Late Anisian radiolarian assemblages from the Yarlung‐Tsangpo Suture Zone in the Jinlu area, Zedong, southern Tibet: Implications for the evolution of Neotethys

Abstract

Abundant Triassic radiolarian fossils were obtained from varicolored bedded cherts exposed in the Buruocang section near Jinlu village, Zedong, southern Tibet. The radiolarian‐bearing rocks represent fragmented remnants of the Neotethys oceanic sediments belonging to the mélange complex of the east part of the Yarlung‐Tsangpo Suture Zone. Two new middle Late Anisian radiolarian assemblages recognized from this section named Oertlispongus inaequispinosus and Triassocampe deweveri, respectively, are compared with those known from Europe, Far East Russia, Japan, and Turkey. These Anisian radiolarian fossils are the first reported in southern Tibet and the oldest radiolarian record within the Yarlung‐Tsangpo Suture Zone. They improve time constraints for the evolution of Neotethys in southern Tibet.

Remnants of middle Triassic oceanic lithosphere in the western Indus–Tsangpo suture zone, southwestern Tibet

“…This is consistent with previous investigations of the plate tectonic history of the Mesozoic Tethyan realm (e.g. Cai et al., 2016; Chen et al., 2019; Kroner, Roscher, & Romer, 2016; Li et al, 2016; Ma, Meert, Xu, & Yi, 2018; Zhou et al., 2016; Zhu et al., 2006).…”

“…Zeng et al., 2019), but the exact timing of its opening is subject to debate. For example, the marine sedimentary sequences in the northern margin of India suggest that initial spreading of the Neo‐Tethys Ocean began during the early Triassic (Gaetani & Garzanti, 1991), while radiolaria from bedded cherts in the eastern ITSZ indicate that the early evolution of the Neo‐Tethys Ocean can be traced back to the middle Triassic (Chen, Luo, Wang, Xu, & Matsuoka, 2019). On the other hand, various mafic rocks from ophiolitic massifs along the ITSZ have widely been used to elucidate the evolution of the Neo‐Tethys Ocean (e.g.…”

Thematic section: Proceedings of InterRad XV

“…Chen et al () report the abundant Triassic radiolarian fossils from varicolored bedded cherts exposed in the Buruocang section near Jinlu village, Zedong, southern Tibet. The radiolarian‐bearing rocks represent fragmented remnants of Neotethys oceanic sediments, belonging to the mélange complex in the eastern part of the Yarlung‐ Tsangpo Suture Zone.…”

A Fragment of Argoland From East Gondwana in the NE Himalaya

“…The Neotethys Ocean suture zone is located in the Yarlung‐Tsangpo belt and in the eastern Indo‐Burma Range (Figure 1b; Aitchison et al., 2019). Middle Jurassic cherts in ophiolitic mélanges from the Indo‐Burma Range (Aitchison et al., 2019; J. E. Zhang et al., 2018), and Late Anisian‐Carnian cherts and siltstones from Zedang City (southern Tibet; Chen et al., 2019) and the eastern Indo‐Burma Range (Figures 1b and 8; J. E. Zhang et al., 2018) indicate the presence of Neotethyan pelagic ocean floor off of East Gondwana before the Middle‐Late Triassic, when the Longzi block was still attached to East Gondwana (Figure 9a and Table 2).…”

“…Locations of amphibolites in metamorphic soles are from Guilmette et al (2009Guilmette et al ( , 2012 and . Ages of cherts in ophiolitic mélanges, and interbedded siltstones and cherts are from Aitchison et al (2019), Chen et al (2019), and Zhang et al (2018). Paleocurrent directions determined from cross-bedding of Late Jurassic and Triassic sediments are from X. H. Li et al (2003), Pan (2018) and Zhang et al (2019).…”