Petroglyph along Spanish Trail (Anza?)

The marking on this rock are cryptic. A cross is maked on it. And many people have worn down whatever is here by sitting on it. That is how I found it. There is a cross and a =A= This areas has been inhabited for 9,000 years or more. The Spanish crossed thru for hundreds of years along the sensible path up and over towards the old Mission. This is near a1970 place for trouble youth and while this could be a Dark Side of the Moon prism symbol it seems far to old, worn, and has old leichen on the rock. This is South of Livermore California on a public trail. Anza was here? Spanish Lt. Colonel Juan Bautista de Anza ; https://www.nps.gov/juba/planyourvisit/maps.htm Source: Objaverse 1.0 / Sketchfab