Paleomagnetism of the Marble Bar Chert Member, Western Australia: Implications for apparent polar wander path for Pilbara craton during Archean time

The Archean Biosphere Drilling Project (ABDP) drilled a continuous 270 m long oriented core from the Towers Formation, which includes the Marble Bar Chert Member (3456.1-3476.0 Ma) in the Pilbara craton, northwestern Australia. A paleomagnetic study of 261 discrete specimens, collected from a 158.5 to 182.0 m section of the Marble Bar Chert Member, revealed two distinct magnetic (LT and MT). The MT component yields seven different mean paleomagnetic directions clustered as MB1 to MB7. These, together with the published paleomagnetic poles of early Archean rocks from the Pilbana craton, draw a continuous paleomagnetic pole path, which likely to be regarded as the early to late Archean apparent polar wander path (APAT) for the Pilbara craton. The APWT implies that the Pilbara craton underwent a latitudinal drift of about 21 degrees during the interval when the magnetization of the Marble Bar Chert Member was acquired. The estimated speed of the lateral drift is 12-112 cm/yr (120-1120 km/Myr), which is large compared with current plate motion velocities, suggesting that continents might have moved during the Archean faster than in the Phanerozoic. (c) 2006 Elsevier B.V. All rights reserved.