The first formation to be deposited in this setting was the Noonday Dolomite, which was formed from an algal mat-covered carbonate bank. Today it is up to thick and is a pale yellowish-gray cliff-former. The area subsided as the continental crust thinned and the new ocean widened; the carbonate bank soon became covered by thin beds of silt and layers of lime-rich ooze. These sediments in time hardened to become the siltstone and limestone of the Ibex Formation. A good outcrop of both the Noonday and overlying Ibex formations can be seen just east of the Ashford Mill Site.