Petr Pruner

Magnetic Record in Cave Sediments: A Review

Dating cave sediments by the application of the palaeomagnetic method – magnetostratigraphy – is a difficult and sometimes risky task, as the method is comparative in its principles and does not provide numerical ages. For dating clastic cave sediments and speleothems it is limited by the complex conditions occurring underground so that it is often necessary to combine it with other methods that offer supplementary absolute-, calibrate-, relative- or correlate-ages. Interpretation of magnetostratigraphic results faces other serious problems that may endanger palaeomagnetic studies in given caves if they are not detected. The sedimentary fills of a number of profiles are separated into individual sequences and cycles, divided by breaks in deposition (unconformities). The dynamic character of cave fill deposition is reflected in the start or termination of individual magnetozones at unconformities in a number of profiles. The general character of cave depositional environments with their numbers of post-depositional changes, hiatuses, reworking and re-deposition does not allow precise calculation of the temporal duration of individual interpreted magnetozones. All these factors contribute to the fact that exact calibration of the geometric characteristics of the magnetostratigraphic logs with the GPTS cannot be attained at all or only with problems, if it is not adjusted using results of other dating methods.