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USGS2007

Sidescan-sonar imagery, multibeam bathymetry, and surficial geologic interpretations of the sea floor in Rhode Island Sound, off Sakonnet Point, Rhode Island

The U.S. Geological Survey (USGS) is working with the National Oceanic and Atmospheric Administration (NOAA) to interpret the surficial geology in estuaries and sounds along the northeastern coast of the United States. This report interprets the area covered by NOAA Survey H11320, about 72 km² of sea floor in eastern Rhode Island Sound (RIS), located about 8 km south of Sakonnet Point, Rhode Island (fig. 1). Previous work in RIS includes studies of both sea-floor processes and subsurface geologic framework. McMaster (1960) mapped surficial sediment samples in Narragansett Bay and RIS and McMaster and others (1968) conducted a seismic-reflection survey in Block Island Sound and RIS. O'Hara and Oldale (1980) collected seismic-reflection profiles, sidescan-sonar data, and vibracores in eastern RIS (fig. 2). They interpreted the geologic history, assessed sand and gravel resources, and evaluated the mining impact of these resources. McMaster's (1960) interpretation of the surficial sediment within this study area consisted of sand with several isolated areas of gravel. Several other sediment samples were previously obtained within the study area: three National Oceanographic Data Center (NODC) dredge samples from 1942 consisted of sand and one National Ocean Service (NOS) sample from 1939 was rocky (fig. 2; Poppe and others, 2003). The purpose of this report is to define the sea-floor morphology and sedimentary environments and interpret processes occurring on the sea floor using sidescan-sonar imagery, multibeam bathymetry, and historic seismic-reflection profiles.

Rhode Island↗

USGS2006

High-resolution geologic mapping of the inner continental shelf: Boston Harbor and approaches, Massachusetts

This report presents the surficial geologic framework data and information for the sea floor of Boston Harbor and Approaches, Massachusetts (fig. 1.1). This mapping was conducted as part of a cooperative program between the U.S. Geological Survey (USGS), the Massachusetts Office of Coastal Zone Management (CZM), and the National Oceanic and Atmospheric Administration (NOAA). The primary objective of this project was to provide sea floor geologic information and maps of Boston Harbor to aid resource management, scientific research, industry and the public. A secondary objective was to test the feasibility of using NOAA hydrographic survey data, normally collected to update navigation charts, to create maps of the sea floor suitable for geologic and habitat interpretations. Defining sea-floor geology is the first steps toward managing ocean resources and assessing environmental changes due to natural or human activity. The geophysical data for these maps were collected as part of hydrographic surveys carried out by NOAA in 2000 and 2001 (fig. 1.2). Bottom photographs, video, and samples of the sediments were collected in September 2004 to help in the interpretation of the geophysical data. Included in this report are high-resolution maps of the sea floor, at a scale of 1:25,000; the data used to create these maps in Geographic Information Systems (GIS) format; a GIS project; and a gallery of photographs of the sea floor. Companion maps of sea floor to the north Boston Harbor and Approaches are presented by Barnhardt and others (2006) and to the east by Butman and others (2003a,b,c). See Butman and others (2004) for a map of Massachusetts Bay at a scale of 1:125,000. The sections of this report are listed in the navigation bar along the left-hand margin of this page. Section 1 (this section) introduces the report. Section 2 presents the large-format map sheets. Section 3 describes data collection, processing, and analysis. Section 4 summarizes the geologic history of the region and discusses geomorphic and anthropogenic features within the study area. Section 4 also provides references that contain additional information about the region. Appendix 1 provides GIS layers of all the data collected in this study, Appendix 2 contains the grain size textural analyses of sediment samples, and Appendix 3 contains bottom photographs of the sea floor in JPG format.

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