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

Abstract

SUMMARY 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 cm 3 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.