Ultimate Facebook logs out of facebook?

Is this normal that on logout from my site, the user is also logged out from Facebook?
Can it be changed so the user just logs out of my site, but stays logged in on their facebook account?

This is happening not just for users that are registered/login via facebook, but also for users that have no connection to facebook (maybe share the same login email address, but they're not logged in using the "login via facebook" button).