TY - JOUR
T1 - Seismic investigation of the Lake Bosumtwi impact crater
T2 - Preliminary results
AU - Karp, Tobias
AU - Milkereit, Bernd
AU - Janle, Peter
AU - Danuor, Sylvester K.
AU - Pohl, Jean
AU - Berckhemer, Hans
AU - Scholz, Christopher A.
N1 - Funding Information:
This research was supported by the Deutsche Forschungsgemeinschaft (DFG), operating grants Ja 290/15-1, -2, Be 299/72-1, -2, -3, Po 156/11-1, and by the Deutsche Akademische Austauschdienst (DAAD). We thank Ernst Flüh, GEOMAR Research Center Kiel, for providing Ocean-Bottom-Hydrophones. We greatly appreciate helpful comments of the reviewers, Richard A.F. Grieve, Geological Survey of Canada, and Fillippos Tsikalas, Department of Geology, University of Oslo.
PY - 2002
Y1 - 2002
N2 - The Lake Bosumtwi impact crater in Ghana, West Africa, has a diameter of 10.5 km and is one of the youngest (1.07 Ma) well-preserved large craters on Earth. It has a total dynamic range of topography of more than 400 m, and it is the source crater of tektites and microtektites of the Ivory Coast strewn field. The crater was excavated in early Proterozoic rocks. According to its size, the Bosumtwi impact crater should be a complex impact structure, with a central peak. Multichannel seismic (MCS) reflection and wide angle data, using Ocean-Bottom-Hydrophones (OBHs), were acquired in order to investigate the structure's subsurface, image the presumed central uplift and determine the thickness of impact-related formations and the post-impact sediments. An integrated interpretation of the seismic data sets, and modelling and inversion of the OBH data yield an initial 2D velocity-depth model, which shows indications for a central peak feature. Due to the relatively low seismic velocity (3.0 kms-1) of the corresponding layer, the top of the uplifted structure is interpreted to consist of allochthonous breccia. The central peak has a width of ∼1.8 km and a maximum height of 120 m above the top of the breccia away from the center. Fracturing may be responsible for the relatively low velocity of 3.8 kms-1 in the crater floor. The post-impact sediments covering the crater structure are 180-300 m thick. The apparent crater depth, defined as the difference between the original target surface and the top of the breccia layer, is ∼550 m and thereby slightly deeper than some other larger complex impact structures on Earth. The results indicate that the Lake Bosumtwi impact structure provides an interesting setting for scientific drilling of a young large impact crater and will be supplemented by complimentary recent geophysical (potential field) and possibly future drilling studies.
AB - The Lake Bosumtwi impact crater in Ghana, West Africa, has a diameter of 10.5 km and is one of the youngest (1.07 Ma) well-preserved large craters on Earth. It has a total dynamic range of topography of more than 400 m, and it is the source crater of tektites and microtektites of the Ivory Coast strewn field. The crater was excavated in early Proterozoic rocks. According to its size, the Bosumtwi impact crater should be a complex impact structure, with a central peak. Multichannel seismic (MCS) reflection and wide angle data, using Ocean-Bottom-Hydrophones (OBHs), were acquired in order to investigate the structure's subsurface, image the presumed central uplift and determine the thickness of impact-related formations and the post-impact sediments. An integrated interpretation of the seismic data sets, and modelling and inversion of the OBH data yield an initial 2D velocity-depth model, which shows indications for a central peak feature. Due to the relatively low seismic velocity (3.0 kms-1) of the corresponding layer, the top of the uplifted structure is interpreted to consist of allochthonous breccia. The central peak has a width of ∼1.8 km and a maximum height of 120 m above the top of the breccia away from the center. Fracturing may be responsible for the relatively low velocity of 3.8 kms-1 in the crater floor. The post-impact sediments covering the crater structure are 180-300 m thick. The apparent crater depth, defined as the difference between the original target surface and the top of the breccia layer, is ∼550 m and thereby slightly deeper than some other larger complex impact structures on Earth. The results indicate that the Lake Bosumtwi impact structure provides an interesting setting for scientific drilling of a young large impact crater and will be supplemented by complimentary recent geophysical (potential field) and possibly future drilling studies.
KW - Bosumtwi
KW - Impact crater
KW - Inversion
KW - Seismics
UR - http://www.scopus.com/inward/record.url?scp=0036621801&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0036621801&partnerID=8YFLogxK
U2 - 10.1016/S0032-0633(02)00049-1
DO - 10.1016/S0032-0633(02)00049-1
M3 - Article
AN - SCOPUS:0036621801
SN - 0032-0633
VL - 50
SP - 735
EP - 743
JO - Planetary and Space Science
JF - Planetary and Space Science
IS - 7-8
ER -