Fossil-rich mudstone and shale

scale in cms

The skeletons of many sea-bottom creatures are common in mudstones and shales directly below the waterfall. Fossils like clams, snails and trilobites are found in these rocks, and may have preferred to live on the soft mud of the sea bottom. Fossils with large, thick (heavy) skeletons are much less common these mudstones and shales than the overlying limestones.

Many types of clams alive today actually live under the surface of the mud. For other creatures that depend on staying above the mud surface, sinking into a soft sea bottom is potentially dangerous. For example, modern corals need to stay above the mud surface to survive. Today, large, thick coral colonies (like "brain corals") are more common on hard sea bottoms and thin branching colonies are more common on soft sea bottoms.