Palaeomagnetic records of the Brunhes/Matuyama polarity transition from ODP Leg 124 (Celebes and Sulu seas)

• Published in: Geophysical Journal International
• Main Authors: Oda, Hirokuni, Shibuya, Hidetoshi, Hsu, Vindell
• Format: Text
• Language: English
• Published: Oxford University Press 2000
• Subjects: Articles; Pacific; New Zealand; North Atlantic
• Online Access: http://gji.oxfordjournals.org/cgi/content/short/142/2/319; https://doi.org/10.1046/j.1365-246x.2000.00130.x

Palaeomagnetic records of the Brunhes/Matuyama geomagnetic polarity transition were obtained from deep‐sea sediments of ODP Leg 124 in the Celebes and Sulu seas. Advanced piston core (APC) samples with high magnetization intensities (2–200 mA m−1 ) and high sedimentation rates (8.4–10 cm kyr−1 ) were recovered from this cruise. Rock‐magnetic measurements revealed the carrier of the remanence to be nearly pure magnetite in the pseudo‐single‐domain range. Pass‐through measurements at intervals of 5 mm on APC cores across the Brunhes/Matuyama polarity transition for Holes 767B, 769A and 769B were deconvolved with the magnetometer sensor response using the ABIC‐minimizing method. Discrete samples were also taken from the polarity transition zones and subjected to either thermal or alternating field stepwise demagnetization. The results were generally consistent with the pass‐through data after the deconvolution. Results from the three holes are in good agreement, particularly those from the two holes 100 m apart at Site 769. The transitional VGP paths from these two holes show two small loops near New Zealand before the equator is crossed. The VGPs continue to swing eastwards to the North Atlantic and then move to the northeastern margin of the Pacific Ocean. The positions of the VGP loops obtained from Site 769 are different from the VGP clusters obtained from both the known volcanic records and the sediment records at the Boso Peninsula and the North Atlantic sites with high sedimentation rates. Such a difference may imply the predominance of the non‐dipole field during the transition. Relatively stable mid‐high northern latitude VGPs are recognized on all three cores just after the reversal, lasting about 4000 years. The plot of relative intensity versus VGP latitude for the sediment records from the North Atlantic (DSDP Hole 609B) shows a remarkable similarity with our records. Similar patterns were also obtained for the plot of the palaeointensity versus VGP latitude for the La Palma volcanic lava records. ...