The Holocene Tüttensee meteorite impact crater in southeast Germany

by Chiemgau Impact Research Team (CIRT) *

1 Introduction

2 Lake Tüttensee - topography and target rocks

3 Geologic setting

The Tüttensee ejecta layer

4 Geophysics

Gravity survey

Soil magnetic susceptibility measurements

5 Shock metamorphism

Shock in the Tüttensee rim wall

Shock in the Tüttensee Bunte breccia layer

6 Summary and the Tüttensee impact cratering process

Summary

The impact cratering process

7 Discussion

Competing glacial model

8 Conclusions

References

Abstract. The 400 m-diameter Lake Tüttensee in southeast Germany is the largest crater in the strewn field of meteorite craters that formed in the Holocene Chiemgau impact event possibly in the 6^th or 5^th century BC. The crater was excavated from a Quaternary target of predominantly moraine and fluvioglacial material and is surrounded by an 8 m-height rim wall and an extensive ejecta blanket. The up to 1 m thick ejecta layer is a polymictic breccia containing heavily fractured cobbles and boulders of Alpine lithologies and is rich in organic material like wood, charcoal, animal bones and teeth. Extremely corroded silicate and carbonate clasts in the breccia point to carbonate melting/decarbonization and/or dissolution by nitric acid. The ejecta layer has conserved an underlying fossil soil rich in organic material, too. A gravity survey reveals a zone of relatively positive anomalies around Lake Tüttensee interpreted by impact shock densification of the highly porous target rocks. Abundant, although moderate, shock metamorphism is observed to occur in clasts from the rim wall and the ejecta layer. An impact cratering process is able to explain all observed features that are completely inconsistent with a formation of Lake Tüttensee by glacial processes.