Carbon Isotope Chemostratigraphy of the Ruby Ranch Member of the Cedar Mountain Formation Near Moore Cut-Off Road West Central Utah




McColloch, Corbin

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The Cretaceous Period is a time of greenhouse conditions, caused primarily by volcanic activity. Associated with the greenhouse conditions are changes in the global carbon cycle. These are typically shown in marine strata as Ocean Anoxic Events (OAEs), and are characterized by deviations in marine strata carbon isotope values. Positive and negative variations in carbon isotope values are called Carbon Isotope Excursions (CIE). The ocean represents a large part of the carbon in the surficial carbon budget, while the terrestrial component is smaller. The interaction of carbon between them is achieved via a well-mixed atmosphere. CIEs that occur in the ocean can thus be seen on land due to atmospheric circulation. One OAE in particular occurring in the Late Aptian-Early Albian stages is the OAE 1b. The Cedar Mountain Formation (CMF) is the oldest and most well preserved continental Cretaceous unit in the continental United States and spans the Aptian-Albian Stages. The Ruby Ranch Member of the CMF documents carbon excursions associated with OAE 1b. The objective of this study is to construct a carbon chemostratigraphic curve for the Ruby Ranch Member in the western extent of the formation and correlate it with existing carbon isotope record for the type sections of the member. Carbon isotope values range from -18.86 to -25.97 ‰ vs VPDB. The curves created seem to correlate with known carbon chemostratigraphic curves from Ludvigson et al. (2010), which identified carbon segments C7-15 of Bralower et al., (1999).


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Carbon, Cretaceous, Isotope, Utah