Paleogene calcareous nannofossil biostratigraphy of the Atlantic coastal plain

Abstract

Reconnaissance nannofossil sampling of outcrops, well cuttings, and cores from New Jersey to North Carolina reveals strata representative of the entire Paleogene except for NP 3 and NP 24–25. Lowest Paleocene strata (NP 1–2) occur in the subsurface of central New Jersey and equivalents may exist in North Carolina. Mid-to-upper Paleocene beds (NP 5–9) occur in central New Jersey, Virginia, and North Carolina, cropping out as the Vincentown, Aquia, and Beaufort Formations respectively. Lower Eocene assemblages appear to occur only in the subsurface of Virginia where a section representing continuous open marine deposition from NP 4–5 to NP 23 exists. Middle Eocene strata (NP 14–17) occur in New Jersey, Delaware, Maryland, Virginia, and North Carolina, whereas upper Eocene beds are represented only in Virginia and North Carolina. The Virginia section is mainly clastic whereas that of North Carolina seems to represent wave-influenced carbonate banks exhibiting several hardgrounds (Castle Hayne Formation). Nannofossil assemblages of NP 15 and NP 18–20 (but not NP 16–17) suggest that the Castle Haynes Formation might represent two separate marine transgressions separated by a hiatus. Lower Oligocene assemblages (NP 21–22) were found only in the subsurface of Virginia and North Carolina, and mid-Oligocene ones only in Virginia. Samplings of the Atlantic Coast onshore sequence is continuing, and undoubtedly some of the many apparent marine hiatuses we encountered might be filled in. Nonetheless, the lower Paleocene, upper Paleocene, middle Eocene, and lower Oligocene appear to represent marine transgression whereas the middle Paleocene, lower and upper Eocene, and upper Oligocene represent marine regressions. These oscillations correlate well with global relative sea-level history, but differ in detail owing to local tectonic overprinting.