Pronounced central uplift identified in the Bosumtwi impact structure, Ghana, using multichannel seismic reflection data

Christopher A. Scholz, Tobias Karp, Keely M. Brooks, Bernd Milkereit, Philip Y.O. Amoako, Justice A. Arko

Research output: Contribution to journalArticle

55 Scopus citations

Abstract

The Lake Bosumtwi impact structure is the youngest and best-preserved complex terrestrial impact crater and serves as an important reference site for the study of cratering processes. Because the impacting body struck continental crystalline target rocks and not a submerged sedimentary platform, no significant backwash processes have modified the crater morphology. Not only may Bosumtwi contain the best-preserved central uplift structure on Earth, but it is the most accessible relatively large, young crater in the solar system generated in a large gravity field. There is a well-established link between the Lake Bosumtwi impact structure and the Ivory Coast tektite field, and the lacustrine sediments within the crater contain a unique 1 m.y. record of paleoclimate in the continental tropics south of the Sahel. Eight profiles of marine-type multichannel seismic reflection (MCS) data were acquired from the 8-km-diameter, ∼75-m-deep lake that fills much of the crater. These were augmented by wide-angle seismic data acquired with ocean-bottom hydrophones. MCS data reveal a well-defined central uplift near the northwest-central part of the lake and a maximum postimpact lacustrine sediment thickness of ∼310 m. The central uplift structure has a diameter of 1.9 km and a maximum height of 130 m above the annular moat inside the crater. An intermediate velocity layer (3200 m/s) beneath the lacustrine sediment is interpreted as fallback breccia or a breccia-melt horizon. The measured apparent depth of the crater (da) is 500 m, implying a slightly higher aspect ratio for the structure than predicted from published empirical relationships. The Bosumtwi structure is a small complex crater that deviates slightly from trends predicted from classical scaling laws, perhaps because of the effects of a large gravity field.

Original languageEnglish (US)
Pages (from-to)939-942
Number of pages4
JournalGeology
Volume30
Issue number10
DOIs
StatePublished - Oct 1 2002

Keywords

  • Impact cratering
  • Lake Bosumtwi
  • Multichannel reflection seismology
  • Paleolimnology
  • Terrestrial impact structures
  • West Africa

ASJC Scopus subject areas

  • Geology

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