Standard Wireline Data Processing
DSDP operator and logging contractor:Scripps Institution of Oceanography
Hole: 542B
Leg: 78A
Location:
Latitude: 15° 31.198' N
Longitude: 58° 42.793' W
Logging date: February 1981
Sea floor depth ("bottom felt"): 5026 mbrf
Total penetration: 323 mbsf
Total core recovered: none
Lithologies: calcareous ooze, clayey mudstone with ash beds (from Holes 542 and 542A)
The logging data was recorded by Gearhart-Owen in GO format and subsequently translated into LIS format. Data were processed at the Borehole Research Group of the Lamont-Doherty Earth Observatory.
| Tool string | Pass | Top depth (mbsf) | Bottom depth (mbsf) | Bit depth (mbsf) | Notes |
| 1. CDL/TEMP/GR |
Downlog
|
23.6
|
229.2
|
|
Temperature
tool only
|
Because any attempt to raise the BHA and pipe had failed, a through-pipe Temperature log was run in an attempt to document the flow of water into the hole.
The depths in the table are for the processed logs (after 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 temperature log was depth shifted to the sea floor (- 5026 m). The sea floor depth corresponds to the "bottom felt" depth given by the drillers, as the temperature log did not cross the mudline.
The quality of the data is usually 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). In the case of Hole 542B, only the temperature log was recorded, thus no comparison could be performed.
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 78A. For further questions about the logs, please contact:
Cristina Broglia
Phone: 845-365-8343
Fax: 845-365-3182
E-mail: Cristina Broglia