Siwalik pollen succession from Surai Khola of western Nepal and its reflection on palaeoecology

Abstract

A palynological report dealing with the Siwalik Group of sediments from Surai Khola area of western Nepal is presented. The clay samples collected from six different lithological units of Lower Middle and Upper Siwalik provide data for palaeoecological interpretations. Significant elements of the palynoflora are:  Zygnema, Mougeotia, Botryococcus, Striatriletes, Lycopodiumsporites, Monoporopollenites, Malvacerumpollis and Poyadopollenites.Periodic changes in qualitative and quantitative composition of the palynological spectra show that the vegetational succession reflects changing palaeogeographical conditions. A fresh-water swampy environment is interpreted for the older horizons. Algal remains of, Botryococcus, Pediastrum, Zygnema and megaspores of Azolla. etc., provide cogent evidence for this observation. Gradually swampy, conditions seem to have changed to a bottom land habitat. Which is evidenced by the presence of a number of pteridophytic elements, viz., Lycopodium, Polypodium, Schizaea, etc. Palynoassociations depict semi-evergreen vegetational pattern during the time of deposition of the Surai Khola Siwalik sequence in West Nepal.