That's a good sign ;-). Any mesa-like mountains are likely to be sills (i.e. Rabbit Mountain, Mount McKay). While checking some references on the Mount McKay article I found Pie Island, Isle Royale and Flatland Island which appear to be sills as well, along with others at Lake Nipigon, which appears to be a failed arm of the main rift called the Nipigon Embayment. The other sills can be found here. I'm wanting to take some pictures of pillow lava formations around my area but I don't have a camera lol. So I'll have to wait until I have one.