Geochemical and diatom records of recent changes in depositional environment of a tropical wetland, central west coast of India
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Date
2015Author
Pande, A.
Nayak, G.N.
Prasad, V.
PrakashBabu, C
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Two mudflat sediment cores collected from a sub-channel (S-61) and the main channel (S-60) of a tropical wetland, along central west coast of India, were investigated for recent changes in depositional environment using geochemical (sediment grain size, total organic carbon, total nitrogen, carbon/nitrogen ratio (TOC/TN), selected metals and pH) and diatom records The sub-channel (S-61) represents river environment which opens into main channel (S-60) which represents marine environment being close to the sea We report a transition from river-dominated to marine-dominated depositional environment over the years The relatively higher sand percentage together with elevated carbon/nitrogen ratio and predominance of freshwater diatoms suggested greater river runoff in the past while marine influence is supported by decrease in TOC/TN ratio and increased dominance of marine diatoms in recent years In the main channel (S-60), distribution of metals is regulated by organic matter (total nitrogen and total organic carbon) while in the sub-channel (S-61), Fe-Mn oxyhydroxides play a significant role in trace metal distribution The highest numbers of diatoms were recorded in the sub-channel (S-61) which is also characterized by higher total nitrogen concentration Geochemical and diatom signatures thus have helped to infer spatial and temporal variations in depositional environment.
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