You can view Chrome's page memory usage by pressing the button in the top right of the Window. There you will get this menu:
When you click 'View Background Pages' you'll see a window like this:
This obviously narrows down page and extension usage by memory and CPU. This should help finding out exactly what's going on with it.
The 'Stats for nerds' link sends you to
chrome://memory-redirect/ which breaks down their memory usage even more.
Side note when I notice chrome using a lot of memory and open
/Applications/Utilities/Activity Monitor.app I typically see it is caused by
PepperFlashPlayer (Chrome Plug-In Host) which is Chrome's built in Flash player. It is known for hogging CPU