when I checked the early marriage index for Wisconsin I find this marriage: (could this be the father of the Frank Marshell listed as adopted on the 1880 census?)
Marriage Record Details
Last Name: Gould
First Name: Elvira E
Day: 10
Month: July
Year: 1881
County: Richland
Volume: 1
Page: 393
Marriage Record Details
Last Name: Marshal
First Name: Charles
Day: 10
Month: July
Year: 1881
County: Richland
Volume: 1
Page: 393