Stratigraphy of Atlantic Coastal Plain Between Long Island and Georgia: Review

ABSTRACT The Atlantic Coastal Plain between Long Island and Georgia is divided into nine major structural features: (1) the Cape May slope (new name); (2) Salisbury embayment; (3) Fort Monroe high; (4) Hatteras low; (5) Cape Fear arch or Great Carolina ridge; (6) Beaufort basin; (7) Okefenokee embayment or Southeast Georgia basin; (8) Central Georgia uplift; and (9) Suwannee River basin. There are also several features in southwestern Georgia that are related to the Gulf Coastal Plain. Outcropping sediments on Long Island are only of Cretaceous and Pleistocene ages. A more nearly complete section is present in New Jersey. The Pliocene and upper Miocene strata are of non-marine origin. The Kirkwood Formation (middle Miocene) is equivalent to the Calvert and St. Marys Formations of the Chesapeake Group of Maryland. The Eocene-Paleocene section consists of highly fossiliferous, glauconitic, and calcareous sandstone. The Upper Cretaceous section is divided into 11 formations whereas beds of Early Cretaceous age are present only in the subsurface. Delaware has a less nearly complete section, with some of the New Jersey formations not represented or not differentiated. The best exposures of Cretaceous strata are present along the Chesapeake and Delaware Canal. The Miocene, which is well represented in Maryland, consists mainly of the deposits of the Chesapeake Group. Five formations of Paleocene-Eocene age are present; correlations with New Jersey and the Gulf Coast are suggested. The Monmouth and Matawan sediments are thinner than farther north and cannot be separated into formations in Maryland as they are in New Jersey and Delaware. The basal Late Cretaceous Raritan sediments grade into a section of marine origin downdip. There are extensive deposits of Early Cretaceous age (Potomac Group). These also grade into a marine section downdip. Sediments of the Chesapeake Group (Miocene), which are well represented in Virginia, generally are highly fossiliferous. The five formations of Paleocene-Eocene age which are present in Virginia are correlated with those of Maryland. The Upper Cretaceous sediments of the Monmouth and Matawan Groups are absent, having pinched out against the Fort Monroe high. Some nearshore Raritan deposits crop out on the Virginia Coastal Plain and grade into a marine section downdip. The Lower Cretaceous (Potomac) section is of nonmarine origin. A thick section is present in North Carolina largely because of the presence of the Hatteras low. In addition to the formations present in Virginia, there are deposits of Pliocene, early Miocene (?), and Oligocene ages. Outliers of early or middle Eocene age are present on the Piedmont area west of the Fall Line. The Cretaceous deposits are much thicker than in Virginia and include formations of Early and Late Cretaceous ages. Jurassic ostracodes have been identified from the bottom of the Cape Hatteras well. The South Carolina section is rather similar to that of North Carolina with a greater thickness of lower Miocene (Tampa Formation) and Oligocene (Flint River Formation and Cooper Marl) strata, as well as seven distinct formations of Paleocene-Eocene age. The section in Georgia is related to both the Atlantic and Gulf Coastal Plains with a somewhat thicker section in the latter region; the Atlantic Coastal region is rather similar to that of adjacent South Carolina except that the Cretaceous is not well differentiated. The term “Tuscaloosa formation” is used generally for the entire Cretaceous section and includes deposits that may be considerably younger. Triassic beds are present below coastal plain deposits in Maryland, South Carolina, and Georgia, whereas buried Paleozoic rocks are present in the Suwannee River basin of Georgia. No commercial oil has been found in the coastal plain between Long Island and Georgia, although some seeps have been reported from Georgia.