A Review of the Geologic Framework of the Long Island Sound Basin, With Some Observations Relating To Postglacial Sedimentation

Abstract

Most of the papers in this thematic section present regional perspectives that build on more than 100 years of geologic investigation in Long Island Sound. When viewed collectively, a common theme emerges in these works. The major geologic components of the Long Island Sound basin (bedrock, buried coastal-plain strata, recessional moraines, glacial-lake deposits, and the remains of a large marine delta) interact with the water body to affect the way the modern sedimentary system functions.

Previous work, along with our present knowledge of the geologic framework of the Long Island Sound basin, is comprehensively reviewed with this theme in mind. Aspects of the crystalline bedrock, and the deltaic deposits associated with glacial Lake Connecticut, are examined with respect to their influence on sedimentation along the Connecticut coast and in the northern and western Sound. We also discuss the influence of the glacial drift that mantles the coastal-plain remnant along the north shore of Long Island and in the southern Sound.

A total of approximately 22.7 billion m³ of marine sediment has accumulated in the Long Island Sound basin. A significant portion (44%) of the fine-grained marine section in the central and western basins was redistributed there from the eastern Sound, as tidal scour removed slightly over 5 billion m³ (5.3 X 10¹² kg) of fine material from glacial lake and early-marine deposits east of the Connecticut River. The remainder of the estimated 1.2 X 10¹³ kg of fine-grained marine sediment that now resides in the central and western Sound can be accounted for by riverine input over the past 13.5 ka.