Research Drilling Baruth (Saxonia)

A geophysical anomaly close to Baruth (east of Bautzen, Saxonia) caused by a concealed Tertiary maar was investigated by two research dillings in 1998. The maar hypothesis could be confirmed by the occurrence of debris flow deposits with basaltic bombs and scoria in the sediments and the proof of granodiorite breccia (collapse breccia) representing the van fill at the base of the research drilling “Baruth 1”. 

The research drilling “Baruth 1” revealed lake sediments between 50 m and 232 m, mostly diatomites with embedded turbidites, which document sediment deposition during stable lake period. Below, deposits of debris flow and turbidites of the early lake period follow and in depths greater 257 m collapse breccias as first sediment input after the eruption was found. This drilling reached a final depth of 279.6 m; core recovery was close to 100 percent. The results suggested by the seismic and gravity pre-site surveys were confirmed. Especially the high resolution reflection seismic profiles, recorded for the first time above such a structure, revealed an excellent image of the Baruth maar.

The spectral analysis of the electrical conductivity data, collected by the dipmeter tool in 1 cm sampling intervals, confirmed a period of 180.000 years for the deposition of the laminated lake sediments between 74 m and 186 m, being equal to a sedimentation rate of about 60 cm / 1000 a. Considering the more or less constant amount of turbidtites of 50 percent – being the proportion of sediments originated from suspension currents – the corrected sedimentation rate is in the order of 30 cm / ka. Fine laminated lake sediments were found in depths between 50 and 75 m. Only these deposits are suitable for further past-climate research. Especially abrupt climate changes during this period of Tertiary and their effect on the ecosystem shall be reconstructed in detail by partners in future. 

The research drilling “Baruth 2”, that was located at the margin of the maar structure and reached a final depth of 100 m, aimed at additional information about the genesis of the maar and the direction of sediment supply. The existence of a steep dipping magnetic body that was expected in about 80 m depth could not be confirmed.