Giant Meteorite Strike - the Pluses and Minuses

A correspondent sent me THIS LINK, concerning a giant meteor strike which happened ~3.26 Ga in what is now the Barberton Greenstone Belt of South Africa. I now know that 8 meteorite impacts (identified by small spherules and iridium anomalies) occurred in the greenstone belt. They have been given S numbers and here we are dealing with S2.

The size of the meteor was huge - 40 to 60km across. The Earth it struck was very different from that of today - mostly sea with a few continents. Life was single celled organisms. The meteorite created a 500km crater, a cloud of hot rock dust that circled the globe, ripped up the sea bed and created a huge tsunami. 

But it is not all bad news. Phosphorus and iron were churned up and dispersed. This could be considered as the spreading of fertiliser! It is always good to look on the bright side of life!

The basis of the BBC article is THIS ACADEMIC PAPER. This goes into the minutiae of the investigation and gives much greater detail. 

Rock and thin section images of the Bruce’s Hill and Umbaumba sections. (A–C) Outcrop photos of the Umbaumba section. (A) Overview of the Umbaumba section showing, from base to top, BWBC, S2, fallback layer, and BWBC. (B) S2 spherule bed. (C) Lower part of the fallback layer showing fine laminations. This black chert is composed of silicified carbonaceous matter, siliciclastic debris, and impact-generated dust settling out of the atmosphere. (D and E) Outcrop photos of the Bruce’s Hill section. (D) BWBC below S2. (E) Alternating siliciclastic and siderite-rich chert beds. (F–G) Representative thin section images of carbonaceous matter. (F) Laminated carbonaceous chert below S2 in the Umbaumba section (SI Appendix, Fig. S4). Red arrows indicate fractures filled by chert. (G) Clots of carbonaceous matter and other siliciclastic debris from the fallback later in the Umbaumba section.