Taphonomy of recent burrows from eastern coast, Sri Lanka

Abstract

Quaternary sediment deposits of the Eastern coast of Sri Lanka were studied for the first time to understand the taphonomy of tube burrows and the impact of structure and mineralogy of the wall on the preservation of burrows, was interpreted. Photography and interpretations were made and described during the field observations on exposed trace fossils. Fine structures were identified using Scanning electron microscopy with energy dispersive x-ray spectroscopy. Simple vertical tube burrows were observed in a fine to medium sandy sediment bed which was above 4 m from the present mean sea level. The average diameter of the tubes was about 1 cm and the recorded maximum length was about 20 cm. Specimens are significant with circular color rims around the central holes. The internal wall of the tube was ornamented by microscopic honeycomb-like sclerite and fecal material secreted by the burrower and rich in iron oxide and clay minerals. Microbial activities on the wall have enhanced the early consolidation of the sediments of shallow marine environments, leading to filming cuticular organic matter, pyritization and aluminosilicatization processes. The environmental change from reducing to fully oxidizing conditions has strengthened the tubes commonly rimmed by iron oxides.