Be safe. Use the used litter only to fill holes; that's about it.
There are a lot of bloggers who demonstrate you CAN compost cat litter (wood and clay), growing even leafy ground crops like lettuce. But they have not tested their cats or their worked soil.
My property is a little wild, and I've spent a few years leveling out some of the larger dips and holes. I do this by digging up the topsoil (one foot down), filling it some, then returning the topsoil. If I need to relocate a lot of soil, I'll use a pick and dig a small pit on the edge of the property (so I immediately have topsoil + sand to mix with clean compost. I can then take my time filling that pit, and eventually cap it with topsoil. Note that if you do this with wood/paper litter, the decomposition will eventually cause the topsoil to "sag" so you may want to balance the paper/wood with clay, or mound a hill of topsoil in anticipation of settling.
Beware that insufficient "normal" topsoil depth over this will present a walking hazard (boots punching through the topsoil into wet contaminated clay). Depending on your locale and laws, it MAY be considered some form of improper waste disposal so use sense and don't create a hazard for yourself or future owners of the property.
I've only dug holes around the treeline as "a" I don't want to see a pit from the home windows, and "b" I don't want a mess where someone may walk over (however the freshly leveled space is OK for planting trees, flowers or other non-edible plants). 4" of sandy topsoil followed by 2" of mulch seems like a reasonable compromise for areas not normally walked on.