Line north of Denville / Denville wye

There is a wye track in Denville at the present NJT pax station. The wye is in place but tracks look disused. Looking at google maps I'm going to assume that line went north somewhere. I did the historic aerials as far back as 1957 and the track ends where it does today. But the topo maps show the line continuing. Can anyone tell me what this line was, when it was removed? Must have been many many moons ago!

Part of the old "Rockaway Loop" that rejoined the main at Denville (N 40.87979 W 74.52390) Last passenger run circa Oct. 17, 1948.

That side of the Y went behind the Grocery Store and across Indian Lake. Then it parallels Route 46 before crossing under a bridge and continues on to the Rt.46 Rockaway River bridge where it now runs under the abutment. It continues on paralleling the M&E trackage and through a parking lot and into the woods.

At one time a Y existed on the other leg so, you could go form Morristown to Boonton for example. Denville is still a great place to view activity.

I seem to recall reading that the Rockaway loop was part of the original DLW mainline (the Morris and Essex Line coming north from Morristown), and the modern straighter alignment that replaced it was part of the Boonton Branch freight bypass from Dover to just west of the Bergen Tunnel around 1870.
JS
For the experts : I also seem to recall, but have no idea of the source, that before the "modern" Boonton branch was built as a thru-line ~1870, there was a stub-ended "Boonton Branch" from Denville to Boonton, because of Boonton's importance as a iron/manufacturing location. Is this really true?