东南极格罗夫山地区新生代冰碛岩(物)中孢粉的发现及其意义

文章报道了东南极格罗夫山地区蓝冰表面碎石带新生代冰碛岩(物)漂砾中微体古生物化石的分析结果及其意义。研究发现这些冰碛物(岩)内含有少量孢粉,而未见硅藻及其他微体化石。孢粉以裸子植物花粉和蕨类植物孢子为主、被子植物花粉含量相对稀少为特征。值得注意的是,在所分析的4个样品中,均发现至今在南半球仍有分布的特有属假山毛榉(Nothofagus)花粉,由于该属花粉及大植物化石曾发现于横跨南极山脉上新的天狼星群(SiriusGroup)中,它的存在反映当时古气候温暖湿润。在样品S1507和S1509中发现蒿属(Artemisia)花粉,其出现所代表的时代推测为新近纪,很可能为上新世。格罗夫山地区冰碛物中的这一孢粉特征可能反映了南极地区上新世曾经发生过较大规模的气候变暖和冰川退缩事件。

PRELIMINARY STUDY ON THE SPORE-POLLEN ASSEMBLAGES FOUND IN THE CENOZOIC SEDIMENTARY ROCKS IN GROVE MOUNTAINS,EAST ANTARCTICA

Glacigenic sedimentary rocks were collected from modern tills of the Grove Mountains, East Antarctica during the 1998-1999 Chinese National Antarctic Research Expedition. These sedimentary rocks are correlated with Cenozoic sedimentary strata of the Pagodroma Group in the neighboring Prince Charles Mountains and the Sφrsdal Formation in Vestfold Hills based on their lithilogic and sedimentary features. Sedimentary clasts contain sparsely Late Tertiary spores and pollens, including: Toroisporis ( Lygodiaceae ) , Osmunda , Granulatispontes ( Pteridaceae?) , Polypodiaceae, Podocarpus , Araucardiaceae, Artemisia, Chenopodiaceae, Rhus , Nothofagidites ( Nothofagus ) , Proteacidites ( Proteaceae ) , Quercus , Fraxinoipollenites ( Oleaceae ) , Oleoidearumpollenites(Oleaceae) , Operculumpollis, and Tricolpopollenites. Most pollen and spores should be of local sources according to their preservation conditions as well as correlations with the diatom assemblages found in the neighboring areas. The majority of the pollen assemblages, as represented by Podocarpus and Nothofagus, belong to the Weddellian biogeocenose. However, some exotic components from the basement sedimentary rocks may have been included during erosion of the proximal ice sheet. If the source areas of glacigenic sedimentary rocks that bear the pollen and spores are assumed to be local, or in the up glacier areas, the pollen assemblages in these samples might represent an inland flora during a warmer period of the ice-sheet evolutionary history. The existing of Artemisia and Chenopodiaceae implies that the pollen assemblages may of the Late Tertiary (most probably Pliocene) age. The absence of diatoms in the samples analyzed may indicate that there are no Cenozoic marine strata in the interior of the East Antarctica beyond the Grove Mountains. The existing of Nothofagus in these pollen assemblages is significant because Nothofagus pollen grains have been discovered also from the Sirius Group and other strata outcropped in Antarctica,and thus bear implication of sedimentary age,phytogeography,and ecological conditions. As a preliminary conclusion, we think that the existence of the Cenozoic glacigenic rocks and their pollen assemblages present new evidence for a large scale glacial retreat event in Grove Mountains of East Antarctica, and thus support a dynamic East Antarctic Ice Sheet (EAIS) . This is consistent with the interpretations of Webb and Harwood (1984) .