三峡东部地区泥盆系写经寺组下部一套可能的海啸沉积

A Possible Tsunami Deposits in the Lower Part of the Devonian Xiejingsi Formation in the East Yangtze Gorges Area

三峡东部地区泥盆系写经寺组中普遍发育一套或数套薄—中层状砾屑灰岩。通过对建始县长梁子、长阳县渔峡口、宜昌市官庄3个剖面的详细研究,发现上部砾屑发育菊花状或倒小字形构造,无疑属风暴沉积;而下部砾屑发育反向叠瓦构造,结合侧向相变关系和空间分布,认为其可能代表了F-F之交小行星坠入海洋引起的全球性海啸在古陆边缘的沉积。

One or more suits of thin-medium bedded calcirudites widely distribute in the Devonian Xiejingsi Formation in the East Yangtze Gorges area. Through detailed study of the Changliangzi section in Jianshi county,Yuxiakou section in Changyang county and Guanzhuang section in Yichang city,we found that daisy-like structure developped in the upper gravels,which undoubtedly belongs to storm deposition. In contrast,inversely directed imbrications developed in the lower gravels. Combined with the lateral facies changes and the spatial distribution,we inferred that the lower gravels may represent the global tsunami deposition in the continental margin across the F-F transition,which could be caused by bolide impacts into ocean.