Potential Superflat generation bug

I have been working on a map for about 2 days now in a superflat world. only moments ago i was just flying around to find myself a place to build and i came a cross a chunk of ocean biome and plains/hill biome just randomly within the ground (as you can see in the picture above). i feel it is important to state i have not opened ths specific world in any exterior programs such as MCedit or opened any other world in one since creating this world. I want to know if anyone else has had this specific bug. (Also i generated the dirt to be 64 blocks high instead of the normal 3 high preset)