Seafloor weathering and the Middle to Late Ordovician seawater <sup>87</sup>Sr/<sup>86</sup>Sr inflection point preserved in conodont apatite
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The Ohio State University / OhioLINK
2019
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| Online Access: | http://rave.ohiolink.edu/etdc/view?acc_num=osu1565961269717394 |
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ndltd-OhioLink-oai-etd.ohiolink.edu-osu15659612697173942021-08-03T07:12:25Z Seafloor weathering and the Middle to Late Ordovician seawater <sup>87</sup>Sr/<sup>86</sup>Sr inflection point preserved in conodont apatite Avila, Teresa D. Geochemistry Geology Geological Paleoclimate Science Earth geochemistry paleoclimatology conodont strontium strontium isotope stratigraphy Ordovician sedimentology seafloor spreading The strontium isotope ratio (<sup>87</sup>Sr/<sup>86</sup>Sr) 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 <sup>87</sup>Sr/<sup>86</sup>Sr 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 <sup>87</sup>Sr/<sup>86</sup>Sr 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 <sup>87</sup>Sr/<sup>86</sup>Sr (7.47 x 10<sup>-6</sup>) is smaller than the external analytical error (8.22 x 10<sup>-6</sup>). 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 <sup>87</sup>Sr/<sup>86</sup>Sr 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 <sup>87</sup>Sr/<sup>86</sup>Sr 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 <sup>87</sup>Sr/<sup>86</sup>Sr to the Taconic Orogeny at c.a. 465 Mya, which may also play an important role in the shift of global <sup>87</sup>Sr/<sup>86</sup>Sr but is unlikely to account for the transgression at the base of the McLish due to asynchronous timing of events. 2019 English text The Ohio State University / OhioLINK http://rave.ohiolink.edu/etdc/view?acc_num=osu1565961269717394 http://rave.ohiolink.edu/etdc/view?acc_num=osu1565961269717394 unrestricted This thesis or dissertation is protected by copyright: all rights reserved. It may not be copied or redistributed beyond the terms of applicable copyright laws. |
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NDLTD |
| language |
English |
| sources |
NDLTD |
| topic |
Geochemistry Geology Geological Paleoclimate Science Earth geochemistry paleoclimatology conodont strontium strontium isotope stratigraphy Ordovician sedimentology seafloor spreading |
| spellingShingle |
Geochemistry Geology Geological Paleoclimate Science Earth geochemistry paleoclimatology conodont strontium strontium isotope stratigraphy Ordovician sedimentology seafloor spreading Avila, Teresa D. Seafloor weathering and the Middle to Late Ordovician seawater <sup>87</sup>Sr/<sup>86</sup>Sr inflection point preserved in conodont apatite |
| author |
Avila, Teresa D. |
| author_facet |
Avila, Teresa D. |
| author_sort |
Avila, Teresa D. |
| title |
Seafloor weathering and the Middle to Late Ordovician seawater <sup>87</sup>Sr/<sup>86</sup>Sr inflection point preserved in conodont apatite |
| title_short |
Seafloor weathering and the Middle to Late Ordovician seawater <sup>87</sup>Sr/<sup>86</sup>Sr inflection point preserved in conodont apatite |
| title_full |
Seafloor weathering and the Middle to Late Ordovician seawater <sup>87</sup>Sr/<sup>86</sup>Sr inflection point preserved in conodont apatite |
| title_fullStr |
Seafloor weathering and the Middle to Late Ordovician seawater <sup>87</sup>Sr/<sup>86</sup>Sr inflection point preserved in conodont apatite |
| title_full_unstemmed |
Seafloor weathering and the Middle to Late Ordovician seawater <sup>87</sup>Sr/<sup>86</sup>Sr inflection point preserved in conodont apatite |
| title_sort |
seafloor weathering and the middle to late ordovician seawater <sup>87</sup>sr/<sup>86</sup>sr inflection point preserved in conodont apatite |
| publisher |
The Ohio State University / OhioLINK |
| publishDate |
2019 |
| url |
http://rave.ohiolink.edu/etdc/view?acc_num=osu1565961269717394 |
| work_keys_str_mv |
AT avilateresad seafloorweatheringandthemiddletolateordovicianseawatersup87supsrsup86supsrinflectionpointpreservedinconodontapatite |
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1719456350138793984 |