Sounds wonderful! Sandstone will weather into arches so you answered my question. The rocks where I live are some of the oldest on the planet, formed before there was life on earth so unfortunately no fossilised life forms but we do have these, which are pretty cool: river estuaries turned to stone. The area was the shoreline of an inland sea back in the day and then the river mouth turned to rock and thereafter the earth's crust was shattered by a massive meteorite strike (it's visible on satellite photos) which would have been an extinction event, had there been any life-forms to kill at that time