Standard Wireline Data Processing
DSDP operator and logging contractor: Scripps Institution of Oceanography
Hole: 459B
Leg: 60
Location: Mariana Trench (Philippine Sea)
Latitude: 17° 51.75' N
Longitude: 147°18.09' E
Logging date: May 1978
Sea floor depth (Bottom felt): 4125.5 mbsf
Total penetration: 691.5 mbsf
Total core recovered: 182.14 m (26% of cored section)
Oldest sediment cored: silicified claystone (pre-Late Eocene)
Lithologies: mud and ooze with ash layers, turbidites and claystones (sediments); basalts (basement)
The logging data was recorded by Gearhart-Owen in analog form only. Data were digitized by Centerline Data in 2004 and processed at the Borehole Research Group of the Lamont-Doherty Earth Observatory in October 2004.
| Tool string | Pass | Top depth (mbsf) | Bottom depth (mbsf) | Bit depth (mbsf) | Notes |
| 1. CDL/GR |
Main
|
110.5
|
513
|
118.3
|
|
|
Repeat
1
|
436.5
|
517.2
|
|
|
|
|
Repeat
2
|
444.7
|
518
|
|
|
|
| Temperature |
Pass
1
|
4.5
|
522.7
|
|
Run with CDL
|
| 2. LL3 NL/GR |
Main
|
120.5
|
490.3
|
118.3
|
|
|
Repeat
|
438.5
|
499
|
|
|
|
| 3. IEL/GR |
Main
|
108.7
|
477.5
|
118.3
|
|
|
Repeat
|
419
|
478.2
|
|
|
|
| 4. Temperature |
Pass
2
|
0
|
474
|
|
|
The depths in the table are for the processed logs (after depth matching between passes and depth shift to the sea floor). Generally, discrepancies may exist between the sea floor depths determined from the downhole logs and those determined by the drillers from the pipe length. Typical reasons for depth discrepancies are ship heave, wireline and pipe stretch, tides, and the difficulty of getting an accurate sea floor from the "bottom felt" depth in soft sediment.
Depth match and depth shift to sea floor: The original logs were depth-matched to the GR log from the main pass of the IEL/GR tool string, and were then shifted to the sea floor (-4125.5 m).
Depth-matching is typically done in the following way. One log is chosen as reference (base) log (usually the gamma ray log from the run with the greatest vertical extent and no sudden changes in cable speed), and then the features in the equivalent logs from the other runs are matched to it in turn. This matching is performed manually. The depth adjustments that were required to bring the match log in line with the base log are then applied to all the other logs from the same tool string.
The sea floor depth could not be determined by the step in gamma ray values because none of the tool strings (except the temperature) reached the mudline. The "bottom felt" depth provided by the drillers was used instead. This is also the amount used to depth shift the cores.
The quality of the data is assessed by checking against reasonable values for the logged lithologies, by repeatability between different passes of the same tool, and by correspondence between logs affected by the same formation property (e.g. the resistivity log should show similar features to the sonic velocity log). At Hole 359B there is a generally good correlation among the different logs.
A wide (>12") and/or irregular borehole affects most recordings, particularly those that CDL, NL). Hole diameter was recorded by the hydraulic caliper on the CDL tool. This shows a pretty smooth hole with values around 13 inches in the upper part of the logged interval and then gradual narrowing to about 10 inches with local enlargements in the lower part of the hole.
A null value of -999.25 may replace invalid log values.
Additional information about the drilling and logging operation can be found in the Operations section of the Site Chapter in DSDP Initial Reports volume 60. For further questions about the logs, please contact:
Cristina Broglia
Phone: 845-365-8343
Fax: 845-365-3182
E-mail: Cristina Broglia