Foraminiferal Characterization and Provenance of Remobilized, Earthquake-Triggered Sediment Deposits, Northern Japan Trench - INSU - Institut national des sciences de l'Univers Accéder directement au contenu
Poster De Conférence Année : 2023

Foraminiferal Characterization and Provenance of Remobilized, Earthquake-Triggered Sediment Deposits, Northern Japan Trench

Sarah Zellers
Jean-Noël Proust
et al.
  • Fonction : Auteur

Résumé

IODP Expedition 386 obtained cores from fifteen sites in hadal water depths between 7.5 and 8 km in the Japan Trench. During preliminary micropaleontological analyses we found displaced calcareous foraminifera in mass transport deposits at all cored sites, even well below the calcium carbonate compensation depth. Although they are allochthonous, displaced calcareous foraminifera in trench sediments can still provide insight into the provenance of turbidites and homogenites generated by megathrust earthquakes. We use displaced foraminifera to help understand the origin of a ~ 16 m Holocene sedimentary event deposit identified at Site M0084 (northern Japan Trench). The 2 m thick basal turbidite is a thick fining-upward medium sand to silt with well-defined planar and ripple lamination. Above, there is a thick (12 -15 m) non-bioturbated, acoustically transparent bed with diatomaceous silty clay and centimeter-scale, contorted silt layers and patches, which may be classified as a homogenite. Although there is an overall decrease in the abundance of foraminifera as a result of gravitational size sorting, separate size fractions exhibit greater faunal variability. Coarse turbidite facies (>150 µm) contain upward decreasing abundances of moderate- to well-preserved infaunal benthic foraminifera (e.g. Elphidium batialis, Uvigerina akitaensis, and species of Bulimina and Nonionellina) indicative of upper to middle bathyal water depths (200 to 1000 m). These larger taxa are scarce to absent in the homogenite. Finer sand facies (<150 µm) include moderately preserved species of Bolivina, Globocassidulina, Stainforthia, and Epistominella indicative of outer neritic to upper bathyal depths (100 to 600 m). Smaller benthic and planktic foraminifera (mainly Neogloboquadrina pachyderma sinistral) abundance is variable in the turbidite and then decreases to zero in the homogenite. This analysis indicates possible earthquake shaking on the outer shelf, entrainment of infaunal shelf and slope foraminifera by a turbidity current, transport into the trench via the Ogawara Canyon, and preservation of fauna by rapid sedimentation and high alkalinity. Finally, fine sediment of unknown provenance accumulated to form the homogenite. Further analyses are needed to determine the complete history of this event deposit.
Fichier non déposé

Dates et versions

insu-04448931 , version 1 (09-02-2024)

Identifiants

  • HAL Id : insu-04448931 , version 1

Citer

Sarah Zellers, Cecilia Mchugh, Jean-Noël Proust, et al.. Foraminiferal Characterization and Provenance of Remobilized, Earthquake-Triggered Sediment Deposits, Northern Japan Trench. American Geophysical Union, Fall Meeting 2023 (AGU 2023), Dec 2023, San Francisco, United States. pp.S33F-0466, 2023. ⟨insu-04448931⟩
3 Consultations
0 Téléchargements

Partager

Gmail Facebook X LinkedIn More