Hi Irene & welcome

The index does show Elizabeth Morrison marrying Easington in Dec Q 1893 but I couldn’t find a Mark Morrison in Co. Durham in 1891 but found this family:
1891 ref RG12/4110/30/13
Water Street, Thornley, Durham
Mark Maddison, head, Mar, age 42, Fireman in Coal Mine, Durham Pittington
Mary Maddision, wife, Mar, age 35, Durham Pittington
Elizabeth Maddison, dau, age 16, Durham Thornley
Sarah Maddison, dau, age 14, Durham Thornley
Bartholomew Maddison, son, age 13, scholar, Durham Thornley
Thos Maddison, son age 12, scholar, Durham Thornley
Francis Ann, dau, age 2, Durham Thornley
Gowan R, son age 1, Durham Thornley
Free bmd has a marriage for a Mark Maddison with a Mary Burns on the same page
Dec Q 1872 Durham, GRO ref 10a/671
Hope this helps
Heather