From the National Park Service:

Mark was the former manager and Supervisory Archeologist at the Midwest Archeological Center, having retired in 2013 after 34 years of service with the National Park Service (please see the link below that was posted on Inside NPS when Mark retired). He was an amazing individual who made major contributions to the profession that he loved and the preservation of resources managed by the National Park Service. He will be forever missed by his family, friends and colleagues.

http://inside.nps.gov/index.cfm?handler=viewcommunityarticle&type=PeopleNews&id=3815