Rock varnish microlamination dating pagdating
Rock varnish microlamination (VML) dating uses the slow buildup of 'varnish' or dark coating on subaerially exposed rock surfaces.
At least some forms of varnish appear to contain an organic component as a result of bacteria that live on or near the surface of the rock.Although these changes were attributed to the preferential leaching of Ca and K from varnish, the existence of such leaching has not been demonstrated.In varnish collected from the Cima volcanic field, California, distributions of the minor elements used in cation-ratio (CR) dating reflect varnish stratigraphy as defined by the major elements Mn, Fe, and Si.Rocks on the surface of the ground sometimes can form something called desert pavement and the surfaces of those rocks may also become covered with desert varnish.The origins of desert varnish have long defied full explanation.
I expect that most people simply look at these dark streaks and think they are simply stains like a stain on a cement driveway or that line of rust color running down a wall from a rusty nail above. But what if you were shown a picture of the same rock taken 50 years earlier and the stains looked identical to you?