The Rock Point Member of the Chinle Formation in the Chinle Valley

On of the great things about this weekend was seeing the entire Chinle Formation type section.  H. E. Gregory divided the Chinle into four divisions A, B, C, D; which since that time have been given formal names.  A = Rock Point Member, B = Owl Rock Member, C = Petrified Forest Member (which in our modern usage also includes the Blue Mesa and Sonsela Members), and D = the lower red member (or Bluewater Creek).  We were able to see all of these divisions as well as the underlying Shinarump Member (which Gregory did not include in hs Chinle). We spent 4th of July evening looking at the Rock Point Member:

The type section of the Rock Point Member is the slope forming base of Little Round Rock.

Rock Point Member on the side of Round Rock.

Close-up of Rock Point strata on Round Rock.

Jeff Martz examining the Rock Point Member at Round Rock.

Photo from a little more than half way up the Rock Point section on Round Rock.  Valley below is the Owl Rock Member.  Note our vehicle to the bottom left of the photo.  These exposures are really high up.

The Owl Rock Member of the Chinle Formation in the Chinle Valley

The Owl Rock Member of the Chinle Formation is widely exposed in the Four Corners area of the western United States.  The unit is characterized by its variegated color scheme and prominent carbonate lenses. In the Chinle Valley the Owl Rock overlies the Petrified Forest Member and is overlain by the Rock Point Member.

Owl Rock Member (top) and the Petrified Forest Member (bottom) at Round Top Ridge.

Prominent carbonate lenses in the Owl Rock Member at Round Top Ridge.

Thick beds of carbonate in the very top of the Owl Rock Member at Round Rock.

Close-up of fallen blocks of the upper carbonate beds at Round Rock.

Contact between the top of the Owl Rock Member and the overlying Rock Point Member at Round Rock.