Bashkirian taeniate bisaccate pollen‐dominated palynological assemblage from northwestern Junggar Basin, Xinjiang Province, China

The Early Pennsylvanian land plant community is characterized by widespread forests consisting of lycopsids, ferns, and seeds fern in swampy wetlands. The contemporaneous palynological assemblages are mainly composed of spores of Lycospora spp., Densosporites spp., and Laevigatosporites spp. and mon...

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Bibliographic Details
Published in:Geological journal (Chichester, England) England), 2021-12, Vol.56 (12), p.6031-6042
Main Authors: Shi, Tianming, Li, Qiong, Amuti, Aliya, Xiao, Jinan, Liu, Feng, Yang, Wan, Li, Qiuli, Zhang, Hua, Lü, Zeng, Peng, Huiping
Format: Article
Language:English
Subjects:
Beds (geology)
Carboniferous
Conifers
Ferns
Geochronology
Jiamuhe Formation
Junggar Basin
Lead isotopes
Northern Hemisphere
Palynology
Pennsylvanian
Plant communities
Pollen
Relative abundance
Seeds
Spores
Uplift
Volcanic ash
zircon U–Pb geochronology
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Summary:The Early Pennsylvanian land plant community is characterized by widespread forests consisting of lycopsids, ferns, and seeds fern in swampy wetlands. The contemporaneous palynological assemblages are mainly composed of spores of Lycospora spp., Densosporites spp., and Laevigatosporites spp. and monosaccate prepollen of Florinites spp. Taeniate bisaccate pollen appeared for the first time during the Early Pennsylvanian but never prevailed in the coeval palynological assemblages. Here, we report a taeniate bisaccate pollen‐dominated palynological assemblage from the Jiamuhe Formation of Well Ke 85 in the Zhongguai Uplift, northwestern Junggar Basin, Xinjiang. Nineteen miospore species belonging to 14 genera were identified from the assemblage. Based on their relative abundance, one assemblage is nominated informally as Calamospora breviradiata–Lunatisporites tersus (BT) assemblage. SIMS U–Pb geochronological analysis of zircons from two volcanic ash beds from the basal and upper parts of the formation yields weighted mean 206Pb/238U dates of 316.3 ± 2.2 Ma (MSWD = 1.2, n = 19) and 316.5 ± 2.8 Ma (MSWD = 0.85, n = 20) in an ascending order. A Bashkirian age is thus assigned to the BT assemblage. Our combined palynological and geochronological investigations reveal an early stage of the rise of conifers in the Kazakhstan Plate and offer a rare glimpse into the Early Pennsylvanian land vegetation in the subtropical area at the northern hemisphere. A taeniate bisaccate pollen‐dominated assemblage from the lowest Pennsylvanian of Well Ke 85 cores provides insight into Late Palaeozoic plants' development in the Kazakhstan Plate. A taeniate bisaccate pollen‐dominated microflora appeared in the Bashkirian of the northwestern Junggar Basin. This age is well constrained by radioisotopic ages dated by the secondary ion mass spectrometry (SIMS) U–Pb zircon technique from two volcanic ash samples of Well Ke 85. The first appearance of taeniate bisaccate pollen in the Junggar Basin is much earlier than that in other phytogeographic provinces and paralleled the first appearance of bisaccate non‐taeniate pollen. It may indicate a potential new approach to early conifer phylogeny in the subtropical areas of the northern hemisphere.
ISSN:0072-1050
1099-1034
DOI:10.1002/gj.4167