* A misspelling: There might be a similar term that's being misspelled, such as "Fountain Formation Sandstone" or "Fremantle Sandstone".
* A local term: It could be a local name for a specific sandstone formation in a particular region.
* A fictional term: It could be a term used in a story or work of fiction.
To help me understand what you're looking for, could you provide more context? For example:
* Where did you encounter this term?
* What was the context of the term's usage?
* Do you have any other information about it?
With more context, I can help you find the correct term or understand its meaning.