Is that an inclusion
Fossils information sheet
The term fossils is derived from the Latin word "fossilis" - "excavated". It appeared for the first time in the 16th century, named by the Saxon naturalist Agricola. Agricola used it to designate strange-looking objects that were found in the earth (e.g. mineral crystals, stones or the remains of living beings). At the time, there was still no conclusive explanation of how the strange-looking objects might have come about.
But already the Greek philosopher Xenophanes discovered in the 5th century BC In the quarries of Syracuse imprints of fish and fossilized shells in the mountains. He concluded that there must have been a sea here once. But it had to be centuries before the fossil record was recognized.
Today fossils are explored through paleontology, the study of the living things of past geological ages. The founders include the French naturalist George L.L. Buffon (1707 - 1788) and Jean Baptist Larmarck (1744 - 1829) as well as the English naturalist Charles Darwin (1809 - 1882).
Importance of the fossils
Fossils are fossilized remains of living things that have survived (animals and plants) or parts of them from past geological ages. Fossils can be used to prove kinship relationships between organisms or the evolutionary evolution of plants and animals. In addition, they provide evidence of the higher development and the change in form of organisms over time.
So-called index fossils are characterized by a low vertical, but a wide horizontal distribution. They are characteristic of a certain time period. The ammonites for the Jurassic Age can be cited as an example.
When a living being dies, putrefaction, putrefaction and fermentation processes usually set in, or the organism is simply eaten up by another. Unless the organism is embedded in resin, ice, fine sand or mud or gets into water containing tannin, in which complete decomposition is prevented so that the entire organism or parts of it are preserved. When this happens, it is called fossils.
- Bone finds: By excluding air, the inorganic components of bones can be retained in the sediment.
- Petrifications: Lignified plant parts or organisms with cavities such as snails get into wet, basic sediments. The organic components are decomposed, so that cavities are created that fill with lime or silica and slowly petrify. The original shape is retained. One of the best-known examples are thunderbolts, the remains of relatives of the ink snails living today.
- Imprint: an animal leaves its mark in the mud and the pressure of the layers later deposited over it turns the mud into solid sedimentary rock. The imprint becomes visible when the rock is split in the plane. The original shape is retained. A well-known example are the feathers of the primitive bird.
- Inclusion: An insect sticks to the resin of the pine. As soon as another drop of resin flows over it, an airtight enclosure of the insect takes place. The resin is transformed into amber over the course of millennia. It can also be entrapped in ice.
- Charring: Normally, organic compounds are slowly decomposed under pressure, in the absence of air and under heat, but the process of charring means that the main component of the organic compounds is carbon. Examples: Peat moss became peat, the wood from large forests became hard coal and lignite.
- Mummification: The decomposition of plants or animals is prevented if they get into tannin-containing water or the organism is deprived of water.
Age determination methods
Various methods are used to determine the age of rock and fossil finds:
- Dendrochronology (annual ring method): Trees have a seasonal increase in thickness, which is reflected in the annual rings. The thickness of the annual rings is very different and the sequence is unique and characteristic of a certain period of time. This method dated exactly for about 800 years.
- Varven method: Deposits of fine sediment in the lake form a light-dark deposit. These camps can be counted. This method dates back to 1.6 million years.
- Radiocarbon method: Every living being contains a small amount of radioactive carbon in the bone and during its lifetime the ratio of isotopes of carbon to the ratio of isotopes of radioactive carbon is the same. After death, the radioactive carbon is converted, the longer the living being is dead, the less radioactive carbon is present in the dead organism. This method dates a period of approximately 100,000 years.
Living fossils are still living, recent organisms that have remained unchanged over geological time. Examples are the ginkgo or the coelacanth.
The coelacanth has been around for millions of years. It represents a transition form between fish and amphibians. Typical fish characteristics are the fish lungs, with which it can also absorb oxygen from the air. For this reason, it was able to survive in warm, oxygen-poor waters and thus develop as a land creature. Further features are an ossified skeleton and fins with strong muscles at the base, which enable it to crawl in shallow water.
Source: Geography Information Center
Author: Andrea Weber
Published by Klett
Source date: 2003
Processing date: 05/17/2012
Fossils, geological history
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