What sedimentary rocks are algae involved in?

Nowadays, sedimentary rocks are practically not formed from algae, as well as from other plants and animal remains. This is because environmental conditions are not suitable for fossil formations. But in ancient times, algae could participate in the formation of some sedimentary rocks. A sedimentary rock – diatomaceous earth – was formed from the shells of diatoms. We cannot observe this, since it takes hundreds, thousands and tens of thousands of years. Although in some places conditions can be found for the formation of sedimentary rocks.