Skip Links

USGS HomeContact USGSSearch USGS

Open-File Report 2014–1018

Pubs Warehouse

### Sea-Floor Geology in Northwestern Block Island Sound, Rhode Island 

----

## Setting

| Title PageList of FiguresConversion FactorsAbstractIntroduction**Setting**MethodsBathymetrySidescan SonarSedimentsBottom PhotographyGIS Data CatalogSummaryAcknowledgmentsReferencesContactsIndexClick on figures for larger images**Figure 1.**Map showing the location of National Oceanic and  Atmospheric Administration survey H12296 offshore  of Rhode Island.**Figure 2.**Map of end moraines  and  submerged ridges in southern New York and New England with the study area.
Block Island Sound is located south of Rhode Island, north  and west of Block Island, and between Long Island Sound in the west and Rhode  Island Sound in the east (figs. 1 and 2).   The sea floor of Block Island Sound, like those of the surrounding  sounds, reflects a history of Pleistocene glaciation, reworking of glacial and  transitional deposits during the subsequent marine transgression associated  with the eustatic rise in sea level, and the effects of scour and sediment  redistribution by modern marine conditions. The Laurentide Ice Sheet reached  its maximum extent around 20,000 to 28,000 years ago at the location marked by  the Ronkonkoma-Nantucket terminal moraine (Stone and Borns, 1986; Uchupi and  others, 2001; Ridge, 2003; Balco, 2011; fig. 2). During the northward retreat  of the ice sheet, the Harbor Hill-Roanoke Point-Charlestown-Buzzards Bay end  moraine was constructed around 18,000 to 23,000 years ago (Uchupi and others,  2001; Balco, 2011). As the ice sheet retreated, ponded meltwater formed glacial  lakes between the ice front and the end moraines. Glaciolacustrine sediments  tens to hundreds of meters thick were deposited in these lakes, which covered much  of modern day Long Island, Block Island, and Rhode Island Sounds (Needell and  others, 1983; Lewis and DiGiacomo-Cohen, 2000; Uchupi and others, 2001; Boothroyd,  2009). After the glacial lakes drained, these areas were exposed to subaerial  erosion before the sea level rose and the shoreline transgressed northward. This  transgression eroded and reworked the glacial and transitional sediments and  left a coarse-grained lag (Knebel and others, 1982). Modern currents and waves  continue to erode, sort, and rework the sea floor and, where currents are weaker,  deposit modern marine sediments (Knebel and others, 1982; Needell and Lewis,  1984). 

AccessibilityFOIAPrivacyPolicies and Notices

U.S. Department of the Interior |            U.S. Geological Survey                                                URL: http://pubs.usgs.gov/of/2014/1018/html/setting.html            Page Contact Information: GS Pubs Web Contact                        Page Last Modified: Friday, February 21, 2014, 12:29:03 PM |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|