First detection of extraterrestrial material in ca. 2.49 Ga impact spherule layer in Kuruman Iron Formation, South Africa

Abstract

Research Article| March 01, 2015 First detection of extraterrestrial material in ca. 2.49 Ga impact spherule layer in Kuruman Iron Formation, South Africa Bruce M. Simonson; Bruce M. Simonson 1Geology Department, Oberlin College, 52 W. Lorain Street, Oberlin, Ohio 44074, USA Search for other works by this author on: GSW Google Scholar Steven Goderis; Steven Goderis 2Earth System Science, Vrije Universiteit Brussel, Pleinlaan 2, B-1050 Brussels, Belgium3Department of Analytical Chemistry, Ghent University, Krijgslaan 281–S12, B-9000 Ghent, Belgium Search for other works by this author on: GSW Google Scholar Nicolas J. Beukes Nicolas J. Beukes 4Geology Department, University of Johannesburg, P.O. Box 524, Auckland Park 2006, South Africa Search for other works by this author on: GSW Google Scholar Author and Article Information Bruce M. Simonson 1Geology Department, Oberlin College, 52 W. Lorain Street, Oberlin, Ohio 44074, USA Steven Goderis 2Earth System Science, Vrije Universiteit Brussel, Pleinlaan 2, B-1050 Brussels, Belgium3Department of Analytical Chemistry, Ghent University, Krijgslaan 281–S12, B-9000 Ghent, Belgium Nicolas J. Beukes 4Geology Department, University of Johannesburg, P.O. Box 524, Auckland Park 2006, South Africa Publisher: Geological Society of America Received: 27 Aug 2014 Revision Received: 26 Dec 2014 Accepted: 13 Jan 2015 First Online: 09 Mar 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 © 2015 Geological Society of America Geology (2015) 43 (3): 251–254. https://doi.org/10.1130/G36225.1 Article history Received: 27 Aug 2014 Revision Received: 26 Dec 2014 Accepted: 13 Jan 2015 First Online: 09 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Bruce M. Simonson, Steven Goderis, Nicolas J. Beukes; First detection of extraterrestrial material in ca. 2.49 Ga impact spherule layer in Kuruman Iron Formation, South Africa. Geology 2015;; 43 (3): 251–254. doi: https://doi.org/10.1130/G36225.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract Thin layers rich in formerly molten spherules interpreted as distal ejecta from large impacts by extraterrestrial bodies have been found in 8 stratigraphic units deposited between ca. 2.63 Ga and 2.49 Ga and attributed to a minimum of 4 separate impacts. Here we report geochemical evidence of extraterrestrial material in the only one of these spherule layers where it has not been previously reported, the Kuruman spherule layer (KSL) in the Kuruman Iron Formation, a banded iron formation (BIF) in the Griqualand West Basin (South Africa). We identified the KSL in 3 drill cores separated by as much as ∼350 km and analyzed 2 core samples that have a mean Ir concentration of ∼12.9 ppb and nearly chondritic interelement ratios of platinum group elements Ir, Ru, Pt, and Rh. This suggests that the samples contain ∼1%–3% by mass extraterrestrial material even though the spherules are highly diluted by ambient sediment. Our geochemical data strongly support the correlation of the KSL with the Dales Gorge spherule layer (DGSL) in a penecontemporaneous BIF in the Hamersley Basin (Western Australia). The KSL and DGSL are close matches in terms of major and various trace element contents and the DGSL has a comparable Ir content of ∼11.5 ppb. Therefore it is very likely the KSL and DGSL are distal ejecta from a ca. 2.49 Ga impact by a single extraterrestrial object >10 km across. The lack of any significant changes in the stratigraphic succession in either basin also implies that large impacts alone are not sufficient to cause long-term changes in Earth’s surface environments. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.