An Archean Impact Layer from the Pilbara and Kaapvaal Cratons
Gary R. Byerly,1*
Donald R. Lowe,2
Joseph L. Wooden,3
Xiaogang Xie1
The Barberton greenstone belt of South Africa and the eastern
Pilbara block of Western Australia provide information about Earth's
surface environments between 3.2 and 3.5 billion years ago, including
evidence for four large bolide impacts that likely created large
craters, deformed the target rocks, and altered the environment. We
have obtained identical single-zircon uranium-lead ages of 3470 ± 2 million years ago for the oldest impact events from each craton.
These deposits represent a single global fallout layer that is
associated with sedimentation by an impact-generated tsunami and in
Western Australia is represented by a major erosional unconformity.
1 Department of Geology and Geophysics,
Louisiana State University, Baton Rouge, LA 70803-4101, USA.
2 Department of Geological and Environmental
Sciences, Stanford University, Stanford, CA 94305-2115, USA.
3 U.S. Geological Survey-SUMAC
(Stanford-USGS Micro Analysis Center), Stanford University, Stanford,
CA 94305-2220, USA.
*
To whom correspondence should be addressed. E-mail:
gary{at}geol.lsu.edu
