Pattern of post-miocene eustatic fluctuation of sea level
Abstract The oldest and highest emergent marine shoreline expressed as a prominent physiographic feature in the southeastern United States is the Late Miocene Orangeburg Scarp at an elevation of 200–250 ft. Any higher shore lines are covered by the terrestrial gravels of the Citronelle Formation, the deposition of which continued into Late Miocene time. The next highest emergent shore line is the Pliocene Surry Scarp at an elevation of 90–100 ft. Shorelines which are recognized by various authors at intermediate elevations are not prominent and do not mark prolonged stands of sea level. Withdrawal of the sea from its Late Miocene to its Pliocene stand appears to have been a eustatic event. The time of its occurrence and the amount of water involved both suggest that this eustatic drop in sea level was caused by the glaciation of Antarctica. Withdrawal from the Pliocene stand was probably caused by the onset of Northern Hemisphere glaciation. Distinct, but not prominent Pleistocene interglacial shorelines occur at elevations of 40–45 and 5–10 ft. A very distinct and prominent interglacial shoreline is found at an elevation of 25–30 ft. The highest and oldest of these is correlated with the relatively brief Aftonian interglacial, the strongly developed shoreline at 25–30 ft. with the prolonged Yarmouth interglacial and the weakly developed one at 5–10 ft. with the relatively brief Sangamon interglacial.