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This stone came out of a stream-bed, so no certain provenance; BUT - I'm sitting on the top of the Oneota dolomite, in extreme SE Fillmore County, SE Minnesota. Ever since I moved here, I've found blocky chunks of what I always called quartzite in nearby stream beds; often with ripple marks like this: Sorry about lack of scale, but if you look at the top of the stone, you can see a northern pin oak leaf - it's about 4 inches long. I was told when I arrived that my Oneota dolomite was overlain by the St. Peter sandstone- which has no record of rippled silicified layers. Two years ago, asking among friends on Facebook, I was plugged into 3 different and authoritative geologists, who suggested my stone had to be from the Sioux quartzite- located well north, and had to have been transported by an older glaciation. That quartzite is supposed to be pink when freshly fractured- and I did indeed find some precisely pink stone eventually; verified as the right color. I stick by my "quartzite" rather than "sandstone", and you can see why. However. Several things did not add up, and I kept the ID tentative in my mind. Then I started finding dolomitic marble- not known in the literature, and indicative of some very active silicification episodes locally- which might make quartzite as well as marble. Digging further, I found a few references that say my own bit of Minnesota has the New Richmond sandstone on top of the Oneota dolomite; just locally. And eventually found a reference that in Indiana, there are rippled sandstones from the New Richmond, so highly silicified that "some call them quartzites". That makes more sense from all aspects- the quartzite I find is so abundant it could easily be a layer overlaying my dolomite, and surviving erosion far better, so quite evident. Also- the Sioux quartzite is measured at around 1.2 to almost 2 billion years old - too old for any critter fossils. I have not yet found any fossils in my quartzite - but it's really metamorphosed hard, and some deformation was going on at the time as some strata are curved; in the Oneota it's strictly flat. The New Richmond is still classified as "lower Ordovician"; somewhere around 450 MYA, I think. There were critters. This next image is the right upper corner of the rippled stone, rotated for a different perspective: Next; same stone; rotated right so you don't have to break your neck looking: and last the same only with "definition" and "sharpness" enhanced as far as I can with my cheapo software. The photo of the entire stone shows you that the rest of the ripples show no disturbances at all; it's only this corner; which looks just a bit like - feet? Hopping along, then 'taking flight"? or if going the other way, landing, causing that different mark? Also note; the "entire stone" photo is of the stone slightly wet; changing some visible details. I have these same photos at about 6 megabytes each, if that might help at some point, and of course I have the stone if you have suggestions for improved images. What do you all think; is there any chance this is actually a trackway- that should perhaps be shown to the real expert folk? I just can't quite dismiss it; there are several aspects that repeat regularly... Theoretically, SE Minnesota was mostly marine tidal flats at this point- the source of the ripples. I eagerly await your thoughts.