Standard Wireline Data Processing
DSDP operator and logging contractor: Scripps Institution of Oceanography
Hole: 493
Leg: 66
Location: Mid America Trench (central NE Atlantic)
Latitude: 16° 22.86' N
Longitude: 98° 55.53' W
Logging date: April 1979
Sea floor depth ("bottom felt"): 675 mbrf
Total penetration: 670.5 mbsf
Total core recovered: 337.3 m (61 % of cored section)
Oldest sediment cored: Sandstone (Early Miocene)
Lithologies: Muddy silt, limestone, sandstone (sediments); diorite (basement)
The logging data was recorded by Gearhart-Owenn 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. Temperature |
Downlog
|
0
|
176
|
103
|
|
A temperature log was recorded after two attempts to release the bit failed. The drill pipe was pulled to leave only the bottom hole assembly in the hole; the logging tool was lowered through the bit but failed to reach total depth at 670 mbsf. Data was recorded open hole from 103 to 1 76 mbsf.
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.
A good temperature log was recorded through pipe from 0 to 103 mbsf and open hole to 176 mbsf.
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 66. For further questions about the logs, please contact:
Cristina Broglia
Phone: 845-365-8343
Fax: 845-365-3182
E-mail: Cristina Broglia