The amendment adopted by Council shall become effective thirty days after the date of the adoption unless within thirty days after the passage of the ordinance, there is presented to the City Clerk a petition, signed by a number of qualified voters residing in the City equal to not less than ten percent (10%) of the total vote cast in the area at the last preceding general election at which a governor was elected, requesting Council to submit the zoning amendment to the electors of the City for approval or rejection at the next general election.
   No amendment for which the referendum vote has been requested shall be put into effect unless a majority of the vote cast on the issue is in favor of the amendment. Upon certification by the Board of Elections that the amendment has been approved by the voters, it shall take immediate effect.