摘要
前言1980年9—10月,笔者随北疆队,在沙湾县马纳斯河剖面,对中生代地层进行了地质调查,并系统地采集了孢粉样品,仅在西山窑组分析出保存完好的孢粉化石(有12块样品含孢粉),对每块样品都进行了孢粉统计。这一孢粉组合的研究对准噶尔盆地侏罗纪煤系地层的划分与对比,以及与我国北方侏罗纪煤系地层进行对比,提供了古生物依据。
The present paper studies the sporo-pollen as semblage from the Xishanyao Formation, Manas River section of the Shawan County, Xiniiang. The total collection consists of 40 genera and 66 species; among them 36 genera and 57 species have been described, which are common in the Mesozoic Era and significant in age-dating.The sporo-pollen assemblage of the Xishanyao Formation is characterized by the dominance of pteridophytc spores (attaining 25—81% and averaging 56%), containing mostly Cyathidites minor(amounting to 18.1—78.39% and averaging 48.6%) of Cyatheaceae and a certain amount of spores of Selaginellaceae, such as Neoraistrickia rotundiformis, N. gristhorpensis, N. samuelssoni (attaining 1.4—17% in total, averagely 4.55%). There are still some other elements, such as Cibotiumspora juncta, Todisporites minor, Osmundacidites wellmanii, Lycopodiumsporites laevigatus, L. clavatoides, Lycopodiacidites rugulatus, Duplexisporites amplectiformis, D. anagrammensis, Densoiporites velatus, etc., each with an average content of<1%.Another characteristic of the assemblage is the smaller amount of gymnospermous pollen grains (attaining 19—75%, averagely 44%), among which the Coniferales bisaccate grains are higher in content, including such species as Protopinus vastus, P. latebrosus, Quadraeculina limbata, Q. anellaeformis, Q, canadensis, Alisporites parvus, Protopicea exilioides, Piceites enodis, P. flavidus, Pteruchipollenites thomasii, Pseudopicea rotundiformis, P. variabiliformis, Pityosporites divulgatus, Pinuspollenites insignis, Abietineaepollenites pectinellus, Abiespollenites pernobilis, Cedripites pusillus, C. microsaccoides, Platysaccus papilionis, Podocarpidites multesimus, P. multicinus, P. minutus, etc., averagely accounting for 33.84%; the content of Coniferales monosaccate grains is extremely low, including Callialasporites dampieri, averagely amounting to only 0.15%, whereas the coment of Coniferales non-saccate grains is relatively lower, including such species as Psophosphaera tenuis, P. grandis, Spheripollenites scabratus, Chasmatasporites apertus C. hians Classopollis annulatus, etc., averagely amounting to 2.17%. In addition, there is a certain amount of Ginkgoales monocolpate pollen, including Ginkgocycadophytus nitidus, amounting from 0.3% to 25.6%, averagely 6.27%.Among those fossil algae already found are Schizosporis parvus and Enretisphaeridium megareticulum.The main feature of this assemblage lies in the presence of abundant Cyathidites minor, with a smaller amount of Neoraistrickia rotundiformis, N. gristhorpensis, N. samuelssoni, often associated with those elements most of which are commonly found in Jurassic. Neoraistrickia rotundiformis, N, gristhorpensis and N. samuelssoni, which are known as the important fossils in Early Middle Jurassic are frequently seen in the Xishanyao Formation, indicating that this assemblage probably can be assigned to early Middle Jurassic.The flora reflected by the present sporo-pollen assemblage is mainly characterized by the dominant Filicales of Pteridophyta, among which the Cyatheaceae are most developed, in addition to Dipteridaceae, Dicksoniaceae and Osmundaceae. The Selaginellaceae of Selaginellales come next, and then the Lycopodiaceae of Lycopodiales, etc. Among the flourishing Coniferales are Pinaceae, Podocarp aceae, Taxodiaceae. Cheirolepidiaceae, etc. There are still some other elements such as the Ginkgoaceae of Ginkgoales, Podozamitales, etc.Judged from the distributiort of those living, plants mentioned above, with the exception of the Ginkgoales which are distributed in the temperate zone, most elements occur in the tropics and sub tropics, reflecting a warm and damp climate. Hence, the flora reflected by the sporo-pollen assem blage of the Xishanyao Formation should belong to the subtropical-type under warm and damp conditions.
出处
《古生物学报》
CAS
CSCD
北大核心
1990年第1期63-83,共21页
Acta Palaeontologica Sinica
