The Matuyama-Brunhes boundary interval (500-900 ka) in North Atlantic drift sediments

Abstract

Ocean Drilling Program (ODP) sites 984 and 983, located on North Atlantic sediment drifts, provide high-resolution records across the Matuyama-Brunhes boundary. At ODP site 984 (Bjorn Drift, Iceland Basin), the mean sedimentation rate in the 500-900 ka interval is ∼12 cm kyr-1 based on an age model derived by matching the planktonic and benthic oxygen isotope records to an Ice Volume Model. The Matuyama-Brunhes polarity transition at site 984, as defined by virtual geomagnetic polar (VGP)latitudes <50°, has an apparent duration of ∼ 7 kyr with a mid-point at 773.5 ka, compared with 772.5 ka at neighbouring site 983. Outside the polarity transition at both sites 984 and 983, excursions in VGP latitudes, to values <20°, at 540, 590 and 670 ka correspond to troughs in the palaeointensity record. New u-channel palaeomagnetic data across the Matuyama-Brunhes boundary, for working and archive halves of core sections from three holes at both sites 984 and 983, augment data published by Channell & Lehman (1997) and are compared with back-to-back 1 cm3 discrete samples. Clusters of VGPs in the South Atlantic and northeast Asia in both u-channel and discrete sample records imply that polarity transition fields have characteristics similar to the modern non-axial-dipole (NAD) field. © 2004 RAS.