Comment on “New Late Pennsylvanian Paleomagnetic Results From Paraná Basin (Southern Brazil): Is the Recent Giant Gaussian Process Model Valid for the Kiaman Superchron?” by Brandt et al.

Abstract

The late Pennsylvanian glacial rhythmites of the Mafra Formation (Itararé Group) from the Paraná Basin of Southern Brazil, have a complex rock-magnetic signature. Rock-magnetic tests imply that both hematite and magnetite in varying grain sizes are responsible for the magnetic remanence. Thermal and alternating field (AF) demagnetization of the natural remanence reveal different behaviors that are attributed to a mixture of remanence-carrying magnetic minerals and grain sizes, implying a series of magnetic overprints. A great circle analysis of the distribution characteristic directions reported suggests that these rocks may not be entirely immune from magnetic overprints acquired during the Jurassic-Cretaceous in the context of widespread remagnetizations in South America. The nature of the magnetization recorded by these rocks warrants caution in their use for the evaluation of paleosecular variation models.