Applied Aspect of Studying Fossil Plants

Applied Aspect of Studying Fossil Plants:- To provide useful information in the exploration of fossil fuel like coal and oil.

> The plant inhabitants of Palaeozoic- Mesozoic swamps served as a source of coal and formed coal seams. Accumulation of plant mate­rials with a variety of minerals coupled with mud, silt and other organic materials constitute a coal bed. Many plant parts get beautifully preserved as fossils in the stratified sedimentary layers which are closely adjacent to coal layers.

> A stratified scale based on fossils can be made to establish the age of coal deposits and their posi­tion in the succession of rocks. Palaeobotanical studies have served as a tool to ascertain age of coal layers, their lateral extent and quality of coal deposits. Such information are required to spe­cify the suitability of a particular coal for energy production. In India, the palaeobotanical study has helped to demarcate the nature and quality of Raniganj coal (Permian Age) from that of Rajmahal coal (Jurassic Age).

> The assemblage of fossil pollen grains and spores has contributed significantly in the field of oil exploration. The problem of oil exploration begins with search of oil reservoirs.

> Exploration of oil is done by:

i. Determining the Thermal Alteration Index:-

- The sporopollenin present in the walls of pollen and spores undergo post depositional thermal changes in course of the geological ages. These thermal changes brought about carbonisa­tion resulting in changes in exine colour of fossil pollen and spores in transmitted light.

- The basic idea involved is the usage of the variation in the exine colour as an indicator of the degree of car­bonisation in the rocks to predict their changes of bearing reservoir. Pearson’s colour chart directly relates exine colour to a numerical index called Thermal Alteration Index (TAI) which is a mea­sure of the degree of carbonisation. TAI having a range of 2+-3+ and exinite flourescence colour white-yellow, dark yellow-brown indicates the possibility of exinite containing rock to possess liquid petroleum and even natural gas.

ii. Palynostratigraphy:- To avoid unneces­sary and costly drilling the determination of oil zone is made by comparing the biostratigraphic data of one to those of the others.

iii. Defining of Ancient Shorelines:- The sediments parallel to sea shore are rich in oil. The density of pollen and spores decreases in the seaward direction. Sedimentary environment with pollen assemblages are limited to near shore marine or lacustrine waters. Thus by the study of microfossils along with marine micro­fossils if presents, one can determine the distance and direction of ancient shore lines, possibly bearing oil deposits.