Title: ALBIAN PALYNOLOGICAL ASSEMBLAGE FROM THE BOREHOLE YU-302 IN YUSHU——WITH FOCUS ON THE AGE OF THE DENGLOUKU FORMATION IN SONGLIAO BASIN
Abstract: The Denlouku Formation, lying unconformably on Barremian-Aptian Yincheng Formation and overlain disconformably by Cenomanian (?)-Turonian Quantou Formation, is a series of terrestrial clastic sediments developed in Songliao Basin (Text-fig.1) and has been divided lithologically into four members named by number ascendingly. Li and Liu (1994) referred the formation to Albian age based on the palynological evidence from the borehole Yu-302 drilling in Yushu at eastern margin of the basin, while Gao et al. (1999) and Zhao (2000) considered the age of the formation to be Aptian (Members 1—3) to Albian (Member 4) on the palynological data from the center of the basin. The present restudy demonstrated that the strata revealed by borehole Yu-302 includes only the Members 2 and 3 of the Denglouku Formation (Text-fig.2) based on lithological correlation within the basin and yield similar palynological assemblages through the whole sequence. The assemblage is composed of 108 species assigning to 67 genus of bryophyte and pteridophyte spores and gymnospermous and angiospermous pollen and other palynomorphs (Tab.1) and dominated by Cicatricosisporites spores (7%—35%). Most taxa of the assemblage are those common seen in the Early Cretaceous assemblages of North China (Li and Liu, 1994), such as the species of Cicatricosisporites, Appendicisporites, Impardecispora, Pilosisporites, Aequitriradites, Kuylisporites and Triporoletes. However, the appearance of the angiospermous pollen Polyporites debilis Hua and Retitricolpite spp. and the spores Balmeisporites holodictyus Cookson et Dettmann, Scopusporis lautus Wingate, Scopusporis verrucosus (Chlonova) com. nov., Trochicola scollardiana Srivastava and Verrucosisporites fuyuensis sp. nov., which were known from Albian or later sediments, and the lack of tricolporate angiospermous pollen may confirm an Early to Middle Albian age to the assemblage. The palynological evidence from the Yu-302 indicates that at least the Members 2 to 4 of the Denglouku Formation in the Songliao Basin may be referred to Early to Middle Albian in age, while the opinion of Aptian age to the Member 1 by Gao (1999) and Zhao (2000) may be retained due to no more fossil data to be under consideration.
Publication Year: 2005
Publication Date: 2005-01-01
Language: en
Type: article
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Cited By Count: 9
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