LATE TRIASSIC (NORIAN) CORAL REEF MOUND FROM GARFIELD HILLS, NEVADA

Reef production took a sharp downturn during the end-Permian mass extinction. Nevertheless, ten million years later, during the Triassic reef recovery, reefs surpassed their Permian predecessors in paleogeographic territory, taxonomic abundance, and diversity. Furthermore, the Triassic began scleractinian corals' inception as a dominant reef bioconstructor. Our understanding of Triassic reef recovery is primarily based on Europe and Asia's expansive and abundant reefs. Triassic reefs in North America are comparably rare and understudied. I collected quantitative microfacies data from a Norian age reef mound in Garfield Hills, Nevada, to characterize reef facies types. I point counted thin sections to assess reef and interstitial components. I statistically compared Garfield Hill's reef components to other North American Norian reefs using hierarchical clustering and SIMPROF analysis. Garfield Hill's reef mound is 14 m wide and 6 m tall and displays vertical zonation. The reef mound is underlain by phylloid packstone and fossiliferous wackestone, including brachiopods, echinoderms, and gastropods. The reef mound is comprised by inozoan sponge bindstone, coral bindstone, and coral framestone. Corals are present in platy and branching ecomorphotypes and ceroid, meandroid, and phaceloid colony forms, and sphinctozoan sponges are present variably. Compared to a Norian reef mound in Mina, Nevada, the Garfield Hills reef mound is smaller, has more calcareous sponges, including inozoan sponges, and preliminary data suggests the reef grew below fair-weather wave base (FWWB). In contrast, the Mina reef may have extended beyond the FWWB. Comparing quantitative microfacies data between reefs will improve our understanding of reef development.