古风暴沉积的化石标志
- 湘潭矿业学校
作者简介:
柳祖汉,男,42岁,副教授,古生物
摘要: 本文根据广泛的野外观察对一些不同寻常的化石保存状态、化石的变形、不同化石群的混合以及化石个体的排列方式进行了研究,认为它们明显地受到过强度猛烈、产生突然、作用短暂的水动力作用。把这些现象与一般的波浪、底流、潮汐以至浊流作用的结果加以对照区别,认为他们可以与其它沉积学特征结合,共同作为识别古风暴沉积的标志。
FOSSIL MARKS OF ANCIENT STORM DEPOSITS
- Xiangtan Mining Institute
Abstract: Ancient storms affected both sediments and organisms and left some special marks on the fossils, which are useful to us to identify the ancient storm deposits. The main marks are listed as follows: 1. The heavy skeleton blocks of the organisms, which lived in the deeper water environments, were transported and mixed with the shallower water biocoenosis. These phenomena usually occurred near the facies change zone. 2. The big masses of the organisms, living in native places, were overthrown and kept in an unstable position. 3. The infauna shells were digged out and mixed with the epifauna shells. All shells preserved in very poor chosen condition. 4. The large frameworks of the organisms, which built wave-resistive structures, were broken and their fragments with sharp edges kept nearby the structures. 5. The layers of encrusting organisms were torn and some upward gaps were formed on it. 6. Numerous broken branches and complete skeletons of the same dendritic organisms accumulated together in their native places. The broken branches were preserved in unworn and unchosen condition. 7. The upset productids with two complete concavo-convex shells were preserved together with the same kind of shells, keeping in their growing positions. 8. Many single corals bent into some marked angles. An angle indicated one of the storms happend during the growing processes of these corals. 9. More or less complete calyxes and long stems of crinoids were preserved with the skeletons of other organisms, which were broken by waves. 10. Numerous small shells accumulated on the top of the layer consisting of larger fossils and showed the positive graded bedding. These small shells only belong to few species. As listed above, the fossil marks of ancient storm deposits are various and sometimes very similar to some phenomena caused by other agencies, such as ordinary waves, tides, bottom currents, turbidity currents and so on. This paper also discusses the differences between them. But, it is still necessary to consult the sedimentological evidences, when these fossil marks are used,
点击查看大图
下载:
