Turntable isolation

I have my TT (Rega P7) on top of my audio cabinet. The cabinet is an Ethan Allen Townhouse component cabinet with a marble top. I noticed this weekend that when I touch the doors to my audio equipment I can hear a light thump via the cartridge. Even when I lightly tap the door the sound travels through the cabinet woodwork, through the marble to the cartridge. How can I isolate the TT from the rest of the cabinet?