what are these marks on the rock?

My guess, Max, furrows caused by the passage of harder rocks

Where are these rocks located? What is the approximate age of the geology in that area? Are these erratics or are they native to the area?

Ros, for what it's worth--probably not much-- it looks like chalcedony deposit on sandstone

I would first suggest identifying the composition (i.e., mineralogy) and rock type (igneous, sedimentary, or metamorphic). Once you understand these two things along with the mineralogy and rock type of surrounding/adjacent formations you can begin to postulate about the desposional or formational environment for this rock and the surrounding formations, which in turn may answer your question.