J Integr Plant Biol. ›› 1984, Vol. 26 ›› Issue (6): -.

• Research Articles •    

Early Cretaceous Sporo-Pollen Assemblage from Lingxiang Group in Southeastern Hubei

Zhang Zhen-lai   

Abstract: The Lingxiang Group is of a volcano-sedimentary rock series, which is situated between Lower volcanic and Upper volccanic Formations in southeastern Hubei. Its geological age is net ascertained either beloning to Late Jurassic or Early Cretaceous period. Thc rich fossils spores and pollen described in this paper is fonnd in thc greyish-black shale from the middle part of this group, including about 120 species of spores and pollen grains assigned to 67 genera. 9 new species and 2 combinations among them arc described, namely, Impardecispora rara, Neoraistrickia dchiscenta, Api-culatisporis taiheensis, Baculatisporites yangziensis, Reticulatisporites hubeiensis, Coptospora lingxiangensis, C. laevigataeformis, Araucariacites grenulatus, Callialasporites shizishanensis and Araucariacites limbatus (Balme), Inaperturopollenites minor (Mal.). The sporo-pollen assemblage is characterized by the predominance of the pollen of gymnospermous (76.3%) in comparison with the spores of pteridophyta (22.7%), the pollen of Angiosper)nous (0.7%) and Acritarchs (0.3%). The pollen of Gymnospermous mainly consists of Classopollis (45.9%), with abundant Inaperturopollenites (6.3%), Araaeariacites (4.6%), Exesipollenites (3.3%), Callialasporites (2.9%), Jiaohepollis (2.4%), Cycadopites (4.8%) and bisaccata pollen (3.7%). The spores of Pterdophyta is characterized the dominance of Lygodiaccae (13.4%), which includes Cicatricosisporites, Plicatella, Schizaeoisporites, Lygodiumsporites, Lygodioisporites, Toroisporis, Converracosisporites, Concavissimisporites, Yerrueosisporites, Klukisporites, Impardecispora, Pilososporites, with abundant Cyathidites (3.0%), Osmnndacidites (1.2%), Leptoledites (0.8%), Pterisisporites (0.7%) etc. It is very rarely that the pollen of Angiospermous designed as Magnopollis and ?Tricolpites. Beside, Jugella amounts merely to 0.7%. The present spore-pollen assemblage is similar to that in south China characterized Classopollis, Psophosphaera-Cicatricosisporites, Schizaeoisporites-absent or present very rarely pollen of Angiospermous. Therefore, the Lingxiang Group is likely to belong to the early to middle lower Cretaceous in age (Valanginian to Barremian). It is suggested that the climate in southeastern Hubei should be dry tropical-subtropical type at that time. Impardecispora rara Zheng sp. nov. (Pl. I, fig. 7) Trilete, laesurae distinct, about 3/4 of sporo-radius; commissures distinctly raised and flanked by a distinctmargo. Equatorial contour triangular. 46 to 47.5 mierons in equatorial diamcter. Distal exine sculptured with low verrucae, verrucae smaller in inter-radial and polar areas, ones crowded on apical regions; basal diameter 2 microns, height less than 1 microns. Neoraistrickia dehiscenta Zhang sp. nov. (Pl. I, fig. 25) Trilete, laesurae short, about 1/2 of sporo-radius, split open a triangular. Equatorial contour rounded-triangular to subeircular, 35–38.5 microns in equatorial diameter. Distalexine sculptured with short, sparse bacula. Bacula size different, basal diameter 2 to 2.5 microns, height 2 to 4 microns. Round and obtuse at the distal end of the bacula. Apiculatisporis taiheensis Zhang sp. nov. (Pl. I, fig. 22) Tetrad, equatorialcontour of single spore subcircular. Equatorial diameter about 30 microns. Distal surface sculptured by small, sparse with sharp points and basal diameter I to 2 microns, longth 2 to 4 microns. Baculatisporitcs yangziensis Zhang sp. nov. (Pl. I, fig. 23) Trilete, lacsurae short, about 1/2 or a bit longer than 1/2 of sporo-radius. Equatorial contour circular. Equa-torialdiameter 40–45 microns. Exine i to 2 microns thick, sculptured with thick bacula in distal and equatorial regions. Bacula reduced in proximal area, about 17 microns in diametcr. Distal bacula 1.5 to 2 microns wide, 3 to 5 microns long. Bacula xpanded papillate at the distal end. Reticulatisporites hubeiensis Zhang sp. nov. (Pl. II, fig. 4) Trilete, laesurae distinct, long, about 4/5 of sporo radius; commissures distinctly raised and flanked by a distinct narrow margo. Equatorial contour rounded-triangular. Equatorial diameter 52.5 to 75 microns. Exine 1.5 to 2 microns thick, distal surface sculptured with big reticulate, lumen of reticulum 6 to 10 microns in diameter, muri i to 2 microns wide and 0.5 microns high. Coptospora lingxiangensis Zhang sp. nov. (Pl. Ⅰ, figs. 28–29) Trilete, laesurae short, thick, about 1/2 to 2/3 of sporo-radius. Equatorial contour subcircular. Distal area broke open an irregular hole about 10.5 to 17.5 microns in diameter. Exine 1.5 to 2.5 microns thick. Proximal surface smooth, distal surface sculptured with regular, fine and close granulate. 25 to 37.5 microns in equatorial diameter. Coptospora laevigataeformis Zhang sp. nov. (Pl. Ⅰ, figs. 30–31) Trilete, laesurae long, ahnost reaching equator. Equatorial contour subcircular. Distal area broke open an irregular hole about 18 to 22.5 microns in diameter. Exine 2 to 3 microns, surface smooth. 40 to 45 microns in equatorial diameter. Araucariacites granulatas Zhang sp. nov. (Pl. Ⅱ, fig. 12) Inaperturate pollen grains, with elliptical amb. Longth of pollen grains 67.5 to 75 microns, breadth 52 to 57.5 microns. Exine 1 to 2 microns thick, usually heavily folded. Exine surface sculptured with thick and dense granulate. Callialasporites shizishancnsis Zhang sp. nov. (Pl. Ⅱ, fig. 8) Pollen grains monosaccate, equatorialcontour subclrcular, size range of equatorial diameter 62.5 te 75 microns, included the saccus. Central body subcircnler, diameter 40 to 57.5 microns. Trilete mark distinct raised and somewhat curved, thick, long, almost reaching equator of pollen grains. Equatorial saccus 10 to 12 microns wide. Body cxine 1 to 2 microns thick. Both body and saccns surface sculptured with thick and dense granulate. Contour line of pollen grains with small zigzag shape.

Key words: Southeastern Hubei, Lower' Cretaceous, Lingxiang group, Spores and Pollen

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