How would the relics of extinct human society affect future civilizations?

My story (same world as here) take place in a future Earth between 3 and 5 million years in the future. What kind of artifacts, if any, would civilizations from this era find from the now extinct humans? What tangible consequences would the Anthropocene have on their life and societies?

Random ideas on this topic:

• Ceramic will last indefinitely because of its molecular stability, similar to fossils in composition. Aluminum and stainless steel in tools (in cookware for example) will survive and so will (probably) plastic: the discovery of readymade tools could bring a sudden technological development and/or the emergence of a religious conscience to explain their presence.
• I expect plastic to be widespread, sometimes conserved in rock as a somewhat recognizable item and other times degraded to invisible dust (maybe even part of some newly evolved food chain?)
• Stone crafts and sculptures, like mount Rushmore, have a pretty good chance to survive the ages, even if terribly distorted by erosion and ice ages.
• In dry climates metals corrode but wood have a chance of being preserved.
• Streets and underground tunnels will collapse and they will probable became riverbeds in temperate climates. When the cities will inevitably crumble, mud and silt from these rivers will bury objects, tires, cars and even entire houses. In time mud will become rock and things will be preserved inside until maybe a river or a glacier will dig a canyon exposing the ancient buildings and relics.
• Structures in steel and reinforced concrete will crumble, be grinded and compressed under new geological strata, leaving this probably reddish layer rich in excellent quality metals (could be reused? Mined?).

Any other ideas?

EDIT: Rephrased the question to address a more specific topic;

DISCLAIMER: this question is different from What would be left of a civilization founded in dinosaur times? That question is about an imaginary society in the past with no interest on its influence on today human society, while my question is about OUR OWN society and how it will influence future civilizations. Things like the Pyramids or Mt. Rushmore can survive a few million years, so they are relevant artifact for the topic i'm talking about.

ALSO, 65 million years and ~4 million years is a really big time difference by all terms. Four geological periods have followed since 65 mya and an entire geological era has passed. Tectonics really plays a crucial role when talking about +65 millions of years; huge impact craters can be eroded, mountains rise and wear away, oceans are formed or vanish. Complex processes like the transformation of biomass in hydrocarbons can take place. My question revolves around a significant smaller time scale. The time frame i'm talking about would be entirely paced inside our own geological period. A difference of just a few millions years is important when talking of radioactive decay and the legacy of other human-related activities.

posted over 8 years ago

JRover‭

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