As I was flying around a world, I noticed these weird chunks. They had part of a dark oak tree in them (see picture). When I flew into them, they loaded properly, but towards the edge of my view, more appeared.
Environment
Java 1.6.0_65 64 bit
GPU: ATI Radeon X1600
CPU: Intel Core 2 Duo @2.16GHz
OS: OS X 10.7.5
Duplicate of MC-62958 – If you have not, please use the search function in the future, to see if your bug has already been submitted.