Paleopalynology of the Tar Heel Formation of Atlantic Coastal Plain of North Carolina, United States.

Abstract

Sediments from the Late Cretaceous Tar Heel Formation in the Atlantic Coastal Plain of North Carolina were investigated for occurrence and distribution of palynomorphs. Exposures along rivers at Elizabethtown, Goldsboro, Ivanhoe, Lock, Willis Creek and Tar River in North Carolina were systematically collected. One hundred and three sediment samples were macerated by standard techniques modified by eliminating treatments with nitric acid and potassium hydroxide, and analyzed for palynomorphs. Eighty species of palynomorphs were distributed in 4 form genera of freshwater algae, 3 of dinoflagellates, 9 of fungi, 15 of pteridophytes, 11 of gymnosperms and 24 of angiosperms. Angiosperms were the dominant components in assemblages at all localities. Representatives of the Normapolles pollen group (characteristic angiosperm pollen group of middle and high northern latitudes of eastern North America and Europe) occur throughout the Tar Heel Formation and collectively comprise 29%-54% of the angiosperm assemblages. Palynological age assessment is in concordance with earlier dating determined by other workers based on invertebrate faunas. Minimum variance clustering with squared Euclidean distances in the Q-mode (clustering of samples) indicates that stratigraphically older layers of Ivanhoe, Lock and Willis Creek are similar in palynofloral composition, and one section of the Goldsboro locality is compositionally equivalent to the Tar River locality. Minimum variance cluster analysis in the R-mode (clustering of taxa) indicates the association of Campanian taxa in the same cluster. This reconfirms that localities of the Tar Heel Formation are of Early Campanian age. Informal biostratigraphic zones of Campanian (CA2-CA4) known from other Atlantic Coastal Plain deposits do not occur in the Tar Heel Formation. Quantitative analysis is consistent with the long-standing hypothesis of diversification and dominance of angiosperm pollen groups during the Campanian. The palynological record of the Tar Heel Formation, based on some indicator taxa with modern equivalents, suggests that subtropical to warm, moist temperate conditions prevailed in the southeastern region of North America during Campanian time.