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Geoscience e-Journals





An International Year of Planet Earth-2008 Initiative

Current Issue Technical

Year 2020

Volume 13 (2)

Diatoms and Phytoliths Records from Sediment Core of Tarna-Satighat Lake, Central India: Implications as Indicators of Changing Wet/Dry Climatic Phases and Trophic Status
Samaya S. Humane, *Sumedh K. Humane and Nandeshwar Borkar
Abstract   A study of diatom and phytolith assemblage from the 78cm long sediment core of the Tarna Satighat Lake of the Umrer Taluka, Nagpur district was done to reconstruct the past trophic status and the variability in the wet/dry climatic phases since the last few decades. The present research work has revealed the occurrence of total 27 species belonging to 18 genera of diatoms representing all the units i.e. Unit I (bottom) to Unit VII (top). The abundant centric diatom taxa discovered from this sediment core were Aulacoseira granulata, Cyclotella meneghiniana andDiscostella stelligera while, Cymbella tumida was only dominant pennate species. Similarly, dumbell, crenate, saddle, cross, and elongate were the main phytolith morpho-types recorded in this sediment core.The diatom and phytolith assemblages have revealed the changingtrophicstatus caused bythe variable strength of wet and dry climatic phases and partly by the anthropogenic activities.
Keywords: Diatoms; Phytoliths; paleoecology; wet and dry climate, Tarna- Satighat Lake; Nagpur district.
Distribution of Benthic Foraminifera and their Palaeoproductivity Changes from Anthakara Nazhi Beach Sediment, West Coast of India
M. Ravichandran, C. Lakshumanan, S. Sajimol and P. Ramki
Abstract  The present study provides details of benthic foraminifera analyzed from hundred beach sediment sub-samples collected from the Anthakara Nazhi beach, Kerala coast, the west coast of India. A total of 27 species of benthic foraminifera were recorded from this region. This study proved that the benthic foraminifera are good proxies to understand the paleoproductivity changes from this region. Oceanographically, important benthic foraminiferal species such as Ammonia beccarii along with Anomalina globulosa, Ammonia gaimardii, Cancris oblongus, Discopulvinulina bertheloti, Gyroidinoides nitidula, Gyroidinoides cibaoensis, Quinqueloculina seminulum, Quinqueloculina venusta and Textularia sp. were identified and counted. Benthic foraminifera analyses suggest a high productivity species are Ammonia beccarii and Ammonia gaimardii from 100 to 80cm and 20 to 5 cm depth an increasing trend an indicative of a shallow-marine environment. A strict interpretation based on the known modern distribution of Ammonia beccarii would confine the species to upper shore-face environments. The moderate values of Cancrisoblongus from 30 to 10 cm depth indicate by tolerance to mesotrophic-eutrophic conditions. Interval of 70 to 40 cm depth of species Gyroidinoides nitidula indicates low organic carbon flux or pulsed food supply and high oxygen environment. From 50 to 20 cm depth, species Gyroidinoides cibaoensis has been described from oxygenated deep waters of the northwestern Indian Ocean receiving intermediate flux of organic matter.
Keywords: Benthic foraminifera, Paleoproductivity changes, Anthakara Nazhi beach sediment, West Coast of India