Depositional Environments of Marine Pleistocene Deposits in Southeastern North Carolina

Abstract

Outcropping marine, fossiliferous Pleistocene beds in southeastern North Carolina (Neuse Formation) consist of four facies, each facies having distinct lithologic and faunal characteristics: (1) bay facies—clay to fine-grained quartz sand, Retusa-Nuculana molluscan assemblage, and Elphidium-Ammonia foraminiferal assemblage; (2) shallow shelf facies—fine-grained quartz sand, Donax-Spisula molluscan assemblage, and Elphidium-Ammonia-Hanzawaia foraminiferal assemblage; (3) lagoonal facies—very fine-grained quartz sand and sand-silt-clay, Crassostrea-Gemma molluscan assemblage, and Elphidium-Ammonia foraminiferal assemblage; (4) high-energy facies—coquina, Donax-Mercenaria molluscan assemblage, and Quinqueloculina foraminiferal assemblage. The bay facies seems to have been deposited in a body of water in which polyhaline and marine salinities prevailed and which was moderately exposed to the open ocean. The shallow shelf facies probably formed in the sublittoral zone in the open ocean. The lagoonal facies seems to have formed in a body of water where mesohaline and polyhaline salinities were dominant. The high-energy facies was probably deposited in inlets between barrier bars or in shoal areas near the littoral zone. The water temperature during deposition of the Neuse Formation seems to have been slightly higher than that now found in North Carolina coastal waters. Changes in temperature and shoreline configuration after Neuse deposition seem to have had a marked effect on molluscan latitudinal migration.