S7 - Impact Deposit

Alternate Names S7 (Barberton)
Coordinates 25° 55' 48" S; 30° 51' 36" E
Notes
  1. Note the Lat and Long provided are for the type locality near the base of the Buck Reef Chert (Lowe et al., 2014). It crops out discontinuously for 30 km along strike
Country South Africa

Related Countries :
  1. South Africa
Region Barberton
Date Confirmed 2010
Notes
  1. Lowe and Byerly, 2010 (petrography)
Age (Ma) 3416 (Kroener et al., 1991)
Notes :
  1. Glass and Simonson 2012; Krull Davatzes et al., 2015; Lowe et al., 2014

Method :
  1. radiometric ages on detrital zircons (Lowe et al., 2014)
Impactor Type Unknown
Notes
  1. Based on thickness (Lowe et al., 2014), all BGB spherule beds would have a larger bolide than the K-Pg impact event (which was about 10 km). Some results suggest bolides that are 20-50 km across (Byerly and Lowe, 1994; Lowe et al., 2003; Kyte et al., 2003) or 30-70 km across (Johnson and Melosh, 2012).

Advanced Data Fields

Notes

Local Language
N/A
Spherules
X (4 compositional types)
Tektites
Unknown
Indivudual Glass Clasts
Unknown
Source Crater
Unknown
Geology
Onverwacht Group; Buck Reef Chert; spherules show pseudomorphs of olivine (Lowe et al., 2014)
  1. altered spherules
Other Shock Metamorphism
Unknown
Shatter Cones
No
Planar Fractures
No
Planar Deformation Features
No
Diaplectic Glass
No
Coesite
No
Stisovite
No

References

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Alfred Krüner, Gary R Byerly, Donald R Lowe (1991) Chronology of early Archaean granite-greenstone evolution in the Barberton Mountain Land, South Africa, based on precise dating by single zircon evaporation, Earth and Planetary Science Letters 103(1), p. 41-54, url, doi:https://doi.org/10.1016/0012-821X(91)90148-B

G R Byerly, D R Lowe (1994) Spinel from Archean impact spherules, Geochimica et Cosmochimica Acta 58(16), p. 3469-3486, doi:10.1016/0016-7037(94)90099-X

Donald R Lowe, Gary R Byerly, Frank T Kyte, Alexander Shukolyukov, Frank Asaro, Alexandra Krull (2003) Spherule Beds 3.47–3.24 Billion Years Old in the Barberton Greenstone Belt, South Africa: A Record of Large Meteorite Impacts and Their Influence on Early Crustal and Biological Evolution, Astrobiology 3(1), p. 7-48, Mary Ann Liebert, Inc., publishers, url, doi:10.1089/153110703321632408

Frank T Kyte, Alex Shukolyukov, Günter W Lugmair, Donald R Lowe, Gary R Byerly (2003) Early Archean spherule beds: Chromium isotopes confirm origin through multiple impacts of projectiles of carbonaceous chondrite type, Geology 31(3), p. 283-286, url, doi:10.1130/0091-7613(2003)031<0283:EASBCI>2.0.CO;2

D R Lowe, G R Byerly (2010) Did LHB end not with a bang but a whimper? The geologic evidence, 41st Lunar and Planetary Science Conference, pdf

B P Glass, B M Simonson (2012) Distal impact ejecta layers: Spherules and more, Elements 8(1), p. 43-48, GeoScienceWorld, pdf, doi:10.2113/gselements.8.1.43

B C Johnson, H J Melosh (2012) Impact spherules as a record of an ancient heavy bombardment of Earth, Nature 485(7396), p. 75-77, url, doi:10.1038/nature10982

B C Johnson, H J Melsoh (2012) New estimates for the number of large impacts throughout Earth's history, Early Solar System Impact Bombardment II, url

D R Lowe, G R Byerly, F T Kyte (2014) Recently discovered 3.42-3.23 Ga impact layers, Barberton belt, South Africa: 3.8 Ga detrital zircons, Archean impact history, and tectonic implications, Geology 42(9), p. 747-750, Geological Society of America, url, doi:10.1130/G35743.1

Alexandra Krull Davatzes, Nicholas Swartz, Matthew Enos (2015) Petrologic and impact size controls on Precambrian spherule diameters, Large Meteorite Impacts and Planetary Evolution V 115, p. 1125, Geological Society of America Boulder