fossils their mode of formation and age determinition
Answers
Answer:
The totality of fossils is known as the fossil record. Paleontology is the study of fossils: their age, method of formation, and evolutionary significance. Specimens are usually considered to be fossils if they are over 10,000 years old. The oldest fossils are around 3.48 billion years old to 4.1 billion years old.
Explanation:
1. Meaning of Fossils:
Remains or vestiges or traces of plants and animals of the past are called fossils. These remains of organisms from past geological ages remain preserved in sedimentary rocks either as actual structures or as impressions, casts or molds.2. Formation of Fossils:
In the basic process of fossilization, the physical part of any plant or animal must be buried within a well-protective matrix in the crust of the earth. This matrix in the earth’s crust is usually sedimentary. The sedimentary environment of this kind can be of several types such as lake, stream, inland sea or estuarine, etc.
In several cases it has also been observed that diatom frustules also get incorporated in deposits of deep sea basins. In rare cases, the sedimentary environment is in the form of volcanic deposits or other subaqueous conditions. The portions of the organisms (plant or animal) preserved in sediment become stony or lithified during course of time.
How Are Sedimentary Rocks Formed? Accumulation of rock particles results in the formation of sedimentary rocks. Weathering and mechanical abrasion of existing rocks take place and give rise to the rock particles.
Chemical weathering and flooding also help in the formation of these particles. These rock particles or sediments accumulate and water is squeezed out of them. During course of time, this makes them much more compact or rocky structure. Such a rocky structure is called sedimentary rock.(i) Anaerobic conditions,
(ii) Low pH,
(iii) Forest fires in the form of fossil charcoal, and
(iv) Presence of sedimentary materials such as carbonates, silicates, salts of iron, etc.
Determination of Age of Fossils:
By finding the age of rock, the age of fossils is calculated. The age of rock is calculated by using radiometric dating techniques. In these techniques, various radioactive isotopes of Uranium (236U, 238U), Thorium (232U) and Potassium (40K) are used. All these radioactive isotopes are also called “geological clocks”.
The radioactive isotopes decay and lead to stable isotopes. In this process, the energy is released. The rate of decaying of any radioactive isotope and its giving rise to stable isotope, is always constant. The age of rock and plant can thus be calculated by measuring relative quantities of radioactive isotope and the stable isotope.
The use of radioactive carbon is called carbon dating. Carbon dating technique is used in ascertaining the age of specimens of plants and animals, back to about 60,000 years. It is because of the fact that half-life of carbon is 5568 + 30 years.