That's what's so surprising to me nowadays I'd just assume they'd have googled and found a paper by some Japanese scientists, but back then someone from the US must have taken those probes across Japan.

That's an interesting aspect to this story to me. Maybe it was truly based on intel and the geological survey was a farce to justify the facilities targeting. That wouldn't surprise me, there's a ton of lore around WWII and military activity in general.

Or maybe the US government chooses to fund all areas of research, like mineral surveys, in the hopes they can call on a field of knowledge repository to use in a war machine.

I'd like to believe there is a soil library that staff were doing microscope slide searches late into the night.

They ran it through a database at Sandia Labs. ;)