Ok so far enough back no fossilized tools, but if the civilization was like ours then would it consider leaving stuff for the future - building repositories of knowledge that would survive a longer time. But probably those 'long range' memorials are not long range enough for the geologic times involved - so my question is, is there a memorial/repository of knowledge we could build that would have a good chance of surviving and being understood as a repository of knowledge until the next civilization?