Magnetic excursions in the late Matuyama Chron (Olduvai to Matuyama‐Brunhes boundary) from North Atlantic IODP sites

Abstract

AbstractThe sedimentary record of late Matuyama magnetic excursions, between the end of the Olduvai Subchron and the Matuyama‐Brunhes boundary, has relied on North Atlantic Ocean Drilling Program (ODP) Sites 983/984, and individual recordings at ODP Site 1021 from the California Margin, and Core MD972143 from the west Philippine Sea. North Atlantic IODP Sites U1305, U1306, U1307 (Eirik Drift, off SE Greenland), and Site U1308 (central Atlantic) provide new records from u‐channel samples and discrete (8 cm3) cubic samples, collected from multiple holes drilled at each site. The results confirm the existence of the Intra‐Jaramillo, Punaruu, Bjorn, Gardar, and Gilsa excursions and possibly the Kamikatsura excursion. These excursions are not recorded at all sampled sites, although they do correspond to excursions recorded at ODP Sites 983/984 and to relative paleointensity minima recorded at all studied sites. For some records, including that of the Bjorn excursion (1251 ka), antipodal magnetization directions yield virtual geomagnetic poles that reach high northern latitudes, implying that the excursion involved reversal of the main axial dipole field. On the other hand, excursions are often partially and inadequately recorded, attributable to a combination of the brevity of geomagnetic excursions, bioturbation, and filtering of the magnetization signal by the detrital remanent magnetization acquisition process, nonuniform sedimentation rates at millennial/centennial scales, and possibly unrecognized drilling/sampling disturbance.