7-31 Chronostratigraphy Using Stable Carbon Isotopes of the Elliot Formation, South Africa

Session: Undergraduate Research, Part I (Posters)

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Abstract:

The Elliot Formation in South Africa preserves a fossiliferous record spanning the Late Triassic–Early Jurassic, a time marked by significant environmental perturbation related to the Central Atlantic Magmatic Province (CAMP) and the end-Triassic extinction event. Despite its importance, the Elliot Formation remains poorly constrained due to limited chronostratigraphic markers. Globally, the Triassic–Jurassic boundary is characterized by a pronounced negative carbon isotope excursion linked to CAMP volcanism and the end Triassic extinction event. This C-isotope excursion is dated to 201.56 Ma and can act as a chronostratigraphic marker for the end Triassic extinction event. This study investigates whether the Elliot Formation records this characteristic carbon isotope excursion at the Qhemegha fossil locality in the Eastern Cape of South Africa. Bulk organic carbon isotope values were measured using isotope ratio mass spectrometry in order to create a high resolution bulk organic carbon isotope profile of the Elliot Formation at the Qhemegha locality. The measured data ranges from -30.73 per mil to -20.59 per mil. A detrital zircon maximum deposition age of 204.11 +/- 0.08 Ma suggests that the initial negative carbon isotope excursion marking the end-Triassic extinction should be positioned above 200 meters in the stratigraphic column. A significant negative C-isotope trend reaches a minimum value of -30.73 just above this point, suggesting that this negative C-isotope excursion may represent the negative C-isotope excursion marking the end-Triassic extinction. Higher resolution sampling will resolve the origin of the C-isotope excursion at the Qhemegha locality.

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