Site 999 was positioned near the crest of Kogi Rise based on the images from multichannel seismic (MCS) Line CT1-12a. One of the objectives at Site 999 was to reach volcanic basement and sample oceanic plateau crust in the Colombian Basin for the first time. Although this objective was not obtained, Site 999 is fully cased to ~525 meters below seafloor (mbsf), reaches a total depth of 1066.4 mbsf, and remains a high-priority target for future investigations of large igneous provinces through scientific drilling.
Downhole log-generated synthetic seismograms are used to determine total two-way traveltime (TWT) reached at Site 999 and to estimate total depth to volcanic basement in preparation for future drilling at this Ocean Drilling Program "legacy" site. The results of these depths and TWT estimates are compared to those made using MCS velocity analyses and velocities measured on recovered cores.
Correlations between synthetic seismograms and observed MCS data indicate that volcanic basement at Site 999 lies at ~1420 mbsf, within the range predicted from MCS data and slightly shallower than estimated by laboratory velocity measurements.
1Leckie, R.M., Sigurdsson, H., Acton, G.D., and Draper, G. (Eds.), 2000. Proc. ODP, Sci. Results, 165 [Online]. Available from World Wide Web: <http://www-odp.tamu.edu/publications/165_SR/165TOC.HTM>. [Cited YYYY-MM-DD]
2University of North Carolina, 601 South College Road, Wilmington, NC 28403-3297, U.S.A. abrams1@uncwil.edu
Date of initial receipt: 24 June 1998
Date of acceptance: 29 April 1999
Ms 165SR-028