Found a marriage for Joseph Plummer to Agnes Hendry 11/2/1850 at The Manse, Freeman St., Adelaide. Bride and Groom's Father's names unrecorded. Grooms age 25 & Brides age 22.
District of Adelaide Book No. 7 Page 204 (used when ordering cert.)
Also 2 marriages for a Alexander Plummer with father Joseph.
1. Alexander Plummer (single) 27y.o. marr. Elizabeth Ann Martin (widow) 40y.o. 11/2/1878 Place of marr. listed as House (East Moonta) Bride's Father's name John James Martin.
District Dal. Book no. 114 Page no. 572
2. Alexander Plummer (widower) 33 y.o. marr. Amy Couch (widow) 39y.o. on 23/2/1884 at Residence of Amy Couch (Moonta) Bride's father William Hocking.
District Dal. Book 138 Page 647
hope this helps,
Wendy