Blundell made 63 while Marshall blasted 105 from 94 balls as the pair coasted Wellington to a seven-wicket win, leaving Canterbury to cast their eyes to Napier to see if Central Districts could hold off Auckland.
Auckland needed an outright victory to win the Shield, so they declared their second innings early in the day to set CD 301 to win.
Their hopes looked slim when George Worker concluded his impressive season with a century, smoking 130 as Central Districts cruised through to 192-2.
His dismissal gave Auckland life however, and a quick barrage of wickets put the game back in the balance at 213-5, with CD having their last two recognised batsmen at the wicket.
Those two batsmen - Tom Bruce and Dane Cleaver - frustrated the Auckland attack with a 66 run partnership. Cleaver made 29 before he departed with just 22 runs required, and the scalp of Ajaz Patel two runs later left Auckland needing three wickets to pull off a come-from-behind triumph.
However, Bruce stayed steady, ending unbeaten on 43 as CD denied Auckland, in the process securing victory for Canterbury, who added the Plunket Shield to this season's Ford Trophy title in their trophy cabinet.
Northern Districts ended up moving past Auckland to finish in second spot, after centuries from Daryl Mitchell (106) and Tim Seifert (151) saw them chase down 347 to beat Otago.