Paleoenvironmental reconstruction of quaternary se

Authors: Madurya Adikaram Amarasooriya Pitawala Hiroaki Ishiga Daham Jayawardhana

Publish Date: 2017/01/25

Volume: 89, Issue: 1, Pages: 71-76

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Abstract

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 isYshaped 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 finescale 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 bioorigination 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 islandAcknowledgement The Head of the Department of Geology University of Peradeniya and Head of the Department of Physical Sciences South Eastern University of Sri Lanka are also acknowledged for providing the laboratory facilities The research was financially supported by University Grant Commission Sri Lanka Grant No UGC/DRIC/PG/2014AUG/SEUSL/01

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