ODP logging contractor: LDEO-BRG
Hole: 1139A
Leg: 183
Location: Kerguelen Plateau (Antarctic Ocean)
Latitude: 50° 11.1030' S
Longitude: 63° 56.1918' E
Logging date: January, 1999
Bottom felt: 1427 mbrf (used for depth shift to sea floor)
Total penetration: 694.2 mbsf
Total core recovered: 356.6 m (51.4 %)

Logging Runs

Logging string 1: DIT/SDT/NGT
The wireline heave compensator was not operational in very rough seas.

Bottom-hole Assembly

The bottom-hole assembly is at 100.5 mbsf.

Processing

Depth shift: Original logs have been depth to the sea floor (- 1427 m). Depth mismatch between the different logs is difficult to account for, as any correlation is generally poor. Several attempts to account for this mismatch proved unsuccessful; thus the data must be used with caution.

Gamma-ray processing: NGT could not be corrected for borehole size due to the lack of a caliper measurement.

Acoustic data processing: Due to the lack of eccentralization, heave compensation and possibly enlarged hole (no hole diameter was measured), the SDT data, recorded in depth-derived, borehole compensated long spacing sonic mode are of poor quality, particularly below 475 mbsf. Using two sets of the four transit time measurements and proper depth justification, four independent measurements over a -2ft interval centered on the depth of interest are determined, each based on the difference between a pair of transmitters and receivers. The program discards any transit time that is negative or falls outside a range of meaningful values selected by the processor. Even after thorough editing and processing from the four transit times, the results yield unreliable information about the true acoustic properties of the lithologies drilled. The results should be used with extreme caution particularly in the interval below 500 mbsf. Processing of the sonic waveforms is recommended in order to get more reliable results.

Quality Control

null value=-999.25. This value may replace recorded log values or results which are considered invalid
During the processing, quality control of the data is mainly performed by cross-correlation of all logging data. In hole 1139A correlation is difficult, even between curves recorded by the same tool (i.e. Dual Induction Tool) because the data is clearly affected by lack of heave compensation and by a possibly large hole. The deep resistivity channel (IDPH) seems to be the least affected by borehole disturbance because of it deeper depth of investigation and is recommended over the other two shallow measurements.
Data recorded through bottom-hole assembly, such as the gamma ray data above100 mbsf, should be used qualitatively only because of the attenuation on the incoming signal.

Additional information about the logs can be found in the "Explanatory Notes" and Site Chapter, ODP IR volume 183. For further questions about the logs, please contact:

Cristina Broglia
Phone: 845-365-8343
Fax: 845-365-3182
E-mail: Cristina Broglia