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Impact structures in Africa: A review
#MMPMID27065753
Reimold WU
; Koeberl C
J Afr Earth Sci
2014[May]; 93
(?): 57-175
PMID27065753
show ga
More than 50 years of space and planetary exploration and concomitant studies of
terrestrial impact structures have demonstrated that impact cratering has been a
fundamental process - an essential part of planetary evolution - ever since the
beginning of accretion and has played a major role in planetary evolution
throughout the solar system and beyond. This not only pertains to the development
of the planets but to evolution of life as well. The terrestrial impact record
represents only a small fraction of the bombardment history that Earth
experienced throughout its evolution. While remote sensing investigations of
planetary surfaces provide essential information about surface evolution and
surface processes, they do not provide the information required for understanding
the ultra-high strain rate, high-pressure, and high-temperature impact process.
Thus, hands-on investigations of rocks from terrestrial impact craters, shock
experimentation for pressure and temperature calibration of impact-related
deformation of rocks and minerals, as well as parameter studies pertaining to the
physics and chemistry of cratering and ejecta formation and emplacement, and
laboratory studies of impact-generated lithologies are mandatory tools. These,
together with numerical modeling analysis of impact physics, form the backbone of
impact cratering studies. Here, we review the current status of knowledge about
impact cratering - and provide a detailed account of the African impact record,
which has been expanded vastly since a first overview was published in 1994. No
less than 19 confirmed impact structures, and one shatter cone occurrence without
related impact crater are now known from Africa. In addition, a number of impact
glass, tektite and spherule layer occurrences are known. The 49 sites with
proposed, but not yet confirmed, possible impact structures contain at least a
considerable number of structures that, from available information, hold the
promise to be able to expand the African impact record drastically - provided the
political conditions for safe ground-truthing will become available. The fact
that 28 structures have also been shown to date NOT to be of impact origin
further underpins the strong interest in impact in Africa. We hope that this
review stimulates the education of students about impact cratering and the
fundamental importance of this process for Earth - both for its biological and
geological evolution. This work may provide a reference volume for those workers
who would like to search for impact craters and their ejecta in Africa.
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