Here's why:
* Formation: Sedimentary rocks form from the accumulation and cementation of sediments like sand, mud, or organic matter. This process often happens in environments where organisms live and die, making them prime locations for fossil preservation.
* Conditions for Preservation: Fossil formation requires specific conditions, including:
* Rapid Burial: Quickly burying an organism prevents decay and decomposition.
* Absence of Oxygen: Oxygen can break down organic matter, so low-oxygen environments are ideal.
* Hard Parts: Bones, shells, and teeth are more durable and likely to be preserved than soft tissues.
While sedimentary rocks are the most common, fossils can be found in other rock types too, but they are less frequent:
* Metamorphic Rocks: Some metamorphic rocks (formed under intense heat and pressure) can contain fossils, but these are often distorted or destroyed by the transformative processes.
* Igneous Rocks: It's extremely rare to find fossils in igneous rocks (formed from cooling magma or lava). The intense heat associated with their formation typically incinerates any organic matter.
Examples of sedimentary rocks containing fossils:
* Limestone: Often formed from the accumulation of marine organisms' shells.
* Sandstone: Can contain fossils of land-dwelling organisms buried in ancient sand dunes.
* Shale: Fine-grained sedimentary rock formed from mud, often rich in fossils of marine life.
Remember, the presence of fossils in a rock doesn't necessarily mean it's a sedimentary rock. However, sedimentary rocks are overwhelmingly the most likely place to find them.