Owl Creek Mountains

This is the north end of the Windriver Canyon in Wyoming. The canyon bisects the owl creek mountains that boarder the Big Horn Basin. Unlike the South aspect there is relatively little erosion and practically none of the 14 or so formations covering the red siltstone Chugwater formation are gone.  The only problem is that the shadowed cliff to the right is an out cropping of the Chugwater. It is either on top of the formations shown in this picture or everything above it has been eroded to reveal it.  If so why did everything north and south of the Owl Creek Mountians erode and the Owl Creek didn't?

This is vista visible from the mouth of the Windriver Canyon of the Chugwater formation north of the Owl Creek Mountians.  Where did all of the formations covering the Chugwater go?  They are present in the Canyon but not here.  An it appers as if the formations making up the canyon actually goes below the Chugwater if that is possible.

This is a view of the Chugwater formation near Thermopolis Wyoming. The same question arises. Where did everything above this formation go while the Owl Creek Mountain suffered hardly any erosion?

This is a vista of the canyon illustrating only a portion of the multiple formations that make up the rock walls.  Supposedly this is on top of the Chugwater which can be seen at both the head and mouth of the canyon.
  Doesn't make any sense to me.  If someone can enlighten me I would appreciate it.