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Seafloor weathering and the Middle to Late Ordovician seawater 87Sr/86Sr inflection point preserved in conodont apatite

Avila, Teresa D
http://rave.ohiolink.edu/etdc/view?acc_num=osu1565961269717394

Abstract Details

2019, Master of Science, Ohio State University, Earth Sciences.
The strontium isotope ratio (87Sr/86Sr) of global seawater varies through geologic time and can serve as a proxy for silicate weathering patterns as well as rates of spreading in midocean ridges. The 87Sr/86Sr value of seawater steadily decreases through the course of the Ordovician, with an increased rate of change during the Darriwilian to Sandbian (Middle to Late Ordovician). The precise age of this inflection point has been poorly constrained, making it difficult to ascertain its possible causes and effects. Here, conodont apatite from the Simpson Group of the Arbuckle Mountains, Oklahoma were analyzed in order to build a higher-resolution 87Sr/86Sr curve. The preparation of conodont samples via leaching in acetic acid is also investigated. In the case of Oklahoma section conodont elements with low thermal alteration (i.e., Color Alteration Index; (CAI) ≤ 1), leaching does appear to strip diagenetic Sr, but the overall effect on 87Sr/86Sr (7.47 x 10-6) is smaller than the external analytical error (8.22 x 10-6). To identify the inflection point in the new data set, a smoothing LOESS curve was used to produce a gradient curve, a process which has not yet been applied to the Middle to Late Ordovician. The 87Sr/86Sr inflection point falls in the transition from the Oil Creek to McLish Formations, within the holodentata conodont zone at 466.4 to 463.8 Mya. The shift in 87Sr/86Sr occurs at the Sauk-Tippecanoe sequence boundary and associated transgression, which may reflect increased spreading rates of mid-ocean ridges. Previous studies have linked the inflection point in 87Sr/86Sr to the Taconic Orogeny at c.a. 465 Mya, which may also play an important role in the shift of global 87Sr/86Sr but is unlikely to account for the transgression at the base of the McLish due to asynchronous timing of events.
Matthew Saltzman (Advisor)
Elizabeth Griffith (Committee Member)
John Olesik (Committee Member)
63 p.
Earth; Geochemistry; Geological; Geology; Paleoclimate Science
geochemistry; paleoclimatology; conodont; strontium; strontium isotope stratigraphy; Ordovician; sedimentology; seafloor spreading

Recommended Citations

Citations

  • Avila, T. D. (2019). Seafloor weathering and the Middle to Late Ordovician seawater 87Sr/86Sr inflection point preserved in conodont apatite [Master's thesis, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1565961269717394

    APA Style (7th edition)

  • Avila, Teresa. Seafloor weathering and the Middle to Late Ordovician seawater 87Sr/86Sr inflection point preserved in conodont apatite . 2019. Ohio State University, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1565961269717394.

    MLA Style (8th edition)

  • Avila, Teresa. "Seafloor weathering and the Middle to Late Ordovician seawater 87Sr/86Sr inflection point preserved in conodont apatite ." Master's thesis, Ohio State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=osu1565961269717394

    Chicago Manual of Style (17th edition)

osu1565961269717394
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