Dunno what to tell you.
What I see at 3 o'clock is a dark patch on the margin of the heartwood. The heartwood is simply structural; the xylem has been plugged and filled with various compounds. Water and mineral transport occurs only in the lighter colored sap wood and, as far as this is concerned, more is carried in the outermost rings, where everything looks fine.
Perhaps a few more sections at other places along the length of the severed branch you are holding will tell more of a story.