UC Riverside

Gastropods, which evolved in the earliest Paleozoic, are one of the most diverse and ecologically dominant clades in the modern ocean. The clade experienced its first global radiation event during the Ordovician, but gastropods were of minor ecological importance throughout the Paleozoic. This study aims to identify the environmental and ecological controls on gastropod occurrence during the height of the Ordovician Radiation Event through a study of the paleoenvironmental context of gastropods from the Ibex Region of the Confusion Range in western Utah, Basin and Range Province.

Gastropods, collected from Ibexian and Whiterockian Middle Ordovician strata (Wah Wah Formation, Juab Formation, Kanosh Shale and Lehman Formation), were identified and analyzed for depositional context and abundance, from which ecological dominance was interpreted. Results demonstrate that gastropods are more diverse (with eleven taxa identified) than previous studies of the Ibex Region have stated. Gastropods were most diverse in shallow environments and most abundant in harsh (low oxygen and/or high salinity) environments. Gastropod occurrences were correlated to muddy substrates, regardless of depth. The only environment in which gastropods were dominant was the hypersaline lagoon, preserved in the Lehman Formation.