* Sandstone Formation: Shoals are typically areas of active sand deposition. Waves and currents constantly move sand, creating layers that eventually become cemented together to form sandstone.
* Limestone Formation: Limestone forms primarily from the accumulation of marine organism skeletons (like coral, shells, and algae). While these organisms can exist in shallow water, shoals are often too dynamic and turbulent for them to thrive.
However, there are some exceptions:
* Biogenic Sandstones: Some sandstones can contain a significant amount of biogenic material, like shell fragments, that contribute to their formation.
* Limestone in Sheltered Shoals: In sheltered shoal areas, where currents are weaker, marine organisms can build up, creating a limestone layer.
Therefore, while sandstone is the more common lithology in shoals, the specific geology of the area determines what type of rock is present.
