Reconstructing Ocean-Plate Stratigraphy (OPS) to Understand Accretionary Style and Mélange Fabric: Insights From the Bangong-Nujiang Suture (Tibet, China)

Min Zeng, Ruisi Zhang, Si Chen, Xinyu Liu, Chenwei Li, Frank R. Ettensohn, Lidong Bie

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Abstract

Ocean-plate stratigraphy (OPS) refers to the lithostratigraphic column atop an ocean plate, which becomes scraped off during subduction and preserved in accretionary complex (AC). Herein, based on structural, stratigraphic, and geochronological studies of ACs from the Bangong-Nujiang suture, we demonstrate that OPS can facilitate interpreting structural and compositional heterogeneities in ACs. Carefully correlated OPSs reveal that, on the overall sediment-rich lower plate, different types of basement topography correspond to the accretion of distinct litho-structural assemblages. In particular, subduction of the major, high-relief Zhonggang seamount eroded the earlier margin and was subsequently accreted as coherent seamount slices. In contrast, subduction of the lower-relief, Gaize seamount halted frontal accretion of trailing sediments, which were dragged downward to the seismogenic depth and underplated as pervasive, shear-related broken formations. Such broken formations may fingerprint past lower-relief-seamount subduction in other fossil ACs.

Original languageEnglish
Article numbere2021GL094457
JournalGeophysical Research Letters
Volume48
Issue number18
DOIs
Publication statusPublished - 28 Sep 2021
Externally publishedYes

Keywords

  • accretionary complex
  • Bangong-Nujiang Meso-Tethys suture
  • Melange fabric
  • ocean-plate stratigraphy
  • oceanic basement topography
  • trench fill

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