Standard Wireline Data Processing
DSDP operator and logging contractor: Scripps Institution of Oceanography
Hole: 70A
Leg: 8
Location: Clipperton Fracture Zone (tropical central S Pacific)
Latitude: 6° 20.08' N
Longitude: 140° 21.72' W
Logging date: October 1969
Sea floor depth: 5059 mbrf
Sea floor depth (step in electrical log): 5059 mbrf
Total penetration: 331.2 mbsf
Total core recovered: 146 m (67 % of cored section)
Oldest sediment cored: middle Eocene
Lithologies: radiolarian and nannofossil oozes.
The logging data was recorded by Welex in analog format only. The data was digitized by Centerline Data in 2004 and processed at the Borehole Research Group at the Lamont-Doherty Earth Observatory in July 2004.
| Tool string | Pass | Top depth (mbsf) | Bottom depth (mbsf) | Bit depth (mbsf) | Notes |
| 1. EL |
uplog
|
0
|
329.8
|
Recorded open hole
|
According to the DSDP Site Report "A Welex drill pipe electric log was run as the drill pipe was pulled on Hole 70A". It is unclear what the sentence means, as at the time there was no technology available in ocean drilling to pull a pipe and log at the same time. Based on the log values, however, it looks like the log was recorded open hole,
The depths in the table are for the processed logs (after depth shift to the sea floor).
Depth shift to sea floor: The electrical log was depth shifted to the sea floor. The sea floor depth was determined by the step in resistivity values at 5059 mbrf, which corresponds to the sea floor depth given by the drillers (see above).
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). This type of assessment could not be performed in Hole 70A, as only one log was recorded.
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 8.
For any question about the data or about the LogDB database, please contact LogDB support: logdb@ldeo.columbia.edu.