Temperature Estimates of Lower Miocene (Burdigalian) Coastal Water of Southern India Using a Revised Otolith “Clumped” Isotope Paleothermometer

In the present study, the assemblages of organic walled dinoflagellate cyst (dinocysts) and calcareous nannofossils from Quilon Formation, Kerala Basin, south-western India are analyzed for age interpretation and reconstruction of the depositional environment. The integrated biostratigraphy based on dinocysts and calcareous nannofossils from the same sediment samples indicates that the studied succession was deposited during the early Miocene (middle Burdigalian, ~19-17.5 Ma) time. The dinocyst assemblages contain abundant taxa (Cleistosphaeridium, Polysphaeridium, Lingulodinium, Homotryblium and Spiniferites) that range from shallow inner to outer neritic marine zone. The abundance of autotrophic, thermophilic taxa suggests relatively high surface water temperatures and high nutrient availability. The dinocyst assemblage in the lower part of the studied succession is dominated by Cleistosphaeridium spp., Polysphaeridium spp., Spiniferites spp., Homotryblium spp. and Lingulodinium spp. An increase in the relative abundances of outer neritic dinocyst taxa such as Spiniferites, Achomosphaera and Hystrichokolpoma in the upper part of the succession suggests a change towards more open marine conditions created during marine ingression. The interpreted marine ingression along the south-western Indian coast probably corresponds to the initial small pulses of transgression at the onset of the long-term global sea-level maximum related to the Mid-Miocene Climatic Optimum (MMCO).

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Early Miocene (Burdigalian) Dinoflagellate Cysts from the Kerala Basin, Southwest India: Indicators of Marine Ingression at the Onset of the Mid-Miocene Climate Optimum (MMCO)

Singh

Verma

Singh

et al. 2023

Journal of the Geological Society of India

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Addressing challenges in marine conservation with fish otoliths and their death assemblages

Leonhard

Agiadi

2023

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Otolith death assemblages provide a valuable source of biological and ecological information that can help address three main problems in marine conservation: a) the lack of pre-industrial, pre-human-impact baselines for evaluating change; b) the inefficiency of survey methods for recording small and cryptic fish species; and c) the absence of long-term data on environmental change impacts on marine ecosystems and fishes. We review here the current knowledge on the formation and preservation of otoliths and their death assemblages, and the methods to obtain, date and analyse them in order to detect changes in the species traits and ecology, the fish population structure and the palaeoceanographic shifts that drove them. Supplementary material at https://doi.org/10.6084/m9.figshare.c.6428742

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Stable Isotopic Analysis of Long-whiskered Catfish (Sperata aor) Otoliths for Characterization of their Habitat and Relationship with Water Temperature in the Ganges River

Ghosh

Nazir

Sakthivel

et al. 2023

CCS

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Background: Spatial variability of stable isotope ratios in water from River Ganges is preserved in aragonite or calcite present in otoliths and formed at equilibrium with ambient water. This technique is used in a set of long-whiskered catfish aragonite otoliths from four different locations along the course of River Ganges. Methods: Acid digestion of otolith and analysis of 13C and18O in these carbonates using an isotope ratio mass spectrometer allowed distinction of fish habitat and to provide an idea about environmental condition of water along the Ganges River. The 18O signature of otolith carbonate revealed distinct compositional trend denoting glacial water input in the upstream segment of Ganges, close to the water reservoir at Narora. However, the 13C values remained constant suggesting similar bicarbonate composition and food intake along the stream length. Results: The 18O signature in otolith from Varanasi was unexpectedly lighter and showed tendency of catfish population to migrate upstream segment of the river. The fish from the Narora location, showed the lowest 18O values, denoting signature of water derived from the melting of glacier. The heavier 18O values were seen in the stock from Kanpur. The upstream migration of fish population is indicated from the 18O values of fish otolith from Varanasi and Bhagalpur. The Varanasi location shows aberration in 18O signature in otoliths and this exists because this catfish moves to other places to avoid anthropogenic stress at this location. Conclusion: The δ18O of otolith carbonate covary with average environmental temperature recorded at individual location and serve as an important thermometry for marking environmental condition and stress in changing climatic parameters along stream length of River Ganges and its tributaries.

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Temperature Estimates of Lower Miocene (Burdigalian) Coastal Water of Southern India Using a Revised Otolith “Clumped” Isotope Paleothermometer

Abstract: Temperature estimates of lower Miocene (Burdigalian) coastal water of Southern India using a revised otolith "clumped" isotope paleothermometer. Geochemistry,

Cited by 3 publications

References 66 publications

Early Miocene (Burdigalian) Dinoflagellate Cysts from the Kerala Basin, Southwest India: Indicators of Marine Ingression at the Onset of the Mid-Miocene Climate Optimum (MMCO)

Early Miocene (Burdigalian) Dinoflagellate Cysts from the Kerala Basin, Southwest India: Indicators of Marine Ingression at the Onset of the Mid-Miocene Climate Optimum (MMCO)

Addressing challenges in marine conservation with fish otoliths and their death assemblages

Stable Isotopic Analysis of Long-whiskered Catfish (Sperata aor) Otoliths for Characterization of their Habitat and Relationship with Water Temperature in the Ganges River

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