HOW LOW DID CONODONTS GO? INSIGHTS INTO CARBONIFEROUS GLACIOEUSTASY FROM CONODONT OCCURRENCE IN ARROW CANYON, NV

Predictions of future eustatic variability may be improved by understanding the mechanisms controlling glacial to interglacial sea-level change in an icehouse climate. An accurate estimate for Late Paleozoic Ice Age glacioeustatic magnitudes continues to elude us, with current values ranging from 10 to 250m (Rygel et al, 2008). Here we present the results of a comparison of sedimentary facies with conodont yield from the Carboniferous of Arrow Canyon, NV. Conodonts are most abundant in photozoan and heterozoan grainstone/packstone beds, and rarely present in calcisiltite and marl facies. The dominance of microfossils in facies traditionally interpreted as shallower than storm wave base deposition and lack of conodonts in deeper facies potentially indicates the conodont-bearing organism did not inhabit waters deeper than storm wave base. Stratigraphic analysis by Bishop and others (2010) suggests that the calcisiltite and marl sediments of the mixed carbonate-siliciclastic Arrow Canyon section were deposited in water depths of 50m. If the Arrow Canyon trend is global in nature and conodonts did not inhabit waters deeper than 50m, then glacioeustatic estimates derived from analyses of the phosphate oxygen isotopic composition of conodont apatite must be similarly limited in magnitude. The results of this work potentially provide an upper limit on the magnitude of Carboniferous sea-level change as estimated from conodont geochemical analyses, as well as highlight the need for further understanding of the climatic processes effecting the oxygen isotope composition of Late Paleozoic conodonts.