Here's why:

* Formation: Limestone is primarily formed from the accumulation of the skeletal remains of marine organisms like corals, mollusks, and algae. These organisms contain calcium carbonate, which forms the main component of limestone.

* Preservation: The slow accumulation and burial of these skeletal fragments in a marine environment create ideal conditions for fossilization. The calcium carbonate in the skeletons is often preserved, creating detailed impressions of the original organisms.

While other sedimentary rocks like shale and sandstone can also contain fossils, limestone is particularly known for its high abundance of fossils.