河南信阳群南湾组化石孢子的发现及其地质意义

NEW DISCOVERY OF SPORES FROM THE NANWAN FORMATION OF THE XINYANG GROUP,HENAN,AND ITS GEOLOGY SIGNIFICANCE

作者在河南信阳附近信阳群南湾组中、上部的轻变质灰色砂板岩中发现了丰富的孢子,此外还有疑源类(Acritarchs),几丁虫(Chitinozoans)和虫颚(Scolecedonts)化石。该孢子组合可与华南和西秦岭中泥盆世晚期和晚泥盆世早期孢子组合比较,亦可与西欧、北美和苏联中泥盆世晚期季维特阶(Givetian)和晚泥盆世早期弗拉斯阶(Frasnian)比较,其时代为中泥盆世晚期至晚泥盆世早期。 信阳群南湾组微体化石的发现不仅解决了长期争论的信阳群南湾组的时代问题,而且对秦岭和大别山构造带的区域地质调查和构造带的演化研究都具有重要意义。

The Xingyang Group rocks are exposed over large ares in the Dabie mountain of Henan Province. They are given as fellows in ascending order the Guishau and Nawan Formation. The Nawan Formation is mainly composed of slightly metamorphosed clastic rocks, the age of the Xingyang Group is not proven and controversies over differing opinions.The age of the Nawan Formation is reassessed and confirmed as Middle Devonian (Givetian) to early Late Devonian (Frasnian) on the basis of an investigation of palynology. They are represented by 23 genera, 48 species, of which two species newly established herein is Brochotriletes foramocus and Samarisporites muricatus.The spore assemblage of the Nawan Formation are characteristically dominated by Relusotriletes (Naumova) Streel and Apiculiretusispora Streel which often constitutes up to 30-50 percent of the total. The Nawan Formation contains the stratigraphically significance species Granulatisporites muninensis Allen, Retusotriletes communis communis Naumova, R. simplex Naumova, R. dibius (Eisenack)Richardson, R. pychovii Naumova, R. distinctus Richardson, R. rugulctus Riegel, Apciculiretusispora granulata Owens, .1. plicata (Allen) Streel, A. nitida Owens, Apiculatasporites microconus (Richardson) M( Gregor and Car. field, Convolutispora crcssata (Naumova) McGregor and Camfield, Aneurospcra greggsii (M Gregor) Streel, Calamospora atava(Naurnova) McGregor, Dibolisporites echincceus (Risenack) Richardson, Verrucosisporites variabilis McGregor, Lophotriletes devonicus (Naumova ex Chibrikova) McGregor and CamfieJd, Stenozonotriletes extensus var. medius Naumova, Geminospora tuberculata (Kedo) Allen var. micronata McGregor and Camfield, Cymbosporites spp., Cristatisporites triangulatus (Allen) McGregor and Camfield, Archaeozonotriletes variabilis (Naumova) Allen, Grandispora inculta Allen, Samarisporites coneinnus Owens, S. inaequus Owens, Contagispo- rites optivus var. vorobjevensis (Chihrikova)Owens,Ancyrospora cf. melvillensis Owens, Auroraspora hyallina (Naumova) Streel and Rhabdosporites langii (Eisenack) Richardson.Acritarchs:Leiosphaeridia eryptogranmulosa (Staplin) Eisenack et al., L. minuta (Staplin) Eisenack et al., Lophosphaeridium cf. segregum Playford, Leiofusa sp., Navifusa ap., Gorgonisphaeridium sp..Scolecodonts: Nereidavus disjunctus (Eller), Menogenys summus(Eller), Comugenys decora (Eller), Marlenites marginatus (Eller) and Paranerites bblticus Eisenack.Chitinozoans: Brichitina sp., Conochitina sp., and Rhabdochitina chavani Tougourdeau.Comparisons with similar assemblages from the northern hemisphare indicate a Givetian to early Late Devonian age for the Nawan Formation material. The Stratigraphical significance and the sediments enviroments of the Nawan Formation are discussed.