Sarah Palin's Son Track Headed for Divorce Court

Sarah Palin's oldest son has pulled the trigger on his marriage by filing for divorce ... TMZ has learned.

Track Palin and his wife, Britta, jointly filed divorce docs in an Alaskan court. Under Alaska law, by filing together, they are signaling they have fully settled property and custody issues, including child support.

As for custody, the now ex-couple has a 1-year-old daughter, Kyla. One interesting point ... Track and Britta had to watch a 48-minute video about the impact of a failed marriage on the child.

Track and Britta married in 2011.

Track is an Army reservist and served time in Iraq. He's a commercial fisherman and plans to go back to college.