Peter -
On my copy of the A CORRELATED HISTORY OF EARTH the Gondwana Buster is
shown as a solid circle (no tentative dashed lines), a crater 300+ km
in diameter, and moreover said to be located in South Gondwana (indicated
to be South America, Africa, and Antartica).
And, as I noted in the previous posting, no further information is
given on the citations sheet concerning the GB.
George.