The Jiachala Formation was fed largely from the Gangdese arc accept long been considered every bit syn-collisional foreland-basin deposits based on the reported occurrence of Paleocene-early Eocene dinoflagellate cysts in addition to pollen assemblages. Because magmatic action inwards the Gangdese arc continued through the Late Cretaceous in addition to Paleogene, this scenario is incompatible alongside U-Pb ages of detrital zircons invariably older than the latest Cretaceous.
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| Paleogeographic scenario for the Jiachala Formation. a) Jiachala Formation, b)&c) other trench deposits to the due west [Credit: ©Science China Press] |
According to this research, the Jiachala Formation was originally deposited on a submarine fan inwards the trench surroundings at the active southern margin of the Asian plate. Sandstone petrography, detrital-zircon U-Pb ages in addition to Hf isotope ratios betoken provenance from the Gangdese arc in addition to the key Lhasa terrane.
Because magmatic action inwards the Gangdese arc was virtually continuous, the youngest population of detrital zircons contained inwards the Jiachala Formation constrain its depositional historic menstruation every bit Late Cretaceous ( 88-84 Ma). What's more, based on the U-Pb historic menstruation spectra of detrital zircons in addition to sandstone petrography, in that place are no Paleocene-Eocene units like to the Jiachala Formation which compares good alongside Upper Cretaceous exposed inside in addition to around the Yalung Zangbo suture zone.
Integrated geological information indicates that the Jiachala Formation accumulated inwards the Neo-Tethyan trench during subduction of oceanic lithosphere. In summary, this interrogation gives a novel interpretation virtually the Jiachala Formation in addition to enriches the illustration study of the arc trench arrangement of the active Asian continental margin.
The findings are published inwards Science China world Sciences.
Source: Science China Press [August 27, 2018]
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