Late Triassic ecosystem variations inferred by palynological records from Hechuan, southern Sichuan Basin, China

The Late Triassic deposits of the Sichuan Basin, southwestern China are significant for hosting abundant and diverse fossil assemblages including plants (containing spores and pollen), bivalves and insects. However, the Late Triassic palaeoecological variations are still poorly documented in this re...

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Bibliographic Details
Published in:Geological Magazine
Main Authors: Li, Liqin （李丽琴）, Wang, Yongdong （王永栋）, Vajda, Vivi, Liu, Zhaosheng
Format: Report
Language:English
Published: CAMBRIDGE UNIV PRESS 2018
Subjects:
End-triassic Event
Palynology
Mass Extinction
Sporomorph Ecogroup
Climate Change
Atlantic Magmatic Province
In-situ Spores
Large Igneous Provinces
Jurassic Boundary
Triassic/jurassic Boundary
East Greenland
Ocean Acidification
Fertile Organs
Northwestern China
Geology
Geosciences
Multidisciplinary
Greenland
Ocean acidification
Online Access:http://ir.nigpas.ac.cn/handle/332004/16903
http://ir.nigpas.ac.cn/handle/332004/16904
https://doi.org/10.1017/S0016756817000735
Description
Summary:The Late Triassic deposits of the Sichuan Basin, southwestern China are significant for hosting abundant and diverse fossil assemblages including plants (containing spores and pollen), bivalves and insects. However, the Late Triassic palaeoecological variations are still poorly documented in this region. Here we present results from a palynological study from the Upper Triassic Xujiahe Formation in Hechuan of Chongqing, southern Sichuan Basin. The palynological analysis revealed a well-preserved terrestrial palynoflora of high diversity, comprising 184 species in 75 genera of spores and pollen. Three palynological assemblages were recognized, reflecting terrestrial successions throughout the entire interval with significant changes in the vegetation. Cycads/bennettites/ginkgophytes and conifers show an increasing trend into younger deposits, while ferns and lycopsids decrease in relative abundance. The Late Triassic vegetation underwent changes from lowland fern forest to a mixed forest with more canopy trees. We applied the Spore-pollen Morphological Group (SMG) method and Sporomorph EcoGroup (SEG) model to interpret the palaeoclimate features. The results reveal that the lower part of the Xujiahe Formation was deposited under relatively warm and humid conditions with an overall cooling and drying trend from latest Norian to Rhaetian time, accompanied by a general decrease of ferns and simultaneous increase of gymnosperms, and a decline in diversity of miospores. This study presents data on variations within the terrestrial ecosystem prior to the end-Triassic extinction event in the Sichuan Basin, and therefore provides important information for understanding the changes in the vegetation preceding the end-Triassic event.

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