Chapter 12
Selected Bottom Photographs of Sedimentary Environments
in Eastern Long Island Sound
By
Lawrence J. Poppe1,
Harley J. Knebel1, and Dann S. Blackwood1
INTRODUCTION
The
bottom photographs presented below were taken in the vicinity of Niantic
Bay, Connecticut (Fig. 1), during
March 1996 aboard the RV John Dempsey
with a still camera attached to a Van
Veen grab sampler (Poppe and others, 1998a). The still camera
was a Photosea model 1000; Kodak Professional Color Negative ASA
400 film was used. Station identifiers, navigation, and descriptions
of these photographs are given in Table 1;
ancillary sediment data are supplied in Poppe and others (1998b). Descriptions
of bottom video collected concurrently with the still photography are available
in Poppe and others (1996) and for viewing at the Woods Hole Field Center.
Although these images were taken from a relatively limited area of the
Long Island Sound sea floor, they are supplied as representative examples
of the common benthic characters and sedimentary environments present throughout
the Sound. Inasmuch as the individual pictures record only a very
small area of the sea floor (approximately 50 cm by 75 cm), they depict
micro-environments that may or may not represent the dominant sediment
type or sedimentary environment shown in the corresponding polygons
on the associated data layers (Poppe and others, this CD-ROM; Knebel and
Poppe, this CD-ROM).
EROSION AND NONDEPOSITION
Environments of erosion and nondeposition occur within areas characterized
by strong bottom currents as well as exposures of glacial drift, coarse
lag deposits, and, along the Connecticut coastline, bedrock outcrops (Knebel
and others, 1999; Knebel and Poppe, in press). Faunal and floral
overgrowth (e.g. mussel beds) is common on these harder substrates.
COARSE-GRAINED BEDLOAD TRANSPORT
Environments of coarse-grained bedload transport occur within areas characterized
by coarse to fine sand with little or no mud (Knebel and Poppe, in press).
Bedforms, which range in size from current ripples to sand waves,
are ubiquitous.
SORTING AND REWORKING
Environments of sediment sorting and reworking occur within areas characterized
by variable amounts of sand and mud (Knebel and Poppe, in press).
Bedforms are of a smaller scale and fainter than in environments characterized
by coarse-grained sediment transport, and shell beds are more common.
FINE-GRAINED DEPOSITION
Environments of fine-grained deposition occur within areas characterized
by weak bottom currents and muddy sediments (Knebel and Poppe, in press).
ACKNOWLEDGMENTS
Collection of the bottom photographs was funded through a State of Connecticut/U.S.
Geological Survey cooperative. We thank P. Simpson, Miles Peterle,
Dave Simpson, and Mark Alexander (Connecticut
Department of Environmental Protection) who provided support onshore
and aboard the RV John Dempsey.
REFERENCES
Knebel, H.J., Signell, R.P., Rendigs, R.R., Poppe, L.J., and List, J.H.,
1999, Seafloor environments in the Long Island Sound estuarine system:
Marine Geology, v. 155, p. 277-318.
Knebel, H.J., and Poppe, L.J., Sea-floor environments within Long Island
Sound: A regional overview: Journal of Coastal Research, in press.
Poppe, L.J., Taylor, B.B., Blackwood, Dann, Lewis, R.S., and DiGiacomo-Cohen,
M.L., 1996, The texture of surficial sediments near Niantic Bay, Connecticut,
U.S. Geological Survey Open-File Report 96-271, 16 p.
Poppe, L.J., Lewis, R.S., Denny, J.F., Parolski, K.F., DiGiacomo-Cohen,
M.L., and Tolderlund, D.S., 1998a, Sidescan sonar image, surficial geologic
interpretation, and bathymetry of the Long Island Sound sea floor in Niantic
Bay and vicinity, Connecticut: U.S. Geological Survey Geologic Investigations
Map I-2625, 2 sheets.
Poppe, L.J., Hastings, M.E., DiGiacomo-Cohen, M.L., Manheim, F.T., and
Mlodzinska, Z.J., 1998b, Surficial sediment database, In: L.J. Poppe and
C. Polloni (eds.), Long Island Sound Environmental Studies: U.S. Geological
Survey Open-File Report 98-502, Chapter 3, CD-ROM.
FIGURE CAPTIONS
Figure 1. Index map of the study
area showing the locations of the bottom-photo stations (solid red circles).
Both new and historical sediment data for this area are compiled in Poppe
and others (1998b).
TABLE CAPTIONS
Table 1. This table, which
is supplied as a Microsoft Excel file (c12tab1.xls),
contains the sample identifiers, navigation, and descriptions associated
with the pictures presented in the gallery of bottom photographs.
Although these bottom photographs were taken in the vicinity of Niantic
Bay, Connecticut, they are supplied as representative examples of benthic
character and sedimentary environment. Inasmuch as the individual
pictures record only a small part of the sea floor, they depict micro-environments
that may or may not represent the dominant sediment type or depositional
environment in these areas.
1 U.S.
Geological Survey, Coastal and Marine
Geology Program, Woods Hole,
MA 02543
[an error occurred while processing this directive]
The
bottom photographs presented below were taken in the vicinity of Niantic
Bay, Connecticut (Fig. 1), during
March 1996 aboard the RV John Dempsey
with a still camera attached to a Van
Veen grab sampler (Poppe and others, 1998a). The still camera
was a Photosea model 1000; Kodak Professional Color Negative ASA
400 film was used. Station identifiers, navigation, and descriptions
of these photographs are given in Table 1;
ancillary sediment data are supplied in Poppe and others (1998b). Descriptions
of bottom video collected concurrently with the still photography are available
in Poppe and others (1996) and for viewing at the Woods Hole Field Center.
