Anna Losiak^1,2, Eva Maria Wild³, Leonard Michlmayr³, Christian Koeberl^1,4

¹Department of Lithospheric Research, University of Vienna, Vienna, Austria
²Institute of Geological Sciences, Polish Academy of Sciences, Wrocław, Poland
³VERA Laboratory, Faculty of Physics, Isotope Research and Nuclear Physics, University of Vienna, Vienna, Austria
⁴Natural History Museum, Vienna, Austria

Rocks from drill cores LB-07A (crater fill) and LB-08A (central uplift) into the Bosumtwi impact crater, Ghana, were analyzed for the presence of the cosmogenic radionuclide ¹⁰Be. The aim of the study was to determine the extent to which target rocks of various depths were mixed during the formation of the crater-filling breccia, and also to detect meteoric water infiltration within the impactite layer. ¹⁰Be abundances above background were found in two (out of 24) samples from the LB-07A core, and in none of five samples from the LB-08A core. After excluding other possible explanations for an elevated ¹⁰Be signal, we conclude that it is most probably due to a preimpact origin of those clasts from target rocks close to the surface. Our results suggest that in-crater breccias were well mixed during the impact cratering process. In addition, the lack of a ¹⁰Be signal within the rocks located very close to the lake sediment–impactite boundary suggests that infiltration of meteoric water below the postimpact crater floor was limited. This may suggest that the infiltration of the meteoric water within the crater takes place not through the aerial pore-space, but rather through a localized system of fractures.

Reference
Losiak A, Wild EM, Michlmayr L and Koeberl C (in press) 10Be content in clasts from fallout suevitic breccia in drill cores from the Bosumtwi impact crater, Ghana: Clues to preimpact target distribution Meteoritics & Planetary Science
[doi:10.1111/maps.12256]
Published by arrangement with John Wiley & Sons

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