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Geochemical Fluxes and Weathering on High Standing Islands: Taranaki and Manawatu-Wanganui Regions New Zealand

Goldsmith, Steven Todd
http://rave.ohiolink.edu/etdc/view?acc_num=osu1391601668

Abstract Details

2005, Master of Science, Ohio State University, Geological Sciences.
Sediment fluxes from high standing oceanic islands (HSIs) such as New Zealand are some of the highest known. Recent geochemical work has suggested that along with their extremely high physical weathering yields, many New Zealand watersheds also have very high chemical weathering yields. In New Zealand, the magnitude of both the physical and chemical weathering yields is related to the lithology of the watershed. Most of the previous work on this topic has been undertaken in Southern Alps watersheds of schist and greywacke and in East Cape watersheds of semi-consolidated marine sediments and greywacke. North Island watersheds in the Taranaki and Manawatu-Wanganui regions which have been subjected to volcanism since the Miocene were sampled. Watersheds that contain both volcanic and sedimentary rocks were sampled. A series of water and sediment samples was collected and analyzed for major, minor and trace elements. This was done to quantify the weathering intensities in the watersheds and to establish the relationship between physical and chemical weathering yields in volcanic lithologies. Results reveal distinct chemical signatures, with waters draining the Taranaki region volcanics significantly enriched in K+ and depleted in Sr2+ compared to those draining the Manawatu-Wanganui region volcanics, which also traverse expanses of sedimentary siltstones and mudstones. These depletions may reflect the relative absence of CaCO3 in the Taranaki region watersheds. In addition, sediment samples from the Taranaki Region show significant enrichment in Ti, Al, Ca, Fe, Mg, Mn, Mg, Ca, and P and depletion in Si and Rb compared to those of the Manawatu-Wanganui region. Stability diagrams for all streamwater samples revealed that primary feldspar minerals present would weather to kaolinite while clay minerals would likely be present as kaolinite, illite, or Mg-montmorillonite. Normalized sediment values for the Taranaki region exhibited a best fit pattern to average Mt. Egmont andesite values with relative soluble alkali and alkaline earth elements Na, K, Rb, Sr, and Ba and insoluble elements Ti, Al, and Fe, while normalized values for the Manawatu-Wanganui region exhibited a best fit pattern to near shore mud. From total dissolved solids concentrations and annual volumetric water discharge, chemical weathering yields of 60-238 tons km-2 a-1 are obtained. These weathering yields fall within the mid- to upper range of those previously documented for New Zealand’s Southern Alps (93-480 tons km-2 a-1) and East Cape (62-400 tons km-2 a-1). Calculated silicate weathering yields of 12-33.6 tons km-2 a-1 and CO2 consumption of 852-2390 x 103 moles km-2 a-1 for the rivers draining the Taranaki volcanic region are higher than those previously recorded for watersheds hosted in sedimentary and metamorphosed rock terrains on HSIs. CO2 consumption is found to be within the range previously measured for the basaltic terrains of the Deccan Traps (580-2450 x 103 moles km-2 a-1) and Reunion Island (1300-4400 x 103 moles km-2 a-1). Calculated chemical weathering yields demonstrate the importance of taking into account HSIs, particularly those with volcanic terrains, when considering global geochemical fluxes.
Anne E. Carey (Advisor)
W. Berry Lyons (Committee Member)
Michael Barton (Committee Member)
98 p.
Geological

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Citations

  • Goldsmith, S. T. (2005). Geochemical Fluxes and Weathering on High Standing Islands: Taranaki and Manawatu-Wanganui Regions New Zealand [Master's thesis, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1391601668

    APA Style (7th edition)

  • Goldsmith, Steven. Geochemical Fluxes and Weathering on High Standing Islands: Taranaki and Manawatu-Wanganui Regions New Zealand. 2005. Ohio State University, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1391601668.

    MLA Style (8th edition)

  • Goldsmith, Steven. "Geochemical Fluxes and Weathering on High Standing Islands: Taranaki and Manawatu-Wanganui Regions New Zealand." Master's thesis, Ohio State University, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=osu1391601668

    Chicago Manual of Style (17th edition)

osu1391601668
318
© 2005, all rights reserved.
This open access ETD is published by The Ohio State University and OhioLINK.