Plant Megaflora from the Siwalik (Upper Miocene) of Darjeeling District, West Bengal, India and its Palaeoclimatic and Phytogeographic Significance

Qualitative and chemical analysis of fossil assemblage so for cured from the Middle Siwalik sediments of Darjeeling district,West Bengal told the occurrence of 35 new taxa belonging to 18 angiospermous kins. On the basis of present dossier as well as already popular data from there, the rebuilding of vegetation synopsises of Himalayan foot hills all the while Siwalik time has been accomplished and also reviewed on problems related to plant difference, endemism, and migratory pathways of for the most part phytogeograpraphically important taxa. The analysis of contemporary distribution of all the recovered taxa from the domain shows that they are mostly famous to occur in Northeast India, Bangladesh, Myanmar and Malayan region unspecified area favourable climatic conditions are free. About 1/3 taxa of total assemblage establish to grow presently in the Himalayan foundation hills of the easterly region and remaining 2/3 taxa are regionally extinct. This indicates that the of or in the atmosphere changes must have taken place subsequently Mio-Piocene, times. The dominance of conifer elements in present relics assemblage indicates the predominance of tropical warm humid surroundings with abundance of rainfall during the dethroning of sediments. Foliar physiognomic approach for reconstruction of palaeoclimate further suggests that the Oodlabari extent in the Himalayan foot-cliffs of West Bengal enjoyed a tropical surroundings (with MAT 28.9∘C and MAP 448mm) all along the Miocene period. This is, however, a suggestion of correction the present day atmosphere of the area accompanying reduced precipitation.On the footing of present fossil assemblage, the Coexistence breaks of different critical parameter ie. Mean annual temperature (MAT), Wormest temporal length of event or entity’s existence temperature (WMT), Coldest period temperature (CMT), and Mean annual precipitation (MAP) have existed estimated as 22∘C-26.5∘C, 17.8∘C -20∘C, 25∘C -30∘C, and 2650mm-3200mm respectively. The different approach, Leaf margin reasoning (LMA) suggests the MAT value as 28.9∘C for the region during Upper Miocene occasions.

Author(s) Details:

Mahesh Prasad,
Birbal Sahni Institute of Palaeosciences, Lucknow -226007, U.P., India.

. Shashi,
Department of Botany, Shiv Harsh Kisan P.G. College, Basti-272001, U.P., India.

Shivendra Mohan Pandey,
Department of Botany, Shiv Harsh Kisan P.G. College, Basti-272001, U.P., India.

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Keywords: Megafossils, leaf impressions middle siwalik, upper Miocene, Himalayan foot hills, Darjeeling District, West Bengal, palaeoclimate, coexistence approach, foliar physiognomy approach, mat and map, phytogeography

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