- Western Interior Seaway 65 Ma K-T Boundary
- Western Interior Seaway 67 Ma Maastrichtian (Late)
- Western Interior Seaway 69.7 Ma Maastrichtian
- Western Interior Seaway 70.4 Ma Campanian/Maastrichtian
- Western Interior Seaway 72.1 Ma Campanian (Late)
- Western Interior Seaway 80 Ma Campanian (Middle)
- Western Interior Seaway 82.9 Ma Campanian (Early)
- Western Interior Seaway 84 Ma Santonian (Late)
- Western Interior Seaway 87.9 Ma Coniacian (Middle)
- Western Interior Seaway 89.8 Ma Turonian (Late)
- Western Interior Seaway 92.1 Ma Turonian (Middle)
- Western Interior Seaway 94.9 Ma Cenomanian (Late)
- Western Interior Seaway 99 Ma Albian/Cenomian
- Western Interior Seaway 105 Ma Albian (Late)
- Western Interior Seaway 120 Ma Aptian
- Western Interior Seaway 130 Ma Barremian
- Western Interior Seaway 145 Ma Berriasian
- Western Interior Seaway 152 Ma Jurassic (Late)
- Western Interior Seaway 161 Ma Jurassic (Late)
- Western Interior Seaway 170 Ma Jurassic (Middle)
- Western Interior Seaway 185 Ma Jurassic (Early)