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Evidence for early-phase explosive basaltic volcanism at Mt. Morning from glass-rich sediments in the ANDRILL AND-2A core and possible response to glacial cyclicity

Nyland, Roseanne E.
http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1308530267

Abstract Details

2011, Master of Science (MS), Bowling Green State University, Geology.
Sediments recovered between ~354 and 765 mbsf (~15.9-18.4 Ma) in the ANDRILL AND-2A core contain dispersed accumulations of volcanic glass up to 50% by volume and are used to investigate the petrological evolution and influence of glaciations on volcanism in the McMurdo Sound region of Antarctica. Glass-rich sediments include muddy-to-fine sandstone and stratified diamictite. The glass varies in color, size, vesicularity, crystal content, angularity, and from fresh to moderately altered. Fresh glass with delicate cuspate forms suggests they were introduced into the basin as ash fall with minimal reworking. Altered glass has low total oxides (< 97 wt.%), low Ca/K ratios (< 2), high Alteration Index (> 40), and are typically more evolved than fresh glass. Pristine basaltic glasses (MgO 3-7 wt.%) are ne-normative (5-30 wt.%) and have restricted average SiO2 content (45.2 ± 0.8 wt.%). Overall the glass composition shows an increase in SiO2 content up-section. Fractional crystallization models indicate differentiation controlled by plagioclase, olivine, clinopyroxene and magnetite ± amphibole and apatite. Trace element concentrations are typical for Erebus Volcanic Province (EVP) volcanism. The data extends known composition of Mount Morning (18.7-11.4 Ma), the only known EVP Early-Middle Miocene source, to a mafic end, revealing a previously unknown phase of explosive, strongly alkaline, basaltic activity. The glass-rich sediments are part of larger sequences that record numerous glacial advances and retreats in the region. Sediments with high glass contents correspond to ice minimums and, geochemically, Ba/LREE ratios correlate to intervals of ice expansion (decreasing values) and contraction (increasing values) at multiple depths. Higher Ba/LREE may indicate tapping of more volatile-rich magmas. Within a single glacimarine cycle, glass angularity, vesicularity and composition also vary systematically. A model is supported where ice loading and unloading affects the stress state of the crust around a shallow (< 5 km) magma system. During peak glacial periods, the propagation of magma filled fractures is suppressed and volatiles accumulate in response to the fractionation of anhydrous minerals and/or recharge by volatile-rich magmas. Changing stress states during deglaciation allows the volatile enriched magmas to then rise and vesiculate at shallower depths promoting explosive eruptions.
Kurt Panter, PhD (Advisor)
John Farver, PhD (Committee Member)
Jeffrey Snyder, PhD (Committee Member)
158 p.
Geology
ANDRILL; Antarctica; Mt. Morning; basaltic volcanism; volcanic glass; geochemistry; glacial-volcanism feedback

Recommended Citations

Citations

  • Nyland, R. E. (2011). Evidence for early-phase explosive basaltic volcanism at Mt. Morning from glass-rich sediments in the ANDRILL AND-2A core and possible response to glacial cyclicity [Master's thesis, Bowling Green State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1308530267

    APA Style (7th edition)

  • Nyland, Roseanne. Evidence for early-phase explosive basaltic volcanism at Mt. Morning from glass-rich sediments in the ANDRILL AND-2A core and possible response to glacial cyclicity. 2011. Bowling Green State University, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1308530267.

    MLA Style (8th edition)

  • Nyland, Roseanne. "Evidence for early-phase explosive basaltic volcanism at Mt. Morning from glass-rich sediments in the ANDRILL AND-2A core and possible response to glacial cyclicity." Master's thesis, Bowling Green State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1308530267

    Chicago Manual of Style (17th edition)

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© 2011, all rights reserved.
This open access ETD is published by Bowling Green State University and OhioLINK.