Morphological variations and depositional processes of microforaminiferal linings in the early Tertiary sediments of northeastern and northwestern India

Abstract

Microforaminiferal linings, the inner organic remnants of the benthic microforaminifera, occur frequently in the palaeopalynological preparations. The linings usually get buried in the organic rich shallow marine sediments and provide a useful data regarding their burial processes in the host sediments. The study presents records of microforaminiferal linings in the early Palaeogene subsurface of Upper Assam and lignite bearing sedimentary succession in the Cambay Basin, India, their morphology and depositional environments. The number of chambers and size of the linings categorize them into various morphological groups, viz. Uniserial type II, Biserial type II, Planispiral type II, Planispiral type III, Planispiral type IV, Trochospiral type I and Trochospiral type II of which two morphotypes, namely Planispiral type II and Trochospiral Type I are most common in the palynoassemblages. The study on microforaminiferal linings will delineate marine and terrestrial realms in the sequences where other palynoforms are not recovered and may facilitate better interpretation of the depositional environment. Morphological attributes of various microforaminiferal linings along with other palynomorphs, viz. spores, pollen grains, dinoflagellate cysts and fungal fruiting bodies indicate near shore, marine shelf depositional conditions of the studied sections.