Sediment mass balance of a large estuary, Long Island Sound

Acoustic reflection profiles and bottom sampling are used to measure the volume of sediments accumulated in Long Island Sound. There is present 1.0 × 10¹⁰m³ of sediment of which 5.3 × 10⁹m³ is marine mud and 4.9 × 10⁸m³ is probably of pre-marine, lacustrine origin. The balance consists of reworked sand derived from glacial drift. The acoustically determined sub-bottom structure of the Sound and available sea level data indicate that the Sound basin was occupied by a large lake for at least 6000 years and has been an arm of the sea since 8000 years b.p. The volume of lacustrine sediment is accounted for by direct riverine input over 6000 years but the volume of marine mud present substantially exceeds the riverine supply over 8000 years. The Sound is shown to act as a trap for sediments originating on the continental shelf.