Magnetostratigraphy of the Hettangian Langmoos section (Adnet, Austria): evidence for time-delayed phases of magnetization

Abstract : Study of the magnetostratigraphy of the earliest Jurassic (mainly Hettangian) section of Langmoos near Adnet in Austria (Northern calcareous Alps) provides a sequence of 10 magnetic polarity intervals. These intervals are often evident in the natural remanent magnetization. However, rather than a true magnetostratigraphic sequence , palaeomagnetic analyses reveal evidence for successive phases of mag-netization within the section. Evidence includes (1) changes in lithology associated with changes in magnetic polarity, (2) different combinations of components of both polarities, and (3) largely non-antipodal directions. Considering the palaeomagnetic directions, we suggest that the apparent magnetostratigraphy is the result of two or three phases of magnetization which occurred at different stages of the tectonic emplacement of the Northern Calcareous Alps.