Which of the following types of rocks contain fossils?

Analyze the question: You are asked which type of rock typically contains fossils (preserved remains or traces of ancient plants and animals).

Explain the concept: Fossils form when dead organisms are buried quickly under layers of mud, sand, or silt. Over millions of years, these layers harden into rock, and the organism's remains are preserved inside. This only works if the rock forms under gentle conditions that do not destroy the remains.

• Igneous rocks (e.g., granite, basalt) form from cooled magma or lava. The heat is so intense that any organism would be destroyed, so they do not contain fossils.
• Sedimentary rocks (e.g., sandstone, limestone, shale, coal) form from layers of deposited sediments. Organisms can be buried and preserved in these layers, so they contain fossils.
• Metamorphic rocks (e.g., marble, slate, gneiss) are changed by heat and pressure. These conditions usually destroy fossils, although rare traces may survive.
• Volcanic rocks are a type of igneous rock (extrusive), formed from lava, so they do not contain fossils.

Solution:

1. Fossils need gentle burial in sediments, not extreme heat.
2. Only sedimentary rocks form in layers (strata) from deposited sediments.
3. So the rock type that contains fossils is sedimentary.

Answer: B. sedimentary

Exam tip: Remember "Fossils = Sediments". Sedimentary rocks are the "storybook" of the Earth, with fossil-bearing layers. If an option says igneous or volcanic, eliminate it, because heat destroys fossils. Also note that options A and D are essentially the same family (volcanic rocks are igneous), so neither can be the single correct answer.