being likely naturally caused by things dropping from the sky,
Yeah, shit falls from the sky and splashes rocks around down here all the time, Buz.
What isn't "complex" about hundreds of acres of stones all gathered up into rings with bare centers? If you saw a dozen rings like those in your backyard, would you think first of gophers or of neighbor kids? Or of shit falling out of the sky?
Hint: neighbor kids would be my first choice if it were in my backyard. There aren't lots of kids in Spitsbergen.