For a single story cabin that is not subject to cold regions design requirements, you may find that doweling into a good sized rock and casting a short concrete pier or pad to support an adjustable "Simpson EPB" bracket (if available in your AO) 6" to a foot above grade will adequately support your 4x floor girder. If you're using RR ties for floor framing, shim using a treated 4x4 (flat) in the EPB. If you keep the exposed threaded base short, they are good for around 3,000 pounds. For the stubby pier, you can use a precast pier block with a center hole set on a pad of concrete above the rock in various fashions.
Insert standard engineering design liability boilerplate here for the above limited suggestions based upon very limited information....
