Tidal rhythmites in offshore shale: A case study from the Palaeoproterozoic Chaibasa shale, eastern India and implications
Tidal rhythmites in offshore shale: A case study from the Palaeoproterozoic Chaibasa shale, eastern India and implications
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DOI：
10.1016/j.marpetgeo.2011.10.005
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发表时间：
2012-02
影响因子：
4.2
通讯作者：
L. Mallik;Rajat Mazumder;B. S. Mazumder;M. Arima;P. Chatterjee
中科院分区：
文献类型：
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作者：
L. Mallik;Rajat Mazumder;B. S. Mazumder;M. Arima;P. Chatterjee
现代大陆架和远岸环境中的潮汐韵律层已被记录下来。在显着的对比，他们的现代同行，沉积学研究的古代潮汐韵律形成的远岸设置和量化的潮汐韵律编码，但是，稀缺。本文介绍了印度古元古代柴巴萨页岩相垂向增生潮汐韵律岩的沉积学分析及其潮汐韵律的定量化。柴巴萨页岩的相特征与砂岩夹层纹层厚度的调和分析相结合，证实了垂直加积潮汐韵律岩产生的远陆棚古地理。后者是横向增生的潮汐“束状”沉积物的远端对应物，保存完好，位于浅海柴巴萨砂岩中。然而，根据柴巴萨页岩相估算的朔望月的太阴日数（23天）远低于根据柴巴萨砂岩相估算的太阴日数（32天），这表明根据柴巴萨页岩相编码的潮汐记录是不完整的。
Tidal rhythmites have been documented from modern continental shelves and distal offshore settings. In significant contrast to their modern counterparts, sedimentological studies of ancient tidal rhythmites formed in distal offshore settings and quantification of tidal rhythms encoded therein are, however, scarce. This paper presents sedimentological analysis of vertically accreted tidal rhythmites from the Palaeoproterozoic Chaibasa shale facies in India, and quantification of their tidal rhythms. The facies characteristics of the Chaibasa Shale coupled with harmonic analysis of the laminae thicknesses of the sandstone inter-layers corroborate a distal shelf palaeogeography for the generation of the vertically accreted tidal rhythmites. The latter are the distal counterparts of laterally accreted, tidal “bundle” deposits, well preserved within the shallow marine Chaibasa sandstones. The number of lunar days in a synodic month (∼23) estimated from the Chaibasa shale facies is, however, considerably lower than that estimated from the Chaibasa sandstone facies (∼32) suggesting that the tidal record encoded from the Chaibasa shale facies is incomplete.