南极乔治王岛海军湾亨内克角早第三纪晚期孢粉化石及其地层学意义

LATE PALEOGENE PALYNOFLORA FROM POINT HENNEQUIN OFADMIRALTY BAY,KING GEORGE ISLAND,ANTARCTICAAND ITS SIGNIFICANCE IN STRATIGRAPHY

根据乔治王岛海军湾亨内克角群上部凝灰质砂泥岩夹层中的孢粉化石组合特征，讨论其时代归属和沉积环境。研究表明亨内克角群上部火山沉积岩中孢粉化石共４０余种，主要成分为冈瓦纳早第三纪群落，属Ｗｅｄｄｅｌｉａｎ生物地理区，Ｎｏｔｈｏｆａｇｉｄｉｔｅｓ为代表分子，其中Ｎ．ｃｆ．ｓａｒａｅｎｓｉｓ和Ｎ．ｃｆ．ｆｌｅｍｉｎｇｉ的存在以及Ｐｒｏｔｅａｃｉｄｉｔｅｓｓｐｐ．的缺失，提示含化石地层时代可能属渐新世，沉积环境为近中低山区的湖沼环境，气候温暖潮湿。

he sample for palynostratigraphic investigation here described was collected by Zhou Tongshun and Ruan Hongnong et al. from the Point Hennequin of Admiralty Bay,King George Island,west Antarctica during the 1990-1991 Chinese expedition to Antarctica.The lithology with palyniferous fossils consists of thin intercalation of tuffaceous mudy siltstone,assigned to the upper part of Point Hennequin Group or Mount Wawel Formation.Although poorly preserved ,the palynoflora fossils are the first time to encounter within the sequence and are of significance to the determination of age for the rocks.The palynoflora fossil from the upper part of Point Hennequin Group includes more than 40 species. They are fungal spores (8%) Fractispronites sp.,Asterina sp.,Multicellaesporites sp. and Trihyphaecites sp.; pteridophyte spores(45%) Cyathidites minor Couper, Extrapunctatospris sp.,Foveasporis cf. arepunctatis Stuchlik,Gleicheniidites sp.,Laevigatosprites sp., Leiotriletes sp.,Polypodiisporites favus (Pot.)and Retitriletes cf.austroclavatidites (Cookson),etc; gymmspoermous pollen (42%) Trisaccites microsaccatum (Couper),Dacrycarpites australiensis Cooksen et Pike, Microcachydites antarctcus  Cookson,Phyllocladidites mawsonii Cookson et Couper,and Podocarpidites marwickii Couper,etc.;angiospermous pollen (5%) Nothofagitites cf.flaemingii (Couper),N. cf. saraensis Menendez et Caccavari and N.spp.,etc. The characteristic of the present palynoflora from the Point Hennequin Group is obviously different from those examinated from the marine Cretaceous in the James Ross Island and the Late CretaceousPalaeocene from the Seymour Island,both two located in Antarctic Peninsula,also different from that found in the Late Cretaceous Half Three Point Formation of Fildes Peninsula,King George Island.However,some of the genus and species here identified are more or less similar to those found from the Ezcurra Inlet Group and Fossil Hill Formation in King George Island.However,there are also existing certain differences in assemblage components among the three places..It is worth pointing out for the present palynoflora fossils that the occurrences of the pollen N.cf.saraensis,originally found from the Oligocene series in Argentina; the N. cf.flemingii from the MidLate Eocene series in the New Zealand and also popular from the Oligocene rocks show significant age determination.Furthermore,in the present assemblage it absents the Proteacidites spp,an index fossil often occurring in the Late CretaceousEocene rocks in South Hemisphere and Antarctic Peninsula.They also encounted in Fossil Hill Formation and Ezcurra Inlet Formation.It is most likely that the palyniferous upper part of Point Hennequin Group,i.e. the Mount Wawel Formation belongs to the Oligocene age,not as it was assigned to the Miocene or Late Oligocene. The principal components of the palynoflora from the Point Hennequin Group demonstrate the Late Paleogene terristral plants in Gondwana continent,assigned to the Weddellian biogeographyical area. It is evidently supported by the existence of index member Nothofagidites. The characteristics of the palynoflora fossils reflected the vegetation community growing in a limnetic zone near mediumlower mountain environment,with warm and humid climate.