Neogene biogenic silica fluxes in the eastern equatorial Pacific
Neogene biogenic silica fluxes in the eastern equatorial Pacific
Recently discovered Neogene diatom mat deposits in the eastern equatorial Pacific afford an unprecedented opportunity to quantify ancient fluxes associated with individual depositional periods and provide important new information for use in models of biogeochemical cycling in the ancient oceans on a scale directly comparable with data for the modern observations. In the equatorial Pacific, laminated diatom mat (LDM) deposits dominated by diatoms from the Thalassiothrix longissima Group form important horizons that can be correlated for distance or over 2000km, at key intervals associated with major change in the ocean/climate system. Bundles of mats form laminae which correspond to single, seasonal-scale deposition events. Because of their great tensile strength, individual mats and laminae can be peeled off sediment cores and analyzed directly.
This study concentrates on the youngest (Zanclean) LDM deposited cores during ODP Leg 138 with some reference to older deposits. Fine scale sediment structure was studied in resin impregnated samples using the scanning electron microscope (SEM) and back-scatter electron imagery (BSEI). Millimetre-scale subsamples were analyzed for opaline silica, organic carbon and carbonate. Modification of the Mortlock and Forelich opal determination method allowed the estimation of lamina T. longissima Group content using differential dissolution. A new method of quantifying diatom frustule dissolution within deep sea sediments was developed, allowing the detection and quantification of a trend of increasing diatom frustule preservation levels with increasing sedimentary opal content.
High levels of fabric preservation associated with the dense meshwork of diatom mats results in the preservation of lamina couplets. These couplets are interpreted as episodic mat flux events, similar to those observed in the eastern equatorial Pacific by the JGOFS Fall '92 survey, separated by more normal deep sea sedimentation patterns. Spectral analysis of lamina couplet thickness records identified two significant periodicities of 6-7 and 21 years.
University of Southampton
Rance, Stephanie Jane
e82a337a-d961-4866-8c50-a9c62916db7d
1997
Rance, Stephanie Jane
e82a337a-d961-4866-8c50-a9c62916db7d
Rance, Stephanie Jane
(1997)
Neogene biogenic silica fluxes in the eastern equatorial Pacific.
University of Southampton, Doctoral Thesis.
Record type:
Thesis
(Doctoral)
Abstract
Recently discovered Neogene diatom mat deposits in the eastern equatorial Pacific afford an unprecedented opportunity to quantify ancient fluxes associated with individual depositional periods and provide important new information for use in models of biogeochemical cycling in the ancient oceans on a scale directly comparable with data for the modern observations. In the equatorial Pacific, laminated diatom mat (LDM) deposits dominated by diatoms from the Thalassiothrix longissima Group form important horizons that can be correlated for distance or over 2000km, at key intervals associated with major change in the ocean/climate system. Bundles of mats form laminae which correspond to single, seasonal-scale deposition events. Because of their great tensile strength, individual mats and laminae can be peeled off sediment cores and analyzed directly.
This study concentrates on the youngest (Zanclean) LDM deposited cores during ODP Leg 138 with some reference to older deposits. Fine scale sediment structure was studied in resin impregnated samples using the scanning electron microscope (SEM) and back-scatter electron imagery (BSEI). Millimetre-scale subsamples were analyzed for opaline silica, organic carbon and carbonate. Modification of the Mortlock and Forelich opal determination method allowed the estimation of lamina T. longissima Group content using differential dissolution. A new method of quantifying diatom frustule dissolution within deep sea sediments was developed, allowing the detection and quantification of a trend of increasing diatom frustule preservation levels with increasing sedimentary opal content.
High levels of fabric preservation associated with the dense meshwork of diatom mats results in the preservation of lamina couplets. These couplets are interpreted as episodic mat flux events, similar to those observed in the eastern equatorial Pacific by the JGOFS Fall '92 survey, separated by more normal deep sea sedimentation patterns. Spectral analysis of lamina couplet thickness records identified two significant periodicities of 6-7 and 21 years.
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Published date: 1997
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Local EPrints ID: 463322
URI: http://eprints.soton.ac.uk/id/eprint/463322
PURE UUID: 5d16dac7-6ce9-4f0d-8cf9-c0ee012a0723
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Date deposited: 04 Jul 2022 20:50
Last modified: 16 Mar 2024 19:03
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Author:
Stephanie Jane Rance
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