Geologic Magnetic Data Processing


ODP logging contractor: LDEO-BRG

Hole: 1093D

Leg: 177

Location: Shona Ridge (Antarctic Ocean)

Latitude: 49° 58.5907' S

Longitude: 5° 51.9338' E

Logging date: January, 1998

Bottom felt: 3635 mbrf

Total penetration: 597.7 mbsf

Total core recovered: 160.4 m (34.7 %)



GHMT Logging Runs


Two passes (main and repeat) were recorded. The total induction (MAGB) measurement was out of range for the tool in this location, so no reliable MAGB data was recorded. The magnetic susceptibility (MAGS) record, however, is of good quality: data is from the main pass, open-hole section (65.8-560 mbsf).

Wireline heave compensator was used to counter ship heave.


Hole Conditions


For most of the logged interval, the borehole is wider than 18 inches (the maximum extent of the caliper tool), except for the intervals 240-290 and 380-460 mbsf, where the hole narrows to 13 and 16 inches respectively. The raw susceptibility has been corrected for these hole diameter variations.


Depth shift


The GHMT logs have been interactively depth shifted with reference to HNGS from DIT/APS/HLDS/HNGS run and to the sea floor (- 3637.5 m). This value corresponds to the sea floor depth shown on the DIT/APS/HLDS/HNGS logs and differs 2.5 m from the "bottom felt" depth given by the drillers. A list of the amount of differential depth shifts applied at this hole is available upon request.


Additional information about the logs can be found in the "Explanatory Notes" and Site Chapter, ODP IR volume 177. For further questions about the logs, please contact:


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