Could that be part of Lake Bonneville? I can’t recall the area it covered, but it seems that the Humboldt Sink is part of it all.
When we were kids, we used to find shell fossils in the red soil in Central Utah. Though I was born in Reno, I was never there long enough as an adult to do any hiking.
Lake Bonneville wasn’t around long enough ago, or for long enough a time. :’)