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首页> 外文期刊>Earth and Planetary Science Letters: A Letter Journal Devoted to the Development in Time of the Earth and Planetary System >Modern spectral climate patterns in rhythmically deposited argillites of the Gowganda Formation (Early Proterozoic), southern Ontario, Canada
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Modern spectral climate patterns in rhythmically deposited argillites of the Gowganda Formation (Early Proterozoic), southern Ontario, Canada

机译：加拿大安大略省南部Gowganda组（早元古代）有节律沉积的泥质岩中的现代光谱气候模式

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摘要

Rhythmically deposited argillites of the Gowganda Formation (ca. 2.0-2.5 Ga) probably formed in a glacial setting. Drop stones and layered sedimentary couplets in the rock presumably indicate formation in a lacustrine environment with repeating freeze-thaw cycles. It is plausible that temporal variations in the thickness of sedimentary layers are related to interannual climatic variability e.g. average seasonal temperature could have influenced melting and the amount of sediment source material carried to the lake. A sequence of layer couplet thickness measurements was made from high-resolution digitized photographs taken at an outcrop in southern Ontario, Canada. The frequency spectrum of thickness measurements displays patterns that resemble some aspects of modern climate. Coherent periodic modes in the thickness spectrum appear at 9.9-10.7 layer couplets and at 14.3 layer couplets. It is unlikely that these coherent modes result from random processes. Modern instrument records of regional temperature and rainfall display similar spectral patterns, with some datasets showing significant modes near 14 yr in both parameters. Rainfall and temperature could have affected sedimentary layering in the Gowganda argillite sequence, and climate modulation of couplet thickness emerges as the most likely explanation of the observed layering pattern. If this interpretation is correct, the layer couplets represent predominantly annual accumulations of sediment (i.e. they are varves), and the thickness spectrum provides a glimpse of Early Proterozoic climatic variability. The presence of interannual climate patterns is not unanticipated, but field evidence presented here may be of some value in developing a climate theory for the Early Proterozoic.
机译：Gowganda组（约2.0-2.5 Ga）的有节奏地沉积的泥质岩可能是在冰川环境中形成的。岩石中的下落石和分层的沉积岩层推测表明是在湖相环境中形成的，具有反复的冻融循环。沉积层厚度的时间变化可能与年际气候变化有关，例如平均季节温度可能会影响融化以及带入湖泊的沉积物来源物质的数量。从加拿大安大略省南部的一个露头处拍摄的高分辨率数字化照片进行了一系列的层对厚度测量。厚度测量的频谱显示出类似于现代气候某些方面的模式。厚度谱中的相干周期模式出现在9.9-10.7层对和14.3层对。这些相干模式不可能由随机过程产生。区域温度和降雨的现代仪器记录显示了相似的光谱模式，一些数据集在两个参数中都显示了接近14年的有效模式。降雨和温度可能会影响Gowganda泥质岩层序中的沉积物分层，而对联厚度的气候调节是最可能解释观测到的分层模式的原因。如果这种解释是正确的，则层联主要代表沉积物的年累积量（即它们是脉），并且厚度谱提供了早期元古代的气候变异性的一瞥。并非没有预料到年际气候模式的存在，但是这里提出的实地证据对于发展早期元古代的气候理论可能具有一定的价值。

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