Shelly limestone is made up of the shells and skeletons of invertebrates that live in the sea (or sometimes in fresh water). The shells are not usually whole, as they are broken up by waves.

Limestone is formed in two ways. It can be formed with the help of living organisms and by evaporation. Ocean-dwelling organisms such as oysters, clams, mussels and coral use calcium carbonate (CaCO3) found in seawater to create their shells and bones. The water pressure compacts the sediment, creating limestone.

350 million years

Oolitic Limestone Oolites (or ooliths) are small, sand-size clasts of calcium carbonate with a spherical to ovate shape. They form by the concentric accumulation of calcium carbonate layers around a nucleus that might be a sand grain, a shell fragment, a coral fragment, or a particle of fecal debris.

Siltstones are formed by particles settling through water and accumulating on the ocean floor, river beds or lagoon and lake bottoms. As the silt is buried and compacted by overlying sediment, the water is squeezed out and it turns into siltstone.

Shales are often found with layers of sandstone or limestone. They typically form in environments where muds, silts, and other sediments were deposited by gentle transporting currents and became compacted, as, for example, the deep-ocean floor, basins of shallow seas, river floodplains, and playas.

Bedrock (also termed Bed rock ) is a layer of undisturbed rock usually located beneath a surface layer of soil or other material. Natural exposures of shale and claystone, both soft, fine-grained rocks, are rare—especially in humid climates. …

Bedrock is made up of igneous, sedimentary, or metamorphic rock, and it often serves as the parent material (the source of rock and mineral fragments) for regolith and soil. A bedrock deposit that occurs at Earth’s surface is called an outcrop.

Bedrock is the hard, solid rock beneath surface materials such as soil and gravel. Bedrock also underlies sand and other sediments on the ocean floor. Overlying material is often unconsolidated rock, which is made up of loose particles.

Bedrock Synonyms – WordHippo Thesaurus….What is another word for bedrock?