.5年）与低频带（2.8-3.5年、4.9-5.6年）的波动具有统计显著性，表明至少在60万年尺度内，藻类生长与背景沉积过程均受ENSO效应调控。这一发现证实了此前假设的强始新世ENSO事件的存在。此外，准十年期（10-11年）、年代际（17-26年）及多年代际带（约52年、约82年）的显著峰值，揭示了周期性不稳定性的持续影响或太阳周期的潜在驱动作用。