Treasure in a chasm are just a pile of items in a crevice, so there's no digging involved. Instead, you need to go to each matching tile and scan pass over them so your character has viewed all of the cliff parts.
For the current version I'd recommend skipping the skis, especially if your character isn't very large. The weight of the skis increase fatigue far more than the slightly increased speed provides range, so you don't have to travel very far before your movement rate on skis is lower than that on foot due to the extra fatigue build-up from the weight. This is going to be rebalanced a bit in the next release, so hopefully skis will be useful then. I'd definitely not waste good furs on skis currently if you're desperate for warmth.