全球变化知识资源中心

Anisotropy of magnetic susceptibility (AMS) measurements, a commonly used method, has been applied in loess to determine the dominant palaeowind direction during the Pleistocene. During the last session of sampling and detailed magnetic investigation of the Early Middle Pleistocene loess/palaeosol succession at Paks (Hungary), 'irregular' (i.e. non-flow-aligned) magnetic fabrics (MFs) were revealed from sedimentary records having uniform sedimentary parameters. Knowledge about the origin of irregular loess fabrics is still limited, although they may carry additional palaeoenvironmental information. The appearance of irregular MF suggests that a constant set of palaeoclimatological conditions, as indicated by the layer characteristics, was interrupted by abrupt events. To characterize the unusual event horizons, the MF of the horizons and those of both the under-and overlying material were analysed and compared by rock magnetic methods, such as hysteresis, temperature dependence of magnetic susceptibility, and AMS.

The analysis separated three types of irregular fabrics and revealed three scenarios that might have been responsible for the forming of the irregular MF: abrupt climate changes, including rapid (catastrophic) weather events (e.g. intensification of strong wind-or water-lain processes); short-term pedogenesis during glacials; and post-depositional deformation triggered by mass movements or seismic activity.