Your own "White Mars" scenario proposes no more than a 1 meter snowpack during S Polar winter. CO2 snow would be unlikely to form an icepack on relatively low latitude dunes

*Russell Crater Dunes = ~54.75°S*

Quite some distance from the pole.

The idea of something heavy plowing through the dunes is intriguing, however. But let's remember that these dunes are gigantic, and their composition is unknown. We can't even be sure they are sand. Most of the channels start in alcoves at the dune crest. The channels are quite long. Deep compared to wide. Many have raised margins but not all. And they abruptly end at nearly the same distance from the starting point. Some trails show chains of pits or a kind of scalloping at some places along their length, mostly near the terminous.

If we are dealing with CO2 here -- and I'm not saying we're not -- it is unlikely to be in the form of significantly heavy blocks. Don't forget, things are lighter on Mars, and CO2 snow and/or ice ain't that heavy anyway.

If we're not dealing with "sand" dunes though, it could be that carbonic acid is "eating" a trail through whatever constitues the dunes.

I think we need to figure out what the dunal composition is, and what the grain size is, what the volatile content of the dunes is, how heavy the winter snowfall is, what constitutes the snow, and we need to find out whether or not volatiles can and do migrate within the dunes.

Simple.

;-)

Cheers, B R Felix