Experimentelle und Analytische Planetologie
Das ICDP Bohrprojekt Lake Bosumtwi, Ghana
The 1.07 Ma old excellently preserved Bosumtwi impact structure (diameter ~10.5 km) is one of only four
known craters associated with tektite strewn fields. It represents a unique archive for the paleo-climatic evolution in
an area for which only limited data exist. The ICDP Bosumtwi drilling project has two major scientific objectives,
i e., to obtain
(i) Detailed information on subsurface structure and fill of this large young impact structure, to correlate these
data with geophysical studies, to determine presence and composition of melt bodies in the crater fill, and to
perform comparative geochemical, isotopic and petrographic studies of impact lithologies, target rocks, and
Bosumtwi-related ejecta.
(ii) The complete one million years
paleo-environmental record in order to get a detailed understanding of long-term variations in the W. African
monsoon.
In summer and fall 2004, drilling, borehole
logging and geophysical studies, were performed. Two boreholes, to depths of 540 and 450 m, respectively,
were drilled in the deep crater moat, and on the outer flank of the central uplift as identified in seismic profiles.
During the sediment drilling phase, five drilling sites were occupied spanning a depth transect and a total of 14
separate holes were drilled. Total sediment recovery was 1.833 km. The new
research project started with on-site geology and core logging operations at the GFZ. It will focus on the study of
Bosumtwi impact melt products that originate according to current views during different stages of a cratering event
and by different mechanisms.
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