Sounds to me like it may very well be squirrel "cuttings" as well. Your woods are "predominantly mature oaks"... If you have a squirrel or two around you have the perfect makings for it this time of year. These are the cuttings from a single Red Oak tree in my yard which I planted maybe 17-18 years ago from an acorn. It just started producing acorns a year or two ago and this year it is just loaded. What you see on the ground has been cut by a single small gray squirrel in one week - the last time my wife mowed the lawn. and there are still more acorns to go... I posted some photos a while back of some broken limbs and branches where a bear climbed up one of my oaks and broke them down so he could eat the acorns on the ground. If you set up your camera you are likely to confirm the culprit.