Changed Late Quaternary Marine Environments on Atlantic Continental Shelf and Upper Slope

Abstract

About 2000 large sediment samples were collected during the early 1960s throughout the continental shelf off the Atlantic coast of the United States to establish and map sediment types including sediments relict from times of glacially low (and subsequently higher) sea levels. In about 510 of these samples we found fossil shells of mollusks remaining from environmental conditions different from those at present. Publications and collections by others contain about 70 additional samples having relict mollusks. Some of these shells indicate lower sea levels, others colder water, and still others warmer water than is now present. Radiocarbon measurements from earlier studies by us and others established the dates of colder water (late Pleistocene), and we made additional measurements to learn the dates of warmer water (about 1000 to 2000 yr B.P.). The results show reasonably enough that continental shelves are the sites of relict faunas as well as of sediments that indicate changed and complex environmental histories.