MICROFAUNA OF THE MID-PALEOZOIC FITCHVILLE FORMATION, LAKESIDE MOUNTAINS, UTAH

The Fitchville Formation is a dolomitic limestone unit in central Utah that spans the late Devonian through early Mississippian. The previously known fossil fauna of this formation consists primarily of silicified rugose and tabulate corals, as well as fragments of gastropod and brachiopod and some crinoid hash. Due to the dolomitization of the Fitchville Formation and its poorly preserved macrofossils, more precise dating of this unit has been challenging and its paleoecology has been largely overlooked. Outcrops of the Fitchville Formation located in the Lakeside Mountains, west of Great Salt Lake, contain layers of nodular chert that may provide a taphonomic opportunity to understand this rock unit in more detail.

We thin sectioned chert nodules from ten different horizons within the Fitchville Formation in order to catalog the diversity of microfossils preserved therein. In addition to finding fragments of the fauna already known from the Fitchville Formation through macrofossils, we found several species of scolecodont and acritarch, as well as red algae. All of these taxa, while previously undescribed from this location, are typical of a mid-Paleozoic backreef environment. We also found additional specimens that allow us to constrain the age of this outcrop more precisely. The presence of chitinozoans and eurypterid cuticle fragments in the chert nodules constrains this particular outcrop of the Fitchville formation to the Devonian.