https://en-gb.topographic-map.com/ma...57%2C-73.97713
It's not much of an elevation but there is a bit of a ridge that runs up basically along Kinderkamack. Although the terms aren't particularly accurate since the higher elevation towns like Dumont are part of the colloquial "Northern Valley" anyway.Though once you get west of that ridge you aren't in the Northern Valley anymore.
Anyway they definitely refer to different areas.
Roughly speaking areas to the east of the Oradell Reservoir are Northern Valley while the areas northwest of it are the Pascack Valley.