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Assessing the impact of diagenesis on foraminiferal geochemistry from a low latitude, shallow-water drift deposit

  • Stainbank, Stephanie Department of Geosciences, University of Fribourg, Chemin du Musée 6, 1700 Fribourg, Switzerland
  • Spezzaferri, Silvia Department of Geosciences, University of Fribourg, Chemin du Musée 6, 1700 Fribourg, Switzerland
  • Boever, Eva De Department of Geosciences, University of Fribourg, Chemin du Musée 6, 1700 Fribourg, Switzerland
  • Bouvier, Anne-Sophie Institute of Earth Sciences, University of Lausanne, Géopolis, 1015 Lausanne, Switzerland
  • Chilcott, Colin School of GeoSciences, University of Edinburgh, Grant Institute, The King's Buildings, James Hutton Road, EH9 3FE Edinburgh, United Kingdom
  • Leau, Erica S.de School of GeoSciences, University of Edinburgh, Grant Institute, The King's Buildings, James Hutton Road, EH9 3FE Edinburgh, United Kingdom
  • Foubert, Anneleen Department of Geosciences, University of Fribourg, Chemin du Musée 6, 1700 Fribourg, Switzerland
  • Kunkelova, Tereza School of GeoSciences, University of Edinburgh, Grant Institute, The King's Buildings, James Hutton Road, EH9 3FE Edinburgh, United Kingdom
  • Pichevin, Laetitia School of GeoSciences, University of Edinburgh, Grant Institute, The King's Buildings, James Hutton Road, EH9 3FE Edinburgh, United Kingdom
  • Raddatz, Jacek Institute of Geosciences, Goethe University Frankfurt, Altenhöferallee 1, 60438 Frankfurt, Germany - Frankfurt Isotope and Element Research Center (FIERCE), Goethe University Frankfurt, Altenhöferallee 1, 60438 Frankfurt, Germany
  • Rüggeberg, Andres Department of Geosciences, University of Fribourg, Chemin du Musée 6, 1700 Fribourg, Switzerland
  • D.Wright, James Department of Earth and Planetary Sciences, Rutgers, the State University of New Jersey, Bush Campus, 610 Taylor Road, Piscataway, NJ 08854-8066, USA
  • M.Yu, Siyao Department of Earth and Planetary Sciences, Rutgers, the State University of New Jersey, Bush Campus, 610 Taylor Road, Piscataway, NJ 08854-8066, USA
  • Zhang, Manlin School of GeoSciences, University of Edinburgh, Grant Institute, The King's Buildings, James Hutton Road, EH9 3FE Edinburgh, United Kingdom
  • Kroon, Dick School of GeoSciences, University of Edinburgh, Grant Institute, The King's Buildings, James Hutton Road, EH9 3FE Edinburgh, United Kingdom
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    01.09.2020
Published in:
  • Earth and Planetary Science Letters. - 2020, vol. 545, p. 116390
English Due to their large heat and moisture storage capabilities, the tropics are fundamental in modulating both regional and global climate. Furthermore, their thermal response during past extreme warming periods, such as super interglacials, is not fully resolved. In this regard, we present high-resolution (analytical) foraminiferal geochemical (δ18O and Mg/Ca) records for the last 1800 kyr from the shallow (487 m) Inner Sea drift deposits of the Maldives archipelago in the equatorial Indian Ocean. Considering the diagenetic susceptibility of these proxies, in carbonate-rich environments, we assess the integrity of a suite of commonly used planktonic and benthic foraminifera geochemical datasets (Globigerinoides ruber (white), Globigerinita glutinata (with bulla), Pulleniatina obliquiloculata (with cortex) and Cibicides mabahethi) and their use for future paleoceanographic reconstructions. Using a combination of spot Secondary Ion Mass Spectrometer, Electron Probe Micro-Analyzer and Scanning Electron Microscope image data, it is evident that authigenic overgrowths are present on both the external and internal test (shell) surfaces, yet the degree down-core as well as the associated bias is shown to be variable across the investigated species and proxies. Given the elevated authigenic overgrowth Mg/Ca (∼12–22 mmol/mol) and δ18O values (closer to the benthic isotopic compositions) the whole-test planktonic G. ruber (w) geochemical records are notably impacted beyond ∼627.4 ka (24.7 mcd). Yet, considering the setting (i.e. bottom water location) for overgrowth formation, the benthic foraminifera δ18O record is markedly less impacted with only minor diagenetic bias beyond ∼790.0 ka (28.7 mcd). Even though only the top of the G. ruber (w) and C. mabahethi records (whole-test data) would be suitable for paleo-reconstructions of absolute values (i.e. sea surface temperature, salinity, seawater δ18O), the long-term cycles, while dampened, appear to be preserved. Furthermore, planktonic species with thicker-tests (i.e. P. obliquiloculata (w/c)) might be better suited, in comparison to thinner-test counter-parts (i.e. G. glutinata (w/b), G. ruber (w)), for traditional whole- test geochemical studies in shallow, carbonate-rich environments. A thicker test equates to a smaller overall bias from the authigenic overgrowth. Overall, if the diagenetic impact is constrained, as done in this study, these types of diagenetically altered geochemical records can still significantly contribute to studies relating to past tropical seawater temperatures, latitudinal scale ocean current shifts and South Asian Monsoon dynamics.
Faculty
Faculté des sciences et de médecine
Department
Département de Géosciences
Language
  • English
Classification
Geology
License
License undefined
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Persistent URL
https://folia.unifr.ch/unifr/documents/308773
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