Complex sentence: The Herkimer Formation is the uppermost stratigraphic unit of the Clinton Group and is underlain by the Willowvale Formation.The Herkimer Formation is overlain disconformibly by the Ilion Formation of the Lockport Group.
Split into simpler sentences: The Herkimer Formation is the uppermost stratigraphic unit of the Clinton Group. It is underlain by the Willowvale Formation and overlain disconformibly by the Ilion Formation of the Lockport Group.