A picture is worth...well, take a look...

https://onedrive.live.com/?cid=b60c11d037429d8e#cid=B60C11D037429D8E&id=B60C11D037429D8E%2130675&v=3

I had to reduce the resolution when generating land as some tiles had too many triangles but I've seen this "effect" with other world spaces. Can it be avoided or is it just the wide open expanse that I have the culprit?

black lands are usually related to wrong normals. Please can you read my thread below yours? I've a purple missing textures with oscape. Maybe you can help me.

Yep, we have similar issues. I use a lot of custom textures but every texture in the distant blacks out.