I was exploring in a cave with a group and one of them started calling the passage we were in a "shaft drain complex". The person using this term had recently heard a talk by Roger Brucker on connecting caves to the Mammoth system.
But I wasn't sure that what we were in would actually qualify as "shaft drain". It sure didn't look like Roger's pictures, but I'm still not an expert. Specifically, we were in a branching canyon passage (with multiple feeders and multiple outlets) that occasionally had pits and domes. One of these pits (approx 10 feet deep) was a simple pit that drained into a gravel floor, but the others flowed down or out into a canyon passage. Additionally, when we first entered the starting canyon passage it was nice and mildly meandering keyhole passage. But after climbing for a while the offshoot passages suddenly began to have frequent 90 degree turns.
Another interesting thing is the type of rock we encountered on the trip. The first 1.8 miles we crawled through smooth/solid phreatic tube which had been [partially] filled with mud. Then we got into huge chambers that had enourmous breakdown piles to hike over but strong rock on the walls. Then we entered a canyon passage and the rock seemed more fragile/worn. It was easier to break pieces off and there was a ton of fluting. There was also quite a few sheets of gypsum on the walls and floors (fallen).
I guess my real question is whether there is a simple online resource that discusses the various types of cave passages beyond the basics. I'm familiar with phreatic tubes, vados (keyhole) passages, fault formed passages....but when someone says "shaft drain complex" I'm not sure whether that is a local slang or something that I can identify.