EGU2020-7139
https://doi.org/10.5194/egusphere-egu2020-7139
EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Micropaleontological proxies as tool to date serpentinite mud volcanisms and seamount subduction and to reconstruct paleoenvironmental conditions in the Mariana convergent margin system (IODP Expedition 366)

Arianna Valentina Del Gaudio1, Werner E. Piller1, Gerald Auer1,3, Patrick Grunert2, and Walter Kurz1
Arianna Valentina Del Gaudio et al.
  • 1Institute of Earth Sciences, University of Graz, Austria (arianna.del-gaudio@uni-graz.at)
  • 2Institute of Geology and Mineralogy, University of Cologne, Zülpicher Straße 49a, 50674 Cologne, Germany
  • 3Department of Biogeochemistry, Frontier Bldg. 4F, Japan Agency for Marine-Earth Science and Technology (JAMSTEC), 2-15 Natsushima-cho, Yokosuka, Kanagawa, 237-0061, Japan

The Mariana forearc system represents the only known currently active serpentine mud volcanism in a convergent margin setting. Here, International Ocean Discovery Program (IODP) Expedition 366 recovered material from three serpentinite mud volcanoes at increasing distances from the Mariana trench subduction zone along a south-to-north transect: Yinazao (Blue Moon), Fantangisña (Celestial), and Asùt Tesoru (Big Blue). Cores contain serpentinite mud with lithic clasts from the subducting Pacific Plate, forearc crust and mantle. Furthermore, at almost all drilled sites, a thin cover of pelagic sediment containing planktic and benthic foraminifera, calcareous nannofossils, radiolaria and sponge spicules was recovered, constraining the most recent mud volcano activity. The base of the seamounts overlies pelagic sediment and volcanic ash/tephra layers which establish a maximum age for the mud activity. Additionally, separate serpentinite mud flows are intercalated by distinct sedimentary layers.

Integrated biostratigraphy, based on planktonic foraminifera and calcareous nannofossils, is used to assess the minimum and maximum age of mud flow activity and of the distinct sedimentary layers and serpentinite mud flow layers. Biostratigraphic information will also provide time indications on lower plate dehydration and serpentinization of the forearc wedge. Preliminary results from Fantangisña seamount (Site U1497 and U1498) reveal the existence of biostratigraphic marker species for both planktonic foraminifera and calcareous nannofossils. Specifically, the presence of Globigerinella calida, Globorotalia flexuosa, Globorotalia truncatulinoides, Globorotalia tumida, Sphaeroidinella dehiscens (amongst planktic foraminifera) and Gephyrocapsa spp., Pseudoemiliania lacunosa, Reticulofenestra asanoi, Discoaster deflandrei, Discoaster variabilis (amongst calcareous nannofossils) allow a possible age assessment from Late Pleistocene to Late Miocene.

Planktonic assemblages are dominated by (sub)tropical Globigerinoides forms such as G. conglobatus, G. ruber, G. elongatus, G. sacculifer, G. trilobus. Other common (sub)tropical species detected are G. menardii, and O. universa, whereas G. siphonifera, N. dutertrei, S. dehiscens and P. obliquiloculata are less common.

Benthic foraminifera are less abundant but show high diversity. Forms of Lagena, Cibicidoides, Fissurina, Ehrenbergina, Gyroidina, Melonis, Pullenia, Osangularia, Favulina, Reophax, Rhabdammina, Saccorhiza, and Hormosinella are present. To the best of our knowledge, the occurrence of benthic forms in such environments is highly unusual and has not been recorded in detail so far.

Quantitative and statistical analyses on foraminifera assemblages will provide information on water column and bottom water conditions. Moreover, a detailed comparison between assemblages pre- and post-volcanism may reflect possible changes in the ecological conditions.

Collected data will not only allow to constrain in time the evolution of submarine volcanoes in the Mariana convergent system but also to investigate foraminifera ecology in such an extreme environment.

 

How to cite: Del Gaudio, A. V., Piller, W. E., Auer, G., Grunert, P., and Kurz, W.: Micropaleontological proxies as tool to date serpentinite mud volcanisms and seamount subduction and to reconstruct paleoenvironmental conditions in the Mariana convergent margin system (IODP Expedition 366), EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-7139, https://doi.org/10.5194/egusphere-egu2020-7139, 2020

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Presentation version 1 – uploaded on 03 May 2020
  • CC1: Comment on EGU2020-7139, R.Valli Divya, 06 May 2020

    What could be the possible source of pelagic sediment containing microfossils?

    • AC1: Reply to CC1, Walter Kurz, 07 May 2020

      A possible source could be the Mariana Arc.

    • AC2: Reply to CC1, Arianna Valentina Del Gaudio, 07 May 2020

      Thank you very much for your question.  The sediments  in the upper part of the core  are siliceous oozes, therefore of biogenic origin. Almost 70% of the sediment consists of microfossils (abundant radiolaria and diatoms) with up to 20% of clay matrix. Those sediments blanket the surface of the serpentinite mud volcano.

       

        

      • CC2: Reply to AC2, R.Valli Divya, 07 May 2020

        Thank you for the explanation.

        Regards,

        Divya