"I also told (church leaders) that it was extremely unusual for the church to pursue someone who hadn't had anything to do with the church for the last seven years," Southerton wrote.

Southerton plans to appeal the decision to the Mormon church's Salt Lake City-based leaders, known as the First Presidency.

Mormon church officials do not comment on the decisions of local church leaders, church spokesman Scott Trotter said Thursday.

If Southerton appeals, the First Presidency triumvirate would have several courses of action, Trotter said. Church President Gordon B. Hinckley and his two advisers could agree with the decision, modify it or send it back to Australian church leaders for a rehearing.

That process "takes some time," Trotter said.

Ultimately, if the decision stands, Southerton's name will be removed from official church rolls in Salt Lake City.

Southerton's excommunication makes him the seventh author from the Salt Lake City-based Signature Books, a publishing house for Western and Mormon studies, to be released from the church after publishing a work critical of Mormon beliefs.

Signature's managing director, Ron Priddis, called the decision "unfortunate for Simon and his family." He agrees with Southerton's contention that a subtext to his excommunication is the author's public use of science to challenge church beliefs.

"We just wish there was a more open, healthier climate for the discussion of matters of science and religion," Priddis said.