I don't think you understand. There were no glaciers there 6K years ago or humans would not have been able to inhabit the area at the time to leave these instruments. At some point in the last 6K years the glaciers in this area grew to expand over top of of the settlement that was there (that is to say, the temperatures grew cold enough long enough to sustain growth and maintenance of glaciers in this area over the past 6,000 years), and buried these instruments. Only now, are the glaciers melting to the point that we can find such instruments again, as we approach similar temperatures to early holocene (which began 11.5K years ago).