Fossils are primarily found in sedimentary rocks due to the way these rocks are formed. Sedimentary rocks are created from the accumulation of sediments, which can include tiny particles of minerals, organic material, and even remnants of living organisms. When an organism dies, its remains can be quickly buried by layers of sediment. This burial process protects the remains from decay and scavenging, increasing the chances of fossilization.
During the formation of sedimentary rocks, the pressure and minerals in the surrounding sediments can gradually replace the organic material in bones or shells, turning them into fossils. Additionally, sedimentary environments often include conditions that are suitable for preserving these remains, such as slow-moving water bodies where sediments can build up without disturbing the remains.
In contrast, igneous and metamorphic rocks are formed under high temperatures and pressures that would typically destroy any organic material, making them unsuitable for fossil preservation. Thus, the unique processes involved in the formation of sedimentary rocks create the ideal conditions for fossils to form and be preserved for millions of years.