163 Preliminary Report

Site 989

After a series of repairs to our top drive and related rig hardware in Reykjavik, we transited back to the more southerly EG63 transect. A brief 3.5-kHz survey completed over the site along the track of seismic line GGU/EG92-24/1 covered proposed Sites EG63-6 and EG63-5. The seismic record suggested that 5-10 m of sediment lay on top of the lava flow sequence and that this was sufficient to allow spudding in the RCB.

Hole 989A

The beacon marking the site was dropped by Global Positioning Sysytem (GPS) coordinates at 1445 GMT on September 16. The beacon prereleased, requiring deployment of a second beacon. The strong southerly current in the area caused this second beacon to drift 150 m aft of the deployment point. Because of the shallow water in the region (459.5 m), it was necessary to offset north of the location and drop a third beacon at 1455 GMT. This deployment was successful.

Because of the near-hard-rock spudding, a shorter and more flexible BHA (6-collar) utilizing a mechanical bit release (MBR) was used. Initial sediment penetration was made without the benefit of a video camera. Hole 989A was spudded at 2000 GMT at 63°31.355'N and 39°54.113'W. After quickly drilling 3 m, the rate of penetration dropped signifiantly. Recovery of the first core revealed that a large, gneissic glacial erratic boulder had been cored, followed by massive basalt.

Another two cores were drilled to 21.4 mbsf before an iceberg forced the ship to abandon operations. At 1100 GMT on 17 September, an iceberg estimated to be 100 m wide and 15 m high approached within 3.5 nmi of the vessel. The Gadus Atlantica was directed to attempt to tow the iceberg away from the JOIDES Resolution. Shortly after the first attempt at towing the iceberg had failed, instructions were given to the drill crew to deploy a free-fall funnel. After four attempts, the Gadus Atlantica was still unable to snare the iceberg with a towing line.

With the iceberg at distance of 1.5 nmi and closing at 1-2 kt, coring was suspended and the bit raised to 14 mbsf. Attempts to lasso the iceberg possibly influenced its course, which suddenly appeared to change, directing it toward the JOIDES Resolution. The change in the path of the iceberg surprised the drilling crew, who were unable to pull the drill pipe from the hole because the elevators and rotary bushing had been set back in preparation to deploy a free-fall funnel. With the iceberg at 0.5 nmi, the Captain gave instructions to offset the vessel 800 m astern, dragging the BHA and bit out of the hole. The iceberg passed within 100 m of the JOIDES Resolution and cleared the vessel to port.

The core barrel was retrieved with no difficulty or drag, which implied that the drill string was not bent. The bit was tripped to the surface, and the drill string and BHA were inspected and found to be in good condition. A new, harder formation C-7 bit was then substituted for the C-4 bit, and three additional drill collars were added to the BHA to add weight.

Hole 989B

An attempt was then made to reenter Hole 989A. Although the iceberg prevented us from deploying a free-fall funnel, the Hole 989A crater was easily detected on the TV camera, as was a noticeable furrow leading away from the hole that resulted from dragging the BHA out of the hole. After several unsuccessful attempts to reenter Hole 989A, Hole 989B was spudded at 2400 GMT on 17 September, at 63°31.355'N and 39°54.110'W. The hole was then washed down to 4 mbsf, where contact was made with basalt.

Because of the light weight on bit (2-4 thousand pounds), the first core took 420 minutes to advance 5.2 m. When the barrel was retrieved, it contained 4.6 m of basalt. Continuous rotary coring then advanced slowly but with spectacular recovery to 74 mbsf (97% of the cored interval), where the basalt noticeably hardened and recovery lowered.

A free-fall funnel was deployed when the depth of the hole reached 21 mbsf. After 52 rotating hours were accumulated, the drill string was tripped to the surface from 84 mbsf to change the bit. The video camera was deployed to observe the retraction of the drill bit out of the hole and ensure that the free-fall funnel was not moved during the process.

Instead of replacing the bit and reentering Hole 989B, we decided to temporarily cease operations at this site and move to the next site. This was done because northwest winds were driving ice to within 4 nmi of the site. The forecast from the Danish Meteorological Society (DMI) indicated that strong winds were expected to continue from this sector for the next couple of days, which implied that the ice threat would only increase at this location. At 1930 GMT on 20 September, the vessel was dynamically offset 5 nmi to the southeast to begin operations at Site 990.

To Operations Site 990

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