The middle Pliocene, ∼3.5-2.5 Ma, was a period of global warmth preceding the growth of major Northern Hemisphere ice sheets. We report on eustatic sea level for the middle Pliocene based on micropaleontologic study of marine deposits of the Duplin Formation of South Carolina and North Carolina. The Duplin was deposited during a middle Pliocene marine transgression that formed the Orangeburg scarp, a prominent wave-cut geomorphic paleoshoreline of the southeastern U.S. Atlantic Coastal Plain. We conclude that (1) the scarp in South Carolina was formed mostly during the middle Pliocene (3.5-3.0 Ma), (2) eustatic sea level was about 35±18 m higher than modern sea level (the scarp has been uplifted about 50-65 m since the middle Pliocene), and (3) ocean-water temperatures along eastern North America were warmer when the scarp was formed than they are at present.

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