Initial Results From the new Long Coring System of RV Knorr
Abstract
A new long piston coring system has been designed and built for RV Knorr. The system is capable of deploying core lengths up to 46 m and weights of ~25000 lbs. With suitable modifications to other ships, a slightly smaller system could be deployed from other large UNOLS vessels. The handling system was designed around a hybrid rope blend of Vectran and Plasma braided with a torque-balanced, non- rotating construction. The rope is 7500 m long with a breaking strength (~360,000 lbs) more than 10 times greater than the pullout tensions experienced by the coring system. The high breaking strength limits stretching during coring operations, which minimizes rebound of the rope and movement of the piston during core penetration. An accelerometer placed on the release system documented that rope rebound was less than 2 m after the release of a ~15000 lb core at a water depth of 4585 m. The handling system for the new core includes a new A-frame mounted with a load transfer winch and a vertically-mounted rigging boom; a new stern-mounted grapple for transferring the corer from starboard to stern; a new deck-mounted traction winch for the Vectran-Plasma rope; and three new computer-controlled davit cranes along the starboard rail to raise and lower the corer between horizontal and vertical orientations. During testing at Bermuda Rise, core recovery exceeded 38 m, with cores generally filling 85% to 90% of the piston core barrel length. The test location has been cored many times before and stratigraphic correlation of the new cores with ODP Site 1063 shows that the new system recovered sediments without stretching. Three cores exhibit some evidence of compression at about 30 mbsf, while two others do not. These two cores were collected with a reduced-diameter core cutter, minimizing internal friction and enhancing core recovery. Four of the new cores completely recovered the last 150,000 years of sedimentation at Bermuda Rise with an average sedimentation rate of greater than 25 cm kyr-1. The millennial-scale climate oscillations characteristic of MIS 2, 3 and 4 in the Greenland ice cores are readily seen in the sediment cores. These cores will provide an excellent archive of changes in North Atlantic deep water circulation recorded at Bermuda Rise.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2008
- Bibcode:
- 2008AGUFMPP13B1438C
- Keywords:
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- 3094 Instruments and techniques;
- 4901 Abrupt/rapid climate change (1605);
- 4962 Thermohaline;
- 4994 Instruments and techniques