--> Abstract: Development of High-Resolution δ13C Records in Tethyan Limestones from the Anisian to Early Norian, by David Mosher, Miriam Katz, Giovanni Muttoni, and Dennis Kent; #90124 (2011)

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AAPG ANNUAL CONFERENCE AND EXHIBITION
Making the Next Giant Leap in Geosciences
April 10-13, 2011, Houston, Texas, USA

Development of High-Resolution δ13C Records in Tethyan Limestones from the Anisian to Early Norian

David Mosher1; Miriam Katz1; Giovanni Muttoni2; Dennis Kent3

(1) Earth and Environmental Sciences, Rensselaer Polytechnic Institute, Troy, NY.

(2) Dipartimento di Scienze della Terra, Universita degli Studi di Milano, Milano, Italy.

(3) Earth and Planetary Sciences, Rutgers University, Piscataway, NJ.

Carbon isotopes are an effective stratigraphic correlation tool in Neogene and Paleogene sections (e.g., Cramer et al., 2003; Dupuis et al., 2003; Woodruff and Savin, 1991), and are proving to be critical in older records where biomagnetostratigraphy is insufficient to accurately correlate high-resolution datasets (e.g., Cramer and Saltzman, 2005; Grocke, 2006; Muttoni et al., 2004; Weissert et al., 1998). Published δ13C records from Triassic sections show promise for establishing δ13C as an important stratigraphic correlation tool during this time period. The Triassic began with large negative δ13C excursions in marine carbonates (up to 8‰) and organic matter (-2 to -5‰), followed by the stabilization of δ13C, punctuated by occasional smaller events (Korte et al., 2005; Muttoni et al., 2004; Payne, 2004).

In this study, we present new high resolution (100 ky) δ13C records of bulk sediment carbonates from Tethyan Triassic sections with excellent biomagnetostratigraphy. Our goal is to establish δ13C event stratigraphy that can be used for correlation in sections that lack good biomagnetostratigraphy.

We analyzed an Anisian-Ladinian (~240-231 Ma) limestone section from Seceda (northwestern Dolomites, Italy) that spans the entire Buchenstein Beds Formation. These limestones contain radiometrically-dated tuff layers (~238.0-241.2 Ma) (Mundil et al., 1996; Brack et al., 1996). Through U-Pb age dating, a sediment accumulation rate of ~10 m/m.y. was determined, this rate doubled in the Bänderkalke member; where turbidite beds became more prevalent (Maurer el al., 2003). The magnetostratigraphy from this core has been used to define the base of the Ladinian for the Global Stratigraphic Section and Point (GSSP), and to complete the Middle Triassic magnetic polarity time scale; in addition, conodont biostratigraphy has been directly tied to the Seceda core from locations throughout the Dolomites and Alps (Muttoni et al., 2004). This published integrated biomagnetostratigraphic framework makes Seceda the best section to use for our Middle Triassic δ13C stratigraphy. In addition, we analyzed a section from Hydra Aghia Marina (Greece) to check Seceda results when the two sections overlap; the Aghia Marina is from Adhami Formation; condont biostratigraphy indicates late Ladinian to early Norian ages.