T128 Cenozoic Paleoclimates and Ecosystems II

Monday, 23 October 2017
1:30 PM - 5:30 PM
Room 609

AN INTEGRATED STUDY OF PALYNOMORPHS AND FORAMINIFERA TO RECORD THE CHANGES IN PALAEOVEGTATION AND PALAEODEPOSITIONAL CONDITIONS FROM EOCENE LIGNITE MINE SECTIONS IN WESTERN INDIA

Paper number: T128-10
Program: Technical Sessions
Time: 3:45 PM – 4:00 PM

Authors

Abstract

The Early and Middle Eocene hyperthermal events have now been established from various lignite mine sections from western India and thus it would be interesting to record the changes in vegetation and depositional conditions during the warming events from these palaeo-tropical sites. Hence, in this study we have quantitatively recorded the presence of various groups of microfossils like pollen/spores, dinoflagellates and foraminifera from Eocene lignite mine sections from Cambay (Vastan and Surkha), Kutch (Matanomadh and Panandhro) and Barmer (Giral and Matasukh) basins in Western India. The palynomorph (pollen/ spore + dinoflagellate) data was further subjected to cluster analysis and correspondence analysis. Three distinct clusters A (mangrove species), B (angiosperm species) and C (dinoflagellate species) were identified. Based on correspondence analysis two distinct biofacies (I and II) were identified. It is inferred that during Early Eocene, biofacies I was deposited which is dominated by cluster A (mangrove: Spinizonocolpites, Spinizonosulcites etc) in Cambay and Rajasthan basins. Further, the foraminiferal assemblage exhibits low diversity (Fisher alpha< 5) and dominance of rectilinear benthic foraminifera (> 80%) indicating high runoff and eutrophic conditions. In the middle Eocene (Kutch basin), biofacies II was deposited which shows a dominance of both angiosperms (Cluster B: Retipollenites, Dipterocarpuspollenites etc) and dinoflagellate species (Cluster C: Polysphaeridium, Spiniferites etc) and drastic decline in mangrove species (from >90% to <5%). The foraminiferal assemblage indicates increase in diversity (Fisher alpha ~10) and abundance of foraminifera compared to Early Eocene foraminiferal assemblage, high runoff and eutrophic conditions. The vegetation during Early Eocene warming events is dominated by marsh conditions (Nypa pollen) and deposition took place in low oxygen and eutrophic marginal marine conditions as indicated by foraminiferal assemblage. However, in the middle Eocene warming event, angiosperms and dinoflagellates dominated the palynofacies. There was also relative increase in diversity and size of foraminifera even though the marginal marine, low oxygen and eutrophic conditions continued to persist in the restricted basins of Kutch during middle Eocene.

Geological Society of America Abstracts with Programs. Vol. 49, No. 6

doi: 10.1130/abs/2017AM-302334

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