Having the checkered flag of our Lake Hamana
piston coring mission in sight, we can already look back at many days of hard
work and dedication. However, we still need to complete a few things.
We have been sampling sediment from four
consecutive sites along a N-S transect within the lake’s central basin, north
of the tidal delta. Two of these sites are entirely finished (site 1 and 2),
whereas we still have to take six more 2 m piston core sections from the
northern two sites (site 3 and 4).
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Location map of Lake Hamana (left) and bathymetry of the lake basin with indication of our coring sites, yellow ones are finished, red ones still need to be completed (right) |
At every site we collect a total of nine cores.
First of all, a short gravity core has to be taken in order to retrieve a relatively
undisturbed top section. Then, we start piston coring in a first hole, acquiring
sections from 0-2 m, 2-4 m, 4-6 m and 6-8 m. Afterwards, 1 m overlap sections
can be gathered from a second hole, which is closely spaced to the first one.
Overlaps comprise sections from 1-3 m, 3-5 m, 5-7 m and 7-9 m. Ideally, one
drilling hole should be sufficient if no stratigraphic gaps existed between
individual sections. Unfortunately, we can never be sure of this continuity,
due to restrictions that are inherent to the piston coring system, tidal influences
on the lake/platform level, drift as a result of strong currents and waves...
With these nine cores, we can eventually reconstruct one complete composite
core.
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Schematic representation of cores that need to be collected on each site |
Our work on Lake Hamana is not just limited to
hammering and getting mud tubes out of the barrel. Maintenance of the equipment
is as, if not more important, because coring is impossible with corroded, rusty
material that is clogged with sediment and salt crystals. After all, we are
working on a brackish lake. Moreover, unexpected material failure due intensive
use and other problems can unpleasantly stall our coring operations. Maintenance,
reparations, modifications, problem-solving… are thus key words for time gaps
in between coring and often have to be executed on our 3x4 m floating platform,
which is not always that evident!
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Hammering, hammering and some more hammering... there is no escaping it! |
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Cleaning the empty liner before inserting it into the barrel |
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Getting the coring barrel ready for use |
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Checking if the piston is still working properly, a crucial task |
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Some more platform maintenance |
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We also need to maintain ourselves with a good lunch... |
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... and even more importantly, a nice cup of coffee once in a while! |
Luckily, our coring team’s spirit is still
alive and we will give it our all during these last few days!
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