One of the tools to reconstruct climate history in the Great Basin and North America Deserts (Mojave, Sonoran, etc.) are packrat middens. From the Wikipedia article on packrat middens:
Pack rats are known for their characteristic searching of materials to bring back to their nests creating an ever expanding collection known as a “midden” for its messiness. In natural environments, the middens are normally built out of sticks in rock crevices or caves for protection from predators. In the absence of crevices or caves, the middens are often built under trees or bushes. The pack rats will also use plant fragments, animal dung and small rocks in building the nest. The vast majority of the materials will be from a radius of several dozen yards of the nest. The pack rats urinate in the midden; sugar and other substances in the urine crystallizes as it dries out, creating a material known as amberat, cementing the midden together.
There are some amusing (or sickening, depending on how black your humors are) tales of Anglo explorers eating amberat, supposing it was some sort of desert bounty. After a couple of days (really) they quickly they were mistaken. shudder
Previously unexamined, perhaps because century- and millennial- depth deposits are seldom, if ever, allowed to accumulate, are the feline urine cemented deposits of ambercat that occur in cat litter boxes. Judging from the rapidity and volume that can be generated in geologically insignificant timescales (24 – 36 hours with multiple felines contributing to the ‘midden’) these proxies could be valuable for climatic reconstruction if deposits could be identified prior to the radiocarbon ‘recent.’
Absent its scientific value, I would personally be overjoyed to discover that ambercat had some sort of commercial value as our felines are apparently ‘top producers’ of ambercat, indeed in commercially viable quantities. I await your offers. There is a bagged sample at the curb right now.