Though it's hard to capture depth in a photo, this bark has deeply "stacked" layers -- see especially the upper right. At least 8 layers of bark, each about 2mm thick, have remained stuck to the outside of the live bark…

Having asked you all for ideas, I think Rajal (via facebook) had the answer: A pignut hickory (Carya glabra). At least one online pignut hickory photo is a dead ringer for this same bark structure, though others might identify this bark as the red hickory (carya ovalis or carya glabra var. odorata ecotype) instead. Either way, thanks!!