The Cambrian sequence in eastern Pennsylvania is: All ages, except the barren Leithsville, are paleontologically established. The Hardyston overlies Precambrian gnesisses; the Allentown is surmounted by the Ordovician Beekmantown limestone. Only the Cambrian-Precambrian and Allentown-Limeport contacts are defined in the literature. Because of lack of understanding of the Leithsville-Limeport relations, the age of the Leithsville has been questioned. Study of new and restudy of old exposures indicates that the Hardyston-Leithsville relations vary between transition and disconformity, the Leithsville-Limeport limestones are mutually transitional thereby implying a Middle Cambrian assignment to the Leithsville. The Beekmantown is ordinarily in conformity with the Allentown, but in at least one instance supposed Beekmantown overlies the Limeport in disconformity.

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