Paleoenvironmental reconstruction of quaternary sedimentation in eastern Sri Lanka: An ichnological study
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- 作者：Madurya Adikaram ; Amarasooriya Pitawala…
- 刊名：Journal of the Geological Society of India
- 出版年：2017
- 出版时间：January 2017
- 年：2017
- 卷：89
- 期：1
- 页码：71-76
- 全文大小：
- 刊物类别：Earth and Environmental Science
- 刊物主题：Geology; Hydrogeology;
- 出版者：Geological Society of India
- ISSN：0974-6889
- 卷排序：89
文摘
Quaternary sediment deposits are well exposed along the eastern coastal margin of Sri Lanka. Systematic trace fossil studies along with sediment characteristics have been carried out for the first time to interpret the paleoenvironment that prevailed during Quaternary sedimentation in eastern Sri Lanka. The trace fossils Thalassinoides, Skolithos and Polykladichnus have been recognized about 5m above the present mean sea level. Features of the major trace fossil, Thalassinoides, indicate that it was formed by Thalassinidean shrimp Calianassa. Isolated, vertical to steeply inclined, cylindrical to sub cylindrical tubes with thin internal wall lining and inner wall striations of Skolithos and Polykladichnus show that they were formed by polychaetes. The typical characteristic of Polykladichnus isY-shaped branching with slight enlargement at junctions. Morphology and association of burrows as well as mineralogy, grain size and roundness of sediments indicate that the environment prevailed was marine soft grounds of the intertidal zone. Presence of preserved fine-scale features of burrows indicate that the bioturbated sandy tidal flat was suddenly exposed to the tropical environment due to sea level regression in Quaternary periods. Due to the microbial activities of wall linings, burrows were preserved and it was supported by other microbial activities that produced secondary iron bearing minerals that suffered subsequent oxidation. The bio-origination of red sediments of eastern coastal area of the present study can be used to interpret the debatable origin of the red beds found in northwestern and southeastern coastal areas of the island.