Royal Terrace Falls, at McDowell Creek County Park, between Lebanon and Sweet Home, Linn County, Oregon. At 110 feet, this is not huge by Oregon standards, but it is awfully nice. I saw an article over the winter about this park, which offers an approximately 2-mile loop hike with numerous falls. I was surprised; I've lived in the area for more than 30 years, and I'm pretty familiar with it. This is close by- a bit more than half an hour away from Corvallis- and I'd never heard of it. Can't be that special, right? Wrong. It really is quite wonderful.
There are two large falls, the above and Majestic, quite a number of mid-sized falls, ten to a few tens of feet, and uncountable small falls and riffles. Add into that picture a dominantly old-growth, low elevation temperate rain forest, and you have a recipe for extraordinary beauty. The bottom of the park is just into the Cascade foothills, which means that except in the coldest weather, this would be nice throughout the winter, when flows are at their peak.
I'm guessing the rock here is mostly early Western Cascades volcanics, interbedded with either sediments or paleosols. The exposures in the park are not good, and heavily weathered, so it's hard to tell exactly what you're looking at. But based on my knowledge of nearby rocks, the clear repeating of resistant and weak layers, and the lack of any geological interpretation at the park, I'm comfortable with my guess.