Physical property measurements: ICDP boreholes LB-07A and LB-08A,Lake Bosumtwi impact structure, Ghana
MetadataShow full item record
CitationMorris, W. A., Ugalde, H., & Clark, C. (2007). Physical property measurements: ICDP boreholes LB‐07A and LB‐08A, Lake Bosumtwi impact structure, Ghana. Meteoritics & Planetary Science, 42(4‐5), 801-809.
PublisherThe Meteoritical Society
JournalMeteoritics & Planetary Science
AbstractPhysical rock property measurements provide the primary constraints for any geological models hypothesized from geophysical observations. Previous geophysical models of the Bosumtwi impact structure hypothesized that a highly magnetic and dense impact-melt sheet might be the source of the observed magnetic anomalies. However, magnetic susceptibility and density measurements made on International Continental Scientific Drilling Program (ICDP) cores LB-07A and LB-08A from the interior of the Bosumtwi meteorite impact structure contain no evidence for that. Both density and magnetic susceptibility logs on both boreholes exhibit low-amplitude contrasts between the uppermost polymict lithic breccia and suevite, the intermediate monomict lithic breccia, and the lowermost bedrock. The depth extent of fracture-related density reduction is much greater at LB-08A than at LB-07A. A total magnetic intensity log from borehole LB-08A supports the suggestion that magnetic anomalies over Lake Bosumtwi are mainly sourced in undetected and/or covered bedrock intrusions, like the ones outcropping at the northeast and to the southwest of the lake.