The oldest fossils may be

A) fossilized bacterial mats called stromatolites.
B) microscopic bits of carbon know as zircons.
C) marine animals from the Burgess Shale.
D) petrified pollen grains from ancient plants.

Stromatolites

Layered structures formed by the mineralization of bacteria.

Zircons

Minerals that are widely used in dating geological structures due to their ability to encapsulate and preserve uranium-lead isotopes over immense periods.

Fossilized

The process by which organic material is converted into a fossil, preserving the remains of organisms that lived in the past.