I would have assumed the following is common knowlege to those who know about vortexs and portals, but I have not seen any common hints of it, up to now. Meditation and spiritualisum existed from the first shaman in the world. And in meditation it is very common to see a spinning vortex. I believe Buddist mandalas are based on it. So does this show up in petroglyphs in any form?
Well yes, of course it does! See attached. Spirals, Dream Catchers, Medicin Wheels. All can be related to that.
I have seen single, reverse and multiple spining vortexes in meditation. Both Native American and Celtic cavings exhibit these spiral carvings, and other apparent mandala patterns. In truth, they appear all over the world as rock/cave cavings.
As to the spiral ones, they only repersent a coiled snake in that a coiled snake is used as a easy icon to remind a shaman about votexes.
With my experience, as I now undersand it, what a shaman would do when encountering a spiral petroglyph, is know that this is a good place to work with votex energy. It may be easier to connect with such at that location. Also I would expect a shaman to leave and read messages left at the rocks in those locations using psychometry.
Leaving a masseage, first obtain a meditative state, then they place thier hand on a rock, ‘intend’ a message and ‘feel’ it into the rock. Reading a message is only the exact reverse of that. Clearing such messages goes beyond what a short email can deliver.
Just my observations. Your mileage may vary. -Me