Having thought about it some more, and thanks to this information, I believe it is maple trees violently cracking. The edge of the pasture that I spoke of in the post is facing south and elevated above the surroundings, so it is likely that the trees there warmed up more than the ones in the woods. This would explain why I heard the noises only for the first few hours following sunset, since the sap was still readily flowing through the tree as it was freezing rapidly. I have definitely heard many loud cracks on a cold winter night, but this was exceptional.