A statistical enquiry into the partial remagnetization of folded old red sandstone rocks

Abstract

The directions of natural remanent magnetization of Old Red Sandstone rocks from five sites in south Wales where the strata are steeply inclined to the horizontal are significantly different from the average direction of magnetization of Old Red Sandstone rocks from flat-lying sites. The hypothesis, that the observed directions of magnetization are resultants of a primary component acquired in the Devonian and a secondary component acquired after folding, either in the Permian or Triassic, is shown to be tenable. A statistical technique, whereby the significance of the normal to the best-fitting plane through the observed and the supposed primary and secondary mean directions, is described. Ovals of confidence surrounding these normals are also calculated. Partial remagnetization of these rocks is shown to be slightly more probable in the Triassic than in the Permian at four out of five sites considered.