Thornton Quarry, the world's largest working commercial limestone quarry, is made up of massive deposits of fossil-bearing dolomitized limestone. Because of the high concentration of fossil corals, brachiopods, crinoids and other shallow marine organisms, it has been viewed as an ancient coral reef of Silurian age (approximately 410 million years) and is often compared to modern reefs for similarity. However, in a brief review of evolutionist literature, it readily can be discerned that these deposits are not comparable to modern reefs and that the standard uniformitarian view is both misleading and imaginary. The actual facts instead readily submit themselves to a flood-geology interpretation, making the Thornton deposits of probable mid-Flood origin, influenced by tidal effects during the Flood. It is suggested that these tidal effects have been greatly underestimated by many creationists, but when coupled with tsunami effects, these become powerful agents for massive erosion, deposition and cyclical deposits. Deposits underlying Thornton probably reflect such activity. A Catastrophic Wave-Action Model of deposition is proposed.