THE AGE OF DINOSAUR-BEARING STRATA AT PHOEBUS LANDING, CAPE FEAR RIVER, NORTH CAROLINA

Upper Cretaceous sediments, exposed at Phoebus Landing on the Cape Fear River, Bladen County, have yielded a rich fauna of thirty-seven species of fossil vertebrates including four kinds of dinosaurs. The geochronometric age of this important fauna has been poorly constrained until now. Palynomorph assemblages at this site are diverse, well preserved, and contain abundant gymnosperm pollen, angiosperm pollen, and terrestrially-derived spores. Marine palynomorphs, such as acritarchs and dinoflagellates, are rare but present; calcareous nannofossils are absent. This assemblage is typical for a marginal marine depositional setting. The palynomorphs from this locality represent “middle Zone C” of Christopher (unpublished), based, in part, on the co-occurrence of Holkopollenites sp. B, Retitrescolpites viviosus, and Longaevipollis fortis. The sediments at Phoebus Landing are part of the Tar Heel Formation of North Carolina. They are specifically age-equivalent to the marine Coachman Formation of South Carolina, based on marine calcareous nannofossil and nonmarine palynomorph assemblages.

Previous biostratigraphic investigations in South Carolina, supported by recent results from nearby coreholes in North Carolina, have produced a detailed correlation between Christopher’s (unpublished) nonmarine palynomorph zonation of the southeastern Atlantic Coastal Plain and the international temperate Campanian marine calcareous nannofossil zonation. First and last occurrence datums for calcareous nannofossils in turn are tied to the global geochronologic timescale, as interpreted by Burnett (1998). Based on this correlation, we can conclude that sediments of the Tar Heel (part)/Coachman accumulated during the time interval represented by nannofossil Zone CC20 (upper part of the lower Campanian). Thus, the age of the fauna from Phoebus Landing lies between 78.5 and 77.1 Ma.