COMPARATIVE STUDY IN ICHNOLOGY, AN EXAMPLE OF DEEP-WATER FLYSCH PHYCOSIPHON ASSEMBLAGE FROM THE LATE TRIASSIC STRATA OF WESTERN SICHUAN
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Abstract:
A deep water flysch trace assemblage dominated by Phycosiphon has been found from the Late Triassic of the Baiyu area, western Sichuan Province. The trace a ssemblage is analogous to the recent Phycosiphon community in the turbidite sequences in Sulu Sea, Philippines, indicating a high sedimentary rate and exaer obic oceanic bottom of active tectonic zones. Accorrding to the changes of sedim entary rate, the specimens of Phycosiphon could be distinguished as four mor photypes. Among them, Phycosiphon A refers to the post depositional traces , suggesting a higher rate; while Phycosiphon D, C are considered to be pre de positional traces, indicating a stable depositional environment with low sedimen tary rate, and Phycosiphon B may represent a transitional morphotype betwee n Phycosiphon A and Phycosiphon D. Taking into account the ecological similarity with the recent Phycosiphon community of Sulu Sea, the paleogeogr aphic aspect of the Baiyu Sea, a volcanic islands arc tensional basin during th e Late Triassic, could be well comparable with the case of the recent Sulu Sea B asin, therefore the Baiyu Basin might have been characterized by steep slope, fr equent turbidite, high depositional rate more than 100cm/ka, and sedimentary bot tom in exaerobic zone; the paleo sea seems to have been a depositional basin si lled by volcanic islands.
