Surface texture, mineralogy and stable isotope studies of nodular calcretes preserved in the YTT ash of Padang Terap river basin and lenggong valley, peninsular Malaysia: Implications in its origin and paleoclimatic reconstruction

Singh, Ajab and Muhammad, Ros Fatihah and Taib, Nur Iskandar and Jha, Deepak Kumar and Srivastava, Ashok K. (2021) Surface texture, mineralogy and stable isotope studies of nodular calcretes preserved in the YTT ash of Padang Terap river basin and lenggong valley, peninsular Malaysia: Implications in its origin and paleoclimatic reconstruction. Rhizosphere, 19. ISSN 2452-2198, DOI https://doi.org/10.1016/j.rhisph.2021.100380.

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Abstract

Rounded to sub-rounded calcrete nodules, preserved in Youngest Toba Tuff (YTT, similar to 75 ka) ash, exposed at the Padang Terap river basin and Lenggong valley of Malaysia, have been investigated for their micromorphology, mineralogy and stable isotope compositions (delta O-18 and delta C-13) with the aim to interpret their origin, climatic conditions and vegetational scenario in the studied areas. These nodules are associated with cylindrical, pipe -like, root calcretes and highly calcretized ant traces. The FESEM study shows dominance of sparry calcite and microsparite as groundmasses and presence of bacteria microfossils and microbial features. The microfossils are represented mainly by microcodium, calcified pedostructures and organic filaments, whereas, the microbial features as extracellular polymers substances (EPS) and bacillus type bacteria. Mineralogical compositions as reflected by X-ray diffractograms show dominant peaks of calcite followed by quartz, chlorite, illite and paly-gorskite. The delta O-18 and delta C-13 values suggest that the precipitation of calcium carbonate might have happened in in-situ manner that leached under the influence of meteoric water in presence of C-4 dominated vegetation during the formations of the nodules. Presence of C-4 vegetation in the area suggests that the same had revived after the YTT event. The study suggests that the CaCO3 would have been supplied to the host sediments by dust, rainwater and local geological set-ups during arid, semi-arid and humid climatic conditions.

Item Type: Article
Funders: Universiti Malaya (RU013-2019)
Uncontrolled Keywords: Nodular calcrete; Ant traces; Biogenic structures; Bacteria microfossils; C-4 vegetation; Stable isotope; Toba volcanism
Subjects: Q Science > QE Geology
Divisions: Faculty of Science > Department of Geology
Depositing User: Ms Zaharah Ramly
Date Deposited: 20 Jul 2022 07:23
Last Modified: 20 Jul 2022 07:23
URI: http://eprints.um.edu.my/id/eprint/28072

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