The notion of authority differs depending on the situation, for example religious authority just means people agree with you. In science, authority is earned, through hard work and demonstrable results.
In other words, to be a scientific authority you don't even need a formal education or title, you just have to demonstrate knowledge in your particular field. To demonstrate this knowledge, your findings must be submitted for scrutiny, or you have to illustrate a thorough understanding of the subject matter.
Once you have demonstrated that you know what you're talking about, you then have to provide demonstrable results. This means you either develop a new tool, or improve our understanding of the topic with empirical evidence.
No matter the path you take, you have to show your work, this is the key to empiricism. You must illustrate your claims in a way that everyone else can verify them.
If they cannot be verified then your claims are meaningless, no matter how popular they are. So when we cite an authority in science, we are talking about someone who has consistently presented empirical evidence.
The use of authority is fallacious if the citation is from someone who has never demonstrated any comprehension of the subject, or if the citation actually opposes the claim it was used to support. But here's the catch, in science no amount of authority can ever replace empirical evidence.
So the reason creationism fails in all scientific arenas is because it lacks any empirical evidence and no one seems willing to present any.