Rhodolith-forming coralline red algae in the CaCO3 biofactory — A case study from the Serravallian of tropical northeastern Indian Ocean

• Main Authors: Dey, Rikee, Basso, Daniela, Chakraborty, Arindam, Roy, Lopamudra, Bhaumik, Ajoy Kumar, Ghosh, Amit K.
• Format: Article
• Language: English
• Published: Academie des sciences, France 2023
• Subjects: QE Geology
• Online Access: http://eprints.um.edu.my/43196/2/Dey%20et%20al%202023.pdf; http://eprints.um.edu.my/43196/; https://doi.org/10.5852/cr-palevol2023v22a26
• Institution: Universiti Malaya

Non-geniculate coral red algae forming rhodoliths have been recorded in the Long Formation, exposed in four different outcrops on Little Andaman Island (Hut Bay). Non-geniculate corallines are represented by species of Sporolithon Heydrich, 1897, Mesophyllum Lemoine, 1928, Lithothamnion Heydrich, 1897, Phymatolithon Foslie, 1898, Lithoporella (Foslie) Foslie, 1909, Spongites Kützing, 1841, Neogoniolithon Setchell & Mason, 1943 and Lithophyllum Philippi, 1837. Algal assemblages also include geniculate corallines belonging to the generaAmphiroa Lamouroux, 1812 and CorallinaLinnaeus, 1758. Additionally, larger benthic foraminifera and some planktonic foraminifera were also identified in the thin section analysis. Based on the previous study carried out on planktonic foraminifera, the Long Formation was dated to the Serravallian (Late Middle Miocene) and chronostratigraphically, the Long Formation was included in the Ongeian Regional Stage. In non-geniculate rhodolith-forming corallines, various growth forms and taphonomic features have been recognized. Diagenesis affects the material studied by micritization, cementation and compaction. The four outcrops are dominated by bioclastic wackestone and packstone composed of coral red algae, benthic and planktonic foraminifera, echinoid spines and unidentified coral fragments. The rhodolith-forming coralline red algae, growth forms and taphonomic characteristics of non-geniculate corallines, and characteristic benthic foraminifera indicate a moderate energy depositional environment. This study shows that carbonate production was considerably high during the Serravallian of the tropical northeast Indian Ocean.