Mark Dennis Nickelson, 73, of Oak Ridge, TN, passed away peacefully on September 10, 2020 due to complications from Dementia. He was born on November 19, 1946 in Davenport, IA. Mark earned his Bachelor of Science from Shippensburg University and his Masters Degree from Indiana University both in Geology. He was a veteran of the U.S. Army having served on active duty in Vietnam. His professional career included teaching high school earth science at John Carrol School in Bel Air, MD, and Edgewood High School in Edgewood, MD. He coached high school football and both mens and womens basketball. He worked as a geologist as a civilian contractor for the Army and in the private sector for Lockheed Martin. Prior to his retirement he worked for URS in New Orleans, LA during the post hurricane Katrina clean up. He is survived by his beloved bride of 52 years Gloria Nickelson of Oak Ridge, TN, his son Mark Nickelson II and his wife Lori Nickelson of Oak Ridge, TN, daughter Tamara Worthy and her husband Allan Worthy of Nashville, TN and daughter Dawn Nickelson of Oak Ridge, TN. He has seven grandchildren including Lauren Nickelson, Ethan Huckwell, Allyson Nickelson, Katelyn Mattus, Mason Mattus, Ari Worthy and Aaliyah Worthy. He was preceded in death by his parents Lawrence and Mildred Nickelson of Le Claire, IA and his brother Nicholas Nickelson of Le Claire, IA. His hobbies included bird watching, playing golf, woodworking, cheering on the Lady Vols basketball team and most importantly spending time with his family and friends. Visitation will be held on Wednesday, September 16, 2020 from 5pm to 7pm at Weatherford Mortuary 158 S. Jefferson Circle, Oak Ridge, TN. The funeral will follow at 7:00 pm with Rev. Kenny Rains officiating. Memorials can be made to the Wounded Warrior Project, P.O. Box 758516, Topeka, Kansas 66675-8516. An online guestbook can be signed at www.weatherfordmortuary.com.