The more research you do to “file in the holes” of what you know, the more questions it brings up. I was able to fill in a bunch of holes the other day with a trip to Shamokin.
I finally found out what kind of bridge was at the Southern end of the yard. I’ve been looking for photos and have not found any to date. It is a ballasted through concrete trough with steel girders under it. The adbuptments were poured concrete on top of stone foundations. It looked like the bridge had a built date of either 1948 or 1949 the diamond on the adbuptment was a little damaged.
Here are some detail images of the bridge.
Notice the yard lead starts just after the bridge, you can still see it in the ballast.