How to hunt down which tab or webpage (on Google Chrome) used a lot of memory?
Chrome has a task manager that will be handy in case you have too many tabs to simply close them manually and note when memory reclaims. 


https://support.google.com/chrome/answer/1385029



  
  On your computer, open Chrome.
  At the top right, click the vertical "dot dot dot" icon.
  Select More Tools and then Task Manager.
  Click “Memory” to sort tasks by memory usage. - Tip: Look for any items labeled "Background page."
  Select the task you want to close.
  Click End Process. - Note: Any unsaved work in your task will be lost.
  


I would also run vm_stat 1 and watch the OS memory allocations and freeing so you can watch the effects as you close tabs and see tasks free in the app.