Standard Wireline Data Processing
DSDP operator and logging contractor: Scripps Institution of Oceanography
Hole: 494A
Leg: 67
Location: Guatemala Basin (tropical NE Pacific)
Latitude: 12° 43.01' N
Longitude: 90° 55.97' W
Logging date: May 1979
Sea floor depth ("bottom felt"): 5529 mbrf
Total penetration: 366.5 mbsf
Total core recovered: 100.31 m (30.49 % of cored section)
Oldest sediment cored: Nannofossil ooze and claystone (Late Cretaceous)
Lithologies: Diatomaceous mud, mud and mudstone. )Note: these are the only lithologies logged).
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 in December 2004.
| Tool string | Pass | Top depth (mbsf) | Bottom depth (mbsf) | Bit depth (mbsf) | Notes |
| 1. CDL/GR |
|
126.7
|
178.3
|
127
|
Reference
|
| Temperature |
Downlog
|
85.8
|
184.6
|
|
|
According to the DSDP Site Report of Hole 794A (Operations), logging was abandoned after 1.5 days of operations because all the logging tools were malfunctioning. Data, however was recorded on tape, though the quality of the data itself is poor, and is presented in the DSDP online database.
The depths in the table are for the processed logs (after depth shift to the sea floor).
Depth shift to sea floor: No depth matching was necessary as only 1 pass was recorded. Because no log reached the sea floor, the CDL/GR and Temperature logs were depth shifted to the sea floor by using the "bottom felt" depth given by the drillers. (- 5529 m).
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). In the case of Hole 494A, only one very short pass was recorded and the data appears to be of poor quality.
Hole diameter was recorded by the hydraulic caliper on the CDL tool (CALI); the tool appears to have malfunctioned during data acquisition and gives no information on the conditions 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 67. For further questions about the logs, please contact:
Cristina Broglia
Phone: 845-365-8343
Fax: 845-365-3182
E-mail: Cristina Broglia