The type of rocks that form where the remains of plants and animals are deposited in thick layers are called sedimentary rocks.

Here's why:

* Sedimentary rocks are formed from the accumulation and cementation of sediments, which can include the remains of organisms.

* Organic sedimentary rocks are a specific type of sedimentary rock that forms primarily from the accumulation of organic material, like plant and animal remains. These can include coal, oil shale, and limestone (which can be formed from the accumulation of shells and coral).

Let me know if you'd like to learn more about sedimentary rocks!