The Late Devonian paleomagnetic field for southeastern Australia: A new result for the Lochiel Formation and a reassessment of results from the Catombal Group


  • B. J. J. Embleton,

  • J. Shepherd


Paleomagnetic results from a new investigation of the Upper Devonian Lochiel Formation from southeastern Australia contrast with results obtained previously. Five flow units yielded a mean direction of magnetic remanence, stable to alternating field treatment, with declination D = 331° and inclination I = 10°. Secondary components of magnetization acquired approximately parallel to the mid-Carboniferous field and the present field were retained after alternating field treatment on specimens from two more flow units. These results are compared with results obtained by the vector reduction technique for isolating primary components from the Upper Devonian Catombal Group. Reassessment of those data shows that corroboration of the earlier results for the Lochiel Formation was fortuitous; they, in fact, support results obtained through this new study. Preliminary observations of the Lochiel volcanics and the overlying Merrimbula Group sediments suggest that they are extensively deformed into zigzag monoclinal folds. The dispersion that remained after correction for bedding tilt can be attributed to an incomplete understanding of the deformational phases in the region.