Primary versus diagenetic isotope signals in Pseudorthoceras sp. from the Buckhorn Asphalt Quarry (mid-Pennsylvanian, Oklahoma) - a detailed study of cameral deposits

Seuß B, Titschack J, Nützel A (2010)


Publication Language: English

Publication Type: Conference contribution, Abstract of a poster

Publication year: 2010

Event location: München

Abstract

Oxygen and carbon stable isotope studies of well-preserved fossils present an important data source for palaeoclimatic studies. Commonly, the older the fossils, the less good they are preserved. The Buckhorn Asphalt Quarry Lagerstätte from the mid-Pennsylvanian of Oklahoma is one of the few Palaeozoic examples, where original (metastable) shell material, such as aragonite and high magnesium calcite (HMC) is found, due to their early post-mortal hydrocarbon impregnation. The Buckhorn Asphalt Quarry is characterised by fossiliferous sediments soaked with hydrocarbons, which commonly prevented diagenesis. This study presents microstructural, mineralogical and stable isotope data from Pseudorthoceras sp. (two chambers with their cameral deposits). Therefore data from thin section analysis, scanning electron microscope (SEM) combined with an energy disperse x-ray (EDX), and x-ray diffraction (XRD) with a general area detection diffraction system (GADDS) analysis were combined. XRD-GADDS is a relatively new method to investigate the shells mineralogy and allows the non-destructive, site-specific identification of mineral phases. Altogether seven microstructures were differed in the sections drilled for isotope dating. These could be divided into two primary mineralogies, aragonite and HMC. We don’t have any knowledge of cameral deposits with a HMC mineralogy or found any evidence of this in literature. The only partially unaltered preserved microstructure is the nacre of the septum. All other microstructures exhibit a partial or complete alteration to low magnesium calcite (LMC), or in case of the primary HMC to LMC and dolomite. According to the isotope signature the diagenesis took place most likely in the meteoric environment. The partial diagenesis results in isotope values, which plot along a linear trend between the two end-members. This linear trend could easily be misinterpreted as kinetic vital effect, if no sorrow phase control was performed. The isotopic signal of the primary nacre of the septum suggest a normal marine environment for these nektonic molluscs, with tropical temperatures of 14°C to 15°C (δ18Oseawater 1.5 ‰, a typical value for modern tropical marginal seas).

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APA:

Seuß, B., Titschack, J., & Nützel, A. (2010). Primary versus diagenetic isotope signals in Pseudorthoceras sp. from the Buckhorn Asphalt Quarry (mid-Pennsylvanian, Oklahoma) - a detailed study of cameral deposits. Poster presentation at Annual Meeting of the Paläontologische Gesellschaft, München.

MLA:

Seuß, Barbara, Jürgen Titschack, and Alexander Nützel. "Primary versus diagenetic isotope signals in Pseudorthoceras sp. from the Buckhorn Asphalt Quarry (mid-Pennsylvanian, Oklahoma) - a detailed study of cameral deposits." Presented at Annual Meeting of the Paläontologische Gesellschaft, München 2010.

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