I probably will not be downtown at the archives for some time, but in case anyone else goes to look, the online data base ( http://register.shelby.tn.us/ ) says the Spickernagle/Davis marriage is recorded in Book 1, page 67.

Just a bit of info that might connect to your family, a William Spickernagle was elected Mayor of Memphis in 1841.
He ran on a "reform ticket" and in 1842, along with the wharf master, led the volunteer milita to force the flatboatmen to pay their wharf fees. It was called locally as the "Flatboat War" William is buried in Historic Elmwood Cemetery, although I have never seen his tombstone.