> 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]
If a civilization develops stone working, metalworking, leaded gasoline, nuclear power, etc , that's all probably recorded in ice cores (that are apparently 5 million years old in bubbles).
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,
