This is the last Daily Message for the Chesapeake Bay Impact Crater Drilling Project. The close-down of the drill site proceeded rapidly during December 6-9. All of the drilling equipment was removed from the site before noon on December 9. Trailers, dumpsters, and other ancillary equipment will be removed during the week of December 12. We thank all of you for your interest in this project.
Coring ended at about 8:00 a.m., local time, on December 4 at a final depth of 5,795 ft (1.1 miles, 1.77 km). Geophysical logging began soon after the end of coring.
The drill bit moved below 5,675 ft (1,730 m) on December 1. The decision has been made to finish coring and start geophysical logging on Sunday, December 4.
The drill bit passed below the mile mark (5,280 ft, 1,609 m) in the early afternoon of November 23 as coring continued in lithic breccia and larger lithic clasts. Additional drilling funds have been received by the Project from ICDP, USGS, and the Solar System Division of the NASA Science Mission Directorate. Coring is now expected to continue into the early days of December.
The drill bit reached a granitic rock at a depth of about 3,600 ft (1,100 m) in the early morning of October 26. The drillers have switched to an NQ bit and rods with the HQ rods now serving as casing.
Finally, the drill bit passed below the previous bottom of the hole at 3,087 ft (941 m). The bit reached a depth of 3,101 ft (945 m) during the evening on October 20.
The drill bit passed below a depth of 2,900 ft (884 m) during the early evening of October 18. Several days ago, the bit deviated from the original hole near a depth of 2,400 ft (732 m). We have been collecting ?bonus? cores below that depth in the second
We continued moving down toward the previously drilled bottom of the corehole, reaching below a depth of 2,700 ft (823 m) late in the day on October 16.
We are continuing our efforts to return to the bottom of the corehole at a depth of 3,087 ft (941 m). Progress has been steady but very slow during the past three days.
Drilling problems have continued in the lower part of the Exmore breccia through October 11. Blocks of Cretaceous red clay continue to slide or expand into the drill hole, requiring repeated reaming in the same intervals, repeated loss of mud circulation, and an inability to return to the bottom of the hole. A new drilling strategy will be determined in the coming days to address these problems.
Coring continued on October 8 to a depth of 3,087 ft (941 m) until mud circulation was lost during the early evening. Efforts to restore the mud flow by pulling the rods and reaming problem intervals continued to midnight on October 9.
The drill rods were pulled from the hole at mid-day on October 6, and a new drill bit and reaming shell were installed. The drill hole was reamed as the rods were replaced in the hole, and coring during did not resume until the early morning hours of October 7. The coring bit passed a depth of 3,000 ft (914 m) at midnight on October 7.
Coring continued in the sediment-clast breccia below a depth of 2,700 ft (823 m). The Eyreville corehole is now the deepest test hole in the Chesapeake Bay impact crater.
The drill string was pulled from the hole to investigate the reason for slow drilling during the past several days. The HQ bit proved to be badly worn (see photograph) and was replaced. The drilling rate significantly improved with the new bit.
During the afternoon of September 23, the PQ-size drill string became stuck in the hole following the loss of mud circulation due to mud collars on the drilling rods. We are addressing this problem by using the PQ rods as casing and proceeding with the smaller HQ rods and sampling system.
We are continuing to make good progress in coring the Exmore breccia within the upper part of the crater section. Coring reached a depth of 1,850 ft (564 m) in the late evening of September 22nd.
The drill bit penetrated the top of the crater impactite section during the late afternoon of 20 September 2005. Since then, we have been drilling in the sediment-clast breccias of the Exmore breccia. The drill bit penetrated below a depth of 1,500 ft (457 m) during the late evening of September 20.
The drilling rate has slowed somewhat within the upper Eocene Chickahominy Formation; however progress and core recovery remain very good. We have reached a depth of about 1,350 ft (411 m) at about 1830 hours, local time, on September 19.
We have reached a depth of 1,148.3 ft within post- impact lower Miocene or Oligocene sediments as of 1:00 pm local time on September 18. Core recovery has been excellent.
Coring is continuing in the post-impact Miocene sedimentary section with excellent recovery. We are at a depth of about 245 m as of 1600 hours local time.
The drilling of the ICDP-USGS deep corehole into the Chesapeake Bay impact crater began during the afternoon of September 15. Coring began at about 420 ft depth in post-impact upper Miocene sediments.