Ok, I've figured what issue was: It turns out that I had to first generate one chunk before generating subsequent ones. I've also found out that ChunkX and ChunkY does nothing. WTH? Problem with chunks not adding up (seams) probably lies in carving step, however I don't know how to fix it.

Problem with ChunkX/ChunkY doing nothing... Well I don't even know what causes it (here's perlin noise unit I'm using, which might be relevant - I didn't wrote it nor I do understand it: http://pastebin.com/CSk62Jdf).