The occurrence and origin of Late Paleozoic remagnetization in the sedimentary rocks of North America

Abstract

Although it has been known for 25 years that some Paleozoic sedimentary rock units in Europe and North America were remagnetized during Pennsylvanian or Permian time, it is only very recently that the complex and widespread nature of the late Paleozoic remagnetization phenomenon has been generally acknowledged. It is now recognized that many Paleozoic paleomagnetic poles for North America that were once considered reliable are in fact the result of remagnetization, and as a consequence the paleomagnetic data base for the Paleozoic is undergoing rapid and drastic revision. The causes of late Paleozoic remagnetization in North America are currently the focus of much interest and active research. The remagnetization can reside in either hematite or magnetite, and different remagnetization mechanisms have been important in different settings. Chemical remagnetization processes, some related to specific diagenetic events, are dominant in hematite‐bearing sandstones and carbonates. In magnetite‐bearing carbonates both chemical and thermoviscous remagnetization processes appear to have been important, but it is difficult to determine which process is the dominant one in some settings. Some of the observed remagnetizations can be linked to the migration of chemically active and perhaps hot fluids during the mountain‐building events that affected much of the continent during the late Paleozoic. Paleomagnetic studies promise to be important in assessing the role of orogeny in driving fluid migrations within sedimentary basins and in constraining the age of the migrations and the nature of the fluids.