Sorry Gofick, I would have answered earlier, this bypassed me. The mark is called a 'bench' mark, or a 'fundamental bench mark'.
http://www.mapzone.co.uk/pagesdidyouknow/answers.cfm?q_id=77
Hoo! Thanks to your enquiry I just found this odd bench mark in Tasmania (well a web page) that 'challenges' global warming theories. Interesting stuff. (Although the very mention of Tasmania is a shame-filled experience):
