Seafloor character and sedimentary processes in eastern Long Island Sound and western Block Island Sound

Geo-Mar Lett (2006) 26: 5968DOI 10.1007/s00367-006-0016-4ORIGINALL. J. Poppe . M. L. DiGiacomo-Cohen . S. M. Smith .H. F. Stewart . N. A. ForfinskiSeafloor character and sedimentary processes in eastern

Long Island Sound and western Block Island SoundReceived: 26 July 2005 / Accepted: 6 January 2006 / Published online: 1 March 2006

# Springer-Verlag 2006Abstract Multibeam bathymetric data and seismic-reflection profiles collected in eastern Long Island Sound and

western Block Island Sound reveal previously unrecognized glacial features and modern bedforms. Glacial

features include an ice-sculptured bedrock surface, a

newly identified recessional moraine, exposed glaciolacustrine sediments, and remnants of stagnant-ice-contact

deposits. Modern bedforms include fields of transverse

sand waves, barchanoid waves, giant scour depressions,

and pockmarks. Bedform asymmetry and scour around

obstructions indicate that net sediment transport is westward across the northern part of the study area near Fishers

Island, and eastward across the southern part near Great

Gull Island.IntroductionDigital terrain models (DTMs) produced from multibeam

bathymetric data provide valuable base maps for marine

geological interpretations (Todd et al. 1999; Mosher and

Thomson 2002; ten Brink et al. 2004; Poppe et al. 2006).

These maps help define the geological variability of the

seafloor (one of the primary controls of benthic habitat

diversity); improve our understanding of the processes that

control the distribution and transport of bottom sediments,

and the distribution of benthic habitats and associated

infaunal community structures; and provide a detailed

framework for future research, monitoring, and management activities.The bathymetric survey interpreted herein (National

Oceanic and Atmospheric Administration (NOAA) survey

H11250) covers roughly 94 km2 of seafloor in an area

where a depression along the Orient Point-Fishers Island

segment of the Harbor Hill-Roanoke Point-Charlestown

moraine forms the Race, the eastern opening to Long Island

Sound. The Race also divides easternmost Long Island

Sound from northwestern Block Island Sound (Fig. 1).

This bathymetry has been examined in relation to seismicreflection data collected concurrently, as well as archived

seismic profiles acquired as part of a long-standing

geologic mapping partnership between the State of

Connecticut and the U.S. Geological Survey (USGS).

The objective of this work was to use these acoustic

datasets to interpret geomorphological attributes of the

seafloor, and to use these interpretations to better understand the Quaternary geologic history and modern

sedimentary processes.Geologic settingBedrock that underlies southeastern...