The upper contact of the Vishnu Basement Rocks is a major unconformity between it and either the Tonto Group or Unkar Group that resulted from uplift and the deep erosion, by at least , of the Vishnu Basement Rocks and any overlying strata. In the case of the unconformity between the Vishnu Basement Rocks and the Unkar Group, studies of the underlying Vishnu Basement Rocks indicate they were uplifted from a depth of about to a depth of about , between 1.75 and 1.66 billion years ago, and from a depth of about to the weathered surface on which the Bass Formation of the Unkar Group accumulated - between 1.66 and 1.25 billion years ago.