S3 - Impact Deposit

Alternate Names S3 (Barberton)
Local Language
Coordinates 25° 55' 12" S; 31° 1' 12" E
Notes
  1. Note the Lat and Long provided are for the type locaility. Other locations listed in Lowe et al., 2003
Country South Africa

Related Countries :
  1. South Africa
Region Barberton
Date Confirmed 1986
Notes
  1. Lowe and Byerly, 1986 (petrography); Lowe et al., 1989 (Ir and PGEs); Byerly and Lowe, 1994 (spinels and geochemistry); Kyte et al., 2003 (extraterrestrial Cr isotopic ratios)
Age (Ma) 3243 ± 4 Ma (Kruener et al., 1991)
Notes :
  1. Glass and Simonson 2012; Krull Davatzes et al 2015; Kruener et al., 1991

Method :
  1. U-Pb dating of a single zircon in tuff immediately underlying S3
Impactor Type CV Chondrite (Krull-Davatzes et al., 2014)
Notes
  1. PCA analysis on the gechemistry of the S3 spherule layer was used to determine the best fit end members for a mixing model. Results suggests the primary target rock resembles N-MORB (typical MORB seen today; depleted mantle) and a likely meteor being a CV chondrite (Krull-Davatzes et al 2014). Ir, Cr, spherule size, and the mixing model PCA analysis have suggested a meteor diameter estimate between 20 and 50 km (Lowe et al., 2003; Kyte et al., 2003; Krull-Davatzes et al., 2014). Assuming a crater diameter of 30 km and a Pi-group scaling calulation (Melosh, 1996), the transient crater diameter would be 159 km and the final crater diameter would be 556 km, with an excavation depth of 16 km (Krull-Davatzes et al., 2014). 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). 41-70 km impactor diameter and 20.6-22.8 km/s impact velocity (Johnson and Melosh, 2012)

Advanced Data Fields

Notes

Spherules
X (4 compositional types)
Tektites
Indivudual Glass Clasts
N/A
Source Crater
Unknown
Geology
In the Fig Tree Group in the Barberton Greenstone Belt; experienced sub- or lower greenschist grade metamorphism; produced from CV Chondrite impacting basaltic and ultramafic rock (Krull-Davatzes et al., 2012); spherules are largely microcrystalline quartz and phyllosilicate minerals (Lowe et al., 2014)
  1. presence of altered spherules with quench textures and altered spherules with relict vesicles. Ir anomaly (Lowe and Byerly, 1986; Lowe et al., 1989), Cr isotope data (Shukolyukov et al., 2000; Kyte et al., 2003), and presence of Ni-rich spinels supporting an impact origin. Glass and Simonson, 2012; Krull-Davatzes et al., 2012; Lowe et al., 2014
Other Shock Metamorphism
Shatter Cones
No
Planar Fractures
No
Planar Deformation Features
No
Diaplectic Glass
No
Coesite
No
Stisovite
No