To clarify, Rauchtown and its tribs are small forested freestone streams. Rauchtown from the one time I fished it, above the SP, appeared to be a roughly 50/50 Brookie/Brown mix. It was meh. I didn’t have a strong desire to fish it again since, and haven’t.
Rauchtown then sinks into limestone geology as noted shortly below the SP, and presumably becomes part of the flow that emerges from the spring several miles to the north as Antes Creek - Along with the water draining the remainder of the bowl like basin to the north and east of where Rauchtown sinks. That whole bowl is underlain by limestone, and presumably that whole watershed emerges all at once as a full on limestoner as Antes Creek, and then cuts through the mountain gap along 44 to the West Branch. I’ve never fished Antes, as it’s high in the running for the most tightly posted stream in PA, but from what I gather it’s a very good wild Brown Trout fishery from the emergence of the spring to its mouth.
But, in the case of Rauchtown and its surface flow above and through the SP area, it’s all freestone geology until it sinks. There’s no surface flow for a distance of 3 or 4 miles until the spring that emerges as Antes.
In that general area, this is fairly common. Streams originate as freestone streams in the mountains, then sink into limestone geology when they hit the valley floor, to re-emerge somewhere further downstream in the watershed via a spring as a limestoner. Honey Creek is very similar for instance, and emerges all at once from a large spring after its tribs have sunk further upstream, and there are numerous small streams that do this in the BFC and Spring Creek watersheds as well.
