Wenben Li

Spores and pollen are productive organs of plants. Pteridophytes and some of the more primitive plants, such as bryophytes, algae and fungi, produce spores by which new generation of plant is reproduced sexually or nonsexually. Seed plants (spermarophytes), including gymno-sperms and angiosperms, produce pollen. Sperms of pollen ( male spores) combine with ova of female ovule and develop into seeds. The reproduction of seed plants depends on germination of the seeds. The study of spores and pollen is called paiynology. Spores and pollen are very small in size, commonly under 200 microns, but very large in quantity. Because of their organic anti-decomposition wall (exine), they can be well preserved together with mineral clastics in the sediments through the geological history. In order to extract spores and pollen from the sediments, the rock containing spores and pollen must be generally macerated in nitric and hydrofluoric solutions to separate the spores and pollen from mineral clastics. After collected from the rock residue, the spores and pollen are mounted with glycerine jelly on glass slides. We can observe and identify them under microscope at power from 600 co 1000 enlargements. Generally speaking, the spores and pollen from different plant raxa show different morphology, including thar of their exinal structure and ornamentation. By means of palynological taxonomic study, we can well reconstruct the vegetation, climate and environment, and date the age when rhey were growing.

The Yixian Formation cropping out at Jianshangou and Huangbanjigou of Beipiao, Zaocishan of Yixian and Sunjialing, Sanguanmiao and Gujialing of Harqin Zuoyi, western l.iaoning yields abundant fossil spores and pollen (Figs. 260~268), with about 70 known species assigned to 40 genera. Most species in the spore-pollen assemblage are common taxa through the whole Mesozoic era, for example, the spores of Stereisporites antiquasporites of bryophytes, Lycopodiumsporites am 1 rocLwatidites, Leptolepidites verrucosus, Neoraistrickia equaiis, Densoisporiies microrugulatus of lycopodiales, Cyathidites minor, Osmundacidites willmanii, Klukisporites pseudoreticulatus and Baculatisporites coma u mens is of fllicales, and the pollen grains of Classopollis annulatus, Ginkgocycadophytus nitidus, Ephedripites sp., Caytonipollenites pallidas, Perinopollenites elatoides, Pmnspoilenites dmdgatus, A bielinenepollenitespeilmelius, Ca/ripiies pustl/us, Cedripites

EphedripitesEphedripites

i264 Schtaeoisporites certus. spore of a filicales,

1263 Cicatricosisporites pacificus, spore of'a filicales.

i264 Schtaeoisporites certus. spore of a filicales, microsaccoides, Piceaepolkniles spp., Abhspolknites spp., Podoeatpidites multesimus, Pudocarpidites omattts, Calltalaspnrites dampicri, Bicestopollis uulanensis, Quadraeatlina limbata, Protoconifertts funarius, Protopinus sp.. Pseudnpicea variabilifotmis and psendoptcea mundiformis of gym oosperms. Hut some others are species rising from the Cretaceous period, such as Cicatricosisporites australiensis, Cicatricosisporites paciftcus, Schizaeoisporites certus of lygodiaccae, Cyclocristella senticosa, Tettuangulasporis qiucbengensis. Tenuangulasporis microi 'errucosus o f selagi nel I ales and J age claribatulata, JiaobepoUis flexuosus and Jiaohepnllis annulatus of gymnospcrms.

Palynologica) study demonstrates that during the accumulation time of deposition of the Yixian Formation, the main part of the vegetation in western Liaoning Province was composed of conifers chat occupies over 90 % of the whole vegetation. Under the coniferous forest sonic bryophytes, pterido-phytes and eyeadophytes grew sparsely. Angiosperm megafossil plant Sinocarpus decussattts and several other purported ones were recorded from different horizons of the Yixian Formation (see the Chapter "Angiosperms"), bur so far mm 265 Pinuspollenites divulgatus, pollen of a gymnosperm.

we have not found a single reliable angiosperm pollen grain from the whole Yixian Formation In consideration of the infrequent appearance of the genera Cicatricosisporites, Schizaeoisporites, Tenuangulasporis andJiaobepoltis, the age of the Yixian Formation should be of the earliest Cretaceous (Berriasian), 135~ 131 million years before present.

The Classopollis of xerophytic cheirolepidiaceae, usually amounts to 15—91% in content, dominating the spore-pollen assemblage of the latest Jurassic Houcheng Formation in Xuanhua and Wanquan, northern Hebei Province. In contrast, Classopollis and other arid-tolerating taxa, Schizaeoisporites and Epbedripites, are rare in the Yixian Formation, only under 2% in content. This fact indicates the climate change from the arid Late Jurassic into the relatively humid F.arly Cretaceous in northern Hebei and western Liaoning Provinces,

(All specimens shown in this chapter are from the upper parr of the Yixian Formation in Sanguanmiao, Harqin Zuoyi Mongolian Autonomous County, Liaoning Province, and photographed by Wen-ben Li/ NIGP)

Gymnosperms Pollen Fossil Exine
mm 266 Podncarpidites urnatus. pollen of a gymnosperm. ■•267 Protocomferus funarius. pollen of a gym oosperm, wta ;'!68 jugella claribaculata. pollenolagymnospenn.

Was this article helpful?

0 0

Post a comment