Wow, that must be heavy!
I live in a fairly remote and isolated area (60 miles to the nearest hospital by road), so I always carry a pack when I am out and about in the desert, geocaching or not:
First aid kit
Sunscreen
Hand sanitzer
Multi-tool
Flashlight
Compass
Spare batteries
Kitchen garbage bags
Toilet paper
Baby wipes
Duct tape
Spotting scope
Point-and-shoot camera
Notebook and pencils
Wide-brim hat
Windproof lighter
Bandanas
Snakebite kit (Sawyer extractor)
Whistle
Parachute cord
100 oz. of water (also carry 2 gal. in vehicle)
Power bars (2,000 calories total)
In addition, I carry my GPSr, a knife, a firearm, sunglasses, leather gloves, etc. on my person.