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Figure 1 -
On the northern flank of the Chukchi Plateau in water depths exceeding
700 m there is a field of pockmarks. These features are most commonly
formed by gas seepages. In this and all of the sidescan images in this
poster, strong acoustic returns are white; low returns and acoustic
shadows are black. Swath width has been trimmed to 3.2 km per side which
exceeds an insonification angle of 80 degrees in the shallowest areas.
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Figure 2 -
Upslope of the pockmarks on the northern flank of the Chukchi Plateau
in water depths between 600 and 700 meters is a large field of glacial
flutes trending NE-SW. These low-relief parallel ridges indicate the
direction of motion for the ice sheet that created them.
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Figure 3 -
The shallowest portions (< 400 m deep) of the Chukchi Plateau are dominated
by randomly oriented plowmarks formed by iceberg keels. The plowmarks
have obscured all other glacigenic features.
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Figure 4 -
On the southern flank of the Chukchi Cap in water depths between 400
and 500 meters, the SCAMP SSBS mapped a number of curvilinear ridges
that follow bathymetric contours. These features are distinct from the
plowmarks in Figure 3 in that they show a preferred orientation and
exhibit a different pattern of acoustic return strength. Plowmarks,
which have negative relief, are characterized by acoustic shadows closest
to nadir and strong acoustic returns farther from nadir. These features
show the opposite pattern of acoustic return strength and therefore
must have positive relief. We interpret them to be stadial moraines
formed during the retreat of ice that covered at least part of the Chukchi
Plateau.
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| Figure 5 - To the east of the morainic ridges, in approximately the same water depths, is another field of glacial flutes with the same orientation as the flutes shown in Figure 2. The consistent strike of the flutes on the northern and southern flanks of the Chukchi Cap suggests that they were formed by a contiguous sheet of ice. | ||
