Ironworking at least produces identifiable traces in ice cores; which may actually be more hydrology and climate science than geology.
Ice core: https://en.wikipedia.org/wiki/Ice_core
Ice core: https://en.wikipedia.org/wiki/Ice_core
Ice core > Ice core data > Dating: https://en.wikipedia.org/wiki/Ice_core#Dating :
> The dating of ice sheets has proved to be a key element in providing dates for palaeoclimatic records. According to Richard Alley, "In many ways, ice cores are the 'rosetta stones' that allow development of a global network of accurately dated paleoclimatic records using the best ages determined anywhere on the planet".[43]
/? ice core samples oldest: https://www.google.com/search?q=ice+core+samples+oldest :
- NSF Ice Core Facility > About Ice Cores: https://icecores.org/about-ice-cores#:~:text=The%20oldest%20.... :
> The oldest continuous ice core records extend to 130,000 years in Greenland, and 800,000 years in Antarctica.
- "Record-shattering 2.7-million-year-old ice core reveals start of the ice ages" (2017) https://www.science.org/content/article/record-shattering-27.... :
> Clues to ancient atmosphere found in bubbles trapped in Antarctic samples
- "World's oldest ice core could stretch back 5 million years" (2022) https://newatlas.com/environment/worlds-oldest-ice-core-5-mi....
What would be a more cost effective way to identify signs of prior civilization?
Read the emissions off in black holes that old, (or rather, black hole accretion disks, which are apparently modified Lorentzian attractors with superfluidity and Hawking radiation)
Fly there and perform multiple geologically and geographically covering miles-deep sediment sample studies,
Fly there and drill ice cores,