The 23-year old, more commonly known as Gabriel, has signed a two-year deal with the Jags after impressing on trial.
Former America and Denia centre-back Gabriel, who joins after his contract with Rayo Vallecano expired, was looking forward to trying his luck in Scotland.
"I'm very happy with the opportunity. Hopefully it will be good for everybody - for the team and for me," he told the club's official website.
"I came over last week and the club just wanted to make sure that I was in good shape and I had a good way of playing. I'm very happy to sign here."