FOSSILIZATION PROCESS

 IN THIS BLOG, I WILL ANSWER THREE QUESTIONS I RAISED IN A PREVIOUS POST:

1. Why can't fossils be found in igneous rocks?
   

   Igneous rocks originate from solidified magma, and magma is a molten silicate (SiO₂) fluid found beneath the Earth's surface. Given that magma exists at extremely high temperatures (at least 650°C), it is impossible for fossilization to occur in such conditions. At these temperatures, any organic material would melt or burn instantly, preventing the preservation process necessary for fossil formation.

2. Why can't fossils be found in metamorphic rocks?
   

   Metamorphic rocks form through a process called metamorphism. During this process, rocks undergo significant increases in temperature (starting at a minimum of 200°C) and pressure. These intense conditions destroy any existing fossils, causing them to disintegrate or deform beyond recognition.

3. So, in what type of rock are fossils found? Why?
   Fossils are found only in sedimentary rocks. This is because sedimentary rocks form from the gradual accumulation of sediments that can bury dead organisms over time. As layers build up, the hard parts of the organisms (like bones or shells) are preserved, allowing the fossilization process to take place. The process itself can be explained as follows:

Figure 1
Altered Remains:

1. The organism dies in the sea.
2. It is consumed by other organisms, leaving behind broken bones.
3. The broken bones fall to the seafloor.
4. Bone fragments are buried and deposited by sediments.
5. Fossilization occurs.
6. More sediment layers accumulate over time.
7. Sea level gradually recedes and eventually disappears.
8. Tectonic activity exposes the fossil at the surface.

Figure 2
Exposed Fossil

Figure 3.
Unaltered remains:

1. The organism dies in the sea.
2. It sinks to the seafloor while soft tissues decompose by decomposers such as bacteria.
3. It becomes buried and deposited by sediments.
4. Fossilization occurs.
5. Sediment layers continue to accumulate.
6. Sea levels gradually recede and eventually disappear.
7. The fossil is exposed at the surface due to tectonic activity.

Both figures above illustrate the fossilization process under calm marine current conditions. In Figure 1, it can be observed that although the organism’s bones are fragmented, they remain in approximately the same area rather than being displaced, indicating minimal disturbance. Meanwhile, Figure 3 clearly shows that the fossil's position within the sedimentary rock matches the organism’s original anatomical position at the time of death, suggesting no marine current interference that could have altered its post-mortem orientation.

The scenario would be different if other factors, such as ocean currents, had influenced the fossil's position within the sediment. Such currents could cause the disarticulated remains of an organism to be transported and scattered, potentially relocating parts of the fossil far from the site of the organism's original death.