DAVIS COUNTY—Utah, as a whole, is famous for the prolific amount of amazing fossils found in the area. In fact, Jurassic National Monument, and the Cleveland Lloyd Dinosaur Quarry host the largest collection of Jurassic-era fossils in the world. With so many of these huge creatures around, however, it begs the question: why aren’t there copious amounts of fossils here in Davis County?

Jackson Smith, of the Utah Geological Survey, shared some insights as to why Davis County residents aren’t digging up dinosaurs in their backyards, and why they aren’t likely to do so anytime soon. While there are many reasons, the basics boil down to the following, which also give a picture of what Davis County was like millions, even billions of years ago.

Longtime residents will be very familiar with the Wasatch Range, which borders the western edge of Davis County and runs along the length of Northern Utah. In many cases, modern-day mountain ranges would be a honeypot of fossil finding, but, Smith explains, “The section of the Wasatch mountains in Davis county is particularly special because it contains very old and heavily altered/metamorphosed rocks. It is made of some of the oldest rock in the state, with radiometric ages of about 1.7 billion years.”

This means that those mountains, instead of providing a great spot for dinosaur bones and tracks to be preserved in, were already hardened stone, deep underground while the dinosaurs were roaming the earth above. It would be millions of years before tectonic activity would shift this rock into the mountains that residents see, drive past, and hike on today. It’s strange to imagine, but, even for the dinosaurs, the stone that would become the Wasatch Range would be extremely old.

The next contributing factor relates to the granddaddy of the Great Salt Lake itself, Lake Bonneville. Davis County residents will be very familiar with the Bonneville shoreline trail, sections of which can be found in the county. Like any lake, with copious amounts of water, came a thousand feet of sediment on what is now the valley floor. This may be the best chance residents have for finding a fossil near home, “there are snails and gastropods from Lake Bonneville that you can find on Bonneville shorelines,” said Smith, “They aren't hosted in rock, though, and may not be much to write home about. But they are there, usually loose in the shoreline gravel.”

Unfortunately, due to the tectonic activity in the region that would become Davis County, the filling and receding of Lake Bonneville, and other forces at work for millions of years, many fossils of larger animals like dinosaurs have likely been pulverized into gravel or dust. Still, it begs the question: what was Davis like during the time of the Dinosaurs? Smith gave us a glimpse of what the late Jurassic and Early Cretaceous periods may have looked like in Davis’ own backyard: 

“(Davis) would have been located in a hot, swampy lowland with rivers and lakes, with Dinosaurs like Allosaurus roaming around in the late Jurassic period. Volcanoes would have been common to the west throughout Nevada. Starting in the Cretaceous period, a new mountain range would start to uplift in Nevada/western Utah called the Sevier Mountain range… Davis County would be sandwiched between uplands to the west and a new seaway beginning to form in the east, encroaching from the north and covering Wyoming and Colorado.”