Geophysics

Early geophysical earth magnetic field measurements (Fehr et al. 2002) across smaller craters revealed faint anomalies that could not be related with definite causative bodies so far. Meanwhile, more geomagnetic measurements have been performed in an exemplarily studied 11 m-diameter crater (Hoffmann et al. 2005) showing significantly enhanced magnetic susceptibilities compared with rocks from the surroundings. Moreover, strong magnetic dipole-like anomalies have been mapped matching well own observations: Outside the craters, the abundant occurrence of strongly magnetic rocks of quite different lithologies among the target rocks is conspicuous. The high, dominantly remanent magnetization seems to be unusual compared with typically magnetic rocks from the Alps (e. g., amphibolites, serpentinites). We suggest that these rocks might have acquired their magnetization as a thermoremanent magnetization in contact with the super-heated impact explosion cloud. More detailed investigations are required.

Soil magnetic susceptibility measurements in the Burghausen area within the so-called 1,000 years old forests (Hoffmann et al. 2004) also reveal substantially increased susceptibilities. A relation of these anomalies (comprising a maximum at depth and not at the surface) with industrial or geologic processes is basically excluded (Hoffmann et al. 2005). From our point of view, these susceptibility anomalies originate from the gupeiite and xifengite magnetic phases widely distributed in the undisturbed soil and deposited in the course of the impact process.

Preliminary pulse-electromagnetic soundings across a 20 m-diameter crater show a signature of larger metallic objects at depth in the center of the structure. A human contamination may of course be responsible and, therefore, a closer inspection is required.

Fig. 1. Equipment for gravity measurements (gravimeter).

A gravity campaign (Fig. 1) was conducted on the frozen Lake Tüttensee and in its surroundings. A remarkable result is hardly compatible with the previous assumption of a dead-ice origin of Lake Tüttensee. The complete article about the campaign (in German with English abstract and figure captions) may be clicked HERE.