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College of Science & Engineering > Dept. of Earth Sciences > Limnological Research Center > LacCore

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Nesje / Percussion Corer

Description

The Nesje corer (Nesje, 1992) is a single-drive, cable-deployed percussion coring system with a piston, and is operable by two people—although three to four are preferable, particularly as core lengths increase. The core head consists of a steel cylinder to which the core tube is bolted; a rod extending from the top of the head guides a weight (another steel cylinder of ~20kg) as the operator repeatedly lifts the weight a short distance and allows it to drop onto the core head. This system is relatively effective at penetrating clastic and/or coarse-grained sediments. However, plastic core tubes attenuate the percussive strikes, thus limiting its effectiveness at increasing sediment depths. As with all single-drive corers, the length of the tube limits the potential coring depth. Most tubing is available in lengths only up to 6m. If longer lengths are desired, multiple tubes can be coupled together by using a larger diameter plastic coupling over the joint between two lengths of tube. However, such longer tubes pose challenges for handling and for tube stability during the coring process. Like all percussion corers, the Nesje can cause disturbance to the recovered sediment, particularly in sediments of continuously alternating density or grain size (e.g. clastic varves).