Once a
core is brought aboard, the sediment together with its plastic liner are
split lengthwise into two halves so that the sediment layers can be analyzed.
These cores have captured the uppermost layers of sediment, revealing the
transition from brown, oxidized layers to greenish-gray clay. Once the water
is drained from above the sediment, the soupy sediment will be carefully
sampled and dated to produce a time series of sediment accumulation extending
back thousands of years. At this site in the tropical eastern Pacific, where
sedimentation rates are typically around 2 cm per thousand years, the bottom
of this 40 cm section probably corresponds to the last ice age 20,000 years
ago.
Photo of marine sediment samples collected with a multicorer. Scientists
use a variety of tools to recover undisturbed seafloor sediments, ranging
from small coring devices like the multicorer, to drilling rigs operated
from specialized ships. The multicorer shown here excels at collecting undisturbed
tubes of the uppermost layers of sediment together with the overlying seawater.
Once the overlying seawater has been drained off, the ends of the tube will
be capped, and the tubes will be split lengthwise so the sediment layers
can be analyzed.
Photo Credits:
David M. Anderson
NOAA Paleoclimatology Program and INSTAAR, University of Colorado, Boulder
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