Sundance Sea A shallow marine embayment that extended over what are now Wyoming and S. Dakota during the late Callovian and Oxfordian. The southern edge of this sea (in modern Colorado) was bordered by tidal flats, the marine connection being northwards through the presentday mid-west and Canada. The sediments resulting from deposition in the Sundance Sea are characterized by a rich ammonite (Ammonoidea) fauna (Quenstedtoceras and Cardioceras), especially the Redwater Shale Member of the Sundance Formation.

Sundance Sea A shallow marine embayment that extended over what are now the states of Wyoming and South Dakota during the Middle and Late Jurassic. The southern edge of this sea (in modern Colorado) was bordered by tidal flats, the marine connection being northwards through the present-day mid-west and Canada.