Simplify the following text for a Grade 9 native English-speaking person.
Original: This type of soil is reddish in color due to the weathering of reddish sandstones , siltstones , and shales of the Permian geologic era .
Simplified: This type of soil is reddish in color due to the weathering of reddish sandstones , siltstones , and shales of the Permian period .