I am not a geologist, but it seems improbable for a technical civilization (like our current one) to not leave a global geological mark. For example, our use o

I am not a geologist, but it seems improbable for a technical civilization (like our current one) to not leave a global geological mark. For example, our use of fossil fuels changed global carbon isotope composition: our atmosphere now has less portion of C13, because photosynthesis favors the lighter C12 atoms, and all our fossil fuels ultimately derives from photosynthesis.[1] The changed isotope ratio will be detectable in every carbon-containing sediment layer ever produced in our age. And this is just one example. [1] https://skepticalscience.com/print.php?r=109 https://skepticalscience.com/print.php?r=109