Cretaceous-Tertiary Boundary in New Jersey, Delaware, and Eastern Maryland

The Cretaceous-Tertiary boundary in New Jersey has been described as both conformable and unconformable. The advocates of each interpretation have been about evenly divided for the past 75 years. Recent geologic quadrangle mapping of more than 600 square miles in the Coastal Plain of New Jersey and detailed reconnaissance in parts of Delaware and eastern Maryland have enabled the authors of this report to offer evidence of the unconformable nature of the contact for 120 miles along the strike. The thinning of the stratigraphic section, the pinchout of some units in outcrop, and the overlap of the basal Tertiary on progressively lower beds in the Cretaceous section from northeast to southwest are evident. Determination of the distinguishing lithologic characteristics, fixing the spatial distribution, and recognition of the cyclical nature of the Coastal Plain formations have aided in determining the unconformity, the changes along the strike, and the correlation of the formations from New Jersey through Delaware into eastern Maryland. In addition to structure and overlap, worn phosphatic and sideritic fossils and pieces of rock reworked from the underlying Cretaceous formations into the base of the overlying Tertiary formations suggest an unconformity similar to that recognized in the southeast part of the Atlantic Coastal Plain and in the Gulf Coastal Plain. Because early workers considered the conspicuous angular unconformity between the lower Eocene and middle Miocene formations to be the Cretaceous-Tertiary boundary, they may have overlooked the more subtle unconformity at the presently accepted Cretaceous-Tertiary boundary.Contributions to Stratigraphy, Geological Survey Bulletin 1274-H.Purpose: To discuss the geology of the Cretaceous-Tertiary boundary of New Jersey, Delaware and Maryland