Palaeobotany is the study of plant remains of the distant past. It exists in the form of ‘fossils’ which are the vestigial remnants of plants that indicate the evolution of the present day plants.
Plants that lived millions of years ago and became embedded in stratified rock provide the most accurate links in plant evolution and genetics. Stratified rocks containing fossil plants are usually found at the bottom of lakes, seas, lagoons, rivers, beaches, swamps and valleys. Fossils that are obtained are, in most cases, not complete and require many samples of the same plant species to complete a particular study or provide accurate or evidentiary material.
Fossils are preserved in many ways. They are;
1. Compressions: The most kind of preservation; the organic matter of the plant is preserved with impressions of the plant. Here, compressions by vertical pressure of soil sediments on the plant parts play a major role.
2. Impressions: Prints made my plants / plant parts on soft clay. When the plant decays and the clay hardens, it leaves behind imprints of its skeletal structure. These are not necessarily enclosed within and can differ from casts.
3. Incrustations / Casts: Most common type of fossils; formed when the plant gets covered up (enclosed within) by sand or mud. The plant rots inside the sand coat leaving behind a hollow of the plant imprint, showing exact details of the plant’s external features.
4. Petrification: This is when the external, internal and at times even the organic matter of plants are preserved.
5. Compactions / Mummified plants: These are Plants compressed by vertical pressure. Usually these are found in peat, lignite and coal where large and thick quantities of the plant gets compacted and make for good microscopic studies.
6. Ambers: Resins which exuded from coniferous plants and fell on the forest floor often collected insects and plant parts with it. When hardened, they preserved the entire plant part, or insects as a whole, preventing decay of the entrapped item.
It is possible to calculate the age of the fossil by using the radioactive isotope C14. It adopts the process of radiocarbon dating or simply carbon dating. the technique of radioactive carbon dating was developed at the University of Chicago by Willard Libby in 1949. Since then there have been great advances in the field of Palaeobotany and in the determination of ages of all types of fossils.