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Williams, Trevor; Louvel, Véronique; Lauer-Leredde, C (2002): (Table T2) Remanent anomaly and Koenigsberger ratio of ODP holes. PANGAEA,, Supplement to: Williams, T et al. (2002): Magnetic polarity stratigraphy from downhole logs, West Antarctic Peninsula, ODP Leg 178. In: Barker, PF; Camerlenghi, A; Acton, GD; Ramsay, ATS (eds.) Proceedings of the Ocean Drilling Program, Scientific Results, College Station, TX (Ocean Drilling Program), 178, 1-23,

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Magnetic field strength and magnetic susceptibility were logged with the geological high-resolution magnetic tool (GHMT) at three of the holes drilled during Ocean Drilling Program Leg 178 to the west of the Antarctic Peninsula. Polarity stratigraphies derived from the GHMT logs bear close resemblance to the polarities determined from core paleomagnetism at two of the holes and were used for magnetostratigraphic dating, especially in intervals where no core was recovered.
Polarity is determined in the following way. First, the susceptibility log is used to determine the induced magnetization of the sediment. Then the background field, the field of the metal drill pipe, and the field anomaly of the sediment's induced magnetization are removed from the measured total field to leave the downhole anomaly of the sediment's remanent magnetization. The sign (positive or negative) of this anomaly gave a good polarity stratigraphy for Holes 1095B and 1096C, which are located in sediment drifts. A further step, correlation analysis, is based on the fact that in an interval of normal polarity sediment the remanent anomaly will correlate with the induced anomaly, whereas in reversed polarity sediment they will anticorrelate.
The magnetite-rich, fine-grained sediments found in the two holes drilled into the sediment drift have a ratio of remanent to induced magnetization (the Koenigsberger ratio) of ~1. In contrast, the coarser-grained diamict sediments on the shelf have a Koenigsberger ratio of ~0.2, and extracting the remanent part of the downhole anomaly is much more difficult.
By the comparison of core and log results, we can assess the viability of the GHMT polarities in detail, what proportion of the overprint in the cores is imparted by the coring process, and whether any paleointensity information is extractable from the GHMT logs.
Median Latitude: -1.970240 * Median Longitude: 20.370108 * South-bound Latitude: -67.696160 * West-bound Longitude: -78.487820 * North-bound Latitude: 77.340600 * East-bound Longitude: 168.336900
Date/Time Start: 1992-08-16T18:45:00 * Date/Time End: 2000-02-21T16:00:00
Minimum DEPTH, sediment/rock: 86.0 m * Maximum DEPTH, sediment/rock: 480.0 m
145-883F * Latitude: 51.198400 * Longitude: 167.768100 * Date/Time Start: 1992-08-16T18:45:00 * Date/Time End: 1992-08-20T04:30:00 * Elevation: -2397.0 m * Penetration: 849.4 m * Recovery: 13.58 m * Location: North Pacific Ocean * Campaign: Leg145 * Basis: Joides Resolution * Method/Device: Drilling/drill rig (DRILL) * Comment: 3 cores; 29.4 m cored; 0 m drilled; 46.2 % recovery
145-884E * Latitude: 51.450600 * Longitude: 168.336900 * Date/Time Start: 1992-08-26T01:45:00 * Date/Time End: 1992-08-31T12:30:00 * Elevation: -3836.0 m * Penetration: 929.8 m * Recovery: 66.78 m * Location: North Pacific Ocean * Campaign: Leg145 * Basis: Joides Resolution * Method/Device: Drilling/drill rig (DRILL) * Comment: 10 cores; 87 m cored; 0 m drilled; 76.8 % recovery
162-986C * Latitude: 77.340600 * Longitude: -9.077780 * Date/Time Start: 1995-08-11T14:25:00 * Date/Time End: 1995-08-14T15:05:00 * Elevation: -2052.0 m * Penetration: 408 m * Recovery: 229.78 m * Location: North Greenland Sea * Campaign: Leg162 * Basis: Joides Resolution * Method/Device: Drilling/drill rig (DRILL) * Comment: 44 cores; 408 m cored; 0 m drilled; 56.3 % recovery
#NameShort NameUnitPrincipal InvestigatorMethod/DeviceComment
1Event labelEvent
2DEPTH, sediment/rockDepthmGeocode
3Depth, top/minDepth topmWilliams, Trevor
4Depth, bottom/maxDepth botmWilliams, Trevor
5Petrography descriptionPetrogr descrWilliams, Trevor
6Remanent anomalyBfrnTWilliams, Trevor
7Remanent anomaly, standard deviationBfr std dev±Williams, Trevor
8Koenigsberger ratioQ-ratioA/mWilliams, Trevor
9Koenigsberger ratioQ-ratioA/mWilliams, Trevorlatitude corrected
70 data points

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