湘南下泥盆统源口组孢子组合及其地层意义

EARLY DEVONIAN MIOSPORE ASSEMBLAGE FROM THE YUANKOU FORMATION IN SOUTHERN HUNAN AND ITS STRATIGRAPHIC SIGNIFICANCE

通过湖南南部下泥盆统源口组孢子研究,确定源口组为早泥盆世西根阶(Siegenian)。本文图示源口组孢子22属,44种和变种,其中新种3个,即Apiculiretusisporahunanensis,Amocosporites hunanensis和Apiculatasporites yuankouensis。源口组孢子组合可与云南曲靖下泥盆统翠峰山群上部桂家屯组、四川龙门山下泥盆统平驿铺群上部关山坡组和广西横县六景下泥盆统纳高岭组孢子组合比较,亦可与西欧、北美早泥盆世四根阶孢子带对比。源口组孢子组合研究不仅有重要的地层和古生物意义,而且对沉积环境和古地理研究也有重要意义。

A new Lower Devonian miospore assemblage zone in the Yuankou Formation, Southerm Hunan is described, in which 22 genera and 44 species and variations of stratigraphic value are diagrammatized. The spores in the Yuankou Formation are small in size, usually less the 60 microns and mostly 30--45 microns(70% of the total content), the mean being 37.6 microns. The assemblage is characterized by containing smooth azonate spores which are frequently retusoid and minutely scuptured in character. The zone is characterized by abundant well-preserved Apiculiretusispora, Retusotriletes and Anapiculatisporites, which make up 60--70% of the total spores investigated. This miospore assemblage is characterized by the following species: Retusotriletes warringtonii, R. aureoladus, Apiculatasporites microconus, Apiculiretusispora, plicata, Anapiculatisporites sp. C of Streel et al., A. isidori, Emphanisporites micrornatus, R. decoratus, Streelispora newportensis, S. granulata, Synorisporites verrucata, Chelinospora cassicula, Cymbosporites dittonensis, Ibreospora guzmani, Amocosporites miserabilis, Crissisporites guangxiensis, Coronaspora mariae, Archaeozonotriletes chulus, var. chulus, Ambitisporites dilutus, Stenozonotriletes pumilus, Acinosporites of. salopiensis, and Brochotriletes rarus etc. It may approximately be correlated with the Breconisporites breconensis-Emphanisporites zavallatus zone and Verrucosisporites polygonalis-Dictyotriletes emsiensis assemblage zone from the Old Red Sandstone continent and adjacent regions proposed respectively by Richardson and McGregor(1986), this would indicate Siegenian in age.