“…During the existence of glacial Lake BIS, glaciolacustrine varve sediments were deposited (Needell and Lewis, 1984). Sediment cores and photos from these deposits confirm that they are composed of layered reddish-brown and gray silts and clays (Bertoni et al, 1977; McMullen et al, 2014; Fig. 3).…”
Section: Regional Settingmentioning
confidence: 78%
“…4 and 5). Figure 3(color online) Photographs of sedimentary deposits in the large depression (McMullen et al, 2014). The top image shows photo location.…”
Section: Mapping Resultsmentioning
confidence: 99%
“…(B) Photograph 298_12a from the gradually sloping southwest entrance to the large depression. Based on a grain-size sample (McMullen et al, 2014), the seafloor here is composed of fine sand and is heavily bioturbated. Scours have formed around objects, delineating the dominant flow direction.Figure 4CHIRP line 16 uninterpreted (top) and interpreted (bottom).…”
Section: Mapping Resultsmentioning
confidence: 99%
“…Two main conceptual models have been proposed to explain the observed morphology and subbottom reflectors in BIS (Bertoni et al, 1977; Needell and Lewis, 1984; Lewis and Stone, 1991; Uchupi et al, 2001; Poppe et al, 2014b; McMullen et al, 2015). Both conceptual models ascribe the regional erosional channels imaged in the bathymetry to glacial lake drainage, with subsequent overprinting by fluvial and storm processes (Needell and Lewis, 1984; Lewis and Stone, 1991; Uchupi et al, 2001; McMullen et al, 2014; McMullen et al, 2015; Poppe et al, 2014a; Fig. 8, Supplementary Figs.…”
Block Island Sound (BIS), in southern New England, was occupied by a glacial meltwater lake (Lake BIS) during the MIS 2 deglaciation. New CHIRP seismic data, swath bathymetry, and legacy seismic profiles from BIS provide important insights and constraints on the morphologic evolution of a glaciated margin from the last glacial maximum to present. Interpretation of seismic data revealed four well-defined sediment units: acoustic basement, glaciolacustrine varved sediments, a lag deposit, and Holocene sediment. The morphology and architecture of the sedimentary units suggest that Lake BIS drained quickly, followed by the catastrophic drainage of glacial Lake Connecticut through BIS (Lake Connecticut occupied present-day Long Island Sound). The draining waters carved depressions ~100 m deep in the floor of BIS and the region between the lakes. The waters also carved Block Island Valley, which extends across the continental shelf. Continued existence of the depressions and valley suggests a rapid transgression over these water depths and limited sediment supply. Our results show the significant impact of glacial lake outburst floods, even during a sea level transgression, and may help explain morphology observed along other glaciated margins.
“…During the existence of glacial Lake BIS, glaciolacustrine varve sediments were deposited (Needell and Lewis, 1984). Sediment cores and photos from these deposits confirm that they are composed of layered reddish-brown and gray silts and clays (Bertoni et al, 1977; McMullen et al, 2014; Fig. 3).…”
Section: Regional Settingmentioning
confidence: 78%
“…4 and 5). Figure 3(color online) Photographs of sedimentary deposits in the large depression (McMullen et al, 2014). The top image shows photo location.…”
Section: Mapping Resultsmentioning
confidence: 99%
“…(B) Photograph 298_12a from the gradually sloping southwest entrance to the large depression. Based on a grain-size sample (McMullen et al, 2014), the seafloor here is composed of fine sand and is heavily bioturbated. Scours have formed around objects, delineating the dominant flow direction.Figure 4CHIRP line 16 uninterpreted (top) and interpreted (bottom).…”
Section: Mapping Resultsmentioning
confidence: 99%
“…Two main conceptual models have been proposed to explain the observed morphology and subbottom reflectors in BIS (Bertoni et al, 1977; Needell and Lewis, 1984; Lewis and Stone, 1991; Uchupi et al, 2001; Poppe et al, 2014b; McMullen et al, 2015). Both conceptual models ascribe the regional erosional channels imaged in the bathymetry to glacial lake drainage, with subsequent overprinting by fluvial and storm processes (Needell and Lewis, 1984; Lewis and Stone, 1991; Uchupi et al, 2001; McMullen et al, 2014; McMullen et al, 2015; Poppe et al, 2014a; Fig. 8, Supplementary Figs.…”
Block Island Sound (BIS), in southern New England, was occupied by a glacial meltwater lake (Lake BIS) during the MIS 2 deglaciation. New CHIRP seismic data, swath bathymetry, and legacy seismic profiles from BIS provide important insights and constraints on the morphologic evolution of a glaciated margin from the last glacial maximum to present. Interpretation of seismic data revealed four well-defined sediment units: acoustic basement, glaciolacustrine varved sediments, a lag deposit, and Holocene sediment. The morphology and architecture of the sedimentary units suggest that Lake BIS drained quickly, followed by the catastrophic drainage of glacial Lake Connecticut through BIS (Lake Connecticut occupied present-day Long Island Sound). The draining waters carved depressions ~100 m deep in the floor of BIS and the region between the lakes. The waters also carved Block Island Valley, which extends across the continental shelf. Continued existence of the depressions and valley suggests a rapid transgression over these water depths and limited sediment supply. Our results show the significant impact of glacial lake outburst floods, even during a sea level transgression, and may help explain morphology observed along other glaciated margins.
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