Apparent tectonic rotations, declination anomaly equations, and declination anomaly charts

Abstract

The conventional method for tilt correction of paleomagnetic data assumes that rock bodies rotate about horizontal axes during deformations. Apparent tectonic rotations, which may produce anomalous declination readings of paleomagnetic directions and other linear elements, can result from the use of such a procedure if the rock bodies deform about inclined axes. The error (declination anomaly) resulting from two apparent tectonic rotations, 1) single rotations about an oblique axis and 2) continuous rotations about a precessing fold axis, can be determined algebraically for given orientations of rotation axis and angles of rotation. A declination anomaly chart (DAC) is constructed for each of the two processes to determine graphically whether anomalous paleomagnetic data obtained from a study area can result from the process. -from Author