Ophir Shale

The Ophir Shale is directly on top of the Tintic Quartzite.  As the Cambrian Ocean transgressed across Utah from west to east it deepened.  This area became farther and farther from shore.  Only finer-grained clay sediments could be transported this far out on the continental shelf.  The Ophir Shale is the accumulation of these shale-forming sediments.  As this shale was buried at great depth the clay minerals became unstable at the higher temperatures and pressures and recrystallized, slightly, to form a low-grade metamorphic rock called phyllite.   Shale is very easily weathered and eroded.  Thus, it forms a distinct slope directly between the cliff-forming Tintic Quartzite and Cambrian and Mississippian limestones. The Ophir formation is composed, mostly, of phyllitic shale with some thin beds of shaley limestone and some quartzite and phyllite.  Click here to view the rock.

Cambrian Carbonates

As the sea continued to migrate across western North America a deep ocean basin developed through crustal subsidence.  In this environment, carbonate sediments were deposited to form the dolomite and limestone layers directly on top of the Ophir Shale.  (Photo by James Miller)