USGS CMG 06027 Metadata

Collect four vibrocores up to 9 m long from Salt Pond and
Nauset Marsh for stratigraphy and porewater analysis.  Actual date
may me changed--dependent on approval by Reston contracts.

Samples and Chemical Analysis;Grain size analysis;

4 cores were collected at the following stations:  Station
Latitude   Longitude       3   41 50.1171
69 58.2639 4   41 50.1490   69 58.3307 2   41 50.0174
69 58.1467 6   41 49.8340   69 57.8076  A total of 63
sediment samples were collected at 30-cm intervals from the four
cores.  Cores were collected in aluminum casing (irrigation pipe)
and split, described, photographed, sampled, and discarded in the
field.  Porewater was extracted from cores for salinity measurement
by refractometer in the lab.  Samples were also processed for
grainsize and two radiocarbon analyses.  Data including core
description table and core images were included in an open-file
report along with electrical resistivity data from the area
collected in 2004 and 2006 and groundwater data from 2005.  Results,
primarily from one core, were presented at the NEGSA meeting in
Durham, NH in March 2007.  Abstract:  HOLOCENE SEDIMENTATION IN A
KETTLE POND BREACHED BY RISING SEA LEVEL ON CAPE COD   BRATTON, John
F., Coastal and Marine Geology Program, U.S. Geological Survey, 384
Woods Hole Rd, Woods Hole, MA 02543-1598, jbratton@usgs.gov  A
sediment coring study was performed in a former kettle pond located
at Cape Cod National Seashore that is connected to a larger estuary
via a narrow channel. The longest core (607 cm) collected near the
center of the pond (water depth approximately 9 m) recovered glacial
sand and gravel directly overlain by 115 cm of fine-grained
lacustrine sediments, and 257 cm of estuarine sediments. Given the
shallow depth of the connecting channel, the thickness of the
estuarine deposits relative to the lacustrine deposits (> twice as
thick) was unexpected, as the pond would have only been breached
within the last 2,000 years based on published sea-level curves for
the region. The fresh kettle pond, however, would have likely
existed for about 15,000 yrs prior to the marine invasion. This
pattern suggests that either, 1) estuarine sedimentation rates are
much higher than lacustrine sedimentation rates in breached kettle
ponds, or 2) the breaching took place earlier than would be expected
by modern sill elevations relative to sea level. Other drowned
kettle depressions that are completely filled with fine-grained
estuarine and marine sediments are known from Cape Cod, consistent
with the first scenario. Land use changes could also have increased
sedimentation rates within the last few centuries. The second
scenario, however, could only be distinguished from the first by
development of core chronologies using radiocarbon dating, and would
not rule out the possibility of multiple episodes of breaching. More
detailed studies of sediments in other breached or drowned kettle
depressions will be necessary to determine how common this pattern
of sedimentation might be in other formerly glaciated coastal
settings. Similar kettle depressions may preserve other sediment
transitions from lacustrine to estuarine that could complement
sea-level reconstructions based on salt marsh peats, as well as
serving as archives of major coastal storms. The nature of the fill
in such depressions also has important implications for coastal
construction and dredging, as well as for investigations of coastal
hydrogeology and submarine groundwater discharge.

1 days at sea.
4 stations occupied.
Related web site(s): 
http://gsa.confex.com/gsa/2007NE/finalprogram/abstract_118256.htm


TG&B MARINE MOONPOOL BOAT

CMGP