Help identifying stone triangle found at Grand Cayman?

[CT-Rich]

I like the stucco theory. A brick or wood structure coated with a cement compound. Storm breaks up the structure and it gets tumbled in the surge for a couple of decades. Wood on an island would be an expensive commodity, so I expect there is a lot of locally sourced lime stone in most of the older buildings.

 

[caydiver]

DOE might be able to help out as well.