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《Acta Palaeontologica Sinica》 1956-04
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MICROFLORA AND GEOLOGICAL AGE OF THE BASAL PART OF THE LOWER HUIHUIPOU FORMATION OF THE CHIUCHAN BASIN,OF WESTERN KANSU

J.HS AND H.I.CHOW  
In this paper the authors present the result of their palynological investiga-tion of the Lower Huihuipou Formation which,owing to lack of proper fossils,hasnot yet been definitely assigned to any geological age.From a bed of the lowermost part of this formation at Chinshankou,numerouspollen grains of gymnosperms are found.Of them,Brachyphyllum,Ginkgoales,Bennettitales,and Cycadales are extremely abundant,amounting to 78% of thetotal number of the microfossils;the rest being those of Cedrus,Pinus,Podocarpusand Taxodiaceae (? Taxodium). The most prominent feature of the flora as a whole is the admixture of thetypical Mesozoic forms along with those of the modern types.Considering thepresence of ?Mohria (or Aneimia) spores which are unknown in the Jurassic,theappearence of a large amount of Brachyphyllum pollen,and the absence of anyangiospermous elements,the authors suggest that the basal part of the Lower Hui-huipou Formation is of Lower Cretaceous age.In this flora there are a large number of tropical plants,such as Cibotium,Lygodium,Gleichenia,?Mohria(or Aneimia),Podocarpus,Cycadales,and Bennetti-tales,thus indicating that the climate of this region in early Cretaceous was ratherwarm and moist.Two new types of Cedrus pollen are described as follows:1.Cedrus-pollenttes brevisaccata sp.nov.(Pl.Ⅰ,fig.10)Pollen grains with 2 air-sacs.Total height about 36.1 μ,and total width about81.6 μ-Body oblate,36.1 μ high and 70.7 μ wide.Distal face smooth,occasionallywith loosely arranged granules.Sexine of proximal face developed into a distinctcap,about 4.7 μ thick,consisting of compactly arranged rod-like structure.Surfaceof cap granular or striate,with irregularly arranged granules.Air-sacs developedat two flanks of distal face,in the shape of a short tongue,about 28.3 μ high and43.9 μ wide.No interruption between cap and root of air-sacs.Surface of air-sacs almost smooth.subsaccate reticulum 4-6 sided;muri slightly undulate,with 2-4 granules developed in lannina of each reticulum.Type specimen:Slide No.1516.2.Cedrus-pollenites aurisaccata sp.nov.(Pl.Ⅱ,fig.36)Pollen grains with 2 air-sacs.Total height about 17.7 μ and total width about59.5 μ Body oblate,17.3 μ high and 43.9 μ wide.Thickness of cap about 3.14 μSurface of cap granular to vermicular.Air-sacs developed at two flanks of dis-tat face,short and auricular,about 26.1 μ high and 29 μ wide.No interruptionbetween cap and root of air-sacs.Surface of air-sacs smooth.Subsaccate reticulum4-6 sided;muri slightly undulate,iwth 3-5 granules developed in lamina of eachreticulum.Type specimen:Slide No.1488.
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